Preparation of Lipid Vesicles

For 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/cholesterol vesicles, dry lipids (41 mg) and cholesterol (7.75 mg) were mixed in CHCl₃ in a round-bottom flask. For dipalmitoylphosphatidylcholine (DOPC)/1,2-dioleoyl-sn-glycero-3-phospho-l-serine (DOPS)/cholesterol vesicles, 47 mg of DOPC, 5 mg of DOPS, and 7.75 mg of cholesterol were mixed in CHCl₃ in a round-bottom flask. The solvent was removed by rotary evaporation for 20 min, and any remaining traces of the solvent were removed under vacuum for an additional 30 min. The resulting lipid/cholesterol mixture was resuspended in 50 mM sodium phosphate (pH 7) via sonication. Following five rounds of freezing and thawing, ∼100 nm unilamellar vesicles were formed by extrusion of the suspension through a 50 or 100 nm filter 10 times at 400 psi. The size of the vesicles was confirmed by dynamic light scattering.