Octacalcium phosphate - a metastable mineral phase controls the evolution of scaffold forming proteins.

The molecular structure of collagen type 1 can be understood as the result of evolutionary selection in the process of formation of calcium phosphate based biocomposites acting as load bearing components in living organisms. The evolutionary selection fulfills the principle of 'survival of the fittest' in a particular biological environment. Disk-like post-nucleation complexes of Ca(HPO) organized in ribbon-like assemblies in the metastable octacalcium phosphate (OCP) phase, and Ca triangles in the stable HAP phase had formed the crystallographic motifs in this selection process.

Absorption and extinction correction in quantitative DAFS analysis.

An approach to X-ray attenuation correction for diffraction anomalous fine-structure (DAFS) measurements is presented, taking into account energy-dependent secondary extinction effects. A numerical model based on the kinematical theory of diffraction is presented. This model is exemplified by DAFS measurements of the Zr 0002 reflection intensities for energies in the vicinity of the Zr K absorption edge of a Co/Zr multilayer exhibiting strong fibre texture.