Reduction dioxygen

Tavagnaco C, Moszner M, Cozzi S, Peressini S, Costa G (1998) Electrocatalytic dioxygen reduction in the presence of a rhodoxime. J Electroanal Chem 448 41-50... 

Coutanceau C, El Hourch A, Crouigneau P, Leger JM, Lamy C. 1995. Conducting polymer electrodes modified by metal tetrasulfonated phthalocyanines Preparation and electro-catalytic behaviour towards dioxygen reduction in acid medium. Electrochim Acta 40 2739-2748. 

Collman JP, Boulatov R, Sunderland CJ. 2003a. Functional and structural analogs of the dioxygen reduction site in terminal oxidases. In Kadish KM, Smith KM, Guilard R, editors. The Porphyrin Handbook. Boston Academic Press, p. 1. 

Guilard R, Brandes S, Tardieux C, Tabard A, L Her M, Miry C, Gouerec P, Knop Y, Collman JP. 1995. Synthesis and characterization of cofacial metaUodiporphyrins involving cobalt and lewis acid metals New dinuclear multielectron redox catalysts of dioxygen reduction. J Am Chem Soc 117 11721. 

Hutchison JE, Postlethweite TA, Murray RW. 1993. Molecular films of thiol-derivatized tetra-phenylporphyrins on gold Film formation and electrocatal)4ic dioxygen reduction. Langmuir 9 3277. 

Vasudevan P, Santosh, Mann N, Tyagi S. 1990. Transition metal complexes of porphyrins and phthalocyanines as electiocatalysts for dioxygen reduction. Transition Metal Chemistry, 15, 81-90. 

Interpreting these results on a detailed molecular basis is difficult because we have at present no direct structural data proving the nature of the split Co(IIl/lI) voltammetry (which seems critical to the electrocatalytic efficacy). Experiments on the dissolved monomeric porphyrin, in CH-C solvent, reveal a strong tendency for association, especially for the tetra(o-aminophenyl)porphyrin. From this observation, we have speculated (3) that the split Co(III/II) wave may represent reactivity of non-associated (dimer ) and associated forms of the cobalt tetra(o-aminophenyl)porphyrins, and that these states play different roles in the dioxygen reduction chemistry. That dimeric cobalt porphyrins in particular can yield more efficient four electron dioxygen reduction pathways is well known (24). Our results suggest that efforts to incorporate more structurally well defined dimeric porphyrins into polymer films may be a worthwhile line of future research. 

Dioxygen reduction (oxidase activity) and activation for incorporation into organic substrates are catalysed by a number of mononuclear non-haem iron enzymes. We will first consider the intramolecular dioxygenases, in which both atoms of oxygen are introduced into the substrate, then the monoxygenases (in which we choose to include the pterin-dependent hydroxylases), the large family of a-hetoacid-dependent enzymes, and finally isopenicillin N-synthase. 

In earlier studies [5,6] superoxide detection in mitochondria was equated to hydrogen peroxide formation. However, while it is quite possible that superoxide is a stoichiometric precursor of mitochondrial hydrogen peroxide, it is understandable that the level of hydrogen peroxide may be decreased due to the reactions with various mitochondrial oxidants. Moreover, superoxide level can be underestimated due to the reaction with mitochondrial MnSOD. Several authors [7,8] assumed that mitochondrial superoxide production may be estimated through cyanide-resistant respiration, which supposedly characterizes univalent dioxygen reduction. This method was applied for the measurement of superoxide production under in vitro normoxic and hyperoxic conditions, in spite of the finding [7] that cyanide-resistant respiration reflects also the oxidation of various substrates (lipids, amino acids, and nucleotides). Earlier,... 

Surface complexation of Ti02 with fluoride also shows a relevant effect on dioxygen reduction. Over illuminated Ti02/F in the presence of dioxygen and an organic donor a sustained production of H202 is observed, with steady state concentration levels of 1-1.3 ulm - nearly 100 x the levels reported for naked... 

A polypyrrole film electrochemically deposited on gold electrodes from an MeCN-liCl04/Co(OAc)2 solution shows electrocatalytic activity in dioxygen reduction [404]. The catalytic electroreduction of dithio dipropionic acid (PSSP) with the water-soluhle cohalt(II I)tetrakis(4-trimethyl-ammonium phenyl) porphyrin (CoTMAP) has heen studied. The Co catalyst adsorbed on the glassy carbon electrode plays a major role in the electroreductive cleavage of the S—S bond [405]. 

Frazao C, Silva G, Gomes CM, et al. 2000. Structure of a dioxygen reduction enzyme from Desulfovibrio gigas. Nat Struct Biol 7 1041-5. 

The standard potential of the 02/02 pair is equal to -0.15 V in water and -0.60 V in DMF. Usually, dioxygen easily captures two electrons in the stepwise reaction O2 + e —> O2 , then O2 + e 02 . In DMSO, dioxygen reductions into the superoxide ion and then into the dioxygen dianion are characterized by Ey2 = -0.5 V and Ey = -1.5 V in regard to the saturated calomel electrode (Sawyer and Gibian 1979). The superoxide ion occupies an intermediate position in the following redox triad O2 —> 02 —> In accordance with such a position, the superoxide ion... 

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