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Single Molecule Fluorescence Microscopy on Planar Supported Bilayers
Published on: October 31, 2015
Fluorescence microscopic characterization of ionic polymer bead-supported phospholipid bilayer membrane systems
Mamoru Haratake1, Samuel Osei-Asante, Takeshi Fuchigami
1Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan. haratake@nagasaki-u.ac.jp
Colloids and Surfaces. B, Biointerfaces
|July 7, 2012
Summary
Supported phospholipid membranes on polymer beads show reduced fluidity due to electrostatic immobilization. Membrane fluidity depends on the anionic phospholipid fraction, with lower dioleoylphosphatidylserine (PS) content yielding more fluid membranes.
Area of Science:
- Biomaterials science
- Materials chemistry
- Biophysics
Background:
- Phospholipid bilayers are fundamental to cell membranes.
- Creating supported membrane systems is crucial for biomimetic applications.
- Understanding lipid-membrane dynamics on solid supports is key for advanced materials.
Purpose of the Study:
- To prepare and characterize supported phospholipid membrane structures on cationic polymer beads.
- To investigate the binding of macromolecules to these supported membranes.
- To analyze the fluidity and factors influencing it in these immobilized phospholipid bilayers.
Main Methods:
- Preparation of supported phospholipid membranes using mixtures of dioleoylphosphatidylserine (PS) and egg yolk phosphatidylcholine (PC) on cationic polymer beads.
- Confocal fluorescence microscopy with a lipid probe to visualize membrane distribution.
- Fluorescence recovery after photobleaching (FRAP) to measure lateral diffusion coefficients (D) and membrane fluidity.
- Electrostatic binding studies with rhodamine isothiocyanate dextran.
Main Results:
- Phospholipids formed structures on the outer surface of polymer beads, not internally.
- Anionic PS on the surface facilitated binding of positively charged macromolecules via electrostatic forces.
- Supported membranes exhibited significantly reduced lateral diffusion coefficients (fluidity) compared to giant unilamellar vesicles.
- Membrane fluidity was dependent on phospholipid composition, with lower PS content resulting in more fluid membranes.
Conclusions:
- Supported phospholipid membranes on cationic polymer beads can be formed with controlled surface properties.
- Electrostatic interactions between anionic phospholipids and the cationic bead surface immobilize the membrane, reducing fluidity.
- The composition of the phospholipid mixture, specifically the fraction of anionic phospholipids, critically influences the fluidity of the supported membrane.
