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Atomic Force Microscopy Imaging and Force Spectroscopy of Supported Lipid Bilayers
Published on: July 22, 2015
Lateral phase separation in cholesterol/diheptadecanoylphosphatidylcholine binary bilayer membrane
Nobutake Tamai1, Maiko Uemura, Masaki Goto
1Department of Life System, Institute of Technology and Science, The University of Tokushima, 2-1 Minamijosanjima-cho, Tokushima 770-8506, Japan.
Colloids and Surfaces. B, Biointerfaces
|May 27, 2008
Summary
This study reveals how cholesterol affects lipid bilayer membranes. Cholesterol influences membrane phases, forming specific complexes and ordered structures at different compositions, impacting membrane fluidity and stability.
Area of Science:
- Biophysics
- Materials Science
- Physical Chemistry
Background:
- Understanding lipid bilayer membrane phase behavior is crucial for cell membrane function.
- Cholesterol is a key component influencing membrane fluidity and structure.
- Diheptadecanoylphosphatidylcholine (C17:0-PC) is a synthetic phospholipid used to model membrane systems.
Purpose of the Study:
- To investigate the phase behavior of cholesterol/C17:0-PC binary membranes.
- To determine the influence of cholesterol composition (X(ch)) on membrane phase transitions.
- To construct a temperature-cholesterol composition phase diagram.
Main Methods:
- Fluorescence spectroscopy using 6-propionyl-2-(dimethylamino)naphthalene (Prodan) to probe bilayer states.
- Differential scanning calorimetry (DSC) to detect phase transitions.
- Analysis of fluorescence spectra (lambda(max)) and DSC thermograms.
Main Results:
- Distinct lambda(max) values (ca. 440 nm and 490 nm) identified lamellar gel/liquid ordered and liquid-crystalline phases, respectively.
- Pre- and main transitions disappeared at X(ch)=0.05 and X(ch)=0.30, respectively.
- A eutectic binary mixture phase diagram with a peritectic point at X(ch)=0.15 was constructed, indicating stoichiometric cholesterol-C17:0-PC complex formation.
Conclusions:
- The phase diagram suggests regular cholesterol distribution in distinct bilayer states (e.g., 1:18 and 1:6 units).
- The disappearance of the main transition at X(ch)=0.30 indicates the existence of a pure liquid ordered (L(o)) phase.
- Eutectic behavior is attributed to phase separation of regions with different cholesterol distributions.
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