Bose Adity, Basu Samita
Chemical Sciences Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700 064, India.
J Phys Chem A. 2008 Nov 27;112(47):12045-53. doi: 10.1021/jp805632j.
Laser flash photolysis and an external magnetic field have been used to study the interaction of two quinone molecules, namely, 9,10-anthraquinone (AQ) and 2-methyl-1,4-naphthoquinone, commonly known as menadione (MQ), with the RNA base uracil (U) and two of its derivatives, 1,3-dimethyluracil (dmU) and uridine (dU). We have conducted our studies in homogeneous organic and heterogeneous micellar media in order to investigate the effect of media on the molecules and any change in reactivity on account of substitution. In organic homogeneous medium, both the quinones have behaved similarly with the bases. Here U has undergone both electron transfer (ET) and hydrogen (H) transfer, while dU and dmU have failed to exhibit any ET. Failure to support ET has been attributed to keto-enol tautomerism, which has been found to have a significant role in determining the occurrence of ET from these pyrimidine bases. However, in SDS micelles some variations regarding the reactivity of these molecules have been discerned. The variations are 2-fold. Here ET from U has been found to get completely eclipsed by a dominant H abstraction with both the quinones, and AQ reveals a difference in the extent of H abstraction with the bases in SDS. With U and dU, the prevailing H abstraction with AQ has succeeded in formation of only AQH(), while dmU has produced both AQH() and AQH(2), the latter being formed by two successive H abstraction. Explanations of this intriguing behavior with U and its derivatives with quinone molecules have been the main concern in this work.
激光闪光光解和外加磁场已被用于研究两种醌分子，即9,10-蒽醌（AQ）和2-甲基-1,4-萘醌（俗称甲萘醌，MQ）与RNA碱基尿嘧啶（U）及其两种衍生物1,3-二甲基尿嘧啶（dmU）和尿苷（dU）的相互作用。我们在均相有机介质和非均相胶束介质中进行了研究，以考察介质对分子的影响以及由于取代作用而导致的反应活性的任何变化。在有机均相介质中，两种醌与碱基的行为相似。在这里，U既发生了电子转移（ET），也发生了氢（H）转移，而dU和dmU未能表现出任何ET。未能支持ET归因于酮-烯醇互变异构，已发现其在决定这些嘧啶碱基发生ET方面具有重要作用。然而，在十二烷基硫酸钠（SDS）胶束中，已发现这些分子的反应活性存在一些变化。这些变化有两方面。在这里，已发现来自U的ET完全被两种醌占主导的氢提取所掩盖，并且AQ显示出在SDS中与碱基氢提取程度上存在差异。对于U和dU，与AQ占主导的氢提取仅成功形成了AQH()，而dmU产生了AQH()和AQH(2)，后者是由两次连续的氢提取形成的。用U及其衍生物与醌分子解释这种有趣的行为一直是这项工作的主要关注点。
