Cubic phases in membrane lipids
Boris Tenchov1, Rumiana Koynova
1Department of Medical Physics and Biophysics, Medical University Sofia, Sofia, Bulgaria. btenchov@gmail.com
European Biophysics Journal : EBJ
|May 16, 2012
Summary
Bilayer cubic phases (QII(B)) form more readily when cooling from the H(II) phase. Charged phospholipids significantly enhance QII(B) formation in phosphatidylethanolamines (PEs).
Area of Science:
- Lipid self-assembly
- Biomembrane biophysics
- Materials science
Background:
- Lipid dispersions exhibit various phases, including lamellar (Lα) and inverted hexagonal (HII).
- Bilayer cubic phases (QII(B)) are complex lipid structures with potential applications.
- Understanding phase transitions is crucial for biomembrane and materials science.
Purpose of the Study:
- Investigate the formation pathways of inverted bicontinuous cubic phases (QII(B)).
- Determine the influence of temperature cycling and lipid composition on QII(B) formation.
- Explore the role of charged phospholipids in facilitating QII(B) induction.
Main Methods:
- Time-resolved X-ray diffraction to study lipid phase transitions.
- Analysis of lipid dispersions including phosphatidylethanolamines (PEs), phosphatidylcholines (PCs), and glycolipids.
- Controlled temperature cycling (cooling and heating) and isothermal conversions.
Main Results:
- QII(B) formation is significantly easier upon cooling from the H(II) phase compared to heating or isothermal conversion from the Lα phase.
- Lipids exhibiting an Lα ↔ H(II) phase transition generally convert to cubic phases upon temperature cycling.
- Anionic and cationic charged phospholipids strongly facilitate QII(B) formation in PEs.
Conclusions:
- Cooling from the H(II) phase offers an efficient route for QII(B) induction.
- Temperature cycling is a general method for inducing cubic phases in lipids with Lα ↔ H(II) transitions.
- Electrostatic repulsion from charged lipids lowers energy barriers for QII(B) formation in PEs.
