In vitro mineralization of collagen in demineralized fish bone

Simultaneous small- and wide-angle X-ray diffraction of in vitro calcified highly ordered decalcified shad fish bone collagen have identified the calcium phosphate (Ca-P) crystals, formed as poorly crystalline apatite, and their highly ordered spatial, axial distribution with respect to the supramolecular packing of collagen fibrils. The extent of in vitro calcification was significantly diminished when the supramolecular collagen packing was disrupted. These findings are similar to both electron microscopic and small angle X-ray scattering (SAXS) studies of native shad and other species of fish bone and other animal species and of in vitro experiments of the calcification of purified and reconstituted native type collagen fibrils. The results emphasize the important role of the supramolecular packing of collagen fibrils in the heterogeneous nucleation of apatite crystals initiating calcification. The exquisite spatial relationships of the inorganic crystal and the supramolecular packing of native collagen fibrils also form a two-phase composite substance, providing distinct mechanical properties and other physiological functions to bone substance and tissue.