The Rotational Diffusion of Albumin in Solutions of Connective‐Tissue Polysaccharides

The rotational behaviour of dansyl‐labelled human serum albumin in solutions of connective tissue polysaccharides (a hyaluronic acid and a sulphated proteoglycan) has been studied by fluorescence depolarization measurements. Over a wide range of pH, including the physiological conditions, the presence of the polymers up to concentrations of 10 mg/ml has no effect on the relaxation time of the protein. At higher concentrations of the sulphated proteoglycan (20–30 mg/ml) a moderate suppression of the rotational diffusion is observed. At pH values below the isoionic point of the protein, a marked effect on the polarization occurs which is interpreted as an extensive associative interaction between the protein and the polysaccharide materials. A quantitative interpretation of the effect is attempted.