Method of characterising a peptide, polypeptide or protein using a nanopore

Abstract

Provided herein are methods of characterising a peptide, polypeptide or protein, as well as associated systems and methods.

Description

[0001] METHOD Cross reference to related This application claims priority from United Kingdom Patent Application No. 2413109.6 filed on 6 September 2024, the entire contents of which are hereby incorporated by reference. Field The present disclosure relates to methods of characterising a peptide, polypeptide or protein using a peptide barcode which is characteristic of the peptide, polypeptide or protein being characterised. Also provided are related systems, kits and analysis methods. The characterisation of biological molecules is of increasing importance in biomedical and biotechnological applications. For example, sequencing of nucleic acids allows the study of genomes and the proteins they encode and, for example, allows correlation between nucleic acid mutations and observable phenomena such as disease indications. Nucleic acid sequencing can be used in evolutionary biology to study the relationship between organisms. Metagenomics involves identifying organisms present in samples, for example microbes in a microbiome, with nucleic acid sequencing allowing the identification of such organisms. Whilst techniques to characterise (e.g. sequence) polynucleotides have been extensively developed, techniques to characterise polypeptides are less advanced, despite being of very significant biotechnological importance. For example, knowledge of a protein sequence can allow structure-activity relationships to be established and has implications in rational drug development strategies for developing ligands for specific receptors. Identification of post-translational modifications is also key to understanding the functional properties of many proteins. For example, typically 30-50% of protein species are phosphorylated in eukaryotes. Some proteins may have multiple phosphorylation sites, serving to activate or inactivate a protein, promote its degradation, or modulate interactions with protein partners. Known methods of characterising polypeptides include mass spectrometry and Edman degradation. Protein mass spectrometry involves characterising whole proteins or fragments thereof in an ionised form. Known methods of protein mass spectrometry include electrospray ionisation (ESI) and matrix-assisted laser desorption / ionisation (MALDI). Mass spectrometry has some benefits, but results obtained can be affected by the presence of contaminants and it can be difficult to process fragile molecules without their fragmentation. Moreover, mass spectrometry is not a single molecule technique and provides only bulk information about the sample interrogated. Mass spectrometry is unsuitable for characterising differences within a population of polypeptide samples and is unwieldy when seeking to distinguish neighbouring residues. Edman degradation is an alternative to mass spectrometry which allows the residue- by-residue sequencing of polypeptides. Edman degradation sequences polypeptides by sequentially cleaving the N-terminal amino acid and then characterising the individually cleaved residues using chromatography or electrophoresis. However, Edman sequencing is slow, involves the use of costly reagents, and like mass spectrometry is not a single molecule technique. As such, there remains a pressing need for new techniques to characterise polypeptides, especially at the single molecule level. Single molecule techniques for characterising biomolecules such as polynucleotides have proven to be particularly attractive due to their high fidelity and avoidance of amplification bias. One attractive method of single molecule characterization of biomolecules such as polypeptides is nanopore sensing. Nanopore sensing is an approach to analyte detection and characterization that relies on the observation of individual binding or interaction events between the analyte molecules and an ion conducting channel. Nanopore sensors can be created by placing a single pore of nanometre dimensions in an electrically insulating membrane and measuring voltage-driven ion currents through the pore in the presence of analyte molecules. The presence of an analyte inside or near the nanopore will alter the ionic flow through the pore, resulting in altered ionic or electric currents being measured over the channel. The identity of an analyte is revealed through its distinctive current signature, notably the duration and extent of current blocks and the variance of current levels during its interaction time with the pore. Nanopore sensing has the potential to allow rapid and cheap polypeptide characterisation. Nanopore sensing and characterisation of polypeptides has been proposed in the art. For example, WO 2013 / 123379 discloses the use of an NTP-driven protein processing unfoldase enzyme to process a protein to be translocated through a nanopore. WO 2021 / 111125 discloses methods in which a target polypeptide is conjugated to a polynucleotide to form a single-stranded polypeptide-polynucleotide conjugate, with the conjugate being moved through a nanopore using a polynucleotide-handling protein. WO 2021 / 133168 discloses protein and polypeptide fingerprinting and sequencing by nanopore translocation of polypeptide-oligonucleotide complexes. PCT / GB2023 / 052838 discloses methods of characterising a target polypeptide as it moves with relation to a nanopore. Each of these documents is incorporated by reference in their entireties. These methods have provided useful techniques for characterising polypeptides using nanopores. However, there remains a need for further methods. In particular, there remains a need for methods that allow complex peptides, polypeptides or proteins to be characterised without necessarily having to subject the entire peptide, polypeptide or protein to nanopore translocation. Such methods would allow for more efficient peptide, polypeptide or protein characterisation. Furthermore, there is a need for methods that can determine information about the peptide, polypeptide or protein such as the relative abundance of multiple peptides, polypeptides and proteins in a sample; whether one peptide, polypeptide or protein binds to another; which fraction of a sample a peptide, polypeptide or protein is found in; whether and how (e.g. with what stoichiometry) two or more peptide, polypeptide or protein may bind together; whether or not a peptide, polypeptide or protein of interest is expressed from an expression system; how expression conditions affect expression yield; and the like. The inventors have recognised that these issues could be addressed by the generation of and sensing of barcodes attached to the peptide, polypeptide or protein of interest. Such barcodes can be designed or chosen to have properties which are characteristic of one or more characteristics of the peptide, polypeptide or protein to which the barcode is associated. By taking measurements of the barcode, the properties of the barcode can be determined, and the properties of the barcode associated with one or more characteristics of the peptide, polypeptide or protein. Accordingly, it could be possible to characterise the peptide, polypeptide or protein by characterising the barcode. The present invention provides such methods. Accordingly, the disclosure relates to methods of characterising a peptide, polypeptide or protein. The method relates to a construct which comprises the peptide, polypeptide or protein attached to a barcode. The construct is contacted with one or more process conditions which cleaves the barcode from the peptide, polypeptide or protein. Such conditions are described in more detail herein. The cleaved barcode is then contacted with a nanopore, and caused to move with respect to the nanopore. One or more measurements characteristic of the barcode are taken as the barcode moves with respect to the nanopore. By taking one or more such measurements, one or more properties of the barcode are determined. The one or more properties of the barcode may include, for example, its identity, length, composition and / or (when the barcode is a peptide barcode) its amino acid sequence. The one or more properties of the barcode are characteristic of one or more characteristics of the peptide, polypeptide or protein. For example, and as described in more detail herein, multiple different types of peptide, polypeptide or protein in a sample may be tagged with different barcodes such that each type of peptide, polypeptide or protein has a different type of barcode attached thereto (e.g. has a barcode of different sequence attached thereto). The sequence of the barcode is thus characteristic of the peptide, polypeptide or protein to which the barcode is attached; for example characteristic of the identity of the peptide, polypeptide or protein. By determining the one or more properties of the barcode, therefore, one or more characteristics of the peptide, polypeptide or protein to which the barcode was attached in the construct can be determined. Accordingly, provided herein is a method of characterising a peptide, polypeptide or protein, the method comprising a) contacting a construct comprising the peptide, polypeptide or protein attached to a barcode with one or more process conditions capable of cleaving the peptide, polypeptide or protein from the attached barcode, thereby cleaving the peptide, polypeptide or protein from the barcode; b) contacting the cleaved barcode with a nanopore under conditions such that the barcode moves with respect to the nanopore; and c) taking one or more measurements characteristic of the barcode as the barcode moves with respect to the nanopore, thereby determining one or more properties of the barcode; wherein said one or more properties of the barcode are characteristic of one or more characteristics of the peptide, polypeptide or protein; thereby characterising the peptide, polypeptide or protein. Also provided is a method of characterising a peptide, polypeptide or protein, the method comprising a) contacting a construct comprising the peptide, polypeptide or protein attached to a barcode with one or more process conditions capable of cleaving the peptide, polypeptide or protein from the attached barcode, thereby cleaving the peptide, polypeptide or protein from the barcode; b) contacting the cleaved barcode with a nanopore under conditions such that the barcode moves with respect to the nanopore; and c) taking one or more measurements characteristic of the barcode as the barcode moves with respect to the nanopore, thereby determining one or more properties of the barcode; d) associating said one or more properties of the barcode with one or more characteristics of the peptide, polypeptide or protein; thereby characterising the peptide, polypeptide or protein. In some embodiments the barcode is a peptide barcode. In some embodiments the barcode is not comprised in the amino acid sequence of the peptide, polypeptide or protein being characterised. In some embodiments the barcode comprises an oligopeptide comprising from about 3 to about 20 amino acids and / or amino acid analogs. In some embodiments the barcode comprises an oligopeptide comprising from about 5 to about 10 amino acids and / or amino acid analogs. In some embodiments the peptide, polypeptide or protein is at least about 30 amino acids in length. In some embodiments the peptide, polypeptide or protein is at least about 2, 4, 6, 8, 10, 15, 20, 25, 30, 40, 50, or 100 amino acids in length. In some embodiments the barcode has a net charge. In some embodiments the barcode has a net negative charge. In some embodiments, step (a) comprises: (a1) producing a construct comprising a peptide, polypeptide or protein attached to a barcode; and (a2) contacting the construct with one or more process conditions capable of cleaving the peptide, polypeptide or protein from the barcode. In some embodiments, step (a1) comprises expressing the peptide, polypeptide or protein under conditions that the peptide, polypeptide or protein is expressed with an attached barcode. In some embodiments, the peptide, polypeptide or protein is expressed from a genetic construct comprising a polynucleotide sequence encoding the peptide, polypeptide or protein and a polynucleotide sequence encoding the barcode. In some embodiments, step (a1) comprises attaching a barcode to the peptide, polypeptide or protein. In some embodiments, the barcode is comprised in a barcode tag comprising the barcode and a purification tag. In some embodiments, step (a) further comprises purifying the construct using the purification tag. In some embodiments, the barcode tag comprises a cleavage site between the barcode and the purification tag. In some embodiments, the construct comprises a cleavage site between the barcode and the peptide, polypeptide or protein. In some embodiments, the construct comprises a cleavage site between the barcode tag and the peptide, polypeptide or protein. In some embodiments, the construct comprises a first cleavage site at the N- terminal of the barcode and a second cleavage site at the C-terminal of the barcode; wherein the first and second cleavage sites may be the same or different. In some embodiments, the first and / or second cleavage sites comprise a protease recognition site. In some embodiments, the first and / or second cleavage sites comprise a lysine residue. In some embodiments, the first and / or second cleavage sites comprise an arginine residue. In some embodiments, the first cleavage site comprises an arginine residue and the second cleavage site comprises a lysine residue. In some embodiments, the first cleavage site comprises a lysine residue and the second cleavage site comprises an arginine residue. In some embodiments, the first and / or second cleavage sites comprise a lysine residue and wherein contacting the construct with the one or more process conditions capable of cleaving the peptide, polypeptide or protein from the barcode comprises contacting the construct with LysC or functional analog, fragment or variant thereof. In some embodiments, each construct comprises a structure of the form: Nterm – P – Z1 – B – Z2 – W – Cterm, Nterm – W – Z2 – B – Z1 – P – Cterm, Nterm – P – Z1– W – Z2– B – Cterm, or Nterm – B – Z2– W – Z1– P – Cterm; wherein Nterm represents the N terminus of the construct; Cterm represents the C terminus of the construct; P represents the peptide, polypeptide or protein being characterised; B represents the barcode; W represents an amino acid sequence comprising a purification tag; optionally wherein W comprises a polyhistidine sequence; Z1 represents a first protease cleavage site; optionally wherein Z1 comprises a lysine residue; and Z2represents a second protease cleavage site; optionally wherein Z2comprises a lysine residue. In some embodiments each construct comprises a structure of the form: Nterm – P – Z1– W – AA1 – B – Z2– Cterm; or Nterm – AA1 – B – Z2– W – Z1– P – Cterm wherein Nterm represents the N terminus of the construct; Cterm represents the C terminus of the construct; P represents the peptide, polypeptide or protein being characterised; Z1 represents a first protease cleavage site; optionally wherein Z1 comprises a TEV protease cleavage site; W represents an amino acid sequence comprising a purification tag; optionally wherein W comprises a polyhistidine sequence; B represents the barcode; and AA1 represents an amino acid recognised by a protease; optionally wherein AA1 represents arginine or lysine; further optionally wherein AA1 represents arginine or lysine at the N-terminus of the barcode (B); Z2represents a second protease cleavage site; optionally wherein Z2comprises a lysine residue; further optionally wherein Z2 corresponds to a lysine residue at the C-terminus of the barcode (B). In some embodiments, the barcode is located within the peptide, polypeptide or protein, i.e. the barcode is internal to the protein. Thus, in some embodiments, the barcode or barcode tag is attached within the peptide, polypeptide or protein, as opposed to at a terminus of the protein. For example, a barcode or barcode tag may be located within an internal loop region of a protein. This may be achieved by inserting the barcode or barcode tag into the amino acid sequence of the peptide, polypeptide or protein of interest, for example in the manner P1– B – P2, where P1is a first portion of the peptide, polypeptide or protein of interest, B is the barcode or barcode tag, and P2is a second portion of the peptide, polypeptide or protein of interest. In some embodiments, step (b) of the method comprises attaching the barcode to one or more sequencing adapters. In some embodiments, cleaving the peptide, polypeptide or protein from the barcode generates one or more reactive functional groups at the N- and / or C- terminus of the barcode; and step (b) comprises attaching one or more sequencing adapters to said one or more reactive functional groups. In some embodiments, step (b) comprises attaching one or more peptide handles to the one or more reactive functional groups, wherein each peptide handle comprises a reactive functional group for attaching to a sequencing adapter; and attaching a sequencing adapter to each peptide handle. In some embodiments, step (b) comprises contacting the barcode and / or a sequencing adapter if present with a motor protein capable of controlling the movement of the barcode with respect to the nanopore. In some embodiments, the peptide, polypeptide or protein is present in a sample comprising a plurality of different peptides, polypeptides and / or proteins, and the method comprises a) contacting a plurality of constructs each comprising a peptide, polypeptide or protein attached to a barcode with one or more process conditions capable of cleaving the peptide, polypeptide or proteins from the attached barcodes, thereby cleaving the peptide, polypeptide or protein from the barcodes, wherein in said constructs different peptide, polypeptide and / or protein sequences have different barcodes attached thereto; b) contacting the cleaved barcodes with one or more nanopores under conditions such that the barcodes move with respect to the nanopore(s); and c) taking one or more measurements characteristic of each barcode as the barcodes move with respect to the nanopore(s), thereby determining one or more properties of each barcode; wherein said one or more properties of each barcode are characteristic of one or more characteristics of the peptide, polypeptide or protein to which the barcode was attached in the construct. In some embodiments, said different barcodes have different sequences each comprising a portion having a common sequence and a portion having a variable sequence. In some embodiments, the peptide, polypeptide or protein; barcode; and / or construct are as defined herein. In some embodiments, the one or more characteristics of the peptide, polypeptide or protein comprise the presence, absence, concentration or relative abundance of the peptide, polypeptide or protein in a sample; the length of the peptide, polypeptide or protein; the identity of the peptide, polypeptide or protein; the sequence of the peptide, polypeptide or protein; whether or not and / or the extent to which the peptide, polypeptide or protein is modified; and / or whether or not and / or the extent to which the peptide, polypeptide or protein associates with a further peptide, polypeptide or protein wherein the further peptide, polypeptide or protein is optionally comprised in a construct as defined herein. Also provided herein is a kit comprising: - a construct comprising a peptide, polypeptide or protein attached to a peptide barcode; wherein the construct comprises a first cleavage site at the N- terminus of the barcode and a second cleavage site at the C-terminus of the barcode; and wherein the first and / or second cleavage site(s) are configured to generate when cleaved one or more reactive functional groups at the N- and / or C- terminus of the barcode; and a) one or more sequencing adapters capable of binding to said one or more reactive functional groups; and / or b) a protease capable of selectively cleaving the construct at said cleavage sites, wherein said cleavage sites each comprise a recognition site for said protease. Further provided herein is a kit comprising: - a construct comprising a peptide, polypeptide or protein attached to a peptide barcode; wherein the construct comprises a cleavage site at the N- terminus or the C-terminus of the barcode; wherein the cleavage site(s) is configured to generate when cleaved one or more reactive functional groups at the N- and / or C- terminus of the barcode; and c) one or more sequencing adapters capable of binding to said one or more reactive functional groups; and / or d) a protease capable of selectively cleaving the construct at said cleavage sites, wherein said cleavage sites each comprise a recognition site for said protease. In some embodiments, the kit further comprises a nanopore, optionally present in an array comprising a plurality of nanopores in a membrane. In some embodiments the kit further comprises a motor protein capable of controlling the movement of the barcode with respect to a nanopore. Also provided is a system, comprising one or more barcodes as described herein; and a nanopore. In some embodiments the nanopore is as described herein. In some embodiments the system further comprises a motor protein capable of controlling the movement of the barcode(s) with respect to the nanopore. In some embodiments the system further comprises computing means configured to detect information characteristic of the barcode(s) and to selectively process the signal obtained as said barcode(s) move with respect to the nanopore. Also provided is a method of analysing measurement signals taken from each of a plurality of barcodes as the barcodes move with respect to a nanopore, the method comprising: identifying, in each measurement signal a barcode signal portion of the measurement signal corresponding to the barcode; in respect of each barcode signal portion, deriving one or more properties of the barcode from which the barcode signal portion is derived; from the derived one or more properties of each barcode, deriving one or more characteristics of the peptide, polypeptide or protein from which the barcode is derived; and associating the one or more characteristics of each peptide, polypeptide or protein with the barcode signal portion of the measurement signal. Also provided is a computer program comprising instructions capable of execution by a computer system which are configured, on execution, to cause the computer system to carry out a method as described herein. Also provided is a computer storage medium storing a computer program as described herein. Also provided is a computer system configured to perform a method as described herein. Figure 1A illustrates a measurement and analysis system 1 comprising a measurement system 2 and an analysis system 3. The measurement system 2 derives a measurement signal from a polymer (such as a barcode as described herein) comprising a series of polymer units during translocation of the polymer with respect to a detector such as a nanopore. The analysis system 3 performs a method of analysing the measurement signal 10 to derive an estimate of the series of polymer units. Figure 1B is a flowchart of a method of associating polypeptide measurement signals with characteristics of the polypeptide which give rise to the signals. Figure 2 shows examples of sequencing traces for the peptide barcode DDDDK (SEQ ID NO: 161). The y-axis shows current (pA), and the x-axis shows time in current samples (described in Example 2). Figure 3 shows calibrated relative counts of detected barcode signals for peptide barcode-DNA conjugates prepared from 4 barcoded GFP proteins. The 4 GFP proteins were barcoded with barcodes labelled 1-4. Data described in Example 2. Detailed Description The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. Any reference signs in the claims shall not be construed as limiting the scope. Of course, it is to be understood that not necessarily all aspects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as may be taught or suggested herein. The invention, both as to organization and method of operation, together with features and advantages thereof, may best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings. The aspects and advantages of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Similarly, it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. It should be appreciated that “embodiments” of the disclosure can be specifically combined together unless the context indicates otherwise. The specific combinations of all disclosed embodiments (unless implied otherwise by the context) are further disclosed embodiments of the claimed invention. In addition as used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to “a polynucleotide” includes two or more polynucleotides, reference to “a motor protein” includes two or more such proteins, reference to “a helicase” includes two or more helicases, reference to “a monomer” refers to two or more monomers, reference to “a pore” includes two or more pores and the like. All publications, patents and patent applications cited herein, whether supra or infra, are hereby incorporated by reference in their entirety. Definitions Where an indefinite or definite article is used when referring to a singular noun e.g. "a" or "an", "the", this includes a plural of that noun unless something else is specifically stated. Where the term "comprising" is used in the present description and claims, it does not exclude other elements or steps. Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. The following terms or definitions are provided solely to aid in the understanding of the invention. Unless specifically defined herein, all terms used herein have the same meaning as they would to one skilled in the art of the present invention. Practitioners are particularly directed to Sambrook et al., Molecular Cloning: A Laboratory Manual, 4thed., Cold Spring Harbor Press, Plainsview, New York (2012); and Ausubel et al., Current Protocols in Molecular Biology (Supplement 114), John Wiley & Sons, New York (2016), for definitions and terms of the art. The definitions provided herein should not be construed to have a scope less than understood by a person of ordinary skill in the art. "About" as used herein when referring to a measurable value such as an amount, a temporal duration, and the like, is meant to encompass variations of ± 20 % or ± 10 %, more preferably ± 5 %, even more preferably ± 1 %, and still more preferably ± 0.1 % from the specified value, as such variations are appropriate to perform the disclosed methods. “Nucleotide sequence”, “DNA sequence” or “nucleic acid molecule(s)” as used herein refers to a polymeric form of nucleotides of any length, either ribonucleotides or deoxyribonucleotides. This term refers only to the primary structure of the molecule. Thus, this term includes double- and single-stranded DNA, and RNA. The term “nucleic acid” as used herein, is a single or double stranded covalently-linked sequence of nucleotides in which the 3' and 5' ends on each nucleotide are joined by phosphodiester bonds. The polynucleotide may be made up of deoxyribonucleotide bases or ribonucleotide bases. Nucleic acids may be manufactured synthetically in vitro or isolated from natural sources. Nucleic acids may further include modified DNA or RNA, for example DNA or RNA that has been methylated, or RNA that has been subject to post-transcriptional modification, for example 5’-capping with 7-methylguanosine, 3’-processing such as cleavage and polyadenylation, and splicing. Nucleic acids may also include synthetic nucleic acids (XNA), such as hexitol nucleic acid (HNA), cyclohexene nucleic acid (CeNA), threose nucleic acid (TNA), glycerol nucleic acid (GNA), locked nucleic acid (LNA) and peptide nucleic acid (PNA). Sizes of nucleic acids, also referred to herein as “polynucleotides” are typically expressed as the number of base pairs (bp) for double stranded polynucleotides, or in the case of single stranded polynucleotides as the number of nucleotides (nt). One thousand bp or nt equal a kilobase (kb). Polynucleotides of less than around 40 nucleotides in length are typically called “oligonucleotides” and may comprise primers for use in manipulation of DNA such as via polymerase chain reaction (PCR). The term “amino acid” in the context of the present disclosure is used in its broadest sense and is meant to include organic compounds containing amine (NH2) and carboxyl (COOH) functional groups, along with a side chain (e.g., a R group) specific to each amino acid. In some embodiments, the amino acids refer to naturally occurring L α- amino acids or residues. The commonly used one and three letter abbreviations for naturally occurring amino acids are used herein: A=Ala; C=Cys; D=Asp; E=Glu; F=Phe; G=Gly; H=His; I=Ile; K=Lys; L=Leu; M=Met; N=Asn; P=Pro; Q=Gln; R=Arg; S=Ser; T=Thr; V=Val; W=Trp; and Y=Tyr (Lehninger, A. L., (1975) Biochemistry, 2d ed., pp. 71-92, Worth Publishers, New York). The general term “amino acid” further includes D- amino acids, retro-inverso amino acids as well as chemically modified amino acids such as amino acid analogues, naturally occurring amino acids that are not usually incorporated into proteins such as norleucine, and chemically synthesised compounds having properties known in the art to be characteristic of an amino acid, such as β-amino acids. For example, analogues or mimetics of phenylalanine or proline, which allow the same conformational restriction of the peptide compounds as do natural Phe or Pro, are included within the definition of amino acid. Such analogues and mimetics are referred to herein as "functional equivalents" of the respective amino acid. Other examples of amino acids are listed by Roberts and Vellaccio, The Peptides: Analysis, Synthesis, Biology, Gross and Meiehofer, eds., Vol.5 p.341, Academic Press, Inc., N.Y.1983, which is incorporated herein by reference. The terms “polypeptide”, and “peptide” are interchangeably used herein to refer to a polymer of amino acid residues and to variants and synthetic analogues of the same. Thus, these terms apply to amino acid polymers in which one or more amino acid residues is a synthetic non-naturally occurring amino acid, such as a chemical analogue of a corresponding naturally occurring amino acid, as well as to naturally-occurring amino acid polymers. Polypeptides can also undergo maturation or post-translational modification processes that may include, but are not limited to: glycosylation, proteolytic cleavage, lipidization, signal peptide cleavage, propeptide cleavage, phosphorylation, and such like. A peptide can be made using recombinant techniques, e.g., through the expression of a recombinant or synthetic polynucleotide. A recombinantly produced peptide is typically substantially free of culture medium, e.g., culture medium represents less than about 20 %, more typically less than about 10 %, and most typically less than about 5 % of the volume of the protein preparation. The term “protein” is used to describe a folded polypeptide having a secondary, tertiary, or quaternary structure. The protein may be composed of a single polypeptide, or may comprise multiple polypeptides that are assembled to form a multimer. The multimer may be a homooligomer, or a heterooligmer. The protein may be a naturally occurring, or wild type protein, or a modified, or non-naturally, occurring protein. The protein may, for example, differ from a wild type protein by the addition, substitution or deletion of one or more amino acids. A “variant” of a protein encompass peptides, oligopeptides, polypeptides, proteins and enzymes having amino acid substitutions, deletions and / or insertions relative to the unmodified or wild-type protein in question and having similar biological and functional activity as the unmodified protein from which they are derived. The term "amino acid identity" as used herein refers to the extent that sequences are identical on an amino acid- by-amino acid basis over a window of comparison. Thus, a "percentage of sequence identity" is calculated by comparing two optimally aligned sequences over the window of comparison, determining the number of positions at which the identical amino acid residue (e.g., Ala, Pro, Ser, Thr, Gly, Val, Leu, Ile, Phe, Tyr, Trp, Lys, Arg, His, Asp, Glu, Asn, Gln, Cys and Met) occurs in both sequences to yield the number of matched positions, dividing the number of matched positions by the total number of positions in the window of comparison (i.e., the window size), and multiplying the result by 100 to yield the percentage of sequence identity. For all aspects and embodiments of the present invention, a “variant” has at least 40%, 50%, 60%, 70%, 80%, 90%, 95% or 99% complete sequence identity to the amino acid sequence of the corresponding wild-type protein. Sequence identity can also be to a fragment or portion of the full length polynucleotide or polypeptide. Hence, a sequence may have only 50 % overall sequence identity with a full length reference sequence, but a sequence of a particular region, domain or subunit could share 80 %, 90 %, or as much as 99 % sequence identity with the reference sequence. The term “wild-type” refers to a gene or gene product isolated from a naturally occurring source. A wild-type gene is that which is most frequently observed in a population and is thus arbitrarily designed the “normal” or “wild-type” form of the gene. In contrast, the term “modified”, “mutant” or “variant” refers to a gene or gene product that displays modifications in sequence (e.g., substitutions, truncations, or insertions), post- translational modifications and / or functional properties (e.g., altered characteristics) when compared to the wild-type gene or gene product. It is noted that naturally occurring mutants can be isolated; these are identified by the fact that they have altered characteristics when compared to the wild-type gene or gene product. Methods for introducing or substituting naturally-occurring amino acids are well known in the art. For instance, methionine (M) may be substituted with arginine (R) by replacing the codon for methionine (ATG) with a codon for arginine (CGT) at the relevant position in a polynucleotide encoding the mutant monomer. Methods for introducing or substituting non-naturally-occurring amino acids are also well known in the art. For instance, non- naturally-occurring amino acids may be introduced by including synthetic aminoacyl- tRNAs in the IVTT system used to express the mutant monomer. Alternatively, they may be introduced by expressing the mutant monomer in E. coli that are auxotrophic for specific amino acids in the presence of synthetic (i.e. non-naturally-occurring) analogues of those specific amino acids. They may also be produced by native chemical ligation if the mutant monomer is produced using partial peptide synthesis. Conservative substitutions replace amino acids with other amino acids of similar chemical structure, similar chemical properties or similar side-chain volume. The amino acids introduced may have similar polarity, hydrophilicity, hydrophobicity, basicity, acidity, neutrality or charge to the amino acids they replace. Alternatively, the conservative substitution may introduce another amino acid that is aromatic or aliphatic in the place of a pre-existing aromatic or aliphatic amino acid. Conservative amino acid changes are well-known in the art and may be selected in accordance with the properties of the 20 main amino acids as defined in Table 1 below. Where amino acids have similar polarity, this can also be determined by reference to the hydropathy scale for amino acid side chains in Table 2. Table 1 - Chemical properties of amino acids Ala aliphatic, hydrophobic, neutral Met hydrophobic, neutral Cys polar, hydrophobic, neutral Asn polar, hydrophilic, neutral Asp polar, hydrophilic, charged (-) Pro hydrophobic, neutral Glu polar, hydrophilic, charged (-) Gln polar, hydrophilic, neutral Phe aromatic, hydrophobic, neutral Arg polar, hydrophilic, charged (+) Gly aliphatic, neutral Ser polar, hydrophilic, neutral His aromatic, polar, hydrophilic, Thr polar, hydrophilic, neutral charged (+) Ile aliphatic, hydrophobic, neutral Val aliphatic, hydrophobic, neutral Lys polar, hydrophilic, charged(+) Trp aromatic, hydrophobic, neutral Leu aliphatic, hydrophobic, neutral Tyr aromatic, polar, hydrophobic

[0002] Table 2 - Hydropathy scale __________________________________ Side Chain Hydropathy ______________________________________ Ile 4.5 Val 4.2 Leu 3.8 Phe 2.8 Cys 2.5 Met 1.9 Ala 1.8 Gly -0.4 Thr -0.7 Ser -0.8 Trp -0.9 Tyr -1.3 Pro -1.6 His -3.2 Glu -3.5 Gln -3.5 Asp -3.5 Asn -3.5 Lys -3.9 Arg -4.5 _______________________________________________ A mutant or modified protein, monomer or peptide can also be chemically modified in any way and at any site. A mutant or modified monomer or peptide may be chemically modified by attachment of a molecule to one or more cysteines (cysteine linkage), attachment of a molecule to one or more lysines, attachment of a molecule to one or more non-natural amino acids, enzyme modification of an epitope or modification of a terminus. Suitable methods for carrying out such modifications are well-known in the art. The mutant of modified protein, monomer or peptide may be chemically modified by the attachment of any molecule. For instance, the mutant of modified protein, monomer or peptide may be chemically modified by attachment of a dye or a fluorophore. Disclosed Methods Provided herein is a method of characterising a peptide, polypeptide or protein, the method comprising: a) contacting a construct comprising the peptide, polypeptide or protein attached to a barcode with one or more process conditions capable of cleaving the peptide, polypeptide or protein from the attached barcode, thereby cleaving the peptide, polypeptide or protein from the barcode; b) contacting the cleaved barcode with a nanopore under conditions such that the barcode moves with respect to the nanopore; and c) taking one or more measurements characteristic of the barcode as the barcode moves with respect to the nanopore, thereby determining one or more properties of the barcode; wherein said one or more properties of the barcode are characteristic of one or more characteristics of the peptide, polypeptide or protein; thereby characterising the peptide, polypeptide or protein. Also provided is a method of characterising a peptide, polypeptide or protein, the method comprising a) contacting a construct comprising the peptide, polypeptide or protein attached to a barcode with one or more process conditions capable of cleaving the peptide, polypeptide or protein from the attached barcode, thereby cleaving the peptide, polypeptide or protein from the barcode; b) contacting the cleaved barcode with a nanopore under conditions such that the barcode moves with respect to the nanopore; and c) taking one or more measurements characteristic of the barcode as the barcode moves with respect to the nanopore, thereby determining one or more properties of the barcode; d) associating said one or more properties of the barcode with one or more characteristics of the peptide, polypeptide or protein; thereby characterising the peptide, polypeptide or protein. As explained below, determining characteristics of the peptide, polypeptide or protein using a barcode is associated with significant technical advantages compared to seeking to directly probe the peptide, polypeptide or protein itself. For example, the barcode is typically much shorter than the peptide, polypeptide or protein to which it is attached in the construct. Accordingly, generation of secondary structure which may impede passage of the peptide, polypeptide or protein through the nanopore in alternative methods is reduced. The process is more efficient in terms of the number of reads that can be processed by a given nanopore in a set amount of time, because the barcode is much shorter than the underlying peptide, polypeptide or protein and so it takes less time to move with respect to the nanopore. Furthermore, as discussed below, sensing barcodes allows information to be determined which may not be readily determined by probing the underlying peptide, polypeptide or protein directly. For example, it is possible to obtain information about whether two peptides, polypeptides or proteins associate together in a sample, and even about the stoichiometry of the association, by labelling each peptide, polypeptide or protein with a barcode in accordance with the methods disclosed herein and characterising the barcode. The use of nanopore characterisation methods is particularly useful because as a single molecule technique such methods allow detailed information about multiple barcodes in a sample to be obtained. For example, nanopore analysis allows information about the abundance of barcodes in a sample, the length of the barcode, and the identity of the barcode (e.g. its sequence, when the barcode is a polypeptide barcode) to be selectively determined. Such information is often inaccessible in other detection methods, such as methods relying on detectable labels such as fluorophores. Cleavage of the barcode from the peptide, polypeptide or protein is also associated with technical advantages in some cases, although as will be apparent from the disclosure herein this is not a requirement of the disclosed methods. For example, cleavage of a barcode from a peptide, polypeptide or protein allows the barcode to easily translocate the nanopore used in its analysis without risking the peptide, polypeptide or protein from blocking the nanopore. The time required to probe the barcode is typically less than the time that is required to probe a barcode-peptide, polypeptide or protein complex. Furthermore, a barcode can in some embodiments be probed using a simpler setup than would be required to probe an entire protein-barcode complex. Still further, a barcode once cleaved from a peptide, polypeptide or protein may be subjected to conditions that would damage the integrity of the peptide, polypeptide or protein rendering it unsuitable for characterisation. Thus, probing a cleaved barcode is typically beneficial. The methods disclosed herein thus involve the use of a barcode. Any suitable barcode can be used in the disclosed methods. Some exemplary barcodes are described in more detail herein. Some disclosed methods involve cleaving the barcode from the peptide, polypeptide or protein to which it is initially attached by contacting the complex of the peptide, polypeptide or protein and barcode with one or more process conditions capable of cleaving the peptide, polypeptide or protein from the barcode. Any suitable process conditions can be used. Some suitable process conditions are described in more detail herein. The disclosed methods involve contacting the barcode with a nanopore. Any suitable nanopore can be used as described herein in more detail. As further described herein, a nanopore is provided as an exemplary detector which can be used in the disclosed methods. Thus, whilst embodiments described herein refer to movement of the barcode with respect to a nanopore, the methods provided herein are also amenable to other detectors including (i) a zero-mode waveguide, (ii) a field-effect transistor, optionally a nanowire field-effect transistor; (iii) an AFM tip; (iv) a nanotube, optionally a carbon nanotube and (v) a nanopore. The disclosed methods are particularly amenable to methods in which a barcode is moved through a detector or through a structure containing a detector, e.g. a well in a detector chip. The disclosed methods involve taking one or more measurements characteristic of the barcode as the barcode moves with respect to the nanopore. Some suitable measurements are described in more detail herein. The one or more properties of the barcode are characteristic of one or more characteristics of the peptide, polypeptide or protein. Because of this, data about the properties of the barcode can be used to infer or otherwise determine characteristics of the peptide, polypeptide or protein. Thus, in the disclosed methods a signal of the barcode can be associated with the characteristics of the peptide, polypeptide or protein which can be determined or inferred from knowledge of the properties of the barcode, which can be determined using methods known in the art. The resulting data can be used to train computer models such as neural networks in order to characterise unknown polypeptides. Thus, in some embodiments the disclosed methods involve associating the one or more properties of the barcode with one or more characteristics of the peptide, polypeptide or protein, thereby characterising the peptide, polypeptide or protein. Some further details of such association steps are described in more detail herein. Barcode Any suitable barcode can be used in the disclosed methods. In some embodiments the barcode is a polymer. In some embodiments the barcode is a synthetic polymer such as a poly-alkylene glycol such as PEG. In some embodiments the barcode is a biological polymer such as a polynucleotide, a polysaccharide or a polypeptide. In some embodiments the barcode is or comprises an oligopeptide. In some embodiments the barcode is a peptide barcode. Typically, the barcode is shorter in length than the peptide, polypeptide or protein to which it is attached in the construct. For example, in some embodiments the barcode is a polymer and contains from about 3 to about 50 monomer units. In some embodiments the barcode is a polymer and contains from about 3 to about 20 monomer units. In some embodiments the barcode is a polymer and contains from about 5 to about 10 monomer units. The monomer units in the polymer may the same or different. The monomer units in the polymer may be the same type of monomer units (e.g. may all be amino acids, if the barcode is a peptide barcode), or may be different types of monomer units (e.g. the barcode may comprise a mixture of monomer units. For example, the barcode may comprise one or more amino acids and one or more non-amino acid monomer units, such as one or more nucleotide monomers and / or one or more synthetic monomers). Typically, the barcode is a peptide barcode comprising natural and / or non-natural amino acids and / or amino acid analogs. In some embodiments the barcode is a peptide barcode and the sequence of the barcode is not comprised in the amino acid sequence of the peptide, polypeptide or protein being characterised. In some embodiments, therefore, the barcode is not naturally part of the peptide, polypeptide or protein. In some embodiments the barcode does not comprise the N-terminal residues of the peptide, polypeptide or protein (e.g. when the barcode comprises n residues, in some embodiments the barcode does not comprise the n N- terminal residues of the peptide, polypeptide or protein). In some embodiments the barcode does not comprise the C-terminal residues of the peptide, polypeptide or protein (e.g. when the barcode comprises n residues, in some embodiments the barcode does not comprise the n C-terminal residues of the peptide, polypeptide or protein). In some embodiments the barcode is a peptide barcode and comprises an oligopeptide comprising from about 3 to about 50 amino acids and / or amino acid analogs. In some embodiments the barcode is a peptide barcode and comprises an oligopeptide comprising from about 3 to about 20 amino acids and / or amino acid analogs. In some embodiments the barcode comprises from about 4 to about 15 amino acids and / or amino acid analogs. In some embodiments the barcode comprises from about 5 to about 10 amino acids and / or amino acid analogs. In some embodiments the barcode comprises about 5, 6, 7, 8, 9 or 10 amino acids and / or amino acid analogs. In some embodiments the barcode comprises from about 3 to about 20 amino acids and / or amino acid analogs (e.g. from about 5 to about 10 amino acids and / or amino acid analogs) and the peptide, polypeptide or protein is at least about 30 amino acids in length. In some embodiments the peptide, polypeptide or protein is at least about 50 amino acids in length, such as at least about 80 amino acids, such as at least about 100 amino acids, e.g. at least about 150 amino acids, e.g. at least about 200 amino acids, e.g. at least about 300 amino acids or more in length. In some embodiments the peptide, polypeptide or protein is at least about 2, 4, 6, 8, 10, 15, 20, 25, 30, 40, 50, 100, 200 or 300 amino acids in length. In some embodiments the barcode has a net charge. In some embodiments the barcode has a net positive charge. In some embodiments the barcode has a net negative charge. When the barcode is a peptide barcode, a net positive charge in the barcode can be provided by including positively charged amino acid and / or amino acid analog residues in the barcode. For example, positively charged amino acids can include histidine, lysine, and / or arginine. When the barcode is a peptide barcode, a net negative charge in the barcode can be provided by including negatively charged amino acid and / or amino acid analog residues in the barcode. For example, negatively charged amino acids can include aspartate (aspartic acid) and / or glutamate (glutamic acid). For avoidance of doubt, a peptide barcode having a net negative charge may still comprise one or more positively charged amino acids and / or amino acid analog residues, providing the overall net charge of the barcode is negative. Similarly, a peptide barcode having a net positive charge may still comprise one or more negatively charged amino acids and / or amino acid analog residues, providing the overall net charge of the barcode is positive. In some embodiments the barcode is flanked by one or more lysine residues e.g. at the C- terminus of the barcode and / or at the N-terminus of the barcode. As described in more detail herein, incorporating lysines into the barcode allows the barcode to be cleaved from the peptide, polypeptide or protein using LysC or similar enzymes. In some embodiments the barcode is flanked by a lysine residue at the C-terminus of the barcode. In some embodiments the barcode comprises a lysine residue at the C-terminus of the barcode. In some embodiments a barcode sequence does not comprise a lysine residue other than at the C terminus of the barcode. In some embodiments the barcode is flanked by one or more arginine residues e.g. at the C- terminus of the barcode and / or at the N-terminus of the barcode. Incorporating arginines into the barcode allows the barcode to be cleaved from the peptide, polypeptide or protein using ArgC protease or similar enzymes. In some embodiments the barcode is flanked by an arginine residue at the N-terminus of the barcode. In some embodiments the barcode comprises an arginine residue at the N-terminus of the barcode. In some embodiments a barcode sequence does not comprise an arginine residue other than at the N terminus of the barcode. The design of suitable barcode sequences is within the skill of those in the art. Suitable sequences can be designed according to the application intended: this is an experimental parameter and is not limiting on the invention. However, it is observed that for some applications it can be beneficial to avoid certain residues in barcode designs in order to simplify the methods. For example, in some embodiments it can be useful that a barcode sequence does not comprise proline and / or cysteine. In some embodiments, different barcodes have different sequences each comprising a portion having a common sequence and a portion having a variable sequence. For example, in some embodiments different barcodes each comprise a common backbone structure or sequence, and a variable portion of the structure or sequence. For example, in some embodiments different barcodes may each comprise a plurality of common amino acid residues, such as a plurality of aspartate and / or glutamate residues. In some embodiments the barcode comprises at least two negatively charged amino acids. In some embodiments the barcode comprises at least three negatively charged amino acids. In some embodiments the barcode comprises a region comprising at least three consecutive negatively charged amino acids. For example, in some embodiments different barcodes may each comprise a moiety of form Xm, wherein each X is independently aspartate or glutamate, and m is an integer from about 1 to about 10. Different barcodes may comprise a different moiety B, wherein group B in each different barcode is different. For example, a set of different barcodes may comprise a sequence of form: ZpB(X)m, wherein in each barcode Z is the same; wherein Z may be the same or different to X; p is zero or is an integer of from about 1 to about 10, and wherein in each barcode B is different; and wherein in each barcode X is independently aspartate or glutamate. For example, three exemplary barcode sequences could comprise sequences such as: DYDDDK (SEQ ID NO: 19) DMDDDK (SEQ ID NO: 20) DVDDDK (SEQ ID NO: 21) further exemplary barcode sequences could comprise sequences such as DDDDDK (SEQ ID NO: 22) SDDDDK (SEQ ID NO: 23) NDDDDK (SEQ ID NO: 24) A barcode may comprise or consist of one of the following exemplary barcode sequences: DDYDDK (SEQ ID NO: 25) LDDDDK (SEQ ID NO: 26) DFDDDK (SEQ ID NO: 27) DDLDDK (SEQ ID NO: 28) DDLDDK (SEQ ID NO: 29) DFDDDK (SEQ ID NO: 30) QDDDDK (SEQ ID NO: 31) IDDDDK (SEQ ID NO: 32) DLDDDK (SEQ ID NO: 33) DNDDDK (SEQ ID NO: 34) ADDDDK (SEQ ID NO: 35) YDDDDK (SEQ ID NO: 36) DIDDDK (SEQ ID NO: 37) DGDDDK (SEQ ID NO: 38) MDDDDK (SEQ ID NO: 39) DDDDDK (SEQ ID NO: 40) DVDDDK (SEQ ID NO: 41) FDDDDK (SEQ ID NO: 42) DDDDDK (SEQ ID NO: 43) EDDDDK (SEQ ID NO: 44) DQDDDK (SEQ ID NO: 45) DSDDDK (SEQ ID NO: 46) FDDDDK (SEQ ID NO: 47) MDDDDK (SEQ ID NO: 48) SDDDDK (SEQ ID NO: 49) HDDDDK (SEQ ID NO: 50) DHDDDK (SEQ ID NO: 51) NDDDDK (SEQ ID NO: 52) GDDDDK (SEQ ID NO: 53) YDDDDK (SEQ ID NO: 54) DLDDDK (SEQ ID NO: 55) HDDDDK (SEQ ID NO: 56) DHDDDK (SEQ ID NO: 57) NDDDDK (SEQ ID NO: 58) ADDDDK (SEQ ID NO: 59) DEDDDK (SEQ ID NO: 60) DTDDDK (SEQ ID NO: 61) SDDDDK (SEQ ID NO: 62) EEYEEK (SEQ ID NO: 63) LEEEEK (SEQ ID NO: 64) EFEEEK (SEQ ID NO: 65) EELEEK (SEQ ID NO: 66) EELEEK (SEQ ID NO: 67) EFEEEK (SEQ ID NO: 68) QEEEEK (SEQ ID NO: 69) IEEEEK (SEQ ID NO: 70) ELEEEK (SEQ ID NO: 71) ENEEEK (SEQ ID NO: 72) AEEEEK (SEQ ID NO: 73) YEEEEK (SEQ ID NO: 74) EIEEEK (SEQ ID NO: 75) EGEEEK (SEQ ID NO: 76) MEEEEK (SEQ ID NO: 77) EEEEEK (SEQ ID NO: 78) EVEEEK (SEQ ID NO: 79) FEEEEK (SEQ ID NO: 80) EEEEEK (SEQ ID NO: 81) DEEEEK (SEQ ID NO: 82) EQEEEK (SEQ ID NO: 83) ESEEEK (SEQ ID NO: 84) FEEEEK (SEQ ID NO: 85) MEEEEK (SEQ ID NO: 86) SEEEEK (SEQ ID NO: 87) HEEEEK (SEQ ID NO: 88) EHEEEK (SEQ ID NO: 89) NEEEEK (SEQ ID NO: 90) GEEEEK (SEQ ID NO: 91) YEEEEK (SEQ ID NO: 92) ELEEEK (SEQ ID NO: 93) HEEEEK (SEQ ID NO: 94) EHEEEK (SEQ ID NO: 95) NEEEEK (SEQ ID NO: 96) AEEEEK (SEQ ID NO: 97) EDEEEK (SEQ ID NO: 98) ETEEEK (SEQ ID NO: 99) SEEEEK (SEQ ID NO: 100) DDDDDDK (SEQ ID NO: 101) DDDDDDDK (SEQ ID NO: 102) DDDDDDDDK (SEQ ID NO: 103) DDDDDDDDDK (SEQ ID NO: 104) DDDDDDDDDDK (SEQ ID NO: 105) DDDDDDDDDDDK (SEQ ID NO: 106) DYDDDDK (SEQ ID NO: 107) DDYDDDDK (SEQ ID NO: 108) DDDYDDDDK (SEQ ID NO: 109) DDDDYDDDDK (SEQ ID NO: 110) DDDDDYDDDDK (SEQ ID NO: 111) DDDDDDYDDDDK (SEQ ID NO: 112) QQEEEPQVDVWELLK (SEQ ID NO: 113) YWTEPEEFRPERFSK (SEQ ID NO: 114) RFSHSGSYSSHISSK (SEQ ID NO: 115) SSVPASDDAYPEIEK (SEQ ID NO: 116) TSLEDATLQIEELWK (SEQ ID NO: 117) CDDDDK (SEQ ID NO: 118) DDDDDC (SEQ ID NO: 119) DDDDDR (SEQ ID NO: 120) DDDDDE (SEQ ID NO: 121) EDDDDD (SEQ ID NO: 122) In one embodiment, a barcode comprises a sequence selected from SEQ ID NOs: 25 to 30. In one embodiment, a barcode comprises a sequence selected from SEQ ID NOs: 31 to 36. In one embodiment, a barcode comprises a sequence selected from SEQ ID NOs: 37 to 42. In one embodiment, a barcode comprises a sequence selected from SEQ ID NOs: 43 to 52. In one embodiment, a barcode comprises a sequence selected from SEQ ID NOs: 53 to 62. In one embodiment, a barcode comprises a sequence selected from SEQ ID NOs: 63 to 68. In one embodiment, a barcode comprises a sequence selected from SEQ ID NOs: 69 to 74. In one embodiment, a barcode comprises a sequence selected from SEQ ID NOs: 75 to 80. In one embodiment, a barcode comprises a sequence selected from SEQ ID NOs: 81 to 90. In one embodiment, a barcode comprises a sequence selected from SEQ ID NOs: 91 to 100. In some embodiments a barcode comprises a sequence as set out herein, flanked by an N- terminal arginine residue. Producing the construct As explained above, the methods involve taking measurements characteristic of a barcode wherein the barcode is present in or has been cleaved from a construct of the barcode and a peptide, polypeptide or protein to be characterised. In some embodiments the construct is produced in the disclosed methods. In some embodiments the construct is produced separately and is used in the disclosed methods. However it is produced, the construct comprises the peptide, polypeptide or protein attached to a barcode. The barcode may be attached to the peptide, polypeptide or protein in any suitable manner. In some embodiments the disclosed methods comprise producing a construct comprising a peptide, polypeptide or protein attached to a barcode. In some embodiments, as described in more detail, the barcode is cleaved from the peptide, polypeptide or protein in the construct. In some embodiments, therefore, the method (e.g. step (a) of the method) comprises: (a1) producing a construct comprising a peptide, polypeptide or protein attached to a barcode; and (a2) contacting the construct with one or more process conditions capable of cleaving the peptide, polypeptide or protein from the barcode. In some embodiments, step (a1) comprises expressing the peptide, polypeptide or protein under conditions that the peptide, polypeptide or protein is expressed with an attached barcode. This is particularly suitable when the barcode is a peptide barcode as described herein. In such embodiments, any suitable expression methods can be used. Expression methods are known to those skilled in the art and many suitable methods are described in more detail in texts such as Sambrook, Molecular Cloning: A Laboratory Manual, 4thed., Cold Spring Harbor Press, Plainsview, New York (2012); and Ausubel et al., Current Protocols in Molecular Biology (Supplement 114), John Wiley & Sons, New York (2016). In some embodiments, for example, the expression is expression in a bacterial cell, a yeast cell, an insect cell or a mammalian cell. In some embodiments the expression is expression in a bacterial cell such as Escherichia coli. In some embodiments the expression is a cell free expression method. In some embodiments the cell free expression is conducted using a translation system selected from rabbit reticulocyte lysate, wheat germ extract, and E. coli cell-free systems. Such systems are available commercially, such as from Thermo Fisher Scientific. In some embodiments the cell free expression method uses a reconstituted cell-free system. In some embodiments the cell free expression method comprises using a reconstituted system comprising purified cellular translation components. In some embodiments the purified components are derived from a bacterium such as E. coli. Such systems are available commercially, such as the PURExpress® systems available from New England Biolabs (Ipswich, MA, USA). In some embodiments the barcode is expressed from a genetic construct comprising a polynucleotide sequence encoding the peptide, polypeptide or protein and a polynucleotide sequence encoding the barcode. Any suitable genetic construct can be used. For example, in some embodiments a genetic construct comprises a polynucleotide sequence encoding the peptide, polypeptide or protein in frame with the barcode. In some embodiments the genetic construct is comprised in the genomic DNA of an organism, such as an organism that has been genetically modified in order to incorporate such a polynucleotide sequence in its genomic DNA. In some embodiments the genetic construct is comprised in, or comprises, an expression vector. In some embodiments the genetic construct is comprised in, or comprises, an expression plasmid. In some embodiments the plasmid comprises a promoter with in-frame DNA encoding the peptide, polypeptide or protein to be characterised and a barcode at the N- and / or C-terminus of the peptide, polypeptide or protein. In some embodiments the plasmid further comprises elements for maintenance and replication in the host, such as an origin of replication and an antibiotic resistance cassette. In some embodiments the peptide, polypeptide or protein is generated or obtained and the barcode is subsequently attached to the peptide, polypeptide or protein. Thus, in some embodiments step (a1) comprises attaching a barcode to the peptide, polypeptide or protein. In some embodiments the barcode is attached to the peptide, polypeptide or protein by chemical methods. Any suitable methods of chemical attachment can be used. For example, in some embodiments the attachment is covalent. In some embodiments the attachment is non-covalent. In some embodiments the attachment comprises ligating the peptide, polypeptide or protein to the barcode. In some embodiments the peptide, polypeptide or protein comprises a barcode-reactive functional group. In some embodiments the barcode-reactive functional group is capable of binding to the barcode. In some embodiments the barcode comprises a peptide-reactive functional group. In some embodiments the peptide-reactive functional group is capable of binding to the peptide, polypeptide or protein. The barcode can be attached to the peptide, polypeptide or protein at any suitable position. Typically, the barcode is attached to the peptide, polypeptide or protein at the N- terminus or the C-terminus of the peptide, polypeptide or protein. The barcode can be attached to the peptide, polypeptide or protein via a side chain group of a residue (e.g. an amino acid residue) in the peptide, polypeptide or protein. Typically the barcode is attached to the peptide, polypeptide or protein at the N- terminus or the C-terminus of the peptide, polypeptide or protein. In some embodiments the barcode is attached to the peptide, polypeptide or protein at the N-terminus of the peptide, polypeptide or protein. In some embodiments the barcode is attached to the peptide, polypeptide or protein at the C-terminus of the peptide, polypeptide or protein. In some embodiments the C-terminus of the barcode is attached to the N-terminus of the peptide, polypeptide or protein. In some embodiments the N-terminus of the barcode is attached to the C-terminus of the peptide, polypeptide or protein. However, the reverse may be used also in the methods disclosed herein, such that in some embodiments the N- terminus of the barcode is attached to the N-terminus of the peptide, polypeptide or protein or the C-terminus of the barcode is attached to the C-terminus of the peptide, polypeptide or protein. As will be apparent from the discussion herein, the attachment between the barcode and the peptide, polypeptide or protein is not especially limited and any suitable attachment means can be used. In some embodiments the attachment means is chosen according to whether or not the barcode is to be cleaved from the construct in the disclosed methods. In some embodiments the attachment means is chosen or designed to be amenable to cleavage under the conditions of the method. In some embodiments the attachment means is designed or chosen to resist cleavage. In some embodiments the peptide, polypeptide or protein is modified in order to facilitate its conjugation to the barcode. For example, in some embodiments the peptide, polypeptide or protein is modified by attaching a moiety comprising a reactive functional group for attaching to the barcode. For example, in some embodiments the peptide, polypeptide or protein can be extended at the N-terminus or the C-terminus by one or more residues (e.g. amino acid residues) comprising one or more reactive functional groups for reacting with a corresponding reactive functional group on the barcode. For example, in some embodiments the polypeptide can be extended at the N-terminus and / or the C- terminus by one or more cysteine residues. Such residues can be used for attachment to the barcode, e.g. by maleimide chemistry (e.g. by reaction of cysteine with an azido- maleimide compound such as azido-[Pol]-maleimide wherein [Pol] is typically a short chain polymer such as PEG, e.g. PEG2, PEG3, or PEG4; followed by coupling to appropriately functionalised residue e.g. a residue carrying a BCN group for reaction with the azide). For avoidance of doubt, when the peptide, polypeptide or protein comprises an appropriate naturally occurring residue at the N- and / or C-terminus (e.g. a naturally occurring cysteine residue at the N- and / or C-terminus) then such residue(s) can be used for attachment to the barcode. In some embodiments a residue in the peptide, polypeptide or protein is modified to facilitate attachment of the polypeptide to the barcode. In some embodiments a residue (e.g. an amino acid residue) in the polypeptide is chemically modified for attachment to the barcode. In some embodiments a residue (e.g. an amino acid residue) in the peptide, polypeptide or protein is enzymatically modified for attachment to the barcode. The conjugation chemistry between the barcode and the peptide, polypeptide or protein is not particularly limited. Any suitable combination of reactive functional groups can be used. Many suitable reactive groups and their chemical targets are known in the art. For example, a peptide, polypeptide or protein may be modified using chemical methods such as the use of 2-PCA derivatives, oxazolone chemistry, photoreductive decarboxylation chemistry and side-chain specific chemistry such as NHS-esters, maleimides, iodoacetamides, fluoroacetamides, chloroacetamides, and others. Further exemplary reactive groups and their corresponding targets include aryl azides which may react with amine, carbodiimides which may react with amines and carboxyl groups, hydrazides which may react with carbohydrates, hydroxmethyl phosphines which may react with amines, imidoesters which may react with amines, isocyanates which may react with hydroxyl groups, carbonyls which may react with hydrazines, maleimides which may react with sulfhydryl groups, NHS-esters which may react with amines, PFP-esters which may react with amines, psoralens which may react with thymine, pyridyl disulfides which may react with sulfhydryl groups, vinyl sulfones which may react with sulfhydryl amines and hydroxyl groups, vinylsulfonamides, and the like. Other suitable chemistry for conjugating the peptide, polypeptide or protein to the barcode includes click chemistry. Many suitable click chemistry reagents are known in the art. Suitable examples of click chemistry include, but are not limited to, the following: (a) copper(I)-catalyzed azide-alkyne cycloadditions (azide alkyne Huisgen cycloadditions); (b) strain-promoted azide-alkyne cycloadditions; including alkene and azide [3+2] cycloadditions; alkene and tetrazine inverse-demand Diels-Alder reactions; and alkene and tetrazole photoclick reactions; (c) copper-free variant of the 1,3 dipolar cycloaddition reaction, where an azide reacts with an alkyne under strain, for example in a cyclooctane ring such as in bicycle[6.1.0]nonyne (BCN); (d) the reaction of an oxygen nucleophile on one linker with an epoxide or aziridine reactive moiety on the other; and (e) the Staudinger ligation, where the alkyne moiety can be replaced by an aryl phosphine, resulting in a specific reaction with the azide to give an amide bond. Any reactive group may be used in the ligation step. Some suitable reactive groups include [1, 4-Bis[3-(2-pyridyldithio)propionamido]butane; 1,11-bis- maleimidotriethyleneglycol; 3,3’-dithiodipropionic acid di(N-hydroxysuccinimide ester); ethylene glycol-bis(succinic acid N-hydroxysuccinimide ester); 4,4’- diisothiocyanatostilbene-2,2’-disulfonic acid disodium salt; Bis[2-(4- azidosalicylamido)ethyl] disulphide; 3-(2-pyridyldithio)propionic acid N- hydroxysuccinimide ester; 4-maleimidobutyric acid N-hydroxysuccinimide ester; Iodoacetic acid N-hydroxysuccinimide ester; S-acetylthioglycolic acid N- hydroxysuccinimide ester; azide-PEG-maleimide; and alkyne-PEG-maleimide. The reactive group may be any of those disclosed in WO 2010 / 086602, particularly in Table 3 of that application. In some embodiments the barcode is attached to the peptide, polypeptide or protein by enzymatic ligation. Most often, however, the barcode is attached to the peptide, polypeptide or protein by expressing the peptide, polypeptide or protein in the form of a construct comprising the peptide, polypeptide or protein attached or linked to the peptide, polypeptide or protein. This is described in more detail herein. In general, however, the peptide, polypeptide or protein may be directly attached to the barcode, or may be attached to the barcode via a linker group. Any suitable linker group can be used and some suitable linkers are described herein. Barcode tags In some embodiments the barcode is comprised in a barcode tag. As used herein, a barcode tag is a construct comprising the barcode and a purification tag. In some embodiments the barcode is attached directly to the purification tag. In some embodiments the barcode is attached to the purification tag via a linker. In some embodiments the barcode is attached to the purification tag and a cleavage site is comprised between the barcode and the purification tag. In some embodiments the cleavage site comprises a cleavable linker. Any suitable cleavable linker can be used in the disclosed methods. For example, the linker may comprise a short chain oligopeptide containing e.g. from about 1 to about 20 amino acids. The linker may comprise one or more serine-glycine motifs such as SG, SSG, SSGSG, etc. The linker may comprise a polymer such as a polyethylene glycol or a saccharide containing from about 1 to about 20 repeat units. For example, the linker may comprise PEG2, PEG3 or PEG 4. Any suitable purification tag can be used. For example, the purification tag may comprise or consist of biotin. Biotin is particularly suitable for use in the disclosed methods as it forms a strong non-covalent attachment with streptavidin and related proteins (neutravidin, avidin, etc). More often, the purification tag is a peptide purification tags suitable for IMAC (immobilised metal affinity chromatography) chemistry. For example, the purification tag may comprise a poly-His tag (e.g. HHHH (SEQ ID NO: 123), HHHHHH (SEQ ID NO: 124) or HHHHHHHH (SEQ ID NO: 125)). Such tags are suitable for binding to a purification support comprising a metal such as nickel or cobalt. Still other purification tags include peptide tags such as Strep (WSHPQFEK; SEQ ID NO: 126), FLAG (DYKDDDDK; SEQ ID NO: 127), Human influenza hemagglutinin (HA) (YPYDVPDYA; SEQ ID NO: 128), Myc (EQKLISEED; SEQ ID NO: 129), and V5 (GKPIPNPLLGLDST; SEQ ID NO: 130), etc. Other suitable purification tags include: Biotin-carboxy carrier protein (BCCP); Calmodulin binding peptide (CBP); Chitin binding domain (CBD); Histidine affinity tag (HAT); Polyarginine (Arg-tag); Polyaspartate (Asp-tag); Polylysine (Lys-tag); Polyphenylalanine (Phe-tag); Streptavadin-binding peptide (SBP); Tetrazine tag; TCO tag; Azide tag; and DBCO / Alkyne tag. In some embodiments the method comprises purifying the construct using the purification tag. In some embodiments step (a) of the method comprises purifying the construct using the purification tag. When the disclosed methods comprise purifying the construct and / or the barcode the method may comprise contacting the purification tag with a support for purification. Any suitable support can be used. In some embodiments the support comprises a chromatography matrix, such as an agarose or sepharose resin. Such resins are commercially available from suppliers such as Sigma Aldrich. In some embodiments the support comprises beads (i.e. one or more beads). Magnetic beads are often used as such beads allow for facile purification e.g. using washing with buffer. Functionalised magnetic beads are commercially available with a variety of functionalisations from suppliers such as Sigma Aldrich and Bio-Rad. In some embodiments the support comprises a solid surface. Any suitable material can be used. Suitable materials include glass, silica, polymers such as polyester, and ceramics such as hydroxyapatite. In some embodiments the support is functionalised for binding to the purification tag. Those skilled in the art will appreciate that the support can be functionalised depending on the purification tag that is used. Alternatively, the purification tag can be chosen depending on the support material to be used. Thus, the choice of purification tag and support material is an operational parameter which can be determined by the user of the disclosed methods. In some embodiments the support comprises streptavidin, neutravidin or avidin, or a derivative of streptavidin, neutravidin or avidin such as traptavidin. Such supports are particularly useful the purification tag comprises biotin. In some embodiments the support comprises a metal such as nickel or cobalt. The metal ion may be provided with a suitable chelator such as nitriloacetic acid (NTA) or iminodiacetic acid (IDA) For example, the support may comprise Ni-NTA. Such supports are particularly useful when the purification tag comprises a His tag. In some embodiments the support comprises streptactin. Such supports are particularly useful when the purification tag comprises a Strep tag. In some embodiments the support comprises an antibody for a sequence such as FLAG, HA, Myc or V5 as discussed above. In some embodiments the barcode tag comprises a cleavage site between the barcode and the purification tag. In some embodiments the barcode is separated from the purification tag by the cleavage site. In some embodiments the barcode is directly attached to the cleavage site and the purification tag is directly attached to the cleavage site. In some embodiments the barcode is directly attached to the cleavage site and the purification tag is attached to the cleavage site via a linker. In some embodiments the purification tag is at the N-terminus of the barcode. In some embodiments the purification tag is at the C-terminus of the barcode. In some embodiments the C-terminus of the barcode is attached to the N-terminus of the peptide, polypeptide or protein, and the N-terminus of the barcode is attached to the purification tag. In some embodiments the C-terminus of the barcode is attached to the N- terminus of the peptide, polypeptide or protein, and the N-terminus of the barcode is attached via a cleavage site and an optional linker to the purification tag. In some embodiments the purification tag is a peptide tag and the C-terminus of the barcode is attached to the N-terminus of the peptide, polypeptide or protein, and the N-terminus of the barcode is attached via a cleavage site and an optional linker to the C-terminus of the purification tag. In some embodiments the N-terminus of the barcode is attached to the C-terminus of the peptide, polypeptide or protein, and the C-terminus of the barcode is attached to the purification tag. In some embodiments the N-terminus of the barcode is attached to the C- terminus of the peptide, polypeptide or protein, and the C-terminus of the barcode is attached via a cleavage site and an optional linker to the purification tag. In some embodiments the purification tag is a peptide tag and the N-terminus of the barcode is attached to the C-terminus of the peptide, polypeptide or protein, and the C-terminus of the barcode is attached via a cleavage site and an optional linker to the N-terminus of the purification tag. In some embodiments the construct comprises a first cleavage site at the N- terminal of the barcode and a second cleavage site at the C-terminal of the barcode. In some embodiments therefore the C-terminus of the barcode is attached to the N-terminus of the peptide, polypeptide or protein via a cleavage site and an optional linker to the peptide, polypeptide or protein; and the N-terminus of the barcode is attached to the purification tag via a cleavage site and an optional linker to the purification tag. In some embodiments the N-terminus of the barcode is attached to the C-terminus of the peptide, polypeptide or protein via a cleavage site and an optional linker to the peptide, polypeptide or protein; and the C-terminus of the barcode is attached to the purification tag via a cleavage site and an optional linker to the purification tag. In some embodiments the construct comprises first and second cleavage sites and the cleavage sites are the same or different. In some embodiments the cleavage sites are configured (designed or chosen) to be cleaved by different cleavage conditions. In some embodiments the cleavage sites are different but are configured (designed or chosen) to be cleaved by the same cleavage conditions. In some embodiments the cleavage sites are the same. When the first and second cleavage sites are the same, the first and second cleavage sites are typically cleaved by the same cleavage conditions. Thus, in such embodiments, exposing the construct to the cleavage conditions typically cleaves both the first and second cleavage sites. Any suitable cleavage sites can be used according to the process conditions used in the methods. Alternatively, the process conditions can be chosen or designed according to the cleavage sites used. As will be apparent, the disclosed methods comprise contacting the construct comprising the peptide, polypeptide or protein attached to a barcode with one or more process conditions capable of cleaving the peptide, polypeptide or protein from the attached barcode, thereby cleaving the peptide, polypeptide or protein from the barcode. The term contacting is used herein in its broadest sense to refer to subjecting the construct to the conditions. For example, when the conditions comprise an enzyme such as a protease, contacting the peptide, polypeptide or protein with the process conditions comprises contacting the peptide, polypeptide or protein with the enzyme (e.g. the protease) under conditions that the enzyme is catalytically competent to act on the peptide, polypeptide or protein (e.g. when the enzyme is a protease, to enzymatically cleave the peptide, polypeptide or protein at a suitable recognition site). Any suitable process conditions can be used. In some embodiments the construct is cleaved by chemical or enzymatic digestion. In some embodiments, therefore, the one or more process conditions comprise the presence of a suitable chemical or enzymatic reagent. Suitable reagents are described in more detail herein. In some embodiments the construct comprises a cleavage site comprising a cleavable moiety which may be e.g. a pH sensitive group; a redox sensitive group; a light- sensitive group; a temperature sensitive group or a chemical-sensitive group which is sensitive to cleavage by reaction of the group with a specific chemical. In some embodiments, the cleavage site is capable of being cleaved photolytically, enzymatically, or by contacting the cleavage site with one or more chemical reagents. In some embodiments the cleavage site is a protease cleavage site. In some embodiments the cleavage site comprises a cleavable moiety cleavable by exposure to light; i.e. it is photocleavable. In some embodiments the cleavable site is cleaved by exposing the construct to light; typically UV light. Photocleavable moieties include (optionally substituted) nitrobenzyl moieties. Such groups are cleavable under UV irradiation. Accordingly, in some embodiments the one or more process conditions comprise photo-irradiation (e.g. UV irradiation). In some embodiments the cleavage site comprises a cleavable moiety cleavable by exposure to a change in pH. Thus, in some embodiments the cleavable site is cleaved by exposing the construct to a change in pH. pH-sensitive cleavable linkers include hydrazones and cis-aconityl. Accordingly, in some embodiments the one or more process conditions comprise a pH. In some embodiments the one or more process conditions comprise an acidic pH (e.g. from about pH 2 to about pH 6). In some embodiments the one or more process conditions comprise a basic pH (e.g. from about pH 8 to about pH 11). In some embodiments the cleavage site comprises a cleavable moiety cleavable by exposure to a chemical reagent. Thus, in some embodiments the cleavable site is cleaved by exposing the construct to a chemical reagent; such as a reducing reagent. Chemical- sensitive cleavable linkers include disulphides. Disulphide bonds are susceptible to cleavage by addition of a reducing agent such as DTT and beta-mercaptoethanol. Accordingly, in some embodiments the one or more process conditions comprise a reducing reagent. In some embodiments the cleavage site comprises a cleavable linker cleavable by exposure to an enzyme such as a protease or nuclease. Thus, in some embodiments the cleavable site is cleaved by exposing the construct to an enzyme; typically a protease. In some embodiments wherein the construct comprises first and / or second cleavage sites, the first and / or second cleavage sites thus comprise a protease recognition site. Accordingly, in some embodiments the one or more process conditions comprise a protease. When a cleavage site comprises a protease recognition site, any suitable protease can be used. Enzyme-sensitive cleavable moieties include protease-sensitive peptides comprising recognition sequences for one or more endo- and / or exo-proteases. Examples include the sequences DDDDK (SEQ ID NO: 131; cleaved by enteropeptidase from E. coli and S. cerevisiae); LVPRGS (SEQ ID NO: 132; cleaved by thrombin and factor Xa); ENLYFQ (SEQ ID NO: 133; cleaved by TEV protease when Q is followed by S, G, A, M, C, or H) and LEVLFQGP (SEQ ID NO: 134; cleaved by Rhinovirus 3C protease). Β- glucuronide linkers can be cleaved by lysosomal β-glucuronidase. In some embodiments the or each cleavage site comprises a recognition motif for the protease LysC or a functional analog, fragment or variant thereof. LysC is a serine protease that hydrolyzes specifically at the carboxyl side of lysines. Lys-C typically retains proteolytic activity under strong protein denaturing conditions such as 8M urea, which can be used to improve digestion of proteolytically resistant proteins. Lys-C typically has optimal activity in the range of pH 7.0—9.0. Accordingly, in some embodiments the process conditions capable of cleaving the peptide, polypeptide or protein from the attached barcode and / or capable of cleaving the barcode from a purification tag comprises a pH of from about 6 to about 10, e.g. from 7 to about 9; and / or denaturing conditions such as the presence of urea. LysC is available from e.g. Promega and New England Biolabs. Accordingly, in some embodiments the first and / or second cleavage sites comprise a lysine residue and contacting the construct with the one or more process conditions capable of cleaving the peptide, polypeptide or protein from the barcode comprises contacting the construct with LysC or functional analog, fragment or variant thereof. In some embodiments the first and / or second cleavage site comprises a recognition sequence for an endo- and / or exo-protease, such as a recognition sequence described herein. For example, in some embodiments the first and / or second cleavage site comprises a recognition sequence for a protease such as TEV. In some embodiments a first cleavage site comprises a recognition sequence for an endo- and / or exo-protease, such as a recognition sequence described herein, such as a recognition sequence for a protease such as TEV; and a second cleavage site comprises a lysine residue such that the first cleavage site can be cleaved by contacting the construct with a protease specific for the recognition sequence; and the second cleavage site can be cleaved by contacting the construct with LysC or a functional analog, fragment or variant thereof. In some embodiments, therefore, each construct comprises a structure of the form: Nterm – P – Z1 – B – Z2 – W – Cterm, Nterm – W – Z2– B – Z1– P – Cterm, Nterm – P – Z1 – W – Z2 – B – Cterm, or Nterm – B – Z2 – W – Z1 – P – Cterm; wherein Nterm represents the N terminus of the construct; Cterm represents the C terminus of the construct; P represents the peptide, polypeptide or protein being characterised; B represents the barcode; W represents an amino acid sequence comprising a purification tag; optionally wherein W comprises a polyhistidine sequence; Z1represents a first protease cleavage site; optionally wherein Z1comprises a lysine residue; and Z2 represents a second protease cleavage site; optionally wherein Z2 comprises a lysine residue. In some embodiments Z1and / or Z2may comprise a recognition sequence for an endo- and / or exo-protease, such as a recognition sequence described herein, e.g. a recognition sequence for a protease such as TEV. In some embodiments one of Z1 and Z2 comprises a recognition sequence for an endo- and / or exo-protease, such as a recognition sequence described herein, e.g. a recognition sequence for a protease such as TEV; and the other of Z1 and Z2 comprises a lysine residue. In some embodiments Z1 comprises a recognition sequence for an endo- and / or exo-protease, such as a recognition sequence described herein, e.g. a recognition sequence for a protease such as TEV; and Z2 comprises a lysine residue. In some embodiments, each construct comprises a structure of the form: Nterm – P – Z1– W – AA1 – B – Z2– Cterm; or Nterm – AA1 – B – Z2 – W – Z1 – P – Cterm wherein Nterm represents the N terminus of the construct; Cterm represents the C terminus of the construct; P represents the peptide, polypeptide or protein being characterised; Z1 represents a first protease cleavage site; optionally wherein Z1 comprises a TEV protease cleavage site; W represents an amino acid sequence comprising a purification tag; optionally wherein W comprises a polyhistidine sequence; B represents the barcode; and AA1 represents an amino acid recognised by a protease; optionally wherein AA1 represents arginine or lysine; further optionally wherein AA1 represents arginine; optionally wherein AA1 represents arginine or lysine (e.g. arginine) at the N- terminus of the barcode (B); Z2 represents a second protease cleavage site; optionally wherein Z2 comprises a lysine residue; further optionally wherein Z2 corresponds to a lysine residue at the C-terminus of the barcode (B). In some embodiments one or more features of the constructs described above are attached together via one or more linkers e.g. one or more linkers as described herein. For example, in some embodiments Z1 is comprised in a linker as described herein. In some embodiments Z1 is attached to P and / or W via linkers as described herein. In some embodiments Z1 is attached to P and / or W via one or more serine-glycine motifs such as SG, SSG, SSGSG, etc. In some embodiments, each construct comprises a structure of the form: Nterm – P – Z1 – W – AA1 – B – Z2 – Cterm; or wherein Nterm represents the N terminus of the construct; Cterm represents the C terminus of the construct; P represents the peptide, polypeptide or protein being characterised; Z1represents a first protease cleavage site; optionally wherein Z1comprises a TEV protease cleavage site; and wherein Z1 is attached to P and W via one ore more linkers; optionally via one or more serine-glycine motifs; W represents an amino acid sequence comprising a purification tag; optionally wherein W comprises a polyhistidine sequence; B represents the barcode; and AA1 is an arginine residue at the N-terminus of the barcode (B); and Z2represents a lysine residue at the C-terminus of the barcode (B). The construct can be generated as described in more detail herein. The construct once generated (e.g. by expression) can be purified as described herein using the purification tag comprised in moiety W. When the construct is contacted with a process condition such as the presence of one or more proteases such as LysC, the construct is cleaved at sites Z1 and Z2. The construct is thus broken down into components including the barcode free of moieties P and / or W. Measurements of the barcode B can be taken as described in more detail here, e.g. by attaching B to one or more sequencing adapters and contacting the resulting construct with a nanopore under conditions such that the barcode moves with respect to the nanopore. In some embodiments the barcode is a barcode as described in more detail herein. In some embodiments the peptide, polypeptide or protein is a peptide, polypeptide or protein as described in more detail herein. In some embodiments the purification tag is as described in more detail herein. As those skilled in the art will appreciate, in some embodiments further sequence features may be present in each construct. In some embodiments additional amino acids may be present at the N- and / or C- terminus of the purification tag. Characterisation As discussed in more detail herein, the disclosed methods comprise contacting the barcode with a nanopore under conditions such that the barcode moves with respect to the nanopore. One or more measurements as described herein are taken during such movements in order to determine one or more properties of the barcode. In some embodiments, the method comprises attaching the barcode to one or more sequencing adapters. Sequencing adapters may be used for example to facilitate the movement of the barcode with respect to the nanopore. Accordingly, in some embodiments, step (b) of the disclosed methods comprises attaching the barcode to one or more sequencing adapters. In some embodiments one or more sequencing adapters can be attached directly or indirectly to one or more reactive groups at the N- and / or C- terminus of the barcode. In some embodiments such reactive groups can be generated by cleaving the peptide, polypeptide or protein from the barcode. Accordingly, in some embodiments, cleaving the peptide, polypeptide or protein from the barcode generates one or more reactive functional groups at the N- and / or C- terminus of the barcode; and step (b) comprises attaching one or more sequencing adapters to said one or more reactive functional groups. For example, cleaving a construct as described herein using LysC may generate a reactive lysine group for reaction with reaction in order to attach a sequencing adapter to the barcode. In some embodiments step (b) comprises attaching one or more peptide handles to the one or more reactive functional groups, wherein each peptide handle comprises a reactive functional group for attaching to a sequencing adapter; and attaching a sequencing adapter to each peptide handle. In some embodiments a peptide handle can be considered as a reactive linker to facilitate attachment of a sequencing adapter to the barcode. Suitable sequencing adapters for use in the disclosed methods are described in more detail herein. Sample In some embodiments, the peptide, polypeptide or protein to be characterised in the disclosed methods is present in a sample. In some embodiments the sample comprises a plurality of different peptides, polypeptides and / or proteins. In some embodiments of the disclosed method, therefore, the peptide, polypeptide or protein is present in a sample comprising a plurality of different peptides, polypeptides and / or proteins, and the method comprises a) contacting a plurality of constructs each comprising a peptide, polypeptide or protein attached to a barcode with one or more process conditions capable of cleaving the peptide, polypeptide or proteins from the attached barcodes, thereby cleaving the peptide, polypeptide or protein from the barcodes, wherein in said constructs different peptide, polypeptide and / or protein sequences have different barcodes attached thereto; b) contacting the cleaved barcodes with one or more nanopores under conditions such that the barcodes moves with respect to the nanopore(s); and c) taking one or more measurements characteristic of each barcode as the barcodes move with respect to the nanopore(s), thereby determining one or more properties of each barcode; wherein said one or more properties of each barcode are characteristic of one or more characteristics of the peptide, polypeptide or protein to which the barcode was attached in the construct. In some embodiments the plurality may comprise at least 2, at least 3, at least 4, at least 5, at least 10, at least 20, at least 50, at least 100, at least 500, at least 1000, at least 5000, at least 10000, at least 100000, at least 1000000 or more peptides, polypeptides and proteins, each attached to a barcode thereby forming a construct as described herein. The constructs in the sample may be the same or different. In some embodiments the sample comprises a plurality of types of construct and each type of construct comprises a plurality of identical constructs. In some embodiments the library comprises at least 2, at least 3, at least 4, at least 5, at least 10, at least 20, at least 50, at least 100, at least 500, or at least 1000 types of construct and each type of construct comprises at least 2, at least 3, at least 4, at least 5, at least 10, at least 20, at least 50, at least 100, at least 500, at least 1000, at least 5000, at least 10000, at least 100000, at least 1000000 or more identical constructs. Polypeptide As explained above, the disclosed methods comprise characterising a target peptide, polypeptide or protein. Any suitable peptide, polypeptide or protein can be characterised in the disclosed methods. In some embodiments the peptide, polypeptide or protein is an unmodified protein or a portion thereof, or a naturally occurring polypeptide or a portion thereof. In some embodiments the peptide, polypeptide or protein is a modified protein or a portion thereof. In some embodiments the peptide, polypeptide or protein is secreted from cells. Alternatively, the target peptide, polypeptide or protein can be produced inside cells such that it must be extracted from cells for characterisation by the disclosed methods. The peptide, polypeptide or protein may comprise the products of cellular expression of a plasmid, e.g. a plasmid used in cloning of proteins in accordance with the methods described in Sambrook et al., Molecular Cloning: A Laboratory Manual, 4thed., Cold Spring Harbor Press, Plainsview, New York (2012); and Ausubel et al., Current Protocols in Molecular Biology (Supplement 114), John Wiley & Sons, New York (2016). The peptide, polypeptide or protein may be obtained from or extracted from any organism or microorganism. The peptide, polypeptide or protein may be obtained from a human or animal, e.g. from urine, lymph, saliva, mucus, seminal fluid or amniotic fluid, or from whole blood, plasma or serum. The peptide, polypeptide or protein may be obtained from a plant e.g. a cereal, legume, fruit or vegetable. The peptide, polypeptide or protein may be obtained from bacteria, protozoa, algae or fungi. The peptide, polypeptide or protein can be provided as an impure mixture of one or more polypeptides and one or more impurities. Impurities may comprise truncated forms of the peptide, polypeptide or protein which are distinct from the intended peptide, polypeptide or protein for characterisation in the disclosed methods. For example, the peptide, polypeptide or protein to be characterised may be a full length protein and impurities may comprise fractions of the protein. Impurities may also comprise proteins other than the peptide, polypeptide or protein e.g. which may be co-purified from a cell culture or obtained from a sample. A peptide, polypeptide or protein may comprise any combination of any amino acids, amino acid analogs and modified amino acids (i.e. amino acid derivatives). Amino acids (and derivatives, analogs etc) in the polypeptide can be distinguished by their physical size and charge. The amino acids / derivatives / analogs can be naturally occurring or artificial. In some embodiments the peptide, polypeptide or protein may comprise any naturally occurring amino acid. Twenty amino acids are encoded by the universal genetic code. These are alanine (A), arginine (R), asparagine (N), aspartic acid (D), cysteine (C), glutamic acid / glutamate (E), glutamine (Q), glycine (G), histidine (H), isoleucine (I), leucine (L), lysine (K), methionine (M), phenylalanine (F), proline (P), serine (S), threonine (T), tryptophan (W), tyrosine (Y) and valine (V). Other naturally occurring amino acids include selenocysteine and pyrrolysine. In some embodiments the peptide, polypeptide or protein is modified. In some embodiments the peptide, polypeptide or protein is modified for detection using the disclosed methods. In some embodiments the disclosed methods are for characterising modifications in the peptide, polypeptide or protein . In some embodiments one or more of the amino acids / derivatives / analogs in the peptide, polypeptide or protein is modified. In some embodiments one or more of the amino acids / derivatives / analogs in the peptide, polypeptide or protein is post- translationally modified. As such, the methods disclosed herein can be used to detect the presence, absence, number of positions of post-translational modifications in a peptide, polypeptide or protein. The disclosed methods can be used to characterise the extent to which a peptide, polypeptide or protein has been post-translationally modified. Any one or more post-translational modifications may be present in the peptide, polypeptide or protein. Typical post-translational modifications include modification with a hydrophobic group, modification with a cofactor, addition of a chemical group, glycation (the non-enzymatic attachment of a sugar), biotinylation and pegylation. Post-translational modifications can also be non-natural, such that they are chemical modifications done in the laboratory for biotechnological or biomedical purposes. This can allow monitoring the levels of the laboratory made peptide, polypeptide or protein in contrast to the natural counterparts. Examples of post-translational modification with a hydrophobic group include myristoylation, attachment of myristate, a C14saturated acid; palmitoylation, attachment of palmitate, a C16 saturated acid; isoprenylation or prenylation, the attachment of an isoprenoid group; farnesylation, the attachment of a farnesol group; geranylgeranylation, the attachment of a geranylgeraniol group; and glypiation, and glycosylphosphatidylinositol (GPI) anchor formation via an amide bond. Examples of post-translational modification with a cofactor include lipoylation, attachment of a lipoate (C8) functional group; flavination, attachment of a flavin moiety (e.g. flavin mononucleotide (FMN) or flavin adenine dinucleotide (FAD)); attachment of heme C, for instance via a thioether bond with cysteine; phosphopantetheinylation, the attachment of a 4'-phosphopantetheinyl group; and retinylidene Schiff base formation. Examples of post-translational modification by addition of a chemical group include acylation, e.g. O-acylation (esters), N-acylation (amides) or S-acylation (thioesters); acetylation, the attachment of an acetyl group for instance to the N-terminus or to lysine; formylation; alkylation, the addition of an alkyl group, such as methyl or ethyl; methylation, the addition of a methyl group for instance to lysine or arginine; amidation; butyrylation; gamma-carboxylation; glycosylation, the enzymatic attachment of a glycosyl group for instance to arginine, asparagine, cysteine, hydroxylysine, serine, threonine, tyrosine or tryptophan; polysialylation, the attachment of polysialic acid; malonylation; hydroxylation; iodination; bromination; citrulination; nucleotide addition, the attachment of any nucleotide such as any of those discussed above, ADP ribosylation; oxidation; phosphorylation, the attachment of a phosphate group for instance to serine, threonine or tyrosine (O-linked) or histidine (N-linked); adenylylation, the attachment of an adenylyl moiety for instance to tyrosine (O-linked) or to histidine or lysine (N-linked); propionylation; pyroglutamate formation; S-glutathionylation; Sumoylation; S- nitrosylation; succinylation, the attachment of a succinyl group for instance to lysine; selenoylation, the incorporation of selenium; and ubiquitinilation, the addition of ubiquitin subunits (N-linked). It is within the scope of the methods provided herein that the peptide, polypeptide or protein is labelled with a molecular label. A molecular label may be a modification to the peptide, polypeptide or protein which promotes the detection of the peptide, polypeptide or protein in the methods provided herein. For example the label may be a modification to the peptide, polypeptide or protein which alters the signal obtained as conjugate is characterised. For example, the label may interfere with a flux of ions through the nanopore. In such a manner, the label may improve the sensitivity of the methods. In some embodiments the peptide, polypeptide or protein contains one or more cross-linked sections, e.g. C-C bridges. In some embodiments the peptide, polypeptide or protein is not cross-linked prior to being characterised using the disclosed methods. In some embodiments the peptide, polypeptide or protein comprises sulphide- containing amino acids and thus has the potential to form disulphide bonds. Typically, in such embodiments, the polypeptide is reduced using a reagent such as DTT (Dithiothreitol) or TCEP (tris(2-carboxyethyl)phosphine) prior to being characterised using the disclosed methods. In some embodiments the peptide, polypeptide or protein is a full length protein or naturally occurring polypeptide. In some embodiments a protein or naturally occurring polypeptide is fragmented prior to attachment to the barcode. In some embodiments the protein or polypeptide is chemically or enzymatically fragmented. In some embodiments polypeptides or polypeptide fragments can be conjugated to form a longer target polypeptide. The peptide, polypeptide or protein can be a polypeptide of any suitable length. In some embodiments the polypeptide has a length of from about 2 to about 1000 peptide units. In some embodiments the polypeptide has a length of from about 10 to about 800 peptide units, for example from about 20 to about 500 peptide units, e.g. from about 30 to about 300 peptide units. In some embodiments the polypeptide has a length of from about 10 to about 500 peptide units, e.g. from about 20 to about 300 peptide units, e.g. from about 30 to about 200 peptide units such as from about 50 to about 100 peptide units. Any number of peptides, polypeptides or proteins can be characterised in the disclosed methods. For instance, the method may comprise characterising 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 50, 100, 200, 500, 1000, 2000 or more peptides, polypeptides or proteins; or about 10, about 50, about 100, about 200, about 500, about 1000, or about 2000 peptides, polypeptides or proteins. If two or more polypeptides are used, they may be different polypeptides or two or more instances of the same polypeptide. Characteristics of the peptide, polypeptide or protein As explained herein, the disclosed methods comprise taking one or more measurements characteristic of the barcode in order to determine one or more properties of the barcode. The one or more properties of the barcode are characteristic of, and can be associated with, one or more characteristics of the peptide, polypeptide or protein. Many different characteristics of the peptide, polypeptide or protein can be associated with the properties of the barcode. Any suitable measurements can be taken. For example, in some embodiments the one or more characteristics of the peptide, polypeptide or protein are selected from (i) the length of the peptide, polypeptide or protein, (ii) the identity of the peptide, polypeptide or protein, (iii) the sequence of the peptide, polypeptide or protein, (iv) the secondary structure of the peptide, polypeptide or protein; (v) whether or not and / or to the extent to which the peptide, polypeptide or protein is modified; (vi) the presence, absence, concentration or relative abundance of the peptide, polypeptide or protein in a sample; and (vii) whether or not and / or to the extent to which the peptide, polypeptide or protein associates with a further peptide, polypeptide or protein wherein the further peptide, polypeptide or protein is optionally comprised in a construct as defined herein. In one embodiment, the one or more characteristics of the peptide, polypeptide or protein comprise the presence, absence, concentration or relative abundance of the peptide, polypeptide or protein in a sample. In typical embodiments the measurements are characteristic of the sequence of the peptide, polypeptide or protein or whether or not the peptide, polypeptide or protein is modified, e.g. by one or more post- translational modifications. In some embodiments the measurements are characteristics of the sequence of the peptide, polypeptide or protein. Other characteristics can also be determined. For example, the disclosed methods can be used to determine the relative abundance of a plurality of types of peptide, polypeptide or protein in a sample. For example, each of a plurality of types of peptide, polypeptide or protein can be labelled with a different barcode. The relative abundance of multiple species can be inferred by classifying the barcode signals, with the number of barcode signals detected in the methods described herein being proportional to the number of species in the original sample. The disclosed methods can also be used to determine whether or not a peptide, polypeptide or protein is an active variant of that peptide, polypeptide or protein. For example, each of a plurality of variants of a peptide, polypeptide or protein can be labelled with a different barcode. An enrichment method such as a pull-down assay can be used to isolate active variants of the peptide, polypeptide or protein. Measurements of their associated barcodes can subsequently be made in accordance with the disclosed methods to identify the isolated active variants. In another aspect, the disclosed methods can be used to determine whether or not two peptides, polypeptides or proteins in a sample interact. For example multiple species can be barcoded and fractionated. Any suitable fractionation technique can be used. In some embodiments the fractionation technique divides the sample into fractions based on the size of the peptides, polypeptides and proteins in the sample. In some embodiments the fractionation technique divides the sample into fractions based on the total charge of the peptides, polypeptides and proteins in the sample. In some embodiments the fractionation technique comprises electrophoresis (e.g. PAGE) or chromatography (e.g. size exclusion, ion exchange, or hydrophobic interaction chromatography). Measurements of barcodes from each individual fraction can then be taken in accordance with the disclosed methods. Co-incidence of two or more barcodes within a fraction indicates that the two peptides, polypeptides or proteins to which the barcodes were originally attached may interact. In another aspect, the disclosed methods can be used to determine the stoichiometry of interacting peptides, polypeptides and proteins in a sample interact. For example multiple species can be barcoded and fractionated. Any suitable fractionation technique can be used. In some embodiments the fractionation technique divides the sample into fractions based on the size of the peptides, polypeptides and proteins in the sample. In some embodiments the fractionation technique divides the sample into fractions based on the total charge of the peptides, polypeptides and proteins in the sample. In some embodiments the fractionation technique comprises electrophoresis (e.g. PAGE) or chromatography (e.g. size exclusion, ion exchange, or hydrophobic interaction chromatography). Measurements of barcodes from each individual fraction can then be taken in accordance with the disclosed methods. Co-incidence of two or more barcodes within a fraction indicates that the two peptides, polypeptides or proteins to which the barcodes were originally attached may interact. Furthermore, the relative abundance of each of the two or more barcodes in the sample can inform on the stoichiometry of the interaction. For example, if the sample contains two types of protein, A and B, and the fraction contains twice as many barcodes associated with protein A as with protein B, the stoichiometry of the A:B interaction is likely to be A2B. In more detail, and with reference to Figures 1A and 1B, measurement signals may be obtained from each of one or more barcodes each derived from a construct and a peptide, polypeptide or protein as described herein, using a detector, for example a nanopore. In some embodiments the barcodes are as described herein. In some embodiments an analysis step comprises analysing such measurements signals. In some embodiments the method comprises identifying a signal portion of the measurement signal corresponding to the barcode. Thus, in some embodiments an identification step S2 comprises identifying, in each measurement signal a barcode signal portion of the measurement signal corresponding to the barcode. In some embodiments the method comprises a first derivation step S3 comprising deriving one or more properties of the barcode from which the barcode signal portion is derived. The one or more properties may be, for example, selected from: (i) the length of the barcode; (ii) the identity of the barcode; (iii) the sequence of the barcode; (iv) the secondary structure of the barcode; and (v) whether or not the barcode is modified. In some embodiments the method comprises an association step S4 comprising associating one or more characteristics of each peptide, polypeptide or protein with the barcode signal portion of the measurement signal. The one or more characteristics of the peptide, polypeptide or protein may be, for example, selected from: (i) the length of the peptide, polypeptide or protein; (ii) the identity of the peptide, polypeptide or protein; (iii) the sequence of the peptide, polypeptide or protein; (iv) the secondary structure of the peptide, polypeptide or protein; and (v) whether or not the peptide, polypeptide or protein is modified. The one or more characteristics of the peptide, polypeptide or protein may for example be derived on the basis of known information about the peptide, polypeptide or protein. In some embodiments the association comprises generation of a database of characteristics of peptide, polypeptide or proteins and associated barcode measurement signals. In some embodiments the database may contain at least 2, at least 3, at least 4, at least 5, at least 10, at least 20, at least 50, at least 100, at least 500, at least 1000, at least 5000, at least 10000, at least 100000, at least 1000000 or more data entries wherein each data entry comprises (i) one or more peptide, polypeptide or protein characteristics and (ii) an associated barcode signal. In some embodiments the associated data (e.g. the database) is used to train an algorithm for characterising a polypeptide analyte as the polypeptide analyte moves with respect to a nanopore. In some embodiments the methods comprise a measurement step S1 of measuring the measurement signals from each of the barcodes. In some embodiments the measurements signals may comprise electrical and / or optical measurements. In some embodiments the measurements signals are obtained as described herein. Also provided herein is a computer program comprising instructions capable of execution by a computer system which are configured, on execution, to cause the computer system to carry out a method as disclosed herein. Also provided is a computer storage medium storing the computer program. Further provided is a computer system configured to perform the method as described herein. In some embodiments the analysis steps discussed above are conducted on an analysis system 3. In some embodiments the measurement steps are conducted on a measurement system 2. The analysis system 3 may be physically associated with the measurement system 2, and may also provide control signals to the measurement system 2. In that case, the measurement and analysis system 1 comprising the measurement system 2 and the analysis system 3 may be arranged as disclosed in any of WO-2008 / 102210, WO- 2009 / 07734, WO-2010 / 122293, WO-2011 / 067559 or WO2014 / 04443. Alternatively, the analysis system 3 may be implemented in a separate apparatus, in which case the series of measurement is transferred from the measurement system 2 to the analysis system 3 by any suitable means, typically a data network. For example, one convenient cloud-based implementation is for the analysis system 3 to be a server to which input signals are supplied over the internet. The analysis system 3 may be implemented by a computer apparatus executing a computer program or may be implemented by a dedicated hardware device, or any combination thereof. In either case, the data used by the method is stored in a memory in the analysis system 3. In the case of a computer apparatus executing a computer program, the computer apparatus may be any type of computer system but is typically of conventional construction. The computer program may be written in any suitable programming language. The computer program may be stored on a computer-readable storage medium, which may be of any type, for example: a recording medium which is insertable into a drive of the computing system and which may store information magnetically, optically or opto-magnetically; a fixed recording medium of the computer system such as a hard drive; or a computer memory. In the case of the computer apparatus being implemented by a dedicated hardware device, then any suitable type of device may be used, for example an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). In a typical embodiment, portions of the computer program may be implemented using hardware amenable to parallelisation of calculations such as a Graphics processing unit (GPU). Therefore, in some embodiments, provided herein is a method of analysing measurement signals taken from each of a plurality of barcodes using a detector (e.g. as the barcode moves with respect to the detector, e.g. wherein the detector is or comprises a nanopore), the method comprising: identifying, in each measurement signal a barcode signal portion of the measurement signal corresponding to the barcode; and in respect of each barcode signal portion, deriving one or more properties of the barcode from which the barcode signal portion is derived; from the derived one or more properties of each barcode, deriving one or more characteristics of the peptide, polypeptide or protein from which the barcode is derived; and associating the one or more characteristics of each peptide, polypeptide or protein with the barcode signal portion of the measurement signal. Sequencing adapters As explained herein, in some embodiments the disclosed methods comprise attaching the barcode to one or more sequencing adapters in order to facilitate its characterisation in the methods disclosed herein. As discussed here, in some embodiments the disclosed method comprises generating one or more reactive functional groups on the barcode. In some embodiments the one or more reactive functional groups are at the N- and / or C- terminus of the barcode. In some embodiments the method comprises attaching one or more sequencing adapters to one or more of said reactive functional groups. An adapter may be attached to just one end of the barcode. A polynucleotide adapter may be added to both ends of the barcode. Alternatively, different adapters may be added to the two ends of a barcode. Methods of adding adapters to polypeptides are known in the art. Adapters may be attached to polypeptides, for example, by ligation, by click chemistry, or by any other suitable method. In one embodiment, the or each adapter is synthetic or artificial. Typically, the or each adapter comprises a polymer as described herein. In some embodiments, the or each adapter comprises a spacer as described herein. In some embodiments, the or each adapter comprises a polynucleotide. The or each polynucleotide adapter may comprise DNA, RNA, modified DNA (such as abasic DNA), RNA, PNA, LNA, BNA and / or PEG. Usually, the or each adapter comprises single stranded and / or double stranded DNA or RNA. In some embodiments, an adapter is a linear adapter. A linear adapter may be bound to either or both ends of a barcode. A linear adapter may comprise a leader sequence as described herein. A linear adapter may comprise a portion for hybridisation with a tag (such as a pore tag) as described herein. A linear adapter may be 10 to 150 nucleotides in length, such as from 20 to 120, e.g.30 to 100, for example 40 to 80 such as 50 to 70 nucleotides in length. A linear adapter may be single stranded. A linear adapter may be double stranded. In some embodiments, an adapter may be a Y adapter. A Y adapter is typically a polynucleotide adapter. A Y adapter is typically double stranded and comprises (a) at one end, a region where the two strands are hybridised together and (b), at the other end, a region where the two strands are not complementary. The non-complementary parts of the strands typically form overhangs. The presence of a non-complementary region in the Y adapter gives the adapter its Y shape since the two strands typically do not hybridise to each other unlike the double stranded portion. The two single-stranded portions of the Y adapter may be the same length, or may be different lengths. For example, one single- stranded portion of the Y adapter may be 10 to 150 nucleotides in length, such as from 20 to 120, e.g.30 to 100, for example 40 to 80 such as 50 to 70 nucleotides in length and the other single stranded portion of the Y adapter may independently by 10 to 150 nucleotides in length, such as from 20 to 120, e.g.30 to 100, for example 40 to 80 such as 50 to 70 nucleotides in length. The double-stranded “stem” portion of the Y adapter may be e.g. from 10 to 150 nucleotides in length, such as from 20 to 120, e.g.30 to 100, for example 40 to 80 such as 50 to 70 nucleotides in length. A Y adapter may be attached to either or both ends of a barcode as described herein. An adapter may be linked to the barcode by any suitable means known in the art. The adapter may be synthesized separately and chemically attached or enzymatically ligated to the strand. Alternatively, the adapter may be generated in the processing of the barcode as described in more detail herein. In some embodiments, an adapter is linked to the barcode at or near one end of the barcode. In some embodiments, the adapter is linked to the barcode within 5, 4, 3, 2 or 1 amino acids of an end of the barcode. In some embodiments the adapter is linked to the barcode at the N-terminus of the barcode. In some embodiments the adapter is linked to the barcode at the C-terminus of the barcode. In some embodiments a first adapter is linked to the barcode at the N-terminus of the barcode and a second adapter is linked to the barcode at the C-terminus of the barcode. Such adapters may also comprise reactive functional groups for binding to the barcode. Click chemistry groups are particularly suitable in this regard. For example, exemplary groups for inclusion in an adapter include groups which can particulate in copper-free click chemistry, for example groups based on BCN (bicyclo[6.1.0]nonyne) and its derivatives, dibenzocyclooctyne (DBCO) groups, and the like. The reaction of such groups is well known in the art. For example, BCN groups typically react with groups such as azides, tetrazines and nitrones. DBCO groups have high reactivity toward azide groups. Other chemical groups which are particularly suitable include 2- pyridinecarboxyaldehyde (2-PCA) groups and their derivatives. For example, 6- (azidomethyl)-2-pyridinecarboxyaldehyde can react with N-terminal amino groups of peptides. Leader An adapter suitable for use in the described methods may in some embodiments comprise a leader. A leader may be useful to assist the capture of the adapter and thus of the barcode by a nanopore as described herein. In some embodiments the leader may be from about 10 to 150 nucleotides (e.g. DNA and / or RNA nucleotides) in length, such as from 20 to 120, e.g.30 to 100, for example 40 to 80 such as 50 to 70 nucleotides in length, or from about 10 to about 60 nucleotides in length, e.g. from about 20 to about 50, such as from about 20 to about 40, e.g. about 30 nucleotides in length. In some embodiments the leader is a charged polymer, e.g. a negatively charged polymer. In some embodiments the leader comprises a polymer such as PEG or a polysaccharide. In such embodiments the leader may be from 10 to 150 monomer units (e.g. ethylene glycol or saccharide units) in length, such as from 20 to 120, e.g.30 to 100, for example 40 to 80 such as 50 to 70 monomer units (e.g. ethylene glycol or saccharide units) in length. Controlling movement of the conjugate with respect to a nanopore As discussed in more detail herein, some embodiments of the disclosed methods comprise contacting the barcode and / or a sequencing adapter if present with a motor protein capable of controlling the movement of the barcode with a the nanopore. In some embodiments the disclosed methods comprise taking one or more measurement as the barcode moves with respect to a nanopore. The movement of the barcode with respect to the nanopore may be driven by any suitable means. In some embodiments, the movement of the barcode is driven by a physical or chemical force (potential). In some embodiments the physical force is provided by an electrical (e.g. voltage) potential or a temperature gradient, etc. In some embodiments, the movement of the barcode comprises mechanically manipulating the barcode thereby moving said barcode with respect to the nanopore. In some embodiments, movement of the barcode by mechanical manipulation does not comprise using a polynucleotide-handling protein. In some embodiments the barcode is moved by mechanical manipulation in a direction opposite to a potential applied across said nanopore. In some embodiments, the potential is a voltage potential applied across said nanopore. In some embodiments, the barcode is moved with respect to the nanopore as described in WO 2020 / 128517, the entire contents of which are hereby incorporated by reference, particularly in regards to discussion in that document of movements of polynucleotides with respect to nanoreactors. In some embodiments, the barcode moves with respect to the nanopore as an electrical potential is applied across the nanopore. Often the barcode is charged (e.g. negatively charged), and so applying a voltage potential across a nanopore will cause the barcode to move with respect to the nanopore under the influence of the applied voltage potential. For example, if a positive voltage potential is applied to the trans side of the nanopore relative to the cis side of the nanopore, then this will induce a negatively charged barcode to move from the cis side of the nanopore to the trans side of the nanopore. Similarly, if a positive voltage potential is applied to the trans side of the nanopore relative to the cis side of the nanopore then this will impede the movement of a negatively charged barcode from the trans side of the nanopore to the cis side of the nanopore. The opposite will occur if a negative voltage potential is applied to the trans side of the nanopore relative to the cis side of the nanopore. Apparatuses and methods of applying appropriate voltages are described in more detail herein. In some embodiments the chemical force is provided by a concentration (e.g. pH) gradient. In some embodiments the movement of the barcode with respect to the nanopore is controlled using a method as described in WO 2020 / 016573, the entire contents of which are incorporated herein by reference. In some embodiments the movement of the barcode is controlled using a method as disclosed in any of WO 2021 / 111125, WO 2021 / 133168, or PCT / GB2023 / 052838, the entire contents of which are incorporated herein by reference. In some embodiments a motor protein controls the movement of the barcode in the same direction as the physical or chemical force (potential). For example, in some embodiments a positive voltage potential is applied to the trans side of the nanopore relative to the cis side of the nanopore, and a motor protein controls the movement of the barcode from the cis side of the nanopore to the trans side of the nanopore. In some embodiments a positive voltage potential is applied to the cis side of the nanopore relative to the trans side of the nanopore, and a motor protein controls the movement of the barcode from the trans side of the nanopore to the cis side of the nanopore. In some embodiments a motor protein controls the movement of the barcode in the opposite direction to the physical or chemical force (potential). For example, in some embodiments a positive voltage potential is applied to the trans side of the nanopore relative to the cis side of the nanopore, and the motor protein controls the movement of the barcode from the trans side of the nanopore to the cis side of the nanopore. In some embodiments a positive voltage potential is applied to the cis side of the nanopore relative to the trans side of the nanopore, and the motor protein controls the movement of the barcode from the cis side of the nanopore to the trans side of the nanopore. In some embodiments the movement of the barcode is driven by the motor protein in the absence of an applied potential. In embodiments of the disclosed methods which comprise the use of a motor protein, the motor protein is typically capable of controlling the movement of the barcode with respect to a nanopore. In other words, the motor protein is capable of controlling the movement of the barcode. Suitable motor proteins are in some embodiments also known as polynucleotide- handling proteins or polynucleotide-handling enzymes, or polypeptide-handling proteins or polypeptide-handling enzymes. Suitable proteins are known in the art and some exemplary motor proteins are described in more detail below. In one embodiment, a motor protein is or is derived from a polynucleotide handling enzyme. A polynucleotide handling enzyme is a polypeptide that is capable of interacting with and modifying at least one property of a polynucleotide. The enzyme may modify the polynucleotide by cleaving it to form individual nucleotides or shorter chains of nucleotides, such as di- or trinucleotides. The enzyme may modify the polynucleotide by orienting it or moving it to a specific position. In some embodiments, a motor protein can be present on a barcode or an adapter attached thereto prior to its contact with a nanopore. For example, a motor protein can be present on a polynucleotide portion of an adapter. In some embodiments the motor protein is designed, configured or selected to remain bound to the barcode. In other words, in some embodiments the motor protein does not dissociate from the barcode. In some embodiments the polynucleotide-handling protein is modified to prevent it from disengaging from the barcode (other than by passing off the end of the barcode or a construct comprising the barcode). Such modified polynucleotide-handling proteins are particularly suitable for use in the disclosed methods. The motor protein can be adapted in any suitable way. For example, the motor protein can be loaded onto the barcode or an adapter attached thereto and then modified in order to prevent it from disengaging. Alternatively, the motor protein can be modified to prevent it from disengaging before it is loaded onto the barcode or an adapter attached thereto. Modification of a motor protein in order to prevent it from disengaging from a ppt can be achieved using methods known in the art, such as those discussed in WO 2014 / 013260, which is hereby incorporated by reference in its entirety, and with particular reference to passages describing the modification of polynucleotide-handling proteins (motor proteins) such as helicases in order to prevent them from disengaging with polynucleotide strands. For example, the motor protein may have a polynucleotide-unbinding opening; e.g. a cavity, cleft or void through which a polynucleotide or polypeptide strand may pass when the motor protein disengages from the strand. In some embodiments, the polynucleotide- unbinding opening for a given motor protein (polynucleotide-handling protein) can be determined by reference to its structure, e.g. by reference to its X-ray crystal structure. The X-ray crystal structure may be obtained in the presence and / or the absence of a polynucleotide substrate. In some embodiments, the location of a polynucleotide- unbinding opening in a given motor protein may be deduced or confirmed by molecular modelling using standard packages known in the art. In some embodiments, the polynucleotide-unbinding opening may be transiently produced by movement of one or more parts e.g. one or more domains of the motor protein. The motor protein (polynucleotide-handling protein) may be modified by closing the polynucleotide-unbinding opening. Closing the polynucleotide-unbinding opening may therefore prevent the motor protein from disengaging from the barcode as well as preventing it from disengaging from an adapter attached thereto. For example, the motor protein may be modified by covalently closing the polynucleotide-unbinding opening. In some embodiments, a motor protein for addressing in this way is a helicase, as described herein. Accordingly, in some embodiments of the disclosed methods, the motor protein is modified to wholly or partially close an opening existing in at least one conformation state of the unmodified protein through which a polynucleotide or polypeptide strand can unbind. In one embodiment, the motor protein is derived from a member of any of the Enzyme Classification (EC) groups 3.1.11, 3.1.13, 3.1.14, 3.1.15, 3.1.16, 3.1.21, 3.1.22, 3.1.25, 3.1.26, 3.1.27, 3.1.30, 3.1.31 and 3.4.21. In some embodiments of the claimed methods, the motor protein is a helicase, a polymerase, an exonuclease, a topoisomerase, or a variant thereof. In one embodiment, the motor protein is an exonuclease. Suitable enzymes include, but are not limited to, exonuclease I from E. coli, exonuclease III enzyme from E. coli, RecJ from T. thermophilus and bacteriophage lambda exonuclease, TatD exonuclease and variants thereof. In one embodiment, the motor protein is a polymerase. The polymerase may be PyroPhage® 3173 DNA Polymerase (which is commercially available from Lucigen® Corporation), SD Polymerase (commercially available from Bioron®), Klenow from NEB or variants thereof. In one embodiment, the enzyme is Phi29 DNA polymerase or a variant thereof. Modified versions of Phi29 polymerase that may be used in the disclosed methods are disclosed in US Patent No.5,576,204. In some embodiments the motor protein is a polymerase, e.g. a polymerase as described herein. In one embodiment the motor protein is a topoisomerase. In one embodiment, the topoisomerase is a member of any of the Moiety Classification (EC) groups 5.99.1.2 and 5.99.1.3. The topoisomerase may be a reverse transcriptase, which are enzymes capable of catalysing the formation of cDNA from a RNA template. They are commercially available from, for instance, New England Biolabs® and Invitrogen®. In one embodiment the motor protein is a translocase. Examples include translocases in the FtsK and SpoIII families. In one embodiment, the motor protein is a helicase. Any suitable helicase can be used in accordance with the methods provided herein. For example, the or each motor protein used in accordance with the present disclosure may be independently selected from a Hel308 helicase, a RecD helicase, a TraI helicase, a TrwC helicase, an XPD helicase, and a Dda helicase, or a variant thereof. Monomeric helicases may comprise several domains attached together. For instance, TraI helicases and TraI subgroup helicases may contain two RecD helicase domains, a relaxase domain and a C-terminal domain. The domains typically form a monomeric helicase that is capable of functioning without forming oligomers. Particular examples of suitable helicases include Hel308, NS3, Dda, UvrD, Rep, PcrA, Pif1 and TraI. These helicases typically work on single stranded DNA. Examples of helicases that can move along both strands of a double stranded DNA include FtsK and hexameric enzyme complexes, or multisubunit complexes such as RecBCD, and are particularly suited to some embodiments disclosed herein. NS3 helicases are particularly suitable for use in the disclosed methods as they are capable of processing both DNA and RNA and so can be used in embodiments of the disclosed methods in which the target double stranded nucleic acid is a DNA-RNA hybrid. Hel308 helicases are described in publications such as WO 2013 / 057495, the entire contents of which are incorporated by reference. RecD helicases are described in publications such as WO 2013 / 098562, the entire contents of which are incorporated by reference. XPD helicases are described in publications such as WO 2013 / 098561, the entire contents of which are incorporated by reference. Dda helicases are described in publications such as WO 2015 / 055981 and WO 2016 / 055777, the entire contents of each of which are incorporated by reference. In one embodiment the helicase comprises the sequence shown in SEQ ID NO: 16 (Trwc Cba) or a variant thereof, the sequence shown in SEQ ID NO: 17 (Hel308 Mbu) or a variant thereof or the sequence shown in SEQ ID NO: 18 (Dda) or a variant thereof. Variants may differ from the native sequences in any of the ways discussed herein. An example variant of SEQ ID NO: 18 comprises E94C / A360C. A further example variant of SEQ ID NO: 18 comprises E94C / A360C and then (ΔM1)G1G2 (i.e. deletion of M1 and then addition of G1 and G2). In some embodiments a motor protein (e.g. a helicase) can control the movement of a strand in at least two active modes of operation (when the motor protein is provided with all the necessary components to facilitate movement, e.g. fuel and cofactors such as ATP and Mg2+discussed herein) and one inactive mode of operation (when the motor protein is not provided with the necessary components to facilitate movement). When provided with all the necessary components to facilitate movement (i.e. in the active modes), the motor protein (e.g. helicase) moves along a construct comprising the barcode and an adapter in a 5’ to 3’ or a 3’ to 5’ direction (depending on the motor protein). The motor protein can be used to either move the construct away from (e.g. out of) the pore (e.g. against an applied force) or the strand towards (e.g. into) the pore (e.g. with an applied force). For example, when the end of the construct towards which the motor protein moves is captured by a pore, the motor protein works against the direction of the force and pulls the threaded construct out of the pore (e.g. into the cis chamber). However, when the end away from which the motor protein moves is captured in the pore, the motor protein works with the direction of the force and pushes the threaded construct into the pore (e.g. into the trans chamber). When the motor protein (e.g. helicase) is not provided with the necessary components to facilitate movement (i.e. in the inactive mode) it can bind to the construct and act as a brake slowing the movement of the construct when it is moved with respect to a nanopore, e.g. by being pulled into the pore by a force. In the inactive mode, it does not matter which end of the construct is captured, it is the applied force which determines the movement with respect to the pore, and the motor protein acts as a brake. When in the inactive mode, the movement control by the motor protein can be described in a number of ways including ratcheting, sliding and braking. In another embodiment the motor protein is a protein translocase. Protein translocases are protein-binding polypeptides which are able to control movement of a protein substrate, for example an enzyme, enzyme complex, or a part of an enzyme complex that operates on a protein substrate and moves it relative to the enzyme in a processive manner, i.e. as a function of enzymatic activity. In some embodiments the motor protein is a NTP driven unfoldase. NTP driven unfoldases are NTP-dependent enzymes that catalyze protein unfolding. NTP driven unfoldases include ATP-dependent proteases, such as proteasomal ATPases, AAA proteases, AAA+ enzymes; membrane fusion proteins, such as NSF (N-Ethylmaleimide- sensitive fusion protein) / Sacl8p (N-Ethylmaleimide-sensitive fusion protein homologue in yeast) or p97 / VCP / Cdc48p (97-kDa valosin-containing protein); Pexlp and Pex6p (peroxisomal ATPase); Katanin and SKD1 (Vps4p homolog in mouse) / Vps4p (Vacuolar protein sorting 4 homolog in yeast); Dynein (motor protein); DNA replication proteins, such as ORC (origin recognition complex), Cdc6 (cell division control protein 6), MCM (minichromosome maintenance protein), DnaA, or RFC (replication factor C) / clamp- loader; RuvB (holliday junction ATP-dependent DNA helicase RuvB, EC=3.6.4.12); TIP49a / TIP49 and TIP49b / TIP48 (eukaryotic RuvB-like protein). In some embodiments the motor protein is an AAA+ enzyme, AAA+ enzymes are members of the AAA+ superfamily of enzymes. AAA+ is an abbreviation for ATPases Associated with diverse cellular Activities. They share a common conserved module of approximately 230 amino acid residues. This is a large, functionally diverse protein family belonging to the AAA+ superfamily of ring-shaped P-loop NTPases, which exert their activity through the energy-dependent remodeling or translocation of macromolecules. Examples include ClpAP, ClpXP, ClpCP, HslYU and Lon in bacteria and their homologues in mitochondria and chloroplasts. With the exception of Lon, AAA+ enzymes (sometimes referred to as unfoldases or proteases) consist of regulatory (ATPase) and proteolytic subunits, while Lon is a single polypeptide containing both regulatory and proteolytic domains. ClpX and ClpA dock with ClpP to form ClpXP and ClpAP proteases, whereas HslU docks with HslY to form another protease, HslVU. ClpA and ClpX form hexamers, in contrast to ClpP which forms heptamers. HslU and HslY each form hexamers, although HslU heptamers have also been reported. The regulatory subunits ClpA, ClpX and HslU function as chaperones. AAA+ enzymes may also be referred to as AAA+ molecular motors. HsIU is a member of the HsplOO and Clp family of ATPase. It can also form complex with HsIY to act as an unfoldase. Lon proteases are ATP-dependent serine peptidases belonging to the MEROPS peptidase family S16 (Ion protease family, clan SF). In some embodiments the motor protein is ClpX or is a derivative thereof. ClpX is a member of the HSP (heat-shock protein) 100 family having the Uniprot designation clpX and having the 424 amino acid sequence given there, processed into mature form, as a subunit. ClpX subunits associate to form a six-membered (homohexameric) ring that is stabilized by binding of ATP or nonhydrolysable analogs of ATP. The N-terminal domain of ClpX is a C4-type zinc binding domain (ZBD) involved in substrate recognition. ZBD forms a very stable dimer that is essential for promoting the degradation of some typical ClpXP substrates such as and MuA. In some embodiments the motor protein is E. coli ClpX. E. coli ClpX generates sufficient mechanical force (>20 pN) to denature stable protein folds, and translocates along proteins at a suitable rate for primary sequence analysis by nanopore sensors (up to 80 amino acids per second). ClpX is part of the ClpXP proteasome-like complex. ClpP is composed of a diheptameric cylinder-like protease that binds at one or both ends a regulatory hexameric ATP-dependent unfoldase / translocase complex (e.g. ClpX). ClpX acts as a gate that allows for tagged proteins to enter into the inner lumen of the ClpP protease complex for subsequent degradation. The ATP-dependent unfoldase / translocase activity of the hexameric protein complex, ClpX, is employed to unfold and thread proteins through a nanopore. In some embodiments the motor protein is a ClpX-deltaN subunits, lacking N- terminal amino acids 1-60, linked with a 20 amino acid long linker and prepared as a single polypeptide chain. In some embodiments the motor protein is a Clp / HsplOO ATPase. Clp / HsplOO ATPases are responsible for selecting protein targets. For example, the two different bacterial ATPases ClpX and ClpA impart distinct substrate preferences to the ClpP peptidase. In some embodiments the motor protein is a mitochondrial protein translocase. Examples include TOM or TIM from human or eukaryotic cells, such as TOMM20 (translocase of outer mitochondrial membrane homolog), TOMM22 (mitochondrial import receptor subunit 22 homolog), TOMM40 (translocase of outer mitochondrial membrane 40 homolog), TOM7 (translocase of mitochondrial outer membrane 7), TOMM7 (translocase of outer mitochondrial membrane 7 homolog), TIMM8A (translocase of inner mitochondrial membrane 8 homolog A), TIMM50 (translocase of inner mitochondrial membrane 50 homolog). Another alternative protein translocase may be prepared from the Sec family of translocases. These include SecB (chaperone protein), SecA (ATPase), SecY (internal membrane complex in prokaryotes), SecE (interal membrane complex in prokaryotes), SecG (internal membrane complex in prokaryotes) or Sec61 (internal membrane complex in eukaryotes), SecD (membrane protein), and SecF (membrane protein). Another alternative protein translocase is Type III Secretion System (TTS) Translocase, such as HrcN and any of the subunits of the TTS translocases, or Sec- independent periplasmic protein translocase TatC. Examples of suitable protein translocases, such as NTP driven unfoldases as described above, are described in WO 2013 / 123379, hereby incorporated by reference. Embodiments in which the motor protein is or comprises an unfoldase are particularly suited to disclosed methods which comprise - contacting a construct comprising the peptide, polypeptide or protein attached to a barcode with a motor protein capable of controlling the movement of the barcode with respect to a nanopore; and - taking one or more measurements characteristic of the barcode as the barcode moves with respect to the nanopore under the control of the motor protein, thereby determining one or more properties of the barcode; wherein said one or more properties of the barcode are characteristic of one or more characteristics of the peptide, polypeptide or protein and / or wherein said method further comprises associating said one or more properties of the barcode with one or more characteristics of the peptide, polypeptide or protein; thereby characterising the peptide, polypeptide or protein. A motor protein typically requires fuel in order to handle the processing of polynucleotides and / or polypeptides. Fuel is typically free nucleotides or free nucleotide analogues. The free nucleotides may be one or more of, but are not limited to, adenosine monophosphate (AMP), adenosine diphosphate (ADP), adenosine triphosphate (ATP), guanosine monophosphate (GMP), guanosine diphosphate (GDP), guanosine triphosphate (GTP), thymidine monophosphate (TMP), thymidine diphosphate (TDP), thymidine triphosphate (TTP), uridine monophosphate (UMP), uridine diphosphate (UDP), uridine triphosphate (UTP), cytidine monophosphate (CMP), cytidine diphosphate (CDP), cytidine triphosphate (CTP), cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP), deoxyadenosine monophosphate (dAMP), deoxyadenosine diphosphate (dADP), deoxyadenosine triphosphate (dATP), deoxyguanosine monophosphate (dGMP), deoxyguanosine diphosphate (dGDP), deoxyguanosine triphosphate (dGTP), deoxythymidine monophosphate (dTMP), deoxythymidine diphosphate (dTDP), deoxythymidine triphosphate (dTTP), deoxyuridine monophosphate (dUMP), deoxyuridine diphosphate (dUDP), deoxyuridine triphosphate (dUTP), deoxycytidine monophosphate (dCMP), deoxycytidine diphosphate (dCDP) and deoxycytidine triphosphate (dCTP). The free nucleotides are usually selected from AMP, TMP, GMP, CMP, UMP, dAMP, dTMP, dGMP or dCMP. The free nucleotides are typically adenosine triphosphate (ATP). A cofactor for the motor protein is a factor that allows the motor protein to function. The cofactor is often a divalent metal cation. The divalent metal cation is often Mg2+, Mn2+, Ca2+or Co2+. The cofactor is most typically Mg2+. Detector Embodiments described herein refer to movement of a barcode with respect to a nanopore. However, whilst the disclosure provides nanopores as exemplary detectors, the methods provided herein are also amenable to other detectors including (i) a zero-mode waveguide, (ii) a field-effect transistor, optionally a nanowire field-effect transistor; (iii) an AFM tip; (iv) a nanotube, optionally a carbon nanotube and (v) a nanopore. The disclosed methods are particularly amenable to methods in which a polypeptide is moved through a detector or through a structure containing a detector, e.g. a well in a detector chip. Nanopore As explained above, in some embodiments the disclosed methods comprise taking one or more measurements as a barcode moves with respect to a nanopore. In the disclosed methods, any suitable nanopore can be used. In one embodiment a nanopore is a transmembrane pore. A transmembrane pore is a structure that crosses the membrane to some degree. It permits hydrated ions driven by an applied potential to flow across or within the membrane. The transmembrane pore typically crosses the entire membrane so that hydrated ions may flow from one side of the membrane to the other side of the membrane. However, the transmembrane pore does not have to cross the membrane. It may be closed at one end. For instance, the pore may be a well, gap, channel, trench or slit in the membrane along which or into which hydrated ions may flow. Any suitable transmembrane pore may be used in the methods provided herein. The pore may be biological or artificial. Suitable pores include, but are not limited to, protein pores, polynucleotide pores, and solid state pores. A solid state pore may, in one embodiment, comprise a nanochannel. In some embodiments the solid state pore is a pore disclosed in WO 2003 / 003446, WO 2009 / 020682 or WO 2016 / 187519, each of which is incorporated by reference in their entirety. In one embodiment, the pore may be a DNA origami pore (Langecker et al., Science, 2012; 338: 932-936). Suitable DNA origami pores are disclosed in WO2013 / 083983, WO 2018 / 011603 and WO 2020 / 025974, each of which is incorporated by reference in their entirety. In one embodiment, the nanopore is a scaffolded polypeptide nanopore. In some embodiments the pore is a scaffolded polypeptide nanopore as disclosed in WO 2020 / 025909 or WO 2020 / 074399, each of which is incorporated by reference in their entirety. In one embodiment, the nanopore is a transmembrane protein pore. A transmembrane protein pore is a polypeptide or a collection of polypeptides that permits hydrated ions, such as polynucleotides, to flow from one side of a membrane to the other side of the membrane. In the methods provided herein, the transmembrane protein pore is capable of forming a pore that permits hydrated ions driven by an applied potential to flow from one side of the membrane to the other. The transmembrane protein pore typically permits polynucleotides and polypeptides to flow from one side of the membrane, such as a polymer membrane, to the other. The transmembrane protein pore allows a polynucleotide or polypeptide to be moved through the pore. Examples of transmembrane protein pores include Wza, Iota toxin, Anthrax protective antigen, Vibrio cholerae cytolysin, Cytotoxin K (CytK), CELIII, CsgG, CsgF, CsgG-CsgF, Aerolysin, alpha hemolysin, MspA, MspB, MspC, PorARr, PorBRr, PorARc, PilQ, necrotic enteritis B-like toxin (NetB), FraC, portal proteins including G20c, P23_45, T4, SPP1, P22 and Phi29, gamma hemolysin, Monalysin, Lysenin, ClyA, an actinoporin, Clostridium perfringens beta toxin, parasporin-2, epsilon toxin, lectin from the parasitic mushroom Laetiporus sulphureus (LSL), volvatoxin, Cry toxins, Cyt1Aa, Cyt2Aa, Complement component 9 (C9), Perfringolysin O, Pleurotolysin, Listeriolysin, Perforin-2, Gasdermin-A3, L-, P- and M-ring protein, Type II secretion system protein D, GspD, InvG, VirB7, SpoIIIAG, Cag8, Cag3, Cag or other proteins in the Type IV secretion system apparatus protein CagY, WzzB, Pentraxin, Afp2, Major vault protein, Thioredoxin- dependent peroxidase reductase, Arf-GAP, Respiratory syncytial virus ribonucleoprotein, Chikungunya virus nonstructural protein 1, PRC, YaxA, XaxA, HfaB, NfpAB, leukocidin and PrgH. In one embodiment, the nanopore is a transmembrane protein pore which is a monomer or an oligomer. The pore is typically made up of several repeating subunits, such as at least 6, at least 7, at least 8, at least 9, at least 10, at least 11, at least 12, at least 13, at least 14, at least 15, or at least 16 subunits. The pore is typically a hexameric, heptameric, octameric or nonameric pore. The pore may be a homo-oligomer or a hetero- oligomer. In one embodiment, the transmembrane protein pore comprises a barrel or channel through which the ions may flow. The subunits of the pore typically surround a central axis and contribute strands to a transmembrane β-barrel or channel or a transmembrane ^- helix bundle or channel. Typically, the barrel or channel of the transmembrane protein pore comprises amino acids that facilitate interaction with an analyte, such as a target polypeptide (as described herein). These amino acids are typically located near a constriction of the barrel or channel. The transmembrane protein pore typically comprises one or more positively charged amino acids, such as arginine, lysine or histidine, or aromatic amino acids, such as tyrosine or tryptophan. These amino acids typically facilitate the interaction between the pore and nucleotides, polynucleotides, nucleic acids and polypeptides. In one embodiment, the nanopore is a transmembrane protein pore derived from ^- barrel pores or ^-helix bundle pores. ^-barrel pores comprise a barrel or channel that is formed from ^-strands. Suitable ^-barrel pores include, but are not limited to, ^-toxins, such as ^-hemolysin, anthrax toxin, CytK, aerolysin and leukocidins, and outer membrane proteins / porins of bacteria, such as Mycobacterium smegmatis porin (Msp), for example MspA, MspB, MspC or MspD, CsgG, outer membrane porin F (OmpF), outer membrane porin G (OmpG), outer membrane phospholipase A and Neisseria autotransporter lipoprotein (NalP) and other pores, such as lysenin. ^-helix bundle pores comprise a barrel or channel that is formed from ^-helices. Suitable ^-helix bundle pores include, but are not limited to, inner membrane proteins and ^ outer membrane proteins, such as WZA, FraC and ClyA toxin. In one embodiment the nanopore is a transmembrane pore derived from or based on Msp, ^-hemolysin (α-HL), lysenin, CsgG, ClyA, Sp1 or haemolytic protein fragaceatoxin C (FraC). In one embodiment, the nanopore is a transmembrane protein pore derived from CsgG, e.g. from CsgG from E. coli Str. K-12 substr. MC4100. Such a pore is oligomeric and typically comprises 7, 8, 9 or 10 monomers derived from CsgG. The pore may be a homo-oligomeric pore derived from CsgG comprising identical monomers. Alternatively, the pore may be a hetero-oligomeric pore derived from CsgG comprising at least one monomer that differs from the others. Examples of suitable pores derived from CsgG are disclosed in WO 2016 / 034591, WO 2017 / 149316, WO 2017 / 149317, WO 2017 / 149318 and WO 2019 / 002893, each of which is hereby incorporated by reference in its entirety. In one embodiment, the nanopore is a transmembrane pore derived from lysenin. Examples of suitable pores derived from lysenin are disclosed in WO 2013 / 153359, which is hereby incorporated by reference in its entirety. In one embodiment, the nanopore is a transmembrane pore derived from or based on ^-hemolysin (α-HL). The wild type α-hemolysin pore is formed of 7 identical monomers or sub-units (i.e., it is heptameric). An α-hemolysin pore may be α-hemolysin- NN or a variant thereof. The variant typically comprises N residues at positions E111 and K147. In one embodiment, the nanopore is a transmembrane protein pore derived from Msp, e.g. from MspA. Examples of suitable pores derived from MspA are disclosed in WO 2012 / 107778. In one embodiment, the nanopore is a transmembrane pore derived from or based on ClyA. Examples of suitable pores derived from ClyA are disclosed in Soskine et al., Nano Letters 201212 (9), 4895-4900; WO 2014 / 153625; and WO 2017 / 098322, each of which is hereby incorporated by reference. In one embodiment, the nanopore is a transmembrane pore derived from Phi29. Examples of suitable pores derived from Phi29 are disclosed in Wendell et al., Nature Nanotech 4, 765–772 (2009), WO 2010 / 062697, WO 2019 / 157365 and WO 2019 / 157424, each of which is hereby incorporated by reference. In some embodiments the nanopore is selected from M-ring protein, perforin-2, PlyAB (pleurotolysin), SpoIIIAG, VirB7, Type II secretion system protein D, GspD, InvG, PilQ, pentraxin, and portal proteins including T4, T7, P23_45, G20c and Phi29 nanopores. In one embodiment, the nanopore is a transmembrane pore derived from or based on a Rhodococcus species of bacteria, for example Rhodococcus corynebacteroides or Rhodococcus ruber, for example PorARr, PorBRr or PorARc. Examples of such pores are described in Piselli et al., Eur Biophys J 51, 309–323 (2022), and in WO 2024 / 089270 hereby incorporated by reference. As explained above, in some embodiments the nanopore comprises a constriction. The constriction is typically a narrowing in the channel which runs through the nanopore which may determine or control the signal obtained when the conjugate moves with respect to the nanopore. As used herein, both protein and solid state nanopores may comprise a “constriction”. In some embodiments the nanopore is designed, modified or chosen to have a constriction that is sized according to the diameter of the construct. In some embodiments the pore has a constriction having a diameter of at least 1 nm, e.g. at least 1.5 nm, such as at least 2 nm, e.g. at least 2.5 nm e.g. at least 3 nm. In some embodiments the pore has a constriction having a diameter of from about 1.5 to about 2.5 nm. Tags In some embodiments of the methods provided herein, a tag on the nanopore can be used, e.g. to promote the capture of a barcode or construct containing a barcode by the nanopore. The interaction between a tag on a nanopore and a binding site on a construct or barcode (which may for example be a binding site present in the polynucleotide portion of an adaptor attached to the barcode) may be reversible. For example, a polynucleotide can bind to a tag on a nanopore, e.g., via its adaptor, and release at some point, e.g., during characterization of the polynucleotide by the nanopore and / or during processing by a motor protein. A strong non-covalent bond (e.g., biotin / avidin) is still reversible and can be useful in some embodiments of the methods described herein. For example, a pair of pore tag and polynucleotide adaptor can be designed to provide a sufficient interaction between the complement of a double stranded polynucleotide (or a portion of an adaptor that is attached to the complement) and the nanopore such that the complement is held close to the nanopore (without detaching from the nanopore and diffusing away) but is able to release from the nanopore as it is processed. A pore tag and polynucleotide adaptor can be configured such that the binding strength or affinity of a binding site on the polynucleotide (e.g., a binding site provided by an anchor or a leader sequence of an adaptor or by a capture sequence within the duplex stem of an adaptor) to a tag on a nanopore is sufficient to maintain the coupling between the nanopore and polynucleotide until an applied force is placed on it to release the bound polynucleotide from the nanopore. In some embodiments, the tags or tethers are uncharged. This can ensure that the tags or tethers are not drawn into the nanopore under the influence of a potential difference if present. One or more molecules that attract or bind the barcode or adapter attached thereto may be linked to the nanopore. Any molecule that hybridizes to the conjugate, adaptor and / or polynucleotide may be used. The molecule attached to the pore may be selected from a PNA tag, a PEG linker, a short oligonucleotide, a positively charged amino acid and an aptamer. Pores having such molecules linked to them are known in the art. For example, pores having short oligonucleotides attached thereto are disclosed in Howarka et al (2001) Nature Biotech.19: 636-639 and WO 2010 / 086620, and pores comprising PEG attached within the lumen of the pore are disclosed in Howarka et al (2000) J. Am. Chem. Soc.122(11): 2411-2416. A short oligonucleotide attached to the nanopore, which comprises a sequence complementary to a sequence in the conjugate (e.g. in a leader sequence or another single stranded sequence in an adaptor) may be used to enhance capture of the barcode or adapter attached thereto in the methods described herein. Membrane Typically, in the disclosed methods, the nanopore is typically present in a membrane. Any suitable membrane may be used in the system. The membrane is typically an amphiphilic layer. An amphiphilic layer is a layer formed from amphiphilic molecules, such as phospholipids, which have both hydrophilic and lipophilic properties. The amphiphilic molecules may be synthetic or naturally occurring. Non-naturally occurring amphiphiles and amphiphiles which form a monolayer are known in the art and include, for example, block copolymers (Gonzalez-Perez et al., Langmuir, 2009, 25, 10447-10450). Block copolymers are polymeric materials in which two or more monomer sub-units that are polymerized together to create a single polymer chain. Block copolymers typically have properties that are contributed by each monomer sub-unit. However, a block copolymer may have unique properties that polymers formed from the individual sub-units do not possess. Block copolymers can be engineered such that one of the monomer sub-units is hydrophobic (i.e. lipophilic), whilst the other sub- unit(s) are hydrophilic whilst in aqueous media. In this case, the block copolymer may possess amphiphilic properties and may form a structure that mimics a biological membrane. The block copolymer may be a diblock (consisting of two monomer sub- units), but may also be constructed from more than two monomer sub-units to form more complex arrangements that behave as amphipiles. The copolymer may be a triblock, tetrablock or pentablock copolymer. In some embodiments, the membrane is one of the membranes disclosed in International Application No. WO2014 / 064443 or WO2014 / 064444. The amphiphilic molecules may be chemically-modified or functionalised to facilitate coupling of the polynucleotide. The amphiphilic layer may be a monolayer or a bilayer. The amphiphilic layer is typically planar. The amphiphilic layer may be curved. The amphiphilic layer may be supported. Amphiphilic membranes are typically naturally mobile, essentially acting as two dimensional fluids with lipid diffusion rates of approximately 10-8cm s-1. This means that the pore and coupled polynucleotide can typically move within an amphiphilic membrane. The membrane may be a lipid bilayer. Lipid bilayers are models of cell membranes and serve as excellent platforms for a range of experimental studies. For example, lipid bilayers can be used for in vitro investigation of membrane proteins by single-channel recording. Alternatively, lipid bilayers can be used as biosensors to detect the presence of a range of substances. The lipid bilayer may be any lipid bilayer. Suitable lipid bilayers include, but are not limited to, a planar lipid bilayer, a supported bilayer or a liposome. The lipid bilayer is typically a planar lipid bilayer. Suitable lipid bilayers are disclosed in WO 2008 / 102121, WO 2009 / 077734 and WO 2006 / 100484. In another embodiment, the membrane comprises a solid state layer. Solid state layers can be formed from both organic and inorganic materials including, but not limited to, microelectronic materials, insulating materials such as Si3N4, A12O3, and SiO, organic and inorganic polymers such as polyamide, plastics such as Teflon® or elastomers such as two-component addition-cure silicone rubber, and glasses. The solid state layer may be formed from graphene. Suitable graphene layers are disclosed in WO 2009 / 035647. If the membrane comprises a solid state layer, the pore is typically present in an amphiphilic membrane or layer contained within the solid state layer, for instance within a hole, well, gap, channel, trench or slit within the solid state layer. The skilled person can prepare suitable solid state / amphiphilic hybrid systems. Suitable systems are disclosed in WO 2009 / 020682 and WO 2012 / 005857. Any of the amphiphilic membranes or layers discussed above may be used. The methods disclosed herein are typically carried out using (i) an artificial amphiphilic layer comprising a pore, (ii) an isolated, naturally-occurring lipid bilayer comprising a pore, or (iii) a cell having a pore inserted therein. The methods are typically carried out using an artificial amphiphilic layer, such as a di- or tri-block copolymer layer. The layer may comprise other transmembrane and / or intramembrane proteins as well as other molecules in addition to the pore. Suitable apparatus and conditions are discussed below. The disclosed methods are typically carried out in vitro. Conditions The disclosed methods may be carried out using any apparatus that is suitable for investigating a membrane / pore system in which a pore is inserted into a membrane. The characterisation method may be carried out using any apparatus that is suitable for transmembrane pore sensing. For example, the apparatus may comprise a chamber comprising an aqueous solution and a barrier that separates the chamber into two sections. The barrier may have an aperture in which a membrane containing a transmembrane pore is formed. Transmembrane pores are described herein. The characterisation methods may be carried out using the apparatus described in WO 2008 / 102120, WO 2010 / 122293 or WO 00 / 28312. The characterisation methods may comprise optical measurements, for example such as described in WO 2016 / 009180 and WO 2021 / 198695. The characterisation methods may involve measuring the ion current flow through the pore, typically by measurement of a current. Alternatively, the ion flow through the pore may be measured optically, such as disclosed by Heron et al: J. Am. Chem. Soc.9 Vol.131, No.5, 2009. Therefore the apparatus may also comprise an electrical circuit capable of applying a potential and measuring an electrical signal across the membrane and pore. The characterisation methods may be carried out using a patch clamp or a voltage clamp. The characterisation methods typically involve the use of a voltage clamp. The characterisation methods may be carried out on a silicon-based array of wells where each array comprises 128, 256, 512, 1024, 2000, 3000, 4000, 6000, 10000, 12000, 15000 or more wells. The characterisation methods may involve the measuring of a current flowing through the pore. The method is typically carried out with a voltage applied across the membrane and pore. The voltage used is typically from +2 V to -2 V, typically -400 mV to +400mV. The voltage used is typically in a range having a lower limit selected from -400 mV, -300 mV, -200 mV, -150 mV, -100 mV, -50 mV, -20mV and 0 mV and an upper limit independently selected from +10 mV, + 20 mV, +50 mV, +100 mV, +150 mV, +200 mV, +300 mV and +400 mV. The voltage used is more typically in the range 100 mV to 240mV and most typically in the range of 120 mV to 220 mV. It is possible to increase discrimination between different nucleotides by a pore by using an increased applied potential. The characterisation methods are typically carried out in the presence of any charge carriers, such as metal salts, for example alkali metal salts, halide salts, for example chloride salts, such as alkali metal chloride salt. Charge carriers may include ionic liquids or organic salts, for example tetramethyl ammonium chloride, trimethylphenyl ammonium chloride, phenyltrimethyl ammonium chloride, or 1-ethyl-3-methyl imidazolium chloride. In the exemplary apparatus discussed above, the salt is present in the aqueous solution in the chamber. Potassium chloride (KCl), sodium chloride (NaCl) or caesium chloride (CsCl) is typically used. KCl is typical. The salt may be an alkaline earth metal salt such as calcium chloride (CaCl2). The salt concentration may be at saturation. The salt concentration may be 3M or lower and is typically from 0.1 to 2.5 M, from 0.3 to 1.9 M, from 0.5 to 1.8 M, from 0.7 to 1.7 M, from 0.9 to 1.6 M or from 1 M to 1.4 M. The salt concentration is typically from 150 mM to 1 M. The characterisation method may be carried out using a salt concentration of at least 0.3 M, such as at least 0.4 M, at least 0.5 M, at least 0.6 M, at least 0.8 M, at least 1.0 M, at least 1.5 M, at least 2.0 M, at least 2.5 M or at least 3.0 M. High salt concentrations provide a high signal to noise ratio and allow for currents indicative of binding / no binding to be identified against the background of normal current fluctuations. The characterisation methods are typically carried out in the presence of a buffer. In the exemplary apparatus discussed above, the buffer is present in the aqueous solution in the chamber. Any suitable buffer may be used. Typically, the buffer is HEPES. Another suitable buffer is Tris-HCl buffer. The methods are typically carried out at a pH of from 4.0 to 12.0, from 4.5 to 10.0, from 5.0 to 9.0, from 5.5 to 8.8, from 6.0 to 8.7 or from 7.0 to 8.8 or 7.5 to 8.5. The pH used may be about 7.5. The characterisation methods may be carried out at from 0oC to 100oC, from 15oC to 95oC, from 16oC to 90oC, from 17oC to 85oC, from 18oC to 80oC, 19oC to 70oC, or from 20oC to 60oC. The characterisation methods are typically carried out at room temperature. The characterisation methods are optionally carried out at a temperature that supports enzyme function, such as about 37oC. Further aspects In one embodiment, also provided herein is a barcode or library comprising a plurality of barcodes as described herein. Also provided is a library comprising a plurality of constructs each comprising a peptide, polypeptide or protein and a barcode as described herein. In some embodiments said constructs each comprise (i) a peptide, polypeptide or protein portion as described herein; a barcode as described herein; a purification tag as described herein and a cleavage site as described herein between the peptide, polypeptide or protein and the barcode. In some embodiments said constructs further comprise a second cleavage site between the barcode and the purification tag. Also provided is a system, comprising a library as described herein, and a nanopore. Further provided is a system, comprising one or more barcodes as described herein; and a nanopore. In some embodiments the nanopore is as described herein. In some embodiments the system further comprises a motor protein capable of controlling the movement of the barcodes in the library with respect to the nanopore. In some embodiments the system comprises computing means configured to detect information characteristic of the barcodes in the library and to selectively process the signal obtained as said barcodes move with respect to the nanopore. In some embodiments the system comprises receiving means for receiving data from detection of the barcode, processing means for processing the signal obtained as the barcode moves with respect to the nanopore, and output means for outputting the characterisation information thus obtained. Also provided is a kit comprising a construct comprising a peptide, polypeptide or protein attached to a peptide barcode; wherein the construct comprises a first cleavage site at the N- terminal of the barcode and a second cleavage site at the C-terminal of the barcode; and wherein the first and / or second cleavage site(s) are configured to generate when cleaved one or more reactive functional groups at the N- and / or C- terminus of the barcode; and one or more sequencing adapters capable of binding to said one or more reactive functional groups. Also provided is a kit comprising a construct comprising a peptide, polypeptide or protein attached to a peptide barcode; wherein the construct comprises a first cleavage site at the N- terminal of the barcode and a second cleavage site at the C-terminal of the barcode; and wherein the first and / or second cleavage site(s) are configured to generate when cleaved one or more reactive functional groups at the N- and / or C- terminus of the barcode; and a protease capable of selectively cleaving the construct at said cleavage sites, wherein said cleavage sites each comprise a recognition sites for said protease. In some embodiments the kits provided herein further comprise a nanopore as described herein. In some embodiments the nanopore is present in an array comprising a plurality of nanopores in a membrane. In some embodiments the kits provided herein further comprise a motor protein capable of controlling the movement of the barcode with respect to a nanopore. Also provided is a kit comprising a nanopore as described herein and instructions for preparing constructs comprising barcodes and / or barcode tags as described herein. The kit may further comprise one or more sequencing adapters as described herein and / or one or more reagents for cleaving the barcode from the construct and / or for cleaving a purification tag from the barcode. It is to be understood that although particular embodiments, specific configurations as well as materials and / or molecules, have been discussed herein for methods according to the present invention, various changes or modifications in form and detail may be made without departing from the scope and spirit of this invention. The preceding embodiments and following examples are provided for illustration only, and should not be considered limiting the application. The application is limited only by the claims. EXAMPLES EXAMPLE 1 Generation of Barcoded Proteins Five example constructs according to the present disclosure are designed. Each example construct features Green Fluorescent Protein (GFP) fused to a barcode tag comprising one of five different peptide barcodes (SEQ ID NOs 1-5), producing barcoded GFP constructs (SEQ ID NOs 6-10). Each construct has the following form: P – L – Z1 – W – Z2 – B wherein P is GFP; L is a linker sequence as described herein; Z1is a TEV protease cleavage site; W is a poly-histidine affinity purification tag; Z2 is a trypsin cleavage site comprising arginine; and B is the barcode. Plasmid DNA encoding the barcoded GFP constructs (SEQ ID NOs: 6-10) under the control of the T7 promoter is expressed by autoinduction in E. coli Bl21 (DE3) cells. The expressed barcoded GFP constructs are purified by immobilised metal affinity chromatography (IMAC). Protein eluted from the IMAC resin is exchanged into 50 mM Tris pH 8.0, 5 mM NaCl using a 10 kDa MWCO spin concentrator by repeated concentration and dilution. Preparation of barcodes for nanopore electrophysiology Barcode tags are removed from the tagged GFP proteins by site-specific proteolysis using a TEV protease and uncleaved proteins are removed from the sample by ultrafiltration. Barcode tags are immobilised on a NEBExpress Ni Spin Column (New England Biolabs). Immobilised barcode tags are then modified to introduce a methyltetrazine group at the C-terminal lysine using NHS-methyltetrazine. Oligonucleotides corresponding to SEQ ID NOs: 11 and 12 are subsequently annealed to the barcode tags by heating and then cooling, designated as Oligo 11 / 12. The methyltetrazine moiety on the immobilised barcode tags is modified with Oligo 11 / 12, possessing a cognate TCO group. Peptide barcodes are removed from resin by cleavage with trypsin and purified by centrifugation. Peptide barcodes are immobilised on SPRI beads and modified with NHS-PEG3- Azide to introduce an Azide group at the N-terminus of the peptide barcode. Unreacted NHS-PEG3-Azide is removed by washing with HEPES buffer. Oligonucleotides corresponding to SEQ ID NOs: 13 and 14 are annealed by heating and then cooling, designated as Oligo 13 / 14. The azide moiety on the immobilised peptide barcodes is modified with Oligo 13 / 14, possessing a cognate BCN group. The immobilised peptide barcodes are subsequently eluted from the beads. Peptide barcodes are ligated to a DNA strand as shown in SEQ ID NO: 15, and Native Barcode and Native Adapter taken from a SQK-NBD114.24 kit from Oxford Nanopore Technologies using Blunt / TA Ligase Master Mix (New England Biolabs). Ligation reactions are then purified using AMPure XP (Beckman), beads are washed with Short fragment buffer (SFB; Oxford Nanopore Technologies) and ligated material is eluted in HEPES buffer. Characterisation of peptide barcodes Analytes prepared for nanopore characterisation are prepared in sequencing buffer (Oxford Nanopore Technologies). Analytes are then loaded onto a FLO-MIN114 flow cell (Oxford Nanopore Technologies) configured to acquire data with applied potential of -200 mV, data acquisition frequency of 1.5 kHz, 21°C, with global flicks every 5 minutes. Data acquisition is performed on a GridION device. EXAMPLE 2 Preparation of barcoded proteins Constructs were designed featuring GFP (SEQ ID NO: 135) genetically fused at its C-terminus to a barcode tag (SEQ ID NO: 136).20 different variants were prepared with different barcode sequences (SEQ ID 137-156) by overexpression in E. coli BL21(DE3) and subsequent purification by IMAC. Library Preparation Proteins were diluted into a guanidine buffer to give a final concentration of 0.1-1 µM, proteins were denatured by boiling and then cooled on ice. Proteins were modified with methyltetrazine-sulfo-NHS ester solution, to introduce a reactive handle onto lysines within the proteins, followed by buffer exchange into a phosphate buffered saline using 7K MWCO Zeba spin columns according to manufacturer’s instructions. The proteins were then treated with TEV-protease to cleave off the barcode tags. PureCube Ni-NTA Agarose (Cube Biotech) was prepared according to manufacturer’s instructions and placed in an empty polypropylene spin column. Beads were washed with phosphate buffered saline and then the TEV-digested sample was applied to the beads. The sample was allowed to equilibrate for 10 minutes, the unbound material was then removed by centrifugation. Beads were then washed with a HEPES buffer to ensure all unbound material was removed. The barcode tags were then modified using click chemistry, labelling the methyltetrazine attached to the lysine in the barcode with a DNA duplex composed of SEQ ID NO: 157 and SEQ ID NO: 158. The beads were then washed with phosphate buffered saline supplemented with 5 mM imidazole. The DNA-modified barcode tag was then eluted with phosphate buffered saline supplemented with 500 mM imidazole. The DNA-modified barcode tag was purified by SPRI using AMPure XP beads. Samples were eluted in a HEPES buffer and subsequently diluted into reaction buffer and digested with Trypsin (NEB) according to manufacturer’s instructions to liberate the protein barcodes. The digested samples were applied to IMAC agarose beads equilibrated with phosphate buffered saline to remove uncleaved barcode tags, the unbound material was retained. Protein barcodes were immobilised onto AMPure XP beads. Beads were washed with 75% ethanol followed by a HEPES buffer supplemented with 2.5M NaCl and 28% PEG 6000. The N-termini of the peptides were activated with azidoacetic acid NHS ester. Beads were subsequently washed with 75% ethanol followed HEPES buffer supplemented with 2.5M NaCl and 28% PEG 6000. Protein barcodes were then modified at the N- terminus using click chemistry with a DNA duplex composed of SEQ ID NO: 159 and SEQ ID NO: 160 to form a DNA-peptide-DNA conjugate. Peptide-DNA conjugates were immobilised on Dynabeads™ MyOne™ Streptavidin C1 (ThermoFisher Scientific) according to manufacturer’s instructions. Beads were washed with a HEPES buffer. Peptide-DNA conjugates were then eluted by digestion with USER (NEB).. Peptide-DNA conjugates were then ligated to sequencing adapters taken from an SQK-NBD114 kit (Oxford Nanopore Technologies) as per manufacturer’s instructions. Constructs were then purified using AMPure XP beads as before. Data were collected on a GridION nanopore sequencing device (Oxford Nanopore Technologies using custom flow cells. Example traces are shown in Figure 2. Recall of protein ratios Four C-terminally barcoded GFP proteins were prepared, with different protein barcodes. The proteins were combined in 1:1:1:1 and 100:10:10:1 ratios and subjected to library preparation as described above. Data were collected on a PromethION nanopore sequencing device (Oxford Nanopore Technologies) using custom flow cells. The identity of the peptides was inferred using a machine learning model that was trained on peptides of the same composition. The data was filtered (Q-score >10) which removed low confidence calls, and counts correction applied to adjust for any model errors. The results are shown in Figure 3. SEQUENCE LISTING SEQ Sequence ID NO: 1 YDDDDK 2 VDDDDK 3 SDDDDK 4 QDDDDK 5 DMDDDK 6 mskgeelftgvvpilveldgdvnghkfsvrgegegdatngkltlkficttgklpvpwptl vttltygvqcfsrypdhmkrhdffksampegyvqertisfkddgtyktraevkfegdtlv nrielkgidfkedgnilghkleynfnshnvyitadkqkngikanfkirhnvedgsvqlad hyqqntpigdgpvllpdnhylstqsvlskdpnekrdhmvllefvtaagithgmdelykSS GSGENLYFQSSGHHHHHHRYDDDDK 7 mskgeelftgvvpilveldgdvnghkfsvrgegegdatngkltlkficttgklpvpwptl vttltygvqcfsrypdhmkrhdffksampegyvqertisfkddgtyktraevkfegdtlv nrielkgidfkedgnilghkleynfnshnvyitadkqkngikanfkirhnvedgsvqlad hyqqntpigdgpvllpdnhylstqsvlskdpnekrdhmvllefvtaagithgmdelykSS GSGENLYFQSSGHHHHHHRVDDDDK 8 mskgeelftgvvpilveldgdvnghkfsvrgegegdatngkltlkficttgklpvpwptl vttltygvqcfsrypdhmkrhdffksampegyvqertisfkddgtyktraevkfegdtlv nrielkgidfkedgnilghkleynfnshnvyitadkqkngikanfkirhnvedgsvqlad hyqqntpigdgpvllpdnhylstqsvlskdpnekrdhmvllefvtaagithgmdelykSS GSGENLYFQSSGHHHHHHRSDDDDK 9 mskgeelftgvvpilveldgdvnghkfsvrgegegdatngkltlkficttgklpvpwptl vttltygvqcfsrypdhmkrhdffksampegyvqertisfkddgtyktraevkfegdtlv nrielkgidfkedgnilghkleynfnshnvyitadkqkngikanfkirhnvedgsvqlad hyqqntpigdgpvllpdnhylstqsvlskdpnekrdhmvllefvtaagithgmdelykSS GSGENLYFQSSGHHHHHHRQDDDDK 10 mskgeelftgvvpilveldgdvnghkfsvrgegegdatngkltlkficttgklpvpwptl vttltygvqcfsrypdhmkrhdffksampegyvqertisfkddgtyktraevkfegdtlv nrielkgidfkedgnilghkleynfnshnvyitadkqkngikanfkirhnvedgsvqlad hyqqntpigdgpvllpdnhylstqsvlskdpnekrdhmvllefvtaagithgmdelykSS GSGENLYFQSSGHHHHHHRDMDDDK 11 PGCACACCTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT3 where P is a 5’ phosphate; 3 is a 3’ amino c3 labelled with TCO 12 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAGGTGTGCTATCCT6CA52 where 2 = 3’ Biotin TEG; 5 = HEG spacer; 6 = deoxyuridine 13 2TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTGGG where 2 = 5’ amino C3 labelled with BCN 14 CCCAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA 5 atg cat gat gag gag gtt aac ggtt gtttctgttg gtgctgatat tgcttttgat gccgacccta aattttttgc ctgtttggtt cgctttgagt cttcttcggt tccgactacc ctcccgactg cctatgatgt ttatcctttg Gatggtcgcc atgatggtgg ttattatacc gtcaaggact gtgtgactat tgacgtcctt ccccgtacgc cgggcaataa Tgtttatgtt ggtttcatgg tttggtctaa ctttaccgct actaaatgcc gcggattggt ttcgctgaat caggttatta aagagattat ttgtctccag ccacttaagt gaggtgattt atgtttggtg ctattgctgg cggtattgct tctgctcttg ctggtggcgc catgtctaaa ttgtttggag gcggtc gag acc gtt aac atc atg cat Where the 3’ of the top strand has a AGGATA overhang and 3’ end of the bottom strand has an A overhang SEQ ID NO: 16– Trwc Cba helicaseMLSVANVRSPSAAASYFASDNYYASADADRSGQWIGDGAKRLGLEGKVEARAFDALLRGE LPDGSSVGNPGQAHRPGTDLTFSVPKSWSLLALVGKDERIIAAYREAVVEALHWAEKNAA ETRVVEKGMVVTQATGNLAIGLFQHDTNRNQEPNLHFHAVIANVTQGKDGKWRTLKNDRL WQLNTTLNSIAMARFRVAVEKLGYEPGPVLKHGNFEARGISREQVMAFSTRRKEVLEARR GPGLDAGRIAALDTRASKEGIEDRATLSKQWSEAAQSIGLDLKPLVDRARTKALGQGMEA TRIGSLVERGRAWLSRFAAHVRGDPADPLVPPSVLKQDRQTIAAAQAVASAVRHLSQREA AFERTALYKAALDFGLPTTIADVEKRTRALVRSGDLIAGKGEHKGWLASRDAVVTEQRIL SEVAAGKGDSSPAITPQKAAASVQAAALTGQGFRLNEGQLAAARLILISKDRTIAVQGIA GAGKSSVLKPVAEVLRDEGHPVIGLAIQNTLVQMLERDTGIGSQTLARFLGGWNKLLDDP GNVALRAEAQASLKDHVLVLDEASMVSNEDKEKLVRLANLAGVHRLVLIGDRKQLGAVDA GKPFALLQRAGIARAEMATNLRARDPVVREAQAAAQAGDVRKALRHLKSHTVEARGDGAQ VAAETWLALDKETRARTSIYASGRAIRSAVNAAVQQGLLASREIGPAKMKLEVLDRVNTT REELRHLPAYRAGRVLEVSRKQQALGLFIGEYRVIGQDRKGKLVEVEDKRGKRFRFDPAR IRAGKGDDNLTLLEPRKLEIHEGDRIRWTRNDHRRGLFNADQARVVEIANGKVTFETSKG DLVELKKDDPMLKRIDLAYALNVHMAQGLTSDRGIAVMDSRERNLSNQKTFLVTVTRLRD HLTLVVDSADKLGAAVARNKGEKASAIEVTGSVKPTATKGSGVDQPKSVEANKAEKELTR SKSKTLDFGI SEQ ID NO: 17 - Hel308 Mbu helicase MMIRELDIPRDIIGFYEDSGIKELYPPQAEAIEMGLLEKKNLLAAIPTASGKTLLAELAM IKAIREGGKALYIVPLRALASEKFERFKELAPFGIKVGISTGDLDSRADWLGVNDIIVAT SEKTDSLLRNGTSWMDEITTVVVDEIHLLDSKNRGPTLEVTITKLMRLNPDVQVVALSAT VGNAREMADWLGAALVLSEWRPTDLHEGVLFGDAINFPGSQKKIDRLEKDDAVNLVLDTI KAEGQCLVFESSRRNCAGFAKTASSKVAKILDNDIMIKLAGIAEEVESTGETDTAIVLAN CIRKGVAFHHAGLNSNHRKLVENGFRQNLIKVISSTPTLAAGLNLPARRVIIRSYRRFDS NFGMQPIPVLEYKQMAGRAGRPHLDPYGESVLLAKTYDEFAQLMENYVEADAEDIWSKLG TENALRTHVLSTIVNGFASTRQELFDFFGATFFAYQQDKWMLEEVINDCLEFLIDKAMVS ETEDIEDASKLFLRGTRLGSLVSMLYIDPLSGSKIVDGFKDIGKSTGGNMGSLEDDKGDD ITVTDMTLLHLVCSTPDMRQLYLRNTDYTIVNEYIVAHSDEFHEIPDKLKETDYEWFMGE VKTAMLLEEWVTEVSAEDITRHFNVGEGDIHALADTSEWLMHAAAKLAELLGVEYSSHAY SLEKRIRYGSGLDLMELVGIRGVGRVRARKLYNAGFVSVAKLKGADISVLSKLVGPKVAY NILSGIGVRVNDKHFNSAPISSNTLDTLLDKNQKTFNDFQ SEQ ID NO: 18 - Dda helicase MTFDDLTEGQKNAFNIVMKAIKEKKHHVTINGPAGTGKTTLTKFIIEALISTGETGIILA APTHAAKKILSKLSGKEASTIHSILKINPVTYEENVLFEQKEVPDLAKCRVLICDEVSMY DRKLFKILLSTIPPWCTIIGIGDNKQIRPVDPGENTAYISPFFTHKDFYQCELTEVKRSN APIIDVATDVRNGKWIYDKVVDGHGVRGFTGDTALRDFMVNYFSIVKSLDDLFENRVMAF TNKSVDKLNSIIRKKIFETDKDFIVGEIIVMQEPLFKTYKIDGKPVSEIIFNNGQLVRII EAEYTSTFVKARGVPGEYLIRHWDLTVETYGDDEYYREKIKIISSDEELYKFNLFLGKTA ETYKNWNKGGKAPWSDFWDAKSQFSKVKALPASTFHKAQGMSVDRAFIYTPCIHYADVEL AQQLLYVGVTRGRYDVFYV SEQ Sequence ID NO135 mskgeelftgvvpilveldgdvnghkfsvrgegegdatngkltlkficttgklpvpwptlvttltygvqcfsrypdhmkrhdffksampegyvqertisfkddgtyktraev kfegdtlvnrielkgidfkedgnilghkleynfnshnvyitadkqkngikanfkir hnvedgsvqladhyqqntpigdgpvllpdnhylstqsvlskdpnekrdhmvllefv taagithgmdelyk136 SSGSGENLYFQSSGHHHHHHRXXXXXKWhere the barcode sequence is underlined, the sequence of X is dependent on which barcode is chosen.137 EDDDDK138 DDDDDK139 DFDDDK140 DDYDDK141 DDLDDK142 DSDDDK143 DQDDDK144 HDDDDK145 FDDDDK146 DNDDDK147 DHDDDK148 DLDDDK149 LDDDDK150 IDDDDK151 MDDDDK152 ADDDDK153 NDDDDK154 QDDDDK155 SDDDDK156 YDDDDK157 X-CAUGCGCTGAAGGTTAANNNNNNNNNNNNNNNNNNTCCGAACAGCACCTAATTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT-Y Where X is Biotin, U is deoxyuridine, and Y is amino C3spacer labelled with TCO Where the underlined sequence is a variable DNA sequence corresponding to a DNA barcode from the SQK-NBD114 kit (Oxford Nanopore Technologies)158 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAATTAGGTGCTGTTCGGANNNNNNNNNNNNNNNNNNTTAACCTTCAGCGCAGCAAT Where the underlined sequence is a variable DNA sequence corresponding to a DNA barcode from the SQK-NBD114 kit (Oxford Nanopore Technologies)159 X-Y-TTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTTCCCGGGTTTAATTTWhere X is BCN (bicyclo[6.1.0]nonyne) and Y is an amino C3 spacer160 AAATTAAACCCGGGAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

Claims

CLAIMS 1. A method of characterising a peptide, polypeptide or protein, the method comprising a) contacting a construct comprising the peptide, polypeptide or protein attached to a barcode with one or more process conditions capable of cleaving the peptide, polypeptide or protein from the attached barcode, thereby cleaving the peptide, polypeptide or protein from the barcode; b) contacting the cleaved barcode with a nanopore under conditions such that the barcode moves with respect to the nanopore; and c) taking one or more measurements characteristic of the barcode as the barcode moves with respect to the nanopore, thereby determining one or more properties of the barcode; wherein said one or more properties of the barcode are characteristic of one or more characteristics of the peptide, polypeptide or protein; thereby characterising the peptide, polypeptide or protein.

2. A method of characterising a peptide, polypeptide or protein, the method comprising a) contacting a construct comprising the peptide, polypeptide or protein attached to a barcode with one or more process conditions capable of cleaving the peptide, polypeptide or protein from the attached barcode, thereby cleaving the peptide, polypeptide or protein from the barcode; b) contacting the cleaved barcode with a nanopore under conditions such that the barcode moves with respect to the nanopore; and c) taking one or more measurements characteristic of the barcode as the barcode moves with respect to the nanopore, thereby determining one or more properties of the barcode; d) associating said one or more properties of the barcode with one or more characteristics of the peptide, polypeptide or protein; thereby characterising the peptide, polypeptide or protein.

3. A method according to claim 1 or 2, wherein the barcode is a peptide barcode.

4. A method according to any one of the preceding claims, wherein the barcode is not comprised in the amino acid sequence of the peptide, polypeptide or protein being characterised.

5. A method according to any one of the preceding claims, wherein the barcode comprises an oligopeptide comprising from about 3 to about 20 amino acids and / or amino acid analogs; optionally from about 5 to about 10 amino acids and / or amino acid analogs; 6. A method according to any one of the preceding claims, wherein the peptide, polypeptide or protein is at least about 30 amino acids in length.

7. A method according to any one of the preceding claims, wherein the barcode has a net charge; optionally wherein the barcode has a net negative charge.

8. A method according to any one of the preceding claims, wherein step (a) comprises: (a1) producing a construct comprising a peptide, polypeptide or protein attached to a barcode; and (a2) contacting the construct with one or more process conditions capable of cleaving the peptide, polypeptide or protein from the barcode.

9. A method according to any one of the preceding claims, wherein step (a1) comprises expressing the peptide, polypeptide or protein under conditions that the peptide, polypeptide or protein is expressed with an attached barcode.

10. A method according to any one of the preceding claims, wherein the peptide, polypeptide or protein is expressed from a genetic construct comprising a polynucleotide sequence encoding the peptide, polypeptide or protein and a polynucleotide sequence encoding the barcode.

11. A method according to any one of claims 1 to 8, wherein step (a1) comprises attaching a barcode to the peptide, polypeptide or protein.

12. A method according to any one of the preceding claims, wherein the barcode is comprised in a barcode tag comprising the barcode and a purification tag.

13. A method according to claim 12, wherein step (a) further comprises purifying the construct using the purification tag.

14. A method according to claim 12 or 13, wherein the barcode tag comprises a cleavage site between the barcode and the purification tag.

15. A method according to any one of the preceding claims, wherein the construct comprises a cleavage site between the barcode and the peptide, polypeptide or protein.

16. A method according to any one of the preceding claims, wherein the construct comprises a first cleavage site at the N- terminal of the barcode and a second cleavage site at the C-terminal of the barcode; wherein the first and second cleavage sites may be the same or different.

17. A method according to claim 16, wherein the first and / or second cleavage sites comprise a protease recognition site.

18. A method according to claim 16 or 17, wherein the first and / or second cleavage sites comprise a lysine residue and wherein contacting the construct with the one or more process conditions capable of cleaving the peptide, polypeptide or protein from the barcode comprises contacting the construct with LysC or functional analog, fragment or variant thereof.

19. A method according to any one of the preceding claims, wherein each construct comprises a structure of the form: Nterm – P – Z1– B – Z2– W – Cterm Nterm – W – Z2– B – Z1– P – Cterm Nterm – P – Z1 – W – Z2 – B – Cterm, or Nterm – B – Z2– W – Z1– P – Cterm;wherein Nterm represents the N terminus of the construct; Cterm represents the C terminus of the construct; P represents the peptide, polypeptide or protein being characterised; B represents the barcode; W represents an amino acid sequence comprising a purification tag; optionally wherein W comprises a polyhistidine sequence; Z1 represents a first protease cleavage site; optionally wherein Z1 comprises a lysine residue; and Z2represents a second protease cleavage site; optionally wherein Z2comprises a lysine residue.

20. A method according to any one of the preceding claims, wherein each construct comprises a structure of the form: Nterm – P – Z1 – W – AA1 – B – Z2 – Cterm; or Nterm – AA1 – B – Z2 – W – Z1 – P – Cterm wherein Nterm represents the N terminus of the construct; Cterm represents the C terminus of the construct; P represents the peptide, polypeptide or protein being characterised; Z1represents a first protease cleavage site; optionally wherein Z1comprises a TEV protease cleavage site; W represents an amino acid sequence comprising a purification tag; optionally wherein W comprises a polyhistidine sequence; B represents the barcode; and AA1 represents an amino acid recognised by a protease; optionally wherein AA1 represents arginine or lysine; further optionally wherein AA1 represents arginine or lysine at the N-terminus of the barcode (B); Z2 represents a second protease cleavage site; optionally wherein Z2 comprises a lysine residue; further optionally wherein Z2corresponds to a lysine residue at the C-terminus of the barcode (B).

21. A method according to any one of the preceding claims, wherein step (b) comprises attaching the barcode to one or more sequencing adapters.

22. A method according to any one of the preceding claims, wherein cleaving the peptide, polypeptide or protein from the barcode generates one or more reactive functional groups at the N- and / or C- terminus of the barcode; and step (b) comprises attaching one or more sequencing adapters to said one or more reactive functional groups.

23. A method according to any one of the preceding claims, wherein step (b) comprises attaching one or more peptide handles to the one or more reactive functional groups, wherein each peptide handle comprises a reactive functional group for attaching to a sequencing adapter; and attaching a sequencing adapter to each peptide handle.

24. A method according to any one of the preceding claims, wherein step (b) comprises contacting the barcode and / or a sequencing adapter if present with a motor protein capable of controlling the movement of the barcode with a the nanopore.

25. A method according to any one of the preceding claims, wherein the peptide, polypeptide or protein is present in a sample comprising a plurality of different peptides, polypeptides and / or proteins, and the method comprises a) contacting a plurality of constructs each comprising a peptide, polypeptide or protein attached to a barcode with one or more process conditions capable of cleaving the peptide, polypeptide or proteins from the attached barcodes, thereby cleaving the peptide, polypeptide or protein from the barcodes, wherein in said constructs different peptide, polypeptide and / or protein sequences have different barcodes attached thereto; b) contacting the cleaved barcodes with one or more nanopores under conditions such that the barcodes move with respect to the nanopore(s); and c) taking one or more measurements characteristic of each barcode as the barcodes move with respect to the nanopore(s), thereby determining one or more properties of each barcode; wherein said one or more properties of each barcode are characteristic of one or more characteristics of the peptide, polypeptide or protein to which the barcode was attached in the construct.

26. A method according to claim 25, wherein said different barcodes have different sequences each comprising a portion having a common sequence and a portion having a variable sequence.

27. A method according to any one of the preceding claims, wherein the one or more characteristics of the peptide, polypeptide or protein comprise the presence, absence, concentration or relative abundance of the peptide, polypeptide or protein in a sample; the length of the peptide, polypeptide or protein; the identity of the peptide, polypeptide or protein; the sequence of the peptide, polypeptide or protein; whether or not and / or the extent to which the peptide, polypeptide or protein is modified; and / or the whether or not and / or the extent to which the peptide, polypeptide or protein associates with a further peptide, polypeptide or protein wherein the further peptide, polypeptide or protein is optionally comprised in a construct as defined herein.

28. A kit comprising: - a construct comprising a peptide, polypeptide or protein attached to a peptide barcode; wherein the construct comprises a first cleavage site at the N- terminus of the barcode and a second cleavage site at the C-terminus of the barcode; and wherein the first and / or second cleavage site(s) are configured to generate when cleaved one or more reactive functional groups at the N- and / or C- terminus of the barcode; and a) one or more sequencing adapters capable of binding to said one or more reactive functional groups; and / or b) a protease capable of selectively cleaving the construct at said cleavage sites, wherein said cleavage sites each comprise a recognition site for said protease; and optionally further comprising - a nanopore, optionally present in an array comprising a plurality of nanopores in a membrane; and / or - a motor protein capable of controlling the movement of the barcode with respect to a nanopore.