Oxygen Permeation Profile in Lipid Membranes: Comparison with Transmembrane Polarity Profile

Dzikovski, Boris; Лившиц, В. А.; Marsh, Derek

doi:10.1016/s0006-3495(03)74539-1

Cited by 57 publications

(54 citation statements)

References 25 publications

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“…As a consequence, we were only able to determine the lower boundary of H 2 S permeability: P M is larger than 0.5 Ϯ 0.4 cm/s. P M is thus approximately sixfold smaller than CO 2 membrane permeability (22) and from threefold to 50-fold smaller than singlet oxygen and oxygen permeabilities (23,35,36), but at least an order of magnitude larger than NH 3 permeability (18, 24). Because of the large H 2 S background membrane permeability, a physiologically important contribution of aquaporins to H 2 S transport is very unlikely, a point that holds true even when considering that the unique structure of archaebacterial lipids lowers H 2 S permeability.…”

Section: Discussionmentioning

confidence: 92%

No facilitator required for membrane transport of hydrogen sulfide

Mathai

Missner²,

Kügler

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

311

226

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Hydrogen sulfide (H2S) has emerged as a new and important member in the group of gaseous signaling molecules. However, the molecular transport mechanism has not yet been identified. Because of structural similarities with H 2O, it was hypothesized that aquaporins may facilitate H 2S transport across cell membranes. We tested this hypothesis by reconstituting the archeal aquaporin AfAQP from sulfide reducing bacteria Archaeoglobus fulgidus into planar membranes and by monitoring the resulting facilitation of osmotic water flow and H2S flux. To measure H2O and H2S fluxes, respectively, sodium ion dilution and buffer acidification by proton release (H 2S % H ؉ ؉ HS ؊ ) were recorded in the immediate membrane vicinity. Both sodium ion concentration and pH were measured by scanning ion-selective microelectrodes. A lower limit of lipid bilayer permeability to H 2S, P M,H 2 S > 0.5 ؎ 0.4 cm/s was calculated by numerically solving the complete system of differential reaction diffusion equations and fitting the theoretical pH distribution to experimental pH profiles. Even though reconstitution of AfAQP significantly increased water permeability through planar lipid bilayers, PM,H 2 S remained unchanged. These results indicate that lipid membranes may well act as a barrier to water transport although they do not oppose a significant resistance to H 2S diffusion. The fact that cholesterol and sphingomyelin reconstitution did not turn these membranes into an H2S barrier indicates that H 2S transport through epithelial barriers, endothelial barriers, and membrane rafts also occurs by simple diffusion and does not require facilitation by membrane channels. aquaporins ͉ gas transport ͉ membrane permeability ͉ unstirred layer ͉ signaling

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Section: Discussionmentioning

confidence: 92%

No facilitator required for membrane transport of hydrogen sulfide

Mathai

Missner²,

Kügler

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

311

226

View full text Add to dashboard Cite

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“…This value accounts for the entire bilayer, including polar phosphocholine headgroups. However, there is evidence indicating that O 2 , ⅐ NO, and other apolar molecules, are less favorably dissolved in this region of the membrane (33)(34)(35)40) and should therefore be excluded from the hydrophobic volume. We assumed a 0.75 bilayer hydrophobic fraction, thus the corrected K P from Smotkin et al (37) would be 4.9 Ϯ 0.8, which is in agreement within experimental errors with that found by ourselves (Table I).…”

Section: Discussionmentioning

confidence: 99%

Direct Measurement of Nitric Oxide and Oxygen Partitioning into Liposomes and Low Density Lipoprotein

Möller

Botti

Batthyány

et al. 2005

Journal of Biological Chemistry

130

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Nitric oxide ( ⅐ NO) has been proposed to play a relevant role in modulating oxidative reactions in lipophilic media like biomembranes and lipoproteins. Two factors that will regulate ⅐ NO reactivity in the lipid milieu are its diffusion and solubility, but there is no data concerning the actual diffusion (D) and partition coefficients (K P ) of ⅐ NO in biologically relevant hydrophobic phases. Herein, a "equilibrium-shift" method was designed to directly determine the ⅐ NO and O 2 partition coefficients in liposomes and low density lipoprotein (LDL) relative to water. It was found that ⅐ NO partitions 4.4-and 3.4-fold in liposomes and LDL, respectively, whereas O 2 behaves similarly with values of 3.9 and 2.9, respectively. In addition, actual diffusion coefficients in these hydrophobic phases were determined using fluorescence quenching and found that ⅐ NO diffuses ϳ2 times slower ). The influence of ⅐ NO and O 2 partitioning and diffusion in membranes and lipoproteins on ⅐ NO reaction with lipid radicals and auto-oxidation is discussed. Particularly, the 3-4-fold increase in O 2 and ⅐ NO concentration within biological hydrophobic phases provides quantitative support for the idea of an accelerated auto-oxidation of ⅐ NO in lipid-containing structures, turning them into sites of enhanced local production of oxidant and nitrosating species.Nitric oxide produced by the oxidation of L-arginine to Lcitrulline by ⅐ NO 1 synthases accomplishes important physiological regulatory functions related to vasodilation, neurotransmission, immune response, and regulation of cell respiration (1, 2). Despite being a free radical, ⅐ NO is a weak redox intermediate, and its reactivity is restricted to paramagnetic species, including metals, metalloproteins (3, 4), and other radical molecules (5, 6).The reactions of ⅐ NO with other radicals can be classified as oxidant or antioxidant, depending on the reactivity of the products. Nitric oxide reacts with the superoxide anion radical (O 2 . ) at diffusion-controlled rates to yield peroxynitrite, a strong oxidant that can induce lipid and protein oxidation and nitration (6, 7). Similarly, the reaction with O 2 yields nitrogen dioxide ( ⅐ NO 2 ) and dinitrogen trioxide (N 2 O 3 ), strong oxidant and nitrosating species (8, 9). Although the reaction with O 2 is complex and not completely understood (8, 9), the rate law is second-order in ⅐ NO and first-order in O 2 , with a third-order rate constant k ϭ 0.8 -1.2 ϫ 10 7 M Ϫ2 s Ϫ1 (8, 9). On the other hand, ⅐ NO has been proposed as an important antioxidant in vivo (10 -12), mainly because it reacts with organic peroxyl radicals at near diffusion-limited rates (k ϭ 1-3 ϫ 10 9 M Ϫ1 s Ϫ1 , see Refs. 5 and 13) effectively inhibiting lipid peroxidation chain reactions (7, 10 -12, 14 -17). This antioxidant activity may be specially relevant in low density lipoprotein (LDL), because oxidatively modified lipoproteins can be recognized by scavenger receptors on macrophages and lead to macrophage lipid loading and eventually to atherosclerosis...

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“…Since oxygen is a nonpolar molecule, its solubility in the nonpolar core of lipid membranes is higher than in aqueous media (Dzikovski et al, 2003;Windrem and Plachy, 1980). Therefore, regardless of the overall O 2 availability in tissues/cells, the pO 2 in the hydrophobic portion of the membrane should be higher than the pO 2 in the aqueous phase of cytosol.…”

Section: Estivationmentioning

confidence: 99%