Sodium ion transporter

Both the oxides (3- and (3"-alumina show extremely high Na+ ion conductivity. As the structure suggests, the conductivity is anisotropic, and rapid sodium ion transport is limited to the two-dimensional conduction plane. There is almost unimpeded motion in the Na+ layers, especially in (3"-alumina, which lacks interstitial oxygen ion defects in the conduction plane, and the conductivity is of the same order of magnitude as in a strong solution of a sodium salt in water. The conductivity is a... 

This group consists of j3-adrenergic receptor blockers, the antiarrhythmic activity of which is associated with inhibition of adrenergic innervation action of the circulatory adrenaline on the heart. Because all 8-adrenoblockers reduce stimulatory sympathetic nerve impulses of catecholamines on the heart, reduce transmembrane sodium ion transport, and reduce the speed of conduction of excitation, sinoatrial node and contractibility of the myocardium is reduced, and automatism of sinus nodes is suppressed and atrial and ventricular tachyarrhythmia is inhibited. 

The mechanism by which the exergonic methyl-transfer reaction is coupled with vectorial electrogenic Na translocation across the membrane is not known. An electron transport chain appears not to be involved in Na transport. Sodium ion transport... 

Martinez-Maldonado Cordova 1990, Rose 1989, 1991, Wilcox 1991). In the absence of a loop diuretic, sodium ions transported into the cell are translocated into the peritubular capillary by the action of the Na, K -ATPase pump. Chloride ions are translocated out of the cell by two pathways a selective chloride channel and an electroneutral K, Cr-cotransporter. These processes maintain low intracellular sodium and chloride ion concentrations and favor continued entry of sodium and chloride from the tubular lumen. In contrast, potassium ion concentrations in the tubular fluid and within the cell are lower and higher, respectively, compared with sodium and chloride. Although these potassium ion concentrations would seem to inhibit the action of the Na, K, 2Cr-cotrans-porter, this problem is overcome by the recycling of much of the reabsorbed potassium (that does... 

Whittingham, M.S. and Huggins, R.A. (1971) Measurement of sodium ion transport in beta alumina using reversible solid electrodes./. Chem. Phys., 54 (1), 414-16. 

Some of these features are illustrated in Figures 14-18. A rather typical literature plot of current efficiency vs, sodium hydroxide concentration for perfluorosulfonate membranes is shown in Fig. 14. Nation 427 is a 1200-EW sulfonate membrane with fabric reinforcement. Poor hydroxide rejection occurs at catholyte concentrations above 10 wt % but a minimum is seen at higher concentrations, wtih increasing current efficiency from 28 to 40% caustic (9-14 M). The current efficiency of a 1200-EW homogeneous perfluorosulfonate film is shown in more detail over this concentration region in Fig. 15. Sodium ion transport number niol F ), which is equivalent to caustic current efficiency, is plotted vs. both brine anolyte and caustic catholyte concentration. These values were determined using radiotracer techniques, which have proven to be rapid and accurate methods for the determination of membrane performance. " " " A rather sharp maximum is seen at 14 M NaOH, and the influence of brine con-... 

Figure 15. Sodium ion transport number for Nafion 120 us. brine anolyte and caustic catholyte concentrations (Ref. 170).

In Figure 17, sodium ion transport number is plotted vs, catholyte concentration for a homogeneous perfluorocarboxylate film. The current efficiency is now higher than 90% over the entire caustic concentration region studied, although a minimum and maximum in performance is again observed. These features are shifted to lower concentration compared to perfluorosulfonate behavior though. Finally, the performance of a sulfonate-carbox-ylate bilayer membrane, Nafion 901, is plotted in Fig. 18. For such... 

Figure 17. Sodium ion transport number vs. caustic catholyte solution for a perfluorinated carboxylate membrane ( ) anolyte is 5 M NaCl and (O) anolyte and catholyte are identical concentrations of NaOH. (Ref. 149 reprinted by permission of the publisher, The Electrochemical Society, Inc.)...

While these membranes exhibit sodium ion transport numbers as high as 0.98 mol F-1 (i.e. only 2% of the electrolysis current is carried by hydroxide ion through the membrane) no comprehensive theoretical treatment of this unusually high permselectivity has yet emerged. The variation of permselectivity as a function of various cell parameters is also of interest, not only for practical reasons but also because of the insight that may be gained into the nature of hydroxide ion rejection. This research is directed at the latter problem, that is the characterization of membrane permselectivity... 

A laboratory membrane brine electrolysis cell, designed for automated operation, was constructed ( 1,2). This system enables the measurement of the sodium ion transport number of a membrane under specific sets of conditions using a radiotracer method. In such an experiment, the sodium chloride anolyte solution is doped with 22Na radio-tracer, a timed electrolysis is performed, and the fraction of current carried by sodium ion through the membrane is determined by the amount of radioactivity that has transferred to the sodium hydroxide catholyte solution. The voltage drop across the membrane during electrolysis is simultaneously measured, so that the overall performance of the material can be evaluated. 

For the application of these membranes to the electrolytic production of chlorine-caustic, other performance characteristics in addition to membrane conductivity are of interest. The sodium ion transport number, in moles Na+ per Faraday of passed current, establishes the cathode current efficiency of the membrane cell. Also the water transport number, expressed as moles of water transported to the NaOH catholyte per Faraday, affects the concentration of caustic produced in the cell. Sodium ion and water transport numbers have been simultaneously determined for several Nafion membranes in concentrated NaCl and NaOH solution environments and elevated temperatures (30-32). Experiments were conducted at high membrane current densities (2-4 kA m 2) to duplicate industrial conditions. Results of some of these experiments are shown in Figure 8, in which sodium ion transport number is plotted vs NaOH catholyte concentration for 1100 EW, 1150 EW, and Nafion 295 membranes (30,31). For the first two membranes, tjja+ decreases with increasing NaOH concentration, as would be expected due to increasing electrolyte sorption into the polymer, it has been found that uptake of NaOH into these membranes does occur, but the relative amount of sorption remains relatively constant as solution concentration increases (23,33) Membrane water sorption decreases significantly over the same concentration range however, and so the ratio of sodium ion to water steadily increases. Mauritz and co-workers propose that a tunneling process of the form... 

Figure 8. Sodium ion transport number vs. NaOH catholyte molarity for Nafion membranes, 80° C. Key O,, Nafion 295 , , 1150 EW A, 1100 EW. Ano-lyte solution is NaOH for light symbols and 5M NaCl for dark symbols.

The electroosmotic transport coefficient for water through Nafion 295 and 1150 membranes is typical and is shown to be highly dependent on the anolyte concentration to the exclusion of all the other variables studied. The water transport coefficient varies almost linearly with anolyte concentration from 6 to 17 molar caustic, giving 2.9 to 0.8 moles/F, as shown in Figure 3. The sodium ion transport number goes through a maximum of 0.82 eq/F in the 7 to 13 molar caustic range (27). 

The physiological action is based on depolarization of neurons and muscie ceils by specific blockade of sodium ion transport through plasma membrane channels whereby muscular and finally respiratory paralysis results Antagonist of B. is tetrodotoxin. 

For each 18 sodium ions transported through the frog s skin, one extra molecule of oxygen is consumed. Toad bladder and guinea-pig intestine behave similarly. Many cathartics (e.g. cascara, phenolphthalein, podophyllin) inhibit absorption of sodium by the membrane of the intestinal lumen (from experiments in living rabbits), thus causing accumulation of sodium salts in the colon, and hence retention of water (Phillips etaL, 1965). 

M. S. Whittingham and R. A. Huggins [1971] Measurement of Sodium Ion Transport in j3-Alumina Using Reversible Solid Electrodes, J. Chem. Phys. 54, 414-416. 

A very interesting analytical approach was chosen by Updike and Treichel [286] who constructed a tissue sensor for antidiuretic hormone (ADH) using a toad bladder tissue membrane over the surface of a sodium ion-sensing glass electrode. The measurement was based on the enhancement of sodium ion transport in the presence of ADH. The bladder membrane must be oriented with its mucosal side towards the sodium electrode because the transport occurs only from the mucosal to the serosal side. The ADH assay was very fast (response time about 10s) however, sodium transport was also affected by some other hormones and thus this method is not specific. 

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