Fig 2. Overlapping of IV and CP lipids that self-assemble to an asymmetric membrane.

IV lipids are mainly consisted of POPC and PPCS, and CP lipids are consisted of POPE and POPS. (A) The self- assembly with 0 nm overlap, in between IV and CP lipid boxes, separates into two membranes. The water molecules inserted (invisible) in between the gap of IV and CP prevents two boxes of lipids aggregating into a single membrane. But (B) in 0.5 nm overlapping, the center of IV + CP boxes is dense in lipids which prevents excessive water insertion leading to an asymmetric membrane with IV and CP leaflet. In both type of simulations the spontaneous formation occurred in 5 ns.