title: Collision-induced dissociation (CID) of guanine radical cation in the gas phase: an experimental and computational study.
abstract: Gas-phase guanine (G) radical cations were generated by electrospraying a solution of guanosine (L) and Cu(NO(3))(2). Collision-induced dissociation (CID) for guanine radical cations yielded five competing dissociation channels, corresponding to the elimination neutral molecules of NH(3), HCN, H(2)NC[triple bond]N (HN=C=NH), HNCO and the neutral radical N=C=NH, respectively. The primary product ions were further characterized by their relevant fragmentions. Ab initio and density functional theory (DFT) calculations were employed to explain the experimental observations. Ten stable radical cation isomers were optimized and the potential energy surfaces (PESs) for the isomerization processes were explored in detail. Starting with the most stable isomer, the primary dissociation channels of guanine radical cations were theoretically investigated. DFT calculations show that the energy barriers for the eliminations of NH(3), HCN, H(2)NC[triple bond]N (HN=C=NH), HNCO and N=C=NH are 397 kJ mol(-1), 479 kJ mol(-1), 294 kJ mol(-1) (298 kJ mol(-1)), 306 kJ mol(-1), and 275 kJ mol(-1), respectively. The results are consistent with the energy-resolved CID of guanine radical cation, in which the eliminations of NH(3) and HCN are less abundant than the other channels.
authors.affiliation: The School of Environmental and Chemical Engineering, Shanghai University, Shanghai, 200444, China. Pingcheng@shu.edu.cn
authors.forename: Ping
authors.initials: P
authors.lastname: Cheng
authors.forename: Yanni
authors.initials: Y
authors.lastname: Li
authors.forename: Shuqi
authors.initials: S
authors.lastname: Li
authors.forename: Mingtao
authors.initials: M
authors.lastname: Zhang
authors.forename: Zhen
authors.initials: Z
authors.lastname: Zhou
mesh_terms: D003198:Computer Simulation; D005609:Free Radicals / Q000737:chemistry; D005740:Gases / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D005609:Free Radicals; D005740:Gases; D006147:Guanine