Peptide sequencing using mass spectrometry

Abstract

The present invention relates to methods for determining the amino acid composition, and more preferably the sequence, of a peptide using mass spectrometric techniques. The method is particularly useful for sequencing peptides isolated from natural sources or from libraries of peptides that have been prepared synthetically, and for peptides that are not amenable to Edman degradation sequencing. In one embodiment, the method for determining the amino acid composition or sequence of a peptide comprises determining the difference of the mass of the peptide from the mass of a deuterium-hydrogen exchanged peptide, and from this difference determining the number of exchangeable (labile) hydrogen atoms (protons). Candidate peptides having amino acid compositions or sequences that do not contain the observed number of exchangeable protons are eliminated. In another embodiment, synthesis of a portion of the peptides in a library of peptides is terminated after each coupling step, whereby a set of sequentially truncated fragments of each peptide is formed. Thus the sequence of the peptide can be determined by determining the difference in the molecular weight between each peptide or fragment thereof and the sequentially smaller fragment of the peptide.