Role of Iron

The abihty of iron to exist in two stable oxidation states, ie, the ferrous, Fe ", and ferric, Fe ", states in aqueous solutions, is important to the role of iron as a biocatalyst (79) (see Iron compounds). Although the cytochromes of the electron-transport chain contain porphyrins like hemoglobin and myoglobin, the iron ions therein are involved in oxidation—reduction reactions (78). Catalase is a tetramer containing four atoms of iron peroxidase is a monomer having one atom of iron. The iron in these enzymes also undergoes oxidation and reduction (80). 

Other non-haem proteins, distinct from the above iron-sulfur proteins are involved in the roles of iron transport and storage. Iron is absorbed as Fe" in the human duodenum and passes into the blood as the Fe protein, transferrin, The Fe is in a distorted octahedral environment consisting of 1 x N, 3x0 and a chelating carbonate ion which... 

The role of iron sulfides in regulating sediment interstitial water concentrations is shown by the following reactions (Di Toro et ai, 1990) ... 

Nelson, M. B., Davis, J. A., Benjamin, M. M. and Leckie, J. O. (1977). The Role of Iron Sulfides in Controlling Trace Heavy Metals in Anaerobic Sediments Oxidative Dissolution of Ferrous Monosulfides and the Behavior of Associated Trace Metals." Air Force Weapons Laboratory, Technical Report 425. 

Scheme 8 Catalytic role of iron in cycloisomerization reactions [17]...

Pyysalo, H. and Kuusi, T., The role of iron and tin in discoloration of berry and red beet juices, Ztschr. Lebensm. Unters. Forsch., 153, 224, 1973. 

The hydroxyl radical plays two essentially different roles (a) as a reactant mediating the transformations of xenobiotics and (b) as a toxicant that damages DNA. They are important in a number of environments (1) in aquatic systems under irradiation, (2) in the troposphere, which is discussed later, and (3) in biological systems in the context of superoxide dismutase and the role of iron. Hydroxyl radicals in aqueous media can be generated by several mechanisms ... 

Chen D, PA Frey (1998) Phenylalanine hydroxylase from Chromobacterium violaceum. Uncoupled oxidation of tetrahydropterin and the role of iron in hydroxylation. J Biol Chem 273 25594-25601. 

Ben-Shackar, D., Eshel, G., Riederer, P. and Youdim, M.B.H. (1992). Role of iron and iron chelation in dopaminergic-induced neurodegeneration implications for Parkinson s disease. Ann. Neurol. 32, S105-S110. 

Minotti, G. and Aust, S.D. (1987). The role of iron in the initiation of lipid peroxidation. Chem. Phys. Lipids 44, 191-208. 

The role of iron in an acute model of skin inflammation induced by reactive oxygen species (ROS). Br. J. Dermatol. 126, 250-256. 

Younes, M. and Strubelt, O. (1990). The role of iron and glutathione in t-butyl hydroperoxide-induced damage towards isolated perfused rat livers. J. Appl. Toxicol. 10, 319-324. 

In addition to the well-characterized role of iron in catalysing redox interactions, other metallic contaminants, for example, nickel, may also contribute. In vivo toxicity studies have demonstrated the capacity of nickel particulate compounds to induce tumours following intraperitoneal injection (Pott etal., 1987). Such activity is proportional to their phagocytic uptake, and to the associated respiratory burst and generation of PMN-derived reactive oxygen metabolites (ROMs), a proposed pathogenic mechanism (Evans et al., 1992a). 

Osmond JK, Ivanovich M (1992) Uraninm series mobilization and surface hydrology. In Uranium-series disequihbrium. Ivanovich M, Harmon RS (eds) Clarendon Press, Oxford, p 259-289 Payne XE, Davis JA, Waite XD (1994) Uranium retention by weathered schists—the role of iron minerals. Radiochim Acta 66/67 297-303... 

The feature of xanthine oxidase which is no doubt of the greatest chemical interest, is the presence of several non-protein components. Much effort has been expended in attempting to elucidate the respective roles of iron, flavin and molybdenum in the various enzyme catalysed reactions. Numerous studies of the iron constituent have been made of late (45, 46, 47, 48, 49, 50), it having been found to be of the iron-sulphur (51 a, 51 b) type. Neither iron (19) nor molybdenum (31) can be removed reversibly from the enzyme, though the FAD can be (52, see below). 

Gilmour, P.S. et al. (1997) Free radical activity of industrial fibers role of iron in oxidative stress and activation of transcription factors. Environmental Health Perspectives, 105, 1313-1317. 

Kagan, V.E. et al. (2006) Direct and indirect effects of single walled carbon nanotubes on RAW 264.7 macrophages role of iron. Toxicology Letters, 165 (1), 88-100. 

The Role of Iron-related Genes on the Risk and Outcome of Infection... 

This situation may be about to change as we look at the role of iron and its implications in the formation of reactive oxygen species, with their potential to attack, modify, and ultimately destroy cells. The signalling function of ROS, not to mention RNS, has been underlined earlier. Yet, we tread a delicate, and poorly understood balance between low levels of ROS, required both for cell signalling and to maintain the antioxidative defences of the cell in a state of alert1"1, and levels which become toxic. This remains an extremely important area of therapeutic concern, since oxidative stress, whether proven to be due to iron or not, is... 

Low-valent cobalt pyridine complexes, electrogenerated from CoCl2 in DMF containing pyridine and associated with a sacrificial zinc anode, are also able to activate aryl halides to form arylzinc halides.223 This electrocatalytic system has also been applied to the addition of aryl bromides containing an electron-withdrawing group onto activated alkenes224 and to the synthesis of 4-phenylquinoline derivatives from phenyl halides and 4-chloroquinoline.225 Since the use of iron as anode appeared necessary, the role of iron ions in the catalytic system remains to be elucidated. 

Halliwell, B., and Gutteridge, J.M. (1984) Role of iron in oxygen radical reactions. Meth. Enzymol. 105, 47-56. 

Of the metals that were just listed as the major participants in biochemical functions, some (such as Mg and Zn) rarely change oxidation states. Therefore, metals such as these are involved in processes in which there is no redox chemistry taking place. These metals function in some other way. On the other hand, metals such as Fe, Mn, Mo, and Cu can change oxidation states more easily, so they are the metals that participate in redox reactions. For example, the role of iron in oxygen transport requires it to bond to oxygen and thereby, at least formally, to become oxidized in the process. There are other instances of this type of behavior. As mentioned earlier, the list of metals that are involved in the vast majority of biochemical processes is not a particularly long one. 

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