Observation of Phosphorylation Site-Specific Dissociation of Singly Protonated Phosphopeptides

In ultraviolet photodissociation of phosphopeptide ions with a basic residue (arginine, lysine, or histidine) at the N-terminus, intense an − 97 peaks were observed. These ions were formed by cleavage at phosphorylated residues only. For multiply phosphorylated peptides, this site-specific cleavage occurred at every phosphorylated residue. H/D exchange studies showed that an − 97 was formed by H3PO4 loss from an + 1 radical cations. The site-specificity of phosphate loss observed here is in contrast to the nonspecific phosphate loss from bn and yn reported previously. Characteristics of the reaction and its potential utility for phosphopeptide analysis are discussed.

Graphical AbstractIn UV-photodissociation of phosphopeptide ions with a basic residue at the N-terminus, an − 97 is formed by selective cleavages at every phosphorylated residue.Figure optionsDownload high-quality image (25 K)Download as PowerPoint slide