Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
Volume 1768, Issue 10, Pages 2635-2645Publisher
ELSEVIER
DOI: 10.1016/j.bbamem.2007.06.018
Keywords
oxygen permeation; lens lipids; lipid bilayer; cholesterol; hydrophobic barrier; membrane rigidity; EPR
Categories
Funding
- NEI NIH HHS [R01 EY015526, R01 EY015526-03, R01 EY015526-01A1, R01 EY015526-02, EY015526] Funding Source: Medline
- NIBIB NIH HHS [EB001980, EB002052, P41 EB001980, R01 EB002052] Funding Source: Medline
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The oxygen permeability coefficient across the membrane made of the total lipid extract from the plasma membrane of calf lens was estimated from the profile of the oxygen transport parameter (local oxygen diffusion-concentration product) and compared with those estimated for membranes made of an equimolar 1-palmitoyl-2-oleoylphosphatidylcholine/cholesterol (POPC/Chol) mixture and of pure POPC. Profiles of the oxygen transport parameter were obtained by observing the collision of molecular oxygen with nitroxide radical spin labels placed at different depths in the membrane using the saturation-recovery EPR technique and were published by us earlier (J. Widomska, M. Raguz, J. Dillon, E. R. Gaillard, W. K. Subczynski, Biochim. Biophys. Acta. 1768 (2007) 1454-1465). At 35 degrees C, the estimated oxygen permeability coefficients were 51.3, 49.7, and 157.4 cm/s for lens lipid, POPC/Chol, and POPC membranes, respectively (compared with 53.3 cm/s for a water layer with the same thickness as a membrane). Membrane permeability significantly decreases at lower temperatures. In the lens lipid membrane, resistance to the oxygen transport is located in and near the polar headgroup region of the membrane to the depth of the ninth carbon, which is approximately where the steroid-ring structure of cholesterol reaches into the membrane. In the central region of the membrane, oxygen transport is enhanced, significantly exceeding that in bulk water. It is concluded that the high level of cholesterol in lens lipids is responsible for these unique membrane properties. (C) 2007 Elsevier B.V. All rights reserved.
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