Study of the interaction of Na9[SbW9O33]·19.5H2O with bovine serum albumin: Spectroscopic and voltammetric methods

The interaction of Na₉[SbW₉O₃₃]·19.5H₂O (SbW) with bovine serum albumin (BSA) is studied by spectroscopic and voltammetric methods. Absorption spectroscopy of BSA and the linear sweep voltammetry of SbW proved the formation of ground-state SbW–BSA complex. Fluorescence quenching of serum albumin by SbW is also found to be a static quenching process. The binding constant K_a is 4.13×10⁴ L mol⁻¹ for SbW–BSA at pH 7.40 Tris–HCl buffer at 295 K. The number of binding sites and the apparent binding constants at different temperatures are obtained from the analysis of the fluorescence quenching data. The thermodynamic parameters determined by the Van’t Hoff analysis of the binding constants (ΔH=−80.01 kJ mol⁻¹ and ΔS=−182.85 J mol⁻¹ K⁻¹) clearly show that the binding is absolutely entropy driven. Hydrogen bonding and van der Waals interaction force play major role in stabilizing the complex. The effect of SbW on the conformation of BSA is analyzed using synchronous fluorescence spectroscopy.