Kinetics and mechanism of the reaction between oxidized cytochrome c and ascorbic acid

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Title:Kinetics and mechanism of the reaction between oxidized cytochrome c and ascorbic acid
Creators:
Perez-Benito, Joaquin F.
Arias, Conchita
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 56, 2, pp. 478-490

Abstract

The reaction between horse-heart cytochrome c and ascorbic acid has been investigated in the pH range 5.5 – 7.1 and at 10.0 – 25.0 °C. The rate shows a first-order dependence on the concentration of cytochrome c, it increases in a non-linear way as the concentration of ascorbic acid increases, it increases markedly with increasing pH and, provided that the ionic strength of the medium is high enough, it fulfills the Arrhenius equation. The apparent activation energy increases as the pH of the solution increases. The results have been explained by means of a mechanism that includes the existence of an equilibrium between two forms (acidic and basic) of oxidized cytochrome c: cyt-H<sup>+</sup> -Fe<sup>3+</sup> + OH<sup>-</sup> cyt -Fe<sup>3+</sup> + H<sub>2</sub>O, whose equilibrium constant is (6.7 ± 1.4). 10<sup>8</sup> at 25.0 °C, the acidic form being more reducible than the basic one. It is suggested that there is a linkage of hydrogenascorbate ion to both forms of cytochrome c previous to the redox reactions. Two possibilities for the oxidant-reductant linkage (binding and adsorption) are discussed in detail.

Title:Kinetics and mechanism of the reaction between oxidized cytochrome c and ascorbic acid
Creators:
Perez-Benito, Joaquin F.
Arias, Conchita
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:56
Number:2
Page Range:pp. 478-490
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc19910478UNSPECIFIED
ID Code:4967
Item Type:Article
Deposited On:22 Feb 2010 11:27
Last Modified:22 Feb 2010 10:27

Citation

Perez-Benito, Joaquin F.; Arias, Conchita (1991) Kinetics and mechanism of the reaction between oxidized cytochrome c and ascorbic acid. Collection of Czechoslovak Chemical Communications, 56 (2). pp. 478-490. ISSN 0010-0765

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