title: Combined NMR and DFT studies for the absolute configuration elucidation of the spore photoproduct, a UV-induced DNA lesion.
abstract: By irradiation of bacterial spores under UV radiation, a photoproduct (SP) bearing a covalent methylene link between two adjacent thymines is formed in DNA. Because of the presence of an asymmetric carbon on the aglycone and of two possible orientations for the formation of the cross-link, four isomers could in principle be obtained. Currently, no conclusive structural information of this photoproduct is available. The structure of the isolated SPTpT dinucleotide was revisited in order to determine the type of cross-link and the absolute configuration of the C5a carbon. For this purpose, a study combining NMR spectroscopy and DFT calculations was pursued on the spore photoproduct of the dinucleoside TpT since its structure was previously shown to be identical to the one produced in DNA. A full characterization of SPTpT by NMR analyses was performed in D2O and DMSO. 2D NMR measurements (1H-13C, 1H-31P, COSY, NOESY, and ROESY) and DFT calculations (geometries optimization of R and S isomers and theoretical chemical shifts) lead us to conclude without ambiguity that the absolute configuration of the C5a carbon is R and that the methylene bridge of the photoproduct corresponds to the methyl group of the thymine located on the 3'-end of the dinucleoside monophosphate.
authors.affiliation: CEA, INAC, SCIB, UMR-E 3 CEA-UJF, Laboratoire de Résonance Magnétique, F-38054 Grenoble, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Mantel
authors.forename: Alexia
authors.initials: A
authors.lastname: Chandor
authors.forename: Didier
authors.initials: D
authors.lastname: Gasparutto
authors.forename: Thierry
authors.initials: T
authors.lastname: Douki
authors.forename: Mohamed
authors.initials: M
authors.lastname: Atta
authors.forename: Marc
authors.initials: M
authors.lastname: Fontecave
authors.forename: Pierre-Alain
authors.initials: PA
authors.lastname: Bayle
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Mouesca
authors.forename: Michel
authors.initials: M
authors.lastname: Bardet
mesh_terms: D004247:DNA / Q000737:chemistry*; D017666:Deuterium Oxide / Q000737:chemistry; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D014466:Ultraviolet Rays
chemical_list: D004247:DNA; D017666:Deuterium Oxide