Balanikas Evangelos, Banyasz Akos, Baldacchino Gérard, Markovitsi Dimitra
Université Paris-Saclay, CEA, CNRS, LIDYL, Gif-sur-Yvette, F-91191, France.
Univ Lyon, ENS de Lyon, CNRS, UMR 5182, Université Claude Bernard Lyon 1, Laboratoire de Chimie, Lyon, F-69342, France.
Photochem Photobiol. 2022 May;98(3):523-531. doi: 10.1111/php.13540. Epub 2021 Nov 17.
This review is dedicated to guanine radical cations (G ) that are precursors to oxidatively generated damage to DNA. (G ) are unstable in neutral aqueous solution and tend to lose a proton. The deprotonation process has been studied by time-resolved absorption experiments in which (G ) radicals are produced either by an electron abstraction reaction, using an external oxidant, or by low-energy/low-intensity photoionization of DNA. Both the position of the released proton and the dynamics of the process depend on the secondary DNA structure. While deprotonation in duplex DNA leads to (G-H1) radicals, in guanine quadruplexes the (G-H2) analogs are observed. Deprotonation in monomeric guanosine proceeds with a time constant of ~60 ns; in genomic DNA, it is completed within 2 µs; and in guanine quadruplexes, it spans from at least 30 ns to over 50 µs. Such a deprotonation dynamics in four-stranded structures, extended over more than three decades of times, is correlated with the anisotropic structure of DNA and the mobility of its hydration shell. In this case, commonly used second-order reaction models are inappropriate for its description.
本综述致力于探讨鸟嘌呤自由基阳离子（G•+），其是DNA氧化损伤的前体。G•+在中性水溶液中不稳定，易于失去一个质子。通过时间分辨吸收实验研究了去质子化过程，其中G•+自由基可通过使用外部氧化剂的电子提取反应或通过DNA的低能/低强度光电离产生。释放质子的位置和过程的动力学均取决于二级DNA结构。虽然双链DNA中的去质子化会产生（G-H1）自由基，但在鸟嘌呤四链体中观察到的是（G-H2）类似物。单体鸟苷中的去质子化以约60 ns的时间常数进行；在基因组DNA中，它在2 μs内完成；而在鸟嘌呤四链体中，其持续时间至少从30 ns到超过50 μs。这种在四链结构中跨越超过三个数量级时间的去质子化动力学与DNA的各向异性结构及其水化层的流动性相关。在这种情况下，常用的二级反应模型不适用于描述它。
