Showing papers on "Ferric published in 1983"
TL;DR: It is proposed that a ferrous-dioxygen-ferric chelate complex may be the initiating species in lipid peroxidation, and studies with oxy-radical scavengers and catalase suggest that O2-., H2O2, or the .OH are not involved in the initiation reactions.
236 citations
TL;DR: In this paper, it was shown that the ferric reducing activity in the roots of iron-deficient bean plants is located in an enzyme in the plasmalemma of the cortex or epidermis cells.
Abstract: Iron-deficient bean plants (Phaseolus vulgaris L. cv. Prelude) exhibited a ferric reducing activity in the roots, with kinetics characteristic for matrix-bound enzymes: the reaction rate was proportional to substrate (Fe-EDTA) concentration until 100 μM, and at higher concentrations it leveled off to a maximum; the Lineweaver-Burk plot yielded a non-linear relationship between rate −1 and substrate −1. The Arrhenius plot yielded apparent activation energies which were dependent on substrate concentration. No evidence was obtained for the secretion by roots of a low molecular weight metabolite involved in the reduction of iron prior to its uptake. The results are interpreted to indicate that the ferric reducing activity in the roots of iron-deficient bean plants is located in an enzyme in the plasmalemma of the cortex or epidermis cells.
220 citations
TL;DR: Two dual isotope studies performed in iron replete human subjects demonstrate that coffee inhibits iron absorption in a concentration-dependent fashion.
188 citations
TL;DR: Amirtharajah et al. as mentioned in this paper derived a more rational approach to the use of coagulants in water treatment, particularly alum and ferric chloride, than is presently practiced.
Abstract: Coagulation is the term used to describe the aggregation of very small particles, usually colloidal sized, often encountered in water and wastewater treatment. Coagulation is practiced in the majority of municipal water treatment plants in the United States as an essential part of the solids-liquids separation process.’ The use of hydrolyzed coagulants (such as aluminum and iron salts] has been an integral part of the purification of water for centuries.* This study seeks to derive a more rational approach to the use of coagulants in water treatment, particularly alum and ferric chloride, than is presently practiced. Amirtharajah and Mills2 produced a detailed design-andoperation diagram for alum coagulation. In this study, a similar operation diagram for Fe(II1) was developed by using data available in the literature and the results of jar tests with ferric chloride. The two diagrams are compared to show under what conditions each or both coagulants are effective.
165 citations
TL;DR: Steady-state spectral studies indicated that the three-electron-reduced form of NADPH-P-450 reductase accumulates, consistent with the view that this form of the reduct enzyme is involved in the reduction of P-450 from the ferric to the ferrous state.
Abstract: A series of equilibrium and kinetic measurements involving the oxidation-reduction properties of purified rat liver NADPH-cytochrome P-450 reductase and eight different purified rat liver cytochromes P-450 (P-450s) were carried out. Apparent spin states of P-450 iron were determined in the absence and presence of a number of known substrates by using second-derivative and conventional near-UV absorbance spectroscopy. Many of the substrates examined did not produce significant changes in the apparent iron spin state, even when binding could be demonstrated with equilibrium dialysis. Further, the spin state was not correlated to catalytic activity of the P-450s in reconstituted enzyme systems. The oxidation-reduction potentials were determined for the ferric/ferrous couples of each of the eight P-450s in the presence and absence of known substrates, as well as other proteins suspected of altering the potentials. The midpoint potential (Em,7) ranged from -350 to -289 mV for the P-450s under these conditions. In some cases Em,7 was raised with the addition of substrates, but the extent of the increase was no greater than +33 mV. The Em,7 of one P-450 (P-450 beta NF/ISF-G) was not changed significantly when the fraction of high-spin iron varied between 11 and 67%. Steady-state spectral studies provided evidence for the accumulation of an oxygenated ferrous intermediate (or a derived product) of one P-450 (P-450PB-B) in the presence of a substrate, cyclohexane. Studies on the donation of electrons from cytochrome b5 and a series of dyes to this complex suggest that it has an effective Em,7 (for reduction) of approximately +50 mV. In studies with one of the P-450s, steady-state spectral studies indicated that the three-electron-reduced form of NADPH-P-450 reductase accumulates, consistent with the view that this form of the reductase is involved in the reduction of P-450 from the ferric to the ferrous state.
165 citations
TL;DR: Although iron bleomycin does not have a polyaromatic structure like heme, many features of its electronic structure at the iron are very similar to those produced by the sulfur-coordinated heme iron of ferric cytochrome P-450, a protein that catalyzes a similar oxygen-dependent reaction.
96 citations
TL;DR: The shapes of the absorption edges further support the assignment of HRP-I and one of the model compounds as Fe(IV)-porphyrin pi-cations and demonstrate that the iron sites in the model porphyrins are not identical to the iron Sites in the enzyme.
93 citations
TL;DR: The N18O isotope shift data indicate that the widely accepted assignment of the Fe(II)--NO stretching vibration at approximately equal to 554 cm-1 in ferrous nitrosyl Mb/HbA is incorrect; instead, it is assigned to the Fe (II)--N--O bending mode.
Abstract: The nature of bonding interactions between Fe(III) and NO in the ferric nitrosyl complexes of myoglobin (Mb), hemoglobin A (HbA), and horseradish peroxidase (HRP) is investigated by Soret-excited resonance Raman spectroscopy. On the basis of 15NO and N18O isotope shifts, we clearly identified the Fe(III)--NO bond stretching frequencies at 595 cm-1 (ferric Mb X NO), 594 cm-1 (ferric HbA X NO), and 604 cm-1 (ferric HRP X NO). The Fe(III)--N--O bending vibrations are located at 573 cm-1 (ferric Mb X NO) and 574 cm-1 (ferric HRP X NO), which are very similar to the Fe(II)--C--O bending modes at 578 cm-1 in Mb X CO and HbA X CO. However, the Fe(III)--NO and Fe(II)--CO stretching frequencies differ by approximately equal to 90 cm-1, indicating a much stronger iron-axial ligand bond for the [Fe(III) + NO] system, which is isoelectronic with the [Fe(II) + CO] system and, hence, presumably also has a linear Fe(III)--N--O linkage (in the absence of distal steric effect). The unusually strong Fe(III)--NO bond may be attributed to the pi bonding involving the unpaired electron in the pi (NO) orbital. The N18O isotope shift data indicate that the widely accepted assignment of the Fe(II)--NO stretching vibration at approximately equal to 554 cm-1 in ferrous nitrosyl Mb/HbA is incorrect; instead, we assign it to the Fe(II)--N--O bending mode. The validity of the assignment of Fe(II)--O2 stretch at 567 cm-1 in oxy-HbA by Brunner [Brunner, H. (1974) Naturwissenschaften 61, 129-130] is now in doubt. Literature data are presented to suggest that it is the Fe(II)--O--O bending vibration.
92 citations
TL;DR: In this article, conditions were optimized for leaching converter slag with ferric chloride/dilute sulphuric acid for the recovery of cobalt, nickel and copper.
91 citations
TL;DR: Results indicate that at serum bicarbonate concentrations, transferrin should have a higher affinity for zinc(II) than serum albumin and therefore could play some role in zinc transport and support mechanisms for iron removal from transferrin in which the ferric ion is reduced to the less tightly bound ferrous ion.
Abstract: Serum transferrin is a mammalian iron-transport protein. It has two specific metal-binding sites that bind a variety of metal ions in addition to ferric ion. Equilibrium constants for the binding of zinc(II) have been determined by difference UV titrations using nitrilotriacetic acid and triethylenetetramine as competing ligands. The values are log K1* = 7.8 and log K2* = 6.4 in 0.10 M N-(2-hydroxyethyl)piperazine-N'-2-ethanesulfonic acid and 15 mM bicarbonate, pH 7.4 at 25 degrees C. Titrations of the two forms of monoferric transferrin show that K1* corresponds to zinc binding to the C-terminal site and K2* corresponds to binding at the N-terminal site. These results indicate that at serum bicarbonate concentrations, transferrin should have a higher affinity for zinc(II) than serum albumin and therefore could play some role in zinc transport. A linear free-energy relationship has been constructed which relates the formation constants of a series of zinc(II) and iron(II) complexes. On the basis of the zinc-transferrin binding constants, this relationship has been used to estimate an iron(II)-transferrin binding constant of 10(7.4). Using this ferrous constant and literature values for the ferric transferrin binding constant, one calculates a ferric transferrin reduction potential of -140 mV, which is easily within the range of physiological reductants. Such a result tends to support mechanisms for iron removal from transferrin in which the ferric ion is reduced to the less tightly bound ferrous ion.
91 citations
TL;DR: It is concluded that the heme ligand arrangement changes on cooling from 298 to 77 K with a concomitant change in the spin state, and the rates of formation of both compounds are consistent with the notion that they are involved in the catalytic cycle.
TL;DR: Two dilute oral iron solutions, made from commonly available nonprescription dietary supplements, were found to enhance the gastrointestinal tract in nuclear magnetic resonance imaging of live rats and one human volunteer.
Abstract: Two dilute oral iron solutions, made from commonly available nonprescription dietary supplements, were found to enhance the gastrointestinal tract in nuclear magnetic resonance imaging of live rats and one human volunteer. The paramagnetic and pharmacologic properties of ferric ammonium citrate were more favorable than those of ferrous sulfate heptahydrate. The paramagnetic iron solutions shorten T1 and T2 relaxation times of water protons in the contrast media-filled gastrointestinal tract, producing easily observable change in NMR intensity. Because these iron solutions are available commercially and are known to be well tolerated, the clinical use of iron-containing NMR contrast agents for the gastrointestinal tract is feasible.
TL;DR: The spectra show unambiguously that both forms of the enzyme contain two distinct, antiferromagnetically coupled, high-spin iron atoms: a ferrous-ferric ion pair in the pink, reduced form, and a pair of ferric ions in the purple, oxidized form.
TL;DR: Kinetic and EPR studies show that the first step in the reaction of NO with ferric myoglobin, opossum hemoglobin, and microperoxidase is the reversible formation of the H-NO complex: H + NO in equilibrium H- NO (where H = Mb+, or Hb+ OP, or MP+).
Abstract: Kinetic and EPR studies show that the first step in the reaction of NO with ferric myoglobin, opossum hemoglobin, and microperoxidase is the reversible formation of the H-NO complex: H + NO in equilibrium H-NO (where H = Mb+, or Hb+ OP, or MP+). The NO-combination rates are markedly affected by the presence or absence of the distal histidine. The distal histidine significantly reduces the NO-combination rates, perhaps by interaction between the distal histidine and the ferric iron. Thus the beta-chains of Hb+ OP and metmyoglobin show similar combination rates. In the absence of a distal histidine, the NO-combination rates in the alpha-chains of Hb+ OP are much faster and similar to those observed for the five-coordinate heme in microperoxidase. The loss of a water molecule from the six-coordination site is assumed to be the rate-limiting step.
TL;DR: Strain 7122 and 1611 can use its endogenous siderophore or schizokinen to promote iron uptake, but at 50-fold-lower rates than are observed with Anabaena sp.
Abstract: Anabaena sp. strain 6411, which produces the dihydroxamate siderophore schizokinen to facilitate iron uptake, is also capable of using the related siderophore aerobactin. The two siderophores compete for the same iron transport system, but there is a markedly higher affinity for ferric schizokinen than for ferric aerobactin. The trihydroxamate siderophore ferrioxamine B is far less effective as an iron donor in this organism. Anabaena sp. strain 7120 appears to be closely related to strain 6411. It synthesizes schizokinen as its major siderophore and shows rates of iron uptake from ferric schizokinen, ferric aerobactin, and ferrioxamine B which are similar to those observed with strain 6411. Anabaena cylindrica Lemm. 7122 and 1611, on the other hand, differ from strain 6411. In contrast to schizokinen, the hydroxamate which they produce in response to iron starvation cannot be extracted with water from the organic layer and does not support the growth of the siderophore auxotroph Arthrobacter flavescens JG-9. Strain 7122 can use its endogenous siderophore or schizokinen to promote iron uptake, but at 50-fold-lower rates than are observed with Anabaena sp. strain 6411 or 7120.
TL;DR: The method has been adapted to determine catechol compounds in the culture medium of bacterial cells grown at different iron concentrations and gives positive results with catechols such as DL-DOPA, L-dopamine, (+/-)-epinephrine, and DL-norepinephrine.
TL;DR: Ferrous/ferric equilibria were determined in alkali-alkaline-earth borosilicate glass as a function of temperature, oxygen partial pressure, and glass composition as discussed by the authors.
Abstract: Ferrous/ferric equilibria were determined in alkali-alkaline-earth borosilicate glass as a function of temperature, oxygen partial pressure, and glass composition. Expected linear relations are found between log(Fe2+/Fe3+) and log(pO2) or 1/T. The slopes of the correlation with 10g(pO2) are near the expected value of -0.25, but are found to decrease with increasing temperature. Reaction enthalpies determined from the correlation with 1/T of –100 to –116 kJ/mol are similar to those reported for other silicate glasses. The ferroudferric equilibrium is not dependent on total iron content in the range 0.5 to 0.09% Fe2O3. More reducing conditions are required at lower temperatures to stabilize the amber chromophore. The ferroudferric equilibria are correlated to the number of bridging and nonbridging oxygen ions in the glass. The results suggest that the oxidation-reduction reaction can be written as: Fe2++ (1/4)O2+ (3/2)O2-= FeO2−
TL;DR: In this article, the thermodynamic stability constants for ferric and ferrous ascorbate complexes, change in net redox potential with pH, and efficacy of bathophenanthroline as an iron reagent was determined.
Abstract: The thermodynamic stability constants for ferric and ferrous ascorbate complexes, change in net redox potential with pH, and efficacy of bathophenanthroline as an iron reagent in the presence of ascorbate were determined. The stability constants for the ferric and ferrous ascorbate complexes were found to be in the range 1.90 × 103 to 2.61 × 104 and 7.69 × 10-3 to 6.95 × 10-2, respectively. The stability of ferric ascorbate over a wide range of pH values suggests its potential use as an iron additive in foods. Redox potential decreased with an increase in pH. Bathophenanthroline analysis of these solutions for free iron proved to have limitations in the presence of ascorbate.
TL;DR: Evidence that these algae with high cellular iron quotas are effectively Fe deficient is provided by a decrease in the cytochrome f/chlorophyll a ratio and a much greater decrease in NO3‐ reductase activity than in aldolase activity or H14C03 assimilation.
Abstract: Cadmium inhibits iron uptake and assimilation in the coastal diatom Thalassiosira weissflogii Grun. The effect of cadmium on short term Fe uptake fits ft competitive binding model:
where (Fe3+) and (Cd2++) tire the free ferric and cadmium ion concentrations, respectively. The apparent binding constant Kcds, is calculated to be ca. lO8.2M-1 compared to a Kfe of lO19 M-1. At low free ferric ion concentrations. interference of cadmium with iron transport (at pCd = 8 and pFe* < 20) results in a simultaneous decrease in growth rate and Fe accumulation to a level known 1o limit growth. Upon decreasing the free cadmium ion concentration, cells accumulate a large amount oj iron prior to resumption of normal growth. At higher free ferric ion concentrations (pFe* < 20) normal or elevated Fe quotas are absented but “luxury consumption” of iron still occurs upon reversal of toxicity. Evidence that these algae with high cellular iron quotas are effectively Fe deficient is provided by a decrease in the cytochrome f/chlorophyll a ratio and a much greater decrease in NO3- reductase activity than in aldolase activity or H14C03 assimilation. Under the conditions of this study, cadmium had little effect on Si accumulation. The transport of methylamine (an analog of NH+4) is unaffected by short term exposure to high free cadmium ion concentration but is greatly inhibited upon long term (97 h) exposure.
TL;DR: A catalytic mechanism for cytochrome c peroxidase is proposed in which the radical site can exist in two conformations having very different reduction potentials and in which a significant flow of oxidizing equivalents between heme and free radical sites occurs only during the hydrogen peroxide oxidation of the resting Fe(III) enzyme to form compound ES.
Journal Article•
TL;DR: Results indicate that transferrin is not required as an iron donor as the inorganic iron was taken up effectively and utilized to stimulate ferritin synthesis, and this should not be confused with the use of transferrin as a donor in other studies.
TL;DR: In this article, the Mossbauer spectra of a cleaned Weipa, Australia, kaolin showed that a considerable fraction of structural iron exhibits paramagnetic relaxation between 4°K and 300°K, the first time that this has been observed for ferric ions in a mineral.
Abstract: 57Fe Mossbauer spectra of a cleaned Weipa, Australia, kaolin showed that a considerable fraction of the structural iron exhibits paramagnetic relaxation between 4°K and 300°K, the first time that this has been observed for ferric ions in a mineral. The sample also contained a very fine particle ferric oxide/oxyhydroxide phase, probably of secondary origin.
TL;DR: Mössbauer studies of SiR complexed with either CO or CN- and ofSiR in the presence of the chaotropic agent dimethyl sulfoxide (Me2SO) are reported, showing that the cluster subsites are equivalent in pairs, one pair having properties reminiscent of ferric sites whereas the other pair has features more typical of ferrous sites.
TL;DR: In this paper, the effect of Fe 2+, Fe 3+ and Ca 2+ on the effective capacity of D2EHPA/TOPO resins has been examined, and it was shown that the resin containing aminophosphonic acid groups possesses a higher effective capacity than the other resins.
TL;DR: In this paper, the complex interrelations of ferric, uranyl and uranous ion inhibition are considered and the kinetics indicate a direct biological mechanism for uranium oxidation by Thiobacillus ferrooxidans.
Abstract: Kinetic constants for the oxidation of uranous and ferrous ions byThiobacillus ferrooxidans were estimated. The kinetics indicate a direct biological mechanism for uranium oxidation. The complex interrelations of ferric, uranyl and uranous ion inhibition are considered.
TL;DR: Evidence is presented that this resulted from iron catalysed decomposition of the lipid hydroperoxide, and suggests a role for free iron or iron chelates in the propagation of lipid peroxidation stimulated by other systems.
Abstract: SummaryThe generation of hydroxyl free radicals in 60Co γ-irradiation of a dilute aqueous suspension of phosphatidyl choline liposomes, resulted in the rapid accumulation of lipid hydroperoxides (linearly with time), but only small concentrations of malondialdehyde. Incubation of the irradiated liposomes with ferric chloride was found to significantly increase the malondialdehyde, and evidence is presented that this resulted from iron catalysed decomposition of the lipid hydroperoxide. This suggests a role for free iron or iron chelates in the propagation of lipid peroxidation stimulated by other systems.
TL;DR: In this paper, the mediating effects of mixed mediator systems consisting of a series of ferric chelate compounds and thionine were studied in bio-fuel cells containing Escherichia coli.