3P-34 PDF
Metastable Ions of Peptides Observed in MALDI-TOF MS – Application for Protein Identification
MALDI-TOFMS-based peptide mass fingerprinting (PMF) and LC-MS/MS- based peptide sequencing are two widely used methods for protein identification by mass spectrometry. In comparison with peptide sequencing, PMF is much faster and easier. However, MALDI-TOF PMF usually requires 10-20 peptides and the resulting data is a list of candidates, each with a ranking score; these conditions limit the reliability and feasibility of using PMF for protein identification. We previously reported on a type of metastable ion, which results from the rearrangement at the C terminus [1] or the C-terminal side of Ser/Thr in a peptide sequence [2]. We found that these rearranged ions could often be detected as metastable ions in MALDI-TOFMS (reflector mode) and that they contain C-terminal information regarding a peptide. Furthermore, a set of the m/z values of precursor ions and their C-terminal amino acid information, when obtained for the peptides derived from a protein digest, could provide a new PMF workflow.