31 results about "Electron-transfer dissociation" patented technology

A multiple function atmospheric pressure ion source interfaced to a mass spectrometer comprises multiple liquid inlet probes configured such that the sprays from two or more probes intersect in a mixing region. Gas phase sample ions or neutral species generated in the spray of one probe can react with reagent gas ions generated from one or more other probes by such ionization methods as Electrospray, photoionization, corona discharge and glow discharge ionization. Reagent ions may be optimally selected to promote such processes as Atmospheric Pressure Chemical Ionization of neutral sample molecules, or charge reduction or electron transfer dissociation of multiply charged sample ions. Selected neutral reagent species can also be introduced into the mixing region to promote charge reduction of multiply charged sample ions through ion-neutral reactions. Different operating modes can be performed alternately or simultaneously, and can be rapidly turned on and off under manual or software control.

A front-end reagent ion source for a mass spectrometer is disclosed. Reagent vapor is supplied to a reagent ionization volume located within a chamber of the mass spectrometer and maintained at a low vacuum pressure. Reagent ions are formed by interaction of the reagent vapor molecules with an electrical discharge (e.g., a glow discharge) within the ionization volume, and pass into the chamber of the mass spectrometer. At least one ion optical element located along the analyte ion path transports the reagent ions to successive chambers of the mass spectrometer. The reagent ions may be combined with the analyte ions to perform ion-ion studies such as electron transfer dissociation (ETD).

An in-source atmospheric pressure electron capture dissociation (AP-ECD) method and apparatus for mass spectrometric analysis of peptides and proteins. An electrified sprayer generates a multiply-charged peptide/protein ions from a sample solution, a source of electrons for negative reagents, and a flow of gas for guiding positively charged ions from the electrified sprayer to a downstream reaction region within the guide. The reaction region being at or near atmospheric pressure and substantially free of the electric field from the electrified sprayer. In another embodiment, the method uses electron transfer dissociation (ETD), in the event that anions are substituted for electrons as the negative reagents. Fragment ions exiting the reaction region are subsequently passed into a mass analyzer of a mass spectrometer for mass analysis of the ions.

The present invention provides methods for enhancing the fragmentation of peptides for mass spectrometry by modifying the peptides with a tagging reagent containing a functional group, such as a tertiary amine, having a greater gas-phase basicity than the amide backbone of the peptide. These high gas-phase basicity functional groups are attached to a peptide by reacting the tagging reagent to one or more available carboxylic acid groups of the peptide. Linking these high gas-phase functional groups to the peptides leads to higher charge state ions from electrospray ionization mass spectrometry (ESI-MS), which fragment more extensively during fragmentation techniques, particularly non-ergodic fragmentation techniques such as electron capture dissociation (ECD) and electron transfer dissociation (ETD).

The present invention is directed to methods of merging spectral data resulting from collision fragmentation processes, such as, for example, Pulsed Q Dissociation (PQD), high-energy collision-induced dissociation (HCD), electron transfer disassociation (ETD), collision-induced dissociation (CID), and photo-dissociation processes, such as, but not limited to, infrared multi-photon photo-dissociation (IRMPD), to provide the desired qualitative and quantitative information on a single peptide. By merging such ETD, CID, or IRMPD scans with corresponding HCD scans that are obtained on the same precursor, the quality of the resulting spectrum is increased so as to provide more confident identification of peptides and correspondingly the quantification is enhanced because the HCD method of the MS/MS spectrum produces higher abundances of detectable reporter ions. Such methods, as disclosed herein, are especially applicable for peptides which experience predominant neutral loss in the ion trap, e.g., phosphorylated.

The present invention relates to a new method for identifying polypeptides by deducing the amino acid sequence of the carboxy and amino termini by a mass spectrometer analysis. The method comprises the steps of dissociating highly charged peptide precursor ions (e.g., z > 4) using electron transfer dissociation inducing anions followed by removal of those reagents and introduction of a second, proton transfer inducing anion type. The second PTR reaction duration is adjusted to convert the ETD products to primarily the + 1 charge-state to reduce the highly charged c and z-type fragments, producing an m/z spectrum containing a series of c and z-type fragment ions that are easily interpreted to reveal the sequence of the amino and carboxy terminus, respectively.

A mass spectrometer is disclosed wherein highly charged fragment ions resulting from Electron Transfer Dissociation fragmentation of parent ions are reduced in charge state within a Proton Transfer Reaction cell by reacting the fragment ions with a neutral superbase reagent gas such as Octahydropyrimidolazepine.

The invention relates to the use of substances for the production of anions suitable for charge transfer reactions in mass spectrometers, particularly for the fragmentation of multiply positively charged biopolymer ions by electron transfer or for charge reduction by proton transfer. Diketones, particularly α-diketones, are proposed as a newly found class of substances which can be used both for the production of radical anions for electron transfer dissociations (ETD) with a high yield of fragment ions and also for the production of non-radical anions for the charge reduction of multiply charged analyte ions by proton transfer reactions (PTR). These substances have favorable properties in terms of their handling and the associated analytical methods: they are largely nontoxic, cover a favorable range of molecular masses, and their volatility means that they can be stored in unheated containers outside of the vacuum system, which facilitates the refilling of the containers.

A method is disclosed for operating a chemical ionization-type (CI-type) source to generate reagent ions for mass spectrometry experiments, such as electron transfer dissociation (ETD) reagent ions. The method includes periodically reversing current flow in the thermionic filament employed to produce the electron stream. Periodic reversal of the filament current avoids or reduces the problem of carbonaceous growth formation associated with prior art reagent ion sources.

The invention provides a method for preprocessing an electron transfer dissociation (ETD) mass spectrum, comprising the steps of: calculating a mass to charge ratio and a charge state of a parent ion; calculating the possible areas of a parent ion peak and isotopic peaks thereof in the ETD mass spectrum; calculating the possible areas of a series of derivative peaks of the parent ion in the ETD mass spectrum; calculating the possible areas of neutral lost peaks of the parent ion in the ETD mass spectrum; and removing the spectrum peaks in the calculated areas in the ETD mass spectrum so as to remove the non-fragmented parent ion peaks, the series of derivative peaks of the parent ion and the neutral lost peaks of the parent ion.

A mass spectrometer is disclosed comprising an Electron Transfer Dissociation device comprising an ion guide. A control system determines the degree of fragmentation and charge reduction of precursor ions within the ion guide and varies the speed at which ions are transmitted through the ion guide in order to optimise the fragmentation and charge reduction process.

A system and method is described for characterizing glycopeptides which includes a first quadrupole mass filter, a multipole rod set of an ion guide, a lens electrode, an ExD device and a mass analyzer. The multipole rod set is adapted to receive a radial radio frequency (RF) trapping voltage and a radial dipole direct current (DC) voltage. The lens electrode is adapted to receive an axial trapping alternating current (AC) voltage and a DC voltage. The ExD device performs electron capture dissociation or electron transfer dissociation, the ExD device being positioned so that an entrance of theExD device is disposed on the other side of the lens electrode opposite the multipole rod set. The mass analyzer is positioned at an exit of the ExD device for receiving ions from the ExD device.