title: Low-energy electron-induced damage in a trinucleotide containing 5-bromouracil.
abstract: The reaction of low-energy electrons (LEEs; 10 eV) with 5'-TpXpT-3' (TXT), where X is uracil (U), thymine (T), and 5-bromouracil (5BrU), was examined by HPLC-UV analysis. The presence of 5BrU increased total damage by >50%. The radiation products of T5BrUT included TUT (40%), free U, T, 5BrU (23%), and fragments (13%). These products may be explained by initial capture of LEEs by the nucleobase to form a transient anion, followed by transfer of the electron within the molecule and cleavage of susceptible bonds by dissociative electron attachment (C-Br, C-N, or C-O bonds). In addition, these products may arise from the uracilyl-5-yl (U-5-yl) radicals that undergo H-atom abstraction from the sugar moiety. Interestingly, several products contained two sites of cleavage (U, pUT, and TUp). The formation of these products was linear with dose, and thus, they arise from the single-electron reactions. To explain these products, we propose that the reaction of LEEs (10 eV) involves the coupling of two dissociative processes in the same molecule (for example, dissociative excitation and dissociative electron attachment). The latter reactions may contribute to the formation of clustered damage, which is the most deleterious damage induced by ionizing radiation.
authors: Center for Radiobiology and Radiotherapy, Department of Nuclear Medicine and Radiobiology, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Québec, Canada J1H 5N4.
authors: Zejun
authors: Z
authors: Li
authors: Pierre
authors: P
authors: Cloutier
authors: Léon
authors: L
authors: Sanche
authors: J Richard
authors: JR
authors: Wagner
mesh_terms: D001483:Base Sequence; D001976:Bromouracil / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000737:chemistry; D004249:DNA Damage; D004583:Electrons; D010782:Photolysis; D013056:Spectrophotometry, Ultraviolet
chemical_list: D001976:Bromouracil; D004247:DNA