Spectroscopic studies on the binding of barbital to bovine serum albumin

In this paper, the interaction between barbital and bovine serum albumin (BSA) was investigated by the method of fluorescence spectroscopy under simulative physiological conditions. Fluorescence data revealed that the fluorescence quenching of BSA by barbital was the result of the formation of BSA-barbital complex, and the effective quenching constants (Ka) were 1.468×104, 1.445×104 and 1.403×104 M−1 at 297, 303 and 310 K, respectively. The thermodynamic parameters enthalpy change (ΔH) and entropy change (ΔS) for the reaction were calculated to be −2.679 kJ mol−1 and 70.76 J mol−1 K−1, respectively, according to the van't Hoff equation. The results indicated that hydrophobic and electrostatic interactions were the dominant intermolecular force in stabilizing the complex. The results of synchronous fluorescence spectra showed that binding of barbital with BSA can induce conformational changes in BSA. In addition, the effects of Cu2+ and Zn2+ on the constants of BSA-barbital complex were also discussed.