Morozova Olga B, Kiryutin Alexey S, Yurkovskaya Alexandra V
International Tomography Center of SB RAS, Institutskaya 3a, 630090 Novosibirsk, Russia.
J Phys Chem B. 2008 Mar 6;112(9):2747-54. doi: 10.1021/jp0752318. Epub 2008 Feb 12.
The efficiency of the chemical pathway of DNA repair is studied by time-resolved chemically induced dynamic nuclear polarization (CIDNP) using the model system containing guanosyl base radicals, and tryptophan as the electron donor. Radicals were generated photochemically by pulsed laser irradiation of a solution containing the photosensitizer 2,2'-dipyridyl, guanosine-5'-monophosphate, and N-acetyl tryptophan. Depending on the pH of the aqueous solution, four protonation states of the guanosyl radical are formed via electron or hydrogen atom transfer to the triplet excited dye. The rate constants of electron transfer from the amino acid to the guanosyl radical were determined by quantitative analysis of the CIDNP kinetics, which is very sensitive to the efficiency of radical reactions in the bulk, and rate constants vary from (1.0 +/- 0.3) x 10(9) M(-1) s(-1) for the cation and dication radicals of the nucleotide to (1.2 +/- 0.3) x 10(7) M(-1) s(-1) for the radical in its anionic form. They were found to be higher than the corresponding values for electron transfer in the case of N-acetyl tyrosine as the reducing agent.
利用含有鸟苷碱基自由基和色氨酸作为电子供体的模型系统，通过时间分辨化学诱导动态核极化（CIDNP）研究了DNA修复化学途径的效率。通过脉冲激光照射含有光敏剂2,2'-联吡啶、5'-单磷酸鸟苷和N-乙酰色氨酸的溶液，光化学产生自由基。根据水溶液的pH值，通过电子或氢原子转移到三重激发染料，形成鸟苷自由基的四种质子化状态。通过对CIDNP动力学的定量分析确定了从氨基酸到鸟苷自由基的电子转移速率常数，CIDNP动力学对本体中自由基反应的效率非常敏感，速率常数从核苷酸阳离子和二价阳离子自由基的(1.0 +/- 0.3) x 10(9) M(-1) s(-1)到其阴离子形式自由基的(1.2 +/- 0.3) x 10(7) M(-1) s(-1)不等。发现它们高于以N-乙酰酪氨酸作为还原剂时电子转移的相应值。
