scholarly journals Effect of the Exchanged Cation in an Algerian Montmorillonite Used as a Heterogeneous Catalyst for Biginelli Reaction

2021 ◽  
Vol 68 (2) ◽  
pp. 355-362
Author(s):  
Fatiha Belferdi ◽  
Farida Bouremmad ◽  
Shalima Shawuti ◽  
Mehmet Ali Gulgun
Keyword(s):  
Heterogeneous Catalyst ◽  
Catalytic Properties ◽  
Biginelli Reaction ◽  
Reaction Medium ◽  
Exchange Capacity ◽  
Basal Spacing ◽  
Exchange Operation ◽  
Kinetics Of

In this work, an Algerian montmorillonite (Mt) is exchanged by different cations from the transition metals family, namely: Cu2+, Ni2+, Cr3+, Co2+, Fe2+ and Fe3+, it is used as a heterogeneous catalyst for Biginelli reaction. The exchanged cations are known for their catalytic properties in homogeneous catalysis. The main purpose is to study the effect of the exchanged cations on the yield and the kinetics of the reaction. The characterization of montmorillonite was carried out by XRD, which allows us to follow the evolution of the basal spacing d001 as a function of the exchanged cation and to show that the exchange operation has not altered the montmorillonite structure. The cation exchange capacity (CEC) is determined by the titration of the exchanged cation by atomic absorption. The product of the reaction is characterized by NMR, IR and by the determination of the melting point. In addition, the importance of the introduction order of the reagents into the reaction medium has been demonstrated on the yield and the kinetics. Finally, the obtained results show that the exchanged montmorillonite is competitive with other costly heterogeneous and homogeneous catalysts.

scholarly journals KD determination from time-resolved experiments on live cells with LigandTracer and reconciliation with end-point flow cytometry measurements

2021 ◽  
Author(s):  
Diana Spiegelberg ◽  
Jonas Stenberg ◽  
Pascale Richalet ◽  
Marc Vanhove
Keyword(s):  
Flow Cytometry ◽  
Live Cells ◽  
Time Resolved ◽  
Surface Receptors ◽  
Full Characterization ◽  
End Point ◽  
Titration Curves ◽  
Kinetics Of

AbstractDesign of next-generation therapeutics comes with new challenges and emulates technology and methods to meet them. Characterizing the binding of either natural ligands or therapeutic proteins to cell-surface receptors, for which relevant recombinant versions may not exist, represents one of these challenges. Here we report the characterization of the interaction of five different antibody therapeutics (Trastuzumab, Rituximab, Panitumumab, Pertuzumab, and Cetuximab) with their cognate target receptors using LigandTracer. The method offers the advantage of being performed on live cells, alleviating the need for a recombinant source of the receptor. Furthermore, time-resolved measurements, in addition to allowing the determination of the affinity of the studied drug to its target, give access to the binding kinetics thereby providing a full characterization of the system. In this study, we also compared time-resolved LigandTracer data with end-point KD determination from flow cytometry experiments and hypothesize that discrepancies between these two approaches, when they exist, generally come from flow cytometry titration curves being acquired prior to full equilibration of the system. Our data, however, show that knowledge of the kinetics of the interaction allows to reconcile the data obtained by flow cytometry and LigandTracer and demonstrate the complementarity of these two methods.

The synthesis and characterization of Zn(ii)/Cd(ii) based MOFs by a mixed ligand strategy: a Zn(ii) MOF as a dual functional material for reversible dye adsorption and as a heterogeneous catalyst for the Biginelli reaction

2021 ◽  
Vol 5 (1) ◽  
pp. 304-314
Author(s):  
Unnati Patel ◽  
Bhavesh Parmar ◽  
Parth Patel ◽  
Abhishek Dadhania ◽  
Eringathodi Suresh
Keyword(s):  
Heterogeneous Catalyst ◽  
Biginelli Reaction ◽  
Dye Adsorption ◽  
Mixed Ligand ◽  
Synthesis And Characterization ◽  
Functional Material ◽  
Dual Functional ◽  
Mixed Ligands ◽  
Efficient Heterogeneous Catalyst

2D Zn(ii)/Cd(ii) based MOF involving mixed ligands have been synthesized. Zn(ii) based MOF has been utilized as a bifunctional material towards reversible dye adsorption and as an efficient heterogeneous catalyst in Biginelli reaction.

scholarly journals Kinetic and substrate complex characterization of RamA, a corrinoid protein reductive activase from Methanosarcina barkeri

2020 ◽  
Vol 367 (17) ◽  
Author(s):  
Katherine A Huening ◽  
Ruisheng Jiang ◽  
Joseph A Krzycki
Keyword(s):  
Direct Evidence ◽  
Atp Hydrolysis ◽  
Methanogenic Archaea ◽  
Methanosarcina Barkeri ◽  
Serine Residue ◽  
Substrate Complex ◽  
Apparent Kinetic Parameters ◽  
Kinetics Of

ABSTRACT In microbial corrinoid-dependent methyltransferase systems, adventitious Co(I)-corrinoid oxidation halts catalysis and necessitates repair by ATP-dependent reductive activases. RamA, an activase with a C-terminal ferredoxin domain with two [4Fe-4S] clusters from methanogenic archaea, has been far less studied than the bacterial activases bearing an N-terminal ferredoxin domain with one [2Fe-2S] cluster. These differences suggest RamA might prove to have other distinctive characteristics. Here, we examine RamA kinetics and the stoichiometry of the corrinoid protein:RamA complex. Like bacterial activases, K+ stimulates RamA. Potassium stimulation had been questioned due to differences in the primary structure of bacterial and methanogen activases. Unlike one bacterial activase, ATP is not inhibitory allowing the first determination of apparent kinetic parameters for any corrinoid activase. Unlike bacterial activases, a single RamA monomer complexes a single corrinoid protein monomer. Alanine replacement of a RamA serine residue corresponding to the serine of one bacterial activase which ligates the corrinoid cobalt during complex formation led to only moderate changes in the kinetics of RamA. These results reveal new differences in the two types of corrinoid activases, and provide direct evidence for the proposal that corrinoid activases act as catalytic monomers, unlike other enzymes that couple ATP hydrolysis to difficult reductions.

scholarly journals Characterization of the CYP3A4 Enzyme Inhibition Potential of Selected Flavonoids

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 3018
Author(s):  
Martin Kondža ◽  
Mirza Bojić ◽  
Ivona Tomić ◽  
Željan Maleš ◽  
Valentina Rezić ◽  
...  
Keyword(s):  
Covalent Binding ◽  
Inhibitory Effect ◽  
Residual Concentration ◽  
Flavonoid Aglycones ◽  
Irreversible Inhibitors ◽  
Cyp3a4 Enzyme ◽  
Kinetics Of ◽  
Kinetics Of Inhibition

Acacetin, apigenin, chrysin, and pinocembrin are flavonoid aglycones found in foods such as parsley, honey, celery, and chamomile tea. Flavonoids can act as substrates and inhibitors of the CYP3A4 enzyme, a heme containing enzyme responsible for the metabolism of one third of drugs on the market. The aim of this study was to investigate the inhibitory effect of selected flavonoids on the CYP3A4 enzyme, the kinetics of inhibition, the possible covalent binding of the inhibitor to the enzyme, and whether flavonoids can act as pseudo-irreversible inhibitors. For the determination of inhibition kinetics, nifedipine oxidation was used as a marker reaction. A hemochromopyridine test was used to assess the possible covalent binding to the heme, and incubation with dialysis was used in order to assess the reversibility of the inhibition. All the tested flavonoids inhibited the CYP3A4 enzyme activity. Chrysin was the most potent inhibitor: IC50 = 2.5 ± 0.6 µM, Ki = 2.4 ± 1.0 µM, kinact = 0.07 ± 0.01 min−1, kinact/Ki = 0.03 min−1 µM−1. Chrysin caused the highest reduction of heme (94.5 ± 0.5% residual concentration). None of the tested flavonoids showed pseudo-irreversible inhibition. Although the inactivation of the CYP3A4 enzyme is caused by interaction with heme, inhibitor-heme adducts could not be trapped. These results indicate that flavonoids have the potential to inhibit the CYP3A4 enzyme and interact with other drugs and medications. However, possible food–drug interactions have to be assessed clinically.

scholarly journals Adsorption of uranyl ion on acid-modified zeolitic mineral clinoptilolite

2009 ◽  
Vol 63 (5) ◽  
pp. 407-414 ◽  
Author(s):  
Srdjan Matijasevic ◽  
Aleksandra Dakovic ◽  
Deana Iles ◽  
Sonja Milicevic
Keyword(s):  
Solid Phase ◽  
Exchange Capacity ◽  
Uranyl Ion ◽  
Ion Adsorption ◽  
Fluorometric Method ◽  
Kinetics Of Adsorption ◽  
Ph Values ◽  
Modified Clinoptilolite ◽  
Kinetics Of

In this paper, the results of adsorption of uranyl ion on acid-modified zeolitic mineral clinoptilolite are presented. Adsorption was investigated at different amounts of solid phase in suspension, as well as at different pH values. The modified clinoptilolite samples were obtained by treatment of clinoptilolite with acids: hydrochloric, oxalyc and citric. Starting and modified clinoptilolites were characterized by chemical analysis, thermal (DT/TG) analysis and by determination of cation exchange capacity, while starting and nonadsorbed amounts of uranyl ion were determined by fluorometric method. Uranyl ion adsorption experiments on natural unmodified zeolitic mineral showed that uranyl ion adsorption was low (29.2%) and that treatment of clinoptilolite with acids significantly increases the adsorption of uranyl ion (>90%). In the case of acid treated clinoptilolites, the highest adsorption of uranyl ion was achieved on clinoptilolite modified with hydrochloric acid. Kinetics of adsorption showed that adsorption of uranyl ion begins very fast and that the most of uranyl ion was adsorbed in first 30 min. Practically, there were no changes in uranyl ion adsorption within next 72 h.

scholarly journals INTERCALATION OF OLYGOMER OF HYDROXYL-CHROMIUM INTO NATURAL KAOLINITE

2010 ◽  
Vol 8 (1) ◽  
pp. 31-36
Author(s):  
Rodiansono Rodiansono ◽  
Reda Ariyantie ◽  
Abdullah Abdullah
Keyword(s):  
Surface Area ◽  
Pore Radius ◽  
Nitrate Solution ◽  
Chemical Properties ◽  
Basal Spacing ◽  
Physico Chemical ◽  
Ft Ir ◽  
N2 Sorption

Preparation of a kaolin-hydroxyl chromium composite and characterization of its physico-chemical properties were conducted. The olygomer hydroxyl-chromium was prepared by adding Na2CO3 to 0.1 M chromium nitrate solution (ratio OH/Cr = 2) and then dried at 110 oC and 400 oC for 4 h. Characterization of kaolin-hydroxyl chromium composite includes determination of acidity, functional groups, basal spacing, and surface area (BET-N2 sorption analyzer). The result showed that intercalation of hydroxyl chromium resulted in the decreasing of basal spacing but increased the specific surface area of kaolin. Drying of the intercalated kaolin at 400 oC decreased surface area, total volume pore and pore radius. FT-IR spectra showed that hydroxyl-chromium detected at wavelength of 2925 and 2855 cm-1.   Keywords: natural kaolin, intercalation, olygomer hydroxyl-chromium, kaolin-hydroxyl chromium composite

scholarly journals Glycoscience@Synchrotron: Synchrotron radiation applied to structural glycoscience

2017 ◽  
Vol 13 ◽  
pp. 1145-1167 ◽  
Author(s):  
Serge Pérez ◽  
Daniele de Sanctis
Keyword(s):  
Synchrotron Radiation ◽  
Structural Characterization ◽  
Crystalline State ◽  
Structural Diversity ◽  
Interacting Proteins ◽  
X Ray ◽  
Wide Range ◽  
Kinetics Of

Synchrotron radiation is the most versatile way to explore biological materials in different states: monocrystalline, polycrystalline, solution, colloids and multiscale architectures. Steady improvements in instrumentation have made synchrotrons the most flexible intense X-ray source. The wide range of applications of synchrotron radiation is commensurate with the structural diversity and complexity of the molecules and macromolecules that form the collection of substrates investigated by glycoscience. The present review illustrates how synchrotron-based experiments have contributed to our understanding in the field of structural glycobiology. Structural characterization of protein–carbohydrate interactions of the families of most glycan-interacting proteins (including glycosyl transferases and hydrolases, lectins, antibodies and GAG-binding proteins) are presented. Examples concerned with glycolipids and colloids are also covered as well as some dealing with the structures and multiscale architectures of polysaccharides. Insights into the kinetics of catalytic events observed in the crystalline state are also presented as well as some aspects of structure determination of protein in solution.

scholarly journals Characterization of Biochar Produced from Different Feed Stocks

2020 ◽  
pp. 1-6
Author(s):  
Dereje Dejene ◽  
Eyob Tilahun
Keyword(s):  
Greenhouse Gas Emission ◽  
Ph Value ◽  
Chemical Properties ◽  
Organic Soil ◽  
Exchange Capacity ◽  
Agricultural Wastes ◽  
Exchangeable Magnesium ◽  
Ph Level

Imprudently disposed and burning of organic wastes have been causing environmental pollution and greenhouse gas emission. The objective of this study was to characterize the biochar produced from different agricultural wastes to explore its potential use as organic soil amendments. The feedstock derived from each of Eucalyptus globules (EG), Acacia decarance (AD), farm yard manure (FYM) and rice straw (RS) were collected and biochar was produced by slow pyrolysis at 300oC in the furnace. The determination of pH, carbon, phosphorus, cation exchange capacity, electrical conductivity and exchangeable basic cations of individual biochar was performed and statistical analyses carried out to compare the means values obtained. Higher carbon content was observed in biochar produced from AD (65.00%) compared with that of biochar produced from other feedstock types included in this study. pH value of Bbiochar produced from EG and RS were moderately acidic (pH 5.94) and neutral (pH 6.6), respectively, whereas biochar produced from AD (pH 8.07 and FYM (pH 8.17) revealed moderately alkaline pH level. High and low EC values were recorded in biochar produced from FYM (4.70 DS m-1) and the low value from EG (0.68 DS m-1), respectively. The maximum concentration of exchangeable magnesium (20.95%), potassium (16.40%) and sodium (1.77%), EC and phosphorous (2288.75 ppm) were testimony in biochar produced from FYM is potential to prove phosphorus fertilizer requirement of a crop but calcium (39.50%) was from biochar produced from AD. Higher CEC (129.75 cmolc kg-1) was detected in biochar produced from EG followed by biochar produced from RS (127.5 cmolc kg-1), AD (117 cmolc kg-1) and FYM (87.25 cmolc kg-1). Generally, the current finding revealed that biochar from different feedstock’s had different chemical properties, so this difference could contribute for soil fertility improvement as the result agricultural wastes is managed without pollution. But, the current work was limited to the characterization of biochar. So, more detailed investigation on the rate and reclaiming the power of the biochar and other issues should be investigated.

Irradiation behavior of pyrolytic silicon carbide

1983 ◽  
Vol 41 ◽  
pp. 72-73
Author(s):  
R. J. Lauf
Keyword(s):  
Silicon Carbide ◽  
Fission Products ◽  
Thermodynamics And Kinetics ◽  
Neutron Fluences ◽  
Fuel Particles ◽  
Sic Coatings ◽  
Irradiation Behavior ◽  
Kinetics Of ◽  
Htgr Fuel

Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain a layer of pyrolytic silicon carbide to act as a miniature pressure vessel and primary fission product barrier. Optimization of the SiC with respect to fuel performance involves four areas of study: (a) characterization of as-deposited SiC coatings; (b) thermodynamics and kinetics of chemical reactions between SiC and fission products; (c) irradiation behavior of SiC in the absence of fission products; and (d) combined effects of irradiation and fission products. This paper reports the behavior of SiC deposited on inert microspheres and irradiated to fast neutron fluences typical of HTGR fuel at end-of-life.

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