title: New insights into the vacuum UV photodissociation of peptides.
abstract: Vacuum ultraviolet laser photodissociation (UVPD) of peptide ions leads to unusual dissociation channels involving backbone C-C bond breaking. However, the molecular basis for the observed behavior is not clearly understood. We now report theoretical investigations using ab initio/density functional theory (DFT) techniques on neutral and protonated dipeptides undergoing vacuum ultraviolet (VUV) induced fragmentation via a Rydberg excitation (and/or electron detachment) and subsequent C-C bond cleavage. New experimental results on VUV photodissociation of dipeptides (protonated Ala_Arg and Arg_Ala) provide strong support for our proposed model. Our mechanism also provides a natural explanation for the presence of immonium ions that are sometimes observed in such experiments.
authors.affiliation: Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
authors.forename: Ramakrishnan
authors.initials: R
authors.lastname: Parthasarathi
authors.forename: Yi
authors.initials: Y
authors.lastname: He
authors.forename: James P
authors.initials: JP
authors.lastname: Reilly
authors.forename: Krishnan
authors.initials: K
authors.lastname: Raghavachari
mesh_terms: D004151:Dipeptides / Q000737:chemistry*; D008958:Models, Molecular; D010777:Photochemistry; D011522:Protons; D014466:Ultraviolet Rays; D014618:Vacuum
chemical_list: D004151:Dipeptides; D011522:Protons