Search

Monovalent cation perm-selective membrane (MCPMs) allow fast and selective transport of monovalent cations, and they are promisingly required for extraction of special ions, such as lithium extraction, acid recovery and sea salt production. Herein, we report a novel strategy to design the critical functional layers of MCPMs with both space charge repulsion and cross-linked dense screenability. The in-situ deposition polymerization of pyrrole was carried out on the surface of sulfonated polyphenyl sulfone (SPPSU) substrate membrane followed by cross-linking quaternization of the polypyrrole (PPy) layer with diiodinated functional molecules, thus, the membrane obtained more excellent selective permeability and stable transport properties of monovalent cations. It confirms that the designed PPy layers with charged surface and cross-linking structure improved the hydrophilicity, facilitated cation transport and increased ion flux. Meanwhile, for the dense PPy layer, the charged cross-linked structure endowed the functional layer with the synergistic characteristics of Donnan exclusion and pore size sieving for positively charged ions, which improved the monovalent cation perm-selectivity of the membranes. At a constant current density of 5.1 mA/cm2, the optimal membrane exhibited superior perm-selectivity ( P Mg Na = 2.07 ) and monovalent cation flux (JNa+ = 2.80 × 10 −8 (mol cm−2 s−1)) during electrodialysis.

A number of artificial cation ionophores (or transporters) have been developed for basic research and biomedical applications. However, their mechanisms of action and the putative correlations between changes in intracellular cation concentrations and induced cell death remain poorly understood. Here we show that three hemispherand-strapped calix[4]pyrrole based ion pair receptors act as efficient Na+/K+ exchangers in the presence of Cl- in liposomal models, and promote Na+ influx and K+ efflux (Na+/K+ exchange) in cancer cells to induce apoptosis. Mechanistic studies reveal that these cation exchangers induce endoplasmic reticulum (ER) stress in cancer cells by perturbing intracellular cation homeostasis, promote generation of reactive oxygen species, and eventually enhance mitochondria-mediated apoptosis. However, they neither induce osmotic stress nor affect autophagy. The present study provides support for the notion that synthetic receptors which perturb cellular cation homeostasis may provide a new approach to generating agents with potentially useful apoptotic activity.

Clayware membrane amalgamated with 20% montmorillonite (M-20), acts as an excellent cost effective proton exchange membrane (PEM) for the application in field-scale microbial fuel cells (MFCs). In this investigation, M-20 membrane was pre-treated by acid (M-A), neutral water (M-N) and alkali (M-B), followed by the determination of the membrane properties to access their applicability in MFCs. With alkali treatment of M-20 membrane, maximum proton mass transfer coefficient of 6 × 10−6 cm s−1 was obtained, which was nearly five times higher than M-A (1.15 × 10−6 cm s−1) and four times higher than the control membrane, M-N. Proton conductivity was also found to be maximum for M-B (17.9 × 10−3 S cm−1), which was four times higher than both M-N (4.4 × 10−3 S cm−1) and M-A (4.6 × 10−3 S cm−1). Oxygen mass transfer coefficient was found to be minimum for M-B (4.02 × 10−5 cm s−1), which was considerably lesser than that observed for M-N (16.2 × 10−5 cm s−1) and M-A (13.8 × 10−5 cm s−1). Cation transport number of M-B (0.15 ± 0.01) was found to be two folds lower than M-N, demonstrating M-B is more selective towards proton transport compared to other cations. The MFC-B with M-B as PEM performed superior as compared with other MFCs, demonstrating coulombic efficiency (CE) of 10.2%, chemical oxygen demand (COD) removal efficiency of 88% and power density of 83.5 mW m−2. On the other hand, MFCs using M-A and M-N as PEM, demonstrated mediocre performance with CE of 6% and 7.6%, COD removal efficiency of 80% and 83% and power density of 40.4 ± 6.2 mW m−2 and 64.0 ± 5.8 mW m−2, respectively. Hence, alkali treatment of clayware ceramic membrane elucidated its appropriateness for proliferating the efficacy of MFCs and these are recommended for scaling up of MFCs.

The mechanisms that generate robust ionic oscillation in circadian pacemaker neurons are under investigation. Here, we demonstrate critical functions of mitochondrial cation antiporter (LETM1), which exchanges K+/H+ in Drosophila and Ca2+/H+ in mammals, in circadian pacemaker neurons. Letm1 knockdown in Drosophila pacemaker neurons reduced circadian cytosolic H+ rhythms and prolonged nuclear PER/TIM expression rhythms and locomotor activity rhythms. In rat pacemaker neurons in the hypothalamic suprachiasmatic nucleus (SCN), circadian rhythms in cytosolic Ca2+ and Bmal1 transcription were dampened by Letm1 knockdown. Mitochondrial Ca2+ uptake peaks late during the day were also observed in rat SCN neurons following photolytic elevation of cytosolic Ca2+. Since cation transport by LETM1 is coupled to mitochondrial energy synthesis, we propose that LETM1 integrates metabolic, ionic and molecular clock rhythms in the central clock system in both invertebrates and vertebrates.

Potassium (K) exerts key physiological functions such as osmoregulation, stomatal movement, membrane transport, protein synthesis and photosynthesis among others. Previously, it was demonstrated in Arabidopsis thaliana that the loss of function of the chloroplast K Efflux Antiporters KEA1 and KEA2, located in the inner envelope membrane, provokes inefficient photosynthesis. Therefore, the main goal of this study was to evaluate the potential impact of the loss of function of those cation transport systems in the metabolism of reactive oxygen and nitrogen species (ROS and RNS). Using 14-day-old seedlings from Arabidopsis double knock-out kea1kea2 mutants, ROS metabolism and NO content in roots and green cotyledons were studied at the biochemical level. The loss of function of AtKEA1 and AtKEA2 did not cause oxidative stress but it provoked an alteration of the ROS homeostasis affecting some ROS-generating enzymes. These included glycolate oxidase (GOX) and NADPH-dependent superoxide generation activity, enzymatic and non-enzymatic antioxidants and both NADP-isocitrate dehydrogenase and NADP-malic enzyme activities. NO content, analyzed by confocal laser scanning microscopy (CLSM), was negatively affected in both photosynthetic and non-photosynthetic organs in kea1kea2 mutant seedlings. Furthermore, the S-nitrosoglutathione reductase (GSNOR) protein expression and activity were downregulated in kea1kea2 mutants, whereas the tyrosine nitrated protein profile, analyzed by immunoblot, was unaffected but the relative expression of each immunoreactive band changed. Moreover, kea1kea2 mutants showed an increased photorespiratory pathway and stomata closure, thus promoting a higher resilience to drought stress. Data suggest that the chloroplast osmotic balance and integrity maintained by AtKEA1 and AtKEA2 are necessary to keep the balance of ROS/RNS metabolism. Moreover, these data open new questions about how endogenous NO generation might be affected by the K/H transport located in the chloroplasts., The projects PID 2019-103924 GB-I00 (MICIT) and P18-FR-1359 (Plan Andaluz de Investigación, Desarrollo e Innovación), Spain, financed the research by ASM, SGG, JMP, and FJC, and the grant BIO 2015–65056 P (MINECO, Spain) that of MNAS, PRR and KV.

In order to promote photosynthetic reactions and biomass yield of microalgae in 15% CO2 from coal-fired flue gas, a self-adaptive microalgal growth system with gene mutation centered on the cellular light response was established through CO2 gradient domestication. The microalgae Nannochloropsis oceanica CCMP1779 was gradually acclimated to 0.04%, 3%, 6%, 10% and 12% CO2 to obtain strains with a predominant adaptation to CO2. The domesticated strain showed a 22.7-fold and 3.98-fold increase compared to wild-type under 6 mL/min and 12 mL/min 15% CO2, respectively. A comprehensive analysis of the genome, transcriptome, photosynthetic fluorescence and RT-qPCR results were conducted to explore the effects of CO2 gradient acclimation on microalgal growth. The CO2 gradient domestication produced multi-targeted genetic mutations and natural selection, leading to successful transcriptional changes and apparent photosynthesis properties. Therefore, a self-adaptive microalgal growth system for high CO2 was built based on photosynthesis enhancement (controlled by magnesium chelatase (EC 6.6.1.1)) in the competition between photosynthesis and respiration. This system was supported by improved cation transport, DNA and RNA synthesis, photosynthetic electron transfer, carbon fixation and metabolism. CO2 gradient acclimation demonstrates a cost-effective method for generating microalgae mutants for efficient CO2 fixation from coal-fired flue gas.

Ceramic membranes can serve as viable alternatives to the less mechanically stable polymeric membranes utilized in microbial fuel cells (MFCs). In this work, a series of polymer-derived ceramic (PDC) proton exchange composite membranes with large ion exchange capacity (IEC) values, high cation transport numbers, and low oxygen diffusion coefficients have been synthesized at various pyrolysis temperatures using a pressing technique. These materials were composed of a polysiloxane matrix mixed with proton-conducting fillers such as montmorillonite and H3PMo12O40/SiO2 at different ratios. By tuning the average pore sizes of the membranes between 0.1 and 1 µm and their hydrophilic/hydrophobic characteristics, the maximum IEC of 0.6072 mequiv/g and cation transport number of 0.6988 were obtained, which is 67% and 72% of polymeric nafion performance, respectively. In addition, the minimal oxygen mass transfer coefficient achieved by this approach was equal to 5.62 × 10−4 cm/s, which is very close to the commercial nafion membrane value. The fabricated PDC composite membranes meet all the essential criteria required for their use in MFC applications and represent a high potential to overcome limitations of polymeric membrane.

Objective Loss of insulin secretion due to failure or death of the insulin secreting β cells is the central cause of diabetes. The cellular response to stress (endoplasmic reticulum (ER), oxidative, inflammatory) is essential to sustain normal β cell function and survival. Pancreatic and duodenal homeobox 1 (PDX1), Activating transcription factor 4 (ATF4), and Activating transcription factor 5 (ATF5) are transcription factors implicated in β cell survival and susceptibility to stress. Our goal was to determine if a PDX1-ATF transcriptional complex or complexes regulate β cell survival in response to stress and to identify direct transcriptional targets. Methods Pdx1, Atf4 and Atf5 were silenced by viral delivery of gRNAs or shRNAs to Min6 insulinoma cells or primary murine islets. Gene expression was assessed by qPCR, RNAseq analysis, and Western blot analysis. Chromatin enrichment was measured in the Min6 β cell line and primary isolated mouse islets by ChIPseq and ChIP PCR. Immunoprecipitation was used to assess interactions among transcription factors in Min6 cells and isolated mouse islets. Activation of caspase 3 by immunoblotting or by irreversible binding to a fluorescent inhibitor was taken as an indication of commitment to an apoptotic fate. Results RNASeq identified a set of PDX1, ATF4 and ATF5 co-regulated genes enriched in stress and apoptosis functions. We further identified stress induced interactions among PDX1, ATF4, and ATF5. PDX1 chromatin occupancy peaks were identified over composite C/EBP-ATF (CARE) motifs of 26 genes; assessment of a subset of these genes revealed co-enrichment for ATF4 and ATF5. PDX1 occupancy over CARE motifs was conserved in the human orthologs of 9 of these genes. Of these, Glutamate Pyruvate Transaminase 2 (Gpt2), Cation transport regulator 1 (Chac1), and Solute Carrier Family 7 Member 1 (Slc7a1) induction by stress was conserved in human islets and abrogated by deficiency of Pdx1, Atf4, and Atf5 in Min6 cells. Deficiency of Gpt2 reduced β cell susceptibility to stress induced apoptosis in both Min6 cells and primary islets. Conclusions Our results identify a novel PDX1 stress inducible complex (es) that regulates expression of stress and apoptosis genes to govern β cell survival., Graphical abstract Image 1, Highlights • PDX1 binds to composite CEBP/ATF (CARE) sites of stress and apoptosis genes. • A novel stress inducible transcriptional complex involving PDX1, ATF4, and ATF5 is discovered. • Novel stress induced targets of the complex involved in fate decisions are identified. • Silencing of one of these targets, Gpt2, protects β cells from apoptosis due to stress.

Due to their preferential cation transport, dense cation exchange membranes like Nafion membranes are unsuitable for Zn/Br redox flow batteries which require bi-ionic transport of Zn2+ and Br- ions. This work shows that scaling the water cluster size of Nafion membranes by a pre-hydration treatment can achieve not only a high ionic conductivity but also a bi-ionic transport property. Small angle X-Ray scattering, diffusion cell, and electrochemical analysis verify that by increasing the pre-hydration temperature, the water clusters are expanded, resulting in an increase of water uptake, ionic conductivity and the anion transference number. The bi-ionic transport and low area specific resistance induced by the pretreatment enable the successful operation of a Zn/Br redox flow battery with a NRE-212 membrane. Compared with a conventional porous membrane, the properly treated Nafion membrane has an 11.3% higher energy efficiency indicating that the dense structured ion exchange membrane can be used for Zn/Br flow batteries by scaling the water cluster size.

While solid polymer electrolytes (SPEs) possess a combination of the requisite properties to merit their use in all-solid-state rechargeable batteries, their low ionic conductivity (σ) at room temperature limits their widespread use in advanced commercial applications. To overcome this limitation, it is necessary to understand the crucial molecular factors that govern the energetics and transport of ions in SPEs. In this Article, all-atom molecular dynamics (MD) and adaptive biasing force (ABF) simulations are used to characterize the mechanism and energetics of polymer-coupled ion transport and to probe the nature of interactions of polymers and ions in a crystalline SPE (PEO3:NaI). In particular, the free energy profiles associated with the cation transport along the polymer helix, the activation energy for hopping of a cation between adjacent energetically favourable coordination sites, and crucial factors determining the features of the free energy profiles are examined. The calculated free energy profiles exhibit well-defined minima (correspond to favourable cation coordination sites) separated by relatively high energy barriers (12–14 kcal/mol) indicating that ion hopping is the likely mechanism of cation transport in PEO3:NaI crystals. The influence of the conformational flexibility of the polymer on the energetics of cation transport is also examined. The dissection of interaction of the cations provides insights into the interplay of ion-ion, ion-polymer, and polymer-polymer interactions in determining the activation barrier for cation transport in the crystalline PEO3:NaI.

International audience; This paper addresses hybrid ion exchange membranes fabricated by the synthesis of amorphous zirconiumphosphate (dopant contents from 0.5 to 24 wt%) directly in the pore and channel system of heterogeneouscation-exchange membrane RALEX® CM (by in situ technique). The incorporation of zirconium phosphate nanoparticlesinto the membrane system of pores and channels leads to the displacement of the pore water. As aresult, the cation transport numbers increase. The hybrid materials thus obtained are characterized by increasedionic resistance and enhanced monovalent ion selectivity. The former effect was eliminated by fabrication of asurface-modified membrane. The relative simplicity of modification, together with the benefits of the hybridmaterials make them promising for some membrane processes. Using 31P MAS NMR and elemental analysis,considerable difference between the zirconium phosphate composition inside and outside the membrane wasfound.

K+-dependent Na+-Ca2+ exchangers (NCKXs) play an important role in Ca2+ homeostasis in many tissues. NCKX proteins are bi-directional plasma membrane Ca2+-transporters which utilize the inward Na+ and outward K+ gradients to move Ca2+ ions into and out of the cytosol (4Na+:1Ca2+ + 1 K+). In this study, we carried out scanning mutagenesis of all the residues of the highly conserved α-1 and α-2 repeats of NCKX2 to identify residues important for K+ transport. These structural elements are thought to be critical for cation transport. Using fluorescent intracellular Ca2+-indicating dyes, we measured the K+ dependence of transport carried out by wildtype or mutant NCKX2 proteins expressed in HEK293 cells and analyzed shifts in the apparent binding affinity (Km) of mutant proteins in comparison with the wildtype exchanger. Of the 93 residue substitutions tested, 34 were found to show a significant shift in the external K+ ion dependence of which 16 showed an increased affinity to K+ ions and 18 showed a decreased affinity and hence are believed to be important for K+ ion binding and transport. We also identified 8 residue substitutions that resulted in a partial loss of K+ dependence. Our biochemical data provide strong support for the cation binding sites identified in a homology model of NCKX2 based on crystal structures reported for distantly related archaeal Na+-Ca2+ exchanger NCX_Mj. In addition, we compare our results here with our previous studies that report on residues important for Ca2+ and Na+ binding. Supported by CIHR MOP-81327.

Jalili syndrome (JS) is an autosomal recessive disease characterized by a combination of cone-rode retinal dytrophy (CRD) and amelogenesis imperfect (AI). Mutations in cyclin and CBS domain divalent metal cation transport mediator 4 (CNNM4) gene cause JS. Here we described 2 families (3 members) affected by JS. In the first family, JS was caused by the homozygous p.Leu324Pro (c.971T > C) missense mutation and the affected patient developed both CRD and AI. In the second family, a specific combination of a compound heterozygous mutation was found – the p.Leu324Pro (c.971T > C) missense transition and the novel p.Tyr581* (c.1743C > G) nonsense mutation. The proband showed CRD and AI, but her father just developed eye alterations. Together, these findings suggest that the p.Leu324Pro mutation in homozygosis induces a complete phenotype with both CRD and AI, but in heterozygosis and in composition with the novel p.Tyr581* nonsense mutation in CNNM4 promotes variable clinical expressivity, particularly with lack of dental phenotypes. These different phenotypes could be explained by deletions affecting the proband's homologous allele, epistasia or interactions with environmental factors leading to residual activity of protein.

Ion exchange membranes (IEMs) have been established as a key component in industrial water desalination and electrolysis processes. Thus, nowadays, they are being studied and developed for application in new energy conversion and storage systems as well as efficient desalination and wastewater treatment processes. These processes include redox flow batteries, reverse electrodialysis, membrane capacitive deionization, microbial fuel cells, and ion exchange membrane bioreactors. Ion permselectivity between counter- and co-ions, the most essential property in IEMs, makes these processes possible and/or efficient. Additionally, ion selectivity between different counter-ions is required for these novel processes to be efficient. This review aims to provide a comprehensive overview of ion exchange membrane permselectivity by summarizing the developments in this field over the past decade. Membrane microstructure and possible mechanisms for ion transport in the membrane phase are discussed with respect to permselectivity, along with the influence of current density and related membrane-solution boundary conditions. A selectivity order for the transport of common anions through conventional anion exchange membranes (AEMs) is generalized, the same is done for cation transport through conventional cation exchange membranes (CEMs). Two types of experimental methods for the determination of ion permselectivity: electrodialysis and the membrane potential method, are summarized. Finally, relevant membrane preparation methods and surface modification of IEMs reported over the past decade are classified and discussed. In summary, we conclude that synthetic methods have evolved rapidly; however, development of fundamental knowledge on the many complex phenomena occurring in the adaptive membrane bulk and solution-interface environments is not sufficiently established. Thus, much effort is required to combine experimental, theoretical, and simulation data for a more comprehensive and coherent understanding of these phenomena.

Thin film composite (TFC) membranes are the gold standard for the application of forward osmosis (FO) in seawater desalination and wastewater treatment. However, bidirectional mass transport phenomena in this process still hinder its wider application. A deeper understanding of ion transport behavior in various solution conditions is critical for the fabrication of FO membrane and future development of FO process. In this work, we systematically investigated the influences of solution chemistry on ion mass transport in TFC FO membranes. Our results suggested that the mass transports of cations were much larger than those of anions in FO processes, and monovalent cations with smaller hydrated radius could induce greater cation exchange than divalent cations. Though anions did not participate in the cation exchange processes directly, cations paired with nitrate could transport through the TFC membrane more readily than those paired with chloride or sulfate. Additionally, a set of experiments with series solution concentrations confirmed the existence of cation transport bottleneck for one TFC FO membrane. We found that the cation transport capacity of TFC membranes was mainly determined by the concentration of feed solution and the generation of cation exchange behavior was independent of water transport. Engineering implications of our findings for FO application were also discussed.

A cationic diode is fabricated by hot-pressing a commercial cation-conducting ionomer membrane (Fumasep FKS-30) onto a polyethylene terephthalate (PET) substrate with microhole of 5, 10, 20, or 40 μm diameter. Both, symmetric (ionomer on both sides) and asymmetric (ionomer only on the working electrode side) cases are investigated in a 4-electrode measurement cell. A 5-electrode measurement cell in generator-collector mode is employed to directly detect competing proton transport through the ionomer. Only the asymmetric device allows ion current rectification to be observed. With decreasing microhole diameter the rectification effect increases. With increasing electrolyte concentration (for aqueous HCl, NaCl, LiCl, NH4Cl, MgCl2, CaCl2) the rectification effect diminishes. Competition between cation transport and proton transport is observed in all cases. A qualitative impedance model is developed to diagnose the quality and performance of these cationic diodes.

Free-standing Ti3C2Tx MXene films with flexible feature are considered to be promising electrodes for the application in flexible energy devices. Exploring the different cation effect and each transport mechanism will help us to identify the optimized cation for special applications. Herein, we investigate the relationship between cation transports and capacitance behavior under different potential windows. In addition, we uncover intercalation mechanisms for Li+, Na+, and K+-containing electrolytes. As a result, we found that capacitive intercalation mechanism of characteristic cation can be influenced by different potential windows. Importantly, after 5000 charge-discharge cycles from −1 V to 0 V, the cation-intercalation behavior is demonstrated by significant electrode expansion in LiCl, NaCl, and KCl electrolytes with the increased d-spacing of 1.344 nm, 1.313 nm, and 1.305 nm, respectively. Additionally, larger size of K+ with fast ion transport is involved in fast electrochemical surface adsorptions, which explains higher capacitance of 346 F cm−3 in KCl than 218 F cm−3 in NaCl electrolyte. In contrast, small ion size of Li+ is vulnerable to adsorb and permeate the spacing between layers of Ti3C2Tx MXene electrode, which delivers volumetric capacitance of 320 F cm−3. The present study provides direct experimental evidence for electrochemical mechanism of cation intercalation between Ti3C2Tx MXene layer sheets.

The present work describes a novel and cleaner approach for large scale (litre) separation of cesium from simulated nuclear waste solutions by electrodriven transport through a hollow fiber supported liquid membrane (HFSLM) containing chlorinated cobalt dicarbollide as the carrier. To the best of our knowledge, this is the first report on electrodriven cation transport through HFSLM. The transport selectivity of Cs + over Na + and other fission products was studied from synthetic nuclear waste solutions. An attempt has also been made to pre-concentrate radio-cesium from an environmental sample containing very low level of 137 Cs (≤ 10 –12 M) with excellent transport efficiency. A very high decontamination factor of cesium over Na + other metal ions have been obtained for all types of feed solution. For neutral feed solution, the current efficiency for the Cs + transport has been found to be 100%. The present work certainly adds a new dimension to the ongoing membrane based separations.

High current densities have been obtained by bioanodes in electrochemical cells, but this performance has not previously been translated into higher power densities in microbial fuel cells (MFCs). The most critical factor for boosting power generation in MFCs was proven here to be OH– ion transfer from the cathode to the bioanode by comparing performance of an MFC with an anion exchange membrane (AEM), in a near zero-gap configuration and no bulk catholyte, to that obtained using a cation exchange membrane (CEM) or non-ion selective ultrafiltration membrane (UFM). In the AEM-MFC hydroxide ion transport primarily balanced charge transfer between the electrodes, enabling 8.8 ± 0.5 W m−2 (at 42 ± 1 A m−2) which is highest power density ever achieved using this anolyte (acetate in a 50 mM phosphate buffer medium). The power density with the AEM was 3 × higher than that obtained using a CEM (3.1 ± 0.1 W m−2) or UFM (2.4 ± 0.1 W m−2) as these other two membranes allowed cations (sodium and magnesium) to be transported to the cathode for balancing charge. The lack of cation transport into the cathode using the AEM without a bulk catholyte also avoided salt precipitation in the cathode, and thus enabling more stable power production over time. The large differences in power obtained using the AEM, compared to the CEM or UFM conclusively demonstrate the critical role of OH– ion transport in MFCs.

While exsolution is widely observed among perovskite hosts as an attractive technique for in-situ catalyst synthesis, our current understanding of the complex exsolution-host relationships is solely based on the conventional approach of using a small amount of a single dopant at a limited high-temperature range (≥ 800 °C). Herein, we develop a charge-balanced double-doping approach that opens new doors for the synthesis of a wide range of compositions, and the highly tunable nature of these compositions provides a basis for controlling exsolved particle size, distribution, composition, and surface anchorage. Against the conventional wisdom that high doping level leads to unstable exsolution, we show that increased double-doping levels, enabled by our novel method, can stabilize the perovskite phase in reducing conditions to provide high conductivity (> 35 S/cm) at low temperatures (450–650 °C) and exsolve smaller, more densely populated particles with different chemistry than their lightly doped analogues. Furthermore, we find that associated defects might be the main factor that determines nucleation sites, and the conductivity of the host may play a crucial role in exsolution kinetics by facilitating cation transport. This study paves the way for controlling exsolved electrocatalyst properties by engineering the charge-balanced B-site and offers new knowledge that links exsolution to defect chemistry.

The transport selectivity of different cations through cation exchange membranes (CEMs) could be estimated with the partitioning selectivity factor ( K j i ) and the cation mobility ratio in the membrane ( u i m / u j m ), which in turn can be related to corresponding membrane conductivity and dimensional swelling ratio data [Journal of Membrane Science, 2020, 597, 117645]. This method has been validated in two hydrocarbon polymer-based CEMs, and the obtained K+/Na+ selectivity equals to the one obtained with conventional electrodialysis (ED) method. However, the K+/Na+ selectivity of perfluorosulfonic acid (PFSA) membranes, and the bi-/monovalent cation (Mg2+/Na+) selectivity of all three types of CEMs estimated with this ionic conductivity experimental approach deviate noticeably from corresponding values obtained with ED. In this work, it is proved that this deviation is partly due to the simplification of cation activity coefficients in the membrane. Here, the cation activity coefficients in three types of CEMs are calculated according to Manning's counter-ion condensation model. In this model, the Manning parameter ( ξ ) characterizing the dimensionless linear charge density is determined by the average distance between two adjacent fixed sulfonate groups ( b ) and the permittivity of hydrated membranes ( e ). In hydrocarbon polymer-based CEMs, the average distance between fixed sulfonate groups can be estimated by assuming homogeneous distribution of the fixed groups, while in PFSA membranes three representative structure models are employed to estimate this average distance. After accounting for the cation activity coefficients in the membrane, the Mg2+/Na+ cation transport selectivity obtained with the ionic conductivity experimental approach gets closer to, but is still smaller than the selectivity obtained with the ED method. This work shows the importance of cation activity coefficients in the membrane phase in interpreting the membrane transport properties, and complements the proposed conductivity approach to characterize the counter-ion selectivity of ion exchange membranes.

Three distinct operational conditions, namely, ohmic, limiting current, and electroconvection region, respectively, can be created by applying different electric fields during ED operations. The fundamental of cation transport under ohmic and limiting current is well understood, however, the mechanism on cation transport under electroconvection is unclear. In order to clarify the feasibility of operating ED under electroconvection for the treatment of industrial wastewater (copper ion as the target pollutant), the methods of current–voltage profiling (C–V curve) and electrochemical impedance spectroscopy (EIS) were used to study the transport characteristics of Cu2+ through a cationic exchange membrane (CEM). The relevant operational parameters obtained above under electroconvection conditions were applied to a continuous ED system as to investigate the removal efficiency of Cu2+-containing wastewater. Results indicated that ED system operated under electroconvection conditions was able to achieve high Cu2+ removal efficiency (around 74% in 4-min treatment) at high electricity efficiency as the theoretical calculation (based on Cu2+ transport number close to 1.0). The pH of copper wastewater in the ED system decreased slightly from 4.7 to 4.0 under electroconvection operation. The interface at the membrane-water was perturbed by the electroconvection operation, which facilitated ions transport across the membrane. An equivalent circuit composed of the Rs, Cm and Rm (parallel circuit representing the CEM), and constant phase element described well the Cu2+ transport behavior in the membrane-solution system according to the p value is greater than 1.0.

In the present work, a new methodology for improving the ionic conductivity and cation transport properties of polymer electrolytes have been synthesized by adding bulky anion based novel lithium bisnonafluoro-1-butanesulfonimidate salt and characterized for its applications in lithium ion batteries. The self-standing solid polymer electrolyte films exhibit excellent mechanical, thermal, and electrochemical stability. The ion–polymer interactions are examined thoroughly by ATR Fourier Transform-Infra Red Spectroscopy. The solid polymer electrolyte prepared with EO/Li ratio 14 exhibits a highest ionic conductivity of 10−4 S cm−1 at 333 K. Also, it achieves a maximum lithium transference number of 0.31 and it is electrochemically stable in the scanned electrochemical window. This new type of polymer electrolytes with high ion conductivity and improved mechanical properties paves way to be a potential candidate along with lithium anode and LiCoO2 cathode in the lithium ion batteries.

Background The Na+/Ca2 +/Li+ exchanger (NCLX) is a member of the Na+/Ca2 + exchanger family. NCLX is unique in its capacity to transport both Na+ and Li+, unlike other members, which are Na+ selective. The major aim of this study was twofold, i.e., to identify NCLX residues that confer Li+ or Na+ selective Ca2 + transport and map their putative location on NCLX cation transport site. Method We combined molecular modeling to map transport site of NCLX with euryarchaeal H+/Ca2 + exchanger, CAX_Af, and fluorescence analysis to monitor Li+ versus Na+ dependent mitochondrial Ca2 + efflux of transport site mutants of NCLX in permeabilized cells. Result Mutation of Asn149, Pro152, Asp153, Gly176, Asn467, Ser468, Gly494 and Asn498 partially or strongly abolished mitochondrial Ca2 + exchange activity in intact cells. In permeabilized cells, N149A, P152A, D153A, N467Q, S468T and G494S demonstrated normal Li+/Ca2 + exchange activity but a reduced Na+/Ca2 + exchange activity. On the other hand, D471A showed dramatically reduced Li+/Ca2 + exchange, but Na+/Ca2 + exchange activity was unaffected. Finally, simultaneous mutation of four putative Ca2 + binding residues was required to completely abolish both Na+/Ca2 + and Li+/Ca2 + exchange activities. Conclusions We identified distinct Na+ and Li+ selective residues in the NCLX transport site. We propose that functional segregation in Li+ and Na+ sites reflects the functional properties of NCLX required for Ca2 + exchange under the unique membrane potential and ion gradient across the inner mitochondrial membrane. General significance The results of this study provide functional insights into the unique Li+ and Na+ selectivity of the mitochondrial exchanger. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech.

Glioblastoma multiforme (GBM) is the high-grade primary glioma in adults. Temozolomide (TMZ), an alkylating agent of the imidazotetrazine series, is a first-line chemotherapeutic drug for clinical therapy. However, the expense of TMZ therapy and increasing drug resistance to TMZ decreases its therapeutic effects. Therefore, our aim was to investigate the detailed molecular mechanisms of TMZ-mediated cytotoxicity to enhance the efficacy of TMZ in clinical GBM therapy. First, TMZ-mediated gene expression profiles and networks in U87-MG cells were identified by transcriptome microarray and bioinformatic analyses. Cation transport regulator-like protein 1 (CHAC1) was the most highly TMZ-upregulated gene. Overexpression and knockdown of CHAC1 expression significantly influenced TMZ-mediated cell viability, apoptosis, caspase-3 activation, and poly(ADP ribose) polymerase (PARP) degradation. The c-Jun N-terminal kinase (JNK)1/c-JUN pathway was identified to participate in TMZ-upregulated CHAC1 expression via transcriptional control. Furthermore, CHAC1 levels were significantly decreased in GBM cell lines, TCGA array data, and tumor tissues. Overexpression of CHAC1 enhanced glioma apoptotic death via caspase-3/9 activation, PARP degradation, autophagy formation, reactive oxygen species generation, increased intracellular calcium, and loss of the mitochondria membrane potential. Finally, we also identified that TMZ significantly reduced Notch3 levels, which are upregulated in gliomas. TMZ also induced CHAC1 to bind to the Notch3 protein and inhibit Notch3 activation, resulting in attenuation of Notch3-mediated downstream signaling pathways. These results emphasize that CHAC1-inhibited Notch3 signaling can influence TMZ-mediated cytotoxicity. Our findings may provide novel therapeutic strategies for future glioblastoma therapy.

Hybrid composite membranes possess the desired properties than that of the pristine polymeric membranes for fuel cell applications. Phase inversion method was used to entrap silicotungstic acid (STA) particles in Sulfonated Poly Ether Ether Ketone (SPEEK) membranes as a source of protons having a high protonic conductivity at room temperature (0.02–0.1 S/cm). The physico-chemical properties of the hybrid membranes were characterized by SEM-EDX, line scanning, 3D non-contact profilometer, FTIR and XRD techniques. These membranes showed better ion exchange, proton conductivity values and were tested in single chamber microbial fuel cell (SCMFC). In addition, these membranes show decreased oxygen crossover and transport of cations other than protons. Among the various weight percentage (2.5%, 5%, 7.5% and 10%) of STA prepared composite membranes, 7.5% STA + SPEEK showed the highest power density of 207 mWm−2 compared to that of commercial Nafion 117 (47 mWm−2) in the same setup of SCMFC. Overall, the composite membranes proved to be excellent candidates as electrolytes for Microbial Fuel Cell (MFC) applications.

The effect of heat treatment and mechanical deformation at different relative humidity on the transport properties of ion exchange Nafion® type membranes and characteristics of the potentiometric sensors based on them were studied. Methods for treatment of ion-exchange Nafion® type membranes were proposed for obtaining materials with given properties, including materials with improved selectivity of cation transport. An explanation for the changes in the pore and channel system during membrane treatment was proposed. A correlation between water uptake, transport properties of Nafion® type membranes and sensitivity of potentiometric sensors based on Donnan potential (DP) to amino acid and hydroxonium ions was revealed. Thermal treatment of membranes at RH

Reverse electrodialysis of saline solutions (RED) is a renewable energy technology with large potential. Key components in the system are the ion exchange membranes. This work evaluates the efficiency of commercially available anion and cation selective membranes for RED. Their efficiency is often described with the apparent transport number for the ion in question, and this number depends on the salt concentration. It is known since long that the water transference coefficient contributes to the apparent transport number, but much of the recent literature on RED takes the permselectivity as defined by the apparent transport number as a direct measure of the membrane selectivity. The purpose of this paper is to clarify that situation with new data on Fumasep membranes. Concentration cell potentials were measured for anion- and cation exchange membranes from Fumasep (FAD and FKS, respectively, Fumatech, Germany) in the temperature range 12−45°C12−45°C in salt solutions relevant for reverse electrodialysis. The results show that the anion exchange membrane is a perfectly selective ion exchange membrane, and has a water transference coefficient of −6±1−6±1. The cation selective membrane has a cation transport number of 0.93 and a water transference coefficient of 8±8± 7. We suggest that the developers of membranes should pay more attention to the water transference coefficient. To enhance the performance of ion selective membranes and RED, it is beneficial to have water transference coefficients as close to zero as possible. Attribution 4.0 International (CC BY 4.0)

Solid electrolytes are widely employed in devices for energy storage and conversion. Extended defects (grain boundaries, surfaces and dislocations) can generate substantial resistance to ionic transport due to defect segregation. When synthesized through solid state reaction or sintered from powders, solid electrolytes go through thermal annealing processes at high temperatures. It is during these annealing phases that cation transport becomes fast enough to affect the distribution of cation defects near the interface. We developed a kinetic model of the annealing process as it affects the near-interface defect behavior based on the Poisson-Cahn model for predicting defect segregation behavior in concentrated solid solutions. Taking the fluorite-structured solid solution CeO 2 -Gd 2 O 3 as a model system, results reveal that dopant profiles approach equilibrium on a timescale of seconds at 1300 °C and 20%, 1% and 0.1% dopant cation concentration. At lower temperatures, the dopant profile developed much more slowly. The quench temperature is predicted to be around 900 °C, where it requires > 15 h for the dopant profile to reach equilibrium.

Aluminum (Al) toxicity is an important factor in limiting peanut growth on acidic soil. The molecular mechanisms underlying peanut responses to Al stress are largely unknown. In this study, we performed transcriptome analysis of the root tips (0–1 cm) of peanut cultivar ZH2 (Al-sensitive) and 99–1507 (Al-tolerant) respectively. Root tips of peanuts that treated with 100 μM Al for 8 h and 24 h were analyzed by RNA-Seq, and a total of 8,587 differentially expressed genes (DEGs) were identified. GO and KEGG pathway analysis excavated a group of important Al-responsive genes related to organic acid transport, metal cation transport, transcription regulation and programmed cell death (PCD). These homologs were promising targets to modulate Al tolerance in peanuts. It was found that the rapid transcriptomic response to Al stress in 99–1507 helped to activate effective Al tolerance mechanisms. Protein and protein interaction analysis indicated that MAPK signal transduction played important roles in the early response to Al stress in peanuts. Moreover, weighted correlation network analysis (WGCNA) identified a predicted EIL (EIN3-like) gene with greatly increased expression as an Al-associated gene, and revealed a link between ethylene signaling transduction and Al resistance related genes in peanut, which suggested the enhanced signal transduction mediated the rapid transcriptomic responses. Our results revealed key pathways and genes associated with Al stress, and improved the understanding of Al response in peanut.

Wild-type cells of Candida albicans, the most common human fungal pathogen, are able to grow at very low micromolar concentrations of potassium in the external milieu. One of the reasons behind that behaviour is the existence of three different types of K+ transporters in their plasma membrane: Trk1, Acu1 and Hak1. This work shows that the transporters are very differently regulated at the transcriptional level upon exposure to saline stress, pH alterations or K+ starvation. We propose that different transporters take the lead in the diverse environmental conditions, Trk1 being the “house-keeping” one, and Acu1/Hak1 dominating upon K+ limiting conditions. Heterologous expression of the genes coding for the three transporters in a Saccharomyces cerevisiae strain lacking its endogenous potassium transporters showed that all of them mediated cation transport but with very different efficiencies. Moreover, expression of the transporters in S. cerevisiae also affected other physiological characteristics such as sodium and lithium tolerance, membrane potential or intracellular pH, being, in general, CaTrk1 the most effective in keeping these parameters close to the usual wild-type physiological levels.

Lithium extraction from saline water by electrodialysis is an energy-efficient process. Herein, we examined a synergetic impact of amino isophthalic acid (AIPA) and the fixed quaternized groups to produce stable, cost-effective, and efficient zwitterion membranes (ZIMs) via a sol-gel process. We developed different membranes such as QAIPA-10, QAIPA-15, and QAIPA-20 by varying the amount of AIPA from 10 to 20 wt% in the base membrane. It was found that when the amount of AIPA increases, the Li+ flux also improved from 1.66 × 10−10 mol cm−2 s−1 to 33.46 × 10−10 mol cm−2 s−1, respectively. By comparing the membranes based on the various amounts of AIPA, the membrane with 20 wt% (QAIPA-20) had a higher Li+ flux and reasonable permselectivity due to the high WU, CEC as compared with the QAIPA-10, QAIPA-15 and base membranes. To further explore the performance of the QAIPA-20, we also studied various cation systems such as Na+/Mg2+, K+/Mg2+, and H+/Fe2+, respectively. The obtained results proved that AIPA strongly dictates the cation transport channels, hydrophilicity, and repulsive centers of the ZIMs. We may conclude that QAIPA-20 is effective for lithium extraction, water desalination, and acid recovery.

The present paper is devoted to the properties of sulfonated cation-exchange membranes obtained by radiation chemical grafting polymerization of styrene with divinylbenzene on a polyethylene film. The mechanical and transport properties (conductivity, diffusion permeability, and transport numbers) of the membranes obtained with various amounts of a cross-linking agent (0–3.5%) and degrees of polystyrene grafting (23–32%) were investigated in comparison with commercially available membranes, i.e. Nafion® 117 and Neosepta® CMX. Tensile strength values around 15–20 MPa were obtained, and they increased with increasing cross-linker amounts. The conductivity of membranes containing no cross-linking agent reached 8.4·10 −2 Ω −1 cm −1 at 25 °C and high relative humidity. As the amount of the cross-linking agent increased, the water uptake in membranes and their conductivity at high relative humidity decreased, whereas the activation energy of conductivity increased. At low humidity (RH=30%), the water uptake and conductivity increased with increasing amounts of the cross-linking agent. The membranes based on cross-linked polystyrene had low diffusion permeability, while the associated cation transport numbers were higher than those with commercial Nafion® 117 membrane. The calculated theoretical power of reverse electrodialysis batteries based on the best membranes was 10% higher than that of the battery based on the Neosepta® CMX membrane.

Electrodialysis (ED) of solutions containing ternary combination of electrolytes (NaCl, KCl, CaCl2, MgCl2, FeCl3) was carried out. Besides linear velocity of the fluid flowing through the ED cell, physical properties of cations and their interaction with the gel phase of membrane significantly influenced ion transport. The role of concentration polarization was evaluated from limiting current density (LCD) measurement. Theoretically estimated LCD values based on effective diffusivity of each ions and mass transfer coefficients (Sherwood number, Sh correlation) satisfactorily (error ± 5–7%) predicted experimental data. Measurement of transport number, adsorption equilibrium, water uptake and membrane resistance were carried out for each composition to understand the role of cations — membrane equilibrium in ion transport. Cations with higher charges showed reduced transport number, higher adsorption and higher resistance over cation exchange membrane (CEM). Water uptake measurement of equilibrated CEM showed negligible difference when cations of similar charges were interchanged while a meager 1.5% variation was noted when cations of different charges were interchanged.

Cadmium (Cd) is a toxic heavy metal and carcinogen, and its entry into the food chain has serious effects on food security and public health (Uraguchi et al., 2011). As rice is a staple food crop for half of the world’s population, Cd in rice grain has become a major source of dietary Cd for this part of the world. Previous gene discovery efforts for the development of low Cd rice have been linked to cation transport; and for the two most effective genes, OsHMA3 and OsNRAMP5, expression in yeast can cause a Cd-sensitive phenotype (Ueno et al., 2010; Ishikawa et al., 2012).

Cation-conducting, solid-state electrolytes represent a burgeoning focus of battery research, offering the potential for enhanced safety profiles, durability, and wide electrochemical stability windows for high energy density. In this review, we focus primarily on the Li/Na ion conductivity as one of the requirements and limiting factors in development of solid-state electrolytes and secondarily on stability. We highlight experimental and computational methods leading to the current state of understanding of solid-state cation transport, with the goal of drawing out structure-property relationships that lead to design strategies. Topics covered include: descriptors and high-throughput search methodologies including machine learning for identification of fast cation conductors; defect chemistry and its relationship to conduction mechanisms including emerging understanding of frustration, disorder, and concerted ion migration; the impact of strain on transport; factors determining stability; and the role of microstructure and extended defects. We conclude certain sections and the overall review with an outlook for the field, offering ideas for necessary research directions to address knowledge and property gaps.

Two super-concentrated aqueous electrolyes, or water-in-salt electrolytes, comprising the lithium trifluoromethanesulfonate (LiTf-H2O) binary system, and the ternary system with bis(trifluoromethanesulfonyl)-imide (LiTFSI-LiTf-H2O), were analyzed in relation to their conductivity, viscosity, diffusion of all the species and cationic transport number. The conductivity–viscosity and the ionic diffusion-viscosity decoupling were analyzed by means of the Walden law and the Stokes–Einstein relationship, respectively. The results, including those already reported for LiTFSI-H2O, reveal the existence of a significant decoupling of the Li+ mobility from the solution viscosity, while the corresponding anions follow the classical hydrodynamic behavior. The Li+ apparent transport number, derived from the self-diffusion coefficients measured by NMR, increases with concentration, due to the decoupling. These facts strongly support the formation of two types of nano-domains in the superconcentrated salt solutions with different mobility characteristics: a region formed by a net of anions with restricted mobility, percolated by clusters of reduced local viscosity that boost the mobility of Li+ ions. Finally, the difference between the experimental conductivity and that calculated using the Nernst–Einstein equation was rationalized in terms of the velocity correlation and resistance coefficients calculated using the measured transport coefficients.

Rectified current-voltage curves were observed by micro-hole voltammetry in various concentrations of sodium ion electrolyte for transport through a micro-hole and a cationic exchange membrane (Nafion). Data suggest a linear current-concentration relation, implying electric migration-control. The rectification is observed as difference in current-potential slopes at positive and at negative applied voltages. The voltammograms are analyzed quantitatively in the context of Ohm's law as a function of both the geometry of the micro-hole and of the entire cell. The conductivity in the direction of the ion transport from the micro-hole to Nafion, corresponding to the lower conductance (closed diode), is proportional both to the cross-section area of the micro-hole and to the inverse micro-hole length. This is consistent with control by electro-migration within the micro-hole. In contrast, the conductivity in the opposite cation transport direction (open diode) is almost independent of the micro-hole geometry but varies with the length of the glass tube of the cell. The current-potential slope is consistent with the value calculated for the NaCl concentration and the geometry of the measurement cell. Under these conditions, the micro-hole is filled with a high concentration of NaCl as the flux of Na+ from the Nafion to the hole, and the high concentration causes the migration current larger that the current in the opposite direction. Consequently, the rectification ratio can be enhanced by careful design of both (i) the cell geometry including ion-exchange membranes and (ii) the micro-hole geometry rather than nano-scaled chemistry in holes.

Lithium/sodium titanates usually demonstrate high ionic conductivity, and people sometimes view them as alternative anode materials for high power battery applications. In this work, we introduce a different amount of Mo6+ self-doping in the Ti sites of Na2Li2Ti6O14 via a facile solid-state reaction method. The electrode specific capacity, cycle life and rate capability were significantly improved due to the enhanced charge transport property. By XRD refinement and XPS characterization, it is confirmed that Mo6+ is successfully doped into Na2Li2Ti6O14. Through optimization of doping level, Na2Li2Ti5.9Mo0.1O14 exhibits superior electrochemical performance, which could deliver a reversible capacity of 206 mAh·g−1 with capacity retention of 81.1% after 200 cycles, even at a current density of 500 mA·g−1. The cation transport and conductivity in Na2Li2Ti5.9Mo0.1O14 is investigated from thermodynamic and kinetic aspects. By reducing particle size, Na2Li2Ti5.9Mo0.1O14 exhibits the best rate-capability. Therefore, Na2Li2Ti5.9Mo0.1O14 is a promising high-rate anode material for future fast charging applications.

Summary The family of cystathionine-β-synthase (CBS)-pair domain divalent metal cation transport mediators (CNNMs) is composed of four integral membrane proteins associated with Mg2+ transport. Structurally, CNNMs contain large cytosolic regions composed of a CBS-pair and a cyclic nucleotide-binding homology (CNBH) domain. How these regulate Mg2+ transport activity is unknown. Here, we determined the crystal structures of cytosolic fragments in two conformations: Mg2+-ATP-analog bound and ligand free. The structures reveal open and closed conformations with functionally important contacts not observed in structures of the individual domains. We also identified a second Mg2+-binding region in the CBS-pair domain and a different dimerization interface for the CNBH domain. Analytical ultracentrifugation and isothermal titration calorimetry experiments revealed a tight correlation between Mg2+-ATP binding and protein dimerization. Mutations that blocked either function prevented cellular Mg2+ efflux activity. The results suggest Mg2+ efflux is regulated by conformational changes associated with Mg2+-ATP binding to CNNM CBS-pair domains.

Electrodialysis (ED) technique is a typical and promising membrane process, for applications like water treatment and ion separation. Especially, the separation between monovalent and multivalent cations is a current central issue in many industries and academic researches. Herein, a series of novel cation exchange membranes were prepared from quaternized polyaniline modified sulfonated polyphenyl sulfone (SPPSU) by in-situ polymerization-deposited polyaniline followed by quaternizing with methyl iodide. Restricted divalent cation penetration and regulated monovalent cation transport were achieved by elevating the kinetic effect of electrostatic repulsion and narrowing water channel. Importantly, positive charge density of modification layer could be adjusted by controlling the degree of quaternization, which was accompanied by the change of water channel. When evaluated in a simulated mixed salt system (Mg2+/Na+ and Mg2+/Li+), the optimal quaternized polyaniline membrane exhibited a higher perm-selectivity (PNaMg=4.1, PLiMg=1.75) than initial polyaniline modified cation exchange membrane (PNaMg=0.8, PLiMg=0.75), and commercial monovalent-selective cations exchange membrane CIMS (PNaMg=3.56, PLiMg=1.11). This presented strategy is straightforward and effective, demonstrating the effect of surface positive charge layer on perm-selectivity.

Rutile TiO 2 was synthesized using the sol gel method and used for the preparation of polymer composite electrolyte membrane of TiO 2 +SPEEK. The composite membranes prepared by solvent casting method showed improved oxygen mass transfer coefficient values and the transport of cations other than protons. The antifouling property of the composite membranes was observed in SEM images which were additionally supported by hemocytometer results. The improved ion exchange and water absorption capacity of composite membranes showed enhanced proton conductivity and electrochemical properties for the composite membranes. The prepared composite membranes were evaluated in single chamber microbial fuel cell and the results were compared with that of the Nafion 117 ® under similar conditions. The results revealed that all the prepared composite membranes showed higher maximum power density and current density than that of the commercially available Nafion117 ® . Among the prepared membranes, SPEEK+7.5% TiO 2 composite membrane showed the highest power density (98.1 mW/m 2 ) and current density (300 mA/m 2 ) along with high proton conductivity, antifouling property.

Bothrops jararacussu venom drastically decreases sarcoplasmic Ca(2+)-ATPase (SERCA) protein expression in vivo and inhibits its activity in vitro, in contrast to a slight increase of Na(+)/K(+)-ATPase expression in murine EDL. We investigated the effect of myotoxins bothropstoxin-I and/or -II (BthTX-I, BthTX-II and BthTX-I+II) on this model. No changes were seen in SERCA1, SERCA2 and Na(+)/K(+)-ATPase α1 protein expression as well as (2+)Ca-ATPase activity, but BthTX-II (1 μg/g) reduced Na(+)/K(+)-ATPase α2 expression by 50% one day after perimuscular injection. Interestingly, BthTX-II inhibited Ca(2+)-ATPase activity (IC50 around 6 nM). Our findings suggest that only BthTX-II affects ion transport ATPases, being a potent SERCA inhibitor and a putative target for antivenom drug development.

Robust oligopeptides that mimic natural ion channels are attractive for use as molecular switches or model systems to study ion transport. Herein, we report octapeptides derived from aminobenzoic acid and l/d amino acids. Two of the alanine containing peptides were found to be most active and the peptide containing p-aminobenzoic acid was found to be most active (2.4 times its m-analog). Experimental studies indicate the peptides do not transport halides and transport alkali metal ions. � 2015 Elsevier Ltd. All rights reserved.

Microbial fuel cells (MFCs) are bio-electrochemical devices that couple organic carbon removal from wastewater and electricity production. Full-scale application of MFCs in a wastewater treatment plant (WWTP) requires high surface, lowcost electrodes to maximize microbial growth and power output. In this study, a high surface MFC anode is constructed by interlacing carbon yarn with stainless steel. The anode is arranged in a double-air cathode MFC configuration with 6 ± 1 Ω internal resistance. When closed on 100 Ω external resistances in batch mode, the MFCs produce maximum power densities of 621 ± 17 and 364 ± 11 mW m −2 for domestic and distillery wastewater, respectively. The chemical oxygen demand (COD) removal is 68% and 58% with a columbic efficiency of 47% and 27% for domestic and distillery wastewater, respectively. The biofouling layer on the Nafion membrane is twofold thicker in the domestic wastewater MFC, thereby suggesting that the power output and COD removal in distillery wastewater MFC are not limited by the cation transport across the membrane, but rather by the chemical composition of the distillery wastewater that does not support an efficient electrochemically active microbial community.

The colonic epithelium is a highly dynamic system important for the regulation of ion and water homeostasis via absorption and secretion and for the maintenance of a protective barrier between the outer milieu and the inside of the body. These processes are known to gradually change along the length of the colon, although a complete characterization at the protein level is lacking. We therefore analyzed the membrane proteome of isolated human (n = 4) colonic epithelial cells from biopsies obtained via routine colonoscopy for four segments along the large intestine: ascending, transverse, descending, and sigmoid colon. Label-free quantitative proteomic analyses using high-resolution mass spectrometry were performed on enriched membrane proteins. The results showed a stable level for the majority of membrane proteins but a distinct decrease in proteins associated with bacterial sensing, cation transport, and O-glycosylation in the proximal to distal regions. In contrast, proteins involved in microbial defense and anion transport showed an opposing gradient and increased toward the distal end. The gradient of ion-transporter proteins could be directly related to previously observed ion transport activities. All individual glycosyltransferases required for the O-glycosylation of the major colonic mucin MUC2 were observed and correlated with the known glycosylation variation along the colon axis. This is the first comprehensive quantitative dataset of membrane protein abundance along the human colon and will add to the knowledge of the physiological function of the different regions of the colonic mucosa. Mass spectrometry data have been deposited to the ProteomeXchange with the identifier PXD000987.

Metabolic intermediates, such as succinate and citrate, regulate important processes ranging from energy metabolism to fatty acid synthesis. Cytosolic concentrations of these metabolites are controlled, in part, by members of the SLC13 gene family. The molecular mechanism underlying Na+-coupled di- and tricarboxylate transport by this family is understood poorly. The human Na+/dicarboxylate cotransporter NaDC3 (SLC13A3) is found in various tissues, including the kidney, liver, and brain. In addition to citric acid cycle intermediates such as α-ketoglutarate and succinate, NaDC3 transports other compounds into cells, including N-acetyl aspartate, mercaptosuccinate, and glutathione, in keeping with its dual roles in cell nutrition and detoxification. In this study, we construct a homology structural model of NaDC3 on the basis of the structure of the Vibrio cholerae homolog vcINDY. Our computations are followed by experimental testing of the predicted NaDC3 structure and mode of interaction with various substrates. The results of this study show that the substrate and cation binding domains of NaDC3 are composed of residues in the opposing hairpin loops and unwound portions of adjacent helices. Furthermore, these results provide a possible explanation for the differential substrate specificity among dicarboxylate transporters that underpin their diverse biological roles in metabolism and detoxification. The structural model of NaDC3 provides a framework for understanding substrate selectivity and the Na+-coupled anion transport mechanism by the human SLC13 family and other key solute carrier transporters. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

La- and Ni-site cation transport was investigated by inter-diffusion couples in Sr- and Cu-substituted La 2 NiO 4+δ (LNO) systems. The diffusion couples between La 1.9 Sr 0.1 NiO 4+δ –Nd 1.9 Sr 0.1 NiO 4+δ , La 2 Ni 0.8 Cu 0.2 O 4+δ –Nd 2 Ni 0.8 Cu 0.2 O 4+δ and La 1.9 Sr 0.1 NiO 4+δ –La 1.9 Sr 0.1 CuO 4+δ were annealed for 200–643 h in dry air at 950–1300 °C. Electron Probe Micro Analysis (EPMA) was used to obtain the concentration profiles of the inter-diffusing cations. The solution of Fick's second law for constant source and the Whipple–Le Claire equation were applied for analysis of bulk and grain boundary diffusion, respectively. The obtained results are in good agreement with our previous investigation of cation diffusion in un-substituted LNO, where La- and Ni-site cations have essentially comparable diffusivities in the bulk material and Ni-site diffusion is strongly enhanced along grain boundaries. The enhanced grain boundary diffusion has been visualised by elemental mapping of the cross-section of La 1.9 Sr 0.1 NiO 4+δ –La 1.9 Sr 0.1 CuO 4+δ diffusion couples. The extracted activation energies are 223 ± 15 and 267 ± 14 kJ/mol for La-site bulk diffusion in Sr- and Cu-substituted LNO, respectively, and 446 ± 43 and 369 ± 31 kJ/mol for Ni-site bulk and grain boundary diffusion, respectively, in Cu-substituted LNO. Possible causes for similar bulk and enhanced grain boundary diffusivities of the Ni-site despite higher activation energies as compared with La-site bulk diffusion are discussed.

Background Euphorbia factor L1 (EFL1) is a lathyrane-type diterpenoid from the medicinal herb Euphorbia lathyris L., and has been reported with intestinal toxicity, but the potential mechanisms remain unknown. Purpose The objective of this study was to investigate the intestinal toxicity of EFL1 and the underlying mechanisms using nematode Caenorhabditis elegans. Methods C. elegans were exposed to 0–200 μM EFL1 for 72 h, then the survival rate, body length and body width, locomotion and chemoreception behavior, intestinal ROS and lipofuscin accumulation, intestinal permeability, and defecation rhythm were detected. The γ-aminobutyric acid（GABA) energic neurons AVL and DVB were shown via green fluorescent protein under a laser scanning confocal microscope. The structure of GABA transporter UNC-47 were predicted by homology modeling, and the interaction between EFL1 and UNC-47 was simulated by molecular docking. The mRNA expression of genes related to oxidative stress, intestinal permeability and defecation after EFL1 exposure were detected by RT-qPCR. Results EFL1 did not induce lethality of nematodes. The general toxicity was characterized by abnormal growth, locomotion and chemoreception. The intestinal barrier was leaky, due to down-regulated cell junction and active cation transport. The mean defecation cycle length in nematodes was decreased, relating to disorder vesicular and ion transport, enhanced rhythm behavior and muscle contraction. The dysfunctional defecation also attributed to injured UNC-47 protein, as well as GABAergic neurons AVL and DVB. Excessive ROS and lipofuscin accumulation were observed in intestine, along with activation of antioxidant enzymes of SOD, COQ7 and CAT. Conclusion This study elucidated the EFL1-induced intestinal toxicity in nematodes, characterized as leaky intestinal barrier and accelerated defecation behavior. The underlying mechanisms were involved in oxidative stress, cell junctions, transportation, rhythm behavior, muscle contraction, and GABAergic neurons.

Four mRNA variants in pooled cDNA samples of the glassy-winged sharpshooter, Homalodisca coagulata, encoding a putative regulator of cation transporters were identified. RT-PCR showed that the hc-chaC variants were expressed during different stages of insect development and in different tissues and sexes. Structural analysis of the hc-chaC gene indicated that intron and exon sequences of the mRNA variants were identical, and similar to chaC-like genes of other insects. The Hc-ChaC protein (22.5 kDa) contained the conserved FGYGSL K+-binding motif near its amino-terminus, and the carboxy-terminal region contained two coiled-coil motifs, which had similarity to the PDZ domain present in well-characterized Na+/H+ exchanger regulatory factors. Our analyses suggest that Hc-ChaC is a regulator of K+ transporters such as K+/H+ antiporters.