Iron redox

C20-0073. Draw a crystal field splitting diagram that illustrates the electron transfer reaction of the simple iron redox protein shown in Figure 20-29a. 

Hard, S. and Kanner, J. (1989). Haemoglobin and myoglobin as inhibitors of hydroxyl radical generation in a model system of iron redox cycle. Free Rad. Res. Commun, 6, 1-10. 

Nitric Oxide Synthase 266 4.5 Iron Redox Cycle Modifiers 272... 

Figure 4. Conceptual model of iron redox chemistry in hematite suspensions containing S(IV). (Reproduced from Ref. 42. Copyright 1985, American Chemical Society.)...

Figure 3.22 (a) Cyclic voltammogram of myoglobin covalently attached to a CNT forest in PBS solution under nitrogen atmosphere. The reversible redox behavior of the iron redox center is observed, (b) and (c) electrocatalytic response of Myoglobin/CNT forest electrode to oxygen and peroxide... 

Glass, B.L. Relation between the degradation of DDT and the iron redox system in soils. J. Agric. Food Chem., 20(2) 324-327, 1972. 

Cytochrome c contains a heme iron, which is reduced by MV from Fe(III) to Fe(II). The unreactivity of cytochrome c at the electrode is possible due to physical isolation of the iron redox center from the electrode by the surrounding protein structure. 

Cotner, J. B., and R. T. Heath. 1990. Iron redox effects on photosensitive phosphorus release from dissolved humic materials. Limnology and Oceanography 35 1175-1181. 

Voelker, B. M., F. M. M. Morel, and B. Sulzberger. 1997. Iron redox cycling in surface waters Effects of humic substances and light. Environmental Science Technology 31 1004-1011. 

Spectrophotometric techniques combined with flow injection analysis (FIA) and on-line preconcentration can meet the required detection limits for natural Fe concentrations in aquatic systems (Table 7.2) by also using very specific and sensitive ligands, such as ferrozine [3-(2-bipyridyl)-5,6-bis(4-phenylsulfonic acid)-l,2,4-triazine], that selectively bind Fe(II). Determining Fe(II) as well as the total Fe after on-line reduction of Fe(III) to Fe(II) with ascorbic acid allows a kind of speciation.37 A drawback is that the selective complexing agents can shift the iron redox speciation in the sample. For example, several researchers have reported a tendency for ferrozine to reduce Fe(III) to Fe(II) under certain conditions.76 Most ferrozine methods involve sample acidification, which may also promote reduction of Fe(III) in the sample. Fe(II) is a transient species in most seawater environments and is rapidly oxidized to Fe(III) therefore, unacidified samples are required in order to maintain redox integrity.8 An alternative is to couple FIA with a chemiluminescence reaction.77-78... 

Figure 4. Distribution of dissolved iron redox species for varying concentrations of reduced and oxidized iron, (a) Hornet effluent (b) Boulder Creek (c) Spring Creek (d) Spring Creek reservoir. Analyses for these four sarriples are...

Rose, A. L., and Waite, T. D. (2003). Predicting iron speciation in coastal waters from the kinetics of sunhght-mediated iron redox cycling. Aquat. Sd. 65, 375—383. 

Nonheme nonPeS iron Redox catalyst—O2 carrier... 

The function of the chelator is to complex the ferrous ion and thus limit the concentration of free iron. Redox systems appear very versatile, permitting polymerization at ambient temperatures and the possibility of control of the rate of radical initiation versus polymerization time. This would thus permit control of heal generation and the minimization of reaction time. The use of the redox system ammonium persulfate (2 mmol) together with sodium pyrosulfite (Na S Oj 2.5 mmol) together with copper sulfate (0.002 mmol) buffered with sodium bicarbonate in I liter of water form an effective redox system for vinyl acetate emulsion polymerization. The reaction was started at 25 C and run nonisothermally to 70 C. The time to almost complete conversion was 30 min (Warson, 1976 and Edelhauser, 1975). 

Voelker B. M., Morel E. M. M., and Sulzberger B. (1997) Iron redox cychng in surface waters effects of humic substances and hght. Environ. Sci. Technol. 31, 1(X)4—1017. 

Kanner, J., I Earel, 5., and Hazan, B. (1986). Muscle membranal lipid peroxidation by an "iron redox cycle." /. Agrk- Food Chem. 34, 506-510. 

Superoxide generated by xanthine oxidase or in the redox cycling of paraquat can cause the reductive release of F3 from ferritin, a process that is dependent on the activity of microsomal NADPH-cytochrome P-450 reductase [119]. Iron appears to be an essential component in the formation of reactive species such as superoxide and hydroxyl radical via redox cycling of cephaloridine. Addition of EDTA or of the specific iron chelator desferrioxamine to an incubation system containing renal cortex microsomes and cephaloridine depressed cephaloridine-induced peroxidation of microsomal lipids significantly EDTA showed a weaker effect than desferrioxamine at equimolar concentrations. By chelating F3 preferentially [120], desferrioxamine reduced the availability of F2 produced by the iron redox cycle and decreased cephaloridine-stimu-lated peroxidation of membrane lipids [36, 37]. 

Heguy, D. L. and Nagl, G. J., Consider Optimized Iron-Redox Processes to Remove Sulfur, Hydrocarbon Processing, January 2003. 

Bou-Abdallah, F. (2010). The iron redox and hydrolysis chemistry of the ferritins. Biochimica et Biophysica Acta, 1800, 719—731. Crichton, R. R., Declercq, J. R (2010). X-ray structures of ferritins and related proteins. Biochimica et Biophysica Acta, 1800, 706-718. 

It looks reasonable to hypothesize that globally ubiquitous iron oxides were incorporated into life development from the early evolutionary stage, but subsequent to the synthesis of simple amines and organic acids. The diffusion of sulfide across primitive membranes is also meaningful for the maintenance of the thioester world . An intracellular iron redox cycle, driven possibly by light and sulfide, could have supported chemosynthesis. Iron respiration and photometabolism could have processed on the external surface of vesicles. This would have contributed to a vectorial transport of thioesters and protons into vesicles and accordingly to the development of the early protonmotive transport system. 

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