Reassessment of Membrane Mechanics – How Cholesterol Stiffens Unsaturated Lipid Membranes

Cholesterol is a ubiquitous component of eukaryotic cell membranes and a key molecule in controlling membrane fluidity, packing state, and various biological processes. It also plays a regulatory function in the immune response and antibiotic drug resistance by augmenting the membrane mechanical properties against structural damage. While it is well understood that, structurally, cholesterol exhibits a universal condensing effect on lipid membranes, its effects on membrane mechanics are assumed to be non-universal; i.e. cholesterol causes noticeable stiffening in saturated lipid membranes, but is surprisingly reported to have no stiffening effect on unsaturated lipid membranes such as DOPC. Here, using neutron spin-echo (NSE) spectroscopy, solid-state deuterium nuclear magnetic resonance (2H-NMR) spectroscopy, and molecular dynamics (MD) simulations, we report that, on the mesoscale, cholesterol increases the bending rigidity of DOPC membranes, similar to saturated membranes, through its effect on the bilayer's packing density. All three techniques show a gradual increase in membrane bending rigidity with increasing cholesterol content. These observations align with the known effects of cholesterol on the area compressibility modulus and on the membrane structure, as confirmed by MD simulations, small angle scattering, and electron spin resonance. These findings have significant biological implications and encourage a reassessment of the effects of cholesterol on membrane mechanics over length and time scales that are relevant to vital biological processes.<br><br>All the raw data and results are submitted as ASCII or pdf files.<br><br><i>For inquiries regarding the contents of this dataset, please contact the Corresponding Author listed in the README.txt file. Administrative inquiries (e.g., removal requests, trouble downloading, etc.) can be directed to [e-mail]</i>