N-Terminal Derivatizing Compound for Peptide Sequencing
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Solution Overview
Problem
Current methods for protein sequencing and quantification, such as Edman degradation and tandem mass spectrometry, face challenges with purity requirements, time consumption, and reliability issues, particularly when analyzing peptides with lysine at the C-terminus or requiring quantification, due to over-reactivity and limitations in database dependence.
Innovation Solution
A compound for N-terminal substitution, specifically 12C-SPITC and 13C-SPITC, is used to derivatize peptides, allowing for simultaneous identification and quantification through mass spectrometry by creating isotopic differences that simplify spectra interpretation and enable de novo sequencing and relative quantification without database reliance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chlorosulfonylacetyl chloride is used to sulfonate the N-terminus of polypeptide, then b-type ions are neutralized and only y-type ions can be observed, but the reagent is over reactive with two reactive sites resulting in complex products
Solution Approach 1:
The patent extracts only the necessary reactive functionality from the original reagent system. By using a reagent with a single reactive site instead of two, the method eliminates unwanted side reactions while retaining the essential sulfonation capability needed to neutralize b-type ions and simplify spectra interpretation.
Solution Approach 2:
The patent applies local quality by ensuring the reagent has uniform reactivity at the reactive site. The sulfonation occurs specifically at the N-terminus amino group with consistent chemical behavior, avoiding the heterogeneous product distribution that arises from multiple reactive sites with different reactivities.
2Reliability
If conventional tandem MS method is used for protein identification, then database comparison can be performed, but results are not absolutely reliable as they depend on database correctness
Solution Approach 1:
The patent replaces the information-theoretic approach (database comparison) with a direct structural observation approach. By modifying the peptides to produce simplified, interpretable fragmentation patterns, the method enables direct de novo sequencing that does not rely on database matching, thereby substituting computational dependency with direct experimental observation.
3Reliability
If lysine modification reagent is used to protect epsilon amino groups, then sulfonation can be controlled, but additional pretreatment step causes significant peptide loss
Solution Approach 1:
The patent extracts only the essential protective function needed for controlled sulfonation while eliminating the requirement for separate pretreatment steps. The reagent system is designed to provide in-situ protection and sulfonation in a single操作流程, removing the intermediate step that causes peptide loss through handling and transfer operations.
Solution Approach 2:
The patent merges the protection and sulfonation steps into a single integrated reaction process. By combining these functions, the method eliminates the intermediate isolation and transfer steps that cause peptide loss, while still achieving the necessary control over sulfonation selectivity.
4Measurement precision
If Edman degradation is used for protein sequencing, then stepwise amino acid determination is possible, but the method is time consuming requiring 30 minutes to one hour per amino acid
Solution Approach 1:
The patent replaces the sequential, stepwise Edman degradation process with a parallel mass spectrometric analysis method. Instead of removing and analyzing one amino acid at a time over extended periods, the modified peptides undergo simultaneous fragmentation and analysis in the mass spectrometer, enabling complete sequence determination in a single experimental run.
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
This approach provides high reliability in protein identification and quantification, minimizing errors and sample loss, and is applicable to peptides with lysine, by using SPITC's selective reactivity and isotopic labeling to distinguish and quantify peptides efficiently.
Implementation Method 1
a compound that derivatizes the peptides by sulfonating their N-terminus
Implementation Method 2
analyzes samples ions according to their mass-to-charge ratios, fragments an ion of interest by kinetic collision with inert gas such as helium
Implementation Method 3
fragments an ion of interest by kinetic collision with inert gas such as helium
Implementation Method 4
creating isotopic differences that simplify spectra interpretation and enable de novo sequencing and relative quantification
Data Source
AI summary
The present invention relates to a compound for N-terminal substitution of polypeptides which is used in sequencing and quantifying amino acids and a method for sequencing and quantifying an amino acid sequence using the same. The method for sequencing and quantifying amino acids in accordance with the present invention leads to a relative quantitative analysis of proteins with very high reliability, and can distinctively discriminate between y-type ions and b-type ions on the MS/MS spectra, providing the means for realization of high-reliability protein identification.