¹²⁹ Xe NMR Relaxation-Based Macromolecular Sensing

Energy Technology Data Exchange (ETDEWEB)

Gomes, Muller D. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Dao, Phuong [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Jeong, Keunhong [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Slack, Clancy C. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Vassiliou, Christophoros C. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Finbloom, Joel A. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Francis, Matthew B. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Wemmer, David E. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Physical Biosciences Division; Pines, Alexander [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

2016-07-29

A ¹²⁹Xe NMR relaxation-based sensing approach is reported on that exploits changes in the bulk xenon relaxation rate induced by slowed tumbling of a cryptophane-based sensor upon target binding. The amplification afforded by detection of the bulk dissolved xenon allows sensitive detection of targets. The sensor comprises a xenon-binding cryptophane cage, a target interaction element, and a metal chelating agent. Xenon associated with the target-bound cryptophane cage is rapidly relaxed and then detected after exchange with the bulk. Here we show that large macromolecular targets increase the rotational correlation time of xenon, increasing its relaxation rate. Upon binding of a biotin-containing sensor to avidin at 1.5 μM concentration, the free xenon T₂ is reduced by a factor of 4.

Transverse magnetic field effects on the relaxation time of the magnetization in Mn12 measured by 55Mn-NMR

International Nuclear Information System (INIS)

Furukawa, Y.; Watanabe, K.; Kumagai, K.; Borsa, F.; Gatteschi, D.

2003-01-01

The longitudinal (H Z ) and transverse (H T ) magnetic field dependence of the relaxation time of the magnetization in Mn12 in its S=10 ground state was measured by NMR. The minima in the relaxation time at the fields for level crossing are due to the quantum tunneling of the magnetization. The shortening of the relaxation time under the application of H T is shown to be due mainly to the reduction of the energy barrier

Luther-Emery liquid in the NMR relaxation rate of carbon nanotubes

International Nuclear Information System (INIS)

Gulacsi, Miklos; Simon, Ferenc; Wzietek, Pawel; Kuzmany, Hans; Dora, Balazs

2008-01-01

We analyze a recent NMR experiments by Singer et al.[Singer et al. Phys. Rev. Lett. 95, 236403 (2005).], which showed a deviation from Fermi-liquid behavior in carbon nanotubes with an energy gap evident at low temperatures. A comprehensive theory for the magnetic field and temperature dependent NMR 13 C spin-lattice relaxation is given in the framework of the Luther-Emery and Luttinger liquids. The low temperature properties are governed by a gapped relaxation due to a spin gap (∝30 K), described by the Luther-Emery liquid picture, which crosses over smoothly to the Luttinger liquid behaviour with increasing temperature. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Anomalous NMR Relaxation in Cartilage Matrix Components and Native Cartilage: Fractional-Order Models

Science.gov (United States)

Magin, Richard L.; Li, Weiguo; Velasco, M. Pilar; Trujillo, Juan; Reiter, David A.; Morgenstern, Ashley; Spencer, Richard G.

2011-01-01

We present a fractional-order extension of the Bloch equations to describe anomalous NMR relaxation phenomena (T1 and T2). The model has solutions in the form of Mittag-Leffler and stretched exponential functions that generalize conventional exponential relaxation. Such functions have been shown by others to be useful for describing dielectric and viscoelastic relaxation in complex, heterogeneous materials. Here, we apply these fractional-order T1 and T2 relaxation models to experiments performed at 9.4 and 11.7 Tesla on type I collagen gels, chondroitin sulfate mixtures, and to bovine nasal cartilage (BNC), a largely isotropic and homogeneous form of cartilage. The results show that the fractional-order analysis captures important features of NMR relaxation that are typically described by multi-exponential decay models. We find that the T2 relaxation of BNC can be described in a unique way by a single fractional-order parameter (α), in contrast to the lack of uniqueness of multi-exponential fits in the realistic setting of a finite signal-to-noise ratio. No anomalous behavior of T1 was observed in BNC. In the single-component gels, for T2 measurements, increasing the concentration of the largest components of cartilage matrix, collagen and chondroitin sulfate, results in a decrease in α, reflecting a more restricted aqueous environment. The quality of the curve fits obtained using Mittag-Leffler and stretched exponential functions are in some cases superior to those obtained using mono- and bi-exponential models. In both gels and BNC, α appears to account for microstructural complexity in the setting of an altered distribution of relaxation times. This work suggests the utility of fractional-order models to describe T2 NMR relaxation processes in biological tissues. PMID:21498095

Quantifying NMR relaxation correlation and exchange in articular cartilage with time domain analysis

Science.gov (United States)

Mailhiot, Sarah E.; Zong, Fangrong; Maneval, James E.; June, Ronald K.; Galvosas, Petrik; Seymour, Joseph D.

2018-02-01

Measured nuclear magnetic resonance (NMR) transverse relaxation data in articular cartilage has been shown to be multi-exponential and correlated to the health of the tissue. The observed relaxation rates are dependent on experimental parameters such as solvent, data acquisition methods, data analysis methods, and alignment to the magnetic field. In this study, we show that diffusive exchange occurs in porcine articular cartilage and impacts the observed relaxation rates in T1-T2 correlation experiments. By using time domain analysis of T2-T2 exchange spectroscopy, the diffusive exchange time can be quantified by measurements that use a single mixing time. Measured characteristic times for exchange are commensurate with T1 in this material and so impacts the observed T1 behavior. The approach used here allows for reliable quantification of NMR relaxation behavior in cartilage in the presence of diffusive fluid exchange between two environments.

Proton NMR relaxation in hydrous melts

International Nuclear Information System (INIS)

Braunstein, J.; Bacarella, A.L.; Benjamin, B.M.; Brown, L.L.; Girard, C.

1976-01-01

Pulse and continuous wave NMR measurements are reported for protons in hydrous melts of calcium nitrate at temperatures between -4 and 120 0 C. Although measured in different temperature ranges, spin-lattice (T 1 ) and spin-spin (T 2 ) relaxation times appear to be nearly equal to each other and proportional to the self-diffusion coefficients of solute metal cations such as Cd 2+ . At temperatures near 50 0 C, mean Arrhenius coefficients Δ H/sub T 1 / (kcal/mol) are 7.9, 7.3, and 4.8, respectively, for melts containing 2.8, 4.0, and 8.0 moles of water per mole of calcium nitrate, compared to 4.6 kcal/mol for pure water. Temperature dependence of T 1 and T 2 in Ca(NO 3 ) 2 -2.8 H 2 O between -4 and 120 0 C are non-Arrhenius and can be represented by a Fulcher-type equation with a ''zero mobility temperature'' (T 0 ) of 225 0 K, close to the value of T 0 for solute diffusion, electrical conductance and viscosity. Resolution of the relaxation rates into correlation times for intramolecular (rotational) and intermolecular (translational) diffusional motion is discussed in terms of the Bloembergen-Purcell-Pound and more recent models for dipolar relaxation

Novel spin dynamics in ferrimagnetic molecular chains from 1H NMR and μSR spin-lattice relaxation measurements

International Nuclear Information System (INIS)

Micotti, E.; Lascialfari, A.; Rigamonti, A.; Aldrovandi, S.; Caneschi, A.; Gatteschi, D.; Bogani, L.

2004-01-01

The spin dynamics in the helical chain Co(hfac) 2 NITPhOMe has been investigated by 1 H NMR and μSR relaxation. In the temperature range 15< T<60 K, the results are consistent with the relaxation of the homogeneous magnetization. For T≤15 K, NMR and μSR evidence a second spin relaxation mechanism, undetected by the magnetization measurements. From the analysis of these data, insights on this novel relaxation process are derived

Novel spin dynamics in ferrimagnetic molecular chains from 1H NMR and μSR spin-lattice relaxation measurements

Science.gov (United States)

Micotti, E.; Lascialfari, A.; Rigamonti, A.; Aldrovandi, S.; Caneschi, A.; Gatteschi, D.; Bogani, L.

2004-05-01

The spin dynamics in the helical chain Co(hfac) 2NITPhOMe has been investigated by 1H NMR and μSR relaxation. In the temperature range 15relaxation of the homogeneous magnetization. For T⩽15 K, NMR and μSR evidence a second spin relaxation mechanism, undetected by the magnetization measurements. From the analysis of these data, insights on this novel relaxation process are derived.

DNP-enhanced solid-state NMR spectroscopy of active pharmaceutical ingredients.

Science.gov (United States)

Zhao, Li; Pinon, Arthur C; Emsley, Lyndon; Rossini, Aaron J

2017-11-28

Solid-state NMR spectroscopy has become a valuable tool for the characterization of both pure and formulated active pharmaceutical ingredients (APIs). However, NMR generally suffers from poor sensitivity that often restricts NMR experiments to nuclei with favorable properties, concentrated samples, and acquisition of one-dimensional (1D) NMR spectra. Here, we review how dynamic nuclear polarization (DNP) can be applied to routinely enhance the sensitivity of solid-state NMR experiments by one to two orders of magnitude for both pure and formulated APIs. Sample preparation protocols for relayed DNP experiments and experiments on directly doped APIs are detailed. Numerical spin diffusion models illustrate the dependence of relayed DNP enhancements on the relaxation properties and particle size of the solids and can be used for particle size determination when the other factors are known. We then describe the advanced solid-state NMR experiments that have been enabled by DNP and how they provide unique insight into the molecular and macroscopic structure of APIs. For example, with large sensitivity gains provided by DNP, natural isotopic abundance, 13 C- 13 C double-quantum single-quantum homonuclear correlation NMR spectra of pure APIs can be routinely acquired. DNP also enables solid-state NMR experiments with unreceptive quadrupolar nuclei such as 2 H, 14 N, and 35 Cl that are commonly found in APIs. Applications of DNP-enhanced solid-state NMR spectroscopy for the molecular level characterization of low API load formulations such as commercial tablets and amorphous solid dispersions are described. Future perspectives for DNP-enhanced solid-state NMR experiments on APIs are briefly discussed. Copyright © 2017 John Wiley & Sons, Ltd.

Characterization of water in hydrated Bombyx mori silk fibroin fiber and films by 2H NMR relaxation and 13C solid state NMR.

Science.gov (United States)

Asakura, Tetsuo; Isobe, Kotaro; Kametani, Shunsuke; Ukpebor, Obehi T; Silverstein, Moshe C; Boutis, Gregory S

2017-03-01

The mechanical properties of Bombyx mori silk fibroin (SF), such as elasticity and tensile strength, change remarkably upon hydration. However, the microscopic interaction with water is not currently well understood on a molecular level. In this work, the dynamics of water molecules interacting with SF was studied by 2 H solution NMR relaxation and exchange measurements. Additionally, the conformations of hydrated [3- 13 C]Ala-, [3- 13 C]Ser-, and [3- 13 C]Tyr-SF fibers and films were investigated by 13 C DD/MAS NMR. Using an inverse Laplace transform algorithm, we were able to identify four distinct components in the relaxation times for water in SF fiber. Namely, A: bulk water outside the fiber, B: water molecules trapped weakly on the surface of the fiber, C: bound water molecules located in the inner surface of the fiber, and D: bound water molecules located in the inner part of the fiber were distinguishable. In addition, four components were also observed for water in the SF film immersed in methanol for 30s, while only two components for the film immersed in methanol for 24h. The effects of hydration on the conformation of Ser and Tyr residues in the site-specific crystalline and non-crystalline domains of 13 C selectively labeled SF, respectively, could be determined independently. Our measurements provide new insight relating the characteristics of water and the hydration structure of silk, which are relevant in light of current interest in the design of novel silk-based biomaterials. The mechanical properties of Bombyx mori silk fibroin (SF) change remarkably upon hydration. However, the microscopic interaction between SF and water is not currently well understood on a molecular level. We were able to identify four distinct components in the relaxation times for water in SF fiber by 2 H solution NMR relaxation and exchange measurements. In addition, the effects of hydration on the conformation of Ser and Tyr residues in the site-specific crystalline and

Transverse magnetic field effects on the relaxation time of the magnetization in Mn12 measured by {sup 55}Mn-NMR

Energy Technology Data Exchange (ETDEWEB)

Furukawa, Y.; Watanabe, K.; Kumagai, K.; Borsa, F.; Gatteschi, D

2003-05-01

The longitudinal (H{sub Z}) and transverse (H{sub T}) magnetic field dependence of the relaxation time of the magnetization in Mn12 in its S=10 ground state was measured by NMR. The minima in the relaxation time at the fields for level crossing are due to the quantum tunneling of the magnetization. The shortening of the relaxation time under the application of H{sub T} is shown to be due mainly to the reduction of the energy barrier.

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...... in the extracted dynamic parameters. By systematic reducing the coverage of the Nyquist grid of (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...

Solution conformation and dynamics of a tetrasaccharide related to the LewisX antigen deduced by NMR relaxation measurements

International Nuclear Information System (INIS)

Poveda, Ana; Asensio, Juan Luis; Martin-Pastor, Manuel; Jimenez-Barbero, Jesus

1997-01-01

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-α-N-acetyl-galactosaminyl-β-galactopyranosyl-(1 → 4)[3-O-α-fucosyl] -glucopyranoside (1), an inhibitor of astrocyte growth. In addition, 13 C-NMR relaxation data have also been recorded at both fields. The 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 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 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 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

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

TOMROP: a sequence for determining the longitudinal relaxation time T1 in NMR

International Nuclear Information System (INIS)

Graumann, R.; Barfuss, H.; Fischer, H.; Hentschel, D.; Oppelt, A.

1987-01-01

We developed the pulse sequence TOMROP (T One by Multiple Read Out Pulses) for determining precisely the spatial distribution of the longitudinal relaxation time T 1 in nuclear magnetic resonance (NMR): a series of small-angle selection pulses is used to read out longitudinal magnetization from its initial state till thermal equilibrium. Hence, one measurement will produce several images with different T 1 weightings whose pixel brilliance depends exponentially from read-out time. T 1 can be determined from these independent of initial magnetization and selection pulse angle. The measuring time corresponds to the time needed in multi-echo imaging for the determination of the transversal relaxation time T 2 . We demonstrate this new method using head images of volunteers produced with a 0.23 T test facility. (orig./HP) [de

Estimating side-chain order in methyl-protonated, perdeuterated proteins via multiple-quantum relaxation violated coherence transfer NMR spectroscopy

International Nuclear Information System (INIS)

Sun Hechao; Godoy-Ruiz, Raquel; Tugarinov, Vitali

2012-01-01

Relaxation violated coherence transfer NMR spectroscopy (Tugarinov et al. in J Am Chem Soc 129:1743–1750, 2007) is an established experimental tool for quantitative estimation of the amplitudes of side-chain motions in methyl-protonated, highly deuterated proteins. Relaxation violated coherence transfer experiments monitor the build-up of methyl proton multiple-quantum coherences that can be created in magnetically equivalent spin-systems as long as their transverse magnetization components relax with substantially different rates. The rate of this build-up is a reporter of the methyl-bearing side-chain mobility. Although the build-up of multiple-quantum 1 H coherences is monitored in these experiments, the decay of the methyl signal during relaxation delays occurs when methyl proton magnetization is in a single-quantum state. We describe a relaxation violated coherence transfer approach where the relaxation of multiple-quantum 1 H– 13 C methyl coherences during the relaxation delay period is quantified. The NMR experiment and the associated fitting procedure that models the time-dependence of the signal build-up, are applicable to the characterization of side-chain order in [ 13 CH 3 ]-methyl-labeled, highly deuterated protein systems up to ∼100 kDa in molecular weight. The feasibility of extracting reliable measures of side-chain order is experimentally verified on methyl-protonated, perdeuterated samples of an 8.5-kDa ubiquitin at 10°C and an 82-kDa Malate Synthase G at 37°C.

NMR relaxation dispersion of Miglyol molecules confined inside polymeric micro-capsules.

Science.gov (United States)

Nechifor, Ruben; Ardelean, Ioan; Mattea, Carlos; Stapf, Siegfried; Bogdan, Mircea

2011-11-01

Frequency dependent NMR relaxation studies have been carried out on Miglyol molecules confined inside core shell polymeric capsules to obtain a correlation between capsule dimension and the measurable parameters. The polymeric capsules were prepared using an interfacial polymerization technique for three different concentrations of Miglyol. It was shown that the variation of Miglyol concentration influences the capsule dimension. Their average size was estimated using the pulsed field gradient diffusometry technique. The relaxation dispersion curves were obtained at room temperature by a combined use of a fast field cycling instrument and a high-field instrument. The frequency dependence of relaxation rate shows a transition from a diffusion-limited to a surface-limited relaxation regime. Copyright © 2011 John Wiley & Sons, Ltd.

Novel spin dynamics in ferrimagnetic molecular chains from {sup 1}H NMR and {mu}SR spin-lattice relaxation measurements

Energy Technology Data Exchange (ETDEWEB)

Micotti, E. E-mail: micotti@fisicavolta.unipv.it; Lascialfari, A.; Rigamonti, A.; Aldrovandi, S.; Caneschi, A.; Gatteschi, D.; Bogani, L

2004-05-01

The spin dynamics in the helical chain Co(hfac){sub 2}NITPhOMe has been investigated by {sup 1}H NMR and {mu}SR relaxation. In the temperature range 15relaxation of the homogeneous magnetization. For T{<=}15 K, NMR and {mu}SR evidence a second spin relaxation mechanism, undetected by the magnetization measurements. From the analysis of these data, insights on this novel relaxation process are derived.

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.

Assigning uncertainties in the inversion of NMR relaxation data.

Science.gov (United States)

Parker, Robert L; Song, Yi-Qaio

2005-06-01

Recovering the relaxation-time density function (or distribution) from NMR decay records requires inverting a Laplace transform based on noisy data, an ill-posed inverse problem. An important objective in the face of the consequent ambiguity in the solutions is to establish what reliable information is contained in the measurements. To this end we describe how upper and lower bounds on linear functionals of the density function, and ratios of linear functionals, can be calculated using optimization theory. Those bounded quantities cover most of those commonly used in the geophysical NMR, such as porosity, T(2) log-mean, and bound fluid volume fraction, and include averages over any finite interval of the density function itself. In the theory presented statistical considerations enter to account for the presence of significant noise in the signal, but not in a prior characterization of density models. Our characterization of the uncertainties is conservative and informative; it will have wide application in geophysical NMR and elsewhere.

relaxGUI: a new software for fast and simple NMR relaxation data analysis and calculation of ps-ns and μs motion of proteins

International Nuclear Information System (INIS)

Bieri, Michael; D’Auvergne, Edward J.; Gooley, Paul R.

2011-01-01

Investigation of protein dynamics on the ps-ns and μs-ms timeframes provides detailed insight into the mechanisms of enzymes and the binding properties of proteins. Nuclear magnetic resonance (NMR) is an excellent tool for studying protein dynamics at atomic resolution. Analysis of relaxation data using model-free analysis can be a tedious and time consuming process, which requires good knowledge of scripting procedures. The software relaxGUI was developed for fast and simple model-free analysis and is fully integrated into the software package relax. It is written in Python and uses wxPython to build the graphical user interface (GUI) for maximum performance and multi-platform use. This software allows the analysis of NMR relaxation data with ease and the generation of publication quality graphs as well as color coded images of molecular structures. The interface is designed for simple data analysis and management. The software was tested and validated against the command line version of relax.

relaxGUI: a new software for fast and simple NMR relaxation data analysis and calculation of ps-ns and μs motion of proteins.

Science.gov (United States)

Bieri, Michael; d'Auvergne, Edward J; Gooley, Paul R

2011-06-01

Investigation of protein dynamics on the ps-ns and μs-ms timeframes provides detailed insight into the mechanisms of enzymes and the binding properties of proteins. Nuclear magnetic resonance (NMR) is an excellent tool for studying protein dynamics at atomic resolution. Analysis of relaxation data using model-free analysis can be a tedious and time consuming process, which requires good knowledge of scripting procedures. The software relaxGUI was developed for fast and simple model-free analysis and is fully integrated into the software package relax. It is written in Python and uses wxPython to build the graphical user interface (GUI) for maximum performance and multi-platform use. This software allows the analysis of NMR relaxation data with ease and the generation of publication quality graphs as well as color coded images of molecular structures. The interface is designed for simple data analysis and management. The software was tested and validated against the command line version of relax.

NMR relaxation rates and Knight shifts in MgB2 and AlB2: theory versus experiments

International Nuclear Information System (INIS)

Pavarini, E; Baek, S H; Suh, B J; Borsa, F; Bud'ko, S L; Canfield, P C

2003-01-01

We have performed 11 B NMR measurements in 11 B enriched MgB 2 powder sample in the normal phase. The Knight shift was accurately determined by using the magic angle spinning technique. Results for 11 B and 27 Al Knight shifts (K) and relaxation rates (1/T 1 ) are also reported for AlB 2 . The data show a dramatic decrease of both K and 1/T 1 for 11 B in AlB 2 with respect to MgB 2 . We compare experimental results with ab initio calculated NMR relaxation rates and Knight shifts. The experimental values for 1/T 1 and K are in most cases in good agreement with the theoretical results. We show that the decrease of K and 1/T 1 for 11 B is consistent with a drastic drop of the density of states at the boron site in AlB 2 with respect to MgB 2

NMR relaxation times in human brain tumors (preliminary results)

International Nuclear Information System (INIS)

Benoist, L.; Certaines, J. de; Chatel, M.; Menault, F.

1981-01-01

Since the early work of Damadian in 1971, proton NMR studies of tumors has been well documented. Present study concerns the spin-lattice T 1 and spin-spin T 2 relaxation times of normal dog brain according to the histological differentiation and of 35 human benignant or malignant tumors. The results principally show T 2 important variations between white and gray substance in normal brain but no discrimination between malignant and benignant tumors [fr

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...... for folding. However, although the values of k f determined by the two methods agree, the values of k u do not. As a result, a combined analysis of all data does not comply with a two-state model but indicates that an unfolding intermediate exists on the native side of the dominant energy barrier...

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

International Nuclear Information System (INIS)

Canales-Mayordomo, Angeles; Fayos, Rosa; Angulo, Jesus; Ojeda, Rafael; Martin-Pastor, Manuel; Nieto, Pedro M.; Martin-Lomas, Manuel; Lozano, Rosa; Gimenez-Gallego, Guillermo; Jimenez-Barbero, Jesus

2006-01-01

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)

Solid state NMR study of cumbaru flour

International Nuclear Information System (INIS)

Nogueira, Jose S.; Bathista, Andre L.B.S.; Silva, Emerson O.; Priante Filho, Nicolau; Tavares, Maria I.B.

2001-01-01

The polysaccharide obtained by seed of Dipteryx alata Vog, has been characterised by 13 C solid state, using the basic routine techniques, like MAS and CPMAS and by the proton spin-lattice relaxation time in the rotating frame parameter (T 1 H ρ). Knowing that the chemical structure and molecular dynamic are extremely necessary route to obtain information on the polysaccharides, this work contributes to the classification of the seed containing in the cumbaru fruit to get response on its application. To obtain the initial responses for our purposes some solid state NMR techniques were chosen. The CPMAS 13 C NMR spectrum of the polysaccharide was investigated to know if it has some crystallinity. The MAS 13 C NMR spectrum showed the presence of domains with distinct molecular mobility, because these domains will differ basically in the distribution size and chain packing. The variable contact time experiment was used to analyse the distribution form of 13 C decays, which give us more information about sample heterogeneity. The T 1 H ρHr values were obtained from the variable contact time and by delayed contact time experiment, because these parameter indicate the order of polysaccharides. From the values of this parameter, we found that this polysaccharide is completely non-ordered. (author)

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

International Nuclear Information System (INIS)

Oktaviani, Nur Alia; Risør, Michael W.; Lee, Young-Ho; Megens, Rik P.; Jong, Djurre H. de; Otten, Renee; Scheek, Ruud M.; Enghild, Jan J.; Nielsen, Niels Chr.; Ikegami, Takahisa; Mulder, Frans A. A.

2015-01-01

Co-solute paramagnetic relaxation enhancement (PRE) is an attractive way to speed up data acquisition in NMR spectroscopy by shortening the T 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 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 1 -antitrypsin by acquiring the necessary suite of multidimensional NMR datasets in 3 h

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.

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)

Measurement of backbone hydrogen-deuterium exchange in the type III secretion system needle protein PrgI by solid-state NMR

Science.gov (United States)

Chevelkov, Veniamin; Giller, Karin; Becker, Stefan; Lange, Adam

2017-10-01

In this report we present site-specific measurements of amide hydrogen-deuterium exchange rates in a protein in the solid state phase by MAS NMR. Employing perdeuteration, proton detection and a high external magnetic field we could adopt the highly efficient Relax-EXSY protocol previously developed for liquid state NMR. According to this method, we measured the contribution of hydrogen exchange on apparent 15N longitudinal relaxation rates in samples with differing D2O buffer content. Differences in the apparent T1 times allowed us to derive exchange rates for multiple residues in the type III secretion system needle protein.

Solid state NMR studies for a new carbonization process with high temperature preheating

Science.gov (United States)

Saito, Koji; Hatakeyama, Moriaki; Komaki, Ikuo; Katoh, Kenji

2002-01-01

A new carbonization process with rapid preheating and coke discharging at medium temperature has been developed in Japan. The result of this process shows that even when no or slightly coking coal is by 50 wt% the coking property is improved and a coking coke with cold strength usable at blast furnace can be manufactured with the new carbonization process. The mechanism of the coking property improvement was examined by coal properties using mainly solid state NMR ( 1H CRAMPS and 13C SPE/MAS, CP/MAS) and NMR imaging (single point imaging, in-situ imaging). It has been clarified that the molecular structure of coal is relaxed by the rapid heating treatment and, in addition, there is a close relation between hydrogen bonding and relaxation of the molecular structure of coal.

The study of NMR relaxation time spectra multi-exponential inversion based on Lloyd–Max optimal quantization

International Nuclear Information System (INIS)

Li, Xuewei; Kong, Li; Cheng, Jingjing; Wu, Lei

2015-01-01

The multi-exponential inversion of a NMR relaxation signal plays a key role in core analysis and logging interpretation in the formation of porous media. To find an efficient metod of inverting high-resolution relaxation time spectra rapidly, this paper studies the effect of inversion which is based on the discretization of the original echo in a time domain by using a simulation model. This paper analyzes the ill-condition of discrete equations on the basis of the NMR inversion model and method, determines the appropriate number of discrete echoes and acquires the optimal distribution of discrete echo points by the Lloyd–Max optimal quantization method, in considering the inverse precision and computational complexity comprehensively. The result shows that this method can effectively improve the efficiency of the relaxation time spectra inversion while guaranteeing inversed accuracy. (paper)

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.

Spin fluctuations in iron based superconductors probed by NMR relaxation rate

Energy Technology Data Exchange (ETDEWEB)

Graefe, Uwe; Kuehne, Tim; Wurmehl, Sabine; Buechner, Bernd; Grafe, Hans-Joachim [IFW Dresden, Institute for Solid State Research, PF 270116, 01171 Dresden (Germany); Hammerath, Franziska [IFW Dresden, Institute for Solid State Research, PF 270116, 01171 Dresden (Germany); Department of Physics ' ' A. Volta' ' , University of Pavia-CNISM, I-27100 Pavia (Italy); Lang, Guillaume [3LPEM-UPR5, CNRS, ESPCI Paris Tech, 10 Rue Vauquelin, 75005 Paris (France)

2013-07-01

We present {sup 75}As nuclear magnetic resonance (NMR) results in F doped LaOFeAs iron pnictides. In the underdoped superconducting samples, pronounced spin fluctuations lead to a peak in the NMR spin lattice relaxation rate, (T{sub 1}T){sup -1}. The peak shows a typical field dependence that indicates a critical slowing of spin fluctuations: it is reduced in height and shifted to higher temperatures. In contrast, a similar peak in the underdoped magnetic samples at the ordering temperature of the spin density wave does not show such a field dependence. Furthermore, the peak is absent in optimally and overdoped samples, suggesting the absence of strong spin fluctuations. Our results indicate a glassy magnetic ordering in the underdoped samples that is in contrast to the often reported Curie Weiss like increase of spin fluctuations towards T{sub c}. Additional measurements of the linewidth and the spin spin relaxation rate are in agreement with such a glassy magnetic ordering that is most likely competing with superconductivity. Our results will be compared to Co doped BaFe{sub 2}As{sub 2}, where a similar peak in (T{sub 1}T){sup -1} has been observed.

Magnetization and 13C NMR spin-lattice relaxation of nanodiamond powder

Energy Technology Data Exchange (ETDEWEB)

Levin, E.M.; Fang, X.W.; Bud' ko, S.L.; Straszheim, W.E.; McCallum, R.W.; Schmidt-Rohr, K.

2008-02-15

The bulk magnetization at temperatures of 1.8-400 K and in magnetic fields up to 70 kOe, the ambient temperature {sup 13}C NMR spin-lattice relaxation, T{sub 1,c}, and the elemental composition of three nanodiamond powder samples have been studied. The total magnetization of nanodiamond can be explained in terms of contributions from (1) the diamagnetic effect of carbon, (2) the paramagnetic effect of unpaired electrons present in nanodiamond grains, and (3) ferromagnetic-like and (4) superparamagnetic contributions from Fe-containing particles detected in spatially resolved energy-dispersive spectroscopy. Contributions (1) and (2) are intrinsic to nanodiamond, while contributions (3) and (4) arise from impurities naturally present in detonation nanodiamond samples. {sup 13}C NMR T{sub 1,c} relaxation would be unaffected by the presence of the ferromagnetic particles with the bulk magnetization of {approx} 0.01 emu/g at 300 K. Thus, a reduction of T{sub 1,c} by 3 orders of magnitude compared to natural and synthetic microdiamonds confirms the presence of unpaired electrons in the nanodiamond grains. The spin concentration in nanodiamond powder corresponds to {approx}30 unpaired electrons per {approx}4.6 nm diameter nanodiamond grain.

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. Copyright © 2017 Elsevier Inc. All rights reserved.

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.

Ground-state magnetization of the molecular cluster Mn12O12-acetate as seen by proton NMR

International Nuclear Information System (INIS)

Furukawa, Y.; Watanabe, K.; Kumagai, K.; Jang, Z. H.; Lascialfari, A.; Borsa, F.; Gatteschi, D.

2000-01-01

1 H nuclear magnetic resonance (NMR) measurements have been carried out in Mn 12 O 12 -acetate clusters at low temperature in order to investigate microscopically the static and dynamic magnetic properties of the molecule in its high-spin S=10 ground state. Below liquid helium temperature it is found that the local hyperfine fields at the proton sites are static as expected for the very slow superparamagnetic relaxation of Mn 12 O 12 at low temperature. The magnitude and distribution of the hyperfine fields can be reproduced to a good approximation by considering only the dipolar interaction of protons with the local Mn magnetic moments and by assigning the magnitude and orientation of the local moments of the different Mn 3+ and Mn 4+ ions according to an accepted coupling scheme for the total S=10 ground state. The relaxation time of the macroscopic magnetization of the cluster was measured by monitoring the change of the intensity of the 1 H-NMR shifted lines following inversion of the applied magnetic field. This is possible because the sudden change of the field orientation changes the sign of the shift of the NMR lines in the proton spectrum. Although important differences are noticed, the relaxation time of the magnetization as measured indirectly by the 1 H-NMR method is comparable to the one obtained directly with a superconducting quantum interference device magnetometer. In particular we could reproduce the minima in the relaxation time as a function of magnetic field at the fields for level crossing, minima which are considered to be a signature of the quantum tunneling of the magnetization

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

International Nuclear Information System (INIS)

Chan, Sammy H. S.; Waudby, Christopher A.; Cassaignau, Anaïs M. E.; Cabrita, Lisa D.; Christodoulou, John

2015-01-01

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 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 1 H magnetization without adversely affecting storage on N 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

An analysis of the NMR-CT image by the measurement of proton-relaxation times in tissue

International Nuclear Information System (INIS)

Naruse, Shoji; Horikawa, Yoshiharu; Tanaka, Chuzo; Hirakawa, Kimiyoshi; Nishikawa, Hiroyasu; Shimizu, Koji; Kiri, Motosada.

1984-01-01

NMR-CT images were analyzed by measuring the proton-relaxation times in tissues. The NMR-CT images were obtained in 10 normal volunteers and 16 patients with brain tumors with a prototype superconducting magnet (Shimadzu Corp., Japan) operating at 0.2 T and 0.375 T. A smooth T 1 relaxation curve was obtained in each part of the brain and the brain tumor by the use of the data of the NMR-CT image; consequently, the in vivo T 1 value was proved to be reliable. The in vivo T 1 value showed the specific value corresponding to each region of the normal brain in all cases. Cerebral gray matter normally had the longest T 1 value, followed by the medulla oblongata, the pons, and white matter. The T 1 value of each region of the brain varied to the same degree in proportion to the strength of the static magnetic field. The in vivo T 1 values of the brain tumor varied with the histological type. All were longer than any part of the brain parenchyma, being between 480 and 780 msec at 0.2 T. The prolongation of the T 1 value does not always correspond to the degree of the malignancy in a tumor. The in vitro T 1 and T 2 values were also prolonged in all tumors. Although the absolute value of T 1 did not coincide between the in vitro and in vivo data, the tendency of the prolongation was the same between them. This result indicated that the NMR-CT images could be analysed by the use of the data of the in vitro T 1 and T 2 values in the tumor tissues. It is important to analyse the NMR-CT image by both in vivo and in vitro examinations of the relaxation times. (J.P.N.)

13C solid state NMR investigation of natural resins components

International Nuclear Information System (INIS)

Tavares, Maria I.B.; Bathista, Andre L.B.S.; Silva, Emerson O.; Priante Filho, Nicolau; Nogueira, Jose S.

2001-01-01

The objective of this work is to establish and analytical methodology as a routine using solid state nuclear magnetic resonance (NMR) techniques to investigate the mainly chemical components presented in natural resins in bulk. And also to evaluate the molecular behaviour of these resins. The routine solid state techniques allow us to assign the main compounds presented in the resins. Therefore, applying specialised techniques, like variable contact time, delayed contact time, dephasing time and proton spin lattice relaxation time in the rotating frame (T 1 H ρ), more information about chemical structure and molecular dynamic is available

Dynamics of solutions and fluid mixtures by NMR

International Nuclear Information System (INIS)

Delpuech, J.J.

1994-01-01

After a short introduction to NMR spectroscopy, with a special emphasis on dynamical aspects, an overview on two fundamental aspects of molecular dynamics, NMR relaxation and its relationship with molecular reorientation, and magnetization transfer phenomena induced by molecular rate processes (dynamic NMR) is presented, followed by specific mechanisms of relaxation encountered in paramagnetic systems or with quadrupolar nuclei. Application fields are then reviewed: solvent exchange on metal ions with a variable pressure NMR approach, applications of field gradients in NMR, aggregation phenomena and micro-heterogeneity in surfactant solutions, polymers and biopolymers in the liquid state, liquid-like molecules in rigid matrices and in soft matter (swollen polymers and gels, fluids in and on inorganic materials, food)

Paramagnetic metal complexes as potential relaxation agents for NMR imaging

International Nuclear Information System (INIS)

Coroiu, Ilioara; Demco, D. E.; Darabont, Al.; Bogdan, M.

1997-01-01

The development of nuclear magnetic resonance (NMR) imaging technique as a clinical diagnostic modality has prompted the need for a new class of pharmaceuticals. These drugs must be administered to a patient in order to enhance the image contrast between the normal and diseased tissue and/or indicate the status of organ function or blood flow. Paramagnetic compounds are presently undergoing extensive evaluation as contrast agents in magnetic resonance imaging (MRI). These agents increase contrast in MRI by differentially localizing in tissue where they increase the relaxation rates of nearby water protons. The longitudinal R 1 and transverse R 2 relaxivities were measured as a function of molar concentrations for some new paramagnetic complexes like the following: dysprosium, erbium and gadolinium citrates, gadolinium methylene diphosphonate, dysprosium and gadolinium iminodiacetate, manganese para-aminobenzoate and copper nicotinate. The available theoretical approaches for quantitative understanding are presented. (authors)

Sup(1)H n.m.r. relaxation of radiation induced crosslinking in polyester-styrene systems

International Nuclear Information System (INIS)

Andreis, M.; Veksli, Z.; Ranogajec, F.; Hedvig, P.

1989-01-01

The structure and dynamics of a network formed by radiation induced crosslinking of polyesters based on 1,6-hexane diol and 1,2-propylene glycol and maleic anhydride (HDF and PGF, respectively) with styrene is studied by proton pulsed n.m.r. spectroscopy. The dependence of spin-lattice, T 1 , and spin-spin, T 2 , relaxation times on the structure of polyester chain, molar ratios of styrene to polyester unsaturations and the radiation doses are analysed in terms of network formation and structure, and their effect on molecular motion. Above the gel point, at temperatures above the glass transition, the presence of two T 2 components reflects the heterogeneity of the network structure in both resins. Parallel with the n.m.r. relaxation measurements the crosslink density was determined from the extracted gel phase or double bonds (fumaric and styrene) participating in the crosslinking process. (author)

Characterization of Two Distinct Amorphous Forms of Valsartan by Solid-State NMR.

Science.gov (United States)

Skotnicki, Marcin; Apperley, David C; Aguilar, Juan A; Milanowski, Bartłomiej; Pyda, Marek; Hodgkinson, Paul

2016-01-04

Valsartan (VAL) is an antihypertensive drug marketed in an amorphous form. Amorphous materials can have different physicochemical properties depending on preparation method, thermal history, etc., but the nature of such materials is difficult to study by diffraction techniques. This study characterizes two different amorphous forms of valsartan (AR and AM) using solid-state NMR (SSNMR) as a primary investigation tool, supported by solution-state NMR, FT-IR, TMDSC, and dissolution tests. The two forms are found to be clearly distinct, with a significantly higher level of structural arrangement in the AR form, as observed in (13)C, (15)N, and (1)H SSNMR. (13)C and (15)N NMR indicates that the fully amorphous material (AM) contains an approximately equal ratio of cis-trans conformers about the amide bond, whereas the AR form exists mainly as one conformer, with minor conformational "defects". (1)H ultrafast MAS NMR shows significant differences in the hydrogen bonding involving the tetrazole and acid hydrogens between the two materials, while (15)N NMR shows that both forms exist as a 1,2,3,4-tetrazole tautomer. NMR relaxation times show subtle differences in local and bulk molecular mobility, which can be connected with the glass transition, the stability of the glassy material, and its response to aging. Counterintuitively the fully amorphous material is found to have a significantly lower dissolution rate than the apparently more ordered AR material.

NMR studies of incommensurate quantum antiferromagnetic state of LiCuVO 4

Science.gov (United States)

Smith, R.; Reyes, A. P.; Ashey, R.; Caldwell, T.; Prokofiev, A.; Assmus, W.; Teitel'baum, G.

2006-05-01

Our 51V NMR measurements in the LiCuVO 4 single crystal reveal that the classical quadrupole split signal transforms upon lowering temperature to the single line with the shape typical for the systems undergoing the phase transition to the incommensurate magnetic state. The angular dependence of such a lineshape together with the anomalies of the 51V nuclear spin relaxation rates make it possible to conclude that the low-temperature magnetic order corresponds to the antiferromagnetic state with the incommensurate modulation along the b-axis of the crystal.

Blends of natural rubber and polyurethane lattices studied by solid-state NMR

International Nuclear Information System (INIS)

Ricardo, Nagila M.P.S.; Franca, Francisco C.F. de; Price, Colin; Heatley, Frank

2001-01-01

Molecular mixing in films formed from a mixture of a polyurethane and natural rubber lattices has been studied using 1 H and 13 C solid-state NMR. The techniques employed include 1 H relaxation measurements, and 13 C cross-polarisation and direct excitation methods. The spectra of the blends were essentially a weighted superposition of the spectra of the individual components, indicating that the polyurethane and rubber remained phase-separated in large domains. (author)

Study of relaxation times of nanocomposites of starch/montmorillonite employing low field NMR

International Nuclear Information System (INIS)

Brito, Luciana M.; Tavares, Maria Ines B.

2011-01-01

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)

Synthesis of compact patterns for NMR relaxation decay in intelligent "electronic tongue" for analyzing heavy oil composition

Science.gov (United States)

Lapshenkov, E. M.; Volkov, V. Y.; Kulagin, V. P.

2018-05-01

The article is devoted to the problem of pattern creation of the NMR sensor signal for subsequent recognition by the artificial neural network in the intelligent device "the electronic tongue". The specific problem of removing redundant data from the spin-spin relaxation signal pattern that is used as a source of information in analyzing the composition of oil and petroleum products is considered. The method is proposed that makes it possible to remove redundant data of the relaxation decay pattern but without introducing additional distortion. This method is based on combining some relaxation decay curve intervals that increment below the noise level such that the increment of the combined intervals is above the noise level. In this case, the relaxation decay curve samples that are located inside the combined intervals are removed from the pattern. This method was tested on the heavy-oil NMR signal patterns that were created by using the Carr-Purcell-Meibum-Gill (CPMG) sequence for recording the relaxation process. Parameters of CPMG sequence are: 100 μs - time interval between 180° pulses, 0.4s - duration of measurement. As a result, it was revealed that the proposed method allowed one to reduce the number of samples 15 times (from 4000 to 270), and the maximum detected root mean square error (RMS error) equals 0.00239 (equivalent to signal-to-noise ratio 418).

NMR water-proton spin-lattice relaxation time of human red blood cells and red blood cell suspensions

International Nuclear Information System (INIS)

Sullivan, S.G.; Rosenthal, J.S.; Winston, A.; Stern, A.

1988-01-01

NMR water-proton spin-lattice relaxation times were studied as probes of water structure in human red blood cells and red blood cell suspensions. Normal saline had a relaxation time of about 3000 ms while packed red blood cells had a relaxation time of about 500 ms. The relaxation time of a red blood cell suspension at 50% hematocrit was about 750 ms showing that surface charges and polar groups of the red cell membrane effectively structure extracellular water. Incubation of red cells in hypotonic saline increases relaxation time whereas hypertonic saline decreases relaxation time. Relaxation times varied independently of mean corpuscular volume and mean corpuscular hemoglobin concentration in a sample population. Studies with lysates and resealed membrane ghosts show that hemoglobin is very effective in lowering water-proton relaxation time whereas resealed membrane ghosts in the absence of hemoglobin are less effective than intact red cells. 9 refs.; 3 figs.; 1 table

Two dimensional solid state NMR

International Nuclear Information System (INIS)

Kentgens, A.P.M.

1987-01-01

This thesis illustrates, by discussing some existing and newly developed 2D solid state experiments, that two-dimensional NMR of solids is a useful and important extension of NMR techniques. Chapter 1 gives an overview of spin interactions and averaging techniques important in solid state NMR. As 2D NMR is already an established technique in solutions, only the basics of two dimensional NMR are presented in chapter 2, with an emphasis on the aspects important for solid spectra. The following chapters discuss the theoretical background and applications of specific 2D solid state experiments. An application of 2D-J resolved NMR, analogous to J-resolved spectroscopy in solutions, to natural rubber is given in chapter 3. In chapter 4 the anisotropic chemical shift is mapped out against the heteronuclear dipolar interaction to obtain information about the orientation of the shielding tensor in poly-(oxymethylene). Chapter 5 concentrates on the study of super-slow molecular motions in polymers using a variant of the 2D exchange experiment developed by us. Finally chapter 6 discusses a new experiment, 2D nutation NMR, which makes it possible to study the quadrupole interaction of half-integer spins. 230 refs.; 48 figs.; 8 tabs

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

Science.gov (United States)

Harter, Andrew

neutron scattering. [Mn12O12(O2CCH2Bu t)16(MeOH)4]·MeOH (Mn12-t-Bu), arguably the most interesting SMM in terms of the structure of the NMR peaks, does appear to be a much cleaner sample than Mn12-Ac. Fine structure is noticed, however, in the Mn4+ peak, requiring either the addition of a quadrupole interaction or isomers to explain the splitting. The five resonances that make up the lower frequency Mn3+ group increase in width upon moving to higher frequency, a most unusual result which may also be explained by the presence of isomers. Finally, the bulky ligands contribute to this SMM having the longest relaxation time at low temperature, with no evidence for temperature independence down to 400 mK. Again, evidence was found for a barrier of 1 K. We thus arrive at three major conclusions important to the understanding of SMM systems: (1) Single crystals provide an order-of-magnitude higher spectral resolution than oriented powder samples, but also show that the powdered samples do not represent a statistical average of a crystal, (2) transverse hyperfine fields are present at the Mn4+ site, contradicting early models which predicted an isotropic hyperfine field, and (3) 55Mn spin-lattice times shows no evidence of temperature independent behavior for any of the molecules studied, in contrast to earlier experiments on powdered Mn12-Ac. This observation could be the most important one, as it may result in a reconsideration of the effective spin Hamiltonian for the electronic system if terms must be added to account for an energy level in between the mS = +/-10 and mS = +/-9 states, at about 1--2 K above the ground state.

Microscopic insights into the NMR relaxation based protein conformational entropy meter

Science.gov (United States)

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

2013-01-01

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 pro! teins 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. PMID:24007504

Relaxed states with plasma flow

International Nuclear Information System (INIS)

Avinash, K.; Taylor, J.B.

1991-01-01

In the theory of relaxation, a turbulent plasma reaches a state of minimum energy subject to constant magnetic helicity. In this state the plasma velocity is zero. Attempts have been made by introducing a number of different constraints, to obtain relaxed states with plasma flow. It is shown that these alternative constraints depend on two self-helicities, one for ions, and one for electrons. However, whereas there are strong arguments for the effective invariance of the original magnetic-helicity, these arguments do not apply to the self-helicities. Consequently the existence of relaxed states with flow remains in doubt. (author)

The effects of bone on proton NMR relaxation times of surrounding liquids

Science.gov (United States)

Davis, C. A.; Genant, H. K.; Dunham, J. S.

1986-01-01

Preliminary attempts by our group at UCSF to assess fat content of vertebral marrow in the lumbar spine using relaxation time information demonstrated that the presence of trabecular bone affects relaxation times. The objective of this work was a thorough study of the effects of bone on NMR relaxation characteristics of surrounding liquids. Trabecular bone from autopsy specimens was ground up and sifted into a series of powders with graded densities ranging from 0.3 gm/cc to 0.8 gm/cc. Each powder was placed first in n-saline and then in cottonseed oil. With spectroscopy, spin-lattice relaxation times (T1) and effective spin-spin relaxation times (T2*) were measured for each liquid in each bone powder. As bone density and surface to volume ratio increased, T1 decreased faster for saline than for oil. T2* decreased significantly for both water and oil as the surface to volume ratio increased. It was concluded that effects of water on T1 could be explained by a surface interaction at the bone/liquid interface, which restricted rotational and translational motion of nearby molecules. The T1s of oil were not affected since oil molecules are nonpolar, do not participate in significant intermolecular hydrogen bonding, and therefore would not be expected to interact strongly with the bone surface. Effects on T2* could be explained by local magnetic field inhomogeneities created by discontinuous magnetic susceptibility near the bone surface. These preliminary results suggest that water in contact with trabecular bone in vivo will exhibit shortened relaxation times.

NMR studies of incommensurate quantum antiferromagnetic state of LiCuVO{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Smith, R. [NHMFL, Florida State University, 1800 E P.Dirac Dr., Tallahassee FL 32310 (United States); Reyes, A.P. [NHMFL, Florida State University, 1800 E P.Dirac Dr., Tallahassee FL 32310 (United States); Ashey, R. [NHMFL, Florida State University, 1800 E P.Dirac Dr., Tallahassee FL 32310 (United States); Caldwell, T. [NHMFL, Los Alamos, NM 87545 (United States); Prokofiev, A. [Goethe University, 60054 Frankfurt (Germany); Assmus, W. [Goethe University, 60054 Frankfurt (Germany); Teitel' baum, G. [E.K.Zavoiskii Institute for Technical Physics of the RAS, Sibirskii Trakt 10/7, Kazan 420029 (Russian Federation)]. E-mail: grteit@kfti.knc.ru

2006-05-01

Our {sup 51}V NMR measurements in the LiCuVO{sub 4} single crystal reveal that the classical quadrupole split signal transforms upon lowering temperature to the single line with the shape typical for the systems undergoing the phase transition to the incommensurate magnetic state. The angular dependence of such a lineshape together with the anomalies of the {sup 51}V nuclear spin relaxation rates make it possible to conclude that the low-temperature magnetic order corresponds to the antiferromagnetic state with the incommensurate modulation along the b-axis of the crystal.

Cross-relaxation solid state lasers

International Nuclear Information System (INIS)

Antipenko, B.M.

1989-01-01

Cross-relaxation functional diagrams provide a high quantum efficiency for pumping bands of solid state laser media and a low waste heat. A large number of the cross-relaxation mechanisms for decay rare earth excited states in crystals have been investigated. These investigations have been a starting-point for development of the cross-relaxation solid state lasers. For example, the cross-relaxation interactions, have been used for the laser action development of LiYF 4 :Gd-Tb. These interactions are important elements of the functional diagrams of the 2 μm Ho-doped media sensitized with Er and Tm and the 3 μm Er-doped media. Recently, new efficient 2 μm laser media with cross-relaxation pumping diagrams have been developed. Physical aspects of these media are the subject of this paper. A new concept of the Er-doped medium, sensitized with Yb, is illustrated

Proton NMR relaxivity of blood samples in the presence of some gadolinium and dysprosium compounds

International Nuclear Information System (INIS)

Coroiu, I.; Darabont, Al.; Bogdan, M.

1999-01-01

The use of some new compounds in MRI tissue and blood characterisation based on nuclear spin relaxation time measurements cannot be sustained until the molecular sources of these variations are understood. Tissues and blood are complex molecular systems with complex NMR properties. A better comprehension of the molecular basis of relaxation offers the possibility to predict the changes expected for a given pathology. The purpose of this contribution is to evidence the different relaxation characteristics of some gadolinium and dysprosium compounds in the presence and absence of the blood and to give a possible explanation about the molecular processes that cause occurrence of changes. Some gadolinium and dysprosium compounds such as: Gd-CIT (gadolinium citrate), Dy-DTPA (DTPA-diethylenetriamine pentaacetic acid), iron oxide - gadolinium oxide (or dysprosium oxide)- dextran complexes were prepared. The longitudinal T 1 -1 and transverse T 2 -1 'relaxation rates' measurements have been carried out as a function of molar concentrations. All measurements have been made at room temperature (about 25 deg.C) and the proton Larmor frequency ν o = 90 MHz. The pulsed NMR spectrometer utilised was a commercial Bruker SXP4/100 spectrometer. Transverse relaxation rate measurements have been made using the Carr-Purcell method, while longitudinal relaxation rate measurements using the inversion recovery pulse sequence, 180 angle-τ-90 angle. The accuracy was about 2-3% for the longitudinal relaxation rates and about 5-7% for the transverse relaxation rates. R 1 and R 2 relaxivities, in mM -1 s -1 were determined from the least square determination of the slopes of plots 1/T 1,2 versus compound molar concentration, using at least five independent measurements at several concentrations between 0 and 2 mM. Increased R 2 relaxivity observed for dysprosium compounds in the blood presence can be explained by PRE effect. The largest gain in R 2 relaxivity seems to imply a noncovalent

NMR relaxation rate in quasi one-dimensional antiferromagnets

Science.gov (United States)

Capponi, Sylvain; Dupont, Maxime; Laflorencie, Nicolas; Sengupta, Pinaki; Shao, Hui; Sandvik, Anders W.

We compare results of different numerical approaches to compute the NMR relaxation rate 1 /T1 in quasi one-dimensional (1d) antiferromagnets. In the purely 1d regime, recent numerical simulations using DMRG have provided the full crossover behavior from classical regime at high temperature to universal Tomonaga-Luttinger liquid at low-energy (in the gapless case) or activated behavior (in the gapped case). For quasi 1d models, we can use mean-field approaches to reduce the problem to a 1d one that can be studied using DMRG. But in some cases, we can also simulate the full microscopic model using quantum Monte-Carlo techniques. This allows to compute dynamical correlations in imaginary time and we will discuss recent advances to perform stochastic analytic continuation to get real frequency spectra. Finally, we connect our results to experiments on various quasi 1d materials.

Oriented solid-state NMR spectrosocpy

DEFF Research Database (Denmark)

Bertelsen, Kresten

This thesis is concerned with driving forward oriented solid-state NMR spectroscopy as a viable technique for studying peptides in membrane bilayers. I will show that structural heterogeneity is an intrinsic part of the peptide/lipid system and that NMR can be used to characterize static...... and dynamic structural features of the peptides and its local surroundings. In fact one need to take into account the dynamical features of the system in order to correctly predict the structure from oriented solid-state NMR spectra.      ...

Low field NMR surface relaxivity studies of chalk and argillaceous sandstones

DEFF Research Database (Denmark)

Katika, Konstantina; Fordsmand, Henrik; Fabricius, Ida Lykke

2017-01-01

the accuracy of predictions of petrophysical properties of various rocks with the use of NMR spectrometry. We perform laboratory transverse relaxation (T2) measurements on water saturated Gorm field chalk, Stevns Klint chalk, Solsort field greensand and Berea sandstone. These rocks are of particular interest...... field chalk and Solsort field greensand have higher ρ at higher Larmor frequency. By contrast, ρ of the purely calcitic Stevns chalk and quartzitic Berea sandstone proved not to be affected by the changes in frequency. T2 distributions at temperatures ranging from 10 °C to 60 °C provided comparison...

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.

Quantifying protein dynamics in the ps–ns time regime by NMR relaxation

Energy Technology Data Exchange (ETDEWEB)

Hernández, Griselda; LeMaster, David M., E-mail: david.lemaster@health.ny.gov [University at Albany - SUNY, Wadsworth Center, New York State Department of Health and Department of Biomedical Sciences, School of Public Health (United States)

2016-11-15

Both {sup 15}N chemical shift anisotropy (CSA) and sufficiently rapid exchange linebroadening transitions exhibit relaxation contributions that are proportional to the square of the magnetic field. Deconvoluting these contributions is further complicated by residue-dependent variations in protein amide {sup 15}N CSA values which have proven difficult to accurately measure. Exploiting recently reported improvements for the implementation of T{sub 1} and T{sub 1ρ} experiments, field strength-dependent studies have been carried out on the B3 domain of protein G (GB3) as well as on the immunophilin FKBP12 and a H87V variant of that protein in which the major conformational exchange linebroadening transition is suppressed. By applying a zero frequency spectral density rescaling analysis to the relaxation data collected at magnetic fields from 500 to 900 MHz {sup 1}H, differential residue-specific {sup 15}N CSA values have been obtained for GB3 which correlate with those derived from solid state and liquid crystalline NMR measurements to a level similar to the correlation among those previously reported studies. Application of this analysis protocol to FKBP12 demonstrated an efficient quantitation of both weak exchange linebroadening contributions and differential residue-specific {sup 15}N CSA values. Experimental access to such differential residue-specific {sup 15}N CSA values should significantly facilitate more accurate comparisons with molecular dynamics simulations of protein motion that occurs within the timeframe of global molecular tumbling.

Tunneling splitting of magnetic levels in Fe8 detected by 1H NMR cross relaxation

Science.gov (United States)

Furukawa, Y.; Aizawa, K.; Kumagai, K.; Ullu, R.; Lascialfari, A.; Borsa, F.

2003-05-01

Measurements of proton NMR and the spin lattice relaxation rate 1/T1 in the octanuclear iron (III) cluster [Fe8(N3C6H15)6O2(OH)12]ṡ[Br8ṡ9H2O], in short Fe8, have been performed at 1.5 K in a powder sample aligned along the main anisotropy z axis, as a function of a transverse magnetic field (i.e., perpendicular to the main easy axis z). A big enhancement of 1/T1 is observed over a wide range of fields (2.5-5 T), which can be attributed to the tunneling dynamics; in fact, when the tunneling splitting of the pairwise degenerate m=±10 states of the Fe8 molecule becomes equal to the proton Larmor frequency a very effective spin lattice relaxation channel for the nuclei is opened. The experimental results are explained satisfactorily by considering the distribution of tunneling splitting resulting from the distribution of the angles in the hard xy plane for the aligned powder, and the results of the direct diagonalization of the model Hamiltonian.

Solid-state NMR covariance of homonuclear correlation spectra.

Science.gov (United States)

Hu, Bingwen; Amoureux, Jean-Paul; Trebosc, Julien; Deschamps, Michael; Tricot, Gregory

2008-04-07

Direct covariance NMR spectroscopy, which does not involve a Fourier transformation along the indirect dimension, is demonstrated to obtain homonuclear correlation two-dimensional (2D) spectra in the solid state. In contrast to the usual 2D Fourier transform (2D-FT) NMR, in a 2D covariance (2D-Cov) spectrum the spectral resolution in the indirect dimension is determined by the resolution along the detection dimension, thereby largely reducing the time-consuming indirect sampling requirement. The covariance method does not need any separate phase correction or apodization along the indirect dimension because it uses those applied in the detection dimension. We compare in detail the specifications obtained with 2D-FT and 2D-Cov, for narrow and broad resonances. The efficiency of the covariance data treatment is demonstrated in organic and inorganic samples that are both well crystallized and amorphous, for spin -1/2 nuclei with 13C, 29Si, and 31P through-space or through-bond homonuclear 2D correlation spectra. In all cases, the experimental time has been reduced by at least a factor of 10, without any loss of resolution and signal to noise ratio, with respect to what is necessary with the 2D-FT NMR. According to this method, we have been able to study the silicate network of glasses by 2D NMR within reasonable experimental time despite the very long relaxation time of the 29Si nucleus. The main limitation of the 2D-Cov data treatment is related to the introduction of autocorrelated peaks onto the diagonal, which does not represent any actual connectivity.

31-P Relaxation times of metabolic compounds in tumors grafted in nude mice

International Nuclear Information System (INIS)

Remy, C.; Benabid, A.L.; Jacrot, M.; Riondel, J.; Albrand, J.P.; Decorps, M.

1985-08-01

The observation that water proton relaxation rates were longer in tumors than in normal tissues provided a basis for the detection of human tumors by the NMR imaging technique. To evaluate the potentiality of 31-P NMR spectroscopy as a diagnostic tool of the pathological state of tissues, T1 and T2 relaxation times have been measured for the phosphates of ATP, inorganic phosphate (Pi), phosphomonoesters (PME) and phosphocreatine (PCr) in the 31-P NMR spectra obtained in vivo for normal rat brain and rat brain tumors implanted in nude mice

NMR diffusion and relaxation studies of 2-nitroimidazole and albumin interactions

Science.gov (United States)

Wijesekera, Dj; Willis, Scott A.; Gupta, Abhishek; Torres, Allan M.; Zheng, Gang; Price, William S.

2018-03-01

Nitroimidazole derivatives are of current interest in the development of hypoxia targeting agents and show potential in the establishment of quantitative measures of tumor hypoxia. In this study, the binding of 2-nitroimidazole to albumin was probed using NMR diffusion and relaxation measurements. Binding studies were conducted at three different protein concentrations (0.23, 0.30 and 0.38 mM) with drug concentrations ranging from 0.005-0.16 M at 298 K. Quantitative assessments of the binding model were made by evaluating the number of binding sites, n, and association constant, K. These were determined to be 21 ± 3 and 53 ± 4 M- 1, respectively.

Solid-State NMR Investigation of Drug-Excipient Interactions and Phase Behavior in Indomethacin-Eudragit E Amorphous Solid Dispersions.

Science.gov (United States)

Lubach, Joseph W; Hau, Jonathan

2018-02-20

To investigate the nature of drug-excipient interactions between indomethacin (IMC) and methacrylate copolymer Eudragit® E (EE) in the amorphous state, and evaluate the effects on formulation and stability of these amorphous systems. Amorphous solid dispersions containing IMC and EE were spray dried with drug loadings from 20% to 90%. PXRD was used to confirm the amorphous nature of the dispersions, and DSC was used to measure glass transition temperatures (T g ). 13 C and 15 N solid-state NMR was utilized to investigate changes in local structure and protonation state, while 1 H T 1 and T 1ρ relaxation measurements were used to probe miscibility and phase behavior of the dispersions. T g values for IMC-EE solid dispersions showed significant positive deviations from predicted values in the drug loading range of 40-90%, indicating a relatively strong drug-excipient interaction. 15 N solid-state NMR exhibited a change in protonation state of the EE basic amine, with two distinct populations for the EE amine at -360.7 ppm (unprotonated) and -344.4 ppm (protonated). Additionally, 1 H relaxation measurements showed phase separation at high drug load, indicating an amorphous ionic complex and free IMC-rich phase. PXRD data showed all ASDs up to 90% drug load remained physically stable after 2 years. 15 N solid-state NMR experiments show a change in protonation state of EE, indicating that an ionic complex indeed forms between IMC and EE in amorphous solid dispersions. Phase behavior was determined to exhibit nanoscale phase separation at high drug load between the amorphous ionic complex and excess free IMC.

Relaxed states of tokamak plasmas

International Nuclear Information System (INIS)

Kucinski, M.Y.; Okano, V.

1993-01-01

The relaxed states of tokamak plasmas are studied. It is assumed that the plasma relaxes to a quasi-steady state which is characterized by a minimum entropy production rate, compatible with a number of prescribed conditions and pressure balance. A poloidal current arises naturally due to the anisotropic resistivity. The minimum entropy production theory is applied, assuming the pressure equilibrium as fundamental constraint on the final state. (L.C.J.A.)

Mozart versus new age music: relaxation states, stress, and ABC relaxation theory.

Science.gov (United States)

Smith, Jonathan C; Joyce, Carol A

2004-01-01

Smith's (2001) Attentional Behavioral Cognitive (ABC) relaxation theory proposes that all approaches to relaxation (including music) have the potential for evoking one or more of 15 factor-analytically derived relaxation states, or "R-States" (Sleepiness, Disengagement, Rested / Refreshed, Energized, Physical Relaxation, At Ease/Peace, Joy, Mental Quiet, Childlike Innocence, Thankfulness and Love, Mystery, Awe and Wonder, Prayerfulness, Timeless/Boundless/Infinite, and Aware). The present study investigated R-States and stress symptom-patterns associated with listening to Mozart versus New Age music. Students (N = 63) were divided into three relaxation groups based on previously determined preferences. Fourteen listened to a 28-minute tape recording of Mozart's Eine Kleine Nachtmusik and 14 listened to a 28-minute tape of Steven Halpern's New Age Serenity Suite. Others (n = 35) did not want music and instead chose a set of popular recreational magazines. Participants engaged in their relaxation activity at home for three consecutive days for 28 minutes a session. Before and after each session, each person completed the Smith Relaxation States Inventory (Smith, 2001), a comprehensive questionnaire tapping 15 R-States as well as the stress states of somatic stress, worry, and negative emotion. Results revealed no differences at Session 1. At Session 2, those who listened to Mozart reported higher levels of At Ease/Peace and lower levels of Negative Emotion. Pronounced differences emerged at Session 3. Mozart listeners uniquely reported substantially higher levels of Mental Quiet, Awe and Wonder, and Mystery. Mozart listeners reported higher levels, and New Age listeners slightly elevated levels, of At Ease/Peace and Rested/Refreshed. Both Mozart and New Age listeners reported higher levels of Thankfulness and Love. In summary, those who listened to Mozart's Eine Kleine Nachtmusik reported more psychological relaxation and less stress than either those who listened to

NMR studies of spin dynamics in cuprates

International Nuclear Information System (INIS)

Takigawa, M.; Mitzi, D.B.

1994-01-01

The authors report recent NMR results in cuprates. The oxygen Knight shift and the Cu nuclear spin-lattice relaxation rate in Bi 2.1 Sr 1.94 Ca 0.88 Cu 2.07 O 8+σ single crystals revealed a gapless superconducting state, which can be most naturally explained by a d-wave pairing state and the intrinsic disorder in this material. The Cu nuclear spin-spin relaxation rate in underdoped YBa 2 Cu 3 O 6.63 shows distinct temperature dependence from the spin-lattice relaxation rate, providing direct evidence for a pseudo spin-gap near the antiferromagnetic wave vector

NMR studies of spin dynamics in cuprates

Science.gov (United States)

Takigawa, M.; Mitzi, D. B.

1994-04-01

We report recent NMR results in cuprates. The oxygen Knight shift and the Cu nuclear spin-lattice relaxation rate in Bi2.1Sr1.94Ca0.88Cu2.07O8+δ single crystals revealed a gapless superconducting state, which can be most naturally explained by a d-wave pairing state and the intrinsic disorder in this material. The Cu nuclear spin-spin relaxation rate in underdoped YBa2Cu3O6.63 shows distinct temperature dependence from the spin-lattice relaxation rate, providing direct evidence for a pseudo spin-gap near the antiferromagnetic wave vector.

General framework for studying the dynamics of folded and nonfolded proteins by NMR relaxation spectroscopy and MD simulation

NARCIS (Netherlands)

Prompers, J.J.; Brüschweiler, R.

2002-01-01

A general framework is presented for the interpretation of NMR relaxation data of proteins. The method, termed isotropic reorientational eigenmode dynamics (iRED), relies on a principal component analysis of the isotropically averaged covariance matrix of the lattice functions of the spin

Spin relaxation of iron in mixed state hemoproteins

International Nuclear Information System (INIS)

Wajnberg, E.; Kalinowski, H.J.; Bemski, G.; Helman, J.S.

1984-01-01

In pure states hemoproteins the relaxation of iron depends on its spin state. It is found that in both mixed state met-hemoglobin and met-myoglobin, the low and high spin states relax through an Orbach-like process. Also, very short (approx. 1 ns) and temperature independent transverse relaxation times T 2 were estimated. This peculiar behaviour of the relaxation may result from the unusual electronic structure of mixed state hemoproteins that allows thermal equilibrium and interconversion of the spin states. (Author) [pt

Measurement of the relaxation rate of the magnetization in Mn12O12-acetate using proton NMR echo

Science.gov (United States)

Jang; Lascialfari; Borsa; Gatteschi

2000-03-27

We present a novel method to measure the relaxation rate W of the magnetization of Mn 12O (12)-acetate (Mn12) magnetic molecular cluster in its S = 10 ground state at low T. It is based on the observation of an exponential growth in time of the proton NMR signal during the thermal equilibration of the magnetization of the molecules. We can explain the novel effect with a simple model which relates the intensity of the proton echo signal to the microscopic reversal of the magnetization of each individual Mn12 molecule during the equilibration process. The method should find wide application in the study of magnetic molecular clusters in off-equilibrium conditions.

Nuclear magnetic resonance studies on brain edema. Time course of /sup 1/H-NMR relaxation times

Energy Technology Data Exchange (ETDEWEB)

Naruse, S; Horikawa, Y; Tanaka, C; Hirakawa, K; Nishikawa, H [Kyoto Prefectural Univ. of Medicine (Japan)

1981-06-01

1. The state of water in normal and edematous brain tissue was studied by measurement of proton longitudinal (T/sub 1/) and transverse (T/sub 2/) relaxation times using pulsed nuclear magnetic resonance (NMR) technique. 2. In control rats, T/sub 1/ and T/sub 2/ of water showed one component, which was more fast in white matter. Those values displayed 1.07 - 1.18 sec. of T/sub 1/ and 75 - 76 msec. of T/sub 2/. 3. When rat brain was injured by cold, T/sub 1/ was observed to become longer (1.18 - 1.27 sec.), and T/sub 2/ was observed be separated into two components, the faster T/sub 2/ (45 - 50 msec.) and slower T/sub 2/ (100 - 105 msec.), in both gray and white matter of the injured side. 4. In triethyltin (TET) induced brain edema, elongation of T/sub 1/ (1.2 sec.) and remarkable separation of T/sub 2/, faster T/sub 2/ (75 msec.) and slower T/sub 2/ (400 - 450 msec.), were observed in white matter. 5. In both cold and TET induced edema, slower T/sub 2/ fraction is suggested to be the extracellular space and faster T/sub 2/ fraction, intracellular. 6. T/sub 2/ changes precede the water content changes in cold injury, and parallel in TET induced edema. Those changes of relaxation times are reversible. 7. T/sub 2/ changes of water is more sensitive than the T/sub 1/ for the detection of production and disappearance of brain edema. 8. These results disclose the dynamic movements of water during the course of brain edema and offered significant information of the clinical application of NMR-CT.

Low electron density of states at the boron site of TMB{sub 2} (TM = Ti, Zr, Hf, and Nb): a {sup 11}B NMR study

Energy Technology Data Exchange (ETDEWEB)

Paluch, S.; Zogal, O.J.; Peshev, P

2004-11-30

The local density of states at the boron site in TMB{sub 2} (TM=Ti, Zr, Hf, and Nb) has been examined using the solid-state {sup 11}B NMR technique. The magic angle spinning (MAS) NMR spectra at room temperature and the spin-lattice relaxation rates have been measured as functions of temperature (30-293 K). The resonance line shifts are small and become more negative in the direction from 3d- to 5d-elements. The relaxation rates follow a linear law characteristic of hyperfine magnetic interaction with conduction electrons. With borides of IV group metals the data can be understood in terms of a very low s-electron density of states and absence of a p-character of the conduction electron wave function at the Fermi level while in the case of NbB{sub 2} a small partial p-electron density of states is assumed. Then, the results are in good agreement with the earlier theoretical prediction.

NMR relaxation in natural soils: Fast Field Cycling and T1-T2 Determination by IR-MEMS

Science.gov (United States)

Haber-Pohlmeier, S.; Pohlmeier, A.; Stapf, S.; van Dusschoten, D.

2009-04-01

Soils are natural porous media of highest importance for food production and sustainment of water resources. For these functions, prominent properties are their ability of water retainment and transport, which are mainly controlled by pore size distribution. The latter is related to NMR relaxation times of water molecules, of which the longitudinal relaxation time can be determined non-invasively by fast-field cycling relaxometry (FFC) and both are obtainable by inversion recovery - multi-echo- imaging (IR-MEMS) methods. The advantage of the FFC method is the determination of the field dependent dispersion of the spin-lattice relaxation rate, whereas MRI at high field is capable of yielding spatially resolved T1 and T2 times. Here we present results of T1- relaxation time distributions of water in three natural soils, obtained by the analysis of FFC data by means of the inverse Laplace transformation (CONTIN)1. Kaldenkirchen soil shows relatively broad bimodal distribution functions D(T1) which shift to higher relaxation rates with increasing relaxation field. These data are compared to spatially resolved T1- and T2 distributions, obtained by IR-MEMS. The distribution of T1 corresponds well to that obtained by FFC.

Solid-state NMR spectroscopy on complex biomolecules

NARCIS (Netherlands)

Renault, M.A.M.; Cukkemane, A.A.; Baldus, M.

2010-01-01

Biomolecular applications of NMR spectroscopy are often merely associated with soluble molecules or magnetic resonance imaging. However, since the late 1970s, solid-state NMR (ssNMR) spectroscopy has demonstrated its ability to provide atomic-level insight into complex biomolecular systems ranging

Measurement and Characterization of Hydrogen-Deuterium Exchange Chemistry Using Relaxation Dispersion NMR Spectroscopy.

Science.gov (United States)

Khirich, Gennady; Holliday, Michael J; Lin, Jasper C; Nandy, Aditya

2018-03-01

One-dimensional heteronuclear relaxation dispersion NMR spectroscopy at 13 C natural abundance successfully characterized the dynamics of the hydrogen-deuterium exchange reaction occurring at the N ε position in l-arginine by monitoring C δ in varying amounts of D 2 O. A small equilibrium isotope effect was observed and quantified, corresponding to ΔG = -0.14 kcal mol -1 . A bimolecular rate constant of k D = 5.1 × 10 9 s -1 M -1 was determined from the pH*-dependence of k ex (where pH* is the direct electrode reading of pH in 10% D 2 O and k ex is the nuclear spin exchange rate constant), consistent with diffusion-controlled kinetics. The measurement of ΔG serves to bridge the millisecond time scale lifetimes of the detectable positively charged arginine species with the nanosecond time scale lifetime of the nonobservable low-populated neutral arginine intermediate species, thus allowing for characterization of the equilibrium lifetimes of the various arginine species in solution as a function of fractional solvent deuterium content. Despite the system being in fast exchange on the chemical shift time scale, the magnitude of the secondary isotope shift due to the exchange reaction at N ε was accurately measured to be 0.12 ppm directly from curve-fitting D 2 O-dependent dispersion data collected at a single static field strength. These results indicate that relaxation dispersion NMR spectroscopy is a robust and general method for studying base-catalyzed hydrogen-deuterium exchange chemistry at equilibrium.

Relaxation time T/sub 1/ and bound water fraction of muscle by NMR imager

Energy Technology Data Exchange (ETDEWEB)

Fukuda, N.; Ikehira, H.; Yamane, T.; Tateno, Y.; Torii, S.; Matsumura, K.

1986-05-01

In order to establish the efficacy of NMR-CT in the diagnostic investigation of muscle disorders, proton NMR-CT imaging was performed and muscle longitudinal relaxation (T1) times were measured in 20 Duchenne muscular dystrophy (DMD) patients and normal controls (NC). In addition, the bound water fraction (BWF) was calculated from the measured T1 value in appropriate cases. Results show that in DMD muscle T1 values were above normal in the early clinical stages, declined rapidly with progress of the disease, and reached the same low level as the subcutaneous fat. This decrease of T1 values was not uniform for all muscles, being most prominent in gluteus maximus and least in sartorius and gracilis. In NC muscle BWF increased with maturation under the age of 10 years, and became fixed beyond that. In the early stages of DMD, BWF was below normal.

Measurement of the Relaxation Rate of the Magnetization in Mn12O12 -Acetate Using Proton NMR Echo

International Nuclear Information System (INIS)

Jang, Z. H.; Lascialfari, A.; Borsa, F.; Gatteschi, D.

2000-01-01

We present a novel method to measure the relaxation rate W of the magnetization of Mn 12 O 12 -acetate (Mn12) magnetic molecular cluster in its S=10 ground state at low T . It is based on the observation of an exponential growth in time of the proton NMR signal during the thermal equilibration of the magnetization of the molecules. We can explain the novel effect with a simple model which relates the intensity of the proton echo signal to the microscopic reversal of the magnetization of each individual Mn12 molecule during the equilibration process. The method should find wide application in the study of magnetic molecular clusters in off-equilibrium conditions. (c) 2000 The American Physical Society

The effects of progressive muscle relaxation and autogenic relaxation on young soccer players' mood states.

Science.gov (United States)

Hashim, Hairul Anuar; Hanafi Ahmad Yusof, Hazwani

2011-06-01

This study was designed to compare the effects of two different relaxation techniques, namely progressive muscle relaxation (PMR) and autogenic relaxation (AGR) on moods of young soccer players. sixteen adolescent athletes (mean age: 14.1 ± 1.3) received either PMR or AGR training. Using Profile of Mood States- Adolescents, their mood states were measured one week before relaxation training, before the first relaxation session, and after the twelfth relaxation session. Mixed ANOVA revealed no significant interaction effects and no significant main effects in any of the subscales. However, significant main effects for testing sessions were found for confusion, depression, fatigue, and tension subscales. Post hoc tests revealed post-intervention reductions in the confusion, depression, fatigue, and tension subscale scores. These two relaxation techniques induce equivalent mood responses and may be used to regulate young soccer players' mood states.

Amplitudes and time scales of picosecond-to-microsecond motion in proteins studied by solid-state NMR: a critical evaluation of experimental approaches and application to crystalline ubiquitin

International Nuclear Information System (INIS)

Haller, Jens D.; Schanda, Paul

2013-01-01

Solid-state NMR provides insight into protein motion over time scales ranging from picoseconds to seconds. While in solution state the methodology to measure protein dynamics is well established, there is currently no such consensus protocol for measuring dynamics in solids. In this article, we perform a detailed investigation of measurement protocols for fast motions, i.e. motions ranging from picoseconds to a few microseconds, which is the range covered by dipolar coupling and relaxation experiments. We perform a detailed theoretical investigation how dipolar couplings and relaxation data can provide information about amplitudes and time scales of local motion. We show that the measurement of dipolar couplings is crucial for obtaining accurate motional parameters, while systematic errors are found when only relaxation data are used. Based on this realization, we investigate how the REDOR experiment can provide such data in a very accurate manner. We identify that with accurate rf calibration, and explicit consideration of rf field inhomogeneities, one can obtain highly accurate absolute order parameters. We then perform joint model-free analyses of 6 relaxation data sets and dipolar couplings, based on previously existing, as well as new data sets on microcrystalline ubiquitin. We show that nanosecond motion can be detected primarily in loop regions, and compare solid-state data to solution-state relaxation and RDC analyses. The protocols investigated here will serve as a useful basis towards the establishment of a routine protocol for the characterization of ps–μs motions in proteins by solid-state NMR

Amplitudes and time scales of picosecond-to-microsecond motion in proteins studied by solid-state NMR: a critical evaluation of experimental approaches and application to crystalline ubiquitin

Energy Technology Data Exchange (ETDEWEB)

Haller, Jens D.; Schanda, Paul, E-mail: paul.schanda@ibs.fr [Univ. Grenoble Alpes, Institut de Biologie Structurale (IBS) (France)

2013-10-09

Solid-state NMR provides insight into protein motion over time scales ranging from picoseconds to seconds. While in solution state the methodology to measure protein dynamics is well established, there is currently no such consensus protocol for measuring dynamics in solids. In this article, we perform a detailed investigation of measurement protocols for fast motions, i.e. motions ranging from picoseconds to a few microseconds, which is the range covered by dipolar coupling and relaxation experiments. We perform a detailed theoretical investigation how dipolar couplings and relaxation data can provide information about amplitudes and time scales of local motion. We show that the measurement of dipolar couplings is crucial for obtaining accurate motional parameters, while systematic errors are found when only relaxation data are used. Based on this realization, we investigate how the REDOR experiment can provide such data in a very accurate manner. We identify that with accurate rf calibration, and explicit consideration of rf field inhomogeneities, one can obtain highly accurate absolute order parameters. We then perform joint model-free analyses of 6 relaxation data sets and dipolar couplings, based on previously existing, as well as new data sets on microcrystalline ubiquitin. We show that nanosecond motion can be detected primarily in loop regions, and compare solid-state data to solution-state relaxation and RDC analyses. The protocols investigated here will serve as a useful basis towards the establishment of a routine protocol for the characterization of ps–μs motions in proteins by solid-state NMR.

The Effects of Progressive Muscle Relaxation and Autogenic Relaxation on Young Soccer Players’ Mood States

Science.gov (United States)

Hashim, Hairul Anuar; Hanafi@Ahmad Yusof, Hazwani

2011-01-01

Purpose This study was designed to compare the effects of two different relaxation techniques, namely progressive muscle relaxation (PMR) and autogenic relaxation (AGR) on moods of young soccer players. Methods Sixteen adolescent athletes (mean age: 14.1 ± 1.3) received either PMR or AGR training. Using Profile of Mood States- Adolescents, their mood states were measured one week before relaxation training, before the first relaxation session, and after the twelfth relaxation session. Results Mixed ANOVA revealed no significant interaction effects and no significant main effects in any of the subscales. However, significant main effects for testing sessions were found for confusion, depression, fatigue, and tension subscales. Post hoc tests revealed post-intervention reductions in the confusion, depression, fatigue, and tension subscale scores. Conclusion These two relaxation techniques induce equivalent mood responses and may be used to regulate young soccer players’ mood states. PMID:22375225

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

Energy Technology Data Exchange (ETDEWEB)

Shmyreva, Anna A. [Center for Magnetic Resonance, St. Petersburg State University, St. Petersburg 198504 (Russian Federation); Safdari, Majid; Furó, István [Department of Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm (Sweden); Dvinskikh, Sergey V., E-mail: sergeid@kth.se [Department of Chemistry, KTH Royal Institute of Technology, SE-10044 Stockholm (Sweden); Laboratory of Biomolecular NMR, St. Petersburg State University, St. Petersburg 199034 (Russian Federation)

2016-06-14

Orders of magnitude decrease of {sup 207}Pb and {sup 199}Hg NMR longitudinal relaxation times T{sub 1} upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX{sub 2} (Me = Pb, Hg and X = Cl, Br, I). In lead(II) halides, the most dramatic decrease of T{sub 1} relative to that in a static sample is in PbI{sub 2}, while it is smaller but still significant in PbBr{sub 2}, and not detectable in PbCl{sub 2}. 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.

13C NMR relaxation times of hepatic glycogen in vitro and in vivo

International Nuclear Information System (INIS)

Zang, Lihsin; Laughlin, M.R.; Rothman, D.L.; Shulman, R.G.

1990-01-01

The field dependence of relaxation times of the C-1 carbon of glycogen was studied in vitro by natural-abundance 13 C NMR. T 1 is strongly field dependent, while T 2 does not change significantly with magnetic field. T 1 and T 2 were also measured for rat hepatic glycogen enriched with [1- 13 C]glucose in vivo at 4.7 T, and similar relaxation times were observed as those obtained in vitro at the same field. The in vitro values of T 1 were 65 ± 5 ms at 2.1 T, 142 ± 10 ms at 4.7 T, and 300 ± 10 ms at 8.4 T, while T 2 values were 6.7 ± 1 ms at 2.1 T, 9.4 ± 1 ms at 4.7 T, and 9.5 ± 1 ms at 8.4 T. Calculations based on the rigid-rotor nearest-neighbor model give qualitatively good agreement with the T 1 field dependence with a best-fit correlation time of 6.4 x 10 -9 s, which is significantly smaller than τ M , the estimated overall correlation time for the glycogen molecule (ca. 10 -5 s). A more accurate fit of T 1 data using a modified Lipari and Szabo approach indicates that internal fast motions dominate the T 1 relaxation in glycogen. On the other hand, the T 2 relaxation is dominated by the overall correlation time τ M while the internal motions are almost but not completely unrestricted

A study of spin-lattice relaxation rates of glucose, fructose, sucrose and cherries using high-T c SQUID-based NMR in ultralow magnetic fields

Science.gov (United States)

Liao, Shu-Hsien; Wu, Pei-Che

2017-08-01

We study the concentration dependence of spin-lattice relaxation rates, T 1 -1, of glucose, fructose, sucrose and cherries by using high-T c SQUID-based NMR at magnetic fields of ˜97 μT. The detected NMR signal, Sy (T Bp), is fitted to [1 - exp(-T Bp/T 1)] to derive T 1 -1, where Sy (T Bp) is the strength of the NMR signal, T Bp is the duration of pre-polarization and T 1 -1 is the spin-lattice relaxation rate. It was found that T 1 -1 increases as the sugar concentrations increase. The increased T 1 -1 is due to the presence of more molecules in the surroundings, which increases the spin-lattice interaction and in turn enhances T 1 -1. The T 1 -1 versus degrees Brix curve provides a basis for determining unknown Brix values for cherries as well as other fruits.

Solid-state NMR of inorganic semiconductors.

Science.gov (United States)

Yesinowski, James P

2012-01-01

Studies of inorganic semiconductors by solid-state NMR vary widely in terms of the nature of the samples investigated, the techniques employed to observe the NMR signal, and the types of information obtained. Compared with the NMR of diamagnetic non-semiconducting substances, important differences often result from the presence of electron or hole carriers that are the hallmark of semiconductors, and whose theoretical interpretation can be involved. This review aims to provide a broad perspective on the topic for the non-expert by providing: (1) a basic introduction to semiconductor physical concepts relevant to NMR, including common crystal structures and the various methods of making samples; (2) discussions of the NMR spin Hamiltonian, details of some of the NMR techniques and strategies used to make measurements and theoretically predict NMR parameters, and examples of how each of the terms in the Hamiltonian has provided useful information in bulk semiconductors; (3) a discussion of the additional considerations needed to interpret the NMR of nanoscale semiconductors, with selected examples. The area of semiconductor NMR is being revitalized by this interest in nanoscale semiconductors, the great improvements in NMR detection sensitivity and resolution that have occurred, and the current interest in optical pumping and spintronics-related studies. Promising directions for future research will be noted throughout.

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

International Nuclear Information System (INIS)

Spyracopoulos, Leo

2006-01-01

A suite of Mathematica notebooks has been designed to ease the analysis of protein main chain 15 N NMR relaxation data collected at a single magnetic field strength. Individual notebooks were developed to perform the following tasks: nonlinear fitting of 15 N-T 1 and -T 2 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 15 N-T 1 , -T 2 , and { 1 H}- 15 N 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

NMR quantification of diffusional exchange in cell suspensions with relaxation rate differences between intra and extracellular compartments.

Science.gov (United States)

Eriksson, Stefanie; Elbing, Karin; Söderman, Olle; Lindkvist-Petersson, Karin; Topgaard, Daniel; Lasič, Samo

2017-01-01

Water transport across cell membranes can be measured non-invasively with diffusion NMR. We present a method to quantify the intracellular lifetime of water in cell suspensions with short transverse relaxation times, T2, and also circumvent the confounding effect of different T2 values in the intra- and extracellular compartments. Filter exchange spectroscopy (FEXSY) is specifically sensitive to exchange between compartments with different apparent diffusivities. Our investigation shows that FEXSY could yield significantly biased results if differences in T2 are not accounted for. To mitigate this problem, we propose combining FEXSY with diffusion-relaxation correlation experiment, which can quantify differences in T2 values in compartments with different diffusivities. Our analysis uses a joint constrained fitting of the two datasets and considers the effects of diffusion, relaxation and exchange in both experiments. The method is demonstrated on yeast cells with and without human aquaporins.

Measuring diffusion-relaxation correlation maps using non-uniform field gradients of single-sided NMR devices.

Science.gov (United States)

Nogueira d'Eurydice, Marcel; Galvosas, Petrik

2014-11-01

Single-sided NMR systems are becoming a relevant tool in industry and laboratory environments due to their low cost, low maintenance and capacity to evaluate quantity and quality of hydrogen based materials. The performance of such devices has improved significantly over the last decade, providing increased field homogeneity, field strength and even controlled static field gradients. For a class of these devices, the configuration of the permanent magnets provides a linear variation of the magnetic field and can be used in diffusion measurements. However, magnet design depends directly on its application and, according to the purpose, the field homogeneity may significantly be compromised. This may prevent the determination of diffusion properties of fluids based on the natural inhomogeneity of the field using known techniques. This work introduces a new approach that extends the applicability of diffusion-editing CPMG experiments to NMR devices with highly inhomogeneous magnetic fields, which do not vary linearly in space. Herein, we propose a method to determine a custom diffusion kernel based on the gradient distribution, which can be seen as a signature of each NMR device. This new diffusion kernel is then utilised in the 2D inverse Laplace transform (2D ILT) in order to determine diffusion-relaxation correlation maps of homogeneous multi-phasic fluids. The experiments were performed using NMR MObile Lateral Explore (MOLE), which is a single-sided NMR device designed to maximise the volume at the sweet spot with enhanced depth penetration. Copyright © 2014 Elsevier Inc. All rights reserved.

13C spin relaxation measurements in RNA: Sensitivity and resolution improvement using spin-state selective correlation experiments

International Nuclear Information System (INIS)

Boisbouvier, Jerome; Brutscher, Bernhard; Simorre, Jean-Pierre; Marion, Dominique

1999-01-01

A set of new NMR pulse sequences has been designed for the measurement of 13 C relaxation rate constants in RNA and DNA bases: the spin-lattice relaxation rate constant R(C z ), the spin-spin relaxation rate constant R(C + ), and the CSA-dipolar cross-correlated relaxation rate constant Γ C,CH xy . The use of spin-state selective correlation techniques provides increased sensitivity and spectral resolution. Sensitivity optimised C-C filters are included in the pulse schemes for the suppression of signals originating from undesired carbon isotopomers. The experiments are applied to a 15% 13 C-labelled 33-mer RNA-theophylline complex. The measured R(C + )/Γ C,CH xy ratios indicate that 13 C CSA tensors do not vary significantly for the same type of carbon (C 2 , C 6 , C 8 ), but that they differ from one type to another. In addition, conformational exchange effects in the RNA bases are detected as a change in the relaxation decay of the narrow 13 C doublet component when varying the spacing of a CPMG pulse train. This new approach allows the detection of small exchange effects with a higher precision compared to conventional techniques

Paramagnetic relaxation enhancements in NMR peptide-membrane interaction studies

International Nuclear Information System (INIS)

Kosol, S.

2011-01-01

Small membrane-bound proteins or peptides are involved in numerous essential biological processes, like cellular recognition, signaling, channel formation, and cytolysis. The secondary structure, orientation, mode of interaction and dynamics of these peptides can be as varied as their functions. Their localization in the membrane, the immersion depth, and their binding mode are factors critical to the function of these peptides. The atomic 3D solution structure of peptides bound to micelles can be determined by NMR spectroscopy. However, by employing paramagnetic relaxation enhancements (PREs) information on the complete topology of peptide bound to a micelle can be obtained. The antimicrobial peptide maximin H6, fst, a bacterial toxin, and the human peptide hormone ghrelin served as membrane-bound model peptides of similar sizes but strongly differing amino acid sequences. Their structures and binding behavior were determined and compared.The measured PREs provided suitable data for determining and distinguishing the different topologies of the investigated peptides bound to micelles. Maximin H6 and fst fold into α-helices upon insertion into a membrane, whereas the unstructured ghrelin is freely mobile in solution and interacts only via a covalently bound octanoyl group with the lipids. Maximin H6 is oriented parallel to the membrane surface, enabling the peptide to aggregate at the membrane water interface. Fst binds in transmembrane orientation with a protruding intrinsically disordered region near the C-terminus. Aside from determining the orientation of the bound peptides from the PREs, the moieties critical for membrane binding could be mapped in ghrelin. If suitable relaxation-edited spectra are acquired, the complete orientation and immersion depth of a peptide bound to a micelle can readily be obtained. (author) [de

Solid state proton spin-lattice relaxation in four structurally related organic molecules

International Nuclear Information System (INIS)

Beckmann, Peter A.; Burbank, Kendra S.; Lau, Matty M.W.; Ree, Jessica N.; Weber, Tracy L.

2003-01-01

We report and interpret the temperature dependence of the proton spin-lattice relaxation rate at 8.50 and 22.5 MHz in four polycrystalline solids composed of structurally related molecules: 2-ethylanthracene, 2-t-butylanthracene, 2-ethylanthraquinone, and 2-t-butylanthraquinone. We have been unable to grow single crystals and therefore do not know the crystal structures. Hence, we use the NMR relaxometry data to make predictions about the solid state structures. As expected, we are able to conclude that the ethyl groups do not reorient in the solid state but that the t-butyl groups do. The anthraquinones have a ''simpler'' structure than the anthracenes. The best dynamical models suggest that there is a unique crystallographic site for the t-butyl groups in 2-t-butylanthraquinone and two sites, each with half the molecules, for the ethyl groups in 2-ethylanthraquinone. There are also two sites in 2-ethylanthracene, but with unequal weights, suggesting four sites in the unit cell with lower symmetry than the two anthraquinones. Finally, the observed relaxation rate data in 2-t-butylanthracene is very complex and its interpretation demonstrates the uniqueness problem that arises in interpreting relaxometry data without the knowledge of the crystal structure

Coexistence of spin frozen state and persistent spin dynamics in NaSrCo{sub 2}F{sub 7} as probed by μSR and NMR

Energy Technology Data Exchange (ETDEWEB)

Dengre, Shanu; Sarkar, Rajib; Braeuninger, Sascha Albert; Brueckner, Felix; Materne, Philipp; Klauss, Hans-Henning [Institute for Solid State Physics, TU Dresden (Germany); Krizan, Jason W.; Cava, Robert J. [Department of Chemistry, Princeton University, Princeton, NJ (United States); Luetkens, Hubertus; Baines, Chris [Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institute, Villigen (Switzerland)

2016-07-01

{sup 23}Na -and {sup 19}F NMR, and μSR experiments are performed to explore the microscopic properties of NaSrCo{sub 2}F{sub 7}, which is a newly discovered magnetically frustrated pyrochlore with weak bond disorder and with a frustration index of f = 42. While {sup 23}Na and {sup 19}F NMR experiments clearly suggest the presence of quasi static field distribution below ∝3 K as reflected in the huge NMR line broadening and wipe out effect of NMR signal intensity, μSR experiments on the other hand remains passive to this spin frozen state. Both NMR and μSR results indicate the slowing down of the magnetic (spin) fluctuations upon cooling towards the NMR spin frozen state. μSR relaxation rate increases slightly below ∝ 3 K, and remains not only constant down to 20 mK, but also stands independent in longitudinal magnetic field upto 4000 G implying that the spin fluctuations are dynamic. These observations suggest the coexistence of partial spin frozen state and persistent spin dynamics in NaSrCo{sub 2}F{sub 7}.

Investigation of new NMR methods for structural and dynamic studies in the liquid state

International Nuclear Information System (INIS)

Desvaux, H.

1993-01-01

After a short presentation of the NMR fundements, three new methods of spin -lattice relaxation in liquids are reported. (1) The method consists of measuring the steady-state nuclear magnetization under strong off-resonance rf irradiation as a function of the angle θ between external field and effective field. For purely dipolar relaxation between homonuclear spins under isotropic Brownian molecular rotation, this variation yields the value of the local correlation time. A departure from the theoretical shape reveals the existence of complex motions or complex relaxation mechanisms. These results have been verified by experimental illustrations. Some numerical simulations have been performed for studying the effects of the distribution of chemical shift and for studying the coherence of the local correlation time concept. (2) The improvements of a modified ROESY experiment are discussed. The use of a time-modulated strong off-resonances rf irradiation permits to suppress totally the problems of the NOESY (suppression of cross-relaxation peaks for molecules where ωτ c ≅ 1.1) and of the ROESY (HOHAHA transfer and angular dispersion due to the chemical shift distribution). The angle θ defined previously can be used as a constraint: either to obtain a ratio of the cross over direct dipolar relaxation rates independent on the correlation time value, or to observe the sole chemical exchange. (3) The difference of the relaxation rates of the coherences at zero and two quanta is always exactly the cross relaxation rates measured by the NOESY experiment. The experimental illustration is presented

A software framework for analysing solid-state MAS NMR data

International Nuclear Information System (INIS)

Stevens, Tim J.; Fogh, Rasmus H.; Boucher, Wayne; Higman, Victoria A.; Eisenmenger, Frank; Bardiaux, Benjamin; Rossum, Barth-Jan van; Oschkinat, Hartmut; Laue, Ernest D.

2011-01-01

Solid-state magic-angle-spinning (MAS) NMR of proteins has undergone many rapid methodological developments in recent years, enabling detailed studies of protein structure, function and dynamics. Software development, however, has not kept pace with these advances and data analysis is mostly performed using tools developed for solution NMR which do not directly address solid-state specific issues. Here we present additions to the CcpNmr Analysis software package which enable easier identification of spinning side bands, straightforward analysis of double quantum spectra, automatic consideration of non-uniform labelling schemes, as well as extension of other existing features to the needs of solid-state MAS data. To underpin this, we have updated and extended the CCPN data model and experiment descriptions to include transfer types and nomenclature appropriate for solid-state NMR experiments, as well as a set of experiment prototypes covering the experiments commonly employed by solid-sate MAS protein NMR spectroscopists. This work not only improves solid-state MAS NMR data analysis but provides a platform for anyone who uses the CCPN data model for programming, data transfer, or data archival involving solid-state MAS NMR data.

Quantitative analysis of protein-ligand interactions by NMR.

Science.gov (United States)

Furukawa, Ayako; Konuma, Tsuyoshi; Yanaka, Saeko; Sugase, Kenji

2016-08-01

Protein-ligand interactions have been commonly studied through static structures of the protein-ligand complex. Recently, however, there has been increasing interest in investigating the dynamics of protein-ligand interactions both for fundamental understanding of the underlying mechanisms and for drug development. NMR is a versatile and powerful tool, especially because it provides site-specific quantitative information. NMR has widely been used to determine the dissociation constant (KD), in particular, for relatively weak interactions. The simplest NMR method is a chemical-shift titration experiment, in which the chemical-shift changes of a protein in response to ligand titration are measured. There are other quantitative NMR methods, but they mostly apply only to interactions in the fast-exchange regime. These methods derive the dissociation constant from population-averaged NMR quantities of the free and bound states of a protein or ligand. In contrast, the recent advent of new relaxation-based experiments, including R2 relaxation dispersion and ZZ-exchange, has enabled us to obtain kinetic information on protein-ligand interactions in the intermediate- and slow-exchange regimes. Based on R2 dispersion or ZZ-exchange, methods that can determine the association rate, kon, dissociation rate, koff, and KD have been developed. In these approaches, R2 dispersion or ZZ-exchange curves are measured for multiple samples with different protein and/or ligand concentration ratios, and the relaxation data are fitted to theoretical kinetic models. It is critical to choose an appropriate kinetic model, such as the two- or three-state exchange model, to derive the correct kinetic information. The R2 dispersion and ZZ-exchange methods are suitable for the analysis of protein-ligand interactions with a micromolar or sub-micromolar dissociation constant but not for very weak interactions, which are typical in very fast exchange. This contrasts with the NMR methods that are used

High resolution NMR study of cellulose in solid state and in solution

International Nuclear Information System (INIS)

Saint-Germain, Jean

1983-01-01

This research thesis reports the study of native cellulose (cotton) and wood by nuclear magnetic resonance (NMR). As far as the cotton spectrum is concerned, the author assigned resonances which more specifically corresponded to amorphous or crystalline areas. Wood was studied in its bulk condition, and resonances have been determined for the different wood components. The behaviour of cellulose in solution in a solvent has been studied by liquid high resolution NMR. The solvation mechanism has been determined and a study of model components of the macromolecule allowed a conformational study of cellulose in this solvent to be performed. Bi-dimensional NMR and longitudinal relaxation time measurements highlighted the existence of an intramolecular hydrogen bond in the cellulose in solution [fr

Ferromagnetic correlations in Yb based heavy fermions probed by NMR relaxation: YbNi{sub 4}P{sub 2} vs. Yb(Rh,Ir){sub 2}Si{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Baenitz, M.; Sarkar, R.; Khuntia, P.; Krellner, C.; Geibel, C.; Steglich, F. [Max - Planck Institute of Chemical Physics of Solids, 01187 Dresden, Germany (Germany)

2012-07-01

Intersite correlations in Ce-based heavy fermion systems close to the quantum critical point separating the magnetic ordered state from the paramagnetic Kondo lattice are in almost all cases predominantly antiferromagnetic (AFM) in nature. The NMR relaxation of these systems show an evolution from localized fluctuations with 1/T{sub 1} nearly constant above the Kondo temperature T{sub K}, to a linear in T Korringa- like behavior with a constant and enhanced (1/T{sub 1}T)- value below T{sub K}. We report on {sup 31}P-NMR results on the ferromagnetic (FM) quantum critical system YbNi{sub 4}P{sub 2} over a wide range in temperature (2-300 K) and field (0.2 - 9 T). Here, {sup 31}(1/T{sub 1}T)(T) does not show such a signature at T{sub K}, instead a continuous increase of (1/T{sub 1}T) down to lowest T is observed. A similar behavior has been reported for YbRh{sub 2}Si{sub 2}, which also exhibits strong FM correlations evidenced by {sup 29}Si - NMR and an enhanced Wilson ratio. Furthermore, in CeFePO, which is likely unique among Ce-based quantum critical system because of its strong FM correlations, (1/T{sub 1}T) also diverges continuously for T {yields}0. This suggests that the difference in the relaxation between most of the Ce systems and the Yb systems is predominantly related to a change from AFM to FM intersite correlations. NMR-results (shift, line width, T{sub 1}) are analyzed and discussed in different models (Korringa, Moriya).

Measurement of the Relaxation Rate of the Magnetization in Mn{sub 12}O{sub 12} -Acetate Using Proton NMR Echo

Energy Technology Data Exchange (ETDEWEB)

Jang, Z. H. [Department of Physics and Astronomy, Ames Laboratory, Iowa State University, Ames, Iowa 50011 (United States); Lascialfari, A. [Dipartimento di Fisica ' ' A. Volta' ' e Unita' , INFM di Pavia, Via Bassi 6, 27100 Pavia, (Italy); Borsa, F. [Department of Physics and Astronomy, Ames Laboratory, Iowa State University, Ames, Iowa 50011 (United States); Dipartimento di Fisica ' ' A. Volta' ' e Unita' , INFM di Pavia, Via Bassi 6, 27100 Pavia, (Italy); Gatteschi, D. [Department of Chemistry, University of Florence, Via Maragliano 77, 50144 Firenze, (Italy)

2000-03-27

We present a novel method to measure the relaxation rate W of the magnetization of Mn{sub 12}O {sub 12} -acetate (Mn12) magnetic molecular cluster in its S=10 ground state at low T . It is based on the observation of an exponential growth in time of the proton NMR signal during the thermal equilibration of the magnetization of the molecules. We can explain the novel effect with a simple model which relates the intensity of the proton echo signal to the microscopic reversal of the magnetization of each individual Mn12 molecule during the equilibration process. The method should find wide application in the study of magnetic molecular clusters in off-equilibrium conditions. (c) 2000 The American Physical Society.

Defining the Structural Basis for Allosteric Product Release from E. coli Dihydrofolate Reductase Using NMR Relaxation Dispersion.

Science.gov (United States)

Oyen, David; Fenwick, R Bryn; Aoto, Phillip C; Stanfield, Robyn L; Wilson, Ian A; Dyson, H Jane; Wright, Peter E

2017-08-16

The rate-determining step in the catalytic cycle of E. coli dihydrofolate reductase is tetrahydrofolate (THF) product release, which can occur via an allosteric or an intrinsic pathway. The allosteric pathway, which becomes accessible when the reduced cofactor NADPH is bound, involves transient sampling of a higher energy conformational state, greatly increasing the product dissociation rate as compared to the intrinsic pathway that obtains when NADPH is absent. Although the kinetics of this process are known, the enzyme structure and the THF product conformation in the transiently formed excited state remain elusive. Here, we use side-chain proton NMR relaxation dispersion measurements, X-ray crystallography, and structure-based chemical shift predictions to explore the structural basis of allosteric product release. In the excited state of the E:THF:NADPH product release complex, the reduced nicotinamide ring of the cofactor transiently enters the active site where it displaces the pterin ring of the THF product. The p-aminobenzoyl-l-glutamate tail of THF remains weakly bound in a widened binding cleft. Thus, through transient entry of the nicotinamide ring into the active site, the NADPH cofactor remodels the enzyme structure and the conformation of the THF to form a weakly populated excited state that is poised for rapid product release.

Solid-state NMR on complex biomolecules: novel methods and applications

NARCIS (Netherlands)

Nand, D.

2011-01-01

Solid-state NMR (ssNMR) represents a versatile technique in providing atomic-resolution information without the need for crystals or fast molecular motion required for X-ray crystallography and solution-state NMR, respectively. Recent past has witnessed the ability of this technique in providing

Relaxation-compensated difference spin diffusion NMR for detecting 13C–13C long-range correlations in proteins and polysaccharides

International Nuclear Information System (INIS)

Wang, Tuo; Williams, Jonathan K.; Schmidt-Rohr, Klaus; Hong, Mei

2015-01-01

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 13 C-labeled biomolecules, inter-residue, inter-segmental, and intermolecular 13 C– 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 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 13 C T 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 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 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-residue and intermolecular correlation peaks

Evaluating the influence of initial magnetization conditions on extracted exchange parameters in NMR relaxation experiments: applications to CPMG and CEST

Energy Technology Data Exchange (ETDEWEB)

Yuwen, Tairan; Sekhar, Ashok; Kay, Lewis E., E-mail: kay@pound.med.utoronto.ca [The University of Toronto, Departments of Molecular Genetics, Biochemistry and Chemistry (Canada)

2016-08-15

Transient excursions of native protein states to functionally relevant higher energy conformations often occur on the μs–ms timescale. NMR spectroscopy has emerged as an important tool to probe such processes using techniques such as Carr–Purcell–Meiboom–Gill (CPMG) relaxation dispersion and Chemical Exchange Saturation Transfer (CEST). The extraction of kinetic and structural parameters from these measurements is predicated upon mathematical modeling of the resulting relaxation profiles, which in turn relies on knowledge of the initial magnetization conditions at the start of the CPMG/CEST relaxation elements in these experiments. Most fitting programs simply assume initial magnetization conditions that are given by equilibrium populations, which may be incorrect in certain implementations of experiments. In this study we have quantified the systematic errors in extracted parameters that are generated from analyses of CPMG and CEST experiments using incorrect initial boundary conditions. We find that the errors in exchange rates (k{sub ex}) and populations (p{sub E}) are typically small (<10 %) and thus can be safely ignored in most cases. However, errors become larger and cannot be fully neglected (20–40 %) as k{sub ex} falls near the lower limit of each method or when short CPMG/CEST relaxation elements are used in these experiments. The source of the errors can be rationalized and their magnitude given by a simple functional form. Despite the fact that errors tend to be small, it is recommended that the correct boundary conditions be implemented in fitting programs so as to obtain as robust estimates of exchange parameters as possible.

Solid state nuclear magnetic resonance of fossil fuels

International Nuclear Information System (INIS)

Axelson, D.E.

1985-01-01

This book contains the following chapters: Principles of solid state NMR; Relaxation processes: Introduction to pulse sequences; Quantitative analysis; Removal of artifacts from CPMAS FT experiments; Line broadening mechanisms; Resolution enhancement of solid state NMR spectra; and /sup 13/C CPMAS NMR of fossil fuels--general applications

Spectroscopic Studies of the Super Relaxed State of Skeletal Muscle.

Directory of Open Access Journals (Sweden)

Leonardo Nogara

Full Text Available In the super-relaxed state of myosin, ATPase activity is strongly inhibited by binding of the myosin heads to the core of the thick filament in a structure known as the interacting-heads motif. In the disordered relaxed state myosin heads are not bound to the core of the thick filament and have an ATPase rate that is 10 fold greater. In the interacting-heads motif the two regulatory light chains appear to bind to each other. We have made single cysteine mutants of the regulatory light chain, placed both paramagnetic and fluorescent probes on them, and exchanged them into skinned skeletal muscle fibers. Many of the labeled light chains tended to disrupt the stability of the super-relaxed state, and showed spectral changes in the transition from the disordered relaxed state to the super-relaxed state. These data support the putative interface between the two regulatory light chains identified by cryo electron microscopy and show that both the divalent cation bound to the regulatory light chain and the N-terminus of the regulatory light chain play a role in the stability of the super-relaxed state. One probe showed a shift to shorter wavelengths in the super-relaxed state such that a ratio of intensities at 440nm to that at 520nm provided a measure of the population of the super-relaxed state amenable for high throughput screens for finding potential pharmaceuticals. The results provide a proof of concept that small molecules that bind to this region can destabilize the super-relaxed state and provide a method to search for small molecules that do so leading to a potentially effective treatment for Type 2 diabetes and obesity.

Characterization of Chemical Exchange Using Relaxation Dispersion of Hyperpolarized Nuclear Spins.

Science.gov (United States)

Liu, Mengxiao; Kim, Yaewon; Hilty, Christian

2017-09-05

Chemical exchange phenomena are ubiquitous in macromolecules, which undergo conformational change or ligand complexation. NMR relaxation dispersion (RD) spectroscopy based on a Carr-Purcell-Meiboom-Gill pulse sequence is widely applied to identify the exchange and measure the lifetime of intermediate states on the millisecond time scale. Advances in hyperpolarization methods improve the applicability of NMR spectroscopy when rapid acquisitions or low concentrations are required, through an increase in signal strength by several orders of magnitude. Here, we demonstrate the measurement of chemical exchange from a single aliquot of a ligand hyperpolarized by dissolution dynamic nuclear polarization (D-DNP). Transverse relaxation rates are measured simultaneously at different pulsing delays by dual-channel 19 F NMR spectroscopy. This two-point measurement is shown to allow the determination of the exchange term in the relaxation rate expression. For the ligand 4-(trifluoromethyl)benzene-1-carboximidamide binding to the protein trypsin, the exchange term is found to be equal within error limits in neutral and acidic environments from D-DNP NMR spectroscopy, corresponding to a pre-equilibrium of trypsin deprotonation. This finding illustrates the capability for determination of binding mechanisms using D-DNP RD. Taking advantage of hyperpolarization, the ligand concentration in the exchange measurements can reach on the order of tens of μM and protein concentration can be below 1 μM, i.e., conditions typically accessible in drug discovery.

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

Backbone dynamics of free barnase and its complex with barstar determined by 15N NMR relaxation study

International Nuclear Information System (INIS)

Sahu, Sarata C.; Bhuyan, Abani K.; Udgaonkar, Jayant B.; Hosur, R.V.

2000-01-01

Backbone dynamics of uniformly 15 N-labeled free barnase and its complex with unlabelled barstar have been studied at 40 deg. C, pH 6.6, using 15 N relaxation data obtained from proton-detected 2D { 1 H}- 15 N NMR spectroscopy. 15 N spin-lattice relaxation rate constants (R 1 ), spin-spin relaxation rate constants (R 2 ), and steady-state heteronuclear { 1 H}- 15 N NOEs have been measured at a magnetic field strength of 14.1 Tesla for 91 residues of free barnase and for 90 residues out of a total of 106 in the complex (excluding three prolines and the N-terminal residue) backbone amide 15 N sites of barnase. The primary relaxation data for both the cases have been analyzed in the framework of the model-free formalism using both isotropic and axially symmetric models of the rotational diffusion tensor. As per the latter, the overall rotational correlation times (τ m ) are 5.0 and 9.5 ns for the free and complexed barnase, respectively. The average order parameter is found to be 0.80 for free barnase and 0.86 for the complex. However, the changes are not uniform along the backbone and for about 5 residues near the binding interface there is actually a significant decrease in the order parameters on complex formation. These residues are not involved in the actual binding. For the residues where the order parameter increases, the magnitudes vary significantly. It is observed that the complex has much less internal mobility, compared to free barnase. From the changes in the order parameters, the entropic contribution of NH bond vector motion to the free energy of complex formation has been calculated. It is apparent that these motions cause significant unfavorable contributions and therefore must be compensated by many other favorable contributions to effect tight complex formation. The observed variations in the motion and their different locations with regard to the binding interface may have important implications for remote effects and regulation of the enzyme

13C NMR and relaxation studies of the nanomagnet Mn12-acetate

Science.gov (United States)

Achey, Randall M.; Kuhns, Philip L.; Reyes, Arneil P.; Moulton, William G.; Dalal, Naresh S.

2001-08-01

The nanomagnet [Mn12O12(CH3COO)16(H2O)4].2CH3COOH.4H2O, also known as Mn12, has been synthesized with 13C labeling at the CH3 groups, and investigated by 13C NMR at fields up to 23 T. Using oriented samples, it is possible to resolve four distinct 13C peaks at room temperature, located on both sides of the unshifted Larmor frequency. These peaks were assigned to the four hyperfine-shifted, magnetically inequivalent sets of 13CH3 groups in the Mn12 lattice, based on a comparison with the crystal structure and point-dipole and spin-density calculations. These results establish that the unpaired electron spin density of the S=10 system in this cluster extends over the entire molecular framework, not just the core. These results are discussed in relationship to inelastic neutron scattering measurements. The temperature and field dependence of the 13C nuclear-spin-lattice-relaxation time T1 on the least shifted peak was measured. A single weakly field-dependent minimum at about 60 K is observed in the temperature dependence of the measured T1. The relaxation mechanism responsible for the T1 minimum is ascribed mainly to hindered rotation of the methyl group of the acetate ligand at higher temperature, and to electronic spin fluctuations at lower temperature.

Excited-state relaxation of some aminoquinolines

Directory of Open Access Journals (Sweden)

2006-01-01

Full Text Available The absorption and fluorescence spectra, fluorescence quantum yields and lifetimes, and fluorescence rate constants ( k f of 2-amino-3-( 2 ′ -benzoxazolylquinoline (I, 2-amino-3-( 2 ′ -benzothiazolylquinoline (II, 2-amino-3-( 2 ′ -methoxybenzothiazolyl-quinoline (III, 2-amino-3-( 2 ′ -benzothiazolylbenzoquinoline (IV at different temperatures have been measured. The shortwavelength shift of fluorescence spectra of compounds studied (23–49 nm in ethanol as the temperature decreases (the solvent viscosity increases points out that the excited-state relaxation process takes place. The rate of this process depends essentially on the solvent viscosity, but not the solvent polarity. The essential increasing of fluorescence rate constant k f (up to about 7 times as the solvent viscosity increases proves the existence of excited-state structural relaxation consisting in the mutual internal rotation of molecular fragments of aminoquinolines studied, followed by the solvent orientational relaxation.

Advances in solid-state NMR of cellulose.

Science.gov (United States)

Foston, Marcus

2014-06-01

Nuclear magnetic resonance (NMR) spectroscopy is a well-established analytical and enabling technology in biofuel research. Over the past few decades, lignocellulosic biomass and its conversion to supplement or displace non-renewable feedstocks has attracted increasing interest. The application of solid-state NMR spectroscopy has long been seen as an important tool in the study of cellulose and lignocellulose structure, biosynthesis, and deconstruction, especially considering the limited number of effective solvent systems and the significance of plant cell wall three-dimensional microstructure and component interaction to conversion yield and rate profiles. This article reviews common and recent applications of solid-state NMR spectroscopy methods that provide insight into the structural and dynamic processes of cellulose that control bulk properties and biofuel conversion. Copyright © 2014 Elsevier Ltd. All rights reserved.

NMR - from basic physics to images of the human body

International Nuclear Information System (INIS)

Richards, Rex.

1985-01-01

Nuclear magnetic resonance (NMR) is a remarkable phenomenon which involves the exchange of very weak radio frequency radiation between atomic nuclei and a sensitive detecting apparatus. It was originally regarded as a rather esoteric effect of great theoretical interest, but has since proved to have an amazing range of applications over many scientific disciplines, including nuclear physics, solid state physics, all branches of chemistry, biochemistry, physiology and most recently in medical diagnosis. In this Discourse the principles of NMR and trace briefly the history of its applications are examined and illustrated. Headings are: early history; nuclear resonance; relaxation time; the chemical shift; spin-spin coupling (NMR spectra); chemical shifts in biological tissue; NMR imaging; conclusions. (author)

An extrapolation scheme for solid-state NMR chemical shift calculations

Science.gov (United States)

Nakajima, Takahito

2017-06-01

Conventional quantum chemical and solid-state physical approaches include several problems to accurately calculate solid-state nuclear magnetic resonance (NMR) properties. We propose a reliable computational scheme for solid-state NMR chemical shifts using an extrapolation scheme that retains the advantages of these approaches but reduces their disadvantages. Our scheme can satisfactorily yield solid-state NMR magnetic shielding constants. The estimated values have only a small dependence on the low-level density functional theory calculation with the extrapolation scheme. Thus, our approach is efficient because the rough calculation can be performed in the extrapolation scheme.

Whole-core analysis by 13C NMR

International Nuclear Information System (INIS)

Vinegar, H.J.; Tutunjian, P.N.; Edelstein, W.A.; Roemer, P.B.

1991-01-01

This paper reports on a whole-core nuclear magnetic resonance (NMR) system that was used to obtain natural abundance 13 C spectra. The system enables rapid, nondestructive measurements of bulk volume of movable oil, aliphatic/aromatic ratio, oil viscosity, and organic vs. carbonate carbon. 13 C NMR can be used in cores where the 1 H NMR spectrum is too broad to resolve oil and water resonances separately. A 5 1/4-in. 13 C/ 1 H NMR coil was installed on a General Electric (GE) CSI-2T NMR imager/spectrometer. With a 4-in.-OD whole core, good 13 C signal/noise ratio (SNR) is obtained within minutes, while 1 H spectra are obtained in seconds. NMR measurements have been made of the 13 C and 1 H density of crude oils with a wide range of API gravities. For light- and medium-gravity oils, the 13 C and 1 H signal per unit volume is constant within about 3.5%. For heavy crudes, the 13 C and 1 H density measured by NMR is reduced by the shortening of spin-spin relaxation time. 13 C and 1 H NMR spin-lattice relaxation times were measured on a suite of Cannon viscosity standards, crude oils (4 to 60 degrees API), and alkanes (C 5 through C 16 ) with viscosities at 77 degrees F ranging from 0.5 cp to 2.5 x 10 7 cp. The 13 C and 1 H relaxation times show a similar correlation with viscosity from which oil viscosity can be estimated accurately for viscosities up to 100 cp. The 13 C surface relaxation rate for oils on water-wet rocks is very low. Nonproton decoupled 13 C NMR is shown to be insensitive to kerogen; thus, 13 C NMR measures only the movable hydrocarbon content of the cores. In carbonates, the 13 C spectrum also contains a carbonate powder pattern useful in quantifying inorganic carbon and distinguishing organic from carbonate carbon

IRMA iterative relaxation matrix approach for NMR structure determination application to DNA fragments

International Nuclear Information System (INIS)

Koning, M.M.G.

1990-01-01

The subject of this thesis is the structure determination of DNA molecules in solution with the use of NMR. For this purpose a new relaxation matrix approach is introduced. The emphasis is on the interpretation of nuclear Overhauser effects (NOEs) in terms of proton-proton distances and related three dimensional structures. The DNA molecules studied are obligonucleotides, unmodifief as well as modified molecules bu UV radiation. From comparison with unmodified molecules it turned out that UV irradiation scarcely influences the helical structure of the DNA string. At one place of the string a nucleotide is rotated towards the high-ANTI conformation which results in a slight unwinding of the DNA string but sufficient for blocking of the normal reading of genetic information. (H.W.). 456 refs.; 50 figs.; 30 tabs

Detection of early gamma-postirradiation effects in murine spleen by proton NMR relaxation times.

Science.gov (United States)

Zebrowska, G; Lewa, C J; Ramee, M P; Husson, F; De Certaines, J D

2001-01-01

It was our aim to evaluate the potential of proton relaxation times for the early detection of radiation-induced spleen changes. Female Swiss mice were irradiated with doses ranging from 0.05 Gy to 4 Gy. The body weight, the spleen weight and the spleen water content of single animals were determined. Measurements of longitudinal (T1) and transversal (T2) proton relaxation times of the spleen samples were performed in a 0.47 T spectrometer. Histological examinations of the control and irradiated organs were performed. NMR measurements during the first five days after irradiation showed that total body gamma-irradiation with doses from 1.5 Gy to 4 Gy results in decreasing T1 of the murine spleen. Significant shortening in T2 was observed for the spleen of animals irradiated with a dose of 4 Gy. Histological examinations demonstrated subnormal architecture in slices derived from animals irradiated with 2 Gy and 4 Gy. The fluctuations of the spleen T1 and T2 of irradiated mice are correlated with relative spleen weight and can be used to estimate radiation induced changes in this organ.

Tunneling splitting of magnetic levels in Fe8 detected by 1H NMR cross relaxation

OpenAIRE

Furukawa, Y.; Aizawa, K.; Kumagai, K.; Ullu, R.; Lascialfari, A.; Borsa, F.

2003-01-01

Measurements of proton NMR and the spin lattice relaxation rate 1/T1 in the octanuclear iron (III) cluster [Fe8(N3C6H15)6O2(OH)12][Br8 9H2O], in short Fe8, have been performed at 1.5 K in a powder sample aligned along the main anisotropy z axis, as a function of a transverse magnetic field (i.e., perpendicular to the main easy axis z). A big enhancement of 1/T1 is observed over a wide range of fields (2.5-5 T), which can be attributed to the tunneling dynamics; in fact, when the tunneling spl...

43Ca NMR in solid state

Science.gov (United States)

Bellot, P.-V.; Trokiner, A.; Zhdanov, Yu.; Yakubovskii, A.

1998-02-01

In this paper we show that 43Ca is a suitable NMR probe to study the properties of high-Tc superconducting oxides. In the normal state, we report the temperature and doping dependencies of the spin susceptibility measured by 43Ca NMR. In the superconducting state and more exactly in the mixed state, by analysing 43Ca NMR linewidth, we have studied the magnetic induction distribution due to the presence of vortices and deduced λ, the penetration depth. Dans cet article, on montre que l'isotope 43 du calcium est une bonne sonde RMN pour l'étude des propriétés des oxydes supraconducteurs à haute température. Dans l'état normal, par la détermination du déplacement de la raie, en fonction de la température, on accède à la variation thermique de la susceptibilité de spin. Dans l'état supraconducteur et plus particulièrement dans l'état mixte, la largeur de raie RMN permet d'étudier la distribution d'induction magnétique due à la présence des vortex et de déterminer λ, la longueur de pénétration.

Hydrogen-1 NMR relaxation time studies in membrane: anesthetic systems

International Nuclear Information System (INIS)

Pinto, L.M.A.; Fraceto, L.; Paula, E. de; Franzoni, L.; Spisni, A.

1997-01-01

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 1 H-NMR longitudinal relaxation times (T 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 1 in this system than in isotropic phases, reflecting LA immobilization caused by insertion in the membrane. T 1 values for the lipid protons in the presence of LA were analyzed, in an attempt to identify specific LA:lipid contact regions. (author)

Anisotropic molecular reorientations of quinuclidine in its plastic solid phase: 1H and 14N NMR relaxation study

International Nuclear Information System (INIS)

Brot, C.; Virlet, J.

1979-01-01

14 N and 1 H NMR relaxation times have been measured in quinuclidine in its plastic phase. These measurements rule out isotropic motion. Correlation times for several anisotropic reorientational models are calculated from these NMR data. The best agreement with the values calculated from neutron scattering experiments (preceding paper) is obtained for a model where the molecules reorient by +-90 0 jumps about the crystallographic C 4 axes with a residence time of (22.2+-2).10 -12 s, and by +-120 0 jumps about the molecular C 3 axes with a residence of (5.25+-2.8).10 -12 s, at room temperature. The activation enthalpy is 15.3 kJ.mol. -1 for the +-90 0 jumps, and higher for the +-120 0 jumps. Translational correlation times have also been measured at high temperature, below the melting point

Fluid-Rock Characterization and Interactions in NMR Well Logging

Energy Technology Data Exchange (ETDEWEB)

George J. Hirasaki; Kishore K. Mohanty

2005-09-05

The objective of this report is to characterize the fluid properties and fluid-rock interactions that are needed for formation evaluation by NMR well logging. The advances made in the understanding of NMR fluid properties are summarized in a chapter written for an AAPG book on NMR well logging. This includes live oils, viscous oils, natural gas mixtures, and the relation between relaxation time and diffusivity. Oil based drilling fluids can have an adverse effect on NMR well logging if it alters the wettability of the formation. The effect of various surfactants on wettability and surface relaxivity are evaluated for silica sand. The relation between the relaxation time and diffusivity distinguishes the response of brine, oil, and gas in a NMR well log. A new NMR pulse sequence in the presence of a field gradient and a new inversion technique enables the T{sub 2} and diffusivity distributions to be displayed as a two-dimensional map. The objectives of pore morphology and rock characterization are to identify vug connectivity by using X-ray CT scan, and to improve NMR permeability correlation. Improved estimation of permeability from NMR response is possible by using estimated tortuosity as a parameter to interpolate between two existing permeability models.

Analysis of porous media and objects of cultural heritage by mobile NMR

International Nuclear Information System (INIS)

Haber, Agnes

2012-01-01

Low-field NMR techniques are used to study porous system, from simple to complex structures, and objects of cultural heritage. It is shown that NMR relaxometry can be used to study the fluid dynamics inside a porous system. A simple theoretical model for multi-site relaxation exchange NMR is used to extract exchange kinetic parameters when applied on a model porous systems. It provides a first step towards the study of more complex systems, where continuous relaxation distributions are present, such as soil systems or building materials. Moisture migration is observed in the soil systems with the help of 1D and 2D NMR relaxometry methods. In case of the concrete samples, the difference in composition makes a significant difference in the ability of water uptake. The single-sided NMR sensor proves to be a useful tool for on-site measurements. This is very important also in the case of the cultural heritage objects, as most of the objects can not be moved out of their environment. Mobile NMR turns out to be a simple but reliable and powerful tool to investigate moisture distributions and pore structures in porous media as well as the conservation state and history of objects of cultural heritage.

Theory and Applications of Solid-State NMR Spectroscopy to Biomembrane Structure and Dynamics

Science.gov (United States)

Xu, Xiaolin

Solid-state Nuclear Magnetic Resonance (NMR) is one of the premiere biophysical methods that can be applied for addressing the structure and dynamics of biomolecules, including proteins, lipids, and nucleic acids. It illustrates the general problem of determining the average biomolecular structure, including the motional mean-square amplitudes and rates of the fluctuations. Lineshape and relaxtion studies give us a view into the molecular properties under different environments. To help the understanding of NMR theory, both lineshape and relaxation experiments are conducted with hexamethylbezene (HMB). This chemical compound with a simple structure serves as a perfect test molecule. Because of its highly symmetric structure, its motions are not very difficult to understand. The results for HMB set benchmarks for other more complicated systems like membrane proteins. After accumulating a large data set on HMB, we also proceed to develop a completely new method of data analysis, which yields the spectral densities in a body-fixed frame revealing internal motions of the system. Among the possible applications of solid-state NMR spectroscopy, we study the light activation mechanism of visual rhodopsin in lipid membranes. As a prototype of G-protein-coupled receptors, which are a large class of membrane proteins, the cofactor isomerization is triggered by photon absorption, and the local structural change is then propagated to a large-scale conformational change of the protein. Facilitation of the binding of transducin then passes along the visual signal to downstream effector proteins like transducin. To study this process, we introduce 2H labels into the rhodopsin chromophore retinal and the C-terminal peptide of transducin to probe the local structure and dynamics of these two hotspots of the rhodopsin activation process. In addition to the examination of local sites with solid-state 2H NMR spectroscopy, wide angle X-ray scattering (WAXS) provides us the chance of

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

Xenon-Water Interaction in Bacterial Suspensions as Studied by NMR

DEFF Research Database (Denmark)

Rodin, V.; Ponomarev, Alexander; Gerasimov, Maxim

2017-01-01

suspensions of Escherichia coli in the presence of xenon using nuclear magnetic resonance (NMR). The work studied how the spin-lattice relaxation times of water protons in suspension change under xenon conditions. Xenon is able to form clathrate hydrates with water molecules at a temperature above the melting...... point of ice. The work studied NMR relaxation times which reflect the rotation freedom of water molecules in suspension. Lower relaxation times indicate reduced rotational freedom of water. Single exponential behavior of spin-lattice relaxation of protons in the suspensions of microorganisms has been...

Interaction study of polyisobutylene with paraffins by NMR using the evaluation of spin-lattice relaxation times for hydrogen nuclei

International Nuclear Information System (INIS)

Marques, Rosana G.G.; Tavares, Maria I.B.

2001-01-01

The evaluation of spin-lattice relaxation times of 1 H for polyisobutylene/paraffin systems, were obtained using the classic inversion recovery technique, and also through Cross Polarization Magic Angle Spinning (CP/MAS) techniques varying the contact time and also by the delayed contact time pulse sequence. NMR results showed that the polyisobutylene/paraffin systems in which high molecular weight paraffins were used, is heterogeneous. However, for paraffins with low molecular weight, the system presents good homogeneity. (author)

Enhanced 29Si spin-lattice relaxation and observation of three-dimensional lattice connectivity in zeolites by two-dimensional 29Si MASS NMR

International Nuclear Information System (INIS)

Sivadinarayana, C.; Choudhary, V.R.; Ganapathy, S.

1994-01-01

It is shown that considerable sensitivity enhancement is achieved in the 29 Si magic angle sample spinning (MASS) NMR spectra of highly siliceous zeolites by pre treating the material with oxygen. The presence of adsorbed molecular oxygen in zeolite channels promotes an efficient 29 Si spin-lattice relaxation via a paramagnetic interaction between the lattice 29 Si T-site and the adsorbed oxygen on zeolite channels. This affords an efficient 2-D data collection and leads to increased sensitivity. The utility of this method is demonstrated in a two-dimensional COSY-45 NMR experiment of a high silica zeolite ZSM-5. (author). 20 refs., 3 figs., 1 tab

Evaluation of PHB nanocomposite by low field NMR

International Nuclear Information System (INIS)

Silva, Mariana Bruno Rocha e; Tavares, Maria Ines Bruno

2009-01-01

Poly(3-hydroxybutyrate) (PHB) based on nanocomposites containing different amounts of a commercial organically modified clay (viscogel B8) were prepared employing solution intercalation method. The relationship among the processing conditions; molecular structure and intermolecular interaction, between both nanocomposite components, were investigated using a nuclear magnetic resonance (NMR), as a part of characterization methodology, which has been used by Tavares et al. It involves the proton spin-lattice relaxation time, T1 H, by solid state nuclear magnetic resonance, employing low field NMR. X-ray diffraction was also employed because it is a conventional technique, generally used to obtain the first information on nanocomposite formation. Changes in PHB crystallinity were observed after the organophilic nanoclay had been incorporated in the polymer matrix. These changes, in the microstructure, were detected by the variation of proton nuclear relaxation time values and by X-ray, which showed an increase in the clay interlamellar space due to the intercalation of the polymer in the clay between lamellae. (author)

Biomolecular solid state NMR with magic-angle spinning at 25K.

Science.gov (United States)

Thurber, Kent R; Tycko, Robert

2008-12-01

A magic-angle spinning (MAS) probe has been constructed which allows the sample to be cooled with helium, while the MAS bearing and drive gases are nitrogen. The sample can be cooled to 25K using roughly 3 L/h of liquid helium, while the 4-mm diameter rotor spins at 6.7 kHz with good stability (+/-5 Hz) for many hours. Proton decoupling fields up to at least 130 kHz can be applied. This helium-cooled MAS probe enables a variety of one-dimensional and two-dimensional NMR experiments on biomolecular solids and other materials at low temperatures, with signal-to-noise proportional to 1/T. We show examples of low-temperature (13)C NMR data for two biomolecular samples, namely the peptide Abeta(14-23) in the form of amyloid fibrils and the protein HP35 in frozen glycerol/water solution. Issues related to temperature calibration, spin-lattice relaxation at low temperatures, paramagnetic doping of frozen solutions, and (13)C MAS NMR linewidths are discussed.

Local electronic structure of TM-based alloys: a pulsed NMR study

International Nuclear Information System (INIS)

Guerra, D.A.

1984-01-01

A pulsed NMR study on several transition metal + metalloid amorphous alloys is reported. The analisis of Knight shifts and nuclear spin-lattice relaxation of metalloids indicates a dominant contribution of p-electrons in the Fermi level density of state, supporting the existence of a p-d hibridization. (author) [pt

Recent advances in solid state NMR and its application to ceramics

International Nuclear Information System (INIS)

Maekawa, Hideki

2006-01-01

The basic principles of solid state NMR are explained. Four application examples contained amorphous glass, determination of defects of oxide crystal, nano particle and ionic materials. The structure of inorganic glass is measured by 29 Si, 11 B, 31 P and 23 Na NMR and Magic Angle Spinning NMR (MAS-NMR), chemical species near hydrogen by Cross-Polarization Magic Angle Spinning (CP/MAS) method, and hydrogen by Combined Rotation And Multiple Pulse Spectroscopy (CRAMPS) and MAS-NMR. Hydrous and anhydrous silicate glass with condensed 17 O was measured by 17 O Multi Quantum Magic Angle Spinning (MQ/MAS). 27 Al in slags was analyzed by 27 Al 5Q-MAS. 89 Y NMR spectrum of YSZ (Yttria Stabilization Zirconia, Y 2 O 3 -ZrO 2 ) was explained. The ion transfer phenomena in the electrolyte are observed directly by the solid state NMR. (S.Y.)

Comparative NMR investigation of the Re-based borides

Science.gov (United States)

Lue, C. S.; Tao, Y. F.; Su, T. H.

2008-07-01

We report a systematic study of the rhenium-based borides, ReB2 , Re7B3 , and Re3B , by means of the B11 nuclear magnetic resonance (NMR) spectroscopy. While Re7B3 and Re3B are superconductors, ReB2 exhibits no superconducting signature but is of current interest due to its superhard mechanical property. Since the major focus of this investigation is their electronic characteristics in the normal states, we performed the measurements at temperatures between 77 and 295 K. For Re7B3 and Re3B , s -character electrons were found to be responsible for the observed B11 NMR Knight shift and spin-lattice relaxation rate (1/T1) . From T1 analysis, we thus deduce the partial Bs Fermi-level density of states (DOS) of both borides. On the other hand, the relaxation rate of ReB2 is mainly associated with p electrons, similar to the cases of OsB2 and RuB2 . In addition, the extracted B2p Fermi-level DOS is in good agreement with the theoretical prediction from band-structure calculations.

NMR Phase Noise in Bitter Magnets

Science.gov (United States)

Sigmund, E. E.; Calder, E. S.; Thomas, G. W.; Mitrović, V. F.; Bachman, H. N.; Halperin, W. P.; Kuhns, P. L.; Reyes, A. P.

2001-02-01

We have studied the temporal instability of a high field resistive Bitter magnet through nuclear magnetic resonance (NMR). This instability leads to transverse spin decoherence in repeated and accumulated NMR experiments as is normally performed during signal averaging. We demonstrate this effect via Hahn echo and Carr-Purcell-Meiboom-Gill (CPMG) transverse relaxation experiments in a 23-T resistive magnet. Quantitative analysis was found to be consistent with separate measurements of the magnetic field frequency fluctuation spectrum, as well as with independent NMR experiments performed in a magnetic field with a controlled instability. Finally, the CPMG sequence with short pulse delays is shown to be successful in recovering the intrinsic spin-spin relaxation even in the presence of magnetic field temporal instability.

Nuclear spin-lattice relaxation in carbon nanostructures

Energy Technology Data Exchange (ETDEWEB)

Panich, A.M., E-mail: pan@bgu.ac.i [Department of Physics, Ben-Gurion University of the Negev, P.O. Box 653, Beer Sheva 84105 (Israel); Sergeev, N.A. [Institute of Physics, University of Szczecin, 70-451 Szczecin (Poland)

2010-04-15

Interpretation of nuclear spin-lattice relaxation data in the carbon nanostructures is usually based on the analysis of fluctuations of dipole-dipole interactions of nuclear spins and anisotropic electron-nuclear interactions responsible for chemical shielding, which are caused by molecular dynamics. However, many nanocarbon systems such as fullerene and nanotube derivatives, nanodiamonds and carbon onions reveal noticeable amount of paramagnetic defects with unpaired electrons originating from dangling bonds. The interaction between nuclear and electron spins strongly influences the nuclear spin-lattice relaxation, but usually is not taken into account, thus the relaxation data are not correctly interpreted. Here we report on the temperature dependent NMR spectra and spin-lattice relaxation measurements of intercalated fullerenes C{sub 60}(MF{sub 6}){sub 2} (M=As and Sb), where nuclear relaxation is caused by both molecular rotation and interaction between nuclei and unpaired electron spins. We present a detailed theoretical analysis of the spin-lattice relaxation data taking into account both these contributions. Good agreement between the experimental data and calculations is obtained. The developed approach would be useful in interpreting the NMR relaxation data in different nanostructures and their intercalation compounds.

Rotational and translational dynamics and their relation to hydrogen bond lifetimes in an ionic liquid by means of NMR relaxation time experiments and molecular dynamics simulation

Science.gov (United States)

Strate, Anne; Neumann, Jan; Overbeck, Viviane; Bonsa, Anne-Marie; Michalik, Dirk; Paschek, Dietmar; Ludwig, Ralf

2018-05-01

We report a concerted theoretical and experimental effort to determine the reorientational dynamics as well as hydrogen bond lifetimes for the doubly ionic hydrogen bond +OH⋯O- in the ionic liquid (2-hydroxyethyl)trimethylammonium bis(trifluoromethylsulfonyl)imide [Ch][NTf2] by using a combination of NMR relaxation time experiments, density functional theory (DFT) calculations, and molecular dynamics (MD) simulations. Due to fast proton exchange, the determination of rotational correlation times is challenging. For molecular liquids, 17O-enhanced proton relaxation time experiments have been used to determine the rotational correlation times for the OH vectors in water or alcohols. As an alternative to those expensive isotopic substitution experiments, we employed a recently introduced approach which is providing access to the rotational dynamics from a single NMR deuteron quadrupolar relaxation time experiment. Here, the deuteron quadrupole coupling constants (DQCCs) are obtained from a relation between the DQCC and the δ1H proton chemical shifts determined from a set of DFT calculated clusters in combination with experimentally determined proton chemical shifts. The NMR-obtained rotational correlation times were compared to those obtained from MD simulations and then related to viscosities for testing the applicability of popular hydrodynamic models. In addition, hydrogen bond lifetimes were derived, using hydrogen bond population correlation functions computed from MD simulations. Here, two different time domains were observed: The short-time contributions to the hydrogen lifetimes and the reorientational correlation times have roughly the same size and are located in the picosecond range, whereas the long-time contributions decay with relaxation times in the nanosecond regime and are related to rather slow diffusion processes. The computed average hydrogen bond lifetime is dominated by the long-time process, highlighting the importance and longevity of

Internal structures of self-organized relaxed states and self-similar decay phase

International Nuclear Information System (INIS)

Kondoh, Yoshiomi

1992-03-01

A thought analysis on relaxation due to nonlinear processes is presented to lead to a set of general thoughts applicable to general nonlinear dynamical systems for finding out internal structures of the self-organized relaxed state without using 'invariant'. Three applications of the set of general thoughts to energy relaxations in resistive MHD plasmas, incompressible viscous fluids, and incompressible viscous MHD fluids are shown to lead to the internal structures of the self-organized relaxed states. It is shown that all of the relaxed states in these three dynamical systems are followed by self-similar decay phase without significant change of the spatial structure. The well known relaxed state of ∇ x B = ±λ B is shown to be derived generally in the low β plasma limit. (author)

Direct NMR Evidence that Transient Tautomeric and Anionic States in dG·dT Form Watson-Crick-like Base Pairs.

Science.gov (United States)

Szymanski, Eric S; Kimsey, Isaac J; Al-Hashimi, Hashim M

2017-03-29

The replicative and translational machinery utilizes the unique geometry of canonical G·C and A·T/U Watson-Crick base pairs to discriminate against DNA and RNA mismatches in order to ensure high fidelity replication, transcription, and translation. There is growing evidence that spontaneous errors occur when mismatches adopt a Watson-Crick-like geometry through tautomerization and/or ionization of the bases. Studies employing NMR relaxation dispersion recently showed that wobble dG·dT and rG·rU mismatches in DNA and RNA duplexes transiently form tautomeric and anionic species with probabilities (≈0.01-0.40%) that are in concordance with replicative and translational errors. Although computational studies indicate that these exceptionally short-lived and low-abundance species form Watson-Crick-like base pairs, their conformation could not be directly deduced from the experimental data, and alternative pairing geometries could not be ruled out. Here, we report direct NMR evidence that the transient tautomeric and anionic species form hydrogen-bonded Watson-Crick-like base pairs. A guanine-to-inosine substitution, which selectively knocks out a Watson-Crick-type (G)N2H 2 ···O2(T) hydrogen bond, significantly destabilized the transient tautomeric and anionic species, as assessed by lack of any detectable chemical exchange by imino nitrogen rotating frame spin relaxation (R 1ρ ) experiments. An 15 N R 1ρ NMR experiment targeting the amino nitrogen of guanine (dG-N2) provides direct evidence for Watson-Crick (G)N2H 2 ···O2(T) hydrogen bonding in the transient tautomeric state. The strategy presented in this work can be generally applied to examine hydrogen-bonding patterns in nucleic acid transient states including in other tautomeric and anionic species that are postulated to play roles in replication and translational errors.

Solid-State NMR Study of New Copolymers as Solid Polymer Electrolytes

Directory of Open Access Journals (Sweden)

Jean-Christophe Daigle

2018-01-01

Full Text Available We report the analysis of comb-like polymers by solid-state NMR. The polymers were previously evaluated as solid-polymer-electrolytes (SPE for lithium-polymer-metal batteries that have suitable ionic conductivity at 60 °C. We propose to develop a correlation between 13C solid-state NMR measurements and phase segregation. 13C solid-state NMR is a perfect tool for differentiating polymer phases with fast or slow motions. 7Li was used to monitor the motion of lithium ions in the polymer, and activation energies were calculated.

State resolved vibrational relaxation modeling for strongly nonequilibrium flows

Science.gov (United States)

Boyd, Iain D.; Josyula, Eswar

2011-05-01

Vibrational relaxation is an important physical process in hypersonic flows. Activation of the vibrational mode affects the fundamental thermodynamic properties and finite rate relaxation can reduce the degree of dissociation of a gas. Low fidelity models of vibrational activation employ a relaxation time to capture the process at a macroscopic level. High fidelity, state-resolved models have been developed for use in continuum gas dynamics simulations based on computational fluid dynamics (CFD). By comparison, such models are not as common for use with the direct simulation Monte Carlo (DSMC) method. In this study, a high fidelity, state-resolved vibrational relaxation model is developed for the DSMC technique. The model is based on the forced harmonic oscillator approach in which multi-quantum transitions may become dominant at high temperature. Results obtained for integrated rate coefficients from the DSMC model are consistent with the corresponding CFD model. Comparison of relaxation results obtained with the high-fidelity DSMC model shows significantly less excitation of upper vibrational levels in comparison to the standard, lower fidelity DSMC vibrational relaxation model. Application of the new DSMC model to a Mach 7 normal shock wave in carbon monoxide provides better agreement with experimental measurements than the standard DSMC relaxation model.

The structure of phosphate and borosilicate glasses and their structural evolution at high temperatures as studied with solid state NMR spectroscopy: Phase separation, crystallisation and dynamic species exchange

International Nuclear Information System (INIS)

Wegner, S.; Van Wullen, L.; Tricot, G.; Tricot, G.

2010-01-01

In this contribution we present an in-depth study of the network structure of different phosphate based and borosilicate glasses and its evolution at high temperatures. Employing a range of advanced solid state NMR methodologies, complemented by the results of XPS, the structural motifs on short and intermediate length scales are identified. For the phosphate based glasses, at temperatures above the glass transition temperature Tg, structural relaxation processes and the devitrification of the glasses were monitored in situ employing MAS NMR spectroscopy and X-ray diffraction. Dynamic species exchange involving rapid P-O-P and P-O-Al bond breaking and reforming was observed employing in situ 27 Al and 31 P MAS NMR spectroscopy and could be linked to viscous flow. For the borosilicate glasses, an atomic scale investigation of the phase separation processes was possible in a combined effort of ex situ NMR studies on glass samples with different thermal histories and in situ NMR studies using high temperature MAS NMR spectroscopy including 11 B MAS, 29 Si MAS and in situ 29 Si{ 11 B} REAPDOR NMR spectroscopy. (authors)

Solid-state NMR studies of form I of atorvastatin calcium.

Science.gov (United States)

Wang, Wei David; Gao, Xudong; Strohmeier, Mark; Wang, Wei; Bai, Shi; Dybowski, Cecil

2012-03-22

Solid-state (13)C, (19)F, and (15)N magic angle spinning NMR studies of Form I of atorvastatin calcium are reported, including chemical shift tensors of all resolvable carbon sites and fluorine sites. The complete (13)C and (19)F chemical shift assignments are given based on an extensive analysis of (13)C-(1)H HETCOR and (13)C-(19)F HETCOR results. The solid-state NMR data indicate that the asymmetric unit of this material contains two atorvastatin molecules. A possible structure of Form I of atorvastatin calcium (ATC-I), derived from solid-state NMR data and density functional theory calculations of various structures, is proposed for this important active pharmaceutical ingredient (API).

Solid-state NMR studies of nucleic acid components

Czech Academy of Sciences Publication Activity Database

Dračínský, Martin; Hodgkinson, P.

2015-01-01

Roč. 5, č. 16 (2015), s. 12300-12310 ISSN 2046-2069 R&D Projects: GA ČR GA13-24880S Institutional support: RVO:61388963 Keywords : NMR spectroscopy * nucleic acid s * solid-state NMR Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.289, year: 2015 http://pubs.rsc.org/en/content/articlepdf/2015/ra/c4ra14404j

Copper NMR and hole depletion in the normal state of Y1-xPrxBa2Cu3O7

International Nuclear Information System (INIS)

MacLaughlin, D.E.; Reyes, A.P.; Takigawa, M.; Hammel, P.C.; Heffner, R.H.; Thompson, J.D.; Crow, J.E.

1990-01-01

Normal-state copper NMR spectra and spin-lattice relaxation rates 1/T 1 have been measured in the planar cuprate system YBa 2 Cu 3 O 7 . With Pr doping the Knight shift K decreases and develops a temperature dependence at both plane and chain sites. Analysis of the bulk susceptibility and NMR data indicate that pair breaking and hole depletion both take part in the suppression of the superconducting transition temperature T c . The Knight shift behavior resembles that in oxygen-deficient YBa 2 Cu 3 O 7-y , as does the temperature dependence of 1/T 1 for plane Cu sites and magnetic field perpendicular to the c axis. This agreement leads to a consistent picture of the role of antiferromagnetic fluctuations in these materials. An analysis of the data in the framework of the phenomenological theory of Millis, Monien, and Pines is given. In the end compound PrBa 2 Cu 3 O 7 the NMR signal from plane Cu sites indicates antiferromagnetic (AF) ordering at a Neel temperature ∼280 K, and in the AF state yields an internal field similar to those found in AF YBa 2 Cu 3 O 6 and La 2 CuO 4 . 32 refs., 7 figs

Proton NMR study of α-MnH 0.06

Science.gov (United States)

Soloninin, A. V.; Skripov, A. V.; Buzlukov, A. L.; Antonov, V. E.; Antonova, T. E.

2004-07-01

Proton nuclear magnetic resonance (NMR) spectra and spin-lattice relaxation rates for the solid solution α-MnH 0.06 have been measured over the temperature range 11-297 K and the resonance frequency range 20-90 MHz. A considerable shift and broadening of the proton NMR line and a sharp peak of the spin-lattice relaxation rate are observed near 130 K. These effects are attributed to the onset of antiferromagnetic ordering below the Néel temperature TN≈130 K. The proton NMR line does not disappear in the antiferromagnetic phase; this suggests a small magnitude of the local magnetic fields at H-sites in α-MnH 0.06. The spin-lattice relaxation rate in the paramagnetic phase is dominated by the effects of spin fluctuations.

Axisymmetric force-free states and relaxation of a spheroidal spheromak

International Nuclear Information System (INIS)

Throumoulopoulos, G.N.; Pantis, G.

1990-01-01

Axisymmetric force-free equilibrium eigenstates for a prolate as well as an oblate spheroidal Spheromak with arbitrary elongation are obtained. In the framework of the Woltjer-Taylor relaxation theory the relaxed states are also identified. A simple hypothesis for the relaxation process is introduced, which implies that the plasma relaxes from multitoroidal formations to a singly toroidal configuration, in qualitative agreement with experimental results. (author)

Axisymmetric force-free states and relaxation of a spheroidal spheromak

International Nuclear Information System (INIS)

Throumoulopoulos, G.N.; Pantis, G.

1990-01-01

Axisymmetric force-free equilibrium eigenstates for a prolate as well as an oblate spheroidal spheromak with arbitrary elongation are obtained. In the framework of the Woltjer-Taylor relaxation theory the relaxed states are also identified. A simple hypothesis for the relaxation process is introduced which implies that the plasma relaxes from multitoroidal formations to a singly toroidal configuration in qualitative agreement with experimental results. (Author)

Theory of spin-lattice relaxation of diffusing light nuclei in glasses

International Nuclear Information System (INIS)

Schirmer, A.; Schirmacher, W.

1988-01-01

NMR data of diffusion-induced spin-lattice relaxation in glasses cannot generally be interpreted in the framework of the classical theory of Bloembergen, Purcell and Pound (BPP). Since it is based on exponential density relaxation, generally bnot found in glasses, the BPP formula must be generalized. Here a combination of standard relaxation theory with a hopping model for diffusion in glasses is present. It is shown that the observed anomaties in the NMR data can be explained as a result of anomalous diffusion. 25 refs.; 1 figure

International school on high field NMR spectroscopy for solids and liquids

Energy Technology Data Exchange (ETDEWEB)

Marion, D.; Meier, B.; Keeler, J.; Berthault, P.; Vedrine, P.; Grandinetti, P.; Delsuc, M.A.; Spiess, H

2006-07-01

The aim of the school is to offer high-level pedagogical courses on a wide range of liquid- and solid-state NMR concepts and techniques: theory, instrumentation (magnets and probes), data acquisition, processing and analysis, measurement of dipolar and quadrupolar couplings, spin relaxation and hyper-polarization. This document gathers only the slides of most presentations.

International school on high field NMR spectroscopy for solids and liquids

International Nuclear Information System (INIS)

Marion, D.; Meier, B.; Keeler, J.; Berthault, P.; Vedrine, P.; Grandinetti, P.; Delsuc, M.A.; Spiess, H.

2006-01-01

The aim of the school is to offer high-level pedagogical courses on a wide range of liquid- and solid-state NMR concepts and techniques: theory, instrumentation (magnets and probes), data acquisition, processing and analysis, measurement of dipolar and quadrupolar couplings, spin relaxation and hyper-polarization. This document gathers only the slides of most presentations

Fast mapping of global protein folding states by multivariate NMR:

DEFF Research Database (Denmark)

Malmendal, Anders; Underhaug, Jarl; Otzen, Daniel

2010-01-01

To obtain insight into the functions of proteins and their specific roles, it is important to establish efficient procedures for exploring the states that encapsulate their conformational space. Global Protein folding State mapping by multivariate NMR (GPS NMR) is a powerful high-throughput method......-lactalbumin in the presence of the anionic surfactant sodium dodecyl sulfate, SDS, and compare these with other surfactants, acid, denaturants and heat....

Measuring the equations of state in a relaxed magnetohydrodynamic plasma

Science.gov (United States)

Kaur, M.; Barbano, L. J.; Suen-Lewis, E. M.; Shrock, J. E.; Light, A. D.; Brown, M. R.; Schaffner, D. A.

2018-01-01

We report measurements of the equations of state of a fully relaxed magnetohydrodynamic (MHD) laboratory plasma. Parcels of magnetized plasma, called Taylor states, are formed in a coaxial magnetized plasma gun, and are allowed to relax and drift into a closed flux conserving volume. Density, ion temperature, and magnetic field are measured as a function of time as the Taylor states compress and heat. The theoretically predicted MHD and double adiabatic equations of state are compared to experimental measurements. We find that the MHD equation of state is inconsistent with our data.

Single crystal NMR studies of high temperature superconductors

International Nuclear Information System (INIS)

Pennington, C.H.; Durand, D.J.; Zax, D.B.; Slichter, C.P.; Rice, J.P.; Bukowski, E.D.; Ginsberg, D.M.

1989-01-01

The authors report Cu NMR studies in the normal state of a single crystal of the T/sub c/ = 90 K superconductor YBa 2 Cu 3 O/sub 7/minus/δ/. The authors have measured the magnetic shift tensor, the electric field gradient tensor, the nuclear spin-lattice relaxation rate tensor, and the time dependence and functional form of the transverse decay. From these data they obtain information about the charge state and magnetic state of the Cu atoms, and the existence and size of the electronic exchange coupling between spins of adjacent Cu atoms. 18 refs., 3 figs., 2 tabs

Spin-spin cross relaxation and spin-Hamiltonian spectroscopy by optical pumping of Pr/sup 3+/:LaF3

International Nuclear Information System (INIS)

Lukac, M.; Otto, F.W.; Hahn, E.L.

1989-01-01

We report the observation of an anticrossing in solid-state laser spectroscopy produced by cross relaxation. Spin-spin cross relaxation between the /sup 141/Pr- and /sup 19/F-spin reservoirs in Pr/sup 3+/:LaF 3 and its influence on the /sup 141/Pr NMR spectrum is detected by means of optical pumping. The technique employed combines optical pumping and hole burning with either external magnetic field sweep or rf resonance saturation in order to produce slow transient changes in resonant laser transmission. At a certain value of the external Zeeman field, where the energy-level splittings of Pr and F spins match, a level repulsion and discontinuity of the Pr/sup 3+/ NMR lines is observed. This effect is interpreted as the ''anticrossing'' of the combined Pr-F spin-spin reservoir energy states. The Zeeman-quadrupole-Hamiltonian spectrum of the hyperfine optical ground states of Pr/sup 3+/:LaF 3 is mapped out over a wide range of Zeeman magnetic fields. A new scheme is proposed for dynamic polarization of nuclei by means of optical pumping, based on resonant cross relaxation between rare spins and spin reservoirs

Applications of high resolution NMR to geochemistry: crystalline, glass, and molten silicates

International Nuclear Information System (INIS)

Schneider, E.

1985-11-01

The nuclear spin interactions and the associated quantum mechanical dynamics which are present in solid state NMR are introduced. A brief overview of aluminosilicate structure is presented and crystalline structure is then reviewed, with emphasis on the contributions made by 29 Si NMR spectroscopy. The local structure of glass aluminosilicates as observed by NMR, is presented with analysis of the information content of 29 Si spectra. A high-temperature (to 1300 0 C) NMR spectroscopic investigation of the local environment and dynamics of molecular motion in molten aluminosilicates is described. A comparison is made of silicate liquid, glass, and crystalline local structure. The atomic and molecular motions present in a melt are investigated through relaxation time (T 1 and T 2 ) measurements as a function of composition and temperature for 23 Na and 29 Si

Solid state low power pulsed NMR spectrometer system

International Nuclear Information System (INIS)

Nadkarni, S.S.; Parthasarathy, T.G.; Menon, M.P.S.; Hannurkar, P.R.

1981-01-01

A pulsed nuclear magnetic resonance spectrometer system is described for relaxation time studies on solid and liquid samples. The spectrometer design is fully solid state and a special microcomputer interface is incorporated for automatic evaluation of the relaxation times. The prototype system has been designed to operate at 9 MHz, but the modular concept used in the construction permits operation at any frequency in the range 5-10 MHz. The system has a recovery time of 15 micro seconds at 9 MHz. The range of measurement for the spin-lattice relaxation time is 0.1 millisecond to 1000 seconds; for spin-spin relaxation time, the range is 14μ seconds to 100 milliseconds. (author)

Solid state NMR of spin-1/2 nuclei

International Nuclear Information System (INIS)

Wind, R.A.

1991-01-01

The detection of nuclear magnetic resonance by Bloch et al. and Purcell and co-workers in 1946 has led to the development of one of the most powerful spectroscopic techniques known today. The reason is that, besides the applied external magnetic field, a nuclear spin also experiences extra local magnetic fields, which are due to surrounding electron clouds (the chemical shift) and other spins. These local fields differ for nuclei located at chemically different positions in a molecule. The result is that an NMR spectrum often consists of several lines, which can be considered to be a fingerprint of the material under investigation an can assist the clarifying its molecular structure. NMR has been especially successful in liquids and liquid like materials, where fast molecular tumblings average out the anisotropies in the local fields, resulting in well-resolved NMR spectra. This paper reports that initially the development of solid-state NMR was less dramatic. Originally, for reasons of sensitivity, attention was focused mainly on 1 H NMR. The result is that the NMR spectrum usually consists of single, broad, featureless line, which, except for special cases such as more or less isolated spin pairs or methyl groups, does not provide much information

Solid-state {sup 2}H NMR investigations in guest-host systems and plastic crystals

Energy Technology Data Exchange (ETDEWEB)

Garibay, J.A.V.

2004-07-01

Variable temperature {sup 2}H NMR investigations have been carried out to study the molecular behavior of perdeuterated benzene and pyridine in the inclusion compound with tris-(1,2-dioxyphenyl)-cyclotriphosphazene. Here, a comprehensive variable temperature {sup 2}H NMR study is presented comprising line shape studies and relaxation experiments. The experimental data clearly indicate the presence of highly mobile guest species. Sample cooling gives rise to characteristic line shape effects that can be attributed to a slow-down of the rotational motion. Additional {sup 2}H NMR measurements were performed on the plastic crystal 1,4-diazabicyclo[2,2,2]octane where highly mobile species were observed. A quantitative analysis of the experimental data is achieved by appropriate computer simulations taking into account various molecular motions for each studied system. The analysis of these theoretical data give rise to the kinetic parameters that are in the order of related systems. (orig.)

Unusual spin frozen state in a frustrated pyrochlore system NaCaCo{sub 2}F{sub 7} as observed by NMR

Energy Technology Data Exchange (ETDEWEB)

Sarkar, R.; Brueckner, F.; Klauss, H.H. [IFP, TU Dresden (Germany); Krizan, J.W.; Cava, R.J. [Department of Chemistry, Princeton University, Princeton, NJ (United States)

2016-07-01

We present {sup 23}Na -and {sup 19}F NMR results on the magnetically frustrated pyrochlore NaCaCo{sub 2}F{sub 7} with a frustration index of f = θ{sub CW}/T{sub f} ∝ 56. Recent neutron scattering experiments proposed XY like antiferromagnetic spin clusters at low energies in NaCaCo{sub 2}F{sub 7}. {sup 23}Na NMR -spectra reveal the presence of two magnetically non equivalent Na sites in conjunction with the local Co{sup 2+} spin structure. Below 3.6 K both the {sup 23}Na -and {sup 19}F spectra broaden due to the formation of static spin correlations. A huge reduction of the {sup 19}F -and {sup 23}Na NMR signal intensity hints at a quasi-static field distribution in NaCaCo{sub 2}F{sub 7} in this regime. The {sup 19}F spin-lattice relaxation rate {sup 19}(1/T{sub 1}) exhibits a peak at around 2.9 K, at the same temperature range where ac and dc susceptibility data show a broad maximum. The character of the spin fluctuation appears to be isotropic. The overall temperature dependence of {sup 19}(1/T{sub 1}) can be described by the BPP theory considering a fluctuating hyperfine field with an autocorrelation function. The correlation time of the autocorrelation function exhibits an activation behavior further indicating the spin-frozen state. While the present NMR studies suggest the spin frozen state at low temperatures, μSR investigations however reveal the presence of so called persistent spin dynamics down to 20 mK implying an exotic ground state in NaCaCo{sub 2}F{sub 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

This thesis describes application and development of advanced solid-state nuclear magnetic resonance techniques for complex materials, in particular organic-inorganic nanocomposites and thermoelectric tellurides. The apatite-collagen interface, essential for understanding the biomineralization process in bone and engineering the interface for controlled bio-mimetic synthesis and optimized mechanical properties, is buried within the nanocomposite of bone. We used multinuclear solid-state NMR to study the composition and structure of the interface. Citrate has been identified as the main organic molecule strongly bound to the apatite surface with a density of 1/(2 nm)², covering 1/6 of the total surface area in bovine bone. Citrate provides more carboxylate groups, one of the key functional groups found to affect apatite nucleation and growth, than all the non-collagenous proteins all together in bone; thus we propose that citrate stabilizes apatite crystals at a very small thickness of ~3 nm (4 unit cells) to increase bone fracture tolerance. The hypothesis has been confirmed in vitro by adding citrate in the bio-mimetic synthesis of polymerhydroxyapatite nanocomposites. The results have shown that the size of hydroxyapatite nanocrystals decreases as increasing citrate concentration. With citrate concentrations comparable to that in body fluids, similar-sized nanocrystals as in bone have been produced. Besides the dimensions of the apatite crystals, the composition of bone also affects its biofunctional and macroscopic mechanical properties; therefore, our team also extended its effort to enhance the inorganic portion in our bio-mimetic synthesis from originally 15 wt% to current 50 wt% compared to 65 wt% in bovine bone, by using Lysine-Leucine hydroxyapatite nucleating diblock co-polypeptide, which forms a gel at very low concentration. In this thesis, various advanced solid state NMR techniques have been employed to characterize nanocomposites

Structural investigation of e-beam cured epoxy resins through solid state NMR

International Nuclear Information System (INIS)

Alessi, Sabina; Spinella, Alberto; Caponetti, Eugenio; Dispenza, Clelia; Spadaro, Giuseppe

2012-01-01

In this paper the network structure of e-beam cured DGEBF based epoxy resins is investigated. Two epoxy systems, having different reactivity and cured in different process conditions, were analyzed through solid state NMR spectroscopy. The analysis shows that the more reactive system has higher cross-linking density and higher uniformity of network distribution. Similar information were obtained, in a previous work, on the same systems through dynamic mechanical thermal analysis. It is worth noting that unlike DMTA tests, which interfere with the molecular structure of the analyzed material, due to the heating during the analysis itself, more reliable information, without any artefact, are obtained by solid state NMR, carried out at constant room temperature. - Highlights: ► The structure of two e-beam cured epoxy systems is investigated through solid state NMR. ► The aim is to have direct information about the structure without inducing modifications. ► The different molecular structures are able to emphasize the response of solid state NMR. ► T 1 H, T 1ρ H and T CH measurements indicate different cross-linking degrees. ► The NMR results are in agreement with DMTA analysis performed in a previous paper.

Untangle soil-water-mucilage interactions: 1H NMR Relaxometry is lifting the veil

Science.gov (United States)

Brax, Mathilde; Buchmann, Christian; Schaumann, Gabriele Ellen

2017-04-01

Mucilage is mainly produced at the root tips and has a high water holding capacity derived from highly hydrophilic gel-forming substances. The objective of the MUCILAGE project is to understand the mechanistic role of mucilage for the regulation of water supply for plants. Our subproject investigates the chemical and physical properties of mucilage as pure gel and mixed with soil. 1H-NMR Relaxometry and PFG NMR represent non-intrusive powerful methods for soil scientific research by allowing quantification of the water distribution as well as monitoring of the water mobility in soil pores and gel phases.Relaxation of gel water differs from the one of pure water due to additional interactions with the gel matrix. Mucilage in soil leads to a hierarchical pore structure, consisting of the polymeric biohydrogel network surrounded by the surface of soil particles. The two types of relaxation rates 1/T1 and 1/T2 measured with 1H-NMR relaxometry refer to different relaxation mechanisms of water, while PFG-NMR measures the water self-diffusion coefficient. The objective of our study is to distinguish in situ water in gel from pore water in a simplified soil system, and to determine how the "gel effect" affects both relaxation rates and the water self-diffusion coefficient in porous systems. We demonstrate how the mucilage concentration and the soil solution alter the properties of water in the respective gel phases and pore systems in model soils. To distinguish gel-inherent processes from classical processes, we investigated the variations of the water mobility in pure chia mucilage under different conditions by using 1H-NMR relaxometry and PFG NMR. Using model soils, the signals coming from pore water and gel water were differentiated. We combined the equations describing 1H-NMR relaxation in porous systems and our experimental results, to explain how the presence of gel in soil affects 1H-NMR relaxation. Out of this knowledge we propose a method, which determines in

15N NMR relaxation studies of calcium-loaded parvalbumin show tight dynamics compared to those of other EF-hand proteins

DEFF Research Database (Denmark)

Baldellon, C; Alattia, J R; Strub, M P

1998-01-01

Dynamics of the rat alpha-parvalbumin calcium-loaded form have been determined by measurement of 15N nuclear relaxation using proton-detected heteronuclear NMR spectroscopy. The relaxation data were analyzed using spectral density functions and the Lipari-Szabo formalism. The major dynamic features...... for the rat alpha-parvalbumin calcium-loaded form are (1) the extreme rigidity of the helix-loop-helix EF-hand motifs and the linker segment connecting them, (2) the N and C termini of the protein being restricted in their mobility, (3) a conformational exchange occurring at the kink of helix D, and (4...... properties which are conserved in the EF-hand domains from different members of this superfamily: (1) a tendency toward higher mobility of NH vectors at relative position 2 in the Ca2+-binding loop, (2) a restricted mobility for the other residues in the binding loop, and (3) an overall rigidity...

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.

Applications of high resolution NMR to geochemistry: crystalline, glass, and molten silicates

Energy Technology Data Exchange (ETDEWEB)

Schneider, E.

1985-11-01

The nuclear spin interactions and the associated quantum mechanical dynamics which are present in solid state NMR are introduced. A brief overview of aluminosilicate structure is presented and crystalline structure is then reviewed, with emphasis on the contributions made by /sup 29/Si NMR spectroscopy. The local structure of glass aluminosilicates as observed by NMR, is presented with analysis of the information content of /sup 29/Si spectra. A high-temperature (to 1300/sup 0/C) NMR spectroscopic investigation of the local environment and dynamics of molecular motion in molten aluminosilicates is described. A comparison is made of silicate liquid, glass, and crystalline local structure. The atomic and molecular motions present in a melt are investigated through relaxation time (T/sub 1/ and T/sub 2/) measurements as a function of composition and temperature for /sup 23/Na and /sup 29/Si.

Hydraulic characterisation of iron-oxide-coated sand and gravel based on nuclear magnetic resonance relaxation mode analyses

Directory of Open Access Journals (Sweden)

S. Costabel

2018-03-01

Full Text Available The capability of nuclear magnetic resonance (NMR relaxometry to characterise hydraulic properties of iron-oxide-coated sand and gravel was evaluated in a laboratory study. Past studies have shown that the presence of paramagnetic iron oxides and large pores in coarse sand and gravel disturbs the otherwise linear relationship between relaxation time and pore size. Consequently, the commonly applied empirical approaches fail when deriving hydraulic quantities from NMR parameters. Recent research demonstrates that higher relaxation modes must be taken into account to relate the size of a large pore to its NMR relaxation behaviour in the presence of significant paramagnetic impurities at its pore wall. We performed NMR relaxation experiments with water-saturated natural and reworked sands and gravels, coated with natural and synthetic ferric oxides (goethite, ferrihydrite, and show that the impact of the higher relaxation modes increases significantly with increasing iron content. Since the investigated materials exhibit narrow pore size distributions, and can thus be described by a virtual bundle of capillaries with identical apparent pore radius, recently presented inversion approaches allow for estimation of a unique solution yielding the apparent capillary radius from the NMR data. We found the NMR-based apparent radii to correspond well to the effective hydraulic radii estimated from the grain size distributions of the samples for the entire range of observed iron contents. Consequently, they can be used to estimate the hydraulic conductivity using the well-known Kozeny–Carman equation without any calibration that is otherwise necessary when predicting hydraulic conductivities from NMR data. Our future research will focus on the development of relaxation time models that consider pore size distributions. Furthermore, we plan to establish a measurement system based on borehole NMR for localising iron clogging and controlling its remediation

Hydraulic characterisation of iron-oxide-coated sand and gravel based on nuclear magnetic resonance relaxation mode analyses

Science.gov (United States)

Costabel, Stephan; Weidner, Christoph; Müller-Petke, Mike; Houben, Georg

2018-03-01

The capability of nuclear magnetic resonance (NMR) relaxometry to characterise hydraulic properties of iron-oxide-coated sand and gravel was evaluated in a laboratory study. Past studies have shown that the presence of paramagnetic iron oxides and large pores in coarse sand and gravel disturbs the otherwise linear relationship between relaxation time and pore size. Consequently, the commonly applied empirical approaches fail when deriving hydraulic quantities from NMR parameters. Recent research demonstrates that higher relaxation modes must be taken into account to relate the size of a large pore to its NMR relaxation behaviour in the presence of significant paramagnetic impurities at its pore wall. We performed NMR relaxation experiments with water-saturated natural and reworked sands and gravels, coated with natural and synthetic ferric oxides (goethite, ferrihydrite), and show that the impact of the higher relaxation modes increases significantly with increasing iron content. Since the investigated materials exhibit narrow pore size distributions, and can thus be described by a virtual bundle of capillaries with identical apparent pore radius, recently presented inversion approaches allow for estimation of a unique solution yielding the apparent capillary radius from the NMR data. We found the NMR-based apparent radii to correspond well to the effective hydraulic radii estimated from the grain size distributions of the samples for the entire range of observed iron contents. Consequently, they can be used to estimate the hydraulic conductivity using the well-known Kozeny-Carman equation without any calibration that is otherwise necessary when predicting hydraulic conductivities from NMR data. Our future research will focus on the development of relaxation time models that consider pore size distributions. Furthermore, we plan to establish a measurement system based on borehole NMR for localising iron clogging and controlling its remediation in the gravel pack of

Proton NMR imaging in experimental ischemic infarction

International Nuclear Information System (INIS)

Buonanno, F.S.; Pykett, I.L.; Brady, T.J.; Vielma, J.; Burt, C.T.; Goldman, M.R.; Hinshaw, W.S.; Pohost, G.M.; Kistler, J.P.

1983-01-01

Proton nuclear magnetic resonance (NMR) images depict the distribution and concentration of mobile protons modified by the relaxation times T1 and T2. Using the steady-state-free-precession (SSFP) technique, serial coronal images were obtained sequentially over time in laboratory animals with experimental ischemic infarction. Image changes were evident as early as 2 hours after carotid artery ligation, and corresponded to areas of ischemic infarction noted pathologically. Resulting SSFP images in experimental stroke are contrasted to inversion-recovery NMR images in an illustrative patient with established cerebral infarction. Bulk T1 and T2 measurements were made in vitro in three groups of gerbils: normal, those with clinical evidence of infarction, and those clinically normal after carotid ligature. Infarcted hemispheres had significantly prolonged T1 and T2 (1.47 +/- .12 sec, 76.0 +/- 9.0 msec, respectively) when compared to the contralateral hemisphere (T1 . 1.28 +/- .05 sec, T2 . 58.7 +/- 3.9 msec) or to the other two groups. These data suggest that changes in NMR parameters occur and can be detected by NMR imaging as early as two hours after carotid artery ligation

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...... 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....

An NMR database for simulations of membrane dynamics.

Science.gov (United States)

Leftin, Avigdor; Brown, Michael F

2011-03-01

Computational methods are powerful in capturing the results of experimental studies in terms of force fields that both explain and predict biological structures. Validation of molecular simulations requires comparison with experimental data to test and confirm computational predictions. Here we report a comprehensive database of NMR results for membrane phospholipids with interpretations intended to be accessible by non-NMR specialists. Experimental ¹³C-¹H and ²H NMR segmental order parameters (S(CH) or S(CD)) and spin-lattice (Zeeman) relaxation times (T(1Z)) are summarized in convenient tabular form for various saturated, unsaturated, and biological membrane phospholipids. Segmental order parameters give direct information about bilayer structural properties, including the area per lipid and volumetric hydrocarbon thickness. In addition, relaxation rates provide complementary information about molecular dynamics. Particular attention is paid to the magnetic field dependence (frequency dispersion) of the NMR relaxation rates in terms of various simplified power laws. Model-free reduction of the T(1Z) studies in terms of a power-law formalism shows that the relaxation rates for saturated phosphatidylcholines follow a single frequency-dispersive trend within the MHz regime. We show how analytical models can guide the continued development of atomistic and coarse-grained force fields. Our interpretation suggests that lipid diffusion and collective order fluctuations are implicitly governed by the viscoelastic nature of the liquid-crystalline ensemble. Collective bilayer excitations are emergent over mesoscopic length scales that fall between the molecular and bilayer dimensions, and are important for lipid organization and lipid-protein interactions. Future conceptual advances and theoretical reductions will foster understanding of biomembrane structural dynamics through a synergy of NMR measurements and molecular simulations. Copyright © 2010 Elsevier B.V. All

NMR investigations of molecular dynamics

Science.gov (United States)

Palmer, Arthur

2011-03-01

NMR spectroscopy is a powerful experimental approach for characterizing protein conformational dynamics on multiple time scales. The insights obtained from NMR studies are complemented and by molecular dynamics (MD) simulations, which provide full atomistic details of protein dynamics. Homologous mesophilic (E. coli) and thermophilic (T. thermophilus) ribonuclease H (RNase H) enzymes serve to illustrate how changes in protein sequence and structure that affect conformational dynamic processes can be monitored and characterized by joint analysis of NMR spectroscopy and MD simulations. A Gly residue inserted within a putative hinge between helices B and C is conserved among thermophilic RNases H, but absent in mesophilic RNases H. Experimental spin relaxation measurements show that the dynamic properties of T. thermophilus RNase H are recapitulated in E. coli RNase H by insertion of a Gly residue between helices B and C. Additional specific intramolecular interactions that modulate backbone and sidechain dynamical properties of the Gly-rich loop and of the conserved Trp residue flanking the Gly insertion site have been identified using MD simulations and subsequently confirmed by NMR spin relaxation measurements. These results emphasize the importance of hydrogen bonds and local steric interactions in restricting conformational fluctuations, and the absence of such interactions in allowing conformational adaptation to substrate binding.

Multinuclear NMR of CaSiO(3) glass: simulation from first-principles.

Science.gov (United States)

Pedone, Alfonso; Charpentier, Thibault; Menziani, Maria Cristina

2010-06-21

An integrated computational method which couples classical molecular dynamics simulations with density functional theory calculations is used to simulate the solid-state NMR spectra of amorphous CaSiO(3). Two CaSiO(3) glass models are obtained by shell-model molecular dynamics simulations, successively relaxed at the GGA-PBE level of theory. The calculation of the NMR parameters (chemical shielding and quadrupolar parameters), which are then used to simulate solid-state 1D and 2D-NMR spectra of silicon-29, oxygen-17 and calcium-43, is achieved by the gauge including projector augmented-wave (GIPAW) and the projector augmented-wave (PAW) methods. It is shown that the limitations due to the finite size of the MD models can be overcome using a Kernel Estimation Density (KDE) approach to simulate the spectra since it better accounts for the disorder effects on the NMR parameter distribution. KDE allows reconstructing a smoothed NMR parameter distribution from the MD/GIPAW data. Simulated NMR spectra calculated with the present approach are found to be in excellent agreement with the experimental data. This further validates the CaSiO(3) structural model obtained by MD simulations allowing the inference of relationships between structural data and NMR response. The methods used to simulate 1D and 2D-NMR spectra from MD GIPAW data have been integrated in a package (called fpNMR) freely available on request.

Magnetic structure and spin dynamics of the ground state of the molecular cluster Mn12O12 acetate studied by 55Mn NMR

International Nuclear Information System (INIS)

Furukawa, Y.; Watanabe, K.; Kumagai, K.; Borsa, F.; Gatteschi, D.

2001-01-01

55 Mn nuclear magnetic resonance (NMR) measurements have been carried out in an oriented powder sample of Mn12 acetate at low temperature (1.4--3 K) in order to investigate locally the static and dynamic magnetic properties of the molecule in its high-spin S=10 ground state. We report the observation of three 55 MnNMR lines under zero external magnetic field. From the resonance frequency and the width of the lines we derive the internal hyperfine field and the quadrupole coupling constant at each of the three nonequivalent Mn ion sites. From the field dependence of the spectrum we obtain a direct confirmation of the standard picture, in which spin moments of Mn 4+ ions (S=3/2) of the inner tetrahedron are polarized antiparallel to that of Mn 3+ ions (S=2) of the outer ring with no measurable canting from the easy axis up to an applied field of 6 T. It is found that the splitting of the 55 Mn-NMR lines when a magnetic field is applied at low temperature allows one to monitor the off-equilibrium population of the molecules in the different low lying magnetic states. The measured nuclear spin-lattice relaxation time T 1 strongly depends on temperature and magnetic field. The behavior could be fitted well by considering the local-field fluctuations at the nuclear 55 Mn site due to the thermal reorientation of the total S=10 spin of the molecule. From the fit of the data one can derive the product of the spin-phonon coupling constant times the mean-square value of the fluctuating hyperfine field. The two constants could be estimated separately by making some assumptions. The comparison of the mean-square fluctuation from relaxation with the static hyperfine field from the spectrum suggests that nonuniform terms (q≠0) are important in describing the spin dynamics of the local Mn moments in the ground state

Some exercises in quantitative NMR imaging

International Nuclear Information System (INIS)

Bakker, C.J.G.

1985-01-01

The articles represented in this thesis result from a series of investigations that evaluate the potential of NMR imaging as a quantitative research tool. In the first article the possible use of proton spin-lattice relaxation time T 1 in tissue characterization, tumor recognition and monitoring tissue response to radiotherapy is explored. The next article addresses the question whether water proton spin-lattice relaxation curves of biological tissues are adequately described by a single time constant T 1 , and analyzes the implications of multi-exponentiality for quantitative NMR imaging. In the third article the use of NMR imaging as a quantitative research tool is discussed on the basis of phantom experiments. The fourth article describes a method which enables unambiguous retrieval of sign information in a set of magnetic resonance images of the inversion recovery type. The next article shows how this method can be adapted to allow accurate calculation of T 1 pictures on a pixel-by-pixel basis. The sixth article, finally, describes a simulation procedure which enables a straightforward determination of NMR imaging pulse sequence parameters for optimal tissue contrast. (orig.)

Applications of NMR in biological metabolic research

International Nuclear Information System (INIS)

Nie Jiarui; Li Xiuqin; He Chunjian

1989-01-01

The nuclear magnetic resonance has become a powerful means of studying biological metabolism in non-invasive and non-destructive way. Being used to study the metabolic processes of living system in normal physiological conditions as well as in molecular level, the method is better than other conventional approaches. Using important parameters such as NMR-chemical shifts, longitudinal relaxation time and transverse relaxation time, it is possible to probe the metabolic processes as well as conformation, concentration, transportation and distribution of reacting and resulting substances. The NMR spectroscopy of 1 H, 31 P and 13 C nuclei has already been widely used in metabolic researches

Nuclear magnetic resonance (NMR): application to examine liver tissues during invasion of the Liver fluke in cattle

International Nuclear Information System (INIS)

Wranicz, M.; Podbielski, T.; Grabiec, S.

1989-01-01

The T 1 and T 2 relaxation times of protons of hydrogen in the liver parenchyma and biliary ducts in normal and parazitized by the Liver fluke cows were determined. A method of the NMR in which a lenght or relaxation time is an index was applied. The value of this index is characteristic for determined physiological and pathological states of cells and it reveals changes which developed in body cells. It was found that tissues of cows parazitized by the Liver fluke (parenchyma and biliary ducts) and healthy ones differ significantly by the lenght of relaxation times. Parazitized tissues show a longer relaxation time than tissues of normal cows. (author)

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.

Experimental solid state NMR of gas hydrates : problems and solutions

Energy Technology Data Exchange (ETDEWEB)

Moudrakovski, I.; Lu, H.; Ripmeester, J. [National Research Council of Canada, Ottawa, ON (Canada). Steacie Inst. for Molecular Sciences; Kumar, R.; Susilo, R. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Chemical and Biological Engineering; Luzi, M. [GeoForschungsZentrum Potsdam, Potsdam (Germany)

2008-07-01

Solid State NMR is a suitable spectroscopic technique for hydrate research for several reasons, including its capability to distinguish between different structural types of hydrates, its quantitative nature and potential for both in-situ and time resolved experiments. This study illustrated the applications of solid state NMR for compositional and structural studies of clathrate hydrates, with particular emphasis on experimental techniques and potential ways to overcome technical difficulties. In order to use the method to its full capacity, some instrumental developments are needed to adapt it to the specific experimental requirements of hydrate studies, such as very low temperatures and high pressures. This presentation discussed the quantification of the Carbon-13 spectra with examples from natural and synthetic hydrates prepared from multi-component mixtures of hydrocarbons. The main approach used for the first two examples was Carbon-13 NMR with Magic Angle Spinning (MAS) at -100 degrees C. The detailed characterization of mixed hydrogen hydrates required low temperature hydrogen MAS. The quantification problems encountered during these experiments were also discussed. The purpose of these recent experimental developments was to prompt wider application of Solid State NMR in hydrate research. NMR proved to be a viable method for analyzing the composition and structure of multi-component mixed gas hydrates; characterizing natural gas hydrates; and, evaluating the formation conditions and properties of mixed hydrogen hydrates. The limitations of the method were highlighted and sensible choices of experimental conditions and techniques that ensure accurate results were discussed. 34 refs., 10 figs.

Characterization of the transverse relaxation rates in lipid bilayers

International Nuclear Information System (INIS)

Watnick, P.I.; Dea, P.; Chan, S.I.

1990-01-01

The 2H NMR transverse relaxation rates of a deuterated phospholipid bilayer reflect slow motions in the bilayer membrane. A study of dimyristoyl lecithin specifically deuterated at several positions of the hydrocarbon chains indicates that these motions are cooperative and are confined to the hydrocarbon chains of the lipid bilayer. However, lipid head group interactions do play an important role in modulating the properties of the cooperative fluctuations of the hydrocarbon chains (director fluctuations), as evidenced by the effects of various lipid additives on the 2H NMR transverse relaxation rates of the dimyristoyl lecithin bilayer

Peakr: simulating solid-state NMR spectra of proteins

International Nuclear Information System (INIS)

Schneider, Robert; Odronitz, Florian; Hammesfahr, Bjorn; Hellkamp, Marcel; Kollmar, Martin

2013-01-01

When analyzing solid-state nuclear magnetic resonance (NMR) spectra of proteins, assignment of resonances to nuclei and derivation of restraints for 3D structure calculations are challenging and time-consuming processes. Simulated spectra that have been calculated based on, for example, chemical shift predictions and structural models can be of considerable help. Existing solutions are typically limited in the type of experiment they can consider and difficult to adapt to different settings. Here, we present Peakr, a software to simulate solid-state NMR spectra of proteins. It can generate simulated spectra based on numerous common types of internuclear correlations relevant for assignment and structure elucidation, can compare simulated and experimental spectra and produces lists and visualizations useful for analyzing measured spectra. Compared with other solutions, it is fast, versatile and user friendly. (authors)

Interpretation of NMR relaxation properties of Pin1, a two-domain protein, based on Brownian dynamic simulations

International Nuclear Information System (INIS)

Bernado, Pau; Fernandes, Miguel X.; Jacobs, Doris M.; Fiebig, Klaus; Garcia de la Torre, Jose; Pons, Miquel

2004-01-01

Many important proteins contain multiple domains connected by flexible linkers. Inter-domain motion is suggested to play a key role in many processes involving molecular recognition. Heteronuclear NMR relaxation is sensitive to motions in the relevant time scales and could provide valuable information on the dynamics of multi-domain proteins. However, the standard analysis based on the separation of global tumbling and fast local motions is no longer valid for multi-domain proteins undergoing internal motions involving complete domains and that take place on the same time scale than the overall motion.The complexity of the motions experienced even for the simplest two-domain proteins are difficult to capture with simple extensions of the classical Lipari-Szabo approach. Hydrodynamic effects are expected to dominate the motion of the individual globular domains, as well as that of the complete protein. Using Pin1 as a test case, we have simulated its motion at the microsecond time scale, at a reasonable computational expense, using Brownian Dynamic simulations on simplified models. The resulting trajectories provide insight on the interplay between global and inter-domain motion and can be analyzed using the recently published method of isotropic Reorientational Mode Dynamics which offer a way of calculating their contribution to heteronuclear relaxation rates. The analysis of trajectories computed with Pin1 models of different flexibility provides a general framework to understand the dynamics of multi-domain proteins and explains some of the observed features in the relaxation rate profile of free Pin1

Interpretation of NMR relaxation properties of Pin1, a two-domain protein, based on Brownian dynamic simulations

Energy Technology Data Exchange (ETDEWEB)

Bernado, Pau [Institut de Biologie Structurale, Jean Pierre Ebel (France); Fernandes, Miguel X. [Universidad de Murcia, Departamento de Quimica Fisica, Facultad de Quimica (Spain); Jacobs, Doris M. [Johann Wolfgang Goethe-Universitaet Frankfurt, Institut fuer Organische Chemie und Chemische Biologie (Germany); Fiebig, Klaus [Affinium Pharmaceuticals (Canada); Garcia de la Torre, Jose [Universidad de Murcia, Departamento de Quimica Fisica, Facultad de Quimica (Spain); Pons, Miquel [Laboratori de RMN de Biomolecules, Parc Cientific de Barcelona (Spain)], E-mail: mpons@ub.edu

2004-05-15

Many important proteins contain multiple domains connected by flexible linkers. Inter-domain motion is suggested to play a key role in many processes involving molecular recognition. Heteronuclear NMR relaxation is sensitive to motions in the relevant time scales and could provide valuable information on the dynamics of multi-domain proteins. However, the standard analysis based on the separation of global tumbling and fast local motions is no longer valid for multi-domain proteins undergoing internal motions involving complete domains and that take place on the same time scale than the overall motion.The complexity of the motions experienced even for the simplest two-domain proteins are difficult to capture with simple extensions of the classical Lipari-Szabo approach. Hydrodynamic effects are expected to dominate the motion of the individual globular domains, as well as that of the complete protein. Using Pin1 as a test case, we have simulated its motion at the microsecond time scale, at a reasonable computational expense, using Brownian Dynamic simulations on simplified models. The resulting trajectories provide insight on the interplay between global and inter-domain motion and can be analyzed using the recently published method of isotropic Reorientational Mode Dynamics which offer a way of calculating their contribution to heteronuclear relaxation rates. The analysis of trajectories computed with Pin1 models of different flexibility provides a general framework to understand the dynamics of multi-domain proteins and explains some of the observed features in the relaxation rate profile of free Pin1.

NMR imaging

International Nuclear Information System (INIS)

Andrew, E.R.

1983-01-01

Since hydrogen is the most abundant element in all living organisms, proton NMR lends itself well as a method of investigation in biology and medicine. NMR imaging has some special advantages as a diagnostic tool: no ionizing radiation is used, it is noninvasive; it provides a safer means of imaging than the use of x-rays, gamma rays, positrons, or heavy ions. In contrast with ultrasound, the radiation penetrates the bony structures without attenuation. In additional to morphological information, NMR imaging provides additional diagnostic insights through relaxation parameters, which are not available from other imaging methods. In the decade since the first primitive NMR images were obtained, the quality of images now obtained approaches those from CT x-ray scanners. Prototype instruments are being constructed for clinical evaluation and the first whole-body scanners are beginning to appear on the market at costs comparable to CT scanners. Primary differences in equipment for conventional NMR and NMR imaging are the much larger aperture magnets that are required for the examination of human subjects and the addition of coils to generate field gradients and facilities for manipulating the gradients. Early results from clinical trials in many parts of the world are encouraging, and in a few years, the usefuleness of this modality of medical imaging to the medical profession in diagnosis and treatment of disease will be defined. 10 figures

The microscopic NMR probe in chiral magnets. Zero field-, field-modulated- and Skyrmion- states in FeGe and MnSi

Energy Technology Data Exchange (ETDEWEB)

Baenitz, Michael; Yasuoka, Hiroshi; Majumder, Mayukh; Khuntia, Panchanan; Schmidt, Marcus [MPI for the Chemical Physics of Solids, Dresden (Germany); Witt, Sebastian; Krellner, Cornelius [Goethe University, Frankfurt am Main (Germany)

2016-07-01

Cubic FeGe is a prototype B20 chiral magnet (T{sub c} = 280 K) which allows to study chiral correlations directly ''on-site'' via the{sup 57}Fe nucleus because of its S=1/2 nuclear spin interacting only with the electron spin moment. NMR provides the static and dynamic staggered local magnetization M{sub Q} through the hyperfine field (H{sub hf}) and the spin lattice relaxation rate (SLRR = 1/T{sub 1}). Measurements were performed on randomly oriented {sup 57}Fe enriched FeGe single crystals between 2-300 K. Helical-, conical- and field-polarized-states could be clearly identified and spin dynamics of each phase was investigated. MnSi single crystals and {sup 29}Si enriched MnSi polycrystals were studied by {sup 29}Si-NMR (S=1/2) in the ordered state (T{sub c} = 29 K) and above. The T- and H- dependence of H{sub hf} and SLRR was investigated in great detail for both FeGe and MnSi.The {sup 29}Si-NMR lines in MnSi are narrow and H{sub hf}-values obtained are smaller than in FeGe. Our results are in general accordance with the extended SCR theory for itinerant helical magnets, although the theory does not include the symmetry breaking in the B20 structure and the multi-band nature. For FeGe correlations are complex due to its more localized magnetism.

Dispersion of Silicate in Tricalcium Phosphate Elucidated by Solid-State NMR

Energy Technology Data Exchange (ETDEWEB)

Rewal, A.; Wei, X.; Akinc, M.; Schmidt-Rohr, K.

2008-03-12

The dispersion of silicate in tricalcium phosphate, a resorbable bioceramics for bone replacement, has been investigated by various solid-state nuclear magnetic resonance (NMR) methods. In samples prepared with 5 and 10 mol% of both {sup 29}SiO{sub 2} and ZnO, three types of silicate have been detected: (i) SiO{sub 4}{sup 4-} (Q{sub 0} sites) with long longitudinal (T{sub 1,Si}) relaxation times ({approx} 10,000 s), which substitute for {approx}1% of PO{sub 4}{sup 3-}; (ii) silicate nanoinclusions containing Q{sub 2}, Q{sub 1}, and Q{sub 0} sites with T{sub 1,Si} 100 s, which account for most of the silicon; and (iii) crystalline Q{sub 4} (SiO{sub 2}) with long T{sub 1,Si}. Sensitivity was enhanced >100-fold by {sup 29}Si enrichment and refocused detection. The inclusions in both samples have a diameter of {approx}8 nm, as proved by {sup 29}Si{l_brace}{sup 31}P{r_brace} REDOR dephasing on a 30-ms time scale, which was simulated using a multispin approach specifically suited for nanoparticles. {sup 29}Si CODEX NMR with 30-s {sup 29}Si spin diffusion confirms that an inclusion contains >10 Si (consistent with the REDOR result of >100 Si per inclusion). Overlapping signals of silicate Q{sub 2}, Q{sub 1}, and Q{sub 0} sites were spectrally edited based on their J-couplings, using double-quantum filtering. The large inhomogeneous broadening of the Q{sub 2}, Q{sub 1}, and Q{sub 0} {sup 29}Si subspectra indicates that the nanoinclusions are amorphous.

Fluid-Rock Characterization and Interactions in NMR Well Logging

Energy Technology Data Exchange (ETDEWEB)

Hirasaki, George J.; Mohanty, Kishore K.

2003-02-10

The objective of this project was to characterize the fluid properties and fluid-rock interactions that are needed for formation evaluation by NMR well logging. The advances made in the understanding of NMR fluid properties are summarized in a chapter written for an AAPG book on NMR well logging. This includes live oils, viscous oils, natural gas mixtures, and the relation between relaxation time and diffusivity.

Unconventional superconductivity in PuRhGa5: Ga NMR/NQR study

International Nuclear Information System (INIS)

Sakai, H.; Tokunaga, Y.; Fujimoto, T.; Kambe, S.; Walstedt, R.E.; Yasuoka, H.; Aoki, D.; Homma, Y.; Yamamoto, E.; Nakamura, A.; Shiokawa, Y.; Nakajima, K.; Arai, Y.; Matsuda, T.D.; Haga, Y.; Onuki, Y.

2006-01-01

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

Introduction to some basic aspects of NMR

International Nuclear Information System (INIS)

Goldman, M.

1992-01-01

The principal interactions are reviewed that are experienced by nuclear spins making magnetic resonance feasible and which disturb it in a way that gives access to the properties of bulk matter. The interactions leading to NMR include Zeeman interaction, dipole-dipole interactions, and exchange interactions. Spin-lattice relaxation relevant to NMR is revisited next. It is followed by an overview of spin temperature. Finally, the care of periodic Hamiltonian is discussed in detail as another contribution to NMR. (R.P.) 48 refs., 12 figs

Solid State NMR Characterization of Complex Metal Hydrides systems for Hydrogen Storage Applications

Directory of Open Access Journals (Sweden)

Son-Jong Hwang

2011-12-01

Full Text Available Solid state NMR is widely applied in studies of solid state chemistries for hydrogen storage reactions. Use of 11B MAS NMR in studies of metal borohydrides (BH4 is mainly focused, revisiting the issue of dodecaborane formation and observation of 11B{1H} Nuclear Overhauser Effect.

A Toolbox of Solid-State NMR Experiments for the Characterization of Soft Organic Nanomaterials

KAUST Repository

Straasø, Lasse Arnt

2016-02-02

Determining how organic molecules self-assemble into a solid material is a challenging and demanding task if a single crystal of the material cannot be produced. Solid-state NMR spectroscopy offers access to such molecular details via an appropriate selection of techniques. This report gives a selected overview of 1D and 2D solid-state NMR techniques for elucidating the structure of soft organic solids. We focus on how the solid-state NMR techniques are designed from the perspective of the different nuclear interactions, using average Hamiltonian theory and product operators. We also introduce recent methods for quantification and reduction of experimental artifacts. Finally, we highlight how the solid-state NMR techniques can be applied to soft organic materials by reviewing recent applications to semicrystalline polymers, π-conjugated polymers, natural silk, and graphene-related materials.

A Toolbox of Solid-State NMR Experiments for the Characterization of Soft Organic Nanomaterials

KAUST Repository

Straasø , Lasse Arnt; Saleem, Qasim; Hansen, Michael Ryan

2016-01-01

Determining how organic molecules self-assemble into a solid material is a challenging and demanding task if a single crystal of the material cannot be produced. Solid-state NMR spectroscopy offers access to such molecular details via an appropriate selection of techniques. This report gives a selected overview of 1D and 2D solid-state NMR techniques for elucidating the structure of soft organic solids. We focus on how the solid-state NMR techniques are designed from the perspective of the different nuclear interactions, using average Hamiltonian theory and product operators. We also introduce recent methods for quantification and reduction of experimental artifacts. Finally, we highlight how the solid-state NMR techniques can be applied to soft organic materials by reviewing recent applications to semicrystalline polymers, π-conjugated polymers, natural silk, and graphene-related materials.

NMR study of LaPb2

International Nuclear Information System (INIS)

Ueda, K.; Kohara, T.; Yamada, Y.

1995-01-01

La and Pb NMR signals were observed in LaPb 2 with a superconducting transition temperature of about 7 K. The width of the Pb NMR spectrum with an asymmetric line shape was rather narrower than those of Er-, Gd- and Ho-Pb 2 . The spin-lattice relaxation time of Pb nuclei was twice longer than that of Pb metal. La NMR spectrum had satellites due to the electric quadrupole interaction. These results show that each local environment at La or Pb site in LaPb 2 compound is uniquely determined, compared with those in randomly substituted alloys. ((orig.))

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 30.2MHz and 28.411MHz 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 (1)H are polarized in the magnetic field B0 while fluorine spins (19)F 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. Copyright © 2015 Elsevier Inc. All rights reserved.

{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.

NMR study of the molecular nanomagnet [Fe8(N3C6H15)6O2(OH)12]·[Br8·9H2O] in the high-spin magnetic ground state

International Nuclear Information System (INIS)

Furukawa, Y.; Kumagai, K.; Lascialfari, A.; Aldrovandi, S.; Borsa, F.; Sessoli, R.; Gatteschi, D.

2001-01-01

The magnetic molecular cluster [Fe 8 (N 3 C 6 H 15 ) 6 O 2 (OH) 12 ] 8+ [Br 8 ·9H 2 O] 8- , in short Fe8, has been investigated at low temperature by 1 H-NMR and relaxation measurements. Some measurements of 2 D-NMR in partially deuterated Fe8 clusters will also be reported. Upon decreasing temperature the NMR spectra display a very broad and structured signal which is the result of the internal local fields at the proton sites due to the local moments of the Fe(III) ions in the total S=10 magnetic ground state. The proton and deuteron NMR spectra have been analyzed and the different resonance peaks have been attributed to the different proton groups in the molecule. The simulation of the spectra by using a dipolar hyperfine field and the accepted model for the orientation of the Fe(III) local moments do not agree with the experiments even when the magnitude of the local Fe(III) moments is allowed to vary. It is concluded that a positive contact hyperfine interaction of the same order of magnitude as the dipolar interaction is present for all proton sites except the water molecules. The temperature and magnetic field dependence of the nuclear spin-lattice relaxation rate is ascribed to the fluctuations of the local Fe(III) moments, which follow rigidly the fluctuations of the total ground state magnetization of the nanomagnet. By using a simple model already utilized for the Mn12 cluster, we derive the value of the spin phonon coupling constant which determines the lifetime broadening of the different magnetic quantum number m substates of the S=10 ground state. It is shown that the lifetime broadening decreases rapidly on lowering the temperature. When the lifetime becomes longer than the reciprocal of the frequency shift of the proton lines a structure emerges in the NMR spectrum reflecting the ''frozen'' local moment configuration

Which kind of aromatic structures are produced during biomass charring? New insights provided by modern solid-state NMR spectroscopy

Science.gov (United States)

Knicker, Heike; Paneque-Carmona, Marina; Velasco-Molina, Marta; de la Rosa, José Maria; León-Ovelar, Laura Regina; Fernandez-Boy, Elena

2017-04-01

Intense research on biochar and charcoal of the last years has revealed that depending on the production conditions, the chemical and physical characteristics of their aromatic network can greatly vary. Since such variations are determining the behavior and stability of charred material in soils, a better understanding of the structural changes occurring during their heating and the impact of those changes on their function is needed. One method to characterize pyrogenic organic matter (PyOM) represents solid-state 13C NMR spectroscopy applying the cross polarization (CP) magic angle spinning technique (MAS). A drawback of this technique is that the quantification of NMR spectra of samples with highly condensed and proton-depleted structures is assumed to be bias. Typical samples with such attributes are charcoals produced at temperatures above 700°C under pyrolytic conditions. Commonly their high condensation degree leads to graphenic structures that are not only reducing the CP efficiency but create also a conductive lattice which acts as a shield and prevents the entering of the excitation pulse into the sample during the NMR experiments. Since the latter can damage the NMR probe and in the most cases the obtained NMR spectra show only one broad signal assignable to aromatic C, this technique is rarely applied for characterizing high temperature chars or soot. As a consequence, a more detailed knowledge of the nature of the aromatic ring systems is still missing. The latter is also true for the aromatic domains of PyOM produced at lower temperatures, since older NMR instruments operating at low magnetic fields deliver solid-state 13C NMR spectra with low resolution which turns a more detailed analysis of the aromatic chemical shift region into a challenging task. In order to overcome this disadvantages, modern NMR spectroscopy offers not only instruments with greatly improved resolution but also special pulse sequences for NMR experiments which allow a more

Sensitivity enhancement in NMR of macromolecules by application of optimal control theory

International Nuclear Information System (INIS)

Frueh, Dominique P.; Ito, Takuhiro; Li, J.-S.; Wagner, Gerhard; Glaser, Steffen J.; Khaneja, Navin

2005-01-01

NMR of macromolecules is limited by large transverse relaxation rates. In practice, this results in low efficiency of coherence transfer steps in multidimensional NMR experiments, leading to poor sensitivity and long acquisition times. The efficiency of coherence transfer can be maximized by design of relaxation optimized pulse sequences using tools from optimal control theory. In this paper, we demonstrate that this approach can be adopted for studies of large biological systems, such as the 800 kDa chaperone GroEL. For this system, the 1 H- 15 N coherence transfer module presented here yields an average sensitivity enhancement of 20-25% for cross-correlated relaxation induced polarization transfer (CRIPT) experiments

Nuclear magnetic relaxation studies of semiconductor nanocrystals and solids

Energy Technology Data Exchange (ETDEWEB)

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

1993-09-01

Semiconductor nanocrystals, small biomolecules, and ¹³C enriched solids were studied through the relaxation in NMR spectra. Surface structure of semiconductor nanocrystals (CdS) was deduced from high resolution ¹H and ¹³C 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 Å. Internal motion is estimated to be slow with a correlation time > 10^-8 s^-1. The surface thiophenol ligands react to form a dithiophenol when the nanocrystals were subjected to O₂ and ultraviolet. A method for measuring ¹⁴N-¹H J-couplings is demonstrated on pyridine and the peptide oxytocin; selective 2D T₁ and T₂ 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 ¹³C enriched solids is demonstrated by experiments on zinc acetate and L-alanine.

Variational formulation of relaxed and multi-region relaxed magnetohydrodynamics

Science.gov (United States)

Dewar, R. L.; Yoshida, Z.; Bhattacharjee, A.; Hudson, S. R.

2015-12-01

> Ideal magnetohydrodynamics (IMHD) is strongly constrained by an infinite number of microscopic constraints expressing mass, entropy and magnetic flux conservation in each infinitesimal fluid element, the latter preventing magnetic reconnection. By contrast, in the Taylor relaxation model for formation of macroscopically self-organized plasma equilibrium states, all these constraints are relaxed save for the global magnetic fluxes and helicity. A Lagrangian variational principle is presented that leads to a new, fully dynamical, relaxed magnetohydrodynamics (RxMHD), such that all static solutions are Taylor states but also allows state with flow. By postulating that some long-lived macroscopic current sheets can act as barriers to relaxation, separating the plasma into multiple relaxation regions, a further generalization, multi-region relaxed magnetohydrodynamics (MRxMHD) is developed.

NMR of geophysical drill cores with a mobile Halbach scanner

International Nuclear Information System (INIS)

Talnishnikh, E.

2007-01-01

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

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

Nuclear spin relaxation due to chemical shift anisotropy of gas-phase 129Xe.

Science.gov (United States)

Hanni, Matti; Lantto, Perttu; Vaara, Juha

2011-08-14

Nuclear spin relaxation provides detailed dynamical information on molecular systems and materials. Here, first-principles modeling of the chemical shift anisotropy (CSA) relaxation time for the prototypic monoatomic (129)Xe gas is carried out, both complementing and predicting the results of NMR measurements. Our approach is based on molecular dynamics simulations combined with pre-parametrized ab initio binary nuclear shielding tensors, an "NMR force field". By using the Redfield relaxation formalism, the simulated CSA time correlation functions lead to spectral density functions that, for the first time, quantitatively determine the experimental spin-lattice relaxation times T(1). The quality requirements on both the Xe-Xe interaction potential and binary shielding tensor are investigated in the context of CSA T(1). Persistent dimers Xe(2) are found to be responsible for the CSA relaxation mechanism in the low-density limit of the gas, completely in line with the earlier experimental findings.

TD-NMR studies on CuSO{sub 4} salt hydrates

Energy Technology Data Exchange (ETDEWEB)

Nestle, Nikolaus; Magin, Peter; Wengeler, Robert [BASF Aktiengesellschaft, Ludwigshafen (Germany); Kleinschmidt, Sebastian [Universitaet Magdeburg, FB Chemie (Germany)

2008-07-01

Despite the high concentration of paramagnetic copper ions, solid CuSO{sub 4} hydrates exhibit surprizingly narrow NMR signals. This is known since the late 1940s. Using TD-NMR methods established for polymer studies, the relaxation behaviour of CuSO{sub 4} preparations with different water content was studied at room temperature. For the water content of the pentahydrate and below, the NMR signal exhibits a pure solid-state-type magnetization decay behaviour. For slightly overstoichiometric moisture contents, a liquid-like signal is observed in addition to the solid signal. However, the relative amplitudes of the solid and the liquid signal do not mirror the stoichiometric composition of the pentahydrate and the excess water. Instead, the solid signal amplitude only accounts for four hydrate water molecules while the fifth water exhibits rapid exchange with the liquid phase and thus contributes to the liquid-type signal. This finding is in good agreement to results from investigations into the crystal structure of solid CuSO4 pentahydrate.

13C-NMR assignment, structure, and dynamics of deoxyoligonucleotides

International Nuclear Information System (INIS)

Zanatta, N.; Borer, P.N.; Levy, G.C.

1986-01-01

The unique spectral properties of 13 C-NMR for studying nucleic acids and some of the important features of 13 C-NMR in oligonucleotide studies are demostrated. The main difficulty in studying oligonucleotides by 13 C-NMR and recent improvements in NMR instrumentation and advances in oligonucleotide synthesis are presented. The high resolution 13 C-NMR spectra, T 1 relaxation times and NOEs were measured for duplex of the self-complementary oligo-DNAs: d(CG) 3 and d(GGTATACC) are studied. The target of this study is to developed a systematic 13 C-NMR spectral assignment and to investigate the structure and dynamics of these two sequences by this techniques. (M.J.C.) [pt

Dynamics of relaxation to a stationary state for interacting molecular motors

Science.gov (United States)

Gomes, Luiza V. F.; Kolomeisky, Anatoly B.

2018-01-01

Motor proteins are active enzymatic molecules that drive a variety of biological processes, including transfer of genetic information, cellular transport, cell motility and muscle contraction. It is known that these biological molecular motors usually perform their cellular tasks by acting collectively, and there are interactions between individual motors that specify the overall collective behavior. One of the fundamental issues related to the collective dynamics of motor proteins is the question if they function at stationary-state conditions. To investigate this problem, we analyze a relaxation to the stationary state for the system of interacting molecular motors. Our approach utilizes a recently developed theoretical framework, which views the collective dynamics of motor proteins as a totally asymmetric simple exclusion process of interacting particles, where interactions are taken into account via a thermodynamically consistent approach. The dynamics of relaxation to the stationary state is analyzed using a domain-wall method that relies on a mean-field description, which takes into account some correlations. It is found that the system quickly relaxes for repulsive interactions, while attractive interactions always slow down reaching the stationary state. It is also predicted that for some range of parameters the fastest relaxation might be achieved for a weak repulsive interaction. Our theoretical predictions are tested with Monte Carlo computer simulations. The implications of our findings for biological systems are briefly discussed.

NMR: its application to the experimental study of hydrocephalus and brain edema

Energy Technology Data Exchange (ETDEWEB)

Asato, R; Murata, T; Mori, K; Handa, H [Kyoto Univ. (Japan). Faculty of Medicine

1981-06-01

The pulsed NMR technique is very sensitive to molecular movement because its observation frequency is in the range of the rates of molecular movement. Furthermore it makes it possible to study the interested molecules in the biological tissues physically and noninvasively. In this report we have investigated the experimental brain edema and hydrocephalus, in both of which the tissue fluid changes are main pathology, through /sup 1/H-NMR relaxation study of water molecule in the brain tissues. The longitudinal (T/sub 1/) and the transverse (T/sub 2/) relaxation times were measured with Varian-HR-220 spectrometer modified with Nicolet-TT-100 PFT system. The experimental materials were the adult male Wister rats suffering from cold injury edema and the adult canines suffering from kaolin hydrocephalus. The study showed firstly that in brain edema no particular changes were found for relaxation times in the white matter, whereas in the gray matter, discrepancy between the changes of T/sub 1/ and T/sub 2/ was observed. That is to say, there were 2 components of T/sub 2/ in contrast with single T/sub 1/ value in the same sample of the edematous gray matter, which indicates the existence of 2 fractions of tissue water, not exchanging on an NMR time scale. Secondary, a good correlation between the longitudinal (T/sub 1/) relaxation time and the tissue water content was found for the dog brains, which suggests that we can analyse the NMR relaxation data of the dog brains based on the two-fraction fast-exchange model.

Application of nonlinear EPR and NMR responses on spin systems in structure and relaxation structures

Energy Technology Data Exchange (ETDEWEB)

Polyakov, A I; Ryabikin, Yu A; Bitenbaev, M M [Inst. of Physics and Technology, Almaty (Kazakhstan)

2004-07-01

Full text: In this work results of investigation of paramagnetic systems (irradiated polymers and crystals, plastic-deformed metals, systems with strong exchange interaction, etc.) by methods of nonlinear relaxation spectroscopy (NRS) are presented. The NRS theoretical grounds were developed in the earlier works. Later the technique was applied successfully to relaxation studies and when analyzing magnetic resonance complicated overlapping spectra. As in course of polymer system irradiation, basically, several type of paramagnetic defects are formed with close values of the g factors, these materials can be used to exemplify NRS capabilities. In this work we use samples of irradiated PMMA copolymers. Analysis of the PMMA spectra shows that several types of paramagnetic defects strongly differing in the spin-lattice relaxation times are formed in irradiated PMMA-based polymer composites. It is found that degradation of the composite physical and engineering characteristics is caused, mainly, by radiation-induced disintegration of macromolecules, following the chain reaction, which can be revealed by occurring lattice radical states. Another portion of work is devoted to NRS application to deterring influence of structural defects (impurity, dislocation, etc.) on variation in times of nuclear spin-lattice relaxation in metal systems. At this stage we managed, for the first time, to separate the distribution functions for spin-lattice relaxation (T{sub l}) and relaxation of nuclear spin dipole-dipole interaction (T{sub d}). It is shown that one can assess an extent of crystal defect by the dependence of T{sub d}=f(c). Also in this work the NRS methods are applied to analyze EPR spectra of polycrystalline solid systems where exchange interaction is strong. It is shown that these systems, as a rule, contain a complete set of spin assemblies having different relaxation times, and the spin assembly distribution over the relaxation time depends on the defect number and

Application of nonlinear EPR and NMR responses on spin systems in structure and relaxation structures

International Nuclear Information System (INIS)

Polyakov, A.I.; Ryabikin, Yu.A.; Bitenbaev, M.M.

2004-01-01

Full text: In this work results of investigation of paramagnetic systems (irradiated polymers and crystals, plastic-deformed metals, systems with strong exchange interaction, etc.) by methods of nonlinear relaxation spectroscopy (NRS) are presented. The NRS theoretical grounds were developed in the earlier works. Later the technique was applied successfully to relaxation studies and when analyzing magnetic resonance complicated overlapping spectra. As in course of polymer system irradiation, basically, several type of paramagnetic defects are formed with close values of the g factors, these materials can be used to exemplify NRS capabilities. In this work we use samples of irradiated PMMA copolymers. Analysis of the PMMA spectra shows that several types of paramagnetic defects strongly differing in the spin-lattice relaxation times are formed in irradiated PMMA-based polymer composites. It is found that degradation of the composite physical and engineering characteristics is caused, mainly, by radiation-induced disintegration of macromolecules, following the chain reaction, which can be revealed by occurring lattice radical states. Another portion of work is devoted to NRS application to deterring influence of structural defects (impurity, dislocation, etc.) on variation in times of nuclear spin-lattice relaxation in metal systems. At this stage we managed, for the first time, to separate the distribution functions for spin-lattice relaxation (T l ) and relaxation of nuclear spin dipole-dipole interaction (T d ). It is shown that one can assess an extent of crystal defect by the dependence of T d =f(c). Also in this work the NRS methods are applied to analyze EPR spectra of polycrystalline solid systems where exchange interaction is strong. It is shown that these systems, as a rule, contain a complete set of spin assemblies having different relaxation times, and the spin assembly distribution over the relaxation time depends on the defect number and type in solid

sup 5 sup 9 Co NMR spectroscopy and relaxation in the metamagnetic system Y sub 1 sub - sub x Gd sub x Co sub 3

CERN Document Server

Reis, M S; García, F; Takeuchi, A Y; Guimarães, A P

2000-01-01

We studied the nuclear magnetic resonance (NMR) in intermetallic compounds of the series Y sub 1 sub - sub x Gd sub x Co sub 3. We found spectra exhibiting four lines, corresponding to four magnetic sites of these compounds. However, the number of lines and their widths are strongly dependent on the radiofrequency (RF) power level, a fact that may help to explain some of the discrepancies found in the NMR literature on these compounds. From the dependence of the NMR spectra with the RF power we concluded that the site labeled 18h presents the largest local magnetic anisotropy. No significant changes are observed on the value of the hyperfine fields at each site as a function of the Gd concentration x, and that is explained in terms of the statistical distribution of Gd magnetic ions in the lattice. On the contrary, the spin-lattice and spin-spin relaxation rates, 1/T sub 1 and 1/T sub 2 , measured at each line, are remarkably dependent on the concentration. 1/T sub 2 exhibits a prominent peak at x approx 0.25...

Structure determination of helical filaments by solid-state NMR spectroscopy

Science.gov (United States)

Ahmed, Mumdooh; Spehr, Johannes; König, Renate; Lünsdorf, Heinrich; Rand, Ulfert; Lührs, Thorsten; Ritter, Christiane

2016-01-01

The controlled formation of filamentous protein complexes plays a crucial role in many biological systems and represents an emerging paradigm in signal transduction. The mitochondrial antiviral signaling protein (MAVS) is a central signal transduction hub in innate immunity that is activated by a receptor-induced conversion into helical superstructures (filaments) assembled from its globular caspase activation and recruitment domain. Solid-state NMR (ssNMR) spectroscopy has become one of the most powerful techniques for atomic resolution structures of protein fibrils. However, for helical filaments, the determination of the correct symmetry parameters has remained a significant hurdle for any structural technique and could thus far not be precisely derived from ssNMR data. Here, we solved the atomic resolution structure of helical MAVSCARD filaments exclusively from ssNMR data. We present a generally applicable approach that systematically explores the helical symmetry space by efficient modeling of the helical structure restrained by interprotomer ssNMR distance restraints. Together with classical automated NMR structure calculation, this allowed us to faithfully determine the symmetry that defines the entire assembly. To validate our structure, we probed the protomer arrangement by solvent paramagnetic resonance enhancement, analysis of chemical shift differences relative to the solution NMR structure of the monomer, and mutagenesis. We provide detailed information on the atomic contacts that determine filament stability and describe mechanistic details on the formation of signaling-competent MAVS filaments from inactive monomers. PMID:26733681

NMR studies of hydrogen diffusion in hydrogen uranyl phosphate tetrahydrate (HUP)

International Nuclear Information System (INIS)

Metcalfe, K.

1988-01-01

1 H NMR spin-lattice relaxation times, T 1 (Zeeman) and T 1p (rotating frame) and spin-spin relaxation times, T 2 , and 31 P NMR solid-echoes are reported for phase I and II of hydrogen uranyl phosphate tetrahydrate (HUP) at temperatures in the range 200-323 K. The spectral density functions extracted from the measured relaxation times for phases I and II are consistent with a 2D diffusion mechanism for hydrogen motion. 31 P second moments determined from the solid-echoes show that all the hydrogens diffuse rapidly in phase I, and that the hydrogen-bond site nearest to the phosphate oxygen is not occupied in phase II. The mechanism for diffusion in phase II is discussed. 30 refs.; 6 figs.; 2 tabs

Electronic relaxation of deep bulk trap and interface state in ZnO ceramics

International Nuclear Information System (INIS)

Yang Yan; Li Sheng-Tao; Ding Can; Cheng Peng-Fei

2011-01-01

This paper investigates the electronic relaxation of deep bulk trap and interface state in ZnO ceramics based on dielectric spectra measured in a wide range of temperature, frequency and bias, in addition to the steady state response. It discusses the nature of net current flowing over the barrier affected by interface state, and then obtains temperature-dependent barrier height by approximate calculation from steady I—V (current—voltage) characteristics. Additional conductance and capacitance arising from deep bulk trap relaxation are calculated based on the displacement of the cross point between deep bulk trap and Fermi level under small AC signal. From the resonances due to deep bulk trap relaxation on dielectric spectra, the activation energies are obtained as 0.22 eV and 0.35 eV, which are consistent with the electronic levels of the main defect interstitial Zn and vacancy oxygen in the depletion layer. Under moderate bias, another resonance due to interface relaxation is shown on the dielectric spectra. The DC-like conductance is also observed in high temperature region on dielectric spectra, and the activation energy is much smaller than the barrier height in steady state condition, which is attributed to the displacement current coming from the shallow bulk trap relaxation or other factors. (fluids, plasmas and electric discharges)

Escape time, relaxation, and sticky states of a softened Henon-Heiles model: Low-frequency vibrational mode effects and glass relaxation

Science.gov (United States)

Toledo-Marín, J. Quetzalcóatl; Naumis, Gerardo G.

2018-04-01

Here we study the relaxation of a chain consisting of three masses joined by nonlinear springs and periodic conditions when the stiffness is weakened. This system, when expressed in their normal coordinates, yields a softened Henon-Heiles system. By reducing the stiffness of one low-frequency vibrational mode, a faster relaxation is enabled. This is due to a reduction of the energy barrier heights along the softened normal mode as well as for a widening of the opening channels of the energy landscape in configurational space. The relaxation is for the most part exponential, and can be explained by a simple flux equation. Yet, for some initial conditions the relaxation follows as a power law, and in many cases there is a regime change from exponential to power-law decay. We pinpoint the initial conditions for the power-law decay, finding two regions of sticky states. For such states, quasiperiodic orbits are found since almost for all components of the initial momentum orientation, the system is trapped inside two pockets of configurational space. The softened Henon-Heiles model presented here is intended as the simplest model in order to understand the interplay of rigidity, nonlinear interactions and relaxation for nonequilibrium systems such as glass-forming melts or soft matter. Our softened system can be applied to model β relaxation in glasses and suggest that local reorientational jumps can have an exponential and a nonexponential contribution for relaxation, the latter due to asymmetric molecules sticking in cages for certain orientations.

Efficient cellular solid-state NMR of membrane proteins by targeted protein labeling

Energy Technology Data Exchange (ETDEWEB)

Baker, Lindsay A. [University of Oxford, Oxford Particle Imaging Centre, The Wellcome Trust Centre for Human Genetics, Division of Structural Biology, Nuffield Department of Medicine (United Kingdom); Daniëls, Mark; Cruijsen, Elwin A. W. van der; Folkers, Gert E.; Baldus, Marc, E-mail: m.baldus@uu.nl [Utrecht University, NMR Spectroscopy, Department of Chemistry, Faculty of Science, Bijvoet Center for Biomolecular Research (Netherlands)

2015-06-15

Solid-state NMR spectroscopy (ssNMR) has made significant progress towards the study of membrane proteins in their native cellular membranes. However, reduced spectroscopic sensitivity and high background signal levels can complicate these experiments. Here, we describe a method for ssNMR to specifically label a single protein by repressing endogenous protein expression with rifampicin. Our results demonstrate that treatment of E. coli with rifampicin during induction of recombinant membrane protein expression reduces background signals for different expression levels and improves sensitivity in cellular membrane samples. Further, the method reduces the amount of time and resources needed to produce membrane protein samples, enabling new strategies for studying challenging membrane proteins by ssNMR.

Efficient cellular solid-state NMR of membrane proteins by targeted protein labeling

International Nuclear Information System (INIS)

Baker, Lindsay A.; Daniëls, Mark; Cruijsen, Elwin A. W. van der; Folkers, Gert E.; Baldus, Marc

2015-01-01

Solid-state NMR spectroscopy (ssNMR) has made significant progress towards the study of membrane proteins in their native cellular membranes. However, reduced spectroscopic sensitivity and high background signal levels can complicate these experiments. Here, we describe a method for ssNMR to specifically label a single protein by repressing endogenous protein expression with rifampicin. Our results demonstrate that treatment of E. coli with rifampicin during induction of recombinant membrane protein expression reduces background signals for different expression levels and improves sensitivity in cellular membrane samples. Further, the method reduces the amount of time and resources needed to produce membrane protein samples, enabling new strategies for studying challenging membrane proteins by ssNMR

Techniques and approaches to proton NMR imaging of the head

International Nuclear Information System (INIS)

Pykett, I.L.; Buonanno, F.S.; Brady, T.J.; Kistler, J.P.

1983-01-01

The next few years will undoubtedly see a refinement of proton imaging technology and a broader data base will indicate to what extent proton relaxation parameters are able to detect and characterize disease. In addition, it is likely that imaging of other nuclei (e.g. 31 P, 23 Na, 19 F) will become a reality, although it must be stated that due to their inherently lower sensitivity to NMR detection and/or lower physiological concentration, clinical images of nuclei other than 1 H will undoubtedly have a low spatial resolution and may require relatively long imaging times. Nonetheless, herein lies the exciting possibility of non-invasive metabolic or functional imaging. The realm of NMR contrast agents is just beginning to be explored, and developments in high-speed imaging indicate useful applications in cardiology. So whilst improvements in image quality can be expected, as was the case with X-ray CT, the application of NMR in medicine will diversify to yield information of a more specifically functional nature. This, together with the very low attendant biological risk, heralds a bright future for NMR in clinical diagnosis

Evaluation of PHB/Clay nanocomposite by spin-lattice relaxation time

Directory of Open Access Journals (Sweden)

Mariana Bruno

2008-12-01

Full Text Available Poly(3-hydroxybutyrate (PHB based on nanocomposites containing different amounts of a commercial organically modified clay (viscogel B7 were prepared employing solution intercalation method. Three solvents, such as: CHCl3, dimethylchloride (DMC and tetrahydrofuran (THF were used. The relationship among the processing conditions; molecular structure and intermolecular interaction, between both nanocomposite components, were investigated using a nuclear magnetic resonance (NMR, as a part of characterization methodology, which has been used by Tavares et al. It involves the hydrogen spin-lattice relaxation time, T1H, by solid state nuclear magnetic resonance, employing low field NMR. X ray diffraction was also employed because it is a conventional technique, generally used to obtain the first information on nanocomposite formation. Changes in PHB crystallinity were observed after the organophilic nanoclay had been incorporated in the polymer matrix. These changes, in the microstructure, were detected by the variation of hydrogen nuclear relaxation time values and by X ray, which showed an increase in the clay interlamelar space due to the intercalation of the polymer in the clay between lamellae. It was also observed, for both techniques, that the solvents affect directly the organization of the crystalline region, promoting a better intercalation, considering that they behave like a plasticizer.

Antiferromagnetism Induced in the Vortex Core of Tl2Ba2CuO6++δ Probed by Spatially-Resolved 205Tl-NMR

International Nuclear Information System (INIS)

Kumagai, K.; Kakuyanagi, K.; Matsuda, Y.; Hasegawa, T.

2003-01-01

Magnetism in the vortex core state has been studied by spatially-resolved NMR. The nuclear spin lattice relaxation rate T 1 -1 of 205 Tl in nearly optimal-doped Tl 2 Ba 2 CuO 6+ δ (T c =85 K) is significantly enhanced in the vortex core region. The NMR results suggest that the suppression of the d-wave superconducting order parameter in the vortex core leads to the nucleation of islands with local antiferromagnetic (AF) order. (author)

Applications of 1H-NMR relaxometry in experimental liver studies

International Nuclear Information System (INIS)

Holzmueller, P.

1992-01-01

Purpose of this study was to investigate applications of proton nuclear magnetic resonance ( 1 H-NMR) relaxometry in experimental medicine. Relaxometry was performed by measurements of spin-lattice (T 1 ) and spin-spin (T 2 ) relaxation time parameters on liver biopsies up to four hours after biopsy excision. Variations of relaxation times due to species and strain, different sample handling and different liver damage models, ethionine fatty liver and paracetamol liver necrosis, were investigated. Cell integrity effects were studied on homogenized liver samples. Relaxation time parameters, especially 'main' components T 1A and T 2A of biexponential model fit, were identified to react very sensitive after tissue damages as well as to cell viability. Thus, investigation of stored liver grafts was performed in order to evaluate the possibility of a rapid liver graft viability testing method for human liver transplantation surgery by 1 H-NMR relaxometry. Another series of measurements was performed to investigate the applicability of isoflurane anesthesia for in vivo NMR experiments. This study proved the good appropriateness of isoflurane for that purpose provided that physiological monitoring and individual adjustment of anesthesia are performed. In these investigations it could be revealed that mainly T 1A and T 2A are influenced by tissue condition and that different information is inherent in these two parameters, with T 2A reflecting tissue viability and changes of tissue conditions very sensitively but rather unspecifically in respect to the damage applied. Based on these results the following future applications of 1 H-NMR relaxometry are suggested : (1) model investigations, (2) investigation of given pathologies, (3) investigation of basic requirements for in vivo NMR and (4) application in a liver graft viability testing protocol, which seems to be the most important future application of 1 H-NMR relaxometry in medicine. (author)

High-pressure low-field 1H NMR relaxometry in nanoporous materials.

Science.gov (United States)

Horch, Carsten; Schlayer, Stefan; Stallmach, Frank

2014-03-01

A low-field NMR sensor with NdFeB permanent magnets (B0=118 mT) and a pressure cell made of PEEK (4 cm outer diameter) were designed for (1)H relaxation time studies of adsorbed molecules at pressures of up to 300 bar. The system was used to investigate methane uptake of microporous metal-organic frameworks and nanoporous activated carbon. T2 relaxation time distribution of pure methane and of methane under co-adsorption of carbon dioxide show that the host-guest interaction lead to a relaxation time contrasts, which may be used to distinguish between the gas phase and the different adsorbed phases of methane. Adsorption isotherms, exchange of methane between adsorbent particles and the surrounding gas phase, successive displacement of methane from adsorption sites by co-adsorption of carbon dioxide and CO2/CH4 adsorption separation factors were determined from the observed NMR relaxation time distributions. Copyright © 2014 Elsevier Inc. All rights reserved.

Automated solid-state NMR resonance assignment of protein microcrystals and amyloids

Energy Technology Data Exchange (ETDEWEB)

Schmidt, Elena [Goethe University Frankfurt am Main, Center for Biomolecular Magnetic Resonance, Institute of Biophysical Chemistry (Germany); Gath, Julia [ETH Zurich, Physical Chemistry (Switzerland); Habenstein, Birgit [UMR 5086 CNRS/Universite de Lyon 1, Institut de Biologie et Chimie des Proteines (France); Ravotti, Francesco; Szekely, Kathrin; Huber, Matthias [ETH Zurich, Physical Chemistry (Switzerland); Buchner, Lena [Goethe University Frankfurt am Main, Center for Biomolecular Magnetic Resonance, Institute of Biophysical Chemistry (Germany); Boeckmann, Anja, E-mail: a.bockmann@ibcp.fr [UMR 5086 CNRS/Universite de Lyon 1, Institut de Biologie et Chimie des Proteines (France); Meier, Beat H., E-mail: beme@ethz.ch [ETH Zurich, Physical Chemistry (Switzerland); Guentert, Peter, E-mail: guentert@em.uni-frankfurt.de [Goethe University Frankfurt am Main, Center for Biomolecular Magnetic Resonance, Institute of Biophysical Chemistry (Germany)

2013-07-15

Solid-state NMR is an emerging structure determination technique for crystalline and non-crystalline protein assemblies, e.g., amyloids. Resonance assignment constitutes the first and often very time-consuming step to a structure. We present ssFLYA, a generally applicable algorithm for automatic assignment of protein solid-state NMR spectra. Application to microcrystals of ubiquitin and the Ure2 prion C-terminal domain, as well as amyloids of HET-s(218-289) and {alpha}-synuclein yielded 88-97 % correctness for the backbone and side-chain assignments that are classified as self-consistent by the algorithm, and 77-90 % correctness if also assignments classified as tentative by the algorithm are included.

NMR study of CeCoSi3

International Nuclear Information System (INIS)

Iwamoto, Y.

1995-01-01

Low-temperature susceptibility, NMR and NQR of the 59 Co signal in CeCoSi 3 have been measured. CeCoSi 3 showed a superconducting transition at 0.7-1.2K. From NQR measurement, the nuclear quadrupole frequency and the full width at half maximum (FWHM) of 59 Co in CeCoSi 3 were estimated to be about 1.08MHz and 0.08MHz, respectively. The 59 Co nuclear spin-lattice relaxation rate (1/T 1 ) in CeCoSi 3 was proportional to the temperature (T) as the Fermi liquid state above the superconducting transition temperature (T c ), and then rapidly decreased below T c . ((orig.))

Effects of amantadine on the dynamics of membrane-bound influenza A M2 transmembrane peptide studied by NMR relaxation

Energy Technology Data Exchange (ETDEWEB)

Cady, Sarah D.; Hong Mei [Iowa State University, Department of Chemistry (United States)], E-mail: mhong@iastate.edu

2009-09-15

The molecular motions of membrane proteins in liquid-crystalline lipid bilayers lie at the interface between motions in isotropic liquids and in solids. Specifically, membrane proteins can undergo whole-body uniaxial diffusion on the microsecond time scale. In this work, we investigate the {sup 1}H rotating-frame spin-lattice relaxation (T{sub 1{rho}}) caused by the uniaxial diffusion of the influenza A M2 transmembrane peptide (M2TMP), which forms a tetrameric proton channel in lipid bilayers. This uniaxial diffusion was proved before by {sup 2}H, {sup 15}N and {sup 13}C NMR lineshapes of M2TMP in DLPC bilayers. When bound to an inhibitor, amantadine, the protein exhibits significantly narrower linewidths at physiological temperature. We now investigate the origin of this line narrowing through temperature-dependent {sup 1}H T{sub 1{rho}} relaxation times in the absence and presence of amantadine. Analysis of the temperature dependence indicates that amantadine decreases the correlation time of motion from 2.8 {+-} 0.9 {mu}s for the apo peptide to 0.89 {+-} 0.41 {mu}s for the bound peptide at 313 K. Thus the line narrowing of the bound peptide is due to better avoidance of the NMR time scale and suppression of intermediate time scale broadening. The faster diffusion of the bound peptide is due to the higher attempt rate of motion, suggesting that amantadine creates better-packed and more cohesive helical bundles. Analysis of the temperature dependence of ln (T{sub 1{rho}}{sup -1}) indicates that the activation energy of motion increased from 14.0 {+-} 4.0 kJ/mol for the apo peptide to 23.3 {+-} 6.2 kJ/mol for the bound peptide. This higher activation energy indicates that excess amantadine outside the protein channel in the lipid bilayer increases the membrane viscosity. Thus, the protein-bound amantadine speeds up the diffusion of the helical bundles while the excess amantadine in the bilayer increases the membrane viscosity.

The characterisation of polymers using pulsed NMR

International Nuclear Information System (INIS)

Charlesby, A.

1983-01-01

Broad line pulsed NMR is applied to obtain information on radiation-induced polymer changes and other aspects of polymer science based on the interpretation of spin-spin relaxation curves. Calculations are made to determine the molecular weight, the crosslink density of simple, low molecular weight, flexible polymers. For higher molecular weight polymers, a conclusion can be drawn on the concentrations of entangled and crosslinked units by means of pulsed NMR. Some typical applications of the technique are illustrated by the examples of polyethylenes, rubbers, filled polymeric systems and aqueous polyethylene oxide solutions. The morphology of polymers can be followed by pulsed NMR. (V.N.)

Quantum process tomography with informational incomplete data of two J-coupled heterogeneous spins relaxation in a time window much greater than T1

Science.gov (United States)

Maciel, Thiago O.; Vianna, Reinaldo O.; Sarthour, Roberto S.; Oliveira, Ivan S.

2015-11-01

We reconstruct the time dependent quantum map corresponding to the relaxation process of a two-spin system in liquid-state NMR at room temperature. By means of quantum tomography techniques that handle informational incomplete data, we show how to properly post-process and normalize the measurements data for the simulation of quantum information processing, overcoming the unknown number of molecules prepared in a non-equilibrium magnetization state (Nj) by an initial sequence of radiofrequency pulses. From the reconstructed quantum map, we infer both longitudinal (T1) and transversal (T2) relaxation times, and introduce the J-coupling relaxation times ({T}1J,{T}2J), which are relevant for quantum information processing simulations. We show that the map associated to the relaxation process cannot be assumed approximated unital and trace-preserving for times greater than {T}2J.

Solid-State NMR Spectroscopy for the Physical Chemistry Laboratory

Science.gov (United States)

Kinnun, Jacob J.; Leftin, Avigdor; Brown, Michael F.

2013-01-01

Solid-state nuclear magnetic resonance (NMR) spectroscopy finds growing application to inorganic and organic materials, biological samples, polymers, proteins, and cellular membranes. However, this technique is often neither included in laboratory curricula nor typically covered in undergraduate courses. On the other hand, spectroscopy and…

NMR and molecular dynamics of small solutes in liquid crystals

International Nuclear Information System (INIS)

Luyten, P.R.

1984-01-01

NMR relaxation measurements, using a wide variety of modern pulse techniques, can yield valuable information about molecular motions. In this thesis the applicability of theories developed to describe spin relaxation phenomena in partially ordered media is studied for small solutes in liquid crystals. 1 H, 2 H, 13 C and 14 N relaxation measurements are interpreted by means of a model, in which fast anisotropic re-orientational motion in an orienting potential combined with contributions from cooperative fluctuations in the surrounding liquid crystal molecules, induce the observed frequency dependent relaxation behavior. (orig.)

Hyperpolarized 129Xe as an NMR probe for functional studies

International Nuclear Information System (INIS)

Wolber, J.

2000-01-01

The nuclear spin polarization of 129 Xe can be enhanced by several orders of magnitude using optical pumping techniques, resulting in a dramatic enhancement of the 129 Xe Nuclear Magnetic Resonance (NMR) signal. The 'hyperpolarized' gas can be used for Magnetic Resonance Imaging (MRI) of the void spaces of the lungs after introduction of the gas into the respiratory system. Furthermore, the high solubility of xenon in blood and lipids suggests the use of 129 Xe NMR for studying blood flow, permeability, perfusion and blood volume. Hyperpolarized 129 Xe MRI has the potential of combining the high sensitivity and functional information of radioactive tracer studies with the high spatial and temporal resolution of MRI. The spin-lattice relaxation time T 1 of 129 Xe in blood determines the loss of polarization during transit from the lungs to the tissue of interest. A difference in the relaxation times of xenon in oxygenated and deoxygenated blood could be used as a contrast mechanism in functional Magnetic Resonance Imaging (fMRI). In this thesis, the hyperpolarized 129 Xe T 1 in human blood is measured in vitro as a function of blood oxygenation, and the relevant relaxation mechanisms are discussed. A new and unexpected finding is that the hyperpolarized 129 Xe NMR spectrum in blood is highly sensitive to blood oxygenation. Therefore, hyperpolarized 129 Xe NMR provides a powerful means of measuring blood oxygenation quantitatively and non-invasively. The interaction of xenon with hemoglobin is responsible for an oxygen-dependent shift of the 129 Xe NMR resonance of xenon in red blood cells. Injection delivery of hyperpolarized 129 Xe in solution could be a more efficient method of administrating the gas for functional NMR studies. For this purpose, suitable biocompatible carrier media have been studied. In particular, the use of perfluorocarbon emulsions, which are already in use as blood substitutes, as delivery media for hyperpolarized 129 Xe has been investigates

NMR mechanisms in gel dosimetry

International Nuclear Information System (INIS)

Schreiner, L J

2009-01-01

Nuclear magnetic resonance was critical to the development of gel dosimetry, as it established the potential for three dimensional dosimetry with chemical dosimeter systems through magnetic resonance imaging [1]. In the last two decades MRI has served as the gold standard for imaging, while NMR relaxometry has played an important role in the development and understanding of the behaviour of new gel dosimetry systems. Therefore, an appreciation of the relaxation mechanisms determining the NMR behaviour of irradiated gel dosimeters is important for a full comprehension of a considerable component of the literature on gel dosimetry. A number of excellent papers have presented this important theory, this brief review will highlight some of the salient points made previously [1-5]. The spin relaxation of gel dosimeters (which determines the dose dependence in most conventional MR imaging) is determined principally by the protons on water molecules in the system. These water protons exist in different environments, or groups (see Figure 1): on bulk water, on water hydrating the chemical species that are being modified under irradiation, and on water hydrating the gel matrix used to spatially stabilize the dosimeter (e.g., gelatin, agarose, etc). The spin relaxation depends on the inherent relaxation rate of each spin group, that is, on the relaxation rate which would be observed for the specific group if it were isolated. Also, the different water environments are not isolated from each other, and the observed relaxation rate also depends on the rate of exchange of magnetization between the groups, and on the fraction of protons in each group. In fact, the water exchanges quickly between the environments, so that relaxation is in what is usually termed the fast exchange regime. In the limit of fast exchange, the relaxation of the water protons is well characterized by a single exponential and hence by a single apparent relaxation rate. In irradiated gel dosimeters this

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...

The bonded in the chestnut-tree (Aesculus hippocastanum L.) bark water freezing process studied by means NMR method

International Nuclear Information System (INIS)

Haranczyk, H.; Weglarz, W.

1994-01-01

The bonded in the chestnut-tree (Aesculus hippocastanum L.) bark water freezing process was studied by means NMR method. The measured relaxation time (as a function of temperature) shows two compounds. First from solid state water (T 2 * 20 μs) and the second one from liquid water (T 2 * = 1 ms). This results are presented and discussed

Non-Bloch decay of Rabi oscillations in liquid state NMR

Science.gov (United States)

Chakrabarti, Arnab; Bhattacharyya, Rangeet

2018-03-01

Rabi oscillations are known to exhibit non-Bloch behaviour in anisotropic media. In this letter, we report an experimental observation of non-Bloch decay of Rabi oscillations in isotropic liquid state NMR. To avoid the dephasing due to the radio-frequency inhomogeneities, we develop a modified version of the rotary echo protocol and use it to determine the decay rates of Rabi oscillations. We find that the measured decay rates are proportional to the square of the Rabi frequencies and the proportionality constant is of the order of tens of picoseconds. Further, we show that this non-Bloch nature of the decay rates becomes less prominent with increasing temperature. The implications of the presence of non-Bloch decay rates in liquid state NMR in the context of ensemble quantum computing are also discussed.

Determination of oil in seeds by a wide line NMR instrument

International Nuclear Information System (INIS)

Marton, Aurel

1983-01-01

The oil content of sunflower, rape and soybean seeds was determined by a wide line NMR instrument. Using various model systems the following conclusions were drawn: the sensitivity of the instrument is much higher for the oil content of the seeds than for their water content. This observation can be interpreted in terms of the longer relaxation time of the water protons. The quantitative determination of the oil content of the seeds can be done with a high accuracy provided that the calibration curve for the respective oil is available and the signal of the solid state components of the seeds is corrected. If the water content of the seeds is reduced below 5 per cent, the oil content values obtained by NMR and extraction techniques are in agreement within the experimental error. (author)

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

Observation of a Relaxed Plasma State in a Quasi-Infinite Cylinder

Science.gov (United States)

Gray, T.; Brown, M. R.; Dandurand, D.

2013-02-01

A helical relaxed plasma state is observed in a long cylindrical volume. The cylinder is long enough so that the predicted minimum energy state is a close approximation to the infinite cylinder solution. The plasma is injected at v≥50km/s by a coaxial magnetized plasma gun located at one end of the cylindrical volume. The relaxed state is rapidly attained in 1-2 axial Alfvén times after initiation of the plasma. Magnetic data are favorably compared with an analytical model. Magnetic data exhibit broadband fluctuations of the measured axial modes during the formation period. The broadband activity rapidly decays as the energy condenses into the lowest energy mode, which is in agreement with the minimum energy eigenstate of ∇×B=λB.

Nuclear magnetic moment of 69As from on-line β-NMR on oriented nuclei

International Nuclear Information System (INIS)

Golovko, V.V.; Kraev, I.S.; Phalet, T.; Severijns, N.; Delaure, B.; Beck, M.; Kozlov, V.Yu.; Lindroth, A.; Coeck, S.; Zakoucky, D.; Venos, D.; Srnka, D.; Honusek, M.; Herzog, P.; Tramm, C.; Koester, U.

2005-01-01

A precise value for the magnetic moment of the 69 As 5/2 - ground state has been obtained from nuclear magnetic resonance on oriented nuclei (NMR/ON) using the NICOLE 3 He- 4 He dilution refrigerator setup at ISOLDE/CERN. The NMR/ON signal was observed by monitoring the anisotropy of the 69 As β particles. The center frequency ν[B ext =0.0994(10)T]=169.98(9) MHz corresponds to μ[ 69 As]=+1.6229(16)μ N . This result differs considerably from the πf 5/2 single-particle value obtained with g factors for a free proton but is in reasonable agreement with the value obtained with effective g factors and with values from a core polarization calculation and from calculations in the framework of the interacting boson-fermion model. Assuming a single exponential spin-lattice relaxation behavior a relaxation time T 1 ' =10(25) s was observed for 69 AsFe -bar at a temperature of about 20 mK in a magnetic field B=0.1 T

Three-way modelling of NMR relaxation profiles from thawed cod muscle

DEFF Research Database (Denmark)

Jensen, Kristina Nedenskov; Guldager, Helle Skov; Jørgensen, Bo Munk

2002-01-01

Low-field 1H nuclear magnetic resonance transverse relaxation was used to measure water mobility and distribution in cod stored at -20°C or -30°C for up to 12 months and subsequently from 0 to 21 days in modified atmosphere at +2°C. The relaxation profiles were decomposed by parallel factor analy...

Modification and intercalation of layered zirconium phosphates: a solid-state NMR monitoring.

Science.gov (United States)

Bakhmutov, Vladimir I; Kan, Yuwei; Sheikh, Javeed Ahmad; González-Villegas, Julissa; Colón, Jorge L; Clearfield, Abraham

2017-07-01

Several layered zirconium phosphates treated with Zr(IV) ions, modified by monomethoxy-polyethyleneglycol-monophosphate and intercalated with doxorubicin hydrochloride have been studied by solid-state MAS NMR techniques. The organic components of the phosphates have been characterized by the 13 C{ 1 H} CP MAS NMR spectra compared with those of initial compounds. The multinuclear NMR monitoring has provided to establish structure and covalent attachment of organic/inorganic moieties to the surface and interlayer spaces of the phosphates. The MAS NMR experiments including kinetics of proton-phosphorus cross polarization have resulted in an unusual structure of zirconium phosphate 6 combining decoration of the phosphate surface by polymer units and their partial intercalation into the interlayer space. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Automated solid-state NMR resonance assignment of protein microcrystals and amyloids

International Nuclear Information System (INIS)

Schmidt, Elena; Gath, Julia; Habenstein, Birgit; Ravotti, Francesco; Székely, Kathrin; Huber, Matthias; Buchner, Lena; Böckmann, Anja; Meier, Beat H.; Güntert, Peter

2013-01-01

Solid-state NMR is an emerging structure determination technique for crystalline and non-crystalline protein assemblies, e.g., amyloids. Resonance assignment constitutes the first and often very time-consuming step to a structure. We present ssFLYA, a generally applicable algorithm for automatic assignment of protein solid-state NMR spectra. Application to microcrystals of ubiquitin and the Ure2 prion C-terminal domain, as well as amyloids of HET-s(218–289) and α-synuclein yielded 88–97 % correctness for the backbone and side-chain assignments that are classified as self-consistent by the algorithm, and 77–90 % correctness if also assignments classified as tentative by the algorithm are included

Hydrodynamic Relaxation of an Electron Plasma to a Near-Maximum Entropy State

International Nuclear Information System (INIS)

Rodgers, D. J.; Servidio, S.; Matthaeus, W. H.; Mitchell, T. B.; Aziz, T.; Montgomery, D. C.

2009-01-01

Dynamical relaxation of a pure electron plasma in a Malmberg-Penning trap is studied, comparing experiments, numerical simulations and statistical theories of weakly dissipative two-dimensional (2D) turbulence. Simulations confirm that the dynamics are approximated well by a 2D hydrodynamic model. Statistical analysis favors a theoretical picture of relaxation to a near-maximum entropy state with constrained energy, circulation, and angular momentum. This provides evidence that 2D electron fluid relaxation in a turbulent regime is governed by principles of maximum entropy.

Cotton fibers encapsulated with homo- and block copolymers: synthesis by the atom transfer radical polymerization grafting-from technique and solid-state NMR dynamic investigations.

Science.gov (United States)

Castelvetro, Valter; Geppi, Marco; Giaiacopi, Simone; Mollica, Giulia

2007-02-01

Cotton fibers were modified by surface-initiated atom transfer radical polymerization of ethyl acrylate (EA) followed by copolymerization with styrene. Either ethyl 2-bromopropionate as a sacrificial free initiator or Cu(II) as a deactivator was used to optimize the EA grafting yield and to preserve the livingness of the chain ends for the subsequent growth of a poly(styrene) (PSty) block from the poly(ethyl acrylate) (PEA) grafts. The polymer-encapsulated cotton fibers were analyzed by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry (DSC), thermogravimetric analysis, and solid-state NMR (high-resolution 13C cross-polarization magic angle spinning, 1H spin-lattice relaxation times, and 1H free induction decay analysis NMR). The latter allowed the detection of the dynamic modifications associated with the presence of homo- and block copolymer grafts. In particular, the results of the DSC and NMR investigations suggest a heterogeneous morphology of the g-PEA-b-PSty grafted skin, which could be described as an inner layer of g-PEA sandwiched between the semicrystalline cellulose of the core fiber and the high glass transition temperature PSty of the covalently linked outer layer. Such morphology results in a reduced molecular mobility of the PEA chains.

Molecular Dynamics and Morphology of High Performance Elastomers and Fibers by Solid State NMR

Science.gov (United States)

2016-06-30

nuclear magnetic resonance (ssNMR) spectroscopy to investigate the chemical structure and physical state of the residual phosphorous in PBO fiber...ssNMR) spectroscopy to investigate the chemical structure and physical state of the residual phosphorous in PBO fiber, which has been long suspected to...Jason Cain, Jian H. Yu, David Veysset, Keith A. Nelson . Probing the Influence of Molecular Dynamics of Matrix Elastomers on Ballistic Impact Back-face

Recent Advances in Characterization of Lignin Polymer by Solution-State Nuclear Magnetic Resonance (NMR Methodology

Directory of Open Access Journals (Sweden)

Run-Cang Sun

2013-01-01

Full Text Available The demand for efficient utilization of biomass induces a detailed analysis of the fundamental chemical structures of biomass, especially the complex structures of lignin polymers, which have long been recognized for their negative impact on biorefinery. Traditionally, it has been attempted to reveal the complicated and heterogeneous structure of lignin by a series of chemical analyses, such as thioacidolysis (TA, nitrobenzene oxidation (NBO, and derivatization followed by reductive cleavage (DFRC. Recent advances in nuclear magnetic resonance (NMR technology undoubtedly have made solution-state NMR become the most widely used technique in structural characterization of lignin due to its versatility in illustrating structural features and structural transformations of lignin polymers. As one of the most promising diagnostic tools, NMR provides unambiguous evidence for specific structures as well as quantitative structural information. The recent advances in two-dimensional solution-state NMR techniques for structural analysis of lignin in isolated and whole cell wall states (in situ, as well as their applications are reviewed.

Permeability in Rotliegend gas sandstones to gas and brine as predicted from NMR, mercury injection and image analysis

DEFF Research Database (Denmark)

Rosenbrand, Esther; Fabricius, Ida Lykke; Fisher, Quentin

2015-01-01

Permeability characterisation of low permeability, clay-rich gas sandstones is part of production forecasting and reservoir management. The physically based Kozeny (1927) equation linking permeability with porosity and pore size is derived for a porous medium with a homogeneous pore size, whereas...... the pore sizes in tight sandstones can range from nm to μm. Nuclear magnetic resonance (NMR) transverse relaxation was used to estimate a pore size distribution for 63 samples of Rotliegend sandstone. The surface relaxation parameter required to relate NMR to pore size is estimated by combination of NMR...

Optimized slice-selective 1H NMR experiments combined with highly accurate quantitative 13C NMR using an internal reference method

Science.gov (United States)

Jézéquel, Tangi; Silvestre, Virginie; Dinis, Katy; Giraudeau, Patrick; Akoka, Serge

2018-04-01

Isotope ratio monitoring by 13C NMR spectrometry (irm-13C NMR) provides the complete 13C intramolecular position-specific composition at natural abundance. It represents a powerful tool to track the (bio)chemical pathway which has led to the synthesis of targeted molecules, since it allows Position-specific Isotope Analysis (PSIA). Due to the very small composition range (which represents the range of variation of the isotopic composition of a given nuclei) of 13C natural abundance values (50‰), irm-13C NMR requires a 1‰ accuracy and thus highly quantitative analysis by 13C NMR. Until now, the conventional strategy to determine the position-specific abundance xi relies on the combination of irm-MS (isotopic ratio monitoring Mass Spectrometry) and 13C quantitative NMR. However this approach presents a serious drawback since it relies on two different techniques and requires to measure separately the signal of all the carbons of the analyzed compound, which is not always possible. To circumvent this constraint, we recently proposed a new methodology to perform 13C isotopic analysis using an internal reference method and relying on NMR only. The method combines a highly quantitative 1H NMR pulse sequence (named DWET) with a 13C isotopic NMR measurement. However, the recently published DWET sequence is unsuited for samples with short T1, which forms a serious limitation for irm-13C NMR experiments where a relaxing agent is added. In this context, we suggest two variants of the DWET called Multi-WET and Profiled-WET, developed and optimized to reach the same accuracy of 1‰ with a better immunity towards T1 variations. Their performance is evaluated on the determination of the 13C isotopic profile of vanillin. Both pulse sequences show a 1‰ accuracy with an increased robustness to pulse miscalibrations compared to the initial DWET method. This constitutes a major advance in the context of irm-13C NMR since it is now possible to perform isotopic analysis with high

Characterizing Slow Chemical Exchange in Nucleic Acids by Carbon CEST and Low Spin-Lock Field R1ρ NMR Spectroscopy

Science.gov (United States)

Zhao, Bo; Hansen, Alexandar L.; Zhang, Qi

2016-01-01

Quantitative characterization of dynamic exchange between various conformational states provides essential insights into the molecular basis of many regulatory RNA functions. Here, we present an application of nucleic-acid-optimized carbon chemical exchange saturation transfer (CEST) and low spin-lock field R1ρ relaxation dispersion (RD) NMR experiments in characterizing slow chemical exchange in nucleic acids that is otherwise difficult if not impossible to be quantified by the ZZ-exchange NMR experiment. We demonstrated the application on a 47-nucleotide fluoride riboswitch in the ligand-free state, for which CEST and R1ρ RD profiles of base and sugar carbons revealed slow exchange dynamics involving a sparsely populated (p ~ 10%) and shortly lived (τ ~ 10 ms) NMR “invisible” state. The utility of CEST and low spin-lock field R1ρ RD experiments in studying slow exchange was further validated in characterizing an exchange as slow as ~60 s−1. PMID:24299272

Characterizing slow chemical exchange in nucleic acids by carbon CEST and low spin-lock field R(1ρ) NMR spectroscopy.

Science.gov (United States)

Zhao, Bo; Hansen, Alexandar L; Zhang, Qi

2014-01-08

Quantitative characterization of dynamic exchange between various conformational states provides essential insights into the molecular basis of many regulatory RNA functions. Here, we present an application of nucleic-acid-optimized carbon chemical exchange saturation transfer (CEST) and low spin-lock field R(1ρ) relaxation dispersion (RD) NMR experiments in characterizing slow chemical exchange in nucleic acids that is otherwise difficult if not impossible to be quantified by the ZZ-exchange NMR experiment. We demonstrated the application on a 47-nucleotide fluoride riboswitch in the ligand-free state, for which CEST and R(1ρ) RD profiles of base and sugar carbons revealed slow exchange dynamics involving a sparsely populated (p ~ 10%) and shortly lived (τ ~ 10 ms) NMR "invisible" state. The utility of CEST and low spin-lock field R(1ρ) RD experiments in studying slow exchange was further validated in characterizing an exchange as slow as ~60 s(-1).

Mapping of unfolding states of integral helical membrane proteins by GPS-NMR and scattering techniques

DEFF Research Database (Denmark)

Calcutta, Antonello; Jessen, Christian M; Behrens, Manja Annette

2012-01-01

induced by unfolding of an integral membrane protein, namely TFE-induced unfolding of KcsA solubilized by the n-dodecyl ß-d-maltoside (DDM) surfactant is investigated by the recently introduced GPS-NMR (Global Protein folding State mapping by multivariate NMR) (Malmendal et al., PlosONE 5, e10262 (2010......)) along with dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS). GPS-NMR is used as a tool for fast analysis of the protein unfolding processes upon external perturbation, and DLS and SAXS are used for further structural characterization of the unfolding states. The combination allows...

Observation of a relaxed plasma state in a quasi-infinite cylinder.

Science.gov (United States)

Gray, T; Brown, M R; Dandurand, D

2013-02-22

A helical relaxed plasma state is observed in a long cylindrical volume. The cylinder is long enough so that the predicted minimum energy state is a close approximation to the infinite cylinder solution. The plasma is injected at v ≥ 50 km/s by a coaxial magnetized plasma gun located at one end of the cylindrical volume. The relaxed state is rapidly attained in 1-2 axial Alfvén times after initiation of the plasma. Magnetic data are favorably compared with an analytical model. Magnetic data exhibit broadband fluctuations of the measured axial modes during the formation period. The broadband activity rapidly decays as the energy condenses into the lowest energy mode, which is in agreement with the minimum energy eigenstate of [Symbol: see text] × B = λB.

Diffusion effects on volume-selective NMR at small length scales; Diffusionseffekte in volumenselektiver NMR auf kleinen Laengenskalen

Energy Technology Data Exchange (ETDEWEB)

Gaedke, Achim

2009-01-21

In this thesis, the interplay between diffusion and relaxation effects in spatially selective NMR experiments at short length scales is explored. This is especially relevant in the context of both conventional and mechanically detected MRI at (sub)micron resolution in biological specimens. Recent results on selectively excited very thin slices showed an in-slice-magnetization recovery orders of magnitude faster than the longitudinal relaxation time T1. However, those experiments were run on fully relaxed samples while MRI and especially mechanically detected NMR experiments are typically run in a periodic fashion with repetition times far below T1. The main purpose of this work therefore was to extend the study of the interplay between diffusion and longitudinal relaxation to periodic excitations. In some way, this is inverse phenomenon to the DESIRE (Diffusive Enhancement of SIgnal and REsolution) approach, proposed 1992 by Lauterbur. Experiments on periodically excited thin slices were carried out at a dedicated static field gradient cryomagnet with magnetic field gradients up to 180 T/m. In order to obtain plane slices, an appropriate isosurface of the gradient magnet had to be identified. It was found at a field of 3.8 T with a gradient of 73 T/m. In this field, slices down to a thickness of 3.2 {mu}m could be excited. The detection of the NMR signal was done using FIDs instead of echoes as the excitation bandwidth of those thin slices is sufficiently small to observe FIDs which are usually considered to be elusive to detection in such strong static field gradients. A simulation toolbox based on the full Bloch-Torrey-equation was developed to describe the excitation and the formation of NMR signals under those unusual conditions as well as the interplay of diffusion and magnetization recovery. Both the experiments and the simulations indicate that diffusion effects lead to a strongly enhanced magnetization modulation signal also under periodic excitation

A Solid-State NMR Experiment: Analysis of Local Structural Environments in Phosphate Glasses

Science.gov (United States)

Anderson, Stanley E.; Saiki, David; Eckert, Hellmut; Meise-Gresch, Karin

2004-01-01

An experiment that can be used to directly study the local chemical environments of phosphorus in solid amorphous materials is demonstrated. The experiment aims at familiarizing the students of chemistry with the principles of solid-state NMR, by having them synthesize a simple phosphate glass, and making them observe the (super 31)P NMR spectrum,…

NMR imaging of the cardiovascular system

International Nuclear Information System (INIS)

Canby, R.C.; Evanochko, W.T.; Pohost, G.M.

1986-01-01

Proton nuclear magnetic resonance (NMR) imaging permits high-resolution tomographic and three-dimensional images of the human body to be obtained without exposure to ionizing radiation. Such imaging not only yields anatomic resolution comparable to X-ray examinations but also provides a potential means to discriminate between healthy tissue and diseased tissue. This potential is based on certain NMR properties known as relaxation times, which determine, in part, the signal intensity in an image. These properties are related to such factors as the sizes and concentrations of proteins and mobile lipids and the compartmentalization of the protons of water. Although NMR imaging (also called magnetic resonance imaging, MRI) is becoming widely available for clinical use, application to the cardiovascular system, though promising, remains primarily a research tool. Gated proton NMR imaging can generate cardiac images with excellent morphologic detail and contrast; however, its ultimate importance as a cardiovascular diagnostic modality will depend on the development of several unique applications. These applications are discussed in this paper

NMR 1D-imaging of water infiltration into meso-porous matrices

International Nuclear Information System (INIS)

Le Feunteun, St.; Diat, O.; Podor, R.; Le Feunteun, St.; Poulesquen, A.; Poulesquen, A.

2011-01-01

It is shown that coupling nuclear magnetic resonance (NMR) 1D-imaging with the measure of NMR relaxation times and self-diffusion coefficients can be a very powerful approach to investigate fluid infiltration into porous media. Such an experimental design was used to study the very slow seeping of pure water into hydrophobic materials. We consider here three model samples of nuclear waste conditioning matrices which consist in a dispersion of NaNO 3 (highly soluble) and/or BaSO 4 (poorly soluble) salt grains embedded in a bitumen matrix. Beyond studying the moisture progression according to the sample depth, we analyze the water NMR relaxation times and self-diffusion coefficients along its 1D-concentration profile to obtain spatially resolved information on the solution properties and on the porous structure at different scales. It is also shown that, when the relaxation or self-diffusion properties are multimodal, the 1D-profile of each water population is recovered. Three main levels of information were disclosed along the depth-profiles. They concern (i) the water uptake kinetics, (ii) the salinity and the molecular dynamics of the infiltrated solutions and (iii) the microstructure of the water-filled porosities: open networks coexisting with closed pores. All these findings were fully validated and enriched by NMR cryo-poro-metry experiments and by performing environmental scanning electronic microscopy observations. Surprisingly, results clearly show that insoluble salts enhance the water progression and thereby increase the capability of the material to uptake water. (authors)

NMR 1D-imaging of water infiltration into mesoporous matrices.

Science.gov (United States)

Le Feunteun, Steven; Diat, Olivier; Guillermo, Armel; Poulesquen, Arnaud; Podor, Renaud

2011-04-01

It is shown that coupling nuclear magnetic resonance (NMR) 1D-imaging with the measure of NMR relaxation times and self-diffusion coefficients can be a very powerful approach to investigate fluid infiltration into porous media. Such an experimental design was used to study the very slow seeping of pure water into hydrophobic materials. We consider here three model samples of nuclear waste conditioning matrices which consist in a dispersion of NaNO(3) (highly soluble) and/or BaSO(4) (poorly soluble) salt grains embedded in a bitumen matrix. Beyond studying the moisture progression according to the sample depth, we analyze the water NMR relaxation times and self-diffusion coefficients along its 1D-concentration profile to obtain spatially resolved information on the solution properties and on the porous structure at different scales. It is also shown that, when the relaxation or self-diffusion properties are multimodal, the 1D-profile of each water population is recovered. Three main levels of information were disclosed along the depth-profiles. They concern (i) the water uptake kinetics, (ii) the salinity and the molecular dynamics of the infiltrated solutions and (iii) the microstructure of the water-filled porosities: open networks coexisting with closed pores. All these findings were fully validated and enriched by NMR cryoporometry experiments and by performing environmental scanning electronic microscopy observations. Surprisingly, results clearly show that insoluble salts enhance the water progression and thereby increase the capability of the material to uptake water. Copyright © 2011 Elsevier Inc. All rights reserved.

NMR relaxation induced by iron oxide particles: testing theoretical models.

Science.gov (United States)

Gossuin, Y; Orlando, T; Basini, M; Henrard, D; Lascialfari, A; Mattea, C; Stapf, S; Vuong, Q L

2016-04-15

Superparamagnetic iron oxide particles find their main application as contrast agents for cellular and molecular magnetic resonance imaging. The contrast they bring is due to the shortening of the transverse relaxation time T 2 of water protons. In order to understand their influence on proton relaxation, different theoretical relaxation models have been developed, each of them presenting a certain validity domain, which depends on the particle characteristics and proton dynamics. The validation of these models is crucial since they allow for predicting the ideal particle characteristics for obtaining the best contrast but also because the fitting of T 1 experimental data by the theory constitutes an interesting tool for the characterization of the nanoparticles. In this work, T 2 of suspensions of iron oxide particles in different solvents and at different temperatures, corresponding to different proton diffusion properties, were measured and were compared to the three main theoretical models (the motional averaging regime, the static dephasing regime, and the partial refocusing model) with good qualitative agreement. However, a real quantitative agreement was not observed, probably because of the complexity of these nanoparticulate systems. The Roch theory, developed in the motional averaging regime (MAR), was also successfully used to fit T 1 nuclear magnetic relaxation dispersion (NMRD) profiles, even outside the MAR validity range, and provided a good estimate of the particle size. On the other hand, the simultaneous fitting of T 1 and T 2 NMRD profiles by the theory was impossible, and this occurrence constitutes a clear limitation of the Roch model. Finally, the theory was shown to satisfactorily fit the deuterium T 1 NMRD profile of superparamagnetic particle suspensions in heavy water.

SIMPSON: A general simulation program for solid-state NMR spectroscopy

Science.gov (United States)

Bak, Mads; Rasmussen, Jimmy T.; Nielsen, Niels Chr.

2011-12-01

A computer program for fast and accurate numerical simulation of solid-state NMR experiments is described. The program is designed to emulate a NMR spectrometer by letting the user specify high-level NMR concepts such as spin systems, nuclear spin interactions, RF irradiation, free precession, phase cycling, coherence-order filtering, and implicit/explicit acquisition. These elements are implemented using the Tel scripting language to ensure a minimum of programming overhead and direct interpretation without the need for compilation, while maintaining the flexibility of a full-featured programming language. Basicly, there are no intrinsic limitations to the number of spins, types of interactions, sample conditions (static or spinning, powders, uniaxially oriented molecules, single crystals, or solutions), and the complexity or number of spectral dimensions for the pulse sequence. The applicability ranges from simple ID experiments to advanced multiple-pulse and multiple-dimensional experiments, series of simulations, parameter scans, complex data manipulation/visualization, and iterative fitting of simulated to experimental spectra. A major effort has been devoted to optimizing the computation speed using state-of-the-art algorithms for the time-consuming parts of the calculations implemented in the core of the program using the C programming language. Modification and maintenance of the program are facilitated by releasing the program as open source software (General Public License) currently at http://nmr.imsb.au.dk. The general features of the program are demonstrated by numerical simulations of various aspects for REDOR, rotational resonance, DRAMA, DRAWS, HORROR, C7, TEDOR, POST-C7, CW decoupling, TPPM, F-SLG, SLF, SEMA-CP, PISEMA, RFDR, QCPMG-MAS, and MQ-MAS experiments.

Gravity-driven pH adjustment for site-specific protein pKa measurement by solution-state NMR

Science.gov (United States)

Li, Wei

2017-12-01

To automate pH adjustment in site-specific protein pKa measurement by solution-state NMR, I present a funnel with two caps for the standard 5 mm NMR tube. The novelty of this simple-to-build and inexpensive apparatus is that it allows automatic gravity-driven pH adjustment within the magnet, and consequently results in a fully automated NMR-monitored pH titration without any hardware modification on the NMR spectrometer.

Isotope labeling strategies for NMR studies of RNA

International Nuclear Information System (INIS)

Lu, Kun; Miyazaki, Yasuyuki; Summers, Michael F.

2010-01-01

The known biological functions of RNA have expanded in recent years and now include gene regulation, maintenance of sub-cellular structure, and catalysis, in addition to propagation of genetic information. As for proteins, RNA function is tightly correlated with structure. Unlike proteins, structural information for larger, biologically functional RNAs is relatively limited. NMR signal degeneracy, relaxation problems, and a paucity of long-range 1 H- 1 H dipolar contacts have limited the utility of traditional NMR approaches. Selective isotope labeling, including nucleotide-specific and segmental labeling strategies, may provide the best opportunities for obtaining structural information by NMR. Here we review methods that have been developed for preparing and purifying isotopically labeled RNAs, as well as NMR strategies that have been employed for signal assignment and structure determination.

Characterization of nonderivatized plant cell walls using high-resolution solution-state NMR spectroscopy

Science.gov (United States)

Daniel J. Yelle; John Ralph; Charles R. Frihart

2008-01-01

A recently described plant cell wall dissolution system has been modified to use perdeuterated solvents to allow direct in-NMR-tube dissolution and high-resolution solution-state NMR of the whole cell wall without derivatization. Finely ground cell wall material dissolves in a solvent system containing dimethylsulfoxide-d6 and 1-methylimidazole-d6 in a ratio of 4:1 (v/...

Natural abundant solid state NMR studies in designed tripeptides for differentiation of multiple conformers.

Science.gov (United States)

Jayanthi, S; Chatterjee, Bhaswati; Raghothama, S

2009-10-01

Solid state NMR (SSNMR) experiments on heteronuclei in natural abundance are described for three synthetically designed tripeptides Piv-(L)Pro-(L)Pro-(L)Phe-OMe (1), Piv-(D)Pro-(L)Pro-(L)Phe-OMe (2), and Piv-(D)Pro-(L)Pro-(L)Phe-NHMe (3). These peptides exist in different conformation as shown by solution state NMR and single crystal X-ray analysis (Chatterjee et al., Chem Eur J 2008, 14, 6192). In this study, SSNMR has been used to probe the conformations of these peptides in their powder form. The (13)C spectrum of peptide (1) showed doubling of resonances corresponding to cis/cis form, unlike in solution where the similar doubling is attributed to cis/trans form. This has been confirmed by the chemical shift differences of C(beta) and C(gamma) carbon of Proline in peptide (1) both in solution and SSNMR. Peptide (2) and (3) provided single set of resonances which represented all trans form across the di-Proline segment. The results are in agreement with the X-ray analysis. Solid state (15)N resonances, especially from Proline residues provided additional information, which is normally not observable in solution state NMR. (1)H chemical shifts are also obtained from a two-dimensional heteronuclear correlation experiment between (1)H--(13)C. The results confirm the utility of NMR as a useful tool for identifying different conformers in peptides in the solid state. (c) 2009 Wiley Periodicals, Inc. Biopolymers 91: 851-860, 2009.

Motional spin relaxation in photoexcited triplet states

International Nuclear Information System (INIS)

Harryvan, D.; Faassen, E. van

1997-01-01

Transient EPR experiments were performed on photoexcited spin triplet states of the luminescent dye EOSIN-Y in diluted (order of 1 nMol) frozen propane-1-ol solutions at various temperatures. Photoexcitation was achieved by irradiation with intense, short laser pulses. The details of the spin relaxation, in particular the dependence on time, magnetic field and microwave field strength are all reproduced by a model which computes the total magnetization in a population of photoexcited triplet states undergoing random reorientational motion. Using this model, we estimated the motional correlation times to be around a microsecond. This timescale is two orders of magnitude slower than the phase memory time of the triplets. (author)

Determination of binder distributions in green-state ceramics by NMR imaging

International Nuclear Information System (INIS)

Garrido, L.; Ackerman, J.L.; Ellingson, W.A.; Weyand, J.D.

1988-03-01

The manufacture of reliable high performance structural ceramics requires a good understanding of the different steps involved in the process. The presence of nonuniformities in the distribution of the polymeric binder could give rise to local fluctuations of density that could produce failure of the ceramic piece. Specimens prepared from Al 2 O 3 with 15 and 2.5% ww binder were imaged using NMR in order to measure binder distribution maps. Results show that NMR imaging could be a useful technique to nondestructively evaluate the quality of green-state specimens. 5 refs., 5 figs

NMR scalar couplings across Watson–Crick base pair hydrogen bonds in DNA observed by transverse relaxation-optimized spectroscopy

Science.gov (United States)

Pervushin, Konstantin; Ono, Akira; Fernández, César; Szyperski, Thomas; Kainosho, Masatsune; Wüthrich, Kurt

1998-01-01

This paper describes the NMR observation of 15N—15N and 1H—15N scalar couplings across the hydrogen bonds in Watson–Crick base pairs in a DNA duplex, hJNN and hJHN. These couplings represent new parameters of interest for both structural studies of DNA and theoretical investigations into the nature of the hydrogen bonds. Two dimensional [15N,1H]-transverse relaxation-optimized spectroscopy (TROSY) with a 15N-labeled 14-mer DNA duplex was used to measure hJNN, which is in the range 6–7 Hz, and the two-dimensional hJNN-correlation-[15N,1H]-TROSY experiment was used to correlate the chemical shifts of pairs of hydrogen bond-related 15N spins and to observe, for the first time, hJHN scalar couplings, with values in the range 2–3.6 Hz. TROSY-based studies of scalar couplings across hydrogen bonds should be applicable for large molecular sizes, including protein-bound nucleic acids. PMID:9826668

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

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......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...... 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...

Mechanism of nuclear cross-relaxation in magnetically ordered media

Energy Technology Data Exchange (ETDEWEB)

Buishvili, L L; Volzhan, E B; Giorgadze, N P [AN Gruzinskoj SSR, Tbilisi. Inst. Fiziki

1975-09-01

A mechanism of two-step nuclear relaxation in magnetic ordered dielectrics is proposed. The case is considered where the energy conservation in the cross relaxation (CR) process is ensured by the lattice itself without spin-spin interactions. Expressions have been obtained describing the temperature dependence of the CR rate. For a nonuniform broadened NMR line it has been shown that the spin-lattice relaxation time for a spin packet taken out from the equilibrium may be determined by the CR time owing to the mechanism suggested. When the quantization axes for electron and nuclear spins coincide, the spin-lattice relaxation is due to the three-magnon mechanism. The cross-relaxation stage has been shown to play a significant role in the range of low temperatures (T<10 deg K) and to become negligible with a temperature increase.

Conformational exchange of aromatic side chains characterized by L-optimized TROSY-selected ¹³C CPMG relaxation dispersion.

Science.gov (United States)

Weininger, Ulrich; Respondek, Michal; Akke, Mikael

2012-09-01

Protein dynamics on the millisecond time scale commonly reflect conformational transitions between distinct functional states. NMR relaxation dispersion experiments have provided important insights into biologically relevant dynamics with site-specific resolution, primarily targeting the protein backbone and methyl-bearing side chains. Aromatic side chains represent attractive probes of protein dynamics because they are over-represented in protein binding interfaces, play critical roles in enzyme catalysis, and form an important part of the core. Here we introduce a method to characterize millisecond conformational exchange of aromatic side chains in selectively (13)C labeled proteins by means of longitudinal- and transverse-relaxation optimized CPMG relaxation dispersion. By monitoring (13)C relaxation in a spin-state selective manner, significant sensitivity enhancement can be achieved in terms of both signal intensity and the relative exchange contribution to transverse relaxation. Further signal enhancement results from optimizing the longitudinal relaxation recovery of the covalently attached (1)H spins. We validated the L-TROSY-CPMG experiment by measuring fast folding-unfolding kinetics of the small protein CspB under native conditions. The determined unfolding rate matches perfectly with previous results from stopped-flow kinetics. The CPMG-derived chemical shift differences between the folded and unfolded states are in excellent agreement with those obtained by urea-dependent chemical shift analysis. The present method enables characterization of conformational exchange involving aromatic side chains and should serve as a valuable complement to methods developed for other types of protein side chains.

Spin-lattice relaxation times and knight shift in InSb and InAs

International Nuclear Information System (INIS)

Braun, P.; Grande, S.

1976-01-01

For a dominant contact interaction between nuclei and conduction electrons the relaxation rate is deduced. The extreme cases of degenerate and non-degenerate semiconductors are separately discussed. At strong degeneracy the product of the Knight shift and relaxation time gives the Korringa relation for metals. Measurements of the NMR spin-lattice relaxation times of 115 InSb and 115 InAs were made between 4.2 and 300 K for strongly degenerated samples. The different relaxation mechanisms are discussed and the experimental and theoretical results are compared. (author)

Solid-state NMR, electrophysiology and molecular dynamics characterization of human VDAC2

International Nuclear Information System (INIS)

Gattin, Zrinka; Schneider, Robert; Laukat, Yvonne; Giller, Karin; Maier, Elke; Zweckstetter, Markus; Griesinger, Christian; Benz, Roland; Becker, Stefan; Lange, Adam

2015-01-01

The voltage-dependent anion channel (VDAC) is the most abundant protein of the outer mitochondrial membrane and constitutes the major pathway for the transport of ADP, ATP, and other metabolites. In this multidisciplinary study we combined solid-state NMR, electrophysiology, and molecular dynamics simulations, to study the structure of the human VDAC isoform 2 in a lipid bilayer environment. We find that the structure of hVDAC2 is similar to the structure of hVDAC1, in line with recent investigations on zfVDAC2. However, hVDAC2 appears to exhibit an increased conformational heterogeneity compared to hVDAC1 which is reflected in broader solid-state NMR spectra and less defined electrophysiological profiles

Solid-state NMR, electrophysiology and molecular dynamics characterization of human VDAC2

Energy Technology Data Exchange (ETDEWEB)

Gattin, Zrinka; Schneider, Robert; Laukat, Yvonne; Giller, Karin [Max Planck Institute for Biophysical Chemistry (Germany); Maier, Elke [Theodor-Boveri-Institut (Biozentrum) der Universität Würzburg, Lehrstuhl für Biotechnologie (Germany); Zweckstetter, Markus; Griesinger, Christian [Max Planck Institute for Biophysical Chemistry (Germany); Benz, Roland [Theodor-Boveri-Institut (Biozentrum) der Universität Würzburg, Lehrstuhl für Biotechnologie (Germany); Becker, Stefan; Lange, Adam, E-mail: alange@fmp-berlin.de [Max Planck Institute for Biophysical Chemistry (Germany)

2015-04-15

The voltage-dependent anion channel (VDAC) is the most abundant protein of the outer mitochondrial membrane and constitutes the major pathway for the transport of ADP, ATP, and other metabolites. In this multidisciplinary study we combined solid-state NMR, electrophysiology, and molecular dynamics simulations, to study the structure of the human VDAC isoform 2 in a lipid bilayer environment. We find that the structure of hVDAC2 is similar to the structure of hVDAC1, in line with recent investigations on zfVDAC2. However, hVDAC2 appears to exhibit an increased conformational heterogeneity compared to hVDAC1 which is reflected in broader solid-state NMR spectra and less defined electrophysiological profiles.

Solid-state NMR of the Yersinia pestis outer membrane protein Ail in lipid bilayer nanodiscs sedimented by ultracentrifugation

International Nuclear Information System (INIS)

Ding, Yi; Fujimoto, L. Miya; Yao, Yong; Marassi, Francesca M.

2015-01-01

Solid-state NMR studies of sedimented soluble proteins has been developed recently as an attractive approach for overcoming the size limitations of solution NMR spectroscopy while bypassing the need for sample crystallization or precipitation (Bertini et al. Proc Natl Acad Sci USA 108(26):10396–10399, 2011). Inspired by the potential benefits of this method, we have investigated the ability to sediment lipid bilayer nanodiscs reconstituted with a membrane protein. In this study, we show that nanodiscs containing the outer membrane protein Ail from Yersinia pestis can be sedimented for solid-state NMR structural studies, without the need for precipitation or lyophilization. Optimized preparations of Ail in phospholipid nanodiscs support both the structure and the fibronectin binding activity of the protein. The same sample can be used for solution NMR, solid-state NMR and activity assays, facilitating structure–activity correlation experiments across a wide range of timescales

Solid-state NMR of the Yersinia pestis outer membrane protein Ail in lipid bilayer nanodiscs sedimented by ultracentrifugation

Energy Technology Data Exchange (ETDEWEB)

Ding, Yi; Fujimoto, L. Miya; Yao, Yong; Marassi, Francesca M., E-mail: fmarassi@sbmri.org [Sanford-Burnham Medical Research Institute (United States)

2015-04-15

Solid-state NMR studies of sedimented soluble proteins has been developed recently as an attractive approach for overcoming the size limitations of solution NMR spectroscopy while bypassing the need for sample crystallization or precipitation (Bertini et al. Proc Natl Acad Sci USA 108(26):10396–10399, 2011). Inspired by the potential benefits of this method, we have investigated the ability to sediment lipid bilayer nanodiscs reconstituted with a membrane protein. In this study, we show that nanodiscs containing the outer membrane protein Ail from Yersinia pestis can be sedimented for solid-state NMR structural studies, without the need for precipitation or lyophilization. Optimized preparations of Ail in phospholipid nanodiscs support both the structure and the fibronectin binding activity of the protein. The same sample can be used for solution NMR, solid-state NMR and activity assays, facilitating structure–activity correlation experiments across a wide range of timescales.

Solid-State NMR Spectroscopy Proves the Presence of Penta-coordinated Sc Sites in MIL-100(Sc).

Science.gov (United States)

Giovine, Raynald; Volkringer, Christophe; Ashbrook, Sharon E; Trébosc, Julien; McKay, David; Loiseau, Thierry; Amoureux, Jean-Paul; Lafon, Olivier; Pourpoint, Frédérique

2017-07-18

Advanced solid-state NMR methods and first-principles calculations demonstrate for the first time the formation of penta-coordinated scandium sites. These coordinatively unsaturated sites were shown during the thermal activation of scandium-based metal-organic frameworks (MOFs). A 45 Sc NMR experiment allows their specific observation in activated Sc 3 BTB 2 (H 3 BTB=1,3,5-tris(4-carboxyphenyl)benzene) and MIL-100(Sc) MOFs. The assignment of the ScO 5 groups is supported by the DFT calculations of NMR parameters. The presence of ScO 5 Lewis acid sites in MIL-100(Sc) explains furthermore its catalytic activity. The first NMR experiment to probe 13 C- 45 Sc distances is also introduced. This advanced solid-state NMR pulse sequence allows the demonstration of the shrinkage of the MIL-100(Sc) network when the activation temperature is raised. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solid state NMR of materials

Energy Technology Data Exchange (ETDEWEB)

Taylor, Sharon A; Ferguson, David B; Haw, James F [Texas A and M Univ., College Station, TX (United States). Dept. of Chemistry

1994-12-31

In situ NMR experiments are studied, including probe of several structures such as the structures of the organic adsorbates, Broensted acid sites, other nuclei associated with active sites, and other framework sites. The authors report that in the absence of high concentrations of paramagnetic sites or metal particles, high resolution MAS spectra are relatively easy to obtain and interpret. It is also concluded that NMR can measure spatial distributions and rates of diffusion; and are able to characterize equilibrium structures and the frequencies and amplitudes of molecular motion

Yeast-expressed human membrane protein aquaporin-1 yields excellent resolution of solid-state MAS NMR spectra

International Nuclear Information System (INIS)

Emami, Sanaz; Fan Ying; Munro, Rachel; Ladizhansky, Vladimir; Brown, Leonid S.

2013-01-01

One of the biggest challenges in solid-state NMR studies of membrane proteins is to obtain a homogeneous natively folded sample giving high spectral resolution sufficient for structural studies. Eukaryotic membrane proteins are especially difficult and expensive targets in this respect. Methylotrophic yeast Pichia pastoris is a reliable producer of eukaryotic membrane proteins for crystallography and a promising economical source of isotopically labeled proteins for NMR. We show that eukaryotic membrane protein human aquaporin 1 can be doubly ( 13 C/ 15 N) isotopically labeled in this system and functionally reconstituted into phospholipids, giving excellent resolution of solid-state magic angle spinning NMR spectra.

Estimates of methyl 13C and 1H CSA values (Δσ) in proteins from cross-correlated spin relaxation

International Nuclear Information System (INIS)

Tugarinov, Vitali; Scheurer, Christoph; Brueschweiler, Rafael; Kay, Lewis E.

2004-01-01

Simple pulse schemes are presented for the measurement of methyl 13 C and 1 H CSA values from 1 H- 13 C dipole/ 13 C CSA and 1 H- 13 C dipole/ 1 H CSA cross-correlated relaxation. The methodology is applied to protein L and malate synthase G. Average 13 C CSA values are considerably smaller for Ile than Leu/Val (17 vs 25 ppm) and are in good agreement with previous solid state NMR studies of powders of amino acids and dipeptides and in reasonable agreement with quantum-chemical DFT calculations of methyl carbon CSA values in peptide fragments. Small averaged 1 H CSA values on the order of 1 ppm are measured, consistent with a solid state NMR determination of the methyl group 1 H CSA in dimethylmalonic acid

State of health assessment for lithium batteries based on voltage–time relaxation measure

International Nuclear Information System (INIS)

Baghdadi, Issam; Briat, Olivier; Gyan, Philippe; Vinassa, Jean Michel

2016-01-01

Highlights: • Calendar aging under different storage conditions for three different battery technologies studied. • Two scenarios of aging under power cycling at two different temperatures investigated for one battery technology. • Relaxation profile of battery voltage just after full charge is highly correlated to aging. • Linear dependence between just after charge open circuit voltage and remaining capacity demonstrated. • No computational method and direct prediction of battery state of health or remaining capacity. - Abstract: The performance of lithium batteries degrades over time. The degradation rate strongly depends on stress conditions during use and even at rest. Thus, accurate and rapid diagnosis of battery state of health (SOH) is necessary for electric vehicle manufacturers to manage their vehicle fleets and warranties. This paper demonstrates a simple method for assessing SOH related to battery energy capability (SOH E ). The presented method is based on the monitoring of U relax over aging. U relax is the open-circuit voltage of the battery measured after full charging and 30 min of rest. A linear dependence between U relax and remaining capacity is noted. This correlation is demonstrated for three different commercial battery technologies (different chemistries) aged under different calendar and power cycling aging conditions. It was determined that the difference between two U relax voltages measured at two different aging states is proportional to SOH E decay. The mean error of the linear model is less than 2% for certain cases. This method could also be a highly useful and rapid tool for a complete battery pack diagnosis.

Investigation of zeolites by solid state quadrapole NMR

International Nuclear Information System (INIS)

Janssen, R.

1990-01-01

The subject of this thesis is the NMR investigation of zeolites. The nature and properties of zeolites are discussed. Some of the basic priniples of NMR techniques on quadrupole nuclei are presented. A special technique, namely a two-dimensional nutation experiment is discussed in detail. The theory of the nutation experiment for quadrupole spin species with spin quantum number 3/2 as well as 5/2 is presented. For both spin spcies the theoretical spectra are compared with experimental results. It is also shown that the nutation expeirment can be performed with several pulse schemes. It is shown how phase-sensitive pure-absorption nutation spectra can be obtained and an NMR-probe is presented that is capable of performing NMR experiments at high (up to 500 degree C) temperatures. The two-dimensional nutation NMR technique has been applied to sodium cations in zeolite NaA. For this purpose a numbre of zeolite samples were prepared that contained different amounts of water. With the aid of nutation NMR the hydration of the zeolite can be studied and conclusions can be drawn about the symmetry of the surrounding of the sodium cations. With the aid of an extension of the nutation NMR experiment: Rotary Echo Nutation NMR, it is shown that in zeolite NaA, in various stages of hydration, the sodium cations or water molecules are mobile. Proof is given by means of high-temperature 23 Na-NMR that dehydrates zeolite NaA undergoes a phase transition at ca. 120 degree C. In a high-temperature NMR investigation of zeolite ZSM-5 it is shown that the sodium ions start to execute motions when the temperature is increased. (author). 198 refs.; 72 figs.; 6 tabs

NMR studies of sodium cholate-lecithin mixed micelles

International Nuclear Information System (INIS)

Eriksson, P.-O.; Lindblom, G.; Arvidson, G.

1983-01-01

T 1 and T 2 2 H-NMR relaxation times have been measured for 2 H-labelled phosphatidylcholine in the aqueous solution phase of the ternary system lecithin-sodium cholate-water. In this phase aggregates are formed by a mixture of cholate and lecithin. Information about the dimension of these miscellar aggregates has been obtained from a simple model of the relaxation times in which two modes of molecular motion are considered. The results obtained accord well with recent investigations using laser-light scattering techniques

Structural diversity of solid dispersions of acetylsalicylic acid as seen by solid-state NMR.

Science.gov (United States)

Policianova, Olivia; Brus, Jiri; Hruby, Martin; Urbanova, Martina; Zhigunov, Alexander; Kredatusova, Jana; Kobera, Libor

2014-02-03

Solid dispersions of active pharmaceutical ingredients are of increasing interest due to their versatile use. In the present study polyvinylpyrrolidone (PVP), poly[N-(2-hydroxypropyl)-metacrylamide] (pHPMA), poly(2-ethyl-2-oxazoline) (PEOx), and polyethylene glycol (PEG), each in three Mw, were used to demonstrate structural diversity of solid dispersions. Acetylsalicylic acid (ASA) was used as a model drug. Four distinct types of the solid dispersions of ASA were created using a freeze-drying method: (i) crystalline solid dispersions containing nanocrystalline ASA in a crystalline PEG matrix; (ii) amorphous glass suspensions with large ASA crystallites embedded in amorphous pHPMA; (iii) solid solutions with molecularly dispersed ASA in rigid amorphous PVP; and (iv) nanoheterogeneous solid solutions/suspensions containing nanosized ASA clusters dispersed in a semiflexible matrix of PEOx. The obtained structural data confirmed that the type of solid dispersion can be primarily controlled by the chemical constitutions of the applied polymers, while the molecular weight of the polymers had no detectable impact. The molecular structure of the prepared dispersions was characterized using solid-state NMR, wide-angle X-ray scattering (WAXS), and differential scanning calorimetry (DSC). By applying various (1)H-(13)C and (1)H-(1)H correlation experiments combined with T1((1)H) and T1ρ((1)H) relaxation data, the extent of the molecular mixing was determined over a wide range of distances, from intimate intermolecular contacts (0.1-0.5 nm) up to the phase-separated nanodomains reaching ca. 500 nm. Hydrogen-bond interactions between ASA and polymers were probed by the analysis of (13)C and (15)N CP/MAS NMR spectra combined with the measurements of (1)H-(15)N dipolar profiles. Overall potentialities and limitations of individual experimental techniques were thoroughly evaluated.

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 chemical shift titration experiments, and the CPMG derived exchange rates agree with those obtained previously from N-15 backbone relaxation measurements. Compared to measurements of backbone nuclei, C-13(epsilon 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 C-13(epsilon 1) dispersion experiments in combination with chemical shift titration experiments to obtain information on exchange dynamics of the histidine side chains...

Solid state CP/MAS 13C n.m.r. analysis of particle size and density fractions of soil incubated with uniformly labelled 13C-glucose

International Nuclear Information System (INIS)

Baldock, J.A.; Oades, J.M.

1990-01-01

A soil incubated for 34 days in the absence (control) and presence (treated) of uniformly labelled 13 C-glucose was dispersed using an ultrasonic probe and fractionated by sedimentation in water and a polytungstate solution of density 2.0 Mg m -3 . Solid state CP/MAS 13 C n.m.r. (cross polarization/magic angle spinning 13 C nuclear magnetic resonance) spectroscopy was used to characterize the chemical structure of the native soil organic carbon and the residual substrate carbon in the fractions of the control and treated soils. To obtain quantitative results it was essential to determine the spin lattice relaxation time in a rotating frame of the individual carbon types in the spectra as the relaxation behaviour of the native organic material in the clay fraction was different from that of the residual substrate carbon. The residual substrate carbon was found to accumulate in predominantly alkyl and O-alkyl structures in both fractions. However, significant amounts of acetal and carboxyl carbon were also observed in the clay fraction. Little if any aromatic or phenolic carbon was synthesized by the soil microorganisms utilizing substrate carbon. Dipolar dephasing CP/MAS 13 C n.m.r. experiments were also performed and allowed the proportion of each type of carbon which was protonated and nonprotonated to be estimated. Essentially all of the O-alkyl and acetal carbon, 25-40% of the aromatic carbon and 66-80% of the alkyl carbon was protonated in the fractions isolated from the treated soil. 24 refs., 4 figs., 2 tabs

Hydration water dynamics in biopolymers from NMR relaxation in the rotating frame.

Science.gov (United States)

Blicharska, Barbara; Peemoeller, Hartwig; Witek, Magdalena

2010-12-01

Assuming dipole-dipole interaction as the dominant relaxation mechanism of protons of water molecules adsorbed onto macromolecule (biopolymer) surfaces we have been able to model the dependences of relaxation rates on temperature and frequency. For adsorbed water molecules the correlation times are of the order of 10(-5)s, for which the dispersion region of spin-lattice relaxation rates in the rotating frame R(1)(ρ)=1/T(1)(ρ) appears over a range of easily accessible B(1) values. Measurements of T(1)(ρ) at constant temperature and different B(1) values then give the "dispersion profiles" for biopolymers. Fitting a theoretical relaxation model to these profiles allows for the estimation of correlation times. This way of obtaining the correlation time is easier and faster than approaches involving measurements of the temperature dependence of R(1)=1/T(1). The T(1)(ρ) dispersion approach, as a tool for molecular dynamics study, has been demonstrated for several hydrated biopolymer systems including crystalline cellulose, starch of different origins (potato, corn, oat, wheat), paper (modern, old) and lyophilized proteins (albumin, lysozyme). Copyright © 2010 Elsevier Inc. All rights reserved.

Structural study of the membrane protein MscL using cell-free expression and solid-state NMR

Science.gov (United States)

Abdine, Alaa; Verhoeven, Michiel A.; Park, Kyu-Ho; Ghazi, Alexandre; Guittet, Eric; Berrier, Catherine; Van Heijenoort, Carine; Warschawski, Dror E.

2010-05-01

High-resolution structures of membrane proteins have so far been obtained mostly by X-ray crystallography, on samples where the protein is surrounded by detergent. Recent developments of solid-state NMR have opened the way to a new approach for the study of integral membrane proteins inside a membrane. At the same time, the extension of cell-free expression to the production of membrane proteins allows for the production of proteins tailor made for NMR. We present here an in situ solid-state NMR study of a membrane protein selectively labeled through the use of cell-free expression. The sample consists of MscL (mechano-sensitive channel of large conductance), a 75 kDa pentameric α-helical ion channel from Escherichia coli, reconstituted in a hydrated lipid bilayer. Compared to a uniformly labeled protein sample, the spectral crowding is greatly reduced in the cell-free expressed protein sample. This approach may be a decisive step required for spectral assignment and structure determination of membrane proteins by solid-state NMR.

Spin-lattice relaxation in phosphorescent triplet state molecules

International Nuclear Information System (INIS)

Verbeek, P.J.F.

1979-01-01

The present thesis contains the results of a study of spin-lattice relaxation (SLR) in the photo-excited triplet state of aromatic molecules, dissolved in a molecular host crystal. It appears that SLR in phosphorescent triplet state molecules often is related to the presence of so-called (pseudo) localized phonons in the molecular mixed crystals. These local phonons can be thought to correspond with vibrations (librations) of the guest molecule in the force field of the surrounding host molecules. Since the intermolecular forces are relatively weak, the frequencies corresponding with these vibrations are relatively low and usually are of the order of 10-30 cm -1 . (Auth.)

Dynamic membrane interactions of antibacterial and antifungal biomolecules, and amyloid peptides, revealed by solid-state NMR spectroscopy.

Science.gov (United States)

Naito, Akira; Matsumori, Nobuaki; Ramamoorthy, Ayyalusamy

2018-02-01

A variety of biomolecules acting on the cell membrane folds into a biologically active structure in the membrane environment. It is, therefore, important to determine the structures and dynamics of such biomolecules in a membrane environment. While several biophysical techniques are used to obtain low-resolution information, solid-state NMR spectroscopy is one of the most powerful means for determining the structure and dynamics of membrane bound biomolecules such as antibacterial biomolecules and amyloidogenic proteins; unlike X-ray crystallography and solution NMR spectroscopy, applications of solid-state NMR spectroscopy are not limited by non-crystalline, non-soluble nature or molecular size of membrane-associated biomolecules. This review article focuses on the applications of solid-state NMR techniques to study a few selected antibacterial and amyloid peptides. Solid-state NMR studies revealing the membrane inserted bent α-helical structure associated with the hemolytic activity of bee venom melittin and the chemical shift oscillation analysis used to determine the transmembrane structure (with α-helix and 3 10 -helix in the N- and C-termini, respectively) of antibiotic peptide alamethicin are discussed in detail. Oligomerization of an amyloidogenic islet amyloid polypeptide (IAPP, or also known as amylin) resulting from its aggregation in a membrane environment, molecular interactions of the antifungal natural product amphotericin B with ergosterol in lipid bilayers, and the mechanism of lipid raft formation by sphingomyelin studied using solid state NMR methods are also discussed in this review article. This article is part of a Special Issue entitled "Biophysical Exploration of Dynamical Ordering of Biomolecular Systems" edited by Dr. Koichi Kato. Copyright © 2017 Elsevier B.V. All rights reserved.

High-resolution solution-state NMR of unfractionated plant cell walls

Science.gov (United States)

John Ralph; Fachuang Lu; Hoon Kim; Dino Ress; Daniel J. Yelle; Kenneth E. Hammel; Sally A. Ralph; Bernadette Nanayakkara; Armin Wagner; Takuya Akiyama; Paul F. Schatz; Shawn D. Mansfield; Noritsugu Terashima; Wout Boerjan; Bjorn Sundberg; Mattias Hedenstrom

2009-01-01

Detailed structural studies on the plant cell wall have traditionally been difficult. NMR is one of the preeminent structural tools, but obtaining high-resolution solution-state spectra has typically required fractionation and isolation of components of interest. With recent methods for dissolution of, admittedly, finely divided plant cell wall material, the wall can...

Thermometry of hot spot using NMR for hyperthermia

International Nuclear Information System (INIS)

Amemiya, Yoshifumi; Kamimura, Yoshitsugu

1983-01-01

Lately noticed hyperthermia in cancer therapy requires non-invasive measurement of the temperature at the warmed site in the deep portion of human body. Nuclear magnetic relaxation time of NMR is also usable for cancer diagnosis. For coordination of these two techniques, it was judged suitable to measure temperature by NMR so that cancer diagnosis and treatment and evaluation of therapeutic effect might be incorporated into one system. This report dealt with concrete procedures of measuring the temperature of deep portions by NMR. Computations revealed that the coefficient of temperature of the thermal equilibrium magnetization was useful, that magnetic field focusing was the most effective imaging technique and that temperature rise in areas about 2 cm in radius could be measured without large errors. (Chiba, N.)

LARGE SCALE PRODUCTION, PURIFICATION, AND 65CU SOLID STATE NMR OF AZURIN

Energy Technology Data Exchange (ETDEWEB)

Gao, A.; Heck, R.W.

2008-01-01

This paper details a way to produce azurin with an effi ciency over 10 times greater than previously described and demonstrates the fi rst solid state nuclear magnetic resonance spectrum of 65Cu(I) in a metalloprotein. A synthetic gene for azurin based upon the DNA sequence from Pseudomonas aeruginosa including the periplasmic targeting sequence was subcloned into a T7 overexpression vector to create the plasmid pGS-azurin, which was transformed into BL21 (DE3) competent cells. The leader sequence on the expressed protein causes it to be exported to the periplasmic space of Escherichia coli. Bacteria grown in a fermentation unit were induced to overexpress the azurin, which was subsequently purifi ed through an endosmotic shock procedure followed by high performance liquid chromatography (HPLC). 1,500 mg of azurin were purifi ed per liter of culture. 65Cu(II) was added to apo-azurin and then reduced. The 65Cu metal cofactor in azurin was observed with solid state nuclear magnetic resonance (NMR) to determine any structural variations that accompanied copper reduction. This is the fi rst solid state NMR spectra of a copper(I) metalloprotein. Analysis of the NMR spectra is being used to complement hypotheses set forth by x-ray diffraction and computational calculations of electron transfer mechanisms in azurin.

Analysis of the backbone dynamics of capsicein using 15N NMR relaxation rate measurements

International Nuclear Information System (INIS)

Van Heijenoort, C.; Bouaziz, S.; Guittet, E.

1994-01-01

15 N relaxation times T 1 and T 1ρ , and heteronuclear steady state nOes, were measured on capsicein, a 98 residue protein. The classical analysis of these data using directly the Lipari and Szabo formalism was shown to give incoherent results, probably due to the presence of a slow exchange along the whole protein. This global exchange broadening made the usual preliminary evaluation of the overall correlation time of capsicein using the Lipari and Szabo expression for the spectral densities impossible. (authors). 2 figs., 23 refs

Fluorine dynamics in BaF2 superionic conductors investigated by NMR

International Nuclear Information System (INIS)

Gumann, Patryk

2008-01-01

In this work the dynamics of fluorine in solid-state electrolytes having BaF 2 -structure was investigated using three different NMR-methods: field cycling relaxometry, lineshape analysis, and static field gradient NMR. For this purpose a pure BaF 2 crystal, as well as crystals doped with trivalent impurities (LaF 3 ), were studied as a function of temperature. Using MAS NMR it was possible to identify two lines in Ba 0.9 La 0.1 F 2.1 having different chemical shift, and to refer them to the modified crystal structure. On this basis a model for the fluorine lineshape has been developed, taking into account three motional processes characterized by their correlation times. It includes jump diffusion of the fluorine ions among equivalent sites within two crystallographically distinct sublattices, and inter-lattice exchange processes. By measuring frequency and temperature-dependent spin lattice relaxation times, it was possible to gain information about fluorine dynamics on microscopic length scales. An attempt was also made to analyze the data for pure BaF 2 and low admixture concentration samples with a non-exponential correlation function. (orig.)

$^{11}$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 ...

Solid-state 29Si NMR and FTIR analyses of lignin-silica coprecipitates

DEFF Research Database (Denmark)

Cabrera Orozco, Yohanna; Cabrera, Andrés; Larsen, Flemming Hofmann

2016-01-01

When agricultural residues are processed to ethanol, lignin and silica are some of the main byproducts. Separation of these two products is difficult and the chemical interactions between lignin and silica are not well described. In the present study, the effect of lignin-silica complexing has been...... investigated by characterizing lignin and silica coprecipitates by FTIR and solid state NMR. Silica particles were coprecipitated with three different lignins, three lignin model compounds, and two silanes representing silica-in-lignin model compounds. Comparison of 29Si SP/MAS NMR spectra revealed differences...

Development of new probes for NMR based analysis of biomolecules' cellular functions

International Nuclear Information System (INIS)

Fernandes, Laetitia

2015-01-01

Most NMR studies are carried out in vitro, but the structure and dynamics of some biomolecules inside cells differ from those in vitro. It thus becomes interesting to analyze biomolecules such as proteins in their natural environment: the cell. Recent progress of in cell NMR allowed to better understand the behaviour of proteins: their dynamics and their interactions with other biomolecules in the cell. But the low concentration of proteins leads to low signal intensity. Moreover, the viscosity of the environment induces faster transverse relaxation, resulting in line broadening for proteins signals. The use of the Long-Lived States and Coherencies (LLS and LLC, respectively) as well as dissolution Dynamic Nuclear Polarization (dissolution-DNP) can improve NMR observations in cells. LLS were used to understand and characterize the structure of the N-terminal domain of c-Src, which is intrinsically disordered. To follow the phosphorylation of proteins, a first preliminary study of a 21-aa peptides derived from IKBa electroporated into HepG2 cell lines was carried out. (author)

Muon spin relaxation and nonmagnetic Kondo state in PrInAg2

International Nuclear Information System (INIS)

MacLaughlin, D. E.; Heffner, R. H.; Nieuwenhuys, G. J.; Canfield, P. C.; Amato, A.; Baines, C.; Schenck, A.; Luke, G. M.; Fudamoto, Y.; Uemura, Y. J.

2000-01-01

Muon spin relaxation experiments have been carried out in the Kondo compound PrInAg 2 . The zero-field muon relaxation rate is found to be independent of temperature between 0.1 and 10 K, which rules out a magnetic origin (spin freezing or a conventional Kondo effect) for the previously observed specific-heat anomaly at ∼0.5 K. At low temperatures the muon relaxation can be quantitatively understood in terms of the muon's interaction with nuclear magnetism, including hyperfine enhancement of the 141 Pr nuclear moment at low temperatures. This argues against a Pr 3+ ground-state electronic magnetic moment, and is strong evidence for the doublet Γ 3 crystalline-electric-field-split ground state required for a nonmagnetic route to heavy-electron behavior. The data imply the existence of an exchange interaction between neighboring Pr 3+ ions of the order of 0.2 K in temperature units, which should be taken into account in a complete theory of a nonmagnetic Kondo effect in PrInAg 2 . (c) 2000 The American Physical Society

Direct synthesis of magnetite nanoparticles from iron(II) carboxymethylcellulose and their performance as NMR contrast agents

Energy Technology Data Exchange (ETDEWEB)

Gomes da Silva, Delmarcio; Hiroshi Toma, Sergio; Menegatti de Melo, Fernando [Instituto de Química, Universidade de São Paulo, São Paulo, SP (Brazil); Carvalho, Larissa Vieira C.; Magalhães, Alvicler; Sabadini, Edvaldo [Instituto de Química, Universidade Estadual de Campinas – UNICAMP, Campinas, SP (Brazil); Domingues dos Santos, Antônio [Instituto de Física, Universidade de São Paulo, São Paulo, SP (Brazil); Araki, Koiti [Instituto de Química, Universidade de São Paulo, São Paulo, SP (Brazil); Toma, Henrique E., E-mail: henetoma@iq.usp.br [Instituto de Química, Universidade de São Paulo, São Paulo, SP (Brazil)

2016-01-01

Iron(II) carboxymethylcellulose (CMC) has been successfully employed in the synthesis of hydrophylic magnetite nanoparticles stabilized with a biopolymer coating, aiming applications in NMR imaging. The new method encompasses a convenient one-step synthetic procedure, allowing a good size control and yielding particles of about 10 nm (core size). In addition to the biocompatibility, the nanoparticles have promoted a drastic reduction in the transverse relaxation time (T{sub 2}) of the water protons. The relaxivity rates have been investigated as a function of the nanoparticles concentration, showing a better performance in relation to the common NMR contrast agents available in the market. - Highlights: • Stable, hydrophylic magnetic nanoparticles have been obtained. • Direct use of iron(II) carboxymethylcellulose improves the synthesis. • The magnetic nanoparticles exhibit high spin–spin relaxivity. • The particles promote dark contrast by decreasing the T{sub 2} relaxation time.

NMR characteristics of rat mammary tumors

International Nuclear Information System (INIS)

Osbakken, M.; Kreider, J.; Taczanowsky, P.

1984-01-01

12 rats were injected intradermally with 13762A rat mammary adenocarcinoma (1 x 10/sup 6/ cells). 3 rats died before completion of the study and 2 rat had tumor regression; the first 3 were excluded from data analysis. NMR imaging with a 1.5K gauss resistive magnet at 2, 3, 4, and 5 weeks after injection demonstrated increasing tumor mass. Saturation recovery (SR), inversion recovery (IR), and spin echo (SE) pulse sequence images and T/sub 1/ calculation were done for tumor characterization. (Tumor size was too small to identify at 2 weeks.) 3 rats were sacrificed after the last 3 imaging periods for histological studies, done to distinguish solid tumor mass from necrosis. Planimetry of tumor areas showed that as tumors grew in size, the ratio of necrotic area to area of solid tumor increased (week 3 = .3 +- .11; week 4 = .45 +- .07; week 5 = .51 +- 05); simultaneous calculated T/sub 1/ values also increased (week 3 = .35 +- .15; week 4 = .45 +- .06; week 5 = .42 +- 03). Qualitative NMR image T/sub 1/ values also increased as evidenced by progression of SR and IR tumor image intensity from very bright compared to the rest of the body at week 3 to less intense than other structures at week 5. These findings indicate that change in T/sub 1/ may be secondary to the pathophysiological change in the tumor (the increasing in necrosis, associated with increased free water). Thus, the range of T/sub 1/ values obtained in tumors in this study (and in previous studies) may be due to change in tumor physiology and anatomy. Careful correlation of histological with NMR data may allow ultimate use of NMR relaxation characteristics for determination of the physiological state of tumors

Solid-State (13)C NMR Delineates the Architectural Design of Biopolymers in Native and Genetically Altered Tomato Fruit Cuticles.

Science.gov (United States)

Chatterjee, Subhasish; Matas, Antonio J; Isaacson, Tal; Kehlet, Cindie; Rose, Jocelyn K C; Stark, Ruth E

2016-01-11

Plant cuticles on outer fruit and leaf surfaces are natural macromolecular composites of waxes and polyesters that ensure mechanical integrity and mitigate environmental challenges. They also provide renewable raw materials for cosmetics, packaging, and coatings. To delineate the structural framework and flexibility underlying the versatile functions of cutin biopolymers associated with polysaccharide-rich cell-wall matrices, solid-state NMR spectra and spin relaxation times were measured in a tomato fruit model system, including different developmental stages and surface phenotypes. The hydrophilic-hydrophobic balance of the cutin ensures compatibility with the underlying polysaccharide cell walls; the hydroxy fatty acid structures of outer epidermal cutin also support deposition of hydrophobic waxes and aromatic moieties while promoting the formation of cell-wall cross-links that rigidify and strengthen the cuticle composite during fruit development. Fruit cutin-deficient tomato mutants with compromised microbial resistance exhibit less efficient local and collective biopolymer motions, stiffening their cuticular surfaces and increasing their susceptibility to fracture.

Protein structural studies by paramagnetic solid-state NMR spectroscopy aided by a compact cyclen-type Cu(II) binding tag

Energy Technology Data Exchange (ETDEWEB)

Sengupta, Ishita; Gao, Min; Arachchige, Rajith J.; Nadaud, Philippe S. [The Ohio State University, Department of Chemistry and Biochemistry (United States); Cunningham, Timothy F.; Saxena, Sunil [University of Pittsburgh, Department of Chemistry (United States); Schwieters, Charles D. [National Institutes of Health, Center for Information Technology (United States); Jaroniec, Christopher P., E-mail: jaroniec@chemistry.ohio-state.edu [The Ohio State University, Department of Chemistry and Biochemistry (United States)

2015-01-15

Paramagnetic relaxation enhancements (PREs) are a rich source of structural information in protein solid-state NMR spectroscopy. Here we demonstrate that PRE measurements in natively diamagnetic proteins are facilitated by a thiol-reactive compact, cyclen-based, high-affinity Cu{sup 2+} binding tag, 1-[2-(pyridin-2-yldisulfanyl)ethyl]-1,4,7,10-tetraazacyclododecane (TETAC), that overcomes the key shortcomings associated with the use of larger, more flexible metal-binding tags. Using the TETAC–Cu{sup 2+} K28C mutant of B1 immunoglobulin-binding domain of protein G as a model, we find that amino acid residues located within ∼10 Å of the Cu{sup 2+} center experience considerable transverse PREs leading to severely attenuated resonances in 2D {sup 15}N–{sup 13}C correlation spectra. For more distant residues, electron–nucleus distances are accessible via quantitative measurements of longitudinal PREs, and we demonstrate such measurements for {sup 15}N–Cu{sup 2+} distances up to ∼20 Å.

Energy relaxation between low lying tunnel split spin-states of the single molecule magnet Ni4

Science.gov (United States)

de Loubens, G.; Chaves-O'Flynn, G. D.; Kent, A. D.; Ramsey, C.; Del Barco, E.; Beedle, C.; Hendrickson, D. N.

2007-03-01

We have developed integrated magnetic sensors to study quantum tunneling of magnetization (QTM) in single molecule magnet (SMMs) single crystals. These sensors incorporate a microstrip resonator (30 GHz) and a micro-Hall effect magnetometer. They have been used to investigate the relaxation rates between the 2 lowest lying tunnel split spin-states of the SMM Ni4 (S=4). EPR spectroscopy at 30 GHz and 0.4 K and concurrent magnetization measurements of several Ni4 single crystals are presented. EPR enables measurement of the energy splitting between the 2 lowest lying superposition states as a function of the longitudinal and transverse fields. The energy relaxation rate is determined in two ways. First, in cw microwave experiments the change in spin-population together with the microwave absorption directly gives the relaxation time from energy conservation in steady-state. Second, direct time-resolved measurements of the magnetization with pulsed microwave radiation have been performed. The relaxation time is found to vary by several orders of magnitude in different crystals, from a few seconds down to smaller than 100 μs. We discuss this and the form of the relaxation found for different crystals and pulse conditions.

Applications of solid-state Nuclear Magnetic Resonance (NMR) in studies of Portland cements-based materials

DEFF Research Database (Denmark)

Skibsted, Jørgen; Andersen, Morten Daugaard; Jakobsen, Hans Jørgen

2007-01-01

Solid-state NMR spectroscopy represents an important research tool in the characterization of a range of structural properties for cement-based materials. Different approaches of the technique can be used to obtain information on hydration kinetics, mobile and bound water, porosity, and local...... atomic structures. After a short introduction to these NMR techniques, it is exemplified how magic-angle spinning (MAS) NMR can provide quantitative and structural information about specific phases in anhydrous and hydrated Portland cements with main emphasis on the incorporation of Al3+ ions...

Temperature-induced transitions in disordered proteins probed by NMR spectroscopy

DEFF Research Database (Denmark)

Kjærgaard, Magnus; Poulsen, Flemming Martin; Kragelund, Birthe Brandt

2012-01-01

Intrinsically disordered proteins are abundant in nature and perform many important physiological functions. Multidimensional NMR spectroscopy has been crucial for the understanding of the conformational properties of disordered proteins and is increasingly used to probe their conformational...... ensembles. Compared to folded proteins, disordered proteins are more malleable and more easily perturbed by environmental factors. Accordingly, the experimental conditions and especially the temperature modify the structural and functional properties of disordered proteins. NMR spectroscopy allows analysis...... of temperature-induced structural changes at residue resolution using secondary chemical shift analysis, paramagnetic relaxation enhancement, and residual dipolar couplings. This chapter discusses practical aspects of NMR studies of temperature-induced structural changes in disordered proteins....

Changes in seed water status as characterized by NMR in developing soybean seed grown under moisture stress conditions

International Nuclear Information System (INIS)

Krishnan, P.; Singh, Ravender; Verma, A.P.S.; Joshi, D.K.; Singh, Sheoraj

2014-01-01

Highlights: • In developing soybean seeds, moisture stress resulted in more proportion of water to bound state. • These changes are further corroborated by concomitant changes in seed metabolites. • Thus there exists a moisture stress and development stage dependence of seed tissue water status. - Abstract: Changes in water status of developing seeds of Soybean (Glycine max L. Merrill.) grown under different moisture stress conditions were characterized by proton nuclear magnetic resonance (NMR)- spin–spin relaxation time (T 2 ). A comparison of the seed development characteristics, composition and physical properties indicated that, characteristics like seed weight, seed number/ear, rate of seed filling increased with development stages but decreased with moisture stress conditions. The NMR- spin–spin relaxation (T 2 ) component like bound water increased with seed maturation (40–50%) but decreased with moisture stress conditions (30–40%). The changes in seed water status to increasing levels of moisture stress and seed maturity indicates that moisture stress resulted in more proportion of water to bound state and intermediate state and less proportion of water in free-state. These changes are further corroborated by significant changes in protein and starch contents in seeds under high moisture stress treatments. Thus seed water status during its development is not only affected by development processes but also by moisture stress conditions. This study strongly indicated a clear moisture stress and development stage dependence of seed tissue water status in developing soybean seeds

Changes in seed water status as characterized by NMR in developing soybean seed grown under moisture stress conditions

Energy Technology Data Exchange (ETDEWEB)

Krishnan, P., E-mail: pkrishnan@iari.res.in; Singh, Ravender; Verma, A.P.S.; Joshi, D.K.; Singh, Sheoraj

2014-02-21

Highlights: • In developing soybean seeds, moisture stress resulted in more proportion of water to bound state. • These changes are further corroborated by concomitant changes in seed metabolites. • Thus there exists a moisture stress and development stage dependence of seed tissue water status. - Abstract: Changes in water status of developing seeds of Soybean (Glycine max L. Merrill.) grown under different moisture stress conditions were characterized by proton nuclear magnetic resonance (NMR)- spin–spin relaxation time (T{sub 2}). A comparison of the seed development characteristics, composition and physical properties indicated that, characteristics like seed weight, seed number/ear, rate of seed filling increased with development stages but decreased with moisture stress conditions. The NMR- spin–spin relaxation (T{sub 2}) component like bound water increased with seed maturation (40–50%) but decreased with moisture stress conditions (30–40%). The changes in seed water status to increasing levels of moisture stress and seed maturity indicates that moisture stress resulted in more proportion of water to bound state and intermediate state and less proportion of water in free-state. These changes are further corroborated by significant changes in protein and starch contents in seeds under high moisture stress treatments. Thus seed water status during its development is not only affected by development processes but also by moisture stress conditions. This study strongly indicated a clear moisture stress and development stage dependence of seed tissue water status in developing soybean seeds.

1H NMR visibility of mammalian glycogen in solution

International Nuclear Information System (INIS)

Zang, L.H.; Rothman, D.L.; Shulman, R.G.

1990-01-01

High-resolution 1 H NMR spectra of rabbit liver glycogen in 2 H 2 O were obtained at 500 MHz, and several resonances were assigned by comparison with the chemical shifts of α-linked diglucose molecules. The NMR relaxation times T 1 and T 2 of glycogen in 2 H 2 O were determined to be 1.1 and 0.029 s, respectively. The measured natural linewidth of the carbon-1 proton is in excellent agreement with that calculated from T 2 . The visibility measurements made by digesting glycogen and comparing glucose and glycogen signal intensities demonstrate that in spite of the very high molecular weight, all of the proton nuclei in glycogen contribute to the NMR spectrum. The result is not unexpected, since 100% NMR visibility was previously observed from the carbon nuclei of glycogen, due to the rapid intramolecular motions

Studying the molecular determinants of potassium channel structure and function in membranes by solid-state NMR

NARCIS (Netherlands)

van der Cruijsen, Elwin

2014-01-01

Solid-state Nuclear Magnetic Resonance (ssNMR) has made remarkable progress in the structural characterization of membrane proteins systems at atomic resolution. Such studies can be further aided by the use of molecular dynamic simulations. Moreover, ssNMR data can be directly compared to functional

Host-guest interaction of styrene and ethylbenzene in MIL-53 studied by solid-state NMR.

Science.gov (United States)

Li, Shenhui; Li, Jing; Tang, Jing; Deng, Feng

Solid-state NMR was utilized to explore the host-guest interaction between adsorbate and adsorbent at atomic level to understand the separation mechanism of styrene (St) and ethylbenzene (EB) in MIL-53(Al). 13 C- 27 Al double-resonance NMR experiments revealed that the host-guest interaction between St and MIL-53 was much stronger than that of EB adsorption. In addition, 13 C DIPSHIFT experiments suggested that the adsorbed St was less mobile than EB confined inside the MIL-53 pore. Furthermore, the host-guest interaction model between St, EB and MIL-53 was established on the basis of the spatial proximities information extracted from 2D 1 H- 1 H homo-nuclear correlation NMR experiments. According to the experimental observation from solid-state NMR, it was found that the presence of π-π interaction between St and MIL-53 resulted in the stronger host-guest interaction and less mobility of St. This work provides direct experimental evidence for understanding the separation mechanism of St and EB using MIL-53 as an adsorbent. Copyright © 2017 Elsevier Inc. All rights reserved.

Dynamics and interactions of ibuprofen in cyclodextrin nanosponges by solid-state NMR spectroscopy

Directory of Open Access Journals (Sweden)

Monica Ferro

2017-01-01

Full Text Available Two different formulations of cyclodextrin nanosponges (CDNS, obtained by polycondensation of β-cyclodextrin with ethylenediaminetetraacetic acid dianhydride (EDTAn, were treated with aqueous solutions of ibuprofen sodium salt (IbuNa affording hydrogels that, after lyophilisation, gave two solid CDNS-drug formulations. 1H fast MAS NMR and 13C CP-MAS NMR spectra showed that IbuNa was converted in situ into its acidic and dimeric form (IbuH after freeze-drying. 13C CP-MAS NMR spectra also indicated that the structure of the nanosponge did not undergo changes upon drug loading compared to the unloaded system. However, the 13C NMR spectra collected under variable contact time cross-polarization (VCT-CP conditions showed that the polymeric scaffold CDNS changed significantly its dynamic regime on passing from the empty CDNS to the drug-loaded CDNS, thus showing that the drug encapsulation can be seen as the formation of a real supramolecular aggregate rather than a conglomerate of two solid components. Finally, the structural features obtained from the different solid-state NMR approaches reported matched the information from powder X-ray diffraction profiles.

The structure of poly(carbonsuboxide) on the atomic scale: a solid-state NMR study.

Science.gov (United States)

Schmedt auf der Günne, Jörn; Beck, Johannes; Hoffbauer, Wilfried; Krieger-Beck, Petra

2005-07-18

In this contribution we present a study of the structure of amorphous poly(carbonsuboxide) (C3O2)x by 13C solid-state NMR spectroscopy supported by infrared spectroscopy and chemical analysis. Poly(carbonsuboxide) was obtained by polymerization of carbonsuboxide C3O2, which in turn was synthesized from malonic acid bis(trimethylsilylester). Two different 13C labeling schemes were applied to probe inter- and intramonomeric bonds in the polymer by dipolar solid-state NMR methods and also to allow quantitative 13C MAS NMR spectra. Four types of carbon environments can be distinguished in the NMR spectra. Double-quantum and triple-quantum 2D correlation experiments were used to assign the observed peaks using the through-space and through-bond dipolar coupling. In order to obtain distance constraints for the intermonomeric bonds, double-quantum constant-time experiments were performed. In these experiments an additional filter step was applied to suppress contributions from not directly bonded 13C,13C spin pairs. The 13C NMR intensities, chemical shifts, connectivities and distances gave constraints for both the polymerization mechanism and the short-range order of the polymer. The experimental results were complemented by bond lengths predicted by density functional theory methods for several previously suggested models. Based on the presented evidence we can unambiguously exclude models based on gamma-pyronic units and support models based on alpha-pyronic units. The possibility of planar ladder- and bracelet-like alpha-pyronic structures is discussed.

NMR-CT scanner

International Nuclear Information System (INIS)

Kose, Katsumi; Sato, Kozo; Sugimoto, Hiroshi; Sato, Masataka.

1983-01-01

A brief explanation is made on the imaging methods for a practical diagnostic NMR-CT scanner : A whole-body NMR-CT scanner utilizing a resistive magnet has been developed by Toshiba in cooperation with the Institute for Solid State Physics, the University of Tokyo. Typical NMR-CT images of volunteers and patients obtained in the clinical experiments using this device are presented. Detailed specifications are also shown about the practical NMR-CTs which are to be put on the market after obtaining the government approval. (author)

Restricted lithium ion dynamics in PEO-based block copolymer electrolytes measured by high-field nuclear magnetic resonance relaxation

Science.gov (United States)

Huynh, Tan Vu; Messinger, Robert J.; Sarou-Kanian, Vincent; Fayon, Franck; Bouchet, Renaud; Deschamps, Michaël

2017-10-01

The intrinsic ionic conductivity of polyethylene oxide (PEO)-based block copolymer electrolytes is often assumed to be identical to the conductivity of the PEO homopolymer. Here, we use high-field 7Li nuclear magnetic resonance (NMR) relaxation and pulsed-field-gradient (PFG) NMR diffusion measurements to probe lithium ion dynamics over nanosecond and millisecond time scales in PEO and polystyrene (PS)-b-PEO-b-PS electrolytes containing the lithium salt LiTFSI. Variable-temperature longitudinal (T1) and transverse (T2) 7Li NMR relaxation rates were acquired at three magnetic field strengths and quantitatively analyzed for the first time at such fields, enabling us to distinguish two characteristic time scales that describe fluctuations of the 7Li nuclear electric quadrupolar interaction. Fast lithium motions [up to O (ns)] are essentially identical between the two polymer electrolytes, including sub-nanosecond vibrations and local fluctuations of the coordination polyhedra between lithium and nearby oxygen atoms. However, lithium dynamics over longer time scales [O (10 ns) and greater] are slower in the block copolymer compared to the homopolymer, as manifested experimentally by their different transverse 7Li NMR relaxation rates. Restricted dynamics and altered thermodynamic behavior of PEO chains anchored near PS domains likely explain these results.

Towards quantification of butadiene content in styrene-butadiene block copolymers and their blends with general purpose polystyrene (GPPS) and the relation between mechanical properties and NMR relaxation times

Energy Technology Data Exchange (ETDEWEB)

Nestle, Nikolaus [BASF Aktiengesellschaft, GKP/P-G 201, D-67056 Ludwigshafen (Germany)], E-mail: nikolaus.nestle@basf.com; Heckmann, Walter; Steininger, Helmut; Knoll, Konrad [BASF Aktiengesellschaft, GKP/P-G 201, D-67056 Ludwigshafen (Germany)

2007-11-26

The properties of styrene-butadiene-styrene (SBS) block copolymers do not only depend on the butadiene content and the degree of polymerisation but also on their chain architecture. In this contribution we present the results of a low-field time domain (TD) NMR study in which the transverse relaxation behaviour of different SBS block copolymers was analysed and correlated with findings from mechanical testing on pure and blended materials and transmission electron microscopy data which provide information on the microphase separation. The results indicate that while a straightforward determination of the butadiene content as in blended materials like ABS is not possible for these materials, the TD-NMR results correlate quite well with the mechanical performance of blends from SBS block copolymers with general purpose polystyrene (GPPS), i.e. industrial grade homopolymer polystyrene. Temperature-dependent experiments on pure and blended materials revealed a slight reduction in the softening temperature of the GPPS fraction in the blends.

Relaxation of helium levels excited by heavy ion impact: III.- Orientation by anisotropic relaxation of excited atoms in previously aligned states

International Nuclear Information System (INIS)

Chamoun, E.; Lombardi, M.; Carre, M.; Gaillard, M.L.

1977-01-01

In the last paper of this series devoted to relaxation phenomena in a low pressure cell of helium excited by an accelerated ion beam, experimental evidence is given for a new mechanism of transfer between alignment and orientation through anisotropic relaxation of initially aligned excited states. The theory predicting this effect is briefly outlined and then description is given of the exact experimental conditions to detect the circularly polarized component of the light emitted by the target excited in the 4 1 D level of He I by Na + impact [fr

Predicting the effect of relaxation during frequency-selective adiabatic pulses

Science.gov (United States)

Pfaff, Annalise R.; McKee, Cailyn E.; Woelk, Klaus

2017-11-01

Adiabatic half and full passages are invaluable for achieving uniform, B1-insensitive excitation or inversion of macroscopic magnetization across a well-defined range of NMR frequencies. To accomplish narrow frequency ranges with adiabatic pulses (computer-calculated data with experimental results demonstrates that, in non-viscous, small-molecule fluids, it is possible to model magnetization and relaxation by considering standard T1 and T2 relaxation in the traditional rotating frame. The proposed model is aimed at performance optimizations of applications in which these pulses are employed. It differs from previous reports which focused on short high-power adiabatic pulses and relaxation that is governed by dipole-dipole interactions, cross polarization, or chemical exchange.

Solid state 13 C NMR quantitative study of wood tar pitches

International Nuclear Information System (INIS)

Prauchner, Marcos Juliano; Pasa, Vanya Marcia Duarte; Menezes, Sonia Maria Cabral de

1999-01-01

In this work, solid-state 13 C NMR is used with other techniques to characterize Eucalyptus tar pitches and to follow their polymerization reactions. The pitches are the residues of distillation (about 50% m;m) of the tar generated in Eucalyptus slow pyrolysis for charcoal production in metal industry

Investigation of the proteins relaxation time in human blood serum; Badania relaksacyjne bialek surowicy krwi II

Energy Technology Data Exchange (ETDEWEB)

Blicharska, B.; Klauza, M. [Inst. Fizyki, Uniwersytet Jagiellonski, Cracow (Poland); Kuliszkiewicz-Janus, M. [Akademia Medyczna, Wroclaw (Poland)

1994-12-31

In this paper the results of human blood serum proteins relaxation time measurements by means of NMR method are presented. The measurements have been done for three samples of human blood: i/laudably ii/leukemia iii/granulomas. The dependences of the relaxation time on the temperature are also presented. 3 refs, 4 figs.

Interaction study of polyisobutylene with paraffins by NMR using the evaluation of spin-lattice relaxation times for hydrogen nuclei; Estudo da interacao do poliisobutileno com parafinas por RMN no estado solido

Energy Technology Data Exchange (ETDEWEB)

Marques, Rosana G.G. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas - CENPES]. E-mail: garrido@cenpes.petrobras.com.br; Tavares, Maria I.B. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Inst. de Macromoleculas]. E-mail: mibt@ima.ufrj.br

2001-07-01

The evaluation of spin-lattice relaxation times of {sup 1}H for polyisobutylene/paraffin systems, were obtained using the classic inversion recovery technique, and also through Cross Polarization Magic Angle Spinning (CP/MAS) techniques varying the contact time and also by the delayed contact time pulse sequence. NMR results showed that the polyisobutylene/paraffin systems in which high molecular weight paraffins were used, is heterogeneous. However, for paraffins with low molecular weight, the system presents good homogeneity. (author)

Fluorine dynamics in BaF{sub 2} superionic conductors investigated by NMR

Energy Technology Data Exchange (ETDEWEB)

Gumann, Patryk

2008-07-01

In this work the dynamics of fluorine in solid-state electrolytes having BaF{sub 2}-structure was investigated using three different NMR-methods: field cycling relaxometry, lineshape analysis, and static field gradient NMR. For this purpose a pure BaF{sub 2} crystal, as well as crystals doped with trivalent impurities (LaF{sub 3}), were studied as a function of temperature. Using MAS NMR it was possible to identify two lines in Ba{sub 0.9}La{sub 0.1}F{sub 2.1} having different chemical shift, and to refer them to the modified crystal structure. On this basis a model for the fluorine lineshape has been developed, taking into account three motional processes characterized by their correlation times. It includes jump diffusion of the fluorine ions among equivalent sites within two crystallographically distinct sublattices, and inter-lattice exchange processes. By measuring frequency and temperature-dependent spin lattice relaxation times, it was possible to gain information about fluorine dynamics on microscopic length scales. An attempt was also made to analyze the data for pure BaF{sub 2} and low admixture concentration samples with a non-exponential correlation function. (orig.)

Joint inversion of NMR and SIP data to estimate pore size distribution of geomaterials

Science.gov (United States)

Niu, Qifei; Zhang, Chi

2018-03-01

There are growing interests in using geophysical tools to characterize the microstructure of geomaterials because of the non-invasive nature and the applicability in field. In these applications, multiple types of geophysical data sets are usually processed separately, which may be inadequate to constrain the key feature of target variables. Therefore, simultaneous processing of multiple data sets could potentially improve the resolution. In this study, we propose a method to estimate pore size distribution by joint inversion of nuclear magnetic resonance (NMR) T2 relaxation and spectral induced polarization (SIP) spectra. The petrophysical relation between NMR T2 relaxation time and SIP relaxation time is incorporated in a nonlinear least squares problem formulation, which is solved using Gauss-Newton method. The joint inversion scheme is applied to a synthetic sample and a Berea sandstone sample. The jointly estimated pore size distributions are very close to the true model and results from other experimental method. Even when the knowledge of the petrophysical models of the sample is incomplete, the joint inversion can still capture the main features of the pore size distribution of the samples, including the general shape and relative peak positions of the distribution curves. It is also found from the numerical example that the surface relaxivity of the sample could be extracted with the joint inversion of NMR and SIP data if the diffusion coefficient of the ions in the electrical double layer is known. Comparing to individual inversions, the joint inversion could improve the resolution of the estimated pore size distribution because of the addition of extra data sets. The proposed approach might constitute a first step towards a comprehensive joint inversion that can extract the full pore geometry information of a geomaterial from NMR and SIP data.

Introduction to quantum calculation methods in high resolution NMR

International Nuclear Information System (INIS)

Goldman, M.

1996-01-01

New techniques as for instance the polarization transfer, the coherence with several quanta and the double Fourier transformation have appeared fifteen years ago. These techniques constitute a considerable advance in NMR. Indeed, they allow to study more complex molecules than it was before possible. But with these advances, the classical description of the NMR is not enough to understand precisely the physical phenomena induced by these methods. It is then necessary to resort to quantum calculation methods. The aim of this work is to present these calculation methods. After some recalls of quantum mechanics, the author describes the NMR with the density matrix, reviews the main methods of double Fourier transformation and then gives the principle of the relaxation times calculation. (O.M.)

NMR measurement of bitumen at different temperatures.

Science.gov (United States)

Yang, Zheng; Hirasaki, George J

2008-06-01

Heavy oil (bitumen) is characterized by its high viscosity and density, which is a major obstacle to both well logging and recovery. Due to the lost information of T2 relaxation time shorter than echo spacing (TE) and interference of water signal, estimation of heavy oil properties from NMR T2 measurements is usually problematic. In this work, a new method has been developed to overcome the echo spacing restriction of NMR spectrometer during the application to heavy oil (bitumen). A FID measurement supplemented the start of CPMG. Constrained by its initial magnetization (M0) estimated from the FID and assuming log normal distribution for bitumen, the corrected T2 relaxation time of bitumen sample can be obtained from the interpretation of CPMG data. This new method successfully overcomes the TE restriction of the NMR spectrometer and is nearly independent on the TE applied in the measurement. This method was applied to the measurement at elevated temperatures (8-90 degrees C). Due to the significant signal-loss within the dead time of FID, the directly extrapolated M0 of bitumen at relatively lower temperatures (viscosity, the extrapolated M0 of bitumen at over 60 degrees C can be reasonably assumed to be the real value. In this manner, based on the extrapolation at higher temperatures (> or = 60 degrees C), the M0 value of bitumen at lower temperatures (index (HI), fluid content and viscosity were evaluated by using corrected T2.

Powder-XRD and (14) N magic angle-spinning solid-state NMR spectroscopy of some metal nitrides.

Science.gov (United States)

Kempgens, Pierre; Britton, Jonathan

2016-05-01

Some metal nitrides (TiN, ZrN, InN, GaN, Ca3 N2 , Mg3 N2 , and Ge3 N4 ) have been studied by powder X-ray diffraction (XRD) and (14) N magic angle-spinning (MAS) solid-state NMR spectroscopy. For Ca3 N2 , Mg3 N2 , and Ge3 N4 , no (14) N NMR signal was observed. Low speed (νr  = 2 kHz for TiN, ZrN, and GaN; νr  = 1 kHz for InN) and 'high speed' (νr  = 15 kHz for TiN; νr  = 5 kHz for ZrN; νr  = 10 kHz for InN and GaN) MAS NMR experiments were performed. For TiN, ZrN, InN, and GaN, powder-XRD was used to identify the phases present in each sample. The number of peaks observed for each sample in their (14) N MAS solid-state NMR spectrum matches perfectly well with the number of nitrogen-containing phases identified by powder-XRD. The (14) N MAS solid-state NMR spectra are symmetric and dominated by the quadrupolar interaction. The envelopes of the spinning sidebands manifold are Lorentzian, and it is concluded that there is a distribution of the quadrupolar coupling constants Qcc 's arising from structural defects in the compounds studied. Copyright © 2015 John Wiley & Sons, Ltd.

Using NMR decay-time measurements to monitor and characterize DNAPL and moisture in subsurface porous media

International Nuclear Information System (INIS)

Timothy A. White; Russel C. Hertzog; Christian Straley

2007-01-01

Knowing how environmental properties affect dense nonaqueous phase liquid (DNAPL) solvent flow in the subsurface is essential for developing models of flow and transport in the vadose zone necessary for designing remediation and long-term stewardship strategies. For example, one must know if solvents are flowing in water-wetted or solvent-wetted environments, the pore-size distribution of the region containing DNAPLs, and the impact of contaminated plumes and their transport mechanisms in porous media. Our research investigates the capability and limitations of low-field proton nuclear magnetic resonance (NMR) relaxation decay-rate measurements for determining environmental properties affecting DNAPL solvent flow in the subsurface. The measurements that can be performed with the laboratory low-field system can also be performed in situ in the field with the current generation of commercial borehole logging tools. The oil and gas industry uses NMR measurements in deep subsurface, consolidated formations to determine porosity and hydrocarbon content and to estimate formation permeability. These determinations rely on the ability of NMR to distinguish between water and hydrocarbons in the pore space and to obtain the distribution of pore sizes from relaxation decay-rate distributions. In this paper we will show how NMR measurement techniques can be used to characterize, monitor, and evaluate the dynamics of mixed-fluids (water-DNAPL) in unconsolidated near-surface porous environments and describe the use of proton NMR T2 (spin-spin relaxation time) measurements in unconsolidated sandy-soil samples to identify and characterize the presence of DNAPLs in these environments. The potential of NMR decay-rate distributions for characterizing DNAPL fluids in the subsurface and understanding their flow mechanisms has not previously been exploited; however, near-surface unsaturated vadose zone environments do provide unique challenges for using NMR measurements. These

Non-Invasive Detection of Adulterated Olive Oil in Full Bottles Using Time-Domain NMR Relaxometry

OpenAIRE

Santos, Poliana M.; Kock, Flávio Vinicius C.; Santos, Maiara S.; Lobo, Carlos Manuel S.; Carvalho, André S.; Colnago, Luiz Alberto

2017-01-01

A fast procedure using time-domain nuclear magnetic resonance (TD-NMR) to detect olive oil adulteration with polyunsaturated vegetable oils in filled bottles is proposed. The 1H transverse relaxation times (T2) of 37 commercial samples were measured using low-field nuclear magnetic resonance (LF-NMR) spectrometer and a unilateral nuclear magnetic resonance (UNMR) sensor. Results obtained with LF-NMR revealed better feasibility when compared with the UNMR sensor, with higher signal-to-noise (S...

Effect of two yoga-based relaxation techniques on memory scores and state anxiety

Directory of Open Access Journals (Sweden)

Telles Shirley

2009-08-01

Full Text Available Abstract Background A yoga practice involving cycles of yoga postures and supine rest (called cyclic meditation was previously shown to improve performance in attention tasks more than relaxation in the corpse posture (shavasana. This was ascribed to reduced anxiety, though this was not assessed. Methods In fifty-seven male volunteers (group average age ± S.D., 26.6 ± 4.5 years the immediate effect of two yoga relaxation techniques was studied on memory and state anxiety. All participants were assessed before and after (i Cyclic meditation (CM practiced for 22:30 minutes on one day and (ii an equal duration of Supine rest (SR or the corpse posture (shavasana, on another day. Sections of the Wechsler memory scale (WMS were used to assess; (i attention and concentration (digit span forward and backward, and (ii associate learning. State anxiety was assessed using Spielberger's State-Trait Anxiety Inventory (STAI. Results There was a significant improvement in the scores of all sections of the WMS studied after both CM and SR, but, the magnitude of change was more after CM compared to after SR. The state anxiety scores decreased after both CM and SR, with a greater magnitude of decrease after CM. There was no correlation between percentage change in memory scores and state anxiety for either session. Conclusion A cyclical combination of yoga postures and supine rest in CM improved memory scores immediately after the practice and decreased state anxiety more than rest in a classical yoga relaxation posture (shavasana.

27Al NMR studies of NpPd5Al2

International Nuclear Information System (INIS)

Chudo, H.; Sakai, H.; Tokunaga, Y.; Kambe, S.; Aoki, D.; Homma, Y.; Shiokawa, Y.; Haga, Y.; Ikeda, S.; Matsuda, T.D.; Onuki, Y.; Yasuoka, H.

2009-01-01

We present 27 Al NMR studies for a single crystal of the Np-based superconductor NpPd 5 Al 2 (T c =4.9K). We have observed a five-line 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 c . The temperature dependence of the 27 Al nuclear spin-lattice relaxation rate shows no coherence peak below T c , indicating that NpPd 5 Al 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 5 Al 2 .

Exploring translocation of proteins on DNA by NMR

International Nuclear Information System (INIS)

Marius Clore, G.

2011-01-01

While an extensive body of knowledge has accumulated on the structures of transcription factors, DNA and their complexes from both NMR and crystallography, much less is known at a molecular level regarding the mechanisms whereby transcription factors locate their specific DNA target site within an overwhelming sea of non-specific DNA sites. Indirect kinetic data suggested that three processes are involved in the search procedure: jumping by dissociation of the protein from the DNA followed by re-association at another site, direct transfer from one DNA molecule or segment to another, and one-dimensional sliding. In this brief perspective I summarize recent NMR developments from our laboratory that have permitted direct characterization of the species and molecular mechanisms involved in the target search process, including the detection of highly transient sparsely-populated states. The main tool in these studies involves the application of paramagnetic relaxation enhancement, supplemented by z-exchange spectroscopy, lineshape analysis and residual dipolar couplings. These studies led to the first direct demonstration of rotation-coupled sliding of a protein along the DNA and the direct transfer of a protein from one DNA molecule to another without dissociating into free solution.

Study of molecular movements in some organic crystals by NMR

International Nuclear Information System (INIS)

Alexandre, M.

1971-01-01

After a discussion on molecular crystals (generalities, movements within molecular solids, study of movements, complexes by charge transfer) and some specific ones (molecular complexes of trinitrobenzene or TNB), this research thesis reports the use of nuclear magnetic resonance (NMR) to study molecular movements: generalities on broadband NMR, spin relaxation and strong field network, observation of the absorption signal and measurement of the second moment. The last part reports and discusses experimental results obtained on TNB-naphthalene, on TNB-azulene, on TNB-benzothiophene, and on TNB-indole

Peptidoglycan architecture of Gram-positive bacteria by solid-state NMR.

Science.gov (United States)

Kim, Sung Joon; Chang, James; Singh, Manmilan

2015-01-01

Peptidoglycan is an essential component of cell wall in Gram-positive bacteria with unknown architecture. In this review, we summarize solid-state NMR approaches to address some of the unknowns in the Gram-positive bacteria peptidoglycan architecture: 1) peptidoglycan backbone conformation, 2) PG-lattice structure, 3) variations in the peptidoglycan architecture and composition, 4) the effects of peptidoglycan bridge-length on the peptidoglycan architecture in Fem mutants, 5) the orientation of glycan strands with respect to the membrane, and 6) the relationship between the peptidoglycan structure and the glycopeptide antibiotic mode of action. Solid-state NMR analyses of Staphylococcus aureus cell wall show that peptidoglycan chains are surprisingly ordered and densely packed. The peptidoglycan disaccharide backbone adopts 4-fold screw helical symmetry with the disaccharide unit periodicity of 40Å. Peptidoglycan lattice in the S. aureus cell wall is formed by cross-linked PG stems that have parallel orientations. The structural characterization of Fem-mutants of S. aureus with varying lengths of bridge structures suggests that the PG-bridge length is an important determining factor for the PG architecture. Copyright © 2014 Elsevier B.V. All rights reserved.

Structure and dynamics of paramagnetic transients by pulsed EPR and NMR detection of nuclear resonance

International Nuclear Information System (INIS)

Trifunac, A.D.

1981-01-01

Structure and dynamics of transient radicals in pulse radiolysis can be studied by time resolved EPR and NMR techniques. EPR study of kinetics and relaxation is illustrated. The NMR detection of nuclear resonance in transient radicals is a new method which allows the study of hyperfine coupling, population dynamics, radical kinetics, and reaction mechanism. 9 figures

NMR relaxation studies with MnDPDP

International Nuclear Information System (INIS)

Southon, T.E.; Grant, D.; Bjoernerud, A.; Moen, O.M.; Spilling, B.; Martinsen, I.; Refsum, H.

1997-01-01

Purpose: Our studies were designed to compare the efficacy of mangafodipir trisodium (MnDPDP, Teslascan) as a tissue-specific MR agent with that of manganese chloride (MnCl 2 ), to compare the efficacy of different doses and rates of administration of MnDPDP, and to collect the data needed for predicting optimum pulse sequences. Material and Methods: The dose response for the relaxation rates R1 and R2 at 0.47 T, and the manganese (Mn) concentrations in rat liver and in the liver, pancreas, heart and adrenals of pigs was determined for both MnDPDP and MnCl 2 administered i.v. Computer simulations were carried out to model the effects of different tissue Mn concentrations and TR on signal intensities and contrast-to-noise ratios. Results: In rat liver and pig organs both compounds produced a positive dose-response in R1 and tissue Mn concentration, and only small or no response in R2. The Mn concentration in rat liver was positively correlated with R1, regardless of the form in which Mn was given, or the rate of administration. Optimal imaging parametes are therefore expected to be different pre- and post-MnDPDP administration. (orig./AJ)

Relaxation height in energy landscapes : an application to multiple metastable states

NARCIS (Netherlands)

Cirillo, E.N.M.; Nardi, F.R.

2012-01-01

The study of systems with multiple (not necessarily degenerate) metastable states presents subtle difficulties from the mathematical point of view related to the variational problem that has to be solved in these cases. We introduce the notion of relaxation height in a general energy landscape and

High resolution NMR spectroscopy of synthetic polymers in bulk

International Nuclear Information System (INIS)

Komorski, R.A.

1986-01-01

The contents of this book are: Overview of high-resolution NMR of solid polymers; High-resolution NMR of glassy amorphous polymers; Carbon-13 solid-state NMR of semicrystalline polymers; Conformational analysis of polymers of solid-state NMR; High-resolution NMR studies of oriented polymers; High-resolution solid-state NMR of protons in polymers; and Deuterium NMR of solid polymers. This work brings together the various approaches for high-resolution NMR studies of bulk polymers into one volume. Heavy emphasis is, of course, given to 13C NMR studies both above and below Tg. Standard high-power pulse and wide-line techniques are not covered

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

International Nuclear Information System (INIS)

Furuita, Kyoko; Kataoka, Saori; Sugiki, Toshihiko; Hattori, Yoshikazu; Kobayashi, Naohiro; Ikegami, Takahisa; Shiozaki, Kazuhiro; Fujiwara, Toshimichi; Kojima, Chojiro

2015-01-01

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

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.

Determining the structural relaxation times deep in the glassy state of the pharmaceutical Telmisartan

Energy Technology Data Exchange (ETDEWEB)

Adrjanowicz, K; Paluch, M [Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Ngai, K L [Naval Research Laboratory, Washington, DC 20375-5320 (United States)

2010-03-31

By using the dielectric relaxation method proposed recently by Casalini and Roland (2009 Phys. Rev. Lett. 102 035701), we were able to determine the structural alpha-relaxation times deep in the glassy state of the pharmaceutical, Telmisartan. Normally, deep in the glassy state tau{sub a}lpha is so long that it cannot be measured but tau{sub b}eta, which is usually much shorter, can be directly determined. The method basically takes advantage of the connection between the alpha-relaxation and the secondary beta-relaxation of the Johari-Goldstein kind, including a relation between their relaxation times tau{sub a}lpha and tau{sub b}eta, respectively. Thus, tau{sub a}lpha of Telmisartan were determined by monitoring the change of the dielectric beta-loss, epsilon'', with physical aging time at temperatures well below the vitrification temperature. The values of tau{sub a}lpha were compared with those expected by the coupling model (CM). Unequivocal comparison cannot be made in the case of Telmisartan because its beta-loss peak is extremely broad, and the CM predicts only an order of magnitude agreement between the primitive relaxation frequency and the beta-peak frequency. We also made an attempt to analyze all isothermal and aging susceptibility data after transformation into the electric modulus representation. The tau{sub a}lpha found in the glass state by using the method of Casalini and Roland in the modulus representation are similar to those obtained in the susceptibility representation. However, it is remarkable that the stretching parameter beta{sub KWWM} = 0.51 in the electric modulus representation gives more precise fits to the aging data than in the susceptibility representation with beta{sub KWW} = 0.61. Our results suggest that the electric modulus representation may be useful as an alternative to analyze aging data, especially in the case of highly polar glassformers having a large ratio of low frequency and high frequency dielectric

Time domain NMR evaluation of poly(vinyl alcohol) xerogels

Energy Technology Data Exchange (ETDEWEB)

Rodrigues, Elton Jorge da Rocha; Cavalcante, Maxwell de Paula; Tavares, Maria Ines Bruno, E-mail: mibt@ima.ufrj.br [Universidade Federal do Rio de Janeiro (IMA/UFRJ), Rio de Janeiro, RJ (Brazil). Centro de Tecnologia. Instituto de Macromoleculas Professora Eloisa Mano

2016-05-15

Poly(vinyl alcohol) (PVA)-based chemically cross-linked xerogels, both neat and loaded with nanoparticulate hydrophilic silica (SiO{sub 2}), were obtained and characterized mainly through time domain NMR experiments (TD-NMR). Fourier-transform infrared (FT-IR) and wide angle X-ray diffraction (WAXD) analyses were employed as secondary methods. TD-NMR, through the interpretation of the spin-lattice relaxation constant values and related information, showed both cross-linking and nanoparticle influences on PVA matrix. SiO{sub 2} does not interact chemically with the PVA chains, but has effect on its molecular mobility, as investigated via TD-NMR. Apparent energy of activation, spin-lattice time constant and size of spin domains in the sample have almost linear dependence with the degree of cross-linking of the PVA and are affected by the addition of SiO{sub 2}. These three parameters were derived from a single set of TD-NMR experiments, which demonstrates the versatility of the technique for characterization of inorganic-organic hybrid xerogels, an important class of materials. (author)

The GNAT: A new tool for processing NMR data.

Science.gov (United States)

Castañar, Laura; Poggetto, Guilherme Dal; Colbourne, Adam A; Morris, Gareth A; Nilsson, Mathias

2018-06-01

The GNAT (General NMR Analysis Toolbox) is a free and open-source software package for processing, visualising, and analysing NMR data. It supersedes the popular DOSY Toolbox, which has a narrower focus on diffusion NMR. Data import of most common formats from the major NMR platforms is supported, as well as a GNAT generic format. Key basic processing of NMR data (e.g., Fourier transformation, baseline correction, and phasing) is catered for within the program, as well as more advanced techniques (e.g., reference deconvolution and pure shift FID reconstruction). Analysis tools include DOSY and SCORE for diffusion data, ROSY T 1 /T 2 estimation for relaxation data, and PARAFAC for multilinear analysis. The GNAT is written for the MATLAB® language and comes with a user-friendly graphical user interface. The standard version is intended to run with a MATLAB installation, but completely free-standing compiled versions for Windows, Mac, and Linux are also freely available. © 2018 The Authors Magnetic Resonance in Chemistry Published by John Wiley & Sons Ltd.

Structural characterization of supramolecular assemblies by {sup 13}C spin dilution and 3D solid-state NMR

Energy Technology Data Exchange (ETDEWEB)

Habenstein, Birgit; Loquet, Antoine; Giller, Karin; Becker, Stefan; Lange, Adam, E-mail: adla@nmr.mpibpc.mpg.de [Max Planck Institute for Biophysical Chemistry, Department of NMR-based Structural Biology (Germany)

2013-01-15

{sup 13}C spin diluted protein samples can be produced using [1-{sup 13}C] and [2-{sup 13}C]-glucose (Glc) carbon sources in the bacterial growth medium. The {sup 13}C spin dilution results in favorable {sup 13}C spectral resolution and polarization transfer behavior. We recently reported the combined use of [1-{sup 13}C]- and [2-{sup 13}C]-Glc labeling to facilitate the structural analysis of insoluble and non-crystalline biological systems by solid-state NMR (ssNMR), including sequential assignment, detection of long-range contacts and structure determination of macromolecular assemblies. In solution NMR the beneficial properties of sparsely labeled samples using [2-{sup 13}C]-glycerol ({sup 13}C labeled C{alpha} sites on a {sup 12}C diluted background) have recently been exploited to provide a bi-directional assignment method (Takeuchi et al. in J Biomol NMR 49(1):17-26, 2011 ). Inspired by this approach and our own recent results using [2-{sup 13}C]-Glc as carbon sources for the simplification of ssNMR spectra, we present a strategy for a bi-directional sequential assignment of solid-state NMR resonances and additionally the detection of long-range contacts using the combination of {sup 13}C spin dilution and 3D NMR spectroscopy. We illustrate our results with the sequential assignment and the collection of distance restraints on an insoluble and non-crystalline supramolecular assembly, the Salmonella typhimurium type III secretion system needle.

Fast hydrogen exchange affects 15N relaxation measurements in intrinsically disordered proteins

International Nuclear Information System (INIS)

Kim, Seho; Wu, Kuen-Phon; Baum, Jean

2013-01-01

Unprotected amide protons can undergo fast hydrogen exchange (HX) with protons from the solvent. Generally, NMR experiments using the out-and-back coherence transfer with amide proton detection are affected by fast HX and result in reduced signal intensity. When one of these experiments, 1 H– 15 N HSQC, is used to measure the 15 N transverse relaxation rate (R 2 ), the measured R 2 rate is convoluted with the HX rate (k HX ) and has higher apparent R 2 values. Since the 15 N R 2 measurement is important for analyzing protein backbone dynamics, the HX effect on the R 2 measurement is investigated and described here by multi-exponential signal decay. We demonstrate these effects by performing 15 N R 2 CPMG experiments on α-synuclein, an intrinsically disordered protein, in which the amide protons are exposed to solvent. We show that the HX effect on R 2 CPMG can be extracted by the derived equation. In conclusion, the HX effect may be pulse sequence specific and results from various sources including the J coupling evolution, the change of steady state water proton magnetization, and the D 2 O content in the sample. To avoid the HX effect on the analysis of relaxation data of unprotected amides, it is suggested that NMR experimental conditions insensitive to the HX should be considered or that intrinsic R 2 CPMG values be obtained by methods described herein.

Parallel β-Sheet Structure of Alanine Tetrapeptide in the Solid State As Studied by Solid-State NMR Spectroscopy.

Science.gov (United States)

Asakura, Tetsuo; Horiguchi, Kumiko; Aoki, Akihiro; Tasei, Yugo; Naito, Akira

2016-09-01

The structural analysis of alanine oligopeptides is important for understanding the crystalline region in silks from spiders and wild silkworms and also the mechanism of cellular toxicity of human diseases arising from expansion in polyalanine sequences. The atomic-level structures of alanine tripeptide and tetrapeptide with antiparallel β-sheet structures (AP-Ala3 and AP-Ala4, respectively) together with alanine tripeptide with parallel β-sheet structures (P-Ala3) have been determined, but alanine tetrapeptide with a parallel β-sheet structure (P-Ala4) has not been reported yet. In this article, first, we established the preparation protocol of P-Ala4 from more stable AP-Ala4. Second, complete assignments of the (13)C, (15)N, and (1)H solid-state NMR spectra were performed with (13)C- and (15)N-labeled Ala4 samples using several solid-state NMR techniques. Then, the structural constraints were obtained, for example, the amide proton peaks of P-Ala4 in the (1)H double-quantum magic-angle spinning NMR spectrum were heavily overlapped and observed at about 7.4 ppm, which was a much higher field than that of 8.7-9.1 ppm observed for AP-Ala4, indicating that the intermolecular hydrogen-bond lengths across strands (N-H···O═C) were considerably longer for P-Ala4, that is, 2.21-2.34 Å, than those reported for AP-Ala4, that is, 1.8-1.9 Å. The structural model was proposed for P-Ala4 by NMR results and MD calculations.

The in-vitro study of human blood leukemic cells by pulsed NMR

International Nuclear Information System (INIS)

Zulkarnaen, M.; Munawir; Wibowo, Tono; Suyitno, Gogot

1983-01-01

The diagram of leukemic cells in human blood has been studied by using the NMR longitudinal relaxation technique. The observation was treated in whole blood, serum and blood cell. Every result was compared with previous observation and show that the values of the proton longitudinal relaxation in the leukemic whole blood almost twice or more that of normal blood, while in the serum and the blood cell, the values are nearly the same. (author)

Describing the anisotropic 133Cs solid state NMR interactions in cesium chromate

Czech Academy of Sciences Publication Activity Database

Czernek, Jiří; Brus, Jiří

2017-01-01

Roč. 684, 16 September (2017), s. 8-13 ISSN 0009-2614 R&D Projects: GA MŠk(CZ) LO1507 Institutional support: RVO:61389013 Keywords : NMR * DFT * solid state Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 1.815, year: 2016

QM/MM studies on the excited-state relaxation mechanism of a semisynthetic dTPT3 base.

Science.gov (United States)

Guo, Wei-Wei; Zhang, Teng-Shuo; Fang, Wei-Hai; Cui, Ganglong

2018-02-14

Semisynthetic alphabets can potentially increase the genetic information stored in DNA through the formation of unusual base pairs. Recent experiments have shown that near-visible-light irradiation of the dTPT3 chromophore could lead to the formation of a reactive triplet state and of singlet oxygen in high quantum yields. However, the detailed excited-state relaxation paths that populate the lowest triplet state are unclear. Herein, we have for the first time employed the QM(MS-CASPT2//CASSCF)/MM method to explore the spectroscopic properties and excited-state relaxation mechanism of the aqueous dTPT3 chromophore. On the basis of the results, we have found that (1) the S 2 ( 1 ππ*) state of dTPT3 is the initially populated excited singlet state upon near-visible light irradiation; and (2) there are two efficient relaxation pathways to populate the lowest triplet state, i.e. T 1 ( 3 ππ*). In the first one, the S 2 ( 1 ππ*) system first decays to the S 1 ( 1 nπ*) state near the S 2 /S 1 conical intersection, which is followed by an efficient S 1 → T 1 intersystem crossing process at the S 1 /T 1 crossing point; in the second one, an efficient S 2 → T 2 intersystem crossing takes place first, and then, the T 2 ( 3 nπ*) system hops to the T 1 ( 3 ππ*) state through an internal conversion process at the T 2 /T 1 conical intersection. Moreover, an S 2 /S 1 /T 2 intersection region is found to play a vital role in the excited-state relaxation. These new mechanistic insights help in understanding the photophysics and photochemistry of unusual base pairs.

Markov state modeling and dynamical coarse-graining via discrete relaxation path sampling.

Science.gov (United States)

Fačkovec, B; Vanden-Eijnden, E; Wales, D J

2015-07-28

A method is derived to coarse-grain the dynamics of complex molecular systems to a Markov jump process (MJP) describing how the system jumps between cells that fully partition its state space. The main inputs are relaxation times for each pair of cells, which are shown to be robust with respect to positioning of the cell boundaries. These relaxation times can be calculated via molecular dynamics simulations performed in each cell separately and are used in an efficient estimator for the rate matrix of the MJP. The method is illustrated through applications to Sinai billiards and a cluster of Lennard-Jones discs.

Structure of the two-dimensional relaxation spectra seen within the eigenmode perturbation theory and the two-site exchange model.

Science.gov (United States)

Bytchenkoff, Dimitri; Rodts, Stéphane

2011-01-01

The form of the two-dimensional (2D) NMR-relaxation spectra--which allow to study interstitial fluid dynamics in diffusive systems by correlating spin-lattice (T(1)) and spin-spin (T(2)) relaxation times--has given rise to numerous conjectures. Herein we find analytically a number of fundamental structural properties of the spectra: within the eigen-modes formalism, we establish relationships between the signs and intensities of the diagonal and cross-peaks in spectra obtained by various 1 and 2D NMR-relaxation techniques, reveal symmetries of the spectra and uncover interdependence between them. We investigate more specifically a practically important case of porous system that has sets of T(1)- and T(2)-eigenmodes and eigentimes similar to each other by applying the perturbation theory. Furthermore we provide a comparative analysis of the application of the, mathematically more rigorous, eigen-modes formalism and the, rather more phenomenological, first-order two-site exchange model to diffusive systems. Finally we put the results that we could formulate analytically to the test by comparing them with computer-simulations for 2D porous model systems. The structural properties, in general, are to provide useful clues for assignment and analysis of relaxation spectra. The most striking of them--the presence of negative peaks--underlines an urgent need for improvement of the current 2D Inverse Laplace Transform (ILT) algorithm used for calculation of relaxation spectra from NMR raw data. Copyright © 2010 Elsevier Inc. All rights reserved.

Ultra-Low Field SQUID-NMR using LN2 Cooled Cu Polarizing Field coil

Science.gov (United States)

Demachi, K.; Kawagoe, S.; Ariyoshi, S.; Tanaka, S.

2017-07-01

We are developing an Ultra-Low Field (ULF) Magnetic Resonance Imaging (MRI) system using a High-Temperature Superconductor superconducting quantum interference device (HTS rf-SQUID) for food inspection. The advantages of the ULF-NMR (Nuclear Magnetic Resonance) / MRI as compared with a conventional high field MRI are that they are compact and of low cost. In this study, we developed a ULF SQUID-NMR system using a polarizing coil to measure fat of which relaxation time T1 is shorter. The handmade polarizing coil was cooled by liquid nitrogen to reduce the resistance and accordingly increase the allowable current. The measured decay time of the polarizing field was 40 ms. The measurement system consisted of the liquid nitrogen cooled polarizing coil, a SQUID, a Cu wound flux transformer, a measurement field coil for the field of 47 μT, and an AC pulse coil for a 90°pulse field. The NMR measurements were performed in a magnetically shielded room to reduce the environmental magnetic field. The size of the sample was ϕ35 mm × L80 mm. After applying a polarizing field and a 90°pulse, an NMR signal was detected by the SQUID through the flux transformer. As a result, the NMR spectra of fat samples were obtained at 2.0 kHz corresponding to the measurement field Bm of 47 μT. The T1 relaxation time of the mineral oil measured in Bm was 45 ms. These results suggested that the ULF-NMR/MRI system has potential for food inspection.

Structural analysis of alanine tripeptide with antiparallel and parallel beta-sheet structures in relation to the analysis of mixed beta-sheet structures in Samia cynthia ricini silk protein fiber using solid-state NMR spectroscopy.

Science.gov (United States)

Asakura, Tetsuo; Okonogi, Michi; Nakazawa, Yasumoto; Yamauchi, Kazuo

2006-05-10

The structural analysis of natural protein fibers with mixed parallel and antiparallel beta-sheet structures by solid-state NMR is reported. To obtain NMR parameters that can characterize these beta-sheet structures, (13)C solid-state NMR experiments were performed on two alanine tripeptide samples: one with 100% parallel beta-sheet structure and the other with 100% antiparallel beta-sheet structure. All (13)C resonances of the tripeptides could be assigned by a comparison of the methyl (13)C resonances of Ala(3) with different [3-(13)C]Ala labeling schemes and also by a series of RFDR (radio frequency driven recoupling) spectra observed by changing mixing times. Two (13)C resonances observed for each Ala residue could be assigned to two nonequivalent molecules per unit cell. Differences in the (13)C chemical shifts and (13)C spin-lattice relaxation times (T(1)) were observed between the two beta-sheet structures. Especially, about 3 times longer T(1) values were obtained for parallel beta-sheet structure as compared to those of antiparallel beta-sheet structure, which could be explicable by the difference in the hydrogen-bond networks of both structures. This very large difference in T(1) becomes a good measure to differentiate between parallel or antiparallel beta-sheet structures. These differences in the NMR parameters found for the tripeptides may be applied to assign the parallel and antiparallel beta-sheet (13)C resonances in the asymmetric and broad methyl spectra of [3-(13)C]Ala silk protein fiber of a wild silkworm, Samia cynthia ricini.

Solid state NMR, basic theory and recent progress for quadrupole nuclei with half-integer spin

International Nuclear Information System (INIS)

Dieter, F.

1998-01-01

This review describes the basic theory and some recently developed techniques for the study of quadrupole nuclei with half integer spins in powder materials. The latter is connected to the introduction of the double rotation (DOR) by A. Samoson et al. (1) and to the introduction of the multiple quantum magic-angle spinning (MQ MAS) technique by L. Frydman et. al. (2). For integer spins, especially the solid-state deuterium magnetic resonance, we refer to the review of G.L. Hoatson and R.L. Vold: '' 2 H-NMR Spectroscopy of Solids and Liquid Crystals'' (3). For single crystals we refer to O. Kanert and M. Mehring: ''Static quadrupole effects in disordered cubic solids''(4) and we would like also to mention the ''classic'' review of M.H. Cohen and F. Reif: ''Quadrupole effects in NMR studies of solids'' (5). Some more recent reviews in the field under study are D. Freude and J. Haase ''Quadrupole effects in solid-state NMR'' (6). Ch. Jager: ''Satellite Transition Spectroscopy of Quadrupolar Nuclei'' (7) and B.F. Chmelka and J.W. Zwanziger: ''Solid State NMR Line Narrowing Methods for Quadrupolar Nuclei - Double Rotation and Dynamic-Angle Spinning'' (8). A survey of nuclear quadrupole frequency data published before the end of 1982 is given by H. Chihara and N. Nakamura in Landolt-Bornstein, Vol. 20 (9). Values of the chemical shift of quadrupole nuclei in solids can be found in books such as ''Multinuclear NMR'' edited by J. Mason (10). In section 9 of ref (6) some electric field gradient and chemical shift data published from 1983 to 1992 for the most studied quadrupole nuclei sup 27 Al, sup 23 Na, and sup 17 O are given

Nuclear magnetic resonance relaxation times for human lung cancer and lung tissues

International Nuclear Information System (INIS)

Matsuura, Yoshifumi; Shioya, Sumie; Kurita, Daisaku; Ohta, Takashi; Haida, Munetaka; Ohta, Yasuyo; Suda, Syuichi; Fukuzaki, Minoru.

1994-01-01

We investigated the nuclear magnetic resonance (NMR) relaxation times, T 1 and T 2 , for lung cancer tissue, and other samples of lung tissue obtained from surgical specimens. The samples were nine squamous cell carcinomas, five necrotic squamous cell carcinomas, 15 adenocarcinomas, two benign mesotheliomas, and 13 fibrotic lungs. The relaxation times were measured with a 90 MHz NMR spectrometer and the results were correlated with histological changes. The values of T 1 and T 2 for squamous cell carcinoma and mesothelioma were significantly longer than those of adenocarcinoma and fibrotic lung tissue. There were no significant differences in values of T 1 and T 2 between adenocarcinoma and lung tissue. The values of T 1 and T 2 for benign mesothelioma were similar to those of squamous cell carcinoma, which suggested that increases in T 1 and T 2 are not specific to malignant tissues. (author)

Thermal Fluctuations in the Magnetic Ground State of the Molecular Cluster Mn12O12 Acetate from μSR and Proton NMR Relaxation

International Nuclear Information System (INIS)

Lascialfari, A.; Borsa, F.; Carretta, P.; Jang, Z.H.; Borsa, F.; Gatteschi, D.

1998-01-01

Measurements of the spin-lattice relaxation rate are reported for muons and protons as a function of temperature for different values of the applied magnetic field in the Mn 12 O 12 molecular cluster. Strongly field dependent maxima in the relaxation rate versus temperature are observed below 50thinspthinspK. The results are explained in terms of thermal fluctuations of the total magnetization of the cluster among the different orientations with respect to the anisotropy axis. The lifetimes of the different m components of the total spin, S T =10 , of the molecule are obtained from the experiment and shown to be consistent with the ones expected from a spin-phonon coupling mechanism. No clear evidence for macroscopic quantum tunneling was observed in the field dependence of the proton relaxation rate at low T . copyright 1998 The American Physical Society

NMR studies of phase behaviour in polyacrylonitrile solutions

International Nuclear Information System (INIS)

Golightly, J.A.

1998-10-01

The aim of the thesis was to study the phase behaviour of aqueous polyacrylonitrile/NaSCN solutions using a variety of nuclear magnetic resonance techniques. Polyacrylonitrile (PAN) is the basis of the acrylic fibre industry, as such fibres contain at least 85% PAN. Despite this industrial importance, the available literature describing the phase behaviour of PAN in solution is far from comprehensive. Bulk 1 H NMR relaxation measurements were carried out over a wide range of concentrations and temperatures to probe the molecular dynamics of the PAN and water molecules. The relaxation data was found to be biexponential decay for all samples, the relative amplitudes of which were shown to be equal to the ratio of PAN protons to water protons. Both species were found to be in the regime of rapid molecular motion. Bulk 1 H NMR self diffusion measurements, using the PFGSTE technique, exhibited a bi-exponential decay of the echo amplitudes. By careful selection of the observation time, Δ, it was possible to independently probe the water and PAN translational diffusion. A background gradient, resulting from inhomogeneities of the magnetic field, complicated the analysis of the data and a novel polynomial least squares fitting procedure was devised to overcome this effect. The measured attenuation of the water diffusion coefficients (D∼10 -6 -10 -5 cm 2 s -1 ) with increasing PAN volume fraction was modelled according to various theories, including free volume and scaling laws. The study of the PAN diffusion coefficient (D∼10 -7 -10 -6 cm 2 s -1 ) was limited by the experimental constraints of the NMR spectrometer. A 1 H NMR one-dimensional imaging technique was used to study the non-solvent induced phase separation (coagulation) of a PAN solution. The time dependence of the measured profiles allowed observation of the coagulation process. A diffusion model was developed to fit the experimental data using a semi-infinite diffusion framework. The fitting parameters

Modeling an in-register, parallel "iowa" aβ fibril structure using solid-state NMR data from labeled samples with rosetta.

Science.gov (United States)

Sgourakis, Nikolaos G; Yau, Wai-Ming; Qiang, Wei

2015-01-06

Determining the structures of amyloid fibrils is an important first step toward understanding the molecular basis of neurodegenerative diseases. For β-amyloid (Aβ) fibrils, conventional solid-state NMR structure determination using uniform labeling is limited by extensive peak overlap. We describe the characterization of a distinct structural polymorph of Aβ using solid-state NMR, transmission electron microscopy (TEM), and Rosetta model building. First, the overall fibril arrangement is established using mass-per-length measurements from TEM. Then, the fibril backbone arrangement, stacking registry, and "steric zipper" core interactions are determined using a number of solid-state NMR techniques on sparsely (13)C-labeled samples. Finally, we perform Rosetta structure calculations with an explicitly symmetric representation of the system. We demonstrate the power of the hybrid Rosetta/NMR approach by modeling the in-register, parallel "Iowa" mutant (D23N) at high resolution (1.2Å backbone rmsd). The final models are validated using an independent set of NMR experiments that confirm key features. Copyright © 2015 Elsevier Ltd. All rights reserved.

Carbon-13 NMR of glycogen: Hydration response studied by using solids methods

International Nuclear Information System (INIS)

Jackson, C.L.; Bryant, R.G.

1989-01-01

The carbon-13 NMR spectra of glycogen are reported by using the methods of magic-angle sample spinning and high-power proton decoupling to provide a dynamic report on the glucose monomer behavior as a function of hydration. Although the glycogen behaves as a typical polymer in the dry state, addition of water makes a significant difference in the spectral appearance. Water addition decreases the carbon spin-lattice relaxation times by 2 orders of magnitude over the range from 7% to 70% water by weight. The proton-carbon dipole-dipole coupling, which broadens the carbon spectrum and permits cross-polarization spectroscopy, is lost with increasing hydration over this range. By 60% water by weight, scalar decoupling methods are sufficient to achieve a reasonably high-resolution spectrum. Further, at this concentration, the carbon spin-lattice relaxation times are near their minimum values at a resonance frequency of 50.3 MHz, making acquisition of carbon spectra relatively insensitive to intensity distortions associated with saturation effects. Though motional averaging places the spectrum in the solution phase limit, the static spectrum shows a residual broader component that would not necessarily be detected readily by using high-resolution liquid-state experiments

Atomic substitutions in synthetic apatite; Insights from solid-state NMR spectroscopy

Science.gov (United States)

Vaughn, John S.

Apatite, Ca5(PO4)3X (where X = F, Cl, or OH), is a unique mineral group capable of atomic substitutions for cations and anions of varied size and charge. Accommodation of differing substituents requires some kind of structural adaptation, e.g. new atomic positions, vacancies, or coupled substitutions. These structural adaptations often give rise to important physicochemical properties relevant to a range of scientific disciplines. Examples include volatile trapping during apatite crystallization, substitution for large radionuclides for long-term storage of nuclear fission waste, substitution for fluoride to improve acid resistivity in dental enamel composed dominantly of hydroxylapatite, and the development of novel biomaterials with enhanced biocompatibility. Despite the importance and ubiquity of atomic substitutions in apatite materials, many of the mechanisms by which these reactions occur are poorly understood. Presence of substituents at dilute concentration and occupancy of disordered atomic positions hinder detection by bulk characterization methods such as X-ray diffraction (XRD) and infrared (IR) spectroscopy. Solid-state nuclear magnetic resonance (NMR) spectroscopy is an isotope-specific structural characterization technique that does not require ordered atomic arrangements, and is therefore well suited to investigate atomic substitutions and structural adaptations in apatite. In the present work, solid-state NMR is utilized to investigate structural adaptations in three different types of apatite materials; a series of near-binary F, Cl apatite, carbonate-hydroxylapatite compositions prepared under various synthesis conditions, and a heat-treated hydroxylapatite enriched in 17O. The results indicate that hydroxyl groups in low-H, near binary F,Cl apatite facilitate solid-solution between F and Cl via column reversals, which result in average hexagonal symmetry despite very dilute OH concentration ( 2 mol percent). In addition, 19F NMR spectra indicate

Postearthquake relaxation after the 2004 M6 Parkfield, California, earthquake and rate-and-state friction

Science.gov (United States)

Savage, J.C.; Langbein, J.

2008-01-01

An unusually complete set of measurements (including rapid rate GPS over the first 10 days) of postseismic deformation is available at 12 continuous GPS stations located close to the epicenter of the 2004 M6.0 Parkfield earthquake. The principal component modes for the relaxation of the ensemble of those 12 GPS stations were determined. The first mode alone furnishes an adequate approximation to the data. Thus, the relaxation at all stations can be represented by the product of a common temporal function and distinct amplitudes for each component (north or east) of relaxation at each station. The distribution in space of the amplitudes indicates that the relaxation is dominantly strike slip. The temporal function, which spans times from about 5 min to 900 days postearthquake, can be fit by a superposition of three creep terms, each of the form ??l loge(1 + t/??l), with characteristic times ??, = 4.06, 0.11, and 0.0001 days. It seems likely that what is actually involved is a broad spectrum of characteristic times, the individual components of which arise from afterslip on different fault patches. Perfettini and Avouac (2004) have shown that an individual creep term can be explained by the spring-slider model with rate-dependent (no state variable) friction. The observed temporal function can also be explained using a single spring-slider model (i.e., single fault patch) that includes rate-and-state-dependent friction, a single-state variable, and either of the two commonly used (aging and slip) state evolution laws. In the latter fits, the rate-and-state friction parameter b is negative.

Proton relaxation relationships of human and animal tissues in vitro. Changes due to autolysis and fixing

International Nuclear Information System (INIS)

Grodd, W.; Schmitt, W.G.H.

1983-01-01

The results of measurements of proton relaxation times of various tissues from rats, pigs and humans are reported; these were obtained by a resonance spectroscope at 20 MHz and 40 0 C. There were specific differences in both relaxation times (T 1 and T 2 ) of the liver and spleen. There was a difference of more than 150 ms in the longitudinal relaxation time between grey and white cerebral tissue. Autolytic changes show an increase in both relaxation times. Fixation produced a reduction in T 1 only. The significance of these findings for NMR tomography is discussed. (orig.) [de

The feasibility of parameterizing four-state equilibria using relaxation dispersion measurements

International Nuclear Information System (INIS)

Li Pilong; Martins, Ilídio R. S.; Rosen, Michael K.

2011-01-01

Coupled equilibria play important roles in controlling information flow in biochemical systems, including allosteric molecules and multidomain proteins. In the simplest case, two equilibria are coupled to produce four interconverting states. In this study, we assessed the feasibility of determining the degree of coupling between two equilibria in a four-state system via relaxation dispersion measurements. A major bottleneck in this effort is the lack of efficient approaches to data analysis. To this end, we designed a strategy to efficiently evaluate the smoothness of the target function surface (TFS). Using this approach, we found that the TFS is very rough when fitting benchmark CPMG data to all adjustable variables of the four-state equilibria. After constraining a portion of the adjustable variables, which can often be achieved through independent biochemical manipulation of the system, the smoothness of TFS improves dramatically, although it is still insufficient to pinpoint the solution. The four-state equilibria can be finally solved with further incorporation of independent chemical shift information that is readily available. We also used Monte Carlo simulations to evaluate how well each adjustable parameter can be determined in a large kinetic and thermodynamic parameter space and how much improvement can be achieved in defining the parameters through additional measurements. The results show that in favorable conditions the combination of relaxation dispersion and biochemical manipulation allow the four-state equilibrium to be parameterized, and thus coupling strength between two processes to be determined.

In situ solid-state NMR spectroscopy of electrochemical cells: batteries, supercapacitors, and fuel cells.

Science.gov (United States)

Blanc, Frédéric; Leskes, Michal; Grey, Clare P

2013-09-17

Electrochemical cells, in the form of batteries (or supercapacitors) and fuel cells, are efficient devices for energy storage and conversion. These devices show considerable promise for use in portable and static devices to power electronics and various modes of transport and to produce and store electricity both locally and on the grid. For example, high power and energy density lithium-ion batteries are being developed for use in hybrid electric vehicles where they improve the efficiency of fuel use and help to reduce greenhouse gas emissions. To gain insight into the chemical reactions involving the multiple components (electrodes, electrolytes, interfaces) in the electrochemical cells and to determine how cells operate and how they fail, researchers ideally should employ techniques that allow real-time characterization of the behavior of the cells under operating conditions. This Account reviews the recent use of in situ solid-state NMR spectroscopy, a technique that probes local structure and dynamics, to study these devices. In situ NMR studies of lithium-ion batteries are performed on the entire battery, by using a coin cell design, a flat sealed plastic bag, or a cylindrical cell. The battery is placed inside the NMR coil, leads are connected to a potentiostat, and the NMR spectra are recorded as a function of state of charge. (7)Li is used for many of these experiments because of its high sensitivity, straightforward spectral interpretation, and relevance to these devices. For example, (7)Li spectroscopy was used to detect intermediates formed during electrochemical cycling such as LixC and LiySiz species in batteries with carbon and silicon anodes, respectively. It was also used to observe and quantify the formation and growth of metallic lithium microstructures, which can cause short circuits and battery failure. This approach can be utilized to identify conditions that promote dendrite formation and whether different electrolytes and additives can help

Crystal structure and tautomerism of Pigment Yellow 138 determined by X-ray powder diffraction and solid-state NMR

DEFF Research Database (Denmark)

Gumbert, Silke D.; Körbitzer, Meike; Alig, Edith

2016-01-01

The crystal structure of C.I. Pigment Yellow 138 was determined from X-ray powder diffraction data using real-space methods with subsequent Rietveld refinements. The tautomeric state was investigated by solid-state 1D and 2D multinuclear NMR experiments. In the crystals, the compound exhibits...... the NH-tautomer with a hydrogen atom situated at the nitrogen of the quinoline moiety. Direct evidence of the presence of the NH-tautomer is provided by 1H–14N HMQC solid-state NMR at very fast MAS. Solid-state dispersion-corrected density functional theory calculations with BLYP-D3 confirm...

Electron-Phonon Coupling and Resonant Relaxation from 1D and 1P States in PbS Quantum Dots.

Science.gov (United States)

Kennehan, Eric R; Doucette, Grayson S; Marshall, Ashley R; Grieco, Christopher; Munson, Kyle T; Beard, Matthew C; Asbury, John B

2018-05-31

Observations of the hot-phonon bottleneck, which is predicted to slow the rate of hot carrier cooling in quantum confined nanocrystals, have been limited to date for reasons that are not fully understood. We used time-resolved infrared spectroscopy to directly measure higher energy intraband transitions in PbS colloidal quantum dots. Direct measurements of these intraband transitions permitted detailed analysis of the electronic overlap of the quantum confined states that may influence their relaxation processes. In smaller PbS nanocrystals, where the hot-phonon bottleneck is expected to be most pronounced, we found that relaxation of parity selection rules combined with stronger electron-phonon coupling led to greater spectral overlap of transitions among the quantum confined states. This created pathways for fast energy transfer and relaxation that may bypass the predicted hot-phonon bottleneck. In contrast, larger, but still quantum confined nanocrystals did not exhibit such relaxation of the parity selection rules and possessed narrower intraband states. These observations were consistent with slower relaxation dynamics that have been measured in larger quantum confined systems. These findings indicated that, at small radii, electron-phonon interactions overcome the advantageous increase in energetic separation of the electronic states for PbS quantum dots. Selection of appropriately sized quantum dots, which minimize spectral broadening due to electron-phonon interactions while maximizing electronic state separation, is necessary to observe the hot-phonon bottleneck. Such optimization may provide a framework for achieving efficient hot carrier collection and multiple exciton generation.

Measurement of sample temperatures under magic-angle spinning from the chemical shift and spin-lattice relaxation rate of 79Br in KBr powder.

Science.gov (United States)

Thurber, Kent R; Tycko, Robert

2009-01-01

Accurate determination of sample temperatures in solid state nuclear magnetic resonance (NMR) with magic-angle spinning (MAS) can be problematic, particularly because frictional heating and heating by radio-frequency irradiation can make the internal sample temperature significantly different from the temperature outside the MAS rotor. This paper demonstrates the use of (79)Br chemical shifts and spin-lattice relaxation rates in KBr powder as temperature-dependent parameters for the determination of internal sample temperatures. Advantages of this method include high signal-to-noise, proximity of the (79)Br NMR frequency to that of (13)C, applicability from 20 K to 320 K or higher, and simultaneity with adjustment of the MAS axis direction. We show that spin-lattice relaxation in KBr is driven by a quadrupolar mechanism. We demonstrate a simple approach to including KBr powder in hydrated samples, such as biological membrane samples, hydrated amyloid fibrils, and hydrated microcrystalline proteins, that allows direct assessment of the effects of frictional and radio-frequency heating under experimentally relevant conditions.

NMR study on the low-temperature state of LaMn4Al8

International Nuclear Information System (INIS)

Muro, Y.; Nakamura, H.; Kohara, T.

2007-01-01

The ground state of the quasi-one-dimensional itinerant electron magnet LaMn 4 Al 8 with strong electron correlation has been investigated by NMR. The presence of weak and broad zero-field 55 Mn resonance, corresponding to internal field of 8-11T, indicates slowing down of spins partially released from the spin-singlet-like state in the spin chains

Some nitrogen-14 NMR studies in solids

International Nuclear Information System (INIS)

Pratum, T.K.

1983-11-01

The first order quadrupolar perturbation of the 14 N NMR spectrum yields information regarding the static and dynamic properties of the surrounding electronic environment. Signal to noise problems caused by long 14 N longitudinal relaxation times (T 1 ) and small equilibrium polarizations are reduced by rotating frame cross polarization (CP) experiments between 14 N and 1 H. Using quadrupolar echo and CP techniques, the 14 N quadrupolar coupling constants (e 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 14 N NMR powder patterns exhibit the effects of anisotropic molecular motion, while choline bromide spectra show no such effects

A relaxation-projection method for compressible flows. Part I: The numerical equation of state for the Euler equations

International Nuclear Information System (INIS)

Saurel, Richard; Franquet, Erwin; Daniel, Eric; Le Metayer, Olivier

2007-01-01

A new projection method is developed for the Euler equations to determine the thermodynamic state in computational cells. It consists in the resolution of a mechanical relaxation problem between the various sub-volumes present in a computational cell. These sub-volumes correspond to the ones traveled by the various waves that produce states with different pressures, velocities, densities and temperatures. Contrarily to Godunov type schemes the relaxed state corresponds to mechanical equilibrium only and remains out of thermal equilibrium. The pressure computation with this relaxation process replaces the use of the conventional equation of state (EOS). A simplified relaxation method is also derived and provides a specific EOS (named the Numerical EOS). The use of the Numerical EOS gives a cure to spurious pressure oscillations that appear at contact discontinuities for fluids governed by real gas EOS. It is then extended to the computation of interface problems separating fluids with different EOS (liquid-gas interface for example) with the Euler equations. The resulting method is very robust, accurate, oscillation free and conservative. For the sake of simplicity and efficiency the method is developed in a Lagrange-projection context and is validated over exact solutions. In a companion paper [F. Petitpas, E. Franquet, R. Saurel, A relaxation-projection method for compressible flows. Part II: computation of interfaces and multiphase mixtures with stiff mechanical relaxation. J. Comput. Phys. (submitted for publication)], the method is extended to the numerical approximation of a non-conservative hyperbolic multiphase flow model for interface computation and shock propagation into mixtures

Diffusion effects on volume-selective NMR at small length scales

International Nuclear Information System (INIS)

Gaedke, Achim

2009-01-01

In this thesis, the interplay between diffusion and relaxation effects in spatially selective NMR experiments at short length scales is explored. This is especially relevant in the context of both conventional and mechanically detected MRI at (sub)micron resolution in biological specimens. Recent results on selectively excited very thin slices showed an in-slice-magnetization recovery orders of magnitude faster than the longitudinal relaxation time T1. However, those experiments were run on fully relaxed samples while MRI and especially mechanically detected NMR experiments are typically run in a periodic fashion with repetition times far below T1. The main purpose of this work therefore was to extend the study of the interplay between diffusion and longitudinal relaxation to periodic excitations. In some way, this is inverse phenomenon to the DESIRE (Diffusive Enhancement of SIgnal and REsolution) approach, proposed 1992 by Lauterbur. Experiments on periodically excited thin slices were carried out at a dedicated static field gradient cryomagnet with magnetic field gradients up to 180 T/m. In order to obtain plane slices, an appropriate isosurface of the gradient magnet had to be identified. It was found at a field of 3.8 T with a gradient of 73 T/m. In this field, slices down to a thickness of 3.2 μm could be excited. The detection of the NMR signal was done using FIDs instead of echoes as the excitation bandwidth of those thin slices is sufficiently small to observe FIDs which are usually considered to be elusive to detection in such strong static field gradients. A simulation toolbox based on the full Bloch-Torrey-equation was developed to describe the excitation and the formation of NMR signals under those unusual conditions as well as the interplay of diffusion and magnetization recovery. Both the experiments and the simulations indicate that diffusion effects lead to a strongly enhanced magnetization modulation signal also under periodic excitation

A comparison study of PET, NMR, and CT imaging in cerebral ischemia

International Nuclear Information System (INIS)

Babikian, V.L.; Ford, C.S.; Buonanno, F.S.; Kistler, J.P.; Ackerman, R.H.; Alpert, N.M.; Correia, J.A.; Johnson, K.A.; Buxton, R.B.

1987-01-01

Whether ischemia without infarction produces recognizable changes in relaxation times of ischemic but viable brain is an important, unresolved issue. Therefore, a study was initiated of patients with cerebral ischemia, using positron emission tomography (PET), NMR, and computed tomography (CT) to compare and contrast the pathophysiologic information provided by each and to study the issue of whether cerebral ischemia without infarction can be appreciated by proton NMR imaging. Here the initial results are reported. 4 refs.; 2 figs.; 1 table

Complex methyl groups dynamics in [(CH3)4P]3Sb2Br9 (PBA) from low to high temperatures by proton spin-lattice relaxation and narrowing of proton NMR spectrum.

Science.gov (United States)

Latanowicz, L; Medycki, W; Jakubas, R

2009-11-01

Molecular dynamics of a polycrystalline sample of [(CH(3))(4)P](3)Sb(2)Br(9) (PBA) has been studied on the basis of the T(1) (24.7 MHz) relaxation time measurement, the proton second moment of NMR and the earlier published T(1) (90 MHz) relaxation times. The study was performed in a wide range of temperatures (30-337 K). The tunnel splitting omega(T) of the methyl groups was estimated as of low frequency (from kHz to few MHz). The proton spin pairs of the methyl group are known to perform a complex internal motion being a resultant of four components. Three of them involve mass transportation over and through the potential barrier and are characterized by the correlation times tau(3) and tau(T)of the jumps over the barrier and tunnel jumps in the threefold potential of the methyl group and tau(iso) the correlation time of isotropic rotation of the whole TMP cation. For tau(3) and tau(iso) the Arrhenius temperature dependence was assumed, while for tau(T)--the Schrödinger one. The fourth motion causes fluctuations of the tunnel splitting frequency, omega(T), and it is related to the lifetime of the methyl spin at the energy level. The correlation function for this fourth motion (tau(omega) correlation time) has been proposed by Müller-Warmuth et al. In this paper a formula for the correlation function and spectral density of the complex motion made of the above-mentioned four components was derived and used in interpretation of the T(1) relaxation time. The second moment of proton NMR line at temperatures below 50K is four times lower than its value for the rigid structure. The three components of the internal motion characterized by tau(T), tau(H), and tau(iso) were proved to reduce the second moment of the NMR line. The tunnel jumps of the methyl group reduce M(2) at almost 0K, the classical jumps over the barrier reduce M(2) in the vicinity of 50K, while the isotropic motion near 150K. Results of the study on the dynamics of CH(3) groups of TMP cation based on

Solid state NMR investigations and MD simulations of triblock copolymers in lipid bilayers

Czech Academy of Sciences Publication Activity Database

Baerenwald, R.; Ferreira, T. M.; Ollila, Samuli; Saalwaechter, K.

2017-01-01

Roč. 46, Suppl 1 (2017), S117 ISSN 0175-7571. [IUPAB congress /19./ and EBSA congress /11./. 16.07.2017-20.07.2017, Edinburgh] Institutional support: RVO:61388963 Keywords : solid state NMR * molecular dynamic simulations Subject RIV: BO - Biophysics

Relaxation and final-state structure in XPS of atoms, molecules, and metals

International Nuclear Information System (INIS)

Shirley, D.A.; Martin, R.L.; McFeely, F.R.; Kowalczyk, S.P.; Ley, L.

1975-03-01

Photoemission from a many-electron system is a many-electron process, even though the transition operator may affect only one electron directly. Relaxation and ''shake-up'' structure are related by a sum rule. When one is present, the other must be also. Shake-up structure is shown to be accurately predictable in atomic neon and molecular HF if the CI calculations are done carefully. In metals the sum rule also applies but final-state effects usually appear as relaxation energy, which is large even for valence electrons. Finally, in rare-earth metals discrete shake-up structure is observable in the 4p region. (7 figs, 30 refs) (auth)

Heteronuclear Adiabatic Relaxation Dispersion (HARD) for quantitative analysis of conformational dynamics in proteins.

Science.gov (United States)

Traaseth, Nathaniel J; Chao, Fa-An; Masterson, Larry R; Mangia, Silvia; Garwood, Michael; Michaeli, Shalom; Seelig, Burckhard; Veglia, Gianluigi

2012-06-01

NMR relaxation methods probe biomolecular motions over a wide range of timescales. In particular, the rotating frame spin-lock R(1ρ) and Carr-Purcell-Meiboom-Gill (CPMG) R(2) experiments are commonly used to characterize μs to ms dynamics, which play a critical role in enzyme folding and catalysis. In an effort to complement these approaches, we introduced the Heteronuclear Adiabatic Relaxation Dispersion (HARD) method, where dispersion in rotating frame relaxation rate constants (longitudinal R(1ρ) and transverse R(2ρ)) is created by modulating the shape and duration of adiabatic full passage (AFP) pulses. Previously, we showed the ability of the HARD method to detect chemical exchange dynamics in the fast exchange regime (k(ex)∼10(4)-10(5) s(-1)). In this article, we show the sensitivity of the HARD method to slower exchange processes by measuring R(1ρ) and R(2ρ) relaxation rates for two soluble proteins (ubiquitin and 10C RNA ligase). One advantage of the HARD method is its nominal dependence on the applied radio frequency field, which can be leveraged to modulate the dispersion in the relaxation rate constants. In addition, we also include product operator simulations to define the dynamic range of adiabatic R(1ρ) and R(2ρ) that is valid under all exchange regimes. We conclude from both experimental observations and simulations that this method is complementary to CPMG-based and rotating frame spin-lock R(1ρ) experiments to probe conformational exchange dynamics for biomolecules. Finally, this approach is germane to several NMR-active nuclei, where relaxation rates are frequency-offset independent. Copyright © 2012 Elsevier Inc. All rights reserved.

The flexibility of SIMPSON and SIMMOL for numerical simulations in solid-and liquid-state NMR spectroscopy

International Nuclear Information System (INIS)

Vosegaard, T.; Malmendal, A.; Nielsen, N.C.

2002-01-01

Addressing the need for numerical simulations in the design and interpretation of advanced solid- and liquid-state NMR experiments, we present a number of novel features for numerical simulations based on the SIMPSON and SIMMOL open source software packages. Major attention is devoted to the flexibility of these Tcl-interfaced programs for numerical simulation of NMR experiments being complicated by demands for efficient powder averaging, large spin systems, and multiple-pulse rf irradiation. These features are exemplified by fast simulation of second-order quadrupolar powder patterns using crystallite interpolation, analysis of rotary resonance triple-quantum excitation for quadrupolar nuclei, iterative fitting of MQ-MAS spectra by combination of SIMIPSON and MINUIT, simulation of multiple-dimensional PISEMA-type correlation experiments for macroscopically oriented membrane proteins, simulation of Hartman-Hahn polarization transfers in liquid-state NMR, and visualization of the spin evolution under complex composite broad-band excitation pulses. (author)

Broad line and pulsed NMR study of molecular motion in furfuryl alcohol resins

International Nuclear Information System (INIS)

Glowinkowski, S.; Pajak, Z.

1978-01-01

Broad line and pulsed nuclear magnetic resonance studies are carried out on a number of furfuryl alcohol resins differentiated by viscosity. Proton NMR spectra and relaxation times T 1 and Tsub(1rho) are measured over a wide temperature range and the results are interpreted in terms of molecular motion. The marked decrease in second moment and existence of high temperature spin-lattice relaxation times minima are presumed to result from rotational motion of polymer chains. The relaxation processes at low temperature are believed to be due to rotational motion of methyl endgroup and paramagnetic centres. (author)

1H NMR methods for the noninvasive study of metabolism and other processes involving small molecules in intact erythrocytes

International Nuclear Information System (INIS)

Rabenstein, D.L.

1984-01-01

1 H NMR methods are described with which resolved resonances can be obtained for many of the small molecules in intact erythrocytes. In one method, the more intense hemoglobin resonances are suppressed by transfer of saturation throughout the hemoglobin spin system by cross relaxation following a selective saturation pulse. In a second method, the hemoglobin resonances are eliminated with the spin-echo pulse sequence by using a between-pulse delay time long enough for complete elimination of the hemoglobin resonances by spin-spin relaxation. Selected examples of the study of erythrocyte biochemistry by 1 H NMR are discussed. (Auth.)

On the relationship between NMR-derived amide order parameters and protein backbone entropy changes.

Science.gov (United States)

Sharp, Kim A; O'Brien, Evan; Kasinath, Vignesh; Wand, A Joshua

2015-05-01

Molecular dynamics simulations are used to analyze the relationship between NMR-derived squared generalized order parameters of amide NH groups and backbone entropy. Amide order parameters (O(2) NH ) are largely determined by the secondary structure and average values appear unrelated to the overall flexibility of the protein. However, analysis of the more flexible subset (O(2) NH  entropy than that reported by the side chain methyl axis order parameters, O(2) axis . A calibration curve for backbone entropy vs. O(2) NH is developed, which accounts for both correlations between amide group motions of different residues, and correlations between backbone and side chain motions. This calibration curve can be used with experimental values of O(2) NH changes obtained by NMR relaxation measurements to extract backbone entropy changes, for example, upon ligand binding. In conjunction with our previous calibration for side chain entropy derived from measured O(2) axis values this provides a prescription for determination of the total protein conformational entropy changes from NMR relaxation measurements. © 2015 Wiley Periodicals, Inc.

Value of NMR logging for heavy oil characterization

Energy Technology Data Exchange (ETDEWEB)

Chen, S.; Chen, J.; Georgi, D. [Baker Hughes, Calgary, AB (Canada); Sun, B. [Chevron Energy Technology Co., Calgary, AB (Canada)

2008-07-01

Non-conventional, heavy oil fields are becoming increasingly important to the security of energy supplies and are becoming economically profitable to produce. Heavy oil reservoirs are difficult to evaluate since they are typically shallow and the connate waters are very fresh. Other heavy oil reservoirs are oil-wet where the resistivities are not indicative of saturation. Nuclear magnetic resonance (NMR) detects molecular level interactions. As such, it responds distinctively to different hydrocarbon molecules, thereby opening a new avenue for constituent analysis. This feature makes NMR a more powerful technique than bulk oil density or viscosity measurements for characterizing oils, and is the basis for detecting gas in heavy oil fields. NMR logging, which measures fluid in pore space directly, is capable of separating oil from water. It is possible to discern movable from bound water by analyzing NMR logs. The oil viscosity can be also quantified from NMR logs, NMR relaxation time and diffusivity estimates. The unique challenges for heavy oil reservoir characterization for the NMR technique were discussed with reference to the extra-fast decay of the NMR signal in response to extra-heavy oil/tars, and the lack of sensitivity in measuring very slow diffusion of heavy oil molecules. This paper presented various methods for analyzing heavy oil reservoirs in different viscosity ranges. Heavy oil fields in Venezuela, Kazakhstan, Canada, Alaska and the Middle East were analyzed using different data interpretation approaches based on the reservoir formation characteristics and the heavy oil type. NMR direct fluid typing was adequate for clean sands and carbonate reservoirs while integrated approaches were used to interpret extra heavy oils and tars. It was concluded that NMR logs can provide quantitative measures for heavy oil saturation, identify sweet spots or tar streaks, and quantify heavy oil viscosity within reasonable accuracy. 14 refs., 16 figs.

Relaxation Time of High-Density Amorphous Ice

Science.gov (United States)

Handle, Philip H.; Seidl, Markus; Loerting, Thomas

2012-06-01

Amorphous water plays a fundamental role in astrophysics, cryoelectron microscopy, hydration of matter, and our understanding of anomalous liquid water properties. Yet, the characteristics of the relaxation processes taking place in high-density amorphous ice (HDA) are unknown. We here reveal that the relaxation processes in HDA at 110-135 K at 0.1-0.2 GPa are of collective and global nature, resembling the alpha relaxation in glassy material. Measured relaxation times suggest liquid-like relaxation characteristics in the vicinity of the crystallization temperature at 145 K. By carefully relaxing pressurized HDA for several hours at 135 K, we produce a state that is closer to the ideal glass state than all HDA states discussed so far in literature.

(13)C and (15)N solid-state NMR studies on albendazole and cyclodextrin albendazole complexes.

Science.gov (United States)

Ferreira, M João G; García, A; Leonardi, D; Salomon, Claudio J; Lamas, M Celina; Nunes, Teresa G

2015-06-05

(13)C and (15)N solid-state nuclear magnetic resonance (NMR) spectra were recorded from albendazole (ABZ) and from ABZ:β-cyclodextrin, ABZ:methyl-β-cyclodextrin, ABZ:hydroxypropyl-β-cyclodextrin and ABZ:citrate-β-cyclodextrin, which were prepared by the spray-drying technique. ABZ signals were typical of a crystalline solid for the pure drug and of an amorphous compound obtained from ABZ:cyclodextrin samples. Relevant spectral differences were correlated with chemical interaction between ABZ and cyclodextrins. The number and type of complexes revealed a strong dependence on the cyclodextrin group substituent. Solid-state NMR data were consistent with the presence of stable inclusion complexes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Selective modification of NMR relaxation time in human colorectal carcinoma by using gadolinium-diethylenetriaminepentaacetic acid conjugated with monoclonal antibody 19-9.

Science.gov (United States)

Curtet, C; Tellier, C; Bohy, J; Conti, M L; Saccavini, J C; Thedrez, P; Douillard, J Y; Chatal, J F; Koprowski, H

1986-01-01

Monoclonal antibody 19-9 (mAb 19-9) against human colon adenocarcinoma was conjugated with gadolinium X diethylenetriaminepentaacetic acid (Gd X DTPA) and used as a contrast agent in nuclear magnetic resonance (NMR) in an effort to improve tumor target selectivity in nude mice. The data indicate that Gd X DTPA-mAb 19-9 in solution decreased the T1 relaxation of water protons at 90 MHz in direct proportion to the gadolinium concentration, and this effect was greater than in Gd X DTPA solutions. T1 relaxation time at 90 MHz, measured in tumors removed from nude mice 24 hr after injection of Gd X DTPA-mAb 19-9 (Gd, 20 mumol/kg; 16 DTPA molecules per mAb molecule), was significantly decreased (by 15%) as compared with the control group. Similar results were obtained in tumors from mice injected with Gd X DTPA-mAb 19-9 solutions in which Gd was used at 2, 6, or 10 mumol/kg (16 DTPA molecules per mAb molecule). These doses are lower than those commonly used for Gd X DTPA (10-100 mumol/kg) as contrast agent. Tumor localization by the Gd X DTPA-mAb 19-9 complex containing radioactive Gd (0.3 microCi/microgram of 153Gd) to confirm scintigraphy revealed significant concentrations of the complex (5% of the injected dose per gram of tissue) in the tumor. Scan images recorded in planar scintigraphy at day 5 showed good visualization of tumors. Images PMID:3459174

The relaxation time approximation

International Nuclear Information System (INIS)

Gairola, R.P.; Indu, B.D.

1991-01-01

A plausible approximation has been made to estimate the relaxation time from a knowledge of the transition probability of phonons from one state (r vector, q vector) to other state (r' vector, q' vector), as a result of collision. The relaxation time, thus obtained, shows a strong dependence on temperature and weak dependence on the wave vector. In view of this dependence, relaxation time has been expressed in terms of a temperature Taylor's series in the first Brillouin zone. Consequently, a simple model for estimating the thermal conductivity is suggested. the calculations become much easier than the Callaway model. (author). 14 refs

Application of solid-state tritium NMR in determining the bioactive conformation of paclitaxel

International Nuclear Information System (INIS)

Lin, T.

2012-01-01

The determination of the conformation of small molecule bound to its biological target would facilitate people to design improved drugs. This determination can be difficult due to technical limitations, as exemplified by the long standing debate on the microtubule-binding conformation of a natural anticancer drug - paclitaxel. Previous studies using X-ray crystallography and solution-state NMR failed to furnish direct information on the expected conformation. Solid-state NMR may help in this task by providing precise interatomic distances, and the selective labeling on different sites with tritium atoms enables accurate measurement of long-range distances (up to 14.4 Angstroms) owing to the high gyromagnetic ratio of this nucleus, without any structural modification of the molecule. So our project aiming at illustrating the bioactive conformation of paclitaxel consists the syntheses of 6 different paclitaxel isotopomers bearing a pair of tritium at specified positions, flowing by the preparations of corresponding microtubule-labeled paclitaxel complexes. The solid-state tritium NMR analyses of these complexes would provide key distances for determining the expected conformation. Up to now, 2 paclitaxel isotopomers have been prepared from labelling the di-brominated paclitaxel precursor and from coupling the tritiated taxane rings and the tritiated side chains, respectively. The synthetic strategy allowed us to realize the syntheses in generally high yield and good stereoselectivity. Different tritiation methods have been used, from which an isotopic enrichment of higher than 92% was obtained. The syntheses of other 4 isotopomers, together with the microtubule complexes are currently underway in our lab. (author) [fr

The contribution of solid-state NMR spectroscopy to understanding biomineralization: Atomic and molecular structure of bone

Science.gov (United States)

Duer, Melinda J.

2015-04-01

Solid-state NMR spectroscopy has had a major impact on our understanding of the structure of mineralized tissues, in particular bone. Bone exemplifies the organic-inorganic composite structure inherent in mineralized tissues. The organic component of the extracellular matrix in bone is primarily composed of ordered fibrils of collagen triple-helical molecules, in which the inorganic component, calcium phosphate particles, composed of stacks of mineral platelets, are arranged around the fibrils. This perspective argues that key factors in our current structural model of bone mineral have come about through NMR spectroscopy and have yielded the primary information on how the mineral particles interface and bind with the underlying organic matrix. The structure of collagen within the organic matrix of bone or any other structural tissue has yet to be determined, but here too, this perspective shows there has been real progress made through application of solid-state NMR spectroscopy in conjunction with other techniques. In particular, NMR spectroscopy has highlighted the fact that even within these structural proteins, there is considerable dynamics, which suggests that one should be cautious when using inherently static structural models, such as those arising from X-ray diffraction analyses, to gain insight into molecular roles. It is clear that the NMR approach is still in its infancy in this area, and that we can expect many more developments in the future, particularly in understanding the molecular mechanisms of bone diseases and ageing.

NMR study of hyper-polarized 129Xe and applications to liquid-phase NMR experiments

International Nuclear Information System (INIS)

Marion, D.

2008-07-01

In liquid samples where both nuclear polarization and spin density are strong, the magnetization dynamics, which can be analysed by NMR (nuclear magnetic resonance) methods, is deeply influenced by the internal couplings induced by local dipolar fields. The present thesis describes some of the many consequences associated to the presence in the sample of concentrated xenon hyper-polarized by an optical pumping process. First, we deal with the induced modifications in frequency and line width of the proton and xenon spectra, then we present the results of SPIDER, a coherent polarization transfer experiment designed to enhance the polarization of protons, in order to increase their NMR signal level. A third part is dedicated to the description of the apparition of repeated chaotic maser emissions by un unstable xenon magnetization coupled to the detection coil tuned at the xenon Larmor frequency (here 138 MHz). In the last part, we present a new method allowing a better tuning of any NMR detection probe and resulting in sensible gains in terms of sensitivity and signal shaping. Finally, we conclude with a partial questioning of the classical relaxation theory in the specific field of highly polarized and concentrated spin systems in a liquid phase. (author)

Navier--Stokes relaxation to sinh--Poisson states at finite Reynolds numbers

International Nuclear Information System (INIS)

Montgomery, D.; Shan, X.; Matthaeus, W.H.

1993-01-01

A mathematical framework is proposed in which it seems possible to justify the computationally-observed relaxation of a two-dimensional Navier--Stokes fluid to a ''most probable,'' or maximum entropy, state. The relaxation occurs at large but finite Reynolds numbers, and involves substantial decay of higher-order ideal invariants such as enstrophy. A two-fluid formulation, involving interpenetrating positive and negative vorticity fluxes (continuous and square integrable) is developed, and is shown to be intimately related to the passive scalar decay problem. Increasing interpenetration of the two fluids corresponds to the decay of vorticity flux due to viscosity. It is demonstrated numerically that, in two dimensions, passive scalars decay rapidly, relative to mean-square vorticity (enstrophy). This observation provides a basis for assigning initial data to the two-fluid field variables

Formation and relaxation of quasistationary states in particle systems with power-law interactions.

Science.gov (United States)

Marcos, B; Gabrielli, A; Joyce, M

2017-09-01

We explore the formation and relaxation of the so-called quasistationary states (QSS) for particle distributions in three dimensions interacting via an attractive radial pair potential V(r→∞)∼1/r^{γ} with γ>0, and either a soft core or hard core regularization at small r. In the first part of the paper, we generalize, for any spatial dimension d≥2, Chandrasekhar's approach for the case of gravity to obtain analytic estimates of the rate of collisional relaxation due to two-body collisions. The resultant relaxation rates indicate an essential qualitative difference depending on the integrability of the pair force at large distances: for γ>d-1, the rate diverges in the large particle number N (mean-field) limit, unless a sufficiently large soft core is present; for γsoft cores leading to the formation of QSS. We find, just as for the previously well studied case of gravity (which we also revisit), excellent agreement between the parametric dependence of the observed relaxation times and our analytic predictions. Further, as in the case of gravity, we find that the results indicate that, when large impact factors dominate, the appropriate cutoff is the size of the system (rather than, for example, the mean interparticle distance). Our results provide strong evidence that the existence of QSS is robust only for long-range interactions with a large distance behavior γstates will be conditioned strongly on the short-range properties of the interaction.

Structural Investigations of Portland Cement Components, Hydration, and Effects of Admixtures by Solid-State NMR Spectroscopy

DEFF Research Database (Denmark)

Skibsted, Jørgen Bengaard; Andersen, Morten D.; Jakobsen, Hans Jørgen

2006-01-01

for the C-S-H phase formed during hydration. It will be demonstrated that Al3+ and flouride guest-ions in the anhydrous and hydrated calcium silicates can be studied in detail by 27Al and 19F MAS NMR, thereby providing information on the local structure and the mechanisms for incorporation of these ions......Solid-state, magic-angle spinning (MAS) NMR spectroscopy represents a valuable tool for structural investigations on the nanoscale of the most important phases in anhydrous and hydrated Portland cements and of various admixtures. This is primarily due to the fact that the method reflects the first......- and second-coordination spheres of the spin nucleus under investigation while it is less sensitive to long-range order. Thus, crystalline as well as amorphous phases can be detected in a quantitative manner by solid-state NMR. In particular the structure of the calcium-silicate-hydrate (C-S-H) phase have...

31P Solid-state MAS NMR spectra

International Nuclear Information System (INIS)

Grobet, P.J.; Geerts, H.; Martens, J.A.; Jacobs, P.A.

1989-01-01

The structures of the silicoaluminiophosphates MCM-1 and MCM9 were characterized by 27 Al and 31 P MAS NMR. The structural identity of MCM-1 and its silicon-free homologue AlPO 4 -H 3 is demonstrated. The presence of a structural mixture in MCM-9 is confirmed. 31 P MAS NMR spectra of MCM-9 could be interpreted as a superposition of spectra of VPI-5, AlPO 4 -H 3 and SAPO-11 phases. (author). 12 refs.; 3 figs.; 1 tab

Solid state multinuclear NMR. A versatile tool for studying the reactivity of solid systems

Energy Technology Data Exchange (ETDEWEB)

MacKenzie, Kenneth J.D. [MacDiarmid Institute for Advanced Materials and Nanotechnology, Victoria University of Wellington, P.O. Box 600, Wellington (New Zealand)

2004-08-31

Traditionally, X-ray powder diffraction has been a favoured method for studying chemical reactions in the solid state, but the increasing importance of energy-efficient synthesis methods for solids (e.g. sol-gel synthesis, mechanochemical synthesis) has led to the need for an analytical method not dependent on long-range structural periodicity. Multinuclear solid state nuclear magnetic resonance (NMR) represents a technique which is equally applicable to amorphous or crystalline solids, and is now used in increasing numbers of solid state studies.This paper briefly outlines the principles and practical details of this powerful technique and gives examples of its use in solid-state chemistry, particularly in very recent studies of mechanochemical synthesis of advanced sialon ceramics. The temperature at which these technically important silicon aluminium oxynitride compounds are formed can be significantly lowered by high-energy grinding of their components to produce X-ray amorphous precursors. Solid-state NMR has been used to provide detailed information which could not have been obtained by any other means about the chemical environment of the Si and Al atoms in these amorphous precursors, and the various atomic movements undergone as they crystallise to the final product.

Continuous monitoring of the zinc-phosphate acid-base cement setting reaction by proton nuclear magnetic relaxation

International Nuclear Information System (INIS)

Apih, T.; Lebar, A.; Pawlig, O.; Trettin, R.

2001-01-01

Proton nuclear magnetic relaxation is a well-established technique for continuous and non destructive monitoring of hydration of conventional Portland building cements. Here, we demonstrate the feasibility of nuclear magnetic resonance (NMR) monitoring of the setting reaction of zinc-phosphate acid-base dental cements, which harden in minutes as compared to days, as in the case of Portland cements. We compare the setting of cement powder (mainly, zinc oxide) prepared with clinically used aluminum-modified orthophosphoric acid solution with the setting of a model system where cement powder is mixed with pure orthophosphoric acid solution. In contrast to previously published NMR studies of setting Portland cements, where a decrease of spin-lattice relaxation time is attributed to enhanced relaxation at the growing internal surface, spin-lattice relaxation time T 1 increases during the set of clinically used zinc-phosphate cement. Comparison of these results with a detailed study of diffusion, viscosity, and magnetic-field dispersion of T 1 in pure and aluminum-modified orthophosphoric acid demonstrates that the increase of T 1 in the setting cement is connected with the increase of molecular mobility in the residual phosphoric acid solution. Although not taken into account so far, such effects may also significantly influence the relaxation times in setting Portland cements, particularly when admixtures with an effect on water viscosity are used. [copyright] 2001 American Institute of Physics

Practical considerations for investigation of protein conformational dynamics by {sup 15}N R{sub 1ρ} relaxation dispersion

Energy Technology Data Exchange (ETDEWEB)

Walinda, Erik [Kyoto University, Department of Molecular and Cellular Physiology, Graduate School of Medicine (Japan); Morimoto, Daichi; Shirakawa, Masahiro; Sugase, Kenji, E-mail: sugase@moleng.kyoto-u.ac.jp [Kyoto University, Department of Molecular Engineering, Graduate School of Engineering (Japan)

2017-03-15

It is becoming increasingly apparent that proteins are not static entities and that their function often critically depends on accurate sampling of multiple conformational states in aqueous solution. Accordingly, the development of methods to study conformational states in proteins beyond their ground-state structure (“excited states”) has crucial biophysical importance. Here we investigate experimental schemes for optimally probing chemical exchange processes in proteins on the micro- to millisecond timescale by {sup 15}N R{sub 1ρ} relaxation dispersion. The schemes use selective Hartmann–Hahn cross-polarization (CP) transfer for excitation, and derive peak integrals from 1D NMR spectra (Korzhnev et al. in J Am Chem Soc 127:713–721, 2005; Hansen et al. in J Am Chem Soc 131:3818–3819, 2009). Simulation and experiment collectively show that in such CP-based schemes care has to be taken to achieve accurate suppression of undesired off-resonance coherences, when using weak spin-lock fields. This then (i) ensures that relaxation dispersion profiles in the absence of chemical exchange are flat, and (ii) facilitates extraction of relaxation dispersion profiles in crowded regions of the spectrum. Further improvement in the quality of the experimental data is achieved by recording the free-induction decays in an interleaved manner and including a heating-compensation element. The reported considerations will particularly benefit the use of CP-based R{sub 1ρ} relaxation dispersion to analyze conformational exchange processes in larger proteins, where resonance line overlap becomes the main limiting factor.

Size dependence of 13C nuclear spin-lattice relaxation in micro- and nanodiamonds

Science.gov (United States)

Panich, A. M.; Sergeev, N. A.; Shames, A. I.; Osipov, V. Yu; Boudou, J.-P.; Goren, S. D.

2015-02-01

Size dependence of physical properties of nanodiamond particles is of crucial importance for various applications in which defect density and location as well as relaxation processes play a significant role. In this work, the impact of defects induced by milling of micron-sized synthetic diamonds was studied by magnetic resonance techniques as a function of the particle size. EPR and 13C NMR studies of highly purified commercial synthetic micro- and nanodiamonds were done for various fractions separated by sizes. Noticeable acceleration of 13C nuclear spin-lattice relaxation with decreasing particle size was found. We showed that this effect is caused by the contribution to relaxation coming from the surface paramagnetic centers induced by sample milling. The developed theory of the spin-lattice relaxation for such a case shows good compliance with the experiment.

A hysteresis phenomenon in NMR spectra of molecular nanomagnets Fe8: a resonant quantum tunneling system

Science.gov (United States)

Yamasaki, Tomoaki; Ueda, Miki; Maegawa, Satoru

2003-05-01

A molecular nanomagnet Fe8 with a total spin S=10 in the ground state attracts much attention as a substance which exhibits the quantum tunneling of magnetization below 300 mK. We performed 1H NMR measurements for a single crystal of Fe8 in temperature range between 20 and 800 mK. The spectra below 300 mK strongly depend on the sequence of the applied field and those in the positive and negative fields are not symmetric about zero field, while they are symmetric above 300 mK. We discuss the origin of this hysteresis phenomenon, relating to the initial spin state of molecules, the resonant quantum tunneling and the nuclear spin relaxation process.

A hysteresis phenomenon in NMR spectra of molecular nanomagnets Fe8: a resonant quantum tunneling system

International Nuclear Information System (INIS)

Yamasaki, Tomoaki; Ueda, Miki; Maegawa, Satoru

2003-01-01

A molecular nanomagnet Fe8 with a total spin S=10 in the ground state attracts much attention as a substance which exhibits the quantum tunneling of magnetization below 300 mK. We performed 1 H NMR measurements for a single crystal of Fe8 in temperature range between 20 and 800 mK. The spectra below 300 mK strongly depend on the sequence of the applied field and those in the positive and negative fields are not symmetric about zero field, while they are symmetric above 300 mK. We discuss the origin of this hysteresis phenomenon, relating to the initial spin state of molecules, the resonant quantum tunneling and the nuclear spin relaxation process

Solution and solid state NMR studies of the structure and dynamics of C60 and C70

International Nuclear Information System (INIS)

Johnson, R.D.; Yannoni, C.S.; Salem, J.; Meijer, G.; Bethune, D.S.

1991-01-01

This paper investigates the structure and dynamics of C 60 and C 70 with 13 C NMR spectroscopy. In solution, high-resolution spectra reveal that C 60 has a single resonance at 143 ppm, indicating a strained, aromatic system with high symmetry. This is strong evidence for a C 60 soccer ball geometry. A 2D NMR INADEQUATE experiment on 13 C-enriched C 70 reveals the bonding connectivity to be a linear string, in firm support of the proposed rugby ball structure with D 5h symmetry, and furnishes resonance assignments. Solid state NMR spectra of C 60 at ambient temperatures yield a narrow resonance, indicative of rapid molecular reorientation. Variable temperature T 1 measurements show that the rotational correlation time is ∼ 10 - 9 s at 230 K. At 77 K, this time increases to more than 1 ms, and the 13 C NMR spectrum of C 60 is a powder pattern due to chemical shift anisotropy (tensor components 220, 186, 40 ppm). At intermediate temperatures a narrow peak is superimposed on the powder pattern, suggesting a distribution of barriers to molecular motion in the sample, or the presence of an additional phase in the solid state. A Carr-Purcell dipolar experiment on C 60 in the solid state allows the first precise determination of the C 60 bond lengths: 1.45 and 1.40 Angstrom

Determination of the Rotational Diffusion Tensor of Macromolecules in Solution from NMR Relaxation Data with a Combination of Exact and Approximate Methods—Application to the Determination of Interdomain Orientation in Multidomain Proteins

Science.gov (United States)

Ghose, Ranajeet; Fushman, David; Cowburn, David

2001-04-01

In this paper we present a method for determining the rotational diffusion tensor from NMR relaxation data using a combination of approximate and exact methods. The approximate method, which is computationally less intensive, computes values of the principal components of the diffusion tensor and estimates the Euler angles, which relate the principal axis frame of the diffusion tensor to the molecular frame. The approximate values of the principal components are then used as starting points for an exact calculation by a downhill simplex search for the principal components of the tensor over a grid of the space of Euler angles relating the diffusion tensor frame to the molecular frame. The search space of Euler angles is restricted using the tensor orientations calculated using the approximate method. The utility of this approach is demonstrated using both simulated and experimental relaxation data. A quality factor that determines the extent of the agreement between the measured and predicted relaxation data is provided. This approach is then used to estimate the relative orientation of SH3 and SH2 domains in the SH(32) dual-domain construct of Abelson kinase complexed with a consolidated ligand.

Determination of the rotational diffusion tensor of macromolecules in solution from nmr relaxation data with a combination of exact and approximate methods--application to the determination of interdomain orientation in multidomain proteins.

Science.gov (United States)

Ghose, R; Fushman, D; Cowburn, D

2001-04-01

In this paper we present a method for determining the rotational diffusion tensor from NMR relaxation data using a combination of approximate and exact methods. The approximate method, which is computationally less intensive, computes values of the principal components of the diffusion tensor and estimates the Euler angles, which relate the principal axis frame of the diffusion tensor to the molecular frame. The approximate values of the principal components are then used as starting points for an exact calculation by a downhill simplex search for the principal components of the tensor over a grid of the space of Euler angles relating the diffusion tensor frame to the molecular frame. The search space of Euler angles is restricted using the tensor orientations calculated using the approximate method. The utility of this approach is demonstrated using both simulated and experimental relaxation data. A quality factor that determines the extent of the agreement between the measured and predicted relaxation data is provided. This approach is then used to estimate the relative orientation of SH3 and SH2 domains in the SH(32) dual-domain construct of Abelson kinase complexed with a consolidated ligand. Copyright 2001 Academic Press.

An NMR thermometer for cryogenic magic-angle spinning NMR: The spin-lattice relaxation of 127I in cesium iodide

Science.gov (United States)

Sarkar, Riddhiman; Concistrè, Maria; Johannessen, Ole G.; Beckett, Peter; Denning, Mark; Carravetta, Marina; al-Mosawi, Maitham; Beduz, Carlo; Yang, Yifeng; Levitt, Malcolm H.

2011-10-01

The accurate temperature measurement of solid samples under magic-angle spinning (MAS) is difficult in the cryogenic regime. It has been demonstrated by Thurber et al. (J. Magn. Reson., 196 (2009) 84-87) [10] that the temperature dependent spin-lattice relaxation time constant of 79Br in KBr powder can be useful for measuring sample temperature under MAS over a wide temperature range (20-296 K). However the value of T1 exceeds 3 min at temperatures below 20 K, which is inconveniently long. In this communication, we show that the spin-lattice relaxation time constant of 127I in CsI powder can be used to accurately measure sample temperature under MAS within a reasonable experimental time down to 10 K.

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.

Fully automated system for pulsed NMR measurements

International Nuclear Information System (INIS)

Cantor, D.M.

1977-01-01

A system is described which places many of the complex, tedious operations for pulsed NMR experiments under computer control. It automatically optimizes the experiment parameters of pulse length and phase, and precision, accuracy, and measurement speed are improved. The hardware interface between the computer and the NMR instrument is described. Design features, justification of the choices made between alternative design strategies, and details of the implementation of design goals are presented. Software features common to all the available experiments are discussed. Optimization of pulse lengths and phases is performed via a sequential search technique called Uniplex. Measurements of the spin-lattice and spin-spin relaxation times and of diffusion constants are automatic. Options for expansion of the system are explored along with some of the limitations of the system

Complete relaxation and conformational exchange matrix (CORCEMA) analysis of intermolecular saturation transfer effects in reversibly forming ligand-receptor complexes.

Science.gov (United States)

Jayalakshmi, V; Krishna, N Rama

2002-03-01

A couple of recent applications of intermolecular NOE (INOE) experiments as applied to biomolecular systems involve the (i) saturation transfer difference NMR (STD-NMR) method and (ii) the intermolecular cross-saturation NMR (ICS-NMR) experiment. STD-NMR is a promising tool for rapid screening of a large library of compounds to identify bioactive ligands binding to a target protein. Additionally, it is also useful in mapping the binding epitopes presented by a bioactive ligand to its target protein. In this latter application, the STD-NMR technique is essentially similar to the ICS-NMR experiment, which is used to map protein-protein or protein-nucleic acid contact surfaces in complexes. In this work, we present a complete relaxation and conformational exchange matrix (CORCEMA) theory (H. N. B. Moseley et al., J. Magn. Reson. B 108, 243-261 (1995)) applicable for these two closely related experiments. As in our previous work, we show that when exchange is fast on the relaxation rate scale, a simplified CORCEMA theory can be formulated using a generalized average relaxation rate matrix. Its range of validity is established by comparing its predictions with those of the exact CORCEMA theory which is valid for all exchange rates. Using some ideal model systems we have analyzed the factors that influence the ligand proton intensity changes when the resonances from some protons on the receptor protein are saturated. The results show that the intensity changes in the ligand signals in an intermolecular NOE experiment are very much dependent upon: (1) the saturation time, (2) the location of the saturated receptor protons with respect to the ligand protons, (3) the conformation of the ligand-receptor interface, (4) the rotational correlation times for the molecular species, (5) the kinetics of the reversibly forming complex, and (6) the ligand/receptor ratio. As an example of a typical application of the STD-NMR experiment we have also simulated the STD effects for a

1H NMR of High-Potential Iron-Sulfur Protein from the Purple Non-Sulfur Bacterium Rhodoferax fermentans

DEFF Research Database (Denmark)

Ciurli, Stefano; Cremonini, Mauro Andrea; Kofod, Pauli

1996-01-01

residues bound to the [4Fe-4S]3+/2+ cluster have been performed using one-dimensional NOE and exchange spectroscopy experiments. 1H-NMR hyperfine shifts and relaxation rates of cluster-bound Cys β-CH2 protons indicate that in the [4Fe-4S]3+ cluster one iron ion can be formally described as Fe(III), while......Oxidized and reduced forms of high-potential iron-sulfur protein (HiPIP) from the purple non-sulfur photosynthetic bacterium Rhodoferux fermentans have been characterized using 1H-NMR spectroscopy. Pairwise and sequence-specific assignments of hyperfine-shifted 1H-NMR signals to protons of cysteine...... longitudinal relaxation rates of Cys β-CH2 protons in HiPIPs from six different sources as a function of the Fe-S-Cβ-Cα dihedral angle, indicate that the major contribution is due to a dipolar metal-centered mechanism, with a non-negligeable contribution from a ligand-centered dipolar mechanism which involves...

Power-law versus exponential relaxation of {sup 29}Si nucleus spins in Si:B crystals

Energy Technology Data Exchange (ETDEWEB)

Koplak, O.V. [Institute of Problems of Chemical Physics, 142432 Chernogolovka, Moscow (Russian Federation); Taras Shevchenko Kiev National University and National Academy of Sciences, 01033 Kiev (Ukraine); Talantsev, A.D., E-mail: adt@icp.ac.ru [Institute of Problems of Chemical Physics, 142432 Chernogolovka, Moscow (Russian Federation); Morgunov, R.B. [Institute of Problems of Chemical Physics, 142432 Chernogolovka, Moscow (Russian Federation); Sholokhov Moscow State University for the Humanities, 109240 Moscow (Russian Federation)

2016-02-15

The Si:B micro-crystals enriched with {sup 29}Si isotope have been studied by high resolution nuclear magnetic resonance (NMR) in the 300–800 K temperature range. The recovery of nuclear magnetization saturated by radiofrequency impulses follows pure power-law kinetics at 300 K, while admixture of exponential relaxation takes place at 500 K. The power-law relaxation corresponds to direct electron–nuclear relaxation due to the inhomogeneous distribution of paramagnetic centers, while exponential kinetics corresponds to the nuclear spin diffusion mechanism. The inhomogeneous distribution of deformation defects is a most probable reason of the power-law kinetics of nuclear spin relaxation. - Highlights: • {sup 29}Si nuclear magnetization relaxation follows mixed power-exponential law. • Power-law corresponds to direct electron–nuclear relaxation. • Admixture of exponential relaxation corresponds to the nuclear spin diffusion. • Inhomogeneously distributed deformation defects are responsible for power low. • Homogeneously distributed Boron acceptors are responsible for exponential part.

Sparse "1"3C labelling for solid-state NMR studies of P. pastoris expressed eukaryotic seven-transmembrane proteins

International Nuclear Information System (INIS)

Liu, Jing; Liu, Chang; Fan, Ying; Munro, Rachel A.; Ladizhansky, Vladimir; Brown, Leonid S.; Wang, Shenlin

2016-01-01

We demonstrate a novel sparse "1"3C labelling approach for methylotrophic yeast P. pastoris expression system, towards solid-state NMR studies of eukaryotic membrane proteins. The labelling scheme was achieved by co-utilizing natural abundance methanol and specifically "1"3C labelled glycerol as carbon sources in the expression medium. This strategy improves the spectral resolution by 1.5 fold, displays site-specific labelling patterns, and has advantages for collecting long-range distance restraints for structure determination of large eukaryotic membrane proteins by solid-state NMR.

sup 5 sup 9 Co-NMR studies on La sub 4 Co sub 3 O sub 1 sub 0 sub + subdelta

CERN Document Server

Miyashita, T; Fukamachi, T; Masuda, H; Sato, M

2002-01-01

Samples of La sub 4 Co sub 3 O sub 1 sub 0 sub + subdelta with delta - 0.1, 0.3 and 0.6 have been prepared. For delta - 0.1, the crossover-like changes of the spin state at approx 100 K and approx 550 K have been confirmed by the measurements of the magnetic susceptibility. At approx 550 K, we have observed for the sample the anomalous T-dependence of the electrical resistivity and the thermoelectric power. Its NMR spectra exhibit the very large broadening at low temperatures due to the antiferromagnetic ordering. NMR spectra of the sample with delta - 0.6 show that there exist two kinds of Co atoms: The NMR signal intensity of one of the two with the larger relaxation rate 1/T sub 2 decreases, while the intensity of the other with the smaller 1/T sub 2 increases, with decreasing T below 100 K, which indicates that the spectra of the latter are from the Co sup 3 sup + in the low spin state. The T-dependence of 1/T sub 1 shows the existence of the energy difference between the low spin (spin S=0) and intermedi...

Process of Fragment-Based Lead Discovery—A Perspective from NMR