共查询到20条相似文献,搜索用时 15 毫秒
1.
Pascal Miéville Puneet Ahuja Riddhiman Sarkar Dr. Sami Jannin Dr. Paul R. Vasos Dr. Sandrine Gerber‐Lemaire Dr. Mor Mishkovsky Dr. Arnaud Comment Dr. Rolf Gruetter Prof. Olivier Ouari Dr. Paul Tordo Prof. Geoffrey Bodenhausen Prof. 《Angewandte Chemie (International ed. in English)》2010,49(35):6182-6185
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Pascal Miéville Puneet Ahuja Dr. Riddhiman Sarkar Dr. Sami Jannin Dr. Paul R. Vasos Dr. Sandrine Gerber‐Lemaire Dr. Mor Mishkovsky Dr. Arnaud Comment Prof. Rolf Gruetter Dr. Olivier Ouari Prof. Paul Tordo Prof. Geoffrey Bodenhausen 《Angewandte Chemie (International ed. in English)》2010,49(43):7834-7834
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Implementation and Characterization of Flow Injection in Dissolution Dynamic Nuclear Polarization NMR Spectroscopy 下载免费PDF全文
The use of dissolution dynamic nuclear polarization (D ‐DNP) offers substantially increased signals in liquid‐state NMR spectroscopy. A challenge in realizing this potential lies in the transfer of the hyperpolarized sample to the NMR detector without loss of hyperpolarization. Here, the use of a flow injection method using high‐pressure liquid leads to improved performance compared to the more common gas‐driven injection, by suppressing residual fluid motions during the NMR experiment while still achieving a short injection time. Apparent diffusion coefficients are determined from pulsed field gradient echo measurements, and are shown to fall below 1.5 times the value of a static sample within 0.8 s. Due to the single‐scan nature of D ‐DNP, pulsed field gradients are often the only choice for coherence selection or encoding, but their application requires stationary fluid. Sample delivery driven by a high‐pressure liquid will improve the applicability of these types of D‐DNP advanced experiments. 相似文献
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Björn C. Dollmann Dr. Andrei L. Kleschyov Dr. Vasily Sen Dr. Valery Golubev Prof. Dr. Laura M. Schreiber Prof. Dr. Hans W. Spiess Dr. Kerstin Münnemann Dr. Dariush Hinderberger 《Chemphyschem》2010,11(17):3656-3663
A potentially biocompatible class of spin‐labeled macromolecules, spin‐labeled (SL) heparins, and their use as nuclear magnetic resonance (NMR) signal enhancers are introduced. The signal enhancement is achieved through Overhauser‐type dynamic nuclear polarization (DNP). All presented SL‐heparins show high 1H DNP enhancement factors up to E=?110, which validates that effectively more than one hyperfine line can be saturated even for spin‐labeled polarizing agents. The parameters for the Overhauser‐type DNP are determined and discussed. A striking result is that for spin‐labeled heparins, the off‐resonant electron paramagnetic resonance (EPR) hyperfine lines contribute a non‐negligible part to the total saturation, even in the absence of Heisenberg spin exchange (HSE) and electron spin‐nuclear spin relaxation (T1ne). As a result, we conclude that one can optimize the use of, for example, biomacromolecules for DNP, for which only small sample amounts are available, by using heterogeneously distributed radicals attached to the molecule. 相似文献
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Vladimir V. Kavtanyuk Hyun Joon Lee Sangwon Oh Keunhong Jeong Jeong Hyun Shim 《Molecules (Basel, Switzerland)》2022,27(5)
Majority of dynamic nuclear polarization (DNP) experiments have been requiring helium cryogenics and strong magnetic fields for a high degree of nuclear polarization. In this work, we instead demonstrate an optical hyperpolarization of naturally abundant C nuclei in a diamond crystal at a low magnetic field and the room temperature. It exploits continuous laser irradiation for polarizing electronic spins of nitrogen vacancy centers and microwave irradiation for transferring the electronic polarization to C nuclear spins. We have studied the dependence of C polarization on laser and microwave powers. For the first time, a triplet structure corresponding to the N hyperfine splitting has been observed in the C polarization spectrum. By simultaneously exciting three microwave frequencies at the peaks of the triplet, we have achieved C bulk polarization of 0.113 %, leading to an enhancement of 90,000 over the thermal polarization at 17.6 mT. We believe that the multi-tone irradiation can be extended to further enhance the C polarization at a low magnetic field. 相似文献
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Geometric isomerizations of olefins following photoinduced electron transfer (PET) are classified according to the relative energetic positions of the radical‐ion pairs and the reactant triplets. Each class exhibits characteristic CIDNP (chemically induced dynamic nuclear polarization) effects, for which typical examples are presented. Time‐resolved CIDNP experiments on the system triphenylamine/fumarodinitrile (= (2E)‐but‐2‐enedinitrile), where formation of the olefin triplet is impossible, show that there is also no isomerization of the olefin radical anion. With triisopropylamine or fumarodinitrile as the reaction partner for 4,4′‐dimethoxystilbene (= 1,1′‐[(1E)‐ethane‐1,2‐diyl]bis[4‐methoxybenzene]), both oxidative and reductive quenching give almost mirror‐image CIDNP spectra because of the pairing theorem; reverse electron transfer of the triplet radical‐ion pairs populates the stilbene triplet only, which then isomerizes. With anethole (= 1‐methoxy‐4‐(prop‐1‐enyl)benzene; M), the competition between electron return of triplet pairs to give either M + 3X or 3M + X was studied by using a second isomerizable olefin (diethyl fumarate (= diethyl (2E)‐but‐2‐enedioate) or cinnamonitrile (= (2E)‐3‐phenylprop‐2‐enenitrile)) as the reaction partner X. Classes can be changed by employing PET sensitization. With ACN (anthracene‐9‐carbonitrile) as the sensitizer, anethole does not produce any directly observable polarizations, but a substitution of ACN.? by the radical anion of 1,4‐benzoquinone (= cyclohexa‐2,5‐diene‐1,4‐dione) or fumarodinitrile within the lifetime of the spin‐correlated radical‐ion pairs leads to very strong CIDNP signals that reflect the effects of both pairs. 相似文献
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Emmanuelle M. M. Weber Dr. Giuseppe Sicoli Dr. Hervé Vezin Ghislaine Frébourg Dr. Daniel Abergel Prof. Geoffrey Bodenhausen Dr. Dennis Kurzbach 《Angewandte Chemie (International ed. in English)》2018,57(18):5171-5175
Mixtures of water and glycerol provide popular matrices for low‐temperature spectroscopy of vitrified samples. However, they involve counterintuitive physicochemical properties, such as spontaneous nanoscopic phase separations (NPS) in solutions that appear macroscopically homogeneous. We demonstrate that such phenomena can substantially influence the efficiency of dynamic nuclear polarization (DNP) by factors up to 20 % by causing fluctuations in local concentrations of polarization agents (radicals). Thus, a spontaneous NPS of water/glycerol mixtures that takes place on time scales on the order of 30–60 min results in a confinement of polarization agents in nanoscopic water‐rich vesicles, which in return affects the DNP. Such effects were found for three common polarization agents, TEMPOL, AMUPol and Trityl. 相似文献
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Yoh Matsuki Dr. Thorsten Maly Dr. Olivier Ouari Dr. Hakim Karoui Dr. François Le Moigne Dr. Egon Rizzato Dr. Sevdalina Lyubenova Dr. Judith Herzfeld Prof. Thomas Prisner Prof. Paul Tordo Prof. Robert G. Griffin Prof. 《Angewandte Chemie (International ed. in English)》2009,48(27):4996-5000
A new polarizing agent with superior performance in dynamic nuclear polarization experiments is introduced, and utilizes two TEMPO (2,2,6,6‐tetramethylpiperidine‐1‐oxyl) moieties connected through a rigid spiro tether (see structure). The observed NMR signal intensities were enhanced by a factor of 1.4 compared to those of TOTAPOL, a previously described TEMPO‐based biradical with a flexible tether.
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Natural Abundance 15N NMR by Dynamic Nuclear Polarization: Fast Analysis of Binding Sites of a Novel Amine‐Carboxyl‐Linked Immobilized Dirhodium Catalyst 下载免费PDF全文
Torsten Gutmann Jiquan Liu Niels Rothermel Yeping Xu Eva Jaumann Mayke Werner Hergen Breitzke Snorri T. Sigurdsson Gerd Buntkowsky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(9):3798-3805
A novel heterogeneous dirhodium catalyst has been synthesized. This stable catalyst is constructed from dirhodium acetate dimer (Rh2(OAc)4) units, which are covalently linked to amine‐ and carboxyl‐bifunctionalized mesoporous silica (SBA‐15?NH2?COOH). It shows good efficiency in catalyzing the cyclopropanation reaction of styrene and ethyl diazoacetate (EDA) forming cis‐ and trans‐1‐ethoxycarbonyl‐2‐phenylcyclopropane. To characterize the structure of this catalyst and to confirm the successful immobilization, heteronuclear solid‐state NMR experiments have been performed. The high application potential of dynamic nuclear polarization (DNP) NMR for the analysis of binding sites in this novel catalyst is demonstrated. Signal‐enhanced 13C CP MAS and 15N CP MAS techniques have been employed to detect different carboxyl and amine binding sites in natural abundance on a fast time scale. The interpretation of the experimental chemical shift values for different binding sites has been corroborated by quantum chemical calculations on dirhodium model complexes. 相似文献
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During the decay of (15N)peroxynitrite (O?15NOO ? ) in the presence of N‐acetyl‐L ‐tyrosine (Tyrac) in neutral solution and at 268 K, the 15N‐NMR signals of 15NO and 15NO show emission (E) and enhanced absorption (A) as it has already been observed by Butler and co‐workers in the presence of L ‐tyrosine (Tyr). The effects are built up in radical pairs [CO , 15NO ]S formed by O? O bond scission of the (15N)peroxynitrite? CO2 adduct (O?15NO? OCO ). In the absence of Tyrac and Tyr, the peroxynitrite decay rate is enhanced, and 15N‐CIDNP does not occur. This is explained by a chain reaction during the peroxynitrite decay involving N2O3 and radicals NO . and NO . The interpretation is supported by 15N‐CIDNP observed with (15N)peroxynitrite generated in situ during reaction of H2O2 with N‐acetyl‐N‐(15N)nitroso‐dl ‐tryptophan ((15N)NANT) at 298 K and pH 7.5. In the presence of Na15NO2 at pH 7.5 and in acidic solution, 15N‐CIDNP appears in the nitration products of Tyrac, 1‐(15N)nitro‐N‐acetyl‐L ‐tyrosine (1‐15NO2‐Tyrac) and 3‐(15N)nitro‐N‐acetyl‐L ‐tyrosine (3‐15NO2‐Tyrac). The effects are built up in radical pairs [Tyrac . , 15NO ]F formed by encounters of independently generated radicals Tyrac . and 15NO . Quantitative 15N‐CIDNP studies show that nitrogen dioxide dependent reactions are the main if not the only pathways for yielding both nitrate and nitrated products. 相似文献
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HeinzD. Roth 《Helvetica chimica acta》2006,89(12):2847-2860
Chemically induced dynamic nuclear polarization (CIDNP) observed during electron transfer (ET) reactions of tertiary amines such as DABCO ( 1 ) or Et3N ( 2 ) with a wide range of electron acceptors support the involvement of amine radical‐cations (e.g., 1. + or 2. + ) as key intermediates. Radical ions such as 2. + may be deprotonated, generating neutral aminoalkyl radicals (e.g., 2. ). When generated by reaction with an electron acceptor of energetically low triplet state such as naphthalene (1Naph*), the resulting pair 2. + /Naph.? reacts mostly by reverse electron transfer (RET) from triplet pairs populating the naphthalene triplet state. 相似文献
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Dynamic Nuclear Polarization Provides New Insights into Chromophore Structure in Phytochrome Photoreceptors 下载免费PDF全文
Daniel Stöppler Dr. Chen Song Dr. Barth‐Jan van Rossum Michel‐Andreas Geiger Christina Lang Prof. Dr. Maria‐Andrea Mroginski Dr. Anil Pandurang Jagtap Prof. Dr. Snorri Th. Sigurdsson Prof. Dr. Jörg Matysik Prof. Dr. Jon Hughes Prof. Dr. Hartmut Oschkinat 《Angewandte Chemie (International ed. in English)》2016,55(52):16017-16020
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Adam N. Smith Dr. Marc A. Caporini Prof. Gail E. Fanucci Prof. Joanna R. Long 《Angewandte Chemie (International ed. in English)》2015,54(5):1542-1546
Dynamic nuclear polarization (DNP) magic‐angle spinning (MAS) solid‐state NMR (ssNMR) spectroscopy has the potential to enhance NMR signals by orders of magnitude and to enable NMR characterization of proteins which are inherently dilute, such as membrane proteins. In this work spin‐labeled lipid molecules (SL‐lipids), when used as polarizing agents, lead to large and relatively homogeneous DNP enhancements throughout the lipid bilayer and to an embedded lung surfactant mimetic peptide, KL4. Specifically, DNP MAS ssNMR experiments at 600 MHz/395 GHz on KL4 reconstituted in liposomes containing SL‐lipids reveal DNP enhancement values over two times larger for KL4 compared to liposome suspensions containing the biradical TOTAPOL. These findings suggest an alternative sample preparation strategy for DNP MAS ssNMR studies of lipid membranes and integral membrane proteins. 相似文献
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Xinyi. Cai Dr. Alessandra Lucini Paioni Agnes Adler Ru Yao Wenxiao Zhang David Beriashvili Adil Safeer Andrei Gurinov Prof. Antal Rockenbauer Prof. Dr. Yuguang Song Prof. Dr. Marc Baldus Prof. Dr. Yangping Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(50):12758-12762
Dynamic nuclear polarization (DNP) is a powerful method to enhance the sensitivity of solid-state magnetic nuclear resonance (ssNMR) spectroscopy. However, its biomolecular applications at high magnetic fields (preferably>14 T) have so far been limited by the intrinsically low efficiency of polarizing agents and sample preparation aspects. Herein, we report a new class of trityl-nitroxide biradicals, dubbed SNAPols that combine high DNP efficiency with greatly enhanced hydrophilicity. SNAPol-1, the best compound in the series, shows DNP enhancement factors at 18.8 T of more than 100 in small molecules and globular proteins and also exhibits strong DNP enhancements in membrane proteins and cellular preparations. By integrating optimal sensitivity and high resolution, we expect widespread applications of this new polarizing agent in high-field DNP/ssNMR spectroscopy, especially for complex biomolecules. 相似文献
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Alexandre Zagdoun Dr. Aaron J. Rossini Dr. Matthew P. Conley Wolfram R. Grüning Martin Schwarzwälder Dr. Moreno Lelli Dr. W. Trent Franks Prof. Dr. Hartmut Oschkinat Prof. Dr. Christophe Copéret Prof. Dr. Lyndon Emsley Dr. Anne Lesage 《Angewandte Chemie (International ed. in English)》2013,52(4):1222-1225
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The influence of Ni(acac)2 added in catalytic amounts on the chemically induced dynamic nuclear polarization (CIDNP) effects, the mechanism of interaction,
and the products of reaction between Et3Al and CCl4 were studied. The radical intermediates were identified and the routes for their transformations were proposed. The thermal
reaction of Et3Al with CCl4 occurs by a radical mechanism. However, in the presence of Ni(acac)2, the reaction proceeds mainlyvia a nonradical route and gives large amounts of ethylene and ethane.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1580–1583, August, 1998. 相似文献