Fragmentations of dipeptides in plasma desorption mass spectrometry: new rules for the sequence elucidation of oligopeptides.

252Cf plasma desorption mass spectrometry is well suited for determining both composition and sequence of unknown small oligopeptides. A systematic study of a large number of dipeptides first leads to establishing common rules of fragmentation from positive ion mass spectra. These rules are then applied to the sequence elucidation of larger peptides.