Kinetics and mechanism of the cytochrome c – sulfite reaction

1991 ◽  
Vol 56 (7) ◽  
pp. 1552-1559
Author(s):  
Joaquin F. Perez-Benito ◽  
Conchita Arias
Keyword(s):  
Activation Energy ◽  
Aqueous Solution ◽  
Cytochrome C ◽  
Apparent Activation Energy ◽  
Sodium Sulfite ◽  
Horse Heart Cytochrome ◽  
First Order ◽  
Cyt C ◽  
Ph Range ◽  
Horse Heart Cytochrome C

The reaction between the oxidized form of horse-heart cytochrome c and sodium sulfite in aqueous solution has been studied in the pH range 6.5 – 8.2. The reaction is first order in both oxidant and reductant, is accelerated by an increase in pH and is slowed down by addition of potassium chloride. An increase in pH results in an increase in the apparent activation energy (66-77kJ . mol-1). A mechanism in which both HSO3- and SO32- act as reducing agents is proposed, the activation energies corresponding to the cyt c-HSO3- and cyt c-SO32- reactions being 63 ± 4 and 79 ± 2 kJ mol-1, respectively.

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

1991 ◽  
Vol 56 (2) ◽  
pp. 478-490 ◽  
Author(s):  
Joaquin F. Perez-Benito ◽  
Conchita Arias
Keyword(s):  
Ascorbic Acid ◽  
Cytochrome C ◽  
Redox Reactions ◽  
Arrhenius Equation ◽  
Horse Heart Cytochrome ◽  
First Order ◽  
Acidic Form ◽  
Ph Range ◽  
Horse Heart Cytochrome C ◽  
Mechanism Of The Reaction

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+ -Fe3+ + OH- cyt -Fe3+ + H2O, whose equilibrium constant is (6.7 ± 1.4). 108 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.

scholarly journals Temperature and pH effects on the kinetics of 2-aminophenol auto-oxidation in aqueous solution

2003 ◽  
Vol 1 (3) ◽  
pp. 233-241 ◽  
Author(s):  
Dumitru Oancea ◽  
Mihaela Puiu
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Aqueous Solution ◽  
Ph Effects ◽  
Influence Of Temperature ◽  
First Order ◽  
Incremental Methods ◽  
First Order Kinetics ◽  
Ph Range ◽  
Kinetics Of

AbstractThe kinetics of the auto-oxidation of 2-aminophenol (OAP) to 2-amino-phenoxazin-3-one (APX) was followed in air-saturated aqueous solutions and the influence of temperature and pH on the auto-oxidation rate was studied. The kinetic analysis was based on a spectrophotometric method following the increase of the absorbance of APX. The process follows first order kinetics according to the rate law—d[OAP]/dt=k′[OAP]. The experimental data, within the pH range 4–9.85, were analyzed using both differential and incremental methods. The temperature variation of the overall rate constant was studied at pH=9.85 within the range 25–50°C and the corresponding activation energy was evaluated.

scholarly journals Identification of the ligand-exchange process in the alkaline transition of horse heart cytochrome c

1987 ◽  
Vol 246 (1) ◽  
pp. 43-54 ◽  
Author(s):  
P M Gadsby ◽  
J Peterson ◽  
N Foote ◽  
C Greenwood ◽  
A J Thomson
Keyword(s):  
Cytochrome C ◽  
Ligand Exchange ◽  
Magnetic Circular Dichroism ◽  
Exchange Process ◽  
Horse Heart Cytochrome ◽  
Ph Values ◽  
Alkaline Transition ◽  
Ph Range ◽  
Horse Heart Cytochrome C ◽  
Cytochrome C551

Magnetic-circular-dichroism (m.c.d.) spectra over the wavelength range 300-2000 nm at room temperature and at 4.2K of horse heart cytochrome c are reported at a series of pH values between 7.8 and 11.0, encompassing the alkaline transition. The effect of glassing agents on the e.p.r. spectrum at various pH values is also reported. Comparison of these results with spectra obtained for the n-butylamine adduct of soybean leghaemoglobin support the hypothesis that lysine is the sixth ligand in the alkaline form of horse heart cytochrome c. The m.c.d. and e.p.r. spectra of horse heart cytochrome c in the presence of 1-methylimidazole have also been examined. These studies strongly suggest that histidine-18, the proximal ligand of the haem, is the ionizing group that triggers the alkaline transition. Low-temperature m.c.d. and e.p.r. spectra are also reported for Pseudomonas aeruginosa cytochrome c551. It is shown that no ligand exchange takes place at the haem in this species over the pH range 6.0-11.3.

Reactions of metallodrugs with proteins: selective binding of phosphane-based platinum(ii) dichlorides to horse heart cytochrome c probed by ESI MS coupled to enzymatic cleavage

Metallomics ◽  
2011 ◽  
Vol 3 (10) ◽  
pp. 987-990 ◽  
Author(s):  
Carolin Mügge ◽  
Elena Micheucci ◽  
Francesca Boscaro ◽  
Chiara Gabbiani ◽  
Luigi Messori ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Adduct Formation ◽  
Enzymatic Cleavage ◽  
Selective Binding ◽  
Horse Heart Cytochrome ◽  
Esi Ms ◽  
Cyt C ◽  
Horse Heart Cytochrome C

The reaction of two cis-diphosphane platinum(ii) dichlorides with horse heart cytochrome c (cyt c) leads to remarkable selectivity in terms of adduct formation.

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