Computer Simulations Suggest a Key Role of Membranous Nanodomains in Biliary Lipid Secretion
Figure 2
Lipid mobility and phase diagram.
Simulation of lipid diffusion and lipid phases in GUV’s with varying lipid composition. (A) Simulated (filled markers) and measured (open markers) average diffusion coefficients in monolayers with 25 different mixtures of CH, PC and SM. Triangles facing up mark values of a liquid-disordered phase, triangles facing down of a liquid-ordered phase. Mixtures with both values show biphasic behavior, mixtures with either of both show respective monophasic behavior. The percentage of each lipid in the mixture is indicated at the bottom (CH—PC—SM).
(B) Ternary phase diagram for mixtures of CH, PC and SM. The bold lines mark regions of lipid compositions for which the model predicts monophasic and biphasic behavior. In the monophasic Lo or Ld compositions more than 90% of the lipids are resident in the respective ordering state, whereas in the biphasic mixtures more than 10% of the lipids are resident in both ordering states thus favoring the formation of segregated microdomains. The triangles mark the measured lipid mixtures shown in (A) and indicate their measured phase state (up-facing triangle: Ld, down-facing triangle: Lo, star: biphasic) which not always matches our model prediction.