Academic literature on the topic 'Ion-Selective Membranes Operated'

Golgi anti-apoptotic protein (GAAP), also known as transmembrane Bax inhibitor-1 motif-containing 4 (TMBIM4) or Lifeguard 4 (Lfg4), shares remarkable amino acid conservation with orthologues throughout eukaryotes, prokaryotes and some orthopoxviruses, suggesting a highly conserved function. GAAPs regulate Ca 2+ levels and fluxes from the Golgi and endoplasmic reticulum, confer resistance to a broad range of apoptotic stimuli, promote cell adhesion and migration via the activation of store-operated Ca 2+ entry, are essential for the viability of human cells, and affect orthopoxvirus virulence. GAAPs are oligomeric, multi-transmembrane proteins that are resident in Golgi membranes and form cation-selective ion channels that may explain the multiple functions of these proteins. Residues contributing to the ion-conducting pore have been defined and provide the first clues about the mechanistic link between these very different functions of GAAP. Although GAAPs are naturally oligomeric, they can also function as monomers, a feature that distinguishes them from other virus-encoded ion channels that must oligomerize for function. This review summarizes the known functions of GAAPs and discusses their potential importance in disease.

The presence of various ions is an important factor in evaluating water quality. Nitrate, nitrite and ammonium in water can cause health issues and pose environmental concerns1,2. Some sources of the nitrogen species are from natural water and some of them arise from industrial and agricultural activities. Currently commercially available sensors for measuring nitrogen compounds in water are based on colorimetric techniques and potentiometric methods incorporating ion selective electrodes. Progress still needs to be made towards fabricating devices with less instrumentation costs, less complexity, less maintenance and without need for any reagents to facilitate measurement of species1. Chemiresistive sensors are solid-state devices which can be simply fabricated from two contacts and a conductive sensing material affixed on a suitable substrate. They operate by detecting modulations in resistance of the conducting film due to surface charge transfer as a result of interactions with the analyte(s)3. Here, we demonstrate chemiresistive devices capable of quantifying aqueous nitrate, nitrite and ammonium ions selectively. Due to challenges in the aqueous phase such as ionic strength effect, probability of side reactions, non-specific bonding on the surface, low interaction energy between analyte and surface, chemiresistive technology has not been developed extensively in water quality sensors4,5. In this study, we have overcome the issues in water by coating the chemiresistive devices with selective membranes. If the fabricated sensors are used as an array, the total nitrogen concentration in water can be measured online which is a significant advance since nitrate, nitrite and ammonium may interconvert and a single nitrate, nitrite or ammonium sensor by itself cannot give the total amount of nitrogen in a sample. For device fabrication, p-doped carbon nanotubes were selected as a sensitive conductive layer which were modified with selective membranes to improve the sensing performance. Nitrite sensors worked over a dynamic range of 67 ppb to 67 ppm with a 27.6% response at 67 ppm. Nitrate showed 13.2% response from 2.2 ppm to 220 ppm. Ammonium devices operated over a dynamic range of 10 ppb to 100 ppm with a 23.6% response at 100 ppm. The proposed response mechanism involves both an electrostatic gating effect and surface charge transfer. Compared with paper-based colorimetric sensors, the proposed devices perform better with a lower detection limit and the ability to perform continuous online measurements. Moreover, the chemiresistive responses of the devices were compared with their potentiometric responses and found to be equally sensitive but more selective. Unlike ion-selective electrodes, the resulting devices do not require the use of reference electrodes and are therefore potentially more robust for use in continuous water analyzers and in resource-poor settings. The chemiresistive devices showed low interferences and good reversibility. They were also tested in river water samples and showed satisfactory results. The fabricated devices are an advanced proof of concept and have the potential to replace the current technology. Nuñez, L., Cetó, X., Pividori, M. I., Zanoni, M. V. B. & del Valle, M. Development and application of an electronic tongue for detection and monitoring of nitrate, nitrite and ammonium levels in waters. Microchem. J. 110, 273–279 (2013). Li, D., Xu, X., Li, Z., Wang, T. & Wang, C. Detection methods of ammonia nitrogen in water: A review. TrAC - Trends Anal. Chem. 127, 115890 (2020). Choi, S. J. & Kim, I. D. Recent Developments in 2D Nanomaterials for Chemiresistive-Type Gas Sensors. Electronic Materials Letters vol. 14 (The Korean Institute of Metals and Materials, 2018). Kruse, P. Review on water quality sensors. J. Phys. D. Appl. Phys. 51, (2018). Dalmieda, J., Zubiarrain-Laserna, A., Saha, D., Selvaganapathy, P. R. & Kruse, P. Impact of Surface Adsorption on Metal-Ligand Binding of Phenanthrolines. J. Phys. Chem. C 125, 21112–21123 (2021). Figure 1

The present work aims at investigating the potentialities of implementation of electrodialysis for the recycling of spent lithium-ion batteries. In this work, the use of highly-selective membrane toward lithium(I) in electrodialysis was investigated to recover selectively lithium(I) toward cobalt(II), nickel(II) and manganese(II) by means of monovalent ion-selective membranes. It was shown that the presence of divalent cations in the leach solution is responsible for a significant decrease of the limiting current despite an increase in ionic conductivity. Therefore, monitoring the ionic conductivity was not sufficient to operate electrodialysis under optimal conditions, especially when highly selective membranes were used. Furthermore, it was demonstrated that the current has to be lower than the limiting current to avoid metal hydroxide precipitation into the membrane porosity by monitoring the limiting current over time.

Electrodialysis (ED) is a well-known electrochemical water desalination technology investigated since the 1950s. In an ED stack, desalination is driven by an applied voltage, which results in selective salt ion electromigration through alternating cation and anion exchange membranes. Transport of hydronium and hydroxide ions during water treatment, together with water dissociation, can lead to unfavorable product acidity or alkalinity, compromise the membrane charge, or enhance scaling. Conversely, pH deviations can also be leveraged to tune the speciation of weak acid/base electrolytes to enhance chlorine disinfectant efficiency, or facilitate electrostatic removal of contaminants with pH-dependent properties. Thus, it is important to understand the effect of varying feedwater salinity and other system parameters on spatial pH deviations in the vicinity of the membrane, and on the pH of the product water. In this work, we extend ED theory to include pH effects in a repeating unit operated in the underlimiting current regime. Different from the single ion exchange membrane repeating unit considered by Sonin and Probstein [1], which is not applicable for systems including pH effects, we solve the concentration profiles of both the salt and water ions in a full repeating unit comprised of a cation exchange membrane and anion exchange membrane pair. To the first time to our knowledge, our model domain encompasses the entire ED repeating unit without assuming prescribed stagnant layer thickness in which the water dissociation reaction occurs. We solve the Nernst-Planck and electroneutrality set of equations in the channels and non-ideal IEMs, following the approach utilized for capturing pH effects in membrane capacitive deionization [2,3] and reverse osmosis [4,5]. We presented results showing fundamental features, including the concentration and pH distribution in the diluate channel, local flux density across the IEMs, and effluent salinity and pH. Our model predicts that including or excluding pH effects lead to essentially identical predictions for salt fluxes across the IEMs, and thus previous models neglecting pH effects are likely accurately predicting desalination. We also show that reducing salinity augments pH perturbations, but that the effluent pH, which consists of mixed acid and alkaline boundary layers at the diluate channel outlet, does not deviate from inlet neutral pH significantly. In the future, this model framework here can be extended to include multi-ionic solution and species with pH-dependent properties, and validated with a dedicated set of experimental results. References [1] A.A. Sonin, R.F. Probstein, A hydrodynamic theory of desalination by electrodialysis, Desalination. 5 (1968) 293–329. https://doi.org/10.1016/S0011-9164(00)80105-8. [2] J.E. Dykstra, K.J. Keesman, P.M. Biesheuvel, A. van der Wal, Theory of pH changes in water desalination by capacitive deionization, Water Res. 119 (2017) 178–186. https://doi.org/10.1016/j.watres.2017.04.039. [3] Y. Bian, X. Chen, Z.J. Ren, PH Dependence of Phosphorus Speciation and Transport in Flow-Electrode Capacitive Deionization, Environ. Sci. Technol. 54 (2020) 9116–9123. https://doi.org/10.1021/acs.est.0c01836. [4] L. Zhang, H.V.M. Hamelers, P.M. Biesheuvel, Modeling permeate pH in RO membranes by the extended Donnan steric partitioning pore model, J. Memb. Sci. 613 (2020) 118511. https://doi.org/10.1016/j.memsci.2020.118511. [5] O. Nir, N.F. Bishop, O. Lahav, V. Freger, Modeling pH variation in reverse osmosis, Water Res. 87 (2015) 328–335. https://doi.org/10.1016/j.watres.2015.09.038. Figure 1

There is a need for safe, reliable, high capacity storage for long duration energy storage. The low cost and high capacity of sulfur make Li-S batteries ideal for this purpose. However, sulfur has poor electrical conductivity and Li-S batteries are prone to polysulfide shuttling that decreases the battery life. Additionally, lithium metal cannot be cycled at high rates or dendritic growth is produced. We have previously addressed the issues with the S by combining aspects of a static Li-S battery with aspects of a redox targeting system and flow battery. With this system we demonstrated that fundamental Li-S chemistry and novel SEI engineering strategies can be adapted to the hybrid redox flow battery architecture, obviating the need for ion-selective membranes or flowing carbon additives, and offering a potential pathway for inexpensive, scalable, safe MWh scale Li-S energy storage. However, with a planar Li anode the current density was limited to 0.5 mA cm-2, severely limiting the flow battery power output. In this study we present recent progress developing higher surface area anodes to enhance the rate performance of Li metal anodes in flow batteries. The high effective surface area of these structures decreases the local current density while maintaining a high device-level current and thus charge rate. The low local current density and seeded nucleation points on the scaffold promote uniform Li deposition during charging. Candidate electrode materials are evaluated in a mediated Li-S flow battery and cycling rate and capacity retention are compared against a traditional planar Li anode. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Anoctamins such as TMEM16A and TMEM16B are Ca2+-dependent Cl− channels activated through purinergic receptor signaling. TMEM16A (ANO1), TMEM16B (ANO2) and TMEM16F (ANO6) are predominantly expressed at the plasma membrane and are therefore well accessible for functional studies. While TMEM16A and TMEM16B form halide-selective ion channels, TMEM16F and probably TMEM16E operate as phospholipid scramblases and nonselective ion channels. Other TMEM16 paralogs are expressed mainly in intracellular compartments and are therefore difficult to study at the functional level. Here, we report that TMEM16E (ANO5), -H (ANO8), -J (ANO9) and K (ANO10) are targeted to the plasma membrane when fused to a C-terminal CAAX (cysteine, two aliphatic amino acids plus methionin, serine, alanin, cystein or glutamin) motif. These paralogs produce Ca2+-dependent ion channels. Surprisingly, expression of the TMEM16 paralogs in the plasma membrane did not produce additional scramblase activity. In contrast, endogenous scrambling induced by stimulation of purinergic P2X7 receptors was attenuated, in parallel with reduced plasma membrane blebbing. This could suggest that intracellular TMEM16 paralogs operate differently when compared to plasma membrane-localized TMEM16F, and may even stabilize intracellular membranes. Alternatively, CAAX tagging, which leads to expression in non-raft compartments of the plasma membrane, may antagonize phosphatidylserine exposure by endogenous raft-located TMEM16F. CAAX-containing constructs may be useful to further investigate the molecular properties of intracellular TMEM16 proteins.

Poly-o-anisidine Sn(IV) arsenophosphate is a newly synthesized nanocomposite material and has been characterized on the basis of its chemical composition, ion exchange capacity, TGA-DTA, FTIR, X-RAY, SEM, and TEM studies. On the basis of distribution studies, the exchanger was found to be highly selective for lead that is an environmental pollutant. For the detection of lead in water a heterogeneous precipitate based ion-selective membrane electrode was developed by means of this composite cation exchanger as electroactive material. The membrane electrode is mechanically stable, with a quick response time, and can be operated over a wide pH range. The selectivity coefficients were determined by mixed solution method and revealed that the electrode is sensitive for Pb(II) in presence of interfering cations. The practical utility of this membrane electrode has been established by employing it as an indicator electrode in the potentiometric titration of Pb(II).

The cholinergic receptor-regulation of K+ transport was studied in human submandibular glands. Acetylcholine stimulation 10 μmol/L results in an increase in membrane permeability (86Rb+ efflux) for, and a net efflux of, K+ ions from the glandular tissue. In the post-stimulus period, there is a net re-uptake of K+ ions into the tissue. Patch-clamp electrophysiological techniques were employed to demonstrate the presence of a large conductance K+ selective ion channel in the basolateral membranes of isolated human submandibular acinar cells. The patch-clamp results indicate that this voltage- and calcium-activated K+ channel operates to regulate the K+ permeability in both the resting and acetylcholine-stimulated acinar cells. We discuss the role of the K+ channel, K+ efflux, and K+ re-uptake in relation to stimulus-secretion coupling.

Microelectromechanical Systems (MEMS) fabrication techniques offer a unique solution for implantable medical drug delivery systems. An implantable medical drug delivery system can relieve the pain associated with frequent injections and deliver a localized dosage. An implantable drug delivery system can also avoid contamination and infection better than conventional injection methods (such as intravenous injection). The major advantage of microfabricated drug delivery systems is the possibility of mass production at low cost. A silicon based peristaltically actuated implantable medical drug delivery system consisting of three pumping chambers was microfabricated and tested. The unique features of this microfabricated drug delivery system include the design of a selectively anodic bonded micropump. The selectively anodic bonded Pyrex glass wafer was used to seal the pump chambers and allow for a view of fluid movement. Chromium was used as a selective bonding material. A 20 nm thick chromium film deposited on the top surface of the silicon valves successfully prevented bonding between the valve and the glass wafer. The pump operates with a normally closed valve which consists of a silicon mesa located at the center of each chamber. This mesa makes intimate contact with the glass wafer. Three 180 μm deep and 12 mm diameter circular chambers were etched into the top surface of the silicon wafer using deep reactive ion etching (DRIE) and connected by two 1 mm wide channels. Directly opposite the chambers, three 12 mm diameter circular features were etched 320 μm deep using DRIE to create a 50 μm thick silicon membrane and provide an attachment point for piezoelectric actuating disks. The piezoelectric disks were applied using a conductive silver epoxy. A positive potential was applied to the gold layer that was e-beam deposited on the substrate, with the negative terminal applied to each individual actuator. The three pump chambers were actuated in a peristaltic motion with driving frequencies ranging from 0.5 to 4 Hz and actuation voltages ranging from 10–130 V. The design goal of 10 μL/min was met at driving frequencies of 2 and 4 Hz where the maximum flowrate was 10.1 and 11.4 μL/min for the 2 and 4 Hz actuation frequencies respectively at an actuation voltage of 130 V. The maximum pressure achieved by the pump was 35.8 mmH20 for the 2 and 4 Hz actuation frequencies at an actuation voltage of 130 V.