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https://www.readbyqxmd.com/read/28817770/photoinduced-copper-catalyzed-alkylation-of-amines-a-mechanistic-study-of-the-cross-coupling-of-carbazole-with-alkyl-bromides
#1
Jun Myun Ahn, Tanvi S Ratani, Kareem Hannoun, Gregory C Fu, Jonas C Peters
We have recently reported that a variety of couplings of nitrogen, sulfur, oxygen, and carbon nucleophiles with organic halides can be achieved under mild conditions (-40 to 30 °C) through the use of light and a copper catalyst. Insight into the various mechanisms by which these reactions proceed may enhance our understanding of chemical reactivity and facilitate the development of new methods. In this report, we apply an array of tools (EPR, NMR, transient absorption, and UV-vis spectroscopy; ESI-MS; X-ray crystallography; DFT calculations; reactivity, stereochemical, and product studies) to investigate the photoinduced, copper-catalyzed coupling of carbazole with alkyl bromides...
August 17, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28815889/c-h-bond-trifluoromethylation-of-arenes-enabled-by-a-robust-high-valent-niiv-complex
#2
Florian D'Accriscio, Pilar Borja, Nathalie Saffon-Merceron, Marie Fustier-Boutignon, Nicolas Mézailles, Noel Nebra
The robust, high-valent NiIV complex [(Py)2NiIVF2(CF3)2] 3, is reported. The structure of 3 was fully characterized by NMR, XRD and EA. 3 reacts with aromatics at 25°C to form the corresponding benzotrifluorides in nearly quantitative yield. Monomeric and dimeric NiIIICF3 complexes 2.Py and 2 were identified as key intermediates, and their structures were unambiguously assigned by EPR and XRD analysis. Preliminary kinetic study coupled to experimental isolation of reaction intermediates proves that the C-H bond breaking/C-CF3 bond forming sequence can occur both with the NiIVCF3 and NiIIICF3 centers...
August 16, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28815875/the-pathogenic-a2v-mutant-exhibits-distinct-aggregation-kinetics-metal-site-structure-and-metal-exchange-of-the-cu2-a%C3%AE-complex
#3
Lars Hemmingsen, Arun K Somavarapu, Fei Shen, Kaare Teillum, Jingdong Zhang, Susanne Mossin, Peter W Thulstrup, Morten J Bjerrum, Manish K Tiwari, Daniel Szunyogh, Peter M Søfotfe, Kasper K Kepp
A prominent current hypothesis is that impaired metal ion homeostasis may contribute to Alzheimer's Disease (AD). We elucidate the interaction of Cu2+ with wild-type (WT) Aβ1-40 and the genetic variants A2T and A2V which display increasing pathogenicity as A2T<WT<A2V. Cu2+ significantly extends the lag phase in aggregation kinetics, in particular for the pathogenic A2V variant. Additionally, a rapid, initial, low intensity ThT response is observed, possibly reflecting formation of Cu2+ induced amorphous aggregates, as supported by AFM and CD spectroscopy, again most notably for the A2V variant...
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
#4
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/28813053/copper-ii-benzimidazole-complexes-as-efficient-fluorescent-probes-for-l-cysteine-in-water
#5
Duraiyarasu Maheshwaran, Selvarasu Priyanga, Ramasamy Mayilmurugan
Copper(ii) complexes [Cu(L1)(H2O)2](SO3CF3)21 and [Cu(L2)(H2O)2](SO3CF3)22 based on 2,6-bis(benzimidazolyl)pyridine were synthesized and are reported herein as highly selective "turn-on" optical probes for l-cysteine. The Cu(ii)/Cu(i) redox potential of probe 1 (0.14 V vs. NHE) was lower than that of 2 (0.233 V vs. NHE) in water. The molecular structure of 2 adopted a square pyramidal geometry (τ = 0.2545), with the Cu-Npy bond (1.958 Å) of its middle pyridine unit being shorter than the other two Cu-Nbenzim bonds (Cu-N, 1...
August 16, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28812088/consecutive-reduction-radical-cyclization-and-oxidative-dehydrogenation-reaction-of-ortho-substituted-diboryl-compounds
#6
Lirong Yu, Yanglizhi Li, Xi Wang, Xingyong Wang, Panpan Zhou, Shangda Jiang, Xiaobo Pan
An elegant synthetic route to a ladder-type di-borate compound 2a was reported based on the reduction, radical-cyclization, and oxidative-dehydrogenation reaction of 1. The existence of the biradical intermediate [1˙˙]2- was supported by both EPR measurements and DFT calculations.
August 16, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28812068/mechanistic-investigations-of-the-2-coumaranone-chemiluminescence
#7
Stefan Schramm, Isabelle Navizet, Durga Prasad Karothu, Pascal Oesau, Veronika Bensmann, Dieter Weiss, Rainer Beckert, Panče Naumov
2-Coumaranones are evolving as a new, efficient, versatile, and synthetically accessible platform for the next generation chemiluminescent probes. Despite the favorable quantum yields, the exact mechanism of their chemiluminescence remains elusive. Here, we analyze the details of the mechanism of the 2-coumaranone chemiluminescence using a combination of experimental and computational methods. By using EPR spectroscopy we show that superoxide radical anions are involved in the reactions, in support of the hypothesis that the mechanism includes a single electron transfer step...
August 16, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28811033/strong-magnetoelectrolysis-effect-during-electrochemical-reaction-monitored-in-situ-by-high-resolution-nmr-spectroscopy
#8
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/28809565/dipicolinic-acid-derivatives-as-inhibitors-of-new-delhi-metallo-%C3%AE-lactamase-1
#9
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/28809186/bridging-the-gap-between-the-social-and-the-technical-the-enrolment-of-socio-technical-information-architects-to-cope-with-the-two-level-model-of-epr-systems
#10
Rune Pedersen
This is a project proposal derived from an urge to re-define the governance of ICT in healthcare towards regional and national standardization of the patient pathways. The focus is on a two-levelled approach for governing EPR systems where the clinicians' model structured variables and patient pathways. The overall goal is a patient centric EPR portfolio. This paper define and enlighten the need for establishing the socio- technical architect role necessary to obtain the capabilities of a modern structured EPR system...
2017: Studies in Health Technology and Informatics
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
#11
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
#12
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
https://www.readbyqxmd.com/read/28806074/mechanical-bond-protected-air-stable-radicals
#13
Junling Sun, Zhichang Liu, Wei-Guang Liu, Yilei Wu, Yuping Wang, Jonathan C Barnes, Keith R Hermann, William A Goddard, Michael R Wasielewski, J Fraser Stoddart
Radical templation centered around a heterotrisradical tricationic inclusion complex DB(•+)⊂DAPQT(2(•+)), assembled from an equimolar mixture of a disubstituted 4,4'-bipyridinium radical cation (DB(•+)) and an asymmetric cyclophane bisradical dication (DAPQT(2(•+))), affords a symmetric [2]catenane (SC•7PF6) and an asymmetric [2]catenane (AC•7PF6) on reaction of the 1:1 complex with diazapyrene and bipyridine, respectively. Both these highly charged [2]catenanes have been isolated as air-stable mono-radicals and characterised by EPR spectroscopy...
August 14, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28805866/low-spin-m-ii-l-2-and-m-iii-l-2-m-fe-and-co-complexes-of-tridentate-azo-containing-pyridine-pyrazine-amide-ligands-structures-properties-and-redox-potential-correlations
#14
Arunava Sengupta, Amit Rajput, Suman K Barman, Rabindranath Mukherjee
Using deprotonated forms of tridentate azo-containing pyridine-2-/pyrazine-2-carboxamide 2-[N-(2-phenylazo)carbamoyl]-pyridine/pyrazine, seven bis-ligand complexes of Fe(II)/Co(II) and Fe(III)/Co(III) have been synthesized. Molecular structures of six of them reveal that these six-coordinate complexes utilize all available donor sites of the ligands and assume M(II/III)N2(pyridine/pyrazine)N'2(amide)N''2(azo) coordination. Complexes of Fe(II) and Co(III) are diamagnetic and those of Fe(III) and Co(II) are paramagnetic (S = 1/2; room-temperature magnetic data and EPR spectra)...
August 14, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28803974/influence-of-amylose-content-and-oxidation-level-of-potato-starch-on-acetylation-granule-structure-and-radicals-formation
#15
Sławomir Pietrzyk, Teresa Fortuna, Lesław Juszczak, Dorota Gałkowska, Małgorzata Bączkowicz, Maria Łabanowska, Magdalena Kurdziel
This study was aimed at determining the effect of the amylose content of starch and oxidation level of potato starch on the structure of starch granules, and susceptibility to chemical modification (acetylation) and subsequent generation of radicals. Potato starch and waxy potato starch were oxidised with sodium hypochlorite applied in doses corresponding to 10, 20, and 30gCl/kg starch, and then acetylated with acetic acid anhydride. The carboxyl, carbonyl, acetyl groups were determined in modified starches...
August 10, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28803092/uniform-field-loop-gap-resonator-and-rectangular-teu02-for-aqueous-sample-epr-at-94ghz
#16
Jason W Sidabras, Tadeusz Sarna, Richard R Mett, James S Hyde
In this work we present the design and implementation of two uniform-field resonators: a seven-loop-six-gap loop-gap resonator (LGR) and a rectangular TEU02 cavity resonator. Each resonator has uniform-field-producing end-sections. These resonators have been designed for electron paramagnetic resonance (EPR) of aqueous samples at 94GHz. The LGR geometry employs low-loss Rexolite end-sections to improve the field homogeneity over a 3mm sample region-of-interest from near-cosine distribution to 90% uniform. The LGR was designed to accommodate large degassable Polytetrafluorethylen (PTFE) tubes (0...
August 5, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28800494/a-time-domain-model-and-experimental-validation-of-the-acoustic-field-radiated-by-air-coupled-transducers
#17
Ji Li, Bogdan Piwakowski
This paper presents a time-domain model for the prediction of an acoustic field in an air-coupled, non-contact, ultrasonic setup, which includes an air-coupled Emitter, the Propagation space and an air-coupled Receiver (EPR). The model takes into account the finite size of the aperture receiver, attenuation in air, and the electric response of the emitter-receiver set he. The attenuation is characterized by a causal time-domain Green's function, allowing the wideband attenuation of a lossy medium obeying the power law α(ω)=α0ω(η),1⩽η⩽2 to be included...
August 1, 2017: Ultrasonics
https://www.readbyqxmd.com/read/28800285/cytogenetic-reconstruction-of-gamma-ray-doses-delivered-to-atomic-bomb-survivors-dealing-with-wide-distributions-of-photon-energies-and-contributions-from-hematopoietic-stem-progenitor-cells
#18
Nori Nakamura, Yuko Hirai, Yoshiaki Kodama, Kanya Hamasaki, Harry M Cullings, Kismet A Cordova, Akio Awa
Retrospective estimation of the doses received by atomic bomb (A-bomb) survivors by cytogenetic methods has been hindered by two factors: One is that the photon energies released from the bomb were widely distributed, and since the aberration yield varies depending on the energy, the use of monoenergetic (60)Co gamma radiation to construct a calibration curve may bias the estimate. The second problem is the increasing proportion of newly formed lymphocytes entering into the lymphocyte pool with increasing time intervals since the exposures...
August 11, 2017: Radiation Research
https://www.readbyqxmd.com/read/28796514/operando-epr-for-simultaneous-monitoring-of-anionic-and-cationic-redox-processes-in-li-rich-metal-oxide-cathodes
#19
Mingxue Tang, Annalisa Dalzini, Xiang Li, Xuyong Feng, Po-Hsiu Chien, Likai Song, Yan-Yan Hu
Anionic redox chemistry offers a transformative approach for significantly increasing specific energy capacities of cathodes for rechargeable Li-ion batteries. This study employs operando electron paramagnetic resonance (EPR) to simultaneously monitor the evolution of both transition metal and oxygen redox reactions, as well as their intertwined couplings in Li2MnO3, Li1.2Ni0.2Mn0.6O2, and Li1.2Ni0.13Mn0.54Co0.13O2 cathodes. Reversible O(2-)/O2(n-) redox takes place above 3.0 V, which is clearly distinguished from transition metal redox in the operando EPR on Li2MnO3 cathodes...
August 14, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28796487/endogenous-catalytic-generation-of-o2-bubbles-for-in-situ-ultrasound-guided-high-intensity-focused-ultrasound-ablation
#20
Tianzhi Liu, Nan Zhang, Zhigang Wang, Meiying Wu, Yu Chen, Ming Ma, Hangrong Chen, Jianlin Shi
High intensity focused ultrasound (HIFU) surgery generally suffers from poor precision and low efficiency in clinical application, especially for cancer therapy. Herein, a multiscale hybrid catalytic nanoreactor (catalase@MONs, abbreviated as C@M) has been developed as a tumor-sensitive contrast and synergistic agent (C&SA) for ultrasound-guided HIFU cancer surgery, by integrating dendritic-structured mesoporous organosilica nanoparticles (MONs) and catalase immobilized in the large open pore channels of MONs...
August 16, 2017: ACS Nano
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