KINETICS OF MINERALIZATION IN VITRO .I. NUCLEATION PROPERTIES OF 640-A COLLAGEN AT 25 DEGREES

As a result of a preliminary study of the kinetics of mineralization of native collagen in vitro at 25°, the following tentative conclusions are reached. The uptake of mineral by collagen in its 640-Å aggregation state takes place by two kinetic processes: nucleation and crystal growth. The rate of growth of the crystals is determined by a diffusion process through the collagen matrix with an apparent diffusion coefficient of approx. 1 · 10-8 cm2 · sec-1 at 25° and pH 7.4. The nucleation step at the concentrations employed at 25° involves the formation of a critical size cluster of 11-13 ions. The surface energy of the collagen cluster complex is 130 ergs · cm-2. It was estimated that the collagen matrix reduces by a factor of two the size of the nucleus needed for mineralization in the absence of matrix under the conditions studied. © 1969.