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Igor E Soshnikov, Nina V Semikolenova, Konstantin P Bryliakov, Artem A Antonov, Vladimir A Zakharov, Evgenii P Talsi
The nature of Ni(ii) species formed upon the activation of the Brookhart's α-diimine polymerization pre-catalyst LNiBr2 with MAO and MMAO (L = 1,4-bis-2,4,6-dimethylphenyl-2,3-dimethyl-1,4-diazabuta-1,3-diene) has been established using 1H and 13C NMR spectroscopy. The heterobinuclear ion pair [LNiII(μ-Me)2AlMe2]+[MeMAO]- is observed at the initial stage of the reaction of LNiBr2 with MAO at -40 °C, whereas the ion pair [LNiII-tBu]+[MeMMAO]- predominates at the initial stage of the reaction of LNiBr2 with MMAO under the same conditions...
March 20, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Jincheng Yang, Qingzhi Lv, Wei Wei, Zhengtao Yang, Jiajun Dong, Ruoshi Zhang, Qiming Kan, Zhonggui He, Youjun Xu
The efficacy of traditional chemotherapy often suffers from rapid clearance and off-target toxicity. Drug delivery systems and controlled release are applied to improve the therapeutic efficiencies of small-molecule drugs. In this work, two novel oxidative/reductive (Ox/Re) -sensitive and one non-sensitive Paclitaxel (PTX) prodrugs were synthesized with a maleimide group, which rapidly conjugates with albumin in vivo. Albumin serves as a good vehicle to deliver more prodrug to tumors due to the enhanced permeation and retention (EPR) effect...
November 2018: Drug Delivery
Zoltán Klencsár, Zoltán Köntös
Lignite is a rich source of humic substances such as humic and fulvic acids that are natural chelating agents with multifold applications in fields ranging from agriculture to biomedicine. Associations of heterogeneous molecular components constitute to their complex and still unresolved structure. In this work we utilize X-band electron paramagnetic resonance (EPR) spectroscopy to characterize Fe3+ and Mn2+ complexation sites in fulvic acid (FA) extracted from lignite. EPR signals of FA-Fe3+ and FA-Mn2+ complexes are identified and investigated in detail under various conditions by the means of a newly developed program code and associated analysis method that yields an accurate description of the low-field ( geff ≈ 10-3) range EPR signal by assuming discrete distributions in the axial ( D) and rhombic (λ) zero field splitting (ZFS) parameters associated with Fe3+ complexation sites...
March 19, 2018: Journal of Physical Chemistry. A
Krishnendu Kundu, Akiva Feintuch, Shimon Vega
Recently it has been shown that experimental ELDOR spectra of amorphous glasses containing free radicals with inhomogeneously broadened EPR spectra can be analyzed using a set of coupled rate equations for the electron polarizations of frequency bins composing these spectra, named the eSD (electron spectral diffusion) model. The rate matrix defining these equations has elements depending on the microwave, the spin lattice relaxation rates and on eSD rate constants responsible for polarization exchange. In this study, we show that in addition to the static dipolar flip-flop terms in the Hamiltonian a zero-quantum electron cross-relaxation mechanism can be responsible for the polarization exchange process in our samples...
March 19, 2018: Journal of Physical Chemistry Letters
Xianyong Feng, Peifang Wang, Jun Hou, Jin Qian, Yanhui Ao, Chao Wang
In the present work, we reported a simple method for the simultaneous phosphorus (P) doping and oxygen vacancies creation on TiO2 in a single step. The obtained P-doped TiO2 with surface oxygen vacancies (PTSOV) samples exhibited efficient photocatalytic activity for the degradation of fluoroquinolone antibacterial agent (ciprofloxacin) under visible light irradiation. The optimized sample showed a rate constant of 0.065 min-1 for degradation of ciprofloxacin (CIP) and it was about 16.2 times as high as that of TiO2 (0...
March 10, 2018: Journal of Hazardous Materials
Derek Marsh
Interpretation of saturation-recovery EPR experiments on nitroxide spin labels whose angular rotation is restricted by the orienting potential of the environment (e.g., membranes) currently concentrates on the influence of rotational rates and not of molecular order. Here, I consider the dependence on molecular ordering of contributions to the rates of electron spin-lattice relaxation and cross relaxation from modulation of N-hyperfine and Zeeman anisotropies. These are determined by the averages 〈cos2 θ〉 and 〈cos4 θ〉, where θ is the angle between the nitroxide z-axis and the static magnetic field, which in turn depends on the angles that these two directions make with the director of uniaxial ordering...
March 2, 2018: Journal of Magnetic Resonance
Huagang Hou, Nadeem Khan, Sangeeta Gohain, M Lakshmi Kuppusamy, Periannan Kuppusamy
Tissue oxygenation is a critical parameter in various pathophysiological situations including cardiovascular disease and cancer. Hypoxia can significantly influence the prognosis of solid malignancies and the efficacy of their treatment by radiation or chemotherapy. Electron paramagnetic resonance (EPR) oximetry is a reliable method for repeatedly assessing and monitoring oxygen levels in tissues. Lithium octa-n-butoxynaphthalocyanine (LiNc-BuO) has been developed as a probe for biological EPR oximetry, especially for clinical use...
March 16, 2018: Biomedical Microdevices
Zachary T Bitzer, Reema Goel, Samantha M Reilly, Ryan J Elias, Alexey Silakov, Jonathan Foulds, Joshua Muscat, John P Richie
BACKGROUND: Flavoring chemicals, or flavorants, have been used in electronic cigarettes (e-cigarettes) since their inception; however, little is known about their toxicological effects. Free radicals present in e-cigarette aerosols have been shown to induce oxidative stress resulting in damage to proliferation, survival, and inflammation pathways in the cell. Aerosols generated from e-liquid solvents alone contain high levels of free radicals but few studies have looked at how these toxins are modulated by flavorants...
March 13, 2018: Free Radical Biology & Medicine
Hendrik Göddeke, M Hadi Timachi, Cedric A Hutter, Laura Galazzo, Markus A Seeger, Mikko Karttunen, Enrica Bordignon, Lars V Schäfer
ATP-binding cassette (ABC) transporters are ATP-driven molecular machines, in which ATP binding and hydrolysis in the nucleotide-binding domains (NBDs) is chemo-mechanically coupled to large-scale, alternating access conformational changes in the transmembrane domains (TMDs), ultimately leading to the translocation of substrates across biological membranes. The precise nature of the structural dynamics behind the large-scale conformational transition as well as the coupling of NBD and TMD motions is still unresolved...
March 16, 2018: Journal of the American Chemical Society
Nimai Pathak, Partha Sarathi Ghosh, Suryansh Saxena, Dhanadeep Dutta, Ashok Kumar Yadav, Dibyendu Bhattacharyya, Shambhu Nath Jha, Ramakant Mahadeo Kadam
Activator-free zinc aluminate (ZA) nanophosphor was synthesized through a sol-gel combustion route, which can be used both as a blue-emitting phosphor material and a white-emitting phosphor material, depending on the annealing temperature during synthesis. The material also has the potential to be used in optical thermometry. These fascinating color-tunable emission characteristics can be linked with the various defect centers present inside the matrix and their changes upon thermal annealing. Various defect centers, such as anionic vacancy, cationic vacancy, antisite defect, etc...
March 16, 2018: Inorganic Chemistry
Donatella Pietraforte, Eleonora Paulicelli, Clarice Patrono, Lucrezia Gambardella, Giuseppe Scorza, Antonella Testa, Paola Fattibene
Reactive oxygen species (ROS) are important mediators of the cytotoxicity induced by the direct reaction of ionising radiation (IR) with all critical cellular components, such as proteins, lipids, and nucleic acids. The derived oxidative damage may propagate in exposed tissues in a dose- and spatiotemporal dependent manner to other cell compartments, affecting intracellular signalling, and cell fate. To understand how cell damage is induced, we studied the oxidative events occurring immediately after cell irradiation by analysing the fate of IR-derived ROS, the intracellular oxidative damage, and the modification of redox environment accumulating in Chinese hamster ovary (CHO) within 1 h after cell irradiation (dose range 0-10 Gy)...
March 16, 2018: Free Radical Research
Henrik Lauridsen, Casper Bindzus Foldager, Line Hansen, Michael Pedersen
Non-invasive methods to track the progress of stem cell therapies are important in the development of future regenerative therapies. Super-paramagnetic iron oxide particles (SPIOs) have previously been applied to track cells using magnetic resonance imaging (MRI) in vivo in non-regenerative animal models. To the best of the author's knowledge, the present study investigated for the first time, the feasibility of tracking SPIO labeled cells in an intrinsic regenerative environment, the regenerating limb of the axolotl, and investigated the homing of stem cell-like blastema cells to the regenerative zone...
April 2018: Experimental and Therapeutic Medicine
Bin Wang, Alistair J Fielding, Robert A W Dryfe
Electron paramagnetic resonance (EPR) spectroscopy is applied in situ to monitor the electrochemical capacitance of activated carbon in aqueous solutions, thereby revealing aspects of the charge storage mechanism. The EPR signal of activated carbon increases during the charging process and returns reversibly when discharged. Simulation of the spectral lineshape and its temperature dependence indicate that two kinds of spins exist: spin at defects giving rise to a narrow signal, and spins associated with surface-bound aromatic moieties causing a broad signal...
March 15, 2018: Chemical Communications: Chem Comm
Lai Lyu, Dengbiao Yan, Guangfei Yu, Wenrui Cao, Chun Hu
Carbon nitride compounds (CN) complexed with the in-situ produced Cu(II) on the surface of CuAlO2 substrate (CN-Cu(II)-CuAlO2) is prepared via a surface growth process for the first time, which exhibits exceptionally high activity and efficiency for the degradation of the refractory pollutants in water through a Fenton-like process in a wide pH range. The reaction rate for BPA removal is ~25 times higher than that of the CuAlO2. According to the characterization, Cu(II) generation on the surface of CuAlO2 during the surface growth process result in the marked decrease of the surface oxygen vacancies and the formation of the C-O-Cu bridges between CN and Cu(II)-CuAlO2 in the catalyst...
March 15, 2018: Environmental Science & Technology
Thomas M Pangia, Casey G Davies, Joshua R Prendergast, Jesse B Gordon, Maxime A Siegler, Guy N L Jameson, David P Goldberg
A nonheme iron(III) terminal methoxide complex, [FeIII (N3PyO2Ph )(OCH3 )]ClO4 , was synthesized. Reaction of this complex with the triphenylmethyl radical (Ph3 C• ) leads to formation of Ph3 COCH3 and the one-electron-reduced iron(II) center, as seen by UV-vis, EPR,1 H NMR, and Mössbauer spectroscopy. These results indicate that homolytic Fe-O bond cleavage occurs together with C-O bond formation, providing a direct observation of the "radical rebound" process proposed for both biological and synthetic nonheme iron centers...
March 14, 2018: Journal of the American Chemical Society
Ronny Neumann, Alexander M Khenkin, Miriam Somekh, Raanan Carmieli
The sustainable, selective direct hydroxylation of arenes, such as benzene to phenol is an important research challenge. Mostly thermochemical approaches have been studied, but these still have various drawbacks. An electrocatalytic transformation using formic acid to oxidize benzene and its halogenated derivatives to selectively yield aryl formates that are easily hydrolyzed by water yielding the corresponding phenols is presented. The formylation reaction occurs on a Pt anode in the presence of [Co(III)W12O40]5- as catalyst and Li formate as electrolyte via formation of a formyloxyl radical as the reactive species, which was trapped by a BMPO spin trap and identified by EPR...
March 14, 2018: Angewandte Chemie
Huanan Li, Deping Zeng, Zhenyu Wang, Liaoqiong Fang, Faqi Li, Zhibiao Wang
AIM: To build up a combined therapy strategy to address limitations of the enhanced permeability and retention (EPR) effect and improve the efficiency of tumor therapy. MATERIALS & METHODS: A pH-sensitive nanocomplex for co-delivery of doxorubicin (DOX) and all-trans retinoic acid (ATRA) was developed based on nanodiamonds (DOX/ATRA-NDs) to enhance intracellular retention of drugs. Meanwhile, ultrasound was employed to enhance tumor vascular penetration of DOX-ATRA-NDs...
March 14, 2018: Nanomedicine
Johannes G Rebelein, Chi Chung Lee, Megan Newcomb, Yilin Hu, Markus W Ribbe
The Mo- and V-nitrogenases are two homologous members of the nitrogenase family that are distinguished mainly by the presence of different heterometals (Mo or V) at their respective cofactor sites (M- or V-cluster). However, the V-nitrogenase is ~600-fold more active than its Mo counterpart in reducing CO to hydrocarbons at ambient conditions. Here, we expressed an M-cluster-containing, hybrid V-nitrogenase in Azotobacter vinelandii and compared it to its native, V-cluster-containing counterpart in order to assess the impact of protein scaffold and cofactor species on the differential reactivities of Mo- and V-nitrogenases toward CO...
March 13, 2018: MBio
Hagit Sade, Jean-Paul Lellouche
Two tungsten disulfide (WS₂)-based core-shell nanocomposites were fabricated using readily available reagents and simple procedures. The surface was pre-treated with a surfactant couple in a layer-by-layer approach, enabling good dispersion of the WS₂ nanostructures in aqueous media and providing a template for the polymerization of a silica (SiO₂) shell. After a Stöber-like reaction, a conformal silica coating was achieved. Inspired by the resulting nanocomposite, a second one was prepared by reacting the surfactant-modified WS₂ nanostructures with aniline and an oxidizing agent in an aqueous medium...
March 10, 2018: Nanomaterials
Kuppuswamy Arumugam, Malathy Selvachandran, Antony Obanda, Mohamed C Shaw, Perumalreddy Chandrasekaran, Sonya L Caston Good, Joel T Mague, Stephen Sproules, James P Donahue
Compounds of the type [(S2 C2 R2 )M(μ-tpbz)M(S2 C2 R2 )] (R = CN, Me, Ph, p-anisyl; M = Ni, Pd, Pt; tpbz = 1,2,4,5-tetrakis(diphenylphosphino)benzene) have been prepared by transmetalation with [(S2 C2 R2 )SnR'2 ] reagents, by direct displacement of dithiolene ligand from [M(S2 C2 R2 )2 ] with 0.5 equiv of tpbz, or by salt metathesis using Na2 [S2 C2 (CN)2 ] in conjunction with X2 M(μ-tpbz)MX2 (X = halide). X-ray crystallography reveals a range of topologies (undulating, chair, bowed) for the (S2 C2 )M(P2 C6 P2 )M(S2 C2 ) core...
March 13, 2018: Inorganic Chemistry
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