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Ferrous Iron (ferrous + iron)
Terms modified by Ferrous Iron Selected AbstractsWeathering control over geomorphology of supermature Proterozoic Delhi quartzites of IndiaEARTH SURFACE PROCESSES AND LANDFORMS, Issue 13 2003Jayant K. Tripathi Abstract Quartz and quartzite are thought to be resistant as a mineral and a rock respectively; however, we have shown that the presence of small amounts of pyrite in the quartzites makes them vulnerable to weathering. We observe that weathering of Proterozoic quartzite in the semi-arid conditions around Delhi proceeded from fractures towards the inside and produced weathering rinds. The chemical index of alteration (CIA), which is actually a measure of weathering of aluminosilicate minerals, increases from the core outwards, through the rinds. Although aluminosilicate minerals occur only as minor phases (<2 per cent), their weathering indicates a movement of the weathering front from the periphery towards the core. We have suggested a coupled mechanism in which the dissolution of pyrites by moving water produced a sulphate-bearing acidic solution and ferrous iron, which reacted with aluminosilicate minerals and quartz, respectively. This initially makes the Delhi quartzite porous and subsequently friable. The total disintegration of grain to grain contacts imparted friability to this quartzite to produce silica sand. Subsequent physical erosion of loose sand, produced during rind development in the outermost zones, has given rise to features like tors, spheroids, gullies, cavities and small-scale caves on these quartzites. Thus, the terrain has acquired ruggedness in semi-arid conditions. Copyright © 2003 John Wiley & Sons, Ltd. [source] Oxidation of ferrous iron by Thiobacillus ferrooxidans in a full-scale rotating biological contactorENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 4 2001L. Nikolov The performance of a full-scale rotating biological contactor used for the oxidation of ferrous iron by Thiobacillus ferrooxidans in drainage waters was studied. It has been shown that high volumetric rates, up to 2.5 g/Lh can be obtained. We also examined the effects of input ferrous iron concentration and liquid retention time on reactor performance. It has been shown that when the input iron concentration increased, volumetric reaction rate increased while substrate conversion decreased. In general, the rotating biological contractor is a promising tool for the biological treatment of acid mine drainage containing ferrous iron. [source] Phototrophs in high iron microbial mats: microstructure of mats in iron-depositing hot springsFEMS MICROBIOLOGY ECOLOGY, Issue 3 2000Beverly K Pierson Abstract Chocolate Pots Hot Springs in Yellowstone National Park are high in ferrous iron, silica and bicarbonate. The springs are contributing to the active development of an iron formation. The microstructure of photosynthetic microbial mats in these springs was studied with conventional optical microscopy, confocal laser scanning microscopy and transmission electron microscopy. The dominant mats at the highest temperatures (48,54°C) were composed of Synechococcus and Chloroflexus or Pseudanabaena and Mastigocladus. At lower temperatures (36,45°C), a narrow Oscillatoria dominated olive green cyanobacterial mats covering most of the iron deposit. Vertically oriented cyanobacterial filaments were abundant in the top 0.5 mm of the mats. Mineral deposits accumulated beneath this surface layer. The filamentous microstructure and gliding motility may contribute to binding the iron minerals. These activities and heavy mineral encrustation of cyanobacteria may contribute to the growth of the iron deposit. Chocolate Pots Hot Springs provide a model for studying the potential role of photosynthetic prokaryotes in the origin of Precambrian iron formations. [source] Dissimilatory ferrous iron oxidation at a low pH: a novel trait identified in the bacterial subclass RubrobacteridaeFEMS MICROBIOLOGY LETTERS, Issue 2 2008Christopher G. Bryan Abstract A novel iron-oxidizing acidophilic actinobacterium was isolated from spoil material at an abandoned copper mine. Phylogenetic analysis placed the isolate within the Rubrobacteridae subclass of the Actinobacteria. Its optimum temperature and pH for growth are 30,35 °C and pH 3.0, respectively. Although it could catalyze the dissimilatory oxidation of ferrous iron, growth yields declined progressively in media containing ferrous iron concentrations >100 ,M. The isolate, Pa33, did not grow or oxidize iron in the absence of organic carbon, and appeared to be an obligate heterotroph. Specific rates of iron oxidation were much smaller than those determined for the autotrophic iron-oxidizing proteobacterium Acidithiobacillus ferrooxidans and the heterotrophic iron-oxidizing actinobacterium Ferrimicrobium acidiphilum. Iron oxidation by isolate Pa33 appears to be a defensive mechanism, in which iron oxidation converts a soluble species to which the bacterium is sensitive to an oxidized species (ferric iron) that is highly insoluble in the spoil from which it was isolated. This is the first report of acidophily or dissimilatory iron oxidation within the Rubrobacteridae subclass and one of very few within the Actinobacteria phylum as a whole. [source] Blockade by ferrous iron of Ca2+ influx through N -methyl- d -aspartate receptor channels in immature cultured rat cortical neuronsJOURNAL OF NEUROCHEMISTRY, Issue 1 2002Noritaka Nakamichi Abstract Rat cortical neurons cultured for 3 days in vitro were loaded with the fluorescent indicator fluo-3 for assessment of intracellular free calcium ion (Ca2+) concentrations with the aid of a confocal laser-scanning microscope. In the absence of added MgCl2, the addition of NMDA induced a rapid but sustained increase in the number of fluorescent neurons in a concentration-dependent manner at a concentration range of 1,100 µm with the increase by KCl being transient. The addition of FeCl2, but not FeCl3, markedly inhibited the increase by NMDA in a reversible manner at concentrations of 10,200 µm, without affecting that by KCl. Extensive analyses revealed clear differentiation between inhibitions by ferrous iron and other channel blockers known to date. The inhibition by FeCl2 was completely prevented by the addition of two different iron chelators. Exposure to NMDA alone did not lead to cell death in immature cultured neurons, however, while further addition of FeCl2 invariably induced neuronal cell death 24 h after exposure. These results give support to our previous proposal that NMDA receptor complex may contain a novel site sensitive to blockade by ferrous iron in rat brain. [source] Astroglia overexpressing heme oxygenase-1 predispose co-cultured PC12 cells to oxidative injury,JOURNAL OF NEUROSCIENCE RESEARCH, Issue 10 2007Linyang Song Abstract The mechanisms responsible for the progressive degeneration of dopaminergic neurons and pathologic iron deposition in the substantia nigra pars compacta of patients with Parkinson's disease (PD) remain unclear. Heme oxygenase-1 (HO-1), the rate-limiting enzyme in the oxidative degradation of heme to ferrous iron, carbon monoxide, and biliverdin, is upregulated in affected PD astroglia and may contribute to abnormal mitochondrial iron sequestration in these cells. To determine whether glial HO-1 hyper-expression is toxic to neuronal compartments, we co-cultured dopaminergic PC12 cells atop monolayers of human (h) HO-1 transfected, sham-transfected, or non-transfected primary rat astroglia. We observed that PC12 cells grown atop hHO-1 transfected astrocytes, but not the astroglia themselves, were significantly more susceptible to dopamine (1 ,M) + H2O2 (1 ,M)-induced death (assessed by nuclear ethidium monoazide bromide staining and anti-tyrosine hydroxylase immunofluorescence microscopy) relative to control preparations. In the experimental group, PC12 cell death was attenuated significantly by the administration of the HO inhibitor, SnMP (1.5 ,M), the antioxidant, ascorbate (200 ,M), or the iron chelators, deferoxamine (400 ,M), and phenanthroline (100 ,M). Exposure to conditioned media derived from HO-1 transfected astrocytes also augmented PC12 cell killing in response to dopamine (1 ,M) + H2O2 (1 ,M) relative to control media. In PD brain, overexpression of HO-1 in nigral astroglia and accompanying iron liberation may facilitate the bioactivation of dopamine to neurotoxic free radical intermediates and predispose nearby neuronal constituents to oxidative damage. © 2007 Wiley-Liss, Inc. [source] p -quinone mediates 6-hydroxydopamine-induced dopaminergic neuronal death and ferrous iron accelerates the conversion of p -quinone into melanin extracellularlyJOURNAL OF NEUROSCIENCE RESEARCH, Issue 6 2005Yasuhiko Izumi Abstract Parkinson's disease (PD) is characterized by the selective loss of dopaminergic neurons in the substantia nigra (SN). 6-Hydroxydopamine (6-OHDA), a dopaminergic neurotoxin, is detected in human brains and the urine of PD patients. Using SH-SY5Y, a human neuroblastoma cell line, we demonstrated that 6-OHDA toxicity was determined by the amount of p -quinone produced in 6-OHDA auto-oxidation rather than by reactive oxygen species (ROS). Glutathione (GSH), which conjugated with p -quinone, provided significant protection whereas catalase, which detoxified hydrogen peroxide and superoxide anions, failed to block cell death caused by 6-OHDA. Although iron accumulated in the SN of patients with PD can cause dopaminergic neuronal degeneration by enhancing oxidative stress, we found that extracellular ferrous iron promoted the formation of melanin and reduced the amount of p -quinone. The addition of ferrous iron to the culture medium inhibited caspase-3 activation and apoptotic nuclear morphologic changes and blocked 6-OHDA-induced cytotoxicity in SH-SY5Y cells and primary cultured mesencephalic dopaminergic neurons. These data suggested that generation of p -quinone played a pivotal role in 6-OHDA-induced toxicity and extracellular iron in contrast to intracellular iron was protective rather than harmful because it accelerated the conversion of p -quinone into melanin. © 2005 Wiley-Liss, Inc. [source] X-ray emission spectroscopy with a laser-heated diamond anvil cell: a new experimental probe of the spin state of iron in the Earth's interiorJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2005Jung-Fu Lin Synchrotron-based X-ray emission spectroscopy (XES) is well suited to probing the local electronic structure of 3d transition metals such as Fe and Mn in their host phases. The laser-heated diamond anvil cell technique is uniquely capable of generating ultra-high static pressures and temperatures in excess of 100,GPa and 3000,K. Here X-ray emission spectroscopy and X-ray diffraction have been interfaced with the laser-heated diamond cell for studying the electronic spin states of iron in magnesiowüstite-(Mg0.75,Fe0.25)O and its crystal structure under lower-mantle conditions. X-ray emission spectra of the ferrous iron in a single crystal of magnesiowüstite-(Mg0.75,Fe0.25)O indicate that a high-spin to low-spin transition of ferrous iron occurs at 54 to 67,GPa and 300,K and the ferrous iron remains in the high-spin state up to 47,GPa and 1300,K. This pilot study points to the unique capability of the synchrotron-based XES and X-ray diffraction techniques for addressing the issue of electronic spin transition or crossover in 3d transition metals and compounds under extreme high- P,T conditions. [source] Role of iron chemistry in controlling the release of pollutants from resuspended sedimentsREMEDIATION, Issue 1 2005Anne Jones-Lee Aquatic sediments often contain a large number of chemical contaminants that are potential pollutants. It is often presumed that such contaminants are released to the water column during sediment resuspension and, in there, adversely impact aquatic life and other beneficial uses of the water. However, extensive laboratory and field studies of about 100 contaminated sediments from across the United States that specifically addressed this type of release showed that of about 30 common heavy metals, organic compounds, and other potential pollutants, only manganese II and ammonia were released to then remain in the water column after sediment resuspension. These results indicated that the chemistry of aqueous iron controls the availability of many contaminants in resuspended sediment. The formation of ferric hydroxide during sediment suspension into the water column, as a result of the reaction between ferrous iron in the sediments and dissolved oxygen in the water column, leads to rapid scavenging of many contaminants in the Fe(OH)3 precipitate. The scavenged contaminants are redeposited in the sediments. This article reviews the role of the aqueous chemistry of iron as it relates to controlling the release of potential pollutants from resuspended sediments. © 2005 Wiley Periodicals, Inc. [source] Involvement of Iron (Ferric) Reduction in the Iron Absorption Mechanism of a Trivalent Iron-Protein Complex (Iron Protein SuccinylateBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 3 2000Kishor B. Raja Iron protein succinylate is a non-toxic therapeutic iron compound. We set out to characterise the structure of this compound and investigate the importance of digestion and intestinal reduction in determining absorption of the compound. The structure of the compound was investigated by variable temperature Mössbauer spectroscopy, molecular size determinations and kinetics of iron release by chelators. Intestinal uptake was determined with radioactive compound force fed to mice. Reduction of the compound was determined by in vitro incubation with intestinal fragments. The compound was found to contain only ferric iron, present as small particles including sizes below 10 nm. The iron was released rapidly to chelators. Digestion with trypsin reduced the molecular size of the compound. Intestinal absorption of the compound was inhibited by a ferrous chelator (ferrozine), indicating that reduction to ferrous iron may be important for absorption. The native compound was a poor substrate for duodenal reduction activity, but digestion with pepsin, followed by pancreatin, released soluble iron complexes with an increased reduction rate. We conclude that iron protein succinylate is absorbed by a mechanism involving digestion to release soluble, available ferric species which may be reduced at the mucosal surface to provide ferrous iron for membrane transport into enterocytes. [source] Structure of Stenotrophomonas maltophilia FeoA complexed with zinc: a unique prokaryotic SH3-domain protein that possibly acts as a bacterial ferrous iron-transport activating factorACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2010Yi-Che Su Iron is vital to the majority of prokaryotes, with ferrous iron believed to be the preferred form for iron uptake owing to its much better solubility. The major route for bacterial ferrous iron uptake is found to be via an Feo (ferrous iron-transport) system comprising the three proteins FeoA, FeoB and FeoC. Although the structure and function of FeoB have received much attention recently, the roles played by FeoA and FeoC have been little investigated to date. Here, the tertiary structure of FeoA from Stenotrophomonas maltophilia (Sm), a vital opportunistic pathogen in immunodepressed hosts, is reported. The crystal structure of SmFeoA has been determined to a resolution of 1.7,Å using an Se single-wavelength anomalous dispersion (Se-SAD) approach. Although SmFeoA bears low sequence identity to eukaryotic proteins, its structure is found to adopt a eukaryotic SH3-domain-like fold. It also bears weak similarity to the C-terminal SH3 domain of bacterial DtxR (diphtheria toxin regulator), with some unique characteristics. Intriguingly, SmFeoA is found to adopt a unique dimer cross-linked by two zinc ions and six anions (chloride ions). Since FeoB has been found to contain a G-protein-like domain with low GTPase activity, FeoA may interact with FeoB through the SH3,G-protein domain interaction to act as a ferrous iron-transport activating factor. [source] Role of haem oxygenase-1 in microbial host defenceCELLULAR MICROBIOLOGY, Issue 2 2009Su Wol Chung Summary Haem oxygenase (HO)-1 is a cytoprotective enzyme that plays a critical role in defending the body against oxidant-induced injury during inflammatory processes. HO catalydes the degradation of haem to carbon monoxide (CO), biliverdin and ferrous iron. Biliverdin is converted to bilirubin, a potent endogenous antioxidant. CO has a number of biological functions, including anti-inflammatory properties. In various models of disease, HO-1 is known to play a critical role by ameliorating the pathological consequences of injury. In many of these models, the beneficial effects of HO-1 and its products of haem catabolism are by suppressing an inflammatory response. However, when investigating diseases due to microbial infections, inhibition of the inflammatory response could disrupt the ability of the immune system to eradicate an invading pathogen. Thus, questions remain regarding the role of HO-1 in microbial host defence. This microreview will address our present understanding of HO-1 and its functional significance in a variety of microbial infections. [source] Facile Oxidation of Leucomethylene Blue and Dihydroflavins by Artemisinins: Relationship with Flavoenzyme Function and Antimalarial Mechanism of ActionCHEMMEDCHEM, Issue 8 2010Richard Abstract The antimalarial drug methylene blue (MB) affects the redox behaviour of parasite flavin-dependent disulfide reductases such as glutathione reductase (GR) that control oxidative stress in the malaria parasite. The reduced flavin adenine dinucleotide cofactor FADH2 initiates reduction to leucomethylene blue (LMB), which is oxidised by oxygen to generate reactive oxygen species (ROS) and MB. MB then acts as a subversive substrate for NADPH normally required to regenerate FADH2 for enzyme function. The synergism between MB and the peroxidic antimalarial artemisinin derivative artesunate suggests that artemisinins have a complementary mode of action. We find that artemisinins are transformed by LMB generated from MB and ascorbic acid (AA) or N -benzyldihydronicotinamide (BNAH) in,situ in aqueous buffer at physiological pH into single electron transfer (SET) rearrangement products or two-electron reduction products, the latter of which dominates with BNAH. Neither AA nor BNAH alone affects the artemisinins. The AA,MB SET reactions are enhanced under aerobic conditions, and the major products obtained here are structurally closely related to one such product already reported to form in an intracellular medium. A ketyl arising via SET with the artemisinin is invoked to explain their formation. Dihydroflavins generated from riboflavin (RF) and FAD by pretreatment with sodium dithionite are rapidly oxidised by artemisinin to the parent flavins. When catalytic amounts of RF, FAD, and other flavins are reduced in,situ by excess BNAH or NAD(P)H in the presence of the artemisinins in the aqueous buffer, they are rapidly oxidised to the parent flavins with concomitant formation of two-electron reduction products from the artemisinins; regeneration of the reduced flavin by excess reductant maintains a catalytic cycle until the artemisinin is consumed. In preliminary experiments, we show that NADPH consumption in yeast GR with redox behaviour similar to that of parasite GR is enhanced by artemisinins, especially under aerobic conditions. Recombinant human GR is not affected. Artemisinins thus may act as antimalarial drugs by perturbing the redox balance within the malaria parasite, both by oxidising FADH2 in parasite GR or other parasite flavoenzymes, and by initiating autoxidation of the dihydroflavin by oxygen with generation of ROS. Reduction of the artemisinin is proposed to occur via hydride transfer from LMB or the dihydroflavin to O1 of the peroxide. This hitherto unrecorded reactivity profile conforms with known structure,activity relationships of artemisinins, is consistent with their known ability to generate ROS in,vivo, and explains the synergism between artemisinins and redox-active antimalarial drugs such as MB and doxorubicin. As the artemisinins appear to be relatively inert towards human GR, a putative model that accounts for the selective potency of artemisinins towards the malaria parasite also becomes apparent. Decisively, ferrous iron or carbon-centered free radicals cannot be involved, and the reactivity described herein reconciles disparate observations that are incompatible with the ferrous iron,carbon radical hypothesis for antimalarial mechanism of action. Finally, the urgent enquiry into the emerging resistance of the malaria parasite to artemisinins may now in one part address the possibilities either of structural changes taking place in parasite flavoenzymes that render the flavin cofactor less accessible to artemisinins or of an enhancement in the ability to use intra-erythrocytic human disulfide reductases required for maintenance of parasite redox balance. [source] Immunostimulating activities of the novel peptidomimetic L-glutamyl-histamineCLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 3 2005M. A. Babizhayev Summary An original representative of histamine-containing peptidomimetics L-glutamyl-histamine (L-Glu-Hist) was synthesized and characterized as a cytokine mimic leading to cellular responses of improved specificity. The energy-minimized 3-D conformations of L-Glu-Hist derived from its chemical structure resulted in stabilization for Fe2+ chelating complexes. L-Glu-Hist accelerated the decrease of ferrous iron in the ferrous sulphate solution in a concentration-dependent mode and showed the ferroxidase-like activity at concentrations less than 3 mm in the phenanthroline assay, whereas in the concentration range 3,20 mm L-Glu-Hist restricted the availability of Fe2+ to phenanthroline due to binding of ferrous ions in chelating complexes. L-Glu-Hist showed a stimulatory effect on phosphatidylcholine liposomal peroxidation (LPO) catalysed by the superoxide anion radical (O2,)-generating system (Fe2++ ascorbate) at low (less or about 1 mm) L-Glu-Hist concentrations and both, revealed, the, inhibitory, effect, on, LPO, in, this, system, of, high, (, 10 mm), L-Glu-Hist concentration. L-Glu-Hist released O2, in concentrations which stimulated [3H]-thymidine incorporation into DNA and proliferation of mouse spleen lymphocytes and mononuclear cells from human blood. The structural peptide-like analogues of L-Glu-Hist such as L-Glu-Trp, carcinine (,-alanylhistamine), but not L-Pro-Glu-Trp were active in stimulating thymidine incorporation and in inducing proliferation of mononuclear cells compared to mitogen concanavalin A at doses 2·5,25·0 µg/ml. Our data provide evidence that L-Glu-Hist may act as a very fast and sensitive trigger for lymphocyte proliferation and immunoregulation. [source] | |||||||||||||||||||||||||||||||