HYDROXYAPATITE MINERALIZATION AND DEMINERALIZATION IN THE PRESENCE OFSYNTHETIC PHOSPHORYLATED PENTAPEPTIDES

A constant composition (CC) method was used to compare the influence o f statherin-like N-terminal 5-residue fragments having different amino acids in the terminal position on hydroxyapatite (HAP) growth and dis solution. The CC experiments were done in solutions containing 4.00 x 10(-4) mol/l calcium and 2.40 x 10(-4) mol/l phosphate. The solutions used in the crystallization studies were supersaturated only with resp ect to HAP (pH = 7.40, sigma(HAP) = 3.60). The CC dissolution studies were done in solutions undersaturated with respect to HAP (pH = 6.00; sigma(HAP) = -0.39). The HAP mineralization and demineralization proce sses were markedly inhibited by the negatively charged pentapeptides. Those containing a phosphorylated terminal residue inhibited dissoluti on to a greater extent than the native statherin fragment having aspar tate as the N-terminal residue. Strong dependencies of the degree of i nhibition of growth and dissolution reaction rates on the extents of r eaction were noted. As the reactions proceeded, the rate inhibition de creased in the case of crystal growth and increased for dissolution.