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6) Problem 2.20 (from textbook); 2.20 Rheology of Hyaluronic Acid Hyaluronic acid is a high-molecular polymer of the repeating disaccharide units glucuronic acid and N-acetylglucosamine. Present in all tissues and usually linked with protein in the form of proteoglycans, hyaluronic acid is a component of the synovial fluid that is present between joints and is thought to play a role in joint lubrication and resisting compressive forces. (a) The data in the table at the bottom of this page were obtained at 25°C in a cone-and-plate visco- meter for solutions of 5 mg mL-¹ hyaluronic acid in phosphate-buffered saline with a pH of 7.2. Deter- mine whether the fluid behaves as a power law fluid, and if so, determine the parameters m and n. (b) The hyaluronic acid solution was treated with the enzyme hyaluronidase for 5 minutes at 25°C, and the data on the right-hand side of the table were recorded. Determine the effect of the enzyme upon the rheology of hyaluronic acid. (c) Explain why the enzyme might change the rheology of hyaluronic acid. Hyaluronic acid Shear rate (s¹) Shear stress (dyn cm2) 2.39 4.28 6.23 8.05 3.75 7.50 11.3 15.0 22.5 30.0 37.5 11.2 14.1 17 Hyaluronic acid plus hyaluronidase Shear stress (dyn cm 2) Shear rate (s) 375 450 525 600 750 900 1,125 3.31 3.93 4.48 5.10 6.37 7.79 9.61 Please use excel or any other graphical computational tool to draw the plots (hand drawn approximate plots are not acceptable).

Fig: 1