Effects of potassium ion on the electron-transfer reaction between Fe(CN)64− and TCNQ or chloranil

1978 ◽  
Vol 56 (16) ◽  
pp. 2216-2220 ◽  
Author(s):  
Sadayuki Matsuda ◽  
Akihiko Yamagishi
Keyword(s):  
Electron Transfer ◽  
Rate Constants ◽  
Transfer Reaction ◽  
Temperature Jump ◽  
Ion Pairing ◽  
Electron Transfer Reaction ◽  
Potassium Ion ◽  
The Other ◽  
Transfer Reactions ◽  
Forward Rate

The effects of potassium ion on the electron-transfer reactions between Fe(CN)64− and 7,7,8,8-tetracyanoquinodimethane (TCNQ) or chloranil (QCl4) were studied with temperature-jump equipment; [Formula: see text]. The solvent was a 1:1 (v/v) mixture of acetonitrile–water. In both Systems, the forward rate constants (kr) were unaffected by the addition of KCl; kf(Fe(CN)64−/TCNQ) = (2.9 ± 0.2) × 106 M−1 s−1, and kr(Fe(CN)64−/QCl4) = (5.2 ± 0.4) × 104 M−1 s−1 On the other hand, the backward rate constants (kb) increased with the increase of the KCl concentration. The results are interpreted in terms of ion-pairing equilibria of Fe(CN)64− and Fe(CN)63−.

scholarly journals Electron transfer studies of a conventional redox probe in human sweat and saliva bio-mimicking conditions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
P. Krishnaveni ◽  
V. Ganesh
Keyword(s):  
Electron Transfer ◽  
Crystalline Phase ◽  
Liquid Crystalline ◽  
Transfer Reaction ◽  
Electron Transfer Reaction ◽  
Redox Couple ◽  
Liquid Crystalline Phase ◽  
Transfer Reactions ◽  
Redox Probe ◽  
Human Sweat

AbstractModern day hospital treatments aim at developing electrochemical biosensors for early diagnosis of diseases using unconventional human bio-fluids like sweat and saliva by monitoring the electron transfer reactions of target analytes. Such kinds of health care diagnostics primarily avoid the usage of human blood and urine samples. In this context, here we have investigated the electron transfer reaction of a well-known and commonly used redox probe namely, potassium ferro/ferri cyanide by employing artificially simulated bio-mimics of human sweat and saliva as unconventional electrolytes. Typically, electron transfer characteristics of the redox couple, [Fe(CN)6]3−/4− are investigated using electrochemical techniques like cyclic voltammetry and electrochemical impedance spectroscopy. Many different kinetic parameters are determined and compared with the conventional system. In addition, such electron transfer reactions have also been studied using a lyotropic liquid crystalline phase comprising of Triton X-100 and water in which the aqueous phase is replaced with either human sweat or saliva bio-mimics. From these studies, we find out the electron transfer reaction of [Fe(CN)6]3−/4− redox couple is completely diffusion controlled on both Au and Pt disc shaped electrodes in presence of sweat and saliva bio-mimic solutions. Moreover, the reaction is partially blocked by the presence of lyotropic liquid crystalline phase consisting of sweat and saliva bio-mimics indicating the predominant charge transfer controlled process for the redox probe. However, the rate constant values associated with the electron transfer reaction are drastically reduced in presence of liquid crystalline phase. These studies are essentially carried out to assess the effect of sweat and saliva on the electrochemistry of Fe2+/3+ redox couple.

scholarly journals A method for extracting rate constants from initial rates of stopped-flow kinetic data: application to a physiological electron-transfer reaction

1993 ◽  
Vol 294 (1) ◽  
pp. 211-213 ◽  
Author(s):  
H B Brooks ◽  
V L Davidson
Keyword(s):  
Electron Transfer ◽  
Rate Constants ◽  
Kinetic Data ◽  
Transfer Reaction ◽  
Dissociation Constants ◽  
Accurate Method ◽  
Electron Transfer Reaction ◽  
Stopped Flow ◽  
Methylamine Dehydrogenase ◽  
Substrate Complex

The most commonly used methods for analysis of stopped-flow kinetic data require performing a series of measurements in which one reactant is varied at concentrations significantly greater than the concentration of the other reactant. For enzyme-catalysed reactions this may not be possible, because the dissociation constants for the enzyme-substrate complex are often of the same order of magnitude as the high concentrations of enzyme that must frequently be used in stopped-flow studies. An alternative method of data analysis is presented which allows the determination of microscopic rate constants from initial rates of stopped-flow kinetic data in which substrate is varied in a range of concentrations approximately the same as the enzyme. This method also provides a simple and accurate method for determining k4, the rate of the reverse reaction. This method has been used to describe a physiological electron transfer reaction between a quinoprotein, methylamine dehydrogenase, and a copper protein, amicyanin. At 20 degrees C, the rate of the electron-transfer reaction from methylamine dehydrogenase to amicyanin was 24 s-1, and the dissociation constant for complex-formation was 1.9 microM.

scholarly journals Studies on partially reduced mammalian cytochrome oxidase reactions with ferrocytochrome c

1976 ◽  
Vol 157 (3) ◽  
pp. 591-598 ◽  
Author(s):  
C Greenwood ◽  
T Brittain
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Transfer Reaction ◽  
Temperature Jump ◽  
Electron Transfer Reaction ◽  
Relaxation Processes ◽  
Stopped Flow ◽  
Rapid Reduction ◽  
Ferrocytochrome C

The kinetics of the electron-transfer process which occurs between ferrocytochrome c and partially reduced mammalian cytochrome oxidase were studied by the rapid spectrophotometric techniques of stopped flow and temperature jump. Stopped-flow experiments showed initial very fast extinction changes at 605 nm and at 563 nm, indicating the simultaneous reduction of cytochrome a and oxidation of ferrocytochrome c. During this ‘burst’ phase, say the first 50 ms after mixing, it was invariably found that more cytochrome c had been oxidized than cytochrome a had been reduced. This discrepancy in electron equivalents may be accounted for by the rapid reduction of another redox site in the enzyme, possibly that associated with the extinction changes observed at 830 nm. During the incubation period in which the partially reduced oxidase was prepared, the rate of reduction of cytochrome a by ferrocytochrome c, at constant reactant concentrations, decreased with time. Temperature-jump experiments showed the presence of two relaxation processes. The faster of the two phases was assigned to the electron-transfer reaction between cytochrome c and cytochrome a. A study of the concentration-dependence of the reciprocal relaxation time for this phase yielded a rate constant of 9 X 10(6)M-1-s-1 for the electron transfer from cytochrome c to cytochrome a, and a value of 8.5 X 10(6)M-1-s-1 for the reverse reaction. The equilibrium constant for the electron-transfer reaction is therefore close to unity. The slower phase has been interpreted as signalling the transfer of electrons between cytochrome a and another redox site within the oxidase molecule.

scholarly journals A temperature-jump study of the reaction between azurin and cytochrome c oxidase from Pseudomonas aeruginosa

1975 ◽  
Vol 151 (1) ◽  
pp. 185-188 ◽  
Author(s):  
M Brunori ◽  
S R Parr ◽  
C Greenwood ◽  
M T Wilson
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Electron Transfer ◽  
Cytochrome Oxidase ◽  
Cytochrome C Oxidase ◽  
Molecular Complex ◽  
Transfer Reaction ◽  
Temperature Jump ◽  
Electron Transfer Reaction ◽  
Internal Transfer ◽  
Rate Limiting

The electron-transfer reaction between azurin and the cytochrome oxidase from Pseudomonas aeruginosa was investigated by temperature-jump relaxation in the absence of O2 and in the presence of CO. The results show that: (i) reduced azurin exists in two forms in equilibrium, only one of which is capable of exchanging electrons with the Pseudomonas cytochrome oxidase, in agreement with M. T. Wilson, C. Greenwood, M. Brunori & E. Antonini (1975) (Biochem. J. 145, 449-457); (ii) the electron transfer between azurin and Pseudomonas cytochrome oxidase occurs within a molecular complex of the two proteins; this internal transfer becomes rate-limiting at high reagent concentrations.

scholarly journals Nonenzymatic NADH-Dependent Reduction of Keggin-Type 12-Tungstocobaltate(III) in Aqueous Medium

2011 ◽  
Vol 8 (3) ◽  
pp. 1152-1157
Author(s):  
Prabla Kumari ◽  
Alaka Das ◽  
Dillip Kumar Baral ◽  
A. K. Pattanaik ◽  
P. Mohanty
Keyword(s):  
Electron Transfer ◽  
Transition State ◽  
Aqueous Medium ◽  
Transfer Reaction ◽  
Activation Parameters ◽  
Electron Transfer Reaction ◽  
Transfer Reactions ◽  
Electron Transfer Reactions ◽  
First Order ◽  
Kinetics Of

The kinetics of the electron transfer reaction of NADH with 12-tungstocobaltate(III) has been studied over the range 5.07 ≤ 104[NADH] ≤ 15.22 mol dm-3, 7.0 ≤ pH ≤ 8.0 and 20 ≤ t ≤ 35oC in aqueous medium. The electron transfer reaction showed first-order dependence each in [NADH]Tand [12-tungstocobaltate(III)]T. The products of the reaction were found to be NAD+and 12-tungstocobaltate(II). The activation parameters ΔH#(kJ mol-1) and ΔS#(JK-1mol-1) of the electron transfer reactions were found to be 64.4±1.8 and -48.86±6.0. Negative value of ΔS#is an indicative of an ordered transition state for the electron transfer reaction.

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