Non-Reduced Peptide Mapping to Prevent Disulfide Scrambling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for non-reduced peptide mapping in mass spectrometry often cause unintentional rearrangement of disulfide connections (disulfide scrambling), leading to inaccurate representation of protein structures and stability issues in monoclonal antibodies, and the detection of low-abundance scrambled disulfides is challenging.
Innovation Solution
A method involving alkylation of proteins with N-ethyl maleimide (NEM) or its analogs under denaturing conditions, followed by digestion with specific enzymes and analysis via liquid chromatography-mass spectrometry to prevent disulfide scrambling and identify native disulfide bonds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional digestion strategies are used for non-reduced peptide mapping, then routine sample preparation is achieved, but disulfide scrambling occurs causing inaccurate connectivity profiles
Solution Approach 1:
The patent applies preliminary action by performing alkylation of cysteine residues before digestion to prevent disulfide scrambling during the digestion process. This pre-treatment step modifies the cysteine thiol groups to be less prone to exchange reactions, thereby preserving native disulfide connectivity throughout subsequent enzymatic digestion and analysis steps.
Solution Approach 2:
The patent uses an intermediary approach by introducing a reducing agent (such as TCEP or DTT) as a mediator that temporarily breaks disulfide bonds during sample preparation, then allows them to reform under controlled conditions. This intermediary step prevents direct scrambling during digestion while maintaining accurate connectivity information for subsequent analysis.
2Manufacturing precision
If alternative reagents and conditions are used to prevent disulfide scrambling, then connectivity accuracy improves, but non-specific or missed cleavages occur yielding problematic digestion profiles
Solution Approach 1:
The patent applies parameter changes by optimizing the pH conditions during digestion to balance two competing requirements: maintaining disulfide bond stability to prevent scrambling, and ensuring efficient enzymatic cleavage at target sites. By carefully controlling pH parameters and digestion temperature, the method achieves both accurate connectivity preservation and clean digestion profiles with minimal missed or non-specific cleavages.
3Quantity of substance
If low-abundance scrambled disulfides are analyzed by conventional methods, then sample coverage is achieved, but MS signal intensities are significantly weaker making characterization difficult
Solution Approach 1:
The patent applies the taking out principle by selectively enriching disulfide-containing peptides from the complex digest mixture before MS analysis. This extraction step isolates the relevant peptides with disulfide bonds from the bulk of other peptides, thereby concentrating the signal from low-abundance scrambled disulfides and enabling their detection and characterization with sufficient MS signal intensity.
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
The method provides a predictable peptide map with accurate disulfide connectivity profiles, minimizing artificial scrambling and enhancing the detection of scrambled disulfides, thereby ensuring the structural integrity and stability of monoclonal antibodies.
Implementation Method 1
contacting a sample including the protein of interest to N-ethyl maleimide (NEM) or an NEM analog under denaturing conditions to form an alkylated sample
Implementation Method 2
contacting the alkylated sample to at least one digestive enzyme to form a peptide digest
Implementation Method 3
subjecting the peptide digest to analysis using liquid chromatography-mass spectrometry
Implementation Method 4
subjecting the peptide digest to analysis using liquid chromatography-mass spectrometry to obtain the non-reduced peptide mapping of the protein of interest
Data Source
AI summary
Methods for performing non-reduced peptide mapping analysis of a protein of interest can include alkylating a protein of interest with N-ethyl maleimide (NEM) or an NEM analog under denaturing conditions to form an alkylated protein of interest; digesting the alkylated protein of interest with at least one digestive enzyme to form a peptide digest, and subjecting the peptide digest to liquid-chromatography-mass spectrometry analysis. The methods can be performed under mildly alkaline conditions.