Cleavable Probes for Isotope-Targeted Glycoproteomics
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Solution Overview
Problem
Current methods for analyzing intact glycopeptides by mass spectrometry are hindered by glycan heterogeneity and substoichiometric nature, leading to reduced detection and computational challenges, as they complicate the identification of glycosylation sites and biological function assessment.
Innovation Solution
A method involving isotopically-labelled peptides is developed, where a sample with a metabolically tagged protein is contacted with a cleavable probe to produce a probe-protein conjugate, separated, digested, and the linker is cleaved to release isotopically labelled peptides, allowing for identification of glycosylation sites through mass spectrometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If enzymatic digestion is used to reduce glycan heterogeneity, then glycosite analysis is advanced, but information correlating glycan structure to protein attachment site is destroyed
Solution Approach 1:
The method segments the analysis into two distinct parts: (1) enzymatic digestion to generate uniform glycosite-specific peptides for precise localization, and (2) separate intact glycopeptide analysis to preserve glycan structure information. This segmentation allows both goals to be achieved independently without interference.
Solution Approach 2:
The invention introduces an intermediary approach using isotope-coded tags that can be attached to proteins while preserving intact glycopeptide structures. These tags serve as mediators that enable tracking and identification without requiring glycan removal, thus preserving structural information while enabling precise analysis.
2Loss of information
If intact glycopeptides are analyzed by mass spectrometry, then glycan structure information is preserved, but detection is reduced due to glycan heterogeneity and substoichiometric nature
Solution Approach 1:
The method changes the isotopic composition parameters of the glycopeptides by incorporating isotope-coded labels during protein synthesis or chemical tagging. This parameter change creates distinct mass signatures that enhance detection sensitivity and allow differentiation of glycopeptides from background noise, directly addressing the detection sensitivity problem.
Solution Approach 2:
The invention performs preliminary action by incorporating isotope labels into the glycopeptides before mass spectrometry analysis. This pre-labeling ensures that even substoichiometric glycopeptides have enhanced detectability, allowing intact glycopeptide analysis to proceed with improved sensitivity while preserving structural information.
3Productivity
If database searches are used for peptide identification, then proteomics platforms can identify peptides, but nontemplated PTMs like glycosylation present significant computational challenges
Solution Approach 1:
The method applies local quality by making only the glycosylated peptides isotopically labeled while leaving the rest of the proteome unchanged. This localized modification allows database search algorithms to efficiently identify labeled glycopeptides using their unique isotopic patterns, reducing computational complexity compared to analyzing the entire glycoproteome without labeling.
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 method enhances the detection and identification of glycopeptides by reducing glycan heterogeneity and enabling precise determination of glycosylation sites and peptide sequences, facilitating the analysis of glycoprotein biosynthesis and biological function.
Implementation Method 1
Z and the metabolically tagged protein cross-link via copper-catalyzed azide-alkyne [3+2] cycloaddition to produce the probe-protein conjugate
Implementation Method 2
L is a cleavable silane linker
Data Source
AI summary
Methods for producing isotopically-labelled peptides are provided. Aspects of the method include: contacting a sample including a metabolically tagged protein with a cleavable probe to produce a probe-protein conjugate; separating the probe-protein conjugate from the sample; digesting the probe-protein conjugate to produce a probe-peptide conjugate; and cleaving a cleavable linker to release an isotopically labelled peptide. The method may further include: identifying a predetermined isotopic pattern in a mass spectrum; determining an amino acid sequence of the isotopically labelled peptide; and identifying the site of protein glycosylation based on the determined amino acid sequence. Also provided are cleavable probes for practicing the subject methods, described by the Formula: A-L-(M-Z) where A is an affinity tag, L is a cleavable linker, M is an isotopic label and Z is a chemoselective tag capable of cross-linking a metabolically tagged protein. Compositions and kits for practicing the subject methods are also provided.