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Vibrational layer eigenmodes of binary phospholipid-cholesterol bilayers at low temperatures.
D V Leonov1, S V Adichtchev2, S A Dzuba1,3
1Department of Physics, Novosibirsk State University, Novosibirsk 630090, Russia.
Physical Review. E
|April 3, 2019
Summary
Cholesterol affects lipid bilayers differently based on phospholipid saturation. Raman spectroscopy reveals how cholesterol influences lipid monolayer vibrations and interleaflet coupling in DOPC, POPC, and DMPC bilayers.
Area of Science:
- Biophysics
- Materials Science
- Spectroscopy
Background:
- Lipid bilayers are fundamental to cell membranes.
- Cholesterol modulates membrane properties.
- Raman spectroscopy probes molecular vibrations.
Purpose of the Study:
- Investigate the effect of cholesterol on lipid bilayers with varying phospholipid saturation.
- Analyze low-frequency Raman spectra to understand molecular dynamics.
- Determine how cholesterol concentration impacts bilayer structure and interleaflet coupling.
Main Methods:
- Preparation of multilamellar bilayers with cholesterol and three types of phospholipids: DOPC, POPC, and DMPC.
- Measurement of low-frequency Raman spectra (5-90 cm⁻¹) at temperatures below 250 K.
- Analysis of peak position, width, and intensity as a function of cholesterol concentration.
Main Results:
- A low-frequency peak attributed to lipid monolayer vibrational eigenmode was observed.
- Cholesterol's effect on peak position and width varied non-monotonically with concentration for POPC and DMPC, but monotonically for DOPC.
- Peak intensity, linked to interleaflet coupling, showed concentration-dependent changes.
- Raman data contradicted domain coexistence models for large domain sizes.
Conclusions:
- Cholesterol's influence on lipid bilayer dynamics is dependent on phospholipid saturation.
- Observed Raman spectral changes provide insights into lipid-cholesterol interactions and membrane phase behavior.
- The study challenges existing models of lipid domain coexistence under specific conditions.
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