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Ferricytochrome reduction

An alternative application of flash photolysis to study myoglobin electron transfer kinetics has been employed by Hofifinan and co-workers 156). In this approach, the photoactive zinc-substituted derivative of Mb is mixed with an equivalent amoimt of ferricytochrome bs to form an electrostatically stabilized binary complex. Upon transient irradiation, the strongly reducing Zn-Mb intermediate is formed, and the kinetics of ferricytochrome reduction within the preformed complex can be monitored spectrophotometrically. The resulting kinetics represents a mixed-order process consistent with electron transfer both within the electrostatically stabilized complex and between the dissociated components of the complex. [Pg.17]

Fig. 3.12 The dependence on pH of the oxidation-reduction potential for c0x = cRcd (1) 6-dibromphenol indophenol, (2) Lauth s violet, (3) methylene blue, (4) ferricytochrome c/ferrocytochrome c, (5) indigo-carmine... [Pg.196]

At present, new developments challenge previous ideas concerning the role of nitric oxide in oxidative processes. The capacity of nitric oxide to oxidize substrates by a one-electron transfer mechanism was supported by the suggestion that its reduction potential is positive and relatively high. However, recent determinations based on the combination of quantum mechanical calculations, cyclic voltammetry, and chemical experiments suggest that °(NO/ NO-) = —0.8 0.2 V [56]. This new value of the NO reduction potential apparently denies the possibility for NO to react as a one-electron oxidant with biomolecules. However, it should be noted that such reactions are described in several studies. Thus, Sharpe and Cooper [57] showed that nitric oxide oxidized ferrocytochrome c to ferricytochrome c to form nitroxyl anion. These authors also proposed that the nitroxyl anion formed subsequently reacted with dioxygen, yielding peroxynitrite. If it is true, then Reactions (24) and (25) may represent a new pathway of peroxynitrite formation in mitochondria without the participation of superoxide. [Pg.698]

Gramicidin was found to uncouple the phosphorylation of ADP from the enzymatic reduction of ferricytochrome C167,168,169,170,171,172,173,174,175 ... [Pg.203]

In a bulk silica matrix that differs from the silica nanomatrix regarding only the matrix size but has a similar network structure of silica, several kinetic parameters have been studied and the results demonstrated a diffusion controlled mechanism for penetration of other species into the silica matrix [89-93]. When the silica is used as a catalyst matrix in the liquid phase, slow diffusion of reactants to the catalytic sites within the silica rendered the reaction diffusion controlled [90]. It was also reported that the reduction rate of encapsulated ferricytochrome by sodium dithionite decreased in a bulk silica matrix by an order of magnitude compared to its original reaction rate in a homogeneous solution [89], In gas-phase reactions in the silica matrix, diffusion limitations were observed occasionally [93],... [Pg.245]

Given that oxidative injury plays an important role in central nervous system (CNS) degenerative diseases, novel drags that protect cells from cytopathic effects of ROS could conceivably be used to treat some of these devastating illnesses. To screen for possible neuroprotective drags, a variety of standardized test systems have been designed mostly based on the in situ generation of superoxide by xanthine/xanthine oxidase. Superoxide decomposition may be followed photometrically by the reduction of ferricytochrome c, as it was reported by McCord and Fridovich (McCord and Fridovich, 1969). [Pg.64]

This enzyme [EC 1.6.2.4] (also referred to as NADPH ferrihemoprotein reductase, NADPHxyto-chrome P450 reductase, TPNH2 cytochrome c reductase, and ferrihemoprotein P450 reductase) catalyzes the reaction of NADPH with two ferricytochrome to produce NADP+ and two ferrocytochrome. The protein requires FMN and FAD. In addition, it also catalyzes the reduction of heme-thiolate-dependent monooxygenases (e.g.,... [Pg.182]

Ferricytochrome c, 32 49 NIR MCD spectrum, 36 233-234 Ferrihemoproteins, reduction rates, 36 430-431 Ferrihydrite, 36 422 chemical composition, 36 455 inside apoferritin cavity, 36 459 mineralization in iron storage proteins, 36 161-164... [Pg.102]

At high fields the NMR spectrum of cyanoferricytochrome c contains resolved hyperfine-shifted fines at +1.2 and +4.4 ppm (Fig. 29). Upon addition of dithionite these fines, as well as the resonances between —10 and —30 ppm, disappear immediately, indicating fast reduction to the diamagnetic ferrous oxidation state. The primary reaction product has no proton resonances at higher field than +1 ppm. However, with time elapsing after the reduction the NMR spectrum of ferrocytochrome c appears slowly. On the other hand the entire ferrocytochrome c spectrum was observed immediately after reduction of ferricytochrome c. [Pg.100]

Experimental evidence that supports HNO as the sole initial reactive species from decomposition of donors under biological conditions include the pH independence of dihydrorhodamine (DHR) oxidation (fluorescent assay) and ferricytochrome c (ferricyt c) reduction (colorimetric assay) (147, 167). Oxidant formation or substrate reduction would be expected to be mediated by NO-rather than HNO due to the rapid autoxidation of NO- to ONOO- (Eq. 9) and the relative reduction potentials. The slow deprotonation of HNO to NO- has been shown to proceed through base catalysis [5 x 104AT1 s-1[OH-] (106)],... [Pg.364]

Cyanide bonds to the iron(III) of the ferricytochrome enzyme, preventing its reduction to iron(II) in the first of the two reactions above. The result is that ferrouscytochrome oxidase, which is required to react with 02, is not formed and utilization of oxygen in cells is prevented, leading to rapid cessation of metabolic processes. The decreased utilization of oxygen in tissue results in a... [Pg.252]

S. H. Northrup, K. A. Thomasson, C. M. Miller, P. D. Barker, L. D. Eltis, J. G. Guillemette, S. C. Inglis and A. G. Mauk, Effects of charged amino-acid mutations on the bimolecular kinetics of reduction of yeast iso-1-ferricytochrome-C by bovine cytochrome-B(5), Biochemistry, 32 (1993) 6613-6623. [Pg.828]

Examples of studies involving small molecules or ions as substrates include the reduction of ferricytochrome c by ascorbate and Cr, and the oxidation of ferrocytochrome c (and C551)... [Pg.621]

Several papers have appeared on the electrochemical behaviour of molybdenum cysteine complexes and the reduction of ferricytochrome c by two molyb-... [Pg.153]

Hydroxylamine oxidoreductase was first purified by Hooper and Nason in 1965. They found that the enzyme catalyzed the reduction of horse ferricytochrome c with hydroxylamine but they found little nitrous acid formed as the result of the reaction nitrite formed was approximately 5% as much as cytochrome c reduced in 0.1 M glycine-NaOH buffer, pH 9.8. As the ammonia-oxidizing bacteria oxidize hydroxylamine to nitrite, they thought that one or more enzymes in addition to the oxidoreductase might participate in the oxidation of hydroxylamine to nitrite or additional factor(s) might be necessary for changing hydroxylamine to nitrite (Hooper et al., 1977). [Pg.22]

Indeed, it has been reported by Arciero et al. (1991) that the enzymatic reduction rate of ferricytochrome c-554 with hydroxylamine is 10 times as fast as that of the ferricytochrome with NOH. Moreover, it has been confirmed by Andersson and Hooper (1983) that the enzymatic oxidation of hydroxylamine to nitrite proceeds in two steps as mentioned above. [Pg.23]


See other pages where Ferricytochrome reduction is mentioned: [Pg.129]    [Pg.150]    [Pg.154]    [Pg.170]    [Pg.196]    [Pg.81]    [Pg.204]    [Pg.414]    [Pg.415]    [Pg.416]    [Pg.263]    [Pg.621]    [Pg.154]    [Pg.170]    [Pg.171]    [Pg.172]    [Pg.206]    [Pg.297]    [Pg.75]    [Pg.352]    [Pg.80]    [Pg.293]    [Pg.107]    [Pg.3548]    [Pg.208]    [Pg.352]    [Pg.320]    [Pg.297]    [Pg.97]    [Pg.98]    [Pg.101]   
See also in sourсe #XX -- [ Pg.621 ]

See also in sourсe #XX -- [ Pg.621 ]

See also in sourсe #XX -- [ Pg.6 , Pg.621 ]




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Ferricytochrome

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