Inhibition ferrous, ferric

I. The oxidation pathway and inhibition of the ferrous-ferric oxidation. Reclamation and Revegetation Research, 4, 279-291. 

The chemical change in the Fricke dosimeter is the oxidation of ferrous ions in acidic aerated solutions. It is prepared from a -1 mM solution of ferrous or fer-roammonium sulfate with 1 mM NaCl in air-saturated 0.4 M H2S04. Addition of the chloride inhibits the oxidation of ferrous ions by organic impurities, so that elaborate reagent purification is not necessary. Nevertheless, the use of redistilled water is recommended for each extensive use. Absorption due to the ferric ion is monitored at its peak -304-305 nm. The dose in the solution is calculated from the formula... 

The mechanism of iron-initiated superoxide-dependent lipid peroxidation has been extensively studied by Aust and his coworkers [15-18]. It was found that superoxide produced by xanthine oxidase initiated lipid peroxidation, but this reaction was not inhibited by hydroxyl radical scavengers and, therefore the formation of hydroxyl radicals was unimportant. Lipid peroxidation depended on the Fe3+/Fe2+ ratio, with 50 50 as the optimal value [19]. Superoxide supposedly stimulated peroxidation both by reducing ferric ions and oxidizing ferrous ions. As superoxide is able to release iron from ferritin, superoxide-promoted lipid peroxidation can probably proceed under in vivo conditions [16,20]. 

It has already been mentioned earlier that similar to LOXs, prostaglandin H synthases can be activated or inhibited by reactive nitrogen species. Nitric oxide may exhibit the inhibitory [58,65,86,101 104] or stimulatory effects [105 110] on PGHSs. Inhibitory effects depend on the ability of nitric oxide to reduce the ferric enzyme to the inactive ferrous form, competition... 

Iron absorption occurs predominantly in the duodenum and upper jejunum. The physical state of iron entering the duodenum greatly influences its absorption. At physiological pH, ferrous iron is rapidly oxidized to the insoluble ferric form. Gastric acid lowers the pH in the proximal duodenum, enhancing the solubility and uptake of ferric iron. When gastric acid production is impaired, iron absorption is reduced substantially. Ascorbic acid enhances iron absorption. Ascorbic acid mobilizes iron from iron-binding proteins in vivo, which in turn could catalyze lipid peroxidation. Iron absorption is inhibited by antacids, phytates, phosphates and tetracyclines. 

Asan, T., and Solberg, M. (1976). Inhibition of ClosCridium perfringens by heated combinations of nitrite, sulfur, and ferrous or ferric ions. Appl. Environ. Microbiol. 31, 49-52. 

The Fe atoms of the cytochromes undergo oxidation and reduction during respiration, cycling between the ferrous (Fe2+) and ferric (Fe3+) oxidation states. The absorption spectra of the oxidized and reduced forms differ (fig. 14.4). In the 1930s, David Keilin used this property to measure the oxidation-reduction states of cytochromes in living cells. Under anaerobic conditions, the cytochromes rapidly became reduced in the presence of 02, they became oxidized. Certain molecules that inhibited respiration (CO, N3, or CN ) blocked the oxidation other inhibitors (amy-tal, rotenone, and malonate) blocked the reduction. Keilin found that the transfer of electrons from cytochrome c to 02... 

The higher stability of ferrous heme nitrosyl complexes compared to the corresponding ferric species is well documented [see Refs (44-46, 69) for reviews]. Since cytochrome P450, catalase, and cytochrome c oxidase are commonly associated with reducing agents, a mechanism exists for longer term inhibition of the activity of these proteins. 

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