CATION-PI INTERACTIONS IN AROMATICS OF BIOLOGICAL AND MEDICINAL INTEREST - ELECTROSTATIC POTENTIAL SURFACES AS A USEFUL QUALITATIVE GUIDE

The cation-pi interaction is an important, general force for molecular recognition in biological receptors. Through the sidechains of aromat ic amino acids, novel binding sites for cationic ligands such as acety lcholine can be constructed. We report here a number of calculations o n prototypical cation-pi systems, emphasizing structures of relevance to biological receptors and prototypical heterocycles of the type ofte n of importance in medicinal chemistry. Trends in the data can be rati onalized using a relatively simple model that emphasizes the electrost atic component of the cation-pi interaction. In particular, plots of t he electrostatic potential surfaces of the relevant aromatics provide useful guidelines for predicting cation-pi interactions in new systems .