Ab initio ionization energy thresholds of DNA and RNA bases in gas phase and in aqueous solution
Ab initio ionization energy thresholds of DNA and RNA bases in gas phase and in aqueous solution
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DOI：
10.1021/jp049270k
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发表时间：
2004-07-29
影响因子：
2.9
通讯作者：
Close, DM
中科院分区：
文献类型：
--
作者：
Crespo-Hernández, CE;Arce, R;Close, DM
使用标准的6-31++G（d,p）基集计算了在HF和MP2理论水平下气相和水溶液中典型DNA和RNA碱基的电离能阈值。结果表明，用自旋投影法修正高自旋态污染的开壳体系，显著提高了计算的电离能。这一修正为气体和水相中计算的电离能提供了实际的实验精度。相对于气相结果，水溶剂对垂直和绝热自由基正离子能的稳定范围分别为2.15 ~ 2.58 eV和2.12 ~ 2.79 eV。从头计算表明，长程体极化相互作用对降低DNA和RNA碱基的第一电离能有重要作用。考虑到溶剂对自由电子的稳定作用，尿嘧啶、胸腺嘧啶、胞嘧啶、腺嘌呤和鸟嘌呤在水溶液中的绝热电离能分别为5.27、5.05、4.91、4.81和4.42 eV。
Ionization energy thresholds have been calculated for the canonical DNA and RNA bases both in the gas phase and in aqueous solution at HF and MP2 levels of theory using standard 6-31++G(d,p) basis set. It is shown that the use of the spin projection procedure to correct the open-shell systems for contamination by higher spin states significantly improves the calculated ionization energies. This correction provides practically experimental accuracy to the calculated ionization energies in gas and in aqueous phase. The stabilization of the vertical and adiabatic radical cation energies by water solvation range from 2.15 to 2.58 eV, and from 2 12 to 2.79 eV, relative to the gas-phase results, respectively. The ab initio calculations show that long-range bulk polarization interactions have a significant role in the lowering of the first ionization energy of the DNA and RNA bases. Taking into account the stabilization of the free electron by the solvent, the adiabatic ionization energies in aqueous solution are estimated to be 5.27, 5.05, 4.91, 4.81, and 4.42 eV for Uracil, thymine, cytosine, adenine, and guanine, respectively.