Makromolekulare Polysaccharid-Proteine, II. Chemische und makromolekulare Altersveränderungen von Polysaccharid-Proteinen aus menschlichem Rippenknorpel
The polysaccharide -protein of human rib cartilage was isolated from fresh material. It was converted into the water-insoluble cetylpyridinium complex, and isolated as fraction PP-V [polysaccharid-Protein fraction 5], which was soluble in 1.5[image] MgCl2. PP-V, isolated under identical conditions from 8 age groups (new born to 80 yr.), and homogeneous in the analytical ultracentrifuge, showed age-dependent changes in chemical composition and macromolecular properties. In the newborn, PP-V consisted of 83% chondroitin sulfate (chondroitin-4-sulfate and chondroitin-6-sulfate), 8% keratan sulfate and 9% protein. With increasing age, the level of chondroitin sulfate fell to 55%, the keratan sulfate increased to 20% and the protein increased to 25%. The separation of keratan sulfate and chondroitin sulfate from the polysaccharide-protein on the basis of the different solubilities of their cetylpyridinium complexes was only possible after the action of 0.2[image] NaOH for 5 hr. at 37[degree]C; the separation is then complete. Chondroitin sulfate and keratan sulfate were isolated in a pure form after the alkaline degradation. The macromolecular properties of PP-V were investigated by the measurement of light scattering (evaluated by the Zimm diagram), and by the determination of the sedimentation constant and intrinsic viscosity. The molecular weight of PP-V from light scattering was 0.81 [center dot] 106 for new-born. Between 16 and 28 yr. the molecular weight reached a maximum of 3.8 to 2.4 [center dot] 106 respectively. Up to the 60th yr. of age, the molecular weight decreased continually to 1.5 [center dot] 106. The same age-dependent increase followed by decrease was exhibited by the intrinsic viscosity, the radius of gyration, and the degree of hydration (effective hydrodynamic volume). Hydration of PP-V was calculated from the molecular weight from light scattering and the sedimentation constant. It was 360 ml/g in new born, 1500 ml/g at 16 yr., and 245 ml/g in the 6th decade. The decrease in the degree of hydration from age 20 to 60 yr. corresponds to a decrease in the water content of fresh rib cartilage from 80 to 60% in the same time period.