2',3'-二脱氧-2',3'-二去氢鸟嘌呤核苷构象稳定性的理论研究

采用密度泛函方法在B3LYP/6-31＋G**水平上研究了2',3'-二脱氧-2',3'-二去氢鸟嘌呤核苷分子(D4G)的构象. 分别研究在气相中的孤立分子和一水合物异构体的相对稳定性和异构体之间的相互转变过程, 分析了水分子的参与对D4G异构体的相对稳定性和几何结构参数以及自然电荷的影响. 结果表明, 孤立的D4G分子在气相中存在8种稳定构象, 其中构象d4g-2是所有构象中最稳定的, 气相中D4G主要以d4g-2存在. 气相中各构象的相对稳定性为: d4g-2＞d4g-1＞d4g-5＞d4g-3＞d4g-6＞d4g-4＞d4g-8＞d4g-7. 计算得到的各构象键长和键角数据与实验值接近. 一个水分子的加入对D4G分子的构型参数有所影响, 基本不改变D4G分子各构象的稳定性顺序, 但构象转变的能垒有所提高. 氢键在分子构象中发挥了重要作用.

Theoretical Study on the Conformational Stability of 2',3'-Dideoxy-2',3'-didehydroguanosine

The DFT (B3LYP/6-31 G**) method was used to study the conformations and isomerization of the isolated and monohydrated 2',3'-dideoxy-2',3'-didehydroguanosine (D4G) molecules in gas phase. The effects of one-water molecule on relative stabilities, conformational parameters and nature charges of D4G were analyzed. The results indicate that there are 8 stable conformers for D4G in gas phase. The conformer d4g-2 is the most stable form of all conformations in gas phase. The relative stability order is as follows: d4g-2>d4g-1>d4g-5>d4g-3>d4g-6>d4g-4>d4g-8>d4g-7. The computational results are in good agreement with the available experimental ones. The addition of one-water molecule did not almost change the order of the relative stability and increased slightly the energy barriers of conformational isomerization of D4G. Hydrogen bonding played an important role in D4G conformations.