Iron Exchange Research Articles

Disregulating processes in the blood system during cancer

Hematologic disturbances in patients with solid malignant tumors, their development mechanism, value, modern pathogenetic principles of correction are considered in the article. The role of cytokines, erythropoietin, blood loss, metastasing of tumors, depressing bone marrow hemopoiesis and increased destroying erythrocytes, microcirculatory disturbances, iron exchange and vitamin B 12 in pathogenesis of cancer anemia and also disregulating processes in myeloid hemopoiesis which manifest in the development of neutrophil leucocytosis , eosinophylia and leukemoid reactions in patients having malignant neoplasms is described in details. Hematologic disturbances in malignant growth are frequent manifestations of paraneoplastic syndrome which is a result of system influence of the tumor on the organism. Radial and chemotherapy increase disregulating processes in this vitally important system which require improved methods of their correction.

Estimation of Reference Values for Cadmium, Cobalt, Chromium, Copper, Nickel, Lead, and Zinc in Brazilian Soils

The objectives of this study were 1) to recommend reference values (RVs) and tolerance limits (TLs) for representative Brazilian soils and 2) to propose a model to calculate natural contents of cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) in a soil from the silt, clay, manganese (Mn), iron (Fe), and cation exchange capacity (CEC) values. A set of 256 soil samples was classified by similarity in seven groups, and the concentrations corresponding to the upper quarter of data collected were then calculated. These concentrations are proposed as RVs for Brazilian soils. Additionally, TLs were obtained for each group from the antilog expression (m+2s), where m=mean value and s=standard deviation of data transformed in log10. The classification functions of discriminant analysis proved to be suitable to allocate new samples in the established groups. Thus, it is possible to evaluate soils under anthropic activity and, by comparison with reference values, to be aware of pollution risks in a given area.

Implementing the retrofitting plan for the European rail freight fleet

In 1998, the International Union of Railways (UIC) agreed on an Action Plan, proposing the retrofitting of the complete European rail freight fleet. Early 2003 the European Commission, Directorate General for Transport and Energy, commissioned the study reported here. The scope of the study was to supply an independent assessment of the conclusions of the UIC Action Plan and elaborate on implementation scenarios and funding options. The retrofitting of existing wagons, by an exchange of cast iron brake blocks with composition blocks, is the preferred option to achieve a substantial noise reduction. K-blocks have been homologated by UIC in 2003, but they require an expensive modification of the wagon. The opportunities for LL-blocks, an economically attractive alternative, are still being investigated to date. The retrofitting reflects some 600,000 wagons and, with an expected reduction of 10 dB(A), probably represents the largest single operation for traffic noise reduction ever. The process could best be combined with the maintenance cycle of freight wagons. In that case the process would require up to 10 years. Through a combination of funding options, the financial burden for wagons owners and freight operators could be softened.

Isocyanic acid hydrolysis over Fe-ZSM5 in urea-SCR

Two different iron exchanged zeolites were studied for the hydrolysis of isocyanic acid (HNCO) to ammonia, which is an important intermediate step in the selective catalytic reduction (SCR) of NO with urea. The hydrolysis reaction proceeded with very high activity and selectivity on over-exchanged as well as low-exchanged Fe-ZSM5 catalyst samples. The hydrolysis activity of the catalysts was inversely correlated with their Brønsted acidity, which decreased with the degree of iron exchange and the degree of ageing. Thus, over-exchanged Fe-ZSM5 had the highest activity, which even increased when the catalyst was aged.

Methods and results of field testing of a retrofitted freight train with composite brake blocks

Legal limits will be applied to pass-by noise of railway vehicles in Switzerland. As a consequence, existing freight wagons have to be retrofitted. The exchange of cast iron brake blocks by composite ones is a well-known low-cost measure to reduce pass-by noise. The Swiss Agency for the Environment (BUWAL) commissioned a measurement campaign in the year 2003 to define the noise limit, test conditions and maintenance procedures for retrofitted freight wagons. The test was set up in order to allow the control, or at least the knowledge of all relevant parameters concerning track, vehicles, test and boundary conditions. A track section was reconstructed. The test train was arranged with one reference group of wagons with cast iron brake blocks and several groups of wagons with composite brake blocks and different characteristics. As all wagon groups were operated together in one test train, boundary conditions and test parameters were identical for all wagons. The noise reduction achieved relative to cast iron block braked vehicles was in the expected range. Additionally, it could be observed that standard procedures in infrastructure and freight wagon maintenance do not ensure a sustained noise reduction. Several effects destroy this noise reduction. Measures to ensure a qualified noise reduction sustained for the full lifetime of a freight wagon were identified.

Autocatalytic partial reduction of FeO(1 1 1) and Fe 3O 4(1 1 1) films by atomic hydrogen

The interaction of atomic hydrogen with thin epitaxial FeO(1 1 1) and Fe 3O 4(1 1 1) films was studied by TDS, XPS and LEED. On the thin, one Fe–O bilayer thick FeO film, partial reduction occurs in two steps during exposure. It ends after removal of 1/4 monolayer (ML) of oxygen with a 2 × 2 pattern appearing in LEED. This FeO 0.75 film is passive against further reduction. The first reduction step saturates after removal of ∼0.2 ML and shows autocatalytic kinetics with the oxygen vacancies formed during reduction causing acceleration. The second step is also autocatalytic and is related with reduction to the final composition and an improvement of the 2 × 2 order. A structure model explaining the two-step reduction is proposed. On the thick Fe 3O 4 film, irregular desorption bursts of H 2O and H 2 were observed during exposure. Their occurrence appears to depend on the film quality and thus on surface order. Because of the healing of reduction-induced oxygen vacancies by exchange of oxygen or iron with the bulk, a change of the surface composition was not visible. The existence of partially reduced oxide phases resistant even to atomic hydrogen is relevant to the mechanism of dehydrogenation reactions using iron oxides as catalysts.

A Sporadic Third Layer in the Ionosphere of Mars

The daytime martian ionosphere has been observed as a two-layer structure with electron densities that peak at altitudes between about 110 and 130 kilometers. The Mars Express Orbiter Radio Science Experiment on the European Mars Express spacecraft observed, in 10 out of 120 electron density profiles, a third ionospheric layer at altitude ranges of 65 to 110 kilometers, where electron densities, on average, peaked at 0.8 x 10(10) per cubic meter. Such a layer has been predicted to be permanent and continuous. Its origin has been attributed to ablation of meteors and charge exchange of magnesium and iron. Our observations imply that this layer is present sporadically and locally.

Kinetics of Contact Deposition of Iron on Aluminum Substrate

Contact exchange of iron(III) with aluminum metal is studied by using chronopotentiometry, voltammetry, and cyclic voltammetry. Some of its kinetic and other electrochemical characteristics are determined. The statement that the process proceeds in stages (which is proved by the use of methods of formal kinetics) is supported by cyclic voltammograms.

Nebular and asteroidal modification of the iron isotope composition of chondritic components

Abstract The Fe-isotope signatures (δ56FeIRMM and δ57FeIRMM) of twelve chondrules, three Ca-, Al-rich inclusions (CAIs) and multiple matrix aliquots from two type 3 chondrites — Allende (CV3) and Chainpur (LL3) were measured by MC-ICP-MS. The mass-fractionation line for these samples is δ57FeIRMM = (1.45 ± 0.05) · δ56FeIRMM − (0.01 ± 0.02) with R2 = 0.9995. Two processes appear to affect the Fe-isotope composition of these chondritic components. Initially, short-lived high-temperature events within the solar nebula drove isotopic signatures towards isotopically heavier compositions. Subsequently, metasomatism shifted isotopic signatures of chondrules and CAIs towards bulk-like compositions. The Fe-isotope composition of Allende matrix (δ56FeIRMM = − 0.07 ± 0.02‰, n = 6) is similar to that of bulk Allende (δ56FeIRMM = − 0.05 ± 0.05‰). The range of Chainpur matrix compositions is − 0.03 ≤ δ56FeIRMM ≤ + 0.02‰. This relatively homogeneous matrix composition appears to be governed by metasomatic exchange of iron, although the possibility that matrix is heterogeneous on a scale smaller than the sample size cannot be ruled out. CAIs from Allende, in which iron has been metasomatically introduced from the matrix, are mainly unfractionated with respect to the bulk composition of Allende. The least altered CAI, which contains minor bulk FeO (0.4 wt.%), is isotopically lighter (δ56FeIRMM = − 0.16‰) with respect to bulk Allende. This signature may reflect condensation of isotopically light iron in the nebula or preferential incorporation of the lighter iron isotopes contained within the matrix. Chondrule Fe-isotope compositions (− 1.33 ≤ δ56FeIRMM ≤ + 0.65‰) are driven by both high-temperature nebular events and subsequent metasomatic exchange. The relationship between compositional and isotopic signatures clearly points to an evaporation origin for type I chondrules, which are isotopically heavier than type II chondrules. Subsequent metasomatic exchange with matrix iron has driven some chondrules (most notably the smaller chondrules) towards a bulk-like Fe-isotopic signature.

Homo‐/Heterotrinuclear Mixed‐Valent Oxo‐Centered Iron/Nickel Clusters—Mössbauer Studies on Internal Electron‐Exchange Processes

In a one-pot reaction of N-(5-methylthiazole-2-yl)-thiazole-2-carboxamide HL2 (3) with iron(II) acetate in air, the homotrinuclear heteroleptic mixed-valent oxo-centered iron cluster [Fe(II)Fe(III)O(L2)3(OAc)3] (4) was formed. Exchange of iron(II) in 4 by nickel(II) afforded the heteronuclear cluster [Ni(II)Fe(III)O(L2)3(OAc)3] (6). To obtain crystals suitable for X-ray structure analyses, in 4 and 6, the OAc- co-ligands were exchanged by OBz- ligands to give [Fe(II)Fe2(III)O(L2)3(OBz)3] (5) and [Ni(II)Fe(III)O(L2)3(OBz)3] (7). The complexes 5 and 7 are isostructural and made up of three ditopic, tridentate ligands (L2)- and three bridging benzoate co-ligands, which fix the three metal ions in the corners of a triangle with an mu3-O2- ion in the center. The mixed-valent character of 4-7, their intramolecular electron-exchange processes, and their redox properties were studied by variable-temperature Mössbauer spectroscopy and cyclic voltammetry.

Thioredoxin Reductase System Mediates Iron Binding in IscA and Iron Delivery for the Iron-Sulfur Cluster Assembly in IscU*

IscA is a key member of the iron-sulfur cluster assembly machinery found in bacteria and eukaryotes. Previously, IscA was characterized as an alternative iron-sulfur cluster assembly scaffold, as purified IscA can host transient iron-sulfur clusters. However, recent studies indicated that IscA is an iron-binding protein that can provide iron for the iron-sulfur cluster assembly in a proposed scaffold IscU (Ding H., Clark, R. J., and Ding, B. (2004) J. Biol. Chem. 279, 37499-37504). To further elucidate the roles of IscA in the biogenesis of iron-sulfur clusters, we reevaluate the iron binding activity of IscA under physiologically relevant conditions. The results indicate that in the presence of the thioredoxin reductase system, Escherichia coli IscA binds iron with an iron association constant of 2.0 x 10(19) M(-1) in vitro. Whereas all three components (thioredoxin 1, thioredoxin reductase and NADPH) in the thioredoxin reductase system are essential for mediating the iron binding in IscA, only catalytic amounts of thioredoxin 1 and thioredoxin reductase are required. In contrast, IscU fails to bind iron in the presence of the thioredoxin reductase system, suggesting that the iron binding in IscA is specific. Nevertheless, the thioredoxin reductase system can promote the iron-sulfur cluster assembly in IscU in the presence of the iron-loaded IscA, cysteine desulfurase (IscS), and L-cysteine, demonstrating a physiologically relevant system for the biogenesis of iron-sulfur clusters. The results provide additional evidence for the hypothesis that IscA is capable of recruiting intracellular "free" iron and delivering the iron for the iron-sulfur cluster assembly in IscU.

Theoretical model for ion exchange of iron (III) in chelating resins: Application to metal ion removal from wine

Equilibrium diagrams have been obtained for the ionic exchange that occurs between Fe 3+ ions in solution and the protons present in a chelating ion exchange resin, in water, in alcohol and in hydroalcohol solvents. These diagrams have also been obtained for a natural complex solvent (a wine matrix). A mathematical model has been developed to predict this equilibria which gives a good fit for the experimental data in the first three types of solvents studied and, after making some modifications, also in the last case. It has been observed that the type of solvent influences not only the resin equivalent capacity but also the equilibrium parameters of the system. In the case of the wine matrix used as the solvent it has been found that other factors influence the equilibrium diagram, i.e., the presence of quelating compounds.

Iodine and Iron Deficiency in Mild Iodine Deficiency Region Under Iodine Supplementation

Objectives: Studying epidemiological criteria deficiency of iron and iodine at the population of Tyumen, on a background of iodine preventive maintenance. Methods: Because iron deficiency may impair the efficacy of iodine supplementation, the aim of this study was to determine the relation between serum ferritin and goiter, urinary iodine following iodized salt supplementation. Schoolboys are included in conformity to recommendations the WHO (1997) in 9—12 years old children (n = 435.). Results: On a background of preventive actions at the Tyumen schoolboys sufficient iodine maintenance (frequency of a craw is determined according to ultrasonic — 1.9%, a median urinary iodine — 113 mkg/l). The average level serum iron has made 13 ± 6.2 mg/dl, serum ferritin — 38.6 ± 30.9 mg/dl. At 30 % of schoolboys deficiency of iron is determined. Conclusion: In conditions compensated endemic goiter authentic correlation between criteria of an exchange of iron and parameters of iodine maintenance it is not established. Key words: iodine deficience, thyroid, goiter, iron, anemia.

Extraction and purification of biologically active intestinal trefoil factor from human meconium

Intestinal trefoil factor (TFF3/ITF), a member of trefoil factor family (TFF) domain peptides, is normally expressed by goblet cells and secreted into the lumen of the intestinal tract, and plays an important role in the maintenance and repair of the intestinal mucosal barrier. Significant amounts of TFF3/ITF are present in the meconium of human infants. Here, we describe a relatively simple method for extraction and purification of natural human TFF3/ITF from meconium. The purification methods include acid treatment, ammonium sulfate precipitation, isoelectric precipitation, and iron exchange chromatography. A relatively large amount of natural TFF3/ITF can be purified from meconium of full-term infants and this purified, natural TFF3/ITF is biologically active in an ethanol-induced rat gastric mucosal injury model.

Syntheses, crystal structures and magnetic properties of two cyano-bridged two-dimensional assemblies [Fe(salpn)]2[Fe(CN)5NO] and [Fe(salpn)]2[Ni(CN)4

Two cyano-bridged assemblies, [FeIII(salpn)]2[FeII(CN)5NO] (1) and [FeIII (salpn)]2[NiII(CN)4] (2) [salpn = N, N′-1,2-propylenebis(salicylideneiminato)dianion], have been prepared and structurally and magnetically characterized. In each complex, [Fe(CN)5NO]2− or [Ni(CN)4]2− coordinates with four [Fe(salpn)]+ cations using four co-planar CN− ligands, whereas each [Fe(salpn)]+ links two [Fe(CN)5NO]2− or [Ni(CN)4]2− ions in the trans form, which results in a two-dimensional (2D) network consisting of pillow-like octanuclear [—MII—CN—FeIII—NC—]4 units (M = Fe or Ni). In complex (1), the NO group of [Fe(CN)5NO]2− remains monodentate and the bond angle of FeII—N—O is 180.0°. The variable temperature magnetic susceptibilities, measured in the 5–300 K range, show weak intralayer antiferromagnetic interactions in both complexes with the intramolecular iron(III)⋯iron(III) exchange integrals of −0.017 cm−1 for (1) and −0.020 cm−1 for (2), respectively.

EPR Investigation of Fe-Exchanged Beta-Zeolites

Iron-exchanged beta-zeolites with an exchange level (300 Fe/Al, mol/mol) of 10−97 were characterized by electron paramagnetic resonance (EPR) after calcination and a redox pretreatment (H2/N2O). According to the EPR spectra, three different types of iron species are present in the samples: isolated ions, polynuclear oxo-iron species (clusters), and superparamagnetic iron particles. Fe-exchanged beta-zeolites (Fe−BEA) with an iron exchange level lower than 24 are mainly constituted by isolated Fe(III) ions. These latter species can be located in the structure or in charge compensation of the BEA zeolite structure. The amount of interacting species above an iron exchange level of 24 increases strongly, and these species become predominant at an iron exchange level of 100. Oxidation of Fe2+−BEA by N2O leads to the generation of new oxo-iron species with superparamagnetic character. These species are considered as the active species in the selective catalytic reduction of N2O by NH3 over fully exchanged Fe−BEA.

Solution equilibria of deferoxamine amides

The physico‐chemical solution properties of deferoxamine were modified by acylating the terminal amino group with short‐chain aliphatic, succinic, and methylsulphonic moieties. The analog iron(III)‐binding constants and stabilities under physiological conditions were determined to confirm that the iron binding ability of the parent molecule was retained following modification. The proton dissociation constants of the lipophilic deferoxamine analogs were determined by potentiometric titration and nonlinear least‐squares analysis. However, because the iron(III) binding complex is fully formed below pH 2, the metal–ligand equilibria could not be studied using potentiometric methods. The iron binding constants of the deferoxamine analogs were determined by spectrophotometrically following the proton‐dependent exchange of iron with EDTA in the pH range of 4.0 to 6.5 and solving mass balance equations. The proton‐dissociation constants and the iron binding constants of the lipophilic deferoxamine analogs were comparable to those of deferoxamine. However, at physiological conditions, the iron‐binding complex of the most lipophilic butylamide derivative was slightly less stable and the succinamide derivative complex was slightly more stable. Like deferoxamine, the hydroxamate groups of the analogs were unhindered and free to form a 1:1 coordination complex with iron(III). Consequently, changes in aqueous solvation, conformation, and steric interference, imparted by the modifications at the terminal amino group of deferoxamine, may have affected the stabilities of the iron(III) complex and the efficiency of iron binding. © 2002 Wiley‐Liss Inc. and the American Pharmaceutical Association J Pharm Sci 91:1733–1741, 2002

Selective Catalytic Reduction of Nitrous Oxide by Ammonia on Iron Zeolite Beta Catalysts in an Oxygen Rich Atmosphere: Effect of Iron Contents

A series of iron-exchanged zeolite beta (BEA) has been characterized by temperature programmed desorption (TPD) of oxygen and tested in the catalytic reduction of N2O by NH3. TPD of O2 has clearly shown that iron-oxo species formed upon reoxidation by nitrous oxide of Fe2+-BEA are more labile than those generated by calcination in air. In the selective catalytic reduction of N2O by NH3 the conversion of N2O increases until a degree of iron exchange level of 100% and then decreases. In contrast, the intrinsic activity per mole of iron decreases drastically with the increase of iron content. Mononuclear iron-oxo species have been proposed as the most active sites for the reduction of N2O by NH3; binuclear iron-oxo species and iron oxides aggregates are less active.

A study on the effect of hydrogen in the compounds with BaCd 11-type structure

A study on the crystallographic and magnetic properties of the BaCd 11-type RFe 9Si 2C x H f ( R= Ce, Nd, Sm; x=0.5, 1.0, 1.5; f denotes full occupation) have been carried out. The hydrogen insertion dilates the volume, and the expansion in the basal plane is larger than that along the c-axis: (Δ a)/ a≈0.3%, (Δ c)/ c≈0.1%. Both the Curie temperature and the saturation magnetization increase with the hydrogen insertion. For the Ce and the Nd compounds, the easy magnetization direction (EMD) lies in the basal plane, and for the Sm compounds, the EMD is along the c-axis. The anisotropy field of the Sm compounds decreases with the hydrogen insertion. The exchange interaction coefficients are also calculated with the molecular field model. Both the rare-earth–iron exchange interaction n RFe and the iron–iron exchange interaction n FeFe increases with the increasing carbon content and the hydrogen insertion. Furthermore, the first order magnetization process (FOMP) is observed in NdFe 9Si 2C x and their corresponding hydrides.

Attempts to exchange iron into H-Y and H-ZSM-5 zeolites by in situ formed chloride-containing mobile species

Three variants of solid-state ion exchange were studied. Iron exchange was found to proceed in the first case, in theFeCl2+NH4ZSM-5→ FeZSM-5 + NH4Cl↑ process, even at low exchange capacity (Si/Al = 25).The second, Fe2O3 (hematite) + HZ direct reaction does not result in any noticeable interaction for eitherZ = Y or ZSM-5. This process can significantly be promoted by introducing CCl4 vapor via forming chlorine-containingmobile species. However, the structure of the Y zeolite largely collapses during this treatment, whereas the crystalline state of ZSM-5is preserved.