Interaction between lysozyme and mixtures of cationic–anionic surfactants decyltriethylammonium bromide–sodium decylsulfonate

The interaction of lysozyme with the mixtures of cationic–anionic surfactants decyltriethylammonium bromide–sodium decylsulfonate (C 10NE–C 10SO 3) was investigated by turbidity, circular dichroism (CD) and lysozyme activity assay. At pH 3.0, the mixtures of C 10NE–C 10SO 3 formed precipitates with lysozyme at a wide range around the equal molar ratio of C 10NE to C 10SO 3. Homogeneous solutions were formed when the mixtures of C 10NE–C 10SO 3 were far from equimolar. CD and lysozyme activity assay showed that lysozyme was in different state in the C 10SO 3-rich and C 10NE-rich mixtures of C 10NE–C 10SO 3. Lysozyme structure changed in C 10SO 3-rich C 10NE–C 10SO 3 mixtures, while was almost kept in native state in C 10NE-rich ones.