These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Investigation of the inside-outside distribution, intermembrane exchange and transbilayer movement of phospholipids in sonicated vesicles by shift reagent NMR.
    Author: Barsukov LI, Victorov AV, Vasilenko IA, Evstigneeva RP, Bergelson LD.
    Journal: Biochim Biophys Acta; 1980 May 08; 598(1):153-68. PubMed ID: 7417424.
    Abstract:
    1. A new NMR approach is described for the investigation of transbilayer asymmetry in phospholipid vesicles consisting of phosphatidylcholine and negatively charged phospholipids. The method makes use of the dependence of the psuedocontact shift of the N-methyl proton resonance induced by paramagnetic ions on the surface concentration of negatively charged phospholipids. When two differently shifting paramagnetic probes are applied from the outside and the inside of a vesicular membrane the transbilayer phospholipid distribution can be estimated without knowledge of the inner and outer radii of the vesicles and the packing density of the phospholipid molecules. 2. The method was employed to study the transbilayer asymmetry in vesicles obtained by cosonication of phosphatidylcholine with phosphatidylserine, phosphatidylglycerol or phosphatidylinositol. The three negative phospholipids were found to distribute with a higher surface concentration in the inner vesicular shell than in the outer one when their total content did not exceed 25 mol%. However, as the amount of negatively charged phospholipids increases the ratio of their inside to outside surface concentrations, i.e., the transbilayer asymmetry of the vesicles, decreases. Prolonged incubation (for several days) does not change the compositional asymmetry of the cosonicated vesicles. 3. By the 'double-probe' technique it was established that spontaneous exchange between separately sonicated phosphatidylcholine and phosphatidylinositol vesicles results in formation of highly asymmetric mixed vesicles with phosphatidylinositol residing only in the outer monolayer. In the presence of antioxidant (alpha-tocopherol) the bilayer asymmetry is preserved for days. However lipid peroxidation induces rapid transbilayer movement (flip-flop) of phospholipids leading to an 'inverted' asymmetry resembling that of cosonicated vesicles. It is suggested that lipid peroxidation promotes phospholipid flip-flop by partially converting the bilayer structure into a non-bilayer configuration. Moderate quantities of lysophosphatidylcholine (up to 15 mol%) induce neither detectable perturbations of the bilayer nor rapid phospholipid flip-flop.
    [Abstract] [Full Text] [Related] [New Search]