POTENTIAL DERIVED CHARGES USING A GEODESIC POINT SELECTION SCHEME

Potential derived (PD) atomic charges, obtained by fitting to molecula r electrostatic potentials, are widely used in molecular modeling and simulation calculations. These charges are known to depend on the samp le of points chosen for the fit, on the particular point selection alg orithm, on molecular translations and rotations in many instances, and even on molecular conformation. Following a critique of currently ava ilable methods, a novel point selection scheme is described which resu lts in a highly isotropic array of points located on a series of fused -sphere van der Waals surfaces. The pattern of points is based on tess elations of the icosahedron, and these are discussed in some detail al ong with their connection with virus morphology, geodesic domes, and s ymmetric fullerene structures. Using methanol as a test case, it is sh own that the new method leads to PD charges which are independent of t ranslation and display minimal rotational dependence, and are hence fa r better suited to the determination of PD charges from electrostatic potentials obtained from both theory and experimental X-ray diffractio n data. The conformation dependence of the newly derived PD charges fo r alanyl dipeptide is found to be substantially less than obtained ear lier by Williams [Biopolymers 29, 1367 (1990)]. (C) 1996 by John Wiley & Sons, Inc.