Analysis of post-translational modifications of proteins by accurate mass measurement in fast atom bombardment mass spectrometry.

A rotatable dual-target probe was used for accurate mass measurement in fast atom bombardment mass spectrometry to determine the structures of unknown amino acid residues or post-translationally modified structures in peptides or proteins. The results obtained in measurement of tryptic peptides (with molecular weights of up to 2000) of the A-subunit of vero-toxin I indicated that the mass values obtained are sufficiently accurate and reproducible to allow the generation of the possible elemental compositions for modifications in peptides. By this method, the structural modifications of the N-terminal of a recombinant human leukocyte interferon A and novel halogenated amino acids in sperm-activating peptides from the egg-jelly of sea urchins were determined.