Patent ID: 7069152
Filing Date: 2006-06-27
Classification: G01N,H01J

Abstract:
1. Apparatus for identifying a most probable sequence of amino acids in an unknown peptide, said apparatus comprising a mass spectrometer for generating a mass spectrum of said unknown peptide and data processing means programmed to: (a) process data generated by said mass spectrometer to produce a processable mass spectrum; and (b) calculate the likelihood that any given trial amino-acid sequence would account for said processable mass spectrum using a fragmentation model which sums probabilistically over a plurality of fragmentation routes which together represent possible ways that said trial sequence might fragment in accordance with a set of predefined rules, each said fragmentation route being assigned a prior probability based on the chemical process involved, wherein a likelihood factor of the processable mass spectrum, given a particular trial sequence, is established according to: where represents the sum over all permitted fragmentation pattems ƒ, P(D GIVEN ƒ) is the probability of the processable mass spectrum assuming a particular fragmentation pattern ƒ, and P(ƒGIVEN S) is the probability of having a fragmentation pattern ƒ from the trail sequence S.