Unusual fragmentation of Pro-Ser/Thr-containing peptides detected in collision-induced dissociation spectra.

ABSTRACT: During collision-induced dissociation (CID)-, phosphoserine- and phosphothreonine-containing peptides frequently undergo neutral loss of phosphoric acid. Subsequent amide bond cleavage N-terminal to the site of phosphorylation results in a y ion with a mass 18 Da lower than the corresponding unmodified y fragment. We report here that when the phosphoserine or phosphothreonine is directly preceded by a proline, an unusual fragment with a mass 10 Da higher than the corresponding unmodified y ion is frequently observed. Accurate mass measurements are consistent with elimination of the phosphoric acid followed by fragmentation between the α carbon and the carbonyl group of the proline residue. We propose a cyclic oxazoline structure for this fragment. Our observation may be explained by the ch

SUBMITTER: Medzihradszky KF 

PROVIDER: S-EPMC3384711 | biostudies-literature | 2012 Apr

REPOSITORIES: biostudies-literature