Partitioning the electrostatic interaction energy between two charge distributions

Treating the interaction between two charge distributions as a joint ventur e, we explore here the possibility of quantifying the extent of participati on of each charge distribution. By introducing the concept of reduced charg e analogous to reduced mass, we show that the interaction energy expression between two charges separates into a sum of two terms, one for each charge . This partitioning, in addition to facilitating a graphical representation of atom-based interaction energy components on complementary surfaces invo lved in a binding reaction, provides additional insights into the mechanism of interaction and binding. We further introduce the idea of representing molecular electrostatic potentials in the interaction view, i.e. potentials at each atom site of charge distribution I due to charge distribution II a nd vice versa and demonstrate the graphical equivalence of the potentials t hus computed with the energy partitioning proposed here. The method is illu strated with applications to a few test cases and binding reactions of smal l molecules in vacuum and complexation of biomolecules in aqueous medium. ( C) 2001 Elsevier Science B.V. All rights reserved.