Dioxygen solubility in aqueous phosphatidylcholine dispersions

Smotkin, Eugene S.; Moy, Frederick T.; Plachy, William Z.

doi:10.1016/0005-2736(91)90265-a

Cited by 61 publications

(44 citation statements)

References 12 publications

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“…The K P of ⅐ NO between lipid and aqueous phases was determined for the first time using this equilibrium-shift method, demonstrating that ⅐ NO concentrates 4.4 -3.4-fold in membranes and LDL, respectively, and similar results were obtained with O 2 (Table I). Evidencing the difficulties in measuring K P using amphiphilic lipid phases, the K P of O 2 between membranes and water has only been measured in dimyristoyl phosphatidylcholine liposomes and erythrocyte plasma mem- branes (37,39). Smotkin et al (37), found K P ϭ 3.7 Ϯ 0.6 for O 2 between dimyristoyl phosphatidylcholine liposomes in the liquid crystalline state and water, measuring total O 2 concentration by a modified Winkler technique.…”

Section: Discussionmentioning

confidence: 99%

“…1A), K P ϭ 3.2 Ϯ 0.4 and the corrected value for water 2.9 Ϯ 0.3. It was observed that O 2 partition between dimyristoyl phosphatidylcholine liposomes and water increases dramatically from the gel to the liquid crystalline state (37). However, the core lipids of LDL exhibit a broad phase transition temperature (20 -40°C, Ref.…”

Section: O 2 Partition Between Lipid and Aqueous Phases-mentioning

confidence: 99%

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

Möller

Botti

Batthyány

et al. 2005

Journal of Biological Chemistry

133

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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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Section: Discussionmentioning

confidence: 99%

Section: O 2 Partition Between Lipid and Aqueous Phases-mentioning

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

133

View full text Add to dashboard Cite

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“…The large quenching rate constant obtained for DP compared to UP implies that PPF must be embedded within the liposome. Indeed, if PPF is well embedded within the liposome, in the DP system, 1 O 2 is generated and mainly distributed in the lipid bilayer because of the higher solubility of 1 O 2 in this medium [40], which is characterized by a high PPF concentration. Thus, the reaction between 1 O 2 and PPF takes place before 1 O 2 can substantially diffuse into the solution.…”

Section: Discussionmentioning

confidence: 99%

Reactivity towards singlet oxygen of propofol inside liposomes and neuronal cells

Heyne

Brault²,

Fontaine‐Aupart

et al. 2005

Biochimica et Biophysica Acta (BBA) - General Subjects

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Singlet oxygen ( 1 O 2 ), a reactive oxygen species, has been found to be implicated in many cellular events and pathological disorders. Herein, we investigated the reactivity of 1 O 2 towards the anaesthetic agent propofol (PPF) encapsulated within DMPC liposomes. By time resolved luminescence, the rate constant of 1 O 2 quenching by PPF was evaluated, depending on the location of the sensitizer, with following values: 1.35 T 0.05 Â 10 7 M À1 s À1 for deuteroporphyrin (as embedded source) and 0.8 T 0.04 Â 10 7 M À1 s À1 for uroporphyrin (as external source), respectively. The nature of the oxidation product, resulting from the reaction of 1 O 2 with PPF, was determined using absorption and HPLC techniques. Finally, the in vitro protective effect of PPF towards the 1 O 2 -induced neuronal cell toxicity was evaluated in terms of cell viability. D

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“…The localization and transport of molecular oxygen in the cell are of primary importance for the cell metabolism. Several groups have addressed the problem of determining the oxygen concentration and diffusion in the lipid bilayer [1][2][3][4][5][6][7][8]. There is a general consensus that oxygen solubility in the lipid phase is higher than in water [2].…”

mentioning

confidence: 99%

“…This conclusion is based on a comparison between oxygen solubility in water and that in hydrocarbons and on direct measurements of oxygen solubility in membrane suspensions. Oxygen solubility has been determined to be higher in membranes in the liquidcrystalline phase than in the gel phase [2].…”

mentioning

confidence: 99%

Packing of phospholipid vesicles studied by oxygen quenching of Laurdan fluorescence

Parasassi

Gratton

1992

J Fluoresc

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Steady-state fluorescence oxygen quenching experiments were performed on phospholipid vesicles where 2-dimethylamino-6-1auroylnaphthalene (Laurdan) was inserted. The quenching efficiency was found to be much higher in vesicles in the liquid-crystalline phase with respect to the gel phase, by a factor of about 50. Since the oxygen solubility in the two phospholipid phases can differ at most by a factor of 4 based on literature values, we concluded that oxygen diffusion must be responsible for the great difference in the quenching efficiency. A relatively high quenching efficiency was also found in vesicles composed of equimolar gel and liquid-crystalline phospholipids. Simulations were performed using the linear superposition of the properties of the pure phases to demonstrate that, in the case of vesicles composed of coexisting phases, the diffusional properties of oxygen in each phase are largely modified by the presence of the other. The addition of 10 mol% cholesterol to the gel phase rendered Laurdan fluorescence approximately as quenchable as in the equimolar mixture of the two phases. This result points out that molecules such as cholesterol, which introduce packing defects in the bilayer, favor oxygen diffusion. From the oxygen quenching experiments and using the properties of generalized polarization, the rate of Laurdan dipolar relaxation can be estimated.

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Dioxygen solubility in aqueous phosphatidylcholine dispersions

Cited by 61 publications

References 12 publications

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

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

Reactivity towards singlet oxygen of propofol inside liposomes and neuronal cells

Packing of phospholipid vesicles studied by oxygen quenching of Laurdan fluorescence

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