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Tryptophan synthetase (TSase), which functions as a tetramer, is a typical enzyme with a substrate channel effect, and shows excellent performance in the production of non-standard amino acids, histamine, and other biological derivatives. Based on previous work, we fused a mutant CE protein (colistin of E. coli, a polypeptide with antibacterial activity) sequence with the sequence of TSase to explore whether its catalytic activity could be enhanced, and we also analyzed whether the addition of a DNA scaffold was a feasible strategy. Here, dCE (CE protein without DNase activity) protein tags were constructed and fused to the TrapA and TrapB subunits of TSase, and the whole cell was used for the catalytic reaction. The results showed that after the dCE protein tag was fused to the TrapB subunit, its whole cell catalytic activity increased by 50%. Next, the two subunits were expressed separately, and the proteins were bound in vitro to ensure equimolar combination between the two subunits. After the dCE label was fused to TrapB, the activity of TSase assembled with TrapA also improved. A series of experiments revealed that the enzyme fused with dCE9 showed higher activity than the wild-type protein. In general, the activity of assembly TSase was optimal when the temperature was 50 °C and the pH was about 9.0. After a long temperature treatment, the enzyme maintained good activity. With the addition of exogenous nucleic acid, the activity of the enzyme increased. The maximum yield was 0.58 g/L, which was almost three times that of the wild-type TSase (0.21 g/L). The recombinant TSase constructed in this study with dCE fusion had the advantages of higher heat resistance and higher activity, and confirmed the feasibility of adding a nucleic acid scaffold, providing a new idea for the improvement of structurally similar enzymes. [ABSTRACT FROM AUTHOR]

• Montmorillonite-loaded copper ferrate (CuFe 2 O 4 /Mt) was synthesized by a solvothermal method. • CuFe 2 O 4 /Mt has an abundance of active sites and magnetic properties. • Effective degradation of Rhodamine B (RhB) was achieved by CuFe 2 O 4 /Mt activation of PDS. • RhB removal is attributed to a combination of free radicals and non-free radicals. : Advanced oxidation techniques based on sulfate radicals can be more effective in dealing with the threats posed by dye wastewater. : In this study, a series of montmorillonite-loaded CuFe 2 O 4 (CFO, 1-CFO/Mt, 2-CFO/Mt, 3-CFO/Mt) composites were prepared using a simple one-pot solvent method for the activation of sodium persulfate (PDS) for the removal of Rhodamine B (RhB) from water. : The efficient catalytic activity of the composite catalyst was verified by the degradation of RhB with different systems, and the efficient adsorption of this catalyst accelerated the reaction process of pollutant degradation. The results showed that 97.7% of RhB could be removed within 25 min using 0.3 g/L of 2-CFO/Mt composite catalyst and 1 mM of PDS at the initial pH = 7.5; In addition, the composite catalyst can show good catalytic performance in a wide pH range. It still has high catalytic activity after 3 cycles. The involvement of SO 4 •−, •OH, 1O 2 , and O 2 •− in the degradation of RhB by the 2-CFO/Mt/PDS system was determined by radical quenching experiments as well as EPR test analysis, in which 1O 2 dominated in the degradation of RhB by the 2-CFO/Mt/PDS system. Overall, 2-CFO/Mt has significant potential as a PDS activator in the treatment of RhB in water. [Display omitted] [ABSTRACT FROM AUTHOR]

The forms of boron atoms are many and varied in the structure of transition metal borides (TMBs). The form of boron atoms determines the structure, morphology, and properties of borides. Herein, transition metal monoborides (CrB and WB) with different arrangement of one-dimensional (1D) boron chains were synthesized under high pressures and high temperatures. The 1D boron chains between the interlayers of CrB are parallel to one another, while the 1D boron chains between the interlayers of WB are perpendicular to one another. The morphologies of CrB and WB also show large differences due to the difference in 1D boron chain arrangement. As electrocatalysts for hydrogen evolution reactions (HERs), CrB and WB show good catalysis activity and durability. WB has the smallest overpotential (210 mV) and Tafel slope (90.09 mV dec−1), which is mainly attributed to the intercrossing boron chains improving the electrical properties of WB, as well as the 5d electrons of W being more chemically active. The TOF value of WB is 1.35 s−1, proving that WB has a higher intrinsic catalytic activity during HERs. This work provides a data reference for the development of high-efficiency electrocatalysts. [ABSTRACT FROM AUTHOR]

It is desirable to design nonprecious metal nanocatalysts with high stability and catalytic performance for fine chemicals production. Here, a method is reported for the preparation of cobalt metal and cobalt oxide cores confined within nanoporous nitrogen‐doped hollow carbon capsules. Core–shell structured Zn/Co‐ZIF@polymer materials are fabricated through a facile coating polymer strategy on the surface of zeolitic imidazolate frameworks (ZIF). A series of hollow carbon capsules with cobalt metal and cobalt oxide are derived from a facile confined pyrolysis of Zn/Co‐ZIF@polymer. The hollow Co‐CoOx@N‐C capsules can prevent sintering and agglomeration of the cobalt nanoparticles and the nanoporous shell allows for efficient mass transport. The specific surface area and Co particle size are optimized through finely tuning the original Zn content in ZIF particles, thus enhancing overall catalytic activity. The yolk–shell structured Zn4Co1Ox@carbon hollow capsules are shown to be a highly active and selective catalyst (selectivity >99%) for hydrogenation of nitrobenzene to aniline. Furthermore, Zn4Co1Ox@carbon hollow particles show superior catalytic stability, and no deactivation after 8 cycles of reaction. The hollow Co‐CoOx@N‐C capsules may shed light on a green and sustainable catalytic process for fine chemicals production. [ABSTRACT FROM AUTHOR]

An effective solvent‐free method based on a solid‐reduction process was developed to fabricate ultrafine gold catalysts. By this method we revealed a strong size‐dependent activity of Au species in which subnanometer‐sized clusters exhibited the best activity in the hydrogenation of CO2 to formate, with a turnover number of up to 9278 over 7 h at 90 °C. [ABSTRACT FROM AUTHOR]

Ancylostoma caninum anticoagulant peptide 5 (AcAP5) is a potent inhibitor for coagulation factor Xa (FXa). Previous studies show that AcAP5 binds to FXa at the active site, and/or the exosite. The active site-binding contributes to direct blocking of FXa catalytic activity, but the effect of exosite-binding and the underlying mechanism remain unknown. To investigate whether and how the exosite-binding affects FXa function, we prepared several AcAP5 mutants with modifications to the active site-binding or exosite-binding region. Their FXa-inhibiting and anticoagulant activities were examined both in vitro and in rabbit plasma, and the interactions with FXa were analyzed using in silico molecular modeling, docking, and molecular dynamics simulation. Mutants abolishing either active site- or exosite-binding resulted in a dramatic decrease in their anti-FXa and anticoagulant activities. Elongation of AcAP5 exosite-binding region also impaired the FXa-inhibiting activity. Computational analysis demonstrated that the conformation of FXa becomes more rigid due to exosite-binding with AcAP5, which consequently affects its catalytic activity. Our results suggest that both active site- and exosite-binding contribute to the FXa inhibitory activity of AcAP5. [ABSTRACT FROM AUTHOR]

Although direct formic acid fuel cell (DFAFC) is regarded as one of the most promising energy-conversion systems, its commercialization process is impeded by the high costs of electrode catalysts as well as the sluggish catalytic reaction kinetics. Herein, we present a convenient bottom-up method to the synthesis of nanosized Pd crystals grown on 3D porous hybrid nanoarchitectures constructed from MXene (Ti 3 C 2 T x) and reduced graphene oxide nanosheets (Pd/MX-rGO) through a co-assembly process. The as-derived 3D Pd/MX-rGO nanoarchitecture is equipped with a number of attractive textural features, such as 3D cross-linked porous networks, large specific surface area, uniform Pd dispersion, optimized electronic structure, and good electron conductivity. As a result, unusual formic acid oxidation properties in terms of high catalytic activity, strong poison tolerance, and reliable long-term stability are achieved for the 3D Pd/MX-rGO catalyst, significantly superior to those for conventional Pd catalysts supported by carbon black, graphene, and Ti 3 C 2 T x matrixes. The controllable growth of Pd nanocrystals on MXene and reduced graphene oxide co-constructed 3D nanoarchitectures is achieved by a bottom-up co-assembly method. By virtue of the porous networks and optimized electronic structure, the resulting 3D catalyst exhibits superior electrocatalytic properties toward formic acid oxidation reaction. Image 1 • The bottom-up construction of 3D Pd-decorated MXene/rGO architecture is achieved. • The 3D porous frameworks facilitate the transportation of both electrons and ions. • The incorporation of MXene can effectively optimize the electronic structure of Pd. • The resulting 3D architecture exhibits high activity for formic acid oxidation. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) nanophotocatalyst is a promising candidate for degrading organic pollutants but has an extremely low photocatalytic activity under nature sunlight. In this work, flower-like MoS 2 quantum dots/ZnO (MQ/ZnO) nanospheres with the size of approximately 1.26 μm are prepared at low temperature. The resultant flower-like MQ/ZnO nanospheres displayed higher photocatalytic activity than pure ZnO nanospheres under natural sunlight and without stirring, with the decomposition rate of the MQ/ZnO composites approximately 3.3 times higher than that of the pure ZnO nanospheres. Furthermore, the introduction of MoS 2 QDs endowed ZnO nanospheres with optical memory ability. The enhanced sunlight-driven photocatalytic activity is dependent on the unique electrical properties of MoS 2 QDs and the synergistic effect between ZnO and MoS 2 QDs. [ABSTRACT FROM AUTHOR]

• 350 mM HMF was converted to BHMF (yield:91.2% & selectivity:99%). • B.subtilis HA70 is the first gram-positive bacteria used for HMF reduction. • The catalytic activity was significantly improved with the addition of glycine. • B.subtilis HA70 also can selectively transform furfural into furfuryl alcohol. 2,5-bis(hydroxymethyl)furan (BHMF) is an important reduction product from biomass-based 5-hydroxymethylfurfural (HMF), and microbial whole-cells are usually employed as the biocatalysts for HMF reduction. Due to the cell toxicity of HMF, the substrate loading was limited to a low concentration (100–200 mM). Herein, we isolated a highly HMF-tolerant strain, Bacillus subtilis HA70, as a whole-cell biocatalyst for the reduction of HMF. The strain exhibited high catalytic activity and excellent selectivity to HMF conversion, and the catalytic activity was significantly improved with the addition of glycine. Under the optimized conditions, 350 mM of HMF was transformed into BHMF with a yield of 91.2% and a selectivity of 99%. In the fed-batch conversion, 443.8 mM of BHMF was obtained within 15 h, giving a productivity of 29.6 mmol/(L h) and a total yield of 88.7%. Additionally, this strain also could selectively transform 100 mM of furfural into furfuryl alcohol with a yield of 97.6% within 4 h. The strong catalytic activity confers B. subtilis HA70 a promising potential for efficient synthesis of BHMF from HMF. [Display omitted] [ABSTRACT FROM AUTHOR]

Catalytic hydrogenation of carbon dioxide to CO by reverse water gas shift reaction plays a vital role in the recycling of the abundant carbon source. Here, the reaction over a series of zeolite L-supported platinum catalysts was systematically investigated to study the promoting role of potassium. The results of activity tests showed that controlled addition of potassium promoter to Pt/L catalyst was beneficial for the catalytic activity and selectivity. It was observed that cage encapsulation by zeolite pores could stabilize Pt nano-particles even at severe reaction conditions. Furthermore, X-ray absorption near edge structure and X-ray photoelectron spectra results demonstrated that the chemical state of platinum was altered by the additional potassium promoter, providing evidence for the formation of Pt-O(OH)-K interfacial sites. Thereafter, the Pt-O(OH)-K interfaces, acting as main active sites to adsorb CO 2 and produce bridge-bonded formate intermediates, were identified by a set of in-situ diffuse reflectance Fourier transform infrared spectroscopy and microcalorimetry measurements. This finding provides new insights into the use of a variety of zeolite as carriers for highly dispersed noble metal in catalytic CO 2 reduction. [ABSTRACT FROM AUTHOR]

The peroxide-like catalytic activity of gold nanoclusters (Au–NCs) is very low under physiological conditions (pH 7.4), which greatly limits its biological detection applications. A new nanoenzyme platform was constructed by self-assembly of Au–NCs and ZIF-8/CQDs. It was found that heparin can significantly promote the peroxidase-like activity of Au–NCs on the nanoenzyme platform at pH 7.4. In the presence of H 2 O 2 , the catalytic activity of Au–NCs on the nanoenzyme platform for TMB increased nearly 50 times. Based on this phenomenon, a colorimetric method was developed to determine heparin in the range of 0.0185–9.25 U/mL, with a detection limit of 0.0027 U/mL. When protamine is introduced, heparin and protamine take the lead in specific binding due to antagonism, which makes heparin unable to adsorb on the surface of ZIF-8/CQDS, thus inhibiting the enhancement of the catalytic activity of Au–NCs. Based on this phenomenon, a colorimetric method was developed to determine protamine in the range of 0.01–0.5 μg/mL, with a detection limit of 0.003 μg/mL. Therefore, this method provides a new idea for the visual detection of heparin and protamine under physiological conditions. [Display omitted] •A new nanoenzyme platform is constructed by self-assembly of Au–NCs and ZIF-8/CQDs. •ZIF-8/CQDs is used as nanoenzyme platform with the peroxidase-like activity of Au–NCs to detect heparin and protamine. •This enhancement signal change of TMB to oxTMB is used as the basic detection condition for heparin with LOD of 0.01 μM. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of Ni based single site metal catalysts (SSMCs) were successfully synthesized. • The pore structure of SSMCs was tuned via altering the silica source as the precursor of SiO 2 template for the generation of carbon spheres. • The nanoarchitecture effect of carbon spheres for the generation of Ni-N single sites and catalytic activity for CO 2 reduction were investigated. • Solid microporous carbon sphere was favorable for the generation of atomic Ni sites in SSMCs. • Hollow mesoporous structures enhanced the diffusion of CO 2 and improved turnover frequencies value of per Ni site for CO 2 RR to CO. Single-site metal catalysts (SSMCs) with high activity and stability have been widely applied as electrocatalysts for electrochemical CO 2 reduction reaction (CO 2 RR) process. However, it remains challenging for precise controlling the nanoarchitectures and atomic metal sites of SSMCs to investigate their corresponding structural and related catalytic properties toward CO 2 RR. In this work, four categories of Ni based SSMCs with different nanoarchitectures were successfully synthesized, including Ni-N doped solid carbon spheres with micropore (Ni-N/C-S-Micro), Ni-N doped hollow carbon spheres with micropore (Ni-N/C–H-Micro), Ni-N doped hollow carbon spheres with mesopore (Ni-N/C–H-Meso), and Ni-N doped hollow carbon spheres with micropore and mesopore (Ni-N/C–H-Micro/Meso). Ni-N/C-S-Micro and Ni-N/C–H-Micro were favorable for the generation of atomic Ni sites in SSMCs, resulting in higher loading amount of Ni, while Ni-N/C–H-Meso with open structure leads to the aggregation of Ni species during pyrolysis. In comparison with Ni-N/C-S-Micro, carbon spheres with hollow and mesoporous structures can enhance the diffusion of CO 2 and improve the catalytic activity of per Ni site toward CO 2 RR process. Thus, Ni-N/C–H-Meso shows the highest turnover frequencies (TOF) value for CO 2 RR to CO. This study provides a SSMCs design protocol for investigation the SSMCs correlation of structure and properties toward electrochemical conversions. [ABSTRACT FROM AUTHOR]

Catalytic hydrogenation of CO 2 to methane was investigated over Ru/rutile TiO 2 , focusing on the influence of the pretreatment temperature on the activity. Rutile TiO 2 stabilized Ru nanoparticles even after pretreatment at 800 °C; therefore it was possible to establish the structure–activity relationship without considering the particle size effect. The CO 2 turnover frequency initially increased with increasing pretreatment temperature from 300 to 800 °C, and reached a maximum value of 1.59 s −1 on Ru/rutile TiO 2 pretreated at 600 °C; it decreased to 1.16 s −1 for the sample pretreated at 800 °C. The characterization results indicated that the activity depended on both the extent of encapsulation of Ru particles by TiO x layers and the number of hydroxyl groups on the TiO x surface. The mechanism of CO 2 methanation was discussed based on in situ diffuse-reflectance infrared Fourier-transform spectroscopy results. [ABSTRACT FROM AUTHOR]