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https://www.readbyqxmd.com/read/28422504/integrated-computational-approach-to-the-electron-paramagnetic-resonance-characterization-of-rigid-310-helical-peptides-with-toac-nitroxide-spin-labels
#1
Marco Gerolin, Mirco Zerbetto, Alessandro Moretto, Fernando Formaggio, Claudio Toniolo, Martin van Son, Maryam Hashemi Shabestari, Martina Huber, Paolo Calligari, Antonino Polimeno
We address the interpretation, via an integrated computational approach, of the experimental continuous-wave electron paramagnetic resonance (cw-EPR) spectra of a complete set of conformationally highly restricted, stable 310-helical peptides from hexa- to nonamers, each bis-labeled with nitroxide radical-containing TOAC (4-amino-1-oxyl-2,2,6,6-tetramethylpiperidine-4-carboxylic acid) residues. The usefulness of TOAC for this type of analysis has been shown already to be due to its cyclic piperidine side chain, which is rigidly connected to the peptide backbone α-carbon...
April 19, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28413754/an-approach-toward-replacing-vanadium-a-single-organic-molecule-for-the-anode-and-cathode-of-an-aqueous-redox-flow-battery
#2
Tobias Janoschka, Christian Friebe, Martin D Hager, Norbert Martin, Ulrich S Schubert
By combining a viologen unit and a 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) radical in one single combi-molecule, an artificial bipolar redox-active material, 1-(4-(((1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)oxy)carbonyl)benzyl)-1'-methyl-[4,4'-bipyridine]-1,1'-diium-chloride (VIOTEMP), was created that can serve as both the anode (-0.49 V) and cathode (0.67 V vs. Ag/AgCl) in a water-based redox-flow battery. While it mimics the redox states of flow battery metals like vanadium, the novel aqueous electrolyte does not require strongly acidic media and is best operated at pH 4...
April 2017: ChemistryOpen
https://www.readbyqxmd.com/read/28385240/in-situ-synthesis-of-silver-nanoparticles-into-tempo-mediated-oxidized-bacterial-cellulose-and-their-antivibriocidal-activity-against-shrimp-pathogens
#3
Sivaramasamy Elayaraja, Kamil Zagorsek, Fuhua Li, Jianhai Xiang
Vibrionaceae is bifolded drug resistant emerging pathogens, active in various aquaculture sectors especially in shrimp culture around the world. V. parahaemolyticus are most dreadful viral outbreaks to shrimp culture. During the last decade the shrimp production level has been increased and also accompanied with various diseases. In the present research bacterial cellulose (BC) membrane produced by Gluconacetobacter xylinus in cell suspension. Further, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) oxidation was done to activate carboxyl group subsequently, TEMPO oxidized BC immersed in AgNO3 solution to generate AgNP anchored with BC to increase vibriocidal activity...
June 15, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28376643/effect-of-tempol-on-peripheral-neuropathy-in-diet-induced-obese-and-high-fat-fed-low-dose-streptozotocin-treated-c57bl6-j-mice
#4
Alexander Obrosov, Hanna Shevalye, Lawrence J Coppey, Mark A Yorek
In this study, we sought to determine the efficacy of tempol on multiple neuropathic endpoints in a diet-induced obese mouse, a model of pre-diabetes, and a high-fat fed low-dose streptozotocin treated mouse, a model of type 2 diabetes. Tempol (4-hydroxy-2,2,6,6-tetramethylpiperdine -1-oxyl) is a low molecular weight, water soluble, membrane permeable, and metal-independent superoxide dismutase mimetic that has been widely used in cellular studies for the removal of intracellular and extracellular superoxide...
April 19, 2017: Free Radical Research
https://www.readbyqxmd.com/read/28375016/intramolecular-oxyl-radical-coupling-promotes-o-o-bond-formation-in-a-homogeneous-mononuclear-mn-based-water-oxidation-catalyst-a-computational-mechanistic-investigation
#5
Douglas W Crandell, Song Xu, Jeremy M Smith, Mu-Hyun Baik
The mechanism of water oxidation performed by a recently discovered manganese pyridinophane catalyst [Mn(Py2N(t)Bu2)(H2O)2](2+) is studied using density functional theory methods. A complete catalytic cycle is constructed and the catalytically active species is identified to consist of a Mn(V)-bis(oxo) moiety that is generated from the resting state by a series of proton-coupled electron transfer reactions. Whereas the electronic ground state of this key intermediate is found to be a triplet, the most favorable pathway for O-O bond formation is found on the quintet potential energy surface and involves an intramolecular coupling of two oxyl radicals with opposite spins bound to the Mn-center that adopts an electronic structure most consistent formally with a high-spin Mn(III) ion...
April 4, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28365302/nitroxides-protect-horseradish-peroxidase-from-h2o2-induced-inactivation-and-modulate-its-catalase-like-activity
#6
Amram Samuni, Eric Maimon, Sara Goldstein
BACKGROUND: Horseradish peroxidase (HRP) catalyzes H2O2 dismutation while undergoing heme inactivation. The mechanism underlying this process has not been fully elucidated. The effects of nitroxides, which protect metmyoglobin and methemoglobin against H2O2-induced inactivation, have been investigated. METHODS: HRP reaction with H2O2 was studied by following H2O2 depletion, O2 evolution and heme spectral changes. Nitroxide concentration was followed by EPR spectroscopy, and its reactions with the oxidized heme species were studied using stopped-flow...
March 29, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28363600/heme-modulates-trypanosoma-cruzi-bioenergetics-inducing-mitochondrial-ros-production
#7
Natália P Nogueira, Francis M S Saraiva, Matheus P Oliveira, Ana Paula M Mendonça, Job D F Inacio, Elmo E Almeida-Amaral, Rubem F Menna-Barreto, Gustavo A T Laranja, Eduardo J Lopes Torres, Marcus F Oliveira, Marcia C Paes
Trypanosoma cruzi is the causative agent of Chagas disease and has a single mitochondrion, an organelle responsible for ATP production and the main site for the formation of reactive oxygen species (ROS). T. cruzi is an obligate intracellular parasite with a complex life cycle that alternates between vertebrate and invertebrate hosts, therefore the development of survival strategies and morphogenetic adaptations to deal with the various environments is mandatory. Over the years our group has been studying the vector-parasite interactions using heme as a physiological oxidant molecule that triggered epimastigote proliferation however, the source of ROS induced by heme remained unknown...
March 29, 2017: Free Radical Biology & Medicine
https://www.readbyqxmd.com/read/28361852/epr-spectroscopy-studies-of-changes-in-erythrocyte-membranes-in-patients-with-laryngeal-cancer
#8
Y B Burlaka, O V Sukhoveev, N V Grin, O M Khilchevskyi, S V Verevka
AIM: To evaluate microviscosity and sorption capacity of erythrocyte membranes (SCEM) from patients with laryngeal cancer (LC). MATERIALS AND METHODS: Samples from 35 patients with LC of stages II and III and 20 healthy volunteers were investigated by electron paramagnetic resonance with Bis(1-oxyl-2,2,6,6-tetramethylpiperidinyl-4)-ester of 5,7-dimethyladamantane-1,3-dicarbonic acid (AdTEMPO) probe. SCEM was evaluated by amount of unabsorbed methylene blue. RESULTS: Microviscosity of erythrocyte membranes was determined by the effective rotational diffusion correlation times (τeff) and a decrease in radical spectrum signal intensity per hour...
March 2017: Experimental Oncology
https://www.readbyqxmd.com/read/28358985/substitution-of-a-fluorine-atom-in-perfluorobenzonitrile-by-a-lithiated-nitronyl-nitroxide
#9
Evgeny V Tretyakov, Pavel A Fedyushin, Elena V Panteleeva, Dmitri V Stass, Irina Yu Bagryanskaya, Irina V Beregovaya, Artem S Bogomyakov
A 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (1) lithium derivative was found to react with perfluorobenzonitrile (2) substituting its para-fluorine atom to form 2-(4-cyanotetrafluorophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl (3), a new nitronyl nitroxide containing a multifunctional framework of strong electron-withdrawing nature. This result shows the possibility of obtaining multifunctional nitronyl nitroxides via the interaction of paramagnetic lithium derivatives as C-nucleophiles with polyfluoroarenes activated for nucleophilic substitution...
April 6, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28350431/cellulose-nanofibers-from-softwood-hardwood-and-tunicate-preparation-structure-film-performance-interrelation
#10
Yadong Zhao, Carl Moser, Mikael E Lindström, Gunnar Henriksson, Jiebing Li
This work reveals the structural variations of cellulose nanofibers (CNF) prepared from different cellulose sources, including softwood (Picea abies), hardwood (Eucalyptus grandis × E. urophylla), and tunicate (Ciona intestinalis), using different preparation processes and their correlations to the formation and performance of the films prepared from the CNF. Here, the CNF are prepared from wood chemical pulps and tunicate isolated cellulose by an identical homogenization treatment subsequent to either an enzymatic hydrolysis or a 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation...
April 10, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28322007/one-electron-initiated-two-electron-oxidation-of-water-by-aluminum-porphyrins-with-earth-s-most-abundant-metal-ion
#11
Fazalurahman Kuttassery, Siby Mathew, Shogo Sagawa, Sebastian Nybin Remello, Arun Thomas, Daisuke Yamamoto, Satomi Onuki, Yu Nabetani, Hiroshi Tachibana, Haruo Inoue
We report here a new molecular catalyst for efficient water splitting, aluminum porphyrins (tetra-methylpyridiniumylporphyrinatealuminum: AlTMPyP), containing the Earth's most abundant metal as the central ion. One-electron oxidation of the aluminum porphyrin initiates the two-electron oxidation of water to form hydrogen peroxide as the primary reaction product with the lowest known overpotential (97 mV). The aluminum-peroxo complex was clearly detected by a cold-spray ionization mass-spectrometry in HRMS mode and the structure of the intermediate was further confirmed using laser-Raman spectroscopy, indicating the hydroperoxy complex of AlTMPyP to be the key intermediate in the reaction...
March 20, 2017: ChemSusChem
https://www.readbyqxmd.com/read/28287515/a-protocol-for-electrochemical-evaluations-and-state-of-charge-diagnostics-of-a-symmetric-organic-redox-flow-battery
#12
Wentao Duan, Rama S Vemuri, Dehong Hu, Zheng Yang, Xiaoliang Wei
Redox flow batteries have been considered as one of the most promising stationary energy storage solutions for improving the reliability of the power grid and deployment of renewable energy technologies. Among the many flow battery chemistries, non-aqueous flow batteries have the potential to achieve high energy density because of the broad voltage windows of non-aqueous electrolytes. However, significant technical hurdles exist currently limiting non-aqueous flow batteries to demonstrate their full potential, such as low redox concentrations, low operating currents, under-explored battery status monitoring, etc...
February 13, 2017: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/28267498/lignocellulosic-nanofibers-from-triticale-straw-the-influence-of-hemicelluloses-and-lignin-in-their-production-and-properties
#13
Quim Tarrés, Nanci Vanesa Ehman, María Evangelina Vallejos, Maria Cristina Area, Marc Delgado-Aguilar, Pere Mutjé
The present work aims to determine the influence of hemicellulose and lignin content in the production of lignocellulosic nanofibers (LCNF) from triticale straws. Triticale straws were digested and then gradually delignified, preserving as much hemicelluloses as possible. The obtained LCNF was characterized and used as paper strength additive, observing that hemicellulose and lignin have a key role on the final properties thereof, as well as on their reinforcing potential as paper additive, obtaining LCNF with the same paper reinforcing potential than CNF obtained by TEMPO ((2,2,6,6-Tetramethyl-piperidin-1-yl)oxyl) mediated oxidation...
May 1, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28257840/non-invasive-imaging-of-the-levels-and-effects-of-glutathione-on-the-redox-status-of-mouse-brain-using-electron-paramagnetic-resonance-imaging
#14
Miho C Emoto, Yuta Matsuoka, Ken-Ichi Yamada, Hideo Sato-Akaba, Hirotada G Fujii
Glutathione (GSH) is the most abundant non-protein thiol that buffers reactive oxygen species in the brain. GSH does not reduce nitroxides directly, but in the presence of ascorbates, addition of GSH increases ascorbate-induced reduction of nitroxides. In this study, we used electron paramagnetic resonance (EPR) imaging and the nitroxide imaging probe, 3-methoxycarbonyl-2,2,5,5-tetramethyl-piperidine-1-oxyl (MCP), to non-invasively obtain spatially resolved redox data from mouse brains depleted of GSH with diethyl maleate compared to control...
April 15, 2017: Biochemical and Biophysical Research Communications
https://www.readbyqxmd.com/read/28257189/the-role-of-the-secondary-coordination-sphere-in-a-fungal-polysaccharide-monooxygenase
#15
Elise A Span, Daniel L M Suess, Marc C Deller, R David Britt, Michael A Marletta
Polysaccharide monooxygenases (PMOs) are secreted metalloenzymes that catalyze the oxidative degradation of polysaccharides in a copper-, oxygen-, and reductant-dependent manner. Cellulose-active fungal PMOs degrade cellulosic substrates to be utilized as a carbon source for fungal growth. To gain insight into the PMO mechanism, the role of conserved residues in the copper coordination sphere was investigated. Here, we report active-site hydrogen-bonding motifs in the secondary copper coordination sphere of MtPMO3*, a C1-oxidizing PMO from the ascomycete fungus Myceliophthora thermophila...
March 3, 2017: ACS Chemical Biology
https://www.readbyqxmd.com/read/28246040/degradation-of-contaminants-by-cu-activated-molecular-oxygen-in-aqueous-solutions-evidence-for-cupryl-species-cu-3
#16
Yong Feng, Po-Heng Lee, Deli Wu, Zhengyuan Zhou, Hangkong Li, Kaimin Shih
Copper ions (Cu(2+) and Cu(+)) have shown potential as Fenton-like activators for the circumneutral removal of organic contaminants from aqueous solutions. However, the major active species (cupryl species (Cu(3+)) versus hydroxyl radical (OH)) produced during the activation of hydrogen peroxide by Cu(+) remain unclear. In this study, Cu(+)-O2 oxidation, in which hydrogen peroxide is produced via the activated decomposition of dissolved molecular oxygen, was used to degrade sulfadiazine, methylene blue, and benzoic acid...
February 20, 2017: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/28240552/ikmtsl-pte-a-phospholipid-based-epr-probe-for-surface-electrostatic-potential-of-biological-interfaces-at-neutral-ph-effects-of-temperature-and-effective-dielectric-constant-of-the-solvent
#17
Maxim A Voinov, Christina T Scheid, Igor A Kirilyuk, Dmitrii G Trofimov, Alex I Smirnov
The synthesis and characterization of a lipidlike electrostatic spin probe, (S)-2,3-bis(palmitoyloxy)propyl 2-((4-(4-(dimethylamino)-2-ethyl-1-oxyl-5,5-dimethyl-2,5-dihydro-1H-imidazol-2-yl)benzyl)disulfanyl)ethyl phosphate (IKMTSL-PTE), are being reported. The intrinsic pKa(0) of IKMTSL-PTE was determined by X-band (9.5 GHz) electron paramagnetic resonance (EPR) titration of a water-soluble model compound, 4-(dimethylamino)-2-ethyl-2-(4-(((2-hydroxyethyl)disulfanyl)methyl)phenyl)-5,5-dimethyl-2,5-dihydro-1H-imidazol-1-oxyl (IKMTSL-ME), an adduct of methanethiosulfonate spin label IKMTSL and 2-mercaptoethanol...
March 10, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28238951/oral-administration-of-the-nitroxide-radical-tempol-exhibits-immunomodulatory-and-therapeutic-properties-in-multiple-sclerosis-models
#18
Sarah Neil, Jaebong Huh, Victoria Baronas, Xinhui Li, Henry F McFarland, Murali Cherukuri, James B Mitchell, Jacqueline A Quandt
Therapies with both immunomodulatory and neuroprotective properties are thought to have the greatest promise in reducing the severity and progression of multiple sclerosis (MS). Several reactive oxygen (ROS) and reactive nitrogen species (RNS) are implicated in inflammatory-mediated damage to the central nervous system (CNS) in MS and its animal model, experimental autoimmune encephalomyelitis (EAE). TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) is a stable nitroxide radical with potent antioxidant activity...
February 24, 2017: Brain, Behavior, and Immunity
https://www.readbyqxmd.com/read/28220127/nitric-oxide-ameliorates-zinc-oxide-nanoparticles-phytotoxicity-in-wheat-seedlings-implication-of-the-ascorbate-glutathione-cycle
#19
Durgesh K Tripathi, Rohit K Mishra, Swati Singh, Samiksha Singh, Kanchan Vishwakarma, Shivesh Sharma, Vijay P Singh, Prashant K Singh, Sheo M Prasad, Nawal K Dubey, Avinash C Pandey, Shivendra Sahi, Devendra K Chauhan
The present study investigates ameliorative effects of nitric oxide (NO) against zinc oxide nanoparticles (ZnONPs) phytotoxicity in wheat seedlings. ZnONPs exposure hampered growth of wheat seedlings, which coincided with reduced photosynthetic efficiency (Fv/Fm and qP), due to increased accumulation of zinc (Zn) in xylem and phloem saps. However, SNP supplementation partially mitigated the ZnONPs-mediated toxicity through the modulation of photosynthetic activity and Zn accumulation in xylem and phloem saps...
2017: Frontiers in Plant Science
https://www.readbyqxmd.com/read/28212027/ferromagnetic-coupling-in-the-heterospin-bis-catecholato-manganese-iv-complex-with-pyridine-substituted-by-nitronyl-nitroxide
#20
Michael P Bubnov, Irina A Teplova, Eugenia A Kopylova, Konstantin A Kozhanov, Artem S Bogomyakov, Marina V Petrova, Vitaly A Morozov, Victor I Ovcharenko, Vladimir K Cherkasov
A new bis(3,6-di-tert-butyl-catecholato)manganese complex with two 4-NIT-Py ligands was synthesized and characterized [4-NIT-Py = pyridine substituted at position 4 with nitronyl-nitroxide radical, 2-(pyridin-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl]. X-ray diffraction indicated an octahedral environment of the manganese atom with a trans arrangement of ligands. Bonds lengths in the inner coordination core of the metal and in the chelate cycles that are representative of the charge distribution between the metal and ligands displayed a Mn(IV)(Cat(2-))2 charge distribution...
February 17, 2017: Inorganic Chemistry
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