基于从头算的缬氨酸两性离子和水分子的相互作用势

AN INTERACTION POTENTIAL BETWEEN AN VALINE ZWITTERION AND A WATER MOLECELE BASED ON AB INTTIO CALCULATIONS

本工作分两个阶段,第一阶段用从头算方法计算纳氨酸两性离子同处于160种不同位置的水分子的相互作用能,计算时采用最小基组并进行了基组重叠修正,最后还对计算得的相互作用能用Slater-Kirwood公式作色散能修正.第二阶段是势函数拟合的工作,做法是舍弃12个相互作用能大于5Kcal/mole或原子间距离小于1.68(?)的布点,对其余148个布点进行拟合.拟合结果的标准偏差为SD=0.48Kcal/mole.

Interaction energies between a valine zwitterion and a water molecule at 160 different positions and orientations have been calculated by ab initio method with the minimal basis set and by the counterpoise method to eliminate the basis set superposition error . Dispersion energies were estimated by using the Slater - Kirkwood formula . Out of a total 160 computed interaction energies , 148 whose SCF interaction energies were below 5 Kcal/mole have been fitted with a summation of atom-atom pair potentials in the form of the Lennard - Jones potential plus an electrostatic term ( -Aij/rij6 + Bij/fij12 + 332.06CijQiQj/rij). During the fitting , we used a new scheme to keep A>0 and B>A . The standard deviation for this fitting is 0.48 Kcal/mole.