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Nitriles are versatile and highly desired chemical intermediates for a range of products. Their economic large-scale production requires highly efficient and selective synthesis. The nickel-catalyzed hydrocyanation of C=C double bonds provides such selective and 100% atom-economical access to nitriles, but the catalysts hitherto lack activity and longevity. Yet, the literature focusing on increased catalytic activity or optimized operational procedures is scarce, at the least. Here, we present a thorough investigation and optimization of operational procedures using a commercially available diphosphite ligand and styrene as a model substrate. This led us to achieve a TOF20 of more than 300,000 h−1. [ABSTRACT FROM AUTHOR]

Enhanced catalysis for organic transformation is essential for the synthesis of high-value compounds. Atomic metal species recently emerged as highly effective catalysts for organic reactions with high activity and metal utilization. However, developing efficient atomic catalysts is always an attractive and challenging topic in the modern chemical industry. In this work, we report the preparation and activity enhancement of nitrogen- and sulfur-codoped holey graphene (NSHG) with the anchoring of atomic metal Pd. When employed as the catalyst for nitroarenes reduction reactions, the resultant Pd/NSHG composite exhibits remarkably high catalytic activity due to the co-existence of dual-active components (i.e., catalytically active NSHG support and homogeneous dispersion of atomic metal Pd). In the catalytic 4-nitrophenol (4-NP) reduction reaction, the efficiency (turnover frequency) is 3.99 × 10−2 mmol 4-NP/(mg cat.·min), which is better than that of metal-free nitrogen-doped holey graphene (NHG) (2.3 × 10−3 mmol 4-NP/(mg cat.·min)) and NSHG carbocatalyst (3.8 × 10−3 mmol 4-NP/(mg cat.·min)), the conventional Pd/C and other reported metal-based catalysts. This work provides a rational design strategy for the atomic metal catalysts loaded on active doped graphene support. The resultant Pd/NSHG dual-active component catalyst (DACC) is also anticipated to bring great application potentials for a broad range of organic fields, such as organic synthesis, environment treatment, energy storage and conversion. [ABSTRACT FROM AUTHOR]

By crushing the prepared cement paste, the recycled powder (RP) was prepared by grinding. The study systematically investigated the effects of microwave power and activation time on the activity of RP. The results showed that the maximum enhancement in the activity of RP occurs when the microwave power is set to 490 W and the activation time is 10 minutes, with the activity increased by 14 %, 15 %, and 22 % at 3, 7, and 28 days, respectively. After microwave activation of RP, the decomposition of C-(A)-S-H and ettringite in the RP provides calcium, silicon, and aluminum phases, and the evaporation of bound water promotes the secondary hydration of RP. After microwave activation, the content of calcium oxide (CaO) in the RP increases, while the contents of silicon dioxide (SiO 2) and alumina oxide (Al 2 O 3) decrease; Adding activated RP to prepare mortar generates more hydration products to fill the pores, making the structure more compact. Compared with the control group, the porosity of the MRP-5 group decreased by 2.38 %. • Studied the effect of microwave excitation on the activity of recycled powder. • The mechanism of microwave-induced recycled powder has been revealed. [ABSTRACT FROM AUTHOR]

RhCu-BMLs with different Rh/Cu molar ratios is synthesised by the high-temperature cyanogel-reduction method. The electronic structure of Rh was optimized by the introduction of Cu atoms, which effectively improves the selectivity of Rh 3 Cu 1 -BMLs for the GEOR. This work provides meaningful insight into the design of advanced electrocatalysts for highly selective GEOR. [Display omitted] • Ultrathin RhCu-BMLs were constructed by the high-temperature cyanogel-reduction method. • RhCu-BMLs showed big surface area, fast mass transport, and optimized electronic structure. • RhCu-BMLs exhibited excellent mass activity (579.3 A g Rh −1) for the GEOR. • RhCu-BMLs revealed a higher selectivity (78.7%) for glyceric acid. The selective electro-oxidation reaction represents an efficient and environmentally friendly pathway to produce value-added chemicals from glycerol. Herein, we introduce a high-temperature cyanogel-reduction method to synthesize ultrathin RhCu bimetallenes (RhCu-BMLs) with varying Rh/Cu molar ratios and investigate their catalytic activity and selectivity for the glycerol electro-oxidation reaction (GEOR). Among these catalysts, the as-prepared Rh 3 Cu 1 -BMLs exhibit outstanding mass activity (579.3 A g Rh −1) for the GEOR under alkaline conditions, marking a 2.32-fold enhancement in mass activity (249.6 A g Rh −1) relative to single-component Rh metallens (Rh-MLs). Meanwhile, both experimental characterizations and theoretical calculations reveal that Cu atoms can attenuate OH− adsorption and block the oxygen insertion reaction for the generation of tartaric acid due to the electronic effect. Consequently, Rh 3 Cu 1 -BMLs achieve a remarkable 78.7 % selectivity for generating glyceric acid during GEOR. This work provides an important reference for fabricating bimetallic Rh-based catalysts and advancing the selectivity and activity in GEOR. [ABSTRACT FROM AUTHOR]

• Fluorine-doping engineering was developed using NH 4 F and HF as precursors. • Fluorine doped Al 2 O 3 shows more oxygen vacancy defects and strong Lewis acid sites. • NF-Al 2 O 3 /O 3 system selectively degrades electron-rich pollutants with high environment tolerance. • It's feasible to reuse the dyeing & finishing wastewater after purification by NF-Al 2 O 3 /O 3 system. Manipulating the electron density of active sties to develop highly efficient catalysts is expected to be one of the most ideal approaches to facilitate overall efficiency of the heterogenous catalytic ozonation (HCO) process. In this study, we demonstrate a fluorine-doping engineering to optimize the HCO activity of aluminum oxide through an improved sol–gel method using NH 4 F (NF-Al 2 O 3) and HF (HF-Al 2 O 3) as the fluorine source. We provide evidence that the fluorine atom is successfully incorporated into crystal structure of NF-Al 2 O 3 via the formation of Al-F-Al bonds, accompany with the generation of oxygen vacancy defects, which allow for ozone molecule adsorption and activation. In contrast, the fabricated HF-Al 2 O 3 only features the presence of Al x F y ·nH 2 O instead of Al-F-Al structure probably due to the unexpected etching reaction. The introduction of fluorine atom largely decreases the local electron density of neighboring Al of NF-Al 2 O 3 catalyst evidenced by the two-fold increment in the amount of strong Lewis acid sites. Consequently, the HCO activity of NF-Al 2 O 3 catalyst is found promotion by 42.9% over pure Al 2 O 3 in terms of the degradation kinetic rate constant (k obs). The NF-Al 2 O 3 catalyst exhibits a powerful capacity to selectively catalyze ozone molecule into singlet oxygen (1O 2), rendering the HCO system with high-tolerance to coexisting water matrixes (e.g., humic acid, chlorine ions, carbonate). Moreover, NF-Al 2 O 3 initiated HCO system can effectively purify wastewaters from textile industry with high-quality enough to be reused for textile dyeing. Therefore, our study provides a novel strategy to develop effective HCO catalysts for promoting wastewater treatment and reuse. [ABSTRACT FROM AUTHOR]

Rationally tailoring a robust artificial coating can enhance the life‐time of fragile biomacromolecules. However, the coating also can restrain the activity of the guest because of the decreased substrate accessibility. Herein, we report a peptide‐directed strategy that enables in situ tailoring of the MOF‐shrouded biohybrids into controllable nanoarchitectures. The MOF biohybrid can be shaped from different 3D microporous architectures into a 2D mesoporous layer by a peptide modulator. Using this mild strategy, we show that the nanoarchitectures of the MOF coatings significantly affect the biological functions of the contained biomacromolecules. The biomacromolecules entrapped within the novel 2D mesoporous spindle‐shaped MOFs (2D MSMOFs) have significantly increased bioactivity compared to when encased within the hitherto explored 3D microporous MOFs. The improvement results from the shortened diffusion path and enlarged pore channel in 2D MSMOFs. Meanwhile, the thin 2D MSMOF layer also can provide excellent protection of the hosted biomacromolecules or protein‐scaffolded biominerals through structural confinement. [ABSTRACT FROM AUTHOR]

Rationally tailoring a robust artificial coating can enhance the life‐time of fragile biomacromolecules. However, the coating also can restrain the activity of the guest because of the decreased substrate accessibility. Herein, we report a peptide‐directed strategy that enables in situ tailoring of the MOF‐shrouded biohybrids into controllable nanoarchitectures. The MOF biohybrid can be shaped from different 3D microporous architectures into a 2D mesoporous layer by a peptide modulator. Using this mild strategy, we show that the nanoarchitectures of the MOF coatings significantly affect the biological functions of the contained biomacromolecules. The biomacromolecules entrapped within the novel 2D mesoporous spindle‐shaped MOFs (2D MSMOFs) have significantly increased bioactivity compared to when encased within the hitherto explored 3D microporous MOFs. The improvement results from the shortened diffusion path and enlarged pore channel in 2D MSMOFs. Meanwhile, the thin 2D MSMOF layer also can provide excellent protection of the hosted biomacromolecules or protein‐scaffolded biominerals through structural confinement. [ABSTRACT FROM AUTHOR]

• A novel method for simultaneous immobilization and activity enhancement of laccase. • CuMNP effectively enhanced the activity of laccase by 18% as compared to free laccase. • Laccase immobilized CuMNP system was stable at harsh conditions and reusable. • SEM, FT-IR, XRD, TGA and VSM data confirmed the immobilization laccase. • Laccase immobilized CuMNP effectively delignifies Ipomoea carnea by 43.28 ± 1.46%. In this paper, a novel method for simultaneous enhancement of catalytic activity and reusability of laccase was carried out to overcome the limitations on industrial application of laccase. The immobilization of laccase onto copper ferrite magnetic nanoparticles (CuMNPs) and ferrite magnetic nanoparticles (MNPs) were optimized at 50 mM glutaraldehyde concentration and 1:5 enzyme:nanoparticles (NPs) ratio for 9 h of cross-linking time, yielding a maximum activity recovery of 94.68 ± 0.92% and 89.78 ± 1.24%, respectively. The laccase immobilized NPs were characterized using physico-chemical methods such as SEM-EDAX, FTIR, XRD, TGA and VSM and the laccase immobilized CuMNPs showed 18% higher activity as compared to free enzyme. The prepared CuMNPs and MNPs showed superior thermal stability (50–70 °C) with t 1/2 increased by 5.7 and 4.1 folds, respectively, as compared to free laccase. The laccase in immobilized forms exhibited higher kinetic potential and stable at wide temperature and pH range. In addition, laccase immobilized NPs retained more than 70% residual activity during reuse up to 6 cycles and storing for 20 days at 4 °C. The laccase immobilized CuMNPs showed higher delignification (43.28 ± 1.46%) on Ipomoea carnea than laccase immobilized MNPs. [ABSTRACT FROM AUTHOR]

MoS2 is a promising material for electrocatalysis and opens up avenues for the development of non‐precious metal electrocatalysts for hydrogen evolution reaction in acidic media. However, the activity of MoS2 has been severely impeded because of its inferior conductivity. Herein, a nanoribbon‐like MoS2/Mo3N2 hybrid is successfully fabricated via partial sulfidation of Mo3N2 in H2S atmosphere. The synergistic effect between the high intrinsic activity of MoS2 and the desirable conductivity of Mo3N2 contributes to the overpotential at the current density of 10 mA cm−2 (η10) of 196 mV towards hydrogen evolution, distinctively lower than Mo3N2 (467 mV) and MoS2 (293 mV). The theoretical simulation discloses that the Gibbs free‐energy for the adsorption of atomic hydrogen (|ΔGH*|) for MoS2/Mo3N2 is less than that of others, and thus facilitating the hydrogen evolution. [ABSTRACT FROM AUTHOR]

Low-cost wood sawdust was investigated as a primary source for preparing active carbon to enhance the lead-acid battery. This can give a scope to determine the suitable active functional groups required to develop that battery. The fraction, −1.0 mm in size, was a potential feedstock for the active carbon preparation using phosphoric acid activation. The resulting precursor/H 3 PO 4 mixture was pre-activated by solidifying at 150 °C for 2 h to eliminate water, leaving it a black adhesive solid. The hardened mixture was heated at 450 °C for an hour at a rate of 10 °C min−1 to complete the carbonization process. The produced active carbon was washed repeatedly with deionized water, dried at 105 °C, and saved in plastic for analysis and use, it was called (oxid-AC). The resulting active carbon has been identified using different analytical methods such as; XRD, SEM, FTIR, and BET. Results obtained revealed that the activated carbon additive, with a 2.5 % weight percentage, can reduce effectively the accumulation of PbSO 4 at the positive active material (PAM) of the lead-acid battery. The role of the active carbon in improving the PAM behavior can be explained based on lead (II) ion adsorption on the carbon surface. [Display omitted] • Preparation of active carbon (AC) from sawdust waste to enhance the lead-acid battery • The resulting AC has been identified using XRD, SEM, FTIR, and BET • The AC additive, with 2.5 wt%, can reduce effectively the accumulation of PbSO4 at PAM. • The improvement has been attributed to adsorption of lead (II) ion on the carbon surface. [ABSTRACT FROM AUTHOR]

Stroke is the most common cause of acquired epilepsy, but treatment for preventing the development of post-stroke epilepsy is still unavailable. Since stroke results in neuronal damage and death as well as initial loss of activity in the affected brain region, homeostatic plasticity may be trigged and contribute to an increase in network hyperexcitability that underlies epileptogenesis. Correspondingly, enhancing brain activity may inhibit hyperexcitability from enhanced homeostatic plasticity and prevent post-stroke epileptogenesis. To test these hypotheses, we first used in vivo two-photon and mesoscopic imaging of activity of cortical pyramidal neurons in Thy1-GCaMP6 transgenic mice to determine longitudinal changes in excitatory activity after a photothrombotic ischemic stroke. At 3-days post-stroke, there was a significant loss of neuronal activity in the peri-injury area as indicated by reductions in the frequency of calcium spikes and percentage of active neurons, which recovered to baseline level at day 7, supporting a homeostatic activity regulation of the surviving neurons in the peri-injury area. We further used optogenetic stimulation to specifically stimulate activity of pyramidal neurons in the peri-injury area of Thy-1 channelrhodopsin transgenic mice from day 5 to day 15 after stroke. Using pentylenetetrazole test to evaluate seizure susceptibility, we showed that stroke mice are more susceptible to Racine stage V seizures (time latency 54.3 ± 12.9 min) compared to sham mice (107.1 ± 13.6 min), but optogenetic stimulation reversed the increase in seizure susceptibility (114.0 ± 9.2 min) in mice with stroke. Similarly, administration of D-cycloserine, a partial N -methyl- d -aspartate (NMDA) receptor agonist that can mildly enhance neuronal activity without causing post-stroke seizure, from day 5 to day 15 after a stroke significantly reversed the increase in seizure susceptibility. The treatment also resulted in an increased survival of glutamic acid decarboxylase 67 (GAD67) positive interneurons and a reduced activation of glial fibrillary acidic protein (GFAP) positive reactive astrocytes. Thus, this study supports the involvement of homeostatic activity regulation in the development of post-stroke hyperexcitability and potential application of activity enhancement as a novel strategy to prevent post-stroke late-onset seizure and epilepsy through regulating cortical homeostatic plasticity. [Display omitted] • Repeated in vivo two-photon and mesoscopic imaging of cortical neuronal activity in a photothrombotic stroke model demonstrates homeostatic activity regulation after stroke. • Enhancing excitatory activity of the injured cortex by optogenetic stimulation or D-cycloserine (DCS) administration reverses the increased seizure susceptibility in stroke mice. • The DCS treatment also results in an increased survival of cortical GABAergic interneurons and a reduced activation of reactive astrocytes. • Enhancing cortical excitatory activity may prevent the development of post-stroke cortical hyperexcitability through inhibiting homeostatic plasticity regulation. [ABSTRACT FROM AUTHOR]

[Display omitted] • We have conducted MCV on seven common methanol oxidation catalysts. • A new mechanism of activity enhancement by MCV was revealed for the first time. • The criteria for the application of the MCV strategy were presented. • Pt-Sn and Pd-CoSn using the MCV strategy exhibited excellent MOR performance. Methanol oxidation catalysts are mainly based on Pt/Pd-based alloys, and various complex strategies are often employed to improve their activity. It is a common practice to clean the contaminants adsorbed on the surface of noble-metal-based catalysts by multiple cyclic voltammetry (MCV) prior to activity test. In this study, we find that this common practice can enhance the activity of noble-metal-based alloy catalysts for methanol oxidation by up to nearly three times. For the first time, a universal criterion is proposed for screening auxiliary metal elements that can significantly improve the activity by this simple practice: oxidable but insoluble in the potential range of CV. Also for the first time, a new activity enhancement mechanism by this common MCV is revealed: noble metal migration, valence state change and oxygen vacancy. As a proof-of-concept, Pt-Sn and Pd-CoSn exhibit high catalytic activity and durability after MCV, making the performance of flexible methanol fuel cells more prominent as well. This work puts forward a universal criterion of auxiliary metal selection and a new mechanism for the remarkably improved activity obtained by MCV, which provides a facile method for obtaining a series of highly active catalysts in the ethaline electrocatalysis field. [ABSTRACT FROM AUTHOR]

To develop an efficient heterogeneous Fenton catalyst over a wide pH range without any external energy input is still a challenging work. In this study, the Fenton activity of mesoporous iron oxide was firstly extended to pH of 3.6–10.0 by the carbon quantum dots (CQDs) and Cu modification (CQDs/Cu-MIO). The characterization studies indicated that CQDs/Cu-MIO had a typical mesoporous structure and CQDs was highly dispersed on the surface of catalyst. While Cu element with Cu (I) and Cu (II) was introduced in the framework of iron oxide by chemical binding of Fe O Cu. Without the aids of UV, CQDs/Cu-MIO exhibited an excellent efficiency and the ofloxacin (OFX) degradation followed the pseudo-first order kinetic model with a reaction constant of 0.1109 min −1 . Moreover, the catalyst can be reused for 6 times with good stability, in which the maximum concentration of leaching Fe and Cu ions were 0.085 and 0.015 mmol/L. The optimum reaction condition was evaluated and the degradation process of OFX was further investigated by FT-IR spectrum. The reactive oxygen species involved in OFX degradation, the effects of mesoporous structure, Cu/Fe multivalent state and the excellent capability of electron transformation/energy exchange of CQDs on the enhancement of CQDs/Cu-MIO Fenton activity were also discussed. Finally, the heterogeneous Fenton reaction mechanism was proposed based on the experimental results. [ABSTRACT FROM AUTHOR]

Undoubtedly, electrocatalyzing the hydrogen evolution reaction (HER) is now becoming the subject of extensive studies due to its crucial role in harvesting clean energy. In general, bare screen-printed carbon electrodes (SPCEs) have negligible ability to catalyze the HER due to the lack of effective sites. Here we find that: 1) a facile anodization treatment can improve the electrocatalytic activity of home-made SPCEs with apparently reduced overpotential and increased current density for the HER; 2) the activity enhancement of SPCEs is highly dependent on anodization conditions including electrolyte, treatment time, and anodization potential; 3) the introduction of negatively charged oxygen-containing functional groups during anodization, together with the increased defect sites and hydrophilicity on electrode surface, leads to the promoted activity of anodized SPCEs synergistically. Similar phenomena are also found in other carbon-based electrodes including glassy carbon electrode and carbon nanotube-modified electrode. These findings reported in this work are expected to guide the future design of advanced electrode systems for efficient hydrogen evolution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Micro-meso hierarchical ZSM-5 zeolites are prepared by an alkali treatment method. • The RuO x /HZ5-nd (n = 2, 3, 4) catalysts exhibit notable cavity-shell morphologies. • The redox property and surface acidity play key roles in vinyl chloride oxidation. • RuO x /HZ5-3d exhibits good catalytic durability and water resistant capacity. Hierarchical ZSM-5 zeolites were synthesized by an alkali hydrothermal treatment strategy and adopted as support materials for the fabrication of RuO x nano catalysts. The physicochemical properties and catalytic activities for vinyl chloride (VC) oxidation over the resultant RuO x /HZ5-nd (n = 2, 3, 4) catalysts were successfully modulated by the treatment time regulation (2d, 3d and 4d) of ZSM-5 solid. Experimental results demonstrated that the RuO x /HZ5-nd catalysts possessed notable cavity-shell structures with micro-meso hierarchical porosity, which brought about the increased specific surface area, the enhanced low-temperature reducibility and the strengthened surface acidity comparable to RuO x /HZ5. All these superiorities were recognized as the crucial origin for boosting catalytic oxidation of VC. Especially, the RuO x @HZ5-3d catalyst exhibited the optimum VC oxidation activity with the lowest T 50 and T 90 (temperature at 50 and 90% conversion) of 275 and 297 °C, which was 22 and 24 °C lower than those of RuO x /HZ5. Importantly, RuO x @HZ5-3d exhibited significantly high thermal stability, water resistant and regeneration capacity from humid conditions, which made it a promising material for the catalytic purification of chlorinated volatile organic compounds. [ABSTRACT FROM AUTHOR]

Bulk graphitic carbon nitride (CN) suffers from small surface area and high recombination of charge carriers, which result in low photocatalytic activity. To enhance the activity of g-C 3 N 4 , the surface area should be enlarged and charge carrier separation should be promoted. In this work, a combined strategy was employed to dramatically enhance the activity of bulk g-C 3 N 4 by simultaneously introducing mesoporous structure and hybridizing with graphene/graphene oxide. The mesoporous g-C 3 N 4 /graphene (MCN-G) and mesoporous g-C 3 N 4 /graphene oxide (MCN-GO) nanocomposites with enhanced photocatalytic activity (NO removal ratio of 64.9% and 60.7%) were fabricated via a facile sonochemical method. The visible light-harvesting ability of MCN-G and MCN-GO hybrids was enhanced and the conduction band was negatively shifted when 1.0 wt% graphene/graphene oxide was incorporated into the matrix of MCN. As electronic conductive channels, the G/GO sheets could efficiently facilitate the separation of chare carriers. MCN-G and MCN-GO exhibited drastically enhanced visible light photocatalytic activity toward NO removal. The NO removal ratio increased from 16.8% for CN to 64.9% for MCN-G and 60.7% for MCN-GO. This enhanced photocatalytic activity could be attributed to the increased surface area and pore volume, improved visible light utilization, enhanced reduction power of electrons, and promoted separation of charge carriers. This work demonstrates that a combined strategy is extremely effective for the development of active photocatalysts in environmental and energetic applications. [ABSTRACT FROM AUTHOR]

We have studied the conversion of hexane isomers on HY zeolites (Si/Al = 40 and 2.6) after different thermal pretreatments (400-600 °C) on a micropulse reactor, which is ideal for evaluating catalyst activity and evolution of product distribution over fresh zeolites at very short times on stream, when coke formation is negligible. We have observed that the catalytic activity of the zeolites is enhanced upon high-temperature pretreatment. This activity enhancement can be ascribed to dehydroxylation, as observed by thermogravimetric analysis upon heating the zeolite above 500 °C. However, this dehydroxylation does not result in a decrease in the density of the original Brønsted acid sites (BAS). Therefore, the newly created Lewis acid sites (LAS) must be associated with either extra-framework alumina (EFAl) or silanol species. We propose that the activity enhancement is associated with the generation of synergistic sites resulting from the interaction between LAS created by the dehydroxylation and the original BAS. Both, protolytic cracking and dehydrogenation reactions are enhanced with paraffin feeds, but such enhancement is not apparent for olefin feeds. The synergistic sites were also deactivated very quickly by strong adsorption of hydrocarbon species, but could be regenerated by a subsequent high-temperature treatment. [ABSTRACT FROM AUTHOR]

Effects of various additives on the lipase from Burkholderia cepacia (BcL) immobilized on mixed-function-grafted mesoporous silica gel support by hydrophobic adsorption and covalent attachment were investigated. Catalytic properties of the immobilized biocatalysts were characterized in kinetic resolution of racemic 1-phenylethanol (rac-1a) and 1-(thiophen-2-yl)ethan-1-ol (rac-1b). Screening of more than 40 additives showed significantly enhanced productivity of immobilized BcL with several additives such as PEGs, oleic acid and polyvinyl alcohol. Effects of substrate concentration and temperature between 0–100 °C on kinetic resolution of rac-1a were studied with the best adsorbed BcLs containing PEG 20 k or PVA 18–88 additives in continuous-flow packed-bed reactor. The optimum temperature of lipase activity for BcL co-immobilized with PEG 20k found at around 30 °C determined in the continuous-flow system increased remarkably to around 80 °C for BcL co-immobilized with PVA 18–88. [ABSTRACT FROM AUTHOR]

Highlights: [•] Crystal structures of esterase rPPE from Pseudomonas putida ECU1011 were determined. [•] Residues His/Trp187 and Asp287 play a key role in substrate binding and chiral recognition. [•] The substrate preference of rPPE towards p-nitrophenyl esters was shifted by M213A mutation. [Copyright &y& Elsevier]

Highlights: [•] Variants of xynlanase Z of Clostridium thermocellum in combination with CBM6 and CBM22 were expressed in E. coli. [•] The construct with CBM22 showed 5-fold higher activity as compared to the one containing CBM6. [•] Location of the binding site inside a tunnel like structure of the CBM6 construct seemed to restrict the substrate binding. [•] The construct with CBM22 produced a more open structure, facilitating substrate binding and release of the product. [ABSTRACT FROM AUTHOR]

Abstract: Silicate nanofibers (palygorskite, Pal) coated with CuO nanoparticles were prepared via a precipitation method using copper oxalate as a precursor and subsequently modified with PVP–Pd solution. Characterization by X-ray diffraction and transmission electron microscope demonstrated that the surfaces of the Pal fibers with 20–30nm in diameter and 400–500nm in length were uniformly decorated with CuO nanoparticles of 16nm in average size. The CuO/Pal and Pd–CuO/Pal nanocomposites exhibited higher photocatalytic activities than the pure CuO for the photodegradation of methyl orange under UV-light. The enhanced photocatalytic activity of CuO/Pal and Pd–CuO/Pal composites may be ascribed to the surface adsorption and efficient electron–hole separation at the coupled interface. The combination of nanoparticles and nano-scale fibers can lead to a remarkable improvement in photocatalytic activity; this concept can be expected to find interesting applications in the environmental field. [Copyright &y& Elsevier]

Abstract: The influences of the heat-treatment of Ketjen Black EC300J in the temperature range 1000–2000 °C on the catalytic activity of loaded Pt for oxygen reduction reaction (ORR) were studied. A maximum enhancement in the specific ORR activities (SOA) was observed for the carbon heat-treatment at 1500 °C. The heat-treatment of carbon induced decreases in porosity and the development of graphitic structures; however, no direct correlations were observed between these properties and the SOA. Transmission electron microscopy and X-ray photoelectron spectroscopy, respectively, showed enhancements in the uniformity of the Pt particle size distribution and of the extent of surface reduction of Pt with increasing heat-treatment temperature (HTT). Cyclic voltammetry in 0.5 M H2SO4 aqueous solution detected changes in the hydrogen adsorption at 0.12 V vs. a reversible hydrogen electrode, depending on the HTT of the carbon support, and this was ascribed to hydrogen adsorption on the Pt(110) surface, the most active crystal face of Pt for ORR. The fraction of Pt atoms belonging to the (110) surface out of the total surface Pt atoms showed an excellent correlation with the SOA. Heat-treatment of the carbon support was therefore concluded to be an effective treatment for enhancing the SOA of Pt. [Copyright &y& Elsevier]

Abstract: The dimethyl ether steam reforming (DME SR) was carried out over the composite catalyst of ZnO–Cr2O3 coupled with Al2O3, TiO2 or TiO2–Al2O3 in the microreactor. The results showed that the catalytic activities were greatly enhanced over the composite catalyst of ZnO–Cr2O3 combined with TiO2–Al2O3 (ZnCr–TiAl) in comparison to those combined with Al2O3 or TiO2 in DME SR. By evaluating the catalytic activity of solid acids in DME hydrolysis, it was proposed that the better performance of TiO2–Al2O3 in DME hydrolysis contributed to the superior activity of ZnCr–TiAl in DME SR, indicating a higher DME hydrolysis activity favored DME SR. In view of the characterization of N2 physisorption, scanning electron microscope, X-ray diffraction and NH3 temperature-programmed desorption, the promotion effect of TiO2 on both DME hydrolysis and steam reforming was discussed in terms of the modification effect of TiO2 on the acid properties of Al2O3 surface. The acid strength or total acid amount was enhanced by the addition of different TiO2 content. In the 150h medium stability test, there was no obvious deactivation for ZnCr–TiAl catalyst with the H2 production rate of and the CO selectivity in the dry reformate remained below 6%. The characterization results of the used catalyst revealed that no change in the crystalline phase and size occurred on the spent catalyst. [Copyright &y& Elsevier]

Abstract: Addition of arginine enhances the activity of the enzyme T7 RNA polymerase. Different methods have been employed to understand the enhancement in the light of arginine induced alteration of the tertiary structure. The increase in activity of the enzyme reaches a maximum value around a concentration of 125mM arginine. Fluorescence, circular dichroism and dynamic light scattering studies indicate an alteration in the tertiary structure of the enzyme. Enthalpy change as a function of input concentration of arginine to a fixed concentration of the enzyme (5μM) shows a dip at 100mM concentration of arginine. Differential scanning calorimetric studies of the denaturation of the enzyme in absence and presence of arginine indicates arginine induced destabilization of the C-terminal domain of the enzyme. Structural alterations induced by arginine have been compared with those induced by the denaturant guanidine hydrochloride. [Copyright &y& Elsevier]

Acetylcholinesterase (AChE) plays a central role in the development of Alzheimer's disease: AChE inhibition for preventing the characteristic dwindling of acetylcholine levels constitutes the current standard treatment for the disorder. Amongst the diverse risk factors contributing to the degenerative process, high cholesterol causes a reduction in the effectiveness of the otherwise therapeutic inhibitors of AChE. Our biochemical study on the activity of AChE elucidates the effect of amphiphilic molecules on the activity and kinetics of AChE, and sheds light onto the nature of the impact of these amphiphilic molecules on enzyme-inhibitor interactions. Using kinetic studies we discovered that detergents alter the enzymatic activity of AChE through an uncompetitive mechanism. Additional experiments using AChE inhibitors (amphiphilic procaine hydrochloride, hydrophobic tetrabutylammonium bromide) in the absence or presence of detergent further illustrate the detergent-enzyme-solvent interactions. The results contribute to the understanding of the importance of hydrophobic-lipophilic interactions for the correct function of AChE and its inhibitors. We present a model system for the study of lipid-related alterations in the activity of isolated AChE in the central nervous system. This model may also be used to assess and predict the effectiveness of AChE inhibitors, which are traditionally used for the treatment of cognitive impairment, under pathological (high-cholesterol) conditions. [ABSTRACT FROM AUTHOR]

Abstract: Ag-based catalysts supported on various metal oxides, Al2O3, TiO2, and TiO2–Al2O3, were prepared by the sol–gel method. The effect of SO2 on catalytic activity was investigated for NO reduction with propene under lean burn condition. The results showed the catalytic activities were greatly enhanced on Ag/TiO2–Al2O3 in comparison to Ag/Al2O3 and Ag/TiO2, especially in the low temperature region. Application of different characterization techniques revealed that the activity enhancement was correlated with the properties of the support material. Silver was highly dispersed over the amorphous system of TiO2–Al2O3. NO3 − rather than NO2 − or NOx reacted with the carboxylate species to form CN or NCO. NO2 was the predominant desorption species in the temperature programmed desorption (TPD) of NO on Ag/TiO2–Al2O3. More amount of formate (HCOO−) and CN were generated on the Ag/TiO2–Al2O3 catalyst than the Ag/Al2O3 catalyst, due to an increased number of Lewis acid sites. Sulfate species, resulted from SO2 oxidation, played dual roles on catalytic activity. On aged samples, the slow decomposition of accumulated sulfate species on catalyst surface led to poor NO conversion due to the blockage of these species on active sites. On the other hand, catalytic activity was greatly enhanced in the low temperature region because of the enhanced intensity of Lewis acid site caused by the adsorbed sulfate species. The rate of sulfate accumulation on the Ag/TiO2–Al2O3 system was relatively slow. As a consequence, the system showed superior capability for selective adsorption of NO and SO2 toleration to the Ag/Al2O3 catalyst. [Copyright &y& Elsevier]

Semicarbazide-sensitive amine oxidase (SSAO) is a multifunctional enzyme with different biological roles that depend on the tissue where it is expressed. Because SSAO activity is altered in several pathological conditions, we were interested in studying the possible regulation of the human enzyme activity. It has been previously reported that SSAO activity is increased in the presence of Dulbecco's modified Eagle medium (DMEM) in vitro. The aim of the present work was to investigate the effects of the different constituents of DMEM on human SSAO activity. We found that sodium bicarbonate was the only component able to mimic the enhancement of both human aorta and plasma SSAO activity in vitro, suggesting a possible physiological role of bicarbonate as an intrinsic modulator of the human enzyme. Failure to take this activating effect into account could also result in inaccuracies in the reported tissue activities of this enzyme. [ABSTRACT FROM PUBLISHER]

Abstract: Carbon-supported platinum or platinum alloys are generally used as the cathodic electrocatalysts in polymer electrolyte membrane fuel cells (PEMFC) to enhance the oxygen reduction reaction (ORR). Main challenges to be addressed in this area are the high electrochemical activity and high stability maintenance for low-Pt-loading catalysts toward the feasibility for fuel cell operation and the reduction of the system cost. The interaction of Pt with carbon support, as well as the interaction of Pt precursor with carbon during the supported catalyst formation, are considered to be beneficial to the improvement of catalytic activity and durability of the electrocatalysts. This paper provides a review of recent advances related to the physico-chemical and electronic interactions at the catalyst–support interface and the catalyst activity enhancement through improved Pt–C interaction, especially focusing on the surface modification of the carbon support to form proper functional groups and chemical links at the Pt/C interface. [Copyright &y& Elsevier]

Abstract: A method for enhancing the useful Au content in Au/TS-1 catalysts for vapor-phase propylene epoxidation is reported. Exposure of calcined TS-1 support to 1 M NH4NO3 at 80 °C, followed by vacuum drying, produced a modified TS-1 support material. Deposition precipitation of gold on these modified TS-1 supports resulted in a fourfold increase in Au capture efficiency and produced catalysts with 5–10% conversion of propylene with 75–85% selectivity for PO, at 200 °C and a space velocity of 7000 ml h−1 g−1 cat. In this system, 10% conversion and 76% selectivity amount to a rate of 134 gPO h−1 kg−1 cat. An optimal Au content that is support dependent is observed for these catalysts. [Copyright &y& Elsevier]

Addition of H2 to a NO/NH3/O2/H2O feed for selective catalytic reduction of nitrogen oxide over Ag/Al2O3 catalysts causes an unusual enhancement of activity, e.g., the marginal activity (<10%) of 1 wt% Ag impregnated on γ-Al2O3 or mesoporous Al2O3 modifications is boosted to nearly 100% over a broad temperature range from 200 to 550°C at a space velocity of 30,000cm3g-1h-1). Contrary, silver on SiO2 or α-Al2O3 shows no improvement of activity in the presence of H2. The effect is tentatively attributed to a higher percentage of intermediary nano-sized Ag clusters on high-surface area Al2O3 in the presence of hydrogen. This promotes oxygen activation and hence NO oxidation to reactive intermediate nitrite species. The required dispersion of Ag cannot be stabilized on SiO2 or α-Al2O3. [ABSTRACT FROM AUTHOR]

Two novel sesquiterpenes, styxone A (1) and styxone B (2), and a novel lactone, styxlactone (3), were isolated from the Jamaican sponge Myrmekioderma styx. Their structures were elucidated by detailed 1H, 13C and 2D NMR data and the absolute stereochemistry of styxone A and B was determined by CD spectra. Styxone A represents a novel sesquiterpene skeleton. (S)-(+)-Curcuphenol (4), (S)-(+)-curcudiol (5), and abolene (6) were also isolated. An activity enhancement by cyanthiwigin B (7) to curcuphenol was observed in the antimicrobial assays when the two compounds were administered together. [Copyright &y& Elsevier]

The crystal structure of three mutants of Escherichia coli alkaline phosphatase with catalytic activity (kcat) enhancement as compare to the wild-type enzyme is described in different states. The biological aspects of this study have been reported elsewhere. The structure of the first mutant, D330N, which is threefold more active than the wild-type enzyme, was determined with phosphate in the active site, or with aluminium fluoride, which mimics the transition state. These structures reveal, in particular, that this first mutation does not alter the active site. The second mutant, D153H-D330N, is 17-fold more active than the wild-type enzyme and activated by magnesium, but its activity drops after few days. The structure of this mutant was solved under four different conditions. The phosphate-free enzyme was studied in an inactivated form with zinc at site M3, or after activation by magnesium. The comparison of these two forms free of phosphate illustrates the mechanism of the magnesium activation of the catalytic serine residue. In the presence of magnesium, the structure was determined with phosphate, or aluminium fluoride. The drop in activity of the mutant D153H-D330N could be explained by the instability of the metal ion at M3. The analysis of this mutant helped in the design of the third mutant, D153G-D330N. This mutant is up to 40-fold more active than the wild-type enzyme, with a restored robustness of the enzyme stability. The structure is presented here with covalently bound phosphate in the active site, representing the first phosphoseryl intermediate of a highly active alkaline phosphatase. This study shows how structural analysis may help to progress in the improvement of an enzyme catalytic activity (kcat), and explains the structural events associated with this artificial evolution. [Copyright &y& Elsevier]

• Reduction of NiFeAlO x catalysts leads to the formation of (γ Fe,Ni) alloy particles. • Aging triggers the segregation of (γ Fe,Ni) particles and partial oxidation of Fe. • (γ Fe,Ni) segregation is accompanied by an increase of intrinsic catalytic activity. • This can be explained by an additional methanation pathway comprising Fe2+ species. Commercial application of the CO 2 methanation reaction demands for the development of catalysts that feature an enhanced stability to increase catalyst lifetime. By time-resolved aging studies, we show that the improved deactivation resistance of co-precipitated NiFeAlO x catalysts compared to NiAlO x is obtained by a temporal increase of the intrinsic catalytic activity of NiFeAlO x , provoked by aging at elevated temperature and pressure in thermodynamic equilibrium. Detailed structural characterization of reduced and aged catalysts resolves that aging triggers the partial segregation of (γ Fe,Ni) nanoparticles initially formed during activation, accompanied by the oxidation of Fe. Thereby, the intrinsic catalytic activity increases, which can be explained by the generation of redox-active Fe2+ sites that offer an additional reaction pathway for CO 2 activation. The deactivation behavior of NiFeAlO x can be described by a superimposition of activity increase related to Fe2+ site formation and decrease due to the loss of active sites by sintering processes. [ABSTRACT FROM AUTHOR]