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

Molecular electrostatic potential (MEP) values on the van der Waals surface s of 20 amino acids were computed using experimental geometries and four di fferent types of charge distributions, that is, (i) potential-derived (CHel pG) charges. obtained from ab initio SCF calculations using the 3-21G basis set, (ii) hybridization displacement charges (HDC) combined with Lowdin ch arges obtained using the AM1 method, (iii) Clementi charges obtained from a simulation of the interaction of a water molecule with each of the amino a cids, and (iv) Clementi-Fraga (CF) charges obtained using a classification scheme of atom types due to Clementi and coworkers and a normalization sche me 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 molecu les much better than do the Clementi and CF charge distributions and with a n accuracy comparable to that of the ab initio method. Thus, HDC can be emp loyed to study the electrostatic properties of proteins reliably and with a great computational economy. (C) 1999 John Wiley & Sons, Inc.