Red Blood Cell Lipids Form Immiscible Liquids

Abstract

Monolayers at the air-water interface were prepared from lipids extracted from human red blood cells. Epifluorescence microscopy was used to show that monolayers simulating the inner and outer leaflets of the red cell membrane form immiscible liquid phases with critical points at surface pressures of 21 and 29 dyn/cm. At these pressures the monolayer lipid density is comparable to that in the red cell membrane. This suggests that lipid bilayers of a red blood cell are near a miscibility critical point, which should significantly affect the biophysical properties of the red cell membrane.