甘氨酸直链寡肽振动光谱频移现象的理论研究

运用密度泛函理论，在6-31G(d)基组水平上对甘氨酸直链寡肽进行几何优化，并对其几何结构、平均结合能、振动频率进行计算。结果表明，平均结合能随着肽链增加单调变化，并趋于稳定;寡肽链键长的分析发现，链向与径向方向上变化趋势相反，存在各向异性。红外光谱的分析发现，位于肽键上同一基团的伸缩振动与弯曲振动分别发生红移和蓝移，并存在各向异性。这些现象源于：准一维的纳米结构导致了键长的各向异性;相同基团之间的诱导效应、耦合效应及氢键等因素导致了振动频率的红移和蓝移等现象。我们得出结论：甘氨酸直链寡肽链的生长利于结构的稳定性，在能量上，推测出寡肽链有自组装生长的趋势;在寡肽链的生长过程中，通过构象和光谱的现象，推断其物理化学属性存在尺寸效应。肽链端部基团的物理化学属性非常稳定，基本不受寡肽链长度的影响。该结果对应用红外光谱测量寡肽链的残基数及长度、特殊功能寡肽链的制备等工作具有指导意义。

Theory Study on Glycine Linear Oligopeptide Vibrational Spectrum Frequency Shift

By using the density functional theory, glycine linear oligopeptide of different lengths was geometrically optimized on the 6-31G (d) basis set level, their growth processes were simulated, and the average binding energy and vibration frequency were calculated with geometry. The results showed that the average binding energies tend to change in a regular pattern and stabilize with the number of residues increasing; With the oligopeptide chain bond length analysis it was found that the chain to the radial direction there is a opposite trend for chain and radial direction, which is anisotropic. It was found by the IR spectrum analysis that red shifts and blue shifts occur respectively when the same group of peptide bond vibrate, which is anisotropic; These phenomena originate from that quasi one-dimensional nanostructures lead to the anisotropy of the bond length; the induced effects, coupling effects and hydrogen bonding etc. between the same groups lead to the vibration frequency red shifts and blue shifts. The authors conclude that the growth of glycine linear oligopeptide is conducive to stability of the structure, and the authors infer that the oligopeptide has the tendency of self-assembled growth; Through the conformation and spectrum, the authors infer that there is a size effect in physical and chemical properties. The physical and chemical properties of peptide chain end group are extremely stable and unaffected by the impact of the oligopeptide chain length. The results are significant to measuring the length and the number of residue of peptide, and to manufacturing the special features oligopeptide chain.