Archaebacterial lipid models: stable liposomes from 1-alky1-2-phytanyl-sn-glycero-3-phosphocholines

1-Alky1-2-phytanyl-sn-glycero-3-phosphocholines (HPhyPC: alkyl = n-C16H33; EPhyPC: alkyl = n-C20H41), which are artificial chimeric lipids between archaebacterial and ordinary glycerolipids, are prepared. Upon sonication in aqueous media, the lipids gave rise to stable unilamellar liposomes having diameter of 200-1,000 A and gel-to-liquid crystalline phase transition temperature of -11.1 degrees C (EPhyPC) and -10.8 degrees C (HPhyPC). The vesicles were thermally stable (to about 70 degrees C) and retained efficiently 5(6)-carboxyfluorescein and sodium chloride in the aqueous interior. Physicochemical properties of their membranes were discussed in comparison with those of the membranes made of an archaebacterial model lipid, 1,2-diphytanyl-sn-glycero-3-phosphocholine.