title: UV Action Spectroscopy of Gas-Phase Peptide Radicals.
abstract: UV photodissociation (UVPD) action spectroscopy is reported to provide a sensitive tool for the detection of radical sites in gas-phase peptide ions. UVPD action spectra of peptide cation radicals of the z-type generated by electron-transfer dissociation point to the presence of multiple structures formed as a result of spontaneous isomerizations by hydrogen atom migration. N-terminal Cα radicals are identified as the dominant components, but the content of isomers differing in the radical defect position in the backbone or side chain depends on the nature of the aromatic residue with phenylalanine being more prone to isomerization than tryptophan. These results illustrate that spontaneous hydrogen atom migrations can occur in peptide cation-radicals upon electron-transfer dissociation.
authors.affiliation: Department of Chemistry, University of Washington , Bagley Hall, Box 351700, Seattle, Washington 981195-1700, United States.
authors.forename: Huong T H
authors.initials: HT
authors.lastname: Nguyen
authors.affiliation: Department of Chemistry, University of Washington , Bagley Hall, Box 351700, Seattle, Washington 981195-1700, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Shaffer
authors.affiliation: Department of Chemistry, University of Washington , Bagley Hall, Box 351700, Seattle, Washington 981195-1700, United States.
authors.forename: Robert
authors.initials: R
authors.lastname: Pepin
authors.affiliation: Department of Chemistry, University of Washington , Bagley Hall, Box 351700, Seattle, Washington 981195-1700, United States.
authors.forename: František
authors.initials: F
authors.lastname: Tureček
mesh_terms: D004579:Electron Transport; D010455:Peptides / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods*; D014466:Ultraviolet Rays
chemical_list: D010455:Peptides
keywords: UV photodissociation; action spectroscopy; electron-transfer dissociation; excited states; peptide ions