Phase diagram and tie-line determination for the ternary mixture DOPC/eSM/cholesterol.

We propose a novel, to our knowledge, method for the determination of tie lines in a phase diagram of ternary lipid mixtures. The method was applied to a system consisting of dioleoylphosphatidylcholine (DOPC), egg sphingomyelin (eSM), and cholesterol (Chol). The approach is based on electrofusion of single- or two-component homogeneous giant vesicles in the fluid phase and analyses of the domain areas of the fused vesicle. The electrofusion approach enables us to create three-component vesicles with precisely controlled composition, in contrast to conventional methods for giant vesicle formation. The tie lines determined in the two-liquid-phase coexistence region are found to be not parallel, suggesting that the dominant mechanism of lipid phase separation in this region changes with the membrane composition. We provide a phase diagram of the DOPC/eSM/Chol mixture and predict the location of the critical point. Finally, we evaluate the Gibbs free energy of transfer of individual lipid components from one phase to the other. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Citation

N Bezlyepkina, R S Gracià, P Shchelokovskyy, R Lipowsky, R Dimova. Phase diagram and tie-line determination for the ternary mixture DOPC/eSM/cholesterol. Biophysical journal. 2013 Apr 02;104(7):1456-64

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PMID: 23561522

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