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Beata Olszewska, Anna Stasiak, Daniel McNaught Flores, Wiesława Agnieszka Fogel, Rob Leurs, Krzysztof Walczyński
Presynaptic histamine H₃ receptors (H₃R) act as auto- or heteroreceptors controlling, respectively, the release of histamine and of other neurotransmitters in the central nervous system (CNS). The extracellular levels of several neurotransmitters are enhanced by H₃R antagonists, and there is a great interest for potent, brain-penetrating H₃ receptor antagonists/inverse agonists to compensate for the neurotransmitter deficits present in various neurological disorders. We have shown that 1-[(benzylfuran-2-yl)methyl]piperidinyl-4-oxyl- and benzyl- derivatives of N -propylpentan-1-amines exhibit high in vitro potencies toward the guinea pig H₃ receptor (jejunum), with pA₂ = 8...
April 19, 2018: International Journal of Molecular Sciences
Sergey A Dobrynin, Yuri I Glazachev, Yuri V Gatilov, Elena Ilinichna Chernyak, George E Salnikov, Igor A Kirilyuk
A simple method of synthesis of sterically shielded pyrrolidine nitroxides, including title compound, have been suggested. The key procedure implies assembling of pyrrolidine ring from α-aminoacid, ketone and activated alkene in a three-component domino process with following oxidation to nitrone and Grignard reagent addition. The new nitroxides demonstrate very high stability to reduction with ascorbate.
April 18, 2018: Journal of Organic Chemistry
Mohammad Asad, Naheed Saba, Abdullah M Asiri, M Jawaid, Eti Indarti, W D Wanrosli
TEMPO-oxidize nanocellulose (TONC) suspension has been obtained from total chlorine free (TCF) oil palm empty-fruit-bunches (OPEFB) pulp using 4-acetamido-TEMPO (2,2,6,6-tetramethyl piperidin-1-oxyl) mediated oxidation with sodium hypochlorite and sodium bromide in water at 25 °C and pH 10. TONC suspension with varied content from 0.5 to 6% (w/w) reinforced polyvinyl alcohol (PVA) polymer based nanocomposite films were prepared by the casting method. The structural interaction between the TONC and PVA was characterized by the Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM)...
July 1, 2018: Carbohydrate Polymers
Yang Jiao, Bohan Tang, Yucheng Zhang, Jiang-Fei Xu, Zhiqiang Wang, Xi Zhang
A new strategy of highly efficient supramolecular catalysis is developed by endowing the reaction intermediate with adaptive reactivity. The supramolecular catalyst, prepared by the host-guest complexation between 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) and cucubit[7]uril (CB[7]), was used for biphasic oxidation of alcohols. Cationic TEMPO+, the key intermediate, was stabilized by the electrostatic effect of CB[7] in aqueous phase, thus promoting the formation of TEMPO+ and inhibiting side reactions. Moreover, through the migration into organic phase, TEMPO+ was separated from CB[7] and recovered the high reactivity to drive a fast oxidation of substrates...
April 12, 2018: Angewandte Chemie
Akira Isogai
Plant cellulose fibers of width and length ∼0.03 mm and ∼3 mm, respectively, can be completely converted to individual cellulose nanofibers of width and length ∼3 nm and ∼1 µm, respectively, by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation under aqueous conditions and subsequent gentle mechanical disintegration of the oxidized cellulose in water. The obtained TEMPO-oxidized cellulose nanofibers (TOCNs) are new bio-based, crystalline nanomaterials with applications in the high-tech and commodity product industries...
2018: Proceedings of the Japan Academy. Series B, Physical and Biological Sciences
Laia Vilella, Ana Conde, David Balcells, M Mar Díaz-Requejo, Agustí Lledós, Pedro J Pérez
A dual mechanism for direct benzene catalytic hydroxylation is described. Experimental studies and DFT calculations have provided a mechanistic explanation for the acid-free, Tp x Cu-catalyzed hydroxylation of benzene with hydrogen peroxide (Tp x = hydrotrispyrazolylborate ligand). In contrast with other catalytic systems that promote this transformation through Fenton-like pathways, this system operates through a copper-oxyl intermediate that may interact with the arene ring following two different, competitive routes: (a) electrophilic aromatic substitution, with the copper-oxyl species acting as the formal electrophile, and (b) the so-called rebound mechanism, in which the hydrogen is abstracted by the Cu-O moiety prior to the C-O bond formation...
December 1, 2017: Chemical Science
Keisuke Kawashima, Tomohiro Takaoka, Hiroki Kimura, Keisuke Saito, Hiroshi Ishikita
In photosystem II, light-induced water oxidation occurs at the Mn4 CaO5 cluster. Here we demonstrate proton releases, dioxygen formation, and substrate water incorporation in response to Mn4 CaO5 oxidation in the protein environment, using a quantum mechanical/molecular mechanical approach and molecular dynamics simulations. In S2 , H2 O at the W1 site forms a low-barrier H-bond with D1-Asp61. In the S2 -to-S3 transition, oxidation of OW1 H- to OW1 •- , concerted proton transfer from OW1 H- to D1-Asp61, and binding of a water molecule Wn-W1 at OW1 •- are observed...
March 28, 2018: Nature Communications
Jie Jiang, Wenbo Ye, Juan Yu, Yimin Fan, Yuko Ono, Tsuguyuki Saito, Akira Isogai
Laccase mediator oxidation was applied to chitin at pH 6.8 and 30 °C to prepare chitin nanocrystals with a catalytic amount of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO). When 40 mM TEMPO and a total of 500 U laccase were added to 1 g chitin, the yield of water-insoluble oxidized chitin was more than 95%, and the carboxylate content was 0.43 mmol/g. Adsorption of laccase molecules on chitin particles occurred in a buffer at pH 6.8, which may have been caused by electrostatic interactions between positively charged C2-ammonium groups of chitin and anionically charged groups of laccase...
June 1, 2018: Carbohydrate Polymers
Yusuke Takahashi, Ryo Matsuhashi, Youhei Miura, Naoki Yoshioka
Three hetero-biradical derivatives having a structure of a back-to-back connected benzotriazinyl and tetramethyl or tetraethylisoindoline N-oxyl sharing a common benzo ring, 1-tBu, 1-Ph, and 2-tBu were synthesized and characterized by single crystal X-ray analyses, variable-temperature magnetic susceptibility studies, and DFT calculations. Temperature dependences of the magnetic susceptibility of 1-tBu, 1-Ph, and 2-tBu exhibit broad maxima at 70, 71, and 43 K, respectively. Though these radical derivatives form a columnar or chained assembly in the solid state, magnetic measurement of the polymer diluted sample and computational results imply that the magnetic property of the polycrystalline sample can be explained by two-spin system with an intramolecular antiferromagnetic interaction...
March 24, 2018: Chemistry: a European Journal
V Venkatesh, Raul Berrocal-Martin, Christopher J Wedge, Isolda Romero-Canelón, Carlos Sanchez-Cano, Ji-Inn Song, James P C Coverdale, Pingyu Zhang, Guy J Clarkson, Abraha Habtemariam, Steven W Magennis, Robert J Deeth, Peter J Sadler
Mitochondria generate energy but malfunction in many cancer cells, hence targeting mitochondrial metabolism is a promising approach for cancer therapy. Here we have designed cyclometallated iridium(iii) complexes, containing one TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) spin label [C43 H43 N6 O2 Ir1 ·PF6 ]˙ ( Ir-TEMPO1 ) and two TEMPO spin labels [C52 H58 N8 O4 Ir1 ·PF6 ]˙ ( Ir-TEMPO2 ). Electron paramagnetic resonance (EPR) spectroscopy revealed spin-spin interactions between the TEMPO units in Ir-TEMPO2 ...
December 1, 2017: Chemical Science
Yuya Tamura, Kyohei Kanomata, Takuya Kitaoka
2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibers (TOCNs), which have a high-density of exposed carboxylic acid groups on their crystalline surfaces, effectively act as acid catalysts in acetal hydrolysis. Carboxy-free cellulose nanofibers, polymeric carboxylic acids, and homogeneous acetic acid do not show significant catalytic activity under the same reaction conditions. Mercerized TOCNs differing from the original TOCNs in a crystalline structure were also ineffective, which suggests that the unique nanoarchitectural features of TOCNs, such as regularly aligned carboxylic acid groups, large specific surface areas, and structural rigidity, must be major factors in the acceleration of acetal hydrolysis...
March 22, 2018: Scientific Reports
Yongho Joo, Varad Agarkar, Seung Hyun Sung, Brett M Savoie, Bryan W Boudouris
Solid-state conducting polymers usually have highly conjugated macromolecular backbones and require intentional doping in order to achieve high electrical conductivities. Conversely, single-component, charge-neutral macromolecules could be synthetically simpler and have improved processibility and ambient stability. We show that poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl), a nonconjugated radical polymer with a subambient glass transition temperature, underwent rapid solid-state charge transfer reactions and had an electrical conductivity of up to 28 siemens per meter over channel lengths up to 0...
March 23, 2018: Science
Xican Li, Yulu Xie, Hong Xie, Jian Yang, Dongfeng Chen
α-Viniferin and caraphenol A, the two oligostilbenes, have the sole difference of the presence or absence of an exocyclic double bond at the π-π conjugative site. In this study, the antioxidant capacity and relevant mechanisms for α-viniferin and caraphenol A were comparatively explored using spectrophotometry, UV-visible spectral analysis, and electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-Q-TOF-MS/MS) analysis. The spectrophotometric results suggested that caraphenol A always gave lower IC50 values than α-viniferin in cupric ion-reducing antioxidant capacity assay, ferric-reducing antioxidant power assay, 1,1-diphenyl-2-picryl-hydrazl radical (DPPH•)-scavenging, and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical-scavenging assays...
March 19, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Engie Safwat, Mohammad L Hassan, Sayed Saniour, Dalia Yehia Zaki, Mervat Eldeftar, Dalia Saba, Mohamed Zazou
Nanofibrillated cellulose, obtained from rice straw agricultural wastes was used as a substrate for the preparation of a new injectable and mineralized hydrogel for bone regeneration. Tetramethyl pyridine oxyl (TEMPO) oxidized nanofibrillated cellulose, was mineralized through the incorporation of a prepared and characterized biphasic calcium phosphate at a fixed ratio of 50 wt%. The TEMPO-oxidized rice straw nanofibrillated cellulose was characterized using transmission electron microscopy, Fourier transform infrared, and carboxylic content determination...
January 1, 2018: Journal of Biomaterials Applications
Guifang Sun, Jianni Guo, Meng Yang, Lu Xi, Licun Li, Jean-Pascal Sutter
Two-dimensional hetero-tri-spin 2p-3d-4f coordination polymers involving Co(ii) and Ln(iii) ions assembled with a polydentate paramagnetic nitronyl nitroxide ligand are reported. [Ln(hfac)3 {Co(hfac)2 }2 (NITPhPyrim)2 ] (LnIII = Gd 1, Tb 2; hfac = hexafluoroacetylacetonate, NITPhPyrim = 2-[4-(5-pyrimidyl)phenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) consists of a two-dimensional network in which the NITPhPyrim ligand is coordinated to the metal ions by means of its pyrimidine and aminoxyl (NO) groups...
March 13, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Yingying Liu, Yulong Sui, Chao Liu, Changqing Liu, Meiyan Wu, Bin Li, Youming Li
In this study, we reported a pH/near-infrared (NIR)-responsive hydrogel for on-demand drug delivery and wound healing. Cellulose nanofibrils (TOCNFs) were produced by 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation method. Polydopamine (PDA) was introduced into TOCNFs network to fabricate a PDA/TOCNFs hydrogel through ion-crosslinking with calcium ion as a crosslinker. Then, tetracycline hydrochloride (TH) which loaded on PDA could be released from the prepared hydrogels in an on-demand fashion under NIR exposure or at lower pH conditions...
May 15, 2018: Carbohydrate Polymers
Kazunari Namegawa, Kyoko Iida, Kaoru Omura, Shoujiro Ogawa, Alan F Hofmann, Takashi Iida
A method for the preparation of 11α-hydroxy derivatives of lithocholic and chenodeoxycholic acids, recently discovered to be natural bile acids, is described. The principal reactions involved were (1) elimination of the 12α-mesyloxy group of the methyl esters of 3α-acetate-12α-mesylate and 3α,7α-diacetate-12α-mesylate derivatives of deoxycholic acid and cholic acid with potassium acetate/hexamethylphosphoramide; (2) simultaneous reduction/hydrolysis of the resulting △11 -3α-acetoxy and △11 -3α,7α-diacetoxy methyl esters with lithium aluminum hydride; (3) stereoselective 11α-hydroxylation of the △11 -3α,24-diol and △11 -3α,7α,24-triol intermediates with B2 H6 /tetrahydrofuran (THF); and (4) selective oxidation at C-24 of the resulting 3α,11α,24-triol and 3α,7α,11α,24-tetrol to the corresponding C-24 carboxylic acids with NaClO2 catalyzed by 2,2,6,6-tetramethylpiperidine 1-oxyl free radical (TEMPO) and NaClO...
March 9, 2018: Lipids
Jovana Z Milanovic, Predrag Milanovic, Rastislav Kragic, Mirjana Kostic
In this paper, we present the construction of a reliable and inexpensive pH stat device, by using open-source "OpenPhControl" software, inexpensive hardware (a peristaltic and a syringe pump, Arduino, a step motor…), readily available laboratory devices: a pH meter, a computer, a webcam, and some 3D printed parts. We provide a methodology for the design, development and test results of each part of the device, as well as of the entire system. In addition to dosing reagents by means of a low-cost peristaltic pump, we also present carefully controlled dosing of reagents by an open-source syringe pump...
2018: PloS One
Basema Balasiny, Matthew D Rolfe, Claire Vine, Charlene Bradley, Jeffrey Green, Jeff Cole
Synthesis of the Escherichia coli YtfE protein, also known as RIC, for the repair of damaged iron centres, is highly induced during anaerobic growth under conditions of nitrosative stress. How YtfE repairs nitrosative damage remains unclear. Contrary to previous reports, we show that strains defective in YtfE that lack the high-affinity NO reductase activity of the hybrid cluster protein (Hcp) are less sensitive to nitrosative stress than isogenic ytfE+ strains, which are extremely sensitive. Evidence that this sensitivity is due to YtfE-dependent release of NO into the cytoplasm includes: relief of growth inhibition by PTIO (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide), which degrades NO; relief of nitrosative stress by deletion of narG encoding the nitrate reductase that is the major source of NO from nitrite; partial suppression of nitrosative stress due to loss of Hcp function by a further mutation in ytfE; YtfE-dependent loss of aconitase and fumarase activities in the absence of Hcp; and YtfE-dependent relief of NsrR repression of the hcp promoter in response to cytoplasmic NO...
March 1, 2018: Microbiology
Taiming Liu, Meijuan Zhang, Michael H Terry, Hobe Schroeder, Sean Wilson, Gordon Power, Qian Li, Trent Tipple, Dan Borchardt, Arlin 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 (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 a NO⋅ donor...
February 23, 2018: Molecular Pharmacology
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