Cholesterol increases membrane tension in PI(4,5)P ₂ -containing membranes. (A) Interfacial tensions (σ) trends measured with pendant drop experiments as a function of time for POPC + 5% PI(4,5)P₂, varying the cholesterol content (0, 10, 15, 30, 50 mol%). A buffer drop (HEPES 25 mM, KCl 150 mM) is immersed in a lipid-squalene solution (1 mg/ml) and its change in shape, which corresponds to the arrangement of the lipids at the newly created buffer-oil interface, is monitored. The σ values recorded after reaching the plateau increase with higher cholesterol content. (B) Average σ values (n = 3) after reaching a plateau at t = 24 min. Errors are given as SD. (C) Values for bilayer tension ϒ of PI(4,5)P₂-containing (5 mol%) membranes as a function of the cholesterol concentration. ϒ is calculated combining the bilayer angles obtained by analysis of the optical micrographs and the σ values after the plateau through the Eq. 1. Errors were calculated using error propagation.