MINERAL INDUCTION BY IMMOBILIZED DENTIN PHOSPHOPROTEIN

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The long-term objective of this research is to gain insights into the mechanisms of biomineralization by determining the capacities of isolated matrix proteins to induce and to promote mineral formation. The purpose of the proposed research is to conduct pilot studies on the mineralization potential of dentin phosphoprotein using an in vitro model system. In this sytem dentin phosphoprotein will be immobilized by covalent linkage to a model substrate, polyacrylamide, to simulate its attachment to the collagen network of dentin. The capacity of the immbolized phosphoprotein to induce mineral formation from metastable solutions which do not spontaneously precipitate and that maintained at constant calcium ad phosphate activities, approximating those of body fluids, will be determined. The phosphoprotein also will be added, in solution, to determine the effects the free protein on the formation and growth of mineral induced by the immobilized protein. The calcium and phosphate concentrations and pH will be held constant with a chemostat that senses minute changes in the incubation solution and corrects for these changes by addition of the ions. Atomic spectroscopy and colorimetry will be used to ascertain that the incubation solution is maintained at cosntant composition. The capacity to induce mineral will be determined in terms of the time lag until the first mineral is formed and the rate of mineral formation. The type of mineral formed will be determined by X-ray diffraction and infrared spectrophotometry. The results obtained in this proposed investigation will contribute to an understanding of the normal mechanisms of mineral induction in calcified tissues. The results will also have implications in the pathological disorders in which the normal mineralization patterns are absent, such as some types of dentiogenesis imperfecta whee the dentin phosphoprotein seems to be absent.