Alyoubi A O, Hilal R H
Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 9028, Jeddah 21413, Saudi Arabia.
Biophys Chem. 1995 Aug;55(3):231-7. doi: 10.1016/0301-4622(95)00002-f.
The electronic structures of all possible tautomers of uracil, thymine, cytosine, adenine and guanine have been carefully examined within the MNDO-MO frame-work. Equilibrium geometries are determined and the relative stabilities are discussed. Allowance for solvent effect on the stabilities is made by assuming a tetrahedral solvent cage with the DNA base occupying its centre. The electronic absorption spectra of the studied DNA bases, in solvents of different polarities are recorded and discussed. Assignments of the observed bands are facilitated using MNDO-CI computations. It is suggested that in solution the DNA bases are in some statistical mixtures of the most stable tautomers, and the Watson-Crick (WC) structure cannot account for the observed spectra alone.
在MNDO-MO框架内，对尿嘧啶、胸腺嘧啶、胞嘧啶、腺嘌呤和鸟嘌呤所有可能的互变异构体的电子结构进行了仔细研究。确定了平衡几何结构并讨论了相对稳定性。通过假设一个以DNA碱基为中心的四面体溶剂笼来考虑溶剂对稳定性的影响。记录并讨论了所研究的DNA碱基在不同极性溶剂中的电子吸收光谱。使用MNDO-CI计算有助于对观察到的谱带进行归属。结果表明，在溶液中DNA碱基处于最稳定互变异构体的某种统计混合物中，仅沃森-克里克（WC）结构无法解释观察到的光谱。
