Osmotically Induced Shape Changes of Large Unilamellar Vesicles Measured by Dynamic Light Scattering

Static and dynamic light scattering measurements have been used to characterize the size, size distribution, and shape of extruded vesicles under isotonic conditions. Dynamic light scattering was then used to characterize osmotically induced shape changes by monitoring changes in the hydrodynamic ra...

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Bibliographic Details
Published in:Biophysical journal 2001-11, Vol.81 (5), p.2716-2728
Main Authors: Pencer, Jeremy, White, Gisèle F., Hallett, F. Ross
Format: Article
Language:English
Subjects:
Elasticity
Light
Lipids
Liposomes - chemistry
Membranes
Membranes, Artificial
Models, Molecular
Osmosis
Osmosis - physiology
Osmotic Pressure
Particle Size
Phosphatidylcholines - chemistry
Physics
Scattering, Radiation
Sodium Chloride - pharmacokinetics
Sucrose - pharmacokinetics
Transport Vesicles - metabolism
Urea - pharmacokinetics
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Summary:Static and dynamic light scattering measurements have been used to characterize the size, size distribution, and shape of extruded vesicles under isotonic conditions. Dynamic light scattering was then used to characterize osmotically induced shape changes by monitoring changes in the hydrodynamic radius ( R h) of large unilamellar vesicles (LUVs). These changes are compared to those predicted for several shapes that appear in trajectories through the phase diagram of the area difference elasticity (ADE) model (Jarić et al. 1995. Phys. Rev. E. 52:6623–6634). Measurements were performed on dioleoylphosphatidylcholine (DOPC) vesicles using two membrane-impermeant osmolytes (NaCl and sucrose) and a membrane-permeant osmolyte (urea). For all conditions, we were able to produce low-polydispersity, nearly spherical vesicles, which are essential for resolving well-defined volume changes and consequent shape changes. Hyper-osmotic dilutions of DOPC vesicles in urea produced no change in R h, whereas similar dilutions in NaCl or sucrose caused reductions in vesicle volume resulting in observable changes to R h. Under conditions similar to those of this study, the ADE model predicts an evolution from spherical to prolate then oblate shapes on increasing volume reduction of LUVs. However, we found that DOPC vesicles became oblate at all applied volume reductions.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(01)75914-0