https://doi.org/10.1140/epjd/e2005-00194-5
Decomposition of purine nucleobases by very low energy electrons
1
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 langerj@chemie.fu-berlin.de
Received:
31
March
2005
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