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Pretransitional effects in dimyristoylphosphatidylcholine vesicle membranes: optical dynamometry study
R Dimova1, B Pouligny, C Dietrich
1Centre de Recherche Paul-Pascal, Centre National de la Recherche Scientifique, 33600 Pessac, France.
Biophysical Journal
|June 27, 2000
Summary
Researchers used latex spheres to study dimyristoylphosphatidylcholine (DMPC) lipid bilayers. They found that membrane viscosity increases near the fluid-gel transition, while elastic resistance decreases, offering insights into bilayer properties.
Area of Science:
- Biophysics
- Materials Science
- Physical Chemistry
Background:
- Lipid bilayers exhibit complex phase transitions affecting their mechanical properties.
- Understanding these properties is crucial for cell membrane function and biomaterial design.
Purpose of the Study:
- To investigate the phase behavior and viscoelastic properties of dimyristoylphosphatidylcholine (DMPC) bilayers.
- To measure membrane hydrodynamic shear viscosity and elastic resistance as a function of temperature.
Main Methods:
- Utilized micron-sized latex spheres manipulated by optical traps on DMPC giant vesicles.
- Analyzed particle motion (Brownian motion, driven motion) to determine membrane viscosity.
- Employed optical dynamometry with two-bead experiments to measure membrane elastic resistance and curvature modulus.
Main Results:
- Hydrodynamic shear viscosity (eta(s)) of DMPC bilayers increased significantly near the main transition temperature (T(m) ≈ 23.4°C).
- Long-distance particle motion was restricted below T(m).
- Membrane elastic resistance decreased considerably, approaching zero at T(m), indicating changes in mechanical response.
Conclusions:
- The study provides direct measurements of membrane viscosity and elastic resistance in DMPC bilayers.
- Results suggest a strong correlation between temperature-induced phase transitions and changes in bilayer mechanical properties.
- The proposed model relates elastic response to the membrane curvature modulus (k(C)), enabling its measurement in the P'(beta) phase.