Abstract
The molecular origin of the fluidizing and condensing effects of cholesterol has been investigated using interacting spin label pairs in multibilayer films of various lecithins. The spin label pair method is a probe of the lateral separation of molecules within the bilayer. The cholestane spin probe separation is found to increase with increasing cholesterol composition in dipalmitoyllecithin bilayers and to decrease with increasing cholesterol composition in both egg and dioleoyllecithin bilayers. These changes in close-packing of the molecules within the lecithin bilayers correspond respectively to the fluidizing and condensing (and rigidifying) effects of cholesterol. The measured decrease in lateral separation corresponding to fluidization of the dipalmitoyllecithin—cholesterol bilayers correlates reasonably well with the latent heat and change in volume at the liquid crystal transition of pure dipalmitoyllecithin. The size of the decrease in lateral separation in egg lecithin bilayers indicates that the condensing effect of cholesterol arises from both molecular interaction with the lecithin chains and the existence of molecular cavities within the lecithin chain region of the bilayer.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - Biomembranes
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