ABSTRACT The aim of this work is to theoretically investigate the guanine–thymine mismatch in the presence of adenine–thymine and guanine–cytosine base pairs. At M06-2X/6-311++G(d,p) level, the absolute values of formation energy of quaternary systems increase by going from systems having enol form of guanine (G*) to those containing enol tautomer of thymine (T*). Moreover, the stacking between T* and purine bases, in comparison with pyrimidine bases, increases the stability of quaternary systems having T*. On the other hand, the stacking between G* and pyrimidine bases more stabilises systems involving G*. From a thermodynamic point of view, the quaternary systems containing G−T* can transform their geometries into systems having G*−T. To gain a better understanding of the influence of hydrogen bonds on the stability of systems, the atoms in molecules and natural bond orbital analyses are used to evaluate the strength of hydrogen bonds in the investigated systems.

中文翻译：

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涉及 DNA 碱基的四元系统中 Watson-Crick 样鸟嘌呤-胸腺嘧啶错配的 DFT 模拟

摘要 这项工作的目的是在理论上研究存在腺嘌呤 - 胸腺嘧啶和鸟嘌呤 - 胞嘧啶碱基对时鸟嘌呤 - 胸腺嘧啶错配。在 M06-2X/6-311++G(d,p) 水平上，四元体系形成能的绝对值从具有烯醇形式的鸟嘌呤 (G*) 到含有烯醇式胸腺嘧啶互变异构体 (T *）。此外，与嘧啶碱基相比，T* 和嘌呤碱基之间的堆叠增加了具有 T* 的四元系统的稳定性。另一方面，G* 和嘧啶碱基之间的堆叠更稳定了涉及 G* 的系统。从热力学的角度来看，包含 G-T* 的四元系统可以将它们的几何形状转换为具有 G*-T 的系统。为了更好地了解氢键对系统稳定性的影响，