title: Spectroscopic evidence for an oxazolone structure of the b(2) fragment ion from protonated tri-alanine.
abstract: Infrared multiple photon dissociation (IRMPD) spectroscopy is used to identify the structure of the b(2)(+) ion generated from protonated tri-alanine by collision induced dissociation (CID). The IRMPD spectrum of b(2)(+) differs markedly from that of protonated cyclo-alanine-alanine, demonstrating that the product is not a diketopiperazine. Instead, comparison of the IRMPD spectrum of b(2)(+) to spectra predicted by density functional theory provides compelling evidence for an oxazolone structure protonated at the oxazolone N-atom.
authors.affiliation: FOM Institute for Plasma Physics Rijnhuizen, Nieuwegein, The Netherlands. joso@rijnhuizen.nl
authors.forename: Jos
authors.initials: J
authors.lastname: Oomens
authors.forename: Sarah
authors.initials: S
authors.lastname: Young
authors.forename: Sam
authors.initials: S
authors.lastname: Molesworth
authors.forename: Michael
authors.initials: M
authors.lastname: van Stipdonk
mesh_terms: D009842:Oligopeptides / Q000737:chemistry*; D010081:Oxazolone / Q000737:chemistry*; D011522:Protons; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared / Q000379:methods*
chemical_list: D009842:Oligopeptides; D011522:Protons; D010081:Oxazolone; C039944:alanyl-alanyl-alanine