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Fluorescence Recovery after Merging a Droplet to Measure the Two-dimensional Diffusion of a Phospholipid Monolayer
Published on: October 15, 2015
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Spontaneous evolution of equilibrium morphology in phospholipid-cholesterol monolayers
Cain Valtierrez-Gaytan1, Joseph M Barakat2, Mitchell Kohler1
1Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, USA.
Science Advances
|April 6, 2022
Summary
Lipid monolayer domains reversibly transform from semicircular to stripe shapes. This shape transition, driven by changes in line tension and dipole density, reveals energy minima for lipid domain morphologies.
Area of Science:
- Lipid monolayer behavior
- Phase separation dynamics
- Surface tension phenomena
Background:
- Lipid monolayers exhibit phase separation into distinct domains.
- Domain morphology is influenced by electrostatic repulsions and line tension.
- The stability of observed lipid domain shapes (energy minima vs. metastable states) remains unclear.
Purpose of the Study:
- To investigate the reversible transformation of lipid domain shapes.
- To determine if observed morphologies represent energy minima or kinetically trapped states.
- To provide the first estimates of the line tension to dipole density difference ratio (λ/μ²) at liquid condensed-liquid expanded phase coexistence.
Main Methods:
- Observation of domain shape transitions in dipalmitoylphosphatidylcholine (DPPC) and hexadecanol (HD) or palmitic acid (PA) monolayers with dihydrocholesterol (DChol).
- Analysis of domain growth and composition changes, including depletion of HD and DPPC precipitation.
- Measurement of stripe domain width to estimate λ/μ².
Main Results:
- Demonstrated reversible evolution from semicircular to uniform width stripe domains.
- Observed changes in domain stoichiometry and composition during growth.
- Showed that decreasing λ/μ² drives the transition to stripe domains as the minimum energy structure.
Conclusions:
- Lipid domain morphologies can reversibly evolve to minimum energy states.
- The observed stripe domains represent thermodynamically stable structures.
- Stripe width measurements offer a novel method for quantifying λ/μ² in phase-coexisting lipid monolayers.
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