Influence of Cholesterol on the Bilayer Properties of Mono-unsaturated Phosphatitylcholine Unilamellar Vesicles*, Norbert Kučerka 1, Jeremy Pencer2, Mu-Ping Nieh2, John Katsaras2 , 1CNBC - NRC, Canada and Comenius University, Slovakia , 2CNBC - NRC — The influence of cholesterol on the structure of a unilamellar vesicle (ULV) phospholipid bilayer is studied using small-angle neutron-scattering. ULV made up of short-, mid- and long-chain mono-unsaturated phospholipids (diCn:1PC, n=14, 18, 22) are examined over a range (0 – 45 mol%) of cholesterol concentrations. The bilayer structure is determined from SANS using a detailed model, which results, compared to a single-strip model, in a more realistic description of the water-lipid interface. Our approach allows us to extract structural parameters (e.g., bilayer thickness, lateral area and head group hydration) which are unaffected by changes due to water penetrating the membrane. Interestingly, increased levels of cholesterol manifest themselves in a monotonic increase, for all three lipids, of the evaluated parameters. While this result is expected for the short- and mid-length chain lipids, it is not in the case of the long-chain lipid. This result implies that cholesterol has a pronounced effect on the hydrocarbon chain organization even for 22-carbons long mono-unsaturated phospholipid.
* This work is being supported by NSERC Visiting Fellows program