[Interaction of hydroxyapatite with amino acids].

The interaction of Hydroxyapatite (HAP) with organic molecules is biologically important. Some proteins display a high adsorption affinity for HAP and they have been implicated in the mineralization of bone. In order to understand the interaction of HAP with proteins, it is important to know which amino acid side-groups are involved in the protein-HAP interaction and what type of interaction takes place. We investigated the interaction of HAP with amino acids and their derivatives by crystal growth experiment. The rate of crystal growth was measured by adding seed crystals of HAP (synthetic apatite) to a solution of CaCl2 and KH2PO4, pH 7.4 at 37 degrees C. Basic amino acids, acidic amino acids and amino acids with polor side-groups inhibit the rate of crystal growth. These findings suggest that amino acid side-groups, such as carboxyl group, amino group, hydroxyl group and imidazole, are related to the affinity for HAP.