Figure 9.

(Top panel) Distribution of the DPPC headgroup inclination angle θ as a function of distance from a single cholesterol molecule. Except for phospholipids in the closest region, which show a broadening toward larger angles, the distributions remain similar to those obtained in pure bilayers. (Bottom panel) Distribution of the headgroup azimuth ϕ—defined as the angle between the P-N separation vector of the headgroup and the O-P separation vector between cholesterol and DPPC, both projected onto the xy plane (see inset)—is shown. Phospholipids within the first three regions, extending up to 0.66 nm, have a tendency of orienting their headgroups toward the cholesterol, whereas phospholipids further away show a uniform angle distribution. To see this figure in color, go online.