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Spontaneously formed unilamellar vesicles with path-dependent size distribution
Mu-Ping Nieh1, Velayudhan A Raghunathan, Steve R Kline
1National Research Council, Steacie Institute for Molecular Sciences, Chalk River, Ontario, K0J 1J0, Canada.
Langmuir : the ACS Journal of Surfaces and Colloids
|July 13, 2005
Summary
Phospholipid vesicles spontaneously form from different structures. Heating bicelles yields monodisperse vesicles, while diluting lamellae forms polydisperse vesicles, revealing phase behavior.
Area of Science:
- Biophysics
- Materials Science
- Physical Chemistry
Background:
- Phospholipids can self-assemble into various structures like micelles, lamellae, and vesicles.
- Understanding the phase transitions and morphology of phospholipids is crucial for biomimetic applications.
Purpose of the Study:
- To investigate the spontaneous formation of phospholipid unilamellar vesicles (ULV) from different equilibrium morphologies.
- To elucidate the role of temperature and lipid concentration in vesicle formation and stability.
Main Methods:
- Thermodynamic analysis of phospholipid phase behavior.
- Temperature-dependent studies of lipid mixtures.
- Morphological characterization using microscopy and scattering techniques.
Main Results:
- Disklike micelles (bicelles) transform into lamellae upon heating above Tc.
- Dilution of lamellae leads to polydisperse ULV formation, indicating lamellar phase instability.
- Heating bicelles above Tc yields monodisperse ULV, which can reform into bicelles or novel oblate ellipsoids upon cooling depending on concentration.
Conclusions:
- Phospholipid vesicle formation is path-dependent, influenced by initial morphology and thermodynamic conditions.
- The study reveals new morphological transitions in lipid mixtures, including the formation of oblate ellipsoids.
- These findings contribute to understanding self-assembly processes and designing novel lipid-based nanostructures.