Channel Pore Research Articles

Steady-state and time-resolved fluorescent methodologies to characterize the conformational landscape of the selectivity filter of K+ channels.

A variety of equilibrium and non-equilibrium methods have been used in a multidisciplinary approach to study the conformational landscape associated with the binding of different cations to the pore of potassium channels. These binding processes, and the conformational changes resulting therefrom, modulate the functional properties of such integral membrane properties, revealing these permeant and blocking cations as true effectors of such integral membrane proteins. KcsA, a prototypic K+ channel from Streptomyces lividans, has been extensively characterized in this regard. Here, we revise several fluorescence-based approaches to monitor cation binding under different experimental conditions in diluted samples, analyzing the advantages and disadvantages of each approach. These studies have contributed to explain the selectivity, conduction, and inactivation properties of K+ channels at the molecular level, together with the allosteric communication between the two gates that control the ion channel flux, and how they are modulated by lipids.

SBA-15 with short-sized channels modified with Fe2O3 nanoparticles. A novel approximation of an efficient adsorbent for As removal in contaminated water

AbstractThe urgent need for technologies to ensure health standards, as per the Sustainable Development Goals established by the United Nations, has prompted research into addressing human health problems associated with chemical contaminants in air, water, and soil. Heavy metals, particularly arsenic, pose significant health risks, with millions of people worldwide exposed to concentrations exceeding recommended limits. Nanostructured materials, including ordered mesoporous substrates such as SBA-15, have shown promise for arsenic removal due to their high surface area and pore characteristics. This study aimed to synthesize a silica mesoporous material with reduced pore channel length to enhance surface area and active sites, thereby improving arsenic removal efficiency. By exploring various surfactant-to-silica precursor ratios, a suitable value was identified to promote the production of shortened SBA-15 particles. These shortened pore channels facilitated the dispersion of iron oxide nanoparticles (Fe2O3) on the SBA-15 surface, resulting in an effective adsorbent that achieved over 95% arsenic removal. The combination of the modified SBA-15 substrate and Fe2O3 nanoparticles demonstrated high efficiency in arsenic removal from aqueous effluents, offering a promising solution to address water pollution and associated health risks.

Nanofibrous Covalent Organic Frameworks Based Hierarchical Porous Separators for Fast‐Charging and Thermally Stable Lithium Metal Batteries

AbstractEngineering multifunctional smart separators are important for the ongoing pursuit of fast‐charging and safe batteries. Herein, a novel nanofibrous covalent organic framework (COF) based separator with well‐designed hierarchical porous channels is fabricated to effectively regulate mass transport for fast‐charging and thermally stable lithium metal batteries (LMBs). Such a hierarchical porous separator consists of electrospun polyacrylonitrile nanofibers with macroporous channels (average diameter of 323 nm) and mesoporous channels (≈7 nm) created between amide‐group‐bonded COF nanoparticles with intrinsic 1.6 nm lithiophilic microporous channels (PAN/AM‐COF). Computational fluid dynamics and density functional theory calculations demonstrate that PAN/AM‐COF can simultaneously facilitate high‐speed and selective transport of Li+, as well as homogeneous deposition of Li, achieving high conductivity (3.33 mS cm−1) and high Li+ transference number (0.79). As a result, Li || LFP full cell with PAN/AM‐COF displays superior cycling stability at 10 C with an acceptable capacity attenuation (0.037% per cycle) over 1000 cycles. Moreover, when operating under an extreme temperature of 100 °C, the Li || LFP full cell with PAN/AM‐COF can still operate stably for 300 cycles at 30 C, highlighting its potential processing scalability for ultrafast‐charging energy storage systems. This study gives insights into designing functional separators for fast‐charging LMBs.

Effect of coal gasification coarse slag on soil water and nutrition at an arid opencast coal mine site in Northwest China

AbstractThough amendment using coal gasification coarse slag (CGCS) has garnered attention, the intrinsic mechanism of how CGCS, a glassy material, works to amend physicochemical properties in the soil is not yet clear. This study aimed to analyze the effects of different CGCS particle sizes on soil water infiltration and nutrient retention, and to identify the relationship between the physicochemical properties of the amended soil and the water nutrient amendment. The continuous infiltration pattern of soil water and plant growth after the amendment was measured using an indoor continuous dynamic soil column simulation experiment and a field pot experiment of CGCS with different particle sizes (0.25, 1, and 2 mm). The CGCS amendment loosened the soil, improved the pore channels, and amended the water infiltration. However, this process was negatively correlated with CGCS particle size. The Kostiakov performed better in simulating soil water infiltration of heterogeneous dump soil. The CGCS amendment had no heavy metal risk and promoted plant growth. Though amendment enhanced nutrients, in terms of soil organic matter (SOM), the presence of C must be verified by a long team of nutrient cycling if it can be transformed into accessible SOM. Therefore, CGCS amended water nutrition by amending the soil's physical structure. Soil pore adsorption improved water nutrient availability and had a positive effect on chemical properties, which promoted crop growth. The amendment effect was greatest at 0.25 mm particle size.

Isoporous Membrane Mediated Imprinting Mass Spectrometry Imaging for Spatially-Resolved Metabolomics and Rapid Histopathological Diagnosis.

Surface-assisted laser desorption/ionization (SALDI) mass spectrometry imaging (MSI) holds great value in spatial metabolomics and tumor diagnosis. Tissue imprinting on the SALDI target can avoid laser-induced tissue ablation and simplifies the sample preparation. However, the tissue imprinting process always causes lateral diffusion of biomolecules, thereby losing the fidelity of metabolite distribution on tissue. Herein, a membrane-mediated imprinting mass spectrometry imaging (MMI-MSI) strategy is proposed using isoporous nuclepore track-etched membrane as a mediating imprinting layer to selectively transport metabolites through uniform and vertical pores onto silicon nanowires (SiNWs) array. Compared with conventional direct imprinting technique, MMI-MSI can not only exclude the adsorption of large biomolecules but also avoid the lateral diffusion of metabolites. The whole time for MMI-based sample preparation can be reduced to 2min, and the lipid peak number can increase from 46 to 113 in kidney tissue detection. Meanwhile, higher resolution of MSI can be achieved due to the confinement effect of the pore channel in the diffusion of metabolites. Based on MMI-MSI, the tumor margins of liver cancer can be clearly discriminated and their different subtypes can be precisely classified. This work demonstrates MMI-MSI is a rapid, highly sensitive, robust and high-resolution technique for spatially-resolved metabolomics and pathological diagnosis.

Temperature-Driven Structural Evolution during Preparation of MCM−41 Mesoporous Silica

This study explores the influence of micelles on the evolution of MCM−41’s pore structure via 24 h hydrothermal treatments in a range of temperatures from 100 °C to 200 °C. MCM−41 was characterized using BET, SAXD, FTIR, TEM, and TG-DSC. The findings demonstrate that with temperature elevation from 100 °C to 160 °C, the micelles undergo expansion, leading to an enhanced lattice constant from 4.50 nm to 4.96 nm and an increase in pore diameter from 3.17 nm to 3.45 nm, while maintaining the structural orderliness of the pore channels. Upon cooling, the reversible contraction of micelles and the strategic addition of water glass contribute to a reduction in pore size. However, at a threshold of 180 °C, the SAXD (100) peak’s half-peak width surges by approximately 40% relative to that at 160 °C, illustrating a progressive disruption of the hexagonal configuration of MCM−41. Coupled with elevated silica dissolution at higher temperatures in an alkaline solution, a total disintegration of the ordered pore structure at 200 °C results in a drastic reduction in the specific surface area to 307 m2/g. These results are beneficial to developing structural transformation mechanisms of MCM−41 materials and designing mesoporous materials via temperature modulation innovatively.

In situ conversion of ZnO anchored on porous carbon foams to antiflexible ZIF-8-X (X = Co or NH2) for sieving linear and mono-branched hexane isomers

Efficient separation of linear hexane from their isomers is a vital petrochemical process to produce high-quality gasoline. Zeolitic imidazolate frameworks-8 (ZIF-8), one of the most famous metal-organic frameworks (MOFs), is a promising separation material due to its special pore size (3.4 Å), whereas the flexible framework limited its separation ability, showing unsatisfied trade-off between adsorption capacity and separation selectivity. Here, we propose a novel strategy of post metal-oxide modification (PMOM) to suppress ZIF-8 flexibility by in situ growth on rigid layer of porous carbon foam (PCF) based the intermediation of anchored ZnO nanoparticles directly obtained from the pyrolysis of sucrose and zinc nitrate mixture. Afterwards, synergistic flexible suppression technology (SFST) was adopted to design antiflexible PCF/ZIFs with mixed-metal and mixed-ligand, including bi-metal PCF/ZIF-8-Co and di-ligand PCF/ZIF-8-NH2. Therein, the tight interfaces generated with benzene-ring inhabited the swinging of linkers and hindered 3-MP entry into the pore channels, showing both remarkable nHex adsorption capacity (q = 2.26 mmol·g−1) and nHex/3-MP selectivity (Su = 9.42). Moreover, bi-component adsorption experiments confirm the practical separation performance and cycling stability, showing promising application in adsorptive separation processes.

Effect of magnetic field on viscous flow through porous wavy channel using boundary element method

AbstractThe study aims to investigate the effect of uniform inclined magnetic field on two‐dimensional flow of a steady, viscous incompressible fluid at low Reynolds number through a porous wavy channel. We consider a channel having sinusoidal walls filled with a fully saturated porous medium. The porous regime is assumed to be homogenous and isotropic. The viscous flow through a porous regime is governed by Brinkman equation, where the viscous forces are dominant. This allows us to assume the no‐slip boundary conditions at the walls of the wavy channel. Boundary element method (BEM) based on non‐primitive variables namely, stream function‐vorticity variables is used to solve the Brinkman equation. Further, we consider a very small magnetic Reynolds number to eliminate the magnetic‐induced equation. We analyzed that an increase in Hartman number, porosity, and reduction in inclination angle of magnetic field, wave amplitude, and Darcy number led to a reduction in horizontal velocity, whereas an increase in Hartman number, porosity, wave amplitude, and decrease in Darcy number and angle of inclination of magnetic field led to an increase in vertical velocity. Moreover, the flow reversal phenomena occur in the vicinity of the crest regime of the porous wavy channel for high wave amplitude and low Hartman number. The proposed investigation has widespread applications, such as drug delivery systems to target the drug precisely, magneto‐hydrodynamic pumps to regulate the blood flow in artificial hearts to reduce the risk of blood clotting, and so forth.

A Porphyrinic Metal-Organic Framework with Cooperative Adsorption Domains for PFAS Removal from Water.

The removal of toxic poly- and perfluoroalkyl substances (PFAS) as persistent pollutants from wastewater is imperative but challenging for water remediation. Many adsorbents including activated carbon, biochar, and clay minerals have been investigated for PFAS removal, but most of these materials are faced with high cost or/and low efficiency. The use of metal-organic frameworks (MOFs) as sorbents is attractive for efficient removal of PFAS due to their tailor-made structures and high surface areas. Herein, we synthesized, characterized a water stable Zr-based porphyrinic MOF (PCN-224) with cooperative adsorption domains, and demonstrated its excellent capture performance toward perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS) and perfluorobutane sulfonate (PFBS). PCN-224 has maximum uptake capacities of 963, 517, and 395 mg g-1 for PFOS, PFHxS, and PFBS, respectively, which are much higher than that of granular activated carbon. Moreover, coexistent anions (Cl-, SO4 2-) and humic acid have negligible effects on PFOS adsorption. The excellent adsorption performance of PCN-224 toward PFOS is due to the orthogonal cationic channel pores with a diameter of 1.9 nm, the hydrophobic porphyrin units, and the Zr6 clusters with acidic sites. PCN-224 can be readily regenerated and reused. This work highlights the potential of MOFs with multiple adsorption domains for water remediation.

An unsteady MHD Williamson fluid flow in a vertical porous channel with porous media and thermal radiation

An unsteady MHD Williamson fluid flow in a vertical porous channel with porous media and thermal radiation

Linear stability analysis of MHD mixed convection flow of a radiating nanofluid in porous channel in presence of viscous dissipation

Purpose This paper aims to investigate the hydrodynamic instability properties of a mixed convection flow of nanofluid in a porous channel. Design/methodology/approach The treated single-phase nanofluid is a suspension consisting of water as the working fluid and alumina as a nanoparticle. The anisotropy of the porous medium and the effects of the inclination of the magnetic field are highlighted. The effects of viscous dissipation and thermal radiation are incorporated into the energy equation. The eigenvalue equation system resulting from the stability analysis is processed numerically by the spectral collocation method. Findings Analysis of the results in terms of growth rate reveals that increasing the volume fraction of nanoparticles increases the critical Reynolds number. Parameters such as the mechanical anisotropy parameter and Richardson number have a destabilizing effect. The Hartmann number, permeability parameter, magnetic field inclination, Prandtl number, wave number and thermal radiation parameter showed a stabilizing effect. The Eckert number has a negligible effect on the growth rate of the disturbances. Originality/value Linear stability analysis of Magnetohydrodynamics (MHD) mixed convection flow of a radiating nanofluid in porous channel in presence of viscous dissipation.

Ultrasound Trigger Ce-Based MOF Nanoenzyme For Efficient Thrombolytic Therapy.

The inflammatory damage caused by thrombus formation and dissolution can increase the risk of thrombotic complications on top of cell death and organ dysfunction caused by thrombus itself. Therefore, a rapid and precise thrombolytic therapy strategy is in urgent need to effectively dissolve thrombus and resist oxidation simultaneously. In this study, Ce-UiO-66, a cerium-based metal-organic framework (Ce-MOF) with reactive oxygen species (ROS) scavenging properties, encapsulated by low-immunogenic mesenchymal stem cell membrane with inflammation-targeting properties, is used to construct a targeted nanomedicine Ce-UiO-CM. Ce-UiO-CM is applied in combination with external ultrasound stimulation for thrombolytic therapy in rat femoral artery. Ce-UiO-66 has abundant Ce (III)/Ce (IV) coupling sites that react with hydrogen peroxide (H2O2) to produce oxygen, exhibiting catalase (CAT) activity. The multi-cavity structure of Ce-UiO-66 can generate electron holes, and its pore channels can act as micro-reactors to further enhance its ROS scavenging capacity. Additionally, the porous structure of Ce-UiO-66 and the oxygen produced by its reaction with H2O2 may enhance the cavitation effects of ultrasound, thereby improving thrombolysis efficacy.

A Halogen‐Bond‐Driven Artificial Chloride‐Selective Channel Constructed from 5‐Iodoisophthalamide‐based Molecules

AbstractDespite considerable emphasis on advancing artificial ion channels, progress is constrained by the limited availability of small molecules with the necessary attributes of self‐assembly and ion selectivity. In this study, a library of small molecules based on 5‐haloisophthalamide and a non‐halogenated isophthalamide were examined for their ion transport properties across the lipid bilayer membranes, and the finding demonstrates that the di‐hexyl‐substituted 5‐iodoisophthalamide derivative exhibits the highest level of activity. Furthermore, it was established that the highest active compound facilitates the selective chloride transport that occurs via an antiport‐mediated mechanism. The crystal structure of the compound unveils a distinctive self‐assembly of molecules, forming a zig‐zag channel pore that is well‐suited for the permeation of anions. Planar bilayer conductance measurements proved the formation of chloride selective channels. A molecular dynamics simulation study, relying on the self‐assembled component derived from the crystal structure, affirmed the paramount significance of intermolecular hydrogen bonding in the formation of supramolecular barrel‐rosette structures that span the bilayer. Furthermore, it was demonstrated that the transport of chloride across the lipid bilayer membrane is facilitated by the synergistic effects of halogen bonding and hydrogen bonding within the channel.

Designing Urchin-Like S@SiO2 with Regulated Pores Toward Ultra-Fast Room Temperature Sodium-Sulfur Battery.

Captured by high theoretical capacity and low-cost, Sodium-Sulfur (Na-S) batteries have been deemed as promising energy-storage systems. However, their electrochemical properties, containing both cycling and rate properties, still suffer from the notorious "shuttle effect" of polysulfide. Herein, through the effective regulation of pore sizes, a series of S@SiO2 cathode materials are obtained. Benefitting from the abundant pore channels of SiO2 particles, the sulfur loading is as high as 76.3%. Importantly, a suitable pore size can lead to adequate reaction and rapid diffusion behaviors, resulting in excellent electrochemical performances. Specifically, at 2.0Ag-1, the initial capacity of the as-optimized sample can be up to 1370.6mAhg-1. Surprisingly, even after 1050 cycles, it could achieve a high reversible capacity of 1280.8mAhg-1 with an attenuation rate of 0.089%. At 5.0Ag-1, after 500 cycles, the capacity can still remain ≈ 1132.6mAhg-1 (capacity retention rate, 97.5%). Given this, the work is anticipated to offer an effective strategy for advanced electrodes for Na-S batteries.

Supporting Information A Halogen-Bond-Driven Artificial Chloride-Selective Channel Constructed from 5-Iodoisophthalamide-based Molecules.

Despite considerable emphasis on advancing artificial ion channels, progress is constrained by the limited availability of small molecules with the necessary attributes of self-assembly and ion selectivity. In this study, a library of small molecules based on 5-haloisophthalamide and a non-halogenated isophthalamide were examined for their ion transport properties across the lipid bilayer membranes, and the finding demonstrates that the di-hexyl-substituted 5-iodoisophthalamide derivative exhibits the highest level of activity. Furthermore, it was established that the highest active compound facilitates the selective chloride transport that occurs via an antiport-mediated mechanism. The crystal structure of the compound unveils a distinctive self-assembly of molecules, forming a zig-zag channel pore that is well-suited for the permeation of anions. Planar bilayer conductance measurements proved the formation of chloride selective channels. A molecular dynamics simulation study, relying on the self-assembled component derived from the crystal structure, affirmed the paramount significance of intermolecular hydrogen bonding in the formation of supramolecular barrel-rosette structures that span the bilayer. Furthermore, it was demonstrated that the transport of chloride across the lipid bilayer membrane is facilitated by the synergistic effects of halogen bonding and hydrogen bonding within the channel.

Preparation and stability of zinc‐based mesoporous sorbent modified with aluminium for high temperature coal gas desulphurization

AbstractZinc‐based sorbents with ordered mesoporous structure were modified with aluminium and the key factors in the preparation were optimized based on the results of desulphurization tests performed in a fixed‐bed reactor with simulated coal gas. It was shown that the sorbents for hydrogen sulphide removal reached an optimum sulphur capacity of 9.14% when prepared under conditions of 10.0 crystalline pH, 30:1 Si:Al molar ratio, 0.32:1 Zn:Si molar ratio, and 1:3 Zn:TAA molar ratio. The sorbent without aluminium was synthesized synchronously as a comparison sample to investigate the effect of aluminium addition on the desulphurization properties. The surface acidity of the sorbents is enhanced by the addition of aluminium, and the sulphur capacity of the aluminium‐doped sorbent is consequently lower compared to that of aluminium‐free sorbent. Nevertheless, the aluminium‐doped sorbent shows a significant advantage in stability of performance over multiple desulphurization–regeneration cycles and reaches an 81% retention rate of sulphur capacity after five desulphurization, while the aluminium‐free sorbent is only 51% in contrast. The characterization results manifest that aluminium enters the carrier skeleton and increases the wall thickness, which alleviates the collapse of the carrier pore channels and the agglomeration of the active components during the desulphurization process. Stable pore structures and highly dispersed active components facilitate the mass transfer in the reaction process after multiple desulphurization. As a result, the aluminium‐doped sorbent exhibits better performance stability in high temperature coal gas desulphurization.

Mechanical activation opens a lipid-lined pore in OSCA ion channels.

OSCA/TMEM63 channels are the largest known family of mechanosensitive channels1-3, playing critical roles in plant4-7 and mammalian8,9 mechanotransduction. Here we determined 44 cryogenic electron microscopy structures of OSCA/TMEM63 channels in different environments to investigate the molecular basis of OSCA/TMEM63 channel mechanosensitivity. In nanodiscs, we mimicked increased membrane tension and observed a dilated pore with membrane access in one of the OSCA1.2 subunits. In liposomes, we captured the fully open structure of OSCA1.2 in the inside-in orientation, in which the pore shows a large lateral opening to the membrane. Unusually for ion channels, structural, functional and computational evidence supports the existence of a 'proteo-lipidic pore' in which lipids act as a wall of the ion permeation pathway. In the less tension-sensitive homologue OSCA3.1, we identified an 'interlocking' lipid tightly bound in the central cleft, keeping the channel closed. Mutation of the lipid-coordinating residues induced OSCA3.1 activation, revealing a conserved open conformation of OSCA channels. Our structures provide a global picture of the OSCA channel gating cycle, uncover the importance of bound lipids and show that each subunit can open independently. This expands both our understanding of channel-mediated mechanotransduction and channel pore formation, with important mechanistic implications for the TMEM16 and TMC protein families.

Compounds based on Adamantyl-Substituted Amino Acids and Peptides as Potential Antiviral Drugs Acting as Viroporin Inhibitors.

The discussion has revolved around the derivatives of amino acids and peptides containing carbocycles and their potential antiviral activity in vitro against influenza A, hepatitis C viruses, and coronavirus. Studies conducted on cell cultures reveal that aminoadamantane amino acid derivatives exhibit the capacity to hinder the replication of viruses containing viroporins. Furthermore, certain compounds demonstrate potent virucidal activity with respect to influenza A/H5N1 and hepatitis C virus particles. A conceptual framework for viroporin inhibitors has been introduced, incorporating carbocyclic motifs as membranotropic carriers in the structure, alongside a functional segment comprised of amino acids and peptides. These components correspond to the interaction with the inner surface of the channel's pore or another target protein.

Preparation of self-standing ultra-thin three-dimensional covalent organic frameworks by interfacial polymerization for dye separation

Preparation of self-standing ultra-thin three-dimensional covalent organic frameworks by interfacial polymerization for dye separation

Tabernanthalog and ibogainalog inhibit the α7 and α9α10 nicotinic acetylcholine receptors via different mechanisms and with higher potency than the GABAA receptor and CaV2.2 channel

In this study, we have investigated the pharmacological activity and structural interaction of two novel psychoplastogens, tabernanthalog (TBG) and ibogainalog (IBG) at heterologously-expressed rat (r) and human (h) nicotinic acetylcholine receptors (nAChRs), the rα1β2γ2L γ-aminobutyric acid type A receptor (GABAAR), and the human voltage-gated N-type calcium channel (CaV2.2 channel). Both compounds inhibited the nAChRs with the following receptor selectivity: α9α10 > α7 > α3β2 ≅ α3β4, indicating that β2/β4 subunits are relatively less important for their activity. The potencies of TBG and IBG were comparable at hα7 and hα9α10 subtypes, and comparable to their rat counterparts. TBG- and IBG-induced inhibition of rα7 was ACh concentration-independent and voltage-dependent, whereas rα9α10 inhibition was ACh concentration-dependent and voltage-independent, suggesting that they interact with the α7 ion channel pore and α9α10 orthosteric ligand binding site, respectively. These results were supported by molecular docking studies showing that at the α7 model TBG forms stable interactions with luminal rings at 9′, 13′, and 16′, whereas IBG mostly interacts with the extracellular-transmembrane junction. In the α9α10 model, however, these compounds interacted with several residues from the principal (+) and complementary (–) sides in the transmitter binding site. Ibogaminalog (DM506) also interacted with a non-luminal site at α7, and one α9α10 orthosteric site. TBG and IBG inhibited the GABAAR and CaV2.2 channels with 10 to 30-fold lower potencies. In sum, we show that TBG and IBG inhibit the α7 and α9α10 nAChRs by noncompetitive and competitive mechanisms, respectively, and with higher potency than the GABAAR and CaV2.2 channel.