Shapes of unilamellar phospholipid containing cardiolipin

Nejc Tomšič1, Blaž Babnik2, Blaž Mavčič2, Maša Kandušer2, Aleš Iglič2, Veronika Kralj-Iglič1

1Faculty of Medicine, University of Ljubljana, Slovenia; 2Faculty of Electrical Engineering, Univesity of Ljubljana, Slovenia

Giant unilamellar phospholipid vesicle present a simple model of the cell membrane as the properties of the vesicle membrane are reflected in its shape. Cardiolipin is a four-tailed phospholipid which is present mostly in mitochondrial membrane. In this work it was of interest to observe the effect of the composition of the membrane containing cardiolipin on the vesicle shape. Phospholipid vesicles were prepared from different ratios of palmitoyloleyl-phosphatidylcholine, cardiolipin and cholesterol in sugar solution by the method of electroformation and observed under the phase contrast microscope. Cardiolipin incorporated readily into the membrane up to 50% of molar ratio of other constituents. It was observed that at room temperatures the vesicles exhibit abrupt changes in the curvature of the vesicle contour indicating regions of phase separation. The deviations from the spherical shape were larger for higher content of cardiolipin. With increasing temperatures the vesicle contour became smooth where the process was reversible. We also observed many multicompartment vesicles with fluctuating single bilayer walls between the compartments.

Email: nejct@siol.net

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