Interaction between a potent corticosteroid drug - dexamethasone with bovine serum albumin and human serum albumin: a fluorescence quenching and fourier transformation infrared spectroscopy study.

This study was designed to examine the interaction of dexamethasone (DEX) with bovine serum albumin (BSA) and human serum albumin (HSA) under physiological conditions with drug concentrations in the range of 2.5-20 microM and BSA/HSA was fixed at 5.0 microM. Spectroscopic analysis of the emission quenching at different temperatures revealed that the quenching mechanism of serum albumin by dexamethasone is static quenching mechanism. The binding sites number, n and binding constant, K were obtained at various temperatures. The distance r between dexamethasone and the protein was evaluated according to the theory of Föster energy transfer. The result of fluorescence spectra UV-vis absorption spectra and FT-IR spectra showed that the conformation of bovine serum albumin and human serum albumin has been changed in the presence of dexamethasone. The thermodynamic parameters, free energy change (DeltaG(0)), enthalpy change (DeltaH(0)) and entropy change (DeltaS(0)) for BSA-DEX and HSA-DEX were calculated according to van't Hoff equation and discussed. Copyright (c) 2010 Elsevier B.V. All rights reserved.