IDENTIFICATION OF NUCLEOTIDES, AMINO ACIDS, OR CARBOHYDRATES BY MASS SPECTROMETRY

摘要

A method for correlating a peptide fragment mass spectrum with amino acid sequences derived from a database is provided. Apeptide is analyzed by a tandem mass spectrometer to yield a peptide fragment mass spectrum. A protein sequence database or a nucleotidesequence database is used to predict one or more fragment spectra for comparison with the experimentally-derived fragment spectrum. Inone embodiment, sub-sequences of the sequences found on the database which define a peptide having a mass substantially equal to the massof the peptide analyzed by the tandem mass spectrometer are identified as candidate sequences. For each candidate sequence, a pluralityof fragments of the sequence are identified and the masses and m/z ratios of the fragments are predicted and used to form a predictedmass spectrum. The various predicted mass spectra are compared to the experimentally derived fragment spectrum using a closeness-of-fitmeasure, preferably calculated with a two-step process, including a calculation of a preliminary score end, for the highest-scoring predictedspectra, calculation of a correlation function.