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          Questions:  What is the role of cholesterol in healthy cell membranes?  Why is there as much as 40-50% cholesterol of the total lipid in a plasma membrane?  How does cholesterol affect the elastic properties and the ordering of lipid chains?

Cholesterol Perturbs Lipid Bilayers Nonuniversally,  PRL 100, 198103 (2008)

Jianjun Pan, Thalia T. Mills, Stephanie Tristram-Nagle, and John F. Nagle

Physics Department, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA

a b s t r a c t                                                                                                                                        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.


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This article was followed up by a longer article on the same subject in Physical Review E.   To read the PRE, click here.