【摘要】 用密度泛函理论研究了胞嘧啶（Cyt）-巴比妥酸（BA）分子间相互作用,以期从理论上预测巴比妥酸类物质对核酸可能产生的影响。在B3LYP/6-311G^**理论水平上优化复合物构型,得到5个Cyt-BAl,8个Cyt-BA2和9个Cyt-BA3稳定复合物,经基组重叠误差和零点振动能校正后,发现在3个系列中最稳定的复合物分别是Cyt-BAl-Ⅳ,Cyt-BA2-Ⅲ和Cyt-BA3-Ⅷ,其结合能各自为53.98,96.48和92.50 kJ/mol,相互作用能主要由氢键贡献。Cyt与BA2-Ⅲ、BA3-Ⅸ以三氢键,其余均以二氢键形成复合物,其稳定性与氢键强度关系非常密切。分析自然键轨道而揭示相互作用的本质。用统计热力学求出常温下从单体形成复合物的热力学性质的变化,发现除Cyt-BA3-Ⅰ、Ⅱ、Ⅵ外,Cyt与BA均可在常温下形成复合物。更多还原

【Abstract】 The interactions between cytosine（Cyt） and barbituric acid（BA） have been studied by examining the van der Waals complexes for the purpose of further investigating the effect of BA on the structure of nucleic acid DFT-B3LYP/6-311G^** theoretical level has been used to optimize the geometries and calculate the binding energiesΔE for five Cyt-BAl,eight Cyt-BA2 and nine Cyt-BA3 stable complexes.In each series,the most stable complex is Cyt-BAl-Ⅳ,Cyt-BA2-Ⅲand Cyt-BA3-Ⅷ,respectively.After the corrections of the basis set superposition error and zero point energies,the corresponding binding energies for the three complexes are 53.98, 96.48 and 92.50 kJ/mol,respectively.The strong hydrogen bonds contribute to the interaction energies dominantly,there is good correlation between stableness of complexes and hydrogen bonding intensity.Natural bond orbital（NBO） analysis was performed to reveal the origin of the interaction.The changes of thermodynamic properties from the monomer to complexes have been obtained with the same method.It was found that complexes can be produced spontaneously from cytosine and barbituric acid at room temperature except Cyt-BA3-I,ⅡandⅥ.更多还原