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Zhou Gong, Charles D Schwieters, Chun Tang
Paramagnetic relaxation enhancement (PRE) has been established as a powerful tool in NMR for investigating protein structure and dynamics. The PRE is usually measured with a paramagnetic probe covalently attached at a specific site of an otherwise diamagnetic protein. The present work provides the numerical formulation for probing protein structure and conformational dynamics based on the solvent PRE (sPRE) measurement, using two alternative approaches. An inert paramagnetic cosolute randomly collides with the protein, and the resulting sPRE manifests the relative solvent exposure of protein nuclei...
April 12, 2018: Methods: a Companion to Methods in Enzymology
Agnieszka Sobianowska-Turek
The utilization of the stream of waste secondary nickel-metal hydride (Ni-MH) and lithium-ion (Li-ion) cells, representing annually about 33% of all consumer batteries and accumulators placed on the Polish market, will soon become a big challenge for both legislators and plants dealing with the recycling of this type of hazardous waste. It is due to the fact that no company in Poland operating on the market has a complete technology for the processing of a full stream of waste chemical energy sources produced in this country...
April 11, 2018: Waste Management
Jan Tarabek, Jin Wen, Paul I Dron, Lubomir Pospisil, Josef Michl
We report the electron paramagnetic resonance spectra of the radical cation and radical anion of 1,2,2,3-tetramethyl-2,3-dihydro-1H-naphtho[2,3-d]imidazole-4,9-dione (1) and its doubly 13C labeled analog 2, of interest for singlet fission. The hyperfine coupling constants are in excellent agreement with density functional theory calculations and establish the structures beyond doubt. Unlike the radical cation 1∙+, the radical anion 1∙- and its parent 1 have pyramidalized nitrogen atoms and inequivalent methyl groups 15 and 16, in agreement with the calculations...
April 13, 2018: Journal of Organic Chemistry
Lan-Zhen Peng, Pei Liu, Qing-Qing Cheng, Wen-Jing Hu, Yahu A Liu, Jiu-Sheng Li, Biao Jiang, Xue-Shun Jia, Hui Yang, Ke Wen
Direct electrosynthesis of hydrogen peroxide (H2O2) by oxygen reduction is a green and safe strategy to replace the traditional anthraquinone process. Herein, we have designed a two-dimensional redox-active cationic covalent triazine network to be used directly as a cost-effective metal-free electrocatalyst for the oxygen reduction reaction (ORR) to form H2O2. Such a dicationic 2D polymer possesses a porous structure with pore diameters of 2-10 nm and a total N content of 13.3 wt%. The electron paramagnetic resonance experiment confirms the reduction of a viologen-based polymer to radical cations and the subsequent generation of superoxygen radicals...
April 13, 2018: Chemical Communications: Chem Comm
Yu Liu, Erik Holmstrom, Ping Yu, Kemin Tan, Xiaobing Zuo, David J Nesbitt, Rui Sousa, Jason R Stagno, Yun-Xing Wang
Site-specific incorporation of labeled nucleotides is an extremely useful synthetic tool for many structural studies (e.g., NMR, electron paramagnetic resonance (EPR), fluorescence resonance energy transfer (FRET), and X-ray crystallography) of RNA. However, specific-position-labeled RNAs >60 nt are not commercially available on a milligram scale. Position-selective labeling of RNA (PLOR) has been applied to prepare large RNAs labeled at desired positions, and all the required reagents are commercially available...
May 2018: Nature Protocols
Johannes J Wittmann, Michael Eckardt, Wolfgang Harneit, Björn Corzilius
Dynamic nuclear polarization (DNP) can be applied to enhance the sensitivity of solid-state NMR experiments by several orders of magnitude due to microwave-driven transfer of spin polarization from unpaired electrons to nuclei. While the underlying quantum mechanical aspects are sufficiently well understood on a microscopic level, the exact description of the large-scale spin dynamics, usually involving hundreds to thousands of nuclear spins per electron, is still lacking consensus. Generally, it is assumed that nuclear hyperpolarization can only be observed on nuclei which do not experience strong influence of the unpaired electrons and thus being significantly removed from the paramagnetic polarizing agents...
April 12, 2018: Physical Chemistry Chemical Physics: PCCP
Shuying Nong, Wujie Dong, Junwen Yin, Bowei Dong, Yue Lu, Xiaotao Yuan, Xin Wang, Kejun Bu, Mingyang Chen, Shangda Jiang, Li-Min Liu, Manling Sui, Fuqiang Huang
TiO2 mesoporous crystal has been prepared by one-step corroding process via an oriented attachment (OA) mechanism with SrTiO3 as precursor. High resolution transmission electron microscopy (HRTEM) and nitrogen adsorption-desorption isotherms confirm its mesoporous crystal structure. Well-dispersed ruthenium (Ru) in the mesoporous nanocrystal TiO2 can be attained by the same process using Ru-doped precursor SrTi1-x Rux O3 . Ru is doped into lattice of TiO2 , which is identified by HRTEM and super energy dispersive spectrometer (super-EDS) elemental mapping...
April 12, 2018: Journal of the American Chemical Society
Chang-Chun Ding, Shao-Yi Wu, Yong-Qiang Xu, Li-Juan Zhang
The local angular distortions Δθ are theoretically studied for the various Ni3+ centers in LiAly Co1-y O2 at different Al concentration y (= 0, 0.1, 0.5 and 0.8) based on the perturbation calculations of electron paramagnetic resonance (EPR) g factors for a trigonally distorted octahedral 3d7 cluster with low spin (S=1/2). Due to the Jahn-Teller effect, the [NiO6 ]9- clusters are found to experience the local angular distortions Δθ (≈ 5 - 9°) along the C3 axis. The variation trend of Δθ with y is in accordance with that of anisotropy Δg (= g// - g⊥ )...
April 12, 2018: Magnetic Resonance in Chemistry: MRC
Shrikant A Mohitkar, Jürgen Nuss, Henning A Höppe, Claudia Felser, Martin Jansen
New Sr5Os3O13, as synthesized from binary constituents, exhibits several uncommon features. Its crystal structure is dominated by quasi-2D poly-oxoanions that correspond to unprecedented cutouts of the perovskite type of structure, where corner sharing (OsO6) octahedra aggregate to form terraced slabs. The Os5+/Os6+ mixed valence oxide displays a particular charge ordering scheme. One osmium atom (Os1) per formula unit is in the valence state of 5+ in the whole temperature range studied, while the two remaining sites (Os2A and Os2B) show full charge disorder at high temperatures, resulting in an average charge of 5...
April 12, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
David Sulzer, Clifford Cassidy, Guillermo Horga, Un Jung Kang, Stanley Fahn, Luigi Casella, Gianni Pezzoli, Jason Langley, Xiaoping P Hu, Fabio A Zucca, Ioannis U Isaias, Luigi Zecca
The diagnosis of Parkinson's disease (PD) occurs after pathogenesis is advanced and many substantia nigra (SN) dopamine neurons have already died. Now that therapies to block this neuronal loss are under development, it is imperative that the disease be diagnosed at earlier stages and that the response to therapies is monitored. Recent studies suggest this can be accomplished by magnetic resonance imaging (MRI) detection of neuromelanin (NM), the characteristic pigment of SN dopaminergic, and locus coeruleus (LC) noradrenergic neurons...
2018: NPJ Parkinson's Disease
H Wang, X Y Qin, Z Y Li, Z Z Zheng, T Y Fan
OBJECTIVE: To prepare and characterize citric acid (CA)-modified super paramagnetic iron oxide nanoparticles (SPIONs) for magnetic targeting, hyperthermia and magnetic resonance imaging (MRI). METHODS: CA-modified SPIONs (CA-SPIONs) were prepared by co-precipitation method and then the magnetic responsiveness, morphology, particle size, infrared feature, weight percentage of CA, magnetic property and X-ray diffraction pattern of CA-SPIONs were respectively characterized by magnet, transmission electron microscope, laser particle size analyzer, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry-differential thermal analyzer, vibrating sample magnetometer and X-ray diffractometer (XRD)...
April 18, 2018: Beijing da Xue Xue Bao. Yi Xue Ban, Journal of Peking University. Health Sciences
Ji-Jing Guan, Yan-Qiu Feng
OBJECTIVE: To evaluate the accuracy and sensitivity of quantitative susceptibility mapping (QSM) and transverse relaxation rate (R2*) mapping in the measurement of brain iron deposition. METHODS: Super paramagnetic iron oxide (SPIO) phantoms and mouse models of Parkinson's disease (PD) related to iron deposition in the substantia nigra (SN) underwent 7.0 T magnetic resonance (MR) scans (Bruker, 70/16) with a multi-echo 3D gradient echo sequence, and the acquired data were processed to obtain QSM and R2*...
March 20, 2018: Nan Fang Yi Ke da Xue Xue Bao, Journal of Southern Medical University
Georgia Prokopiou, Michael D Lee, Alberto Collauto, Elwy H Abdelkader, Thorsten Bahrenberg, Akiva Feintuch, Marie Ramirez-Cohen, Jessica Clayton, James D Swarbrick, Bim Graham, Gottfried Otting, Daniella Goldfarb
The C7-Gd and C8-Gd tags are compact hydrophilic cyclen-based lanthanide tags for conjugation to cysteine residues in proteins. The tags are enantiomers, which differ in the configuration of the 2-hydroxylpropyl pendant arms coordinating the lanthanide ion. Here, we report the electron paramagnetic resonance (EPR) performance of the C7-Gd ( S configuration) and C8-Gd ( R configuration) tags loaded with Gd(III) on two mutants of the homodimeric ERp29 protein. The W-band EPR spectra were found to differ between the tags in the free state and after conjugation to the protein...
April 9, 2018: Inorganic Chemistry
A Giannoulis, K Ackermann, P E Spindler, C Higgins, D B Cordes, A M Z Slawin, T F Prisner, B E Bode
Fundamentally, the stability of coordination complexes and of templated (bio)macromolecular assemblies depends on the thermodynamic and kinetic properties of the intermediates and final complexes formed. Here, we used pulse EPR (electron paramagnetic resonance) spectroscopy to determine the stabilities of nanoscopic assemblies formed between one or two nitroxide spin-labelled tridentate 2,2':6',2''-terpyridine (tpy) ligands and divalent metal ions (FeII, ZnII, CoII and CuII). In three distinct approaches we exploited (a) the modulation depth of pulsed electron-electron double resonance (PELDOR) experiments in samples with increasing metal-to-ligand ratios, (b) the frequencies of PELDOR under broadband excitation using shaped pulses and (c) the distances recovered from well-resolved PELDOR data in fully deuterated solvents measured at 34 GHz...
April 9, 2018: Physical Chemistry Chemical Physics: PCCP
Craig Gourlay, David J Nielsen, David J Evans, Jonathan M White, Charles G Young
Reaction of [CoCp2 ][TpiPr MoOS(OAr)] [Cp = η5 -cyclopentadienyl; TpiPr = hydrotris(3-isopropylpyrazol-1-yl)borate; OAr = phenolate or derivative thereof] with [Cu(NCMe)(Me3 tcn)]BF4 (Me3 tcn = 1,4,7-trimethyl-1,4,7-triazacyclononane) in MeCN at -30 °C results in the formation of red-brown/black, paramagnetic, μ-sulfido-Mo(v)/Cu(i) complexes, TpiPr MoO(OAr)(μ-S)Cu(Me3 tcn). The complexes possess the MoO(μ-S)Cu core found in aerobic carbon monoxide dehydrogenases (CODHs) and exhibit X-band EPR spectra closely related to those of semi-reduced CODH, with g iso ∼ 1...
January 28, 2018: Chemical Science
Zekai Lin, Nathan C Thacker, Takahiro Sawano, Tasha Drake, Pengfei Ji, Guangxu Lan, Lingyun Cao, Shubin Liu, Cheng Wang, Wenbin Lin
We report the synthesis of a terpyridine-based metal-organic layer (TPY-MOL) and its metalation with CoCl2 and FeBr2 to afford CoCl2 ·TPY-MOL and FeBr2 ·TPY-MOL, respectively. Upon activation with NaEt3 BH, CoCl2 ·TPY-MOL catalyzed benzylic C-H borylation of methylarenes whereas FeBr2 ·TPY-MOL catalyzed intramolecular Csp3 -H amination of alkyl azides to afford pyrrolidines and piperidines. X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy, UV-Vis-NIR spectroscopy, and electron paramagnetic spectroscopy (EPR) measurements as well as density functional theory (DFT) calculations identified M(THF)2 ·TPY-MOL (M = Co or Fe) as the active catalyst with a MII -(TPY˙˙)2- electronic structure featuring divalent metals and TPY diradical dianions...
January 7, 2018: Chemical Science
Ruramayi M Nzuma, Fuquan Liu, Irene R Grant
Campylobacter jejuni is a leading cause of foodborne illness worldwide, mainly due to consumption and handling of contaminated raw chicken. Rapid detection methods for C. jejuni are vital for monitoring contamination levels in chicken products and reducing human Campylobacteriosis cases. The 'gold standard' culture-based method of Campylobacter detection takes 3-5 days and is too slow to permit effective intervention. Immuno-based methods are faster, but usually necessitate use of animals or hybridoma technology to produce antibodies; making them difficult and expensive to produce...
April 7, 2018: Applied Microbiology and Biotechnology
Huey Hian Ng, Hwee Chen Ang, See Ying Hoe, Mae-Lynn Lim, Hua Eng Tai, Richard Choon Hock Soh, Christopher Kiu-Choong Syn
Urine samples are commonly analysed in cases with suspected illicit drug consumption. In events of alleged sample mishandling, urine sample source identification may be necessary. A simple DNA extraction procedure suitable for STR typing of urine samples was established on the Promega Maxwell® 16 paramagnetic silica bead platform. A small sample volume of 1.7mL was used. Samples were stored at room temperature, 4°C and -20°C for 100days to investigate the influence of storage temperature and time on extracted DNA quantity and success rate of STR typing...
March 29, 2018: Forensic Science International
Juanshan Du, Wanqian Guo, Huazhe Wang, Renli Yin, Heshan Zheng, Xiaochi Feng, Di Che, Nanqi Ren
In this study, batch experiments were carried out to investigate the key factors on sulfamethoxazole (SMX) removal kinetics in a new AOPs based on the combination of zero valent iron (Fe0 ) and bisulfite (S(IV)). With the increase of Fe0 from 0.25 mM to 5 mM, the removal rate of SMX was linearly increased in the Fe0 /S(IV)/O2 system by accelerating the activation of S(IV) and Fe0 corrosion to accelerate. In the first 10 min of reaction, the increasing concentration of S(IV) inhibited SMX removal after since the high S(IV) concentration quenched reactive oxidative species (ROS)...
December 22, 2017: Water Research
Changyin Zhu, Fengxiao Zhu, Dionysios D Dionysiou, Dongmei Zhou, Guodong Fang, Juan Gao
Alcohols such as ethanol (EtOH) and tert-butanol (TBA) are frequently used as quenching agents to identify the primary radical species in the persulfate (PS)-based oxidation processes. However, the contribution of alcohol radicals (ARs) to contaminant degradation in this process has rarely been assessed. In this study, trichloroacetic acid (TCA), phenol, and carbon tetrachloride were selected as probes to test the role of ARs in the thermally activated PS system. It was found that the degradation rates of these compounds were largely depended on their reactivities with ARs and the concentration of dissolved oxygen in the reaction system...
March 31, 2018: Water Research
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