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Updated: Aug 9, 2026

Realistic Membrane Modeling Using Complex Lipid Mixtures in Simulation Studies
Published on: September 1, 2023
Closed-loop miscibility gap and quantitative tie-lines in ternary membranes containing diphytanoyl PC
Sarah L Veatch1, Klaus Gawrisch, Sarah L Keller
1Department of Chemistry, University of Washington, Seattle, Washington, USA.
Abstract:
Vesicles containing ternary mixtures of diphytanoylphosphatidylcholine, dipalmitoylphosphatidylcholine (DPPC), and cholesterol produce coexisting liquid phases over an unusually large range of temperature and composition. Liquid domains persist well above the DPPC chain melting temperature (41 degrees C), resulting in a closed-loop miscibility gap bounded by two critical points at fixed temperature. Quantitative tie-lines are determined directly from 2H NMR spectra using a novel analysis, and are found to connect a liquid-disordered phase rich in diphytanoyl PC with a liquid-ordered phase rich in DPPC. The direction of the tie-lines implies that binary DPPC/cholesterol mixtures are in one uniform phase above 41 degrees C. All 2H NMR results for tie-lines are verified by independent fluorescence microscopy results.
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