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Sample records for nmr relaxation study

  1. Relaxation dispersion NMR spectroscopy for the study of protein allostery.

    Science.gov (United States)

    Farber, Patrick J; Mittermaier, Anthony

    2015-06-01

    Allosteric transmission of information between distant sites in biological macromolecules often involves collective transitions between active and inactive conformations. Nuclear magnetic resonance (NMR) spectroscopy can yield detailed information on these dynamics. In particular, relaxation dispersion techniques provide structural, dynamic, and mechanistic information on conformational transitions occurring on the millisecond to microsecond timescales. In this review, we provide an overview of the theory and analysis of Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion NMR experiments and briefly describe their application to the study of allosteric dynamics in the homeodomain from the PBX transcription factor (PBX-HD). CPMG NMR data show that local folding (helix/coil) transitions in one part of PBX-HD help to communicate information between two distant binding sites. Furthermore, the combination of CPMG and other spin relaxation data show that this region can also undergo local misfolding, reminiscent of conformational ensemble models of allostery.

  2. Tacrine derivatives-acetylcholinesterase interaction: 1H NMR relaxation study.

    Science.gov (United States)

    Delfini, Maurizio; Di Cocco, Maria Enrica; Piccioni, Fabiana; Porcelli, Fernando; Borioni, Anna; Rodomonte, Andrea; Del Giudice, Maria Rosaria

    2007-06-01

    Two acetylcholinesterase (AChE) inhibitors structurally related to Tacrine, 6-methoxytacrine (1a) and 9-heptylamino-6-methoxytacrine (1b), and their interaction with Electrophorus Electricus AChE were investigated. The complete assignment of the 1H and 13C NMR spectra of 1a and 1b was performed by mono-dimensional and homo- and hetero-correlated two-dimensional NMR experiments. This study was undertaken to elucidate the interaction modes between AChE and 1a and 1b in solution, using NMR. The interaction between the two inhibitors and AChE was studied by the analysis of the motional parameters non-selective and selective spin-lattice relaxation times, thereby allowing the motional state of 1a and 1b, both free and bound with AChE, to be defined. The relaxation data pointed out the ligands molecular moiety most involved in the binding with AChE. The relevant ligand/enzyme interaction constants were also evaluated for both compounds and resulted to be 859 and 5412M(-1) for 1a and1b, respectively.

  3. 13C NMR relaxation studies on cartilage and cartilage components.

    Science.gov (United States)

    Naji, L; Kaufmann, J; Huster, D; Schiller, J; Arnold, K

    2000-08-07

    We have investigated the molecular motions of polysaccharides of bovine nasal and pig articular cartilage by measuring the 13C NMR relaxation times (T1 and T2). Both types of cartilage differ significantly towards their collagen/glycosaminoglycan ratio, leading to different NMR spectra. As chondroitin sulfate is the main constituent of cartilage, aqueous solutions of related poly- and monosaccharides (N-acetylglucosamine and glucuronic acid) were also investigated. Although there are only slight differences in T1 relaxation of the mono- and the polysaccharides, T2 decreases about one order of magnitude, when glucuronic acid or N-acetylglucosamine and chondroitin sulfate are compared. It is concluded that the ring carbons are motion-restricted primarily by the embedment in the rigid pyranose structure and, thus, additional limitations of mobility do not more show a major effect. Significant differences were observed between bovine nasal and pig articular cartilage, resulting in a considerable line-broadening and a lower signal to noise ratio in the spectra of pig articular cartilage. This is most likely caused by the higher collagen content of articular cartilage in comparison to the polysaccharide-rich bovine nasal cartilage.

  4. NMR relaxation and micro-imaging study of polystyrene in concentrated cyclohexane solution

    Institute of Scientific and Technical Information of China (English)

    毛诗珍; 丁广良; 袁汉珍; 冯汉桥; 杜有如

    1997-01-01

    13C-NMR relaxation times of polystyrene (PS) in its 8 solvent, cyclohexane, are measured at different temperatures. A two-step model for the dissolution is proposed. Swelling of the polymer below the 8 temperature is eventually the dispersion of the side group phenyl rings only. While above the 6 temperature, complete dissolution is the dispersion of the main chain at a molecular level. The results of T1(C) are confirmed by 1H-NMR imaging. NMR and its imaging are powerful tools to study the dynamic behavior of dissolution process of polymers in their 6 solvents.

  5. Molecular motions in thermotropic liquid crystals studied by NMR spin-lattice relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Zamar, R.C.; Gonzalez, C.E.; Mensio, O. [Cordoba Univ. Nacional (Argentina). Facultad de Matematica, Astronomia y Fisica

    1998-12-01

    Nuclear magnetic resonance relaxation experiments with field cycling techniques proved to be a valuable tool for studying molecular motions in liquid crystals, allowing a very broad Larmor frequency variation, sufficient to separate the cooperative motions from the liquid like molecular diffusion. In new experiments combining NMR field cycling with the Jeener-Broekaert order-transfer pulse sequence, it is possible to measure the dipolar order relaxation time (T{sub 1D}), in addition to the conventional Zeeman relaxation time (T{sub 1Z}) in a frequency range of several decades. When applying this technique to nematic thermotropic liquid crystals, T{sub 1D} showed to depend almost exclusively on the order fluctuation of the director mechanism in the whole frequency range. This unique characteristic of T{sub 1D} makes dipolar order relaxation experiments specially useful for studying the frequency and temperature dependence of the spectral properties of the collective motions. (author)

  6. Spectral Estimation of NMR Relaxation

    Science.gov (United States)

    Naugler, David G.; Cushley, Robert J.

    2000-08-01

    In this paper, spectral estimation of NMR relaxation is constructed as an extension of Fourier Transform (FT) theory as it is practiced in NMR or MRI, where multidimensional FT theory is used. nD NMR strives to separate overlapping resonances, so the treatment given here deals primarily with monoexponential decay. In the domain of real error, it is shown how optimal estimation based on prior knowledge can be derived. Assuming small Gaussian error, the estimation variance and bias are derived. Minimum bias and minimum variance are shown to be contradictory experimental design objectives. The analytical continuation of spectral estimation is constructed in an optimal manner. An important property of spectral estimation is that it is phase invariant. Hence, hypercomplex data storage is unnecessary. It is shown that, under reasonable assumptions, spectral estimation is unbiased in the context of complex error and its variance is reduced because the modulus of the whole signal is used. Because of phase invariance, the labor of phasing and any error due to imperfect phase can be avoided. A comparison of spectral estimation with nonlinear least squares (NLS) estimation is made analytically and with numerical examples. Compared to conventional sampling for NLS estimation, spectral estimation would typically provide estimation values of comparable precision in one-quarter to one-tenth of the spectrometer time when S/N is high. When S/N is low, the time saved can be used for signal averaging at the sampled points to give better precision. NLS typically provides one estimate at a time, whereas spectral estimation is inherently parallel. The frequency dimensions of conventional nD FT NMR may be denoted D1, D2, etc. As an extension of nD FT NMR, one can view spectral estimation of NMR relaxation as an extension into the zeroth dimension. In nD NMR, the information content of a spectrum can be extracted as a set of n-tuples (ω1, … ωn), corresponding to the peak maxima

  7. Active site dynamics in NADH oxidase from Thermus thermophilus studied by NMR spin relaxation.

    Science.gov (United States)

    Miletti, Teresa; Farber, Patrick J; Mittermaier, Anthony

    2011-09-01

    We have characterized the backbone dynamics of NADH oxidase from Thermus thermophilus (NOX) using a recently-developed suite of NMR experiments designed to isolate exchange broadening, together with (15)N R (1), R (1ρ ), and {(1)H}-(15)N steady-state NOE relaxation measurements performed at 11.7 and 18.8 T. NOX is a 54 kDa homodimeric enzyme that belongs to a family of structurally homologous flavin reductases and nitroreductases with many potential biotechnology applications. Prior studies have suggested that flexibility is involved in the catalytic mechanism of the enzyme. The active site residue W47 was previously identified as being particularly important, as its level of solvent exposure correlates with enzyme activity, and it was observed to undergo "gating" motions in computer simulations. The NMR data are consistent with these findings. Signals from W47 are dynamically broadened beyond detection and several other residues in the active site have significant R ( ex ) contributions to transverse relaxation rates. In addition, the backbone of S193, whose side chain hydroxyl proton hydrogen bonds directly with the FMN cofactor, exhibits extensive mobility on the ns-ps timescale. We hypothesize that these motions may facilitate structural rearrangements of the active site that allow NOX to accept both FMN and FAD as cofactors.

  8. Solvent dynamical behavior in an organogel phase as studied by NMR relaxation and diffusion experiments.

    Science.gov (United States)

    Yemloul, Mehdi; Steiner, Emilie; Robert, Anthony; Bouguet-Bonnet, Sabine; Allix, Florent; Jamart-Grégoire, Brigitte; Canet, Daniel

    2011-03-24

    An organogelation process depends on the gelator-solvent pair. This study deals with the solvent dynamics once the gelation process is completed. The first approach used is relaxometry, i.e., the measurement of toluene proton longitudinal relaxation time T(1) as a function of the proton NMR resonance frequency (here in the 5 kHz to 400 MHz range). Pure toluene exhibits an unexpected T(1) variation, which has been identified as paramagnetic relaxation resulting from an interaction of toluene with dissolved oxygen. In the gel phase, this contribution is retrieved with, in addition, a strong decay at low frequencies assigned to toluene molecules within the gel fibers. Comparison of dispersion curves of pure toluene and toluene in the gel phase leads to an estimate of the proportion of toluene embedded within the organogel (found around 40%). The second approach is based on carbon-13 T(1) and nuclear Overhauser effect measurements, the combination of these two parameters providing direct information about the reorientation of C-H bonds. It appears clearly that reorientation of toluene is the same in pure liquid and in the gel phase. The only noticeable changes in carbon-13 longitudinal relaxation times are due to the so-called chemical shift anisotropy (csa) mechanism and reflect slight modifications of the toluene electronic distribution in the gel phase. NMR diffusion measurements by the pulse gradient spin-echo (PGSE) method allow us to determine the diffusion coefficient of toluene inside the organogel. It is roughly two-thirds of the one in pure toluene, thus indicating that self-diffusion is the only dynamical parameter to be slightly affected when the solvent is inside the gel structure. The whole set of experimental observations leads to the conclusion that, once the gel is formed, the solvent becomes essentially passive, although an important fraction is located within the gel structure.

  9. High resolution NMR study of T{sub 1} magnetic relaxation dispersion. IV. Proton relaxation in amino acids and Met-enkephalin pentapeptide

    Energy Technology Data Exchange (ETDEWEB)

    Pravdivtsev, Andrey N.; Yurkovskaya, Alexandra V.; Ivanov, Konstantin L., E-mail: ivanov@tomo.nsc.ru [International Tomography Center, Institutskaya 3a, Novosibirsk 630090 (Russian Federation); Department of Physics, Novosibirsk State University, Pirogova 2, Novosibirsk 630090 (Russian Federation); Vieth, Hans-Martin [Institut für Experimentalphysik, Freie Universität Berlin Arnimallee 14, 14195 Berlin (Germany)

    2014-10-21

    Nuclear Magnetic Relaxation Dispersion (NMRD) of protons was studied in the pentapeptide Met-enkephalin and the amino acids, which constitute it. Experiments were run by using high-resolution Nuclear Magnetic Resonance (NMR) in combination with fast field-cycling, thus enabling measuring NMRD curves for all individual protons. As in earlier works, Papers I–III, pronounced effects of intramolecular scalar spin-spin interactions, J-couplings, on spin relaxation were found. Notably, at low fields J-couplings tend to equalize the apparent relaxation rates within networks of coupled protons. In Met-enkephalin, in contrast to the free amino acids, there is a sharp increase in the proton T{sub 1}-relaxation times at high fields due to the changes in the regime of molecular motion. The experimental data are in good agreement with theory. From modelling the relaxation experiments we were able to determine motional correlation times of different residues in Met-enkephalin with atomic resolution. This allows us to draw conclusions about preferential conformation of the pentapeptide in solution, which is also in agreement with data from two-dimensional NMR experiments (rotating frame Overhauser effect spectroscopy). Altogether, our study demonstrates that high-resolution NMR studies of magnetic field-dependent relaxation allow one to probe molecular mobility in biomolecules with atomic resolution.

  10. Changes in Porcine Muscle Water Characteristics during Growth—An in Vitro Low-Field NMR Relaxation Study

    Science.gov (United States)

    Bertram, Hanne Christine; Rasmussen, Marianne; Busk, Hans; Oksbjerg, Niels; Karlsson, Anders Hans; Andersen, Henrik Jørgen

    2002-08-01

    This study investigates the effects of developmental stage and muscle type on the mobility and distribution of water within skeletal muscles, using low-field 1H-NMR transverse relaxation measurements in vitro on four different porcine muscles ( M. longissimus dorsi, M. semitendinosus, M. biceps femoris, M. vastus intermedius) from a total of 48 pigs slaughtered at various weight classes between 25 kg and 150 kg. Principal component analysis (PCA) revealed effects of both slaughter weight and muscle type on the transverse relaxation decay. Independent of developmental stage and muscle type, distributed exponential analysis of the NMR T 2 relaxation data imparted the existence of three distinct water populations, T 2b, T 21, and T 22, with relaxation times of approximately 1-10, 45-120, and 200-500 ms, respectively. The most profound change during muscle growth was a shift toward faster relaxation in the intermediate time constant, T 21. It decreased by approx. 24% in all four muscle types during the period from 25 to 150 kg live weight. Determination of dry matter, fat, and protein content in the muscles showed that the changes in relaxation time of the intermediate time constant, T 21, during growth should be ascribed mainly to a change in protein content, as the protein content explained 77% of the variation in the T 21 time constant. Partial least squares (PLS) regression revealed validated correlations in the region of 0.58 to 0.77 between NMR transverse relaxation data and muscle development for all the four muscle types, which indicates that NMR relaxation measurements may be used in the prediction of muscle developmental stage.

  11. Solid-state NMR paramagnetic relaxation enhancement immersion depth studies in phospholipid bilayers

    KAUST Repository

    Chu, Shidong

    2010-11-01

    A new approach for determining the membrane immersion depth of a spin-labeled probe has been developed using paramagnetic relaxation enhancement (PRE) in solid-state NMR spectroscopy. A DOXYL spin label was placed at different sites of 1-palmitoyl-2-stearoyl-sn-glycero-3-phosphocholine (PSPC) phospholipid bilayers as paramagnetic moieties and the resulting enhancements of the longitudinal relaxation (T1) times of 31P nuclei on the surface of the bilayers were measured by a standard inversion recovery pulse sequence. The 31P NMR spin-lattice relaxation times decrease steadily as the DOXYL spin label moves closer to the surface as well as the concentration of the spin-labeled lipids increase. The enhanced relaxation vs. the position and concentration of spin-labels indicate that PRE induced by the DOXYL spin label are significant to determine longer distances over the whole range of the membrane depths. When these data were combined with estimated correlation times τc, the r-6-weighted, time-averaged distances between the spin-labels and the 31P nuclei on the membrane surface were estimated. The application of using this solid-state NMR PRE approach coupled with site-directed spin labeling (SDSL) may be a powerful method for measuring membrane protein immersion depth. © 2010 Elsevier Inc. All rights reserved.

  12. Interaction of ferulic acid derivatives with human erythrocytes monitored by pulse field gradient NMR diffusion and NMR relaxation studies.

    Science.gov (United States)

    Anselmi, Cecilia; Bernardi, Francesca; Centini, Marisanna; Gaggelli, Elena; Gaggelli, Nicola; Valensin, Daniela; Valensin, Gianni

    2005-04-01

    Ferulic acid (Fer), a natural anti-oxidant and chemo-protector, is able to suppress experimental carcinogenesis in the forestomach, lungs, skin, tongue and colon. Several Fer derivatives have been suggested as promising candidates for cancer prevention, being the biological activity related also to the capacity of partitioning between aqueous and lipid phases. In the present work, pulsed field gradient (PFG) NMR diffusion measurement and NMR relaxation rates have been adopted for investigating the interaction of three Fer derivatives (Fer-C11, Fer-C12 and Fer-C13) with human erythrocytes. Binding to the erythrocyte membrane has been shown for all derivatives, which displayed a similar interaction mode such that the aromatic moiety and the terminal part of the alkyl chain were the most affected. Quantitative analysis of the diffusion coefficients was used to show that Fer-C12 and Fer-C13 display higher affinity for the cell membrane when compared with Fer-C11. These findings agree with the higher anti-oxidant activity of the two derivatives.

  13. A proton NMR relaxation study of water dynamics in bovine serum albumin nanoparticles.

    Science.gov (United States)

    Belotti, Monica; Martinelli, Andrea; Gianferri, Raffaella; Brosio, Elvino

    2010-01-14

    Water dynamics and compartmentation in glutaraldehyde cross-linked bovine serum albumin nanoparticles have been investigated by an integrated nuclear magnetic resonance (NMR) protocol based on water relaxation times and self-diffusion coefficients measurements. Multi-exponentially of water relaxation curves has been accounted for according to a diffusive and chemical exchange model (see B. P. Hills, S. F. Takacs and P. S. Belton, Mol. Phys., 1989, 67(4), 903, and Mol. Phys., 1989, 67(4), 913; E. Brosio, M. Belotti and R. Gianferri, in Food Science and Technology: New Research, ed. L. V. Greco and M. N. Bruno, Nova Science Publishers, Hauppauge (NY), 2008) that made it possible to single out water molecules in the molecular spaces in the interior of albumin nanoparticles, in the meso-cavities formed by packed nanoparticles and in the meniscus on top of the nanoparticles suspension. A quantitative rationalization of T(2) values of water different components allowed morphological information to be acquired as for the size of water filled compartments, while self-diffusion coefficient measurements of water excess or fluxed packed nanoparticles suspensions are describers of transport properties of soft biomaterials. The paper reports an NMR approach that can be seen as a general and relevant method to characterize excess-water-swollen soft biomaterials.

  14. Non-polymeric asymmetric binary glass-formers. II. Secondary relaxation studied by dielectric, (2)H NMR, and (31)P NMR spectroscopy.

    Science.gov (United States)

    Pötzschner, B; Mohamed, F; Bächer, C; Wagner, E; Lichtinger, A; Bock, D; Kreger, K; Schmidt, H-W; Rössler, E A

    2017-04-28

    We investigate the secondary (β-) relaxations of an asymmetric binary glass former consisting of a spirobichroman derivative (SBC; Tg = 356 K) as the high-Tg component and the low-Tg component tripropyl phosphate (TPP; Tg = 134 K). The main relaxations are studied in Paper I [B. Pötzschner et al., J. Chem. Phys. 146, 164503 (2017)]. A high Tg contrast of ΔTg = 222 K is put into effect in a non-polymeric system. Component-selective studies are carried out by combining results from dielectric spectroscopy (DS) for mass concentrations cTPP ≥ 60% and those from different methods of (2)H and (31)P NMR spectroscopy. In the case of NMR, the full concentration range (10% ≤ cTPP ≤ 100%) is covered. The neat components exhibit a β-relaxation (β1 (SBC) and β2 (TPP)). The latter is rediscovered by DS in the mixtures for all concentrations with unchanged time constants. NMR spectroscopy identifies the β-relaxations as being alike to those in neat glasses. A spatially highly restricted motion with angular displacement below ±10° encompassing all molecules is involved. In the low temperature range, where TPP shows the typical (31)P NMR echo spectra of the β2-process, very similar spectral features are observed for the (deuterated) SBC component by (2)H NMR, in addition to its "own" β1-process observed at high temperatures. Apparently, the small TPP molecules enslave the large SBC molecules to perform a common hindered reorientation. The temperature dependence of the spin-lattice relaxation time of both components is the same and reveals an angular displacement of the SBC molecules somewhat smaller than that of TPP, though the time constants τβ2 are the same. Furthermore, T1(T) of TPP in the temperature region of the β2-process is absolutely the same as in the mixture TPP/polystyrene investigated previously. It appears that the manifestations of the β-process introduced by one component are essentially independent of the second component. Finally, at cTPP

  15. Non-polymeric asymmetric binary glass-formers. II. Secondary relaxation studied by dielectric, 2H NMR, and 31P NMR spectroscopy

    Science.gov (United States)

    Pötzschner, B.; Mohamed, F.; Bächer, C.; Wagner, E.; Lichtinger, A.; Bock, D.; Kreger, K.; Schmidt, H.-W.; Rössler, E. A.

    2017-04-01

    We investigate the secondary (β-) relaxations of an asymmetric binary glass former consisting of a spirobichroman derivative (SBC; Tg = 356 K) as the high-Tg component and the low-Tg component tripropyl phosphate (TPP; Tg = 134 K). The main relaxations are studied in Paper I [B. Pötzschner et al., J. Chem. Phys. 146, 164503 (2017)]. A high Tg contrast of ΔTg = 222 K is put into effect in a non-polymeric system. Component-selective studies are carried out by combining results from dielectric spectroscopy (DS) for mass concentrations cTPP ≥ 60% and those from different methods of 2H and 31P NMR spectroscopy. In the case of NMR, the full concentration range (10% ≤ cTPP ≤ 100%) is covered. The neat components exhibit a β-relaxation (β1 (SBC) and β2 (TPP)). The latter is rediscovered by DS in the mixtures for all concentrations with unchanged time constants. NMR spectroscopy identifies the β-relaxations as being alike to those in neat glasses. A spatially highly restricted motion with angular displacement below ±10° encompassing all molecules is involved. In the low temperature range, where TPP shows the typical 31P NMR echo spectra of the β2-process, very similar spectral features are observed for the (deuterated) SBC component by 2H NMR, in addition to its "own" β1-process observed at high temperatures. Apparently, the small TPP molecules enslave the large SBC molecules to perform a common hindered reorientation. The temperature dependence of the spin-lattice relaxation time of both components is the same and reveals an angular displacement of the SBC molecules somewhat smaller than that of TPP, though the time constants τβ2 are the same. Furthermore, T1(T) of TPP in the temperature region of the β2-process is absolutely the same as in the mixture TPP/polystyrene investigated previously. It appears that the manifestations of the β-process introduced by one component are essentially independent of the second component. Finally, at cTPP ≤ 20% one

  16. NMR relaxation and water self-diffusion studies in whey protein solutions and gels.

    Science.gov (United States)

    Colsenet, Roxane; Mariette, François; Cambert, Mireille

    2005-08-24

    The changes in water proton transverse relaxation behavior induced by aggregation of whey proteins are explained in terms of the simple molecular processes of diffusion and chemical exchange. The water self-diffusion coefficient was measured in whey protein solutions and gels by the pulsed field gradient NMR method. As expected, water self-diffusion was reduced with increased protein concentrations. Whatever the concentration, the water molecules were free to diffuse over distances varying from 15 to 47 mum. Water diffusion was constant over these distances, demonstrating that no restrictions were found to explain the water hindrance. The modification in protein structure by gelation induced a decrease in water diffusion. The effects of protein concentration on water diffusion are discussed and modeled. Two approaches were compared, the obstruction effect induced by a spherical particle and the cell model, which considered two water compartments with specific self-diffusion coefficients.

  17. Molecular motions and phase transitions. NMR relaxation times studies of several lecithins.

    OpenAIRE

    Bar-Adon, R; Gilboa, H

    1981-01-01

    The spin-lattice relaxation time, T1, and the dipolar energy relaxation time, TD, were measured as a function of temperature. The materials studied were samples of anhydrous L-dipalmitoyl lecithin, DL-dipalmitoyl lecithin, L-dimyristoyl lecithin, DL-dimyristoyl lecithin and their monohydrates, and of anhydrous egg yolk lecithin. It is shown that TD is a much more sensitive parameter than T1 for the determination of the Chapman phase transition. Comparison between T1 and TD provides informatio...

  18. Mineralogical controls on NMR rock surface relaxivity: A case study of the Fontainebleau Sandstone

    Science.gov (United States)

    Livo, Kurt

    Pore size distribution is derived from nuclear magnetic resonance, but is scaled by surface relaxivity. While nuclear magnetic resonance studies generally focus on the difficulty of determining pore size distribution in unconventional shale reservoirs, there is a lack of discussion concerning pure quartz sandstones. Long surface relaxivity causes complications analyzing nuclear magnetic resonance data for pore size distribution determination. Currently, I am unaware of research that addresses the complicated pore size distribution determination in long relaxing, pure sandstone formations, which is essential to accurate downhole petrophysical modeling. The Fontainebleau sandstone is well known for its homogenous mineralogical makeup and wide range of porosity and permeability. The Hibernia sandstone exhibits a similar mineralogy and is characterized by a similar and porosity-permeability range to the Fontainebleau sandstones, but with a significantly higher portion of clay minerals (1-6%). I present systematic petrophysical properties such as porosity, pore size distribution from nuclear magnetic resonance transverse relaxation times, permeability, and volumetric magnetic susceptibility to aide in characterization of the Fontainebleau sandstone. Analysis of collected nuclear magnetic resonance data is then compared to other petrophysical studies from literature such as helium porosity and permeability, magnetic susceptibility, and electrical conductivity. I find that the lack of impurities on the grain surfaces of pure quartz samples imparts a lower surface relaxivity as compared to clay containing sandstones and makes nuclear magnetic resonance analysis more complex. Thus, inverted nuclear magnetic resonance data from cleaner outcrop samples incorrectly models pore size distribution without accounting for wider surface relaxivity variation and is improperly used when characterizing the Fontainebleau sandstone. This is further supported by evidence from less

  19. (1)H NMR Relaxation Study of a Magnetic Ionic Liquid as a Potential Contrast Agent.

    Science.gov (United States)

    Daniel, Carla I; Vaca Chávez, Fabián; Portugal, Carla A M; Crespo, João G; Sebastião, Pedro J

    2015-09-03

    A proton nuclear magnetic relaxation dispersion (1)H NMRD study of the molecular dynamics in mixtures of magnetic ionic liquid [P66614][FeCl4] with [P66614][Cl] ionic liquid and mixtures of [P66614][FeCl4] with dimethyl sulfoxide (DMSO) is presented. The proton spin-lattice relaxation rate, R1, was measured in the frequency range of 8 kHz-300 MHz. The viscosity of the binary mixtures was measured as a function of an applied magnetic field, B, in the range of 0-2 T. In the case of DMSO/[P66614][FeCl4] the viscosity was found to be independent from the magnetic field, while in the case of the [P66614][Cl]/[P66614][FeCl4] system viscosity decreased with the increase of the magnetic field strength. The spin-lattice relaxation results were analyzed for all systems taking into account the relaxation mechanisms associated with the molecular motions with correlation times in a range between 10(-11) and 10(-7)s, usually observed by NMRD, and the paramagnetic relaxation contributions associated with the presence of the magnetic ions in the systems. In the case of the DMSO/[P66614][FeCl4] system the R1 dispersion shows the relaxation enhancement due to the presence of the magnetic ions, similar to that reported for contrast agents. For the [P66614][Cl]/[P66614][FeCl4] system, the R1 dispersion presents a much larger paramagnetic relaxation contribution, in comparison with that observed for the DMSO/[P66614][FeCl4] mixtures but different from that reported for other magnetic ionic liquid system. In the [P66614][Cl]/[P66614][FeCl4] system the relaxation enhancement associated with the paramagnetic ions is clearly not proportional to the concentration of magnetic ions, in contrast with what is observed for the DMSO/[P66614][FeCl4] system.

  20. Relaxation time estimation in surface NMR

    Science.gov (United States)

    Grunewald, Elliot D.; Walsh, David O.

    2017-03-21

    NMR relaxation time estimation methods and corresponding apparatus generate two or more alternating current transmit pulses with arbitrary amplitudes, time delays, and relative phases; apply a surface NMR acquisition scheme in which initial preparatory pulses, the properties of which may be fixed across a set of multiple acquisition sequence, are transmitted at the start of each acquisition sequence and are followed by one or more depth sensitive pulses, the pulse moments of which are varied across the set of multiple acquisition sequences; and apply processing techniques in which recorded NMR response data are used to estimate NMR properties and the relaxation times T.sub.1 and T.sub.2* as a function of position as well as one-dimensional and two-dimension distributions of T.sub.1 versus T.sub.2* as a function of subsurface position.

  1. Relaxation time estimation in surface NMR

    Energy Technology Data Exchange (ETDEWEB)

    Grunewald, Elliot D.; Walsh, David O.

    2017-03-21

    NMR relaxation time estimation methods and corresponding apparatus generate two or more alternating current transmit pulses with arbitrary amplitudes, time delays, and relative phases; apply a surface NMR acquisition scheme in which initial preparatory pulses, the properties of which may be fixed across a set of multiple acquisition sequence, are transmitted at the start of each acquisition sequence and are followed by one or more depth sensitive pulses, the pulse moments of which are varied across the set of multiple acquisition sequences; and apply processing techniques in which recorded NMR response data are used to estimate NMR properties and the relaxation times T.sub.1 and T.sub.2* as a function of position as well as one-dimensional and two-dimension distributions of T.sub.1 versus T.sub.2* as a function of subsurface position.

  2. Non-polymeric asymmetric binary glass-formers. I. Main relaxations studied by dielectric, (2)H NMR, and (31)P NMR spectroscopy.

    Science.gov (United States)

    Pötzschner, B; Mohamed, F; Bächer, C; Wagner, E; Lichtinger, A; Minikejew, R; Kreger, K; Schmidt, H-W; Rössler, E A

    2017-04-28

    In Paper I of this series of two papers we study the main relaxations of a binary glass former made of the low-Tg component tripropyl phosphate (TPP, Tg = 134 K) and of a specially synthesized (deuterated) spirobichroman derivative (SBC, Tg = 356 K) as the non-polymeric high-Tg component for the full concentration range. A large Tg contrast of the neat components is put into effect. Dielectric spectroscopy and different techniques of (2)H nuclear magnetic resonance (NMR) as well as of (31)P NMR spectroscopy allow to selectively probe the dynamics of the components. For all concentrations, two well separated liquid-like processes are identified. The faster α2-process associated with the low-Tg component TPP shows pronounced dynamic heterogeneities reflected by quasi-logarithmic correlation functions at low TPP concentrations. The slower α1-process involves the reorientation of the high-Tg component SBC. Its correlation function is Kohlrausch-like as in neat glass formers. The corresponding time constants and consequently their glass transition temperatures Tg1 and Tg2 differ more the lower the TPP concentration is. Plasticizer and anti-plasticizer effect, respectively, is observed. At low temperatures a situation arises that the TPP molecules isotropically reorient in an arrested SBC matrix (Tg2 < T < Tg1). At T < Tg2 the liquid-like reorientation of TPP gets arrested too. We find indications that a fraction of the TPP molecule takes part in the slower α1-process of the high-Tg component. All the features known from polymer-plasticizer systems are rediscovered in this non-polymeric highly asymmetric binary mixture. In Paper II [B. Pötzschner et al., J. Chem. Phys. 146, 164504 (2017)] we study the secondary (β-) relaxations of the mixtures.

  3. Non-polymeric asymmetric binary glass-formers. I. Main relaxations studied by dielectric, 2H NMR, and 31P NMR spectroscopy

    Science.gov (United States)

    Pötzschner, B.; Mohamed, F.; Bächer, C.; Wagner, E.; Lichtinger, A.; Minikejew, R.; Kreger, K.; Schmidt, H.-W.; Rössler, E. A.

    2017-04-01

    In Paper I of this series of two papers we study the main relaxations of a binary glass former made of the low-Tg component tripropyl phosphate (TPP, Tg = 134 K) and of a specially synthesized (deuterated) spirobichroman derivative (SBC, Tg = 356 K) as the non-polymeric high-Tg component for the full concentration range. A large Tg contrast of the neat components is put into effect. Dielectric spectroscopy and different techniques of 2H nuclear magnetic resonance (NMR) as well as of 31P NMR spectroscopy allow to selectively probe the dynamics of the components. For all concentrations, two well separated liquid-like processes are identified. The faster α2-process associated with the low-Tg component TPP shows pronounced dynamic heterogeneities reflected by quasi-logarithmic correlation functions at low TPP concentrations. The slower α1-process involves the reorientation of the high-Tg component SBC. Its correlation function is Kohlrausch-like as in neat glass formers. The corresponding time constants and consequently their glass transition temperatures Tg1 and Tg2 differ more the lower the TPP concentration is. Plasticizer and anti-plasticizer effect, respectively, is observed. At low temperatures a situation arises that the TPP molecules isotropically reorient in an arrested SBC matrix (Tg2 < T < Tg1). At T < Tg2 the liquid-like reorientation of TPP gets arrested too. We find indications that a fraction of the TPP molecule takes part in the slower α1-process of the high-Tg component. All the features known from polymer-plasticizer systems are rediscovered in this non-polymeric highly asymmetric binary mixture. In Paper II [B. Pötzschner et al., J. Chem. Phys. 146, 164504 (2017)] we study the secondary (β-) relaxations of the mixtures.

  4. Study of cross - relaxation and molecular dynamics in the solid 3-(trifluoromethyl) benzoic acid by solid state NMR off - resonance.

    Science.gov (United States)

    Woźniak-Braszak, Aneta

    2017-02-01

    Molecular dynamics of the solid 3-(trifluoromethyl) benzoic acid containing proton (1)H and fluorine (19)F nuclei was explored by the solid-state NMR off - resonance technique. Contrary to the previous experiments the proton nuclei system I relaxed in the off - resonance effective field B→e while fluorine nuclei system S was saturated for short time in comparison to the relaxation time T1I. New cross - relaxation solid - state NMR off - resonance experiments were conducted on a homebuilt pulse spectrometer operating at the on-resonance frequency of 30.2MHz, at the off - resonance frequency varied between 30.2 and 30.6MHz for protons and at the frequency of 28.411MHz for fluorines, respectively. Based on the experimental data the dispersions of the proton off - resonance spin - lattice relaxation rate ρρ(I), the fluorine off - resonance spin - lattice relaxation rate ρρ(S) and the cross - relaxation rate σρ in the rotating frame were determined. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Extracting protein dynamics information from overlapped NMR signals using relaxation dispersion difference NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Konuma, Tsuyoshi [Icahn School of Medicine at Mount Sinai, Department of Structural and Chemical Biology (United States); Harada, Erisa [Suntory Foundation for Life Sciences, Bioorganic Research Institute (Japan); Sugase, Kenji, E-mail: sugase@sunbor.or.jp, E-mail: sugase@moleng.kyoto-u.ac.jp [Kyoto University, Department of Molecular Engineering, Graduate School of Engineering (Japan)

    2015-12-15

    Protein dynamics plays important roles in many biological events, such as ligand binding and enzyme reactions. NMR is mostly used for investigating such protein dynamics in a site-specific manner. Recently, NMR has been actively applied to large proteins and intrinsically disordered proteins, which are attractive research targets. However, signal overlap, which is often observed for such proteins, hampers accurate analysis of NMR data. In this study, we have developed a new methodology called relaxation dispersion difference that can extract conformational exchange parameters from overlapped NMR signals measured using relaxation dispersion spectroscopy. In relaxation dispersion measurements, the signal intensities of fluctuating residues vary according to the Carr-Purcell-Meiboon-Gill pulsing interval, whereas those of non-fluctuating residues are constant. Therefore, subtraction of each relaxation dispersion spectrum from that with the highest signal intensities, measured at the shortest pulsing interval, leaves only the signals of the fluctuating residues. This is the principle of the relaxation dispersion difference method. This new method enabled us to extract exchange parameters from overlapped signals of heme oxygenase-1, which is a relatively large protein. The results indicate that the structural flexibility of a kink in the heme-binding site is important for efficient heme binding. Relaxation dispersion difference requires neither selectively labeled samples nor modification of pulse programs; thus it will have wide applications in protein dynamics analysis.

  6. Nuclear Spin Relaxation Studied by {beta}-NMR of {sup 12}N Implanted in TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Mihara, M., E-mail: mihara@vg.phys.sci.osaka-u.ac.jp; Nakashima, Y.; Kumashiro, S.; Fujiwara, H. [Osaka University, Graduate School of Science (Japan); Zheng, Y. N. [China Institute of Atomic Energy (China); Ogura, M. [Osaka University, Graduate School of Science (Japan); Sumikama, T. [RIKEN (Japan); Nagatomo, T. [Osaka University, Graduate School of Science (Japan); Minamisono, K. [RIKEN (Japan); Fukuda, M.; Matsuta, K. [Osaka University, Graduate School of Science (Japan); Minamisono, T. [Fukui University of Technology (Japan)

    2004-12-15

    The {beta}-NMR of short-lived {beta}-emitter {sup 12}N(I{sup {pi}=}1{sup +}, T{sub 1/2}=11ms) in a rutile TiO{sub 2} single crystal has been measured as functions of temperature and external magnetic field. Atomic motion induced spin lattice relaxation was observed for two known sites, O substitutional and interstitial sites. The data were analyzed in terms of the thermal atomic jump, which suggests that the motion of defects around the substitutional {sup 12}N atom for O, and of the interstitial {sup 12}N atom are attributed to the spin lattice relaxation. The electric field gradients have shown temperature dependence for both sites, which is probably due to the thermal expansion of rutile.

  7. NMR Water Self-Diffusion and Relaxation Studies on Sodium Polyacrylate Solutions and Gels in Physiologic Ionic Solutions.

    Science.gov (United States)

    Bai, Ruiliang; Basser, Peter J; Briber, Robert M; Horkay, Ferenc

    2014-03-15

    Water self-diffusion coefficients and longitudinal relaxation rates in sodium polyacrylate solutions and gels were measured by NMR, as a function of polymer content and structure in a physiological concentration range of monovalent and divalent cations, Ca(2+) and Na(+). Several physical models describing the self-diffusion of the solvent were applied and compared. A free-volume model was found to be in good agreement with the experimental results over a wide range of polymer concentrations. The longitudinal relaxation rate exhibited linear dependence on polymer concentration below a critical concentration and showed non-linear behavior at higher concentrations. Both the water self-diffusion and relaxation were less influenced by the polymer in the gel state than in the uncrosslinked polymer solutions. The effect of Na(+) on the mobility of water molecules was practically undetectable. By contrast, addition of Ca(2+) strongly increased the longitudinal relaxation rate while its effect on the self-diffusion coefficient was much less pronounced.

  8. Microscale simulations of NMR relaxation in porous media

    Science.gov (United States)

    Mohnke, Oliver; Klitzsch, Norbert

    2010-05-01

    In petrophysical applications of nuclear magnetic resonance (NMR), the measured relaxation signals originate from the fluid filled pore space. Hence, in rocks or sediments the water content directly corresponds to the initial amplitude of the recorded NMR relaxation signals. The relaxation rate (longitudinal/transversal decay time T1, T2) is sensitive to pore sizes and physiochemical properties of rock-fluid interfaces (surface relaxivity), as well as the concentration of paramagnetic ions in the fluid phases (bulk relaxivity). In the subproject A2 of the TR32 we aim at improving the basic understanding of these processes at the pore scale and thereby advancing the interpretation of NMR data by reducing the application of restrictive approximated interpretation schemes, e.g. for deriving pore size distributions, connectivity or permeability. In this respect we numerically simulate NMR relaxation data at the micro sale to study the impact of physical and hydrological parameters such as internal field gradients or pore connectivities on NMR signals. Joint numerical simulations of the NMR relaxation behavior (Bloch equations) in the presence of internal gradients (Ampere's law) and fluid flow (Navier-Stokes) on a pore scale dimension have been implemented in a finite element (FE) model using Comsol Multiphysics. Processes governing the time and spatial behavior of the nuclear magnetization density in a porous medium are diffusion and surface interactions at the rock-fluid interface. Based on Fick's law of diffusive motion Brownstein and Tarr (1979) introduced differential equations that describe the relaxation behavior of the Spin magnetization in single isolated pores and derived analytical solutions for simple geometries, i.e. spherical, cylindrical and planar. However, by numerically solving these equations in a general way using a FE algorithm this approach can be applied to study and simulate coupled complex pore systems, e.g. derived from computer tomography (CT

  9. Effect of gel firmness at cutting time, pH, and temperature on rennet coagulation and syneresis: an in situ 1H NMR relaxation study.

    Science.gov (United States)

    Hansen, Christian Lyndgaard; Rinnan, Asmund; Engelsen, Søren Balling; Janhøj, Thomas; Micklander, Elisabeth; Andersen, Ulf; van den Berg, Frans

    2010-01-13

    The objective of this study was to monitor rennet-induced milk gel formation and mechanically induced gel syneresis in situ by low-field NMR. pH, temperature, and gel firmness at cutting time were varied in a factorial design. The new curve-fitting method Doubleslicing revealed that during coagulation two proton populations with distinct transverse relaxation times (T2,1=181, T2,2=465 ms) were present in fractions (f1=98.9%, f2=1.1%). Mechanical cutting of the gel in the NMR tube induced macrosyneresis, which led to the appearance of an additional proton population (T2,3=1500-2200 ms) identified as whey. On the basis of NMR quantification of whey water the syneresis rate was calculated and found to be significantly dependent on pH and temperature.

  10. Sodium-23 NMR spin-lattice relaxation rate studies of mono- and bis-intercalation in DNA

    Energy Technology Data Exchange (ETDEWEB)

    Eggert, H.; Dinesen, J.; Jacobsen, J.P. (Univ. of Copenhagen (Denmark))

    1989-04-18

    Sodium-23 spin-lattice relaxation rate measurements have been used to study the intercalation of a series of 9-aminoacridine derivatives in DNA. The {sup 23}Na relaxation rate is strongly dependent upon the amount of intercalator added to a sodium DNA solution. The results are analyzed by a combined use of the ion condensation theory and the quadrupolar relaxation theory of polyelectrolyte solutions. This interpretation shows that the major effect in lowering the relaxation rate by intercalation is not due to the release of sodium ions but is caused by a substantial decrease in the relaxation rate R{sub b} for the remaining bound sodium ions. Likewise, titration of NaDNA solutions with MgCl{sub 2} shows that condensation of Mg{sup 2+} on the DNA double helix reduces R{sub b}. A good agreement between experiment and theory is found if the average lengthening following intercalation of a 9-aminoacridine moiety is assumed to be approximately 2.7 {angstrom}. The distinction between mono- and bis-intercalation is clearly indicated by the results. The two bis-intercalating drugs examined are found to bis-intercalate only up to r {le} 0.02. For r > 0.02 the drugs apparently mono-intercalate.

  11. $^{11}$B and $^{27}$Al NMR spin-lattice relaxation and Knight shift study of Mg$_{1-x}$Al$_x$B$_2$. Evidence for anisotropic Fermi surface

    OpenAIRE

    Papavassiliou, G.; Pissas, M.; Karayanni, M.; Fardis, M.; Koutandos, S.; Prassides, K.

    2002-01-01

    We report a detailed study of $^{11}$B and $^{27}$Al NMR spin-lattice relaxation rates ($1/T_1$), as well as of $^{27}$Al Knight shift (K) of Mg$_{1-x}$Al$_x$B$_2$, $0\\leq x\\leq 1$. The obtained ($1/T_1T$) and K vs. x plots are in excellent agreement with ab initio calculations. This asserts experimentally the prediction that the Fermi surface is highly anisotropic, consisting mainly of hole-type 2-D cylindrical sheets from bonding $2p_{x,y}$ boron orbitals. It is also shown that the density ...

  12. Dispersion Properties of NMR Relaxation for Crude Oil

    Institute of Scientific and Technical Information of China (English)

    Xie Ranhong; Xiao Lizhi

    2007-01-01

    Special requirements for design of tools used for wireline NMR logging and NMR logging while drilling and for interpretation model are demanded due to the dispersion properties of NMR relaxation for crude oil.NMR longitudinal relaxation time (T1) and transverse relaxation time (T2) of the dead oil samples with different viscosities were measured by NMR spectrometers with a Larmor frequency of 2 MHz and 23 MHz at five different temperatures respectively.The results showed that T1 was obviously dependent on the Larmor frequency of NMR spectrometer.The degree of T1 dispersion became stronger with the increasing crude oil viscosity,Larmor frequency and the viscosity/temperature ratio.T2 was independent of NMR spectrometer measuring frequency.It is suggested that the resonance frequency should be selected lower than 2 MHz when measuring T1 in logging while-drilling and that T1 dispersion should be corrected when Larmor frequency is higher than 2 MHz.

  13. Another challenge to paramagnetic relaxation theory: a study of paramagnetic proton NMR relaxation in closely related series of pyridine-derivatised dysprosium complexes.

    Science.gov (United States)

    Rogers, Nicola J; Finney, Katie-Louise N A; Senanayake, P Kanthi; Parker, David

    2016-02-14

    Measurements of the relaxation rate behaviour of two series of dysprosium complexes have been performed in solution, over the field range 1.0 to 16.5 Tesla. The field dependence has been modelled using Bloch-Redfield-Wangsness theory, allowing estimates of the electronic relaxation time, T1e, and the size of the magnetic susceptibility, μeff, to be made. Changes in relaxation rate of the order of 50% at higher fields were measured, following variation of the para-substituent in the single pyridine donor. The magnetic susceptibilities deviated unexpectedly from the free-ion values for certain derivatives in each series examined, in a manner that was independent of the electron-releasing/withdrawing ability of the pyridine substituent, suggesting that the polarisability of just one pyridine donor in octadenate ligands can play a significant role in defining the magnetic susceptibility anisotropy.

  14. Non-uniform sampling of NMR relaxation data

    DEFF Research Database (Denmark)

    Schwarz-Linnet, Troels; Teilum, Kaare

    2016-01-01

    The use of non-uniform sampling of NMR spectra may give significant reductions in the data acquisition time. For quantitative experiments such as the measurement of spin relaxation rates, non-uniform sampling is however not widely used as inaccuracies in peak intensities may lead to errors...

  15. Interaction between reduced glutathione and PEO-PPO-PEO copolymers in aqueous solutions: studied by 1H NMR and spin-lattice relaxation.

    Science.gov (United States)

    Jia, Lianwei; Guo, Chen; Yang, Liangrong; Xiang, Junfeng; Tang, Yalin; Liu, Huizhou

    2011-03-17

    In order to investigate the effect of PEO-PPO-PEO copolymers on the glutathione (GSH)/glutathione-S-transferase (GST) detoxification system, interaction between the copolymers and GSH is studied by NMR measurements. Selective rotating-frame nuclear Overhauser effect (ROE) experiment confirms that glutamyl (Glu) α-H of GSH has spatial contact with EO methylene protons. Spin-lattice relaxation times of GSH Glu α-H show a decrease when PEO-PPO-PEO copolymers are added, and the decrease is greater with copolymers possessing more EO units. Other protons of GSH show little change in the presence of the copolymers. The addition of GSH promotes the dehydration of PEO-PPO-PEO copolymers. This results from the breaking of hydrogen bonds between water and the polymers and the forming of hydrogen bonds between Glu α-carboxylate protons and oxygen atoms of EO units. The dissociation constant between GSH and P85 copolymer is determined by spin-lattice relaxation measurements, which shows the binding is of low affinity and the two molecules are in fast dissociation kinetics. This study suggests that GSH transporting or utilizing systems may be affected by treatment of PEO-PPO-PEO copolymers.

  16. Adiabatic fast passage application in solid state NMR study of cross relaxation and molecular dynamics in heteronuclear systems

    Science.gov (United States)

    Baranowski, M.; Woźniak-Braszak, A.; Jurga, K.

    2016-01-01

    The paper presents the benefits of using fast adiabatic passage for the study of molecular dynamics in the solid state heteronuclear systems in the laboratory frame. A homemade pulse spectrometer operating at the frequency of 30.2 MHz and 28.411 MHz for protons and fluorines, respectively, has been enhanced with microcontroller direct digital synthesizer DDS controller [1-4]. This work briefly describes how to construct a low-cost and easy-to-assemble adiabatic extension set for homemade and commercial spectrometers based on recently very popular Arduino shields. The described set was designed for fast adiabatic generation. Timing and synchronization problems are discussed. The cross-relaxation experiments with different initial states of the two spin systems have been performed. Contrary to our previous work [5] where the steady-state NOE experiments were conducted now proton spins 1H are polarized in the magnetic field B0 while fluorine spins 19F are perturbed by selective saturation for a short time and then the system is allowed to evolve for a period in the absence of a saturating field. The adiabatic passage application leads to a reversal of magnetization of fluorine spins and increases the amplitude of the signal.

  17. Distribution of NMR relaxations in a random Heisenberg chain.

    Science.gov (United States)

    Shiroka, T; Casola, F; Glazkov, V; Zheludev, A; Prša, K; Ott, H-R; Mesot, J

    2011-04-01

    NMR measurements of the (29)Si spin-lattice relaxation time T(1) were used to probe the spin-1/2 random Heisenberg chain compound BaCu(2)(Si(1-x)Ge(x))(2)O(7). Remarkable differences between the pure (x=0) and the fully random (x=0.5) cases are observed, indicating that randomness generates a distribution of local magnetic relaxations. This distribution, which is reflected in a stretched exponential NMR relaxation, exhibits a progressive broadening with decreasing temperature, caused by a growing inequivalence of magnetic sites. Compelling independent evidence for the influence of randomness is also obtained from magnetization data and Monte Carlo calculations. These results suggest the formation of random-singlet states in this class of materials, as previously predicted by theory.

  18. Solid State NMR Study of Polystyrene Nanolatex Particles(I) 13C Spin-Lattice Relaxation Time

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    13C spin-lattice relaxtion times for polystyrene nanolatex particles have been investigated. It was found that the dramatic increase at 80℃ annealing temperature is well below the Tg temperature of bulk polystyrene, the increase of relaxation time of aromatic carbons is larger than that of for aliphatic carbons at transition annealing temperature.

  19. Water mobility and microstructure evolution in the germinating Medicago truncatula seed studied by NMR relaxometry. A revisited interpretation of multicomponent relaxation.

    Science.gov (United States)

    Lahaye, Marc; Falourd, Xavier; Limami, Anis M; Foucat, Loïc

    2015-02-18

    The water status of Medicago truncatula Gaertn. seed was followed by low-field NMR relaxometry during germination with and without oryzalin or fusicoccin used as growth modulators. T1 and T2 relaxation times and proportions P1 and P2 were determined on fresh, frozen, and freeze-thawed samples to characterize changes in water dynamics and compartmentation and in the nonfreezing water fraction. The results demonstrate that low-field NMR relaxometry allowed differentiating germination phases and events occurring during them as well as perturbations related to the presence of growth modulators. The results provide clear evidence that the classical multicomponent relaxation interpretation cannot directly relate T2 components and morphological compartments in biological tissue.

  20. Effective rotational correlation times of proteins from NMR relaxation interference

    Science.gov (United States)

    Lee, Donghan; Hilty, Christian; Wider, Gerhard; Wüthrich, Kurt

    2006-01-01

    Knowledge of the effective rotational correlation times, τc, for the modulation of anisotropic spin-spin interactions in macromolecules subject to Brownian motion in solution is of key interest for the practice of NMR spectroscopy in structural biology. The value of τc enables an estimate of the NMR spin relaxation rates, and indicates possible aggregation of the macromolecular species. This paper reports a novel NMR pulse scheme, [ 15N, 1H]-TRACT, which is based on transverse relaxation-optimized spectroscopy and permits to determine τc for 15N- 1H bonds without interference from dipole-dipole coupling of the amide proton with remote protons. [ 15N, 1H]-TRACT is highly efficient since only a series of one-dimensional NMR spectra need to be recorded. Its use is suggested for a quick estimate of the rotational correlation time, to monitor sample quality and to determine optimal parameters for complex multidimensional NMR experiments. Practical applications are illustrated with the 110 kDa 7,8-dihydroneopterin aldolase from Staphylococcus aureus, the uniformly 15N-labeled Escherichia coli outer membrane protein X (OmpX) in 60 kDa mixed OmpX/DHPC micelles with approximately 90 molecules of unlabeled 1,2-dihexanoyl- sn-glycero-3-phosphocholine (DHPC), and the 16 kDa pheromone-binding protein from Bombyx mori, which cover a wide range of correlation times.

  1. Distinguishing magnetic vs. quadrupolar relaxation in b-NMR using 8Li and 9Li

    Science.gov (United States)

    Chatzichristos, A.; McFadden, R. M. L.; Karner, V. L.; Cortie, D. L.; Fang, A.; Levy, C. D. P.; Macfarlane, W. A.; Morris, G. D.; Pearson, M. R.; Salman, Z.; Kiefl, R. F.

    2016-09-01

    Beta-detected NMR is a powerful technique in condensed matter physics. It uses the parity violation of beta decay to detect the NMR signal from a beam of highly polarized radionuclides implanted in a sample material. Spin-lattice relaxation (SLR) is studied by monitoring the rate with which the asymmetry between the beta counts in two opposing detectors is lost. Unlike classical NMR, b-NMR can study thin films and near-surface effects. The most common b-NMR isotope at TRIUMF is 8Li, which has a quadrupole moment, thus it is sensitive to both magnetic fields and electric field gradients. A challenge with 8Li b-NMR is identifying the predominant mechanism of SLR in a given sample. It is possible to distinguish between SLR mechanisms by varying the probe isotope. For two isotopes with different nuclear moments, the ratio of SLR rates should be different in the limits of either pure magnetic or quadrupolar relaxation. This method has been used in classical NMR and we report its first application to b-NMR. We measured the SLR rates for 8Li and 8Li in Pt foil and SrTiO3. Pt is a test case for pure magnetic relaxation. SrTiO3 is a non-magnetic insulator, but the source of its relaxation is not well understood. Here we show that its relaxation is mainly quadrupolar. We thank TRIUMF's CMMS for their technical support. This work was supported by: NSERC Discovery Grants to R.F.K. and W.A.M.; and IsoSiM fellowships to A.C. and R.M.L.M.

  2. NMR relaxation rate and the libron energy of solid hydrogen

    Science.gov (United States)

    Sugawara, K.; Woollam, J. A.

    1978-01-01

    By taking the rotational relaxation of orthohydrogen (o-H2) in solid hydrogen into account, the authors have theoretically investigated the longitudinal NMR spin lattice relaxation rate of o-H2. The rate is characterized by an anomalous maximum, as a function of temperature, at temperatures close to the mean libron energy of o-H2. Application of the theory for o-H2 concentrations between 42% and 75% reveals a nearly concentration-independent mean libron energy equivalent to about 1 K. This qualitatively and quantitatively contradicts the conclusions of other theories, but agrees with recent experiments.

  3. Analysis of 2D NMR relaxation data using Chisholm approximations

    Science.gov (United States)

    Huber, S.; Haase, A.; Gleich, B.

    2017-08-01

    To analyze 2D NMR relaxation data based on a discrete delta-like relaxation map we extended the Padé-Laplace method to two dimensions. We approximate the forward Laplace image of the time domain signal by a Chisholm approximation, i.e. a rational polynomial in two dimensions. The poles and residues of this approximation correspond to the relaxation rates and weighting factors of the underlying relaxation map. In this work we explain the principle ideas of our algorithm and demonstrate its applicability. Therefore we compare the inversion results of the Chisholm approximation and Tikhonov regularization method as a function of SNR when the investigated signal is based on a given discrete relaxation map. Our algorithm proved to be reliable for SNRs larger than 50 and is able to compete with the Tikhonov regularization method. Furthermore we show that our method is also able to detect the simulated relaxation compartments of narrow Gaussian distributions with widths less or equal than 0.05 s-1. Finally we investigate the resolution limit with experimental data. For a SNR of 750 the Chisholm approximation method was able to resolve two relaxation compartments in 8 of 10 cases when both compartments differ by a factor of 1.7.

  4. Theoretical tools for the design of NMR relaxation dispersion pulse sequences.

    Science.gov (United States)

    Salvi, Nicola

    2015-08-01

    Recent decades have witnessed tremendous progress in the development of new experimental methods for studying biomolecules, particularly in the field of NMR relaxation dispersion. Here we review the theoretical frameworks that provided the insights necessary for such progress. The effect of radio-frequency manipulations on spin systems is discussed using Average Hamiltonian Theory (AHT), Average Liouvillian Theory (ALT), and Bloch-Wangsness-Redfield (BWR) relaxation theory. We illustrate these concepts using the case of Heteronuclear Double Resonance (HDR) methods.

  5. Relaxation of coherent states in a two-qubit NMR quadrupole system

    Energy Technology Data Exchange (ETDEWEB)

    Sarthour, R.S.; Guimaraes, A.P.; Oliveira, I.S. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Azevedo, E.R. de; Bonk, F.A.; Vidoto, E.L.G.; Bonagamba, T.J. [Universidade de Sao Paulo (IFSC/USP), Sao Carlos, SP (Brazil). Inst. de Fisica; Freitas, J.C.C. [Universidade Federal do Espirito Santo (UFES), Vitoria, ES (Brazil). Dept. de Fisica

    2003-07-01

    Full text: Pulse Nuclear Magnetic Resonance (NMR) is one of the most serious candidates as an experimental technique for implementing quantum algorithms. To the present date, this technique is in fact the only one where full demonstrations of quantum algorithms implementations have been carried out, in spite of various technical difficulties. On NMR quantum computers, gates and subroutines are encoded as radiofrequency pulse sequences, which must act over coherent states. These sequences usually take tens of milliseconds to be implemented, and during this time the system relax towards equilibrium. Therefore, studies of relaxation times are very important to the realization of quantum algorithms via NMR. In this work we studied the longitudinal relaxation of various coherent states on the NMR quantum computing two-qubit quadrupole system, {sup 23}Na in C{sub 10}H{sub 21}NaO{sub 4}S liquid crystal at room temperature. Relaxation of pseudo-pure states |00>, |01>, |10>, |11>, pseudo-Bell states |01> + |10> and |00> + |11> and Hadamard states |00> + |01> and |10> + |11> were investigated. Experimental curves follow a multi exponential model of relaxation which takes into account mixed, dipolar magnetic and quadrupolar electric interactions. (author)

  6. NMR relaxation times of trabecular bone-reproducibility, relationships to tissue structure and effects of sample freezing

    Energy Technology Data Exchange (ETDEWEB)

    Prantner, Viktoria; Isaksson, Hanna; Nissi, Mikko J; Jurvelin, Jukka S [Department of Physics and Mathematics, University of Eastern Finland, PO Box 1627, 70211 Kuopio (Finland); Naervaeinen, Johanna; Groehn, Olli H J [Department of Neurobiology, A I Virtanen Institute for Molecular Sciences, University of Eastern Finland, PO Box 1627, 70211 Kuopio (Finland); Lammentausta, Eveliina [Department of Diagnostic Radiology, Oulu University Hospital, PO Box 50, 90029 OYS, Oulu (Finland); Avela, Janne, E-mail: hanna.isaksson@uef.f [Department of Biology of Physical Activity, University of Jyvaeskylae, PO Box 35, 40014 Jyvaeskylae (Finland)

    2010-12-07

    Nuclear magnetic resonance (NMR) spectroscopy provides a potential tool for non-invasive evaluation of the trabecular bone structure. The objective of this study was to determine the reproducibility of the NMR relaxation parameters (T{sub 2}, Carr-Purcel-T{sub 2}, T{sub 1}{rho}) for fat and water and relate those to the structural parameters obtained by micro-computed tomography ({mu}CT). Especially, we aimed to evaluate the effect of freezing on the relaxation parameters. For storing bone samples, freezing is the standard procedure during which the biochemical and cellular organization of the bone marrow may be affected. Bovine trabecular bone samples were stored at -20 {sup 0}C for 7 days and measured by NMR spectroscopy before and after freezing. The reproducibility of NMR relaxation parameters, as expressed by the coefficient of variation, ranged from 3.1% to 27.9%. In fresh samples, some correlations between NMR and structural parameters (Tb.N, Tb.Sp) were significant (e.g. the relaxation rate for T{sub 2} of fat versus Tb.Sp: r = -0.716, p < 0.01). Freezing did not significantly change the NMR relaxation times but the correlations between relaxation parameters and the {mu}CT structural parameters were not statistically significant after freezing, suggesting some nonsystematic alterations of the marrow structure. Therefore, the use of frozen bone samples for NMR relaxation studies may provide inferior information about the trabecular bone structure.

  7. Hydrogen-1 NMR relaxation time studies in membrane: anesthetic systems; Variacao dos tempos de relaxacao longitudinal de protons em sistemas membranares contendo anestesicos locais

    Energy Technology Data Exchange (ETDEWEB)

    Pinto, L.M.A.; Fraceto, L.; Paula, E. de [Universidade Estadual de Campinas, SP (Brazil). Dept. de Bioquimica; Franzoni, L.; Spisni, A. [Universita degli Studi di Parma, Parma (Italy). Ist. di Chimica Biologica

    1997-12-31

    The study of local anesthetics`(LA) interaction with model phospholipid membranes is justified by the direct correlation between anesthetic`s hydrophobicity and its potency/toxicity. By the same reason, uncharged LA species seems to play a crucial role in anesthesia. Most clinically used LA are small amphiphilics with a protonated amine group (pKa around 8). Although both charged (protonated) and uncharged forms can coexist at physiological pH, it has been shown (Lee, Biochim. Biophys. Acta 514:95, 1978; Screier et al. Biochim. Biophys. Acta 769:231, 1984) that the real anesthetic pka can be down-shifted, due to differential partition into membranes, increasing the ratio of uncharged species at pH 7.4. We have measured {sup 1}H-NMR longitudinal relaxation times (T{sub 1}) for phospholipid and three local anesthetics (tetracaine, lidocaine, benzocaine), in sonicated vesicles at a 3:1 molar ratio. All the LA protons have shown smaller T{sub 1} in this system than in isotropic phases, reflecting LA immobilization caused by insertion in the membrane. T{sub 1} values for the lipid protons in the presence of LA were analyzed, in an attempt to identify specific LA:lipid contact regions. (author) 13 refs., 3 figs., 1 tabs.

  8. Cooperative binding of midazolam with testosterone and alpha-naphthoflavone within the CYP3A4 active site: a NMR T1 paramagnetic relaxation study.

    Science.gov (United States)

    Cameron, Michael D; Wen, Bo; Allen, Kyle E; Roberts, Arthur G; Schuman, Jason T; Campbell, A Patricia; Kunze, Kent L; Nelson, Sidney D

    2005-11-01

    Recent studies have indicated that CYP3A4 exhibits non-Michaelis-Menten kinetics for numerous substrates. Both homo- and heterotropic activation have been reported, and kinetic models have suggested multiple substrates within the active site. We provide some of the first physicochemical data supporting the hypothesis of allosteric substrate binding within the CYP3A4 active site. Midazolam (MDZ) is metabolized by CYP3A4 to two hydroxylated metabolites, 1'- and 4-hydroxymidazolam. Incubations using purified CYP3A4 and MDZ showed that both alpha-naphthoflavone (alpha-NF) and testosterone affect the ratio of formation rates of 1'- and 4-hydroxymidazolam. Similar to previous reports, alpha-NF was found to promote formation of 1'-hydroxymidazolam, while testosterone stimulated formation of 4-hydroxymidazolam. NMR was used to measure the closest approach of individual MDZ protons to the paramagnetic heme iron of CYP3A4 using paramagnetic T(1) relaxation measurements. Solutions of 0.2 microM CYP3A4 with 500 microM MDZ resulted in calculated distances between 7.4 and 8.3 A for all monitored MDZ protons. The distances were statistically equivalent for all protons except C3-H and were consistent with the rotation within the active site or sliding parallel to the heme plane. When 50 microM alpha-NF was added, proton-heme iron distances ranged from 7.3 to 10.0 A. Consistent with kinetics of activation, the 1' position was situated closest to the heme, while the fluorophenyl 5-H proton was the furthest. Proton-heme iron distances for MDZ with CYP3A4 and 50 microM testosterone ranged from 7.7 to 9.0 A, with the flourophenyl 5-H proton furthest from the heme iron and the C4-H closest to the heme, also consistent with kinetic observations. When titrated with CYP3A4 in the presence of MDZ, testosterone and alpha-NF resonances themselves exhibited significant broadening and enhanced relaxation rates, indicating that these effector molecules were also bound within the CYP3A4 active

  9. A new method for multi-exponential inversion of NMR relaxation measurements

    Institute of Scientific and Technical Information of China (English)

    WANG; Zhongdong; XIAO; Lizhi; LIU; Tangyan

    2004-01-01

    A new method for multi-exponential inversion to NMR T1 and T2 relaxation time distributions is suggested and tested. Inversion results are compared with MAP-II which is based on SVD algorithm and widely accepted in the industry. Inversed NMR relaxation spectra that have different pre-assigned relaxation times from echo trains with different SNR confirm that the new method with 16 to 64 equally spaced time constants in logarithm scale will ensure the relaxation distribution. Testing results show that the new inversion algorithm is a valuable tool for rock core NMR experimental analysis and NMR logging data process and interpretation.

  10. Characterizing RNA Excited States using NMR Relaxation Dispersion

    Science.gov (United States)

    Xue, Yi; Kellogg, Dawn; Kimsey, Isaac J; Sathyamoorthy, Bharathwaj; Stein, Zachary W; McBrairty, Mitchell; Al-Hashimi, Hashim M.

    2016-01-01

    Changes in RNA secondary structure play fundamental roles in the cellular functions of a growing number of non-coding RNAs. This chapter describes NMR-based approaches for characterizing microsecond-to-millisecond changes in RNA secondary structure that are directed toward short-lived and low-populated species often referred to as “excited states”. Compared to larger-scale changes in RNA secondary structure, transitions towards excited states do not require assistance from chaperones, are often orders of magnitude faster, and are localized to a small number of nearby base pairs in and around non-canonical motifs. Here we describe a procedure for characterizing RNA excited states using off-resonance R1ρ NMR relaxation dispersion utilizing low-to-high spin-lock fields (25–3000 Hz). R1ρ NMR relaxation dispersion experiments are used to measure carbon and nitrogen chemical shifts in base and sugar moieties of the excited state. The chemical shift data is then interpreted with the aid of secondary structure prediction to infer potential excited states that feature alternative secondary structures. Candidate structures are then tested by using mutations, single-atom substitutions, or by changing physiochemical conditions, such as pH and temperature, to either stabilize or destabilize the candidate excited state. The resulting chemical shifts of the mutants or under different physiochemical conditions are then compared to those of the ground and excited state. Application is illustrated with a focus on the transactivation response element (TAR) from the human immune deficiency virus type 1 (HIV-1), which exists in dynamic equilibrium with at least two distinct excited states. PMID:26068737

  11. NMR studies of metalloproteins.

    Science.gov (United States)

    Li, Hongyan; Sun, Hongzhe

    2012-01-01

    Metalloproteins represent a large share of the proteomes, with the intrinsic metal ions providing catalytic, regulatory, and structural roles critical to protein functions. Structural characterization of metalloproteins and identification of metal coordination features including numbers and types of ligands and metal-ligand geometry, and mapping the structural and dynamic changes upon metal binding are significant for understanding biological functions of metalloproteins. NMR spectroscopy has long been used as an invaluable tool for structure and dynamic studies of macromolecules. Here we focus on the application of NMR spectroscopy in characterization of metalloproteins, including structural studies and identification of metal coordination spheres by hetero-/homo-nuclear metal NMR spectroscopy. Paramagnetic NMR as well as (13)C directly detected protonless NMR spectroscopy will also be addressed for application to paramagnetic metalloproteins. Moreover, these techniques offer great potential for studies of other non-metal binding macromolecules.

  12. Non-uniform sampling of NMR relaxation data

    Energy Technology Data Exchange (ETDEWEB)

    Linnet, Troels E.; Teilum, Kaare, E-mail: kaare.teilum@bio.ku.dk [University of Copenhagen, SBiNLab and the Linderstrøm-Lang Centre for Protein Science, Department of Biology (Denmark)

    2016-02-15

    The use of non-uniform sampling of NMR spectra may give significant reductions in the data acquisition time. For quantitative experiments such as the measurement of spin relaxation rates, non-uniform sampling is however not widely used as inaccuracies in peak intensities may lead to errors in the extracted dynamic parameters. By systematic reducing the coverage of the Nyquist grid of {sup 15}N Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion datasets for four different proteins and performing a full data analysis of the resulting non-uniform sampled datasets, we have compared the performance of the multi-dimensional decomposition and iterative re-weighted least-squares algorithms in reconstructing spectra with accurate peak intensities. As long as a single fully sampled spectrum is included in a series of otherwise non-uniform sampled two-dimensional spectra, multi-dimensional decomposition reconstructs the non-uniform sampled spectra with high accuracy. For two of the four analyzed datasets, a coverage of only 20 % results in essentially the same results as the fully sampled data. As exemplified by other data, such a low coverage is in general not enough to produce reliable results. We find that a coverage level not compromising the final results can be estimated by recording a single full two-dimensional spectrum and reducing the spectrum quality in silico.

  13. The eigenmode perspective of NMR spin relaxation in proteins

    Energy Technology Data Exchange (ETDEWEB)

    Shapiro, Yury E., E-mail: shapiro@nmrsgi4.ls.biu.ac.il, E-mail: eva.meirovitch@biu.ac.il; Meirovitch, Eva, E-mail: shapiro@nmrsgi4.ls.biu.ac.il, E-mail: eva.meirovitch@biu.ac.il [The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900-02 (Israel)

    2013-12-14

    We developed in recent years the two-body (protein and probe) coupled-rotator slowly relaxing local structure (SRLS) approach for elucidating protein dynamics from NMR spin relaxation. So far we used as descriptors the set of physical parameters that enter the SRLS model. They include the global (protein-related) diffusion tensor, D{sub 1}, the local (probe-related) diffusion tensor, D{sub 2}, and the local coupling/ordering potential, u. As common in analyzes based on mesoscopic dynamic models, these parameters have been determined with data-fitting techniques. In this study, we describe structural dynamics in terms of the eigenmodes comprising the SRLS time correlation functions (TCFs) generated by using the best-fit parameters as input to the Smoluchowski equation. An eigenmode is a weighted exponential with decay constant given by an eigenvalue of the Smoluchowski operator, and weighting factor determined by the corresponding eigenvector. Obviously, both quantities depend on the SRLS parameters as determined by the SRLS model. Unlike the set of best-fit parameters, the eigenmodes represent patterns of motion of the probe-protein system. The following new information is obtained for the typical probe, the {sup 15}N−{sup 1}H bond. Two eigenmodes, associated with the protein and the probe, dominate when the time scale separation is large (i.e., D{sub 2} ≫ D{sub 1}), the tensorial properties are simple, and the local potential is either very strong or very weak. When the potential exceeds these limits while the remaining conditions are preserved, new eigenmodes arise. The multi-exponentiality of the TCFs is associated in this case with the restricted nature of the local motion. When the time scale separation is no longer large, the rotational degrees of freedom of the protein and the probe become statistically dependent (coupled dynamically). The multi-exponentiality of the TCFs is associated in this case with the restricted nature of both the local and the

  14. Parameterization of NMR relaxation curves in terms of logarithmic moments of the relaxation time distribution

    Science.gov (United States)

    Petrov, Oleg V.; Stapf, Siegfried

    2017-06-01

    This work addresses the problem of a compact and easily comparable representation of multi-exponential relaxation data. It is often convenient to describe such data in a few parameters, all being of physical significance and easy to interpret, and in such a way that enables a model-free comparison between different groups of samples. Logarithmic moments (LMs) of the relaxation time constitute a set of parameters which are related to the characteristic relaxation time on the log-scale, the width and the asymmetry of an underlying distribution of exponentials. On the other hand, the calculation of LMs does not require knowing the actual distribution function and is reduced to a numerical integration of original data. The performance of this method has been tested on both synthetic and experimental NMR relaxation data which differ in a signal-to-noise ratio, the sampling range and the sampling rate. The calculation of two lower-order LMs, the log-mean time and the log-variance, has proved robust against deficiencies of the experiment such as scattered data point and incomplete sampling. One may consider using them as such to monitor formation of a heterogeneous structure, e.g., in phase separation, vitrification, polymerization, hydration, aging, contrast agent propagation processes. It may also assist in interpreting frequency and temperature dependences of relaxation, revealing a crossover from slow to fast exchange between populations. The third LM was found to be a less reliable quantity due to its susceptibility to the noise and must be used with caution.

  15. Studies on irradiation stability of polystyrene by NMR

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xin; SUN Wan-Fu; XIE Cheng-Xi

    2004-01-01

    The irradiation stability of polystyrene (PS) was studied by 13C and 1H NMR spectra, Nuclear Overhauser Relaxation (NOE) and 13C NMR spin-lattice relaxation time (T1). The results indicate that 13C and 1H NMR chemical shifts, NOE and T1 were almost invariant with the increase of irradiation dose. This shows that polystyrene is particularly stable within 2.5 kGy doses and the mechanism of its stability is discussed.

  16. Refined solution structure and backbone dynamics of 15N-labeled C12A-p8MTCP studied by NMR relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Barthe, Philippe; Chiche, Laurent; Declerck, Nathalie; Delsuc, Marc-Andre [Universite de Montpellier I, Faculte de Pharmacie, Centre de Biochimie Structurale, CNRS-UMR 9955, INSERM-U414 (France); Lefevre, Jean-Francois [Universite Louis Pasteur, CNRS UPR-9003, ESBS (France); Malliavin, Therese [Universite de Montpellier I, Faculte de Pharmacie, Centre de Biochimie Structurale, CNRS-UMR 9955, INSERM-U414 (France); Mispelter, Joel [Centre Universitaire Bat 112, INSERM-U350, Institut Curie, Biologie (France); Stern, Marc-Henri [Hopital Saint-Louis, Unite INSERM-U462 (France); Lhoste, Jean-Marc; Roumestand, Christian [Universite de Montpellier I, Faculte de Pharmacie, Centre de Biochimie Structurale, CNRS-UMR 9955, INSERM-U414 (France)

    1999-12-15

    MTCP1 (for Mature-T-Cell Proliferation) was the first gene unequivocally identified in the group of uncommon leukemias with a mature phenotype. The three-dimensional solution structure of the human p8{sup MTCP} protein encoded by the MTCP1 oncogene has been previously determined by homonuclear proton two-dimensional NMR methods at 600 MHz: it consists of an original scaffold comprising three {alpha}-helices, associated with a new cysteine motif. Two of the helices are covalently paired by two disulfide bridges, forming an {alpha}-hairpin which resembles an antiparallel coiled-coil. The third helix is orientated roughly parallel to the plane defined by the {alpha}-antiparallel motif and appears less well defined. In order to gain more insight into the details of this new scaffold, we uniformly labeled with nitrogen-15 a mutant of this protein (C12A-p8{sup MTCP1}) in which the unbound cysteine at position 12 has been replaced by an alanine residue, thus allowing reproducibly high yields of recombinant protein. The refined structure benefits from 211 additional NOEs, extracted from {sup 15}N-edited 3D experiments, and from a nearly complete set of {phi} angular restraints allowing the estimation of the helical content of the structured part of the protein. Moreover, measurements of {sup 15} N spin relaxation times and heteronuclear {sup 15} N{sup 1}HNOEs provided additional insights into the dynamics of the protein backbone. The analysis of the linear correlation between J(0) and J({omega}) was used to interpret relaxation parameters. It appears that the apparent relative disorder seen in helix III is not simply due to a lack of experimental constraints, but associated with substantial contributions of sub-nanosecond motions in this segment.

  17. Mobility and relaxation determinations of lithium in lithium aluminate ceramics using solid-state NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, F.F.; Peterson, E.S. [Idaho National Engineering Lab., Idaho Falls, ID (United States); Stebbins, J.F. [Stanford Univ., CA (United States)] [and others

    1995-02-01

    Lithium aluminate is one of the materials being considered for fusion reactor blankets. When preparing the ceramic, it is important to be able to monitor the microstructures since it is a controlling factor in the rate of tritium release from the blanket. Nuclear magnetic resonance spectroscopy (NMR) has been shown to be a useful tool for the nondestructive analysis of ceramics. Studies detailed in this paper include spectral acquisition, assignment, spin-lattice relaxation time measurements, temperature effects, their correlation to structure, and material purity. The ceramic of interest was lithium aluminate, LiAl{sub 5}O{sub 8}. This material was studied by observation of the NMR active nuclei {sup 6}Li, {sup 7}Li, and {sup 27}Al. For these nuclei, spin-lattice relaxation times (T{sub 1}) were measured and were found to vary considerably, correlating to the presence of paramagnetic impurities within the crystalline lattice. Previous research has shown that the coordination about the aluminum nucleus can be determined using {sup 27}Al NMR spectroscopy. Aluminum-27 NMR spectroscopy was successfully applied, and it provided valuable insight into composition of the ceramic. 20 refs., 4 figs., 3 tabs.

  18. High-resolution NMR field-cycling device for full-range relaxation and structural studies of biopolymers on a shared commercial instrument

    Energy Technology Data Exchange (ETDEWEB)

    Redfield, Alfred G., E-mail: redfield@brandeis.edu [Brandeis University, Biochemistry Department (United States)

    2012-02-15

    Improvements are described in a shuttling field-cycling device (Redfield in Magn Reson Chem 41:753-768, 2003), designed to allow widespread access to this useful technique by configuring it as a removable module to a commercial 500 MHz NMR instrument. The main improvements described here, leading to greater versatility, high reliability and simple construction, include: shuttling provided by a linear motor driven by an integrated-control servomotor; provision of automated bucking magnets to allow fast two-stage cycling to nearly zero field; and overall control by a microprocessor. A brief review of history and publications that have used the system is followed by a discussion of topics related to such a device including discussion of some future applications. A description of new aspects of the shuttling device follows. The minimum round trip time to 1T and above is less than 0.25 s and to 0.002 T is 0.36 s. Commercial probes are used and sensitivity is that of the host spectrometer reduced only by relaxation during travel. A key element is development of a linkage that prevents vibration of the linear motor from reaching the probe.

  19. High-resolution NMR field-cycling device for full-range relaxation and structural studies of biopolymers on a shared commercial instrument.

    Science.gov (United States)

    Redfield, Alfred G

    2012-02-01

    Improvements are described in a shuttling field-cycling device (Redfield in Magn Reson Chem 41:753-768, 2003), designed to allow widespread access to this useful technique by configuring it as a removable module to a commercial 500 MHz NMR instrument. The main improvements described here, leading to greater versatility, high reliability and simple construction, include: shuttling provided by a linear motor driven by an integrated-control servomotor; provision of automated bucking magnets to allow fast two-stage cycling to nearly zero field; and overall control by a microprocessor. A brief review of history and publications that have used the system is followed by a discussion of topics related to such a device including discussion of some future applications. A description of new aspects of the shuttling device follows. The minimum round trip time to 1T and above is less than 0.25 s and to 0.002 T is 0.36 s. Commercial probes are used and sensitivity is that of the host spectrometer reduced only by relaxation during travel. A key element is development of a linkage that prevents vibration of the linear motor from reaching the probe.

  20. Contribution of proton NMR relaxation to the investigation of molecular dynamics in columnar mesophases of discotic and polycatenar molecules

    Indian Academy of Sciences (India)

    A C Ribeiro; P J Sebastiao; C Cruz

    2003-08-01

    We present in this work a review concerning wide frequency range 1 proton NMR relaxation studies performed in compounds exhibiting columnar mesophases, namely the Colho mesophase in the case of a liquid crystal of discotic molecules and the h mesophase in the case of a liquid crystal of biforked molecules. These NMR relaxation studies were performed combining conventional and fast field cycling NMR techniques in a frequency range between 100 Hz and 300 MHz. The possibility of probing such a large frequency range has provided a way to effectively distinguish the influence, on the 1 relaxation profiles, of the different molecular movements observed in this type of mesophases. In addition, we present a comparison between the molecular dynamics in columnar (h) and lamellar (SmC) mesophases exhibited by the same biforked compound.

  1. {sup 75}As NMR relaxation in glassy Ge-As-Se

    Energy Technology Data Exchange (ETDEWEB)

    Mammadov, Eldar; Mehdiyeva, Salima [Institute of Physics, National Academy of Sciences, H. Javid Avenue 33, Baku, AZ 1143 (Azerbaijan); Taylor, P.C. [Physics Department, Colorado School of Mines, 1523 Illinois Street, Golden, CO 80401 (United States); Reyes, Arneil; Kuhns, Phillip [National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, FL 32310 (United States)

    2010-03-15

    We have used high magnetic fields to perform {sup 75}As nuclear magnetic resonance (NMR) relaxation measurements in Ge-As-Se glasses. The spin-lattice relaxation time T{sub 1} has been studied as a function of average coordination number, left angle r right angle and temperature, T. We show that the relaxation time constant, T{sub 1}, in this system can be a useful tool to probe rigidity of the glassy matrix. In the two extreme cases, zero-field nuclear quadrupole resonance (NQR) and high-field NMR, T{sub 1} exhibits a similar dependence on the average coordination number. Namely, there is a region in this dependence at low left angle r right angle values, where the spin-lattice relaxation time does not change remarkably, followed by an increase in T{sub 1} in glasses with left angle r right angle more than 2.54. This transition can be correlated with the onset of rigidity percolation in the glassy matrix. The temperature dependence of the spin-lattice relaxation rate is found in the form T{sub 1}{sup -1} {proportional_to} T{sup 2}. This behavior is typical for As and other nuclei in glasses at temperatures below 300 K and is indicative of Raman-like relaxation mechanism involving low-frequency modes. Spin-echo intensity for Ge{sub 2}As{sub 2}Se{sub 5} as a function of pulse separation exhibits exponential decay whose slope is the same as one of the average of the decay found from {sup 75}As NQR measurements. This result indicates to the presence of indirect dipolar coupling of arsenic atoms in this composition. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  2. Solid-state NMR (31)P paramagnetic relaxation enhancement membrane protein immersion depth measurements.

    Science.gov (United States)

    Maltsev, Sergey; Hudson, Stephen M; Sahu, Indra D; Liu, Lishan; Lorigan, Gary A

    2014-04-24

    Paramagnetic relaxation enhancement (PRE) is a widely used approach for measuring long-range distance constraints in biomolecular solution NMR spectroscopy. In this paper, we show that (31)P PRE solid-state NMR spectroscopy can be utilized to determine the immersion depth of spin-labeled membrane peptides and proteins. Changes in the (31)P NMR PRE times coupled with modeling studies can be used to describe the spin-label position/amino acid within the lipid bilayer and the corresponding helical tilt. This method provides valuable insight on protein-lipid interactions and membrane protein structural topology. Solid-state (31)P NMR data on the 23 amino acid α-helical nicotinic acetylcholine receptor nAChR M2δ transmembrane domain model peptide followed predicted behavior of (31)P PRE rates of the phospholipid headgroup as the spin-label moves from the membrane surface toward the center of the membrane. Residue 11 showed the smallest changes in (31)P PRE (center of the membrane), while residue 22 shows the largest (31)P PRE change (near the membrane surface), when compared to the diamagnetic control M2δ sample. This PRE SS-NMR technique can be used as a molecular ruler to measure membrane immersion depth.

  3. Temperature dependence of proton NMR relaxation times at earth's magnetic field

    Science.gov (United States)

    Niedbalski, Peter; Kiswandhi, Andhika; Parish, Christopher; Ferguson, Sarah; Cervantes, Eduardo; Oomen, Anisha; Krishnan, Anagha; Goyal, Aayush; Lumata, Lloyd

    The theoretical description of relaxation processes for protons, well established and experimentally verified at conventional nuclear magnetic resonance (NMR) fields, has remained untested at low fields despite significant advances in low field NMR technology. In this study, proton spin-lattice relaxation (T1) times in pure water and water doped with varying concentrations of the paramagnetic agent copper chloride have been measured from 6 to 92oC at earth's magnetic field (1700 Hz). Results show a linear increase of T1 with temperature for each of the samples studied. Increasing the concentration of the copper chloride greatly reduced T1 and reduced dependence on temperature. The consistency of the results with theory is an important confirmation of past results, while the ability of an ultra-low field NMR system to do contrast-enhanced magnetic resonance imaging (MRI) is promising for future applicability to low-cost medical imaging and chemical identification. This work is supported by US Dept of Defense Award No. W81XWH-14-1-0048 and the Robert A. Welch Foundation Grant No. AT-1877.

  4. Determining pore length scales and pore surface relaxivity of rock cores by internal magnetic fields modulation at 2MHz NMR.

    Science.gov (United States)

    Liu, Huabing; Nogueira d'Eurydice, Marcel; Obruchkov, Sergei; Galvosas, Petrik

    2014-09-01

    Pore length scales and pore surface relaxivities of rock cores with different lithologies were studied on a 2MHz Rock Core Analyzer. To determine the pore length scales of the rock cores, the high eigenmodes of spin bearing molecules satisfying the diffusion equation were detected with optimized encoding periods in the presence of internal magnetic fields Bin. The results were confirmed using a 64MHz NMR system, which supports the feasibility of high eigenmode detection at fields as low as 2MHz. Furthermore, this methodology was combined with relaxometry measurements to a two-dimensional experiment, which provides correlation between pore length and relaxation time. This techniques also yields information on the surface relaxivity of the rock cores. The estimated surface relaxivities were then compared to the results using an independent NMR method.

  5. Molecular dynamics simulations of NMR relaxation and diffusion of bulk hydrocarbons and water

    Science.gov (United States)

    Singer, Philip M.; Asthagiri, Dilip; Chapman, Walter G.; Hirasaki, George J.

    2017-04-01

    Molecular dynamics (MD) simulations are used to investigate 1H nuclear magnetic resonance (NMR) relaxation and diffusion of bulk n-C5H12 to n-C17H36 hydrocarbons and bulk water. The MD simulations of the 1H NMR relaxation times T1,2 in the fast motion regime where T1 =T2 agree with measured (de-oxygenated) T2 data at ambient conditions, without any adjustable parameters in the interpretation of the simulation data. Likewise, the translational diffusion DT coefficients calculated using simulation configurations agree with measured diffusion data at ambient conditions. The agreement between the predicted and experimentally measured NMR relaxation times and diffusion coefficient also validate the forcefields used in the simulation. The molecular simulations naturally separate intramolecular from intermolecular dipole-dipole interactions helping bring new insight into the two NMR relaxation mechanisms as a function of molecular chain-length (i.e. carbon number). Comparison of the MD simulation results of the two relaxation mechanisms with traditional hard-sphere models used in interpreting NMR data reveals important limitations in the latter. With increasing chain length, there is substantial deviation in the molecular size inferred on the basis of the radius of gyration from simulation and the fitted hard-sphere radii required to rationalize the relaxation times. This deviation is characteristic of the local nature of the NMR measurement, one that is well-captured by molecular simulations.

  6. NMR cross-correlated relaxation rates reveal ion coordination sites in DNA

    NARCIS (Netherlands)

    Fiala, R.; Spackova, N.; Foldynová-Trantírková, S.; Sponer, J.; Sklenár, V.; Trantirek, L.

    2011-01-01

    In this work, a novel NMR method for the identification of preferential coordination sites between physiologically relevant counterions and nucleic acid bases is demonstrated. In this approach, the NMR cross-correlated relaxation rates between the aromatic carbon chemical shift anisotropy and the pr

  7. Observation of the relaxivity and thickness of surface phase in porous rock with the combination of PFG NMR and relaxation measurements

    Institute of Scientific and Technical Information of China (English)

    肖立志; 杜有如; 叶朝辉

    1996-01-01

    Nuclear magnetic resonance (NMR) relaxation of fluids in porous media is affected by the solid-liquid interface. Quantitative determination of the surface relaxivity is significantly important for both investigation and application of relaxation mechanisms in porous media. A method to estimate the surface relaxivity with the combination of relaxation and diffusion measurements is proposed. According to this method, a criterion for testing the current diffusion and relaxation theory for porous media is available.

  8. Requirements on paramagnetic relaxation enhancement data for membrane protein structure determination by NMR.

    Science.gov (United States)

    Gottstein, Daniel; Reckel, Sina; Dötsch, Volker; Güntert, Peter

    2012-06-06

    Nuclear magnetic resonance (NMR) structure calculations of the α-helical integral membrane proteins DsbB, GlpG, and halorhodopsin show that distance restraints from paramagnetic relaxation enhancement (PRE) can provide sufficient structural information to determine their structure with an accuracy of about 1.5 Å in the absence of other long-range conformational restraints. Our systematic study with simulated NMR data shows that about one spin label per transmembrane helix is necessary for obtaining enough PRE distance restraints to exclude wrong topologies, such as pseudo mirror images, if only limited other NMR restraints are available. Consequently, an experimentally realistic amount of PRE data enables α-helical membrane protein structure determinations that would not be feasible with the very limited amount of conventional NOESY data normally available for these systems. These findings are in line with our recent first de novo NMR structure determination of a heptahelical integral membrane protein, proteorhodopsin, that relied extensively on PRE data.

  9. NMR spin-lattice relaxation study of 7Li and 93Nb nuclei in Ti- or Fe-doped LiNbO3:Mg single crystals

    Directory of Open Access Journals (Sweden)

    Tae Ho Yeom

    2016-04-01

    Full Text Available In this study, to understand the effects of paramagnetic impurities, we investigated the temperature dependent of the spin-lattice relaxation times of pure LiNbO3, LiNbO3:Mg, LiNbO3:Mg/Ti, LiNbO3:Mg/Fe, and LiNbO3:Mg/Fe (thermally treated at 500°C single crystals. The results for the LiNbO3:Mg single crystals doped with Fe3+ or Ti3+ are discussed with respect to the site distribution and atomic mobility of Li and Nb. In addition, the effects of a thermal treatment on LiNbO3:Mg/Fe single crystals were examined based on the T1 analysis of 7Li and 93Nb. It was found that the presence of impurities in the crystals induced systematic changes of activation energies concerning atomic mobility.

  10. New approach for understanding experimental NMR relaxivity properties of magnetic nanoparticles: focus on cobalt ferrite.

    Science.gov (United States)

    Rollet, Anne-Laure; Neveu, Sophie; Porion, Patrice; Dupuis, Vincent; Cherrak, Nadine; Levitz, Pierre

    2016-12-07

    Relaxivities r1 and r2 of cobalt ferrite magnetic nanoparticles (MNPs) have been investigated in the aim of improving the models of NMR relaxation induced by magnetic nanoparticles. On one hand a large set of relaxivity data has been collected for cobalt ferrite MNP dispersions. On the other hand the relaxivity has been calculated for dispersions of cobalt ferrite MNPs with size ranging from 5 to 13 nm, without using any fitting procedure. The model is based on the magnetic dipolar interaction between the magnetic moments of the MNPs and the (1)H nuclei. It takes into account both the longitudinal and transversal contributions of the magnetic moments of MNPs leading to three contributions in the relaxation equations. The comparison of the experimental and theoretical data shows a good agreement of the NMR profiles as well as the temperature dependence.

  11. Translational diffusion of macromolecular assemblies measured using transverse-relaxation-optimized pulsed field gradient NMR.

    Science.gov (United States)

    Horst, Reto; Horwich, Arthur L; Wüthrich, Kurt

    2011-10-19

    In structural biology, pulsed field gradient (PFG) NMR spectroscopy for the characterization of size and hydrodynamic parameters of macromolecular solutes has the advantage over other techniques that the measurements can be recorded with identical solution conditions as used for NMR structure determination or for crystallization trials. This paper describes two transverse-relaxation-optimized (TRO) (15)N-filtered PFG stimulated-echo (STE) experiments for studies of macromolecular translational diffusion in solution, (1)H-TRO-STE and (15)N-TRO-STE, which include CRINEPT and TROSY elements. Measurements with mixed micelles of the Escherichia coli outer membrane protein X (OmpX) and the detergent Fos-10 were used for a systematic comparison of (1)H-TRO-STE and (15)N-TRO-STE with conventional (15)N-filtered STE experimental schemes. The results provide an extended platform for evaluating the NMR experiments available for diffusion measurements in structural biology projects involving molecular particles with different size ranges. An initial application of the (15)N-TRO-STE experiment with very long diffusion delays showed that the tedradecamer structure of the 800 kDa Thermus thermophilus chaperonin GroEL is preserved in aqueous solution over the temperature range 25-60 °C.

  12. Translational diffusion of macromolecular assemblies measured using transverse relaxation-optimized PFG-NMR

    Science.gov (United States)

    Horst, Reto; Horwich, Arthur L.

    2012-01-01

    In structural biology, pulsed field gradient (PFG) NMR for characterization of size and hydrodynamic parameters of macromolecular solutes has the advantage over other techniques that the measurements can be recorded with identical solution conditions as used for NMR structure determination or for crystallization trials. This paper describes two transverse relaxation-optimized (TRO) 15N-filtered PFG stimulated-echo (STE) experiments for studies of macromolecular translational diffusion in solution, 1H-TRO-STE and 15N-TRO-STE, which include CRINEPT and TROSY elements. Measurements with mixed micelles of the Escherichia coli outer membrane protein X (OmpX) and the detergent Fos-10 were used for a systematic comparison of 1H-TRO-STE and 15N-TRO-STE with conventional 15N-filtered STE experimental schemes. The results provide an extended platform for evaluating the NMR experiments available for diffusion measurements in structural biology projects with molecular particles of different size ranges. An initial application of the 15N-TRO-STE experiment with very long diffusion delays showed that the tedradecamer structure of the 800 kDa Thermus thermophilus chaperonin GroEL is preserved in aqueous solution over the temperature range 25–60°C. PMID:21919531

  13. Interfaces in polymer nanocomposites – An NMR study

    Energy Technology Data Exchange (ETDEWEB)

    Böhme, Ute; Scheler, Ulrich, E-mail: scheler@ipfdd.de [Leibniz-Institut für Polymerforschung Dresden e.V., Hohe Str. 6, 01069 Dresden (Germany)

    2016-03-09

    Nuclear Magnetic Resonance (NMR) is applied for the investigation of polymer nanocomposites. Solid-state NMR is applied to study the modification steps to compatibilize layered double hydroxides with non-polar polymers. {sup 1}H relaxation NMR gives insight on the polymer dynamics over a wide range of correlation times. For the polymer chain dynamics the transverse relaxation time T{sub 2} is most suited. In this presentation we report on two applications of T{sub 2} measurements under external mechanical stress. In a low-field system relaxation NMR studies are performed in-situ under uniaxial stress. High-temperature experiments in a Couette cell permit the investigation of the polymer dynamics in the melt under shear flow.

  14. A carbon-13 NMR spin-lattice relaxation study of the molecular conformation of the nootropic drug 2-oxopyrrolidin-1-ylacetamide

    Science.gov (United States)

    Baldo, M.; Grassi, A.; Guidoni, L.; Nicolini, M.; Pappalardo, G. C.; Viti, V.

    The spin-lattice relaxation times ( T1) of carbon-13 resonances of the drug 2-oxopyrrolidin- 1-ylacetamide ( 2OPYAC) were determined in CDCl 3 + DMSO and H 2O solutions to investigate the internal conformational flexibility. The measured T1s for the hydrogen-bearing carbon atoms of the 2-pyrrolidone ring fragment were diagnostic of a rigid conformation with respect to the acetamide linked moiety. The model of anisotropic reorientation of a rigid body was used to analyse the measured relaxation data in terms of a single conformation. Owing to the small number of T1 data available the fitting procedure for each of the possible conformations failed. The structure corresponding to the rigid conformation was therefore considered to be the one that is strongly stabilized by internal hydrogen bonding as predicted on the basis of theoretical MO ab initio quantum chemical calculations.

  15. Challenging lanthanide relaxation theory: erbium and thulium complexes that show NMR relaxation rates faster than dysprosium and terbium analogues.

    Science.gov (United States)

    Funk, Alexander M; Harvey, Peter; Finney, Katie-Louise N A; Fox, Mark A; Kenwright, Alan M; Rogers, Nicola J; Senanayake, P Kanthi; Parker, David

    2015-07-07

    Measurements of the proton NMR paramagnetic relaxation rates for several series of isostructural lanthanide(III) complexes have been performed in aqueous solution over the field range 1.0 to 16.5 Tesla. The field dependence has been modeled using Bloch-Redfield-Wangsness theory, allowing values for the electronic relaxation time, Tle and the magnetic susceptibility, μeff, to be estimated. Anomalous relaxation rate profiles were obtained, notably for erbium and thulium complexes of low symmetry 8-coordinate aza-phosphinate complexes. Such behaviour challenges accepted theory and can be interpreted in terms of changes in Tle values that are a function of the transient ligand field induced by solvent collision and vary considerably between Ln(3+) ions, along with magnetic susceptibilities that deviate significantly from free-ion values.

  16. Ultra-low-field NMR relaxation and diffusion measurements using an optical magnetometer.

    Science.gov (United States)

    Ganssle, Paul J; Shin, Hyun D; Seltzer, Scott J; Bajaj, Vikram S; Ledbetter, Micah P; Budker, Dmitry; Knappe, Svenja; Kitching, John; Pines, Alexander

    2014-09-08

    Nuclear magnetic resonance (NMR) relaxometry and diffusometry are important tools for the characterization of heterogeneous materials and porous media, with applications including medical imaging, food characterization and oil-well logging. These methods can be extremely effective in applications where high-resolution NMR is either unnecessary, impractical, or both, as is the case in the emerging field of portable chemical characterization. Here, we present a proof-of-concept experiment demonstrating the use of high-sensitivity optical magnetometers as detectors for ultra-low-field NMR relaxation and diffusion measurements.

  17. Increasing the sensitivity of NMR diffusion measurements by paramagnetic longitudinal relaxation enhancement, with application to ribosome–nascent chain complexes

    Energy Technology Data Exchange (ETDEWEB)

    Chan, Sammy H. S.; Waudby, Christopher A.; Cassaignau, Anaïs M. E.; Cabrita, Lisa D.; Christodoulou, John, E-mail: j.christodoulou@ucl.ac.uk [University College London and Birkbeck College, Institute of Structural and Molecular Biology (United Kingdom)

    2015-10-15

    The translational diffusion of macromolecules can be examined non-invasively by stimulated echo (STE) NMR experiments to accurately determine their molecular sizes. These measurements can be important probes of intermolecular interactions and protein folding and unfolding, and are crucial in monitoring the integrity of large macromolecular assemblies such as ribosome–nascent chain complexes (RNCs). However, NMR studies of these complexes can be severely constrained by their slow tumbling, low solubility (with maximum concentrations of up to 10 μM), and short lifetimes resulting in weak signal, and therefore continuing improvements in experimental sensitivity are essential. Here we explore the use of the paramagnetic longitudinal relaxation enhancement (PLRE) agent NiDO2A on the sensitivity of {sup 15}N XSTE and SORDID heteronuclear STE experiments, which can be used to monitor the integrity of these unstable complexes. We exploit the dependence of the PLRE effect on the gyromagnetic ratio and electronic relaxation time to accelerate recovery of {sup 1}H magnetization without adversely affecting storage on N{sub z} during diffusion delays or introducing significant transverse relaxation line broadening. By applying the longitudinal relaxation-optimized SORDID pulse sequence together with NiDO2A to 70S Escherichia coli ribosomes and RNCs, NMR diffusion sensitivity enhancements of up to 4.5-fold relative to XSTE are achieved, alongside ∼1.9-fold improvements in two-dimensional NMR sensitivity, without compromising the sample integrity. We anticipate these results will significantly advance the use of NMR to probe dynamic regions of ribosomes and other large, unstable macromolecular assemblies.Graphical Abstract.

  18. Using relaxation dispersion NMR spectroscopy to determine structures of excited, invisible protein states

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, D. Flemming; Vallurupalli, Pramodh; Kay, Lewis E. [University of Toronto, Departments of Molecular Genetics, Biochemistry and Chemistry (Canada)], E-mail: kay@pound.med.utoronto.ca

    2008-07-15

    Currently the main focus of structural biology is the determination of static three-dimensional representations of biomolecules that for the most part correspond to low energy (ground state) conformations. However, it is becoming increasingly well recognized that higher energy structures often play important roles in function as well. Because these conformers are populated to only low levels and are often only transiently formed their study is not amenable to many of the tools of structural biology. In this perspective we discuss the role of CPMG-based relaxation dispersion NMR spectroscopy in characterizing these low populated, invisible states. It is shown that robust methods for measuring both backbone chemical shifts and residual anisotropic interactions in the excited state are in place and that these data provide valuable restraints for structural studies of invisible conformers.

  19. NMR Studies of 3-Acylcamphor

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    NMR studies of some chiral 3-acyclcamphor were conducted.A complete assignment was given to 3-(4-pyridyl)carbonylcamphor by the 2D NMR technology.Assignments were also given to other b -diketones.The results showed that those 3-acylcamphors exist in the enol forms,while 2-benzoyl menthone exists in diketon form.

  20. Reorientational eigenmode dynamics: a combined MD/NMR relaxation analysis method for flexible parts in globular proteins.

    Science.gov (United States)

    Prompers, J J; Brüschweiler, R

    2001-08-01

    An approach is presented for the interpretation of heteronuclear NMR spin relaxation data in mobile protein parts in terms of reorientational eigenmode dynamics. The method is based on the covariance matrix of the spatial functions of the nuclear spin interactions that cause relaxation expressed as spherical harmonics of rank 2. The approach was applied to characterize the dynamics of a loop region of ubiquitin. The covariance matrix was determined from a conformational ensemble generated by a 5 ns molecular dynamics simulation. It was found that the time correlation functions of the dominant eigenmodes decay in good approximation with a single correlation time. From the reorientational eigenmodes, their eigenvalues, and correlation times, NMR relaxation data were calculated in accordance with Bloch-Wangsness-Redfield relaxation theory and directly compared with experimental (15)N relaxation parameters. Using a fitting procedure, agreement between calculated and experimental data was improved significantly by adjusting eigenvalues and correlation times of the dominant modes. The presented procedure provides detailed information on correlated reorientational dynamics of flexible parts in globular proteins. The covariance matrix was linked to the covariance matrix of backbone dihedral angle fluctuations, allowing one to study the motional behavior of these degrees of freedom on nano- and subnanosecond time scales.

  1. Microphase structures and 13C NMR relaxation parameters in ultrahigh molecular weight polyethylene

    Institute of Scientific and Technical Information of China (English)

    朱清仁; 洪昆仑; 鲁非; 戚嵘嵘; 庞文民; 周贵恩; 宋名实

    1995-01-01

    The phase transformations in ultrahigh molecular weight polyethylene(UHMWPE)gel-filmsupon superdrawing have been studied by X-ray diffraction and high resolution solid state 13C NMR.Themorphological change and molecular motions in the crystalline phase,amorphous phase and interphase are dis-cussed according to the 13C nuclear relaxation time(T1c,T2cresults.A brief interpretation to the three orfour T1cvalues in the crystalline phase is presented.It is found that the component with the highest T1c(T1cα)plays a key role in the forming of ’Shish-Kebab’ microfibril which determines the sample strength andmodulus,namely,the greater the T1cα,the higher the modulus and strength of the drawn UHMWPEgel-film.These results support the ’Shish-Kebabs’ model in crystalline polymers.

  2. Studies of DNA-binding properties of lafutidine as adjuvant anticancer agent to calf thymus DNA using multi-spectroscopic approaches, NMR relaxation data, molecular docking and dynamical simulation.

    Science.gov (United States)

    Yang, Hongqin; Tang, Peixiao; Tang, Bin; Huang, Yanmei; He, Jiawei; Li, Shanshan; Li, Hui

    2017-06-01

    The interactions between lafutidine (LAF) and calf thymus DNA (ctDNA) have been investigated both experimentally and theoretically. UV-vis absorption studies confirmed that LAF binds to ctDNA through non-covalent interactions. Fluorescence quenching and time-resolved fluorescence spectroscopy studies showed that the binding of LAF with ctDNA occurred through static quenching mechanism, resulting in the formation of a LAF-ctDNA complex. The binding constants (K) of the complex were found to be around 10(3)M(-1) via NMR relaxation rates and fluorescence data, and the calculated thermodynamic parameters indicated that hydrogen bonds and van der Waals forces played major roles in the binding of LAF to ctDNA. The changes in CD spectra indicated that LAF induced a slight perturbation on the base stacking and helicity of B-DNA. A comparative study of the LAF-ctDNA complex with respect to potassium iodide quenching experiments and competition displacement assays with ethidium bromide, acridine orange, and Hoechst 33258 probes suggested that LAF interacted with ctDNA by minor groove mode. Molecular docking analysis further supported the minor groove binding. Molecular dynamics simulation indicated that LAF depart from the C-G region of DNA, but it can steadily bind with the middle part of DNA composed by A-T base pairs. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Relationship between the crystallization rates of amorphous nifedipine, phenobarbital, and flopropione, and their molecular mobility as measured by their enthalpy relaxation and (1)H NMR relaxation times.

    Science.gov (United States)

    Aso, Y; Yoshioka, S; Kojima, S

    2000-03-01

    Isothermal crystallization of amorphous nifedipine, phenobarbital, and flopropione was studied at temperatures above and below their glass transition temperatures (T(g)). A sharp decrease in the crystallization rate with decreasing temperature was observed for phenobarbital and flopropione, such that no crystallization was observed at temperatures 20-30 degrees C lower than their T(g) within ordinary experimental time periods. In contrast, the crystallization rate of nifedipine decreased moderately with decreasing temperature, and considerable crystallization was observed at 40 degrees C below its T(g) within 4 months. The molecular mobility of these amorphous drugs was assessed by enthalpy relaxation and (1)H-NMR relaxation measurements. The enthalpy relaxation time of nifedipine was smaller than that of phenobarbital or flopropinone at the same T - T(g) values, suggesting higher molecular mobility of nifedipine. The spin-lattice relaxation time in the rotating frame (T(1rho)) decreased markedly at temperature above T(g). The slope of the Arrhenius type plot of the T(1rho) for nifedipine protons changed at about 10 degrees C below the T(g), whereas the slope for phenobarbital protons became discontinuous at about 10 degrees C above the T(g). Even at temperatures below its T(g), the spin-spin relaxation process of nifedipine could be described by the sum of its Gaussian relaxation, which is characteristic of solid protons, and its Lorentzian relaxation, which is characteristic of protons with higher mobility. In contrast, no Lorentzian relaxation was observed for phenobarbital or flopropione at temperatures below their T(g). These results also suggest that nifedipine has higher molecular mobility than phenobarbital and flopropione at temperatures below T(g). The faster crystallization of nifedipine than that of phenobarbital or flopropione observed at temperatures below its T(g) may be partly ascribed to its higher molecular mobility at these temperatures.

  4. Interdomain orientation of cardiac troponin C characterized by paramagnetic relaxation enhancement NMR reveals a compact state.

    Science.gov (United States)

    Cordina, Nicole M; Liew, Chu Kong; Gell, David A; Fajer, Piotr G; Mackay, Joel P; Brown, Louise J

    2012-09-01

    Cardiac troponin C (cTnC) is the calcium binding subunit of the troponin complex that triggers the thin filament response to calcium influx into the sarcomere. cTnC consists of two globular EF-hand domains (termed the N- and C-domains) connected by a flexible linker. While the conformation of each domain of cTnC has been thoroughly characterized through NMR studies involving either the isolated N-domain (N-cTnC) or C-domain (C-cTnC), little attention has been paid to the range of interdomain orientations possible in full-length cTnC that arises as a consequence of the flexibility of the domain linker. Flexibility in the domain linker of cTnC is essential for effective regulatory function of troponin. We have therefore utilized paramagnetic relaxation enhancement (PRE) NMR to assess the interdomain orientation of cTnC. Ensemble fitting of our interdomain PRE measurements reveals that isolated cTnC has considerable interdomain flexibility and preferentially adopts a bent conformation in solution, with a defined range of relative domain orientations.

  5. NMR studies of metalloproteins

    OpenAIRE

    Li, H; H. Sun

    2011-01-01

    Metalloproteins represent a large share of the proteomes, with the intrinsic metal ions providing catalytic, regulatory, and structural roles critical to protein functions. Structural characterization of metalloproteins and identification of metal coordination features including numbers and types of ligands and metal-ligand geometry, and mapping the structural and dynamic changes upon metal binding are significant for understanding biological functions of metalloproteins. NMR spectroscopy has...

  6. Measurement of interfacial area from NMR time dependent diffusion and relaxation measurements.

    Science.gov (United States)

    Fleury, M

    2017-09-07

    The interfacial area between two immiscible phases in porous media is an important parameter for describing and predicting 2 phase flow. Although present in several models, experimental investigations are sparse due to the lack of appropriate measurement techniques. We propose two NMR techniques for the measurement of oil-water interfacial area: (i) a time dependent NMR diffusion technique applicable in static conditions, similar to those used for the measurement of the solid specific surface of a porous media, and (ii) a fast relaxation technique applicable in dynamic conditions while flowing, based on an interfacial relaxation mechanism induced by the inclusion of paramagnetic salts in the water phase. For dodecane relaxing on doped water, we found an oil interfacial relaxivity of 1.8μm/s, large enough to permit the measurement of specific interfacial surface as small as 1000cm(2)/cm(3). We demonstrate both NMR techniques in drainage followed by imbibition, in a model porous media with a narrow pore size distribution. While flowing, we observe that the interfacial area is larger in imbibition than in drainage, implying a different organization of the oil phase. In a carbonate sample with a wide pore size distribution, we evidence the gradual invasion of the smallest pores as the oil-water pressure difference is increased. Copyright © 2017. Published by Elsevier Inc.

  7. Study of relaxation times of nanocomposites of starch/montmorillonite employing low field NMR; Estudo dos tempos de relaxacao de nanocompositos de amido e argila montmorilonita por RMN de baixo campo

    Energy Technology Data Exchange (ETDEWEB)

    Brito, Luciana M.; Tavares, Maria Ines B. [Universidade Federal do Rio de Janeiro, Instituto de Macromoleculas Professora Eloisa Mano, Rio de Janeiro, RJ (Brazil)

    2011-07-01

    Due to its various applications and features, especially in therapies for controlled release of pharmaceuticals, polymers are among the most widely used excipients in pharmaceutical technology. One of the most promising nanocomposites is formed from organic polymer and inorganic clay minerals. Nanocomposites of starch/montmorillonite were prepared employing solution intercalation and characterized by proton spin-lattice relaxation time, through NMR relaxometry. The characterization of nanocomposites was done by X-ray diffraction and by nuclear magnetic resonance. The results showed that nanostructured films were obtained by intercalation from solution. Furthermore, the use of low field NMR, T1H, provided more precise information about the movement of materials, being complementary to the results obtained by X-ray diffraction. (author)

  8. Motions and entropies in proteins as seen in NMR relaxation experiments and molecular dynamics simulations.

    Science.gov (United States)

    Allnér, Olof; Foloppe, Nicolas; Nilsson, Lennart

    2015-01-22

    Molecular dynamics simulations of E. coli glutaredoxin1 in water have been performed to relate the dynamical parameters and entropy obtained in NMR relaxation experiments, with results extracted from simulated trajectory data. NMR relaxation is the most widely used experimental method to obtain data on dynamics of proteins, but it is limited to relatively short timescales and to motions of backbone amides or in some cases (13)C-H vectors. By relating the experimental data to the all-atom picture obtained in molecular dynamics simulations, valuable insights on the interpretation of the experiment can be gained. We have estimated the internal dynamics and their timescales by calculating the generalized order parameters (O) for different time windows. We then calculate the quasiharmonic entropy (S) and compare it to the entropy calculated from the NMR-derived generalized order parameter of the amide vectors. Special emphasis is put on characterizing dynamics that are not expressed through the motions of the amide group. The NMR and MD methods suffer from complementary limitations, with NMR being restricted to local vectors and dynamics on a timescale determined by the rotational diffusion of the solute, while in simulations, it may be difficult to obtain sufficient sampling to ensure convergence of the results. We also evaluate the amount of sampling obtained with molecular dynamics simulations and how it is affected by the length of individual simulations, by clustering of the sampled conformations. We find that two structural turns act as hinges, allowing the α helix between them to undergo large, long timescale motions that cannot be detected in the time window of the NMR dipolar relaxation experiments. We also show that the entropy obtained from the amide vector does not account for correlated motions of adjacent residues. Finally, we show that the sampling in a total of 100 ns molecular dynamics simulation can be increased by around 50%, by dividing the

  9. Some specific features of the NMR study of fluid flows

    Science.gov (United States)

    Davydov, V. V.

    2016-07-01

    Some specific features of studying fluid flows with a NMR spectrometer are considered. The consideration of these features in the NMR spectrometer design makes it possible to determine the relative concentrations of paramagnetic ions and measure the longitudinal and transverse relaxation times ( T 1 and T 2, respectively) in fluid flows with an error no larger than 0.5%. This approach allows one to completely avoid errors in determining the state of a fluid from measured relaxation constants T 1 and T 2, which is especially urgent when working with medical suspensions and biological solutions. The results of an experimental study of fluid flows are presented.

  10. Resonances in field-cycling NMR on molecular crystals. (reversible) Spin dynamics or (irreversible) relaxation?; Resonanzen in Field-Cycling-NMR an Molekuelkristallen. (reversible) Spindynamik oder (irreversible) Relaxation?

    Energy Technology Data Exchange (ETDEWEB)

    Tacke, Christian

    2015-07-01

    Multi spin systems with spin 1/2 nuclei and dipolar coupled quadrupolar nuclei can show so called ''quadrupolar dips''. There are two main reasons for this behavior: polarization transfer and relaxation. They look quite alike and without additional research cannot be differentiated easily in most cases. These two phenomena have quite different physical and theoretical backgrounds. For no or very slow dynamics, polarization transfer will take place, which is energy conserving inside the spin system. This effect can entirely be described using quantum mechanics on the spin system. Detailed knowledge about the crystallography is needed, because this affects the relevant hamiltonians directly. For systems with fast enough dynamics, relaxation takes over, and the energy flows from the spin system to the lattice; thus a more complex theoretical description is needed. This description has to include a dynamic model, usually in the form of a spectral density function. Both models should include detailed modelling of the complete spin system. A software library was developed to be able to model complex spin systems. It allows to simulate polarization transfer or relaxation effects. NMR measurements were performed on the protonic conductor K{sub 3}H(SO{sub 4}){sub 2}. A single crystal shows sharp quadrupolar dips at room temperature. Dynamics could be excluded using relaxation measurements and literature values. Thus, a polarization transfer analysis was used to describe those dips with good agreement. As a second system, imidazolium based molecular crystals were analyzed. The quadrupolar dips were expected to be caused by polarization transfer; this was carefully analyzed and found not to be true. A relaxation based analysis shows good agreement with the measured data in the high temperature area. It leverages a two step spectral density function, which indicates two distinct dynamic processes happening in this system.

  11. The generalized Phillips-Twomey method for NMR relaxation time inversion.

    Science.gov (United States)

    Gao, Yang; Xiao, Lizhi; Zhang, Yi; Xie, Qingming

    2016-10-01

    The inversion of NMR relaxation time involves the Fredholm integral equation of the first kind. Due to its ill-posedness, numerical solutions to this type of equations are often found much less accurate and bear little resemblance to the true solution. There has been a strong interest in finding a well-posed method for this ill-posed problem since 1950s. In this paper, we prove the existence, the uniqueness, the stability and the convergence of the generalized Phillips-Twomey regularization method for solving this type of equations. Numerical simulations and core analyses arising from NMR transverse relaxation time inversion are conducted to show the effectiveness of the generalized Phillips-Twomey method. Both the simulation results and the core analyses agree well with the model and the realities.

  12. NMR Study of Water Distribution inside Tomato Cells: Effects of Water Stress

    OpenAIRE

    Musse, M.; Cambert, M.; Mariette, F.

    2010-01-01

    Tomato pericarp tissue was studied by low-field nuclear magnetic res-onance (NMR) relaxometry. Two kinds of experiments were performed to inves-tigate the correlation between multi-exponential NMR relaxation and the subcellular compartments. The longitudinal (T 1 ) versus transverse (T 2 ) relaxation times were first measured on fresh samples and then the transverse relaxation time was measured on samples exposed to water stress. Four signal components were found in all experiments. The resul...

  13. Application of chemometrics to low-field H-1 NMR relaxation data of intact fish flesh

    DEFF Research Database (Denmark)

    Jepsen, Signe Munk; Pedersen, H.T.; Engelsen, S.B.

    1999-01-01

    and subsequently analysed for oil or water content by standard chemical methods. In a second experiment, 58 differently thawed cod (Gadus morhua) samples were measured by NMR and subsequently analysed for water-holding capacity. Correlations between chemical data and NMR data were evaluated using partial least...... squares (PLS) regression on complete relaxation curves and compared with conventional regression models on exponential fitting parameters. Predictions on an independent test set were superior for the PLS regression models, with optimal prediction errors of 12 g kg(-1), 6 g kg(-1) and 3.9% for oil...... and water content in fresh salmon flesh and water-holding capacity in thawed cod flesh respectively. Thus rapid, non-invasive low- field NMR can be used to simultaneously determine both oil and water content of fish flesh. Furthermore, it can predict water- holding capacity of cod flesh, with an R-2 of 0...

  14. Ultrafast NMR T1 relaxation measurements: probing molecular properties in real time.

    Science.gov (United States)

    Smith, Pieter E S; Donovan, Kevin J; Szekely, Or; Baias, Maria; Frydman, Lucio

    2013-09-16

    The longitudinal relaxation properties of NMR active nuclei carry useful information about the site-specific chemical environments and about the mobility of molecular fragments. Molecular mobility is in turn a key parameter reporting both on stable properties, such as size, as well as on dynamic ones, such as transient interactions and irreversible aggregation. In order to fully investigate the latter, a fast sampling of the relaxation parameters of transiently formed molecular species may be needed. Nevertheless, the acquisition of longitudinal relaxation data is typically slow, being limited by the requirement that the time for which the nucleus relaxes be varied incrementally until a complete build-up curve is generated. Recently, a number of single-shot-inversion-recovery methods have been developed capable of alleviating this need; still, these may be challenged by either spectral resolution restrictions or when coping with very fast relaxing nuclei. Here, we present a new experiment to measure the T1s of multiple nuclear spins that experience fast longitudinal relaxation, while retaining full high-resolution chemical shift information. Good agreement is observed between T1s measured with conventional means and T1s measured using the new technique. The method is applied to the real-time investigation of the reaction between D-xylose and sodium borate, which is in turn elucidated with the aid of ancillary ultrafast and conventional 2D TOCSY measurements. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Determination of protein rotational correlation time from NMR relaxation data at various solvent viscosities

    Energy Technology Data Exchange (ETDEWEB)

    Korchuganov, Denis S.; Gagnidze, Ivan E.; Tkach, Elena N.; Schulga, Alexey A.; Kirpichnikov, Mikhail P.; Arseniev, Alexander S. [Russian Academy of Sciences, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry (Russian Federation)], E-mail: aars@nmr.ru

    2004-12-15

    An accurate determination of the overall rotation of a protein plays a crucial role in the investigation of its internal motions by NMR. In the present work, an innovative approach to the determination of the protein rotational correlation time {tau}{sub R} from the heteronuclear relaxation data is proposed. The approach is based on a joint fit of relaxation data acquired at several viscosities of a protein solution. The method has been tested on computer simulated relaxation data as compared to the traditional {tau}{sub R} determination method from T{sub 1}/T{sub 2} ratio. The approach has been applied to ribonuclease barnase from Bacillus amyloliquefaciens dissolved in an aqueous solution and deuterated glycerol as a viscous component. The resulting rotational correlation time of 5.56 {+-} 0.01 ns and other rotational diffusion tensor parameters are in good agreement with those determined from T{sub 1}/T{sub 2} ratio.

  16. DIRECT MEASUREMENT OF TRANSVERSE RELAXATION TIME OF INTERMOLECULAR MULTIPLE QUANTUM COHERENCES IN NMR

    Institute of Scientific and Technical Information of China (English)

    ZHENG SHAO-KUAN; CHEN ZHONG; CHEN ZHI-WEI; ZHONG JIAN-HUI

    2001-01-01

    A one-dimensional NMR method is presented for measuring the transverse relaxation time, T2,n, of intermolecular multiple quantum coherences (IMQCs) of coherence order n in highly polarized spin systems. The pulse sequence proposed in this paper effectively suppresses the effects of radiation damping, molecular diffusion, inhomogeneity of magnetic field, and variations of dipolar correlation distance, all of which may affect quantitation of T2,n. This pulse sequence can be used to measure not only IMQC transverse relaxation time T2,n(n > 1) quickly and directly, but also the conventional transverse relaxation time. Experimental results demonstrate that the quantitative relationship between T2,n(n≥1) and T2 is T2,n≈T2/n. These results will be helpful for understanding the fundamental properties and mechanisms of IMQCs.

  17. Acceleration of natural-abundance solid-state MAS NMR measurements on bone by paramagnetic relaxation from gadolinium-DTPA

    Science.gov (United States)

    Mroue, Kamal H.; Zhang, Rongchun; Zhu, Peizhi; McNerny, Erin; Kohn, David H.; Morris, Michael D.; Ramamoorthy, Ayyalusamy

    2014-07-01

    Reducing the data collection time without affecting the signal intensity and spectral resolution is one of the major challenges for the widespread application of multidimensional nuclear magnetic resonance (NMR) spectroscopy, especially in experiments conducted on complex heterogeneous biological systems such as bone. In most of these experiments, the NMR data collection time is ultimately governed by the proton spin-lattice relaxation times (T1). For over two decades, gadolinium(III)-DTPA (Gd-DTPA, DTPA = Diethylene triamine pentaacetic acid) has been one of the most widely used contrast-enhancement agents in magnetic resonance imaging (MRI). In this study, we demonstrate that Gd-DTPA can also be effectively used to enhance the longitudinal relaxation rates of protons in solid-state NMR experiments conducted on bone without significant line-broadening and chemical-shift-perturbation side effects. Using bovine cortical bone samples incubated in different concentrations of Gd-DTPA complex, the 1H T1 values were calculated from data collected by 1H spin-inversion recovery method detected in natural-abundance 13C cross-polarization magic angle spinning (CPMAS) NMR experiments. Our results reveal that the 1H T1 values can be successfully reduced by a factor of 3.5 using as low as 10 mM Gd-DTPA without reducing the spectral resolution and thus enabling faster data acquisition of the 13C CPMAS spectra. These results obtained from 13C-detected CPMAS experiments were further confirmed using 1H-detected ultrafast MAS experiments on Gd-DTPA doped bone samples. This approach considerably improves the signal-to-noise ratio per unit time of NMR experiments applied to bone samples by reducing the experimental time required to acquire the same number of scans.

  18. An NMR study of adsorbed helium films

    Science.gov (United States)

    Kent, Anthony Joseph

    The properties of sub-monolayer Helium-3 films adsorbed on two totally different but planar substrates, Mylar† film and exfoliated graphite have been studied using NMR. The nuclear magnetic relaxation times T1 and T 2 have been measured as functions of fractional monolayer completion, temperature, substrate plane orientation and Larmor frequency using a specially designed and constructed NMR spectrometer system. The results obtained with a Mylar film substrate are consistent3with the formation of patches of solid 3He at regions of preferential adsorption on the substrate. Measurements of T2 m very low coverage 3He films on exfoliated graphite also indicate that the adsorbate forms areas of relatively high density solid, in agreement with the thermodynamic analysis of Elgin and Goodstein. Finally, detailed measurements of T2 as a function of all of the above parameters at low areal densities will help us to characterise the relaxation processes for the fluid phase of 33He on exfoliated graphite. †Mylar is the tradename of poly(ethelene-terephthalate) film, marketed by Du Pont.

  19. NMR Studies of Cartilage Dynamics, Diffusion, Degradation

    Science.gov (United States)

    Huster, Daniel; Schiller, Jurgen; Naji, Lama; Kaufmann Jorn; Arnold, Klaus

    An increasing number of people is suffering from rheumatic diseases, and, therefore, methods of early diagnosis of joint degeneration are urgently required. For their establishment, however, an improved knowledge about the molecular organisation of cartilage would be helpful. Cartilage consists of three main components: Water, collagen and chondroitin sulfate (CS) that is (together with further polysaccharides and proteins) a major constituent of the proteoglycans of cartilage. 1H and 13C MAS (magic-angle spinning) NMR (nuclear magnetic resonance) opened new perspectives for the study of the macromolecular components in cartilage. We have primarily studied the mobilities of CS and collagen in bovine nasal and pig articular cartilage (that differ significantly in their collagen/polysaccharide content) by measuring 13C NMR relaxation times as well as the corresponding 13C CP (cross polarisation) MAS NMR spectra. These data clearly indicate that the mobility of cartilage macromolecules is broadly distributed from almost completely rigid (collagen) to highly mobile (polysaccharides), which lends cartilage its mechanical strength and shock-absorbing properties.

  20. Theory of nonrigid rotational motion applied to NMR relaxation in RNA.

    Science.gov (United States)

    Emani, Prashant S; Olsen, Gregory L; Varani, Gabriele; Drobny, Gary P

    2011-11-10

    Solution NMR spectroscopy can elucidate many features of the structure and dynamics of macromolecules, yet relaxation measurements, the most common source of experimental information on dynamics, can sample only certain ranges of dynamic rates. A complete characterization of motion of a macromolecule thus requires the introduction of complementary experimental approaches. Solid-state NMR spectroscopy successfully probes the time scale of nanoseconds to microseconds, a dynamic window where solution NMR results have been deficient, and probes conditions where the averaging effects of rotational diffusion of the molecule are absent. Combining the results of the two distinct techniques within a single framework provides greater insight into dynamics, but this task requires the common interpretation of results recorded under very different experimental conditions. Herein, we provide a unified description of dynamics that is robust to the presence of large-scale conformational exchange, where the diffusion tensor of the molecule varies on a time scale comparable to rotational diffusion in solution. We apply this methodology to the HIV-1 TAR RNA molecule, where conformational rearrangements are both substantial and functionally important. The formalism described herein is of greater generality than earlier combined solid-state/solution NMR interpretations, if detailed molecular structures are available, and can offer a more complete description of RNA dynamics than either solution or solid-state NMR spectroscopy alone.

  1. NMR spin relaxation in proteins: The patterns of motion that dissipate power to the bath

    Energy Technology Data Exchange (ETDEWEB)

    Shapiro, Yury E., E-mail: eva.meirovitch@biu.ac.il, E-mail: yuryeshapiro@gmail.com; Meirovitch, Eva, E-mail: eva.meirovitch@biu.ac.il, E-mail: yuryeshapiro@gmail.com [The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900-02 (Israel)

    2014-04-21

    We developed in recent years the two-body coupled-rotator slowly relaxing local structure (SRLS) approach for the analysis of NMR relaxation in proteins. The two bodies/rotators are the protein (diffusion tensor D{sub 1}) and the spin-bearing probe, e.g., the {sup 15}N−{sup 1}H bond (diffusion tensor, D{sub 2}), coupled by a local potential (u). A Smoluchowski equation is solved to yield the generic time correlation functions (TCFs), which are sums of weighted exponentials (eigenmodes). By Fourier transformation one obtains the generic spectral density functions (SDFs) which underlie the experimental relaxation parameters. The typical paradigm is to characterize structural dynamics in terms of the best-fit values of D{sub 1}, D{sub 2}, and u. Additional approaches we pursued employ the SRLS TCFs, SDFs, or eigenmodes as descriptors. In this study we develop yet another perspective. We consider the SDF as function of the angular velocity associated with the fluctuating fields underlying NMR relaxation. A parameter called j-fraction, which represents the relative contribution of eigenmode, i, to a given value of the SDF function at a specific frequency, ω, is defined. j-fraction profiles of the dominant eigenmodes are derived for 0 ≤ ω ≤ 10{sup 12} rad/s. They reveal which patterns of motion actuate power dissipation at given ω-values, what are their rates, and what is their relative contribution. Simulations are carried out to determine the effect of timescale separation, D{sub 1}/D{sub 2}, axial potential strength, and local diffusion axiality. For D{sub 1}/D{sub 2} ≤ 0.01 and strong local potential of 15 k{sub B}T, power is dissipated by global diffusion, renormalized (by the strong potential) local diffusion, and probe diffusion on the surface of a cone (to be called cone diffusion). For D{sub 1}/D{sub 2} = 0.1, power is dissipated by mixed eigenmodes largely of a global-diffusion-type or cone-diffusion-type, and a nearly bare renormalized

  2. Manganese-55 NMR and relaxation in single crystals of manganese(12)-Ac and analogs

    Science.gov (United States)

    Harter, Andrew

    This dissertation presents the first single crystal 55Mn NMR characterization of three compounds related to Mn12-acetate [Mn12O12(O2CCH3)16(H 2O)4]·2CH3COOH·4H2O (henceforth Mn12-Ac) that have come to be known as Single-Molecule Magnets (SMMs). This study was undertaken because they exhibit novel phenomena such as quantum mechanical tunneling of their magnetization (QTM), the origin of which is still not fully understood, and also because they have the potential to form elements of magnetic memory storage at the molecular dimensions. The investigations herein involve studies related to both the bonding as well as spin-dynamics in these compounds to much higher precision than in earlier work. These experiments were made possible by the design of a high frequency goniometer probe and a 3He temperature facility. The first single crystal NMR of any Mn12-based molecule was conducted on [Mn12O12(O2CCH2Br) 16(H2O)4]·4CH2Cl2 (Mn12-BrAc). Its 55Mn NMR spectrum, field dependence, angular dependence, and spin-lattice relaxation time (T 1) measurements were conducted. Most importantly, data are presented that (a) confirm the alteration of the magnetic core of these molecules when the samples are crushed into powder (a practice used in earlier studies), (b) show the presence of transverse hyperfine fields at the nuclear site, and (c) do not yield any evidence of temperature independent relaxation below 1 K, suggesting that QTM is not the dominant relaxation mechanism at these temperatures, in contrast to earlier studies. Data from single crystals of Mn12-Ac, the most studied SMM, concur with previous x-ray findings in that isomers are present. Such detailed information was not obtainable with powder samples. T 1-1 measurements over 400 mK--1 K indicate the existence of an energy barrier, in this case ˜1.65 K, which does not fit the current understanding of the electronic energy diagram. This value supports an earlier, yet unexplained observation of such a level by inelastic

  3. NMR Relaxation and Diffusion in Polymerized Microemulsions of HEMA and MMA

    Science.gov (United States)

    von Meerwall, E.; Chandran, S.; Slivka, J.; Lopina, S.; Cheung, M.

    2002-10-01

    In an effort to develop a class of materials for use in controlled drug delivery via implantation, we have used proton NMR T2 relaxation and pulsed-field-gradient diffusion (D) measurements to study bicontinuous microemulsions formed with methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA), polymerized and crosslinked with 4 wt. percent ethylene glycol dimethacrylate, in the presence of water containing ten percent surfactant, either the inert sodium alkyl sulfate or the polymerizable TREM-LF-40. Measurements were made at 50 deg. C over the full two-phase range (e. g., 30 to 96 percent aqueous, depending on HEMA/MMA ratio). We identify a trimodal T2 spectrum with components attributable to the semi-glassy network, adsorbed surfactant and ingested water, and the interstitial aqueous phase. In the latter, two distinct D rates are due to free water and dissolved surfactant; specimens are permeable to both. Component intensity ratios are non-monotonic in aqueous content. Results suggest a wide range of pore sizes and complex interactions between the mobile molecules and the network surfaces, pores, and swellable bulk. Surfactant reactivity seems to play a minor role. Results of other characterizations complement and support these findings.

  4. Interactions of acetylcholinesterase with salvianolic acid B and rosmarinic acid from Salvia miltiorhiza water extract investigated by NMR relaxation rate

    Institute of Scientific and Technical Information of China (English)

    Guo Wei Yin; Yi Ming Li; Wei Wei; Shan Hao Jiang; Da Yuan Zhu; Wei Hong Du

    2008-01-01

    In order to understand whether the ameliorating effect on old ages memory disorder by the root of Salvia miltiorhiza is related to the acetylcholinesterase (AChE) inhibition, two main ingredients, salvianolic acid B (1) and rosmarinic acid (2), which were isolated from S. Miltiorhiza water extract, were investigated in vitro by NMR relaxation rate in this work. The results showed that the proton selective relaxation rates and the molecular rotational correlation time of proton pairs for compounds 1 and 2 increased significantly by adding of AChE in mixing solution. The study reveals that the two compounds might bind to the enzyme and have AChE inhibitory effect, which could contribute to the ameliorating effect at some extent on old ages memory disorder.

  5. Microscopic insights into the NMR relaxation-based protein conformational entropy meter.

    Science.gov (United States)

    Kasinath, Vignesh; Sharp, Kim A; Wand, A Joshua

    2013-10-09

    Conformational entropy is a potentially important thermodynamic parameter contributing to protein function. Quantitative measures of conformational entropy are necessary for an understanding of its role but have been difficult to obtain. An empirical method that utilizes changes in conformational dynamics as a proxy for changes in conformational entropy has recently been introduced. Here we probe the microscopic origins of the link between conformational dynamics and conformational entropy using molecular dynamics simulations. Simulation of seven proteins gave an excellent correlation with measures of side-chain motion derived from NMR relaxation. The simulations show that the motion of methyl-bearing side chains are sufficiently coupled to that of other side chains to serve as excellent reporters of the overall side-chain conformational entropy. These results tend to validate the use of experimentally accessible measures of methyl motion--the NMR-derived generalized order parameters--as a proxy from which to derive changes in protein conformational entropy.

  6. NMR Dynamic Studies in Living Systems

    Institute of Scientific and Technical Information of China (English)

    闫永彬; 范明杰; 罗雪春; 张日清

    2002-01-01

    Nuclear magnetic resonance (NMR) can noninvasively monitor the intracellular concentrations and kinetic properties of numerous inorganic and organic compounds. These characteristics have made NMR a useful tool for dynamic studies of living systems. Applications of NMR to living systems have successfully extended to many areas, including studies of metabolic regulation, ion transport, and intracellular reaction rates in vivo. The major purpose of this review is to summarize the results that can be obtained by modern NMR techniques in living systems. With the advances of new techniques, NMR measurements of various nuclides have been performed for specific physiological purposes. Although some technical problems still remain and there are still discrepancies between NMR and traditional biochemical results, the abundant and unique information obtained from NMR spectra suggests that NMR will be more extensively applied in future studies of living systems. The fast development of these new techniques is providing many new NMR applications in living systems, as well as in structural biology.

  7. Histidine side-chain dynamics and protonation monitored by C-13 CPMG NMR relaxation dispersion

    DEFF Research Database (Denmark)

    Hass, M. A. S.; Yilmaz, A.; Christensen, Hans Erik Mølager;

    2009-01-01

    The use of C-13 NMR relaxation dispersion experiments to monitor micro-millisecond fluctuations in the protonation states of histidine residues in proteins is investigated. To illustrate the approach, measurements on three specifically C-13 labeled histidine residues in plastocyanin (PCu) from...... Anabaena variabilis (A.v.) are presented. Significant Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion is observed for C-13(epsilon 1) nuclei in the histidine imidazole rings of A.v. PCu. The chemical shift changes obtained from the CPMG dispersion data are in good agreement with those obtained from...... or other kinds of conformational changes of histidine side chains or their environment. Advantages and shortcomings of using the C-13(epsilon 1) dispersion experiments in combination with chemical shift titration experiments to obtain information on exchange dynamics of the histidine side chains...

  8. A subzero 1H NMR relaxation investigation of water dynamics in tomato pericarp.

    Science.gov (United States)

    Foucat, Loïc; Lahaye, Marc

    2014-09-01

    (1)H NMR relaxation times (T1 and T2) were measured at low field (0.47 T) in pericarp tissues of three tomato genotypes (Ferum, LA0147 and Levovil) at subzero temperature (-20 °C) and two ripening stages (mature green and red). The unfrozen water dynamics was characterised by two T1 and three T2 components. The relaxation time values and their associated relative populations allowed differentiating the ripening stage of only LA0147 and Levovil lines. But the three genotypes were unequivocally discriminated at the red ripe stage. The unfrozen water distribution was discussed in terms of specific interactions, especially with sugars, in relation with their osmoprotectant effects.

  9. On the reliability of NMR relaxation data analyses: a Markov Chain Monte Carlo approach.

    Science.gov (United States)

    Abergel, Daniel; Volpato, Andrea; Coutant, Eloi P; Polimeno, Antonino

    2014-09-01

    The analysis of NMR relaxation data is revisited along the lines of a Bayesian approach. Using a Markov Chain Monte Carlo strategy of data fitting, we investigate conditions under which relaxation data can be effectively interpreted in terms of internal dynamics. The limitations to the extraction of kinetic parameters that characterize internal dynamics are analyzed, and we show that extracting characteristic time scales shorter than a few tens of ps is very unlikely. However, using MCMC methods, reliable estimates of the marginal probability distributions and estimators (average, standard deviations, etc.) can still be obtained for subsets of the model parameters. Thus, unlike more conventional strategies of data analysis, the method avoids a model selection process. In addition, it indicates what information may be extracted from the data, but also what cannot.

  10. NMR longitudinal relaxation enhancement in metal halides by heteronuclear polarization exchange during magic-angle spinning.

    Science.gov (United States)

    Shmyreva, Anna A; Safdari, Majid; Furó, István; Dvinskikh, Sergey V

    2016-06-14

    Orders of magnitude decrease of (207)Pb and (199)Hg NMR longitudinal relaxation times T1 upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX2 (Me = Pb, Hg and X = Cl, Br, I). In lead(ii) halides, the most dramatic decrease of T1 relative to that in a static sample is in PbI2, while it is smaller but still significant in PbBr2, and not detectable in PbCl2. The effect is magnetic-field dependent but independent of the spinning speed in the range 200-15 000 Hz. The observed relaxation enhancement is explained by laboratory-frame heteronuclear polarization exchange due to crossing between energy levels of spin-1/2 metal nuclei and adjacent quadrupolar-spin halogen nuclei. The enhancement effect is also present in lead-containing organometal halide perovskites. Our results demonstrate that in affected samples, it is the relaxation data recorded under non-spinning conditions that characterize the local properties at the metal sites. A practical advantage of fast relaxation at slow MAS is that spectral shapes with orientational chemical shift anisotropy information well retained can be acquired within a shorter experimental time.

  11. Molecular dynamics simulation of spin-lattice NMR relaxation in poly-L-lysine dendrimers: manifestation of the semiflexibility effect.

    Science.gov (United States)

    Markelov, Denis A; Falkovich, Stanislav G; Neelov, Igor M; Ilyash, Maxim Yu; Matveev, Vladimir V; Lähderanta, Erkki; Ingman, Petri; Darinskii, Anatolii A

    2015-02-07

    NMR relaxation experiments are widely used to investigate the local orientation mobility in dendrimers. In particular, the NMR method allows one to measure the spin-lattice relaxation rate, 1/T1, which is connected with the orientational autocorrelation function (ACF) of NMR active groups. We calculate the temperature (Θ) and frequency (ω) dependences of the spin-lattice NMR relaxation rates for segments and NMR active CH2 groups in poly-L-lysine (PLL) dendrimers in water, on the basis of full-atomic molecular dynamics simulations. It is shown that the position of the maximum of 1/T1(ω) depends on the location of the segments inside the dendrimer. This dependence of the maximum is explained by the restricted flexibility of the dendrimer. Such behavior has been predicted recently by the analytical theory based on the semiflexible viscoelastic model. The simulated temperature dependences of 1/T1 for terminal and inner groups in PLL dendrimers of n = 2 and n = 4 generations dissolved in water are in good agreement with the NMR experimental data, which have been obtained for these systems previously by us. It is shown that in the case of PLL dendrimers, the traditional procedure of the interpretation of NMR experimental data - when smaller values of 1/T1 correspond to higher orientation mobility - is applicable to the whole accessible frequency interval only for the terminal groups. For the inner groups, this procedure is valid only at low frequencies.

  12. Measuring {sup 13}C{sup {beta}} chemical shifts of invisible excited states in proteins by relaxation dispersion NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lundstroem, Patrik [Linkoeping University, Molecular Biotechnology/IFM (Sweden); Lin Hong [Hospital for Sick Children, Molecular Structure and Function (Canada); Kay, Lewis E. [University of Toronto, Department of Medical Genetics (Canada)], E-mail: kay@pound.med.utoronto.ca

    2009-07-15

    A labeling scheme is introduced that facilitates the measurement of accurate {sup 13}C{sup {beta}} chemical shifts of invisible, excited states of proteins by relaxation dispersion NMR spectroscopy. The approach makes use of protein over-expression in a strain of E. coli in which the TCA cycle enzyme succinate dehydrogenase is knocked out, leading to the production of samples with high levels of {sup 13}C enrichment (30-40%) at C{sup {beta}} side-chain carbon positions for 15 of the amino acids with little {sup 13}C label at positions one bond removed ({approx}5%). A pair of samples are produced using [1-{sup 13}C]-glucose/NaH{sup 12}CO{sub 3} or [2-{sup 13}C]-glucose as carbon sources with isolated and enriched (>30%) {sup 13}C{sup {beta}} positions for 11 and 4 residues, respectively. The efficacy of the labeling procedure is established by NMR spectroscopy. The utility of such samples for measurement of {sup 13}C{sup {beta}} chemical shifts of invisible, excited states in exchange with visible, ground conformations is confirmed by relaxation dispersion studies of a protein-ligand binding exchange reaction in which the extracted chemical shift differences from dispersion profiles compare favorably with those obtained directly from measurements on ligand free and fully bound protein samples.

  13. Site-resolved 2H relaxation experiments in solid materials by global line-shape analysis of MAS NMR spectra

    Science.gov (United States)

    Lindh, E. L.; Stilbs, P.; Furó, I.

    2016-07-01

    We investigate a way one can achieve good spectral resolution in 2H MAS NMR experiments. The goal is to be able to distinguish between and study sites in various deuterated materials with small chemical shift dispersion. We show that the 2H MAS NMR spectra recorded during a spin-relaxation experiment are amenable to spectral decomposition because of the different evolution of spectral components during the relaxation delay. We verify that the results are robust by global least-square fitting of the spectral series both under the assumption of specific line shapes and without such assumptions (COmponent-REsolved spectroscopy, CORE). In addition, we investigate the reliability of the developed protocol by analyzing spectra simulated with different combinations of spectral parameters. The performance is demonstrated in a model material of deuterated poly(methacrylic acid) that contains two 2H spin populations with similar chemical shifts but different quadrupole splittings. In 2H-exchanged cellulose containing two 2H spin populations with very similar chemical shifts and quadrupole splittings, the method provides new site-selective information about the molecular dynamics.

  14. Miscibility of nifedipine and hydrophilic polymers as measured by (1)H-NMR spin-lattice relaxation.

    Science.gov (United States)

    Aso, Yukio; Yoshioka, Sumie; Miyazaki, Tamaki; Kawanishi, Tohru; Tanaka, Kazuyuki; Kitamura, Satoshi; Takakura, Asako; Hayashi, Takashi; Muranushi, Noriyuki

    2007-08-01

    The miscibility of a drug with excipients in solid dispersions is considered to be one of the most important factors for preparation of stable amorphous solid dispersions. The purpose of the present study was to elucidate the feasibility of (1)H-NMR spin-lattice relaxation measurements to assess the miscibility of a drug with excipients. Solid dispersions of nifedipine with the hydrophilic polymers poly(vinylpyrrolidone) (PVP), hydroxypropylmethylcellulose (HPMC) and alpha,beta-poly(N-5-hydroxypentyl)-L-aspartamide (PHPA) with various weight ratios were prepared by spray drying, and the spin-lattice relaxation decay of the solid dispersions in a laboratory frame (T(1) decay) and in a rotating frame (T(1rho) decay) were measured. T(1rho) decay of nifedipine-PVP solid dispersions (3 : 7, 5 : 5 and 7 : 3) was describable with a mono-exponential equation, whereas T(1rho) decay of nifedipine-PHPA solid dispersions (3 : 7, 4 : 6 and 5 : 5) was describable with a bi-exponential equation. Because a mono-exponential T(1rho) decay indicates that the domain sizes of nifedipine and polymer in solid dispersion are less than several nm, it is speculated that nifedipine is miscible with PVP but not miscible with PHPA. All the nifedipine-PVP solid dispersions studied showed a single glass transition temperature (T(g)), whereas two glass transitions were observed for the nifedipine-PHPA solid dispersion (3 : 7), thus supporting the above speculation. For nifedipine-HPMC solid dispersions (3 : 7 and 5 : 5), the miscibility of nifedipine and HPMC could not be determined by DSC measurements due to the lack of obviously evident T(g). In contrast, (1)H-NMR spin-lattice relaxation measurements showed that nifedipine and HPMC are miscible, since T(1rho) decay of the solid dispersions (3 : 7, 5 : 5 and 7 : 3) was describable with a mono-exponential equation. These results indicate that (1)H-NMR spin-lattice relaxation measurements are useful for assessing the miscibility of a drug and an

  15. NMR study of magnetism and superparamagnetism

    Science.gov (United States)

    Yuan, Shaojie

    The research described in this dissertation is concerned with two different types of magnetic materials. Both types of systems involve competing interactions between transition metal ions. New approaches involving magnetic resonance in the large hyperfine fields at nuclear sites have been developed. The interactions responsible for the properties that have been investigated in the materials studied are geometric frustration in an insulator and ferromagnetic and antiferromagnetic interactions in a metal alloy. Further details are given below. The extended kagome frustrated system YBaCo4O7 has 2D kagome and triangular lattices of Co ions stacked along the c-axis. Antiferromagnetic (AF) ordering accompanied by a structural transition has been reported in the literature. From a zero field (ZF) NMR single crystal rotation experiment, we have obtained the Co spin configurations for both the kagome and triangular layers. A 'spin-flop' configuration between the spins on the kagome layer and the spins on the triangular layer is indicated by our results. Our NMR findings are compared with neutron scattering results for this intriguing frustrated AF spin system. The non-stoichiometric oxygenated sister compound YBaCo4O7.1 has application potential for oxygen storage. While, its' magnetic properties are quite different from those of the stoichiometric compound, in spite of their similar structures of alternating kagome and triangular Co layers. Various techniques, including ZF NMR have been used to investigate the spin dynamics and spin configuration in a single crystal of YBaCo4O7.1. A magnetic transition at 80 K is observed, which is interpreted as the freezing out of spins in the triangular layers. At low temperatures (below 50 K), the spin dynamics persists and a fraction of spins in the kagome layers form a viscous spin liquid. Below 10 K, a glass-like spin structure forms and a large distribution of spin correlation times are suggested by nuclear spin lattice relaxation

  16. Histidine side-chain dynamics and protonation monitored by {sup 13}C CPMG NMR relaxation dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Hass, Mathias A. S. [Leiden University, Institute of Chemistry (Netherlands); Yilmaz, Ali [University of Copenhagen, Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences (Denmark); Christensen, Hans E. M. [Technical University of Denmark, Department of Chemistry (Denmark); Led, Jens J. [University of Copenhagen, Department of Chemistry (Denmark)], E-mail: led@kiku.dk

    2009-08-15

    The use of {sup 13}C NMR relaxation dispersion experiments to monitor micro-millisecond fluctuations in the protonation states of histidine residues in proteins is investigated. To illustrate the approach, measurements on three specifically {sup 13}C labeled histidine residues in plastocyanin (PCu) from Anabaena variabilis (A.v.) are presented. Significant Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion is observed for {sup 13}C{sup {epsilon}}{sup 1} nuclei in the histidine imidazole rings of A.v. PCu. The chemical shift changes obtained from the CPMG dispersion data are in good agreement with those obtained from the chemical shift titration experiments, and the CPMG derived exchange rates agree with those obtained previously from {sup 15}N backbone relaxation measurements. Compared to measurements of backbone nuclei, {sup 13}C{sup {epsilon}}{sup 1} dispersion provides a more direct method to monitor interchanging protonation states or other kinds of conformational changes of histidine side chains or their environment. Advantages and shortcomings of using the {sup 13}C{sup {epsilon}}{sup 1} dispersion experiments in combination with chemical shift titration experiments to obtain information on exchange dynamics of the histidine side chains are discussed.

  17. Dynamical theory of spin noise and relaxation - prospects for real time NMR measurements

    Science.gov (United States)

    Field, Timothy

    2014-03-01

    The dynamics of a spin system is usually calculated using the density matrix. However, the usual formulation in terms of the density matrix predicts that the signal will decay to zero, and does not address the stochastic dynamics of individual spins. Spin fluctuations are to be viewed as an intrinsic quantum mechanical property of such systems immersed in random magnetic environments, and are observed as ``spin noise'' in the absence of any radio frequency (RF) excitation. Using stochastic calculus we develop a dynamical theory of spin noise and relaxation whose origins lie in the component spin fluctuations. This entails consideration of random pure states for individual protons, and how these pure states are correctly combined when the density matrix is formulated. Both the lattice and the spins are treated quantum mechanically. Such treatment incorporates both the processes of spin-spin and (finite temperature) spin-lattice relaxation. Our results reveal the intimate connections between spin noise and conventional spin relaxation, in terms of a modified spin density (MSD), distinct from the density matrix, which is necessary to describe non-ensemble averaged properties of spin systems. With the prospect of ultra-fast digitization, the role of spin noise in real time parameter extraction for (NMR) spin systems, and the advantage over standard techniques, is of essential importance, especially for systems containing a small number of spins. In this presentation we outline prospects for harnessing the recent dynamical theory in terms of spin noise measurement, with attention to real time properties.

  18. Solution conformation and dynamics of a tetrasaccharide related to the Lewis{sup X} antigen deduced by NMR relaxation measurements

    Energy Technology Data Exchange (ETDEWEB)

    Poveda, Ana [Universidad Autonoma de Madrid, Servicio Interdepartamental de Investigacion (Spain); Asensio, Juan Luis; Martin-Pastor, Manuel; Jimenez-Barbero, Jesus [Instituto de Quimica Organica, CSIC, Grupo de Carbohidratos (Spain)

    1997-07-15

    {sup 1}H-NMR cross-relaxation rates and nonselective longitudinal relaxation times have been obtained at two magnetic fields (7.0 and 11.8 T) and at a variety of temperatures for the branched tetrasaccharide methyl 3-O-{alpha}-N-acetyl-galactosaminyl-{beta}-galactopyranosyl-(1{sup {yields}}4)[3-O-{alpha}-fucosyl] -glucopyranoside (1), an inhibitor of astrocyte growth. In addition, {sup 13}C-NMR relaxation data have also been recorded at both fields. The {sup 1}H-NMR relaxation data have been interpreted using different motional models to obtain proton-proton correlation times. The results indicate that the GalNAc and Fuc rings display more extensive local motion than the two inner Glc and Gal moieties, since those present significantly shorter local correlation times. The{sup 13}C-NMR relaxation parameters have been interpreted in terms of the Lipari-Szabo model-free approach. Thus, order parameters and internal motion correlation times have been deduced. As obtained for the{sup 1}H-NMR relaxation data, the two outer residues possess smaller order parameters than the two inner rings. Internal correlation times are in the order of 100 ps. The hydroxymethyl groups have also different behaviour,with the exocyclic carbon on the glucopyranoside unit showing the highestS{sup 2}. Molecular dynamics simulations using a solvated system have also been performed and internal motion correlation functions have been deduced from these calculations. Order parameters and interproton distances have been compared to those inferred from the NMR measurements. The obtained results are in fair agreement with the experimental data.

  19. Estimating the surface relaxivity as a function of pore size from NMR T2 distributions and micro-tomographic images

    Science.gov (United States)

    Benavides, Francisco; Leiderman, Ricardo; Souza, Andre; Carneiro, Giovanna; Bagueira, Rodrigo

    2017-09-01

    In the present work, we formulate and solve an inverse problem to recover the surface relaxivity as a function of pore size. The input data for our technique are the T2 distribution measurement and the micro-tomographic image of the rock sample under investigation. We simulate the NMR relaxation signal for a given surface relaxivity function using the random walk method and rank different surface relaxivity functions according to the correlation of the resulting simulated T2 distributions with the measured T2 distribution. The optimization is performed using genetic algorithms and determines the surface relaxivity function whose corresponding simulated T2 distribution best matches the measured T2 distribution. In the proposed methodology, pore size is associated with a number of collisions in the random walk simulations. We illustrate the application of the proposed method by performing inversions from synthetic and laboratory input data and compare the obtained results with those obtained using the uniform relaxivity assumption.

  20. Very short NMR relaxation times of anions in ionic liquids: new pulse sequence to eliminate the acoustic ringing.

    Science.gov (United States)

    Klimavicius, Vytautas; Gdaniec, Zofia; Balevicius, Vytautas

    2014-11-11

    NMR relaxation processes of anions were studied in two neat imidazolium-based room temperature ionic liquids (RTILs) 1-decyl-3-methyl-imidazolium bromide- and chloride. The spin-lattice and spin-spin relaxations of 81Br and 35Cl nuclei were found to be extremely fast due to very strong quadrupolar interactions. The determined relaxation rates are comparable with those observed in the solids or in some critical organic solute/water/salt systems. In order to eliminate the acoustic ringing of the probe-head during relaxation times measurements the novel pulse sequence has been devised. It is based on the conventional inversion recovery pulse sequence, however, instead of the last 90° pulse the subsequence of three 90° pulses applied along axes to fulfill the phase cycling condition is used. Using this pulse sequence it was possible to measure T1 for both studied nuclei. The viscosity measurements have been carried out and the rotational correlation times were calculated. The effective 35Cl quadrupolar coupling constant was found to be almost one order lower than that for 81Br, i.e. 1.8 MHz and 16.0 MHz, respectively. Taking into account the facts that the ratio of (Q(35Cl)/Q(81Br))2≈0.1 and EFG tensors on the anions are quite similar, analogous structural organizations are expected for both RTILs. The observed T1/T2 (1.27-1.44) ratios were found to be not sufficiently high to confirm the presence of long-living (on the time scale of ≥10(-8) s) mesoscopic structures or heterogeneities in the studied neat ionic liquids.

  1. Relationships between 1H NMR Relaxation Data and Some Technological Parameters of Meat: A Chemometric Approach

    Science.gov (United States)

    Brown, Robert J. S.; Capozzi, Francesco; Cavani, Claudio; Cremonini, Mauro A.; Petracci, Massimiliano; Placucci, Giuseppe

    2000-11-01

    In this paper chemometrics (ANOVA and PCR) is used to measure unbiased correlations between NMR spin-echo decays of pork M. Longissimus dorsi obtained through Carr-Purcell-Meiboom-Gill (CPMG) experiments at low frequency (20 MHz) and the values of 14 technological parameters commonly used to assess pork meat quality. On the basis of the ANOVA results, it is also found that the CPMG decays of meat cannot be best interpreted with a "discrete" model (i.e., by expanding the decays in a series of a discrete number of exponential components, each with a different transverse relaxation time), but rather with a "continuous" model, by which a continuous distribution of T2's is allowed. The latter model also agrees with literature histological results.

  2. Relationships between (1)H NMR relaxation data and some technological parameters of meat: a chemometric approach.

    Science.gov (United States)

    Brown, R J; Capozzi, F; Cavani, C; Cremonini, M A; Petracci, M; Placucci, G

    2000-11-01

    In this paper chemometrics (ANOVA and PCR) is used to measure unbiased correlations between NMR spin-echo decays of pork M. Longissimus dorsi obtained through Carr-Purcell-Meiboom-Gill (CPMG) experiments at low frequency (20 MHz) and the values of 14 technological parameters commonly used to assess pork meat quality. On the basis of the ANOVA results, it is also found that the CPMG decays of meat cannot be best interpreted with a "discrete" model (i.e., by expanding the decays in a series of a discrete number of exponential components, each with a different transverse relaxation time), but rather with a "continuous" model, by which a continuous distribution of T(2)'s is allowed. The latter model also agrees with literature histological results. Copyright 2000 Academic Press.

  3. General order parameter based correlation analysis of protein backbone motions between experimental NMR relaxation measurements and molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Qing; Shi, Chaowei [Hefei National Laboratory for Physical Sciences at The Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026 (China); Yu, Lu [Hefei National Laboratory for Physical Sciences at The Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026 (China); High Magnetic Field Laboratory, Chinese Academy of Science, Hefei, Anhui, 230031 (China); Zhang, Longhua [Hefei National Laboratory for Physical Sciences at The Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026 (China); Xiong, Ying, E-mail: yxiong73@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at The Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026 (China); Tian, Changlin, E-mail: cltian@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at The Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026 (China); High Magnetic Field Laboratory, Chinese Academy of Science, Hefei, Anhui, 230031 (China)

    2015-02-13

    Internal backbone dynamic motions are essential for different protein functions and occur on a wide range of time scales, from femtoseconds to seconds. Molecular dynamic (MD) simulations and nuclear magnetic resonance (NMR) spin relaxation measurements are valuable tools to gain access to fast (nanosecond) internal motions. However, there exist few reports on correlation analysis between MD and NMR relaxation data. Here, backbone relaxation measurements of {sup 15}N-labeled SH3 (Src homology 3) domain proteins in aqueous buffer were used to generate general order parameters (S{sup 2}) using a model-free approach. Simultaneously, 80 ns MD simulations of SH3 domain proteins in a defined hydrated box at neutral pH were conducted and the general order parameters (S{sup 2}) were derived from the MD trajectory. Correlation analysis using the Gromos force field indicated that S{sup 2} values from NMR relaxation measurements and MD simulations were significantly different. MD simulations were performed on models with different charge states for three histidine residues, and with different water models, which were SPC (simple point charge) water model and SPC/E (extended simple point charge) water model. S{sup 2} parameters from MD simulations with charges for all three histidines and with the SPC/E water model correlated well with S{sup 2} calculated from the experimental NMR relaxation measurements, in a site-specific manner. - Highlights: • Correlation analysis between NMR relaxation measurements and MD simulations. • General order parameter (S{sup 2}) as common reference between the two methods. • Different protein dynamics with different Histidine charge states in neutral pH. • Different protein dynamics with different water models.

  4. NMR studies of nucleic acid dynamics

    Science.gov (United States)

    Al-Hashimi, Hashim M.

    2013-12-01

    Nucleic acid structures have to satisfy two diametrically opposite requirements; on one hand they have to adopt well-defined 3D structures that can be specifically recognized by proteins; on the other hand, their structures must be sufficiently flexible to undergo very large conformational changes that are required during key biochemical processes, including replication, transcription, and translation. How do nucleic acids introduce flexibility into their 3D structure without losing biological specificity? Here, I describe the development and application of NMR spectroscopic techniques in my laboratory for characterizing the dynamic properties of nucleic acids that tightly integrate a broad set of NMR measurements, including residual dipolar couplings, spin relaxation, and relaxation dispersion with sample engineering and computational approaches. This approach allowed us to obtain fundamental new insights into directional flexibility in nucleic acids that enable their structures to change in a very specific functional manner.

  5. Functional dynamics of human FKBP12 revealed by methyl C-13 rotating frame relaxation dispersion NMR spectroscopy

    NARCIS (Netherlands)

    Brath, U; Akke, M; Yang, DW; Kay, LE; Mulder, FAA

    2006-01-01

    Transverse relaxation dispersion NMR spectroscopy can provide atom-specific information about time scales, populations, and the extent of structural reorganization in proteins under equilibrium conditions. A method is described that uses side-chain methyl groups as local reporters for conformational

  6. Functional dynamics of human FKBP12 revealed by methyl C-13 rotating frame relaxation dispersion NMR spectroscopy

    NARCIS (Netherlands)

    Brath, U; Akke, M; Yang, DW; Kay, LE; Mulder, FAA

    2006-01-01

    Transverse relaxation dispersion NMR spectroscopy can provide atom-specific information about time scales, populations, and the extent of structural reorganization in proteins under equilibrium conditions. A method is described that uses side-chain methyl groups as local reporters for conformational

  7. Sensitivity and resolution of two-dimensional NMR diffusion-relaxation measurements

    Science.gov (United States)

    Kausik, Ravinath; Hürlimann, Martin D.

    2016-09-01

    The performance of 2D NMR diffusion-relaxation measurements for fluid typing applications is analyzed. In particular, we delineate the region in the diffusion - relaxation plane that can be determined with a given gradient strength and homogeneity, and compare the performance of the single and double echo encoding with the stimulated echo diffusion encoding. We show that the diffusion editing based approach is able to determine the diffusion coefficient only if the relaxation time T2 exceeds a cutoff value T2,cutoff , that scales like T2,cutoff ∝g - 2 / 3D - 1 / 3 . For stimulated echo encoding, the optimal diffusion encoding times (Td and δ), that provide the best diffusion sensitivity, rely only on the T1 /T2 ratios and not on the diffusion coefficients of the fluids or the applied gradient strengths. Irrespective of T1 , for high enough gradients (i.e. when γ2g2 DT23 >102), the Hahn echo based encoding is superior to encoding based on the stimulated echo. For weaker gradients, the stimulated echo is superior only if the T1 /T2 ratio is much larger than 1. For single component systems, the diffusion sensitivity is not adversely impacted by the uniformity of the gradients and the diffusion distributions can be well measured. The presence of non-uniform gradients can affect the determination of the diffusion distributions when you have two fluids of comparable T2 . In such situations the effective single component diffusion coefficient is always closer to the geometric mean diffusion coefficient of the two fluids.

  8. Wide-ranging molecular mobilities of water in active pharmaceutical ingredient (API) hydrates as determined by NMR relaxation times.

    Science.gov (United States)

    Yoshioka, Sumie; Aso, Yukio; Osako, Tsutomu; Kawanishi, Toru

    2008-10-01

    In order to examine the possibility of determining the molecular mobility of hydration water in active pharmaceutical ingredient (API) hydrates by NMR relaxation measurement, spin-spin relaxation and spin-lattice relaxation were measured for the 11 API hydrates listed in the Japanese Pharmacopeia using pulsed (1)H-NMR. For hydration water that has relatively high mobility and shows Lorentzian decay, molecular mobility as determined by spin-spin relaxation time (T(2)) was correlated with ease of evaporation under both nonisothermal and isothermal conditions, as determined by DSC and water vapor sorption isotherm analysis, respectively. Thus, T(2) may be considered a useful parameter which indicates the molecular mobility of hydration water. In contrast, for hydration water that has low mobility and shows Gaussian decay, T(2) was found not to correlate with ease of evaporation under nonisothermal conditions, which suggests that in this case, the molecular mobility of hydration water was too low to be determined by T(2). A wide range of water mobilities was found among API hydrates, from low mobility that could not be evaluated by NMR relaxation time, such as that of the water molecules in pipemidic acid hydrate, to high mobility that could be evaluated by this method, such as that of the water molecules in ceftazidime hydrate. (c) 2008 Wiley-Liss, Inc. and the American Pharmacists Association

  9. 1H NMR relaxometry, viscometry, and PFG NMR studies of magnetic and nonmagnetic ionic liquids.

    Science.gov (United States)

    Daniel, Carla I; Chávez, Fabián Vaca; Feio, Gabriel; Portugal, Carla A M; Crespo, João G; Sebastião, Pedro J

    2013-10-03

    A study is presented of the molecular dynamics and of the viscosity in pure [Aliquat][Cl] ionic liquid and in a mixture of [Aliquat][Cl] with 1% (v/v) of [Aliquat][FeCl4]. The (1)H spin-lattice relaxation rate, R1, was measured by NMR relaxometry between 8 and 300 MHz. In addition, the translation self-diffusion, D, was measured by pulse field gradient NMR. The ILs' viscosity was measured as a function of an applied magnetic field, B, and it was found that the IL mixture's viscosity decreased with increasing B, whereas the [Aliquat][Cl] viscosity is independent of B. All experimental results were analyzed taking into account the viscosity's magnetic field dependence, assuming a modified Stokes-Einstein diffusion/viscosity relation. The main difference between the relaxation mechanisms responsible for R1 in the two IL systems is related to the additional paramagnetic relaxation contribution associated with the (1)H spins-[FeCl4] paramagnetic moments' interactions. Cross-relaxation cusps in the R1 dispersion, associated with (35)Cl and (1)H nuclear spins in the IL systems, were detected. The R1 model considered was successfully fitted to the experimental results, and it was possible to estimate the value of D at zero field in the case of the IL mixture which was consistent with the values of D measured at 7 and 14.1 T and with the magnetic field dependence estimated from the viscosity measurements. It was observed that a small concentration of [Aliquat][FeCl4] in the [Aliquat][Cl] was enough to produce a "superparamagnetic"-like effect and to change the IL mixture's molecular dynamics and viscosity and to allow for their control with an external magnetic field.

  10. NMR studies of isotopically labeled RNA

    Energy Technology Data Exchange (ETDEWEB)

    Pardi, A. [Univ. of Colorado, Boulder, CO (United States)

    1994-12-01

    In summary, the ability to generate NMR quantities of {sup 15}N and {sup 13}C-labeled RNAs has led to the development of heteronuclear multi-dimensional NMR techniques for simplifying the resonance assignment and structure determination of RNAs. These methods for synthesizing isotopically labeled RNAs are only several years old, and thus there are still relatively few applications of heteronuclear multi-dimensional NMR techniques to RNA. However, given the critical role that RNAs play in cellular function, one can expect to see an increasing number of NMR structural studies of biologically active RNAs.

  11. Effect of spatial spin modulation on relaxation and NMR frequencies of sup 5 sup 7 Fe nuclei in ferroelectric antiferromagnetic BiFeO sub 3

    CERN Document Server

    Zalessky, A V; Zvezdin, A K; Gippius, A A; Morozova, E N; Khozeev, D F; Bush, A S; Pokatilov, V S

    2002-01-01

    The NMR spectra on the iron nuclei in the BiFeO sub 3 antiferromagnetic sample enriched by the sup 5 sup 7 Fe (95.43%) with the spatially-modulated magnetic structure are studied. It is established that the cycloid-type spin modulation in the BiFeO sub 3 produces spatial modulation of the nuclear spin-spin relaxation velocity and leads to the spectral nonuniform widening of the NMR local line. It is determined also that the local magnetic moments of the iron ions on various cycloid sections differently depend on temperature which testifies to different character of the spin waves excitation. The analogy of the experimental results with the NMR regularities in the Bloch wall is discussed

  12. The mechanism of paramagnetic NMR relaxation produced by Mn(II): role of orthorhombic and fourth-order zero field splitting terms.

    Science.gov (United States)

    Sharp, Robert

    2008-10-14

    Mn(II) is a spin-5/2 paramagnetic ion that mediates a characteristically large NMR paramagnetic relaxation enhancement (NMR-PRE) of nuclear spins in solution. In the range of high magnetic field strengths (above about 0.3 T), where the electronic Zeeman interaction provides the largest term of the electron spin Hamiltonian, NMR relaxation mechanism is well understood. In the lower field range, the physical picture is more complex because of the presence in the spin Hamiltonian of zero field splitting (ZFS) terms that are comparable to or greater than the Zeeman term. This work describes a systematic study of the relaxation mechanism in the low field range, particularly aspects involving the dependence of NMR-PRE on the orthorhombic (E) and fourth-order (a(q)(4), q=0,2,4) ZFS tensor components. It is shown that the fourfold (a(4)(4)) and twofold (a(2)(4)) fourth-order components exert large orientation-dependent influences on the NMR-PRE. Thus, fourth-order terms with magnitudes equal to only a few percent of the quadratic ZFS terms (D,E) produce large changes in the shape of the magnetic field profile of the PRE. Effects arising from the orthorhombic quadratic ZFS term (E) are much smaller than those of the fourth-order terms and can in most cases be neglected. However, effects due to a(4)(4) and a(2)(4) need to be included in simulations of low field data.

  13. ¹³C solid-state NMR analysis of the most common pharmaceutical excipients used in solid drug formulations Part II: CP kinetics and relaxation analysis.

    Science.gov (United States)

    Pisklak, Dariusz Maciej; Zielińska-Pisklak, Monika; Szeleszczuk, Łukasz; Wawer, Iwona

    2016-04-15

    Excipients used in the solid drug formulations differ in their NMR relaxation and (13)C cross-polarization (CP) kinetics parameters. Therefore, experimental parameters like contact time of cross-polarization and repetition time have a major impact on the registered solid state NMR spectra and in consequence on the results of the NMR analysis. In this work the CP kinetics and relaxation of the most common pharmaceutical excipients: anhydrous α-lactose, α-lactose monohydrate, mannitol, sucrose, sorbitol, sodium starch glycolate type A and B, starch of different origin, microcrystalline cellulose, hypromellose, ethylcellulose, methylcellulose, hydroxyethylcellulose, sodium alginate, magnesium stearate, sodium laurilsulfate and Kollidon(®) were analyzed. The studied excipients differ significantly in their optimum repetition time (from 5 s to 1200 s) and T(1ρ)(I) parameters (from 2 ms to 73 ms). The practical use of those differences in the excipients composition analysis was demonstrated on the example of commercially available tablets containing indapamide as an API. The information presented in this article will help to choose the correct acquisition parameters and also will save the time and effort needed for their optimization in the NMR analysis of the solid drug formulations.

  14. Unraveling the complexity of protein backbone dynamics with combined (13)C and (15)N solid-state NMR relaxation measurements.

    Science.gov (United States)

    Lamley, Jonathan M; Lougher, Matthew J; Sass, Hans Juergen; Rogowski, Marco; Grzesiek, Stephan; Lewandowski, Józef R

    2015-09-14

    Typically, protein dynamics involve a complex hierarchy of motions occurring on different time scales between conformations separated by a range of different energy barriers. NMR relaxation can in principle provide a site-specific picture of both the time scales and amplitudes of these motions, but independent relaxation rates sensitive to fluctuations in different time scale ranges are required to obtain a faithful representation of the underlying dynamic complexity. This is especially pertinent for relaxation measurements in the solid state, which report on dynamics in a broader window of time scales by more than 3 orders of magnitudes compared to solution NMR relaxation. To aid in unraveling the intricacies of biomolecular dynamics we introduce (13)C spin-lattice relaxation in the rotating frame (R1ρ) as a probe of backbone nanosecond-microsecond motions in proteins in the solid state. We present measurements of (13)C'R1ρ rates in fully protonated crystalline protein GB1 at 600 and 850 MHz (1)H Larmor frequencies and compare them to (13)C'R1, (15)N R1 and R1ρ measured under the same conditions. The addition of carbon relaxation data to the model free analysis of nitrogen relaxation data leads to greatly improved characterization of time scales of protein backbone motions, minimizing the occurrence of fitting artifacts that may be present when (15)N data is used alone. We also discuss how internal motions characterized by different time scales contribute to (15)N and (13)C relaxation rates in the solid state and solution state, leading to fundamental differences between them, as well as phenomena such as underestimation of picosecond-range motions in the solid state and nanosecond-range motions in solution.

  15. NMR studies of actinide dioxides

    Energy Technology Data Exchange (ETDEWEB)

    Tokunaga, Y. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)], E-mail: tokunaga.yo@jaea.go.jp; Sakai, H.; Fujimoto, T.; Kambe, S.; Walstedt, R.E.; Ikushima, K.; Yasuoka, H. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Aoki, D.; Homma, Y. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Haga, Y.; Matsuda, T.D.; Ikeda, S.; Yamamoto, E.; Nakamura, A. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Shiokawa, Y. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Nakajima, K.; Arai, Y. [Department of Nuclear Energy System, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Onuki, Y. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Department of Physics, Osaka University, Toyonaka, Osaka 560-0043 (Japan)

    2007-10-11

    {sup 17}O NMR measurements have been performed on a series of the actinide dioxides, UO{sub 2}, NpO{sub 2} and PuO{sub 2}. Although the {sup 17}O NMR spectra in these materials are similar at higher temperatures, the low-temperature spectra present are significantly different. In UO{sub 2} we have observed a wide spectrum, forming a rectangular shape below T{sub N}=30 K. In NpO{sub 2}, on the other hand, the spectra broaden rather gradually and exhibit a two-peak structure below T{sub 0}=26 K. In PuO{sub 2}, neither spectrum broadening nor splitting has been observed. We show that these NMR spectra clearly indicate the different nature of the low-temperature magnetic ground states in these actinide compounds.

  16. Model-independent interpretation of NMR relaxation data for unfolded proteins: the acid-denatured state of ACBP

    DEFF Research Database (Denmark)

    Modig, Kristofer; Poulsen, Flemming

    2008-01-01

    We have investigated the acid-unfolded state of acyl-coenzyme A binding protein (ACBP) using (15)N laboratory frame nuclear magnetic resonance (NMR) relaxation experiments at three magnetic field strengths. The data have been analyzed using standard model-free fitting and models involving....... The analysis also shows that the relaxation data are consistent with and complementary to information obtained from other parameters, especially secondary chemical shifts and residual dipolar couplings, and strengthens the conclusions of previous observations that three out of the four regions that form...

  17. Some nitrogen-14 NMR studies in solids

    Energy Technology Data Exchange (ETDEWEB)

    Pratum, T.K.

    1983-11-01

    The first order quadrupolar perturbation of the /sup 14/N NMR spectrum yields information regarding the static and dynamic properties of the surrounding electronic environment. Signal to noise problems caused by long /sup 14/N longitudinal relaxation times (T/sub 1/) and small equilibrium polarizations are reduced by rotating frame cross polarization (CP) experiments between /sup 14/N and /sup 1/H. Using quadrupolar echo and CP techniques, the /sup 14/N quadrupolar coupling constants (e/sup 2/qQ/h) and asymmetry parameters (eta) have been obtained for a variety of tetraalkylammonium compounds by observation of their quadrupolar powder patterns at various temperatures. For choline chloride and iodide the /sup 14/N NMR powder patterns exhibit the effects of anisotropic molecular motion, while choline bromide spectra show no such effects.

  18. Fresco paintings studied by unilateral NMR

    Science.gov (United States)

    Proietti, N.; Capitani, D.; Lamanna, R.; Presciutti, F.; Rossi, E.; Segre, A. L.

    2005-11-01

    Unilateral NMR has been used to monitor the state of conservation of frescoes in the Vasari's house in Florence. The causes of deterioration of ancient frescoes are varied, which result in the detachment and crumbling of the painted film from the supporting plaster and in the outcropping of salts. Unilateral measurements of Hahn echo performed on such frescoes have allowed a perfect identification of the detachment of the painted film from the plaster. The presence of soluble salts on the pictorial film affects the spin-spin relaxation times, T2. It is then possible using this technique, to characterize the effect of chemical treatments, of cleansing and consolidation procedures using the distribution of T2 spin-spin relaxation times.

  19. Nuclear magnetic relaxation studies of semiconductor nanocrystals and solids

    Energy Technology Data Exchange (ETDEWEB)

    Sachleben, J. R. [Lawrence Berkeley Lab., CA (United States); California Univ., Berkeley, CA (United States). Dept. of Chemistry

    1993-09-01

    Semiconductor nanocrystals, small biomolecules, and {sup 13}C enriched solids were studied through the relaxation in NMR spectra. Surface structure of semiconductor nanocrystals (CdS) was deduced from high resolution {sup 1}H and {sup 13}C liquid state spectra of thiophenol ligands on the nanocrystal surfaces. The surface coverage by thiophenol was found to be low, being 5.6 and 26% for nanocrystal radii of 11.8 and 19.2 {angstrom}. Internal motion is estimated to be slow with a correlation time > 10{sup {minus}8} s{sup {minus}1}. The surface thiophenol ligands react to form a dithiophenol when the nanocrystals were subjected to O{sub 2} and ultraviolet. A method for measuring {sup 14}N-{sup 1}H J-couplings is demonstrated on pyridine and the peptide oxytocin; selective 2D T{sub 1} and T{sub 2} experiments are presented for measuring relaxation times in crowded spectra with overlapping peaks in 1D, but relaxation effects interfere. Possibility of carbon-carbon cross relaxation in {sup 13}C enriched solids is demonstrated by experiments on zinc acetate and L-alanine.

  20. Optimized co-solute paramagnetic relaxation enhancement for the rapid NMR analysis of a highly fibrillogenic peptide

    Energy Technology Data Exchange (ETDEWEB)

    Oktaviani, Nur Alia [University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute (Netherlands); Risør, Michael W. [University of Aarhus, Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry (Denmark); Lee, Young-Ho [Osaka University, Institute for Protein Research (Japan); Megens, Rik P. [University of Groningen, Stratingh Institute for Chemistry (Netherlands); Jong, Djurre H. de; Otten, Renee; Scheek, Ruud M. [University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute (Netherlands); Enghild, Jan J. [University of Aarhus, Interdisciplinary Nanoscience Center (iNANO) and Department of Molecular Biology and Genetics (Denmark); Nielsen, Niels Chr. [University of Aarhus, Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry (Denmark); Ikegami, Takahisa [Yokohama City University, Graduate School of Medical Life Science (Japan); Mulder, Frans A. A., E-mail: fmulder@chem.au.dk [University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute (Netherlands)

    2015-06-15

    Co-solute paramagnetic relaxation enhancement (PRE) is an attractive way to speed up data acquisition in NMR spectroscopy by shortening the T{sub 1} relaxation time of the nucleus of interest and thus the necessary recycle delay. Here, we present the rationale to utilize high-spin iron(III) as the optimal transition metal for this purpose and characterize the properties of its neutral chelate form Fe(DO3A) as a suitable PRE agent. Fe(DO3A) effectively reduces the T{sub 1} values across the entire sequence of the intrinsically disordered protein α-synuclein with negligible impact on line width. The agent is better suited than currently used alternatives, shows no specific interaction with the polypeptide chain and, due to its high relaxivity, is effective at low concentrations and in ‘proton-less’ NMR experiments. By using Fe(DO3A) we were able to complete the backbone resonance assignment of a highly fibrillogenic peptide from α{sub 1}-antitrypsin by acquiring the necessary suite of multidimensional NMR datasets in 3 h.

  1. A suite of Mathematica notebooks for the analysis of protein main chain 15N NMR relaxation data.

    Science.gov (United States)

    Spyracopoulos, Leo

    2006-12-01

    A suite of Mathematica notebooks has been designed to ease the analysis of protein main chain 15N NMR relaxation data collected at a single magnetic field strength. Individual notebooks were developed to perform the following tasks: nonlinear fitting of 15N-T1 and -T2 relaxation decays to a two parameter exponential decay, calculation of the principal components of the inertia tensor from protein structural coordinates, nonlinear optimization of the principal components and orientation of the axially symmetric rotational diffusion tensor, model-free analysis of 15N-T1, -T2, and {1H}-15N NOE data, and reduced spectral density analysis of the relaxation data. The principle features of the notebooks include use of a minimal number of input files, integrated notebook data management, ease of use, cross-platform compatibility, automatic visualization of results and generation of high-quality graphics, and output of analyses in text format.

  2. NMR paramagnetic relaxation due to the S=5/2 complex, Fe(III)-(tetra-p-sulfonatophenyl)porphyrin: central role of the tetragonal fourth-order zero-field splitting interaction.

    Science.gov (United States)

    Schaefle, Nathaniel; Sharp, Robert

    2005-05-08

    The metalloporphyrins, Me-TSPP [Me=Cr(III), Mn(III), Mn(II), Fe(III), and TSPP=meso-(tetra-p-sulfonatophenyl)porphyrin], which possess electron spins S=3/2, 2, 5/2, and 5/2, respectively, comprise an important series of model systems for mechanistic studies of NMR paramagnetic relaxation enhancement (NMR-PRE). For these S>1/2 spin systems, the NMR-PRE depends critically on the detailed form of the zero-field splitting (zfs) tensor. We report the results of experimental and theoretical studies of the NMR relaxation mechanism associated with Fe(III)-TSPP, a spin 5/2 complex for which the overall zfs is relatively large (D approximately = 10 cm(-1)). A comparison of experimental data with spin dynamics simulations shows that the primary determinant of the shape of the magnetic relaxation dispersion profile of the water proton R1 is the tetragonal fourth-order component of the zfs tensor. The relaxation mechanism, which has not previously been described, is a consequence of zfs-induced mixing of the spin eigenfunctions of adjacent Kramers doublets. We have also investigated the magnetic-field dependence of electron-spin relaxation for S=5/2 in the presence of a large zfs, such as occurs in Fe(III)-TSPP. Calculations show that field dependence of this kind is suppressed in the vicinity of the zfs limit, in agreement with observation.

  3. Revisiting spin-lattice relaxation time measurements for dilute spins in high-resolution solid-state NMR spectroscopy

    Science.gov (United States)

    Fu, Riqiang; Li, Jun; Cui, Jingyu; Peng, Xinhua

    2016-07-01

    Numerous nuclear magnetic resonance (NMR) measurements of spin-lattice relaxation times (T1S) for dilute spins such as 13C have led to investigations of the motional dynamics of individual functional groups in solid materials. In this work, we revisit the Solomon equations and analyze how the heteronuclear cross relaxation between the dilute S (e.g. 13C) and abundant I (e.g. 1H) spins affects the measured T1S values in solid-state NMR in the absence of 1H saturation during the recovery time. It is found theoretically that at the beginning of the S spin magnetization recovery, the existence of non-equilibrium I magnetization introduces the heteronuclear cross relaxation effect onto the recovery of the S spin magnetization and confirmed experimentally that such a heteronuclear cross relaxation effect results in the recovery overshoot phenomena for the dilute spins when T1S is on the same order of T1H, leading to inaccurate measurements of the T1S values. Even when T1S is ten times larger than T1H, the heteronuclear cross relaxation effect on the measured T1S values is still noticeable. Furthermore, this cross relaxation effect on recovery trajectory of the S spins can be manipulated and even suppressed by preparing the initial I and S magnetization, so as to obtain the accurate T1S values. A sample of natural abundance L-isoleucine powder has been used to demonstrate the T1S measurements and their corresponding measured T1C values under various experimental conditions.

  4. 2H NMR studies of supercooled and glassy aspirin

    Science.gov (United States)

    Nath, R.; Nowaczyk, A.; Geil, B.; Bohmer, R.

    2007-11-01

    Acetyl salicylic acid, deuterated at the methyl group, was investigated using 2H-NMR in its supercooled and glassy states. Just above the glass transition temperature the molecular reorientations were studied using stimulated-echo spectroscopy and demonstrated a large degree of similarity with other glass formers. Deep in the glassy phase the NMR spectra look similar to those reported for the crystal [A. Detken, P. Focke, H. Zimmermann, U. Haeberlen, Z. Olejniczak, Z. T. Lalowicz, Z. Naturforsch. A 50 (1995) 95] and below 20 K they are indicative for rotational tunneling with a relatively large tunneling frequency. Measurements of the spin-lattice relaxation times for temperatures below 150 K reveal a broad distribution of correlation times in the glass. The dominant energy barrier characterizing the slow-down of the methyl group is significantly smaller than the well defined barrier in the crystal.

  5. NMR STUDY ON THE COMPATIBILITY OF ACR/PVC BLENDS

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiaoqing; QIU Lingshi; WANG Dongsheng; WANG Yuanshen

    1988-01-01

    A 300MHz solid NMR study on the compatibility of ACR (poly (methyl methacrylate-co-methacrylate),in the ratio of 1:1)-PVC (poly (vinyl chloride)) blends is reported. Spin-lattice (T1) and spin-spin (T2)relaxation time of ACR, PVC and their blends are recorded in the temperature range from 215K to 355K.Experimental results indicate that ACR and PVC are compatible with each other and the domain size is smaller than 25 nm, but heterogeneities of molecular dimensions still exist. Some problems of mechanism of compatibility and data analysis are also discussed.

  6. Probing Microsecond Time Scale Dynamics in Proteins by Methyl H-1 Carr-Purcell-Meiboom-Gill Relaxation Dispersion NMR Measurements. Application to Activation of the Signaling Protein NtrC(r)

    NARCIS (Netherlands)

    Otten, Renee; Villali, Janice; Kern, Dorothee; Mulder, Frans A. A.

    2010-01-01

    To study microsecond processes by relaxation dispersion NMR spectroscopy, low power deposition and short pulses are crucial and encourage the development of experiments that employ H-1 Carr-Purcell-Meiboom-Gill (CPMG) pulse trains. Herein, a method is described for the comprehensive study of microse

  7. Probing Microsecond Time Scale Dynamics in Proteins by Methyl H-1 Carr-Purcell-Meiboom-Gill Relaxation Dispersion NMR Measurements. Application to Activation of the Signaling Protein NtrC(r)

    NARCIS (Netherlands)

    Otten, Renee; Villali, Janice; Kern, Dorothee; Mulder, Frans A. A.

    2010-01-01

    To study microsecond processes by relaxation dispersion NMR spectroscopy, low power deposition and short pulses are crucial and encourage the development of experiments that employ H-1 Carr-Purcell-Meiboom-Gill (CPMG) pulse trains. Herein, a method is described for the comprehensive study of microse

  8. Probing Microsecond Time Scale Dynamics in Proteins by Methyl H-1 Carr-Purcell-Meiboom-Gill Relaxation Dispersion NMR Measurements. Application to Activation of the Signaling Protein NtrC(r)

    NARCIS (Netherlands)

    Otten, Renee; Villali, Janice; Kern, Dorothee; Mulder, Frans A. A.

    2010-01-01

    To study microsecond processes by relaxation dispersion NMR spectroscopy, low power deposition and short pulses are crucial and encourage the development of experiments that employ H-1 Carr-Purcell-Meiboom-Gill (CPMG) pulse trains. Herein, a method is described for the comprehensive study of

  9. The inverted chevron plot measured by NMR relaxation reveals a native-like unfolding intermediate in acyl-CoA binding protein

    DEFF Research Database (Denmark)

    Teilum, Kaare; Poulsen, F. M.; Akke, M.

    2006-01-01

    those from stopped-flow kinetics and define an "inverted chevron" plot. The combination of NMR relaxation and stopped-flow kinetic measurements allowed determination of k f and k u in the range from 0.48 M GuHCl to 1.28 M GuHCl. Individually, the stopped-flow and NMR data fit two-state models...

  10. The inverted chevron plot measured by NMR relaxation reveals a native-like unfolding intermediate in acyl-CoA binding protein

    DEFF Research Database (Denmark)

    Teilum, Kaare; Poulsen, F. M.; Akke, M.

    2006-01-01

    those from stopped-flow kinetics and define an "inverted chevron" plot. The combination of NMR relaxation and stopped-flow kinetic measurements allowed determination of k f and k u in the range from 0.48 M GuHCl to 1.28 M GuHCl. Individually, the stopped-flow and NMR data fit two-state models...

  11. Analysis of amorphous solid dispersions using 2D solid-state NMR and (1)H T(1) relaxation measurements.

    Science.gov (United States)

    Pham, Tran N; Watson, Simon A; Edwards, Andrew J; Chavda, Manisha; Clawson, Jacalyn S; Strohmeier, Mark; Vogt, Frederick G

    2010-10-04

    Solid-state NMR (SSNMR) can provide detailed structural information about amorphous solid dispersions of pharmaceutical small molecules. In this study, the ability of SSNMR experiments based on dipolar correlation, spin diffusion, and relaxation measurements to characterize the structure of solid dispersions is explored. Observation of spin diffusion effects using the 2D (1)H-(13)C cross-polarization heteronuclear correlation (CP-HETCOR) experiment is shown to be a useful probe of association between the amorphous drug and polymer that is capable of directly proving glass solution formation. Dispersions of acetaminophen and indomethacin in different polymers are examined using this approach, as well as (1)H double-quantum correlation experiments to probe additional structural features. (1)H-(19)F CP-HETCOR serves a similar role for fluorinated drug molecules such as diflunisal in dispersions, providing a rapid means to prove the formation of a glass solution. Phase separation is detected using (13)C, (19)F, and (23)Na-detected (1)H T(1) experiments in crystalline and amorphous solid dispersions that contain small domains. (1)H T(1) measurements of amorphous nanosuspensions of trehalose and dextran illustrate the ability of SSNMR to detect domain size effects in dispersions that are not glass solutions via spin diffusion effects. Two previously unreported amorphous solid dispersions involving up to three components and containing voriconazole and telithromycin are analyzed using these experiments to demonstrate the general applicability of the approach.

  12. Rapid and simple determination of T1 relaxation times in time-domain NMR by Continuous Wave Free Precession sequence

    Science.gov (United States)

    Moraes, Tiago Bueno; Monaretto, Tatiana; Colnago, Luiz Alberto

    2016-09-01

    Longitudinal (T1) and transverse (T2) relaxation times have been widely used in time-domain NMR (TD-NMR) to determine several physicochemical properties of petroleum, polymers, and food products. The measurement of T2 through the CPMG pulse sequence has been used in most of these applications because it denotes a rapid, robust method. On the other hand, T1 has been occasionally used in TD-NMR due to the long measurement time required to collect multiple points along the T1 relaxation curve. Recently, several rapid methods to measure T1 have been proposed. Those methods based upon single shot, known as Continuous Wave Free Precession (CWFP) pulse sequences, have been employed in the simultaneous measurement of T1 and T2 in a rapid fashion. However, these sequences can be used exclusively in instrument featuring short dead time because the magnitude of the signal at thermal equilibrium is required. In this paper, we demonstrate that a special CWFP sequence with a low flip angle can be a simple and rapid method to measure T1 regardless of instruments dead time. Experimental results confirmed that the method called CWFP-T1 may be used to measure both single T1 value and T1 distribution in heterogeneous samples. Therefore, CWFP-T1 sequence can be a feasible alternative to CPMG in the determination of physicochemical properties, particularly in processes where fast protocols are requested such as industrial applications.

  13. Solid State NMR Studies of Energy Conversion and Storage Materials

    Science.gov (United States)

    Jankuru Hennadige, Sohan Roshel De Silva

    NMR (Nuclear magnetic resonance) spectroscopy is utilized to study energy conversion and storage materials. Different types of NMR techniques including Magic Angle Spinning, Cross-polarization and relaxation measurement experiments were employed. Four different projects are discussed in this dissertation. First, three types of CFx battery materials were investigated. Electrochemical studies have demonstrated different electrochemical performances by one type, delivering superior performance over the other two. 13C and 19F MAS NMR techniques are employed to identify the atomic/molecular structural factors that might account for differences in electrochemical performance among different types. Next as the second project, layered polymer dielectrics were investigated by NMR. Previous studies have shown that thin film capacitors are improved by using alternate layers of two polymers with complementary properties: one with a high breakdown strength and one with high dielectric constant as opposed to monolithic layers. 13C to 1H cross-polarization techniques were used to investigate any inter-layer properties that may cause the increase in the dielectric strength. The third project was to study two types of thermoelectric materials. These samples were made of heavily doped phosphorous and boron in silicon by two different methods: ball-milled and annealed. These samples were investigated by NMR to determine the degree of disorder and obtain insight into the doping efficiency. The last ongoing project is on a lithium-ion battery system. The nature of passivating layers or the solid electrolyte interphase (SEI) formed on the electrodes surface is important because of the direct correlation between the SEI and the battery life time/durability. Multinuclear (7Li, 19F, 31P) techniques are employed to identify the composition of the SEI formation of both positive and negative electrodes.

  14. Is the manifestation of the local dynamics in the spin-lattice NMR relaxation in dendrimers sensitive to excluded volume interactions?

    Science.gov (United States)

    Shavykin, Oleg V; Neelov, Igor M; Darinskii, Anatolii A

    2016-09-21

    The effect of excluded volume (EV) interactions on the manifestation of the local dynamics in the spin-lattice NMR relaxation in dendrimers has been studied by using Brownian dynamics simulations. The study was motivated by the theory developed by Markelov et al., [J. Chem. Phys., 2014, 140, 244904] for a Gaussian dendrimer model without EV interactions. The theory connects the experimentally observed dependence of the spin-lattice relaxation rate 1/T(1)H on the location of NMR active groups with the restricted flexibility (semiflexibility) of dendrimers. Semiflexibility was introduced through the correlations between the orientations of different segments. However, these correlations exist even in flexible dendrimer models with EV interactions. We have simulated coarse-grained flexible and semiflexible dendrimer models with and without EV interactions. Every dendrimer segment consisted of two rigid bonds. Semiflexibility was introduced through a potential which restricts the fluctuations of angles between neighboring bonds but does not change orientational correlations in the EV model as compared to the flexible case. The frequency dependence of the reduced 1/T(1)H(ωH) for segments and bonds belonging to different dendrimer shells was calculated. It was shown that the main effect of EV interactions consists of a much stronger contribution of the overall dendrimer rotation to the dynamics of dendrimer segments as compared to phantom models. After the exclusion of this contribution the manifestation of internal dynamics in spin-lattice NMR relaxation appears to be practically insensitive to EV interactions. For the flexible models, the position ωmax of the peak of the modified 1/T(1)H(ωH) does not depend on the shell number. For semiflexible models, the maximum of 1/T(1)H(ωH) for internal segments or bonds shifts to lower frequencies as compared to outer ones. The dependence of ωmax on the number of dendrimer shells appears to be universal for segments and

  15. nmr spectroscopic study and dft calculations of giao nmr shieldings ...

    African Journals Online (AJOL)

    Preferred Customer

    various fields of science and industry such as microelectronic and aerospace ... GIAO/DFT (Gauge Including Atomic Orbitals/Density Functional Theory) approach is .... successfully by using NMR and quantum chemical calculations.

  16. NMR studies on UPt 3

    Science.gov (United States)

    Kitaoka, Y.; Tou, H.; Ishida, K.; Kimura, N.; Ōnuki, Y.; Yamamoto, E.; Haga, Y.; Maezawa, K.

    2000-06-01

    A complete set of the 195Pt Knight-shift (KS) data on the superconducting (SC) state in UPt 3 identified the spin structure of the Cooper pair corresponding to the multiple SC phases. UPt 3 was acclaimed as the first odd-parity superconductor including a non-unitary pairing state characterized by the two-component d vector like db+ idc at low T and low H [H. Tou et al., Phys. Rev. Lett. 77 (1996) 1374; 80 (1998) 3129]. We have shed further light on these novel results through a comparison with the singlet even-parity anisotropic superconductors CeCu 2Si 2 and UPd 2Al 3. In the singlet pairing state, the fractional decrease in KS below T c, δK obs is independent of the crystal direction. We have found that δ χobs=( NAμ B/ Ahf)δ Kobs where Ahf is the hyperfine coupling constant, is in good agreement with spin susceptibilities χγel calculated from an enhanced electronic specific heat γel and χnmr from the quasiparticle Korringa relation T1TKs2=const. This gives direct evidence that the χs of heavy quasiparticles in CeCu 2Si 2 and UPd 2Al 3 is rather isotropic and decreases to zero as T→0 due to the Cooper-pair formation. On the other hand in UPt 3, the δ χobsb, cs along the b- and c-axis in the non-unitary-pairing state (B phase) are two orders of magnitude smaller than χγel and χnmr. These anomalously small values for δ χobsb, cs may suggest either that the spin degree of freedom in the B phase is not perfectly locked to the a-axis or that χs is not enhanced although γel is. The latter is theoretically pointed out by Ikeda and Miyake [J. Phys. Soc. Japan 66 (1997) 3714] to be possible if 5f electrons in the non-Kramerse singlet ground state for 5f 2 are hybridized with conduction electrons. We need further effort towards coherent understanding of a microscopic mechanism leading to the occurrence of the odd-parity superconductivity in UPt 3.

  17. A nonlinear BOLD model accounting for refractory effect by applying the longitudinal relaxation in NMR to the linear BOLD model.

    Science.gov (United States)

    Jung, Kwan-Jin

    2009-09-01

    A mathematical model to regress the nonlinear blood oxygen level-dependent (BOLD) fMRI signal has been developed by incorporating the refractory effect into the linear BOLD model of the biphasic gamma variate function. The refractory effect was modeled as a relaxation of two separate BOLD capacities corresponding to the biphasic components of the BOLD signal in analogy with longitudinal relaxation of magnetization in NMR. When tested with the published fMRI data of finger tapping, the nonlinear BOLD model with the refractory effect reproduced the nonlinear BOLD effects such as reduced poststimulus undershoot and saddle pattern in a prolonged stimulation as well as the reduced BOLD signal for repetitive stimulation.

  18. Ionic-liquid-like local structure in $LiNO_3-Ca(NO_3)_2-H_2O$ as studied by ion and solvent nuclei NMR relaxation

    CERN Document Server

    Matveev, Vladimir V; Lähderanta, Erkki

    2010-01-01

    Relaxation rates in the $13mLiNO_3-6,5mCa(NO_3)_2-H_2O$ ternary system have been measured for nuclei of water ($^1H$ and $^{17}O$), anion ($^{14}N$), and both cations ($^7Li$, $^{43}Ca$). The data analysis reveals the system structure as consisting of two main charged units: [Li(H$_2$O)$_4$]$^+$ and [Ca(NO$_3$)$_4$]$^{2-}$. Thus the system presents inorganic ionic liquid like structure.

  19. NMR structural studies on antifreeze proteins.

    Science.gov (United States)

    Sönnichsen, F D; Davies, P L; Sykes, B D

    1998-01-01

    Antifreeze proteins (AFPs) are a structurally diverse class of proteins that bind to ice and inhibit its growth in a noncolligative manner. This adsorption-inhibition mechanism operating at the ice surface results in a lowering of the (nonequilibrium) freezing point below the melting point. A lowering of approximately 1 degree C, which is sufficient to prevent fish from freezing in ice-laden seawater, requires millimolar AFP levels in the blood. The solubility of AFPs at these millimolar concentrations and the small size of the AFPs (typically 3-15 kDa) make them ideal subjects for NMR analysis. Although fish AFPs are naturally abundant, seasonal expression, restricted access to polar fishes, and difficulties in separating numerous similar isoforms have made protein expression the method of choice for producing AFPs for structural studies. Expression of recombinant AFPs has also facilitated NMR analysis by permitting isotopic labeling with 15N and 13C and has permitted mutations to be made to help with the interpretation of NMR data. NMR analysis has recently solved two AFP structures and provided valuable information about the disposition of ice-binding side chains in a third. The potential exists to solve other AFP structures, including the newly described insect AFPs, and to use solid-state NMR techniques to address fundamental questions about the nature of the interaction between AFPs and ice.

  20. Moisture in untreated, a cetylated, and furfurylated Norway spruce studied during drying using time domain NMR

    Science.gov (United States)

    Lisabeth G. Thygesen; Thomas Elder

    2008-01-01

    Using time domain NMR, the moisture in Norway spruce (Picea abies (L.) Karst.) sapwood subjected to four different treatments (never-dried, dried and remoistened, acetylated, and furfurylated) was studied during drying at 40°C, at sample average moisture contents above fiber saturation. Spin-spin relaxation time distributions were derived from CPMG...

  1. Pulsed NMR studies of water under extreme conditions

    Energy Technology Data Exchange (ETDEWEB)

    DeFries, Timothy Hatmaker

    1978-01-01

    The dynamic structure of water and heavy water was studied using NMR spin-lattice relaxation and self-diffusion techniques. For both compounds, the relaxation rate is proportional to the ratio of viscosity to absolute temperature at constant density. The coupling between rotational and translational motions decreases with increasing temperature and increasing density. The temperature and density dependence of the deuteron quadrupole coupling constant in D/sub 2/O was determined. The proton spin-lattice relaxation times of supercritical H/sub 2/O were measured from 400 to 700/sup 0/C and to 1 kbar. The times were found to be roughly proportional to density and were found to decrease with temperature. The angular momentum correlation times tau/sub J/ were calculated and compared with the times between collisions for a hard sphere fluid, the Enskog times, tau/sub E/. The values of tau/sub E//tau/sub J/ were roughly 6 at 400/sup 0/C and low densities. The values decreased at higher densities and higher temperatures. The proton spin-lattice relaxation times of H/sub 2/O were also measured from 90 to 350/sup 0/C up to 2 to 5 kbar. The data clearly show the change from dipolar to spin-rotation relaxation as a function of temperature and density. Both the low and the high temperature results agree with the idea that it is the strong and anisotropic intermolecular potential which causes the dynamic behavior of water to be so different from that of normal liquids.

  2. Structural Studies of Biological Solids Using NMR

    Science.gov (United States)

    Ramamoorthy, Ayyalusamy

    2011-03-01

    High-resolution structure and dynamics of biological molecules are important in understanding their function. While studies have been successful in solving the structures of water-soluble biomolecules, it has been proven difficult to determine the structures of membrane proteins and fibril systems. Recent studies have shown that solid-state NMR is a promising technique and could be highly valuable in studying such non-crystalline and non-soluble biosystems. I will present strategies to study the structures of such challenging systems and also about the applications of solid-state NMR to study the modes of membrane-peptide interactions for a better assessment of the prospects of antimicrobial peptides as substitutes to antibiotics in the control of human disease. Our studies on the mechanism of membrane disruption by LL-37 (a human antimicrobial peptide), analogs of the naturally occurring antimicrobial peptide magainin2 extracted from the skin of the African frog Xenopus Laevis, and pardaxin will be presented. Solid-state NMR experiments were used to determine the secondary structure, dynamics and topology of these peptides in lipid bilayers. Similarities and difference in the cell-lysing mechanism, and their dependence on the membrane composition, of these peptides will be discussed. Atomic-level resolution NMR structures of amyloidogenic proteins revealing the misfolding pathway and early intermediates that play key roles in amyloid toxicity will also be presented.

  3. Flexible and rigid structures in HIV-1 p17 matrix protein monitored by relaxation and amide proton exchange with NMR.

    Science.gov (United States)

    Ohori, Yuka; Okazaki, Honoka; Watanabe, Satoru; Tochio, Naoya; Arai, Munehito; Kigawa, Takanori; Nishimura, Chiaki

    2014-03-01

    The HIV-1 p17 matrix protein is a multifunctional protein that interacts with other molecules including proteins and membranes. The dynamic structure between its folded and partially unfolded states can be critical for the recognition of interacting molecules. One of the most important roles of the p17 matrix protein is its localization to the plasma membrane with the Gag polyprotein. The myristyl group attached to the N-terminus on the p17 matrix protein functions as an anchor for binding to the plasma membrane. Biochemical studies revealed that two regions are important for its function: D14-L31 and V84-V88. Here, the dynamic structures of the p17 matrix protein were studied using NMR for relaxation and amide proton exchange experiments at the physiological pH of 7.0. The results revealed that the α12-loop, which includes the 14-31 region, was relatively flexible, and that helix 4, including the 84-88 region, was the most protected helix in this protein. However, the residues in the α34-loop near helix 4 had a low order parameter and high exchange rate of amide protons, indicating high flexibility. This region is probably flexible because this loop functions as a hinge for optimizing the interactions between helices 3 and 4. The C-terminal long region of K113-Y132 adopted a disordered structure. Furthermore, the C-terminal helix 5 appeared to be slightly destabilized due to the flexible C-terminal tail based on the order parameters. Thus, the dynamic structure of the p17 matrix protein may be related to its multiple functions.

  4. NMR RELAXIVITY AND IMAGING OF NEUTRAL MACROMOLECULAR POLYESTER GADOLINIUM (Ⅲ) COMPLEXES

    Institute of Scientific and Technical Information of China (English)

    Kai-chao Yu; Hong-bing Hu; Mai-li Liu; Han-zhen Yuan; Chao-hui Ye; Ren-xi Zhuo

    1999-01-01

    Five neutral macromolecular polyester gadolinium (Ⅲ) complexes with pendant hydrophobic alkyl and aromatic functional groups were prepared. The longitudinal relaxation rates of these complexes were measured. One of these Gd (Ⅲ) complexes was chosen for the acute toxicity test and T1-weighted imaging measurement. Preliminary results showed that. compared with Gd-DTPA, the neutral macromolecular gadolinium (Ⅲ) complexes provide higher T1 relaxivity enhancement and longer function duration.

  5. NMR Studies of Lithium Iodide Based Solid Electrolytes

    DEFF Research Database (Denmark)

    Dupree, R.; Howells, R. J.; Hooper, A.

    1983-01-01

    In mixture of LiI with γAl2O3 the ionic conductivity is found to increase by up to three orders of magnitude over pure LiI. NMR measurements of7Li relaxation times were performed on both anhydrous LiI and a mixture of LiI with 30m/o γAl2O3. The relaxation is found to be purely dipolar in origin f...

  6. The Frequency-Dependence of the NMR Longitudinal Relaxation Rate, T(1)(-1), of Water in Cysts of the Brine Shrimp

    Science.gov (United States)

    Egan, Thomas F.

    The NMR spin-lattice relaxation rate, T(,1)(' -1), of water is independent of the Larmor frequency, (omega)/2(pi), in the normal rf range. However, T(,1)('-1) of intracellular water in biological systems, which accounts for as much as 80% of the cell mass, is frequency-dependent. This indicates that the NMR properties of water in the cellular environment are influenced by long-correlation time processes due to the interaction of water with proteins and other macromolecular constituents of the cell. In this research, the relaxation rate T(,1)(' -1) of water in the Artemia (brine shrimp) cyst is examined as a function of: (1) the proton NMR Larmor frequency for .01 Artemia cysts between 10 and 500 MHz. At lower Larmor frequencies, below 1 MHz, the relaxation rates of water in brine shrimp cysts are influenced by additional relexation mechanisms; translational diffusion of hydration water is one possibility.

  7. Intrinsic unfoldase/foldase activity of the chaperonin GroEL directly demonstrated using multinuclear relaxation-based NMR

    Science.gov (United States)

    Libich, David S.; Tugarinov, Vitali; Clore, G. Marius

    2015-01-01

    The prototypical chaperonin GroEL assists protein folding through an ATP-dependent encapsulation mechanism. The details of how GroEL folds proteins remain elusive, particularly because encapsulation is not an absolute requirement for successful re/folding. Here we make use of a metastable model protein substrate, comprising a triple mutant of Fyn SH3, to directly demonstrate, by simultaneous analysis of three complementary NMR-based relaxation experiments (lifetime line broadening, dark state exchange saturation transfer, and Carr–Purcell–Meinboom–Gill relaxation dispersion), that apo GroEL accelerates the overall interconversion rate between the native state and a well-defined folding intermediate by about 20-fold, under conditions where the “invisible” GroEL-bound states have occupancies below 1%. This is largely achieved through a 500-fold acceleration in the folded-to-intermediate transition of the protein substrate. Catalysis is modulated by a kinetic deuterium isotope effect that reduces the overall interconversion rate between the GroEL-bound species by about 3-fold, indicative of a significant hydrophobic contribution. The location of the GroEL binding site on the folding intermediate, mapped from 15N, 1HN, and 13Cmethyl relaxation dispersion experiments, is composed of a prominent, surface-exposed hydrophobic patch. PMID:26124125

  8. NMR and dynamics of biopolymers

    Energy Technology Data Exchange (ETDEWEB)

    Lian, L.Y.; Barsukov, I.L. [Leicester Univ. (United Kingdom)

    1994-12-31

    Several basic experimental analytical NMR techniques that are frequently used for the qualitative and quantitative analysis of dynamic and exchange processes, focusing on proteins systems, are described: chemical exchange (slow exchange, fast exchange, intermediate exchange), heteronuclear relaxation measurements (relaxation parameters, strategy of relaxation data analysis, experimental results and examples, motional model interpretation of relaxation data, homonuclear relaxation); slow large-scale exchange and hydrogen-deuterium exchange are also studied: mechanisms of hydrogen exchange in a native protein, methods for measuring amide exchange rates by NMR, interpretation of amide exchange rates. 9 fig., 3 tab., 56 ref.

  9. Cross-validation of the structure of a transiently formed and low populated FF domain folding intermediate determined by relaxation dispersion NMR and CS-Rosetta.

    Science.gov (United States)

    Barette, Julia; Velyvis, Algirdas; Religa, Tomasz L; Korzhnev, Dmitry M; Kay, Lewis E

    2012-06-14

    We have recently reported the atomic resolution structure of a low populated and transiently formed on-pathway folding intermediate of the FF domain from human HYPA/FBP11 [Korzhnev, D. M.; Religa, T. L.; Banachewicz, W.; Fersht, A. R.; Kay, L.E. Science 2011, 329, 1312-1316]. The structure was determined on the basis of backbone chemical shift and bond vector orientation restraints of the invisible intermediate state measured using relaxation dispersion nuclear magnetic resonance (NMR) spectroscopy that were subsequently input into the database structure determination program, CS-Rosetta. As a cross-validation of the structure so produced, we present here the solution structure of a mimic of the folding intermediate that is highly populated in solution, obtained from the wild-type domain by mutagenesis that destabilizes the native state. The relaxation dispersion/CS-Rosetta structures of the intermediate are within 2 Å of those of the mimic, with the nonnative interactions in the intermediate also observed in the mimic. This strongly confirms the structure of the FF domain folding intermediate, in particular, and validates the use of relaxation dispersion derived restraints in structural studies of invisible excited states, in general.

  10. An NMR study on shale wettability

    Energy Technology Data Exchange (ETDEWEB)

    Odusina, Elijah; Sondergeld, Carl; Rai, Chandra [University of Oklahoma (United States)

    2011-07-01

    In recent years, the importance of shales as unconventional gas resources has grown significantly. It is therefore important to reach a better understanding of their petrophysical properties. One of the important rock properties that is directly linked to successful hydrocarbon recovery is wettability. This paper presents a study on shale wettability using nuclear magnetic resonance (NMR) to monitor sequential imbibition of brine and oil. Due to the presence of mineralogical variations, low permeability and viscosity, and complex pore structure, the interpretation of wettability using conventional approaches becomes complex. Samples that included 21 core plugs from the Eagle Ford shale, 12 from the Barnett, 11 from the Floyd, and 10 from the Woodford shale were analyzed. The NMR study confirmed the water-wet behavior of Berea sandstone. From the study, it was seen that the Woodford shale showed more affinity for dodecane than did the other shales.

  11. Paraffin molecule mobility in channel clathrates of urea on spectroscopic NMR relaxation data

    CERN Document Server

    Kriger, Y G; Chekhova, G N

    2001-01-01

    The temperature dependences of the protons spin-lattice relaxation time (T sub I) in the channel clathrates of urea with paraffins are measured. The data on the T sub I are interpreted within the frames of the model of the paraffins molecules and their fragments orientation in the clathrate channels. The dynamics peculiarities are connected with the disproportion effects of these compounds

  12. Determination of Leu Side-Chain Conformations in Excited Protein States by NMR Relaxation Dispersion

    NARCIS (Netherlands)

    Hansen, D. Flemming; Neudecker, Philipp; Vallurupalli, Pramodh; Mulder, Frans A. A.; Kay, Lewis E.

    2010-01-01

    Fits of Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion profiles allow extraction of the kinetics and thermodynamics of exchange reactions that interconvert highly populated, ground state and low Populated, excited state conformers. Structural information is also available in the form of chem

  13. NMR methodologies for studying mitochondrial bioenergetics.

    Science.gov (United States)

    Alves, Tiago C; Jarak, Ivana; Carvalho, Rui A

    2012-01-01

    Nuclear magnetic resonance (NMR) spectroscopy is a technique with an increasing importance in the study of metabolic diseases. Its initial important role in the determination of chemical structures (1, 2) has been considerably overcome by its potential for the in vivo study of metabolism (3-5). The main characteristic that makes this technique so attractive is its noninvasiveness. Only nuclei capable of transitioning between energy states, in the presence of an intense and constant magnetic field, are studied. This includes abundant nuclei such as proton ((1)H) and phosphorous ((31)P), as well as stable isotopes such as deuterium ((2)H) and carbon 13 ((13)C). This allows a wide range of applications that vary from the determination of water distribution in tissues (as obtained in a magnetic resonance imaging scan) to the calculation of metabolic fluxes under ex vivo and in vivo conditions without the need to use radioactive tracers or tissue biopsies (as in a magnetic resonance spectroscopy (MRS) scan). In this chapter, some technical aspects of the methodology of an NMR/MRS experiment as well as how it can be used to study mitochondrial bioenergetics are overviewed. Advantages and disadvantages of in vivo MRS versus high-resolution NMR using proton high rotation magic angle spinning (HRMAS) of tissue biopsies and tissue extracts are also discussed.

  14. MEASURING VARIABILITY SOURCES IN NMR METABOLOMIC STUDIES

    OpenAIRE

    Rozet, Eric; de Tullio, Pascal; Hubert, Philippe; Govaerts., B.

    2013-01-01

    Due to the huge amount of information available in NMR spectra obtained from the analysis of metabolomic experiments, multivariate analysis such as Principal Component Analysis (PCA) are required to understand the influence of treatments over the metabolites [1]. However, many experiments in metabolomics studies have more complexes variability structures than simply comparing several treatments: they may include time effects, biological effects such as diet or hormonal status, and other bloc...

  15. NMR Structural Studies on Alamethicin Dimers

    Institute of Scientific and Technical Information of China (English)

    李星

    2003-01-01

    15N labeled alamethicin dimer was synthesized. The structure and dynamics of alamethicin dimers were studied with nuclear magnetic resonance (NMR) spectroscopy. The data from 15N-labeled alamethicin dimer suggest little differences in conformation between the dimer and monomer in the Aib1-Pro14 region. Significant difference in the conformation of the C-terminus are manifest in the NH chemical shifts in the Val15-Pho20 region.

  16. Measurement of relaxation times by NMR-CT of electric superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, Koji; Yoshitoshi, Motosada (Shimadzu Corp., Kyoto (Japan)); Narise, Shoji; Hirakawa, Kogi

    1984-08-01

    Relaxation curves of T/sub 1/ in various tissues of the brain in patients with cerebral tumor and in healthy controls were obtained by saturation-recovery and inversion-recovery methods, whereby T/sub 1/ values were calculated. The results obtained were in good agreement with in vitro measurement results of excised brain tissues. Prolongation of T/sub 1/ values was evidently observed with increasing the strength of static magnetic field.

  17. Utilization of paramagnetic relaxation enhancements for high-resolution NMR structure determination of a soluble loop-rich protein with sparse NOE distance restraints

    Energy Technology Data Exchange (ETDEWEB)

    Furuita, Kyoko; Kataoka, Saori; Sugiki, Toshihiko; Hattori, Yoshikazu; Kobayashi, Naohiro; Ikegami, Takahisa [Osaka University, Institute for Protein Research (Japan); Shiozaki, Kazuhiro [Nara Institute of Science and Technology, Graduate School of Biological Sciences (Japan); Fujiwara, Toshimichi; Kojima, Chojiro, E-mail: kojima@protein.osaka-u.ac.jp [Osaka University, Institute for Protein Research (Japan)

    2015-01-15

    NMR structure determination of soluble proteins depends in large part on distance restraints derived from NOE. In this study, we examined the impact of paramagnetic relaxation enhancement (PRE)-derived distance restraints on protein structure determination. A high-resolution structure of the loop-rich soluble protein Sin1 could not be determined by conventional NOE-based procedures due to an insufficient number of NOE restraints. By using the 867 PRE-derived distance restraints obtained from the NOE-based structure determination procedure, a high-resolution structure of Sin1 could be successfully determined. The convergence and accuracy of the determined structure were improved by increasing the number of PRE-derived distance restraints. This study demonstrates that PRE-derived distance restraints are useful in the determination of a high-resolution structure of a soluble protein when the number of NOE constraints is insufficient.

  18. Dielectric relaxation studies in polyvinyl butyral

    Science.gov (United States)

    Mehendru, P. C.; Kumar, Naresh; Arora, V. P.; Gupta, N. P.

    1982-10-01

    Dielectric measurements have been made in thick films (˜100 μm) of polyvinyl butyral (PVB) having degree of polymerization n=1600, in the frequency range 100 Hz-100 KHz and temperature range 300-373 K. The results indicated that PVB was in the amorphous phase and observed dielectric dispersion has been assigned as the β-relaxation process. The β relaxation is of Debye type with symmetrical distribution of relaxation times. The dielectric relaxation strength Δɛ and the distribution parameters β¯ increase with temperature. The results can be qualitatively explained by assuming the hindered rotation of the side groups involving hydroxyl/acetate groups.

  19. Polymeric proanthocyanidins 13C NMR studies of procyanidins

    Science.gov (United States)

    Lawrence J. Porter; Roger H. Newman; Lai Yeap Foo; Herbert Wong; Richard W. Hemingway

    1982-01-01

    Proanthocyanidin polymers have been shown to consist entirely of flavan-3-ol units by a combination of techniques including 13C n.m.r. spectroscopy. The 13C n.m.r. spectra of the polymers and related molecules are now considered in more detail. Prior to this study UC n.m.r. data has been published of procyanidins and...

  20. 11B and 27Al NMR spin-lattice relaxation and Knight shift of Mg1-xAlxB2: Evidence for an anisotropic Fermi surface

    Science.gov (United States)

    Papavassiliou, G.; Pissas, M.; Karayanni, M.; Fardis, M.; Koutandos, S.; Prassides, K.

    2002-10-01

    We report a detailed study of the 11B and 27Al NMR spin-lattice relaxation rates (1/T1) and the 27Al Knight shift (K) in Mg1-xAlxB2, 0<=x<=1. The evolution of (1/T1T) and K with x is in excellent agreement with the prediction of ab initio calculations of a highly anisotropic Fermi surface, consisting mainly of hole-type two-dimensional (2D) cylindrical sheets from bonding 2px,y boron orbitals. The density of states at the Fermi level also decreases sharply on Al doping and the 2D sheets collapse at x~0.55, where the superconducting phase disappears.

  1. On the suppression of background signals originating from NMR hardware components. Application to zero echo time imaging and relaxation time analysis.

    Science.gov (United States)

    Dreher, Wolfgang; Bardenhagen, Ingo; Huang, Li; Bäumer, Marcus

    2016-04-01

    Modern NMR imaging systems used for biomedical research are equipped with B0 gradient systems with strong maximum gradient strength and short switching time enabling (1)H NMR measurements of samples with very short transverse relaxation times. However, background signal originating from non-optimized RF coils may hamper experiments with ultrashort delays between RF excitation and signal reception. We demonstrate that two simple means, outer volume suppression and the use of shaped B0 fields produced by higher-order shim coils, allow a considerable suppression of disturbing background signals. Thus, the quality of NMR images acquired at ultrashort or zero echo time is improved and systematic errors in quantitative data evaluation are avoided. Fields of application comprise MRI with ultrashort echo time or relaxation time analysis, for both biomedical research and characterizing porous media filled with liquids or gases.

  2. Low-temperature NMR studies of Ce-Al compounds

    Energy Technology Data Exchange (ETDEWEB)

    Gavilano, J.L. (Laboratorium fuer Festkoerperphysik, ETH-Hoenggerberg, CH-8093 Zuerich (Switzerland)); Hunziker, J. (Laboratorium fuer Festkoerperphysik, ETH-Hoenggerberg, CH-8093 Zuerich (Switzerland)); Vonlanthen, P. (Laboratorium fuer Festkoerperphysik, ETH-Hoenggerberg, CH-8093 Zuerich (Switzerland)); Ott, H.R. (Laboratorium fuer Festkoerperphysik, ETH-Hoenggerberg, CH-8093 Zuerich (Switzerland))

    1994-04-01

    Ce-Al compounds display a variety of unconventional magnetic properties at low temperatures. This is particularly well demonstrated by the results of our low-frequency NMR studies on CeAl[sub 2], CeAl[sub 3] and Ce[sub 3]Al[sub 11]. Although CeAl[sub 2] orders antiferromagnetically below 3.4 K, the temperature dependence of the spin-lattice relaxation rate follows a Korringa law below 1 K. For CeAl[sub 3], we observe an increase of the line width below 0.9 K, but no indication of a phase transition is discernible from the temperature dependence of the spin-lattice relaxation rate. Ce[sub 3]Al[sub 11] is ferromagnetic below 6.2 K, but develops an antiferromagnetic and modulated structure below 3.3 K. A field of the order of 3 kG, however, appears to stabilize the ferromagnetic phase. Our spectroscopic data are important in view of some of the unusual thermal properties of these materials. ((orig.))

  3. Relaxation time: a proton NMR-based approach as a metric to measure reactivity of engineered nanomaterials

    Science.gov (United States)

    Paruthi, Archini; Misra, Superb K.

    2017-08-01

    The toxicological impact of engineered nanoparticles in environmental or biological milieu is very difficult to predict and control because of the complexity of interactions of nanoparticles with the varied constituents in the suspended media. Nanoparticles are different from their bulk counterparts due to their high surface area-to-volume ratio per unit mass, which plays a vital role in bioavailability of these nanoparticles to its surroundings. This study explores how changes in the spin-spin nuclear relaxation time can be used to gauge the availability of surface area and suspension stability of selected nanoparticles (CuO, ZnO, and SiO2), in a range of simulated media. Spin-spin nuclear relaxation time can be mathematically correlated to wetted surface area, which is well backed up by the data of hydrodynamic size measurements and suspension stability. We monitored the change in spin-spin relaxation time for all the nanoparticles, over a range of concentrations (2.5 -100 ppm) in deionized water and artificial seawater. Selective concentrations of nanoparticle suspensions were subjected for temporal studies over a period of 48 hrs to understand the concept of spin-spin nuclear relaxation time-based reactivity of nanoparticle suspension. The nanoparticles showed high degree of agglomeration, when suspended in artificial seawater. This was captured by a decrease in spin-spin nuclear relaxation time and also an increment in the hydrodynamic size of the nanoparticles.

  4. Temperature dependence of the NMR spin-lattice relaxation rate for spin-1/2 chains

    Science.gov (United States)

    Coira, E.; Barmettler, P.; Giamarchi, T.; Kollath, C.

    2016-10-01

    We use recent developments in the framework of a time-dependent matrix product state method to compute the nuclear magnetic resonance relaxation rate 1 /T1 for spin-1/2 chains under magnetic field and for different Hamiltonians (XXX, XXZ, isotropically dimerized). We compute numerically the temperature dependence of the 1 /T1 . We consider both gapped and gapless phases, and also the proximity of quantum critical points. At temperatures much lower than the typical exchange energy scale, our results are in excellent agreement with analytical results, such as the ones derived from the Tomonaga-Luttinger liquid (TLL) theory and bosonization, which are valid in this regime. We also cover the regime for which the temperature T is comparable to the exchange coupling. In this case analytical theories are not appropriate, but this regime is relevant for various new compounds with exchange couplings in the range of tens of Kelvin. For the gapped phases, either the fully polarized phase for spin chains or the low-magnetic-field phase for the dimerized systems, we find an exponential decrease in Δ /(kBT ) of the relaxation time and can compute the gap Δ . Close to the quantum critical point our results are in good agreement with the scaling behavior based on the existence of free excitations.

  5. A NMR reverse diffusion filter for the simplification of spectra of complex mixtures and the study of drug receptor interactions.

    Science.gov (United States)

    Vega-Vázquez, M; Cobas, J C; Oliveira de Sousa, F F; Martin-Pastor, M

    2011-08-01

    A reverse diffusion filter NMR experiment (Drev) is proposed for the study of small molecules in binding with macromolecules. The filtering efficiency of Drev to eliminate the signals of the macromolecule is shown to be superior to conventional transverse relaxation filters at least for macromolecules containing a significant fraction of flexible residues. The Drev filter was also a useful complement for ligand-based NMR screening in combination with saturation transfer difference experiments.

  6. Fast Li ion dynamics in the solid electrolyte Li7 P3 S11 as probed by (6,7) Li NMR spin-lattice relaxation.

    Science.gov (United States)

    Wohlmuth, Dominik; Epp, Viktor; Wilkening, Martin

    2015-08-24

    The development of safe and long-lasting all-solid-state batteries with high energy density requires a thorough characterization of ion dynamics in solid electrolytes. Commonly, conductivity spectroscopy is used to study ion transport; much less frequently, however, atomic-scale methods such as nuclear magnetic resonance (NMR) are employed. Here, we studied long-range as well as short-range Li ion dynamics in the glass-ceramic Li7 P3 S11 . Li(+) diffusivity was probed by using a combination of different NMR techniques; the results are compared with those obtained from electrical conductivity measurements. Our NMR relaxometry data clearly reveal a very high Li(+) diffusivity, which is reflected in a so-called diffusion-induced (6) Li NMR spin-lattice relaxation peak showing up at temperatures as low as 313 K. At this temperature, the mean residence time between two successful Li jumps is in the order of 3×10(8) s(-1) , which corresponds to a Li(+) ion conductivity in the order of 10(-4) to 10(-3) S cm(-1) . Such a value is in perfect agreement with expectations for the crystalline but metastable glass ceramic Li7 P3 S11 . In contrast to conductivity measurements, NMR analysis reveals a range of activation energies with values ranging from 0.17 to 0.26 eV, characterizing Li diffusivity in the bulk. In our case, through-going Li ion transport, when probed by using macroscopic conductivity spectroscopy, however, seems to be influenced by blocking grain boundaries including, for example, amorphous regions surrounding the Li7 P3 S11 crystallites. As a result of this, long-range ion transport as seen by impedance spectroscopy is governed by an activation energy of approximately 0.38 eV. The findings emphasize how surface and grain boundary effects can drastically affect long-range ionic conduction. If we are to succeed in solid-state battery technology, such effects have to be brought under control by, for example, sophisticated densification or through the preparation

  7. Study of NMR porosity for terrestrial formation in China

    Institute of Scientific and Technical Information of China (English)

    WANG Xiaowen; XIAO Lizhi; XIE Ranhong; ZHANG Yuanzhong

    2006-01-01

    NMR logging is an effective method for porosity measurement. NMR-derived porosity only comes from the pore fluid and is, in principle, not affected by rock matrix. However, it is found that the difference between NMR-derived and conventional log-derived porosities is often between 2 to 6 pu, which is unacceptable, in terrestrial formation in China. In the paper, the theory of NMR porosity was reviewed. The influence factors on NMR porosity error were analyzed based on NMR core measurements. More than 30 core samples with a wide range of porosities including sandstone, limestone and artificial ceramic were chosen for the conventional and NMR porosity measurements. The current NMR data acquisition method was studied based on laboratory NMR core measurements and found to be not good for terrestrial formation. A new NMR data acquisition method suiting for terrestrial formation in China was proposed and much improved the accuracy of NMR porosity measurement. It is suggested that the analysis of core samples from different regions should be carried out before logging in order to obtain accurate NMR porosity.

  8. Solid state 1H NMR studies of cell wall materials of potatoes

    Science.gov (United States)

    Tang, Huiru; Belton, Peter S.; Ng, Annie; Waldron, Keith W.; Ryden, Peter

    1999-04-01

    Cell wall materials from potatoes ( Solanum tuberosum) prepared by two different methods have been studied using NMR proton relaxation times. Spin lattice relaxation in both the rotating and laboratory frames as well as transverse relaxation have been measured over a range of temperatures and hydration levels. It was observed that the sample prepared using a DMSO extraction showed anomalous behaviour of spin lattice relaxation in the laboratory frame probably due to residual solvent in the sample. Spin lattice relaxation in the laboratory frame is the result of hydroxymethyl rotation and another unidentified high frequency motion. In the rotating frame relaxation is adequately explained by hydroxymethyl rotation alone. In neither experiment is methyl group rotation observed, calculation suggests that this is due to the low density of methyl groups in the sample. Non-freezing water in potato cell walls, α-cellulose and pectin was found about 0.2, 0.04 and 0.18 g per gram dry matter, indicating preferable hydration of pectin compared to cellulose. The effects of hydration are most noticeable in the measurements that reflect low frequency motions, particularly transverse relaxation, where both second moments and the relative intensity of signals arising from immobile material are reduced by hydration.

  9. Probing microsecond time scale dynamics in proteins by methyl (1)H Carr-Purcell-Meiboom-Gill relaxation dispersion NMR measurements. Application to activation of the signaling protein NtrC(r).

    Science.gov (United States)

    Otten, Renee; Villali, Janice; Kern, Dorothee; Mulder, Frans A A

    2010-12-01

    To study microsecond processes by relaxation dispersion NMR spectroscopy, low power deposition and short pulses are crucial and encourage the development of experiments that employ (1)H Carr-Purcell-Meiboom-Gill (CPMG) pulse trains. Herein, a method is described for the comprehensive study of microsecond to millisecond time scale dynamics of methyl groups in proteins, exploiting their high abundance and favorable relaxation properties. In our approach, protein samples are produced using [(1)H, (13)C]-d-glucose in ∼100% D(2)O, which yields CHD(2) methyl groups for alanine, valine, threonine, isoleucine, leucine, and methionine residues with high abundance, in an otherwise largely deuterated background. Methyl groups in such samples can be sequence-specifically assigned to near completion, using (13)C TOCSY NMR spectroscopy, as was recently demonstrated (Otten, R.; et al. J. Am. Chem. Soc. 2010, 132, 2952-2960). In this Article, NMR pulse schemes are presented to measure (1)H CPMG relaxation dispersion profiles for CHD(2) methyl groups, in a vein similar to that of backbone relaxation experiments. Because of the high deuteration level of methyl-bearing side chains, artifacts arising from proton scalar coupling during the CPMG pulse train are negligible, with the exception of Ile-δ1 and Thr-γ2 methyl groups, and a pulse scheme is described to remove the artifacts for those residues. Strong (13)C scalar coupling effects, observed for several leucine residues, are removed by alternative biochemical and NMR approaches. The methodology is applied to the transcriptional activator NtrC(r), for which an inactive/active state transition was previously measured and the motions in the microsecond time range were estimated through a combination of backbone (15)N CPMG dispersion NMR spectroscopy and a collection of experiments to determine the exchange-free component to the transverse relaxation rate. Exchange contributions to the (1)H line width were detected for 21 methyl

  10. CF3 Rotation in 3-(Trifluoromethyl)phenanthrene: Solid State 19F and 1H NMR relaxation and Bloch-Wangsness-Redfield theory.

    Science.gov (United States)

    Beckmann, Peter A; Rosenberg, Jessie; Nordstrom, Kerstin; Mallory, Clelia W; Mallory, Frank B

    2006-03-23

    We have observed and modeled the 1H and 19F solid-state nuclear spin relaxation process in polycrystalline 3-(trifluoromethyl)phenanthrene. The relaxation rates for the two spin species were observed from 85 to 300 K at the low NMR frequencies of omega/2pi = 22.5 and 53.0 MHz where CF3 rotation, characterized by a mean time tau between hops, is the only motion on the NMR time scale. All motional time scales (omegatau 1) are observed. The 1H spins are immobile on the NMR time scale but are coupled to the 19F spins via the unlike-spin dipole-dipole interaction. The temperature dependence of the observed relaxation rates (the relaxation is biexponential) shows considerable structure and a thorough analysis of Bloch-Wangsness-Redfield theory for this coupled spin system is provided. The activation energy for CF3 rotation is 11.5 +/- 0.7 kJ/mol, in excellent agreement with the calculation in a 13-molecule cluster provided in the companion paper where the crystal structure is reported and detailed ab initio electronic structure calculations are performed [Wang, X.; Mallory F. B.; Mallory, C. W; Beckmann, P. A.; Rheingold, A. L.; Francl, M. M J. Phys. Chem. A 2006, 110, 3954].

  11. /sup 13/C NMR studies of the molecular flexibility of antidepressants

    Energy Technology Data Exchange (ETDEWEB)

    Munro, S.L.; Andrews, P.R.; Craik, D.J.; Gale, D.J.

    1986-02-01

    The solution dynamics of a series of clinically potent antidepressants have been investigated by measuring /sup 13/C NMR relaxation parameters. Correlation times and internal motional rates were calculated from spin-lattice relaxation times and nuclear Overhauser effects for the protonated carbons in mianserin, imipramine-like antidepressants, and amitriptyline-like antidepressants. These data were interpreted in terms of overall molecular tumbling, internal rotations, and inherent flexibility of these structures. Of particular interest was the conformational variability of the tricyclic nucleus of the tricyclic antidepressants, where the data indicated a fivefold difference in mobility of the dimethylene bridge of imipramine-like antidepressants relative to amitriptyline-like compounds. The implications of such a difference in internal motions is discussed in relation to previous NMR studies and to the reported differences in pharmacological activity of these antidepressants.

  12. A Field Study of NMR Logging to Quantify Petroleum Contamination in Subsurface Sediments

    Science.gov (United States)

    Fay, E. L.; Knight, R. J.; Grunewald, E. D.

    2016-12-01

    Nuclear magnetic resonance (NMR) measurements are directly sensitive to hydrogen-bearing fluids including water and petroleum products. NMR logging tools can be used to detect and quantify petroleum hydrocarbon contamination in the sediments surrounding a well or borehole. An advantage of the NMR method is that data can be collected in both cased and uncased holes. In order to estimate the volume of in-situ hydrocarbon, there must be sufficient contrast between either the relaxation times (T2) or the diffusion coefficients (D) of water and the contaminant. In a field study conducted in Pine Ridge, South Dakota, NMR logging measurements were used to investigate an area of hydrocarbon contamination from leaking underground storage tanks. A contaminant sample recovered from a monitoring well at the site was found to be consistent with a mixture of gasoline and diesel fuel. NMR measurements were collected in two PVC-cased monitoring wells; D and T2 measurements were used together to detect and quantify contaminant in the sediments above and below the water table at both of the wells. While the contrast in D between the fluids was found to be inadequate for fluid typing, the T2 contrast between the contaminant and water in silt enabled the estimation of the water and contaminant volumes. This study shows that NMR logging can be used to detect and quantify in-situ contamination, but also highlights the importance of sediment and contaminant properties that lead to a sufficiently large contrast in T2 or D.

  13. Solid-state and unilateral NMR study of deterioration of a Dead Sea Scroll fragment.

    Science.gov (United States)

    Masic, A; Chierotti, M R; Gobetto, R; Martra, G; Rabin, I; Coluccia, S

    2012-02-01

    Unilateral and solid-state nuclear magnetic resonance (NMR) analyses were performed on a parchment fragment of the Dead Sea Scroll (DSS). The analyzed sample belongs to the collection of non-inscribed and nontreated fragments of known archaeological provenance from the John Rylands University Library in Manchester. Therefore, it can be considered as original DSS material free from any contamination related to the post-discovery period. Considering the paramount significance of the DSS, noninvasive approaches and portable in situ nondestructive methods are of fundamental importance for the determination of composition, structure, and chemical-physical properties of the materials under study. NMR studies reveal low amounts of water content associated with very short proton relaxation times, T(1), indicating a high level of deterioration of collagen molecules within scroll fragments. In addition, (13)C cross-polarization magic-angle-spinning (CPMAS) NMR spectroscopy shows characteristic peaks of lipids whose presence we attribute to the production technology that did not involve liming. Extraction with chloroform led to the reduction of both lipid and protein signals in the (13)C CPMAS spectrum indicating probable involvement of lipids in parchment degradation processes. NMR absorption and relaxation measurements provide nondestructive, discriminative, and sensitive tools for studying the deterioration effects on the organization and properties of water and collagen within ancient manuscripts.

  14. Probing the hydration of composite cement pastes containing fly ash and silica fume by proton NMR spin-lattice relaxation

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Proton NMR spin-lattice relaxation (T1) was used as a prober for observing the hydration process of composite cement pastes blending fly ash and silica fume during the early age.The distribution at initial time,evolution curves and signals intensity of T1 were shown in this paper.Results demonstrate that the T1 distribution curves at initial time exhibit two peaks,which are regarded as two different water phases in the pastes.The evolution curves of T1 are in good agreement with the hydration process of composite pastes and could be roughly divided into four stages:initial period,dormant period,acceleration period and steady period.The hydration mechanism for each stage was discussed.The hydration of the composite cement pastes was retarded by the addition of fly ash and silica fume when compared to that of pure cement.However,the hydration degree of the cement in the blends was promoted.

  15. Solid state NMR study of bone mineral

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Y.

    1992-01-01

    In high field (9.4 T) CP MASS (cross polarization magic angle sample spinning) studies, in contrast to the scheme in the literature that infers the presence of minor constituents in spectra, we developed a new scheme to suppress the main part of the spectra to show the minor constituents. In order to perform in vivo solid state NMR studies, a double tuned two port surface coil probe was constructed. This probe is a modified version of the traditional Cross probe, which utilizes two 1/4 wave length 50 ohm transmission line, one with open ended and the other with shorted end, to isolate the high and low frequency circuits. The two resonance frequencies in Cross probe were proton and carbon. Our probe is designed to resonate at the proton and phosphorus frequencies, which are much closer to each other and hence more difficult to be tuned and matched simultaneously. Our approach to solve this problem is that instead of using standard 50 ohm transmission lines, we constructed a low capacity open end coaxial transmission line and low inductance shorted end coaxial transmission line. The Q of the phosphorus channel is high. We developed a short contact time cross polarization technique for non-MASS spectroscopy which reduces the signal of the major component of bone mineral to emphasize the minor component. By applying this technique on intact pork bone samples with our home made surface coil, we observed the wide line component, acid phosphate, for the first time. Hydroxyapatite, brushite and octacalcium are considered in the literature to be the model compounds for bone mineral. Cross polarization dynamics has been studied on hydroxyapatite and brushite, which yielded an NMR value for the distance between proton and phosphorus. One and two dimensional CP MASS spectroscopy of octacalcium phosphate were also studied, which revealed the different cross polarization rates and anisotropic channel shifts of acid phosphate and phosphate ions in octacalcium phosphate.

  16. Backbone dynamics of a biologically active human FGF-1 monomer, complexed to a hexasaccharide heparin-analogue, by {sup 15}N NMR relaxation methods

    Energy Technology Data Exchange (ETDEWEB)

    Canales-Mayordomo, Angeles; Fayos, Rosa [Centro de Investigaciones Biologicas, CSIC, Departamento de Estructura y Funcion de Proteinas (Spain); Angulo, Jesus; Ojeda, Rafael [Instituto de Investigaciones Quimicas, CSIC, Grupo de Carbohidratos (Spain); Martin-Pastor, Manuel [Unidad de RM y Unidad de RMN de Biomoleculas Asociada al CSIC, Laboratorio de Estructura e Estructura de Biomoleculas Jose Carracido (Spain); Nieto, Pedro M.; Martin-Lomas, Manuel [Instituto de Investigaciones Quimicas, CSIC, Grupo de Carbohidratos (Spain); Lozano, Rosa; Gimenez-Gallego, Guillermo; Jimenez-Barbero, Jesus [Centro de Investigaciones Biologicas, CSIC, Departamento de Estructura y Funcion de Proteinas (Spain)], E-mail: jjbarbero@cib.csic.es

    2006-08-15

    The binding site and backbone dynamics of a bioactive complex formed by the acidic fibroblast growth factor (FGF-1) and a specifically designed heparin hexasaccharide has been investigated by HSQC and relaxation NMR methods. The comparison of the relaxation data for the free and bound states has allowed showing that the complex is monomeric, and still induces mutagenesis, and that the protein backbone presents reduced motion in different timescale in its bound state, except in certain points that are involved in the interaction with the fibroblast growth factor receptor (FGFR)

  17. {sup 27}Al NMR studies of NpPd{sub 5}Al{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Chudo, H., E-mail: chudo.hiroyuki@jaea.go.j [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Sakai, H.; Tokunaga, Y.; Kambe, S. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Aoki, D.; Homma, Y.; Shiokawa, Y. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Haga, Y.; Ikeda, S.; Matsuda, T.D. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Onuki, Y. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Yasuoka, H. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)

    2009-10-15

    We present {sup 27}Al NMR studies for a single crystal of the Np-based superconductor NpPd{sub 5}Al{sub 2}(T{sub c}=4.9K). We have observed a five-line {sup 27}Al NMR spectrum with a center line and four satellite lines separated by first-order nuclear quadrupole splittings. The Knight shift clearly drops below T{sub c}. The temperature dependence of the {sup 27}Al nuclear spin-lattice relaxation rate shows no coherence peak below T{sub c}, indicating that NpPd{sub 5}Al{sub 2} is an unconventional superconductor with an anisotropic gap. The analysis of the present NMR data provides evidence for strong-coupling d-wave superconductivity in NpPd{sub 5}Al{sub 2}.

  18. 125Te and 139La NMR Studies of Single Crystal LaTe3

    Science.gov (United States)

    Chudo, Hiroyuki; Michioka, Chishiro; Itoh, Yutaka; Yoshimura, Kazuyoshi

    2007-12-01

    We report 125Te and 139La NMR studies for single crystals of LaTe3 between 10 and 160 K under an applied field of H = 7.4841 T. We observed the broad 125Te(1) NMR signals of metallic Te(1) sheets with a superlattice modulation and the sharp 125Te(2) and 139La NMR signals of LaTe(2) bi-layers. Temperature dependence of 125Te(1) nuclear spin-lattice relaxation times of the modulated Te(1) sheets obeys a modified Korringa relation. The results indicate that the electronic state on the Te(1) sheets is a Landau-Fermi liquid on a misfit superlattice or a Tomonaga-Luttinger liquid in a two-dimensional charge-density wave ordering state.

  19. NMR studies of polysaccharides from brown seaweeds

    Energy Technology Data Exchange (ETDEWEB)

    Noseda, M.D.; Tisher, C.A.; Gorin, P.A.J.; Duarte, M.E.R. [Parana Univ., Curitiba, PR (Brazil). Dept. de Bioquimica; Cerezo, A.S. [Buenos Aires Univ. Nacional (Argentina). Dept. de Quimica Organica

    1997-12-31

    Alginic acid is the major intercellular polysaccharide serving as matrix in the brown algae and is comprised of an unbranched chain of (1->4)-linked {beta}-D-mannuronic acid (M) and {alpha}-L-guluronic acid (G), arranged in a blockwise fashion. The composition of the monomer residues and the block structure varies depending on the source of the polymer. The selective binding of cations to alginate accounts for its ability to form gels, which is dependent on the number and lenght of the G-blocks. They are widely used industrially for their ability to retain water, and for their gelling, viscosifying and stabilizing properties (Smidsrod and draget, 1996). In this study, alginate composition and block structure in Sargassum stenophyllum has been determined by chemical methods and NMR spectroscopic analysis. (author) 4 refs., 3 figs.

  20. Dynamical properties of confined supercooled water: an NMR study

    Science.gov (United States)

    Mallamace, Francesco; Broccio, Matteo; Corsaro, Carmelo; Faraone, Antonio; Liu, Li; Mou, Chung-Yuan; Chen, Sow-Hsin

    2006-09-01

    We report a set of dynamical data of confined water measured in a very deeply supercooled regime (290-190 K). Water is contained in silica matrices (MCM-41-S) which consist of 1D cylindrical pores with diameters d = 14,18 and 24 Å. When confined in these tubular pores, water does not crystallize, and can be supercooled well below 200 K. We use the NMR technique to obtain the characteristic proton relaxation time-constants (the spin-lattice relaxation time-constant T1 and the spin-spin relaxation time-constant T2) and a direct measurement of the self-diffusion coefficient in the whole temperature range. We give evidence of the existence of a fragile-to-strong dynamic crossover (FSC) at TL = 225 K from the temperature dependence of the self-diffusion coefficient. A combination of the NMR self-diffusion coefficient with the average translational relaxation time, as measured by quasi-elastic neutron scattering, shows a well defined decoupling of transport coefficients, i.e. the breakdown of the Stokes-Einstein relation, on approaching the crossover temperature TL.

  1. Dynamical properties of confined supercooled water: an NMR study

    Energy Technology Data Exchange (ETDEWEB)

    Mallamace, Francesco [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Broccio, Matteo [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Corsaro, Carmelo [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Faraone, Antonio [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Liu Li [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Mou, C-Y [Department of Chemistry, National Taiwan University, Taipei, Taiwan (China); Chen, S-H [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2006-09-13

    We report a set of dynamical data of confined water measured in a very deeply supercooled regime (290-190 K). Water is contained in silica matrices (MCM-41-S) which consist of 1D cylindrical pores with diameters d = 14,18 and 24 A. When confined in these tubular pores, water does not crystallize, and can be supercooled well below 200 K. We use the NMR technique to obtain the characteristic proton relaxation time-constants (the spin-lattice relaxation time-constant T1 and the spin-spin relaxation time-constant T2) and a direct measurement of the self-diffusion coefficient in the whole temperature range. We give evidence of the existence of a fragile-to-strong dynamic crossover (FSC) at T{sub L} = 225 K from the temperature dependence of the self-diffusion coefficient. A combination of the NMR self-diffusion coefficient with the average translational relaxation time, as measured by quasi-elastic neutron scattering, shows a well defined decoupling of transport coefficients, i.e. the breakdown of the Stokes-Einstein relation, on approaching the crossover temperature T{sub L}.

  2. Spin dynamics in charge doped antiferromagnets : a Li-7 NMR study in Ni1-xLixO

    NARCIS (Netherlands)

    Tedoldi, F; Marini, S; Corti, M

    1997-01-01

    The effects of heterovalent substitutions causing itinerant holes in strongly correlated 3d electron systems are studied by means of Li-7 NMR in lithium-doped antiferromagnetic NiO. The spin-lattice relaxation rates, driven by the fluctuation of Ni2+ (S = 1) ions, in the temperature range 10 K

  3. Spin dynamics in charge doped antiferromagnets : a Li-7 NMR study in Ni1-xLixO

    NARCIS (Netherlands)

    Tedoldi, F; Marini, S; Corti, M

    1997-01-01

    The effects of heterovalent substitutions causing itinerant holes in strongly correlated 3d electron systems are studied by means of Li-7 NMR in lithium-doped antiferromagnetic NiO. The spin-lattice relaxation rates, driven by the fluctuation of Ni2+ (S = 1) ions, in the temperature range 10 K

  4. Spin dynamics in charge doped antiferromagnets : a Li-7 NMR study in Ni1-xLixO

    NARCIS (Netherlands)

    Tedoldi, F; Marini, S; Corti, M

    1997-01-01

    The effects of heterovalent substitutions causing itinerant holes in strongly correlated 3d electron systems are studied by means of Li-7 NMR in lithium-doped antiferromagnetic NiO. The spin-lattice relaxation rates, driven by the fluctuation of Ni2+ (S = 1) ions, in the temperature range 10 K

  5. Isotope labeling for NMR studies of macromolecular structure and interactions

    Energy Technology Data Exchange (ETDEWEB)

    Wright, P.E. [Scripps Research Institute, La Jolla, CA (United States)

    1994-12-01

    Implementation of biosynthetic methods for uniform or specific isotope labeling of proteins, coupled with the recent development of powerful heteronuclear multidimensional NMR methods, has led to a dramatic increase in the size and complexity of macromolecular systems that are now amenable to NMR structural analysis. In recent years, a new technology has emerged that combines uniform {sup 13}C, {sup 15}N labeling with heteronuclear multidimensional NMR methods to allow NMR structural studies of systems approaching 25 to 30 kDa in molecular weight. In addition, with the introduction of specific {sup 13}C and {sup 15}N labels into ligands, meaningful NMR studies of complexes of even higher molecular weight have become feasible. These advances usher in a new era in which the earlier, rather stringent molecular weight limitations have been greatly surpassed and NMR can begin to address many central biological problems that involve macromolecular structure, dynamics, and interactions.

  6. NMR-Metabolic Methodology in the Study of GM Foods

    Science.gov (United States)

    The 1H NMR methodology used in the study of genetically modified (GM) foodstuff is discussed. The study of transgenic lettuce (Lactuca sativa cv "Luxor") over-expressing the KNAT1 gene from Arabidopsis is presented as a novel study-case. The 1H NMR metabolic profiling was carried out. Twenty-two wat...

  7. NMR studies of multiphase flows II

    Energy Technology Data Exchange (ETDEWEB)

    Altobelli, S.A.; Caprihan, A.; Fukushima, E. [Lovelace Institutes, Albuquerque, NM (United States)] [and others

    1995-12-31

    NMR techniques for measurements of spatial distribution of material phase, velocity and velocity fluctuation are being developed and refined. Versions of these techniques which provide time average liquid fraction and fluid phase velocity have been applied to several concentrated suspension systems which will not be discussed extensively here. Technical developments required to further extend the use of NMR to the multi-phase flow arena and to provide measurements of previously unobtainable parameters are the focus of this report.

  8. Site-specific protein backbone and side-chain NMR chemical shift and relaxation analysis of human vinexin SH3 domain using a genetically encoded {sup 15}N/{sup 19}F-labeled unnatural amino acid

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Pan [National Laboratory for Physical Science at Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); School of Life Science, University of Science and Technology of China, Hefei, Anhui 230026 (China); Xi, Zhaoyong; Wang, Hu [School of Chemistry, University of Science and Technology of China, Hefei, Anhui 230026 (China); Shi, Chaowei [National Laboratory for Physical Science at Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); School of Life Science, University of Science and Technology of China, Hefei, Anhui 230026 (China); Xiong, Ying, E-mail: yxiong73@ustc.edu.cn [School of Life Science, University of Science and Technology of China, Hefei, Anhui 230026 (China); Tian, Changlin, E-mail: cltian@ustc.edu.cn [National Laboratory for Physical Science at Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2010-11-19

    Research highlights: {yields} Chemical synthesis of {sup 15}N/{sup 19}F-trifluomethyl phenylalanine. {yields} Site-specific incorporation of {sup 15}N/{sup 19}F-trifluomethyl phenylalanine to SH3. {yields} Site-specific backbone and side chain chemical shift and relaxation analysis. {yields} Different internal motions at different sites of SH3 domain upon ligand binding. -- Abstract: SH3 is a ubiquitous domain mediating protein-protein interactions. Recent solution NMR structural studies have shown that a proline-rich peptide is capable of binding to the human vinexin SH3 domain. Here, an orthogonal amber tRNA/tRNA synthetase pair for {sup 15}N/{sup 19}F-trifluoromethyl-phenylalanine ({sup 15}N/{sup 19}F-tfmF) has been applied to achieve site-specific labeling of SH3 at three different sites. One-dimensional solution NMR spectra of backbone amide ({sup 15}N){sup 1}H and side-chain {sup 19}F were obtained for SH3 with three different site-specific labels. Site-specific backbone amide ({sup 15}N){sup 1}H and side-chain {sup 19}F chemical shift and relaxation analysis of SH3 in the absence or presence of a peptide ligand demonstrated different internal motions upon ligand binding at the three different sites. This site-specific NMR analysis might be very useful for studying large-sized proteins or protein complexes.

  9. A multinuclear static NMR study of geopolymerisation

    Energy Technology Data Exchange (ETDEWEB)

    Favier, Aurélie, E-mail: aurelie.favier@epfl.ch [Univ Paris-Est, IFSTTAR, Materials Department, 14-20 bd Newton, F-77447 Marne la Vallée Cedex 2 (France); Habert, Guillaume [Institute for Construction and Infrastructure Management, ETH Zurich, CH-8093 Zurich (Switzerland); Roussel, Nicolas [Univ Paris-Est, IFSTTAR, Materials Department, 14-20 bd Newton, F-77447 Marne la Vallée Cedex 2 (France); D' Espinose de Lacaillerie, Jean-Baptiste [Ecole Supérieure de Physique et de Chimie Indusrtrielles de la Ville de Paris (ESPCI), ParisTech, PSL Research University, Soft Matter Sciences and Engineering Laboratory SIMM, CNRS UMR 7615, 10 rue Vauquelin, F-75005 Paris (France)

    2015-09-15

    Geopolymers are inorganic binders obtained by alkali activation of aluminosilicates. While the structure of geopolymers is now well understood, the details of the geopolymerisation reaction and their impact on the rheology of the paste remain uncertain. In this work, we follow the elastic properties of a paste made with metakaolin and sodium silicate solution. After the first sharp increase of elastic modulus occurring a few hundred of seconds after mixing and related to the heterogeneous formation of an alumina–silicate gel with a molar ratio Si/Al < 4 located at the grains boundaries, we focus on the progressive increase in elastic modulus on a period of few hours during the setting of the geopolymer. In this study, we combine the study of rheological properties of the paste with {sup 23}Na, {sup 27}Al and {sup 29}Si static NMR measurement in order to better understand the origin of this second increase in elastic modulus. Our results show that, after a few hours, Al and Na evolution in the liquid phase are concomitant. This suggests the precipitation of an aluminosilicate phase where Al is in tetrahedral position and Na compensates the charge. Furthermore, Si speciation confirms this result and allows us to identify the precipitation of a product, which has a chemical composition close to the final composition of geopolymer. This study provides strong evidence for a heterogeneous formation of an aluminosilicate glass directly from the first gel and the silicate solution without the need for a reorganisation of Gel 1 into Gel 2.

  10. Phenol-formaldehyde resins: A quantitative NMR study of molecular structure and molecular dynamics

    Science.gov (United States)

    Ottenbourgs, Benjamin Tony

    Phenol-formaldehyde (PF) resins have been the subject of this work. 13C liquid-state and solid-state NMR has been used to investigate the molecular structure of mainly novolak and partially of resole resins. 1H wideline in combination with 13C solid-state NMR relaxometry has been applied to study the curing and the molecular dynamics of phenolic resins. It was the intention to provide an insight in the relationship between resin composition, resin structure and subsequent resin properties (by means of the molecular dynamics). An improved 13C liquid-state NMR quantification technique of novolaks in THF-CDCl3 solutions is demonstrated. Full quantitative 13C liquid-state spectra of phenol-formaldehyde resins with high signal- to-noise ratio were obtained by using chromium acetylacetonate under optimized spectral conditions within a few hours spectrometer time. Attached proton test (APT) spectra enabled proper peak assignments in the region with significant overlap. For several novolaks, prepared under different catalytic conditions, the degree of polymerization, degree of branching, number average molecular weight, isomeric distribution, and the number of unreacted ortho and para phenol ring positions was determined with a reduced margin of error, by analyzing and integrating the 13C spectra. The power of 13C solid-state NMR in the analysis of cured PF resins is shown. Particular importance was ascribed to the question of the quantifiability of the experiments when it was desired to measure the degree of conversion by means of a 13C CP/MAS contact time study. The network structure present, and thus also the mechanical properties, is critically dependent upon the final degree of conversion obtained after curing. The degree of conversion, which depended on the cure conditions (cure temperature, cure pressure and cure time), was limited by vitrification as was demonstrated by DSC experiments. Changes in the spin-lattice relaxation time T 1H were observed, providing

  11. Wettability of quartz surface as observed by NMR transverse relaxation time (T2)

    DEFF Research Database (Denmark)

    Alam, Mohammad Monzurul; Katika, Konstantina; Fabricius, Ida Lykke

    Injection of optimized water composition (smart water) is an advanced water flooding method for Enhanced Oil Recovery (EOR). Low saline waterflooding has been proved successful in sandstone reservoir. However, there is still controversy on the mechanism of smart water flooding. We studied...

  12. Two-dimensional NMR relaxometry study of pore space characteristics of carbonate rocks from a Permian aquifer

    Science.gov (United States)

    Schoenfelder, Wiete; Gläser, Hans-Reinhard; Mitreiter, Ivonne; Stallmach, Frank

    2008-06-01

    Limestones and karstified limestones (dolostones) from a Permian aquifer in Central Germany were studied by 1H 2D NMR relaxometry and PFG NMR diffusometry, aiming at a non-destructive characterization of the pore space. Information concerning pore size distribution and water diffusion were in accord for different samples of each type of rock, but differed fundamentally between limestones and dolostones. The results of the 2D relaxometry measurements revealed a ratio of surface relaxation times Ts1/ Ts2 of about 2 for the limestones and about 4.5 for the dolostones, mirroring the different content of iron and manganese in the solid pore walls. In consideration of thin section interpretation, the corresponding fraction in the T1- T2 relaxation time distributions was attributed to interparticle porosity. Porosity of large vugs is clearly displayed by relaxation times longer than 1 s in the dolostones only. A third fraction of the total water-saturated pore space in the dolostones, which is clearly displayed in the 2D relaxation time distributions at the smallest relaxation times and a Ts1/ Ts2 ratio of about 12, is attributed to intrafossil porosity. The porosity classification, basing on non-destructive NMR experiments, is verified by mercury intrusion porosimetry and thin section interpretation.

  13. NMR Study of Hydroxyl-Substituted Macrocyclic Hexaamine in Solution

    Institute of Scientific and Technical Information of China (English)

    Liang; Feng; Wu; Chengtai; 等

    2003-01-01

    The NMR methods (including 1H NMR, variable temperature method and the 2D COSY technique) were employed to study the conformation of 3,13-dihydroxyl-1,5,8,11,15,18-hexaazacyclicamine hexahydrobromide in aqueous solution. It was found that the ring is flexible.

  14. NMR Study of Hydroxyl-Substituted Macrocyclic Hexaamine in Solution

    Institute of Scientific and Technical Information of China (English)

    Liang Feng; Wu Xiao-jun; Wu Cheng-tai

    2003-01-01

    The NMR methods (including 1H NMR, vari-able temperature method and the 2D COSY technique) were employed to study the conformation of 3,13-dihydroxyl-1,5,8,11,15,18-hexaazacyclicamine hexahydrobromide in aqueous solution. It was found that the ring is flexible.

  15. Applications de la résonance magnétique nucléaire (RMN en milieu poreux Lissage des courbes de relaxation RMN du domaine du temps par une méthode discrète et continue Nuclear Magnetic Resonance (Nmr Applications in Porous Media Time-Dependent Nmr Relaxation Curve Smoothing Using a Discrete Continuous Method

    Directory of Open Access Journals (Sweden)

    Le Botlan D.

    2006-12-01

    Full Text Available Dans un champ magnétique hétérogène, le signal RMN de précession libre (FID suit une évolution gaussienne. Le traitement du signal par une méthode discrète peut donner des composantes qui ne correspondent pas à un état physique réel. Par contre l'utilisation d'une méthode de déconvolution continue nous a donné des résultats quantitatifs tout à fait satisfaisants permettant de déterminer les distributions de temps de relaxation correspondant à des états intermédiaires entre les phases solides et liquides. La RMN du domaine du temps peut ainsi être considérée comme une méthode analytique complémentaire des techniques habituellement utilisées pour l'étude de composés complexes hétérogènes ATD, ACD, isothermes de sorption, etc. In a heterogeneous magnetic field, the freely precessing NMR signal (FID describes a Gaussian curve. Processing the signal using a discrete method can give rise to components that do not correspond to a real physical state. However, with a continuous deconvolution method, which gives quite satisfactory quantitative results, it is possible to determine the distributions of relaxation times that correspond to intermediate states between solid and liquid phases. Time-dependent NMR can thus be used to supplement the usual analytical methods, such as DTA, DCA and sorption isotherms, for studying complex heterogeneous compounds.

  16. Studies on metabolic regulation using NMR spectroscopy.

    Science.gov (United States)

    Bachelard, H; Badar-Goffer, R; Ben-Yoseph, O; Morris, P; Thatcher, N

    1993-01-01

    The effects of hypoxia and hypoglycaemia on cerebral metabolism and calcium have been studied using multinuclear magnetic resonance spectroscopy. 13C MRS showed that severe hypoxia did not cause any further increase in metabolic flux into lactate seen in mild hypoxia, but there was a further increase in 13C labelling of alanine and glycerol 3-phosphate. These results are discussed in terms of the ability of lactate dehydrogenase to maintain normal levels of NADH in mild hypoxia, but not in severe hypoxia. We conclude that glycerol 3-phosphate and alanine may provide novel means of monitoring severe hypoxia whereas lactate is a reliable indicator only of mild hypoxia. 19F- and 31P NMR spectroscopy showed that neither hypoxia nor hypoglycaemia alone caused any significant change in [Ca2+]i. Combined sequential insults (hypoxia, followed by hypoxia plus hypoglycaemia), or vice versa, produced a 100% increase in [Ca2+]i, whereas immediate exposure to the combined insult (hypoxia plus hypoglycaemia) resulted in a large 5-fold increase in [Ca2+]i, with severe irreversible effects on the energy state. These results are discussed in terms of metabolic adaptation to the single type of insult, which renders the tissue less vulnerable to the combined insult. The effects of this combined insult are far more severe than those caused by glutamate or NMDA, which throws doubt on the current excitoxic hypothesis of cell damage.

  17. 125Te NMR study of IrTe 2

    Science.gov (United States)

    Mizuno, Kiyoshi; Magishi, Ko-ichi; Shinonome, Yasuaki; Saito, Takahito; Koyama, Kuniyuki; Matsumoto, Nobuhiro; Nagata, Shoichi

    2002-03-01

    We have measured 125Te NMR of IrTe2 in order to elucidate the origin of the anomalous behaviors in electrical and magnetic properties around 270 K. In high-temperature region, the NMR spectrum exhibits a sharp line. On the other hand, in low-temperature region, the spectrum shifts to higher magnetic field and splits into three lines. Also, the nuclear spin-lattice relaxation rate, 1/T1, is proportional to the temperature in both temperature sides; Korringa-like behavior which is characteristic of a metallic state. From the T dependences of the spectrum and 1/T1 around 270 K, it is suggested that these anomalous behaviors may not be due to the charge density wave formation but be caused by a kind of lattice distortion at low temperature.

  18. Redox-controlled backbone dynamics of human cytochrome c revealed by {sup 15}N NMR relaxation measurements

    Energy Technology Data Exchange (ETDEWEB)

    Sakamoto, Koichi [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Kamiya, Masakatsu [Graduate School of Life Science, Hokkaido University, Sapporo 060-0810 (Japan); Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810 (Japan); Uchida, Takeshi [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810 (Japan); Kawano, Keiichi [Graduate School of Life Science, Hokkaido University, Sapporo 060-0810 (Japan); Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810 (Japan); Ishimori, Koichiro, E-mail: koichiro@sci.hokudai.ac.jp [Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan); Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810 (Japan)

    2010-07-23

    Research highlights: {yields} The dynamic parameters for the backbone dynamics in Cyt c were determined. {yields} The backbone mobility of Cyt c is highly restricted due to the covalently bound heme. {yields} The backbone mobility of Cyt c is more restricted upon the oxidation of the heme. {yields} The redox-dependent dynamics are shown in the backbone of Cyt c. {yields} The backbone dynamics of Cyt c would regulate the electron transfer from Cyt c. -- Abstract: Redox-controlled backbone dynamics in cytochrome c (Cyt c) were revealed by 2D {sup 15}N NMR relaxation experiments. {sup 15}N T{sub 1} and T{sub 2} values and {sup 1}H-{sup 15}N NOEs of uniformly {sup 15}N-labeled reduced and oxidized Cyt c were measured, and the generalized order parameters (S{sup 2}), the effective correlation time for internal motion ({tau}{sub e}), the {sup 15}N exchange broadening contributions (R{sub ex}) for each residue, and the overall correlation time ({tau}{sub m}) were estimated by model-free dynamics formalism. These dynamic parameters clearly showed that the backbone dynamics of Cyt c are highly restricted due to the covalently bound heme that functions as the stable hydrophobic core. Upon oxidation of the heme iron in Cyt c, the average S{sup 2} value was increased from 0.88 {+-} 0.01 to 0.92 {+-} 0.01, demonstrating that the mobility of the backbone is further restricted in the oxidized form. Such increases in the S{sup 2} values were more prominent in the loop regions, including amino acid residues near the thioether bonds to the heme moiety and positively charged region around Lys87. Both of the regions are supposed to form the interaction site for cytochrome c oxidase (CcO) and the electron pathway from Cyt c to CcO. The redox-dependent mobility of the backbone in the interaction site for the electron transfer to CcO suggests an electron transfer mechanism regulated by the backbone dynamics in the Cyt c-CcO system.

  19. Membrane protein-lipid interactions in mixed micelles studied by NMR spectroscopy with the use of paramagnetic reagents.

    Science.gov (United States)

    Hilty, Christian; Wider, Gerhard; Fernández, César; Wüthrich, Kurt

    2004-04-02

    For solution NMR studies of the structure and function of membrane proteins, these macromolecules have to be reconstituted and solubilized in detergent micelles. Detailed characterization of the mixed detergent/protein micelles is then of key importance to validate the results from such studies, and to evaluate how faithfully the natural environment of the protein in the biological membrane is mimicked by the micelle. In this paper, a selection of paramagnetic probes with different physicochemical properties are used to characterize the 60 kDa mixed micelles consisting of about 90 molecules of the detergent dihexanoylphosphatidylcholine (DHPC) and one molecule of the Escherichia coli outer-membrane protein X (OmpX), which had previously been extensively studied by solution NMR techniques. The observation of highly selective relaxation effects on the NMR spectra of OmpX and DHPC from a water-soluble relaxation agent and from nitroxide spin labels attached to lipophilic molecules, confirmed data obtained previously with more complex NMR studies of the diamagnetic OmpX/DHPC system, and yielded additional novel insights into the protein-detergent interactions in the mixed micelles. The application of paramagnetic probes to the well-characterized OmpX/DHPC system indicates that such probes should be widely applicable as an efficient support of NMR studies of the topology of mixed membrane protein-detergent micelles.

  20. Proton NMR studies on Megaphaera elsdenii flavodoxin : structure elucidation by 2D-NMR and implications

    NARCIS (Netherlands)

    Mierlo, van C.

    1990-01-01

    1H NMR techniques have been applied for a thorough study of the uncrystallizable Megasphaera elsdenii flavodoxin in its three redox states. The aim of the research project described in this thesis was to obtain answers regarding questions concerni

  1. Relaxation study of cement based grouting material using nuclear magnetic resonance

    Institute of Scientific and Technical Information of China (English)

    Li Xianzhong; Lin Baiquan; Zhai Cheng; Ni Guanhua; Li Ziwen

    2012-01-01

    Aiming at actual condition of poor effect of hole sealing for the reason of poor cement paste fluidity in the process of coal mine gas drainage,by adding a water reducing agent,cement paste for hole sealing was produced.The changes of initial distribution,weighted average values and total relaxation signal intensity of transverse relaxation time (T2) of water in pure cement paste and water reducing agent added cement paste were studied with low field proton nuclear magnetic resonance (NMR).The results show that there are four peaks in T2 distribution curves of cement paste:the first peak is related to the bound water in flocculation,the second and the third peaks are related to the water in flocculation,water reducing agent makes it extending towards the long relaxation time,increasing its liquidity,and the fourth peak is related to the free water.By using weighted average values of T2 and total relaxation signal intensity,hydration process of cement pastes could be roughly divided into four stages:the initial period,reaction period,accelerated period and steady period.By analyzing the periods,it makes sure that the grouting process should be completed in the reaction period in the site,and the drainage process should be started in the steady period.The results have great guiding significance to the hole sealing and methane drainage.

  2. Relaxation study of cement based grouting material using nuclear magnetic resonance

    Institute of Scientific and Technical Information of China (English)

    Li; Xianzhong; Lin; Baiquan; Zhai; Cheng; Ni; Guanhua; Li; Ziwen

    2012-01-01

    Aiming at actual condition of poor effect of hole sealing for the reason of poor cement paste fluidity in the process of coal mine gas drainage,by adding a water reducing agent,cement paste for hole sealing was produced.The changes of initial distribution,weighted average values and total relaxation signal intensity of transverse relaxation time(T 2) of water in pure cement paste and water reducing agent added cement paste were studied with low field proton nuclear magnetic resonance(NMR).The results show that there are four peaks in T2 distribution curves of cement paste:the first peak is related to the bound water in flocculation,the second and the third peaks are related to the water in flocculation,water reducing agent makes it extending towards the long relaxation time,increasing its liquidity,and the fourth peak is related to the free water.By using weighted average values of T2 and total relaxation signal intensity,hydration process of cement pastes could be roughly divided into four stages:the initial period,reaction period,accelerated period and steady period.By analyzing the periods,it makes sure that the grouting process should be completed in the reaction period in the site,and the drainage process should be started in the steady period.The results have great guiding significance to the hole sealing and methane drainage.

  3. NMR contributions to structural dynamics studies of intrinsically disordered proteins☆

    Science.gov (United States)

    Konrat, Robert

    2014-01-01

    Intrinsically disordered proteins (IDPs) are characterized by substantial conformational plasticity. Given their inherent structural flexibility X-ray crystallography is not applicable to study these proteins. In contrast, NMR spectroscopy offers unique opportunities for structural and dynamic studies of IDPs. The past two decades have witnessed significant development of NMR spectroscopy that couples advances in spin physics and chemistry with a broad range of applications. This article will summarize key advances in basic physical-chemistry and NMR methodology, outline their limitations and envision future R&D directions. PMID:24656082

  4. EXPERIMENTAL AND THEORETICAL NMR STUDY OF 4-(1 ...

    African Journals Online (AJOL)

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    3 Department of Physics, Arts and Science Faculty, Dumlupınar University, Kütahya, Turkey. 4 Department ... been studied experimentally and theoretically using nuclear magnetic resonance (NMR) spectroscopy. 1H, 13C, ... INTRODUCTION.

  5. Dihydroflavanonols from Cedrus deodara, A (13)C NMR study.

    Science.gov (United States)

    Agrawal, P K; Agarwal, S K; Rastogi, R P; Osterdahal, B G

    1981-09-01

    High resolution (13)C NMR study of taxifolin, cedeodarin, cedrin and their methyl ethers allowed unambiguous placement of the Me in 5,7-dihydroxyflavanonol nucleus, besides providing other valuable information on the substitution pattern in the molecule.

  6. Studies of Molecular Dynamics by Solid State Deuterium NMR Spectroscopy

    Science.gov (United States)

    Zhao, Baiyi

    The rotational dynamics of molecules in a number of solid systems were followed by variable temperature deuterium (^2H), nuclear magnetic resonance (NMR) spectroscopy via changes in the spectral lineshapes and spin-lattice relaxation times (T _1). First the pure solid trimethylamine-borane adduct, (CH_3)_3NBH_3, was studied. For a methyl deuterated sample, T _1 measurements yielded two T_1 minima, 6.9 ms and 4.3 ms corresponding to the slowing of methyl and trimethyl rotation, respectively, with decreasing temperature. Activation energies for methyl and trimethyl rotation, obtained from fitting the T _1 curve as a function of temperature, were 32.8 and 15.0 kJ/mol, respectively; simulations of the spectral lineshapes gave 26.6 and 18.9 kT/mol, respectively. Fitting of the ^2H T_1 curve for the borane deuterated sample gave a BH _3 rotation activation energy of 14.1 kT/mol and a ^2H quadrupolar coupling constant, chi, of 101 kHz. The activation energy for BH_3 rotation obtained from the spectral lineshape simulations gave 12.6 kT/mol. A series of deuterated organic chalcogen cations: (CH_3)_3S^+, (CH_3)_3Se^+ and (CH_3)_3Te^+, were ion exchanged into the cavities of sodium Mordenite LZ-M5 and the dynamics of these guests within the hydrated zeolite were followed by ^2H NMR. All three undergo isotropic motion above about -80 to -90^circC. Below this temperature two superimposed ^2H powder spectra appear; the broad lineshape is consistent with only methyl rotation in a hindered, coordinated site, and the other narrow lineshape is due to both methyl and trimethyl rotation in a less hindered, uncoordinated site. As the temperature is lowered the population of the lower energy coordinated site increases. Relative peak areas yield adsorption enthalpies of 6.7, 7.8 and 10.0 kJ/mol for (CH_3)_3S^+, (CH_3)_3Se^+ and (CH_3)_3Te^+, respectively. The series of methyl deuterated ammonium and phosphonium cations: (CH_3)NH_3^+ , (CH_3)_2NH^+ , (CH_3)_3NH^+ and (CH_3)_4P^+ , were

  7. NMR studies on polyphosphide Ce6Ni6P17

    Science.gov (United States)

    Koyama, T.; Yamada, H.; Ueda, K.; Mito, T.; Aoyama, Y.; Nakano, T.; Takeda, N.

    2016-02-01

    We report the result of 31P nuclear magnetic resonance (NMR) studies on Ce6Ni6P17. The observed NMR spectra show a Lorentzian-type and an asymmetric shapes, reflecting the local symmetry around each P site in the cubic unit cell. We have identified the observed NMR lines corresponding to three inequivalent P sites and deduced the temperature dependence of the Knight shift for each site. The Knight shifts increase with decreasing temperature down to 1.5 K, indicating a localized spin system of Ce6Ni6P17. Antiferromagnetic correlation between 4f spins is suggested from the negative sign of the Weiss-temperature.

  8. Study of molecular interactions with 13C DNP-NMR.

    Science.gov (United States)

    Lerche, Mathilde H; Meier, Sebastian; Jensen, Pernille R; Baumann, Herbert; Petersen, Bent O; Karlsson, Magnus; Duus, Jens Ø; Ardenkjaer-Larsen, Jan H

    2010-03-01

    NMR spectroscopy is an established, versatile technique for the detection of molecular interactions, even when these interactions are weak. Signal enhancement by several orders of magnitude through dynamic nuclear polarization alleviates several practical limitations of NMR-based interaction studies. This enhanced non-equilibrium polarization contributes sensitivity for the detection of molecular interactions in a single NMR transient. We show that direct (13)C NMR ligand binding studies at natural isotopic abundance of (13)C gets feasible in this way. Resultant screens are easy to interpret and can be performed at (13)C concentrations below muM. In addition to such ligand-detected studies of molecular interaction, ligand binding can be assessed and quantified with enzymatic assays that employ hyperpolarized substrates at varying enzyme inhibitor concentrations. The physical labeling of nuclear spins by hyperpolarization thus provides the opportunity to devise fast novel in vitro experiments with low material requirement and without the need for synthetic modifications of target or ligands.

  9. 31P NMR Study on Some Phosphorus-Containing Compounds

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    31P NMR has become a widely applied spectroscopic probe of the structure of phosphorus-containing compounds. Meanwhile, the application of 31P NMR has been rapidly expanded to biochemistry and medicinal chemistry of phosphorus-containing compounds because the growing importance of the phosphorus compounds is now widely realized. We report here the results of 31P NMR study on some phosphorus-containing compounds, namely, O-alkyl O-4-nitrophenyl methyl phosphonates with different alkyl chain-length (MePO-n), 4-nitrophenyl alkylphenylphosphinates with different alkyl chain-length (PhP-n), diethyl phosphono- acetonitrile anion and diethyl phosphite anion . Our results indicate that 31P NMR can not only be applied to not only the study of the hydrolytic reactions of MePO-8 and PhP-8 but also be applied to the study of the presence of the anions of diethylphosphonoacetonitrile and diethyl phosphite in nucleophilic reactions.

  10. Water exchange in plant tissue studied by proton NMR in the presence of paramagnetic centers.

    Science.gov (United States)

    Bacić, G; Ratković, S

    1984-04-01

    The proton NMR relaxation of water in maize roots in the presence of paramagnetic centers, Mn2+, Mn- EDTA2 -, and dextran-magnetite was measured. It was shown that the NMR method of Conlon and Outhred (1972, Biochem. Biophys. Acta. 288:354-361) can be applied to a heterogenous multicellular system, and the water exchange time between cortical cells and the extracellular space can be calculated. The water exchange is presumably controlled by the intracellular unstirred layers. The Mn- EDTA2 - complex is a suitable paramagnetic compound for complex tissue, while the application of dextran-magnetite is probably restricted to studies of water exchange in cell suspensions. The water free space of the root and viscosity of the cells cytoplasm was estimated with the use of Mn- EDTA2 -. The convenience of proton NMR for studying the multiphase uptake of paramagnetic ions by plant root as well as their transport to leaves is demonstrated. A simple and rapid NMR technique (spin-echo recovery) for continuous measurement of the uptake process is presented.

  11. Feasibility of high-resolution one-dimensional relaxation imaging at low magnetic field using a single-sided NMR scanner applied to articular cartilage

    Science.gov (United States)

    Rössler, Erik; Mattea, Carlos; Stapf, Siegfried

    2015-02-01

    Low field Nuclear Magnetic Resonance increases the contrast of the longitudinal relaxation rate in many biological tissues; one prominent example is hyaline articular cartilage. In order to take advantage of this increased contrast and to profile the depth-dependent variations, high resolution parameter measurements are carried out which can be of critical importance in an early diagnosis of cartilage diseases such as osteoarthritis. However, the maximum achievable spatial resolution of parameter profiles is limited by factors such as sensor geometry, sample curvature, and diffusion limitation. In this work, we report on high-resolution single-sided NMR scanner measurements with a commercial device, and quantify these limitations. The highest achievable spatial resolution on the used profiler, and the lateral dimension of the sensitive volume were determined. Since articular cartilage samples are usually bent, we also focus on averaging effects inside the horizontally aligned sensitive volume and their impact on the relaxation profiles. Taking these critical parameters into consideration, depth-dependent relaxation time profiles with the maximum achievable vertical resolution of 20 μm are discussed, and are correlated with diffusion coefficient profiles in hyaline articular cartilage in order to reconstruct T2 maps from the diffusion-weighted CPMG decays of apparent relaxation rates.

  12. Structural studies of proteins by paramagnetic solid-state NMR spectroscopy

    Science.gov (United States)

    Jaroniec, Christopher P.

    2015-04-01

    Paramagnetism-based nuclear pseudocontact shifts and spin relaxation enhancements contain a wealth of information in solid-state NMR spectra about electron-nucleus distances on the ∼20 Å length scale, far beyond that normally probed through measurements of nuclear dipolar couplings. Such data are especially vital in the context of structural studies of proteins and other biological molecules that suffer from a sparse number of experimentally-accessible atomic distances constraining their three-dimensional fold or intermolecular interactions. This perspective provides a brief overview of the recent developments and applications of paramagnetic magic-angle spinning NMR to biological systems, with primary focus on the investigations of metalloproteins and natively diamagnetic proteins modified with covalent paramagnetic tags.

  13. Structural studies of proteins by paramagnetic solid-state NMR spectroscopy

    Science.gov (United States)

    Jaroniec, Christopher P.

    2015-01-01

    Paramagnetism-based nuclear pseudocontact shifts and spin relaxation enhancements contain a wealth of information in solid-state NMR spectra about electron-nucleus distances on the ~20 Å length scale, far beyond that normally probed through measurements of nuclear dipolar couplings. Such data are especially vital in the context of structural studies of proteins and other biological molecules that suffer from a sparse number of experimentally-accessible atomic distances constraining their three-dimensional fold or intermolecular interactions. This perspective provides a brief overview of the recent developments and applications of paramagnetic magic-angle spinning NMR to biological systems, with primary focus on the investigations of metalloproteins and natively diamagnetic proteins modified with covalent paramagnetic tags. PMID:25797004

  14. Chiral Magnetism in an Itinerant Helical Magnet, MnSi - An Extended 29Si NMR Study

    Science.gov (United States)

    Yasuoka, Hiroshi; Motoya, Kiyoichiro; Majumder, Mayukh; Witt, Sebastian; Krellner, Cornelius; Baenitz, Michael

    2016-07-01

    The microscopic magnetism in the helical, conical and ferromagnetically polarized phases in an itinerant helical magnet, MnSi, has been studied by an extended 29Si NMR at zero field and under external magnetic fields. The temperature dependence of the staggered moment, MQ(T), determined by the 29Si NMR frequency, ν(T), and the nuclear relaxation rate, 1/T1(T), at zero field is in general accord with the SCR theory for weak itinerant ferromagnetic metals and its extension to helical magnets. The external field dependence of resonance frequency, ν(H), follows a vector sum of the contributions from the atomic hyperfine and macroscopic fields with a field induced moment characteristic to itinerant magnets. A discontinuous jump of the resonance frequency at the critical field, Hc, between the conical and the polarized phases has also been found, which suggests a first order like change of the electronic states at Hc.

  15. NMR studies of organic liquids confined in mesoporous materials: (1) Pore size distribution and (2) Phase behaviour and dynamic studies in restricted geometry

    Energy Technology Data Exchange (ETDEWEB)

    Foerland, Kjersti

    2005-07-01

    In the thesis NMR spectroscopy is used for studying liquids confined in various porous materials. In the first part, pore size distributions of mesoporous silicas and controlled pore glasses were determined by measuring the 1H NMR signal from the non-frozen fraction of the confined liquid as a function of temperature, using benzene, acetonitrile and HMDS as probe molecules. In the second part, the molecular dynamics of acetonitrile, hexamethyldisilane, cyclohexane and cyclopentane confined in mesoporous materials were studied as a function of temperature. 6 papers are included with titles: 1) Pore-size determination of mesoporous materials by 1H NMR spectroscopy. 2) Pore-size distribution in mesoporous materials as studied by 1H NMR. 3) Dynamic 1H and 2H NMR investigations of acetonitrile confined in porous silica. 4) NMR investigations of hexamethyldisilane confined in controlled pore glasses: Pore size distribution and molecular dynamics studies. 5) 1H and 2H NMR studies of cyclohexane nano crystals in controlled pore glasses. 6) 1H NMR relaxation and diffusion studies of cyclohexane and cyclopentane confined in MCM-41.

  16. Unconventional superconductivity in PuRhGa{sub 5}: Ga NMR/NQR study

    Energy Technology Data Exchange (ETDEWEB)

    Sakai, H. [Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan)]. E-mail: sakai.hironori@jaea.go.jp; Tokunaga, Y. [Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Fujimoto, T. [Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Kambe, S. [Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Walstedt, R.E. [Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Yasuoka, H. [Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Aoki, D. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Homma, Y. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Yamamoto, E. [Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Nakamura, A. [Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Shiokawa, Y. [Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Nakajima, K. [Department of Nuclear Energy System, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Arai, Y. [Department of Nuclear Energy System, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Matsuda, T.D. [Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Haga, Y. [Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Onuki, Y. [Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)

    2006-05-01

    {sup 69,71}Ga NMR/NQR studies have been performed on a single crystal of the transuranium superconductor PuRhGa{sub 5} with T{sub c}{approx}9K. The spin-lattice relaxation rate 1/T{sub 1} reveals that PuRhGa{sub 5} is an unconventional superconductor having an anisotropic superconducting gap. Moreover, Korringa behavior (1/T{sub 1}T=const.) is observed in the normal state below {approx}30K. This result suggests that the superconductivity sets in after the formation of a Fermi liquid state in this compound.

  17. Fetal response to abbreviated relaxation techniques. A randomized controlled study.

    Science.gov (United States)

    Fink, Nadine S; Urech, Corinne; Isabel, Fornaro; Meyer, Andrea; Hoesli, Irène; Bitzer, Johannes; Alder, Judith

    2011-02-01

    stress during pregnancy can have adverse effects on the course of pregnancy and on fetal development. There are few studies investigating the outcome of stress reduction interventions on maternal well-being and obstetric outcome. this study aims (1) to obtain fetal behavioral states (quiet/active sleep, quiet/active wakefulness), (2) to investigate the effects of maternal relaxation on fetal behavior as well as on uterine activity, and (3) to investigate maternal physiological and endocrine parameters as potential underlying mechanisms for maternal-fetal relaxation-transferral. the behavior of 33 fetuses was analyzed during laboratory relaxation/quiet rest (control group, CG) and controlled for baseline fetal behavior. Potential associations between relaxation/quiet rest and fetal behavior (fetal heart rate (FHR), FHR variation, FHR acceleration, and body movements) and uterine activity were studied, using a computerized cardiotocogram (CTG) system. Maternal heart rate, blood pressure, cortisol, and norepinephrine were measured. intervention (progressive muscle relaxation, PMR, and guided imagery, GI) showed changes in fetal behavior. The intervention groups had higher long-term variation during and after relaxation compared to the CG (p=.039). CG fetuses had more FHR acceleration, especially during and after quiet rest (p=.027). Women in the PMR group had significantly more uterine activity than women in the GI group (p=.011) and than CG women. Maternal heart rate, blood pressure, and stress hormones were not associated with fetal behavior. this study indicates that the fetus might participate in maternal relaxation and suggests that GI is superior to PMR. This could especially be true for women who tend to direct their attention to body sensations such as abdominal activity. 2010 Elsevier Ltd. All rights reserved.

  18. Protein folding on the ribosome studied using NMR spectroscopy

    Science.gov (United States)

    Waudby, Christopher A.; Launay, Hélène; Cabrita, Lisa D.; Christodoulou, John

    2013-01-01

    NMR spectroscopy is a powerful tool for the investigation of protein folding and misfolding, providing a characterization of molecular structure, dynamics and exchange processes, across a very wide range of timescales and with near atomic resolution. In recent years NMR methods have also been developed to study protein folding as it might occur within the cell, in a de novo manner, by observing the folding of nascent polypeptides in the process of emerging from the ribosome during synthesis. Despite the 2.3 MDa molecular weight of the bacterial 70S ribosome, many nascent polypeptides, and some ribosomal proteins, have sufficient local flexibility that sharp resonances may be observed in solution-state NMR spectra. In providing information on dynamic regions of the structure, NMR spectroscopy is therefore highly complementary to alternative methods such as X-ray crystallography and cryo-electron microscopy, which have successfully characterized the rigid core of the ribosome particle. However, the low working concentrations and limited sample stability associated with ribosome–nascent chain complexes means that such studies still present significant technical challenges to the NMR spectroscopist. This review will discuss the progress that has been made in this area, surveying all NMR studies that have been published to date, and with a particular focus on strategies for improving experimental sensitivity. PMID:24083462

  19. NMR relaxometry study of plaster mortar with polymer additives

    Energy Technology Data Exchange (ETDEWEB)

    Jumate, E.; Manea, D. [Technical University of Cluj-Napoca, Faculty of Civil Engineering. 15 C Daicoviciu Str., 400020, Cluj-Napoca (Romania); Moldovan, D.; Fechete, R. [Technical University of Cluj-Napoca, Department of Physics and Chemistry, 25 G. Baritiu Str., 400027, Cluj-Napoca (Romania)

    2013-11-13

    The cement mixed with water forms a plastic paste or slurry which stiffness in time and finally hardens into a resistant stone. The addition of sand aggregates, polymers (Walocel) and/or calcium carbonate will modify dramatically the final mortar mechanic and thermal properties. The hydration processes can be observed using the 1D NMR measurements of transverse T{sub 2} relaxation times distributions analysed by a Laplace inversion algorithm. These distributions were obtained for mortar pasta measured at 2 hours after preparation then at 3, 7 and 28 days after preparation. Multiple components are identified in the T{sub 2} distributions. These can be associated with the proton bounded chemical or physical to the mortar minerals characterized by a short T{sub 2} relaxation time and to water protons in pores with three different pore sizes as observed from SEM images. The evaporation process is faster in the first hours after preparation, while the mortar hydration (bonding of water molecules to mortar minerals) can be still observed after days or months from preparation. Finally, the mechanic resistance was correlated with the transverse T{sub 2} relaxation rates corresponding to the bound water.

  20. Membrane interactions in small fast-tumbling bicelles as studied by 31P NMR.

    Science.gov (United States)

    Bodor, Andrea; Kövér, Katalin E; Mäler, Lena

    2015-03-01

    Small fast-tumbling bicelles are ideal for studies of membrane interactions at molecular level; they allow analysis of lipid properties using solution-state NMR. In the present study we used 31P NMR relaxation to obtain detailed information on lipid head-group dynamics. We explored the effect of two topologically different membrane-interacting peptides on bicelles containing either dimyristoylphosphocholine (DMPC), or a mixture of DMPC and dimyristoylphosphoglycerol (DMPG), and dihexanoylphosphocholine (DHPC). KALP21 is a model transmembrane peptide, designed to span a DMPC bilayer and dynorphin B is a membrane surface active neuropeptide. KALP21 causes significant increase in bicelle size, as evidenced by both dynamic light scattering and 31P T2 relaxation measurements. The effect of dynorphin B on bicelle size is more modest, although significant effects on T2 relaxation are observed at higher temperatures. A comparison of 31P T1 values for the lipids with and without the peptides showed that dynorphin B has a greater effect on lipid head-group dynamics than KALP21, especially at elevated temperatures. From the field-dependence of T1 relaxation data, a correlation time describing the overall lipid motion was derived. Results indicate that the positively charged dynorphin B decreases the mobility of the lipid molecules--in particular for the negatively charged DMPG--while KALP21 has a more modest influence. Our results demonstrate that while a transmembrane peptide has severe effects on overall bilayer properties, the surface bound peptide has a more dramatic effect in reducing lipid head-group mobility. These observations may be of general importance for understanding peptide-membrane interactions.

  1. NMR spectroscopy study of agar-based polymers electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Mattos, R.I.; Tambelli, C.E. [Universidade de Sao Paulo (USP), Pirassununga, SP (Brazil). Fac. de Zootecnia e Engenharia de Alimentos; Raphael, E. [Universidade Federal de Sao Joao del-Rey (UFSJ), MG (Brazil). Dept. de Ciencias Naturais; Silva, I.D.A.; Magon, C.J.; Donoso, J.P. [Universidade de Sao Paulo (IFSC/USP), Sao Carlos, SP (Brazil). Inst. de Fisica

    2012-07-01

    Full text: This communication presents the results of preparation and characterization of transparent films obtained from agar and acetic acid. The films were characterized by electrochemical impedance spectroscopy (EIS) and nuclear magnetic resonance (NMR). The film formed by agar (Sigma Aldrich) was dispersed in water and kept under stirring and heating at 100 deg C. Next, glycerol, formaldehyde and different quantities of acetic acid (25 and 50 wt%) were added to this solution. The obtained solution was placed on a glass plate and left to dry for 48 hours in oven at 50 deg C to obtain the films, which were kept under vacuum before characterization. The ionic conductivity of the films display an Arrhenius behavior with activation energy E{sub a} = 78 (25 wt% of acetic acid) and E{sub a} = 87 kJ/mol (50 wt% of acetic acid). The conductivity values were 3:0 X 10{sup -6} and 1:2 X 10{sup -4} S/cm at room temperature and 4:4 X 10{sup -4} and 1:5 X 10{sup -3}S/cm at 70 deg C, for the 25 and 50 wt% of acetic acid respectively. To investigate the mechanism of protonic conduction in the polymer proton conductor proton NMR measurements were performed in the temperature range 200-370 K. The {sup 1}H-NMR results exhibit the qualitative feature associated with the proton mobility, namely the presence of well defined {sup 1}H spin-lattice relaxation maxima at 300 K. Activation energy of the order of 40 kJ/mol was obtained from the {sup 1}H-NMR line narrowing data. The ionic conductivity of the film combined with their transparency, flexibility, homogeneity and good adhesion to the glasses or metals indicate that agar-based SPEs are promising materials for used on optoelectronic applications. (author)

  2. Nuclear magnetic relaxation studies of water in frozen biological tissues. Cross-relaxation effects between protein and bound water protons

    Science.gov (United States)

    Escanyé, J. M.; Canet, D.; Robert, J.

    Water proton longitudinal relaxation has been investigated in frozen mouse tissues including tumors. The nonfreezable water which gives rise to a relatively sharp NMR signal at this temperature (263 K) is identified as water bound to macromolecules. Measurements have been carried out by the nonselective inversion-recovery method at 90 and 6 MHz. Partially selective inversion has been achieved at 90 MHz by the DANTE sequence. The experimental data are analyzed by means of Solomon-type equations. This analysis provides the cross-relaxation term from which the dipolar contribution to water relaxation rate, arising from interactions with macromolecular protons, is calculated. This contribution seems to be dominant. The number of water protons interacting with a given macromolecular proton is found to be of the order of 10. The data at both frequencies can be consistently interpreted in terms of water diffusion, with a characteristic time of about 10 -9 sec. These conclusions are valid for all the tissues investigated here, their relaxation parameters exhibiting only slight differences.

  3. Solid state NMR study calcium phosphate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Miquel, J.L.; Facchini, L.; Legrand, A.P. (Laboratoire de Physique Quantique, Paris (France). CNRS, URA421, ESPCI); Rey, C. (CNRS, Toulouse (France). ENSC. Laboratoire de Physico-chimie des Solides); Lemaitre, J. (EPF Lausanne (France). Laboratoire de Technologie des Poudres)

    1990-04-01

    High-resolution {sup 31}P and {sup 1}H NMR spectra at 40 and 121 MHz {sup 31}P and 300 MHz {sup 1}H of synthetic and biological samples of calcium phosphates have been obtained by magic angle spinning (MAS) at spinning speeds up to 6.5 kHz, and high power proton decoupling. The samples include crystalline hydroxyapatite, a deficient hydroxyapatite characterized by a Ca/P atomic ratio of 1.5, a poorly crystallized hydroxyapatite, monetite, brushite, octacalcium phosphate, {beta}-tricalcium phosphate and rabbit femoral bone. The interactions between nuclei in unlike structures and the mobility of acid protons are discussed. (author). 11 refs.; 2 figs.; 1 tab.

  4. Site-specific protonation kinetics of acidic side chains in proteins determined by pH-dependent carboxyl (13)C NMR relaxation.

    Science.gov (United States)

    Wallerstein, Johan; Weininger, Ulrich; Khan, M Ashhar I; Linse, Sara; Akke, Mikael

    2015-03-04

    Proton-transfer dynamics plays a critical role in many biochemical processes, such as proton pumping across membranes and enzyme catalysis. The large majority of enzymes utilize acid-base catalysis and proton-transfer mechanisms, where the rates of proton transfer can be rate limiting for the overall reaction. However, measurement of proton-exchange kinetics for individual side-chain carboxyl groups in proteins has been achieved in only a handful of cases, which typically have involved comparative analysis of mutant proteins in the context of reaction network modeling. Here we describe an approach to determine site-specific protonation and deprotonation rate constants (kon and koff, respectively) of carboxyl side chains, based on (13)C NMR relaxation measurements as a function of pH. We validated the method using an extensively studied model system, the B1 domain of protein G, for which we measured rate constants koff in the range (0.1-3) × 10(6) s(-1) and kon in the range (0.6-300) × 10(9) M(-1) s(-1), which correspond to acid-base equilibrium dissociation constants (Ka) in excellent agreement with previous results determined by chemical shift titrations. Our results further reveal a linear free-energy relationship between log kon and pKa, which provides information on the free-energy landscape of the protonation reaction, showing that the variability among residues in these parameters arises primarily from the extent of charge stabilization of the deprotonated state by the protein environment. We find that side-chain carboxyls with extreme values of koff or kon are involved in hydrogen bonding, thus providing a mechanistic explanation for the observed stabilization of the protonated or deprotonated state.

  5. Ultrafast studies of photodissociation in solution: Dissociation, recombination and relaxation

    Energy Technology Data Exchange (ETDEWEB)

    King, Jason Christopher [Univ. of California, Berkeley, CA (United States)

    1995-05-01

    Photodissociation of M(CO)6 (M=Cr,Mo,W) and the formation of solvated M(CO)5•S complex was studied in cyclohexane; rate-limiting step is vibrational energy relaxation from the new bond to the solvent. For both M=Cr and Mo, the primary relaxation occurs in 18 ps; for Cr, there is an additional vibrational relaxation (150 ps time scale) of a CO group poorly coupled to other modes. Relaxation of M=W occurs in 42 ps; several possible mechanisms for the longer cooling are discussed. Vibrational relaxation is also investigated for I2- and IBr- in nonpolar and slightly polar solvents. Attempts were made to discover the mechanism for the fast energy transfer in nonpolar solvent. The longer time scale dynamics of I3- and IBr2- were also studied; both formed a metastable complex following photodissociation and 90-95% return to ground state in 100 ps, implying a barrier to recombination of 4.3 kcal/mol and a barrier to escape of ≥5.5 kcal/mol. The more complex photochemistry of M3(CO)12 (M=Fe,Ru) is also investigated, using visible and ultraviolet radiations, dissociation, geminate recombination, vibrational relaxation, and bridging structures and their reactions were studied. Attempts were made to extend ultrafast spectroscopy into the mid-infrared, but signal-to-noise was poor.

  6. Measurement of carbonyl chemical shifts of excited protein states by relaxation dispersion NMR spectroscopy: comparison between uniformly and selectively {sup 13}C labeled samples

    Energy Technology Data Exchange (ETDEWEB)

    Lundstroem, Patrik; Hansen, D. Flemming; Kay, Lewis E. [University of Toronto, Department of Medical Genetics (Canada)], E-mail: kay@pound.med.utoronto.ca

    2008-09-15

    Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion nuclear magnetic resonance (NMR) spectroscopy has emerged as a powerful method for quantifying chemical shifts of excited protein states. For many applications of the technique that involve the measurement of relaxation rates of carbon magnetization it is necessary to prepare samples with isolated {sup 13}C spins so that experiments do not suffer from magnetization transfer between coupled carbon spins that would otherwise occur during the CPMG pulse train. In the case of {sup 13}CO experiments however the large separation between {sup 13}CO and {sup 13}C{sup {alpha}} chemical shifts offers hope that robust {sup 13}CO dispersion profiles can be recorded on uniformly {sup 13}C labeled samples, leading to the extraction of accurate {sup 13}CO chemical shifts of the invisible, excited state. Here we compare such chemical shifts recorded on samples that are selectively labeled, prepared using [1-{sup 13}C]-pyruvate and NaH{sup 13}CO{sub 3,} or uniformly labeled, generated from {sup 13}C-glucose. Very similar {sup 13}CO chemical shifts are obtained from analysis of CPMG experiments recorded on both samples, and comparison with chemical shifts measured using a second approach establishes that the shifts measured from relaxation dispersion are very accurate.

  7. Nuclear magnetic relaxation study of poly(ethylene oxide)-lithium salt based electrolytes

    Science.gov (United States)

    Donoso, J. P.; Bonagamba, T. J.; Panepucci, H. C.; Oliveira, L. N.; Gorecki, W.; Berthier, C.; Armand, M.

    1993-06-01

    We have studied the low-temperature NMR line shape for three nuclei (1H, 7Li, and 19F) in poly(ethylene oxide)-lithium salts (LiClO4, LiBF4, and LiAsF6) solid polymer ionic conductors and measured their spin-lattice relaxation rates as functions of frequency and temperature. The three nuclei probe the dynamics of the polymer segments, the cations, and the anions. We find that the Li+ cations follow the segmental motion of the chain, while the anions move independently. Homonuclear interactions and heteronuclear interactions with the polymer and the anion contribute to the 7Li line shape. When the heteronuclear contributions were selectively eliminated by the decoupling method, it was found that the Li-H interaction accounts for 80%-90% of the linewidth. Additional evidence for the correlation between the cationic and the polymeric motions is provided by the remarkably similar temperature dependences of the measured relaxation rates for 7Li and 1H, which differ significantly from the dependence for 19F. The frequency dependence of the relaxation rates is poorly described by the Bloembergen, Purcell, and Pound model; a recently developed graphical procedure nevertheless shows that the motion of the protons and the anions is governed by a single time scale, while the 7Li ions are affected by an additional scale, associated with the coupling of its quadrupolar moment to the electric-field gradient.

  8. Structure determination of uniformly {sup 13}C, {sup 15}N labeled protein using qualitative distance restraints from MAS solid-state {sup 13}C-NMR observed paramagnetic relaxation enhancement

    Energy Technology Data Exchange (ETDEWEB)

    Tamaki, Hajime [Hokkaido University, Graduate School of Life Science (Japan); Egawa, Ayako [Osaka University, Institute for Protein Research (Japan); Kido, Kouki [Hokkaido University, Graduate School of Life Science (Japan); Kameda, Tomoshi [National Institute of Advanced Industrial Science and Technology, Biotechnology Research Institute for Drug Discovery (Japan); Kamiya, Masakatsu; Kikukawa, Takashi; Aizawa, Tomoyasu [Hokkaido University, Faculty of Advanced Life Science (Japan); Fujiwara, Toshimichi [Osaka University, Institute for Protein Research (Japan); Demura, Makoto, E-mail: demura@sci.hokudai.ac.jp [Hokkaido University, Faculty of Advanced Life Science (Japan)

    2016-01-15

    Magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) is a powerful method for structure determination of insoluble biomolecules. However, structure determination by MAS solid-state NMR remains challenging because it is difficult to obtain a sufficient amount of distance restraints owing to spectral complexity. Collection of distance restraints from paramagnetic relaxation enhancement (PRE) is a promising approach to alleviate this barrier. However, the precision of distance restraints provided by PRE is limited in solid-state NMR because of incomplete averaged interactions and intermolecular PREs. In this report, the backbone structure of the B1 domain of streptococcal protein G (GB1) has been successfully determined by combining the CS-Rosetta protocol and qualitative PRE restraints. The derived structure has a Cα RMSD of 1.49 Å relative to the X-ray structure. It is noteworthy that our protocol can determine the correct structure from only three cysteine-EDTA-Mn{sup 2+} mutants because this number of PRE sites is insufficient when using a conventional structure calculation method based on restrained molecular dynamics and simulated annealing. This study shows that qualitative PRE restraints can be employed effectively for protein structure determination from a limited conformational sampling space using a protein fragment library.

  9. Cross-Correlated Relaxation of Dipolar Coupling and Chemical-Shift Anisotropy in Magic-Angle Spinning R1ρ NMR Measurements: Application to Protein Backbone Dynamics Measurements.

    Science.gov (United States)

    Kurauskas, Vilius; Weber, Emmanuelle; Hessel, Audrey; Ayala, Isabel; Marion, Dominique; Schanda, Paul

    2016-09-01

    Transverse relaxation rate measurements in magic-angle spinning solid-state nuclear magnetic resonance provide information about molecular motions occurring on nanosecond-to-millisecond (ns-ms) time scales. The measurement of heteronuclear ((13)C, (15)N) relaxation rate constants in the presence of a spin-lock radiofrequency field (R1ρ relaxation) provides access to such motions, and an increasing number of studies involving R1ρ relaxation in proteins have been reported. However, two factors that influence the observed relaxation rate constants have so far been neglected, namely, (1) the role of CSA/dipolar cross-correlated relaxation (CCR) and (2) the impact of fast proton spin flips (i.e., proton spin diffusion and relaxation). We show that CSA/D CCR in R1ρ experiments is measurable and that the CCR rate constant depends on ns-ms motions; it can thus provide insight into dynamics. We find that proton spin diffusion attenuates this CCR due to its decoupling effect on the doublet components. For measurements of dynamics, the use of R1ρ rate constants has practical advantages over the use of CCR rates, and this article reveals factors that have so far been disregarded and which are important for accurate measurements and interpretation.

  10. Rotational Mobility in a Crystal Studied by Dielectric Relaxation Spectroscopy

    Science.gov (United States)

    Dionisio, Madalena S. C.; Diogo, Herminio P.; Farinha, J. P. S.; Ramos, Joaquim J. Moura

    2005-01-01

    A laboratory experiment for undergraduate physical chemistry courses that uses the experimental technique of dielectric relaxation spectroscopy to study molecular mobility in a crystal is proposed. An experiment provides an excellent opportunity for dealing with a wide diversity of important basic concepts in physical chemistry.

  11. NMR studies of alkali C{sub 60} superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Stenger, V.A.; Recchia, C.; Pennington, C.H. [Ohio State Univ., Columbus, OH (United States)] [and others

    1994-12-01

    The authors report {sup 13}C, {sup 87}Rb, {sup 39}K, and {sup 133}Cs nuclear magnetic resonance (NMR) measurements of lineshapes, Knight shifts, and spin-lattice relaxation rates in the normal and superconducting states of M{sub 3}C{sub 60}, where M{sub 3} = Rb{sub 3}, K{sub 3}, Rb{sub 2}K, RbK{sub 2}, Rb{sub 2}Cs, and RbCs{sub 2}. Measurements are used as a guide to a new ammonia solvent synthesis technique. Temperature dependence of the superconducting state electron spin susceptibility is found to follow BCS weak coupling predictions. The issue of the Hebel-Slichter coherence peak is addressed.

  12. Molecular dynamics of solid cortisol studied by NMR

    Science.gov (United States)

    Andrew, E. R.

    Polycrystalline cortisol (hydrocortisone; 11β,17α,21-trihydroxy-4-preg- nene-3,20-dione; C21H30O5) has been investigated by continuous and pulse proton NMR methods between 78 and 400 K at Larmor frequencies of 7, 25 and 60 MHz. A reduced value of second moment was found above 90 K and is ascribed to reorientation of two methyl groups. A single asymmetric minimum was found in the temperature dependence of the spin-lattice relaxation times and this also is attributed to reorientation of two methyl groups. The asymmetry suggests an asymmetric distribution of correlation times of the motion. Using the Cole-Davidson distribution, the best computer fit yields the following parameters characterizing the motion: Ea = 11ṡ8 ± 0ṡ1 kJ mol-1, τ0 = 4ṡ6 ± 0ṡ4) x 10-13s, distribution parameter δ = 0ṡ62.

  13. NMR study of size effects in relaxor PMN nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Blinc, Robert [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Zalar, Bostjan; Zupancic, Blaz [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); EN-FIST Centre of Excellence, Dunajska cesta 156, 1000 Ljubljana (Slovenia); Morozovska, Anna N. [Institute for Problems of Material Science, National Academy of Sciences of Ukraine, Krjijanovskogo 3, 03142 Kiev (Ukraine); V. Lashkarev Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, prospekt Nauki 41, 03028 Kiev (Ukraine); Glinchuk, Maya D. [Institute for Problems of Material Science, National Academy of Sciences of Ukraine, Krjijanovskogo 3, 03142 Kiev (Ukraine)

    2011-11-15

    {sup 93}Nb 1/2{yields} -1/2 NMR line shape and spin-lattice measurements show that microcrystalline PbMg{sub 1/3}Nb{sub 2/3}O{sub 3} (PMN) powder is dynamically disordered at room temperature, whereas nanocrystalline PMN powder is orientationally frozen out and long-range ordered at room temperature. The dynamical disorder of the microcrystalline powder results in a motional averaging of the anisotropic part of the {sup 93}Nb chemical shift tensor and second order quadrupole shift, whereas this averaging is absent in the nanocrystalline powder, resulting in a broader central line and a longer spin-lattice relaxation time. This seems to be the first observation of such size effects in a relaxor. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Nuclear spin relaxation in liquids theory, experiments, and applications

    CERN Document Server

    Kowalewski, Jozef

    2006-01-01

    Nuclear magnetic resonance (NMR) is widely used across many fields because of the rich data it produces, and some of the most valuable data come from the study of nuclear spin relaxation in solution. While described to varying degrees in all major NMR books, spin relaxation is often perceived as a difficult, if not obscure, topic, and an accessible, cohesive treatment has been nearly impossible to find.Collecting relaxation theory, experimental techniques, and illustrative applications into a single volume, this book clarifies the nature of the phenomenon, shows how to study it, and explains why such studies are worthwhile. Coverage ranges from basic to rigorous theory and from simple to sophisticated experimental methods, and the level of detail is somewhat greater than most other NMR texts. Topics include cross-relaxation, multispin phenomena, relaxation studies of molecular dynamics and structure, and special topics such as relaxation in systems with quadrupolar nuclei and paramagnetic systems.Avoiding ove...

  15. NMR study of a membrane protein in detergent-free aqueous solution.

    Science.gov (United States)

    Zoonens, Manuela; Catoire, Laurent J; Giusti, Fabrice; Popot, Jean-Luc

    2005-06-21

    One of the major obstacles to membrane protein (MP) structural studies is the destabilizing effect of detergents. Amphipols (APols) are short amphipathic polymers that can substitute for detergents to keep MPs water-soluble under mild conditions. In the present work, we have explored the feasibility of studying the structure of APol-complexed MPs by NMR. As a test MP, we chose the 171-residue transmembrane domain of outer MP A from Escherichia coli (tOmpA), whose x-ray and NMR structures in detergent are known. 2H,15N-labeled tOmpA was produced as inclusion bodies, refolded in detergent solution, trapped with APol A8-35, and the detergent removed by adsorption onto polystyrene beads. The resolution of transverse relaxation-optimized spectroscopy-heteronuclear single-quantum correlation spectra of tOmpA/A8-35 complexes was found to be close to that of the best spectra obtained in detergent solutions. The dispersion of chemical shifts indicated that the protein had regained its native fold and retained it during the exchange of surfactants. MP-APol interactions were mapped by substituting hydrogenated for deuterated A8-35. The resulting dipolar broadening of amide proton linewidths was found to be limited to the beta-barrel region of tOmpA, indicating that A8-35 binds specifically to the hydrophobic transmembrane surface of the protein. The potential of this approach to MP studies by solution NMR is discussed.

  16. NMR-Metabolic Methodology in the Study of GM Foods

    Directory of Open Access Journals (Sweden)

    Irene D’Amico

    2010-01-01

    Full Text Available The 1H-NMR methodology used in the study of genetically modified (GM foods is discussed. Transgenic lettuce (Lactuca sativa cv "Luxor" over-expressing the Arabidopsis KNAT1 gene is presented as a case study. Twenty-two water-soluble metabolites (amino acids, organic acids, sugars present in leaves of conventional and GM lettuce were monitored by NMR and quantified at two developmental stages. The NMR spectra did not reveal any difference in metabolite composition between the GM lettuce and the wild type counterpart. Statistical analyses of metabolite variables highlighted metabolism variation as a function of leaf development as well as the transgene. A main effect of the transgene was in altering sugar metabolism.

  17. Computer Code for Interpreting 13C NMR Relaxation Measurements with Specific Models of Molecular Motion: The Rigid Isotropic and Symmetric Top Rotor Models and the Flexible Symmetric Top Rotor Model

    Science.gov (United States)

    2017-01-01

    resonance (NMR) Spectral density functions Spin - spin relaxation Molecular dynamics Nuclear Overhauser effect Symmetric top rotor Spin -lattice relaxation...SYMMETRIC TOP ROTOR MODELS AND THE FLEXIBLE SYMMETRIC TOP ROTOR MODEL ECBC-TR-1428 Terry J. Henderson RESEARCH AND TECHNOLOGY DIRECTORATE...Symmetric Top Rotor Models and the Flexible Symmetric Top Rotor Model 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR

  18. Relaxation-compensated difference spin diffusion NMR for detecting {sup 13}C–{sup 13}C long-range correlations in proteins and polysaccharides

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Tuo; Williams, Jonathan K. [Massachusetts Institute of Technology, Department of Chemistry (United States); Schmidt-Rohr, Klaus [Brandeis University, Department of Chemistry (United States); Hong, Mei, E-mail: meihong@mit.edu [Massachusetts Institute of Technology, Department of Chemistry (United States)

    2015-02-15

    The measurement of long-range distances remains a challenge in solid-state NMR structure determination of biological macromolecules. In 2D and 3D correlation spectra of uniformly {sup 13}C-labeled biomolecules, inter-residue, inter-segmental, and intermolecular {sup 13}C–{sup 13}C cross peaks that provide important long-range distance constraints for three-dimensional structures often overlap with short-range cross peaks that only reflect the covalent structure of the molecule. It is therefore desirable to develop new approaches to obtain spectra containing only long-range cross peaks. Here we show that a relaxation-compensated modification of the commonly used 2D {sup 1}H-driven spin diffusion (PDSD) experiment allows the clean detection of such long-range cross peaks. By adding a z-filter to keep the total z-period of the experiment constant, we compensate for {sup 13}C T{sub 1} relaxation. As a result, the difference spectrum between a long- and a scaled short-mixing time spectrum show only long-range correlation signals. We show that one- and two-bond cross peaks equalize within a few tens of milliseconds. Within ∼200 ms, the intensity equilibrates within an amino acid residue and a monosaccharide to a value that reflects the number of spins in the local network. With T{sub 1} relaxation compensation, at longer mixing times, inter-residue and inter-segmental cross peaks increase in intensity whereas intra-segmental cross-peak intensities remain unchanged relative to each other and can all be subtracted out. Without relaxation compensation, the difference 2D spectra exhibit both negative and positive intensities due to heterogeneous T{sub 1} relaxation in most biomolecules, which can cause peak cancellation. We demonstrate this relaxation-compensated difference PDSD approach on amino acids, monosaccharides, a crystalline model peptide, a membrane-bound peptide and a plant cell wall sample. The resulting difference spectra yield clean multi-bond, inter

  19. An inversion method of 2D NMR relaxation spectra in low fields based on LSQR and L-curve

    Science.gov (United States)

    Su, Guanqun; Zhou, Xiaolong; Wang, Lijia; Wang, Yuanjun; Nie, Shengdong

    2016-04-01

    The low-field nuclear magnetic resonance (NMR) inversion method based on traditional least-squares QR decomposition (LSQR) always produces some oscillating spectra. Moreover, the solution obtained by traditional LSQR algorithm often cannot reflect the true distribution of all the components. Hence, a good solution requires some manual intervention, for especially low signal-to-noise ratio (SNR) data. An approach based on the LSQR algorithm and L-curve is presented to solve this problem. The L-curve method is applied to obtain an improved initial optimal solution by balancing the residual and the complexity of the solutions instead of manually adjusting the smoothing parameters. First, the traditional LSQR algorithm is used on 2D NMR T1-T2 data to obtain its resultant spectra and corresponding residuals, whose norms are utilized to plot the L-curve. Second, the corner of the L-curve as the initial optimal solution for the non-negative constraint is located. Finally, a 2D map is corrected and calculated iteratively based on the initial optimal solution. The proposed approach is tested on both simulated and measured data. The results show that this algorithm is robust, accurate and promising for the NMR analysis.

  20. Intrinsic Proton NMR Studies of Mg(OH)2 and Ca(OH)2

    Science.gov (United States)

    Itoh, Yutaka; Isobe, Masahiko

    2016-09-01

    We studied the short proton free induction decay signals and the broad 1H NMR spectra of Mg(OH)2 and Ca(OH)2 powders at 77-355 K and 42 MHz using pulsed NMR techniques. Using a Gaussian-type back extrapolation procedure for the obscured data of the proton free induction decay signals, we obtained more precise values of the second moments of the Fourier-transformed broad NMR spectra than those in a previous report [Y. Itoh and M. Isobe, http://doi.org/10.7566/JPSJ.84.113601, J. Phys. Soc. Jpn. 84, 113601 (2015)] and compared with the theoretical second moments. The decrease in the second moment could not account for the large decrease in the magnitude of the intrinsic proton spin-lattice relaxation rate 1/T1 from Mg(OH)2 to Ca(OH)2. The analysis of 1/T1 ∝ exp(-Eg/kBT) with Eg ˜ 0.01 eV points to a local hopping mechanism, and that of 1/T1 ∝ Tn with n ˜ 0.5 points to an anharmonic rattling mechanism.

  1. Mn(II) binding to human serum albumin: a ¹H-NMR relaxometric study.

    Science.gov (United States)

    Fanali, Gabriella; Cao, Yu; Ascenzi, Paolo; Fasano, Mauro

    2012-12-01

    Human serum albumin (HSA) displays several metal binding sites, participating to essential and toxic metal ions disposal and transport. The major Zn(II) binding site, called Site A, is located at the I/II domain interface, with residues His67, Asn99, His247, and Asp249 contributing with five donor atoms to the metal ion coordination. Additionally, one water molecule takes part of the octahedral coordination geometry. The occurrence of the metal-coordinated water molecule allows the investigation of the metal complex geometry by water (1)H-NMR relaxation, provided that the diamagnetic Zn(II) is replaced by the paramagnetic Mn(II). Here, the (1)H-NMR relaxometric study of Mn(II) binding to HSA is reported. Mn(II) binding to HSA is modulated by Zn(II), pH, and myristate through competitive inhibition and allosteric mechanisms. The body of results indicates that the primary binding site of Zn(II) corresponds to the secondary binding site of Mn(II), i.e. the multimetal binding site A. Excess Zn(II) completely displaces Mn(II) from its primary site suggesting that the primary Mn(II) site corresponds to the secondary Zn(II) site. This uncharacterized site is functionally-linked to FA1; moreover, metal ion binding is modulated by myristate and pH. Noteworthy, water (1)H-NMR relaxometry allowed a detailed analysis of thermodynamic properties of HSA-metal ion complexes.

  2. NMR Study of HD Adsorbed in a Z-type Metal-Organic Framework

    Science.gov (United States)

    Ji, Yu; Tang, Y.; Hamida, J. A.; Sullivan, N. S.

    2012-12-01

    We report the results of measurements of the nuclear spin-lattice and spin-spin relaxation rates of hydrogen deuteride trapped in the mesoporous cages of a metal organic framework (MOF) for temperatures 2.2 hydrogen storage because of the high density of adsorption. NMR studies can provide important information about the molecular interactions and dynamics inside the cages of the MOF structure. Samples were studied with filling factors of 0.1 and 1.0 molecules per cage as determined by the adsorption isotherm at 77 K The results show strong peaks in the relaxation times at several well defined temperatures that are very different from the adsorption energy levels. The origin of these peaks is discussed in terms of the quantization of the translational degrees of freedom of the molecules inside the cages and the associated discrete energy levels. Measurements of the nuclear spin-spin relaxation times also provide an important measure of the diffusivity of hydrogen through the MOF structure which is a critical parameter for the use of MOFs for storage and transport.

  3. Spin-lattice relaxation study of the methyl proton dynamics in solid 9,10-dimethyltriptycene (DMT).

    Science.gov (United States)

    Piślewski, N; Tritt-Goc, J; Bielejewski, M; Rachocki, A; Ratajczyk, T; Szymański, S

    2009-06-01

    Proton spin-lattice relaxation studies are performed for powder samples of 9,10-dimethyltriptycene (DMT) and its isotopomer DMT-d(12) in which all the non-methyl protons in the molecule are replaced by deuterons. The relaxation data are interpreted in terms of the conventional relaxation theory based on the random jump model in which the Pauli correlations between the relevant spin and torsional states are discarded. The Arrhenius activation energies, obtained from the relaxation data, 25.3 and 24.8 kJ mol(-1) for DMT and DMT-d(12), respectively, are very high as for the methyl groups. The validity of the jump model in the present case is considered from the perspective of Haupt theory in which the Pauli principle is explicitly invoked. To this purpose, the dynamic quantities entering the Haupt model are reinterpreted in the spirit of the damped quantum rotation (DQR) approach introduced recently for the purpose of NMR lineshape studies of hindered molecular rotators. Theoretical modelling of the relevant methyl group dynamics, based on the DQR theory, was performed. From these calculations it is inferred that direct assessments of the torsional barrier heights, based on the Arrhenius activation energies extracted from relaxation data, should be treated with caution.

  4. Proton magnetic relaxation study of the thermodynamic characteristics of water adsorbed by cellulose fibers

    Science.gov (United States)

    Grunin, Yu. B.; Grunin, L. Yu.; Masas, D. S.; Talantsev, V. I.; Sheveleva, N. N.

    2016-11-01

    The possibility of determining the thermodynamic parameters that characterize the sorption properties of cellulose and the state of water associated with its fibers is demonstrated using modern concepts of the structure of this vegetable polymer and methods based on theories of adsorption and NMR relaxation in heterogeneous systems.

  5. Biomolecular recognition mechanisms studied by NMR spectroscopy and MD simulations

    NARCIS (Netherlands)

    Hsu, Shang-Te Danny

    2004-01-01

    This thesis describes the use of solution Nuclear Magnetic Resonance (NMR) spectroscopy and Molecular Dynamics (MD) simulations to study the mechanism of biomolecular recognition with two model systems: i) lipid II-binding lantibiotics (lanthionine-containing antibiotics) and ii) the human immunodef

  6. Novel Dodecaarylporphyrins: Synthesis and Variable Temperature NMR Studies

    Energy Technology Data Exchange (ETDEWEB)

    Cancilla, Mark; Lebrilla, Carlito; Ma, Jian-Guo; Medforth, Craig J.; Muzzi, Cinzia M.; Shelnutt, John A.; Smith, Kevin M.; Voss, Lisa

    1999-05-05

    An investigation of the synthesis of novel dodecaarylporphyrins using the Suzuki coupling reaction of arylboronic acids with octabromotetraarylporphyrins is reported. Studies of the dynamic properties of these new porphyrins using variable temperature (VT) 1H NMR spectroscopy and molecular mechanics provide interesting insights into their dynamic properties, including the first determination of {beta} aryl rotation in a porphyrin system.

  7. Magnetic hyperthermia efficiency and 1H-NMR relaxation properties of iron oxide/paclitaxel-loaded PLGA nanoparticles

    Science.gov (United States)

    Ruggiero, Maria R.; Geninatti Crich, Simonetta; Sieni, Elisabetta; Sgarbossa, Paolo; Forzan, Michele; Cavallari, Eleonora; Stefania, Rachele; Dughiero, Fabrizio; Aime, Silvio

    2016-07-01

    Magnetic iron oxide nanoparticles (Fe-NPs) can be exploited in biomedicine as agents for magnetic fluid hyperthermia (MFH) treatments and as contrast enhancers in magnetic resonance imaging. New, oleate-covered, iron oxide particles have been prepared either by co-precipitation or thermal decomposition methods and incorporated into poly(lactic-co-glycolic acid) nanoparticles (PLGA-Fe-NPs) to improve their biocompatibility and in vivo stability. Moreover, the PLGA-Fe-NPs have been loaded with paclitaxel to pursue an MFH-triggered drug release. Remarkably, it has been found that the nanoparticle formulations are characterized by peculiar 1H nuclear magnetic relaxation dispersion (NMRD) profiles that directly correlate with their heating potential when exposed to an alternating magnetic field. By prolonging the magnetic field exposure to 30 min, a significant drug release was observed for PLGA-Fe-NPs in the case of the larger-sized magnetic nanoparticles. Furthermore, the immobilization of lipophilic Fe-NPs in PLGA-NPs also made it possible to maintain Néel relaxation as the dominant relaxation contribution in the presence of large iron oxide cores (diameters of 15-20 nm), with the advantage of preserving their efficiency when they are entrapped in the intracellular environment. The results reported herein show that NMRD profiles are a useful tool for anticipating the heating capabilities of Fe-NPs designed for MFH applications.

  8. Studies of Transition Metal Complexes Using Dynamic NMR Techniques.

    Science.gov (United States)

    Coston, Timothy Peter John

    Available from UMI in association with The British Library. This Thesis is primarily concerned with the quantitative study of fluxional processes in, predominantly platinum(IV) complexes, with the ligands 1,1,2,2-tetrakis(methylthio)ethane (MeS)_2CHCH(SMe)_2 , and 1,1,2,2-tetrakis(methylthio)ethene (MeS) _2C=C(SMe)_2. Quantitative information relating to the energetics of these processes has been obtained by a combination of one- and two-dimensional NMR techniques. Chapter One provides an introduction to the background of fluxional processes in transition metal complexes together with data concerning the energetics of the processes that have already been studied by NMR techniques. Chapter Two provides a thorough grounding in NMR techniques, in particular those concerned with the quantitative measurement of rates involved in chemical exchange processes. A description of the use of 2D EXSY NMR spectroscopy in obtaining rate data is given. The properties of the magnetic isotope of platinum are given in Chapter Three. A general survey is also given of some additional compounds that have already been studied by platinum-195 spectroscopy. Chapter Four is concerned with the quantitative study of low temperature (complexes (PtXMe_3 (MeS)_2CHCH(SMe) _2) (X = Cl, Br, I). These complexes were studied by dynamic nuclear magnetic resonance and the information regarding the rates of sulphur inversion was obtained by complete band-shape analysis. Chapter Five is concerned with high temperature (>333 K) fluxionality, of the previous complexes, as studied by a combination of one- and two -dimensional NMR techniques. Aside from obtaining thermodynamic parameters for all the processes, a new novel mechanism is proposed. Chapter Six is primarily concerned with the NMR investigation of the new dinuclear complexes ((PtXMe _3)_2(MeS) _2CHCH(SMe)_2) (X = Cl, Br, I). The solution properties have been established and thermo-dynamic parameters obtained for low and high temperature

  9. NMR spectroscopy applied to the eye: Drugs and metabolic studies

    Energy Technology Data Exchange (ETDEWEB)

    Saether, Oddbjoern

    2005-07-01

    NMR spectroscopy has been extensively applied in biomedical research during the last decades. It has proved to be an analytical tool of great value. From being mainly used in chemistry, technological developments have expanded the application of NMR spectroscopy to a great wealth of disciplines. With this method, biochemical information can be obtained by analysing tissue extracts. Moreover, NMR spectroscopy is increasingly employed for pharmacokinetic studies and analysis of biofluids. Technological progress has provided increased sensitivity and resolution in the spectra, which enable even more of the complexity of biological samples to be elucidated. With the implementation of high-resolution magic angle spinning (HR-MAS) NMR spectroscopy in biomedicine, intact tissue samples or biopsies can be investigated. Thus, NMR spectroscopy has an ever-increasing impact in metabolic screening of human samples and in animal models, and methods are also increasingly realised in vivo. The present work, NMR spectroscopy applied to eye research, consists of two main parts. Firstly, the feasibility to monitor fluorinated ophthalmic drugs directly in the eye was assessed. Secondly, HR-MAS H1 NMR spectroscopy was applied for metabolic profiling of the anterior eye segment, specifically to analyse metabolic changes in intact corneal and lenticular samples after cataractogenic insults. This work included metabonomics with the application of pattern recognition methods to analyse HR-MAS spectra of eye tissues. Optimisation strategies were explored for F19 NMR detection of fluorinated drugs in a phantom eye. S/N gains in F19 NMR spectroscopy were achieved by implementing time-share H1 decoupling at 2.35 T. The method is advantageous for compounds displaying broad spectral coupling patterns, though detection of drugs at concentrations encountered in the anterior eye segment after topical application was not feasible. Higher magnetic fields and technological improvements could enable

  10. The PAW/GIPAW approach for computing NMR parameters: a new dimension added to NMR study of solids.

    Science.gov (United States)

    Charpentier, Thibault

    2011-07-01

    In 2001, Mauri and Pickard introduced the gauge including projected augmented wave (GIPAW) method that enabled for the first time the calculation of all-electron NMR parameters in solids, i.e. accounting for periodic boundary conditions. The GIPAW method roots in the plane wave pseudopotential formalism of the density functional theory (DFT), and avoids the use of the cluster approximation. This method has undoubtedly revitalized the interest in quantum chemical calculations in the solid-state NMR community. It has quickly evolved and improved so that the calculation of the key components of NMR interactions, namely the shielding and electric field gradient tensors, has now become a routine for most of the common nuclei studied in NMR. Availability of reliable implementations in several software packages (CASTEP, Quantum Espresso, PARATEC) make its usage more and more increasingly popular, maybe indispensable in near future for all material NMR studies. The majority of nuclei of the periodic table have already been investigated by GIPAW, and because of its high accuracy it is quickly becoming an essential tool for interpreting and understanding experimental NMR spectra, providing reliable assignments of the observed resonances to crystallographic sites or enabling a priori prediction of NMR data. The continuous increase of computing power makes ever larger (and thus more realistic) systems amenable to first-principles analysis. In the near future perspectives, as the incorporation of dynamical effects and/or disorder are still at their early developments, these areas will certainly be the prime target.

  11. Relaxation-optimised Hartmann-Hahn transfer using a specifically Tailored MOCCA-XY16 mixing sequence for carbonyl-carbonyl correlation spectroscopy in {sup 13}C direct detection NMR experiments

    Energy Technology Data Exchange (ETDEWEB)

    Felli, Isabella C.; Pierattelli, Roberta [University of Florence, Department of Chemistry and Magnetic Resonance Center (CERM) (Italy); Glaser, Steffen J.; Luy, Burkhard [Technische Universitaet Muenchen, Department of Chemistry (Germany)], E-mail: Burkhard.Luy@ch.tum.de

    2009-03-15

    Isotropic mixing sequences are one of the key methods to achieve efficient coherence transfer. Among them, the MOCCA-XY16, which keeps the magnetization longitudinal for a significant amount of time, is characterised by favourable relaxation properties. We show here that its adapted version is particularly suited for carbonyl-carbonyl correlations in {sup 13}C direct detection NMR experiments.

  12. Characterization of Maytenus ilicifolia samples by {sup 1}H NMR relaxation in the solid state; Caracterizacao dos constituintes polimericos da Maytenus ilicifolia por relaxacao nuclear de {sup 1}H por RMN no estado solido

    Energy Technology Data Exchange (ETDEWEB)

    Preto, Monica S. de M.; Tavares, Maria I.B., E-mail: mibt@ima.ufrj.br [Universidade Federal do Rio de Janeiro (IMA/UFRJ), RJ (Brazil). Inst. de Macromoleculas Professora Eloisa Mano. Lab de Ressonancia Magnetica Nuclear; Sebastiao, Pedro J.O. [Departamento de Fisica, Instituto Superior Tecnico, Lisboa (Portugal)

    2011-07-01

    The Maytenus ilicifolia (espinheira-santa) is a popular medicinal plant with different uses. It is native of South America and can be found in Brazil. In the Brazilian market it is possible found products labeled as M. ilicifolia. So far, the studies published in the literature involve the modification of the natural materials and do not concern the comparison between commercial the raw natural materials. Different non-destructive NMR techniques can be used to study natural materials. In this work it is presented a characterization study by Fast Field Cycling of the {sup 1}H spin-lattice relaxation time (T{sub 1}) NMR, in the frequency range 100 khz-10 MHz. The results obtained in two commercial M. ilicifolia samples and one control sample collected in natura are compared. It was intended to study the possibility to elaborate a characterization method using FFCNMR suitable for the verification of authenticity and/or evaluation of tampering on products. The differences detected by FFCNMR relaxometry were confirmed by thermogravimetric analysis and infrared spectroscopy. (author)

  13. Studies on supramolecular gel formation using DOSY NMR.

    Science.gov (United States)

    Nonappa; Šaman, David; Kolehmainen, Erkki

    2015-04-01

    Herein, we present the results obtained from our studies on supramolecular self-assembly and molecular mobility of low-molecular-weight gelators (LMWGs) in organic solvents using pulsed field gradient (PFG) diffusion ordered spectroscopy (DOSY) NMR. A series of concentration-dependent DOSY NMR experiments were performed on selected LMWGs to determine the critical gelation concentration (CGC) as well as to understand the behaviour of the gelator molecules in the gel state. In addition, variable-temperature DOSY NMR experiments were performed to determine the gel-to-sol transition. The PFG NMR experiments performed as a function of gradient strength were further analyzed using monoexponential DOSY processing, and the results were compared with the automated Bayesian DOSY transformation to obtain 2D plots. Our results provide useful information on the stepwise self-assembly of small molecules leading to gelation. We believe that the results obtained from these experiments are applicable in determining the CGC and gel melting temperatures of supramolecular gels.

  14. Quantifying millisecond time-scale exchange in proteins by CPMG relaxation dispersion NMR spectroscopy of side-chain carbonyl groups

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, Alexandar L.; Kay, Lewis E., E-mail: kay@pound.med.utoronto.ca [University of Toronto, Departments of Molecular Genetics, Biochemistry and Chemistry (Canada)

    2011-08-15

    A new pulse sequence is presented for the measurement of relaxation dispersion profiles quantifying millisecond time-scale exchange dynamics of side-chain carbonyl groups in uniformly {sup 13}C labeled proteins. The methodology has been tested using the 87-residue colicin E7 immunity protein, Im7, which is known to fold via a partially structured low populated intermediate that interconverts with the folded, ground state on the millisecond time-scale. Comparison of exchange parameters extracted for this folding 'reaction' using the present methodology with those obtained from more 'traditional' {sup 15}N and backbone carbonyl probes establishes the utility of the approach. The extracted excited state side-chain carbonyl chemical shifts indicate that the Asx/Glx side-chains are predominantly unstructured in the Im7 folding intermediate. However, several crucial salt-bridges that exist in the native structure appear to be already formed in the excited state, either in part or in full. This information, in concert with that obtained from existing backbone and side-chain methyl relaxation dispersion experiments, will ultimately facilitate a detailed description of the structure of the Im7 folding intermediate.

  15. 13C NMR Quantitative Study-Part 1: Relationships between the Conformation of Amino Acids, Peptide, Carboxylic Acids and Integration Intensity of 13C NMR

    Institute of Scientific and Technical Information of China (English)

    TIAN; JinPing

    2001-01-01

    In proton broad band decoupling 13C NMR, carbon atoms have different integration intensity because of NOE effects and their different relaxation time(T1), thus it makes a 13C NMR quantitative analyses very difficult. To acquire a 3C NMR quantitative analyses, a gated decoupling with suppressed NOE technology, i.e., an inversed gated decoupling pulse (IGDP), must be used. In IGDP relay time (tR) between two acquisition cycles must be more than 5T1, the time needed for a acquisition cycles is so long that makes the total 13C NMR quantitative analyses time much longer. For this reason, the 13C NMR quantitative analyses is paid less attention.  ……

  16. 13C NMR Quantitative Study-Part 1: Relationships between the Conformation of Amino Acids, Peptide, Carboxylic Acids and Integration Intensity of 13C NMR

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@ In proton broad band decoupling 13C NMR, carbon atoms have different integration intensity because of NOE effects and their different relaxation time(T1), thus it makes a 13C NMR quantitative analyses very difficult. To acquire a 3C NMR quantitative analyses, a gated decoupling with suppressed NOE technology, i.e., an inversed gated decoupling pulse (IGDP), must be used. In IGDP relay time (tR) between two acquisition cycles must be more than 5T1, the time needed for a acquisition cycles is so long that makes the total 13C NMR quantitative analyses time much longer. For this reason, the 13C NMR quantitative analyses is paid less attention.

  17. 2H NMR studies of glycerol dynamics in protein matrices.

    Science.gov (United States)

    Herbers, C R; Sauer, D; Vogel, M

    2012-03-28

    We use (2)H NMR spectroscopy to investigate the rotational motion of glycerol molecules in matrices provided by the connective tissue proteins elastin and collagen. Analyzing spin-lattice relaxation, line-shape properties, and stimulated-echo decays, we determine the rates and geometries of the motion as a function of temperature and composition. It is found that embedding glycerol in an elastin matrix leads to a mild slowdown of glycerol reorientation at low temperatures and glycerol concentrations, while the effect vanishes at ambient temperatures or high solvent content. Furthermore, it is observed that the nonexponential character of the rotational correlation functions is much more prominent in the elastin matrix than in the bulk liquid. Results from spin-lattice relaxation and line shape measurements indicate that, in the mixed systems, the strong nonexponentiality is in large part due to the existence of distributions of correlation times, which are broader on the long-time flank and, hence, more symmetric than in the neat system. Stimulated-echo analysis of slow glycerol dynamics reveals that, when elastin is added, the mechanism for the reorientation crosses over from small-angle jump dynamics to large-angle jump dynamics and the geometry of the motion changes from isotropic to anisotropic. The results are discussed against the background of present and previous findings for glycerol and water dynamics in various protein matrices and compared with observations for other dynamically highly asymmetric mixtures so as to ascertain in which way the viscous freezing of a fast component in the matrix of a slow component differs from the glassy slowdown in neat supercooled liquids.

  18. 2H NMR studies of glycerol dynamics in protein matrices

    Science.gov (United States)

    Herbers, C. R.; Sauer, D.; Vogel, M.

    2012-03-01

    We use 2H NMR spectroscopy to investigate the rotational motion of glycerol molecules in matrices provided by the connective tissue proteins elastin and collagen. Analyzing spin-lattice relaxation, line-shape properties, and stimulated-echo decays, we determine the rates and geometries of the motion as a function of temperature and composition. It is found that embedding glycerol in an elastin matrix leads to a mild slowdown of glycerol reorientation at low temperatures and glycerol concentrations, while the effect vanishes at ambient temperatures or high solvent content. Furthermore, it is observed that the nonexponential character of the rotational correlation functions is much more prominent in the elastin matrix than in the bulk liquid. Results from spin-lattice relaxation and line shape measurements indicate that, in the mixed systems, the strong nonexponentiality is in large part due to the existence of distributions of correlation times, which are broader on the long-time flank and, hence, more symmetric than in the neat system. Stimulated-echo analysis of slow glycerol dynamics reveals that, when elastin is added, the mechanism for the reorientation crosses over from small-angle jump dynamics to large-angle jump dynamics and the geometry of the motion changes from isotropic to anisotropic. The results are discussed against the background of present and previous findings for glycerol and water dynamics in various protein matrices and compared with observations for other dynamically highly asymmetric mixtures so as to ascertain in which way the viscous freezing of a fast component in the matrix of a slow component differs from the glassy slowdown in neat supercooled liquids.

  19. Direct 13C-detection for carbonyl relaxation studies of protein dynamics

    Science.gov (United States)

    Pasat, Gabriela; Zintsmaster, John S.; Peng, Jeffrey W.

    2008-08-01

    We describe a method that uses direct 13C-detection for measuring rotating-frame carbonyl ( 13CO) relaxation rates to describe protein functional dynamics. Key advantages of method include the following: (i) unique access to 13CO groups that lack a scalar-coupled 15N- 1H group; (ii) insensitivity to 15N/ 1H exchange-broadening that can derail 1H-detected 15N and HNCO methods; (iii) avoidance of artifacts caused by incomplete water suppression. We demonstrate the approach for both backbone and side-chain 13CO groups. Accuracy of the 13C-detected results is supported by their agreement with those obtained from established HNCO-based approaches. Critically, we show that the 13C-detection approach provides access to the 13CO groups of functionally important residues that are invisible via 1H-detected HNCO methods because of exchange-broadening. Hence, the 13C-based method fills gaps inherent in canonical 1H-detected relaxation experiments, and thus provides a novel complementary tool for NMR studies of biomolecular flexibility.

  20. An NMR Study of Enzyme Activity.

    Science.gov (United States)

    Peterman, Keith E.; And Others

    1989-01-01

    A laboratory experiment designed as a model for studying enzyme activity with a basic spectrometer is presented. Included are background information, experimental procedures, and a discussion of probable results. Stressed is the value of the use of Nuclear Magnetic Resonance in biochemistry. (CW)

  1. An NMR Study of Enzyme Activity.

    Science.gov (United States)

    Peterman, Keith E.; And Others

    1989-01-01

    A laboratory experiment designed as a model for studying enzyme activity with a basic spectrometer is presented. Included are background information, experimental procedures, and a discussion of probable results. Stressed is the value of the use of Nuclear Magnetic Resonance in biochemistry. (CW)

  2. Dielectric Relaxation in Dimethyl Sulfoxide/Water Mixtures Studied by Microwave Dielectric Relaxation Spectroscopy

    Science.gov (United States)

    Lu, Zijie; Manias, Evangelos; MacDonald, Digby D.; Lanagan, Michael

    2009-10-01

    Dielectric spectra of dimethyl sulfoxide (DMSO)/water mixtures, over the entire concentration range, have been measured using the transmission line method at frequencies from 45 MHz to 26 GHz and at temperatures of 298-318 K. The relaxation times of the mixtures show a maximum at an intermediate molar fraction of DMSO. The specific structure of mixtures in different concentration regions was determined by the dielectric relaxation dynamics, obtained from the effect of temperature on the relaxation time. A water structure "breaking effect" is observed in dilute aqueous solutions. The average number of hydrogen bonds per water molecule in these mixtures is found to be reduced compared to pure water. The increase in the dielectric relaxation time in DMSO/water mixtures is attributed to the spatial (steric) constraints of DMSO molecules on the hydrogen-bond network, rather than being due to hydrophobic hydration of the methyl groups. The interaction between water and DMSO by hydrogen bonding reaches a maximum at a DMSO molar fraction of 0.33, reflected by the maximum activation enthalpy for dielectric relaxation in this concentration, suggesting the formation of a stoichiometric compound, H2O-DMSO-H2O. In highly concentrated solutions, negative activation entropies are observed, indicating the presence of aggregates of DMSO molecules. A distinct antiparallel arrangement of dipoles is obtained for neat DMSO in the liquid state according to the Kirkwood correlation factor (gK = 0.5), calculated from the static permittivity. The similarity of the dielectric behavior of pure DMSO and DMSO-rich mixtures suggests that dipole-dipole interactions contribute significantly to the rotational relaxation process in these solutions.

  3. Dynamic regulation of GDP binding to G proteins revealed by magnetic field-dependent NMR relaxation analyses.

    Science.gov (United States)

    Toyama, Yuki; Kano, Hanaho; Mase, Yoko; Yokogawa, Mariko; Osawa, Masanori; Shimada, Ichio

    2017-02-22

    Heterotrimeric guanine-nucleotide-binding proteins (G proteins) serve as molecular switches in signalling pathways, by coupling the activation of cell surface receptors to intracellular responses. Mutations in the G protein α-subunit (Gα) that accelerate guanosine diphosphate (GDP) dissociation cause hyperactivation of the downstream effector proteins, leading to oncogenesis. However, the structural mechanism of the accelerated GDP dissociation has remained unclear. Here, we use magnetic field-dependent nuclear magnetic resonance relaxation analyses to investigate the structural and dynamic properties of GDP bound Gα on a microsecond timescale. We show that Gα rapidly exchanges between a ground-state conformation, which tightly binds to GDP and an excited conformation with reduced GDP affinity. The oncogenic D150N mutation accelerates GDP dissociation by shifting the equilibrium towards the excited conformation.

  4. Dynamic regulation of GDP binding to G proteins revealed by magnetic field-dependent NMR relaxation analyses

    Science.gov (United States)

    Toyama, Yuki; Kano, Hanaho; Mase, Yoko; Yokogawa, Mariko; Osawa, Masanori; Shimada, Ichio

    2017-01-01

    Heterotrimeric guanine-nucleotide-binding proteins (G proteins) serve as molecular switches in signalling pathways, by coupling the activation of cell surface receptors to intracellular responses. Mutations in the G protein α-subunit (Gα) that accelerate guanosine diphosphate (GDP) dissociation cause hyperactivation of the downstream effector proteins, leading to oncogenesis. However, the structural mechanism of the accelerated GDP dissociation has remained unclear. Here, we use magnetic field-dependent nuclear magnetic resonance relaxation analyses to investigate the structural and dynamic properties of GDP bound Gα on a microsecond timescale. We show that Gα rapidly exchanges between a ground-state conformation, which tightly binds to GDP and an excited conformation with reduced GDP affinity. The oncogenic D150N mutation accelerates GDP dissociation by shifting the equilibrium towards the excited conformation. PMID:28223697

  5. NMR Studies of Some Plasma Proteins.

    Science.gov (United States)

    Lawrence, Mark P.

    Available from UMI in association with The British Library. Requires signed TDF. The work reported in this thesis consists of a study of the solution structure of a domain of protein structure found in some of the enzymes involved in blood coagulation. These domains, known as kringles, are of between 78 and 82 residues and contain three conserved disulphide bridges in their primary sequence. The study attempts to elucidate the nature of the lysine-binding site of the fourth kringle of human plasminogen to probe its physiological action, and a theory is developed to explain the overall fold of the protein in terms of its physiological role. The protein structure is found to contain only one small region of secondary structure, an antiparallel beta-sheet of about 8 residues, which provides the support for the binding site. The binding site itself consists of a hydrophobic channel provided by the aromatic residues at positions 61, 63, 71 and 73 in the beta-sheet and a negatively charged site at one end of this channel provided by the aspartic acid residues at positions 54 and 56. The beta-sheet appears to become more tightly defined on binding the kringle with alpha,omega -amino acids which are analogues of lysine and exhibit known anti-fibrinolytic properties. The rest of the solution structure appears to be less clearly defined and relies mainly on the three disulphide bridges and some rather isolated hydrogen bonding for maintenance of the fold. An explanation for this structure with a rigid binding site and a more flexible region for the remainder of the domain is proposed. Shorter studies are reported on the second kringle of bovine prothrombin and the first of human plasminogen which suggest strongly that the kringle fold is conserved.

  6. Time-domain NMR study of the drying of hemicellulose extracted aspen (Populus tremuloides Michx.)

    Science.gov (United States)

    Thomas Elder; Carl Houtman

    2013-01-01

    The effect of hot water on aspen chips has been evaluated using time-domain low-field nuclear magnetic resonance (NMR) spectroscopy. At moisture contents above fiber saturation point, treated chips exhibit relaxation times of free water longer than for the control. This is consistent with the removal of hemicelluloses given the hydrophilicity of these polysaccharides....

  7. Effects of Studying to Music and Post-Study Relaxation on Reading Comprehension.

    Science.gov (United States)

    Etaugh, Claire; Ptasnik, Patricia

    1982-01-01

    Twenty female and 20 male college students studied a passage in quiet surroundings or while listening to preferred music and then either relaxed or read unrelated material. Reading comprehension of the passage was facilitated by silent study for subjects who seldom listen to music and by poststudy relaxation. (Author)

  8. NMR spectroscopic study on methanolysis reaction of vegetable oil

    Energy Technology Data Exchange (ETDEWEB)

    Fangming Jin; Kohei Kawasaki; Hisanori Kishida; Kazuyuki Tohji; Takehoko Moriya; Heiji Enomoto [Tohoku University, Sendai (Japan). Graduate School of Environmental Studies

    2007-05-15

    This study is to clarify the pathways of the transesterification of vegetable oil by applying NMR to the identification of intermediates in the transesterification reaction. Results showed that the significant methanolysis product was sn-1,3-diglycerides in diglycerides, and sn-2-monoglycerides was not found. These analytical results suggest that the methanolysis reaction may occur easily at the sn-2-position for both sn-tri- and sn-1,2-diglycerides. Short communication. 16 refs., 6 figs., 2 tabs.

  9. NMR study of magnetic fluctuations in 115 actinide compounds

    Energy Technology Data Exchange (ETDEWEB)

    Kambe, S. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki 319-1195 (Japan)]. E-mail: kambe.shinsaku@jaea.go.jp; Sakai, H. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki 319-1195 (Japan); Tokunaga, Y. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki 319-1195 (Japan); Kato, H. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki 319-1195 (Japan); Fujimoto, T. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki 319-1195 (Japan); Walstedt, R.E. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki 319-1195 (Japan); Ikeda, S. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki 319-1195 (Japan); Matsuda, T.D. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki 319-1195 (Japan); Haga, Y. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki 319-1195 (Japan); Aoki, D. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Homma, Y. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Shiokawa, Y. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Onuki, Y. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)

    2007-03-15

    We report NMR measurements in isostructural compounds (HoCoGa{sub 5}: 115 type) AnTGa{sub 5} (An: U, Np and Pu, T: Fe, Co and Pt) with different ground states (paramagnet, antiferromagnet and superconductor) using single crystal samples. The electrical field gradient at the Ga and Co sites are similar in all compounds, indicating that the charge distribution around these sites is determined mainly by intra-atomic orbitals. In contrast, the hyperfine coupling constants at the Ga and Co sites depend on the compounds considerably. Since the hyperfine coupling at the ligand sites is a transferred hyperfine coupling due to hybridization between 5f and ligand orbitals, it is natural that the hyperfine coupling constant depends on the 5f electronic states. Spin-lattice relaxation rates (1/T{sub 1}) in the paramagnetic state show more drastic differences between the compounds. In the antiferromagnets UPtGa{sub 5}, NpFeGa{sub 5} and NpCoGa{sub 5}, 1/T{sub 1}T shows a Curie-Weiss behavior at high temperatures, indicating a strong localized character. By contrast, in the paramagnet UFeGa{sub 5}1/T{sub 1}T is small and almost independent of T, indicating an ordinary metallic state with weak exchange enhancement. Finally, in the superconductor PuRhGa{sub 5} the magnitude of 1/T{sub 1}T lies between those of the antiferromagnets and the paramagnet.

  10. STUDY OF THE MOLECULAR MOTION IN POLYEPICHLOROHYDRIN BY HIGH RESOLUTION NMR

    Institute of Scientific and Technical Information of China (English)

    JIA Mingchun; SHEN Lianfang; QIAN Baogong

    1993-01-01

    The molecular motion in polyepichlorohydrin (PEPCH ), in solution and bulk, was studied by high resolution NMR by means of line width, spin-lattice relaxation time T1 and nuclear Overhauser effect NOE. The results show that the VJGM model can describe the main chain motion of PEPCH in solution perfectly. In bulk state, the relationship between the line width and the temperature is consistent with WLF equation, but that between the high frequency molecular motion correlation time (in T1 scale ) and temperature is consistent with Arrhenius equation. The motion parameters of PEPCH in both states were calculated. The internal rotation motion of side -CH2C1 group was analyzed by using equal three-site jump and diffusion internal rotation model in both states.

  11. 1H NMR Study of Polyvinylalcohol Irradiated by Ultra-violet

    Institute of Scientific and Technical Information of China (English)

    Xiu Ling YAN; Wan Fu SUN; Jun TANG; Xin ZHAO

    2005-01-01

    The effect of Ultra-violet light on the structure and motion of the polyvinyl alcohol(PVA) chains was studied by 1H NMR, spin-lattice relaxation and IR spectroscopy. The results indicated that with the increase of irradiation time, the intensity of the polymer hydroxyl proton peaks decreased and finally vanished, which suggested the self-condensation between the hydroxyl groups proceeded. No methyl proton peaks appeared in the spectra after irradiation shows that there is no cleavage of polymer chain. The longer the irradiation time is, the wider the proton peak of the residual water of the solvent is and it shifted toward low field. This result implies that the hydrogen bonds formed between the polymer and the residual water. The absorption peak of hydroxyl group of the polymer moves toward the lower wave number in the IR spectrum that showed the existence of the hydrogen bonds between the PVA macromolecules.

  12. Chain motion in poly(ethylene oxide) crystallites as studied by NMR

    Energy Technology Data Exchange (ETDEWEB)

    Achilles, Anja; Petzold, Albrecht; Thurn-Albrecht, Thomas; Saalwachter, Kay [Institut fuer Physik, Martin-Luther-Universitaet Halle Wittenberg, Halle (Saale) (Germany)

    2008-07-01

    Many stereoregular polymers exhibit pronounced large-scale dynamics in the crystalline phase. 'Helical-jump' processes mediate chain transport over large distances through the crystallites, and they are often related to the mechanically active {alpha}{sub (c)} relaxation and macroscopic properties such as yield processes and ultradrawability. While the timescale of such processes has been studied for many different polymers, their dependence on morphological parameters, such as crystalline and amorphous layer thickness, has received less attention. In this contribution, we report on NMR investigations of helical jumps in PEO crystallites, using advanced high-resolution {sup 13}C exchange spectroscopy as well as simple analyses of the {sup 1}H time-domain signal. These results are correlated with SAXS-determined changes in the morphology and crystallinity as a function of molecular weight and the crystallization conditions.

  13. Study of β-NMR for Liquid Biological Samples

    CERN Document Server

    Beattie, Caitlin

    2017-01-01

    β-NMR is an exotic form of NMR spectroscopy that allows for the characterization of matter based on the anisotropic β-decay of radioactive probe nuclei. This has been shown to be an effective spectroscopic technique for many different compounds, but its use for liquid biological samples is relatively unexplored. The work at the VITO line of ISOLDE seeks to employ this technique to study such samples. Currently, preparations are being made for an experiment to characterize DNA G-quadruplexes and their interactions with stabilizing cations. More specifically, the work in which I engaged as a summer student focused on the experiment’s liquid handling system and the stability of the relevant biological samples under vacuum.

  14. Double rotation NMR studies of zeolites and aluminophosphate molecular sieves

    Energy Technology Data Exchange (ETDEWEB)

    Jelinek, R. [California Univ., Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States)

    1993-07-01

    Goal is to study the organization and structures of guest atoms and molecules and their reactions on internal surfaces within pores of zeolites and aluminophosphate molecular sieves. {sup 27}Al and {sup 23}Na double rotation NMR (DOR) is used since it removes the anisotropic broadening in NMR spectra of quadrupolar nuclei, thus increasing resolution. This work concentrates on probing aluminum framework atoms in aluminophosphate molecular sieves and sodium extra framework cations in porous aluminosilicates. In aluminophosphates, ordering and electronic environments of the framework {sup 27}Al nuclei are modified upon adsorption of water molecules within the channels; a relation is sought between the sieve channel topology and the organization of adsorbed water, as well as the interaction between the Al nuclei and the water molecules. Extra framework Na{sup +} cations are directly involved in adsorption processes and reactions in zeolite cavities.

  15. 1H NMR Studies of MgH2

    Science.gov (United States)

    Itoh, Yutaka; Kado, Ryoichi

    We report on 1H NMR studies of commercially available powder MgH2 exposed to air and maybe humidity, which has been believed to be a promising material for hydrogen storage. The Fourier transform of the free-induction decay of the protons indicatesd superposition of broad and narrow components in the NMR spectrum, while the Fourier transform of the 1H nuclear spin-echo reproduced the narrow component. With cooling down below room temperature, the ratio of the narrow peak to the broad spectrum decreased. The broad spectrum is associated with direct dipolar coupled protons on an inhomogeneous rigid lattice. The narrow peak is associated with interstitial protons with more inhomogeneous surroundings.

  16. 1H NMR and Rheological Studies of the Calcium Induced Gelation Process in Aqueous Low Methoxyl Pectin Solutions

    Science.gov (United States)

    Dobies, M.; Kuśmia, S.; Jurga, S.

    2006-07-01

    The 1H NMR relaxometry in combination with water proton spin-spin relaxation time measurements and rheometry have been applied to study the ionic gelation of 1% w/w aqueous low methoxyl pectin solution induced by divalent Ca2+ cations from a calcium chloride solution. The model-free approach to the analysis of 1H NMR relaxometry data has been used to separate the information on the static (β) and dynamic () behaviour of the systems tested. The 1H NMR results confirm that the average mobility of both water and the pectin molecules is largely dependent on the concentration of the cross-linking agent. The character of this dependency (β, and T2 vs. CaCl2 concentration) is consistent with the two-stage gelation process of low methoxyl pectin, in which the formation of strongly linked dimer associations (in the range of 0-2.5 mM CaCl2) is followed by the appearance of weak inter-dimer aggregations (for CaCl2≥ 3.5 mM). The presence of the weak gel structure for the sample with 3.5 mM CaCl2 has been confirmed by rheological measurements. Apart from that, the T1 and T2 relaxation times have been found to be highly sensitive to the syneresis phenomenon, which can be useful to monitor the low methoxyl pectin gel network stability.

  17. Measuring {sup 1}H{sup N} temperature coefficients in invisible protein states by relaxation dispersion NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bouvignies, Guillaume; Vallurupalli, Pramodh [University of Toronto, Departments of Molecular Genetics, Biochemistry and Chemistry (Canada); Cordes, Matthew H. J. [The University of Arizona, Department of Chemistry and Biochemistry (United States); Hansen, D. Flemming [University College London, Institute of Structural and Molecular Biology (United Kingdom); Kay, Lewis E., E-mail: kay@pound.med.utoronto.ca [University of Toronto, Departments of Molecular Genetics, Biochemistry and Chemistry (Canada)

    2011-05-15

    A method based on the Carr-Purcell-Meiboom-Gill relaxation dispersion experiment is presented for measuring the temperature coefficients of amide proton chemical shifts of low populated 'invisible' protein states that exchange with a 'visible' ground state on the millisecond time-scale. The utility of the approach is demonstrated with an application to an I58D mutant of the Pfl6 Cro protein that undergoes exchange between the native, folded state and a cold denatured, unfolded conformational ensemble that is populated at a level of 6% at 2.5 Degree-Sign C. A wide distribution of amide temperature coefficients is measured for the unfolded state. The distribution is centered about -5.6 ppb/K, consistent with an absence of intra-molecular hydrogen bonds, on average. However, the large range of values (standard deviation of 2.1 ppb/K) strongly supports the notion that the unfolded state of the protein is not a true random coil polypeptide chain.

  18. Mapping of the spectral density function of a C alpha-H alpha bond vector from NMR relaxation rates of a 13C-labelled alpha-carbon in motilin.

    Science.gov (United States)

    Allard, P; Jarvet, J; Ehrenberg, A; Gräslund, A

    1995-02-01

    The peptide hormone motilin was synthesised with a 13C-enriched alpha-carbon in the leucine at position 10. In aqueous solution, six different relaxation rates were measured for the 13C alpha-H alpha fragment as a function of temperature and with and without the addition of 30% (v/v) of the cosolvent d2-1,1,1,3,3,3-hexafluoro-2-propanol (HFP). The relaxation rates were analysed employing the spectral density mapping technique introduced by Peng and Wagner [(1992) J. Magn. Reson., 98, 308-332] and using the model-free approach by Lipari and Szabo [(1982) J. Am. Chem. Soc., 104, 4546-4570]. The fit to various models of dynamics was also considered. Different procedures to evaluate the overall rotational correlation time were compared. A single exponential time correlation function was found to give a good fit to the measured spectral densities only for motilin in 30% (v/v) HFP at low temperatures, whereas at high temperatures in this solvent, and in D2O at all temperatures, none of the considered models gave an acceptable fit. A new empirical spectral density function was tested and found to accurately fit the experimental spectral density mapping points. The application of spectral density mapping based on NMR relaxation data for a specific 13C-1H vector is shown to be a highly useful method to study biomolecular dynamics. Advantages are high sensitivity, high precision and uniform sampling of the spectral density function over the frequency range.

  19. The interaction of small molecules with phospholipid membranes studied by 1H NOESY NMR under magic-angle spinning1

    Institute of Scientific and Technical Information of China (English)

    Holger A SCHEIDT; Daniel HUSTER

    2008-01-01

    The interaction of small molecules with lipid membranes and the exact knowledge of their binding site and bilayer distribution is of great pharmacological impor-tance and represents an active field of current biophysical research. Over the last decade, a highly resolved 1H solid-state NMR method has been developed that allows measuring localization and distribution of small molecules in membranes. The classical solution 1H NMR NOESY technique is applied to lipid membrane samples under magic-angle spinning (MAS) and NOESY cross-relaxation rates are determined quantitatively. These rates are proportional to the contact probability between molecular segments and therefore an ideal tool to study intermolecular interactions in membranes. Here, we review recent 1H MAS NOESY applications that were carried out to study lateral lipid organization in mixed membranes and the interaction of membranes with water, ethanol, small aromatic compounds, peptides, fluorescence labels, and lipophilic nucleosides.

  20. NMR spectroscopy study of local correlations in water

    Science.gov (United States)

    Mallamace, Francesco; Corsaro, Carmelo; Mallamace, Domenico; Vasi, Sebastiano; Stanley, H. Eugene

    2016-12-01

    Using nuclear magnetic resonance we study the dynamics of the hydrogen bond (HB) sub-domains in bulk and emulsified water across a wide temperature range that includes the supercooled regime. We measure the proton spin-lattice T1 and spin-spin T2 relaxation times to understand the hydrophilic interactions that determine the properties of water. We use (i) the Bloembergen, Purcell, and Pound approach that focuses on a single characteristic correlation time τc, and (ii) the Powles and Hubbard approach that measures the proton rotational time τθ. We find that when the temperature is low both relaxation times are strongly correlated when the HB lifetime is long, and that when the temperature is high a decrease in the HB lifetime destroys the water clusters and decouples the dynamic modes of the system.

  1. Dielectric relaxation and birefringence study of 7.O5O.7 dimeric liquid crystal compound

    Science.gov (United States)

    Bhattacharjee, Debanjan; Paul-Choudhury, Sandip; Alapati, Parameswara Rao; Bhattacharjee, Ayon

    2016-05-01

    Measurement of dielectric relaxation and birefringence phenomenon of dimeric liquid crystal compound with the dependence of temperature was reported in this paper. Homogeneous (HG) and homeotropic (HT) alignment of the cell are introduced to investigate the dielectric relaxation, activation energy and birefringence. Cole-Cole plots analyzed the dielectric relaxation of the dimeric compound. The observed Cole-Cole plots were semi-circular, and the relaxation mechanism obeys the non-Debye type of relaxation behaviour. Slater's perturbation equations have been used to analysis the activation energy of the compound. The birefringence of the compound has positively anisotropy and thin prism mechanism was used to study the anisotropy of the compound.

  2. The Effect of Orientation Relaxation on Polymer Melt Crystallization Studied by Monte Carlo Simulations

    Institute of Scientific and Technical Information of China (English)

    WANG Mao-Xiang

    2009-01-01

    We use dynamic Monte Carlo simulations to study the athermal relaxation of bulk extended chains and the isothermal crystallization in intermediately relaxed melts. It is found that the memory of chain orientations in the melt can significantly enhance the crystallization rates. The crystal orientation and lamellar thickness essentially depend on the orientational relaxation. Moreover, there is a transition of the nucleation mechanism during the isothermal crystallization from the intermediately relaxed melts. These results explain the mechanism of the self-nucleation by orientation and suggest that in flow-induced polymer crystallization, the orientational relaxation of chains decides the crystal orientation.

  3. Solid-State NMR Studies of Chemically Lithiated CFx

    Science.gov (United States)

    Leifer, N. D.; Johnson, V. S.; Ben-Ari, R.; Gan, H.; Lehnes, J. M.; Guo, R.; Lu, W.; Muffoletto, B. C.; Reddy, T.; Stallworth, P. E.; Greenbaum, S. G.

    2010-01-01

    Three types of fluorinated carbon, all in their original form and upon sequential chemical lithiations via n-butyllithium, were investigated by 13C and 19F solid-state NMR methods. The three starting CFx materials [where x = 1 (nominally)] were fiber based, graphite based, and petroleum coke based. The aim of the current study was to identify, at the atomic/molecular structural level, factors that might account for differences in electrochemical performance among the different kinds of CFx. Differences were noted in the covalent F character among the starting compounds and in the details of LiF production among the lithiated samples. PMID:20676233

  4. NMR potentials for studying physical processes in fossil coals

    Energy Technology Data Exchange (ETDEWEB)

    Alekseev, Anatolii D; Ul' yanova, Ekaterina V; Vasilenko, Tat' yana A [Institute of Mining Processes Physics, National Academy of Sciences of Ukraine, Donetsk (Ukraine)

    2005-11-30

    High-resolution, pulsed, and wide-line NMR studies of fossil coals are reviewed. Coal substance conversion due to outbursts is discussed. Results on water and methane interactions with coal substance, which provide insight into the dynamic characteristics of boundary water, the location of methane in coal structure, and water and methane's hazard implications for coal beds (gas- or geodynamic phenomena) are presented; these are shown to have potential for predicting and preventing life threatening situations. (instruments and methods of investigation)

  5. Experimental study of 199Hg spin anti-relaxation coatings

    CERN Document Server

    Chowdhuri, Z; Horras, M; Kirch, K; Krempel, J; Lauss, B; Mtchedlishvili, A; Rebreyend, D; Roccia, S; Schmidt-Wellenburg, P; Zsigmond, G

    2013-01-01

    We report on a comparison of spin relaxation rates in a $^{199}$Hg magnetometer using different wall coatings. A compact mercury magnetometer was built for this purpose. Glass cells coated with fluorinated materials show longer spin coherence times than if coated with their hydrogenated homologues. The longest spin relaxation time of the mercury vapor was measured with a fluorinated paraffin wall coating.

  6. Nonlinear optical studies of relaxation in semiconductor microstructures

    Science.gov (United States)

    Remillard, Jeffrey Thomas

    1990-11-01

    Exposing a semiconductor to optical radiation near the fundamental band gap results in the creation of populations or elementary excitations including electrons, holes, and excitons, and also results in the creation of a superposition state between the ground and excited state of the solid. The relaxation of optically generated excitons and carriers in semiconductor microstructures was studied using four wave mixing (FWM) spectroscopy. The systems studied include CdSSe microcrystallite doped glasses and GaA/AlGaAs multiple quantum well structures (MQWS). First, the nonlinear optical response of simple two level systems is examined in order to provide insight into the types of line shapes expected from semiconductors. It is shown that the line shape is strongly dependent on how the system is coupled to the reservoir and the consequences of coupling to a reservoir are examined in a FWM measurement made in atomic sodium. The first semiconductor system studied is CdSSe microcrystallite doped glass. This system is shown to have a very slow component to the nonlinear response which has an optical intensity dependence and temperature dependence which suggests that the FWM response in these materials is trap mediated. Room temperature FWM measurements in GaAs MQWS enables the measurement of the carrier recombination time and the ambipolar diffusion coefficient. Using the technique of correlated optical fields, a slow component to the nonlinear response was measured showing an interference profile which suggests a possible shift of the exciton resonance due to the optically generated carriers. At low temperatures, measurements of the exciton line shape and relaxation time were made and evidence for exciton spectral diffusion was found. The low temperature line shapes can be qualitatively reproduced using Modified Optical Bloch equations which include the effects of spectral diffusion.

  7. Monochord sounds and progressive muscle relaxation reduce anxiety and improve relaxation during chemotherapy: a pilot EEG study.

    Science.gov (United States)

    Lee, Eun-Jeong; Bhattacharya, Joydeep; Sohn, Christof; Verres, Rolf

    2012-12-01

    Chemotherapy is the most distressing form of cancer treatment in oncology, but listening to music can be an adjuvant during chemotherapy. Monochord (MC) sounds are used in music therapy for the alleviation of pain, enhanced body perception, and relaxation. This study investigated the relaxation effect of MC sounds for patients during chemotherapy compared with progressive muscle relaxation (PMR), an established relaxation technique. Two randomized groups of patients were observed during chemotherapy. One group listened to recorded MC sounds (n=20) and the other group listened to recorded PMR (n=20). Each session was investigated pre and post using Spielberger's State Anxiety Inventory (SAI) and a questionnaire about the patient's physical and psychological states. Further, for the first and the last session, multivariate electroencephalogram (EEG) signals were recorded. Patients in both MC and PMR groups showed significant improvement in their physical and psychological states and in state anxiety. The EEG data showed that the MC and the PMR groups were associated with an increase of posterior theta (3.5-7.5 Hz) and a decrease of midfrontal beta-2 band (20-29.5 Hz) activity during the end phase of relaxation treatment. Further, the MC group was associated with decreased alpha band (8-12 Hz) activity in comparison with PMR group. This study shows that both listening to recorded MC sounds and practising PMR have a useful and comparable effect on gynaecologic oncological patients during chemotherapy, with partially overlapping but also notably divergent neural correlates. Future research should establish the systematic use of MC in oncological contexts. Copyright © 2012 Elsevier Ltd. All rights reserved.

  8. Some double resonance and multiple quantum NMR studies in solids

    Energy Technology Data Exchange (ETDEWEB)

    Wemmer, D.E.

    1978-08-01

    The first section of this work presents the theory and experimental applications to analysis of molecular motion of chemical shielding lineshapes obtained with high resolution double resonance NMR techniques. Analysis of /sup 13/C powder lineshapes in hexamethylbenzene (HMB) and decamethylferrocene (DMFe) show that these molecules reorient in a jumping manner about the symmetry axis. Analysis of proton chemical shielding lineshapes of residual protons in heavy ice (D/sub 2/O) show that protons are exchanged among the tetrahedral positions of neighboring oxygen atoms, consistent with motion expected from defect migration. The second section describes the application of Fourier Transform Double Quantum NMR to measurement of chemical shielding of deuterium in powder samples. Studies of partially deuterated benzene and ferrocene give equal shielding anisotropies, ..delta..sigma = -6.5 ppM. Theoretical predictions and experimental measurements of dipolar couplings between deuterons using FTDQ NMR are presented. Crystals of BaClO/sub 3/.D/sub 2/O, ..cap alpha..,..beta.. d-2 HMB and ..cap alpha..,..beta..,..gamma.. d-3 HMB were studied, as were powders of d-2 HMB and anisic acid. The third section discusses general multiple quantum spectroscopy in dipolar coupled spin systems. Theoretical description is made for creation and detection of coherences between states without quantum number selection rules ..delta..m = +-1. Descriptions of techniques for partial selectivity of order in preparation and detection of multiple quantum coherences are made. The effects on selectivity and resolution of echo pulses during multiple quantum experiments are discussed. Experimental observation of coherences up to order 6 have been made in a sample of benzene dissolved in a liquid crystal. Experimental verifications of order selection and echo generation have been made.

  9. A 1-year time course study of the relaxation times and histology for irradiated rat lungs

    Energy Technology Data Exchange (ETDEWEB)

    Shioya, S.; Haida, M.; Fukuzaki, M.; Ono, Y.; Tsuda, M.; Ohta, Y.; Yamabayashi, H. (Tokai Univ. School of Medicine, Kanagawa (Japan))

    1990-05-01

    To investigate the NMR relaxation times for irradiated rat lung tissue, we measured T1 and T2 at 11 different times during the injury's 1-year time course. A biexponential analysis of T2 was used to determine T2 fast (T2f) and T2 slow (T2s). In addition, we measured water content and correlated changes in the relaxation times with pathological changes. The correlation indicates the following: (1) Shortly after irradiation, the biexponential T2 decay for 1/3 of the samples became monoexponential and there were no noticeable pathological changes observed using light microscopy. (2) During radiation pneumonitis, T2f and T2s were prolonged. This accompanied acute edematous changes and inflammatory cell infiltration. (3) Finally, during radiation fibrosis T1 shortened and collagen increased. We observed no significant correlation between relaxation time changes and water content changes throughout the 1-year time course.

  10. {sup 77}Se NMR study of nonmagnetic-magnetic transition in (TMTSF){sub 2}X

    Energy Technology Data Exchange (ETDEWEB)

    Mito, T., E-mail: mito_takeshi@hotmail.co [Graduate School of Material Science, University of Hyogo, Hyogo 678-1297 (Japan); Nishiyama, K.; Koyama, T.; Ueda, K.; Kohara, T.; Takeuchi, K.; Akutsu, H.; Yamada, J. [Graduate School of Material Science, University of Hyogo, Hyogo 678-1297 (Japan); Kornilov, A.; Pudalov, V.M. [P.N. Lebedev Physics Institute, Moscow 119991 (Russian Federation); Qualls, J.S. [Sonoma State University, Rohnert Park, CA 94928 (United States)

    2010-12-15

    {sup 77}Se NMR measurements have been carried out on (TMTSF){sub 2}X (X = PF{sub 6} and AsF{sub 6}) single crystals. For both compounds, NMR lines split into double-peaked spectra in the SDW state, which is explained with sinusoidal internal field at Se nucleus positions having the same incommensurate wave number with that of the SDW order. No change in the lineshape was observed at T{sub x} at which the spin-relaxation rate shows a kink, suggesting that this anomaly does not cause significant static changes in internal field at the Se-site.

  11. Dielectric and molecular dynamics study of the secondary relaxations of poly(styrene-co-methylmethacrylate) copolymers: Influence of the molecular architecture.

    Science.gov (United States)

    Encinar, M; Prolongo, M G; Rubio, R G; Ortega, F; Ahmadi, A; Freire, J J

    2011-12-01

    The effect of the structure of copolymers (random, alternate or diblock) on their dynamics has been studied by dielectric spectroscopy. Six copolymers of styrene and methyl methacrylate (three diblocks, one alternate and two random) have been studied. The results show that the sub- T (g) transitions of the diblock samples can be described by one asymmetric Havriliak-Negami (HN) function, while two are necessary for the rest of the copolymers (β and γ relaxations). The characteristic times of the sub- T (g) relaxations show an Arrhenius temperature dependence and there is a strong coupling of the α and β relaxations at high temperatures. The deconvolution of the merging relaxations has been made in the framework of the Williams Ansatz set out in terms of Havriliak-Negami distributions. Because the 2D (2)H-NMR results excluded any significant contribution from the rotation of the methoxy group of the methacrylate group around the C-OCH(3) bond, the γ relaxation may be assigned to the rotation of the methyl methacrylate group in a styrene-rich environment. The Molecular Dynamics simulations of a poly(methyl methacrylate) homopolymer and of the alternate copolymer are in qualitative agreement with the experimental results, although they predict smaller values for the activation energy of the sub- T (g) relaxations.

  12. Relaxation dynamics of amorphous dibucaine using dielectric studies

    Science.gov (United States)

    Sahra, M.; Jumailath, K.; Thayyil, M. Shahin; Capaccioli, S.

    2015-06-01

    Using broadband dielectric spectroscopy the molecular mobility of dibucaine is investigated in the supercooled liquid and gassy states, over a wide temperature range for some test frequencies. Above the glass transition temperature Tg, the presence of structural α- relaxation peak was observed due to the cooperative motions of the molecule and upon cooling frozen kinetically to form the glass. The secondary relaxation process was perceivable below Tg due to localized motions. The peak loss frequency of α-relaxation process shows non-Arrhenius behavior and obeys Vogel-Fulcher-Tammann equation over the measured temperature range whereas the β- process shows Arrhenius behavior.

  13. Structural plasticity and Mg2+ binding properties of RNase P P4 from combined analysis of NMR residual dipolar couplings and motionally decoupled spin relaxation.

    Science.gov (United States)

    Getz, Melissa M; Andrews, Andy J; Fierke, Carol A; Al-Hashimi, Hashim M

    2007-02-01

    The P4 helix is an essential element of ribonuclease P (RNase P) that is believed to bind catalytically important metals. Here, we applied a combination of NMR residual dipolar couplings (RDCs) and a recently introduced domain-elongation strategy for measuring "motionally decoupled" relaxation data to characterize the structural dynamics of the P4 helix from Bacillus subtilis RNase P. In the absence of divalent ions, the two P4 helical domains undergo small amplitude (approximately 13 degrees) collective motions about an average interhelical angle of 10 degrees. The highly conserved U7 bulge and helical residue C8, which are proposed to be important for substrate recognition and metal binding, are locally mobile at pico- to nanosecond timescales and together form the pivot point for the collective domain motions. Chemical shift mapping reveals significant association of Mg2+ ions at the P4 major groove near the flexible pivot point at residues (A5, G22, G23) previously identified to bind catalytically important metals. The Mg2+ ions do not, however, significantly alter the structure or dynamics of P4. Analysis of results in the context of available X-ray structures of the RNA component of RNase P and structural models that include the pre-tRNA substrate suggest that the internal motions observed in P4 likely facilitate adaptive changes in conformation that take place during folding and substrate recognition, possibly aided by interactions with Mg2+ ions. Our results add to a growing view supporting the existence of functionally important internal motions in RNA occurring at nanosecond timescales.

  14. NMR study of hydroxy and amide protons in hyaluronan polymers.

    Science.gov (United States)

    Nestor, Gustav; Sandström, Corine

    2017-02-10

    Hyaluronan (HA) is an important and well characterized glycosaminoglycan with high viscosity and water-retaining capacity. Nonetheless, it is not fully understood whether conformational properties of the easily characterized HA oligomers can be transferred to HA polymers. To investigate possible differences in hydration, hydrogen bonding and flexibility between HA polymers and oligomers, hydroxy and amide protons of HA polymers were studied by solution-state and high-resolution magic angle spinning (HR-MAS) NMR spectroscopy. Measurements of chemical shifts, temperature coefficients and NOEs in HA polymers revealed that the NMR data are very similar compared to the interior of a HA octasaccharide, supporting transient hydrogen bond interactions across the β(1→3) and β(1→4) glycosidic linkages. However, differences in NOEs suggested a cis-like orientation between NH and H2 in the HA polymer. The lack of concentration dependence of the hydroxy proton chemical shifts suggests that there are no direct inter-chain interactions involving hydroxy protons at the concentrations investigated.

  15. A Study of Quantum Error Correction by Geometric Algebra and Liquid-State NMR Spectroscopy

    CERN Document Server

    Sharf, Y; Somaroo, S S; Havel, T F; Knill, E H; Laflamme, R; Sharf, Yehuda; Cory, David G.; Somaroo, Shyamal S.; Havel, Timothy F.; Knill, Emanuel; Laflamme, Raymond

    2000-01-01

    Quantum error correcting codes enable the information contained in a quantum state to be protected from decoherence due to external perturbations. Applied to NMR, quantum coding does not alter normal relaxation, but rather converts the state of a ``data'' spin into multiple quantum coherences involving additional ancilla spins. These multiple quantum coherences relax at differing rates, thus permitting the original state of the data to be approximately reconstructed by mixing them together in an appropriate fashion. This paper describes the operation of a simple, three-bit quantum code in the product operator formalism, and uses geometric algebra methods to obtain the error-corrected decay curve in the presence of arbitrary correlations in the external random fields. These predictions are confirmed in both the totally correlated and uncorrelated cases by liquid-state NMR experiments on 13C-labeled alanine, using gradient-diffusion methods to implement these idealized decoherence models. Quantum error correcti...

  16. Soils, Pores, and NMR

    Science.gov (United States)

    Pohlmeier, Andreas; Haber-Pohlmeier, Sabina; Haber, Agnes; Sucre, Oscar; Stingaciu, Laura; Stapf, Siegfried; Blümich, Bernhard

    2010-05-01

    Within Cluster A, Partial Project A1, the pore space exploration by means of Nuclear Magnetic Resonance (NMR) plays a central role. NMR is especially convenient since it probes directly the state and dynamics of the substance of interest: water. First, NMR is applied as relaxometry, where the degree of saturation but also the pore geometry controls the NMR signature of natural porous systems. Examples are presented where soil samples from the Selhausen, Merzenhausen (silt loams), and Kaldenkirchen (sandy loam) test sites are investigated by means of Fast Field Cycling Relaxometry at different degrees of saturation. From the change of the relaxation time distributions with decreasing water content and by comparison with conventional water retention curves we conclude that the fraction of immobile water is characterized by T1 samples (Haber-Pohlmeier et al. 2010). Third, relaxometric information forms the basis of understanding magnetic resonance imaging (MRI) results. The general difficulty of imaging in soils are the inherent fast T2 relaxation times due to i) the small pore sizes, ii) presence of paramagnetic ions in the solid matrix, and iii) diffusion in internal gradients. The last point is important, since echo times can not set shorter than about 1ms for imaging purposes. The way out is either the usage of low fields for imaging in soils or special ultra-short pulse sequences, which do not create echoes. In this presentation we will give examples on conventional imaging of macropore fluxes in soil cores (Haber-Pohlmeier et al. 2010), and the combination with relaxometric imaging, as well as the advantages and drawbacks of low-field and ultra-fast pulse imaging. Also first results on the imaging of soil columns measured by SIP in Project A3 are given. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Waterflow Monitored by Tracer Transport in Natural Porous Media Using MRI." Vadose Zone J.: submitted. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Relaxation in a

  17. AN EXPERIMENTAL STUDY ON THE RELAXATION OF BOLTS

    Directory of Open Access Journals (Sweden)

    Muhammad Abid

    2015-05-01

    Full Text Available Loss of pre-load with time, commonly known as ‘Relaxation’ is an established phenomena. Behaviour of a bolted joint depends upon the pre-load in the bolts in use, not the pre-load introduced by the mechanic. Loss of pre-load is expected due to the many factors such as embedment relaxation, gasket creep, elastic interactions, and vibration loosening or stress relaxation. In a gasketed joint, due to the gasket flexibility, relaxation is always substantial during preliminary passes, as 80 to 100% loss is not uncommon in almost all the bolts, resulting in a dynamic behaviour. Pre-load in a gasketed joint is stabilized and retained to certain extent in the final passes only. In a non-gasketed joint, due to no gasket and no rotation its static behaviour is concluded. This paper highlights the factors affecting the amount of relaxation with time and presents important considerations that can reduce this. Both the short and long term relaxations are recorded and a ‘best fit’ model for relaxation behaviour is derived.

  18. Study of multi-site chemical exchange in solution state by NMR: 1D experiments with multiply selective excitation

    Indian Academy of Sciences (India)

    Samanwita Pal

    2010-07-01

    Chemical exchange in solution state has been investigated traditionally by both 1D and 2D NMR, permitting the extraction of kinetic parameters (e.g. the spin-lattice relaxation time 1, the exchange rate constant and the activation parameters). This work demonstrates a simple 1D NMR approach employing multiply selective excitation to study multi-site exchange processes in solution, applying it to systems that exhibit three-site exchange. This approach involves simultaneous excitation of all - or a chosen subset of - the exchanging sites by using an appropriately modulated shaped radiofrequency pulse. The pulse sequence, as well as analysis is summarized. Significant features of the experiment, which relies on sign labelling of the exchanging sites, include considerably shorter experiment time compared to standard 2D exchange work, clear definition of the exchange time window and uniform pulse non-ideality effects for all the exchanging sites. Complete kinetic information is reported in the study of dynamic processes in superacid solutions of two weak bases, studied by 1H NMR. An analytical solution, leading to the determination of four rate parameters, is presented for proton exchange studies on these systems, which involve a mixture of two weak bases in arbitrary concentration ratio, and stoichiometric excess of the superacid.

  19. Compact NMR

    Energy Technology Data Exchange (ETDEWEB)

    Bluemich, Bernhard; Haber-Pohlmeier, Sabina; Zia, Wasif [RWTH Aachen Univ. (Germany). Inst. fuer Technische und Makromolekulare Chemie (ITMC)

    2014-06-01

    Nuclear Magnetic Resonance (NMR) spectroscopy is the most popular method for chemists to analyze molecular structures, while Magnetic Resonance Imaging (MRI) is a non-invasive diagnostic tool for medical doctors that provides high-contrast images of biological tissue. In both applications, the sample (or patient) is positioned inside a large, superconducting magnet to magnetize the atomic nuclei. Interrogating radio-frequency pulses result in frequency spectra that provide the chemist with molecular information, the medical doctor with anatomic images, and materials scientist with NMR relaxation parameters. Recent advances in magnet technology have led to a variety of small permanent magnets to allow compact and low-cost instruments. The goal of this book is to provide an introduction to the practical use of compact NMR at a level nearly as basic as the operation of a smart phone.

  20. NMR study of pyrochlore lattice antiferromagnet, melanothallite Cu2OCl2

    Science.gov (United States)

    Nishiyama, Masahide; Oyamada, Akira; Itou, Tetsuaki; Maegawa, Satoru; Okabe, Hirotaka; Akimitsu, Jun

    2011-09-01

    The melanothallite Cu2OCl2 is a new example of pyrochlore-like antiferromagnet, which is composed of 3d transition metal electrons. We performed Cu- and Cl-NMR experiments on powder samples of Cu2OCl2 below transition temperature TN = 70 K and we observed six resonant peaks of Cu nuclei, which are composed of three symmetric peaks corresponding to 63Cu and three corresponding to 65Cu. The Cu nuclei feel the strong hyperfine fields because of ordered magnetic moments and the electric field gradients. We determined the spin structure by analyzing the Cu-NMR spectra. The melanothallite has an all-in-all-out spin structure. The spin lattice relaxation rates T1-1 of Cu- and Cl-NMR in the ordered phase are proportional to the temperature; This suggests that although long-range ordering occurs at rather high temperature, the large spin fluctuations caused by the geometrical frustration still remain.

  1. NMR studies of two spliced leader RNAs using isotope labeling

    Energy Technology Data Exchange (ETDEWEB)

    Lapham, J.; Crothers, D.M. [Yale Univ., New Haven, CT (United States)

    1994-12-01

    Spliced leader RNAs are a class of RNA molecules (<200 nts) involved in the trans splicing of messenger RNA found in trypanosomes, nematodes, and other lower eukaryotes. The spliced leader RNA from the trypanosome Leptomonas Collosoma exists in two alternate structural forms with similar thermal stabilities. The 54 nucleotides on the 5{prime} end of the SL molecule is structurally independent from the 3{prime} half of the RNA, and displays the two structural forms. Furthermore, the favored of the two structures was shown to contain anomalous nuclease sensitivity and thermal stability features, which suggests that there may be tertiary interactions between the splice site and other nucleotides in the 5{prime} end. Multidimensional NMR studies are underway to elucidate the structural elements present in the SL RNAs that give rise to their physical properties. Two spliced leader sequences have been studied. The first, the 54 nucleotides on the 5{prime} end of the L. Collosoma sequence, was selected because of earlier studies in our laboratory. The second sequence is the 5{prime} end of the trypanosome Crithidia Fasciculata, which was chosen because of its greater sequence homology to other SL sequences. Given the complexity of the NMR spectra for RNA molecules of this size, we have incorporated {sup 15}N/{sup 13}C-labeled nucleotides into the RNA. One of the techniques we have developed to simplify the spectra of these RNA molecules is isotope labeling of specific regions of the RNA. This has been especially helpful in assigning the secondary structure of molecules that may be able to adopt multiple conformations. Using this technique one can examine a part of the molecule without spectral interference from the unlabeled portion. We hope this approach will promote an avenue for studying the structure of larger RNAs in their native surroundings.

  2. A randomised controlled study of mindfulness meditation versus relaxation therapy in the management of tinnitus.

    Science.gov (United States)

    Arif, M; Sadlier, M; Rajenderkumar, D; James, J; Tahir, T

    2017-06-01

    Psychotherapeutic interventions have been adopted effectively in the management of tinnitus for a long time. This study compared mindfulness meditation and relaxation therapy for management of tinnitus. In this randomised controlled trial, patients were recruited for five sessions of mindfulness meditation or five sessions of relaxation therapy. Patients' responses were evaluated using the Tinnitus Reaction Questionnaire as a primary outcome measure, and the Hospital Anxiety and Depression Scale, visual analogue scale and a health status indicator as secondary outcome measures. A total of 86 patients were recruited. Thirty-four patients completed mindfulness meditation and 27 patients completed relaxation therapy. Statistically significant improvement was seen in all outcome measures except the health status indicator in both treatment groups. The change in treatment scores was greater in the mindfulness meditation group than in the relaxation therapy group. This study suggests that although both mindfulness meditation and relaxation therapy are effective in the management of tinnitus, mindfulness meditation is superior to relaxation therapy.

  3. Experimental study of residual stresses relaxation in ring details during multicyclic loading

    Science.gov (United States)

    Korolev, A. V.; Korolev, A. A.; Balaev, A. F.; Savran, S. A.; Yakovishin, A. S.

    2016-11-01

    The paper presents the results of experimental studies of vibro-mechanical mechanism of residual stresses relaxation in ringed parts. There was described the mechanism of vibro-mechanical relaxation that includes machining of ringed parts among three rotating rolls under pressure. This leads to multicyclic loading due to which there occurs relaxation of residual stresses. To study the process of vibro-mechanical relaxation a complete factorial experiment was carried out. As a result of experiments we obtained empirical dependence of residual stresses on processing factors.

  4. Study of an S = 1 Ni(II) pincer electrocatalyst precursor for aqueous hydrogen production based on paramagnetic 1H NMR.

    Science.gov (United States)

    Luca, Oana R; Konezny, Steven J; Paulson, Eric K; Habib, Fatemah; Luthy, Kurt M; Murugesu, Muralee; Crabtree, Robert H; Batista, Victor S

    2013-06-28

    A tridentate NNN Ni(II) complex, shown to be an electrocatalyst for aqueous H2 production at low overpotentials, is studied by using temperature-dependent paramagnetic (1)H NMR. The NMR T1 relaxation rates, temperature dependence of the chemical shifts, and dc SQUID magnetic susceptibility are correlated to DFT chemical shifts and compared with the properties of a diamagnetic Zn analogue complex. The resulting characterization provides an unambiguous assignment of the six proton environments in the meridionally coordinating tridentate NNN ligand. The demonstrated NMR/DFT methodology should be valuable in the search for appropriate ligands to optimize the reactivity of 3d metal complexes bound to attract increasing attention in catalytic applications.

  5. β-NMR study of boron in diamond

    Energy Technology Data Exchange (ETDEWEB)

    Izumikawa, T., E-mail: izumika@med.niigata-u.ac.jp [Niigata University, Isotope Center (Japan); Mihara, M.; Matsuta, K.; Fukuda, M. [Osaka University, Department of Physics (Japan); Ohtsubo, T.; Ohya, S. [Niigata University, Graduate School of Science (Japan); Minamisono, T. [Osaka University, Department of Physics (Japan)

    2015-04-15

    A β-NMR study of {sup 12}B implanted in diamond was performed in order to investigate the implantation sites and the defects. The maintained polarization of {sup 12}B was measured by use of widely modulated rf around the Larmor frequency (ν = ν{sub L} ± 200 kHz) as a function of temperature from 160 K to 320 K. The observed polarization was found to be almost constant at about 0.9 % in this temperature range. The initial polarization for this system was obtained as about 8.1 %. Therefore about 10 % of the implanted {sup 12}B maintained its polarization in this frequency range. Conversely, about 90 % of the implanted {sup 12}B was undetected in the present experiment.

  6. Pharmaceutical Applications of Relaxation Filter-Selective Signal Excitation Methods for ¹⁹F Solid-State Nuclear Magnetic Resonance: Case Study With Atorvastatin in Dosage Formulation.

    Science.gov (United States)

    Asada, Mamiko Nasu; Nemoto, Takayuki; Mimura, Hisashi

    2016-03-01

    We recently developed several new relaxation filter-selective signal excitation (RFS) methods for (13)C solid-state nuclear magnetic resonance (NMR) that allow (13)C signal extraction of the target components from pharmaceuticals. These methods were successful in not only qualification but also quantitation over the wide range of 5% to 100%. Here, we aimed to improve the sensitivity of these methods and initially applied them to (19)F solid-state NMR, on the basis that the fluorine atom is one of the most sensitive NMR-active nuclei. For testing, we selected atorvastatin calcium (ATC), an antilipid BCS class II drug that inhibits 3-hydroxy-3-methylglutaryl-coenzyme A reductase and is marketed in crystalline and amorphous forms. Tablets were obtained from 2 generic drug suppliers, and the ATC content occurred mainly as an amorphous form. Using the RFS method with (19)F solid-state NMR, we succeeded in qualifying trace amounts (less than 0.5% w/w level) of crystalline phase (Form I) of ATC in the tablets. RFS methods with (19)F solid-state NMR are practical and time efficient and can contribute not only to the study of pharmaceutical drugs, including those with small amounts of a highly potent active ingredient within a formulated product, but also to the study of fluoropolymers in material sciences. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  7. Molecular dynamics of solid benzothiadiazine derivatives (Thiazides). A study by NMR, DTA and DFT methods

    Science.gov (United States)

    Latosińska, J. N.; Latosińska, M.; Utrecht, R.; Mielcarek, S.; Pietrzak, J.

    2004-06-01

    The 1H solid state NMR spectra of four sulphonamide derivatives of 1,2,4-benzothiadiazine-1,1-dioxides (thiazides) were recorded at different temperatures in the range 100-400 K and the temperature dependencies of the second moment ( M2) of the resonant line and spin-lattice relaxation time ( T1) were measured. The minimum in the temperature dependence of the T1 revealed an activation process related to the hindered rotation (jumps) of the -NH 2 group. The activation energy of this motion estimated on the basis of the fit of the theoretical model to the experimental points was 36.5 kJ/mol for HCTZ, 31.8 kJ/mol for ATZ, 35.2 kJ/mol for TCTZ and 40.6 kJ/mol for CTZ, and was close to that calculated by the DFT (B3LYP/6-311+G(2d,p)) method for the model assuming the -NH 2 jumps between two equilibrium positions. This type motion is responsible for the reduction in the NMR line second moment by approximately 1Gs 2 observed for all the thiazides studied. Thiazides also perform a quasi-isotropic motion tumbling whose activation energy is higher than that of the hindered jumps of the NH 2 group. This motion is characterized only by M2 reduction. According to the increasing strength of the NH 2 group bonding in the crystalline lattice, the thiazides studied can be ordered as: ATZ

  8. Laboratory Studies of Vibrational Relaxation: Important Insights for Mesospheric OH

    Science.gov (United States)

    Kalogerakis, Konstantinos S.; Matsiev, Daniel

    2016-04-01

    The hydroxyl radical has a key role in the chemistry and energetics of the Earth's middle atmosphere. A detailed knowledge of the rate constants and relevant pathways for OH(high v) vibrational relaxation by atomic and molecular oxygen and their temperature dependence is absolutely critical for understanding mesospheric OH and extracting reliable chemical heating rates from atmospheric observations. We have developed laser-based experimental approaches to study the complex collisional energy transfer processes involving the OH radical and other relevant atmospheric species. Previous work in our laboratory indicated that the total removal rate constant for OH(v = 9) + O at room temperature is more than one order of magnitude larger than that for removal by O2. Thus, O atoms are expected to significantly influence the intensity and vibrational distribution extracted from the Meinel OH(v) emissions. We will report our most recent laboratory experiments that corroborate the aforementioned result for OH(v = 9) + O and provide important new insights on the mechanistic pathways involved. We will also highlight relevant atmospheric implications, including warranted revisions of current mesospheric OH models. Research supported by SRI International Internal R&D and NSF Aeronomy grant AGS-1441896. Previously supported by NASA Geospace Science grant NNX12AD09G.

  9. Informing saccharide structural NMR studies with density functional theory calculations.

    Science.gov (United States)

    Klepach, Thomas; Zhao, Hongqiu; Hu, Xiaosong; Zhang, Wenhui; Stenutz, Roland; Hadad, Matthew J; Carmichael, Ian; Serianni, Anthony S

    2015-01-01

    Density functional theory (DFT) is a powerful computational tool to enable structural interpretations of NMR spin-spin coupling constants ( J-couplings) in saccharides, including the abundant (1)H-(1)H ( JHH), (13)C-(1)H ( JCH), and (13)C-(13)C ( JCC) values that exist for coupling pathways comprised of 1-4 bonds. The multiple hydroxyl groups in saccharides, with their attendant lone-pair orbitals, exert significant effects on J-couplings that can be difficult to decipher and quantify without input from theory. Oxygen substituent effects are configurational and conformational in origin (e.g., axial/equatorial orientation of an OH group in an aldopyranosyl ring; C-O bond conformation involving an exocyclic OH group). DFT studies shed light on these effects, and if conducted properly, yield quantitative relationships between a specific J-coupling and one or more conformational elements in the target molecule. These relationships assist studies of saccharide structure and conformation in solution, which are often challenged by the presence of conformational averaging. Redundant J-couplings, defined as an ensemble of J-couplings sensitive to the same conformational element, are particularly helpful when the element is flexible in solution (i.e., samples multiple conformational states on the NMR time scale), provided that algorithms are available to convert redundant J-values into meaningful conformational models. If the latter conversion is achievable, the data can serve as a means of testing, validating, and refining theoretical methods like molecular dynamics (MD) simulations, which are currently relied upon heavily to assign conformational models of saccharides in solution despite a paucity of experimental data needed to independently validate the method.

  10. EXPERIMENTAL STUDY OF THE ASYNCHRONOUS MULTISPLITTING RELAXATION METHODS FOR THE LINEAR COMPLEMENTARITY PROBLEMS

    Institute of Scientific and Technical Information of China (English)

    Zhong-zhi Bai

    2002-01-01

    We study the numerical behaviours of the relaxed asynchronous multisplitting methods for the linear complementarity problems by solving some typical problems from practical applications on a real multiprocessor system. Numerical results show that the parallel multisplitting relaxation methods always perform much better than the corresponding sequential alternatives, and that the asynchronous multisplitting relaxation methods often outperform their corresponding synchronous counterparts. Moreover, the two-sweep relaxed multisplitting methods have better convergence properties than their corresponding one-sweep relaxed ones in the sense that they have larger convergence domains and faster convergence speeds. Hence, the asynchronous multisplitting unsymmetric relaxation iterations should be the methods of choice for solving the large sparse linear complementarity problems in the parallel computing environments.

  11. Epitope Mapping of Antigenic MUC1 Peptides to Breast Cancer Antibody Fragment B27.29: A Heteronuclear NMR Study

    Energy Technology Data Exchange (ETDEWEB)

    Grinstead, Jeffrey S.; Schuman, Jason T.; Campbell, Ann P.

    2003-11-13

    MUC1 mucin is a breast cancer-associated transmembrane glycoprotein, of which the extracellular domain is formed by the repeating 20-amino acid sequence GVTSAPDTRPAPGSTAPPAH. In neoplastic breast tissue, the highly immunogenic sequence PDTRPAP (in bold above) is exposed. Antibodies raised directly against MUC1-expressing tumors offer unique access to this neoplastic state, as they represent immunologically relevant ''reverse templates'' of the tumor-associated mucin. In a previous study [Grinstead, J. S., et al. (2002) Biochemistry 41, 9946-9961], 1H NMR methods were used to correlate the effects of cryptic glycosylation outside of the PDTRPAP core epitope sequence on the recognition and binding of Mab B27.29, a monoclonal antibody raised against breast tumor cells. In the study presented here, isotope-edited NMR methods, including 15N and 13C relaxation measurements, were used to probe the recognition and binding of the PDTRPAP epitope sequence to Fab B27.29. Two peptides were studied: a one-repeat MUC1 16mer peptide of the sequence GVTSAPDTRPAPGSTA and a two-repeat MUC1 40mer peptide of the sequence (VTSAPDTRPAPGSTAPPAHG)2. 15N and 13C NMR relaxation parameters were measured for both peptides free in solution and bound to Fab B27.29. The 13CR T1 values best represent changes in the local correlation time of the peptide epitope upon binding antibody, and demonstrate that the PDTRPAP sequence is immobilized in the antibody-combining site. This result is also reflected in the appearance of the 15N- and 13C-edited HSQC spectra, where line broadening of the same peptide epitope resonances is observed. The PDTRPAP peptide epitope expands upon the peptide epitope identified previously in our group as PDTRP by homonuclear NMR experiments [Grinstead, J. S., et al. (2002) Biochemistry 41, 9946-9961], and illustrates the usefulness of the heteronuclear NMR experiments. The implications of these results are discussed within the context of MUC1 breast

  12. Experimental study on relaxation time in direction changing movement

    Science.gov (United States)

    Liu, Chi; Song, Weiguo; Fu, Libi; Lian, Liping; Lo, Siuming

    2017-02-01

    Controlled experiments were conducted to clarify the movement characteristics of pedestrians in direction changing processes. We track pedestrians' trajectories and map them into real space coordinates by the direct linear transformation method. In the acceleration process, the relaxation time and free moving speed in our experiments respectively equal 0.659 s and 1.540 m/s, which are consistent with those for Chinese participants in other experiments. Meanwhile, the values of relaxation time in the direction changing process are calculated by a derived equation from the concept of the social force model. It is observed that the relaxation time is not an invariable parameter, and tends to increase with an increase in the angular difference. Furthermore, results show that pedestrians are insensitive to a tiny angular difference between instantaneous velocity and desired velocity. These experimental results presented in this work can be applied in model development and validation.

  13. Micellar kinetics of a fluorosurfactant through stopped-flow NMR.

    Science.gov (United States)

    Yushmanov, Pavel V; Furó, István; Stilbs, Peter

    2006-02-28

    19F NMR chemical shifts and transverse relaxation times T2 were measured as a function of time after quick stopped-flow dilution of aqueous solutions of sodium perfluorooctanoate (NaPFO) with water. Different initial concentrations of micellar solution and different proportions of mixing were tested. Previous stopped-flow studies by time-resolved small-angle X-ray scattering (TR-SAXS) detection indicated a slow (approximately 10 s) micellar relaxation kinetics in NaPFO solutions. In contrast, no evidence of any comparable slow (>100 ms) relaxation process was found in our NMR studies. Possible artifacts of stopped-flow experiments are discussed as well as differences between NMR and SAXS detection methods. Upper bounds on the relative weight of a slow relaxation process are given within existing kinetic theories of micellar dissolution.

  14. Shock-tube study of relaxation in HCN

    Science.gov (United States)

    Srinivasan, N. K.; Gupte, K. S.; Kiefer, J. H.

    2008-08-01

    Thermal vibrational relaxation in HCN mixtures with Kr has been observed with the laser-schlieren technique. The experiments cover the temperatures 750-2900 K and a large pressure range of 13-420 Torr in 5% and 20% HCN/Kr mixtures. Relaxation is extremely fast but appears to occur in two well-separated stages that are assigned to the vibrational transitions (000)-->(010) and (000)-->(100) with perhaps some lesser contribution from (000)-->(001). This interpretation is strongly supported by a comparison of net density changes to thermodynamic calculations. The first and faster process shows near constant relaxation times whereas the latter slower stage has a slight decrease of these with T. Relaxation times in pure HCN obtained by neglecting the small contribution of krypton are as follows: (a) PτHCN-HCN=27 exp(1.473/T1/3) ns atm (000)-->(010) (b) PτHCN-HCN=11 exp(32.6/T1/3) ns atm (000)-->(100). Probabilities suggested by these results are around 0.05 for the fast step and 0.0035 to 0.005 for the slow process. These results are close to those found by laser fluorescence measurements for deactivation of levels involving excitation of the C-H stretch (001) at 3312 cm-1. These results are also consistent with the notion of a dominance of the fast stage by T,R-V transfer (thermal relaxation) occurring in a weakly bound complex. However, the slow step most likely occurs through a V-V process (03 10)-->(100), ΔE=27.7 cm-1, after multiple excitation of the (010) mode. These are the first thermal measurements of relaxation in HCN and the first to see energy transfer involving the low-frequency modes.

  15. Relaxation Kinetic Study of Eudragit® NM30D Film Based on Complex Modulus Formalism

    OpenAIRE

    Penumetcha, Sai Sumana; Stephen R. Byrn; Morris, Kenneth R.

    2015-01-01

    This study is aimed at resolving and characterizing the primary (α) and secondary relaxations (β) in Eudragit® NM30D film based on apparent activation energies derived from complex modulus formalism using dielectric analysis (DEA). The glass transition (Tg) of the film was determined using differential scanning calorimetry (DSC). The α relaxation corresponding to Tg and the β relaxations occurring below Tg were probed using DEA. The occurrence of α and β relaxations in Eudragit® NM30D film wa...

  16. Relaxation Kinetic Study of Eudragit® NM30D Film Based on Complex Modulus Formalism.

    Science.gov (United States)

    Penumetcha, Sai Sumana; Byrn, Stephen R; Morris, Kenneth R

    2015-10-01

    This study is aimed at resolving and characterizing the primary (α) and secondary relaxations (β) in Eudragit® NM30D film based on apparent activation energies derived from complex modulus formalism using dielectric analysis (DEA). The glass transition (T g) of the film was determined using differential scanning calorimetry (DSC). The α relaxation corresponding to T g and the β relaxations occurring below T g were probed using DEA. The occurrence of α and β relaxations in Eudragit® NM30D film was elucidated using the complex modulus of the dielectric response employing loss modulus and permittivity data. Activation energies of these relaxations and the fundamental frequency so determined support the assignment of the relaxation pattern in the Eudragit® NM30D film. DEA methodology of the complex modulus formalism is a useful tool for differentiating the α and β relaxation kinetics in Eudragits® not easily studied using traditional thermal methods such as DSC. The kinetics associated with α and β relaxations so determined will provide formulation design support for solid orals that incorporate Eudragit® polymers. As mobility changes can affect stability and diffusion, the dipolar α and β relaxations revealed through DEA analysis may enable a better correlation to functionality of Eudragit® based pharmaceutical dosage forms.

  17. On the use of Liouville relaxation supermatrices in Mössbauer studies. III : Application to Mössbauer relaxation in superconductors

    OpenAIRE

    Hartmann-Boutron, F.

    1980-01-01

    Wagner et al. recently studied the Mössbauer relaxation of paramagnetic dysprosium as an impurity in superconducting thorium. In connection with this study, we have derived simple formulas for interpreting relaxation effects in 2+ 0+ Mössbauer transitions of rare earth ions in superconductors.

  18. Methyl quantum tunneling and nitrogen-14 NQR NMR studies using a SQUID magnetic resonance spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Black, Bruce Elmer [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1993-07-01

    Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) techniques have been very successful in obtaining molecular conformation and dynamics information. Unfortunately, standard NMR and NQR spectrometers are unable to adequately detect resonances below a few megahertz due to the frequency dependent sensitivity of their Faraday coil detectors. For this reason a new spectrometer with a dc SQUID (Superconducting Quantum Interference Device) detector, which has no such frequency dependence, has been developed. Previously, this spectrometer was used to observe 11B and 27Al NQR resonances. The scope of this study was increased to include 23Na, 51V, and 55Mn NQR transitions. Also, a technique was presented to observe 14N NQR resonances through cross relaxation of the nitrogen polarization to adjacent proton spins. When the proton Zeeman splitting matches one nitrogen quadrupoler transition the remaining two 14N transitions can be detected by sweeping a saturating rf field through resonance. Additionally, simultaneous excitation of two nitrogen resonances provides signal enhancement which helps to connect transitions from the same site. In this way, nitrogen-14 resonances were observed in several amino acids and polypeptides. This spectrometer has also been useful in the direct detection of methyl quantum tunneling splittings at 4.2 K. Tunneling, frequencies of a homologous series of carboxylic acids were measured and for solids with equivalent crystal structures, an exponential correlation between the tunneling frequency and the enthalpy of fusion is observed. This correlation provides information about the contribution of intermolecular interactions to the energy barrier for methyl rotation.

  19. Integrated computational approach to the analysis of NMR relaxation in proteins: application to ps-ns main chain 15N-1H and global dynamics of the Rho GTPase binding domain of plexin-B1.

    Science.gov (United States)

    Zerbetto, Mirco; Buck, Matthias; Meirovitch, Eva; Polimeno, Antonino

    2011-01-20

    An integrated computational methodology for interpreting NMR spin relaxation in proteins has been developed. It combines a two-body coupled-rotator stochastic model with a hydrodynamics-based approach for protein diffusion, together with molecular dynamics based calculations for the evaluation of the coupling potential of mean force. The method is applied to ¹⁵N relaxation of N-H bonds in the Rho GTPase binding (RBD) domain of plexin-B1, which exhibits intricate internal mobility. Bond vector dynamics are characterized by a rhombic local ordering tensor, S, with principal values S₀² and S₂², and an axial local diffusion tensor, D₂, with principal values D(2,||) and D(2,⊥). For α-helices and β-sheets we find that S₀² ~ -0.5 (strong local ordering), -1.2 computational approach for treating NMR relaxation in proteins by combining stochastic modeling and molecular dynamics. The approach developed provides new insights by its application to a protein that experiences complex dynamics.

  20. Study of Conformation and Dynamics of Molecules Adsorbed in Zeolites by 1H NMR

    Science.gov (United States)

    Michel, Dieter; Bohlmann, Winfried; Roland, Jorg; Mulla-Osman, Samir

    The chapter Study of Conformation and Dynamics of Molecules Adsorbed in Zeolites by 1H NMR is concerned with the application of high-resolution (HR) solid-state NMR techniques to study the behavior of molecules adsorbed on surfaces of nanoporous solids, such as zeolitic molecular sieves. This includes a combined or alternative application of conventional high-resolution NMR methods and of high-resolution solid-state NMR techniques, including magic-angle sample spinning (MAS), cross-polarization (CP), high-power decoupling and appropriate multiple-pulse sequences for two- or higher dimensional NMR and multiple-quantum spectroscopy. The interaction of adsorbed molecules with adsorption centers in the internal surfaces of porous solids does not only lead to changes in the reorientational and translational mobility of the molecular species but influences also the molecular conformation. Examples will be given for simple olefins in interaction with inner zeolite surfaces. Conclusions about the correlation times of the internal reorientational and translational dynamics are derived in complete agreement with the conclusion obtained from diffusion coefficients by means of PFG NMR (second chapter). Since the methodical approach of HR MAS NMR in heterogeneous systems presented here is also valuable for the investigation of lyotropic crystalline phases using HR MAS NMR (in Chap. 12) And for the NMR studies of cartilage (in Chap. 13) it was also the aim of this chapter to elucidate also the methodical background of these measurements in some more detail.

  1. Relaxation of Small Molecules:an ab initio Study

    Institute of Scientific and Technical Information of China (English)

    CAOYi-Gang; A.Antons; 等

    2002-01-01

    Using an ab inito total energy and force method,we have relaxed several group IV and group V elemental clusters,in detail the arsenic and antimony dimers,silicon,phosphorus,arsenic and antimony tetraners,The obtained bond lengths and cohesive energies are more accurate than other calculating methods,and in excellent agreement with the experimental results.

  2. Relaxation of Small Molecules: an ab initio Study

    Institute of Scientific and Technical Information of China (English)

    CAO Yi-Gang; JIAO Zheng-Kuan; A. Antons; K. Schroeder; S. Blügel2

    2002-01-01

    Using an ab initio total energy and force method, we have relaxed several group IV and group V elementalclusters, in detail the arsenic and antimony dimers, silicon, phosphorus, arsenic and antimony tetramers. The obtainedbond lengths and cohesive energies are more accurate than other calculating methods, and in excellent agreement withthe experimental results.

  3. Iodine-xenon studies and the relax mass spectrometer

    Science.gov (United States)

    Gilmour, J. D.; Ash, R. D.; Lyon, I. C.; Johnston, W. A.; Hutchison, R.; Bridges, J. C.; Turner, G.

    1994-07-01

    RELAX combines a resonance ionization ion source with a cryogenic sample concentrator to achieve ultrasensitivity. Gas is extracted from samples using either a continuous wave laser microprobe based on an argon-ion laser or a filament microfurnace. Recent refinements in the operating procedure have resulted in optimum sensitivities such that detection rates of 1 cps are achieved from fewer than 500 atoms. A Xe-128 spike reservoir has also been added and characterized, allowing accurate determinations of absolute amounts of gas. We have completed a preliminary study of the iodine-xenon system in samples from the Bjurbole and Parnallee meteorites. Bjurbole chondrules ranging in mass from 5.45 mg to 260 micrograms were analyzed by laser microprobe. The results from these samples are consistent with an effectively uniform formation age, suggesting that the use of Bjurbole chondrules for calibration of this chronometer can be extended to samples in this size range. Samples from two chondrules from the Parnallee meteorite have been analyzed to date. An alpha-cristobalite-bearing chondrule (designated CB1) was found to have a formation age 4.62 +/- 0.44 Ma after Bjurboele, while a porphyritic olivine macrochondrule appears to have been reset after the decay of I-129(t1/2 17 Ma). Consideration of these results alongside Ar-Ar data from the macrochondrule and whole rock samples suggests that Parnallee has a complex history: The macrochondrule underwent an early postcrystallization degassing event but appears to have been essentially unaffected by the later (1.9 Ga) partial resetting of the bulk meteorite.

  4. Tetrapropylammonium Occlusion in Nanoaggregates of Precursor of Silicalite-1 Zeolite Studied by 1H and 13C NMR

    Directory of Open Access Journals (Sweden)

    Mohamed Haouas

    2016-06-01

    Full Text Available The dynamic behavior of tetrapropylammonium (TPA cations in the clear precursor sols for silicalite synthesis has been investigated by 1H diffusion ordered spectroscopy (DOSY, T1, T2, and T1ρ 1H relaxation, as well as 1H→13C cross polarization (CP nuclear magnetic resonance. The DOSY NMR experiments showed the presence of strong solute–solvent interactions in concentrated sols, which are decreasing upon dilution. Similarities in dependence of diffusion coefficients with fractional power of the viscosity constant observed for nanoparticles, TPA cations and water led to the conclusion that they aggregate as anisotropic silicate-TPA particles. Relaxation studies as well as 1H→13C CP experiments provide information on dynamic properties of ethanol, water and TPA cations, which are function of silicate aggregates. The general tendency showed that the presence of silicate as oligomers and particles decreases the relaxation times, in particular T2 and T1ρH, as a consequence of involvement of these latter in ion-pairing interactions with water-solvated TPA molecules slowing down their mobility. Furthermore, from the 1H→13C CP dynamics curve profiles a change in the CP transfer regime was observed from fast (TCH << T1ρH for solutions without silicates to moderate (TCH~T1ρH when silicates are interacting with the TPA cations that may reflect the occlusion of TPA into flexible silicate hydrate aggregates.

  5. Rovibrational and temperature effects in theoretical studies of NMR parameters

    DEFF Research Database (Denmark)

    Faber, Rasmus; Kaminsky, Jakub; Sauer, Stephan P. A.

    2016-01-01

    The demand for high precision calculations of NMR shieldings (or their related values, chemical shifts δ) and spin-spin coupling constants facilitating and supporting detailed interpretations of NMR spectra increases hand in hand with the development of computational techniques and hardware...... for molecular equilibrium geometries creates a demand for zero point vibrational and temperature corrections. In this chapter we describe briefly the theory behind rovibrational corrections and review then some important contributions to this field....

  6. Evaluation of relaxation time measurements by magnetic resonance imaging. A phantom study

    DEFF Research Database (Denmark)

    Kjaer, L; Thomsen, C; Henriksen, O

    1987-01-01

    Several circumstances may explain the great variation in reported proton T1 and T2 relaxation times usually seen. This study was designed to evaluate the accuracy of relaxation time measurements by magnetic resonance imaging (MRI) operating at 1.5 tesla. Using a phantom of nine boxes with different...

  7. Solid state NMR method development and studies of biological and biomimetic nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Yanyan [Iowa State Univ., Ames, IA (United States)

    2011-01-01

    . Meanwhile, we have developed new methods to achieve broadband high resolution NMR and improve the accuracy of inter-nuclear distance measurements involving quadrupolar spins. Broadband high resolution NMR of spin-1/2 nuclei has been accomplished by the adaptation of the magic angle turning (MAT) method to fast magic angle spinning, termed fast MAT, by solving technical problems such as off resonance effects. Fast MAT separates chemical shift anisotropy and isotropic chemical shifts over a spectral range of ~1.8 γB1 without significant distortions. Fast MAT 125Te NMR has been applied to study technologically important telluride materials with spectra spreading up to 190 kHz. The signal-to-noise ratio of the spectra is significantly improved by using echo-matched Gaussian filtering in offline data processing. The accuracy of the measured distances between spin-1/2 and quadrupolar nuclei with methods such as SPIDER and REAPDOR has been improved by compensating for the fast longitudinal quadrupolar relaxation on the sub-millisecond with a modified S0 pulse sequence. Also, the T1Q effect on the spin coherence and its spinning speed dependency has been explored and documented with analytical and numerical simulations as well as experimental measurements.

  8. Characterization of mu s-ms dynamics of proteins using a combined analysis of N-15 NMR relaxation and chemical shift: Conformational exchange in plastocyanin induced by histidine protonations

    DEFF Research Database (Denmark)

    Hass, M. A. S.; Thuesen, Marianne Hallberg; Christensen, Hans Erik Mølager

    2004-01-01

    An approach is presented that allows a detailed, quantitative characterization of conformational exchange processes in proteins on the mus-ms time scale. The approach relies on a combined analysis of NMR relaxation rates and chemical shift changes and requires that the chemical shift...... of the exchanging species can be determined independently of the relaxation rates. The applicability of the approach is demonstrated by a detailed analysis of the conformational exchange processes previously observed in the reduced form of the blue copper protein, plastocyanin from the cyanobacteria Anabaena...... quantitatively by the correlation between the R-ex terms and the corresponding chemical shift differences of the exchanging species. By this approach, the R-ex terms of N-15 nuclei belonging to contiguous regions in the protein could be assigned to the same exchange process. Furthermore, the analysis...

  9. Diffusion NMR methods applied to xenon gas for materials study

    Science.gov (United States)

    Mair, R. W.; Rosen, M. S.; Wang, R.; Cory, D. G.; Walsworth, R. L.

    2002-01-01

    We report initial NMR studies of (i) xenon gas diffusion in model heterogeneous porous media and (ii) continuous flow laser-polarized xenon gas. Both areas utilize the pulsed gradient spin-echo (PGSE) techniques in the gas phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients--a brief overview of this area is provided in the Introduction. The heterogeneous or multiple-length scale model porous media consisted of random packs of mixed glass beads of two different sizes. We focus on observing the approach of the time-dependent gas diffusion coefficient, D(t) (an indicator of mean squared displacement), to the long-time asymptote, with the aim of understanding the long-length scale structural information that may be derived from a heterogeneous porous system. We find that D(t) of imbibed xenon gas at short diffusion times is similar for the mixed bead pack and a pack of the smaller sized beads alone, hence reflecting the pore surface area to volume ratio of the smaller bead sample. The approach of D(t) to the long-time limit follows that of a pack of the larger sized beads alone, although the limiting D(t) for the mixed bead pack is lower, reflecting the lower porosity of the sample compared to that of a pack of mono-sized glass beads. The Pade approximation is used to interpolate D(t) data between the short- and long-time limits. Initial studies of continuous flow laser-polarized xenon gas demonstrate velocity-sensitive imaging of much higher flows than can generally be obtained with liquids (20-200 mm s-1). Gas velocity imaging is, however, found to be limited to a resolution of about 1 mm s-1 owing to the high diffusivity of gases compared with liquids. We also present the first gas-phase NMR scattering, or diffusive-diffraction, data, namely flow-enhanced structural features in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack. c2002 John Wiley & Sons, Ltd.

  10. STUDY ON INTERMITTENT SHEAR FLOW AND RELAXATION BEHAVIOR OF THERMOTROPIC LIQUID CRYSTALLINE POLYMER

    Institute of Scientific and Technical Information of China (English)

    Ruo-Bing Yu; Chi-Xing Zhou; Wei Yu

    2005-01-01

    Intermittent shear flow including start-up flow and small oscillatory amplitude time sweep or stress relaxation after cessation of shear flow was used to study the rheological behavior and internal structure of thermotropic liquid crystalline polymer (TLCP). There are two kinds of intermittent shear flow: all start-up flows are in the same direction (intermittent flow forward: IFF) and start-up flows change their directions alternately (intermittent flow reversal: IFR). The results show that the stress of start-up flow of IFF and IFR in the test process is not superposed, indicating different changes of internal structure of thermotropic LCP (TLCP). Two main factors affect structure changes in the experimental time scale. One relates to long-term texture relaxation process, the other is an interchain reaction that becomes important after 30 min. The two factors raise the stress of IFF, but express complex effects for the stress of IFR. The latter factor becomes very important at long time annealing process. The relaxation behavior was also studied by the application of wide range relaxation spectrum calculated from the combined dynamic modulus, which gave three characteristic relaxation times (0.3, 10 and 600 s)ascribable to the relaxations of less-phase orientation, domain orientation, and domain deformation, respectively. The result also shows that the domain coalescence (texture relaxation), a long relaxation time, is a much slow process and lasts beyond 2400 s of the test time.

  11. Structure and dynamics of aqueous 2-propanol: a THz-TDS, NMR and neutron diffraction study.

    Science.gov (United States)

    McGregor, James; Li, Ruoyu; Zeitler, J Axel; D'Agostino, Carmine; Collins, James H P; Mantle, Mick D; Manyar, Haresh; Holbrey, John D; Falkowska, Marta; Youngs, Tristan G A; Hardacre, Christopher; Stitt, E Hugh; Gladden, Lynn F

    2015-11-11

    Aqueous liquid mixtures, in particular, those involving amphiphilic species, play an important role in many physical, chemical and biological processes. Of particular interest are alcohol/water mixtures; however, the structural dynamics of such systems are still not fully understood. Herein, a combination of terahertz time-domain spectroscopy (THz-TDS) and NMR relaxation time analysis has been applied to investigate 2-propanol/water mixtures across the entire composition range; while neutron diffraction studies have been carried out at two specific concentrations. Excellent agreement is seen between the techniques with a maximum in both the relative absorption coefficient and the activation energy to molecular motion occurring at ∼90 mol% H2O. Furthermore, this is the same value at which well-established excess thermodynamic functions exhibit a maximum/minimum. Additionally, both neutron diffraction and THz-TDS have been used to provide estimates of the size of the hydration shell around 2-propanol in solution. Both methods determine that between 4 and 5 H2O molecules per 2-propanol are found in the 2-propanol/water clusters at 90 mol% H2O. Based on the acquired data, a description of the structure of 2-propanol/water across the composition range is presented.

  12. Synthesis, characterization, and relaxation studies of Gd-DO3A conjugate of chlorambucil as a potential theranostic agent.

    Science.gov (United States)

    Kaur, Jasleen; Tsvetkova, Yoanna; Arroub, Karim; Sahnoun, Sabri; Kiessling, Fabian; Mathur, Sanjay

    2017-02-01

    DO3A-based macrocycles serve as attractive templates from which clinically useful theranostic agents can be obtained after coupling with molecular targeted therapeutic drugs. In this study, we describe the chemical synthesis, relaxation, and cytotoxicity studies of a new DO3A conjugate of chlorambucil (CHL) as a magnetic resonance imaging (MRI) theranostic agent. A convenient route of synthesis is reported, which allowed conjugation of the macrocyclic ligand (DO3A) to the chemotherapeutic drug (CHL) via tyrosine for the preparation of an attractive chelate-drug ensemble (DO3A-TR-CHL). The structures of all intermediates and final compound have been determined by (1) H, (13) C NMR, and MS. The efficacy of DO3A-TR-CHL as a non-ionic magnetic contrast agent was tested by performing relaxometric studies on its gadolinium complex. The complex exhibited relaxivities (7.11 mm(-1) /s) higher than that of currently used MR contrast agents and showed enhanced contrast in T1 -weighted images. MTT assays revealed that both DO3A-TR-CHL and Gd(III)-DO3A-TR-CHL conjugates exhibited dose-dependent toxicity and an enhanced antiproliferative activity against tumor (A549 and HeLa) cell lines compared to that of parent drug (CHL), thereby demonstrating their potential to be used as a magnetic resonance imaging theranostic for improved molecular imaging and therapy of human cancers. © 2017 John Wiley & Sons A/S.

  13. DSC and NMR Study on the Inclusion Complex of Lappaconitine with β—Cyclodextrin

    Institute of Scientific and Technical Information of China (English)

    KaiJunLIAO; XiaoHuaYAN; 等

    2002-01-01

    The inclusion complex of lappaconitine(Lap) with β-cyclodextrin (β-CD) has been studied by the differential scanning calorimetry (DSC) and 1H-NMR,2D-NMR spectroscopy. The structure of the complex has been deduced.

  14. DSC and NMR Study on the Inclusion Complex of Lappaconitine with β-Cyclodextrin

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The inclusion complex of lappaconitine (Lap) with β-cyclodextrin (β-CD) has been studied by the differential scanning calorimetry (DSC) and 1H-NMR, 2D-NMR spectroscopy.The structure of the complex has been deduced.``

  15. Investigating sorption on iron-oxyhydroxide soil minerals by solid-state NMR spectroscopy: a 6Li MAS NMR study of adsorption and absorption on goethite

    DEFF Research Database (Denmark)

    Nielsen, Ulla Gro; Paik, Younkee; Julmis, Keinia;

    2005-01-01

    High-resolution 2H MAS NMR spectra can be obtained for nanocrystalline particles of goethite (alpha-FeOOH, particle size approximately 4-10 nm) at room temperature, facilitating NMR studies of sorption under environmentally relevant conditions. Li sorption was investigated as a function of pH, th...

  16. NMR Study of Laser-polarized 129Xe in Low Pressure Natural Xenon Gas

    Institute of Scientific and Technical Information of China (English)

    SUN Xianping; WANG Shenglie; ZENG Xizhi

    2001-01-01

    The NMR signal from the laser-polarized t29 Xe in low-pressure natural xenon gas has been observed with a Bruker WP-80SY NMR spectrometer. The laser-polarized 129 Xe was produced by the method of laser pumping and spin exchange in a magnetic field of 1.87 Tesla. It is obtained experimentally that the nuclear spin relaxation rate 1/T1 of laser-polarized 129Xe are (4.03±1.97)×10-3/see~(2.21±0.78)×10-3/see in the range of the 3.33×103 Pa~8.29×104 Pa Xe gas pressures, the apparent wall relaxation rate 1/Tw* =(1.98±0.18)×10-3/see, and the relaxation rate coefficient C of 133Cs-129Xe spin exchange is (2.81±0.74)×10-16 em3/sec.

  17. NMR study of small molecule adsorption in MOF-74-Mg.

    Science.gov (United States)

    Lopez, M G; Canepa, Pieremanuele; Thonhauser, T

    2013-04-21

    We calculate the carbon nuclear magnetic resonance (NMR) shielding for CO2 and the hydrogen shieldings for both H2 and H2O inside the metal organic framework MOF-74-Mg. Our ab initio calculations are at the density functional theory level using the van der Waals including density functional vdW-DF. The shieldings are obtained while placing the small molecules throughout the structure, including the calculated adsorption site for various loading scenarios. We then explore relationships between loading, rotational and positional characteristics, and the NMR shieldings for each adsorbate. Our NMR calculations show a change in the shielding depending on adsorbate, position, and loading in a range that is experimentally observable. We further provide a simple model for the energy and the NMR shieldings throughout the cavity of the MOF. By providing this mapping of shielding to position and loading for these adsorbates, we argue that NMR probes could be used to provide additional information about the position at which these small molecules bind within the MOF, as well as the loading of the adsorbed molecule.

  18. NMR study of small molecule adsorption in MOF-74-Mg

    Science.gov (United States)

    Lopez, M. G.; Canepa, Pieremanuele; Thonhauser, T.

    2013-04-01

    We calculate the carbon nuclear magnetic resonance (NMR) shielding for CO2 and the hydrogen shieldings for both H2 and H2O inside the metal organic framework MOF-74-Mg. Our ab initio calculations are at the density functional theory level using the van der Waals including density functional vdW-DF. The shieldings are obtained while placing the small molecules throughout the structure, including the calculated adsorption site for various loading scenarios. We then explore relationships between loading, rotational and positional characteristics, and the NMR shieldings for each adsorbate. Our NMR calculations show a change in the shielding depending on adsorbate, position, and loading in a range that is experimentally observable. We further provide a simple model for the energy and the NMR shieldings throughout the cavity of the MOF. By providing this mapping of shielding to position and loading for these adsorbates, we argue that NMR probes could be used to provide additional information about the position at which these small molecules bind within the MOF, as well as the loading of the adsorbed molecule.

  19. Intramolecular hydrogen-bonding studies by NMR spectroscopy

    CERN Document Server

    Cantalapiedra, N A

    2000-01-01

    o-methoxybenzamide and N-methyl-o-methylbenzamide, using the pseudo-contact shifts calculated from the sup 1 H and sup 1 sup 3 C NMR spectra. The main conformation present in solution for o-fluorobenzamide was the one held by an intramolecular N-H...F hydrogen bond. Ab-initio calculations (at the RHF/6-31G* level) have provided additional data for the geometry of the individual molecules. A conformational equilibrium study of some nipecotic acid derivatives (3-substituted piperidines: CO sub 2 H, CO sub 2 Et, CONH sub 2 , CONHMe, CONEt sub 2) and cis-1,3-disubstituted cyclohexane derivatives (NHCOMe/CO sub 2 Me, NHCOMe/CONHMe, NH sub 2 /CO sub 2 H) has been undertaken in a variety of solvents, in order to predict the intramolecular hydrogen-bonding energies involved in the systems. The conformer populations were obtained by direct integration of proton peaks corresponding to the equatorial and axial conformations at low temperature (-80 deg), and by geometrically dependent coupling constants ( sup 3 J sub H s...

  20. Molecular and Vibrational Dynamics in the Cholesterol-Lowering Agent Lovastatin: Solid-State NMR, Inelastic Neutron Scattering, and Periodic DFT Study.

    Science.gov (United States)

    Bilski, Paweł; Drużbicki, Kacper; Jenczyk, Jacek; Mielcarek, Jadwiga; Wąsicki, Jan

    2017-03-23

    Molecular and vibrational dynamics of a widely used cholesterol-lowering agent, lovastatin, have been studied by combining nuclear magnetic resonance relaxation experiments ((1)H NMR) with inelastic neutron scattering (INS) and periodic density functional theory modeling (plane-wave DFT). According to a complementary experimental study, lovastatin shows no phase transitions down to cryogenic conditions, while a progressive, stepwise activation of several molecular motions is observed below room temperature. The molecular packing and intermolecular forces were analyzed theoretically, supported by a (13)C NMR study and further correlated with observed molecular dynamics. The NMR relaxation experiments combined with theoretical calculations disclose that molecular dynamics in solid lovastatin is related to methyl group motions and conformational disorder in the methylbutanoate fragment. This is precisely assigned and analyzed quantitatively from both experimental and theoretical perspectives. The neutron vibrational spectroscopy further corroborates that the methyl rotors have a classical nature. In addition to the intramolecular reorientations, the vibrational dynamics was analyzed with an emphasis on the low-wavenumber range. For the first time, the terahertz response of lovastatin was studied by confronting neutron and optical techniques and clearly illustrating their complementarity. The consistent picture of the molecular dynamics is provided, which may support further considerations on alternative drug formulations and the amorphization tendency in this important lipid-lowering drug.

  1. NMR Study of Polymer-Surfactant Mixing Systems%聚合物-表面活性剂复合体系的核磁共振研究

    Institute of Scientific and Technical Information of China (English)

    刘雪锋; 方云; 杨扬; 范歆

    2001-01-01

    Study on polymer- surfactant mixing systems by NMR methods were introduced in detail. 13C- NMR, 13C and 23Na+ relaxation rate, paramagnetic relaxation NMR (PR- NMR) and two dimensional nuclear overhauser enhancement NMR (2D - NOESY - NMR) were aplied in studying interaction of polymer- surfactant cluster. The carbon bridge of C12BE in PVP - C12BE clusters was associated with the methine (α), methylene (β) carbons in the polymer backbone and the methyl carbon attached with the N in the PVP ring , which was proven by 13C - NMR. The results of13C - NMR and 23Na+ NMR showed that some chains of the PEG in PEGSDS were directly absorbed at the hydrocarbon/water interface of micelles, whereas most of them formed loops in the surrounding water.2D - NOESY - NMR confirmed that PEG penetrated partly into the interior of the SDS mieelles. PR - NMR results indicated that only a small fraction of PEG located in electric double layer of micellar surface and the stoichiometric composition of PEG - SDS cluster is 1.9EO units per SDS molecule. Cluster structure of PVP - AS looded ilke a necklace whereas PVP - SDS likes a swollen cage.%用核磁共振(NMR)研究聚合物-表面活性剂复合体系的具体实例,分别对用于聚合物与表面活性剂相互作用及聚合物-表面活性剂团簇结构剖析等领域的13C-NMR、13C-及反离子23Na+-弛豫、顺磁共振驰豫(PR-NMR)、二维核子Overhauser增强核磁共振(2D-NOESY-NMR)等手段作了详尽的概述。在13C-NMR研究中发现PVP-C12BE体系中PVP骨架上α-CH、β-CH2和吡咯环上与N相连的亚甲基吸附在C12BE胶束表面的碳氢链部位,其相互作用驱动力为疏水力。13CNMR、23Na+-NMR研究表明在PEG-SDS团簇结构中大部分PEG链节环绕在SDS胶束周围,少部分PEG链节吸附在烃/水界面上;2D-NOESY-NMR研究结果表明,有少部分PEG链节渗入到SDS胶束内部;PR-NMR结果显示少部分PEG链节存在于SDS胶束双电层内,PEG-SDS团簇的

  2. Solid state NMR studies of gels derived from low molecular mass gelators.

    Science.gov (United States)

    Nonappa; Kolehmainen, E

    2016-07-13

    Since its invention more than six decades ago, nuclear magnetic resonance (NMR) spectroscopy has evolved as an inevitable part of chemical as well as structural analysis of small molecules, polymers, biomaterials and hybrid materials. In the solution state, due to the increased viscosity of complex viscoelastic fluids such as gels, liquid crystals and other soft materials, the rate of molecular tumbling is reduced, which in turn affects the chemical shift anisotropy, dipolar and quadrupolar interactions. As a consequence the solution state NMR spectra show broad lines, and therefore, extracting detailed structural information is a challenging task. In this context, solid state (SS) NMR has the ability to distinguish between a minute amount of polymorphic forms, conformational changes, and the number of non-equivalent molecules in an asymmetric unit of a crystal lattice, and to provide both qualitative as well as quantitative analytical data with a short-range order. Therefore, SS NMR has continued to evolve as an indispensable tool for structural analysis and gave birth to a new field called NMR crystallography. Solid state cross polarization (CP) and high resolution (HR) magic angle spinning (MAS) NMR spectroscopy has been used to study weak interactions in polymer gels. However, the application of SS NMR spectroscopy to study gels derived from low molecular weight gelators has been limited until recently. In this review, we will focus on the importance of solid state NMR spectroscopy in understanding and elucidating the structure of supramolecular gels derived from low molecular weight gelators with selected examples.

  3. Solid state NMR studies of gels derived from low molecular mass gelators

    Science.gov (United States)

    Kolehmainen, E.

    2016-01-01

    Since its invention more than six decades ago, nuclear magnetic resonance (NMR) spectroscopy has evolved as an inevitable part of chemical as well as structural analysis of small molecules, polymers, biomaterials and hybrid materials. In the solution state, due to the increased viscosity of complex viscoelastic fluids such as gels, liquid crystals and other soft materials, the rate of molecular tumbling is reduced, which in turn affects the chemical shift anisotropy, dipolar and quadrupolar interactions. As a consequence the solution state NMR spectra show broad lines, and therefore, extracting detailed structural information is a challenging task. In this context, solid state (SS) NMR has the ability to distinguish between a minute amount of polymorphic forms, conformational changes, and the number of non-equivalent molecules in an asymmetric unit of a crystal lattice, and to provide both qualitative as well as quantitative analytical data with a short-range order. Therefore, SS NMR has continued to evolve as an indispensable tool for structural analysis and gave birth to a new field called NMR crystallography. Solid state cross polarization (CP) and high resolution (HR) magic angle spinning (MAS) NMR spectroscopy has been used to study weak interactions in polymer gels. However, the application of SS NMR spectroscopy to study gels derived from low molecular weight gelators has been limited until recently. In this review, we will focus on the importance of solid state NMR spectroscopy in understanding and elucidating the structure of supramolecular gels derived from low molecular weight gelators with selected examples. PMID:27374054

  4. A new secondary relaxation in the rigid and planar 1-methylindole: Evidence from binary mixture studies

    Science.gov (United States)

    Wang, Meng; Li, Xiangqian; Guo, Yuxing; Wu, Tao; Liu, Ying Dan; Ngai, K. L.; Wang, Li-Min

    2016-12-01

    Found in our recent dielectric study of a planar and rigid glass-former, 1-methylindole (1MID), is an unusual secondary relaxation unrelated in its dynamic properties to the structural α-relaxation. We speculated that it originates from the in-plane motion of the molecules, and the supposedly universal Johari-Goldstein (JG) β-relaxation with strong connection to the structural α-relaxation in rigid glass-formers is not resolved [X. Q. Li et al. J. Chem. Phys. 143, 104505 (2015)]. In this work, dielectric measurements are performed in binary mixtures of 1MID with two aromatics of weak polarity, ethylbenzene (EB) and triphenylethylene (TPE), in the highly viscous regimes near glass transition. EB and TPE have smaller and larger molecular sizes and glass transition temperatures Tg than 1MID, respectively. Strikingly, the results show that the resolved secondary relaxations of 1MID in the two mixtures share the same relaxation time and their temperature dependence as pure 1MID, independent of the mode and degree of dilution. The results indicate that the unusual secondary relaxation is not directly coupled with the α-relaxation, and support the in-plane-rotation interpretation of its origin. On the other hand, the supposedly universal and intermolecular JG β-relaxation coming from the out-of-plane motion of the planar molecule has weaker dielectric strength, and it cannot be resolved from the more intense in-plane-rotation secondary relaxation because the dipole moment of 1MID lies on the plane.

  5. NMR Study of Layered Transition Metal Ditelluride (Ir,Pt)Te2

    Science.gov (United States)

    Magishi, K.; Saito, T.; Koyama, K.; Matsumoto, N.; Nagata, S.

    2012-12-01

    We report the results of 125Te and 195Pt NMR measurements on (Ir,Pt)Te2 in order to elucidate the characteristic electronic states. For PtTe2, the NMR spectrum exhibits a sharp line, which shows the uniaxially symmetric powder pattern due to the anisotropic Knight shift. The Knight shift is almost independent of temperature and is larger than that for IrTe2. Also, the nuclear spin-lattice relaxation rate 1/T1 of PtTe2 is proportional to the temperature in a wide temperature range, that is, obeys the Korringa relation as expected for simple metallic systems. From the analyses of the Knight shift and 1/T1, it is suggested that the antiferromagnetic correlations slightly exist.

  6. NMR studies on the new iron arsenide superconductors including the superconducting state

    Energy Technology Data Exchange (ETDEWEB)

    Grafe, Hans-Joachim; Lang, Guillaume; Hammerath, Franziska; Manthey, Katarina; Behr, Guenther; Werner, Jochen; Buechner, Bernd [IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Paar, Dalibor [IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Dept. of Physics, Faculty of Science, Univ. of Zagreb (Croatia); Curro, Nicholas [Dept. of Physics, Univ. of California, Davis, CA 95616 (United States)

    2009-07-01

    We summarize our Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) results on the new iron arsenide superconductor LaO{sub 1-x}F{sub x}FeAs in the normal state, and show new NMR data in the superconducting state. Beyond early evidence of nodes and spin-singlet pairing[2], we find evidence of a deviation of the T{sup 3} behaviour of the spin lattice relaxation rate, 1/T{sub 1}, at temperatures significantly below T{sub c}, which would agree with the suggested extended s-wave symmetry. The deviation of the T{sup 3} behaviour is induced by the pair breaking effect of impurities. Different amounts of impurities would lead to different temperature dependences of 1/T{sub 1}, which would allow to differentiate between d-wave and extended s-wave symmetries.

  7. NMR studies of the conformation and motion of tetrahydrofuran in graphite intercalation compounds

    Energy Technology Data Exchange (ETDEWEB)

    Caplan, D. F. [Lawrence Berkeley Lab., CA (United States); California Univ., Berkeley, CA (United States). Dept. of Chemistry

    1991-11-01

    The behavior of tetrahydrofuran (THF) molecules intercalated in graphite layers in compounds Cs(THF){sub 1.3}C{sub 24} and K(THF){sub 2.5}C{sub 24} was studied by proton NMR. The graphite layers in these compounds impose a uniform ordering on the THF molecules, giving rise to sharp NMR spectra. Experimental and simulated proton NMR spectra were used to investigate geometry, orientation and conformation of intercalated THF, and to determine whether pseudorotation, a large amplitude low-frequency vibration observed in gaseous THF, can also occur in the constrained environment provided by the graphite intercalation compounds. Deuterium and multiple quantum proton NMR spectra were also simulated in order to determine if these techniques could further refine the proton NMR results.

  8. CPMG relaxation dispersion NMR experiments measuring glycine {sup 1}H{sup {alpha}} and {sup 13}C{sup {alpha}} chemical shifts in the 'invisible' excited states of proteins

    Energy Technology Data Exchange (ETDEWEB)

    Vallurupalli, Pramodh; Hansen, D. Flemming; Lundstroem, Patrik; Kay, Lewis E. [University of Toronto, Departments of Molecular Genetics, Biochemistry and Chemistry (Canada)], E-mail: kay@pound.med.utoronto.ca

    2009-09-15

    Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion NMR experiments are extremely powerful for characterizing millisecond time-scale conformational exchange processes in biomolecules. A large number of such CPMG experiments have now emerged for measuring protein backbone chemical shifts of sparsely populated (>0.5%), excited state conformers that cannot be directly detected in NMR spectra and that are invisible to most other biophysical methods as well. A notable deficiency is, however, the absence of CPMG experiments for measurement of {sup 1}H{sup {alpha}} and {sup 13}C{sup {alpha}} chemical shifts of glycine residues in the excited state that reflects the fact that in this case the {sup 1}H{sup {alpha}}, {sup 13}C{sup {alpha}} spins form a three-spin system that is more complex than the AX {sup 1}H{sup {alpha}}-{sup 13}C{sup {alpha}} spin systems in the other amino acids. Here pulse sequences for recording {sup 1}H{sup {alpha}} and {sup 13}C{sup {alpha}} CPMG relaxation dispersion profiles derived from glycine residues are presented that provide information from which {sup 1}H{sup {alpha}}, {sup 13}C{sup {alpha}} chemical shifts can be obtained. The utility of these experiments is demonstrated by an application to a mutant of T4 lysozyme that undergoes a millisecond time-scale exchange process facilitating the binding of hydrophobic ligands to an internal cavity in the protein.

  9. Study of entangled network formation in concentrated solutions of polymer by 13C NMR

    Institute of Scientific and Technical Information of China (English)

    毛诗珍; 倪少儒; 杜有如; 沈联芳

    1996-01-01

    Information about the exact location of topological and cohesional entanglements at molecular level has been obtained by 13C NMR relaxation analysis. The results show that about 20% of the carbon atoms in the main chain are entangled in the 25% (by weight) solution, which is independent of the content of the 1,2-segment in polybutadiene and of the kind of solvent. However, the entanglement of the carbon atone on the end group of the side chain is very weak, they behave as slipping freely at the junctions.

  10. NMR structural studies of protein-small molecule interactions

    NARCIS (Netherlands)

    Shah, Dipen M.

    2014-01-01

    The research presented in the thesis describes the development and implementation of solution based NMR methods that provide 3D structural information on the protein-small molecule complexes. These methods can be critical for structure based drug design and can be readily applied in the early stages

  11. 129Xe NMR studies of biochar made from biobased materials

    Science.gov (United States)

    Biochar is created by pyrolysis of biobased materials under controlled oxidative environments. The product is charcoal-like and can be used as filtration medium, sequestrant for metallic ions, soil conditioner, and other applications. In our work we have found 129Xe NMR to be an excellent technique...

  12. NMR and NQR study of the thermodynamically stable quasicrystals

    Energy Technology Data Exchange (ETDEWEB)

    Shastri, Ananda [Iowa State Univ., Ames, IA (United States)

    1995-02-10

    27Al and 61,65Cu NMR measurements are reported for powder samples of stable AlCuFe and AlCuRu icosahedral quasicrystals and their crystalline approximants, and for a AlPdMn single grain quasicrystal. Furthermore, 27Al NQR spectra at 4.2 K have been observed in the AlCuFe and AlCuRu samples. From the quadrupole perturbed NMR spectra at different magnetic fields, and from the zero field NQR spectra, a wide distribution of local electric field gradient (EFG) tensor components and principal axis system orientations was found at the Al site. A model EFG calculation based on a 1/1 AlCuFe approximant was successful in explaining the observed NQR spectra. It is concluded that the average local gradient is largely determined by the p-electron wave function at the Al site, while the width of the distribution is due to the lattice contribution to the EFG. Comparison of 63Cu NMR with 27Al NMR shows that the EFG distribution at the two sites is similar, but that the electronic contribution to the EFG is considerably smaller at the Cu site, in agreement with a more s-type wave function of the conduction electrons.

  13. Dynamics in photosynthetic transient complexes studied by paramagnetic NMR spectroscopy

    NARCIS (Netherlands)

    Scanu, Sandra

    2013-01-01

    This PhD thesis focuses on fundamental aspects of protein-protein interactions. A multidisciplinary methodology for the detection and visualization of transient, lowly-populated encounter protein complexes is described. The new methodology combined paramagnetic NMR spectroscopy with computational

  14. Influence of lipid type on water and fat mobility in fermented sausages studied by low-field NMR.

    Science.gov (United States)

    Miklos, R; Mora-Gallego, H; Larsen, F H; Serra, X; Cheong, L-Z; Xu, X; Arnau, J; Lametsch, R

    2014-01-01

    The effects of diacylglycerols (DAG), pork back fat and sunflower oil on water and fat mobility in fermented sausages were studied with (1)H NMR relaxometry. The added fat affected the physicochemical parameters weight loss, water activity, moisture content and moisture content on a defatted-dry-matter basis of reduced-fat non-acid fermented sausages. The weight losses were the lowest in sausages prepared with DAG and sunflower oil, which resulted in higher water activity compared to sausages prepared with back fat. The relaxation times related to fat mobility differed between fat types and increased in the order: control

  15. The influence of thermochemical treatments on the lignocellulosic structure of wheat straw as studied by natural abundance 13C NMR

    Energy Technology Data Exchange (ETDEWEB)

    Habets, S.; Van Eck, E. [Solid-State NMR, Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen (Netherlands); De Wild, P.J.; Huijgen, W.J.J. [ECN Biomass and Energy Efficiency, Petten (Netherlands)

    2013-10-15

    The effects of thermochemical treatments (aquathermolysis, pyrolysis, and combinations thereof) on the lignocellulosic structure and composition of wheat straw were studied with 13C and 1H solid state NMR spectroscopy and proton T{sub 1p} relaxation measurements. Results show that aquathermolysis removes hemicellulose, acetyl groups, and ash minerals. As a result, the susceptibility of lignocellulose to pyrolysis is reduced most likely due to the removal of catalytically active salts, although recondensation of lignin during aquathermolysis treatment can also play a role. In contrast to pyrolysis of wheat straw, pyrolysis of aquathermolysed wheat straw leaves traces of cellulose in the char as well as more intense lignin methoxy peaks. Finally, it was found that both pyrolysis chars contain aliphatic chains, which were attributed to the presence of cutin or cutin-like materials, a macromolecule that covers the aerial surface of plants, not soluble in water and seemingly stable under the pyrolysis conditions applied.

  16. Study of advanced ion conducting polymers by relaxation, diffusion and spectroscopy NMR methods

    OpenAIRE

    Daniel Jardón Álvarez

    2016-01-01

    Advances on secondary lithium ion batteries imply the use of solid polymer electrolytes, which represent a promising solution to improve safety issues in high energy density batteries. Through dissolution of lithium salts into a polymeric host, such as poly(ethylene oxide) (PEO), ion conducting polymers are obtained. The Li+ ions will be localized in the proximity of the oxygen atoms in the PEO chains and thus, their motion strongly correlated with the segmental reorientation of the polymer. ...

  17. Characterization of natural porous media by NMR and MRI techniques. High and low magnetic field studies for estimation of hydraulic properties

    Energy Technology Data Exchange (ETDEWEB)

    Stingaciu, Laura-Roxana

    2010-07-01

    The aim of this thesis is to apply different NMR techniques for: i) understanding the relaxometric properties of unsaturated natural porous media and ii) for a reliable quantification of water content and its spatial and temporal change in model porous media and soil cores. For that purpose, porous media with increasing complexity and heterogeneity were used (coarse and fine sand and different mixture of sand/clay) to determine the relaxation parameters in order to adapt optimal sequence and parameters for water imaging. Conventional imaging is mostly performed with superconducting high field scanners but low field scanners promise longer relaxation times and therefore smaller loss of signal from water in small and partially filled pores. By this reason high and low field NMR experiments were conducted on these porous media to characterize the dependence on the magnetic field strength. Correlations of the NMR experiments with classical soil physics method like mercury intrusion porosimetry; water retention curves (pF) and multi-step-outflow (MSO) were performed for the characterization of the hydraulic properties of the materials. Due to the extensive research the experiments have been structured in three major parts as follows. In the first part a comparison study between relaxation experiments in high and low magnetic field was performed in order to observe the influence of the magnetic field on the relaxation properties. Due to these results, in the second part of the study only low field relaxation experiments were used in the attempt of correlations with classical soil physics methods (mercury intrusion porosimetry and water retention curves) for characterizing the hydraulic behavior of the samples. Further, the aim was to combine also MRI experiments (2D and 3D NMR) with classical soil physics methods (multi-step-outflow, MSO) for the same purpose of investigating the hydraulic properties. Because low field MRI systems are still under developing for the

  18. High pressure NMR study of a small protein, gurmarin

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, Kyoko; Yamada, Hiroaki [Kobe University, Division of Molecular Science, Graduate School of Science and Technology, and Department of Chemistry, Faculty of Science (Japan); Imoto, Toshiaki [Tottori University, Faculty of Medicine (Japan); Akasaka, Kazuyuki [Kobe University, Division of Molecular Science, Graduate School of Science and Technology, and Department of Chemistry, Faculty of Science (Japan)

    1998-11-15

    The effect of pressure on the structure of gurmarin, a globular, 35-residue protein from Gymnema sylvestre, was studied in aqueous environment (95% 1H2O/5% 2H2O, pH 2.0) with an on-line variable pressure NMR system operating at 750 MHz. Two-dimensional TOCSY and NOESY spectra were measured as functions of pressure between 1 and 2000 bar at 40 deg. C . Practically all the proton signals of gurmarin underwent some shifts with pressure, showing that the entire protein structure responds to, and is altered by, pressure. Most amide protons showed different degrees of low field shifts with pressure, namely 0-0.2 ppm with an average of 0.051 ppm at 2000 bar, showing that they are involved in hydrogen bonding and that these hydrogen bonds are shortened by pressure by different degrees. The tendency was also confirmed that the chemical shifts of the amide protons exposed to the solvent (water) are more sensitive to pressure than those internally hydrogen bonded with carbonyls. The pressure-induced shifts of the H{alpha} signals of the residues in the {beta}-sheet showed a negative correlation with the 'folding' shifts (difference between the shift at 1 bar and that of a random coil), suggesting that the main-chain torsion angles of the {beta}-sheet are slightly altered by pressure. Significant pressure-induced shifts were also observed for the side-chain protons (but no larger than 10% of the 'folding' shifts), demonstrating that the tertiary structure of gurmarin is also affected by pressure. Finally, the linearity of the pressure-induced shifts suggests that the compressibility of gurmarin is invariant in the pressure range between 1 and 2000 bar.

  19. Mobility of TOAC spin-labelled peptides binding to the Src SH3 domain studied by paramagnetic NMR

    Energy Technology Data Exchange (ETDEWEB)

    Lindfors, Hanna E. [Leiden University, Leiden Institute of Chemistry, Gorlaeus Laboratories (Netherlands); Koning, Peter E. de; Wouter Drijfhout, Jan [Leiden University Medical Centre, Department of Immunohematology and Blood Transfusion (Netherlands); Venezia, Brigida; Ubbink, Marcellus [Leiden University, Leiden Institute of Chemistry, Gorlaeus Laboratories (Netherlands)], E-mail: m.ubbink@chem.leidenuniv.nl

    2008-07-15

    Paramagnetic relaxation enhancement provides a tool for studying the dynamics as well as the structure of macromolecular complexes. The application of side-chain coupled spin-labels is limited by the mobility of the free radical. The cyclic, rigid amino acid spin-label TOAC (2,2,6,6-Tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid), which can be incorporated straightforwardly by peptide synthesis, provides an attractive alternative. In this study, TOAC was incorporated into a peptide derived from focal adhesion kinase (FAK), and the interaction of the peptide with the Src homology 3 (SH3) domain of Src kinase was studied, using paramagnetic NMR. Placing TOAC within the binding motif of the peptide has a considerable effect on the peptide-protein binding, lowering the affinity substantially. When the TOAC is positioned just outside the binding motif, the binding constant remains nearly unaffected. Although the SH3 domain binds weakly and transiently to proline-rich peptides from FAK, the interaction is not very dynamic and the relative position of the spin-label to the protein is well-defined. It is concluded that TOAC can be used to generate reliable paramagnetic NMR restraints.

  20. Relaxation in distal and proximal arm muscles: a reaction time study.

    Science.gov (United States)

    Buccolieri, A; Avanzino, L; Trompetto, C; Abbruzzese, G

    2003-02-01

    To investigate whether the same mechanisms underlie muscle relaxation in proximal and distal arm muscles of normal subjects. Fourteen healthy subjects were studied using a simple visual reaction time paradigm. Relaxation reaction time (R-RT) and contraction reaction time (C-RT) were compared across different tasks involving distal (first dorsal interosseus, FDI, flexor carpi radialis, FCR) and proximal (biceps brachii, BB, triceps brachii, TR) arm muscles. Changes of FCR H-reflex before and during voluntary relaxation were investigated in two subjects. No significant difference was observed between R-RT and C-RT in the distal muscles. The R-RT was significantly shorter than C-RT in both the BB and TR muscles. The relaxation latency (R-RT) was significantly correlated to the subjects' age in all the muscles except the FDI. No inhibition of the FCR H-reflex could be observed in the 20 ms preceding muscle relaxation. Our findings suggest that neural mechanisms contribute differently to the relaxation of muscles with a different functional role. Voluntary relaxation in distal arm muscles is mainly related to the reduction of motor cortical output, while in proximal muscles a spinal disfacilitation is also present and possibly sustained by the modulation of presynaptic inhibition.

  1. Isolation and NMR Study on Swainsonine from Locoweed, Astragalus strictus

    Institute of Scientific and Technical Information of China (English)

    ZHAO Bao-yu; LIU Zhong-yan; WANG Jian-jun; SUN Li-sha; WANG Zhan-xin; WANG Yin-chao

    2009-01-01

    Locoweed is a poisonous plant wildly distributed in most area of the world and can cause livestock poisoning or death with significant economic loss. The principal responsible for its toxicity is indolizidine alkaloid swainsonine, a new potential anticancer and antiviral drug. Astragalus strictus is mainly distributed in Tibet of China and is a serious hazard to the local livestock industry. To analyze its main toxic ingredients and supply more structural information and more accurate data, swainsonine has been isolated from this plant by D101 macroporous resin and the 1H and 13C chemical shifts of the compound has been assigned by 1D-NMR and 2D-NMR techniques. At the same time, complete assignments of swainsonine's 13C spectral signals are reported.

  2. Study of Magnetic Nanocomposites by NMR and Bulk Magnetization Techniques

    Directory of Open Access Journals (Sweden)

    Matveev V.

    2014-07-01

    Full Text Available Magnetic nanocomposites possess complex and nonuniform magnetic structure. As a result it is necessary to use different physical methods to describe their properties. In this work we have applied a combination of micro and macro approaches to understand more deeply magnetic properties of some cobaltcontaining nanocomposites. Testing of magnetic structure of the samples at molecular level was done with NMR and Mössbauer techniques whereas static (SQUID and dynamic magnetic (M2, see below measurements – at macro level.

  3. First-principles study of fully relaxed vacancies in GaAs

    OpenAIRE

    Laasonen, K; Nieminen, Risto M.; Puska, Martti J.

    1992-01-01

    The structural and electronic properties of vacancies in GaAs have been studied using ab initio molecular dynamics. The atomic structures of vacancies in different charge states have been optimized by using a simulated-annealing procedure. The neighbor-atom relaxations are modest for neutral, singly negative, and doubly negative Ga vacancies as well as for the neutral As vacancy. In the case of singly and doubly negative As vacancies, very strong inward relaxations are found. These inward rel...

  4. A study of sup 3 He films using SQUID NMR

    CERN Document Server

    Dyball, H C J

    2001-01-01

    Confinement of superfluid sup 3 He to a geometry of order the coherence length is predicted to produce interesting size effects and modify the superfluid phase diagram. This thesis describes the development of an experiment to measure these effects using NMR as a probe of the spin dynamics. A pulsed NMR spectrometer was developed with a low T sub c SQUID as the first stage amplifier. The sample was located in a receiver coil that formed part of a tuned circuit with the SQUID input coil. The first spectrometer was operated in an open-loop configuration but was later converted to use feedback to stabilize the SQUID gain. This later version used a DC SQUID with APF operating in flux-locked loop using the Direct Offset Integration Technique. The noise was limited by the Johnson noise in the tuned circuit in tests down to 1.5 K and the estimated noise temperature was approx 100 mK. NMR signals were observed at approx 1 MHz from low-density sup 3 He samples adsorbed on a Mylar substrate which were in reasonable agr...

  5. O-17 NMR studies of some silicate crystals and glasses

    CERN Document Server

    Yildirim, E K

    2000-01-01

    structure. Therefore some of the Sn has to be in three coordinated to oxygen for charge balancing. The sup 1 sup 7 O MAS NMR spectra of a partially crystallised sample showed three distinct sites which are assigned as Sn-O-Sn, Si-O-Sn, and Si-O-Si on the basis of their chemical shift. The C sub Q values obtained from the simulations of these peaks supports this assignment. The sup 2 sup 9 Si MAS NMR of the same sample showed two crystalline and a glassy peaks which are fitted to two crystalline and two glassy sites. The possible composition of this sample was calculated and found to be SiSn sub 8 O sub 1 sub 0. Crystalline and glassy silicates were investigated by means of sup 1 sup 7 O NMR. The dependence of the measured efg on the Si-O-AI bond angle was investigated in some crystalline aluminosilicate sodalites and kalsilite. The results show that C sub Q increases with increasing bond angle while eta decreases with increasing bond angle and they both follow a similar function to that found for the Si-O-Si ...

  6. The Surface of Nanoparticle Silicon as Studied by Solid-State NMR

    Directory of Open Access Journals (Sweden)

    Gary E. Maciel

    2012-12-01

    Full Text Available The surface structure and adjacent interior of commercially available silicon nanopowder (np-Si was studied using multinuclear, solid-state NMR spectroscopy. The results are consistent with an overall picture in which the bulk of the np-Si interior consists of highly ordered (“crystalline” silicon atoms, each bound tetrahedrally to four other silicon atoms. From a combination of 1H, 29Si and 2H magic-angle-spinning (MAS NMR results and quantum mechanical 29Si chemical shift calculations, silicon atoms on the surface of “as-received” np-Si were found to exist in a variety of chemical structures, with apparent populations in the order (a (Si–O–3Si–H > (b (Si–O–3SiOH > (c (HO–nSi(Sim(–OSi4−m−n ≈ (d (Si–O–2Si(HOH > (e (Si–O–2Si(–OH2 > (f (Si–O–4Si, where Si stands for a surface silicon atom and Si represents another silicon atom that is attached to Si by either a Si–Si bond or a Si–O–Si linkage. The relative populations of each of these structures can be modified by chemical treatment, including with O2 gas at elevated temperature. A deliberately oxidized sample displays an increased population of (Si–O–3Si–H, as well as (Si–O–3SiOH sites. Considerable heterogeneity of some surface structures was observed. A combination of 1H and 2H MAS experiments provide evidence for a substantial population of silanol (Si–OH moieties, some of which are not readily H-exchangeable, along with the dominant Si–H sites, on the surface of “as-received” np-Si; the silanol moieties are enhanced by deliberate oxidation. An extension of the DEPTH background suppression method is also demonstrated that permits measurement of the T2 relaxation parameter simultaneously with background suppression.

  7. Structure and Dynamics Studies of Cytolytic Peptides in Lipid Bilayers using NMR Spectroscopy

    DEFF Research Database (Denmark)

    Hansen, Sara Krogh

    2015-01-01

    different and cytolytic peptides were investigated in this work. The peptides were SPF-5506-A4 from Trichoderma sp, Conolysin-Mt1 from Conus mustelinus, and Alamethicin from Trichoderma viride. The studies employed solution and solid-state NMR spectroscopy in combination with different biophysical methods......- and 2H-labelled peptides. While the solution NMR experiments were performed to determine the structure of SPF-5506-A4 and Conolysin-Mt1, the oriented solid-state NMR experiments served to derive information about the orientation of the peptides with respect to the bilayer normal in order to understand...

  8. Authenticity study of Phyllanthus species by NMR and FT-IR techniques coupled with chemometric methods

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Maiara S.; Pereira-Filho, Edenir R.; Ferreira, Antonio G. [Universidade Federal de Sao Carlos (UFSCAR), SP (Brazil). Dept. de Quimica; Boffo, Elisangela F. [Universidade Federal da Bahia (UFBA), Salvador, BA (Brazil). Inst. de Quimica; Figueira, Glyn M., E-mail: maiarassantos@yahoo.com.br [Universidade Estadual de Campinas (UNICAMP), Campinas, SP (Brazil). Centro Pluridisciplinar de Pesquisas Quimicas, Biologicas e Agricolas

    2012-07-01

    The importance of medicinal plants and their use in industrial applications is increasing worldwide, especially in Brazil. Phyllanthus species, popularly known as 'quebra-pedras' in Brazil, are used in folk medicine for treating urinary infections and renal calculus. This paper reports an authenticity study, based on herbal drugs from Phyllanthus species, involving commercial and authentic samples using spectroscopic techniques: FT-IR, {sup 1}H HR-MAS NMR and {sup 1}H NMR in solution, combined with chemometric analysis. The spectroscopic techniques evaluated, coupled with chemometric methods, have great potential in the investigation of complex matrices. Furthermore, several metabolites were identified by the NMR techniques. (author)

  9. Authenticity study of Phyllanthus species by NMR and FT-IR Techniques coupled with chemometric methods

    Directory of Open Access Journals (Sweden)

    Maiara S. Santos

    2012-01-01

    Full Text Available The importance of medicinal plants and their use in industrial applications is increasing worldwide, especially in Brazil. Phyllanthus species, popularly known as "quebra-pedras" in Brazil, are used in folk medicine for treating urinary infections and renal calculus. This paper reports an authenticity study, based on herbal drugs from Phyllanthus species, involving commercial and authentic samples using spectroscopic techniques: FT-IR, ¹H HR-MAS NMR and ¹H NMR in solution, combined with chemometric analysis. The spectroscopic techniques evaluated, coupled with chemometric methods, have great potential in the investigation of complex matrices. Furthermore, several metabolites were identified by the NMR techniques.

  10. NMR Study of the Dimerized State in CuIr{sub 2}S{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Kumagai, Ken-ichi, E-mail: kumagai@phys.sci.hokudai.ac.jp; Sasaki, Mayumi; Kakuyanagi, Kosuke [Hokkaido University, Division of Physics, Graduate School of Science (Japan); Nagata, Shoichi [Muroran Institute of Technology, Department of Materials Science and Engineering (Japan)

    2004-12-15

    We have investigated the metal-insulator transition (MIT) of CuIr{sub 2}S{sub 4} by a high resolution NMR measurement. The Cu-NMR spectrum below T{sub MI} is broadened and split into four Cu signals with sizable electric quadrupole interactions. The NMR results are consistent with the charge ordering of Ir{sup 3+} and Ir{sup 4+} and the spin dimerization of Ir{sup 4+} spins, as revealed by a recent X-ray study.

  11. Petrophysical properties of greensand as predicted from NMR measurements

    DEFF Research Database (Denmark)

    Hossain, Zakir; Grattoni, Carlos A.; Solymar, Mikael

    2011-01-01

    ABSTRACT: Nuclear magnetic resonance (NMR) is a useful tool in reservoir evaluation. The objective of this study is to predict petrophysical properties from NMR T2 distributions. A series of laboratory experiments including core analysis, capillary pressure measurements, NMR T2 measurements...... and image analysis were carried out on sixteen greensand samples from two formations in the Nini field of the North Sea. Hermod Formation is weakly cemented, whereas Ty Formation is characterized by microcrystalline quartz cement. The surface area measured by the BET method and the NMR derived surface...... with macro-pores. Permeability may be predicted from NMR by using Kozeny's equation when surface relaxivity is known. Capillary pressure drainage curves may be predicted from NMR T2 distribution when pore size distribution within a sample is homogeneous....

  12. Study into the correlation of dominant pore throat size and SIP relaxation frequency

    Science.gov (United States)

    Kruschwitz, Sabine; Prinz, Carsten; Zimathies, Annett

    2016-12-01

    There is currently a debate within the SIP community about the characteristic textural length scale controlling relaxation time of consolidated porous media. One idea is that the relaxation time is dominated by the pore throat size distribution or more specifically the modal pore throat size as determined in mercury intrusion capillary pressure tests. Recently new studies on inverting pore size distributions from SIP data were published implying that the relaxation mechanisms and controlling length scale are well understood. In contrast new analytical model studies based on the Marshall-Madden membrane polarization theory suggested that two relaxation processes might compete: the one along the short narrow pore (the throat) with one across the wider pore in case the narrow pores become relatively long. This paper presents a first systematically focused study into the relationship of pore throat sizes and SIP relaxation times. The generality of predicted trends is investigated across a wide range of materials differing considerably in chemical composition, specific surface and pore space characteristics. Three different groups of relaxation behaviors can be clearly distinguished. The different behaviors are related to clay content and type, carbonate content, size of the grains and the wide pores in the samples.

  13. A theoretical study of the stress relaxation in HMX on the picosecond time scale

    Science.gov (United States)

    Long, Yao; Chen, Jun

    2015-12-01

    The stress relaxation model of β-HMX on the picosecond time scale is studied by a theoretical approach. The relaxation of normal stress is contributed by lattice vibration, and the relaxation of shear stress is contributed by molecular rotation. Based on this model, the energy dissipation rule of the elastic wave and the profile of the shock wave are investigated. We find at low frequency the dissipation rate of the elastic wave is proportional to the power function of frequency, and under high speed shock loading the width of the stress relaxation zone is less than 0.3 μm there is a pressure peak with a height of 14 GPa near the wave front.

  14. High Resolution Magic Angle Spinning Nuclear Magnetic Resonance (HRMAS NMR) for Studies of Reactive Fabrics

    Science.gov (United States)

    2015-11-01

    Magnetic Resonance (HRMAS NMR) for Studies of Reactive Fabrics 5a. CONTRACT NUMBER W911SR-11-C-0047 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER...ECBC-TR-1326 HIGH RESOLUTION MAGIC ANGLE SPINNING NUCLEAR MAGNETIC RESONANCE (HRMAS NMR) FOR STUDIES OF REACTIVE FABRICS David J. McGarvey...unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT An analytical chemistry method is described for measuring the reactivity and permeation of

  15. Gelation of Na-alginate aqueous solution: A study of sodium ion dynamics via NMR relaxometry.

    Science.gov (United States)

    Zhao, Congxian; Zhang, Chao; Kang, Hongliang; Xia, Yanzhi; Sui, Kunyan; Liu, Ruigang

    2017-08-01

    Sodium alginate (SA) hydrogels have a wide range of applications including tissue engineering, drug delivery and formulations for preventing gastric reflux. The dynamics of sodium ions during the gelation process of SA solution is critical for clarification of the gelation procedure. In this work, nuclear magnetic resonance (NMR) relaxometry and pulsed-field-gradient (PFG) NMR diffusometry were used to investigate the dynamics of the sodium ions during the gelation of SA alginate. We find that sodium ions are in two different states with the addition of divalent calcium ions, corresponding to Ca(2+) crosslinked and un-crosslinked regions in the hydrogels. The sodium ions within the un-crosslinked regions are those released from the alginate chains without Ca(2+) crosslinking. The relative content of sodium ions within the Ca(2+) crosslinked regions decreased with the increase in the content of calcium ions in the system. The relaxation time T2 of sodium ions within the Ca(2+) crosslinked and un-crosslinked regions shift to shorter and longer relaxation time with the increase in concentration of calcium ion, which indicates the closer package of SA chains and the larger space for the diffusion of free sodium ions. This work clarifies the dynamics of (23)Na(+) in a calcium alginate gel at the equilibrium state. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Synthesis and NMR Spectral Studies of the 7-C60-Adduct of N,N-(Tetrachlorophthaloyl Dehydroabietylamine

    Directory of Open Access Journals (Sweden)

    Zhi Zhou

    2012-04-01

    Full Text Available The 7-C60-adduct of N,N-(tetrachlorophthaloyldehydroabietylamine was synthesized for the first time and characterized by IR, UV-vis, mass and NMR spectral studies. The 1H-NMR and 13C-NMR resonance signals of the new compound are unambiguously assigned by using homo- and heteronuclear 2D NMR spectroscopic techniques such as COSY, ROESY, HSQC and HMBC. The C1 symmetric structure with 6,6-junction of compound was determined.

  17. NMR T1 relaxation time measurements and calculations with translational and rotational components for liquid electrolytes containing LiBF4 and propylene carbonate

    Science.gov (United States)

    Richardson, P. M.; Voice, A. M.; Ward, I. M.

    2013-12-01

    Longitudinal relaxation (T1) measurements of 19F, 7Li, and 1H in propylene carbonate/LiBF4 liquid electrolytes are reported. Comparison of T1 values with those for the transverse relaxation time (T2) confirm that the measurements are in the high temperature (low correlation time) limit of the T1 minimum. Using data from pulsed field gradient measurements of self-diffusion coefficients and measurements of solution viscosity measured elsewhere, it is concluded that although in general there are contributions to T1 from both translational and rotational motions. For the lithium ions, this is mainly translational, and for the fluorine ions mainly rotational.

  18. Theoretical Studies of the Relaxation Matrix for Molecular Systems

    Science.gov (United States)

    Ma, Qiancheng; Boulet, C.

    2016-06-01

    The phenomenon of collisional transfer of intensity due to line mixing has an increasing importance for atmospheric monitoring. From a theoretical point of view, all relevant information about the collisional processes is contained in the relaxation matrix where the diagonal elements give half-widths and shifts, and the off-diagonal elements correspond to line interferences. For simple systems such as those consisting of diatom-atom or diatom-diatom, accurate fully quantum calculations based on interaction potentials are feasible. However, fully quantum calculations become unrealistic for more complex systems. On the other hand, the semi-classical Robert-Bonamy formalism, which has been widely used to calculate half-widths and shifts for decades, fails in calculating the off-diagonal matrix elements resulting from applying the isolated line approximation. As a result, in order to simulate atmospheric spectra where the effects from line mixing are important, semi-empirical fitting or scaling laws such as the energy corrected sudden (ECS) and the infinite order sudden (IOS) models are commonly used. Recently, we have found that in developing this semi-classical line shape theory, to rely on the isolated line approximation is not necessary. By eliminating this unjustified assumption, and accurately evaluating matrix elements of the exponential operators, we have developed a more capable formalism that enables one not only to reduce uncertainties for calculated half-widths and shifts, but also to calculate the whole relaxation matrix. This implies that we can address the line mixing with the semi-classical theory based on interaction potentials between molecular absorber and molecular perturber. We have applied this formalism for Raman and infrared spectra of linear and asymmetric-top molecules. Recently, the method has been extended into symmetric-tops with inverse symmetry such as the NH3 molecule. Our calculated half-widths of NH3 lines in the νb{1} and the pure

  19. Magnetic fluctuations and superconducting properties of CaKFe4As4 studied by 75As NMR

    Science.gov (United States)

    Cui, J.; Ding, Q.-P.; Meier, W. R.; Böhmer, A. E.; Kong, T.; Borisov, V.; Lee, Y.; Bud'ko, S. L.; Valentí, R.; Canfield, P. C.; Furukawa, Y.

    2017-09-01

    We report 75As nuclear magnetic resonance (NMR) studies on a new iron-based superconductor, CaKFe4As4 , with Tc=35 K. 75As NMR spectra show two distinct lines corresponding to the As(1) and As(2) sites close to the K and Ca layers, respectively, revealing that K and Ca layers are well ordered without site inversions. We found that nuclear quadrupole frequencies νQ of the As(1) and As(2) sites show an opposite temperature T dependence. Nearly T independent behavior of the Knight shifts K is observed in the normal state, and a sudden decrease in K in the superconducting (SC) state suggests spin-singlet Cooper pairs. 75As spin-lattice relaxation rates 1 /T1 show a power-law T dependence with different exponents for the two As sites. The isotropic antiferromagnetic spin fluctuations characterized by the wave vector q =(π ,0 ) or (0 ,π ) in the single-iron Brillouin zone notation are revealed by 1 /T1T and K measurements. Such magnetic fluctuations are necessary to explain the observed temperature dependence of the 75As quadrupole frequencies, as evidenced by our first-principles calculations. In the SC state, 1 /T1 shows a rapid decrease below Tc without a Hebel-Slichter peak and decreases exponentially at low T , consistent with an s± nodeless two-gap superconductor.

  20. 127I NMR study of quadrupolar echoes in KI

    Science.gov (United States)

    Lee, Nelson; Sanctuary, B. C.; Halstead, T. K.

    Potassium iodide (K 121I), like KBr and many other alkali halide solids, has cubic symmetry. Distortion of this cubic symmetry in single crystals of KI creates electric field gradients of sufficient strength for the quadrupolar interactions to dominate the dynamics of the system. Simple one-, two-, and three-pulse sequences applied to such crystals permit the observation, in the time domain, of the solid- or quadrupolar-echo phenomenon for spin I = {5}/{2}( 127I) . Using the multipole approach to interpret the experimental responses of three-pulse sequences, the characteristic relaxation behavior of the first-, second-, third-, and fifth-rank zero- and multiquantum polarizations are determined. The experimental determination of distinct relaxation times for the higher rank polarizations in both KI and KBr ( I = {3}/{2}) lends credibility to the concept of the multipoles as physical quantities.

  1. Solid State NMR and Fluorescence Studies of Conjugated Polymer Nanocomposties

    Institute of Scientific and Technical Information of China (English)

    Chao Jun JING; Liu Sheng CHEN; Yi SHI; Xi Gao JIN

    2005-01-01

    13C spin-lattice relaxation times (T1) of a conjugated polymer MEH-PPV in polymer/layered silicate nanocomposites together with the steady state fluorescence emission and transient fluorescence decay measurements have been investigated. The T1 values of the conjugated carbons decrease dramatically according to the reduction of polymer concentration in the nano composites, while the fluorescence life times (τ) show a linear prolonging tendency. The results are explained from the point of view of molecular dynamics.

  2. Nonequilibrium relaxation study of Ising spin glass models

    Science.gov (United States)

    Ozeki, Yukiyasu; Ito, Nobuyasu

    2001-07-01

    As an analysis of equilibrium phase transitions, the nonequilibrium relaxation method is extended to the spin glass (SG) transition. The +/-J Ising SG model is analyzed for three-dimensional (cubic) lattices up to the linear size of L=127 and for four-dimensional (hypercubic) lattice up to L=41. These sizes of systems are quite large as compared with those calculated, so far, by equilibrium simulations. As a dynamical order parameter, we calculate the clone correlation function (CCF) Q(t,tw)≡[F], which is a spin correlation of two replicas produced after the waiting time tw from a simple starting state. It is found that the CCF shows an exponential decay in the paramagnetic phase, and a power-law decay after aginglike development (t>>tw) in the SG phase. This provides a reliable upper bound of the transition temperature Tg. It is also found that a scaling relation, Q(t,tw)=t-λqwq¯(t/tw), holds just around the transition point providing the lower bound of Tg. Together with these two bounds, we propose a new dynamical way for the estimation of Tg from much larger systems. In the SG phase, the power-law behavior of the CCF for t>>tw suggests that the SG phase in short-range Ising models has a rugged phase space.

  3. Thermolysis and solid state NMR studies of NaB3H8, NH3B3H7, and NH4B3H8.

    Science.gov (United States)

    Huang, Zhenguo; Eagles, Mitch; Porter, Spencer; Sorte, Eric G; Billet, Beau; Corey, Robert L; Conradi, Mark S; Zhao, Ji-Cheng

    2013-01-21

    In an effort to broaden the search for high-capacity hydrogen storage materials, three triborane compounds, NaB(3)H(8), NH(3)B(3)H(7), and NH(4)B(3)H(8), were studied. In addition to hydrogen, thermal decomposition also releases volatile boranes, and the relative amounts and species depend on the cations (Na(+), NH(4)(+)) and the Lewis base (NH(3)). Static-sample hydrogen NMR is used to probe molecular motion in the three solids. In each case, the line width decreases from low temperatures to room temperature in accordance with a model of isotropic or nearly isotropic reorientations. Such motions also explain a deep minimum in the relaxation time T(1). Translational diffusion never appears to be rapid on the 10(-5) s time scale of NMR.

  4. 31P NMR for the study of P metabolism and translocation in arbuscular mycorrhizal fungi

    DEFF Research Database (Denmark)

    Rasmussen, N.; Lloyd, D.C.; Ratcliffe, R.G.

    2000-01-01

    P-31 nuclear magnetic resonance (NMR) spectroscopy was used to study phosphate (P) metabolism in mycorrhizal and nonmycorrhizal roots of cucumber (Cucumis sativus L) and in external mycelium of the arbuscular mycorrhizal (AM) fungus Glomus intraradices Schenck & Smith. The in vivo NMR method allows...... biological systems to be studied non-invasively and non-destructively. (3)1P NMR experiments provide information about cytoplasmic and vacuolar pH, based on the pH-dependent chemical shifts of the signals arising from the inorganic P (P-i) located in the two compartments. Similarly, the resonances arising...... from alpha, beta and gamma phosphates of nucleoside triphosphates (NTP) and nucleoside diphosphates (NDP) supply knowledge about the metabolic activity and the energetic status of the tissue. In addition, the kinetic behaviour of P uptake and storage can be determined with this method. The (3)1P NMR...

  5. 29Si and 27AI MAS NMR Study of Alkali Feldspars

    Institute of Scientific and Technical Information of China (English)

    周玲棣; 郭九皋; 袁汉珍; 李丽云

    1994-01-01

    12 natural alkali feldspars have been studied by(29)~Si and(27)~Al MAS NMR as well as XRD,IR,EPMA and chemical analysis.Three kinds of(29)~Si NMR spectra,i.e.the spectra of microcline,perthiteand perthite with minor plagioclase,have been obtained.There are two types of(27)~Al NMR spectra.The(27)~Alspectrum of microcline is the same as that of perthite,but is different from the spectrum for perthite contain-ing plagioclase.Through this study,we found that the results of NMR and IR are inconsistent with that ofXRD,which shows that the transition of alkali feldspar from monoclinic to triclinic system might be a rathercomplicated process.

  6. Gd[sup 3+] chelates of interest in magnetic resonance imaging (MRI): studies using [sup 17]O NMR and EPR at several magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Hugh Powell, D. (Institute of Inorganic and Analytical Chemistry, University of Lausanne, Place du Chateau 3, CH-1005 Lausanne (Switzerland)); Gonzalez, Gabriel (Institute of Inorganic and Analytical Chemistry, University of Lausanne, Place du Chateau 3, CH-1005 Lausanne (Switzerland)); Tissieres, Veronique (Institute of Inorganic and Analytical Chemistry, University of Lausanne, Place du Chateau 3, CH-1005 Lausanne (Switzerland)); Micskei, Karoly (Institute of Inorganic and Analytical Chemistry, University of Lausanne, Place du Chateau 3, CH-1005 Lausanne (Switzerland) Institute of Inorganic and Analytical Chemistry, Kossuth University, 4010, Debrecen (Hungary)); Bruecher, Ernoe (Institute of Inorganic and Analytical Chemistry, Kossuth University, 4010, Debrecen (Hungary)); Helm, Lothar (Institute of Inorganic and Analytical Chemistry, University of Lausanne, Place du Chateau 3, CH-1005 Lausanne (Switzerland)); Merbach, Andre E. (Institute of Inorganic and Analytical Chemistry,

    1994-06-01

    The combination of [sup 17]O NMR relaxation rate and chemical shift measurements and EPR linewidth measurements at several magnetic fields provides a powerful probe of water exchange, rotational dynamics and electronic relaxation in aqueous solutions of Gd[sup 3+] complexes. This information is important for the understanding of the proton relaxivity of the complexes. Variable pressure measurements show a change of water exchange mechanism from associatively activated on [Gd(H[sub 2]O)[sub 8

  7. The gel-forming behaviour of dextran in the presence of KCl: a quantitative 13C and pulsed field gradient (PFG) NMR study.

    Science.gov (United States)

    Naji, L; Schiller, J; Kaufmann, J; Stallmach, F; Kärger, J; Arnold, K

    2003-05-01

    Although the gel forming ability of certain polysaccharides in the presence of ions is a well-known phenomenon, detailed physicochemical mechanisms of such processes are still unknown. In this investigation high resolution 13C NMR as well as 1H pulsed field gradient (PFG) NMR were used to investigate the mobility of dextran in the sol and in the gel state. Gel-formation of dextran can be easily induced by the addition of large amounts of potassium chloride. No major differences in the T(1) relaxation times of dextran in the sol and in the gel state could be observed. Accordingly, the analysis of the 13C NMR spectroscopic data did not provide any indication of an observable line-broadening upon gel-formation. However, a KCl concentration dependent decrease of signal intensity in comparison to an internal standard was detected. On the other hand, the PFG NMR studies clearly indicated a gradual diminution of the self-diffusion coefficient of the dextran with increasing molecular weight as well as in the presence of potassium chloride. These measurements revealed in agreement with spectroscopic data that at least one potassium ion per monomer subunit (i.e. one glycopyranose residue) is necessary for gel formation.

  8. NMR studies on antitumor drug candidates, berberine and berberrubine

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Young Wook; Jung, Jin Won; Kang, Mi Ran; Chung, In Kwon; Lee, Weon Tae [Yonsei Univ., Seoul (Korea, Republic of)

    2002-03-01

    Berberine and berberrubine, which display antitumor activity, have also demonstrated distinct enzyme-poisoning activities by stabilizing topoisomerase II-DNA cleavable complexes. The protoberberine berberrubine differs in chemical structure with berberine at only one position, however, it shows a prominent activity different from berberine. Solution structures of berberine and berberrubine determined by NMR spectroscopy are similar, however, the minor structural rearrangement has been observed near 19 methoxy or hydroxyl group. We suggest that the DNA cleavage activities of topoisomerase II poisons could be correlated with both chemical environments and minor structural change together with hydrophobicity of interacting side chains of drugs with DNA molecules.

  9. An NMR Study on Chrysathain%马钱苷的NMR数据解析

    Institute of Scientific and Technical Information of China (English)

    范毅; 张海艳; 李坤威; 张剑; 赵天增

    2014-01-01

    通过DEPT及1H-1HCOSY,HSQC,HMBC,NOESY等2D NMR技术,对环烯醚萜苷化合物--马钱苷的1H和13C NMR信号进行了详细解析和全归属,尤其利用NOESY技术确证了其立体结构。%Loganin,an important iro doid,was usually isolated from Cornus officinalis Sieb,et Zucc. and Lonicera chrysatha Thunb.. The 1H and 13C NMR chemical shifts of loganin were completely assigned by using a combination of 1D NMR(1H,13C NMR and DEPT)and 2D NMR(1H- 1H COSY,HSQC,HMBC and NOESY)techniques, especially its stereoscopic strcture was studied with NOESY.

  10. NMR study of CeTe at low temperatures

    Science.gov (United States)

    Hinderer, J.; Weyeneth, S. M.; Weller, M.; Gavilano, J. L.; Felder, E.; Hulliger, F.; Ott, H. R.

    2006-05-01

    We present 125Te NMR measurements on CeTe powder at temperatures between 1 and 150 K and in magnetic fields between 5 and 8 T. CeTe is a rocksalt-type intermetallic compound. It orders antiferromagnetically at TN≈2.2 K with a much reduced ordered moment [H.R. Ott, J.K. Kjems, F. Hulliger, Phys. Rev. Lett. 42 20 (1979) 1378]. From our low-temperature NMR spectra we infer the presence of at least three inequivalent Te sites at low temperatures. Considering the crystal structure this result is completely unexpected. The linewidths and the Knight shifts of the individual lines are significantly different and increase substantially with decreasing temperature. They follow the temperature dependence of the magnetic susceptibility above 20 K. Above TN, hyperfine fields of 1.6, 0.8 and 0.0 T at the three Te sites per Bohr magneton of Ce moment are deduced from Knight shift vs. magnetic susceptibility data. These values are typical for transferred hyperfine fields via conduction electrons.

  11. NMR probe of metallic states in nanoscale topological insulators.

    Science.gov (United States)

    Koumoulis, Dimitrios; Chasapis, Thomas C; Taylor, Robert E; Lake, Michael P; King, Danny; Jarenwattananon, Nanette N; Fiete, Gregory A; Kanatzidis, Mercouri G; Bouchard, Louis-S

    2013-01-11

    A 125Te NMR study of bismuth telluride nanoparticles as a function of particle size revealed that the spin-lattice relaxation is enhanced below 33 nm, accompanied by a transition of NMR spectra from the single to the bimodal regime. The satellite peak features a negative Knight shift and higher relaxivity, consistent with core polarization from p-band carriers. Whereas nanocrystals follow a Korringa law in the range 140-420 K, micrometer particles do so only below 200 K. The results reveal increased metallicity of these nanoscale topological insulators in the limit of higher surface-to-volume ratios.

  12. Theoretical and experimental NMR studies on muscimol from fly agaric mushroom (Amanita muscaria)

    Science.gov (United States)

    Kupka, Teobald; Wieczorek, Piotr P.

    2016-01-01

    In this article we report results of combined theoretical and experimental NMR studies on muscimol, the bioactive alkaloid from fly agaric mushroom (Amanita muscaria). The assignment of 1H and 13C NMR spectra of muscimol in DMSO-d6 was supported by additional two-dimensional heteronuclear correlated spectra (2D NMR) and gauge independent atomic orbital (GIAO) NMR calculations using density functional theory (DFT). The effect of solvent in theoretical calculations was included via polarized continuum model (PCM) and the hybrid three-parameter B3LYP density functional in combination with 6-311++G(3df,2pd) basis set enabled calculation of reliable structures of non-ionized (neutral) molecule and its NH and zwitterionic forms in the gas phase, chloroform, DMSO and water. GIAO NMR calculations, using equilibrium and rovibrationally averaged geometry, at B3LYP/6-31G* and B3LYP/aug-cc-pVTZ-J levels of theory provided muscimol nuclear magnetic shieldings. The theoretical proton and carbon chemical shifts were critically compared with experimental NMR spectra measured in DMSO. Our results provide useful information on its structure in solution. We believe that such data could improve the understanding of basic features of muscimol at atomistic level and provide another tool in studies related to GABA analogs.

  13. Effect of intra-abdominal hypertension on left ventricular relaxation: a preliminary animal study.

    Science.gov (United States)

    Mahjoub, Y; Lorne, E; Maizel, J; Plantefève, G; Massy, Z A; Dupont, H; Slama, M

    2012-02-01

    In the intensive care unit, intra-abdominal hypertension (IAH) is a frequently encountered, life-threatening condition. The aim of this animal study was to evaluate the effect of IAH on left ventricular (LV) relaxation (i.e. the active phase of diastole). Seven male rabbits were anaesthetized before mechanical ventilation. A 20 mm Hg increase in intra-abdominal pressure (IAP) was then induced by intraperitoneal infusion of 1.5% glycine solution. Haemodynamic parameters were recorded and the relaxation time constant tau (considered to be the best index of left ventricle relaxation) was calculated. All haemodynamic measurements were recorded at baseline and then after induction of IAH. A 20 mm Hg increase in IAP was not followed by a significant change in arterial pressure, but was associated with increases in central venous pressure (from 2 [-2 to 6] to 7 [-2 to 12] mm Hg, P= 0.03), LV end-diastolic pressure (from 7 [6-8] to 15 [11-19] mm Hg, P= 0.04) and the relaxation time constant tau (from 16 [14-18] to 43 [34-52] ms, P= 0.048). In this animal study, a 20 mm Hg increase in IAP impaired LV relaxation. Further studies are necessary to identify the causes of this impairment.

  14. NMR structural studies of oligosaccharides and other natural products

    DEFF Research Database (Denmark)

    Kjærulff, Louise

    produce secondary metabolites for signaling and competing against other organisms, and these molecules are important in drug discovery due to their inherent biological activities. From a marine Photobacterium (P. halotolerans) we isolated the solonamides and the ngercheumicins, two families of cyclic....... fijiensis, was also investigated for production of novel secondary metabolites, and a new pyranonigrin (E) was isolated and structure elucidated by NMR spectroscopy along with JBIR-74 and decumbenone A, two known metabolites previously isolated from Aspergillus and Penicillium species. Oligosaccharides...... with respect to n+1JHH between these two experiments, observed in the nJCH HMBC cross peak. Through a double editing procedure this enables straightforward determination of both sign and magnitude of n+1JHH, including for very small coupling constants. Excellent results were obtained for the natural product...

  15. Dynamics in Thermotoga neapolitana adenylate kinase: 15N relaxation and hydrogen-deuterium exchange studies of a hyperthermophilic enzyme highly active at 30 degrees C.

    Science.gov (United States)

    Krishnamurthy, Harini; Munro, Kim; Yan, Honggao; Vieille, Claire

    2009-03-31

    Backbone conformational dynamics of Thermotoga neapolitana adenylate kinase in the free form (TNAK) and inhibitor-bound form (TNAK*Ap5A) were investigated at 30 degrees C using (15)N NMR relaxation measurements and NMR monitored hydrogen-deuterium exchange. With kinetic parameters identical to those of Escherichia coli AK (ECAK) at 30 degrees C, TNAK is a unique hyperthermophilic enzyme. These catalytic properties make TNAK an interesting and novel model to study the interplay between protein rigidity, stability, and activity. Comparison of fast time scale dynamics (picosecond to nanosecond) in the open and closed states of TNAK and ECAK at 30 degrees C reveals a uniformly higher rigidity across all domains of TNAK. Within this framework of a rigid TNAK structure, several residues located in the AMP-binding domain and in the core-lid hinge regions display high picosecond to nanosecond time scale flexibility. Together with the recent comparison of ECAK dynamics with those of hyperthermophilic Aquifex aeolicus AK (AAAK), our results provide strong evidence for the role of picosecond to nanosecond time scale fluctuations in both stability and activity. In the slow time scales, TNAK's increased rigidity is not uniform but localized in the AMP-binding and lid domains. The core domain amides of ECAK and TNAK in the open and closed states show comparable protection against exchange. Significantly, the hinges framing the lid domain show similar exchange data in ECAK and TNAK open and closed forms. Our NMR relaxation and hydrogen-deuterium exchange studies therefore suggest that TNAK maintains high activity at 30 degrees C by localizing flexibility to the hinge regions that are key to facilitating conformational changes.

  16. Quantifying two-bond 1HN-13CO and one-bond 1H(alpha)-13C(alpha) dipolar couplings of invisible protein states by spin-state selective relaxation dispersion NMR spectroscopy.

    Science.gov (United States)

    Hansen, D Flemming; Vallurupalli, Pramodh; Kay, Lewis E

    2008-07-02

    Relaxation dispersion NMR spectroscopy has become a valuable probe of millisecond dynamic processes in biomolecules that exchange between a ground (observable) state and one or more excited (invisible) conformers, in part because chemical shifts of the excited state(s) can be obtained that provide insight into the conformations that are sampled. Here we present a pair of experiments that provide additional structural information in the form of residual dipolar couplings of the excited state. The new experiments record (1)H spin-state selective (13)CO and (13)C(alpha) dispersion profiles under conditions of partial alignment in a magnetic field from which two-bond (1)HN-(13)CO and one-bond (1)H(alpha)-(13)C(alpha) residual dipolar couplings of the invisible conformer can be extracted. These new dipolar couplings complement orientational restraints that are provided through measurement of (1)HN-(15)N residual dipolar couplings and changes in (13)CO chemical shifts upon alignment that have been measured previously for the excited-state since the interactions probed here are not collinear with those previously investigated. An application to a protein-ligand binding reaction is presented, and the accuracies of the extracted excited-state dipolar couplings are established. A combination of residual dipolar couplings and chemical shifts as measured by relaxation dispersion will facilitate a quantitative description of excited protein states.

  17. QENS and NMR studies of 3-picoline-water solutions

    CERN Document Server

    Almasy, L; Bokor, M; Cser, L; Tompa, K; Zanotti, J M; Jancso, G

    2002-01-01

    Quasi-elastic neutron scattering measurements were performed on aqueous solutions of 3-picoline (3-methylpyridine) at room temperature. H-D substitution on both the solute and the water was used to separate the dynamics of the two species. The analysis of the translational diffusive motion at different concentrations shows that at high picoline content the diffusion coefficient of water decreases strongly and becomes similar to that of the solute, indicating strong coupling between the motions of the solute and the solvent. Activation energies characteristic of the dynamic behavior of the methyl group were determined from sup 1 H spin-lattice relaxation rate measurements for H sub 2 O and D sub 2 O solutions of 3-picoline above 310 K. (orig.)

  18. A study of relaxation techniques for the transient analysis of digital circuits

    Science.gov (United States)

    Chia, W. K.

    1985-06-01

    In the VLSI microelectronics era, the cost of the immense CPU time and memory storage for a standard circuit simulator has become prohibitive. In order to achieve dramatic improvement in the performance of the circuit simulator, there are two principal points of departure from the standard simulation approach, namely, tearing decomposition and relaxation decomposition. This research is to study the numerical convergence and stability properties of several of the relaxation algorithms that have been proposed for the simulation of VLSI circuits. The time-point Gauss-Seidel method with prediction, the exploitation of latency and event scheduling algorithms are implemented into a general purpose circuit simulator SLATE-R (a Simulator with Latency and Tearing--Relaxed version). The performance of the SLATE-R program in the analysis of various types of integrated circuit technologies is studied.

  19. NMR studies of proton exchange kinetics in aqueous formaldehyde solutions

    Science.gov (United States)

    Rivlin, Michal; Eliav, Uzi; Navon, Gil

    2014-05-01

    Aqueous solutions of formaldehyde, formalin, are commonly used for tissue fixation and preservation. Treatment with formalin is known to shorten the tissue transverse relaxation time T2. Part of this shortening is due to the effect of formalin on the water T2. In the present work we show that the shortening of water T2 is a result of proton exchange between water and the major constituent of aqueous solutions of formaldehyde, methylene glycol. We report the observation of the signal of the hydroxyl protons of methylene glycol at 2 ppm to high frequency of the water signal that can be seen at low temperatures and at pH range of 6.0 ± 1.5 and, at conditions where it cannot be observed by the single pulse experiment, it can be detected indirectly through the water signal by the chemical exchange saturation transfer (CEST) experiment. The above finding made it possible to obtain the exchange rate between the hydroxyl protons of the methylene glycol and water in aqueous formaldehyde solutions, either using the dispersion of the spin-lattice relaxation rate in the rotating frame (1/T1ρ) or, at the slow exchange regime, from the line width hydroxyl protons of methylene glycol. The exchange rate was ∼104 s-1 at pH 7.4 and 37 °C, the activation energy, 50.2 kJ/mol and its pH dependence at 1.1 °C was fitted to: k (s-1) = 520 + 6.5 × 107[H+] + 3.0 × 109[OH-].

  20. Hyperpolarized 131Xe NMR spectroscopy

    Science.gov (United States)

    Stupic, Karl F.; Cleveland, Zackary I.; Pavlovskaya, Galina E.; Meersmann, Thomas

    2011-01-01

    Hyperpolarized (hp) 131Xe with up to 2.2% spin polarization (i.e., 5000-fold signal enhancement at 9.4 T) was obtained after separation from the rubidium vapor of the spin-exchange optical pumping (SEOP) process. The SEOP was applied for several minutes in a stopped-flow mode, and the fast, quadrupolar-driven T1 relaxation of this spin I = 3/2 noble gas isotope required a rapid subsequent rubidium removal and swift transfer into the high magnetic field region for NMR detection. Because of the xenon density dependent 131Xe quadrupolar relaxation in the gas phase, the SEOP polarization build-up exhibits an even more pronounced dependence on xenon partial pressure than that observed in 129Xe SEOP. 131Xe is the only stable noble gas isotope with a positive gyromagnetic ratio and shows therefore a different relative phase between hp signal and thermal signal compared to all other noble gases. The gas phase 131Xe NMR spectrum displays a surface and magnetic field dependent quadrupolar splitting that was found to have additional gas pressure and gas composition dependence. The splitting was reduced by the presence of water vapor that presumably influences xenon-surface interactions. The hp 131Xe spectrum shows differential line broadening, suggesting the presence of strong adsorption sites. Beyond hp 131Xe NMR spectroscopy studies, a general equation for the high temperature, thermal spin polarization, P, for spin I⩾1/2 nuclei is presented.

  1. High pressure studies on structural and secondary relaxation dynamics in silyl derivative of D-glucose

    Science.gov (United States)

    Minecka, Aldona; Kamińska, Ewa; Tarnacka, Magdalena; Dzienia, Andrzej; Madejczyk, Olga; Waliłko, Patrycja; Kasprzycka, Anna; Kamiński, Kamil; Paluch, Marian

    2017-08-01

    In this paper, broadband dielectric spectroscopy was applied to investigate molecular dynamics of 1,2,3,4,6-penta-O-(trimethylsilyl)-D-glucopyranose (S-GLU) at ambient and elevated pressures. Our studies showed that apart from the structural relaxation, one well resolved asymmetric secondary process (initially labeled as β) is observed in the spectra measured at p = 0.1 MPa. Analysis with the use of the coupling model and criterion proposed by Ngai and Capaccioli indicated that the β-process in S-GLU is probably a Johari-Goldstein relaxation of intermolecular origin. Further high pressure experiments demonstrated that there are in fact two secondary processes contributing to the β-relaxation. Therefore, one can postulate that the coupling model is a necessary, but not sufficient criterion to identify the true nature of the given secondary relaxation process. The role of pressure experiments in better understanding of the molecular origin of local mobility seems to be much more important. Interestingly, our research also revealed that the structural relaxation in S-GLU is very sensitive to compression. It was reflected in an extremely high pressure coefficient of the glass transition temperature (dTg/dp = 412 K/GPa). According to the literature data, such a high value of dTg/dp has not been obtained so far for any H-bonded, van der Waals, or polymeric glass-formers.

  2. Charge-carrier relaxation in disordered organic semiconductors studied by dark injection: Experiment and modeling

    Science.gov (United States)

    Mesta, M.; Schaefer, C.; de Groot, J.; Cottaar, J.; Coehoorn, R.; Bobbert, P. A.

    2013-11-01

    Understanding of stationary charge transport in disordered organic semiconductors has matured during recent years. However, charge-carrier relaxation in nonstationary situations is still poorly understood. Such relaxation can be studied in dark injection experiments, in which the bias applied over an unilluminated organic semiconductor device is abruptly increased. The resulting transient current reveals both charge-carrier transport and relaxation characteristics. We performed such experiments on hole-only devices of a polyfluorene-based organic semiconductor. Modeling the dark injection by solving a one-dimensional master equation using the equilibrium carrier mobility leads to a too-slow current transient, since this approach does not account for carrier relaxation. Modeling by solving a three-dimensional time-dependent master equation does take into account all carrier transport and relaxation effects. With this modeling, the time scale of the current transient is found to be in agreement with experiment. With a disorder strength somewhat smaller than extracted from the temperature-dependent stationary current-voltage characteristics, also the shape of the experimental transients is well described.

  3. T2 star relaxation times for assessment of articular cartilage at 3 T: a feasibility study.

    Science.gov (United States)

    Mamisch, Tallal Charles; Hughes, Timothy; Mosher, Timothy J; Mueller, Christoph; Trattnig, Siegfried; Boesch, Chris; Welsch, Goetz Hannes

    2012-03-01

    T2 mapping techniques use the relaxation constant as an indirect marker of cartilage structure, and the relaxation constant has also been shown to be a sensitive parameter for cartilage evaluation. As a possible additional robust biomarker, T2* relaxation time is a potential, clinically feasible parameter for the biochemical evaluation of articular cartilage. The knees of 15 healthy volunteers and 15 patients after microfracture therapy (MFX) were evaluated with a multi-echo spin-echo T2 mapping technique and a multi-echo gradient-echo T2* mapping sequence at 3.0 Tesla MRI. Inline maps, using a log-linear least squares fitting method, were assessed with respect to the zonal dependency of T2 and T2* relaxation for the deep and superficial regions of healthy articular cartilage and cartilage repair tissue. There was a statistically significant correlation between T2 and T2* values. Both parameters demonstrated similar spatial dependency, with longer values measured toward the articular surface for healthy articular cartilage. No spatial variation was observed for cartilage repair tissue after MFX. Within this feasibility study, both T2 and T2* relaxation parameters demonstrated a similar response in the assessment of articular cartilage and cartilage repair tissue. The potential advantages of T2*-mapping of cartilage include faster imaging times and the opportunity for 3D acquisitions, thereby providing greater spatial resolution and complete coverage of the articular surface.

  4. T2 star relaxation times for assessment of articular cartilage at 3 T: a feasibility study

    Energy Technology Data Exchange (ETDEWEB)

    Mamisch, Tallal Charles [University Bern, Department of Orthopedic Surgery, Inselspital, Bern (Switzerland); University Bern, Magnetic Resonance Spectroscopy and Methodology, Department of Clinical Research, Bern (Switzerland); Hughes, Timothy [Siemens Medical Solutions, Erlangen (Germany); Mosher, Timothy J. [Penn State University College of Medicine, Musculoskeletal Imaging and MRI, Department of Radiology, Hershey, PA (United States); Mueller, Christoph [University of Erlangen, Department of Trauma Surgery, Erlangen (Germany); Trattnig, Siegfried [Medical University of Vienna, MR Center - High Field MR, Department of Radiology, Vienna (Austria); Boesch, Chris [University Bern, Magnetic Resonance Spectroscopy and Methodology, Department of Clinical Research, Bern (Switzerland); Welsch, Goetz Hannes [University of Erlangen, Department of Trauma Surgery, Erlangen (Germany); Medical University of Vienna, MR Center - High Field MR, Department of Radiology, Vienna (Austria)

    2012-03-15

    T2 mapping techniques use the relaxation constant as an indirect marker of cartilage structure, and the relaxation constant has also been shown to be a sensitive parameter for cartilage evaluation. As a possible additional robust biomarker, T2* relaxation time is a potential, clinically feasible parameter for the biochemical evaluation of articular cartilage. The knees of 15 healthy volunteers and 15 patients after microfracture therapy (MFX) were evaluated with a multi-echo spin-echo T2 mapping technique and a multi-echo gradient-echo T2* mapping sequence at 3.0 Tesla MRI. Inline maps, using a log-linear least squares fitting method, were assessed with respect to the zonal dependency of T2 and T2* relaxation for the deep and superficial regions of healthy articular cartilage and cartilage repair tissue. There was a statistically significant correlation between T2 and T2* values. Both parameters demonstrated similar spatial dependency, with longer values measured toward the articular surface for healthy articular cartilage. No spatial variation was observed for cartilage repair tissue after MFX. Within this feasibility study, both T2 and T2* relaxation parameters demonstrated a similar response in the assessment of articular cartilage and cartilage repair tissue. The potential advantages of T2*-mapping of cartilage include faster imaging times and the opportunity for 3D acquisitions, thereby providing greater spatial resolution and complete coverage of the articular surface. (orig.)

  5. Paramagnetic nuclear magnetic resonance relaxation and molecular mechanics studies of the chloroperoxidase-indole complex: insights into the mechanism of chloroperoxidase-catalyzed regioselective oxidation of indole.

    Science.gov (United States)

    Zhang, Rui; He, Qinghao; Chatfield, David; Wang, Xiaotang

    2013-05-28

    To unravel the mechanism of chloroperoxidase (CPO)-catalyzed regioselective oxidation of indole, we studied the structure of the CPO-indole complex using nuclear magnetic resonance (NMR) relaxation measurements and computational techniques. The dissociation constant (KD) of the CPO-indole complex was calculated to be approximately 21 mM. The distances (r) between protons of indole and the heme iron calculated via NMR relaxation measurements and molecular docking revealed that the pyrrole ring of indole is oriented toward the heme with its 2-H pointing directly at the heme iron. Both KD and r values are independent of pH in the range of 3.0-6.5. The stability and structure of the CPO-indole complex are also independent of the concentration of chloride or iodide ion. Molecular docking suggests the formation of a hydrogen bond between the NH group of indole and the carboxyl O of Glu 183 in the binding of indole to CPO. Simulated annealing of the CPO-indole complex using r values from NMR experiments as distance restraints reveals that the van der Waals interactions were much stronger than the Coulomb interactions in the binding of indole to CPO, indicating that the association of indole with CPO is primarily governed by hydrophobic rather than electrostatic interactions. This work provides the first experimental and theoretical evidence of the long-sought mechanism that leads to the "unexpected" regioselectivity of the CPO-catalyzed oxidation of indole. The structure of the CPO-indole complex will serve as a lighthouse in guiding the design of CPO mutants with tailor-made activities for biotechnological applications.

  6. 1H-NMR and photochemically-induced dynamic nuclear polarization studies on bovine pancreatic phospholipase A2.

    Science.gov (United States)

    Egmond, M R; Slotboom, A J; De Haas, G H; Dijkstra, K; Kaptein, R

    1980-06-26

    Proton-NMR resonances of trytophan 3 and tyrosine 69 in bovine pancreatic phospholipase A2, its pro-enzyme and in Ala1-transaminated protein were assigned using photochemically-induced dynamic nuclear polarization (photo-CIDNP) as such or in combination with spin-echo measurements. In addition assignments were made by suppression of cross-relaxation effects using short (0.1 s) high-power laser pulses.

  7. A study on oscillating second-kind boundary condition for Pennes equation considering thermal relaxation

    Science.gov (United States)

    Zhu, Weiping; Xu, Peng; Xu, Dong; Zhang, Meimei; Liu, Huiming; Gong, Linghui; Lu, Junfeng

    2014-05-01

    To study the effects of the thermal relaxation, the blood perfusion and the oscillating of ambient heat flux on the living tissue temperature in detail, we analytically investigated the one-dimensional CV model, a thermal wave model presented by Cattaneo and Vernott, for Pennes' bio-heat transfer equation under oscillating second-kind boundary condition. The results showed that the blood perfusion has the effect of maintaining the tissue's temperature. The heat propagation velocity decreases with the thermal relaxation time, while the absolute value of tissue's mean excess temperature at steady state increases with the thermal relaxation time. When the ambient heat flux oscillates, the tissue's temperature oscillates in the same period with a lag time. The results obtained in this paper are valuable for the research reference on the topic of tumor hyperthermia, heat injury, etc.

  8. Relaxation Study of N-Submitted Amides with Alcohol Mixtures by Time Domain Reflectometry

    Directory of Open Access Journals (Sweden)

    A. Arunkumar

    2016-08-01

    Full Text Available Using Time Domain Reflectometry (TDR, dielectric relaxation studies have been carried out on binary mixtures of amides (N-methylacetamide, N,N-dimethylacetamide with alcohols (1-butanol, 1-pentanol for various concentrations over the frequency range from 10 MHz to 10 GHz at 303 K. The Kirkwood correlation factor and excess dielectric constant properties were determined and discussed to yield information on the molecular interactions of the systems. The relaxation time is vary with the chain length of alcohols and substituted amides are noticed. The Bruggeman plot shows a deviation from linearity. This deviation was attributed to some sort of molecular interaction which may take place between the alcohols and substituted amides. The excess static permittivity and excess inverse relaxation time values vary from negative to positive for all the systems indicating the solute-solvent interaction to exist between alcohols and substituted amides for all the dynamics of the mixture.

  9. Study of Relaxation by Traditional Medicinal Methods on Biological Indexes of the Elderly (Abstract)

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The objective of the study was to prove the relaxation effect of traditional medicine by objective biological indexes by modern scientific methods.  Fifty healthy elderly people, aged from 60 to 75, were selected to have traditional medicinal relaxing practice, that is, to relax their body in 3 directions: two sides, in front and backward, and breath naturally, 30 minutes a day, 8 weeks as a cycle. (1) The changes of electroencephalogram (EEG), rheoencephalogram (REG) were measured before and after the treatment cycle. Breath frequency and SaO2 contents were measured before and after the treatment cycle by Pulse oxymeter. (2) As for the circulatory system, pulse frequency, blood pressure, blood influx of limbs were measured before and after the treatment cycle. (3) Biochemical indexes (including index of cholesterol, triglyceride, blood sugar, cortisone, catecholamine) were measured before and after the treatment cycle.……

  10. Study of Relaxation by Traditional Medicinal Methods on Biological Indexes of the Elderly (Abstract)

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@The objective of the study was to prove the relaxation effect of traditional medicine by objective biological indexes by modern scientific methods. Fifty healthy elderly people, aged from 60 to 75, were selected to have traditional medicinal relaxing practice, that is, to relax their body in 3 directions: two sides, in front and backward, and breath naturally, 30 minutes a day, 8 weeks as a cycle. (1) The changes of electroencephalogram (EEG), rheoencephalogram (REG) were measured before and after the treatment cycle. Breath frequency and SaO2 contents were measured before and after the treatment cycle by Pulse oxymeter. (2) As for the circulatory system, pulse frequency, blood pressure, blood influx of limbs were measured before and after the treatment cycle. (3) Biochemical indexes (including index of cholesterol, triglyceride, blood sugar, cortisone, catecholamine) were measured before and after the treatment cycle.

  11. Pseudogap and anharmonic phonon behavior in Ba8Ga16Ge30: An NMR study

    Science.gov (United States)

    Sirusi, Ali A.; Ross, Joseph H.

    2016-08-01

    We have performed 69Ga, 71Ga, and 137Ba NMR on Ba8Ga16Ge30, a clathrate semiconductor which has been of considerable interest due to its large figure of merit for thermoelectric applications. In measurements from 4 K to 450 K, we used measurements on the two Ga nuclei to separate the magnetic and electric quadrupole hyperfine contributions and thereby gain information about the metallic and phonon behavior. The results show the presence of a pseudogap in the Ga electronic states within the conduction band, superposed upon a large Ba contribution to the conduction band. Meanwhile the phonon contributions to the Ga relaxation rates are large and increase more rapidly with temperature than typical semiconductors. These results provide evidence for enhanced anharmonicity of the propagative phonon modes over a wide range, providing experimental evidence for enhanced phonon-phonon scattering as a mechanism for the reduced thermal conductivity.

  12. NMR study of filled skutterudite NdOs{sub 4}P{sub 12}

    Energy Technology Data Exchange (ETDEWEB)

    Magishi, K; Nagata, K; Iwahashi, Y; Sugawara, H; Saito, T; Koyama, K, E-mail: magishi@ias.tokushima-u.ac.j [Institute of Socio-Arts and Sciences, The University of Tokushima, Tokushima 770-8502 (Japan)

    2010-01-15

    We have succeeded in growing the single crystals of NdOs{sub 4}P{sub 12} and investigated the electrical resistivity, magnetic susceptibility and nuclear magnetic resonance (NMR). NdOs{sub 4}P{sub 12} shows metallic behavior in the electric resistivity and undergoes a ferromagnetic transition at 1.15 K. The Knight shift increases upon cooling, similar to the magnetic susceptibility, and little depends on the magnetic field except for below 10 K. Also, the nuclear spin-lattice relaxation rate divided by temperature 1/T{sub 1}T is largely enhanced with decreasing temperature, implying the significant development of the magnetic fluctuations. 1/T{sub 1}T is strongly suppressed by the magnetic field, in contrast to the Knight shift. It suggests the coexistence of the ferromagnetic and antiferromagnetic spin fluctuations, similar to the results for NdRu{sub 4}P{sub 12}.

  13. {sup 1}H NMR study of hydrogen self-diffusion in ternary Ti–V–Cr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Vyvodtceva, A.V. [Faculty of Physics, Saint-Petersburg State University, 1 Ulyanovskaya St., Peterhof, Saint Petersburg 198504 (Russian Federation); Shelyapina, M.G., E-mail: marina.shelyapina@spbu.ru [Faculty of Physics, Saint-Petersburg State University, 1 Ulyanovskaya St., Peterhof, Saint Petersburg 198504 (Russian Federation); Privalov, A.F. [Institute für Ferstkoerperphysik, TU Darmstadt, 6 Hochschulstarsse, Darmstadt 64289 (Germany); Chernyshev, Yu.S. [Faculty of Physics, Saint-Petersburg State University, 1 Ulyanovskaya St., Peterhof, Saint Petersburg 198504 (Russian Federation); Fruchart, D. [MCMF Institut Néel, CNRS, BP 166, 38042 Grenoble Cedex 9 (France)

    2014-11-25

    Highlights: • SFG NMR was applied to study the hydrogen self-diffusion in hydrides of disordered Ti–V–Cr alloys. • All studied hydrides exhibit slow hydrogen diffusion that is usual for hydrides with high hydrogen concentration. • The activation energy E{sub a} strongly depends on the both composition and structure type of the hydride. • The obtained results are partially in agreement with recent research of proton relaxation studies. • Diffusion measurements results in higher activation energy values for hydrogen motion. - Abstract: Here we report on the results of proton NMR study of hydrogen self-diffusion in hydrides of Ti–V–Cr alloys of different composition, pure and with 4 wt.% of Zr{sub 7}Ni{sub 10} additives, namely, TiV{sub 0.8}Cr{sub 1.2}H{sub 5.29}, Ti{sub 0.5}V{sub 1.9}Cr{sub 0.6}H{sub 5.03} and Ti{sub 0.33}V{sub 1.27}Cr{sub 1.4}H{sub 1.13}. The measurements have been made using the static field gradient nuclear magnetic resonance technique. The hydrogen self-diffusion coefficient at room temperature lies within the range of 1.4–3.7 × 10{sup −11} m{sup 2}/s. The activation energy E{sub a} strongly depends on the both composition and structure type of the hydride. The samples with bcc structure (and with the lowest hydrogen concentration) exhibit the highest E{sub a} value of 0.2 eV. For the samples with fcc structure the E{sub a} value is lower and decreases with increasing the vanadium fraction. The influence of Zr{sub 7}Ni{sub 10} additives on the measured parameters is also discussed.

  14. Dielectric relaxation study of gamma irradiated oriented low-density polyethylene

    CERN Document Server

    Suljovrujic, E; Kostoski, D

    2003-01-01

    The influence of drawing, gamma irradiation and accelerated aging on the dielectric relaxation of low-density polyethylene has been studied using dielectric loss tangent measurements in the temperature range from 25 to 325 K and in the frequency range from 10 sup 3 to 10 sup 6 Hz. The intensity, position and activation energy of the gamma- and beta-dielectric relaxations were found to be strongly dependent upon the changes in the microstructure of the amorphous phase induced by uniaxial orientation, oxidation and crosslinking.

  15. Relaxation in the glass former acetylsalicylic acid studied by deuteron magnetic resonance and dielectric spectroscopy

    Science.gov (United States)

    Nath, R.; El Goresy, T.; Geil, B.; Zimmermann, H.; Böhmer, R.

    2006-08-01

    Supercooled liquid and glassy acetylsalicylic acid was studied using dielectric spectroscopy and deuteron relaxometry in a wide temperature range. The supercooled liquid is characterized by major deviations from thermally activated behavior. In the glass the secondary relaxation exhibits the typical features of a Johari-Goldstein process. Via measurements of spin-lattice relaxation times the selectively deuterated methyl group was used as a sensitive probe of its local environments. There is a large difference in the mean activation energy in the glass with respect to that in crystalline acetylsalicylic acid. This can be understood by taking into account the broad energy barrier distribution in the glass.

  16. SYNTHESIS, INFRARED AND NMR STUDIES OF SOME SULFATO DIORGANOSTANNIC DERIVATIVES

    Directory of Open Access Journals (Sweden)

    DAOUDA NDOYE

    2014-08-01

    Full Text Available EthylendiammoniumSO4•SnBu2Cl2•1/4ethylendiammoniumCl2 (A, 2ethylendiammoniumSO4•SnBu2Cl2 (B and Cy2NH2SO4H•Cy2NH2SnBu2Cl3 (C complexes have been obtained on allowing ethylendiammoniumSO4 and Cy2NH2HSO4 to react respectively with SnBu2Cl2 in specific ratios. The molecular structures of these compounds have been determined on the basis of infrared and NMR data. The suggested structures are dimeric and tetrameric, the tin atom being hexacoordinated, the sulphate anions behaving as a monochelating ligand or non-coordinating and only involved in hydrogen bonds. The hydrogenosulfate is a non-sigma coordinating anion but only involved in hydrogen bonds of acetic acid type or NH…O bonds. The presence of dimeric [(SnBu2Cl32]2- in one of the structures is noteworthy. The key role of the cations involved in hydrogen bonds is outlined.

  17. High Pressure Light Scattering Study of Relaxation in the Glass Former Cumene

    Science.gov (United States)

    Ransom, Tim; Lyon, Kevin; Oliver, William

    2014-03-01

    To understand relaxation dynamics in glassy systems, a light scattering study on Cumene has been carried out in a diamond anvil cell (DAC) at pressures from 0.2 GPa to 2.5 GPa isothermally at 75 °C. Polarized and depolarized spectra were taken in both near-backscattering and equal-angle 60° forward-scattering geometries at several free spectral ranges from 0.5 GHz to 300 GHz. Depolarized backscattering spectra are converted into susceptibility featuring the evolution of the α-relaxation peak, yielding structural relaxation times τα from 10 ps to 1 ns. We have also developed photon correlation spectroscopy (PCS) in a DAC, giving τα from ~ 1 μs to 1 s. We fit τα over these many decades with a modified VFTH equation τα =τ0 exp[DP/(P0-P)] giving parameters τ0 = 9.2 ps, D = 17.5, and P0 = 4.5 GPa at 75°C. After the α-relaxation peak moves into lower frequencies (P ~ 1 GPa), we observe the emergence of the β-relaxation minimum region. We fit the β-minimum to a power law scaling form χ''(ω) = b(ω/ωmin)a + a(ωmin/ ω)b. Polarized backscattering and forward scattering gives frequency shift ωB and linewidth ΓB values of the longitudinal acoustic modes at two different q. We observe that the usual peak in linewidths does not coincide with ωBτalpha ~ 1, indicating that the longitudinal acoustic modes do not couple with structural relaxation. Tansverse acoustic modes also appear in the depolarized forward scattering spectra. NSF Grant Number: DMR 0552944.

  18. Solid-state NMR studies of bacteriorhodopsin and the purple membrane

    CERN Document Server

    Mason, A J

    2001-01-01

    proteins. This technique may prove particularly useful when studying large proteins that are difficult to orient where the MAS lineshapes will remain relatively unaffected in comparison with current static NMR methods. Finally the MAOSS method was extended to the study of the lipid components of the purple membrane and the feasibility of determining structural constraints from phospholipid headgroups was assessed. The potential of using sup 3 sup 1 P NMR to observe qualitative protein-lipid interactions in both the purple membrane and reconstituted membranes containing bovine rhodopsin was also demonstrated. Following the demonstration of a new MAS NMR method for resolving orientational constraints in uni-axially oriented biological membranes (Glaubitz and Watts, 1998), experiments were performed to realise the potential of the new method on large, oriented membrane proteins. Using bacteriorhodopsin in the purple membrane as a paradigm for large membrane proteins, the protein was specifically labelled with de...

  19. Solution NMR Studies of Mycobacterium tuberculosis Proteins for Antibiotic Target Discovery

    Directory of Open Access Journals (Sweden)

    Do-Hee Kim

    2017-08-01

    Full Text Available Tuberculosis is an infectious disease caused by Mycobacterium tuberculosis, which triggers severe pulmonary diseases. Recently, multidrug/extensively drug-resistant tuberculosis strains have emerged and continue to threaten global health. Because of the development of drug-resistant tuberculosis, there is an urgent need for novel antibiotics to treat these drug-resistant bacteria. In light of the clinical importance of M. tuberculosis, 2067 structures of M. tuberculsosis proteins have been determined. Among them, 52 structures have been solved and studied using solution nuclear magnetic resonance (NMR. The functional details based on structural analysis of M. tuberculosis using NMR can provide essential biochemical data for the development of novel antibiotic drugs. In this review, we introduce diverse structural and biochemical studies on M. tuberculosis proteins determined using NMR spectroscopy.

  20. Experimental and theoretical NMR studies of interaction between phenylalanine derivative and egg yolk lecithin.

    Science.gov (United States)

    Wałęsa, Roksana; Ptak, Tomasz; Siodłak, Dawid; Kupka, Teobald; Broda, Małgorzata A

    2014-06-01

    The interaction of phenylalanine diamide (Ac-Phe-NHMe) with egg yolk lecithin (EYL) in chloroform was studied by (1)H and (13)C NMR. Six complexes EYL-Ac-Phe-NHMe, stabilized by N-H···O or/and C-H···O hydrogen bonds, were optimized at M06-2X/6-31G(d,p) level. The assignment of EYL and Ac-Phe-NHMe NMR signals was supported using GIAO (gauge including atomic orbital) NMR calculations at VSXC and B3LYP level of theory combined with STO-3Gmag basis set. Results of our study indicate that the interaction of peptides with lecithin occurs mainly in the polar 'head' of the lecithin. Additionally, the most probable lecithin site of H-bond interaction with Ac-Phe-NHMe is the negatively charged oxygen in phosphate group that acts as proton acceptor. Copyright © 2014 John Wiley & Sons, Ltd.

  1. STUDY OF THE MOLECULAR MOTION AND COMPATIBILITY IN AB-CROSSLINKED POLYMER BASED ON POLYURETHANE AND POLYSTYRENE-co-ACRYLIC ACID BY SOLID STATE HIGH RESOLUTION NMR

    Institute of Scientific and Technical Information of China (English)

    JIA Mingchun; SHEN Lianfang; QIAN Baogong; ZHANG Baozhen; YAO Shuren

    1994-01-01

    The 13C T1s of -CH3 side group in PPU/P(St-co-AA), AB-crosslinked polymers (i. e.ABCP) was studied by using high resolution solid state NMR. The rotation motion of -CH3 side group in PPU was analyzed by means of the average spectral density functions of internal rotation. The results showed that the rotation of the -CH3 side group is related closely to the compatibility between the two components. The compatibility was studied by analyzing the proton spin-lattice relaxation in rotating frame, spin-spin relaxation and spin-diffusion. The results showed that the hydrogen bonds between the components play a major role in determining the compatibility. Through spin diffusion studying, the soft phase domain size was calculated. By studying proton spin-spin relaxation, the content of each component in each phase and that of each phase in the samples can be obtained. The result shows that the content of interphase is related closely to the compatibility.

  2. Synergistic Applications of MD and NMR for the Study of Biological Systems

    Directory of Open Access Journals (Sweden)

    Olivier Fisette

    2012-01-01

    same time, theoretical and computational approaches gain in reliability and their field of application widens. In this short paper, we discuss recent advances in the areas of solution nuclear magnetic resonance (NMR spectroscopy and molecular dynamics (MD simulations that were made possible by the combination of both methods, that is, through their synergistic use. We present the main NMR observables and parameters that can be computed from simulations, and how they are used in a variety of complementary applications, including dynamics studies, model-free analysis, force field validation, and structural studies.

  3. Dynamic NMR study of dinitrophenyl derivatives of seven-membered cyclic ketals of pyridoxine.

    Science.gov (United States)

    Rakhmatullin, Ilfat Z; Galiullina, Leisan F; Garipov, Marsel' R; Strel'nik, Alexey D; Shtyrlin, Yurii G; Klochkov, Vladimir V

    2015-10-01

    Two pyridoxine derivatives containing a dinitrophenyl moiety were investigated by (1)H NMR spectroscopy. Conformational dynamics in solution were studied for each compound using dynamic NMR experiments. It was shown that both compounds studied are involved into two conformational exchange processes. The first process is a transformation of the seven-membered cycle conformation between the enantiomeric P-twist and M-twist forms, and the second is a rotation of the dinitrophenyl fragment of the molecules around the C-O bond. Energy barriers of both conformational transitions were determined.

  4. Instructional Set, Deep Relaxation and Growth Enhancement: A Pilot Study

    Science.gov (United States)

    Leeb, Charles; And Others

    1976-01-01

    This study provides experimental evidence that instructional set can influence access to altered states of consciousness. Fifteen male subjects were randomly assigned to three groups, each of which received the same autogenic biofeedback training in hand temperature control, but each group received a different attitudinal set. (Editor)

  5. 31p NMR and ESI-MS Studies on Some Intermediates of the Peptide Coupling Reagents Triphenyl-chlorophosphoranes

    Institute of Scientific and Technical Information of China (English)

    Guo TANG; Gui Ji ZHOU; Feng NI; Li Ming HU; Yu Fen ZHAO

    2005-01-01

    The intermediates of the Appel coupling reagents were studied in acetonitrile,dimethoxyethane and dioxane by 31P NMR, C NMR spectrum and ESI-MS. In dioxane a new high coordinated phosphorous compound with 31p NMR shift at -39 ppm was observed. The ESI-MS showed that it could be a penta-coordinated phosphorous compound containing dioxane. The carboxyl activated intermediates were also studied in three solvents.

  6. STUDIES ON THE CHEMICAL STRUCTURES OF ACTIVATED CARBON FIBERS BY SOLID STATE NMR

    Institute of Scientific and Technical Information of China (English)

    FURuowen; HuangWenqiang; 等

    1999-01-01

    The solid state C13-NMR spectra of different ACFs from various precursor fibers were recorded in this paper,The effects of activation conditions on chemical structures of ACFs,as well as the changes of chemical structures during carbonization and redox reaction were inverstigated by NMR technique,At same time,the soild state P31-NMR spectra of ACFS are studied.The C13-NMR spectra of ACFs can be divided into six bands that are assigned to methyl and methylene groups,hydroxyl and ether groups.acetal (or methylenedioxy) carbon,graphite-like aromatic carbon structure,phenol,and quinone groups,respectively.Only phosphorous pentoxide exists on ACFs and CFs.Moreover,most of them are stuck over the crystal face but not at the edge of graphite-like micro-crystal.The carbonization and activation conditions affect the C13-NMR spectra of ACFs.The experimental rsults indicate that the redox reaction of ACFs with oxidants greatly consumes C-H group.

  7. Proteolysis process in fermented sausage model systems as studied by NMR relaxometry.

    Science.gov (United States)

    García García, Ana Belén; Larsen, Lotte Bach; Cambero Rodríguez, María Isabel; Cruz Díaz, Karen Paola; Bertram, Hanne Christine

    2015-03-25

    Proton NMR relaxation analyses were performed in sausage model systems (SMS) at different manufacturing times (0, 1, 3, 5, 7, and 9 days) to evaluate changes in water distribution and mobility. Three different water populations were identified, T2b (5-10 ms), T21 (30-70 ms), and T22 (100-300 ms), and the progress of ripening could be followed as a shift toward shorter relaxation times. In addition, the combined effect of adding commercial proteases (Pronase E and aspartyl proteinase) on protein breakdown and structural integrity of sausage models (SMS+P) was investigated, resulting in the formation of a more fluid and less organized meat matrix that led to changes in water populations T2b2 and T22 compared with SMS. A very different protein degradation pattern between SMS and SMS+P was observed by means of SDS-PAGE and fluorescamine assay, supporting that some degree of protein aggregation is needed for the presence of the T22 population in fermented sausages.

  8. High-field 1H T1 and T2 NMR relaxation time measurements of H2O in homeopathic preparations of quartz, sulfur, and copper sulfate

    Science.gov (United States)

    Baumgartner, Stephan; Wolf, Martin; Skrabal, Peter; Bangerter, Felix; Heusser, Peter; Thurneysen, André; Wolf, Ursula

    2009-09-01

    Quantitative meta-analyses of randomized clinical trials investigating the specific therapeutic efficacy of homeopathic remedies yielded statistically significant differences compared to placebo. Since the remedies used contained mostly only very low concentrations of pharmacologically active compounds, these effects cannot be accounted for within the framework of current pharmacology. Theories to explain clinical effects of homeopathic remedies are partially based upon changes in diluent structure. To investigate the latter, we measured for the first time high-field (600/500 MHz) 1H T1 and T2 nuclear magnetic resonance relaxation times of H2O in homeopathic preparations with concurrent contamination control by inductively coupled plasma mass spectrometry (ICP-MS). Homeopathic preparations of quartz (10 c-30 c, n = 21, corresponding to iterative dilutions of 100-10-100-30), sulfur (13 x-30 x, n = 18, 10-13-10-30), and copper sulfate (11 c-30 c, n = 20, 100-11-100-30) were compared to n = 10 independent controls each (analogously agitated dilution medium) in randomized and blinded experiments. In none of the samples, the concentration of any element analyzed by ICP-MS exceeded 10 ppb. In the first measurement series (600 MHz), there was a significant increase in T1 for all samples as a function of time, and there were no significant differences between homeopathic potencies and controls. In the second measurement series (500 MHz) 1 year after preparation, we observed statistically significant increased T1 relaxation times for homeopathic sulfur preparations compared to controls. Fifteen out of 18 correlations between sample triplicates were higher for controls than for homeopathic preparations. No conclusive explanation for these phenomena can be given at present. Possible hypotheses involve differential leaching from the measurement vessel walls or a change in water molecule dynamics, i.e., in rotational correlation time and/or diffusion. Homeopathic preparations

  9. Muon spin relaxation and Moessbauer studies of iron pnictide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Klauss, Hans-Henning; Maeter, H.; Dellmann, T. [Technische Universitaet, Dresden (Germany); Luetkens, H.; Khasanov, R.; Amato, A. [PSI, Villigen (Switzerland); Pashkevich, Y. [Donetsk Phystech, NASU (Ukraine); Hess, C.; Klingeler, R.; Buechner, B. [IFW, Dresden (Germany); Leithe-Jasper, A.; Rosner, H.; Geibel, C.; Schnelle, W. [MPI-CPfS, Dresden (Germany); Braden, M. [Universitaet Koeln (Germany); Litterst, J. [Technische Universitaet, Braunschweig (Germany)

    2010-07-01

    We have determined the electronic phase diagrams and order parameters of ReO{sub 1-x}F{sub x}FeAs and (Sr,Eu)Fe{sub 2-x}Co{sub x}As{sub 2} superconductors. The results prove an important role of the structural distortion for the SDW magnetism and reveal two gap multiband superconductivity. We examined the interplay of iron and rare earth magnetic order in ReO{sub 1-x}F{sub x}FeAs. The undoped compounds show different magnetic coupling strength of the rare earth ion to the antiferromagnetic iron layers ranging from independent order to strong polarization of the rare earth moments by the ordered iron. Finally, we present recent studies on (Ca,Sr,Ba,Eu)Fe{sub 2}As{sub 2} and (Fe{sub 2}As{sub 2})(Sr{sub 4}T{sub 2}O{sub 6})based pnictide superconductors.

  10. Impact of opal nanoconfinement on electronic properties of sodium particles: NMR studies

    Energy Technology Data Exchange (ETDEWEB)

    Charnaya, E.V., E-mail: charnaya@live.com [Department of Physics, National Cheng Kung University, Tainan, 70101 Taiwan (China); Institute of Physics, St. Petersburg State University, St. Petersburg, 198504 (Russian Federation); Lee, M.K. [Department of Physics, National Cheng Kung University, Tainan, 70101 Taiwan (China); MoST Instrument Center at NCKU, Tainan, 70101 Taiwan (China); Chang, L.J. [Department of Physics, National Cheng Kung University, Tainan, 70101 Taiwan (China); Kumzerov, Yu.A.; Fokin, A.V. [A.F. Ioffe Physico-Technical Institute RAS, St. Petersburg, 194021 (Russian Federation); Samoylovich, M.I. [Moscow Institute of Physics and Technology, Moscow, 141700 (Russian Federation); Bugaev, A.S. [CSR Institute of Technology “Technomash”, Moscow, 121108 (Russian Federation)

    2015-03-20

    The {sup 23}Na Knight shift of NMR line which is highly correlated with the electron spin susceptibility and density of states at the Fermi level was studied for the sodium loaded opal. The measurements were carried out within a temperature range from 100 to 400 K for solid and melted confined sodium nanoparticles. The NMR line below 305 K was a singlet with the Knight shift reduced compared to that in bulk. Above this temperature the NMR line split reproducibly into two components with opposite trends in the Knight shift temperature dependences which evidenced a nanoconfinement-induced transformation and heterogeneity in the electron system. The findings were suggested to be related to changes in the topology of the Fermi surface.

  11. NMR and Infrared Study of Thermal Oxidation of cis-1, 4-Polybutadiene

    Science.gov (United States)

    Gemmer, Robert V.; Golub, Morton A.

    1978-01-01

    A study of the microstructural changes occuring in CB during thermal, uncatalyzed oxidation was carried out. Although the oxidation of CB is accompanied by extensive crosslinking with attendant insolubilization, it was found possible to follow the oxidation of solid CB directly with C-13 NMR spectroscopy. The predominant products appearing in the C-13 NMR spectra of oxidized CB are epoxides. The presence of lesser amounts of alcohols, peroxides, and carbonyl structures was adduced from complementary infrared and NMR spectra of soluble extracts obtained from the oxidized, crosslinked CB. This distribution of functional groups contrasts with that previously reported for the autooxidation of 1,4-polyisoprene. The difference was rationalized in terms of the relative stabilities of intermediate radical species involved in the autoxidation of CB and 1,4-polyisoprene.

  12. High-temperature NMR study of zeolite Na-A: Detection of a phase transition

    Energy Technology Data Exchange (ETDEWEB)

    Janssen, R.; Tijink, G.A.H.; Veeman, W.S.; Maesen, T.L.M.; van Lent, J.F. (Univ. of Nijmegen (Netherlands))

    1989-01-26

    The zeolite Linde 4A is studied by {sup 23}Na, {sup 27}al, and {sup 29}Si NMR at temperatures up to 953 K. {sup 23}Na NMR shows that the quadrupole interaction of sodium ions sited at 6-rings decreases when the temperature increases. With the aid of two-dimensional nutation and exchange experiments it can be shown that large-amplitude motions of the sodium ions, which in principle could explain a decrease of quadrupole interactions, do not occur. The decrease of the quadrupole interaction can be interpreted in terms of a phase transition. From a comparison of the NMR spectra of {sup 23}Na and {sup 27}Al it is concluded that the zeolite framework undergoes a major structural change upon increasing the temperature, before the sodium ions are displaced at higher temperatures. The exchange of sodium ions for potassium ions shifts this transition to higher temperatures.

  13. Solid-state NMR of polymers

    Energy Technology Data Exchange (ETDEWEB)

    Mirau, P

    2001-07-01

    Nuclear magnetic resonance (NMR) spectroscopy has emerged as one of the most important methods for the solid-state characterisation of polymers. The popularity of NMR is due to the fact that many molecular level features can be measured from the NMR spectra, including the polymer chain conformation, the morphology and the dynamics. The spectral features and relaxation times are affected by local interactions, so they provide information about the structure of polymers on a length scale (2-200 A) that is difficult to measure by other methods. In favourable cases, the NMR experiments provide a molecular-level explanation for the transitions observed by differential scanning calorimetry (DSC) and other methods, and the NMR properties can often be related to the bulk properties. Solid-state NMR has long been of interest in polymer science, and the first solid-state NMR studies of polymers were reported approximately a year after the discovery of nuclear resonance in bulk matter. It was reported in this initial study that the proton line width for natural rubber at room temperature is more like that of a mobile liquid than of a solid, but that the resonance broadens near the glass transition temperature (T{sub g}). This was recognised as being related to a change in chain dynamics above and below the T{sub g}. NMR methods developed rapidly after these initial observations, first for polymers in solution and, more recently, for polymers in the solid-state. Solid-state NMR studies of polymers were developed more slowly than their solution-state counterparts because solid-state NMR requires more specialised equipment. Solid-state NMR is now such an important tool that most modern spectrometers are capable of performing these studies. The interest in the NMR of solid polymers is due in part to the fact that most polymers are used in the solid state, and in many cases the NMR properties can be directly related to the macroscopic properties. Polymers have restricted mobility

  14. Enzyme dynamics from NMR spectroscopy.

    Science.gov (United States)

    Palmer, Arthur G

    2015-02-17

    CONSPECTUS: Biological activities of enzymes, including regulation or coordination of mechanistic stages preceding or following the chemical step, may depend upon kinetic or equilibrium changes in protein conformations. Exchange of more open or flexible conformational states with more closed or constrained states can influence inhibition, allosteric regulation, substrate recognition, formation of the Michaelis complex, side reactions, and product release. NMR spectroscopy has long been applied to the study of conformational dynamic processes in enzymes because these phenomena can be characterized over multiple time scales with atomic site resolution. Laboratory-frame spin-relaxation measurements, sensitive to reorientational motions on picosecond-nanosecond time scales, and rotating-frame relaxation-dispersion measurements, sensitive to chemical exchange processes on microsecond-millisecond time scales, provide information on both conformational distributions and kinetics. This Account reviews NMR spin relaxation studies of the enzymes ribonuclease HI from mesophilic (Escherichia coli) and thermophilic (Thermus thermophilus) bacteria, E. coli AlkB, and Saccharomyces cerevisiae triosephosphate isomerase to illustrate the contributions of conformational flexibility and dynamics to diverse steps in enzyme mechanism. Spin relaxation measurements and molecular dynamics (MD) simulations of the bacterial ribonuclease H enzymes show that the handle region, one of three loop regions that interact with substrates, interconverts between two conformations. Comparison of these conformations with the structure of the complex between Homo sapiens ribonuclease H and a DNA:RNA substrate suggests that the more closed state is inhibitory to binding. The large population of the closed conformation in T. thermophilus ribonuclease H contributes to the increased Michaelis constant compared with the E. coli enzyme. NMR spin relaxation and fluorescence spectroscopy have characterized a

  15. Studies on the Interactions between Potassium oxalato oxodiperoxovanadate and Histidine by NMR and MS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Multi-nuclear NMR and ESI-MS have been applied to study the interactions between oxalato-oxodiperoxovanadate and histidine in neutral solution. Coordination between the complex and histidine was monitored by 51V NMR. A pair of new isomers produced via vanadium atom binding separately to N1 and N3 of the imidazole ring of histidine was characterized by several spectroscopic methods. Experimental results show that the structure activity relationship of peroxovanadium complexes bearing organic ligands may be related to the specific recognition between peroxovanadium and histidine residue of tyrosine phosphatase.

  16. NMR and IR Studies on Eight Complexes of Eu with Three Kinds of Ligands

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Eight binary and ternary solid complexes of Eu3+ with pyridine-2, 6-dicarboxylic acid (H2DPC), 1,10-phen-anthroline (phen) and methylbenzoic acid (MBA), including o-MBA, m-MBA and p-MBA, were synthesised. Their compositions were confirmed by elemental analysis. The coordination mode of ligands with Eu3+ was studied by NMR and IR. The coordination number of eight complexes was also investigated. Furthermore, the influence on chemical shift and NMR spectrum shape by induction effect, screening effect and paramagnetic character of Eu3+ were discussed in detail.

  17. Lithium substitution in strontium chlorapatite studied by solid state NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Subramanian, S.; Sairam, T. N., E-mail: sai@igcar.gov.in; Amarendra, G. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102 (India); Maji, B. K.; Jena, H. [Chemical Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603102 (India)

    2016-05-23

    Strontium Chlorapatites with various amounts of Li substitution (Sr{sub 10-x}Li{sub x}(PO{sub 4}){sub 6}Cl{sub 2-δ}) were prepared by solid state reaction method and characterized by powder XRD and solid state NMR spectroscopy. XRD reveals shortening of lattice parameters upon Li incorporation. The linewidth of {sup 31}P solid state Magic Angle Spinning NMR spectra decreases with increase in Li content within the apatite phase. This study confirms Li uptake within the apatite phase.

  18. Variable temperature NMR studies on the conformations of tonalensin in solution

    Science.gov (United States)

    Ortega, Alfredo; Maldonado, Emma; Díaz, Eduardo; Reynolds, William F.

    1998-05-01

    NMR studies on tonalensin 1, a diterpene containing a ten membered ring, made evident the presence of three conformational isomers in solution. At room temperature compound 1 exists as a mixture of the conformers 1A and 1B in a ratio 1:1 in a CDC1 3 solution and 1.5:1 in a Me 2CO-d 6/DMSO-d 6 solution. At lower temperatures a third conformer, 1C, was detected. It was responsible for the line broadening observed for 1A. Temperature dependent 2D NMR experiments have been employed to elucidate the automerization of compound 1.

  19. {sup 11}B-NMR spectroscopic study on the interaction of epinephrine and p-BPA

    Energy Technology Data Exchange (ETDEWEB)

    Ichihara, K.; Yoshino, K. [Shinshu Univ., Department of Chemistry, Matsumoto, Nagano (Japan)

    2000-10-01

    It is studied that p-BPA (p-bronophenylalanine) which formed complex with catechol functional group has interaction with epinephrine by {sup 11}B-NMR. Two {sup 11}B-NMR resonance signals were observed at pH 7.0. The signal at 29.6 ppm is assigned to p-BPA and at 10.8 ppm is assigned to that of complex. We can determine complex formation constants (logK') in various pH. (author)

  20. 2H and 13C NMR studies on the temperature-dependent water and protein dynamics in hydrated elastin, myoglobin and collagen.

    Science.gov (United States)

    Lusceac, Sorin A; Vogel, Michael R; Herbers, Claudia R

    2010-01-01

    (2)H NMR spin-lattice relaxation and line-shape analyses are performed to study the temperature-dependent dynamics of water in the hydration shells of myoglobin, elastin, and collagen. The results show that the dynamical behaviors of the hydration waters are similar for these proteins when using comparable hydration levels of h=0.25-0.43. Since water dynamics is characterized by strongly nonexponential correlation functions, we use a Cole-Cole spectral density for spin-lattice relaxation analysis, leading to correlation times, which are in nice agreement with results for the main dielectric relaxation process observed for various proteins in the literature. The temperature dependence can roughly be described by an Arrhenius law, with the possibility of a weak crossover in the vicinity of 220 K. Near ambient temperatures, the results substantially depend on the exact shape of the spectral density so that deviations from an Arrhenius behavior cannot be excluded in the high-temperature regime. However, for the studied proteins, the data give no evidence for the existence of a sharp fragile-to-strong transition reported for lysozyme at about 220 K. Line-shape analysis reveals that the mechanism for the rotational motion of hydration waters changes in the vicinity of 220 K. For myoglobin, we observe an isotropic motion at high temperatures and an anisotropic large-amplitude motion at low temperatures. Both mechanisms coexist in the vicinity of 220 K. (13)C CP MAS spectra show that hydration results in enhanced elastin dynamics at ambient temperatures, where the enhancement varies among different amino acids. Upon cooling, the enhanced mobility decreases. Comparison of (2)H and (13)C NMR data reveals that the observed protein dynamics is slower than the water dynamics.

  1. Potentiometric and ³¹P NMR studies on inositol phosphates and their interaction with iron(III) ions.

    Science.gov (United States)

    Sala, Martin; Makuc, Damjan; Kolar, Jana; Plavec, Janez; Pihlar, Boris

    2011-03-01

    Potentiometric, conductometric and ³¹P NMR titrations have been applied to study interactions between myo-inositol hexakisphosphate (phytic acid), (±)-myo-inositol 1,2,3,5-tetrakisphosphate and (±)-myo-inositol 1,2,3-trisphosphate with iron(III) ions. Potentiometric and conductometric titrations of myo-inositol phosphates show that addition of iron increases acidity and consumption of hydroxide titrant. By increasing the Fe(III)/InsP(6) ratio (from 0.5 to 4) 3 mol of protons are released per 2 mol of iron(III). At first, phytates coordinate iron octahedrally between P2 and P1,3. The second coordination site represents P5 and neighbouring P4,6 phosphate groups. Complexation is accompanied with the deprotonation of P1,3 and P4,6 phosphate oxygens. At higher concentration of iron(III) intermolecular P-O-Fe-O-P bonds trigger formation of a polymeric network and precipitation of the amorphous Fe(III)-InsP(6) aggregates. (31)P NMR titration data complement the above results and display the largest chemical shift changes at pD values between 5 and 10 in agreement with strong interactions between iron and myo-inositol phosphates. The differences in T(1) relaxation times of phosphorous atoms have shown that phosphate groups at positions 1, 2 and 3 are complexated with iron(III). The interactions between iron(III) ions and inositol phosphates depend significantly on the metal to ligand ratio and an attempt to coordinate more than two irons per InsP(6) molecule results in an unstable heterogeneous system.

  2. Electronic properties of GeTe and Ag- or Sb-substituted GeTe studied by low-temperature 125Te NMR

    Science.gov (United States)

    Cui, J.; Levin, E. M.; Lee, Y.; Furukawa, Y.

    2016-08-01

    We have carried out 125Te nuclear magnetic resonance (NMR) in a wide temperature range of 1.5-300 K to investigate the electronic properties of Ge50Te50 ,Ag2Ge48Te50 , and Sb2Ge48Te50 from a microscopic point of view. From the temperature dependence of the NMR shift (K ) and nuclear spin lattice relaxation rate (1 /T1 ), we found that two bands contribute to the physical properties of the materials. One band overlaps the Fermi level providing the metallic state where no strong electron correlations are revealed by Korringa analysis. The other band is separated from the Fermi level by an energy gap of Eg/kB˜67 K, which gives rise to semiconductorlike properties. First-principles calculation reveals that the metallic band originates from the Ge vacancy while the semiconductorlike band is related to the fine structure of the density of states near the Fermi level. Low-temperature 125Te NMR data for the materials studied here clearly show that Ag substitution increases hole concentration while Sb substitution decreases it.

  3. Impact of electron-impurity scattering on the spin relaxation time in graphene: a first-principles study.

    Science.gov (United States)

    Fedorov, Dmitry V; Gradhand, Martin; Ostanin, Sergey; Maznichenko, Igor V; Ernst, Arthur; Fabian, Jaroslav; Mertig, Ingrid

    2013-04-12

    The effect of electron-impurity scattering on momentum and spin relaxation times in graphene is studied by means of relativistic ab initio calculations. Assuming carbon and silicon adatoms as natural impurities in graphene, we are able to simulate fast spin relaxation observed experimentally. We investigate the dependence of the relaxation times on the impurity position and demonstrate that C or Si adatoms act as real-space spin hot spots inducing spin-flip rates about 5 orders of magnitude larger than those of in-plane impurities. This fact confirms the hypothesis that the adatom-induced spin-orbit coupling leads to fast spin relaxation in graphene.

  4. NMR studies of the molecules dynamics to the solid-liquid interfaces: from graded porous materials to oil rocks; Etudes RMN de la dynamique des molecules aux interfaces solide-liquide: des materiaux poreux calibres aux roches petroliferes

    Energy Technology Data Exchange (ETDEWEB)

    Godefroy, S.

    2001-11-01

    Low field NMR relaxation for laboratory or in-situ applications provides critical information for oil recovery such as porosity, saturation, and permeability of rocks. In addition, pore size distribution and wettability can also be obtained in some cases. The technique relies on the measurement of proton longitudinal (T{sub 1}) or transverse (T{sub 2}) nuclear relaxation times. For better predictions, the surface micro-dynamics and the chemical properties of the liquids entrapped in the pore space are important and must be characterized. It is well known that the NMR relaxation is enhanced by the paramagnetic impurities at the pore surface but many other parameters influence the relaxation time distributions. These parameters are used to derive the petrophysical properties of the rocks. We propose here an original method to probe the dynamics of water and oil at the pore surface. In the present study, we used both nuclear relaxation at 2.2 MHz and field cycling Nuclear Magnetic Relaxation Dispersion (NMRD) techniques. We applied these two techniques to different kinds of water or oil saturated macroporous media (grain packings, outcrop and reservoir rocks with SiO{sub 2} or CaCO{sub 3} surfaces). We studied the dependence of NMR relaxation on pore size, magnetic field and temperature. Varying the pore size and the surface density of paramagnetic impurities of water saturated grain packings allowed experimental evidence for the two limiting regimes of the water relaxation in pores (surface- and diffusion-limited regimes). NMRD technique (evolution of 1/T{sub 1} with the magnetic field) allowed us to probe liquid surface dynamics in water or oil fully saturated grain packing, outcrop rocks or reservoir rocks (water- and oil-wet surfaces). We evidenced a two-dimensional molecular surface diffusion and directly estimated important parameters such as correlation times, residence times and molecular self-diffusion on the surface. Finally, we proved that the temperature

  5. Studies of the Active Sites for Methane Dehydroaromatization Using Ultrahigh-Field Solid-State Mo95 NMR Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jian Z.; Kwak, Ja Hun; Wang, Yong; Peden, Charles HF; Zheng, Heng; Ma, Ding; Bao, Xinhe

    2009-01-26

    Abstract It is found that the spin-lattice relaxation time, T1, corresponding to the surface exchanged molybdenum species in Mo/HZSM-5 catalysts is short, i.e., less than about 100ms at 21.1 T while the value of T1 for the crystallite MoO3 molecules is longer, i.e., about 30 s. Such a difference, more than two orders in magnitude, is utilized to differentiate the exchanged Mo species from the agglomerate MoO3 in Mo/HZSM-5 catalyst. An approximately linear correlation between the amount of exchanged species and the aromatics formation rate is obtained. This result significantly strengthens our prior conclusion that the exchanged Mo species are the active centers for the methane dehydroaromatization reaction on Mo/HZSM-5 catalysts (J. Am. Chem. Soc. 2008, 130, 3722-3723). Our results also suggest that one exchanged Mo atom anchors on two ion exchange sites and the exchanged Mo species on catalysts are possibly monomeric. Analyzing the linshapes obtained from both the 95Mo MAS and the static spectra indicates that the exchanged sites are heterogeneous, resulting in a significantly broadened MAS spectrum and essentially a featureless but nearly symmetric static lineshape for the exchanged Mo species. Furthermore, for crystallite MoO3 powder sample, the parameters related to the electric-field-gradient (EFG) tensor, the chemical shift anisotropy (CSA) and the three Euler angles required to align the CSA principal axis system with the quadrupolar principal axis system are determined by analyzing both the 95Mo MAS and the static spectra obtained at ultra-high field of 21.1 T. The new results obtained from this study on crystallite MoO3 powders should help to clarify some of the contradictions in prior literature reports from other groups. Key words: 95Mo NMR, MAS, relaxation, surface exchanged species, HZSM-5, electric-field-gradient (EFG), chemical shift anisotropy (CSA), active centers.

  6. Intracellular PHB conversion in a type II methanotroph studied by 13 C NMR

    NARCIS (Netherlands)

    Vecherskaya, M.; Dijkema, C.; Stams, A.J.M.

    2001-01-01

    Poly-g-hydroxybutyrate (PHB) formation under aerobic conditions via incorporation of [13C-2]acetate as a cosubstrate and its intracellular degradation under anaerobic conditions in a Type II methanotroph was studied by 13C NMR. During PHB synthesis in the presence of labelled acetate, low levels of

  7. MODERN NMR TECHNIQUES FOR THE STUDY OF LARGE PROTEINS IN SOLUTION

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    @@ A number of important methodological developments in high resolution NMR spectroscopy have led to significant increases in the size limitations that previously impeded solution structural studies of macromolecules. Specifically, isotope labeling and TROSY triple resonance spectroscopy has resulted in substantial sensitivity and resolution gain for applications to large molecular weight proteins.

  8. Complexation of roxatidine acetate hydrochloride with beta-cyclodextrin: NMR spectroscopic study.

    Science.gov (United States)

    Ali, S M; Maheshwari, A; Asmat, F

    2004-08-01

    A NMR spectroscopic study of mixtures of varying ratios of roxatidine acetate hydrochloride (RAH) and beta-cyclodextrin (beta-CD) in D2O revealed the formation of a 1:1 inclusion compound. The aromatic ring of RAH selectively penetrates the beta-CD cavity in preference to the piperidine ring.

  9. Solid-state NMR and ESR studies of activated carbons produced from pecan shells

    Science.gov (United States)

    Activated carbon from pecan shells has shown promise as an adsorbent in water treatment and sugar refining. However, the chemistry of the material is complex and not fully understood. We report here the application of solid state NMR and ESR to study the chemical structure, mobility, and pore volu...

  10. Positron annihilation lifetime spectroscopy study on the structural relaxation of phenylmethylsiloxane-modified epoxy hybrids at different aging temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Chia-Wen [Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan (China); Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan (China); Ma, Chen-Chi M., E-mail: ccma@che.nthu.edu.tw [Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan (China); Tan, Chung-Sung [Department of Chemical Engineering, National Tsing Hua University, Hsinchu, Taiwan (China); Li, Hsun-Tien [Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan (China)

    2015-07-15

    The cured network conformations and structural relaxation behaviours of the diglycidyl ether of bisphenol A (DGEBA)-methylhexahydrophthalic anhydride (MHHPA) modified with phenylmethylsiloxane-modified epoxy (PMSE) at different aging temperatures were studied using dynamic mechanical analysis (DMA) and positron annihilation lifetime spectroscopy (PALS). The DMA results revealed that the cured PMSE network can insert into the cured DGEBA network to form interpenetrating polymer networks (IPNs). The structural relaxation behaviours of DGEBA–PMSE-0.4 produced using DGEBA, PMSE, and MHHPA at a ratio of 0.6:0.4:1 by equivalent weight were studied using PALS at 150 °C and 55 °C. The aging-induced free volume relaxation parameters of DGEBA–PMSE-0.4 at 150 °C and 55 °C were investigated using the double additive exponential model and the Kohlrausch–Williams–Watts exponential model. For double additive exponential model, only one relaxation time (ζ) of 584.5 h was found at 150 °C; By contrast, there were two separate relaxation times of 37.4 h (ζ{sub 1}) and 753.6 h (ζ{sub 2}) at 55 °C. The ζ{sub 1} of the IPNs hybrid can be attributed to the network relaxation of PMSE, and the ζ{sub 2} can be attributed to the network relaxation of DGEBA at 55 °C. The results suggested the double additive exponential model can effectively predict DGEBA–PMSE hybrid relaxation behaviours. - Highlights: • The cured network conformations of DGEBA–PMSE hybrids were studied using DMA. • The structural relaxation behaviours of DGEBA–PMSE hybrids were studied using PALS. • The cured DGEBA–PMSE hybrids were interpenetrating polymer networks (IPNs). • PALS studies provided a quantitative demonstration of relaxation behaviours. • Double additive exponential model effectively predicted the relaxation times of hybrids.

  11. Study of relaxation and transport processes by means of AFM based dielectric spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Miccio, Luis A. [Centro de Física de Materiales CSIC-UPV/EHU, P. M. de Lardizabal 5, 20018 San Sebastian, Spain and Departamento de Física de Materiales UPV/EHU, Fac. de Química, 20080 San Sebastian (Spain); Schwartz, Gustavo A. [Centro de Física de Materiales CSIC-UPV/EHU, P. M. de Lardizabal 5, 20018 San Sebastian, Spain and Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 San Sebastian (Spain)

    2014-05-15

    Since its birth a few years ago, dielectric spectroscopy studies based on atomic force microscopy (AFM) have gained a growing interest. Not only the frequency and temperature ranges have become broader since then but also the kind of processes that can be studied by means of this approach. In this work we analyze the most adequate experimental setup for the study of several dielectric processes with a spatial resolution of a few nanometers by using force mode AFM based dielectric spectroscopy. Proof of concept experiments were performed on PS/PVAc blends and PMMA homopolymer films, for temperatures ranging from 300 to 400 K. Charge transport processes were also studied by this approach. The obtained results were analyzed in terms of cantilever stray contribution, film thickness and relaxation strength. We found that the method sensitivity is strongly coupled with the film thickness and the relaxation strength, and that it is possible to control it by using an adequate experimental setup.

  12. NMR of geophysical drill cores with a mobile Halbach scanner

    Energy Technology Data Exchange (ETDEWEB)

    Talnishnikh, E.

    2007-08-21

    This thesis is devoted to a mobile NMR with an improved Halbach scanner. This is a lightweight tube-shaped magnet with sensitive volume larger and a homogeneity of the magnetic field higher than the previous prototype version. The improved Halbach scanner is used for analysis of water-saturated drill cores and plugs with diameters up to 60 mm. To provide the analysis, the standard 1D technique with the CPMG sequence as well as 2D correlation experiments were successfully applied and adapted to study properties of fluid-saturated sediments. Afterwards the Halbach scanner was calibrated to fast non-destructive measurements of porosity, relaxation time distributions, and estimation of permeability. These properties can be calculated directly from the NMR data using the developed methodology. Any independent measurements of these properties with other methods are not needed. One of the main results of this work is the development of a new NMR on-line core scanner for measurements of porosity in long cylindrical and semi cylindrical drill cores. Also dedicated software was written to operate the NMR on-line core scanner. The physical background of this work is the study of the diffusion influence on transverse relaxation. The diffusion effect in the presence of internal gradients in porous media was probed by 1D and 2D experiments. The transverse relaxation time distributions obtained from 1D and from 2D experiments are comparable but different in fine details. Two new methodologies were developed based on the results of this study. First is the methodology quantifying the influence of diffusion in the internal gradients of water-saturated sediments on transverse relaxation from 2D correlation experiments. The second one is the correction of the permeability estimation from the NMR data taking in account the influence of the diffusion. Furthermore, PFG NMR technique was used to study restricted diffusion in the same kind of samples. Preliminary results are reported

  13. High-resolution study of nuclear magnetic relaxation dispersion of purine nucleotides: effects of spin-spin coupling.

    Science.gov (United States)

    Kiryutin, Alexey; Ivanov, Konstantin; Yurkovskaya, Alexandra; Vieth, Hans-Martin

    2008-01-01

    By combining magnetic field cycling in the range from 0.1mT to 7T with high-resolution NMR detection the T(1) relaxation dispersion (nuclear magnetic relaxation dispersion (NMRD)) of protons in the nucleotides adenosine mono-phosphate and guanosine mono-phosphate was measured in a site-specific way. While at high field the individual spins have distinctly different T(1) times, their scalar spin-spin interaction fulfills at low field the condition of strong coupling and leads to convergence of their T(1) dispersion curves. In addition, the spin-spin coupling can lead to oscillatory components in the relaxation kinetics traceable to a coupling between spin polarization and coherence in the relaxation process. As a consequence the NMRD curves do not directly reflect the spectral density function of the motional processes, but the effects of motion and spin coupling must be separated for a reliable evaluation. A theoretical approach is described allowing such an analysis.

  14. NMR characterization of hydrocarbon adsorption on calcite surfaces: A first principles study

    Energy Technology Data Exchange (ETDEWEB)

    Bevilaqua, Rochele C. A.; Miranda, Caetano R. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, UFABC, Santo André, SP (Brazil); Rigo, Vagner A. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, UFABC, Santo André, SP (Brazil); Universidade Tecnológica Federal do Paraná, UTFPR, Cornélio Procópio, PR (Brazil); Veríssimo-Alves, Marcos [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, UFABC, Santo André, SP (Brazil); Departamento de Física, ICEx, Universidade Federal Fluminense, UFF, Volta Redonda, RJ (Brazil)

    2014-11-28

    The electronic and coordination environment of minerals surfaces, as calcite, are very difficult to characterize experimentally. This is mainly due to the fact that there are relatively few spectroscopic techniques able to detect Ca{sup 2+}. Since calcite is a major constituent of sedimentary rocks in oil reservoir, a more detailed characterization of the interaction between hydrocarbon molecules and mineral surfaces is highly desirable. Here we perform a first principles study on the adsorption of hydrocarbon molecules on calcite surface (CaCO{sub 3} (101{sup ¯}4)). The simulations were based on Density Functional Theory with Solid State Nuclear Magnetic Resonance (SS-NMR) calculations. The Gauge-Including Projector Augmented Wave method was used to compute mainly SS-NMR parameters for {sup 43}Ca, {sup 13}C, and {sup 17}O in calcite surface. It was possible to assign the peaks in the theoretical NMR spectra for all structures studied. Besides showing different chemical shifts for atoms located on different environments (bulk and surface) for calcite, the results also display changes on the chemical shift, mainly for Ca sites, when the hydrocarbon molecules are present. Even though the interaction of the benzene molecule with the calcite surface is weak, there is a clearly distinguishable displacement of the signal of the Ca sites over which the hydrocarbon molecule is located. A similar effect is also observed for hexane adsorption. Through NMR spectroscopy, we show that aromatic and alkane hydrocarbon molecules adsorbed on carbonate surfaces can be differentiated.

  15. T2-Filtered T2 - T2 Exchange NMR

    Science.gov (United States)

    d'Eurydice, Marcel Nogueira; Montrazi, Elton Tadeu; Fortulan, Carlos Alberto; Bonagamba, Tito José

    2016-05-01

    This work introduces an alternative way to perform the T2 - T2 Exchange NMR experiment. Rather than varying the number of π pulses in the first CPMG cycle of the T2 - T2 Exchange NMR pulse sequence, as used to obtain the 2D correlation maps, it is fixed and small enough to act as a short T2-filter. By varying the storage time, a set of 1D measurements of T2 distributions can be obtained to reveal the effects of the migration dynamics combined with relaxation effects. This significantly reduces the required time to perform the experiment, allowing a more in-depth study of exchange dynamics and relaxation processes with improved signal-to-noise ratio. These aspects stand as basis of this novel experiment, T2-Filtered T2 - T2 Exchange NMR or simply T2 F-TREx.

  16. The therapeutically anti-prion active antibody-fragment scFv-W226: paramagnetic relaxation-enhanced NMR spectroscopy aided structure elucidation of the paratope-epitope interface.

    Science.gov (United States)

    Mangels, Christian; Kellner, Ruth; Einsiedel, Jürgen; Weiglmeier, Philipp R; Rosch, Paul; Gmeiner, Peter; Schwarzinger, Stephan

    2010-08-01

    Antibodies have become indispensable reagents with numerous applications in biological and biotechnical analysis, in diagnostics as well as in therapy. In all cases, selective interaction with an epitope is crucial and depends on the conformation of the paratope. While epitopes are routinely mapped at high throughput, methods revealing structural insights on a rather short timescale are rare. We here demonstrate paramagnetic relaxation-enhanced (PRE) NMR spectroscopy to be a powerful tool unraveling structural information about epitope-orientation in a groove spanned by the complementary determining regions. In particular, we utilize the spin label TOAC, which is fused to the peptidic epitope using standard solid-phase chemistry and which is characterized by a reduced mobility compared to, e.g., spin labels attached to the side-chain functionalities of cysteine or lysine residues. We apply the method to determine the orientation of helix 1 of the prion protein, which is the epitope for the therapeutically anti-prion active scF(v) fragment W226.

  17. Uterus-Relaxing Study of a Sudanese Herb (El-Hazha

    Directory of Open Access Journals (Sweden)

    Aimun A.E. Ahmed

    2010-01-01

    Full Text Available Problem statement: The aim of this study is to investigate the pharmacological effects of the Methanolic-extract (AH2 of El-Hazha and its sub-fractions. Approach: These investigations were carried out on in vitro isolated uterus preparations from Non-Pregnant (NP and Late-Pregnant rats (LP. In parallel displacement radio-ligand binding assay was performed for â-Adrenergic Receptors (â-ADR. Results: Showed that the herb and its different fractions produced dose-dependent relaxant effect (pConclusion: We validate the fractionation effect on its relaxant activity and found partial role for â-ADR on mediating this activity. Future study was recommended to isolate and investigate its active components to enhance this activity or to discover a new novel natural therapeutic agent(s.

  18. Effect of massage therapy on pain, anxiety, relaxation, and tension after colorectal surgery: A randomized study.

    Science.gov (United States)

    Dreyer, Nikol E; Cutshall, Susanne M; Huebner, Marianne; Foss, Diane M; Lovely, Jenna K; Bauer, Brent A; Cima, Robert R

    2015-08-01

    The purpose of this randomized controlled trial was to evaluate the effect of postoperative massage in patients undergoing abdominal colorectal surgery. One hundred twenty-seven patients were randomized to receive a 20-min massage (n = 61) or social visit and relaxation session (no massage; n = 66) on postoperative days 2 and 3. Vital signs and psychological well-being (pain, tension, anxiety, satisfaction with care, relaxation) were assessed before and after each intervention. The study results indicated that postoperative massage significantly improved the patients' perception of pain, tension, and anxiety, but overall satisfaction was unchanged. In conclusion, massage may be beneficial during postoperative recovery for patients undergoing abdominal colorectal surgery. Further studies are warranted to optimize timing and duration and to determine other benefits in this clinical setting.

  19. Solution NMR studies on Helicobacter pylori proteins for antibiotic target discovery.

    Science.gov (United States)

    Lee, Ki-Young; Lee, Bong-Jin

    2016-07-01

    Helicobacter pylori (H. pylori) is a well-known widespread pathogenic bacterium that survives in the extremely acidic conditions of the human gastric mucosa. The global prevalence of H. pylori-resistant antibiotics has become an emerging issue in the 21st century and has necessitated the development of novel antibiotic drugs. Many efforts have aimed to discover antibiotic target proteins of H. pylori based on its genome of more than 1600 genes. This article highlights NMR spectroscopy as a valuable tool for determining the structure and dynamics of potential antibiotic-targeted proteins of H. pylori and evaluating their modes of interaction with native or synthetic binding partners. The residue-specific information on binding in solution provides a structural basis to identify and optimize lead compounds. NMR spectroscopy is a powerful method for obtaining details of biomolecular interactions with a broad range of binding affinities. This strength facilitates the identification of the binding interface of the encounter complex that plays an integral role in a variety of biological functions. This low-affinity complex is difficult to crystallize, which impedes structure determination using X-ray crystallography. Additionally, the relative binding affinities can be predicted from the type of spectral change upon binding. High-resolution NMR spectroscopy in combination with advanced computer simulation would provide more confidence in complex structures. The application of NMR to studies of the H. pylori protein could contribute to the development of these targeted novel antibiotics.

  20. Homonuclear 1H NMR and circular dichroism study of the HIV-1 Tat Eli variant

    Science.gov (United States)

    Watkins, Jennifer D; Campbell, Grant R; Halimi, Hubert; Loret, Erwann P

    2008-01-01

    Background The HIV-1 Tat protein is a promising target to develop AIDS therapies, particularly vaccines, due to its extracellular role that protects HIV-1-infected cells from the immune system. Tat exists in two different lengths, 86 or 87 residues and 99 or 101 residues, with the long form being predominant in clinical isolates. We report here a structural study of the 99 residue Tat Eli variant using 2D liquid-state NMR, molecular modeling and circular dichroism. Results Tat Eli was obtained from solid-phase peptide synthesis and the purified protein was proven biologically active in a trans-activation assay. Circular dichroism spectra at different temperatures up to 70°C showed that Tat Eli is not a random coil at 20°C. Homonuclear 1H NMR spectra allowed us to identify 1639 NMR distance constraints out of which 264 were interresidual. Molecular modeling satisfying at least 1474 NMR constraints revealed the same folding for different model structures. The Tat Eli model has a core region composed of a part of the N-terminus including the highly conserved Trp 11. The extra residues in the Tat Eli C-terminus protrude from a groove between the basic region and the cysteine-rich region and are well exposed to the solvent. Conclusion We show that active Tat variants share a similar folding pattern whatever their size, but mutations induce local structural changes. PMID:18808674

  1. {sup 1}H NMR spectroscopic studies establish that heparanase is a retaining glycosidase

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, Jennifer C., E-mail: jennifer.wilson@griffith.edu.au [Institute for Glycomics, Griffith University Gold Coast Campus, QLD 4222 (Australia); Laloo, Andrew Elohim [School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072 (Australia); Singh, Sanjesh [Institute for Glycomics, Griffith University Gold Coast Campus, QLD 4222 (Australia); Ferro, Vito, E-mail: v.ferro@uq.edu.au [School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072 (Australia)

    2014-01-03

    Highlights: •{sup 1}H and {sup 13}C NMR chemical shifts of fondaparinux were fully assigned by 1D and 2D NMR techniques. •Hydrolysis of fondaparinux by heparanase was monitored by {sup 1}H NMR spectroscopy. •Heparanase is established to be a retaining glycosidase. -- Abstract: Heparanase is an endo-β-glucuronidase that cleaves heparan sulfate side chains of proteoglycans in basement membranes and the extracellular matrix (ECM). Heparanase is implicated in several diverse pathological processes associated with ECM degradation such as metastasis, inflammation and angiogenesis and is thus an important target for anti-cancer and anti-inflammatory drug discovery. Heparanase has been classed as belonging to the clan A glycoside hydrolase family 79 based on sequence analysis, secondary structure predictions and mutagenic analysis, and thus it has been inferred that it is a retaining glycosidase. However, there has been no direct experimental evidence to support this conclusion. Herein we describe {sup 1}H NMR spectroscopic studies of the hydrolysis of the pentasaccharide substrate fondaparinux by heparanase, and provide conclusive evidence that heparanase hydrolyses its substrate with retention of configuration and is thus established as a retaining glycosidase. Knowledge of the mechanism of hydrolysis may have implications for future design of inhibitors for this important drug target.

  2. High resolution NMR theory and chemical applications

    CERN Document Server

    Becker, Edwin D

    1969-01-01

    High Resolution NMR: Theory and Chemical Applications focuses on the applications of nuclear magnetic resonance (NMR), as well as chemical shifts, lattices, and couplings. The book first offers information on the theory of NMR, including nuclear spin and magnetic moment, spin lattice relaxation, line widths, saturation, quantum mechanical description of NMR, and ringing. The text then ponders on instrumentation and techniques and chemical shifts. Discussions focus on the origin of chemical shifts, reference compounds, empirical correlations of chemical shifts, modulation and phase detection,

  3. STUDY ON SYNTHESIS AND RELAXIVITY OF PARAMAGNETIC POLYESTER METAL COMPLEXES FOR MRI

    Institute of Scientific and Technical Information of China (English)

    Ouyangming; ZhuoRenxi; 等

    1995-01-01

    Fifteen new polyester ligands were prepared by copolymerization of EDTA (ethylenediaminetertraacetic acid)dianhydride or DTPA (diethylenetriamine pentaacetic acid) dianhydride and dihydric alcohol or dihydric phenol.Their paramagnetic metal complexes were also synthesized.All polyester ligands and metal complexes were characterized by 1HNMR,IR spectra and elemental analyses.Preliminary study showed that the polyester metal complexes had higher relaxation effectiveness as compared to corresponding small molecular metal complexes.

  4. Structural relaxation mechanisms in liquid Eugenol. A depolarized light scattering study

    Science.gov (United States)

    Bezot, P.; Hesse-Bezot, C.; Roynard, D.; Jeanneaux, F.

    1988-07-01

    A depolarized light scattering study of liquid Eugenol, over a large temperature range including the supercooled region, is proposed. Comparisons with shear mechanical impedance measurements, obtained at lower frequencies, lead to more precise information on the viscoelastic parameters in the supercooled region. The structural relaxation process measurements by means of the photon correlation technique are compared to the dielectric and mechanical measurements. Molecular mechanisms are proposed.

  5. Incorporation of antimicrobial peptides into membranes: a combined liquid-state NMR and molecular dynamics study of alamethicin in DMPC/DHPC bicelles.

    Science.gov (United States)

    Dittmer, Jens; Thøgersen, Lea; Underhaug, Jarl; Bertelsen, Kresten; Vosegaard, Thomas; Pedersen, Jan M; Schiøtt, Birgit; Tajkhorshid, Emad; Skrydstrup, Troels; Nielsen, Niels Chr

    2009-05-14

    Detailed insight into the interplay between antimicrobial peptides and biological membranes is fundamental to our understanding of the mechanism of bacterial ion channels and the action of these in biological host-defense systems. To explore this interplay, we have studied the incorporation, membrane-bound structure, and conformation of the antimicrobial peptide alamethicin in lipid bilayers using a combination of 1H liquid-state NMR spectroscopy and molecular dynamics (MD) simulations. On the basis of experimental NMR data, we evaluate simple in-plane and transmembrane incorporation models as well as pore formation for alamethicin in DMPC/DHPC (1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine/1,2-dihexanoyl-sn-glycero-3-phosphatidylcholine) bicelles. Peptide-lipid nuclear Overhauser effect (NOE) and paramagnetic relaxation enhancement (PRE) data support a transmembrane configuration of the peptide in the bilayers, but they also reveal that the system cannot be described by a single simple conformational model because there is a very high degree of dynamics and heterogeneity in the three-component system. To explore the origin of this heterogeneity and dynamics, we have compared the NOE and PRE data with MD simulations of an ensemble of alamethicin peptides in a DMPC bilayer. From all-atom MD simulations, the contacts between peptide, lipid, and water protons are quantified over a time interval up to 95 ns. The MD simulations provide a statistical base that reflects our NMR data and even can explain some initially surprising NMR results concerning specific interactions between alamethicin and the lipids.

  6. The study of magnetic properties and relaxation processes in Co/Au bimetallic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hrubovčák, Pavol [Department of Condensed Matter Physics, P.J. Šafárik University, Park Angelinum 9, Košice (Slovakia); Zeleňáková, Adriana, E-mail: adriana.zelenakova@upjs.sk [Department of Condensed Matter Physics, P.J. Šafárik University, Park Angelinum 9, Košice (Slovakia); Zeleňák, Vladimir [Department of Inorganic Chemistry, P.J. Šafárik University, Moyzesova 11, Košice (Slovakia); Kováč, Jozef [Institute of Experimental Physics, SAS, Watsonova 41, Košice (Slovakia)

    2015-11-15

    Co/Au bimetallic fine nanoparticles were prepared employing the method of microemulsion using reverse micelle as nanoreactor, controlling the particles size. Magnetic and structural properties of two different samples Co/Au1 and Co/Au2 with almost comparable size of Co core and different size of Au layer were studied. The investigation of magnetic relaxation processes present in the particles was carried out by means of ac and dc magnetization data obtained at different temperatures and magnitudes of magnetic field. We observed the existence of superspin glass state characterized by the strong inter-particle interactions in the nanoparticle systems. In this paper, we discuss the attributes of novel superspin glass magnetic state reflected on various features (saturated FC magnetization at low temperatures, shift of the Cole–Cole arc downwards) and calculated parameters (relaxation time, critical exponent zv ∼ 10 and frequency dependent criterion p < 0.05). Comparison of the magnetic properties of two studied samples show that the thickness of diamagnetic Au shell significantly influences the magnetic interactions and change the relaxation dynamics. - Highlights: • Co/Au fine nanoparticles prepared by reverse micelle as nanoreactor, controlling the size. • Existence of superspin glass state confirmed from ac magnetic susceptibility study. • Individual particles exhibit the collective behavior below glass temperature T{sub SSG}. • Influence of diamagnetic shell on the magnetic properties of core–shell nanoparticles.

  7. Exercise and relaxation intervention for patients with advanced lung cancer: a qualitative feasibility study.

    Science.gov (United States)

    Adamsen, L; Stage, M; Laursen, J; Rørth, M; Quist, M

    2012-12-01

    Lung cancer patients experience loss of physical capacity, dyspnea, pain, reduced energy and psychological distress. The aim of this study was to explore feasibility, health benefits and barriers of exercise in former sedentary patients with advanced stage lung cancer, non-small cell lung cancer (NSCLC) (III-IV) and small cell lung cancer (SCLC) (ED), undergoing chemotherapy. The intervention consisted of a hospital-based, supervised, group exercise and relaxation program comprising resistance-, cardiovascular- and relaxation training 4 h weekly, 6 weeks, and a concurrent unsupervised home-based exercise program. An explorative study using individual semi-structured interviews (n=15) and one focus group interview (n=8) was conducted among the participants. Throughout the intervention the patients experienced increased muscle strength, improvement in wellbeing, breathlessness and energy. The group exercise and relaxation intervention showed an adherence rate of 76%, whereas the patients failed to comply with the home-based exercise. The hospital-based intervention initiated at time of diagnosis encouraged former sedentary lung cancer patients to participation and was undertaken safely by cancer patients with advanced stages of disease, during treatment. The patients experienced physical, functional and emotional benefits. This study confirmed that supervised training in peer-groups was beneficial, even in a cancer population with full-blown symptom burden and poor prognosis.

  8. Myowater dynamics and protein secondary structural changes as affected by heating rate in three pork qualities: a combined FT-IR microspectroscopic and 1H NMR relaxometry study.

    Science.gov (United States)

    Wu, Zhiyun; Bertram, Hanne Christine; Böcker, Ulrike; Ofstad, Ragni; Kohler, Achim

    2007-05-16

    The objective of this study was to investigate the influence of heating rate on myowater dynamics and protein secondary structures in three pork qualities by proton NMR T2 relaxation and Fourier transform infrared (FT-IR) microspectroscopy measurements. Two oven temperatures at 100 degrees C and 200 degrees C corresponding to slow and fast heating rates were applied on three pork qualities (DFD, PSE, and normal) to an internal center temperature of 65 degrees C. The fast heating induced a higher cooking loss, particularly for PSE meat. The water proton T21 distribution representing water entrapped within the myofibrillar network was influenced by heating rate and meat quality. Fast heating broadened the T21 distribution and decreased the relaxation times of the T21 peak position for three meat qualities. The changes in T21 relaxation times in meat can be interpreted in terms of chemical and diffusive exchange. FT-IR showed that fast heating caused a higher gain of random structures and aggregated beta-sheets at the expense of native alpha-helixes, and these changes dominate the fast-heating-induced broadening of T21 distribution and reduction in T21 times. Furthermore, of the three meat qualities, PSE meat had the broadest T21 distribution and the lowest T21 times for both heating rates, reflecting that the protein aggregation of PSE caused by heating is more extensive than those of DFD and normal, which is consistent with the IR data. The present study demonstrated that the changes in T2 relaxation times of water protons affected by heating rate and raw meat quality are well related to the protein secondary structural changes as probed by FT-IR microspectroscopy.

  9. Enhancement of relaxation rates in the normal state of superconductor PuRhGa{sub 5}:NQR relaxation study

    Energy Technology Data Exchange (ETDEWEB)

    Sakai, H. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)]. E-mail: sakai.hironori@jaea.go.jp; Kambe, S. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Tokunaga, Y. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Fujimoto, T. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Walstedt, R.E. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Yasuoka, H. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Aoki, D. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Homma, Y. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Yamamoto, E. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Nakamura, A. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Shiokawa, Y. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Nakajima, K. [Department of Nuclear Energy System, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Arai, Y. [Department of Nuclear Energy System, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Matsuda, T.D. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Haga, Y. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Onuki, Y. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)

    2007-03-15

    The spin-lattice relaxation rates (1/T{sub 1}) have been measured under zero field using nuclear quadrupole resonance (NQR) lines in superconductor PuRhGa{sub 5} and Pauli-paramagnet LuCoGa{sub 5}. In the reference LuCoGa{sub 5} with fully-occupied 4f shell, the 1/T{sub 1} shows the constant behavior of (T{sub 1}T){sup -1}=0.495+/-0.002(sK){sup -1}. On the other hand, in PuRhGa{sub 5}, 1/T{sub 1} is much larger than in LuCoGa{sub 5} and the 1/T{sub 1}{proportional_to}T behavior below {approx}30K is seen, where its (T{sub 1}T){sup -1} value is 3.27+/-0.005(sK){sup -1}. These results suggest a development of coherent Fermi liquid state incorporated with 5f electrons below {approx}30K in PuRhGa{sub 5}.

  10. Dynamic processes and chemical composition of Lepidium sativum seeds determined by means of field-cycling NMR relaxometry and NMR spectroscopy.

    Science.gov (United States)

    Rachocki, A; Latanowicz, L; Tritt-Goc, J

    2012-12-01

    Proton nuclear magnetic resonance (NMR) techniques, such as field-cycling relaxometry, wide-line NMR spectroscopy, and magic angle spinning NMR spectroscopy, were applied to study the seeds of cress, Lepidium sativum. Field-cycling NMR relaxometry was used for the first time to investigate the properties of the whole molecular system of dry cress seeds. This method not only allowed the dynamics to be studied, but was also successful in the differentiation among the solid (i.e., carbohydrates, proteins, or fats forming a solid form of lipids) and liquid-like (oil compounds) components of the seeds. The (1)H NMR relaxation dispersion of oils was interpreted as a superposition of intramolecular and intermolecular contributions. The intramolecular part was described in terms of a Lorentzian spectral density function, whereas a log-Gaussian distribution of correlation times was applied for the intermolecular dipole-dipole contribution. The models applied led to very good agreement with the experimental data and demonstrate that the contribution of the intermolecular relaxation to the overall relaxation should not be disregarded, especially at low frequencies. A power-law frequency dependence of the proton relaxation dispersion was used for the interpretation of the solid components. From the analysis of the (1)H wide-line NMR spectra of the liquid-like component of hydrated cress seeds, we can conclude that the contribution of oil protons should always be taken into account when evaluating the spin-lattice relaxation times values or measuring the moisture and oil content. The application of (1)H magic angle spinning NMR significantly improves resolution in the liquid-like spectrum of seeds and allows the determination of the chemical composition of cress seeds.

  11. Structural relaxation in the hydrogen-bonding liquids N-methylacetamide and water studied by optical Kerr-effect spectroscopy

    CERN Document Server

    Turton, David A; 10.1063/1.2897432

    2009-01-01

    Structural relaxation in the peptide model N-methylacetamide (NMA) is studied experimentally by ultrafast optical Kerr-effect spectroscopy over the normal-liquid temperature range and compared to the relaxation measured in water at room temperature. It is seen that in both hydrogen-bonding liquids, beta relaxation is present and in each case it is found that this can be described by the Cole-Cole function. For NMA in this temperature range, the alpha and beta relaxations are each found to have an Arrhenius temperature dependence with indistinguishable activation energies. It is known that the variations on the Debye function, including the Cole-Cole function, are unphysical, and we introduce two general modifications: one allows for the initial rise of the function, determined by the librational frequencies, and the second allows the function to be terminated in the alpha relaxation.

  12. Structural relaxation in the hydrogen-bonding liquids N-methylacetamide and water studied by optical Kerr effect spectroscopy.

    Science.gov (United States)

    Turton, David A; Wynne, Klaas

    2008-04-21

    Structural relaxation in the peptide model N-methylacetamide (NMA) is studied experimentally by ultrafast optical Kerr effect spectroscopy over the normal-liquid temperature range and compared to the relaxation measured in water at room temperature. It is seen that in both hydrogen-bonding liquids, beta relaxation is present, and in each case, it is found that this can be described by the Cole-Cole function. For NMA in this temperature range, the alpha and beta relaxations are each found to have an Arrhenius temperature dependence with indistinguishable activation energies. It is known that the variations on the Debye function, including the Cole-Cole function, are unphysical, and we introduce two general modifications: One allows for the initial rise of the function, determined by the librational frequencies, and the second allows the function to be terminated in the alpha relaxation.

  13. Structure and Dynamics in Amphiphilic Bilayers: NMR and MD simulation Studies

    OpenAIRE

    2013-01-01

    Solid-state nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) simulations were employed to study molecular structure and dynamics in amphiphilic bilayers. This thesis reports on method development and practical applications to two types of bilayer systems: simple cell membrane models composed of phosphatidylcholine lipids and cholesterol; and liquid crystals composed of ethyleneoxide-based surfactants often used in technological applications and in fundamental studies ...

  14. Enzymatic synthesis and NMR studies of acylated sucrose acetates

    NARCIS (Netherlands)

    Steverink-De Zoete, M.C.; Kneepkens, M.F.M.; Waard, de P.; Woudenberg-van Oosterom, M.; Gotlieb, K.F.; Slaghek, T.

    1999-01-01

    The lipase-catalyzed esterification of partially acetylated sucrose has been studied. It was shown that the chemical acetylation increased the reaction rate of the subsequent enzymatic acylation. Thus it was possible to perform the enzymatic acylation in the absence of solvents while underivatized s

  15. NMR Study of Damage on Isolated Perfused Rat Heart Exposed to Ischemia and Hypoxia

    Institute of Scientific and Technical Information of China (English)

    罗雪春; 闫永彬; 张日清; 王小寅; 范礼理

    2001-01-01

    Myocardial ischemia is the most common and primary cause of myocardium damage. Numerous conventional techniques and methods have been developed for ischemia and reperfusion studies. However, because of damage to the heart sample, most of these techniques can not be used to continuously monitor the full dynamic course of the myocardial metabolic pathway. The nuclear magnetic resonnance (NMR) surface coil technique, which overcomes the limitations of conventional instrumentation, can be used to quantitatively study every stage of the perfused heart (especially after perfusion stoppage) continuously, dynamically, and without damage under normal or designed physiological conditions at the molecular level. In this paper, 31p-NMR was used to study the effects of ischemia and hypoxia on isolated perfused hearts. The results show that complete hypoxia caused more severe functional damage to the myocardial cells than complete ischemia.

  16. 14N NMR Spectroscopy Study of Binding Interaction between Sodium Azide and Hydrated Fullerene

    Directory of Open Access Journals (Sweden)

    Tamar Chachibaia

    2017-04-01

    Full Text Available Our study is the first attempt to study the interaction between NaN3 and hydrated fullerenes C60 by means of a non-chemical reaction-based approach. The aim is to study deviations of signals obtained by 14N NMR spectroscopy to detect the binding interaction between sodium azide and hydrated fullerene. We considered 14N NMR spectroscopy as one of the most suitable methods for the characterization of azides to show resonance signals corresponding to the three non-equivalent nitrogen atoms. The results demonstrate that there are changes in the chemical shift positions and line-broadening, which are related to the different molar ratios of NaN3:C60 in the samples.

  17. Electronic relaxation dynamics of PCDA-PDA studied by transient absorption spectroscopy.

    Science.gov (United States)

    Joung, Joonyoung F; Baek, Junwoo; Kim, Youngseo; Lee, Songyi; Kim, Myung Hwa; Yoon, Juyoung; Park, Sungnam

    2016-08-17

    Photo-curable polymers originating from 10,12-pentacosadiynoic acid (PCDA-PDA) are commonly used polydiacetylenes (PDAs). PCDA-PDA exhibits thermochromic properties undergoing a unique colorimetric transition from blue to red as the temperature is increased from low to high. In this work, we have carefully studied the temperature-dependent optical properties of PCDA-PDA by using UV-visible absorption, FTIR, Raman, and transient absorption (TA) spectroscopy in combination with quantum chemical calculations. Temperature-dependent UV-visible absorption spectra indicate that PCDA-PDA exhibits reversible thermochromic properties up to 60 °C and its thermochromic properties become irreversible above 60 °C. Such distinct thermochromic properties are also manifested in TA signals so that the electronically excited PCDA-PDA relaxes to the ground state via an intermediate state at 20 °C (blue form) but it relaxes directly back to the ground state at 80 °C (red form). The electronic relaxation dynamics of PCDA-PDA are comprehensively analyzed based on different kinetic models by using the global fitting analysis method. The intermediate state in the blue form of PCDA-PDA is clearly found to be responsible for fluorescence quenching. FTIR and Raman spectroscopy and quantum chemical calculations confirm that the H-bonds between the carboxylic acid groups in PCDA-PDA are broken at high temperatures leading to an irreversible structural change of PCDA-PDA.

  18. A COMPARATIVE STUDY ON EFFECTIVENESS OF STATIC STRETCH AND HOLD RELAX TECHNIQUES OVER HAMSTRING FLEXIBILITY

    Directory of Open Access Journals (Sweden)

    N. Vamsidhar

    2014-12-01

    Full Text Available Background: Flexibility is important in prevention of injury, muscular and postural imbalance more over the Hamstring flexibility has a lion share in sports performances and preventing DOMS. Stretching procedures increases the ROM by embarking on biomechanics and Neurologic and molecular mechanics. Hamstrings, the two joint muscle plays a crucial role in two joints integrity and also spine as they are in closed kinematic chain. The hamstring muscles represent the primary flexors of Knee. Hamstrings tightness results in Limits Knee extension when hip is flexed, Posterior Pelvic tilt, and flatten the lumbar spine. Methods: The subjects selected randomly and divided into two groups (Experimental group and control group.30 samples in One group applied with Static Stretch once a day for 3 repetitions 5 days a week for six weeks and 30 samples in other group applied with Hold relax technique once a day for 4 repetitions 5 days a week for six weeks. The knee joint range of motion was measured at the end of every week with Universal goniometer. Results: By comparing the means of Group – I, given Static Stretch and Group – II, given Hold relax Technique for six weeks implied that there is improvement of flexibility in Group – II and the ‘P’ value < 0.01 shows the difference is highly significant. Conclusion: This study concludes that the hold relax Technique method has proved to be better technique then the static stretch for improving hamstring flexibility.

  19. A Microstructural Study of Load Distribution in Cartilage: A Comparison of Stress Relaxation versus Creep Loading

    Directory of Open Access Journals (Sweden)

    Ashvin Thambyah

    2015-01-01

    Full Text Available The compressive response of articular cartilage has been extensively investigated and most studies have focussed largely on the directly loaded matrix. However, especially in relation to the tissue microstructure, less is known about load distribution mechanisms operating outside the directly loaded region. We have addressed this issue by using channel indentation and DIC microscopy techniques that provide visualisation of the matrix microstructural response across the regions of both direct and nondirect loading. We hypothesise that, by comparing the microstructural response following stress relaxation and creep compression, new insights can be revealed concerning the complex mechanisms of load bearing. Our results indicate that, with stress relaxation, the initial mode of stress decay appears to primarily involve relaxation of the surface layer. In the creep loading protocol, the main mode of stress release is a lateral distribution of load via the mid matrix. While these two modes of stress redistribution have a complex relationship with the zonally differentiated tissue microstructure and the depth of strain, four mechanostructural mechanisms are proposed to describe succinctly the load responses observed.

  20. Strain relaxation of CdTe on Ge studied by medium energy ion scattering

    Science.gov (United States)

    Pillet, J. C.; Pierre, F.; Jalabert, D.

    2016-10-01

    We have used the medium energy ion scattering (MEIS) technique to assess the strain relaxation in molecular-beam epitaxial (MBE) grown CdTe (2 1 1)/Ge (2 1 1) system. A previous X-ray diffraction study, on 10 samples of the same heterostructure having thicknesses ranging from 25 nm to 10 μm has allowed the measurement of the strain relaxation on a large scale. However, the X-ray diffraction measurements cannot achieve a stress measurement in close proximity to the CdTe/Ge interface at the nanometer scale. Due to the huge lattice misfit between the CdTe and Ge, a high degree of disorder is expected at the interface. The MEIS in channeling mode is a good alternative in order to profile defects with a high depth resolution. For a 21 nm thick CdTe layer, we observed, at the interface, a high density of Cd and/or Te atoms moved from their expected crystallographic positions followed by a rapid recombination of defects. Strain relaxation mechanisms in the vicinity of the interface are discussed