Morphometric image analysis of giant vesicles: a new tool for quantitative thermodynamics studies of phase separation in lipid membranes

Biophys J. 2012 Dec 5;103(11):2304-10. doi: 10.1016/j.bpj.2012.10.031.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Lipid Bilayers / chemistry*
  • Membrane Fluidity*
  • Membrane Lipids / chemistry*
  • Membrane Microdomains / chemistry*
  • Membrane Microdomains / ultrastructure*
  • Microscopy, Confocal / methods*
  • Microscopy, Fluorescence / methods*
  • Phase Transition
  • Thermodynamics

Substances

  • Lipid Bilayers
  • Membrane Lipids