scholarly journals Characterization of a broadly specific cadaverine N-hydroxylase involved in desferrioxamine B biosynthesis in Streptomyces sviceus

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0248385
Author(s):  
Lesley-Ann Giddings ◽  
George T. Lountos ◽  
Kang Woo Kim ◽  
Matthew Brockley ◽  
Danielle Needle ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Substrate Inhibition ◽  
Product Formation ◽  
Desferrioxamine B ◽  
Hydroxamate Siderophores ◽  
Nadph Oxidation ◽  
High Concentrations ◽  
The Individual ◽  
Clinical Drug

N-hydroxylating flavin-dependent monooxygenases (FMOs) are involved in the biosynthesis of hydroxamate siderophores, playing a key role in microbial virulence. Herein, we report the first structural and kinetic characterization of a novel alkyl diamine N-hydroxylase DesB from Streptomyces sviceus (SsDesB). This enzyme catalyzes the first committed step in the biosynthesis of desferrioxamine B, a clinical drug used to treat iron overload disorders. X-ray crystal structures of the SsDesB holoenzyme with FAD and the ternary complex with bound NADP+ were solved at 2.86 Å and 2.37 Å resolution, respectively, providing a structural view of the active site environment. SsDesB crystallized as a tetramer and the structure of the individual protomers closely resembles the structures of homologous N-hydroxylating FMOs from Erwinia amylovora (DfoA), Pseudomonas aeruginosa (PvdA), and Aspergillus fumigatus (SidA). Using NADPH oxidation, oxygen consumption, and product formation assays, kinetic parameters were determined for various substrates with SsDesB. SsDesB exhibited typical saturation kinetics with substrate inhibition at high concentrations of NAD(P)H as well as cadaverine. The apparent kcat values for NADPH in steady-state NADPH oxidation and oxygen consumption assays were 0.28 ± 0.01 s-1 and 0.24 ± 0.01 s-1, respectively. However, in product formation assays used to measure the rate of N-hydroxylation, the apparent kcat for NADPH (0.034 ± 0.008 s-1) was almost 10-fold lower under saturating FAD and cadaverine concentrations, reflecting an uncoupled reaction, and the apparent NADPH KM was 33 ± 24 μM. Under saturating FAD and NADPH concentrations, the apparent kcat and KM for cadaverine in Csaky assays were 0.048 ± 0.004 s-1 and 19 ± 9 μM, respectively. SsDesB also N-hydroxylated putrescine, spermidine, and L-lysine substrates but not alkyl (di)amines that were branched or had fewer than four methylene units in an alkyl chain. These data demonstrate that SsDesB has wider substrate scope compared to other well-studied ornithine and lysine N-hydroxylases, making it an amenable biocatalyst for the production of desferrioxamine B, derivatives, and other N-substituted products.

Preparation and Characterization of a Calcium Phosphate Ceramic for the Immobilization of Chloride-containing Intermediate Level Waste

2002 ◽  
Vol 757 ◽  
Author(s):  
Brian L. Metcalfe ◽  
Ian W. Donald ◽  
Randy D. Scheele ◽  
Denis M. Strachan
Keyword(s):  
Calcium Phosphate ◽  
Rate Data ◽  
Volatile Species ◽  
Calcium Phosphate Ceramic ◽  
Radioactive Materials ◽  
Mineral Phases ◽  
Simulated Waste ◽  
High Concentrations ◽  
The Individual

ABSTRACTAttention has recently been given to the immobilization of special categories of radioactive wastes, some of which contain high concentrations of actinide chlorides. Although vitrification in phosphate glass has been proposed, this was rejected because of the high losses of chloride through the mobilization of volatile species.On the basis of non-radioactive and, more recently, radioactive studies, we have shown that calcium phosphate is an effective host for immobilizing the chloride constituents [1]. In this instance, the chlorine is retained as chloride, rather than evolved as a chlorine-bearing gas. The immobilized product is in the form of a free-flowing, non-hygroscopic powder, in which the chlorides are chemically combined within the synthetic mineral phases chlorapatite [Ca5(PO4)3Cl] and spodiosite [Ca2(PO4)Cl]. Data from studies on non-radioactive simulated waste consisting of a mixture of CaCl2 and SmCl3, and radioactive simulated waste composed of CaCl2 with PuCl3 or PuCl3 and AmCl3, are presented and compared.The XRD data confirm the presence of chlorapatite and spodiosite in the non-radioactive and radioactive materials. The durability of all specimens was measured with a modified MCC-1 test. Normalized releases of Cl after 28 days were 1.6 × 10-3 g m-2 for the non-radioactive specimens and 7 × 10-3 g m-2 for the Pu bearing specimens. Releases of Ca after 28 days were 0.3 × 10-3 and 2.0 × 10-3 g m-2 for the non-radioactive composition and the Pu composition, respectively, whilst release of Pu from the radioactive specimens was higher for the mixed Pu/Am specimen at 1.2 × 10-5g m-2 than for the Pu only specimens. The release of Am from the mixed Pu/Am composition was exceptionally low at 2.4 × 10-7 g m-2. Overall, the release rate data suggest that the ceramics dissolve congruently, followed by precipitation of Sm, Pu and Am as less soluble phases, possibly oxides or phosphates. The differences in behaviour noted between non-radioactive and radioactive specimens are interpreted in terms of the crystal chemistry of the individual systems.

scholarly journals Brain arylamidase. Purification and characterization of the soluble bovine enzyme

1969 ◽  
Vol 112 (3) ◽  
pp. 335-342 ◽  
Author(s):  
A. S. Brecher ◽  
J. B. Suszkiw
Keyword(s):  
Soluble Fraction ◽  
Substrate Inhibition ◽  
Gel Filtration ◽  
Bovine Brain ◽  
Purification And Characterization ◽  
Sephadex Column ◽  
Optimum Ph ◽  
Ammonium Sulphate Fractionation ◽  
High Concentrations

1. An enzyme acting on aminoacyl-β-naphthylamides has been isolated from the soluble fraction of bovine brain and purified 205-fold by means of ammonium sulphate fractionation, hydroxyapatite adsorption and DEAE-Sephadex column chromatography. 2. Arylamidase requires thiol groups for retention of its activity, is heat-labile and is susceptible to freezing. p-Chloromercuribenzoate and N-ethylmaleimide inactivate the enzyme rapidly. 3. Metal ions are not required for its activity, but stimulation by Mn2+ and Mg2+ and inactivation by Co2+ and Zn2+ are observed. 4. Optimum pH7·5 in phosphate buffer was exhibited for all substrates tested except l-leucyl-β-naphthylamide, for which optimum pH is 6·5. 5. Km values for a number of substrates have been obtained and substrate inhibition at high concentrations was demonstrated. 6. The molecular weight is approx. 70000 as determined by Sephadex-gel filtration.

scholarly journals Advances in the Study of Candida stellata

Fermentation ◽  
2018 ◽  
Vol 4 (3) ◽  
pp. 74 ◽  
Author(s):  
Margarita García ◽  
Braulio Esteve-Zarzoso ◽  
Juan Cabellos ◽  
Teresa Arroyo
Keyword(s):  
Chemical Characterization ◽  
Wine Aroma ◽  
Wine Quality ◽  
Starmerella Bombicola ◽  
Balsamic Vinegar ◽  
High Concentrations ◽  
Wine Flavor ◽  
The Individual ◽  
Candida Stellata

Candida stellata is an imperfect yeast of the genus Candida that belongs to the order Saccharomycetales, while phylum Ascomycota. C. stellata was isolated originally from a must overripe in Germany but is widespread in natural and artificial habitats. C. stellata is a yeast with a taxonomic history characterized by numerous changes; it is either a heterogeneous species or easily confused with other yeast species that colonize the same substrates. The strain DBVPG 3827, frequently used to investigate the oenological properties of C. stellata, was recently renamed as Starmerella bombicola, which can be easily confused with C. zemplinina or related species like C. lactis-condensi. Strains of C. stellata have been used in the processing of foods and feeds for thousands of years. This species, which is commonly isolated from grape must, has been found to be competitive and persistent in fermentation in both white and red wine in various wine regions of the world and tolerates a concentration of at least 9% (v/v) ethanol. Although these yeasts can produce spoilage, several studies have been conducted to characterize C. stellata for their ability to produce desirable metabolites for wine flavor, such as acetate esters, or for the presence of enzymatic activities that enhance wine aroma, such as β-glucosidase. This microorganism could also possess many interesting technological properties that could be applied in food processing. Exo and endoglucosidases and polygalactosidase of C. stellata are important in the degradation of β-glucans produced by Botrytis cinerea. In traditional balsamic vinegar production, C. stellata shapes the aromatic profile of traditional vinegar, producing ethanol from fructose and high concentrations of glycerol, succinic acid, ethyl acetate, and acetoin. Chemical characterization of exocellular polysaccharides produced by non-Saccharomyces yeasts revealed them to essentially be mannoproteins with high mannose contents, ranging from 73–74% for Starmerella bombicola. Numerous studies have clearly proven that these macromolecules make multiple positive contributions to wine quality. Recent studies on C. stellata strains in wines made by co-fermentation with Saccharomyces cerevisiae have found that the aroma attributes of the individual strains were apparent when the inoculation protocol permitted the growth and activity of both yeasts. The exploitation of the diversity of biochemical and sensory properties of non-Saccharomyces yeast could be of interest for obtaining new products.

Separation and Characterization of Standard Propoxyphene Diastereomers and Their Determination in Pharmaceutical and Illicit Preparations

1981 ◽  
Vol 64 (4) ◽  
pp. 875-883
Author(s):  
Shiv K Soni ◽  
Daniel Van Gelder
Keyword(s):  
High Pressure ◽  
Optical Isomers ◽  
Gold Chloride ◽  
Melting Points ◽  
Eutectic Melting ◽  
Racemic Mixtures ◽  
The Individual ◽  
Isomeric Mixtures ◽  
Asymmetric Carbon

Abstract Due to the existence of 2 asymmetric carbon atoms in: the propoxyphene molecule, there are 4 diastereomers: alpha dextro, alpha levo, beta dextro, and beta levo. Only α-d-propoxyphene is included under the federal Controlled Substances Act. Baseline separations of propoxyphene from various incipients (aspirin, caffeine, phenacetin, and acetaminophen) present in pharmaceutical and illicit preparations, and between the alpha and beta diastereomers, were achieved by high pressure liquid chromatography. The column eluant was collected and propoxyphene was extracted. The optical isomers were differentiated and characterized by melting points and by chemical microcrystalline tests. Using hot stage thermomicroscopy, the eutectic melting points of binary isomeric mixtures of propoxyphene bases and salts were found to be depressed about 10° and 15-30°C, respectively, below the individual isomer melting points. The characteristic microcrystals formed with the alpha racemic mixtures by using a glycerin-aqueous gold chloride reagent were not produced by the beta racemic mixtures.

scholarly journals Does higher education properly prepare graduates for the growing artificial intelligence market? Gaps identification using text mining

2021 ◽  
pp. 1-13
Author(s):  
Lamiae Benhayoun ◽  
Daniel Lang
Keyword(s):  
Artificial Intelligence ◽  
Natural Language Processing ◽  
Text Mining ◽  
Natural Language ◽  
Language Processing ◽  
Academic Training ◽  
Market Requirements ◽  
Job Advertisements ◽  
The Individual

BACKGROUND: The renewed advent of Artificial Intelligence (AI) is inducing profound changes in the classic categories of technology professions and is creating the need for new specific skills. OBJECTIVE: Identify the gaps in terms of skills between academic training on AI in French engineering and Business Schools, and the requirements of the labour market. METHOD: Extraction of AI training contents from the schools’ websites and scraping of a job advertisements’ website. Then, analysis based on a text mining approach with a Python code for Natural Language Processing. RESULTS: Categorization of occupations related to AI. Characterization of three classes of skills for the AI market: Technical, Soft and Interdisciplinary. Skills’ gaps concern some professional certifications and the mastery of specific tools, research abilities, and awareness of ethical and regulatory dimensions of AI. CONCLUSIONS: A deep analysis using algorithms for Natural Language Processing. Results that provide a better understanding of the AI capability components at the individual and the organizational levels. A study that can help shape educational programs to respond to the AI market requirements.

scholarly journals Adsorption Studies on Magnetic Nanoparticles Functionalized with Silver to Remove Nitrates from Waters

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1757
Author(s):  
Yesica Vicente-Martínez ◽  
Manuel Caravaca ◽  
Antonio Soto-Meca ◽  
Miguel Ángel Martín-Pereira ◽  
María del Carmen García-Onsurbe
Keyword(s):  
Magnetic Nanoparticles ◽  
Nitrate Content ◽  
Adsorption Efficiency ◽  
Experimental Conditions ◽  
Dependent Behavior ◽  
Before And After ◽  
Naoh Solution ◽  
High Concentrations ◽  
Interference Studies

This paper presents a novel procedure for the treatment of contaminated water with high concentrations of nitrates, which are considered as one of the main causes of the eutrophication phenomena. For this purpose, magnetic nanoparticles functionalized with silver (Fe3O4@AgNPs) were synthesized and used as an adsorbent of nitrates. Experimental conditions, including the pH, adsorbent and adsorbate dose, temperature and contact time, were analyzed to obtain the highest adsorption efficiency for different concentration of nitrates in water. A maximum removal efficiency of 100% was reached for 2, 5, 10 and 50 mg/L of nitrate at pH = 5, room temperature, and 50, 100, 250 and 500 µL of Fe3O4@AgNPs, respectively. The characterization of the adsorbent, before and after adsorption, was performed by energy dispersive X-ray spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller analysis and Fourier-transform infrared spectroscopy. Nitrates can be desorbed, and the adsorbent can be reused using 500 µL of NaOH solution 0.01 M, remaining unchanged for the first three cycles, and exhibiting 90% adsorption efficiency after three regenerations. A deep study on equilibrium isotherms reveals a pH-dependent behavior, characterized by Langmuir and Freundlich models at pH = 5 and pH = 1, respectively. Thermodynamic studies were consistent with physicochemical adsorption for all experiments but showed a change from endothermic to exothermic behavior as the temperature increases. Interference studies of other ions commonly present in water were carried out, enabling this procedure as very selective for nitrate ions. In addition, the method was applied to real samples of seawater, showing its ability to eliminate the total nitrate content in eutrophized waters.

scholarly journals Material Geometry of Binary Composites

Symmetry ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 892
Author(s):  
Marcelo Epstein
Keyword(s):  
Continuum Mechanics ◽  
Mathematical Framework ◽  
Double Groupoid ◽  
The Individual ◽  
Elastic Composites

The constitutive characterization of the uniformity and homogeneity of binary elastic composites is presented in terms of a combination of the material groupoids of the individual constituents. The incorporation of these two groupoids within a single double groupoid is proposed as a viable mathematical framework for a unified formulation of this and similar kinds of problems in continuum mechanics.

scholarly journals Preclinical Testing of Radiopharmaceuticals for the Detection and Characterization of Osteomyelitis: Experiences from a Porcine Model

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4221
Author(s):  
Aage Kristian Olsen Alstrup ◽  
Svend Borup Jensen ◽  
Ole Lerberg Nielsen ◽  
Lars Jødal ◽  
Pia Afzelius
Keyword(s):  
Animal Model ◽  
Animal Models ◽  
Porcine Model ◽  
Animal Experiments ◽  
Radioactive Tracers ◽  
The Individual ◽  
Selection Of

The development of new and better radioactive tracers capable of detecting and characterizing osteomyelitis is an ongoing process, mainly because available tracers lack selectivity towards osteomyelitis. An integrated part of developing new tracers is the performance of in vivo tests using appropriate animal models. The available animal models for osteomyelitis are also far from ideal. Therefore, developing improved animal osteomyelitis models is as important as developing new radioactive tracers. We recently published a review on radioactive tracers. In this review, we only present and discuss osteomyelitis models. Three ethical aspects (3R) are essential when exposing experimental animals to infections. Thus, we should perform experiments in vitro rather than in vivo (Replacement), use as few animals as possible (Reduction), and impose as little pain on the animal as possible (Refinement). The gain for humans should by far exceed the disadvantages for the individual experimental animal. To this end, the translational value of animal experiments is crucial. We therefore need a robust and well-characterized animal model to evaluate new osteomyelitis tracers to be sure that unpredicted variation in the animal model does not lead to a misinterpretation of the tracer behavior. In this review, we focus on how the development of radioactive tracers relies heavily on the selection of a reliable animal model, and we base the discussions on our own experience with a porcine model.

scholarly journals Halogenated Volatile Organic Compounds in Water Samples and Inorganic Elements Levels in Ores for Characterizing a High Anthropogenic Polluted Area in the Northern Latium Region (Italy)

2021 ◽  
Vol 18 (4) ◽  
pp. 1628
Author(s):  
Mario Vincenzo Russo ◽  
Ivan Notardonato ◽  
Alberto Rosada ◽  
Giuseppe Ianiri ◽  
Pasquale Avino
Keyword(s):  
Organic Compounds ◽  
Mean Value ◽  
Greenhouse Crops ◽  
River Waters ◽  
Liquid Liquid Extraction ◽  
Volatile Organic ◽  
High Concentrations ◽  
Very High ◽  
Inorganic Fraction

This paper shows a characterization of the organic and inorganic fraction of river waters (Tiber and Marta) and ores/soil samples collected in the Northern Latium region of Italy for evaluating the anthropogenic/natural source contribution to the environmental pollution of this area. For organic compounds, organochloride volatile compounds in Tiber and Marta rivers were analyzed by two different clean-up methods (i.e., liquid–liquid extraction and static headspace) followed by gas chromatography–electron capture detector (GC-ECD) analysis. The results show very high concentrations of bromoform (up to 1.82 and 3.2 µg L−1 in Tiber and Marta rivers, respectively), due to the presence of greenhouse crops, and of chloroform and tetrachloroethene, due to the presence of handicrafts installations. For the qualitative and quantitative assessment of the inorganic fraction, it is highlighted the use of a nuclear analytical method, instrumental neutron activation analysis, which allows having more information as possible from the sample without performing any chemical-physical pretreatment. The results have evidenced high levels of mercury (mean value 88.6 µg g−1), antimony (77.7 µg g−1), strontium (12,039 µg g−1) and zinc (103 µg g−1), whereas rare earth elements show levels similar to the literature data. Particular consideration is drawn for arsenic (414 µg g−1): the levels found in this paper (ranging between 1 and 5100 µg g−1) explain the high content of such element (as arsenates) in the aquifer, a big issue in this area.

scholarly journals Effects of face masks on performance and cardiorespiratory response in well-trained athletes

2021 ◽  
Author(s):  
Florian Egger ◽  
Dominic Blumenauer ◽  
Patrick Fischer ◽  
Andreas Venhorst ◽  
Saarraaken Kulenthiran ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Minute Ventilation ◽  
Anaerobic Exercise ◽  
Peak Oxygen Consumption ◽  
Exercise Tests ◽  
Maximum Performance ◽  
Outdoor Sports ◽  
Cardiorespiratory Response ◽  
Individual Anaerobic Threshold ◽  
The Individual

Abstract Background During the COVID-19 pandemic, compulsory masks became an integral part of outdoor sports such as jogging in crowded areas (e.g. city parks) as well as indoor sports in gyms and sports centers. This study, therefore, aimed to investigate the effects of medical face masks on performance and cardiorespiratory parameters in athletes. Methods In a randomized, cross-over design, 16 well-trained athletes (age 27 ± 7 years, peak oxygen consumption 56.2 ± 5.6 ml kg−1 min−1, maximum performance 5.1 ± 0.5 Watt kg−1) underwent three stepwise incremental exercise tests to exhaustion without mask (NM), with surgical mask (SM) and FFP2 mask (FFP2). Cardiorespiratory and metabolic responses were monitored by spiroergometry and blood lactate (BLa) testing throughout the tests. Results There was a large effect of masks on performance with a significant reduction of maximum performance with SM (355 ± 41 Watt) and FFP2 (364 ± 43 Watt) compared to NM (377 ± 40 Watt), respectively (p < 0.001; ηp2 = 0.50). A large interaction effect with a reduction of both oxygen consumption (p < 0.001; ηp2 = 0.34) and minute ventilation (p < 0.001; ηp2 = 0.39) was observed. At the termination of the test with SM 11 of 16 subjects reported acute dyspnea from the suction of the wet and deformed mask. No difference in performance was observed at the individual anaerobic threshold (p = 0.90). Conclusion Both SM and to a lesser extent FFP2 were associated with reduced maximum performance, minute ventilation, and oxygen consumption. For strenuous anaerobic exercise, an FFP2 mask may be preferred over an SM.

Sign in / Sign up

Export Citation Format

Share Document