How sterol tilt regulates properties and organization of lipid membranes and membrane insertions

► Specific property related to sterol tilt in lipid membranes, the sterol tilt modulus χ, is derived from molecular dynamics simulations. ► The tilt modulus χ quantifies the energetic cost of tilting sterol molecules inside the lipid membrane. ► We relate molecular tilt to the bending rigidity of the lipid bilayer through effective tilt and splay energy contributions to the elastic deformations. ► We demonstrate how the tilt modulus quantitatively describes the aligning field that sterol molecules create inside the phospholipid bilayers. ► The cholesterol aligning field is important for the proper folding and interactions of membrane peptides.