Incorporation of iron

Formation of Heme Involves Incorporation of Iron Into Protoporphyrin... 

In the enterocyte as it enters the absorptive zone near to the villus tips, dietary iron is absorbed either directly as Fe(II) after reduction in the gastrointestinal tract by reductants like ascorbate, or after reduction of Fe(III) by the apical membrane ferrireductase Dcytb, via the divalent transporter Nramp2 (DCT1). Alternatively, haem is taken up at the apical surface, perhaps via a receptor, and is degraded by haem oxygenase to release Fe(II) into the same intracellular pool. The setting of IRPs (which are assumed to act as iron biosensors) determines the amount of iron that is retained within the enterocyte as ferritin, and that which is transferred to the circulation. This latter process is presumed to involve IREG 1 (ferroportin) and the GPI-linked hephaestin at the basolateral membrane with incorporation of iron into apotransferrin. (b) A representation of iron absorption in HFE-related haemochromatosis. 

Thin films of a composite nickel-iron (9 1 Ni/Fe ratio) and iron-free oxyhydroxides were deposited from metal nitrate solutions onto Ni foils by electroprecipitation at constant current density. A comparison of the cyclic voltammetry of such films in 1M KOH at room temperature (see Fig. 6) shows that the incorporation of iron in the lattice shifts the potentials associated formally with the Ni00H/Ni(0H)2 redox processes towards negative potentials, and decreases considerably the onset potential for oxygen evolution. The oxidation peak, as shown in the voltammo-gram, is much larger than the reduction counterpart, providing evidence that within the time scale of the cyclic voltammetry, a fraction of the nickel sites remains in the oxidized state at potentials more negative than the reduction peak. 

Desai et al. [86] reported on the photolytic degradation of the anti-viral, sorivudine, which formed the inactive Z-isomer. On the basis of extensive dmg-excipient compatibility studies it was found that the incorporation of iron oxide pigments into the blends (direct compression or wet granulated) stabilised the dmg to photodegradation indeed, so much so that the tablet was found not to require a film coat. The data are summarised in Table 2.6. 

The incorporation of iron(II) into the protoporphyrin IX ring, the final step in heme biosynthesis, is catalyzed by ferrochelatase. Kinetic parameters were reported both for this process and for the reaction of Fe " with ferrochelatase, whose kinetics were used to characterize the latter. ... 

Iron(III) citrate, " " or iron(III) ammonium citrate, is the usual vehicle for administering supplementary iron to an iron-deficient patient, for inducing iron-overload in rats or other creatures prior to testing the efficacy of iron chelators, or for introducing the isotope Fe for metabolic tracer studies. Stability constants for the aqueous iron(III)-citrate system have been established. " The 2 1 complex is claimed to be the dominant species in iron(III)/citrate/DMF systems. " There has been a very qualitative study of the incorporation of iron into transferrin from iron citrate. " Iron(III) citrate reacts relatively slowly with the aluminum(III)-transferrin complex to give the thermodynamically strongly favored combination of iron(III)-transferrin with aluminum(lll) citrate. " The mechanism of iron uptake from citrate complexes in cells has been briefly discussed. An octa-iron citrate complex appears in Section 5.4.5.4.3 below. 

Laux Process. This is a modification of the Bechamp process for the iron reduction of nitrobenzene to aniline which leaves iron oxide as the residue. Incorporation of iron or aluminium chlorides into the reduction process produces high quality yellow and red iron oxide pigments... 

Steinbiichel A, Muller M (1986) Anaerobic pyruvate metabolism of Tritrichomonas foetus and Trichomonas vaginalis hydrogenosomes. Mol Biochem Parasitol 20 57-65 Suchan P et al. (2003) Incorporation of iron into Tritrichomonas foetus cell compartments reveals ferredoxin as a major iron-binding protein in hydrogenosomes. Microbiology 149 1911-1921... 

These results show that technetium can be contained by magnetite in the geosphere, provided reducing conditions can be maintained. This can be aided, for example, by the incorporation of iron or iron oxides in the buffer and backfill materials in the waste disposal vault. 

Since this review was originally completed, Foster (1969) published a review in which similar conclusions are drawn about the glauconites and celadonites. The lack of correlation between iron and potassium content in glauconite is substantiated in her paper. Foster considered the process of glauconitization to be of two separate, unrelated processes, incorporation of iron into the crystal structure and fixation of potassium in interlayer positions, with incorporation of iron and development of negative layer charge preceding complete fixation of potassium . 

Komlosi, A., E. Kuzmann, N. M. Nagy, Z. Homonnay, S. Kubuki, and J. Konya. 2007. Interlayer incorporation of iron into Na-bentonite via treatment with FeCl3 in acetone. Clays Clay Miner. 55 91-97. 

The early, dose-related type of chloramphenicol toxicity is usually seen after the second week of treatment, and is characterized by inhibited proliferation of erythroid cells and reduced incorporation of iron into heme. The clinical correlates in the peripheral blood are anemia, reticulo-cytopenia, normoblastosis, and a shift to early erythrocyte forms. The plasma iron concentration is increased. Early erythroid forms and granulocyte precursors show cytoplasmic vacuolation. After withdrawal, complete recovery is the rule. Leukopenia and thrombocytopenia are less frequent. 

Copper-dependent enzymes include tyrosinase (which is involved in melanin pigment formation) and the various oxidases (i.e., cytochrome oxidase, superoxide dismutase, amine oxidase, and uricase). Copper plays a major role in the incorporation of iron into the heme of hemoglobin. Copper deficiency is characterized by hypochromic, microcytic anemia resulting from defective hemoglobin synthesis. 

Since the roles played by iron are so diverse, we clearly cannot cover aU of them, so we have chosen only to give a small sample of selected illustrations. The incorporation of iron into porphyrins and Fe—S clusters has already been discussed in Chapter 4. 

The use of carbon whiskers instead of graphite as the host cathode material markedly improved the rate of oxygenation of cyclohexane and benzene, especially for cathodes containing iron compounds and Pd black [15]. The incorporation of iron compounds together with Pd black showed a marked... 

The evidence for association of the iron atoms with platinum in samples similar to B has been discussed elsewhere in some detail (55). Incorporation of iron atoms into the platinum clusters is indicated by the agreement of the isomer shift for iron in the catalyst with that for iron in a PtFe bulk alloy of similar composition. In addition, it is found that the iron in samples such as B, after reduction at 500°C, exhibits a unique chemical behavior in that it can be reversibly oxidized and reduced at room temperature. This property appears to be characteristic of iron in association with metals such as platinum and palladium (54-57). It is not observed when the iron is present by itself on alumina. 

P-17 - Influence of alcali cations on the incorporation of iron into MFI structure in fluoride media... 

---