Fig. 8. Impact of abnormal sterol expression on membrane curvature. (A) Membrane bending rigidity K_C obtained from measured interactions of multilamellar DMPC vesicles at 35°C containing 30 mol% sterols. The importance of double-bond location in the sterol ring is illustrated, with cholesterol the most efficient at enhancing membrane rigidity. (B) X-ray scattering of highly curved, inverse hexagonal phase DOPE/30mol% sterol mixtures. The shift of scattering peaks with sterol type corresponds to changes in the radius of curvature of bent DOPE monolayers with the smallest values measured for cholesterol and the largest for 7-DHC. Depletion of cholesterol or replacement with 7-DHC or lathosterol modifies the distribution of forces (bending stress) within biomembranes contributing to cellular morphological changes. (C) Distribution of granule sizes in the lathosterol model. 30 images from each of three animals were analyzed. Granule areas are distributed over a greater range compared with the normal WT range.