1. Rat tail-tendon collagen was coupled to activated Sepharose 4B at 2.5 mg of collagen/ml of gel. Chromatographic columns of this gel were calibrated with T2 virus (Vo) and Dnp-alanine (Vt). 2. The chromatographic behaviour of cartilage proteoglycans on the collagen-substituted gel was studied under conditions of varying ionic strength. Proteoglycan subunit obtained from bovine nasal cartilage, the proteoglycan obtained after digestion with chondroitnase ABC and purified chondriotin sulphate were all retarded on the collagen gel by an interaction that abolished at I0.17. Purified keratan sulphate and hyaluronic acid were not retarded. 3. A strong ionic interaction between cartilage proteoglycan and collagen was demonstrated to depend on the structure of the protein core of the proteoglycan.
