Proton-coupled electron transfer in DNA on formation of radiation-produced ion radicals.
Proton-coupled electron transfer in DNA on formation of radiation-produced ion radicals.
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DOI：
10.1021/cr100023g
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发表时间：
2010-12-08
期刊：
影响因子：
62.1
通讯作者：
Sevilla, Michael D.
中科院分区：
文献类型：
--
作者：
Kumar, Anil;Sevilla, Michael D.
众所周知，DNA 暴露于高能辐射会导致 DNA 发生各种物理和化学变化，包括链断裂、突变和 DNA 损伤。 1-16 最初，高能辐射随机电离或激发 DNA 成分（碱基、糖和磷酸主链）以及周围的水分子，它们是 DNA 结构的组成部分。产生的空穴迅速释放多余的能量并产生基态阳离子自由基。 12-15, 17, 18 具有动能的二次电子沿着电离辐射的轨道大量产生（每 MeV 能量沉积 4× 104 个）19，并且最近已被证明可以在 DNA 中产生单链和双链断裂。 20-26 只有一小部分二次电子能够造成 DNA 损伤。大多数二次电子会因与介质的碰撞而损失能量，并在皮秒内热化。然后它们要么与空穴重组，要么被嘧啶（胸腺嘧啶 (T) 和胞嘧啶 (C)）捕获，形成 DNA 自由基阴离子 T•- 和 C•-。 DNA 中初始电离事件期间产生的 27 个孔大部分转移到电离势最低的碱基。鸟嘌呤 (G) 具有四种 DNA 碱基（腺嘌呤 (A)、T、G 和 C）28-31 中最低的电离势，因此，鸟嘌呤成为 DNA 中空穴捕获的位点。 32-34 糖磷酸骨架的电离引发了所形成空穴的两个竞争性反应：(i) 从糖环碳位点去质子化，形成中性糖自由基 34-39 和 (ii) 空穴转移到邻近的 DNA 碱基，在碱基到碱基空穴转移后，最终会到达鸟嘌呤。 37, 38, 39b 图1 概述了从DNA 中辐射诱导空穴和二次电子产生到空穴和电子转移、质子转移过程以及随后的分子产物形成（例如从G•+ 形成8-oxo-G）的过程。 32-34 质子耦合电子和空穴转移是辐射损伤过程的一个重要特征。一个例子是图 1 左侧所示的平衡，其中 N3 处胞嘧啶阴离子自由基的质子化导致电子从胸腺嘧啶转移到胞嘧啶。这些质子平衡与辐射产生的离子自由基的电荷转移的耦合是本综述的重点。分子的单电子氧化或还原深刻影响分子的酸/碱性质。失去一个电子后，DNA 碱基的酸性大大增加，而获得一个电子后，与中性碱基相比，DNA 碱基的碱性显着增强。
It is well established that exposure of DNA to high-energy radiation results in a variety of physical and chemical changes in DNA including strand breakage, mutation, and DNA damage. 1-16 Initially, high-energy radiation randomly ionizes or excites DNA components (base, sugar, and phosphate backbone) as well as the surrounding water molecules, which are an integral part of the DNA structure. Holes produced quickly shed excess energy and result in ground-state cation radicals. 12-15, 17, 18 Secondary electrons with kinetic energy are produced in a large quantity (4× 104 per MeV of energy deposited) 19 along the tracks of the ionizing radiation and have been recently shown to produce single-and doublestrand breaks in DNA. 20-26 Only a small fraction of the secondary electrons are able to cause DNA damage. Most secondary electrons undergo collisional loss of energy with the medium and thermalize within picoseconds. They then either recombine with holes or are captured by the pyrimidines (thymine (T) and cytosine (C)) to form DNA radical anions T•-and C•-. 27 Holes produced during the initial ionizing event in DNA for the most part transfer to the base with the lowest ionization potential. Guanine (G) has the lowest ionization potentials of the four DNA bases (adenine (A), T, G, and C), 28-31 and as a consequence, guanine becomes the locus for hole trapping in DNA. 32-34 Ionization of the sugar phosphate backbone initiates two competitive reactions for the hole formed:(i) deprotonation from sugar ring carbon sites to form neutral sugar radicals34-39 and (ii) hole transfer to a neighboring DNA base that after base-tobase hole transfer would end up on guanine. 37, 38, 39b Figure 1 gives an overview of the processes that lead from radiationinduced hole and secondary electron generation in DNA to hole and electron transfer, proton transfer processes, and subsequent molecular product formation such as 8-oxo-G from G•+. 32-34 Proton-coupled electron and hole transfer is an important feature of the radiation damage process. An example is the equilibrium shown in Figure 1, left side, in which protonation of the cytosine anion radical at N3 results in transfer of electrons from thymine to cytosine. Coupling of these prototropic equilibria to charge transfer of radiationproduced ion radicals is the focus of this review. One-electron oxidation or reduction of a molecule profoundly affects the acid/base properties of the molecule. On loss of one electron, DNA bases greatly increase in acidity, whereas, on gain of one electron, DNA bases become substantially more basic in comparison to the neutral base.
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影响因子：
15
作者：
Adhikary A;Kumar A;Khanduri D;Sevilla MD
通讯作者：
Sevilla MD
影响因子：
15
作者：
Adhikary A;Khanduri D;Sevilla MD
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15
作者：
Anderson, Robert F.;Shinde, Sujata S.;Maroz, Andrej
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影响因子：
3.4
作者：
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影响因子：
3.3
作者：
Anderson, RF;Wright, GA
通讯作者：
Wright, GA