DERIVATION OF FUSED-SPHERE MOLECULAR-SURFACES FROM PROPERTIES OF THE ELECTROSTATIC POTENTIAL DISTRIBUTION

The distribution of molecular electrostatic potential (MEP) on a surfa ce is a common model used to describe simultaneously steric properties (e.g., size, shape) and reactive properties (e.g., electro- and nucle ophilic positions) of a molecule. In this work, we analyze some relati ons between these two properties. In particular, we explore the possib le definition of an optimum fused-sphere molecular surface from proper ties of the MEP distribution. With this goal, we study how several sta tistical descriptors of the two-dimensional MEP distribution change up on shrinking or enlarging a van der Waals surface. We find that some o f the descriptors exhibit critical points in terms of a scaling factor . We use this property to define effective atomic radii. In particular , we find that a reasonable molecular envelope is defined as the surfa ce having the lowest (i.e., most negative) average negative MEP, with the largest possible dispersion about the mean. We discuss the resulti ng atomic radii and compare them with others in the literature derived from only steric considerations. The present results expand the scope of fused-sphere surfaces,for modeling microscopic or structural molec ular properties. (C) 1996 by John Wiley & Sons, Inc.