title: Spectroscopic and theoretical evidence for oxazolone ring formation in collision-induced dissociation of peptides.
abstract: Infrared spectroscopy of the b4+ fragment of Leu-enkephalin demonstrates that the oxazolone ring is formed during collision-induced dissociation of protonated peptides, whereas the linear acylium structure is not observed. Three distinct oxazolone structures are identified, based on the highly conformer-diagnostic C=O stretching mode of the oxazolone ring, clearly showing that proton transfer from the oxazolone ring to the N-terminus takes place. Note that the presence of a cyclic peptide b4+ isomer cannot be excluded.
authors.affiliation: FOM Institute for Plasmaphysics Rijnhuizen, Edisonbaan 14, NL-3439 MN Nieuwegein, The Netherlands. polfer@rijnh.nl
authors.forename: Nick C
authors.initials: NC
authors.lastname: Polfer
authors.forename: Jos
authors.initials: J
authors.lastname: Oomens
authors.forename: Sándor
authors.initials: S
authors.lastname: Suhai
authors.forename: Béla
authors.initials: B
authors.lastname: Paizs