DNA cleavage via superoxide anion formed in photoinduced electron transfer from NADH to γ-cyclodextrin-bicapped C60 in an oxygen-saturated aqueous solution
DNA cleavage via superoxide anion formed in photoinduced electron transfer from NADH to γ-cyclodextrin-bicapped C60 in an oxygen-saturated aqueous solution
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DOI：
10.1021/jp013215j
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发表时间：
2002-03-07
影响因子：
3.3
通讯作者：
Miyata, N
中科院分区：
文献类型：
--
作者：
Nakanishi, I;Fukuzumi, S;Miyata, N
γ-环糊精-双帽C-60（C-60/γ-CyD）在可见光照射下在O-2饱和水溶液中存在NADH（β-烟酰胺腺嘌呤二核苷酸，还原形式）时显示出有效的DNA切割活性。在其他相同的实验条件下，没有观察到没有NADH的DNA裂解，尽管通过C-60/γ-CyD-O-2系统的ESR自旋捕获检测到单线态氧（O-1（2））。这表明C60/γ-CyD的三重激发态（C-3（60）*/γ-CyD）和通过从C-3（60）*/γ-CyD到O-2的能量转移产生的O-1（2）都不是实际的反应性物种，其在本实验条件下负责DNA损伤。在存在NADH的情况下，发生从NADH到C-3（60）*/γ-CyD的光诱导电子转移，以产生两当量的自由基阴离子（C-60（.-）/γ-CyD）。γ-CyD），其在1080 nm处显示其特征NIR带。光诱导电子转移的动力学已经通过监测在740 nm处的三重态-三重态吸收带的衰减和由于C60（.-）/γ-CyD与C-60/γ-CyD-NADH系统的激光闪光光解。在O-2、C-60（.-）/γ-CyD通过电子转移到O-2和电子从NADH转移到O-1（2）到产生的O-2（.-）而消失，O-2（.-）的形成已被证实的自旋陷阱与DEPMPO（5-二乙氧基磷酰基-5-甲基-1-吡咯啉-N-氧化物），这是一个有效的O-2（.-）-捕集剂O-2还原为O-2（.-）计算值为43.4 kcal mol（-1），这与直接测定O-36（2）之间自交换的文献值一致。O-32（2）。这表明，从C-60（.-）/γ-CyD到O-2通过外层途径进行。O-2（.-）由此产生H2 O2，最终产生羟基自由基，其被证明是实际的DNA裂解试剂。
gamma-Cyclodextrin-bicapped C-60 (C-60/gamma-CyD) shows an efficient DNA cleaving-activity in the presence of NADH (beta-nicotinamide adenine dinucleotide, reduced form) in an O-2-saturated aqueous solution under visible-light irradiation. No DNA cleavage has been observed without NADH under experimental conditions that are otherwise the same, although singlet oxygen (O-1(2)) has been detected by the ESR spin-trapping of the C-60/gamma-CyD-O-2 system. This indicates that neither triplet excited state of C60/gamma-CyD (C-3(60)*/gamma-CyD) nor O-1(2) produced via an energy transfer from C-3(60)*/gamma-CyD to O-2 is an actual reactive species, which is responsible for the DNA damage under the present experimental conditions. In the presence of NADH, photoinduced electron transfer from NADH to C-3(60)*/gamma-CyD occurs to yield two equivalents of the radical anion (C-60(.-)/gamma-CyD), which exhibits its characteristic NIR band at 1080 nm. The dynamics of the photoinduced electron transfer have been examined by monitoring the decay of triplet-triplet absorption band at 740 nm and concomitant rise of the NIR absorption band at 1080 nm due to C60(.-)/gamma-CyD with use of the laser flash photolysis for the C-60/gamma-CyD-NADH system. In the presence Of O-2, C-60(.-)/gamma-CyD disappears via the electron transfer to O-2 and an electron transfer from NADH to O-1(2) to produced O-2(.-), The formation Of O-2(.-) has been confirmed by the spin trap with DEPMPO (5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide), which is an efficient O-2(.-)-trapping agent. The reorganization energy for the reduction Of O-2 to O-2(.-) is evaluated as 43.4 kcal mol(-1), which agrees with the literature value determined directly for the self-exchange between O-36(2).- and O-32(2). This indicates that the electron transfer from C-60(.-)/gamma-CyD to O-2 proceeds via an outer-sphere pathway. The O-2(.-) thus produced gives H2O2, ultimately yielding hydroxyl radical, which is shown to be an actual DNA-cleaving reagent.