Antioxidant effects of hydroxybenzalacetones on peroxynitrite-induced lipid peroxidation in red blood cell membrane ghost and SOS response in Salmonella typhimurium TA4107/pSK1002

Antioxidant activity of a series of hydroxybenzalacetones was determined against peroxynitrite-induced lipid peroxidation in red blood cell membrane and SOS response through DNA damage in bacterial cells. Hydroxybenzalacetone derivatives with hydroxy, methoxy, ethoxy or methyl substitution were analyzed and found to be more effective than the water-soluble vitamin E analogue Trolox. The inhibitory effect against lipid peroxidation correlated well to that against the SOS response, which is dependent on decomposition of peroxynitrite by hydroxybenzalacetones outside of the cell membrane. The antioxidant activity was shown to correlate well with the electric parameter sigma+. Electron-donating substituents with more negative sigma+ values increased the potencies. The result suggests that hydroxybenzalacetones with more electron-donating substituents will protect tissue more effectively against oxidative stress.     

Transport of alkali halides through a liquid organic membrane containing a ditopic salt-binding receptor

A ditopic receptor is shown to have an impressive ability to recognize and extract the ion pairs of various alkali halides into organic solution. X-ray diffraction analysis indicates that the salts are bound in the solid state as contact ion pairs. Transport experiments, using a supported liquid membrane and high salt concentration in the source phase, show that the ditopic receptor can transport alkali halide salts up to 10-fold faster than a monotopic cation or anion receptor and 2-fold faster than a binary mixture of cation and anion receptors. All transport systems exhibit the same qualitative order of ion selectivity; that is, for a constant anion, the cation selectivity order is K+ > Na+ > Li+, and for a constant cation, the anion transport selectivity order is I- > Br- > Cl-. The data suggest that with a ditopic receptor, the polarity of the receptor-salt complex can be lowered if the salt is bound as an associated ion pair, which leads to a faster diffusion through the membrane and a higher maximal flux.     

Relation between K+ leakage and damage to band 3 in photodynamically treated red cells

Potassium leakage is one of the first events that appear after photosensitization of red blood cells. This event may subsequently lead to colloid osmotic hemolysis. The aim of our study was to determine which photodynamically induced damage is responsible for increased membrane cation permeability. This was done by studying the effect of dimethylmethylene blue (DMMB)-mediated photodynamic treatment (PDT) on different membrane transport systems. Inhibition of band 3 activity (anion transport) showed a comparable light dose dependency as PDT-induced potassium leakage, whereas glycerol transport activity was inhibited only at higher light doses. Dipyridamole (DIP), an inhibitor of anion transport, protects band 3 against DMMB-induced damage, and prevents the increase in cation permeability of the membrane. Damage to glycerol transport was partially reduced when PDT was performed in the presence of DIP. Because DIP has no affinity for the glycerol transporter, this protection might result from the reduced photodamage to band 3. These results support the hypothesis that band 3 might be involved in glycerol transport. Glucose transport was not affected by DMMB-mediated PDT. The present results are the first to show a causal relationship between DMMB-mediated photodamage to band 3 and increased cation permeability of red blood cells.     

Asymmetric bipolar membrane: A tool to improve product purity

Bipolar membranes (BPMs) are catalytic membranes for electro-membrane processes splitting water into protons and hydroxyl ions. To improve selectivity and current efficiency of BPMs, we prepare new asymmetric BPMs with reduced salt leakages. The flux of salt ions across a BPM is determined by the co-ion transport across the respective layer of the membrane. BPM asymmetry can be used to decrease the co-ion fluxes through the membrane and shows that the change of the layer thickness and charge density of the corresponding ion exchange layer determines the co-ion flux. The modification of a commercial BP-1 with a thin additional cation exchange layer on the cationic side results in a 47% lower salt leakage. Thicker layers result in water diffusion limitations. In order to avoid water diffusion limitations we prepared tailor made BPMs with thin anion exchange layers, to increase the water flux into the membrane. Therefore a BPM could be prepared with a thick cation exchange layer showing a 62% decreased salt ion leakage through the cationic side of the membrane.     

Oxygen sensitivity of red cell membrane transporters revisited

In this paper, we provide an update on O2-dependent membrane transport in red cells. O2-sensitive membrane transport was compared in nucleated (chicken) and enucleated (human) red cells, to investigate effects on organic (glucose transporter [GLUT]) and inorganic (K(+)-Cl- cotransporter [KCC]/Na(+)-K(+)-2Cl- cotransporter [NKCC]) transporters, to study the response of so-called "housekeeping" transporters (Na+/K+ pump and anion exchanger [AE]) and, finally, to compare O2 sensitivity in normal human red cells with those from sickle cell patients. The Na+/K+ pump showed no change in activity between oxygenated and deoxygenated cells in any of the samples. KCC in normal human red cells had the greatest O2 sensitivity, being stimulated some 20-fold on oxygenation. It was more modestly stimulated by O2 in chicken red cells and HbS cells. By contrast, NKCC was stimulated by deoxygenation in all cases. GLUT showed little response to O2 tension, other than a small stimulation in deoxygenated chicken red cells. Finally, AE1 was stimulated by oxygenation in HbA cells, but this stimulation by O2 was absent in HbS cells and pink ghosts prepared from HbA cells. The significance of these findings is discussed.     

Ion channels in the human red blood cell membrane: their further investigation and physiological relevance.

Using the patch-clamp technique, two different ion channels have been characterized further in the human red blood cell (RBC) membrane. We demonstrate that the non-selective cation channel (NSC) is permeable to Ca(2+) and can be activated by prostaglandin E(2) (PGE(2)). Therefore, the physiological role of this channel could be, together with the Ca(2+)-activated K(+) channel, the participation in the process of blood clot formation. We give also evidence that another channel in the RBC membrane, so far assumed to be a small conductance anion channel, is more likely to be a proton or a hydroxyl ion channel.     

The non-selective voltage-activated cation channel in the human red blood cell membrane: reconciliation between two conflicting reports and further characterisation

Using the patch-clamp technique, the non-selective, voltage-activated cation channel in the human red blood cell (RBC) membrane was further characterised. Activity of the cation channel could be demonstrated at a range of salt concentrations with the current-voltage characteristics for monovalent cations going from linear to superlinear functions, depending on the cation concentration in the range of 100-500 mM. The non-selective voltage-activated cation channel was demonstrated to be permeable to the divalent cations Ca2+ and Ba2+, and even Mg2+. The current-voltage relations for the divalent cations were superlinear even at 75 mM salt concentration, but indicated outward rectification in contrast to the I-V curve for monovalent cations. The degree of activation at a given membrane potential depended strongly on the prehistory of the channel. The gating exhibited hysteretic-like behaviour, since the quasi steady-state deactivation and activation curves were displaced by approximately 25 mV. This result fully explains apparent discrepancies between V0.5-values previously obtained by slightly different experimental protocols. The possible physiological/pathophysiological role of the channel is discussed in the context of the demonstrated permeability for divalent cations.     

Mass transport in a boundary layer and in an ion exchange membrane: Mechanism of concentration polarization and water dissociation

In an unforced flowing NaCl solution in bulk, gravitational or electro convection supplies ions from bulk toward the membrane surface through a boundary layer. In a boundary layer formed on an anion exchange membrane, the convection converts to migration and diffusion and carries an electric current. In a boundary layer formed on a cation exchange membrane, the convection converts to migration and carry an electric current. In a forced flowing solution in bulk, the boundary layer thickness is reduced and gravitation or electro convection is disappeared. An electric current is carried by diffusion and migration on the anion exchange membrane and by migration on the cation exchange membrane. Ion transport in a boundary layer on the cation exchange membrane immersed in a NaCl solution is more restricted comparing to the phenomenon on the anion exchange membrane. This is due to lower counter-ion mobility in the boundary layer and the restricted water dissociation reaction in the membrane. The water dissociation reaction is generated in an ion exchange membrane and promoted due to the increased forward reaction rate constant. However, the current efficiency for the water dissociation reaction is generally low. The intensity of the water dissociation is more suppressed in the strong acid cation exchange membrane comparing to the phenomenon in the strong base anion exchange membrane due to lower forward reaction rate constant in the cation exchange membrane. In the strong acid cation exchange membrane, the intensity of electric potential is larger than the values in the strong base anion exchange membrane. Accordingly, the stronger repulsive force is developed between ion exchange groups (SO ₃ ^? groups) and co-ions (OH^? ions) in the cation exchange membrane, and the water dissociation reaction is suppressed. In the strong base anion exchange membrane, the repulsive force between ion exchange groups (N⁺(CH₃)₃ groups) and co-ions (H⁺ ions) is relatively low, and the water dissociation reaction is not suppressed. Violent water dissociation is generated in metallic hydroxides precipitated on the desalting surface of the cation exchange membrane. This phenomenon is caused by a catalytic effect of metallic hydroxides. Such violent water dissociation does not occur on the anion exchange membrane.     

Charge‐mosaic membrane prepared from microspheres

A new type of charge‐mosaic membrane was prepared from poly(4‐vinyl pyridine) microspheres 250–350 nm in diameter as an anion‐exchange element and from linear poly(sodium styrene sulfonic acid) as a cation‐exchange element. The mosaic structure on the surface of the membrane and the continuous connection of the microspheres in the membrane were confirmed by scanning electron microscopy observations and the electrical conductivity of the membrane. The microspheres were continuously connected from one side to the other side of the membrane surface when the weight fraction of the microspheres increased more than 20–25 wt % in the membrane. The flux of KCl, the permeability coefficient of KCl, the volume flux, and the selectivity dialysis separation of the electrolyte (KCl) and nonelectrolyte (glucose and saccharose) of the membrane indicated that it had the characteristic properties of a charge‐mosaic membrane. Ion‐exchange membranes composed of each raw material of the charge‐mosaic membrane did not show these properties. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1251–1261, 2003     

A highly selective and sensitive thorium(IV) PVC membrane electrode based on a dithio-tetraaza macrocyclic compound.

A poly(vinyl chloride)-based membrane composed of dithio-tetraaza macrocyclic compound as a neutral carrier with sodium tetraphenylborate (NaTPB) as an anion excluder and nitrobenzene (NB) as plasticizer was prepared and investigated as a Th(IV)-selective electrode. The electrode exhibits a Nernstian slope of 14.2 +/- 0.3 mV per decade over a wide concentration range (1.0 x 10(-6) to 1.0 x 10(-1) M) with a detection limit of 8.0 x 10(-7) M between pH 3.5 and 9.5. The response time of the sensor is about 10 s and it can be used over a period of 5 months without any divergence in potential. The proposed membrane sensor revealed a good selectivity for Th(IV) over a wide variety of other metal ions and proved to be a better electrode in many respects than those reported in the literature. It was successfully applied as an electrode indicator as well as in the direct determination of thorium ions in standard and real samples.     

Diffusion of electrolytes of different natures through the cation-exchange membrane

Diffusion of different electrolytes through a negatively charged (cation-exchange) membrane into distilled water has been studied. It has been established theoretically (with no regard to the presence of diffusion layers) that the integral diffusion permeability coefficient of an electrolyte depends on the diffusion coefficients and the ratio between the charge numbers of a cation–anion pair, the ratio between the density of charges fixed in the membrane and electrolyte concentration, and the averaged coefficient of equilibrium distribution of cation?anion ion pairs in the membrane matrix. It has been found that, when co-ions have a higher mobility, the dependence of diffusion permeability on electrolyte concentration passes through a maximum. Derived equations have been compared with experimental dependences of the diffusion permeability of an MC-40 membrane with respect to different solutions of inorganic 1: 1 and 2: 1 electrolytes. The developed method has been shown to be applicable for describing diffusion of any electrolytes (including asymmetric ones) through arbitrary uniformly charged membranes.     

499 bis—The surface compartment model—voltage clamp

Solutions of the SCM equations under voltage clamp show that a transient inward sodium flux can occur at certain settings of the parameters. If there is a nonspecific increase in cation permeability upon depolarization, the positive sodium flux arises because the ion concentration changes in the electrical double layer compensate for the decrease in the electrical driving force, while parallell changes in the potassium ion concentrations lead to a decreased (but still outward) potassium flux. The sodium flux is quite sensitive to the magnitudes of the ionic permeabilities and mobilities, as well as the ion binding equilibrium and release rate constants. The values of the parameters determined here suggest magnitudes for the properties of the membrane components associated with the permeability change.     

Interaction between anionic polyelectrolytes and anion exchange membranes and change in membrane properties

Electrodialytic transport properties of anion exchange membranes were measured after formation of anionic polyelectrolyte layers on the membrane surfaces: relative transport number of various anions to chloride ions, current efficiency and apparent diffusion coefficients of neutral molecules. The anionic polyelectrolyte layers were formed by immersing the membrane into an aqueous solution of polycondensation product of sodium naphthalene sulfonate and formaldehyde or polystyrene sulfonic acid.

The change in the relative transport number between anions was remarkable in the anion exchange membrane with high ion exchange capacity by forming the layer. Results were: the relative transport number of sulfate ions to chloride ions decreased and those of nitrate ions to chloride ions, fluoride ions to chloride ions and bromide ions to chloride ions increased compared with the corresponding membrane. Although the apparent diffusion coefficient of neutral molecules suggested clogging of the membrane pores by the polyelectrolyte, anions with higher hydrated ionic diameter were able to permeate through the membrane easily. This means that difference of electrostatic repulsion force against two anions is effective on the change in the relative transport number of anions.     

Change in permselectivity between sulfate and chloride ions through anion exchange membrane with hydrophilicity of the membrane

The transport number of sulfate ions relative to chloride ions through an anion exchange membrane was measured by electrodialyzing a sodium sulfate and sodium chloride mixed solution containing diethylene glycol after immersing the membrane in diethylene glycol because the membrane had good affinity to ethylene glycol and diethylene glycol. The transport number of sulfate ions relative to chloride ions increased in the presence of diethylene glycol in the membrane. This is due to the increase in the uptake of sulfate ions in the membrane compared with chloride ions, not to the change in a ratio of mobilities of both anions.     

Ion-exchange across a cationic membrane in concentrated solutions

Summary Equations have been derived, using the quasi-thermodynamic method, relating the diffusion potential, ion and solvent fluxes across a cation exchange membrane with its electrical conductivity and electro-osmotic permeability. A membrane separating two solutions of equal total concentration but containing different cations has been considered and the effect of sorbed anions taken into account. The membrane potential was calculated first and the fluxes of anions and solvent related very closely to this. The cation fluxes were calculated from the membrane potential and the electro-osmotic permeability.The theory has been tested with steady-state flux and potential measurements made using a cation exchange membrane and solutions of sodium and hydrogen chlorides at three temperatures, concentrations and membrane compositions. Excellent agreement was obtained between theory and experiment for the membrane potentials, anion fluxes and solvent fluxes. The cation fluxes were also in good agreement with the theory except when the membrane contained a high proportion of hydrogen ions; then the calculated fluxes were about 30% too small. The suggestion has been made that this may be due to a difference between the electrophoretic and relaxation corrections to the cationic mobilities in conduction and diffusion. These corrections were particularly large with the cations studied.

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Zusammenfassung Mit einer quasithermodynamischen Methode wurden Gleichungen abgeleitet, die das Diffusionspotential und Ionen- und Lösungsmittelstrom durch eine Kationenaustauschermembran mit deren elektrischer Leitfähigkeit und elektroosmotischer Durchlässigkeit in Zusammenhang setzt. Eine Membran, die zwei Lösungen gleicher Gesamtkonzentration, aber verschiedene Kationen enthaltend, trennt, wird betrachtet und der Einfluß der sorbierten Anionen berücksichtigt. Das Membranpotential wurde zunächst berechnet und dann Anionenstrom und Lösungsmittelstrom in enge Beziehung hierzu gesetzt. Die Kationenströme wurden aus dem Membranpotential und der elektroosmotischen Permeabilität ermittelt.Die Theorie wurde am stationären Fall und durch Potentialmessungen an einer Kationenaustauschermembran geprüft mit Lösungen von Natriumchlorid und Salzzäure bei drei verschiedenen Temperaturen, Konzentrationen und Membranzusammensetzungen. Es ergab sich zwischen Theorie und Experiment ausgezeichnete Übereinstimmung für die Membranpotentiale, die Anionen und Lösungsmittelströme. Die Kationenströme waren ebenfalls in guter Übereinstimmung mit der Theorie, ausgenommen der Fall, daß die Membran einen hohen Anteil an Wasserstoffionen enthielt; dann waren die berechneten Ströme ungefähr 30% zu niedrig. Man kann vermuten, daß dies einer Differenz zwischen elektophoretischen und Relaxationskorrekturen auf die Kationenbeweglichkeiten bei Leitung und Diffusion zuzuschreiben ist. Diese Korrekturen waren für die untersuchten Kationen besonders hoch.

     

Highly selective and efficient membrane transport of silver as AgBr2- ion using K+-decyl-18-crown-6 as carrier.

Potassium-decyl-18-crown-6 was used as a highly selective and efficient carrier for uphill transport of silver as AgBr2-complex ion through a chloroform bulk liquid membrane. When thiosulfate anion was used as a metal ion acceptor in the receiving phase the amounts of silver transported across the liquid membrane after 120 and 180 min were 87.0 +/- 1.8% and 96.0 +/- 1.9%, respectively. The selectivity and efficiency of silver transport from aqueous solution containing Cu2+, Zn2+, Ni2+, Cd2+, Pb2+ and Fe3+ ions were investigated. In the presence of EDTA at pH = 4 as suitable masking agent in the source phase, the interfering effects of Pb2+ and Fe3+ ions were diminished drastically.     

Reverse permeation of sodium ions driven by pH difference across a liquid membrane: time dependencies of membrane resistance and membrane potential in a reverse permeation system

The diffusional flux of sodium ions across a liquid membrane was observed as a reverse permeation phenomenon: sodium ions were transported across the membrane against their own concentration difference. A supported liquid membrane having stearic acid as an ionic carrier was used. The internal aqueous phase contained NaCl and HCl and the external aqueous phase contained NaOH of the same initial concentration as NaCl in the internal aqueous phase. The reverse permeation occurred with a long time delay. During the delay, sodium ions flowed from the acidic to alkaline solution. The diffusion coefficient of sodium ion estimated from the flux equation taking into account the Donnan equilibrium at the interface was found to be much greater than that in the membrane solvent, 1-octanol. In the same membrane system as for the flux measurement, the membrane conductance and the membrane potential were measured as a function of time. The time dependence of the membrane potential in the presteady state showed a biphasic behavior. The initial rapid phase could be attributed to the change in the phase boundary potential and the subsequent slow step to the change in the diffusion potential within the membrane. Before the steady membrane potential had been reached, the reverse permeation of sodium ions against their own concentration difference was not observed. During the slow relaxation process of the membrane potential, the membrane resistance decreased to approach the steady state. Moreover, the oscillation of membrane potential abruptly started at a time in the slow step of the potential change and continued during the steady state. It was suggested that, at the presteady state, the increase in the amount of water in the membrane would drive a drastic change in the state of the liquid membrane in the filter pore, e.g. an inverted micellar structure making.     

The transport of Cu(II) through a sulfonated styrene/divinylbenzene copolymer membrane

The transport of copper (II) ions through sulfonated styrene/divinylbenzene copolymer ion permeable membranes under Donnan dialysis conditions has been investigated. The flux increases strongly with the copper (II) ion concentration and temperature. The other cation transported through the membrane and its concentration can also have some influence but it is relatively small.     

A novel potassium ion membrane sensor based on rifamycin neutral ionophore

A novel potentiometric membrane sensor for potassium ion based on the use of rifamycin as a neutral ionophore is described. The sensing membrane is formulated with 2 wt.% rifamycin-SV, 69 wt.% dibutylsebacate plasticizer and 29 wt.% PVC. Linear and stable potential response with near-Nernstian slope of 56.7 +/- 0.2 mV decade(-1) are obtained over the concentration range 1 x 10(-1)-3 x 10(-5) M K(+). The detection limit is 0.3 microg ml(-1) K(+), the response time is 10-30 s and the working pH range is 4-11. Responses of the sensor toward alkali and alkaline earth metal ions are in the order K(+) > Rb(+) > Cs(+) > Na(+) > NH(4)(+) > Ba(2+) > Mg(2+) > Ca(2+) > Sr(2+) > Li(+). The selectivity coefficient data reveal negligible interference from transition metal ions. Direct potentiometric determination of K(+) in the presence of 10-50-fold excess of alkali and alkaline earth metals gives results with an average recovery of 99.1%, and a mean standard deviation of 1.2%. The data agree fairly well with those obtained by flame photometry.     

CuPc(COOH)8-SA/CuTAPc-CS双极膜的制备及表征

分别用八羧基铜酞菁[CuPc(COOH)₈]和四氨基铜酞菁(CuTAPc)改性海藻酸钠(SA)阳膜层和壳聚糖(CS)阴膜层, 制备了CuPc(COOH)₈-SA/CuTAPc-CS双极膜. 实验结果表明, 经八羧基铜酞菁和四氨基铜酞菁改性后, 促进了双极膜中间层水的解离, 增大了阳离子交换膜层和阴离子交换膜层的离子交换容量及H⁺和OH^-的透过率. 与Fe³⁺改性的Fe-SA/mCS双极膜相比, CuPc(COOH)₈-SA/CuTAPc-CS双极膜的阻抗、电阻压降(即IR降)和溶胀度降低. 当电流密度高达120 mA/cm²时, CuPc(COOH)₈-SA/CuTAPc-CS双极膜的IR降仅为0.9 V.