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 (C10NE–C10SO3) was investigated by turbidity, circular dichroism (CD) and lysozyme activity assay. At pH 3.0, the mixtures of C10NE–C10SO3 formed precipitates with lysozyme at a wide range around the equal molar ratio of C10NE to C10SO3. Homogeneous solutions were formed when the mixtures of C10NE–C10SO3 were far from equimolar. CD and lysozyme activity assay showed that lysozyme was in different state in the C10SO3-rich and C10NE-rich mixtures of C10NE–C10SO3. Lysozyme structure changed in C10SO3-rich C10NE–C10SO3 mixtures, while was almost kept in native state in C10NE-rich ones.