Steric mass-action model for dye-ligand affinity adsorption of protein

The steric mass-action (SMA) model has been reported in the literature for ion-exchange and metal-affinity interaction adsorption equilibrium of proteins. In this work, an SMA model was developed for protein adsorption equilibrium to dye-ligand affinity adsorbent, Cibacron Blue-modified Sepharose CL-6B (CB-Sepharose). Static adsorption experiments with bovine serum albumin as a model protein were carried out to determine the model parameters, that is, equilibrium constant (K), characteristic number of binding sites (n), and steric factor (sigma). It was found that the linear model parameters, K and n decreased with the increase of ionic strength, while the nonlinear parameter, sigma, increased with ionic strength and the dye-ligand concentration. Thus, expressions correlating these parameters with the dye-ligand concentration and/or ionic strength were derived. With these correlations, the SMA model gave promising results in predicting protein adsorption isotherms. Thus, it is considered that the model would be useful in the theoretical analysis of dye-ligand affinity chromatography.