COLLISION-INDUCED DISSOCIATIONS OF DEPROTONATED PEPTIDES - DIPEPTIDESCONTAINING METHIONINE OR CYSTEINE

The collisional activation mass spectra of the [M - H]- ions of dipept ides containing Met or Cys show the usual backbone fragmentation allow ing the sequence of the peptide to be determined. A methionine residue may be identified by the presence of a pronounced peak resulting from loss of MeSH, while a cysteine residue may be identified by the prese nce of a peak corresponding to loss of either H2S or (H2S + CO2).