摘要
选择鸟嘌呤脱氧单核苷酸（Ｇ）作为模型，在一定范围内改变确定ＤＮＡ分子构象的８ 个扭转角，对Ｂ→Ｚ转换过程中的不同构象进行量子化学计算。通过能量分析，可将转换中扭转角的作用分为三类：从Ｂ型到Ｚ型，随扭转角γ的变化，势能曲线呈现两个能垒，与８ 个扭转角同时变化一致，说明γ是最重要的。α角和δ角的变化使能量升高对Ｚ构象的形成有显著影响，而β、ε、χ、ν０、ν４ 的变化使能量基本保持不变对新构象的生成影响不大。
The conformations, which might reflect B→Z transition, were modeled by changing 8 torsion angles of 5' deoxyguanylic acid (G) and were calculated by quantum chemistry method. The results showed that torsion angle γ , whose change results in the energy feature as the 8 torsion angles change together, is of crucial importance in the transition. The others could be divided into two groups: α, δ and β, ε, χ, ν 0, ν 4. The former affects Z conformation emergence with going up of the total molecular energy. However, the latter makes little difference in the formation of new conformations due to the smooth energy curves.\;
