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Proteoglycans were extracted from bovine (15-18 months old) femoral-head cartilage. The heterogeneity of the A1D1 proteoglycan fraction was examined by gel chromatography, sedimentation velocity, sucrose rate-zonal centrifugation and CS2SO4 isopycnic centrifugation. In all cases polydisperse but unimodal distributions were obtained. Chemical analysis of the preparation yielded a galactosamine/glucosamine molar ratio of 7:1, and 13C n.m.r. spectroscopy showed that the chondroitin sulphate comprised equal proportions of the 4- and 6-sulphate isomers. Gel chromatography of a papain and Pronase digest of the proteoglycan indicated that the chondroitin sulphate chains had a Mn of approx. 10500. The mean buoyant density of the proteoglycan in pure CS2SO4 was 1.46 g/ml. Physical characterization of the proteoglycan preparation in 4M-guanidine hydrochloride, pH 7.4, by using conventional light-scattering gave a radius of gyration of 42 nm and a Mw of 0.96 X 10(6). Quasi-elastic light-scattering in the same solvent yielded a translational diffusion coefficient, D020, of 5.41 X 10(-8) cm2 X S-1, and ultracentrifugation gave a sedimentation coefficient, S020, of 12.0S. Thus from sedimentation-diffusion studies a Mw of 1.36 X 10(6) was calculated. The possible origins for the differences in the two molecular-weight estimates are discussed. It is concluded that the high-buoyant-density proteoglycans from bovine articular cartilage are significantly smaller than those from bovine nasal septum, and that this is largely due to the smaller size of their chondroitin sulphate chains.

This compound has recently been prepared by alumina isomerisation of the oxido-ketone (I)