A mammal neurotoxin was isolated from the Buthus marttensii Karch with chromatography. Its Edman degradation-derived sequence was verified by FAB mapping of the tryptic digest of the sample. The results reveal that the sixtieth residue is proline instead of tryptophan and that the C-terminal residue is histidine without glycine. The revised sequence is further confirmed by comparing above FAB map with that of those peptides produced after further step of carboxypeptidase B digestion. FAB mapping of the partial tryptic digest also supports the correction. Chemical modification was applied to minimize the problem of surface suppression.

Key words: FAST ATOM BOMBARDMENT, RESIDUE (BIOCHEMISTRY), AMINO ACID, PROLINE