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PubMed1996

[Ferrous compounds].

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Anemia, Iron-Deficiency↗
PubMed2004

Kinetic isotope effects implicate the iron-oxene as the sole oxidant in P450-catalyzed N-dealkylation.

Multiple oxidants have been implicated as playing a role in cytochrome P450-mediated oxidations. Herein, we report results on N-dealkylation, one of the most facile reactions mediated by P450 enzymes. We have employed the N-oxides of a series of para-substituted 13C2H2-labeled N,N-dimethylanilines to function as both substrates and surrogate oxygen atom donors for P450cam and P4502E1. Kinetic isotope effect profiles obtained using the N-oxide system were found to closely match the profiles produced using the complete NAD(P)H/NAD(P)-P450 reductase/O2 system. The results are consistent with oxidation occurring solely through an iron-oxene species.

Alkylation↗
PubMed2003

Longevity of granular iron in groundwater treatment processes: solution composition effects on reduction of organohalides and nitroaromatic compounds.

Although granular iron permeable reactive barriers (PRBs) are increasingly employed to contain subsurface contaminants, information pertaining to system longevity is sparse. The present investigation redresses this situation by examining the long-term effects of carbonate, silica, chloride, and natural organic matter (NOM) on reactivity of Master Builders iron toward organohalides and nitroaromatic contaminants. Six columns were operated for 1100 days (approximately 4500 pore volumes) and five others for 407 days (approximately 1800 pore volumes). Nine were continuously exposed to mixtures of contaminant species, while the other two were only intermittently exposed in order to differentiate deactivation induced by water (and inorganic cosolutes) from that resulting from contaminant reduction. Contaminants investigated were trichloroethylene, 1,2,3-trichloropropane, 1,1-dichloroethane, 2-nitrotoluene, 4-nitroacetophenone, and 4-nitroanisole. Column reactivity declined substantially over the first 300 days and was dependent on the feed solution chemistry. High carbonate concentrations enhanced reactivity slightly within the first 90 days but produced poorer performance over the long term. Both silica and NOM adversely affected reactivity, while chloride evinced a somewhat mixed effect. Observed contrasts in relative reactivities suggest that trichloroethylene, 1,2,3-trichloropropane, and nitroaromatic compounds all react at different types of reactive sites. Our results indicate that differences in groundwater chemistry should be considered in the PRB design process.

Chlorides↗
PubMed2005

EXAFS analysis of arsenite adsorption onto two-line ferrihydrite, hematite, goethite, and lepidocrocite.

The modes of As(III) sorption onto two-line ferrihydrite (Fh), hematite (Hm), goethite (Gt), and lepidocrocite (Lp) have been investigated under anoxic condition using X-ray absorption spectroscopy (XAS). X-ray absorption near-edge structure spectroscopy (XANES) indicates that the absence of oxygen minimized As(III) oxidation due to Fenton reactions. Extended X-ray absorption fine structure spectroscopy (EXAFS) indicates thatAs(III)forms similar inner-sphere surface complexes on two-line ferrihydrite and hematite that differ from those formed on goethite and lepidocrocite. At high surface coverage, the dominant complex types on Fh and Hm are bidentate mononuclear edge-sharing (2E) and bidentate binuclear corner-sharing (2C), with As-Fe distances of 2.90 +/- 0.05 and 3.35 +/- 0.05 A, respectively. The same surface complexes are observed for ferrihydrite at low surface coverage. In contrast, As(III) forms dominantly bidentate binuclear corner-sharing (2C) sorption complexes on Gt and Lp [d(As-Fe) = 3.3-3.4 A], with a minor amount of monodentate mononuclear corner-sharing (1V) complexes [d(As-Fe) = 3.5-3.6 A]. Bidentate mononuclear edge-sharing (2E) complexes are virtually absent in Gt and Lp at the high surface coverages that were investigated in the present study. These results are compared with available literature data and discussed in terms of the reactivity of iron(III) (oxyhydr)oxide surface sites.

Adsorption↗
PubMed1978

Metronidazole (Flagyl), misonidazole (Ro 07-0582), iron, zinc and sulphur compounds in cancer therapy.

The nitro radiosensitizers, metronidazole and misonidazole, have been shown to react rapidly with the sulphydryl compounds cysteine and cysteamine in the presence of ferrous ions. Similar reactions occur in the presence of copper ions but these are much slower. The initial interactions of the drugs and of oxygen with an iron-cysteine complex are extremely rapid: in the case of oxygen reaction half-lives of 27 ms have been measured. Misonidazole also reacts rapidly with glutathione in the presence of ferrous ions and is subsequently reduced: metronidazole is reduced only slowly if at all. These reactions, which have been found to be inhibited by high concentrations of zince ions, are discussed in the light of the known radiosensitizing and chemotherapeutic efficiencies of the nitro drugs and the side effect of peripheral neuropathy sometimes observed during their clinical use.

Cysteamine↗