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Frontispiece: Matrix‐Free DNP‐Enhanced NMR Spectroscopy of Liposomes Using a Lipid‐Anchored Biradical
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Dr. Carlos Fernández‐de‐Alba Dr. Hiroki Takahashi Alexandre Richard Yves Chenavier Dr. Lionel Dubois Vincent Maurel Dr. Daniel Lee Dr. Sabine Hediger Dr. Gaël De Paëpe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12)
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Chemical‐Shift‐Resolved 19F NMR Spectroscopy between 13.5 and 135 MHz: Overhauser–DNP‐Enhanced Diagonal Suppressed Correlation Spectroscopy
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Dr. Christy George Prof. Narayanan Chandrakumar 《Angewandte Chemie (International ed. in English)》2014,53(32):8441-8444
Overhauser–DNP‐enhanced homonuclear 2D 19F correlation spectroscopy with diagonal suppression is presented for small molecules in the solution state at moderate fields. Multi‐frequency, multi‐radical studies demonstrate that these relatively low‐field experiments may be operated with sensitivity rivalling that of standard 200–1000 MHz NMR spectroscopy. Structural information is accessible without a sensitivity penalty, and diagonal suppressed 2D NMR correlations emerge despite the general lack of multiplet resolution in the 1D ODNP spectra. This powerful general approach avoids the rather stiff excitation, detection, and other special requirements of high‐field 19F NMR spectroscopy. 相似文献
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Cover Picture: On The Potential of Dynamic Nuclear Polarization Enhanced Diamonds in Solid‐State and Dissolution 13C NMR Spectroscopy (ChemPhysChem 17/2016)
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Dr. Christian O. Bretschneider Prof. Dr. Ümit Akbey Dr. Fabien Aussenac Dr. Greg L. Olsen Dr. Akiva Feintuch Prof. Dr. Hartmut Oschkinat Prof. Dr. Lucio Frydman 《Chemphyschem》2016,17(17):2609-2609
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Sarah Schmitz Anthony C. Dona Patrice Castignolles Robert G. Gilbert Marianne Gaborieau 《Macromolecular bioscience》2009,9(5):506-514
Complete dissolution is needed for the separation, characterization, or homogeneous labeling of whole starch molecules. A method is presented to quantify the extent of starch dissolution in DMSO for the first time; it is validated on a commercial rice starch. It is used directly on starch dispersions containing possible undissolved or co‐dissolved species. High‐amylose maize starches, known to be digested slowly in vivo, only quantitatively dissolve in the presence of high concentrations of an H‐bond disrupter, LiBr, although they form clear dispersions at low LiBr concentrations. Starch quantitatively dissolves from waxy rice flours; non‐starch components partially co‐dissolve but do not interfere with the dissolution quantification.
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Alaitz Ruiz de Luzuriaga Jos A. Pomposo Hans Grande Agustin Etxeberria 《Macromolecular rapid communications》2009,30(11):932-935
We have studied the kinetics of polymeric nanoparticle formation for poly(styrene‐block‐4‐vinylpyridine) [P(S‐b‐4‐VPy)], chains in a non‐selective solvent using 1,4‐dibromobutane (DBB) as a cross‐linker by means of different nuclear magnetic resonance (NMR) spectroscopy techniques. The kinetic process was followed using 1H, 13C, and 2‐D Heteronuclear Single Quantum Correlation (HSQC) NMR experiments. The kinetic data obtained from 2‐D HSQC and 1H NMR experiments were in good agreement between them, proving the reliability of the 2‐D HSQC NMR technique for the in situ study of the kinetics of core‐shell nanoparticle formation. A value of 1.5 × 10−5 s−1 was determined for the apparent kinetic constant of the P(S‐b‐4‐VPy)‐DBB core‐shell nanoparticle formation process.
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G. Mladenov B. Ameduri G. Kostov R. Mateva 《Journal of polymer science. Part A, Polymer chemistry》2006,44(4):1470-1485
The synthesis of original fluorinated (co)telomers containing vinylidene fluoride (VDF) or VDF and hexafluoropropene (HFP) was achieved by radical telomerizations and (co)telomerizations of VDF (or VDF and HFP) in the presence of 1, 6‐diiodoperfluorohexane via a semisuspension process. tert‐Butyl peroxypivalate (TBPPi) was used as an efficient thermal initiator. The numbers of VDF and VDF/HFP base units in the (co)telomers were determined by 19F and 1H NMR spectroscopy. They ranged from 10 to 190 VDF base units. Fluorinated telomers of various molecular weights (1200–12,600 g/mol) were obtained by the alteration of the initial [1,6‐diiodoperfluorohexane]0/[fluoroalkenes]0 and [TBPPi]0/[fluoroalkenes]0 molar ratios. The thermal properties of these fluorinated (co)telomers, such as the glass‐transition temperature and melting temperature, were examined. As expected, these telomers exhibited good thermal stability. They were stable at least up to 350 °C. The compounds containing more than 30 VDF units were crystalline, whereas all those containing VDF‐co‐HFP were amorphous with elastomeric properties, whatever the number was of the fluorinated base units. The structures of I–(VDF)n–RF–(VDF)m–I and I–(HFP)x(VDF)n–RF–(VDF)m(HFP)y–I (co)telomers were obtained, and the defects of the VDF chain and the ? CH2CF2I and ? CF2CH2I functionalities were studied successfully (where RF = C6F12). The functionality in the iodine atoms was modified: the higher the VDF content in the telomers, the lower the normal end functionality (? CH2CF2I) and the higher the reversed extremity (? CF2CH2I). In addition, the percentage of defects increased when the number of VDF units increased. The molecular weights and molecular weight distributions of different telomers and cotelomers were also studied. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1470–1485, 2006 相似文献
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Self‐diffusion and interactions in mixtures of imidazolium bis(mandelato)borate ionic liquids with polyethylene glycol: 1H NMR study
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Andrei Filippov Nail Azancheev Mamoun Taher Faiz Ullah Shah Sergei Glavatskih Oleg N. Antzutkin 《Magnetic resonance in chemistry : MRC》2015,53(7):493-497
We used 1H nuclear magnetic resonance pulsed‐field gradient to study the self‐diffusion of polyethylene glycol (PEG) and ions in a mixture of PEG and imidazolium bis(mandelato)borate ionic liquids (ILs) at IL concentrations from 0 to 10 wt% and temperatures from 295 to 370 K. PEG behaves as a solvent for these ILs, allowing observation of separate lines in 1H NMR spectra assigned to the cation and anion as well as to PEG. The diffusion coefficients of PEG, as well as the imidazolium cation and bis(mandelato)borate (BMB) anion, differ under all experimental conditions tested. This demonstrates that the IL in the mixture is present in at least a partially dissociated state, while the lifetimes of the associated states of the ions and ions with PEG are less than ~30 ms. Generally, increasing the concentration of the IL leads to a decrease in the diffusion coefficients of PEG and both ions. The diffusion coefficient of the anion is less than that of the cation; the molecular mass dependence of diffusion of ions can be described by the Stokes–Einstein model. NMR chemical shift alteration analysis showed that the presence of PEG changes mainly the chemical shifts of protons belonging to imidazole ring of the cation, while chemical shifts of protons of anions and PEG remain unchanged. This demonstrated that the imidazolium cation interacts mainly with PEG, which most probably occurs through the oxygen of PEG and the imidazole ring. The BMB anion does not strongly interact with PEG, but it may be indirectly affected by PEG through interaction with the cation, which directly interacts with PEG. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Metabolic phenotyping of human plasma by 1H‐NMR at high and medium magnetic field strengths: a case study for lung cancer
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Evelyne Louis Francois‐Xavier Cantrelle Liesbet Mesotten Gunter Reekmans Liene Bervoets Karolien Vanhove Michiel Thomeer Guy Lippens Peter Adriaensens 《Magnetic resonance in chemistry : MRC》2017,55(8):706-713
Accurate identification and quantification of human plasma metabolites can be challenging in crowded regions of the NMR spectrum with severe signal overlap. Therefore, this study describes metabolite spiking experiments on the basis of which the NMR spectrum can be rationally segmented into well‐defined integration regions, and this for spectrometers having magnetic field strengths corresponding to 1H resonance frequencies of 400 MHz and 900 MHz. Subsequently, the integration data of a case–control dataset of 69 lung cancer patients and 74 controls were used to train a multivariate statistical classification model for both field strengths. In this way, the advantages/disadvantages of high versus medium magnetic field strength were evaluated. The discriminative power obtained from the data collected at the two magnetic field strengths is rather similar, i.e. a sensitivity and specificity of respectively 90 and 97% for the 400 MHz data versus 88 and 96% for the 900 MHz data. This shows that a medium‐field NMR spectrometer (400–600 MHz) is already sufficient to perform clinical metabolomics. However, the improved spectral resolution (reduced signal overlap) and signal‐to‐noise ratio of 900 MHz spectra yield more integration regions that represent a single metabolite. This will simplify the unraveling and understanding of the related, disease disturbed, biochemical pathways. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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The title Zintl phases are prepared by reactions of the corresponding elemental alkali metals with pre‐prepared M‐Sn alloys (M: Ni, Co) at 550—880 °C for 48 h. 相似文献
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In crystalline molecular solids, in the absence of strong intermolecular interactions, entropy-driven processes play a key role in the formation of dynamically modulated transient phases. Specifically, in crystalline simvastatin, the observed fully reversible enantiotropic behavior is associated with multiple order–disorder transitions: upon cooling, the dynamically disordered high-temperature polymorphic Form I is transformed to the completely ordered low-temperature polymorphic Form III via the intermediate (transient) modulated phase II. This behavior is associated with a significant reduction in the kinetic energy of the rotating and flipping ester substituents, as well as a decrease in structural ordering into two distinct positions. In transient phase II, the conventional three-dimensional structure is modulated by periodic distortions caused by cooperative conformation exchange of the ester substituent between the two states, which is enabled by weakened hydrogen bonding. Based on solid-state NMR data analysis, the mechanism of the enantiotropic phase transition and the presence of the transient modulated phase are documented. 相似文献
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Ali Alaaeddine Frédéric Boschet Bruno Ameduri 《Journal of polymer science. Part A, Polymer chemistry》2014,52(12):1721-1729
Methallylic monomers bearing triethyl or 4‐diazabicyclo[2.2.2]octane (DABCO) ammonium side‐groups are prepared and copolymerized with chlorotrifluoroethylene (CTFE). First, three different monomers are synthesized from chloro‐2‐methylprop‐1‐ene or 3‐chloro‐2‐chloromethylprop‐1‐ene in fair to good yields (57–95%). Then, several parameters (initiators, aqueous or solution processes, temperature) of the radical copolymerization of these monomers with chlorotrifluoroethylene are investigated. Various initiators are tested in the presence of ammonium perfluorooctanoate (APFO) as water‐soluble surfactant, and tert‐butyl peroxypivalate/APFO leads to the best results in a mixed solvent (H2O/CH3CN/C4F5H5). In all experiments, the radical copolymerization shows that CTFE is more reactive than the methallylic monomer as evidenced by the characterization of poly(CTFE‐co‐M) copolymer by nuclear magnetic resonance spectroscopy and elemental analysis. Thermal degradation of these copolymers by thermogravimetric analyses indicates that the copolymers are stable up to 180 °C without any degradation and have a Td,10% above 300 °C. Finally, their ionic exchange capacities range between 0.94 and 1.69 meq g?1. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1721–1729 相似文献
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Andr M. Striegel Michael R. Krejsa 《Journal of Polymer Science.Polymer Physics》2000,38(23):3120-3135
The quantitation of long‐chain branching (LCB) and short‐chain branching (SCB) in polyethylene (PE) was accomplished with a combination of carbon nuclear magnetic resonance (13C NMR) spectroscopy and size exclusion chromatography (SEC) with universal calibration. We demonstrate how the spectroscopic and chromatographic techniques can supplement each other, as neither is capable individually of completely describing the molecular architecture imparted by the various types of branching. The essential lack of impact of SCB on the hydrodynamic volume imposes a limit on SEC for determining this type of branching, whereas highly effective LCB in the PE molecule may not offer a statistically large enough amount of long chains for accurate determination by NMR. A variety of examples are given for PE, showcasing the advantages and shortcomings of each analytical method and their complementarity. Additionally, the importance of choosing an appropriate linear standard and viscosity shielding ratio (ϵ) for the Zimm–Stockmayer branching calculations employed for analyzing SEC data is emphasized with an examination of the effect on the results of using a branched standard and various ϵ values. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 3120–3135, 2000 相似文献
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Hanne Wigum Linda Tangen Jon Andreas Stvneng Erling Rytter 《Journal of polymer science. Part A, Polymer chemistry》2000,38(17):3161-3172
Ethene homopolymerization and copolymerization with 1‐hexene were catalyzed by methyl‐substituted cyclopentadienyl (Cp) zirconium dichlorides, (Rn C5H5−n)2ZrCl2 (Rn = H, Me, 1,2‐Me2, 1,3‐Me2, 1,2,3‐Me3, 1,2,4‐Me3, Me4, or Me5), and methylaluminoxane. The polymers were characterized with Fourier transform infrared, nuclear magnetic resonance, gel permeation chromatography, and differential scanning calorimetry techniques. Generally, an increasing number of methyl substituents on the Cp ligand results in lower 1‐hexene incorporation in the copolymer. The two catalysts with split methyl substitution (Rn = 1,3‐Me2 and Rn = 1,2,4‐Me3) show a higher comonomer response than their disubstituted and trisubstituted counterparts (Rn = 1,2‐Me2 and Rn = 1,2,3‐Me3). They even incorporate more 1‐hexene than Rn = H and Rn = Me. These findings are qualitatively in agreement with the results of a theoretical study based on density functional calculations. The presence of comonomer does not influence the termination reactions after the insertion of ethene. There is more frequent termination after each hexene insertion with increasing comonomer incorporation except for the two catalysts with split methyl substituents. The termination probability per inserted comonomer is highest for the less substituted catalysts. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3161–3172, 2000 相似文献
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Insights into the Catalytic Activity of Nitridated Fibrous Silica (KCC‐1) Nanocatalysts from 15N and 29Si NMR Spectroscopy Enhanced by Dynamic Nuclear Polarization
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Dr. Aany Sofia Lilly Thankamony Dr. Cédric Lion Dr. Frédérique Pourpoint Baljeet Singh Dr. Angel J. Perez Linde Dr. Diego Carnevale Prof. Geoffrey Bodenhausen Dr. Hervé Vezin Prof. Olivier Lafon Prof. Vivek Polshettiwar 《Angewandte Chemie (International ed. in English)》2015,54(7):2190-2193
Fibrous nanosilica (KCC‐1) oxynitrides are promising solid‐base catalysts. Paradoxically, when their nitrogen content increases, their catalytic activity decreases. This counterintuitive observation is explained here for the first time using 15N‐solid‐state NMR spectroscopy enhanced by dynamic nuclear polarization. 相似文献