Bimolecular interaction of zwitterionic surfactant with hen egg white lysozyme (HEWL): A biophysical study

Abstract The interaction between Hen Egg White Lysozyme (HEWL) and 3-[(3-cholamidopropyl) dimethyl-ammonio]-1-propanesulphonate (CHAPS) was examined using biophysical techniques (spectrofluorometric, circular dichroism, and dynamic light scattering) at pH 9.0. The results obtained from multi-techniques showed that CHAPS interact with the HEWL strongly and affects protein conformations. The far-UV CD results suggest that lower as well as higher (1.0-15.0 mM) concentrations of CHAPS are inducing α-helical structure in HEWL. The near-UV CD and fluorescence data indicated that the tertiary structure of HEWL is alter in the presence of CHAPS. The ANS dye binding suggest that the exposure of HEWL tertiary structure is dependent on CHAPS concentration. As the concentrations of CHAPS is increasing the exposure of HEWL tertiary structure is also increasing and maximum exposure was found at 15.0 mM of CHAPS concentrations. The hydrodynamic radii of HEWL is also increase in the presence of sub-micellar and micellar concentrations of CHAPS because the tertiary structure of HEWL is disrupted. Overall, the results suggest that CHAPS is inducing secondary structure and disrupting tertiary structure of HEWL. This study provides detailed interaction of CHAPS with HEWL at the molecular level.