Pharmacophoric features and Ca2+ ion holding capacity of verapamil.

Ab initio Hartree-Fock calculations have been performed at the 6-31G level to study the pharmacophoric features of verapamil. Both the unprotonated and the protonated forms of verapamil have been studied. The study predicts that the drug enters the body in protonated form and is anchored to the receptor via H-bond formation involving protonated amine. Huge conformational change as well as deprotonation is required before the drug is capable of holding Ca(2+) ions. Folded form of drug is capable of holding Ca(2+) ion and the chiral center also seems to be involved to certain extent.