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Assembly of Cell Mimicking Supported and Suspended Lipid Bilayer Models for the Study of Molecular Interactions
Published on: August 3, 2021
Cholesterol effect on water permeability through DPPC and PSM lipid bilayers: a molecular dynamics study
Hiroaki Saito1, Wataru Shinoda
1Faculty of Mathematics and Physics, Institute of Science and Engineering, Kanazawa University, Kanazawa 920-1192, Japan. saito@wriron1.s.kanazawa-u.ac.jp
The Journal of Physical Chemistry. B
|November 16, 2011
Summary
Cholesterol addition to lipid bilayers, like DPPC and PSM, reduces water leakage by increasing the free energy barrier. This barrier increase is due to reduced cavity density within the membrane core.
Area of Science:
- Biophysics
- Computational Chemistry
- Membrane Biophysics
Background:
- Lipid bilayers form cell membranes, regulating transport.
- Cholesterol modulates membrane properties, impacting fluidity and permeability.
- Understanding cholesterol's effect on different lipid types is crucial for membrane science.
Purpose of the Study:
- To investigate the molecular mechanism by which cholesterol reduces water permeability in dipalmitoylphosphatidylcholine (DPPC) and palmitoylsphingomyelin (PSM) lipid bilayers.
- To elucidate the role of free energy barriers and membrane structural changes in cholesterol-mediated water transport reduction.
- To compare the behavior of DPPC and PSM bilayers with varying cholesterol concentrations.
Main Methods:
- Molecular dynamics simulations were employed to study water permeability.
- Free energy barriers for water permeation were calculated.
- Structural properties like cavity density, trans conformers, order parameters, and cross-sectional area per molecule were analyzed.
Main Results:
- Increased cholesterol concentration enhanced the free energy barrier in both DPPC and PSM bilayers, reducing water leakage.
- Reduced cavity density in the hydrophobic core, caused by increased trans conformers in lipid chains near cholesterol, was identified as the mechanism.
- Palmitoylsphingomyelin (PSM) bilayers showed a higher free energy barrier than dipalmitoylphosphatidylcholine (DPPC) bilayers at low cholesterol concentrations; this difference diminished at higher concentrations (>30 mol %).
Conclusions:
- The enhanced free energy barrier is the primary factor reducing water permeability with increasing cholesterol.
- DPPC and PSM bilayers exhibit similar physical properties at high cholesterol concentrations, suggesting cholesterol's significant influence on membrane characteristics.
- The solubility and integration of cholesterol are critical for understanding the behavior of complex, multicomponent lipid membranes.
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