The interaction between bovine serum albumin and the molybdate ions

Abstract

The binding of molybdenum(VI) has been studied with BSA using polarographic (pH 5.57) and equilibrium dialysis (pH 5.57, 7.50 and 9.50) techniques. The intrinsic association constants and the number of binding sites have been calculated from Scatchard plots. The effect of temperature on these constants was studied at pH 5.57 by polarographic technique and it was found that these values were decreased with increasing temperature. The effect of pH was found to be similar by equilibrium dialysis technique. The number of sites available for binding with the molybdate ions is much less than the actual number of cationic groups, which are 26, 21 and 18 at pH values 5.57, 7.50 and 9.50 respectively. Statistical effects seem to be more pronounced at lower molybdate ion concentrations and electrostatic at higher concentrations. The values of different thermodynamic parameters have been reported. The large positive entropy change of binding, coupled with the small enthalpy change of binding, have been interpreted to mean that the major contribution to the free energy of binding comes from the release of the solvent molecule from the molybdate-BSA complex.