Osteocalcin Active Center Models: Electrochemical Adsorption on Platinum and Quantum Chemical Analysis

An attempt was made to simulate the electrochemical behavior of the osteocalcin active site simple models on the platinum component of a bimetallic Ti/Pt implant. Dicarboxylic glutamic acid and dicarboxylic aspartic acid, and ethylmalonic acid as the third model successfully complementing the model range. The surface coverage of the platinum electrode during adsorption of model dicarboxylic acids was estimated using cyclic voltammetry and electrochemical impedance spectroscopy. All three compounds demonstrate similar trends in the surface coverage dependencies on the adsorption potential, acids' adsorption onto platinum surface is weak, and in none of cases studied amino group participates in adsorption on the platinum electrode surface. Using quantum chemical calculations, the most stable conformations of model compounds and the values of voids between adsorbed dicarboxylic acid molecules were obtained. Since all three models have a relatively low surface coverage and are participants in the outer sphere process of nonspecific adsorption on platinum, the residues of γ-carboxyglutamic acid present in osteocalcin will not be specifically adsorbed on the platinum component of the bimetallic implant, and the absence of interactions between it and the platinum electrode should have a positive effect on the dynamics of osteoregeneration.