Husen, Peter Rasmussen4; Arriaga, Laura3; Monroy, Francisco3; Ipsen, John Hjort4; Bagatolli, Luis5
1 Department of Biochemistry and Molecular Biology, Faculty of Science, SDU2 Department of Physics, Chemistry and Pharmacy, Faculty of Science, SDU3 Mechanics of Biological Membranes and Biorheology, Departamento de Quimica Fisica I, Universidad Complutense de Madrid, Madrid, Spain4 Department of Physics, Chemistry and Pharmacy, Faculty of Science, SDU5 Department of Biochemistry and Molecular Biology, Faculty of Science, SDU
We have developed a strategy to determine lengths and orientations of tie lines in the coexistence region of liquid-ordered and liquid-disordered phases of cholesterol containing ternary lipid mixtures. The method combines confocal-fluorescence-microscopy image stacks of giant unilamellar vesicles (GUVs), a dedicated 3D-image analysis, and a quantitative analysis based in equilibrium thermodynamic considerations. This approach was tested in GUVs composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine/1,2-palmitoyl-sn-glycero-3-phosphocholine/cholesterol. In general, our results show a reasonable agreement with previously reported data obtained by other methods. For example, our computed tie lines were found to be nonhorizontal, indicating a difference in cholesterol content in the coexisting phases. This new, to our knowledge, analytical strategy offers a way to further exploit fluorescence-microscopy experiments in GUVs, particularly retrieving quantitative data for the construction of three lipid-component-phase diagrams containing cholesterol.