Comparison of binding of vanadium(V) with bovine serum albumin and bovine pancreatic trypsin

Abstract

The binding of vanadium(V) ion has been studied with bovine serum albumin and bovine pancreatic trypsin at different pH values and temperatures by the polarographic technique. The binding data were found to be pH and temperature dependent. The intrinsic association constants (K) and the number of binding sites (n) were calculated from Scatchard plots and found to be at the maximum at lower pH and at lower temperatures. The values of enthalpy change (ΔH0) and entropy change (ΔS0) at pH 7.50 have been found to be −2.090 kcal mole−1 and +6.372 cal mole−1 degree−1 respectively, for the vanadium (V)-bovine serum albumin system. The free energy change (ΔG0) of the combining sites were least at the higher pH and highest at the low pH; therefore, a lower temperature and lower pH offered more sites in the protein molecule for interaction with vanadium(V) ions. Statistical effects seem to be more significant at lower vanadium(V) ion concentrations while at higher concentrations electrostatic effects and heterogeneity of sites are more significant.