title: Dissociative electron attachment to the gas-phase nucleobase hypoxanthine.
abstract: We present high-resolution measurements of the dissociative electron attachment (DEA) to isolated gas-phase hypoxanthine (C5H4N4O, Hyp), a tRNA purine base. The anion mass spectra and individual ion efficiency curves from Hyp were measured as a function of electron energy below 9 eV. The mass spectra at 1 and 6 eV exhibit the highest anion yields, indicating possible common precursor ions that decay into the detectable anionic fragments. The (Hyp - H) anion (C5H3N4O(-)) exhibits a sharp resonant peak at 1 eV, which we tentatively assign to a dipole-bound state of the keto-N1H,N9H tautomer in which dehydrogenation occurs at either the N1 or N9 position based upon our quantum chemical computations (B3LYP/6-311+G(d,p) and U(MP2-aug-cc-pVDZ+)) and prior studies with adenine. This closed-shell dehydrogenated anion is the dominant fragment formed upon electron attachment, as with other nucleobases. Seven other anions were also observed including (Hyp - NH)(-), C4H3N4 (-)/C4HN3O(-), C4H2N3 (-), C3NO(-)/HC(HCN)CN(-), OCN(-), CN(-), and O(-). Most of these anions exhibit broad but weak resonances between 4 and 8 eV similar to many analogous anions from adenine. The DEA to Hyp involves significant fragmentation, which is relevant to understanding radiation damage of biomolecules.
authors.affiliation: Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA.
authors.forename: M Michele
authors.initials: MM
authors.lastname: Dawley
authors.affiliation: Institut für Ionenphysik und Angewandte Physik, and Center for Molecular Biosciences Innsbruck (CMBI), Leopold-Franzens Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria.
authors.forename: Katrin
authors.initials: K
authors.lastname: Tanzer
authors.affiliation: Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA.
authors.forename: Ian
authors.initials: I
authors.lastname: Carmichael
authors.affiliation: Institut für Ionenphysik und Angewandte Physik, and Center for Molecular Biosciences Innsbruck (CMBI), Leopold-Franzens Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria.
authors.forename: Stephan
authors.initials: S
authors.lastname: Denifl
authors.affiliation: Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana 46556, USA.
authors.forename: Sylwia
authors.initials: S
authors.lastname: Ptasińska
mesh_terms: D004583:Electrons; D005740:Gases / Q000737:chemistry*; D019271:Hypoxanthine / Q000737:chemistry*; D015394:Molecular Structure; D011789:Quantum Theory
chemical_list: D005740:Gases; D019271:Hypoxanthine