丝素氨基酸寡肽链生长过程中的尺寸效应

摘要

A theoretical study on 13 oligopeptides of glycine and alanine by density function theory (DFT) is given in this paper. Geometric structures, vibration frequency, average binding energies, dipole moment are studied, and IR spectra of the oligopeptides are examined. Results show that with increasing number of residues the average binding energies tend to a regular pattern, IR frequencies of typical functional groups start to shift, but stretching and bending vibrations of the groups show the opposite trend of red shift and blue shift. It is revealed that the physical and chemical properties of the silk fibroin peptide chain show size effect and anisotropic in the growth process. This phenomenon may come from the coupling effect of the similar groups, and the different effects of intramolecular hydrogen bond on the stretching and bending vibration.%运用密度泛函理论，对甘氨酸丙氨酸依次交替组成的13条丝素寡肽链进行结构优化，并计算了平均结合能、偶极矩，绘出寡肽链的振动红外光谱。计算结果发现，随着寡肽链的生长，平均结合能单调变化，典型官能团的红外特征峰均发生频移。但官能团的伸缩振动和弯曲振动表现出相反的红移和蓝移趋势。揭示出丝素氨基肽链的物理化学性质在生长过程存在尺寸效应及各向异性。该现象源于同类官能团之间的耦合效应，以及分子内氢键作用对伸缩振动和弯曲振动具有不同的影响。