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Formation of domains in multilamellar liposomes by sphingomyelin and cholesterol

In order to examine lipid domains formation in multilamellar liposomes due to the presence of sphingomyelin and cholesterol, liposomes composed of egg-phosphatidylcholine, sphingomyelin, cholesterol and dipalmitoylphosphatidylglycerol were prepared. Spin-labelled dipalmitoylphosphatidylcholine and palmitoyloleoylphosphatidylcholine were incorporated into liposomes. Spin label TEMPO was covalently attached to amino-group (instead of one methyl group). EPR parameters[1] from experimental and simulated spectra of the spin-labelled liposomes with different amount of cholesterol (0, 8, 15, 22, 29, 38 and 45 mol %) gave information about surface structure of the liposomes and lipid domain formation. Dynamics of the system was investigated by temperature dependence of the EPR spectra. Simulations of the spectra were performed by EasySpin software package[2] in the MatLab platform. [1] D. Marsh, Electron Spin Resonance (Membrane Spectroscopy), Springer-Verlag, Berlin Heidelberg, 1981, str. 51-142. [2] S. Stoll, A. Schweiger, J. Magn. Reson. 178 (2006) 42-55.

spin labelling; ESR; membrane model; phospholipids

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