Dissociative electron attachment to gas-phase 5-bromouracil

Abstract

We report measurements of dissociative electron attachment (DEA) to gaseous 5-bromouracil (BrU) for incident electron energies between 0 and 16 eV. Low energy electron impact on BrU leads not only to the formation of a long lived parent anion BrU−, but also various anion fragments resulting from endo- and exo-cyclic bond ruptures, such as Br−, uracil-yl anions, i.e., (U-yl)−, OCN−, and a 68 amu anion tentatively attributed to H2C3NO−. The incident electron energy dependent signatures of either the Br− and (U-yl)− yields (at 0, 1.4, and 6 eV), or the OCN− and H2C3NO− yields (at 1.6 and 5.0 eV) suggests competing DEA channels for anion fragment formation. The production cross sections, at 0 eV incident electron energy, for BrU−, Br−, and (U-yl)− are estimated to be about 6×10−15, 6×10−14, and 1.0×10−15 cm2, respectively.

Measurement of inelastic cross sections for low-energy electron scattering from DNA bases

“…In an effort to provide a number of answers to these interrogations, several experimental studies have been carried out on electron impact on individual DNA bases to understand what fragments are generated. Most of them concern the formation of various anion fragments produced by dissociative electron attachment to these molecules in gas phase (Huels et al 1998, Aflatooni et al 1998, Abdoul-Carime et al 2000, Abouaf et al 2003, 2003b, Denifl et al 2003, 2004a, 2004b, Ptasinska et al 2005a, Abouaf and Dunet 2005 and sublimated as thin films (Herve Du Penhoat et al 2001, Abdoul-Carime et al 2001. Few studies have also examined their electronic and vibrational excitations by electron-energy loss (EEL) spectroscopy in the gas phase (Dillon et al 1989, Abouaf et al 2003a.…”

Probing biomolecules: Gas phase experiments and biological relevance

“…Such experiments have been carried out in different laboratories [1][2][3][4] with crossed electron/molecular beam arrangements where a monochromatised electron beam interacts with an effusive molecular beam containing the DNA bases. The beam is generated by moderatelyheating the powder sample containing the DNA bases to 150 -200°C and effusing the molecules through the collision region.…”

“…The necessary prerequisite for effective and controlled therapy strategies is the understanding of the molecular mechanisms of the underlying processes. In an effort to describe these effects on a molecular level, different laboratories have started programs to study the building blocks ofbiomolecules in the gas phase [1][2][3][4]. The advantage of gas phase studies is that experimental techniques like mass spectrometry or electron spectroscopy (eventually in combination with laser pump and probe techniques) can easilybe applied.…”

Density functional theory for the photoionization dynamics of uracil

“…Thus, the suggestion that metastable electron capture of the large amount of non-thermal secondary electrons produced upon the interaction of ionizing radiation with the cell environment [5] by the various DNA components could initiate the formation of SSBs and DSBs, stimulated a wealth of experimental work on electron collisions with gaseous [6][7][8][9] and thin films DNA and RNA bases [10]. Recently theoretical studies have also given a better understanding of these insights [11,12].…”