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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Specific Solvation Effects on Structures and Properties of Isocytosine-Cytosine Complexes: A Theoretical ab Initio Study
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Specific Solvation Effects on Structures and Properties of Isocytosine-Cytosine Complexes: A Theoretical ab Initio Study

机译：对异胞嘧啶-胞嘧啶复合物的结构和性质的特定溶剂作用：理论从头算研究

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Ab initio quantum chemical studies at the Hartree-Fock (HF) level with the 6-31G↑(*) basis set were performed for four different hydrogen-bonded isocytosine-cytosine (iCC) complexes in the gas phase and in a water solution. Full geometry optimizations without any constraints on the planarity of these complexes were carried out. The water solution was modeled by explicit inclusion of different numbers of water molecules, up to six, which creates the first coordination sphere around the iCC base pair. Single point calculations were also performed at the correlated MP2/6-31G↑(*)//HF/6-31G↑(*) level. The interaction and solvation energies were corrected for the basis set superposition error by using the full Boys-Bernardi counterpoise correction scheme. It was shown that the base pair corresponding to the standard Watson-Crick pair (denoted as iCC1) is the global minimum on the potential energy surface both in the gas phase and in a water solution. Inclusion of six instead of four water molecules has crucial effects both on the geometries and relative stabilities of iCC complexes. Complexes involving six water molecules become strongly nonplanar, whereas in the case of four or fewer water molecules, only a slight deviation from planarity is observed. Moreover, the relative stability order changes when one considers six water molecules, and the zwitterionic form (denoted as iCC4) becomes the second most stable species after the Watson-Crick iCC1 base pair. Since the structure of isocytosine mimics the six-membered parts of guanine, the results of this study could provide important insights into the structures and properties of analogous guanine-cytosine complexes in a water solution.
机译：在气相和水溶液中，对四种不同的氢键结合的异胞嘧啶-胞嘧啶（iCC）配合物，进行了Hartree-Fock（HF）浓度为6-31G↑（*）的从头算量子化学研究。进行了完整的几何优化，对这些配合物的平面度没有任何限制。通过显式包含多达六个的不同数量的水分子对水溶液进行建模，从而创建了围绕iCC碱基对的第一个配位球。还以相关的MP2 / 6-31G↑（*）// HF / 6-31G↑（*）级别执行单点计算。通过使用完整的Boys-Bernardi平衡校正方案，校正了基团叠加误差的相互作用和溶剂化能。结果表明，对应于标准沃森-克里克对的碱基对（表示为iCC1）在气相和水溶液中在势能面上都是全局最小值。包含六个而不是四个水分子对iCC配合物的几何形状和相对稳定性均具有至关重要的作用。包含六个水分子的复合物变得非常不平坦，而在四个或更少的水分子的情况下，仅观察到与平面度的轻微偏差。此外，当人们考虑六个水分子时，相对稳定性顺序发生变化，两性离子形式（表示为iCC4）成为仅次于Watson-Crick iCC1碱基对的第二稳定物种。由于异胞嘧啶的结构模拟鸟嘌呤的六元部分，因此本研究的结果可为水溶液中类似鸟嘌呤-胞嘧啶复合物的结构和性质提供重要的见识。

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