New insights into the vacuum UV photodissociation of peptides.
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.
Parthasarathi
Ramakrishnan
R
Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
He
Yi
Y
Reilly
James P
JP
Raghavachari
Krishnan
K
D004151:Dipeptides / Q000737:chemistry*; D008958:Models, Molecular; D010777:Photochemistry; D011522:Protons; D014466:Ultraviolet Rays; D014618:Vacuum
D004151:Dipeptides; D011522:Protons