Further evidence on the protein complexes of some hyaluronic acids.

This work follows from that of Blumberg & Ogston (1957). They showed that papain is a specific agent for degrading the protein part of the hyaluronic acid complex isolated from ox synovial fluid by filtration (Ogston & Stanier, 1950), and that when this protein is degraded marked changes in the non-Newtonian viscosity occur. This is associated with a marked decrease in the molecular weight and the hydrodynamic specific volume as well as changes irn other physical characteristics, which indicate that the material has been depolymerized. The correlation between the degradation of protein which forms the complex with hyaluronic acid and the change of non-Newtonian viscosity makes possible the use of papain as a reagent for detecting whether hyaluronic acid from any source contains protein in such a state as to determine its physicochemical properties. This test can be applied in the presence of free protein since free protein, its hydrolysis products, or excess of enzyme do not contribute significantly to the nonNewtonian viscosity of solutions which contain hyaluronic acid, and preliminary separation of the hyaluronic acid from other materials is therefore unnecessary. The test has been applied to several preparations containing hyaluronic acid from different sources. A preparation of plasmin has been found to have effects on the viscosity of solutions containing the hyaluronic acid-protein complex similar to those produced by papain. This gives weight to the suggestion that changes in the protein part of the complex may have physiological and pathological significance. A method based upon that of Scott (1955, 1956), for isolating acid polysaccharides by precipitating them with cetylpyridinium chloride, has been applied to synovial fluid. Preliminary results show that the product contains protein and appears to resemble closely the material isolated by filtration by the method of Ogston & Stanier (1950).