High Catalytic Rate Research Articles

Photoluminescent gold nanoclusters as two-photon excited ratiometric pH sensor and photoactivated peroxidase.

Atwo-photon excited ratiometric fluorescent pH sensor is reportedby combining L-cysteine-protected AuNCs (Cys@AuNCs) with fluorescein isothiocyanate (FITC). Cys@AuNCs were synthesized through a one-step self-reduction route and showed pH-responsive photoluminescence at 650 nm. Benefiting from the opposite pH response of Cys@AuNCs and FITC, the fluorescence ratio (F515 nm/F650 nm) of FITC&Cys@AuNCs provided a large dynamic range of 200-fold for pH measurement in the response interval of pH 5.0-8.0. Based on the excellent two-photon absorption coefficient of Cys@AuNCs, the sensor was expected to achieve sensitive quantitation of pH in living cells under two-photon excitation. In addition, colorimetric biosensing based on enzyme-like metal nanoclusters has attracted wide attention due to their low-cost, simplicity, and practicality. It is crucial to develop high catalytic activity nanozyme from the viewpoint of practical application. The synthesized Cys@AuNCs exhibited excellent photoactivated peroxidase-like activity with high substrate affinity and catalytic reaction rate, promising for rapid colorimetric biosensing of field analysis and the control of catalytic reactions by photostimulation.

Carbonic Anhydrase-Embedded Hydrogen-Bonded Organic Frameworks Coating for Facilitated Offshore CO2 Fixation.

Exhausted emission of carbon dioxide (CO2 ) from ships or offshore platforms has become one of the major contributors to global carbon emissions. Enzymes such as carbonic anhydrase (CA) have been widely used for CO2 mineralization because of their high catalytic rate. However, CA in seawater is easy to inactivate and difficult to reuse. Immobilization would be a feasible solution to address the stability issue, which, however, may cause an increase of internal diffusion resistance and reduced catalytic activity. In this regard, design of high-performance biocatalysts for acquiring high catalytic activity and stability of CA is highly desirable. Herein, a monolithic catalyst of Filler-CA@Lys-HOF-1 (FCLH) was prepared by chemical sorption of CA on the surface of the Filler followed by the coating of Lys-HOF-1. The highest catalytic activity of FCLH was obtained by regulating the amount of HOF-1 monomer added. Due to the protection of Lys-HOF-1, the FCLH showed good tolerance against acidity and salinity, which could retain about 80.2 % of the original activity after 9 h incubation in simulated seawater. The catalytic activity of FCLH could retain 85.4 % of the initial activity after 10 cycles. Hopefully, our study can provide a promising biocatalyst for CO2 mineralization, which may drive down carbon emissions when used for CO2 capture and conversion on offshore platforms.

A Thermostable Lipase Isolated from Brevibacillus thermoruber Strain 7 Degrades Ɛ-Polycaprolactone.

The tremendous problem with plastic waste accumulation has determined an interest in biodegradation by effective degraders and their enzymes, such as thermophilic enzymes, which are characterized by high catalytic rates, thermostability, and optimum temperatures close to the melting points of some plastics. In the present work, we report on the ability of a thermophilic lipase, by Brevibacillus thermoruber strain 7, to degrade Ɛ-polycaprolactone (PCL), as well as the enzyme purification, the characterization of its physicochemical properties, the product degradation, and its disruptive effect on the PCL surface. The pure enzyme showed the highest reported optimum temperature at 55 °C and a pH of 7.5, while its half-life at 60 °C was more than five hours. Its substrate specificity referred the enzyme to the subgroup of lipases in the esterase group. A strong inhibitory effect was observed by detergents, inhibitors, and Fe3+ while Ca2+ enhanced its activity. The monomer Ɛ-caprolactone was a main product of the enzyme degradation. Similar elution profiles of the products received after treatment with ultra-concentrate and pure enzyme were observed. The significant changes in PCL appearance comprising the formation of shallower or deeper in-folds were observed after a week of incubation. The valuable enzyme properties of the lipase from Brevibacillus thermoruber strain 7, which caused a comparatively quick degradation of PCL, suggests further possible exploration of the enzyme for effective and environment-friendly degradation of PCL wastes in the area of thermal basins, or in thermophilic remediation processes.

Laser-generated defect-rich MnOx nanobelts with high oxidase mimic activity for glutathione detection

Nanozymes with oxidase (OXD) mimic activity have shown great prospects for biomarker sensing, but their lower activity compared to natural enzymes has limited their further application. The catalytic activity of OXD mimics can be remarkably improved by material morphology design and defect engineering. In this work, we developed MnOx nanobelts (NBs) using a laser irradiation in liquid (LIL) technique. Among the MnOx NB structure, the ultrathin layered structure was conducive to exposing the catalytic active sites of the MnOx NBs, and the negative charge layer of the birnessite-type MnOx NBs helped to improve the affinity for positive substrate 3,3’,5,5’-tetramethylbenzidine (TMB). Importantly, laser-irradiation-generated oxygen vacancies significantly reduced the adsorption energy of the MnOx NBs for oxygen. As expected, the excellent substrate affinity (Km = 0.0087 mM) and high catalytic rate (Vmax = 6.04 × 10−7 M/s) of the MnOx NBs as OXD mimics were verified. Meanwhile, based on the inhibition of glutathione (GSH) on the OXD mimics, we established a fast and highly sensitive method for GSH determination. These new findings may provide a new strategy for synthesizing highly active nanozymes for biomarker applications.

Green preparation of silver nanocluster composite AgNCs@CF-g-PAA and its application: 4-NP catalytic reduction and hydrogen production.

4-Nitrophenol (4-NP) is a serious organic environmental pollutant. Conversion of 4-nitrophenol to 4-aminophenol (4-AP) by catalytic hydrogenation is an effective solution. In this work, a catalyst (AgNCs@CF-g-PAA) loaded with silver nanoclusters (AgNCs) was prepared by radiation technique. Firstly, the template polyacrylic acid (PAA) was grafted onto the cotton fiber (CF) by radiation grafting technique to obtain a solid template (CF-g-PAA). After that, AgNCs were synthesized in situ on CF-g-PAA by radiation reduction, and the composite material AgNCs@CF-g-PAA was obtained directly. AgNCs@CF-g-PAA has an obvious photoluminescence phenomenon, which is attributed to the stable AgNCs binding to the carboxyl on the PAA molecular chain. Due to the extremely small size of AgNCs, AgNCs@CF-g-PAA has good catalytic characteristics. The prepared AgNCs@CF-g-PAA catalyst has a very high catalytic rate for the hydrogenation of 4-NP. Even at high concentrations of 4-NP, AgNCs@CF-g-PAA can still maintain a high catalytic rate. At the same time, the AgNCs@CF-g-PAA catalyst can also be used to catalyze the rapid hydrolysis of sodium borohydride, which is conducive to hydrogen production. In summary, we have prepared a practical catalyst AgNCs@CF-g-PAA with high catalytic performance based on cheap raw materials and a simple synthesis route, which provides a catalyst candidate for the treatment of water contaminant 4-NP and the production of hydrogen from sodium borohydride.

Controllable Preparation of 2D V2 O5 Peroxidase-Mimetic Nanozyme to Develop Portable Paper-Based Analytical Device for Intelligent Pesticide Assay.

Given severe harmfulness of pesticides, unique characteristics of peroxidase-mimetic nanozymes, and favorable prospects of paper-based analytical devices (PADs), it is highly desirable to construct a nanozyme-based PAD for intelligent analysis of pesticide without enzyme/aptamer/antibody and interference of O2 . Herein, 2D nanosheet-like V2 O5 (2D-VONz) with exclusive peroxidase-mimetic activity is controllably prepared under the optimal reactants concentration and reaction temperature. Experimental characterizations demonstrate that 2D-VONz exhibits high affinity and catalytic rate, and catalytic oxidation is dependent on •OH yielded from the decomposition of H2 O2 catalyzed by 2D-VONz, and the catalytic performance is relevant to π-π stacking force-controlled surface zeta potential of 2D-VONz changed by substrates, giving a comprehensive understand of the inherent mechanism. Interestingly, 2D-VONz activity is inhibited by pesticide glyphosate (Gly), and then is exploited to develop a PAD, on which, Gly declines 2D-VONz activity to prevent it from catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine, contributing to rapid, naked-eye, and portable analysis of pesticide using a smartphone. The current strategy on preparing exclusive peroxidase-mimetic 2D nanozyme, investigating catalytic mechanism, developing nanozyme-based PAD, and achieving direct pesticide sensing will set up new avenues to improve the analytical performance, strengthen the practicability, and broaden the application scope of nanozymes.

Combined Photoredox Catalysis for Value-Added Conversion of Contaminants at Spatially Separated Dual Active Sites.

As 2 indispensable counterparts in one catalysis system, the independent reduction and oxidation reactions require synergetic regulation for cooperatively promoting redox efficiency. Despite the current success in promoting the catalytic efficiency of half reduction or oxidation reactions, the lack of redox integration leads to low energy efficiency and unsatisfied catalytic performance. Here, we exploit an emerging photoredox catalysis system by combining the reactions of nitrate reduction for ammonia synthesis and formaldehyde oxidation for formic acid production, in which superior photoredox efficiency is achieved on the spatially separated dual active sites of Ba single atoms and Ti3+. High catalytic redox rates are accomplished for respective ammonia synthesis (31.99 ± 0.79 mmol gcat -1 h-1) and formic acid production (54.11 ± 1.12 mmol gcat -1 h-1), reaching a photoredox apparent quantum efficiency of 10.3%. Then, the critical roles of the spatially separated dual active sites are revealed, where Ba single atoms as the oxidation site using h+ and Ti3+ as the reduction site using e- are identified, respectively. The efficient photoredox conversion of contaminants is accomplished with environmental importance and competitive economic value. This study also represents a new opportunity to upgrade the conventional half photocatalysis into the complete paradigm for sustainable solar energy utilization.

Recyclable Mussel-Inspired Magnetic Nanocellulose@Polydopamine-Ag Nanocatalyst for Efficient Degradation of Refractory Organic Pollutants and Bacterial Disinfection.

Development of a novel strategy to tackle bacterial-contaminated complex industrial wastewaters containing refractory organic pollutants is of great demand. In this study, polydopamine (PDA)-coated magnetic cellulose nanofiber (MCNF)-loaded silver nanoparticle (AgNP) (MCNF/PDA-Ag) nanocomposites were designed and applied for efficient degradation of organic dye pollutants and inactivation of Escherichia coli (E. coli) in wastewater. In the presence of NaBH4, MCNF/PDA-Ag could achieve a high catalytic reduction rate of 6.54 min-1 for the removal of methylene blue. Similarly, it showed good catalytic reduction performance for methyl orange (0.63 min-1) and 4-nitrophenol (2.94 min-1). The MCNF/PDA-Ag nanocomposites can be easily magnetically recycled and reused with negligible loss of catalytic performance. Moreover, this nanocatalyst also exhibited excellent disinfection performance against E. coli, with more than 99% disinfection ratio at very low doses (50 μg/mL). Overall, this work provides new insights into a delicate design of advanced magnetically recyclable silver nanocomposites with ultrahigh catalytic rates and excellent antibacterial properties from sustainable nature biomass.

Molecular Catalyst Synthesis Strategies to Prepare Atomically Dispersed Fe-N-C Heterogeneous Catalysts.

We report a strategy to integrate atomically dispersed iron within a heterogeneous nitrogen-doped carbon (N-C) support, inspired by routes for metalation of molecular macrocyclic iron complexes. The N-C support, derived from pyrolysis of a ZIF-8 metal-organic framework, is metalated via solution-phase reaction with FeCl2 and tributyl amine, as a Brønsted base, at 150 °C. Fe active sites are characterized by 57Fe Mössbauer spectroscopy and aberration-corrected scanning transmission electron microscopy. The site density can be increased by selective removal of Zn2+ ions from the N-C support prior to metalation, resembling the transmetalation strategy commonly employed for the preparation of molecular Fe-macrocycles. The utility of this approach is validated by the higher catalytic rates (per total Fe) of these materials relative to established Fe-N-C catalysts, benchmarked using an aerobic oxidation reaction.

Mechanism research on hydrogen production from catalytic pyrolysis of waste tire rubber

Waste tires are currently disposed of through various approaches such as landfill and incineration, which not only causes environmental pollution, but also lead to the wastage of resources. As an important type of solid waste, tire rubber has a high carbon-to-hydrogen ratio, which makes it a good material for hydrogen production from pyrolysis. In this study, molecular dynamics simulations combined with experimental methods are used to explore the mechanism of hydrogen production from the catalytic pyrolysis (CP) of waste tire rubber (WTR) over Ni, ZSM-5 and Ni/ZSM-5. The simulation results show that the three catalysts potentially promote the release of hydrogen radicals from monomers and facilitate attack by H· radicals to generate hydrogen. Compared with ZSM-5 and Ni, the Ni/ZSM-5 catalyst exerts better catalytic effects, leading to higher contents of produced H2 and hydrocarbons. In the low-temperature stage, the long chain cracks into monomer compounds, which mainly include isoprene, styrene, and 1,3-butadiene. Meanwhile, in the high-temperature stage, free radicals attack monomers to generate small molecules. The main gas products from the catalytic pyrolysis of waste tire rubber are hydrogen, methane, and ethylene. The use of all three catalysts leads to a low final catalytic pyrolysis temperature, high catalytic pyrolysis rate, and excellent catalytic effect. This work aims to provide a deeper understanding of the reaction thermodynamics and kinetics for the formation mechanisms of gaseous products, primarily hydrogen.

Membrane-anchored HDCR nanowires drive hydrogen-powered CO2 fixation.

Filamentous enzymes have been found in all domains of life, but the advantage of filamentation is often elusive1. Some anaerobic, autotrophic bacteria have an unusual filamentous enzyme for CO2 fixation-hydrogen-dependent CO2 reductase (HDCR)2,3-which directly converts H2 and CO2 into formic acid. HDCR reduces CO2 with a higher activity than any other known biological or chemical catalyst4,5, and it has therefore gained considerable interest in two areas of global relevance: hydrogen storage and combating climate change by capturing atmospheric CO2. However, the mechanistic basis of the high catalytic turnover rate of HDCR has remained unknown. Here we use cryo-electron microscopy to reveal the structure of a short HDCR filament from the acetogenic bacterium Thermoanaerobacter kivui. The minimum repeating unit is a hexamer that consists of a formate dehydrogenase (FdhF) and two hydrogenases (HydA2) bound around a central core of hydrogenase Fe-S subunits,one HycB3 and two HycB4. These small bacterial polyferredoxin-like proteins oligomerize through their C-terminal helices to form the backbone of the filament. By combining structure-directed mutagenesis with enzymatic analysis, we show that filamentation and rapid electron transfer through the filament enhance the activity of HDCR. To investigate the structure of HDCR in situ, we imaged T. kivui cells with cryo-electron tomography and found that HDCR filaments bundle into large ring-shaped superstructures attached to the plasma membrane. This supramolecular organization may further enhance the stability and connectivity of HDCR to form a specialized metabolic subcompartment within the cell.

Preparation and Electrocatalytic Properties of CuS/NCNT Composites

Copper sulfide was prepared successfully by reflux method in the research. To improve the dispersion and conductivity of copper sulfide, CuS/NCNTs composites were prepared by one-step hydrothermal method using nitrogen doped carbon nanotubes (NCNTs) and copper sulfide. The conductivity and dispersion of the composites were improved, and the catalytic effect of oxygen reduction was significantly increased. The precursor of CuS/NCNTs oxygen reduction catalyst was calcined to obtain CuS/NCNTs oxygen reduction catalyst with good stability and methanol resistance. The onset potential, current density and half-wave potential were significantly improved. In the process of composite materials calcination, the oxygen reduction catalyst with high catalytic rate was obtained by adjusting the proportion of CuS, CNTs and nitrogen sources, which provided a practical experimental method for sulfide oxidant catalysis. This cheap catalytic material was expected to replace noble metal catalyst like Pt/C, and be widely used in the field of oxygen reduction catalyst.

Use of a residue containing chromium(VI) for dye decomposition using an advanced oxidative process

In this study, a Cr2O3 catalyst was produced from a sulfochromic residue (SCR) generated in the analysis of soil organic matter. The Cr2O3 obtained from the residue was then characterized by techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), and scanning electron microscopy (SEM). To evaluate the applicability of Cr2O3 as a catalyst, methylene blue (MB) dye was evaluated as a model molecule in discoloration and degradation tests. The catalytic tests were performed in the absence (Cr2O3/H2O2) and in the presence of UV radiation (Cr2O3/H2O2/UV) at room temperature (25 ± 1 °C) under constant agitation at 200 rpm. The H2O2 dose, catalyst mass, initial concentration, and pH of the MB solution were optimized for each treatment. The optimized conditions were applied in dye degradation/discoloration. The results showed that Cr2O3 has high catalytic activity, with discoloration and degradation rates of 97% and 60%, respectively, at an equilibrium time of 6 h for both treatments. The catalyst reuse performance was evaluated, and discoloration greater than 80% was observed for MB concentrations of 50 and 100 mg L-1 after 7 cycles. These results showed that SCR treatment minimized the environmental impact by ensuring adequate properties for disposal in accordance with the current Brazilian legislation, in addition to recovering Cr2O3, which was demonstrated to be an efficient catalyst in the degradation of organic compounds via advanced oxidative processes (AOPs).

Palladium/ melamine-based porous network thin film at oil/water interface as effective catalyst for reduction of p-nitrophenol to p-aminophenol and dye degradation

Melamine-based porous network was prepared by the strong binding ability of amino functional groups of melamine with Pd(0) surface and pre-polymerization at the oil-water interface that confirmed by X-ray diffraction analysis. Palladium nanoparticles not only stimulate the pre-polymerization, but also stabilize themselves by this porous structure. Fourier-transform infrared spectroscopy, transmission electron microscopy, field-emission scanning electron microscopy, energy dispersive analysis of X-ray and thermal gravimetric analysis were applied for the catalyst characterization. The as-prepared catalyst forms an inclusion complex according to the host-guest chemistry in the presence of nitrophenols or different dyes. An efficient catalytic activity of this catalyst is due to the entrapment of the guest molecule in the cavity of the mesoporous structure and reaction progress on the Pd(0) nanoparticles surfaces which was approved by Brunauer-Emmett-Teller (BET) analysis. Simple preparation, unique structure and high catalytic reaction rate are some of the considerable advantages of this catalyst that can play key roles in the industrial processes. A practical, cost-effective and facile route for the synthesis of Pd(0)/melamine-based porous network thin film as an applicable catalyst for eliminating the water-pollution is reported. Melamine-based mesoporous polymer network was applied for the stabilization and immobilization of Pd nanoparticles, stimulating the room temperature pre-polymerization at liquid-liquid interface. • Room temperature pre-polymerization at the oil-water interface. • Simple preparation of Pd/melamine-based porous network thin film. • Unique mesoporous structure and high catalytic reaction rate. • Inclusion complex formation by entrapment of dye/nitrophenol molecules. • Eliminating the water-pollution using melamine-based mesoporous Pd-polymer networks.

Reaction mechanism for NO oxidation on the soot surface using a quantum chemistry

Compared with the gas phase oxidation of NO, the NO surface oxidation on soot is more effective, which is critical to keep efficient diesel particulate filter regeneration and high selective catalytic reduction conversion rates. To fill the knowledge gaps in catalytic oxidation of NO on the soot surface, it is integral to study the detailed mechanism in the NO-O2-soot reaction. This paper explores soot surface catalytic role in changing NO into NO2 using density functional theory and chemical kinetic analysis. The results exhibit that the adsorption stability of NO on the soot sites is higher than that of O2. The adsorbed NO interacts with O2 on the soot surface, which reduces the activation energy of C(O2) decomposition. The NO by N-down adsorption is oxidized readily by O2 with an energy barrier of 10.9 kJ/mol, and the reaction rate is 8.8 × 1011 s−1 at 300 K. The formation of NO2 depends mainly on C(NO2) and C(ONO2) decomposition during surface oxidation. The NO cleavage will produce C(O) and C(N), which is difficult to be further oxidized by O2 or NO. This study reveals the mechanism for soot surface catalytic of NO oxidation, which explains the results of previous experiments for the NO-O2-soot reaction system.

Design of a Full-Consensus Glutamate Decarboxylase and Its Application to GABA Biosynthesis.

Glutamate decarboxylase (GAD) catalyses the decarboxylation of L-glutamate to gamma-aminobutyric acid (GABA). Improvement of the enzymatic properties of GAD is important for the low-cost synthesis of GABA. In this study, utilizing sequences of enzymes homologous with GAD from lactic acid bacteria, highly mutated GADs were designed using sequence-based protein design methods. Two mutated GADs, FcGAD and AncGAD, generated by full-consensus design and ancestral sequence reconstruction, had more desirable properties than native GADs. With respect to thermal stability, the half-life of the designed GADs was about 10 °C higher than that of native GAD. The productivity of FcGAD was considerably higher than those of known GADs; more than 250 mg/L of purified enzyme could be produced in the E. coli expression system. In a production test using 26.4 g of l-glutamate and 3.0 g of resting cells, 17.2 g of GABA could be prepared within one hour, without purification, in a one-pot synthesis.

Solid-Binding Peptide-Guided Spatially Directed Immobilization of Kinetically Matched Enzyme Cascades in Membrane Nanoreactors.

Biocatalysis is a useful strategy for sustainable green synthesis of fine chemicals due to its high catalytic rate, reaction specificity, and operation under ambient conditions. Addressable immobilization of enzymes onto solid supports for one-pot multistep biocatalysis, however, remains a major challenge. In natural pathways, enzymes are spatially coupled to prevent side reactions, eradicate inhibitory products, and channel metabolites sequentially from one enzyme to another. Construction of a modular immobilization platform enabling spatially directed assembly of multiple biocatalysts would, therefore, not only allow the development of high-efficiency bioreactors but also provide novel synthetic routes for chemical synthesis. In this study, we developed a modular cascade flow reactor using a generalizable solid-binding peptide-directed immobilization strategy that allows selective immobilization of fusion enzymes on anodic aluminum oxide (AAO) monoliths with high positional precision. Here, the lactate dehydrogenase and formate dehydrogenase enzymes were fused with substrate-specific peptides to facilitate their self-immobilization through the membrane channels in cascade geometry. Using this cascade model, two-step biocatalytic production of l-lactate is demonstrated with concomitant regeneration of soluble nicotinamide adenine dinucleotide (NADH). Both fusion enzymes retained their catalytic activity upon immobilization, suggesting their optimal display on the support surface. The 85% cascading reaction efficiency was achieved at a flow rate that kinetically matches the residence time of the slowest enzyme. In addition, 84% of initial catalytic activity was preserved after 10 days of continuous operation at room temperature. The peptide-directed modular approach described herein is a highly effective strategy to control surface orientation, spatial localization, and loading of multiple enzymes on solid supports. The implications of this work provide insight for the single-step construction of high-power cascadic devices by enabling co-expression, purification, and immobilization of a variety of engineered fusion enzymes on patterned surfaces.

Electrocatalytic Oxidation of Methanol over An Electrode with Ni‐MOF‐74 Catalyst

AbstractDeveloping non‐noble metal catalysts for methanol oxidation in fuel cells is of importance. In this work, Ni‐MOF‐74 was synthesized through a simple solvothermal method and fully characterized. The as‐made Ni‐MOF‐74 modified carbon paste electrode (Ni‐MOF‐74/CPE) was applied for methanol electrooxidation reaction in 0.1 M NaOH solution. Ni‐MOF‐74 had high electrochemical stability and exhibited good electrocatalytic property for methanol oxidation, a mechanism for the reaction was proposed, the current density increases impressively on Ni‐MOF‐74/CPE compared with carbon paste electrode, and a really high catalytic rate constant (kcat) of 8.1×105 cm3 ⋅ mol−1 ⋅ s−1 was obtained in this work. The given results indicate that Ni‐MOF‐74 can be a promising candidate of electrocatalysts for direct methanol fuel cells (DMFCs).

CuxO nanorods with excellent regenerable NADH peroxidase mimics and its application for selective and sensitive fluorimetric ethanol sensing

CuxO nanorods with excellent NADH peroxidase mimics were synthesized by a simple hydrothermal method. The catalytic oxidation of NADH to NAD cofactor strictly follows the enzymatic kinetics with high catalytic rate and strong affinity. The catalytic mechanism of CuxO NRs was that in the presence of hydrogen peroxide, the catalytic oxidizing NADH to NAD + involving with O2.-.anion production, making it realistic to mutually convert between coenzymes. Considering that the mutual transformation of NADH/NAD cofactors plays an important role in biological function, combination of CuxO NRs with alcohol dehydrogenase, a highly selective method for fluorimetric detection of ethanol was established. The as-proposed sensing platform is capable of dectecting alcohol with the limit of detection of 26.7 μM (S/N = 3) and applied in practical sample with satisfied accuracy and recovery. The as-developed regenerable NADH peroxidase mimics would also cast lights in biocatalysis, synthetic biology and bioenergy.

Biochemical and biophysical characterization of the OXA-48-like carbapenemase OXA-436.

The crystal structure of the class D β-lactamase OXA-436 was solved to a resolution of 1.80 Å. Higher catalytic rates were found at higher temperatures for the clinically important antibiotic imipenem, indicating better adaptation of OXA-436 to its mesophilic host than OXA-48, which is believed to originate from an environmental source. Furthermore, based on the most populated conformations during 100 ns molecular-dynamics simulations, it is postulated that the modulation of activity involves conformational shifts of the α3-α4 and β5-β6 loops. While these changes overall do not cause clinically significant shifts in the resistance profile, they show that antibiotic-resistance enzymes exist in a continuum. It is believed that these seemingly neutral differences in the sequence exist on a path leading to significant changes in substrate selectivity.