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Cholesteryl hemisuccinate exhibits pH sensitive polymorphic phase behavior
1Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of British Columbia, 2146 Health Sciences Mall, Vancouver, B.C., Canada. ismail@interchange.ubc.ca
Cholesteryl hemisuccinate (CHEMS) exhibits pH-sensitive polymorphism, undergoing fusion below pH 4.3. This pH-dependent behavior of CHEMS is key to the sensitivity of mixed CHEMS and DOPE vesicles.
Area of Science:
- Lipid bilayer self-assembly
- Membrane biophysics
- Drug delivery systems
Background:
- Cholesteryl hemisuccinate (CHEMS) is an acidic cholesterol ester.
- CHEMS forms bilayers in neutral and alkaline aqueous media.
- CHEMS is used with dioleoylphosphatidylethanolamine (DOPE) for pH-sensitive fusogenic vesicles.
Purpose of the Study:
- To investigate the pH-sensitive polymorphism of CHEMS itself.
- To understand the contribution of CHEMS to the pH sensitivity of CHEMS/DOPE vesicles.
Main Methods:
- Large unilamellar vesicles (LUV) composed of CHEMS were prepared.
- Lipid mixing assays were used to monitor vesicle fusion.
- Freeze-fracture electron microscopy visualized lipid phases.
Main Results:
- CHEMS LUV demonstrated pH-sensitive fusogenic properties.
- Below pH 4.3, CHEMS LUV underwent fusion.
- Freeze-fracture electron microscopy revealed H( parallel) phase lipid structures below pH 4.3.
Conclusions:
- CHEMS exhibits intrinsic pH-sensitive polymorphism.
- The pH-dependent phase behavior of CHEMS influences the sensitivity of CHEMS/DOPE vesicles.
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