Double-Isotopic Labeling for Peptide Quantification Fragment Overlap
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Solution Overview
Problem
Current mass spectrometry methods, such as DIA and mPRM, face challenges in fragment overlap between unlabeled and labeled peptides, leading to incomplete quantification and data analysis complications due to shared fragments and fragment overlap issues, which limits the full potential of isotopic labeling in proteomics studies.
Innovation Solution
Introducing a second isotopic label at the N-terminus of peptides in addition to the existing C-terminal label, allowing for distinct fragment series and reducing overlap, enabling separate quantification and improved data analysis by distinguishing N-terminal and C-terminal fragments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single C-terminal isotopic label is used for peptide quantification, then the labeling process is simple and cost-effective, but fragment overlap occurs between N-terminal fragments of labeled and unlabeled peptides, leading to incomplete quantification
Solution Approach 1:
The patent applies local quality by placing isotopic labels at specific positions (N-terminus and C-terminus) of peptides rather than uniformly labeling all positions. This selective positioning ensures that N-terminal fragments carry the N-terminal label while C-terminal fragments carry the C-terminal label, preventing fragment overlap and enabling accurate quantification without requiring complete uniform labeling of the entire peptide.
Solution Approach 2:
The patent transitions from single-label to double-labeling strategy, adding an additional dimension of labeling information. By incorporating both N-terminal and C-terminal labels, the system creates distinct mass signatures for different fragment types, allowing differentiation between labeled and unlabeled fragments across multiple mass dimensions rather than relying on a single labeling approach.
2Quantity of substance
If combined fragment spectra are acquired for DIA and mPRM methods, then comprehensive peptide coverage is achieved, but fragment overlap between labeled and unlabeled peptides complicates data analysis and reduces quantification reliability
Solution Approach 1:
The patent uses local quality by strategically positioning isotopic labels at N- and C-terminal positions to create distinct fragment mass signatures. This localized labeling approach ensures that when combined fragment spectra are acquired, N-terminal fragments and C-terminal fragments from labeled peptides can be distinguished from unlabeled peptides based on their characteristic mass shifts, preventing analysis complications while maintaining comprehensive peptide coverage.
Solution Approach 2:
The patent applies parameter changes by modifying the mass-to-charge ratio parameters of fragment ions through strategic isotopic labeling. By introducing controlled mass shifts at specific positions, the system changes the detectable parameters of fragments in combined spectra, allowing reliable differentiation and quantification even when multiple precursors are fragmented simultaneously in DIA and mPRM methods.
3Measurement precision
If isotopically labeled amino acids are incorporated at both N- and C-termini, then distinct fragment series are achieved with reduced overlap, but the cost and complexity of peptide synthesis increase
Solution Approach 1:
The patent applies local quality by incorporating isotopically labeled amino acids only at specific terminal positions (N- and C-termini) rather than throughout the entire peptide sequence. This targeted approach creates distinct fragment signatures where N-terminal fragments carry the N-terminal label and C-terminal fragments carry the C-terminal label, achieving excellent fragment distinction capability while limiting the number of labeled positions to minimize synthesis complexity.
Solution Approach 2:
The patent uses partial action by implementing double-labeling only at the critical terminal positions that generate the most diagnostically useful fragments for quantification. This partial labeling strategy provides sufficient information for accurate quantification without the excessive complexity and cost of labeling all amino acid positions in the peptide, achieving an optimal balance between measurement precision and synthesis feasibility.
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 enhances the ability to quantify peptides by reducing fragment overlap, increasing the number of usable fragments for analysis, and improving peptide identification and quantification accuracy in proteomics studies, particularly in DIA and mPRM methods.
Implementation Method 1
the mass-to-charge (m/z) ratios of the fragments of a single precursor are detected
Data Source
AI summary
Methods for peptide and/or protein quantification by mass spectrometry using labeled peptides, wherein multiple labels lead to distinct fragments for the labeled peptides and their unlabeled variant, thus facilitating data analysis and enhancing the potential for quantification. Methods for selecting the label and label position are further given, as well as sets of labeled peptides resulting from or for use in the above-mentioned methods. The methods and substances are especially useful for data-independent or multiplexed parallel reaction monitoring proteomics applications involving peptide quantification.