中文摘要：

使用B3LYP／6-31G＊方法优化得到了丙氨酸-α-四肽分子的48个稳定构象．定义了丙氨酸-α-多肽中的特殊氢原子，对构象中与特殊氢原子有关的主要非键相互作用进行分析，提出了使用与特殊氢原子有关的非键相互作用来预测多肽构象的相对稳定性，并将之称为特殊氢方法．基于丙氨酸-α-二肽分子的5个构象和三肽分子的7个构象，确定了特殊氢方法中的与特殊氢原子有关的非键相互作用参数．利用特殊氢方法预测丙氨酸-α-四肽分子的48个构象的相对稳定性，与B3LYP／6-31G＊方法的相对能量比较，得到了满意的结果．特殊氢方法得到的相对能量（功和B3LYP／6-31G＊方法得到的相对能量（X）的线性相关方程为Y=0．9296X＋2．2041，相关系数R=0．9532，标准偏差为3．0kJ／mol，偏差绝对值≤4．18kJ／mol的构象占87．5％．

英文摘要：

Total 48 conformers of alanine-α-tetrapeptide molecule were completely optimized at B3LYP/6-31G＊ level of theory. The special hydrogen atom was defined in this paper and the special hydrogen method was then proposed to predict the conformer relative stability of the alanine-α-polypeptide. The parameters of the seven-membered ring H…O interaction, the five-membered ring H…O interaction and the interaction between two special hydrogen atoms were determined from five conformers of alanine-α-dipeptide. The parameters of the ten-membered ring H…O interaction and the four-membered ring H…O interaction were determined from seven conformers of alanine-α-tripeptide. The relative energies of the 48 conformers of the alanine-α-tetrapeptide molecule were then calculated by the special hydrogen method and by B3LYP/6-31G＊ method, respectively. Compared with the relative energies of the alanine-α-tetrapeptide conformers obtained by B3LYP/6-31G＊ method, it can be concluded that the special hydrogen method is quite reasonable for prediction of the conformation stability of alanine-α-polypeptides. The linear correlation equation between the relative energies Y （kJ/mol） obtained by the special hydrogen method and the relative energies X （kJ/mol） by the B3LYP/6-31G＊ is Y=0.9296X＋2.2041 with the correlation coefficient R= 0.9532 and the standard deviation of 3.0 kJ/mol. The population of the conformations with deviation smaller than 4.18 kJ/mol was up to 87.5%.