应用ABEEMσπ方法估算含有羟基的分子的pK_a值

Estimation of pK_a values of hydroxyl molecules by using ABEEMσπ method

使用B3LYP/6-311++G(d,p)方法,优化获得含有羟基的训练集分子的稳定几何结构,以HF/STO-3G方法所计算的Mulliken电荷为基准,采用线性回归和最小二乘法调试出ABEEMσπ方法计算电荷所需要的参数(价态电负性χ*和价态硬度η*).探讨拟合训练集分子中与羟基相连的C原子和与羟基的H原子的电荷差值与实验pK_a值的线性方程.通过该线性方程和ABEEMσπ所计算的电荷,估算出一些含有羟基测试集分子的pK_a值.这些分子包括了12个含有羟基的有机小分子;1个Tyr二肽、6个Ser二肽;质子化和中性的Trp-cage蛋白质.使用ABEEMσπ方法所估算的pK_a值与实验值很接近.因此,ABEEMσπ方法能快速估算其他含有羟基分子的pK_a值.

The B3LYP/6-311＋＋G（d,p）method is used to optimize a training set of small molecules with an OH group and to obtain their geometry structures.ABEEMσπparameters including the valence-state electronegativityχ＊and the valence-state hardnessη＊have been determined through a linear regression and least-square optimization procedure to reproduce HF/STO-3G Mulliken charge distribution for the molecules mentioned above.We have obtained the linear equation of the difference between C connected with OH group atomic charges and H atom with experimental pK_a.The pK_a values of test set molecules with OH group are estimated by this linear equation.These molecules include twelve organic small molecules with an OH group,one Tyr dipeptide,six Ser dipeptides,protonated and neutral Trp-cage proteins.The pK_avalues estimated by ABEEMσπ method are close to the experimental pK_avalues.Thus,ABEEMσπ method can be used to fast estimate pK_avalues of the other molecules containing OH group.