title: Selectivity in fragmentation of N-methylacetamide after resonant K-shell excitation.
abstract: The fragmentation pattern of the peptide model system, N-methylacetamide, is investigated using ion time-of-flight (TOF) spectroscopy after resonant K-shell excitation. Corresponding near-edge X-ray absorption fine structure (NEXAFS) spectra recorded at high resolution at the C1s, N1s and O1s edges are presented. Analysis of the ion TOF data reveals a multitude of fragmentation channels and dissociation pathways. Comparison between the excitation of six different resonances in the vicinity of the C1s, N1s and O1s edges suggests evidence for site-selective bond breaking. In particular the breaking of the peptide bond and the N-C(α) bond show a clear correlation with resonant excitation at the N1s edge. Also, stronger tendencies towards site-selective bond breaking are found for the generation of single ions compared with ion pairs. Analysis of angular distributions of ions from breakage of the peptide bond yields a fragmentation time of <400 fs.
authors.affiliation: Department of Physics, Stockholm University, 106 91 Stockholm, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Salén
authors.forename: Magdalena
authors.initials: M
authors.lastname: Kamińska
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Squibb
authors.forename: Robert
authors.initials: R
authors.lastname: Richter
authors.forename: Michele
authors.initials: M
authors.lastname: Alagia
authors.forename: Stefano
authors.initials: S
authors.lastname: Stranges
authors.forename: Peter
authors.initials: P
authors.lastname: van der Meulen
authors.forename: John H D
authors.initials: JH
authors.lastname: Eland
authors.forename: Raimund
authors.initials: R
authors.lastname: Feifel
authors.forename: Vitali
authors.initials: V
authors.lastname: Zhaunerchyk
mesh_terms: D000081:Acetamides / Q000737:chemistry*; D007477:Ions; D008956:Models, Chemical; D010446:Peptide Fragments / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D000081:Acetamides; D007477:Ions; D010446:Peptide Fragments; C018595:N-methylacetamide