Interaction of Bovine Serum Albumin with N‐(4‐Ethoxyphenyl)‐N′‐(4‐Antipyrinyl)Thiourea (EPAT) Using Spectroscopies

The interaction between N‐(4‐ethoxyphenyl)‐N′‐(4‐antipyrinyl)thiourea (EPAT) and bovine serum albumin (BSA) was studied by fluorescence spectroscopy in combination with UV absorption spectroscopy. The intrinsic fluorescence of bovine serum albumin was quenched by EPAT through a static quenching procedure. The binding constants of EPAT with BSA were estimated according to the fluorescence quenching results at different temperatures. The thermodynamic parameters: enthalpy change (ΔH) and entropy change (ΔS) were calculated to be ?10.69 kJ/mol and 42.64 J·mol^?1·K^?1 according to thermodynamic equations, respectively, and indicating that the binding force was suggested to be mainly a hydrophobic force. The effect of common ions on the binding constant was also investigated. A new fluorescence spectroscopy assay of the proteins was presented in this paper. The determination results of the proteins in bovine serum by means of this method were very close to those obtained using Coomassie Brilliant Blue G‐250 colorimetry.