Document Detail

Thermodynamic stability and osmotic sensitivity of small unilamellar phosphatidylcholine vesicles.
MedLine Citation:
PMID:  8399305     Owner:  NLM     Status:  MEDLINE    
Evidence is presented to show that small unilamellar phosphatidylcholine vesicles with a diameter of approx. 20 nm are osmotically sensitive. Such vesicles respond to osmotic pressure by swelling or shrinking depending on the direction of the applied salt gradient. This is true for small unilamellar vesicles of egg phosphatidylcholine and dimyristoylphosphatidylcholine below and above their crystal-to-liquid crystal transition temperature. At the transition temperature the vesicles are osmotically insensitive due to the increased bilayer permeability resulting in rapid dissipation of salt gradients. Positive salt gradients produce shrinking and collapse of spherical phospholipid vesicles to disks. Shrinking of vesicles is associated with H2O and solute efflux, but only limited solute influx. Clustering of lipid molecules in the bilayers of the resulting disks can be detected by EPR spin labeling. Negative salt gradients produce swelling of vesicles which is associated with H2O and solute influx. Our experiments are consistent with an osmotically perturbed bilayer. In the presence of osmotic gradients the influx and efflux of H2O is coupled with the movement of ions and small molecules which in the absence of salt gradients or osmotic stress cannot pass the phospholipid bilayer. However, during osmotically induced shrinking and swelling of SUV the integrity of the phospholipid bilayer is maintained to the extent that vesicles do not break, and therefore equilibration between external medium and vesicle cavity does not take place.
B Lerebours; E Wehrli; H Hauser
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  1152     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  1993 Oct 
Date Detail:
Created Date:  1993-11-09     Completed Date:  1993-11-09     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  49-60     Citation Subset:  IM    
Laboratorium für Biochemie, Eidgenössische Technische Hochschule, ETH Zentrum, Zürich, Switzerland.
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MeSH Terms
Dimyristoylphosphatidylcholine / chemistry
Electron Spin Resonance Spectroscopy
Freeze Fracturing
Microscopy, Electron / methods
Particle Size
Phosphatidylcholines / chemistry*
Spectrometry, Fluorescence
Spin Labels
Reg. No./Substance:
0/Phosphatidylcholines; 0/Spin Labels; 13699-48-4/Dimyristoylphosphatidylcholine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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