A TOPOLOGICAL ANALYSIS OF MOLECULAR ELECTROSTATIC POTENTIAL ON VANDERWAALS SURFACES FOR HISTAMINE AND 4-SUBSTITUTED DERIVATIVES AS H2-RECEPTOR AGONISTS

The molecular electrostatic potential is an important property for characterizing chemical reactivity and the interactions between biomolecules. A joint description of the molecular electrostatics and the molecular shape in 3-space is more complete than the one provided by only the electrostatics. The characterization of the interrelation between the shape features of a formal "molecular surface" and electrostatic potential is of importance in assessing the degree of similarity within a family of molecules. In this work, we have applied a recently developed topological technique to characterize these aspects of the molecular shape. The approach allows one to calculate simple and concise shape codes which can be used for rationalizing structure-activity correlations. These shape codes are related to topological invariants which characterize the topological structure given to the molecular surface by the electrostatic potential. In this work the molecules of interest are a series of four agonists of the H-2-receptor of histamine with very different pharmacological activities. We have analyzed the electrostatics on the fused-sphere (van der Waals) surfaces of these compounds for a number of conformations. Some structural properties and the shape descriptions have been found to correlate with the activity. The results are discussed in the context of the current H-2-receptor models.