Cholesterol Perturbs Lipid Bilayers Nonuniversally
Cholesterol is well known to modulate the physical properties of biomembranes. Using modern x-ray scattering methods, we have studied the effects of cholesterol on the bending modulus KC, the thickness DHH, and the orientational order parameter Sxray of lipid bilayers. We find that the effects are different for at least three classes of phospholipids characterized by different numbers of saturated hydrocarbon chains. Most strikingly, cholesterol strongly increases KC when both chains of the phospholipid are fully saturated but not at all when there are two monounsaturated chains.