Interactions between poly(L-lysine) and chondroitin 6 sulfate. Quasi-elastic light scattering studies

Quasi-elastic laser light scattering studies have shown that large multimolecular aggregates are formed on mixing dilute aqueous solutions of poly(L-lysine) and chondroitin 6-sulfate. For the two components in equimolar residue proportions at a total concentration of 0.178 mg/mL, the aggregates have hydrodynamic radii of 1200 A. Circular dichroism spectroscopy indicates that the polypeptide conformation changes from a coil to the alpha-helix on cooling the solution. This change can be reversed by increasing the temperature; the midpoint for the transition is 47 degrees C. Throughout these changes the size of the aggregates remains approximately constant, and thus the conformational transition detected by circular dichroism occurs within the aggregates, which otherwise remain intact. In addition, changes in ratio of the two components, pH, and ionic strength, affect the size of the aggregates.