Solely electrochemical synthesis of Prussian Blue based nanozymes ‘artificial peroxidase’

2021 ◽  
Author(s):  
Maria A. Komkova ◽  
Kirill R. Vetoshev ◽  
Egor A Andreev ◽  
Arkady Karyakin
Keyword(s):  
Prussian Blue ◽  
Rate Constant ◽  
Electrochemical Synthesis ◽  
Catalytic Rate Constant ◽  
Flow Through ◽  
Catalytic Rate

We report on fully electrochemical flow-through synthesis of Prussian Blue based nanozymes defeating peroxidase in terms of more than 200 times higher catalytic rate constant (kcat=6∙104 s-1). Being reagentless, reproducible,...

Solvent effects on kinetics and mechanism of acid-catalyzed decomposition of 1,3-bis(4-methylphenyl)-triazene II. Reactions in aprotic solvents

1990 ◽  
Vol 55 (1) ◽  
pp. 156-164 ◽  
Author(s):  
Oldřich Pytela ◽  
Taťjana Nevěčná ◽  
Miroslav Ludwig
Keyword(s):  
Rate Constant ◽  
Acid Catalyst ◽  
Kinetics And Mechanism ◽  
Aprotic Solvents ◽  
Catalytic Rate Constant ◽  
Negative Effect ◽  
Acid Catalyzed ◽  
Catalytic Rate ◽  
Positive Effect ◽  
Solvent Acidity

The effect of aprotic solvents (hexane, cyclohexane, dichloromethane, 1,2-dichloroethane, benzene, acetonitrile, acetone, 1,2-dimethoxyethane, ethyl acetate, dioxane) on kinetics and mechanism of acid-catalyzed decomposition of 1,3-bis(4-methylphenyl)triazene has been studied with trichloroacetic acid as the acid catalyst. It has been found that beside the non-dissociated monomer of the acid also its dimer acts as the catalytic species. With regard to the results obtained in protic solvents (the catalysis by proton and general acid) three cases can be encountered of the dependence of observed rate constant on analytical concentration of the acid. The effect of solvents (inclusive of the protic ones) on the catalytic rate constant of the reaction with the non-dissociated monomer of acid is best interpreted by the equation suggested by Koppel and Palm and by the solvent scale suggested by us earlier. The solvent acidity and polarity have positive effect, whereas its basicity has negative effect. The catalytic rate constant of the reaction with the acid dimer decreases with increasing solvent basicity and polarity, due predominantly to the decrease in the equilibrium constant of dimerization.

Steric Effects in Acid-Catalyzed Decomposition and Base-Catalyzed Cyclization of 1-(2-Alkoxycarbonylphenyl)-3-phenyltriazenes

1996 ◽  
Vol 61 (5) ◽  
pp. 751-763 ◽  
Author(s):  
Oldřich Pytela ◽  
Aleš Halama
Keyword(s):  
Rate Constant ◽  
Nmr Spectra ◽  
Steric Effects ◽  
Catalytic Rate Constant ◽  
Rate Limiting Step ◽  
Acid Catalyzed ◽  
Catalytic Rate ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Derivatives Of

Eight derivatives of 1-(2-alkoxycarbonylphenyl)-3-phenyltriazene (R = methyl, ethyl, propyl, isopropyl, butyl, isobutyl, hexyl, and allyl) have been synthesized and their UV-VIS, IR, 1H and 13C NMR spectra measured. The NMR spectra have been interpreted in detail. The kinetics of acid-catalyzed decomposition and base-catalyzed cyclization of the title compounds have been measured in 52.1% w/w methanol at 25.0 °C. The unit reaction order has been verified and the cyclization product has been identified. The pH-profiles obtained have been used to calculate the catalytic rate constants kA (acid-catalyzed decomposition) and kB (base-catalyzed cyclization) of all the derivatives; the constants have been interpreted with regard to inductive and steric effects. The catalytic rate constant kA has been found to be independent of the substituents. The catalytic rate constant kB depends statistically significantly upon both inductive and steric effects, the sensitivity to the former being more significant. The experimental results and their interpretation confirm the base-catalyzed cyclization mechanism with formation of tetrahedral intermediate as the rate-limiting step.

Effect of Medium on Acid-Catalyzed Decomposition of N-(Phenylazo)-Substituted Nitrogen Heterocycles

1999 ◽  
Vol 64 (10) ◽  
pp. 1654-1672 ◽  
Author(s):  
Miroslav Ludwig ◽  
Iva Bednářová ◽  
Patrik Pařík
Keyword(s):  
Rate Constant ◽  
Principal Component ◽  
Catalyst Particle ◽  
Pivalic Acid ◽  
Linear Regression Method ◽  
Catalytic Rate Constant ◽  
Rate Limiting Step ◽  
Acid Catalyzed ◽  
Rate Limiting ◽  
Kinetics Of

Four N-(phenylazo)-substituted saturated nitrogen heterocyclics were synthesized and their structure was confirmed by 1H and 13C NMR spectroscopy. The kinetics of their acid-catalyzed decomposition were studied at various concentrations of the catalyst (pivalic acid) in 40, 30, and 20% (v/v) aqueous ethanol at 25 °C. The values obtained for the observed rate constants were processed by the non-linear regression method according to the suggested kinetic models and by the method of principal component analysis (PCA). The interpretation of the results has shown that the acid-catalyzed decomposition of the heterocyclics under the conditions used proceeds by the mechanism of general acid catalysis, the proton being the dominant catalyst particle of the rate-limiting step. The decrease in the observed rate constant at higher concentrations of the catalyst was explained by the formation of a non-reactive complex composed of the undissociated acid and the respective N-(phenylazo)heterocycle. The effect of medium and steric effect of the heterocyclic moiety on the values of catalytic rate constant are discussed.

scholarly journals The significance of abrupt transitions in Lineweaver–Burk plots with particular reference to glutamate dehydrogenase. Negative and positive co-operativity in catalytic rate constants

1973 ◽  
Vol 131 (1) ◽  
pp. 97-105 ◽  
Author(s):  
Paul C. Engel ◽  
William Ferdinand
Keyword(s):  
Glutamate Dehydrogenase ◽  
Rate Equation ◽  
Rate Constants ◽  
Initial Rate ◽  
Current Knowledge ◽  
The Other ◽  
Catalytic Rate Constant ◽  
Catalytic Rate ◽  
Linear Sections ◽  
Glucose 6 Phosphate Dehydrogenase

1. Lineweaver–Burk plots for glutamate dehydrogenase, glucose 6-phosphate dehydrogenase and several other enzymes show one or more abrupt transitions between apparently linear sections. These transitions correspond to abrupt increases in the apparent Km and Vmax. with increasing concentration of the varied substrate. 2. The generalized reciprocal initial-rate equation for a multi-site enzyme requires several restrictions to be put on it in order to generate such plots. These mathematical conditions are explored. 3. It is shown that the effective omission of a term in the denominator of the reciprocal initial-rate equation represents a minimal requirement for generation of abrupt transitions. This corresponds in physical terms to negative co-operativity followed by positive co-operativity affecting the catalytic rate constant for the reaction. 4. Previous models for glutamate dehydrogenase cannot adequately account for the results. On the other hand, the model based on both negative and positive co-operativity gives a good fit to the experimental points. 5. The conclusions are discussed in relation to current knowledge of the structure and mechanism of glutamate dehydrogenase.

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