Role Of Catalytic Iron Research Articles

Transition metals in brewing and their role in wort and beer oxidative stability: a review

Beer inevitably changes over time: the colour will darken, haze may form, and stale flavours develop, while others fade. The challenge of maintaining the fresh flavour quality of beer (over a typical 9-12 month storage period) is generally the determining factor of a beer's shelf-life for brewers, as opposed to colloidal or microbiological stability. Fortunately, as early as the brewhouse, oxidative degradation can - to a certain extent - be controlled, enabling the shelf-life to be increased. This review considers the general issues of oxidative stability, mechanisms of ageing, ways of quantifying staleness and staling potential, and current practical approaches to prevent oxidative beer ageing. Emphasis is placed on the catalytic role of iron, copper and manganese on oxidation during brewing and storage; and how the removal and/or inhibition of these prooxidative transition metal ions leads to prolonged beer (flavour) stability.

The role of catalytic iron in enhancing volumetric sugar productivity during autothermal pyrolysis of woody biomass

Passivation of naturally occurring AAEM in biomass enhances sugar yields from the fast pyrolysis of biomass by preventing these metals from catalyzing the fragmentation of pyranose rings in cellulose and hemicellulose. However, because AAEM also catalyzes lignin depolymerization, its passivation can be accompanied by undesirable char agglomeration. Pretreatment of biomass with ferrous sulfate both passivates AAEM and substitutes ferrous ions as lignin depolymerization catalysts. This pretreatment has been particularly successful for high ash biomass like corn stover, but of limited value for low ash biomass like wood. This study explores the reasons for this discrepancy and offers a combined pretreatment of ferrous sulfate and ferrous acetate pretreatment to overcome char agglomeration in wood. This new pretreatment increased sugar yields from 4.4 wt% to 15.5 wt% and 5.4 wt% to 19.0 wt% for hardwood and softwood biomasses, respectively. This pretreatment produces an iron-rich biochar that catalyzes oxidation of the biochar under the oxygen-rich conditions of autothermal pyrolysis, which is preferentially consumed to provide the enthalpy for pyrolysis, preserving bio-oil as a more desirable energy product. Instead of producing carbon monoxide, which dominates oxidation of biochar from untreated biomass, the iron catalyzes oxidation to carbon dioxide, producing more energy per mole of oxygen consumed. In fact, oxygen demand to support autothermal pyrolysis of red oak and southern yellow pine was reduced 15% by the presence of iron in the biochar.

Iron Catalyzed Hydrogen Sulfide and Its Prevalence during Oxidative Events in Sickle Cell Disease

In sickle cell disease (SCD), red blood cell (RBC) oxidation-reduction (redox) status is a critical determinant of hemolysis and RBC adhesion/vaso-occlusive crises (VOC). Iron, while essential for hemoglobin and RBC production, also is an important catalyst in processes that produce reactive oxygen species (ROS) which damage RBCs and ultimately other tissues. This has necessitated mechanisms for iron sequestration to control its activity, primarily achieved through binding of iron to heme, hemoglobin, and ferritin. In hemolytic disorders such as SCD, however, there is overload of protein-free, unbound iron, which by increasing ROS, significantly contributes to disease pathology. There is hence a need for novel druggable targets and treatments to attenuate this pathway of ROS production and pathophysiology. Previously, we determined a novel catalytic role of iron in which hydrogen sulfide (H2S) gas is produced both in vitro and in blood ex vivo by iron- and Vitamin B6- mediated catalysis of cysteine. We additionally determined that the bound versus unbound status of iron as well as the integrity of RBCs dictates this non-enzymatic capacity for H2S production. H2S serves as a potent regulatory redox factor throughout the body, and here we hypothesize that excess H2S in blood produced via iron catalysis protects against oxidative stress generated during SCD-related hemolytic crisis and VOC. In the current study, we further show that H2S produced in vitro from iron and Vitamin B6 catalysis of cysteine not only exists as a gas in the headspace, but itself reacts with iron in the solution. This was determined by the formation of acid labile iron sulfide, which formed a light yellow precipitate. The addition of a strong acid removed the yellow colored precipitate and resulted in further release of H2S in to the headspace. This indicates that H2S was interacting with free iron (Fe3+) and formed the iron sulfide product, which may have decreased capabilities for the formation of tissue- and cellular-damaging ROS. On-going work will examine the inhibition of H2S on iron-induced ROS generation in vitro and test the therapeutic potential of applying D-/L-cysteine and/or Vitamin B6- supplemented dietary interventions to enhance iron/B6 catalyzed H2S production in blood to lessen oxidative stress and VOC events in SCD mice in vivo. Free-iron in SCD is conventionally considered only to be a liability. However, here we exploit iron as a catalyst for beneficial H2S production in blood that can protect against oxidative stress and SCD-related pathologies. This recently discovered pathway has the potential to create novel opportunities and approaches to modulate the devastating pathophysiology of SCD. Figure Disclosures Saunthararajah: Novo Nordisk: Consultancy; EpiDestiny: Consultancy, Equity Ownership, Patents & Royalties.

Catalytic role of iron in the formation of silver nanoparticles in photo-irradiated Ag+-dissolved organic matter solution

Photo-reduction of Ag+ to silver nanoparticle (AgNPs) by dissolved organic matter (DOM) is a possible source of naturally occurring AgNPs. However, how this photo-reduction process is influenced by ubiquitous metal ions is still not well understood. In addition, in previous studies, the formation of AgNPs in DOM solution was usually monitored by UV-Vis spectroscopy, and there is still lack of quantitative analysis for the formed AgNPs. In the present study, the role of Fe2+/Fe3+ at environmental concentration level on this photochemical process was investigated, and the enhanced formation of AgNPs by Fe2+/Fe3+ was probed and quantified by using UV-Vis spectroscopy, transmission electron microscopy, and liquid chromatography-inductively coupled plasma mass spectrometry. It was demonstrated that while Fe3+ can oxidize AgNPs to release Ag+, Fe2+ can reduce Ag+ into AgNPs. However, the DOM-induced reduction of Fe3+ makes iron an effective electron shuttle between DOM and Ag+, and both Fe2+ and Fe3+ enhanced AgNP formation. The impacts of environmentally relevant factors, including DOM concentration and solution pH, on this process were studied comprehensively, which showed that the catalytic role of iron was more significant at higher DOM concentration and lower pH. This iron-enhanced formation of AgNPs in photo-irradiated Ag+-DOM solution have great environmental implications on the formation of natural AgNPs and the transformation of engineered AgNPs in acidic surface water with high iron content.

Role of catalytic iron and oxidative stress in nitrofen-induced congenital diaphragmatic hernia and its amelioration by Saireito (TJ-114).

Congenital diaphragmatic hernia (CDH) is a life-threatening neonatal disease that leads to lung hypoplasia and pulmonary hypertension. We recently found that maternal prenatal administration of Saireito (TJ-114) ameliorates fetal CDH in a nitrofen-induced rat model. Here, we studied the role of iron and oxidative stress in neonates of this model and in lung fibroblasts IMR90-SV in association with nitrofen and Saireito. We observed increased immunostaining of 8-hydroxy-2'-deoxyguanosine in the lungs of neonates with CDH, which was ameliorated by maternal Saireito intake. Pulmonary transferrin receptor expression was significantly decreased in both CDH and CDH after Saireito in comparison to normal controls, indicating functional lung immaturity, whereas catalytic Fe(II) and pulmonary DMT1/ferroportin expression remained constant among the three groups. Saireito revealed a dose-dependent scavenging capacity with electron spin resonance spin trapping in vitro against hydroxyl radicals but not against superoxide. Finally, nitrofen revealed dose-dependent cytotoxicity to IMR90-SV cells, accompanied by an increase in oxidative stress, as seen by 5(6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate and catalytic Fe(II). Saireito ameliorated all of these in IMR90-SV cells. In conclusion, catalytic Fe(II)-dependent oxidative stress by nitrofen may be the pathogenic cause of CDH, and the antioxidative activity of Saireito is at least partially responsible for improving nitrofen-induced CDH.

Study of Serum Ferritin and its relation with Glycemic control in Type 2 Diabetes Mellitus

Introduction: Type 2 diabetes mellitus is a common metabolic disorder. It has been hypothesized that, oxidative stress plays a major role in the etiology of the diabetic process, as well as in pathogenesis of various diabetic complications. Appreciating the role of catalytic Iron released by high serum Ferritin levels, in causation of oxidative stress and insulin resistance, we carried out this study to understand the relationship between the serum Ferritin and type 2 diabetes mellitus and we also studied glycated haemoglobin to know the correlation between glycemic control and serum Ferritin.Objectives: To compare the levels of serum Ferritin in patients with type 2 diabetes mellitus and non-diabetic healthy individuals. To know if any correlation exists between serum Ferritin and Glycated Hemoglobin in type 2 diabetes mellitus.Methods: The study was conducted at Rajarajeswari Medical College and Hospital, Bengaluru, Karnataka from January 2012 to December 2012. The subjects of our study were fifty clinically diagnosed cases of type 2 diabetes mellitus and fifty non-diabetic healthy volunteers in the age group of 30 70 years who have satisfied the inclusion and exclusion criteria. Serum Ferritin levels and Glycated Hemoglobin were estimated by microplate immunoenzymo metric assay and ion exchange resin method respectively.Results: Serum Ferritin levels were significantly high in all cases compared to controls. There was moderate co-relation between serum Ferritin and Glycated Haemoblobin.Conclusion: The findings of the study project that, estimation of serum Ferritin may be useful in screening diabetics with poor glycemic control who are at high risk of developing complications. Thus serum Ferritin estimations in type 2 diabetes mellitus can be one of the adjuvant aids in investigations which guides in taking timely medical intervention and preventing further progression of disease.

Iron-Catalyzed Boron Removal from Molten Silicon in Ammonia

A high-temperature process of refining metallurgical-grade silicon to solar-grade silicon was developed. In this gas purging treatment, boron impurity in silicon reacts with ammonia and the products are removed as volatiles at high temperature. 1 mass pct metallic iron was added to molten silicon as a catalyst, improving the boron removal ratio from 14 to 80 pct at 1723 K (1450 °C). At 1823 K (1550 °C), this reaction could reduce boron concentration from more than 120 ppmw to <1 ppmw within 6 hours, meeting the purity requirement of solar-grade silicon. Nickel was tested in place of iron but showed no catalytic effect on boron removal. The result confirmed the catalytic role of iron in boron removal from molten silicon in ammonia. Possible mechanisms of catalysis, influence from iron concentration, and temperature effect on the catalytic reaction were explored. An apparent activation energy of 329 ± 129 kJ mol−1 was calculated from experimental data.

On the catalytic role of IrOn+(n = 0–2) in the oxygen transport activation of N2O by H2: A density functional study

A computational study of the oxygen-transfer reaction of N2O and H2 catalyzed by IrOn+(n=0–2) is completed, incorporates two possible reaction pathways along with quintet and triplet states. In this work, density functional theory method is used to determine all possible intermediates, transition states and products. The crossing points with the possible spin inversion processes are discussed using the intrinsic reaction coordinate approach. According to the calculated results of O-atom affinities, we predict that the 5/3IrOn+(n=0–2) has good O-transfer function from N2O to H2.

Adsorption of bovine serum albumin onto synthetic Fe-doped geomimetic chrysotile.

Synthetic stoichiometric and Fe-doped geomimetic chrysotile nanocrystals represent a reference standard to investigate the health hazard associated with mineral asbestos fibres. Experimental evidence suggests that the generation of reactive oxygen species and other radicals, catalysed by iron ions at the fibre surface, plays an important role in asbestos-induced cytotoxicity and genotoxicity. In this study, structural modification of bovine serum albumin (BSA) adsorbed onto synthetic chrysotile doped with different amounts of Fe has been investigated by Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA) and analytical pyrolysis coupled with gas chromatography-mass spectrometry. FT-IR data evidenced a marked increase in disordered structures like random coil and β-turn of BSA-nanocrystal adduct with 0.52 wt% of Fe doped. The TGA profile of the BSA revealed that its interaction with the synthetic chrysotile surface was strongly affected by the substitution of Fe into the chrysotile structure. The 2,5-diketopiperazine yields, formed upon thermal degradation of the polypeptide chain (pyrolysis-gas chromatography), changed when the BSA was adsorbed on the nanofibres. In general, results suggested that minute amount (less than 1 wt%) of Fe doping in chrysotile affected the protein-nanofibre interactions, supporting the role that this element may play in asbestos toxicity. The catalytic role of iron and the consequent unfolding of protein due to the structural surface modification of nanofibres were also evaluated.

The Role of Catalytic Iron in Acute Kidney Injury

The pathologic effects of iron accumulation in tissue in iron-overload states, such as are described in patients with thalassemia, are widely known. What is new in the field is the recognition that iron plays an important role in the pathophysiology of tissue injury in the absence of systemic iron

Urinary Catalytic Iron in Obesity

Obesity precedes the development of many cardiovascular disease risk factors, including type 2 diabetes mellitus (DM), hypertension, and chronic kidney disease. Catalytic iron, which has been associated with these chronic diseases, may be one of the links between obesity and these multifactorial diverse disorders. We investigated whether urinary catalytic iron is increased in obese individuals without DM and overt kidney disease. We measured urinary catalytic iron using established methods in 200 randomly selected individuals without DM [100 who were obese (body mass index ≥30 kg/m(2)) and 100 who were nonobese (body mass index ≤27)]. Participants were selected from an outpatient clinic and community setting and were part of an ongoing cross-sectional study of obesity in individuals between the ages of 18 and 70 years. There was a significant difference in mean (95% CI) urinary catalytic iron excretion between the obese participants and the nonobese participants, 463 (343-582) nmol/mg [52.3 (38.8-65.8) nmol/μmol] vs 197 (141-253) nmol/mg [22.3 (15.9-28.6) nmol/μmol]; P < 0.001. The significant predictors of increased urinary catalytic iron were obesity (P = 0.001) and waist-to-hip ratio (P = 0.03). Our study results demonstrate that obesity and waist-to-hip ratio are associated with increased urinary catalytic iron, which may be a useful marker of oxidative stress. Additional studies are needed to determine the role of catalytic iron in increased cardiovascular disease and chronic kidney disease associated with obesity.

The role of reactive oxygen and nitrogen species in cellular iron metabolism

The catalytic role of iron in the Haber–Weiss chemistry, which results in propagation of damaging reactive oxygen species (ROS), is well established. In this review, we attempt to summarize the recent evidence showing the reverse: That reactive oxygen and nitrogen species can significantly affect iron metabolism. Their interaction with iron-regulatory proteins (IRPs) seems to be one of the essential mechanisms of influencing iron homeostasis. Iron depletion is known to provoke normal iron uptake via IRPs, superoxide and hydrogen peroxide are supposed to cause unnecessary iron uptake by similar mechanism. Furthermore, ROS are able to release iron from iron-containing molecules. On the contrary, nitric oxide (NO) appears to be involved in cellular defense against the iron-mediated ROS generation probably mainly by inducing iron removal from cells. In addition, NO may attenuate the effect of superoxide by mutual reaction, although the reaction product—peroxynitrite—is capable to produce highly reactive hydroxyl radicals.

Some preventive cellulose antioxidants studied by an aromatic hydroxylation assay

Since the oxidative degradation of cellulose is enhanced in the presence of ferric compounds, the N,N′-(5-nitro,1,3-phenylene)bisglutaramide hydroxylation assay was used to test the efficiency of possible preventive antioxidants: EDTA, DTPA, citrate, desferrioxamine methanesulphonate (desferal) and phytate. The corresponding rate constants and apparent activation energies for hydroxyl radical production in the aqueous systems in the pH interval 6.5–8 were obtained. The rate constants were correlated with the decrease of degree of polymerisation of artificially aged cellulose samples enriched with CaCO 3 and iron in the form of the corresponding complex ( R=0.9891). It is concluded that the catalytic role of iron is similar in both systems and that the hydroxylation assay may provide valuable estimations of the degradation rates of cellulosic materials in the conditions of use. The chelating compounds shown to have an antioxidant effect at 20 °C in the pH interval studied are DTPA, phytate, and desferal, in the order of increasing positive effect.

The role of catalytic iron in asbestos induced lipid peroxidation and DNA-strand breakage in C3H10T1/2 cells.

The involvement of catalytic iron in the vitro activities of crocidolite asbestos has been investigated. Exposure of C3H10T1/2 cells to either the UICC crocidolite standard reference sample or a non fibrous (milled) derivative resulted in an increase of thiobarbituric acid reactive substances. This catalytic activity was inhibited by pretreatment with the iron chelator desferrioxamine. The effect of this activity on cellular DNA was measured in an assay based on the production of DNA-strand breaks. Increased levels of DNA-strand breaks were detected in cultures treated with both the milled and UICC crocidolite. Inclusion of desferrioxamine with the asbestos inhibited DNA-strand breakage. It is concluded the catalytic iron present on the dust is capable of damaging both lipid and DNA and that this could be an important mechanism in asbestos pathogenicity.

Effects of scavengers of oxygen free radicals on the anaerobic oxidation of 6-hydroxydopamine by H2O2

Abstract H 2 O 2 , a product of the aerobic autoxidation of 6-hydroxydopamine, is also consumed as a reactant, contributing progressively more to the oxidation as the concentration of O 2 becomes limiting H 2 O 2 is a less effective oxidant than O 2 , since the anaerobic peroxidatic oxidation of 6-hydrodopamine is slower than the aerobic oxidation by three orders of magnitude. The anaerobic peroxidation was inhibited by the hydroxyl scavengers mannitol (13–40%), glucose (41–62%) and benzoate (15–100%), implying a catalytic role for . OH. -9e strongly inhibitory action of desferrioxamine (76–91%), regardless of which other scavengers were present, suggests a specific role for iron in the reaction, despite the use of Chelex 100-treated buffers. Further addition of diethylenetriaminepentaacetate (DTPA), benzoate or formate to the desferrioxamine-treated reactions resulted in complete inhibition. In contrast, the presence of DTPA alone, accelerated the reaction by 160%. This acceleration is in part due to stimulation by DTPA of production of . OH (by Fenton-type reactions), since it was partially prevented by the hydroxyl scavengers benzoate (32% inhibition) and glucose (41%). Thus, DTPA inhibits the participation of metals other than iron, but potentiates the catalytic role of iron, in the reduction of hydrogen peroxide. The semidehydromannitol radical can reduce the DTPA-Fe 3+ chelate directly, since mannitol further accelerated the DTPA-stimulated peroxidation (by 55%). Superoxide dismutase also accelerated the reaction (by 57–84%). This activation was seen regardless of which other scavengers were present. These effects are explained in terms of potentiating or moderating interactions among the reactive intermediates which propagate the overall reaction.