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Mengdi Wu, Kun Feng, Qiuhui Li, Huiya Ma, Hongli Zhu, Yudou Xie, Gaofei Yan, Chao Chen, Kunping Yan
A Tempol compound with an amine group (4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl, NH2-Tempol) was cross-linked to hemoglobin in a one-step polymerization reaction to produce a novel hemoglobin-based oxygen carrier (HBOC) designated PolyHb-Tempol. The reaction parameters, including the reaction time, pH, temperature, and ratio of reactants, were optimized, and the physiochemical properties of the resulting product were characterized. PolyHb-Tempol didn't show any toxicity towards endothelial cells. Furthermore, from observations of cell morphology and viability, PolyHb-Tempol showed a significant ability to inhibit or eliminate oxidative stress induced by superoxide free radicals...
May 18, 2017: Artificial Cells, Nanomedicine, and Biotechnology
Yu Guo, Hui Li, Lan-Lan He, Dong-Xia Zhao, Li-Dong Gong, Zhong-Zhi Yang
The dioxygen formation mechanism of biological water oxidation in nature has long been the focus of argument; many diverse mechanistic hypotheses have been proposed. Based on a recent breakthrough in the resolution of the electronic and structural properties of the oxygen-evolving complex in the S3 state, our density functional theory (DFT) calculations reveal that the open-cubane oxo-oxyl coupling mechanism, whose substrates preferably originate from W2 and O5 in the S2 state, emerges as the best candidate for O-O bond formation in the S4 state...
May 17, 2017: Physical Chemistry Chemical Physics: PCCP
Amram Samuni, Eric Maimon, Sara Goldstein
The peroxidative activity of horseradish peroxidase (HRP) undergoes progressive inactivation while catalyzing the oxidation of nitrite by H2O2. The extent of inactivation increases as the pH increases, [nitrite] decreases or [H2O2] increases, and is accompanied by a loss of the Soret peak of HRP along with yellow-greenish coloration of the solution. HRP-catalyzed nitrite oxidation by H2O2 involves not only the formation of compounds I and II as transient heme species, but also compound III, all of which in turn, oxidize nitrite yielding (•)NO2...
May 8, 2017: Free Radical Biology & Medicine
Taku Matsushita, Yuya Moriyama, Genta Nagae, Hiroyuki Aburatani, Akimitsu Okamoto
The mixture of copper(ii) perchlorate and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) mildly and specifically oxidized 5-hydroxymethylcytosine to yield 5-formylcytosine because of its allyl alcohol specificity. The genomic DNA oxidized at 5-hydroxymethylcytosine by the copper(ii)/TEMPO oxidation was efficiently analyzed using various practical methods: DNA cleavage by piperidine, specific functionalization by hydrazone formation, and genome-wide high-resolution microarray.
May 11, 2017: Chemical Communications: Chem Comm
Xin Li, Lan Zhang, Golam Jalal Ahammed, Zhi-Xin Li, Ji-Peng Wei, Chen Shen, Peng Yan, Li-Ping Zhang, Wen-Yan Han
Flavonoids are one of the key secondary metabolites determining the quality of tea. Although exogenous brassinosteroid (BR), a steroidal plant hormone, can stimulate polyphenol biosynthesis in tea plants (Camellia sinensis L.), the relevance of endogenous BR in flavonoid accumulation and the underlying mechanisms remain largely unknown. Here we show that BR enhances flavonoid concentration in tea leaves by inducing an increase in the endogenous concentration of nitric oxide (NO). Notably, exogenous BR increased levels of flavonoids as well as NO in a concentration dependent manner, while suppression of BR levels by an inhibitor of BR biosynthesis, brassinazole (BRz), decreased the concentrations of both flavonoids and NO in tea leaves...
April 12, 2017: Journal of Plant Physiology
Massimo Bietti, Osvaldo Lanzalunga, Andrea Lapi, Teo Martin, Marco Mazzonna, Mariangela Polin, Michela Salamone
A change in regioselectivity has been observed in the hydrogen atom transfer (HAT) reactions from 4-alkyl-N,N-dimethylbenzylamines (alkyl = ethyl, isopropyl, and benzyl) to the phthalimide N-oxyl radical (PINO) by effect of protonation. This result can be rationalized on the basis of an acid-induced deactivation of the C-H bonds α to nitrogen toward HAT to PINO as evidenced by the 10(4)-10(7)-fold decrease in the HAT rate constants in acetonitrile following addition of 0.1 M HClO4. This acid-induced change in regioselectivity has been successfully applied for selective functionalization of the less activated benzylic C-H bonds para to the CH2N(CH3)2 group in the aerobic oxidation of 4-alkyl-N,N-dimethylbenzylamines catalyzed by N-hydroxyphthalimide in acetic acid...
May 17, 2017: Journal of Organic Chemistry
Qian Jiang, Xican Li, Yage Tian, Qiaoqi Lin, Hong Xie, Wenbiao Lu, Yuguang Chi, Dongfeng Chen
BACKGROUND: Mori Fructus and Mori Ramulus are two traditional Chinese herbal medicines from mulberries. The present work explores their beneficial effects on •OH-treated mesenchymal stem cells (MSCs) and discusses possible mechanisms. METHODS: Lyophilized aqueous extracts of Mori Fructus (LAMF) and Mori Ramulus (LAMR) were prepared and analyzed using HPLC. LAMF and LAMR (along with morin) were further investigated for their effects on •OH-treated MSCs using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl (MTT) assay...
May 2, 2017: BMC Complementary and Alternative Medicine
David Jebaraj D, Hideo Utsumi, Milton Franklin Benial A
Detailed dynamic nuclear polarization and electron spin resonance studies were carried out for 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl, 3-carboxy-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl,3-methoxycarbonyl-2,2,5,5-tetramethy pyrolidine-1-oxyl nitroxyl radicals and their corresponding deuterated nitroxyl radicals, used in Overhauser-enhanced magnetic resonance imaging for the first time. The dynamic nuclear polarization parameters such as DNP factor, longitudinal relaxivity, saturation parameter, leakage factor and coupling factor were estimated for deuterated nitroxyl radicals...
April 26, 2017: Magnetic Resonance in Chemistry: MRC
Per E M Siegbahn
Two different types of mechanisms are at present suggested for the O-O bond-formation step in photosystem II. The first one is a coupling between an oxyl radical and a bridging oxo. The second one is a nucleophilic water attack on a terminal oxo (or oxyl) group. In the present short paper, the six most reasonable versions of the latter mechanism have been studied and compared with the oxo-oxyl mechanism. The barriers are found to be much too high for the water attack, and that mechanism can therefore safely be ruled out...
April 24, 2017: Proceedings of the National Academy of Sciences of the United States of America
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...
May 4, 2017: Journal of Physical Chemistry. B
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
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
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
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
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
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
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
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
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
Fazalurahman Kuttassery, Siby Mathew, Shogo Sagawa, Sebastian Nybin Remello, Arun Thomas, Daisuke Yamamoto, Satomi Onuki, Yu Nabetani, Hiroshi Tachibana, Haruo Inoue
We report herein a new molecular catalyst for efficient water splitting, aluminum porphyrins (tetra-methylpyridiniumylporphyrinatealuminum: AlTMPyP), containing 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 detected by a cold-spray ionization mass-spectrometry in high-resolution MS (HRMS) mode and the structure of the intermediate species 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
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