Study on the interaction of puerarin with lysozyme by spectroscopic methods

The interaction between lysozyme (LYSO) and puerarin has been studied at three temperatures (294, 302 and 310 K) through/using fluorescence spectroscopy and circular dichroism (CD). The LYSO fluorescence was quenched by the binding of puerarin to LYSO. The binding constants and the number of binding sites can be calculated from the data obtained from fluorescence quenching experiments. According to the van’t Hoff equation, the standard enthalpy change (ΔH°) and standard entropy change (ΔS°) for the reaction were calculated to be 17.47 kJ/mol and 163.5 J/mol K. It indicated that the hydrophobic interactions play a main role in the binding of puerarin to LYSO. In addition, the distance between puerarin (acceptor) and tryptophan residues of LYSO (donor) was estimated to be 1.47 nm on the basis of fluorescence energy transfer. The changes of LYSO secondary structure in the presence of puerarin were observed from CD spectroscopy.