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Determination of the Gas-phase Acidities of Oligopeptides
Published on: June 24, 2013
Sulfopeptide fragmentation in electron-capture and electron-transfer dissociation
K F Medzihradszky1, S Guan, D A Maltby
1Mass Spectrometry Facility, Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California 94143-0446, USA. folkl@cgl.ucsf.edu
Journal of the American Society for Mass Spectrometry
|July 17, 2007
Summary
Distinguishing sulfopeptides from phosphopeptides is crucial for understanding biological function. New fragmentation methods reveal SO(3) losses in electron capture dissociation, which can be reduced using peptide-alkali metal adducts.
Area of Science:
- Proteomics
- Mass Spectrometry
- Post-Translational Modifications
Background:
- Sulfopeptides and phosphopeptides are isobaric, leading to misidentification.
- Accurate mass measurement can distinguish them by mass defect.
- Site-specific modification assignment is essential for biological function studies.
Purpose of the Study:
- To investigate the fragmentation behavior of sulfopeptides under various dissociation conditions.
- To identify methods for improving the distinction between sulfo- and phosphopeptides.
- To enhance the site-specific analysis of O-sulfo modifications.
Main Methods:
- Collision-induced dissociation (CID) of O-sulfo- and O-phospho-peptides.
- Electron capture dissociation (ECD) and electron-transfer dissociation (ETD) experiments.
- Fragmentation of peptide-alkali metal adducts (sodiated, potassiated peptides).
Main Results:
- O-sulfo moieties exhibit distinct fragmentation behavior compared to O-phospho moieties.
- Neutral SO(3) losses were observed during ECD and ETD.
- Fragmenting peptide-alkali metal adducts reduced neutral SO(3) losses.
Conclusions:
- Fragmentation analysis, particularly with ECD and ETD, can differentiate sulfopeptides from phosphopeptides.
- Neutral SO(3) loss is a characteristic fragmentation pathway for O-sulfo peptides under ECD/ETD.
- Using peptide-alkali metal adducts mitigates neutral losses, improving the analysis of O-sulfo modifications.
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