DNA cleavage by UVA irradiation of NADH with dioxygen via radical chain processes.
DNA cleavage by UVA irradiation of NADH with dioxygen via radical chain processes.
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DOI：
10.1021/jp064130r
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发表时间：
2006-08
期刊：
影响因子：
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通讯作者：
Makiko Tanaka;K. Ohkubo;S. Fukuzumi
中科院分区：
文献类型：
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作者：
Makiko Tanaka;K. Ohkubo;S. Fukuzumi
通过UVA照射O（2）-饱和的NADH（β-烟酰胺腺嘌呤二核苷酸，还原型）水溶液，观察到有效的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切割。在存在NADH的情况下，发生从NADH的三重激发态（（3）NADH*）到O（2）的能量转移以产生单线态氧（（1）O（2）），其通过1270 nm处的磷光发射检测。在不同浓度的NADH存在下，（1）O（2）在1270 nm处的磷光发射强度没有变化，这表明没有观察到NADH对（1）O（2）的猝灭。除了能量转移外，光诱导电子从（3）NADH* 转移到O（2），产生NADH（*+）和O（2）（*-），这两种情况都通过ESR观察到。O（2）光氧化NADH的量子产率随NADH浓度的增加而线性增加，但随NADH吸收光强的增加而降低。这种不寻常的量子产率对NADH浓度和吸收光强的依赖性表明，O（2）与NADH的光化学氧化通过自由基链过程进行。在光诱导电子转移中产生的O（2）（*-）与HO（2）（*）处于质子化平衡，HO（2）（*）作为链载体，用于自由基链氧化NADH，产生NAD（+）和H（2）O（2），导致DNA切割。
Efficient DNA cleaving-activity is observed by UVA irradiation of an O(2)-saturated aqueous solution of NADH (beta-nicotinamide adenine dinucleotide, reduced form). No DNA cleavage has been observed without NADH under otherwise the same experimental conditions. In the presence of NADH, energy transfer from the triplet excited state of NADH ((3)NADH*) to O(2) occurs to produce singlet oxygen ((1)O(2)) that is detected by the phosphorescence emission at 1270 nm. No quenching of (1)O(2) by NADH was observed as indicated by no change in the intensity of phosphorescence emission of (1)O(2) at 1270 nm in the presence of various concentrations of NADH. In addition to the energy transfer, photoinduced electron transfer from (3)NADH* to O(2) occurs to produce NADH(*+) and O(2)(*-), both of which was observed by ESR. The quantum yield of the photochemical oxidation of NADH with O(2) increases linearly with increasing concentration of NADH but decreases with increasing the light intensity absorbed by NADH. Such unusual dependence of the quantum yield on concentration of NADH and the light intensity absorbed by NADH indicates that the photochemical oxidation of NADH with O(2) proceeds via radical chain processes. The O(2)(*-) produced in the photoinduced electron transfer is in the protonation equilibrium with HO(2)(*), which acts as a chain carrier for the radical chain oxidation of NADH with O(2) to produce NAD(+) and H(2)O(2), leading to the DNA cleavage.