丙氨酸三肽的稳定构象的探究

探究快速地获得丙氨酸三肽的稳定构象。利用Gaussian09程序包中的 H F/6-31G （d ，p ）方法得到丙氨酸三肽势能面。固定二面角φ2、ψ2的度数，改变二面角φ1、ψ1，计算了丙氨酸三肽不同结构的相对能量，这些结构的相对能量的图像趋势大致相同，可知两组二面角之间影响不大。使用丙氨酸二肽稳定构象所对应的骨架二面角的组合，获得丙氨酸三肽的初始构型，使用B3LYP/6-31G（d ，p）方法优化获得其稳定构象。这种方法可为多肽分子寻找稳定构象提供1种简单而快速的方法。

Exploration of the stable conformations of ala-tripeptide

In this paper ,we explored how to quickly obtain the stable conformations of ala-tripeptide . The potential surface of ala-tripeptide was obtained by using the HF/6-31G（d ,p） in the Gaussian09 . We calculated and displayed the relative energies of different structures of ala-tripeptide by fixing the dihedral angels φ2 and ψ2 andchanging the dihedral angels φ1 and ψ1 .The figures of the relative ener-gies of these structures are alike .It can be seen from the figures that the dihedral angels φ2 and ψ2 have no large effect on the change of φ1 and ψ1 . We obtained the initial structures from the combina-tions of the backbone dihedral angels of the stable conformations of ala-dipeptide .B3LYP/6-31G （d , p） was employed to optimize the initial structures and to get the stable conformations of ala-tripep-tide .This method can supply an easy and quick way to obtain the stable conformation of polypeptide .