Influence of cholesterol on the polar region of phosphatidylcholine and phosphatidylethanolamine bilayers.
The structural changes in the polar head group region of unsonicated bilayer membranes of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine produced by addition of cholesterol have been determined using deuterium and phosphorus-31 NMR. Incorportion of up to 50 mol percent cholesterol produces little change in the phosphorus-31 chemical shielding anisotropies, compared with the values in pure bilayers above the phase transition temperatures, while some of the deuterium quadrupole splittings are reduced by almost a factor of two. Adjustment of the head group torsion angles by only a few degrees accounts for the observed spectral changes. Addition of cholesterol therefore has opposite effects on the hydrocarbon and polar regions of membranes: although cholesterol makes the hydrocarbon region gel-like, with an increased probability of trans conformations, the conformation of the polar head groups is very similar to that found in the liquid crystalline phase of pure phospholipid bilayers.
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002784:Cholesterol; D009682:Magnetic Resonance Spectroscopy; D008567:Membranes, Artificial; D008968:Molecular Conformation; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D013696:Temperature; D013816:Thermodynamics
D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D002784:Cholesterol