Ferricytochrome

Finzel, B.C., et al. Stmcture of ferricytochrome c from Rhodospirillum molischianiim at 1.67 A resolution. 

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... 

Fig. 40. Far-UV CD spectra of /Flactamase from Bacillus cereus (A), horse apomyo-globin (B), and horse ferricytochrome c (C) as a function of HC1 concentration. Protein concentrations were 10 fiM. The numbers refer to the HC1 concentration (mM). The spectra of the native state (A), the A state induced by KC1, pH ss 2), (O) and GdmCl-unfolded state (4-5 M GdmCl, 25 mM phosphate buffer, pH 7.0) ( ) are shown for comparison. From Goto et al (1990a). 1990, with permission of the authors.

FIGURE 5.3 Axial anisotropy in an S = 1/2 system. A simplified representation is drawn of the porphyrin prosthetic group in low-spin ferricytochrome c in a magnet (Hagen 2006). (Reproduced by permission of The Royal Society of Chemistry.)... 

G. Fiandaca, E. Vitrano, and A. Cupane, Ferricytochrome c encapsulated in silica nanoparticles structural stability and functional properties. Biopolymers 74, 55—59 (2004). 

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. 

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

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],... 

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). 

In addition to the effect of mutations at Phe-82 on the stability of the cytochrome c active site, the intense, negative Soret Cotton effect in the circular dichroism spectrum of ferricytochrome c is profoundly affected by the presence of non-aromatic amino acid residues at this position [115]. Recent examination of six position-82 iso-l-ferricytochrome c mutants establishes that while Tyr-82 exhibits a Soret CD spectrum closely similar to that of the wild-type protein, the intensity of the negative Soret Cotton affect varies with the identity of the residue at this position in the order Phe > Tyr > Gly > Ser = Ala > Leu > He, though the Ser, Ala, He, and Leu variants have effectively no negative Soret Cotton effect [108]. 

The absorbance changes shown below occur for the reaction of the radicals with penta-ammine(histidine-33)ruthenium(III) ferricytochrome c, PFe "-Ru" (see (5.84)). The final product is PFe Ru ". Absorbance increases at 550 nm are largely as a result of the step PFe " PFe . Interpret the changes (particularly the relative absorbances associated with the very fast and slower absorbances). 

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. 

This enzyme [EC 1.10.2.1] catalyzes the reaction of ascorbate with ferricytochrome bs to yield monodehydroasc-orbate and ferrocytochrome bs. 

This enzyme [EC 1.12.2.1], also called hydrogenase, catalyzes the reaction of H2 with two ferricytochrome C3 to produce two H+ and two ferrocytochrome C3. The enzyme uses iron ions as well as a cofactor. Methylene blue... 

This enzyme [EC 1.9.3.1] (also referred to as cytochrome cytochrome oxidase) catalyzes the reaction of four ferrocytochrome c with dioxygen to produce four ferricytochrome c and two water molecules. This protein also contains copper ions as cofactors. 

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.,... 

This FAD-dependent enzyme [EC 1.1.2.4] catalyzes the reaction of (R)-lactate with two ferricytochrome c to produce pyruvate and two ferrocytochrome c. 

Nitrite reductase (NAD(P)H) [EC 1.6.6.4] catalyzes the reaction of three NAD(P)H with nitrite to yield three NAD(P)+, NH4OH, and water. Cofactors for this enzyme include FAD, non-heme iron, and siroheme. (2) Nitrite reductase (cytochrome) [EC 1.7.2.1] is a copper-depen-dent system that catalyzes the reaction of nitric oxide with two ferricytochrome c and water to produce nitrite and two ferrocytochrome c. (3) Ferredoxin-nitrite reductase [EC 1.7.7.1], a heme- and iron-dependent enzyme, catalyzes the reaction of ammonia with three oxidized ferredoxin to produce nitrite and three reduced ferredoxin. (4) Nitrite reductase [EC 1.7.99.3] is a copper- and FAD-dependent enzyme that catalyzes the reaction of two nitric oxide with an acceptor substrate and two water to produce two nitrite and the reduced acceptor. 

This enzyme complex [EC 1.10.2.2], also known as cytochrome bci and complex 111, catalyzes the reaction of ubiquinol (QH2) with two ferricytochrome c to produce ubiquinone (Q) and two ferrocytochrome c. The complex also contains cytochrome h-562, cytochrome h-566, cytochrome Ci, and a two-iron ferredoxin. 

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