Scaling behaviour of hyaluronic acid in solution with mono- and divalent ions.

The effect of the simultaneous presence of mono- and divalent cations on the thermodynamics of polyelectrolyte solutions is not fully understood. In physiological conditions, combinations of these ions affect structure formation in biopolymer systems. It is known that divalent counterions form a tight sheath around the polymer backbone, while monovalent ions are distributed in a diffuse cloud. Dynamic light scattering measurements of the collective diffusion coefficient D and the osmotic compressibility of semi-dilute hyaluronan solutions containing different ratios of sodium and calcium ions are compared with simple polyelectrolyte models. Scaling relationships are derived in terms of polymer concentration and ionic strength J of the added salt. Differences in the effects of sodium and calcium ions are expressed only through J.