<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kaloudis, Panagiotis</style></author><author><style face="normal" font="default" size="100%">D‚ÄôAngelantonio, Mila</style></author><author><style face="normal" font="default" size="100%">Guerra, Maurizio</style></author><author><style face="normal" font="default" size="100%">Spadafora, Marie</style></author><author><style face="normal" font="default" size="100%">CismasÃß, Crina</style></author><author><style face="normal" font="default" size="100%">Gimisis, Thanasis</style></author><author><style face="normal" font="default" size="100%">Mulazzani, Quinto G.</style></author><author><style face="normal" font="default" size="100%">Chatgilialoglu, Chryssostomos</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">{Comparison of Isoelectronic 8-HO-G and 8-NH2-G Derivatives in Redox Processes}</style></title><secondary-title><style face="normal" font="default" size="100%">J. Am. Chem. Soc.</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://dx.doi.org/10.1021/ja9065464</style></url></web-urls></urls><number><style face="normal" font="default" size="100%">43</style></number><publisher><style face="normal" font="default" size="100%">American Chemical Society</style></publisher><volume><style face="normal" font="default" size="100%">131</style></volume><pages><style face="normal" font="default" size="100%">15895–15902</style></pages><isbn><style face="normal" font="default" size="100%">0002-7863</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">8-Oxo-7,8-dihydroguanine (8-oxo-G) is the major lesion of oxidatively generated DNA damage. Despite two decades of intense study, several fundamental properties remain to be defined. Its isoelectronic 8-aminoguanine (8-NH2-G) has also received considerable attention from a biological point of view, although its chemistry involving redox processes remains to be discovered. We investigated the one-electron oxidation and one-electron reduction reactions of 8-oxo-G and 8-NH2-G derivatives. The reactions of hydrated electrons (eaq‚àí) and azide radicals (N3‚Ä¢) with both derivatives were studied by pulse radiolysis techniques, and the transient absorption spectra were assigned to specific tautomers computationally by means of time-dependent DFT (TD-B3LYP/6-311G**//B1B95/6-31+G**) calculations. The protonated electron adducts of 8-NH2-G and 8-oxo-G showed a substantial difference in their absorption spectra, the unpaired electron being mainly delocalized in the imidazolyl ring and in the six-membered ring, respectively. On the other hand, the deprotonated forms of one-electron oxidation of 8-NH2-G and 8-oxo-G showed quite similar spectral characteristics. In a parallel study, the one-electron reduction of 8-azidoguanine (8-N3-G) afforded the same transient of one-electron oxidation of 8-NH2-G, which represents another example of generation of one-electron oxidized guanine derivatives under reducing conditions. Moreover, the fate of transient species was investigated by radiolytic methods coupled with product studies and allowed self- and cross-termination rate constants associated with these reactions to be estimated.</style></abstract></record></records></xml>