PATTERN-BASED ALGORITHM FOR PEPTIDE SEQUENCING FROM TANDEM HIGH-ENERGY COLLISION-INDUCED DISSOCIATION MASS-SPECTRA

A new strategy is reported for extracting complete and partial sequence information from collision-induced dissociation (CID) spectra of peptides. CID spectra are obtained from high energy CID of peptide molecular ions on a four-sector tandem mass spectrometer with an electro-optically coupled microchannel array detector. A peak detection routine reduces the spectrum to a list of peak masses and peak heights, which is then used for sequencing. The sequencing algorithm was designed to use spectral data to generate sequence fits directly rather than to use data to test the fit of series of sequence guesses. The peptide sequencing algorithm uses a pattern based on the polymeric nature of peptides to classify spectral peaks into sets that are related in a sequence-independent manner. It then establishes sequence relationships among these sets. Peak detection from raw data takes 10-20 s, with sequence generation requiring an additional 10-60 s on a Sun 3/60 workstation. The program is written in the C language to run on a Unix platform. The principal advantages of our method are in the speed of analysis and the potential for identifying modified or rare amino acids. The algorithm was designed to permit real-time sequencing but awaits hardware modifications to allow real-time access to CID spectra.