Adsorption of glycosaminoglycans onto hydroxyapatite using chromatography

Proteoglycans are known to play an important role in the mineralization pro cess, acting either as promoters or inhibitors. In this study the binding a ffinity of a variety of constituent glycosaminoglycan to hydroxyapatite was studied. Glycosaminoglycans (10-1000 mu g ml(-1)) in 0.02 M sodium acetate (pH 6.8) were constantly circulated through a hydroxyapatite column for 1 h. The total amount of glycosaminoglycan bound was determined by dimethylme thylene blue assay. The relative affinities of the different glycosaminogly cans remaining bound to hydroxyapatite was investigated by examining their release in a 0-1 M sodium phosphate gradient. Differences were noted betwee n the desorption profiles of dermatan sulfate with two elution peaks and ch ondroitin 4-sulfate and chondroitin 6-sulfate each with a single peak. Derm atan sulfate and chondroitin 6-sulfate had a higher affinity for hydroxyapa tite than chondroitin 4-sulfate possibly due to the presence of differing d i-sulfated disaccharide ratios in the glycosaminoglycan chains. These findi ngs suggest the presence of a variety of binding forms of each glycosaminog lycan or the differing orientation of these forms to yield different comple xes with hydroxyapatite. The Ca2+ co-ordinates of the glycosaminoglycans ar e known to vary and may in part explain these findings. (C) 1999 Elsevier S cience Ltd. All rights reserved.