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J W González, T Alonso-Lanza, F Delgado, F Aguilera-Granja, A Ayuela
Organometallic clusters based on transition metal atoms are interesting because of their possible applications in spintronics and quantum information processing. In addition to the enhanced magnetism at the nanoscale, the organic ligands may provide a natural shield against unwanted magnetic interactions with the matrices required for applications. Here we show that the organic ligands may lead to non-collinear magnetic order as well as the expected quenching of the magnetic moments. We use different density functional theory (DFT) methods to study the experimentally relevant three cobalt atoms surrounded by benzene rings (Co3Bz3)...
May 26, 2017: Physical Chemistry Chemical Physics: PCCP
Eduardo Mendive-Tapia, Julie B Staunton
We describe a disordered local moment theory for long-period magnetic phases and investigate the temperature and magnetic field dependence of the magnetic states in the heavy rare earth elements (HREs), namely, paramagnetic, conical and helical antiferromagnetic (HAFM), fan, and ferromagnetic (FM) states. We obtain a generic HRE magnetic phase diagram which is consequent on the response of the common HRE valence electronic structure to f-electron magnetic moment ordering. The theory directly links the first-order HAFM-FM transition to the loss of Fermi surface nesting, induced by this magnetic ordering, as well as provides a template for analyzing the other phases and exposing where f-electron correlation effects are particularly intricate...
May 12, 2017: Physical Review Letters
Qi Chen, Di Li, Jianhan Lin, Mao-Hua Wang, Xiangchun Xuan
Magnetic fluids (e.g., paramagnetic solutions and ferrofluids) have been increasingly used for label-free separation of non-magnetic particles in microfluidic devices. Their biocompatibility, however, becomes a concern in high-throughput or large-volume applications. One way to potentially resolve this issue is re-suspending the particles that are separated in a magnetic fluid immediately into a biocompatible buffer. We demonstrate herein the proof-of-principle of the first integration of negative magnetophoresis and inertial focusing for a simultaneous separation and washing of non-magnetic particles in co-flowing ferrofluid and water streams...
May 26, 2017: Analytical Chemistry
Li-Na Wu, Shao-Yi Wu, Li-Juan Zhang, Xu-Sheng Liu, Li Peng
The copper electron paramagnetic resonance (EPR) gyromagnetic factors are theoretically studied for three novel Cu(2+) coordination polymers [Cu(XL)(NO3 )2 ]n (1), {[Cu(XL)(4,4'-bpy)(NO3 )2 ]•CH3 CN}n (1a) and {[Cu(XL)3 ](NO3 )2 •3.5H2 O}n (2) with bi-triazole ligand (XL)=N,N'-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxdiimide bi(1,2,4-triazole) from the high order perturbation calculations of the g factors for a rhombically elongated octahedral 3d(9) group. The order (1 ≤ 1a < 2) of gz can be illustrated by the dominant second-order perturbation term roughly proportional to the square of the covalency factor N...
May 25, 2017: Magnetic Resonance in Chemistry: MRC
Ariel R Levy, Meital Turgeman, Lada Gevorkyan-Aiapetov, Sharon Ruthstein
Metallochaperones are responsible for shuttling metal ions to target proteins. Thus, a metallochaperone's structure must be sufficiently flexible both to hold onto its ion while traversing the cytoplasm and to transfer the ion to or from a partner protein. Here, we sought to shed light on the structure of Atox1, a metallochaperone involved in the human copper regulation system. Atox1 shuttles copper ions from the main copper transporter, Ctr1, to the ATP7b transporter in the Golgi apparatus. Conventional biophysical tools such as X-ray or NMR cannot always target the various conformational states of metallochaperones, owing to a requirement for crystallography or low sensitivity and resolution...
May 20, 2017: Protein Science: a Publication of the Protein Society
Alexander A Pavlov, Svetlana A Savkina, Alexander S Belov, Yulia V Nelyubina, Nikolay N Efimov, Yan Z Voloshin, Valentin V Novikov
High magnetic anisotropy is a key property of paramagnetic shift tags, which are mostly studied by NMR spectroscopy, and of single molecule magnets, for which magnetometry is usually used. We successfully employed both these methods in analyzing magnetic properties of a series of transition metal complexes, the so-called clathrochelates. A cobalt complex was found to be both a promising paramagnetic shift tag and a single molecule magnet because of it having large axial magnetic susceptibility tensor anisotropy at room temperature (22...
May 25, 2017: Inorganic Chemistry
Jesús Vega-Castillo, Gaëtan Buvat, Gwenaël Corbel, Abdelhadi Kassiba, Philippe Lacorre, Alberto Caneiro
The amorphous reduction product of the oxide ion conductor La2Mo2O9 was previously shown to be a good, sulphur-tolerant, anode material for solid oxide fuel cell devices (X. C. Lu, J. H. Zhu, J. Electrochem. Soc., 2008, 155(10), B1053). In this paper, we study the local order of amorphous La2Mo2O6.7 using X-ray absorption spectroscopy analyses and electronic paramagnetic resonance. The extended X-ray absorption fine structure analysis of local arrangements around Mo in La2Mo2O6.7 is first carried out on the basis of strong distortions from three crystalline models of La2Mo2O9, La7Mo7O30 and La2Mo2O7...
May 25, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
S S Gupta, M A van Huis
A detailed understanding of the water-semiconductor interface is of major importance for elucidating the molecular interactions at the photocatalyst's surface. Here, we studied the effect of vacancy defects on the adsorption of a water molecule on the (101̅0) and (112̅0) CdS surfaces, using spin-polarized density functional theory. We observed that the local spin polarization did not persist for most of the cationic vacancies on the surfaces, unlike in bulk, owing to surface reconstructions caused by displaced S atoms...
May 11, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Andrey A Kuzhelev, Victor M Tormyshev, Olga Yu Rogozhnikova, Dmitry V Trukhin, Tatiana I Troitskaya, Rodion K Strizhakov, Olesya A Krumkacheva, Matvey V Fedin, Elena G Bagryanskaya
Triarylmethyl (TAM) radicals are widely used in Electron Paramagnetic Resonance (EPR) spectroscopy as spin labels and in EPR imaging as spin probes for in vivo oxymetry. One of the key advantages of TAMs is extremely narrow EPR line, especially in case of deuterated analogues (~5 μT). Another advantage is their slow spin relaxation even at physiological temperatures allowing, in particular, application of pulsed dipolar EPR methods for distance measurements in biomolecules. In this paper a large series of TAM radicals and their deuterated analogues is synthesized, and corresponding spectroscopic parameters including (13)C hyperfine constants are obtained for the first time...
April 2017: Zeitschrift Für Physikalische Chemie
Xiaoquan Zhu, Shaodong Su, Wenhai Cao, Yuehong Wen, Shengmin Hu, Xintao Wu, Tianlu Sheng
A new one-dimensional cyanide-bridged complex [Mn(III)(salphen)Ru(II)(DMAP)4(CN)2](PF6) (1) and its oxidized derivative [Mn(III)(salphen)Ru(III)(DMAP)4(CN)2](PF6)2 (2) have been synthesized and fully characterized. Magnetic measurements showed that 1 shows simple paramagnetism but 2 shows intrachain ferromagnetic interaction with slow magnetic relaxation.
May 24, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Chaoqun Qiu, Zhangzhen He, Meiyan Cui, Sihuai Chen
Two fluorophosphates, BaMPO4F (M = Cu, Co), have been synthesized by a conventional hydrothermal method, and they crystallize in the orthorhombic system with the space group P212121, exhibiting a tunnel structure built by distorted MO4F square-pyramids and PO4 tetrahedra. The magnetic behaviors of the two compounds are investigated by means of magnetic susceptibility, magnetization, and heat capacity measurements. The results indicate that BaCuPO4F exhibits a paramagnetic behavior down to 2 K, while BaCoPO4F undergoes long-range antiferromagnetic ordering at 11...
May 24, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Alasdair Formanuik, Ana-Maria Ariciu, Fabrizio Ortu, Reece Beekmeyer, Andrew Kerridge, Floriana Tuna, Eric J L McInnes, David P Mills
Our knowledge of actinide chemical bonds lags far behind our understanding of the bonding regimes of any other series of elements. This is a major issue given the technological as well as fundamental importance of f-block elements. Some key chemical differences between actinides and lanthanides-and between different actinides-can be ascribed to minor differences in covalency, that is, the degree to which electrons are shared between the f-block element and coordinated ligands. Yet there are almost no direct measures of such covalency for actinides...
June 2017: Nature Chemistry
Andrea Bertarello, Tobias Schubeis, Carmelo Fuccio, Enrico Ravera, Marco Fragai, Giacomo Parigi, Lyndon Emsley, Guido Pintacuda, Claudio Luchinat
We present the first solid-state NMR study of an iron-sulfur protein. The combined use of very fast (60 kHz) magic-angle spinning and tailored radiofrequency irradiation schemes allows the detection and the assignment of most of the (1)H and (13)C resonances of the oxidized high-potential iron-sulfur protein I from Ectothiorhodospira halophila (EhHiPIP I), including those in residues coordinating the Fe4S4 cluster. For these residues, contact shifts as large as 100 and 400 ppm for (1)H and (13)C resonances, respectively, were observed, which represent the most shifted solid-state NMR signals ever measured in metalloproteins...
May 24, 2017: Inorganic Chemistry
Ruiting Zhang, Ying Zhou, Chang Liu, Meixia Zhang, Shenqiang Yan, David S Liebeskind, Min Lou
BACKGROUND AND PURPOSE: The extent of blooming artifact may reflect the amount of paramagnetic material. We thus assessed the overestimation ratio of susceptibility vessel sign (SVS) on susceptibility-weighted imaging, defined as the extent of SVS width beyond the lumen and examined its value for predicting the stroke cause in acute ischemic stroke patients. METHODS: We included consecutive acute ischemic stroke patients with proximal large artery occlusion who underwent both susceptibility-weighted imaging and time-of-flight magnetic resonance angiography within 8 hours poststroke onset...
May 23, 2017: Stroke; a Journal of Cerebral Circulation
Dominic Barthelmes, Katja Barthelmes, Kai Schnorr, Hendrik R A Jonker, Bianca Bodmer, Karen N Allen, Barbara Imperiali, Harald Schwalbe
Encodable lanthanide binding tags (LBTs) have become an attractive tool in modern structural biology as they can be expressed as fusion proteins of targets of choice. Previously, we have demonstrated the feasibility of inserting encodable LBTs into loop positions of interleukin-1β (Barthelmes et al. in J Am Chem Soc 133:808-819, 2011). Here, we investigate the differences in fast dynamics of selected loop-LBT interleukin-1β constructs by measuring (15)N nuclear spin relaxation experiments. We show that the loop-LBT does not significantly alter the dynamic motions of the host protein in the sub-τc-timescale and that the loop-LBT adopts a rigid conformation with significantly reduced dynamics compared to the terminally attached encodable LBT leading to increased paramagnetic alignment strength...
May 22, 2017: Journal of Biomolecular NMR
Chunming Yang, Guimei Gao, Junjun Zhang, Ruiping Liu, Ruicheng Fan, Ming Zhao, Yongwang Wang, Shucai Gan
A CdWO4/Bi2O2CO3 core-shell heterostructure photocatalyst was fabricated via a facile two-step hydrothermal process. Flower-like Bi2O2CO3 was synthesized and functioned as the cores on which CdWO4 nanorods were coated as the shells. Photoluminescence (PL) spectra and electron paramagnetic resonance (EPR) demonstrate that the CdWO4/Bi2O2CO3 core-shell heterostructure photocatalyst possesses a large amount of oxygen vacancies, which induce defect levels in the band gap and help to broaden light absorption. The photocatalyst exhibits enhanced photocatalytic activity for Rhodamine B (RhB), methylene blue (MB), methyl orange (MO), and colorless contaminant phenol degradation under solar light irradiation...
May 22, 2017: Physical Chemistry Chemical Physics: PCCP
Balázs Bognár, Muthulakshmi Kuppusamy, Esha Madan, Tamás Kálai, Mária Balog, József Jekő, Periannan Kuppusamy, Kálmán Hideg
BACKGROUND: Natural products and their derivatives are widely used to treat cancer and other diseases associated with ROS- and RNS-induced damages. METHODS: A series of paramagnetic modified curcumin analogues and 3,5-diarylidene-piperidones (DAP) have been designed, synthesized, and characterized on their anti-proliferative and antioxidant activity. RESULTS: Biological characterization of the new compounds supported the earlier results that incorporation of a nitroxide moiety or its precursor into curcumin or diarylidenylpiperidone (DAP) scaffolds resulted in anti-proliferative effect toward cancerous cell-lines in case of aryl hydroxy and/or methoxy substituent containing derivatives suggesting their potential for targeted therapeutic applications...
May 22, 2017: Medicinal Chemistry
Joanna Palion-Gazda, Barbara Machura, Rafal Kruszynski, Thais Grancha, Nicolás Moliner, Francesc Lloret, Miguel Julve
The preparation and spectroscopic and structural characterization of three cobalt(II) complexes of formulas [Co(tppz)2](dca)2 (1), [Co(tppz)2][Co(NCS)4]·MeOH (2), and [Co(tppz)2][Co(NCO)4]·2H2O (3) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and dca = dicyanamide] are reported here. Compounds 1-3 have in common the presence of the cationic [Co(tppz)2](2+) entity where each mer-tridentate tppz ligand coordinates to the cobalt(II) ion equatorially through two pyridyl donors and axially via the pyrazine, completing the six-coordination...
May 22, 2017: Inorganic Chemistry
Jan Girovsky, Jan Nowakowski, Md Ehesan Ali, Milos Baljozovic, Harald R Rossmann, Thomas Nijs, Elise A Aeby, Sylwia Nowakowska, Dorota Siewert, Gitika Srivastava, Christian Wäckerlin, Jan Dreiser, Silvio Decurtins, Shi-Xia Liu, Peter M Oppeneer, Thomas A Jung, Nirmalya Ballav
Realization of long-range magnetic order in surface-supported two-dimensional systems has been challenging, mainly due to the competition between fundamental magnetic interactions as the short-range Kondo effect and spin-stabilizing magnetic exchange interactions. Spin-bearing molecules on conducting substrates represent a rich platform to investigate the interplay of these fundamental magnetic interactions. Here we demonstrate the direct observation of long-range ferrimagnetic order emerging in a two-dimensional supramolecular Kondo lattice...
May 22, 2017: Nature Communications
Mirjam Gosenca Matjaž, Janez Mravljak, Marija Bešter Rogač, Marjeta Šentjurc, Mirjana Gašperlin, Alenka Zvonar Pobirk
Insight into the microstructure of lyotropic liquid crystals (LCs) is of crucial importance for development of novel dermal delivery systems. Our aim was to evaluate the phase behaviour of dermally applicable LCs composed of isopropyl myristate/Tween 80/lecithin/water, along the dilution line, where phase transitions are predominantly driven by increased water content. Additionally, identification of LC temperature dependence is of great importance for skin application. Selected LCs were evaluated using electron paramagnetic resonance (EPR) plus conventionally used methods of polarization microscopy, small-angle X-ray scattering, differential scanning calorimetry, and rheological measurements...
May 18, 2017: International Journal of Pharmaceutics
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