scholarly journals Diffusional Electrochemical Catalytic (EC’) Mechanism Featuring Chemical Reversibility of Regenerative Reaction-Theoretical Analysis in Cyclic Voltammetry

2020 ◽  
Vol 92 (4) ◽  
pp. 495-502
Author(s):  
Sofija Petkovska ◽  
Rubin Gulaboski
Keyword(s):  
Chemical Reaction ◽  
Catalytic Mechanism ◽  
Electrode Reaction ◽  
Time Frame ◽  
Cyclic Voltammograms ◽  
Kinetic And Thermodynamic Parameters ◽  
Enzyme Substrate ◽  
Ec Mechanism ◽  
Current Measuring ◽  
Product Red

We consider theoretically a specific electrochemical-catalytic mechanism associated with reversible regenerative chemical reaction, under conditions of cyclic staircase voltammetry (CSV). We suppose scenario in which two electrochemically inactive substrates “S” and “Y”, together with initial electrochemically active reactant Ox are present in voltammetric cell from the beginning of the experiment. Substrate “S” selectively reacts with initial electroactive reactant Ox and creates electroactive “product” Red (+ Y) in a reversible chemical fashion. The initial chemical equilibrium determines the amounts of Ox and Red available for electrode transformation at the beginning of the electrochemical experiment. Under conditions of applied potential, the electrode reaction Ox(aq) + ne– ⇋ Red(aq) occurs, producing flow of electric current. Under such circumstances, the chemical reaction coupled to the electrochemical step causes a regeneration of initial electroactive species during the time-frame of current-measuring segment in CSV. The features of cyclic voltammograms get significantly affected by the kinetics and thermodynamics of reversible regenerative reaction. We elaborate several aspects of this specific electrode mechanism, and we focus on the role of parameters related to chemical step to the features of calculated voltammograms. While we provide a specific set of results of this particular mechanism, we propose methods to get access to relevant kinetic and thermodynamic parameters relevant to regenerative chemical reaction. The results elaborated in this work can be valuable in evaluating kinetics of many drug-drug interactions, but they can be relevant to study interactions of many enzyme-substrate systems, as well.

Noncovalent Enzyme−Substrate Interactions in the Catalytic Mechanism of Yeast Aldose Reductase†

Biochemistry ◽  
1998 ◽  
Vol 37 (4) ◽  
pp. 1116-1123 ◽  
Author(s):  
Wilfried Neuhauser ◽  
Dietmar Haltrich ◽  
Klaus D. Kulbe ◽  
Bernd Nidetzky
Keyword(s):  
Aldose Reductase ◽  
Catalytic Mechanism ◽  
Substrate Interactions ◽  
Enzyme Substrate ◽  
Enzyme Substrate Interactions

Crystal structures of penicillin acylase enzyme-substrate complexes: structural insights into the catalytic mechanism 1 1Edited by K. Nagai

2001 ◽  
Vol 313 (1) ◽  
pp. 139-150 ◽  
Author(s):  
Colin E McVey ◽  
Martin A Walsh ◽  
G.Guy Dodson ◽  
Keith S Wilson ◽  
James A Brannigan
Keyword(s):  
Crystal Structures ◽  
Catalytic Mechanism ◽  
Penicillin Acylase ◽  
Enzyme Substrate ◽  
Structural Insights

scholarly journals Current calculation of irreversible electrode reaction mechanismsin linear sweep voltammetry

2021 ◽  
Vol 9 (3) ◽  
Author(s):  
Ján Mocák ◽  
Estera Rábarová
Keyword(s):  
Chemical Reaction ◽  
Infinite Series ◽  
Digital Simulation ◽  
Linear Sweep Voltammetry ◽  
Electrode Reaction ◽  
Potential Range ◽  
Linear Sweep ◽  
Potential Region ◽  
Current Function ◽  
Simulation Techniques

Application of exponential infinite series gives highly accurate analytical solution contributing to the theory of linear sweep voltammetry for single scan experiments. We have calculated theoretical dimensionless current function (usually denoted as π1/2χ(bt)) at relevant potentials for irreversible charge transfer without a coupled chemical reaction. For this purpose several transformation techniques were used, which convert the derived infinite series into summable sequences. Since infinite series of further electrochemical mechanisms with irreversible electrode reaction have similar features (particularly those comprising preceding and catalytic chemical reaction), the same approach can be successfully applied also for further electrochemical mechanisms. The respective infinite series are divergent in the most important potential region at and after voltammetric peak therefore their transformation by Epsilon and Levin transform techniques was used. Necessary arbitrary precision arithmetic (APA) was implemented by UBASIC. The results were compared to the customary solution of Nicholson and Shain, who computed the current-potential curves by means of numerical solution of the integral equations but with a much lower precision. Our results were obtained in a broad potential range including the potential regions where the series are divergent. Obtained current functions are precise to 12 valid decimal numbers, which is utilizable for evaluation of the results achieved by various faster but less precise digital simulation techniques.

scholarly journals Microfluidic ELISA employing an enzyme substrate and product species with similar detection properties

The Analyst ◽  
2018 ◽  
Vol 143 (4) ◽  
pp. 989-998 ◽  
Author(s):  
Basant Giri ◽  
Yukari Liu ◽  
Fidelis N. Nchocho ◽  
Robert C. Corcoran ◽  
Debashis Dutta
Keyword(s):  
Chemical Reaction ◽  
Large Change ◽  
Elisa Method ◽  
Enzyme Substrate ◽  
Enzyme Label ◽  
Product Species

The reported ELISA method relaxes the requirement for an enzyme label to carry out a chemical reaction directly at the signaling region of the enzyme substrate in order to produce a large change in its detectability, thereby, significantly expanding the scope of this bioanalytical technique.

scholarly journals Single-Route Linear Catalytic Mechanism: A New, Kinetico-Thermodynamic Form of the Complex Reaction Rate

Symmetry ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 1748 ◽  
Author(s):  
Gregory S. Yablonsky ◽  
Denis Constales ◽  
Guy B. Marin
Keyword(s):  
Reaction Rate ◽  
Catalytic Mechanism ◽  
Equilibrium Constants ◽  
Complex Reaction ◽  
Thermodynamic Factor ◽  
Kinetic And Thermodynamic Parameters ◽  
Kinetic Factor ◽  
Buffer Substance ◽  
Apparent Equilibrium ◽  
Thermodynamic Factors

For a complex catalytic reaction with a single-route linear mechanism, a new, kinetico-thermodynamic form of the steady-state reaction rate is obtained, and we show how its symmetries in terms of the kinetic and thermodynamic parameters allow better discerning their influence on the result. Its reciprocal is equal to the sum of n terms (n is the number of complex reaction steps), each of which is the product of a kinetic factor multiplied by a thermodynamic factor. The kinetic factor is the reciprocal apparent kinetic coefficient of the i-th step. The thermodynamic factor is a function of the apparent equilibrium constants of the i-th equilibrium subsystem, which includes the (n−1) other steps. This kinetico-thermodynamic form separates the kinetic and thermodynamic factors. The result is extended to the case of a buffer substance. It is promising for distinguishing the influence of kinetic and thermodynamic factors in the complex reaction rate. The developed theory is illustrated by examples taken from heterogeneous catalysis.

Synthesis and electroreduction of 2-[(8-hydroxyquinoline-5-yl)azo]benzo[c]cinnoline in DMSO–H2O (1:1) medium

2010 ◽  
Vol 75 (11) ◽  
pp. 1201-1216
Author(s):  
Funda Öztürk ◽  
Zehra Durmuş ◽  
Öznur Ölmez Uçkan ◽  
Emine Kiliç ◽  
Esma Kiliç
Keyword(s):  
Reaction Diffusion ◽  
Electrode Reaction ◽  
Basic Medium ◽  
Cyclic Voltammograms ◽  
H Nmr ◽  
Controlled Potential Electrolysis ◽  
Controlled Potential ◽  
Constant Potential ◽  
Ph Range ◽  
Tlc Analysis

2-[(8-Hydroxyquinoline-5-yl)azo]benzo[c]cinnoline (HQAB) was prepared and characterized by elemental analysis, MS, FTIR and 1H NMR techniques. The electrochemical reduction of HQAB has been investigated by cyclic voltammetry, chronoamperometry and controlled potential electrolysis at mercury pool electrode in the pH range 3.5–9.4. The number of electrons transferred in the electrode reaction, diffusion coefficients and standart rate constants were calculated. In acidic medium, cyclic voltammograms display four cathodic peaks, with the total exchange of 6 e– and 6 H+. By contrast, the reverse scan displays two anodic peaks. Constant potential electrolysis at –1.0 V and TLC analysis of the product reveals that the reduction of azo group (in the bridge) in HQAB does not stop at the hydrazo stage but goes further through the cleavage of –NH–NH– linkage to give amino compounds as the final products. The voltammograms recorded in basic medium exhibit two cathodic peaks corresponding to 4 e–, 4 H+ and two reverse anodic peaks, and thus the reduction stopped at hydrazo stage. A tentative mechanism for the reduction has been suggested.

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