Indications of 5' to 3' Interbase Electron Transfer as the First Step of Pyrimidine Dimer Formation Probed by a Dinucleotide Analog.
Chemistry
; 23(31): 7526-7537, 2017 Jun 01.
Article
em En
| MEDLINE
| ID: mdl-28370554
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 254â
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.
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MEDLINE
Assunto principal:
Dímeros de Pirimidina
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Fosfatos de Dinucleosídeos
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Elétrons
Idioma:
En
Ano de publicação:
2017
Tipo de documento:
Article