Analysis of transition-metal acetylacetonate complexes by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

PubMed

Wyatt, Mark F; Havard, Stephen; Stein, Bridget K; Brenton, A Gareth

2008-01-01

Transition-metal acetylacetonate complexes of the form Metal(acac)(2), where Metal = Fe(II), Co(II), Ni(II), Cu(II), and Zn(II), and Metal(acac)(3), where Metal = V(III), Cr(III), Mn(III), Fe(III), and Co(III), were investigated by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The data was acquired using the aprotic, electron transfer matrix, 2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB), and the observation of positive radical ions is shown clearly to depend on the metal element and the oxidation state it occupies. The ionization energy of DCTB was calculated to be 8.08 eV by density functional theory methods, which is notably lower than the experimental value, but within the range of other computational values. This value is very close to those of the analytes, so the existing electron transfer mechanism which is based on the ionization energies of the matrix and analyte, cannot be used predictively. Similarly, the data neither proves nor disproves the validity of the existing electron transfer ionization mechanism, with respect to metal coordination complexes without strong chromophores. In this case, periodic trends may be more useful in explaining the observed species and the prediction of species from sets of similar complexes. The addition of a sodium salt benefits the MALDI-TOFMS characterization of certain compounds studied, but the benefit of the addition of ammonium or silver salts is negligible.

Determination of Chromium(III), Chromium(VI), and Chromium(III) acetylacetonate in water by ion-exchange disk extraction/metal furnace atomic absorption spectrometry

NASA Astrophysics Data System (ADS)

Kamakura, Nao; Inui, Tetsuo; Kitano, Masaru; Nakamura, Toshihiro

A new method for the separate determination of Chromium(III) (Cr(III)), Chromium(VI) (Cr(VI)), and Cr(III) acetylacetonate (Cr(acac)3) in water was developed using a cation-exchange extraction disk (CED) and an anion-exchange extraction disk (AED) combined with metal furnace atomic absorption spectrometry (MFAAS). A 100-mL water sample was adjusted to pH 5.6 and passed through the CED placed on the AED. Cr(acac)3 and Cr(III) were adsorbed on the CED, and Cr(VI) was adsorbed on the AED. The adsorbed Cr(acac)3 was eluted with 50 mL of carbon tetrachloride, followed by the elution of Cr(III) with 50 mL of 3 mol L- 1 nitric acid. Cr(VI) was eluted with 50 mL of 3 mol L- 1 nitric acid. The chemical species of Cr eluted from the CED with carbon tetrachloride was identified as Cr(acac)3 using infrared spectroscopy. The eluate of Cr(acac)3 was diluted to 100 mL with carbon tetrachloride, and those of Cr(III) and Cr(VI) were diluted to 100 mL with deionized water. All of the solutions were subsequently analyzed by MFAAS. The calibration curve for the Cr(acac)3 aqueous solutions exhibited good linearity in the range of 0.1 to 1 ng. The detection limit of Cr, which corresponded to three times the standard deviation (n = 10) of the blank values, was 20 pg. The recovery test for Cr(III), Cr(VI), and Cr(acac)3 exhibited desirable results (96.0%-107%) when 5 μg of each species (50 μg L- 1) was added to 100 mL water samples (i.e., tap water, rainwater, and bottled drinking water). In a humic acid solution, Cr(acac)3 was quantitatively recovered (103%), but Cr(III) and Cr(VI) exhibited poor recoveries (i.e., 84.8% and 78.4%, respectively).

Unconventional Synthesis of γ-Fe2O3: Excellent Low-Concentration Ethanol Sensing Performance

NASA Astrophysics Data System (ADS)

Naskar, Atanu; Narjinary, Mousumi; Kundu, Susmita

2017-01-01

This study reports on a simple unconventional procedure for synthesis of γ-Fe2O3 nanopowder and its fabrication as a resistive ethanol sensor. γ-Fe2O3 powder having an average particle size of ˜15 nm was prepared by thermal decomposition of iron(III) acetylacetonate. Platinum incorporation (0.5-1.5 wt.%) was also carried out for enhancing sensing performance. The powders were characterized using an x-ray diffractometer, x-ray photoelectron spectroscopy, Brunauer-Emmett-Teller surface area, field area scanning electron microscopy, transmission electron microscopy along with energy dispersion x-ray analyses. Sensor fabricated from pure γ-Fe2O3 exhibited excellent ethanol sensing performance at concentrations down to 1 ppm, having a great demand in medical diagnosis and food-processing industries. The response observed for pure γ-Fe2O3 (˜75% for 1 ppm ethanol) was enhanced ˜10% after 1 wt.% Pt impregnation. Sensors were quite stable and selective towards ethanol vapour detection. A possible mechanism for high sensing performance has been discussed.

Monodisperse gold-palladium alloy nanoparticles and their composition-controlled catalysis in formic acid dehydrogenation under mild conditions.

PubMed

Metin, Önder; Sun, Xiaolian; Sun, Shouheng

2013-02-07

Monodisperse 4 nm AuPd alloy nanoparticles with controlled composition were synthesized by co-reduction of hydrogen tetrachloroaurate(III) hydrate and palladium(II) acetylacetonate with a borane-morpholine complex in oleylamine. These NPs showed high activity (TOF = 230 h(-1)) and stability in catalyzing formic acid dehydrogenation and hydrogen production in water at 50 °C without any additives.

Synthesis, Structure and Electrochemistry of Tetranuclear Oxygen-Centered Copper(II) Clusters with Acetylacetone and Benz-pyrazole Hydrolyzed Derivatives as Ligand.

PubMed

Vafazadeh, Rasoul; Willis, Anthony C

2016-01-01

Two copper(II) clusters Cu(4)OCl(6)(pyrazole)4, 1, and Cu(4)OBr(6)(Br-pyrazole)4, 2, have been synthesized by reacting acetylacetone and benzohydrazide (1:1 ratio) with CuX(2) (X = Cl for 1 and X= Br for 2) in methanol solutions. The structures of both clusters have been established by X-ray crystallography. The clusters contain four Cu, one O, six μ(2)-X atoms, and four pyrazole ligands. The pyrazoles was prepared in situ by the reaction of acetylacetone with benzohydrazide in methanol under reflux. In 2, the methine hydrogens of the pyrazole ligands have been replaced by bromine atoms. The four copper atoms encapsulate the central O atom in a tetrahedral arrangement. All copper atoms are five-coordinate and have similar coordination environments with slightly distorted trigonal bipyramidal geometry. The cyclic voltammogram of the clusters 1 and 2 show a one-electron quasi-reversible reduction wave in the region 0.485 to 0.731 V, and a one-electron quasi-reversible oxidation wave in the region 0.767 to 0.898 V. In 1, one irreversible oxidative response is observed on the positive of side of the voltammogram at 1.512 V and this can be assigned to Cu(II) to Cu(III) oxidation.

Construction of an electrode modified with gallium(III) for voltammetric detection of ovalbumin.

PubMed

Sugawara, Kazuharu; Okusawa, Makoto; Takano, Yusaku; Kadoya, Toshihiko

2014-01-01

Electrodes modified with gallium(III) complexes were constructed to detect ovalbumin (OVA). For immobilization of a gallium(III)-nitrilotriacetate (NTA) complex, the electrode was first covered with collagen film. After the amino groups of the film had reacted with isothiocyanobenzyl-NTA, the gallium(III) was then able to combine with the NTA moieties. Another design featured an electrode cast with a gallium(III)-acetylacetonate (AA) complex. The amount of gallium(III) in the NTA complex was equivalent to one-quarter of the gallium(III) that could be utilized from an AA complex. However, the calibration curves of OVA using gallium(III)-NTA and gallium(III)-AA complexes were linear in the ranges of 7.0 × 10(-11) - 3.0 × 10(-9) M and 5.0 × 10(-10) - 8.0 × 10(-9) M, respectively. The gallium(III) on the electrode with NTA complex had high flexibility due to the existence of a spacer between the NTA and the collagen film, and, therefore, the reactivity of the gallium(III) to OVA was superior to that of the gallium(III)-AA complex with no spacer.

Structure and reactivity of a mononuclear non-haem iron(III)–peroxo complex

PubMed Central

Cho, Jaeheung; Jeon, Sujin; Wilson, Samuel A.; Liu, Lei V.; Kang, Eun A; Braymer, Joseph J.; Lim, Mi Hee; Hedman, Britt; Hodgson, Keith O.; Valentine, Joan Selverstone; Solomon, Edward I.; Nam, Wonwoo

2012-01-01

Oxygen-containing mononuclear iron species—iron(III)–peroxo, iron(III)–hydroperoxo and iron(IV)–oxo—are key intermediates in the catalytic activation of dioxygen by iron-containing metalloenzymes1–7. It has been difficult to generate synthetic analogues of these three active iron–oxygen species in identical host complexes, which is necessary to elucidate changes to the structure of the iron centre during catalysis and the factors that control their chemical reactivities with substrates. Here we report the high-resolution crystal structure of a mononuclear non-haem side-on iron(III)–peroxo complex, [Fe(III)(TMC)(OO)]+. We also report a series of chemical reactions in which this iron(III)–peroxo complex is cleanly converted to the iron(III)–hydroperoxo complex, [Fe(III)(TMC)(OOH)]2+, via a short-lived intermediate on protonation. This iron(III)–hydroperoxo complex then cleanly converts to the ferryl complex, [Fe(IV)(TMC)(O)]2+, via homolytic O–O bond cleavage of the iron(III)–hydroperoxo species. All three of these iron species—the three most biologically relevant iron–oxygen intermediates—have been spectroscopically characterized; we note that they have been obtained using a simple macrocyclic ligand. We have performed relative reactivity studies on these three iron species which reveal that the iron(III)–hydroperoxo complex is the most reactive of the three in the deformylation of aldehydes and that it has a similar reactivity to the iron(IV)–oxo complex in C–H bond activation of alkylaromatics. These reactivity results demonstrate that iron(III)–hydroperoxo species are viable oxidants in both nucleophilic and electrophilic reactions by iron-containing enzymes. PMID:22031443

Long-chain amine-templated synthesis of gallium sulfide and gallium selenide nanotubes

NASA Astrophysics Data System (ADS)

Seral-Ascaso, A.; Metel, S.; Pokle, A.; Backes, C.; Zhang, C. J.; Nerl, H. C.; Rode, K.; Berner, N. C.; Downing, C.; McEvoy, N.; Muñoz, E.; Harvey, A.; Gholamvand, Z.; Duesberg, G. S.; Coleman, J. N.; Nicolosi, V.

2016-06-01

We describe the soft chemistry synthesis of amine-templated gallium chalcogenide nanotubes through the reaction of gallium(iii) acetylacetonate and the chalcogen (sulfur, selenium) using a mixture of long-chain amines (hexadecylamine and dodecylamine) as a solvent. Beyond their role as solvent, the amines also act as a template, directing the growth of discrete units with a one-dimensional multilayer tubular nanostructure. These new materials, which broaden the family of amine-stabilized gallium chalcogenides, can be tentatively classified as direct large band gap semiconductors. Their preliminary performance as active material for electrodes in lithium ion batteries has also been tested, demonstrating great potential in energy storage field even without optimization.We describe the soft chemistry synthesis of amine-templated gallium chalcogenide nanotubes through the reaction of gallium(iii) acetylacetonate and the chalcogen (sulfur, selenium) using a mixture of long-chain amines (hexadecylamine and dodecylamine) as a solvent. Beyond their role as solvent, the amines also act as a template, directing the growth of discrete units with a one-dimensional multilayer tubular nanostructure. These new materials, which broaden the family of amine-stabilized gallium chalcogenides, can be tentatively classified as direct large band gap semiconductors. Their preliminary performance as active material for electrodes in lithium ion batteries has also been tested, demonstrating great potential in energy storage field even without optimization. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01663d

Synthesis of BiFeO3 thin films by chemical solution deposition - Structural and magnetic studies

NASA Astrophysics Data System (ADS)

Angappane, S.; Kambhala, Nagaiah

2012-06-01

BiFeO3 thin films were deposited on Si (100) substrates by chemical solution deposition. A precursor solution of bismuth acetate and iron acetylacetonate dissolved in distilled water and acetic acid was spin coated on to silicon substrates at ambient conditions, followed by drying and annealing at 650 °C. The films were characterized by XRD and FESEM to study structural properties and morphology. The magnetic properties studied by SQUID magnetometer shows the ferromagnetic nature of the chemical solution deposited BiFeO3 films which are crucial for low cost device applications.

Benzyl and Methyl Fatty Hydroxamic Acids Based on Palm Kernel Oil as Chelating Agent for Liquid-Liquid Iron(III) Extraction

PubMed Central

Haron, Md Jelas; Jahangirian, Hossein; Silong, Sidik; Yusof, Nor Azah; Kassim, Anuar; Rafiee-Moghaddam, Roshanak; Mahdavi, Behnam; Peyda, Mazyar; Abdollahi, Yadollah; Amin, Jamileh

2012-01-01

Liquid-liquid iron(III) extraction was investigated using benzyl fatty hydroxamic acids (BFHAs) and methyl fatty hydroxamic acids (MFHAs) as chelating agents through the formation of iron(III) methyl fatty hydroxamate (Fe-MFHs) or iron(III) benzyl fatty hydroxamate (Fe-BFHs) in the organic phase. The results obtained under optimized conditions, showed that the chelating agents in hexane extract iron(III) at pH 1.9 were realized effectively with a high percentage of extraction (97.2% and 98.1% for MFHAs and BFHAs, respectively). The presence of a large amount of Mg(II), Ni(II), Al(III), Mn(II) and Co(II) ions did affect the iron(III) extraction. Finally stripping studies for recovering iron(III) from organic phase (Fe-MFHs or Fe-BFHs dissolved in hexane) were carried out at various concentrations of HCl, HNO3 and H2SO4. The results showed that the desired acid for recovery of iron(III) was 5 M HCl and quantitative recovery of iron(III) was achieved from Fe(III)-MFHs and Fe(III)-BFHs solutions in hexane containing 5 mg/L of Fe(III). PMID:22408444

JPRS Report Science & Technology Japan

DTIC Science & Technology

1989-03-02

Oxychlorides MOCln_2 (Organic Metal Salts) Alkoxides M(OR)n Acetylacetonate M(C5H702)n Acetates M(C2H302)n Oxalates M(C204)n/2 2.2 Hydrolysis and Gel...more deeply understanding hydrothermal dynamics during not only a major rupture LOCA but also a minor rupture LOCA and clarifying the combination of... hydrothermal dynamics of the coolant from the beginning of LOCA to its end, using a scale model of PWR (pressurized water reactor). Under the ROSA-III Plan

Luminescence behaviour and deposition of Sc2O3 thin films from scandium(III) acetylacetonate at ambient pressure

NASA Astrophysics Data System (ADS)

Dixon, Sebastian C.; Jiamprasertboon, Arreerat; Carmalt, Claire J.; Parkin, Ivan P.

2018-05-01

Scandium(III) oxide thin film deposition has been historically difficult to achieve without the use of vacuum-based or wet chemical systems due to precursor limitations of low vapour pressure or ambient instability. In this letter, the adoption of aerosol-assisted delivery of scandium(III) acetylacetonate has enabled the chemical vapour deposition of polycrystalline and amorphous Sc2O3 thin films at ambient pressure with high growth rates (ca. 500 nm h-1). The scandia films were intrinsically highly photoluminescent, exhibiting broad emission bands centred at 3.6 and 3.0 eV, which increased significantly in intensity upon aerobic annealing, accompanying a transition from amorphous to crystalline, while bands appearing at 2.1 and 2.3 eV seemed to occur only in the crystalline films. In addition, both amorphous and crystalline scandia films exhibited blue-green vibronic fine structure between 2.3 and 3.2 eV attributed to the electronic transition B→κ Σ+ 2 Σ+ in surface ⋯ O - ⋯ O - S c = O groups and split by a vibrational mode observed at 920 ± 60 cm - 1 by infrared spectroscopy. Band gaps of amorphous and crystalline Sc2O3 were determined to be 5.3 and 5.7 eV, respectively via diffuse reflectance. All films had high refractive indices, varying between 1.8 and 2.0 at 400 nm depending on film thickness and carrier gas used in the deposition; film thicknesses less than ca. 300 nm were observed to have a strong influence on the refractive index measured, while there was little variation for films thicker than this. The synthesis process itself is exceedingly low-cost and facile thus promising streamlined industrial scalability.

[Preliminary studies on physicochemical properties of Angelica sinensis polysaccharide-iron complex].

PubMed

Wang, Kai-ping; Zhang, Yu; Dai, Li-quan

2006-05-01

To study some physicochemical properties of Angelica sinensis polysaccharide-iron complex (APC). Based on the qualitatively identified reactions of iron (III), the qualitatively identified reactions of APC were found out by comparing hydroxide. The content of iron (III) in APC was determined with iodometry. The stability of APC under physiological pH conditions was judged by titrating APC with sodium hydroxide. The deoxidization of APC was tested with colorimetric analysis. APC showed the qualitatively identified reactions of iron (III). The content of iron (III) in APC ranged from 10% to 40%, and the water-solubility of APC was related to the content of iron (III). The complex was stable at physiological pH from 3 to 12, without precipitation and dissociation. At 37 degrees C, Fe (III) in the complex was completely reduced to Fe (III) by ascorbic acid in about 6 hours. APC can be qualitatively identified by using the qualitatively identified reactions of iron (III). When its iron (III) content is within 20%-25%, APC has a better ability to dissolve in water. And the complex is stable under physiological pH conditions.

Phosphorescence white organic light-emitting diodes with single emitting layer based on isoquinolinefluorene-carbazole containing host.

PubMed

Koo, Ja Ryong; Lee, Seok Jae; Hyung, Gun Woo; Kim, Bo Young; Shin, Hyun Su; Lee, Kum Hee; Yoon, Seung Soo; Kim, Woo Young; Kim, Young Kwan

2013-03-01

We have demonstrated a stable phosphorescent white organic light-emitting diodes (WOLEDs) using an orange emitter, Bis(5-benzoyl-2-(4-fluorophenyl)pyridinato-C,N) iridium(III)acetylacetonate [(Bz4Fppy)2Ir(III)acac] doped into a newly synthesized blue host material, 2-(carbazol-9-yl)-7-(isoquinolin-1-yl)-9,9-diethylfluorene (CzFliq). When 1 wt.% (Bz4Fppy)2Ir(III)acac was doped into emitting layer, it was realized an improved EL performance and a pure white color in the OLED. The optimum WOLED showed maximum values as a luminous efficiency of 10.14 cd/A, a power efficiency of 10.24 Im/W, a peak external quantum efficiency 4.07%, and Commission Internationale de L'Eclairage coordinates of (0.34, 0.39) at 8 V.

Long-Range Intramolecular Electronic Communication in a Trinuclear Ruthenium Tropolonate Complex.

PubMed

Yoshida, Jun; Kuwahara, Kyohei; Suzuki, Kota; Yuge, Hidetaka

2017-02-20

Dinuclear and trinuclear ruthenium complexes, [Ru(trop) 2 (C 2 trop)Ru(dppe)Cp] [2b; trop = tropolonato, C 2 trop = ethynyltropolonato, dppe = 1,2-bis(diphenylphosphino)ethane] and [Ru(trop){(C 2 trop)Ru(dppe)Cp} 2 ] (3), were synthesized, and their electronic and electrochemical properties were investigated in comparison with our previously reported complex [Ru(acac) 2 (C 2 trop)Ru(dppe)Cp] (2a). The electron-donating Ru II (dppe)Cp unit and electron-accepting Ru III O 6 unit are connected by C 2 trop in these complexes. 2a incorporates acetylacetonate as an ancillary ligand, while 2b and 3 incorporate tropolonate as an ancillary ligand. Every complex, 2a, 2b, and 3, exhibits similar UV-vis-near-IR (NIR) absorption spectra, demonstrating the lack of explicit intramolecular electronic communication between the units at least in the neutral state. The weak NIR absorption in 2a further diminished upon electrochemical oxidation, indicating almost no electronic communication between the units. In contrast, 2b and 3 exhibit broad NIR absorptions upon oxidation. Additionally, 3 exhibits four stepwise redox couples in the electrochemical study, which are formally attributed to [Ru II (trop) 3 ] - /[Ru III (trop) 3 ], two [Ru II (dppe)Cp]/[Ru III (dppe)Cp] + , and [Ru III (trop) 3 ]/[Ru IV (trop) 3 ] + couples. Clear separation of the redox couples attributed to the two terminal [Ru(dppe)Cp] units demonstrates the thermodynamic stability of the intermediate oxidation states with respect to disproportionation. Further electrochemical studies using an electrolyte including perfluorinated weakly coordinating anions and density functional theory/time-dependent density functional theory calculations confirmed the effect of ancillary ligands, acetylacetonate and tropolonate. In the case of 2a, electronic delocalization over the whole complex, especially over the [Ru(acac) 2 (trop)] unit, appears to be small. In contrast, the electronic communication between [Ru(dppe)Cp] and [Ru(trop) 3 ] units in 3 seems to be enhanced upon oxidation, resulting in the long-range intramolecular electronic communication.

Synthesis and characterization of a new Inonotus obliquus polysaccharide-iron(III) complex.

PubMed

Wang, Jia; Chen, Haixia; Wang, Yanwei; Xing, Lisha

2015-04-01

A new Inonotus obliquus polysaccharide-iron(III) complex (IOPS-iron) was synthesized and characterized. The preparation conditions of IOPS-iron(III) were optimized and the physicochemical properties were characterized by physicochemical methods, scanning electron microscopy (SEM), electron paramagnetic resonance (EPR) spectroscopy, fourier transform infrared (FTIR) spectroscopy, circular dichroism (CD) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy, respectively. The highest iron content of IOPS-iron(III) complex (19.40%) was obtained at the conditions: the ratio of IOPS and FeCl3 • 6H2O was 3:5 (w/w), the pH value of alkali solution was 10, the reaction temperature was 30 °C and the reaction time was 6h. The iron(III) was shown to be bound through the binding sites of the polysaccharide IOPS and it could form spatially separated iron centers on the polysaccharide backbone. IOPS-iron(III) complex was found to have good digestive availability and antioxidant activities in the in vitro assays, which suggested the IOPS-iron(III) complex might be used as a new iron supplement candidate. Copyright © 2015 Elsevier B.V. All rights reserved.

Thermal neutron capture cross section for 56Fe(n ,γ )

NASA Astrophysics Data System (ADS)

Firestone, R. B.; Belgya, T.; Krtička, M.; Bečvář, F.; Szentmikloṡi, L.; Tomandl, I.

2017-01-01

The 56Fe(n ,γ ) thermal neutron capture cross section and the 57Fe level scheme populated by this reaction have been investigated in this work. Singles γ -ray spectra were measured with an isotopically enriched 56Fe target using the guided cold neutron beam at the Budapest Reactor, and γ γ -coincidence data were measured with a natural Fe target at the LWR-15 research reactor in Řež, Czech Republic. A detailed level scheme consisting of 448 γ rays populating/depopulating 97 levels and the capture state in 57Fe has been constructed, and ≈99 % of the total transition intensity has been placed. The transition probability of the 352-keV γ ray was determined to be Pγ(352 ) =11.90 ±0.07 per 100 neutron captures. The 57Fe level scheme is substantially revised from earlier work and ≈33 previously assigned levels could not be confirmed while a comparable number of new levels were added. The 57Feγ -ray cross sections were internally calibrated with respect to 1H and 32Sγ -ray cross section standards using iron(III) acetylacetonate (C15H21FeO6) and iron pyrite (FeS2) targets. The thermal neutron cross section for production of the 352-keV γ -ray cross section was determined to be σγ(352 ) =0.2849 ±0.015 b. The total 56Fe(n ,γ ) thermal radiative neutron cross section is derived from the 352-keV γ -ray cross section and transition probability as σ0=2.394 ±0.019 b. A least-squares fit of the γ rays to the level scheme gives the 57Fe neutron separation energy Sn=7646.183 ±0.018 keV.

Synthesis of Nanometric-Sized Barium Titanate Powders Using Acetylacetone as the Chelating Agent in a Sol-Precipitation Process

NASA Astrophysics Data System (ADS)

Hung, Kun Ming; Hsieh, Ching Shieh; Yang, Wein Duo; Tsai, Hui Ju

2007-03-01

Nanometric-sized barium titanate powders were prepared by using titanium isopropoxid as the raw material and acetylacetone as a chelating agent, in a strong alkaline solution (pH > 13) through the sol-precipitation method. The preparatory variables affect the extent of cross-linking in the structure, change the mode of condensation of the gels, and even control the particle size of the powder. The reaction rate of forming powder, at a higher temperature such as 100°C and more water content (the molar ratio of water to titanium isopropoxide is 25) or fewer acetylacetone (the molar ratio of acetylacetone to titanium isopropoxide is 1), is rapid and the particle size formed is finer at 60 80 nm. On the contrary, that of forming powder, at lower temperature (40°C) and less water content (molar ratio of water/titanium isopropoxide = 5) or higher acetylacetone (acetylacetone/titanium isopropoxide = 7), is slow and the particle size of the powder is larger. The optimal preparatory conditions were obtained by using the experimental statistical method; as a result, nanometric-sized BaTiO3 powder with an average particle size of about 50 nm was prepared.

Cobalt- and iron-based nanoparticles hosted in SBA-15 mesoporous silica and activated carbon from biomass: Effect of modification procedure

NASA Astrophysics Data System (ADS)

Tsoncheva, Tanya; Genova, Izabela; Paneva, Daniela; Dimitrov, Momtchil; Tsyntsarski, Boyko; Velinov, Nicolay; Ivanova, Radostina; Issa, Gloria; Kovacheva, Daniela; Budinova, Temenujka; Mitov, Ivan; Petrov, Narzislav

2015-10-01

Ordered mesoporous silica of SBA-15 type and activated carbon, prepared from waste biomass (peach stones), are used as host matrix of nanosized iron and cobalt particles. The effect of preparation procedure on the state of loaded nanoparticles is in the focus of investigation. The obtained materials are characterized by Boehm method, low temperature physisorption of nitrogen, XRD, UV-Vis, FTIR, Mossbauer spectroscopy and temperature programmed reduction with hydrogen. The catalytic behaviour of the samples is tested in methanol decomposition. The dispersion, oxidative state and catalytic behaviour of loaded cobalt and iron nanoparticles are successfully tuned both by the nature of porous support and the metal precursor used during the samples preparation. Facile effect of active phase deposition from aqueous solution of nitrate precursors is assumed for activated carbon support. For the silica based materials the catalytic activity could be significantly improved when cobalt acetylacetonate is used during the modification. The complex effect of pore topology and surface functionality of different supports on the active phase formation is discussed.

Stabilized gold nanoparticles by laser ablation in ferric chloride solutions

NASA Astrophysics Data System (ADS)

Nouraddini, M. I.; Ranjbar, M.; Dobson, P. J.; Farrokhpour, H.; Johnston, C.; Jurkschat, K.

2017-12-01

In this study, laser ablation of gold was performed in different ferric chloride solutions and water as a reference. The ferric chloride solutions included hexachloro iron(III) and aquachloro iron(III) having low and high hydrolysis degree. Transmission electron microscope (TEM) images showed spherical gold nanoparticles (GNPs) in water, particles which are strongly agglomerated with intimate contact at their interfaces in hexachloro iron(III) and individual separated particles with a halo of an iron component in aquachloro iron(III). In addition, no combination of Au and Fe was found in HAADF analysis or X-ray diffraction (XRD) patterns. In optical investigations, it was observed that gold nanoparticles made in hexachloro iron(III) solutions have localized surface plasmon resonance (LSPR) peaks broader than in the case of water that are quenched after a few hours, while ablation in the aquachloro iron(III) solution provides narrow LSPR absorption with a long-term stability. According to X-ray photoelectron spectroscopy (XPS) there are metallic Au and Fe2+ states in the drop-casted samples. By comparison of cyclic voltammetry of solutions before and after laser ablation, strong agglomeration in hexachloro iron(III) was attributed to the reducing role of iron(III) creating an unstable gold surface in the chloride solution. In aquachloro iron(III), however, the observed stability was attributed to the formation of the halo of an iron compound around the particles.

An isoelectronic NO dioxygenase reaction using a nonheme iron(III)-peroxo complex and nitrosonium ion.

PubMed

Yokoyama, Atsutoshi; Han, Jung Eun; Karlin, Kenneth D; Nam, Wonwoo

2014-02-18

Reaction of a nonheme iron(III)-peroxo complex, [Fe(III)(14-TMC)(O2)](+), with NO(+), a transformation which is essentially isoelectronic with that for nitric oxide dioxygenases [Fe(III)(O2˙(-)) + NO], affords an iron(IV)-oxo complex, [Fe(IV)(14-TMC)(O)](2+), and nitrogen dioxide (NO2), followed by conversion to an iron(III)-nitrato complex, [Fe(III)(14-TMC)(NO3)(F)](+).

An isoelectronic NO dioxygenase reaction using a nonheme iron(III)-peroxo complex and nitrosonium ion†

PubMed Central

Yokoyama, Atsutoshi; Han, Jung Eun; Karlin, Kenneth D.; Nam, Wonwoo

2014-01-01

Reaction of a nonheme iron(III)-peroxo complex, [FeIII(14-TMC)(O2)]+, with NO+, a transformation which is essentially isoelectronic with that for nitric oxide dioxygenases [Fe(III)(O2•−) + NO], affords an iron(IV)-oxo complex, [FeIV(14-TMC)(O)]2+, and nitrogen dioxide (NO2), followed by conversion to an iron(III)-nitrato complex, [FeIII(14-TMC)(NO3)(F)]+. PMID:24394960

Transgenic Petunia with the Iron(III)-Phytosiderophore Transporter Gene Acquires Tolerance to Iron Deficiency in Alkaline Environments

PubMed Central

Murata, Yoshiko; Itoh, Yoshiyuki; Iwashita, Takashi; Namba, Kosuke

2015-01-01

Iron is an essential nutrient for all plants. However, terrestrial plants often suffer from iron deficiency in alkaline soil due to its extremely low solubility. Alkaline soil accounts for about 30% of all cultivated ground in the world. Plants have evolved two distinct strategies, I and II, for iron uptake from the soil. Dicots and non-graminaceous monocots use Strategy I, which is primarily based on the reduction of iron(III) to iron(II) and the uptake of iron(II) by the iron-regulated transporter, IRT1. In contrast, graminaceous plants use Strategy II to efficiently acquire insoluble iron(III). Strategy II comprises the synthesis and secretion of iron-chelating phytosiderophores, such as mugineic acids and the Yellow Stripe 1 transporter proteins of the iron(III)-phytosiderophore complex. Barley, which exhibits the highest tolerance to iron deficiency in alkaline soil among graminaceous plants, utilizes mugineic acids and the specific iron(III)-mugineic acids transporter, HvYS1. In this study, we established the transgenic plant Petunia hybrida, which originally had only Strategy I, by introducing the HvYS1 transporter gene derived from barley. When the transgenic plants were grown hydroponically in media containing the iron(III)-2′-deoxymugineic acid complex, free 2′-deoxymugineic acid and its iron(III) complex were detected in the root extract of the transgenic plant by electrospray ionization-Fourier transform-ion cyclotron resonance mass spectrometry. The growth of the transgenic petunia was significantly better than that of the control host in alkaline conditions. Consequently, the transgenic plant acquired a significantly enhanced tolerance to alkaline hydroponic media in the presence of the iron(III)-2′-deoxymugineic acid complex. Furthermore, the flower color of the transgenic plant deepened. The results showed that iron-phytosiderophore complexes and their transporters can potentially be utilized to overcome the worldwide iron uptake problems to diverse plant species that are found in areas with alkaline conditions. PMID:25781941

Transgenic petunia with the iron(III)-phytosiderophore transporter gene acquires tolerance to iron deficiency in alkaline environments.

PubMed

Murata, Yoshiko; Itoh, Yoshiyuki; Iwashita, Takashi; Namba, Kosuke

2015-01-01

Iron is an essential nutrient for all plants. However, terrestrial plants often suffer from iron deficiency in alkaline soil due to its extremely low solubility. Alkaline soil accounts for about 30% of all cultivated ground in the world. Plants have evolved two distinct strategies, I and II, for iron uptake from the soil. Dicots and non-graminaceous monocots use Strategy I, which is primarily based on the reduction of iron(III) to iron(II) and the uptake of iron(II) by the iron-regulated transporter, IRT1. In contrast, graminaceous plants use Strategy II to efficiently acquire insoluble iron(III). Strategy II comprises the synthesis and secretion of iron-chelating phytosiderophores, such as mugineic acids and the Yellow Stripe 1 transporter proteins of the iron(III)-phytosiderophore complex. Barley, which exhibits the highest tolerance to iron deficiency in alkaline soil among graminaceous plants, utilizes mugineic acids and the specific iron(III)-mugineic acids transporter, HvYS1. In this study, we established the transgenic plant Petunia hybrida, which originally had only Strategy I, by introducing the HvYS1 transporter gene derived from barley. When the transgenic plants were grown hydroponically in media containing the iron(III)-2'-deoxymugineic acid complex, free 2'-deoxymugineic acid and its iron(III) complex were detected in the root extract of the transgenic plant by electrospray ionization-Fourier transform-ion cyclotron resonance mass spectrometry. The growth of the transgenic petunia was significantly better than that of the control host in alkaline conditions. Consequently, the transgenic plant acquired a significantly enhanced tolerance to alkaline hydroponic media in the presence of the iron(III)-2'-deoxymugineic acid complex. Furthermore, the flower color of the transgenic plant deepened. The results showed that iron-phytosiderophore complexes and their transporters can potentially be utilized to overcome the worldwide iron uptake problems to diverse plant species that are found in areas with alkaline conditions.

Mössbauer spectroscopic characterization of iron methyl pyropheophorbide a and its derivatives

NASA Astrophysics Data System (ADS)

Inoue, H.; Soeda, K.; Akahori, H.; Nonomura, Y.; Yoshioka, N.

1994-12-01

Two kinds of iron chlorophylls, i.e. (methyl pyropheophorbide a)iron(III) chloride and its bis-pyridine adduct, were prepared and characterized by57Fe Mössbauer spectroscopy. (Methyl pyropheophorbide a)iron(III) chloride gave an asymmetric quadrupole-split doublet typical of high-spin iron(III) chlorophylls, while its bis-pyridine adduct showed a symmetric quadrupole-split doublet characteristic of low-spin iron(II) chlorophylls. The isomer shift and quadrupole splitting obtained for (methyl pyropheophorbide a)iron(III) chloride and its bis-pyridine adduct have led to the following conclusions. The substitution of the bulky phytyl group for the methyl group hardly affects the electronic state of the iron(II,III) ion, but the elimination of the methoxycarbonyl group increases the planarity of the macrocyclic chlorin ligand.

Magnetic Susceptibility: A Practical Introduction.

ERIC Educational Resources Information Center

Greenaway, A. M.; Trail, L. E.

1983-01-01

Describes an experiment in which students: (1) synthesize tris(acetylacetonato)iron(III), tris(diethyldithiocarbamato)iron(III), and chlorobis(diethyldithiocarbmamato)iron(III); (2) are given a sample of potassium hexocyanoferrate(III); and (3) are then asked to measure the room temperature of these samples using the Guoy technique. Background…

Indirect Redox Transformations of Iron, Copper, and Chromium Catalyzed by Extremely Acidophilic Bacteria

PubMed Central

Johnson, D. Barrie; Hedrich, Sabrina; Pakostova, Eva

2017-01-01

Experiments were carried out to examine redox transformations of copper and chromium by acidophilic bacteria (Acidithiobacillus, Leptospirillum, and Acidiphilium), and also of iron (III) reduction by Acidithiobacillus spp. under aerobic conditions. Reduction of iron (III) was found with all five species of Acidithiobacillus tested, grown aerobically on elemental sulfur. Cultures maintained at pH 1.0 for protracted periods displayed increasing propensity for aerobic iron (III) reduction, which was observed with cell-free culture liquors as well as those containing bacteria. At. caldus grown on hydrogen also reduced iron (III) under aerobic conditions, confirming that the unknown metabolite(s) responsible for iron (III) reduction were not (exclusively) sulfur intermediates. Reduction of copper (II) by aerobic cultures of sulfur-grown Acidithiobacillus spp. showed similar trends to iron (III) reduction in being more pronounced as culture pH declined, and occurring in both the presence and absence of cells. Cultures of Acidithiobacillus grown anaerobically on hydrogen only reduced copper (II) when iron (III) (which was also reduced) was also included; identical results were found with Acidiphilium cryptum grown micro-aerobically on glucose. Harvested biomass of hydrogen-grown At. ferridurans oxidized iron (II) but not copper (I), and copper (I) was only oxidized by growing cultures of Acidithiobacillus spp. when iron (II) was also included. The data confirmed that oxidation and reduction of copper were both mediated by acidophilic bacteria indirectly, via iron (II) and iron (III). No oxidation of chromium (III) by acidophilic bacteria was observed even when, in the case of Leptospirillum spp., the redox potential of oxidized cultures exceeded +900 mV. Cultures of At. ferridurans and A. cryptum reduced chromium (VI), though only when iron (III) was also present, confirming an indirect mechanism and contradicting an earlier report of direct chromium reduction by A. cryptum. Measurements of redox potentials of iron, copper and chromium couples in acidic, sulfate-containing liquors showed that these differed from situations where metals are not complexed by inorganic ligands, and supported the current observations of indirect copper oxido-reduction and chromium reduction mediated by acidophilic bacteria. The implications of these results for both industrial applications of acidophiles and for exobiology are discussed. PMID:28239375

Ferrocene and cobaltocene derivatives for non-aqueous redox flow batteries.

PubMed

Hwang, Byunghyun; Park, Min-Sik; Kim, Ketack

2015-01-01

Ferrocene and cobaltocene and their derivatives are studied as new redox materials for redox flow cells. Their high reaction rates and moderate solubility are attractive properties for their use as active materials. The cyclability experiments are carried out in a static cell; the results showed that these materials exhibit stable capacity retention and predictable discharge potentials, which agree with the potential values from the cyclic voltammograms. The diffusion coefficients of these materials are 2 to 7 times higher than those of other non-aqueous materials such as vanadium acetylacetonate, iron tris(2,2'-bipyridine) complexes, and an organic benzene derivative. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation and in vitro evaluation of folate-receptor-targeted SPION-polymer micelle hybrids for MRI contrast enhancement in cancer imaging

NASA Astrophysics Data System (ADS)

Mahajan, Shveta; Koul, Veena; Choudhary, Veena; Shishodia, Gauri; Bharti, Alok C.

2013-01-01

Polymer-SPION hybrids were investigated for receptor-mediated localization in tumour tissue. Superparamagnetic iron oxide nanoparticles (SPIONs) prepared by high-temperature decomposition of iron acetylacetonate were monodisperse (9.27 ± 3.37 nm), with high saturation magnetization of 76.8 emu g-1. Amphiphilic copolymers prepared from methyl methacrylate and PEG methacrylate by atom transfer radical polymerization were conjugated with folic acid (for folate-receptor specificity). The folate-conjugated polymer had a low critical micellar concentration (0.4 mg l-1), indicating stability of the micellar formulation. SPION-polymeric micelle clusters were prepared by desolvation of the SPION dispersion/polymer solution in water. Magnetic resonance imaging of the formulation revealed very good contrast enhancement, with transverse (T2) relaxivity of 260.4 mM-1 s-1. The biological evaluation of the SPION micelles included cellular viability assay (MTT) and uptake in HeLa cells. These studies demonstrated the potential use of these nanoplatforms for imaging and targeting.

Differences and Comparisons of the Properties and Reactivities of Iron(III)–hydroperoxo Complexes with Saturated Coordination Sphere

PubMed Central

Faponle, Abayomi S; Quesne, Matthew G; Sastri, Chivukula V; Banse, Frédéric; de Visser, Sam P

2015-01-01

Heme and nonheme monoxygenases and dioxygenases catalyze important oxygen atom transfer reactions to substrates in the body. It is now well established that the cytochrome P450 enzymes react through the formation of a high-valent iron(IV)–oxo heme cation radical. Its precursor in the catalytic cycle, the iron(III)–hydroperoxo complex, was tested for catalytic activity and found to be a sluggish oxidant of hydroxylation, epoxidation and sulfoxidation reactions. In a recent twist of events, evidence has emerged of several nonheme iron(III)–hydroperoxo complexes that appear to react with substrates via oxygen atom transfer processes. Although it was not clear from these studies whether the iron(III)–hydroperoxo reacted directly with substrates or that an initial O–O bond cleavage preceded the reaction. Clearly, the catalytic activity of heme and nonheme iron(III)–hydroperoxo complexes is substantially different, but the origins of this are still poorly understood and warrant a detailed analysis. In this work, an extensive computational analysis of aromatic hydroxylation by biomimetic nonheme and heme iron systems is presented, starting from an iron(III)–hydroperoxo complex with pentadentate ligand system (L52). Direct C–O bond formation by an iron(III)–hydroperoxo complex is investigated, as well as the initial heterolytic and homolytic bond cleavage of the hydroperoxo group. The calculations show that [(L52)FeIII(OOH)]2+ should be able to initiate an aromatic hydroxylation process, although a low-energy homolytic cleavage pathway is only slightly higher in energy. A detailed valence bond and thermochemical analysis rationalizes the differences in chemical reactivity of heme and nonheme iron(III)–hydroperoxo and show that the main reason for this particular nonheme complex to be reactive comes from the fact that they homolytically split the O–O bond, whereas a heterolytic O–O bond breaking in heme iron(III)–hydroperoxo is found. PMID:25399782

Lattice Matched Carbide–Phosphide Composites with Superior Electrocatalytic Activity and Stability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Regmi, Yagya N.; Roy, Asa; King, Laurie A.

Composites of electrocatalytically active transition-metal compounds present an intriguing opportunity toward enhanced activity and stability. Here, to identify potentially scalable pairs of a catalytically active family of compounds, we demonstrate that phosphides of iron, nickel, and cobalt can be deposited on molybdenum carbide to generate nanocrystalline heterostructures. Composites synthesized via solvothermal decomposition of metal acetylacetonate salts in the presence of highly dispersed carbide nanoparticles show hydrogen evolution activities comparable to those of state-of-the-art non-noble metal catalysts. Investigation of the spent catalyst using high resolution microscopy and elemental analysis reveals that formation of carbide–phosphide composite prevents catalyst dissolution in acid electrolyte.more » Lattice mismatch between the two constituent electrocatalysts can be used to rationally improve electrochemical stability. Among the composites of iron, nickel, and cobalt phosphide, iron phosphide displays the lowest degree of lattice mismatch with molybdenum carbide and shows optimal electrochemical stability. Turnover rates of the composites are higher than that of the carbide substrate and compare favorably to other electrocatalysts based on earth-abundant elements. Lastly, our findings will inspire further investigation into composite nanocrystalline electrocatalysts that use molybdenum carbide as a stable catalyst support.« less

Lattice Matched Carbide–Phosphide Composites with Superior Electrocatalytic Activity and Stability

DOE PAGES

Regmi, Yagya N.; Roy, Asa; King, Laurie A.; ...

2017-10-19

Composites of electrocatalytically active transition-metal compounds present an intriguing opportunity toward enhanced activity and stability. Here, to identify potentially scalable pairs of a catalytically active family of compounds, we demonstrate that phosphides of iron, nickel, and cobalt can be deposited on molybdenum carbide to generate nanocrystalline heterostructures. Composites synthesized via solvothermal decomposition of metal acetylacetonate salts in the presence of highly dispersed carbide nanoparticles show hydrogen evolution activities comparable to those of state-of-the-art non-noble metal catalysts. Investigation of the spent catalyst using high resolution microscopy and elemental analysis reveals that formation of carbide–phosphide composite prevents catalyst dissolution in acid electrolyte.more » Lattice mismatch between the two constituent electrocatalysts can be used to rationally improve electrochemical stability. Among the composites of iron, nickel, and cobalt phosphide, iron phosphide displays the lowest degree of lattice mismatch with molybdenum carbide and shows optimal electrochemical stability. Turnover rates of the composites are higher than that of the carbide substrate and compare favorably to other electrocatalysts based on earth-abundant elements. Lastly, our findings will inspire further investigation into composite nanocrystalline electrocatalysts that use molybdenum carbide as a stable catalyst support.« less

Effect of iron(III) ion on moso bamboo pyrolysis under microwave irradiation.

PubMed

Dong, Qing; Li, Xiangqian; Wang, Zhaoyu; Bi, Yanhong; Yang, Rongling; Zhang, Jinfeng; Luo, Hongzhen; Niu, Miaomiao; Qi, Bo; Lu, Chen

2017-11-01

The effect of iron(III) ion on microwave pyrolysis of moso bamboo was investigated. Hydrofluoric acid washing was used as a pilot process to demineralize moso bamboo in order to eliminate the influences of the other inorganics contained in moso bamboo itself. The results indicated that the addition of iron(III) ion increased the maximal reaction temperatures under microwave condition dependent on the amount of the added iron(III) ion. The production of the non-condensable gases was promoted by the addition of iron(III) ion mainly at the expense of liquid products. Iron(III) ion exhibited the positive effect for syngas production and inhibited the formation of CO 2 and CH 4 . The formation of Fe 2 O 3 and Fe 3 O 4 was found during microwave pyrolysis and the mechanism of the two metallic oxides formation was described in this work. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of iron on optical properties of dissolved organic matter.

PubMed

Poulin, Brett A; Ryan, Joseph N; Aiken, George R

2014-09-02

Iron is a source of interference in the spectroscopic analysis of dissolved organic matter (DOM); however, its effects on commonly employed ultraviolet and visible (UV-vis) light adsorption and fluorescence measurements are poorly defined. Here, we describe the effects of iron(II) and iron(III) on the UV-vis absorption and fluorescence of solutions containing two DOM fractions and two surface water samples. In each case, regardless of DOM composition, UV-vis absorption increased linearly with increasing iron(III). Correction factors were derived using iron(III) absorption coefficients determined at wavelengths commonly used to characterize DOM. Iron(III) addition increased specific UV absorbances (SUVA) and decreased the absorption ratios (E2:E3) and spectral slope ratios (SR) of DOM samples. Both iron(II) and iron(III) quenched DOM fluorescence at pH 6.7. The degree and region of fluorescence quenching varied with the iron:DOC concentration ratio, DOM composition, and pH. Regions of the fluorescence spectra associated with greater DOM conjugation were more susceptible to iron quenching, and DOM fluorescence indices were sensitive to the presence of both forms of iron. Analyses of the excitation-emission matrices using a 7- and 13-component parallel factor analysis (PARAFAC) model showed low PARAFAC sensitivity to iron addition.

Effects of iron on optical properties of dissolved organic matter

USGS Publications Warehouse

Poulin, Brett; Ryan, Joseph N.; Aiken, George R.

2014-01-01

Iron is a source of interference in the spectroscopic analysis of dissolved organic matter (DOM); however, its effects on commonly employed ultraviolet and visible (UV–vis) light adsorption and fluorescence measurements are poorly defined. Here, we describe the effects of iron(II) and iron(III) on the UV–vis absorption and fluorescence of solutions containing two DOM fractions and two surface water samples. In each case, regardless of DOM composition, UV–vis absorption increased linearly with increasing iron(III). Correction factors were derived using iron(III) absorption coefficients determined at wavelengths commonly used to characterize DOM. Iron(III) addition increased specific UV absorbances (SUVA) and decreased the absorption ratios (E2:E3) and spectral slope ratios (SR) of DOM samples. Both iron(II) and iron(III) quenched DOM fluorescence at pH 6.7. The degree and region of fluorescence quenching varied with the iron:DOC concentration ratio, DOM composition, and pH. Regions of the fluorescence spectra associated with greater DOM conjugation were more susceptible to iron quenching, and DOM fluorescence indices were sensitive to the presence of both forms of iron. Analyses of the excitation–emission matrices using a 7- and 13-component parallel factor analysis (PARAFAC) model showed low PARAFAC sensitivity to iron addition.

Reactive oxygen species and associated reactivity of peroxymonosulfate activated by soluble iron species

NASA Astrophysics Data System (ADS)

Watts, Richard J.; Yu, Miao; Teel, Amy L.

2017-10-01

The activation of peroxymonosulfate by iron (II), iron (III), and iron (III)-EDTA for in situ chemical oxidation (ISCO) was compared using nitrobenzene as a hydroxyl radical probe, anisole as a hydroxyl radical + sulfate radical probe, and hexachloroethane as a reductant + nucleophile probe. In addition, activated peroxymonosulfate was investigated for the treatment of the model groundwater contaminants perchloroethylene (PCE) and trichloroethylene (TCE). The relative activities of hydroxyl radical and sulfate radical in the degradation of the probe compounds and PCE and TCE were isolated using the radical scavengers tert-butanol and isopropanol. Iron (II), iron (III), and iron (III)-EDTA effectively activated peroxymonosulfate to generate hydroxyl radical and sulfate radical, but only a minimal flux of reductants or nucleophiles. Iron (III)-EDTA was a more effective activator than iron (II) and iron (III), and also provided a non-hydroxyl radical, non-sulfate radical degradation pathway. The contribution of sulfate radical relative to hydroxyl radical followed the order of anisole > > TCE > PCE > > nitrobenzene; i.e., sulfate radical was less dominant in the oxidation of more oxidized target compounds. Sulfate radical is often assumed to be the primary oxidant in activated peroxymonosulfate and persulfate systems, but the results of this research demonstrate that the reactivity of sulfate radical with the target compound must be considered before drawing such a conclusion.

In vivo anti-radiation activities of the Ulva pertusa polysaccharides and polysaccharide-iron(III) complex.

PubMed

Shi, Jinming; Cheng, Cuilin; Zhao, Haitian; Jing, Jing; Gong, Ning; Lu, Weihong

2013-09-01

Polysaccharides with different molecular weights were extracted from Ulva pertusa and fractionated by ultrafiltration. Iron(III) complex of the low molecular-weight U. pertusa polysaccharides were synthesized. Atomic absorption spectrum showed that the iron content of iron(III)-polysaccharide complex was 27.4%. The comparison between U. pertusa polysaccharides and their iron(III) complex showed that iron chelating altered the structural characteristics of the polysaccharides. The bioactivity analysis showed that polysaccharide with low molecular weight was more effective than polysaccharide with high molecular weight in protecting mice from radiation induced damages on bone marrow cells and immune system. Results also proved that the anti-radiation and anti-oxidative activity of iron(III) complex of low molecular-weight polysaccharides were not less than that of low molecular-weight polysaccharides. Copyright © 2013 Elsevier B.V. All rights reserved.

ROLE OF IRON (II, III) HYDROXYCARBONATE GREEN RUST IN ARSENIC REMEDIATION USING ZEROVALENT IRON IN COLUMN TESTS

EPA Science Inventory

We examined corrosion products of zerovalent iron (Peerless iron) that was used in three column tests for removing arsenic under dynamic flow conditions with and without added phosphate and silicate. Iron(II, III) hydroxycarbonate and magnetite were major iron corrosion products...

ZT 0.1 Electron-Carrying Polymer Thermoelectric Composites with In Situ SnCl 2 Microstructure Growth (Open Access)

DTIC Science & Technology

2015-05-08

derivatives as potential dopants , [ 21 ] achieving elec- trical conductivities of nearly 0.01 S cm −1 and PF of 0.6 W m −1 K −2 . Segalman and co-workers...Weinheim cobalt (III) acetylacetonate (Co(acac) 3 )) to show more broadly that weakly doping microstructured inclusions can act synergis- tically with...P3 ) and PBTTT-C14 ( P4 ). The weak dopant Co(acac) 3 will form large crystals readily in p-type polymers such as P3 and P4 . S > 2000 µV K

Simple solvothermal synthesis of hydrophobic magnetic monodispersed Fe{sub 3}O{sub 4} nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jing; Wang, Lu; Wang, Jing, E-mail: Jingwang@home.ipe.ac.cn

Graphical abstract: A facile method to produce monodispersed magnetite nanoparticles is based on the solvothermal reaction of iron acetylacetonate (Fe(acac)3) decomposition. The sizes ranged from 7 to 12 nm, which could be controlled by adjusting the volume ratio of oleylamine to n-hexane. Display Omitted Highlights: ► The solvethermal reaction of Fe(acac){sub 3} decomposition was carried out at mild temperature in the presence of oleylamine and n-hexane. ► The size of nanocrystals is controlled by adjusting the volume ratio of oleylamine to n-hexane. ► The low-boiling-point solvent n-hexane offered autogenous pressure parameter after gasified in the reaction temperature. ► The asmore » prepared hydrophobic monodisperse Fe{sub 3}O{sub 4} NPs can be used to prepare the magnetic micelles for future biomedical applications. -- Abstract: A new solvothermal method is proposed for the preparation of Fe{sub 3}O{sub 4} nanoparticles (NPs) from iron acetylacetonate in the presence of oleylamine and n-hexane. The products are characterized by X-ray powder diffraction, infrared (IR) spectroscopy, transmission electron microscopy, thermogravimetry/differential thermogravimetry (TG/DTG) analysis, and vibrating sample magnetometery. The new procedure yields superparamagnetic monodispersed Fe{sub 3}O{sub 4} particles with sizes ranging from 7 nm to 12 nm. The nanocrystal sizes are controlled by adjusting the volume ratio of oleylamine to n-hexane. IR and TG/DTG analyses indicate that the oleylamine molecules, as stabilizers, are adsorbed on the surface of Fe{sub 3}O{sub 4} NPs as bilayer adsorption models. The surface adsorption quantities of oleylamine on 7.5 and 10.4 nm-diameter Fe{sub 3}O{sub 4} NPs are 18% and 11%, respectively. The hydrophobic surface of the obtained nanocrystals is passivated by adsorbed organic solvent molecules. These molecules provide stability against agglomeration, enable solubility in nonpolar solvents, and allow the formation of magnetic polymer micelles.« less

A comparative study of the biosorption of iron(III)-cyanide complex anions to Rhizopus arrhizus and Chlorella vulgaris

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aksu, Z.; Calik, A.

1999-03-01

In this study a comparative biosorption of iron(III)-cyanide complex anions from aqueous solutions to Rhizopus arrhizus and Chlorella vulgaris was investigated. The iron(III)-cyanide complex ion-binding capacities of the biosorbents were shown as a function of initial pH, initial iron(III)-cyanide complex ion, and biosorbent concentrations. The results indicated that a significant reduction of iron(III)-cyanide complex ions was achieved at pH 13, a highly alkaline condition for both the biosorbents. The maximum loading capacities of the biosorbents were found to be 612.2 mg/g for R.arrhizus at 1,996.2 mg/L initial iron(III)-cyanide complex ion concentration and 387.0 mg/g for C. vulgaris at 845.4 mg/Lmore » initial iron(III)-cyanide complex ion concentration at this pH. The Freundlich, Langmuir, and Redlich-Peterson adsorption models were fitted to the equilibrium data at pH 3, 7, and 13. The equilibrium data of the biosorbents could be best fitted by all the adsorption models over the entire concentration range at pH 13.« less

Nanoparticulate iron(III) oxo-hydroxide delivers safe iron that is well absorbed and utilised in humans

PubMed Central

Pereira, Dora I.A.; Bruggraber, Sylvaine F.A.; Faria, Nuno; Poots, Lynsey K.; Tagmount, Mani A.; Aslam, Mohamad F.; Frazer, David M.; Vulpe, Chris D.; Anderson, Gregory J.; Powell, Jonathan J.

2014-01-01

Iron deficiency is the most common nutritional disorder worldwide with substantial impact on health and economy. Current treatments predominantly rely on soluble iron which adversely affects the gastrointestinal tract. We have developed organic acid-modified Fe(III) oxo-hydroxide nanomaterials, here termed nano Fe(III), as alternative safe iron delivery agents. Nano Fe(III) absorption in humans correlated with serum iron increase (P < 0.0001) and direct in vitro cellular uptake (P = 0.001), but not with gastric solubility. The most promising preparation (iron hydroxide adipate tartrate: IHAT) showed ~80% relative bioavailability to Fe(II) sulfate in humans and, in a rodent model, IHAT was equivalent to Fe(II) sulfate at repleting haemoglobin. Furthermore, IHAT did not accumulate in the intestinal mucosa and, unlike Fe(II) sulfate, promoted a beneficial microbiota. In cellular models, IHAT was 14-fold less toxic than Fe(II) sulfate/ascorbate. Nano Fe(III) manifests minimal acute intestinal toxicity in cellular and murine models and shows efficacy at treating iron deficiency anaemia. From the Clinical Editor This paper reports the development of novel nano-Fe(III) formulations, with the goal of achieving a magnitude less intestinal toxicity and excellent bioavailability in the treatment of iron deficiency anemia. Out of the tested preparations, iron hydroxide adipate tartrate met the above criteria, and may become an important tool in addressing this common condition. PMID:24983890

Reactive oxygen species and associated reactivity of peroxymonosulfate activated by soluble iron species.

PubMed

Watts, Richard J; Yu, Miao; Teel, Amy L

2017-10-01

The activation of peroxymonosulfate by iron (II), iron (III), and iron (III)-EDTA for in situ chemical oxidation (ISCO) was compared using nitrobenzene as a hydroxyl radical probe, anisole as a hydroxyl radical+sulfate radical probe, and hexachloroethane as a reductant+nucleophile probe. In addition, activated peroxymonosulfate was investigated for the treatment of the model groundwater contaminants perchloroethylene (PCE) and trichloroethylene (TCE). The relative activities of hydroxyl radical and sulfate radical in the degradation of the probe compounds and PCE and TCE were isolated using the radical scavengers tert-butanol and isopropanol. Iron (II), iron (III), and iron (III)-EDTA effectively activated peroxymonosulfate to generate hydroxyl radical and sulfate radical, but only a minimal flux of reductants or nucleophiles. Iron (III)-EDTA was a more effective activator than iron (II) and iron (III), and also provided a non-hydroxyl radical, non-sulfate radical degradation pathway. The contribution of sulfate radical relative to hydroxyl radical followed the order of anisole>TCE>PCE >nitrobenzene; i.e., sulfate radical was less dominant in the oxidation of more oxidized target compounds. Sulfate radical is often assumed to be the primary oxidant in activated peroxymonosulfate and persulfate systems, but the results of this research demonstrate that the reactivity of sulfate radical with the target compound must be considered before drawing such a conclusion. Published by Elsevier B.V.

Influence of atmospheric processes on the solubility and composition of iron in Saharan dust

DOE PAGES

Longo, Amelia F.; Feng, Yan; Lai, Barry; ...

2016-06-10

Aerosol iron was examined in Saharan dust plumes using a combination of iron near-edge X-ray absorption spectroscopy and wet-chemical techniques. Aerosol samples were collected at three sites located in the Mediterranean, the Atlantic, and Bermuda to characterize iron at different atmospheric transport lengths and time scales. Iron(III) oxides were a component of aerosols at all sampling sites and dominated the aerosol iron in Mediterranean samples. In Atlantic samples, iron(II and III) sulfate, iron(III) phosphate, and iron(II) silicates were also contributors to aerosol composition. With increased atmospheric transport time, iron(II) sulfates are found to become more abundant, aerosol iron oxidation statemore » became more reduced, and aerosol acidity increased. As a result, atmospheric processing including acidic reactions and photoreduction likely influence the form of iron minerals and oxidation state in Saharan dust aerosols and contribute to increases in aerosol-iron solubility.« less

Influence of Atmospheric Processes on the Solubility and Composition of Iron in Saharan Dust.

PubMed

Longo, Amelia F; Feng, Yan; Lai, Barry; Landing, William M; Shelley, Rachel U; Nenes, Athanasios; Mihalopoulos, Nikolaos; Violaki, Kalliopi; Ingall, Ellery D

2016-07-05

Aerosol iron was examined in Saharan dust plumes using a combination of iron near-edge X-ray absorption spectroscopy and wet-chemical techniques. Aerosol samples were collected at three sites located in the Mediterranean, the Atlantic, and Bermuda to characterize iron at different atmospheric transport lengths and time scales. Iron(III) oxides were a component of aerosols at all sampling sites and dominated the aerosol iron in Mediterranean samples. In Atlantic samples, iron(II and III) sulfate, iron(III) phosphate, and iron(II) silicates were also contributors to aerosol composition. With increased atmospheric transport time, iron(II) sulfates are found to become more abundant, aerosol iron oxidation state became more reduced, and aerosol acidity increased. Atmospheric processing including acidic reactions and photoreduction likely influence the form of iron minerals and oxidation state in Saharan dust aerosols and contribute to increases in aerosol-iron solubility.

Sorption Studies and Characterization of As (III) Adsorption over Developed Iron-Biochar Composites from Water.

NASA Astrophysics Data System (ADS)

Singh, P.; Mohan, D.

2016-12-01

Problem related to arsenic occurrence in groundwater has caused severe threat to human health in worldwide. Thus there is an increasing demand to find the chemistry and plausible mechanism of arsenic adsorption while remediating it from water. In present study iron-biochar composites are synthesised using agricultural waste materials. The rice husk iron-biochar composite (RIBC) and wheat husk iron-biochar composite (WIBC) were characterised and utilised for As (III) remediation from aqueous solution. The rice husk (RIBC) and wheat husk (WIBC) iron biochar composites were characterised. XPS, FT-IR, and XRD, were studied to analyse their elemental composition and functional group identification. While SEM, TEM, SEM-EDX were conducted to study their surface chemistry, mineralogy, porosity and crystallinity etc. Batch sorption studies were conducted for both rice husk (RIBC) and wheat husk (WIBC) iron-biochar composites to find sorption efficiency. Maximum As (III) adsorption was achieved in pH range 6-8 for both iron-biochar composites. Kinetic studies were conducted to establish the mechanism of As (III) adsorption at different dose and time. Optimum dose of 2g/L and 1g/L were reported for rice husk (RIBC) and wheat husk (WIBC) iron-biochar composites respectively. Electrostatic forces developed between arsenites and iron hydroxyl surface developed over the surface may have caused the removal of As (III). Significant amount of oxygen containing groups have been revealed through studies. Higher As (III) adsorption capacities were obtained for both iron-biochar composites to measure the amount of surface sites. Furthermore, various adsorption models are used to find the monolayer adsorption capacity. These findings suggest that developed iron-biochar composites may be used to remediate As (III) from contaminated water.

A Nanoparticulate Ferritin-Core Mimetic Is Well Taken Up by HuTu 80 Duodenal Cells and Its Absorption in Mice Is Regulated by Body Iron12

PubMed Central

Latunde-Dada, Gladys O; Pereira, Dora IA; Tempest, Bethan; Ilyas, Hibah; Flynn, Angela C; Aslam, Mohamad F; Simpson, Robert J; Powell, Jonathan J

2014-01-01

Background: Iron (Fe) deficiency anemia remains the largest nutritional deficiency disorder worldwide. How the gut acquires iron from nano Fe(III), especially at the apical surface, is incompletely understood. Objective: We developed a novel Fe supplement consisting of nanoparticulate tartrate-modified Fe(III) poly oxo-hydroxide [here termed nano Fe(III)], which mimics the Fe oxide core of ferritin and effectively treats iron deficiency anemia in rats. Methods: We determined transfer to the systemic circulation of nano Fe(III) in iron-deficient and iron-sufficient outbread Swiss mouse strain (CD1) mice with use of 59Fe-labeled material. Iron deficiency was induced before starting the Fe-supplementation period through reduction of Fe concentrations in the rodent diet. A control group of iron-sufficient mice were fed a diet with adequate Fe concentrations throughout the study. Furthermore, we conducted a hemoglobin repletion study in which iron-deficient CD1 mice were fed for 7 d a diet supplemented with ferrous sulfate (FeSO4) or nano Fe(III). Finally, we further probed the mechanism of cellular acquisition of nano Fe(III) by assessing ferritin formation, as a measure of Fe uptake and utilization, in HuTu 80 duodenal cancer cells with targeted inhibition of divalent metal transporter 1 (DMT1) and duodenal cytochrome b (DCYTB) before exposure to the supplemented iron sources. Differences in gene expression were assessed by quantitative polymerase chain reaction. Results: Absorption (means ± SEMs) of nano Fe(III) was significantly increased in iron-deficient mice (58 ± 19%) compared to iron-sufficient mice (18 ± 17%) (P = 0.0001). Supplementation of the diet with nano Fe(III) or FeSO4 significantly increased hemoglobin concentrations in iron-deficient mice (170 ± 20 g/L, P = 0.01 and 180 ± 20 g/L, P = 0.002, respectively). Hepatic hepcidin mRNA expression reflected the nonheme-iron concentrations of the liver and was also comparable for both nano Fe(III)– and FeSO4-supplemented groups, as were iron concentrations in the spleen and duodenum. Silencing of the solute carrier family 11 (proton-coupled divalent metal ion transporter), member 2 (Slc11a2) gene (DMT1) significantly inhibited ferritin formation from FeSO4 (P = 0.005) but had no effect on uptake and utilization of nano Fe(III). Inhibiting DCYTB with an antibody also had no effect on uptake and utilization of nano Fe(III) but significantly inhibited ferritin formation from ferric nitrilotriacetate chelate (Fe-NTA) (P = 0.04). Similarly, cellular ferritin formation from nano Fe(III) was unaffected by the Fe(II) chelator ferrozine, which significantly inhibited uptake and utilization from FeSO4 (P = 0.009) and Fe-NTA (P = 0.005). Conclusions: Our data strongly support direct nano Fe(III) uptake by enterocytes as an efficient mechanism of dietary iron acquisition, which may complement the known Fe(II)/DMT1 uptake pathway. PMID:25342699

Heterogeneous biomimetic catalysis using iron porphyrin for cyclohexane oxidation promoted by chitosan

NASA Astrophysics Data System (ADS)

Huang, Guan; Liu, Yao; Cai, Jing Li; Chen, Xiang Feng; Zhao, Shu Kai; Guo, Yong An; Wei, Su Juan; Li, Xu

2017-04-01

This study investigates how ligands modulate metalloporphyrin activity with the goal of producing a practical biomimetic catalyst for use in the chemical industry. We immobilized iron porphyrinate [iron-tetrakis-(4-sulfonatophenyl)-porphyrin; Fe(III) (TPPS)] on powdered chitosan (pd-CTS) to form an immobilized catalyst Fe(III) (TPPS)/pd-CTS, which was characterized using modern spectroscopic techniques and used for catalytic oxidation of cyclohexane with O2. Amino coordination to iron porphyrin in Fe(III) (TPPS)/pd-CTS altered the electron cloud density around the iron cation, probably by reducing the activation energy of Fe(III) (TPPS) and raising the reactivity of the iron ion catalytic center, thereby improving the catalytic efficiency. One milligram of Fe(III) (TPPS) catalyst can be reused three times for the oxidation reaction to yield an average of 22.9 mol% of cyclohexanone and cyclohexanol.

N-butylamine functionalized graphene oxide for detection of iron(III) by photoluminescence quenching.

PubMed

Gholami, Javad; Manteghian, Mehrdad; Badiei, Alireza; Ueda, Hiroshi; Javanbakht, Mehran

2016-02-01

An N-butylamine functionalized graphene oxide nanolayer was synthesized and characterized by ultraviolet (UV)-visible spectrometry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. Detection of iron(III) based on photoluminescence spectroscopy was investigated. The N-butylamine functionalized graphene oxide was shown to specifically interact with iron (III), compared with other cationic trace elements including potassium (I), sodium (I), calcium (II), chromium (III), zinc (II), cobalt (II), copper (II), magnesium (II), manganese (II), and molybdenum (VI). The quenching effect of iron (III) on the luminescence emission of N-butylamine functionalized graphene oxide layer was used to detect iron (III). The limit of detection (2.8 × 10(-6)  M) and limit of quantitation (2.9 × 10(-5)  M) were obtained under optimal conditions. Copyright © 2015 John Wiley & Sons, Ltd.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Longo, Amelia F.; Feng, Yan; Lai, Barry

Aerosol iron was examined in Saharan dust plumes using a combination of iron near-edge X-ray absorption spectroscopy and wet-chemical techniques. Aerosol samples were collected at three sites located in the Mediterranean, the Atlantic, and Bermuda to characterize iron at different atmospheric transport lengths and time scales. Iron(III) oxides were a component of aerosols at all sampling sites and dominated the aerosol iron in Mediterranean samples. In Atlantic samples, iron(II and III) sulfate, iron(III) phosphate, and iron(II) silicates were also contributors to aerosol composition. With increased atmospheric transport time, iron(II) sulfates are found to become more abundant, aerosol iron oxidation statemore » became more reduced, and aerosol acidity increased. As a result, atmospheric processing including acidic reactions and photoreduction likely influence the form of iron minerals and oxidation state in Saharan dust aerosols and contribute to increases in aerosol-iron solubility.« less

Oxygen Activation at Mononuclear Nonheme Iron Centers: A Superoxo Perspective

PubMed Central

Mukherjee, Anusree; Cranswick, Matthew A.; Chakraborti, Mrinmoy; Paine, Tapan K.; Fujisawa, Kiyoshi; Münck, Eckard; Que, Lawrence

2010-01-01

Dioxygen activation by iron enzymes is responsible for many metabolically important transformations in biology. Often a high-valent iron-oxo oxidant is proposed to form upon dioxygen activation at a mononuclear nonheme iron center, presumably via intervening iron-superoxo and iron-peroxo species. While iron(IV)-oxo intermediates have been trapped and characterized in enzymes and models, less is known of the putative iron(III)-superoxo species. Utilizing a synthetic model for the 2-oxoglutarate-dependent monoiron enzymes, [(TpiPr2)FeII(O2CC(O)CH3)], we have obtained indirect evidence for the formation of the putative iron(III)-superoxo species, which can undergo one-electron reduction, hydrogen-atom transfer, or conversion to an iron(IV)-oxo species, depending on the reaction conditions. These results demonstrate the various roles the iron(III)-superoxo species can play in the course of dioxygen activation at a nonheme iron center. PMID:20380464

Oxygen activation at mononuclear nonheme iron centers: a superoxo perspective.

PubMed

Mukherjee, Anusree; Cranswick, Matthew A; Chakrabarti, Mrinmoy; Paine, Tapan K; Fujisawa, Kiyoshi; Münck, Eckard; Que, Lawrence

2010-04-19

Dioxygen (O(2)) activation by iron enzymes is responsible for many metabolically important transformations in biology. Often a high-valent iron oxo oxidant is proposed to form upon O(2) activation at a mononuclear nonheme iron center, presumably via intervening iron superoxo and iron peroxo species. While iron(IV) oxo intermediates have been trapped and characterized in enzymes and models, less is known of the putative iron(III) superoxo species. Utilizing a synthetic model for the 2-oxoglutarate-dependent monoiron enzymes, [(Tp(iPr2))Fe(II)(O(2)CC(O)CH(3))], we have obtained indirect evidence for the formation of the putative iron(III) superoxo species, which can undergo one-electron reduction, hydrogen-atom transfer, or conversion to an iron(IV) oxo species, depending on the reaction conditions. These results demonstrate the various roles that the iron(III) superoxo species can play in the course of O(2) activation at a nonheme iron center.

Accumulation and distribution of iron, cadmium, lead and nickel in cucumber plants grown in hydroponics containing two different chelated iron supplies.

PubMed

Csog, Árpád; Mihucz, Victor G; Tatár, Eniko; Fodor, Ferenc; Virág, István; Majdik, Cornelia; Záray, Gyula

2011-07-01

Cucumber plants grown in hydroponics containing 10 μM Cd(II), Ni(II) and Pb(II), and iron supplied as Fe(III) EDTA or Fe(III) citrate in identical concentrations, were investigated by total-reflection X-ray fluorescence spectrometry with special emphasis on the determination of iron accumulation and distribution within the different plant compartments (root, stem, cotyledon and leaves). The extent of Cd, Ni and Pb accumulation and distribution were also determined. Generally, iron and heavy-metal contaminant accumulation was higher when Fe(III) citrate was used. The accumulation of nickel and lead was higher by about 20% and 100%, respectively, if the iron supply was Fe(III) citrate. The accumulation of Cd was similar. In the case of Fe(III) citrate, the total amounts of Fe taken up were similar in the control and heavy-metal-treated plants (27-31 μmol/plant). Further, the amounts of iron transported from the root towards the shoot of the control, lead- and nickel-contaminated plants were independent of the iron(III) form. Although Fe mobility could be characterized as being low, its distribution within the shoot was not significantly affected by the heavy metals investigated. Copyright © 2011 Elsevier GmbH. All rights reserved.

Nanoparticulate iron(III) oxo-hydroxide delivers safe iron that is well absorbed and utilised in humans.

PubMed

Pereira, Dora I A; Bruggraber, Sylvaine F A; Faria, Nuno; Poots, Lynsey K; Tagmount, Mani A; Aslam, Mohamad F; Frazer, David M; Vulpe, Chris D; Anderson, Gregory J; Powell, Jonathan J

2014-11-01

Iron deficiency is the most common nutritional disorder worldwide with substantial impact on health and economy. Current treatments predominantly rely on soluble iron which adversely affects the gastrointestinal tract. We have developed organic acid-modified Fe(III) oxo-hydroxide nanomaterials, here termed nano Fe(III), as alternative safe iron delivery agents. Nano Fe(III) absorption in humans correlated with serum iron increase (P < 0.0001) and direct in vitro cellular uptake (P = 0.001), but not with gastric solubility. The most promising preparation (iron hydroxide adipate tartrate: IHAT) showed ~80% relative bioavailability to Fe(II) sulfate in humans and, in a rodent model, IHAT was equivalent to Fe(II) sulfate at repleting haemoglobin. Furthermore, IHAT did not accumulate in the intestinal mucosa and, unlike Fe(II) sulfate, promoted a beneficial microbiota. In cellular models, IHAT was 14-fold less toxic than Fe(II) sulfate/ascorbate. Nano Fe(III) manifests minimal acute intestinal toxicity in cellular and murine models and shows efficacy at treating iron deficiency anaemia. This paper reports the development of novel nano-Fe(III) formulations, with the goal of achieving a magnitude less intestinal toxicity and excellent bioavailability in the treatment of iron deficiency anemia. Out of the tested preparations, iron hydroxide adipate tartrate met the above criteria, and may become an important tool in addressing this common condition. Crown Copyright © 2014. Published by Elsevier Inc. All rights reserved.

Kinetics of the Reaction Between Alcohols and Isocyanates Catalyzed by Ferric Acetylacetonate

NASA Technical Reports Server (NTRS)

Schieler, Leroy

1961-01-01

The rate and temperature dependence of reaction for the ferric acetylacetonate catalyzed reaction between a-naphthyl, ortho-tolyl, and para-tolyl isocyanates and n-butyl alcohol are investigated. The effect of substituents on the reactivity of isocyanate and hydroxyl group are reported and for substituted isocyanates are correlated by means of the Hammett equation. Several metal chelates were studied and their catalytic activity was compared to that of ferric acetylacetonate. All rate data are interpreted in terms of a mechanism involving simultaneous second-order uncatalyzed and catalyzed reactions between alcohol and isocyanate.

Arsenic mobilization and immobilization in paddy soils

NASA Astrophysics Data System (ADS)

Kappler, A.; Hohmann, C.; Zhu, Y. G.; Morin, G.

2010-05-01

Arsenic is oftentimes of geogenic origin and in many cases bound to iron(III) minerals. Iron(III)-reducing bacteria can harvest energy by coupling the oxidation of organic or inorganic electron donors to the reduction of Fe(III). This process leads either to dissolution of Fe(III)-containing minerals and thus to a release of the arsenic into the environment or to secondary Fe-mineral formation and immobilisation of arsenic. Additionally, aerobic and anaerobic iron(II)-oxidizing bacteria have the potential to co-precipitate or sorb arsenic during iron(II) oxidation at neutral pH that is usually followed by iron(III) mineral precipitation. We are currently investigating arsenic immobilization by Fe(III)-reducing bacteria and arsenic co-precipitation and immobilization by anaerobic iron(II)-oxidizing bacteria in batch, microcosm and rice pot experiments. Co-precipitation batch experiments with pure cultures of nitrate-dependent Fe(II)-oxidizing bacteria are used to quantify the amount of arsenic that can be immobilized during microbial iron mineral precipitation, to identify the minerals formed and to analyze the arsenic binding environment in the precipitates. Microcosm and rice pot experiments are set-up with arsenic-contaminated rice paddy soil. The microorganisms (either the native microbial population or the soil amended with the nitrate-dependent iron(II)-oxidizing Acidovorax sp. strain BoFeN1) are stimulated either with iron(II), nitrate, or oxygen. Dissolved and solid-phase arsenic and iron are quantified. Iron and arsenic speciation and redox state in batch and microcosm experiments are determined by LC-ICP-MS and synchrotron-based methods (EXAFS, XANES).

Gallium(iii) and iron(iii) complexes of quinolone antimicrobials.

PubMed

Mjos, Katja Dralle; Cawthray, Jacqueline F; Polishchuk, Elena; Abrams, Michael J; Orvig, Chris

2016-08-16

Iron is an essential nutrient for many microbes. According to the "Trojan Horse Hypothesis", biological systems have difficulties distinguishing between Fe(3+) and Ga(3+), which constitutes the antimicrobial efficacy of the gallium(iii) ion. Nine novel tris(quinolono)gallium(iii) complexes and their corresponding iron(iii) analogs have been synthesized and fully characterized. Quinolone antimicrobial agents from three drug generations were used in this study: ciprofloxacin, enoxacin, fleroxacin, levofloxacin, lomefloxacin, nalidixic acid, norfloxacin, oxolinic acid, and pipemidic acid. The antimicrobial efficacy of the tris(quinolono)gallium(iii) complexes was studied against E. faecalis and S. aureus (both Gram-positive), as well as E. coli, K. pneumonia, and P. aeruginosa (all Gram-negative) in direct comparison to the tris(quinolono)iron(iii) complexes and the corresponding free quinolone ligands at various concentrations. For the tris(quinolono)gallium(iii) complexes, no combinational antimicrobial effects between Ga(3+) and the quinolone antimicrobial agents were observed.

Ascorbate Efflux as a New Strategy for Iron Reduction and Transport in Plants*

PubMed Central

Grillet, Louis; Ouerdane, Laurent; Flis, Paulina; Hoang, Minh Thi Thanh; Isaure, Marie-Pierre; Lobinski, Ryszard; Curie, Catherine; Mari, Stéphane

2014-01-01

Iron (Fe) is essential for virtually all living organisms. The identification of the chemical forms of iron (the speciation) circulating in and between cells is crucial to further understand the mechanisms of iron delivery to its final targets. Here we analyzed how iron is transported to the seeds by the chemical identification of iron complexes that are delivered to embryos, followed by the biochemical characterization of the transport of these complexes by the embryo, using the pea (Pisum sativum) as a model species. We have found that iron circulates as ferric complexes with citrate and malate (Fe(III)3Cit2Mal2, Fe(III)3Cit3Mal1, Fe(III)Cit2). Because dicotyledonous plants only transport ferrous iron, we checked whether embryos were capable of reducing iron of these complexes. Indeed, embryos did express a constitutively high ferric reduction activity. Surprisingly, iron(III) reduction is not catalyzed by the expected membrane-bound ferric reductase. Instead, embryos efflux high amounts of ascorbate that chemically reduce iron(III) from citrate-malate complexes. In vitro transport experiments on isolated embryos using radiolabeled 55Fe demonstrated that this ascorbate-mediated reduction is an obligatory step for the uptake of iron(II). Moreover, the ascorbate efflux activity was also measured in Arabidopsis embryos, suggesting that this new iron transport system may be generic to dicotyledonous plants. Finally, in embryos of the ascorbate-deficient mutants vtc2-4, vtc5-1, and vtc5-2, the reducing activity and the iron concentration were reduced significantly. Taken together, our results identified a new iron transport mechanism in plants that could play a major role to control iron loading in seeds. PMID:24347170

Ascorbate efflux as a new strategy for iron reduction and transport in plants.

PubMed

Grillet, Louis; Ouerdane, Laurent; Flis, Paulina; Hoang, Minh Thi Thanh; Isaure, Marie-Pierre; Lobinski, Ryszard; Curie, Catherine; Mari, Stéphane

2014-01-31

Iron (Fe) is essential for virtually all living organisms. The identification of the chemical forms of iron (the speciation) circulating in and between cells is crucial to further understand the mechanisms of iron delivery to its final targets. Here we analyzed how iron is transported to the seeds by the chemical identification of iron complexes that are delivered to embryos, followed by the biochemical characterization of the transport of these complexes by the embryo, using the pea (Pisum sativum) as a model species. We have found that iron circulates as ferric complexes with citrate and malate (Fe(III)3Cit2Mal2, Fe(III)3Cit3Mal1, Fe(III)Cit2). Because dicotyledonous plants only transport ferrous iron, we checked whether embryos were capable of reducing iron of these complexes. Indeed, embryos did express a constitutively high ferric reduction activity. Surprisingly, iron(III) reduction is not catalyzed by the expected membrane-bound ferric reductase. Instead, embryos efflux high amounts of ascorbate that chemically reduce iron(III) from citrate-malate complexes. In vitro transport experiments on isolated embryos using radiolabeled (55)Fe demonstrated that this ascorbate-mediated reduction is an obligatory step for the uptake of iron(II). Moreover, the ascorbate efflux activity was also measured in Arabidopsis embryos, suggesting that this new iron transport system may be generic to dicotyledonous plants. Finally, in embryos of the ascorbate-deficient mutants vtc2-4, vtc5-1, and vtc5-2, the reducing activity and the iron concentration were reduced significantly. Taken together, our results identified a new iron transport mechanism in plants that could play a major role to control iron loading in seeds.

Molecular structure, magnetic properties, cyclic voltammetry of the low-spin iron(III) Bis(4-ethylaniline) complex with the para-chloro substituted meso-tetraphenylporphyrin

NASA Astrophysics Data System (ADS)

Dhifaoui, Selma; Mchiri, Chadlia; Quatremare, Pierre; Marvaud, Valérie; Bujacz, Anna; Nasri, Habib

2018-02-01

In this study, the preparation of a new iron(III) hexacoordinated metalloporphyrin namely the bis(4-ethylaniline){meso-tetra(para-chlorophenyl)porphyrinato}iron(III) triflate hemi-4-ethylaniline monohydrate with the formula [FeIII(TClPP)(PhEtNH2)2]SO3CF3•1/2PhEtNH2•H2O (I) was reported. This is the first example of an iron(III) metalloporphyrin bis(primary amine) with an aryl group adjacent to the amino group. This species was characterized by elemental, spectroscopic analysis including UV-visible and IR data, cyclic voltammetry, SQUID measurements and X-ray molecular structure. The mean equatorial distance between the iron(III) and the nitrogens of the porphyrin is appropriate for a low-spin (S = 1/2) iron(III) porphyrin complex. The magnetic data confirm the low-spin state of our ferric derivative while the cyclic voltammetry indicates a shift of the half potential E1/2[Fe(III)/Fe(II)] of complex (I) toward more negative value. In the crystal of (I), the [FeIII(TClPP)(PhEtNH2)2]+ ions, the triflate counterions and the water molecules are involved in a number of O__H⋯O, N__H⋯O, C-H⋯O and C__H⋯π intermolecular interactions forming a three-dimension network.

ARSENIC INTERACTION WITH IRON (II, III) HYDROXYCARBONATE GREEN RUST: IMPLICATIONS FOR ARSENIC REMEDIATION

EPA Science Inventory

Zerovalent iron is being used in permeable reactive barriers (PRBs) to remediate groundwater arsenic contamination. Iron(II, III) hydroxycarbonate green rust is a major corrosion product of zerovalent iron under anaerobic conditions. The interaction between arsenic and this green...

Size effect on L10 ordering and magnetic properties of chemically synthesized FePt and FePtAu nanoparticles

NASA Astrophysics Data System (ADS)

Jia, Zhiyong; Kang, Shishou; Shi, Shifan; Nikles, David E.; Harrell, J. W.

2005-05-01

There is growing evidence that FePt nanoparticles become increasingly difficult to chemically order as the size approaches a few nanometers. We have studied the chemical ordering of FePt and FePtAu nanoparticle arrays as a function of particle size. Monodisperse Fe49Pt51 and Fe48Pt44Au8 nanoparticles with a size about 6nm were synthesized by the simultaneous decomposition of iron pentacarbonyl and reduction of platinum acetylacetonate and gold (III) acetate in a mixture of phenyl ether and hexadecylamine (HDA), with 1-adamantanecarboxylic acid and HDA as stabilizers. The nanoparticles were dispersed in toluene, films of the particles were cast onto silicon wafers from the dispersion, and the films were annealed in a tube furnace with flowing Ar +5%H2. The magnetic anisotropy and switching volumes were determined from time- and temperature-dependent coercivity measurements. By comparing with 3-nm FePt and FePtAu nanoparticles of comparable composition, the phase transformation is easier for the larger particles. Under the same annealing conditions, the larger particles have higher anisotropy and order parameter. Additive Au is very effective in enhancing the chemical ordering in both small and large particles, with x-ray diffraction superlattice peaks appearing after annealing at 350°C. Dynamic remnant coercivity measurements and magnetic switching volumes suggest particle aggregation at the higher annealing temperatures in both small and large particles.

Predicting the potentials, solubilities and stabilities of metal-acetylacetonates for non-aqueous redox flow batteries using density functional theory calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kucharyson, J. F.; Cheng, L.; Tung, S. O.

New active materials are needed to improve the performance and reduce the cost of non-aqueous redox flow batteries (RFBs) for grid-scale energy storage applications. Efforts to develop better performing materials, which have largely been empirical, would benefit from a better understanding of relationships between structural, electronic and RFB-relevant functional properties. This paper focuses on metal-acetylacetonates, a class of metal coordination complexes that has shown promise for use in RFBs, and describes correlations between their experimentally measured standard potentials, solubilities, and stabilities (cycle lifes), and selected chemical, structural and electronic properties determined from Density Functional Theory (DFT) calculations. The training setmore » consisted of 16 complexes including 5 different metals and 11 different substituents on the acetylacetonate ligand. Standard potentials for those compounds were calculated and are in good agreement with experimentally measured results. A predictive equation based on the solvation energies and dipole moments, two easily computed properties, reasonably modeled the experimentally determined solubilities. Importantly, we were able to identify a descriptor for the stability of acetylacetonates. The experimentally determined stability, quantified as the cycle life to a given degree of degradation, correlated with the percentage of the highest occupied (HOMO) or lowest unoccupied molecular orbital (LUMO) on the metal of the complex. This percentage is influenced by the degree of ligand innocence (irreducibility), and complexes with the most innocent ligands yielded the most stable redox reactions. To this end, VO(acetylacetonate)(2) and Fe(acetylacetonate)(3), with nearly 80% of the HOMO and LUMO on the metal, possessed the most stable oxidation and reduction half-reactions, respectively. The structure-function relationships and correlations presented in this paper could be used to predict new, highly soluble and stable complexes for RFB applications.« less

Dinuclear Cu(II) complexes of isomeric bis-(3-acetylacetonate)benzene ligands: synthesis, structure, and magnetic properties.

PubMed

Rancan, Marzio; Dolmella, Alessandro; Seraglia, Roberta; Orlandi, Simonetta; Quici, Silvio; Sorace, Lorenzo; Gatteschi, Dante; Armelao, Lidia

2012-05-07

Highly versatile coordinating ligands are designed and synthesized with two β-diketonate groups linked at the carbon 3 through a phenyl ring. The rigid aromatic spacer is introduced in the molecules to orient the two acetylacetone units along different angles and coordination vectors. The resulting para, meta, and ortho bis-(3-acetylacetonate)benzene ligands show efficient chelating properties toward Cu(II) ions. In the presence of 2,2'-bipyridine, they promptly react and yield three dimers, 1, 2, and 3, with the bis-acetylacetonate unit in bridging position between two metal centers. X-ray single crystal diffraction shows that the compounds form supramolecular chains in the solid state because of intermolecular interactions. Each of the dinuclear complexes shows a magnetic behavior which is determined by the combination of structural parameters and spin polarization effects. Notably, the para derivative (1) displays a moderate antiferromagnetic coupling (J = -3.3 cm(-1)) along a remarkably long Cu···Cu distance (12.30 Å).

Characterization of submicrometer aqueous iron(III) colloids formed in the presence of phosphate by sedimentation field flow fractionation with multiangle laser light scattering detection.

PubMed

Magnuson, M L; Lytle, D A; Frietch, C M; Kelty, C A

2001-10-15

Iron colloids play a major role in the water chemistry of natural watersheds and of engineered drinking water distribution systems. Phosphate is frequently added to distribution systems to control corrosion problems, so iron-phosphate colloids may form through reaction of iron in water pipes. In this study, sedimentation field flow fractionation (SdFFF) is coupled on-line with multiangle laser light scattering (MALLS) detection to characterize these iron colloids formed following the oxygenation of iron(II) in the presence of phosphate. The SdFFF-MALLS data were used to calculate the hydrodynamic diameter, density, and particle size distribution of these submicrometer colloids. The system was first verified with standard polystyrene beads, and the results compared well with certified values. Iron(III) colloids were formed in the presence of phosphate at a variety of pH conditions. The colloids' hydrodynamic diameters, which ranged from 218 +/- 3 (pH 7) to 208 +/- 4 nm (pH 10), did not change significantly within the 95% confidence limit. Colloid density did increase significantly from 1.12 +/- 0.01 (pH 7) to 1.36 +/- 0.02 g/mL (pH 10). Iron(III) colloids formed at pH 10 in the presence of phosphate were compared to iron(III) colloids formed without phosphate and also to iron(III) colloids formed with silicate. The iron(III) colloids formed without phosphate or silicate were 0.46 g/mL more dense than any other colloids and were >6 times more narrowly distributed than the other colloids. The data suggest competitive incorporation of respective anions into the colloid during formation.

Molecular modelling, spectroscopic characterization and biological studies of tetraazamacrocyclic metal complexes

NASA Astrophysics Data System (ADS)

Rathi, Parveen; Sharma, Kavita; Singh, Dharam Pal

2014-09-01

Macrocyclic complexes of the type [MLX]X2; where L is (C30H28N4), a macrocyclic ligand, M = Cr(III) and Fe(III) and X = Cl-, CH3COO- or NO3-, have been synthesized by template condensation reaction of 1,8-diaminonaphthalene and acetylacetone in the presence of trivalent metal salts in a methanolic medium. The complexes have been formulated as [MLX]X2 due to 1:2 electrolytic nature of these complexes. The complexes have been characterized with the help of elemental analyses, molar conductance measurements, magnetic susceptibility measurements, electronic, infrared, far infrared, Mass spectral studies and molecular modelling. Molecular weight of these complexes indicates their monomeric nature. On the basis of all these studies, a five coordinated square pyramidal geometry has been proposed for all these complexes. These metal complexes have also been screened for their in vitro antimicrobial activities.

Arsenic removal with iron(II) and iron(III) in waters with high silicate and phosphate concentrations.

PubMed

Roberts, Linda C; Hug, Stephan J; Ruettimann, Thomas; Billah, Morsaline; Khan, Abdul Wahab; Rahman, Mohammad Tariqur

2004-01-01

Arsenic removal by passive treatment, in which naturally present Fe(II) is oxidized by aeration and the forming iron(III) (hydr)oxides precipitate with adsorbed arsenic, is the simplest conceivable water treatment option. However, competing anions and low iron concentrations often require additional iron. Application of Fe(II) instead of the usually applied Fe(III) is shown to be advantageous, as oxidation of Fe(II) by dissolved oxygen causes partial oxidation of As(III) and iron(III) (hydr)oxides formed from Fe(II) have higher sorption capacities. In simulated groundwater (8.2 mM HCO3(-), 2.5 mM Ca2+, 1.6 mM Mg2+, 30 mg/L Si, 3 mg/L P, 500 ppb As(III), or As(V), pH 7.0 +/- 0.1), addition of Fe(II) clearly leads to better As removal than Fe(III). Multiple additions of Fe(II) further improved the removal of As(II). A competitive coprecipitation model that considers As(III) oxidation explains the observed results and allows the estimation of arsenic removal under different conditions. Lowering 500 microg/L As(III) to below 50 microg/L As(tot) in filtered water required > 80 mg/L Fe(III), 50-55 mg/L Fe(II) in one single addition, and 20-25 mg/L in multiple additions. With As(V), 10-12 mg/L Fe(II) and 15-18 mg/L Fe(III) was required. In the absence of Si and P, removal efficiencies for Fe(II) and Fe(III) were similar: 30-40 mg/L was required for As(II), and 2.0-2.5 mg/L was required for As(V). In a field study with 22 tubewells in Bangladesh, passive treatment efficiently removed phosphate, but iron contents were generally too low for efficient arsenic removal.

ARSENATE AND ARSENITE SORPTION AND ARSENITE OXIDATION BY IRON (II, III) HYDROXYCARBONATE GREEN RUST

EPA Science Inventory

Iron (II, III) hydroxycarbonate green rust is a major corrosion product of zerovalent iron that is being used in permeable reactive barriers to remediate groundwater arsenic contamination. To optimize the design of iron barriers, it is important to evaluate the influence of geoch...

CHEMICAL INTERACTIONS OF ARSENATE, ARSENITE, PHOSPHATE, AND SILICATE WITH IRON (II, III) HYDROXYCARBONATE GREEN RUST

EPA Science Inventory

Granular zerovalent iron has been proposed to be used as a medium in permeable reactive barriers (PRBs) to remove arsenic from contaminated groundwater. Iron(II, III) hydroxycarbonate green rust (carbonate green rust, or CGR) is a major corrosion product of zerovalent iron under ...

CHEMICAL INTERACTIONS OF ARSENATE, ARSENITE, PHOSPHATE, AND SILICATE WITH IRON (II,III) HYDROXYCARBONATE GREEN RUST

EPA Science Inventory

Granular zerovalent iron has been proposed to be used as a medium in permeable reactive barriers (PRBs) to remove arsenic from contaminated groundwater. Iron(II, III) hydroxycarbonate green rust (carbonate green rust, or CGR) is a major corrosion product of zerovalent iron under ...

Silica functionalized Cu(II) acetylacetonate Schiff base complex: An efficient catalyst for the oxidative condensation reaction of benzyl alcohol with amines

NASA Astrophysics Data System (ADS)

Anbarasu, G.; Malathy, M.; Karthikeyan, P.; Rajavel, R.

2017-09-01

Silica functionalized Cu(II) acetylacetonate Schiff base complex via the one pot reaction of silica functionalized 3-aminopropyltriethoxysilane with acetyl acetone and copper acetate has been reported. The synthesized material was well characterized by analytical techniques such as FT-IR, UV-DRS, XRD, SEM-EDX, HR-TEM, EPR, ICP-AES and BET analysis. The characterization results confirmed the grafting of Cu(II) Schiff base complex on the silica surface. The catalytic activity of synthesized silica functionalized Cu(II) acetylacetonate Schiff base complex was evaluated through the oxidative condensation reaction of benzyl alcohol to imine.

Effect of iron salt counter ion in dose-response curves for inactivation of Fusarium solani in water through solar driven Fenton-like processes

NASA Astrophysics Data System (ADS)

Aurioles-López, Verónica; Polo-López, M. Inmaculada; Fernández-Ibáñez, Pilar; López-Malo, Aurelio; Bandala, Erick R.

2016-02-01

The inactivation of Fusarium solani in water was assessed by solar driven Fenton-like processes using three different iron salts: ferric acetylacetonate (Fe(acac)3), ferric chloride (FeCl3) and ferrous sulfate (FeSO4). The experimental conditions tested were [Fe] ≈ 5 mg L-1, [H2O2] ≈ 10 mg L-1 and [Fe] ≈ 10 mg L-1; [H2O2] ≈ 20 mg L-1 mild and high, respectively, and pH 3.0 and 5.0, under solar radiation. The highest inactivation rates were observed at high reaction conditions for the three iron salts tested at pH 5.0 with less than 3.0 kJ L-1 of accumulate energy (QUV) to achieve over 99.9% of F. solani inactivation. Fe(acac)3 was the best iron salt to accomplishing F. solani inactivation. The modified Fermi equation was used to fix the experimental inactivation, data showed it was helpful for modeling the process, adequately describing dose-response curves. Inactivation process using FeSO4 at pH 3.0 was modeled fairly with r2 = 0.98 and 0.99 (mild and high concentration, respectively). Fe(acac)3, FeCl3 and FeSO4 at high concentration (i.e. [Fe] ≈ 10 mg L-1; [H2O2] ≈ 20 mg L-1) and pH 5.0 showed the highest fitting values (r2 = 0.99). Iron salt type showed a remarkable influence on the Fenton-like inactivation process.

Fabrication of patterned calcium cross-linked alginate hydrogel films and coatings through reductive cation exchange.

PubMed

Bruchet, Marion; Melman, Artem

2015-10-20

Calcium cross-linked alginate hydrogels are widely used in targeted drug delivery, tissue engineering, wound treatment, and other biomedical applications. We developed a method for preparing homogeneous alginate hydrogels cross-linked with Ca(2+) cations using reductive cation exchange in homogeneous iron(III) cross-linked alginate hydrogels. Treatment of iron(III) cross-linked alginate hydrogels with calcium salts and sodium ascorbate results in reduction of iron(III) cations to iron(II) that are instantaneously replaced with Ca(2+) cations, producing homogeneous ionically cross-linking hydrogels. Alternatively, the cation exchange can be performed by photochemical reduction in the presence of calcium chloride using a sacrificial photoreductant. This approach allows fabrication of patterned calcium alginate hydrogels through photochemical patterning of iron(III) cross-linked alginate hydrogel followed by the photochemical reductive exchange of iron cations to calcium. Copyright © 2015 Elsevier Ltd. All rights reserved.

Iron isotope fractionation during microbially stimulated Fe(II) oxidation and Fe(III) precipitation

USGS Publications Warehouse

Balci, N.; Bullen, T.D.; Witte-Lien, K.; Shanks, Wayne C.; Motelica, M.; Mandernack, K.W.

2006-01-01

Interpretation of the origins of iron-bearing minerals preserved in modern and ancient rocks based on measured iron isotope ratios depends on our ability to distinguish between biological and non-biological iron isotope fractionation processes. In this study, we compared 56Fe/54Fe ratios of coexisting aqueous iron (Fe(II)aq, Fe(III)aq) and iron oxyhydroxide precipitates (Fe(III)ppt) resulting from the oxidation of ferrous iron under experimental conditions at low pH (<3). Experiments were carried out using both pure cultures of Acidothiobacillus ferrooxidans and sterile controls to assess possible biological overprinting of non-biological fractionation, and both SO42- and Cl- salts as Fe(II) sources to determine possible ionic/speciation effects that may be associated with oxidation/precipitation reactions. In addition, a series of ferric iron precipitation experiments were performed at pH ranging from 1.9 to 3.5 to determine if different precipitation rates cause differences in the isotopic composition of the iron oxyhydroxides. During microbially stimulated Fe(II) oxidation in both the sulfate and chloride systems, 56Fe/54Fe ratios of residual Fe(II)aq sampled in a time series evolved along an apparent Rayleigh trend characterized by a fractionation factor ??Fe(III)aq-Fe(II)aq???1.0022. This fractionation factor was significantly less than that measured in our sterile control experiments (???1.0034) and that predicted for isotopic equilibrium between Fe(II)aq and Fe(III)aq (???1.0029), and thus might be interpreted to reflect a biological isotope effect. However, in our biological experiments the measured difference in 56Fe/54Fe ratios between Fe(III)aq, isolated as a solid by the addition of NaOH to the final solution at each time point under N2-atmosphere, and Fe(II)aq was in most cases and on average close to 2.9??? (??Fe(III)aq-Fe(II)aq ???1.0029), consistent with isotopic equilibrium between Fe(II)aq and Fe(III)aq. The ferric iron precipitation experiments revealed that 56Fe/54Fe ratios of Fe(III)aq were generally equal to or greater than those of Fe(III)ppt, and isotopic fractionation between these phases decreased with increasing precipitation rate and decreasing grain size. Considered together, the data confirm that the iron isotope variations observed in our microbial experiments are primarily controlled by non-biological equilibrium and kinetic factors, a result that aids our ability to interpret present-day iron cycling processes but further complicates our ability to use iron isotopes alone to identify biological processing in the rock record. ?? 2005 Elsevier Inc. All rights reserved.

Disproportionation of hydroxylamine by water-soluble iron(III) porphyrinate compounds.

PubMed

Bari, Sara E; Amorebieta, Valentín T; Gutiérrez, María M; Olabe, José A; Doctorovich, Fabio

2010-01-01

The reactions of hydroxylamine (HA) with several water-soluble iron(III) porphyrinate compounds, namely iron(III) meso-tetrakis-(N-ethylpyridinium-2yl)-porphyrinate ([Fe(III)(TEPyP)](5+)), iron(III) meso-tetrakis-(4-sulphonatophenyl)-porphyrinate ([Fe(III)(TPPS)](3-)), and microperoxidase 11 ([Fe(III)(MP11)]) were studied for different [Fe(III)(Porph)]/[HA] ratios, under anaerobic conditions at neutral pH. Efficient catalytic processes leading to the disproportionation of HA by these iron(III) porphyrinates were evidenced for the first time. As a common feature, only N(2) and N(2)O were found as gaseous, nitrogen-containing oxidation products, while NH(3) was the unique reduced species detected. Different N(2)/N(2)O ratios obtained with these three porphyrinates strongly suggest distinctive mechanistic scenarios: while [Fe(III)(TEPyP)](5+) and [Fe(III)(MP11)] formed unknown steady-state porphyrinic intermediates in the presence of HA, [Fe(III)(TPPS)](3-) led to the well characterized soluble intermediate, [Fe(II)(TPPS)NO](4-). Free-radical formation was only evidenced for [Fe(III)(TEPyP)](5+), as a consequence of a metal centered reduction. We discuss the catalytic pathways of HA disproportionation on the basis of the distribution of gaseous products, free radicals formation, the nature of porphyrinic intermediates, the Fe(II)/Fe(III) redox potential, the coordinating capabilities of each complex, and the kinetic analysis. The absence of NO(2)(-) revealed either that no HAO-like activity was operative under our reaction conditions, or that NO(2)(-), if formed, was consumed in the reaction milieu.

Exploration of pro-oxidant and antioxidant activities of the flavonoid myricetin.

PubMed

Chobot, Vladimir; Hadacek, Franz

2011-01-01

Flavonoids are ubiquitous phenolic plant metabolites. Many of them are well known for their pro- and antioxidant properties. Myricetin has been reported to be either a potent antioxidant or a pro-oxidant depending on the conditions. The reaction conditions for the pro- and antioxidant activities were therefore investigated using variations of the deoxyribose degradation assay systems. The deoxyribose degradation assay systems were conducted as follows; H(2)O(2)/Fe(III)/ascorbic acid, H(2)O(2)/Fe(III), Fe(III)/ascorbic acid, and Fe(III). Each system was carried out in two variants, FeCl(3) (iron ions added as FeCl(3)) and FeEDTA (iron added in complex with ethylenediaminetetraacetic acid). When ascorbic acid was present, myricetin showed antioxidant properties, especially when it occurred in complex with iron. In ascorbic acid-free systems, pro-oxidant activities prevailed, which where enhanced if iron was in complex with EDTA. Myricetin's antioxidant activity depends on both the reactive oxygen species (ROS) scavenging and iron ions chelation properties. The pro-oxidative properties are caused by reduction of molecular oxygen to ROS and iron(III) to iron(II). Myricetin is able to substitute for ascorbic acid albeit less efficiently.

Octa- and hexametallic iron(III)-potassium phosphonate cages.

PubMed

Gopal, Kandasamy; Tuna, Floriana; Winpenny, Richard E P

2011-12-07

Two new iron(III)-potassium phosphonate cage complexes with {K(2)Fe(6)} and {K(2)Fe(4)} cores are reported. Magnetic studies reveal antiferromagnetic interactions between the Fe(III) centres occur in these cages.

Different arsenate and phosphate incorporation effects on the nucleation and growth of iron(III) (Hydr)oxides on quartz.

PubMed

Neil, Chelsea W; Lee, Byeongdu; Jun, Young-Shin

2014-10-21

Iron(III) (hydr)oxides play an important role in the geochemical cycling of contaminants in natural and engineered aquatic systems. The ability of iron(III) (hydr)oxides to immobilize contaminants can be related to whether the precipitates form heterogeneously (e.g., at mineral surfaces) or homogeneously in solution. Utilizing grazing incidence small-angle X-ray scattering (GISAXS), we studied heterogeneous iron(III) (hydr)oxide nucleation and growth on quartz substrates for systems containing arsenate and phosphate anions. For the iron(III) only system, the radius of gyration (Rg) of heterogeneously formed precipitates grew from 1.5 to 2.5 (± 1.0) nm within 1 h. For the system containing 10(-5) M arsenate, Rg grew from 3.6 to 6.1 (± 0.5) nm, and for the system containing 10(-5) M phosphate, Rg grew from 2.0 to 4.0 (± 0.2) nm. While the systems containing these oxyanions had more growth, the system containing only iron(III) had the most nucleation events on substrates. Ex situ analyses of homogeneously and heterogeneously formed precipitates indicated that precipitates in the arsenate system had the highest water content and that oxyanions may bridge iron(III) hydroxide polymeric embryos to form a structure similar to ferric arsenate or ferric phosphate. These new findings are important because differences in nucleation and growth rates and particle sizes will impact the number of available reactive sites and the reactivity of newly formed particles toward aqueous contaminants.

Adrenaline and triiodothyronine modify the iron handling in the freshwater air-breathing fish Anabas testudineus Bloch: role of ferric reductase in iron acquisition.

PubMed

Rejitha, V; Peter, M C Subhash

2013-01-15

The effects of in vivo adrenaline and triiodothyronine (T(3)) on ferric reductase (FR) activity, a membrane-bound enzyme that reduces Fe(III) to Fe(II) iron, were studied in the organs of climbing perch (Anabas testudineus Bloch). Adrenaline injection (10 ng g(-1)) for 30 min produced significant inhibition of FR activity in the liver and kidney and that suggests a role for this stress hormone in iron acquisition in this fish. Short-term T(3) injection (40 ng g(-1)) reduced FR activity in the gills of fed fish but not in the unfed fish. Similar reduction of FR activity was also obtained in the intestine and kidney of fed fish after T(3) injection. Feeding produced pronounced decline in FR activity in the spleen but T(3) challenge in fed and unfed fish increased its activity in this iron storing organ and that point to the sensitivity of FR system to feeding activity. The in vitro effects of Fe on FR activity in the gill explants of freshwater fish showed correlations of FR with Na(+), K(+)-ATPase and H(+)-ATPase activities. Substantial increase in the FR activity was found in the gill explants incubated with all the tested doses of Fe(II) iron (1.80, 3.59 and 7.18 μM) and Fe(III) iron (1.25, 2.51 and 5.02 μM) and this indicate that FR and Na pump activity are positively correlated. On the contrary, substantial reduction of gill H(+)-ATPase activity was found in the gill explants incubated with Fe(II) iron and Fe(III) iron indicating that perch gills may not require a high acidic microenvironment for the reduction of Fe(III) iron. Accumulation of iron in the gill explants after Fe(III) iron incubation implies a direct relationship between Fe acquisition and FR activity in this tissue. The inverse correlation between FR activity and H(+)-ATPase activity in Fe(II) or Fe(III) loaded gills and the significant positive correlations of FR activity with total [Fe] content in the Fe(III) loaded gills substantiate that FR which shows sensitivity to sodium and proton pumps, has a vital role in Fe(II) and Fe(III) iron handling in this fish. Our data also provide evidence that adrenaline, T(3) and the feeding status are the vital factors that can regulate the storage and handling of iron in fish. Copyright © 2012 Elsevier Inc. All rights reserved.

Syntheses, crystal structures, and magnetic properties of the oxalato-bridged mixed-valence complexes (FeII(bpm)3]2[FeIII2(ox)5].8H2O and FeII(bpm)3Na(H2O)2Fe(ox)(3).4H2O (bpm = 2,2'-bipyrimidine).

PubMed

Armentano, D; De Munno, G; Faus, J; Lloret, F; Julve, M

2001-02-12

The preparation and crystal structures of two oxalato-bridged FeII-FeIII mixed-valence compounds, [FeII(bpm)3]2[FeIII2(ox)5].8H2O (1) and FeII(bpm)3Na(H2O)2FeIII(ox)(3).4H2O (2) (bpm = 2,2'-bipyrimidine; ox = oxalate dianion) are reported here. Complex 1 crystallizes in the triclinic system, space group P1, with a = 10.998(2) A, b = 13.073(3) A, c = 13.308(3) A, alpha = 101.95(2) degrees, beta = 109.20(2) degrees, gamma = 99.89(2) degrees, and Z = 1. Complex 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 12.609(2) A, b = 19.670(5) A, c = 15.843(3) A, beta = 99.46(1) degrees, and Z = 4. The structure of complex 1 consists of centrosymmetric oxalato-bridged dinuclear high-spin iron(III) [Fe2(ox)5]2- anions, tris-chelated low-spin iron(II) [Fe(bpm)3]2+ cations, and lattice water molecules. The iron atoms are hexacoordinated: six oxygen atoms (iron(III)) from two bidentate and one bisbidentate oxalato ligands and six nitrogen atoms (iron(II)) from three bidentate bpm groups. The Fe(III)-O(ox) and Fe(II)-N(bpm) bond distances vary in the ranges 1.967(3)-2.099(3) and 1.967(4)-1.995(3) A, respectively. The iron(III)-iron(III) separation across the bridging oxalato is 5.449(2) A, whereas the shortest intermolecular iron(III)-iron(II) distance is 6.841(2) A. The structure of complex 2 consists of neutral heterotrinuclear Fe(bpm)2Na(H2O)2Fe(ox)3 units and water molecules of crystallization. The tris-chelated low-spin iron(II) ([Fe(bpm)3]2+) and high-spin iron(III) ([Fe(ox)3]3-) entities act as bidentate ligands (through two bpm-nitrogen and two oxalato-oxygen atoms, respectively) toward the univalent sodium cation, yielding the trinuclear (bpm)2Fe(II)-bpm-Na(I)-ox-Fe(III)(ox)2 complex. Two cis-coordinated water molecules complete the distorted octahedral surrounding of the sodium atom. The ranges of the Fe(II)-N(bpm) and Fe(III)-O(ox) bond distances [1.968(6)-1.993(5) and 1.992(6)-2.024(6) A, respectively] compare well with those observed in 1. The Na-N(bpm) bond lengths (2.548(7) and 2.677(7) A) are longer than those of Na-O(ox) (2.514(7) and 2.380(7) A) and Na-O(water) (2.334(15) and 2.356(12) A). The intramolecular Fe(II)...Fe(III) separation is 6.763(2) A, whereas the shortest intermolecular Fe(II)...Fe(II) and Fe(III)...Fe(III) distances are 8.152(2) and 8.992(2) A, respectively. Magnetic susceptibility measurements in the temperature range 2.0-290 K for 1 reveal that the high-spin iron(III) ions are antiferromagnetically coupled (J = -6.6 cm-1, the Hamiltonian being defined as H = -JS1.S2). The magnitude of the antiferromagnetic coupling through the bridging oxalato in the magneto-structurally characterized family of formula [M2(ox)5](2m-10)+ (M = Fe(III) (1), Cr(III), and Ni(II)) is analyzed and discussed by means of a simple orbital model.

DEMONSTRATION OF A BIOAVAILABLE FERRIC IRON TEST KIT

EPA Science Inventory

Bioavailable ferric iron (BAFeIII) is used by iron-reducing bacteria as an electron acceptor during the oxidation of various organic contaminants such as vinyl chloride and benzene. Quantification of BAFeIII is important with respect to characterizing candidate natural attenuati...

The Electrochemical Synthesis of Transition-Metal Acetylacetonates

ERIC Educational Resources Information Center

Long, S. R.; Browning, S. R.; Lagowski, J. J.

2008-01-01

The electrochemical synthesis of transition-metal acetylacetonates described here can form the basis of assisting in the transformation of an entry-level laboratory course into a research-like environment where all members of a class are working on the same problem, but where each member has a personal responsibility for the synthesis and…

ESTCP DEMONSTRATION OF A BIOAVAILABLE FERRIC IRON TEST KIT

EPA Science Inventory

Bioavailable ferric iron (BAFeIII) is used by iron-reducing bacteria as an electron acceptor during the oxidation of various organic contaminants such as vinyl chloride and benzene. Quantification of BAFeIII is important with respect to characterizing candidate natural attenuati...

The catalytic center of ferritin regulates iron storage via Fe(II)-Fe(III) displacement.

PubMed

Honarmand Ebrahimi, Kourosh; Bill, Eckhard; Hagedoorn, Peter-Leon; Hagen, Wilfred R

2012-11-01

A conserved iron-binding site, the ferroxidase center, regulates the vital iron storage role of the ubiquitous protein ferritin in iron metabolism. It is commonly thought that two Fe(II) simultaneously bind the ferroxidase center and that the oxidized Fe(III)-O(H)-Fe(III) product spontaneously enters the cavity of ferritin as a unit. In contrast, in some bacterioferritins and in archaeal ferritins a persistent di-iron prosthetic group in this center is believed to mediate catalysis of core formation. Using a combination of binding experiments and isotopically labeled (57)Fe(II), we studied two systems in comparison: the ferritin from the hyperthermophilic archaeal anaerobe Pyrococcus furiosus (PfFtn) and the eukaryotic human H ferritin (HuHF). The results do not support either of the two paradigmatic models; instead they suggest a unifying mechanism in which the Fe(III)-O-Fe(III) unit resides in the ferroxidase center until it is sequentially displaced by Fe(II).

Real-Time Studies of Iron Oxalate-Mediated Oxidation of Glycolaldehyde as a Model for Photochemical Aging of Aqueous Tropospheric Aerosols.

PubMed

Thomas, Daniel A; Coggon, Matthew M; Lignell, Hanna; Schilling, Katherine A; Zhang, Xuan; Schwantes, Rebecca H; Flagan, Richard C; Seinfeld, John H; Beauchamp, J L

2016-11-15

The complexation of iron(III) with oxalic acid in aqueous solution yields a strongly absorbing chromophore that undergoes efficient photodissociation to give iron(II) and the carbon dioxide anion radical. Importantly, iron(III) oxalate complexes absorb near-UV radiation (λ > 350 nm), providing a potentially powerful source of oxidants in aqueous tropospheric chemistry. Although this photochemical system has been studied extensively, the mechanistic details associated with its role in the oxidation of dissolved organic matter within aqueous aerosol remain largely unknown. This study utilizes glycolaldehyde as a model organic species to examine the oxidation pathways and evolution of organic aerosol initiated by the photodissociation of aqueous iron(III) oxalate complexes. Hanging droplets (radius 1 mm) containing iron(III), oxalic acid, glycolaldehyde, and ammonium sulfate (pH ∼3) are exposed to irradiation at 365 nm and sampled at discrete time points utilizing field-induced droplet ionization mass spectrometry (FIDI-MS). Glycolaldehyde is found to undergo rapid oxidation to form glyoxal, glycolic acid, and glyoxylic acid, but the formation of high molecular weight oligomers is not observed. For comparison, particle-phase experiments conducted in a laboratory chamber explore the reactive uptake of gas-phase glycolaldehyde onto aqueous seed aerosol containing iron and oxalic acid. The presence of iron oxalate in seed aerosol is found to inhibit aerosol growth. These results suggest that photodissociation of iron(III) oxalate can lead to the formation of volatile oxidation products in tropospheric aqueous aerosols.

Phenazine-1-Carboxylic Acid Promotes Bacterial Biofilm Development via Ferrous Iron Acquisition▿†

PubMed Central

Wang, Yun; Wilks, Jessica C.; Danhorn, Thomas; Ramos, Itzel; Croal, Laura; Newman, Dianne K.

2011-01-01

The opportunistic pathogen Pseudomonas aeruginosa forms biofilms, which render it more resistant to antimicrobial agents. Levels of iron in excess of what is required for planktonic growth have been shown to promote biofilm formation, and therapies that interfere with ferric iron [Fe(III)] uptake combined with antibiotics may help treat P. aeruginosa infections. However, use of these therapies presumes that iron is in the Fe(III) state in the context of infection. Here we report the ability of phenazine-1-carboxylic acid (PCA), a common phenazine made by all phenazine-producing pseudomonads, to help P. aeruginosa alleviate Fe(III) limitation by reducing Fe(III) to ferrous iron [Fe(II)]. In the presence of PCA, a P. aeruginosa mutant lacking the ability to produce the siderophores pyoverdine and pyochelin can still develop into a biofilm. As has been previously reported (P. K. Singh, M. R. Parsek, E. P. Greenberg, and M. J. Welsh, Nature 417:552-555, 2002), biofilm formation by the wild type is blocked by subinhibitory concentrations of the Fe(III)-binding innate-immunity protein conalbumin, but here we show that this blockage can be rescued by PCA. FeoB, an Fe(II) uptake protein, is required for PCA to enable this rescue. Unlike PCA, the phenazine pyocyanin (PYO) can facilitate biofilm formation via an iron-independent pathway. While siderophore-mediated Fe(III) uptake is undoubtedly important at early stages of infection, these results suggest that at later stages of infection, PCA present in infected tissues may shift the redox equilibrium between Fe(III) and Fe(II), thereby making iron more bioavailable. PMID:21602354

Complexation Effect on Redox Potential of Iron(III)-Iron(II) Couple: A Simple Potentiometric Experiment

ERIC Educational Resources Information Center

Rizvi, Masood Ahmad; Syed, Raashid Maqsood; Khan, Badruddin

2011-01-01

A titration curve with multiple inflection points results when a mixture of two or more reducing agents with sufficiently different reduction potentials are titrated. In this experiment iron(II) complexes are combined into a mixture of reducing agents and are oxidized to the corresponding iron(III) complexes. As all of the complexes involve the…

Lifetime enhanced phosphorescent organic light emitting diode using an electron scavenger layer

NASA Astrophysics Data System (ADS)

Hong, Seokhwan; Kim, Ji Whan; Lee, Sangyeob

2015-07-01

We demonstrate a method to improve lifetime of a phosphorescent organic light emitting diode (OLED) using an electron scavenger layer (ESL) in a hole transporting layer (HTL) of the device. We use a bis(1-(phenyl)isoquinoline)iridium(III)acetylacetonate [Ir(piq)2(acac)] doped HTL to stimulate radiative decay, preventing thermal degradation in HTL. The ESL effectively prevented non-radiative decay of leakage electron in HTL by converting non-radiative decay to radiative decay via a phosphorescent red emitter, Ir(piq)2(acac). The lifetime of device (t95: time after 5% decrease of luminance) has been increased from 75 h to 120 h by using the ESL in a phosphorescent green-emitting OLED.

High efficiency yellow organic light-emitting diodes with optimized barrier layers

NASA Astrophysics Data System (ADS)

Mu, Ye; Zhang, Shiming; Yue, Shouzhen; Wu, Qingyang; Zhao, Yi

2015-12-01

High efficiency Iridium (III) bis (4-phenylthieno [3,2-c] pyridinato-N,C2‧) acetylacetonate (PO-01) based yellow organic light-emitting devices are fabricated by employing multiple emission layers. The efficiency of the device using 4,4‧,4″-tris(N-carbazolyl) triphenylamine (TCTA) as potential barrier layer (PBL) outperforms those devices based on other PBLs and detailed analysis is carried out to reveal the mechanisms. A forward-viewing current efficiency (CE) of 65.21 cd/A, which corresponds to a maximum total CE of 110.85 cd/A is achieved at 335.8 cd/m2 in the optimized device without any outcoupling enhancement structures.

THE WIDESPREAD OF Fe(III)-REDUCING BACTERIA IN NATURAL ECOSYSTEMS OF ECUADOR.

PubMed

Tashyrev, O B; Govorukha, V M

2015-01-01

The widespread of Fe(III)-reducing microorganisms in natural ecosystems of Ecuador of La Favorita, Tungurahua volcano and Papallacta areas was experimentally proved. High efficiency of microbial precipitation of soluble iron compounds was also demonstrated. Obtained results indicate the potential ability of Fe(III)-reducing microorganisms to influence the formation of carbon and iron vector fluxes in ecosystems, as well as development of effective biotechnologies of water purification from iron compounds.

Synthesis and characterization of the tetranuclear iron(III) complex of a new asymmetric multidentate ligand. A structural model for purple acid phosphatases.

PubMed

Boudalis, Athanassios K; Aston, Robyn E; Smith, Sarah J; Mirams, Ruth E; Riley, Mark J; Schenk, Gerhard; Blackman, Allan G; Hanton, Lyall R; Gahan, Lawrence R

2007-11-28

The ligand, 2-((2-hydroxy-5-methyl-3-((pyridin-2-ylmethylamino)methyl)benzyl)(2-hydroxybenzyl)amino)acetic acid (H(3)HPBA), which contains a donor atom set that mimics that of the active site of purple acid phosphatase is described. Reaction of H(3)HPBA with iron(III) or iron(II) salts results in formation of the tetranuclear complex, [Fe(4)(HPBA)(2)(OAc)(2)(mu-O)(mu-OH)(OH(2))(2)]ClO(4) x 5H(2)O. X-Ray structural analysis reveals the cation consists of four iron(III) ions, two HPBA(3-) ligands, two bridging acetate ligands, a bridging oxide ion and a bridging hydroxide ion. Each binucleating HPBA(3-) ligand coordinates two structurally distinct hexacoordinate iron(III) ions. The two metal ions coordinated to a HPBA(3-) ligand are linked to the two iron(III) metal ions of a second, similar binuclear unit by intramolecular oxide and hydroxide bridging moieties to form a tetramer. The complex has been further characterised by elemental analysis, mass spectrometry, UV-vis and MCD spectroscopy, X-ray crystallography, magnetic susceptibility measurements and variable-temperature Mössbauer spectroscopy.

Self-assembled Targeting of Cancer Cells by Iron(III)-doped, Silica Nanoparticles.

PubMed

Mitchell, K K Pohaku; Sandoval, S; Cortes-Mateos, M J; Alfaro, J G; Kummel, A C; Trogler, W C

2014-12-07

Iron(III)-doped silica nanoshells are shown to possess an in vitro cell-receptor mediated targeting functionality for endocytosis. Compared to plain silica nanoparticles, iron enriched ones are shown to be target-specific, a property that makes them potentially better vehicles for applications, such as drug delivery and tumor imaging, by making them more selective and thereby reducing the nanoparticle dose. Iron(III) in the nanoshells can interact with endogenous transferrin, a serum protein found in mammalian cell culture media, which subsequently promotes transport of the nanoshells into cells by the transferrin receptor-mediated endocytosis pathway. The enhanced uptake of the iron(III)-doped nanoshells relative to undoped silica nanoshells by a transferrin receptor-mediated pathway was established using fluorescence and confocal microscopy in an epithelial breast cancer cell line. This process was also confirmed using fluorescence activated cell sorting (FACS) measurements that show competitive blocking of nanoparticle uptake by added holo-transferrin.

Studies on different iron source absorption by in situ ligated intestinal loops of broilers.

PubMed

Jia, Y F; Jiang, M M; Sun, J; Shi, R B; Liu, D S

2015-02-01

The objective of this study was to investigate the iron source absorption in the small intestine of broiler. In situ ligated intestinal loops of 70 birds were poured into one of seven solutions, including inorganic iron (FeSO4, Fe2(SO4)3), organic Fe glycine chelate (Fe-Gly(II), Fe-Gly(III)), the mixtures (FeSO4 with glycine (Fe+Gly(II)), Fe2(SO4)3 with glycine (Fe+Gly(III)), and no Fe source (control). The total volume of 3-mL solution (containing 1 mg of elemental Fe) was injected into intestinal loops, and then 120-min incubation was performed. Compared with inorganic iron groups, in which higher FeSO4 absorption than Fe2(SO4)3 was observed, supplementation with organic Fe glycine chelate significantly increased the Fe concentration in the duodenum and jejunum (P < 0.05), however, decreased DMT1 and DcytB messenger RNA (mRNA) levels (P < 0.05). Organic Fe glycine chelate (Fe-Gly(II), Fe-Gly(III)) increased serum iron concentration (SI), compared with inorganic 3 valence iron groups (Fe2(SO4)3 and Fe+Gly(III)) (P < 0.05); moreover, lower TIBC value was observed for the chelate (P < 0.05); however, mixture of inorganic iron and glycine did not have a positive role at DMT1 and DcytB mRNA levels, SI and Fe concentrations in the small intestine. Those results indicated that the absorption of organic Fe glycine chelate was more effective than that of inorganic Fe, and the orders of iron absorption in the small intestine were: Fe-Gly(II), Fe-Gly(III) > FeSO4, Fe+Gly(II) > Fe2(SO4)3, Fe+Gly(III). Additionally, the simple mixture of inorganic iron and glycine could not increase Fe absorption, and the duodenum was the main site of Fe absorption in the intestines of broilers and the ileum absorbed iron rarely.

Measuring “Free” Iron Levels in Caenorhabditis Elegans Using Low-Temperature Fe(III) Electron Paramagnetic Resonance Spectroscopy

PubMed Central

Pate, Kira T.; Rangel, Natalie A.; Fraser, Brian; Clement, Matthew H. S.; Srinivasan, Chandra

2007-01-01

Oxidative stress, caused by free radicals within the body, has been associated with the process of aging and many human diseases. As free radicals, in particular superoxide, are difficult to measure, an alternative indirect method for measuring oxidative stress levels has been successfully used in E. coli and yeast. This method is based on a proposed connection between elevated superoxide levels and release of iron from solvent exposed [4Fe-4S] enzyme clusters, which eventually leads to an increase in hydroxyl radical production. In past studies using bacteria and yeast, a positive correlation was found between superoxide production or oxidative stress due to superoxide within the organism and EPR (electron paramagnetic resonance) detectable “free” iron levels. In the present study, we have developed a reliable and an efficient method for measuring “free” iron levels in C. elegans using low temperature Fe(III) EPR at g = 4.3. This method utilizes synchronized worm cultures grown on plates, which are homogenized and treated with desferrioxamine, an Fe(III) chelator, prior to packing the EPR tube. Homogenization was found not to alter “free” iron levels, while desferrioxamine treatment significantly raised these levels, indicating presence of both Fe(II) and Fe(III) in the “free” iron pool. The correlation between free radical levels and the observed “free” iron levels was examined by using heat stress and paraquat treatment. The intensity of the Fe(III) EPR signal and thus, the concentration of the “free” iron pool, varied with the treatments that altered radical levels without changing the total iron levels. This study provides the groundwork needed to uncover the correlation between oxidative stress, “free” iron levels, and longevity in C. elegans. PMID:17010298

New approach towards the polyol route to fabricate MFe2O4 magnetic nanoparticles: The use of MCl2 and Fe(acac)3 as chemical precursors

NASA Astrophysics Data System (ADS)

Solano, Eduardo; Yáñez, Ramón; Ricart, Susagna; Ros, Josep

2015-05-01

A new more efficient approach of the polyol route to generate MFe2O4 (M=Mn, Fe, Co, Ni, Cu, Zn) nanoparticles in triethylene glycol (TREG) is presented. The selected thermal procedure is based on the Fe metalorganic precursor (iron(III) acetylacetonate) decomposition in presence of an inorganic transition metal chloride salt (MCl2, M=Mn, Fe, Co, Ni, Cu, Zn) to produce high quality polar dispersible nanoparticles with lower production cost. In addition, the nanoparticles are stabilized by ionic (from the Cl-) and steric (TREG as capping ligand) effects inducing into the nanoparticles an extraordinary stability in different polar solvents. As result of this optimized methodology, the colloidal polar dispersible nanoparticles present a size around 10 nm with an adequate size dispersion demonstrated by analyzing transmission electron microscopy (TEM) images. X-ray powder diffraction (XRPD) results corroborate the absence of secondary phases and the high crystalline degree obtained for the spinel structure, fact proved by using synchrotron X-ray diffraction. The high magnetic performance at low and room temperature of the nanoparticles studied by magnetometry proves the high internal crystal order of the spinel. Parallel to this, the influence of the heating ramp and annealing time in the thermal procedure were also investigated for the CuFe2O4 case, where a relationship between these two parameters and the final size and their associated diameter distribution was found, allowing a possible size control of the final ferrite magnetic nanoparticles synthesized.

New Mechanism for the Reduction of Vanadyl Acetylacetonate to Vanadium Acetylacetonate for Room Temperature Flow Batteries.

PubMed

Shamie, Jack S; Liu, Caihong; Shaw, Leon L; Sprenkle, Vincent L

2017-02-08

In this study, a new mechanism for the reduction of vanadyl acetylacetonate, VO(acac) 2 , to vanadium acetylacetonate, V(acac) 3 , is introduced. V(acac) 3 has been studied for use in redox flow batteries (RFBs) for some time; however, contamination by moisture leads to the formation of VO(acac) 2 . In previous work, once this transformation occurs, it is no longer reversible because there is a requirement for extreme low potentials for the reduction to occur. Here, we propose that, in the presence of excess acetylacetone (Hacac) and free protons (H + ), the reduction can take place between 2.25 and 1.5 V versus Na/Na + via a one-electron-transfer reduction. This reduction can take place in situ during discharge in a novel hybrid Na-based flow battery (HNFB) with a molten Na-Cs alloy as the anode. The in situ recovery of V(acac) 3 during discharge is shown to allow the Coulombic efficiency of the HNFB to be ≈100 % with little or no capacity decay over cycles. In addition, utilizing two-electron-transfer redox reactions (i.e., V 3+ /V 4+ and V 2+ /V 3+ redox couples) per V ion to increase the energy density of RFBs becomes possible owing to the in situ recovery of V(acac) 3 during discharge. The concept of in situ recovery of material can lead to more advances in maintaining the cycle life of RFBs in the future. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Isolation of microorganisms involved in reduction of crystalline iron(III) oxides in natural environments

PubMed Central

Hori, Tomoyuki; Aoyagi, Tomo; Itoh, Hideomi; Narihiro, Takashi; Oikawa, Azusa; Suzuki, Kiyofumi; Ogata, Atsushi; Friedrich, Michael W.; Conrad, Ralf; Kamagata, Yoichi

2015-01-01

Reduction of crystalline Fe(III) oxides is one of the most important electron sinks for organic compound oxidation in natural environments. Yet the limited number of isolates makes it difficult to understand the physiology and ecological impact of the microorganisms involved. Here, two-stage cultivation was implemented to selectively enrich and isolate crystalline iron(III) oxide reducing microorganisms in soils and sediments. Firstly, iron reducers were enriched and other untargeted eutrophs were depleted by 2-years successive culture on a crystalline ferric iron oxide (i.e., goethite, lepidocrocite, hematite, or magnetite) as electron acceptor. Fifty-eight out of 136 incubation conditions allowed the continued existence of microorganisms as confirmed by PCR amplification. High-throughput Illumina sequencing and clone library analysis based on 16S rRNA genes revealed that the enrichment cultures on each of the ferric iron oxides contained bacteria belonging to the Deltaproteobacteria (mainly Geobacteraceae), followed by Firmicutes and Chloroflexi, which also comprised most of the operational taxonomic units (OTUs) identified. Venn diagrams indicated that the core OTUs enriched with all of the iron oxides were dominant in the Geobacteraceae while each type of iron oxides supplemented selectively enriched specific OTUs in the other phylogenetic groups. Secondly, 38 enrichment cultures including novel microorganisms were transferred to soluble-iron(III) containing media in order to stimulate the proliferation of the enriched iron reducers. Through extinction dilution-culture and single colony isolation, six strains within the Deltaproteobacteria were finally obtained; five strains belonged to the genus Geobacter and one strain to Pelobacter. The 16S rRNA genes of these isolates were 94.8–98.1% identical in sequence to cultured relatives. All the isolates were able to grow on acetate and ferric iron but their physiological characteristics differed considerably in terms of growth rate. Thus, the novel strategy allowed to enrich and isolate novel iron(III) reducers that were able to thrive by reducing crystalline ferric iron oxides. PMID:25999927

Isolation of microorganisms involved in reduction of crystalline iron(III) oxides in natural environments.

PubMed

Hori, Tomoyuki; Aoyagi, Tomo; Itoh, Hideomi; Narihiro, Takashi; Oikawa, Azusa; Suzuki, Kiyofumi; Ogata, Atsushi; Friedrich, Michael W; Conrad, Ralf; Kamagata, Yoichi

2015-01-01

Reduction of crystalline Fe(III) oxides is one of the most important electron sinks for organic compound oxidation in natural environments. Yet the limited number of isolates makes it difficult to understand the physiology and ecological impact of the microorganisms involved. Here, two-stage cultivation was implemented to selectively enrich and isolate crystalline iron(III) oxide reducing microorganisms in soils and sediments. Firstly, iron reducers were enriched and other untargeted eutrophs were depleted by 2-years successive culture on a crystalline ferric iron oxide (i.e., goethite, lepidocrocite, hematite, or magnetite) as electron acceptor. Fifty-eight out of 136 incubation conditions allowed the continued existence of microorganisms as confirmed by PCR amplification. High-throughput Illumina sequencing and clone library analysis based on 16S rRNA genes revealed that the enrichment cultures on each of the ferric iron oxides contained bacteria belonging to the Deltaproteobacteria (mainly Geobacteraceae), followed by Firmicutes and Chloroflexi, which also comprised most of the operational taxonomic units (OTUs) identified. Venn diagrams indicated that the core OTUs enriched with all of the iron oxides were dominant in the Geobacteraceae while each type of iron oxides supplemented selectively enriched specific OTUs in the other phylogenetic groups. Secondly, 38 enrichment cultures including novel microorganisms were transferred to soluble-iron(III) containing media in order to stimulate the proliferation of the enriched iron reducers. Through extinction dilution-culture and single colony isolation, six strains within the Deltaproteobacteria were finally obtained; five strains belonged to the genus Geobacter and one strain to Pelobacter. The 16S rRNA genes of these isolates were 94.8-98.1% identical in sequence to cultured relatives. All the isolates were able to grow on acetate and ferric iron but their physiological characteristics differed considerably in terms of growth rate. Thus, the novel strategy allowed to enrich and isolate novel iron(III) reducers that were able to thrive by reducing crystalline ferric iron oxides.

Planktonic Marine Iron-Oxidizers Drive Iron(III) Mineralization Under Low Oxygen Conditions

NASA Astrophysics Data System (ADS)

Luther, G. W., III; Field, E.; Findlay, A.; MacDonald, D. J.; Chan, C. S. Y.; Kato, S.

2016-02-01

Observations of modern microbes have led to several hypotheses on how microbes precipitated the extensive banded iron formations in the geologic record, but we have yet to resolve the exact microbial contributions. An initial hypotheses was that cyanobacteria produced oxygen that oxidized iron(II) abiotically; however, in modern environments such as microbial mats, where Fe(II) and O2 coexist, we commonly find microaerophilic chemolithotrophic iron(II)-oxidizing bacteria producing Fe(III) oxyhydroxides. This suggests that such iron-oxidizers could have inhabited niches in ancient coastal oceans where Fe(II) and O2 coexisted, and therefore contributed to iron deposits, but there is currently little evidence for planktonic marine iron-oxidizers in modern analogs. Here, we demonstrate successful cultivation of planktonic microaerophilic iron-oxidizing Zetaproteobacteria from the Chesapeake Bay during seasonal stratification. Iron-oxidizers were associated with low oxygen concentrations and active iron redox cycling in the oxic-anoxic transition zone (<3 µM O2, <0.2 µM H2S). While cyanobacteria were also detected in this transition zone, oxygen concentrations were too low to support significant rates of abiotic iron oxidation. Instead, cyanobacteria may be providing oxygen for microaerophilic iron(II) oxidation through a symbiotic relationship that promotes oxygen consumption rather than build-up. Our results suggest that once oxygenic photosynthesis evolved, microaerophilic chemolithotrophic iron(II)-oxidizers were likely important drivers of iron(III) mineralization in ancient oceans.

Gallium-based anti-infectives: targeting microbial iron-uptake mechanisms.

PubMed

Kelson, Andrew B; Carnevali, Maia; Truong-Le, Vu

2013-10-01

Microbes have evolved elaborate iron-acquisition systems to sequester iron from the host environment using siderophores and heme uptake systems. Gallium(III) is structurally similar to iron(III), except that it cannot be reduced under physiological conditions, therefore gallium has the potential to serve as an iron analog, and thus an anti-microbial. Because Ga(III) can bind to virtually any complex that binds Fe(III), simple gallium salts as well as more complex siderophores and hemes are potential carriers to deliver Ga(III) to the microbes. These gallium complexes represent a new class of anti-infectives that is different in mechanism of action from conventional antibiotics. Simple gallium salts such as gallium nitrate, maltolate, and simple gallium siderophore complexes such as gallium citrate have shown good antibacterial activities. The most studied complex has been gallium citrate, which exhibits broad activity against many Gram negative bacteria at ∼1-5μg/ml MICs, strong biofilm activity, low drug resistance, and efficacy in vivo. Using the structural features of specific siderophore and heme made by pathogenic bacteria and fungi, researchers have begun to evaluate new gallium complexes to target key pathogens. This review will summarize potential iron-acquisition system targets and recent research on gallium-based anti-infectives. Copyright © 2013 Elsevier Ltd. All rights reserved.

Curing of a Bisphenol-E Based Cyanate Ester using Magnetic Nanoparticles as an Internal Heat Source through Induction Heating

DTIC Science & Technology

2013-11-01

magnetic field as a heat source for the polymerization avoids some of these difficulties. EXPERIMENTAL SECTION Iron (III) chloride hexahydrate (ACS...reagent, 97%), iron (II) chloride tetrahydrate (ReagentPlus®, 98%), tetramethylammonium hydroxide solution (25 wt. % in water), and oleic acid (technical...Edwards Air Force Base and used without further purification. Preparation of Iron Oxide Magnetic Nanoparticles.51 Iron (III) chloride hexahydrate (11.75

Mössbauer spectroscopic study of 57Fe metabolic transformations in the rhizobacterium Azospirillum brasilense Sp245

NASA Astrophysics Data System (ADS)

Kamnev, Alexander A.; Tugarova, Anna V.; Kovács, Krisztina; Biró, Borbála; Homonnay, Zoltán; Kuzmann, Ernő

2014-04-01

Preliminary 57Fe transmission Mössbauer spectroscopic data were obtained for the first time for live cells of the plant-growth-promoting rhizobacterium Azospirillum brasilense (wild-type strain Sp245) grown aerobically with 57FeIII-nitrilotriacetate (NTA) complex as a sole source of iron. The results obtained have shown that live cells actively reduce part of the assimilated iron(III) to iron(II), the latter amounting up to 33 % of total cellular iron after 18 h of growth, and 48 % after additional 3 days of storage of the dense wet cell suspension in nutrient-free saline solution in air at room temperature (measured at 80 K). The cellular iron(II) was found to be represented by two quadrupole doublets of different high-spin forms, while the parameters of the cellular iron(III) were close to those typical for bacterioferritins.

Kinetics and thermodynamics of irreversible inhibition of matrix metalloproteinase 2 by a Co(III) Schiff base complex

PubMed Central

Harney, Allison S.; Sole, Laura B.

2012-01-01

Cobalt(III) Schiff base complexes have been used as potent inhibitors of protein function through the coordination to histidine residues essential for activity. The kinetics and thermodynamics of the binding mechanism of Co(acacen)(NH3)2Cl [Co(acacen); where H2acacen is bis(acetylacetone)ethylenediimine] enzyme inhibition has been examined through the inactivation of matrix metalloproteinase 2 (MMP-2) protease activity. Co(acacen) is an irreversible inhibitor that exhibits time- and concentration-dependent inactivation of MMP-2. Co(acacen) inhibition of MMP-2 is temperature-dependent, with the inactivation increasing with temperature. Examination of the formation of the transition state for the MMP-2/Co(acacen) complex was determined to have a positive entropy component indicative of greater disorder in the MMP-2/Co(acacen) complex than in the reactants. With further insight into the mechanism of Co(acacen) complexes, Co(III) Schiff base complex protein inactivators can be designed to include features regulating activity and protein specificity. This approach is widely applicable to protein targets that have been identified to have clinical significance, including matrix metalloproteinases. The mechanistic information elucidated here further emphasizes the versatility and utility of Co(III) Schiff base complexes as customizable protein inhibitors. PMID:22729838

QM/MM structural and spectroscopic analysis of the di-iron(II) and di-iron(III) ferroxidase site in M ferritin.

PubMed

Harris, Travis V; Morokuma, Keiji

2013-08-05

Ferritins are cage-like proteins composed of 24 subunits that take up iron(II) and store it as an iron(III) oxide mineral core. A critical step is the ferroxidase reaction, in which oxygen reacts with a di-iron(II) site, proceeding through a peroxo intermediate, to form μ-oxo/hydroxo-bridged di-iron(III) products. The recent crystal structures of copper(II)- and iron(III)-bound frog M ferritin at 2.8 Å resolution [Bertini; et al. J. Am. Chem. Soc. 2012, 134, 6169-6176] provided an opportunity to theoretically investigate the detailed structures of the reactant state and products. In this study, the quantum mechanical/molecular mechanical ONIOM method is used to structurally optimize a series of single-subunit models with various hydration, protonation, and coordination states of the ferroxidase site. Calculated exchange coupling constants (J), Mössbauer parameters, and time-dependent density functional theoretical (TD-DFT) circular dichroism spectra with electronic embedding are compared with the available experimental data. The di-iron(II) model with the most experimentally consistent structural and spectroscopic parameters has 5-coordinate iron centers with Glu23, Glu58, His61, and two waters completing one coordination sphere, and His54, Glu58, Glu103, and Asp140 completing the other. In contrast to a previously proposed structure, Gln137 is not directly coordinated, but it is involved in hydrogen bonding with several iron ligands. For the di-iron(III) products, we find that a μ-oxo-bridged and two doubly bridged (μ-hydroxo and μ-oxo/hydroxo) species are likely coproduced. Although four quadrupole doublets were observed experimentally, we find that two doublets may arise from a single asymmetrically coordinated ferroxidase site. These proposed key structures will help to explore the pathway connecting the di-Fe(II) state to the peroxo intermediate and the branching mechanisms leading to the multiple products.

The kinetics of the reaction of nitrogen dioxide with iron(II)- and iron(III) cytochrome c.

PubMed

Domazou, Anastasia S; Gebicka, Lidia; Didik, Joanna; Gebicki, Jerzy L; van der Meijden, Benjamin; Koppenol, Willem H

2014-04-01

The reactions of NO2 with both oxidized and reduced cytochrome c at pH 7.2 and 7.4, respectively, and with N-acetyltyrosine amide and N-acetyltryptophan amide at pH 7.3 were studied by pulse radiolysis at 23 °C. NO2 oxidizes N-acetyltyrosine amide and N-acetyltryptophan amide with rate constants of (3.1±0.3)×10(5) and (1.1±0.1)×10(6) M(-1) s(-1), respectively. With iron(III)cytochrome c, the reaction involves only its amino acids, because no changes in the visible spectrum of cytochrome c are observed. The second-order rate constant is (5.8±0.7)×10(6) M(-1) s(-1) at pH 7.2. NO2 oxidizes iron(II)cytochrome c with a second-order rate constant of (6.6±0.5)×10(7) M(-1) s(-1) at pH 7.4; formation of iron(III)cytochrome c is quantitative. Based on these rate constants, we propose that the reaction with iron(II)cytochrome c proceeds via a mechanism in which 90% of NO2 oxidizes the iron center directly-most probably via reaction at the solvent-accessible heme edge-whereas 10% oxidizes the amino acid residues to the corresponding radicals, which, in turn, oxidize iron(II). Iron(II)cytochrome c is also oxidized by peroxynitrite in the presence of CO2 to iron(III)cytochrome c, with a yield of ~60% relative to peroxynitrite. Our results indicate that, in vivo, NO2 will attack preferentially the reduced form of cytochrome c; protein damage is expected to be marginal, the consequence of formation of amino acid radicals on iron(III)cytochrome c. Copyright © 2014 Elsevier Inc. All rights reserved.

Main and interaction effects of iron, zinc, lead, and parenting on children's cognitive outcomes.

PubMed

Hubbs-Tait, Laura; Mulugeta, Afework; Bogale, Alemtsehay; Kennedy, Tay S; Baker, Eric R; Stoecker, Barbara J

2009-01-01

This study examined relations of blood lead < 10 microg/dL, iron, zinc, and parenting to Head Start children's (N = 112) scores on Peabody Picture Vocabulary Test-III (PPVT-III) and McCarthy Scales of Children's Abilities (MSCA). Venous whole blood and plasma samples were analyzed for lead and zinc by ICP-MS and iron status was assessed by serum transferrin receptors. Hierarchical regressions revealed significant effects of lead on MSCA perceptual scores and iron on PPVT-III and MSCA verbal scores. Children with lead > 2.5 microg/dL had significantly lower MSCA perceptual scores than children < 2.5 microg/dL. Permissive parenting significantly exacerbated negative effects of higher lead or lower iron on children's perceptual or verbal scores, respectively.

Depth-dependent geochemical and microbiological gradients in Fe(III) deposits resulting from coal mine-derived acid mine drainage

PubMed Central

Brantner, Justin S.; Haake, Zachary J.; Burwick, John E.; Menge, Christopher M.; Hotchkiss, Shane T.; Senko, John M.

2014-01-01

We evaluated the depth-dependent geochemistry and microbiology of sediments that have developed via the microbially-mediated oxidation of Fe(II) dissolved in acid mine drainage (AMD), giving rise to a 8–10 cm deep “iron mound” that is composed primarily of Fe(III) (hydr)oxide phases. Chemical analyses of iron mound sediments indicated a zone of maximal Fe(III) reducing bacterial activity at a depth of approximately 2.5 cm despite the availability of dissolved O2 at this depth. Subsequently, Fe(II) was depleted at depths within the iron mound sediments that did not contain abundant O2. Evaluations of microbial communities at 1 cm depth intervals within the iron mound sediments using “next generation” nucleic acid sequencing approaches revealed an abundance of phylotypes attributable to acidophilic Fe(II) oxidizing Betaproteobacteria and the chloroplasts of photosynthetic microeukaryotic organisms in the upper 4 cm of the iron mound sediments. While we observed a depth-dependent transition in microbial community structure within the iron mound sediments, phylotypes attributable to Gammaproteobacterial lineages capable of both Fe(II) oxidation and Fe(III) reduction were abundant in sequence libraries (comprising ≥20% of sequences) from all depths. Similarly, abundances of total cells and culturable Fe(II) oxidizing bacteria were uniform throughout the iron mound sediments. Our results indicate that O2 and Fe(III) reduction co-occur in AMD-induced iron mound sediments, but that Fe(II)-oxidizing activity may be sustained in regions of the sediments that are depleted in O2. PMID:24860562

[Effects of iron on azoreduction by Shewanella decolorationis S12].

PubMed

Chen, Xing-Juan; Xu, Mei-Ying; Sun, Guo-Ping

2010-01-01

The effects of soluble and insoluble Fe(III) on anaerobic azoreduction by Shewanella decolorationis S12 were examined in a series of experiments. Results showed that the effects of iron on anaerobic azoreduction depended on the solubility and concentration of the compounds. Azoreduction was inhibited by insoluble Fe(III) and 0.05-2 mmol/L Fe2 O3 all decelerated the azoreduction activity of 0.2 mmol/L amaranth, but the increase in the concentrations of Fe2O3 did not cause an increasing inhibition. Soluble Fe(III) of which concentration less than 0.4 mmol/L enhanced azoreduction activity of 0.2 mmol/L amaranth but there was no linear relationship between the concentration of soluble Fe(III) and azoreduction activity. Soluble Fe(III) of which concentration more than 1 mmol/L inhibited azoreduction activity of 0.2 mmol/L amaranth and an increasing concentration resulted in an increased inhibition. The inhibition was strengthened under the conditions of limited electron donor. On the other hand, soluble Fe(III) and Fe(II) could relieve the inhibition of azoreduction by dicumarol which blocked quinone cycle. It suggests that in addition to quinone cycle, there is a Fe(III) <--> Fe(II) cycle shuttling electrons in cytoplasmic and periplasmic environment. That is the reason why low concentration of soluble Fe(III) or Fe (II) can enhance azoreduction of S. decolorationis S12. It also indicates that insoluble Fe(III) and high concentration of soluble Fe(III) do compete with azo dye for electrons once it acts as electron acceptor. Thus, when iron and azo dye coexisted, iron could serve as an electron transfer agent or electron competitive inhibitor for anaerobic azoreduction under different conditions. High efficiency of azoreduction can be achieved through controlling the solubility and concentration of irons.

An unprecedented Fe(36) phosphonate cage.

PubMed

Beavers, Christine M; Prosvirin, Andrey V; Prosverin, Andrey V; Cashion, John D; Dunbar, Kim R; Richards, Anne F

2013-02-18

The reaction of 2-pyridylphosphonic acid (LH(2)) with iron(II) perchlorate and iron(III) nitrate afforded an interconnected, double-layered, cationic iron cage, [{Fe(36)L(44)(H(2)O)(48)}](20+) (1a), the largest interconnected, polynuclear ferric cage reported to date. Magnetic studies on 1a revealed antiferromagnetic coupling between the spins on adjacent Fe(III) ions.

River-derived humic substances as iron chelators in seawater

PubMed Central

Krachler, Regina; Krachler, Rudolf F.; Wallner, Gabriele; Hann, Stephan; Laux, Monika; Cervantes Recalde, Maria F.; Jirsa, Franz; Neubauer, Elisabeth; von der Kammer, Frank; Hofmann, Thilo; Keppler, Bernhard K.

2015-01-01

The speciation of iron(III) in oxic seawater is dominated by its hydrolysis and sedimentation of insoluble iron(III)-oxyhydroxide. As a consequence, many oceanic areas have very low iron levels in surface seawater which leads to iron deficiency since phytoplankton require iron as a micronutrient in order to grow. Fortunately, iron solubility is not truly as low as Fe(III) solubility measurements in inorganic seawater would suggest, since oceanic waters contain organic molecules which tend to bind the iron and keep it in solution. Various iron-binding organic ligands which combine to stabilize dissolved iron have been detected and thoroughly investigated in recent years. However, the role of iron-binding ligands from terrestrial sources remains poorly constrained. Blackwater rivers supply large amounts of natural organic material (NOM) to the ocean. This NOM (which consists mainly of vascular plant-derived humic substances) is able to greatly enhance iron bioavailability in estuaries and coastal regions, however, breakdown processes lead to a rapid decrease of river-derived NOM concentrations with increasing distance from land. It has therefore been argued that the influence of river-derived NOM on iron biogeochemistry in offshore seawater does not seem to be significant. Here we used a standard method based on 59Fe as a radiotracer to study the solubility of Fe(III)-oxyhydroxide in seawater in the presence of riverine NOM. We aimed to address the question how effective is freshwater NOM as an iron chelator under open ocean conditions where the concentration of land-derived organic material is about 3 orders of magnitude smaller than in coastal regions, and does this iron chelating ability vary between NOM from different sources and between different size fractions of the river-borne NOM. Our results show that the investigated NOM fractions were able to substantially enhance Fe(III)-oxyhydroxide solubility in seawater at concentrations of the NOM ≥ 5 μg L− 1. Terrigenous NOM concentrations ≥ 5 μg L− 1 are in no way unusual in open ocean surface waters especially of the Arctic and the North Atlantic Oceans. River-derived humic substances could therefore play a greater role as iron carriers in the ocean than previously thought. PMID:26412934

The life cycle of iron Fe(III) oxide: impact of fungi and bacteria

NASA Astrophysics Data System (ADS)

Bonneville, Steeve

2014-05-01

Iron oxides are ubiquitous reactive constituents of soils, sediments and aquifers. They exhibit vast surface areas which bind a large array of trace metals, nutrients and organic molecules hence controlling their mobility/reactivity in the subsurface. In this context, understanding the "life cycle" of iron oxide in soils is paramount to many biogeochemical processes. Soils environments are notorious for their extreme heterogeneity and variability of chemical, physical conditions and biological agents at play. Here, we present studies investigating the role of two biological agents driving iron oxide dynamics in soils, root-associated fungi (mycorrhiza) and bacteria. Mycorrhiza filaments (hypha) grow preferentially around, and on the surface of nutrient-rich minerals, making mineral-fungi contact zones, hot-spots of chemical alteration in soils. However, because of the microscopic nature of hyphae (only ~ 5 µm wide for up to 1 mm long) and their tendency to strongly adhere to mineral surface, in situ observations of this interfacial micro-environment are scarce. In a microcosm, ectomycorrhiza (Paxillus involutus) was grown symbiotically with a pine tree (Pinus sylvestris) in the presence of freshly-cleaved biotite under humid, yet undersaturated, conditions typical of soils. Using spatially-resolved ion milling technique (FIB), transmission electron microscopy and spectroscopy (TEM/STEM-EDS), synchrotron based X-ray microscopy (STXM), we were able to quantify the speciation of Fe at the biotite-hypha interface. The results shows that substantial oxidation of biotite structural-Fe(II) into Fe(III) subdomains occurs at the contact zone between mycorrhiza and biotite. Once formed, iron(III) oxides can reductively dissolve under suboxic conditions via several abiotic and microbial pathways. In particular, they serve as terminal electron acceptors for the oxidation of organic matter by iron reducing bacteria. We aimed here to understand the role of Fe(III) mineral properties, in particular the influence of solubility, in the kinetics of microbial iron reduction. We used the facultative anaerobic gram-positive bacterium Shewanella putrefaciens as model iron reducing bacterium, with several ferrihydrite, hematite, goethite or lepidocrocite as electron acceptor, and lactate as electron donor. Maximum microbial Fe(III) reduction rates and solubility of Fe(III) phases were found to positively correlated in a Linear Free Energy Relationship suggesting a rate limitation by the electron transfer between iron reductases and a Fe(III) center, or by the subsequent desorption of Fe2+ from the iron oxide mineral surface.

Organic acids influence iron uptake in the human epithelial cell line Caco-2.

PubMed

Salovaara, Susan; Sandberg, Ann-Sofie; Andlid, Thomas

2002-10-09

It has previously been suggested that organic acids enhance iron absorption. We have studied the effect of nine organic acids on the absorption of Fe(II) and Fe(III) in the human epithelial cell line Caco-2. The effect obtained was dose-dependent, and the greatest increase (43-fold) was observed for tartaric acid (4 mmol/L) on Fe(III) (10 micromol/L). Tartaric, malic, succinic, and fumaric acids enhanced Fe(II) and Fe(III) uptake. Citric and oxalic acid, on the other hand, inhibited Fe(II) uptake but enhanced Fe(III) uptake. Propionic and acetic acid increased the Fe(II) uptake, but had no effect on Fe(III) uptake. Our results show a correlation between absorption pattern and chemical structure; e.g. hydroxyl groups, in addition to carboxyls, were connected with a positive influence. The results may be important for elucidating factors affecting iron bioavailability in the small intestine and for the development of foods with improved iron bioavailability.

The Acute Effect of Humic Acid on Iron Accumulation in Rats.

PubMed

Cagin, Yasir Furkan; Sahin, N; Polat, A; Erdogan, M A; Atayan, Y; Eyol, E; Bilgic, Y; Seckin, Y; Colak, C

2016-05-01

Free iron leads to the formation of pro-oxidant reactive oxygen species (ROS). Humic acids (HAs) enhance permeability of cellular wall and act as a chelator through electron transferring. This study was designed to test chelator effect of HA on iron as well as its anti-oxidant effect against the iron-induced hepatotoxicity and cardiotoxicity. The rats used were randomly divided into four groups (n = 8/group): group I (the control group); group II (the HA group), humic acid (562 mg/kg) was given over 10 days by oral gavage; group III (the iron group), iron III hydroxide polymaltose (250 mg/kg) was given over 10 days by intraperitoneal route; and group IV (the HA plus iron group), received the iron (similar to group II) plus humic acid (similar to those in groups II and III) group. Blood and two tissue samples both from liver and heart were obtained for biochemical and histopathological evaluations. Iron deposition, the iron-induced hepatotoxicity, and cardiotoxicity were demonstrated by histopathological and biochemical manner. However, no significant differences were observed in the serum biochemical values and the histopathological results among the iron and the HA plus iron groups in the liver tissue but not in the heart tissue. The protective effects of humic acid against iron-induced cardiotoxicity were shown but not against hepatotoxicity in our study.

Spectrophotometric Determination of Iron(III)-Glycine Formation Constant in Aqueous Medium Using Competitive Ligand Binding

ERIC Educational Resources Information Center

Prasad, Rajendra; Prasad, Surendra

2009-01-01

The formation constant of iron(III) complex with glycine (Gly) ligand in aqueous acidic medium (0.2 M HNO[subscript 3], I = 0.2 M at 28 plus or minus 1 degree C) was determined spectrophotometrically in which a competing color reaction between Fe(III) and SCN[superscript -] was used as an indicator reaction. Under the specified conditions Fe(III)…

The synthesis of chlorophyll-a biosynthetic precursors and methyl substituted iron porphyrins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matera, K.M.

1988-01-01

The biosynthetic intermediates were incubated in a plant system. The activity levels calculated show that magnesium 6-acrylate porphyrins and one of the magnesium 6-{beta}-hydroxypropionate porphyrins are not intermediates. In addition, plant systems incubated with {sup 18}O{sub 2} were found to synthesize magnesium 2,4-divinyl pheoporphyrin-a{sub 5} incorporated with {sup 18}O at the 9-carbonyl oxygen. Mass spectroscopy confirmed the presence of the oxygen label, thus eliminating one of two hypothesized pathways to chlorophyll-a. An overall description is given of iron porphyrins and iron porphyrin containing proteins. The function of the propionic side chains of the heme prosthetic group during electron transport reactionsmore » will be investigated. The synthesis of a series of iron(III) hexamethyl porphyrins with increasingly longer substituents in the remaining two peripheral positions of the porphyrin is described. Models for NMR studies of iron chlorin containing enzymes are discussed. Iron(III) pyropheophorbide-a and methyl pyropheophorbide-a were synthesized in addition to 5-CD{sub 3}, 10-CD{sub 2} iron(III) pyropheophorbide-a and methyl pyropheophorbide-a. Together, these pyropheophorbides were used to assign NMR resonances and ultimately provide a model for other iron chlorins. The synthesis of nickel(II) anhydro-mesorhodoporphyrin from zinc(III) anhydromesorhodochlorin is described; this nickel porphyrin was used as a standard for ring current calculations of reduced nickel analogs of anhydromesorhodoporphyrin.« less

Fibrous materials on polyhydroxybutyrate and ferric iron (III)-based porphyrins basis: physical-chemical and antibacterial properties

NASA Astrophysics Data System (ADS)

Olkhov, A.; Lobanov, A.; Staroverova, O.; Tyubaeva, P.; Zykova, A.; Pantyukhov, P.; Popov, A.; Iordanskii, A.

2017-02-01

Ferric iron (III)-based complexes with porphyrins are the homogenous catalysts of auto-oxidation of several biogenic substances. The most perspective carrier for functional low-molecular substances is the polymer fibers with nano-dimensional parameters. Application of natural polymers, poly-(3-hydroxybutyrate) or polylactic acid for instance, makes possible to develop fiber and matrice systems to solve ecological problem in biomedicine The aim of the article is to obtain fibrous material on poly-(3-hydroxybutyrate) and ferric iron (III)-based porphyrins basis and to examine its physical-chemical and antibacterial properties. The work is focused on possibility to apply such material to biomedical purposes. Microphotographs of obtained material showed that addition of 1% wt. ferric iron (III)-based porphyrins to PHB led to increased average diameter and disappeared spindly structures in comparison with initial PHB. Biological tests of nonwoven fabrics showed that fibers, containing ferric iron (III)-based tetraphenylporphyrins, were active in relation to bacterial test-cultures. It was found that materials on polymer and metal complexes with porphyrins basis can be applied to production of decontamination equipment in relation to pathogenic and opportunistic microorganisms.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swanner, E. D.; Bayer, T.; Wu, W.

In this study, we couple iron isotope analysis to microscopic and mineralogical investigation of iron speciation during circumneutral Fe(II) oxidation and Fe(III) precipitation with photosynthetically produced oxygen. In the presence of the cyanobacterium Synechococcus PCC 7002, aqueous Fe(II) (Fe(II) aq) is oxidized and precipitated as amorphous Fe(III) oxyhydroxide minerals (iron precipitates, Fe ppt), with distinct isotopic fractionation (ε 56Fe) values determined from fitting the δ 56Fe(II) aq (1.79‰ and 2.15‰) and the δ 56Fe ppt (2.44‰ and 2.98‰) data trends from two replicate experiments. Additional Fe(II) and Fe(III) phases were detected using microscopy and chemical extractions and likely represent Fe(II)more » and Fe(III) sorbed to minerals and cells. The iron desorbed with sodium acetate (FeNaAc) yielded heavier δ 56Fe compositions than Fe(II) aq. Modeling of the fractionation during Fe(III) sorption to cells and Fe(II) sorption to Feppt, combined with equilibration of sorbed iron and with Fe(II) aq using published fractionation factors, is consistent with our resulting δ 56FeNaAc. The δ 56Fe ppt data trend is inconsistent with complete equilibrium exchange with Fe(II)aq. Because of this and our detection of microbially excreted organics (e.g., exopolysaccharides) coating Feppt in our microscopic analysis, we suggest that electron and atom exchange is partially suppressed in this system by biologically produced organics. These results indicate that cyanobacteria influence the fate and composition of iron in sunlit environments via their role in Fe(II) oxidation through O 2 production, the capacity of their cell surfaces to sorb iron, and the interaction of secreted organics with Fe(III) minerals.« less

Yb3+ can be much better than Dy3+: SMM properties and controllable self-assembly of novel lanthanide 3,5-dinitrobenzoate-acetylacetonate complexes.

PubMed

Gavrikov, Andrey V; Efimov, Nikolay N; Ilyukhin, Andrey B; Dobrokhotova, Zhanna V; Novotortsev, Vladimir M

2018-05-01

The first representatives of the binuclear lanthanide 3,5-dinitrobenzoate-acetylacetonate complexes, namely isostructural compounds [Ln(dnbz)(acac)2(H2O)(EtOH)]2 (Ln = Eu (1), Gd (2), Tb (3), Dy (4), Ho (5), Er (6), Tm (7), and Yb (8); dnbz - 3,5-dinitrobenzoate anion; acac - acetylacetonate (pentane-2,4-dionate) anion) were prepared and characterized. The SMM behavior of the Yb compound 8 was shown to be surprisingly less sensitive to the composition of the Yb3+ coordination environment in comparison with that of the Dy derivative. For Yb compound 8, the anisotropy barrier is Δeff/kB = 26 K under the dc field of 2000 Oe. This value is the highest one currently known for binuclear Yb complexes.

Lifetime enhanced phosphorescent organic light emitting diode using an electron scavenger layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Seokhwan; Kim, Ji Whan; Lee, Sangyeob, E-mail: sy96.lee@samsung.com

2015-07-27

We demonstrate a method to improve lifetime of a phosphorescent organic light emitting diode (OLED) using an electron scavenger layer (ESL) in a hole transporting layer (HTL) of the device. We use a bis(1-(phenyl)isoquinoline)iridium(III)acetylacetonate [Ir(piq){sub 2}(acac)] doped HTL to stimulate radiative decay, preventing thermal degradation in HTL. The ESL effectively prevented non-radiative decay of leakage electron in HTL by converting non-radiative decay to radiative decay via a phosphorescent red emitter, Ir(piq){sub 2}(acac). The lifetime of device (t{sub 95}: time after 5% decrease of luminance) has been increased from 75 h to 120 h by using the ESL in a phosphorescent green-emitting OLED.

Removal of gallium (III) ions from acidic aqueous solution by supercritical carbon dioxide extraction in the green separation process.

PubMed

Chou, Wei-Lung; Wang, Chih-Ta; Yang, Kai-Chiang; Huang, Yen-Hsiang

2008-12-15

Supercritical carbon dioxide extraction, which is a feasible "green" alternative, was applied in this study as a sample pretreatment step for the removal of gallium (III) ions from acidic aqueous solution. The effect of various process parameters, including various chelating agents, extraction pressure and temperature, dimensionless CO(2) volume, the concentration of the chelating agent, and the pH of the solution, governing the efficiency and throughput of the procedure were systematically investigated. The performance of the various chelating agents from different studies indicated that the extraction efficiency of supercritical CO(2) was in the order: thiopyridine (PySH)>thenoyltrifluoroacetone (TTAH)>acetylacetone (AcAcH). The optimal extraction pressure and temperature for the supercritical CO(2) extraction of gallium (III) with chelating agent PySH were found to be 70 degrees C and 3000psi, respectively. The optimum concentration of the chelating agent was found to be 50ppm. A value of 7.5 was selected as the optimum dimensionless CO(2) volume. The optimum pH of the solution for supercritical CO(2) extraction should fall in the range of 2.0-3.0.

Solid-State Kinetic Investigations of Nonisothermal Reduction of Iron Species Supported on SBA-15

PubMed Central

2017-01-01

Iron oxide catalysts supported on nanostructured silica SBA-15 were synthesized with various iron loadings using two different precursors. Structural characterization of the as-prepared FexOy/SBA-15 samples was performed by nitrogen physisorption, X-ray diffraction, DR-UV-Vis spectroscopy, and Mössbauer spectroscopy. An increasing size of the resulting iron species correlated with an increasing iron loading. Significantly smaller iron species were obtained from (Fe(III), NH4)-citrate precursors compared to Fe(III)-nitrate precursors. Moreover, smaller iron species resulted in a smoother surface of the support material. Temperature-programmed reduction (TPR) of the FexOy/SBA-15 samples with H2 revealed better reducibility of the samples originating from Fe(III)-nitrate precursors. Varying the iron loading led to a change in reduction mechanism. TPR traces were analyzed by model-independent Kissinger method, Ozawa, Flynn, and Wall (OFW) method, and model-dependent Coats-Redfern method. JMAK kinetic analysis afforded a one-dimensional reduction process for the FexOy/SBA-15 samples. The Kissinger method yielded the lowest apparent activation energy for the lowest loaded citrate sample (Ea ≈ 39 kJ/mol). Conversely, the lowest loaded nitrate sample possessed the highest apparent activation energy (Ea ≈ 88 kJ/mol). For samples obtained from Fe(III)-nitrate precursors, Ea decreased with increasing iron loading. Apparent activation energies from model-independent analysis methods agreed well with those from model-dependent methods. Nucleation as rate-determining step in the reduction of the iron oxide species was consistent with the Mampel solid-state reaction model. PMID:29230346

Arsenite and Ferrous Iron Oxidation Linked to Chemolithotrophic Denitrification for the Immobilization of Arsenic in Anoxic Environments

PubMed Central

Sun, Wenjie; Sierra-Alvarez, Reyes; Milner, Lily; Oremland, Ron; Field, Jim A.

2014-01-01

The objective of this study was to explore a bioremediation strategy based on injecting NO3− to support the anoxic oxidation of ferrous iron (Fe(II)) and arsenite (As(III)) in the subsurface as a means to immobilize As in the form of arsenate (As(V)) adsorbed onto biogenic ferric (Fe(III)) (hydr)oxides. Continuous flow sand filled columns were used to simulate a natural anaerobic groundwater and sediment system with co-occurring As(III) and Fe(II) in the presence (SF1) or absence (SF2) of nitrate, respectively. During operation for 250 days, the average influent arsenic concentration of 567 µg l−1 was reduced to 10.6 (±9.6) µg l−1 in the effluent of column SF1. The cumulative removal of Fe(II) and As(III) in SF1 was 6.5–10-fold higher than that in SF2. Extraction and measurement of the mass of iron and arsenic immobilized on the sand packing of the columns was close to the iron and arsenic removed from the aqueous phase during column operation. The dominant speciation of the immobilized iron and arsenic was Fe(III) and As(V) in SF1, compared with Fe(II) and As(III) in SF2. The speciation was confirmed by XRD and XPS. The results indicate that microbial oxidation of As(III) and Fe(II) linked to denitrification resulted in the enhanced immobilization of aqueous arsenic in anaerobic environments by forming Fe(III) (hydr)oxides coated sands with adsorbed As(V). PMID:19764221

Sorption of Ferric Iron from Ferrioxamine B to Synthetic and Biogenic Layer Type Manganese Oxides

NASA Astrophysics Data System (ADS)

Duckworth, O.; John, B.; Sposito, G.

2006-12-01

Siderophores are biogenic chelating agents produced in terrestrial and marine environments to increase the bioavailablity of ferric iron. Recent work has suggested that both aqueous and solid-phase Mn(III) may affect siderophore-mediated iron transport, but no information appears to be available about the effect of solid-phase Mn(IV). To probe the effects of predominantly Mn(IV) oxides, we studied the sorption reaction of ferrioxamine B [Fe(III)HDFOB+, an Fe(III) chelate of the trihydroxamate siderophore desferrioxamine B (DFOB)] with two synthetic birnessites [layer type Mn(III, IV) oxides] and a biogenic birnessite produced by Pseudomonas putida MnB1. We found that all of these predominantly Mn(IV) oxides greatly reduced the aqueous concentration of Fe(III)HDFOB+ over at pH 8. After 72 hours equilibration time, the sorption behavior for the synthetic birnessites could be accurately described by a Langmuir isotherm; for the biogenic oxide, a Freundlich isotherm was best utilized to model the sorption data. To study the molecular nature of the interaction between the Fe(III)HDFOB+ complex and the oxide surface, Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy was employed. Analysis of the EXAFS spectra indicated that Fe(III) associated with the Mn(IV) oxides is not complexed by DFOB as in solution, but instead Fe(III) is specifically adsorbed to into the mineral structure at multiple sites with no evidence of DFOB complexation, thus indicating that the Mn(IV) oxides displaced Fe(III) from the siderophore complex. These results indicate that manganese oxides, including biominerals, may strongly sequester iron from soluble ferric complexes and thus may play a significant role in the biogeochemical cycling of iron in marine and terrestrial environments.

Phosphate inhibits in vitro Fe3+ loading into transferrin by forming a soluble Fe(III)-phosphate complex: a potential non-transferrin bound iron species.

PubMed

Hilton, Robert J; Seare, Matthew C; Andros, N David; Kenealey, Zachary; Orozco, Catalina Matias; Webb, Michael; Watt, Richard K

2012-05-01

In chronic kidney diseases, NTBI can occur even when total iron levels in serum are low and transferrin is not saturated. We postulated that elevated serum phosphate concentrations, present in CKD patients, might disrupt Fe(3+) loading into apo-transferrin by forming Fe(III)-phosphate species. We report that phosphate competes with apo-transferrin for Fe(3+) by forming a soluble Fe(III)-phosphate complex. Once formed, the Fe(III)-phosphate complex is not a substrate for donating Fe(3+) to apo-transferrin. Phosphate (1-10mM) does not chelate Fe(III) from diferric transferrin under the conditions examined. Complexed forms of Fe(3+), such as iron nitrilotriacetic acid (Fe(3+)-NTA), and Fe(III)-citrate are not susceptible to this phosphate complexation reaction and efficiently deliver Fe(3+) to apo-transferrin in the presence of phosphate. This reaction suggests that citrate might play an important role in protecting against Fe(III), phosphate interactions in vivo. In contrast to the reactions of Fe(3+) and phosphate, the addition of Fe(2+) to a solution of apo-transferrin and phosphate lead to rapid oxidation and deposition of Fe(3+) into apo-transferrin. These in vitro data suggest that, in principle, elevated phosphate concentrations can influence the ability of apo-transferrin to bind iron, depending on the oxidation state of the iron. Copyright © 2012 Elsevier Inc. All rights reserved.

Influence of Atmospheric Processes on the Solubility and Composition of Iron in Saharan Dust

NASA Astrophysics Data System (ADS)

Ingall, E. D.; Longo, A.; Feng, Y.; Lai, B.; Landing, W. M.; Shelley, R.; Nenes, A.; Mihalopoulos, N.; Violaki, K.

2016-12-01

Iron is a key micronutrient that is vital for all organisms. The supply of bioavailable, soluble iron controls primary productivity in approximately 30% of the world's oceans. The significant contribution of atmospheric aerosols to the bioavailable iron budget in vast ocean regions, underscores the need to understand the controls and transformations of aerosol iron solubility during atmospheric transport. The Sahara Desert contains the largest and most active sources of aerosol dust globally and can be a key source of nutrients to the Mediterranean Sea, much of the North Atlantic Ocean, and even as far as the Gulf of Mexico. Aerosol iron was examined in Saharan dust plumes using a combination of iron near-edge X-ray absorption spectroscopy and wet chemical techniques. Aerosol samples were collected at three sites located in the Mediterranean, the Atlantic, and Bermuda to characterize iron at different atmospheric transport lengths and time scales. Iron(III) oxides were a component of aerosols at all sampling sites and dominated aerosol iron in Mediterranean samples. In Atlantic samples, iron(II & III) sulfate, iron(III) phosphate, and iron(II) silicates were also contributors to aerosol composition. With increased atmospheric transport time, iron(II) sulfates are found to become more abundant, aerosol iron oxidation state became more reduced, and aerosol acidity increased. Atmospheric processing, including acidic reactions and photo-reduction, likely influence the form of iron minerals and the oxidation state in Saharan dust aerosols and contribute to increases in aerosol iron solubility. Overall, these findings suggest that a combination of factors affects aerosol iron solubility during long-distance atmospheric transport and emphasize the need to consider reductive mechanisms as well as proton-induced solubilization of aerosol iron in modeling studies.

Monosodium glutamate for simple photometric iron analysis

NASA Astrophysics Data System (ADS)

Prasetyo, E.

2018-01-01

Simple photometric method for iron analysis using monosodium glutamate (MSG) was proposed. The method could be used as an alternative method, which was technically simple, economic, quantitative, readily available, scientifically sound and environmental friendly. Rapid reaction of iron (III) with glutamate in sodium chloride-hydrochloric acid buffer (pH 2) to form red-brown complex was served as a basis in the photometric determination, which obeyed the range of iron (III) concentration 1.6 - 80 µg/ml. This method could be applied to determine iron concentration in soil with satisfactory results (accuracy and precision) compared to other photometric and atomic absorption spectrometry results.

Cloud point extraction of iron(III) and vanadium(V) using 8-quinolinol derivatives and Triton X-100 and determination of 10(-7)moldm(-3) level iron(III) in riverine water reference by a graphite furnace atomic absorption spectroscopy.

PubMed

Ohashi, Akira; Ito, Hiromi; Kanai, Chikako; Imura, Hisanori; Ohashi, Kousaburo

2005-01-30

The cloud point extraction behavior of iron(III) and vanadium(V) using 8-quinolinol derivatives (HA) such as 8-quinolinol (HQ), 2-methyl-8-quinolinol (HMQ), 5-butyloxymethyl-8-quinolinol (HO(4)Q), 5-hexyloxymethyl-8-quinolinol (HO(6)Q), and 2-methyl-5-octyloxymethyl-8-quinolinol (HMO(8)Q) and Triton X-100 solution was investigated. Iron(III) was extracted with HA and 4% (v/v) Triton X-100 in the pH range of 1.70-5.44. Above pH 4.0, more than 95% of iron(III) was extracted with HQ, HMQ, and HMO(8)Q. Vanadium(V) was also extracted with HA and 4% (v/v) Triton X-100 in the pH range of 2.07-5.00, and the extractability increased in the following order of HMQ < HQ < HO(4)Q < HO(6)Q. The cloud point extraction was applied to the determination of iron(III) in the riverine water reference by a graphite furnace atomic absorption spectroscopy. When 1.25 x 10(-3)M HMQ and 1% (v/v) Triton X-100 were used, the found values showed a good agreement with the certified ones within the 2% of the R.S.D. Moreover, the effect of an alkyl group on the solubility of 5-alkyloxymethyl-8-quinolinol and 2-methyl-5-alkyloxymethyl-8-quinolinol in 4% (v/v) Triton X-100 at 25 degrees C was also investigated.

The fate of arsenic adsorbed on iron oxides in the presence of arsenite-oxidizing bacteria.

PubMed

Zhang, Zhennan; Yin, Naiyi; Du, Huili; Cai, Xiaolin; Cui, Yanshan

2016-05-01

Arsenic (As) is a redox-active metalloid whose toxicity and mobility in soil depend on its oxidation state. Arsenite [As(III)] can be oxidized by microbes and adsorbed by minerals in the soil. However, the combined effects of these abiotic and biotic processes are not well understood. In this study, the fate of arsenic in the presence of an isolated As(III)-oxidizing bacterium (Pseudomonas sp. HN-1, 10(9) colony-forming units (CFUs)·ml(-1)) and three iron oxides (goethite, hematite, and magnetite at 1.6 g L(-1)) was determined using batch experiments. The total As adsorption by iron oxides was lower with bacteria present and was higher with iron oxides alone. The total As adsorption decreased by 78.6%, 36.0% and 79.7% for goethite, hematite and magnetite, respectively, due to the presence of bacteria. As(III) adsorbed on iron oxides could also be oxidized by Pseudomonas sp. HN-1, but the oxidation rate (1.3 μmol h(-1)) was much slower than the rate in the aqueous phase (96.2 μmol h(-1)). Therefore, the results of other studies with minerals only might overestimate the adsorptive capacity of solids in natural systems; the presence of minerals might hinder As(III) oxidation by microbes. Under aerobic conditions, in the presence of iron oxides and As(III)-oxidizing bacteria, arsenic is adsorbed onto iron oxides within the adsorption capacity, and As(V) is the primary form in the solid and aqueous phases. Copyright © 2016 Elsevier Ltd. All rights reserved.

Role of Humic-Bound Iron as an Electron Transfer Agent in Dissimilatory Fe(III) Reduction

PubMed Central

Lovley, Derek R.; Blunt-Harris, Elizabeth L.

1999-01-01

The dissimilatory Fe(III) reducer Geobacter metallireducens reduced Fe(III) bound in humic substances, but the concentrations of Fe(III) in a wide range of highly purified humic substances were too low to account for a significant portion of the electron-accepting capacities of the humic substances. Furthermore, once reduced, the iron in humic substances could not transfer electrons to Fe(III) oxide. These results suggest that other electron-accepting moieties in humic substances, such as quinones, are the important electron-accepting and shuttling agents under Fe(III)-reducing conditions. PMID:10473447

Importance of acetylacetone and 2,2'-bipyridyl ligands in radiation-chemical processes of complex compounds

NASA Astrophysics Data System (ADS)

Kalecińska, E.; Kaleciński, J.

The study of radiation response of free ligands: acetylacetone and 2,2'-bipyridyl in frozen chloride-alcohol-water glasses allows us to identify the intermediates playing the significant role in radiation decomposition of the complexes. On the basis of absorption spectra of the intermediates it has been shown that both examined ligands are effective scavengers of electrons. In the case of acetylacetone the intermediate most probably acacOH (exhibiting absorption band with λ max at ca. 580 nm) is not sensitive for bleaching light and its concentration increases during the warming up (from 77 to 160 K) of the sample. In the case of 2,2'-bipyridyl two intermediates (high intensity narrow bands with λ max at ca. 385 and 370 nm) are formed depending on pH of the system. Their formation and interconversion have also been studied.

Low molecular weight carboxylic acids in oxidizing porphyry copper tailings.

PubMed

Dold, Bernhard; Blowes, David W; Dickhout, Ralph; Spangenberg, Jorge E; Pfeifer, Hans-Rudolf

2005-04-15

The distribution of low molecular weight carboxylic acids (LMWCA) was investigated in pore water profiles from two porphyry copper tailings impoundments in Chile (Piuquenes at La Andina and Cauquenes at El Teniente mine). The objectives of this study were (1) to determine the distribution of LMWCA, which are interpreted to be the metabolic byproducts of the autotroph microbial community in this low organic carbon system, and (2) to infer the potential role of these acids in cycling of Fe and other elements in the tailings impoundments. The speciation and mobility of iron, and potential for the release of H+ via hydrolysis of the ferric iron, are key factors in the formation of acid mine drainage in sulfidic mine wastes. In the low-pH oxidation zone of the Piuquenes tailings, Fe(III) is the dominant iron species and shows high mobility. LMWCA, which occur mainly between the oxidation front down to 300 cm below the tailings surface at both locations (e.g., max concentrations of 0.12 mmol/L formate, 0.17 mmol/L acetate, and 0.01 mmol/L pyruvate at Piuquenes and 0.14 mmol/L formate, 0.14 mmol/L acetate, and 0.006 mmol/L pyruvate at Cauquenes), are observed at the same location as high Fe concentrations (up to 71.2 mmol/L Fe(II) and 16.1 mmol/L Fe(III), respectively). In this zone, secondary Fe(III) hydroxides are depleted. Our data suggest that LMWCA may influence the mobility of iron in two ways. First, complexation of Fe(III), through formation of bidentate Fe(III)-LMWCA complexes (e.g., pyruvate, oxalate), may enhance the dissolution of Fe(III) (oxy)hydroxides or may prevent precipitation of Fe(III) (oxy)hydroxides. Soluble Fe(III) chelate complexes which may be mobilized downward and convert to Fe(II) by Fe(III) reducing bacteria. Second, monodentate LMWCA (e.g., acetate and formate) can be used by iron-reducing bacteria as electron donors (e.g., Acidophilum spp.), with ferric iron as the electron acceptor. These processes may, in part, explain the low abundances of secondary Fe(III) hydroxide precipitates below the oxidation front and the high concentrations of Fe(II) observed in the pore waters of some low-sulfide systems. The reduction of Fe(III) and the subsequent increase of iron mobility and potential acidity transfer (Fe(II) oxidation can result in the release of H+ in an oxic environment) should be taken in account in mine waste management strategies.

Removal of arsenic from synthetic acid mine drainage by electrochemical pH adjustment and coprecipitation with iron hydroxide.

PubMed

Wang, Jenny Weijun; Bejan, Dorin; Bunce, Nigel J

2003-10-01

Acid mine drainage (AMD), which is caused by the biological oxidation of sulfidic materials, frequently contains arsenic in the form of arsenite, As(III), and/or arsenate, As(V), along with much higher concentrations of dissolved iron. The present work is directed toward the removal of arsenic from synthetic AMD by raising the pH of the solution by electrochemical reduction of H+ to elemental hydrogen and coprecipitation of arsenic with iron(III) hydroxide, following aeration of the catholyte. Electrolysis was carried out at constant current using two-compartment cells separated with a cation exchange membrane. Four different AMD model systems were studied: Fe(III)/As(V), Fe(III)/As(III), Fe(II)/As(V), and Fe(II)/As(III) with the initial concentrations for Fe(III) 260 mg/L, Fe(II) 300 mg/L, As(V), and As(III) 8 mg/L. Essentially quantitative removal of arsenic and iron was achieved in all four systems, and the results were independent of whether the pH was adjusted electrochemically or by the addition of NaOH. Current efficiencies were approximately 85% when the pH of the effluent was 4-7. Residual concentrations of arsenic were close to the drinking water standard proposed by the World Health Organization (10 microg/L), far below the mine waste effluent standard (500 microg/L).

Speciation and characterization of arsenic in gold ores and cyanidation tailings using X-ray absorption spectroscopy

USGS Publications Warehouse

Paktunc, D.; Foster, A.; Heald, S.; Laflamme, G.

2004-01-01

The knowledge of mineralogy and molecular structure of As is needed to better understand the stability of As in wastes resulting from processing of gold ores. In this study, optical microscopy, scanning electron microscopy, electron microprobe, X-ray diffraction and X-ray absorption fine structure (XAFS) spectroscopy (including both XANES and EXAFS regimes) were employed to determine the mineralogical composition and local coordination environment of As in gold ores and process tailings from bench-scale tests designed to mimic a common plant practice. Arsenic-bearing minerals identified in the ores and tailings include iron (III) oxyhydroxides, scorodite (FeAsO4??2H2O), ferric arsenates, arseniosiderite (Ca2Fe3 (AsO4)3O2??3H2O), Ca-Fe arsenates, pharmacosiderite (KFe4 (AsO4)3(OH)4??6-7H2O), jarosite (K2Fe6(SO4)4 (OH)12) and arsenopyrite (FeAsS). Iron (III) oxyhydroxides contain variable levels of As from trace to about 22 wt% and Ca up to approximately 9 wt%. Finely ground ore and tailings samples were examined by bulk XAFS and selected mineral grains were analyzed by microfocused XAFS (micro-EXAFS) spectroscopy to reconcile the ambiguities of multiple As sources in the complex bulk EXAFS spectra. XANES spectra indicated that As occurs as As5+in all the samples. Micro-EXAFS spectra of individual iron (III) oxyhydroxide grains with varying As concentrations point to inner-sphere bidentate-binuclear arsenate complexes as the predominant form of As. There are indications for the presence of a second Fe shell corresponding to bidentate-mononuclear arrangement. Iron (III) oxyhydroxides with high As concentrations corresponding to maximum adsorption densities probably occur as nanoparticles. The discovery of Ca atoms around As in iron (III) oxyhydroxides at interatomic distances of 4.14-4.17 A?? and the coordination numbers suggest the formation of arseniosiderite-like nanoclusters by coprecipitation rather than simple adsorption of Ca onto iron (III) oxyhydroxides. Correlation of Ca with As in iron (III) oxyhydroxides as determined by electron microprobe analysis supports the coprecipitate origin for the presence of Ca in iron (III) oxyhydroxides. The samples containing higher abundances of ferric arsenates released higher As concentrations during the cyanidation tests. The presence of highly soluble ferric arsenates and Ca-Fe arsenates, and relatively unstable iron (III) oxyhydroxides with Fe/As molar ratios of less than 4 in the ore and process tailings suggests that not only the tailings in the impoundment will continue to release As, but also there is the potential for mobilization of As from the natural sources such as the unmined ore. ?? 2004 Elsevier Ltd.

Speciation and characterization of arsenic in gold ores and cyanidation tailings using X-ray absorption spectroscopy

NASA Astrophysics Data System (ADS)

Paktunc, Dogan; Foster, Andrea; Heald, Steve; Laflamme, Gilles

2004-03-01

The knowledge of mineralogy and molecular structure of As is needed to better understand the stability of As in wastes resulting from processing of gold ores. In this study, optical microscopy, scanning electron microscopy, electron microprobe, X-ray diffraction and X-ray absorption fine structure (XAFS) spectroscopy (including both XANES and EXAFS regimes) were employed to determine the mineralogical composition and local coordination environment of As in gold ores and process tailings from bench-scale tests designed to mimic a common plant practice. Arsenic-bearing minerals identified in the ores and tailings include iron (III) oxyhydroxides, scorodite (FeAsO 4·2H 2O), ferric arsenates, arseniosiderite (Ca 2Fe 3(AsO 4) 3O 2·3H 2O), Ca-Fe arsenates, pharmacosiderite (KFe 4(AsO 4) 3(OH) 4·6-7H 2O), jarosite (K 2Fe 6(SO 4) 4(OH) 12) and arsenopyrite (FeAsS). Iron (III) oxyhydroxides contain variable levels of As from trace to about 22 wt% and Ca up to approximately 9 wt%. Finely ground ore and tailings samples were examined by bulk XAFS and selected mineral grains were analyzed by microfocused XAFS (micro-EXAFS) spectroscopy to reconcile the ambiguities of multiple As sources in the complex bulk EXAFS spectra. XANES spectra indicated that As occurs as As 5+in all the samples. Micro-EXAFS spectra of individual iron (III) oxyhydroxide grains with varying As concentrations point to inner-sphere bidentate-binuclear arsenate complexes as the predominant form of As. There are indications for the presence of a second Fe shell corresponding to bidentate-mononuclear arrangement. Iron (III) oxyhydroxides with high As concentrations corresponding to maximum adsorption densities probably occur as nanoparticles. The discovery of Ca atoms around As in iron (III) oxyhydroxides at interatomic distances of 4.14-4.17 Å and the coordination numbers suggest the formation of arseniosiderite-like nanoclusters by coprecipitation rather than simple adsorption of Ca onto iron (III) oxyhydroxides. Correlation of Ca with As in iron (III) oxyhydroxides as determined by electron microprobe analysis supports the coprecipitate origin for the presence of Ca in iron (III) oxyhydroxides. The samples containing higher abundances of ferric arsenates released higher As concentrations during the cyanidation tests. The presence of highly soluble ferric arsenates and Ca-Fe arsenates, and relatively unstable iron (III) oxyhydroxides with Fe/As molar ratios of less than 4 in the ore and process tailings suggests that not only the tailings in the impoundment will continue to release As, but also there is the potential for mobilization of As from the natural sources such as the unmined ore.

Arsenite and ferrous iron oxidation linked to chemolithotrophic denitrification for the immobilization of arsenic in anoxic environments

USGS Publications Warehouse

Sun, W.; Sierra-Alvarez, R.; Milner, L.; Oremland, R.; Field, J.A.

2009-01-01

The objective of this study was to explore a bioremediation strategy based on injecting NO3- to support the anoxic oxidation of ferrous iron (Fe(II)) and arsenite (As(III)) in the subsurface as a means to immobilize As in the form of arsenate (As(V)) adsorbed onto biogenic ferric (Fe(III)) (hydr)oxides. Continuous flows and filled columns were used to simulate a natural anaerobic groundwater and sediment system with co-occurring As(III) and Fe(II) in the presence (column SF1) or absence (column SF2) of nitrate, respectively. During operation for 250 days, the average influent arsenic concentration of 567 ??g L-1 was reduced to 10.6 (??9.6) ??g L-1 in the effluent of column SF1. The cumulative removal of Fe(II) and As(III) in SF1 was 6.5 to 10-fold higher than that in SF2. Extraction and measurement of the mass of iron and arsenic immobilized on the sand packing of the columns were close to the iron and arsenic removed from the aqueous phase during column operation. The dominant speciation of the immobilized iron and arsenic was Fe(III) and As(V) in SF1, compared with Fe(II) and As(III) in SF2. The speciation was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results indicate that microbial oxidation of As(III) and Fe(II) linked to denitrification resulted in the enhanced immobilization of aqueous arsenic in anaerobic environments by forming Fe(III) (hydr)oxide coated sands with adsorbed As(V). ?? 2009 American Chemical Society.

Investigation of the interaction of iron(III) complexes with dAMP by ESI-MS, MALDI-MS and potentiometric titration: insights into synthetic nuclease behavior.

PubMed

Fernandes, Christiane; Oliveira Moreira, Rafaela; Lube, Leonardo M; Horn, Adolfo; Szpoganicz, Bruno; Sherrod, Stacy; Russell, David H

2010-06-07

We report herein the characterization by electrospray ionization (ESI) mass spectrometry (MS), matrix assisted laser desorption ionization (MALDI-MS) and potentiometric titration of three iron(III) compounds: [Fe(III)(HPClNOL)Cl2]·NO3 (1), [Cl(HPClNOL)Fe(III)-(μ-O)-Fe(III)(HPClNOL)Cl]·Cl2·H2O (2) and [(SO4)(HPClNOL)Fe(III)-(μ-O)-Fe(III)(HPClNOL)(SO4)]·6H2O (3), where HPClNOL= 1-(bis-pyridin-2-ylmethyl-amino)-3-chloropropan-2-ol). Despite the fact that the compounds have distinct structures in solid state and non-buffered solution, all compounds present similar ESI and MALDI mass spectra in a buffered medium (pH 7.0). At this pH, the species [(PClNOL)Fe(III)-(μ-O)-Fe(III)(PClNOL)](2+) (m/z 354) was observed for all the compounds under investigation. Potentiometric titration confirms a similar behavior for all compounds, indicating that the dihydroxo form [(OH)(HPClNOL)Fe(III)-(μ-O)-Fe(III)(HPClNOL)(OH)](2+) is the major species at pH 7.0, for all the compounds. The products of the interaction between compounds (1), (2) and (3) and dAMP (2'-deoxyadenosine-5'-monophosphate) in a buffered medium (pH 7.0) were identified by MALDI-MS/MS. The fragmentation data obtained by MS/MS allow one to identify the nature of the interaction between the iron(III) compounds and dAMP, revealing the direct interaction between the iron center and phosphate groups.

Sorption of arsenic to biogenic iron (oxyhydr)oxides produced in circumneutral environments

NASA Astrophysics Data System (ADS)

Sowers, Tyler D.; Harrington, James M.; Polizzotto, Matthew L.; Duckworth, Owen W.

2017-02-01

Arsenic (As) is a widespread and problematic pollutant that can be derived from natural or anthropogenic sources. Iron (oxyhydr)oxides readily sorb As and thus play critical roles in As cycling in terrestrial environments; however, little is known about the affinity and mechanism of As sorption by biogenic iron (oxyhydr)oxides formed in circumneutral environments. To investigate this, we conducted sorption isotherm and kinetics experiments to compare As(V) and As(III) sorption to synthetic 2-line ferrihydrite and iron biominerals harvested from the hyporheic zone of an uncontaminated creek. Inductively coupled plasma mass spectrometry (ICP-MS) was used to quantify both As(V) and As(III), and X-ray absorption spectroscopy (XAS) was utilized to obtain As and Fe K-edge spectra for As(V) and As(III) sorbed to environmentally collected and laboratory produced Fe(III) minerals. All environmental Fe(III) biominerals were determined to be structurally similar to 2-line ferrihydrite. However, environmental Fe(III) biominerals have a surface area normalized affinity for As(V) and for As(III) that is greater than or equivalent to synthetic 2-line ferrihydrite. Whereas the extent of sorption was similar for As(III) on all minerals, As(V) sorption to environmental Fe(III) biominerals was approximately three times higher than what was observed for synthetic 2-line ferrihydrite. Structural modeling of EXAFS spectra revealed that the same surface complexation structure was formed by As(V) and by As(III) on environmental Fe(III) biominerals and ferrihydrite. These results suggest that, despite similarities in binding mechanisms, Fe(III) biominerals may be more reactive sorbents that synthetic surrogates often used to model environmental reactivity.

Exploring Iron Silicate Precursors of Ancient Iron Formations through Rock Record, Laboratory and Field Analogue Investigations

NASA Astrophysics Data System (ADS)

Johnson, J. E.; Rasmussen, B.; Muhling, J.; Benzerara, K.; Jezequel, D.; Cosmidis, J.; Templeton, A. S.

2016-12-01

In direct contrast to today's oceans, iron-rich chemical precipitates dominate the deep marine sedimentary record > 2.3 billion years ago. The deposition of these minerals resulted in massive iron formations and indicate that the ocean was previously ferruginous and largely anoxic. To precipitate and concentrate iron in the sediments, many hypotheses have centered on the oxidation of soluble Fe(II) to solid Fe(III)-oxyhydroxides; these ideas have stimulated extensive research using iron-oxidizing bacteria to produce Fe(III)-oxides and trace metal sorption experiments on Fe(III)-oxides, leading to inferences of trace metal availability and implications for enzymatic and microbial evolution as well as pO2 levels and seawater chemistry. However, recent discoveries of disseminated iron-silicate nanoparticles in early-silicifying chert indicate that iron-silicates may have instead been the primary precipitates from these Archean ferruginous oceans (Rasmussen et al, 2015). Considering the significant paradigm shift this discovery implies for interpretations of Archean elemental cycling, redox state and potential microbial metabolisms, we investigated these iron-silicate inclusions and their implications for ancient seawater chemistry in a multi-faceted approach using spectroscopic- and diffraction-based techniques. The crystal structure, Fe oxidation state and Fe coordination environment of iron-silicate nanoparticles have been interrogated using microscale X-ray absorption spectroscopy, TEM and nanoscale scanning transmission X-ray microscopy. To further explore the chemical and potential biological controls on iron-silicate formation, we have also performed laboratory experiments to mimic Archean seawater and precipitate iron-bearing silicate minerals under abiotic conditions and in the presence of iron-oxidizing bacteria. In a complementary study, sediments from a natural Archean analogue system were sampled to determine if iron-silicate minerals form in Mexican crater lakes that are variably iron- and silica-rich. As we continue to probe the mechanism of Fe(II/III)-silicate formation, we can constrain the activity of silica, pH, and pO2 on early Earth and describe any potential influence of microbial activity on the precipitation of these phases.

Electron Spin Relaxation Rates for High-Spin Fe(III) in Iron Transferrin Carbonate and Iron Transferrin Oxalate

PubMed Central

Gaffney, Betty Jean; Eaton, Gareth R.; Eaton*, Sandra S.

2005-01-01

To optimize simulations of CW EPR spectra for high-spin Fe(III) with zero-field splitting comparable to the EPR quantum, information is needed on the factors that contribute to the line shapes and line widths. Continuous wave electron paramagnetic resonance (EPR) spectra obtained for iron transferrin carbonate from 4 to 150 K and for iron transferrin oxalate from 4 to 100 K did not exhibit significant temperature dependence of the line shape, which suggested that the line shapes were not relaxation determined. To obtain direct information concerning the electron spin relaxation rates, electron spin echo and inversion recovery EPR were used to measure T1 and Tm for the high-spin Fe(III) in iron transferrin carbonate and iron transferrin oxalate between 5 and 20–30 K. For comparison with the data for the transferrin complexes, relaxation times were obtained for tris(oxalato)ferrate(III). The relaxation rates are similar for the three complexes and do not exhibit a strong dependence on position in the spectrum. Extrapolation of the observed temperature dependence of the relaxation rates to higher temperatures gives values consistent with the conclusion that the CW line shapes are not relaxation determined up to 150 K. PMID:16429607

Motor associations of iron accumulation in deep grey matter nuclei in Parkinson's disease: a cross-sectional study of iron-related magnetic resonance imaging susceptibility.

PubMed

Martin-Bastida, A; Lao-Kaim, N P; Loane, C; Politis, M; Roussakis, A A; Valle-Guzman, N; Kefalopoulou, Z; Paul-Visse, G; Widner, H; Xing, Y; Schwarz, S T; Auer, D P; Foltynie, T; Barker, R A; Piccini, P

2017-02-01

To determine whether iron deposition in deep brain nuclei assessed using high-pass filtered phase imaging plays a role in motor disease severity in Parkinson's disease (PD). Seventy patients with mild to moderate PD and 20 age- and gender-matched healthy volunteers (HVs) underwent susceptibility-weighted imaging on a 3 T magnetic resonance imaging scanner. Phase shifts (radians) in deep brain nuclei were derived from high-pass filtered phase images and compared between groups. Analysis of clinical laterality and correlations with motor severity (Unified Parkinson's Disease Rating Scale, Part III, UPDRS-III) were performed. Phase shifts (in radians) were compared between HVs and three PD subgroups divided according to UPDRS-III scores using analysis of covariance, adjusting for age and regional area. Parkinson's disease patients had significantly (P < 0.001) higher radians than HVs bilaterally in the putamen, globus pallidus and substantia nigra (SN). The SN contralateral to the most affected side showed higher radians (P < 0.001) compared to the less affected side. SN radians positively correlated with UPDRS-III and bradykinesia-rigidity subscores, but not with tremor subscores. ancova followed by post hoc Bonferroni-adjusted pairwise comparisons revealed that SN radians were significantly greater in the PD subgroup with higher UPDRS-III scores compared to both lowest UPDRS-III PD and HV groups (P < 0.001). Increased nigral iron accumulation in PD appears to be stratified according to disease motor severity and correlates with symptoms related to dopaminergic neurodegeneration. This semi-quantitative in vivo iron assessment could prove useful for objectively monitoring PD progression, especially in clinical trials concerning iron chelation therapies. © 2016 EAN.

Revision of iron(III)-citrate speciation in aqueous solution. Voltammetric and spectrophotometric studies.

PubMed

Vukosav, Petra; Mlakar, Marina; Tomišić, Vladislav

2012-10-01

A detailed study of iron (III)-citrate speciation in aqueous solution (θ=25°C, I(c)=0.7 mol L(-1)) was carried out by voltammetric and UV-vis spectrophotometric measurements and the obtained data were used for reconciled characterization of iron (III)-citrate complexes. Four different redox processes were registered in the voltammograms: at 0.1 V (pH=5.5) which corresponded to the reduction of iron(III)-monocitrate species (Fe:cit=1:1), at about -0.1 V (pH=5.5) that was related to the reduction of FeL(2)(5-), FeL(2)H(4-) and FeL(2)H(2)(3-) complexes, at -0.28 V (pH=5.5) which corresponded to the reduction of polynuclear iron(III)-citrate complex(es), and at -0.4V (pH=7.5) which was probably a consequence of Fe(cit)(2)(OH)(x) species reduction. Reversible redox process at -0.1 V allowed for the determination of iron(III)-citrate species and their stability constants by analyzing E(p) vs. pH and E(p) vs. [L(4-)] dependence. The UV-vis spectra recorded at varied pH revealed four different spectrally active species: FeLH (logβ=25.69), FeL(2)H(2)(3-) (log β=48.06), FeL(2)H(4-) (log β=44.60), and FeL(2)(5-) (log β=38.85). The stability constants obtained by spectrophotometry were in agreement with those determined electrochemically. The UV-vis spectra recorded at various citrate concentrations (pH=2.0) supported the results of spectrophotometric-potentiometric titration. Copyright © 2012 Elsevier B.V. All rights reserved.

Chemical compositional study of 35 iron meteorites and its application in taxonomy

NASA Technical Reports Server (NTRS)

Wang, D.; Malvin, D. J.; Wasson, J. T.

1985-01-01

Structural and compositional data are reported as a guide to the classification of 35 iron meteorites. The Xinjiang iron meteorite, previously classified as III AB, is reclassified as III E on the basis of its lower Ga/Ni and Ge/Ni ratios, its wider, swollen kamacite bands, and the ubiquitous presence of haxonite, (Fe,Ni)22C. The Dongling (III CD) appears not to be a new meteorite, but to be paired with the Nantan. Four Antarctic iron meteorites, IAB Allan Hills A77250, A77263, A77289, and A77290, are classified as a paired meteorite because of their similarities in structure and in concentrations of various elements. It is shown that Cu shares certain properties with Ga and Ge, which makes them excellent taxonomic parameters.

Mechanisms and efficiency of the simultaneous removal of metals and cyanides by using ferrate(VI): crucial roles of nanocrystalline iron(III) oxyhydroxides and metal carbonates.

PubMed

Filip, Jan; Yngard, Ria A; Siskova, Karolina; Marusak, Zdenek; Ettler, Vojtech; Sajdl, Petr; Sharma, Virender K; Zboril, Radek

2011-08-29

The reaction of potassium ferrate(VI), K(2)FeO(4), with weak-acid dissociable cyanides--namely, K(2)[Zn(CN)(4)], K(2)[Cd(CN)(4)], K(2)[Ni(CN)(4)], and K(3)[Cu(CN)(4)]--results in the formation of iron(III) oxyhydroxide nanoparticles that differ in size, crystal structure, and surface area. During cyanide oxidation and the simultaneous reduction of iron(VI), zinc(II), copper(II), and cadmium(II), metallic ions are almost completely removed from solution due to their coprecipitation with the iron(III) oxyhydroxides including 2-line ferrihydrite, 7-line ferrihydrite, and/or goethite. Based on the results of XRD, Mössbauer and IR spectroscopies, as well as TEM, X-ray photoelectron emission spectroscopy, and Brunauer-Emmett-Teller measurements, we suggest three scavenging mechanisms for the removal of metals including their incorporation into the ferrihydrite crystal structure, the formation of a separate phase, and their adsorption onto the precipitate surface. Zn and Cu are preferentially and almost completely incorporated into the crystal structure of the iron(III) oxyhydroxides; the formation of the Cd-bearing, X-ray amorphous phase, together with Cd carbonate is the principal mechanism of Cd removal. Interestingly, Ni remains predominantly in solution due to the key role of nickel(II) carbonate, which exhibits a solubility product constant several orders of magnitude higher than the carbonates of the other metals. Traces of Ni, identified in the iron(III) precipitate, are exclusively adsorbed onto the large surface area of nanoparticles. We discuss the relationship between the crystal structure of iron(III) oxyhydroxides and the mechanism of metal removal, as well as the linear relationship observed between the rate constant and the surface area of precipitates. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A potential new biosignature of life in iron-rich extreme environments: An iron (III) complex of scytonemin and proposal for its identification using Raman spectroscopy

NASA Astrophysics Data System (ADS)

Varnali, Tereza; Edwards, Howell G. M.

2013-07-01

Scytonemin is a cyanobacterial sheath pigment with potent UV absorbing (UV-A, UV-B and UV-C) properties. The importance of this biomolecule is its photoprotective function which is one of the major survival strategies adopted by extremophiles to combat high energy radiation insolation in environmentally stressed conditions. Also, iron (III) oxides offering an additional UV-protecting facility to subsurface biological colonization as well as banded iron formations with zones of iron depletion in rock matrices have attracted attention with special interest in the mobilisation and transportation of iron compounds through the rock. This study represents a novel proposal that an iron-scytonemin complex could facilitate the movement of iron through the subsurface rock as part of the this extremophilic survival strategy. The predicted Raman wavenumbers for the proposed scytonemin complex of iron(III) are derived computationally using DFT calculations. Comparison of the experimentally observed Raman spectra of scytonemin with the theoretically predicted Raman spectra of the iron-scytonemin complex show that the latter may be discriminated and the expected characteristic bands are reported in relation to structural changes that are effected upon complexation. This information will inform the future search for experimental evidence for an iron-scytonemin complex, which has not been recognised hitherto and which could provide a novel biosignature for the extremophilic colonization of terrestrial iron-rich geological matrices. Such a terrestrial scenario would be potentially of significance for the remote robotic analytical exploration of the iron-rich surface and immediate subsurface of Mars.

Identification and Spectroscopic Characterization of Nonheme Iron(III) Hypochlorite Intermediates.

PubMed

Draksharapu, Apparao; Angelone, Davide; Quesne, Matthew G; Padamati, Sandeep K; Gómez, Laura; Hage, Ronald; Costas, Miquel; Browne, Wesley R; de Visser, Sam P

2015-03-27

Fe III -hypohalite complexes have been implicated in a wide range of important enzyme-catalyzed halogenation reactions including the biosynthesis of natural products and antibiotics and post-translational modification of proteins. The absence of spectroscopic data on such species precludes their identification. Herein, we report the generation and spectroscopic characterization of nonheme Fe III -hypohalite intermediates of possible relevance to iron halogenases. We show that Fe III -OCl polypyridylamine complexes can be sufficiently stable at room temperature to be characterized by UV/Vis absorption, resonance Raman and EPR spectroscopies, and cryo-ESIMS. DFT methods rationalize the pathways to the formation of the Fe III -OCl, and ultimately Fe IV =O, species and provide indirect evidence for a short-lived Fe II -OCl intermediate. The species observed and the pathways involved offer insight into and, importantly, a spectroscopic database for the investigation of iron halogenases.

Effect of iron ion on doxycycline photocatalytic and Fenton-based autocatatalytic decomposition.

PubMed

Bolobajev, Juri; Trapido, Marina; Goi, Anna

2016-06-01

Doxycycline plays a key role in Fe(III)-to-Fe(II) redox cycling and therefore in controlling the overall reaction rate of the Fenton-based process (H2O2/Fe(III)). This highlights the autocatalytic profile of doxycycline degradation. Ferric iron reduction in the presence of doxycycline relied on doxycycline-to-Fe(III) complex formation with an ensuing reductive release of Fe(II). The lower ratio of OH-to-contaminant in an initial H2O2/Fe(III) oxidation step than in that of classical Fenton (H2O2/Fe(II)) decreased the doxycycline degradation rate. The quantum yield of doxycycline in direct UV-C photolysis was 3.1 × 10(-3) M E(-1). In spite of doxycycline-Fe(III) complexes could produce the adverse effect on the doxycycline degradation in the UV/Fe(III) system some acceleration of the rate was observed upon irradiation of the Fe(III)-hydroxy complex. Acidic reaction media (pH 3.0) and the molar ratio of DC/Fe(III) = 2/1 favored the complex formation. Doxycycline close degradation rates and complete mineralization achieved for 120 min (Table 1) with both UV/H2O2 and UV/H2O2/Fe(III) indicated the unsubstantial role of the reduction of Fe(III) to Fe(II) in UV/H2O2/Fe(III) system efficacy. Thus, factors such as doxycycline's ability to form complexes with ferric iron and the ability of complexes to participate in a reductive pathway should be considered at a technological level in process optimization, with chemistry based on iron ion catalysis to enhance the doxycycline oxidative pathway. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evidence for ferritin as dominant iron-bearing species in the rhizobacterium Azospirillum brasilense Sp7 provided by low-temperature/in-field Mössbauer spectroscopy.

PubMed

Kovács, Krisztina; Kamnev, Alexander A; Pechoušek, Jiří; Tugarova, Anna V; Kuzmann, Ernő; Machala, Libor; Zbořil, Radek; Homonnay, Zoltán; Lázár, Károly

2016-02-01

For the ubiquitous diazotrophic rhizobacterium Azospirillum brasilense, which has been attracting the attention of researchers worldwide for the last 35 years owing to its significant agrobiotechnological and phytostimulating potential, the data on iron acquisition and its chemical speciation in cells are scarce. In this work, for the first time for azospirilla, low-temperature (at 80 K, 5 K, as well as at 2 K without and with an external magnetic field of 5 T) transmission Mössbauer spectroscopic studies were performed for lyophilised biomass of A. brasilense (wild-type strain Sp7 grown with (57)Fe(III) nitrilotriacetate complex as the sole source of iron) to enable quantitative chemical speciation analysis of the intracellular iron. In the Mössbauer spectrum at 80 K, a broadened quadrupole doublet of high-spin iron(III) was observed with a few percent of a high-spin iron(II) contribution. In the spectrum measured at 5 K, a dominant magnetically split component appeared with the parameters typical of ferritin species from other bacteria, together with a quadrupole doublet of a superparamagnetic iron(III) component and a similarly small contribution from the high-spin iron(II) component. The Mössbauer spectra recorded at 2 K (with or without a 5 T external field) confirmed the assignment of ferritin species. About 20% of total Fe in the dry cells of A. brasilense strain Sp7 were present in iron(III) forms superparamagnetic at both 5 and 2 K, i.e. either different from ferritin cores or as ferritin components with very small particle sizes.

Comparison of dye doping and ultrathin emissive layer in white organic light-emitting devices with dual emissive layers

NASA Astrophysics Data System (ADS)

Wang, Xu; Qi, Yige; Yu, Junsheng

2014-09-01

White organic light-emitting devices (WOLEDs) with combined doping emissive layer (EML) and ultrathin EML have been fabricated to investigate the effect of each EML on the electroluminescent (EL) performance of the WOLEDs. Through tailoring doping concentration of bis[(4,6-difluorophenyl)-pyridinato-N,C2'](picolinate) iridium(III) (FIrpic) and thickness of ultrathin bis[2-(4-tertbutylphenyl)benzothiazolato-N,C2'] iridium (acetylacetonate) [(tbt)2Ir(acac)] EML, it is found that the change in the doping ratio of FIrpic significantly influenced the EL efficiencies and spectra, while the alteration of ultrathin EML thickness had much milder effect on the EL performance. The results indicated that ultrathin EML is in favor of reproducibility in mass production compared with doping method.

Mössbauer study of the effect of pH on Fe valence in iron-polygalacturonate as a medicine for human anaemia

NASA Astrophysics Data System (ADS)

Kuzmann, E.; Garg, V. K.; de Oliveira, A. C.; Klencsár, Z.; Szentmihályi, K.; Fodor, J.; May, Z.; Homonnay, Z.

2015-02-01

Iron-polygalacturonate complexes have been synthesized from polygalacturonic acid by applying a novel preparation method in order to develop medicine suitable for the effective iron supplementation of the human body in the case of anemia. Since the iron uptake depends on the oxidation state of iron, 57Fe Mössbauer spectroscopy was used to study the occurrence of different valence states in the iron-polygalacturonate complexes prepared under different circumstances. The Mössbauer-spectra indicated the presence of iron both in FeII and FeIII states in the investigated iron-polygalacturonate compounds, the occurrence of which varied with the preparation parameters. A correlation of the relative occurrence of iron valence states with the pH has been found. The relative occurrence of FeIII was found to increase with increasing pH. The knowledge of this correlation can help find optimum preparation conditions of iron-polygalacturonates to cure human anemia.

Organic iron (III) complexing ligands during an iron enrichment experiment in the western subarctic North Pacific

NASA Astrophysics Data System (ADS)

Kondo, Yoshiko; Takeda, Shigenobu; Nishioka, Jun; Obata, Hajime; Furuya, Ken; Johnson, William Keith; Wong, C. S.

2008-06-01

Complexation of iron (III) with natural organic ligands was investigated during a mesoscale iron enrichment experiment in the western subarctic North Pacific (SEEDS II). After the iron infusions, ligand concentrations increased rapidly with subsequent decreases. While the increases of ligands might have been partly influenced by amorphous iron colloids formation (12-29%), most in-situ increases were attributable to the <200 kDa fraction. Dilution of the fertilized patch may have contributed to the rapid decreases of the ligands. During the bloom decline, ligand concentration increased again, and the high concentrations persisted for 10 days. The conditional stability constant was not different between inside and outside of the fertilized patch. These results suggest that the chemical speciation of the released iron was strongly affected by formation of the ligands; the production of ligands observed during the bloom decline will strongly impact the iron cycle and bioavailability in the surface water.

Magnetic bead-based enzyme-chromogenic substrate system for ultrasensitive colorimetric immunoassay accompanying cascade reaction for enzymatic formation of squaric acid-iron(III) chelate.

PubMed

Lai, Wenqiang; Tang, Dianping; Zhuang, Junyang; Chen, Guonan; Yang, Huanghao

2014-05-20

This work reports on a simple and feasible colorimetric immunoassay with signal amplification for sensitive determination of prostate-specific antigen (PSA, used as a model) at an ultralow concentration by using a new enzyme-chromogenic substrate system. We discovered that glucose oxidase (GOx), the enzyme broadly used in enzyme-linked immunosorbent assay (ELISA), has the ability to stimulate in situ formation of squaric acid (SQA)-iron(III) chelate. GOx-catalyzed oxidization of glucose leads to the formation of gluconic acid and hydrogen peroxide (H2O2). The latter can catalytically oxidize iron(II) to iron(III), which can rapidly (<1 min) coordinate with the SQA. Formation of the iron-squarate complex causes the color of the solution to change from bluish purple to bluish red accompanying the increasing absorbance with the increment of iron(III) concentration. On the basis of the SQA-iron(III) system, a new immunoassay protocol with GOx-labeled anti-PSA detection antibody can be designed for the detection of target PSA on capture antibody-functionalized magnetic immunosensing probe, monitored by recording the color or absorbance (λ = 468 nm) of the generated SQA-iron(III) chelate. The absorbance intensity shows to be dependent on the concentration of target PSA. A linear dependence between the absorbance and target PSA concentration is obtained under optimal conditions in the range from 1.0 pg mL(-1) to 30 ng mL(-1) with a detection limit (LOD) of 0.5 pg mL(-1) (0.5 ppt) estimated at the 3Sblank level. The sensitivity displays to be 3-5 orders of magnitude better than those of most commercialized human PSA ELISA kits. In addition, the developed colorimetric immunoassay was validated by assaying 12 human serum samples, receiving in good accordance with those obtained by the commercialized PSA ELISA kit. Importantly, the SQA-based immunosensing system can be further extended for the detection of other low-abundance proteins or biomarkers by controlling the target antibody.

A One-Step Delamination Procedure to Form Single Sheet Iron(III)-(oxy)Hydroxides

EPA Science Inventory

The dispersion of a layered iron(III)-(oxy)hydroxide intercalated with dodecanoate (oxGR_C12, Fe₃^IIIO_2.18(OH)_3.13(C₁₂H₂₃O₂)_0.56(SO₄)_0.47; derived from the corr...

The Siderocalin/Enterobactin Interaction: A Link between Mammalian Immunity and Bacterial Iron Transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meux, Susan C.

2008-05-12

The siderophore enterobactin (Ent) is produced by enteric bacteria to mediate iron uptake. Ent scavenges iron and is taken up by the bacteria as the highly stable ferric complex [Fe{sup III}(Ent)]{sup 3-}. This complex is also a specific target of the mammalian innate immune system protein, Siderocalin (Scn), which acts as an anti-bacterial agent by specifically sequestering siderophores and their ferric complexes during infection. Recent literature suggesting that Scn may also be involved in cellular iron transport has increased the importance of understanding the mechanism of siderophore interception and clearance by Scn; Scn is observed to release iron in acidicmore » endosomes and [Fe{sup III}(Ent)]{sup 3-} is known to undergo a change from catecholate to salicylate coordination in acidic conditions, which is predicted to be sterically incompatible with the Scn binding pocket (also referred to as the calyx). To investigate the interactions between the ferric Ent complex and Scn at different pH values, two recombinant forms of Scn with mutations in three residues lining the calyx were prepared: Scn-W79A/R81A and Scn-Y106F. Binding studies and crystal structures of the Scn-W79A/R81A:[Fe{sup III}(Ent)]{sup 3-} and Scn-Y106F:[Fe{sup III}(Ent)]{sup 3-} complexes confirm that such mutations do not affect the overall conformation of the protein but do weaken significantly its affinity for [Fe{sup III}(Ent)]{sup 3-}. Fluorescence, UV-Vis and EXAFS spectroscopies were used to determine Scn/siderophore dissociation constants and to characterize the coordination mode of iron over a wide pH range, in the presence of both mutant proteins and synthetic salicylate analogs of Ent. While Scn binding hinders salicylate coordination transformation, strong acidification results in the release of iron and degraded siderophore. Iron release may therefore result from a combination of Ent degradation and coordination change.« less

The Siderocalin/Enterobactin Interaction: a Link Between Mammalian Immunity And Bacterial Iron Transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abergel, R.J.; Clifton, M.C.; Pizarro, J.C.

2009-05-12

The siderophore enterobactin (Ent) is produced by enteric bacteria to mediate iron uptake. Ent scavenges iron and is taken up by the bacteria as the highly stable ferric complex [Fe{sup III}(Ent)]{sup 3-}. This complex is also a specific target of the mammalian innate immune system protein, Siderocalin (Scn), which acts as an antibacterial agent by specifically sequestering siderophores and their ferric complexes during infection. Recent literature suggesting that Scn may also be involved in cellular iron transport has increased the importance of understanding the mechanism of siderophore interception and clearance by Scn; Scn is observed to release iron in acidicmore » endosomes and [Fe{sup III}(Ent)]{sup 3-} is known to undergo a change from catecholate to salicylate coordination in acidic conditions, which is predicted to be sterically incompatible with the Scn binding pocket (also referred to as the calyx). To investigate the interactions between the ferric Ent complex and Scn at different pH values, two recombinant forms of Scn with mutations in three residues lining the calyx were prepared: Scn-W79A/R81A and Scn-Y106F. Binding studies and crystal structures of the Scn-W79A/R81A:[Fe{sup III}(Ent)]{sup 3-} and Scn-Y106F:[Fe{sup III}(Ent)]{sup 3-} complexes confirm that such mutations do not affect the overall conformation of the protein but do weaken significantly its affinity for [Fe{sup III}(Ent)]{sup 3-}. Fluorescence, UV-vis, and EXAFS spectroscopies were used to determine Scn/siderophore dissociation constants and to characterize the coordination mode of iron over a wide pH range, in the presence of both mutant proteins and synthetic salicylate analogues of Ent. While Scn binding hinders salicylate coordination transformation, strong acidification results in the release of iron and degraded siderophore. Iron release may therefore result from a combination of Ent degradation and coordination change.« less

Novel two-component transmembrane transcription control: regulation of iron dicitrate transport in Escherichia coli K-12.

PubMed

Van Hove, B; Staudenmaier, H; Braun, V

1990-12-01

Citrate and iron have to enter only the periplasmic space in order to induce the citrate-dependent iron(III) transport system of Escherichia coli. The five transport genes fecABCDE form an operon and are transcribed from fecA to fecE. Two genes, termed fecI and fecR, that mediate induction by iron(III) dicitrate have been identified upstream of fecA. The fecI gene encodes a protein of 173 amino acids (molecular weight, 19,478); the fecR gene encodes a protein of 317 amino acids (molecular weight, 35,529). Chromosomal fecI::Mu d1 mutants were unable to grow with iron(III) dicitrate as the sole iron source and synthesized no FecA outer membrane receptor protein. Growth was restored by transformation with plasmids encoding fecI or fecI and fecR. FecA and beta-galactosidase syntheses under transcription control of the fecB gene (fecB::Mu d1) were constitutive in fecI transformants and were regulated by iron(III) dicitrate in fecI fecR transformants. The amino acid sequence of the FecI protein contains a region close to the carboxy-terminal end for which a helix-turn-helix motif is predicted, which is typical for DNA-binding regulatory proteins. The FecI protein was found in the membrane, and the FecR protein was found in the periplasmic fraction. It is proposed that the FecR protein is the sensor that recognizes iron(III) dicitrate in the periplasm. The FecI protein activates fec gene expression by binding to the fec operator region. In the absence of citrate, FecR inactivates FecI. The lack of sequence homologies to other transmembrane signaling proteins and the location of the two proteins suggest a new type of transmembrane control mechanism.

Ellagic acid inhibits iron-mediated free radical formation

NASA Astrophysics Data System (ADS)

Dalvi, Luana T.; Moreira, Daniel C.; Andrade, Roberto; Ginani, Janini; Alonso, Antonio; Hermes-Lima, Marcelo

2017-02-01

Polyphenols are reported to have some health benefits, which are link to their antioxidant properties. In the case of ellagic acid (EA), there is evidence that it has free radical scavenger properties and that it is able to form complexes with metal ions. However, information on a possible link between the formation of iron-EA complexes and their interference in Haber-Weiss/Fenton reactions was not yet determined. Thus, the present study investigated the in vitro antioxidant mechanism of EA in a system containing ascorbate, Fe(III) and different iron ligands (EDTA, citrate and NTA). Iron-mediated oxidative degradation of 2-deoxyribose was poorly inhibited (by 12%) in the presence of EA (50 μM) and EDTA. When citrate or NTA - which form weak iron complexes - were used, the 2-deoxyribose protection increased to 89-97% and 45%, respectively. EA also presented equivalent inhibitory effects on iron-mediated oxygen uptake and ascorbyl radical formation. Spectral analyses of iron-EA complexes show that EA removes Fe(III) from EDTA within hours, and from citrate within 1 min. This difference in the rate of iron-EA complex formation may explain the antioxidant effects of EA. Furthermore, the EA antioxidant effectiveness was inversely proportional to the Fe(III) concentration, suggesting a competition with EDTA. In conclusion, the results indicate that EA may prevent in vitro free radical formation when it forms a complex with iron ions.

A longitudinal study of serum ferritin in 319 adolescent Danish boys and girls examined in 1986 and 1992.

PubMed

Milman, N; Byg, K E; Backer, V; Ulrik, C; Graudal, N

1999-10-01

This study examined trends in iron status in adolescents. Serum ferritin was measured in 1986 and 1992 in 319 Danes (161 males) stratified into 5 groups: I. median age 9 yr in 1986 vs. 15 yr in 1992; II. 11 vs. 17 yr; III. 13 vs. 19 yr; IV. 15 vs. 21 yr; V. 17 vs. 23 yr. Males in group I demonstrated no change in ferritin or estimated iron stores in mg/kg; groups II-V displayed an increase in iron status parameters. All groups showed an increase in estimated total iron stores. Changes in iron status parameters were inversely correlated with height velocity in group III, and positively correlated with height velocity in group V. Females in age groups I and II demonstrated a fall in ferritin and estimated iron stores in mg/kg in association with menarche; values were unchanged in groups III and IV, and increased in group V. All groups showed an increase in estimated total iron stores. Changes in iron status parameters were inversely correlated with height velocity in groups I and II. In conclusion, ferritin levels in adolescents display great variation during growth spurt and at menarche. Changes in ferritin showed no consistent association with growth velocity. In both genders, estimated total iron stores increased with age.

Tuning the properties of metal–organic framework nodes as supports of single-site iridium catalysts: node modification by atomic layer deposition of aluminium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Dong; Momeni, Mohammad R.; Demir, Hakan

The metal–organic framework NU-1000, with Zr 6-oxo, hydroxo, and aqua nodes, was modified by incorporation of hydroxylated Al(iii) ions by ALD-like chemistry with [Al(CH 3) 2(iso-propoxide)] 2followed by steam (ALD = atomic layer deposition). Al ions were installed to the extent of approximately 7 per node. Single-site iridium diethylene complexes were anchored to the nodes of the modified and unmodified MOFs by reaction with Ir(C 2H 4) 2(acac) (acac = acetylacetonate) and converted to Ir(CO) 2complexes by treatment with CO. Infrared spectra of these supported complexes show that incorporation of Al weakened the electron donor tendency of the MOF. Correspondingly,more » the catalytic activity of the initial supported iridium complexes for ethylene hydrogenation increased, as did the selectivity for ethylene dimerization. The results of density functional theory calculations with a simplified model of the nodes incorporating Al(iii) ions are in qualitative agreement with some catalyst performance data.« less

New cyclometalated Iridium(III) beta-dicetone complex as phosphorescent dopant in Organic light emitting devices

NASA Astrophysics Data System (ADS)

Ivanov, P.; Petrova, P.; Stanimirov, S.; Tomova, R.

2017-01-01

A new Bis[4-(benzothiazolato-N,C2‧-2-yl)-N,N-dimethylaniline]Iridium(III) acetylacetonate (Me2N-bt) 2Ir(acac) was synthesized and identified by 1H NMR and elemental analysis. The application of the new compound as a dopant in the hole transporting layer (HTL) of Organic light emitting diode (OLED) structure: HTL/EL/ETL, where HTL was N,N’-bis(3-methylphenyl)-N,N’-diphenylbenzidine (TPD), incorporated in Poly(N-vinylcarbazole) (PVK) matrix, EL - electroluminescent layer of Bis(8-hydroxy-2-methylquinoline)-(4-phenylpheno-xy)aluminum (BAlq) and ETL - electron-transporting layer of Tris-(8-hydroxyquinoline) aluminum (Alq3) or Bis[2-(2-benzothiazoly) phenolato]zinc (Zn(btz)2). We established that the electroluminescent spectra of OLEDs at different concentrations of the dopant were basically the sum of the greenish-blue emission of BAlq and yellowish-green emission of Ir complex. It was found that with increasing of the dopant concentration the relative electroluminescent intensity of Iridium complex emission increased and this of BAlq decreased and as a result the fine tuning of OLED color was observed.

Evidence for Microbial Fe(III) Reduction in Anoxic, Mining-Impacted Lake Sediments (Lake Coeur d'Alene, Idaho)

PubMed Central

Cummings, David E.; March, Anthony W.; Bostick, Benjamin; Spring, Stefan; Caccavo, Frank; Fendorf, Scott; Rosenzweig, R. Frank

2000-01-01

Mining-impacted sediments of Lake Coeur d'Alene, Idaho, contain more than 10% metals on a dry weight basis, approximately 80% of which is iron. Since iron (hydr)oxides adsorb toxic, ore-associated elements, such as arsenic, iron (hydr)oxide reduction may in part control the mobility and bioavailability of these elements. Geochemical and microbiological data were collected to examine the ecological role of dissimilatory Fe(III)-reducing bacteria in this habitat. The concentration of mild-acid-extractable Fe(II) increased with sediment depth up to 50 g kg−1, suggesting that iron reduction has occurred recently. The maximum concentrations of dissolved Fe(II) in interstitial water (41 mg liter−1) occurred 10 to 15 cm beneath the sediment-water interface, suggesting that sulfidogenesis may not be the predominant terminal electron-accepting process in this environment and that dissolved Fe(II) arises from biological reductive dissolution of iron (hydr)oxides. The concentration of sedimentary magnetite (Fe3O4), a common product of bacterial Fe(III) hydroxide reduction, was as much as 15.5 g kg−1. Most-probable-number enrichment cultures revealed that the mean density of Fe(III)-reducing bacteria was 8.3 × 105 cells g (dry weight) of sediment−1. Two new strains of dissimilatory Fe(III)-reducing bacteria were isolated from surface sediments. Collectively, the results of this study support the hypothesis that dissimilatory reduction of iron has been and continues to be an important biogeochemical process in the environment examined. PMID:10618217

Application Of Bacterial Iron Reduction For The Removal Of Iron Impurities From Industrial Silica Sand And Kaolin

NASA Astrophysics Data System (ADS)

Zegeye, A.; Yahaya, S.; Fialips, C. I.; White, M.; Manning, D. A.; Gray, N.

2008-12-01

Biogeochemical evidence exists to support the potential importance of crystalline or amorphous Fe minerals as electron acceptor for Fe reducing bacteria in soils and subsurface sediments. This microbial metabolic activity can be exploited as alternative method in different industrial applications. For instance, the removal of ferric iron impurities from minerals for the glass and paper industries currently rely on physical and chemical treatments having substantial economical and environmental disadvantages. The ability to remove iron by other means, such as bacterial iron reduction, may reduce costs, allow lower grade material to be mined, and improve the efficiency of mineral processing. Kaolin clay and silica sand are used in a wide range of industrial applications, particularly in paper, ceramics and glass manufacturing. Depending on the geological conditions of deposition, they are often associated with iron (hydr)oxides that are either adsorbed to the mineral surfaces or admixed as separate iron bearing minerals. In this study, we have examined the Fe(III) removal efficiency from kaolin and silica sand by a series of iron- reducing bacteria from the Shewanella species (S. alga BrY, S. oneidensis MR-1, S. putrefaciens CN32 and S. putrefaciens ATCC 8071) in the presence of anthraquinone 2,6 disulfonate (AQDS). We have also investigated the effectiveness of a natural organic matter, extracted with the silica sand, as a substitute to AQDS for enhancing Fe(III) reduction kinetics. The microbial reduction of Fe(III) was achieved using batch cultures under non-growth conditions. The rate and the extent of Fe(III) reduction was monitored as a function of the initial Fe(III) content, Shewanella species and temperature. The bacterially- treated minerals were analyzed by transmission electron microscopy (TEM) and X-ray diffraction (XRD) to observe any textural and mineralogical transformation. The whiteness and ISO brightness of the kaolin was also measured by spectrophotometry for quality testing. All Shewanella species were able to couple the oxidation of lactate to the reduction of Fe(III) associated with the kaolins and silica sands. However, there are differences among species with respect to the rate and extent of iron leaching. S. putrefaciens ATCC 8071 is the most effective, with a 10% increase in kaolin whiteness and 4% increase in ISO brightness in less than 5 days.

Iron as a catalyst of human low-density lipoprotein oxidation: Critical factors involved in its oxidant properties.

PubMed

Lapenna, Domenico; Ciofani, Giuliano; Obletter, Gabriele

2017-05-01

Iron-induced human LDL oxidation, which is relevant to atherosclerosis, has not yet been properly investigated. We addressed such issue using iron(II) and (III) basically in the presence of phosphates, which are present in vivo and influence iron oxidative properties, at pH 4.5 and 7.4, representative, respectively, of the lysosomal and plasma environment. In 10mM phosphate buffered saline (PBS), iron(II) induces substantial LDL oxidation at pH 4.5 at low micromolar concentrations, while at pH 7.4 has low oxidative effects; iron(III) promotes small LDL oxidation only at pH 4.5. In 10mM sodium acetate/NaCl buffer, pH 4.5, iron-induced LDL oxidation is far higher than in PBS, highlighting the relevance of phosphates in the inhibitory modulation of iron-induced LDL oxidation. LDL oxidation is related to iron binding to the protein and lipid moiety of LDL, and requires the presence of iron(II) bound to LDL together with iron(III). Chemical modification of LDL carboxyl groups, which could bind iron especially at pH 4.5, decreases significantly iron binding to LDL and iron-induced LDL oxidation. Hydroxyl radical scavengers are ineffective on iron-induced LDL oxidation, which is inhibited by metal chelation, scavengers of alkoxyl/peroxyl radicals, or removal of LDL lipid hydroperoxides (LOOH). Overall, substantial human LDL oxidation is induced LOOH-dependently by iron(II) at pH 4.5 even in the presence of phosphates, suggesting the occurrence of iron(II)-induced LDL oxidation in vivo within lysosomes, where pH is about 4.5, iron(II) and phosphates coexist, plasma with its antioxidants is absent, and glutathione peroxidase is poorly expressed resulting in LOOH accumulation. Copyright © 2017 Elsevier GmbH. All rights reserved.

Complexation equilibria and spectrophotometric determination of iron(III) with 1-amino-4-hydroxyanthraquinone.

PubMed

Abu-Bakr, M S; Sedaira, H; Hashem, E Y

1994-10-01

The complex equilibria of iron(III) with 1-amino-4-hydroxyanthraquinone (AMHA) were studied spectrophotometrically in 40% (v/v) ethanol and an ionic strength of 0.1M (NaClO(4)). The complexation reactions were demonstrated and characterized using graphical logarithmic analysis of the absorbance-pH graphs. A simple, rapid, selective and sensitive method for the spectrophotometric determination of trace amounts of Fe(III) is developed based on the formation of Fe(AMHA) complex at pH 2.5 (lambda(max) = 640 nm, epsilon approximately = 2.1 x 10(4) L. mol(-1) . cm(-1)) in the presence of a large number of foreign ions. Interferences caused by palladium(II) was masked by the addition of cyanide ions. The method has been applied to the determination of iron in some synthetic samples and polymetallic iron ores.

Uranium(VI) reduction by nanoscale zero-valent iron in anoxic batch systems: the role of Fe(II) and Fe(III).

PubMed

Yan, Sen; Chen, Yongheng; Xiang, Wu; Bao, Zhengyu; Liu, Chongxuan; Deng, Baolin

2014-12-01

The role of Fe(II) and Fe(III) in U(VI) reduction by nanoscale zerovalent iron (nanoFe0) was investigated using two iron chelators 1,10-phenanthroline and triethanolamine (TEA) under a CO2-free anoxic condition. The results showed that U(VI) reduction was strongly inhibited by 1,10-phenanthroline and TEA in a pH range from 6.9 to 9.0. For instance, at pH 6.9 the observed U(VI) reduction rates decreased by 81% and 82% in the presence of 1,10-phenanthroline and TEA, respectively. The inhibition was attributed to the formation of stable complexes between 1,10-phenanthroline and Fe(II) or TEA and Fe(III). In the absence of iron chelators, U(VI) reduction can be enhanced by surface-bound Fe(II) on nanoFe0. Our results suggested that Fe(III) and Fe(II) possibly acted as an electron shuttle to ferry the electrons from nanoFe0 to U(VI), therefore a combined system with Fe(II), Fe(III) and nanoFe0 could facilitate U(VI) reductive immobilization in the contaminated groundwater.

Uranium(VI) reduction by nanoscale zero-valent iron in anoxic batch systems: The role of Fe(II) and Fe(III)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Sen; Chen, Yongheng; Xiang, Wu

2014-12-01

The role of Fe(II) and Fe(III) on U(VI) reduction by nanoscale zerovalent iron (nanoFe0) was investigated using two iron chelators 1,10-phenanthroline and triethanolamine (TEA) under a CO2-free anoxic condition. The results showed U(VI) reduction was strongly inhibited by 1,10-phenanthroline and TEA in a pH range from 6.92 to 9.03. For instance, at pH 6.92 the observed U(VI) reduction rates decreased by 80.7% and 82.3% in the presence of 1,10-phenanthroline and TEA, respectively. The inhibition was attributed to the formation of stable complexes between 1,10-phenanthroline and Fe(II) or TEA and Fe(III). In the absence of iron chelators, U(VI) reduction can bemore » enhanced by surface-bound Fe(II) on nanoFe0. Our results suggested that Fe(III) and Fe(II) probably acted as an electron shuttle to mediate the transfer of electrons from nanoFe0 to U(VI), therefore a combined system with Fe(II), Fe(III) and nanoFe0 can facilitate the U(VI) reductive immobilization in the contaminated groundwater.« less

Synthesis of iron based hydrocracking catalysts

DOEpatents

Farcasiu, Malvina; Eldredge, Patricia A.; Ladner, Edward P.

1993-01-01

A method of preparing a fine particle iron based hydrocracking catalyst and the catalyst prepared thereby. An iron (III) oxide powder and elemental sulfur are reacted with a liquid hydrogen donor having a hydroaromatic structure present in the range of from about 5 to about 50 times the weight of iron (III) oxide at a temperature in the range of from about 180.degree. C. to about 240.degree. C. for a time in the range of from about 0 to about 8 hours. Various specific hydrogen donors are disclosed. The catalysts are active at low temperature (<350.degree. C.) and low pressure.

Influence of iron solubility and charged surface-active compounds on lipid oxidation in fatty acid ethyl esters containing association colloids.

PubMed

Homma, Rika; Johnson, David R; McClements, D Julian; Decker, Eric A

2016-05-15

The impact of iron compounds with different solubilities on lipid oxidation was studied in the presence and absence of association colloids. Iron (III) sulfate only accelerated lipid oxidation in the presence of association colloids while iron (III) oleate accelerated oxidation in the presence and absence of association colloids. Further, iron (III) oxide retarded lipid oxidation both with and without association colloids. The impact of charged association colloids on lipid oxidation in ethyl oleate was also investigated. Association colloids consisting of the anionic surface-active compound dodecyl sulphosuccinate sodium salt (AOT), cationic surface-active compound hexadecyltrimethylammonium bromide (CTAB), and nonionic surface-active compound 4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (Triton X-100) retarded, promoted, and had no effect on lipid oxidation rates, respectively. These results indicate that the polarity of metal compounds and the charge of association colloids play a big role in lipid oxidation. Copyright © 2015 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toczydlowska, Diana; Kedra-Krolik, Karolina; Nejbert, Krzysztof

The role of surface electrostatics on the reductive dissolution of iron (III) oxides is poorly understood, despite its importance in controlling the amount of mobilized iron. We report the potentiometric titration of the a; y -Fe2O3 oxides exposed to reductants and complexing ligands (Fe(II), ascorbate, oxalate, malonate). We monitored in situ surface and potentials, the ratio of mobilized ferric to ferrous ions, and periodically analyzed nanoparticle crystal structure using X-ray diffraction. We found that addition of Fe2+ ions produces a response consistent with the iron solubilityactivity curve, whereas the presence of ascorbate significantly decreases the amount of mobilized Fe(III) duemore » to reduction to Fe(II). In addition, XRD analysis proved that y-Fe2O3 particles remain structurally unchanged along the titration pathway despite iron cycling between aqueous and solid reservoirs. Our studies, suggest that the surface redoxactivity of iron oxides is primarily governed by the balance between Fe(III) and Fe(II) ions in aqueous phase, which may be easily altered by complexing and reducing agents.« less

Novel spin transition between S = 5/2 and S = 3/2 in highly saddled iron(III) porphyrin complexes at extremely low temperatures.

PubMed

Ohgo, Yoshiki; Chiba, Yuya; Hashizume, Daisuke; Uekusa, Hidehiro; Ozeki, Tomoji; Nakamura, Mikio

2006-05-14

A novel spin transition between S = 5/2 and S = 3/2 has been observed for the first time in five-coordinate, highly saddled iron(III) porphyrinates by EPR and SQUID measurements at extremely low temperatures.

Development and characterisation of polymeric microparticle of poly(d,l-lactic acid) loaded with holmium acetylacetonate.

PubMed

de Azevedo, Mariangela de Burgos M; de Melo, Vitor H S; Soares, Carlos Roberto J; Miyamoto, Douglas M; Katayama, Ricardo A; Squair, Peterson L; Barros, Caio H N; Tasic, Ljubica

2018-06-14

Biodegradable polymers containing radioactive isotopes such as Holmium 166 ( 166 Ho) have potential applications as beta particle emitters in tumour tissues. It is also a gamma ray emitter, allowing nuclear imaging of any tissue to be acquired. It is frequently used in the form of complexes such as holmium acetylacetonate (HoAcAc), which may cause damages in tissues next to the targets cancer cells, as it is difficult to control its linkage or healthy tissues radiotherapy effects. Poly(d,l-lactic acid), PDLLA, was used to encapsulate holmium acetylacetonate (HoAcAc) using an emulsion solvent extraction/evaporation technique. Microspheres with sizes between 20-53 µm were extensively characterised. HoAcAc release from the microspheres was assessed through studies using Inductively Coupled Plasma - Optical Emission Spectroscopy, and the microspheres showed no holmium leakage after a period of 10 half-lives and following gamma irradiation. Thus, HoAcAc loaded microspheres are here presented as a potential system for brachytherapy and imaging purposes.

Iron Overload and Apoptosis of HL-1 Cardiomyocytes: Effects of Calcium Channel Blockade

PubMed Central

Chen, Mei-pian; Cabantchik, Z. Ioav; Chan, Shing; Chan, Godfrey Chi-fung; Cheung, Yiu-fai

2014-01-01

Background Iron overload cardiomyopathy that prevails in some forms of hemosiderosis is caused by excessive deposition of iron into the heart tissue and ensuing damage caused by a raise in labile cell iron. The underlying mechanisms of iron uptake into cardiomyocytes in iron overload condition are still under investigation. Both L-type calcium channels (LTCC) and T-type calcium channels (TTCC) have been proposed to be the main portals of non-transferrinic iron into heart cells, but controversies remain. Here, we investigated the roles of LTCC and TTCC as mediators of cardiac iron overload and cellular damage by using specific Calcium channel blockers as potential suppressors of labile Fe(II) and Fe(III) ingress in cultured cardiomyocytes and ensuing apoptosis. Methods Fe(II) and Fe(III) uptake was assessed by exposing HL-1 cardiomyocytes to iron sources and quantitative real-time fluorescence imaging of cytosolic labile iron with the fluorescent iron sensor calcein while iron-induced apoptosis was quantitatively measured by flow cytometry analysis with Annexin V. The role of calcium channels as routes of iron uptake was assessed by cell pretreatment with specific blockers of LTCC and TTCC. Results Iron entered HL-1 cardiomyocytes in a time- and dose-dependent manner and induced cardiac apoptosis via mitochondria-mediated caspase-3 dependent pathways. Blockade of LTCC but not of TTCC demonstrably inhibited the uptake of ferric but not of ferrous iron. However, neither channel blocker conferred cardiomyocytes with protection from iron-induced apoptosis. Conclusion Our study implicates LTCC as major mediators of Fe(III) uptake into cardiomyocytes exposed to ferric salts but not necessarily as contributors to ensuing apoptosis. Thus, to the extent that apoptosis can be considered a biological indicator of damage, the etiopathology of cardiosiderotic damage that accompanies some forms of hemosiderosis would seem to be unrelated to LTCC or TTCC, but rather to other routes of iron ingress present in heart cells. PMID:25390893

Transcriptional Profiling of the Iron Starvation Response in Bordetella pertussis Provides New Insights into Siderophore Utilization and Virulence Gene Expression ▿ §

PubMed Central

Brickman, Timothy J.; Cummings, Craig A.; Liew, Sin-Yee; Relman, David A.; Armstrong, Sandra K.

2011-01-01

Serological studies of patients with pertussis and the identification of antigenic Bordetella pertussis proteins support the hypothesis that B. pertussis perceives an iron starvation cue and expresses multiple iron source utilization systems in its natural human host environment. Furthermore, previous studies using a murine respiratory tract infection model showed that several of these B. pertussis iron systems are required for colonization and persistence and are differentially expressed over the course of infection. The present study examined genome-wide changes in B. pertussis gene transcript abundance in response to iron starvation in vitro. In addition to known iron source utilization genes, we identified a previously uncharacterized iron-repressed cytoplasmic membrane transporter system, fbpABC, that is required for the utilization of multiple structurally distinct siderophores including alcaligin, enterobactin, ferrichrome, and desferrioxamine B. Expression of type III secretion system genes was also found to be upregulated during iron starvation in both B. pertussis strain Tohama I and Bordetella bronchiseptica strain RB50. In a survey of type III secretion system protein production by an assortment of B. pertussis laboratory-adapted and low-passage clinical isolate strains, iron limitation increased the production and secretion of the type III secretion system-specific translocation apparatus tip protein Bsp22 in all Bvg-proficient strains. These results indicate that iron starvation in the infected host is an important environmental cue influencing not only Bordetella iron transport gene expression but also the expression of other important virulence-associated genes. PMID:21742863

Synthesis, characterization and electrochemistry studies of iron(III) complex with curcumin ligand.

PubMed

Özbolat, Gülüzar; Yegani, Arash Alizadeh; Tuli, Abdullah

2018-05-11

Iron overload is a serious clinical condition for humans and is a key target in drug development. The aim of this study was to investigate the coordination of iron(III) ions with curcumin ligand that may be used in the treatment of iron overload. Iron(III) complex of curcumin was synthesized and structurally characterized in its solid and solution state by FT-IR, UV-Vis, elemental analysis, and magnetic susceptibility. Electrochemical behaviour of the ligand and the complexes were examined using cyclic voltammetry. The cytotoxic activities of the ligand and the iron(III) complex were evaluated by the MTT assay. Curcumin reacted with iron in high concentrations at physiological pH at room temperature. Subsequently, a brown-red complex was formed. Data regarding magnetic susceptibility showed that the complexes with a 1:2 (metal/ligand) mole ratio had octahedral geometry. The complex showed higher anti-oxidant effect towards the cell line ECV304 at IC 50 values of 4.83 compared to curcumin. The complex exhibited very high cytotoxic activity and showed a cytotoxic effect that was much better than that of the ligand. The potentials for redox were calculated as 0.180 V and 0.350 V, respectively. The electrochemistry studies showed that Fe 3+ /Fe 2+ couple redox process occurred at low potentials. This value was within the range of compounds that are expected to show superoxide dismutase activity. This finding indicates that the iron complex is capable of removing free radicals. The observed cytotoxicity could be pursued to obtain a potential drug. Further studies investigating the use of curcumin for this purpose are needed. © 2018 John Wiley & Sons Australia, Ltd.

Isolation and identification of ferric reducing bacteria and evaluation of their roles in iron availability in two calcareous soils

NASA Astrophysics Data System (ADS)

Ghorbanzadeh, N.; Lakzian, A.; Haghnia, G. H.; Karimi, A. R.

2014-12-01

Iron is an essential element for all organisms which plays a crucial role in important biochemical processes such as respiration and photosynthesis. Iron deficiency seems to be an important problem in many calcareous soils. Biological dissimilatory Fe(III) reduction increases iron availability through reduction of Fe(III) to Fe(II). The aim of this study was to isolate, identify and evaluate some bacterial isolates for their abilities to reduce Fe(III) in two calcareous soils. Three bacterial isolates were selected and identified from paddy soils by using 16S rRNA amplification and then inoculated to sterilized and non-sterilized calcareous soils in the presence and absence of glucose. The results showed that all isolates belonged to Bacillus genus and were capable of reducing Fe(III) to Fe(II) in vitro condition. The amount of Fe(III) reduction in sterilized calcareous soils was significantly higher when inoculated with PS23 isolate and Shewanella putrefaciens ( S. putrefaciens) (as positive control) compared to PS16 and PS11 isolates. No significant difference was observed between PS11 and PS16 isolates in the presence of indigenous microbial community. The results also revealed that glucose had a significant effect on Fe(III) reduction in the examined calcareous soil samples. The amount of Fe(III) reduction increased two-fold when soil samples were treated with glucose and inoculated by S. putrefaciens and PS23 in non-sterilized soils.

Prion protein conversion induced by trivalent iron in vesicular trafficking.

PubMed

Choi, Bo-Ran; Lee, Jeongmin; Kim, Su Yeon; Yim, Inbeen; Kim, Eun-Hee; Woo, Hee-Jong

2013-03-15

Iron dyshomeostasis has been observed in prion diseases; however, little is known regarding the contribution of the oxidation state of iron to prion protein (PrP) conversion. In this study, PrP(C)-deficient HpL3-4 cells were exposed to divalent [Fe(II)] or trivalent [Fe(III)] iron, followed by exogenous recombinant PrP (rPrP) treatment. We then analyzed the accumulation of internalized rPrP and its biochemical properties, including its resistance to both proteinase K (PK) digestion and detergent solubility. Fe(III), but not Fe(II), induced the accumulation of internalized rPrP, which was partially converted to detergent-insoluble and PK-resistant PrP (PrP(res)). The Fe(III)-induced PrP(res) generation required an intact cell structure, and it was hindered by U18666A, an inhibitor of vesicular trafficking, but not by NH4Cl, an inhibitor of endolysosomal acidification. These observations implicated that the Fe(III)-mediated PrP(res) conversion likely occurs during endosomal vesicular trafficking rather than in the acidic environment of lysosomes. Copyright © 2013 Elsevier Inc. All rights reserved.

Impact of Microcystis aeruginosa Exudate on the Formation and Reactivity of Iron Oxide Particles Following Fe(II) and Fe(III) Addition.

PubMed

Garg, Shikha; Wang, Kai; Waite, T David

2017-05-16

Impact of the organic exudate secreted by a toxic strain of Microcystis aeruginosa on the formation, aggregation, and reactivity of iron oxides that are formed on addition of Fe(II) and Fe(III) salts to a solution of the exudate is investigated in this study. The exudate has a stabilizing effect on the particles formed with decreased aggregation rate and increased critical coagulant concentration required for diffusion-limited aggregation to occur. These results suggest that the presence of algal exudates from Microcystis aeruginosa may significantly influence particle aggregation both in natural water bodies where Fe(II) oxidation results in oxide formation and in water treatment where Fe(III) salts are commonly added to aid particle growth and contaminant capture. The exudate also affects the reactivity of iron oxide particles formed with exudate coated particles undergoing faster dissolution than bare iron oxide particles. This has implications to iron availability, especially where algae procure iron via dissolution of iron oxide particles as a result of either reaction with reducing moieties, light-mediated ligand to metal charge transfer and/or reaction with siderophores. The increased reactivity of exudate coated particles is attributed, for the most part, to the smaller size of these particles, higher surface area and increased accessibility of surface sites.

Arsenic Mobilization Influenced By Iron Reduction And Sulfidogenesis Under Dynamic Flow

NASA Astrophysics Data System (ADS)

Kocar, B. D.; Stewart, B. D.; Herbel, M.; Fendorf, S.

2004-12-01

Sulfidogenesis and iron reduction are ubiquitous processes that occur in a variety of anoxic subsurface and surface environments, which profoundly impact the cycling of arsenic. Of the iron (hydr)oxides, ferrihydrite possesses one of the highest capacities to retain arsenic, and is globally distributed within soils and sediments. Upon dissimilatory iron reduction, ferrihydrite may transform to lower surface area minerals, such as goethite and magnetite, which decreases arsenic retention, thus enhancing its transport. Here we examine how arsenic retained on ferrihydrite is mobilized under dynamic flow in the presence of Sulfurosprillum barnesii strain SES-3, a bacteria capable of reducing both As(V) and Fe(III). Ferrihydrite coated sands, loaded with 150 mg kg-1 As(V), were inoculated with S. barnesii, packed into a column and reacted with a synthetic groundwater solution. Within several days after initiation of flow, the concentration of arsenic in the column effluent increased dramatically coincident with the mineralogical transformation of ferrihydrite and As(V) reduction to As(III). Following the initial pulse of arsenic, effluent concentration then declined to less than 10 μ M. Thus, arsenic release into the aqueous phase is contingent upon the incongruent reduction of As(V) and Fe(III) as mediated by biological activity. Reaction of abiotically or biotically generated dissolved sulfide with iron (hydr)oxides may have a dramatic influence on the fate of arsenic within surface and subsurface environments. Accordingly, we examined the reaction of dissolved bisulfide and iron (hydr)oxide complexed with arsenic in both batch and column systems. Low ratios of sulfide to iron in batch reaction systems result in the formation of elemental sulfur and concomitant arsenic release from the iron (hydr)oxide surface. High sulfide to iron ratios, in contrast, appear to favor the formation of iron and arsenic sulfides. Our findings demonstrate that iron (hydr)oxides may quench reactions between sulfide and constituents sorbed to iron (hydr)oxide surfaces, forming elemental sulfur as opposed to sulfide-arsenic complexes. In addition, reductive transformation of iron (hydr)oxide by dissolved sulfide may release sorbed constituents. Hence, moderate to low concentrations of dissolved sulfide in association with iron (hydr)oxides may inhibit sequestration of important contaminants that are attenuated by Fe(III) and/or S(-II) bearing phases.

Transformation impacts of dissolved and solid phase Fe(II) on trichloroethylene (TCE) reduction in an iron-reducing bacteria (IRB) mixed column system: a mathematical model.

PubMed

Bae, Yeunook; Kim, Dooil; Cho, Hyun-Hee; Singhal, Naresh; Park, Jae-Woo

2012-12-01

In this research, we conducted trichloroethylene (TCE) reduction in a column filled with iron and iron-reducing bacteria (IRB) and developed a mathematical model to investigate the critical reactions between active species in iron/IRB/contaminant systems. The formation of ferrous iron (Fe(II)) in this system with IRB and zero-valent iron (ZVI, Fe(0)) coated with a ferric iron (Fe(III)) crust significantly affected TCE reduction and IRB respiration in various ways. This study presents a new framework for transformation property and reducing ability of both dissolved (Fe(II)(dissolved)) and solid form ferrous iron (Fe(II)(solid)). Results showed that TCE reduction was strongly depressed by Fe(II)(solid) rather than by other inhibitors (e.g., Fe(III) and lactate), suggesting that Fe(II)(solid) might reduce IRB activation due to attachment to IRB cells. Newly exposed Fe(0) from the released Fe(II)(dissolved) was a strong contributor to TCE reduction compared to Fe(II)(solid). In addition, our research confirmed that less Fe(II)(solid) production strongly supported long-term TCE reduction because it may create an easier TCE approach to Fe(0) or increase IRB growth. Our findings will aid the understanding of the contributions of iron media (e.g., Fe(II)(solid), Fe(II)(dissolved), Fe(III), and Fe(0)) to IRB for decontamination in natural groundwater systems. Copyright © 2012 Elsevier Ltd. All rights reserved.

Reduction of Fe(III) colloids by Shewanella putrefaciens: A kinetic model

NASA Astrophysics Data System (ADS)

Bonneville, Steeve; Behrends, Thilo; van Cappellen, Philippe; Hyacinthe, Christelle; Röling, Wilfred F. M.

2006-12-01

A kinetic model for the microbial reduction of Fe(III) oxyhydroxide colloids in the presence of excess electron donor is presented. The model assumes a two-step mechanism: (1) attachment of Fe(III) colloids to the cell surface and (2) reduction of Fe(III) centers at the surface of attached colloids. The validity of the model is tested using Shewanella putrefaciens and nanohematite as model dissimilatory iron reducing bacteria and Fe(III) colloidal particles, respectively. Attachment of nanohematite to the bacteria is formally described by a Langmuir isotherm. Initial iron reduction rates are shown to correlate linearly with the relative coverage of the cell surface by nanohematite particles, hence supporting a direct electron transfer from membrane-bound reductases to mineral particles attached to the cells. Using internally consistent parameter values for the maximum attachment capacity of Fe(III) colloids to the cells, Mmax, the attachment constant, KP, and the first-order Fe(III) reduction rate constant, k, the model reproduces the initial reduction rates of a variety of fine-grained Fe(III) oxyhydroxides by S. putrefaciens. The model explains the observed dependency of the apparent Fe(III) half-saturation constant, Km∗, on the solid to cell ratio, and it predicts that initial iron reduction rates exhibit saturation with respect to both the cell density and the abundance of the Fe(III) oxyhydroxide substrate.

New Electronic Materials and CO2 Reduction.

DTIC Science & Technology

1988-02-02

REPORT DOCUMENTATION PAGE ! a ;t, C ’ SE -R .r N ’ D RE--R’tThVE "j f ’ .NUS UNCLASSIFIED APPROVED FOR PUBLIC RELEASE AD-A240 192 Lit R 11 II6 NOOO 14...by H12 have been carried out at 290C in a microreactor with a H2 /CO ration of 9/1. The catalysts studied were iron(III) oxide, iron(1I) diiron(1II...Methanation studies have been carried out at 290’C in a microreactor with a H 2 /CO ratio of 9/1. The catalysts studied were iron(III) oxide, iron(IT

Surface reactions of iron - enriched smectites: adsorption and transformation of hydroxy fatty acids and phenolic acids

NASA Astrophysics Data System (ADS)

Polubesova, Tamara; Olshansky, Yaniv; Eldad, Shay; Chefetz, Benny

2014-05-01

Iron-enriched smectites play an important role in adsorption and transformation of soil organic components. Soil organo-clay complexes, and in particular humin contain hydroxy fatty acids, which are derived from plant biopolymer cutin. Phenolic acids belong to another major group of organic acids detected in soil. They participate in various soil processes, and are of concern due to their allelopathic activity. We studied the reactivity of iron-enriched smectites (Fe(III)-montmorillonite and nontronite) toward both groups of acids. We used fatty acids- 9(10),16-dihydroxypalmitic acid (diHPA), isolated from curtin, and 9,10,16-trihydroxypalmitic acid (triHPA); the following phenolic acids were used: ferulic, p-coumaric, syringic, and vanillic. Adsorption of both groups of acids was measured. The FTIR spectra of fatty acid-mineral complexes indicated inner-sphere complexation of fatty acids with iron-enriched smectites (versus outer-sphere complexation with Ca(II)-montmorillonite). The LC-MS results demonstrated enhanced esterification of fatty acids on the iron-enriched smectite surfaces (as compared to Ca(II)-montmorillonite). This study suggests that fatty acids can be esterified on the iron-enriched smectite surfaces, which results in the formation of stable organo-mineral complexes. These complexes may serve as a model for the study of natural soil organo-clay complexes and humin. The reaction of phenolic acids with Fe(III)-montmorillonite demonstrated their oxidative transformation by the mineral surfaces, which was affected by molecular structure of acids. The following order of their transformation was obtained: ferulic >syringic >p-coumaric >vanillic. The LC-MS analysis demonstrated the presence of dimers, trimers, and tetramers of ferulic acid on the surface of Fe(III)-montmorillonite. Oxidation and transformation of ferulic acid were more intense on the surface of Fe(III)-montmorillonite as compared to Fe(III) in solution due to stronger complexation on the Fe(III)-motnomrillonite surface. Our study demonstrate the importance of iron-enriched minerals for the abiotic formation of humic materials and for the transformation of aromatic (phenolic) pollutants.

New Measurements of Doubly Ionized Iron Group Spectra by High Resolution Fourier Transform and Grating Spectroscopy

NASA Technical Reports Server (NTRS)

Smillie, D. G.; Pickering, J. C.; Blackwell-Whitehead, R. J.; Smith, Peter L.; Nave, G.

2006-01-01

We report new measurements of doubly ionized iron group element spectra, important in the analysis of B-type (hot) stars whose spectra they dominate. These measurements include Co III and Cr III taken with the Imperial College VUV Fourier transform (FT) spectrometer and measurements of Co III taken with the normal incidence vacuum spectrograph at NIST, below 135 nm. We report new Fe III grating spectra measurements to complement our FT spectra. Work towards transition wavelengths, energy levels and branching ratios (which, combined with lifetimes, produce oscillator strengths) for these ions is underway.

Metal interferences and their removal prior to the determination of As(T) and As(III) in acid mine waters by hydride generation atomic absorption spectrometry

USGS Publications Warehouse

McCleskey, R. Blaine; Nordstrom, D. Kirk; Ball, James W.

2003-01-01

Hydride generation atomic absorption spectrometry (HGAAS) is a sensitive and selective method for the determination of total arsenic (arsenic(III) plus arsenic(V)) and arsenic(III); however, it is subject to metal interferences for acid mine waters. Sodium borohydride is used to produce arsine gas, but high metal concentrations can suppress arsine production. This report investigates interferences of sixteen metal species including aluminum, antimony(III), antimony(V), cadmium, chromium(III), chromium(IV), cobalt, copper(II), iron(III), iron(II), lead, manganese, nickel, selenium(IV), selenium(VI), and zinc ranging in concentration from 0 to 1,000 milligrams per liter and offers a method for removing interfering metal cations with cation exchange resin. The degree of interference for each metal without cation-exchange on the determination of total arsenic and arsenic(III) was evaluated by spiking synthetic samples containing arsenic(III) and arsenic(V) with the potential interfering metal. Total arsenic recoveries ranged from 92 to 102 percent for all metals tested except antimony(III) and antimony(V) which suppressed arsine formation when the antimony(III)/total arsenic molar ratio exceeded 4 or the antimony(V)/total arsenic molar ratio exceeded 2. Arsenic(III) recoveries for samples spiked with aluminum, chromium(III), cobalt, iron(II), lead, manganese, nickel, selenium(VI), and zinc ranged from 84 to 107 percent over the entire concentration range tested. Low arsenic(III) recoveries occurred when the molar ratios of metals to arsenic(III) were copper greater than 120, iron(III) greater than 70, chromium(VI) greater than 2, cadmium greater than 800, antimony(III) greater than 3, antimony(V) greater than 12, or selenium(IV) greater than 1. Low recoveries result when interfering metals compete for available sodium borohydride, causing incomplete arsine production, or when the interfering metal oxidizes arsenic(III). Separation of interfering metal cations using cation-exchange prior to hydridegeneration permits accurate arsenic(III) determinations in acid mine waters containing high concentrations of interfering metals. Stabilization of the arsenic redox species for as many as 15 months is demonstrated for samples that have been properly filtered and acidified with HCl in the field. The detection limits for the method described in this report are 0.1 micrograms per liter for total arsenic and 0.8 micrograms per liter for arsenic(III).

Amphorous hydrated Fe(III) sulfate: metastable product and bio-geochemical marker of iron oxidizing thiobacilli

NASA Astrophysics Data System (ADS)

Lazaroff, Norman; Jollie, John; Dugan, Patrick R.

1998-07-01

Chemolithotrophic iron oxidation by Thiobacillus ferrooxidans and other iron oxidizing thiobacilli produce an Fe(III) sulfato complex that polymerizes as x-ray amorphous filaments approximately 40 nm in diameter. The precursor complex in solutionis seen by ATR-FTIR spectroscopy to have a sulfate spectrum resembling the v(subscript 3) and v(subscript 1) vibrational modes of the precipitated polymer. Chemically similar precipitates prepared by oxidation of acid ferrous sulfate with hydrogen peroxide have a different micromorphology, higher iron/sulfur ratio and acid solubility than the bacterial product. They possess coalescing globular microstructures composed of compacted micro-fibrils. Scanning electron microscopy and diffuse reflectance FTIR show the formation of iron polymer on the surface of immobilized cells of T. ferrooxidans, oxidizing iron during the corrosion of steel. Although spatially separated form the steel coupons by a membrane filter, the cell walls become covered with tufts of amorphous hydrated Fe(III) sulfate. The metastable polymer is converted to crystalline goethite, lepidocrocite, and magnetite in that order, as the pH rises due to proton reduction at cathodic sites on the steel. The instability of the iron polymer to changes in pH is also evidenced by the loss of sulfate when washed with lithium hydroxide solution at pH 8. Under those conditions there is little change in micromorphology, but restoration of sulfate with sulfuric acid at pH 2.5, fails to re-establish the original chemical structure. Adding sulfate salts of appropriate cations to solutions of the Fe(III) sulfato complex or suspensions of its precipitated polymer in dilute sulfuric acid, result in dissociation of the metastable complex followed by crystallization of ferric ions and sulfate in jarosites. Jarosites and other derivatives of iron precipitation by iron oxidizing thiobacilli, form conspicuous deposits in areas of natural pyrite leaching. The role of iron oxidizing thiobacilli in pyrite leaching, biohydrometallurgy, acid mine drainage, and the cycle of iron and sulfur in nature, has been studied for nearly 50 years. The manifestation of those activities, so widespread on Earth, can be a clue for seeking evidence of life elsewhere.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beam, Jake; Bernstein, Hans C.; Jay, Z.

Iron oxide microbial mats are ubiquitous geobiological features on Earth and occur in extant acidic hot springs of Yellowstone National Park (YNP), WY, USA, and form as a result of microbial processes. The relative contribution of different organisms to the development of these mat ecosystems is of specific interest. We hypothesized that chemolithoautotrophic organisms contribute to the early development and production of Fe(III)-oxide mats, which could support later-colonizing heterotrophic microorganisms. Sterile glass slides were incubated in the outflow channels of two acidic geothermal springs in YNP, and spatiotemporal changes in Fe(III)-oxide accretion and abundance of relevant community members were measured.more » Lithoautotrophic Hydrogenobaculum spp. were first colonizers and the most abundant taxa identified during early successional stages (7 – 40 days). Populations of M. yellowstonensis colonized after ~ 7 days, corresponding to visible Fe(III)-oxide accretion. Heterotrophic archaea colonized after 30 days, and emerge as the dominant functional guild in mature iron oxide mats (1 – 2 cm thick) that form after 70 – 120 days. First-order rate constants of iron oxide accretion ranged from 0.05 – 0.046 day-1, and reflected the absolute amount of iron accreted. Micro- and macroscale microterracettes were identified during iron oxide mat development, and suggest that the mass transfer of oxygen limits microbial growth. This was also demonstrated using microelectrode measurements of oxygen as a function of mat depth, which showed steep gradients in oxygen from the aqueous mat interface to ~ 1 mm. The formation and succession of amorphous Fe(III)-oxide mat communities follows a predictable pattern of distinct stages and growth. The successional stages and microbial signatures observed in these extant Fe(III)-oxide mat communities may be relevant to other past or present Fe(III)-oxide mineralizing systems.« less

Oxidation and deprotonation of synthetic Fe{sup II}-Fe{sup III} (oxy)hydroxycarbonate Green Rust: An X-ray photoelectron study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mullet, M.; Guillemin, Y.; Ruby, C.

X-ray photoelectron spectroscopy (XPS) was used to investigate chemical bonding and distribution of iron and oxygen species at the surface of Green Rusts (GRs). GRs with variable composition, i.e. Fe{sup II}{sub 6(1-x)}Fe{sup III}{sub 6x}O{sub 12}H{sub 2(7-3x)} CO{sub 3}.3H{sub 2}O where the Fe{sup III} molar fraction of the positively charged hydroxide sheets, x=[Fe(III)]/[Fe(total)] belongs to [1/3, 1], were synthesised under an inert atmosphere. The broadened Fe(2p{sub 3/2}) spectra were fitted using Gupta and Sen multiplets peaks and additional satellite and surface features. The [Fe(III)]/[Fe(total)] surface atomic ratios closely agree with the x ratios expected from the bulk composition, which gives amore » high degree of confidence on the validity of the proposed fitting procedure. The valence band spectra are also reported and show dependencies on iron speciation. The O(1s) spectra revealed the presence of O{sup 2-}, OH{sup -} species and adsorbed water. The hydroxyl component decreases with increasing x values, i.e. with the amount of ferric iron, while the oxide component increases. This study provides direct spectroscopic evidence of the deprotonation of hydroxyl groups that occurs simultaneously with the oxidation of ferrous iron within the GR structure. - Graphical abstract: X-ray photoelectron spectroscopy (XPS) is used to investigate chemical bonding and distribution of iron and oxygen species at the surface of Green Rust (GR) compounds. First spectroscopic evidence of the deprotonation of hydroxyls groups occurring simultaneously to the oxidation of Fe(II) into Fe(III) species is provided.« less

Low-Fe(III) Greenalite Was a Primary Mineral From Neoarchean Oceans

NASA Astrophysics Data System (ADS)

Johnson, Jena E.; Muhling, Janet R.; Cosmidis, Julie; Rasmussen, Birger; Templeton, Alexis S.

2018-04-01

Banded iron formations (BIFs) represent chemical precipitation from Earth's early oceans and therefore contain insights into ancient marine biogeochemistry. However, BIFs have undergone multiple episodes of alteration, making it difficult to assess the primary mineral assemblage. Nanoscale mineral inclusions from 2.5 billion year old BIFs and ferruginous cherts provide new evidence that iron silicates were primary minerals deposited from the Neoarchean ocean, contrasting sharply with current models for BIF inception. Here we used multiscale imaging and spectroscopic techniques to characterize the best preserved examples of these inclusions. Our integrated results demonstrate that these early minerals were low-Fe(III) greenalite. We present potential pathways in which low-Fe(III) greenalite could have formed through changes in saturation state and/or iron oxidation and reduction. Future constraints for ancient ocean chemistry and early life's activities should include low-Fe(III) greenalite as a primary mineral in the Neoarchean ocean.

Hydroquinone-Mediated Redox Cycling of Iron and Concomitant Oxidation of Hydroquinone in Oxic Waters under Acidic Conditions: Comparison with Iron-Natural Organic Matter Interactions.

PubMed

Jiang, Chao; Garg, Shikha; Waite, T David

2015-12-15

Interactions of 1,4-hydroquinone with soluble iron species over a pH range of 3-5 in the air-saturated and partially deoxygenated solution are examined here. Our results show that 1,4-hydroquinone reduces Fe(III) in acidic conditions, generating semiquinone radicals (Q(•-)) that can oxidize Fe(II) back to Fe(III). The oxidation rate of Fe(II) by Q(•-)increases with increase in pH due to the speciation change of Q(•-) with its deprotonated form (Q(•-)) oxidizing Fe(II) more rapidly than the protonated form (HQ(•)). Although the oxygenation of Fe(II) is negligible at pH < 5, O2 still plays an important role in iron redox transformation by rapidly oxidizing Q(•-) to form benzoquinone (Q). A kinetic model is developed to describe the transformation of quinone and iron under all experimental conditions. The results obtained here are compared with those obtained in our previous studies of iron-Suwannee River fulvic acid (SRFA) interactions in acidic solutions and support the hypothesis that hydroquinone moieties can reduce Fe(III) in natural waters. However, the semiquinone radicals generated in pure hydroquinone solution are rapidly oxidized by dioxygen, while the semiquinone radicals generated in SRFA solution are resistant to oxidation by dioxygen, with the result that steady-state semiquinone concentrations in SRFA solutions are 2-3 orders of magnitude greater than in solutions of 1,4-hydroquinone. As a result, semiquinone moieties in SRFA play a much more important role in iron redox transformations than is the case in solutions of simple quinones such as 1,4-hydroquinone. This difference in the steady-state concentration of semiquinone species has a dramatic effect on the cycling of iron between the +II and +III oxidation states, with iron turnover frequencies in solutions containing SRFA being 10-20 times higher than those observed in solutions of 1,4-hydroquinone.

Vivianite as an important iron phosphate precipitate in sewage treatment plants.

PubMed

Wilfert, P; Mandalidis, A; Dugulan, A I; Goubitz, K; Korving, L; Temmink, H; Witkamp, G J; Van Loosdrecht, M C M

2016-11-01

Iron is an important element for modern sewage treatment, inter alia to remove phosphorus from sewage. However, phosphorus recovery from iron phosphorus containing sewage sludge, without incineration, is not yet economical. We believe, increasing the knowledge about iron-phosphorus speciation in sewage sludge can help to identify new routes for phosphorus recovery. Surplus and digested sludge of two sewage treatment plants was investigated. The plants relied either solely on iron based phosphorus removal or on biological phosphorus removal supported by iron dosing. Mössbauer spectroscopy showed that vivianite and pyrite were the dominating iron compounds in the surplus and anaerobically digested sludge solids in both plants. Mössbauer spectroscopy and XRD suggested that vivianite bound phosphorus made up between 10 and 30% (in the plant relying mainly on biological removal) and between 40 and 50% of total phosphorus (in the plant that relies on iron based phosphorus removal). Furthermore, Mössbauer spectroscopy indicated that none of the samples contained a significant amount of Fe(III), even though aerated treatment stages existed and although besides Fe(II) also Fe(III) was dosed. We hypothesize that chemical/microbial Fe(III) reduction in the treatment lines is relatively quick and triggers vivianite formation. Once formed, vivianite may endure oxygenated treatment zones due to slow oxidation kinetics and due to oxygen diffusion limitations into sludge flocs. These results indicate that vivianite is the major iron phosphorus compound in sewage treatment plants with moderate iron dosing. We hypothesize that vivianite is dominating in most plants where iron is dosed for phosphorus removal which could offer new routes for phosphorus recovery. Copyright © 2016 Elsevier Ltd. All rights reserved.

Salicylate Detection by Complexation with Iron(III) and Optical Absorbance Spectroscopy: An Undergraduate Quantitative Analysis Experiment

ERIC Educational Resources Information Center

Mitchell-Koch, Jeremy T.; Reid, Kendra R.; Meyerhoff, Mark E.

2008-01-01

An experiment for the undergraduate quantitative analysis laboratory involving applications of visible spectrophotometry is described. Salicylate, a component found in several medications, as well as the active by-product of aspirin decomposition, is quantified. The addition of excess iron(III) to a solution of salicylate generates a deeply…

Bacterial iron transport: coordination properties of azotobactin, the highly fluorescent siderophore of Azotobacter vinelandii.

PubMed

Palanché, Tania; Blanc, Sylvie; Hennard, Christophe; Abdallah, Mohamed A; Albrecht-Gary, Anne-Marie

2004-02-09

Azotobacter vinelandii, a nitrogen-fixing soil bacterium, secretes in iron deficiency azotobactin delta, a highly fluorescent pyoverdin-like chromopeptidic hexadentate siderophore. The chromophore, derived from 2,3-diamino-6,7 dihydroxyquinoline, is bound to a peptide chain of 10 amino acids: (L)-Asp-(D)-Ser-(L)-Hse-Gly-(D)-beta-threo-HOAsp-(L)-Ser-(D)-Cit-(L)-Hse-(L)-Hse lactone-(D)-N(delta)-Acetyl, N(delta)-HOOrn. Azotobactin delta has three different iron(III) binding sites which are one hydroxamate group at the C-terminal end of the peptidic chain (N(delta)-Acetyl, N(delta)-HOOrn), one alpha-hydroxycarboxylic function in the middle of the chain (beta-threo-hydroxyaspartic acid), and one catechol group on the chromophore. The coordination properties of its iron(III) and iron(II) complexes were measured by spectrophotometry, potentiometry, and voltammetry after the determination of the acid-base functions of the uncomplexed free siderophore. Strongly negatively charged ferric species were observed at neutral p[H]'s corresponding to a predominant absolute configuration Lambda of the ferric complex in solution as deduced from CD measurements. The presence of an alpha-hydroxycarboxylic chelating group does not decrease the stability of the iron(III) complex when compared to the main trishydroxamate siderophores or to pyoverdins. The value of the redox potential of ferric azotobactin is highly consistent with a reductive step by physiological reductants for the iron release. Formation and dissociation kinetics of the azotobactin delta ferric complex point out that both ends of this long siderophore chain get coordinated to Fe(III) before the middle. The most striking result provided by fluorescence measurements is the lasting quenching of the fluorophore in the course of the protonation of the ferric azotobactin delta complex. Despite the release of the hydroxyacid and of the catechol, the fluorescence remains indeed quenched, when iron(III) is bound only to the hydroxamic acid, suggesting a folded conformation at this stage, around the metal ion, in contrast to the unfolded species observed for other siderophores such as ferrioxamine or pyoverdin PaA.

High-efficiency emitting materials based on phenylquinoline/carbazole-based compounds for organic light emitting diode applications

NASA Astrophysics Data System (ADS)

Jin, Sung-Ho

2009-08-01

Highly efficient light-emitting materials based on phenylquinoline-carbazole derivative has been synthesized for organic-light emitting diodes (OLEDs). The materials form high quality amorphous thin films by thermal evaporation and the energy levels can be easily adjusted by the introduction of different electron donating and electron withdrawing groups on carbazoylphenylquinoline. Non-doped deep-blue OLEDs using Et-CVz-PhQ as the emitter show bright emission (CIE coordinates, x=0.156, y=0.093) with an external quantum efficiency of 2.45 %. Furthermore, the material works as an excellent host material for BCzVBi to get high-performance OLEDs with excellent deep-blue CIE coordinates (x=0.155, y=0.157), high power efficiency (5.98 lm/W), and high external quantum efficiency (5.22 %). Cyclometalated Ir(III) μ-chloride bridged dimers were synthesized by iridium trichloride hydrate with an excess of our developed deep-blue emitter, Et-CVz-PhQ. The Ir(III) complexes were prepared by the dimers with the corresponding ancillary ligands. The chloride bridged diiridium complexes can be easily converted to mononuclear Ir(III) complexes by replacing the two bridging chlorides with bidentate monoanionic ancillary ligands. Among the various types of ancillary ligands, we firstly used picolinic acid N-oxide, including picolinic acid and acetylacetone as an ancillary ligands for Ir(III) complexes. The PhOLEDs also shows reasonably high brightness and good luminance efficiency of 20,000 cd/m2 and 12 cd/A, respectively.

Radiative rates for forbidden M1 and E2 transitions of astrophysical interest in doubly ionized iron-peak elements

NASA Astrophysics Data System (ADS)

Fivet, V.; Quinet, P.; Bautista, M. A.

2016-01-01

Aims: Accurate and reliable atomic data for lowly ionized Fe-peak species (Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) are of paramount importance for analyzing the high-resolution astrophysical spectra currently available. The third spectra of several iron group elements have been observed in different galactic sources, such as Herbig-Haro objects in the Orion Nebula and stars like Eta Carinae. However, forbidden M1 and E2 transitions between low-lying metastable levels of doubly charged iron-peak ions have been investigated very little so far, and radiative rates for those lines remain sparse or nonexistent. We attempt to fill that gap and provide transition probabilities for the most important forbidden lines of all doubly ionized iron-peak elements. Methods: We carried out a systematic study of the electronic structure of doubly ionized Fe-peak species. The magnetic dipole (M1) and electric quadrupole (E2) transition probabilities were computed using the pseudo-relativistic Hartree-Fock (HFR) code of Cowan and the central Thomas-Fermi-Dirac-Amaldi potential approximation implemented in AUTOSTRUCTURE. This multiplatform approach allowed for consistency checks and intercomparison and has proven very useful in many previous works for estimating the uncertainties affecting the radiative data. Results: We present transition probabilities for the M1 and E2 forbidden lines depopulating the metastable even levels belonging to the 3dk and 3dk-14s configurations in Sc III (k = 1), Ti III (k = 2), V III (k = 3), Cr III (k = 4), Mn III (k = 5), Fe III (k = 6), Co III (k = 7), and Ni III (k = 8).

Synthesis, crystal structure and magnetic properties of a novel tetranuclear oxo-bridged iron(III) butterfly

NASA Astrophysics Data System (ADS)

Arizaga, Livia; Gancheff, Jorge S.; Faccio, Ricardo; Cañón-Mancisidor, Walter; González, Ricardo; Kremer, Carlos; Chiozzone, Raúl

2014-01-01

A novel carboxylate/picolinate oxo-bridged iron(III) cluster, namely [Na2(H2O)8][Fe4(μ-O)2(O2CPh)7(pic)2]2·2H2O (1) where pic = picolinate, has been obtained by reacting "basic iron benzoate" [Fe3O(O2CPh)6(H2O)3](O2CPh) with sodium picolinate in acetonitrile. The compound has been characterized by elemental analysis and IR spectroscopy and its crystal structure has been determined by single-crystal X-ray diffraction.

Tetraalykylammonium polyoxoanionic oxidation catalysts

DOEpatents

Ellis, Paul E.; Lyons, James E.; Myers, Jr., Harry K.; Shaikh, Shahid N.

1998-01-01

Alkanes are catalytically oxidized in air or oxygen using iron-substituted polyoxoanions (POAs) of the formula: H.sub.e-z ›(n-C.sub.4 H.sub.9).sub.4 N!.sub.z (XM.sub.11 M'O.sub.39).sup.-e The M' (e.g., iron(III)/iron(II)) reduction potential of the POAs is affected by selection of the central atom X and the framework metal M, and by the number of tetrabutyl-ammonium groups. Decreased Fe(III)/Fe(II) reduction potential has been found to correlate to increased oxidation activity.

Tetraalklylammonium polyoxoanionic oxidation catalysts

DOEpatents

Ellis, P.E.; Lyons, J.E.; Myers, H.K. Jr.; Shaikh, S.N.

1998-10-06

Alkanes are catalytically oxidized in air or oxygen using iron-substituted polyoxoanions (POAs) of the formula: H{sub e{minus}z}[(n-C{sub 4}H{sub 9}){sub 4}N]{sub z}(XM{sub 11}M{prime}O{sub 39}){sup {minus}e}. The M{prime} (e.g., iron(III)/iron(II)) reduction potential of the POAs is affected by selection of the central atom X and the framework metal M, and by the number of tetrabutyl-ammonium groups. Decreased Fe(III)/Fe(II) reduction potential has been found to correlate to increased oxidation activity.

Preparation and characterization of Fe3O4-Pt nanoparticles

NASA Astrophysics Data System (ADS)

Andrade, Ângela Leão; Cavalcante, Luis Carlos Duarte; Fabris, José Domingos; Pereira, Márcio César; Ardisson, José Domingos; Domingues, Rosana Zacarias

2017-11-01

Pt and Pt-based nanomaterials are active anticancer drugs for their ability to inhibit the division of living cells. Nanoparticles of magnetite containing variable proportions of platinum were prepared in the laboratory. The magnetite nanoparticles with platinum (Pt-Fe3O4) were obtained by reducing the Fe3+ of the maghemite ( γ Fe2O3) mixed with platinum (II) acetylacetonate and sucrose in two inversely coupled ceramic crucibles and heated in a furnace at 400 °C for 20 min. The formed carbon during this preparation acts to chemically reduce the ferric iron in maghemite. Moreover, its residual layer on the particle surface prevents the forming magnetite from oxidizing in air and helps retain the platinum in the solid mixture. The produced Pt-magnetite samples were characterized by 57Fe-Mössbauer spectroscopy, powder X-ray diffraction, scanning electron microscopy, and magnetization measurements. Measurements of AC magnetic-field-induced heating properties of the obtained nanocomposites, in aqueous solution, showed that they are suitable as a hyperthermia agent for biological applications.

Synthesis and Characterization of Biodegradable Polyurethane for Hypopharyngeal Tissue Engineering

PubMed Central

Shen, Zhisen; Lu, Dakai; Li, Qun; Zhang, Zongyong

2015-01-01

Biodegradable crosslinked polyurethane (cPU) was synthesized using polyethylene glycol (PEG), L-lactide (L-LA), and hexamethylene diisocyanate (HDI), with iron acetylacetonate (Fe(acac)3) as the catalyst and PEG as the extender. Chemical components of the obtained polymers were characterized by FTIR spectroscopy, 1H NMR spectra, and Gel Permeation Chromatography (GPC). The thermodynamic properties, mechanical behaviors, surface hydrophilicity, degradability, and cytotoxicity were tested via differential scanning calorimetry (DSC), tensile tests, contact angle measurements, and cell culture. The results show that the synthesized cPU possessed good flexibility with quite low glass transition temperature (T g, −22°C) and good wettability. Water uptake measured as high as 229.7 ± 18.7%. These properties make cPU a good candidate material for engineering soft tissues such as the hypopharynx. In vitro and in vivo tests showed that cPU has the ability to support the growth of human hypopharyngeal fibroblasts and angiogenesis was observed around cPU after it was implanted subcutaneously in SD rats. PMID:25839041

Synthesis and characterization of biodegradable polyurethane for hypopharyngeal tissue engineering.

PubMed

Shen, Zhisen; Lu, Dakai; Li, Qun; Zhang, Zongyong; Zhu, Yabin

2015-01-01

Biodegradable crosslinked polyurethane (cPU) was synthesized using polyethylene glycol (PEG), L-lactide (L-LA), and hexamethylene diisocyanate (HDI), with iron acetylacetonate (Fe(acac)3) as the catalyst and PEG as the extender. Chemical components of the obtained polymers were characterized by FTIR spectroscopy, (1)H NMR spectra, and Gel Permeation Chromatography (GPC). The thermodynamic properties, mechanical behaviors, surface hydrophilicity, degradability, and cytotoxicity were tested via differential scanning calorimetry (DSC), tensile tests, contact angle measurements, and cell culture. The results show that the synthesized cPU possessed good flexibility with quite low glass transition temperature (T g , -22°C) and good wettability. Water uptake measured as high as 229.7 ± 18.7%. These properties make cPU a good candidate material for engineering soft tissues such as the hypopharynx. In vitro and in vivo tests showed that cPU has the ability to support the growth of human hypopharyngeal fibroblasts and angiogenesis was observed around cPU after it was implanted subcutaneously in SD rats.

Geobacter bemidjiensis sp. nov. and Geobacter psychrophilus sp. nov., two novel Fe(III)-reducing subsurface isolates

USGS Publications Warehouse

Nevin, Kelly P.; Holmes, Dawn E.; Woodard, Trevor L.; Hinlein, Erich S.; Ostendorf, David W.; Lovely, Derek R.

2005-01-01

Fe(III)-reducing isolates were recovered from two aquifers in which Fe(III) reduction is known to be important. Strain BemT was enriched from subsurface sediments collected in Bemidji, MN, USA, near a site where Fe(III) reduction is important in aromatic hydrocarbon degradation. Strains P11, P35T and P39 were isolated from the groundwater of an aquifer in Plymouth, MA, USA, in which Fe(III) reduction is important because of long-term inputs of acetate as a highway de-icing agent to the subsurface. All four isolates were Gram-negative, slightly curved rods that grew best in freshwater media. Strains P11, P35T and P39 exhibited motility via means of monotrichous flagella. Analysis of the 16S rRNA and nifD genes indicated that all four strains are δ-proteobacteria and members of the Geobacter cluster of the Geobacteraceae. Differences in phenotypic and phylogenetic characteristics indicated that the four isolates represent two novel species within the genus Geobacter. All of the isolates coupled the oxidation of acetate to the reduction of Fe(III) [iron(III) citrate, amorphous iron(III) oxide, iron(III) pyrophosphate and iron(III) nitrilotriacetate]. All four strains utilized ethanol, lactate, malate, pyruvate and succinate as electron donors and malate and fumarate as electron acceptors. Strain BemT grew fastest at 30 °C, whereas strains P11, P35T and P39 grew equally well at 17, 22 and 30 °C. In addition, strains P11, P35T and P39 were capable of growth at 4 °C. The names Geobacter bemidjiensis sp. nov. (type strain BemT=ATCC BAA-1014T=DSM 16622T=JCM 12645T) and Geobacter psychrophilus sp. nov. (strains P11, P35T and P39; type strain P35T=ATCC BAA-1013T=DSM 16674T=JCM 12644T) are proposed.

Spectroscopic and Computational Investigation of Iron(III) Cysteine Dioxygenase: Implications for the Nature of the Putative Superoxo-Fe(III) Intermediate

PubMed Central

2015-01-01

Cysteine dioxygenase (CDO) is a mononuclear, non-heme iron-dependent enzyme that converts exogenous cysteine (Cys) to cysteine sulfinic acid using molecular oxygen. Although the complete catalytic mechanism is not yet known, several recent reports presented evidence for an Fe(III)-superoxo reaction intermediate. In this work, we have utilized spectroscopic and computational methods to investigate the as-isolated forms of CDO, as well as Cys-bound Fe(III)CDO, both in the absence and presence of azide (a mimic of superoxide). An analysis of our electronic absorption, magnetic circular dichroism, and electron paramagnetic resonance data of the azide-treated as-isolated forms of CDO within the framework of density functional theory (DFT) computations reveals that azide coordinates directly to the Fe(III), but not the Fe(II) center. An analogous analysis carried out for Cys-Fe(III)CDO provides compelling evidence that at physiological pH, the iron center is six coordinate, with hydroxide occupying the sixth coordination site. Upon incubation of this species with azide, the majority of the active sites retain hydroxide at the iron center. Nonetheless, a modest perturbation of the electronic structure of the Fe(III) center is observed, indicating that azide ions bind near the active site. Additionally, for a small fraction of active sites, azide displaces hydroxide and coordinates directly to the Cys-bound Fe(III) center to generate a low-spin (S = 1/2) Fe(III) complex. In the DFT-optimized structure of this complex, the central nitrogen atom of the azide moiety lies within 3.12 Å of the cysteine sulfur. A similar orientation of the superoxide ligand in the putative Fe(III)-superoxo reaction intermediate would promote the attack of the distal oxygen atom on the sulfur of substrate Cys. PMID:25093959

On the structure and spin states of Fe(III)-EDDHA complexes.

PubMed

Gómez-Gallego, Mar; Fernández, Israel; Pellico, Daniel; Gutiérrez, Angel; Sierra, Miguel A; Lucena, Juan J

2006-07-10

DFT methods are suitable for predicting both the geometries and spin states of EDDHA-Fe(III) complexes. Thus, extensive DFT computational studies have shown that the racemic-Fe(III) EDDHA complex is more stable than the meso isomer, regardless of the spin state of the central iron atom. A comparison of the energy values obtained for the complexes under study has also shown that high-spin (S = 5/2) complexes are more stable than low-spin (S = 1/2) ones. These computational results matched the experimental results of the magnetic susceptibility values of both isomers. In both cases, their behavior has been fitted as being due to isolated high-spin Fe(III) in a distorted octahedral environment. The study of the correlation diagram also confirms the high-spin iron in complex 2b. The geometry optimization of these complexes performed with the standard 3-21G* basis set for hydrogen, carbon, oxygen, and nitrogen and the Hay-Wadt small-core effective core potential (ECP) including a double-xi valence basis set for iron, followed by single-point energy refinement with the 6-31G* basis set, is suitable for predicting both the geometries and the spin-states of EDDHA-Fe(III) complexes. The presence of a high-spin iron in Fe(III)-EDDHA complexes could be the key to understanding their lack of reactivity in electron-transfer processes, either chemically or electrochemically induced, and their resistance to photodegradation.

The long term tsunami impact: Evolution of iron speciation and major elements concentration in tsunami deposits from Thailand.

PubMed

Kozak, Lidia; Niedzielski, Przemyslaw

2017-08-01

The article describes the unique studies of the chemical composition changes of new geological object (tsunami deposits in south Thailand - Andaman Sea Coast) during four years (2005-2008) from the beginning of formation of it (deposition of tsunami transported material, 26 December 2004). The chemical composition of the acid leachable fraction of the tsunami deposits has been studied in the scope of concentration macrocompounds - concentration of calcium, magnesium, iron, manganese and iron speciation - the occurrence of Fe(II), Fe(III) and non-ionic iron species described as complexed iron (Fe complex). The changes of chemical composition and iron speciation in the acid leachable fraction of tsunami deposits have been observed with not clear tendencies of changes direction. For iron speciation changes the transformation of the Fe complex to Fe(III) has been recorded with no significant changes of the level of Fe(II). Copyright © 2017 Elsevier Ltd. All rights reserved.

Iron ion and iron hydroxide adsorption to charge-neutral phosphatidylcholine templates

DOE PAGES

Wang, Wenjie; Zhang, Honghu; Feng, Shuren; ...

2016-07-13

Surface-sensitive X-ray scattering and spectroscopy techniques reveal significant adsorption of iron ions and iron-hydroxide (Fe(III)) complexes to a charge-neutral zwitterionic template of phosphatidylcholine (PC). The PC template is formed by a Langmuir monolayer of dipalmitoyl-PC (DPPC) that is spread on the surface of 2 to 40 μM FeCl 3 solutions at physiological levels of KCl (100 mM). At 40 μM of Fe(III) as many as ~3 iron atoms are associated with each PC group. Grazing incidence X-ray diffraction measurements indicate a significant disruption in the in-plane ordering of DPPC molecules upon iron adsorption. The binding of iron-hydroxide complexes to amore » neutral PC surface is yet another example of nonelectrostatic, presumably covalent bonding to a charge-neutral organic template. Furthermore, the strong binding and the disruption of in-plane lipid structure has biological implications on the integrity of PC-derived lipid membranes, including those based on sphingomyelin.« less

Optimation and Determination of Fe-Oxinate Complex by Using High Performance Liquid Chromatography

NASA Astrophysics Data System (ADS)

Oktavia, B.; Nasra, E.; Sary, R. C.

2018-04-01

The need for iron will improve the industrial processes that require iron as its raw material. Control of industrial iron waste is very important to do. One method of iron analysis is to conduct indirect analysis of iron (III) ions by complexing with 8-Hydroxyquinoline or oxine. In this research, qualitative and quantitative tests of iron (III) ions in the form of complex with oxine. The analysis was performed using HPLC at a wavelength of 470 nm with an ODS C18 column. Three methods of analysis were performed: 1) Fe-oxinate complexes were prepared in an ethanol solvent so no need for separation anymore, (2) Fe-oxinate complexes were made in chloroform so that a solvent extraction was required before the complex was injected into the column while the third complex was formed in the column, wherein the eluent contains the oxide and the metal ions are then injected. The resulting chromatogram shows that the 3rd way provides a better chromatogram for iron analysis.

Iron specificity of a biosensor based on fluorescent pyoverdin immobilized in sol-gel glass

PubMed Central

2011-01-01

Two current technologies used in biosensor development are very promising: 1. The sol-gel process of making microporous glass at room temperature, and 2. Using a fluorescent compound that undergoes fluorescence quenching in response to a specific analyte. These technologies have been combined to produce an iron biosensor. To optimize the iron (II or III) specificity of an iron biosensor, pyoverdin (a fluorescent siderophore produced by Pseudomonas spp.) was immobilized in 3 formulations of porous sol-gel glass. The formulations, A, B, and C, varied in the amount of water added, resulting in respective R values (molar ratio of water:silicon) of 5.6, 8.2, and 10.8. Pyoverdin-doped sol-gel pellets were placed in a flow cell in a fluorometer and the fluorescence quenching was measured as pellets were exposed to 0.28 - 0.56 mM iron (II or III). After 10 minutes of exposure to iron, ferrous ion caused a small fluorescence quenching (89 - 97% of the initial fluorescence, over the range of iron tested) while ferric ion caused much greater quenching (65 - 88%). The most specific and linear response was observed for pyoverdin immobilized in sol-gel C. In contrast, a solution of pyoverdin (3.0 μM) exposed to iron (II or III) for 10 minutes showed an increase in fluorescence (101 - 114%) at low ferrous concentrations (0.45 - 2.18 μM) while exposure to all ferric ion concentrations (0.45 - 3.03 μM) caused quenching. In summary, the iron specificity of pyoverdin was improved by immobilizing it in sol-gel glass C. PMID:21554740

Changes in iron, sulfur, and arsenic speciation associated with bacterial sulfate reduction in ferrihydrite-rich systems.

PubMed

Saalfield, Samantha L; Bostick, Benjamin C

2009-12-01

Biologically mediated redox processes have been shown to affect the mobility of iron oxide-bound arsenic in reducing aquifers. This work investigates how dissimilatory sulfate reduction and secondary iron reduction affect sulfur, iron, and arsenic speciation. Incubation experiments were conducted with As(III/V)-bearing ferrihydrite in carbonate-buffered artificial groundwater enriched with lactate (10 mM) and sulfate (0.08-10 mM) and inoculated with Desulfovibrio vulgaris (ATCC 7757, formerly D. desulfuricans), which reduces sulfate but not iron or arsenic. Sulfidization of ferrihydrite led to formation of magnetite, elemental sulfur, and trace iron sulfides. Observed reaction rates imply that the majority of sulfide is recycled to sulfate, promoting microbial sulfate reduction in low-sulfate systems. Despite dramatic changes in Fe and S speciation, and minimal formation of Fe or As sulfides, most As remained in the solid phase. Arsenic was not solubilized in As(V)-loaded incubations, which experienced slow As reduction by sulfide, whereas As(III)-loaded incubations showed limited and transient As release associated with iron remineralization. This suggests that As(III) production is critical to As release under reducing conditions, with sulfate reduction alone unlikely to release As. These data also suggest that bacterial reduction of As(V) is necessary for As sequestration in sulfides, even where sulfate reduction is active.

Effect of dissolved ozone or ferric ions on photodegradation of thiacloprid in presence of different TiO2 catalysts.

PubMed

Cernigoj, Urh; Stangar, Urska Lavrencic; Jirkovský, Jaromír

2010-05-15

Combining TiO(2) photocatalysis with inorganic oxidants (such as O(3) and H(2)O(2)) or transition metal ions (Fe(3+), Cu(2+) and Ag(+)) often leads to a synergic effect. Electron transfer between TiO(2) and the oxidant is usually involved. Accordingly, the degree of synergy could be influenced by TiO(2) surface area. With this in mind, the disappearance of thiacloprid, a neonicotinoid insecticide, was studied applying various photochemical AOPs and different TiO(2) photocatalysts. In photocatalytic ozonation experiments, synergic effect of three different TiO(2) photocatalysts was quantified. Higher surface area resulted in a more pronounced synergic effect but an increasing amount of TiO(2) did not influence the degree of the synergy. This supports the theory that the synergy is a consequence of adsorption of ozone on the TiO(2) surface. No synergy was observed in photocatalytic degradation of thiacloprid in the presence of dissolved iron(III) species performed under varied experimental conditions (concentration, age of iron(III) solution, different TiO(2) films, usage of TiO(2) slurries). This goes against the literature for different organic compounds (i.e., monuron). It indicates different roles of iron(III) in the photodegradation of different organic molecules. Moreover, TiO(2) surface area did not affect photodegradation efficiency in iron(III)-based experiments which could confirm absence of electron transfer between TiO(2) photocatalyst and iron(III). Copyright (c) 2009 Elsevier B.V. All rights reserved.

Iron persistence in a distal hydrothermal plume supported by dissolved-particulate exchange

NASA Astrophysics Data System (ADS)

Fitzsimmons, Jessica N.; John, Seth G.; Marsay, Christopher M.; Hoffman, Colleen L.; Nicholas, Sarah L.; Toner, Brandy M.; German, Christopher R.; Sherrell, Robert M.

2017-02-01

Hydrothermally sourced dissolved metals have been recorded in all ocean basins. In the oceans' largest known hydrothermal plume, extending westwards across the Pacific from the Southern East Pacific Rise, dissolved iron and manganese were shown by the GEOTRACES program to be transported halfway across the Pacific. Here, we report that particulate iron and manganese in the same plume also exceed background concentrations, even 4,000 km from the vent source. Both dissolved and particulate iron deepen by more than 350 m relative to 3He--a non-reactive tracer of hydrothermal input--crossing isopycnals. Manganese shows no similar descent. Individual plume particle analyses indicate that particulate iron occurs within low-density organic matrices, consistent with its slow sinking rate of 5-10 m yr-1. Chemical speciation and isotopic composition analyses reveal that particulate iron consists of Fe(III) oxyhydroxides, whereas dissolved iron consists of nanoparticulate Fe(III) oxyhydroxides and an organically complexed iron phase. The descent of plume-dissolved iron is best explained by reversible exchange onto slowly sinking particles, probably mediated by organic compounds binding iron. We suggest that in ocean regimes with high particulate iron loadings, dissolved iron fluxes may depend on the balance between stabilization in the dissolved phase and the reversibility of exchange onto sinking particles.

As(III) and As(V) sorption on iron-modified non-pyrolyzed and pyrolyzed biomass from Petroselinum crispum (parsley).

PubMed

Jiménez-Cedillo, M J; Olguín, M T; Fall, C; Colin-Cruz, A

2013-03-15

The sorption of As(III) and As(V) from aqueous solutions onto iron-modified Petroselinum crispum (PCFe) and iron-modified carbonaceous material from the pyrolysis of P. crispum (PCTTFe) was investigated. The modified sorbents were characterized with scanning electron microscopy. The sorbent elemental composition was determined with energy-dispersive X-ray spectroscopy (EDS). The principal functional groups from the sorbents were determined with FT-IR. The specific surfaces and points of zero charge (pzc) of the materials were also determined. As(III) and As(V) sorption onto the modified sorbents were performed in a batch system. After the sorption process, the As content in the liquid and solid phases was determined with atomic absorption and neutron activation analyses, respectively. After the arsenic sorption processes, the desorption of Fe from PCFe and PCTTFe was verified with atomic absorption spectrometry. The morphology of PC changed after iron modification. The specific area and pzc differed significantly between the iron-modified non-pyrolyzed and pyrolyzed P. crispum. The kinetics of the arsenite and arsenate sorption processes were described with a pseudo-second-order model. The Langmuir-Freundlich model provided the isotherms with the best fit. Less than 0.02% of the Fe was desorbed from the PCFe and PCTTFe after the As(III) and As(V) sorption processes. Copyright © 2013 Elsevier Ltd. All rights reserved.

Malfunctioning of the iron-sulfur cluster assembly machinery in Saccharomyces cerevisiae produces oxidative stress via an iron-dependent mechanism, causing dysfunction in respiratory complexes.

PubMed

Gomez, Mauricio; Pérez-Gallardo, Rocío V; Sánchez, Luis A; Díaz-Pérez, Alma L; Cortés-Rojo, Christian; Meza Carmen, Victor; Saavedra-Molina, Alfredo; Lara-Romero, Javier; Jiménez-Sandoval, Sergio; Rodríguez, Francisco; Rodríguez-Zavala, José S; Campos-García, Jesús

2014-01-01

Biogenesis and recycling of iron-sulfur (Fe-S) clusters play important roles in the iron homeostasis mechanisms involved in mitochondrial function. In Saccharomyces cerevisiae, the Fe-S clusters are assembled into apoproteins by the iron-sulfur cluster machinery (ISC). The aim of the present study was to determine the effects of ISC gene deletion and consequent iron release under oxidative stress conditions on mitochondrial functionality in S. cerevisiae. Reactive oxygen species (ROS) generation, caused by H2O2, menadione, or ethanol, was associated with a loss of iron homeostasis and exacerbated by ISC system dysfunction. ISC mutants showed increased free Fe2+ content, exacerbated by ROS-inducers, causing an increase in ROS, which was decreased by the addition of an iron chelator. Our study suggests that the increment in free Fe2+ associated with ROS generation may have originated from mitochondria, probably Fe-S cluster proteins, under both normal and oxidative stress conditions, suggesting that Fe-S cluster anabolism is affected. Raman spectroscopy analysis and immunoblotting indicated that in mitochondria from SSQ1 and ISA1 mutants, the content of [Fe-S] centers was decreased, as was formation of Rieske protein-dependent supercomplex III2IV2, but this was not observed in the iron-deficient ATX1 and MRS4 mutants. In addition, the activity of complexes II and IV from the electron transport chain (ETC) was impaired or totally abolished in SSQ1 and ISA1 mutants. These results confirm that the ISC system plays important roles in iron homeostasis, ROS stress, and in assembly of supercomplexes III2IV2 and III2IV1, thus affecting the functionality of the respiratory chain.

Mononuclear nonheme iron(III) complexes that show superoxide dismutase-like activity and antioxidant effects against menadione-mediated oxidative stress.

PubMed

Hitomi, Yutaka; Iwamoto, Yuji; Kashida, Akihiro; Kodera, Masahito

2015-05-21

This communication describes the superoxide dismutase (SOD)-like activity of mononuclear iron(III) complexes with pentadentate monocarboxylamido ligands. The SOD activity can be controlled by the electronic nature of the substituent group on the ligand. The nitro-substituted complex showed clear cytoprotective activity against menadione-mediated oxidative stress in cultured cells.

Kinetics and Mechanism of Iodide Oxidation by Iron(III): A Clock Reaction Approach

ERIC Educational Resources Information Center

Bauer, Jurica; Tomisic, Vladislav; Vrkljan, Petar B. A.

2008-01-01

A simple method for studying the kinetics of a chemical reaction is described and the significance of reaction orders in deducing reaction mechanisms is demonstrated. In this student laboratory experiment, oxidation of iodide by iron(III) ions in an acidic medium is transformed into a clock reaction. By means of the initial rates method, it is…

Using environmental chemistry technologies for the removal of arsenic from drinking water, and fat and oil based phase change materials for thermal energy storage

NASA Astrophysics Data System (ADS)

Sutterlin, William R.

The first four chapters of this dissertation involve the removal of arsenic from drinking water. Various forms of a macroporous char prepared by partial gasification of subbituminous coal were studied for removal of arsenic(V) and arsenic(III) from water. In increasing order of effectiveness for arsenic(V) removal were untreated char < acid-washed char < char impregnated with iron(III) and gasified < char impregnated with FeS < char impregnated with iron(III) hydroxide < char coated with zerovalent iron < char impregnated with iron(III) oxide. A mass of 10 g of iron(III) oxide char removed arsenic(V) and arsenic(III) from 10,000 mL of water containing 500 micrograms/L of arsenic to levels below 10 micrograms/L. The capacity of the solid to remove arsenic was significantly diminished in water containing 4 mg/L of phosphate. An electrical current passed over 4 g of iron(III) oxide char in a column enabled removal of arsenic(III) from 14,000 mL of 500 micrograms/L arsenic(III) to below 10 micrograms/liter and at significantly higher flow rates than could be employed without electrolysis. The fifth chapter in this dissertation focused on the retention of organics onto a char/concrete pellet. A mixture of naphthalene, pentachlorophenol, biphenyl, toluene, tetrachloroethane, and chlorobenzene were impregnated into a loose granular char, a char/concrete pellet and a sand/concrete pellet. The results showed that the char/concrete pellet had significant advantages over the other forms. Chapters 6--9 focus on phase change materials (PCMs). These PCMs are made from fats and oils. PCMs are perhaps the only proven method that can provide near 100% thermal energy storage. In chapter 7 a novel HPLC method was developed that could provide quantification and qualification of the resulting products formed after PCM synthesis. In chapter 8 thermal cycling studies were conducted on the fat and oil based PCMs. These thermal cycle demonstrated that these PCMs were capable of going through a multitude of freeze and melt processes with little to no degradation if the appropriate preservative is used. Finally in chapter 9 the PCM is incorporated into a simulated 100 th scale house. A traditional freon based evaporator is used to freeze the PCM at night during electrical-off-peak hours. During the peak-load of the day the evaporator is turned off and the PCM provides the cooling for the house.

Investigation of iron(III) reduction and trace metal interferences in the determination of dissolved iron in seawater using flow injection with luminol chemiluminescence detection.

PubMed

Ussher, Simon J; Milne, Angela; Landing, William M; Attiq-ur-Rehman, Kakar; Séguret, Marie J M; Holland, Toby; Achterberg, Eric P; Nabi, Abdul; Worsfold, Paul J

2009-10-12

A detailed investigation into the performance of two flow injection-chemiluminescence (FI-CL) manifolds (with and without a preconcentration column) for the determination of sub-nanomolar dissolved iron (Fe(II)+Fe(III)), following the reduction of Fe(III) by sulphite, in seawater is described. Kinetic experiments were conducted to examine the efficiency of reduction of inorganic Fe(III) with sulphite under different conditions and a rigorous study of the potential interference caused by other transition metals present in seawater was conducted. Using 100microM concentrations of sulphite a reduction time of 4h was sufficient to quantitatively reduce Fe(III) in seawater. Under optimal conditions, cobalt(II) and vanadium(IV)/(III) were the major positive interferences and strategies for their removal are reported. Specifically, cobalt(II) was masked by the addition of dimethylglyoxime to the luminol solution and vanadium(IV) was removed by passing the sample through an 8-hydroxyquinoline column in a low pH carrier stream. Manganese(II) also interfered by suppression of the CL response but this was not significant at typical open ocean concentrations.

Arsenic transformation and adsorption by iron hydroxide/manganese dioxide doped straw activated carbon

NASA Astrophysics Data System (ADS)

Xiong, Ying; Tong, Qiang; Shan, Weijun; Xing, Zhiqiang; Wang, Yuejiao; Wen, Siqi; Lou, Zhenning

2017-09-01

Iron hydroxide/manganese dioxide doped straw activated carbon was synthesized for As(III) adsorption. The Fe-Mn-SAc adsorbent has two advantages, on the one hand, the straw active carbon has a large surface area (1360.99 m2 g-1) for FeOOH and MnO2 deposition, on the other hand, the manganese dioxide has oxidative property as a redox potential of (MnO2 + H+)/Mn2+, which could convert As(III) into As(V). Combined with the arsenic species after reacting with Fe-Mn-SAc, the As(III) transformation and adsorption mechanism was discussed. H2AsO4-oxidized from As(III) reacts with the Fe-Mn-SAc by electrostatic interaction, and unoxidized As(III) as H3AsO3 reacts with SAc and/or iron oxide surface by chelation effect. The adsorption was well-described by Langmuir isotherms model, and the adsorption capacity of As(III) was 75.82 mg g-1 at pH 3. Therefore, considering the straw as waste biomass material, the biosorbent (Fe-Mn-SAc) is promising to be exploited for applications in the treatment of industrial wastewaters containing a certain ratio of arsenic and germanium.

Assessing bioavailability levels of metals in effluent-affected rivers: effect of Fe(III) and chelating agents on the distribution of metal speciation.

PubMed

Han, Shuping; Naito, Wataru; Masunaga, Shigeki

To assess the effects of Fe(III) and anthropogenic ligands on the bioavailability of Ni, Cu, Zn, and Pb, concentrations of bioavailable metals were measured by the DGT (diffusive gradients in thin films) method in some urban rivers, and were compared with concentrations calculated by a chemical equilibrium model (WHAM 7.0). Assuming that dissolved Fe(III) (<0.45 μm membrane filtered) was in equilibrium with colloidal iron oxide, the WHAM 7.0 model estimated that bioavailable concentrations of Ni, Cu, and Zn were slightly higher than the corresponding values estimated assuming that dissolved Fe(III) was absent. In contrast, lower levels of free Pb were predicted by the WHAM 7.0 model when dissolved Fe(III) was included. Estimates showed that most of the dissolved Pb was present as colloidal iron-Pb complex. Ethylene-diamine-tetra-acetic acid (EDTA) concentrations at sampling sites were predicted from the relationship between EDTA and the calculated bioavailable concentration of Zn. When both colloidal iron and predicted EDTA concentrations were included in the WHAM 7.0 calculations, dissolved metals showed a strong tendency to form EDTA complexes, in the order Ni > Cu > Zn > Pb. With the inclusion of EDTA, bioavailable concentrations of Ni, Cu, and Zn predicted by WHAM 7.0 were different from those predicted considering only humic substances and colloidal iron.

Reactivity of tris(acetylacetonato) iron(III) with tridentate [ONO] donor Schiff base as an access to newer mixed-ligand iron(III) complexes

NASA Astrophysics Data System (ADS)

Bhattacharjee, Chira R.; Goswami, Pankaj; Pramanik, Harun A. R.; Paul, Pradip C.; Mondal, Paritosh

2011-05-01

Two new mixed-ligand iron(III) complexes, [Fe(L n)(acac)(C 2H 5OH)] incorporating coordinated ethanol from the reaction solvent were accessed from the reaction of [Fe(acac) 3] with [ONO] donor dibasic tridentate unsymmetrical Schiff base ligands derived from condensation of 2-hydroxy-1-napthaldehyde with 2-aminophenol (H 2L 1) or 2-aminobenzoic acid (H 2L 2). The thermal study (TGA-DTA) provided evidence for weakly bound ethanol which is readily substituted by neutral N-donor molecule imidazole, benzimidazole or pyridine to produce an array of newer complexes, [Fe(L n)(acac)X] ( n = 1, 2; X = Im, Bim, Py). The compounds were characterized by elemental analyses, FT-IR, UV-vis, solution electrical conductivity, FAB mass, 1H and 13C NMR spectroscopy. Room temperature magnetic susceptibility measurements ( μeff ˜ 5.8 B.M.) are consistent with spin-free octahedral iron(III) complexes. Cyclic voltammetry of ethanol complexes revealed a quasi-reversible one electron redox response (Δ Ep > 100 mV) for the Fe(III)/Fe(II) couple. Low half wave redox potential ( E1/2) values suggested easy redox susceptibility. The ground state geometries of the ethanol and imidazole complexes have been ascertained to be distorted octahedral by density functional theory using DMol3 program at BLYP/DNP level.

Structure and Magnetic Properties of a Dodecanuclear Twisted-Ring Iron(III) Cluster.

PubMed

Caneschi, Andrea; Cornia, Andrea; Fabretti, Antonio C; Gatteschi, Dante

1999-05-03

An unprecedented nonplanar structure characterizes the complex [Fe(OCH 3 ) 2 (dbm)] 12 (on the left in the picture), which contains the largest cyclic ferric cluster yet reported with chemically equivalent bridging units. It is made up of twelve high-spin, antiferromagnetically coupled iron(III) centers and neatly reacts with Na I or Li I templates in organic solution to give hexairon(III) coronates (right). Fe=•, O=○, NaI or LiI=• Hdbm=dibenzoylmethane. © 1999 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.

Effects of oral iron(III) hydroxide polymaltose complex supplementation on hemoglobin increase, cognitive function, affective behavior and scholastic performance of adolescents with varying iron status: a single centre prospective placebo controlled study.

PubMed

Devaki, Pallaki Baby; Chandra, Ranjit K; Geisser, Peter

2009-01-01

To assess the effects of iron supplementation on iron status, cognitive function, affective behavior and scholastic performance in adolescents with varying iron status. Adolescents of both sexes with varying iron status were allocated to four treatment groups by using inclusion criteria. Three of the four groups (iron deficient anemic, iron deficient and control supplement) received iron(III) hydroxide polymaltose complex (IPC, Maltofer) containing 100 mg of elemental iron 6 days a week for 8 months, while the fourth group (control placebo) was given a placebo. Hematological parameters, cognitive function, affective behavior and scholastic performance were assessed at baseline, 4 months and 8 months of supplementation. Cognitive and scholastic performance test scores for the three supplemented groups increased from baseline to 4 months and from 4 months to 8 months (with concomitant increases in hematological parameters), whereas no increase was observed in the placebo group. No increase was seen in affective behavior scores for any of the groups during or after supplementation. IPC supplementation for eight months yielded significant improvements in cognitive function and scholastic performance in Indian adolescents with and without iron deficiency and anemia.

Adding remnant magnetization and anisotropic exchange to propeller-like single-molecule magnets through chemical design.

PubMed

Westrup, Kátia Cristina M; Boulon, Marie-Emmanuelle; Totaro, Pasquale; Nunes, Giovana G; Back, Davi F; Barison, Andersson; Jackson, Martin; Paulsen, Carley; Gatteschi, Dante; Sorace, Lorenzo; Cornia, Andrea; Soares, Jaísa F; Sessoli, Roberta

2014-10-13

The selective replacement of the central iron(III) ion with vanadium(III) in a tetrairon(III) propeller-shaped single-molecule magnet has allowed us to increase the ground spin state from S=5 to S=13/2. As a consequence of the pronounced anisotropy of vanadium(III), the blocking temperature for the magnetization has doubled. Moreover, a significant remnant magnetization, practically absent in the parent homometallic molecule, has been achieved owing to the suppression of zero-field tunneling of the magnetization for the half-integer molecular spin. Interestingly, the contribution of vanadium(III) to the magnetic anisotropy barrier occurs through the anisotropic exchange interaction with iron(III) spins and not through single ion anisotropy as in most single-molecule magnets. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sorption of Ferrioxime B to Synthetic and Biogenic layer type Mn Oxides

NASA Astrophysics Data System (ADS)

Duckworth, O. W.; Bargar, J. R.; Sposito, G.

2005-12-01

Siderophores are biogenic chelating agents produced in terrestrial and marine environments to increase the bioavailablity of ferric iron. Recent work has suggested that both aqueous and solid-phase Mn(III) may affect siderophore-mediated iron transport, but no information appears to be available about the effect of solid-phase Mn(IV). To probe the effect of solid-phase Mn(IV), we studied the sorption reaction of ferrioxamine B [principally the species, Fe(III)HDFOB+, an Fe(III) chelate of the trihydroxamate siderophore, desferrioxamine B (DFOB)] with two synthetic birnessites [layer type Mn(IV) oxides] and a biogenic birnessite produced by Pseudomonas putida MnB1. We found that all of these predominantly Mn(IV) oxides greatly reduced the aqueous concentration of Fe(III)HDFOB+ over the pH range between 5 and 9. After 72 h equilibration time at pH 8, the sorption behavior for the synthetic birnessites could be accurately described by a Langmuir isotherm; for the biogenic oxide, a Freundlich isotherm was best utilized to model the sorption data. To study the molecular nature of the interaction between the Fe(III)HDFOB+ complex and the oxide surface, Fe K-edge extended X-Ray absorption fine structure (EXAFS) spectroscopy was employed. Analysis of the X-ray absorption spectra indicated that Fe(III) associated with the Mn(IV) oxides is not complexed with DFOB, but instead is incorporated into the mineral structure, thus implying that the Mn(IV) oxides displaced Fe(III) from the siderophore complex. These results indicate that manganese oxides, including biominerals, may strongly sequester iron from soluble ferric complexes and thus may play a significant role in the biogeochemical cycling of iron.

Iron in the aquifer system of Suffolk County, New York, 1990–98

USGS Publications Warehouse

Brown, Craig J.; Walter, Donald A.; Colabufo, Steven

1999-01-01

High concentrations of dissolved iron in ground water contribute to the biofouling of public-supply wells, and the treatment and remediation of biofouling are costly. Water companies on Long Island, N.Y., spend several million dollars annually to recondition, redevelop, and replace supply wells and distribution lines; treat dissolved iron with sequestering agents or by filtration; and respond to iron-related complaints by customers. This report summarizes the results of studies done by the U.S. Geological Survey, in cooperation with the Suffolk County Water Authority, to characterize the geochemistry and microbiology of iron in the aquifer system of Suffolk County. This information should be helpful for the siting and operation of supply wells.Concentrations of dissolved iron in Long Island's ground water, and the frequency of iron biofouling of wells, are highest in ground-water-discharge zones, particularly near the south shore. Ground water along a deep north-south flowpath of the Magothy aquifer in southwestern Suffolk County becomes anaerobic (oxygen deficient) and Fe(III) reducing at a distance of 8 to 10 kilometers south of the ground-water divide, and this change coincides with the downgradient increase in dissolved iron concentrations. The distribution of organic carbon, and the distribution and local variations in reactivity of Fe(III), in Magothy aquifer sediments have resulted in localized differences in redox microenvironments. For example, Fe(III)-reducing zones are associated with anaerobic conditions, where relatively large amounts of Fe(III) oxyhydroxide grain coatings are present, whereas sulfate-reducing zones are associated with lignite-rich lenses of silt and clay and appear to have developed in response to the depletion of available Fe(III) oxyhydroxides. The sulfate-reducing zones are characterized by relatively low concentrations of dissolved iron (resulting from iron-disulfide precipitation) and may be large enough to warrant water-supply development.Specific-capacity and water-quality data from wells screened in the Magothy aquifer indicate that water from biofouled wells contains higher median concentrations of total and dissolved iron and manganese, total phosphate, and dissolved sulfate, and lower median concentrations of dissolved oxygen and alkalinity, and lower pH, than does water from unaffected wells. Corresponding data from wells screened in the upper glacial aquifer indicate that water from biofouled wells contains higher median concentrations of total and dissolved manganese and dissolved sulfate, and lower pH, than does water from unaffected wells.Filamentous bacteria were detected in 31 (or 72 percent) of the 43 biofilm samples obtained from biofouled wells during reconditioning. The predominant filamentous organism was Gallionella ferruginea, a major biofouling agent in the upper glacial and Magothy aquifers throughout Suffolk County. Mineral-saturation indices indicate that most of the well-encrusting material is deposited when the wells are shut down. Furthermore, the use of treated water (which has a high pH and sometimes high concentrations of dissolved iron) for pump prelubrication when wells are shut down could greatly increase the rate of iron oxidation.

Pelagic photoferrotrophy and iron cycling in a modern ferruginous basin.

PubMed

Llirós, Marc; García-Armisen, Tamara; Darchambeau, François; Morana, Cédric; Triadó-Margarit, Xavier; Inceoğlu, Özgül; Borrego, Carles M; Bouillon, Steven; Servais, Pierre; Borges, Alberto V; Descy, Jean-Pierre; Canfield, Don E; Crowe, Sean A

2015-09-08

Iron-rich (ferruginous) ocean chemistry prevailed throughout most of Earth's early history. Before the evolution and proliferation of oxygenic photosynthesis, biological production in the ferruginous oceans was likely driven by photoferrotrophic bacteria that oxidize ferrous iron {Fe(II)} to harness energy from sunlight, and fix inorganic carbon into biomass. Photoferrotrophs may thus have fuelled Earth's early biosphere providing energy to drive microbial growth and evolution over billions of years. Yet, photoferrotrophic activity has remained largely elusive on the modern Earth, leaving models for early biological production untested and imperative ecological context for the evolution of life missing. Here, we show that an active community of pelagic photoferrotrophs comprises up to 30% of the total microbial community in illuminated ferruginous waters of Kabuno Bay (KB), East Africa (DR Congo). These photoferrotrophs produce oxidized iron {Fe(III)} and biomass, and support a diverse pelagic microbial community including heterotrophic Fe(III)-reducers, sulfate reducers, fermenters and methanogens. At modest light levels, rates of photoferrotrophy in KB exceed those predicted for early Earth primary production, and are sufficient to generate Earth's largest sedimentary iron ore deposits. Fe cycling, however, is efficient, and complex microbial community interactions likely regulate Fe(III) and organic matter export from the photic zone.

FeS-coated sand for removal of arsenic(III) under anaerobic conditions in permeable reactive barriers

USGS Publications Warehouse

Han, Y.-S.; Gallegos, T.J.; Demond, A.H.; Hayes, K.F.

2011-01-01

Iron sulfide (as mackinawite, FeS) has shown considerable promise as a material for the removal of As(III) under anoxic conditions. However, as a nanoparticulate material, synthetic FeS is not suitable for use in conventional permeable reactive barriers (PRBs). This study developed a methodology for coating a natural silica sand to produce a material of an appropriate diameter for a PRB. Aging time, pH, rinse time, and volume ratios were varied, with a maximum coating of 4.0 mg FeS/g sand achieved using a pH 5.5 solution at a 1:4 volume ratio (sand: 2 g/L FeS suspension), three days of aging and no rinsing. Comparing the mass deposited on the sand, which had a natural iron-oxide coating, with and without chemical washing showed that the iron-oxide coating was essential to the formation of a stable FeS coating. Scanning electron microscopy images of the FeS-coated sand showed a patchwise FeS surface coating. X-ray photoelectron spectroscopy showed a partial oxidation of the Fe(II) to Fe(III) during the coating process, and some oxidation of S to polysulfides. Removal of As(III) by FeS-coated sand was 30% of that by nanoparticulate FeS at pH 5 and 7. At pH 9, the relative removal was 400%, perhaps due to the natural oxide coating of the sand or a secondary mineral phase from mackinawite oxidation. Although many studies have investigated the coating of sands with iron oxides, little prior work reports coating with iron sulfides. The results suggest that a suitable PRB material for the removal of As(III) under anoxic conditions can be produced through the deposition of a coating of FeS onto natural silica sand with an iron-oxide coating. ?? 2010 Elsevier Ltd.

Significance of Iron(II,III) Hydroxycarbonate Green Rust in Arsenic Remediation Using Zerovalent Iron in Laboratory Column Tests

EPA Science Inventory

We examined the corrosion products of zerovalent iron used in three column tests for removing arsenic from water under dynamic flow conditions. Each column test lasted three- to four-months using columns consisting of a 10.3-cm depth of 50 : 50 (w : w, Peerless iron : sand) in t...

Low frequency vibrational spectra and the nature of metal-oxygen bond of alkaline earth metal acetylacetonates

NASA Astrophysics Data System (ADS)

Fakheri, Hamideh; Tayyari, Sayyed Faramarz; Heravi, Mohammad Momen; Morsali, Ali

2017-12-01

Theoretical quantum chemistry calculations were used to assign the observed vibrational band frequencies of Be, Mg, Ca, Sr, and Ba acetylacetonates complexes. Density functional theory (DFT) calculations have been carried out at the B3LYP level, using LanL2DZ, def2SVP, and mixed, GenECP, (def2SVP for metal ions and 6-311++G** for all other atoms) basis sets. The B3LYP level, with mixed basis sets, was utilized for calculations of vibrational frequencies, IR intensity, and Raman activity. Analysis of the vibrational spectra indicates that there are several bands which could almost be assigned mainly to the metal-oxygen vibrations. The strongest Raman band in this region could be used as a measure of the stability of the complex. The effects of central metal on the bond orders and charge distributions in alkaline earth metal acetylacetonates were studied by the Natural Bond Orbital (NBO) method for fully optimized compounds. Optimization were performed at the B3LYP/6-311++G** level for the lighter alkaline earth metal complexes (Be, Mg, and Ca acetylacetonates) while the B3LYP level, using LanL2DZ (extrabasis, d and f on oxygen and metal atoms), def2SVP and mixed (def2SVP on metal ions and 6-311++G** for all other atoms) basis sets for all understudy complexes. Calculations indicate that the covalence nature of metal-oxygen bonds considerably decreases from Be to Ba complexes. The nature of metal-oxygen bond was further studied by using Atoms In Molecules (AIM) analysis. The topological parameters, Wiberg bond orders, natural charges of O and metal ions, and also some vibrational band frequencies were correlated with the stability constants of understudy complexes.

Influence of post-deposition annealing on structural, morphological and optical properties of copper (II) acetylacetonate thin films.

PubMed

Abdel-Khalek, H; El-Samahi, M I; El-Mahalawy, Ahmed M

2018-05-21

In this study, the effect of thermal annealing under vacuum conditions on structural, morphological and optical properties of thermally evaporated copper (II) acetylacetonate, cu(acac) 2 , thin films were investigated. The copper (II) acetylacetonate thin films were deposited using thermal evaporation technique at vacuum pressure ~1 × 10 -5  mbar. The deposited films were thermally annealed at 323, 373, 423, and 473 K for 2 h in vacuum. The thermogravimetric analysis of cu(acac) 2 powder indicated a thermal stability of cu(acac) 2 up to 423 K. The effects of thermal annealing on the structural properties of cu(acac) 2 were evaluated employing X-ray diffraction method and the analysis showed a polycrystalline nature of the as-deposited and annealed films with a preferred orientation in [1¯01] direction. Fourier transformation infrared (FTIR) technique was used to negate the decomposition of copper (II) acetylacetonate during preparation or/and annealing up to 423 K. The surface morphology of the prepared films was characterized by means of field emission scanning electron microscopy (FESEM). A significant enhancement of the morphological properties of cu(acac) 2 thin films was obtained till the annealing temperature reaches 423 K. The variation of optical constants that estimated from spectrophotometric measurements of the prepared thin films was investigated as a function of annealing temperature. The annealing process presented significantly impacted the nonlinear optical properties such as third-order optical susceptibility χ (3) and nonlinear refractive index n 2 of cu(acac) 2 thin films. Copyright © 2018 Elsevier B.V. All rights reserved.

Comment on “Isotopic fractionation between Fe(III) and Fe(II) in aqueous solutions” by Clark Johnson et al., [Earth Planet. Sci. Lett. 195 (2002) 141–153

USGS Publications Warehouse

Bullen, Thomas D.; White, Arthur F.; Childs, Cyril W.

2003-01-01

In a recent contribution [1], Johnson et al. reported the equilibrium isotope fractionation factor between dissolved Fe(II) and Fe(III) in aqueous solutions at pH=2.5 and 5.5. They suggest that because the iron isotope fractionation observed in their experiments spans virtually the entire range observed in sedimentary rocks, Fe(II)–Fe(III) aqueous speciation may play a major role in determining iron isotope variations in nature where Fe(II) and Fe(III) can become physically separated. They discounted earlier conclusions by us and others [2] ;  [3] that significant equilibrium fractionation between specific coexisting Fe(II)- or Fe(III)-aqueous complexes (e.g., between aqueous Fe(II)(OH)x(aq)and Fe(II)(aq) ion) is capable of producing iron isotope contrasts that can be preserved in nature. This is an important contribution not only because the authors recognize the importance of abiotic equilibrium iron isotope fractionation in nature in contrast to previous assertions [4], but also because it will help to focus discussion on the development and evaluation of experimental approaches that can reveal abiotic fractionation mechanisms. However, in this Comment we propose that the experiments presented in this paper cannot be interpreted as straightforwardly as Johnson et al. contend. In particular, we show that in one of their critical experiments attainment of either isotope mass balance or equilibrium was not demonstrated, and thus the results of that experiment cannot be used to calculate an Fe(II)–Fe(III) equilibrium fractionation factor.

Extracellular polymeric substances mediate bioleaching/biocorrosion via interfacial processes involving iron(III) ions and acidophilic bacteria.

PubMed

Sand, Wolfgang; Gehrke, Tilman

2006-01-01

Extracellular polymeric substances seem to play a pivotal role in biocorrosion of metals and bioleaching, biocorrosion of metal sulfides for the winning of precious metals as well as acid rock drainage. For better control of both processes, the structure and function of extracellular polymeric substances of corrosion-causing or leaching bacteria are of crucial importance. Our research focused on the extremophilic bacteria Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans, because of the "simplicity" and knowledge about the interactions of these bacteria with their substrate/substratum and their environment. For this purpose, the composition of the corresponding extracellular polymeric substances and their functions were analyzed. The extracellular polymeric substances of both species consist mainly of neutral sugars and lipids. The functions of the exopolymers seem to be: (i) to mediate attachment to a (metal) sulfide surface, and (ii) to concentrate iron(III) ions by complexation through uronic acids or other residues at the mineral surface, thus, allowing an oxidative attack on the sulfide. Consequently, dissolution of the metal sulfide is enhanced, which may result in an acceleration of 20- to 100-fold of the bioleaching process over chemical leaching. Experiments were performed to elucidate the importance of the iron(III) ions complexed by extracellular polymeric substances for strain-specific differences in oxidative activity for pyrite. Strains of A. ferrooxidans with a high amount of iron(III) ions in their extracellular polymeric substances possess greater oxidation activity than those with fewer iron(III) ions. These data provide insight into the function of and consequently the advantages that extracellular polymeric substances provide to bacteria. The role of extracellular polymeric substances for attachment under the conditions of a space station and resulting effects like biofouling, biocorrosion, malodorous gases, etc. will be discussed.

Emission characteristics in solution-processed asymmetric white alternating current field-induced polymer electroluminescent devices

NASA Astrophysics Data System (ADS)

Chen, Yonghua; Xia, Yingdong; Smith, Gregory M.; Gu, Yu; Yang, Chuluo; Carroll, David L.

2013-01-01

In this work, the emission characteristics of a blue fluorophor poly(9, 9-dioctylfluorene) (PFO) combined with a red emitting dye: Bis(2-methyl-dibenzo[f,h]quinoxaline)(acetylacetonate)iridium (III) [Ir(MDQ)2(acac)], are examined in two different asymmetric white alternating current field-induced polymer electroluminescent (FIPEL) device structures. The first is a top-contact device in which the triplet transfer is observed resulting in the concentration-dependence of the emission similar to the standard organic light-emitting diode (OLED) structure. The second is a bottom-contact device which, however, exhibits concentration-independence of emission. Specifically, both dye emission and polymer emission are found for the concentrations as high as 10% by weight of the dye in the emitter. We attribute this to the significant different carrier injection characteristics of the two FIPEL devices. Our results suggest a simple and easy way to realize high-quality white emission.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Jung-Bum; Lee, Jeong-Hwan; Moon, Chang-Ki

We report a highly efficient phosphorescent green inverted top emitting organic light emitting diode with excellent color stability by using the 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile/indium zinc oxide top electrode and bis(2-phenylpyridine)iridium(III) acetylacetonate as the emitter in an exciplex forming co-host system. The device shows a high external quantum efficiency of 23.4% at 1000 cd/m{sup 2} corresponding to a current efficiency of 110 cd/A, low efficiency roll-off with 21% at 10 000 cd/m{sup 2} and low turn on voltage of 2.4 V. Especially, the device showed very small color change with the variation of Δx = 0.02, Δy = 0.02 in the CIE 1931 coordinates as the viewing angle changes from 0° tomore » 60°. The performance of the device is superior to that of the metal/metal cavity structured device.« less

Iron silylamide-grafted periodic mesoporous silica.

PubMed

Deschner, Thomas; Törnroos, Karl W; Anwander, Reiner

2011-08-01

The surface chemistry of a series of well-defined metalorganic ferrous and ferric iron complexes on periodic mesoporous silica (PMS) was investigated. In addition to literature known Fe(II)[N(SiMe(3))(2)](2)(THF), Fe(II)[N(SiPh(2)Me(2))(2)](2), and Fe(III)[N(SiMe(3))(2)](2)Cl(THF), the new complexes [Fe(II){N(SiHMe(2))(2)}(2)](2) and Fe(III)[N(SiHMe(2))(2)](3)(μ-Cl)Li(THF)(3) were employed as grafting precursors. Selection criteria for the molecular precursors were the molecular size (monoiron versus diiron species), the oxidation state of the iron center (II versus III), and the functionality of the silylamido ligand (e.g., built-in spectroscopic probes). Hexagonal channel-like MCM-41 and cubic cage-like SBA-1 were chosen as two distinct PMS materials. The highest iron load (12.8 wt %) was obtained for hybrid material [Fe(II){N(SiHMe(2))(2)}(2)](2)@MCM-41 upon stirring the reaction mixture iron silylamide/PMS/n-hexane for 18 h at ambient temperature. Size-selective grafting and concomitantly extensive surface silylation were found to be prominent for cage-like SBA-1. Here, the surface metalation is governed by the type of iron precursor, the pore size, the reaction time, and the solvent. The formation of surface-attached iron-ligand species is discussed on the basis of diffuse reflectance infrared Fourier transform (DRIFT) and electron paramagnetic resonance (EPR) spectroscopy, nitrogen physisorption, and elemental analysis. © 2011 American Chemical Society

The effect of oxidant addition on ferrous iron removal from multi-element acidic sulphate solutions

NASA Astrophysics Data System (ADS)

Mbedzi, Ndishavhelafhi; Ibana, Don; Dyer, Laurence; Browner, Richard

2017-01-01

This study was an investigation on the hydrolytic precipitation of iron from simulated pregnant leach solution (PLS) of nickel laterite atmospheric leaching. The effect of equilibrium pH, temperature and the addition of oxidant on total iron (ferrous (Fe (II)) and ferric (Fe (III)), aluminium and chromium removal was investigated together with the associated nickel and cobalt losses to the precipitate. Systematic variations of the experimental variables revealed ≥99% of the ferric iron can be removed from solution at conditions similar to those used in standard partial neutralisation in zinc and nickel production, pH of 2.5 and temperature less than 100 °C with minimal losses (<0.5%) of both nickel and cobalt. Temperature variation from 55 to 90 °C had no significant effect on the magnitude of Fe (III) precipitation but led to a significant increase in aluminium removal from 67% to 95% and improved the filterability of the precipitates. There was no ferrous iron precipitation even at a pH of 3.75 in the absence of an oxidant with its removal (98%) achieved by oxidative precipitation with oxygen gas at pH 3.5. Unlike Fe (III) precipitation, the operating temperature significantly affects oxidative precipitation of Fe (II). Hence, in practical application, the hydrolytic precipitation and oxidation to remove iron must be operated at 85 °C to ensure both ferrous and ferric iron are precipitated.

Potentiometric and electrokinetic signatures of iron(II) interactions with (α,γ)-Fe2O3.

PubMed

Toczydłowska, Diana; Kędra-Królik, Karolina; Nejbert, Krzysztof; Preočanin, Tajana; Rosso, Kevin M; Zarzycki, Piotr

2015-10-21

The electrochemical signatures of Fe(II) interactions with iron(III) oxides are poorly understood, despite their importance in controlling the amount of mobilized iron. Here, we report the potentiometric titration of α,γ-Fe2O3 oxides exposed to Fe(II) ions. We monitored in situ surface and ζ potentials, the ratio of mobilized ferric to ferrous, and the periodically analyzed nanoparticle crystal structure using X-ray diffraction. Electrokinetic potential reveals weak but still noticeable specific sorption of Fe(II) to the oxide surface under acidic conditions, and pronounced adsorption under alkaline conditions that results in a surface potential reversal. By monitoring the aqueous iron(II/III) fraction, we found that the addition of Fe(II) ions produces platinum electrode response consistent with the iron solubility-activity curve. Although, XRD analysis showed no evidence of γ-Fe2O3 transformations along the titration pathway despite iron cycling between aqueous and solid reservoirs, the magnetite formation cannot be ruled out.

Spectroscopic and functional characterization of iron-bound forms of Azotobacter vinelandii (Nif)IscA.

PubMed

Mapolelo, Daphne T; Zhang, Bo; Naik, Sunil G; Huynh, Boi Hanh; Johnson, Michael K

2012-10-16

The ability of Azotobacter vinelandii(Nif)IscA to bind Fe has been investigated to assess the role of Fe-bound forms in NIF-specific Fe-S cluster biogenesis. (Nif)IscA is shown to bind one Fe(III) or one Fe(II) per homodimer and the spectroscopic and redox properties of both the Fe(III)- and Fe(II)-bound forms have been characterized using the UV-visible absorption, circular dichroism, and variable-temperature magnetic circular dichroism, electron paramagnetic resonance, Mössbauer and resonance Raman spectroscopies. The results reveal a rhombic intermediate-spin (S = 3/2) Fe(III) center (E/D = 0.33, D = 3.5 ± 1.5 cm(-1)) that is most likely 5-coordinate with two or three cysteinate ligands and a rhombic high spin (S = 2) Fe(II) center (E/D = 0.28, D = 7.6 cm(-1)) with properties similar to reduced rubredoxins or rubredoxin variants with three cysteinate and one or two oxygenic ligands. Iron-bound (Nif)IscA undergoes reversible redox cycling between the Fe(III)/Fe(II) forms with a midpoint potential of +36 ± 15 mV at pH 7.8 (versus NHE). l-Cysteine is effective in mediating release of free Fe(II) from both the Fe(II)- and Fe(III)-bound forms of (Nif)IscA. Fe(III)-bound (Nif)IscA was also shown to be a competent iron source for in vitro NifS-mediated [2Fe-2S] cluster assembly on the N-terminal domain of NifU, but the reaction occurs via cysteine-mediated release of free Fe(II) rather than direct iron transfer. The proposed roles of A-type proteins in storing Fe under aerobic growth conditions and serving as iron donors for cluster assembly on U-type scaffold proteins or maturation of biological [4Fe-4S] centers are discussed in light of these results.

Prebiotic Oxidative Polymerization of 2,3 Dimercaptopropanol on the Surface of Iron(III) Hydroxide Oxide

NASA Technical Reports Server (NTRS)

Weber, Arthur L.

1994-01-01

The oxidation of 2,3-Dimercapto-1-propanol by ferric ions on the surface of iron (III) hydroxide oxide yielded polydisulfide polymers. This polymerization occured readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron (III) hydroxide oxide (20 mg, 160 micro mole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the mineral phase. Reactions at higher dithiol concentrations with the same ratio of dithiol to mineral gave a higher yield of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis will be discussed.

Synthesis, iron(III) complexation properties, molecular dynamics simulations and P. aeruginosa siderophore-like activity of two pyoverdine analogs.

PubMed

Antonietti, Viviane; Boudesocque, Stéphanie; Dupont, Laurent; Farvacques, Natacha; Cézard, Christine; Da Nascimento, Sophie; Raimbert, Jean-François; Socrier, Larissa; Robin, Thierry-Johann; Morandat, Sandrine; El Kirat, Karim; Mullié, Catherine; Sonnet, Pascal

2017-09-08

P. aeruginosa ranks among the top five organisms causing nosocomial infections. Among the many novel strategies for developing new therapeutics against infection, targeting iron uptake mechanism seems promising as P. aeruginosa needs iron for its growth and survival. To scavenge iron, the bacterium produces siderophores possessing a very high affinity towards Fe(III) ions such as pyoverdines. In this work, we decided to study two pyoverdine analogs, aPvd2 and aPvd3, structurally close to the endogen pyoverdine. The pFe constants calculated with the values of formation showed a high affinity of aPvd3 towards Fe(III). Molecular dynamics calculations demonstrated that aPvd3-Fe forms with Fe(III) stable 1:1 complexes in water, whereas aPvd2 does not. Only aPvd3 is able to increase the bacterial growth and represents thus an alternative to pyoverdine for iron acquisition by the bacterium. The aPvd2-3 interaction studies with a lipid membrane indicated that they were unable to interact and to cross the plasma membrane of bacteria by passive diffusion. Consequently, the penetration of aPvd3 is ruled by a transport membrane protein. These results showed that aPvd3 may be used to inhibit pyoverdine uptake or to promote the accumulation and release of antibiotics into the cell following a Trojan horse strategy. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Magnetoviscoelastic characteristics of superparamagnetic oxides (Fe, Ni) based ferrofluids

NASA Astrophysics Data System (ADS)

Katiyar, Ajay; Dhar, Purbarun; Nandi, Tandra; Das, Sarit K.

2017-08-01

Ferrofluids have been popular among the academic and scientific communities owing to their intelligent physical characteristics under external stimuli and are in fact among the first nanotechnology products to be employed in real world applications. However, studies on the magnetoviscoelastic behavior of concentrated ferrofluids, especially of superparamagnetic oxides of iron and nickel are rare. The present article comprises the formulation of magneto-colloids utilizing the three various metal oxides nanoparticles viz. Iron (II, III) oxide (Fe3O4), Iron (III) oxide (Fe2O3) and Nickel oxide (NiO) in oil. Iron (II, III) oxide based colloids demonstrate high magnetoviscous characteristics over the other oxides based colloids under external magnetic fields. The maximum magnitude of yield stress and viscosity is found to be 3.0 kPa and 2.9 kPa.s, respectively for iron (II, III) oxide based colloids at 2.6 vol% particle concentration and 1.2 T magnetic field. Experimental investigations reveal that the formulated magneto-nanocolloids are stable, even in high magnetic fields and almost reversible when exposed to rising and drop of magnetic fields of the same magnitude. Observations also reveal that the elastic behavior dominates over the viscous behavior with enhanced relaxation and creep characteristics under the magnetic field. The effect of temperature on viscosity and yield stress of magneto-nanocolloids under magnetic fields has also been discussed. Thus, the present findings have potential applications in various fields such as electromagnetic clutch and brakes of automotive, damping, sealing, optics, nanofinishing etc.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wenjie; Zhang, Honghu; Feng, Shuren

Surface-sensitive X-ray scattering and spectroscopy techniques reveal significant adsorption of iron ions and iron-hydroxide (Fe(III)) complexes to a charge-neutral zwitterionic template of phosphatidylcholine (PC). The PC template is formed by a Langmuir monolayer of dipalmitoyl-PC (DPPC) that is spread on the surface of 2 to 40 μM FeCl 3 solutions at physiological levels of KCl (100 mM). At 40 μM of Fe(III) as many as ~3 iron atoms are associated with each PC group. Grazing incidence X-ray diffraction measurements indicate a significant disruption in the in-plane ordering of DPPC molecules upon iron adsorption. The binding of iron-hydroxide complexes to amore » neutral PC surface is yet another example of nonelectrostatic, presumably covalent bonding to a charge-neutral organic template. Furthermore, the strong binding and the disruption of in-plane lipid structure has biological implications on the integrity of PC-derived lipid membranes, including those based on sphingomyelin.« less

ON THE RELATIVE STABILITY OF ALUMINUM, TITANIUM, VANADIUM, IRON, AND COPPER TARTRATE COMPLEXES IN ALKALI MEDIA (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pyatnitskii, I.V.; Kostyshina, A.P.

1959-06-01

The stability of aluminum, copper, iron, titunium, and vanadium tartrate complexes was determined using bond magnitudes as criteria (the ratio between the concentrations of complexed and free ions at a certain standard acid condition). A method is suggested for determining the ratio of the bonds combining the complexes of two metals. The partition constaats of aluminum, copper, iron(III), and vanadium hydroxyquinolinates between the aqueous solution and chloroform were 2.6 x 10/sup -33/, 7.3 x 10/sup -23/, 1.5 x 10/sup -37/, and 4.2 x 10/sup -23/, respectively. The relative stability of copper and iron turtrate complexes in alkali solution (pH 13)more » and aluminum, iron(III), titunium, and vanadium(IV) tartrate complexes in ammonium solution (pH 9.5) was determined. (R.V.J.)« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Byrne, James; Klueglein, Nicole; Pearce, Carolyn I.

Despite the regular occurrence of both magnetite and iron-metabolizing bacteria in the same environments, it is currently unknown whether the iron(II) and iron(III) in magnetite can be cycled between different bacteria and whether or how magnetic properties are affected by this metabolic activity. We show through magnetic and spectroscopic measurements that the phototrophic Fe(II)-oxidizer Rhodopseudomonas palustris TIE-1 can oxidize solid-phase magnetite nanoparticles using light energy, leading to a decrease in the measured magnetic susceptibility (MS). This process likely occurs at the surface and is reversible in the dark by the Fe(III)-reducer Geobacter sulfurreducens resulting in an increase in MS. Thesemore » results show that iron ions bound in highly crystalline mineral magnetite are bioavailable as electron stores and electron sinks under varying environmental conditions, making magnetite a potential “biogeobattery” during day/night cycles. These findings are relevant for environmental studies and reinforce the impact of microbial redox processes on the global iron cycle.« less

Redox inactive metal ion triggered N-dealkylation by an iron catalyst with dioxygen activation: a lesson from lipoxygenases.

PubMed

Zhang, Jisheng; Wang, Yujuan; Luo, Nengchao; Chen, Zhuqi; Wu, Kangbing; Yin, Guochuan

2015-06-07

Utilization of dioxygen as the terminal oxidant at ambient temperature is always a challenge in redox chemistry, because it is hard to oxidize a stable redox metal ion like iron(III) to its high oxidation state to initialize the catalytic cycle. Inspired by the dioxygenation and co-oxidase activity of lipoxygenases, herein, we introduce an alternative protocol to activate the sluggish iron(III) species with non-redox metal ions, which can promote its oxidizing power to facilitate substrate oxidation with dioxygen, thus initializing the catalytic cycle. In oxidations of N,N-dimethylaniline and its analogues, adding Zn(OTf)2 to the [Fe(TPA)Cl2]Cl catalyst can trigger the amine oxidation with dioxygen, whereas [Fe(TPA)Cl2]Cl alone is very sluggish. In stoichiometric oxidations, it has also been confirmed that the presence of Zn(OTf)2 can apparently improve the electron transfer capability of the [Fe(TPA)Cl2]Cl complex. Experiments using different types of substrates as trapping reagents disclosed that the iron(IV) species does not occur in the catalytic cycle, suggesting that oxidation of amines is initialized by electron transfer rather than hydrogen abstraction. Combined experiments from UV-Vis, high resolution mass spectrometry, electrochemistry, EPR and oxidation kinetics support that the improved electron transfer ability of iron(III) species originates from its interaction with added Lewis acids like Zn(2+) through a plausible chloride or OTf(-) bridge, which has promoted the redox potential of iron(III) species. The amine oxidation mechanism was also discussed based on the available data, which resembles the co-oxidase activity of lipoxygenases in oxidative dealkylation of xenobiotic metabolisms where an external electron donor is not essential for dioxygen activation.

Effect of Humic Acid on the Removal of Chromium(VI) and the Production of Solids in Iron Electrocoagulation.

PubMed

Pan, Chao; Troyer, Lyndsay D; Liao, Peng; Catalano, Jeffrey G; Li, Wenlu; Giammar, Daniel E

2017-06-06

Iron-based electrocoagulation can be highly effective for Cr(VI) removal from water supplies. However, the presence of humic acid (HA) inhibited the rate of Cr(VI) removal in electrocoagulation, with the greatest decreases in Cr(VI) removal rate at higher pH. This inhibition was probably due to the formation of Fe(II) complexes with HA that are more rapidly oxidized than uncomplexed Fe(II) by dissolved oxygen, making less Fe(II) available for reduction of Cr(VI). Close association of Fe(III), Cr(III), and HA in the solid products formed during electrocoagulation influenced the fate of both Cr(III) and HA. At pH 8, the solid products were colloids (1-200 nm) with Cr(III) and HA concentrations in the filtered fraction being quite high, while at pH 6 these concentrations were low due to aggregation of small particles. X-ray diffraction and X-ray absorption fine structure spectroscopy indicated that the iron oxides produced were a mixture of lepidocrocite and ferrihydrite, with the proportion of ferrihydrite increasing in the presence of HA. Cr(VI) was completely reduced to Cr(III) in electrocoagulation, and the coordination environment of the Cr(III) in the solids was similar regardless of the humic acid loading, pH, and dissolved oxygen level.

The Effect of Temperature and Ionic Strength on the Oxidation of Iodide by Iron(III): A Clock Reaction Kinetic Study

ERIC Educational Resources Information Center

Bauer, Jurica; Tomisic, Vladislav; Vrkljan, Petar B. A.

2012-01-01

A laboratory exercise has recently been reported in which the students use the initial rates method based on the clock reaction approach to deduce the rate law and propose a reaction mechanism for the oxidation of iodide by iron(III) ions. The same approach is used in the exercise proposed herein; the students determine the dependence of the…

Redox-dependent open and closed forms of the active site of the bacterial respiratory nitric-oxide reductase revealed by cyanide binding studies.

PubMed

Grönberg, Karin L C; Watmough, Nicholas J; Thomson, Andrew J; Richardson, David J; Field, Sarah J

2004-04-23

The bacterial respiratory nitric-oxide reductase (NOR) catalyzes the respiratory detoxification of nitric oxide in bacteria and Archaea. It is a member of the well known super-family of heme-copper oxidases but has a [heme Fe-non-heme Fe] active site rather than the [heme Fe-Cu(B)] active site normally associated with oxygen reduction. Paracoccus denitrificans NOR is spectrally characterized by a ligand-to-metal charge transfer absorption band at 595 nm, which arises from the high spin ferric heme iron of a micro-oxo-bridged [heme Fe(III)-O-Fe(III)] active site. On reduction of the nonheme iron, the micro-oxo bridge is broken, and the ferric heme iron is hydroxylated or hydrated, depending on the pH. At present, the catalytic cycle of NOR is a matter of much debate, and it is not known to which redox state(s) of the enzyme nitric oxide can bind. This study has used cyanide to probe the nature of the active site in a number of different redox states. Our observations suggest that the micro-oxo-bridged [heme Fe(III)-O-Fe(III)] active site represents a closed or resting state of NOR that can be opened by reduction of the non-heme iron.

Gamma-resonance investigation of the kinetics of the reduction of (. cap alpha. -benzil dioximato-1)(. cap alpha. -benzil dioximato-2)di(pyridine)iron(III)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turte, K.I.; Bulgak, I.I.; Stukan, R.A.

1986-07-01

(..cap alpha..-Benzil dioximato-1)(..cap alpha..-benzil dioximato-2)di(pyridine)iron(III) in the form of the diacetone solvate (II) is spontaneously converted at room temperature into (..cap alpha..-benzil dioximato-1)(..cap alpha..-benzil dioximato-2)di(pyridine)iron(II) (III). The quantitative composition of a sample containing complexes II and III has been determined as a function of the temperature and the time by gamma-resonance spectroscopy, which made it possible to investigate the kinetics of this reaction. The changes obtained in the percentage of complex II in the sample as a function of time at a given temperature was treated with the use of the Kolmogorov-Erofeev equation for a topochemical reaction of the typemore » A/sub s/ ..-->.. B/sub s/ + C/sub g/. The rate constants of the reaction at various temperatures and the activation energy *E have been determined. In the temperature range from 293 to 304/sup 0/K *E = 25.6 kcal/mole. The possibilities of gamma-resonance spectroscopy in the investigation of topochemical reactions associated with changes in the oxidation state of iron ions have been demonstrated.« less

An investigation into the enhancement of sea-spray exposed fingerprints on glass.

PubMed

Goldstone, S L; Francis, S C; Gardner, S J

2015-07-01

Fingerprints are considered one of the best forms of personal identification. While numerous enhancement techniques exist to develop fingerprints under various conditions, the enhancement of fingerprints exposed to sea spray aerosol (SSA) still remains problematic. 1056 fingerprints from four donors, using a depletion series and triplicate repeats, were deposited onto glass panels and exposed to SSA for 1 week and 1 month. Control prints were deposited in the same manner and left under laboratory conditions. All prints were enhanced using fingerprint enhancement techniques available to Forensic Police Officers and subsequently examined for identifiability by a Fingerprint Expert. Significantly fewer identifiable prints (p<0.01) were developed after exposure to SSA for 1 month (11%) compared to exposure for 1 week (69%) (compared to the control prints 99%) for all enhancement techniques. After 1 week's exposure, all techniques enhanced over 50% of prints, except SPR white (12%), with iron (III) oxide and Wetwop™ white producing over 90% identifiable prints. Only iron (III) oxide, Wetwop™ white and SPR black returned any identifiable prints following 1 month's SSA exposure. Iron (III) oxide being significantly better (p<0.01, 67%) than the other techniques. Iron (III) oxide suspension and Wetwop™ white were found to be superior at enhancing prints at both SSA exposure times. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

[Determination of iron(III) in Chinese herbal medicine and tea based on fluorescence quenching of 2,4-dichro-phenylfluorone].

PubMed

Dai, Gang; Aodeng, Gao-wa

2004-07-01

A new spectrofluorimetric method for the determination of trace amount of Fe(III) has been developed. This method is based on the fluorescence quenching of 2,4-dichro-phenylfluorone due to the formation of complex Fe(III)-DCIPF. In pH 5.2-5.9 buffer solution, Fe (III) and DCIPF react on each other to form a red complex. Its composition was established by method of continuous variations and molar-ratio as Fe(III): DCIPF = 1:4, the excitation and emission wavelengths were found to be 282 and 560 nm, respectively. There is a linear relationship in the range 4-24 ng x mL(-1) for Fe(III). This method is simple and rapid, and has been applied to the determination of trace iron in Chinese herbal medicine and tea samples with satisfactory results.

Impact of two iron(III) chelators on the iron, cadmium, lead and nickel accumulation in poplar grown under heavy metal stress in hydroponics.

PubMed

Mihucz, Victor G; Csog, Árpád; Fodor, Ferenc; Tatár, Enikő; Szoboszlai, Norbert; Silaghi-Dumitrescu, Luminiţa; Záray, Gyula

2012-04-15

Poplar (Populus jacquemontiana var. glauca cv. Kopeczkii) was grown in hydroponics containing 10 μM Cd(II), Ni(II) or Pb(II), and Fe as Fe(III) EDTA or Fe(III) citrate in identical concentrations. The present study was designed to compare the accumulation and distribution of Fe, Cd, Ni and Pb within the different plant compartments. Generally, Fe and heavy-metal accumulation were higher by factor 2-7 and 1.6-3.3, respectively, when Fe(III) citrate was used. Iron transport towards the shoot depended on the Fe(III) chelate and, generally, on the heavy metal used. Lead was accumulated only in the root. The amounts of Fe and heavy metals accumulated by poplar were very similar to those of cucumber grown in an identical way, indicating strong Fe uptake regulation of these two Strategy I plants: a cultivar and a woody plant. The Strategy I Fe uptake mechanism (i.e. reducing Fe(III) followed by Fe(II) uptake), together with the Fe(III) chelate form in the nutrient solution had significant effects on Fe and heavy metal uptake. Poplar appears to show phytoremediation potential for Cd and Ni, as their transport towards the shoot was characterized by 51-54% and 26-48% depending on the Fe(III) supply in the nutrient solution. Copyright © 2012 Elsevier GmbH. All rights reserved.

Geochemical modeling of iron, sulfur, oxygen and carbon in a coastal plain aquifer

USGS Publications Warehouse

Brown, C.J.; Schoonen, M.A.A.; Candela, J.L.

2000-01-01

Fe(III) reduction in the Magothy aquifer of Long Island, NY, results in high dissolved-iron concentrations that degrade water quality. Geochemical modeling was used to constrain iron-related geochemical processes and redox zonation along a flow path. The observed increase in dissolved inorganic carbon is consistent with the oxidation of sedimentary organic matter coupled to the reduction of O2 and SO4/2- in the aerobic zone, and to the reduction of SO4/2- in the anaerobic zone; estimated rates of CO2 production through reduction of Fe(III) were relatively minor by comparison. The rates of CO2 production calculated from dissolved inorganic carbon mass transfer (2.55 x 10-4 to 48.6 x 10-4 mmol 1-1 yr-1) generally were comparable to the calculated rates of CO2 production by the combined reduction of O2, Fe(III) and SO4/2- (1.31 x 10-4 to 15 x 10-4 mmol 1-1 yr-1). The overall increase in SO4/2- concentrations along the flow path, together with the results of mass-balance calculations, and variations in ??34S values along the flow path indicate that SO4/2- loss through microbial reduction is exceeded by SO4/2- gain through diffusion from sediments and through the oxidation of FeS2. Geochemichal and microbial data on cores indicate that Fe(III) oxyhydroxide coatings on sediment grains in local, organic carbon- and SO4/2- -rich zones have localized SO4/2- -reducing zones in which the formation of iron disulfides been depleted by microbial reduction and resulted in decreases dissolved iron concentrations. These localized zones of SO4/2- reduction, which are important for assessing zones of low dissolved iron for water-supply development, could be overlooked by aquifer studies that rely only on groundwater data from well-water samples for geochemical modeling. (C) 2000 Elsevier Science B.V.Fe(III) reduction in the Magothy aquifer of Long Island, NY, results in high dissolved-iron concentrations that degrade water quality. Geochemical modeling was used to constrain iron-related geochemical processes and redox zonation along a flow path. The observed increase in dissolved inorganic carbon is consistent with the oxidation of sedimentary organic matter coupled to the reduction of O2 and SO42- in the aerobic zone, and to the reduction of SO42- in the anaerobic zone; estimated rates of CO2 production through reduction of Fe(III) were relatively minor by comparison. The rates of CO2 production calculated from dissolved inorganic carbon mass transfer (2.55??10-4 to 48.6??10-4mmol l-1yr-1) generally were comparable to the calculated rates of CO2 production by the combined reduction of O2, Fe(III) and SO42- (1.31??10-4 to 15??10-4mmol l-1yr-1). The overall increase in SO42- concentrations along the flow path, together with the results of mass-balance calculations, and variations in ??34S values along the flow path indicate that SO42- loss through microbial reduction is exceeded by SO42- gain through diffusion from sediments and through the oxidation of FeS2. Geochemical and microbial data on cores indicate that Fe(III) oxyhydroxide coatings on sediment grains in local, organic carbon- and SO42--rich zones have been depleted by microbial reduction and resulted in localized SO42--reducing zones in which the formation of iron disulfides decreases dissolved iron concentrations. These localized zones of SO42- reduction, which are important for assessing zones of low dissolved iron for water-supply development, could be overlooked by aquifer studies that rely only on groundwater data from well-water samples for geochemical modeling.

Iron dynamics: Transformation of Fe(II)/Fe(III) during injection of natural organic matter in a sandy aquifer

NASA Astrophysics Data System (ADS)

Liang, Liyuan; McCarthy, John F.; Jolley, Louwanda W.; McNabb, J. Andrew; Mehlhorn, Tonia L.

1993-05-01

The dynamics of dissolved, colloidal, and deposited iron phases were examined during a forced-gradient field experiment. The experiment involved the injection of oxygenated water containing high levels of natural organic matter (NOM) into a sandy aquifer. The initial redox potential of the aquifer favored Fe(II) in the groundwater. The changes in the concentrations of Fe(II) and Fe(III) were observed in sampling wells. Under the increased dissolved oxygen (DO) conditions, Fe(II) oxygenation was rapid, resulting in the formation of Fe(III) (hydr) oxide colloids. The oxidation follows the rate law as given in STUMM and MORGAN (1981): d[ Fe(II)] /dt = - k obs[ O2( aq)] /[ H+] 2[ Fe(II)] , with a rate constant, kobs to be 1.9 × 10 -12 M min -1. For an averaged pH and DO of the groundwater, the half time of Fe(II) oxidation is 49 h. The NOM was postulated to stabilize the newly formed colloids, thereby increasing the turbidity in the groundwater. The additional increase in the colloidal fraction of Fe(III) oxide suggested that transport of the colloidal particles was occurring. At those locations where DO remained constantly low, the turbidity increase was moderate, and up to 80% of Fe(III) was in the dissolved phase (< 3000 mol. wt). The latter observation was attributed to the presence of NOM, forming Fe(III)-organic complexes. In addition, NOM may play a role in the oxygen consumption through a Fe(II)/Fe(III) catalyzed oxidation of organic matter as outlined by STUMM and MORGAN (1981, p. 469). In this mechanism, Fe(II) oxidation is slow, maintaining a near constant Fe(II) concentration, in agreement with field data. The overall increase in Fe(III) under low DO conditions was postulated to be a combination of (1) slow oxidation, (2) ligand-promoted and catalytic dissolution of deposited iron phases, and (3) the transport of newly formed iron oxide colloids along flow paths.

Microbial production of isotopically light iron(II) in a modern chemically precipitated sediment and implications for isotopic variations in ancient rocks

USGS Publications Warehouse

Tangalos, G.E.; Beard, B.L.; Johnson, C.M.; Alpers, Charles N.; Shelobolina, E.S.; Xu, H.; Konishi, H.; Roden, E.E.

2012-01-01

The inventories and Fe isotope composition of aqueous Fe(II) and solid-phase Fe compounds were quantified in neutral-pH, chemically precipitated sediments downstream of the Iron Mountain acid mine drainage site in northern California, USA. The sediments contain high concentrations of amorphous Fe(III) oxyhydroxides [Fe(III)am] that allow dissimilatory iron reduction (DIR) to predominate over Fe–S interactions in Fe redox transformation, as indicated by the very low abundance of Cr(II)-extractable reduced inorganic sulfur compared with dilute HCl-extractable Fe. δ56Fe values for bulk HCl- and HF-extractable Fe were ≈ 0. These near-zero bulk δ56Fe values, together with the very low abundance of dissolved Fe in the overlying water column, suggest that the pyrite Fe source had near-zero δ56Fe values, and that complete oxidation of Fe(II) took place prior to deposition of the Fe(III) oxide-rich sediment. Sediment core analyses and incubation experiments demonstrated the production of millimolar quantities of isotopically light (δ56Fe ≈ -1.5 to -0.5‰) aqueous Fe(II) coupled to partial reduction of Fe(III)am by DIR. Trends in the Fe isotope composition of solid-associated Fe(II) and residual Fe(III)am are consistent with experiments with synthetic Fe(III) oxides, and collectively suggest an equilibrium Fe isotope fractionation between aqueous Fe(II) and Fe(III)am of approximately -2‰. These Fe(III) oxide-rich sediments provide a model for early diagenetic processes that are likely to have taken place in Archean and Paleoproterozoic marine sediments that served as precursors for banded iron formations. Our results suggest pathways whereby DIR could have led to the formation of large quantities of low-δ56Fe minerals during BIF genesis.

CHARACTERIZATION OF SUB-MICRON AQUEOUS IRON(III) COLLOIDS FORMED IN THE PRESENCE OF PHOSPHATE BY SEDIMENTATION FIELD FLOW FRACTIONATION WITH MULTI-ANGLE LASER LIGHT SCATTERING DETECTION

EPA Science Inventory

Iron colloids play a major role in the water chemistry of natural watersheds and of engineered drinking water distribution systems. Phosphate is frequently added to distribution systems to control corrosion problems, so iron-phosphate colloids may form through reaction of iron in...

The role of order-disorder transitions in the quest for molecular multiferroics: structural and magnetic neutron studies of a mixed valence iron(II)-iron(III) formate framework.

PubMed

Cañadillas-Delgado, Laura; Fabelo, Oscar; Rodríguez-Velamazán, J Alberto; Lemée-Cailleau, Marie-Hélène; Mason, Sax A; Pardo, Emilio; Lloret, Francesc; Zhao, Jiong-Peng; Bu, Xian-He; Simonet, Virginie; Colin, Claire V; Rodríguez-Carvajal, Juan

2012-12-05

Neutron diffraction studies have been carried out to shed light on the unprecedented order-disorder phase transition (ca. 155 K) observed in the mixed-valence iron(II)-iron(III) formate framework compound [NH(2)(CH(3))(2)](n)[Fe(III)Fe(II)(HCOO)(6)](n). The crystal structure at 220 K was first determined from Laue diffraction data, then a second refinement at 175 K and the crystal structure determination in the low temperature phase at 45 K were done with data from the monochromatic high resolution single crystal diffractometer D19. The 45 K nuclear structure reveals that the phase transition is associated with the order-disorder of the dimethylammonium counterion that is weakly anchored in the cavities of the [Fe(III)Fe(II)(HCOO)(6)](n) framework. In the low-temperature phase, a change in space group from P31c to R3c occurs, involving a tripling of the c-axis due to the ordering of the dimethylammonium counterion. The occurrence of this nuclear phase transition is associated with an electric transition, from paraelectric to antiferroelectric. A combination of powder and single crystal neutron diffraction measurements below the magnetic order transition (ca. 37 K) has been used to determine unequivocally the magnetic structure of this Néel N-Type ferrimagnet, proving that the ferrimagnetic behavior is due to a noncompensation of the different Fe(II) and Fe(III) magnetic moments.

Tracer test with As(V) under variable redox conditions controlling arsenic transport in the presence of elevated ferrous iron concentrations

USGS Publications Warehouse

Hohn, R.; Isenbeck-Schroter, M.; Kent, D.B.; Davis, J.A.; Jakobsen, R.; Jann, S.; Niedan, V.; Scholz, C.; Stadler, S.; Tretner, A.

2006-01-01

To study transport and reactions of arsenic under field conditions, a small-scale tracer test was performed in an anoxic, iron-reducing zone of a sandy aquifer at the USGS research site on Cape Cod, Massachusetts, USA. For four weeks, a stream of groundwater with added As(V) (6.7????M) and bromide (1.6??mM), was injected in order to observe the reduction of As(V) to As(III). Breakthrough of bromide (Br-), As(V), and As(III) as well as additional parameters characterizing the geochemical conditions was observed at various locations downstream of the injection well over a period of 104??days. After a short lag period, nitrate and dissolved oxygen from the injectate oxidized ferrous iron and As(V) became bound to the freshly formed hydrous iron oxides. Approximately one week after terminating the injection, anoxic conditions had been reestablished and increases in As(III) concentrations were observed within 1??m of the injection. During the observation period, As(III) and As(V) were transported to a distance of 4.5??m downgradient indicating significant retardation by sorption processes for both species. Sediment assays as well as elevated concentrations of hydrogen reflected the presence of As(V) reducing microorganisms. Thus, microbial As(V) reduction was thought to be one major process driving the release of As(III) during the tracer test in the Cape Cod aquifer. ?? 2006 Elsevier B.V. All rights reserved.

Adsorption Mechanisms of Trivalent Gold onto Iron Oxy-Hydroxides: From the Molecular Scale to the Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cances, Benjamin; /Marne La Vallee U.; Benedetti, Marc

2006-12-13

Gold is a highly valuable metal that can concentrate in iron-rich exogenetic horizons such as laterites. An improved knowledge of the retention mechanisms of gold onto highly reactive soil components such as iron oxyhydroxides is therefore needed to better understand and predict the geochemical behavior of this element. In this study, we use EXAFS information and titration experiments to provide a realistic thermochemical description of the sorption of trivalent gold onto iron oxy-hydroxides. Analysis of Au L{sub III}-edge XAFS spectra shows that aqueous Au(III) adsorbs from chloride solutions onto goethite surfaces as inner-sphere square-planar complexes (Au(III)(OH,Cl){sub 4}), with dominantly OHmore » ligands at pH > 6 and mixed OH/Cl ligands at lower pH values. In combination with these spectroscopic results, Reverse Monte Carlo simulations were used to constraint the possible sorption sites on the surface of goethite. Based on this structural information, we calculated sorption isotherms of Au(III) on Fe oxy-hydroxides surfaces, using the CD-MUSIC (Charge Distribution--Multi Site Complexation) model. The various Au(III)-sorbed species were identified as a function of pH, and the results of these EXAFS+CD-MUSIC models are compared with titration experiments. The overall good agreement between the predicted and measured structural models shows the potential of this combined approach to better model sorption processes of transition elements onto highly reactive solid surfaces such as goethite and ferrihydrite.« less

Reactivity of tris(acetylacetonato) iron(III) with tridentate [ONO] donor Schiff base as an access to newer mixed-ligand iron(III) complexes.

PubMed

Bhattacharjee, Chira R; Goswami, Pankaj; Pramanik, Harun A R; Paul, Pradip C; Mondal, Paritosh

2011-05-01

Two new mixed-ligand iron(III) complexes, [Fe(L(n))(acac)(C(2)H(5)OH)] incorporating coordinated ethanol from the reaction solvent were accessed from the reaction of [Fe(acac)(3)] with [ONO] donor dibasic tridentate unsymmetrical Schiff base ligands derived from condensation of 2-hydroxy-1-napthaldehyde with 2-aminophenol (H(2)L(1)) or 2-aminobenzoic acid (H(2)L(2)). The thermal study (TGA-DTA) provided evidence for weakly bound ethanol which is readily substituted by neutral N-donor molecule imidazole, benzimidazole or pyridine to produce an array of newer complexes, [Fe(L(n))(acac)X] (n=1, 2; X=Im, Bim, Py). The compounds were characterized by elemental analyses, FT-IR, UV-vis, solution electrical conductivity, FAB mass, (1)H and (13)C NMR spectroscopy. Room temperature magnetic susceptibility measurements (μ(eff)∼5.8 B.M.) are consistent with spin-free octahedral iron(III) complexes. Cyclic voltammetry of ethanol complexes revealed a quasi-reversible one electron redox response (ΔE(p)>100 mV) for the Fe(III)/Fe(II) couple. Low half wave redox potential (E(1/2)) values suggested easy redox susceptibility. The ground state geometries of the ethanol and imidazole complexes have been ascertained to be distorted octahedral by density functional theory using DMol3 program at BLYP/DNP level. Copyright © 2011 Elsevier B.V. All rights reserved.

Electronic structure of binuclear acetylacetonates of boron difluoride

NASA Astrophysics Data System (ADS)

Tikhonov, Sergey A.; Svistunova, Irina V.; Samoilov, Ilya S.; Osmushko, Ivan S.; Borisenko, Aleksandr V.; Vovna, Vitaliy I.

2018-05-01

The electronic structure of boron difluoride acetylacetonate and its three derivatives was studied using photoelectron and absorption spectroscopy, as well as the density functional theory. In a series of binuclear acetylacetonate complexes containing bridge-moieties of sulfur and selenium atoms, it was found an appreciable mixing of the π3-orbital of the chelate cycle with atomic orbitals S 3p and Se 4p resulting in destabilization of the HOMO levels by 0.4-0.6 eV, in comparison with the monomer. The positively charged fragment C(CH3)-CX-C(CH3) causes the field effect, which leads to stabilization of the LUMO levels by 0.3-0.4 eV and C 1s-levels by 0.5-1.2 eV. An analysis of the research results on the electronic structure made it possible to determine the effect of substituents in the γ position on the absorption spectra, which is mainly determined by the electron density transfer from the chalcogen atoms to the chelate cycles. It is shown that the calculated energy intervals between electron levels correlate well with the structure of the photoelectron spectra of valence and core electrons.

Preparation and Biodistribution Studies of a Radiogallium-Acetylacetonate Bis (Thiosemicarbazone) Complex in Tumor-Bearing Rodents

PubMed Central

Jalilian, Amir Reza; Yousefnia, Hassan; Shafaii, Kamaleddin; Novinrouz, Aytak; Rajamand, Amir Abbas

2012-01-01

Various radiometal complexes have been developed for tumor imaging, especially Ga-68 tracer. In the present study, the development of a radiogallium bis-thiosemicarbazone complex has been reported. [67Ga] acetylacetonate bis(thiosemicarbazone) complex ([67Ga] AATS) was prepared starting [67Ga]Gallium acetate and freshly prepared acetylacetonate bis (thiosemicarbazone) (AATS) in 30 min at 90°C. The partition co-efficient and the stability of the tracer were determined in final solution (25°C) and the presence of human serum (37°C) up to 24 h. The biodistribution of the labeled compound in wild-type and fibrosarcoma-bearing rodents were determined up to 72 h. The radiolabled Ga complex was prepared in high radiochemical purity (> 97%, HPLC) followed by initial biodistribution data with the significant tumor accumulation of the tracer in 2 h which is far higher than free Ga-67 cation while the compound wash-out is significantly faster. Above-mentioned pharmacokinetic properties suggest an interesting radiogallium complex while prepared by the PET Ga radioisotope, 68Ga, in accordance with the physical half life, for use in fibrosarcoma tumors, and possibly other malignancies. PMID:24250475

Antitumor activity of Ru(III) complexes carrying beta-diketonato ligands in vitro and in vivo.

PubMed

Arandjelovic, S S; Bjelogrlic, K S; Malesevic, N N; Tesic, Lj Z; Radulovic, S S

2009-01-01

To investigate the antitumor activity of two newly synthesized ruthenium(III) [Ru(III)] compounds carrying bidentate ligands: (acac)-acetylacetonate, [Ru(acac)3), and (tfac)-trifluoroacetylacetonate [Ru(tfac)3]. The activity of ruthenium(III) analogues was evaluated on HeLa, B16, and Femx cell lines for cytotoxicity in vitro using MTT assay, and inhibition on tumor invading ability in vitro using cell migration and invasion assays, whereas inhibition of tumor growth in vivo was estimated on advanced B16 murine melanoma model. Both compounds were also investigated in combinations with cisplatin, oxaliplatin, or poly ADP-ribose polymerase- 1 (PARP-1) inhibitor, in order to determine the pattern of mutual interactions. Applied as single drugs, Ru(tfac)3 showed high cytotoxic activity against HeLa and Femx cell lines, while Ru(acac)3 did not reach the IC50 on any of the cell lines tested. In combinations, Ru(acac)3 with cisplatin gained synergistic interaction, antagonistic with oxaliplatin, and of different kind with (PARP-1) inhibitor in concentration-and cell line-dependent manner. Ru(acac)3 exhibited inhibition of HeLa cell migration and gelatinolytic activity of MMP-2 and MMP-9. Ru(tfac)3 complexes did not induce significant reduction of melanoma growth in vivo, whereas Ru(acac)3 did, but the latter failed to contribute in lifespan improvement. The investigated ruthenium complexes showed different levels of antitumor activity in vitro and in vivo, implicating on different mechanisms of their action as well as diverse perspectives in cancer treatment.

Ba2F2Fe(1.5)Se3: An Intergrowth Compound Containing Iron Selenide Layers.

PubMed

Driss, Dalel; Janod, Etienne; Corraze, Benoit; Guillot-Deudon, Catherine; Cario, Laurent

2016-03-21

The iron selenide compound Ba2F2Fe(1.5)Se3 was synthesized by a high-temperature ceramic method. The single-crystal X-ray structure determination revealed a layered-like structure built on [Ba2F2](2+) layers of the fluorite type and iron selenide layers [Fe(1.5)Se3](2-). These [Fe1.5Se3](2-) layers contain iron in two valence states, namely, Fe(II+) and Fe(III+) located in octahedral and tetrahedral sites, respectively. Magnetic measurements are consistent with a high-spin state for Fe(II+) and an intermediate-spin state for Fe(III+). Moreover, susceptibility and resistivity measurements demonstrate that Ba2F2Fe(1.5)Se3 is an antiferromagnetic insulator.

Stability of bacterial carotenoids in the presence of iron in a model of the gastric compartment - comparison with dietary reference carotenoids.

PubMed

Sy, Charlotte; Dangles, Olivier; Borel, Patrick; Caris-Veyrat, Catherine

2015-04-15

Recently isolated spore-forming pigmented marine bacteria, Bacillus indicus HU36 and Bacillus firmus GB1 are sources of carotenoids (∼fifteen distinct yellow and orange pigments and ∼thirteen distinct pink pigments, respectively). They are glycosides of oxygenated lycopene derivatives (apo-lycopenoids) and are assumed to be more heat- and gastric-stable than common carotenoids. In this study, the oxidation by O2 of the bacterial carotenoids was initiated by free iron (Fe(II) and Fe(III)) or by heme iron (metmyoglobin) in a mildly acidic aqueous solution mimicking the gastro-intestinal compartment and compared to the oxidation of the common dietary carotenoids β-carotene, lycopene and astaxanthin. Under these conditions, all bacterial carotenoids appear more stable in the presence of heme iron vs. free iron. Carotenoid autoxidation initiated by Fe(II) is relatively fast and likely involves reactive oxygen-iron species derived from Fe(II) and O2. By contrast, the corresponding reaction with Fe(III) is kinetically blocked by the slow preliminary reduction of Fe(III) into Fe(II) by the carotenoids. The stability of carotenoids toward autoxidation increases as follows: β-carotene

Distribution and genetic diversity of the microorganisms in the biofilter for the simultaneous removal of arsenic, iron and manganese from simulated groundwater.

PubMed

Yang, Liu; Li, Xiangkun; Chu, Zhaorui; Ren, Yuhui; Zhang, Jie

2014-03-01

A biofilter was developed in this study, which showed an excellent performance with the simultaneous removal of AsIII from 150 to 10mg L(-1) during biological iron and manganese oxidation. The distribution and genetic diversity of the microorganisms along the depth of the biofilter have been investigated using DGGE. Results suggested that Iron oxidizing bacteria (IOB, such as Gallionella, Leptothrix), Manganese oxidizing bacteria (MnOB, such as Leptothrix, Pseudomonas, Hyphomicrobium, Arthrobacter) and AsIII-oxidizing bacteria (AsOB, such as Alcaligenes, Pseudomonas) are dominant in the biofilter. The spatial distribution of IOB, MnOB and AsOB at different depths of the biofilter determined the removal zone of FeII, MnII and AsIII, which site at the depths of 20, 60 and 60cm, respectively, and the corresponding removal efficiencies were 86%, 84% and 87%, respectively. This process shows great potential to the treatment of groundwater contaminated with iron, manganese and arsenic due to its stable performance and significant cost-savings. Copyright © 2014 Elsevier Ltd. All rights reserved.

Kinetic studies on the oxidation of oxyhemoglobin by biologically active iron thiosemicarbazone complexes: relevance to iron-chelator-induced methemoglobinemia.

PubMed

Basha, Maram T; Rodríguez, Carlos; Richardson, Des R; Martínez, Manuel; Bernhardt, Paul V

2014-03-01

The oxidation of oxyhemoglobin to methemoglobin has been found to be facilitated by low molecular weight iron(III) thiosemicarbazone complexes. This deleterious reaction, which produces hemoglobin protein units unable to bind dioxygen and occurs during the administration of iron chelators such as the well-known 3-aminopyridine-2-pyridinecarbaldehyde thiosemicarbazone (3-AP; Triapine), has been observed in the reaction with Fe(III) complexes of some members of the 3-AP structurally-related thiosemicarbazone ligands derived from di-2-pyridyl ketone (HDpxxT series). We have studied the kinetics of this oxidation reaction in vitro using human hemoglobin and found that the reaction proceeds with two distinct time-resolved steps. These have been associated with sequential oxidation of the two different oxyheme cofactors in the α and β protein chains. Unexpected steric and hydrogen-bonding effects on the Fe(III) complexes appear to be the responsible for the observed differences in the reaction rate across the series of HDpxxT ligand complexes used in this study.

21 CFR 184.1296 - Ferric ammonium citrate.

Code of Federal Regulations, 2013 CFR

2013-04-01

... citrate (iron (III) ammonium citrate) is prepared by the reaction of ferric hydroxide with citric acid... 18.5 percent iron, approximately 9 percent ammonia, and 65 percent citric acid and occurs as reddish... composed of 14.5 to 16 percent iron, approximately 7.5 percent ammonia, and 75 percent citric acid and...

21 CFR 184.1296 - Ferric ammonium citrate.

Code of Federal Regulations, 2010 CFR

2010-04-01

... citrate (iron (III) ammonium citrate) is prepared by the reaction of ferric hydroxide with citric acid... 18.5 percent iron, approximately 9 percent ammonia, and 65 percent citric acid and occurs as reddish... composed of 14.5 to 16 percent iron, approximately 7.5 percent ammonia, and 75 percent citric acid and...

21 CFR 184.1296 - Ferric ammonium citrate.

Code of Federal Regulations, 2011 CFR

2011-04-01

... citrate (iron (III) ammonium citrate) is prepared by the reaction of ferric hydroxide with citric acid... 18.5 percent iron, approximately 9 percent ammonia, and 65 percent citric acid and occurs as reddish... composed of 14.5 to 16 percent iron, approximately 7.5 percent ammonia, and 75 percent citric acid and...

21 CFR 184.1296 - Ferric ammonium citrate.

Code of Federal Regulations, 2012 CFR

2012-04-01

... citrate (iron (III) ammonium citrate) is prepared by the reaction of ferric hydroxide with citric acid... 18.5 percent iron, approximately 9 percent ammonia, and 65 percent citric acid and occurs as reddish... composed of 14.5 to 16 percent iron, approximately 7.5 percent ammonia, and 75 percent citric acid and...

Orenia metallireducens sp. nov. Strain Z6, a Novel Metal-Reducing Member of the Phylum Firmicutes from the Deep Subsurface

PubMed Central

Sanford, Robert A.; Boyanov, Maxim I.; Kemner, Kenneth M.; O'Loughlin, Edward J.; Chang, Yun-juan; Locke, Randall A.; Weber, Joseph R.; Egan, Sheila M.; Mackie, Roderick I.; Cann, Isaac; Fouke, Bruce W.

2016-01-01

ABSTRACT A novel halophilic and metal-reducing bacterium, Orenia metallireducens strain Z6, was isolated from briny groundwater extracted from a 2.02 km-deep borehole in the Illinois Basin, IL. This organism shared 96% 16S rRNA gene similarity with Orenia marismortui but demonstrated physiological properties previously unknown for this genus. In addition to exhibiting a fermentative metabolism typical of the genus Orenia, strain Z6 reduces various metal oxides [Fe(III), Mn(IV), Co(III), and Cr(VI)], using H2 as the electron donor. Strain Z6 actively reduced ferrihydrite over broad ranges of pH (6 to 9.6), salinity (0.4 to 3.5 M NaCl), and temperature (20 to 60°C). At pH 6.5, strain Z6 also reduced more crystalline iron oxides, such as lepidocrocite (γ-FeOOH), goethite (α-FeOOH), and hematite (α-Fe2O3). Analysis of X-ray absorption fine structure (XAFS) following Fe(III) reduction by strain Z6 revealed spectra from ferrous secondary mineral phases consistent with the precipitation of vivianite [Fe3(PO4)2] and siderite (FeCO3). The draft genome assembled for strain Z6 is 3.47 Mb in size and contains 3,269 protein-coding genes. Unlike the well-understood iron-reducing Shewanella and Geobacter species, this organism lacks the c-type cytochromes for typical Fe(III) reduction. Strain Z6 represents the first bacterial species in the genus Orenia (order Halanaerobiales) reported to reduce ferric iron minerals and other metal oxides. This microbe expands both the phylogenetic and physiological scopes of iron-reducing microorganisms known to inhabit the deep subsurface and suggests new mechanisms for microbial iron reduction. These distinctions from other Orenia spp. support the designation of strain Z6 as a new species, Orenia metallireducens sp. nov. IMPORTANCE A novel iron-reducing species, Orenia metallireducens sp. nov., strain Z6, was isolated from groundwater collected from a geological formation located 2.02 km below land surface in the Illinois Basin, USA. Phylogenetic, physiologic, and genomic analyses of strain Z6 found it to have unique properties for iron reducers, including (i) active microbial iron-reducing capacity under broad ranges of temperatures (20 to 60°C), pHs (6 to 9.6), and salinities (0.4 to 3.5 M NaCl), (ii) lack of c-type cytochromes typically affiliated with iron reduction in Geobacter and Shewanella species, and (iii) being the only member of the Halanaerobiales capable of reducing crystalline goethite and hematite. This study expands the scope of phylogenetic affiliations, metabolic capacities, and catalytic mechanisms for iron-reducing microbes. PMID:27565620

Abiotic transformation of high explosives by freshly precipitated iron minerals in aqueous Fe¹¹ solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boparai, Hardiljeet K.; Comfort, Steve; Satapanajaru, Tunlawit

Zerovalent iron barriers have become a viable treatment for field-scale cleanup of various ground water contaminants. While contact with the iron surface is important for contaminant destruction, the interstitial pore water within and near the iron barrier will be laden with aqueous, adsorbed and precipitated FeII phases. These freshly precipitated iron minerals could play an important role in transforming high explosives (HE). Our objective was to determine the transformation of RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), and TNT (2,4,6-trinitrotoluene) by freshly precipitated iron FeII/FeIII minerals. This was accomplished by quantifying the effects of initial FeII concentration, pH, and the presence of aquifermore » solids (FeIII phases) on HE transformation rates. Results showed that at pH 8.2, freshly precipitated iron minerals transformed RDX, HMX, and TNT with reaction rates increasing with increasing FeII concentrations. RDX and HMX transformations in these solutions also increased with increasing pH (5.8-8.55). By contrast, TNT transformation was not influenced by pH (6.85-8.55) except at pH values <6.35. Transformations observed via LC/MS included a variety of nitroso products (RDX, HMX) and amino degradation products (TNT). XRD analysis identified green rust and magnetite as the dominant iron solid phases that precipitated from the aqueous FeII during HE treatment under anaerobic conditions. Geochemical modeling also predicted FeII activity would likely be controlled by green rust and magnetite. These results illustrate the important role freshly precipitated FeII/FeIII minerals in aqueous FeII solutions play in the transformation of high explosives.« less

Biological activity of Fe(III) aquo-complexes towards ferric chelate reductase (FCR).

PubMed

Escudero, Rosa; Gómez-Gallego, Mar; Romano, Santiago; Fernández, Israel; Gutiérrez-Alonso, Ángel; Sierra, Miguel A; López-Rayo, Sandra; Nadal, Paloma; Lucena, Juan J

2012-03-21

In this study we have obtained experimental evidence that confirms the high activity of aquo complexes III and IV towards the enzyme FCR, responsible for the reduction of Fe(III) to Fe(II) in the process of iron acquisition by plants. The in vivo FCR assays in roots of stressed cucumber plants have shown a higher efficiency of the family of complexes III and a striking structure-activity relationship with the nature of the substituent placed in a phenyl group far away from the metal center. The results obtained in this work demonstrate that all the aquo compounds tested interact efficiently with the enzyme FCR and hence constitute a new concept of iron chelates that could be of great use in agronomy.

Importance of clay size minerals for Fe(III) respiration in a petroleum-contaminated aquifer

USGS Publications Warehouse

Shelobolina, Evgenya S.; Anderson, Robert T.; Vodyanitskii, Yury N.; Sivtsov, Anatolii V.; Yuretich, Richard; Lovely, Derek R.

2004-01-01

The availability of Fe(III)-bearing minerals for dissimilatory Fe(III) reduction was evaluated in sediments from a petroleum-contaminated sandy aquifer near Bemidji, Minnesota (USA). First, the sediments from a contaminated area of the aquifer, in which Fe(III) reduction was the predominant terminal electron accepting process, were compared with sediments from a nearby, uncontaminated site. Data from 0.5 m HCl extraction of different size fractions of the sediments revealed that the clay size fraction contributed a significant portion of the ‘bio-available’ Fe(III) in the background sediment and was the most depleted in ‘bio-available’ Fe(III) in the iron-reducing sediment. Analytical transmission electron microscopy (TEM) revealed the disappearance of thermodynamically unstable Fe(III) and Mn(IV) hydroxides (ferrihydrite and Fe vernadite), as well as a decrease in the abundance of goethite and lepidocrocite in the clay size fraction from the contaminated sediment. TEM observations and X-ray diffraction examination did not provide strong evidence of Fe(III)-reduction-related changes within another potential source of ‘bio-available’ Fe(III) in the clay size fraction – ferruginous phyllosilicates. However, further testing in the laboratory with sediments from the methanogenic portion of the aquifer that were depleted in microbially reducible Fe(III) revealed the potential for microbial reduction of Fe(III) associated with phyllosilicates. Addition of a clay size fraction from the uncontaminated sediment, as well as Fe(III)-coated kaolin and ferruginous nontronite SWa-1, as sources of poorly crystalline Fe(III) hydroxides and structural iron of phyllosilicates respectively, lowered steady-state hydrogen concentrations consistent with a stimulation of Fe(III) reduction in laboratory incubations of methanogenic sediments. There was no change in hydrogen concentration when non-ferruginous clays or no minerals were added. This demonstrated that Fe(III)-bearing clay size minerals were essential for microbial Fe(III) reduction and suggested that both potential sources of ‘bio-available’ Fe(III) in the clay size fraction, poorly crystalline Fe(III) hydroxides and structural Fe(III) of phyllosilicates, were important sources of electron acceptor for indigenous iron-reducing microorganisms in this aquifer.

Identification and Spectroscopic Characterization of Nonheme Iron(III) Hypochlorite Intermediates**

PubMed Central

Draksharapu, Apparao; Angelone, Davide; Quesne, Matthew G; Padamati, Sandeep K; Gómez, Laura; Hage, Ronald; Costas, Miquel; Browne, Wesley R; de Visser, Sam P

2015-01-01

FeIII–hypohalite complexes have been implicated in a wide range of important enzyme-catalyzed halogenation reactions including the biosynthesis of natural products and antibiotics and post-translational modification of proteins. The absence of spectroscopic data on such species precludes their identification. Herein, we report the generation and spectroscopic characterization of nonheme FeIII–hypohalite intermediates of possible relevance to iron halogenases. We show that FeIII-OCl polypyridylamine complexes can be sufficiently stable at room temperature to be characterized by UV/Vis absorption, resonance Raman and EPR spectroscopies, and cryo-ESIMS. DFT methods rationalize the pathways to the formation of the FeIII-OCl, and ultimately FeIV=O, species and provide indirect evidence for a short-lived FeII-OCl intermediate. The species observed and the pathways involved offer insight into and, importantly, a spectroscopic database for the investigation of iron halogenases. PMID:25663379

Prebiotic Polymerization: Oxidative Polymerization of 2,3 Dimercapto-1- Propanol on the Surface of Iron(III) Hydroxide Oxide

NASA Technical Reports Server (NTRS)

Weber, Arthur L.

1995-01-01

The oxidation of 2,3-dimercapto-1-propanol by ferric ions on the surface of iron(III) hydroxide oxide (Fe(OH)O) yielded polydisulfide oligomers. This polymerization occurred readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron(III) hydroxide oxide (20 mg, 160 micromole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the FE(OH)O phase. Reactions carried out at the same ratio of dithiol to FE(OH)O but at higher dithiol concentrations gave higher yields of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis is discussed.

Prebiotic polymerization: Oxidative polymerization of 2, 3-dimercapto-1-propanol on the surface of iron(III) hydroxide oxide

NASA Technical Reports Server (NTRS)

Weber, Arthur L.

1995-01-01

The oxidation of 2, 3-dimercapto-1-propanol by ferric ions on the surface of iron(III) hydroxide oxide (Fe(OH)O) yielded polydisulfide oligomers. This polymerization occurred readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron(III) hydroxide oxide (20 mg, 160 micromole Fe) for 3 days under anaerobic conditions at 40 C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the Fe(OH)O phase. Reactions carried out at the same ratio of dithiol to Fe(OH)O but at higher dithiol concentrations gave higher yields of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis is discussed.

Detox{sup SM} wet oxidation system studies for engineering scale up

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robertson, D.T.; Moslander, J.E.; Zigmond, J.A.

1995-12-31

Catalyzed wet oxidation utilizing iron(III) has been shown to have promise for treating many hazardous and mixed wastes. The reaction occurs at the surface of contact between an aqueous iron(III) solution and organic material. Studies with liquid- and vapor-phase organic waste surrogates have established reaction kinetics and the limits of reaction rate based on organic concentration and iron(III) diffusion. Continuing engineering studies have concentrated on reaction vessel agitator and solids feed configurations, an improved bench scale reflux condenser and reflux condenser calculations, sparging of organic compounds from the process condensate water, filtration of solids from the process solution, and flammabilitymore » limits for volatile organic compounds in the headspace of the reaction vessel under the reaction conditions. Detailed engineering design and fabrication of a demonstration unit for treatment of mixed waste is in progress.« less

The effect of iron to manganese substitution on microperoxidase 8 catalysed peroxidase and cytochrome P450 type of catalysis.

PubMed

Primus, J L; Boersma, M G; Mandon, D; Boeren, S; Veeger, C; Weiss, R; Rietjens, I M

1999-06-01

This study describes the catalytic properties of manganese microperoxidase 8 [Mn(III)MP8] compared to iron microperoxidase 8 [Fe(III)MP8]. The mini-enzymes were tested for pH-dependent activity and operational stability in peroxidase-type conversions, using 2-methoxyphenol and 3,3'-dimethoxybenzidine, and in a cytochrome P450-like oxygen transfer reaction converting aniline to para-aminophenol. For the peroxidase type of conversions the Fe to Mn replacement resulted in a less than 10-fold decrease in the activity at optimal pH, whereas the aniline para-hydroxylation is reduced at least 30-fold. In addition it was observed that the peroxidase type of conversions are all fully blocked by ascorbate and that aniline para-hydroxylation by Fe(III)MP8 is increased by ascorbate whereas aniline para-hydroxylation by Mn(III)MP8 is inhibited by ascorbate. Altogether these results indicate that different types of reactive metal oxygen intermediates are involved in the various conversions. Compound I/II, scavenged by ascorbate, may be the reactive species responsible for the peroxidase reactions, the polymerization of aniline and (part of) the oxygen transfer to aniline in the absence of ascorbate. The para-hydroxylation of aniline by Fe(III)MP8, in the presence of ascorbate, must be mediated by another reactive iron-oxo species which could be the electrophilic metal(III) hydroperoxide anion of microperoxidase 8 [M(III)OOH MP8]. The lower oxidative potential of Mn, compared to Fe, may affect the reactivity of both compound I/II and the metal(III) hydroperoxide anion intermediate, explaining the differential effect of the Fe to Mn substitution on the pH-dependent behavior, the rate of catalysis and the operational stability of MP8.

^1H NMR studies of the diamagnetic gallium (III) and paramagnetic iron (III) complexes of a chiral macrobicyclic ligand of bicapped tris (binaphtol) type

NASA Astrophysics Data System (ADS)

Baret, P.; Beaujolais, V.; Bougault, C.; Gaude, D.; Pierre, J.-L.

1998-01-01

^1H NMR studies of the diamagnetic gallium (III) and paramagnetic iron (III) complexes of a chiral macrobicyclic ligand of bicapped tris (binaphtol) type are described. The study of the gallium complex emphasizes: (i) that the inversion of the octahedral center is not observed and: (ii) the absence of exchange between free ligand and complex, at room temperature. In the case of the iron complex, assignments of the hyperfine shifted resolved resonances are achieved, based on temperature-behavior studies, which evidence the D3 symmetry of the complex. These assignments are in complete agreement with measured T1 values and proton-to-iron distances obtained from molecular modelling. Les complexes du gallium (III) et du fer (III) d'un ligand macrobicyclique chiral impliquant trois sous-unités de type binaphtol sont étudiés en RMN du proton en solution méthanolique. L'étude du complexe (diamagnétique) du gallium permet de montrer que le complexe : (i) ne subit pas d'inversion de la configuration (Δ/Λ) du site octaédrique et : (ii) qu'il n'y a pas d'échange entre ligand libre et complexe à la température ambiante. L'évolution du spectre du complexe paramagnétique du fer avec la température permet une attribution des protons du ligand et met en évidence la symétrie D3 du complexe. Une bonne corrélation est obtenue entre la distance fer-proton (donnée par la modélisation moléculaire) et le T1 du proton considéré.

Adsorptive removal of arsenic by novel iron/olivine composite: Insights into preparation and adsorption process by response surface methodology and artificial neural network.

PubMed

Ghosal, Partha S; Kattil, Krishna V; Yadav, Manoj K; Gupta, Ashok K

2018-03-01

Olivine, a low-cost natural material, impregnated with iron is introduced in the adsorptive removal of arsenic. A wet impregnation method and subsequent calcination were employed for the preparation of iron/olivine composite. The major preparation process parameter, viz., iron loading and calcination temperature were optimized through the response surface methodology coupled with a factorial design. A significant variation of adsorption capacity of arsenic (measured as total arsenic), i.e., 63.15 to 310.85 mg/kg for arsenite [As(III) T ] and 76.46 to 329.72 mg/kg for arsenate [As(V) T ] was observed, which exhibited the significant effect of the preparation process parameters on the adsorption potential. The iron loading delineated the optima at central points, whereas a monotonous decreasing trend of adsorption capacity for both the As(III) T and As(V) T was observed with the increasing calcination temperature. The variation of adsorption capacity with the increased iron loading is more at lower calcination temperature showing the interactive effect between the factors. The adsorbent prepared at the optimized condition of iron loading and calcination temperature, i.e., 10% and 200 °C, effectively removed the As(III) T and As(V) T by more than 96 and 99%, respectively. The material characterization of the adsorbent showed the formation of the iron compound in the olivine and increase in specific surface area to the tune of 10 multifold compared to the base material, which is conducive to the enhancement of the adsorption capacity. An artificial neural network was applied for the multivariate optimization of the adsorption process from the experimental data of the univariate optimization study and the optimized model showed low values of error functions and high R 2 values of more than 0.99 for As(III) T and As(V) T . The adsorption isotherm and kinetics followed Langmuir model and pseudo second order model, respectively demonstrating the chemisorption in this study. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effects of exogenous pyoverdines on Fe availability and their impacts on Mn(II) oxidation by Pseudomonas putida GB-1

PubMed Central

Lee, Sung-Woo; Parker, Dorothy L.; Geszvain, Kati; Tebo, Bradley M.

2014-01-01

Pseudomonas putida GB-1 is a Mn(II)-oxidizing bacterium that produces pyoverdine-type siderophores (PVDs), which facilitate the uptake of Fe(III) but also influence MnO2 formation. Recently, a non-ribosomal peptide synthetase mutant that does not synthesize PVD was described. Here we identified a gene encoding the PVDGB-1 (PVD produced by strain GB-1) uptake receptor (PputGB1_4082) of strain GB-1 and confirmed its function by in-frame mutagenesis. Growth and other physiological responses of these two mutants and of wild type were compared during cultivation in the presence of three chemically distinct sets of PVDs (siderotypes n°1, n°2, and n°4) derived from various pseudomonads. Under iron-limiting conditions, Fe(III) complexes of various siderotype n°1 PVDs (including PVDGB-1) allowed growth of wild type and the synthetase mutant, but not the receptor mutant, confirming that iron uptake with any tested siderotype n°1 PVD depended on PputGB1_4082. Fe(III) complexes of a siderotype n°2 PVD were not utilized by any strain and strongly induced PVD synthesis. In contrast, Fe(III) complexes of siderotype n°4 PVDs promoted the growth of all three strains and did not induce PVD synthesis by the wild type, implying these complexes were utilized for iron uptake independent of PputGB1_4082. These differing properties of the three PVD types provided a way to differentiate between effects on MnO2 formation that resulted from iron limitation and others that required participation of the PVDGB-1 receptor. Specifically, MnO2 production was inhibited by siderotype n°1 but not n°4 PVDs indicating PVD synthesis or PputGB1_4082 involvement rather than iron-limitation caused the inhibition. In contrast, iron limitation was sufficient to explain the inhibition of Mn(II) oxidation by siderotype n°2 PVDs. Collectively, our results provide insight into how competition for iron via siderophores influences growth, iron nutrition and MnO2 formation in more complex environmental systems. PMID:25009534

Iron-Mediated Oxidation of Methoxyhydroquinone under Dark Conditions: Kinetic and Mechanistic Insights.

PubMed

Yuan, Xiu; Davis, James A; Nico, Peter S

2016-02-16

Despite the biogeochemical significance of the interactions between natural organic matter (NOM) and iron species, considerable uncertainty still remains as to the exact processes contributing to the rates and extents of complexation and redox reactions between these important and complex environmental components. Investigations on the reactivity of low-molecular-weight quinones, which are believed to be key redox active compounds within NOM, toward iron species, could provide considerable insight into the kinetics and mechanisms of reactions involving NOM and iron. In this study, the oxidation of 2-methoxyhydroquinone (MH2Q) by ferric iron (Fe(III)) under dark conditions in the absence and presence of oxygen was investigated within a pH range of 4-6. Although Fe(III) was capable of stoichiometrically oxidizing MH2Q under anaerobic conditions, catalytic oxidation of MH2Q was observed in the presence of O2 due to further cycling between oxygen, semiquinone radicals, and iron species. A detailed kinetic model was developed to describe the predominant mechanisms, which indicated that both the undissociated and monodissociated anions of MH2Q were kinetically active species toward Fe(III) reduction, with the monodissociated anion being the key species accounting for the pH dependence of the oxidation. The generated radical intermediates, namely semiquinone and superoxide, are of great importance in reaction-chain propagation. The kinetic model may provide critical insight into the underlying mechanisms of the thermodynamic and kinetic characteristics of metal-organic interactions and assist in understanding and predicting the factors controlling iron and organic matter transformation and bioavailability in aquatic systems.

Interactions between iron(III)-hydroxide polymaltose complex and commonly used medications / laboratory studies in rats.

PubMed

Funk, Felix; Canclini, Camillo; Geisser, Peter

2007-01-01

Simple iron salts, such as iron sulphate, often interact with food and other medications reducing bioavailability and tolerability. Iron(III)-hydroxide polymaltose complex (IPC, Maltofer) provides a soluble form of non-ionic iron, making it an ideal form of oral iron supplementation. The physicochemical properties of IPC predict a low potential for interactions. The effects of co-administration with aluminium hydroxide (CAS 21645-51-2), acetylsalicylic acid (CAS 50-78-2), bromazepam (CAS 1812-30-2), calcium acetate (CAS 62-54-4), calcium carbonate (CAS 471-34-1), auranofin (CAS 34031-32-8), magnesium-L-aspartate hydrochloride (CAS 28184-71-6), methyldopa sesquihydrate (CAS 41372-08-1), paracetamol (CAS 103-90-2), penicillamine (CAS 52-67-5), sulfasalazine (CAS 599-79-1), tetracycline hydrochloride (CAS 64-75-5), calcium phosphate (CAS 7757-93-9) in combination with vitamin D3 (CAS 67-97-0), and a multi-vitamin preparation were tested in rats fed an iron-deficient diet. Uptake of iron from radiolabelled IPC with and without concomitant medications was compared. None of the medicines tested had a significant effect on iron uptake. Iron-59 retrieval from blood and major storage organs was 64-76% for IPC alone compared with 59-85% following co-administration with other medications. It is concluded that, under normal clinical conditions, IPC does not interact with these medications.

A Description of an Acidophilic, Iron Reducer, Geobacter sp. FeAm09 Isolated from Tropical Soils

NASA Astrophysics Data System (ADS)

Healy, O.; Souchek, J.; Heithoff, A.; LaMere, B.; Pan, D.; Hollis, G.; Yang, W. H.; Silver, W. L.; Weber, K. A.

2014-12-01

Iron (Fe) is the fourth most abundant element in the Earth's crust and plays a significant role controlling the geochemistry in soils, sediments, and aquatic systems. As part of a study to understand microbially-catalysed iron biogeochemical cycling in tropical soils, an iron reducing isolate, strain FeAm09, was obtained. Strain FeAm09 was isolated from acidic, Fe-rich soils collected from a tropical forest (Luquillo Experimental Forest, Puerto Rico). Strain FeAm09 is a rod-shaped, motile, Gram-negative bacterium. Taxonomic analysis of the near complete 16S rRNA gene sequence revealed that strain FeAm09 is 94.7% similar to Geobacter lovleyi, placing it in the genus Geobacter within the Family Geobacteraceae in the Deltaproteobacteria. Characterization of the optimal growth conditions revealed that strain FeAm09 is a moderate acidophile with an optimal growth pH of 5.0. The optimal growth temperature was 37°C. Growth of FeAm09 was coupled to the reduction of soluble Fe(III), Fe(III)-NTA, with H2, fumarate, ethanol, and various organic acids and sugars serving as the electron donor. Insoluble Fe(III), in the form of synthetic ferrihydrite, was reduced by strain FeAm09 using acetate or H2 as the electron donor. The use of H2 as an electron donor in the presence of CO2 and absence of organic carbon and assimilation of 14C-labelled CO2 into biomass indicate that strain FeAm09 is an autotrophic Fe(III)-reducing bacterium. Together, these data describe the first acidophilic, autotrophic Geobacter species. Iron reducing bacteria were previously shown to be as abundant in tropical soils as in saturated sediments (lake-bottoms) and saturated soils (wetlands) where Fe(III) reduction is more commonly recognized as a dominant mode of microbial respiration. Furthermore, Fe(III) reduction was identified as a primary driver of carbon mineralization in these tropical soils (Dubinsky et al. 2010). In addition to mineralizing organic carbon, Geobacter sp. FeAm09 is likely to also play an indirect role in carbon cycling by consuming H2 promoting microbial carbon fermentation in iron-rich tropical soils.

Effect of sulfide on As(III) and As(V) sequestration by ferrihydrite.

PubMed

Zhao, Zhixi; Wang, Shaofeng; Jia, Yongfeng

2017-10-01

The sulfide-induced change in arsenic speciation is often coupled to iron geochemical processes, including redox reaction, adsorption/desorption and precipitation/dissolution. Knowledge about how sulfide influenced the coupled geochemistry of iron and arsenic was not explored well up to now. In this work, retention and mobilization of As(III) and As(V) on ferrihydrite in sulfide-rich environment was studied. The initial oxidation states of arsenic and the contact order of sulfide notably influenced arsenic sequestration on ferrihydrite. For As(III) systems, pre-sulfidation of As(III) decreased arsenic sequestration mostly. The arsenic adsorption capacity decreased about 50% in comparison with the system without sulfide addition. For As(V) systems, pre-sulfidation of ferrihydrite decreased 30% sequestration of arsenic on ferrihydrite. Reduction of ferrihydrite by sulfide in As(V) system was higher than that in As(III) system. Geochemical modeling calculations identified formation of thioarsenite in the pre-sulfidation of As(III) system. Formation of arsenic thioanions enhanced As solubility in the pre-sulfidation of As(III) system. The high concentration of sulfide and Fe(II) in pre-sulfidation of ferrihydrite system contributed to saturation of FeS. This supplied new solid phase to immobilize soluble arsenic in aqueous phase. X-ray absorption near edge spectroscopy (XANES) of sulfur K-edge, arsenic K-edge and iron L-edge analysis gave the consistent evidence for the sulfidation reaction of arsenic and ferrihydrite under specific geochemical settings. Copyright © 2017 Elsevier Ltd. All rights reserved.

Functional Significance of Iron Deficiency. Annual Nutrition Workshop Series, Volume III.

ERIC Educational Resources Information Center

Enwonwu, Cyril O., Ed.

Iron deficiency anemia impairs cognitive performance, physical capacity, and thermoregulation. Recent evidence suggests that these functional impairments are also evident in subclinical nonanemic iron deficiency. Very little is known about the relevance of the latter to the health of blacks, who have been shown to have the highest prevalence of…

Effect of Organic Substances on the Efficiency of Fe(Ii) to Fe(Iii) Oxidation and Removal of Iron Compounds from Groundwater in the Sedimentation Process

NASA Astrophysics Data System (ADS)

Krupińska, Izabela

2017-09-01

One of the problems with iron removal from groundwater is organic matter. The article presents the experiments involved groundwater samples with a high concentration of total iron - amounting to 7.20 mgFe/dm3 and an increased amount of organic substances (TOC from 5.50 to 7.50 mgC/dm3). The water samples examined differed in terms of the value of the ratio of the TOC concentration and the concentration of total iron (D). It was concluded that with increase in the coexistence ratio of organic substances and total iron in water (D = [TOC]/[Fetot]), efficiency of Fe(II) to Fe(III) oxidization with dissolved oxygen decreased, while the oxidation time was increasing. This rule was not demonstrated for potassium manganate (VII) when used as an oxidizing agent. The application of potassium manganate (VII) for oxidation of Fe(II) ions produced the better results in terms of total iron concentration reduction in the sedimentation process than the oxidation with dissolved oxygen.

Analysis of Crystal Structure of Fe3O4 Thin Films Based on Iron Sand Growth by Spin Coating Method

NASA Astrophysics Data System (ADS)

Rianto, D.; Yulfriska, N.; Murti, F.; Hidayati, H.; Ramli, R.

2018-04-01

Recently, iron sand used as one of base materials in the steel industry. However, the content of iron sand can be used as starting materials in sensor technology in the form of thin films. In this paper, we report the analysis of crystal structure of magnetite thin film based on iron sand from Tiram’s Beach. The magnetic content of sand separated by a permanent magnet, then it was milled at 30 hours milling time. In order to increase the purity of magnetite, it washed after milling using aquades under magnetic separation by a magnet permanent. The thin film has been prepared using iron (III) nitrate by sol–gel technique. The precursor is resulted by dissolving magnetite in oxalic acid and nitric acid. Then, solution of iron (III) nitrate dissolved in ethylene glycol was applied on glass substrates by spin coating. The X-Ray Diffraction is operated thin film characterization. The structure of magnetite has been studied based on X-Ray Peaks that correspond to magnetite content of thin films.

Siderophores in Cloud Waters and Potential Impact on Atmospheric Chemistry: Photoreactivity of Iron Complexes under Sun-Simulated Conditions.

PubMed

Passananti, Monica; Vinatier, Virginie; Delort, Anne-Marie; Mailhot, Gilles; Brigante, Marcello

2016-09-06

In the present work, the photoreactivity of a mixture of iron(III)–pyoverdin (Fe(III)–Pyo) complexes was investigated under simulated cloud conditions. Pyoverdins are expected to complex ferric ions naturally present in cloudwater, thus modifying their availability and photoreactivity. The spectroscopic properties and photoreactivity of Fe(III)-Pyo were investigated, with particular attention to their fate under solar irradiation, also studied through simulations. The photolysis of the Fe(III)–Pyo complex leads to the generation of Fe(II), with rates of formation (RFe(II)f) of 6.98 and 3.96 × 10–9 M s–1 at pH 4.0 and 6.0, respectively. Interestingly, acetate formation was observed during the iron-complex photolysis, suggesting that fragmentation can occur after the ligand-to-metal charge transfer (LMCT) via a complex reaction mechanism. Moreover, photogenerated Fe(II) represent an important source of hydroxyl radical via the Fenton reaction in cloudwater. This reactivity might be relevant for the estimation of the rates of formation and steady-state concentrations of the hydroxyl radical by cloud chemistry models and for organic matter speciation in the cloud aqueous phase. In fact, the conventional models, which describe the iron photoreactivity in terms of iron–aqua and oxalate complexes, are not in accordance with our results.

Formation of Fe(III) oxyhydroxide colloids in freshwater and brackish seawater, with incorporation of phosphate and calcium

NASA Astrophysics Data System (ADS)

Gunnars, Anneli; Blomqvist, Sven; Johansson, Peter; Andersson, Christian

2002-03-01

The formation of Fe(III) oxyhydroxide colloids by oxidation of Fe(II) and their subsequent aggregation to larger particles were studied in laboratory experiments with natural water from a freshwater lake and a brackish coastal sea. Phosphate was incorporated in the solid phase during the course of hydrolysis of iron. The resulting precipitated amorphous Fe(III) oxyhydroxide phases were of varying composition, depending primarily on the initial dissolved Fe/P molar ratio, but with little influence by salinity or concentration of calcium ions. The lower limiting Fe/P ratio found for the solid phase suggests the formation of a basic Fe(III) phosphate compound with a stoichiometric Fe/P ratio of close to two. This implies that an Fe/P stoichiometry of ≈2 ultimately limits the capacity of precipitating Fe(III) to fix dissolved phosphate at oxic/anoxic boundaries in natural waters. In contrast to phosphorus, the uptake of calcium seemed to be controlled by sorption processes at the surface of the iron-rich particles formed. This uptake was more efficient in freshwater than in brackish water, suggesting that salinity restrains the uptake of calcium by newly formed Fe(III) oxyhydroxides in natural waters. Moreover, salinity enhanced the aggregation rate of the colloids formed. The suspensions were stabilised by the presence of organic matter, although this effect was less pronounced in seawater than in freshwater. Thus, in seawater of 6 to 33 ‰S, the removal of particles was fast (removal half time < 200 h), whereas the colloidal suspensions formed in freshwater were stable (removal half time > 900 h). Overall, oxidation of Fe(II) and removal of Fe(III) oxyhydroxide particles were much faster in seawater than in freshwater. This more rapid turnover results in lower iron availability in coastal seawater than in freshwater, making iron more likely to become a limiting element for chemical scavenging and biologic production.

Introducing saccharic acid as an efficient iron chelate to enhance photo-Fenton degradation of organic contaminants.

PubMed

Subramanian, Gokulakrishnan; Madras, Giridhar

2016-11-01

The identification of iron chelates that can enhance photo-Fenton degradation is of great interest in the field of advanced oxidation process. Saccharic acid (SA) is a polyhydroxy carboxylic acid and completely non-toxic. Importantly, it can effectively bind Fe(III) as well as induce photoreduction of Fe(III). Despite having these interesting properties, the effect of SA on photo-Fenton degradation has not been studied. Herein, we demonstrate the first assessment of SA as an iron chelate in photo-Fenton process using methylene blue (MB) as a model organic contaminant. Our results demonstrate that SA has the ability to (i) enhance the photo-Fenton degradation of MB by about 11 times at pH 4.5 (ii) intensify photochemical reduction of Fe(III) to Fe(II) by about 17 times and (iii) accelerate the rate of consumption of H 2 O 2 in photo-Fenton process by about 5 times (iv) increase the TOC reduction by about 2 times and (v) improve the photo-Fenton degradation of MB in the presence of a variety of common inorganic ions and organic matter. The influential properties of SA on photo-Fenton degradation is attributed to the efficient photochemical reduction of Fe(III) via LMCT (ligand to metal charge transfer reaction) to Fe(II), which then activated H 2 O 2 to generate OH and accelerated photo-Fenton degradation efficiency. Moreover, the effect of operational parameters such as oxidant: contaminant (H 2 O 2 : MB) ratio, catalyst: contaminant (Fe(III)SA: MB) ratio, Fe(III): SA stoichiometry and pH on the degradation of MB by photo-Fenton in the presence of SA is demonstrated. Importantly, SA assisted photo-Fenton caused effective degradation of MB and 4-Chlorophenol under natural sunlight irradiation in natural water matrix. The findings strongly support SA as a deserving iron chelate to enhance photo-Fenton degradation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Induction of root Fe(lll) reductase activity and proton extrusion by iron deficiency is mediated by auxin-based systemic signalling in Malus xiaojinensis.

PubMed

Wu, Ting; Zhang, Heng-Tao; Wang, Yi; Jia, Wen-Suo; Xu, Xue-Feng; Zhang, Xin-Zhong; Han, Zhen Hai

2012-01-01

Iron is a critical cofactor for a number of metalloenzymes involved in respiration and photosynthesis, but plants often suffer from iron deficiency due to limited supplies of soluble iron in the soil. Iron deficiency induces a series of adaptive responses in various plant species, but the mechanisms by which they are triggered remain largely unknown. Using pH imaging and hormone localization techniques, it has been demonstrated here that root Fe(III) reductase activity and proton extrusion upon iron deficiency are up-regulated by systemic auxin signalling in a Fe-efficient woody plant, Malus xiaojinensis. Split-root experiments demonstrated that Fe-deprivation in a portion of the root system induced a dramatic increase in Fe(III) reductase activity and proton extrusion in the Fe-supplied portion, suggesting that the iron deficiency responses were mediated by a systemic signalling. Reciprocal grafting experiments of M. xiaojinensis with Malus baccata, a plant with no capability to produce the corresponding responses, indicate that the initiation of the systemic signalling is likely to be determined by roots rather than shoots. Iron deficiency induced a substantial increase in the IAA content in the shoot apex and supplying exogenous IAA analogues (NAA) to the shoot apex could mimic the iron deficiency to trigger the corresponding responses. Conversely, preventing IAA transport from shoot to roots blocked the iron deficiency responses. These results strongly indicate that the iron deficiency-induced physiological responses are mediated by systemic auxin signalling.

Adsorption of antimony onto iron oxyhydroxides: adsorption behavior and surface structure.

PubMed

Guo, Xuejun; Wu, Zhijun; He, Mengchang; Meng, Xiaoguang; Jin, Xin; Qiu, Nan; Zhang, Jing

2014-07-15

Antimony is detected in soil and water with elevated concentration due to a variety of industrial applications and mining activities. Though antimony is classified as a pollutant of priority interest by the United States Environmental Protection Agency (USEPA) and Europe Union (EU), very little is known about its environmental behavior and adsorption mechanism. In this study, the adsorption behaviors and surface structure of antimony (III/V) on iron oxides were investigated using batch adsorption techniques, surface complexation modeling (SCM), X-ray photon spectroscopy (XPS) and extended X-ray absorption fine structure spectroscopy (EXAFS). The adsorption isotherms and edges indicated that the affinity of Sb(V) and Sb(III) toward the iron oxides depended on the Sb species, solution pH, and the characteristics of iron oxides. Sb(V) adsorption was favored at acidic pH and decreased dramatically with increasing pH, while Sb(III) adsorption was constant over a broad pH range. When pH is higher than 7, Sb(III) adsorption by goethite and hydrous ferric oxide (HFO) was greater than Sb(V). EXAFS analysis indicated that the majority of Sb(III), either adsorbed onto HFO or co-precipitated by FeCl3, was oxidized into Sb(V) probably due to the involvement of O2 in the long duration of sample preservation. Only one Sb-Fe subshell was filtered in the EXAFS spectra of antimony adsorption onto HFO, with the coordination number of 1.0-1.9 attributed to bidentate mononuclear edge-sharing ((2)E) between Sb and HFO. Copyright © 2014 Elsevier B.V. All rights reserved.

Mechanistic investigation of Fe(III) oxide reduction by low molecular weight organic sulfur species

NASA Astrophysics Data System (ADS)

Eitel, Eryn M.; Taillefert, Martial

2017-10-01

Low molecular weight organic sulfur species, often referred to as thiols, are known to be ubiquitous in aquatic environments and represent important chemical reductants of Fe(III) oxides. Thiols are excellent electron shuttles used during dissimilatory iron reduction, and in this capacity could indirectly affect the redox state of sediments, release adsorbed contaminants via reductive dissolution, and influence the carbon cycle through alteration of bacterial respiration processes. Interestingly, the reduction of Fe(III) oxides by thiols has not been previously investigated in environmentally relevant conditions, likely due to analytical limitations associated with the detection of thiols and their oxidized products. In this study, a novel electrochemical method was developed to simultaneously determine thiol/disulfide pair concentrations in situ during the reduction of ferrihydrite in batch reactors. First order rate laws with respect to initial thiol concentration were confirmed for Fe(III) oxyhydroxide reduction by four common thiols: cysteine, homocysteine, cysteamine, and glutathione. Zero order was determined for both Fe(III) oxyhydroxide and proton concentration at circumneutral pH. A kinetic model detailing the molecular mechanism of the reaction was optimized with proposed intermediate surface structures. Although metal oxide overall reduction rate constants were inversely proportional to the complexity of the thiol structure, the extent of metal reduction increased with structure complexity, indicating that surface complexes play a significant role in the ability of these thiols to reduce iron. Taken together, these results demonstrate the importance of considering the molecular reaction mechanism at the iron oxide surface when investigating the potential for thiols to act as electron shuttles during dissimilatory iron reduction in natural environments.

Characterization of a Novel Polysaccharide-Iron(III) Complex and Its Anti-Anemia and Nonspecific Immune Regulating Activities.

PubMed

Zhang, Yun; Ma, Fanyi; Zhu, Jinhua; Du, Zuliang; Zhao, Ying-Yong; Liu, Xiuhua

2017-01-01

Dioscorea opposita Thunb is the famous food and traditional medicine in China and it was rich in polysaccharides. Polysaccharides of Dioscorea Opposita Thunb possess immunoregulatory activity, free radical scavenging activity and anti-diabetic activity. A novel polysaccharide- iron(III) complex (CYPIC) was synthesized by using crude polysaccharide extracted from Dioscorea opposita Thunb. The component, structure, morphology and molecular weights of CYPIC were analysed, and the anti-anemia, acute toxicity and nonspecific immune regulating activities of CYPIC were assayed. The results showed that CYPIC could increase red blood cell count (RBC), hemoglobin (Hb), hematocrit (HCT), thymus and spleen index of mice with iron deficiency anemia (IDA). Although the structure and deeper mechanisms of CYPIC should be further studied, CYPIC has the potential to be used as an iron supplement for the treatment of iron deficiency anemia. The large scale industrial production was suggested due to the simple preparation processing of CYPIC. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Abrupt spin transition with thermal hysteresis of iron(III) complex [Fe(III)(Him)2(hapen)]AsF6 (Him = imidazole, H2hapen = N,N'-bis(2-hydroxyacetophenylidene)ethylenediamine).

PubMed

Fujinami, Takeshi; Koike, Masataka; Matsumoto, Naohide; Sunatsuki, Yukinari; Okazawa, Atsushi; Kojima, Norimichi

2014-02-17

The solvent-free spin crossover iron(III) complex [Fe(III)(Him)2(hapen)]AsF6 (Him = imidazole, H2hapen = N,N'-bis(2-hydroxyacetophenylidene)ethylenediamine), exhibiting thermal hysteresis, was synthesized and characterized. The Fe(III) ion has an octahedral coordination geometry, with N2O2 donor atoms of the planar tetradentate ligand (hapen) and two nitrogen atoms of two imidazoles at the axial positions. One of two imidazoles is hydrogen-bonded to the phenoxo oxygen atom of hapen of the adjacent unit to give a hydrogen-bonded one-dimensional chain, while the other imidazole group is free from hydrogen bonding. The temperature dependencies of the magnetic susceptibilities and Mössbauer spectra revealed an abrupt spin transition between the high-spin (S = 5/2) and low-spin (S = 1/2) states, with thermal hysteresis.

Latent iron deficiency at birth influences auditory neural maturation in late preterm and term infants.

PubMed

Choudhury, Vivek; Amin, Sanjiv B; Agarwal, Asha; Srivastava, L M; Soni, Arun; Saluja, Satish

2015-11-01

In utero latent iron deficiency has been associated with abnormal neurodevelopmental outcomes during childhood. Its concomitant effect on auditory neural maturation has not been well studied in late preterm and term infants. The objective was to determine whether in utero iron status is associated with auditory neural maturation in late preterm and term infants. This prospective cohort study was performed at Sir Ganga Ram Hospital, New Delhi, India. Infants with a gestational age ≥34 wk were eligible unless they met the exclusion criteria: craniofacial anomalies, chromosomal disorders, hemolytic disease, multiple gestation, third-trimester maternal infection, chorioamnionitis, toxoplasmosis, other infections, rubella, cytomegalovirus infection, and herpes simplex virus infections (TORCH), Apgar score <5 at 5 min, sepsis, cord blood not collected, or auditory evaluation unable to be performed. Sixty consecutive infants with risk factors for iron deficiency, such as small for gestational age and maternal diabetes, and 30 without risk factors for iron deficiency were enrolled. Absolute wave latencies and interpeak latencies, evaluated by auditory brainstem response within 48 h after birth, were measured and compared between infants with latent iron deficiency (serum ferritin ≤75 ng/mL) and infants with normal iron status (serum ferritin >75 ng/mL) at birth. Twenty-three infants had latent iron deficiency. Infants with latent iron deficiency had significantly prolonged wave V latencies (7.10 ± 0.68 compared with 6.60 ± 0.66), III-V interpeak latencies (2.37 ± 0.64 compared with 2.07 ± 0.33), and I-V interpeak latencies (5.10 ± 0.57 compared with 4.72 ± 0.56) compared with infants with normal iron status (P < 0.05). This difference remained significant on regression analyses after control for confounders. No difference was noted between latencies I and III and interpeak latencies I-III. Latent iron deficiency is associated with abnormal auditory neural maturation in infants at ≥34 wk gestational age. This trial was registered at clinicaltrials.gov as NCT02503397. © 2015 American Society for Nutrition.

Iron deficiency enhances bioactive phenolics in lemon juice.

PubMed

Mellisho, Carmen D; González-Barrio, Rocío; Ferreres, Federico; Ortuño, María F; Conejero, Wenceslao; Torrecillas, Arturo; García-Mina, José M; Medina, Sonia; Gil-Izquierdo, Angel

2011-09-01

This study was designed to describe the phenolic status of lemon juice obtained from fruits of lemon trees differing in iron (Fe) nutritional status. Three types of Fe(III) compound were used in the experiment, namely a synthetic chelate and two complexes derived from natural polymers of humic and lignine nature. All three Fe(III) compounds were able to improve the Fe nutritional status of lemon trees, though to different degrees. This Fe(III) compound effect led to changes in the polyphenol content of lemon juice. Total phenolics were decreased (∼33% average decrease) and, in particular, flavanones, flavones and flavonols were affected similarly. Iron-deficient trees showed higher phenolic contents than Fe(III) compound-treated trees, though Fe deficiency had negative effects on the yield and visual quality of fruits. However, from a human nutritional point of view and owing to the health-beneficial properties of their bioavailable phenolic compounds, the nutritional quality of fruits of Fe-deficient lemon trees in terms of phenolics was higher than that of fruits of Fe(III) compound-treated lemon trees. Moreover, diosmetin-6,8-di-C-glucoside in lemon juice can be used as a marker for correction of Fe deficiency in lemon trees. Copyright © 2011 Society of Chemical Industry.

Reactivity of catecholamine-driven Fenton reaction and its relationships with iron(III) speciation.

PubMed

Melin, Victoria; Henríquez, Adolfo; Freer, Juanita; Contreras, David

2015-03-01

Fenton reaction is the main source of free radicals in biological systems. The reactivity of this reaction can be modified by several factors, among these iron ligands are important. Catecholamine (dopamine, epinephrine, and norepinephrine) are able to form Fe(III) complexes whose extension in the coordination number depends upon the pH. Fe(III)-catecholamine complexes have been related with the development of several pathologies. In this work, the ability of catecholamines to enhance the oxidative degradation of an organic substrate (veratryl alcohol, VA) through Fenton and Fenton-like reactions was studied. The initial VA degradation rate at different pH values and its relationship to the different iron species present in solution were determined. Furthermore, the oxidative degradation of VA after 24 hours of reaction and its main oxidation products were also determined. The catecholamine-driven Fenton and Fenton-like systems showed higher VA degradation compared to unmodified Fenton or Fenton-like systems, which also showed an increase in the oxidation state of the VA degradation product. All of this oxidative degradation takes place at pH values lower than 5.50, where the primarily responsible species would be the Fe(III) mono-complex. The presence of Fe(III) mono-complex is essential in the ability of catecholamines to increase the oxidative capacity of Fenton systems.

The Alternative Route to Heme in the Methanogenic Archaeon Methanosarcina barkeri

PubMed Central

Haufschildt, Kristin; Neumann, Alexander; Storbeck, Sonja; Streif, Judith

2014-01-01

In living organisms heme is formed from the common precursor uroporphyrinogen III by either one of two substantially different pathways. In contrast to eukaryotes and most bacteria which employ the so-called “classical” heme biosynthesis pathway, the archaea use an alternative route. In this pathway, heme is formed from uroporphyrinogen III via the intermediates precorrin-2, sirohydrochlorin, siroheme, 12,18-didecarboxysiroheme, and iron-coproporphyrin III. In this study the heme biosynthesis proteins AhbAB, AhbC, and AhbD from Methanosarcina barkeri were functionally characterized. Using an in vivo enzyme activity assay it was shown that AhbA and AhbB (Mbar_A1459 and Mbar_A1460) together catalyze the conversion of siroheme into 12,18-didecarboxysiroheme. The two proteins form a heterodimeric complex which might be subject to feedback regulation by the pathway end-product heme. Further, AhbC (Mbar_A1793) was shown to catalyze the formation of iron-coproporphyrin III in vivo. Finally, recombinant AhbD (Mbar_A1458) was produced in E. coli and purified indicating that this protein most likely contains two [4Fe-4S] clusters. Using an in vitro enzyme activity assay it was demonstrated that AhbD catalyzes the conversion of iron-coproporphyrin III into heme. PMID:24669201

Growth process and magnetic properties of α-FeSe nanostructures

NASA Astrophysics Data System (ADS)

Li, S. J.; Li, D.; Jiang, J. J.; Liu, G. B.; Ma, S.; Liu, W.; Zhang, Z. D.

2014-05-01

Growth process and magnetic properties of PbO-type α-FexSe nanostructures with shape changing from nanocacti to nanopetals and then to nanosheets are investigated. With iron acetylacetonate [Fe(acac)3] and Se powder as raw materials, the diffusion process of Fe atoms dominates the synthesis of α-FexSe nanocacti following phase transitions from FeSe2 to Fe3Se4 and finally to α-FexSe. When a mixed solution containing Se precursor and Fe(acac)3 was used as the raw material, the formation of FeSe2 and Fe3Se4 can be avoided and, bended α-FexSe nanopetals can be prepared at 345 °C, which became flat nanosheets with a [001] preferred orientation as extending the reaction time from 1 to 4 h. No superconducting transition occurs in the α-FexSe (0.84 ≤ x ≤ 1.05) nanostructures due to composition heterogeneity or size effect. Magnetic measurements indicate that an antiferromagnetic component with a Néel point at about 45 K dominates the magnetic properties of the α-Fe0.87Se nanosheets.

A versatile single molecular precursor for the synthesis of layered oxide cathode materials for Li-ion batteries.

PubMed

Li, Maofan; Liu, Jiajie; Liu, Tongchao; Zhang, Mingjian; Pan, Feng

2018-02-01

A carbonyl-bridged single molecular precursor LiTM(acac) 3 [transition metal (TM) = cobalt/manganese/nickel (Co/Mn/Ni), acac = acetylacetone], featuring a one-dimensional chain structure, was designed and applied to achieve the layered oxide cathode materials: LiTMO 2 (TM = Ni/Mn/Co, NMC). As examples, layered oxides, primary LiCoO 2 , binary LiNi 0.8 Co 0.2 O 2 and ternary LiNi 0.5 Mn 0.3 Co 0.2 O 2 were successfully prepared to be used as cathode materials. When they are applied to lithium-ion batteries (LIBs), all exhibit good electrochemical performance because of their unique morphology and great uniformity of element distribution. This versatile precursor is predicted to accommodate many other metal cations, such as aluminum (Al 3+ ), iron (Fe 2+ ), and sodium (Na + ), because of the flexibility of organic ligand, which not only facilitates the doping-modification of the NMC system, but also enables synthesis of Na-ion layered oxides. This opens a new direction of research for the synthesis of high-performance layered oxide cathode materials for LIBs.

Regulation of iron transport systems in Enterobacteriaceae in response to oxygen and iron availability.

PubMed

Carpenter, Chandra; Payne, Shelley M

2014-04-01

Iron is an essential nutrient for most bacteria. Depending on the oxygen available in the surrounding environment, iron is found in two distinct forms: ferrous (Fe(II)) or ferric (Fe(III)). Bacteria utilize different transport systems for the uptake of the two different forms of iron. In oxic growth conditions, iron is found in its insoluble, ferric form, and in anoxic growth conditions iron is found in its soluble, ferrous form. Enterobacteriaceae have adapted to transporting the two forms of iron by utilizing the global, oxygen-sensing regulators, ArcA and Fnr to regulate iron transport genes in response to oxygen. Copyright © 2014 Elsevier Inc. All rights reserved.

Assessment of some cultural experimental methods to study the effects of antibiotics on microbial activities in a soil: An incubation study

PubMed Central

Molaei, Ali; Haghnia, Gholamhosain; Astaraei, Alireza; Rasouli-Sadaghiani, MirHassan; Teresa Ceccherini, Maria; Datta, Rahul

2017-01-01

Oxytetracycline (OTC) and sulfamethoxazole (SMX) are two of most widely used antibiotics in livestock and poultry industry. After consumption of antibiotics, a major portion of these compounds is excreted through the feces and urine of animals. Land application of antibiotic-treated animal wastes has caused increasing concern about their adverse effects on ecosystem health. In this regard, inconsistent results have been reported regarding the effects of antibiotics on soil microbial activities. This study was conducted based on the completely randomized design to the measure microbial biomass carbon, cumulative respiration and iron (III) reduction bioassays. Concentrations of OTC and SMX including 0, 1, 10, 25, 50, and 100 mg/kg were spiked in triplicate to a sandy loam soil and incubated for 21 days at 25°C. Results showed that the effects of OTC and SMX antibiotics on cumulative respiration and microbial biomass carbon were different. SMX antibiotic significantly affected soil microbial biomass carbon and cumulative respiration at different treatments compared to control with increasing incubation time. OTC antibiotic, on the other hand, negatively affected cumulative respiration compared to control treatment throughout the incubation period. Although OTC antibiotic positively affected microbial biomass carbon at day one of incubation, there was no clear trend in microbial biomass carbon between different treatments of this antibiotic after that time period. Nevertheless, sulfamethoxazole and oxytetracycline antibiotics had similar effects on iron (III) reduction such that they considerably affected iron (III) reduction at 1 and 10 mg/kg, and iron (III) reduction was completely inhibited at concentrations above 10 mg/kg. Hence, according to our results, microbial biomass carbon and cumulative respiration experiments are not able alone to exhibit the effect of antibiotics on soil microbial activity, but combination of these two experiments with iron (III) reduction test could well display the effects of sulfamethoxazole (SMX) and oxytetracycline (OTC) antibiotics on soil biochemical activities. PMID:28683144

Iron transport and storage in the coccolithophore: Emiliania huxleyi.

PubMed

Hartnett, Andrej; Böttger, Lars H; Matzanke, Berthold F; Carrano, Carl J

2012-11-01

Iron is an essential element for all living organisms due to its ubiquitous role in redox and other enzymes, especially in the context of respiration and photosynthesis. The iron uptake and storage systems of terrestrial/higher plants are now reasonably well understood with two basic strategies for iron uptake being distinguished: strategy I plants use a mechanism involving soil acidification and induction of Fe(III)-chelate reductase (ferrireductase) and Fe(II) transporter proteins while strategy II plants have evolved sophisticated systems based on high-affinity, iron specific, binding compounds called phytosiderophores. In contrast, there is little knowledge about the corresponding systems in marine plant-like lineages. Herein we report a study of the iron uptake and storage mechanisms in the coccolithophore Emiliania huxleyi. Short term radio-iron uptake studies indicate that iron is taken up by Emiliania in a time and concentration dependent manner consistent with an active transport process. Based on inhibitor studies it appears that iron is taken up directly as Fe(iii). However if a reductive step is involved the Fe(II) must not be accessible to the external environment. Upon long term exposure to (57)Fe we have been able, using a combination of Mössbauer and XAS spectroscopies, to identify a single metabolite which displays spectral features similar to the phosphorus-rich mineral core of bacterial and plant ferritins.

The iron-chelate transporter OsYSL9 plays a role in iron distribution in developing rice grains.

PubMed

Senoura, Takeshi; Sakashita, Emi; Kobayashi, Takanori; Takahashi, Michiko; Aung, May Sann; Masuda, Hiroshi; Nakanishi, Hiromi; Nishizawa, Naoko K

2017-11-01

Rice OsYSL9 is a novel transporter for Fe(II)-nicotianamine and Fe(III)-deoxymugineic acid that is responsible for internal iron transport, especially from endosperm to embryo in developing seeds. Metal chelators are essential for safe and efficient metal translocation in plants. Graminaceous plants utilize specific ferric iron chelators, mugineic acid family phytosiderophores, to take up sparingly soluble iron from the soil. Yellow Stripe 1-Like (YSL) family transporters are responsible for transport of metal-phytosiderophores and structurally similar metal-nicotianamine complexes. Among the rice YSL family members (OsYSL) whose functions have not yet been clarified, OsYSL9 belongs to an uncharacterized subgroup containing highly conserved homologs in graminaceous species. In the present report, we showed that OsYSL9 localizes mainly to the plasma membrane and transports both iron(II)-nicotianamine and iron(III)-deoxymugineic acid into the cell. Expression of OsYSL9 was induced in the roots but repressed in the nonjuvenile leaves in response to iron deficiency. In iron-deficient roots, OsYSL9 was induced in the vascular cylinder but not in epidermal cells. Although OsYSL9-knockdown plants did not show a growth defect under iron-sufficient conditions, these plants were more sensitive to iron deficiency in the nonjuvenile stage compared with non-transgenic plants. At the grain-filling stage, OsYSL9 expression was strongly and transiently induced in the scutellum of the embryo and in endosperm cells surrounding the embryo. The iron concentration was decreased in embryos of OsYSL9-knockdown plants but was increased in residual parts of brown seeds. These results suggested that OsYSL9 is involved in iron translocation within plant parts and particularly iron translocation from endosperm to embryo in developing seeds.

PVDF membranes containing hybrid nanoparticles for adsorbing cationic dyes: physical insights and mechanism

NASA Astrophysics Data System (ADS)

Sharma, Maya; Madras, Giridhar; Bose, Suryasarathi

2016-07-01

In this study, Fe (iron) and Ag (silver) based adsorbents were synthesized using solution combustion and in situ reduction techniques. The synthesized adsorbents were comprehensively characterized by different techniques including electron microscopy, BET, XRD, Zeta potential etc. Three chlorinated cationic dyes used were malachite green, methyl violet and pyronin Y. These dyes were adsorbed on various synthesized adsorbents [iron III oxide (Fe2O3)], iron III oxide decorated silver nanoparticles by combustion synthesis technique [Fe2O3-Ag(C)] and iron III oxide decorated silver nanoparticles using in situ reduction, [Fe2O3-Ag (S)]. The isotherm and the adsorption kinetics have been studied systematically. The kinetic data can be explained by the pseudo second order model and the adsorption equilibrium followed Langmuir isotherm. The equilibrium and kinetics results suggest that Fe2O3-Ag(S) nanoparticles showed the maximum adsorption among all the adsorbents. Hence, Polyvinylidene fluoride based membranes containing Fe2O3-Ag(S) nanoparticles were prepared via phase inversion (precipitation immersion using DMF/water) technique. The adsorption kinetics were studied in detail and it was observed that the composite membrane showed synergistic improvement in dye adsorption. Such membranes can be used for water purification.

Mineral ecophysiological evidence for microbial activity in banded iron formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Dr. Yi-Liang; Konhauser, Dr, Kurt; Cole, David R

2011-01-01

The phosphorus composition of banded-iron formations (BIFs) has been used as a proxy for Precambrian seawater composition and the paleoeredox state of Earth's surface environment. However, it is unclear whether the phosphorus in BIFs originally entered the sediment as a sorbed component of the iron oxyhydroxide particles, or whether it was incorporated into the biomass of marine phytoplankton. We conducted high-resolution mineral analyses and report here the first detection of an Fe(III) acetate salt, as well as nanocrystals of apatite in association with magnetite, in the 2.48 Ga Dales Gorge Member of the Brockman Iron Formation (a BIF), Hamersley, Westernmore » Australia. The clusters of apatite are similar in size and morphology to biogenic apatite crystals resulting from biomass decay in Phanerozoic marine sediments, while the formation of an Fe(III) acetate salt and magnetite not only implies the original presence of biomass in the BIF sediments, but also that organic carbon likely served as an electron donor during bacterial Fe(III) reduction. This study is important because it suggests that phytoplankton may have played a key role in the transfer of phosphorus (and other trace elements) from the photic zone to the seafloor.« less

Electron transport chain dysfunction by H(2)O (2) is linked to increased reactive oxygen species production and iron mobilization by lipoperoxidation: studies using Saccharomyces cerevisiae mitochondria.

PubMed

Cortés-Rojo, Christian; Estrada-Villagómez, Mirella; Calderón-Cortés, Elizabeth; Clemente-Guerrero, Mónica; Mejía-Zepeda, Ricardo; Boldogh, Istvan; Saavedra-Molina, Alfredo

2011-04-01

The mitochondrial electron transport chain (ETC) contains thiol groups (-SH) which are reversibly oxidized to modulate ETC function during H(2)O(2) overproduction. Since deleterious effects of H(2)O(2) are not limited to -SH oxidation, due to the formation of other H(2)O(2)-derived species, some processes like lipoperoxidation could enhance the effects of H(2)O(2) over ETC enzymes, disrupt their modulation by -SH oxidation and increase superoxide production. To verify this hypothesis, we tested the effects of H(2)O(2) on ETC activities, superoxide production and iron mobilization in mitochondria from lipoperoxidation-resistant native yeast and lipoperoxidation-sensitized yeast. Only complex III activity from lipoperoxidation-sensitive mitochondria exhibited a higher susceptibility to H(2)O(2) and increased superoxide production. The recovery of ETC activity by the thiol reductanct β-mercaptoethanol (BME) was also altered at complex III, and a role was attributed to lipoperoxidation, the latter being also responsible for iron release. A hypothetical model linking lipoperoxidation, increased complex III damage, superoxide production and iron release is given.

Ultrafast electron and energy transfer in dye-sensitized iron oxide and oxyhydroxide nanoparticles.

PubMed

Gilbert, Benjamin; Katz, Jordan E; Huse, Nils; Zhang, Xiaoyi; Frandsen, Cathrine; Falcone, Roger W; Waychunas, Glenn A

2013-10-28

An emerging area in chemical science is the study of solid-phase redox reactions using ultrafast time-resolved spectroscopy. We have used molecules of the photoactive dye 2',7'-dichlorofluorescein (DCF) anchored to the surface of iron(III) oxide nanoparticles to create iron(II) surface atoms via photo-initiated interfacial electron transfer. This approach enables time-resolved study of the fate and mobility of electrons within the solid phase. However, complete analysis of the ultrafast processes following dye photoexcitation of the sensitized iron(III) oxide nanoparticles has not been reported. We addressed this topic by performing femtosecond transient absorption (TA) measurements of aqueous suspensions of uncoated and DCF-sensitized iron oxide and oxyhydroxide nanoparticles, and an aqueous iron(III)-dye complex. Following light absorption, excited state relaxation times of the dye of 115-310 fs were found for all samples. Comparison between TA dynamics on uncoated and dye-sensitized hematite nanoparticles revealed the dye de-excitation pathway to consist of a competition between electron and energy transfer to the nanoparticles. We analyzed the TA data for hematite nanoparticles using a four-state model of the dye-sensitized system, finding electron and energy transfer to occur on the same ultrafast timescale. The interfacial electron transfer rates for iron oxides are very close to those previously reported for DCF-sensitized titanium dioxide (for which dye-oxide energy transfer is energetically forbidden) even though the acceptor states are different. Comparison of the alignment of the excited states of the dye and the unoccupied states of these oxides showed that the dye injects into acceptor states of different symmetry (Ti t2gvs. Fe eg).

Arsenate and Arsenite Sorption on Magnetite: Relations to Groundwater Arsenic Treatment Using Zerovalent Iron and Natural Attenuation

EPA Science Inventory

Magnetite (Fe3O4) is a zerovalent iron corrosion product; it is also formed in natural soil and sediment. Sorption of arsenate (As(V)) and arsenite (As(III)) on magnetite is an important process of arsenic removal from groundwater using zerovalent iron-based permeable reactive ba...

THE EFFECT OF PH, PHOSPHATE AND OXIDANT TYPE ON THE REMOVAL OF ARSENIC FROM DRINKING WATER DURING IRON REMOVAL

EPA Science Inventory

In many regions of the United States, groundwaters that contain arsenic (primarily As[III]) also contain significant amounts of iron (Fe[II]). Arsenic removal will most likely be achieved by iron removal in many of those cases which will consist of oxidization followed by filtra...

Colorimetric Determination of the Iron(III)-Thiocyanate Reaction Equilibrium Constant with Calibration and Equilibrium Solutions Prepared in a Cuvette by Sequential Additions of One Reagent to the Other

ERIC Educational Resources Information Center

Nyasulu, Frazier; Barlag, Rebecca

2011-01-01

The well-known colorimetric determination of the equilibrium constant of the iron(III-thiocyanate complex is simplified by preparing solutions in a cuvette. For the calibration plot, 0.10 mL increments of 0.00100 M KSCN are added to 4.00 mL of 0.200 M Fe(NO[subscript 3])[subscript 3], and for the equilibrium solutions, 0.50 mL increments of…

Highly efficient blue- and white-organic light emitting diodes base on triple-emitting layer.

PubMed

Shin, Hyun Su; Lee, Seok Jae; Lee, Ho Won; Lee, Dong Hyung; Kim, Woo Young; Yoon, Seung Soo; Kim, Young Kwan

2013-12-01

We have demonstrated highly efficient blue phosphorescent organic light-emitting diodes (PHOLEDs) using iridium (III) bis[(4,6-di-fluoropheny)-pyridinato-N,C2] picolinate (Flrpic) doped in three kinds of host materials, such as 9-(4-(triphenylsilyl)phenyl)-9H-carbazole (SPC), N,N'-dicarbazolyl-3,5-benzene (mCP), and 2,2',2"-(1,3,5-benzenetriyl)tris-[1-phenyl-1H-benzimidazole] (TPBi) as triple-emitting layer (T-EML). The properties of device with T-EML using the stepwise structure was found to be superior to the other blue PHOLEDs and exhibited a maximum luminous efficiency of 23.02 cd/A, a maximum external quantum efficiency of 11.09%, and a maximum power efficiency of 14.89 lm/W, respectively. An optimal blue device has improving charge balance and triplet excitons confinement within emitting layers (EMLs) each. Additionally, we also fabricated white PHOLED using a phosphorescent red dopant, bis(2-phenylquinolinato)-acetylacetonate iridium III (Ir(pq)2acac) doped in mCP and TPBi between blue EMLs. The properties of white PHOLED showed a maximum luminous efficiency and a maximum external quantum efficiency of 33.03 cd/A and 16.95%, respectively. It also showed the white emission with CIEx,y coordinates of (x = 0.36, y = 0.39) at 10 V.

Chromium and Ruthenium-Doped Zinc Oxide Thin Films for Propane Sensing Applications

PubMed Central

Gómez-Pozos, Heberto; González-Vidal, José Luis; Torres, Gonzalo Alberto; Rodríguez-Baez, Jorge; Maldonado, Arturo; de la Luz Olvera, María; Acosta, Dwight Roberto; Avendaño-Alejo, Maximino; Castañeda, Luis

2013-01-01

Chromium and ruthenium-doped zinc oxide (ZnO:Cr) and (ZnO:Ru) thin solid films were deposited on soda-lime glass substrates by the sol-gel dip-coating method. A 0.6 M solution of zinc acetate dihydrate dissolved in 2-methoxyethanol and monoethanolamine was used as basic solution. Chromium (III) acetylacetonate and Ruthenium (III) trichloride were used as doping sources. The Ru incorporation and its distribution profile into the films were proved by the SIMS technique. The morphology and structure of the films were studied by SEM microscopy and X-ray diffraction measurements, respectively. The SEM images show porous surfaces covered by small grains with different grain size, depending on the doping element, and the immersions number into the doping solutions. The sensing properties of ZnO:Cr and ZnO:Ru films in a propane (C3H8) atmosphere, as a function of the immersions number in the doping solution, have been studied in the present work. The highest sensitivity values were obtained for films doped from five immersions, 5.8 and 900, for ZnO:Cr and ZnO:Ru films, respectively. In order to evidence the catalytic effect of the chromium (Cr) and ruthenium (Ru), the sensing characteristics of undoped ZnO films are reported as well. PMID:23482091

Structural study of Ni- or Mg-based complexes incorporated within UiO-66-NH{sub 2} framework and their impact on hydrogen sorption properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Žunkovič, E.; Mazaj, M.; Mali, G.

2015-05-15

Nickel and magnesium acetylacetonate molecular complexes were post-synthetically incorporated into microporous zirconium-based MOF (UiO-66-NH{sub 2}) in order to introduce active open-metal sites for hydrogen sorption. Elemental analysis, nitrogen physisorption and DFT calculations revealed that 5 molecules of Ni(acac){sub 2} or 2 molecules of Mg(acac){sub 2} were incorporated into one unit cell of UiO-66-NH{sub 2}. {sup 1}H–{sup 13}C CPMAS and {sup 1}H MAS NMR spectroscopy showed that, although embedded within the pores, both Ni- and Mg-complexes interacted with the UiO-66-NH{sub 2} framework only through weak van der Waals bonds. Inclusion of metal complexes led to the decrease of hydrogen sorption capacitiesmore » in Ni-modified as well as in Mg-modified samples in comparison with the parent UiO-66-NH{sub 2}. The isosteric hydrogen adsorption enthalpy slightly increased in the case of Ni-modified material, but not in the case of Mg-modified analogue. - Graphical abstract: A post-synthesis impregnation of Mg- and Ni-acetylacetonate complexes performed on zirconium-based MOF UiO-66-NH{sub 2} does influence the hydrogen sorption performance with respect to the parent matrix. The structural study revealed that Mg- and Ni-acetylacetonate molecules interact with zirconium-terephthalate framework only by weak interactions and they are not covalently bonded to aminoterephthalate ligand. Still, they remain confined into the pores even after hydrogen sorption experiments. - Highlights: • Mg- and Ni-acetylacetonate molecules embedded in the pores of UiO-66-NH{sub 2} by PSM. • Molecules of complexes interact with framework only by van der Waals interactions. • Type/structure of deposited metal-complex impact hydrogen enthalpy of adsorption.« less

Geochemical modeling of iron, sulfur, oxygen and carbon in a coastal plain aquifer

NASA Astrophysics Data System (ADS)

Brown, C. J.; Schoonen, M. A. A.; Candela, J. L.

2000-11-01

Fe(III) reduction in the Magothy aquifer of Long Island, NY, results in high dissolved-iron concentrations that degrade water quality. Geochemical modeling was used to constrain iron-related geochemical processes and redox zonation along a flow path. The observed increase in dissolved inorganic carbon is consistent with the oxidation of sedimentary organic matter coupled to the reduction of O 2 and SO 42- in the aerobic zone, and to the reduction of SO 42- in the anaerobic zone; estimated rates of CO 2 production through reduction of Fe(III) were relatively minor by comparison. The rates of CO 2 production calculated from dissolved inorganic carbon mass transfer (2.55×10 -4 to 48.6×10 -4 mmol l -1 yr-1) generally were comparable to the calculated rates of CO 2 production by the combined reduction of O 2, Fe(III) and SO 42- (1.31×10 -4 to 15×10 -4 mmol l -1 yr-1). The overall increase in SO 42- concentrations along the flow path, together with the results of mass-balance calculations, and variations in δ34S values along the flow path indicate that SO 42- loss through microbial reduction is exceeded by SO 42- gain through diffusion from sediments and through the oxidation of FeS 2. Geochemical and microbial data on cores indicate that Fe(III) oxyhydroxide coatings on sediment grains in local, organic carbon- and SO 42--rich zones have been depleted by microbial reduction and resulted in localized SO 42--reducing zones in which the formation of iron disulfides decreases dissolved iron concentrations. These localized zones of SO 42- reduction, which are important for assessing zones of low dissolved iron for water-supply development, could be overlooked by aquifer studies that rely only on groundwater data from well-water samples for geochemical modeling.

Modelling and Microstructural Characterization of Sintered Metallic Porous Materials

PubMed Central

Depczynski, Wojciech; Kazala, Robert; Ludwinek, Krzysztof; Jedynak, Katarzyna

2016-01-01

This paper presents selected characteristics of the metallic porous materials produced by the sintering of metal powders. The authors focus on materials produced from the iron powder (Fe) of ASC 100.29 and Distaloy SE. ASC 100.29 is formed by atomization and has a characteristic morphology. It consists of spherical particles of different sizes forming agglomerates. Distaloy SE is also based on the sponge-iron. The porous material is prepared using the patented method of sintering the mixture of iron powder ASC 100.29, Fe(III) oxide, Distaloy SE and Fe(III) oxide in the reducing atmosphere of dissociated ammonia. As a result, the materials with open pores of micrometer sizes are obtained. The pores are formed between iron particles bonded by diffusion bridges. The modelling of porous materials containing diffusion bridges that allows for three-dimensional (3D) imaging is presented. PMID:28773690

Iron-based radiochromic systems for UV dosimetry applications

NASA Astrophysics Data System (ADS)

Lee, Hannah J.; Alqathami, Mamdooh; Blencowe, Anton; Ibbott, Geoffrey

2018-01-01

Phototherapy treatment using ultraviolet (UV) A and B light sources has long existed as a treatment option for various skin conditions. Quality control for phototherapy treatment recommended by the British Association of Dermatologists and British Photodermatology Group generally focused on instrumentation-based dosimetry measurements. The purpose of this study was to present an alternative, easily prepared dosimeter system for the measurement of UV dose and as a simple quality assurance technique for phototherapy treatments. Five different UVA-sensitive radiochromic dosimeter formulations were investigated and responded with a measurable and visible optical change both in solution and in gel form. Iron(III) reduction reaction formulations were found to be more sensitive to UVA compared to iron(II) oxidation formulations. One iron(III) reduction formulation was found to be especially promising due to its sensitivity to UVA dose, ease of production, and linear response up to a saturation point.

Effective sulfur and energy recovery from hydrogen sulfide through incorporating an air-cathode fuel cell into chelated-iron process.

PubMed

Sun, Min; Song, Wei; Zhai, Lin-Feng; Cui, Yu-Zhi

2013-12-15

The chelated-iron process is among the most promising techniques for the hydrogen sulfide (H2S) removal due to its double advantage of waste minimization and resource recovery. However, this technology has encountered the problem of chelate degradation which made it difficult to ensure reliable and economical operation. This work aims to develop a novel fuel-cell-assisted chelated-iron process which employs an air-cathode fuel cell for the catalyst regeneration. By using such a process, sulfur and electricity were effectively recovered from H2S and the problem of chelate degradation was well controlled. Experiment on a synthetic sulfide solution showed the fuel-cell-assisted chelated-iron process could maintain high sulfur recovery efficiencies generally above 90.0%. The EDTA was preferable to NTA as the chelating agent for electricity generation, given the Coulombic efficiencies (CEs) of 17.8 ± 0.5% to 75.1 ± 0.5% for the EDTA-chelated process versus 9.6 ± 0.8% to 51.1 ± 2.7% for the NTA-chelated process in the pH range of 4.0-10.0. The Fe (III)/S(2-) ratio exhibited notable influence on the electricity generation, with the CEs improved by more than 25% as the Fe (III)/S(2-) molar ratio increased from 2.5:1 to 3.5:1. Application of this novel process in treating a H2S-containing biogas stream achieved 99% of H2S removal efficiency, 78% of sulfur recovery efficiency, and 78.6% of energy recovery efficiency, suggesting the fuel-cell-assisted chelated-iron process was effective to remove the H2S from gas streams with favorable sulfur and energy recovery efficiencies. Copyright © 2013 Elsevier B.V. All rights reserved.

Fe(II) formation after interaction of the amyloid β-peptide with iron-storage protein ferritin.

PubMed

Balejcikova, Lucia; Siposova, Katarina; Kopcansky, Peter; Safarik, Ivo

2018-05-09

The interaction of amyloid β-peptide (Aβ) with the iron-storage protein ferritin was studied in vitro. We have shown that Aβ during fibril formation process is able to reduce Fe(III) from the ferritin core (ferrihydrite) to Fe(II). The Aβ-mediated Fe(III) reduction yielded a two-times-higher concentration of free Fe(II) than the spontaneous formation of Fe(II) by the ferritin itself. We suggest that Aβ can also act as a ferritin-specific metallochaperone-like molecule capturing Fe(III) from the ferritin ferrihydrite core. Our observation may partially explain the formation of Fe(II)-containing minerals in human brains suffering by neurodegenerative diseases.

Recovery of indium ions by nanoscale zero-valent iron

NASA Astrophysics Data System (ADS)

Chen, Wen; Su, Yiming; Wen, Zhipan; Zhang, Yalei; Zhou, Xuefei; Dai, Chaomeng

2017-03-01

Indium and its compounds have plenty of industrial applications and high demand. Therefore, indium recovery from various industrial effluents is necessary. It was sequestered by nanoscale zero-valent iron (nZVI) whose size mainly ranged from 50 to 70 nm. Adsorption kinetics and isotherm, influence of pH, and ionic strength were thoroughly investigated. The reaction process was well fitted to a pseudo second-order model, and the maximum adsorption capacity of In(III) was 390 mg In(III)/g nZVI similar to 385 mg In(III)/g nZVI at 298 K calculated by Langmuir model. The mole ratio of Fe(II) released to In(III) immobilized was 3:2, which implied a special chemical process of co-precipitation combined Fe(OH)2 with In(OH)3. Transmission electron microscopy with an energy-disperse X-ray (TEM-EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize surface morphology, corrosion products, and valence state of indium precipitate formed on nanoparticles. The structural evolution changed from core-shell structure of iron oxide to sheet structure of co-precipitation, to sphere structure that hydroxide gradually dissolved as the pH decreased, and to cavity structures for the pH continually decreased. Furthermore, below pH 4.7, the In(III) enrichment was inhibited for the limited capacity of co-precipitation. Also, it was found that Ca2+ and HPO4 2- have more negative influence on In(III) recovery compared with Na+, NO3 -, HCO3 -, and SO4 2-. Therefore, the In(III) recovery can be described by a mechanism which consists of adsorption, co-precipitation, and reduction and was over 78% even after 3 cycles. The results confirmed that it was applicable to employ nZVI for In(III) immobilization.

Analysis of Yellow Striped Mutants of Zea mays Reveals Novel Loci Contributing to Iron Deficiency Chlorosis

PubMed Central

Chan-Rodriguez, David; Walker, Elsbeth L.

2018-01-01

The micronutrient iron (Fe) is essential for photosynthesis, respiration, and many other processes, but it is only sparingly soluble in aqueous solution, making adequate acquisition by plants a serious challenge. Fe is a limiting factor for plant growth on approximately 30% of the world’s arable lands. Moreover, Fe deficiency in humans is a global health issue, affecting 1.62 billion people, or about 25% of the world’s population. It is imperative that we gain a better understanding of the mechanisms that plants use to regulate iron homeostasis, since these will be important targets for future biofortification and crop improvement strategies. Grasses and non-grasses have evolved independent mechanisms for primary iron uptake from the soil. The grasses, which include most of the world’s staple grains, have evolved a distinct ‘chelation’ mechanism to acquire iron from the soil. Strong iron chelators called phytosiderophores (PSs) are synthesized by grasses and secreted into the rhizosphere where they bind and solubilize Fe(III). The Fe(III)-PS complex is then taken up into root cells via transporters specific for the Fe(III)-PS complex. In this study, 31 novel, uncharacterized striped maize mutants available through the Maize Genetics Cooperation Stock Center (MGCSC) were analyzed to determine whether their mutant phenotypes are caused by decreased iron. Many of these proved to be either pale yellow or white striped mutants. Complementation tests were performed by crossing the MGCSC mutants to ys1 and ys3 reference mutants. This allowed assignment of 10 ys1 alleles and 4 ys3 alleles among the novel mutants. In addition, four ys∗ mutant lines were identified that are not allelic to either ys1 or ys3. Three of these were characterized as being non-allelic to each other and as having low iron in leaves. These represent new genes involved in iron acquisition by maize, and future cloning of these genes may reveal novel aspects of the grass iron acquisition mechanism. PMID:29515599

Removal of Trace Arsenic to Meet Drinking Water Standards Using Iron Oxide Coated Multiwall Carbon Nanotubes.

PubMed

Ntim, Susana Addo; Mitra, Somenath

2011-05-12

This study presents the removal of trace level arsenic to meet drinking water standards using an iron oxide-multi-walled carbon nanotube (Fe-MWCNT) hybrid as a sorbent. The synthesis was facilitated by the high degree of nanotube functionalization using a microwave assisted process, and a controlled assembly of iron oxide was possible where the MWCNT served as an effective support for the oxide. In the final product, 11 % of the carbon atoms were attached to Fe. The Fe-MWCNT was effective in arsenic removal to below the drinking water standard levels of 10 µg L(-1). The absorption capacity of the composite was 1723 µg g(-1) and 189 µg g(-1) for As(III) and As(V) respectively. The adsorption of As(V) on Fe-MWCNT was faster than that of As(III). The pseudo-second order rate equation was found to effectively describe the kinetics of arsenic adsorption. The adsorption isotherms for As(III) and As(V) fitted both the Langmuir and Freundlich models.

Coordination polymer nanocapsules prepared using metal-organic framework templates for pH-responsive drug delivery

NASA Astrophysics Data System (ADS)

Tang, Lei; Shi, Jiafu; Wang, Xiaoli; Zhang, Shaohua; Wu, Hong; Sun, Hongfan; Jiang, Zhongyi

2017-07-01

A facile, efficient, and versatile approach is presented to synthesize pH-responsive nanocapsules (˜120 nm) by combining the advantages of metal-organic frameworks (MOFs) and metal-organic thin films. ZIF-8 nanoparticles are used as templates on which a thin film coating of iron(III)-catechol complexes is derived from the coordination between dopamine-modified alginate (AlgDA) and iron(III) ions. After the template removal, nanocapsules with a pH-responsive wall are obtained. Doxorubicin (Dox), a typical anticancer drug, is first immobilized in ZIF-8 frameworks through coprecipitation and then encapsulated in nanocapsules after the removal of ZIF-8. The structure of the iron(III)-catechol complex varies with pH value, thus conferring the Dox@Nanocapsules with tailored release behavior in vitro. Cytotoxicity tests illustrate the highly effective cytotoxicity of Dox@Nanocapsules towards cancer cells. This study provides a new method for preparing smart nanocapsules and offers more opportunities for the controlled delivery of drugs.

Iron and aluminum interaction with amyloid-beta peptides associated with Alzheimer's disease

NASA Astrophysics Data System (ADS)

Drochioiu, Gabi; Murariu, Manuela; Ion, Laura; Habasescu, Laura

2014-10-01

An elevation in the concentration of heavy metal ions in Alzheimer's disease (AD) brain has been demonstrated in many studies. Aβ precipitation and toxicity in AD brains seem to be caused by abnormal interactions with neocortical metal ions, especially iron, copper, zinc, and aluminum [1-3]. There is increasing evidence that iron and aluminum ions are involved in the mechanisms that underlie the neurodegenerative diseases [4,5]. However, evidence was brought to demonstrate that some Aβ fragments, at physiological pH, are not able to form binary complexes with Fe(III) ions of sufficient stability to compete with metal hydroxide precipitation [6]. On the contrary, multiple metal ions are known to interact with Aβ peptides [7]. Consequently, we investigated here the interaction of Fe(II/III) and Al(III) ions with some amyloid-β peptides and fragments that results in peptide aggregation and fibrillation [8,9]. Infrared spectroscopy, atomic force microscopy, scanning electron microscopy, electrophoresis and mass spectrometry demonstrated conformational changes of peptides in the presence of such metals.

Reverse osmosis membrane composition, structure and performance modification by bisulphite, iron(III), bromide and chlorite exposure.

PubMed

Ferrer, O; Gibert, O; Cortina, J L

2016-10-15

Reverse osmosis (RO) membrane exposure to bisulphite, chlorite, bromide and iron(III) was assessed in terms of membrane composition, structure and performance. Membrane composition was determined by Rutherford backscattering spectrometry (RBS) and membrane performance was assessed by water and chloride permeation, using a modified version of the solution-diffusion model. Iron(III) dosage in presence of bisulphite led to an autooxidation of the latter, probably generating free radicals which damaged the membrane. It comprised a significant raise in chloride passage (chloride permeation coefficient increased 5.3-5.1 fold compared to the virgin membrane under the conditions studied) rapidly. No major differences in terms of water permeability and membrane composition were observed. Nevertheless, an increase in the size of the network pores, and a raise in the fraction of aggregate pores of the polyamide (PA) layer were identified, but no amide bond cleavage was observed. These structural changes were therefore, in accordance with the transport properties observed. Copyright © 2016 Elsevier Ltd. All rights reserved.

Removal of hexavalent chromium in soil and groundwater by supported nano zero-valent iron on silica fume.

PubMed

Li, Yongchao; Jin, Zhaohui; Li, Tielong; Li, Shujing

2011-01-01

Silica fume supported-Fe(0) nanoparticles (SF-Fe(0)) were prepared using commercial silica fume as a support. The feasibility of using this SF-Fe(0) for reductive immobilization of Cr(VI) was investigated through batch tests. Compared with unsupported Fe(0), SF-Fe(0) was significantly more active in Cr(VI) removal especially in 84 wt% silica fume loading. Silica fume had also been found to inhibit the formation of Fe(III)/Cr(III) precipitation on Fe nanoparticles' surface, which was increasing the deactivation resistance of iron. Cr(VI) was removed through physical adsorption of Cr(VI) onto the SF-Fe(0) surface and subsequent reduction of Cr(VI) to Cr(III). The rate of reduction of Cr(VI) could be expressed by pseudo first-order reaction kinetics. The rate constant increased with the increase in iron loading but decreased with the increase in initial Cr(VI) concentration. Furthermore, column tests showed that the SF-Fe(0) could be readily transported in model soil.

Genomic insights into the iron uptake mechanisms of the biomining microorganism Acidithiobacillus ferrooxidans.

PubMed

Quatrini, Raquel; Jedlicki, Eugenia; Holmes, David S

2005-12-01

Commercial bioleaching of copper and the biooxidation of gold is a cost-effective and environmentally friendly process for metal recovery. A partial genome sequence of the acidophilic, bioleaching bacterium Acidithiobacillus ferrooxidans is available from two public sources. This information has been used to build preliminary models that describe how this microorganism confronts unusually high iron loads in the extremely acidic conditions (pH 2) found in natural environments and in bioleaching operations. A. ferrooxidans contains candidate genes for iron uptake, sensing, storage, and regulation of iron homeostasis. Predicted proteins exhibit significant amino acid similarity with known proteins from neutrophilic organisms, including conservation of functional motifs, permitting their identification by bioinformatics tools and allowing the recognition of common themes in iron transport across distantly related species. However, significant differences in amino acid sequence were detected in pertinent domains that suggest ways in which the periplasmic and outer membrane proteins of A. ferrooxidans maintain structural integrity and relevant protein-protein contacts at low pH. Unexpectedly, the microorganism also contains candidate genes, organized in operon-like structures that potentially encode at least 11 siderophore systems for the uptake of Fe(III), although it does not exhibit genes that could encode the biosynthesis of the siderophores themselves. The presence of multiple Fe(III) uptake systems suggests that A. ferrooxidans can inhabit aerobic environments where iron is scarce and where siderophore producers are present. It may also help to explain why it cannot tolerate high Fe(III) concentrations in bioleaching operations where it is out-competed by Leptospirillum species.

Ribonucleotide reductase inhibition by metal complexes of Triapine (3-aminopyridine-2-carboxaldehyde thiosemicarbazone): A combined experimental and theoretical study

PubMed Central

Popović-Bijelić, Ana; Kowol, Christian R.; Lind, Maria E.S.; Luo, Jinghui; Himo, Fahmi; Enyedy, Éva A.; Arion, Vladimir B.; Gräslund, Astrid

2012-01-01

Triapine (3-aminopyridine-2-carboxaldehyde thiosemicarbazone, 3-AP) is currently the most promising chemotherapeutic compound among the class of α-N-heterocyclic thiosemicarbazones. Here we report further insights into the mechanism(s) of anticancer drug activity and inhibition of mouse ribonucleotide reductase (RNR) by Triapine. In addition to the metal-free ligand, its iron(III), gallium(III), zinc(II) and copper (II) complexes were studied, aiming to correlate their cytotoxic activities with their effects on the diferric/tyrosyl radical center of the RNR enzyme in vitro. In this study we propose for the first time a potential specific binding pocket for Triapine on the surface of the mouse R2 RNR protein. In our mechanistic model, interaction with Triapine results in the labilization of the diferric center in the R2 protein. Subsequently the Triapine molecules act as iron chelators. In the absence of external reductants, and in presence of the mouse R2 RNR protein, catalytic amounts of the iron(III)–Triapine are reduced to the iron(II)–Triapine complex. In the presence of an external reductant (dithiothreitol), stoichiometric amounts of the potently reactive iron (II)–Triapine complex are formed. Formation of the iron(II)–Triapine complex, as the essential part of the reaction outcome, promotes further reactions with molecular oxygen, which give rise to reactive oxygen species (ROS) and thereby damage the RNR enzyme. Triapine affects the diferric center of the mouse R2 protein and, unlike hydroxyurea, is not a potent reductant, not likely to act directly on the tyrosyl radical. PMID:21955844

Magnetite production and transformation in the methanogenic consortia from coastal riverine sediments.

PubMed

Zheng, Shiling; Wang, Bingchen; Liu, Fanghua; Wang, Oumei

2017-11-01

Minerals that contain ferric iron, such as amorphous Fe(III) oxides (A), can inhibit methanogenesis by competitively accepting electrons. In contrast, ferric iron reduced products, such as magnetite (M), can function as electrical conductors to stimulate methanogenesis, however, the processes and effects of magnetite production and transformation in the methanogenic consortia are not yet known. Here we compare the effects on methanogenesis of amorphous Fe (III) oxides (A) and magnetite (M) with ethanol as the electron donor. RNA-based terminal restriction fragment length polymorphism with a clone library was used to analyse both bacterial and archaeal communities. Iron (III)-reducing bacteria including Geobacteraceae and methanogens such as Methanosarcina were enriched in iron oxide-supplemented enrichment cultures for two generations with ethanol as the electron donor. The enrichment cultures with A and non-Fe (N) dominated by the active bacteria belong to Veillonellaceae, and archaea belong to Methanoregulaceae and Methanobacteriaceae, Methanosarcinaceae (Methanosarcina mazei), respectively. While the enrichment cultures with M, dominated by the archaea belong to Methanosarcinaceae (Methanosarcina barkeri). The results also showed that methanogenesis was accelerated in the transferred cultures with ethanol as the electron donor during magnetite production from A reduction. Powder X-ray diffraction analysis indicated that magnetite was generated from microbial reduction of A and M was transformed into siderite and vivianite with ethanol as the electron donor. Our data showed the processes and effects of magnetite production and transformation in the methanogenic consortia, suggesting that significantly different effects of iron minerals on microbial methanogenesis in the iron-rich coastal riverine environment were present.

A nano-disperse ferritin-core mimetic that efficiently corrects anemia without luminal iron redox activity

PubMed Central

Powell, Jonathan J.; Bruggraber, Sylvaine F.A.; Faria, Nuno; Poots, Lynsey K.; Hondow, Nicole; Pennycook, Timothy J.; Latunde-Dada, Gladys O.; Simpson, Robert J.; Brown, Andy P.; Pereira, Dora I.A.

2014-01-01

The 2-5 nm Fe(III) oxo-hydroxide core of ferritin is less ordered and readily bioavailable compared to its pure synthetic analogue, ferrihydrite. We report the facile synthesis of tartrate-modified, nano-disperse ferrihydrite of small primary particle size, but with enlarged or strained lattice structure (~ 2.7 Å for the main Bragg peak versus 2.6 Å for synthetic ferrihydrite). Analysis indicated that co-precipitation conditions can be achieved for tartrate inclusion into the developing ferrihydrite particles, retarding both growth and crystallization and favoring stabilization of the cross-linked polymeric structure. In murine models, gastrointestinal uptake was independent of luminal Fe(III) reduction to Fe(II) and, yet, absorption was equivalent to that of ferrous sulphate, efficiently correcting the induced anemia. This process may model dietary Fe(III) absorption and potentially provide a side effect-free form of cheap supplemental iron. From the Clinical Editor Small size tartrate-modified, nano-disperse ferrihydrite was used for efficient gastrointestinal delivery of soluble Fe(III) without the risk for free radical generation in murine models. This method may provide a potentially side effect-free form iron supplementation. PMID:24394211

Occurrence and behaviour of dissolved, nano-particulate and micro-particulate iron in waste waters and treatment systems: new insights from electrochemical analysis.

PubMed

Matthies, R; Aplin, A C; Horrocks, B R; Mudashiru, L K

2012-04-01

Cyclic-, Differential Pulse- and Steady-state Microdisc Voltammetry (CV, DPV, SMV) techniques have been used to quantify the occurrence and fate of dissolved Fe(ii)/Fe(iii), nano-particulate and micro-particulate iron over a 12 month period in a series of net-acidic and net-alkaline coal mine drainages and passive treatment systems. Total iron in the mine waters is typically 10-100 mg L(-1), with values up to 2100 mg L(-1). Between 30 and 80% of the total iron occurs as solid phase, of which 20 to 80% is nano-particulate. Nano-particulate iron comprises 20 to 70% of the nominally "dissolved" (i.e. <0.45 μm) iron. Since coagulation and sedimentation are the only processes required to remove solid phase iron, these data have important implications for the generation or consumption of acidity during water treatment. In most waters, the majority of truly dissolved iron occurs as Fe(ii) (average 64 ± 22%). Activities of Fe(ii) do not correlate with pH and geochemical modelling shows that no Fe(ii) mineral is supersaturated. Removal of Fe(ii) must proceed via oxidation and hydrolysis. Except in waters with pH < 4.4, activities of Fe(iii) are strongly and negatively correlated with pH. Geochemical modelling suggests that the activity of Fe(iii) is controlled by the solubility of hydrous ferric oxides and oxyhydroxysulfates, supported by scanning and transmission electron microscopic analysis of solids. Nevertheless, the waters are generally supersaturated with respect to ferrihydrite and schwertmannite, and are not at redox equilibrium, indicating the key role of oxidation and hydrolysis kinetics on water treatment. Typically 70-100% of iron is retained in the treatment systems. Oxidation, hydrolysis, precipitation, coagulation and sedimentation occur in all treatment systems and - independent of water chemistry and the type of treatment system - hydroxides and oxyhydroxysulfates are the main iron sinks. The electrochemical data thus reveal the rationale for incomplete iron retention in individual systems and can thus inform future design criteria. The successful application of this low cost and rapid electrochemical method demonstrates its significant potential for real-time, on-site monitoring of iron-enriched waters and may in future substitute traditional analytical methods.

Reaction Mechanisms of Metals with Hydrogen Sulfide and Thiols in Model Wine. Part 2: Iron- and Copper-Catalyzed Oxidation.

PubMed

Kreitman, Gal Y; Danilewicz, John C; Jeffery, David W; Elias, Ryan J

2016-05-25

Sulfidic off-odors arising during wine production are frequently removed by Cu(II) fining. In part 1 of this study ( 10.1021/acs.jafc.6b00641 ), the reaction of H2S and thiols with Cu(II) was examined; however, the interaction of iron and copper is also known to play an important synergistic role in mediating non-enzymatic wine oxidation. The interaction of these two metals in the oxidation of H2S and thiols (cysteine, 3-sulfanylhexan-1-ol, and 6-sulfanylhexan-1-ol) was therefore examined under wine-like conditions. H2S and thiols (300 μM) were reacted with Fe(III) (100 or 200 μM) alone and in combination with Cu(II) (25 or 50 μM), and concentrations of H2S and thiols, oxygen, and acetaldehyde were monitored over time. H2S and thiols were shown to be slowly oxidized in the presence of Fe(III) alone and were not bound to Fe(III) under model wine conditions. However, Cu(II) added to model wine containing Fe(III) was quickly reduced by H2S and thiols to form Cu(I) complexes, which then rapidly reduced Fe(III) to Fe(II). Oxidation of Fe(II) in the presence of oxygen regenerated Fe(III) and completed the iron redox cycle. In addition, sulfur-derived oxidation products were observed, and the formation of organic polysulfanes was demonstrated.

Voltammetric determination of arsenic in high iron and manganese groundwaters.

PubMed

Gibbon-Walsh, Kristoff; Salaün, Pascal; Uroic, M Kalle; Feldmann, Joerg; McArthur, John M; van den Berg, Constant M G

2011-09-15

Determination of the speciation of arsenic in groundwaters, using cathodic stripping voltammetry (CSV), is severely hampered by high levels of iron and manganese. Experiments showed that the interference is eliminated by addition of EDTA, making it possible to determine the arsenic speciation on-site by CSV. This work presents the CSV method to determine As(III) in high-iron or -manganese groundwaters in the field with only minor sample treatment. The method was field-tested in West-Bengal (India) on a series of groundwater samples. Total arsenic was subsequently determined after acidification to pH 1 by anodic stripping voltammetry (ASV). Comparative measurements by ICP-MS as reference method for total As, and by HPLC for its speciation, were used to corroborate the field data in stored samples. Most of the arsenic (78±0.02%) was found to occur as inorganic As(III) in the freshly collected waters, in accordance with previous studies. The data shows that the modified on-site CSV method for As(III) is a good measure of water contamination with As. The EDTA was also found to be effective in stabilising the arsenic speciation for longterm sample storage at room temperature. Without sample preservation, in water exposed to air and sunlight, the As(III) was found to become oxidised to As(V), and Fe(II) oxidised to Fe(III), removing the As(V) by adsorption on precipitating Fe(III)-hydroxides within a few hours. Copyright © 2011 Elsevier B.V. All rights reserved.

Oxidative mutagenesis of doxorubicin-Fe(III) complex.

PubMed

Kostoryz, E L; Yourtee, D M

2001-02-20

Doxorubicin has a high affinity for inorganic iron, Fe(III), and has potential to form doxorubicin-Fe(III) complexes in biological systems. Indirect involvement of iron has been substantiated in the oxidative mutagenicity of doxorubicin. In this study, however, direct involvement of Fe(III) was evaluated in mutagenicity studies with the doxorubicin-Fe(III) complex. The Salmonella mutagenicity assay with strain TA102 was used with a pre-incubation step. The highest mutagenicity of doxorubicin-Fe(III) complex was observed at the dose of 2.5nmol/plate of the complex. The S9-mix decreased this highest mutagenicity but increased the number of revertants at a higher dose of 10nmol/plate of the complex. On the other hand, the mutagenicity of the doxorubicin-Fe(III) complex at the doses of 0.25, 0.5, 1 and 2nmol/plate was enhanced about twice by the addition of glutathione plus H(2)O(2). This enhanced mutagenicity as well as of the complex itself, the complex plus glutathione, and the complex plus H(2)O(2) were reduced by the addition of ADR-529, an Fe(III) chelator, and potassium iodide, a hydroxyl radical scavenger. These results indicate that doxorubicin-Fe(III) complex exert the mutagenicity through oxidative DNA damage and that Fe(III) is a required element in the mutagenesis of doxorubicin.

Determining Iron Content in Foods by Spectrophotometry.

ERIC Educational Resources Information Center

Adams, Paul E.

1995-01-01

Describes a laboratory experiment for secondary school chemistry students utilizing the classic reaction between the iron(III) ion and the thiocyanate ion. The experiment also works very well in other chemistry courses as an experience in spectrophotometric analysis. (PVD)

New method for the direct determination of dissolved Fe(III) concentration in acid mine waters

USGS Publications Warehouse

To, T.B.; Nordstrom, D. Kirk; Cunningham, K.M.; Ball, J.W.; McCleskey, R. Blaine

1999-01-01

A new method for direct determination of dissolved Fe(III) in acid mine water has been developed. In most present methods, Fe(III) is determined by computing the difference between total dissolved Fe and dissolved Fe(II). For acid mine waters, frequently Fe(II) >> Fe(III); thus, accuracy and precision are considerably improved by determining Fe(III) concentration directly. The new method utilizes two selective ligands to stabilize Fe(III) and Fe(II), thereby preventing changes in Fe reduction-oxidation distribution. Complexed Fe(II) is cleanly removed using a silica-based, reversed-phase adsorbent, yielding excellent isolation of the Fe(III) complex. Iron(III) concentration is measured colorimetrically or by graphite furnace atomic absorption spectrometry (GFAAS). The method requires inexpensive commercial reagents and simple procedures that can be used in the field. Calcium(II), Ni(II), Pb(II), AI(III), Zn(II), and Cd(II) cause insignificant colorimetric interferences for most acid mine waters. Waters containing >20 mg of Cu/L could cause a colorimetric interference and should be measured by GFAAS. Cobalt(II) and Cr(III) interfere if their molar ratios to Fe(III) exceed 24 and 5, respectively. Iron(II) interferes when its concentration exceeds the capacity of the complexing ligand (14 mg/L). Because of the GFAAS elemental specificity, only Fe(II) is a potential interferent in the GFAAS technique. The method detection limit is 2 ??g/L (40 nM) using GFAAS and 20 ??g/L (0.4 ??M) by colorimetry.A new method for direct determination of dissolved Fe(III) in acid mine water has been developed. In most present methods, Fe(III) is determined by computing the difference between total dissolved Fe and dissolved Fe(II). For acid mine waters, frequently Fe(II)???Fe(III); thus, accuracy and precision are considerably improved by determining Fe(III) concentration directly. The new method utilizes two selective ligands to stabilize Fe(III) and Fe(II), thereby preventing changes in Fe reduction-oxidation distribution. Complexed Fe(II) is cleanly removed using a silica-based, reversed-phase adsorbent, yielding excellent isolation of the Fe(III) complex. Iron(III) concentration is measured colorimetrically or by graphite furnace atomic absorption spectrometry (GFAAS). The method requires inexpensive commercial reagents and simple procedures that can be used in the field. Calcium(II), Ni(II), Pb(II), Al(III), Zn(II), and Cd(II) cause insignificant colorimetric interferences for most acid mine waters. Waters containing >20 mg of Cu/L could cause a colorimetric interference and should be measured by GFAAS. Cobalt(II) and Cr(III) interfere if their molar ratios to Fe(III) exceed 24 and 5, respectively. Iron(II) interferes when its concentration exceeds the capacity of the complexing ligand (14 mg/L). Because of the GFAAS elemental specificity, only Fe(II) is a potential interferent in the GFAAS technique. The method detection limit is 2/??g/L (40 nM) using GFAAS and 20 ??g/L (0.4 ??M) by colorimetry.

Synthesis and Characterization of Potassium Tris(oxalato)ferrate(III) Trihydrate: A Spectrophotometric Method of Iron Analysis

NASA Astrophysics Data System (ADS)

Dallinger, Richard F.

1995-10-01

A previous Journal article [J. Chem. Educ. 1984, 61, 1098--1099] described a potassium tris(oxalato)ferrate(III) trihydrate empirical formula experiment that offered an excellent integrative experience in synthesis and characterization for general chemistry laboratory students. However, we have introduced a fast and accurate spectrophotometric method for the determination of iron in the product that takes the place of the photochemical-gravimetric procedure described in the article. Besides the pedagogic interest of bringing three different types of chemical analysis (titrimetric, gravimetric, and spectrophotometric) to bear on one compound, the new iron determination allows students to complete the experiment in 2, 3-hr laboratory periods rather than the 5 periods allotted in the original experiment.

Magnetic iron(III)-based framework composites for the magnetic solid-phase extraction of fungicides from environmental water samples.

PubMed

Huang, Yan-Feng; Liu, Qiao-Huan; Li, Kang; Li, Ying; Chang, Na

2018-03-01

We adopted a facile hydrofluoric acid-free hydro-/solvothermal method for the preparation of four magnetic iron(III)-based framework composites (MIL-101@Fe 3 O 4 -COOH, MIL-101-NH 2 @Fe 3 O 4 -COOH, MIL-53@Fe 3 O 4 -COOH, and MIL-53-NH 2 @Fe 3 O 4 -COOH). The obtained four magnetic iron(III)-based framework composites were applied to magnetic separation and enrichment of the fungicides (prochloraz, myclobutanil, tebuconazole, and iprodione) from environmental samples before high-performance liquid chromatographic analysis. MIL-101-NH 2 @Fe 3 O 4 -COOH showed more remarkable pre-concentration ability for the fungicides as compared to the other three magnetic iron(III)-based framework composites. The extraction parameters affecting enrichment efficiency including extraction time, sample pH, elution time, and the desorption solvent were investigated and optimized. Under the optimized conditions, the standard curve of correlation coefficients were all above 0.991, the limits of detection were 0.04-0.4 μg/L, and the relative standard deviations were below 10.2%. The recoveries of two real water samples ranged from 71.1-99.1% at the low spiking level (30 μg/L). Therefore, the MIL-101-NH 2 @Fe 3 O 4 -COOH composites are attractive for the rapid and efficient extraction of fungicides from environmental water samples. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Adsorption Mechanisms of Trivalent Gold onto Iron Oxy-Hydroxides: From the Molecular Scale to the Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cances, Benjamin; Benedetti, Marc; Farges, Francois

2007-02-02

Gold is a highly valuable metal that can concentrate in iron-rich exogenetic horizons such as laterites. An improved knowledge of the retention mechanisms of gold onto highly reactive soil components such as iron oxy-hydroxides is therefore needed to better understand and predict the geochemical behavior of this element. In this study, we use EXAFS information and titration experiments to provide a realistic thermochemical description of the sorption of trivalent gold onto iron oxy-hydroxides. Analysis of Au LIII-edge XAFS spectra shows that aqueous Au(III) adsorbs from chloride solutions onto goethite surfaces as inner-sphere square-planar complexes (Au(III)(OH,Cl)4), with dominantly OH ligands atmore » pH > 6 and mixed OH/Cl ligands at lower pH values. In combination with these spectroscopic results, Reverse Monte Carlo simulations were used to constraint the possible sorption sites on the surface of goethite. Based on this structural information, we calculated sorption isotherms of Au(III) on Fe oxy-hydroxides surfaces, using the CD-MUSIC (Charge Distribution - MUlti SIte Complexation) model. The various Au(III)-sorbed species were identified as a function of pH, and the results of these EXAFS+CD-MUSIC models are compared with titration experiments. The overall good agreement between the predicted and measured structural models shows the potential of this combined approach to better model sorption processes of transition elements onto highly reactive solid surfaces such as goethite and ferrihydrite.« less

Stabilization of higher-valent states of iron porphyrin by hydroxide and methoxide ligands: electrochemical generation of iron(IV)-oxo porphyrins.

PubMed Central

Lee, W A; Calderwood, T S; Bruice, T C

1985-01-01

An electrochemical study of hydroxide- and methoxide-ligated iron(III) tetraphenylporphyrins possessing ortho-phenyl substituents that block mu-oxo dimer formation has been carried out. Ligation by these strongly basic oxyanions promotes the formation of iron(IV)-oxo porphyrins upon one-electron oxidation. Further one-electron oxidation of the latter provides the iron(IV)-oxo porphyrin pi-cation radical. These results are discussed in terms of chemical model studies and the enzymatic intermediate compounds I and II of the peroxidases. PMID:3859865

Anaerobic hydrocarbon degradation in petroleum-contaminated harbor sediments under sulfate-reducing and artificially imposed iron-reducing conditions

USGS Publications Warehouse

Coates, J.D.; Anderson, R.T.; Woodward, J.C.; Phillips, E.J.P.; Lovley, D.R.

1996-01-01

The potential use of iron(III) oxide to stimulate in-situ hydrocarbon degradation in anaerobic petroleum-contaminated harbor sediments was investigated. Previous studies have indicated that Fe(III)-reducing bacteria (FeRB) can oxidize some electron donors more effectively than sulfate- reducing bacteria (SRB). In contrast to previous results in freshwater sediments, the addition of Fe(III) to marine sediments from San Diego Bay, CA did not switch the terminal electron-accepting process (TEAP) from sulfate reduction to Fe-(III) reduction. Addition of Fe(III) also did not stimulate anaerobic hydrocarbon oxidation. Exposure of the sediment to air [to reoxidize Fe(II) to Fe(III)] followed by anaerobic incubation of the sediments, resulted in Fe-(III) reduction as the TEAP, but contaminant degradation was not stimulated and in some instances was inhibited. The difference in the ability of FeRB to compete with the SRB in the different sediment treatments was related to relative population sizes. Although the addition of Fe(III) did not stimulate hydrocarbon degradation, the results presented here as well as other recent studies demonstrate that there may be significant anaerobic hydrocarbon degradation under sulfate-reducing conditions in harbor sediments.

Iron speciation in peats: Chemical and spectroscopic evidence for the co-occurrence of ferric and ferrous iron in organic complexes and mineral precipitates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharyya, Amrita; Schmidt, Michael P.; Stavitski, Eli

The speciation of iron (Fe) in organic matter (OM)-rich environments under in situ variable redox conditions is largely unresolved. Peatlands provide a natural setting to study Fe–OM interactions. Utilizing chemical, spectroscopic and theoretical modeling approaches, we report the chemical forms, oxidation states and local coordination environment of naturally occurring Fe in the vertically redox-stratified Manning peatlands of western New York. In addition, we report dominant carbon, sulfur and nitrogen species that can potentially stabilize the various Fe species present in these peatlands. Our results provide clear direct and indirect evidence for the co-occurrence of ferrous (Fe 2+) and ferric (Femore » 3+) iron species in peats under both oxic and anoxic conditions. Iron is mostly present within the operationally defined organic and amorphous (i.e., short range ordered, SRO) fractions; ferric iron primarily as magnetically isolated paramagnetic Fe 3+ in Fe(III)-organic complexes, but also in mineral forms such as ferrihydrite; ferrous iron in tetrahedral coordination in Fe(II)-organic complexes with minor contribution from pyrite. All of the Fe species identified stabilize Fe(III) and/or Fe(II) in anoxic and oxic peats. Fundamental differences are also observed in the relative proportion of C, S and N functionalities of OM in oxic and anoxic peats. Aromatic C=C, ester, phenol and anomeric C (R-O-C-O-R), as well as thiol, sulfide and heterocyclic N functionalities are more prevalent in anoxic peats. Collectively, our experimental evidence suggests iron forms coordination complexes with O-, S- and N-containing functional groups of OM. We posit the co-occurrence of organic and mineral forms of Fe(II) and Fe(III) in both oxic and anoxic peat layers results from dynamic complexation and hydrolysis-precipitation reactions that occur under variable redox conditions. In conclusion, our findings aid in understanding the crucial role OM plays in determining Fe species in soils and sediments.« less

Iron speciation in peats: Chemical and spectroscopic evidence for the co-occurrence of ferric and ferrous iron in organic complexes and mineral precipitates

DOE PAGES

Bhattacharyya, Amrita; Schmidt, Michael P.; Stavitski, Eli; ...

2017-10-31

The speciation of iron (Fe) in organic matter (OM)-rich environments under in situ variable redox conditions is largely unresolved. Peatlands provide a natural setting to study Fe–OM interactions. Utilizing chemical, spectroscopic and theoretical modeling approaches, we report the chemical forms, oxidation states and local coordination environment of naturally occurring Fe in the vertically redox-stratified Manning peatlands of western New York. In addition, we report dominant carbon, sulfur and nitrogen species that can potentially stabilize the various Fe species present in these peatlands. Our results provide clear direct and indirect evidence for the co-occurrence of ferrous (Fe 2+) and ferric (Femore » 3+) iron species in peats under both oxic and anoxic conditions. Iron is mostly present within the operationally defined organic and amorphous (i.e., short range ordered, SRO) fractions; ferric iron primarily as magnetically isolated paramagnetic Fe 3+ in Fe(III)-organic complexes, but also in mineral forms such as ferrihydrite; ferrous iron in tetrahedral coordination in Fe(II)-organic complexes with minor contribution from pyrite. All of the Fe species identified stabilize Fe(III) and/or Fe(II) in anoxic and oxic peats. Fundamental differences are also observed in the relative proportion of C, S and N functionalities of OM in oxic and anoxic peats. Aromatic C=C, ester, phenol and anomeric C (R-O-C-O-R), as well as thiol, sulfide and heterocyclic N functionalities are more prevalent in anoxic peats. Collectively, our experimental evidence suggests iron forms coordination complexes with O-, S- and N-containing functional groups of OM. We posit the co-occurrence of organic and mineral forms of Fe(II) and Fe(III) in both oxic and anoxic peat layers results from dynamic complexation and hydrolysis-precipitation reactions that occur under variable redox conditions. In conclusion, our findings aid in understanding the crucial role OM plays in determining Fe species in soils and sediments.« less

Oxidation of Cr(III)-Fe(III) Mixed-phase Hydroxides by Chlorine: Implications on the Control of Hexavalent Chromium in Drinking Water.

PubMed

Chebeir, Michelle; Liu, Haizhou

2018-05-17

The occurrence of chromium (Cr) as an inorganic contaminant in drinking water is widely reported. One source of Cr is its accumulation in iron-containing corrosion scales of drinking water distribution systems as Cr(III)-Fe(III) hydroxide, i.e., FexCr(1-x)(OH)3(s), where x represents the Fe(III) molar content and typically varies between 0.25 and 0.75. This study investigated the kinetics of inadvertent hexavalent chromium Cr(VI) formation via the oxidation of FexCr(1-x)(OH)3(s) by chlorine as a residual disinfectant in drinking water, and examined the impacts of Fe(III) content and drinking water chemical parameters including pH, bromide and bicarbonate on the rate of Cr(VI) formation. Data showed that an increase in Fe(III) molar content resulted in a significant decrease in the stoichiometric Cr(VI) yield and the rate of Cr(VI) formation, mainly due to chlorine decay induced by Fe(III) surface sites. An increase in bicarbonate enhanced the rate of Cr(VI) formation, likely due to the formation of Fe(III)-carbonato surface complexes that slowed down the scavenging reaction with chlorine. The presence of bromide significantly accelerated the oxidation of FexCr(1-x)(OH)3(s) by chlorine, resulting from the catalytic effect of bromide acting as an electron shuttle. A higher solution pH between 6 and 8.5 slowed down the oxidation of Cr(III) by chlorine. These findings suggested that the oxidative conversion of chromium-containing iron corrosion products in drinking water distribution systems can lead to the occurrence of Cr(VI) at the tap, and the abundance of iron, and a careful control of pH, bicarbonate and bromide levels can assist the control of Cr(VI) formation.

Comparative response to single or divided doses of parenteral iron for functional iron deficiency in hemodialysis patients receiving erythropoietin (EPO).

PubMed

Saltissi, D; Sauvage, D; Westhuyzen, J

1998-01-01

EPO treatment rapidly corrects anemia in patients with end-stage renal failure treated with hemodialysis, as long as sufficient iron is available. Absolute and relative (to demand) iron deficiency blunts the erythropoietic response and parenteral iron is frequently required during the course of therapy to restore EPO efficacy. Since the optimum time course of iron administration to restore EPO response in the short term is unknown, we compared three protocols of i.v. iron dextran administration in apparent functionally iron-deficient HD patients on oral iron therapy (hemoglobin < 10.0 g/dl plus ferritin < 100 micrograms/l and/or transferrin saturation < 20%). Intravenous iron (Imferon; Fisons Pty Ltd.) was given either as a single 600 mg dose (n = 15, Group I) or in divided doses of 100 mg administered on 6 successive dialyses (n = 14, Group II) or weekly for 6 weeks (n = 14, Group III). Response was monitored for 8 weeks. No adverse effects were observed. Collectively, mean hemoglobin increased (p < 0.01) by 0.4-0.5 g/dl plateauing at 4 weeks (between group comparison, p = 0.92). Mean ferritin concentrations changed with time (p < 0.01), peaking at 2 weeks in Groups I and II and at 4 weeks in Group III. Mean transferrin saturation levels also increased during the study (p < 0.001). The between group comparisons for the trends in iron indices were significant (p < 0.01 and 0.05 respectively). As there were no clinically significant differences in hemoglobin response at 4 weeks, single dose iron infusion would seem to be the most expedient in the short term, however frequent small doses are similarly effective.

Removal of Arsenic (III, V) from aqueous solution by nanoscale zero-valent iron stabilized with starch and carboxymethyl cellulose

PubMed Central

2014-01-01

In this work, synthetic nanoscale zerovalent iron (NZVI) stabilized with two polymers, Starch and Carboxymethyl cellulose (CMC) were examined and compared for their ability in removing As (III) and As (V) from aqueous solutions as the most promising iron nanoparticles form for arsenic removal. Batch operations were conducted with different process parameters such as contact time, nanoparticles concentration, initial arsenic concentration and pH. Results revealed that starch stabilized particles (S-nZVI) presented an outstanding ability to remove both arsenate and arsenite and displayed ~ 36.5% greater removal for As (V) and 30% for As (III) in comparison with CMC-stabilized nanoparticles (C-nZVI). However, from the particle stabilization viewpoint, there is a clear trade off to choosing the best stabilized nanoparticles form. Removal efficiency was enhanced with increasing the contact time and iron loading but reduced with increasing initial As (III, V) concentrations and pH. Almost complete removal of arsenic (up to 500 μg/L) was achieved in just 5 min when the S-nZVI mass concentration was 0.3 g/L and initial solution pH of 7 ± 0.1. The maximum removal efficiency of both arsenic species was obtained at pH = 5 ± 0.1 and starched nanoparticles was effective in slightly acidic and natural pH values. The adsorption kinetics fitted well with pseudo-second-order model and the adsorption data obeyed the Langmuir equation with a maximum adsorption capacity of 14 mg/g for arsenic (V), and 12.2 mg/g for arsenic (III). It could be concluded that starch stabilized Fe0 nanoparticles showed remarkable potential for As (III, V) removal from aqueous solution e.g. contaminated water. PMID:24860660

Genetic and biochemical investigations of the role of MamP in redox control of iron biomineralization in Magnetospirillum magneticum.

PubMed

Jones, Stephanie R; Wilson, Tiffany D; Brown, Margaret E; Rahn-Lee, Lilah; Yu, Yi; Fredriksen, Laura L; Ozyamak, Ertan; Komeili, Arash; Chang, Michelle C Y

2015-03-31

Magnetotactic bacteria have evolved complex subcellular machinery to construct linear chains of magnetite nanocrystals that allow the host cell to sense direction. Each mixed-valent iron nanoparticle is mineralized from soluble iron within a membrane-encapsulated vesicle termed the magnetosome, which serves as a specialized compartment that regulates the iron, redox, and pH environment of the growing mineral. To dissect the biological components that control this process, we have carried out a genetic and biochemical study of proteins proposed to function in iron mineralization. In this study, we show that the redox sites of c-type cytochromes of the Magnetospirillum magneticum AMB-1 magnetosome island, MamP and MamT, are essential to their physiological function and that ablation of one or both heme motifs leads to loss of function, suggesting that their ability to carry out redox chemistry in vivo is important. We also develop a method to heterologously express fully heme-loaded MamP from AMB-1 for in vitro biochemical studies, which show that its Fe(III)-Fe(II) redox couple is set at an unusual potential (-89 ± 11 mV) compared with other related cytochromes involved in iron reduction or oxidation. Despite its low reduction potential, it remains competent to oxidize Fe(II) to Fe(III) and mineralize iron to produce mixed-valent iron oxides. Finally, in vitro mineralization experiments suggest that Mms mineral-templating peptides from AMB-1 can modulate the iron redox chemistry of MamP.

Reduction of structural Fe(III) in nontronite by methanogen Methanosarcina barkeri

USGS Publications Warehouse

Liu, D.; Dong, Hailiang H.; Bishop, M.E.; Wang, Hongfang; Agrawal, A.; Tritschler, S.; Eberl, D.D.; Xie, S.

2011-01-01

Clay minerals and methanogens are ubiquitous and co-exist in anoxic environments, yet it is unclear whether methanogens are able to reduce structural Fe(III) in clay minerals. In this study, the ability of methanogen Methanosarcina barkeri to reduce structural Fe(III) in iron-rich smectite (nontronite NAu-2) and the relationship between iron reduction and methanogenesis were investigated. Bioreduction experiments were conducted in growth medium using three types of substrate: H2/CO2, methanol, and acetate. Time course methane production and hydrogen consumption were measured by gas chromatography. M. barkeri was able to reduce structural Fe(III) in NAu-2 with H2/CO2 and methanol as substrate, but not with acetate. The extent of bioreduction, as measured by the 1,10-phenanthroline method, was 7-13% with H2/CO2 as substrate, depending on nontronite concentration (5-10g/L). The extent was higher when methanol was used as a substrate, reaching 25-33%. Methanogenesis was inhibited by Fe(III) reduction in the H2/CO2 culture, but enhanced when methanol was used. High charge smectite and biogenic silica formed as a result of bioreduction. Our results suggest that methanogens may play an important role in biogeochemical cycling of iron in clay minerals and may have important implications for the global methane budget. ?? 2010 Elsevier Ltd.

Highly efficient inverted top emitting organic light emitting diodes using a transparent top electrode with color stability on viewing angle

NASA Astrophysics Data System (ADS)

Kim, Jung-Bum; Lee, Jeong-Hwan; Moon, Chang-Ki; Kim, Jang-Joo

2014-02-01

We report a highly efficient phosphorescent green inverted top emitting organic light emitting diode with excellent color stability by using the 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile/indium zinc oxide top electrode and bis(2-phenylpyridine)iridium(III) acetylacetonate as the emitter in an exciplex forming co-host system. The device shows a high external quantum efficiency of 23.4% at 1000 cd/m2 corresponding to a current efficiency of 110 cd/A, low efficiency roll-off with 21% at 10 000 cd/m2 and low turn on voltage of 2.4 V. Especially, the device showed very small color change with the variation of Δx = 0.02, Δy = 0.02 in the CIE 1931 coordinates as the viewing angle changes from 0° to 60°. The performance of the device is superior to that of the metal/metal cavity structured device.

Molecular and phenotypic characterization of transgenic soybean expressing the Arabidopsis ferric chelate reductase gene, FRO2.

PubMed

Vasconcelos, Marta; Eckert, Helene; Arahana, Venancio; Graef, George; Grusak, Michael A; Clemente, Tom

2006-10-01

Soybean (Glycine max Merr.) production is reduced under iron-limiting calcareous soils throughout the upper Midwest regions of the US. Like other dicotyledonous plants, soybean responds to iron-limiting environments by induction of an active proton pump, a ferric iron reductase and an iron transporter. Here we demonstrate that heterologous expression of the Arabidopsis thaliana ferric chelate reductase gene, FRO2, in transgenic soybean significantly enhances Fe(+3) reduction in roots and leaves. Root ferric reductase activity was up to tenfold higher in transgenic plants and was not subjected to post-transcriptional regulation. In leaves, reductase activity was threefold higher in the transgenic plants when compared to control. The enhanced ferric reductase activity led to reduced chlorosis, increased chlorophyll concentration and a lessening in biomass loss in the transgenic events between Fe treatments as compared to control plants grown under hydroponics that mimicked Fe-sufficient and Fe-deficient soil environments. However, the data indicate that constitutive FRO2 expression under non-iron stress conditions may lead to a decrease in plant productivity as reflected by reduced biomass accumulation in the transgenic events under non-iron stress conditions. When grown at Fe(III)-EDDHA levels greater than 10 microM, iron concentration in the shoots of transgenic plants was significantly higher than control. The same observation was found in the roots in plants grown at iron levels higher than 32 microM Fe(III)-EDDHA. These results suggest that heterologous expression of an iron chelate reductase in soybean can provide a route to alleviate iron deficiency chlorosis.

Chelation of Thallium (III) in Rats Using Combined Deferasirox and Deferiprone Therapy.

PubMed

Salehi, Samie; Saljooghi, Amir Sh; Badiee, Somayeh; Moqadam, Mojtaba Mashmool

2017-10-01

Thallium and its compounds are a class of highly toxic chemicals that cause wide-ranging symptoms such as gastrointestinal disturbances; polyneuritis; encephalopathy; tachycardia; skin eruptions; hepatic, renal, cardiac, and neurological toxicities; and have mutagenic and genotoxic effects. The present research aimed to evaluate the efficacy of the chelating agents deferasirox (DFX) and deferiprone (L1) in reducing serum and tissue thallium levels after the administration of thallium (III), according to two different dosing regimens, to several groups of Wistar rats for 60 days. It was hypothesized that the two chelators might be more efficient as a combined therapy than as monotherapies in removing thallium (III) from the rats' organs. The chelators were administered orally as either single or combined therapies for a period of 14 days. Serum and tissue thallium (III) and iron concentrations were determined by flame atomic absorption spectroscopy. Serum and tissue thallium (III) levels were significantly reduced by combined therapy with DFX and L1. Additionally, iron concentrations returned to normal levels and symptoms of toxicity decreased.

Microbial reduction of Fe(III)-bearing clay minerals in the presence of humic acids

NASA Astrophysics Data System (ADS)

Liu, Guangfei; Qiu, Shuang; Liu, Baiqing; Pu, Yiying; Gao, Zhanming; Wang, Jing; Jin, Ruofei; Zhou, Jiti

2017-03-01

Both Fe(III)-bearing clay minerals and humic acids (HAs) are abundant in the soils and sediments. Previous studies have shown that bioreduction of structural Fe(III) in clay minerals could be accelerated by adding anthraquinone compound as a redox-active surrogate of HAs. However, a quinoid analogue could not reflect the adsorption and complexation properties of HA, and little is known about the effects of real HAs at environmental concentration on bioreduction of clay minerals. Here, it was shown that 10-200 mg l-1 of natural or artificially synthesized HAs could effectively stimulate the bioreduction rate and extent of Fe(III) in both iron-rich nontronite NAu-2 and iron-deficient montmorillonite SWy-2. After adsorption to NAu-2, electron-transfer activities of different HA fractions were compared. Additionally, Fe(II) complexation by HAs also contributed to improvement of clay-Fe(III) bioreduction. Spectrosopic and morphological analyses suggested that HA addition accelerated the transformation of NAu-2 to illite, silica and siderite after reductive dissolution.

Mussel-Inspired Protein Nanoparticles Containing Iron(III)-DOPA Complexes for pH-Responsive Drug Delivery.

PubMed

Kim, Bum Jin; Cheong, Hogyun; Hwang, Byeong Hee; Cha, Hyung Joon

2015-06-15

A novel bioinspired strategy for protein nanoparticle (NP) synthesis to achieve pH-responsive drug release exploits the pH-dependent changes in the coordination stoichiometry of iron(III)-3,4-dihydroxyphenylalanine (DOPA) complexes, which play a major cross-linking role in mussel byssal threads. Doxorubicin-loaded polymeric NPs that are based on Fe(III)-DOPA complexation were thus synthesized with a DOPA-modified recombinant mussel adhesive protein through a co-electrospraying process. The release of doxorubicin was found to be predominantly governed by a change in the structure of the Fe(III)-DOPA complexes induced by an acidic pH value. It was also demonstrated that the fabricated NPs exhibited effective cytotoxicity towards cancer cells through efficient cellular uptake and cytosolic release. Therefore, it is anticipated that Fe(III)-DOPA complexation can be successfully utilized as a new design principle for pH-responsive NPs for diverse controlled drug-delivery applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nonaqueous System of Iron-Based Ionic Liquid and DMF for the Oxidation of Hydrogen Sulfide and Regeneration by Electrolysis.

PubMed

Guo, Zhihui; Zhang, Tingting; Liu, Tiantian; Du, Jun; Jia, Bing; Gao, Shujing; Yu, Jiang

2015-05-05

To improve the hydrogen sulfide removal efficiency with the application of an iron-based imidazolium chloride ionic liquid (Fe(III)-IL) as desulfurizer, Fe(II) and N,N-dimethylformamide (DMF) are introduced to Fe(III)-IL to construct a new nonaqueous desulfurization system (Fe(III/II)-IL/DMF). Following desulfurization, the system can be regenerated using the controlled-potential electrolysis method. The addition of Fe(II) in Fe(III)-IL is beneficial for the hydrogen sulfide removal and the electrochemical regeneration of the desulfurizer. The addition of DMF in Fe(III/II)-IL does not change the structure of Fe(III/II)-IL but clearly decreases the acidity, increases the electrolytic current, and decreases the stability of the Fe-Cl bond in Fe(III/II)-IL. Fe(III/II)-IL/DMF can remove hydrogen sulfide and can be regenerated through an electrochemical method more efficiently than can Fe(III/II)-IL. After six cycles, the desulfurization efficiency remains higher than 98%, and the average conversion rate of Fe(II) is essentially unchanged. No sulfur peroxidation occurs, and the system remains stable. Therefore, this new nonaqueous system has considerable potential for removing H2S in pollution control applications.

Iron(III)-oxo centers on TiO{sub 2} for visible light photocatalysis.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Libera, J. A.; Elam, J. W.; Sather, N. F.

Isolated iron(III)-oxo clusters were synthesized onto TiO{sub 2} using atomic layer deposition. The Fe{sub x}O{sub y}/TiO{sub 2} nanocomposites have unique properties that enable not only absorption of visible light, but efficient photocatalysis as demonstrated by methylene blue degradation. The localization of photogenerated electrons in core TiO{sub 2} nanocrystallites upon visible light excitation demonstrates coupling of conduction bands of mixed oxides. The redox properties of photogenerated charges in nanocomposites were studied using in situ electron paramagnetic resonance spectroscopy.

Biological Oxidation of As (III) in a Full-Scale Iron Removal Plant

EPA Science Inventory

The effectiveness of arsenic removal from water is largely dependent on the oxidation state of the arsenic. As (III) is much more difficult to remove relative to the oxidized As (V) form. Arsenic in ground waters across the Midwest is typically in the form of As (III), and ther...

Study on competitive adsorption mechanism among oxyacid-type heavy metals in co-existing system: Removal of aqueous As(V), Cr(III) and As(III) using magnetic iron oxide nanoparticles (MIONPs) as adsorbents

NASA Astrophysics Data System (ADS)

Lin, Sen; Lian, Cheng; Xu, Meng; Zhang, Wei; Liu, Lili; Lin, Kuangfei

2017-11-01

The adsorption and co-adsorption of As(V), Cr(VI) and As(III) onto the magnetic iron oxide nanoparticles (MIONPs) surface were investigated comprehensively to clarify the competitive processes. The results reflected that the MIONPs had remarkable preferential adsorption to As(V) compared with Cr(VI) and As(III). And it was determined, relying on the analysis of heavy metals variations on the MIONPs surface at different co-adsorption stages using FTIR and XPS, that the inner-sphere complexation made vital contribution to the preferential adsorption for As(V), corresponding with the replacement experiments where As(V) could grab extensively active sites on the MIONPs pre-occupied by As(III) or Cr(V) uniaxially. The desorption processes displayed that the strongest affinity between the MIONPs and As(V) where As(III) and Cr(VI) were more inclined to wash out. It is wish to provide a helpful direction with this study for the wastewater treatment involving multiple oxyacid-type heavy metals using MIONPs as adsorbents.

Coastal eutrophication thresholds: a matter of sediment microbial processes.

PubMed

Lehtoranta, Jouni; Ekholm, Petri; Pitkänen, Heikki

2009-09-01

In marine sediments, the major anaerobic mineralization processes are Fe(III) oxide reduction and sulfate reduction. In this article, we propose that the two alternative microbial mineralization pathways in sediments exert decisively different impacts on aquatic ecosystems. In systems where iron reduction dominates in the recently deposited sediment layers, the fraction of Fe(III) oxides that is dissolved to Fe(II) upon reduction will ultimately be transported to the oxic layer, where it will be reoxidized. Phosphorus, which is released from Fe(III) oxides and decomposing organic matter from the sediment, will be largely trapped by this newly formed Fe(III) oxide layer. Consequently, there are low concentrations of phosphorus in near-bottom and productive water layers and primary production tends to be limited by phosphorus (State 1). By contrast, in systems where sulfate reduction dominates, Fe(III) oxides are reduced by sulfides. This chemical reduction leads to the formation and permanent burial of iron as solid iron sulfides that are unable to capture phosphorus. In addition, the cycling of iron is blocked, and phosphorus is released to overlying water. Owing to the enrichment of phosphorus in water, the nitrogen : phosphorus ratio is lowered and nitrogen tends to limit algal growth, giving an advantage to nitrogen-fixing blue-green algae (State 2). A major factor causing a shift from State 1 to State 2 is an increase in the flux of labile organic carbon to the bottom sediments; upon accelerating eutrophication a critical point will be reached when the availability of Fe(III) oxides in sediments will be exhausted and sulfate reduction will become dominant. Because the reserves of Fe(III) oxides are replenished only slowly, reversal to State 1 may markedly exceed the time needed to reduce the flux of organic carbon to the sediment. A key factor affecting the sensitivity of a coastal system to such a regime shift is formed by the hydrodynamic alterations that decrease the transport of O2 to the near-bottom water, e.g., due to variations in salinity and temperature stratification.

Separation and Precipitation of Nickel from Acidic Sulfate Leaching Solution of Molybdenum-Nickel Black Shale by Potassium Nickel Sulfate Hexahydrate Crystallization

NASA Astrophysics Data System (ADS)

Deng, Zhigan; Wei, Chang; Fan, Gang; Li, Xingbin; Li, Minting; Li, Cunxiong

2018-02-01

Nickel was separated and precipitated with potassium nickel sulfate hexahydrate [K2Ni(SO4)2·6H2O] from acidic sulfate solution, a leach solution from molybdenum-nickel black shale. The effects of the potassium sulfate (K2SO4) concentration, crystallization temperature, solution pH, and crystallization time on nickel(II) recovery and iron(III) precipitation were investigated, revealing that nickel and iron were separated effectively. The optimum parameters were K2SO4 concentration of 200 g/L, crystallization temperature of 10°C, solution pH of 0.5, and crystallization time of 24 h. Under these conditions, 97.6% nickel(II) was recovered as K2Ni(SO4)2·6H2O crystals while only 2.0% of the total iron(III) was precipitated. After recrystallization, 98.4% pure K2Ni(SO4)2·6H2O crystals were obtained in the solids. The mother liquor was purified by hydrolysis-precipitation followed by cooling, and more than 99.0% K2SO4 could be crystallized. A process flowsheet was developed to separate iron(III) and nickel(II) from acidic-sulfate solution.

Mineral ecophysiological evidence for biogeochemical cycles in 2461-2495 million year old banded iron formations (BIF).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Y; Konhauser, Dr, Kurt; Cole, David

2011-01-01

The phosphorus composition of banded-iron formations (BIFs) has been used as a proxy for Precambrian seawater composition and the paleoeredox state of Earth's surface environment. However, it is unclear whether the phosphorus in BIFs originally entered the sediment as a sorbed component of the iron oxyhydroxide particles, or whether it was incorporated into the biomass of marine phytoplankton. We conducted high-resolution mineral analyses and report here the first detection of an Fe(III) acetate salt, as well as nanocrystals of apatite in association with magnetite, in the 2.48 Ga Dales Gorge Member of the Brockman Iron Formation (a BIF), Hamersley, Westernmore » Australia. The clusters of apatite are similar in size and morphology to biogenic apatite crystals resulting from biomass decay in Phanerozoic marine sediments, while the formation of an Fe(III) acetate salt and magnetite not only implies the original presence of biomass in the BIF sediments, but also that organic carbon likely served as an electron donor during bacterial Fe(III) reduction. This study is important because it suggests that phytoplankton may have played a key role in the transfer of phosphorus (and other trace elements) from the photic zone to the seafloor.« less

IRON-PEROXYMONOSULFATE: A NOVEL SULFATE RADICAL BASED ADVANCED OXIDATION TECHNOLOGY FOR DEGRADATION OF PCBS

EPA Science Inventory

This study investigates the degradation of recalcitrant polychlorinated biphenyl (PCBs) using sulfate radical-based advanced oxidation technologies. Sulfate radicals are generated through coupling of peroxymonosulfate (PMS) with iron (Fe(II), Fe(III)). Sulfate radicals have very ...

New tris(dopamine) derivative as an iron chelator. Synthesis, solution thermodynamic stability, and antioxidant research.

PubMed

Zhang, Qingchun; Jin, Bo; Shi, Zhaotao; Wang, Xiaofang; Lei, Shan; Tang, Xingyan; Liang, Hua; Liu, Qiangqiang; Gong, Mei; Peng, Rufang

2017-06-01

A new tris(dopamine) derivative, containing three dopamine chelate moieties which were attached to a trimesic acid molecular scaffold, has been prepared and fully characterized by NMR, FTIR and HRMS. The solution thermodynamic stability of the chelator with Fe(III), Mg(II), Zn(II) and Fe(II) ions was investigated. Results demonstrated that the chelator exhibited effective binding ability and improved selectivity to Fe(III) ion. The chelator possessed affinity similar to that of diethylenetriaminepentaacetic acid chelator for Fe(III) ion. The high affinity could be attributed to the favorable geometric arrangement between the chelator and Fe(III) ion coordination preference. The chelator also exhibited high antioxidant activity and nontoxicity to neuron-like rat pheochromocytoma cells. Hence, the chelator could be used as chelating agent for iron overload situations without depleting essential metal ions, such as Mg(II) and Zn(II) ions. Copyright © 2017. Published by Elsevier Inc.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shamie, Jack S.; Liu, Caihong; Shaw, Leon L.

In this study, a new mechanism for the reduction of vanadyl acetylacetonate, VO(acac)2, to vanadium acetylacetonate, V(acac)3, is introduced. V(acac)3 has been studied for use in redox flow batteries (RFBs) for some time; however, contamination by moisture leads to the formation of VO(acac)2. In previous work, once this transformation occurs, it is no longer reversible because there is a requirement for extreme low potentials for the reduction to occur. Here, we propose that, in the presence of excess acetylacetone (Hacac) and free protons (H+), the reduction can take place between 2.25 and 1.5 V versus Na/Na+ via a one-electron-transfer reduction.more » This reduction can take place in situ during discharge in a novel hybrid Na-based flow battery (HNFB) with a molten Na–Cs alloy as the anode. The in situ recovery of V(acac)3 during discharge is shown to allow the Coulombic efficiency of the HNFB to be ≈100 % with little or no capacity decay over cycles. In addition, utilizing two-electron-transfer redox reactions (i.e., V3+/V4+ and V2+/V3+ redox couples) per V ion to increase the energy density of RFBs becomes possible owing to the in situ recovery of V(acac)3 during discharge. The concept of in situ recovery of material can lead to more advances in maintaining the cycle life of RFBs in the future.« less

Plasma impact on structural, morphological and optical properties of copper acetylacetonate thin films

NASA Astrophysics Data System (ADS)

Abdel-Khalek, H.; El-Samahi, M. I.; El-Mahalawy, Ahmed M.

2018-06-01

The influence of plasma exposure on structural, morphological and optical properties of copper (II) acetylacetonate thin films deposited by thermal evaporation technique was investigated. Copper (II) acetylacetonate as-grown thin films were exposed to the atmospheric plasma for different times. The exposure of as-grown cu(acac)2 thin film to atmospheric plasma for 5 min modified its structural, morphological and optical properties. The effect of plasma exposure on structure and roughness of cu(acac)2 thin films was evaluated by XRD and AFM techniques, respectively. The XRD results showed an increment in crystallinity due to exposure for 5 min, but, when the exposure time reaches 10 min, the film was transformed to an amorphous state. The AFM results revealed a strong modification of films roughness when the average roughness decreased from 63.35 nm to 1 nm as a result of interaction with plasma. The optical properties of as-grown and plasma exposured cu(acac)2 thin films were studied using spectrophotometric method. The exposure of cu(acac)2 thin films to plasma produced the indirect energy gap decrease from 3.20 eV to 2.67 eV for 10 min exposure time. The dispersion parameters were evaluated in terms of single oscillator model for as-grown and plasma exposured thin films. The influence of plasma exposure on third order optical susceptibility was studied.

Adsorption properties of Silochrom chemically modified with nickel acetylacetonate

NASA Astrophysics Data System (ADS)

Pakhnutova, Evgeniya; Slizhov, Yuriy

2017-11-01

One of the areas of development of gas chromatography is the creation of new chromatographic materials that have improved sorption and analytical characteristics. In this work, for the first time, a new sorbent based on Silochrom C-120 modified with nickel acetylacetonate was studied using a complex of physico-chemical methods. It has been established that due to chemical modification of silica gel surface with nickel acetylacetonate the surface area of the specific surface decreases from 112 to 98 m2/g and surface acidity diminishes by 1.2 pH units. Using the thermogravimetric analysis it has been revealed that the obtained sorbent can be used in gas chromatography up to 290°C. Gas chromatography method was used to investigate the adsorption properties of the modified materials. According to the retention data of adsorbates: n-alkanes (C6-C9), benzene, ethanol, nitropropane and butanone-2 the differential molar adsorption energy q¯dif, 1, Henry adsorption constants K1,C, the differential molar entropy ΔS¯S1 and Δ q¯dif, 1 (special) of adsorbates in dispersion and specific interactions were calculated. The influence of the modifying additive on the changings in the thermodynamic retention characteristics of all sorbates because of the manifestation of specific sorbate-sorbent interactions has been shown. The highest values of the thermodynamic parameters were indicative for sorbates forming hydrogen bonds and capable of donor-acceptor interaction.

Effect of chaotropes on the kinetics of iron release from ferritin by flavin nucleotides.

PubMed

Johnson, Lindsay E; Wilkinson, Tyler; Arosio, Paolo; Melman, Artem; Bou-Abdallah, Fadi

2017-12-01

Ferritins are ubiquitous multi-subunit iron storage and detoxification proteins that play a critical role in iron homeostasis. Ferrous ions that enter the protein's shell through hydrophilic channels are rapidly oxidized at dinuclear centers on the H-subunit before transfer to the protein's cavity for storage. The mechanisms of iron loading have been extensively studied, but little is known about iron mobilization. Fe(III) reduction can occur via rapid reduction by suitable reducing agents followed by chelation of Fe(II) ions or via direct and slow Fe(III) chelation. Here, the iron release kinetics from ferritin by FMNH 2 in the presence of various chaotropic agents are studied and their in-vivo physiological significance discussed. The iron release kinetics from horse and human ferritins by FMNH 2 were monitored at 522nm where the Fe(II)-bipyridine complex absorbs. The experiments were performed in the presence of different concentrations of three chaotropic agents, urea, guanidine HCl, and triton. Under our experimental conditions, iron reductive mobilization by the non-enzymatic FMN/NAD(P)H system is limited by the concentration of FMNH 2 and is independent on the type or amount of chaotropes present. Diffusion of FMNH 2 through the ferritin pores is an unlikely mechanism for ferritin iron reduction. An iron mobilization mechanism involving rapid electron transfer through the protein shell is discussed. Caution must be exercised when interpreting the kinetics of iron mobilization from ferritin using the FMN/NAD(P)H system. The kinetics are highly dependent on the amount of dissolved oxygen and the concentration of reagents used. Copyright © 2017 Elsevier B.V. All rights reserved.

INORGANIC COORDINATION POLYMERS. IV. THE ATTEMPTED REPLACEMENT OF ACETYLACETONATE LIGANDS WITH PICOLINATE LIGANDS,

DTIC Science & Technology

HETEROCYCLIC COMPOUNDS, PHOSPHENE OXIDES, BENZENE, CHROMIUM COMPOUNDS, CHEMICAL REAC, SYNTHESIS (CHEMISTRY), CHEMICAL ANALY, SPECTRA (INFRARED), ABSORPTION, DISPLACE, POLYMERIZATION, ORGANIC NITROGEN, AROMATIC COMPOUNDS.

Interaction of Triapine and related thiosemicarbazones with iron(III)/(II) and gallium(III): a comparative solution equilibrium study†

PubMed Central

Enyedy, Éva A.; Primik, Michael F.; Kowol, Christian R.; Arion, Vladimir B.; Kiss, Tamás; Keppler, Bernhard K.

2012-01-01

Stoichiometry and stability of GaIII, FeIII, FeII complexes of Triapine and five related α-N heterocyclic thiosemicarbazones with potential antitumor activity have been determined by pH-potentiometry, UV-vis spectrophotometry, 1H NMR spectroscopy, and spectrofluorimetry in aqueous solution (with 30% DMSO), together with the characterization of the proton dissociation processes. Additionally, the redox properties of the iron complexes were studied by cyclic voltammetry at various pH values. Formation of high stability bis-ligand complexes was found in all cases, which are predominant at physiological pH with FeIII/FeII, whilst only at the acidic pH range with GaIII. The results show that among the thiosemicarbazones with various substituents the N-terminal dimethylation does not exert a measurable effect on the redox potential, but has the highest impact on the stability of the complexes as well as the cytotoxicity, especially in the absence of a pyridine-NH2 group in the molecule. In addition the fluorescence properties of the ligands in aqueous solution and their changes caused by GaIII were studied. PMID:21523301

Enhancement of arsenite removal using manganese oxide coupled with iron (III) trimesic

NASA Astrophysics Data System (ADS)

Phanthasri, Jakkapop; Khamdahsag, Pummarin; Jutaporn, Panitan; Sorachoti, Kwannapat; Wantala, Kitirote; Tanboonchuy, Visanu

2018-01-01

A simultaneous removal of As(III) was investigated on a mixture of manganese oxide based octahedral molecular sieves (K-OMS2) and iron-benzenetricarboxylate (Fe-BTC). As(III) removal was stimulated by an oxidation cooperated with adsorption process. K-OMS2 and Fe-BTC were separately synthesized and characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). K-OMS2 showed characters of pure cryptomelane phase, nanorod structure, and a mixed-valent manganese framework with the coexistence of Mn(IV) and Mn(III). As(III) was successfully oxidized to As(V) by K-OMS2 in a temperature range of 303-333 K. An intermediate adsorption of As(V) was carried out with Fe-BTC in the same batch. A maximum adsorption capacity, described by Langmuir isotherm model, was observed at 76.34 mg/g. With an As(III) initial concentration of 5 mg/L, when K-OMS2 and Fe-BTC were simultaneously introduced into the solution, the As(III) removal process was completed within 60 min. Thus, it shortened the process time compared to the case where K-OMS2 was added first, followed by the addition of Fe-BTC.

Toxic Compounds in Our Food: Arsenic Uptake By Rice and Potential Mitigation By Silicon

NASA Astrophysics Data System (ADS)

Seyfferth, A.; Gill, R.; Penido, E.

2014-12-01

Arsenic is a ubiquitous element in soils worldwide and has the potential to negatively impact human and ecosystem health under certain biogeochemical conditions. While arsenic is relatively immobile in most oxidized soils due to a high affinity for soil solids, arsenic becomes mobilized under reduced soil conditions due to the reductive dissolution of iron(III) oxides thereby releasing soil-bound arsenic. Since arsenic is a well-known carcinogen, this plant-soil process has the potential to negatively impact the lives of billions of rice consumers worldwide upon plant uptake and grain storage of released arsenic. Moreover, arsenic uptake by rice is excacerbated by the use of As-laden groundwater for rice irrigation. One proposed strategy to decrease arsenic uptake by rice plants is via an increase in dissolved silicon in paddy soil solution (pore-water), since silicic acid and arsenous acid share an uptake pathway. However, several soil processes that influence arsenic cycling may be affected by silicon including desorption from bulk soil, formation and mineralogy of iron(III) oxide plaque, and adsorption/desorption onto/from iron plaque; the effect of silicon on these soil processes will ultimately dictate the effectiveness of altered dissolved silicon in decreasing arsenic uptake at the root, which in turn dictates the concentration of arsenic found in grains. Furthermore, the source of silicon may impact carbon cycling and, in particular, methane emissions. Here, impacts of altered dissolved silicon on processes that affect rhizospheric biogeochemical cycling of arsenic and subsequent plant-uptake, and how it influences other biogeochemical cycles such as carbon and iron are investigated. We show that silicon can decrease arsenic uptake and grain storage under certain conditions, and that altered silicon affects the type of iron (III) oxide that comprises iron plaque.

Thermally-induced solid state transformation of β‐Fe{sub 2}O{sub 3} nanoparticles in various atmospheres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malina, Ondrej, E-mail: ondrej.malina@upol.cz; Kaslik, Josef, E-mail: ondrej.malina@upol.cz; Tucek, Jiri, E-mail: ondrej.malina@upol.cz

2014-10-27

To date, iron oxides have become one of the most studied nanomaterials due to their interesting and aaplication appealing physical, chemical, and biological properties in comparison with their bulk counterparts. In general, four forms of iron(III) oxide can be distinguished depending on their crystallographic and magnetic properties. In this work, one of the rare phases of iron(III) oxide, β‐Fe{sub 2}O{sub 3}, prepared by the solid state reaction was explored for the thermal transformations in various ambient atmospheres, including O{sub 2}, N{sub 2}, and CO{sub 2} atmospheres. The thermally treated products were investigated employing X-ray powder diffraction and {sup 57}Fe Mössbauermore » spectroscopy.« less

Formation of Environmentally Persistent Free Radical (EPFR) in Iron(III) Cation-Exchanged Smectite Clay

PubMed Central

Nwosu, Ugwumsinachi G.; Roy, Amitava; dela Cruz, Albert Leo N.; Dellinger, Barry; Cook, Robert

2016-01-01

Environmentally persistent free radicals (EPFRs) have been found at a number of Superfund sites, with EPFRs being formed via a proposed redox process at ambient environmental conditions. The possibility of such a redox process taking place at ambient environmental conditions is studied utilizing a surrogate soil system of phenol and iron(III)-exchanged calcium montmorillonite clay, Fe(III)CaM. Sorption of phenol by the Fe(III)CaM is demonstrated by Fourier-transformed infra-red (FT-IR) spectroscopy, as evidenced by the peaks between 1345 cm−1 and 1595 cm−1, and at lower frequencies between 694 cm−1 and 806 cm−1, as well as X-ray diffraction (XRD) spectroscopy, as shown by an increase in interlayer spacing within Fe(III)CaM. The formation and characterization of the EPFRs is determined by electron paramagnetic resonance (EPR) spectroscopy, showing phenoxyl-type radical with a g-factor of 2.0034 and ΔHp-p of 6.1 G at an average concentration of 7.5 × 1017 spins/g. EPFRs lifetime data are indicative of oxygen and water molecules being responsible for EPFR decay. The change in the oxidation state of the iron redox center is studied by X-ray absorption near-edge structure (XANES) spectroscopy, showing that 23% of the Fe(III) is reduced to Fe(II). X-ray photoemission spectroscopy (XPS) results confirm the XANES results. These findings, when combined with the EPFR concentration data, demonstrate that the stoichiometry of the EPFR formation under the conditions of this study is 1.5 × 10−2 spins/Fe(II) atom. PMID:26647158

Formation of environmentally persistent free radical (EPFR) in iron(III) cation-exchanged smectite clay.

PubMed

Nwosu, Ugwumsinachi G; Roy, Amitava; dela Cruz, Albert Leo N; Dellinger, Barry; Cook, Robert

2016-01-01

Environmentally persistent free radicals (EPFRs) have been found at a number of Superfund sites, with EPFRs being formed via a proposed redox process at ambient environmental conditions. The possibility of such a redox process taking place at ambient environmental conditions is studied utilizing a surrogate soil system of phenol and iron(III)-exchanged calcium montmorillonite clay, Fe(III)CaM. Sorption of phenol by the Fe(III)CaM is demonstrated by Fourier-transformed infra-red (FT-IR) spectroscopy, as evidenced by the peaks between 1345 cm(-1) and 1595 cm(-1), and at lower frequencies between 694 cm(-1) and 806 cm(-1), as well as X-ray diffraction (XRD) spectroscopy, as shown by an increase in interlayer spacing within Fe(III)CaM. The formation and characterization of the EPFRs is determined by electron paramagnetic resonance (EPR) spectroscopy, showing phenoxyl-type radical with a g-factor of 2.0034 and ΔHP-P of 6.1 G at an average concentration of 7.5 × 10(17) spins per g. EPFRs lifetime data are indicative of oxygen and water molecules being responsible for EPFR decay. The change in the oxidation state of the iron redox center is studied by X-ray absorption near-edge structure (XANES) spectroscopy, showing that 23% of the Fe(III) is reduced to Fe(II). X-ray photoemission spectroscopy (XPS) results confirm the XANES results. These findings, when combined with the EPFR concentration data, demonstrate that the stoichiometry of the EPFR formation under the conditions of this study is 1.5 × 10(-2) spins per Fe(II) atom.

Nitric oxide activation by distal redox modulation in tetranuclear iron nitrosyl complexes.

PubMed

de Ruiter, Graham; Thompson, Niklas B; Lionetti, Davide; Agapie, Theodor

2015-11-11

A series of tetranuclear iron complexes displaying a site-differentiated metal center was synthesized. Three of the metal centers are coordinated to our previously reported ligand, based on a 1,3,5-triarylbenzene motif with nitrogen and oxygen donors. The fourth (apical) iron center is coordinatively unsaturated and appended to the trinuclear core through three bridging pyrazolates and an interstitial μ4-oxide moiety. Electrochemical studies of complex [LFe3(PhPz)3OFe][OTf]2 revealed three reversible redox events assigned to the Fe(II)4/Fe(II)3Fe(III) (-1.733 V), Fe(II)3Fe(III)/Fe(II)2Fe(III)2 (-0.727 V), and Fe(II)2Fe(III)2/Fe(II)Fe(III)3 (0.018 V) redox couples. Combined Mössbauer and crystallographic studies indicate that the change in oxidation state is exclusively localized at the triiron core, without changing the oxidation state of the apical metal center. This phenomenon is assigned to differences in the coordination environment of the two metal sites and provides a strategy for storing electron and hole equivalents without affecting the oxidation state of the coordinatively unsaturated metal. The presence of a ligand-binding site allowed the effect of redox modulation on nitric oxide activation by an Fe(II) metal center to be studied. Treatment of the clusters with nitric oxide resulted in binding of NO to the apical iron center, generating a {FeNO}(7) moiety. As with the NO-free precursors, the three reversible redox events are localized at the iron centers distal from the NO ligand. Altering the redox state of the triiron core resulted in significant change in the NO stretching frequency, by as much as 100 cm(-1). The increased activation of NO is attributed to structural changes within the clusters, in particular, those related to the interaction of the metal centers with the interstitial atom. The differences in NO activation were further shown to lead to differential reactivity, with NO disproportionation and N2O formation performed by the more electron-rich cluster.

Nanophase iron phosphate, iron arsenate, iron vanadate, and iron molybdate minerals synthesized within the protein cage of ferritin.

PubMed

Polanams, Jup; Ray, Alisha D; Watt, Richard K

2005-05-02

Nanoparticles of iron phosphate, iron arsenate, iron molybdate, and iron vanadate were synthesized within the 8 nm interior of ferritin. The synthesis involved reacting Fe(II) with ferritin in a buffered solution at pH 7.4 in the presence of phosphate, arsenate, vanadate, or molybdate. O2 was used as the oxidant to deposit the Fe(III) mineral inside ferritin. The rate of iron incorporation into ferritin was stimulated when oxo-anions were present. The simultaneous deposition of both iron and the oxo-anion was confirmed by elemental analysis and energy-dispersive X-ray analysis. The ferritin samples containing iron and one of the oxo-anions possessed different UV/vis spectra depending on the anion used during mineral formation. TEM analysis showed mineral cores with approximately 8 nm mineral particles consistent with the formation of mineral phases inside ferritin.

A universal approach to the synthesis of nanodendrites of noble metals.

PubMed

Feng, Yan; Ma, Xiaohong; Han, Lin; Peng, Zhijian; Yang, Jun

2014-06-07

Nanomaterials usually exhibit structure-dependent catalytic activity, selectivity, and stability. Herein, we report a universal approach for the synthesis of noble metal nanoparticles with a dendritic structure, which is based on the reduction of metal acetylacetonate precursors in oleylamine at a temperature of 160 °C. In this strategy, the metal acetylacetonate precursors are reduced into metal atoms by oleylamine and grow into metal nanoparticles, while oleylamine is simultaneously converted into oleylamide to protect the nanoparticles. The competition between particle aggregation and oleylamide passivation is essential to the formation of a large number of particle aggregates, which eventually grow into nanodendrites via Ostwald ripening process. In particular, in comparison with commercial PtRu/C catalysts, the alloy PtRuOs nanodendrites exhibited superior catalytic activity toward methanol oxidation.

Iron(II,III)-polyphenol complex nanoparticles derived from green tea with remarkable ecotoxicological impact

EPA Science Inventory

There are several greener methods exist to synthesize zero–valent iron nanoparticles (nZVI) using different bio-based reducing agents. Although their useful properties in degradation of organic dyes, chlorinated organics, or arsenic have been described earlier, their characteriza...

REMOVAL OF HIGH-LEVEL ARSENIC BY ZERO-VALENT IRON

EPA Science Inventory

The objectives of this study were to conduct batch and column studies to (i) assess the effectiveness of zero-valent iron for arsenic remediation in groundwater, (ii) determine removal mechanisms of arsenic, and (iii) evaluate implications of these processes with regard to the st...

ZERO-VALENT IRON FOR HIGH-LEVEL ARSENITE REMOVAL

EPA Science Inventory

This study conducted by flow through column systems was aimed at investigating the feasibility of using zero-valent iron for arsenic remediation in groundwater. A high concentration arsenic solution (50 mg l-1) was prepared by using sodium arsenite (arsenic (III)) to simulate gr...

Iron (III) Matrix Effects on Mineralization and Immobilization of Actinides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cynthia-May S. Gong; Tyler A. Sullens; Kenneth R. Czerwinski

2006-01-01

Abstract - A number of models for the Yucca Mountain Project nuclear waste repository use studies of actinide sorption onto well-defined iron hydroxide materials. In the case of a waste containment leak, however, a complex interaction between dissolved waste forms and failed containment vessel components can lead to immediate precipitation of migratory iron and uranyl in the silicate rich near-field environment. Use of the Fe(III) and UO22+ complexing agent acetohydroxamic acid (AHA) as a colorimetric agent for visible spectrophotometry is well-known. Using the second derivative of these spectra a distinct shift in iron complexation in the presence of silicate ismore » seen that is not seen with uranyl or alone. Silica also decreases the ability of uranyl and ferric solutions to absorb hydroxide, hastening precipitation. These ferric silicate precipitates are highly amorphous and soluble. Precipitates formed in the presence of uranyl below ~1 mol% exhibit lower solubility than precipitates from up to 50 mol % and of uranyl silicates alone.« less

Uptake and release of metal ions by transferrin and interaction with receptor 1.

PubMed

El Hage Chahine, Jean-Michel; Hémadi, Miryana; Ha-Duong, Nguyêt-Thanh

2012-03-01

For a metal to follow the iron acquisition pathway, four conditions are required: 1-complex formation with transferrin; 2-interaction with receptor 1; 3-metal release in the endosome; and 4-metal transport to cytosol. This review deals with the mechanisms of aluminum(III), cobalt(III), uranium(VI), gallium(III) and bismuth(III) uptake by transferrin and interaction with receptor 1. The interaction of the metal-loaded transferrin with receptor 1 takes place in one or two steps: a very fast first step (μs to ms) between the C-lobe and the helical domain of the receptor, and a second slow step (2-6h) between the N-lobe and the protease-like domain. In transferrin loaded with metals other than iron, the dissociation constants for the interaction of the C-lobe with TFR are in a comparable range of magnitudes 10 to 0.5μM, whereas those of the interaction of the N-lobe are several orders of magnitudes lower or not detected. Endocytosis occurs in minutes, which implies a possible internalization of the metal-loaded transferrin with only the C-lobe interacting with the receptor. A competition with iron is possible and implies that metal internalization is more related to kinetics than thermodynamics. As for metal release in the endosome, it is faster than the recycling time of transferrin, which implies its possible liberation in the cell. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders. Copyright © 2011 Elsevier B.V. All rights reserved.

Formation, reactivity and aging of amorphous ferric oxides in the presence of model and membrane bioreactor derived organics.

PubMed

Bligh, Mark W; Maheshwari, Pradeep; David Waite, T

2017-11-01

Iron salts are routinely dosed in wastewater treatment as a means of achieving effluent phosphorous concentration goals. The iron oxides that result from addition of iron salts partake in various reactions, including reductive dissolution and phosphate adsorption. The reactivity of these oxides is controlled by the conditions of formation and the processes, such as aggregation, that lead to a reduction in accessible surface sites following formation. The presence of organic compounds is expected to significantly impact these processes in a number of ways. In this study, amorphous ferric oxide (AFO) reactivity and aging was investigated following the addition of ferric iron (Fe(III)) to three solution systems: two synthetic buffered systems, either containing no organic or containing alginate, and a supernatant system containing soluble microbial products (SMPs) sourced from a membrane bioreactor (MBR). Reactivity of the Fe(III) phases in these systems at various times (1-60 min) following Fe(III) addition was quantified by determining the rate constants for ascorbate-mediated reductive dissolution over short (5 min) and long (60 min) dissolution periods and for a range (0.5-10 mM) of ascorbate concentrations. AFO particle size was monitored using dynamic light scattering during the aging and dissolution periods. In the presence of alginate, AFO particles appeared to be stabilized against aggregation. However, aging in the alginate system was remarkably similar to the inorganic system where aging is associated with aggregation. An aging mechanism involving restructuring within the alginate-AFO assemblage was proposed. In the presence of SMPs, a greater diversity of Fe(III) phases was evident with both a small labile pool of organically complexed Fe(III) and a polydisperse population of stabilized AFO particles present. The prevalence of low molecular weight organic molecules facilitated stabilization of the Fe(III) oxyhydroxides formed but subsequent aging observed in the alginate system did not occur. The reactivity of the Fe(III) in the supernatant system was maintained with little loss in reactivity over at least 24 h. The capacity of SMPs to maintain high reactivity of AFO has important implications in a reactor where Fe(III) phases encounter alternating redox conditions due to sludge recirculation, creating a cycle of reductive dissolution, oxidation and precipitation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Preservation of organic matter in marine sediments by inner-sphere interactions with reactive iron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barber, Andrew; Brandes, Jay; Leri, Alessandra

Interactions between organic matter and mineral matrices are critical to the preservation of soil and sediment organic matter. In addition to clay minerals, Fe(III) oxides particles have recently been shown to be responsible for the protection and burial of a large fraction of sedimentary organic carbon (OC). Through a combination of synchrotron X-ray techniques and high-resolution images of intact sediment particles, we assessed the mechanism of interaction between OC and iron, as well as the composition of organic matter co-localized with ferric iron. We present scanning transmission x-ray microscopy images at the Fe L 3 and C K1 edges showingmore » that the organic matter co-localized with Fe(III) consists primarily of C=C, C=O and C-OH functional groups. Coupling the co-localization results to iron K-edge X-ray absorption spectroscopy fitting results allowed to quantify the relative contribution of OC-complexed Fe to the total sediment iron and reactive iron pools, showing that 25–62% of total reactive iron is directly associated to OC through inner-sphere complexation in coastal sediments, as much as four times more than in low OC deep sea sediments. Direct inner-sphere complexation between OC and iron oxides (Fe-O-C) is responsible for transferring a large quantity of reduced OC to the sedimentary sink, which could otherwise be oxidized back to CO 2.« less

The abiotic degradation of soil organic matter to oxalic acid

NASA Astrophysics Data System (ADS)

Studenroth, Sabine; Huber, Stefan; Schöler, H. F.

2010-05-01

The abiotic degradation of soil organic matter to volatile organic compounds was studied intensely over the last years (Keppler et al., 2000; Huber et al., 2009). It was shown that soil organic matter is oxidised due to the presence of iron (III), hydrogen peroxide and chloride and thereby produces diverse alkyl halides, which are emitted into the atmosphere. The formation of polar halogenated compounds like chlorinated acetic acids which are relevant toxic environmental substances was also found in soils and sediments (Kilian et al., 2002). The investigation of the formation of other polar halogenated and non-halogenated compounds like diverse mono- and dicarboxylic acids is going to attain more and more importance. Due to its high acidity oxalic acid might have impacts on the environment e.g., nutrient leaching, plant diseases and negative influence on microbial growth. In this study, the abiotic formation of oxalic acid in soil is examined. For a better understanding of natural degradation processes mechanistic studies were conducted using the model compound catechol as representative for structural elements of the humic substances and its reaction with iron (III) and hydrogen peroxide. Iron is one of the most abundant elements on earth and hydrogen peroxide is produced by bacteria or through incomplete reduction of oxygen. To find suitable parameters for an optimal reaction and a qualitative and quantitative analysis method the following reaction parameters are varied: concentration of iron (III) and hydrogen peroxide, time dependence, pH-value and influence of chloride. Analysis of oxalic acid was performed employing an ion chromatograph equipped with a conductivity detector. The time dependent reaction shows a relatively fast formation of oxalic acid, the optimum yield is achieved after 60 minutes. Compared to the concentration of catechol an excess of hydrogen peroxide as well as a low concentration of iron (III) are required. In absence of chloride the degradation of catechol to oxalic acid delivers a maximum yield of approximately 60 %, whereas the presence of chloride reduces the formation of oxalic acid to 30 %. Chloride possibly induces further competing reactions of catechol leading to a lower concentration of oxalic acid. Freeze-dried soil samples have been tested for production of oxalic acid, where the rate of organic matter seems to play an important role for the formation. By adding iron (III) and/or hydrogen peroxide oxalic acid yields increase, which demonstrates the reaction of soil organic matter with iron (III) and hydrogen peroxide as expected. Thus the natural abiotic formation of oxalic acid is confirmed. The results of the soil measurements are similar to those obtained with catechol. Therefore, the newly gained insights with model compounds appear to be applicable to soil conditions and these findings increase our understanding of the degradation pathways of soil organic matter. Furthermore an overview of the rates of oxalic acid formation of a variety of soil samples is shown and discussed in the light of different soil parameter.

Iron uptake and storage in the HAB dinoflagellate Lingulodinium polyedrum.

PubMed

Yarimizu, Kyoko; Cruz-López, Ricardo; Auerbach, Hendrik; Heimann, Larissa; Schünemann, Volker; Carrano, Carl J

2017-12-01

The iron uptake and storage systems of terrestrial/higher plants are now reasonably well understood with two basic strategies being distinguished: Strategy I involves the induction of an Fe(III)-chelate reductase (ferrireductase) along with Fe(II) or Fe(III) transporter proteins while strategy II plants have evolved sophisticated systems based on high-affinity, iron specific, binding compounds called phytosiderophores. In contrast, there is little knowledge about the corresponding systems in marine, plant-like lineages. Herein we report a study of the iron uptake and storage mechanisms in the harmful algal bloom dinoflagellate Lingulodinium polyedrum. L. polyedrum is an armored dinoflagellate with a mixotrophic lifestyle and one of the most common bloom species on Southern California coast widely noted for its bioluminescent properties and as a producer of yessotoxins. Short term radio-iron uptake studies indicate that iron is taken up by L. polyedrum in a time dependent manner consistent with an active transport process. Based on inhibitor and other studies it appears that a reductive-oxidative pathway such as that found in yeast and the green alga Chlamydomonas reinhardtii is likely. Of the various iron sources tested vibrioferrin, a photoactive and relatively weak siderophore produced by potentially mutualistic Marinobacter bacterial species, was the most efficient. Other more stable and non-photoactive siderophores such as ferrioxamine E were ineffective. Several pieces of data including long term exposure to 57 Fe using Mössbauer spectroscopy suggest that L. polyedrum does not possess an iron storage system but rather presumably relies on an efficient iron uptake system, perhaps mediated by mutualistic interactions with bacteria.

The effect of copper(II), iron(II) sulphate, and vitamin C combinations on the weak antimicrobial activity of (+)-catechin against Staphylococcus aureus and other microbes.

PubMed

Holloway, Andrew C; Mueller-Harvey, Irene; Gould, Simon W J; Fielder, Mark D; Naughton, Declan P; Kelly, Alison F

2012-12-01

Few attempts have been made to improve the activity of plant compounds with low antimicrobial efficacy. (+)-Catechin, a weak antimicrobial tea flavanol, was combined with putative adjuncts and tested against different species of bacteria. Copper(II) sulphate enhanced (+)-catechin activity against Pseudomonas aeruginosa but not Staphylococcus aureus, Proteus mirabilis or Escherichia coli. Attempts to raise the activity of (+)-catechin against two unresponsive species, S. aureus and E. coli, with iron(II) sulphate, iron(III) chloride, and vitamin C, showed that iron(II) enhanced (+)-catechin against S. aureus, but not E. coli; neither iron(III) nor combined iron(II) and copper(II), enhanced (+)-catechin activity against either species. Vitamin C enhanced copper(II) containing combinations against both species in the absence of iron(II). Catalase or EDTA added to active samples removed viability effects suggesting that active mixtures had produced H(2)O(2)via the action of added metal(II) ions. H(2)O(2) generation by (+)-catechin plus copper(II) mixtures and copper(II) alone could account for the principal effect of bacterial growth inhibition following 30 minute exposures as well as the antimicrobial effect of (+)-catechin-iron(II) against S. aureus. These novel findings about a weak antimicrobial flavanol contrast with previous knowledge of more active flavanols with transition metal combinations. Weak antimicrobial compounds like (+)-catechin within enhancement mixtures may therefore be used as efficacious agents. (+)-Catechin may provide a means of lowering copper(II) or iron(II) contents in certain crop protection and other products.

Polyaminoquinoline iron chelators for vectorization of antiproliferative agents: design, synthesis, and validation.

PubMed

Corcé, Vincent; Morin, Emmanuelle; Guihéneuf, Solène; Renault, Eric; Renaud, Stéphanie; Cannie, Isabelle; Tripier, Raphaël; Lima, Luís M P; Julienne, Karine; Gouin, Sébastien G; Loréal, Olivier; Deniaud, David; Gaboriau, François

2012-09-19

Iron chelation in tumoral cells has been reported as potentially useful during antitumoral treatment. Our aim was to develop new polyaminoquinoline iron chelators targeting tumoral cells. For this purpose, we designed, synthesized, and evaluated the biological activity of a new generation of iron chelators, which we named Quilamines, based on an 8-hydroxyquinoline (8-HQ) scaffold linked to linear polyamine vectors. These were designed to target tumor cells expressing an overactive polyamine transport system (PTS). A set of Quilamines bearing variable polyamine chains was designed and assessed for their ability to interact with iron. Quilamines were also screened for their cytostatic/cytotoxic effects and their selective uptake by the PTS in the CHO cell line. Our results show that both the 8-HQ moiety and the polyamine part participate in the iron coordination. HQ1-44, the most promising Quilamine identified, presents a homospermidine moiety and was shown to be highly taken up by the PTS and to display an efficient antiproliferative activity that occurred in the micromolar range. In addition, cytotoxicity was only observed at concentrations higher than 100 μM. We also demonstrated the high complexation capacity of HQ1-44 with iron while much weaker complexes were formed with other cations, indicative of a high selectivity. We applied the density functional theory to study the binding energy and the electronic structure of prototypical iron(III)-Quilamine complexes. On the basis of these calculations, Quilamine HQ1-44 is a strong tridentate ligand for iron(III) especially in the form of a 1:2 complex.

Removal of Trace Arsenic to Meet Drinking Water Standards Using Iron Oxide Coated Multiwall Carbon Nanotubes

PubMed Central

Ntim, Susana Addo; Mitra, Somenath

2011-01-01

This study presents the removal of trace level arsenic to meet drinking water standards using an iron oxide-multi-walled carbon nanotube (Fe-MWCNT) hybrid as a sorbent. The synthesis was facilitated by the high degree of nanotube functionalization using a microwave assisted process, and a controlled assembly of iron oxide was possible where the MWCNT served as an effective support for the oxide. In the final product, 11 % of the carbon atoms were attached to Fe. The Fe-MWCNT was effective in arsenic removal to below the drinking water standard levels of 10 µg L−1. The absorption capacity of the composite was 1723 µg g−1 and 189 µg g−1 for As(III) and As(V) respectively. The adsorption of As(V) on Fe-MWCNT was faster than that of As(III). The pseudo-second order rate equation was found to effectively describe the kinetics of arsenic adsorption. The adsorption isotherms for As(III) and As(V) fitted both the Langmuir and Freundlich models. PMID:21625394

Synthesis, structural characterisation and magnetic studies of polymetallic iron phosphonate cages.

PubMed

Khanra, Sumit; Helliwell, Madeleine; Tuna, Floriana; McInnes, Eric J L; Winpenny, Richard E P

2009-08-21

Four new polymetallic iron(III) phosphonate cages have been made and structurally characterised. These are an octanuclear cage [Fe(8)O(3)(OH)(2)(O(2)C(t)Bu)(11)(PhCH(2)PO(3))(3)(py)(3)], a decanuclear cage [Fe(10)O(2)(OH)(8)(O(2)C(t)Bu)(10)(PhCH(2)PO(3))(4)(pip)(2)], a heterometallic cage [Fe(6)Li(5)(mu(3)-O)(2)((t)BuPO(3))(6)(O(2)C(t)Bu)(8)(MeOH)(2)(Py)(4)] and a tridecanuclear cage [Et(3)NH](2)[Fe(13)(mu(3)-O)(3)(mu(2)-OH)(7)((t)BuPO(3))(7)(Me(3)CCO(2))(14)(H(2)O)] (pip = piperidine, py = pyridine). Magnetic studies of the first three compounds show anti-ferromagnetic exchange between the iron(III) centers leading to diamagnetic ground states for the homometallic cages. For the heterometallic cage, the six Fe(III) centers are arranged in two triangles, and each triangle has an S = 1/2 spin ground state.

Deferiprone, a non-toxic reagent for determination of iron in samples via sequential injection analysis

NASA Astrophysics Data System (ADS)

Pragourpun, Kraivinee; Sakee, Uthai; Fernandez, Carlos; Kruanetr, Senee

2015-05-01

We present for the first time the use of deferiprone as a non-toxic complexing agent for the determination of iron by sequential injection analysis in pharmaceuticals and food samples. The method was based on the reaction of Fe(III) and deferiprone in phosphate buffer at pH 7.5 to give a Fe(III)-deferiprone complex, which showed a maximum absorption at 460 nm. Under the optimum conditions, the linearity range for iron determination was found over the range of 0.05-3.0 μg mL-1 with a correlation coefficient (r2) of 0.9993. The limit of detection and limit of quantitation were 0.032 μg mL-1 and 0.055 μg mL-1, respectively. The relative standard deviation (%RSD) of the method was less than 5.0% (n = 11), and the percentage recovery was found in the range of 96.0-104.0%. The proposed method was satisfactorily applied for the determination of Fe(III) in pharmaceuticals, water and food samples with a sampling rate of 60 h-1.

Exome sequencing identifies NFS1 deficiency in a novel Fe-S cluster disease, infantile mitochondrial complex II/III deficiency.

PubMed

Farhan, Sali M K; Wang, Jian; Robinson, John F; Lahiry, Piya; Siu, Victoria M; Prasad, Chitra; Kronick, Jonathan B; Ramsay, David A; Rupar, C Anthony; Hegele, Robert A

2014-01-01

Iron-sulfur (Fe-S) clusters are a class of highly conserved and ubiquitous prosthetic groups with unique chemical properties that allow the proteins that contain them, Fe-S proteins, to assist in various key biochemical pathways. Mutations in Fe-S proteins often disrupt Fe-S cluster assembly leading to a spectrum of severe disorders such as Friedreich's ataxia or iron-sulfur cluster assembly enzyme (ISCU) myopathy. Herein, we describe infantile mitochondrial complex II/III deficiency, a novel autosomal recessive mitochondrial disease characterized by lactic acidemia, hypotonia, respiratory chain complex II and III deficiency, multisystem organ failure and abnormal mitochondria. Through autozygosity mapping, exome sequencing, in silico analyses, population studies and functional tests, we identified c.215G>A, p.Arg72Gln in NFS1 as the likely causative mutation. We describe the first disease in man likely caused by deficiency in NFS1, a cysteine desulfurase that is implicated in respiratory chain function and iron maintenance by initiating Fe-S cluster biosynthesis. Our results further demonstrate the importance of sufficient NFS1 expression in human physiology.

Iron and aluminum interaction with amyloid-beta peptides associated with Alzheimer’s disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drochioiu, Gabi; Ion, Laura; Murariu, Manuela

2014-10-06

An elevation in the concentration of heavy metal ions in Alzheimer’s disease (AD) brain has been demonstrated in many studies. Aβ precipitation and toxicity in AD brains seem to be caused by abnormal interactions with neocortical metal ions, especially iron, copper, zinc, and aluminum [1–3]. There is increasing evidence that iron and aluminum ions are involved in the mechanisms that underlie the neurodegenerative diseases [4,5]. However, evidence was brought to demonstrate that some Aβ fragments, at physiological pH, are not able to form binary complexes with Fe(III) ions of sufficient stability to compete with metal hydroxide precipitation [6]. On themore » contrary, multiple metal ions are known to interact with Aβ peptides [7]. Consequently, we investigated here the interaction of Fe(II/III) and Al(III) ions with some amyloid-β peptides and fragments that results in peptide aggregation and fibrillation [8,9]. Infrared spectroscopy, atomic force microscopy, scanning electron microscopy, electrophoresis and mass spectrometry demonstrated conformational changes of peptides in the presence of such metals.« less

Deferasirox for the treatment of chronic iron overload in transfusional hemosiderosis.

PubMed

Shashaty, George; Frankewich, Raymond; Chakraborti, Tamal; Choudary, Jasti; Al-Fayoumi, Suliman; Kacuba, Alice; Castillo, Sonia; Robie-Suh, Kathy; Rieves, Dwaine; Weiss, Karen; Pazdur, Richard

2006-12-01

This report describes the Food and Drug Administration's review of data and analyses leading to the approval of the oral iron chelator, deferasirox for the treatment of chronic iron overload due to transfusional hemosiderosis. The FDA reviewed findings of a controlled, open-label, randomized multicenter phase III study of deferasirox vs. deferoxamine in 586 patients with beta-thalessemia and transfusional hemosiderosis. The study results as well as the results of the FDA review of chemistry, preclinical pharmacology, and supportive studies are described. Following 48 weeks of treatment in the phase III study, patients' liver iron concentrations (a key endpoint variable) had decreased an average of 2.4 mg of iron (Fe)/g dry weight (dw) and 2.9 mg Fe/g dw in the deferasirox and deferoxamine groups, respectively, despite continued blood transfusions in both cohorts. Deferasirox was associated with serum creatinine increases in approximately a third of patients. Common adverse events included gastrointestinal symptoms and skin rash. Other data provided supportive evidence of deferasirox safety and efficacy. The FDA granted deferasirox accelerated approval on November 2, 2005, for use in treating chronic iron overload due to transfusional hemosiderosis in patients > or =2 years of age. The sponsor must obtain clinical data demonstrating the drug's long-term safety and effectiveness.

Incorporation of zero valent iron nanoparticles in the matrix of cationic resin beads for the remediation of Cr(VI) contaminated waters.

PubMed

Toli, Aikaterini; Chalastara, Konstantina; Mystrioti, Christiana; Xenidis, Anthimos; Papassiopi, Nymphodora

2016-07-01

The objective of present study was to obtain the fixation of nano zero valent iron (nZVI) particles on a permeable matrix and evaluate the performance of this composite material for the removal of Cr(VI) from contaminated waters. The experiments were carried out using the cationic resin Dowex 50WX2 as porous support of the iron nanoparticles. The work was carried out in two phases. The first phase involved the fixation of nZVI on the resin matrix. The resin granules were initially mixed with a FeCl3 solution to obtain the adsorption of Fe(III). Then the Fe(III) loaded resin (RFe) was treated with polyphenol solutions to obtain the reduction of Fe(III) to the elemental state. Two polyphenol solutions were tested as reductants, i.e. green tea extract and gallic acid. Green tea was found to be inefficient, probably due to the relatively big size of the contained polyphenol molecules, but gallic acid molecules were able to reach adsorbed Fe(III) and reduce the cations to the elemental state. The second phase was focused on the investigation of Cr(VI) reduction kinetics using the nanoiron loaded resins (R-nFe). It was found that the reduction follows a kinetic law of first order with respect to Cr(VI) and to the embedded nanoiron. Compared to other similar products, this composite material was found to have comparable performance regarding reaction rates and higher degree of iron utilization. Namely the rate constant for the reduction of Cr(VI), in the presence of 1 mM nZVI, was equivalent to 1.4 h of half-life time at pH 3.2 and increased to 24 h at pH 8.5. The degree of iron utilization was as high as 0.8 mol of reduced Cr(VI) per mole of iron. It was also found that this composite material can be easily regenerated and reused for Cr(VI) reduction without significant loss of efficiency. Copyright © 2016 Elsevier Ltd. All rights reserved.

Trapping a Highly Reactive Nonheme Iron Intermediate That Oxygenates Strong C-H Bonds with Stereoretention.

PubMed

Serrano-Plana, Joan; Oloo, Williamson N; Acosta-Rueda, Laura; Meier, Katlyn K; Verdejo, Begoña; García-España, Enrique; Basallote, Manuel G; Münck, Eckard; Que, Lawrence; Company, Anna; Costas, Miquel

2015-12-23

An unprecedentedly reactive iron species (2) has been generated by reaction of excess peracetic acid with a mononuclear iron complex [Fe(II)(CF3SO3)2(PyNMe3)] (1) at cryogenic temperatures, and characterized spectroscopically. Compound 2 is kinetically competent for breaking strong C-H bonds of alkanes (BDE ≈ 100 kcal·mol(-1)) through a hydrogen-atom transfer mechanism, and the transformations proceed with stereoretention and regioselectively, responding to bond strength, as well as to steric and polar effects. Bimolecular reaction rates are at least an order of magnitude faster than those of the most reactive synthetic high-valent nonheme oxoiron species described to date. EPR studies in tandem with kinetic analysis show that the 490 nm chromophore of 2 is associated with two S = 1/2 species in rapid equilibrium. The minor component 2a (∼5% iron) has g-values at 2.20, 2.19, and 1.99 characteristic of a low-spin iron(III) center, and it is assigned as [Fe(III)(OOAc)(PyNMe3)](2+), also by comparison with the EPR parameters of the structurally characterized hydroxamate analogue [Fe(III)(tBuCON(H)O)(PyNMe3)](2+) (4). The major component 2b (∼40% iron, g-values = 2.07, 2.01, 1.95) has unusual EPR parameters, and it is proposed to be [Fe(V)(O)(OAc)(PyNMe3)](2+), where the O-O bond in 2a has been broken. Consistent with this assignment, 2b undergoes exchange of its acetate ligand with CD3CO2D and very rapidly reacts with olefins to produce the corresponding cis-1,2-hydroxoacetate product. Therefore, this work constitutes the first example where a synthetic nonheme iron species responsible for stereospecific and site selective C-H hydroxylation is spectroscopically trapped, and its catalytic reactivity against C-H bonds can be directly interrogated by kinetic methods. The accumulated evidence indicates that 2 consists mainly of an extraordinarily reactive [Fe(V)(O)(OAc)(PyNMe3)](2+) (2b) species capable of hydroxylating unactivated alkyl C-H bonds with stereoretention in a rapid and site-selective manner, and that exists in fast equilibrium with its [Fe(III)(OOAc)(PyNMe3)](2+) precursor.

Geochemical patterns and microbial contribution to iron plaque formation in the rice plant rhizosphere

NASA Astrophysics Data System (ADS)

Maisch, Markus; Murata, Chihiro; Unger, Julia; Kappler, Andreas; Schmidt, Caroline

2015-04-01

Rice is the major food source for more than half of the world population and 80 percent of the worldwide rice cultivation is performed on water logged paddy soils. The establishment of reducing conditions in the soil and across the soil-water interface not only stimulates the microbial production and release of the greenhouse gas methane. These settings also create optimal conditions for microbial iron(III) reduction and therefore saturate the system with reduced ferrous iron. Through the reduction and dissolution of ferric minerals that are characterized by their high surface activity, sorbed nutrients and contaminants (e.g. arsenic) will be mobilized and are thus available for uptake by plants. Rice plants have evolved a strategy to release oxygen from their roots in order to prevent iron toxification in highly ferrous environments. The release of oxygen to the reduced paddy soil causes ferric iron plaque formation on the rice roots and finally increases the sorption capacity for toxic metals. To this date the geochemical and microbiological processes that control the formation of iron plaque are not deciphered. It has been hypothesized that iron(II)-oxidizing bacteria play a potential role in the iron(III) mineral formation along the roots. However, not much is known about the actual processes, mineral products, and geochemical gradients that establish within the rhizosphere. In the present study we have developed a growth set-up that allows the co-cultivation of rice plants and iron(II)-oxidizing bacteria, as well as the visual observation and in situ measurement of geochemical parameters. Oxygen and dissolved iron(II) gradients have been measured using microelectrodes and show geochemical hot spots that offer optimal growth conditions for microaerophilic iron(II) oxidizers. First mineral identification attempts of iron plaque have been performed using Mössbauer spectroscopy and microscopy. The obtained results on mineraology and crystallinity have been compared to mineralogical data from purely biotic (microaerophilic) and abiotic iron mineral formation processes.

Electronic structure and reactivity of three-coordinate iron complexes.

PubMed

Holland, Patrick L

2008-08-01

[Reaction: see text]. The identity and oxidation state of the metal in a coordination compound are typically thought to be the most important determinants of its reactivity. However, the coordination number (the number of bonds to the metal) can be equally influential. This Account describes iron complexes with a coordination number of only three, which differ greatly from iron complexes with octahedral (six-coordinate) geometries with respect to their magnetism, electronic structure, preference for ligands, and reactivity. Three-coordinate complexes with a trigonal-planar geometry are accessible using bulky, anionic, bidentate ligands (beta-diketiminates) that steer a monodentate ligand into the plane of their two nitrogen donors. This strategy has led to a variety of three-coordinate iron complexes in which iron is in the +1, +2, and +3 oxidation states. Systematic studies on the electronic structures of these complexes have been useful in interpreting their properties. The iron ions are generally high spin, with singly occupied orbitals available for pi interactions with ligands. Trends in sigma-bonding show that iron(II) complexes favor electronegative ligands (O, N donors) over electropositive ligands (hydride). The combination of electrostatic sigma-bonding and the availability of pi-interactions stabilizes iron(II) fluoride and oxo complexes. The same factors destabilize iron(II) hydride complexes, which are reactive enough to add the hydrogen atom to unsaturated organic molecules and to take part in radical reactions. Iron(I) complexes use strong pi-backbonding to transfer charge from iron into coordinated alkynes and N 2, whereas iron(III) accepts charge from a pi-donating imido ligand. Though the imidoiron(III) complex is stabilized by pi-bonding in the trigonal-planar geometry, addition of pyridine as a fourth donor weakens the pi-bonding, which enables abstraction of H atoms from hydrocarbons. The unusual bonding and reactivity patterns of three-coordinate iron compounds may lead to new catalysts for oxidation and reduction reactions and may be used by nature in transient intermediates of nitrogenase enzymes.

Old iron, young copper: from Mars to Venus.

PubMed

Crichton, R R; Pierre, J L

2001-06-01

Iron and copper are metals which play an important role in the living world. From a brief consideration of their chemistry and biochemistry we conclude that the early chemistry of life used water soluble ferrous iron while copper was in the water-insoluble Cu(I) state as highly insoluble sulphides. The advent of oxygen was a catastrophic event for most living organisms, and can be considered to be the first general irreversible pollution of the earth. In contrast to the oxidation of iron and its loss of bioavailability as insoluble Fe(III), the oxidation of insoluble Cu(I) led to soluble Cu(II). A new iron biochemistry became possible after the advent of oxygen, with the development of chelators of Fe(III), which rendered iron once again accessible, and with the control of the potential toxicity of iron by its storage in a water soluble, non-toxic, bio-available storage protein (ferritin). Biology also discovered that whereas enzymes involved in anaerobic metabolism were designed to operate in the lower portion of the redox spectrum, the arrival of dioxygen created the need for a new redox active metal which could attain higher redox potentials. Copper, now bioavailable, was ideally suited to exploit the oxidizing power of dioxygen. The arrival of copper also coincided with the development of multicellular organisms which had extracellular cross-linked matrices capable of resisting attack by oxygen free radicals. After the initial 'iron age' subsequent evolution moved, not towards a 'copper age', but rather to an 'iron-copper' age. In the second part of the review, this symbiosis of iron and copper is examined in yeast. We then briefly consider iron and copper metabolism in mammals, before looking at iron-copper interactions in mammals, particularly man, and conclude with the reflection that, as in Greek and Roman mythology, a better understanding of the potentially positive interactions between Mars (iron) and Venus (copper) can only be to the advantage of our species.

Theoretical study of novel complexed structures for methoxy derivatives of scytonemin: potential biomarkers in iron-rich stressed environments.

PubMed

Varnali, Tereza; Edwards, Howell G M

2013-09-01

Scytonemin is a cyanobacterial sheath pigment with potent UV (UVA, UVB, and UVC) absorbing properties. Di- and tetramethoxy derivatives of scytonemin have also been found and described in the literature. The importance of these biomolecules is their photoprotective function, which is one of the major survival strategies adopted by extremophiles in environmentally stressed conditions. Also, iron compounds [particularly iron(III) oxides] offer an additional UV-protecting facility to subsurface endolithic biological colonization; hence, banded iron formations (accompanied by zones of depletion of iron) in rock matrices have attracted attention with special interest in the method of transportation of iron compounds through the rock. Di- and tetramethoxyscytonemin and their iron(III) complexes have been modeled and studied computationally by using density functional theory calculations at the level of B3LYP/6-31G** methodology. We propose new structures that could feature in survival strategy and facilitate the movement of iron through the rock especially for iron-rich stressed terrestrial environments exemplified by the Río Tinto system with the added potential of subsurface Mars exploration. This study represents a continuation of our previous work on scytonemin. The calculated Raman spectra of the proposed iron complexes are compared with those of their parent compounds and discussed in relation to structural changes effected in the parent ligand upon complexation. This information leads to new insights to be gained by experimental Raman spectroscopists and the characterization of spectroscopic biosignatures for the database being compiled for the remote Raman analytical interrogation of the martian surface and subsurface being proposed for the ESA ExoMars mission planned for launch in 2018.

HIGH-LEVEL ARSENITE REMOVAL FROM GROUNDWATER BY ZERO-VALENT IRON

EPA Science Inventory

The objectives of this study were to conduct batch and column studies to (i) assess the effectiveness of zero-valent iron for arsenic remediation in groundwater, (ii) determine removal mechanisms of arsenic, and (iii) evaluate implications of these processes with regard to the st...

The pH Requirement for in Vivo Activity of the Iron-Deficiency-Induced "Turbo" Ferric Chelate Reductase (A Comparison of the Iron-Deficiency-Induced Iron Reductase Activities of Intact Plants and Isolated Plasma Membrane Fractions in Sugar Beet).

PubMed Central

Susin, S.; Abadia, A.; Gonzalez-Reyes, J. A.; Lucena, J. J.; Abadia, J.

1996-01-01

The characteristics of the Fe reduction mechanisms induced by Fe deficiency have been studied in intact plants of Beta vulgaris and in purified plasma membrane vesicles from the same plants. In Fe-deficient plants the in vivo Fe(III)-ethylenediaminetetraacetic complex [Fe(III)-EDTA] reductase activity increased over the control values 10 to 20 times when assayed at a pH of 6.0 or below ("turbo" reductase) but increased only 2 to 4 times when assayed at a pH of 6.5 or above. The Fe(III)-EDTA reductase activity of root plasma membrane preparations increased 2 and 3.5 times over the controls, irrespective of the assay pH. The Km for Fe(III)-EDTA of the in vivo ferric chelate reductase in Fe-deficient plants was approximately 510 and 240 [mu]M in the pH ranges 4.5 to 6.0 and 6.5 to 8.0, respectively. The Km for Fe(III)-EDTA of the ferric chelate reductase in intact control plants and in plasma membrane preparations isolated from Fe-deficient and control plants was approximately 200 to 240 [mu]M. Therefore, the turbo ferric chelate reductase activity of Fe-deficient plants at low pH appears to be different from the constitutive ferric chelate reductase. PMID:12226175

The pH Requirement for in Vivo Activity of the Iron-Deficiency-Induced "Turbo" Ferric Chelate Reductase (A Comparison of the Iron-Deficiency-Induced Iron Reductase Activities of Intact Plants and Isolated Plasma Membrane Fractions in Sugar Beet).

PubMed

Susin, S.; Abadia, A.; Gonzalez-Reyes, J. A.; Lucena, J. J.; Abadia, J.

1996-01-01

The characteristics of the Fe reduction mechanisms induced by Fe deficiency have been studied in intact plants of Beta vulgaris and in purified plasma membrane vesicles from the same plants. In Fe-deficient plants the in vivo Fe(III)-ethylenediaminetetraacetic complex [Fe(III)-EDTA] reductase activity increased over the control values 10 to 20 times when assayed at a pH of 6.0 or below ("turbo" reductase) but increased only 2 to 4 times when assayed at a pH of 6.5 or above. The Fe(III)-EDTA reductase activity of root plasma membrane preparations increased 2 and 3.5 times over the controls, irrespective of the assay pH. The Km for Fe(III)-EDTA of the in vivo ferric chelate reductase in Fe-deficient plants was approximately 510 and 240 [mu]M in the pH ranges 4.5 to 6.0 and 6.5 to 8.0, respectively. The Km for Fe(III)-EDTA of the ferric chelate reductase in intact control plants and in plasma membrane preparations isolated from Fe-deficient and control plants was approximately 200 to 240 [mu]M. Therefore, the turbo ferric chelate reductase activity of Fe-deficient plants at low pH appears to be different from the constitutive ferric chelate reductase.

Orenia metallireducens sp. nov. strain Z6, a Novel Metal-reducing [member of the Phylum] Firmicute from the Deep Subsurface

DOE PAGES

Dong, Yiran; Sanford, Robert A.; Boyanov, Maxim I.; ...

2016-08-26

A novel halophilic and metal-reducing bacterium, Orenia metallireducens strain Z6, was isolated from briny groundwater extracted from a 2.02 km-deep borehole in the Illinois Basin, IL. This organism shared 96% 16S rRNA gene similarity with Orenia marismortui but demonstrated physiological properties previously unknown for this genus. In addition to exhibiting a fermentative metabolism typical of the genus Orenia, strain Z6 reduces various metal oxides [Fe(III), Mn(IV), Co(III), and Cr(VI)], using H 2 as the electron donor. Strain Z6 actively reduced ferrihydrite over broad ranges of pH (6 to 9.6), salinity (0.4 to 3.5 M NaCl), and temperature (20 to 60°C).more » At pH 6.5, strain Z6 also reduced more crystalline iron oxides, such as lepidocrocite (γ-FeOOH), goethite (α-FeOOH), and hematite (α-Fe 2O 3). Analysis of X-ray absorption fine structure (XAFS) following Fe(III) reduction by strain Z6 revealed spectra from ferrous secondary mineral phases consistent with the precipitation of vivianite [Fe 3(PO 4) 2] and siderite (FeCO 3). The draft genome assembled for strain Z6 is 3.47 Mb in size and contains 3,269 protein-coding genes. Unlike the well-understood iron-reducing Shewanella and Geobacter species, this organism lacks the c-type cytochromes for typical Fe(III) reduction. Strain Z6 represents the first bacterial species in the genus Orenia (order Halanaerobiales) reported to reduce ferric iron minerals and other metal oxides. This microbe expands both the phylogenetic and physiological scopes of iron-reducing microorganisms known to inhabit the deep subsurface and suggests new mechanisms for microbial iron reduction. In conclusion, these distinctions from other Orenia spp. support the designation of strain Z6 as a new species, Orenia metallireducens sp. nov.« less

New oxyfluorotellurates(IV): MTeO3F (M = FeIII, GaIII and CrIII).

PubMed

Laval, Jean Paul; Jennene Boukharrata, Nefla; Thomas, Philippe

2008-02-01

The crystal structures of the new isomorphous compounds iron(III) oxyfluorotellurate(IV), FeTeO(3)F, gallium(III) oxyfluorotellurate(IV), GaTeO(3)F, and chromium(III) oxyfluorotellurate(IV), CrTeO(3)F, consist of zigzag chains of MO(4)F(2) distorted octahedra alternately sharing O-O and F-F edges and connected via TeO(3) trigonal pyramids. A full O/F anionic ordering is observed and the electronic lone pair of the Te(IV) cation is stereochemically active.

Thermodynamic model for solution behavior and solid-liquid equilibrium in Na-Al(III)-Fe(III)-Cr(III)-Cl-H2O system at 25°C

NASA Astrophysics Data System (ADS)

André, Laurent; Christov, Christomir; Lassin, Arnault; Azaroual, Mohamed

2018-03-01

The knowledge of the thermodynamic behavior of multicomponent aqueous electrolyte systems is of main interest in geo-, and environmental-sciences. The main objective of this study is the development of a high accuracy thermodynamic model for solution behavior, and highly soluble M(III)Cl3(s) (M= Al, Fe, Cr) minerals solubility in Na-Al(III)-Cr(III)-Fe(III)-Cl-H2O system at 25°C. Comprehensive thermodynamic models that accurately predict aluminium, chromium and iron aqueous chemistry and M(III) mineral solubilities as a function of pH, solution composition and concentration are critical for understanding many important geochemical and environmental processes involving these metals (e.g., mineral dissolution/alteration, rock formation, changes in rock permeability and fluid flow, soil formation, mass transport, toxic M(III) remediation). Such a model would also have many industrial applications (e.g., aluminium, chromium and iron production, and their corrosion, solve scaling problems in geothermal energy and oil production). Comparisons of solubility and activity calculations with the experimental data in binary and ternary systems indicate that model predictions are within the uncertainty of the data. Limitations of the model due to data insufficiencies are discussed. The solubility modeling approach, implemented to the Pitzer specific interaction equations is employed. The resulting parameterization was developed for the geochemical Pitzer formalism based PHREEQC database.

Analysis of the structure of poly-3-hydroxybutyrate ultrathin fibers modified with iron (III) complex with tetraphenylporphyrin

NASA Astrophysics Data System (ADS)

Olkhov, A. A.; Karpova, S. G.; Lobanov, A. V.; Tyubaeva, P. M.; Artemov, N. S.; Iordansky, A. L.

2017-12-01

In the treatment of many infectious diseases and cancer, transdermal systems based on solid polymer matrices or gels containing functional substances with antiseptic (antibacterial) properties are often used. One of the most promising types of matrices with antiseptic properties are the ones of nano- and microfiber-bonded cloth obtained by electrospinning based on biopolymer poly(3-hydroxybutyrate). The present work investigates the effects of iron (III) complex with tetraphenylporphyrin and the influence on the geometry, crystalline order and molecular dynamics in the intercrystalline (amorphous phase) of ultrathin PHB fibers.

Aluminium substitution in iron(II-III)-layered double hydroxides: Formation and cationic order

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruby, Christian; Abdelmoula, Mustapha; Aissa, Rabha

The formation and the modifications of the structural properties of an aluminium-substituted iron(II-III)-layered double hydroxide (LDH) of formula Fe{sub 4}{sup II}Fe{sub (2-6y)}{sup III}Al{sub 6y}{sup III} (OH){sub 12} SO{sub 4}, 8H{sub 2}O are followed by pH titration curves, Moessbauer spectroscopy and high-resolution X-ray powder diffraction using synchrotron radiation. Rietveld refinements allow to build a structural model for hydroxysulphate green rust, GR(SO{sub 4}{sup 2-}), i.e. y=0, in which a bilayer of sulphate anions points to the Fe{sup 3+} species. A cationic order is proposed to occur in both GR(SO{sub 4}{sup 2-}) and aluminium-substituted hydroxysulphate green rust when y<0.08. Variation of the cellmore » parameters and a sharp decrease in average crystal size and anisotropy are detected for an aluminium content as low as y=0.01. The formation of Al-GR(SO{sub 4}{sup 2-}) is preceded by the successive precipitation of Fe{sup III} and Al{sup III} (oxy)hydroxides. Adsorption of more soluble Al{sup III} species onto the initially formed ferric oxyhydroxide may be responsible for this slowdown of crystal growth. Therefore, the insertion of low aluminium amount (y{approx}0.01) could be an interesting way for increasing the surface reactivity of iron(II-III) LDH that maintains constant the quantity of the reactive Fe{sup II} species of the material. - Graphical abstract: (a) Crystallographical structure of sulphated green rust: SO{sub 4}{sup 2-} point to the Fe{sup 3+} cations (red) that form an ordered array with the Fe{sup 2+} cations (green). (b) Width and asymmetry of the synchrotron XRD peaks increase rapidly when some Al{sup 3+} species substitute the Fe{sup 3+} cations; z is molar ratio Al{sup 3+}/Fe{sup 3+}.« less

Nitrous-acid-mediated synthesis of iron-nitrosyl-porphyrin: pH-dependent release of nitric oxide.

PubMed

Bhuyan, Jagannath; Sarkar, Sabyasachi

2012-11-01

Two iron-nitrosyl-porphyrins, nitrosyl[meso-tetrakis(3,4,5-trimethoxyphenylporphyrin]iron(II) acetic acid solvate (3) and nitrosyl[meso-tetrakis(4-methoxyphenylporphyrin]iron(II) CH(2)Cl(2) solvate (4), were synthesized in quantitative yield by using a modified procedure with nitrous acid, followed by oxygen-atom abstraction by triphenylphosphine under an argon atmosphere. These nitrosyl porphyrins are in the {FeNO}(7) class. Under an argon atmosphere, these compounds are relatively stable over a broad range of pH values (4-8) but, under aerobic conditions, they release nitric oxide faster at high pH values than that at low pH values. The generated nitric-oxide-free iron(III)-porphyrin can be re-nitrosylated by using nitrous acid and triphenylphosphine. The rapid release of NO from these Fe(II) complexes at high pH values seems to be similar to that in nitrophorin, a nitric-oxide-transport protein, which formally possesses Fe(III). However, because the release of NO occurs from ferrous-nitrosyl-porphyrin under aerobic conditions, these compounds are more closely related to nitrobindin, a recently discovered heme protein. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Respiration-linked proton translocation coupled to anaerobic reduction of manganese(IV) and iron(III) in Shewanella putrefaciens MR-1.

PubMed Central

Myers, C R; Nealson, K H

1990-01-01

An oxidant pulse technique, with lactate as the electron donor, was used to study respiration-linked proton translocation in the manganese- and iron-reducing bacterium Shewanella putrefaciens MR-1. Cells grown anaerobically with fumarate or nitrate as the electron acceptor translocated protons in response to manganese (IV), fumarate, or oxygen. Cells grown anaerobically with fumarate also translocated protons in response to iron(III) and thiosulfate, whereas those grown with nitrate did not. Aerobically grown cells translocated protons only in response to oxygen. Proton translocation with all electron acceptors was abolished in the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone (20 microM) and was partially to completely inhibited by the electron transport inhibitor 2-n-heptyl-4-hydroxyquinoline N-oxide (50 microM). PMID:2172208

New iridium dopants forg white phosphorescent devices: enhancement of efficiency and color stability by an energy-harvesting layer.

PubMed

Chou, Ho-Hsiu; Li, Yi-Kai; Chen, Yu-Han; Chang, Ching-Chih; Liao, Chuang-Yi; Cheng, Chien-Hong

2013-07-10

A new light blue complex (fmoppy)2Ir(tfpypz) [bis(4'-fluoro-6'-methoxylphenyl pyridinato)-iridium(III)-3-(trifluoromethyl)-5-(pyridin-2-yl)-1,2,4-triazolate] and a new orange complex (dpiq)2Ir(acac) [bis(3,4-diphenylisoquinoline)-iridium(III)-acetylacetonate] were synthesized. These two complexes were used as the dopants for the fabrication of two-element white phosphorescent devices. Via the introduction of a thin energy-harvesting layer (EHL) to harvest the extra energy and exciton from the emission zone, highly efficient two-element white devices with excellent color stability were created. One of the best devices shows yellow-white color emission with an extremely high external quantum efficiency (EQE) of 21.5% and a current efficiency of 68.8 cd/A. The other device gave a pure white emission with an external quantum efficiency of 19.2% and a current efficiency of 53.2 cd/A. At a high brightness of 1000 cd/m(2), the EQE still remains as high as 18.9 and 17.2%. With a brightness of 1000-10000 cd/m(2), the CIE coordinates of these two devices shift by only (0.02, ≤0.01). The white phosphorescent devices with the EHL showed much higher efficiency and better color stability than the one without the EHL.

Characterization of multi-dye pressure-sensitive microbeads

NASA Astrophysics Data System (ADS)

Lacroix, Daniel; Viraye-Chevalier, Teddy; Seiter, Guillaume; Howard, Jonathan; Dabiri, Dana; Khalil, Gamal E.; Xia, Younan; Zhu, Cun

2013-11-01

The response times of pressure-sensitive particles to passing shockwaves were measured to investigate their ability to accurately determine pressure changes in unsteady flows. The particles tested were loaded with novel pressure-sensitive dyes such as Pt (II) meso-tetra(pentafluorophenyl)porphine, Pt(II) octaethylporphine, bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl))iridium III, and iridium(III) bis(4-phenylthieno[3,2-c] pyridinato-N,C2')acetylacetonate. For this work, porous silicon dioxide pressure-sensitive beads (PSBeads) were used. Two synthetic procedures were used to fabricate the particles. In the first, a one-step method loaded dyes during the synthesis of microbeads, in the second a two-step method synthesized the microbeads first, then loaded the dyes. The shock tube facility was used to measure the response times of microbeads to fast pressure jumps. The study involved testing multiple luminophors loaded in microbeads with various size distributions. Response times for the silica-based microbeads ranged between 26 μs and 462 μs (at 90% of the amplitude response), which are much faster than previously reported polystyrene-based microbead response times, which range from 507 μs to 1582 μs (at 90% of the amplitude response) [F. Kimura, M. Rodriguez, J. McCann, B. Carlson, D. Dabiri, G. Khalil, J. B. Callis, Y. Xia, and M. Gouterman, "Development and characterization of fast responding pressure sensitive microspheres," Rev. Sci. Instrum. 79, 074102 (2008)].

SUNLIGHT AND IRON(III)-INDUCED PHOTOCHEMICAL PRODUCTION OF DISSOLVED GASEOUS MERCURY IN FRESHWATER. (R827632)

EPA Science Inventory

Mechanistic understanding of sunlight-induced natural processes for
production of dissolved gaseous mercury (DGM) in freshwaters has remained
limited, and few direct field tests of the mechanistic hypotheses are available.
We exposed ferric iron salt-spiked fresh s...

POLLUTION EFFECTS OF ABNORMAL OPERATIONS IN IRON AND STEEL MAKING. VOLUME III. BLAST FURNACE IRONMAKING, MANUAL OF PRACTICE

EPA Science Inventory

The report is one in a six-volume series considering abnormal operating conditions (AOCs) in the primary section (sintering, blast furnace ironmaking, open hearth, electric furnace, and basic oxygen steelmaking) of an integrated iron and steel plant. Pollution standards, generall...

Mössbauer investigations to characterize Fe lattice sites in sheet silicates and Peru Basin deep-sea sediments

NASA Astrophysics Data System (ADS)

Lougear, André; König, Iris; Trautwein, Alfred X.; Suess, Erwin

A procedure to classify different Fe lattice sites, i.e., OH-group geometries, in the clay mineral content of deep-sea sediments was developed using Mössbauer spectroscopy at low temperature (77 K). This speciation is of interest with regard to the redox behavior, reactivity and color of marine sediments, since substantial iron redox transitions (associated with sediment color change) have been documented for the structural sheet silicate iron. Lattice site classification was achieved for the Fe(II) fraction, all of which is structural clay Fe(II) in the sediments under investigation. Whereas the major part of the Fe(III) is structural clay iron as well, there is a small Fe(III) fraction in oxide minerals. Therefore, further elaboration of the procedure would be required to also achieve lattice site classification for the Fe(III) fraction. Analysis of the Mössbauer spectra is based on computer fits, the input parameters of which were derived from a separate study of Fe(II)-rich pure chlorites. The procedure of classification is qualified to investigate, e.g., in laboratory experiments, the site-specific reaction rates and the effects on sediment color of iron redox transitions in the sheet silicate content of sediments. The new skills were successfully applied in environmental impact studies on the mining of polymetallic nodules from the Peru Basin deep-sea floor.

Transient state kinetic investigation of ferritin iron release

NASA Astrophysics Data System (ADS)

Ciasca, G.; Papi, M.; Chiarpotto, M.; Rodio, M.; Campi, G.; Rossi, C.; De Sole, P.; Bianconi, A.

2012-02-01

Increased iron concentration in tissues appears to be a factor in the genesis and development of inflammatory and degenerative diseases. By means of real-time small angle x-ray scattering measurements, we studied the kinetics of iron release from the ferritin inorganic core as a function of time and distance from the iron core centre. Accordingly, the iron release process follows a three step model: (i) a defect nucleation in the outer part of the mineral core, (ii) the diffusion of the reducing agent towards the inner part of the core, and (iii) the erosion of the core from the inner to the outer part.

A rectangular Ni-Fe cluster with unusual cyanide bridges.

PubMed

Krüger, Christoph; Sato, Hiroki; Matsumoto, Takuto; Shiga, Takuya; Newton, Graham N; Renz, Franz; Oshio, Hiroki

2012-10-07

An asymmetric polycyanide iron complex, K(2)[Fe(III)(L1)(CN)(4)](MeOH) (HL1 = 2,2'-(1H-pyrazole-3,5-diyl)bis-pyridine), was synthesized and its complexation compatibility with nickel ions was examined. Two kinds of enantiomeric nickel-iron squares were obtained in the presence of a chiral bidentate capping ligand. The compounds display unusual cyanide bridge geometry and have ferromagnetic interactions between nickel and iron ions.

STABILITY: AN INVESTIGATION OF AS(III)/AS(V) STABILITY IN IRON RICH DRINKING WATER MATRICES

EPA Science Inventory

Arsenic in drinking water is predominantly inorganic arsenic. The two oxidation states of inorganic arsenic are As(III)(pKa=9.3) and As(V)(pKa2=6.9). The distribution of As(III) and AS(V) in a water is dependent on the redox potential of the water. The actual distribution can ...

Enzymatic iron and uranium reduction by sulfate-reducing bacteria

USGS Publications Warehouse

Lovley, D.R.; Roden, E.E.; Phillips, E.J.P.; Woodward, J.C.

1993-01-01

The potential for sulfate-reducing bacteria (SRB) to enzymatically reduce Fe(III) and U(VI) was investigated. Five species of Desulfovibrio as well as Desulfobacterium autotrophicum and Desulfobulbus propionicus reduced Fe(III) chelated with nitrilotriacetic acid as well as insoluble Fe(III) oxide. Fe(III) oxide reduction resulted in the accumulation of magnetite and siderite. Desulfobacter postgatei reduced the chelated Fe(III) but not Fe(III) oxide. Desulfobacter curvatus, Desulfomonile tiedjei, and Desulfotomaculum acetoxidans did not reduce Fe(III). Only Desulfovibrio species reduced U(VI). U(VI) reduction resulted in the precipitation of uraninite. None of the SRB that reduced Fe(III) or U(VI) appeared to conserve enough energy to support growth from this reaction. However, Desulfovibrio desulfuricans metabolized H2 down to lower concentrations with Fe(III) or U(VI) as the electron acceptor than with sulfate, suggesting that these metals may be preferred electron acceptors at the low H2 concentrations present in most marine sediments. Molybdate did not inhibit Fe(III) reduction by D. desulfuricans. This indicates that the inability of molybdate to inhibit Fe(III) reduction in marine sediments does not rule out the possibility that SRB are important catalysts for Fe(III) reduction. The results demonstrate that although SRB were previously considered to reduce Fe(III) and U(VI) indirectly through the production of sulfide, they may also directly reduce Fe(III) and U(VI) through enzymatic mechanisms. These findings, as well as our recent discovery that the So-reducing microorganism Desulfuromonas acetoxidans can reduce Fe(III), demonstrate that there are close links between the microbial sulfur, iron, and uranium cycles in anaerobic marine sediments. ?? 1993.

Characterization of a Novel Iron Acquisition Activity That Coordinates the Iron Response with Population Density under Iron-Replete Conditions in Bacillus subtilis.

PubMed

Roy, Emily M; Griffith, Kevin L

2017-01-01

Iron is an essential micronutrient required for the viability of many organisms. Under oxidizing conditions, ferric iron is highly insoluble (∼10 -9 to 10 -18 M), yet bacteria typically require ∼10 -6 M for survival. To overcome this disparity, many bacteria have adopted the use of extracellular iron-chelating siderophores coupled with specific iron-siderophore uptake systems. In the case of Bacillus subtilis, undomesticated strains produce the siderophore bacillibactin. However, many laboratory strains, e.g., JH642, have lost the ability to produce bacillibactin during the process of domestication. In this work, we identified a novel iron acquisition activity from strain JH642 that accumulates in the growth medium and coordinates the iron response with population density. The molecule(s) responsible for this activity was named elemental Fe(II/III) (Efe) acquisition factor because efeUOB (ywbLMN) is required for its activity. Unlike most iron uptake molecules, including siderophores and iron reductases, Efe acquisition factor is present under iron-replete conditions and is regulated independently of Fur repressor. Restoring bacillibactin production in strain JH642 inhibits the activity of Efe acquisition factor, presumably by sequestering available iron. A similar iron acquisition activity is produced from a mutant of Escherichia coli unable to synthesize the siderophore enterobactin. Given the conservation of efeUOB and its regulation by catecholic siderophores in B. subtilis and E. coli, we speculate that Efe acquisition factor is utilized by many bacteria, serves as an alternative to Fur-mediated iron acquisition systems, and provides cells with biologically available iron that would normally be inaccessible during aerobic growth under iron-replete conditions. Iron is an essential micronutrient required for a variety of biological processes, yet ferric iron is highly insoluble during aerobic growth. In this work, we identified a novel iron acquisition activity that coordinates the iron response with population density in laboratory strains of Bacillus subtilis We named the molecule(s) responsible for this activity elemental Fe(II/III) (Efe) acquisition factor after the efeUOB (ywbLMN) operon required for its uptake into cells. Unlike most iron uptake systems, Efe acquisition factor is present under iron-replete conditions and is regulated independently of Fur, the master regulator of the iron response. We speculate that Efe acquisition factor is highly conserved among bacteria and serves as a backup to Fur-mediated iron acquisition systems. Copyright © 2016 American Society for Microbiology.

Organic Exudates Enhance Iron Bioavailability to Trichodesmium (IMS101) by Modifying Fe Speciation

NASA Astrophysics Data System (ADS)

Tohidi Farid, H.; Rose, A.; Schulz, K.

2016-02-01

Although ferrous iron (Fe (II)) is believed to be the most readily absorbed form of Fe by cells, under alkaline and oxygenated conditions typical of marine environments, the thermodynamically stable Fe(III) state dominates. In marine environments, this Fe(III) is primarily presents as organic Fe(III)L complexes whose bioavailability is highly variable. However, it has been demonstrated that some eukaryotic marine algae are able to release organic ligands into their surrounding environments that change Fe bioavailability through complexation and/or redox reactions. Nevertheless, it is unclear how Fe(II) oxidation and Fe(III) reduction rates might be modified by these exudates and how this might increase or decrease iron bioavailability to microorganisms. Here, the role of natural organic ligands excreted by the cyanobacterium Trichodesmium erythraeum on the oxidation kinetics of Fe(II) was studied using the luminol chemiluminescence technique. The oxidation kinetics of Fe(II) were examined at nanomolar Fe concentrations in presence of different concentrations of EDTA and dissolved organic carbon exuded by Trichodesmium cells. The results indicated that an increase in the concentration of exuded organic matter, and consequently L:Fe(II) ratio, resulted in decreasing rates of Fe(II) oxidation by oxygen, primarily due to formation of Fe(II) complexes. Moreover, the results demonstrated that the exudates from Trichodesmium may be able to reduce Fe(III) to the more bioavailable Fe(II) state under some circumstances. This study therefore supports the ability of microorganisms to manipulate Fe bioavailability by releasing organic compounds into the extracellular environment that retard Fe(II) oxidation rates or reducing Fe(III) species to Fe(II). It also provides new insight into the potential mechanism(s) by which Trichdesmium may acquire Fe under conditions where Fe bioavailability is otherwise limited.

Speciation And Uptake of Arsenic Accumulated By Corn Seedlings Using XAS And DRC-ICP-MS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parsons, J.G.; Martinez-Martinez, A.; Peralta-Videa, J.R.

ICP-MS was used to investigate the uptake of As(III) and As(V) from hydroponics growth media by corn seedlings. It was found that arsenic uptake by the plant roots for the arsenic(V) and arsenic(III) treatments were 95 and 112 ppm, respectively. However, in the shoots of the arsenic (V) treatments had 18 ppm whereas arsenic(III) treatments had 12 ppm. XANES studies showed that As for both treatments arsenic was present as a mixture of an As(III) sulfur complex and an As(V) oxygen complex. The XANES data was corroborated by the EXAFS studies showing the presence of both oxygen and sulfur ligandsmore » coordinated to the arsenic. Iron concentrations were found to increase by 4 fold in the As(V) contaminated growth media and 7 fold in the As(III) treatment compared to the control iron concentration of 500 ppm. Whereas, the total iron concentration in the shoots was found to decrease by approximately the same amount for both treatments from 360 ppm in the control to approximately 125 ppm in both arsenic treatments. Phosphorus concentrations were found to decrease in both the roots and shoots compared to the control plants. The total sulfur in the roots was found to increase in the arsenic(III) and arsenic(V) treatments to 560 ppm and 800 ppm, respectively, compared to the control plants 358 ppm. In addition, the total sulfur in shoots of the plants was found to remain relatively constant at approximately 1080 ppm. The potassium concentrations in the plants were found to increase in the roots and decrease in the shoots.« less

Plasma impact on structural, morphological and optical properties of copper acetylacetonate thin films.

PubMed

Abdel-Khalek, H; El-Samahi, M I; El-Mahalawy, Ahmed M

2018-06-15

The influence of plasma exposure on structural, morphological and optical properties of copper (II) acetylacetonate thin films deposited by thermal evaporation technique was investigated. Copper (II) acetylacetonate as-grown thin films were exposed to the atmospheric plasma for different times. The exposure of as-grown cu(acac) 2 thin film to atmospheric plasma for 5min modified its structural, morphological and optical properties. The effect of plasma exposure on structure and roughness of cu(acac) 2 thin films was evaluated by XRD and AFM techniques, respectively. The XRD results showed an increment in crystallinity due to exposure for 5min, but, when the exposure time reaches 10min, the film was transformed to an amorphous state. The AFM results revealed a strong modification of films roughness when the average roughness decreased from 63.35nm to ~1nm as a result of interaction with plasma. The optical properties of as-grown and plasma exposured cu(acac) 2 thin films were studied using spectrophotometric method. The exposure of cu(acac) 2 thin films to plasma produced the indirect energy gap decrease from 3.20eV to 2.67eV for 10min exposure time. The dispersion parameters were evaluated in terms of single oscillator model for as-grown and plasma exposured thin films. The influence of plasma exposure on third order optical susceptibility was studied. Copyright © 2018 Elsevier B.V. All rights reserved.

Nano/microstructure and optical properties of ZnO particles precipitated from zinc acetylacetonate

NASA Astrophysics Data System (ADS)

Petrović, Željka; Ristić, Mira; Musić, Svetozar; Fabián, Martin

2015-06-01

The influence of experimental conditions on the nano/microstructure and optical properties of ZnO particles produced by rapid hydrolysis of zinc acetylacetonate, followed by aging of the precipitation system at 160 °C, was investigated. Samples were characterized by XRD, FE scanning electron microscopy (FE-SEM), FT-IR, UV/Vis/NIR and photoluminescence (PL) spectroscopies. XRD patterns of all samples were assigned to the hexagonal ZnO phase (wurtzite-type), as well as the corresponding FT-IR spectra. FE-SEM inspection showed a high dependence of the ZnO nano/microstructure on the chemical composition of the reaction mixture and autoclaving time after the rapid hydrolysis of zinc acetylacetonate. Microstructural differences were noticed between C2H5OH/H2O and H2O media, as well as under the influence of NH4OH addition. Measurements of nanocrystallite sizes showed no significant preferential orientation in the (1 0 0) and (0 0 2) directions relative to the (1 0 1) and (1 1 0) directions. Somewhat smaller crystallite sizes were noticed for ZnO samples synthesized by adding the NH4OH solution. Dissolution/recrystallization of ZnO particles played an important role in the formation of different ZnO nano/microstructures. The band gap values for prepared ZnO samples were calculated on the basis of recorded UV/Vis spectra. PL spectra were recorded for ZnO samples in powder form and their suspensions in pure ethanol. Noticed differences are discussed.

Availability of ferric iron for microbial reduction in bottom sediments of the freshwater tidal potomac river.

PubMed

Lovley, D R; Phillips, E J

1986-10-01

The distribution of Fe(III), its availability for microbial reduction, and factors controlling Fe(III) availability were investigated in sediments from a freshwater site in the Potomac River Estuary. Fe(III) reduction in sediments incubated under anaerobic conditions and depth profiles of oxalate-extractable Fe(III) indicated that Fe(III) reduction was limited to depths of 4 cm or less, with the most intense Fe(III) reduction in the top 1 cm. In incubations of the upper 4 cm of the sediments, Fe(III) reduction was as important as methane production as a pathway for anaerobic electron flow because of the high rates of Fe(III) reduction in the 0- to 0.5-cm interval. Most of the oxalate-extractable Fe(III) in the sediments was not reduced and persisted to a depth of at least 20 cm. The incomplete reduction was not the result of a lack of suitable electron donors. The oxalate-extractable Fe(III) that was preserved in the sediments was considered to be in a form other than amorphous Fe(III) oxyhydroxide, since synthetic amorphous Fe(III) oxyhydroxide, amorphous Fe(III) oxyhydroxide adsorbed onto clay, and amorphous Fe(III) oxyhydroxide saturated with adsorbed phosphate or fulvic acids were all readily reduced. Fe(3)O(4) and the mixed Fe(III)-Fe(II) compound(s) that were produced during the reduction of amorphous Fe(III) oxyhydroxide in an enrichment culture were oxalate extractable but were not reduced, suggesting that mixed Fe(III)-Fe(II) compounds might account for the persistence of oxalate-extractable Fe(III) in the sediments. The availability of microbially reducible Fe(III) in surficial sediments demonstrates that microbial Fe(III) reduction can be important to organic matter decomposition and iron geochemistry. However, the overall extent of microbial Fe(III) reduction is governed by the inability of microorganisms to reduce most of the Fe(III) in the sediment.

Gallium-Protoporphyrin IX Inhibits Pseudomonas aeruginosa Growth by Targeting Cytochromes.

PubMed

Hijazi, Sarah; Visca, Paolo; Frangipani, Emanuela

2017-01-01

Pseudomonas aeruginosa is a challenging pathogen due to both innate and acquired resistance to antibiotics. It is capable of causing a variety of infections, including chronic lung infection in cystic fibrosis (CF) patients. Given the importance of iron in bacterial physiology and pathogenicity, iron-uptake and metabolism have become attractive targets for the development of new antibacterial compounds. P. aeruginosa can acquire iron from a variety of sources to fulfill its nutritional requirements both in the environment and in the infected host. The adaptation of P. aeruginosa to heme iron acquisition in the CF lung makes heme utilization pathways a promising target for the development of new anti- Pseudomonas drugs. Gallium [Ga(III)] is an iron mimetic metal which inhibits P. aeruginosa growth by interfering with iron-dependent metabolism. The Ga(III) complex of the heme precursor protoporphyrin IX (GaPPIX) showed enhanced antibacterial activity against several bacterial species, although no inhibitory effect has been reported on P. aeruginosa . Here, we demonstrate that GaPPIX is indeed capable of inhibiting the growth of clinical P. aeruginosa strains under iron-deplete conditions, as those encountered by bacteria during infection, and that GaPPIX inhibition is reversed by iron. Using P. aeruginosa PAO1 as model organism, we show that GaPPIX enters cells through both the heme-uptake systems has and phu , primarily via the PhuR receptor which plays a crucial role in P. aeruginosa adaptation to the CF lung. We also demonstrate that intracellular GaPPIX inhibits the aerobic growth of P. aeruginosa by targeting cytochromes, thus interfering with cellular respiration.

Iron-targeting antitumor activity of gallium compounds and novel insights into triapine(®)-metal complexes.

PubMed

Chitambar, Christopher R; Antholine, William E

2013-03-10

Despite advances made in the treatment of cancer, a significant number of patients succumb to this disease every year. Hence, there is a great need to develop new anticancer agents. Emerging data show that malignant cells have a greater requirement for iron than normal cells do and that proteins involved in iron import, export, and storage may be altered in cancer cells. Therefore, strategies to perturb these iron-dependent steps in malignant cells hold promise for the treatment of cancer. Recent studies show that gallium compounds and metal-thiosemicarbazone complexes inhibit tumor cell growth by targeting iron homeostasis, including iron-dependent ribonucleotide reductase. Chemical similarities of gallium(III) with iron(III) enable the former to mimic the latter and interpose itself in critical iron-dependent steps in cellular proliferation. Newer gallium compounds have emerged with additional mechanisms of action. In clinical trials, the first-generation-compound gallium nitrate has exhibited activity against bladder cancer and non-Hodgkin's lymphoma, while the thiosemicarbazone Triapine(®) has demonstrated activity against other tumors. Novel gallium compounds with greater cytotoxicity and a broader spectrum of antineoplastic activity than gallium nitrate should continue to be developed. The antineoplastic activity and toxicity of the existing novel gallium compounds and thiosemicarbazone-metal complexes should be tested in animal tumor models and advanced to Phase I and II clinical trials. Future research should identify biologic markers that predict tumor sensitivity to gallium compounds. This will help direct gallium-based therapy to cancer patients who are most likely to benefit from it.

From iron coordination compounds to metal oxide nanoparticles.

PubMed

Iacob, Mihail; Racles, Carmen; Tugui, Codrin; Stiubianu, George; Bele, Adrian; Sacarescu, Liviu; Timpu, Daniel; Cazacu, Maria

2016-01-01

Various types, shapes and sizes of iron oxide nanoparticles were obtained depending on the nature of the precursor, preparation method and reaction conditions. The mixed valence trinuclear iron acetate, [Fe 2 III Fe II O(CH 3 COO) 6 (H 2 O) 3 ]·2H 2 O (FeAc1), μ 3 -oxo trinuclear iron(III) acetate, [Fe 3 O(CH 3 COO) 6 (H 2 O) 3 ]NO 3 ∙4H 2 O (FeAc2), iron furoate, [Fe 3 O(C 4 H 3 OCOO) 6 (CH 3 OH) 3 ]NO 3 ∙2CH 3 OH (FeF), iron chromium furoate, FeCr 2 O(C 4 H 3 OCOO) 6 (CH 3 OH) 3 ]NO 3 ∙2CH 3 OH (FeCrF), and an iron complex with an original macromolecular ligand (FePAZ) were used as precursors for the corresponding oxide nanoparticles. Five series of nanoparticle samples were prepared employing either a classical thermal pathway (i.e., thermal decomposition in solution, solvothermal method, dry thermal decomposition/calcination) or using a nonconventional energy source (i.e., microwave or ultrasonic treatment) to convert precursors into iron oxides. The resulting materials were structurally characterized by wide-angle X-ray diffraction and Fourier transform infrared, Raman, energy-dispersive X-ray, and X-ray fluorescence spectroscopies, as well as thermogravimetric analysis. The morphology was characterized by transmission electron microscopy, atomic force microscopy and dynamic light scattering. The parameters were varied within each route to fine tune the size and shape of the formed nanoparticles.

Gallium-Protoporphyrin IX Inhibits Pseudomonas aeruginosa Growth by Targeting Cytochromes

PubMed Central

Hijazi, Sarah; Visca, Paolo; Frangipani, Emanuela

2017-01-01

Pseudomonas aeruginosa is a challenging pathogen due to both innate and acquired resistance to antibiotics. It is capable of causing a variety of infections, including chronic lung infection in cystic fibrosis (CF) patients. Given the importance of iron in bacterial physiology and pathogenicity, iron-uptake and metabolism have become attractive targets for the development of new antibacterial compounds. P. aeruginosa can acquire iron from a variety of sources to fulfill its nutritional requirements both in the environment and in the infected host. The adaptation of P. aeruginosa to heme iron acquisition in the CF lung makes heme utilization pathways a promising target for the development of new anti-Pseudomonas drugs. Gallium [Ga(III)] is an iron mimetic metal which inhibits P. aeruginosa growth by interfering with iron-dependent metabolism. The Ga(III) complex of the heme precursor protoporphyrin IX (GaPPIX) showed enhanced antibacterial activity against several bacterial species, although no inhibitory effect has been reported on P. aeruginosa. Here, we demonstrate that GaPPIX is indeed capable of inhibiting the growth of clinical P. aeruginosa strains under iron-deplete conditions, as those encountered by bacteria during infection, and that GaPPIX inhibition is reversed by iron. Using P. aeruginosa PAO1 as model organism, we show that GaPPIX enters cells through both the heme-uptake systems has and phu, primarily via the PhuR receptor which plays a crucial role in P. aeruginosa adaptation to the CF lung. We also demonstrate that intracellular GaPPIX inhibits the aerobic growth of P. aeruginosa by targeting cytochromes, thus interfering with cellular respiration. PMID:28184354

Thermo-mechanical characterization of siliconized E-glass fiber/hematite particles reinforced epoxy resin hybrid composite

NASA Astrophysics Data System (ADS)

V. R., Arun prakash; Rajadurai, A.

2016-10-01

In this present work hybrid polymer (epoxy) matrix composite has been strengthened with surface modified E-glass fiber and iron(III) oxide particles with varying size. The particle sizes of 200 nm and <100 nm has been prepared by high energy ball milling and sol-gel methods respectively. To enhance better dispersion of particles and improve adhesion of fibers and fillers with epoxy matrix surface modification process has been done on both fiber and filler by an amino functional silane 3-Aminopropyltrimethoxysilane (APTMS). Crystalline and functional groups of siliconized iron(III) oxide particles were characterized by XRD and FTIR spectroscopy analysis. Fixed quantity of surface treated 15 vol% E-glass fiber was laid along with 0.5 and 1.0 vol% of iron(III) oxide particles into the matrix to fabricate hybrid composites. The composites were cured by an aliphatic hardener Triethylenetetramine (TETA). Effectiveness of surface modified particles and fibers addition into the resin matrix were revealed by mechanical testing like tensile testing, flexural testing, impact testing, inter laminar shear strength and hardness. Thermal behavior of composites was evaluated by TGA, DSC and thermal conductivity (Lee's disc). The scanning electron microscopy was employed to found shape and size of iron(III) oxide particles adhesion quality of fiber with epoxy matrix. Good dispersion of fillers in matrix was achieved with surface modifier APTMS. Tensile, flexural, impact and inter laminar shear strength of composites was improved by reinforcing surface modified fiber and filler. Thermal stability of epoxy resin was improved when surface modified fiber was reinforced along with hard hematite particles. Thermal conductivity of epoxy increased with increase of hematite content in epoxy matrix.

Localized sulfate-reducing zones in a coastal plain aquifer

USGS Publications Warehouse

Brown, C.J.; Coates, J.D.; Schoonen, M.A.A.

1999-01-01

High concentrations of dissolved iron in ground water of coastal plain or alluvial aquifers contribute to the biofouling of public supply wells for which treatment and remediation is costly. Many of these aquifers, however, contain zones in which microbial sulfate reduction and the associated precipitation of iron-sulfide minerals decreases iron mobility. The principal water-bearing aquifer (Magothy Aquifer of Cretaceous age) in Suffolk County, New York, contains localized sulfate-reducing zones in and near lignite deposits, which generally are associated with clay lenses. Microbial analyses of core samples amended with [14C]-acetate indicate that microbial sulfate reduction is the predominant terminal-electron-accepting process (TEAP) in poorly permeable, lignite-rich sediments at shallow depths and near the ground water divide. The sulfate-reducing zones are characterized by abundant lignite and iron-sulfide minerals, low concentrations of Fe(III) oxyhydroxides, and by proximity to clay lenses that contain pore water with relatively high concentrations of sulfate and dissolved organic carbon. The low permeability of these zones and, hence, the long residence time of ground water within them, permit the preservation and (or) allow the formation of iron-sulfide minerals, including pyrite and marcasite. Both sulfate-reducing bacteria (SRB) and iron-reducing bacteria (IRB) are present beneath and beyond the shallow sulfate-reducing zones. A unique Fe(III)-reducing organism, MD-612, was found in core sediments from a depth of 187 m near the southern shore of Long Island. The distribution of poorly permeable, lignite-rich, sulfate-reducing zones with decreased iron concentration is varied within the principal aquifer and accounts for the observed distribution of dissolved sulfate, iron, and iron sulfides in the aquifer. Locating such zones for the placement of production wells would be difficult, however, because these zones are of limited aerial extent.

Solid surface photochemistry of montmorillonite: mechanisms for the arsenite oxidation under UV-A irradiation.

PubMed

Yuan, Yanan; Wang, Yajie; Ding, Wei; Li, Jinjun; Wu, Feng

2016-01-01

Transformation of inorganic arsenic species has drawn great concern in recent decades because of worldwide and speciation-dependent pollution and the hazards that they pose to the environment and to human health. As(III) photooxidation in aquatic systems has received much attention, but little is known about photochemical transformation of arsenic species on top soil. As(III) photooxidation on natural montmorillonite under UV-A radiation was investigated by using a moisture- and temperature-controlled photochemical chamber with two black-light lamps. Initial As(III) concentration, pH, layer thickness, humic acid (HA) concentration, the presence of additional iron ions, and the contribution of reactive oxygen species (ROS) were examined. The results show that pH values of the clay layers greatly influenced As(III) photooxidation on montmorillonite. As(III) photooxidation followed the Langmuir-Hinshelwood model. HA and additional iron ions greatly promoted photooxidation, but excess Fe(II) competed with As(III) for oxidation by ROS. Scavenging experiments revealed that natural montmorillonite induced the conversion of As(III) to As(V) by generating ROS (mainly HO(•) and HO2(•)/O2(•-)) and that HO(•) radical was the predominant oxidant in this system. Our work demonstrates that photooxidation on the surface of natural clay minerals in top soil can be important to As(III) transformation. This allows understanding and predicting the speciation and behavior of arsenic on the soil surface.

Selective sensing of submicromolar iron(III) with 3,3‧,5,5‧-tetramethylbenzidine as a chromogenic probe

NASA Astrophysics Data System (ADS)

Zhang, Lufeng; Du, Jianxiu

2016-04-01

The development of highly selective and sensitive method for iron(III) detection is of great importance both from human health as well as environmental point of view. We herein reported a simple, selective and sensitive colorimetric method for the detection of Fe(III) at submicromolar level with 3,3,‧5,5‧-tetramethylbenzidine (TMB) as a chromogenic probe. It was observed that Fe(III) could directly oxidize TMB to form a blue solution without adding any extra oxidants. The reaction has a stoichiometric ratio of 1:1 (Fe(III)/TMB) as determined by a molar ratio method. The resultant color change can be perceived by the naked eye or monitored the absorbance change at 652 nm. The method allowed the measurement of Fe(III) in the range 1.0 × 10- 7-1.5 × 10- 4 mol L- 1 with a detection limit of 5.5 × 10- 8 mol L- 1. The relative standard deviation was 0.9% for eleven replicate measurements of 2.5 × 10- 5 mol L- 1 Fe(III) solution. The chemistry showed high selectivity for Fe(III) in contrast to other common cation ions. The practically of the method was evaluated by the determination of Fe in milk samples; good consistency was obtained between the results of this method and atomic absorption spectrophotometry as indicated by statistical analysis.

Biodegradation of pharmaceuticals and endocrine disruptors with oxygen, nitrate, manganese (IV), iron (III) and sulfate as electron acceptors

NASA Astrophysics Data System (ADS)

Schmidt, Natalie; Page, Declan; Tiehm, Andreas

2017-08-01

Biodegradation of pharmaceuticals and endocrine disrupting compounds was examined in long term batch experiments for a period of two and a half years to obtain more insight into the effects of redox conditions. A mix including lipid lowering agents (e.g. clofibric acid, gemfibrozil), analgesics (e.g. diclofenac, naproxen), beta blockers (e.g. atenolol, propranolol), X-ray contrast media (e.g. diatrizoic acid, iomeprol) as well as the antiepileptic carbamazepine and endocrine disruptors (e.g. bisphenol A, 17α-ethinylestradiol) was analyzed in batch tests in the presence of oxygen, nitrate, manganese (IV), iron (III), and sulfate. Out of the 23 selected substances, 14 showed a degradation of > 50% of their initial concentrations under aerobic conditions. The beta blockers propranolol and atenolol and the analgesics pentoxifylline and naproxen showed a removal of > 50% under anaerobic conditions. In particular naproxen proved to be degradable with oxygen and under most anaerobic conditions, i.e. with manganese (IV), iron (III), or sulfate. The natural estrogens estriol, estrone and 17β-estradiol showed complete biodegradation under aerobic and nitrate-reducing conditions, with a temporary increase of estrone during transformation of estriol and 17β-estradiol. Transformation of 17β-estradiol under Fe(III)-reducing conditions resulted in an increase of estriol as well. Concentrations of clofibric acid, carbamazepine, iopamidol and diatrizoic acid, known for their recalcitrance in the environment, remained unchanged.

Effect of ionic strength on the thermodynamic characteristics of complexation between Fe(III) ion and nicotinamide in water-ethanol and water-dimethyl sulfoxide mixtures

NASA Astrophysics Data System (ADS)

Gamov, G. A.; Grazhdan, K. V.; Gavrilova, M. A.; Dushina, S. V.; Sharnin, V. A.; Baranski, A.

2013-06-01

Solutions of iron(III) perchlorate in water, water-ethanol, and water-dimethyl sulfoxide solvents (x_{H_2 O} = 0.7 and 0.25 mole fractions) at ionic strength values I = 0.1, 0.25, and 0.5 are studied by IR spectroscopy. Analysis of the absorption bands of perchlorate ion shows that it does not participate in association processes. It is demonstrated that in the range of ionic strength values between 0 and 0.5 (NaClO4), it affects neither the results from potentiometric titration to determine the stability constants of the iron(III)-nicotinamide complex nor the thermal effects of complexation determined via direct calorimetry in a binary solvent containing 0.3 mole fractions (m.f.) of a non-aqueous component.

Antibacterial activity and spectral studies of trivalent chromium, manganese, iron macrocyclic complexes derived from oxalyldihydrazide and glyoxal.

PubMed

Singh, D P; Kumar, Ramesh; Singh, Jitender

2009-06-01

A new series of complexes is synthesized by template condensation of oxalyldihydrazide and glyoxal in methanolic medium in the presence of trivalent chromium, manganese and iron salts forming complexes of the type: [M(C(8)H(8)N(8)O(4))X]X(2) where M = Cr(III), Mn(III), Fe(III) and X = Cl(-1), NO(-1)(3), CH(3)COO(-1). The complexes have been characterized with the help of elemental analyses, conductance measurements, magnetic susceptibility measurements, electronic, NMR, infrared and far infrared spectral studies. On the basis of these studies, a five coordinate square pyramidal geometry for these complexes has been proposed. The biological activities of the metal complexes were tested in vitro against a number of pathogenic bacteria and some of the complexes exhibited remarkable antibacterial activities.

Solvent free oxidation of primary alcohols and diols using thymine iron(III) catalyst.

PubMed

Al-Hunaiti, Afnan; Niemi, Teemu; Sibaouih, Ahlam; Pihko, Petri; Leskelä, Markku; Repo, Timo

2010-12-28

In this study, we developed an efficient and selective iron-based catalyst system for the synthesis of ketones from secondary alcohols and carboxylic acids from primary alcohol. In situ generated iron catalyst of thymine-1-acetate (THA) and FeCl(3) under solvent-free condition exhibits high activity. As an example, 1-octanol and 2-octanol were oxidized to 1-octanoic acid and 2-octanone with 89% and 98% yields respectively.

Removal of hexavalent chromium in carbonic acid solution by oxidizing slag discharged from steelmaking process in electric arc furnace

NASA Astrophysics Data System (ADS)

Yokoyama, Seiji; Okazaki, Kohei; Sasano, Junji; Izaki, Masanobu

2014-02-01

Hexavalent chromium (Cr(VI)) is well-known to be a strong oxidizer, and is recognized as a carcinogen. Therefore, it is regulated for drinking water, soil, groundwater and sea by the environmental quality standards all over the world. In this study, it was attempted to remove Cr(VI) ion in a carbonic acid solution by the oxidizing slag that was discharged from the normal steelmaking process in an electric arc furnace. After the addition of the slag into the aqueous solution contained Cr(VI) ion, concentrations of Cr(VI) ion and total chromium (Cr(VI) + trivalent chromium (Cr(III)) ions decreased to lower detection limit of them. Therefore, the used slag could reduce Cr(VI) and fix Cr(III) ion on the slag. While Cr(VI) ion existed in the solution, iron did not dissolve from the slag. From the relation between predicted dissolution amount of iron(II) ion and amount of decrease in Cr(VI) ion, the Cr(VI) ion did not react with iron(II) ion dissolved from the slag. Therefore, Cr(VI) ion was removed by the reductive reaction between Cr(VI) ion and the iron(II) oxide (FeO) in the slag. This reaction progressed on the newly appeared surface of iron(II) oxide due to the dissolution of phase composed of calcium etc., which existed around iron(II) oxide grain in the slag.

Continuing Treatment with Salvia miltiorrhiza Injection Attenuates Myocardial Fibrosis in Chronic Iron-Overloaded Mice

PubMed Central

Zhang, Ying; Wang, Hao; Cui, Lijing; Zhang, Yuanyuan; Liu, Yang; Chu, Xi; Liu, Zhenyi; Zhang, Jianping; Chu, Li

2015-01-01

Iron overload cardiomyopathy results from iron accumulation in the myocardium that is closely linked to iron-mediated myocardial fibrosis. Salvia miltiorrhiza (SM, also known as Danshen), a traditional Chinese medicinal herb, has been widely used for hundreds of years to treat cardiovascular diseases. Here, we investigated the effect and potential mechanism of SM on myocardial fibrosis induced by chronic iron overload (CIO) in mice. Kunming male mice (8 weeks old) were randomized to six groups of 10 animals each: control (CONT), CIO, low-dose SM (L-SM), high-dose SM (H-SM), verapamil (VRP) and deferoxamine (DFO) groups. Normal saline was injected in the CONT group. Mice in the other five groups were treated with iron dextran at 50 mg/kg per day intraperitoneally for 7 weeks, and those in the latter four groups also received corresponding daily treatments, including 3 g/kg or 6 g/kg of SM, 100 mg/kg of VRP, or 100 mg/kg of DFO. The iron deposition was estimated histologically using Prussian blue staining. Myocardial fibrosis was determined by Masson’s trichrome staining and hydroxyproline (Hyp) quantitative assay. Superoxide dismutase (SOD) activity, malondialdehyde (MDA) content and protein expression levels of type I collagen (COL I), type I collagen (COL III), transforming growth factor-β1 (TGF-β1) and matrix metalloproteinase-9 (MMP-9) were analyzed to investigate the mechanisms underlying the effects of SM against iron-overloaded fibrosis. Treatment of chronic iron-overloaded mice with SM dose-dependently reduced iron deposition levels, fibrotic area percentage, Hyp content, expression levels of COL I and COL III, as well as upregulated the expression of TGF- β1 and MMP-9 proteins in the heart. Moreover, SM treatment decreased MDA content and increased SOD activity. In conclusion, SM exerted activities against cardiac fibrosis induced by CIO, which may be attributed to its inhibition of iron deposition, as well as collagen metabolism and oxidative stress. PMID:25850001

Expanding the Therapeutic Potential of the Iron Chelator Deferasirox in the Development of Aqueous Stable Ti(IV) Anticancer Complexes.

PubMed

Loza-Rosas, Sergio A; Vázquez-Salgado, Alexandra M; Rivero, Kennett I; Negrón, Lenny J; Delgado, Yamixa; Benjamín-Rivera, Josué A; Vázquez-Maldonado, Angel L; Parks, Timothy B; Munet-Colón, Charlene; Tinoco, Arthur D

2017-07-17

The recent X-ray structure of titanium(IV)-bound human serum transferrin (STf) exhibiting citrate as a synergistic anion reveals a difference in Ti(IV) coordination versus iron(III), the metal endogenously delivered by the protein to cells. This finding enriches our bioinspired drug design strategy for Ti(IV)-based anticancer therapeutics, which applies a family of Fe(III) chelators termed chemical transferrin mimetic (cTfm) ligands to inhibit Fe bioavailability in cancer cells. Deferasirox, a drug used for iron overload disease, is a cTfm ligand that models STf coordination to Fe(III), favoring Fe(III) binding versus Ti(IV). This metal affinity preference drives deferasirox to facilitate the release of cytotoxic Ti(IV) intracellularly in exchange for Fe(III). An aqueous speciation study performed by potentiometric titration from pH 4 to 8 with micromolar levels of Ti(IV) deferasirox at a 1:2 ratio reveals exclusively Ti(deferasirox) 2 in solution. The predominant complex at pH 7.4, [Ti(deferasirox) 2 ] 2- , exhibits the one of the highest aqueous stabilities observed for a potent cytotoxic Ti(IV) species, demonstrating little dissociation even after 1 month in cell culture media. UV-vis and 1 H NMR studies show that the stability is unaffected by the presence of biomolecular Ti(IV) binders such as citrate, STf, and albumin, which have been shown to induce dissociation or regulate cellular uptake and can alter the activity of other antiproliferative Ti(IV) complexes. Kinetic studies on [Ti(deferasirox) 2 ] 2- transmetalation with Fe(III) show that a labile Fe(III) source is required to induce this process. The initial step of this process occurs on the time scale of minutes, and equilibrium for the complete transmetalation is reached on a time scale of hours to a day. This work reveals a mechanism to deliver Ti(IV) compounds into cells and trigger Ti(IV) release by a labile Fe(III) species. Cellular studies including other cTfm ligands confirm the Fe(III) depletion mechanism of these compounds and show their ability to induce early and late apoptosis.

ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT, REMOVAL OF ARSENIC IN DRINKING WATER: DELTA INDUSTRIAL SERVICES, INC., CAMPWATER PORTA-5 SYSTEM

EPA Science Inventory

The CampWater system uses ozonation followed by cartridge filtration to remove arsenic via co-precipitation. The system utilizes ozone to oxidize iron and arsenic (III) to arsenic (V). The arsenic bound to the iron precipitates is then removed by cartridge filtration. No additi...

Spectroscopic studies of Fe(III) ion-exchanged ETS-10 and ETAS-10 molecular sieves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sommerfeld, D.A.; Ellis, W.R. Jr.; Eyring, E.M.

1992-11-26

Two new titanium silicate molecular sieves, designated ETS-10 and ETAS-10, have been ion-exchanged with Fe(III). Both products exhibit prominent EPR signals, at g = 6.0 and 4.3, that are assigned to populations of ferric iron on the surface and in the interior cavities, respectively, of the molecular sieve microcrystals. Corollary XPS measurements on these samples indicate that a substantial fraction of the surface iron is present as Fe(II). Chemical modification procedures have been explored in an effort to produce ion-exchanged materials containing no exterior iron. Acid treatment (pH 1.0) proved to be an effective means of achieving this goal inmore » the case of ETS-10-based materials. ETAS-10-based samples do not retain their crystallinity under these conditions. 35 refs., 4 figs., 2 tabs.« less

New spectrophotometric methods for the determinations of hydrogen sulfide present in the samples of lake water, industrial effluents, tender coconut, sugarcane juice and egg

NASA Astrophysics Data System (ADS)

Shyla, B.; Nagendrappa, G.

2012-10-01

The new methods are working on the principle that iron(III) is reduced to iron(II) by hydrogen sulfide, catechol and p-toluidine the system 1/hydrogen sulfide the system 2, in acidic medium followed by the reduced iron forming complex with 1,10-phenanthroline with λmax 510 nm. The other two methods are based on redox reactions between electrolytically generated manganese(III) sulfate taken in excess and hydrogen sulfide followed by the unreacted oxidant oxidizing diphenylamine λmax 570 the system 3/barium diphenylamine sulphonate λmax 540 nm, the system 4. The increase/decrease in the color intensity of the dye products of the systems 1 and 2 or 3 and 4 are proportional to the concentration of hydrogen sulfide with its quantification range 0.035-1.40 μg ml-1/0.14-1.40 μg ml-1.

Thermodynamic studies of iron chelation with doxycycline in acidic medium

NASA Astrophysics Data System (ADS)

Javed, Javeria; Zahir, Erum

2017-06-01

Doxycycline (DOX) is a broad-spectrum tetracycline antibiotic synthetically derived from oxytetracycline. The complex formation of this drug with iron(III) was studied using spectrophotometry. The thermodynamic parameters of the systems were calculated using the changes in the absorption spectra which occur due to hydrogen bond or complex formation. Thermodynamic parameters of the formation of iron(III) complex with doxycycline (Δ H, Δ G, Δ S, and stability constants) were determined spectrophotometrically at a wavelength corresponding to absorption maximum (374.5 nm) at three different temperatures (22, 35, and 45°C). The obtained data show that the complex has metal to ligand molar ratio of 1: 2 at pH 2-3. The stability constants were calculated to be 13.99 × 106, 7.06 × 105, and 1.29 × 106 by mole ratio method at 22, 35, and 45°C, respectively.

Enzyme Induced Formation of Monodisperse Hydrogel Nanoparticles Tunable in Size

DOE PAGES

Bocharova, Vera; Sharp, Danna; Jones, Aaron; ...

2015-03-09

Here, we report a novel approach to synthesize monodisperse hydrogel nanoparticles that are tunable in size. The distinctive feature of our approach is the use of a multicopper oxidase enzyme, laccase, as both a biocatalyst and template for nanoparticle growth. We utilize the ferroxidase activity of laccase to initiate localized production of iron(III) cations from the oxidation of iron(II) cations. We demonstrate that nanoparticles are formed in a dilute polymer solution of alginate as a result of cross-linking between alginate and enzymatically produced iron(III) cations. Exerting control over the enzymatic reaction allows for nanometer-scale tuning of the hydrogel nanoparticle radiimore » in the range of 30–100 nm. Moreover, the nanoparticles and their growth kinetics were characterized via dynamic light scattering, atomic force microscopy, and UV–vis spectroscopy. Our finding opens up a new avenue for the synthesis of tunable nanoscale hydrogel particles for biomedical applications.« less

Equilibrium and kinetics of adsorption of phosphate onto iron-doped activated carbon.

PubMed

Wang, Zhengfang; Nie, Er; Li, Jihua; Yang, Mo; Zhao, Yongjun; Luo, Xingzhang; Zheng, Zheng

2011-08-01

Two series of activated carbons modified by Fe (II) and Fe (III) (denoted as AC/N-Fe(II) and AC/N-Fe(III)), respectively, were used as adsorbents for the removal of phosphate in aqueous solutions. The synthesized adsorbent materials were investigated by different experimental analysis means. The adsorption of phosphate on activated carbons has been studied in kinetic and equilibrium conditions taking into account the adsorbate concentration, temperature, and solution pH as major influential factors. Maximum removals of phosphate are obtained in the pH range of 3.78-6.84 for both adsorbents. Langmuir isotherm adsorption equation well describes the experimental adsorption isotherms. Kinetic studies revealed that the adsorption process followed a pseudo-second order kinetic model. Results suggest that the main phase formed in AC/N-Fe(II) and AC/N-Fe(III) is goethite and akaganeite, respectively; the presence of iron oxides significantly affected the surface area and the pore structure of the activated carbon. Studies revealed that iron-doped activated carbons were effective in removing phosphate. AC/N-Fe(II) has a higher phosphate removal capacity than AC/N-Fe(III), which could be attributed to its better intra-particle diffusion and higher binding energy. The activation energy for adsorption was calculated to be 22.23 and 10.89 kJ mol(-1) for AC/N-Fe(II) and AC/N-Fe(III), respectively. The adsorption process was complex; both surface adsorption and intra-particle diffusion were simultaneously occurring during the process and contribute to the adsorption mechanism.

A new iron(III) complex-containing sulfadiazine inhibits the proliferation and induces cystogenesis of Toxoplasma gondii.

PubMed

Portes, Juliana de A; Azeredo, Nathália F B; Siqueira, Pedro G T; de Souza, Tatiana Guinancio; Fernandes, Christiane; Horn, Adolfo; Candela, Dalber R S; de Souza, Wanderley; DaMatta, Renato A; Seabra, Sérgio H

2018-06-22

We have previously shown that metallocomplexes can control the growth of Toxoplasma gondii, the agent that causes toxoplasmosis. In order to develop new metallodrugs to treat this disease, we investigated the influence of the coordination of sulfadiazine (SDZ), a drug used to treat toxoplasmosis, on the biological activity of the iron(III) complex [Fe(HBPClNOL)Cl 2 ]·H 2 O, 1, (H 2 BPClNOL=N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)(3-chloro)(2-hydroxy)-propylamine). The new complex [(Cl)(SDZ)Fe(III)(μ-BPClNOL) 2 Fe(III)(SDZ)(Cl)]·2H 2 O, 2, which was obtained by the reaction between complex 1 and SDZ, was characterized using a range of physico-chemical techniques. The cytotoxic effect of the complexes and the ability of T. gondii to infect LLC-MK2 cells were assessed. It was found that both complexes reduced the growth of T. gondii while also causing low cytotoxicity in the host cells. After 48 h of treatment, complex 2 reduced the parasite's ability to proliferate by about 50% with an IC 50 of 1.66 μmol/L. Meanwhile, complex 1 or SDZ alone caused a 40% reduction in proliferation, and SDZ displayed an IC 50 of 5.3 μmol/L. In addition, complex 2 treatment induced distinct morphological and ultrastructural changes in the parasites and triggered the formation of cyst-like forms. These results show that the coordination of SDZ to the iron(III) complex is a good strategy for increasing the anti-toxoplasma activity of these compounds.

As(III) oxidation by MnO2 during groundwater treatment.

PubMed

Gude, J C J; Rietveld, L C; van Halem, D

2017-03-15

The top layer of natural rapid sand filtration was found to effectively oxidise arsenite (As(III)) in groundwater treatment. However, the oxidation pathway has not yet been identified. The aim of this study was to investigate whether naturally formed manganese oxide (MnO 2 ), present on filter grains, could abiotically be responsible for As(III) oxidation in the top of a rapid sand filter. For this purpose As(III) oxidation with two MnO 2 containing powders was investigated in aerobic water containing manganese(II) (Mn(II)), iron(II) (Fe(II)) and/or iron(III) (Fe(III)). The first MnO 2 powder was a very pure - commercially available - natural MnO 2 powder. The second originated from a filter sand coating, produced over 22 years in a rapid filter during aeration and filtration. Jar test experiments showed that both powders oxidised As(III). However, when applying the MnO 2 in aerated, raw groundwater, As(III) removal was not enhanced compared to aeration alone. It was found that the presence of Fe(II)) and Mn(II) inhibited As(III) oxidation, as Fe(II) and Mn(II) adsorption and oxidation were preferred over As(III) on the MnO 2 surface (at pH 7). Therefore it is concluded that just because MnO 2 is present in a filter bed, it does not necessarily mean that MnO 2 will be available to oxidise As(III). However, unlike Fe(II), the addition of Fe(III) did not hinder As(III) oxidation on the MnO 2 surface; resulting in subsequent effective As(V) removal by the flocculating hydrous ferric oxides. Copyright © 2016 Elsevier Ltd. All rights reserved.

Spin-crossover in an iron(III)-bispidine-alkylperoxide system.

PubMed

Bautz, Jochen; Comba, Peter; Que, Lawrence

2006-09-04

The iron(II) complex of a tetradentate bispidine ligand with two tertiary amines and two pyridine groups (L = dimethyl [3,7-dimethyl-9,9'-dihydroxy-2,4-di-(2-pyridyl)-3,7-diazabicyclo nonan-1,5-dicaboxylate]) is oxidized with tert-butyl hydroperoxide to the corresponding end-on tert-butylperoxo complex [Fe(III)(L)(OOtBu)(X)]n+ (X = solvent, anion). UV-vis, resonance Raman, and EPR spectroscopy, as a function of the solvent, show that this is a spin-crossover compound. The experimentally observed Raman vibrations for both low-spin and high-spin isomers are in good agreement with those computed by DFT.

Nano iron oxide impregnated in chitosan bead as a highly efficient sorbent for Cr(VI) removal from water.

PubMed

Lu, Jianbo; Xu, Kai; Yang, Jinmei; Hao, Yarong; Cheng, Fang

2017-10-01

Using Fe(III) salts and chitosan, nano iron oxide impregnated in chitosan bead (NIOC) was successfully synthesized for aqueous Cr(VI) detoxification via sol-gel technique without any additional crosslinking agent. NIOC characterization demonstrated that the iron in NIOC mainly existed as nano akaganeite (β-FeOOH) and complex with chitosan. Intraparticle diffusion was the major rate-limiting step. The maximal adsorption capacity was 69.8mg/g (pH 5.0, 20°C). Normal concentration of coexisting anions (SO 4 2- , CO 3 2- , SiO 3 2 -) showed insignificant competition, whereas PO 4 3- suppressed the Cr(VI) sorption. Cr(VI)-loaded NIOC could be effectively regenerated by alkaline solutions. Column adsorption runs using granular NIOC could effectively treat about 1600 bed volumes of Cr(VI) solution (from 3.7mg Cr/L in influent to <0.5mg Cr/L in effluent). The Cr(VI) removal mechanisms involved the direct sorption of Cr(VI) (electrostatic attraction and ligand exchange), reduction of Cr(VI) into Cr(III) and re-sorption of Cr(III) via chelation on NIOC surface. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spectroscopic, potentiometric and theoretical studies on the binding properties of a novel tripodal polycatechol-imine ligand towards iron(III)

NASA Astrophysics Data System (ADS)

Kanungo, B. K.; Sahoo, Suban K.; Baral, Minati

2008-12-01

A novel multidentate tripodal ligand, cis, cis-1,3,5-tris[(2,3-dihydroxybenzylidene)aminomethyl]cyclohexane (TDBAC, L) containing one catechol unit in each arms of a tripodal amine, cis, cis-1,3,5-tris(aminomethyl)cyclohexane was investigated as a chelator for iron(III) through potentiometric and spectrophotometric methods in an aqueous medium of 0.1N ionic strength and 25 ± 1 °C as well as in ethanol by continuous variation method. From pH metric in water, three protonation constants characterized for the three-hydroxyl groups of the catechol units at ortho were used as input data to evaluate the stability constants of the complexes. Formation of monomeric complexes FeLH 3, FeLH 2, FeLH and FeL were depicted. In ethanol, formation of complexes FeL, Fe 2L and Fe 3L were characterized. Structures of the complexes were explained by using the experimental evidences and predicted through molecular modeling calculations. The ligand showed potential to coordinate iron(III) through three imine nitrogens and three catecholic oxygens at ortho to form a tris(iminocatecholate) type complex.

Ultrafast primary processes of an iron-(III) azido complex in solution induced with 266 nm light.

PubMed

Vennekate, Hendrik; Schwarzer, Dirk; Torres-Alacan, Joel; Krahe, Oliver; Filippou, Alexander C; Neese, Frank; Vöhringer, Peter

2012-05-14

The ultrafast photo-induced primary processes of the iron-(III) azido complex, [Fe(III)N(3)(cyclam-acetato)] PF(6) (1), in acetonitrile solution at room temperature were studied using femtosecond spectroscopy with ultraviolet (UV) excitation and mid-infrared (MIR) detection. Following the absorption of a 266 nm photon, the complex undergoes an internal conversion back to the electronic doublet ground state at a time scale below 2 ps. Subsequently, the electronic ground state vibrationally cools with a characteristic time constant of 13 ps. A homolytic bond cleavage was also observed by the appearance of ground state azide radicals, which were identified by their asymmetric stretching vibration at 1659 cm(-1). The azide radical recombines in a geminate fashion with the iron containing fragment within 20 ps. The cage escape leading to well separated fragments after homolytic Fe-N bond breakage was found to occur with a quantum yield of 35%. Finally, non-geminate recombination at nanosecond time scales was seen to further reduce the photolytic quantum yield to below 20% at a wavelength of 266 nm. This journal is © the Owner Societies 2012

Growth of Iron(III)-Reducing Bacteria on Clay Minerals as the Sole Electron Acceptor and Comparison of Growth Yields on a Variety of Oxidized Iron Forms†

PubMed Central

Kostka, Joel E.; Dalton, Dava D.; Skelton, Hayley; Dollhopf, Sherry; Stucki, Joseph W.

2002-01-01

Smectite clay minerals are abundant in soils and sediments worldwide and are typically rich in Fe. While recent investigations have shown that the structural Fe(III) bound in clay minerals is reduced by microorganisms, previous studies have not tested growth with clay minerals as the sole electron acceptor. Here we have demonstrated that a pure culture of Shewanella oneidensis strain MR-1 as well as enrichment cultures of Fe(III)-reducing bacteria from rice paddy soil and subsurface sediments are capable of conserving energy for growth with the structural Fe(III) bound in smectite clay as the sole electron acceptor. Pure cultures of S. oneidensis were used for more detailed growth rate and yield experiments on various solid- and soluble-phase electron acceptors [smectite, Fe(III) oxyhydroxide FeOOH, Fe(III) citrate, and oxygen] in the same minimal medium. Growth was assessed as direct cell counts or as an increase in cell carbon (measured as particulate organic carbon). Cell counts showed that similar growth of S. oneidensis (108 cells ml−1) occurred with smectitic Fe(III) and on other Fe forms [amorphous Fe(III) oxyhydroxide, and Fe citrate] or oxygen as the electron acceptor. In contrast, cell yields of S. oneidensis measured as the increase in cell carbon were similar on all Fe forms tested while yields on oxygen were five times higher, in agreement with thermodynamic predictions. Over a range of particle loadings (0.5 to 4 g liter−1), the increase in cell number was highly correlated to the amount of structural Fe in smectite reduced. From phylogenetic analysis of the complete 16S rRNA gene sequences, a predominance of clones retrieved from the clay mineral-reducing enrichment cultures were most closely related to the low-G+C gram-positive members of the Bacteria (Clostridium and Desulfitobacterium) and the δ-Proteobacteria (members of the Geobacteraceae). Results indicate that growth with smectitic Fe(III) is similar in magnitude to that with Fe(III) oxide minerals and is dependent upon the mineral surface area available. Iron(III) bound in clay minerals should be considered an important electron acceptor supporting the growth of bacteria in soils or sedimentary environments. PMID:12450850

Investigating the effect of ascorbate on the Fe(II)-catalyzed transformation of the poorly crystalline iron mineral ferrihydrite.

PubMed

Xiao, Wei; Jones, Adele M; Collins, Richard N; Waite, T David

2018-05-09

The inorganic core of the iron storage protein, ferritin, is recognized as being analogous to the poorly crystalline iron mineral, ferrihydrite (Fh). Fh is also abundant in soils where it is central to the redox cycling of particular soil contaminants and trace elements. In geochemical circles, it is recognized that Fh can undergo Fe(II)-catalyzed transformation to form more crystalline iron minerals, vastly altering the reactivity of the iron oxide and, in some cases, the redox poise of the system. Of relevance to both geochemical and biological systems, we investigate here if the naturally occurring reducing agent, ascorbate, can effect such an Fe(II)-catalyzed transformation of Fh at 25 °C and circumneutral pH. The transformation of ferrihydrite to possible secondary Fe(III) mineralization products was quantified using Fourier transform infrared (FTIR) spectroscopy, with supporting data obtained using X-ray absorbance spectroscopy (XAS) and X-ray diffraction (XRD). Whilst the amount of Fe(II) formed in the presence of ascorbate has resulted in Fh transformation in previous studies, no transformation of Fh to more crystalline Fe(III) (oxyhydr)oxides was observed in this study. Further experiments indicated this was due to the ability of ascorbate to inhibit the formation of goethite, lepidocrocite and magnetite. The manner in which ascorbate associated with Fh was investigated using FTIR and total organic carbon (TOC) analysis. The majority of ascorbate was found to adsorb to the Fh surface under anoxic conditions but, under oxic conditions, ascorbate was initially adsorbed then became incorporated within the Fe(III) (oxyhydr)oxide structure (i.e., co-precipitated) over time. Copyright © 2018 Elsevier B.V. All rights reserved.

HRTEM/AEM and SEM study of fluid-rock interactions: Interaction of copper, silver, selenium, chromium, and cadmium-bearing solutions with geological materials at near surface conditions, with an emphasis on phyllosilicates. Progress report, September 1, 1992--September 1, 1993

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veblen, D.R.; Ilton, E.S.

1993-05-01

TEM of naturally occurring Cu-rich biotites and feldspars from weathered portions of porphyry copper deposits has shown that copper is not in the structure of these minerals, is present in their weathering products such as copper-rich vermiculite layers, submicroscopic iron oxyhydroxides and native copper inclusions, and chrysocoua. Reaction of acidic solutions bearing-Cu{sup 2+}, Ag{sup +}, Cr{sup 6+}, and Se{sup 4+}, at 25C, with biotite indicates that ferrous iron in biotite can reduce Cu{sup 2+}, Ag+, and Cr{sup 6+} to Cu{degrees}, Ag{degrees}, and Cr(III), respectively. However, Se{sup 4+} does not appear to be reduced. Copper is reduced in the interlayer region,more » silver is reduced in the interlayer and on the biotite surfaces, and chromium is reduced at the biotite surface. TEM shows that the reduction of copper and silver by biotite can produce native metal inclusions, whereas reduction of Cr(VI) to CR(III) did not produce any Cr-bearing precipitates. The copper and silver experiments show that iron in biotite can be a much stronger reducing agent than iron in solution. TEM and XPS of biotites reacted with CR(VI) clearly show that edges or (hkO) faces are much more reactive than the basal planes, where the edges are strongly enriched in CR(III) relative to the basal planes. In contrast, biotites reacted with Cr(IH)-bearing solutions show little fractionation between the edges and basal planes. Another important result of our XPS studies is that we demonstrated that the oxidation state of near surface iron in biotite can be quantified.« less

Synthesis, iron binding and antimicrobial properties of hexadentate 3-hydroxypyridinones-terminated dendrimers.

PubMed

Zhou, Tao; Chen, Kai; Kong, Li-Min; Liu, Mu-Song; Ma, Yong-Min; Xie, Yuan-Yuan; Hider, Robert C

2018-05-30

Macromolecular chelators have potential applications in the medical area, for instance, in treatment of iron overload-related disorders and in the treatment of external infections. In this investigation, several novel iron(III)-selective hydroxypyridinone hexadentate-terminated first and second generation dendrimeric chelators were synthesized using a convergent strategy. Their iron chelating ability was demonstrated by UV/Visible spectrometry and high resolution mass spectrometry (HRMS). The iron binding affinities were also investigated by the competition with a fluorescent iron chelator CP691. The result indicated that these dendrimers possesses a high affinity for iron with a very high pFe 3+ value, which is close to that of an isolated hexadentate unit. These dendrimeric chelators were found to exhibit inhibitory effect on the growth of both Gram-positive and Gram-negative bacteria. Copyright © 2018 Elsevier Ltd. All rights reserved.

Study of adsorption process of iron colloid substances on activated carbon by ultrasound

NASA Astrophysics Data System (ADS)

Machekhina, K. I.; Shiyan, L. N.; Yurmazova, T. A.; Voyno, D. A.

2015-04-01

The paper reports on the adsorption of iron colloid substances on activated carbon (PAC) Norit SA UF with using ultrasound. It is found that time of adsorption is equal to three hours. High-frequency electrical oscillation is 35 kHz. The adsorption capacity of activated carbon was determined and it is equal to about 0.25 mg iron colloid substances /mg PAC. The iron colloid substances size ranging from 30 to 360 nm was determined. The zeta potential of iron colloid substances which consists of iron (III) hydroxide, silicon compounds and natural organic substances is about (-38mV). The process of destruction iron colloid substances occurs with subsequent formation of a precipitate in the form of Fe(OH)3 as a result of the removal of organic substances from the model solution.

Sparkle model for AM1 calculation of lanthanide complexes: improved parameters for europium.

PubMed

Rocha, Gerd B; Freire, Ricardo O; Da Costa, Nivan B; De Sá, Gilberto F; Simas, Alfredo M

2004-04-05

In the present work, we sought to improve our sparkle model for the calculation of lanthanide complexes, SMLC,in various ways: (i) inclusion of the europium atomic mass, (ii) reparametrization of the model within AM1 from a new response function including all distances of the coordination polyhedron for tris(acetylacetonate)(1,10-phenanthroline) europium(III), (iii) implementation of the model in the software package MOPAC93r2, and (iv) inclusion of spherical Gaussian functions in the expression which computes the core-core repulsion energy. The parametrization results indicate that SMLC II is superior to the previous version of the model because Gaussian functions proved essential if one requires a better description of the geometries of the complexes. In order to validate our parametrization, we carried out calculations on 96 europium(III) complexes, selected from Cambridge Structural Database 2003, and compared our predicted ground state geometries with the experimental ones. Our results show that this new parametrization of the SMLC model, with the inclusion of spherical Gaussian functions in the core-core repulsion energy, is better capable of predicting the Eu-ligand distances than the previous version. The unsigned mean error for all interatomic distances Eu-L, in all 96 complexes, which, for the original SMLC is 0.3564 A, is lowered to 0.1993 A when the model was parametrized with the inclusion of two Gaussian functions. Our results also indicate that this model is more applicable to europium complexes with beta-diketone ligands. As such, we conclude that this improved model can be considered a powerful tool for the study of lanthanide complexes and their applications, such as the modeling of light conversion molecular devices.

Nitrogen loss from anaerobic ammonium oxidation coupled to Iron(III) reduction in a riparian zone.

PubMed

Ding, Bangjing; Li, Zhengkui; Qin, Yunbin

2017-12-01

Anaerobic ammonium oxidation coupled to iron(III) reduction (termed Feammox) is a recently discovered pathway of nitrogen cycling. However, little is known about the pathways of N transformation via Feammox process in riparian zones. In this study, evidence for Feammox in riparian zones with or without vegetation cover was demonstrated using isotope tracing technique and high-throughput sequencing technology. The results showed that Feammox could occur in riparian zones, and demonstrated that N 2 directly from Feammox was dominant Feammox pathway. The Feammox rates in vegetated soil samples was 0.32-0.37 mg N kg -1 d -1 , which is higher than that in un-vegetated soil samples (0.20 mg N kg -1 d -1 ). Moreover, the growth of vegetation led to a 4.99-6.41% increase in the abundance of iron reducing bacteria (Anaeromyxobacter, Pseudomonas and Geobacter) and iron reducing bacteria play an essential role in Feammox process. An estimated loss of 23.7-43.9 kg N ha -1 year -1 was associated with Feammox in the examined riparian zone. Overall, the co-occurrence of ammonium oxidation and iron reduction suggest that Feammox can play an essential role in the pathway of nitrogen removal in riparian zones. Copyright © 2017 Elsevier Ltd. All rights reserved.

Schwertmannite stability in acidified coastal environments

NASA Astrophysics Data System (ADS)

Collins, Richard N.; Jones, Adele M.; Waite, T. David

2010-01-01

A combination of analytical and field measurements has been used to probe the speciation and cycling of iron in coastal lowland acid sulfate soils. Iron K-edge EXAFS spectroscopy demonstrated that schwertmannite dominated (43-77%) secondary iron mineralization throughout the oxidized and acidified soil profile, while pyrite and illite were the major iron-bearing minerals in the reduced potential acid sulfate soil layers. Analyses of contemporary precipitates from shallow acid sulfate soil groundwaters indicated that 2-line ferrihydrite, in addition to schwertmannite, is presently controlling secondary Fe(III) mineralization. Although aqueous pH values and concentrations of Fe(II) were seasonally high, no evidence was obtained for the Fe(II)-catalyzed crystallization of either mineral to goethite. The results of this study indicate that: (a) schwertmannite is likely to persist in coastal lowland acid sulfate soils on a much longer time-scale than predicted by laboratory experiments; (b) this mineral is less reactive in these types of soils due to surface-site coverage by components such as silicate and possibly, to a lesser extent, natural organic matter and phosphate and; (c) active water table management to promote oxic/anoxic cycles around the Fe(II)-Fe(III) redox couple, or reflooding of these soils, will be ineffective in promoting the Fe(II)-catalyzed transformation of either schwertmannite or 2-line ferrihydrite to crystalline iron oxyhydroxides.

Characterization of a tricationic trigonal bipyramidal iron(IV) cyanide complex, with a very high reduction potential, and its iron(II) and iron(III) congeners.

PubMed

England, Jason; Farquhar, Erik R; Guo, Yisong; Cranswick, Matthew A; Ray, Kallol; Münck, Eckard; Que, Lawrence

2011-04-04

Currently, there are only a handful of synthetic S = 2 oxoiron(IV) complexes. These serve as models for the high-spin (S = 2) oxoiron(IV) species that have been postulated, and confirmed in several cases, as key intermediates in the catalytic cycles of a variety of nonheme oxygen activating enzymes. The trigonal bipyramidal complex [Fe(IV)(O)(TMG(3)tren)](2+) (1) was both the first S = 2 oxoiron(IV) model complex to be generated in high yield and the first to be crystallographically characterized. In this study, we demonstrate that the TMG(3)tren ligand is also capable of supporting a tricationic cyanoiron(IV) unit, [Fe(IV)(CN)(TMG(3)tren)](3+) (4). This complex was generated by electrolytic oxidation of the high-spin (S = 2) iron(II) complex [Fe(II)(CN)(TMG(3)tren)](+) (2), via the S = 5/2 complex [Fe(III)(CN)(TMG(3)tren)](2+) (3), the progress of which was conveniently monitored by using UV-vis spectroscopy to follow the growth of bathochromically shifting ligand-to-metal charge transfer (LMCT) bands. A combination of X-ray absorption spectroscopy (XAS), Mössbauer and NMR spectroscopies was used to establish that 4 has a S = 0 iron(IV) center. Consistent with its diamagnetic iron(IV) ground state, extended X-ray absorption fine structure (EXAFS) analysis of 4 indicated a significant contraction of the iron-donor atom bond lengths, relative to those of the crystallographically characterized complexes 2 and 3. Notably, 4 has an Fe(IV/III) reduction potential of ∼1.4 V vs Fc(+/o), the highest value yet observed for a monoiron complex. The relatively high stability of 4 (t(1/2) in CD(3)CN solution containing 0.1 M KPF(6) at 25 °C ≈ 15 min), as reflected by its high-yield accumulation via slow bulk electrolysis and amenability to (13)C NMR at -40 °C, highlights the ability of the sterically protecting, highly basic peralkylguanidyl donors of the TMG(3)tren ligand to support highly charged high-valent complexes.

Characterization of a Tricationic Trigonal Bipyramidal Iron(IV) Cyanide Complex, with a Very High Reduction Potential, and Its Iron(II) and Iron(III) Congeners

PubMed Central

England, Jason; Farquhar, Erik R.; Guo, Yisong; Cranswick, Matthew A.; Ray, Kallol

2011-01-01

Currently, there are only a handful of synthetic S = 2 oxoiron(IV) complexes. These serve as models for the high-spin (S = 2) oxoiron(IV) species that have been postulated, and confirmed in several cases, as key intermediates in the catalytic cycles of a variety of non-heme oxygen activating enzymes. The trigonal bipyramidal complex [FeIV(O)(TMG3tren)]2+ (1) was both the first S = 2 oxoiron(IV) model complex to be generated in high yield and the first to be crystallographically characterized. In this study, we demonstrate that the TMG3tren ligand is also capable of supporting a tricationic cyanoiron(IV) unit, [FeIV(CN)(TMG3tren)]3+ (4). This complex was generated by electrolytic oxidation of the high-spin (S = 2) iron(II) complex [FeII(CN)(TMG3tren)]+ (2), via the S = 5/2 complex [FeIII(CN)(TMG3tren)]2+ (3), the progress of which was conveniently monitored by using UV-Vis spectroscopy to follow the growth of bathochromically shifting LMCT bands. A combination of XAS, Mössbauer and NMR spectroscopies was used to establish that 4 has a S = 0 iron(IV) center. Consistent with its diamagnetic iron(IV) ground state, EXAFS analysis of 4 indicated a significant contraction of the iron-donor atom bond lengths, relative to those of the crystallographically characterized complexes 2 and 3. Notably, 4 has an FeIV/III reduction potential of ~1.4 V vs Fc+/o, the highest value yet observed for a monoiron complex. The relatively high stability of 4 (t1/2 in CD3CN solution containing 0.1 M KPF6 at 25 °C ≈ 15 min), as reflected by its high-yield accumulation via slow bulk electrolysis and amenability to 13C NMR at −40 °C, highlights the ability of the sterically protecting, highly basic peralkylguanidyl donors of the TMG3tren ligand to support highly charged high-valent complexes. PMID:21381646

Low cost disposal of MMH

NASA Technical Reports Server (NTRS)

Thomas, J. J.; French, T.

1980-01-01

Concentration of gaseous toxic monomethylhydrazine (MMH) can be removed at 99.9% efficiency using scrubbers containing acetylacetone solutions as scrubbing liquors. Resulting product is easily disposable and expensive liners for protecting scrubber from strong oxidizing agents are not needed.

Arsenic removal from acidic solutions with biogenic ferric precipitates.

PubMed

Ahoranta, Sarita H; Kokko, Marika E; Papirio, Stefano; Özkaya, Bestamin; Puhakka, Jaakko A

2016-04-05

Treatment of acidic solution containing 5g/L of Fe(II) and 10mg/L of As(III) was studied in a system consisting of a biological fluidized-bed reactor (FBR) for iron oxidation, and a gravity settler for iron precipitation and separation of the ferric precipitates. At pH 3.0 and FBR retention time of 5.7h, 96-98% of the added Fe(II) precipitated (99.1% of which was jarosite). The highest iron oxidation and precipitation rates were 1070 and 28mg/L/h, respectively, and were achieved at pH 3.0. Subsequently, the effect of pH on arsenic removal through sorption and/or co-precipitation was examined by gradually decreasing solution pH from 3.0 to 1.6 (feed pH). At pH 3.0, 2.4 and 1.6, the highest arsenic removal efficiencies obtained were 99.5%, 80.1% and 7.1%, respectively. As the system had ferric precipitates in excess, decreased arsenic removal was likely due to reduced co-precipitation at pH<2.4. As(III) was partially oxidized to As(V) in the system. In shake flask experiments, As(V) sorbed onto jarosite better than As(III). Moreover, the sorption capacity of biogenic jarosite was significantly higher than that of synthetic jarosite. The developed bioprocess simultaneously and efficiently removes iron and arsenic from acidic solutions, indicating potential for mining wastewater treatment. Copyright © 2015 Elsevier B.V. All rights reserved.

An improved soft-chemistry approach to the preparation of spinel powders

NASA Astrophysics Data System (ADS)

Cook, Ronald

2007-04-01

Spinel powders for the production of transparent polycrystalline ceramic windows have been produced using a number of traditional ceramic and sol-gel methods. We have demonstrated that magnesium aluminate spinel powders produced from the reaction of organo-magnesium compounds with surface modified boehmite precursors can be used to produce high quality transparent spinel parts. In previous work, the spinel powders were prepared by the reaction of surface-modified boehmite nanoparticles with magnesium acetylacetonate. While the magnesium acetylacetonate can produce small quantities of high quality spinel powders, it use for large scale production of spinel powders is problematic. Through a thermodynamic analysis we have identified a new high-purity, low-cost, low-toxicity organomagnesium compound that reacts the with surface modified boehmite nanoparticles to produce a spinel precursor. The magnesium doped precursor readily transforms into pure phase spinel at temperature between 900°C and 1200°C.

Spectroscopic studies on some fluorescent mixed-ligand titanium(IV) complexes.

PubMed

Baranwal, Balram Prasad; Singh, Alok Kumar; Varma, Anand

2011-12-15

A novel route to synthesize some titanium(IV) complexes containing acetylacetone, straight chain carboxylic acid and hydroxycarboxylic acid ligands has been investigated. Complexes with the general formula [Ti(acac)Cl(2-n)(OOCR*)(n)(OOCC(15)H(31))] (where Hacac=acetylacetone, R*COOH=hydroxycarboxylic acids and n=1 or 2) have been isolated and characterized. Molecular weight determinations indicated mononuclear nature of the complexes. LMCT bands were observed in the electronic spectra. Infrared spectra suggested bidentate nature of the ligands. Fluorescent behaviour of the complexes was noticed on the basis of fluorescence spectra. Powder XRD indicated them to be semi-crystalline having the crystallite size in 136-185 nm range. Transmission electron microscopy (TEM) indicated spherical particles of ~ 200 nm diameter. On the basis of physico-chemical studies, it is suggested that titanium is having coordination number 7 or 8 in these complexes. Copyright © 2011 Elsevier B.V. All rights reserved.

Efficient alkene epoxidation catalyzed by molybdenyl acetylacetonate supported on aminated UiO-66 metal-organic framework

NASA Astrophysics Data System (ADS)

Kardanpour, Reihaneh; Tangestaninejad, Shahram; Mirkhani, Valiollah; Moghadam, Majid; Mohammadpoor-Baltork, Iraj; Zadehahmadi, Farnaz

2015-03-01

Metal-organic frameworks (MOFs) containing Mo Schiff base complexes were prepared by post-synthesis method and applied as efficient catalysts in the epoxidation of alkenes with tert-BuOOH. In this manner, UiO-66-NH2 (UiO=University of Oslo) MOF was reacted with salicylaldehyde and thiophene-2-carbaldehyde to produce bidentate Schiff bases. Then, the Schiff base ligands were used for immobilization of molybdenyl acetylacetonate. These new catalysts were characterized by FT-IR, UV-vis spectroscopic techniques, X-ray diffraction (XRD), BET, inductively coupled plasma atomic emission spectroscopy (ICP-AES) and field emission scanning electron microscopy (FE-SEM). These catalytic systems showed excellent activity in the epoxidation of alkenes such as cyclic and linear ones with tert-butyl hydroperoxide (TBHP) in 1,2-dichloroethane, and reused several times without any appreciable loss of their activity.

Effect of carrier properties on surface characteristics of sorbents modified with acetylacetonates Ni (II), Cu (II)

NASA Astrophysics Data System (ADS)

Faustova, Zhanna; Matveeva, Tatiana; Slizhov, Yuriy

2017-11-01

Sorbents based on Chromaton N-AW with layers of mesoporous silica gel modified with acetylacetonate nickel (II) and copper (II) were obtained. The porous structure of sorbents based on synthesized silica gel and industrial samples of Chromaton N, Silipore 075, Silochrom C-120 was studied. All studied samples are mesoporous. For sorbents based on commercially available Chromaton N, Silipore 075, and Silochrome 120, the mesopore dimensions vary in a wide range from 10 to 50 nm. For synthesized silica gel and chelate-containing sorbents, a narrower pore distribution is observed in the range of 5-15 nm, which indicates the uniformity of its surface. A comparative analysis of the effect of carrier properties on the acid-base properties of the surface of chelate-containing sorbents is carried out. The acid-base nature of the modifier is more pronounced in the case of synthesized silica gel by the sol-gel method.

Direct observation of iron-induced conformational changes of mitochondrial DNA by high-resolution field-emission in-lens scanning electron microscopy.

PubMed Central

Yaffee, M; Walter, P; Richter, C; Müller, M

1996-01-01

When respiring rat liver mitochondria are incubated in the presence of Fe(III) gluconate, their DNA (mtDNA) relaxes from the supercoiled to the open circular form dependent on the iron dose. Anaerobiosis or antioxidants fail to completely inhibit the unwinding. High-resolution field-emission in-lens scanning electron microscopy imaging, in concert with backscattered electron detection, pinpoints nanometer-range iron colloids bound to mtDNA isolated from iron-exposed mitochondria. High-resolution field-emission in-lens scanning electron microscopy with backscattered electron detection imaging permits simultaneous detailed visual analysis of DNA topology, iron dose-dependent mtDNA unwinding, and assessment of iron colloid formation on mtDNA strands. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 PMID:8643576

Iron-Targeting Antitumor Activity of Gallium Compounds and Novel Insights Into Triapine®-Metal Complexes

PubMed Central

Antholine, William E.

2013-01-01

Abstract Significance: Despite advances made in the treatment of cancer, a significant number of patients succumb to this disease every year. Hence, there is a great need to develop new anticancer agents. Recent Advances: Emerging data show that malignant cells have a greater requirement for iron than normal cells do and that proteins involved in iron import, export, and storage may be altered in cancer cells. Therefore, strategies to perturb these iron-dependent steps in malignant cells hold promise for the treatment of cancer. Recent studies show that gallium compounds and metal-thiosemicarbazone complexes inhibit tumor cell growth by targeting iron homeostasis, including iron-dependent ribonucleotide reductase. Chemical similarities of gallium(III) with iron(III) enable the former to mimic the latter and interpose itself in critical iron-dependent steps in cellular proliferation. Newer gallium compounds have emerged with additional mechanisms of action. In clinical trials, the first-generation-compound gallium nitrate has exhibited activity against bladder cancer and non-Hodgkin's lymphoma, while the thiosemicarbazone Triapine® has demonstrated activity against other tumors. Critical Issues: Novel gallium compounds with greater cytotoxicity and a broader spectrum of antineoplastic activity than gallium nitrate should continue to be developed. Future Directions: The antineoplastic activity and toxicity of the existing novel gallium compounds and thiosemicarbazone-metal complexes should be tested in animal tumor models and advanced to Phase I and II clinical trials. Future research should identify biologic markers that predict tumor sensitivity to gallium compounds. This will help direct gallium-based therapy to cancer patients who are most likely to benefit from it. Antioxid. Redox Signal. 00, 000–000. PMID:22900955

Direct accessibility of mixed-metal (III/II) acid sites through the rational synthesis of porous metal carboxylates.

PubMed

Wongsakulphasatch, S; Nouar, F; Rodriguez, J; Scott, L; Le Guillouzer, C; Devic, T; Horcajada, P; Grenèche, J-M; Llewellyn, P L; Vimont, A; Clet, G; Daturi, M; Serre, C

2015-06-25

The scalable and environmentally-friendly synthesis of mixed Fe(III)/M(II) (M = Ni, Co, Mg) polycarboxylate porous MOFs based on the Secondary Building Unit approach is reported. A combination of in situ infrared spectroscopy, (57)Fe Mössbauer spectrometry and adsorption microcalorimetry confirms the direct accessibility of the iron(III) and metal(II) sites under low temperature activation conditions.

PRESERVATION OF AS(III) AND AS(V) IN DRINKING WATER SUPPLY SAMPLES FROM ACROSS THE UNITED STATES USING EDTA AND ACETIC ACID AS A MEANS OF MINIMIZING IRON-ARSENIC CO-PRECIPITATION

EPA Science Inventory

This paper evaluates seven different treatment/storage conditions for the preservation of the native As(III)/As(V) found in ten drinking water supplies from across the US. These ten waters were chosen because they have different As(III)/As(V) distributions; six of these waters c...

Highly Efficient Solution-Processed Deep-Red Organic Light-Emitting Diodes Based on an Exciplex Host Composed of a Hole Transporter and a Bipolar Host.

PubMed

Huang, Manli; Jiang, Bei; Xie, Guohua; Yang, Chuluo

2017-10-19

With the aim to achieve highly efficient deep-red emission, we introduced an exciplex forming cohost, 4,4',4″-tris(3-methylphenylphenylamino)triphenylamine (m-MTDATA): 2,5-bis(2-(9H-carbazol-9-yl)phenyl)-1,3,4-oxadiazole (o-CzOXD) (1:1). Due to the efficient triplet up-conversion processes upon the exciplex forming cohost, excellent performances of the devices were achieved with deep-red emission. Using the heteroleptic iridium complexes as the guest dopants, the solution-processed deep-red phosphorescent organic light-emitting diodes (PhOLEDs) with the iridium(III) bis(6-(4-(tert-butyl)phenyl)phenanthridine)acetylacetonate [(TP-BQ) 2 Ir(acac)]-based phosphorescent emitter exhibited an electroluminescent peak at 656 nm and a maximum external quantum efficiency (EQE) of 11.9%, which is 6.6 times that of the device based on the guest emitter doped in the polymer-based cohost. The unique exciplex with a typical hole transporter and a bipolar material is ideal and universal for hosting the red PhOLEDs and tremendously improves the device performances.

Storage of charge carriers on emitter molecules in organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Weichsel, Caroline; Burtone, Lorenzo; Reineke, Sebastian; Hintschich, Susanne I.; Gather, Malte C.; Leo, Karl; Lüssem, Björn

2012-08-01

Organic light-emitting diodes (OLEDs) using the red phosphorescent emitter iridium(III)bis(2-methyldibenzo[f,h]quinoxaline) (acetylacetonate) [Ir(MDQ)2(acac)] are studied by time-resolved electroluminescence measurements. A transient overshoot after voltage turn-off is found, which is attributed to electron accumulation on Ir(MDQ)2(acac) molecules. The mechanism is verified via impedance spectroscopy and by application of positive and negative off-voltages. We calculate the density of accumulated electrons and find that it scales linearly with the doping concentration of the emitter. Using thin quenching layers, we locate the position of the emission zone during normal OLED operation and after voltage turn-off. In addition, the transient overshoot is also observed in three-color white-emitting OLEDs. By time- and spectrally resolved measurements using a streak camera, we directly attribute the overshoot to electron accumulation on Ir(MDQ)2(acac). We propose that similar processes are present in many state-of-the-art OLEDs and believe that the quantification of charge carrier storage will help to improve the efficiency of OLEDs.

Metal Ir coatings on endocardial electrode tips, obtained by MOCVD

NASA Astrophysics Data System (ADS)

Vikulova, Evgeniia S.; Kal'nyi, Danila B.; Shubin, Yury V.; Kokovkin, Vasily V.; Morozova, Natalya B.; Hassan, Aseel; Basova, Tamara V.

2017-12-01

The present work demonstrates the application of the Metal-Organic Chemical Vapor Deposition technique to fabricate metal iridium coatings onto the pole tips of endocardial electrodes. Using iridium (III) acetylacetonate as a volatile precursor, the target coatings were successfully applied to the working surface of cathodes and anodes of pacemaker electrodes in the flow type reactor in hydrogen atmosphere at deposition temperature of 550 °C. The coating samples were characterized by means of XRD, SEM, Raman- and XPS-spectroscopies. The formation of non-textured coatings with fractal-like morphology and 7-24 nm crystallite size has been realized. The electrochemical properties of the coatings were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The charge storage capacity values of the electrochemically activated samples were 17.0-115 mC cm-2 and 14.4-76.5 mC cm-2 for measurements carried out in 0.1 M sulfuric acid and in phosphate buffer saline solutions, respectively. A comparison of some characteristics of the samples obtained with commercially available cathode of pacemaker electrodes is also presented.

Redox process catalysed by growing crystal-strengite, FePO4,2H2O, crystallizing from solution with iron(II) and hydroxylamine

NASA Astrophysics Data System (ADS)

Lundager Madsen, Hans Erik

2014-09-01

In an attempt to grow pure crystals of the iron(II) phosphate vivianite, Fe3(PO4)2,8H2O, from a solution of Mohr's salt, Fe(NH4)2(SO4)2,6H2O, added to a solution of ammonium phosphate, hydroxylammonium chloride, NH3OHCl, was added to the iron(II) stock solution to eliminate oxidation of iron(II) by oxygen from the air. However, the effect turned out to be the opposite of the expected: whereas hydroxylamine reduces iron(III) in bulk solution, it acted as a strong oxidant in the presence of growing iron phosphate crystals, causing the crystallization of the iron(III) phosphate strengite, FePO4,2H2O, as the only solid phase. Evidently the crystal surface catalyses oxidation of iron(II) by hydroxylamine. The usual composite kinetics of spiral growth and surface nucleation was found. The surface-nucleation part yielded edge free energy λ in the range 12-45 pJ/m, virtually independent of temperature and in the range typical for phosphates of divalent metals. The scatter of values for λ presumably arises from contributions from different crystal forms to the overall growth rate. The low mean value points to strong adsorption of iron(II), which is subsequently oxidized at the crystal surface, forming strengite. The state of the system did not tend to thermodynamic equilibrium, but to a metastable state, presumably controlled by the iron(II) rich surface layer of the crystal. In addition to crystal growth, it was possible to measure nucleation kinetics by light scattering (turbidimetry). A point of transition from heterogeneous to homogeneous nucleation was found, and from the results for the homogeneous domain a rather precise value of crystal surface free energy γ=55 mJ/m2 was found. This is a relatively low value as well, indicating that the redox process plays a role already at the nucleation stage.

Diurnal shifts in co-distributions of sulfide and iron(II) and profiles of phosphate and ammonium in the rhizosphere of Zostera capricorni

NASA Astrophysics Data System (ADS)

Pagès, Anaïs; Welsh, David T.; Robertson, David; Panther, Jared G.; Schäfer, Jörg; Tomlinson, Rodger B.; Teasdale, Peter R.

2012-12-01

High resolution, two dimensional distributions of porewater iron(II) and sulfide were measured, using colourimetric DET (diffusive equilibration in a thin film) and DGT (diffusive gradients in a thin film) techniques, respectively, in Zostera capricorni colonised sediments under both light and dark conditions. Low resolution depth profiles of ammonium and phosphate were measured using conventional DET and DGT methods, respectively. Porewater iron(II) and sulfide distributions showed a high degree of spatial heterogeneity under both light and dark conditions, and distributions were characterised by a complex mosaic of sediment zones dominated by either iron(II) or sulfide. However, there was a clear shift in overall redox conditions between light and dark conditions. During light deployments, iron(II) and sulfide concentrations were generally low throughout the rhizosphere, apart from a few distinct "hotspots" of high concentration. Whereas during dark deployments, high concentrations of iron(II) were sometimes measured in the near surface sediments and sulfide depth distributions migrated towards the sediment surface. Profiles of porewater ammonium and phosphate demonstrated an increase in ammonium concentrations under dark compared to light conditions. Surprisingly, despite the large changes in iron(II) distributions between light and dark conditions, phosphate profiles remained similar, indicating that adsorption/release of phosphate by iron(III) hydr(oxide) mineral formation and reduction was not a major factor regulating porewater phosphate concentrations in these sediments or that phosphate uptake by the seagrass roots persisted during the dark period. Overall, the results demonstrate that the photosynthetic activity of the seagrass played a significant role in regulating sulfide, iron(II) and ammonium concentrations in the rhizosphere, due to rates of radial oxygen loss and ammonium uptake by the roots and rhizomes being lower under dark compared to light conditions. This cyclic production and reduction of iron(III) hydr(oxides) in the rhizosphere may act as a buffering system preventing sulfide accumulation.

Modeling As(III) oxidation and removal with iron electrocoagulation in groundwater.

PubMed

Li, Lei; van Genuchten, Case M; Addy, Susan E A; Yao, Juanjuan; Gao, Naiyun; Gadgil, Ashok J

2012-11-06

Understanding the chemical kinetics of arsenic during electrocoagulation (EC) treatment is essential for a deeper understanding of arsenic removal using EC under a variety of operating conditions and solution compositions. We describe a highly constrained, simple chemical dynamic model of As(III) oxidation and As(III,V), Si, and P sorption for the EC system using model parameters extracted from some of our experimental results and previous studies. Our model predictions agree well with both data extracted from previous studies and our observed experimental data over a broad range of operating conditions (charge dosage rate) and solution chemistry (pH, co-occurring ions) without free model parameters. Our model provides insights into why higher pH and lower charge dosage rate (Coulombs/L/min) facilitate As(III) removal by EC and sheds light on the debate in the recent published literature regarding the mechanism of As(III) oxidation during EC. Our model also provides practically useful estimates of the minimum amount of iron required to remove 500 μg/L As(III) to <50 μg/L. Parameters measured in this work include the ratio of rate constants for Fe(II) and As(III) reactions with Fe(IV) in synthetic groundwater (k(1)/k(2) = 1.07) and the apparent rate constant of Fe(II) oxidation with dissolved oxygen at pH 7 (k(app) = 10(0.22) M(-1)s(-1)).

Effect of weak magnetic field on arsenate and arsenite removal from water by zerovalent iron: an XAFS investigation.

PubMed

Sun, Yuankui; Guan, Xiaohong; Wang, Jianmin; Meng, Xiaoguang; Xu, Chunhua; Zhou, Gongming

2014-06-17

In this study, a weak magnetic field (WMF), superimposed with a permanent magnet, was utilized to improve ZVI corrosion and thereby enhance As(V)/As(III) removal by ZVI at pHini 3.0-9.0. The experiment with real arsenic-bearing groundwater revealed that WMF could greatly improve arsenic removal by ZVI even in the presence of various cations and anions. The WMF-induced improvement in As(V)/As(III) removal by ZVI should be primarily associated with accelerated ZVI corrosion, as evidenced by the pH variation, Fe(2+) release, and the formation of corrosion products as characterized with X-ray absorption fine structure spectroscopy. The arsenic species analysis in solution/solid phases at pHini 3.0 revealed that As(III) oxidation to As(V) in aqueous phase preceded its subsequent sequestration by the newly formed iron (hydr)oxides. However, both As(V) adsorption following As(III) oxidation to As(V) in solution and As(III) adsorption preceding its conversion to As(V) in solid phase were observed at pHini 5.0-9.0. The application of WMF accelerated the transformation of As(III) to As(V) in both aqueous and solid phases at pHini 5.0-9.0 and enhanced the oxidation of As(III) to As(V) in solution at pHini 3.0.