Linear dichroism and radial flow birefringence of stream‐oriented hyaluronate solutions as a function of system pH

Abstract

AbstractThe linear dischroism in the radial direction of solution flow over a velocity gradient of approximately 10–850 sec−1 has been obtained for human umbilical cord hyaluronic acid at concentrations of 0.1, 0.0666, and 0.0333%, and pHs 6.0, 6.5, 7.0, 7.5, 8.0, and 8.5, at constant ionic strength 0.1. The redial flow briefingenece has also been obtained for these solutions by a Kroing‐Kramers transformation. The data indicate a change in linear dichroism and optical anisotrophy as a function of pH, with most of the transition across the physiological range: 7.0–7.5. Previously reported axial flow birefringence and extinction angles indicating a similar pH‐dependent structural change in hyaluronate solutions across the same pH range are thus confirmed with other instrumentation. The radial birefringence measurements reported here, together with the axial measurements previously reported, permit a complete description of the refractive index tensor for each of the six solutions. The interpretation of these tensors in terms of the Peterlin modification of the Rouse‐Zimm Gaussian subchain theory results in a description of entropy production induced by changes in system pH.