Effects of cholesterol on the orientational order of unsaturated lipids in the membranes of acholeplasma laidlawii. A 2H-NMR study.
We have investigated by 2H-NMR the effects of the incorporation of cholesterol on the orientational order of unsaturated lipid acyl chains in the membranes of acholeplasma laidlawii B. This is the only 2H-NMR study to date of the influence of cholesterol in a biological membrane using specifically labelled fatty acids. We observed the characteristic condensing effect of cholesterol on the lipid acyl chain order in the liquid crystalline phase. In terms of the percentage increase in the quadrupolar splittings, the presence of cholesterol has its greatest effect on the methyl end of the labelled oleoyl chains, with a maximum at the C-14 segment. In absolute terms, the perturbation is greatest in the carboxyl end of the chains. The temperature dependence of the 2H spectra for the cholesterol-containing membranes is very similar to that for the cholesterol-free membranes. The broad phase transition of the membrane lipids, which is characteristic for the samples lacking cholesterol, is apparently little affected by the presence of up to 27 mol% cholesterol. In addition, the temperature of onset of the phase transition is not significantly depressed by the presence of cholesterol.
D000128:Acholeplasma laidlawii / Q000502:physiology* / Q000648:ultrastructure; D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002784:Cholesterol / Q000502:physiology*; D005231:Fatty Acids, Unsaturated; D009682:Magnetic Resonance Spectroscopy; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000502:physiology; D009038:Motion; D013696:Temperature
D005231:Fatty Acids, Unsaturated; D008563:Membrane Lipids; D002784:Cholesterol