Advantages of using nested collision induced dissociation/post-source decay with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: sequencing of novel peptides from wasp venom

We have examined the applicability of the 'nested' collision induced dissoc iation/post-source decay (CID/PSD) method to the sequencing of novel peptid es from solitary wasps which have neurotoxic venom for paralyzing other ins ects. The CID/PSD spectrum of a ladder peptide derived from an exopeptidase digest was compared with that of the intact peptide. The mass peaks observ ed only in the CID/PSD spectrum of a ladder peptide were extracted as C-ter minal fragment ions. Assignment of C-terminal fragment ions enabled calcula tion of N-terminal fragment masses, leading to differentiation between N-te rminal fragment ions and internal fragment ions. This methodology allowed r apid and sensitive identification by removing ambiguity in the assignment o f the fragment ions, and proved useful for sequencing unknown peptides, in particular those available as natural products with a limited supply. Copyr ight (C) 2000 John Wiley & Sons, Ltd.