Steady-State and Transient Reactivity Study of TiO2-Supported V2O5−WO3De-NOxCatalysts:  Relevance of the Vanadium−Tungsten Interaction on the Catalytic Activity

1996 ◽  
Vol 35 (11) ◽  
pp. 3884-3892 ◽  
Author(s):  
Luca Lietti ◽  
Pio Forzatti ◽  
Fiorenzo Bregani
Keyword(s):  
Catalytic Activity ◽  
Steady State ◽  
Reactivity Study ◽  
Transient Reactivity

scholarly journals Copper(ii)-benzotriazole coordination compounds in click chemistry: a diagnostic reactivity study

2018 ◽  
Vol 47 (31) ◽  
pp. 10491-10508 ◽  
Author(s):  
Edward Loukopoulos ◽  
Alaa Abdul-Sada ◽  
Gizella Csire ◽  
Csilla Kállay ◽  
Adam Brookfield ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Click Chemistry ◽  
Coordination Compounds ◽  
Diagnostic Study ◽  
Reactivity Study ◽  
Shed Light

This diagnostic study aims to shed light on the catalytic activity of a library of Cu(ii) based coordination compounds with benzotriazole-based ligands.

scholarly journals Formation and properties of flavoprotein-cytochrome hybrids by recombination of subunits from different species

1985 ◽  
Vol 231 (2) ◽  
pp. 383-387 ◽  
Author(s):  
S C Koerber ◽  
D J Hopper ◽  
W S McIntire ◽  
T P Singer
Keyword(s):  
Catalytic Activity ◽  
Steady State ◽  
Isoelectric Focusing ◽  
Dissociation Constants ◽  
The Other ◽  
High Dilution ◽  
Steady State Kinetic ◽  
Isoelectric Points ◽  
State Kinetic ◽  
Enzyme Species

p-Cresol methylhydroxylases from four different pseudomonads differ in their isoelectric points and, to a lesser extent, in Mr values and substrate specificity. The enzymes from three species were isolated in homogeneous form, then resolved into their flavoprotein and cytochrome subunits, and the subunits were recombined to yield the nine possible hybrids (i.e. three intraspecies and six interspecies). The resulting flavocytochromes showed extensive similarities in steady-state kinetic parameters and in the dissociation constants of their subunits. Evidence is also presented that a fourth type of p-cresol methylhydroxylase, from Pseudomonas putida (N.C.I.B. 9869, form ‘B’), the subunits of which cannot be isolated by the isoelectric focusing technique used to separate the subunits of the other flavocytochromes, nevertheless dissociates slowly at high dilution. The dissociation is reflected by a decline of catalytic activity with time. This process for the ‘B’ enzyme is prevented by the presence of substrate or an excess of a cytochrome subunit isolated from another enzyme species. Incubation of the dissociated subunits with p-cresol brings about extensive, albeit incomplete, re-association and regeneration of activity.

Glycine-assisted enhancement of 1,4-β-d-xylan xylanohydrolase activity at alkaline pH with a pH optimum shift

2007 ◽  
Vol 388 (1) ◽  
pp. 61-65 ◽  
Author(s):  
Vinod Vathipadiekal ◽  
Anamika Verma ◽  
Mala Rao
Keyword(s):  
Catalytic Activity ◽  
Steady State ◽  
Amino Acid ◽  
Protein Engineering ◽  
Xylanase Activity ◽  
Neutral Amino Acid ◽  
Alkaline Ph ◽  
Ph Optimum ◽  
Steady State Kinetics ◽  
Amino Acid Glycine

Abstract This is the first report describing the enhancement of xylanase activity by the neutral amino acid glycine. Xylanase activity is increased seven-fold at alkaline pH in the presence of glycine and its pH optimum is shifted from pH 7 to 8 without using any protein engineering techniques. Analysis of the steady-state kinetics revealed that glycine in the reaction mixture increases the K m and k cat values of the enzyme. Chemoaffinity labeling and studies using glycine esters indicate an involvement of the carboxylate ion of glycine in enhancing xylanase catalytic activity. A novel possible mechanism for the glycine-assisted catalytic action of xylanase is proposed.

Preparation of NixCo3-xTiO4 Ternary Nanowire and Study on their Electrocatalytic Performances

2017 ◽  
Vol 1142 ◽  
pp. 197-200
Author(s):  
Xiao Bo Zhang ◽  
Hai Ping Liu
Keyword(s):  
Cyclic Voltammetry ◽  
Catalytic Activity ◽  
Steady State ◽  
Anode Materials ◽  
Catalytic Performance ◽  
High Catalytic Activity ◽  
Deposition Method ◽  
Good Crystallinity ◽  
Constant Potential ◽  
Cobalt And Nickel

In this paper, NixCo3-xTiO4 nanowire as anode materials was prepared by co-deposition method, and the characterized results showed that had good crystallinity by SEM. The cobalt and nickel were enriched in the surface in the sample by XPS. The catalytic performance of NixCo3-xTiO4 was studied by cyclic voltammetry and constant potential. The results showed that when the Co: Ni = 4:1, the temperature was 120°C, NixCo3-xTiO4 nanowires had high catalytic activity and good stability by the cyclic voltammetry and the steady state polarization curves.

scholarly journals Dissociation and catalysis in yeast hexokinase A.

1976 ◽  
Vol 155 (3) ◽  
pp. 661-667 ◽  
Author(s):  
D C Williams ◽  
J G Jones
Keyword(s):  
Catalytic Activity ◽  
Steady State ◽  
Ternary Complex ◽  
Specific Activity ◽  
Temperature Dependent ◽  
Gradual Decline ◽  
Experimental Conditions ◽  
Progress Curve ◽  
Catalytically Active ◽  
Yeast Hexokinase

1. The specific activity of yeast hexokinase A depends on the concentration of the protein in the solution being assayed. When a solution containing 13.5 mg of hexokinase A/ml is diluted 10-100-fold at various values of pH and temperature, there is a gradual decline in the specific activity of the enzyme until an equilibrium value is reached, which varies with the chosen experimental conditions. 2. The catalytic activity lost when hexokinase A (1 mg/ml) is incubated at 30degreesC is recovered by lowering the temperature to 25degreesC. 3. These concentration- and temperature-dependent phenomena are consistent with the existence of a monomer-dimer equilibrium in which the dimer alone is the catalytic form of the enzyme. 4. Glucose alone prevents the decline in specific activity of hexokinase A after dilution, but it does not re-activate dilute solutions solutions of the enzyme. It is concluded that glucose binds to both the dimer and the monomer and prevents both association and dissociation. 5. The progress curve describing the phosphorylation of glucose catalysed by hexokinase A does not attain a steady state. It is possible that dissociation of catalytically active dimers in a ternary complex with glucose and ATP (or glucose 6-phosphate and ADP) could explain the non-linearity of this progress curve.

scholarly journals Bulgecin A: a novel inhibitor of binuclear metallo-β-lactamases

2005 ◽  
Vol 387 (3) ◽  
pp. 585-590 ◽  
Author(s):  
Alan M. SIMM ◽  
E. Joel LOVERIDGE ◽  
John CROSBY ◽  
Matthew B. AVISON ◽  
Timothy R. WALSH ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Steady State ◽  
Stenotrophomonas Maltophilia ◽  
Competitive Inhibition ◽  
Zinc Ion ◽  
Glycosidic Linkage ◽  
Sugar Moiety ◽  
Aeromonas Veronii ◽  
Steady State Kinetic ◽  
State Kinetic

Bulgecin A, a sulphonated N-acetyl-D-glucosamine unit linked to a 4-hydroxy-5-hydroxymethylproline ring by a β-glycosidic linkage, is a novel type of inhibitor for binuclear metallo-β-lactamases. Using steady-state kinetic analysis with nitrocefin as the β-lactam substrate, bulgecin A competitively inhibited the metallo-β-lactamase BceII from Bacillus cereus in its two-zinc form, but failed to inhibit when the enzyme was in the single-zinc form. The competitive inhibition was restored by restoring the second zinc ion. The single-zinc metallo-β-lactamase from Aeromonas veronii bv. sobria, ImiS, was not inhibited by bulgecin A. The tetrameric L1 metallo-β-lactamase from Stenotrophomonas maltophilia was subject to partial non-competitive inhibition, which is consistent with a kinetic model in which the enzyme bound to inhibitor retains catalytic activity. Docking experiments support the conclusion that bulgecin A co-ordinates to the zinc II site in metallo-β-lactamases via the terminal sulphonate group on the sugar moiety.

Evaluation of the intrinsic catalytic activity of nanoparticles without prior knowledge of the mass loading

2018 ◽  
Vol 210 ◽  
pp. 317-332 ◽  
Author(s):  
Tobias Löffler ◽  
Patrick Wilde ◽  
Denis Öhl ◽  
Yen-Ting Chen ◽  
Kristina Tschulik ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Steady State ◽  
Prior Knowledge ◽  
Mass Loading ◽  
Diffusion Limited ◽  
Steady State Current

We propose a method enabling the evaluation of intrinsic catalytic activity of nanoparticles based on the diffusion-limited steady-state current.

scholarly journals Flow as a regulator of the activation of factor X by tissue factor

Blood ◽  
1988 ◽  
Vol 72 (4) ◽  
pp. 1404-1406 ◽  
Author(s):  
CH Gemmell ◽  
VT Turitto ◽  
Y Nemerson
Keyword(s):  
Catalytic Activity ◽  
Steady State ◽  
Tissue Factor ◽  
Transmembrane Protein ◽  
Enzyme Concentration ◽  
Phospholipid Bilayer ◽  
Factor Vii ◽  
Factor X ◽  
Enzyme Reactor ◽  
Closed Systems

A novel enzyme reactor for phospholipid-dependent reactions was used to study the effects of flow on tissue factor-initiated coagulation. Microcapillaries were coated with a phospholipid bilayer containing tissue factor, a transmembrane protein that is an essential cofactor for a plasma procoagulant enzyme, factor VII. We show that, in contrast to static, closed systems, the steady-state catalytic activity is independent of enzyme concentration and the time to steady state becomes a function of the enzyme concentration.

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