Patent ID: 8137982

Claim:
A method for selecting a precursor ion of a soft ionisation mass spectrum of a partially degraded sample polypeptide for fragmentation, said soft ionisation mass spectrum comprising a set of m/z peaks of ion species obtained from said partially degraded sample polypeptide, said method comprising the steps of: (i) with at least two candidate m/z peak sets determined from said soft ionisation mass spectrum, each m/z peak in each candidate m/z peak set differing from its at least one neighbour by the mass of an amino acid, and a putative amino acid sequence determined from each candidate m/z peak set, each amino acid sequence being that of the amino acids which correspond to the mass differences between each m/z peak and its at least one neighbour; and (ii) analysing using fuzzy logic principles said m/z peaks of said at least two candidate m/z peak sets, to select at least one m/z peak for fragmentation.