Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK.
J Phys Chem B. 2010 Mar 18;114(10):3660-7. doi: 10.1021/jp9106958.
Oxidation of DNA represents a major pathway of genetic mutation. We have applied infrared spectroscopy in 77 K glass with supporting density functional theory (DFT) calculations (EDF1/6-31+G*) to provide an IR signature of the guanine radical cation G(+), formed as a result of 193 nm photoionization of DNA. Deprotonation of this species to produce the neutral radical G(-H)() does not occur in 77 K glass. DFT calculations indicate that the formation of G(+) within the double helix does not significantly perturb the geometry of the G/C pair, even though there is a significant movement of the N(1) proton away from G toward C. However, this is in stark contrast to drastic changes that are expected if full deprotonation of G/C occurs, producing the G(-H)()/C pair. These results are discussed in light of solution-phase time-resolved IR spectroscopic studies and demonstrate the power of IR to follow dynamics of DNA damage in natural environments.
DNA 的氧化是遗传突变的主要途径。我们应用 77 K 玻璃中的红外光谱和支持的密度泛函理论（DFT）计算（EDF1/6-31+G*），为鸟嘌呤自由基阳离子 G(+)提供了一个红外特征，该物质是 DNA 193nm 光致电离的结果。在 77 K 玻璃中，该物质不会发生去质子化生成中性自由基 G(-H)()。DFT 计算表明，在双螺旋内形成 G(+)不会显著扰动 G/C 对的几何形状，尽管 N(1)质子从 G 向 C 显著移动。然而，如果 G/C 完全去质子化生成 G(-H)()/C 对，预计会发生剧烈变化，这与实际情况形成鲜明对比。这些结果结合溶液相时间分辨红外光谱研究进行了讨论，并证明了红外在跟踪自然环境中 DNA 损伤动力学方面的强大功能。
