Oxidation Half-Reaction of Aqueous Nucleosides and Nucleotides via Photoelectron Spectroscopy Augmented by ab Initio Calculations
Oxidation Half-Reaction of Aqueous Nucleosides and Nucleotides via Photoelectron Spectroscopy Augmented by ab Initio Calculations
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DOI：
10.1021/ja508149e
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发表时间：
2015-01-14
影响因子：
15
通讯作者：
Bradforth, Stephen E.
中科院分区：
文献类型：
--
作者：
Schroeder, Christi A.;Pluharova, Eva;Bradforth, Stephen E.
对DNA的氧化损伤和氧化DNA中核碱基之间的空穴传输是损伤形成中的重要过程，对于损伤形成，存在令人惊讶的差的热力学数据，氧化四个核碱基的相对容易性就是这样一个例子。DNA辐射损伤和电荷输运的理论模拟依赖于垂直电离能、重组能和标准还原电位的精确值。液体喷射光电子能谱可用于直接研究氧化半反应。核酸结构单元的VIE在其天然缓冲水性环境中测量。嘌呤和嘧啶核苷酸、核苷、戊糖和无机磷酸盐的实验研究表明，核苷酸的光电子光谱是其各个化学成分的光谱总和;也就是说，每个成分之间的电子相互作用被水有效地相互屏蔽。电子结构理论将所有研究的核苷和核苷酸中最低能量的光电子带分配给仅以核碱基为中心的单个电离跃迁。因此，结合测得的VIE与理论上确定的重组能量允许光谱测定的单电子氧化还原电位，已难以建立通过电化学。
Oxidative damage to DNA and hole transport between nucleobases in oxidized DNA are important processes in lesion formation for which surprisingly poor thermodynamic data exist, the relative ease of oxidizing the four nucleobases being one such example. Theoretical simulations of radiation damage and charge transport in DNA depend on accurate values for vertical ionization energies (VIEs), reorganization energies, and standard reduction potentials. Liquid-jet photoelectron spectroscopy can be used to directly study the oxidation half-reaction. The VIEs of nucleic acid building blocks are measured in their native buffered aqueous environment. The experimental investigation of purine and pyrimidine nucleotides, nucleosides, pentose sugars, and inorganic phosphate demonstrates that photoelectron spectra of nucleotides arise as a spectral sum over their individual chemical components; that is, the electronic interactions between each component are effectively screened from one another by water. Electronic structure theory affords the assignment of the lowest energy photoelectron band in all investigated nucleosides and nucleotides to a single ionizing transition centered solely on the nucleobase. Thus, combining the measured VIEs with theoretically determined reorganization energies allows for the spectroscopic determination of the one-electron redox potentials that have been difficult to establish via electrochemistry.