Electron properties of aryl moieties in agonists and antagonists of opioid receptors

Abstract

The electron properties of aryl moieties in the molecules of opioid receptor agonists and antagonists are compared in terms of the normalized atomic contributions of electron density to the frontal boundary molecular orbitals. Ligands in the neutral and protonated forms, as well as in the “ligand — receptor fragment” complexes (associates), are considered. The electron properties of the aryl moiety depend on the order in which the active centers of its tyramine fragment interact with the complementary region of an opioid receptor. It is suggested that the electron properties of aryl moieties determine the affinity of molecules to opioid receptors but do not influence the level of internal activity of such ligands.