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Nitroxyl Radical

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https://www.readbyqxmd.com/read/30461277/n-o-bond-activation-and-cleavage-reactions-of-the-nitrosyl-bridged-complexes-m-2-cp-2-%C3%AE-pcy-2-%C3%AE-no-no-2-m-mo-w
#1
M Angeles Alvarez, M Esther García, Daniel García-Vivó, Alberto Ramos, Miguel A Ruiz, Adrián Toyos
The title complexes (1a,b) were prepared in two steps by first reacting the hydrides [M2 Cp2 (μ-H)(μ-PCy2 )(CO)4 ] with [NO](BF4 ) in the presence of Na2 CO3 to give dinitrosyls [M2 Cp2 (μ-PCy2 )(CO)2 (NO)2 ](BF4 ), which were then fully decarbonylated upon reaction with NaNO2 at 323 K. An isomer of the Mo2 complex having a cisoid arrangement of the terminal ligands ( cis-1a) was prepared upon irradiation of toluene solutions of 1a with visible-UV light at 288 K. The structure of these trinitrosyl complexes was investigated using X-ray diffraction and density functional theory (DFT) calculations, these revealing a genuine pyramidalization of the bridging NO that might be associated in part to an increase of charge at the N atom and anticipated a weakening of the N-O bond upon reaction with bases or reducing reagents...
November 21, 2018: Inorganic Chemistry
https://www.readbyqxmd.com/read/30388530/nitroxide-supported-on-nanometric-metal-oxides-as-new-hybrid-catalysts-for-selective-sugar-oxidation
#2
Mehdi Omri, Matthieu Becuwe, Carine Davoisne, Gwladys Pourceau, Anne Wadouachi
A new series of supported organocatalysts, prepared by a simple method, were used for selective sugar oxidation. This approach is based on the immobilization of a nitroxide derivative through a carboxylic function on nanometric metal oxides (TiO2 , Al2 O3 and CeO2 ), allowing the recovery of the catalyst. These hybrid materials were carefully characterized by Diffuse Reflectance FT-IR spectroscopy (DRIFT), ThermoGravimetric Analysis (TGA), X-Ray Diffraction (XRD), Brunauer-Emmet-Teller surface area measurements (B...
February 15, 2019: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/30372035/in-vivo-extracellular-ph-mapping-of-tumors-using-electron-paramagnetic-resonance
#3
Denis A Komarov, Yuki Ichikawa, Kumiko Yamamoto, Neil J Stewart, Shingo Matsumoto, Hironobu Yasui, Igor A Kirilyuk, Valery V Khramtsov, Osamu Inanami, Hiroshi Hirata
An electron paramagnetic resonance (EPR)-based method for noninvasive three-dimensional extracellular pH mapping was developed using a pH-sensitive nitroxyl radical as an exogenous paramagnetic probe. Fast projection scanning with a constant magnetic field sweep enabled the acquisition of four-dimensional (3D spatial +1D spectral) EPR images within 7.5 min. Three-dimensional maps of pH were reconstructed by processing the pH-dependent spectral information on the images. To demonstrate the proposed method of pH mapping, the progress of extracellular acidosis in tumor-bearing mouse legs was studied...
November 8, 2018: Analytical Chemistry
https://www.readbyqxmd.com/read/30226058/2-azaadamantane-n-oxyl-azado-cu-catalysis-enables-chemoselective-aerobic-oxidation-of-alcohols-containing-electron-rich-divalent-sulfur-functionalities
#4
Yusuke Sasano, Naoki Kogure, Shota Nagasawa, Koki Kasabata, Yoshiharu Iwabuchi
The chemoselective oxidation of alcohols containing electron-rich sulfur functionalities (e.g., 1,3-dithianes and sulfides) into their corresponding carbonyl compounds with the sulfur groups can sometimes be a demanding task in modern organic chemistry. A reliable method for this transformation, which features azaadamantane-type nitroxyl radical/copper catalysis using ambient air as the terminal oxidant is reported. The superiority of the developed method was demonstrated by comparing it with various conventional alcohol oxidation methods...
October 5, 2018: Organic Letters
https://www.readbyqxmd.com/read/30080991/don-t-just-say-no-differential-pathways-and-pharmacological-responses-to-diverse-nitric-oxide-donors
#5
REVIEW
Juan J Chiesa, Fernando M Baidanoff, Diego A Golombek
Nitric oxide (NO) is a gaseous free radical molecule with a short half-life (∼1 s), which can gain or lose an electron into three interchangeable redox-dependent forms, the radical (NO), the nitrosonium cation (NO+ ), and nitroxyl anion (HNO). NO acts as an intra and extracellular signaling molecule regulating a wide range of functions in the cardiovascular, immune, and nervous system. NO donors are collectively known by their ability to release NOin vitro and in vivo, being proposed as therapeutic pharmacological tools for the treatment of several pathologies, such as cardiovascular disease...
August 3, 2018: Biochemical Pharmacology
https://www.readbyqxmd.com/read/29771534/nitroxyl-modified-tobacco-mosaic-virus-as-a-metal-free-high-relaxivity-mri-and-epr-active-superoxide-sensor
#6
Madushani Dharmarwardana, André F Martins, Zhuo Chen, Philip M Palacios, Chance M Nowak, Raymond P Welch, Shaobo Li, Michael A Luzuriaga, Leonidas Bleris, Brad S Pierce, A Dean Sherry, Jeremiah J Gassensmith
Superoxide overproduction is known to occur in multiple disease states requiring critical care; yet, noninvasive detection of superoxide in deep tissue remains a challenge. Herein, we report a metal-free magnetic resonance imaging (MRI) and electron paramagnetic resonance (EPR) active contrast agent prepared by "click conjugating" paramagnetic organic radical contrast agents (ORCAs) to the surface of tobacco mosaic virus (TMV). While ORCAs are known to be reduced in vivo to an MRI/EPR silent state, their oxidation is facilitated specifically by reactive oxygen species-in particular, superoxide-and are largely unaffected by peroxides and molecular oxygen...
August 6, 2018: Molecular Pharmaceutics
https://www.readbyqxmd.com/read/29608853/nitrogen-dioxide-reaction-with-nitroxide-radical-derived-from-hydroxamic-acids-the-intermediacy-of-acyl-nitroso-and-nitroxyl-hno
#7
Eric Maimon, Amram Samuni, Sara Goldstein
Hydroxamic acids (RC(O)NHOH) form a class of compounds that display interesting chemical and biological properties The chemistry of RC(O)NHOH) is associated with one- and two-electron oxidations forming the respective nitroxide radical (RC(O)NHO• ) and acyl nitroso (RC(O)N═O), respectively, which are relatively unstable species. In the present study, the kinetics and mechanism of the • NO2 reaction with nitroxide radicals derived from acetohydroxamic acid, suberohydroxamic acid, benzohydroxamic acid, and suberoylanilide hydroxamic acid have been studied in alkaline solutions...
April 19, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29573493/magnetic-interactions-through-a-nonconjugated-framework-observed-in-back-to-back-connected-triazinyl-nitroxyl-biradical-derivatives
#8
Yusuke Takahashi, Ryo Matsuhashi, Youhei Miura, Naoki Yoshioka
Three hetero-biradical derivatives, with the structure of a back-to-back connected benzotriazinyl and tetramethyl or tetraethylisoindoline N-oxyl sharing a common benzo ring, 3-tert-butyl-1-phenyl-1,4,6,8-tetrahydro-6,6,8,8-tetramethyl-pyrrolo[4,5-g]-1,2,4-benzotriazin-4-yl-7-oxyl (1-tBu), 1,3-diphenyl-1,4,6,8-tetrahydro-6,6,8,8-tetramethyl-pyrrolo[4,5-g]-1,2,4-benzotriazin-4-yl-7-oxyl (1-Ph), and 3-tert-butyl-1-phenyl-1,4,6,8-tetrahydro-6,6,8,8-tetraethyl-pyrrolo[4,5-g]-1,2,4-benzotriazin-4-yl-7-oxyl (2-tBu), were synthesized and characterized by single-crystal X-ray analyses, variable-temperature magnetic susceptibility studies, and DFT calculations...
June 4, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29517233/when-do-strongly-coupled-diradicals-show-strongly-coupled-reactivity-thermodynamics-and-kinetics-of-hydrogen-atom-transfer-reactions-of-palladium-and-platinum-bis-iminosemiquinone-complexes
#9
Kyle M Conner, AnnaMaria C Arostegui, Daniel D Swanson, Seth N Brown
The 2,2'-biphenylene-bridged bis(iminosemiquinone) complexes ( t BuClip)M [ t BuClipH4 = 4,4'-di- tert-butyl- N, N'-bis(3,5-di- tert-butyl-2-hydroxyphenyl)-2,2'-diaminobiphenyl; M = Pd, Pt] can be reduced to the bis(aminophenoxide) complexes ( t BuClipH2 )M by reaction with hydrazobenzene (M = Pd) or by catalytic hydrogenation (M = Pt). The palladium complex with one aminophenoxide ligand and one iminosemiquinone ligand, ( t BuClipH)Pd, is generated by comproportionation of ( t BuClip)Pd with ( t BuClipH2 )Pd in a process that is both slow (0...
August 20, 2018: Inorganic Chemistry
https://www.readbyqxmd.com/read/29476040/hemodynamic-effects-of-glutathione-liganded-binuclear-dinitrosyl-iron-complex-evidence-for-nitroxyl-generation-and-modulation-by-plasma-albumin
#10
Taiming Liu, Meijuan Zhang, Michael H Terry, Hobe Schroeder, Sean M Wilson, Gordon G Power, Qian Li, Trent E Tipple, Dan Borchardt, Arlin B Blood
Glutathione-liganded binuclear dinitrosyl iron complex (glut-BDNIC) has been proposed to be a donor of nitric oxide (NO). This study was undertaken to investigate the mechanisms of vasoactivity, systemic hemodynamic effects, and pharmacokinetics of glut-BDNIC. To test the hypothesis that glut-BDNICs vasodilate by releasing NO in its reduced [nitroxyl (HNO)] state, a bioassay method of isolated, preconstricted ovine mesenteric arterial rings was used in the presence of selective scavengers of HNO or NO free radical (NO• ); the vasodilatory effects of glut-BDNIC were found to have characteristics similar to those of an HNO donor and markedly different than an NO• donor...
May 2018: Molecular Pharmacology
https://www.readbyqxmd.com/read/29469215/dinitrosyl-iron-complexes-formation-and-antiradical-action-in-heart-mitochondria
#11
Konstantin B Shumaev, Arina L Dudylina, Marina V Ivanova, Igor S Pugachenko, Enno K Ruuge
Mitochondria are widely known as a major source of reactive oxygen and nitrogen species for the cardiovascular system. Numerous studies established that superoxide anion radical production by heart mitochondria is only slightly suppressed under conditions of deep hypoxia, but is completely blocked under anoxia. It was found also that dinitrosyl iron complexes (DNIC) compare favourably with other physiologically active derivatives of nitric oxide (NO). DNIC with glutathione effectively scavenge superoxide radicals generated by mitochondria at different partial pressures of oxygen...
May 2018: BioFactors
https://www.readbyqxmd.com/read/29432006/enantioselective-synthesis-of-pyrroloindolines-via-noncovalent-stabilization-of-indole-radical-cations-and-applications-to-the-synthesis-of-alkaloid-natural-products
#12
Emily C Gentry, Lydia J Rono, Martina E Hale, Rei Matsuura, Robert R Knowles
While interest in the synthetic chemistry of radical cations continues to grow, controlling enantioselectivity in the reactions of these intermediates remains a challenge. Based on recent insights into the oxidation of tryptophan in enzymatic systems, we report a photocatalytic method for the generation of indole radical cations as hydrogen-bonded adducts with chiral phosphate anions. These noncovalent open-shell complexes can be intercepted by the stable nitroxyl radical TEMPO· to form alkoxyamine-substituted pyrroloindolines with high levels of enantioselectivity...
March 7, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29385348/electrochemically-controlled-cationic-polymerization-of-vinyl-ethers
#13
Brian M Peterson, Song Lin, Brett P Fors
Control of polymer initiation, propagation and termination is important in the development of complex polymer structures and advanced materials. Typically, this has been achieved chemically, electrochemically, photochemically or mechanochemically. Electrochemical control has been demonstrated in radical polymerizations; however, regulation of a cationic polymerization has yet to be achieved. Through the reversible oxidation of a polymer chain end with an electrochemical mediator, temporal control over polymer chain growth in cationic polymerizations was realized...
February 14, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29379338/synthesis-structure-antioxidant-activity-and-water-solubility-of-trolox-ion-conjugates
#14
Yuliya V Yushkova, Elena I Chernyak, Yuriy V Gatilov, Vladimir G Vasil'ev, Sergey V Morozov, Igor A Grigor'ev
The interaction of trolox with ammonia, alkylamines of different classes, and amino derivatives of heterocyclic compounds, including nitroxyl radicals and alkaloids, led to the production of ammonium salts called ion conjugates (ICs). Five ICs were characterised by X-ray diffraction. This is the first time a wide range of ICs were made from trolox with amines, and ESI-MS data demonstrated they have the potential to generate pseudomolecular [(A- B+ ) + H]+ ions. For all obtained trolox ICs, a significant increase (1-3 orders of magnitude) in water solubility was achieved while retaining high antioxidant activity...
January 2018: Saudi Pharmaceutical Journal: SPJ: the Official Publication of the Saudi Pharmaceutical Society
https://www.readbyqxmd.com/read/29320888/comparative-studies-with-epr-and-mri-on-the-in-vivo-tissue-redox-status-estimation-using-redox-sensitive-nitroxyl-probes-influence-of-the-choice-of-the-region-of-interest
#15
COMPARATIVE STUDY
Ken-Ichiro Matsumoto, James B Mitchell, Murali C Krishna
In vivo decay rates of a nitroxyl contrast agent were estimated by a MR redox imaging (MRRI) technique and compared with the decay rates obtained by the electron paramagnetic resonance spectroscopy (EPRS) and imaging (EPRI). MRRI is a dynamic imaging technique employing T1 -weighted pulse sequence, which can visualise a nitroxyl-induced enhancement of signal intensity by T1 -weighted contrast. EPR techniques can directly measure the paramagnetic nitroxyl radical. Both the squamous cell carcinoma (SCC) tumour-bearing and normal legs of a female C3H mouse were scanned by T1 -weighted SPGR sequence at 4...
February 2018: Free Radical Research
https://www.readbyqxmd.com/read/29205482/low-frequency-esr-studies-on-permeable-and-impermeable-deuterated-nitroxyl-radicals-in-corn-oil-solution
#16
D David Jebaraj, Hideo Utsumi, A Milton Franklin Benial
Low-frequency electron spin resonance studies were performed for 2 mM concentration of deuterated permeable and impermeable nitroxyl spin probes, 3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl and 3-carboxy-2,2,5,5,-tetramethyl-1-pyrrolidinyloxy in pure water and various concentrations of corn oil solution. The electron spin resonance parameters such as the line width, hyperfine coupling constant, g factor, rotational correlation time, permeability, and partition parameter were estimated. The broadening of line width was observed for nitroxyl radicals in corn oil mixture...
April 2018: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/29165366/nitroxides-as-antioxidants-and-anticancer-drugs
#17
REVIEW
Marcin Lewandowski, Krzysztof Gwozdzinski
Nitroxides are stable free radicals that contain a nitroxyl group with an unpaired electron. In this paper, we present the properties and application of nitroxides as antioxidants and anticancer drugs. The mostly used nitroxides in biology and medicine are a group of heterocyclic nitroxide derivatives of piperidine, pyrroline and pyrrolidine. The antioxidant action of nitroxides is associated with their redox cycle. Nitroxides, unlike other antioxidants, are characterized by a catalytic mechanism of action associated with a single electron oxidation and reduction reaction...
November 22, 2017: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/29130334/pulsed-electron-paramagnetic-resonance-imaging-applications-in-the-studies-of-tumor-physiology
#18
Shun Kishimoto, Ken-Ichiro Matsumoto, Keita Saito, Ayano Enomoto, Shingo Matsumoto, James B Mitchell, Nallathamby Devasahayam, Murali C Krishna
SIGNIFICANCE: Electron paramagnetic resonance imaging (EPRI) is capable of generating images of tissue oxygenation using exogenous paramagnetic probes such as trityl radicals or nitroxyl radicals. The spatial distribution of the paramagnetic probe can be generated using magnetic field gradients as in magnetic resonance imaging and, from its spectral features, spatial maps of oxygen can be obtained from live objects. In this review, two methods of signal acquisition and image formation/reconstruction are described...
May 20, 2018: Antioxidants & Redox Signaling
https://www.readbyqxmd.com/read/29127716/conformational-properties-membrane-interaction-and-antibacterial-activity-of-the-peptaibiotic-chalciporin-a-multitechnique-spectroscopic-and-biophysical-investigations-on-the-natural-compound-and-labeled-analogs
#19
Barbara Biondi, Cristina Peggion, Marta De Zotti, Chiara Pignaffo, Annalisa Dalzini, Marco Bortolus, Simona Oancea, Geta Hilma, Annalisa Bortolotti, Lorenzo Stella, Jens Z Pedersen, Victoria N Syryamina, Yuri D Tsvetkov, Sergei A Dzuba, Claudio Toniolo, Fernando Formaggio
In this work, an extensive set of spectroscopic and biophysical techniques (including FT-IR absorption, CD, 2D-NMR, fluorescence, and CW/PELDOR EPR) was used to study the conformational preferences, membrane interaction, and bioactivity properties of the naturally occurring synthetic 14-mer peptaibiotic chalciporin A, characterized by a relatively low (≈20%), uncommon proportion of the strongly helicogenic Aib residue. In addition to the unlabeled peptide, we gained in-depth information from the study of two labeled analogs, characterized by one or two residues of the helicogenic, nitroxyl radical-containing TOAC...
November 11, 2017: Biopolymers
https://www.readbyqxmd.com/read/29118910/feasibility-of-magnetic-resonance-redox-imaging-at-low-magnetic-field-comparison-at-1-t-and-7-t
#20
Mizuki Nakamura, Sayaka Shibata, Toshihide Yamasaki, Megumi Ueno, Ikuo Nakanishi, Ken-Ichiro Matsumoto, Tadashi Kamada, Ken-Ichi Yamada, Ichio Aoki
The effect of different static magnetic field strengths, 1 T or 7 T, on the quality of nitroxyl radical-based magnetic resonance redox imaging (MRRI) was examined. A stable nitroxyl radical, 3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine- N -oxyl (MC-PROXYL), was used as a T1 contrast agent. Phantoms and animals were scanned at 1 T and 7 T using a similar gradient echo sequence. The quality of T1 -weighted images and susceptibility of T1 -weighted signals were compared. The nitroxyl radical-based T1 -weighted signal enhancement ratio was higher at 1 T compared with at 7 T when the identical phantom was scanned using a similar gradient echo sequence...
2017: American Journal of Translational Research
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