Sturdy Yvette K, Skylaris Chris-Kriton, Clary David C
Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
J Phys Chem B. 2006 Mar 2;110(8):3485-92. doi: 10.1021/jp053225a.
Schemes to include a treatment of torsional anharmonicity in the conformational analysis of biological molecules are introduced. The approaches combine ab initio electronic energies and harmonic frequencies with anharmonic torsional partition functions calculated using the torsional path integral Monte Carlo method on affordable potential energy surfaces. The schemes are applied to the conformational study of the monosaccharide beta-d-galactose in the gas phase. The global minimum structure is almost exclusively populated at 100 K, but a large number of conformers are present at ambient and higher temperatures. Both quantum mechanical and anharmonic effects in the torsional modes have little effect on the populations at all temperatures considered, and it is, therefore, expected that standard harmonic treatments are satisfactory for the conformational study of monosaccharides.
介绍了在生物分子构象分析中纳入扭转非谐性处理的方案。这些方法将从头算电子能量和谐波频率与使用扭转路径积分蒙特卡罗方法在经济适用的势能面上计算的非谐扭转配分函数相结合。该方案应用于气相中单糖β - D - 半乳糖的构象研究。在100 K时几乎只存在全局最小结构，但在环境温度及更高温度下存在大量构象异构体。在所有考虑的温度下，扭转模式中的量子力学和非谐效应对构象分布影响很小，因此预计标准的谐波处理对于单糖的构象研究是令人满意的。
