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Biophysical Reports Jun 2024In vitro assays of ion transport are an essential tool for understanding molecular mechanisms associated with ATP-dependent pumps. Because ion transport is generally...
In vitro assays of ion transport are an essential tool for understanding molecular mechanisms associated with ATP-dependent pumps. Because ion transport is generally electrogenic, principles of electrophysiology are applicable, but conventional tools like patch clamp are ineffective due to relatively low turnover rates of the pumps. Instead, assays have been developed to measure either voltage or current generated by transport activity of a population of molecules either in cell-derived membrane fragments or after reconstituting purified protein into proteoliposomes. In order to understand the nuances of these assays and to characterize effects of various operational parameters, we have developed a numerical model to simulate data produced by two relevant assays: fluorescence from voltage sensitive dyes and current recorded by capacitive coupling on solid supported membranes. Parameters of the model, which has been implemented in Python, are described along with underlying principles of the computational algorithm. Experimental data from KdpFABC, a K pump associated with P-type ATPases, are presented and model parameters have been adjusted to mimic these data. In addition, effects of key parameters such as non-selective leak conductance and turnover rate are demonstrated. Finally, simulated data are used to illustrate the effects of capacitive coupling on measured current and to compare alternative methods for quantification of raw data.
PubMed: 38950825
DOI: 10.1016/j.bpr.2024.100169 -
Journal of Colloid and Interface Science Jun 2024Silicon-based material is regarded as one of the most promising anodes for next-generation high-performance lithium-ion batteries (LIBs) due to its high theoretical...
Silicon-based material is regarded as one of the most promising anodes for next-generation high-performance lithium-ion batteries (LIBs) due to its high theoretical capacity and low cost. Harnessing silicon carbide's robustness, we designed a novel porous silicon with a sandwich structure of carbon/silicon carbide/Ag-modified porous silicon (Ag-PSi@SiC@C). Different from the conventional SiC interface characterized by a frail connection, a robust dual covalent bond configuration, dependent on SiC and SiOC, has been successfully established. Moreover, the innovative sandwich structure effectively reduces detrimental side reactions on the surface, eases volume expansion, and bolsters the structural integrity of the silicon anode. The incorporation of silver nanoparticles contributes to an improvement in overall electron transport capacity and enhances the kinetics of the overall reaction. Consequently, the Ag-PSi@SiC@C electrode, benefiting from the aforementioned advantages, demonstrates a notably elevated lithium-ion mobility (2.4 * 10 cm·s), surpassing that of silicon (5.1 * 10 cm·s). The half-cell featuring Ag-PSi@SiC@C as the anode demonstrated robust rate cycling stability at 2.0 A/g, maintaining a capacity of 1321.7 mAh/g, and after 200 cycles, it retained 962.6 mAh/g. Additionally, the full-cell, featuring an Ag-PSi@SiC@C anode and a LiFePO (LFP) cathode, exhibits outstanding longevity. Hence, the proposed approach has the potential to unearth novel avenues for the extended exploration of high-performance silicon-carbon anodes for LIBs.
PubMed: 38950463
DOI: 10.1016/j.jcis.2024.06.223 -
Plant Physiology and Biochemistry : PPB Jun 2024Methyl viologen (MV), also known as paraquat, is a widely used herbicide but has also been reported as highly toxic to different life forms. The mode of its operation is...
Methyl viologen (MV), also known as paraquat, is a widely used herbicide but has also been reported as highly toxic to different life forms. The mode of its operation is related to superoxide radical (O) production and consequent oxidative damage. However, besides the damage to key macromolecules, reactive oxygen species (ROS; to which O belongs) are also known as regulators of numerous ion transport systems located at cellular membranes. In this study, we used MV as a tool to probe the role of O in regulating membrane-transport activity and systemic acquired tolerance in halophytic Chenopodium quinoa and glycophytic spinach plants. Both plant species showed growth reduction in terms of reduced shoot length, lower shoot fresh and dry weight, photosynthesis rate, and chlorophyll contents; however, quinoa showed less reduction in growth compared with spinach. This whole plant response was further examined by measuring the ion concentration, gene expression of ion transporters, activation of antioxidants, and osmolyte accumulation. We observed that at the mechanistic level, the differences in growth in response to MV were conferred by at least four complementary physiological mechanisms: (1) higher K loss from spinach leaves resulted from higher expression of MV-induced plasma membrane-based depolarization-activated K efflux GORK channel, (2) higher activation of high-affinity K uptake transporter HAK5 in quinoa, (3) higher antioxidant production and osmolyte accumulation in quinoa as compared with spinach, and (4) maintaining a higher rate of photosynthesis due to higher chlorophyll contents, and efficiency of photosystem II and reduced ROS and MDA contents. Obtained results also showed that MV induced O significantly reduced N contents in both species but with more pronounced effects in glycophytic spinach. Taken together this study has shown the role of O in regulating membrane ion transport and N metabolism in the leaves of halophyte vs. glycophyte in the context of oxidative stress tolerance.
PubMed: 38950461
DOI: 10.1016/j.plaphy.2024.108886 -
Accounts of Chemical Research Jul 2024ConspectusMembranes are pivotal in a myriad of energy production processes and modern separation techniques. They are essential in devices for energy generation,...
ConspectusMembranes are pivotal in a myriad of energy production processes and modern separation techniques. They are essential in devices for energy generation, facilities for extracting energy elements, and plants for wastewater treatment, each of which hinges on effective ion separation. While biological ion channels show exceptional permeability and selectivity, designing synthetic membranes with defined pore architecture and chemistry on the (sub)nanometer scale has been challenging. Consequently, a typical trade-off emerges: highly permeable membranes often sacrifice selectivity and vice versa. To tackle this dilemma, a comprehensive understanding and modeling of synthetic membranes across various scales is imperative. This lays the foundation for establishing design criteria for advanced membrane materials. Key attributes for such materials encompass appropriately sized pores, a narrow pore size distribution, and finely tuned interactions between desired permeants and the membrane. The advent of covalent-organic-framework (COF) membranes offers promising solutions to the challenges faced by conventional membranes in selective ion separation within the water-energy nexus. COFs are molecular Legos, facilitating the precise integration of small organic structs into extended, porous, crystalline architectures through covalent linkage. This unique molecular architecture allows for precise control over pore sizes, shapes, and distributions within the membrane. Additionally, COFs offer the flexibility to modify their pore spaces with distinct functionalities. This adaptability not only enhances their permeability but also facilitates tailored interactions with specific ions. As a result, COF membranes are positioned as prime candidates to achieve both superior permeability and selectivity in ion separation processes.In this Account, we delineate our endeavors aimed at leveraging the distinctive attributes of COFs to augment ion separation processes, tackling fundamental inquiries while identifying avenues for further exploration. Our strategies for fabricating COF membranes with enhanced ion selectivity encompass the following: (1) crafting (sub)nanoscale ion channels to enhance permselectivity, thereby amplifying energy production; (2) implementing a multivariate (MTV) synthesis method to control charge density within nanochannels, optimizing ion transport efficiency; (3) modifying the pore environment within confined mass transfer channels to establish distinct pathways for ion transport. For each strategy, we expound on its chemical foundations and offer illustrative examples that underscore fundamental principles. Our efforts have culminated in the creation of groundbreaking membrane materials that surpass traditional counterparts, propelling advancements in sustainable energy conversion, waste heat utilization, energy element extraction, and pollutant removal. These innovations are poised to redefine energy systems and industrial wastewater management practices. In conclusion, we outline future research directions and highlight key challenges that need addressing to enhance the ion/molecular recognition capabilities and practical applications of COF membranes. Looking forward, we anticipate ongoing advancements in functionalization and fabrication techniques, leading to enhanced selectivity and permeability, ultimately rivaling the capabilities of biological membranes.
PubMed: 38950424
DOI: 10.1021/acs.accounts.4c00268 -
ACS Applied Materials & Interfaces Jul 2024Metal-organic frameworks (MOFs), with their tunable pore sizes and high surface areas, are gaining prominence in Li metal battery applications, including their use as...
Metal-organic frameworks (MOFs), with their tunable pore sizes and high surface areas, are gaining prominence in Li metal battery applications, including their use as nanofillers in solid composite electrolytes (SCEs) for enhanced ionic conductivity. Yet, when used in SCEs, individual dispersed MOF particles in isolation as nanofillers can impede efficient ion transport in all-solid-state batteries due to the insufficient supply of ionic transport pathways within SCEs. Here, we introduced a continuous SCE nanofiller with long-range assembly interconnected porous MOFs (IMOF_SCE) for effective ion transport pathway supply along the interface between the nanofiller and the polymer matrix. IMOF_SCE achieved Li-ion conductivity (6.72 × 10 S cm at 20 °C) and Li-ion transference number ( = 0.855), resulting in the improved electrochemical performance of Li metal batteries. Additionally, the Li/LiFePO full cell integrated with IMOF_SCE achieved an outstanding stable capacity retention of 98.8% in 300 cycles. This work offers insights into the design strategy of effective nanofillers for SCEs and can be adapted for other porous materials.
PubMed: 38950001
DOI: 10.1021/acsami.4c07495 -
Nano Letters Jul 2024Recent years have seen a growing interest in zero-dimensional (0D) transport phenomena occurring across two-dimensional (2D) materials for their potential applications...
Recent years have seen a growing interest in zero-dimensional (0D) transport phenomena occurring across two-dimensional (2D) materials for their potential applications to nanopore technology such as ion separation and molecular sensing. Herein, we investigate ion transport through 1 nm-wide nanopores in TiC MXene using molecular dynamics simulations. The high polarity and fish-bone arrangement of the TiC MXene offer a built-in potential and an atomic-scale distortion to the nanopore, causing an adsorption preference for cations. Our observation of variable cation-specific ion selectivity and Coulomb blockade highlights the complex interplay between adsorption affinity and cation size. The cation-specific ion selectivity can induce both the ion current and electro-osmotic water transmission, which can be regulated by tailoring the ions' preferential pathways through electric field tilting. Our finding underscores the pivotal role of the atomic arrangement of MXenes in 0D ion transport and provides fundamental insight into the application of 2D material in nanopores-based technologies.
PubMed: 38949896
DOI: 10.1021/acs.nanolett.4c01892 -
Nano Letters Jul 2024The ion permeability and selectivity of membranes are crucial in nanofluidic behavior, impacting industries ranging from traditional to advanced manufacturing. Herein,...
The ion permeability and selectivity of membranes are crucial in nanofluidic behavior, impacting industries ranging from traditional to advanced manufacturing. Herein, we demonstrate the engineering of ion-conductive membranes featuring angstrom-scale ion-transport channels by introducing ionic polyamidoamine (PAMAM) dendrimers for ion separation. The exterior quaternary ammonium-rich structure contributes to significant electrostatic charge exclusion due to enhanced local charge density; the interior protoplasmic channels of PAMAM dendrimer are assembled to provide additional degrees of free volume. This facilitates the monovalent ion transfer while maintaining continuity and efficient ion screening. The dendrimer-assembled hybrid membrane achieves high monovalent ion permeance of 2.81 mol m h (K), reaching excellent mono/multivalent selectivity up to 20.1 (K/Mg) and surpassing the permselectivities of state-of-the-art membranes. Both experimental results and simulating calculations suggest that the impressive ion selectivity arises from the significant disparity in transport energy barrier between mono/multivalent ions, induced by the "exterior-interior" synergistic effects of bifunctional membrane channels.
PubMed: 38949785
DOI: 10.1021/acs.nanolett.4c01997 -
Medical Physics Jul 2024MR-integrated proton therapy is under development. It consists of the unique challenge of integrating a proton pencil beam scanning (PBS) beam line nozzle with an...
BACKGROUND
MR-integrated proton therapy is under development. It consists of the unique challenge of integrating a proton pencil beam scanning (PBS) beam line nozzle with an magnetic resonance imaging (MRI) scanner. The magnetic interaction between these two components is deemed high risk as the MR images can be degraded if there is cross-talk during beam delivery and image acquisition.
PURPOSE
To create and benchmark a self-consistent proton PBS nozzle model for empowering the next stages of MR-integrated proton therapy development, namely exploring and de-risking complete integrated prototype system designs including magnetic shielding of the PBS nozzle.
MATERIALS AND METHODS
Magnetic field (COMSOL ) and radiation transport (Geant4) models of a proton PBS nozzle located at OncoRay (Dresden, Germany) were developed according to the manufacturers specifications. Geant4 simulations of the PBS process were performed by using magnetic field data generated by the COMSOL simulations. In total 315 spots were simulated which consisted of a scan pattern with 5 cm spot spacings and for proton energies of 70, 100, 150, 200, and 220 MeV. Analysis of the simulated deflection at the beam isocenter plane was performed to determine the self-consistency of the model. The magnetic fringe field from a sub selection of 24 of the 315 spot simulations were directly compared with high precision magnetometer measurements. These focused on the maximum scanning setting of 20 cm beam deflection as generated from the second scanning magnet in the PBS for a proton beam energy of 220 MeV. Locations along the beam line central axis (CAX) were measured at beam isocenter and downstream of 22, 47, 72, 97, and 122 cm. Horizontal off-axis positions were measured at 22 cm downstream of isocenter ( 50, 100, and 150 cm from CAX).
RESULTS
The proton PBS simulations had good spatial agreement to the theoretical values in all 315 spots examined at the beam line isocenter plane (0-2.9 mm differences or within 1.5 % of the local spot deflection amount). Careful analysis of the experimental measurements were able to isolate the changes in magnetic fields due solely to the scanning magnet contribution, and showed 1.9 1.2 -9.4 1.2 changes over the range of measurement locations. Direct comparison with the equivalent simulations matched within the measurement apparatus and setup uncertainty in all but one measurement point.
CONCLUSIONS
For the first time a robust, accurate and self-consistent model of a proton PBS nozzle assembly has been created and successfully benchmarked for the purposes of advancing MR-integrated proton therapy research. The model will enable confidence in further simulation based work on fully integrated designs including MRI scanners and PBS nozzle magnetic shielding in order to de-risk and realize the full potential of MR-integrated proton therapy.
PubMed: 38949569
DOI: 10.1002/mp.17279 -
Small Methods Jul 2024Adverse side reactions and uncontrolled Zn dendrites growth are the dominant factors that have restricted the application of Zn ion batteries. Herein, a 3D...
Adverse side reactions and uncontrolled Zn dendrites growth are the dominant factors that have restricted the application of Zn ion batteries. Herein, a 3D self-supporting porous carbon fibers (denoted as PCFs) host is developed with "trap" effect to adjust the Zn deposition. The unique open structural design of N-doped carbon can act as the zincophilic sites to induce uniform deposition and inhibit adverse side reactions. More importantly, the porous hollow PCFs host with "trap" effect can induce Zn deposition in the fiber by adjusting the local electric field and current density, thereby increasing the specific energy density of the battery and inhibiting dendrite growth. In addition, the 3D open frameworks can regulate Zn flux to enable outstanding cycling performance at ultra-high current densities. As expected, the PCFs framework guarantees the uniform Zn plating and stripping with an outstanding stability over 6000 cycles at the current density of 40 mA cm. And the Zn@PCFs||MnO full battery shows an excellent lifespan over 1300 cycles at 2000 mA g.
PubMed: 38949412
DOI: 10.1002/smtd.202400408 -
The Journal of Clinical Investigation Jul 2024Cystic fibrosis is a debilitating disease characterized by a poor medical prognosis due to devastating lung injury. Recent medical advances targeting the major genetic...
Cystic fibrosis is a debilitating disease characterized by a poor medical prognosis due to devastating lung injury. Recent medical advances targeting the major genetic mutation ΔF508 of the cystic fibrosis transmembrane conductance regulator (CFTR) protein have dramatically increased the lifespan of patients with this mutation. This development has led to major changes in the field and has pushed research beyond the ion transport nature of cystic fibrosis and toward multiorgan physiological reprogramming. In this issue of the JCI, Bae, Kim, and colleagues utilized a large animal pig model prior to the onset of disease. They revealed metabolic reprogramming and organ crosstalk that occurred prior to disease progression. These findings provide paradigm-shifting insight into this complex disease.
Topics: Cystic Fibrosis; Animals; Humans; Cystic Fibrosis Transmembrane Conductance Regulator; Swine; Disease Models, Animal
PubMed: 38949023
DOI: 10.1172/JCI182329