The aim of this work is the characterization of interfaces in calcified tissues. Thermally Stimulated Currents and Gel Permeation Chromatography have been used for investigating extracts and residues from calf femoral diaphysis, at various stages of demineralization. In residues, the evolution of molecular mobility shows that the organic-mineral linkage is insured by several proteins: Collagen is not directly linked to apatite.