title: UV photodissociation of proline-containing peptide ions: insights from molecular dynamics.
abstract: UV photodissociation of proline-containing peptide ions leads to unusual product ions. In this paper, we report laser-induced dissociation of a series of proline-containing peptides at 213 nm. We observe specific fragmentation pathways corresponding to the formation of (y-2), (a + 2) and (b + 2) fragment ions. This was not observed at 266 nm or for peptides which do not contain proline residues. In order to obtain insights into the fragmentation dynamics at 213 nm, a small peptide (RPK for arginine-proline-lysine) was studied both theoretically and experimentally. Calculations of absorption spectra and non-adiabatic molecular dynamics (MD) were made. Second and third excited singlet states, S(2) and S(3), lie close to 213 nm. Non-adiabatic MD simulation starting from S(2) and S(3) shows that these transitions are followed by C-C and C-N bond activation close to the proline residue. After this first relaxation step, consecutive rearrangements and proton transfers are required to produce unusual (y-2), (a + 2) and (b + 2) fragment ions. These fragmentation mechanisms were confirmed by H/D exchange experiments.
authors.affiliation: Université de Lyon, F-69622, Lyon, France, marion.girod@univ-lyon1.fr.
authors.forename: Marion
authors.initials: M
authors.lastname: Girod
authors.forename: Zeljka
authors.initials: Z
authors.lastname: Sanader
authors.forename: Marin
authors.initials: M
authors.lastname: Vojkovic
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Antoine
authors.forename: Luke
authors.initials: L
authors.lastname: MacAleese
authors.forename: Jérôme
authors.initials: J
authors.lastname: Lemoine
authors.forename: Vlasta
authors.initials: V
authors.lastname: Bonacic-Koutecky
authors.forename: Philippe
authors.initials: P
authors.lastname: Dugourd
mesh_terms: D041961:Deuterium Exchange Measurement; D056004:Molecular Dynamics Simulation; D010455:Peptides / Q000737:chemistry* / Q000528:radiation effects*; D010782:Photolysis; D011392:Proline / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D010455:Peptides; D011392:Proline