Rate-limiting Step Research Articles

Modulation on Surface Termination Groups to Optimize the Adsorption Energy and Work Function of Nb2CTx for Enhanced Hydrogen Storage in Magnesium Hydride

AbstractExploring high‐performance catalysts for hydrogen storage in magnesium hydride (MgH2) is crucial but still a challenge. Herein, Nb2CTx with controllable surface termination groups is developed as an efficient catalyst and the bifunctional modulation (adsorption energy and work function) of different surface termination groups (F, O, OH, or defects) is explored. First, compared to F and O, the introduction of OH on the surface or the direct removal of functional groups both leads to a significant increase in the adsorption of H by Nb2CTx. Second, compared to the surface bare, OH‐rich Nb2CTx has a lower work function, making it easier for hydrogen to enter Mg/MgH2 from the Nb2CTx surface or escape from the Mg/MgH2 surface into the Nb2CTx, thus facilitating the hydrogen ad/desorption properties of MgH2, i.e., the rate‐determining step (RDS) shifts from penetration to diffusion. The Nb2CTx‐KOH‐catalyzed MgH2 with optimal surface termination groups, therefore exhibits a release of 6.56 wt.% H2 in 5 min at 250 °C, and 6.46 wt.% H2 uptake within 5 min at 150 °C. The dehydrogenation and hydrogen uptake activation energies show 49.5% and 60.1% enhancements over pristine MgH2. In addition, a storage capacity of 5.51 wt.% is maintained after 50 dehydrogenation/hydrogenation cycles.

Subcellular mRNA kinetic modeling reveals nuclear retention as rate-limiting.

Eukaryotic mRNAs are transcribed, processed, translated, and degraded in different subcellular compartments. Here, we measured mRNA flow rates between subcellular compartments in mouse embryonic stem cells. By combining metabolic RNA labeling, biochemical fractionation, mRNA sequencing, and mathematical modeling, we determined the half-lives of nuclear pre-, nuclear mature, cytosolic, and membrane-associated mRNAs from over 9000 genes. In addition, we estimated transcript elongation rates. Many matured mRNAs have long nuclear half-lives, indicating nuclear retention as the rate-limiting step in the flow of mRNAs. In contrast, mRNA transcripts coding for transcription factors show fast kinetic rates, and in particular short nuclear half-lives. Differentially localized mRNAs have distinct rate constant combinations, implying modular regulation. Membrane stability is high for membrane-localized mRNA and cytosolic stability is high for cytosol-localized mRNA. mRNAs encoding target signals for membranes have low cytosolic and high membrane half-lives with minor differences between signals. Transcripts of nuclear-encoded mitochondrial proteins have long nuclear retention and cytoplasmic kinetics that do not reflect co-translational targeting. Our data and analyses provide a useful resource to study spatiotemporal gene expression regulation.

Mn3O4-MnOOH nanocomposites for the adsorption-based removal of nickel ions from wastewater.

The removal of nickel from wastewater is a significant environmental concern because of its potential hazards to environment. Adsorption is known as an efficient water treatment strategy and there is a growing interest in the development of new adsorbent materials providing rapid adsorption kinetics, cost-effectiveness, and high adsorption capacity. In this study, the feasibility of Mn3O4-MnOOH nanocomposites was evaluated as the adsorbent material for the removal of nickel ions from wastewater. The nanocomposites were prepared using a modified sonochemical method and characterized by XRD analysis and SEM images. Batch adsorption experiments were carried out under different experimental conditions obtained by varying solution pH, adsorbent amount, and contact period. Under the optimum adsorption conditions, the %RE value was recorded around 80% for 10mg/L Ni(II) ions. The adsorption characteristics were investigated with respect to adsorption isotherms and kinetics. Langmuir and Freundlich isotherm models were used to fit the adsorption data and the results indicated that adsorption of nickel ions onto nanocomposite could be complex and obey both monolayer adsorption and heterogeneous surface. Accordingly, maximum adsorption capacity of nanocomposites were calculated as 12.387mg/g. Research works comparing the kinetic models of pseudo-first-order, pseudo-second-order, and Elovich revealed that chemical sorption plays an important role as the rate-limiting step in the adsorption of nickel ions.

Kinetic Features of Degradation of R-Loops by RNase H1 from Escherichia coli

R-loops can act as replication fork barriers, creating transcription–replication collisions and inducing replication stress by arresting DNA synthesis, thereby possibly causing aberrant processing and the formation of DNA strand breaks. RNase H1 (RH1) is one of the enzymes that participates in R-loop degradation by cleaving the RNA strand within a hybrid RNA–DNA duplex. In this study, the kinetic features of the interaction of RH1 from Escherichia coli with R-loops of various structures were investigated. It was found that the values of the dissociation constants Kd were minimal for complexes of RH1 with model R-loops containing a 10–11-nt RNA–DNA hybrid part, indicating effective binding. Analysis of the kinetics of RNA degradation in the R-loops by RH1 revealed that the rate-limiting step of the process was catalytic-complex formation. In the presence of RNA polymerase, the R-loops containing a ≤16-nt RNA–DNA hybrid part were efficiently protected from cleavage by RH1. In contrast, R-loops containing longer RNA–DNA hybrid parts, as a model of an abnormal transcription process, were not protected by RNA polymerase and were effectively digested by RH1.

Phthalate esters in baltic lagoons: Spatial distribution, ecological risks, and novel insights into their fate using transcriptomics.

Plasticizers such as phthalate esters (PAEs) are organic compounds widely used in various consumer and industrial products, raising strong environmental concerns due to their pervasive presence and potential adverse effects. Lagoon ecosystems are particularly vulnerable to PAE pollution as they are semi-enclosed and receive high loads of organic materials. The present study investigates the distribution of seven common PAEs in three large European lagoons (Curonian, Vistula and Szczecin) in the southern Baltic Sea. The concentration levels of PAEs in the water column, encompassing both the dissolved and particulate-bound phases, and in sediments were assessed to elucidate distribution patterns and potential ecological risks within these lagoon ecosystems. The average concentration of total PAEs in the water column ranged from 0.03 to 1.45 μg L-1, whereas sediment concentration varied from 0.008 to 1.06 μg g-1, levels comparable to or lower than those found in other European coastal areas. Distribution patterns of PAEs in sediment showed notable similarity across all three lagoons, whereas variations were observed in the water column. Notably, di(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DOP) and dimethyl phthalate (DMP) emerged as the most concerning congeners in studied lagoons, all of which pose a moderate risk to aquatic organisms. This study applied shotgun transcriptomic analysis to field samples, revealing active microbial communities involved in PAEs degradation in the Baltic lagoons for the first time. The degradation of phthalic acid (PA) into intermediate compounds such as protocatechuate was not identified as a rate-limiting step in the studied environment. The degradation activity was primarily localized in the sediment layers, with Gram-negative bacteria playing a major role, while Gram-positive bacteria appeared incapable of degrading PA. These findings provide valuable insights into the distribution and transformation mechanisms of PAEs in estuarine environments.

Low-Spin Fe3+ Evoked by Multiple Defects with Optimal Intermediate Adsorption Attaining Unparalleled Performance in Water Oxidation.

Electrocatalytic water splitting is long constrained by the sluggish kinetics of anodic oxygen evolution reaction (OER), and rational spin-state manipulation holds great promise to break through this bottleneck. Low-spin Fe3+ (LS, t2g 5eg 0) species are identified as highly active sites for OER in theory, whereas it is still a formidable challenge to construct experimentally. Herein, a new strategy is demonstrated for the effective construction of LS Fe3+ in NiFe-layered double hydroxide (NiFe-LDH) by introducing multiple defects, which induce coordination unsaturation over Fe sites and thus enlarge their d orbital splitting energy. The as-obtained catalyst exhibits extraordinary OER performance with an ultra-low overpotential of 244 mV at the industrially required current density of 500 mA cm-2, which is 110 mV lower than that of the conventional NiFe-LDH with high-spin Fe3+ (HS, t2g 3eg 2) and superior to most previously reported NiFe-based catalysts. Comprehensive experimental and theoretical studies reveal that LS Fe3+ configuration effectively reduces the adsorption strength of the O* intermediate compared with that of the HS case, thereby altering the rate-determining step from (O* → OOH*) to (OH* → O*) of OER and lowering its reaction energy barrier. This work paves a new avenue for developing efficient spin-dependent electrocatalysts for OER and beyond.

Purification of Enzymatically Active Xrn1 for Removal of Non-capped mRNAs from In Vitro Transcription Reactions and Evaluation of mRNA Decapping Status In Vivo.

The cap is a 7-methylguanosine attached to the first messenger RNA (mRNA) nucleotide with a 5'-5' triphosphate bridge. This conserved eukaryotic modification confers stability to the transcripts and is essential for translation initiation. The specific mechanisms that govern transcript cytoplasmic longevity and translatability were always of substantial interest. Multiple works aimed at modeling mRNA decay mechanisms, including the onset of decapping, which is the rate-limiting step of mRNA decay. Additionally, with the recent advances in RNA-based vaccines, the importance of efficient synthesis of fully functional mRNAs has increased. Non-capped mRNAs arising during in vitro transcription are highly immunogenic, and multiple approaches were developed to reduce their levels. Efficient and low-cost methods for elimination of non-capped mRNAs in vitro are therefore essential to basic sciences and to pharmaceutical applications. Here, we present a protocol for heterologous expression and purification of catalytically active recombinant Xrn1 from Thermothelomyces (Myceliophthora) thermophilus (Tt_Xrn1). We also describe protocols needed to verify the enzyme quality.

Potassium and Boron Co-Doping of g-C3N4 Tuned CO2 Reduction Mechanism for Enhanced Photocatalytic Performance: A First-Principles Investigation

Graphitic phase carbon nitride (g-C3N4, abbreviated as CN) can be used as a photocatalyst to reduce the concentration of atmospheric carbon dioxide. However, there is still potential for improvement in the small band gap and carrier migration properties of intrinsic materials. K-B co-doped CN (KBCN) was investigated as a promising photocatalyst for carbon dioxide reduction via the Density Functional Theory (DFT) method. The electronic and optical properties of CN and KBCN indicate that doping K and B can improve the catalytic performance of CN by promoting charge migration and separation. In terms of the Gibbs free energy change, the CO2 reduction reaction catalysed by KBCN results in CH3OH, and its optimal pathway is CO2 → *CO2 → *COOH → CO → *OCH → HCHO → *OCH3 → CH3OH. Compared with CN, the doping elements K and B shift the rate-determining step from CO2 → *CO2 to *CO2 → *COOH. The K and B elements co-doping tuned the charge distribution between the catalyst and the adsorbate and reduced the Gibbs free energy of the rate-determining step from 1.571 to 0.861 eV, suggesting that the CO2 reduction activity of KBCN is superior to that of CN. Our work provides useful insights for the design of metallic–nonmetallic co-doped CN for photocatalytic CO2 reduction (CO2PR) reactions.

Activating Oxygen via the 3-Electron Pathway to Hydroxyl Radical by La-O4 Single-atom on WO3 for Water Purification.

Shifting photocatalytic oxygen activation towards 3-electron (e-) pathway to hydroxyl radicals, instead of the normal 1 e- to superoxide radicals, becomes increasingly important for pollution degradation since hydroxyl radicals possess a high oxidation potential (2.80 V). Here, we demonstrate a selective oxygen activation to hydroxyl radicals via 3 e- pathway using single atomically dispersed La based on WO3 fabricated with oxygen vacancies to weaken La-O coordination strength (denoted as LaO4-WOv). Unsaturated-state La overcomes the rate-limited step of 2 e- oxygen reduction reaction towards to hydrogen peroxide via tuning binding free energy of key reaction intermediate *OOH, stepped by easy generation of hydroxyl radicals via 1 e-. This strategy alters the activation of oxygen process from 1 e- to 3 e-. Hydrogen peroxide and hydroxyl radicals over LaO4-WOv produces 3.8 and 3.3 mmol L-1 h-1, 35 and 8 times that of detected over WO3, respectively. Rapid and complete removal of tetracycline realizes over LaO4-WOv with 0.077 min-1 of rate constant, 38 times that of WO3. Degradation efficiencies keep greater than 98% following five repeats, revealing a practical-utilization-level robust stability. This work builds an unsaturated-state transition metal site for manipulating oxygen activation towards an effective water purification as a representative application.

Biosorption of cypermethrin from aqueous solutions by Pediococcus acidilactici: kinetics, isotherms, and mechanisms.

Pediococcus acidilactici is an effective adsorbent for removing of pyrethroid insecticides. This study investigated the biosorption characteristics and mechanisms of P. acidilactici D15 using adsorption measurement, scanning electron microscopy, and Fourier-transform infrared spectroscopy. Isotherm and kinetic models were used to analyze the biosorption process. The Langmuir isotherm model best described the cypermethrin biosorption process, with the maximum adsorption capacity of P. acidilactici D15 being 21.404 mg/g. The biosorption appeared to involve monolayer coverage with uniform forces. The pseudo-second-order model also fits well. The rate-controlling steps involved intraparticle diffusion, film diffusion and chemosorption. The main cellular components involved in cypermethrin biosorption were exopolysaccharides, spheroplast, and cell wall, especially peptidoglycan. The functional groups (-OH, -NH, -CH3, -CH2, -CH, -CONH-, -CO, and -C-O-C-) from proteins, polysaccharides, and peptidoglycan on the cell surface likely played a role in binding cypermethrin. Additionally, P. acidilactici D15 effectively reduced cypermethrin in pickle wastewater. These findings suggest that P. acidilactici D15 could be a potential agent for reducing pesticide residues, laying the groundwork for treating pickle wastewater containing such pesticide residues. © 2024 Society of Chemical Industry.

Quenching Rate Constants of Lewis Base-Boryl Radical by Substrates: a Laser Flash Photolysis Study.

The advanced strategy using Lewis base-boryl radicals (LBRs) has recently been proposed for the addition of alkyl substituents to the full-carbon quaternary center of an organic molecule. However, as the rate-determining step in the whole route, reaction rate constants of LBRs with substrates are extremely lacking. In this paper, 4-dimethylaminopyridine (DMAP)-BH2• was selected as a representative of LBRs, and its reactions with six monochloro-substituted substrates, including three methyl chlorobenzoates and three chlorinated acetanilides were studied in experiments and theoretical calculations. The bimolecular reaction rate constants, kq, were determined using laser flash photolysis approach. By comparing activation energies along the two addition pathways, we have clarified the rate-determining step as the attacking to carbonyl oxygen instead of chlorine atom. Furthermore, noncovalent interaction (NCI) analyses on these substrates indicate that weak interactions, such as hydrogen-bonding and van der Waals interactions, have significant influence on the reactivity of these substrates. Our study provides concrete clues to extend this synthetic strategy.

Local depletion of large molecule drugs due to target binding in tissue interstitial space.

Drug-target binding determines a drug's pharmacodynamics but can also have a profound impact on a drug's pharmacokinetics, known as target-mediated drug disposition (TMDD). TMDD models describe the influence of drug-target binding and target turnover on unbound drug concentrations and are frequently used for biologics and drugs with nonlinear plasma pharmacokinetics. For drug targets expressed in tissues, the effect of TMDD may not be detected when analyzing plasma concentration curves, but it might still affect tissue concentrations and occupancy. This review aimed to investigate the likeliness of such a scenario by reviewing the literature for a typical range of TMDD parameter values and their impact on local drug concentrations and target occupancy in a whole-body PBPK model with TMDD. Our analysis demonstrated that tissue drug concentrations are impacted and significantly depleted in many physiological scenarios. In contrast, the effect on plasma concentrations is much lower, specifically for smaller organs with lower perfusion. Moreover, in scenarios with fast internalization of the drug-target complex, the distribution of large molecules from plasma to tissue interstitial space emerges as a rate-limiting step for the drug-target interaction. These factors may lead to overpredicting local drug concentrations when considering only plasma pharmacokinetics. A sensitivity analysis revealed the high and not always intuitive impact of drug-specific parameters, including the drug molecule hydrodynamic radius, dissociation constant (Kd), drug-target complex internalization rate constant (kint), and target dissociation rate constant (koff), on the drug's pharmacokinetics. Our analysis demonstrated that tissue TMDD needs to be considered even if plasma pharmacokinetics are linear.

Pd-Catalyzed Site-Selective Defluorinative Etherification between Unactivated Perfluoroarenes and Hydrobenzoxazoles.

Polyfluoroaryl ethers represent an important framework of biologically active molecules and materials. Owing to the strong bond dissociation energy of C-F bond, selectivity and other issues, transition metal-catalyzed synthesis of polyfluoroaryl ethers from perfluoroarenes via the activation of C-F bond is challenging and underdeveloped, as compared to the well-documented C-O bond formation starting from aryl iodides, aryl bromides or aryl chlorides. Herein, an unprecedented Pd-catalyzed defluorinative etherification for the synthesis of polyfluoroaryl ether skeletons using hydrobenzoxazoles as phenol surrogate, has been reported. The substrate scope for this protocol is broad, with respect to hydrobenzoxazoles and perfluoroarenes, under mild reaction conditions. More importantly, challenging alkenyl and alkynyl substituted polyfluoroarenes could be successfully used as the coupling component for Pd-catalyzed etherification reaction. Density functional theory (DFT) calculations were employed to investigate the reaction mechanism, which suggested that oxidative addition between polyfluorobenzene and Pd(0) constituted the ratedetermining step.

Removal of As(V) and Cr(VI) using quinoxaline chitosan schiff base: synthesis, characterization and adsorption mechanism.

Elevated Arsenic and Chromium levels in surface and ground waters are a significant health concern in several parts of the world. Chitosan quinoxaline Schiff base (CsQ) and cross-linked chitosan quinoxaline Schiff base (CsQG) were prepared to adsorb both Arsenate [As(V)] and Chromium [Cr(VI)] ions. The thermo-gravimetric analysis (TGA), X-ray diffraction analysis (XRD), and Fourier-transform infrared spectroscopy (FTIR) were used to investigate the prepared Schiff bases (CsQ) and (CsQG). The UV-VIS spectra showed a shift in the wavelength area of the modified polymer, indicating the reaction occurrence, besides the variation of the shape and intensity of the peaks. The XRD patterns showed the incensement of the amorphous characteristic. On the other hand, the thermal stability of the modified polymers is better according to TGA studies; also, the morphology of the modified chitosan was investigated before and after crosslinking (CsQ and CsQG) using a scanning electron microscope (SEM) where the surface was fall of wrinkles and pores, which then were decreased after cross-linking. Contact time, temperature, pH, and initial metal ion concentration were all studied as factors influencing metal ion uptake behavior. The Langmuir, Temkin, Dubinin-Radushkevich, and Freundlich isotherm models were used to describe the equilibrium data using metal concentrations of 10-1000 mg/L at pH = 7 and 1 g of adsorbent. The pseudo-first-order and pseudo-second-order kinetic parameters were evaluated. The experimental data revealed that the adsorption kinetics follow the mechanism of the pseudo-second-order equation with R2 values (0.9969, 0.9061) in case of using CsQ and R2 values (0.9989, 0.9999) in case of using CsQG, demonstrating chemical sorption is the rate-limiting step of the adsorption mechanism. Comparing the adsorption efficiency of the synthesized Schiff base and the cross-linked one, it was found that CsQ is a better adsorbent than CsQG in both cases of As(V) and Cr(VI) removal. This means that cross-linking doesn't enhance the efficiency as expected, but on the contrary, in some cases, it decreases the removal. In addition, the newly modified chitosan polymers work better in As(V) removal than Cr(VI); the removal is 22.33% for Cr(VI) and 98.36% for As(V) using CsQ polymer, whereas using CsQG, the values are 6.20% and 91.75% respectively. On the other hand, the maximum adsorption capacity (Qm) for As(V) and Cr(VI) are 8.811 and 3.003 mg/g, respectively, using CsQ, while in the case of using CsQG, the Qm value reaches 31.95 mg/g for As(V), and 103.09 mg/g for Cr(VI).

CeO2‐Accelerated Surface Reconstruction of CoSe2 Nanoneedle Forms Active CeO2@CoOOH Interface to Boost Oxygen Evolution Reaction for Water Splitting

AbstractInterface engineering is an efficient strategy to create high‐performance electrocatalysts for water splitting. In the present work, CeO2@CoSe2 nanoneedle on carbon cloth (CeO2@CoSe2/CC) demonstrates high efficiency for oxygen evolution reaction (OER) and water splitting. CeO2 with abundant O vacancies facilitates the adsorption of OH− and boosts the reconstruction of CoSe2 into CoOOH at lower potentials. The in situ generated active CeO2@CoOOH heterointerface upshifts the d‐band center of Co site, thereby decreasing the free energy of rate‐determining step (RDS) (*O to *OOH) during the OER process. It delivers a low OER overpotential of 245 mV at 10 mA cm−2. CeO2@CoSe2/CC is also found to be active for hydrogen evolution reaction (HER, 138 mV overpotential at 10 mA cm−2), profiting from CeO2‐facilitated *H2O dissociation and *H adsorption on CoSe2. The overall water splitting is achieved over the CeO2@CoSe2/CC bifunctional electrode with a low electrolysis voltage of 1.54 V at 10 mA cm−2. This work offers valuable insights into CeO2‐assisted surface reconstruction as well as provides water electrolysis catalysts through interface engineering.

Promoting Cl2O Generation from the HOCl + HOCl Reaction on Aqueous/Frozen Air-Water Interfaces.

Hypochlorous acid (HOCl) is considered a temporary reservoir of dichlorine monoxide (Cl2O). Previous studies have suggested that Cl2O is difficult to generate from the reaction of HOCl + HOCl in the gas phase. Here, we demonstrate that Cl2O can be generated from the HOCl + HOCl reaction at aqueous/frozen air-water interfaces, which is confirmed by ab initio molecular dynamic calculations. Distinct from the one-step reaction in the gas phase, our results show that Cl2O generation from HOCl + HOCl on aqueous/frozen interfaces involves two elementary steps, namely, one HOCl deprotonation and one Cl-abstraction from the other HOCl. Specifically, the mechanisms of neutral/acidic catalysis from interfacial water/nitric acid and base catalysis from ammonia, methylamine and dimethylamine have been examined. For the former, HOCl deprotonation is the rate-limiting step, and the total k of Cl2O generation increases to 9.23 × 10-9-9.10 × 10-1 M-1 s-1 at the aqueous interface and 3.20 × 10-7-4.10 × 10-3 M-1 s-1 at the frozen interface, which is at least 23 and 25 orders of magnitude greater than that of gaseous k (3.31 × 10-32 M-1 s-1). For the latter, the rate-limiting step is changed to Cl-abstraction, whose total k dramatically increases to 1.40-8.97 × 107 M-1 s-1 at the aqueous interface and 7.12-9.99 × 106 M-1 s-1 at the frozen interface. Interestingly, the Cl2O production rates ranked in the order of dimethylamine < methylamine < ammonia and decreased with increasing catalytic alkalinity. These findings provide new insights for understanding other Cl2O sources beyond the ClONO2 + HOCl reaction.

Tailoring ORR Activity in Fe-N-C Catalysts through Phosphorus Incorporation.

Atomically dispersed iron and nitrogen co-doped carbon materials (Fe-N-C) represent promising non-precious metal catalysts for the oxygen reduction reaction (ORR), offering potential alternatives to noble metal-based benchmarks. In our study, we investigated the influence of phosphorus doping on the catalytic activity of Fe-N-C. The experimental research demonstrate that the doping of phosphorus significantly enhances the ORR activity. Specifically, the resulting Fe-NPC exhibits high metal loading and excellent ORR activity in 0.1 M KOH with an onset potential of 1.00 V and a half-wave potential of 0.864 V. Density functional theory (DFT) simulations reveal that phosphorus improves the electrocatalytic activity by activating O2 molecules and reducing the energy barrier (the hydrogenation reaction *OH→H2O) of the rate-determining step. Furthermore, Fe-NPC exhibits promising application prospects as an air cathode in Zn-air batteries, delivering a high maximum discharge power density of 180.3 mW cm-2 and outstanding discharge specific capacity (758.8 mAh g-1Zn) at a discharge current density of 10 mA cm-2.

Tailoring-Orientated Deposition of Li2S for Extreme Fast-Charging Lithium-Sulfur Batteries.

Precipitation/dissolution of insulating Li2S has long been recognized as the rate-determining step in lithium-sulfur (Li-S) batteries, which dramatically undermines sulfur utilization at elevated charging rates. Herein, we present an orientated Li2S deposition strategy to achieve extreme fast charging (XFC, ≤15 min) through synergistic control of porosity, electronic conductivity, and anchoring sites of electrode substrate. Via magnesiothermic reduction of a zeolitic imidazolate framework, a nitrogen-doped and hierarchical porous carbon with highly graphitic phase was developed. This design effectively reduces interfacial resistance and ensures efficient sequestration of polysulfides during deposition, leading to (110)-preferred growth of Li2S nanocrystalline between (002)-dominated graphitic layers. Our approach directs an alternative Li2S deposition pathway to the commonly reported lateral growth and 3D thickening growth mode, ameliorating the electrode passivation. Therefore, a Li-S cell capable of charging/discharging at 5C (12 min) while maintaining excellent cycling stability (82% capacity retention) for 1000 cycles is demonstrated. Even under high S loading (8.3 mg cm-2) and low electrolyte/sulfur ratio (3.8 mL mg-1), the sulfur cathode still delivers a high areal capacity of >7 mAh cm-2 for 80 cycles.

NiIr Nanowire Assembles as an Efficient Electrocatalyst Towards Oxygen Evolution Reaction in Both Acid and Alkaline Media.

Oxygen evolution reaction (OER) is the rate-limiting step in water electrolysis due to its sluggish kinetic, and it is challenging to develop an OER catalyst that could work efficiently in both acid and alkaline environment. Herein, NiIr nanowire assembles (NAs) with unique nanoflower morphology were prepared by a facile hydrothermal method. As a result, the NiIr NAs exhibited superior OER activity in both acid and alkaline media. Specifically, in 0.1 M HClO4, NiIr NAs presented a superior electrocatalytic performance with a low overpotential of merely 242 mV at 10 mA cm-2 and a Tafel slope of only 58.1 mV dec-1, surpassing that of commercial IrO2 and pure Ir NAs. And it achieved a significantly higher mass activity of 148.40 A/g at -1.5 V versus RHE. In 1.0 M KOH, NiIr NAs has an overpotential of 291 mV at 10 mA cm-2 and a Tafel slope of 42.1 mV dec-1. Such remarkable activity makes the NiIr NAs among the best of recently reported representative Ir-based OER electrocatalysts. Density functional theory (DFT) calculations confirmed alloying effect promotes surface bonding of NiIr with oxygen-containing reactants, resulting in excellent catalytic properties.

Targeting ketone body metabolism in mitigating gemcitabine resistance.

Chemotherapy is often combined with surgery for muscle invasive and non-muscle invasive bladder cancer. However, 70% of the patients recur within 5 years. Metabolic reprogramming is an emerging hallmark in cancer chemoresistance. Here, we report a gemcitabine resistance mechanism which promotes cancer reprogramming via the metabolic enzyme, OXCT1. This mitochondrial enzyme, responsible for the rate-limiting step in β-hydroxybutyrate (βHB) catabolism, was elevated in muscle invasive disease and in chemo-resistant bladder cancer patients. Resistant orthotopic tumors presented an OXCT1-dependent rise in mitochondrial oxygen consumption rate, ATP, and nucleotide biosynthesis. In resistant bladder cancer, knocking out OXCT1 restored gemcitabine sensitivity, and administering the non-metabolizable βHB, enantiomer (S-βHB) only partially restored gemcitabine sensitivity. Suggesting an extra-metabolic role for OXCT1, multi-omics analysis of gemcitabine sensitive and resistant cells revealed an OXCT1-dependent signature with the transcriptional repressor, OVOL1, as a master regulator of epithelial differentiation. The elevation of OVOL1 target genes was associated with its cytoplasmic translocation and poor prognosis in a chemotherapy-treated BCa patient cohort. The knockout of OXCT1 restored OVOL1 transcriptional repressive activity by its nuclear translocation. Orthotopic mouse models of bladder cancer supported OXCT1 as a mediator of gemcitabine sensitivity through ketone metabolism and regulating cancer stem cell differentiation.