Synthesis, Characterization and Catalytic Properties of the Novel Manganese-Containing Amorphous Mesoporous Material MnTUD-1

2008 ◽  
Vol 112 (19) ◽  
pp. 7468-7476 ◽  
Author(s):  
Anand Ramanathan ◽  
Tanja Archipov ◽  
Rajamanickam Maheswari ◽  
Ulf Hanefeld ◽  
Emil Roduner ◽  
...  
Keyword(s):  
Mesoporous Material ◽  
Catalytic Properties ◽  
The Novel

A monovacant heteropolytungstate-incorporated trimeric carbonyl rhenium cluster, [(AsW11O39){Re(CO)3}3(μ3-OH)(μ2-OH)]6−: synthesis, structure and catalytic properties

RSC Advances ◽  
2014 ◽  
Vol 4 (55) ◽  
pp. 28848-28851 ◽  
Author(s):  
Yanhui Zhang ◽  
Dongdi Zhang ◽  
Zhiyuan Huo ◽  
Pengtao Ma ◽  
Jingyang Niu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
High Selectivity ◽  
Catalytic Properties ◽  
The Novel ◽  
Rhenium Cluster

The novel undecatungstoarsenate-supported carbonyl rhenium derivative exhibits prominent catalytic activity and high selectivity in the cycloaddition of epoxides.

Synthesis of Surfactant-Assisted C/Fe–FeVO4 Nanostructure: Characterization and Photocatalytic Degradation of Ciprofloxacin

2020 ◽  
Vol 20 (9) ◽  
pp. 5636-5641
Author(s):  
Shi-Jie Chen ◽  
Guang-Shan Zhang ◽  
Ying-Jie Li ◽  
Jin-Long Li ◽  
Ren-Jiang Lv ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Hydrothermal Synthesis ◽  
Catalytic Properties ◽  
Synthesis Method ◽  
Analytical Techniques ◽  
The Novel ◽  
Composite Photocatalyst ◽  
Porosity Structure ◽  
Simulated Solar Light ◽  
Surfactant Assisted

The novel C/Fe–FeVO4 composite photocatalyst were synthesized by using a two-step hydrothermal synthesis method. Through a detailed exploration on the chemical and phisical properties by some spectroscopic and analytical techniques, the as-prepared C/Fe–FeVO4 exhibted a nanosheet and meso porosity structure. Accordingly, we further utilized this C/Fe–FeVO4 composite as a photocatalist for degradating the notorious ciprofloxacin (CIP) under simulated solar light (SSL) irradiation. Due to its outstanding catalytic properties, the C/Fe–FeVO4 exhibited superior photocatalytic activity. The possible photocatalytic mechanism has been discussed.

scholarly journals CO oxidization catalyzed by B, N, and their co-doped fullerenes: a first-principles investigation

RSC Advances ◽  
2019 ◽  
Vol 9 (38) ◽  
pp. 21626-21636 ◽  
Author(s):  
Boya Gao ◽  
Gang Chen
Keyword(s):  
First Principles ◽  
Catalytic Properties ◽  
The Novel ◽  
Doped Fullerenes ◽  
Co Doped

The novel catalytic properties of the oxides of B and N, and their co-doped fullerenes are investigated.

Catalytic properties of the Gas family β-(1,3)-glucanosyltransferases active in fungal cell-wall biogenesis as determined by a novel fluorescent assay

2011 ◽  
Vol 438 (2) ◽  
pp. 275-282 ◽  
Author(s):  
Marián Mazáň ◽  
Enrico Ragni ◽  
Laura Popolo ◽  
Vladimír Farkaš
Keyword(s):  
Cell Walls ◽  
Biochemical Characterization ◽  
Catalytic Properties ◽  
Degree Of Polymerization ◽  
The Novel ◽  
Fluorescent Assay ◽  
Fungal Cell ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cell Wall Biogenesis

BGTs [β-(1,3)-glucanosyltransglycosylases; EC 2.4.1.-] of the GH72 (family 72 of glycosylhydrolases) are GPI (glycosylphosphatidylinositol)-anchored proteins that play an important role in the biogenesis of fungal cell walls. They randomly cleave glycosidic linkages in β-(1,3)-glucan chains and ligate the polysaccharide portions containing newly formed reducing ends to C3(OH) at non-reducing ends of other β-(1,3)-glucan molecules. We have developed a sensitive fluorescence-based method for the assay of transglycosylating activity of GH72 enzymes. In the new assay, laminarin [β-(1,3)-glucan] is used as the glucanosyl donor and LamOS (laminarioligosaccharides) fluorescently labelled with SR (sulforhodamine) serve as the acceptors. The new fluorescent assay was employed for partial biochemical characterization of the heterologously expressed Gas family proteins from the yeast Saccharomyces cerevisiae. All the Gas enzymes specifically used laminarin as the glucanosyl donor and a SR–LamOS of DP (degree of polymerization) ≥5 as the acceptors. Gas proteins expressed in distinct stages of the yeast life cycle showed differences in their pH optima. Gas1p and Gas5p, which are expressed during vegetative growth, had the highest activity at pH 4.5 and 3.5 respectively, whereas the sporulation-specific Gas2p and Gas4p were most active between pH 5 and 6. The novel fluorescent assay provides a suitable tool for the screening of potential glucanosyltransferases or their inhibitors.

scholarly journals Low Dimensional Carbon-Based Catalysts for Efficient Photocatalytic and Photo/Electrochemical Water Splitting Reactions

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 114 ◽  
Author(s):  
Yoongu Lim ◽  
Dong-Kyu Lee ◽  
Seong Min Kim ◽  
Woosung Park ◽  
Sung Yong Cho ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Water Splitting ◽  
Carbon Materials ◽  
Catalytic Properties ◽  
Energy Sources ◽  
Electrochemical Reactions ◽  
The Novel ◽  
Excellent Performance ◽  
Low Dimensional ◽  
Carbon Based

A universal increase in energy consumption and the dependency on fossil fuels have resulted in increasing severity of global warming, thus necessitating the search of new and environment-friendly energy sources. Hydrogen is as one of the energy sources that can resolve the abovementioned problems. Water splitting promotes ecofriendly hydrogen production without the formation of any greenhouse gas. The most common process for hydrogen production is electrolysis, wherein water molecules are separated into hydrogen and oxygen through electrochemical reactions. Solar-energy-induced chemical reactions, including photocatalysis and photoelectrochemistry, have gained considerable attention because of the simplicity of their procedures and use of solar radiation as the energy source. To improve performance of water splitting reactions, the use of catalysts has been widely investigated. For example, the novel-metal catalysts possessing extremely high catalytic properties for various reactions have been considered. However, due to the rarity and high costs of the novel-metal materials, the catalysts were considered unsuitable for universal use. Although other transition-metal-based materials have also been investigated, carbon-based materials, which are obtained from one of the most common elements on Earth, have potential as low-cost, nontoxic, high-performance catalysts for both photo and electrochemical reactions. Because abundancy, simplicity of synthesis routes, and excellent performance are the important factors for catalysts, easy optimization and many variations are possible in carbon-materials, making them more attractive. In particular, low-dimensional carbon materials, such as graphene and graphitic carbon nitride, exhibit excellent performance because of their unique electrical, mechanical, and catalytic properties. In this mini-review, we will discuss the performance of low-dimensional carbon-based materials for water splitting reactions.

scholarly journals PEG-chitosan branched copolymers to improve the biocatalytic properties of erwinia carotovora recombinant L-asparaginase

2015 ◽  
Vol 61 (4) ◽  
pp. 480-487 ◽  
Author(s):  
E.V. Kudryashova ◽  
K.V. Suhoverkov ◽  
N.N. Sokolov
Keyword(s):  
Catalytic Properties ◽  
Catalytic Efficiency ◽  
Erwinia Carotovora ◽  
Antitumor Agent ◽  
Amide Bond ◽  
The Novel ◽  
Amino Groups ◽  
Characteristic Absorption Band ◽  
New Approach ◽  
Pharmacokinetic Properties

A new approach to the regulation of catalytic properties of medically relevant enzymes has been proposed using the novel recombinant preparation of L-asparaginase from Erwinia carotovora (EwA), a promising antitumor agent. New branched co-polymers of different composition based on chitosan modified with polyethylene glycol (PEG) molecules, designated as PEG-chitosan, have been synthesized. PEG-chitosan copolymers were further conjugated with EwA. In order to optimize the catalytic properties of asparaginase two types of conjugates differing in their architecture have been synthesized: (1) crown-type conjugates were synthesized by reductive amination reaction between the reducing end of the PEG-chitosan copolymer and enzyme amino groups; (2) multipoint-conjugates were synthesized using the reaction of multipoint amide bond formation between PEG-chitosan amino groups and carboxyl groups of the enzyme in the presence of the Woodward’s reagent. The structure and composition of these conjugates were determined by IR spectroscopy. The content of the copolymers in the conjugates was controlled by the characteristic absorption band of C-O-C bonds in the PEG structure at the frequency of 1089 cm-1. The study of catalytic characteristics of EwA preparations by conductometry showed that at physiological pH values the enzyme conjugates with PEG-chitosan with optimized structure and the optimal composition demonstrated 5-8-fold higher catalytic efficiency (kcat/Km) than the native enzyme. To certain extent, this can be attributed to favorable shift of pH-optima in result of positively charged amino-groups introduction in the vicinity of the active site. The proposed approach, chito-pegylation, is effective for regulating the catalytic and pharmacokinetic properties of asparaginase, and is promising for the development of prolonged action dosage forms for other enzyme therapeutics

MUTANTS OF TPA AND THEIR CATALYTIC PROPERTIES

1987 ◽  
Author(s):  
B Chaudhuri ◽  
J Heim ◽  
B Meyhack ◽  
J van Oostrum
Keyword(s):  
Catalytic Properties ◽  
Clot Lysis ◽  
In Vitro Mutagenesis ◽  
The Novel ◽  
Single Chain ◽  
Mutant Proteins ◽  
Novel Proteins ◽  
Lysis Activity ◽  
Insight Into

Mutants of tPA were obtained by in vitro mutagenesis to study the effects of N-linked glycosylation, and to gain insight into the properties of pure single-chain tPA. The glycosylation mutants were obtained by modification of the last residue of the sequence Asn.X.Ser/Thr, . known to be specific for N-linked glycosylation, whereas the plasmin sensitive sequence Arg275 Ile276 was modified to Asp 275 Ile276 to obtain a plasmin insensitive tPA. Mutant proteins were expressed in yeast under the control of the repressible acid-phosphatase promoter, and in CHO-cells. The novel proteins were isolated mainly by affinity chromatography using the selective protease inhibitor DE-3. A tPA mutant containing a modification in the sequence Asnl84 Glyl85 Ser 186 showed similar results as compared to recombinant yeast tPA in the clot lysis test, a direct fluoresence assay (FU test), and the indirect double rate assay according to Verheyen (Verheyen test). A mutant with modifications in the sequences Asnll7 Ser 118 Serll9, Asnl84 Glyl85 Serl86, and Asn448 Arg449 Thr450, showed an increased clot lysis activity with no increase in activity in the FU test and Verheyen test. However, the stimulation by fibrinogen fragments in the Verheyen assay was found to be doubled as compared to yeast tPA. An even further increase in stimulation by fibrinogen fragments, upto 500% over yeast tPA, was observed with the plasmin insensitive tPA, although this mutant only showed 20% of the yeast tPA activity in the FU and Verheyen tests

scholarly journals Controlling the regioselectivity and stereospecificity of FAD-dependent polyamine oxidases with the use of amine-attached guide molecules as conformational modulators

2018 ◽  
Vol 38 (4) ◽  
Author(s):  
Tuomo A. Keinänen ◽  
Nikolay Grigorenko ◽  
Alex R. Khomutov ◽  
Qingqiu Huang ◽  
Anne Uimari ◽  
...  
Keyword(s):  
Catalytic Properties ◽  
Isonicotinic Acid ◽  
The Novel ◽  
Fundamental Properties ◽  
Competitive Inhibitors ◽  
Substrate Mixtures ◽  
Derivatives Of ◽  
Acetylpolyamine Oxidase ◽  
Acyl Derivatives ◽  
Polyamine Oxidases

Enzymes generally display strict stereospecificity and regioselectivity for their substrates. Here by using FAD-dependent human acetylpolyamine oxidase (APAO), human spermine (Spm) oxidase (SMOX) and yeast polyamine oxidase (Fms1), we demonstrate that these fundamental properties of the enzymes may be regulated using simple guide molecules, being either covalently attached to polyamines or used as a supplement to the substrate mixtures. APAO, which naturally metabolizes achiral N1-acetylated polyamines, displays aldehyde-controllable stereospecificity with chiral 1-methylated polyamines, like (R)- and (S)-1-methylspermidine (1,8-diamino-5-azanonane) (1-MeSpd). Among the novel N1-acyl derivatives of MeSpd, isonicotinic acid (P4) or benzoic acid (Bz) with (R)-MeSpd had Km of 3.6 ± 0.6/1.2 ± 0.7 µM and kcat of 5.2 ± 0.6/4.6 ± 0.7 s−1 respectively, while N1-AcSpd had Km 8.2 ± 0.4 µM and kcat 2.7 ± 0.0 s−1. On the contrary, corresponding (S)-MeSpd amides were practically inactive (kcat < 0.03 s−1) but they retained micromole level Km for APAO. SMOX did not metabolize any of the tested compounds (kcat < 0.05 s−1) that acted as non-competitive inhibitors having Ki ≥ 155 µM for SMOX. In addition, we tested (R,R)-1,12-bis-methylspermine (2,13-diamino-5,10-diazatetradecane) (R,R)-(Me2Spm) and (S,S)-Me2Spm as substrates for Fms1. Fms1 preferred (S,S)- to (R,R)-diastereoisomer, but with notably lower kcat in comparison with spermine. Interestingly, Fms1 was prone to aldehyde supplementation in its regioselectivity, i.e. the cleavage site of spermidine. Thus, aldehyde supplementation to generate aldimines or N-terminal substituents in polyamines, i.e. attachment of guide molecule, generates novel ligands with altered charge distribution changing the binding and catalytic properties with polyamine oxidases. This provides means for exploiting hidden capabilities of polyamine oxidases for controlling their regioselectivity and stereospecificity.

The Novel UDP Glycosyltransferase 3A2: Cloning, Catalytic Properties, and Tissue Distribution

2010 ◽  
Vol 79 (3) ◽  
pp. 472-478 ◽  
Author(s):  
Peter I. MacKenzie ◽  
Anne Rogers ◽  
David J. Elliot ◽  
Nuy Chau ◽  
Julie-Ann Hulin ◽  
...  
Keyword(s):  
Tissue Distribution ◽  
Catalytic Properties ◽  
The Novel
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