Single-Molecule Peptide Sequencing in Complex Protein Mixtures
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Solution Overview
Problem
Current methods for sequencing peptides in complex mixtures are limited by the inability to sequence and identify individual peptides within a mixture, especially when the N-terminal amino acid is chemically modified or buried, and they cannot handle more than 50-60 amino acid residues, making high-throughput identification and quantitation of proteins in complex samples challenging.
Innovation Solution
A method involving selective labeling of amino acids on immobilized peptides with fluorescent labels, followed by successive cycles of Edman degradation and signal detection at the single molecule level, allowing for the identification and quantitation of individual peptides in a mixture, including those with unnatural amino acids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional peptide sequencing methods are used, then sequencing can be performed on purified peptides, but individual peptides cannot be identified within complex mixtures
Solution Approach 1:
The patent segments the complex mixture analysis into individual single-molecule sequencing events. Each peptide molecule is sequenced independently through multiple imaging cycles, with fluorescent labels on specific amino acids (like Lysine) providing segment-specific detection. This allows individual peptide identification within complex mixtures by treating each molecule separately rather than as a bulk sample.
Solution Approach 2:
The patent transitions from bulk chemical analysis to single-molecule optical detection, adding the dimension of spatial resolution. By using total internal reflection fluorescence microscopy, the system detects fluorescent signals from individual peptide molecules at the nanoscale, enabling identification of peptides in mixtures based on their unique fluorescent decay patterns across multiple imaging cycles.
2Measurement precision
If Edman degradation is used for sequencing, then N-terminal amino acids can be identified, but peptides with modified or buried N-termini cannot be sequenced
Solution Approach 1:
The patent extracts the sequencing capability from the N-terminal requirement by using internal amino acid labeling. Instead of relying on N-terminal accessibility, the method labels internal amino acids (such as Lysine residues) with fluorescent tags that remain detectable throughout Edman degradation cycles, allowing sequencing of peptides regardless of N-terminal modification or burial status.
Solution Approach 2:
The patent introduces fluorescent labels on internal amino acids as intermediaries for detection. These labels serve as mediators that provide detectable signals independent of N-terminal accessibility, allowing the sequencing process to proceed and be monitored through the behavior of these internal markers during degradation cycles.
3Productivity
If traditional sequencing methods are used, then peptide sequences can be identified, but high-throughput analysis of complex proteomes is not achievable
Solution Approach 1:
The patent merges multiple sequencing observations into a single integrated analysis framework. By simultaneously monitoring fluorescent decay patterns of multiple labeled peptides across multiple imaging cycles and combining these observations, the system achieves high-throughput identification of many peptides in parallel, dramatically increasing productivity compared to sequential analysis methods.
Solution Approach 2:
The patent employs periodic imaging cycles to accumulate sequencing data. Multiple rapid fluorescence images are captured in succession, with each cycle providing additional information about the peptide sequence based on label removal patterns. This periodic data collection enables high-throughput analysis by efficiently gathering information over time without requiring prolonged continuous observation of each individual peptide.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables rapid and accurate sequencing of intact peptides in complex mixtures, capable of identifying a majority of proteins from species like yeast and human proteomes, providing unique peptide sequences and enabling high-throughput analysis.
Implementation Method 1
selective labeling of amino acids on immobilized peptides with fluorescent labels, followed by successive cycles of Edman degradation and signal detection at the single molecule level
Data Source
AI summary
Methods of identifying a sequence of a polypeptide within a heterogenous mixture of polypeptides, the polypeptide being immobilized to a support and having at least one labeled amino acid residue. Methods involve detecting at least one signal or signal change from the immobilized polypeptide and subjecting the polypeptide to conditions sufficient to remove at least one amino acid residue from the polypeptide.