In this work, DNA base monomers, 15 B-form stacking dimers and two G-quadruplex stacking dimers were studied by quantum chemical computations. Detailed anharmonic vibrational analysis was carried out to reveal vibrational signatures for structural aspect of the base monomers and dimers. It was found that from isolated base monomers to stacking dimers, particularly those containing guanine, the interaction between the C=O stretching is very strong, as depicted by the significant changes of their vibrational frequencies and anharmonicities. Such changes can be manifested well in simulated 1D IR and 2D IR spectra. Delocalization degree of the C = O vibrational modes in stacking dimers, represented by the potential energy distribution and the contribution to the diagonal anharmonicity composition from the vibrators, was found to have significant variations in comparison with isolated bases, which resulted from the influences of the C = O stretching and the nearby vibrations of stacking bases.%用量子化学计算方法研究了DNA碱基单体及其15个B型和2个G-四链体的叠加二聚体的非谐性振动光谱特征.研究发现,从碱基单体到二聚体,C=O伸缩模式之间的相互作用很强,表现在其非谐性振动频率和非谐性常数都发生了明显的改变,特别是在含碱基G的叠加体中.这些变化能在一维和二维红外光谱中很好地表现出来.利用振动模式的势能分布和非谐性常数的组成分析,讨论了叠加二聚体中C=O模式的离域化程度.
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