Interaction between Liposomal Membrane and Sodium Dodecyl Sulfate as Studied by an ESR Spin Probe Method

Interactions between phospholipid liposomal membranes and sodiumdodcyl sulfate in a phosphate buffer solution (50 mM, pH 7) were studied by the ESR spin probe, 2- (3-carboxypropyl) -4, 4-dimethyl-2-tridecyl-1, 3-oxazolidin-3-oxyl. Sodium dodecyl sulfate molecules (2mM) incorporated into phospholipid bilayers (13.6 mM) appeared to form clusters by themselves, causing phase separation of the bilayers. The possibility of two distict liposomes, one phospholipid-rich and the other, SDS-rich, was excluded on the basis of results obtained by a centrifugal experiment under the above conditions.