Polarographic studies on the binding of azo dyes with proteins

Abstract

Polarographic studies on the binding of two anionic azo dyes, methyl orange and congo red, with two proteins, transfusion gelatin and ovalbumin, have been carried out. Phosphate buffer at three pH values, viz., 5.8, 7.2 and 8.0 was taken to study the pH effect on the binding. The value of id/(id)0 was found to increase with pH in each case showing complex formation between the dye and the protein. More binding was observed at low pH due to positive charge on the protein. The number of available binding sites and the values of the intrinsic association constants have been determined. The greater binding in the case of transfusion gelatin was due to the open structure and greater number of cationic groups in the former. Methyl orange, being a smaller molecule, approaches the binding sites more easily than congo red. The binding was found to be statistical in nature.