Chemical Radiation Studies of 8-Bromoguanosine in Aqueous Solutions

• Published in: Journal of the American Chemical Society 2000-03, Vol.122 (9), p.1900-1907
• Main Authors: Ioele, Marcella, Bazzanini, Rita, Chatgilialoglu, Chryssostomos, Mulazzani, Quinto G
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja991785f

Chemical radiolytic methods were used to investigate the reactions of hydrated electrons (eaq -) with 8-bromoguanosine (8-Br-Guo) as a function of pH. γ-Radiolysis of 8-Br-Guo in aqueous solutions followed by product studies showed the formation of guanosine (Guo) as a single product at various pH. In D2O solutions the quantitative incorporation of deuterium at the 8-position was also observed. Pulse radiolysis revealed the “instantaneous” formation of a guanosine radical cation (Guo•+ or its deprotonated forms) in acid or basic solutions. The same transient species results from the reaction of H• with 8-Br-Guo at pH 3, as well as from the reaction of (CH3)2CO•- with 8-Br-Guo at pH 13. In neutral solution, the initial electron adduct was rapidly protonated to give the first observable transient species that decays by first-order kinetics (k = 5 × 104 s-1) to produce the Guo(-H+)• radical once again. Tailored experiments allowed the reaction mechanism to be defined in some detail.