Verapamil Series Diphosphonic Acid And Hydroxyapatite Mechanism Of Action

The structures of Pamidronate bisphosphonate(Pami-BPs) and its analogs were optimized by means of density functional theory(DFT) of quantum chemical calculation, at the level of B3LYP with the 6-31G* basis set. Some quantum parameters were calculated, such as atomic charges, highest occupied molecular orbit energies (HOMO) and lowest unoccupied molecular orbit energies (LUMO),△E and Fukui indices. The results indicate protonated structures of Pami-BPs are more reasonable than neutral structures. The relationship between the quantum parameters and antiresorptive potency has been analyzed. The abilities of offering electron of the oxygen atoms of phosphate groups in Pami-BPs are closely asscociated with the antiresorptive potency.Interactions between protonated Pami-BPs and hydroxyapatite(HAP) crystal surfaces (010), (001), (110) have been simulated by Molecular Dynamics method using Discover module of Material Studio. The simulation was performed at NVT ensemble and Compass force field, then binding energy, nonbond interaction energy, theoretic sequence and pair correlation function were obtained to discuss the mechanism of antiresorptive potency. The pair correlation function analysis results indicate that the oxygen atoms of Pami-BPs and the calcium atoms of HAP can form strong electrovalent bonds. The correction binding energies of three surfaces rank N4> N7> N8> N6> N9> N5> N10> N3> N2> N1> N11, which are consistently related to their experimental antiresorptive potency.