Study of the interaction between doxepin hydrochloride and bovine serum albumin by spectroscopic techniques

The binding of doxepin hydrochloride (DH) to bovine serum albumin (BSA) was investigated by spectroscopic (fluorescence, UV–vis absorption and circular dichroism) techniques. The binding parameters have been evaluated by fluorescence quenching method. The thermodynamic parameters, ΔH°, ΔS° and ΔG° calculated at different temperatures indicated that the hydrogen bond and hydrophobic forces played a major role in the interaction of DH with BSA. Based on the Förster's theory of non-radiation energy transfer, the binding average distance, r between the donor (BSA) and acceptor (DH) was evaluated and found to be 2.7 nm. Spectral results observed showed that the binding of DH to BSA induced conformational changes in BSA. The effect of common ions on the binding of DH to BSA was also examined.