A stable low-temperature H2-production catalyst by crowding Pt on α-MoC.

The water-gas shift (WGS) reaction is an industrially important source of pure hydrogen (H2) at the expense of carbon monoxide and water1,2. This reaction is of interest for fuel-cell applications, but requires WGS catalysts that are durable and highly active at low temperatures3. Here we demonstrate that the structure (Pt1-Ptn)/α-MoC, where isolated platinum atoms (Pt1) and subnanometre platinum clusters (Ptn) are stabilized on α-molybdenum carbide (α-MoC), catalyses the WGS reaction even at 313 kelvin, with a hydrogen-production pathway involving direct carbon monoxide dissociation identified. We find that it is critical to crowd the α-MoC surface with Pt1 and Ptn species, which prevents oxidation of the support that would cause catalyst deactivation, as seen with gold/α-MoC (ref. 4), and gives our system high stability and a high metal-normalized turnover number of 4,300,000 moles of hydrogen per mole of platinum. We anticipate that the strategy demonstrated here will be pivotal for the design of highly active and stable catalysts for effective activation of important molecules such as water and carbon monoxide for energy production.

A single gene mutation underpins metabolic adaptation and acquisition of filamentous competence in the emerging fungal pathogen Candida auris.

Filamentous cell growth is a vital property of fungal pathogens. The mechanisms of filamentation in the emerging multidrug-resistant fungal pathogen Candida auris are poorly understood. Here, we show that exposure of C. auris to glycerol triggers a rod-like filamentation-competent (RL-FC) phenotype, which forms elongated filamentous cells after a prolonged culture period. Whole-genome sequencing analysis reveals that all RL-FC isolates harbor a mutation in the C2H2 zinc finger transcription factor-encoding gene GFC1 (Gfc1 variants). Deletion of GFC1 leads to an RL-FC phenotype similar to that observed in Gfc1 variants. We further demonstrate that GFC1 mutation causes enhanced fatty acid ß-oxidation metabolism and thereby promotes RL-FC/filamentous growth. This regulation is achieved through a Multiple Carbon source Utilizer (Mcu1)-dependent mechanism. Interestingly, both the evolved RL-FC isolates and the gfc1Δ mutant exhibit an enhanced ability to colonize the skin. Our results reveal that glycerol-mediated GFC1 mutations are beneficial during C. auris skin colonization and infection.

Methanooceanicella nereidis gen. nov., sp. nov., the first oceanic Methanocellaceae methanogen, isolated from potential methane hydrate bearing area offshore southwestern Taiwan.

A novel mesophilic, hydrogenotrophic methanogen, strain CWC-04T, was obtained from a sediment sample extracted from a gravity core retrieved at station 22 within the KP-9 area off the southwestern coast of Taiwan during the ORIII-1368 cruise in 2009. Cells of strain CWC-04T were rod-shaped, 1.4-2.9 µm long by 0.5-0.6 µm wide, and occurred singly. Strain CWC-04Tutilized formate, H2/CO2, 2-propanol/CO2 or 2-butanol/CO2 as catabolic substrates. The optimal growth conditions were 42 °C, 0.17 M NaCl and pH 5.35. The genomic DNA G+C content calculated from the genome sequence of strain CWC-04T was 46.19 mol%. Phylogenetic analysis of 16S rRNA gene revealed that strain CWC-04T is affiliated with the genus Methanocella. The 16S rRNA gene sequences similarities within strains Methanocella arvoryzae MRE50T, Methanocella paludicola SANAET and Methanocella conradii HZ254T were 93.7, 93.0 and 91.3 %, respectively. In addition, the optical density of CWC-04T culture dropped abruptly upon entering the late-log growth phase, with virus-like particles (150 nm in diameter) being observed on and around the cells. This observation suggests that strain CWC-04T harbours a lytic virus. Based on these phenotypic, phylogenetic and genomic results, we propose that strain CWC-04T represents a novel species of a novel genus in the family Methanocellaceae, for which the name Methanooceanicella nereidis gen. nov., sp. nov. is proposed. The type strain is CWC-04T (=BCRC AR10050T=NBRC 113165T).

Imaging biological samples by integrated differential phase contrast (iDPC) STEM technique.

Scanning transmission electron microscopy (STEM) is a powerful imaging technique and has been widely used in current material science research. The attempts of applying STEM (annual dark field (ADF)-STEM or annular bright field (ABF)-STEM) into biological research have been going on for decades while applications have still been limited because of the existing bottlenecks in dose efficiency and non-linearity in contrast. Recently, integrated differential phase contrast (iDPC) STEM technique emerged and achieved a linear phase contrast imaging condition, while resolving signals of light elements next to heavy ones even at low electron dose. This enables successful investigation of beam sensitive materials. Here, we investigate iDPC-STEM advantages in biology, in particular, chemically fixed and resin embedded biological tissues. By comparing results to the conventional TEM, we have found that iDPC-STEM not only shows better contrast but also resolves more structural details at molecular level, including conditions of extremely low dose and minimal heavy-atom staining. We also compare iDPC-STEM with ABF-STEM and found that contrast of iDPC-STEM is even further improved, moderately in lower frequency domains while highly with preserving high frequency biological structural details. For thick sample sections, iDPC-STEM is particularly advantageous. It avoids contrast inversion canceling effects, and by adjusting the depth of focus, fully preserves the contrast of structural details along with the sample. In addition, using depth-sectioning, iDPC-STEM enables resolving in-depth structural variation. Our results suggest that iDPC-STEM have the place and advantages within the future biological research.

Few-Atom Pt Ensembles Enable Efficient Catalytic Cyclohexane Dehydrogenation for Hydrogen Production.

Identification of catalytic active sites is pivotal in the design of highly effective heterogeneous metal catalysts, especially for structure-sensitive reactions. Downsizing the dimension of the metal species on the catalyst increases the dispersion, which is maximized when the metal exists as single atoms, namely, single-atom catalysts (SACs). SACs have been reported to be efficient for various catalytic reactions. We show here that the Pt SACs, although with the highest metal atom utilization efficiency, are totally inactive in the cyclohexane (C6H12) dehydrogenation reaction, an important reaction that could enable efficient hydrogen transportation. Instead, catalysts enriched with fully exposed few-atom Pt ensembles, with a Pt-Pt coordination number of around 2, achieve the optimal catalytic performance. The superior performance of a fully exposed few-atom ensemble catalyst is attributed to its high d-band center, multiple neighboring metal sites, and weak binding of the product.

Anti-Excitotoxic Effects of N-Butylidenephthalide Revealed by Chemically Insulted Purkinje Progenitor Cells Derived from SCA3 iPSCs.

Spinocerebellar ataxia type 3 (SCA3) is characterized by the over-repetitive CAG codon in the ataxin-3 gene (ATXN3), which encodes the mutant ATXN3 protein. The pathological defects of SCA3 such as the impaired aggresomes, autophagy, and the proteasome have been reported previously. To date, no effective treatment is available for SCA3 disease. This study aimed to study anti-excitotoxic effects of n-butylidenephthalide by chemically insulted Purkinje progenitor cells derived from SCA3 iPSCs. We successfully generated Purkinje progenitor cells (PPs) from SCA3 patient-derived iPSCs. The PPs, expressing both neural and Purkinje progenitor's markers, were acquired after 35 days of differentiation. In comparison with the PPs derived from control iPSCs, SCA3 iPSCs-derived PPs were more sensitive to the excitotoxicity induced by quinolinic acid (QA). The observations of QA-treated SCA3 PPs showing neural degeneration including neurite shrinkage and cell number decrease could be used to quickly and efficiently identify drug candidates. Given that the QA-induced neural cell death of SCA3 PPs was established, the activity of calpain in SCA3 PPs was revealed. Furthermore, the expression of cleaved poly (ADP-ribose) polymerase 1 (PARP1), a marker of apoptotic pathway, and the accumulation of ATXN3 proteolytic fragments were observed. When SCA3 PPs were treated with n-butylidenephthalide (n-BP), upregulated expression of calpain 2 and concurrent decreased level of calpastatin could be reversed, and the overall calpain activity was accordingly suppressed. Such findings reveal that n-BP could not only inhibit the cleavage of ATXN3 but also protect the QA-induced excitotoxicity from the Purkinje progenitor loss.

Maximizing the Synergistic Effect of CoNi Catalyst on α-MoC for Robust Hydrogen Production.

We report the syntheses of highly dispersed CoNi bimetallic catalysts on the surface of α-MoC based on the strong metal support interaction (SMSI) effect. The interaction between the nearly atomically dispersed Co and Ni atoms was observed for the first time by the real-space chemical mapping at the atomic level. Combined with the ability of α-MoC to split water at low temperatures, the as-synthesized CoNi/α-MoC catalysts exhibited robust and synergistic performance for the hydrogen production from hydrolysis of ammonia borane. The metal-normalized activity of the bimetallic 1.5Co1.5Ni/α-MoC catalyst reached 321.1 molH2·mol-1CoNi·min-1 at 298 K, which surpasses all the noble metal-free catalysts ever reported and is four times higher than that of the commercial Pt/C catalyst.

Tunable Covalent Organic Frameworks with Different Heterocyclic Nitrogen Locations for Efficient Cr(VI) Reduction, Escherichia coli Disinfection, and Paracetamol Degradation under Visible-Light Irradiation.

Covalent organic frameworks (COFs) have great application potentials in photocatalytic water treatment. By using p-phenylenediamine with different numbers and locations of heterocyclic nitrogen atoms as a precursor, five types of COFs with different nitrogen positions were synthesized. We found that Cr(VI) photoreduction,Escherichia coli inactivation, and paracetamol degradation by COFs were heterocyclic nitrogen location-dependent. Particularly, the photocatalytic performance for all three tested pollutants by five types of COFs followed the order of the best performance for COF-PDZ with two ortho position heterocyclic N atoms, medium for COF-PMD with two meta position heterocyclic N atoms, and COF-PZ with two para position heterocyclic N atoms, and COF-PD with a single heterocyclic N atom, the worst performance for COF-1 without a heterocyclic N atom. Compared to the other COFs, COF-PDZ contained improved quantum efficiency and thus enhanced generation of electrons. The lower energy barriers and larger energy gaps of COF-PDZ contributed to its improved quantum efficiencies. The stronger affinity to Cr(VI) with lower adsorption energy of COF-PDZ also contributed to its excellent Cr(VI) reduction performance. By transferring into a more stable keto form, COF-PDZ showed great stability through five regeneration and reuse cycles. Overall, this study provided an insight into the synthesis of high-performance structure-dependent COF-based photocatalysts.

Molybdenum Carbide: Controlling the Geometric and Electronic Structure of Noble Metals for the Activation of O-H and C-H Bonds.

In the field of heterogeneous catalysis, transition metal carbides (TMCs) have attracted growing and extensive attention as a group of important catalytic materials for a variety of energy-related reactions. Due to the incorporation of carbon atoms at the interstitial sites, TMCs possess much higher density of states near the Fermi level, endowing the material with noble-metal-like electron configuration and catalytic behaviors. Crystal structure, site occupancies, surface termination, and metal/carbon defects in the bulk phase or at the surface are the structural factors that influence the behavior of the TMCs in catalytic reactions. In the early studies of heterogeneous catalytic applications of TMCs, the carbide itself was used individually as the catalytically active site, which exhibited unique catalytic performance comparable to precious metal catalysts toward hydrogenation, dehydrogenation, isomerization, and hydrodeoxygenation. To promote the catalytic performance, the doping of secondary transition metals into the carbide lattice to form bimetallic carbides was extensively studied. As a recent development, the utilization of TMCs as functionalized catalyst supports has achieved a series of significant breakthroughs in low-temperature catalytic applications, including the reforming of alcohols, water-gas shift reactions, and the hydrogenation of functional groups for chemical production and biomass conversion. Generally, the excellence of TMCs as supports is attributed to three factors: the modulation of geometric and electronic structures of the supported metal centers, the special reactivity of TMC supports that accelerates certain elementary step and influences the surface coverage of intermediates, and the special interfacial properties at the metal-carbide interface that enhance the synergistic effect. In this Account, we will review recent discoveries from our group and other researchers on the special catalytic properties of face-centered cubic MoC (α-MoC) as both a special catalyst and a functional support that enables highly efficient low-temperature O-H bond activation for several important energy-related catalytic applications, including hydrogen evolution from aqueous phase methanol reforming, ultralow temperature water-gas shift reaction, and biomass conversion. In particular, α-MoC has been demonstrated to exhibit unprecedented strong interaction with the supported metals compared with other TMCs, which not only stabilizes the under-coordinated metal species (single atoms and layered clusters) under strong thermal perturbation and harsh reaction conditions but also tunes the charge density at the metal sites and modifies their catalytic behavior in C-H activation and CO chemisorption. We will discuss how to exploit the metal/α-MoC interaction and interfacial properties to construct CO-tolerant selective hydrogenation catalysts for nitroarene derivatives. Several examples of constructing bifunctional tandem catalytic systems using molybdenum carbides that enable hydrogen extraction and utilization in one-pot conversion of biomass substrates and Fischer-Tropsch synthesis are also highlighted.

The role of echocardiography in prognosis for dysfunction and abandonment of radiocephalic arteriovenous fistula in elderly Chinese patients on hemodialysis.

The objective of this study was to examine the impact of cardiac structure and function at baseline on the outcomes associated with arteriovenous fistula (AVF) in patients on hemodialysis (HD). Patients who initiated HD aged ≥70 years and received a mature AVF creation were included retrospectively. Echocardiographic parameters measured within 1 week before AVF creation were acquired. The observational period for each patient was from the point of AVF creation to the last time of follow-up unless AVF abandonment or death occurred. Kaplan-Meier and Cox proportional hazard regression analyses were conducted. A total of 82 elderly Chinese HD patients with mature radiocephalic AVF (RCAVF) and EF ≥50% were analyzed. During the median study period of 26.8 (12-40) months, 42 (51.2%) experienced RCAVF dysfunction and 34 (41.5%) progressed to abandonment. Primary and cumulative patencies at 6, 12, 24, and 36 months were 81%, 73%, 48%, 38%, and 84%, 81%, 68%, 55%, respectively. Left ventricle end-diastolic volume (LVEDV) ≤103.5 mL (HR = 2.5, P = .019) and the right side of RCAVF (HR = 3.59, P = .003) significantly predicted RCAVF dysfunction. The main pulmonary artery internal diameter (MPAID) ≤21.5 mm (HR = 4.3, P = .001) as well as the right side (HR = 2.95, P = .047) were the independent predictors for RCAVF abandonment. In conclusion, LVEDV, MPAID assessed by echocardiography and the right side of RCAVF, showed significant predictive implications for the outcomes of RCAVF. Disparities among nationalities in the areas of utilization and patency of AVFs necessitate additional studies.

Highly Selective Olefin Production from CO2 Hydrogenation on Iron Catalysts: A Subtle Synergy between Manganese and Sodium Additives.

Mn and Na additives have been widely studied to improve the efficiency of CO2 hydrogenation to valuable olefins on Fe catalysts, but their effects on the catalytic properties and mechanism are still under vigorous debate. This study shows that Fe-based catalysts with moderate Mn and Na contents are highly selective for CO2 hydrogenation to olefins, together with low selectivities for both CO and CH4 and much improved space-time olefin yields compared to state-of-the-art catalysts. Combined kinetic assessment and quasi in situ characterizations further unveil that the sole presence of Mn suppresses the activity of Fe catalysts because of the close contact between Fe and Mn, whereas the introduction of Na mediates the Fe-Mn interaction and provides strong basic sites. This subtle synergy between Na and Mn sheds light on the importance of the interplay of multiple additives that could bring an enabling strategy to improve catalytic activity and selectivity.

Low Temperature Oxidation of Ethane to Oxygenates by Oxygen over Iridium-Cluster Catalysts.

Direct selective oxidation of light alkanes, such as ethane, into value-added chemical products under mild reaction conditions remains a challenge in both industry and academia. Herein, the iridium cluster and atomically dispersed iridium catalysts have been successfully fabricated using nanodiamond as support. The obtained iridium cluster catalyst shows remarkable performance for selective oxidation of ethane under oxygen at 100 °C, with an initial activity as high as 7.5 mol/mol/h and a selectivity to acetic acid higher than 70% after five in situ recycles. The presence of CO in the reaction feed is pivotal for the excellent reaction performance. On the basis of X-ray photoelectron spectroscopy (XPS) analysis, the critical role of CO was revealed, which is to maintain the metallic state of reactive Ir species during the oxidation cycles.

Zn+-O- Dual-Spin Surface State Formation by Modification of ZnO Nanoparticles with Diboron Compounds.

ZnO semiconductor oxides are versatile functional materials that are used in photoelectronics, catalysis, sensing, etc. The Zn+-O- surface electronic states of semiconductor oxides were formed on the ZnO surface by Zn 4s and O 2p orbital coupling with the diboron compound's B 2p orbitals. The formation of spin-coupled surface states was based on the spin-orbit interaction on the interface, which has not been reported before. This shows that the semiconductor oxide's spin surface states can be modulated by regulating surface orbital energy. The Zn+-O- surface electronic states were confirmed by electron spin resonance results, which may help in expanding the fundamental research on spintronics modulation and quantum transport.

Ammonia-Responsive Luminescence of Ln3+-ß-diketonate Complex Encapsulated within Zeolite Y.

Assembling Ln3+(HPBAn) (Ln = Eu or Tb, HPBA = N-(2-pyridinyl)benzoylacetamide) in the cavities of zeolite Y (ZY) via the "ship-in-a-bottle" strategy leads to the formation of novel luminescent composite, Ln(HPBAn)@ZY, whose luminescence can be easily modulated by ammonia on the basis of the energy level variation of HPBA after deprotonation process. Additionally the bimetallic complex doping sample, Eu0.5Tb0.5(HPBAn)@ZY, show great potential as self-referencing luminescent sensor for detecting low ammonia concentration of 10-12⁻0.25 wt%.

Solvent Tunes the Selectivity of Hydrogenation Reaction over α-MoC Catalyst.

Selective activation of chemical bonds in multifunctional oxygenates on solid catalysts is a crucial challenge for sustainable biomass upgrading. Molybdenum carbides and nitrides preferentially activate C═O and C-OH bonds over C═C and C-C bonds in liquid-phase hydrogenation of bioderived furfural, leading to highly selective formations of furfuryl alcohol (FA) and its subsequent hydrogenolysis product (2-methyl furan (2-MF)). We demonstrate that pure-phase α-MoC is more active than ß-Mo2C and γ-Mo2N for catalyzing furfural hydrogenation, and the hydrogenation selectivity on these catalysts can be conveniently manipulated by alcohol solvents without significant changes in reaction rates (e.g., > 90% yields of FA in methanol solvent and of 2-MF in 2-butanol solvent at 423 K). Combined experimental and theoretical assessments of these solvent effects unveil that it is the hydrogen donating ability of the solvents that governs the hydrogenation rate of the reactants, while strong dissociative adsorption of the alcohol solvent on Mo-based catalysts results in surface decoration which controls the reaction selectivity via enforcing steric hindrance on the formation of relevant transient states. Such solvent-induced surface modification of Mo-based catalysts provides a compelling strategy for highly selective hydrodeoxygenation processes of biomass feedstocks.

Atomically Dispersed Pd on Nanodiamond/Graphene Hybrid for Selective Hydrogenation of Acetylene.

We reported here a strategy to use a defective nanodiamond-graphene (ND@G) to prepare an atomically dispersed metal catalyst, i.e., in the current case atomically dispersed palladium catalyst which is used for selective hydrogenation of acetylene in the presence of abundant ethylene. The catalyst exhibits remarkable performance for the selective conversion of acetylene to ethylene: high conversion (100%), ethylene selectivity (90%), and good stability. The unique structure of the catalyst (i.e., atomically dispersion of Pd atoms on graphene through Pd-C bond anchoring) blocks the formation of unselective subsurface hydrogen species and ensures the facile desorption of ethylene against the overhydrogenation to undesired ethane, which is the key for the outstanding selectivity of the catalyst.

Tuning the Selectivity of Catalytic Carbon Dioxide Hydrogenation over Iridium/Cerium Oxide Catalysts with a Strong Metal-Support Interaction.

A one-step ligand-free method based on an adsorption-precipitation process was developed to fabricate iridium/cerium oxide (Ir/CeO2 ) nanocatalysts. Ir species demonstrated a strong metal-support interaction (SMSI) with the CeO2 substrate. The chemical state of Ir could be finely tuned by altering the loading of the metal. In the carbon dioxide (CO2 ) hydrogenation reaction it was shown that the chemical state of Ir species-induced by a SMSI-has a major impact on the reaction selectivity. Direct evidence is provided indicating that a single-site catalyst is not a prerequisite for inhibition of methanation and sole production of carbon monoxide (CO) in CO2 hydrogenation. Instead, modulation of the chemical state of metal species by a strong metal-support interaction is more important for regulation of the observed selectivity (metallic Ir particles select for methane while partially oxidized Ir species select for CO production). The study provides insight into heterogeneous catalysts at nano, sub-nano, and atomic scales.

ICON: 3D reconstruction with 'missing-information' restoration in biological electron tomography.

Electron tomography (ET) plays an important role in revealing biological structures, ranging from macromolecular to subcellular scale. Due to limited tilt angles, ET reconstruction always suffers from the 'missing wedge' artifacts, thus severely weakens the further biological interpretation. In this work, we developed an algorithm called Iterative Compressed-sensing Optimized Non-uniform fast Fourier transform reconstruction (ICON) based on the theory of compressed-sensing and the assumption of sparsity of biological specimens. ICON can significantly restore the missing information in comparison with other reconstruction algorithms. More importantly, we used the leave-one-out method to verify the validity of restored information for both simulated and experimental data. The significant improvement in sub-tomogram averaging by ICON indicates its great potential in the future application of high-resolution structural determination of macromolecules in situ.

FIRT: Filtered iterative reconstruction technique with information restoration.

Electron tomography (ET) combining subsequent sub-volume averaging has been becoming a unique way to study the in situ 3D structures of macromolecular complexes. However, information missing in electron tomography due to limited angular sampling is still the bottleneck in high-resolution electron tomography application. Here, based on the understanding of smooth nature of biological specimen, we present a new iterative image reconstruction algorithm, FIRT (filtered iterative reconstruction technique) for electron tomography by combining the algebra reconstruction technique (ART) and the nonlinear diffusion (ND) filter technique. Using both simulated and experimental data, in comparison to ART and weight back projection method, we proved that FIRT could generate a better reconstruction with reduced ray artifacts and significant improved correlation with the ground truth and partially restore the information at the non-sampled angular region, which was proved by investigating the 90° re-projection and by the cross-validation method. This new algorithm will be subsequently useful in the future for both cellular and molecular ET with better quality and improved structural details.