Back to Search
Start Over
Differentiating N-Terminal Aspartic and Isoaspartic Acid Residues in Peptides
- Source :
- Analytical Chemistry. 83:6675-6682
- Publication Year :
- 2011
- Publisher :
- American Chemical Society (ACS), 2011.
-
Abstract
- Formation of isoaspartic acid (isoAsp) is a common modification of aspartic acid (Asp) or asparagine (Asn) residue in proteins. Differentiation of isoAsp and Asp residues is a challenging task owing to their similar properties and identical molecular mass. It was recently shown that they can be differentiated using ion-electron or ion-ion interaction fragmentation methods (ExD) because these methods provide diagnostic fragments c + 57 and z(•) - 57 specific to the isoAsp residue. To date, however, the presence of such fragments has not been explored on peptides with an N-terminal isoAsp residue. To address this question, several N-terminal isoAsp-containing peptides were analyzed using ExD methods alone or combined with chromatography. A diagnostic fragment [M + 2H - 74](+•) was observed for the doubly charged precursor ions with N-terminal isoAsp residues. For some peptides, identification of the N-terminal isoAsp residue was challenging because of the low diagnostic ion peak intensity and the presence of interfering peaks. Supplemental activation was used to improve diagnostic ion detection. Further, N-terminal acetylation was offered as a means to overcome the interference problem by shifting the diagnostic fragment peak to [M + 2H - 116](+•).
Details
- ISSN :
- 15206882 and 00032700
- Volume :
- 83
- Database :
- OpenAIRE
- Journal :
- Analytical Chemistry
- Accession number :
- edsair.doi.dedup.....7b559b50dcaa5ae9817fd44981d3dc54