Journal articles: 'Pulsní 1H-NMR'

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SATO, KAZUO. "1H Pulsed NMR." Sen'i Gakkaishi 44, no. 6 (1988): P224—P227. http://dx.doi.org/10.2115/fiber.44.6_p224.

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Haase, J., M. B. Kozlov, A. G. Webb, B. Büchner, H. Eschrig, K. H. Müller, and H. Siegel. "2GHz 1H NMR in pulsed magnets." Solid State Nuclear Magnetic Resonance 27, no. 3 (May 2005): 206–8. http://dx.doi.org/10.1016/j.ssnmr.2004.10.002.

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Rashid, Haroon, Yury Golitsyn, Muhammad Humayun Bilal, Karsten Mäder, Detlef Reichert, and Jörg Kressler. "Polymer Networks Synthesized from Poly(Sorbitol Adipate) and Functionalized Poly(Ethylene Glycol)." Gels 7, no. 1 (February 20, 2021): 22. http://dx.doi.org/10.3390/gels7010022.

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Polymer networks were prepared by Steglich esterification using poly(sorbitol adipate) (PSA) and poly(sorbitol adipate)-graft-poly(ethylene glycol) mono methyl ether (PSA-g-mPEG12) copolymer. Utilizing multi-hydroxyl functionalities of PSA, poly(ethylene glycol) (PEG) was first grafted onto a PSA backbone. Then the cross-linking of PSA or PSA-g-mPEG12 was carried out with disuccinyl PEG of different molar masses (Suc-PEGn-Suc). Polymers were characterized through nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). The degree of swelling of networks was investigated through water (D2O) uptake studies, while for detailed examination of their structural dynamics, networks were studied using 13C magic angle spinning NMR (13C MAS NMR) spectroscopy, 1H double quantum NMR (1H DQ NMR) spectroscopy, and 1H pulsed field gradient NMR (1H PFG NMR) spectroscopy. These solid state NMR results revealed that the networks were composed of a two component structure, having different dipolar coupling constants. The diffusion of solvent molecules depended on the degree of swelling that was imparted to the network by the varying chain length of the PEG based cross-linking agent.

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Fukumori, Kenzo, Norio Sato, and Toshio Kurauchi. "Pulsed NMR Study of Motional Heterogeneity in Acrylonitrile-Butadiene/Poly(Vinyl Chloride) Blends." Rubber Chemistry and Technology 64, no. 4 (September 1, 1991): 522–33. http://dx.doi.org/10.5254/1.3538570.

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Abstract Motional heterogeneity in blends of NBR (AN = 38%) and PVC was studied by 1H pulsed NMR. It was estimated from NMR relaxation measurements that the PVC molecules in the NBR phase form phase domains of the order of less than 10 nm, consistent with the microheterogeneous structure observed by TEM. Furthermore, by spin diffusion experiments using the Goldman-Shen pulse sequence, the size of the PVC phase domains was semiquantitatively evaluated to be 4.2 nm in the case of the cylindrical domains and to be 5.1 nm in the case of the spherical domains. It becomes clear that pulsed NMR complements the results of other analytical methods with more detailed information on the state of the molecular mixing in the blends.

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Odedra, Smita, and Stephen Wimperis. "Improved background suppression in 1H MAS NMR using composite pulses." Journal of Magnetic Resonance 221 (August 2012): 41–50. http://dx.doi.org/10.1016/j.jmr.2012.05.010.

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Furihata, Kazuo, and Mitsuru Tashiro. "Sensitive Water Ligand Observed via Gradient Spectroscopy with 19F Detection for Analysis of Fluorinated Compounds Bound to Proteins." Magnetochemistry 5, no. 2 (May 1, 2019): 29. http://dx.doi.org/10.3390/magnetochemistry5020029.

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The water ligand observed via a gradient spectroscopy type experiment with 19F detection was applied to selectively detect fluorinated compounds with affinity to the target proteins. The 19F signals of bound and unbound compounds were observed as opposite phases, which was advantageous to distinguish the binding state. The proposed NMR method was optimized based on the 19F{1H} saturation transfer difference pulse sequence, and various inversion pulses for the water resonance were evaluated with the aim of high sensitivity.

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Kozlov, Mikhail B., Jürgen Haase, Christoph Baumann, and Andrew G. Webb. "56T 1H NMR at 2.4GHz in a pulsed high-field magnet." Solid State Nuclear Magnetic Resonance 28, no. 1 (July 2005): 64–67. http://dx.doi.org/10.1016/j.ssnmr.2005.06.003.

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Lens, P., F. Vergeldt, G. Lettinga, and H. Van As. "1H NMR characterisation of the diffusional properties of methanogenic granular sludge." Water Science and Technology 39, no. 7 (April 1, 1999): 187–94. http://dx.doi.org/10.2166/wst.1999.0358.

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The diffusive properties of mesophilic methanogenic granular sludge have been studied using diffusion analysis by relaxation time separated pulsed field gradient nuclear magnetic resonance (DARTS PFG NMR) spectroscopy. NMR measurements were performed at 22°C with 10 ml granular sludge at a magnetic field strength of 0.5 T (20 MHz resonance frequency for protons). Spin-spin relaxation (T2) time measurements indicate that three 1H populations can be distinguished in methanogenic granular sludge beds, corresponding to water in three different environments. The T2 relaxation time measurements clearly differentiate the extragranular water (T2 ≈ 1000 ms) from the water present in the granular matrix (T2 = 40-100 ms) and bacterial cell associated water (T2 = 10-15 ms). Self-diffusion coefficient measurements at 22°C of the different 1H-water populations as the tracer show that methanogenic granular sludge does not contain one unique diffusion coefficient. The observed distribution of self-diffusion coefficients varies between 1.1 × 10−9 m2/s (bacterial cell associated water) and 2.1 × 10−9 m2/s (matrix associated water).

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Lens, Piet N. L., Rakel Gastesi, Frank Vergeldt, Adriaan C. van Aelst, Antonio G. Pisabarro, and Henk Van As. "Diffusional Properties of Methanogenic Granular Sludge: 1H NMR Characterization." Applied and Environmental Microbiology 69, no. 11 (November 2003): 6644–49. http://dx.doi.org/10.1128/aem.69.11.6644-6649.2003.

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ABSTRACT The diffusive properties of anaerobic methanogenic and sulfidogenic aggregates present in wastewater treatment bioreactors were studied using diffusion analysis by relaxation time-separated pulsed-field gradient nuclear magnetic resonance (NMR) spectroscopy and NMR imaging. NMR spectroscopy measurements were performed at 22°C with 10 ml of granular sludge at a magnetic field strength of 0.5 T (20 MHz resonance frequency for protons). Self-diffusion coefficients of H2O in the investigated series of mesophilic aggregates were found to be 51 to 78% lower than the self-diffusion coefficient of free water. Interestingly, self-diffusion coefficients of H2O were independent of the aggregate size for the size fractions investigated. Diffusional transport occurred faster in aggregates growing under nutrient-rich conditions (e.g., the bottom of a reactor) or at high (55°C) temperatures than in aggregates cultivated in nutrient-poor conditions or at low (10°C) temperatures. Exposure of aggregates to 2.5% glutaraldehyde or heat (70 or 90°C for 30 min) modified the diffusional transport up to 20%. In contrast, deactivation of aggregates by HgCl2 did not affect the H2O self-diffusion coefficient in aggregates. Analysis of NMR images of a single aggregate shows that methanogenic aggregates possess a spin-spin relaxation time and self-diffusion coefficient distribution, which are due to both physical (porosity) and chemical (metal sulfide precipitates) factors.

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Sun, Y. H., J. C. Xiong, H. Lock, M. L. Buszko, J. A. Haase, and G. E. Maciel. "Solid-State 1H CRAMPS NMR Imaging with Pulsed Rotating Magnetic Field Gradients." Journal of Magnetic Resonance, Series A 110, no. 1 (September 1994): 1–6. http://dx.doi.org/10.1006/jmra.1994.1172.

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Kinmond, E. J., S. R. Coulson, J. P. S. Badyal, S. A. Brewer, and C. Willis. "High structural retention during pulsed plasma polymerization of 1H,1H,2H-perfluorododecene: an NMR and TOF-SIMS study." Polymer 46, no. 18 (August 2005): 6829–35. http://dx.doi.org/10.1016/j.polymer.2005.05.112.

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Price, William S., Yuichi Aihara, and Kikuko Hayamizu. "NMR Studies of Nanoscale Organization and Dynamics in Polymer Electrolytes." Australian Journal of Chemistry 57, no. 12 (2004): 1185. http://dx.doi.org/10.1071/ch04155.

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Multinuclear (i.e., 7Li, 19F, and 1H) NMR relaxation and pulsed field gradient spin-echo (PGSE) NMR translational diffusion measurements have been used to study the reorientational and translational dynamics of the polymeric, anionic, and cationic species in a polymer electrolyte system composed of high-molecular-weight comb-branched polyethers and their precursor macromonomers of cross-linked random copolymers, with and without LiN(SO2CF3)2 (LiTFSI) doping. The macromonomers are derivatives of glycerol bonded to ethylene oxide-co-propylene oxide (m(EO-PO)) and are viscous liquids with a molecular weight of approximately 8000. The results were consistent with a picture of the lithium ions undergoing local motions near the polymer chains, whereas the anions diffuse through a slowly fluctuating three-dimensional porous polymer matrix. Four years later, the macromonomer electrolyte samples were re-measured to investigate the effects of long-term aging. The NMR data revealed that the electrolyte has undergone significant structural relaxation. The findings shed light on the evolving molecular architectures that influence conductivity and help to explain the non-ideal conductivity behaviour.

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Lens, Piet, Look Hulshoff Pol, Gatze Lettinga, and Henk Van As. "Use of 1H NMR to study transport processes in sulfidogenic granular sludge." Water Science and Technology 36, no. 6-7 (September 1, 1997): 157–63. http://dx.doi.org/10.2166/wst.1997.0587.

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Pulsed field gradient nuclear magnetic resonance (NMR) techniques have been applied to study diffusion and flow in a sulfidogenic granular sludge bed. When sulfidogenic granular sludge is exposed to a 20 MHz magnetic field, a multi-exponential spin-spin relaxation (T2) with at least 5 populations is observed. One of these populations (T2 ≈ 30 ms) is intracellular water. Diffusion measurements at 22°C with 1H-water as tracer indicated that sulfidogenic granular sludge contains a distribution of diffusion coefficients between 1.0 × 10−9 m2/s and 2.1 × 10−9 m2/s. Analysing the data set using a monoexponential fit gives a general parameter that can be used to describe the apparent diffusion coefficient in granular sludge. This approach showed that sulfidogenic granular sludge cultivated in different reactor configurations (UASB, USSB and baffled reactors) has comparable diffusional characteristics. Finally, the use of flow and imaging measurements in sulfidogenic granular sludge beds is discussed.

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Volkov, Vitaliy I., Alexander V. Chernyak, Daniil V. Golubenko, Vladimir A. Tverskoy, Georgiy A. Lochin, Ervena S. Odjigaeva, and Andrey B. Yaroslavtsev. "Hydration and Diffusion of H+, Li+, Na+, Cs+ Ions in Cation-Exchange Membranes Based on Polyethylene- and Sulfonated-Grafted Polystyrene Studied by NMR Technique and Ionic Conductivity Measurements." Membranes 10, no. 10 (October 1, 2020): 272. http://dx.doi.org/10.3390/membranes10100272.

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The main particularities of sulfonate groups hydration, water molecule and alkaline metal cation translation mobility as well as ionic conductivity were revealed by NMR and impedance spectroscopy techniques. Cation-exchange membranes MSC based on cross-linked sulfonated polystyrene (PS) grafted on polyethylene with ion-exchange capacity of 2.5 mg-eq/g were investigated. Alkaline metal cation hydration numbers (h) calculated from temperature dependences of 1H chemical shift of water molecule for membranes equilibrated with water vapor at RH = 95% are 5, 6, and 4 for Li+, Na+, and Cs+ ions, respectively. These values are close to h for equimolar aqueous salt solutions. Water molecules and counter ions Li+, Na+, and Cs+ diffusion coefficients were measured by pulsed field gradient NMR on the 1H, 7Li, 23Na, and 133Cs nuclei. For membranes as well as for aqueous chloride solutions, cation diffusion coefficients increased in the following sequence: Li+ < Na+ < Cs+. Cation and water molecule diffusion activation energies in temperature range from 20 °C to 80 °C were close to each other (about 20 kJ/mol). The cation conductivity of MSC membranes is in the same sequence, Li+ < Na+ < Cs+ << H+. The conductivity values calculated from the NMR diffusion coefficients with the use of the Nernst–Einstein equation are essentially higher than experimentally determined coefficients. The reason for this discrepancy is the heterogeneity of membrane pore and channel system. Ionic conductivity is limited by cation transfer in narrow channels, whereas the diffusion coefficient characterizes ion mobility in wide pores first of all.

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Herbert-Pucheta, José Enrique, José Daniel Lozada-Ramírez, Ana E. Ortega-Regules, Luis Ricardo Hernández, and Cecilia Anaya de Parrodi. "Nuclear Magnetic Resonance Metabolomics with Double Pulsed-Field-Gradient Echo and Automatized Solvent Suppression Spectroscopy for Multivariate Data Matrix Applied in Novel Wine and Juice Discriminant Analysis." Molecules 26, no. 14 (July 7, 2021): 4146. http://dx.doi.org/10.3390/molecules26144146.

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The quality of foods has led researchers to use various analytical methods to determine the amounts of principal food constituents; some of them are the NMR techniques with a multivariate statistical analysis (NMR-MSA). The present work introduces a set of NMR-MSA novelties. First, the use of a double pulsed-field-gradient echo (DPFGE) experiment with a refocusing band-selective uniform response pure-phase selective pulse for the selective excitation of a 5–10-ppm range of wine samples reveals novel broad 1H resonances. Second, an NMR-MSA foodomics approach to discriminate between wine samples produced from the same Cabernet Sauvignon variety fermented with different yeast strains proposed for large-scale alcohol reductions. Third a comparative study between a nonsupervised Principal Component Analysis (PCA), supervised standard partial (PLS-DA), and sparse (sPLS-DA) least squares discriminant analysis, as well as orthogonal projections to a latent structures discriminant analysis (OPLS-DA), for obtaining holistic fingerprints. The MSA discriminated between different Cabernet Sauvignon fermentation schemes and juice varieties (apple, apricot, and orange) or juice authentications (puree, nectar, concentrated, and commercial juice fruit drinks). The new pulse sequence DPFGE demonstrated an enhanced sensitivity in the aromatic zone of wine samples, allowing a better application of different unsupervised and supervised multivariate statistical analysis approaches.

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Porion, Patrice, and Alfred Delville. "A Multi-Scale Study of Water Dynamics under Confinement, Exploiting Numerical Simulations in Relation to NMR Relaxometry, PGSE and NMR Micro-Imaging Experiments: An Application to the Clay/Water Interface." International Journal of Molecular Sciences 21, no. 13 (June 30, 2020): 4697. http://dx.doi.org/10.3390/ijms21134697.

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Water mobility within the porous network of dense clay sediments was investigated over a broad dynamical range by using 2H nuclear magnetic resonance spectroscopy. Multi-quanta 2H NMR spectroscopy and relaxation measurements were first performed to identify the contributions of the various relaxation mechanisms monitoring the time evolution of the nuclear magnetisation of the confined heavy water. Secondly, multi-quanta spin-locking NMR relaxation measurements were then performed over a broad frequency domain, probing the mobility of the confined water molecules on a time-scale varying between microseconds and milliseconds. Thirdly, 1H NMR pulsed-gradient spin-echo attenuation experiments were performed to quantify water mobility on a time-scale limited by the NMR transverse relaxation time of the confined NMR probe, typically a few milliseconds. Fourthly, the long living quantum state of the magnetisation of quadrupolar nuclei was exploited to probe a two-time correlation function at a time-scale reaching one second. Finally, magnetic resonance imaging measurements allow probing the same dynamical process on time-scales varying between seconds and several hours. In that context, multi-scale modelling is required to interpret these NMR measurements and extract information on the influences of the structural properties of the porous network on the apparent mobility of the diffusing water molecules. That dual experimental and numerical approach appears generalizable to a large variety of porous networks, including zeolites, micelles and synthetic or biological membranes.

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Gómez, Jennifer S., Andrew G. M. Rankin, Julien Trébosc, Frédérique Pourpoint, Yu Tsutsumi, Hiroki Nagashima, Olivier Lafon, and Jean-Paul Amoureux. "Improved NMR transfer of magnetization from protons to half-integer spin quadrupolar nuclei at moderate and high magic-angle spinning frequencies." Magnetic Resonance 2, no. 1 (June 17, 2021): 447–64. http://dx.doi.org/10.5194/mr-2-447-2021.

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Abstract. Half-integer spin quadrupolar nuclei are the only magnetic isotopes for the majority of the chemical elements. Therefore, the transfer of polarization from protons to these isotopes under magic-angle spinning (MAS) can provide precious insights into the interatomic proximities in hydrogen-containing solids, including organic, hybrid, nanostructured and biological solids. This transfer has recently been combined with dynamic nuclear polarization (DNP) in order to enhance the NMR signal of half-integer quadrupolar isotopes. However, the cross-polarization transfer lacks robustness in the case of quadrupolar nuclei, and we have recently introduced as an alternative technique a D-RINEPT (through-space refocused insensitive nuclei enhancement by polarization transfer) scheme combining a heteronuclear dipolar recoupling built from adiabatic pulses and a continuous-wave decoupling. This technique has been demonstrated at 9.4 T with moderate MAS frequencies, νR≈10–15 kHz, in order to transfer the DNP-enhanced 1H polarization to quadrupolar nuclei. Nevertheless, polarization transfers from protons to quadrupolar nuclei are also required at higher MAS frequencies in order to improve the 1H resolution. We investigate here how this transfer can be achieved at νR≈20 and 60 kHz. We demonstrate that the D-RINEPT sequence using adiabatic pulses still produces efficient and robust transfers but requires large radio-frequency (rf) fields, which may not be compatible with the specifications of most MAS probes. As an alternative, we introduce robust and efficient variants of the D-RINEPT and PRESTO (phase-shifted recoupling effects a smooth transfer of order) sequences using symmetry-based recoupling schemes built from single and composite π pulses. Their performances are compared using the average Hamiltonian theory and experiments at B0=18.8 T on γ-alumina and isopropylamine-templated microporous aluminophosphate (AlPO4-14), featuring low and significant 1H–1H dipolar interactions, respectively. These experiments demonstrate that the 1H magnetization can be efficiently transferred to 27Al nuclei using D-RINEPT with SR412(270090180) recoupling and using PRESTO with R2227(1800) or R1676(270090180) schemes at νR=20 or 62.5 kHz, respectively. The D-RINEPT and PRESTO recoupling schemes complement each other since the latter is affected by dipolar truncation, whereas the former is not. We also analyze the losses during these recoupling schemes, and we show how these magnetization transfers can be used at νR=62.5 kHz to acquire in 72 min 2D HETCOR (heteronuclear correlation) spectra between 1H and quadrupolar nuclei, with a non-uniform sampling (NUS).

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Hemnani, Preeti, A. K. Rajarajan, Gopal Joshi, and S. V. G. Ravindranath. "The Building of Pulsed NQR/NMR Spectrometer." International Journal of Electrical and Computer Engineering (IJECE) 8, no. 3 (June 1, 2018): 1442. http://dx.doi.org/10.11591/ijece.v8i3.pp1442-1450.

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<p>NQR spectrometer designed is composed of four modules; Transmitter, Probe, Receiver and computer controlled (FPGA & Software) module containing frequency synthesizer, synchronous demodulator, pulse programmer and display. The function of the Transmitter module is to amplify the RF pulse sequence to about 200 W power level into the probe (50 Ohm) which is a parallel resonance circuit with a tapped capacitor. The probe excites the nucleus and picks-up the signal emitted from the nuclei. The nuclear signal at the same frequency as the excitation, which is typically in the range of a few microvolts is amplified, demodulated and filtered (1 kHz to 100 kHz) by receiver module. 14N NQR, 1H and 2H NMR signals are observed from the spectrometer.As the SNR of NQR signal is very low, NQR signal processing based on Adaptive Line Enhancement is presented.</p>

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Pulst, Martin, Yury Golitsyn, Detlef Reichert, and Jörg Kressler. "Ion Transport Properties and Ionicity of 1,3-Dimethyl-1,2,3-Triazolium Salts with Fluorinated Anions." Materials 11, no. 9 (September 14, 2018): 1723. http://dx.doi.org/10.3390/ma11091723.

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1,2,3-Triazolium salts are an important class of materials with a plethora of sophisticated applications. A series of three novel 1,3-dimethyl-1,2,3-triazolium salts with fluorine, containing anions of various size, is synthesized by methylation of 1,2,3-triazole. Their ion conductivity is measured by impedance spectroscopy, and the corresponding ionicities are determined by diffusion coefficients obtained from 1H and 19F pulsed field gradient nuclear magnetic resonance (PFG NMR) spectroscopy data, revealing that the anion strongly influences their ion conductive properties. Since the molar ion conductivities and ionicities of the 1,3-dimethyl-1,2,3-triazolium salts are enhanced in comparison to other 1,2,3-triazolium salts with longer alkyl substituents, they are promising candidates for applications as electrolytes in electrochemical devices.

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Farhat, I. "A pulsed 1H NMR study of the hydration properties of extruded maize-sucrose mixtures." Carbohydrate Polymers 30, no. 4 (August 1996): 219–27. http://dx.doi.org/10.1016/s0144-8617(96)00089-6.

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Konuma, Tsuyoshi, Aritaka Nagadoi, Jun-ichi Kurita, and Takahisa Ikegami. "Analysis of Artifacts Caused by Pulse Imperfections in CPMG Pulse Trains in NMR Relaxation Dispersion Experiments." Magnetochemistry 4, no. 3 (July 30, 2018): 33. http://dx.doi.org/10.3390/magnetochemistry4030033.

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Nuclear magnetic resonance relaxation dispersion (rd) experiments provide kinetics and thermodynamics information of molecules undergoing conformational exchange. Rd experiments often use a Carr-Purcell-Meiboom-Gill (CPMG) pulse train equally separated by a spin-state selective inversion element (U-element). Even with measurement parameters carefully set, however, parts of 1H–15N correlations sometimes exhibit large artifacts that may hamper the subsequent analyses. We analyzed such artifacts with a combination of NMR measurements and simulation. We found that particularly the lowest CPMG frequency (νcpmg) can also introduce large artifacts into amide 1H–15N and aromatic 1H–13C correlations whose 15N/13C resonances are very close to the carrier frequencies. The simulation showed that the off-resonance effects and miscalibration of the CPMG π pulses generate artifact maxima at resonance offsets of even and odd multiples of νcpmg, respectively. We demonstrate that a method once introduced into the rd experiments for molecules having residual dipolar coupling significantly reduces artifacts. In the method the 15N/13C π pulse phase in the U-element is chosen between x and y. We show that the correctly adjusted sequence is tolerant to miscalibration of the CPMG π pulse power as large as ±10% for most amide 15N and aromatic 13C resonances of proteins.

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Jeican, Ionut Isaia, Horea Matei, Alexandru Istrate, Eugen Mironescu, and Ştefana Bâlici. "CHANGES OBSERVED IN ERYTHROCYTE CELLS EXPOSED TO AN ALTERNATING CURRENT." Medicine and Pharmacy Reports 90, no. 2 (April 26, 2017): 154–60. http://dx.doi.org/10.15386/cjmed-696.

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Background and aims. Appliance of electric pulses induces red blood cells (RBCs) membrane poration, membrane aminophospholipid perturbation and alteration of the normal flip-flop process, resulting in various shape changes of theRBCs. We studied morphological and water permeability changes of RBCs bombarded with electrons in an alternating current circuit.Methods. We used three venous blood samples of 100 mL and an alternating current device. The harvested blood was divided into four experimental sets to be used for various exposure times: 0 hours (control RBCs), 0.5h, 3h and 6h (electricstimulated RBCs).Following the electric current each of the four sets were further divided into three samples: one for the assessment of the echinocytes/RBCs ratio, another for the electron microscopy study of ultrastructural changes induced by the alternating electrical current and a larger third one for determining water permeability of RCBs by 1H-NMR spectroscopy and morphological measurements.Results. There is a small but statistically significant effect of the RBC exposure to alternating electric current on cell diameters. Exposure to electric current is positively and strongly correlated with the percentage of echinocytes in a duration-dependentmanner. There is a strong and statistically significant correlation between electric current exposure and permeability to water as measured by 1H-NMR spectroscopy.Conclusion. Following interactions between electric current and RBCmembrane, certain modifications were observed in the erythrocyte structure. We attribute the increased cell size to a higher permeability to water and a decreased tonicity. This leads to the transformation of the RBCs into echinocytes.

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Konefał, Rafał, Zuzana Morávková, Bartosz Paruzel, Vitalii Patsula, Sabina Abbrent, Kosma Szutkowski, and Stefan Jurga. "Effect of PAMAM Dendrimers on Interactions and Transport of LiTFSI and NaTFSI in Propylene Carbonate-Based Electrolytes." Polymers 12, no. 7 (July 18, 2020): 1595. http://dx.doi.org/10.3390/polym12071595.

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Poly(amidoamine) (PAMAM)-based electrolytes are prepared by dissolving the PAMAM half-generations G1.5 or G2.5 in propylene carbonate (PC), either with lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) or sodium bis(trifluoromethylsulfonyl)imide (NaTFSI) salts. The solutions, designed for ion battery applications, are studied in terms of ions transport properties. Raman Spectroscopy reveals information about the interactions between cations and PAMAM dendrimers as well as full dissociation of the salts in all solutions. Pulsed-field gradient Nuclear Magnetic Resonance (PFG NMR), measured as a function of both temperature and PAMAM concentration, are obtained for the cation, anion, solvent, and dendrimer molecules using lithium (7Li), sodium (23Na), fluorine (19F), and hydrogen (1H) NMR, respectively. It was found that lithium diffusion is slow compared to the larger TFSI anion and decreases with PAMAM concentration due to interactions between cation and dendrimer. Comparison of conductivities calculated from diffusion coefficients using the Nernst–Einstein equation, with conductivity measurements obtained from Impedance Spectroscopy (IS), shows slightly higher IS conductivities, caused among others by PAMAM conductivity.

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Miller, Michelle C., Anna-Kristin Ludwig, Kanin Wichapong, Herbert Kaltner, Jürgen Kopitz, Hans-Joachim Gabius, and Kevin H. Mayo. "Adhesion/growth-regulatory galectins tested in combination: evidence for formation of hybrids as heterodimers." Biochemical Journal 475, no. 5 (March 15, 2018): 1003–18. http://dx.doi.org/10.1042/bcj20170658.

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The delineation of the physiological significance of protein (lectin)–glycan recognition and the structural analysis of individual lectins have directed our attention to studying them in combination. In this report, we tested the hypothesis of hybrid formation by using binary mixtures of homodimeric galectin-1 and -7 as well as a proteolytically truncated version of chimera-type galectin-3. Initial supportive evidence is provided by affinity chromatography using resin-presented galectin-7. Intriguingly, the extent of cell binding by cross-linking of surface counter-receptor increased significantly for monomeric galectin-3 form by the presence of galectin-1 or -7. Pulsed-field gradient NMR (nuclear magnetic resonance) diffusion measurements on these galectin mixtures indicated formation of heterodimers as opposed to larger oligomers. 15N-1H heteronuclear single quantum coherence NMR spectroscopy and molecular dynamics simulations allowed us to delineate how different galectins interact in the heterodimer. The possibility of domain exchange between galectins introduces a new concept for understanding the spectrum of their functionality, particularly when these effector molecules are spatially and temporally co-expressed as found in vivo.

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Ueda, Takahiro, and Nobuo Nakamura. "Nature of Hydration Water in (±)-Tris(ethylenediamine)cobalt(III) Chloride Hydrate, (±)-[Co(en)3]Cl3 · nH2O, as Studied by 1H, 2H, and 17O Solid State NMR." Zeitschrift für Naturforschung A 55, no. 1-2 (February 1, 2000): 362–68. http://dx.doi.org/10.1515/zna-2000-1-266.

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The static and dynamics properties of hydration water molecules in (±)-[Co(en)3]Cl3 were studied by means of 1H, 2H, and , 17O solid state NMR. By 'H pulsed field gradient (PFG) NMR the apparent diffusion coefficient of mobile water through a micropore along the crystalline unique c-axis was found to be 1.0 x 10-9 m2 s-1 . The 2H NMR spectrum at 141 K consists of two components, one being a Pake doublet corresponding to a quadrupole coupling constant (QCC) of (226 ± 2) kHz and an asymmetry parameter of the electric field gradient η of 0.08 ± 0.01, and another being a Gaussian line with a linewidth of 3.5 kHz. The 17O NMR spectrum at 300 K also consists of a narrow Gaussian peak and a broad powder pattern with a second order quadrupole effect corresponding to QCC = (6.3 ± 0.5) MHz and η = 0.55±0.02. The broad and narrow components are assigned to water molecules accommodated at general 12g positions and special 2a and 2b positions in the trigonal lattice with space group P1c1. From the ratio of the populations at these positions their potential energy difference was estimated to be between (2.7 ±0.1) and (3.5 ± 0.1) kJmol-1 . The 2H NMR spectrum at room temperature indicates a finite quadrupole interaction which is attributable to the rapid rotation of water molecule about the molecular C2-axis. When the water content exceeds 2.7, the QCC is reduced sharply to (5.0 ±0.1) kHz at 285 K, suggesting that there occurs rapid rotation of water and rapid exchange of 2H between nonequivalent positions.

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Ma, Junhe, Chen Guo, Yalin Tang, Junfeng Xiang, Shu Chen, Jing Wang, and Huizhou Liu. "Micellization in aqueous solution of an ethylene oxide–propylene oxide triblock copolymer, investigated with 1H NMR spectroscopy, pulsed-field gradient NMR, and NMR relaxation." Journal of Colloid and Interface Science 312, no. 2 (August 2007): 390–96. http://dx.doi.org/10.1016/j.jcis.2007.03.013.

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Polozov, Ivan V., and Klaus Gawrisch. "Domains in Binary SOPC/POPE Lipid Mixtures Studied by Pulsed Field Gradient 1H MAS NMR." Biophysical Journal 87, no. 3 (September 2004): 1741–51. http://dx.doi.org/10.1529/biophysj.104.040725.

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Davies, H. A., M. M. Phelan, and J. Madine. "1H, 15N and 13C assignment of the amyloidogenic protein medin using fast-pulsing NMR techniques." Biomolecular NMR Assignments 10, no. 1 (September 16, 2015): 75–77. http://dx.doi.org/10.1007/s12104-015-9641-z.

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Norgren, Magnus, and Birger Lindström. "Physico-Chemical Characterization of a Fractionated Kraft Lignin." Holzforschung 54, no. 5 (September 6, 2000): 528–34. http://dx.doi.org/10.1515/hf.2000.089.

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Summary A kraft lignin was leached from a softwood pulp and fractionated by ultrafiltration. The fractions were characterized in respect to phenolic group content, molecular weight distributions and self-diffusion coefficients. The 1H-Pulsed Field Gradient (PFG) NMR self-diffusion measurements and the High-Pressure Size Exclusion Chromatography (HPSEC) analysis of the fractions, were seen to correlate fairly well. From the self-diffusion measurements, the mass-weighted median hydrodynamic radii of the diffusants in the fractions, were calculated assuming spherical fragments. Furthermore, the content of phenolic groups in the fractions, was found to decrease by increasing hydrodynamic radius and molecular weight, but the calculated median surface charge densities of the macromolecules, were determined to be constant in the range of oligomers up to at least 65 structural units.

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Furukawa, Taiichi, Koji Ishizu, Yuji Yamane, and Isao Ando. "Diffusional behavior of multi-arm star polymers by 1H pulsed field gradient spin-echo NMR method." Polymer 46, no. 6 (February 2005): 1893–98. http://dx.doi.org/10.1016/j.polymer.2004.12.054.

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Choi, Sung-Gil, and William L. Kerr. "Effects of chemical modification of wheat starch on molecular mobility as studied by pulsed 1H NMR." LWT - Food Science and Technology 36, no. 1 (February 2003): 105–12. http://dx.doi.org/10.1016/s0023-6438(02)00200-1.

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Asakura, Tetsuo, Makoto Demura, Yasuo Watanabe, and Kazuo Sato. "1H pulsed NMR study of bombyx mori silk fibroin: Dynamics of fibroin and of absorbed water." Journal of Polymer Science Part B: Polymer Physics 30, no. 7 (June 1992): 693–99. http://dx.doi.org/10.1002/polb.1992.090300706.

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Vincent, Pauline, Frédérique Ham-Pichavant, Christelle Michaud, Gérard Mignani, Sergio Mastroianni, Henri Cramail, and Stéphane Grelier. "Extraction and Characterization of Hemicelluloses from a Softwood Acid Sulfite Pulp." Polymers 13, no. 13 (June 22, 2021): 2044. http://dx.doi.org/10.3390/polym13132044.

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Hemicelluloses were extracted from a softwood acid sulfite pulp in a three-step procedure. Further delignification step resulted in a holocellulose pulp containing only 1.7 wt.% of the lignin left. Cold caustic extraction (CCE) with 18 wt.% NaOH at 60 °C for 1 h was performed to solubilize hemicelluloses of the holocellulose. An unbleached cellulose pulp was then obtained 97% pure, which indicates that 89% of the hemicelluloses were removed. After purification, extraction yields between 1.1 wt.% and 9.5 wt.% were obtained from the delignified pulp and the hemicelluloses’ chemical compositions and structures were investigated by 1H, 13C nuclear magnetic resonance spectroscopy (NMR) and two-dimensional NMR by correlation spectroscopy (2D-COSY) and proton-detected heteronuclear single-quantum correlation (2D-HSQC), high-performance anion-exchange chromatography coupled with a pulsed amperometry detector (HPAEC-PAD), size-exclusion chromatography coupled with a refractive index detector (SEC-RI) and thermogravimetric analyses (TGA). Hemicelluloses were obtained with a purity of 96%, with short cellulosic chains as the only residue. Sulfite pulping modified the hemicelluloses’ structure, and it was found that two types of hemicelluloses were isolated, glucomannans, predominant at 67%, and methylglucuronoxylans. Finally, alkali-soluble hemicelluloses displayed relatively narrow size distributions and low molar masses, Mw varying between 18,900 and 30,000 g/mol after acid sulfite pulping.

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Sun, Ximei, Avraam I. Isayev, Tirtha R. Joshi, and Ernst von Meerwall. "Molecular Mobility of Unfilled and Carbon-Black-Filled Isoprene Rubber: Proton NMR Transverse Relaxation and Diffusion." Rubber Chemistry and Technology 80, no. 5 (November 1, 2007): 854–72. http://dx.doi.org/10.5254/1.3539421.

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Abstract In an effort to understand the effect of ultrasound on the devulcanization of gum and filled isoprene rubber vulcanizates, solid state NMR 1H transverse relaxation (T2) was employed to analyze rubber molecular mobility. The T2 relaxation decay of the unfilled and the black filled IR was successfully described by a two-component model. The short T2 component arose from the chemically crosslinked (gel) and physically entangled (heavy sol) network. The long T2 decay came from the unentangled sol and dangling network chain ends. Vulcanization decreased the molecular mobility; however, ultrasound devulcanization partially reversed this effect. Addition of processing oil in the filled IR significantly altered the dependence of T2 on the sol fraction. T2 and pulsed-gradient diffusion experiments were carried out on IR melt specimens after sonication with or without subsequent vulcanization. The lowered and broadened M-distribution produced results quantitatively related to earlier work in natural rubber.

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Rámirez, Hegira, Juan R. Rodrigues, Michael R. Mijares, Juan B. De Sanctis, and Jaime E. Charris. "Synthesis and biological activity of 2-[2-(7-chloroquinolin-4-ylthio)-4-methylthiazol-5-yl]-N-phenylacetamide derivatives as antimalarial and cytotoxic agents." Journal of Chemical Research 44, no. 5-6 (January 20, 2020): 305–14. http://dx.doi.org/10.1177/1747519819899073.

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A novel series of 2-[2-(7-chloroquinolin-4-ylthio)-4-methylthiazol-5-yl]- N-phenylacetamide derivatives is synthesized via substitution with 2-mercapto-4-methyl-5-thiazoleacetic acid at position 4 of 4,7-dichloroquinoline to obtain an intermediate acetic acid derivative. The chemical behavior of these reactants was investigated using different reaction conditions to optimize the nucleophilic substitution at position 4. The final compounds are prepared using a modified version of the Steglich esterification reaction between the acetic acid intermediate 3 and different anilines. The structures are confirmed by infrared, 1H, 13C, distortionless enhancement by polarization transfer 135°, Correlated Spectroscopy, heteronuclear correlation spectroscopy and (Long range HETCOR using three BIRD pulses) FLOCK-NMR spectral studies, and by elemental analysis. The synthesized compounds are tested in vitro and in vivo for their potential antimalarial and anticancer activities, with derivative 11 being the most promising candidate.

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Ngernpimai, S., C. Thomas, S. Maensiri, and Sineenat Siri. "Stability and Cytotoxicity of Well-Dispersed Magnetite Nanoparticles Prepared by Hydrothermal Method." Advanced Materials Research 506 (April 2012): 122–25. http://dx.doi.org/10.4028/www.scientific.net/amr.506.122.

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A preparation of well-dispersed magnetite nanoparticles was demonstrated in this study. Magnetite nanoparticles (MNPs) were synthesized by a hydrothermal method using aloe vera extract and serial centrifugation was employed to separate the sizes of well-dispersed particles. Well-dispersed MNPs with average sizes of 241, 227, 195, 165, 141 and 93 nm were obtained. They were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and vibrating sample magnetometry (VSM). XRD results indicated the MNPs were Fe3O4. Magnetic hysteresis loop measurements of the samples showed superparamagnetic properties. Pulsed nuclear magnetic resonance (NMR) showed stable proton (1H) spin-spin relaxation time (T2) values of water with suspended magnetite nanoparticles over a time course of 20 min, suggesting they were well-dispersed. The synthesized magnetite nanoparticles showed low cytotoxicity to NIH 3T3 cells at concentrations of 1-10%.

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Dutta, N. K., N. Roy Choudhury, B. Haidar, A. Vidal, J. B. Donnet, L. Delmotte, and J. M. Chezeau. "High-Resolution Solid State NMR Investigation of the Filler-Rubber Interaction: Part III. Investigation on the Structure and Formation Mechanism of Carbon Gel in the Carbon Black-Filled Styrene—Butadiene Rubber." Rubber Chemistry and Technology 74, no. 2 (May 1, 2001): 260–80. http://dx.doi.org/10.5254/1.3544949.

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Abstract This investigation describes the elastomer—filler interaction and its formation mechanism using solid state high-resolution, high-speed 1H magic-angle spinning nuclear magnetic resonance (NMR) spectroscopy. Pulsed NMR measurements were carried out on pure styrene-butadiene rubber (SBR), and solvent extracted carbon gels from freshly prepared and storage matured master batches. The effects of filler loading, storage maturation, severity of extraction and experimental temperature on the elastomer-filler interaction were examined and discussed. High resolution in NMR was achieved by higher temperature/low spinning rate, room temperature/high spinning and combined rotation and multiple-pulse spectroscopy (CRAMPS) techniques. High-speed magic-angle spinning (MAS) was found to be the most suitable method to achieve high resolution. Proton spin—spin relaxation time, T2, was measured successfully for each of the principal resonance species present in the samples. These measurements reveal an insight into the site-specific nature of the polymer—filler interaction. The relative immobilization of the dynamics of different protons, due to the presence of carbon black filler, and their temperature dependence evidence that the main chain vinyl proton is the most significantly immobilized one compared to the aromatic and methylene species. The effects of storage maturation and severity of extraction on the dynamics of the conformational jump have also been discussed. This work clearly demonstrates the importance of unsaturation on the bound rubber formation. It also provides first direct physical evidence confirming the hypothesis that bound rubber variation during the storage maturation is due to slow progressive replacement of short rubber chains by larger ones.

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SEO, Yoshiteru, Yasushi MORITA, Yoshiaki KUSAKA, Martin C. STEWARD, and Masataka MURAKAMI. "Diffusion of Water in Rat Sciatic Nerve Measured by 1H Pulsed Field Gradient NMR: Compartmentation and Anisotropy." Japanese Journal of Physiology 46, no. 2 (1996): 163–69. http://dx.doi.org/10.2170/jjphysiol.46.163.

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39

Capitani, D., A. L. Segre, M. Barsacchi, and M. Pentimalli. "Poly-1-oxy-2-phenyltrimethylene as studied by 1H pulsed low resolution NMR: a possible oxygen scavenger." European Polymer Journal 35, no. 4 (April 1999): 681–90. http://dx.doi.org/10.1016/s0014-3057(98)00158-x.

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40

Yasuda, Akiko, Manabu Miyata, Osamu Sano, Tatsufumi Sogo, Seiichiro Kishishita, Takuo Yamamoto, Hajime Aga, and Koryu Yamamoto. "A novel dextrin produced by the enzymatic reaction of 6-α-glucosyltransferase. I. The effect of nonreducing ends of glucose with by α-1,6 bonds on the retrogradation inhibition of high molecular weight dextrin." Bioscience, Biotechnology, and Biochemistry 85, no. 7 (April 9, 2021): 1737–45. http://dx.doi.org/10.1093/bbb/zbab062.

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ABSTRACT We prepared a high-molecular-weight modified dextrin (MWS-1000) from a partial hydrolysate of waxy corn starch with a weight average molecular weight of 1 × 106 (WS-1000) using Paenibacillus alginolyticus PP710 α-glucosyltransferase. The gel permeation chromatography showed that the weight average molecular weight of MWS-1000 was almost the same as that of WS-1000. The side chain lengths of WS-1000 and MWS-1000 after isomaltodextranase digestion were also shown to be similar to each other by high-performance anion exchange chromatography with pulsed amperometric detection. Since MWS-1000 confirmed the presence of α-1,6 bonds by enzyme digestibility, methylation, and 1H-NMR analyses, it was presumed that the structure of MWS-1000 was based on the introduction of α-1,6 glucosyl residues at the nonreducing ends of the partial hydrolysate of waxy corn starch. Furthermore, the MWS-1000 solution was not retrograded even during refrigerated storage or after repeated freeze–thaw cycles.

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41

Soong, Ronald, and Peter M. Macdonald. "Lateral Diffusion of PEG-Lipid in Magnetically Aligned Bicelles Measured Using Stimulated Echo Pulsed Field Gradient 1H NMR." Biophysical Journal 88, no. 1 (January 2005): 255–68. http://dx.doi.org/10.1529/biophysj.104.043620.

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42

Klimavicius, Vytautas, Vytautas Bacevicius, Zofia Gdaniec, and Vytautas Balevicius. "Pulsed-field gradient 1H NMR study of diffusion and self-aggregation of long-chain imidazolium-based ionic liquids." Journal of Molecular Liquids 210 (October 2015): 223–26. http://dx.doi.org/10.1016/j.molliq.2015.05.034.

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43

Chevelkov, Veniamin, Barth J. van Rossum, Federica Castellani, Kristina Rehbein, Anne Diehl, Morten Hohwy, Stefan Steuernagel, Frank Engelke, Hartmut Oschkinat, and Bernd Reif. "1H Detection in MAS Solid-State NMR Spectroscopy of Biomacromolecules Employing Pulsed Field Gradients for Residual Solvent Suppression⊥." Journal of the American Chemical Society 125, no. 26 (July 2003): 7788–89. http://dx.doi.org/10.1021/ja029354b.

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44

T. de Carvalho, Layde, Maria Luiza da S. Paula, Rodolfo M. de Moraes, Gizelda M. Alves, Talita M. Lacerda, Julio C. dos Santos, Amilton M. dos Santos, and Simone de F. Medeiros. "Chemical Modification of Pullulan Exopolysaccharide by Grafting Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) via Click Chemistry." Polymers 12, no. 11 (October 29, 2020): 2527. http://dx.doi.org/10.3390/polym12112527.

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Biodegradable and biocompatible copolymers have been often studied for the development of biomaterials for drug delivery systems. In this context, this work reports the synthesis and characterization of a novel pullulan-g-poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (Pull-g-PHBHV) graft copolymer using click chemistry. Well-defined and functional pullulan backbones containing azide groups (PullN3) previously prepared by our group were successfully used for this purpose and propargyl-terminated poly(3-hydroxybutyrate-co-3-hydroxyvalerate) was prepared via transesterification using propargyl alcohol as a chain transfer agent. By an alkyne-azide cycloaddition reaction catalyzed by copper (Cu (I)) (CuAAC), the graft copolymer Pull-g-PHBHV was obtained. The chemical structures of the polymers were accessed by 1H NMR and 13C NMR FTIR. Disappearance of the bands referring to the main bonds evidenced success in the grafting reaction. Besides that, DRX, DSC and TGA were used in order to access the changes in crystallinity and thermal behavior of the material. The remaining crystallinity of the Pull-g-PHBHV structure evidences the presence of PHBHV. Pull-g-PHBHV presented lower degradation maximum temperature values than the starting materials, indicating its minor thermal stability. Finally, the synthesized material is an innovative biopolymer, which has never been reported in the previous literature. It is a bio-derived and biodegradable polymer, chemically modified, resulting in interesting properties which can be useful for their further applications as biomedical systems for controlled delivery, for example.

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45

Scheidt, Holger A., Daniel Huster, and Klaus Gawrisch. "Diffusion of Cholesterol and Its Precursors in Lipid Membranes Studied by 1H Pulsed Field Gradient Magic Angle Spinning NMR." Biophysical Journal 89, no. 4 (October 2005): 2504–12. http://dx.doi.org/10.1529/biophysj.105.062018.

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Liu, M., R. D. Farrant, J. K. Nicholson, and J. C. Lindon. "Selective Detection of 1H NMR Resonances of CHn Groups Using a Heteronuclear Maximum-Quantum Filter and Pulsed Field Gradients." Journal of Magnetic Resonance, Series B 106, no. 3 (March 1995): 270–78. http://dx.doi.org/10.1006/jmrb.1995.1043.

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47

Idiyatullin, D. Sh, V. S. Smirnov, M. P. Letunovskii, and V. V. Strakhov. "Pulsed 1H NMR study of the effects of the rigid block content on the phase state of segmented polyurethanes." Polymer Science U.S.S.R. 30, no. 7 (January 1988): 1581–86. http://dx.doi.org/10.1016/0032-3950(88)90449-2.

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48

Slade, R. "Protonic conduction and 1H self-diffusion in nafion film studied by ac conductivity and pulsed field gradient NMR techniques." Solid State Ionics 35, no. 1-2 (August 1989): 11–15. http://dx.doi.org/10.1016/0167-2738(89)90006-4.

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49

Hertkorn, N., M. Harir, K. M. Cawley, P. Schmitt-Kopplin, and R. Jaffé. "Molecular characterization of dissolved organic matter from subtropical wetlands: a comparative study through the analysis of optical properties, NMR and FTICR/MS." Biogeosciences Discussions 12, no. 16 (August 25, 2015): 13711–65. http://dx.doi.org/10.5194/bgd-12-13711-2015.

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Abstract. Wetlands provide quintessential ecosystem services such as maintenance of water quality, water supply and biodiversity, among others; however, wetlands are also among the most threatened ecosystems worldwide. They are usually characterized by high levels of natural dissolved organic matter (DOM), representing a critical component in wetland biogeochemistry. This study describes the first detailed, comparative, molecular characterization of DOM in sub-tropical, pulsed, wetlands, namely the Everglades (USA), the Pantanal (Brazil) and the Okavango Delta (Botswana), using optical properties, high field nuclear magnetic resonance (NMR) and ultrahigh resolution mass spectrometry (FT-ICRMS), and compares compositional features to variations in organic matter sources and flooding characteristics (i.e. differences in hydroperiod). While optical properties showed both similarities and differences between these ecosystems, these differences were mainly based on the degree of aromaticity of the DOM. Analogies were such that an established excitation emission matrix fluorescence parallel factor analysis (EEM-PARAFAC) model for the Everglades was perfectly applicable to the other two wetlands. High-field (500 and 800 MHz) NMR spectra with cryogenic detection provided exceptional coverage and chemical description of wetland solid phase extracted (SPE) DOM. Area-normalized 1H NMR spectra of selected samples revealed clear distinctions of samples along with pronounced congruence within the three pairs of wetland DOM. Within sample pairs (long vs. short hydroperiod sites), internal differences mainly referred to intensity variations (denoting variable abundance) rather than to alterations of NMR resonances positioning (denoting diversity of molecules). The relative disparity was largest between the Everglades long and short hydroperiod samples, whereas Pantanal and Okavango samples were more alike among themselves. Otherwise, molecular divergence was most obvious in the case of unsaturated protons (δH > 5 ppm). The larger discrimination observed between 1H NMR spectra of DOM from different wetlands in comparison with the intrinsic variance among DOM within each wetland readily suggests the presence of an individual molecular signature, characteristic of each particular wetland. 2-D NMR spectroscopy for a particular sample revealed a large richness of aliphatic and unsaturated substructures, likely derived from microbial sources such as periphyton in the Everglades. In contrast, the chemical diversity of aromatic wetland DOM likely originates from a combination of higher plant sources, progressive microbial and photochemical oxidation, and contributions from combustion-derived products (e.g. black carbon). In addition, FT-ICRMS spectra allowed far-reaching classifications of wetland DOM. While DOM of both Okavango and Pantanal showed near 57 ± 2 % CHO, 8 ± 2 % CHOS, 33 ± 2 CHNO, and < 1 % CHNOS molecules, the mass spectra of Everglades samples were fundamentally different compared to those as well as among long and short hydroperiod samples, as they were markedly enriched in CHOS and CHNOS at the expense of CHO and CHNO compounds. Here, four groups of CHOS molecules were differentiated as (a) saturated sulfolipids, (b) unsaturated sulfolipids, (c) molecularly diverse DOM-type CHOS molecules, (d) and particularly enriched in the Everglades short hydroperiod site, a large set of aromatic and oxygen-deficient "black sulphur" compounds. The significantly higher proportion of CHOS compounds in general for the Everglades samples is likely the result of higher inputs of agriculture-derived and sea spray derived sulphate to this wetland compared to the others. Although wetland DOM samples were found to share many molecular features, each sample was unique in its composition, which reflected specific environmental drivers and/or specific biogeochemical processes.

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Salakhov, R. Kh, M. Seitzhanova, D. U. Bodykov, L. R. Sassykova, N. K. Zhakirova, and T. M. Seilkhanov. "Investigation of Electrohydraulic Effect on Physicochemical Characteristics of High-Resinous Oil “Karazhanbas”." Eurasian Chemico-Technological Journal 22, no. 4 (December 30, 2020): 315. http://dx.doi.org/10.18321/ectj999.

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In order to change the viscosity of high-resinous oil of the “Karazhanbas” field (Kazakhstan), the effect of electrohydraulic action on it was studied. The effect of adding an organic solvent xylene on the rheological properties of oil is investigated. A comparative study of the hydrocarbon composition of oil before and after electrohydraulic impact was carried out by the method of gas chromatographymass spectrometry. Fragment composition of oil hydrocarbons before and after electrohydraulic treatment was determined by 1H and 13C NMR spectroscopy. It is shown that the conversion of heavy oil fractions to light ones begins with a five-time electrohydraulic impact. It is determined that 20‒25 electric discharge pulses are sufficient for the quantitative process of splitting hydrocarbons. It was found that the addition of xylene to high-viscosity oil leads to an increase in the conversion of hydrocarbons under electrohydraulic action. The content of paraffins and naphthalenes in high-viscosity oil is slightly reduced during electrohydraulic processing. In oil, after electrohydraulic action, a decrease in the proportion of protons of long alkyl terminal СН3-groups of hydrocarbons is observed, which indicates the process of decomposition of heavy oil fractions into light fractions.

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Journal articles on the topic 'Pulsní 1H-NMR'

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