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A A Maksimova, M I Oshtrakh, A V Chukin, I Felner, G A Yakovlev, V A Semionkin
Northwest Africa (NWA) 6286 and 7857 meteorites were studied in detail by using optical microscopy, scanning electron microscopy with energy dispersion spectroscopy, X-ray diffraction, magnetization measurements and (57)Fe Mössbauer spectroscopy with a high velocity resolution. The main and the minor iron-bearing phases were identified in both meteorites. The unit cell parameters as well as Fe(2+) and Mg(2+) cation distribution were determined for the M1 and M2 sites in silicate microcrystals. Saturation magnetic moments were obtained for both meteorites...
October 25, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Isao Kagomiya, Yuki Hirota, Ken-Ichi Kakimoto, Kotaro Fujii, Masahiro Shiraiwa, Masatomo Yashima, Akio Fuwa, Shin Nakamura
Brownmillerite Ca2Fe2O5 (CFO) exhibits a magnetic transition at TN ∼ 730 K. Many studies have reported the magnetic properties of CFO. However, the magnetic structure of CFO is still debated, i.e., whether the magnetic ordering is purely antiferromagnetic or weakly ferromagnetic, which originated from canted magnetic moments. In addition, the reason for the CFO showing large magnetoresistance is still unclear. This study attempts to address the unresolved issues stated above by multiple investigations on the crystal structure, magnetization, and Mössbauer parameters...
November 15, 2017: Physical Chemistry Chemical Physics: PCCP
Federico Spizzo, Paolo Sgarbossa, Elisabetta Sieni, Alessandra Semenzato, Fabrizio Dughiero, Michele Forzan, Roberta Bertani, Lucia Del Bianco
Ferrofluids are nanomaterials consisting of magnetic nanoparticles that are dispersed in a carrier fluid. Their physical properties, and hence their field of application are determined by intertwined compositional, structural, and magnetic characteristics, including interparticle magnetic interactions. Magnetic nanoparticles were prepared by thermal decomposition of iron(III) chloride hexahydrate (FeCl₃·6H₂O) in 2-pyrrolidone, and were then dispersed in two different fluids, water and polyethylene glycol 400 (PEG)...
November 5, 2017: Nanomaterials
Sergey Antipov, Sergey Turishchev, Yuriy Purtov, Uliana Shvyreva, Alexander Sinelnikov, Yuriy Semov, Elena Preobrazhenskaya, Andrey Berezhnoy, Natalia Shusharina, Natalia Novolokina, Viktor Vakhtel, Valeriy Artyukhov, Olga Ozoline
The Dps protein of Escherichia coli, which combines ferroxidase activity and the ability to bind DNA, is effectively used by bacteria to protect their genomes from damage. Both activities depend on the integrity of this multi-subunit protein, which has an inner cavity for iron oxides; however, the diversity of its oligomeric forms has only been studied fragmentarily. Here, we show that iron ions stabilize the dodecameric form of Dps. This was found by electrophoretic fractionation and size exclusion chromatography, which revealed several oligomers in highly purified protein samples and demonstrated their conversion to dodecamers in the presence of 1 mM Mohr's salt...
November 5, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Uttam K Das, Stephanie L Daifuku, Theresa E Iannuzzi, Serge I Gorelsky, Ilia Korobkov, Bulat Gabidullin, Michael L Neidig, R Tom Baker
We report an easily prepared bis(thioether) amine ligand, S(Me)N(H)S(Me), along with the synthesis, characterization, and reactivity of the paramagnetic iron(II) bis(amido) complex, [Fe(κ(3)-S(Me)NS(Me))2] (1). Binding of the two different thioethers to Fe generates both five- and six-membered rings with Fe-S bonds in the five-membered rings (av 2.54 Å) being significantly shorter than those in the six-membered rings (av 2.71 Å), suggesting hemilability of the latter thioethers. Consistent with this hypothesis, magnetic circular dichroism (MCD) and computational (TD-DFT) studies indicate that 1 in solution contains a five-coordinate component [Fe(κ(3)-S(Me)NS(Me))(κ(2)-S(Me)NS(Me))] (2)...
November 7, 2017: Inorganic Chemistry
Alexander V Polezhaev, Cameron J Liss, Joshua Telser, Chun-Hsing Chen, Kenneth G Caulton
Reaction of the unsymmetrically-armed pincer PNNH (phosphine, pyridyl, pyrazole) with FeCl2 yields a five coordinate monomer (PNNH)FeCl2, whose NH proton hydrogen bonds to capture THF. Deprotonation of this NH functionality with Li[N(SiMe3)2] does not give four coordinate (PNN)FeCl, but instead retains LiCl to yield (PNNLi)FeCl2, where Li bridges between the pyrazolate beta nitrogen and one chloride on Fe. One electron reduction of this compound under CO occurs with loss of LiCl to form square pyramidal monovalent iron in (PNN)Fe(CO)2, which is characterized by IR, Mössbauer, X-ray diffraction, EPR measurements and DFT calculations...
November 3, 2017: Chemistry: a European Journal
I V Alenkina, A Kumar, A L Berkovsky, M I Oshtrakh
A comparative study of tetrameric rabbit hemoglobin and monomeric soybean leghemoglobin a in the oxy- and deoxy-forms was carried out using (57)Fe Mössbauer spectroscopy with a high velocity resolution in order to analyze the heme iron electronic structure and stereochemistry in relation to the Mössbauer hyperfine parameters. The Mössbauer spectra of tetrameric rabbit hemoglobin in both forms were fitted using two quadrupole doublets related to the (57)Fe in ɑ- and β-subunits. In contrast, the Mössbauer spectra of monomeric soybean leghemoglobin a were fitted using: (i) two quadrupole doublets for the oxy-form related to two conformational states of the distal His E7 imidazole ring and different hydrogen bonding of oxygen molecule in the oxy-form and (ii) using three quadrupole doublets for deoxy-form related to three conformational states of the proximal His F8 imidazole ring...
October 25, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Sivaraj Ramasamy, Beniya Samathanam, Helfried Reuther, Muthukumar Nadar Meenakshi Subbaraman Adyanpuram, Israel Vijayaraj Muthu Vijayan Enoch, Kay Potzger
Magnetic nanoparticles (MNPs) are intriguing due to their potency to deliver anti-cancer drugs. This paper presents the inference from our experimental attempts to add merit to the concept of magnetic drug carrier, by designing calcium ferrite nanoparticles and coating them with a biocompatible dextran tethered with a hydrophobic cavity-containing molecule, β-cyclodextrin (β-CD). The size, crystal system, and the morphology of the MNPs are studied. The magnetic properties are explored using vibrating sample magnetometry, SQUID and Mössbauer spectroscopy...
October 18, 2017: Colloids and Surfaces. B, Biointerfaces
Diming Xu, Maxim Avdeev, Peter D Battle, D H Ryan
Polycrystalline samples of Ln2CoGe4O12 (Ln = Gd, Tb, Dy, Ho or Er) and LnBCoGe4O12 (B = Sc or Lu) have been prepared and characterised by a combination of magnetometry, (155)Gd Mössbauer spectroscopy and, in the case of Tb2CoGe4O12 and TbScCoGe4O12, neutron diffraction. The holmium- and erbium-containing compositions remain paramagnetic down to 2 K, those containing dysprosium behave as spin glasses and the terbium and gadolinium-containing compounds show long-range magnetic order with transition temperatures below 4 K in all cases...
November 21, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
F Caporaletti, A I Chumakov, R Rüffer, G Monaco
Time-domain interferometry (TDI) based on nuclear resonant scattering of synchrotron radiation by Mössbauer nuclei is a promising technique to study slow dynamics at the interatomic length scale. In order to improve the efficiency of this technique, a new TDI scheme is developed involving the use of a nuclear absorber with a two-line energy spectrum combined with a single-line spectrum. Different from other TDI setups, the issue of external vibrations is much reduced since the two absorbers are at rest and no velocity transducer is used...
October 2017: Review of Scientific Instruments
Dominic H Ryan, J M Cadogan, Vasily Krylov, Anaëlle Legros, Rasa Rejali, Chad Boyer
We have determined the magnetic structures of GdCuSn, GdAgSn and GdAuSn using a combination of <sup>155</sup>Gd Mössbauer spectroscopy and neutron powder diffraction. Each compound shows the same antiferromagnetic ordering of the Gd sublattice. The magnetic cell is doubled along the crystallographic <i>a</i>-axis (propagation vector <b>k</b>=[1/2,0,0]$) with the moments aligned along the hexagonal <i>c</i>-axis, forming alternating ferromagnetic sheets of up/down Gd moments along the <i>a</i>-axis...
November 1, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Salman Seyedi, Dmitry V Matyushov
We present a model of the dynamical transition of atomic displacements in proteins. Increased mean-square displacement at higher temperatures is caused by the softening of the force constant for atomic/molecular displacements by electrostatic and van der Waals forces from the protein-water thermal bath. Displacement softening passes through a nonergodic dynamical transition when the relaxation time of the force-force correlation function enters, with increasing temperature, the instrumental observation window...
November 15, 2017: Soft Matter
Kyoko Yarimizu, Ricardo Cruz-López, Hendrik Auerbach, Larissa Heimann, Volker Schünemann, Carl J Carrano
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...
October 24, 2017: Biometals: An International Journal on the Role of Metal Ions in Biology, Biochemistry, and Medicine
Ventrapati Pavan Kumar, Laura Paradis-Fortin, Pierric Lemoine, Vincent Caignaert, Bernard Raveau, Bernard Malaman, Gérard Le Caër, Stéphane Cordier, Emmanuel Guilmeau
This study shows that the design of copper-rich sulfides by mimicking natural minerals allows a new germanite-type sulfide Cu22Fe8Ge4S32 with promising thermoelectric properties to be synthesized. The Mössbauer spectroscopy and X-ray diffraction analyses provide evidence that the structure of our synthetic compound differs from that of the natural germanite mineral Cu26Fe4Ge4S32 by its much higher Cu(+)/Cu(2+) ratio and different cationic occupancies. The coupled substitution Cu/Fe in the Cu26-xFe4+xGe4S32 series also appears as a promising approach to optimize the thermoelectric properties...
November 6, 2017: Inorganic Chemistry
Sameh K Elsaidi, Michael A Sinnwell, Debasis Banerjee, Arun Devaraj, Ravi K Kukkadapu, Timothy C Droubay, Zimin Nie, Libor Kovarik, Murugesan Vijayakumar, Sandeep Manandhar, Manjula Nandasiri, B Peter McGrail, Praveen K Thallapally
The magnetic susceptibility of synthesized magnetite (Fe3O4) microspheres was found to decline after the growth of a metal-organic framework (MOF) shell on the magnetite core. Detailed structural analysis of the core-shell particles using scanning electron microscopy, transmission electron microscopy, atom probe tomography, and(57)Fe-Mössbauer spectroscopy suggests that the distribution of MOF precursors inside the magnetic core resulted in the oxidation of the iron oxide core.
October 24, 2017: Nano Letters
Maksym Moskvin, Michal Babič, Salette Reis, M Margarida Cruz, Liliana P Ferreira, Maria Deus Carvalho, Sofia A Costa Lima, Daniel Horák
Magnetic nanoparticles offer multiple possibilities for biomedical applications. Besides their physico-chemical properties, nanoparticle-cellular interactions are determinant for biological safety. In this work, magnetic nanoparticles were synthesized by one-shot precipitation or two-step reaction and coated with biocompatible polymers, such as poly(l-lysine) and poly(N,N-dimethylacrylamide-co-acrylic acid), and carbohydrates, like l-ascorbic acid, d-galactose, d-mannose, and sucrose. The resulting magnetic nanoparticles were characterized by dynamic light scattering, FT-Raman spectroscopy, transmission electron microscopy, SQUID magnetometry, and Mössbauer spectroscopy...
October 12, 2017: Colloids and Surfaces. B, Biointerfaces
X Li, L Lachmanski, S Safi, S Sene, C Serre, J M Grenèche, J Zhang, R Gref
A versatile method based on Raman microscopy was developed to follow the degradation of iron carboxylate Metal Organic Framework (MOF) nano- or micro-particles in simulated body fluid (phosphate buffer). The analysis of both the morphology and chemical composition of individual particles, including observation at different regions on the same particle, evidenced the formation of a sharp erosion front during particle degradation. Interestingly, this front separated an intact non eroded crystalline core from an amorphous shell made of an inorganic network...
October 13, 2017: Scientific Reports
Max Mörtel, Alexander Witt, Frank W Heinemann, Sebastian Bochmann, Julien Bachmann, Marat M Khusniyarov
Spin-crossover molecular switches [Fe(II)(H2B(pz)2)2L] (L = novel phenanthroline-based ligands featuring photochromic diarylethene units; pz = 1-pyrazolyl) were synthesized and thoroughly characterized by variable-temperature X-ray crystallography, Mössbauer spectroscopy, and magnetic measurements. The effect of substituents introduced into the phenanthroline backbone (L2) and into the photochromic diarylethene unit (L3) on photophysical properties of metal-free ligands and spin-crossover iron(II) complexes 2 and 3, respectively, were investigated in detail...
November 6, 2017: Inorganic Chemistry
Nibedita Das, Satyendra Singh, Amish G Joshi, Meganathan Thirumal, V Raghavendra Reddy, Laxmi Chand Gupta, Ashok Kumar Ganguli
We synthesized double perovskite Pr2FeCrO6 by solid-state method. Analysis of its X-ray powder diffraction shows that the compound crystallizes in a centrosymmetric structure with space group Pbnm. Our X-ray photoelectron spectroscopy (XPS) studies show that all the cations are present in +3 oxidation state. Magnetization studies of Pr2FeCrO6 show that the material is paramagnetic at room temperature and undergoes a magnetic transition below TCM = 250 K. We observe clear magnetic hysteresis loop, for example, below 150 K...
November 6, 2017: Inorganic Chemistry
Zhen Yao, Charles E Schulz, Nana Zhan, Jianfeng Li
A new sterically hindered "picket fence-like" porphyrin with chelates for the second metal atom, H2TImPP (TImPP = meso-tetrakis[α,α,α,α-o-(5-imidazolecarboxylaminophenyl)]porphyrinato), is developed and used in the synthesis of four iron(II) bis(imidazole) derivatives, which are characterized by single crystal X-ray and other spectroscopies. The comprehensive studies on the crystal structures revealed noteworthy features including new axial ligand arrangements, deformed porphyrin planes, and strongly tilted pickets which can be rationalized by analysis of the intra- and intermolecular interactions...
October 5, 2017: Inorganic Chemistry
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