Archaebacterial lipid models: formation of stable vesicles from single isoprenoid chain-amphiphiles

Surfactants, PhyN+(Me)3 (OH-/Br-), PhyPO4H- (H+/Na+), PhySO4- (H+/Na+) and Phy(CO2-) (H+/Na+), were prepared; Phy is a (3RS,7R,11R)-3,7,11,15-tetramethylhexadecyl group; phytanic acid or its sodium salt is expressed by Phy(CO2-) (H+/Na+). Equimolecular mixtures of the cationic surfactant and the anionic ones in aqueous media, upon sonication, gave rise to stable suspensions of multilamellar vesicles (MLVs). Unlike the molecular assemblies from cationic and anionic pairs of straight chain-surfactants, the MLVs could trap ionic and nonionic compounds such as 5(6)-carboxyfluorescein and glucose with the captured volume of 0.6-1.6 l/mol in water. The vesicles were tolerant to about 25 mM aqueous NaCl. The packing mode of the surfactants in the membranes are discussed in conjunction with the thickness (about 60 A) and the zeta-potential which was as large as 30-45 mV in water at 20 degrees C.