[Inclusion compounds of collagen (author's transl)]

Small angle X-ray diagrams of collagen of rat tail treated with phospho tungstic acid or mercury chloride or cobalt- and uranyl-nitrate, osmiumoxide or hydroxy apatite show the same characteristic new reflections and reflection lines. The only remarkable difference exists between fibers treated under stress or relaxed. These experiments give new evidence for the paracrystallinity of collagen. More than 100 parallel aligned ca. 40 A thick octafibrils consist of 670 A long microparacrystals with 5 ca. 25 A thick soft segment layers. In these soft segments the holes of the octafibrils build up a lattice of vacancies with lattice cells of 38,5 x 35 x 135 A3 length. The above mentioned molecules penetrate from the lateral sides through the soft segments into these vacancies building up complexes with peptide groups of collagen. Under stress only a small amount of vacancies is occupied, statistically distributed over the vacancy-lattice, because the soft segments of the octafibrils are constricted. Without stress about 10 to 25% of the octafibrils within one paracrystal are filled up with sediments in the soft regions. With increasing precipitation finally 500 A long needles are formed of the inclusive material as detected by Höhling with the electron microscope in collagen of turkey tendon. The importance of the paracrystalline collagen model is emphasized to understand the biological process like the mineralisation of collagen and beta-keratin in organism or the activity of bone apatite in exchanging calcium ions.