Decomposition of purine nucleobases by very low energy electrons
Institut für Physikalische und Theoretische Chemie, Freie Universität Berlin, Takustrasse 3, 14195 Berlin, Germany
2 Départment de Médicine et Radiobiologie, Faculté de Médicine, Université de Sherbrooke, Sherbrooke, QC, Canada
Corresponding author: a email@example.com
Published online: 26 July 2005
We show that low energy electrons effectively decompose the gas phase purine nucleobases adenine (A) and guanine (G) via dissociative electron attachment (DEA) involving low lying (<3 eV) shape resonances, but also via core excited resonances (located near 6 eV). In adenine the low energy resonances exclusively lead to dehydrogenation, i.e. ejection of a neutral hydrogen radical with the excess electron remaining on the molecule. This reaction by far dominates DEA in the entire energy range 0–15 eV, similar to the situation recently observed in the pyrimidine bases thymine (T), cytosine (C) and uracil (U). In striking contrast to that, guanine behaves very different in that dehydrogenation is comparatively weak while various further decomposition reactions are observed from the low energy * precursor ions. These reactions lead to fragment ions of the form (G–O/NH, O-/NH, (G–HOCN)-, OCN-, CN- indicative of single bond cleavages but also more complex unimolecular decompositions associated with the excision of cyano units from the cyclic structure. Since electrons are the predominant secondary species in the interaction of high energy quanta with biological material, electron driven reactions represent initial steps in the molecular description of radiation damage.
PACS: 34.80.Ht – Dissociation and dissociative attachment by electron impact / 82.30.Lp – Decomposition reactions (pyrolysis, dissociation, and fragmentation) / 87.50.Gi – Ionizing radiations (ultraviolet, X-rays, gamma-rays, ions, electrons, positrons, neutrons, and mesons, etc.)
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2005