核酸碱基的非谐性振动:正规及错配碱基对的一维和二维红外光谱及其结构基础

Anharmonic vibrations of nucleobases:Structural basis of one-and two-dimensional infrared spectra for canonical and mismatched base pairs

用量子化学计算研究了正规Watson-Crick碱基对和四例典型的错配碱基对.对碱基单体和二聚体进行了详细的非谐性频率分析,以揭示其结构方面的一些振动特征.研究发现这些振动特征能在模拟的一维和二维红外光谱中很好地表现出来.利用势能分布研究了所选简正模式的离域化程度,发现从孤立的碱基单体到参与氢键的二聚体,模式的离域化程度变化很大;同时,这些模式的非谐性常数也发生了相应的改变.以人们通常认为的位于红外光谱中6-μm波长区域的羰基伸缩模式为例进行了探讨.

In this work, canonical Watson-Crick base pairs and four representative mismatched base pairs were studied by quantum chemical computations. Detailed anharmonic vibrational analysis was carried out to reveal some vibrational signatures in structural aspect of the base monomers and dimers, which, were well manifested in simulated 1D IR and 2D IR spectra. Delocalization degree of the selected normal modes, represented by the potential energy distribution, was found to vary significantly from isolated bases to H-bonded dimers, accompanied by changes in anharmonicities of these modes. Examples were given for the commonly believed carbonyl stretching mode of base pair appeared in the 6-μm wavelength region of IR spectra.