Charge distributions and molecular electrostatic potentials around amino acids: Usefulness of hybridization displacement charge

Abstract

Molecular electrostatic potential (MEP) values on the van der Waals surfaces of 20 amino acids were computed using experimental geometries and four different types of charge distributions, that is, (i) potential-derived (CHelpG) charges obtained from ab initio SCF calculations using the 3-21G basis set, (ii) hybridization displacement charges (HDC) combined with Löwdin charges obtained using the AM1 method, (iii) Clementi charges obtained from a simulation of the interaction of a water molecule with each of the amino acids, and (iv) Clementi–Fraga (CF) charges obtained using a classification scheme of atom types due to Clementi and coworkers and a normalization scheme due to Fraga. Taking the MEP values obtained using the CHelpG charges as a standard, it has been shown that HDC describe MEP patterns of the molecules much better than do the Clementi and CF charge distributions and with an accuracy comparable to that of the ab initio method. Thus, HDC can be employed to study the electrostatic properties of proteins reliably and with a great computational economy. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 74: 271–289, 1999