Related Experiment Video
Updated: Aug 11, 2026
08:01
LERLIC-MS/MS for In-depth Characterization and Quantification of Glutamine and Asparagine Deamidation in Shotgun Proteomics
Published on: April 9, 2017
Detecting deamidation products in proteins by electron capture dissociation
Jason J Cournoyer1, Cheng Lin, Peter B O'Connor
1Mass Spectrometry Resource, Department of Biochemistry, Boston University School of Medicine, 715 Albany Street R806, Boston, MA 02118, USA.
Analytical Chemistry
|February 16, 2006
Summary
Detecting protein deamidation is challenging due to isomeric aspartyl and isoaspartyl residues. Electron capture dissociation mass spectrometry offers unique ions to identify and locate these modifications in various proteins.
Area of Science:
- Biochemistry
- Analytical Chemistry
- Proteomics
Background:
- Nonenzymatic deamidation of asparagine residues is a common posttranslational modification.
- This process forms aspartyl and isoaspartyl residues, which are difficult to distinguish using standard mass spectrometry.
- Isoaspartic acid is isomeric with aspartic acid, presenting no mass difference.
Purpose of the Study:
- To demonstrate the utility of electron capture dissociation (ECD) for differentiating aspartyl and isoaspartyl residues in peptides.
- To detect and localize isoaspartyl modifications in deamidated peptides derived from intact proteins.
Main Methods:
- Utilizing electron capture dissociation (ECD) mass spectrometry.
- Analyzing characteristic fragment ions: cr. + 58 and z(l-r) - 57 for isoaspartyl, and (M + nH)(n-1)+. - 60 for aspartyl.
- Applying the method to peptides from cytochrome c, ribonuclease A, and calmodulin.
Main Results:
- ECD successfully differentiated between aspartyl and isoaspartyl residues in synthetic peptides using unique diagnostic ions.
- Isoaspartyl residues were detected and localized in deamidated peptides from cytochrome c, ribonuclease A, and calmodulin.
- The presence of aspartyl residues was confirmed by the detection of the Asp side chain loss ions.
Conclusions:
- Electron capture dissociation mass spectrometry is a powerful tool for identifying and localizing isoaspartyl residues in proteins.
- This method enables the determination of the isomerization state of deamidated proteins.
- The findings are applicable to studying protein aging and modifications in various biological contexts.
