title: Low ionic strength reduces cytosine photoreactivity in UVC-irradiated isolated DNA.
abstract: Exposure of DNA to far-UV radiation leads to the formation of several types of dimeric lesions, including cyclobutane dimers and (6-4) photoproducts. In order to gain insights into the main parameters driving DNA photochemistry, the effect of ionic strength on the yield of formation of these photoproducts was investigated in UVC-irradiated samples of isolated genomic DNA. The main consequence of lowering the ionic strength was a decrease in the UVC-induced formation of thymine-cytosine and cytosine-cytosine photoproducts. The reactivity of thymine-thymine and cytosine-thymine doublets was hardly affected. Evidence was obtained against a major role played by duplex denaturation in these observations. A more likely explanation is a change in the DNA structure as the result of a larger extent of protonation at low counter-ions concentration.
authors.affiliation: Laboratoire Lésions des Acides Nucléiques, Service de Chimie Inorganique et Biologique UMR-E 3 CEA-UJF, CEA/DSM/Département de Recherche Fondamentale sur la Matière Condensée, CEA-Grenoble, 38054, Grenoble Cedex 9, France. thierry.douki@cea.fr
authors.forename: Thierry
authors.initials: T
authors.lastname: Douki
mesh_terms: D000818:Animals; D002417:Cattle; D003596:Cytosine / Q000737:chemistry*; D004247:DNA / Q000737:chemistry / Q000528:radiation effects*; D006863:Hydrogen-Ion Concentration; D009691:Nucleic Acid Denaturation; D009994:Osmolar Concentration; D010777:Photochemistry; D014466:Ultraviolet Rays
chemical_list: D003596:Cytosine; D004247:DNA