Interaction of serum albumin with vinyl sulfonate azo dye

The interaction between bovine serum albumin and the mono azo reactive dye Orange ZT has been investigated using absorption difference spectroscopy. The influence of pH and ionic strength of the solution on the stability of the dye-protein complex has been determined. At 25°C, the complex dissociation constants were equal to 24.0, 28.0, 7.0, 11.0, 17.6 and 46.0 μM at pH 7.0, 6.5, 6.0, 5.5, 5.0 and 4.3, respectively. In the presence of 0.1, 0.2, 0.3 M KCl, at pH 6.0 and 25°C, the complex dissociation constants were 8.8, 20.0, 18.0 μM, respectively. The protein-dye complex dissociation constants show that Orange ZT could be used as an affinity ligand for protein purification.