Triplet state mechanism for electron transfer oxidation of DNA

The interaction of anthraquinone-2-sulfonate with nucleotides and DNA in ac etonitrile and acetonitrile water solvent mixture have been studied using K rF laser photolysis aimed at elucidation of the reaction mechanism. Laser s pectroscopy directly demonstrates that the initial species from interaction of anthraquinone-2-sulfonate with nucleotides are radical cations of nucle otides and radical anion of anthraquinone-2-sulfonate. In addition, formati on of ion pair from interaction of any of mucleotides with anthraquinone-2- sulfonate is synchronous with decay of triplet anthraquinone-2-sulfonate, w hich has provided dynamic evidence for initiation of electron transfer from DNA bases to tripler anthraquinone-2-sulfonate. Moreover, direct observati on of stabilized DNA guanyl radical cation from interaction of anthraquinon e-2-sulfonate with DNA has provided initial evidence for selective cleavage of DNA at guanine moiety. The solvent-separated ion pairs in acetonitrile have evidently dissociated into free ions, thereby enabling independent stu dy of the behavior of guanyl radical cations and radical anion of anthraqui none-2-sulfonate. (C) 2000 Elsevier Science S.A. All rights reserved.