The tricarboxylic acid cycle is inhibited under acute stress from carbonate alkalinity in the gills of Eriocheir sinensis.

Owing to population growth and environmental pollution, freshwater aquaculture has been rapidly shrinking in recent years. Aquaculture in saline-alkaline waters is a crucial strategy to meet the increasing demand for aquatic products. The Chinese mitten crab is an important economic food in China, but the molecular mechanism by which it tolerates carbonate alkalinity (CA) in water remains unclear. Here, we found that enzyme activities of the tricarboxylic acid (TCA) cycle in the gills, such as citrate synthase, isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, and malate dehydrogenase, were markedly reduced under CA stress induced by 40 mM NaHCO3. Secondly, the TCA cycle in the gills is inhibited under acute CA stress, according to proteomic and metabolomic analyses. The expressions of six enzymes, namely aconitate hydratase, isocitrate dehydrogenase, 2-oxoglutarate dehydrogenase, dihydrolipoyl dehydrogenase, succinate-CoA ligase, and malate dehydrogenase, were downregulated, resulting in the accumulation of phosphoenolpyruvic acid, citric acid, cis-aconitate, and α-ketoglutaric acid. Finally, we testified that if the TCA cycle is disturbed by malonate, the survival rate increases in CA water. To our knowledge, this is the first study to show that the TCA cycle in the gills is inhibited under CA stress. Overall, the results provide new insights into the molecular mechanism of tolerance to saline-alkaline water in crabs, which helped us expand the area for freshwater aquaculture and comprehensively understand the physiological characteristics of crab migration.

Efficient C-N coupling for urea electrosynthesis on defective Co3O4 with dual-functional sites.

Urea electrosynthesis under ambient conditions is emerging as a promising alternative to conventional synthetic protocols. However, the weak binding of reactants/intermediates on the catalyst surface induces multiple competing pathways, hindering efficient urea production. Herein, we report the synthesis of defective Co3O4 catalysts that integrate dual-functional sites for urea production from CO2 and nitrite. Regulating the reactant adsorption capacity on defective Co3O4 catalysts can efficiently control the competing reaction pathways. The urea yield rate of 3361 mg h-1 gcat-1 was achieved with a corresponding faradaic efficiency (FE) of 26.3% and 100% carbon selectivity at a potential of -0.7 V vs. the reversible hydrogen electrode. Both experimental and theoretical investigations reveal that the introduction of oxygen vacancies efficiently triggers the formation of well-matched adsorption/activation sites, optimizing the adsorption of reactants/intermediates while decreasing the C-N coupling reaction energy. This work offers new insights into the development of dual-functional catalysts based on non-noble transition metal oxides with oxygen vacancies, enabling the efficient electrosynthesis of essential C-N fine chemicals.

[Prokaryotic expression and biological activities of the hemolysin BL subunit of a pathogenic Bacillus cereus of cattle origin].

Bacillus cereus belongs to Gram-positive bacteria, which is widely distributed in nature and shows certain pathogenicity. Different B. cereus strains carry different subsets of virulence factors, which directly determine the difference in their pathogenicity. It is therefore important to study the distribution of virulence factors and the biological activity of specific toxins for precise prevention and control of B. cereus infection. In this study, the hemolysin BL triayl was expressed, purified, and characterized. The results showed that the bovine pathogenic B. cereus hemolysin BL could be expressed and purified in the prokaryotic expression system, and the bovine pathogenic B. cereus hemolysin BL showed hemolysis, cytotoxicity, good immunogenicity and certain immune protection in mice. In this study, the recombinant expression of hemolysin BL triayl was achieved, and the biological activity of hemolysin BL of bovine pathogenic ceroid spore was investigated. This study may facilitate further investigating the pathogenic mechanism of B. cereus hemolysin BL and developing a detection method for bovine pathogenic B. cereus disease.

Catalytic Conversion of Lignin into Valuable Chemicals: Full Utilization of Aromatic Nuclei and Side Chains.

ConspectusIn recent years, significant efforts have been directed toward achieving efficient and mild lignocellulosic biomass conversion into valuable chemicals and fuels, aiming to address energy and environmental concerns and realize the goal of carbon neutrality. Lignin is one of the three primary building blocks of lignocellulose and the only aromatic renewable feedstock. However, the complex and diverse nature of lignin feedstocks, characterized by their three-dimensional, highly branched polymeric structure and intricate C-O/C-C chemical bonds, results in substantial challenges. To tackle these challenges, we carried out extensive research on selectively activating and transforming chemical bonds in lignin for chemical synthesis. In this Account, we discuss our recent progress in catalytic lignin conversion.Our work is focused on two main objectives: (i) achieving precise and selective transformation of C-O/C-C bonds in lignin (and its model compounds) and (ii) fully utilizing the aromatic nuclei and side chains present in lignin to produce valuable chemicals. Lignin consists of interconnected phenylpropanoid subunits linked by interlaced C-C/C-O bonds. To unlock the full potential of lignin, we propose the concept of "the full utilization of lignin", which encompasses both the aromatic nuclei and the side chains (e.g., methoxyl and polyhydroxypropyl groups).For the conversion of aromatic nuclei, selective activation of C-O and/or C-C bonds is crucial in synthesizing targeted aromatic products. We begin with model compounds (such as anisole, phenol, guaiacol, etc.) and then transition to protolignin feedstocks. Various reaction routes are developed, including self-supported hydrogenolysis, direct Caryl-Csp3 cleavage, coupled Caryl-Csp3 cleavage and Caryl-O hydrogenolysis, and tandem selective hydrogenation and hydrolysis processes. These tailored pathways enable high-yield and sustainable production of a wide range of aromatic (and derived) products, including arenes (benzene, toluene, alkylbenzenes), phenols, ketones, and acids.In terms of side chain utilization, we have developed innovative strategies such as selective methyl transfer, coupling depolymerization-methyl shift, selective acetyl utilization, and new activation methods such as amine-assisted prefunctionalization. These strategies enable the direct synthesis of methyl-/alkyl-derived products, such as acetic acid, 4-ethyltoluene, dimethylethylamine, and amides. Additionally, aromatic residues can be transformed into chemicals or functionalized ingredients that can serve as catalysts or functional biopolymer materials. These findings highlight promising opportunities for harnessing both the aromatic nuclei and side chains of lignin in a creative manner, thereby improving the overall atom economy of lignin upgrading.Through innovative catalyst engineering and reaction route strategies, our work achieves the sustainable and efficient production of various valuable chemicals from lignin. By integrating side chains and aromatic rings, we have successfully synthesized methyl-/alkyl-derived and aromatic-derived products with high yields. The full utilization of lignin not only minimizes waste but also opens up new possibilities for generating chemical products from lignin. These novel approaches unlock the untapped potential of lignin, expand the boundaries of lignin upgrading, and enhance the efficiency and economic viability of lignin biorefining.

Glutamate-pantothenate pathway promotes antibiotic resistance of Edwardsiella tarda.

Although cellular metabolic states have been shown to modulate bacterial susceptibility to antibiotics, the interaction between glutamate (Glu) and chloramphenicol (CAP) resistance remains unclear because of the specificity of antibiotics and bacteria. We found that the level of Glu was upregulated in the CAP-resistant strain of Edwardsiella tarda according to a comparative metabolomics approach based on LC-MS/MS. Furthermore, we verified that exogenous metabolites related to Glu, the tricarboxylic acid (TCA) cycle, and glutathione (GSH) metabolism could promote CAP resistance in survival assays. If GSH metabolism or the TCA cycle is inhibited by L-buthionine sulfoximine or propanedioic acid, the promotion of CAP resistance by Glu in the corresponding pathway disappears. According to metabolomic analysis, exogenous Glu could change pantothenate metabolism, affecting GSH biosynthesis and the TCA cycle. These results showed that the glutamate-pantothenate pathway could promote CAP resistance by being involved in the synthesis of GSH, entering the TCA cycle by direct deamination, or indirectly affecting the metabolism of the two pathways by pantothenate. These results extend our knowledge of the effect of Glu on antibiotic resistance and suggest that the potential effect, which may aggravate antibiotic resistance, should be considered before Glu and GSH administration in the clinic.

Progress in the application of Enterococcus faecium in animal husbandry.

As a probiotic, enterococcus faecium (E. faecium) has the characteristics of high temperature resistance, gastric acid resistance, bile salt resistance, etc. It can also effectively improve animal performance and immunity and improve the animal's intestinal environment, so in recent years it has been more widely used in the livestock industry. However, due to the improper use of antibiotics and the growing environmental stress of strains, the drug resistance of enterococcus faecium has become more and more serious, and because some enterococcus faecium carry virulence genes, leading to the emergence of pathogenic strains, its safety issues have been widely concerned. This paper focuses on the biological characteristics of enterococcus faecium, the application of this bacterium in animal husbandry and the safety issues in its use, with a view to providing a reference for the application of enterococcus faecium in the development of animal husbandry.

A novel whole-head RF coil design tailored for concurrent multichannel brain stimulation and imaging at 3T.

PURPOSE: Multichannel Transcranial Magnetic Stimulation (mTMS) [1] is a novel non-invasive brain stimulation technique allowing multiple sites to be stimulated simultaneously or sequentially under electronic control without movement of the coils. To enable simultaneous mTMS and MR imaging, we have designed and constructed a whole-head 28-channel receive-only RF coil at 3T. METHODS: A helmet-shaped structure was designed considering a specific layout for a mTMS system with holes for positioning the TMS units next to the scalp. Diameter of the TMS units defined the diameter of RF loops. The placement of the preamplifiers was designed to minimize possible interactions and to allow straightforward positioning of the mTMS units around the RF coil. Interactions between TMS-MRI were analyzed for the whole-head system extending the results presented in previous publications [2]. Both SNR- and g-factors maps were obtained to compare the imaging performance of the coil with commercial head coils. RESULTS: Sensitivity losses for the RF elements containing TMS units show a well-defined spatial pattern. Simulations indicate that the losses are predominantly caused by eddy currents on the coil wire windings. The average SNR performance of the TMSMR 28-channel coil is about 66% and 86% of the SNR of the 32/20-channel head coil respectively. The g-factor values of the TMSMR 28-channel coil are similar to the 32-channel coil and significantly better than the 20-channel coil. CONCLUSION: We present the TMSMR 28-channel coil, a head RF coil array to be integrated with a multichannel 3-axisTMS coil system, a novel tool that will enable causal mapping of human brain function.

Application of Flow Cytometry in the Diagnosis of Bovine Epidemic Disease.

As science and technology continue to advance, the use of flow cytometry is becoming more widespread. It can provide important information about cells in the body by detecting and analysing them, thereby providing a reliable basis for disease diagnosis. In the diagnosis of bovine epidemic diseases, flow cytometry can be used to detect bovine viral diarrhoea, bovine leukaemia, bovine brucellosis, bovine tuberculosis, and other diseases. This paper describes the structure of a flow cytometer (liquid flow system, optical detection system, data storage and analysis system) and its working principles for rapid quantitative analysis and sorting of single cells or biological particles. Additionally, the research progress of flow cytometry in the diagnosis of bovine epidemic diseases was reviewed in order to provide a reference for future research and application of flow cytometry in the diagnosis of bovine epidemic diseases.

Aerobic Oxidative Cleavage of C(OH)-C Bonds to Produce Aromatic Aldehydes Catalyzed by CuI -1,10-phenanthroline Complex.

Effective cleavage and functionalization of C(OH)-C bonds is of great importance for the production of value-added chemicals from renewable biomass resources such as carbohydrates, lignin and their derivatives. The efficiency and selectivity of oxidative cleavage of C(OH)-C bonds are hindered by their inert nature and various side reactions associated with the hydroxyl group. The oxidative conversion of secondary alcohols to produce aldehydes is particularly challenging because the generated aldehydes tend to be over-oxidized to acids or the other side products. Noble-metal based catalysts are necessary to get satisfactory aldehyde yields. Herein, for the first time, the efficient aerobic oxidative conversion of secondary aromatic alcohols into aromatic aldehydes is reported using non-noble metal catalysts and environmentally benign oxygen, without any additional base. It was found that CuI -1,10-phenanthroline (Cu-phen) complex showed outstanding performance for the reactions. The C(OH)-C bonds of a diverse array of aromatic secondary alcohols were effectively cleaved and functionalized, selectively affording aldehydes with excellent yields. Detailed mechanism study revealed a radical mediated pathway for the oxidative reaction. We believe that the findings in this work will lead to many explorations in non-noble metal catalyzed oxidative reactions.

Modeling transcranial magnetic stimulation coil with magnetic cores.

Objective.Accurate modeling of transcranial magnetic stimulation (TMS) coils with the magnetic core is largely an open problem since commercial (quasi) magnetostatic solvers do not output specific field characteristics (e.g. induced electric field) and have difficulties when incorporating realistic head models. Many open-source TMS softwares do not include magnetic cores into consideration. This present study reports an algorithm for modeling TMS coils with a (nonlinear) magnetic core and validates the algorithm through comparison with finite-element method simulations and experiments.Approach.The algorithm uses the boundary element fast multipole method applied to all facets of a tetrahedral core mesh for a single-state solution and the successive substitution method for nonlinear convergence of the subsequent core states. The algorithm also outputs coil inductances, with or without magnetic cores. The coil-core combination is solved only once i.e. before incorporating the head model. The resulting primary TMS electric field is proportional to the total vector potential in the quasistatic approximation; it therefore also employs the precomputed core magnetization.Main results.The solver demonstrates excellent convergence for typical TMS field strengths and for analyticalB-Happroximations of experimental magnetization curves such as Froelich's equation or an arctangent equation. Typical execution times are 1-3 min on a common multicore workstation. For a simple test case of a cylindrical core within a one-turn coil, our solver computed the small-signal inductance nearly identical to that from ANSYS Maxwell. For a multiturn rodent TMS coil with a core, the modeled inductance matched the experimental measured value to within 5%.Significance.Incorporating magnetic core in TMS coil design has advantages of field shaping and energy efficiency. Our software package can facilitate model-informed design of more efficiency TMS systems and guide selection of core material. These models can also inform dosing with existing clinical TMS systems that use magnetic cores.

Co-based Catalysts for Selective H2 O2 Electroproduction via 2-electron Oxygen Reduction Reaction.

Electrochemical production of hydrogen peroxide (H2 O2 ) via two-electron oxygen reduction reaction (ORR) process is emerging as a promising alternative method to the conventional anthraquinone process. To realize high-efficiency H2 O2 electrosynthesis, robust and low cost electrocatalysts have been intensively pursued, among which Co-based catalysts attract particular research interests due to the earth-abundance and high selectivity. Here, we provide a comprehensive review on the advancement of Co-based electrocatalyst for H2 O2 electroproduction. The fundamental chemistry of 2-electron ORR is discussed firstly for guiding the rational design of electrocatalysts. Subsequently, the development of Co-based electrocatalysts involving nanoparticles, compounds and single atom catalysts is summarized with the focus on active site identification, structure regulation and mechanism understanding. Moreover, the current challenges and future directions of the Co-based electrocatalysts are briefly summarized in this review.

Selective Hydrodeoxygenation of Aromatics to Cyclohexanols over Ru Single Atoms Supported on CeO2.

Cyclohexanols are widely used chemicals, which are mainly produced by oxidation of fossil feedstocks. Selective hydrodeoxygenation of lignin derivatives has great potential for producing these chemicals but is challenging to obtain high yields. Here, we report that CeO2-supported Ru single-atom catalysts (SACs) enabled the hydrogenation of the benzene ring and catalyzed etheric C-O(R) bond cleavage without changing the C-O(H) bond, which could afford 99.9% yields of cyclohexanols. As far as we know, this is the first to report that SACs catalyze hydrogenation of the aromatic ring. The reaction mechanism was studied by control experiments and density functional theory calculations. In the catalysts, the Ru-O-Ce sites were formed and one Ru atom was coordinated with about four O atoms. These catalytic sites could realize both the hydrogenation and deoxygenation reactions efficiently, and thus desired cyclohexanols were generated. This work pioneers the single-atom catalysis in aromatic transformation and provides a novel route for synthesis of cyclohexanols.

[Research progress of c-di-GMP in the regulation of Escherichia coli biofilm].

Escherichia coli biofilm is a complex membrane aggregation produced by the adhesion and secretion of extracellular polymeric substances by E. coli cells aggregated on specific media. Pathogenic E. coli will evade the immune system and the impact of various harmful factors in the environment after the formation of biofilm, causing sustained and even fatal damage to the host. Cyclic diguanosine monophosphate (c-di-GMP) is a second messenger ubiquitous in bacteria and plays a crucial role in regulating biofilm formation. This paper reviewed the recent studies about the role of c-di-GMP in the movement, adhesion, and EPS production mechanism of E. coli during biofilm formation, aiming to provide a basis for inhibiting E. coli biofilm from the perspective of c-di-GMP.

Highly efficient C(CO)-C(alkyl) bond cleavage in ketones to access esters over ultrathin N-doped carbon nanosheets.

Selective oxidative cleavage of the C(CO)-C bond in ketones to access esters is a highly attractive strategy for upgrading ketones. However, it remains a great challenge to realize this important transformation over heterogeneous metal-free catalysts. Herein, we designed a series of porous and ultrathin N-doped carbon nanosheets (denoted as CN-X, where X represents the pyrolysis temperature) as heterogeneous metal-free catalysts. It was observed that the fabricated CN-800 could efficiently catalyze the oxidative cleavage of the C(CO)-C bond in various ketones to generate the corresponding methyl esters at 130 °C without using any additional base. Detailed investigations revealed that the higher content and electron density of the graphitic-N species contributed to the excellent performance of CN-800. Besides, the high surface area, affording active sites that are more easily accessed, could also enhance the catalytic activity. Notably, the catalysts have great potential for practical applications because of some obvious advantages, such as low cost, neutral reaction conditions, heterogeneous nature, high efficiency, and broad ketone scope. To the best of our knowledge, this is the first work on efficient synthesis of methyl esters via oxidative esterification of ketones over heterogeneous metal-free catalysts.

A high-density theta burst paradigm enhances the aftereffects of transcranial magnetic stimulation: Evidence from focal stimulation of rat motor cortex.

BACKGROUND: Theta burst stimulation (TBS) is an efficient noninvasive neuromodulation paradigm that has been widely adopted, clinically. However, the efficacy of TBS treatment remains similarly modest as conventional 10 Hz repetitive transcranial magnetic stimulation (rTMS). OBJECTIVE/HYPOTHESIS: To develop a new TBS paradigm that enhances the effects of TMS administration while maintaining high time-efficiency. METHODS: We describe here a new TMS paradigm, named High-Density Theta Burst Stimulation (hdTBS). This paradigm delivers up to 6 pulses per burst, as opposed to only 3 in conventional TBS, while maintaining the inter-burst interval of 200 ms (or 5 Hz) - a critical parameter in inducing long-term potentiation. This paradigm was implemented on a TMS stimulator developed in-house; its physiological effects were assessed in the motor cortex of awake rats using a rodent specific focal TMS coil. Microwire electrodes were implanted into each rat's limb muscles to longitudinally record motor-evoked potential (MEP). Four different TBS paradigms (3, 4, 5 or 6 pulses per burst, 200 s per session) were tested; MEP signals were recorded immediately before (baseline) and up to 35 min post each TBS session. RESULTS: We developed a stimulator based on a printed-circuit board strategy. The stimulator was able to deliver stable outputs of up to 6 pulses per burst. Animal experiments (n = 15) revealed significantly different aftereffects induced by the four TBS paradigms (Friedman test, p = 0.018). Post hoc analysis further revealed that, in comparison to conventional 3-pulse TBS, 5- and 6-pulse TBS enhanced the aftereffects of MEP signals by 56% and 92%, respectively, while maintaining identical time efficiency. CONCLUSION(S): A new stimulation paradigm is proposed, implemented and tested in the motor cortex of awake rats using a focal TMS coil developed in the lab. We observed enhanced aftereffects as assessed by MEP, with no obvious adverse effects, suggesting the translational potentials of this paradigm.

Angle-tuned coils: attractive building blocks for TMS with improved depth-spread performance.

Objective.A novel angle-tuned ring coil is proposed for improving the depth-spread performance of transcranial magnetic stimulation (TMS) coils and serve as the building blocks for high-performance composite coils and multisite TMS systems.Approach.Improving depth-spread performance by reducing field divergence through creating a more elliptical emitted field distribution from the coil. To accomplish that, instead of enriching the Fourier components along the planarized (x-y) directions, which requires different arrays to occupy large brain surface areas, we worked along the radial (z) direction by using tilted coil angles and stacking coil numbers to reduce the divergence of the emitted near field without occupying large head surface areas. The emitted electric field distributions were theoretically simulated in spherical and real human head models to analyze the depth-spread performance of proposed coils and compare with existing figure-8 coils. The results were then experimentally validated with field probes andin-vivoanimal tests.Main results.The proposed 'angle-tuning' concept improves the depth-spread performance of individual coils with a significantly smaller footprint than existing and proposed coils. For composite structures, using the proposed coils as basic building blocks simplifies the design and manufacturing process and helps accomplish a leading depth-spread performance. In addition, the footprint of the proposed system is intrinsically small, making them suitable for multisite stimulations of inter and intra-hemispheric brain regions with an improved spread and less electric field divergence.Significance.Few brain functions are operated by isolated single brain regions but rather by coordinated networks involving multiple brain regions. Simultaneous or sequential multisite stimulations may provide tools for mechanistic studies of brain functions and the treatment of neuropsychiatric disorders. The proposed AT coil goes beyond the traditional depth-spread tradeoff rule of TMS coils, which provides the possibility of building new composite structures and new multisite TMS tools.

Electrochemical Strategy for the Simultaneous Production of Cyclohexanone and Benzoquinone by the Reaction of Phenol and Water.

Cyclohexanone and benzoquinone are important chemicals in chemical and manufacturing industries. The simultaneous production of cyclohexanone and benzoquinone by the reaction of phenol and water is an ideal route for the economical production of the two chemicals. In principle, this can be achieved in an electrochemical reaction system that couples the cathodic reduction of phenol to cyclohexanone and the anodic oxidation of phenol to benzoquinone, which has not been realized. Here, we report the first work on this integration strategy, where nitrogen-doped hierarchically porous carbon (NHPC)-supported NiPt and FeRu designed in this work are very efficient and selective cathode and anode catalysts, affording >99.9% selectivities to both cyclohexanone and benzoquinone. The excellent electrocatalytic performance of the catalysts can be ascribed to the poor absorption capability of the NiPt alloy nanoparticles (NPs) for cyclohexanone and Fe single-atom decorated Ru NPs for benzoquinone, which avoids the excessive reduction and oxidation of the desired products. The reaction pathway is proposed on the basis of control experiments, in which two phenol molecules react with one H2O molecule with 100% atom-efficiency. In the scale-up experiment at the 1 g scale, NiPt/NHPC and FeRu/NHPC exhibit excellent durability and stability, which enables this integrated system to afford 645.3 mg of cyclohexanone and 691.7 mg of benzoquinone synchronously in an operating time of 90 h.

High-Performance Magnetic-core Coils for Targeted Rodent Brain Stimulations.

Objective and Impact Statement. There is a need to develop rodent coils capable of targeted brain stimulation for treating neuropsychiatric disorders and understanding brain mechanisms. We describe a novel rodent coil design to improve the focality for targeted stimulations in small rodent brains. Introduction. Transcranial magnetic stimulation (TMS) is becoming increasingly important for treating neuropsychiatric disorders and understanding brain mechanisms. Preclinical studies permit invasive manipulations and are essential for the mechanistic understanding of TMS effects and explorations of therapeutic outcomes in disease models. However, existing TMS tools lack focality for targeted stimulations. Notably, there has been limited fundamental research on developing coils capable of focal stimulation at deep brain regions on small animals like rodents. Methods. In this study, ferromagnetic cores are added to a novel angle-tuned coil design to enhance the coil performance regarding penetration depth and focality. Numerical simulations and experimental electric field measurements were conducted to optimize the coil design. Results. The proposed coil system demonstrated a significantly smaller stimulation spot size and enhanced electric field decay rate in comparison to existing coils. Adding the ferromagnetic core reduces the energy requirements up to 60% for rodent brain stimulation. The simulated results are validated with experimental measurements and demonstration of suprathreshold rodent limb excitation through targeted motor cortex activation. Conclusion. The newly developed coils are suitable tools for focal stimulations of the rodent brain due to their smaller stimulation spot size and improved electric field decay rate.

CO-Tolerant PEMFC Anodes Enabled by Synergistic Catalysis between Iridium Single-Atom Sites and Nanoparticles.

Proton-exchange membrane fuel cells (PEMFCs) are limited by their extreme sensitivity to trace-level CO impurities, thus setting a strict requirement for H2 purity and excluding the possibility to directly use cheap crude hydrogen as fuel. Herein, we report a proof-of-concept study, in which a novel catalyst comprising both Ir particles and Ir single-atom sites (IrNP @IrSA -N-C) addresses the CO poisoning issue. The Ir single-atom sites are found not only to be good CO oxidizing sites, but also excel in scavenging the CO molecules adsorbed on Ir particles in close proximity, thereby enabling the Ir particles to reserve partial active sites towards H2 oxidation. The interplay between Ir nanoparticles and Ir single-atom centers confers the catalyst with both excellent H2 oxidation activity (1.19 W cm-2 ) and excellent CO electro-oxidation activity (85 mW cm-2 ) in PEMFCs; the catalyst also tolerates CO in H2 /CO mixture gas at a level that is two times better than that of the current best PtRu/C catalyst.

The immune response of pIgR and Ig to Flavobacterium columnare in grass carp (Ctenopharyngodon idellus).

The polymeric immunoglobulin receptor (pIgR) plays an important role in mediating the transcytosis of polymeric immunoglobulins (pIgs) to protect organisms against pathogen invasion. Here, a polyclonal antibody against grass carp (Ctenopharyngodon idellus) recombinant pIgR was developed by immunizing New Zealand white rabbit, and the responses of pIgR, IgM and IgZ were analyzed after bath immunization and intraperitoneal administration with Flavobacterium columnare. The results showed that pIgR transcription level was similar to IgM and IgZ, but pIgR rose much faster and peaked earlier than IgM and IgZ; the pIgR mRNA levels were higher in the skin and spleen for both immunized groups, while IgM and IgZ mRNA expression were higher in skin, gills, and intestines in bath immersion group, or spleen and head kidney in intraperitoneal immunization group. ELISA revealed that the IgM, IgZ and pIgR protein levels were up-regulated in skin mucus, gill mucus, gut mucus and bile, reaching a higher peak level earlier in skin mucus and gill mucus in bath immersion group, but a higher peak level in bile in injection group. Moreover, secretory component molecules were detected in grass carp's skin, gill and intestine mucus and bile, but not in serum, which molecular mass was near the theoretical mass obtained from the sequence of grass carp pIgR. These results demonstrated that bath and intraperitoneal immunization up-regulated pIgR and secretory Ig expression in secretions, which provided more insights into the role of pIgR in immunity and offer insight into ways of protecting teleost against pathogen invasion.