scholarly journals Characterization of highly active 2-keto-3-deoxy-L-arabinonate and 2-keto-3-deoxy-D-xylonate dehydratases in terms of the biotransformation of hemicellulose sugars to chemicals

2020 ◽  
Vol 104 (16) ◽  
pp. 7023-7035
Author(s):  
Samuel Sutiono ◽  
Bettina Siebers ◽  
Volker Sieber
Keyword(s):  
Racemic Mixture ◽  
Highly Active ◽  
Key Points ◽  
Deoxy Sugar ◽  
Weimberg Pathway ◽  
One Step ◽  
The One ◽  
Increased Activity ◽  
Enzyme Class

Abstract2-keto-3-L-arabinonate dehydratase (L-KdpD) and 2-keto-3-D-xylonate dehydratase (D-KdpD) are the third enzymes in the Weimberg pathway catalyzing the dehydration of respective 2-keto-3-deoxy sugar acids (KDP) to α-ketoglutaric semialdehyde (KGSA). The Weimberg pathway has been explored recently with respect to the synthesis of chemicals from L-arabinose and D-xylose. However, only limited work has been done toward characterizing these two enzymes. In this work, several new L-KdpDs and D-KdpDs were cloned and heterologously expressed in Escherichia coli. Following kinetic characterizations and kinetic stability studies, the L-KdpD from Cupriavidus necator (CnL-KdpD) and D-KdpD from Pseudomonas putida (PpD-KdpD) appeared to be the most promising variants from each enzyme class. Magnesium had no effect on CnL-KdpD, whereas increased activity and stability were observed for PpD-KdpD in the presence of Mg2+. Furthermore, CnL-KdpD was not inhibited in the presence of L-arabinose and L-arabinonate, whereas PpD-KdpD was inhibited with D-xylonate (I50 of 75 mM), but not with D-xylose. Both enzymes were shown to be highly active in the one-step conversions of L-KDP and D-KDP. CnL-KdpD converted > 95% of 500 mM L-KDP to KGSA in the first 2 h while PpD-KdpD converted > 90% of 500 mM D-KDP after 4 h. Both enzymes in combination were able to convert 83% of a racemic mixture of D,L-KDP (500 mM) after 4 h, with both enzymes being specific toward the respective stereoisomer. Key points• L-KdpDs and D-KdpDs are specific toward L- and D-KDP, respectively.• Mg2+affected activity and stabilities of D-KdpDs, but not of L-KdpDs.• CnL-KdpD and PpD-KdpD converted 0.5 M of each KDP isomer reaching 95 and 90% yield.• Both enzymes in combination converted 0.5 M racemic D,L-KDP reaching 83% yield.

scholarly journals Improving the Activity of Fe/C/N ORR Electrocatalyst Using Double Ammonia Promoted CO2 Laser Pyrolysis

2020 ◽  
Vol 6 (4) ◽  
pp. 63
Author(s):  
Henri Perez ◽  
Mathieu Frégnaux ◽  
Emeline Charon ◽  
Arnaud Etcheberry ◽  
Olivier Sublemontier
Keyword(s):  
Co2 Laser ◽  
Large Scale ◽  
Laser Energy ◽  
Reduction Reaction ◽  
Laser Pyrolysis ◽  
Highly Active ◽  
One Step ◽  
Orr Activity ◽  
Set Up ◽  
The One

Recently, we reported the use of CO2 laser pyrolysis for the synthesis of promising Fe/C/N electrocatalysts for Oxygen Reduction Reaction (ORR) in fuel cells. The set-up used single laser pyrolysis of an aerosolized solution of iron acetylacetonate in toluene with ammonia, both as laser energy transfer agent and nitrogen source. In the present paper, we investigate the effect of a second ammonia promoted CO2 laser pyrolysis on the feature and ORR activity of Fe/C/N electrocatalysts. Indeed, compared to single pyrolysis, the second ammonia promoted CO2 laser pyrolysis could be an interesting way to synthesize in one-step performing ORR electrocatalysts on a large scale. For this comparison, a two-stage reactor was built, allowing both single ammonia-induced CO2 laser pyrolysis as reported previously or double ammonia-induced CO2 laser pyrolysis. In the latter configuration, the catalyst nanopowder flow is formed at the first stage of the reactor, then mixed with a second ammonia flow and allowed to cross a second CO2 laser beam, thus undergoing a second ammonia-induced CO2 laser pyrolysis before being collected on filters. It is found that the second ammonia-induced CO2 laser pyrolysis significantly improves the ORR performances of the materials prepared by single CO2 laser pyrolysis. The effect is demonstrated for three different catalysts for which the onset potentials for the ORR from single-stage to double-stage configuration increase from 625 mV to 845 mV, 790 mV to 860 mV, and 800 mV to 885 mV, respectively. The selectivity of the ORR was determined at 600 mV/SHE and lie between 3.41 and 3.72. These promising performances suggesting potentialities for the one-step formation of highly active Fe/C/N ORR electrocatalysts are discussed, based on results of surface analysis by XPS, specific surface area measurements, and Raman spectroscopy.

scholarly journals Influence of the calibration on experimental UV index at a midlatitude site, Granada (Spain)

2010 ◽  
Vol 3 (6) ◽  
pp. 5645-5670
Author(s):  
M. Antón ◽  
J. E. Gil ◽  
A. Cazorla ◽  
J. M. Vilaplana ◽  
F. J. Olmo ◽  
...  
Keyword(s):  
Calibration Method ◽  
Conversion Factors ◽  
Uv Index ◽  
Calibration Methods ◽  
One Step ◽  
The Difference ◽  
Mean Differences ◽  
Experimental Values ◽  
The One

Abstract. The ultraviolet (UV) index is the variable most commonly used to inform the general public about the levels and potential harmful effects of UV radiation incident at Earth's surface. This variable is derived from the output signal of the UV radiometers applying conversion factors obtained by calibration methods. This paper focused on the influence of the use of two of these methods (called one-step and two-steps methods) on the resulting experimental UV Index (UVI) as measured by a YES UVB-1 radiometer located in a midlatitude station, Granada (Spain) for the period 2006–2009. In addition, it is also analyzed the difference with the UVI values obtained when the calibration factors provided by the manufacturer are used. For this goal, the detailed characterization of the UVB-1 radiometer obtained in the first Spanish calibration campaign of broadband UV radiometers at the "El Arenosillo" INTA station in 2007 is used. In addition, modeled UVI data derived from the LibRadtran/UVSPEC radiative transfer code are compared with the experimental values recorded at Granada for cloud-free conditions. The absolute mean differences between the measured and modeled UVI data at Granada are around 5% using the one-step and two-steps calibration methods. This result indicates the excellent performance of these two techniques for obtaining UVI data from the UVB-1 radiometer. In contrast, the application of the calibration factor supplied by the manufacturer produces a high overestimation (~14%) of the UVI values. This fact generates unreliable alarming high UVI data in summer when the manufacturer's factor is used. Thus, days with an extreme erythemal risk (UVI higher than 10) increase up to 46% of all cases measured between May and September at Granada when the manufacturer's factor is applied. This percentage is reduced to a more reliable value of 3% when the conversion factors obtained with the two-steps calibration method are used. All these results report about the need of a sound calibration of the broadband UV instruments in order to obtain reliable measurements.

scholarly journals One-step isolation and biochemical characterization of a highly active plant PSII monomeric core

2011 ◽  
Vol 108 (1) ◽  
pp. 33-46 ◽  
Author(s):  
Cristina Pagliano ◽  
Fabiana Chimirri ◽  
Guido Saracco ◽  
Francesco Marsano ◽  
James Barber
Keyword(s):  
Biochemical Characterization ◽  
Highly Active ◽  
One Step

scholarly journals Chitosan-Capped Au Nanoparticles for Laser Photothermal Ablation Therapy: UV-Vis Characterization and Optothermal Performances

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Giancarlo Margheri ◽  
Silvana Trigari ◽  
Mariabeatrice Berti ◽  
Maurizio Muniz Miranda ◽  
Rita Traversi
Keyword(s):  
Near Infrared ◽  
Au Nanoparticles ◽  
Ablation Therapy ◽  
Synthesis Conditions ◽  
Photothermal Ablation ◽  
Nir Absorption ◽  
One Step ◽  
The One ◽  
Refined Version

We have reported on the synthesis and characterization of near-infrared- (NIR-) absorbing colloidal nanoparticles prepared by exploiting the one-step reaction of HAuCl4 and Na2S2O3, followed by their stabilization with chitosan. This reaction also produces a big amount of unwanted nanoparticles detuned with respect to the NIR spectral region. For this reason, it is usually assumed that the product has to be filtered and enriched to enhance its NIR absorption, and the possible exploitation of the simpler raw product has never been worthy to be considered. Aiming to investigate this missing aspect, we chose to avoid the purification steps and rather focused on the preparation of the unrefined colloid, identifying the synthesis conditions that maximize its NIR absorbance and, subsequently, testing it as an optothermal transducer by measuring its molar heating rate (MHR). As expected, we found that the performances of the raw colloid are indeed lower than those of its refined version, but only to a limited extent. Moreover, MHR is unexpectedly higher than that deducible for other classical NIR-absorbing nanoparticles, like Au nanorods or Au nanostars. Thus, the product of the simpler preparation protocol appears as a competitive trade-off solution between easy manufacturing and optothermal performances.

scholarly journals CHARACTERIZATION OF T4 MUTANTS THAT PARTIALLY SUPPRESS THE INABILITY OF T4rII TO GROW IN LAMBDA LYSOGENS

Genetics ◽  
1976 ◽  
Vol 83 (3) ◽  
pp. 477-487
Author(s):  
Theodore Homyk ◽  
Angel Rodriguez ◽  
Jon Weil
Keyword(s):  
Burst Size ◽  
Personal Communication ◽  
Growth Cycle ◽  
Plaque Morphology ◽  
One Step ◽  
Step Growth ◽  
The One ◽  
Phage Growth ◽  
L1 And L2

ABSTRACT In the course of isolating viable T4 deletions that affect plaque morphology (Homyk and Weil 1974), two closely linked point mutants, sip1 and sip2, were obtained. They map between genes t and 52, cause a reduction in plaque size and burst size, and partially suppress the lethality of rII mutants for growth in lambda lysogens. These characteristics demonstrate that sip1 and sip2 are similar to mutants previously reported by Freedman and Brenner (1972). In addition, D. Hall (personal communication) has shown that sip1 and sip2 are similar to the mutant farP85, which affects the regulation of a number of early genes (Chace and Hall 1975).—Sip suppression of rII mutants can be demonstrated in one-step growth experiments, even when both rII genes are completely deleted. This indicates that sip mutants do not simply reduce the level of rII gene products required for growth in a lambda lysogen. Instead, they alter the growth cycle so as to partially circumvent the need for any rII products.—Mutations at two other sites, designated L1 and L2, reverse the poor phage growth caused by sip and, in the one case tested, reverse the rII-suppressing ability of sip.

Immobilization and Thermostability Characterization of Cephalosporin C Acylase

2013 ◽  
Vol 634-638 ◽  
pp. 682-688
Author(s):  
Kai Hua Han ◽  
Hui Luo ◽  
Yao Zhen Xie ◽  
Shun Yao ◽  
Yan Hong Chang ◽  
...  
Keyword(s):  
Immobilized Enzyme ◽  
Ph Value ◽  
Cephalosporin C ◽  
Sodium Phosphate Buffer ◽  
Cephalosporin C Acylase ◽  
Key Enzyme ◽  
One Step ◽  
Enzyme Dosage ◽  
The One

Some kinds of epoxy supports, LX1000-EP(C), LX1000-EP(D), LKZ-116, LKZ-118 and LKZ-126 were utilized to covalently immobilize cephalosporin C (CPC) acylase, the key enzyme in the one-step enzymatic process of 7-aminocephalosporanic acid (7-ACA) production. After preliminary carrier screening, the immobilized CPC acylase with LKZ-118 as the support shows the highest activity (115 U/g) suggesting its potential application in industrial 7-ACA production. The conditions of CPC acylase immobilized on LKZ-118 to achieve higher activity and thermostability of the immobilized enzyme were optimized by adjusting pH value, buffer concentration, enzyme dosage and immobilized time. The activity of immobilized enzyme was found to be optimal at pH 8.5, in 0.85 M sodium phosphate buffer when the enzyme dosage was 500 U/g and immobilization time was 28 h.

Structural characterization of the aquaporin inhibitor 2-nicotinamido-1,3,4-thiadiazole

2015 ◽  
Vol 71 (12) ◽  
pp. 1074-1079 ◽  
Author(s):  
Marianne E. Burnett ◽  
Hannah M. Johnston ◽  
Kayla N. Green
Keyword(s):  
Biological Activity ◽  
Structural Characterization ◽  
Antimicrobial Agents ◽  
2D Nmr ◽  
Brain Barrier Permeability ◽  
Nmr Techniques ◽  
One Step ◽  
Uv Visible ◽  
The One

Nicotinamides are a class of compounds with a wide variety of applications, from use as antimicrobial agents to inhibitors of biological processes. These compounds are also cofactors, which are necessary components of metabolic processes. Structural modification gives rise to the activities observed. Similarly, 1,3,4-thiadiazoles have been shown to possess antioxidant, antimicrobial, or anti-inflammatory biological activity. To take advantage of each of the inherent characteristics of the two aforementioned functional groups, 2-nicotinamido-1,3,4-thiadiazole, C8H6N4OS, was synthesized. Since defining chemical connectivity is paramount in understanding biological activity, in this report, the structural characterization of 2-nicotinamido-1,3,4-thiadiazole has been carried out using X-ray crystallographic methods. The NMR-derived assignments were made possible by utilizing one- (1D) and two-dimensional (2D) NMR techniques. In addition, UV–Visible and IR spectroscopies, and elemental analysis were used to fully characterize the product synthesized by the one-step reaction between nicotinoyl chloride hydrochloride and 2-amino-1,3,4-thiadiazole. Computational parameters related to blood–brain barrier permeability are also presented.

scholarly journals Trifluoroacetic Acid Hydroxylamine System as Organocatalyst Reagent in a One-Pot Salt Free Process for the Synthesis of Caprolactam and Amides of Industrial Interest

2021 ◽  
Author(s):  
F. Manente ◽  
L. Pietrobon ◽  
L. Ronchin ◽  
A. Vavasori
Keyword(s):  
Trifluoroacetic Acid ◽  
Room Temperature ◽  
Beckmann Rearrangement ◽  
One Pot ◽  
Free Process ◽  
Hydrogenation Reactions ◽  
One Step ◽  
The One ◽  
Industrial Relevance

AbstractIn this work we studied the reactivity of the Trifluoroacetic acid hydroxylamine system in the one step salt free synthesis of amides from ketones. A particular regards was paid to the caprolactam synthesis because of its industrial relevance. Synthesis, reactivity and characterization of the hydroxylamine trifluoroacetate is given. Fast oximation reaction of several ketones was gained at room temperature (1 h of reaction quantitative conversion for several ketones). In the same reactor, by raising the temperature at 383 K, the Beckmann rearrangement of the so obtained oximes is easily accomplished in the presence of three equivalent of TFA. The possibility of obtaining the trifluoroacetate of the hydroxylamine with a modified nitric acid hydrogenation reactions was verified, too. Reuse of solvent and trifluoroacetic acid is easily achieved by distillation. Graphical abstract Salt free one-pot caprolactam and amides process catalyzed by CF3COOH, in the presence of NH2OH TFA as the oximation agent.

scholarly journals Selectivity descriptors for the direct hydrogenation of CO2 to hydrocarbons during zeolite-mediated bifunctional catalysis

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Adrian Ramirez ◽  
Xuan Gong ◽  
Mustafa Caglayan ◽  
Stefan-Adrian F. Nastase ◽  
Edy Abou-Hamad ◽  
...  
Keyword(s):  
Large Degree ◽  
Great Promise ◽  
Product Selectivity ◽  
Highly Active ◽  
Cascade Processes ◽  
One Step ◽  
Selectivity Control ◽  
Direct Hydrogenation ◽  
The One ◽  
Hydrogenation Of Co

AbstractCascade processes are gaining momentum in heterogeneous catalysis. The combination of several catalytic solids within one reactor has shown great promise for the one-step valorization of C1-feedstocks. The combination of metal-based catalysts and zeolites in the gas phase hydrogenation of CO2 leads to a large degree of product selectivity control, defined mainly by zeolites. However, a great deal of mechanistic understanding remains unclear: metal-based catalysts usually lead to complex product compositions that may result in unexpected zeolite reactivity. Here we present an in-depth multivariate analysis of the chemistry involved in eight different zeolite topologies when combined with a highly active Fe-based catalyst in the hydrogenation of CO2 to olefins, aromatics, and paraffins. Solid-state NMR spectroscopy and computational analysis demonstrate that the hybrid nature of the active zeolite catalyst and its preferred CO2-derived reaction intermediates (CO/ester/ketone/hydrocarbons, i.e., inorganic-organic supramolecular reactive centers), along with 10 MR-zeolite topology, act as descriptors governing the ultimate product selectivity.

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