On-line liquid chromatography electron capture dissociation for the characterization of phosphorylation sites in proteins.

Electron capture dissociation (ECD) allows fragmentation of the phosphopeptide backbone while keeping the labile phospho-amino acid intact. This feature of ECD fragmentation, coupled with the acquisition of mass spectra at high mass accuracy, makes ECD well-suited to phosphorylation mapping. The following methods are designed to focus ECD events on phosphopeptides within a complex peptide sample, either by using phosphoric acid neutral loss peaks as a trigger or by targeted analysis of predetermined precursor masses.