Interaction between the natural lipopeptide [Glu1, Asp5] surfactin-C15 and hemoglobin: A spectroscopic and electrochemical investigation

Interactions between hemoglobin (Hb) and the natural lipopeptide [Glu1, Asp5] surfactin-C15 (surfactin) have been investigated by fluorescence spectroscopy and cyclic voltammetry. Surfactin can facilitate the conversion of aquometHb to hemichrome in 0.01 M phosphate buffer solution (PBS, pH 7.4) due to the interaction between Hb and surfactin. The electrochemistry results reveal that the changes between Fe (II) and Fe (III) of heme produce a reversible process in surfactin solution as indicated by cyclic voltammograms. In other words, the electron transfer which takes place is due to the interaction between Hb and surfactin. The binding constants of surfactin on hemoglobin were calculated by the Scatchard method and the characteristic signs of the thermodynamic parameters at two classes of binding sites for surfactin on Hb were obtained. The thermodynamic function of the binding process suggests that the hydrophobic interaction is the predominant intermolecular force between Hb and surfactin.