Oxygen permeability of the lipid bilayer membrane made of calf lens lipids

Abstract

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.

Oxygen Transport to Tissue XL

“…3). This is in agreement with experimental observations that membrane permeability increases for POPC between 35°C and 45°C [3]. The effect of T is larger for POPC than for DOPC, with even a reduction of a factor 2 for D⊥ of POPC near the head group region.…”

“…The rafts are believed to function together with integral and peripheral proteins and could play a role in signal transduction, intracellular transport, and protein sorting in these membranes [1,2]. Both experimental [3] and computational [4] work have demonstrated that addition of cholesterol reduces the permeability of POPC phospholipid bilayers, and experimental work [5] confirms this trend for DOPC. Another characteristic of rafts is the richness in saturated lipids.…”

Fungal Morphogenesis, from the Polarized Growth of Hyphae to Complex Reproduction and Infection Structures

“…As O 2 normally diffuses from the extracellular aqueous medium into the cytoplasm, hydrophobins might hinder direct O 2 diffusion from air, forcing O 2 ministration to the aerial hyphae mainly through the mycelial substrate. Cholesterol in mammalian cells (314,315) and hopanoids in bacteria (316) also reduce plasma membrane O 2 permeability. The transcription repressor CSP-1 (conidial separation 1) regulates ergosterol synthesis and membrane lipid composition in N. crassa (317).…”

Lipids and the ocular lens

“…Electron spin resonance probe studies have shown that cholesterol contributes to the impermeability of oxygen across lens membranes ( 202,203 ). Maintaining low levels of oxygen is critical to the lens to prevent oxidation and opacifi cation.…”