Study on the binding of puerarin to bovine serum albumin by isothermal titration calorimetry and spectroscopic approaches

摘要

The interaction of a flavonoid molecule (puerarin) with bovine serum albumin (BSA) was characterized by isothermal titration calorimetry (ITC), optical spectroscopic technique, and molecular modeling method under physiological conditions. The binding parameters for the reaction were calculated according to ITC experiments at different temperatures. The thermodynamic parameters, negative enthalpy changes (ΔH), and positive entropy (ΔS) indicated that the binding processes were entropically driven. The alterations of protein secondary structure in the presence of puerarin in aqueous solution were estimated by the evidences from FT-IR and CD spectroscopy with reductions of α-helices. On the basis of fluorescence resonance energy transfer (FRET) between excited tryptophan in BSA and BSA bound puerarin, the critical transfer distance and mean distance between tryptophan in BSA and puerarin were estimated.