INTERACTION BETWEEN WATER-SOLUBLE PROTEINS AND ACID DYES

Abstract

Listen

Translate article

The interaction between water-soluble proteins and acid dyes was investigated spectrophotometrically, where the crystalline bovine serum albumin (Ia) and egg albumin (Ib) were used. The acid dyes used were C. I. Acid Orange 7 (IIa), C. I. Mordant Violet 5 (IIb), C. I. Acid Red 178 (IIc), Acid Complex Violet 4R (IId) and C. I. Acid Blue 158 (IIe). The absorption spectra were measured with aqueous solutions of different concentrations of Ia and Ib. The absorption intensities of IIaand IIb at λmax, respectively, decreased in low concentration of albumin, reached the minimumat certain amount of I, and they began to increase with increase in I. In the case of IIc, however, the absorption intensity at the concentration of 4.3×10-5mol/l did not decrease until the added Ia reached 2.0×10-3g/l, and increased markedly from this point. The higher pH, the more quantity of I was required to reach the minimum absorption intensity of II. More quantity of Ib was required than Ia, since the charge Ib is lower than that of Ia. No significant change was observed in the spectrum of the aqueous solutions of IId and IIe upon addition of various amounts of I. The association equilibrium exists between monomer and dimer in the aqueous solutions of IIa, IIb and IIc. But IId and IIe could not be measured owing to little change.In view of the observations on basic vinyl copolymer, it may be concluded that the bonding between I and II is ionic in character and changes in absorption intensity are attributable to the changes in aggregation of II on I.