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Kota Sasaki, Tomohiro Ito, Hirotada G Fujii, Shingo Sato
The hybrid compounds 1-5 comprised of five nitroxides with ibuprofen were synthesized and their reduction rate for ascorbic acid (AsA) and methyl radicals were measured in comparison with 3-hydroxy-tetramethylpyrrolidine-1-oxyl (PROXYL) 6. The rate constants in reduction reaction with 200-fold excess of AsA were determined in following order: 1 (0.42±0.06), 3 (0.17±0.06), 2 (0.10±0.05), and 6 (0.09±0.02 M(-1)s(-1)). The remaining two sterically shielded nitroxides 4 and 5 scarcely reacted with AsA. In the reaction with the more reactive methyl radicals, produced by 200-fold excess of Fenton's reagent, the reduction rates of 2, 4, and 5 were in the following decreasing order: 2 (1...
2016: Chemical & Pharmaceutical Bulletin
Yoshihiro Shimoyama, Tomoya Ishizuka, Hiroaki Kotani, Yoshihito Shiota, Kazunari Yoshizawa, Kaoru Mieda, Takashi Ogura, Toshihiro Okajima, Shunsuke Nozawa, Takahiko Kojima
Proton-coupled electron-transfer oxidation of a Ru(II) -OH2 complex, having an N-heterocyclic carbene ligand, gives a Ru(III) -O(.) species, which has an electronically equivalent structure of the Ru(IV) =O species, in an acidic aqueous solution. The Ru(III) -O(.) complex was characterized by spectroscopic methods and DFT calculations. The oxidation state of the Ru center was shown to be close to +3; the Ru-O bond showed a lower-energy Raman scattering at 732 cm(-1) and the Ru-O bond length was estimated to be 1...
October 6, 2016: Angewandte Chemie
Inae Jang, Sun Young Lee, Song Hwangbo, Dukjin Kang, Hookeun Lee, Hugh I Kim, Bongjin Moon, Han Bin Oh
The present study demonstrates that one-step peptide backbone fragmentations can be achieved using the TEMPO [2-(2,2,6,6-tetramethyl piperidine-1-oxyl)]-assisted free radical-initiated peptide sequencing (FRIPS) mass spectrometry in a hybrid quadrupole time-of-flight (Q-TOF) mass spectrometer and a Q-Exactive Orbitrap instrument in positive ion mode, in contrast to two-step peptide fragmentation in an ion-trap mass spectrometer (reference Anal. Chem. 85, 7044-7051 (30)). In the hybrid Q-TOF and Q-Exactive instruments, higher collisional energies can be applied to the target peptides, compared with the low collisional energies applied by the ion-trap instrument...
September 29, 2016: Journal of the American Society for Mass Spectrometry
Imre Farkas, Csaba Vastagh, Erzsébet Farkas, Flóra Bálint, Katalin Skrapits, Erik Hrabovszky, Csaba Fekete, Zsolt Liposits
Glucagon-like peptide-1 (GLP-1), a metabolic signal molecule, regulates reproduction, although, the involved molecular mechanisms have not been elucidated, yet. Therefore, responsiveness of gonadotropin-releasing hormone (GnRH) neurons to the GLP-1 analog Exendin-4 and elucidation of molecular pathways acting downstream to the GLP-1 receptor (GLP-1R) have been challenged. Loose patch-clamp recordings revealed that Exendin-4 (100 nM-5 μM) elevated firing rate in hypothalamic GnRH-GFP neurons of male mice via activation of GLP-1R...
2016: Frontiers in Cellular Neuroscience
Yuan Yuan Ji, Yan Jun Ma, Jian Wen Wang
Hypocrellin B (HB), a natural perylenequinone pigment, has been successfully employed in the photodynamic therapy (PDT) in a variety of human cancer cells due to its high singlet oxygen yield. To investigate the generation of nitric oxide (NO) and its role on cancer cell death induced by PDT, we used human hepatocellular carcinoma (HepG2) cells and HB as a photosensitizer. HB/light treatment decreased the growth of HepG2 cells in a dose-dependent manner with an IC50 of 3.10μM, activated caspase-3, -9 and induced apoptosis in HepG2 cells...
October 2016: Journal of Photochemistry and Photobiology. B, Biology
Jian Luo, Jian Zhang
A metal-free protocol to generate phthalimide-N-oxyl (PINO) radicals from N-hydroxyphthalimide (NHPI) via a photoinduced proton-coupled electron transfer process is reported. Using donor-substituted aromatic ketones, such as 4,4'-bis(diphenylamino)benzophenone (DPA-BP), PINO radicals are efficiently produced and subsequently utilized to functionalize olefins to afford a new class of alkyl hydroperoxides. The DPA-BP/NHPI/O2 photocatalytic system exhibits high efficiency toward the aerobic oxidation of β-O-4 lignin models...
October 7, 2016: Journal of Organic Chemistry
Yuanyuan Yu, Qiang Wang, Jiugang Yuan, Xuerong Fan, Ping Wang
This study demonstrated a new enzymatic methodology to graft β-cyclodextrin onto wool. The primary hydroxyl groups in β-cyclodextrin were oxidized to aldehyde groups using laccase/2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), which reacted with the amino groups of wool to form Schiff bases. The effects of treatment conditions (treatment temperature, laccase dosage, TEMPO dosage, treatment time) on the aldehyde and carboxyl contents in β-cyclodextrin were studied. FTIR spectrum of oxidized β-cyclodextrin showed the presence of aldehyde and carboxyl groups...
November 20, 2016: Carbohydrate Polymers
Yoko Hase, Juntaro Seki, Tohru Shiga, Fuminori Mizuno, Hidetaka Nishikoori, Hideki Iba, Kensuke Takechi
A novel indirect charging system that uses a redox mediator was demonstrated for Li-O2 batteries. 4-Methoxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl (MeO-TEMPO) was applied as a mediator to enable the oxidation of Li2O2, even though Li2O2 is electrochemically isolated. This system promotes the oxidation of Li2O2 without parasitic reactions attributed to electrochemical charging and reduces the charging time.
October 6, 2016: Chemical Communications: Chem Comm
Svyatoslav E Tolstikov, Evgeny V Tretyakov, Dmitry E Gorbunov, Irina F Zhurko, Matvey V Fedin, Galina V Romanenko, Artem S Bogomyakov, Nina P Gritsan, Dmitry G Mazhukin
It was shown that dipole-stabilized paramagnetic carbanion lithiated 4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide can be attached in a nucleophilic manner to either isolated or conjugated aldonitrones of the 2,5-dihydroimidazole 3-oxide and 2H-imidazole 1-oxide series to afford adducts the subsequent oxidation of which leads to polyfunctional mono- and diradicals. According to XRD, at least two polymorphic modifications can be formed during crystallization of the resulting paramagnetic compounds, and for each of them, geometric parameters of the molecules are similar...
October 4, 2016: Chemistry: a European Journal
Keisuke Furukawa, Haruki Inada, Masatoshi Shibuya, Yoshihiko Yamamoto
The chemoselective oxidation of α-hydroxy acids to α-keto acids catalyzed by 2-azaadamantane N-oxyl (AZADO), a nitroxyl radical catalyst, is described. Although α-keto acids are labile and can easily release CO2 under oxidation conditions, the use of molecular oxygen as a cooxidant enables the desired chemoselective oxidation.
September 2, 2016: Organic Letters
Saber Ghasemi Karaj-Abad, Mojtaba Abbasian, Mehdi Jaymand
For the first time, nitroxide-mediated polymerization (NMP) was used for synthesis of graft and block copolymers using cellulose (Cell) as a backbone, and polystyrene (PSt) and poly(methyl metacrylate) (PMMA) as the branches. For this purpose, Cell was acetylated by 2-bromoisobutyryl bromide (BrBiB), and then the bromine group was converted to 4-oxy-2,2,6,6-tetramethylpiperidin-1-oxyl group by a substitution nucleophilic reaction to afford a macroinitiator (Cell-TEMPOL). The macroinitiator obtained was subsequently used in controlled graft and block copolymerizations of St and MMA monomers to yield Cell-g-PSt and Cell-g-(PMMA-b-PSt)...
November 5, 2016: Carbohydrate Polymers
Bianca Hemmeryckx, Philipp Hohensinner, Melissa Swinnen, Ward Heggermont, Johann Wojta, Henri Roger Lijnen
Bmal1 (brain and muscle ARNT-like protein-1) deficient (Bmal1) mice prematurely age due to an increased reactive oxygen species (ROS) production. These mice also show a decline in cardiac function with age. We investigated whether an anti-oxidant treatment can ameliorate the declining cardiac function in prematurely aged Bmal1 mice. Male Bmal1 and wild-type (Bmal1) mice were exposed for 15 weeks to a high fat and high cholesterol diet with or without the anti-oxidant 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL; 5 mmol/l; in drinking water during the last 10 weeks)...
August 4, 2016: Journal of Cardiovascular Pharmacology
Bhawna Soni, El Barbary Hassan, M Wes Schilling, Barakat Mahmoud
The development of biobased active films for use in food packaging is increasing due to low cost, environmental appeal, renewability and availability. The objective of this research was to develop an effective and complete green approach for the production of bionanocomposite films with enhanced mechanical and barrier properties. This was accomplished by incorporating TEMPO-oxidized cellulose nanofibers (2,2,6,6-tetramethylpiperidine-1-oxyl radical) into a chitosan matrix. An aqueous suspension of chitosan (100-75wt%), sorbitol (25wt%) and TEMPO-oxidized cellulose nanofibers (TEMPO-CNFs, 0-25wt%) were cast in an oven at 40°C for 2-4days...
October 20, 2016: Carbohydrate Polymers
Chao Liu, Bin Li, Haishun Du, Dong Lv, Yuedong Zhang, Guang Yu, Xindong Mu, Hui Peng
In this work, nanocellulose was extracted from bleached corncob residue (CCR), an underutilized lignocellulose waste from furfural industry, using four different methods (i.e. sulfuric acid hydrolysis, formic acid (FA) hydrolysis, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, and pulp refining, respectively). The self-assembled structure, morphology, dimension, crystallinity, chemical structure and thermal stability of prepared nanocellulose were investigated. FA hydrolysis produced longer cellulose nanocrystals (CNCs) than the one obtained by sulfuric acid hydrolysis, and resulted in high crystallinity and thermal stability due to its preferential degradation of amorphous cellulose and lignin...
October 20, 2016: Carbohydrate Polymers
Julia Catalán, Elina Rydman, Kukka Aimonen, Kati-Susanna Hannukainen, Satu Suhonen, Esa Vanhala, Carlos Moreno, Valérie Meyer, Denilson da Silva Perez, Asko Sneck, Ulla Forsström, Casper Højgaard, Martin Willemoes, Jacob R Winther, Ulla Vogel, Henrik Wolff, Harri Alenius, Kai M Savolainen, Hannu Norppa
Nanofibrillated cellulose (NFC) is a sustainable and renewable nanomaterial, with diverse potential applications in the paper and medical industries. As NFC consists of long fibres of high aspect ratio, we examined here whether TEMPO-(2,2,6,6-tetramethyl-piperidin-1-oxyl) oxidised NFC (length 300-1000nm, thickness 10-25nm), administrated by a single pharyngeal aspiration, could be genotoxic to mice, locally in the lungs or systemically in the bone marrow. Female C57Bl/6 mice were treated with four different doses of NFC (10, 40, 80 and 200 µg/mouse), and samples were collected 24h later...
July 28, 2016: Mutagenesis
Martin Kaupp, Amir Karton, Florian A Bischoff
The radical anion [Al2O4](-) has been identified as a rare example of a small gas-phase mixed-valence system with partially localized, weakly coupled class II character in the Robin/Day classification. It exhibits a low-lying C2v minimum with one terminal oxyl radical ligand and a high-lying D2h minimum at about 70 kJ/mol relative energy with predominantly bridge-localized-hole character. Two identical C2v minima and the D2h minimum are connected by two C2v-symmetrical transition states, which are only ca. 6-10 kJ/mol above the D2h local minimum...
August 9, 2016: Journal of Chemical Theory and Computation
Vera P Kashparova, Victor A Klushin, Daria V Leontyeva, Nina V Smirnova, Victor M Chernyshev, Valentine P Ananikov
A new method was developed for the selective gram-scale synthesis of 2,5-diformylfuran (DFF), which is an important chemical with a high application potential, via oxidation of biomass-derived 5-hydroxylmethylfurfural (HMF) catalyzed by 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-AcNH-TEMPO) in a two-phase system consisting of a methylene chloride and aqueous solution containing sodium hydrogen carbonate and potassium iodide. The key feature of this method is the generation of the I2 (co-)oxidant by anodic oxidation of iodide anions during pulse electrolysis...
September 20, 2016: Chemistry, An Asian Journal
Meenakumari V, Utsumi Hideo, Jawahar A, Milton Franklin Benial A
Electron spin resonance (ESR) and Overhauser-enhanced magnetic resonance imaging (OMRI) studies were carried out for various concentrations of (14) N-labeled 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl (carbamoyl-PROXYL), in pure water. Overhauser-enhancement factor (OEF) attains maxima in the range of 2.5-3 mM concentration. The leakage factor showed an asymptotic increase with increasing agent concentration. The coupling parameter showed the interaction between the electron and nuclear spins to be mainly dipolar in origin...
July 19, 2016: Magnetic Resonance in Chemistry: MRC
Eun Young Jang, Chae Ha Yang, David M Hedges, Soo Phil Kim, Jun Yeon Lee, Tyler G Ekins, Brandon T Garcia, Hee Young Kim, Ashley C Nelson, Nam Jun Kim, Scott C Steffensen
Methamphetamine (METH) markedly increases dopamine (DA) release in the mesolimbic DA system, which plays an important role in mediating the reinforcing effects of METH. METH-induced DA release results in the formation of reactive oxygen species (ROS), leading to oxidative damage. We have recently reported that ROS are implicated in behavior changes and DA release in the nucleus accumbens (NAc) following cocaine administration. The aim of this study was to evaluate the involvement of ROS in METH-induced locomotor activity, self-administration and enhancement of DA release in the NAc...
July 14, 2016: Addiction Biology
Kelsey C Miles, M Leigh Abrams, Clark R Landis, Shannon S Stahl
A method for aerobic oxidation of aldehydes to carboxylic acids has been developed using organic nitroxyl and NOx cocatalysts. KetoABNO (9-azabicyclo[3.3.1]nonan-3-one N-oxyl) and NaNO2 were identified as the optimal nitroxyl and NOx sources, respectively. The mildness of the reaction conditions enables sequential asymmetric hydroformylation of alkenes/aerobic aldehyde oxidation to access α-chiral carboxylic acids without racemization. The scope, utility, and limitations of the oxidation method are further evaluated with a series of achiral aldehydes bearing diverse functional groups...
August 5, 2016: Organic Letters
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