Patent ID: 8620588

Claim:
A system for determining at least one putative amino acid sequence for a sample polypeptide, said sample polypeptide being partially degraded, said system comprising: (a) a memory storing processor readable instructions; and (b) a processor arranged to read and execute instructions stored in said memory; wherein said processor readable instructions contain instructions to: (i) control the processor to store in said memory a set of m/z peaks obtained from a soft ionization mass spectrum of said sample polypeptide giving said set of m/z peaks of ion species obtained from said partially degraded sample polypeptide and determine from said set of m/z peaks a plurality of candidate m/z peak sets, each m/z peak in each candidate m/z peak set differing from its at least one neighbor by the mass of an amino acid residue; (ii) control the processor to store in said memory each candidate m/z peak set determined at step (i); for each candidate m/z peak set stored in said memory: determine an associated sequence of mass differences between each m/z peak in the set and its at least one neighbor; and determine an associated sequence of mass differences in reverse order; process the determined sequences of mass differences and determined sequences of mass differences in reverse order using a reflective predicate filter to determine a plurality of candidate m/z peak sets in which each m/z peak set has an associated sequence of mass differences in reverse order that forms at least part of the sequence of mass differences of another of said candidate m/z peak sets determined at step (i); and discard any candidate m/z peaks not in the determined plurality of candidate m/z peak sets; (iii) control the processor to: identify candidate m/z peak sets in which mass differences between each m/z peak and at least one peak in the candidate m/z peak set having a closest m/z value above and/or below the peak correspond to that of a daughter ion or an end ion cluster; and discard any identified candidate m/z peak sets from the plurality of candidate m/z peak sets; (iv) control the processor to process the plurality of candidate m/z peak sets to: identify any candidate m/z peak set which is a contiguous subsequence of another candidate m/z peak set; and discard the identified candidate m/z peak sets from the plurality of candidate m/z peak sets; and (v) control the processor to determine an amino acid sequence for each remaining 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 neighbor, said at least one putative amino acid sequence of said sample polypeptide being made up of one or more of said determined amino acid sequences.