title: Indications of 5' to 3' Interbase Electron Transfer as the First Step of Pyrimidine Dimer Formation Probed by a Dinucleotide Analog.
abstract: Pyrimidine dimers are the most common DNA lesions generated under UV radiation. To reveal the molecular mechanisms behind their formation, it is of significance to reveal the roles of each pyrimidine residue. We thus replaced the 5'-pyrimidine residue with a photochemically inert xylene moiety (X). The electron-rich X can be readily oxidized but not reduced, defining the direction of interbase electron transfer (ET). Irradiation of the XpT dinucleotide under 254 nm UV light generates two major photoproducts: a pyrimidine (6-4) pyrimidone analog (6-4PP) and an analog of the so-called spore photoproduct (SP). Both products are formed by reaction at C4=O of the photo-excited 3'-thymidine (T), which indicates that excitation of a single "driver" residue is sufficient to trigger pyrimidine dimerization. Our quantum-chemical calculations demonstrated that photo-excited 3'-T accepts an electron from 5'-X. The resulting charge-separated radical pair lowers its energy upon formation of interbase covalent bonds, eventually yielding 6-4PP and SP.
authors.affiliation: Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis (IUPUI), 402 North Blackford Street, Indianapolis, Indiana, 46202, USA.|School of Chemistry & Chemical Engineering, Shaanxi Normal University (SNNU), No. 620, West Chang'an Avenue, Xi'an, Shaanxi, 710119, P. R. China.
authors.forename: Yajun
authors.initials: Y
authors.lastname: Jian
authors.affiliation: Department of Biomolecular Mechanisms, Max-Planck Institute for Medical Research, Jahnstrasse 29, 69120, Heidelberg, Germany.
authors.forename: Egle
authors.initials: E
authors.lastname: Maximowitsch
authors.affiliation: Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis (IUPUI), 402 North Blackford Street, Indianapolis, Indiana, 46202, USA.
authors.forename: Degang
authors.initials: D
authors.lastname: Liu
authors.affiliation: Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis (IUPUI), 402 North Blackford Street, Indianapolis, Indiana, 46202, USA.
authors.forename: Surya
authors.initials: S
authors.lastname: Adhikari
authors.affiliation: Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis (IUPUI), 402 North Blackford Street, Indianapolis, Indiana, 46202, USA.|Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana, 46202, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Li
authors.affiliation: Department of Biomolecular Mechanisms, Max-Planck Institute for Medical Research, Jahnstrasse 29, 69120, Heidelberg, Germany.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Domratcheva
mesh_terms: D015226:Dinucleoside Phosphates / Q000737:chemistry / Q000378:metabolism*; D004583:Electrons; D011740:Pyrimidine Dimers / Q000096:biosynthesis*
chemical_list: D015226:Dinucleoside Phosphates; D011740:Pyrimidine Dimers
keywords: DNA photochemistry; electron transfer; pyrimidine (6-4) pyrimidone photoproduct; spore photoproduct; thymine dimer