title: Electron induced single strand break and cyclization: a DFT study on the radiosensitization mechanism of the nucleotide of 8-bromoguanine.
abstract: Cleavage of the O-P bond in 8-bromo-2'-deoxyguanosine-3',5'-diphosphate (BrdGDP), considered as a model of single strand break (SSB) in labelled double-stranded DNA (ds DNA), is investigated at the B3LYP/6-31++G(d,p) level. The thermodynamic and kinetic characteristics of the formation of SSB are compared to those related to the 5',8-cycloguanosine lesion. The first reaction step, common to both damage types, which is the formation of the reactive guanyl radical, proceeds with a barrier-free or low-barrier release of the bromide anion. The guanyl radical is then stabilized by hydrogen atom transfer from the C3' or C5' sites of the 2'-deoxyribose moiety to its C8 center. The C3' path, via the O-P bond cleavage, leads to a ketone derivative (the SSB model), while the C5' path is more likely to yield 5',8-cycloguanosine.
authors.affiliation: Department of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland. janusz.rak@ug.edu.pl.
authors.forename: Lidia
authors.initials: L
authors.lastname: Chomicz
authors.forename: Al'ona
authors.initials: A
authors.lastname: Furmanchuk
authors.forename: Jerzy
authors.initials: J
authors.lastname: Leszczynski
authors.forename: Janusz
authors.initials: J
authors.lastname: Rak
mesh_terms: D003500:Cyclization; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D053904:DNA Breaks, Single-Stranded; D004583:Electrons; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D009711:Nucleotides / Q000737:chemistry*; D011839:Radiation, Ionizing; D011838:Radiation-Sensitizing Agents / Q000737:chemistry* / Q000378:metabolism; D013816:Thermodynamics
chemical_list: C502319:8-bromoguanine; D009711:Nucleotides; D011838:Radiation-Sensitizing Agents; D006147:Guanine; D004247:DNA