Figure 5.

Thickness, area, and lipid tail order vs cholesterol concentration in DOPC bilayers compared between experiment, united-atom, and different coarse-grained simulations. A: Bilayer thickness (phosphate-phosphate distance across the leaflets), averaged over a grid as described in the Methods, with experimental data from Kucerka et al.⁵⁰ We estimated headgroup-headgroup distances (d_HH) from their data by d_TOT – d_H, where d_TOT is the total bilayer thickness measured in their paper and d_H = 1.0 nm is the estimated thickness of the headgroup layer.⁷⁶ B: Difference in bilayer thickness from 0% cholesterol. C: Projected area per molecule, with experimental areas in monolayers from Smaby et al. at a surface pressure of 30 mN/m;⁵⁶ D: estimated slope of the A_M curve as a function of mol % cholesterol; the slope between two consecutive X_cholx_i and x_i+1 is plotted at (x_i + x_i+1)/2. Panel E shows the C2A-D3A P₂ order parameter for the sn-1 oleoyl chain, and panel F shows the C2B-D3B P₂ order parameter for the sn-2 oleoyl chain. For all panels, black indicates the united-atom model.³⁶ The estimated experimental POPC oleoyl chain P₂ order parameter data derived from Ferreira et al.⁴³ (Figure 2E) are included in both panels as an approximate experimental reference. For coarse-grained simulations, the phospholipid model is indicated by blue lines (MARTINI) or red lines (angle-corrected POPC), while the sterol model is indicated by circles (MARTINI cholesterol) or triangles (optimized cholesterol, that is, CT₃-Me_2b). Where available, experimental data are indicated in green. Error bars indicate the standard deviation of each metric over simulation time.