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Published on: October 15, 2016
Low pH Stabilizes the Inverted Hexagonal II Phase in Dipalmitoleoylphosphatidylethanolamine Membrane
Shu Jie Li1, Masahito Yamazaki
1Department of Physics, Dalian University, Dalian Economic and Technical Development Zone, Dalian, 116622 China ; Division of Protein Crystallography, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita-shi Osaka, 565-0871 Japan.
Journal of Biological Physics
|January 25, 2013
Summary
Low pH induces a phase transition in dipalmitoleoylphosphatidylethanolamine (DPOPE) membranes, shifting them to the H(II) phase. Cationic dioctadecyldimethylammonium (DODMA) further stabilizes this H(II) phase.
Area of Science:
- Membrane biophysics
- Lipid self-assembly
- Phase transitions
Background:
- Dipalmitoleoylphosphatidylethanolamine (DPOPE) membranes exhibit the L(α) phase at neutral pH and 20 °C.
- Understanding lipid phase behavior is crucial for biomembrane function and drug delivery systems.
Purpose of the Study:
- To investigate the effect of pH and cationic additives on DPOPE membrane structure and phase transitions.
- To elucidate the mechanism driving the L(α) to H(II) phase transition in DPOPE membranes.
Main Methods:
- Small-angle X-ray scattering (SAXS) was employed to analyze membrane structures.
- Investigated phase behavior under varying pH and salt (KCl) concentrations.
- Assessed the influence of dioctadecyldimethylammonium (DODMA) on DPOPE membrane properties.
Main Results:
- An L(α) to H(II) phase transition in DPOPE membranes was observed at pH 1.9 (no salt) and pH 2.8 (0.5 M KCl).
- Spontaneous curvature of the DPOPE monolayer remained unchanged with decreasing pH.
- Low concentrations of DODMA were found to stabilize the H(II) phase over the L(α) phase in DPOPE membranes.
Conclusions:
- Low pH promotes H(II) phase stability in DPOPE membranes, influenced by spontaneous curvature and acyl chain packing energy.
- Cationic DODMA enhances H(II) phase stabilization in DPOPE lipid systems.
- These findings contribute to understanding lipid phase behavior and interactions in complex membrane systems.
Keywords:
inverted hexagonal phaseliquid-crystalline phaselow pHphase transitionspontaneous curvatureMore Related Videos
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