Figure 4.

Tensionless leaflets attained via flip-flops (or transbilayer motion) of cholesterol: An asymmetric bilayer with 66 POPCs and 24 lollipop-like GM1s in the upper leaflet, 87 POPCs in the lower leaflet, and 20 cholesterols flip-flopping between the two leaflets was simulated for 100 μs. (A) Cholesterol distributions show the preference for the lower (black) over the upper (striped blue) leaflet; the average cholesterol numbers were 9.0 ± 0.2 in the upper and 11.0 ± 0.2 in the lower leaflet. The inset shows a sketch of the Martini cholesterol model.³⁵ (B) Dependence of the tension difference between the leaflets, ΔΣ, on the number of cholesterols residing in the lower leaflet at a given instant of time. (C) Average relaxation (black solid line) toward the state with tensionless leaflets following the observed 258 events in which the number of cholesterols in the lower leaflet fell below 7. The shaded area shows the 68% confidence interval around an exponential decay (white dashed line) determined from the data. The inset zooms in on the first 2.5 ns.