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#36919558   2023/03/15 To Up

Defective TiO for High-Performance Electrocatalytic NO Reduction toward Ambient NH Production.

Synthesis of green ammonia (NH ) via electrolysis of nitric oxide (NO) is extraordinarily sustainable, but multielectron/proton-involved hydrogenation steps as well as low concentrations of NO can lead to poor activities and selectivities of electrocatalysts. Herein, it is reported that oxygen-defective TiO nanoarray supported on Ti plate (TiO /TP) behaves as an efficient catalyst for NO reduction to NH . In 0.2 m phosphate-buffered electrolyte, such TiO /TP shows competitive electrocatalytic NH synthesis activity with a maximum NH yield of 1233.2 µg h  cm and Faradaic efficiency of 92.5%. Density functional theory calculations further thermodynamically faster NO deoxygenation and protonation processes on TiO (101) compared to perfect TiO (101). And the low energy barrier of 0.7 eV on TiO (101) for the potential-determining step further highlights the greatly improved intrinsic activity. In addition, a Zn-NO battery is fabricated with TiO /TP and Zn plate to obtain an NH yield of 241.7 µg h  cm while providing a peak power density of 0.84 mW cm .
Zixiao Li, Qiang Zhou, Jie Liang, Longcheng Zhang, Xiaoya Fan, Donglin Zhao, Zhengwei Cai, Jun Li, Dongdong Zheng, Xun He, Yongsong Luo, Yan Wang, Binwu Ying, Hong Yan, Shengjun Sun, Jing Zhang, Abdulmohsen Ali Alshehri, Feng Gong, Yinyuan Zheng, Xuping Sun

2390 related Products with: Defective TiO for High-Performance Electrocatalytic NO Reduction toward Ambient NH Production.



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#33890593   // To Up

Kinetics of chain reaction driven by proton-coupled electron transfer: α-hydroxyethyl radical and bromoacetate in buffered aqueous solutions.

We measured and computed the rate constants of the reaction between the α-hydroxyethyl radical (˙CH(CH3)OH) and bromoacetate (BrCH2CO2-) in the non-buffered (NB), as well as in the bicarbonate (HCO3-) and hydrogen phosphate (HPO42-) buffered aqueous solutions in the presence of ethanol. These complex multistep reactions are initiated by the proton-coupled electron transfer (PCET) which reduces BrCH2CO2- and incites its debromination. The PCET is followed by the step in which the resulting carboxymethyl radical propagates a radical chain reaction thus recovering ˙CH(CH3)OH and enhancing the debromination yields. It is found that the rate constants for the initial PCET step (k1) are raised by ca. an order of magnitude in the presence of the buffers (k1(NB) = 1.4 × 105 dm3 mol-1 s-1; k1(HCO3-) = 1.4 × 106 dm3 mol-1 s-1; k1(HPO42-) = 1.1 × 106 dm3 mol-1 s-1). To rationalize this, we used density functional theory at the M06-2X-D3/6-311+G(2d,p) level in conjunction with the polarizable continuum model (PCM) for an implicit description of the aqueous environment. To acceptably reproduce the measured rate constants, the minimal solute, consisting of ˙CH(CH3)OH, BrCH2CO2- and the buffer anion, has to be expanded by at least 2-3 explicit molecules of the water solvent. The used kinetic model consisting of a set of coupled differential equations indicates the sigmoid dependence of yields vs. k1 thereby confirming the autocatalytic trait of these reactions. The computations unravel the profound influence of the presence of buffers on these reaction systems. On the one hand, the buffer anions promote the PCET by accelerating the proton transfer; on the other hand, they slow down the propagation step by forming the strong hydrogen bonds with the carboxymethyl radical. The two opposing effects cancel out and cause the Br- yields to remain approximately comparable in the non-buffered and buffered media.
Igor Sviben, Iva DŽeba, Marija Bonifačić, Ivan Ljubić

1241 related Products with: Kinetics of chain reaction driven by proton-coupled electron transfer: α-hydroxyethyl radical and bromoacetate in buffered aqueous solutions.

2000 Units500 Units10 2000 Units1000 Units1000 Units1 mg500 Units2 2000 Units250 Units500 Units

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#25495904   2014/12/12 To Up

PCR amplification of a triple-repeat genetic target directly from whole blood in 15 minutes as a proof-of-principle PCR study for direct sample analysis for a clinically relevant target.

Most PCR-based diagnostics are still considered time- and labor-intensive due to disparate purification, amplification, and detection steps. Advancements in PCR enzymes and buffer chemistry have increased inhibitor tolerance, facilitating PCR directly from crude samples. Obviating the need for DNA purification, while lacking a concentration step, these direct sample methods are particularly apt for human genetic testing. However, direct PCR protocols have traditionally employed thermal cyclers with slow ramp rates and conservative hold times that significantly increase an assay's time-to-result. For this proof-of-principle study, our objective was to significantly reduce sample preparation and assay time for a PCR-based genetic test, for myotonic dystrophy type 1 (DM1), by pairing an inhibitor-resistant enzyme mix with a rapid thermal cycler to analyze samples directly in whole blood.
Christopher M Connelly, Laura R Porter, Joel R TerMaat

2097 related Products with: PCR amplification of a triple-repeat genetic target directly from whole blood in 15 minutes as a proof-of-principle PCR study for direct sample analysis for a clinically relevant target.

0.1 mg25 µg0.1 ml0.2 mg1 ml48 samples0.25 mg250 ml0.1ml (1mg/ml)25 µg0.1ml (1mg/ml)

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#24061544   // To Up

An efficient buffer-mediated control between free radical substitution and proton-coupled electron transfer: dehalogenation of iodoethane by the α-hydroxyethyl radical in aqueous solution.

A remarkable buffer-mediated control between free-radical substitution (FRS) and proton-coupled electron transfer (PCET) is demonstrated for the reaction between iodoethane and the α-hydroxyethyl radical in neutral aqueous solution in the presence of bicarbonate or phosphate buffer. The reaction is initiated by the γ-radiolysis of the water solvent, and the products, either the iodine atom (FRS) or anion (PCET), are analysed using ion chromatographic and spectrophotometric techniques. A detailed insight into the mechanism is gained by employing density functional theory (M06-2X), Møller-Plesset perturbation treatment to the second order (MP2), and multireference methods (CASSCF/CASPT2). Addition of a basic buffer anion is indispensable for the reaction to occur and the competition between the two channels depends subtly on its proton accepting affinity, with FRS being the dominant channel in the phosphate and PCET in the bicarbonate containing solutions. Unlike the former, the latter channel sustains a chain-like process which significantly enhances the dehalogenation. The present systems furnish an example of the novel PCET/FRS dichotomy, as well as insights into possibilities of its efficient control.
Ivan Ljubić, Brunislav Matasović, Marija Bonifačić

1908 related Products with: An efficient buffer-mediated control between free radical substitution and proton-coupled electron transfer: dehalogenation of iodoethane by the α-hydroxyethyl radical in aqueous solution.

5 G250 2 Pieces/Box1 mg

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#22671132   2012/06/06 To Up

Toward a small molecule, biomimetic carbonic anhydrase model: theoretical and experimental investigations of a panel of zinc(II) aza-macrocyclic catalysts.

A panel of five zinc-chelated aza-macrocycle ligands and their ability to catalyze the hydration of carbon dioxide to bicarbonate, H(2)O + CO(2) → H(+) + HCO(3)(–), was investigated using quantum-mechanical methods and stopped-flow experiments. The key intermediates in the reaction coordinate were optimized using the M06-2X density functional with aug-cc-pVTZ basis set. Activation energies for the first step in the catalytic cycle, nucleophilic CO(2) addition, were calculated from gas-phase optimized transition-state geometries. The computationally derived trend in activation energies was found to not correspond with the experimentally observed rates. However, activation energies for the second, bicarbonate release step, which were estimated using calculated bond dissociation energies, provided good agreement with the observed trend in rate constants. Thus, the joint theoretical and experimental results provide evidence that bicarbonate release, not CO(2) addition, may be the rate-limiting step in CO(2) hydration by zinc complexes of aza-macrocyclic ligands. pH-independent rate constants were found to increase with decreasing Lewis acidity of the ligand-Zn complex, and the trend in rate constants was correlated with molecular properties of the ligands. It is suggested that tuning catalytic efficiency through the first coordination shell of Zn(2+) ligands is predominantly a balance between increasing charge-donating character of the ligand and maintaining the catalytically relevant pK(a) below the operating pH.
Lucas Koziol, Carlos A Valdez, Sarah E Baker, Edmond Y Lau, William C Floyd, Sergio E Wong, Joe H Satcher, Felice C Lightstone, Roger D Aines

2605 related Products with: Toward a small molecule, biomimetic carbonic anhydrase model: theoretical and experimental investigations of a panel of zinc(II) aza-macrocyclic catalysts.

100ug100ug 100ul100.00 ug50 mg100ug Lyophilized200ug10 mg0.025 mg

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#30727439   // To Up

First Report of Bacterial Spot of Peony Caused by a Xanthomonas sp. in the United States.

In early May 2008 and 2009, peony samples (Paeonia spp.) with symptoms of leaf spot and blight were submitted to the Virginia Tech Plant Disease Clinic. The 2008 peony was an unknown cultivar from a northern Virginia landscape. The three cultivars (Dr. Alexander Fleming, Felix Crousse, and Karl Rosenfield) submitted in 2009 were from a commercial nursery in southwestern Virginia that was reporting leaf spot progressing to severe blight, which rendered plants unsalable, on 75% of a 1,219 m block during a 10-day period of heavy rainfall. Bacterial streaming from spots was observed. On the basis of phenotypic and biochemical tests, the isolates were determined to be xanthomonads. Two isolates (one recovered from the 2008 sample and one from the 2009 sample) were used in the following work. Isolates were characterized by multilocus sequencing (MLST) (4). PCR reactions were prepared and cycled using 2X ImmoMix (Bioline, Tauton, MA) according to manufacturer's recommendations with an annealing temperature of 58°C. Template DNA was added by touching a single colony with a 20-μl pipette tip and placing the tip into the reaction mix for 1 min. Four bands of the expected size were visualized on an electrophoresis gel and cleaned products were sequenced in forward and reverse directions at the University of Chicago, Cancer Research Center DNA Sequencing Facility. Corresponding gene fragments of each isolate were identical. A consensus sequence (PAMDB Isolate ID No. 936) for each of the four gene fragments was constructed and compared with sequences in NCBI ( http://www.ncbi.nlm.nih.gov/nuccore/ ) and PAMDB ( http://genome.ppws.vt.edu/cgi-bin/MLST/home.pl ) (1) databases using Blastn (2). No perfect match was found. Genetic distances between the peony isolates and all strains in PAMDB were determined by MegAlign (Lasergene; DNAStar, Madison, WI). The Xanthomonas strain most similar to the isolates recovered from the peony samples was Xanthomonas hortorum pv. hederae ICMP 1661 with a genetic distance of 0.023; this strongly suggests that the peony isolates belong to X. hortorum. For Koch's postulates, six surface-disinfested young leaflets from Paeonia lactiflora 'Karl Rosenfield' were inoculated by forcefully spraying a phosphate-buffered saline suspension of each bacterial isolate (~4.3 × 10 CFU/ml) into the underside of the leaf until leaf tissue appeared water soaked. Controls were inoculated similarly with phosphate-buffered saline solution. Moist chambers with inoculated leaves were incubated at ambient temperature under two 48W fluorescent grow lights with 12 h of light and dark. Circular spots were observed on leaves inoculated with the 2009 and 2008 isolates in 18 and 20 days, respectively. No symptoms were observed on controls. Bacterial streaming from leaf spots was observed by phase-contrast microscopy; bacteria were isolated and confirmed to be identical to the original isolates by the methods described above. To our knowledge, this is the first report of a Xanthomonas sp. causing leaf spot and blight on peony. Although bacterial blight of peony has been attributed to a xanthomonad in recent years, the pathogen had not been further characterized (3). References: (1) N. F. Almeida et al. Phytopathology 100:208, 2010. (2) D. J. Altschul et al. J. Mol. Biol. 215:403, 1990. (3) M. L. Gleason et al. Diseases of Herbaceous Perennials. The American Phytopathological Society, St. Paul, MN. 2009. (4) J. M. Young et al. Syst. Appl. Microbiol. 31:366, 2008.
C L Oliver, R Cai, B A Vinatzer, E A Bush, M A Hansen

1662 related Products with: First Report of Bacterial Spot of Peony Caused by a Xanthomonas sp. in the United States.

1100 μg

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#22101072   2011/11/06 To Up

Enzymatic hydrolysis of microcrystalline cellulose in concentrated seawater.

This communication explores the use of seawater (1X) and concentrated seawater (2X and 4X) as reaction media for the enzyme-catalyzed depolymerization of cellulose. The commercially available Accellerase-1500® - a "cocktail" of different glycosidases - is able to depolymerize several amorphous celluloses and microcrystalline cellulose Avicel® in these reaction media, at slightly lower rates (ca. 90%) than those observed when reactions are performed in pure citrate buffer (control reactions). Remarkably, at concentrated seawater effluents enzymes also display significant rates of cellulose hydrolysis. Considering the expected increasing shortages in accessibility to fresh drinkable water, the herein-reported concept may provide novel inspiring leads for a smart use of resources in an environmentally-friendly and efficient manner, and for the genetic development of cellulases highly active and stable in concentrated seawater solutions.
Philipp M Grande, Pablo Domínguez de María

2445 related Products with: Enzymatic hydrolysis of microcrystalline cellulose in concentrated seawater.

1 Set1 mg1 Set100 μg2ug100 μg100 10µg100 μg

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#16701584   // To Up

Occurrence of restriction-modification systems in ruminal butyrate-producing bacteria.

Thirty-five strains of ruminal bacteria belonging to the former Butyrivibrio fibrisolvens species were screened for the presence of site-specific restriction endonuclease and modification methyltransferase activities. Seven strains possessed endonuclease activities detectable in crude cell extracts. The recognition sequences and optimal reaction conditions for seven of them were determined. Five enzymes were found to be isoschizomers of type II endonucleases (EcoRV, NsiI, AseI (2x) and SauI), one was type IIS (FokI) and two remained unknown. The optimal reaction buffer was found to be a low ionic strength buffer and all enzymes possessed sufficient activity at 39 degrees C. The presence of DNA modification among all strains was also determined. Most of the methylation activities correlated with restriction activities, yet some strains possessed unaccompanied modification methyltransferases.
J Mrázek, M Piknová, P Pristas, J Kopecný

1548 related Products with: Occurrence of restriction-modification systems in ruminal butyrate-producing bacteria.



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