Non-apatitic environments in Ca-P biominerals; implications in reactivity of the mineral phase and its interactions with the organic matrix constituents

Although the calcium-phosphate crystals of vertebrates occur mainly as apatites, they also exhibit short range arrangements of atoms and ions that are not found in pure, well crystallized apatites (non-apatitic environments). The proportion of non-apatitic environments appears very high in the newly formed crystals of biological tissues and slowly decreases as the tissues mature. These non-apatitic environments are significantly altered by disorders of Ca-P metabolism. Preliminary experiments in which the non-apatitic environments have been modified by chemical treatments lead to significant differences in the amount and the nature of the proteins released from the crystals of bone. With its enormous specific surface area and its very reactive labile environments, the mineral phase cannot be considered simply and only as a passive component of the extracellular matrix of bone, but rather as one of its most reactive constituents