Pyrazine dicarboxylate-bridged arsenotungstate: synthesis, characterization, and catalytic activities in epoxidation of olefins and oxidation of alcohols

2019 ◽  
Vol 48 (34) ◽  
pp. 12956-12963 ◽  
Author(s):  
Xinyi Ma ◽  
Peipei He ◽  
Baijie Xu ◽  
Jingkun Lu ◽  
Rong Wan ◽  
...  
Keyword(s):  
Catalytic Properties ◽  
Catalytic Activities ◽  
Oxidation Of Alcohols ◽  
Epoxidation Of Olefins

The catalytic properties and polyanionic structure of pyrazine dicarboxylate-bridged arsenotungstate are reported.

scholarly journals Catalytic Diversity of GH30 Xylanases

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4528
Author(s):  
Katarína Šuchová ◽  
Vladimír Puchart ◽  
Nikolaj Spodsberg ◽  
Kristian B. R. Mørkeberg Krogh ◽  
Peter Biely
Keyword(s):  
Methyl Ester ◽  
Catalytic Properties ◽  
Specific Activity ◽  
Current Knowledge ◽  
Carboxyl Group ◽  
Weak Effect ◽  
Bacterial Enzymes ◽  
Catalytic Activities ◽  
Almost All ◽  
Free Carboxyl

Catalytic properties of GH30 xylanases belonging to subfamilies 7 and 8 were compared on glucuronoxylan, modified glucuronoxylans, arabinoxylan, rhodymenan, and xylotetraose. Most of the tested bacterial GH30-8 enzymes are specific glucuronoxylanases (EC 3.2.1.136) requiring for action the presence of free carboxyl group of MeGlcA side residues. These enzymes were not active on arabinoxylan, rhodymenan and xylotetraose, and conversion of MeGlcA to its methyl ester or its reduction to MeGlc led to a remarkable drop in their specific activity. However, some GH30-8 members are nonspecific xylanases effectively hydrolyzing all tested substrates. In terms of catalytic activities, the GH30-7 subfamily is much more diverse. In addition to specific glucuronoxylanases, the GH30-7 subfamily contains nonspecific endoxylanases and predominantly exo-acting enzymes. The activity of GH30-7 specific glucuronoxylanases also depend on the presence of the MeGlcA carboxyl, but not so strictly as in bacterial enzymes. The modification of the carboxyl group of glucuronoxylan had only weak effect on the action of predominantly exo-acting enzymes, as well as nonspecific xylanases. Rhodymenan and xylotetraose were the best substrates for exo-acting enzymes, while arabinoxylan represented hardly degradable substrate for almost all tested GH30-7 enzymes. The results expand current knowledge on the catalytic properties of this relatively novel group of xylanases.

scholarly journals Novel class of glutathione transferases from cyanobacteria exhibit high catalytic activities towards naturally occurring isothiocyanates

2007 ◽  
Vol 406 (1) ◽  
pp. 115-123 ◽  
Author(s):  
Eric Wiktelius ◽  
Gun Stenberg
Keyword(s):  
Catalytic Properties ◽  
Structural Features ◽  
Glutathione Transferases ◽  
Substrate Specificities ◽  
Catalytic Activities ◽  
Genome Databases ◽  
Naturally Occurring ◽  
Physiological Relevance ◽  
Associated Proteins

In the present paper, we report a novel class of GSTs (glutathione transferases), called the Chi class, originating from cyanobacteria and with properties not observed previously in prokaryotic enzymes. GSTs constitute a widespread multifunctional group of proteins, of which mammalian enzymes are the best characterized. Although GSTs have their origin in prokaryotes, few bacterial representatives have been characterized in detail, and the catalytic activities and substrate specificities observed have generally been very modest. The few well-studied bacterial GSTs have largely unknown physiological functions. Genome databases reveal that cyanobacteria have an extensive arsenal of glutathione-associated proteins. We have studied two cyanobacterial GSTs which are the first examples of bacterial enzymes that are as catalytically efficient as the best mammalian enzymes. GSTs from the thermophile Thermosynechococcus elongatus BP-1 and from Synechococcus elongatus PCC 6301 were found to catalyse the conjugation of naturally occurring plant-derived isothiocyanates to glutathione at high rates. The cyanobacterial GSTs studied are smaller than previously described members of this enzyme family, but display many of the typical structural features that are characteristics of GSTs. They are also active towards several classical substrates, but at the same moderate rates that have been observed for other GSTs derived from prokaryotes. The cloning, expression and characterization of two cyanobacterial GSTs are described. The possible significance of the observed catalytic properties is discussed in the context of physiological relevance and GST evolution.

Controllable synthesis of Ni nanotube arrays and their structure-dependent catalytic activity toward dye degradation

CrystEngComm ◽  
2014 ◽  
Vol 16 (21) ◽  
pp. 4406-4413 ◽  
Author(s):  
Xiang-Zi Li ◽  
Kong-Lin Wu ◽  
Yin Ye ◽  
Xian-Wen Wei
Keyword(s):  
Catalytic Activity ◽  
Catalytic Properties ◽  
Dye Degradation ◽  
Nanotube Arrays ◽  
Nanorod Arrays ◽  
Growth Mechanisms ◽  
Controllable Synthesis ◽  
Catalytic Activities ◽  
One Step ◽  
The Relationship

Ni nanotube (nanorod) arrays are controllably fabricated by a one-step approach, the GDDATG and DDCG growth mechanisms are introduced. The Ni nanostructures present higher catalytic activities for dye degradation, the relationship between structures and catalytic properties is also studied.

The Effect of Silver and Silver-Platinum Doped Into 5A Zeolite on the Degradation of Naptalam

2013 ◽  
Vol 856 ◽  
pp. 43-47 ◽  
Author(s):  
Sofian M. Kanan ◽  
Saeed E. Nusri
Keyword(s):  
Phthalic Acid ◽  
Catalytic Properties ◽  
Catalytic Activities ◽  
5A Zeolite

This study investigated the synthesis and catalytic properties of silver, platinum, and mixed Ag-Pt dopants into the 5A zeolite host. The prepared materials were tested toward the photodecomposition of the pesticide naptalam. The results indicate strong catalytic activities for the Ag-Pt-5A catalyst whereas, the Ag5A was found out to be the only doped zeolite that adsorbs the pesticide as soon as it came in contact with its surface. a-naphtylamine and phthalic acid were determined to be major photodecomposition products.

scholarly journals Surface and Catalytic Properties of NiO–Fe2O3 Solids Supported on Al2O3

1996 ◽  
Vol 13 (5) ◽  
pp. 409-421 ◽  
Author(s):  
G.A. El-Shobaky ◽  
A.M. Ghozza ◽  
N.M. Deraz
Keyword(s):  
Rate Constant ◽  
Reaction Rate ◽  
Catalytic Properties ◽  
Unit Area ◽  
Surface Characteristics ◽  
Reaction Rate Constant ◽  
Oxidation Of Co ◽  
Catalytic Activities ◽  
Surface Areas ◽  
Specific Surface Areas

A series of NiO–Fe2O3 catalysts supported on γ-Al2O3 was prepared. The effect of the NiO and Fe2O3 contents and the precalcination temperature on the surface and catalytic properties of the various solids has been investigated. The surface characteristics, viz. SBET, Vp and r, were determined using N2 adsorption conducted at –196°C. The catalytic activities of the various solids were studied using the oxidation of CO by O2 at temperatures in the range between 150°C and 400°C. The prepared solids were preheated in air at various temperatures between 400°C and 1000°C. The results obtained revealed that the SBET values of the different solids decrease progressively on increasing the precalcination temperature above 400°C due to sintering. The specific surface areas were also found to decrease on increasing both the NiO and Fe2O3 contents. The catalytic activities, expressed as reaction rate constant (k) and reaction rate constant per unit area (k), were found to decrease on increasing the precalcination temperature in the range 400–1000°C. Furthermore, the amounts of NiO and Fe2O3 in the different solids modified their catalytic activities in different manners.

Noble metal ions in CeO2 and TiO2: synthesis, structure and catalytic properties

RSC Advances ◽  
2015 ◽  
Vol 5 (115) ◽  
pp. 94949-94979 ◽  
Author(s):  
Parthasarathi Bera ◽  
M. S. Hegde
Keyword(s):  
Metal Ions ◽  
Noble Metal ◽  
Catalytic Properties ◽  
Water Gas Shift ◽  
Electronic Interactions ◽  
Catalytic Activities ◽  
Water Gas ◽  
Very High

CeO2 and TiO2 based noble metal ionic catalysts show very high catalytic activities toward several reactions such as auto exhaust, water gas shift, H2 + O2 recombination compared to supported nanometal catalysts due to their electronic interactions.

FEATURES AND CATALYTIC PROPERTIES OF RhCu: A REVIEW

2010 ◽  
Vol 24 (25n26) ◽  
pp. 5128-5138 ◽  
Author(s):  
SILVIA GONZALEZ ◽  
CARMEN SOUSA ◽  
FRANCESC ILLAS
Keyword(s):  
Catalytic Activity ◽  
Bimetallic Catalysts ◽  
Catalytic Properties ◽  
Catalytic Activities ◽  
Cu Content ◽  
Bimetallic System

The study of bimetallic catalysts has scientific and technologic importance because of special catalytic activity towards several reactions. RhCu is an interesting bimetallic system due to combination of the very different catalytic activities of Rh and Cu. The catalytic activity of this bimetallic does not result from simple interpolation of the constituents. In fact, at low Cu content, the catalytic activity of RhCu is superior to that of Rh but when the Cu content is higher the activity decays. This is a curious trend which theoretical works had attempted to explain. This paper reports an overview of the most recent research works about this bimetallic system with emphasis in its especial characteristics.

scholarly journals Multiple personalities of the RNA polymerase active centre

Microbiology ◽  
2014 ◽  
Vol 160 (7) ◽  
pp. 1316-1320 ◽  
Author(s):  
Nikolay Zenkin
Keyword(s):  
Rna Synthesis ◽  
Catalytic Properties ◽  
Amino Acid Content ◽  
Annual Conference ◽  
Active Centre ◽  
Catalytic Activities ◽  
Trigger Loop ◽  
Living Organisms ◽  
Unique Ability ◽  
Active Centres

Transcription in all living organisms is accomplished by highly conserved multi-subunit RNA polymerases (RNAPs). Our understanding of the functioning of the active centre of RNAPs has transformed recently with the finding that a conserved flexible domain near the active centre, the trigger loop (TL), participates directly in the catalysis of RNA synthesis and serves as a major determinant for fidelity of transcription. It also appears that the TL is involved in the unique ability of RNAPs to exchange catalytic activities of the active centre. In this phenomenon the TL is replaced by a transcription factor which changes the amino acid content and, as a result, the catalytic properties of the active centre. The existence of a number of transcription factors that act through substitution of the TL suggests that the RNAP has several different active centres to choose from in response to external or internal signals. A video of this Prize Lecture, presented at the Society for General Microbiology Annual Conference 2014, can be viewed via this link: https://www.youtube.com/watch?v=79Z7iXVEPo4

Structurally characterized homo-trinuclear ZnII and hetero-pentanuclear [ZnII4LnIII] complexes constructed from an octadentate bis(Salamo)-based ligand: Hirshfeld surfaces, fluorescence and catalytic properties

2019 ◽  
Vol 43 (11) ◽  
pp. 4605-4619 ◽  
Author(s):  
Xiao-Yan Li ◽  
Quan-Peng Kang ◽  
Chang Liu ◽  
Yang Zhang ◽  
Wen-Kui Dong
Keyword(s):  
Catalytic Properties ◽  
Hirshfeld Surface ◽  
Fluorescence Properties ◽  
X Ray ◽  
Catalytic Activities ◽  
X Ray Crystallography ◽  
Hirshfeld Surfaces ◽  
Vis Spectroscopy ◽  
Elemental Analyses ◽  
Ft Ir

One 3d and five 3d-4f complexes were synthesized. Complexes 1–6 were characterized via elemental analyses, FT-IR, UV-Vis spectroscopy and X-ray crystallography, and their fluorescence properties, catalytic activities and Hirshfeld surface analyses were studied.

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