Fig. 2. Morphology of proteoliposomes. Cryo-EM was used to study liposomes composed of mixtures of DOPC, DOPE and DOPG (20 mg/ml, prepared in 100 mM KPi pH 7.0). Samples were prepared under iso- and hyperosmotic conditions; the latter was effected by the addition of 200 mM KCl. The iso- and hyperosmotic conditions correspond to 190 and 535 mosmol/kg, respectively. (A and D) Liposomes composed of DOPC/DOPE in a 1:1 mole ratio, under iso- and hyperosmotic conditions, respectively. (B and E) Liposomes composed of DOPC/DOPE/DOPG in a 3:4:1 mole ratio, under iso- and hyperosmotic conditions, respectively. (C and F) Liposomes composed of DOPC/DOPE/DOPG in a 1:4:3 mole ratio, under iso- and hyperosmotic conditions, respectively. The vast majority of the proteoliposomes were unilamellar, and the appearance of a spherical shape inside a vesicle (E and F) generally represents a top view of an invaginated liposome.