SEQUENCE-ION ENHANCEMENT OF PEPTIDES DIGESTED WITH PROTEINASE-K

Proteinase K has been employed to proteolyze peptides before their mas s spectrometric analysis. This combination of the two methods yields a bundant sequence ions in the mass spectrum, thus leading to an easy pr ediction of the primary structure of the peptide. It was found that bo th the variety of available sequence ions and also their abundances ar e increased strongly after proteinase K digestion, when compared with the normal mass spectrum. The shortcoming of little fragmentation enco untered using conventional mass spectrometric ionization methods can m ostly be overcome. The H'(n) and Y''(m) ions produced from proteolysis provided a double check of the peptide sequence.