Chiral analyses of peptides by ion/molecule reactions

Protonated complexes comprised of guest peptides with permethylated hosts (beta-cyclodextrin and maltoheptaose) were produced in the gas phase by electrospray ionization and reacted with a gaseous amine in a Fourier transform ion cyclotron resonance mass spectrometer. An exchange reaction was observed whereby the guest peptide was replaced by the gaseous alkyl amine. The exchange reaction was enantioselective and was used to determine enantiomeric excess in mixtures of enantiomers. The nature of the recognition is probed by the selection of the peptides and the use of molecular dynamics calculations. (C) 2004 Elsevier B.V. All rights reserved.