STRUCTURAL STUDIES OF A PHOSPHATIDYL SERINE-AMORPHOUS CALCIUM-PHOSPHATE COMPLEX

A phosphatidyl serine-amorphous calcium phosphate complex has been syn thesized as a model of the matrix vesicle system that is associated wi th the induction of mineral deposition in bone, cartilage and dentine. The complex has been studied using a novel technique of subtractive e xtended X-ray absorption fine structure (EXAFS). This enables spectra of the components of the molecules to be subtracted from the complex s o as to identify the sites of interaction. The results suggest there i s a movement in the nitrogen atom of the phosphatidyl serine which app roaches the calcium atom in the mineral phase. This interpretation wou ld link the membrane structure of the vesicle to the structure of the mineral in a way that could explain some of its roles in biomineraliza tion.