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https://www.readbyqxmd.com/read/28818940/two-dimensional-sp-2-carbon-conjugated-covalent-organic-frameworks
#1
Enquan Jin, Mizue Asada, Qing Xu, Sasanka Dalapati, Matthew A Addicoat, Michael A Brady, Hong Xu, Toshikazu Nakamura, Thomas Heine, Qiuhong Chen, Donglin Jiang
We synthesized a two-dimensional (2D) crystalline covalent organic framework (sp(2)c-COF) that was designed to be fully π-conjugated and constructed from all sp(2) carbons by C=C condensation reactions of tetrakis(4-formylphenyl)pyrene and 1,4-phenylenediacetonitrile. The C=C linkages topologically connect pyrene knots at regular intervals into a 2D lattice with π conjugations extended along both x and y directions and develop an eclipsed layer framework rather than the more conventionally obtained disordered structures...
August 18, 2017: Science
https://www.readbyqxmd.com/read/28817975/triarylmethyl-based-biradical-as-a-superoxide-probe
#2
Martin Poncelet, Benoit Driesschaert, Andrey A Bobko, Valery V Khramtsov
Superoxide radical represents one of the most biologically relevant reactive oxygen species involved in numerous physiological and pathophysiological processes. Superoxide measurement through the decay of an electron paramagnetic resonance (EPR) signal of a triarylmethyl (TAM) radical possesses the advantage of a high selectivity and relatively high rate constant of TAM reaction with the superoxide. Hereby we report a straightforward synthesis and characterization of a tam-tam biradical showing a high reactivity with superoxide (second-order rate constant, (6...
August 17, 2017: Free Radical Research
https://www.readbyqxmd.com/read/28816463/signaling-related-mobility-changes-in-bacterial-chemotaxis-receptors-revealed-by-solid-state-nmr
#3
Maryam Kashefi, Lynmarie K Thompson
Bacteria employ remarkable membrane-bound nanoarrays to sense their environment and direct their swimming. Arrays consist of chemotaxis receptor trimers of dimers that are bridged at their membrane-distal tips by rings of two cytoplasmic proteins, a kinase CheA and a coupling protein CheW. It is not clear how ligand binding to the periplasmic domain of the receptor deactivates the CheA kinase bound to the cytoplasmic tip ~300 Å away, but the mechanism is thought to involve changes in dynamics within the cytoplasmic domain...
August 17, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28815905/degradable-vanadium-disulfide-nanostructures-with-unique-optical-and-magnetic-functions-for-cancer-theranostics
#4
Yuyan Chen, Liang Cheng, Ziliang Dong, Yu Chao, Huali Lei, He Zhao, Jian Wang, Zhuang Liu
Multifunctional biodegradable inorganic theranostic nano-agents are of great interests to the field of nanomedicine. Herein, VS2 nanosheets upon lipid modification could be converted into ultra-small VS2 nanodots encapsulated inside polyethylene glycol (PEG) modified lipid micelles. Owing to the paramagnetic property, high near-infrared (NIR) absorbance, and chelator-free 99mTc4+ labeling of VS2, such VS2@lipid-PEG nanoparticles could be used for T1-weighted magnetic resonance (MR), photoacoustic (PA),and single photon emission computed tomography (SPECT) tri-modal imaging guided photothermal ablation of tumors...
August 16, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28815766/preparation-of-robust-metal-free-magnetic-nanoemulsions-encapsulating-low-molecular-weight-nitroxide-radicals-and-hydrophobic-drugs-directed-toward-mri-visible-targeted-delivery
#5
Rui Tamura, Kota Nagura, Yusa Takemoto, Satori Moronaga, Yoshiaki Uchida, Satoshi Shimono, Akihiko Shiino, Kenji Tanigaki, Tsukuru Amano, Fumi Yoshino, Yohei Noda, Satoshi Koizumi, Naoki Komatsu, Tatsuhisa Kato, Jun Yamauchi
With a view to developing a theranostic nanomedicine for magnetic resonance (MR) imaging-visible targeted drug delivery system, robust metal-free magnetic nanoemulsions (mean particle sizes of less than 20 nm) consisting of the biocompatible surfactant 1 and the incorporated hydrophobic low-molecular-weight 2,2,5-trimethyl-5-(4-alkoxy)phenylpyrrolidine-N-oxyl radicals [(±)-2] have been prepared in pH 7.4 phosphate-buffered saline. The structure of the nanoemulsions has been characterized by electron paramagnetic resonance spectroscopy, and dynamic light scattering and small angle neutron scattering measurements...
August 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28815154/spin-trapping-a-review-for-the-study-of-obesity-related-oxidative-stress-and-na-k-atpase
#6
Athar Nawab, Alexandra Nichols, Rebecca Klug, Joseph I Shapiro, Komal Sodhi
Reactive oxygen species (ROS) have gained attention with mounting evidence of their importance in cell signaling and various disease states. ROS is produced continuously as a natural by-product of normal oxygen metabolism. However, high levels ROS causes oxidative stress and damage to biomolecules. This results in loss of protein function, DNA cleavage, lipid peroxidation, or ultimately cell injury or death. Obesity has become a worldwide epidemic; studies show fat accumulation is associated with increased ROS and oxidative stress...
June 2017: Journal of Clinical & Cellular Immunology
https://www.readbyqxmd.com/read/28813006/samarium-monosulfide-sms-reviewing-properties-and-applications
#7
REVIEW
Andreas Sousanis, Philippe F Smet, Dirk Poelman
In this review, we give an overview of the properties and applications of samarium monosulfide, SmS, which has gained considerable interest as a switchable material. It shows a pressure-induced phase transition from the semiconducting to the metallic state by polishing, and it switches back to the semiconducting state by heating. The material also shows a magnetic transition, from the paramagnetic state to an antiferromagnetically ordered state. The switching behavior between the semiconducting and metallic states could be exploited in several applications, such as high density optical storage and memory materials, thermovoltaic devices, infrared sensors and more...
August 16, 2017: Materials
https://www.readbyqxmd.com/read/28812903/synergic-on-off-photoswitching-spin-state-and-magnetic-coupling-between-spin-crossover-centers
#8
Jun-Li Wang, Qiang Liu, Yin-Shan Meng, Hui Zheng, Hai-Lang Zhu, Quan Shi, Tao Liu
The existence of a correlation between spin crossover and dielectric properties is a hot topic in the field of multiresponse materials, which has potential applications in the memory devices, switches, and sensors. One formidable challenge is the simultaneous and rapid on/off switching of spin states of the spin carriers and magnetic coupling between them, which is crucial for both reversible photomagnetic behavior and variations in dielectric properties. Here, we report a dinuclear Fe(II) spin crossover complex, wherein each Fe(II) center exhibits an interconversion between Fe(II)HS (HS = high-spin) and Fe(II)LS (LS = low-spin) achieved upon heating and cooling...
August 16, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28812873/ultrathin-manganese-based-metal-organic-framework-nanosheets-low-cost-and-energy-dense-lithium-storage-anodes-with-the-coexistence-of-metal-and-ligand-redox-activities
#9
Chao Li, Xiaoshi Hu, Wei Tong, Wensheng Yan, Xiaobing Lou, Ming Shen, Bingwen Hu
We herein demonstrate the fabrication of Mn- and Ni-based ultrathin metal-organic framework nanosheets with the same coordination mode (defined as 'Mn-UMOFNs' and 'Ni-UMOFNs', respectively) through an expedient and versatile ultrasonic approach, and scrutinize their electrochemical properties as anode materials for rechargeable lithium battery for the first time. The obtained Mn-UMOFNs with structure advantages over Ni-UMOFNs (thinner nanosheets, smaller metal-ion radius, higher specific surface area) exhibit high reversible capacity (1187 mAh g-1 at 100 mA g-1 for 100 cycles), excellent rate capability (701 mAh g-1 even at 2 A g-1), rapid Li+ diffusion coefficient (2...
August 16, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28812125/recombinant-expression-and-biochemical-characterization-of-mycobacterium-tuberculosis-3fe-4s-ferredoxin-rv1786
#10
Yun Lu, Feng Qiao, Yue Li, Xiao-Hong Sang, Cong-Ran Li, Jian-Dong Jiang, Xin-Yi Yang, Xue-Fu You
Ferredoxins are iron-sulfur protein that mediate electron transfer in cytochrome P450 mono-oxygenase (CYP)-related catalytic reactions in a wide variety of organisms. Rv1786 is a putative ferredoxin, encoded by a gene located downstream of the gene encoding CYP143A1 in the Mycobacterium tuberculosis genome. However, the structure and function of Rv1786 have remained unclear. Here, the recombinant Mtb Rv1786 was expressed, purified as a His-tagged form and characterized with [3Fe-4S] clusters as its cofactors using a series of measurements including SDS-PAGE, western blot, UV/Visible, MALDI-TOF/TOF-MS, and electron paramagnetic resonance spectroscopic analysis...
August 15, 2017: Applied Microbiology and Biotechnology
https://www.readbyqxmd.com/read/28811033/strong-magnetoelectrolysis-effect-during-electrochemical-reaction-monitored-in-situ-by-high-resolution-nmr-spectroscopy
#11
Bruna Ferreira Gomes, Pollyana Ferreira da Silva, Carlos Manuel Silva Lobo, Maiara da Silva Santos, Luiz Alberto Colnago
The strong effect of magnetic field on the electrochemical (EC) reduction of a diamagnetic species was monitored in situ in a 600 MHz (14 T) NMR spectrometer. Throughout EC-NMR experiments, the diamagnetic species is influenced by the Lorentz force (cross product of current density and magnetic field), which in turn acts on analyte transport and, as a result, enhances reaction rates. This phenomenon, known as magnetoelectrolysis, has not been considered in several in situ EC-NMR studies in solution, electron paramagnetic resonance (EC-EPR) spectroscopy, and magnetic resonance imaging (EC-MRI) involving the oxidation and reduction of organic compounds and lithium ion batteries...
August 29, 2017: Analytica Chimica Acta
https://www.readbyqxmd.com/read/28810753/dynamical-transition-in-molecular-glasses-and-proteins-observed-by-spin-relaxation-of-nitroxide-spin-probes-and-labels
#12
Elena A Golysheva, Georgiy Yu Shevelev, Sergei A Dzuba
In glassy substances and biological media, dynamical transitions are observed in neutron scattering that manifests itself as deviations of the translational mean-squared displacement, 〈x(2)〉, of hydrogen atoms from harmonic dynamics. In biological media, the deviation occurs at two temperature intervals, at ∼100-150 K and at ∼170-230 K, and it is attributed to the motion of methyl groups in the former case and to the transition from harmonic to anharmonic or diffusive motions in the latter case. In this work, electron spin echo (ESE) spectroscopy-a pulsed version of electron paramagnetic resonance-is applied to study the spin relaxation of nitroxide spin probes and labels introduced in molecular glass former o-terphenyl and in protein lysozyme...
August 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28810231/cr-induced-cellular-injury-and-necrosis-in-glycine-max-l-biochemical-mechanism-of-oxidative-damage-in-chloroplast
#13
Kalimuthu Balasaraswathi, Sivalingam Jayaveni, Janardhanam Sridevi, Dhanasingh Sujatha, Kavati Phebe Aaron, Chellan Rose
Chromium-induced toxicity and mechanisms of cell death involved in plants are yet to be fully elucidated. To understand the events of these processes, the stress response of the soybean plant using trivalent and hexavalent chromium compounds, namely, basic chromium sulphate (BCS) and potassium dichromate (K2Cr2O7) was investigated. The leaf surface morphology for stomatal aperture, wax deposition and presence of trichomes for chromium accumulation was examined by SEM-EDAX and light microscopy. The leaf mesophyll cell integrity was identified by trypan blue staining; chlorophyll autofluorescence, ROS generation and mitochondrial function were studied by fluorescence microscopy using different dyes...
August 2, 2017: Plant Physiology and Biochemistry: PPB
https://www.readbyqxmd.com/read/28810137/time-gated-luminescence-imaging-of-singlet-oxygen-photoinduced-by-fluoroquinolones-and-functionalized-graphenes-in-daphnia-magna
#14
Tianlie Luo, Jingwen Chen, Bo Song, Hua Ma, Zhiqiang Fu, Willie J G M Peijnenburg
Singlet oxygen ((1)O2) can be photogenerated by photoactive xenobiotics and is capable of causing adverse effects due to its electrophilicity and its high reactivity with biological molecules. Detection of the production and distribution of (1)O2 in living organisms is therefore of great importance. In this study, a luminescent probe ATTA-Eu(3+) combined with time-gated luminescence imaging was adopted to detect the distribution and temporal variation of (1)O2 photoinduced by fluoroquinolone antibiotics and carboxylated/aminated graphenes in Daphnia magna...
July 29, 2017: Aquatic Toxicology
https://www.readbyqxmd.com/read/28809565/dipicolinic-acid-derivatives-as-inhibitors-of-new-delhi-metallo-%C3%AE-lactamase-1
#15
Allie Y Chen, Pei W Thomas, Alesha C Stewart, Alexander Bergstrom, Zishuo Cheng, Callie Miller, Christopher R Bethel, Steven H Marshall, Cy V Credille, Christopher L Riley, Richard C Page, Robert A Bonomo, Michael W Crowder, David L Tierney, Walter Fast, Seth M Cohen
The efficacy of β-lactam antibiotics is threatened by the emergence and global spread of metallo-β-lactamase-(MBL) mediated resistance, specifically New Delhi-Metallo-β- lactamase-1 (NDM-1). Utilizing fragment-based drug discovery (FBDD), a new class of inhibitors for NDM-1 and two related β-lactamases, IMP-1 and VIM-2, was identified. Based on 2,6-dipicolinic acid (DPA), several libraries were synthesized for structure-activity relationship (SAR) analysis. Inhibitor 36 (IC50 = 80 nM) was identified to be highly selective for MBLs when compared to other Zn(II) metalloenzymes...
August 15, 2017: Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/28809559/on-the-influence-of-the-bridge-on-triplet-state-delocalization-in-linear-porphyrin-oligomers
#16
Sabine Richert, Bart Limburg, Harry L Anderson, Christiane R Timmel
The extent of triplet state delocalization is investigated in rigid linear zinc porphyrin oligomers as a function of interporphyrin bonding characteristics, specifically in meso-meso singly linked and β,meso,β fused structures, using electron paramagnetic resonance techniques. The results are compared with those of earlier measurements on porphyrin oligomers with alkyne linkers exhibiting different preferred conformations. It is shown that dihedral angles near 90° between the porphyrin planes in directly meso-to-meso linked porphyrin oligomers lead to localization of the photoexcited triplet state on a single porphyrin unit, whereas previous work demonstrated even delocalization over two units in meso-to-meso ethyne or butadiyne-bridged oligomers, where the preferred dihedral angles amount to roughly 30° and 0°, respectively...
August 15, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28809478/ruthenium-ii-and-ruthenium-iii-complexes-of-p-benziporphyrin-merging-equatorial-and-axial-organometallic-coordination
#17
Aneta Idec, Miłosz Pawlicki, Lechosław Latos-Grażyński
A diamagnetic ruthenium(II) complex of 5,10,15,20-tetraphenyl-p-benziporphyrin [Ru(II)(p-BzP)(CO)Cl] was obtained via the insertion of ruthenium into p-benziporphyrin using triruthenium(0) dodecacarbonyl [Ru3(CO)12] as the metal source. The procedure applying dichloro(cycloocta-1,5-diene)ruthenium(II) (polymer, [Ru(COD)Cl2]n) afforded the paramagnetic six-coordinate ruthenium(III) p-benziporphyrin [Ru(III)(p-BzP)Cl2]. As shown by X-ray crystallography, the p-phenylene ring in both complexes is sharply tilted out of the N3 plane, as reflected by the respective N3 (pyrrole)-C6 (p-phenylene) dihedral angle [Ru(II)(p-BzP)(CO)Cl, 52...
August 15, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28808201/thalamic-paramagnetic-iron-by-t2-relaxometry-correlates-with-severity-of-multiple-sclerosis
#18
Eva Baranovicova, Ema Kantorova, Dagmar Kalenska, Lucia Lichardusova, Michal Bittsan-Sky, Dusan Dobrota
Iron can contribute to the pathogenesis and progression of multiple sclerosis (MS) due to its accumulation in the human brain. We focus on the thalamus as an information transmitter between various subcortical and cortical areas. Thalamic iron seems to follow different rules than iron in other deep gray matter structures and its relation to the clinical outcomes of MS is still indistinct. In our study, we investigated a connection between thalamic iron and patients' disability and course of the disease. The presence of paramagnetic substances in the tissues was tracked by T2* quantification...
July 13, 2017: Journal of Biomedical Research
https://www.readbyqxmd.com/read/28806698/fluorescence-and-electron-paramagnetic-resonance-studies-of-norfloxacin-and-n-donor-mixed-ligand-ternary-copper-ii-complexes-stability-and-interaction-with-sds-micelles
#19
Gabriel S Vignoli Muniz, Jimmy Llontop Incio, Odivaldo C Alves, Klaus Krambrock, Letícia R Teixeira, Sonia R W Louro
The stability of ternary copper(II) complexes of a heterocyclic ligand, L (L being 2,2'-bipyridine (bipy) or 1,10-phenanthroline (phen)) and the fluorescent antibacterial agent norfloxacin (NFX) as the second ligand was studied at pH7.4 and different ionic strengths. Fluorescence quenching upon titration of NFX with the binary complexes allowed to obtain stability constants for NFX binding, Kb, as a function of ionic strength. The Kb values vary by more than two orders of magnitude when buffer concentration varies from 0...
August 5, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28806645/evaluation-of-the-binding-of-four-anti-tumor-casiope%C3%A3-nas%C3%A2-to-human-serum-albumin
#20
Isabel Correia, Sladjana Borovic, Isabel Cavaco, Cristina P Matos, Somnath Roy, Hugo M Santos, Luz Fernandes, José L Capelo, Lena Ruiz-Azuara, João Costa Pessoa
The metal complexes designated by Casiopeínas® are mixed-ligand Cu(II)-compounds some of them having promising antineoplastic properties. We report studies of binding of Cu(glycinato)(4,7-dimethyl-1,10-phenanthroline) (Cas-II-Gly (1)), Cu(acetylacetonato)(4,7-dimethyl-1,10-phenanthroline) (Cas-III-Ea (2)), Cu(glycinato)(4,4'-dimethyl-2,2'-bipyridine) (Cas-IV-Gly (3)) and Cu(acetylacetonato)(4,4'-dimethyl-2,2'-bipyridine) (Cas-III-ia (4)) to human serum albumin (HSA) by circular dichroism (CD), Electron paramagnetic resonance (EPR) and fluorescence spectroscopy...
July 29, 2017: Journal of Inorganic Biochemistry
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