A Comparative Photomechanistic Study (Spin Trapping, EPR Spectroscopy, Transient Kinetics, Photoproducts) of Nucleoside Oxidation (dG and 8-oxodG) by Triplet-Excited Acetophenones and by the Radicals Generated from α-Oxy-Substituted Derivatives through Norrish-Type I Cleavage
作者:Waldemar Adam、Markus A. Arnold、Werner M. Nau、Uwe Pischel、Chantu R. Saha-Möller
DOI:10.1021/ja017600y
日期:2002.4.1
These results imply that peroxyl radicals are responsible for the photooxidation by the group B ketones, which are formed by alpha cleavage of the triplet ketone and subsequent O(2) trapping of the carbon-centered radicals. At higher dG concentrations, direct electron transfer from dG to the triplet ketone, as observed for the group A ketones, competes with the radical activity.
研究了一系列苯乙酮 (AP-X) 和二苯甲酮 (BP) 对 2'-脱氧鸟苷 (dG) 及其衍生物 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) 的光氧化. 苯甲酰基发色团的良好吸收特性使三线态酮的时间分辨光谱能够通过 dG 和 8-oxodG 评估其淬灭动力学。虽然苯乙酮 (AP)、2-乙酰氧基苯乙酮 (AP-OAc) 和二苯甲酮 (BP) 的光解不产生自由基(A 组酮),但羟甲基取代的衍生物 2-羟基苯乙酮 (AP-OH) 和 2-叔-丁氧基苯乙酮 (AP-O(t)Bu) 通过 α 裂解(B 组酮)产生以碳为中心的自由基。对于后一种酮,这被自旋陷阱 5 的 EPR 研究证实,5-二甲基吡咯啉 N-氧化物 (DMPO) 及其三线态寿命比未取代的苯乙酮短。两组酮均光氧化 dG 和 8-oxodG;在 dG 和 AP-OH 的情况下,氧化产物是螺亚氨基二乙内酰脲和胍释放产物