Characterizing Radiation-Induced Oxidation of DNA by Way of the Monohydrated Guanine−Cytosine Radical Cation

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• 作者：Heather M. Jaeger ; Henry F. Schaefer
• 刊名：Journal of Physical Chemistry B
• 出版年：2009
• 出版时间：June 11, 2009
• 年：2009
• 卷：113
• 期：23
• 页码：8142-8148
• 全文大小：237K
• 年卷期：v.113,no.23(June 11, 2009)
• ISSN：1520-5207

文摘

The interaction of one water molecule with the guanine−cytosine radical cation has been studied with ab initio and density functional methods in order to help elucidate the nature of oxidized aqueous DNA. The theoretical spin density of [GC]•⁺ reveals that the radical center is localized on guanine. The adiabatic ionization potential lowers from 7.63 to 6.71 eV in concurrence with the formation of the Watson−Crick base pair and hydration by one water molecule. A natural bond orbital analysis of partial charges shows that approximately 80% of the positive charge persists on guanine upon hydration and formation of the Watson−Crick base pair with cytosine. Hydration energies were computed with second-order Z-averaged perturbation theory (ZAPT2) using the aug-cc-pVDZ basis set at 11 stationary points on the B3LYP/DZP++ potential energy surface. The hydration energy at the global minimum is 14.2 kcal mol⁻¹. The lowest energy structures correspond to hydration near the glycosidic bond sites. Structural changes in the Watson−Crick base pair are predominantly seen for monohydration in the groove regions of double-helix DNA.