C-Terminal Peptide Labeling for Isobaric Amino Acid Sequencing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing mass spectrometry methods struggle to distinguish isobaric amino acids such as Leucine and Isoleucine, as well as certain amino acid combinations, due to their identical masses, leading to sequencing uncertainties and increased primer requirements for recombinant protein generation.
Innovation Solution
A method involving the addition of a basic functional group at the C-terminal side of peptides, using coupling reagents to derivatize the C-terminal carboxylic acid function, allowing the detection of w ions for accurate differentiation between isobaric amino acids and combinations like I/L, GG, GA, and AG/Q.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mass spectrometry is used for peptide sequencing, then peptide sequence information can be obtained, but isobaric amino acids (Leucine and Isoleucine) and certain amino acid combinations cannot be distinguished due to identical masses
Solution Approach 1:
The patent uses C-terminal derivatization reagents as intermediaries that attach to the C-terminus of peptides. These derivatization agents introduce mass differences or spectral differences that allow distinction between isobaric amino acids (Leucine and Isoleucine) and certain amino acid combinations (Asparagine vs. Glycine-Glycine, Glutamine vs. Glycine-Alanine/Alanine-Glycine) that would otherwise have identical masses in standard mass spectrometry analysis
Solution Approach 2:
The patent changes the mass-to-charge ratio parameters by adding derivatization groups to the C-terminus of peptides. This parameter change creates distinguishable mass differences for previously isobaric amino acids, enabling their identification through mass spectrometry by altering the physical-chemical properties of the peptide molecules
2Reliability
If multiple gene primers are used to resolve isobaric amino acid uncertainties, then accurate protein sequencing can be achieved, but cost and time increase significantly
Solution Approach 1:
The patent applies C-terminal derivatization as a preliminary action before mass spectrometry analysis. By modifying the C-terminus with derivatization reagents that create distinguishable mass or spectral signatures, the method resolves isobaric amino acid ambiguities during the initial sequencing step, eliminating the need for subsequent confirmatory experiments with multiple gene primers and thereby reducing both time and cost
3Measurement precision
If C-terminal fragment ions are detected in mass spectrometry, then sequencing information is obtained, but detectability is poor for fragments without basic residues
Solution Approach 1:
The patent uses C-terminal derivatization reagents as intermediaries that attach to the C-terminus of peptide fragments. These derivatization agents enhance the ionization efficiency and detectability of C-terminal fragment ions, particularly for fragments lacking basic residues, by introducing functional groups that improve interaction with the mass spectrometer's ionization source and detector
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
Enhances the detection of C-terminal fragment ions, enabling precise identification of isobaric amino acids and resolving sequencing ambiguities, reducing the number of required gene primers and costs.
Implementation Method 1
reacting the obtained and/or generated peptides with a coupling reagent capable of derivatizing the free C-terminal carboxylic acid function of the peptides
Implementation Method 2
fragmenting the derivatized peptides in a mass spectrometer under conditions effective to generate at least w ions; detecting said w ions by mass spectrometry
Data Source
AI summary
A method for increasing peptide fragmentation by labelling the peptide at the C-terminal end with a guanidinium group or other basic functional group and distinguishing isobaric amino acids and amino acid combinations of asparagine and glycine-glycine; glutamine and glycine-alanine; and/or glutamine and alanine-glycine, during polypeptide sequencing. The method involves: obtaining a peptide of interest and/or digesting a polypeptide of interest with a protease, such as pepsin, chymotrypsin or trypsin, or by chemical cleavage to produce shorter peptides; reacting the obtained and/or generated peptides with a coupling reagent to derivatize the free C-terminal carboxylic acid function of the peptides, thus adding a basic functional group rendering C-terminal peptide fragment ions detectable by mass spectrometry; selecting a charge state of 2+ or more, and fragmenting the derivatized peptides in a mass spectrometer under conditions effective to generate at least w ions; and detecting the w ions by mass spectrometry, and identifying derivatized peptides which incorporate the additional mass of the basic functional group.