The Sequence Dependence of Photoinduced Single Strand Break in 5-Bromo-2′-deoxyuridine Labeled DNA Supports That Electron Transfer Is Responsible for the Damage

• DOI: 10.1021/acs.jpcb.7b07338
• Publication Date: 2017-09-11T21:26:58Z
• Authors: Kinga Westphal; Samanta Makurat; Janusz Rak
• Keywords: Electron Transport; 0301 basic medicine; 03 medical and health sciences; Bromodeoxyuridine; Light; Electrons; DNA; Models, Biological; DNA Damage

The UVB irradiation of DNA labeled with 5-bromo-2'-deoxyuridine (BrdU) leads to single-strand breaks (SSBs) as a major photochemical damage. Some time ago, we demonstrated that SSB is a secondary damage forming due to thermal dissociation of 2'-deoxyribonolactone generated photochemically in DNA labeled with BrdU. For the first time, we study here the variation of the yield of UVB generated SSBs with the alteration of 3'-neighbor nucleobase of electron donor (2'-deoxyguanine (dG)) and acceptor (excited BrdU) in double-stranded DNA. We showed that the experimental damage yields can be explained by the calculated ionization potentials of dG and electron affinities of excited BrdU via a kinetic scheme based on the Marcus model of electron transfer (ET). Hence, our studies on the sequence dependence of photochemical damage in DNA labeled with BrdU constitute a further argument that photochemically generated SSBs occur as a result of long-range ET.