Effect of the Ionic Strength on the Behavior of the Soluble Complexes between Sodium Chondroitin Sulfate C and Bovine Serum A lbumin

Abstract

Light scattering measurements were carried out for the mixed aqueous solutions of bovine serum albumin (BSA) and chondroitinsulfate (Chs) at various mixing ratios and at various sodium chloride concentrations. The values of the molecular vcieikkit and of the molecular dimensions decreased remarkably with the increase in the ionic strength. At the infinite con centration of NaCl, the molecular weight approached the value expected when there is no interaction between them. At the finite concentration of NaCl, bowever; it was seen that a complex is formed between them. When the soluble complex was formed, a relation between the number of the BSA molecules bound to one Chs molecule arid the amount of excess BSA existing free in the solution was expressed by a Langmuir-type equation. Thee number of the bound BSA molecules per Chs molecule were 20.6, 11.5 and 5.02, when the concentrations of sodium chloride (mol/l) were 0.0 1, 0.0 25 and 0.0 5, respectively. The constant expressing the strength of the binding in a Langmuir equation k decreased remarkably with the increase in the sodium chloride concentration. It is concluded from these results that BSA molecule would mainly bind to the Chs molecule by the electrostatic force.