The investigation of the interaction between oxybutynin hydrochloride and bovine serum albumin by spectroscopic methods

The mutual interaction of oxybutynin hydrochloride (OB) with bovine serum albumin (BSA) was investigated by fluorescence, UV-vis absorption, circular dichroism (CD), and Fourier transform infrared (FT-IR) spectroscopies under simulative physiological conditions. The results of fluorescence titration revealed that OB could quench the intrinsic fluorescence of BSA by static quenching and there was a single class of binding sites on BSA for this drug. The thermodynamic parameters ΔH, ΔS, and ΔG calculated at different temperatures indicated that hydrogen bonds and van der Waals interactions were the dominant intermolecular forces in stabilizing the OB-BSA complexes. According to the theory of Förster's non-radiation energy transfer, the binding distance r between OB and BSA was evaluated to be 3.27 nm. The displacement experiments confirmed that OB could bind to site I of BSA. The FT-IR and CD spectra showed that the binding of OB to BSA induced conformational changes in BSA.