(581e) Leaflet Asymmetry in Biological Lipid Membranes

Lipid membrane asymmetry is observed in biological membranes, although a comprehensive understanding of the membrane lipidome is not well-established. We have studied multiple biological membranes—human red blood cells, neural cells, and placental trophoblast cells—to gain a comprehensive understanding of the role of leaflet asymmetry in the physiological function of a cell membrane. Here we report a molecular-level description of the replicates of the experimentally determined composition of the lipid families (phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and sphingomyelin) that constitute the exoplasmic and cytoplasmic leaflets. In the red blood cells, sphingomyelin lipids cause interdigitation of the opposing leaflets. The cholesterol also exhibits asymmetry with higher concentration in the exoplasmic leaflet leading. Compared to the exoplasmic leaflet, the cytoplasmic leaflet carries a higher negative charge due to the higher density of the negatively charged lipids. Besides RBCs, impact of leaflet symmetry is observed in the neural and placental cell membrane. The study evaluates the lipidome of biological membranes and demonstrates relationships among different lipid families that cause membrane asymmetry.