Interaction of Jatrorrhizine with Human Gamma Globulin in membrane mimetic environments: Probing of the binding mechanism and binding site by spectroscopic and molecular modeling methods

The interaction between Jatrorrhizine and Human Gamma Globulin (HGG) in AOT/isooctane/water microemulsions was studied by using fluorescence quenching, UV absorption spectroscopy, circular dischroism (CD) spectroscopy and dynamic light scattering (DLS). Fluorescence data in water-surfactant molar ratio (ω0) 25 microemulsions revealed the presence of the binding site of Jatrorrhizine on HGG and its binding constants at four temperatures were obtained. The affinities in microemulsions were similar to that in buffer solution. The alterations of ΗGG secondary structure in the microemulsions in the absence and presence of Jatrorrhizine compared with the free form of HGG in buffer were analyzed by CD spectroscopy. In addition, the DLS data suggested that HGG may locate inside the microemulsion and Jatrorrhizine could interact with them. Furthermore, the thermodynamic functions, i.e. standard enthalpy (ΔH0ΔH0) and standard entropy (ΔS0ΔS0) for the reaction were also calculated, according to Van’t Hoff equation. These data showed that hydrophobic and electrostatic interaction played the main role in the binding of Jatrorrhizine to HGG.