- TOTAPOL: A biradical polarizing agent for dynamic nuclear polarization experiments in aqueous media
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In a previous publication, we described the use of biradicals, in that case two TEMPO molecules tethered by an ethylene glycol chain of variable length, as polarizing agents for microwave driven dynamic nuclear polarization (DNP) experiments. The use of biradicals in place of monomeric paramagnetic centers such as TEMPO yields enhancements that are a factor of approximately 4 larger (ε ~ 175 at 5 T and 90 K) and concurrently the concentration of the polarizing agent is a factor of 4 smaller (10 mM electron spins), reducing the residual electron nuclear dipole broadening. In this paper we describe the synthesis and characterization by EPR and DNP/NMR of an improved polarizing agent 1-(TEMPO-4-oxy)-3-(TEMPO-4-amino)propan-2-ol (TOTAPOL). Under the same experimental conditions and using 2.5 mm magic angle rotors, this new biradical yields larger enhancements (ε ~ 290) at lower concentrations (6 mM electron spins) and has the additional important property that it is compatible with experiments in aqueous media, including salt solutions commonly used in the study of proteins and nucleic acids.
- Song, Changsik,Hu, Kan-Nian,Joo, Chan-Gyu,Swager, Timothy M.,Griffin, Robert G.
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- TEMPO-Modified Linear Poly(ethylenimine) for Immobilization-Enhanced Electrocatalytic Oxidation of Alcohols
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We demonstrate a method to simultaneously immobilize the oxidation catalyst, TEMPO, while dramatically enhancing its electrocatalytic activity toward several biologically available alcohols. TEMPO is covalently immobilized onto linear poly(ethylenimine), which is then cross-linked onto the surface of a glassy carbon electrode to form a hydrogel through which substrates can readily diffuse. The TEMPO-LPEI electrode is used as an anode capable of generating currents from 0.41 ± 0.06 mA cm-2 in the presence of 250 mM sucrose to 8.20 ± 0.04 mA cm-2 in the presence of 2 M methanol and 33.4 ± 9.4 mA cm-2 in the presence of 500 mM formate under neutral pH and at 25 °C. The newly described anode is combined with an enzymatic biocathode to construct a hybrid biofuel cell to produce 0.38 ± 0.04 mA cm-2 while using 2 M methanol as a fuel source.
- Hickey, David P.,Milton, Ross D.,Chen, Dayi,Sigman, Matthew S.,Minteer, Shelley D.
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- Efficient charge transport of a radical polyether/SWCNT composite electrode for an organic radical battery with high charge-storage density
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A crosslinked poly(4-glycidyloxy TEMPO) was synthesized via anionic ring-opening copolymerization of 4-glycidyloxy TEMPO and a diglycidyl ether using a pentaerythritol/phosphazene base initiator. A fast and reversible charge storage capability was established for the polyether/SWCNT composite layer with a large layer thickness of several tens of micrometres, despite the low SWCNT content of 10% which was much closer to the percolation limit than the amount required for the previously reported TEMPO-substituted polymethacrylate. This journal is
- Sukegawa, Takashi,Sato, Kan,Oyaizu, Kenichi,Nishide, Hiroyuki
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- Synthesizing and characterization of comb-shaped carbazole containing copolymer via combination of ring opening polymerization and nitroxide-mediated polymerization
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The macro-TEMPO agent (poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl), PGTEMPO) was synthesized by anion ring-opening polymerization (ROP) of 4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (GTEMPO) using potassium t-butoxide as the initiator
- Chang, Cheng,Zhu, Jian,Zhang, Zhengbiao,Zhou, Nianchen,Cheng, Zhenping,Zhu, Xiulin
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- Synthesis and evaluation of nitroxide-based oligoradicals for low-temperature dynamic nuclear polarization in solid state NMR
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We describe the synthesis of new nitroxide-based biradical, triradical, and tetraradical compounds and the evaluation of their performance as paramagnetic dopants in dynamic nuclear polarization (DNP) experiments in solid state nuclear magnetic resonance (NMR) spectroscopy with magic-angle spinning (MAS). Under our experimental conditions, which include temperatures in the 25-30 K range, a 9.4 T magnetic field, MAS frequencies of 6.2-6.8 kHz, and microwave irradiation at 264.0 GHz from a 800 mW extended interaction oscillator source, the most effective compounds are triradicals that are related to the previously-described compound DOTOPA-TEMPO (see Thurber et al., 2010), but have improved solubility in glycerol/water solvent near neutral pH. Using these compounds at 30 mM total nitroxide concentration, we observe DNP enhancement factors of 92-128 for cross-polarized 13C NMR signals from 15N, 13C-labeled melittin in partially protonated glycerol/water, and build-up times of 2.6-3.8 s for 1H spin polarizations. Net sensitivity enhancements with biradical and tetraradical dopants, taking into account absolute 13C NMR signal amplitudes and build-up times, are approximately 2-4 times lower than with the best triradicals.
- Yau, Wai-Ming,Thurber, Kent R.,Tycko, Robert
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- Synthesis of end-functional poly(vinyl acetate) by cobalt-mediated radical polymerization
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PolyCvinyl acetate) (PVAc) chains prepared by cobalt-mediated radical polymerization in the presence of cobalt(II) acetylacetonate (Co(acac) 2) were quenched by radical scavengers, such as thiol compounds and nitroxides, to displace the covalently bonded Co(acac)2 moiety and to end-cap them with a reactive group. The cobalt complex was completely removed by filtration, as confirmed by the induction coupled plasma (ICP) analysis of the polymer before and after treatment. Growing poly(vinyl acetate) chains can be end-functionalized either by addition of an appropriately functionalized nonpolymerizable olefin or by displacement of the Co(acac)2 moiety by a functionalized nitroxide. This strategy allows PVAc to be synthesized with a predictable molecular weight, a reasonably low polydispersity (M 2/Mn ~ 1.1-1.3), and a functional ω end group, e.g., hydroxyl and epoxy.
- Debuigne, Antoine,Caille, Jean-Raphael,Jerome, Robert
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- Matrix-Free DNP-Enhanced NMR Spectroscopy of Liposomes Using a Lipid-Anchored Biradical
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Magic-angle spinning dynamic nuclear polarization (MAS-DNP) has been proven to be a powerful technique to enhance the sensitivity of solid-state NMR (SSNMR) in a wide range of systems. Here, we show that DNP can be used to polarize lipids using a lipid-anchored polarizing agent. More specifically, we introduce a C16-functionalized biradical, which allows localization of the polarizing agents in the lipid bilayer and DNP experiments to be performed in the absence of excess cryo-protectant molecules (glycerol, dimethyl sulfoxide, etc.). This constitutes another original example of the matrix-free DNP approach that we recently introduced.
- Fernández-de-Alba, Carlos,Takahashi, Hiroki,Richard, Alexandre,Chenavier, Yves,Dubois, Lionel,Maurel, Vincent,Lee, Daniel,Hediger, Sabine,De Pa?pe, Ga?l
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- Room temperature self-healable epoxy elastomer with reversible alkoxyamines as crosslinkages
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To provide room temperature self-healing ability to crosslinked epoxy elastomer, alkoxyamine-based diglycidyl ether (DiEPO) is synthesized and cured with polythiol. The C-ON bonds in both the alkoxyamine monomer and the cured epoxy are able to be synchronously cleft and recombined, achieving a dynamic reversible equilibrium state. This habit can thus be used as a healing chemistry for repeatedly re-bonding cracked polymer. Moreover, because the nitrile group that possesses strong capability of adsorbing electrons is attached to the carbon atom of C-ON bonds, homolysis temperature of the alkoxyamine is greatly reduced. The reversible reaction becomes oxygen insensitive in the meantime. As a result, multiple self-healing of the epoxy elastomer in air without manual intervention (heating) is observed by visual inspection and tensile test. Compared to the self-healing crosslinked polymers containing alkoxyamine moieties, which were previously developed in our lab and had to operate at elevated temperature in argon, the current work represents an interesting progress towards practical application in this aspect.
- Zhang, Ze Ping,Rong, Min Zhi,Zhang, Ming Qiu
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- TEMPO Containing Radical Polymonothiocarbonate Polymers with Regio- and Stereo-Regularities: Synthesis, Characterization, and Electrical Conductivity Studies
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We report the synthesis of a (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl) (TEMPO) appended polymonothiocarbonates through the ring-opening copolymerization of (4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl) (GTEMPO) in the presence of carbonyl sulfide under ambient conditions. We have prepared the atactic and isotactic versions of this polymer, using enantiopure R or S forms of the GTEMPO monomer in the latter instances. Cyclic voltammetry studies revealed both oxidation and reduction events that were characteristic of TEMPO radicals. Electrical conductivity of these polymers was measured as solid-state films after annealing the samples above their glass transition temperatures. At room temperature the isotactic polymer shows much greater conductivity (ca. 10?4 S cm?1) than the atactic (ca. 10?7 S cm?1), attributed to the well-defined stereochemistry and regulated charge transport pathway of isotactic polymer chains in contrast to the irregular structure of the atactic counterpart.
- Bhat, Gulzar A.,Rashad, Ahmed Z.,Ji, Xiaozhou,Quiroz, Manuel,Fang, Lei,Darensbourg, Donald J.
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- NOVEL COMPOUNDS, FUNCTIONALISED DIOXABOROLANE OR DIOXABORINANE DERIVATIVES, METHOD FOR PREPARING SAME AND USES THEREOF
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The invention relates to functionalised dioxaborolane or dioxaborinane derivatives of formula (I), wherein R1 is covalently bonded to the boron atom by a carbon atom; one of R2, R3, R′3 or R4 is a radical of formula —X; or one of R1, R2, R3, R′3 or R4 is a radical of formula —X; and X is a functionalised radical. The invention relates to the method for preparing same and the uses thereof.
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Paragraph 0329-0331
(2020/08/05)
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