Showing papers on "Ferric published in 2016"

Microbial siderophores and their potential applications: a review

Abstract: Siderophores are small organic molecules produced by microorganisms under iron-limiting conditions which enhance the uptake of iron to the microorganisms. In environment, the ferric form of iron is insoluble and inaccessible at physiological pH (7.35-7.40). Under this condition, microorganisms synthesize siderophores which have high affinity for ferric iron. These ferric iron-siderophore complexes are then transported to cytosol. In cytosol, the ferric iron gets reduced into ferrous iron and becomes accessible to microorganism. In recent times, siderophores have drawn much attention due to its potential roles in different fields. Siderophores have application in microbial ecology to enhance the growth of several unculturable microorganisms and can alter the microbial communities. In the field of agriculture, different types of siderophores promote the growth of several plant species and increase their yield by enhancing the Fe uptake to plants. Siderophores acts as a potential biocontrol agent against harmful phyto-pathogens and holds the ability to substitute hazardous pesticides. Heavy-metal-contaminated samples can be detoxified by applying siderophores, which explicate its role in bioremediation. Siderophores can detect the iron content in different environments, exhibiting its role as a biosensor. In the medical field, siderophore uses the "Trojan horse strategy" to form complexes with antibiotics and helps in the selective delivery of antibiotics to the antibiotic-resistant bacteria. Certain iron overload diseases for example sickle cell anemia can be treated with the help of siderophores. Other medical applications of siderophores include antimalarial activity, removal of transuranic elements from the body, and anticancer activity. The aim of this review is to discuss the important roles and applications of siderophores in different sectors including ecology, agriculture, bioremediation, biosensor, and medicine.

Hydrogen Sulfide Oxidation by Myoglobin

Abstract: Enzymes in the sulfur network generate the signaling molecule, hydrogen sulfide (H2S), from the amino acids cysteine and homocysteine. Since it is toxic at elevated concentrations, cells are equipped to clear H2S. A canonical sulfide oxidation pathway operates in mitochondria, converting H2S to thiosulfate and sulfate. We have recently discovered the ability of ferric hemoglobin to oxidize sulfide to thiosulfate and iron-bound hydropolysulfides. In this study, we report that myoglobin exhibits a similar capacity for sulfide oxidation. We have trapped and characterized iron-bound sulfur intermediates using cryo-mass spectrometry and X-ray absorption spectroscopy. Further support for the postulated intermediates in the chemically challenging conversion of H2S to thiosulfate and iron-bound catenated sulfur products is provided by EPR and resonance Raman spectroscopy in addition to density functional theory computational results. We speculate that the unusual sensitivity of skeletal muscle cytochrome c oxidas...

Iron uptake and transport across physiological barriers.

Abstract: Iron is an essential element for human development. It is a major requirement for cellular processes such as oxygen transport, energy metabolism, neurotransmitter synthesis, and myelin synthesis. Despite its crucial role in these processes, iron in the ferric form can also produce toxic reactive oxygen species. The duality of iron's function highlights the importance of maintaining a strict balance of iron levels in the body. As a result, organisms have developed elegant mechanisms of iron uptake, transport, and storage. This review will focus on the mechanisms that have evolved at physiological barriers, such as the intestine, the placenta, and the blood-brain barrier (BBB), where iron must be transported. Much has been written about the processes for iron transport across the intestine and the placenta, but less is known about iron transport mechanisms at the BBB. In this review, we compare the established pathways at the intestine and the placenta as well as describe what is currently known about iron transport at the BBB and how brain iron uptake correlates with processes at these other physiological barriers.

Removal of Pb, Cd, Cu and Ni from aqueous solution using nano scale zero valent iron particles

Abstract: Nanoparticles offer the potential to improve environmental treatment technologies due to their unique properties. Adsorption of metal ions Pb(II), Cd(II), Cu(II), Ni(II) to nano zero valent iron (nZVI) particles of surface iron oxide was examined. nZVI particles were synthesized by reduction of ferric chloride with sodium borohydride. In this work, transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy are applied to study the compositional and structural of nZVI. Batch equilibrium experiments were performed to study the removal efficiency of heavy metal ions. The effect of different parameters such as contact time, initial concentration, pH and nZVI dose on the adsorption process were investigated. The adsorption kinetics well fitted using a pseudo-second order kinetic model. SEM and TEM images showed that of particles were mostly spherical shape in chains with an average size 43.1 ± 11.9 nm. The initial sorption rate for all the metals is in order Pb 2+ > Cu 2+ > Cd 2+ > Ni 2+ . Short adsorption equilibrium contact time favors the application of the adsorption process. The formation of FeOOH on the surface of nZVI could be the main factor of cations removal due to its high adsorption affinity for aqueous solutes. Therefore, with the strong adsorption at pH 6.5 which is representative of several natural groundwater and the ability to adsorb multiple metal ions simultaneously, nZVI may offer a potential remediation method for the removal of metals from water and environment.

Vibrio Iron Transport: Evolutionary Adaptation to Life in Multiple Environments

Abstract: Iron is an essential element for Vibrio spp., but the acquisition of iron is complicated by its tendency to form insoluble ferric complexes in nature and its association with high-affinity iron-binding proteins in the host. Vibrios occupy a variety of different niches, and each of these niches presents particular challenges for acquiring sufficient iron. Vibrio species have evolved a wide array of iron transport systems that allow the bacteria to compete for this essential element in each of its habitats. These systems include the secretion and uptake of high-affinity iron-binding compounds (siderophores) as well as transport systems for iron bound to host complexes. Transporters for ferric and ferrous iron not complexed to siderophores are also common to Vibrio species. Some of the genes encoding these systems show evidence of horizontal transmission, and the ability to acquire and incorporate additional iron transport systems may have allowed Vibrio species to more rapidly adapt to new environmental niches. While too little iron prevents growth of the bacteria, too much can be lethal. The appropriate balance is maintained in vibrios through complex regulatory networks involving transcriptional repressors and activators and small RNAs (sRNAs) that act posttranscriptionally. Examination of the number and variety of iron transport systems found in Vibrio spp. offers insights into how this group of bacteria has adapted to such a wide range of habitats.

A Close-up of the Effect of Iron Oxide Type on the Interfacial Interaction between Epoxy and Carbon Steel: Combined Molecular Dynamics Simulations and Quantum Mechanics

Abstract: In the present study, the effect of different types of iron oxides, which naturally exist on steel substrate, on the interfacial interaction between an epoxy coating and a carbon steel substrate was studied at the molecular/atomic level by employing molecular dynamics (MD) simulations and quantum mechanics (QM) calculations. Three types of iron oxide, that is, ferrous oxide (FeO), ferric oxide (Fe2O3, hematite), and ferrous ferric oxide (Fe3O4, magnetite), were considered for modeling, and their binding energies were calculated and compared by altering the concentration of hydroxide groups on the surface. To probe the effect of curing agent on interfacial interactions, computations were performed for either uncured or aminoamide-cured epoxy resins. The effect of the acid–base properties of the iron oxide on the molecular bonding was theoretically investigated by imposing diverse iron hydroxide/oxide termination groups. Noticeably, MD and QM calculations confirmed rather well earlier experimental evaluatio...

Ferric reducing anti-oxidant power assay in plant extract

Abstract: The ferric reducing anti-oxidant power (FRAP) assay involved the following steps: a) preparation of samples, b) reactions and c) finally measuring absorbance of sample and standard at 700 nm using spectrophotometer. The samples were methanolic extract, different fractions ( n -hexane, chloroform) and standard ascorbic acid. The solutions prepared were buffer solution (pH 6.6), 1% potassium ferricyanide solution, 10% trichloroacetic acid and 0.1% ferric chloride. Video Clip of Methodology: Ferric reducing anti-oxidant power assay: 21 min 18 sec Full Screen Alternate

Viewing the Valence Electronic Structure of Ferric and Ferrous Hexacyanide in Solution from the Fe and Cyanide Perspectives

Abstract: The valence-excited states of ferric and ferrous hexacyanide ions in aqueous solution were mapped by resonant inelastic X-ray scattering (RIXS) at the Fe L2,3 and N K edges. Probing of both the central Fe and the ligand N atoms enabled identification of the metal- and ligand-centered excited states, as well as ligand-to-metal and metal-to-ligand charge-transfer excited states. Ab initio calculations utilizing the RASPT2 method were used to simulate the Fe L2,3-edge RIXS spectra and enabled quantification of the covalencies of both occupied and empty orbitals of π and σ symmetry. We found that π back-donation in the ferric complex is smaller than that in the ferrous complex. This is evidenced by the relative amounts of Fe 3d character in the nominally 2π CN– molecular orbital of 7% and 9% in ferric and ferrous hexacyanide, respectively. Utilizing the direct sensitivity of Fe L3-edge RIXS to the Fe 3d character in the occupied molecular orbitals, we also found that the donation interactions are dominated by...

Lead (Pb2+) adsorption by monodispersed magnetite nanoparticles: surface analysis and effects of solution chemistry.

Abstract: Monodispersed magnetite nanoparticles [Fe 3 O 4 -NPs] were synthesized by chemical co-precipitation using ferrous and ferric chloride as iron precursors. The composition, surface properties and morphology were investigated using X-ray powder diffraction, transmission electron microscopy, dynamic light scattering, scanning electron microscopy and Fourier transform infrared spectroscopy. Synthesized magnetite nanoparticles have zeta potential of +22.0 mV and an energy bandgap of 2.2 eV. These NPs were used for aqueous Pb 2+ removal at different initial pHs, equilibrium time, temperature and adsorbent/adsorbate concentrations. Pb 2+ adsorption was increased with rise in solution pH. Almost 100% Pb 2+ removal was achieved [at magnetite NPs dose: 0.2 g/L; Pb 2+ concentration: 50 mg/L; pH 5.0; shaking speed: 200 rpm; temperature: 25 °C and equilibrium time: 30 min]. Pseudo-first and pseudo-second order kinetic equations were applied to evaluate the kinetic data. Pseudo-second-order rate equation better fitted the data. Spent NPs were regenerated using 0.005 M HNO 3 . Exhausted magnetite NPs were successfully recovered from aqueous system using a simple magnet. These magnetite NPs can also be used for Pb 2+ removal from waters having high concentration of suspended particles.

Green and cost-effective fluorescent carbon nanoparticles for the selective and sensitive detection of iron (III) ions in aqueous solution: Mechanistic insights and cell line imaging studies

Abstract: In this work, a simple, green and cost-effective fluorescence based analytical procedure using water soluble carbon nanoparticles (CNPs) is described for selective and sensitive detection of Iron (III) (i.e. ferric (Fe3+)) ions in water. The CNPs were synthesized by acid treatment of naturally occurring d -glucose followed by heating at 80 °C. The fluorescence intensity of the CNPs (excited at 360 nm) was found to decrease with the increase in concentration of Fe3+ ions. The fluorescence lifetime of CNPs remained unchanged with increasing Fe3+ concentration, suggesting the quenching to be static. The zeta potential which was negative for CNPs became positive on addition of Fe3+, thus indicating the adsorption of Fe3+ on CNPs surface. The sensing of Fe3+ by CNPs was also observed in-vivo using DLD cells. The limit of quantification and limit of detection of Fe3+ ions were found to be 18 ppm and as 56.0 ppb, respectively. Validation of the proposed fluorescence quenching based technique was achieved by comparing with Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES).

Bacterial inactivation with iron citrate complex: A new source of dissolved iron in solar photo-Fenton process at near-neutral and alkaline pH

Abstract: This study reports the first application of Fe-citrate-based photo-Fenton chemistry for the inactivation of Escherichia coil. Promising results of bacterial inactivation at near-neutral and alkaline pH conditions were obtained, while using low iron concentration (Fe-citrate concentration: 0.6 mg/L, relative to the Fe content) and avoiding precipitation of ferric hydroxides. The effects of the solution pH and Fe-citrate complex concentration on E. coil inactivation during the photo-Fenton reaction were investigated. The efficiency of the homogeneous photo-Fenton process using Fe-citrate complex as a source of iron strongly improved bacterial inactivation as compared with the heterogeneous photo-Fenton treatment (FeSO4 and goethite as sources of iron) at near-neutral pH. The bacterial inactivation rate increased in the order of goethite< FeSO4 < Fe-citrate, which agreed well with the trend for the HO center dot radical formation, monitored by ESR. Encouraging results were also obtained while applying this treatment for bacterial inactivation in natural water samples from Lake Geneva (Switzerland) at pH 8.5, since no bacterial reactivation and/or growth were observed after photo-Fenton treatment. This type of application is promising, considering the simplicity of the installations and procedures, the ability to use the Sun as the light source, and the safety of all of the chemicals in this system. (C) 2015 Elsevier B.V. All rights reserved.

Iron–copper bimetallic nanoparticles supported on hollow mesoporous silica spheres: the effect of Fe/Cu ratio on heterogeneous Fenton degradation of a dye

Abstract: A series of iron–copper bimetallic nanoparticles supported on hollow mesoporous silica spheres with different Fe/Cu ratios were prepared using a simple post-impregnation and sodium borohydride reduction strategy. Different Fe/Cu ratios were obtained by addition of various amounts of ferric and copper salts. The catalysts were characterized by XRD, XPS, nitrogen physisorption, SEM and TEM. To explore the difference of catalytic reactivity among the various FeCu/HMS composites, Fenton-like catalytic oxidation of orange II was chosen as the model catalysis reaction. The catalytic results showed that the catalytic activity depended highly upon the Fe/Cu ratio. Particularly, 1/3 (2Fe6Cu/HMS) is the optimum Fe/Cu mass ratio to achieve the best catalytic activity. Based on the results of detection of ˙OH radicals and cyclic voltammograms, the important origin of the synergetic effect in 2Fe6Cu/HMS is considered as the combination of iron and copper species, which can accelerate the interfacial electron transfer in redox cycles of Fe3+/Fe2+ and Cu2+/Cu+ pairs, followed by the increase in the ˙OH radical generation. The 2Fe6Cu/HMS also possesses less pH dependence and maintains its high activity even under alkaline conditions. The optimal parameters in the degradation of 100 mg L−1 orange II are 27.4 mM of H2O2 with 1.0 g L−1 of catalyst, performed at a pH of 7.0 and 30 degree celsius. It is worth noting that 2Fe6Cu/HMS also possesses potential to treat a high concentration of dye pollutants. 77.7% of orange II was removed when conducted at 1000 mg L−1 initial dye concentration. The stability and recoverability of the composite catalyst were assessed it exhibited a good performance after 5 consecutive runs. The as-synthesized composite catalyst proved to be an attractive alternative for dye wastewater treatment applications.

Interaction of tannic acid with ferric iron to assist 2,4,6-trichlorophenol catalytic decomposition and reuse of ferric sludge as a source of iron catalyst in Fenton-based treatment

Abstract: A comprehensive study of the catalytic behaviour of Fe3+ in the presence of tannic acid during the Fenton-based treatment of chlorophenols-contaminated water was performed. The ability of the iron-containing sludge to catalyse the Fenton-based process was assessed and the mechanistic behaviour of tannic acid in the iron dissolution was evaluated. Tannic acid, a constituent of pulp and paper industry water effluent and natural water, enhanced the 2,4,6-trichlorophenol catalytic decomposition in Fe3+-activated H2O2 oxidation system by reducing of the Fe3+. The Fe3+ reductive mechanism by tannic acid incorporated tannic acid–Fe3+ complex formation and decay through an electron transfer reaction to form Fe2+. An indirect measurement of hydroxyl radical (HO ) by the deoxyribose method indicated a considerable increase in HO by Fe3+/H2O2 in the presence of tannic acid. A pseudo-first reaction rate constant of 2,4,6-trichlorophenol degradation by Fe2+/H2O2 was high and close to that of Fe3+/H2O2 with tannic acid. Degradation of tannic acid along with that of 2,4,6-trichlorophenol required optimization of H2O2 and Fe3+ dosages to balance HO formation and scavenging. Acidic reaction media (pH 3.0) and the presence of tannic acid favoured 2,4,6-trichlorophenol degradation by H2O2 oxidation induced by iron dissolved from ferric oxyhydroxide sludge. The reuse of ferric oxyhydroxide sludge as a catalyst source in the Fenton–based process can minimise the production of hazardous solid waste and the overall cost of the treatment. This study highlights the ability of tannic acid-Fe3+ complexes to participate in Fe3+ reductive pathway and, as a result, to allow reuse of non-regenerated ferric oxyhydroxide sludge for activation of H2O2 oxidation in wastewater treatment at acidic pH.