Passage Of Ions Research Articles

Cellulose filter papers derived separator featuring effective ion transferring channels for sodium-ion batteries

As a basic component of batteries, separators are proposed to apart the two electrodes while allowing the transport of ionic charge carriers. Cellulose separators have attracted tremendous attention due to their excellent thermal stability and wettability. In this study, we prepare all-cellulose composite (ACC) separators coated with Zn5(OH)8Cl2·H2O (ZHC) particles. The surface of the cellulose filter paper is partially dissolved by the 65% ZnCl2 solution, forming a tortuous and porous all-cellulose composite membrane. At the same time, ZHC is generated in situ on the surface during the removal of residual ZnCl2 from the cellulose, which effectively promotes the passage of a sodium ion (Na+) and substantially improves the cycling performance of the batteries. Density functional theory (DFT) calculations demonstrate that suitable adsorption energy on ZHC is favorable for promoting Na+ transport. The corresponding ACC separator exhibits high ionic conductivity (2.75 mS/cm) and Na+ transference number (0.82), correspondingly the assembled Na/hard carbon half-cells show an excellent reversible specific capacity (315 mA h/g at 25 mA/g) and cycling stability (the retention is 97.77% after 50 cycles at 50 mA/g), outperforming the glass fiber separator in both sodium-ion half-cell and full-cell.

Transcriptome analysis reveals the high temperature induced damage is a significant factor affecting the osmotic function of gill tissue in Siberian sturgeon (Acipenser baerii)

BackgroundMaintaining osmotic equilibrium plays an important role in the survival of cold-water fishes. Heat stress has been proven to reduce the activity of Na+/K+-ATPase in the gill tissue, leading to destruction of the osmotic equilibrium. However, the mechanism of megatemperature affecting gill osmoregulation has not been fully elucidated.ResultsIn this study, Siberian sturgeon (Acipenser baerii) was used to analyze histopathological change, plasma ion level, and transcriptome of gill tissue subjected to 20℃, 24℃and 28℃. The results showed that ROS level and damage were increased in gill tissue with the increasing of heat stress temperature. Plasma Cl− level at 28℃ was distinctly lower than that at 20℃ and 24℃, while no significant difference was found in Na+ and K+ ion levels among different groups. Transcriptome analysis displayed that osmoregulation-, DNA-repair- and apoptosis-related terms or pathways were enriched in GO and KEGG analysis. Moreover, 194 osmoregulation-related genes were identified. Amongst, the expression of genes limiting ion outflow, occluding (OCLN), and ion absorption, solute carrier family 4, member 2 (AE2) solute carrier family 9, member 3 (NHE3) chloride channel 2 (CLC-2) were increased, while Na+/K+-ATPase alpha (NKA-a) expression was decreased after heat stress.ConclusionsThis study reveals for the first time that the effect of heat stress on damage and osmotic regulation in gill tissue of cold-water fishes. Heat stress increases the permeability of fish’s gill tissue, and induces the gill tissue to keep ion balance through active ion absorption and passive ion outflow. Our study will contribute to research of global-warming-caused effects on cold-water fishes.

Connexins Biology in the Pathophysiology of Retinal Diseases.

Connexins (Cx) are a family of transmembrane proteins that form gap junction intercellular channels that connect neighboring cells. These channels allow the passage of ions and other biomolecules smaller than 1kDa, thereby synchronizing the cells both electrically and metabolically. Cxs are expressed in all retinal cell types and the diversity of Cx isoforms involved in the assembly of the channels provides a functional syncytium required for visual transduction. In this chapter, we summarize the status of current knowledge regarding Cx biology in retinal tissues and discuss how Cx dysfunction is associated with retinal disease pathophysiology. Although the contribution of Cx deficiency to retinal degeneration is not well understood, recent findings present Cx as a potential therapeutic target. Therefore, we will briefly discuss pharmacological approaches and gene therapies that are being explored to modulate Cx function and fight sight-threatening eye diseases.

The impact of pathogenic and artificial mutations on Claudin-5 selectivity from molecular dynamics simulations

Tight-junctions (TJs) are multi-protein complexes between adjacent endothelial or epithelial cells. In the blood-brain-barrier (BBB), they seal the paracellular space and the Claudin-5 (Cldn5) protein forms their backbone. Despite the fundamental role in brain homeostasis, little is known on Cldn5-based TJ assemblies. Different structural models were suggested, with Cldn5 protomers generating paracellular pores that restrict the passage of ions and small molecules. Recently, the first Cldn5 pathogenic mutation, G60R, was identified and shown to induce Cl−-selective channels and Na+ barriers in BBB TJs, providing an excellent opportunity to validate the structural models. Here, we used molecular dynamics to study the permeation of ions and water through two distinct G60R-Cldn5 paracellular architectures. Only the so-called Pore I reproduces the functional modification observed in experiments, displaying a free energy (FE) minimum for Cl− and a barrier for Na+ consistent with anionic selectivity. We also studied the artificial Q57D and Q63D mutations in the constriction region, Q57 being conserved in Cldns except for cation permeable homologs. In both cases, we obtain FE profiles consistent with facilitated passage of cations. Our calculations provide the first in-silico description of a Cldn5 pathogenic mutation, further assessing the TJ Pore I model and yielding new insight on BBB’s paracellular selectivity.

Self-reconstruction of highly active NiCo2O4 with triple-continuous transfer of electrons, ions, and oxygen for Zn-air batteries

The prohibitive cost and scarcity of the noble-metal catalysts needed for catalyzing the oxygen reduction/evolution reaction (ORR/OER) in the Zn–air battery (ZAB) limit the commercialization of this clean energy technology. Herein, a noble-metal-free spinel-type NiCo2O4 electrocatalyst with high activity and 3D porous structure is rationally designed by duplexing interface engineering concept through an adaptive combination of surfactant assistance and electrochemical reconstruction processes, resulting in co-enhanced behaviors of overall oxygen electrochemistry in ZABs. As expected, the conventional three-phase electrochemical interface could be expanded into 3D networks in whole air electrode, which allows the 3D triple-continuous passage of electrons, ions, and oxygen, thus boosting the oxygen electrochemistry of OER (1.62 V at Ej = 10) and ORR (0.79 V at E1/2) in 0.1 M KOH electrolyte. Moreover, the ZAB with the as-prepared electrocatalyst demonstrates a low potential gap of 0.77 V and impressive long-term reversibility over 600 h at 5 mA cm−2, surpassing most previous reports. Such superiority is ascribed, in part, to the self-reconstruction of NiOOH-NiCo2O4 interfacial layer with 3D networks during the OER process as observed by in-situ Raman, ex-situ XPS, and SEM, which contributes additionally to the high activity and durability of the air electrode by enhancing the charge and mass transfer in ZABs.

The membrane potential arising from the adsorption of ions at the biological interface.

Membrane theory makes it possible to compute the membrane potential of living cells accurately. The principle is that the plasma membrane is selectively permeable to ions and that its permeability to mobile ions determines the characteristics of the membrane potential. However, an artificial experimental cell system with an impermeable membrane can exhibit a nonzero membrane potential, and its characteristics are consistent with the prediction of the Goldman-Hodgkin-Katz eq., which is a noteworthy concept of membrane theory, despite the membrane's impermeability to mobile ions. We noticed this troublesome facet of the membrane theory. We measured the potentials through permeable and impermeable membranes where we used the broad varieties of membranes. Then we concluded that the membrane potential must be primarily, although not wholly, governed by the ion adsorption-desorption process rather than by the passage of ions across the cell membrane. A theory based on the Association-Induction Hypothesis seems to be a more plausible mechanism for the generation of the membrane potential and to explain this unexpected physiological fact. The Association-Induction Hypothesis states that selective ion permeability of the membrane is not a condition for the generation of the membrane potential in living cells, which contradicts the prediction of the membrane theory. Therefore, the Association-Induction Hypothesis is the actual cause of membrane potential. We continued the theoretical analysis by taking into account the Association-Induction Hypothesis and saw that its universality as a cause of potential generation mechanism. We then concluded that the interfacial charge distribution is one of the fundamental causes of the membrane potential.

Rapid metal speciation of cell culture media using reversed-phase separations and inductively coupled plasma optical emission spectrometry.

Cell culture media metal content is critical in mammalian cell growth and monoclonal antibody productivity. The variability in metal concentrations has multiple sources of origin. As such, there is a need to analyze media before, during, and after production. Furthermore, it is not the simple presence of a given metal that can impact processes, but also their chemical form that is, speciation. To a first approximation, it is instructive to simply and quickly ascertain if the metals exist as inorganic (free metal) ions or are part of an organometallic complex (ligated). Here we present a simple workflow involving the capture of ligated metals on a fiber stationary phase with passage of the free ions to an inductively coupled plasma optical emission spectrometry for quantification; the captured species are subsequently eluted for quantification. This first level of speciation (free vs. ligated) can be informative towards sources of contaminant metal species and means to assess bioreactor processes.

Structural basis for the activation of the lipid scramblase TMEM16F

TMEM16F, a member of the conserved TMEM16 family, plays a central role in the initiation of blood coagulation and the fusion of trophoblasts. The protein mediates passive ion and lipid transport in response to an increase in intracellular Ca2+. However, the mechanism of how the protein facilitates both processes has remained elusive. Here we investigate the basis for TMEM16F activation. In a screen of residues lining the proposed site of conduction, we identify mutants with strongly activating phenotype. Structures of these mutants determined herein by cryo-electron microscopy show major rearrangements leading to the exposure of hydrophilic patches to the membrane, whose distortion facilitates lipid diffusion. The concomitant opening of a pore promotes ion conduction in the same protein conformation. Our work has revealed a mechanism that is distinct for this branch of the family and that will aid the development of a specific pharmacology for a promising drug target.

On the temporal selectivity of desalination for a porous composite graphene-copper membrane (GCuM): A molecular dynamics study

The concept of the temporal selectivity breaks the spatial selectivity-based paradigm of permeability and selectivity in membrane separation technology, and its realization can provide simultaneous efficient salt rejection and high permeability with large pores. In this work, a rotating centrifuge model made of porous copper foil covered with porous graphene is designed to explore the possibility to realize the temporal selectivity on a porous composite graphene‑copper membrane (GCuM) in a molecular dynamics study. The results show that the permeability of porous rotating GCuM increases up to 156 L/cm2/day/MPa with a salt rejection larger than 90 %, which is 2.6 to 1000 times larger than the commercial and other advanced reverse osmosis membranes. The boundary slip velocity between the seawater-GCuM interface inhibits the passage of salt ions, resulting in high salt rejection even in the case of 2–4 nm diameter pores. The stability of the ionic hydration shell and the energy barrier of the ions passing through the pores increase with the increase of the angular velocity, which explains the influence of the boundary slip velocity on the salt rejection from the molecular mechanism. The geometric relation that governs the temporal selectivity principle on porous rotating GCuM has been further derived to explain pore size, membrane thickness, and hydrated ion mass on high permeability and salt rejection. The findings further verify and expand the application scope of the temporal selectivity mechanism, and will promote the application of graphene-based nanoporous centrifuges.

Structural insights into light-driven anion pumping in cyanobacteria

Transmembrane ion transport is a key process in living cells. Active transport of ions is carried out by various ion transporters including microbial rhodopsins (MRs). MRs perform diverse functions such as active and passive ion transport, photo-sensing, and others. In particular, MRs can pump various monovalent ions like Na+, K+, Cl−, I−, NO3−. The only characterized MR proposed to pump sulfate in addition to halides belongs to the cyanobacterium Synechocystis sp. PCC 7509 and is named Synechocystis halorhodopsin (SyHR). The structural study of SyHR may help to understand what makes an MR pump divalent ions. Here we present the crystal structure of SyHR in the ground state, the structure of its sulfate-bound form as well as two photoreaction intermediates, the K and O states. These data reveal the molecular origin of the unique properties of the protein (exceptionally strong chloride binding and proposed pumping of divalent anions) and sheds light on the mechanism of anion release and uptake in cyanobacterial halorhodopsins. The unique properties of SyHR highlight its potential as an optogenetics tool and may help engineer different types of anion pumps with applications in optogenetics.

Investigation on the chloride ion erosion mechanism of cement mortar in coastal areas: From experiments to molecular dynamics simulation

• The influences of chloride ions on the phsysical and mechanical properties of cement mortar were analyzed. • The mechanism of bound and free chloride ions on the cement mortars properties were investigated in long-term erosion. • The effect of chloride ions in pores on C S H adsorption was investigated by molecular dynamics simulation. Chloride salts in groundwater are a serious threat to the durability of underground reinforced concrete structures in coastal areas. In order to effectively improve the durability performance of underground structural concrete in coastal areas, physical and mechanical properties such as compressive strength, water absorption rate and chloride ion permeability of cement mortar were studied. The influence laws of mineral additives such as fly ash, ground granulated blast-furnace slag and chloride ions on the relevant properties of cement mortar were analyzed. The effect of chloride ions on these physical and mechanical properties was investigated. The main hydration product categories of cement mortar were derived using microscopic analysis (XRD). The internal microstructure and the surface morphology of cement mortar were obtained by scanning electron microscopy (SEM). The effect of chloride ions in pores on C S H adsorption was studied by using molecular dynamics simulations. The results showed that chloride ion erosion increased the compressive strength of cement mortars doped with FA and GGBS at 28, 100, and 180 days by 2.76 %, 14.32 %, and 7.83 %, respectively. Chloride ion erosion moderately increased the compressive strength of cement mortar doped with FA and GGBS at all curing period. After chloride ion erosion, the electric fluxes of the four groups of specimens at 180 days decreased by 30.37 %, 31.64 %, 23.22 % and 17.41 %, respectively. After the addition of mineral additive, the bound chloride ions changed the influence law of water absorption rate of cement mortar, and reduced the electric flux of cement mortar. The molecular dynamics simulations revealed that the chloride ions in the pores weakened the physical adsorption of external chloride ions by C S H, resulting in the easier passage of external chloride ions through the pores. Microscopic analysis showed that the Friedel's salt generated by chloride ions attacking the cement-based materials filled communicating pores, which may be one of the reasons for the reduced electric flux of the cement mortar.

Active fast ion charge exchange measurements using a neutral particle analyzer and multiple beam species in C-2W.

In order to measure the fast ion using neutral particle analyzers (NPAs) in the low neutral density core region of a magnetic confinement fusion device, active change exchange measurements are often performed using a neutral beam (NB) as a charge-exchange (CX) target. One of the complications with this approach is that an NB injected as a CX target can also contribute to the total fast ion source. C-2W has a unique solution to this difficulty in that it is equipped with both eight NB injectors, which can inject beams of different particle species, and an electro-magnetic NPA (EM-NPA), which can measure multiple ion species simultaneously. This enables the active and passive fast ion CX components to be clearly distinguished. The decrease in amplitude of the CX spectra when a hydrogen NB is terminated was clearly observed by the EM-NPA in both hydrogen and deuterium channels. This reduction of observed fast ion flux was mainly caused by the diminished fast ion source, not crosstalk or a general reduction in fast ion confinement. As an example application of this technique on C-2W, fast ion behavior during a periodic density drop is explored. The large difference between the active and passive CX components of the EM-NPA signals clearly demonstrates the usefulness of the active fast ion CX measurement.

Thermal conductivity of Al2O3 irradiated with swift heavy ions

• Comprehensive study of thermal conductivity under swift heavy ion irradiation. • Very strong effect of a narrow highly damaged track core on heat propagation. • Classical thermal transport model may be not valid for nanometric SHI tracks. Thermal transport in α -Al 2 O 3 irradiated with 167 MeV Xe ions is studied within direct method based on the Fourier law implemented into classical molecular dynamics. Formation of defective regions as a result of ion passages is described using the original multiscale approach developed in previous works. Degradation of the thermal conductivity coefficient of single-crystalline alumina with ion fluence shows reasonable agreement with the experimental thermoreflectance data. The applied method demonstrated good applicability in the considered case and allowed to distinguish effects of discontinuous crystalline tracks on thermal conductivity of the alumina target. It was surprisingly observed that a nanometric highly damaged core of swift heavy ion tracks strongly affect the heat transport in the irradiated material, which is in contradiction with classical Rayleigh model.

Enthalpic and Entropic Contributions to Fast Lithium Ion Conduction in Solid-State Aqueous Polymer Electrolytes

Solid-state aqueous polymer electrolytes (SAPEs), a mixture of hydrophilic polymers and an appropriate amount of water, can produce high Li-ion conductivity while maintaining a solid state. Also, they can overcome the limitations of normal solid electrolytes. This study reports that the very high SAPE ionic conductivity (∼10 mS/cm at T = 298.15 K) originates from a low energy barrier (∼0.28 eV) closely correlated with water-filled ion passages in the medium. The low energy barrier is ascribed to a considerable reduction of the enthalpic barrier due to water addition despite a growth of the entropic barrier incurred by the negative nature of entropy change across water tubes. The extremely high ionic conductivity, coupled with an exceptionally low energy barrier, provides a unique advantage to SAPEs over conventional solid electrolytes.

Is conductivity measurement or inductively coupled plasma-atomic emission spectrometry reliable to define rejection of different ions?

Rejection of single salts or ions is a basic and crucial characteristic of nanofiltration (NF) membranes. The simple and most pursued method to quantify the salt concentration has been via conductivity measurement. Pitfalls exist when ions hydrolysis or feed water contains monovalent ions. This could be explained in two possible scenarios: (1) easily hydrolyzed single salts form low charged ions and reduce feed pH, resulting in increased permeate conductivity and low nominal rejection; (2) for membranes with high multivalent ion rejections (>99%) or the concentration of target ions in feed is low, conductivity measurement results in low rejection due to the passage of monovalent ions if deionized water is used for the feed solution. A correction formula by subtracting the concentration of monovalent ions in water to obtain an accurate rejection value is proposed. This work provides an accurate, simple and robust evaluation of rejection for NF membranes, which promotes fair comparison of performance in literature, reliable analysis of separation mechanisms as well as a precise determination of product purity.

Synthesis, biological evaluation and molecular modeling studies of novel 1,2,3-triazole-linked menadione-furan derivatives as P2X7 inhibitors.

The P2X7 receptor (P2X7R) is an ion channel that promotes the passage of ions through the membrane through brief stimulation once activated by ATP, its endogenous opener. However, prolonged stimulation with ATP, which occurs in pathological processes, opens a nonselective pore in the plasma membrane, allowing the passage of large molecules and leading to cytokine release or even cell death. In this sense, the search for new inhibitors for this receptor has attracted a great deal of attention in recent years. Considering the booming of biomass upgrading reactions in recent years and the continued efforts to synthesize biologically active molecules containing the 1,2,3-triazole ring, in the present work, we aimed to investigate whether triazole-linked menadione-furan derivatives could present P2X7R inhibitory activity. The novel compounds were tested for their inhibitory activity on ATP-induced dye uptake in peritoneal macrophages. Some have shown promising results, having displayed IC50 values lower than that of the P2X7R inhibitor BBG. Molecular docking studies also indicated that the active compounds bind to an allosteric site on P2X7R, presenting potential P2X7R inhibition.

Pyrene‐Derived Carbon Nanomembranes Selectively Pass Metal Ions in Water

AbstractDespite the potential environmental benefits, the use of membranes for extracting, reclaiming, and purifying alkali metals from aqueous feedstocks remains challenging due to low inter‐cation selectivity. Two‐dimensional materials equipped with nanoscale pores have revealed intriguing performance in ion separation, but their practical implementation is bottlenecked by the perforation procedures. This work presents electrodialysis experiments with intrinsically porous carbon nanomembranes (CNMs) that are featured by a high areal density of sub‐nanometer channels. The free‐standing membranes prepared from pyrene are shown to have great mechanical strength and a narrow pore size distribution enabling selective passage of metal ions. CNMs can sieve hydrated cations following the order K+ > Na+ > Li+ > Ca2+ > Mg2+, while the K+/Mg2+, Na+/Mg2+, Li+/Mg2+ selectivity amounts to 220, 86, and 13 respectively. It is found that the ion transport selectivity is attributed to the combined effect of the small pore dimensions and electrostatic exclusion induced by surface charges. It has been also observed that the membrane thickness in the range from 3 to 6.5 nm has little impact on the ion transport which suggests interesting implications for ion batteries and other energy conversion systems.

Nanoscale segregation of channel and barrier claudins enables paracellular ion flux

The paracellular passage of ions and small molecules across epithelia is controlled by tight junctions, complex meshworks of claudin polymers that form tight seals between neighboring cells. How the nanoscale architecture of tight junction meshworks enables paracellular passage of specific ions or small molecules without compromising barrier function is unknown. Here we combine super-resolution stimulated emission depletion microscopy in live and fixed cells and tissues, multivariate classification of super-resolution images and fluorescence resonance energy transfer to reveal the nanoscale organization of tight junctions formed by mammalian claudins. We show that only a subset of claudins can assemble into characteristic homotypic meshworks, whereas tight junctions formed by multiple claudins display nanoscale organization principles of intermixing, integration, induction, segregation, and exclusion of strand assemblies. Interestingly, channel-forming claudins are spatially segregated from barrier-forming claudins via determinants mainly encoded in their extracellular domains also known to harbor mutations leading to human diseases. Electrophysiological analysis of claudins in epithelial cells suggests that nanoscale segregation of distinct channel-forming claudins enables barrier function combined with specific paracellular ion flux across tight junctions.

Hierarchical architecture: A novel, facile and cost-efficient strategy to boost electrochemical performance of Li-O2 battery cathodes

The sluggish performance of cathodes, which is eagerly awaiting optimal design, is a major impediment to the practical implementation of lithium-oxygen batteries (LOBs). We present the meticulous design and synthesis of hierarchical porous graphene foam (HPGF) cathodes with various pore size architectures. A novel and facile method was proposed to prepare highly porous Ni foam from which graphene foam with a surface area increase of more than ten times was derived. To enable the transportation of Li+ and O2 species through graphene sheet thickness, Ni(NO3)2 was used as an ignition source to generate adjustable holes in graphene layers, resulting in a tri-continuous passage of electrons, ions, and oxygen. As a result, superior electrochemical performances such as high capacity, good rate capability, and cycling stability (5 percent degradation in 2500 h) were achieved. A pouch-type battery demonstrated good flexibility and a broad application perspective by operating directly in ambient air.

AC Conductivity and dielectric relaxation in Li2O-PbO-As2O3-B2O3 glasses

New Li2O-based oxide glasses containing heavy metal oxide as in the PbO–As2O3–B2O3-Li2O quaternary system were prepared using a melt-quenching method. An impedance spectroscopy technique is used and the Cole – Cole impedance reaction method is used to analyze data. The action of the AC conductivity of these glasses has been studied in the frequency range of 100 Hz to 1 MHz, and the recorded AC results are analysed as a function of temperature using the universal power rule of Jonscher to describe the dispersive conduct of the electric conductivity observed. The frequency reaction of a dielectric constant ε′and a dielectric loss tanδ are investigated according to the temperature. The tanδ is modified to a higher frequency at increasing temperatures, suggesting that dielectric loss in the present glasses is a dipolar relief feature. The presence of PbO results in a decrease in direct current conductivity and a boost in theenergy of activation. It is possibly because of a decreased fraction of charges on the oxygen atoms and a lonely pair existence in the lead atom, both of which obstruct the passage of lithium ion. This assumption is supported by the acconductivity and dielectricity of these glasses.