The role of nucleophile--electrophile interactions in the unimolecular and bimolecular gas-phase ion chemistry of peptides and related systems.

This account describes the experimental tools (multi-stage mass spectrometric experiments, isotopic and structural labelling, kinetics and theoretical modelling) and physical organic concepts (influence of charge, the intermediacy of ion-molecule complexes, etc.) that can be used to unravel the mechanisms of gas-phase unimolecular and bimolecular ionic reactions of peptides. The role that nucleophile-electrophile interactions play in charge-directed reactions is highlighted for both unimolecular fragmentations (examples are illustrated for protonated sulfur-containing amino acids and peptides) and bimolecular ion-molecule reactions which cleave peptide bonds. Copyright 2000 John Wiley & Sons, Ltd.