Binding of the bioactive component isothipendyl hydrochloride with bovine serum albumin

The binding of isothipendyl hydrochloride (IPH) to bovine serum albumin (BSA) was investigated by fluorescence spectroscopy combined with UV–visible absorption and circular dichroism (CD) techniques under simulative physiological conditions for the first time. The quenching mechanism of fluorescence BSA by IPH was discussed. The binding parameters have been evaluated by fluorescence quenching method. The thermodynamic parameters, ΔH°, ΔS° and ΔG° calculated at different temperatures indicated that the hydrophobic force played a major role in the interaction of IPH to BSA. The distance, r between donor (BSA) and acceptor (IPH) was obtained according to the Förster's theory of non-radiation energy transfer and was found to be 2.21 nm. Experimental results showed that the α-helicity of BSA decreased from 66.4% (in free BSA) to 39.1% (in bound BSA). The effect of common ions on the binding constant was also investigated.