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Sample records for 17o nmr parameters

  1. (17)O NMR Investigation of Water Structure and Dynamics.

    PubMed

    Keeler, Eric G; Michaelis, Vladimir K; Griffin, Robert G

    2016-08-18

    The structure and dynamics of the bound water in barium chlorate monohydrate were studied with (17)O nuclear magnetic resonance (NMR) spectroscopy in samples that are stationary and spinning at the magic-angle in magnetic fields ranging from 14.1 to 21.1 T. (17)O NMR parameters of the water were determined, and the effects of torsional oscillations of the water molecule on the (17)O quadrupolar coupling constant (CQ) were delineated with variable temperature MAS NMR. With decreasing temperature and reduction of the librational motion, we observe an increase in the experimentally measured CQ explaining the discrepancy between experiments and predictions from density functional theory. In addition, at low temperatures and in the absence of (1)H decoupling, we observe a well-resolved (1)H-(17)O dipole splitting in the spectra, which provides information on the structure of the H2O molecule. The splitting arises because of the homogeneous nature of the coupling between the two (1)H-(17)O dipoles and the (1)H-(1)H dipole.

  2. Solid-state 17O NMR of pharmaceutical compounds: salicylic acid and aspirin.

    PubMed

    Kong, Xianqi; Shan, Melissa; Terskikh, Victor; Hung, Ivan; Gan, Zhehong; Wu, Gang

    2013-08-22

    We report solid-state NMR characterization of the (17)O quadrupole coupling (QC) and chemical shift (CS) tensors in five site-specifically (17)O-labeled samples of salicylic acid and o-acetylsalicylic acid (Aspirin). High-quality (17)O NMR spectra were obtained for these important pharmaceutical compounds under both static and magic angle spinning (MAS) conditions at two magnetic fields, 14.0 and 21.1 T. A total of 14 (17)O QC and CS tensors were experimentally determined for the seven oxygen sites in salicylic acid and Aspirin. Although both salicylic acid and Aspirin form hydrogen bonded cyclic dimers in the solid state, we found that the potential curves for the concerted double proton transfer in these two compounds are significantly different. In particular, while the double-well potential curve in Aspirin is nearly symmetrical, it is highly asymmetrical in salicylic acid. This difference results in quite different temperature dependencies in (17)O MAS spectra of the two compounds. A careful analysis of variable-temperature (17)O MAS NMR spectra of Aspirin allowed us to obtain the energy asymmetry (ΔE) of the double-well potential, ΔE = 3.0 ± 0.5 kJ/mol. We were also able to determine a lower limit of ΔE for salicylic acid, ΔE > 10 kJ/mol. These asymmetrical features in potential energy curves were confirmed by plane-wave DFT computations, which yielded ΔE = 3.7 and 17.8 kJ/mol for Aspirin and salicylic acid, respectively. To complement the solid-state (17)O NMR data, we also obtained solid-state (1)H and (13)C NMR spectra for salicylic acid and Aspirin. Using experimental NMR parameters obtained for all magnetic nuclei present in salicylic acid and Aspirin, we found that plane-wave DFT computations can produce highly accurate NMR parameters in well-defined crystalline organic compounds.

  3. 17O NMR studies of ortho-substituent effects in substituted phenyl tosylates.

    PubMed

    Nummert, Vilve; Mäemets, Vahur; Piirsalu, Mare; Koppel, Ilmar A

    2012-10-01

    (17)O NMR spectra for 35 ortho-, para-, and meta-substituted phenyl tosylates (phenyl 4-methylbenzenesulfonates), 4-CH(3)-C(6)H(4) SO(2)OC(6)H(4)-X, at natural abundance in acetonitrile at 50 °C were recorded. The (17)O NMR chemical shifts, δ((17)O), of the sulfonyl (SO(2)) and the single-bonded phenoxy (OPh) oxygens for para and meta derivatives correlated well with dual substituent parameter treatment using the Taft inductive, σ(I), and resonance, σº(R), constants. The influence of ortho substituents on the sulfonyl oxygen and the single-bonded phenoxy oxygen chemical shifts, δ((17)O), was found to be nicely described by the Charton equation: δ((17)O)(ortho) = δ((17)O)(H) + ρ(I)σ(I) + ρ(R)σ°(R) + δE(s)(B) when the data treatment was performed separately for electron-donating +R substituents and electron-attracting -R substituents. Electron-attracting meta and para substituents in the phenyl moiety caused deshielding while the electron-donating meta, para and ortho +R substituents produce shielding effects on the sulfonyl (SO(2)) and single-bonded phenoxy (OPh) oxygens. The influence of ortho inductive and resonance effects in the case of +R substituents was found to be approximately twice higher than the corresponding influence from the para position. Due to the steric effect of ortho substituents a decrease in shielding of the oxygens at the sulfonyl group (δE(s)(B) > 0, E(s)(B) < 0) was detected.

  4. (17)O NMR and Raman Spectroscopies of Green Tea Infusion with Nanomaterial to Investigate Their Properties.

    PubMed

    Zhou, Changyan; Zhang, Huiping; Yan, Ying; Zhang, Xinya

    2016-09-01

    (17)O NMR and Raman spectrograms of green tea infusions with nanomaterial were investigated. Different green tea infusions were prepared by steeping tea powder with different concentrations of nanomaterial aqueous solution. The tea infusions were tested with (17)O NMR and Raman spectroscopies. The (17)O NMR results showed that line width increased to 90 in the tea infusions after nanomaterial was added as a result of the effects of the self-association of Ca(2+) and tea polyphenol. The results of Raman spectroscopy showed that, in tea infusions, the enhancement of C─C and C─O stretching vibrations suggest an increase in the number of effective components in water.

  5. Natural abundance 17O DNP two-dimensional and surface-enhanced NMR spectroscopy

    DOE PAGES

    Perras, Frédéric A.; Kobayashi, Takeshi; Pruski, Marek

    2015-06-22

    Due to its extremely low natural abundance and quadrupolar nature, the 17O nuclide is very rarely used for spectroscopic investigation of solids by NMR without isotope enrichment. Additionally, the applicability of dynamic nuclear polarization (DNP), which leads to sensitivity enhancements of 2 orders of magnitude, to 17O is wrought with challenges due to the lack of spin diffusion and low polarization transfer efficiency from 1H. Here, we demonstrate new DNP-based measurements that extend 17O solid-state NMR beyond its current capabilities. The use of the PRESTO technique instead of conventional 1H–17O cross-polarization greatly improves the sensitivity and enables the facile measurementmore » of undistorted line shapes and two-dimensional 1H–17O HETCOR NMR spectra as well as accurate internuclear distance measurements at natural abundance. This was applied for distinguishing hydrogen-bonded and lone 17O sites on the surface of silica gel; the one-dimensional spectrum of which could not be used to extract such detail. As a result, this greatly enhanced sensitivity has enabled, for the first time, the detection of surface hydroxyl sites on mesoporous silica at natural abundance, thereby extending the concept of DNP surface-enhanced NMR spectroscopy to the 17O nuclide.« less

  6. Ultra-high resolution 17O solid-state NMR spectroscopy of biomolecules: a comprehensive spectral analysis of monosodium L-glutamate·monohydrate.

    PubMed

    Wong, Alan; Howes, Andy P; Yates, Jonathan R; Watts, Anthony; Anupõld, Tiit; Past, Jaan; Samoson, Ago; Dupree, Ray; Smith, Mark E

    2011-07-14

    Monosodium L-glutamate monohydrate, a multiple oxygen site (eight) compound, is used to demonstrate that a combination of high-resolution solid-state NMR spectroscopic techniques opens up new possibilities for (17)O as a nuclear probe of biomolecules. Eight oxygen sites have been resolved by double rotation (DOR) and multiple quantum (MQ) NMR experiments, despite the (17)O chemical shifts lying within a narrow shift range of <50 ppm. (17)O DOR NMR not only provides high sensitivity and spectral resolution, but also allows a complete set of the NMR parameters (chemical shift anisotropy and electric-field gradient) to be determined from the DOR spinning-sideband manifold. These (17)O NMR parameters provide an important multi-parameter comparison with the results from the quantum chemical NMR calculations, and enable unambiguous oxygen-site assignment and allow the hydrogen positions to be refined in the crystal lattice. The difference in sensitivity between DOR and MQ NMR experiments of oxygen in bio/organic molecules is also discussed. The data presented here clearly illustrates that a high resolution (17)O solid-state NMR methodology is now available for the study of biomolecules, offering new opportunities for resolving structural information and hence new molecular insights.

  7. 17O NMR study of diamagnetic and paramagnetic lanthanide(III)-DOTA complexes in aqueous solution.

    PubMed

    Fusaro, Luca; Luhmer, Michel

    2014-08-18

    The complexes between the polyaminocarboxylate DOTA ligand and the whole series of stable lanthanide(III) metal ions, except Gd(3+), were studied in aqueous solution by (17)O NMR. For all of the paramagnetic systems, the (17)O NMR signals of both the nonchelating (O1) and chelating (O2) oxygen atoms could be detected, and for some of them, the signals of both the SAP and TSAP (TSAP') conformational isomers were also observed. Line width data analysis reveals that signal broadening is not dominated by paramagnetic relaxation enhancement, as it was believed to be. The data indicate that quadrupole relaxation and, for some complexes, chemical exchange between the SAP and TSAP isomers are the major contributions to the (17)O NMR line width at 25 °C. Besides, the Fermi contact and pseudocontact contributions to the observed lanthanide-induced shifts could be extracted. The (17)O hyperfine coupling constants determined for O2 in the SAP and TSAP isomers are similar to each other and to the values reported for several Gd(III) complexes comprising fast-exchanging ligands. Interestingly, the results suggest that (17)O NMR should prove to be useful for the study of highly paramagnetic Gd(III) complexes of nonlabile ligands.

  8. Structural Insights into Bound Water in Crystalline Amino Acids: Experimental and Theoretical (17)O NMR.

    PubMed

    Michaelis, Vladimir K; Keeler, Eric G; Ong, Ta-Chung; Craigen, Kimberley N; Penzel, Susanne; Wren, John E C; Kroeker, Scott; Griffin, Robert G

    2015-06-25

    We demonstrate here that the (17)O NMR properties of bound water in a series of amino acids and dipeptides can be determined with a combination of nonspinning and magic-angle spinning experiments using a range of magnetic field strengths from 9.4 to 21.1 T. Furthermore, we propose a (17)O chemical shift fingerprint region for bound water molecules in biological solids that is well outside the previously determined ranges for carbonyl, carboxylic, and hydroxyl oxygens, thereby offering the ability to resolve multiple (17)O environments using rapid one-dimensional NMR techniques. Finally, we compare our experimental data against quantum chemical calculations using GIPAW and hybrid-DFT, finding intriguing discrepancies between the electric field gradients calculated from structures determined by X-ray and neutron diffraction.

  9. Multivariate Analysis and Quantitation of (17)O-NMR in Primary Alcohol Mixtures

    SciTech Connect

    Alam, M.Kathleen; Alam, Todd M.

    1999-07-01

    Multivariate techniques were used to address the quantification of {sup 17}O-NMR (nuclear magnetic resonance) spectra for a series of primary alcohol mixtures. Due to highly overlapping resonances, quantitative spectral evaluation using standard integration and deconvolution techniques proved difficult. Multivariate evaluation of the {sup 17}O-NMR spectral data obtained for 26 mixtures of five primary alcohols demonstrated that obtaining information about spectral overlap and interferences allowed the development of more accurate models. Initial partial least squares (PLS) models developed for the {sup 17}O-NMR data collected from the primary alcohol mixtures resulted in very poor precision, with signal overlap between the different chemical species suspected of being the primary contributor to the error. To directly evaluate the question of spectral overlap in these alcohol mixtures, net analyte signal (NAS) analyses were performed. The NAS results indicate that alcohols with similar chain lengths produced severely overlapping {sup 17}O-NMR resonances. Grouping the alcohols based on chain length allowed more accurate and robust calibration models to be developed.

  10. Constraining 17O and 27Al NMR spectra of high-pressure crystals and glasses: New data for jadeite, pyrope, grossular, and mullite

    USGS Publications Warehouse

    Kelsey, K.E.; Stebbins, J.F.; Du, L.-S.; Hankins, B.

    2007-01-01

    The 17O NMR spectra of glasses quenched from melts at high pressure are often difficult to interpret due to overlapping peaks and lack of crystalline model compounds. High-pressure aluminosilicate glasses often contain significant amounts of [5]Al and [6]Al, thus these high-pressure glasses must contain oxygen bonded to high-coordinated aluminum. The 17O NMR parameters for the minerals jadeite, pyrope, grossular, and mullite are presented to assist interpretation of glass spectra and to help test quantum chemical calculations. The 17O NMR parameters for jadeite and grossular support previous peak assignments of oxygen bonded to Si and high-coordinated Al in high-pressure glasses as well as quantum chemical calculations. The oxygen tricluster in mullite is very similar to the previously observed tricluster in grossite (CaAl4 O7) and suspected triclusters in glasses. We also present 27Al NMR spectra for pyrope, grossular, and mullite.

  11. Investigation of Oxidative Degradation in Polymers Using (17)O NMR Spectroscopy

    SciTech Connect

    Alam, Todd M.; Celina, Mathew; Assink, Roger A.; Clough, Roger L.; Gillen, Kenneth T.; Wheeler David R.

    1999-07-20

    The thermal oxidation of pentacontane (C{sub 50}H{sub 102}), and of the homopolymer polyisoprene, has been investigated using {sup 17}O NMR spectroscopy. By performing the oxidation using {sup 17}O labeled O{sub 2} gas, it is possible to easily identify degradation products, even at relatively low concentrations. It is demonstrated that details of the degradation mechanism can be obtained from analysis of the {sup 17}O NMR spectra as a function of total oxidation. Pentacontane reveals the widest variety of reaction products, and exhibits changes in the relative product distributions with increasing O{sub 2} consumption. At low levels of oxygen incorporation, peroxides are the major oxidation product, while at later stages of degradation these species are replaced by increasing concentrations of ketones, alcohols, carboxylic acids and esters. Analyzing the product distribution can help in identification of the different free-radical decomposition pathways of hydroperoxides, including recombination, proton abstraction and chain scission, as well as secondary reactions. The {sup 17}O NMR spectra of thermally oxidized polyisoprene reveal fewer degradation functionalities, but exhibit an increased complexity in the type of observed degradation species due to structural features such as unsaturation and methyl branching. Alcohols and ethers formed from hydrogen abstraction and free radical termination.

  12. Identification of different oxygen species in oxide nanostructures with (17)O solid-state NMR spectroscopy.

    PubMed

    Wang, Meng; Wu, Xin-Ping; Zheng, Sujuan; Zhao, Li; Li, Lei; Shen, Li; Gao, Yuxian; Xue, Nianhua; Guo, Xuefeng; Huang, Weixin; Gan, Zhehong; Blanc, Frédéric; Yu, Zhiwu; Ke, Xiaokang; Ding, Weiping; Gong, Xue-Qing; Grey, Clare P; Peng, Luming

    2015-02-01

    Nanostructured oxides find multiple uses in a diverse range of applications including catalysis, energy storage, and environmental management, their higher surface areas, and, in some cases, electronic properties resulting in different physical properties from their bulk counterparts. Developing structure-property relations for these materials requires a determination of surface and subsurface structure. Although microscopy plays a critical role owing to the fact that the volumes sampled by such techniques may not be representative of the whole sample, complementary characterization methods are urgently required. We develop a simple nuclear magnetic resonance (NMR) strategy to detect the first few layers of a nanomaterial, demonstrating the approach with technologically relevant ceria nanoparticles. We show that the (17)O resonances arising from the first to third surface layer oxygen ions, hydroxyl sites, and oxygen species near vacancies can be distinguished from the oxygen ions in the bulk, with higher-frequency (17)O chemical shifts being observed for the lower coordinated surface sites. H2 (17)O can be used to selectively enrich surface sites, allowing only these particular active sites to be monitored in a chemical process. (17)O NMR spectra of thermally treated nanosized ceria clearly show how different oxygen species interconvert at elevated temperature. Density functional theory calculations confirm the assignments and reveal a strong dependence of chemical shift on the nature of the surface. These results open up new strategies for characterizing nanostructured oxides and their applications.

  13. Microsolvation of methylmercury: structures, energies, bonding and NMR constants ((199)Hg, (13)C and (17)O).

    PubMed

    Flórez, Edison; Maldonado, Alejandro F; Aucar, Gustavo A; David, Jorge; Restrepo, Albeiro

    2016-01-21

    Hartree-Fock (HF) and second order perturbation theory (MP2) calculations within the scalar and full relativistic frames were carried out in order to determine the equilibrium geometries and interaction energies between cationic methylmercury (CH3Hg(+)) and up to three water molecules. A total of nine structures were obtained. Bonding properties were analyzed using the Quantum Theory of Atoms In Molecules (QTAIM). The analyses of the topology of electron densities reveal that all structures exhibit a partially covalent HgO interaction between methylmercury and one water molecule. Consideration of additional water molecules suggests that they solvate the (CH3HgOH2)(+) unit. Nuclear magnetic shielding constants σ((199)Hg), σ((13)C) and σ((17)O), as well as indirect spin-spin coupling constants J((199)Hg-(13)C), J((199)Hg-(17)O) and J((13)C-(17)O), were calculated for each one of the geometries. Thermodynamic stability and the values of NMR constants correlate with the ability of the system to directly coordinate oxygen atoms of water molecules to the mercury atom in methylmercury and with the formation of hydrogen bonds among solvating water molecules. Relativistic effects account for 11% on σ((13)C) and 14% on σ((17)O), which is due to the presence of Hg (heavy atom on light atom, HALA effect), while the relativistic effects on σ((199)Hg) are close to 50% (heavy atom on heavy atom itself, HAHA effect). J-coupling constants are highly influenced by relativity when mercury is involved as in J((199)Hg-(13)C) and J((199)Hg-(17)O). On the other hand, our results show that the values of NMR constants for carbon and oxygen, atoms which are connected through mercury (C-HgO), are highly correlated and are greatly influenced by the presence of water molecules. Water molecules introduce additional electronic effects to the relativistic effects due to the mercury atom.

  14. Identification of different oxygen species in oxide nanostructures with 17O solid-state NMR spectroscopy

    PubMed Central

    Wang, Meng; Wu, Xin-Ping; Zheng, Sujuan; Zhao, Li; Li, Lei; Shen, Li; Gao, Yuxian; Xue, Nianhua; Guo, Xuefeng; Huang, Weixin; Gan, Zhehong; Blanc, Frédéric; Yu, Zhiwu; Ke, Xiaokang; Ding, Weiping; Gong, Xue-Qing; Grey, Clare P.; Peng, Luming

    2015-01-01

    Nanostructured oxides find multiple uses in a diverse range of applications including catalysis, energy storage, and environmental management, their higher surface areas, and, in some cases, electronic properties resulting in different physical properties from their bulk counterparts. Developing structure-property relations for these materials requires a determination of surface and subsurface structure. Although microscopy plays a critical role owing to the fact that the volumes sampled by such techniques may not be representative of the whole sample, complementary characterization methods are urgently required. We develop a simple nuclear magnetic resonance (NMR) strategy to detect the first few layers of a nanomaterial, demonstrating the approach with technologically relevant ceria nanoparticles. We show that the 17O resonances arising from the first to third surface layer oxygen ions, hydroxyl sites, and oxygen species near vacancies can be distinguished from the oxygen ions in the bulk, with higher-frequency 17O chemical shifts being observed for the lower coordinated surface sites. H217O can be used to selectively enrich surface sites, allowing only these particular active sites to be monitored in a chemical process. 17O NMR spectra of thermally treated nanosized ceria clearly show how different oxygen species interconvert at elevated temperature. Density functional theory calculations confirm the assignments and reveal a strong dependence of chemical shift on the nature of the surface. These results open up new strategies for characterizing nanostructured oxides and their applications. PMID:26601133

  15. Solid-State 17O NMR Study of Benzoic Acid Adsorption On Metal Oxide Surfaces

    SciTech Connect

    Hagaman, Edward {Ed} W; Chen, Banghao; Jiao, Jian; Parsons, Williams

    2012-01-01

    Solid-state 17O NMR spectra of 17O-labeled benzoic and anisic acids are reported and benzoic acid is used to probe the surface of metal oxides. Complexes formed when benzoic acid is dry-mixed with mesoporous silica, and nonporous titania and alumina are characterized. Chemical reactions with silica are not observed. The nature of benzoic acid on silica is a function of the water content of the oxide. The acid disperses in the pores of the silica if the silica is in equilibrium with ambient laboratory humidity. The acid displays high mobility as evidenced by a liquid-like, Lorentzian resonance. Excess benzoic acid remains as the crystalline hydrogen-bonded dimer. Benzoic acid reacts with titania and alumina surfaces in equilibrium with laboratory air to form the corresponding titanium and aluminum benzoates. In both materials the oxygen of the 17O-labeled acid is bound to the metal, showing the reaction proceeds by bond formation between oxygen deficient metal sites and the oxygen of the carboxylic acid. 27Al MAS NMR confirms this mechanism for the reaction on alumina. Dry mixing of benzoic acid with alumina rapidly quenches pentacoordinate aluminum sites, excellent evidence that these sites are confined to the surface of the alumina particles.

  16. Solid-State (17)O NMR of Oxygen-Nitrogen Singly Bonded Compounds: Hydroxylammonium Chloride and Sodium Trioxodinitrate (Angeli's Salt).

    PubMed

    Lu, Jiasheng; Kong, Xianqi; Terskikh, Victor; Wu, Gang

    2015-07-23

    We report a solid-state NMR study of (17)O-labeled hydroxylammonium chloride ([H(17)O-NH3]Cl) and sodium trioxodinitrate monohydrate (Na2[(17)ONNO2]·H2O, Angeli's salt). The common feature in these two compounds is that they both contain oxygen atoms that are singly bonded to nitrogen. For this class of oxygen-containing functional groups, there is very limited solid-state (17)O NMR data in the literature. In this work, we experimentally measured the (17)O chemical shift and quadrupolar coupling tensors. With the aid of plane-wave DFT computation, the (17)O NMR tensor orientations were determined in the molecular frame of reference. We found that the characteristic feature of an O-N single bond is that the (17)O nucleus exhibits a large quadrupolar coupling constant (13-15 MHz) but a rather small chemical shift anisotropy (100-250 ppm), in sharp contrast with the nitroso (O═N) functional group for which both quantities are very large (e.g., 16 MHz and 3000 ppm, respectively).

  17. 23 Na and 17O NMR studies of hyperkagome Na4Ir3O8

    NASA Astrophysics Data System (ADS)

    Shockley, Abigail; Bert, Fabrice; Orain, Jean-Christophe; Okamoto, Yoshihiko; Mendels, Philippe

    2015-03-01

    Na4Ir3O8 is a unique case of a 3D corner sharing triangular lattice which can be decorated with quantum spins. It has spurred a lot of theoretical interest as a spin liquid candidate of a new kind where the Hamiltonian might not be thought in terms of a simple Heisenberg case because of spin orbit coupling on the Ir 5d element. We present a comprehensive set of NMR data taken on both the 23Na and 17O sites. We have found that magnetic freezing of all Ir sites sets in below Tf ~ 7.5K ~ 0 . 019 J with a clear hyperfine field transferred from Ir moments and a drastic decrease of 1 /T1 . Above Tf, physical properties are expected to be a landmark of frustration in this exotic geometry. We will discuss our shift and relaxation data in the temperature range of 300K to 7.5 K in the light of published thermodynamic measurements (Y. Okamotoa et al, PRL 99 137207, 2007 and Y. Singh et al, PRB 88 220413(R), 2013) and comment on their implications for the already existing large body of theoretical work.

  18. Joint Experimental and Computational 17O and 1H Solid State NMR Study of Ba2In2O4(OH)2 Structure and Dynamics

    PubMed Central

    2015-01-01

    A structural characterization of the hydrated form of the brownmillerite-type phase Ba2In2O5, Ba2In2O4(OH)2, is reported using experimental multinuclear NMR spectroscopy and density functional theory (DFT) energy and GIPAW NMR calculations. When the oxygen ions from H2O fill the inherent O vacancies of the brownmillerite structure, one of the water protons remains in the same layer (O3) while the second proton is located in the neighboring layer (O2) in sites with partial occupancies, as previously demonstrated by Jayaraman et al. (Solid State Ionics2004, 170, 25−32) using X-ray and neutron studies. Calculations of possible proton arrangements within the partially occupied layer of Ba2In2O4(OH)2 yield a set of low energy structures; GIPAW NMR calculations on these configurations yield 1H and 17O chemical shifts and peak intensity ratios, which are then used to help assign the experimental MAS NMR spectra. Three distinct 1H resonances in a 2:1:1 ratio are obtained experimentally, the most intense resonance being assigned to the proton in the O3 layer. The two weaker signals are due to O2 layer protons, one set hydrogen bonding to the O3 layer and the other hydrogen bonding alternately toward the O3 and O1 layers. 1H magnetization exchange experiments reveal that all three resonances originate from protons in the same crystallographic phase, the protons exchanging with each other above approximately 150 °C. Three distinct types of oxygen atoms are evident from the DFT GIPAW calculations bare oxygens (O), oxygens directly bonded to a proton (H-donor O), and oxygen ions that are hydrogen bonded to a proton (H-acceptor O). The 17O calculated shifts and quadrupolar parameters are used to assign the experimental spectra, the assignments being confirmed by 1H–17O double resonance experiments. PMID:26321789

  19. Probing surface hydrogen bonding and dynamics by natural abundance, multidimensional, 17O DNP-NMR spectroscopy

    DOE PAGES

    Perras, Frederic A.; Chaudhary, Umesh; Slowing, Igor I.; ...

    2016-05-06

    Dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR) spectroscopy is increasingly being used as a tool for the atomic-level characterization of surface sites. DNP surface-enhanced SSNMR spectroscopy of materials has, however, been limited to studying relatively receptive nuclei, and the particularly rare 17O nuclide, which is of great interest for materials science, has not been utilized. We demonstrate that advanced 17O SSNMR experiments can be performed on surface species at natural isotopic abundance using DNP. We use 17O DNP surface-enhanced 2D SSNMR to measure 17O{1H} HETCOR spectra as well as dipolar oscillations on a series of thermally treatedmore » mesoporous silica nanoparticle samples having different pore diameters. These experiments allow for a nonintrusive and unambiguous characterization of hydrogen bonding and dynamics at the surface of the material; no other single experiment can give such details about the interactions at the surface. Lastly, our data show that, upon drying, strongly hydrogen-bonded surface silanols, whose motions are greatly restricted by the interaction when compared to lone silanols, are selectively dehydroxylated.« less

  20. Qualitative study of substituent effects on NMR (15)N and (17)O chemical shifts.

    PubMed

    Contreras, Rubén H; Llorente, Tomás; Pagola, Gabriel I; Bustamante, Manuel G; Pasqualini, Enrique E; Melo, Juan I; Tormena, Cláudio F

    2009-09-10

    A qualitative approach to analyze the electronic origin of substituent effects on the paramagnetic part of chemical shifts is described and applied to few model systems, where its potentiality can be appreciated. The formulation of this approach is based on the following grounds. The influence of different inter- or intramolecular interactions on a second-order property can be qualitatively predicted if it can be known how they affect the main virtual excitations entering into that second-order property. A set of consistent approximations are introduced in order to analyze the behavior of occupied and virtual orbitals that define some experimental trends of magnetic shielding constants. This approach is applied first to study the electronic origin of methyl-beta substituent effects on both (15)N and (17)O chemical shifts, and afterward it is applied to a couple of examples of long-range substituent effects originated in charge transfer interactions such as the conjugative effect in aromatic compounds and sigma-hyperconjugative interactions in saturated multicyclic compounds.

  1. First-principles calculation of 17O and 25Mg NMR shieldings in MgO at finite temperature: rovibrational effect in solids.

    PubMed

    Rossano, Stéphanie; Mauri, Francesco; Pickard, Chris J; Farnan, Ian

    2005-04-21

    The temperature dependence of (17)O and (25)Mg NMR chemical shifts in solid MgO have been calculated using a first-principles approach. Density functional theory, pseudopotentials, a plane-wave basis set, and periodic boundary conditions were used both to describe the motion of the nuclei and to compute the NMR chemical shifts. The chemical shifts were obtained using the gauge-including projector augmented wave method. In a crystalline solid, the temperature dependence is due to both (i) the variation of the averaged equilibrium structure and (ii) the fluctuation of the atoms around this structure. In MgO, the equilibrium structure at each temperature is uniquely defined by the cubic lattice parameters, which we take from experiment. We evaluate the effect of the fluctuations within a quasiharmonic approximation. In particular, the dynamical matrix, defining the harmonic Hamiltonian, has been computed for each equilibrium volume. This harmonic Hamiltonian was used to generate nuclear configurations that obey quantum statistical mechanics. The chemical shifts were averaged over these nuclear configurations. The results reproduce the previously published experimental NMR data measured on MgO between room temperature and 1000 degrees C. It is shown that the chemical shift behavior with temperature cannot be explained by thermal expansion alone. Vibrational corrections due to the fluctuations of atoms around their equilibrium position are crucial to reproduce the experimental results.

  2. GC-MS and /sup 17/O NMR tracer studies of Et/sub 3/PO formation from auranofin and H/sub 2//sup 17/O in the presence of bovine serum albumin: an in vitro model for auranofin metabolism

    SciTech Connect

    Isab, A.A.; Shaw, C.F. III; Locke, J.

    1988-09-21

    /sup 17/O NMR spectroscopy and gas chromatographic-mass spectral analysis have been used to monitor the source of oxygen in the triethylphosphine oxide formed by the reaction of the antiarthritic drug auranofin ((2,3,4,6-tetra-O-acetyl-..beta..-D-1-glucopyranosato)(triethylphosphine)gold(I)) and bovine serum albumin (BSA) in the presence of reduced glutathione (GtSH). A procedure to extract Et/sub 3/PO from aqueous solutions and concentrate it for subsequent analyses was developed. When the in vitro reaction is carried out aerobically in /sup 17/O-enriched water, Et/sub 3/P/sup 17/O is generated. The chemical ionization (CH/sub 4/) mass measurement, (m + 1)/z = 135, and the /sup 17/O NMR parameters (delta/sub O/ = 40.6 and /sup 1/J/sub PO/ = 156 /plus minus/ 5 Hz) unambiguously establish its identity. The SH titer of the albumin (mole ratio of protein SH groups to BSA) increases during the reaction, confirming that albumin disulfide bonds are reduced in the reaction. Under aerobic conditions, the enriched Et/sub 3/PO accounts for at least 60% of the Et/sub 3/PO formed. The significance of these results for the in vivo formation of Et/sub 3/PO, an auranofin metabolite, is discussed. 25 references, 2 figures.

  3. Toward Relatively General and Accurate Quantum Chemical Predictions of Solid-State (17)O NMR Chemical Shifts in Various Biologically Relevant Oxygen-Containing Compounds.

    PubMed

    Rorick, Amber; Michael, Matthew A; Yang, Liu; Zhang, Yong

    2015-09-03

    Oxygen is an important element in most biologically significant molecules, and experimental solid-state (17)O NMR studies have provided numerous useful structural probes to study these systems. However, computational predictions of solid-state (17)O NMR chemical shift tensor properties are still challenging in many cases, and in particular, each of the prior computational works is basically limited to one type of oxygen-containing system. This work provides the first systematic study of the effects of geometry refinement, method, and basis sets for metal and nonmetal elements in both geometry optimization and NMR property calculations of some biologically relevant oxygen-containing compounds with a good variety of XO bonding groups (X = H, C, N, P, and metal). The experimental range studied is of 1455 ppm, a major part of the reported (17)O NMR chemical shifts in organic and organometallic compounds. A number of computational factors toward relatively general and accurate predictions of (17)O NMR chemical shifts were studied to provide helpful and detailed suggestions for future work. For the studied kinds of oxygen-containing compounds, the best computational approach results in a theory-versus-experiment correlation coefficient (R(2)) value of 0.9880 and a mean absolute deviation of 13 ppm (1.9% of the experimental range) for isotropic NMR shifts and an R(2) value of 0.9926 for all shift-tensor properties. These results shall facilitate future computational studies of (17)O NMR chemical shifts in many biologically relevant systems, and the high accuracy may also help the refinement and determination of active-site structures of some oxygen-containing substrate-bound proteins.

  4. 15N, 17O NMR and X-ray diffraction study of mesoionic 1,2,3,4-thiatriazolium-5-olate and its ethylated derivative

    NASA Astrophysics Data System (ADS)

    Jaźiwińsk, J.; Staszewska, O.; Staszewski, P.; Stefaniak, L.; Wiench, J. W.; Webb, G. A.

    1999-02-01

    Two mesoionic compounds with oxygenous exocyclic groups: 3-phenyl-1,2,3,4-thiatriazolium-5-olate 1 and its ethylated derivative 2 were investigated by means of 15N, 17O NMR and X-ray diffraction techniques. The exocyclic C5-O6 bond of thiatriazole 1 [1.224(3) Å] has a strong double bond character. Bond lengths in the thiatriazole ring are intermediate between single and double bond values except for S1-C5 [1.800(2) Å] which is close to a single Csp 3-S bond. The C5-O6 bond is significantly longer for the ethylated derivative 2 [1.314(4) Å]. The ethyl group attached to O6 is located in the trans position in relation to the ring S1 atom. The experimental data are compared with the results of ab initio molecular orbital calculations. The calculated absolute nuclear shieldings, chemical shifts and charge densities, in spite of some limitations, can be useful as an aid to signal assignments and for an understanding of the NMR parameters.

  5. Ab initio and sup 17 O NMR study of aromatic compounds with dicoordinate oxygen atoms. (1) Methoxy- and (methylenedioxy)benzene derivatives

    SciTech Connect

    Biekofsky, R.R.; Pomilio, A.B.; Contreras, R.H. ); Orendt, A.M.; Facelli, J.C. )

    1990-09-20

    {sup 17}O NMR data at natural abundance in toluene-d{sub 8} at 74{degree}C were obtained for aromatic compounds containing methoxy and methylenedioxy groups as side-chains substituents. {sup 17}O chemical shifts of this series of compounds are significantly influenced by both electronic and steric effects. Ortho electronic and steric substituent chemical shift effects for methoxy and methylenedioxy groups were estimated. Ab initio calculations at the 4-31G level were used to determine geometries of the compounds to gain insight into the structural aspects of these compounds. A correlation between the calculated bond orders, P{sub C{sub Ar}P{minus}O}, and the {sup 17}O chemical shift was found.

  6. In Situ Natural Abundance (17)O and (25)Mg NMR Investigation of Aqueous Mg(OH)2 Dissolution in the Presence of Supercritical CO2.

    PubMed

    Hu, Mary Y; Deng, Xuchu; Thanthiriwatte, K Sahan; Jackson, Virgil E; Wan, Chuan; Qafoku, Odeta; Dixon, David A; Felmy, Andrew R; Rosso, Kevin M; Hu, Jian Zhi

    2016-11-15

    We report an in situ high-pressure NMR capability that permits natural abundance (17)O and (25)Mg NMR characterization of dissolved species in aqueous solution and in the presence of supercritical CO2 fluid (scCO2). The dissolution of Mg(OH)2 (brucite) in a multiphase water/scCO2 fluid at 90 atm pressure and 50 °C was studied in situ, with relevance to geological carbon sequestration. (17)O NMR spectra allowed identification and distinction of various fluid species including dissolved CO2 in the H2O-rich phase, scCO2, aqueous H2O, and HCO3(-). The widely separated spectral peaks for various species can all be observed both dynamically and quantitatively at concentrations as low as 20 mM. Measurement of the concentrations of these individual species also allows an in situ estimate of the hydrogen ion concentration, or pCH(+) values, of the reacting solutions. The concentration of Mg(2+) can be observed by natural abundance (25)Mg NMR at a concentration as low as 10 mM. Quantum chemistry calculations of the NMR chemical shifts on cluster models aided in the interpretation of the experimental results. Evidence for the formation of polymeric Mg(2+) clusters at high concentrations in the H2O-rich phase, a possible critical step needed for magnesium carbonate formation, was found.

  7. Probing Oxide-Ion Mobility in the Mixed Ionic-Electronic Conductor La2NiO4+δ by Solid-State (17)O MAS NMR Spectroscopy.

    PubMed

    Halat, David M; Dervişoğlu, Rıza; Kim, Gunwoo; Dunstan, Matthew T; Blanc, Frédéric; Middlemiss, Derek S; Grey, Clare P

    2016-09-14

    While solid-state NMR spectroscopic techniques have helped clarify the local structure and dynamics of ionic conductors, similar studies of mixed ionic-electronic conductors (MIECs) have been hampered by the paramagnetic behavior of these systems. Here we report high-resolution (17)O (I = 5/2) solid-state NMR spectra of the mixed-conducting solid oxide fuel cell (SOFC) cathode material La2NiO4+δ, a paramagnetic transition-metal oxide. Three distinct oxygen environments (equatorial, axial, and interstitial) can be assigned on the basis of hyperfine (Fermi contact) shifts and quadrupolar nutation behavior, aided by results from periodic DFT calculations. Distinct structural distortions among the axial sites, arising from the nonstoichiometric incorporation of interstitial oxygen, can be resolved by advanced magic angle turning and phase-adjusted sideband separation (MATPASS) NMR experiments. Finally, variable-temperature spectra reveal the onset of rapid interstitial oxide motion and exchange with axial sites at ∼130 °C, associated with the reported orthorhombic-to-tetragonal phase transition of La2NiO4+δ. From the variable-temperature spectra, we develop a model of oxide-ion dynamics on the spectral time scale that accounts for motional differences of all distinct oxygen sites. Though we treat La2NiO4+δ as a model system for a combined paramagnetic (17)O NMR and DFT methodology, the approach presented herein should prove applicable to MIECs and other functionally important paramagnetic oxides.

  8. Probing Oxide-Ion Mobility in the Mixed Ionic–Electronic Conductor La2NiO4+δ by Solid-State 17O MAS NMR Spectroscopy

    PubMed Central

    2016-01-01

    While solid-state NMR spectroscopic techniques have helped clarify the local structure and dynamics of ionic conductors, similar studies of mixed ionic–electronic conductors (MIECs) have been hampered by the paramagnetic behavior of these systems. Here we report high-resolution 17O (I = 5/2) solid-state NMR spectra of the mixed-conducting solid oxide fuel cell (SOFC) cathode material La2NiO4+δ, a paramagnetic transition-metal oxide. Three distinct oxygen environments (equatorial, axial, and interstitial) can be assigned on the basis of hyperfine (Fermi contact) shifts and quadrupolar nutation behavior, aided by results from periodic DFT calculations. Distinct structural distortions among the axial sites, arising from the nonstoichiometric incorporation of interstitial oxygen, can be resolved by advanced magic angle turning and phase-adjusted sideband separation (MATPASS) NMR experiments. Finally, variable-temperature spectra reveal the onset of rapid interstitial oxide motion and exchange with axial sites at ∼130 °C, associated with the reported orthorhombic-to-tetragonal phase transition of La2NiO4+δ. From the variable-temperature spectra, we develop a model of oxide-ion dynamics on the spectral time scale that accounts for motional differences of all distinct oxygen sites. Though we treat La2NiO4+δ as a model system for a combined paramagnetic 17O NMR and DFT methodology, the approach presented herein should prove applicable to MIECs and other functionally important paramagnetic oxides. PMID:27538437

  9. A faster way to characterize by triple-quantum-filtered (17)O NMR water molecules strongly bound to macromolecules in solution.

    PubMed

    Lehoux, A; Krzystyniak, M; Baguet, E

    2001-01-01

    The simultaneous use of transverse and longitudinal relaxation rates, together with a transverse triple-quantum-filtering NMR sequence, was estimated for the adequate characterization of (17)O-water relaxation behavior in protein solutions. A complementary contribution to transverse relaxation was found, which was interpreted as chemical exchange of (17)O-water between different sites of the proteins. This contribution was estimated via calibration measurements. Then, for other similar samples, faster experiments could be performed. The analysis of the results obtained in this way gave adequate values of the relaxation rate of water in fast motion, of the fraction of water in slow motion, and of its correlation time. Hence, it permitted the complete characterization of the sample in a reasonable experimental time.

  10. 17O NMR studies of local structure and phase evolution for materials in the Y 2Ti 2O 7-ZrTiO 4 binary system

    NASA Astrophysics Data System (ADS)

    Palumbo, John L.; Schaedler, Tobias A.; Peng, Luming; Levi, Carlos G.; Grey, Clare P.

    2007-07-01

    17O MAS NMR and XRD studies of precursor-derived Y 1.6Zr 0.4Ti 2O 7.2 and Y 1.2Zr 0.8Ti 2O 7.4 have been performed to investigate the development of local and long-range order in these materials as they evolve from a metastable amorphous state upon heating. Zirconium titanate (ZrTiO 4) was also investigated to help interpret the 17O NMR spectra of the ternary compositions. Consistent with earlier studies, crystallization was observed at 800 °C to form a fluorite structure and a small amount of rutile; weak broad reflections were also observed which were ascribed to the presence of small pyrochlore-like ordered domains or particles within the fluorite phase. As the temperature was increased further, the sizes of these domains grew along with the concentration of rutile. At the highest temperature studied (1300 °C), the reflections of the thermodynamic phases, pyrochlore and zirconium titanate (ZrTiO 4), dominated the XRD pattern. The 17O NMR spectra revealed a series of different peaks that were assigned to different 3- and 4-coordinate O local environments. The data were consistent with the formation of a metastable phase Y 2-xZr xTi 2-yZr yO 7+x with pyrochlore-like ordering but with Zr substitution on both cation sites of the pyrochlore structure. At low temperatures, doping on the A (Y 3+) sites predominates (i.e., x> y), consistent with the fact that the pyrochlore develops out of a more disordered fluorite-like, phase. As the temperature is raised, the Zr doping on the A site decreases and the metastable phase at this temperature can now be written as Y 2-x'Zr x'Ti 2-y'Zr y'O 7+x' (i.e., x'< y'); TiO 2 is also observed, consistent with this suggestion. At high temperatures, doping on the B site decreases and the resonances due to the stoichiometric pyrochlore yttrium titanate (Y 2Ti 2O 7) dominate the NMR spectra. Weaker 17O NMR resonances due zirconium titanate (ZrTiO 4) are also observed.

  11. 17O NMR and density functional theory study of the dynamics of the carboxylate groups in DOTA complexes of lanthanides in aqueous solution.

    PubMed

    Mayer, Florian; Platas-Iglesias, Carlos; Helm, Lothar; Peters, Joop A; Djanashvili, Kristina

    2012-01-02

    The rotation of the carboxylate groups in DOTA (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate) complexes of several lanthanide ions and Sc(3+) was investigated with density functional theory (DFT) calculations and with variable temperature (17)O NMR studies at 4.7-18.8 T. The data obtained show that the rotation is much slower than the other dynamic processes taking place in these complexes. The exchange between the bound and unbound carboxylate oxygen atoms for the largest Ln(3+) ions (La(3+)→Sm(3+)) follows a pathway via a transition state in which both oxygens of the carboxylate group are bound to the Ln(3+) ion, whereas for the smaller metal ions (Tm(3+), Lu(3+), Sc(3+)) the transition state has a fully decoordinated carboxylate group. The activation free energies show a steady increase from about 75 to 125-135 kJ·mol(-1) going from La(3+) to Lu(3+). This computed trend is consistent with the results of the (17)O NMR measurements. Fast exchange between bound and unbound carboxylate oxygen atoms was observed for the diamagnetic La-DOTA, whereas for Pr-, Sm-, Lu-, and Sc-DOTA the exchange was slow on the NMR time scale. The trends in the linewidths for the various metal ions as a function of the temperature agree with trends in the rates as predicted by the DFT calculations.

  12. Simple (17) O NMR method for studying electron self-exchange reaction between UO2 (2+) and U(4+) aqua ions in acidic solution.

    PubMed

    Bányai, István; Farkas, Ildikó; Tóth, Imre

    2016-06-01

    (17) O NMR spectroscopy is proven to be suitable and convenient method for studying the electron exchange by following the decrease of (17) O-enrichment in U(17) OO(2+) ion in the presence of U(4+) ion in aqueous solution. The reactions have been performed at room temperature using I = 5 M ClO4 (-) ionic medium in acidic solutions in order to determine the kinetics of electron exchange between the U(4+) and UO2 (2+) aqua ions. The rate equation is given as R = a[H(+) ](-2)  + R', where R' is an acid independent parallel path. R' depends on the concentration of the uranium species according to the following empirical rate equation: R' = k1 [UO(2 +) ](1/2) [U(4 +) ](1/2)  + k2 [UO(2 +) ](3/2) [U(4 +) ](1/2) . The mechanism of the inverse H(+) concentration-dependent path is interpreted as equilibrium formation of reactive UO2 (+) species from UO2 (2+) and U(4+) aqua ions and its electron exchange with UO2 (2+) . The determined rate constant of this reaction path is in agreement with the rate constant of UO2 (2+) -UO2 (+) , one electron exchange step calculated by Marcus theory, match the range given experimentally of it in an early study. Our value lies in the same order of magnitude as the recently calculated ones by quantum chemical methods. The acid independent part is attributed to the formation of less hydrolyzed U(V) species, i.e. UO(3+) , which loses enrichment mainly by electron exchange with UO2 (2+) ions. One can also conclude that (17) O NMR spectroscopy, or in general NMR spectroscopy with careful kinetic analysis, is a powerful tool for studying isotope exchange reactions without the use of sophisticated separation processes. Copyright © 2015 John Wiley & Sons, Ltd.

  13. Natural abundance 17O, 6Li NMR and molecular modeling studies of the solvation structures of lithium bis(fluorosulfonyl)imide/1,2-dimethoxyethane liquid electrolytes

    SciTech Connect

    Wan, Chuan; Hu, Mary Y.; Borodin, Oleg; Qian, Jiangfeng; Qin, Zhaohai; Zhang, Ji-Guang; Hu, Jian Zhi

    2016-03-01

    Natural abundance 17O and 6Li NMR experiments, quantum chemistry and molecular dynamics studies were employed to investigate the solvation structures of Li+ at various concentrations of LiFSI in DME electrolytes in an effort to solve this puzzle. It was found that the chemical shifts of both 17O and 6Li changed with the concentration of LiFSI, indicating the changes of solvation structures with concentration. For the quantum chemistry calculations, the coordinated cluster LiFSI(DME)2 forms at first, and its relative ratio increases with increasing LiFSI concentration to 1 M. Then the solvation structure LiFSI(DME) become the dominant component. As a result, the coordination of forming contact ion pairs between Li+ and FSI- ion increases, but the association between Li+ and DME molecule decreases. Furthermore, at LiFSI concentration of 4 M the solvation structures associated with Li+(FSI-)2(DME), Li+2(FSI-)(DME)4 and (LiFSI)2(DME)3 become the dominant components. For the molecular dynamics simulation, with increasing concentration, the association between DME and Li+ decreases, and the coordinated number of FSI- increases, which is in perfect accord with the DFT results. These results provide more insight on the fundamental mechanism on the very high CE of Li deposition in these electrolytes, especially at high current density conditions.

  14. Natural abundance 17O, 6Li NMR and molecular modeling studies of the solvation structures of lithium bis(fluorosulfonyl)imide/1,2-dimethoxyethane liquid electrolytes

    NASA Astrophysics Data System (ADS)

    Wan, Chuan; Hu, Mary Y.; Borodin, Oleg; Qian, Jiangfeng; Qin, Zhaohai; Zhang, Ji-Guang; Hu, Jian Zhi

    2016-03-01

    Natural abundance 17O and 6Li NMR experiments, quantum chemistry and molecular dynamics studies were employed to investigate the solvation structures of Li+ at various concentrations of LiFSI in DME electrolytes. It was found that the chemical shifts of both 17O and 6Li changed with the concentration of LiFSI, indicating the changes of solvation structures with concentration. For the quantum chemistry calculations, the coordinated cluster LiFSI(DME)2 forms at first, and its relative ratio increases with increasing LiFSI concentration to 1 M. Then the solvation structure LiFSI(DME) become the dominant component. As a result, the coordination of forming contact ion pairs between Li+ and FSI- ion increases, but the association between Li+ and DME molecule decreases. Furthermore, at LiFSI concentration of 4 M the solvation structures associated with Li+(FSI-)2(DME), Li+2(FSI-)(DME)4 and (LiFSI)2(DME)3 become the dominant components. For the molecular dynamics simulation, with increasing concentration, the association between DME and Li+ decreases, and the coordinated number of FSI- increases, which is in perfect accord with the DFT results.

  15. Structure and disorder in iron-bearing sodium silicate glasses and melts: High-resolution 29Si and 17O solid-state NMR study

    NASA Astrophysics Data System (ADS)

    Kim, H.; Lee, S.

    2012-12-01

    Understanding of the effect of iron content on the structure (Si coordination environment and the degree of polymerization) of iron-bearing silicate melts and glasses is essential for studying their macroscopic properties and diverse geological processes in Earth's interior. Although the recent advances in high-resolution solid-state NMR techniques provide detailed structural information of a diverse iron-free oxide glasses with varying composition (e.g., Lee, P. Natl. Acad. Sci. USA., 2011, 108, 6847; Lee and Sung, Chem. Geol., 2008, 256, 326; Park and Lee, Geochim. Cosmochim. Acta, 2012, 80, 125; Lee et al., Phys. Rev., 103, 095501, 2009), their application to iron-bearing silicate glasses has a limited usefulness in resolving atomic configurations due to the effect of paramagnetic cation (i.e., Fe) on the NMR spectra. Here, we report the first ^{29}Si and ^{17}O NMR spectra for sodium-iron silicate glasses with varying iron content (Na_{2}O-Fe_{2}O_{3}-SiO_{2} glasses, up to 34.60 wt% Fe_{2}O_{3}), revealing previously unknown details of iron-induced changes in structure and disorder. While signal intensity decreases and peak width increases exponentially with increasing iron content [=Fe_{2}O_{3}/(Na_{2}O+Fe_{2}O_{3})], ^{29}Si MAS NMR spectra for sodium-iron silicate glasses present the slight peak shift and an asymmetrical peak broadening toward higher Q^{n} species with increasing iron content. This result implies an increase in the degree of polymerization with increasing iron content. Additionally, ^{29}Si spin-relaxation time (T_{1}) for the glasses decreases with increasing of iron content by several orders of magnitude. ^{17}O 3QMAS NMR spectra for the glasses show well-resolved non-bridging oxygen (NBO, Na-O-Si) and bridging oxygen (BO, Si-O-Si) even at relatively high iron content, providing the first direct experimental estimation of the degree of polymerization. In sodium-iron silicate glasses, the fraction of NBO decreases with increasing iron

  16. Effect of iron content on the structure and disorder of iron-bearing sodium silicate glasses: A high-resolution 29Si and 17O solid-state NMR study

    NASA Astrophysics Data System (ADS)

    Kim, Hyo-Im; Sur, Jung Chul; Lee, Sung Keun

    2016-01-01

    Despite its geochemical importance and implications for the properties of natural magmatic melts, understanding the detailed structure of iron-bearing silicate glasses remains among the outstanding problems in geochemistry. This is mainly because solid-state NMR techniques, one of the most versatile experimental methods to probe the structure of oxide glasses, cannot be fully utilized for exploring the structural details of iron-bearing glasses as the unpaired electrons in Fe induce strong local magnetic fields that mask the original spectroscopic features (i.e., paramagnetic effect). Here, we report high-resolution 29Si and 17O solid-state NMR spectra of iron-bearing sodium silicate glasses (Na2O-Fe2O3-SiO2, Fe3+/ΣFe = 0.89 ± 0.04, thus containing both ferric and ferrous iron) with varying XFe2O3 [=Fe2O3/(Na2O + Fe2O3)], containing up to 22.9 wt% Fe2O3. This compositional series involves Fe-Na substitution at constant SiO2 contents of 66.7 mol% in the glasses. For both nuclides, the NMR spectra exhibit a decrease in the signal intensities and an increase in the peak widths with increasing iron concentration partly because of the paramagnetic effect. Despite the intrinsic difficulties that result from the pronounced paramagnetic effect, the 29Si and 17O NMR results yield structural details regarding the effect of iron content on Q speciation, spatial distribution of iron, and the extent of polymerization in the iron-bearing silicate glasses. The 29Si NMR spectra show an apparent increase in highly polymerized Q species with increasing XFe2O3 , suggesting an increase in the degree of melt polymerization. The 17O 3QMAS NMR spectra exhibit well-resolved non-bridging oxygen (NBO, Na-O-Si) and bridging oxygen (BO, Si-O-Si) peaks with varying iron concentration. By replacing Na2O with Fe2O3 (and thus with increasing iron content), the fraction of Na-O-Si decreases. Quantitative consideration of this effect confirms that the degree of polymerization is likely to

  17. Ab Initio Quality NMR Parameters in Solid-State Materials Using a High-Dimensional Neural-Network Representation.

    PubMed

    Cuny, Jérôme; Xie, Yu; Pickard, Chris J; Hassanali, Ali A

    2016-02-09

    Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful experimental tools to probe the local atomic order of a wide range of solid-state compounds. However, due to the complexity of the related spectra, in particular for amorphous materials, their interpretation in terms of structural information is often challenging. These difficulties can be overcome by combining molecular dynamics simulations to generate realistic structural models with an ab initio evaluation of the corresponding chemical shift and quadrupolar coupling tensors. However, due to computational constraints, this approach is limited to relatively small system sizes which, for amorphous materials, prevents an adequate statistical sampling of the distribution of the local environments that is required to quantitatively describe the system. In this work, we present an approach to efficiently and accurately predict the NMR parameters of very large systems. This is achieved by using a high-dimensional neural-network representation of NMR parameters that are calculated using an ab initio formalism. To illustrate the potential of this approach, we applied this neural-network NMR (NN-NMR) method on the (17)O and (29)Si quadrupolar coupling and chemical shift parameters of various crystalline silica polymorphs and silica glasses. This approach is, in principal, general and has the potential to be applied to predict the NMR properties of various materials.

  18. NMR parameters in gapped graphene systems

    NASA Astrophysics Data System (ADS)

    Crisan, Mircea; Grosu, Ioan; Ţifrea, Ionel

    2016-06-01

    We calculate the nuclear spin-lattice relaxation time and the Knight shift for the case of gapped graphene systems. Our calculations consider both the massive and massless gap scenarios. Both the spin-lattice relaxation time and the Knight shift depend on temperature, chemical potential, and the value of the electronic energy gap. In particular, at the Dirac point, the electronic energy gap has stronger effects on the system nuclear magnetic resonance parameters in the case of the massless gap scenario. Differently, at large values of the chemical potential, both gap scenarios behave in a similar way and the gapped graphene system approaches a Fermi gas from the nuclear magnetic resonance parameters point of view. Our results are important for nuclear magnetic resonance measurements that target the 13C active nuclei in graphene samples.

  19. Characterization of the Dynamics in the Protonic Conductor CsH2PO4 by 17O Solid-State NMR Spectroscopy and First-Principles Calculations: Correlating Phosphate and Protonic Motion

    PubMed Central

    2015-01-01

    17O NMR spectroscopy combined with first-principles calculations was employed to understand the local structure and dynamics of the phosphate ions and protons in the paraelectric phase of the proton conductor CsH2PO4. For the room-temperature structure, the results confirm that one proton (H1) is localized in an asymmetric H-bond (between O1 donor and O2 acceptor oxygen atoms), whereas the H2 proton undergoes rapid exchange between two sites in a hydrogen bond with a symmetric double potential well at a rate ≥107 Hz. Variable-temperature 17O NMR spectra recorded from 22 to 214 °C were interpreted by considering different models for the rotation of the phosphate anions. At least two distinct rate constants for rotations about four pseudo C3 axes of the phosphate ion were required in order to achieve good agreement with the experimental data. An activation energy of 0.21 ± 0.06 eV was observed for rotation about the P–O1 axis, with a higher activation energy of 0.50 ± 0.07 eV being obtained for rotation about the P–O2, P–O3d, and P–O3a axes, with the superscripts denoting, respectively, dynamic donor and acceptor oxygen atoms of the H-bond. The higher activation energy of the second process is most likely associated with the cost of breaking an O1–H1 bond. The activation energy of this process is slightly lower than that obtained from the 1H exchange process (0.70 ± 0.07 eV) (Kim, G.; Blanc, F.; Hu, Y.-Y.; Grey, C. P. J. Phys. Chem. C2013, 117, 6504−6515) associated with the translational motion of the protons. The relationship between proton jumps and phosphate rotation was analyzed in detail by considering uncorrelated motion, motion of individual PO4 ions and the four connected/H-bonded protons, and concerted motions of adjacent phosphate units, mediated by proton hops. We conclude that, while phosphate rotations aid proton motion, not all phosphate rotations result in proton jumps. PMID:25732257

  20. Dinuclear complexes formed with the triazacyclononane derivative ENOTA4-: high-pressure 17O NMR evidence of an associative water exchange on [MnII2(ENOTA)(H2O)2].

    PubMed

    Balogh, Edina; He, Zhenjie; Hsieh, Wenyuan; Liu, Shuang; Tóth, Eva

    2007-01-08

    Mn2+ has five unpaired d-electrons, a long electronic relaxation time, and labile water exchange, all of which make it an attractive candidate for contrast agent application in medical magnetic resonance imaging. In the quest for stable and nonlabile Mn2+ complexes, we explored a novel dimeric triazacyclononane-based ligand bearing carboxylate functional groups, H4ENOTA. The protonation constants of the ligand and the stability constants of the complexes formed with some endogenously important metals (Ca2+, Cu2+, Zn2+), as well as with Mn2+ and Ce3+, have been assessed by NMR methods, potentiometry, and UV-vis spectrophotometry. Overall, the thermodynamic stability of the complexes is lower as compared to that of the corresponding NOTA analogues (H3NOTA, 1,4,7-triaazacyclononane-1,4,7-triacetic acid). The crystal structure of Mn2(ENOTA)(H2O) x 5H2O contains two six-coordinated Mn2+, in addition to the three amine nitrogens and the two oxygens from the pendent monodentate carboxylate groups, and one water (Mn2) or one bridging carboxylate oxygen (Mn1) completes the coordination sphere of the metal ion. In an aqueous solution, this bridging carboxylate is replaced by a water molecule, as evidenced by the 17O chemical shifts and proton relaxivity data that point to monohydration for both metal ions in the dinuclear complex. A variable-temperature and -pressure 17O NMR study has been performed on [Mn2(ENOTA)(H2O)2] to assess the rate and, for the first time on a Mn2+ chelate, also the mechanism of the water exchange. The inner sphere water is slightly more labile in [Mn2(ENOTA)(H2O)2] (k298ex = 5.5 x 107 s-1) than in the aqua ion (2.1 x 107 s-1, Merbach, A. E.; et al. Inorg. Chem. 1980, 19, 3696). The water exchange proceeds via an almost limiting associative mechanism, as evidenced by the large negative activation volume (deltaV = -10.7 cm3 mol-1). The proton relaxivities measured on [Mn2(ENOTA)(H2O)2] show a low-field dispersion at approximately 0.1 MHz arising from

  1. A systematic investigation of hydrogen-bonding effects on the 17O, 14N, and 2H nuclear quadrupole resonance parameters of anhydrous and monohydrated cytosine crystalline structures: a density functional theory study.

    PubMed

    Mirzaei, Mahmoud; Elmi, Fatemeh; Hadipour, Nasser L

    2006-06-08

    A systematic computational study was carried out to characterize the 17O, 14N, and 2H nuclear quadrupole resonance (NQR) parameters in the anhydrous and monohydrated cytosine crystalline structures. To include the hydrogen-bonding effects in the calculations, the most probable interacting molecules with the central molecule in the crystalline phase were considered in the pentameric clusters of both structures. To calculate the parameters, couples of the methods B3LYP and B3PW91 and the basis sets 6-311++G** and CC-pVTZ were employed. The mentioned methods calculated reliable values of 17O, 14N, and 2H NQR tensors in the pentameric clusters, which are in good agreements with the experiment. The different influences of various hydrogen-bonding interactions types, N-H...N, N-H...O, and O-H...O, were observed on the 17O, 14N, and 2H NQR tensors. Lower values of quadrupole coupling constants and higher values of asymmetry parameters in the crystalline monohydrated cytosine indicate the presence of stronger hydrogen-bonding interactions in the monohydrated form rather than that of crystalline anhydrous cytosine.

  2. Combined high resolution NMR and 1H and 17O relaxometric study sheds light on the solution structure and dynamics of the lanthanide(III) complexes of HPDO3A.

    PubMed

    Delli Castelli, Daniela; Caligara, Maria C; Botta, Mauro; Terreno, Enzo; Aime, Silvio

    2013-06-17

    the (17)O NMR transverse relaxation rate of GdHPDO3A, R2, reveals an unusual trend at low temperatures and at high magnetic field strength (>9.4 T). This behavior has been attributed to the occurrence of a very large difference in the rate of water exchange, k(ex), for the two isomeric species (1/k(ex) = τM = 640 ± 35 ns and 8.9 ± 0.5 ns, for the major and minor isomer respectively).

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

    PubMed

    Charpentier, Thibault

    2011-07-01

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

  4. Quantitative structure parameters from the NMR spectroscopy of quadrupolar nuclei

    SciTech Connect

    Perras, Frederic A.

    2015-12-15

    Here, nuclear magnetic resonance (NMR) spectroscopy is one of the most important characterization tools in chemistry, however, 3/4 of the NMR active nuclei are underutilized due to their quadrupolar nature. This short review centers on the development of methods that use solid-state NMR of quadrupolar nuclei for obtaining quantitative structural information. Namely, techniques using dipolar recoupling as well as the resolution afforded by double-rotation are presented for the measurement of spin–spin coupling between quadrupoles, enabling the measurement of internuclear distances and connectivities.

  5. Signal intensities derived from different NMR probes and parameters contribute to variations in quantification of metabolites.

    PubMed

    Lacy, Paige; McKay, Ryan T; Finkel, Michael; Karnovsky, Alla; Woehler, Scott; Lewis, Michael J; Chang, David; Stringer, Kathleen A

    2014-01-01

    We discovered that serious issues could arise that may complicate interpretation of metabolomic data when identical samples are analyzed at more than one NMR facility, or using slightly different NMR parameters on the same instrument. This is important because cross-center validation metabolomics studies are essential for the reliable application of metabolomics to clinical biomarker discovery. To test the reproducibility of quantified metabolite data at multiple sites, technical replicates of urine samples were assayed by 1D-(1)H-NMR at the University of Alberta and the University of Michigan. Urine samples were obtained from healthy controls under a standard operating procedure for collection and processing. Subsequent analysis using standard statistical techniques revealed that quantitative data across sites can be achieved, but also that previously unrecognized NMR parameter differences can dramatically and widely perturb results. We present here a confirmed validation of NMR analysis at two sites, and report the range and magnitude that common NMR parameters involved in solvent suppression can have on quantitated metabolomics data. Specifically, saturation power levels greatly influenced peak height intensities in a frequency-dependent manner for a number of metabolites, which markedly impacted the quantification of metabolites. We also investigated other NMR parameters to determine their effects on further quantitative accuracy and precision. Collectively, these findings highlight the importance of and need for consistent use of NMR parameter settings within and across centers in order to generate reliable, reproducible quantified NMR metabolomics data.

  6. Cluster structure of 17O

    NASA Astrophysics Data System (ADS)

    Mezhevych, S. Yu.; Rudchik, A. T.; Rudchik, A. A.; Ponkratenko, O. A.; Keeley, N.; Kemper, K. W.; Mazzocco, M.; Rusek, K.; Sakuta, S. B.

    2017-03-01

    The transfer reaction 13C(11B,7Li)17O leading to the ground and several excited states of 17O was investigated at an incident boron beam energy of 45 MeV. The experimental data were analyzed by means of coupled-channel Born approximation calculations and 17O=α +13C spectroscopic factors were extracted from a comparison of the data and the calculations at forward angles. The largest spectroscopic factor obtained was that for the subthreshold 6.356 MeV 1 /2+ state, important for the production of neutrons in the stellar environment, and the squared Coulomb modified asymptotic normalization coefficient, C˜2, is consistent with previous determinations. A significant rise in the experimental data at backward scattering angles suggested the possibility of 17O=6Li+11B clustering in some 17O states, including the ground state. However, explicit inclusion of 6Li transfer in the calculations could not explain the observed effect. Compound nucleus calculations suggested that while the backward angle rise could be explained by such processes for two of the populated 17O states other multistep direct processes must contribute significantly to the other two.

  7. Laboratory Precision Measurements of the Rotational Spectrum of 12C17O and 13C17O

    NASA Astrophysics Data System (ADS)

    Klapper, Gabriele; Surin, Leonid; Lewen, Frank; Müller, Holger S. P.; Pak, Igor; Winnewisser, Gisbert

    2003-01-01

    High-precision millimeter and submillimeter wave measurements were performed on two 17O isotopically substituted carbon monoxide species, i.e., 12C17O and 13C17O. Covering the frequency region from 100 GHz to 1 THz, the accuracy achievable is estimated to be +/-5 kHz in the Doppler-limited mode and +/-1 kHz for sub-Doppler-resolution measurements. From a weighted least-squares fit, the following molecular rotational parameters for 12C17O and 13C17O were obtained: for 12C17O,B0=56,179.99110(28)MHz,D0=174.330(6)kHzand for 13C17O,B0=53,644.7906(29)MHz,D0=158.918(19)kHzin both instances, the H0 values were kept fixed to IR data. The oxygen 17O nucleus exhibits a sizeable electric nuclear quadrupole moment, which has been measured for both isotopomers, i.e., eQq(12C17O)=4.298(44)MHz and eQq(13C17O)=4.355(182)MHz. The high precision of the Lamb dip measurements allowed us to observe additional small hyperfine effects caused by the magnetic moment of the 17O nucleus. These precision measurements allowed the determination of the nuclear spin-rotation constant CI(17O)=-31.60(72)Hz for 12C17O, solely from the Cologne data set. The highly precise transition frequencies reported here should warrant deep interstellar searches for the two molecules 12C17O and 13C17O. The latter has not been detected in space until very recently. On the basis of our laboratory data, we were able to report the discovery of 13C17O (by Bensch and coworkers) along with the observations of two additionalrare CO isotopomers including 12C17O and 12C18O toward core C of the ρ Ophiucus molecular cloud.

  8. Structure simulation with calculated NMR parameters - integrating COSMOS into the CCPN framework.

    PubMed

    Schneider, Olaf; Fogh, Rasmus H; Sternberg, Ulrich; Klenin, Konstantin; Kondov, Ivan

    2012-01-01

    The Collaborative Computing Project for NMR (CCPN) has build a software framework consisting of the CCPN data model (with APIs) for NMR related data, the CcpNmr Analysis program and additional tools like CcpNmr FormatConverter. The open architecture allows for the integration of external software to extend the abilities of the CCPN framework with additional calculation methods. Recently, we have carried out the first steps for integrating our software Computer Simulation of Molecular Structures (COSMOS) into the CCPN framework. The COSMOS-NMR force field unites quantum chemical routines for the calculation of molecular properties with a molecular mechanics force field yielding the relative molecular energies. COSMOS-NMR allows introducing NMR parameters as constraints into molecular mechanics calculations. The resulting infrastructure will be made available for the NMR community. As a first application we have tested the evaluation of calculated protein structures using COSMOS-derived 13C Cα and Cβ chemical shifts. In this paper we give an overview of the methodology and a roadmap for future developments and applications.

  9. Spin Saturation Transfer Difference NMR (SSTD NMR): A New Tool to Obtain Kinetic Parameters of Chemical Exchange Processes

    PubMed Central

    Quirós, María Teresa; Macdonald, Colin; Angulo, Jesús; Muñoz, María Paz

    2016-01-01

    This detailed protocol describes the new Spin Saturation Transfer Difference Nuclear Magnetic Resonance protocol (SSTD NMR), recently developed in our group to study processes of mutual-site chemical exchange that are difficult to analyze by traditional methods. As the name suggests, this method combines the Spin Saturation Transfer method used for small molecules, with the Saturation Transfer Difference (STD) NMR method employed for the study of protein-ligand interactions, by measuring transient spin saturation transfer along increasing saturation times (build-up curves) in small organic and organometallic molecules undergoing chemical exchange. Advantages of this method over existing ones are: there is no need to reach coalescence of the exchanging signals; the method can be applied as long as one signal of the exchanging sites is isolated; there is no need to measure T1 or reach steady state saturation; rate constant values are measured directly, and T1 values are obtained in the same experiment, using only one set of experiments. To test the method, we have studied the dynamics of the hindered rotation of N,N-dimethylamides, for which much data is available for comparison. The thermodynamic parameters obtained using SSTD are very similar to the reported ones (spin-saturation transfer techniques and line-shape analysis). The method can be applied to more challenging substrates that cannot be studied by previous methods. We envisage that the simple experimental set up and the wide applicability of the method to a great variety of substrates will make this a common technique amongst organic and organometallic chemists without extensive expertise in NMR. PMID:27911361

  10. A new approach to NMR chemical shift additivity parameters using simultaneous linear equation method.

    PubMed

    Shahab, Yosif A; Khalil, Rabah A

    2006-10-01

    A new approach to NMR chemical shift additivity parameters using simultaneous linear equation method has been introduced. Three general nitrogen-15 NMR chemical shift additivity parameters with physical significance for aliphatic amines in methanol and cyclohexane and their hydrochlorides in methanol have been derived. A characteristic feature of these additivity parameters is the individual equation can be applied to both open-chain and rigid systems. The factors that influence the (15)N chemical shift of these substances have been determined. A new method for evaluating conformational equilibria at nitrogen in these compounds using the derived additivity parameters has been developed. Conformational analyses of these substances have been worked out. In general, the results indicate that there are four factors affecting the (15)N chemical shift of aliphatic amines; paramagnetic term (p-character), lone pair-proton interactions, proton-proton interactions, symmetry of alkyl substituents and molecular association.

  11. Thermal and solvent effects on the NMR and UV parameters of some bioreductive drugs

    NASA Astrophysics Data System (ADS)

    Ramalho, Teodorico C.; Taft, Carlton A.

    2005-08-01

    N15 NMR chemical shifts and n →π* electronic transition energy for metronidazole (1) has been calculated and compared with experimental data. A detailed computational study of 1 is presented, with special attention to the performance of various theoretical methods for reproducing spectroscopic parameters in solution. The most sophisticated approach involves density functional based on the Car-Parrinello molecular dynamics simulations of 1 in aqueous solution (BP86 level) and averaging chemical shifts and ΔE(n →π*) over snapshots from the trajectory. In the NMR and UV calculations for these snapshots (performed at the B3LYP level), a small number of discrete water molecules are retained, and the remaining bulk solution effects are included via a polarizable continuum model (PCM). A good agreement with experiment is also obtained using static geometry optimization and NMR computation of pristine 1 employing a PCM approach. Further theoretical predictions are also reported for O17 NMR and ΔE(n →π*) of three hydroxycinnamic acid derivatives, which suggest that it is essential to incorporate the dynamics and solvent effects for NMR and UV calculations in the condensed phase.

  12. Ab initio crystal structure prediction of magnesium (poly)sulfides and calculation of their NMR parameters.

    PubMed

    Mali, Gregor

    2017-03-01

    Ab initio prediction of sensible crystal structures can be regarded as a crucial task in the quickly-developing methodology of NMR crystallography. In this contribution, an evolutionary algorithm was used for the prediction of magnesium (poly)sulfide crystal structures with various compositions. The employed approach successfully identified all three experimentally detected forms of MgS, i.e. the stable rocksalt form and the metastable wurtzite and zincblende forms. Among magnesium polysulfides with a higher content of sulfur, the most probable structure with the lowest formation energy was found to be MgS2, exhibiting a modified rocksalt structure, in which S(2-) anions were replaced by S2(2-) dianions. Magnesium polysulfides with even larger fractions of sulfur were not predicted to be stable. For the lowest-energy structures, (25)Mg quadrupolar coupling constants and chemical shift parameters were calculated using the density functional theory approach. The calculated NMR parameters could be well rationalized by the symmetries of the local magnesium environments, by the coordination of magnesium cations and by the nature of the surrounding anions. In the future, these parameters could serve as a reference for the experimentally determined (25)Mg NMR parameters of magnesium sulfide species.

  13. Visualization and processing of computed solid-state NMR parameters: MagresView and MagresPython.

    PubMed

    Sturniolo, Simone; Green, Timothy F G; Hanson, Robert M; Zilka, Miri; Refson, Keith; Hodgkinson, Paul; Brown, Steven P; Yates, Jonathan R

    2016-09-01

    We introduce two open source tools to aid the processing and visualisation of ab-initio computed solid-state NMR parameters. The Magres file format for computed NMR parameters (as implemented in CASTEP v8.0 and QuantumEspresso v5.0.0) is implemented. MagresView is built upon the widely used Jmol crystal viewer, and provides an intuitive environment to display computed NMR parameters. It can provide simple pictorial representation of one- and two-dimensional NMR spectra as well as output a selected spin-system for exact simulations with dedicated spin-dynamics software. MagresPython provides a simple scripting environment to manipulate large numbers of computed NMR parameters to search for structural correlations.

  14. On the relationship between NMR-derived amide order parameters and protein backbone entropy changes.

    PubMed

    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  < 0.8) shows that these report both on the local flexibility of the protein and on a different component of the conformational 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.

  15. Solid-state 17O nuclear magnetic resonance spectroscopy without isotopic enrichment: direct detection of bridging oxygen in radiation damaged zircon.

    PubMed

    Ashbrook, Sharon E; Farnan, IanIan

    2004-09-01

    Protocols are presented for obtaining natural abundance (17)O magic angle spinning and static NMR spectra in the solid state. Rotor-assisted population transfer (RAPT), Carr-Purcell-Meiboom-Gill (CPMG) echo trains and cross-polarisation (CP) are all used to obtain spectra of sites with large as well as small electric field gradients in proton and non-proton containing inorganic materials. Spectra are of sufficient quality to obtain the typical NMR parameters by standard fitting of the spectra. The protocol is then applied to identifying the changes that accompany radioactive decay in zircon (ZrSiO(4)) where enrichment is impossible. The (17)O NMR spectra of a partially metamict zircon sample clearly show evidence of bridging oxygens being produced as a consequence of radiation damage. The spectra have been acquired at moderate magnetic fields over periods typically of 60 h (1 weekend) and it is concluded that a 'routine' overnight (17)O experiment of 15 h at high field (e.g. 21 T) may well be possible.

  16. Filtering and parameter estimation of surface-NMR data using singular spectrum analysis

    NASA Astrophysics Data System (ADS)

    Ghanati, Reza; Kazem Hafizi, Mohammad; Mahmoudvand, Rahim; Fallahsafari, Mahdi

    2016-07-01

    Ambient electromagnetic interferences at the site of investigation often degrade the signal quality of the Surface-NMR measurements leading to inaccurate estimation of the signal parameters. This paper proposes a new powerful de-noising method based on singular spectrum analysis (SSA), which is a nonparametric method for analyzing time series. SSA is a relatively simple method and can be understood using basic algebra notations. Singular value decomposition (SVD) plays a crucial role in SSA. As the length of recordings increases, the computational time required for computing SVD raises which restricts the usage of SSA in long-term time series. In order to overcome this drawback, we propose a randomized version of the singular value decomposition to accelerate the decomposition step of the algorithm. To evaluate the performance of the proposed strategy, the method is tested on synthetic signals corrupted by both simulated noise (including Gaussian white noise, spiky events and harmonic noise) and real noise recordings obtained from surface-NMR field surveys and a real data set. Our results show that the proposed algorithm can enhance the signal to noise ratio significantly, and gives an improvement in estimation of the surface-NMR signal parameters.

  17. Low-field NMR logging sensor for measuring hydraulic parameters of model soils

    NASA Astrophysics Data System (ADS)

    Sucre, Oscar; Pohlmeier, Andreas; Minière, Adrien; Blümich, Bernhard

    2011-08-01

    SummaryKnowing the exact hydraulic parameters of soils is very important for improving water management in agriculture and for the refinement of climate models. Up to now, however, the investigation of such parameters has required applying two techniques simultaneously which is time-consuming and invasive. Thus, the objective of this current study is to present only one technique, i.e., a new non-invasive method to measure hydraulic parameters of model soils by using low-field nuclear magnetic resonance (NMR). Hereby, two model clay or sandy soils were respectively filled in a 2 m-long acetate column having an integrated PVC tube. After the soils were completely saturated with water, a low-field NMR sensor was moved up and down in the PVC tube to quantitatively measure along the whole column the initial water content of each soil sample. Thereafter, both columns were allowed to drain. Meanwhile, the NMR sensor was set at a certain depth to measure the water content of that soil slice. Once the hydraulic equilibrium was reached in each of the two columns, a final moisture profile was taken along the whole column. Three curves were subsequently generated accordingly: (1) the initial moisture profile, (2) the evolution curve of the moisture depletion at that particular depth, and (3) the final moisture profile. All three curves were then inverse analyzed using a MATLAB code over numerical data produced with the van Genuchten-Mualem model. Hereby, a set of values ( α, n, θr and θs) was found for the hydraulic parameters for the soils under research. Additionally, the complete decaying NMR signal could be analyzed through Inverse Laplace Transformation and averaged on the 1/ T2 space. Through measurement of the decay in pure water, the effect on the relaxation caused by the sample could be estimated from the obtained spectra. The migration of the sample-related average <1/ T2, Sample> with decreasing saturation speaks for a enhancement of the surface relaxation as

  18. Sensitivity of the NMR density matrix to pulse sequence parameters: a simplified analytic approach.

    PubMed

    Momot, Konstantin I; Takegoshi, K

    2012-08-01

    We present a formalism for the analysis of sensitivity of nuclear magnetic resonance pulse sequences to variations of pulse sequence parameters, such as radiofrequency pulses, gradient pulses or evolution delays. The formalism enables the calculation of compact, analytic expressions for the derivatives of the density matrix and the observed signal with respect to the parameters varied. The analysis is based on two constructs computed in the course of modified density-matrix simulations: the error interrogation operators and error commutators. The approach presented is consequently named the Error Commutator Formalism (ECF). It is used to evaluate the sensitivity of the density matrix to parameter variation based on the simulations carried out for the ideal parameters, obviating the need for finite-difference calculations of signal errors. The ECF analysis therefore carries a computational cost comparable to a single density-matrix or product-operator simulation. Its application is illustrated using a number of examples from basic NMR spectroscopy. We show that the strength of the ECF is its ability to provide analytic insights into the propagation of errors through pulse sequences and the behaviour of signal errors under phase cycling. Furthermore, the approach is algorithmic and easily amenable to implementation in the form of a programming code. It is envisaged that it could be incorporated into standard NMR product-operator simulation packages.

  19. Solid state 19F NMR parameters of fluorine-labeled amino acids. Part I: Aromatic substituents

    NASA Astrophysics Data System (ADS)

    Dürr, Ulrich H. N.; Grage, Stephan L.; Witter, Raiker; Ulrich, Anne S.

    2008-03-01

    Structural parameters of peptides and proteins in biomembranes can be directly measured by solid state NMR of selectively labeled amino acids. The 19F nucleus is a promising label to overcome the low sensitivity of 2H, 13C or 15N, and to serve as a background-free reporter group in biological compounds. To make the advantages of solid state 19F NMR fully available for structural studies of polypeptides, we have systematically measured the chemical shift anisotropies and relaxation properties of the most relevant aromatic and aliphatic 19F-labeled amino acids. In this first part of two consecutive contributions, six different 19F-substituents on representative aromatic side chains were characterized as polycrystalline powders by static and MAS experiments. The data are also compared with results on the same amino acids incorporated in synthetic peptides. The spectra show a wide variety of lineshapes, from which the principal values of the CSA tensors were extracted. In addition, temperature-dependent T1 and T2 relaxation times were determined by 19F NMR in the solid state, and isotropic chemical shifts and scalar couplings were obtained in solution.

  20. Influence of N-H...O and O-H...O hydrogen bonds on the (17)O, (15)N and (13)C chemical shielding tensors in crystalline acetaminophen: a density functional theory study.

    PubMed

    Esrafili, Mehdi D; Behzadi, Hadi; Hadipour, Nasser L

    2007-06-01

    A computational investigation was carried out to characterize the (17)O, (15)N and (13)C chemical shielding tensors in crystalline acetaminophen. We found that N-H...O and O-H...O hydrogen bonds around the acetaminophen molecule in the crystal lattice have different influences on the calculated (17)O, (15)N and (13)C chemical shielding eigenvalues and their orientations in the molecular frame of axes. The calculations were performed with the B3LYP method and 6-311++G(d, p) and 6-311+G(d) standard basis sets using the Gaussian 98 suite of programs. Calculated chemical shielding tensors were used to evaluate the (17)O, (15)N, and (13)C NMR chemical shift tensors in crystalline acetaminophen, which are in reasonable agreement with available experimental data. The difference between the calculated NMR parameters of the monomer and molecular clusters shows how much hydrogen-bonding interactions affect the chemical shielding tensors of each nucleus. The computed (17)O chemical shielding tensor on O(1), which is involved in two intermolecular hydrogen bonds, shows remarkable sensitivity toward the choice of the cluster model, whereas the (17)O chemical shielding tensor on O(2) involved in one N-H...O hydrogen bond, shows smaller improvement toward the hydrogen-bonding interactions. Also, a reasonably good agreement between the experimentally obtained solid-state (15)N and (13)C NMR chemical shifts and B3LYP/6-311++G(d, p) calculations is achievable only in molecular cluster model where a complete hydrogen-bonding network is considered. Moreover, at the B3LYP/6-311++G(d, p) level of theory, the calculated (17)O, (15)N and (13)C chemical shielding tensor orientations are able to reproduce the experimental values to a reasonably good degree of accuracy.

  1. 17O NMR Study of Solvent Exchange in Some Aqueous [Co(tren)(X)(OH(2)/OH)](n)()(+), [Co(cyclen)(X)(OH(2)/OH)](n)()(+), and [Co(N-Mecyclen)(X)(OH(2)/OH)](n)()(+) Systems (X = NH(3), OH(2)/OH; n = 3, 2, 1)(1).

    PubMed

    Brasch, Nicola E.; Buckingham, David A.; Clark, Charles R.; Rogers, Andrew J.

    1998-09-21

    A (17)O NMR study (I = 1.0 M, NaClO(4) or NaOSO(2)CF(3), 25.0 degrees C) of solvent exchange in labeled p- and t-[Co(tren)(NH(3))OH(2)](3+), [Co(tren)(OH(2))(2)](3+), [Co(cyclen)(OH(2))(2)](3+), and [Co(N-Mecyclen)(OH(2))(2)](3+) ions (ca. 30% (17)O) in aqueous solution has shown that loss of coordinated OH(2) is slow for all of the complexes (k(ex)/s(-)(1) = 1.1 x 10(-)(5), 1.2 x 10(-)(5), 3.7 x 10(-)(5) (p-site)/8.7 x 10(-)(6) (t-site), 2 x 10(-)(4), and 2 x 10(-)(4), respectively). Values of k(ex) for solvent exchange in [Co(tren)(OH)(2)](+) have been determined as 9.7 x 10(-)(5) s(-)(1) (p-site) and 2.2 x 10(-)(7) s(-)(1) (t-site) Coordinated OH(-) in both p- and t-[Co(tren)(NH(3))OH](2+) also exchanges only slowly with solvent (k(ex)/s(-)(1)= 1.7 x 10(-)(4), and <1 x 10(-)(6), respectively), whereas exchange of coordinated solvent in the aqua-hydroxo complexes [Co(tren)(t-OH(2))(p-OH)](2+), [Co(cyclen)(OH(2))OH](2+), and [Co(N-Mecyclen)(OH(2))OH](2+) is much more rapid (k(ex)/s(-)(1) = 0.03 (p-site)/0.01 (t-site), 12 and 15, respectively). Ligand-OH(-) exchange in these latter systems is interpreted as occurring via (indirect) S(N)1(CB)-type processes on the corresponding aqua complexes: [Co(amine)OH](2+) right harpoon over left harpoon [Co(amine-H)OH(2)](2+) --> exchange. This type of pathway is seen to be more efficient when leaving-group departure is synchronous with proton transfer, and this appears to be more important for exchange in the cyclen and N-Mecyclen complexes where a reasonably acidic, adjacent syn NH proton is involved.

  2. Gas phase NMR spectra of N,N-dimethylnitrosamine. Environmental effects on kinetic parameters

    NASA Astrophysics Data System (ADS)

    Chauvel, J. Paul; Leung, Doris Y.; True, Nancy S.

    1984-04-01

    Gas phase 1H NMR spectra of N,N-dimethylnitrosamine are consistent with first order chemical exchange rate constants which are ca. 25 times faster than those observed in neat liquids at corresponding temperatures. The associated kinetic parameters: Eact(∞), 20.5(1.1) kcal mol -1, Δ H‡, 19.7(1.0) kcal mol -1 and Δ G‡, 21.1(0.4) kcal mol -1 are approximately 2.5 kcal mol -1 lower than the most recently reported values for the neat liquid. The observed phase dependence is consistent with a process proceeding via a freely rotating transition state.

  3. Crystal structure and proton conductivity of BaSn0.6Sc0.4O3–δ: insights from neutron powder diffraction and solid-state NMR spectroscopy† †Electronic supplementary information (ESI) available: Rietveld fit of dry BaSn0.6Sc0.4O3–δ sample (Fig. S1). 119Sn (Fig. S2), 45Sc (Fig. S3–S6) and 17O (Fig. S7) spectra of all materials as a function of Sc doping concentration, 45Sc MQMAS of deuterated BaSn0.9Sc0.1O3–δ (Fig. S4), 45Sc MQMAS of dry and deuterated BaSn0.8Sc0.2O3–δ (Fig. S5), 45Sc MQMAS of dry and deuterated BaSn0.7Sc0.3O3–δ (Fig. S6), 17O MQMAS of 17O enriched BaSn0.8Sc0.2O3–δ and BaSn0.6Sc0.4O3–δ (Fig. S8). See DOI: 10.1039/c5ta09744d Click here for additional data file.

    PubMed Central

    Norberg, Stefan T.; Knee, Christopher S.; Ahmed, Istaq; Hull, Stephen; Buannic, Lucienne; Hung, Ivan; Gan, Zhehong; Blanc, Frédéric; Grey, Clare P.; Eriksson, Sten G.

    2016-01-01

    The solid-state synthesis and structural characterisation of perovskite BaSn1–xScxO3–δ (x = 0.0, 0.1, 0.2, 0.3, 0.4) and its corresponding hydrated ceramics are reported. Powder and neutron X-ray diffractions reveal the presence of cubic perovskites (space group Pm3m) with an increasing cell parameter as a function of scandium concentration along with some indication of phase segregation. 119Sn and 45Sc solid-state NMR spectroscopy data highlight the existence of oxygen vacancies in the dry materials, and their filling upon hydrothermal treatment with D2O. It also indicates that the Sn4+ and Sc3+ local distribution at the B-site of the perovskite is inhomogeneous and suggests that the oxygen vacancies are located in the scandium dopant coordination shell at low concentrations (x ≤ 0.2) and in the tin coordination shell at high concentrations (x ≥ 0.3). 17O NMR spectra on 17O enriched BaSn1–xScxO3–δ materials show the existence of Sn–O–Sn, Sn–O–Sc and Sc–O–Sc bridging oxygen environments. A further room temperature neutron powder diffraction study on deuterated BaSn0.6Sc0.4O3–δ refines the deuteron position at the 24k crystallographic site (x, y, 0) with x = 0.579(3) and y = 0.217(3) which leads to an O–D bond distance of 0.96(1) Å and suggests tilting of the proton towards the next nearest oxygen. Proton conduction was found to dominate in wet argon below 700 °C with total conductivity values in the range 1.8 × 10–4 to 1.1 × 10–3 S cm–1 between 300 and 600 °C. Electron holes govern the conduction process in dry oxidizing conditions, whilst in wet oxygen they compete with protonic defects leading to a wide mixed conduction region in the 200 to 600 °C temperature region, and a suppression of the conductivity at higher temperature. PMID:27358734

  4. Non-Linear Problems in NMR: Application of the DFM Variation of Parameters Method

    NASA Astrophysics Data System (ADS)

    Erker, Jay Charles

    This Dissertation introduces, develops, and applies the Dirac-McLachlan-Frenkel (DFM) time dependent variation of parameters approach to Nuclear Magnetic Resonance (NMR) problems. Although never explicitly used in the treatment of time domain NMR problems to date, the DFM approach has successfully predicted the dynamics of optically prepared wave packets on excited state molecular energy surfaces. Unlike the Floquet, average Hamiltonian, and Van Vleck transformation methods, the DFM approach is not restricted by either the size or symmetry of the time domain perturbation. A particularly attractive feature of the DFM method is that measured data can be used to motivate a parameterized trial function choice and that the DFM theory provides the machinery to provide the optimum, minimum error choices for these parameters. Indeed a poor parameterized trial function choice will lead to a poor match with real experiments, even with optimized parameters. Although there are many NMR problems available to demonstrate the application of the DFM variation of parameters, five separate cases that have escaped analytical solution and thus require numerical methods are considered here: molecular diffusion in a magnetic field gradient, radiation damping in the presence of inhomogeneous broadening, multi-site chemical exchange, and the combination of molecular diffusion in a magnetic field gradient with chemical exchange. The application to diffusion in a gradient is used as an example to develop the DFM method for application to NMR. The existence of a known analytical solution and experimental results allows for direct comparison between the theoretical results of the DFM method and Torrey's solution to the Bloch equations corrected for molecular diffusion. The framework of writing classical Bloch equations in matrix notation is then applied to problems without analytical solution. The second example includes the generation of a semi-analytical functional form for the free

  5. Essential Parameters for Structural Analysis and Dereplication by 1H NMR Spectroscopy

    PubMed Central

    2015-01-01

    The present study demonstrates the importance of adequate precision when reporting the δ and J parameters of frequency domain 1H NMR (HNMR) data. Using a variety of structural classes (terpenoids, phenolics, alkaloids) from different taxa (plants, cyanobacteria), this study develops rationales that explain the importance of enhanced precision in NMR spectroscopic analysis and rationalizes the need for reporting Δδ and ΔJ values at the 0.1–1 ppb and 10 mHz level, respectively. Spectral simulations paired with iteration are shown to be essential tools for complete spectral interpretation, adequate precision, and unambiguous HNMR-driven dereplication and metabolomic analysis. The broader applicability of the recommendation relates to the physicochemical properties of hydrogen (1H) and its ubiquity in organic molecules, making HNMR spectra an integral component of structure elucidation and verification. Regardless of origin or molecular weight, the HNMR spectrum of a compound can be very complex and encode a wealth of structural information that is often obscured by limited spectral dispersion and the occurrence of higher order effects. This altogether limits spectral interpretation, confines decoding of the underlying spin parameters, and explains the major challenge associated with the translation of HNMR spectra into tabulated information. On the other hand, the reproducibility of the spectral data set of any (new) chemical entity is essential for its structure elucidation and subsequent dereplication. Handling and documenting HNMR data with adequate precision is critical for establishing unequivocal links between chemical structure, analytical data, metabolomes, and biological activity. Using the full potential of HNMR spectra will facilitate the general reproducibility for future studies of bioactive chemicals, especially of compounds obtained from the diversity of terrestrial and marine organisms. PMID:24895010

  6. Banding of NMR-derived methyl order parameters: implications for protein dynamics.

    PubMed

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

    2014-09-01

    Our understanding of protein folding, stability, and function has begun to more explicitly incorporate dynamical aspects. Nuclear magnetic resonance has emerged as a powerful experimental method for obtaining comprehensive site-resolved insight into protein motion. It has been observed that methyl-group motion tends to cluster into three "classes" when expressed in terms of the popular Lipari-Szabo model-free squared generalized order parameter. Here the origins of the three classes or bands in the distribution of order parameters are examined. As a first step, a Bayesian based approach, which makes no a priori assumption about the existence or number of bands, is developed to detect the banding of Oaxis2 values derived either from NMR experiments or molecular dynamics simulations. The analysis is applied to seven proteins with extensive molecular dynamics simulations of these proteins in explicit water to examine the relationship between O2 and fine details of the motion of methyl bearing side chains. All of the proteins studied display banding, with some subtle differences. We propose a very simple yet plausible physical mechanism for banding. Finally, our Bayesian method is used to analyze the measured distributions of methyl group motions in the catabolite activating protein and several of its mutants in various liganded states and discuss the functional implications of the observed banding to protein dynamics and function.

  7. Polarization propagators: A powerful theoretical tool for a deeper understanding of NMR spectroscopic parameters

    NASA Astrophysics Data System (ADS)

    Aucar, Gustavo A.; Romero, Rodolfo H.; Maldonado, Alejandro F.

    Magnetic molecular spectroscopic properties, like NMR J-coupling and magnetic shielding σ, have been studied by non-relativistic quantum methods since their discovery. When they were found to depend strongly on relativistic effects in molecules containing heavy atoms, this started a new area of intensive research into the development of methods that include such effects. In most cases non-relativistic concepts were extended to the new field though keeping the previous non-relativistic point of view. Quantum mechanics can be formulated by two different formal approaches. Molecular physics and quantum chemistry were developed mostly within the Schrödinger or Heisenberg approaches. The path integral formalism of Feynman is less well known. This may be the reason why propagators are not broadly known in this field of research. Polarization propagators were developed in the early 1970s. Since that time they have been successfully applied to calculate NMR spectroscopic parameters. They are special theoretical devices from which one can do a deep analysis of the electronic mechanisms that underly any molecular response property from basic theoretical elements, like molecular orbitals, electronic excitation energies, coupling pathways, entanglement, contributions within different levels of theory, etc. All this is obtained in a natural way in both regimes: relativistic and non-relativistic. Its relativistic generalization in the early 1990s and the finding of a quantum electrodynamic (QED)-based theory for them, has given us the opportunity to improve our understanding of the physics behind such parameters. In this paper we give a presentation of polarization propagators that start in non-relativistic quantum physics and end up with the introduction of QED effects. The same and powerful basic quantum ideas are applied throughout this review, so that coherence and beauty arise in a natural way. We will give a new understanding that comes from the three levels of theory

  8. Accurate structure and dynamics of the metal-site of paramagnetic metalloproteins from NMR parameters using natural bond orbitals.

    PubMed

    Hansen, D Flemming; Westler, William M; Kunze, Micha B A; Markley, John L; Weinhold, Frank; Led, Jens J

    2012-03-14

    A natural bond orbital (NBO) analysis of unpaired electron spin density in metalloproteins is presented, which allows a fast and robust calculation of paramagnetic NMR parameters. Approximately 90% of the unpaired electron spin density occupies metal-ligand NBOs, allowing the majority of the density to be modeled by only a few NBOs that reflect the chemical bonding environment. We show that the paramagnetic relaxation rate of protons can be calculated accurately using only the metal-ligand NBOs and that these rates are in good agreement with corresponding rates measured experimentally. This holds, in particular, for protons of ligand residues where the point-dipole approximation breaks down. To describe the paramagnetic relaxation of heavy nuclei, also the electron spin density in the local orbitals must be taken into account. Geometric distance restraints for (15)N can be derived from the paramagnetic relaxation enhancement and the Fermi contact shift when local NBOs are included in the analysis. Thus, the NBO approach allows us to include experimental paramagnetic NMR parameters of (15)N nuclei as restraints in a structure optimization protocol. We performed a molecular dynamics simulation and structure determination of oxidized rubredoxin using the experimentally obtained paramagnetic NMR parameters of (15)N. The corresponding structures obtained are in good agreement with the crystal structure of rubredoxin. Thus, the NBO approach allows an accurate description of the geometric structure and the dynamics of metalloproteins, when NMR parameters are available of nuclei in the immediate vicinity of the metal-site.

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

    PubMed

    Liu, Qing; Shi, Chaowei; Yu, Lu; Zhang, Longhua; Xiong, Ying; Tian, Changlin

    2015-02-13

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

  10. Recent advances in computational predictions of NMR parameters for the structure elucidation of carbohydrates: methods and limitations.

    PubMed

    Toukach, Filip V; Ananikov, Valentine P

    2013-11-07

    All living systems are comprised of four fundamental classes of macromolecules--nucleic acids, proteins, lipids, and carbohydrates (glycans). Glycans play a unique role of joining three principal hierarchical levels of the living world: (1) the molecular level (pathogenic agents and vaccine recognition by the immune system, metabolic pathways involving saccharides that provide cells with energy, and energy accumulation via photosynthesis); (2) the nanoscale level (cell membrane mechanics, structural support of biomolecules, and the glycosylation of macromolecules); (3) the microscale and macroscale levels (polymeric materials, such as cellulose, starch, glycogen, and biomass). NMR spectroscopy is the most powerful research approach for getting insight into the solution structure and function of carbohydrates at all hierarchical levels, from monosaccharides to oligo- and polysaccharides. Recent progress in computational procedures has opened up novel opportunities to reveal the structural information available in the NMR spectra of saccharides and to advance our understanding of the corresponding biochemical processes. The ability to predict the molecular geometry and NMR parameters is crucial for the elucidation of carbohydrate structures. In the present paper, we review the major NMR spectrum simulation techniques with regard to chemical shifts, coupling constants, relaxation rates and nuclear Overhauser effect prediction applied to the three levels of glycomics. Outstanding development in the related fields of genomics and proteomics has clearly shown that it is the advancement of research tools (automated spectrum analysis, structure elucidation, synthesis, sequencing and amplification) that drives the large challenges in modern science. Combining NMR spectroscopy and the computational analysis of structural information encoded in the NMR spectra reveals a way to the automated elucidation of the structure of carbohydrates.

  11. Periodic ab initio calculation of nuclear quadrupole parameters as an assignment tool in solid-state NMR spectroscopy: applications to 23Na NMR spectra of crystalline materials.

    PubMed

    Johnson, Clive; Moore, Elaine A; Mortimer, Michael

    2005-05-01

    Periodic ab initio HF calculations using the CRYSTAL code have been used to calculate (23)Na NMR quadrupole parameters for a wide range of crystalline sodium compounds including Na(3)OCl. An approach is developed that can be used routinely as an alternative to point-charge modelling schemes for the assignment of distinct lines in (23)Na NMR spectra to specific crystallographic sodium sites. The calculations are based on standard 3-21 G and 6-21 G molecular basis sets and in each case the same modified basis set for sodium is used for all compounds. The general approach is extendable to other quadrupolar nuclei. For the 3-21 G calculations a 1:1 linear correlation between experimental and calculated values of C(Q)((23)Na) is obtained. The 6-21 G calculations, including the addition of d-polarisation functions, give better accuracy in the calculation of eta((23)Na). The sensitivity of eta((23)Na) to hydrogen atom location is shown to be useful in testing the reported hydrogen-bonded structure of Na(2)HPO(4).

  12. The hyperfine structure in the rotational spectra of D2(17)O and HD(17)O: Confirmation of the absolute nuclear magnetic shielding scale for oxygen.

    PubMed

    Puzzarini, Cristina; Cazzoli, Gabriele; Harding, Michael E; Vázquez, Juana; Gauss, Jürgen

    2015-03-28

    Guided by theoretical predictions, the hyperfine structures of the rotational spectra of mono- and bideuterated-water containing (17)O have been experimentally investigated. To reach sub-Doppler resolution, required to resolve the hyperfine structure due to deuterium quadrupole coupling as well as to spin-rotation (SR) and dipolar spin-spin couplings, the Lamb-dip technique has been employed. The experimental investigation and in particular, the spectral analysis have been supported by high-level quantum-chemical computations employing coupled-cluster techniques and, for the first time, a complete experimental determination of the hyperfine parameters involved was possible. The experimentally determined (17)O spin-rotation constants of D2 (17)O and HD(17)O were used to derive the paramagnetic part of the corresponding nuclear magnetic shielding constants. Together with the computed diamagnetic contributions as well as the vibrational and temperature corrections, the latter constants have been employed to confirm the oxygen nuclear magnetic shielding scale, recently established on the basis of spin-rotation data for H2 (17)O [Puzzarini et al., J. Chem. Phys. 131, 234304 (2009)].

  13. Natural Abundance 17O Nuclear Magnetic Resonance and Computational Modeling Studies of Lithium Based Liquid Electrolytes

    SciTech Connect

    Deng, Xuchu; Hu, Mary Y.; Wei, Xiaoliang; Wang, Wei; Chen, Zhong; Liu, Jun; Hu, Jian Z.

    2015-07-01

    Natural abundance 17O NMR measurements were conducted on electrolyte solutions consisting of Li[CF3SO2NSO2CF3] (LiTFSI) dissolved in the solvents of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and their mixtures at various concentrations. It was observed that 17O chemical shifts of solvent molecules change with the concentration of LiTFSI. The chemical shift displacements of carbonyl oxygen are evidently greater than those of ethereal oxygen, strongly indicating that Li+ ion is coordinated with carbonyl oxygen rather than ethereal oxygen. To understand the detailed molecular interaction, computational modeling of 17O chemical shifts was carried out on proposed solvation structures. By comparing the predicted chemical shifts with the experimental values, it is found that a Li+ ion is coordinated with four double bond oxygen atoms from EC, PC, EMC and TFSI- anion. In the case of excessive amount of solvents of EC, PC and EMC the Li+ coordinated solvent molecules are undergoing quick exchange with bulk solvent molecules, resulting in average 17O chemical shifts. Several kinds of solvation structures are identified, where the proportion of each structure in the liquid electrolytes investigated depends on the concentration of LiTFSI.

  14. Natural abundance 17O nuclear magnetic resonance and computational modeling studies of lithium based liquid electrolytes

    NASA Astrophysics Data System (ADS)

    Deng, Xuchu; Hu, Mary Y.; Wei, Xiaoliang; Wang, Wei; Chen, Zhong; Liu, Jun; Hu, Jian Zhi

    2015-07-01

    Natural abundance 17O NMR measurements were conducted on electrolyte solutions consisting of Li[CF3SO2NSO2CF3] (LiTFSI) dissolved in the solvents of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and their mixtures at various concentrations. It was observed that 17O chemical shifts of solvent molecules change with the concentration of LiTFSI. The chemical shift displacements of carbonyl oxygen are evidently greater than those of ethereal oxygen, strongly indicating that Li+ ion is coordinated with carbonyl oxygen rather than ethereal oxygen. To understand the detailed molecular interaction, computational modeling of 17O chemical shifts was carried out on proposed solvation structures. By comparing the predicted chemical shifts with the experimental values, it is found that a Li+ ion is coordinated with four double bond oxygen atoms from EC, PC, EMC and TFSI- anion. In the case of excessive amount of solvents of EC, PC and EMC the Li+ coordinated solvent molecules are undergoing quick exchange with bulk solvent molecules, resulting in average 17O chemical shifts. Several kinds of solvation structures are identified, where the proportion of each structure in the liquid electrolytes investigated depends on the concentration of LiTFSI.

  15. NMR Parameters Determination through ACE Committee Machine with Genetic Implanted Fuzzy Logic and Genetic Implanted Neural Network

    NASA Astrophysics Data System (ADS)

    Asoodeh, Mojtaba; Bagheripour, Parisa; Gholami, Amin

    2015-06-01

    Free fluid porosity and rock permeability, undoubtedly the most critical parameters of hydrocarbon reservoir, could be obtained by processing of nuclear magnetic resonance (NMR) log. Despite conventional well logs (CWLs), NMR logging is very expensive and time-consuming. Therefore, idea of synthesizing NMR log from CWLs would be of a great appeal among reservoir engineers. For this purpose, three optimization strategies are followed. Firstly, artificial neural network (ANN) is optimized by virtue of hybrid genetic algorithm-pattern search (GA-PS) technique, then fuzzy logic (FL) is optimized by means of GA-PS, and eventually an alternative condition expectation (ACE) model is constructed using the concept of committee machine to combine outputs of optimized and non-optimized FL and ANN models. Results indicated that optimization of traditional ANN and FL model using GA-PS technique significantly enhances their performances. Furthermore, the ACE committee of aforementioned models produces more accurate and reliable results compared with a singular model performing alone.

  16. Parameter independent low-power heteronuclear decoupling for fast magic-angle spinning solid-state NMR

    NASA Astrophysics Data System (ADS)

    Equbal, Asif; Madhu, P. K.; Meier, Beat H.; Nielsen, Niels Chr.; Ernst, Matthias; Agarwal, Vipin

    2017-02-01

    Major advances have recently been made in the field of heteronuclear dipolar decoupling in solid-state nuclear magnetic resonance (NMR). These developments have improved the resolution and sensitivity of the NMR spectrum of spins coupled to protons. One such new scheme, denoted as rCWApA, has proven to be robust with practically no need for parameter optimization [A. Equbal et al. Chem. Phys. Lett., 635, 339 (2015)]. Most of the experiments with rCWApA have been carried out in the regimes of slow to moderate magic-angle spinning while simultaneously applying high decoupling radio-frequency amplitudes. Here, we explore the performance of the rCWApA sequence and its predecessor rCWA in the regime of low-power radio-frequency irradiation and fast magic-angle spinning. The robustness of the refocused continuous-wave (rCW) schemes to experimental parameters such as pulse lengths and offset irradiation is demonstrated. Numerical simulations and analytical theory have been used to understand the effects of various nuclear spin interactions on the decoupling performance of the low-power rCW decoupling scheme relative to other decoupling methods. This has lead to the design of an "optimum low-power decoupling sequence" that can be used without parameter optimization. This result is particularly important in the context of samples with low signal to noise.

  17. Parameter independent low-power heteronuclear decoupling for fast magic-angle spinning solid-state NMR.

    PubMed

    Equbal, Asif; Madhu, P K; Meier, Beat H; Nielsen, Niels Chr; Ernst, Matthias; Agarwal, Vipin

    2017-02-28

    Major advances have recently been made in the field of heteronuclear dipolar decoupling in solid-state nuclear magnetic resonance (NMR). These developments have improved the resolution and sensitivity of the NMR spectrum of spins coupled to protons. One such new scheme, denoted as rCW(ApA), has proven to be robust with practically no need for parameter optimization [A. Equbal et al. Chem. Phys. Lett., 635, 339 (2015)]. Most of the experiments with rCW(ApA) have been carried out in the regimes of slow to moderate magic-angle spinning while simultaneously applying high decoupling radio-frequency amplitudes. Here, we explore the performance of the rCW(ApA) sequence and its predecessor rCW(A) in the regime of low-power radio-frequency irradiation and fast magic-angle spinning. The robustness of the refocused continuous-wave (rCW) schemes to experimental parameters such as pulse lengths and offset irradiation is demonstrated. Numerical simulations and analytical theory have been used to understand the effects of various nuclear spin interactions on the decoupling performance of the low-power rCW decoupling scheme relative to other decoupling methods. This has lead to the design of an "optimum low-power decoupling sequence" that can be used without parameter optimization. This result is particularly important in the context of samples with low signal to noise.

  18. Longitudinal NMR parameter measurements of Japanese pear fruit during the growing process using a mobile magnetic resonance imaging system

    NASA Astrophysics Data System (ADS)

    Geya, Yuto; Kimura, Takeshi; Fujisaki, Hirotaka; Terada, Yasuhiko; Kose, Katsumi; Haishi, Tomoyuki; Gemma, Hiroshi; Sekozawa, Yoshihiko

    2013-01-01

    Longitudinal nuclear magnetic resonance (NMR) parameter measurements of Japanese pear fruit (Pyrus pyrifolia Nakai, Kosui) were performed using an electrically mobile magnetic resonance imaging (MRI) system with a 0.2 T and 16 cm gap permanent magnet. To measure the relaxation times and apparent diffusion coefficients of the pear fruit in relation to their weight, seven pear fruits were harvested almost every week during the cell enlargement period and measured in a research orchard. To evaluate the in situ relaxation times, six pear fruits were longitudinally measured for about two months during the same period. The measurements for the harvested samples showed good agreement with the in situ measurements. From the measurements of the harvested samples, it is clear that the relaxation rates of the pear fruits linearly change with the inverse of the linear dimension of the fruits, demonstrating that the relaxation mechanism is a surface relaxation. We therefore conclude that the mobile MRI system is a useful device for measuring the NMR parameters of outdoor living plants.

  19. Reparameterization of RNA chi Torsion Parameters for the AMBER Force Field and Comparison to NMR Spectra for Cytidine and Uridine.

    PubMed

    Yildirim, Ilyas; Stern, Harry A; Kennedy, Scott D; Tubbs, Jason D; Turner, Douglas H

    2010-05-11

    A reparameterization of the torsional parameters for the glycosidic dihedral angle, chi, for the AMBER99 force field in RNA nucleosides is used to provide a modified force field, AMBER99chi. Molecular dynamics simulations of cytidine, uridine, adenosine, and guanosine in aqueous solution using the AMBER99 and AMBER99chi force fields are compared with NMR results. For each nucleoside and force field, 10 individual molecular dynamics simulations of 30 ns each were run. For cytidine with AMBER99chi force field, each molecular dynamics simulation time was extended to 120 ns for convergence purposes. Nuclear magnetic resonance (NMR) spectroscopy, including one-dimensional (1D) (1)H, steady-state 1D (1)H nuclear Overhauser effect (NOE), and transient 1D (1)H NOE, was used to determine the sugar puckering and preferred base orientation with respect to the ribose of cytidine and uridine. The AMBER99 force field overestimates the population of syn conformations of the base orientation and of C2'-endo sugar puckering of the pyrimidines, while the AMBER99chi force field's predictions are more consistent with NMR results. Moreover, the AMBER99 force field prefers high anti conformations with glycosidic dihedral angles around 310 degrees for the base orientation of purines. The AMBER99chi force field prefers anti conformations around 185 degrees , which is more consistent with the quantum mechanical calculations and known 3D structures of folded ribonucleic acids (RNAs). Evidently, the AMBER99chi force field predicts the structural characteristics of ribonucleosides better than the AMBER99 force field and should improve structural and thermodynamic predictions of RNA structures.

  20. Correlation between electronic parameters and corrosion inhibition of benzothiazole derivatives- NMR parameters as important and neglected descriptors

    NASA Astrophysics Data System (ADS)

    Behzadi, Hadi; Forghani, Ali

    2017-03-01

    The relation between electronic properties and corrosion inhibitive performance of three benzothiazole derivatives 1,3-benzothiazol-2-amine (BTA), 6-methyl-1,3-benzothiazol-2-amine (MBTA) and 2-amino-1,3-benzthiazole-6-thiol (TBTA) has been investigated by density functional theory. The electronic properties including EHOMO, ELUMO and related parameters were calculated at the B3LYP/6-311++G(d,p) level. The chemical shielding CS tensors were introduced as important and neglected descriptors to evaluate inhibitive efficiency of corrosion inhibitors. Nuclear independent chemical shift (NICS) components, as an aromaticity criterion, were also investigated as local descriptor. Polarizability and CS descriptors, as second rank tensors, show the best correlations with inhibition efficiencies of studied inhibitors.

  1. Factors determining the reliable description of global tumbling parameters in solution NMR.

    PubMed

    Pawley, Norma H; Gans, Jason D; Nicholson, Linda K

    2002-11-01

    An accurate description of global tumbling of a protein is essential for correct analysis and interpretation of internal dynamics and thermodynamics. The accurate fitting of global tumbling parameters is affected by the number of experimental relaxation data points available for analysis, the distribution of data points over the domain of the function describing the tumbling, the measurement error associated with the data, the error associated with use of an approximate functional form, and errors in the protein structure. We present an analysis of the influence of these factors on the error in global tumbling parameters and the corresponding error in the calculated T(1)/T(2) values. We find that reduction of experimental and approximation error can compensate for a less-than-ideal quantity or distribution of data points, and that accurate parameters can be obtained for proteins with highly anisotropic distributions of bond vectors, as illustrated using the helical bundle protein G-CSF. This indicates that proteins with anisotropic distributions, such as the helical bundle class of proteins, should not summarily be excluded when selecting proteins for dynamic and thermodynamic analyses of (15)N backbone relaxation measurements.

  2. Analysis and theoretical modeling of 18O enriched carbon dioxide spectrum by CRDS near 1.35 μm: (II) 16O13C18O, 16O13C17O, 12C18O2, 17O12C18O, 12C17O2, 13C18O2 and 17O13C18O

    NASA Astrophysics Data System (ADS)

    Karlovets, E. V.; Campargue, A.; Kassi, S.; Tashkun, S. A.; Perevalov, V. I.

    2017-04-01

    This contribution is the second part of the analysis of the room temperature absorption spectrum of 18O enriched carbon dioxide by very high sensitivity Cavity Ring Down spectroscopy between 6977 and 7918 cm-1 (1.43-1.26 μm). Overall, more than 8600 lines belonging to 166 bands of eleven carbon dioxide isotopologues were rovibrationnally assigned. In a first part (Kassi et al. J Quant Spectrosc Radiat Transfer 187 (2017) 414-425, http://dx.doi.org/10.1016/j.jqsrt.2016.09.002), the results relative to mono-substituted isotopologues, 16O12C18O, 16O12C17O, 12C16O2 and 13C16O2, were presented. This second contribution is devoted to the multiply-substituted isotopologues or clumped isotopologues of particular importance in geochemistry: 16O13C18O, 16O13C17O, 12C18O2, 17O12C18O, 12C17O2, 13C18O2 and 17O13C18O. On the basis of the predictions of effective Hamiltonian models, a total of 3195 transitions belonging to 73 bands were rovibrationnally assigned for these seven species. Among the 73 observed bands, 55 are newly reported. All the identified bands correspond to ΔP=10 and 11 series of transitions, where P= 2V1+V2+3V3 is the polyad number (Vi are vibrational quantum numbers). The accurate spectroscopic parameters of 70 bands have been determined from the standard band-by-band analysis. Global fits of the measured line intensities of the ΔP=10 series of transitions of 17O12C18O and 16O13C18O and of the ΔP=11 series of transitions of 12C18O2, 17O12C18O, 16O13C18O and 13C18O2 were performed to determine the corresponding sets of the effective dipole moment parameters.

  3. Corrections for 17O interference, effects on Δ47 determination

    NASA Astrophysics Data System (ADS)

    Olack, G.; He, B.; Colman, A. S.

    2013-12-01

    The measurements of 13C on CO2 samples are routinely corrected for 17O contribution to the m/z 45 signal (Craig, 1957; Santrock, et al., 1985). The 17O abundance affects the Δ47 calculation, and the amount of 17O present is routinely determined using the relationship between 18O and 17O presented in IAEA TECDOC 825 (Dennis, et al., 2011; Huntington, et al., 2009; Gonfiantini, et al., 1995). In 2010, the IAEA released new recommendations for 17O determinations to be used for 13C corrections (Brand, et al., 2010). We compare the effect of using different ways to determine 17O interference, as well as using the currently accepted N(13C)/N(12C) value for VPDB (Brand, et al., 2010), on heated gas lines, model data, and on CO2 gases made to have similar δ47 and Δ47, but with highly contrasting δ18O and δ13C values. The 2010 IAEA recommendations give a better fit for heated gas data than the TECDOC 825 recommendations. Comparing differences in the data points relative to their respective fitted lines, we see differences on the order of 5 to 10 ppm in Δ47. That corresponds to a systematic error of 2 °C in the temperature estimate (room temperature range), and one that varies with δ13C and δ18O, but not necessarily with δ47. The preliminary work on equilibrated CO2 gases having similar δ47, but very different δ13C and δ18O, showed large (ca. 70 ppm) differences in Δ47 when using the (standard) TECDOC 825 recommendations. The Δ47 values were much closer when the 2010 IUPAC recommendations were used. This also serves as a test of the updated factors for 17O determination, as well as the overall robustness of the Δ47 measurement.

  4. The rotational spectrum of 17O2 up to the THz region

    NASA Astrophysics Data System (ADS)

    Cazzoli, Gabriele; Kirsch, Till; Gauss, Jürgen; Puzzarini, Cristina

    2016-01-01

    The investigation of the pure rotational spectrum of the 17O2 isotopic species of molecular oxygen has been extended with respect to previous investigations to the submillimeter-wave region, from 230 GHz up to 1.06 THz. The resulting spectroscopic parameters, which have an accuracy comparable to that of the constants obtained from an updated isotopic invariant fit involving data for three electronic states and six isotopologues [Yu et al. High resolution spectral analysis of oxygen. IV. Energy levels, partition sums, bandconstants, RKR potentials, Franck-Condon factors involving the X3 Σg-, a1Δg, and b1 Σg+ states. J Chem Phys 2014;141:174302/1-12], permit the prediction of the pure rotational transitions up to 2 THz with an estimated uncertainty not greater than 100 kHz. In the present study, high-level quantum-chemical calculations guided, supported, and complemented the determination of the hyperfine parameters of 17O, with particular effort made in determining an accurate and reliable experimental value for the nuclear spin-rotation constant. A detailed discussion about the magnitude of the nuclear spin-rotation constant in the 17O-containing O2 species for both the ground and the first excited electronic state is presented.

  5. An NMR study and ab initio molecular orbital calculation of substituted benzofuroxans and the salt of 4,6-dinitrobenzofuroxan

    NASA Astrophysics Data System (ADS)

    Cmoch, P.; Wiench, J. W.; Stefaniak, L.; Webb, G. A.

    1999-09-01

    13C, 15N and 17O NMR data are reported for a series of substituted benzofuroxans in aprotic and acidic solutions and for a potassium salt of a substituted benzofuroxan. Some of the title compounds can exhibit fast furoxan valence equilibrium at room temperature regardless of a solvent used, whereas for the others no evidence of above-mentioned process exists. The NMR parameters most sensitive to salt formation are the chemical shifts of the C7, N1, N3 and all of the oxygen nuclei. Hence these are reported as the most satisfactory chemical shifts to be used in distinguishing between the salt and non-ionic forms of the substituted benzofuroxans studied. Calculated energies at the self-consistent field (SCF) level of theory for both tautomeric forms (N1- and N3-oxide) of some compounds studied are used for predicting the tautomeric equilibrium constants. Absolute 17O shieldings are employed in the reversal of the assignments of 17O NMR signals existing in the literature.

  6. The hyperfine structure in the rotational spectra of D{sub 2}{sup 17}O and HD{sup 17}O: Confirmation of the absolute nuclear magnetic shielding scale for oxygen

    SciTech Connect

    Puzzarini, Cristina Cazzoli, Gabriele; Harding, Michael E.; Vázquez, Juana; Gauss, Jürgen

    2015-03-28

    Guided by theoretical predictions, the hyperfine structures of the rotational spectra of mono- and bideuterated-water containing {sup 17}O have been experimentally investigated. To reach sub-Doppler resolution, required to resolve the hyperfine structure due to deuterium quadrupole coupling as well as to spin-rotation (SR) and dipolar spin-spin couplings, the Lamb-dip technique has been employed. The experimental investigation and in particular, the spectral analysis have been supported by high-level quantum-chemical computations employing coupled-cluster techniques and, for the first time, a complete experimental determination of the hyperfine parameters involved was possible. The experimentally determined {sup 17}O spin-rotation constants of D{sub 2}{sup 17}O and HD{sup 17}O were used to derive the paramagnetic part of the corresponding nuclear magnetic shielding constants. Together with the computed diamagnetic contributions as well as the vibrational and temperature corrections, the latter constants have been employed to confirm the oxygen nuclear magnetic shielding scale, recently established on the basis of spin-rotation data for H{sub 2}{sup 17}O [Puzzarini et al., J. Chem. Phys. 131, 234304 (2009)].

  7. Investigations of the structure and "interfacial" surface chemistry of Bioglass (RTM) materials by solid-state multinuclear NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Sarkar, Gautam

    Bioactive materials such as BioglassRTM 45S5 (45% SiO 2, 24.5% CaO, 24.5% Na2O, and 6% P2O5 by weight) are sodium-phosphosilicate glasses containing independent three-dimensional silicate and phosphate networks and Na+ and Ca2+ ions as modifying cations. Due to their bioactivity, these materials are currently used as implants and for other surgical and clinical applications. The bioactivity of BioglassesRTM is due to their unique capability to form chemical bonds to tissues through an octacalciumphosphate (OCP)- and/or hydroxyapatite-like (HA) "interfacial" matrix. The formation of OCP and/or HA is preceded by the formation of a silica-rich surface layer and the subsequent growth of an amorphous calcium phosphate (a-CP) layer. Structural characterization of a series of commercial and synthesized Bioglass materials 45S5 52S, 55S, 60S, and synthesized 17O-labelled "Bioglass materials 45S, 52S, 55S and 60S" have been obtained using solid-state single-pulse magic-angle spinning (SP/MAS) 17O, 23Na, 29Si and 31P NMR. The 17O NMR isotropic chemical shifts and estimates of the quadrupole coupling constants (Cq) [at fixed asymmetry parameter ( hQ ) values of zero] have been obtained from solid-state spin-echo 17O SP/MAS NMR spectra of 17O-labelled "Bioglasses". The simulation results of these spectra reveal the presence of both bridging-oxygens (BO, i.e. ≡ Si-17OSi ≡ ) and non-bridging oxygens (NBO, i.e. ≡ Si-17O-Na+/Ca2+ ) in the silicate networks in these materials. 17O NMR spectra of these Bioglass materials do not show any direct evidence for the presence of BO and NBO atoms in the phosphate units; however, they are expected to be present in small amounts. In vitro reactions of BioglassRTM 45S5, 60S and 77S powders have been used to study the "interfacial" surface chemistry of these materials in simulated body-fluid (SBF, Kyoto or K9 solution) and/or 17O-enriched tris-buffer solution. 29Si and 31P SP/MAS NMR have been used to identify and quantify the extent of

  8. Semi-empirical refinements of crystal structures using (17)O quadrupolar-coupling tensors.

    PubMed

    Holmes, Sean T; Iuliucci, Robbie J; Mueller, Karl T; Dybowski, Cecil

    2017-02-14

    We demonstrate a modification of Grimme's two-parameter empirical dispersion force field (referred to as the PW91-D2* method), in which the damping function has been optimized to yield geometries that result in predictions of the principal values of (17)O quadrupolar-coupling tensors that are systematically in close agreement with experiment. The predictions of (17)O quadrupolar-coupling tensors using PW91-D2*-refined structures yield a root-mean-square deviation (RMSD) (0.28 MHz) for twenty-two crystalline systems that is smaller than the RMSD for predictions based on X-ray diffraction structures (0.58 MHz) or on structures refined with PW91 (0.53 MHz). In addition, (13)C, (15)N, and (17)O chemical-shift tensors and (35)Cl quadrupolar-coupling tensors determined with PW91-D2*-refined structures are compared to the experiment. Errors in the prediction of chemical-shift tensors and quadrupolar-coupling tensors are, in these cases, substantially lowered, as compared to predictions based on PW91-refined structures. With this PW91-D2*-based method, analysis of 42 (17)O chemical-shift-tensor principal components gives a RMSD of only 18.3 ppm, whereas calculations on unrefined X-ray structures give a RMSD of 39.6 ppm and calculations of PW91-refined structures give an RMSD of 24.3 ppm. A similar analysis of (35)Cl quadrupolar-coupling tensor principal components gives a RMSD of 1.45 MHz for the unrefined X-ray structures, 1.62 MHz for PW91-refined structures, and 0.59 MHz for the PW91-D2*-refined structures.

  9. Advanced NMR characterization of zeolite catalysts. Third quarterly report, March 1-May 31, 1984

    SciTech Connect

    Welsh, L.B.

    1984-06-01

    The program discussed in this report is a two-year two-phase joint UOP-University of Illinois study of the application of improved high resolution solid state nuclear magnetic resonance (NMR) techniques to the characterization of zeolite catalysts. During the first phase of this program very pure, and in some cases isotopically enriched faujasites will be prepared and studied by majic angle sample spinning NMR (MASS NMR) and variable angle sample spinning NMR (VASS NMR) on 500 and 360 MHz (Proton frequency) NMR spectrometers. During the second phase of this program these NMR techniques will be used to study the effects of impurity concentration, dealumination treatments and cation exchange on the NMR properties of faujasites. The initial emphasis of this program during Phase I is on the preparation and measurement of the NMR properties of /sup 17/O enriched Na-Y faujasites. The effort in each phase is broken into four tasks: (1) zeolite preparation. (2) standard zeolite characterization; (3) measurement of zeolite NMR properties; and (4) analysis of NMR data. The main efforts during the third three month period of the program have been the characterization of the /sup 17/O enriched zeolites, particularly X and Y zeolites, by high resolution sample spinning /sup 17/O NMR, and the preparation of additional /sup 17/O enriched zeolites. X and Y zeolites with Si/Al framework ratios from 1.22 to 7.6 have been prepared in either the Na, NH/sub 4/ or Ba form. MASS NMR and VASS NMR as well as static NMR measurements have been made on these materials for /sup 17/O NMR frequencies from 20.4 to 67.8 MHz. Computer simulations of the experimental NMR lineshapes are in progress. Results to date indicate that the observed spectra arise from two different types of oxygen sites, possibly O in Al-O-Si links and chemically bound OH groups. 2 references, 1 figure, 1 table.

  10. Multinuclear NMR studies of gaseous and liquid sevoflurane

    NASA Astrophysics Data System (ADS)

    Macięga, E.; Makulski, W.; Jackowski, K.; Blicharska, B.

    2006-03-01

    For the first time, a small amount of sevoflurane ((CF 3) 2CHOCH 2F) in carbon dioxide and xenon as the gaseous solvents has been studied using 19F and 1H NMR spectra. Density-dependent 19F and 1H nuclear magnetic shielding was observed when the pressure of each solvent was increased. After extrapolation of the results to the zero-density limit it was possible to determine the appropriate shielding constants free from intermolecular interactions, σ0(F) and σ0(H). Similar procedure has also been applied for the investigation of fluorine-proton spin-spin couplings and the 2J 0(FH) and 3J 0(FH) constants of an isolated (CF 3) 2CHOCH 2F molecule were also obtained. Additionally, high-resolution 1H, 13C, 17O and 19F NMR spectra of pure liquid sevoflurane were also recorded and all the 1H- 13C, 1H- 19F and 19F- 13C spin-spin coupling constants and NMR chemical shifts were measured. It is shown that the experimental NMR parameters are suitable for comparison with the results of recent quantum-chemical calculations.

  11. Mn2+ complexes with 12-membered pyridine based macrocycles bearing carboxylate or phosphonate pendant arm: crystallographic, thermodynamic, kinetic, redox, and 1H/17O relaxation studies.

    PubMed

    Drahoš, Bohuslav; Kotek, Jan; Císařová, Ivana; Hermann, Petr; Helm, Lothar; Lukeš, Ivan; Tóth, Éva

    2011-12-19

    potentials (E(ox) = 0.73 V for MnL(1) and E(ox) = 0.68 V for MnL(2)), in accordance with air-oxidation. The parameters governing the relaxivity of the Mn(2+) complexes were determined from variable-temperature (17)O NMR and (1)H NMRD data. The water exchange is extremely fast, k(ex) = 3.03 and 1.77 × 10(9) s(-1) for MnL(1) and MnL(2), respectively. Variable-pressure (17)O NMR measurements have been performed to assess the water exchange mechanism on MnL(1) and MnL(2) as well as on other Mn(2+) complexes. The negative activation volumes for both MnL(1) and MnL(2) complexes confirmed an associative mechanism of the water exchange as expected for a hexacoordinated Mn(2+) ion. The hydration number of q = 1 was confirmed for both complexes by (17)O chemical shifts. A relaxometric titration with phosphate, carbonate or citrate excluded the replacement of the coordinated water molecule by these small endogenous anions.

  12. 1H NMR z-spectra of acetate methyl in stretched hydrogels: Quantum-mechanical description and Markov chain Monte Carlo relaxation-parameter estimation

    NASA Astrophysics Data System (ADS)

    Shishmarev, Dmitry; Chapman, Bogdan E.; Naumann, Christoph; Mamone, Salvatore; Kuchel, Philip W.

    2015-01-01

    The 1H NMR signal of the methyl group of sodium acetate is shown to be a triplet in the anisotropic environment of stretched gelatin gel. The multiplet structure of the signal is due to the intra-methyl residual dipolar couplings. The relaxation properties of the spin system were probed by recording steady-state irradiation envelopes ('z-spectra'). A quantum-mechanical model based on irreducible spherical tensors formed by the three magnetically equivalent spins of the methyl group was used to simulate and fit experimental z-spectra. The multiple parameter values of the relaxation model were estimated by using a Bayesian-based Markov chain Monte Carlo algorithm.

  13. Correlation of tryptophan fluorescence intensity decay parameters with sup 1 H NMR-determined rotamer conformations: (tryptophan sup 2 )oxytocin

    SciTech Connect

    Ross, J.B.A.; Schwartz, G.P.; Laws, W.R. ); Wyssbrod, H.R.; Porter, R.A. ); Michaels, C.A. )

    1992-02-18

    While the fluorescence decay kinetics of tyrosine model compounds can be explained in terms of heterogeneity derived from the three ground-state {chi}{sup 1} rotamers, a similar correlation has yet to be directly observed for a tryptophan residue. In addition, the asymmetric indole ring might also lead to heterogeneity from {chi}{sup 2} rotations. In this paper, the time-resolved and steady-state fluorescence properties of (tryptophan{sup 2})oxytocin at pH 3 are presented and compared with {sup 1}H NMR results. According to the unrestricted analyses of individual fluorescence decay curves taken as a function of emission wavelength-independent decay constants, only three exponential terms are required. In addition, the preexponential weighting factors (amplitudes) have the same relative relationship (weights) as the {sup 1}H NMR-determined {chi}{sup 1} rotamer populations of the indole side chain. {sup 15}N was used in heteronuclear coupling experiments to confirm the rotamer assignments. Inclusion of a linked function restricting the decay amplitudes to the {chi}{sup 1} rotamer populations in the individual decay curve analyses and in the global analysis confirms this correlation. According to qualitative nuclear Overhauser data, there are two {chi}{sup 2} populations.

  14. The impact of the revised 17O(p, α)14N reaction rate on 17O stellar abundances and yields

    NASA Astrophysics Data System (ADS)

    Straniero, O.; Bruno, C. G.; Aliotta, M.; Best, A.; Boeltzig, A.; Bemmerer, D.; Broggini, C.; Caciolli, A.; Cavanna, F.; Ciani, G. F.; Corvisiero, P.; Cristallo, S.; Davinson, T.; Depalo, R.; Di Leva, A.; Elekes, Z.; Ferraro, F.; Formicola, A.; Fülöp, Zs.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Menegazzo, R.; Mossa, V.; Pantaleo, F. R.; Piatti, D.; Piersanti, L.; Prati, P.; Samorjai, E.; Strieder, F.; Szücs, T.; Takács, M. P.; Trezzi, D.

    2017-02-01

    Context. Material processed by the CNO cycle in stellar interiors is enriched in 17O. When mixing processes from the stellar surface reach these layers, as occurs when stars become red giants and undergo the first dredge up, the abundance of 17O increases. Such an occurrence explains the drop of the 16O/17O observed in RGB stars with mass larger than 1.5M⊙. As a consequence, the interstellar medium is continuously polluted by the wind of evolved stars enriched in 17O. Aims: Recently, the Laboratory for Underground Nuclear Astrophysics (LUNA) collaboration released an improved rate of the 17O(p, α)14N reaction. In this paper we discuss the impact that the revised rate has on the 16O/17O ratio at the stellar surface and on 17O stellar yields. Methods: We computed stellar models of initial mass between 1 and 20 M⊙ and compared the results obtained by adopting the revised rate of the 17O(p, α)14N to those obtained using previous rates. Results: The post-first dredge up 16O/17O ratios are about 20% larger than previously obtained. Negligible variations are found in the case of the second and the third dredge up. In spite of the larger 17O(p, α)14N rate, we confirm previous claims that an extra-mixing process on the red giant branch, commonly invoked to explain the low carbon isotopic ratio observed in bright low-mass giant stars, marginally affects the 16O/17O ratio. Possible effects on AGB extra-mixing episodes are also discussed. As a whole, a substantial reduction of 17O stellar yields is found. In particular, the net yield of stars with mass ranging between 2 and 20 M⊙ is 15 to 40% smaller than previously estimated. Conclusions: The revision of the 17O(p, α)14N rate has a major impact on the interpretation of the 16O/17O observed in evolved giants, in stardust grains and on the 17O stellar yields.

  15. Curie-type paramagnetic NMR relaxation in the aqueous solution of Ni(II).

    PubMed

    Mareš, Jiří; Hanni, Matti; Lantto, Perttu; Lounila, Juhani; Vaara, Juha

    2014-04-21

    Ni(2+)(aq) has been used for many decades as a model system for paramagnetic nuclear magnetic resonance (pNMR) relaxation studies. More recently, its magnetic properties and also nuclear magnetic relaxation rates have been studied computationally. We have calculated electron paramagnetic resonance and NMR parameters using quantum-mechanical (QM) computation of molecular dynamics snapshots, obtained using a polarizable empirical force field. Statistical averages of hyperfine coupling, g- and zero-field splitting tensors, as well as the pNMR shielding terms, are compared to the available experimental and computational data. In accordance with our previous work, the isotropic hyperfine coupling as well as nuclear shielding values agree well with experimental measurements for the (17)O nuclei of water molecules in the first solvation shell of the nickel ion, whereas larger deviations are found for (1)H centers. We report, for the first time, the Curie-type contribution to the pNMR relaxation rate using QM calculations together with Redfield relaxation theory. The Curie relaxation mechanism is analogous to chemical shift anisotropy relaxation, well-known in diamagnetic NMR. Due to the predominance of other types of paramagnetic relaxation mechanisms for this system, it is possible to extract the Curie term only computationally. The Curie mechanism alone would result in around 16 and 20 s(-1) of relaxation rates (R1 and R2 respectively) for the (1)H nuclei of water molecules bonded to the Ni(2+) center, in a magnetic field of 11.7 T. The corresponding (17)O relaxation rates are around 33 and 38 s(-1). We also report the Curie contribution to the relaxation rate for molecules beyond the first solvation shell in a 1 M solution of Ni(2+) in water.

  16. Investigation of the Herzberg (C1Σ+→A1Π) band system in 12C17O

    NASA Astrophysics Data System (ADS)

    Hakalla, Rafał

    2015-10-01

    The C→A (0,1), (0,2) and (0,3) rovibronic bands of the less-abundant 12C17O isotopologue are studied in high resolution using a high-accuracy dispersive optical spectroscopy in the region of 22,800-26,100 cm-1. Calibration with respect to simultaneously recorded thorium atomic lines, obtained from several overlapped orders of the spectrum in the visible range, as well as a stainless steel hollow-cathode molecular lamp with two anodes, yields an absolute accuracy of wavenumbers measurements of about 0.0025 cm-1 for the CO spectra. All 261 spectra lines of the Herzberg band system in 12C17O, up to Jmax=34, were precisely measured and rotationally analyzed. As a result, the merged rotational constants and rotational equilibrium constants for the C1Σ+ Rydberg state, as well as the band origins, the isotope shifts, the RKR turning points, Franck-Condon factors, relative intensities, and r-centroids of the C→A system in the 12C17O isotopologue were obtained. An experimental RKR potential energy curve and vibrational levels of the C1Σ+ state in 12C17O together with highly excited k3Π, c3Π, E1Π, B1Σ+ and D‧1Σ+ states lying in the region between the first dissociation limit and the ionization potential of CO were plotted. A detailed investigation of possible perturbations that should occur in the C1Σ+(υ=0) Rydberg state of less-abundant 12C17O isotopologue in the close vicinity of the k3Π(υ=1, 2) and c3Π(υ=0) states in the region 92,000 cm-1 was performed. In the A1Π, υ=3 state of 12C17O, extensive, multi-state rotational perturbations were found and analyzed. Also, a global isotopic analysis of the C1Σ+ Rydberg state was carried out in the 12C16O, 12C17O, 13C16O, 12C18O, 13C17O, and 13C18O as well as in 14C16O and 14C18O isotopologues. This analysis enabled us to determine, amongst others, the vibrational equilibrium constants in 12C17O for the C1Σ+ state, to improve these constants in the 12C16O, 13C16O, 12C18O, 13C17O, and 13C18O isotopologues and

  17. Simulation of the diurnal variations of the isotope anomaly (?17O) of reactive trace gases (NOx, HOx) and implications for the ?17O of nitrate.

    NASA Astrophysics Data System (ADS)

    Morin, Samuel; Sander, Rolf; Savarino, Joël.

    2010-05-01

    The isotope anomaly of secondary atmospheric species such as nitrate (NO3-) has potential to provide useful constrains on their formation pathways. Indeed, the ?17O of their precursors (NOx, HOx etc.) differs and depends on their interactions with ozone, which is the main source of non-zero ?17O in the atmosphere. Interpreting variations of ?17O in nitrate requires an in-depth understanding of the ?17O of its precursors taking into account non-linear chemical regimes operating under various environmental settings. In addition, the role of isotope exchange reactions must be carefully accounted for. To investigate the relevance of various assessments of the isotopic signature of nitrate production pathways that have recently been proposed in the literature, an atmospheric chemistry box model (MECCA, Sander et al., 2005, ACP)) was used to explicitly compute the diurnal variations of the isotope anomaly of NOx, HOx under several conditions prevailing in the marine boundary layer. ?17O was propagated from ozone to other species (NO, NO2, OH, HO2, RO2, NO3, N2O5, HONO, HNO3, HNO4, H2O2) according to the classical mass-balance equation applied at each time step of the model (30 seconds typically). The model confirms that diurnal variations in ?17O of NOx are well predicted by the photochemical steady-state relationship introduced by Michalski et al. (2003, GRL) during the day, but that at night a different approach must be employed (e.g. « fossilization » of the ?17O of NOx as soon as the photochemical lifetime of NOx drops below ca. 5 minutes). The model also allows to evaluate the impact on ?17O of NOx and nitrate of the frequently made simplifying assumption that ?17O(HOx)=0 permil, with and without mass-independent fractionation during the H+O2-HO2 reaction. Recommendations for the modeling of ?17O of nitrate will be given, based on the extensive model work carried out. In addition, the link between diurnal variations of the ?17O of nitrate precursors and seasonal

  18. 53Cr, 17O and 14N nuclear quadrupole resonance in ammonium dichromate

    NASA Astrophysics Data System (ADS)

    Stephenson, David; Singh, Nadia

    2016-12-01

    The 53Cr resonance frequency in ammonium dichromate has been detected at 4202 kHz giving a Qcc of 8404 kHz (assuming η= 0). Calculations suggest that the value of the 53Cr quadrupole moment is about 84 mB lower that the currently accepted value. The resonance frequencies of two 17O nuclei have also been detected giving Qcc = 2800, 2890 kHz and η = 0.726, 0.780 respectively. The value for coupling and asymmetry parameter for 14N has been refined using zero field NQR giving a value Qcc = 78.8 kHz and η= 0.645 the asymmetry value being considerably lower than the value previous reported.

  19. Tracing atmospheric nitrate deposition in a complex semiarid ecosystem using delta17O.

    PubMed

    Michalski, Greg; Meixner, Thomas; Fenn, Mark; Hernandez, Larry; Sirulnik, Abby; Allen, Edith; Thiemens, Mark

    2004-04-01

    The isotopic composition of nitrate collected from aerosols, fog, and precipitation was measured and found to have a large 17O anomaly with delta17O values ranging from 20 percent per thousand to 30% percent per thousand (delta17O = delta17O - 0.52(delta18O)). This 17O anomaly was used to trace atmospheric deposition of nitrate to a semiarid ecosystem in southern California. We demonstrate that the delta17O signal is a conserved tracer of atmospheric nitrate deposition and is a more robust indicator of N deposition relative to standard delta18O techniques. The data indicate that a substantial portion of nitrate found in the local soil, stream, and groundwater is of atmospheric origin and does not undergo biologic processing before being exported from the system.

  20. Variations of 17O/ 16O and 18O/ 16O in meteoric waters

    NASA Astrophysics Data System (ADS)

    Luz, Boaz; Barkan, Eugeni

    2010-11-01

    The variations of δ 17O and δ 18O in recent meteoric waters and in ice cores have proven to be an important tool for investigating the present and past hydrologic cycle. In order to close significant information gaps in the present distribution of δ 17O and δ 18O of meteoric water, we have run precise measurements, with respect to VSMOW, on samples distributed globally from low to high latitudes. Based on the new and existing data, we present the Global Meteoric Water Line (GMWL) for δ 17O and δ 18O as: ln(δ17O+1)=0.528ln(δ18O+1)+0.000033(R2=0.99999) In addition to meteoric water, we carried out the first measurements of seawater from the Pacific and Atlantic oceans with respect to VSMOW. The obtained results show that the slope of the trend line ln(δ 17O + 1) vs. ln(δ 18O + 1) of seawater samples is 0.528, the same as for meteoric water, but the regression intercept is -5 per meg. Thus, the positive intercept in the GMWL indicates an excess of 17O in meteoric waters with respect to the ocean. An excess (or depletion) of 17O in water is defined as: 17O-excess=ln(δ17O+1)-0.528(δ18O+1) Most meteoric water samples have positive 17O-excess of varying magnitudes with an average of 37 per meg with respect to VSMOW. We explain how these positive values originate from evaporation of sea water into marine air, which is undersaturated in water vapor, and how subsequent increase of 17O-excess occurs when atmospheric vapor condenses to form liquid and solid precipitation. We also clarify the effect of excessive evaporation on 17O-excess. Finally, based on the new results on 17O-excess of seawater we recalculated the relationship of δ 17O vs. δ 18O in vapor diffusion in air as 18α diff = 1.0096.

  1. Continental scale variation in 17O-excess of meteoric waters in the United States

    NASA Astrophysics Data System (ADS)

    Li, Shuning; Levin, Naomi E.; Chesson, Lesley A.

    2015-09-01

    High-precision triple oxygen isotope analysis of waters is an emerging tool in hydrological and paleoclimate research. The existing research on 17O-excess in waters includes surveys of meteoric waters and region-specific studies of high-latitude snow and tropical storms. However, a better understanding of the variation in 17O-excess of waters across large geographic regions is needed to expand the utility of triple oxygen isotope measurements. Here we present 17O-excess data from tap waters across the continental U.S., which we used as a proxy for precipitation. The 17O-excess values of tap waters ranged from -6 to +43 per meg and averaged 17 ± 11 per meg which is lower than the average 17O-excess reported for global meteoric waters, but overlaps with reported 17O-excess values of rainfall from the tropics. We observed relatively high 17O-excess values (>25 per meg) of tap waters in the northwestern U.S. and some of the lowest 17O-excess values (<5 per meg) in the states bordering the Gulf of Mexico. The latitudinal variation of 17O-excess among tap waters likely reflects the different controls on 17O-excess in precipitation. For example, re-evaporation of precipitation and convective processes influence the isotopic composition of tap waters from the southern portions of the U.S., resulting in relatively low 17O-excess values. In contrast, these effects are reduced in tap waters from the northern portions of the U.S. where snow and cold-season rainfall are primarily responsible for the majority of annual precipitation. Exceptions to the latitudinal trend are prevalent in the central portions of the U.S., where mixing and convection are likely responsible for 17O-excess values that are lower than would be expected at their latitudes. The results of this study provide both a first look at the variation of 17O-excess in meteoric waters on a continental scale and a predictive map for 17O-excess of meteoric waters in the U.S.

  2. NMR characterization of hydrocarbon adsorption on calcite surfaces: A first principles study

    SciTech Connect

    Bevilaqua, Rochele C. A.; Miranda, Caetano R.; Rigo, Vagner A.; Veríssimo-Alves, Marcos

    2014-11-28

    The electronic and coordination environment of minerals surfaces, as calcite, are very difficult to characterize experimentally. This is mainly due to the fact that there are relatively few spectroscopic techniques able to detect Ca{sup 2+}. Since calcite is a major constituent of sedimentary rocks in oil reservoir, a more detailed characterization of the interaction between hydrocarbon molecules and mineral surfaces is highly desirable. Here we perform a first principles study on the adsorption of hydrocarbon molecules on calcite surface (CaCO{sub 3} (101{sup ¯}4)). The simulations were based on Density Functional Theory with Solid State Nuclear Magnetic Resonance (SS-NMR) calculations. The Gauge-Including Projector Augmented Wave method was used to compute mainly SS-NMR parameters for {sup 43}Ca, {sup 13}C, and {sup 17}O in calcite surface. It was possible to assign the peaks in the theoretical NMR spectra for all structures studied. Besides showing different chemical shifts for atoms located on different environments (bulk and surface) for calcite, the results also display changes on the chemical shift, mainly for Ca sites, when the hydrocarbon molecules are present. Even though the interaction of the benzene molecule with the calcite surface is weak, there is a clearly distinguishable displacement of the signal of the Ca sites over which the hydrocarbon molecule is located. A similar effect is also observed for hexane adsorption. Through NMR spectroscopy, we show that aromatic and alkane hydrocarbon molecules adsorbed on carbonate surfaces can be differentiated.

  3. {sup 17}O({alpha},{gamma}){sup 21}Ne and {sup 17}O({alpha},n){sup 20}Ne for the weak s process

    SciTech Connect

    Best, A.; Goerres, J.; Beard, M.; Couder, M.; Boer, R. de; Falahat, S.; Gueray, R. T.; Kontos, A.; Kratz, K.-L.; LeBlanc, P. J.; Li, Q.; O'Brien, S.; Oezkan, N.; Pignatari, M.; Sonnabend, K.; Talwar, R.; Tan, W.; Uberseder, E.; Wiescher, M.

    2012-11-20

    The ratio of the reaction rates of the competing channels {sup 17}O({alpha}{gamma}){sup 21}Ne and {sup 17}O({alpha},n){sup 20}Ne determines the efficiency of {sup 16}O as a neutron poison in the s process in low metallicity rotating stars. It has a large impact on the element production, either producing elements to the mass range of A=90 in case of a significant poisoning effect or extending the mass range up to the region of A=150 if the {gamma} channel is of negligible strength. We present an improved study of the reaction {sup 17}O({alpha},n){sup 20}Ne, including an independent measurement of the {sup 17}O({alpha},n{sub 1}){sup 20}Ne channel. A simultaneous R-Matrix fit to both the n{sub 0} and the n{sub 1} channels has been performed. New reaction rates, including recent data on the {sup 17}O({alpha},{gamma}){sup 21}Ne reaction, have been calculated and used as input for stellar network calculations and their impact on the s process in rotating massive stars is discussed.

  4. Rapid parameter optimization of low signal-to-noise samples in NMR spectroscopy using rapid CPMG pulsing during acquisition: application to recycle delays.

    PubMed

    Farooq, Hashim; Courtier-Murias, Denis; Soong, Ronald; Masoom, Hussain; Maas, Werner; Fey, Michael; Kumar, Rajeev; Monette, Martine; Stronks, Henry; Simpson, Myrna J; Simpson, André J

    2013-03-01

    A method is presented that combines Carr-Purcell-Meiboom-Gill (CPMG) during acquisition with either selective or nonselective excitation to produce a considerable intensity enhancement and a simultaneous loss in chemical shift information. A range of parameters can theoretically be optimized very rapidly on the basis of the signal from the entire sample (hard excitation) or spectral subregion (soft excitation) and should prove useful for biological, environmental, and polymer samples that often exhibit highly dispersed and broad spectral profiles. To demonstrate the concept, we focus on the application of our method to T(1) determination, specifically for the slowest relaxing components in a sample, which ultimately determines the optimal recycle delay in quantitative NMR. The traditional inversion recovery (IR) pulse program is combined with a CPMG sequence during acquisition. The slowest relaxing components are selected with a shaped pulse, and then, low-power CPMG echoes are applied during acquisition with intervals shorter than chemical shift evolution (RCPMG) thus producing a single peak with an SNR commensurate with the sum of the signal integrals in the selected region. A traditional (13)C IR experiment is compared with the selective (13)C IR-RCPMG sequence and yields the same T(1) values for samples of lysozyme and riverine dissolved organic matter within error. For lysozyme, the RCPMG approach is ~70 times faster, and in the case of dissolved organic matter is over 600 times faster. This approach can be adapted for the optimization of a host of parameters where chemical shift information is not necessary, such as cross-polarization/mixing times and pulse lengths.

  5. Nucleosynthesis in AGB stars traced by oxygen isotopic ratios. I. Determining the stellar initial mass by means of the 17O/18O ratio

    NASA Astrophysics Data System (ADS)

    De Nutte, R.; Decin, L.; Olofsson, H.; Lombaert, R.; de Koter, A.; Karakas, A.; Milam, S.; Ramstedt, S.; Stancliffe, R. J.; Homan, W.; Van de Sande, M.

    2017-03-01

    Aims: We seek to investigate the 17O/18O ratio for a sample of AGB stars containing M-, S-, and C-type stars. These ratios are evaluated in relation to fundamental stellar evolution parameters: the stellar initial mass and pulsation period. Methods: Circumstellar 13C16O, 12C17O, and 12C18O line observations were obtained for a sample of nine stars with various single-dish long-wavelength facilities. Line intensity ratios are shown to relate directly to the surface 17O/18O abundance ratio. Results: Stellar evolution models predict the 17O/18O ratio to be a sensitive function of initial mass and to remain constant throughout the entire TP-AGB phase for stars initially less massive than 5 M⊙. This makes the measured ratio a probe of the initial stellar mass. Conclusions: Observed 17O/18O ratios are found to be well in the range predicted by stellar evolution models that do not consider convective overshooting. From this, accurate initial mass estimates are calculated for seven sources. For the remaining two sources, there are two mass solutions, although there is a larger probability that the low-mass solution is correct. Finally, we present hints at a possible separation between M/S- and C-type stars when comparing the 17O/18O ratio to the stellar pulsation period. The reduced spectra are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/600/A71

  6. Multitude of 2+ discrete states in 124Sn observed via the (17O 17O'γ) reaction: Evidence for pygmy quadrupole states

    NASA Astrophysics Data System (ADS)

    Pellegri, L.; Bracco, A.; Tsoneva, N.; Avigo, R.; Benzoni, G.; Blasi, N.; Bottoni, S.; Camera, F.; Ceruti, S.; Crespi, F. C. L.; Giaz, A.; Leoni, S.; Lenske, H.; Million, B.; Morales, A. I.; Nicolini, R.; Wieland, O.; Bazzacco, D.; Bednarczyk, P.; Birkenbach, B.; Ciemała, M.; de Angelis, G.; Farnea, E.; Gadea, A.; Görgen, A.; Gottardo, A.; Grebosz, J.; Isocrate, R.; Kmiecik, M.; Krzysiek, M.; Lunardi, S.; Maj, A.; Mazurek, K.; Mengoni, D.; Michelagnoli, C.; Napoli, D. R.; Recchia, F.; Siebeck, B.; Siem, S.; Ur, C.; Valiente-Dobón, J. J.

    2015-07-01

    A multitude of discrete 2+ states in 124Sn with energy up to 5 MeV were populated and identified with the (17O, 17O'γ) reaction at 340 MeV. Cross sections were compared with distorted wave Born approximation predictions and in general a good agreement was found. The measured energy and intensity distributions of the 2+ states are very similar to the predictions based on self-consistent density functional theory and extended QRPA approach accounting for multiphonon degrees of freedom. This provides evidence of the excitation of the pygmy quadrupole resonance in skin nuclei.

  7. Oxygen isotope dynamics of atmospheric nitrate over the Antarctic plateau: First combined measurements of ozone and nitrate 17O-excess (Δ17O)

    NASA Astrophysics Data System (ADS)

    Vicars, William; Savarino, Joël; Erbland, Joseph; Preunkert, Susanne; Jourdain, Bruno; Frey, Markus; Gil, Jaime; Legrand, Michel

    2013-04-01

    Variations in the isotopic composition of atmospheric nitrate (NO3-) provide novel indicators for important processes in boundary layer chemistry, often acting as source markers for reactive nitrogen (NOx = NO + NO2) and providing both qualitative and quantitative constraints on the pathways that determine its fate. Stable isotope ratios of nitrate (δ15N, δ17O, δ18O) offer direct insight into the nature and magnitude of the fluxes associated with different processes, thus providing unique information regarding phenomena that are often difficult to quantify from concentration measurements alone. The unique and distinctive 17O-excess (Δ17O = δ17O - 0.52 × δ18O ) of ozone (O3), which is transferred to NOx via oxidation reactions in the atmosphere, has been found to be a particularly useful isotopic fingerprint in studies of NOx transformations. Constraining the propagation of 17O-excess within the NOx cycle is critical in polar areas where there exists the possibility of extending atmospheric interpretations to the glacial/interglacial time scale using deep ice core records of nitrate. Here we present measurements of the comprehensive isotopic composition of atmospheric nitrate collected at Dome C, Antarctica during December 2011 to January 2012. Sampling was conducted within the framework of the OPALE (Oxidant Production over Antarctic Land and its Export) project, thus providing an opportunity to combine our isotopic observations with a wealth of meteorological and chemical data, including in-situ concentration measurements of the gas-phase precursors involved in nitrate production (NOx, O3, OH, HO2, etc.). Furthermore, nitrate isotope analysis has been combined in this study for the first time with parallel observations of the transferrable Δ17O of surface ozone, which was measured concurrently at Dome C using our recently developed analytical approach. This unique dataset has allowed for a direct comparison of observed Δ17O(NO3-) values to those that are

  8. Measurement of the 17 O(p,γ)18F reaction rate at astrophysically relevant energies

    NASA Astrophysics Data System (ADS)

    Hager, U.; Buchmann, L.; Davids, B.; Fallis, J.; Fulton, B. R.; Galinski, N.; Greife, U.; Hutcheon, D. A.; Ottewell, D.; Rojas, A.; Ruiz, C.; Setoodehnia, K.

    2012-03-01

    The 17O(p,γ)18F reaction plays an important role in hydrogen-burning nucleosynthesis. Conflicting values for the low-energy behavior of its cross section exist in the literature. We present direct measurements of the astrophysical S factor of the 17O(p,γ)18F reaction at center-of-mass energies between 250 and 500 keV. These measurements were conducted in inverse kinematics at the DRAGON recoil separator.

  9. Analyzing drivers of variability in the Δ17O of nitrate in the northwestern United States

    NASA Astrophysics Data System (ADS)

    Anderson, S. M.; Chung, S. H.; Welker, J. M.; Harlow, B.; Evans, R. D.

    2015-12-01

    The Δ17O of nitrate (NO3-) has beens used to track atmospheric inputs to ecosystems with biological sources near 0‰ and atmospheric sources from 20 to 40‰. The elevated Δ17O of atmospheric NO3- is due to oxidation with ozone. We analyzed the isotope composition of NO3- in weekly precipitation samples from 8 NADP/USNIP sites in the northwestern US between 1997-2004. Each site exhibits annual variation with lowest Δ17O during summer and highest Δ17O during winter. WA24 and WA19 exhibited the greatest (14.0‰) and least (8.9‰) annual variation, respectively. This significant and variable amount of seasonal change motivated analyzing drivers of this variability. Potential factors that influence Δ17O were evaluated with linear regression. Meteorological variables were tested which may account for inter-week variation. Measures of fire activity were included for effects on atmospheric oxidation. Lastly, NADP ion concentrations were used as potential indicators of marine influence which could introduce halogen chemistry and alter oxidation. Temperature was the only variable to significantly correlate with Δ17O at all sites (P<0.0001 at ID11 to P=0.05 at WA98). Fire activity (number of fires, area burned) significantly correlated with Δ17O at 4 of 8 sites (p<0.05) and suggested potential influence at 3 additional sites (0.1> P >0.05). No potential indicators of marine influence showed a relationship with Δ17O at coastal sites (WA19 and WA98), but there was a significant relationship between concentrations of Na and Cl with Δ17O at UT01 site which is influenced by the Great Salt Lake. Overall, temperature and fire activity best explain variability in the Δ17O of NO3- in the northwestern US. Understanding this variability is crucial to correctly attribute NO3- sources in ecological studies between biological and atmospheric inputs in mixing models. Incorrect accounting of variability leads to unnecessary error and incorrect identification of NO3- sources in

  10. Novel use of chemical shift in NMR as molecular descriptor: a first report on modeling carbonic anhydrase inhibitory activity and related parameters.

    PubMed

    Khadikar, Padmakar V; Sharma, Vimukta; Karmarkar, Sneha; Supuran, Claudiu T

    2005-02-15

    A novel use of NMR chemical shift of the SO(2)NH(2) protons (in dioxane as solvent) as a molecular descriptor is described for modeling the inhibition constant for benzene sulfonamides against the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1). The methodology is extended to model diuretic activity and lipophilicity of benzene sulfonamide derivatives. The regression analysis of the data has shown that the NMR chemical shift is incapable of modeling lipophilicity. However, it is quite useful for modeling the diuretic activity of these derivatives. The results are compared with those obtained using distance-based topological indices: Wiener (W)-, Szeged (Sz)-, and PI (Padmakar-Ivan) indices.

  11. A density functional study of (17)O, (14)N and (2)H electric field gradient tensors in the real crystalline structure of alpha-glycine.

    PubMed

    Behzadi, Hadi; Hadipour, Nasser L; Mirzaei, Mahmoud

    2007-01-01

    A density functional theory (DFT) study was carried out to calculate (17)O, (14)N and (2)H electric field gradient (EFG) tensors in accurate neutron diffraction structures of alpha-glycine at 288 and 427 K. B3LYP is the used method and 6-311+G(*) and 6-311++G(**) are the basis sets in the calculations of EFG tensors at the sites of (17)O, (14)N and (2)H nuclei in the monomer and the octameric cluster of alpha-glycine at two temperatures. Quadrupole coupling constants and asymmetry parameters are the converted parameters of calculated EFG tensors to experimentally measurable ones. The calculated results of monomer and the target molecule in octameric cluster reveal that hydrogen-bonding interactions play an important role in the crystalline structure of alpha-glycine where the results of the target molecule in octameric cluster are in good agreement with the experiments.

  12. Interference effects between /sup 17/O states populated in the /sup 13/C(/sup 6/Li,d)/sup 17/O*. --> cap alpha. +/sup 13/C reaction

    SciTech Connect

    Cardella, G.; Cunsolo, A.; Foti, A.; Imme, G.; Pappalardo, G.; Raciti, G.; Rizzo, F.; Alamanos, N.; Berthier, B.; Saunier, N.

    1987-12-01

    An analysis of the /sup 13/C(/sup 6/Li,d..cap alpha..)/sup 13/C reaction in the collinear (theta/sub d/ = 0/sup 0/) and noncollinear (theta/sub d/ = 10/sup 0/,8/sup 0/) geometry is made for two peaks observed in the deuteron energy spectrum and corresponding to excitation energies of 16.1 and 13.6 MeV in the /sup 17/O nucleus. It is shown that the reaction proceeds via a direct alpha-transfer process which populates doublets of interfering /sup 17/O levels. Spins, weights, and parities of these levels are obtained by means of a least square procedure.

  13. Solution oxygen-17 NMR application for observing a peroxidized cysteine residue in oxidized human SOD1

    NASA Astrophysics Data System (ADS)

    Fujiwara, Noriko; Yoshihara, Daisaku; Sakiyama, Haruhiko; Eguchi, Hironobu; Suzuki, Keiichiro

    2016-12-01

    NMR active nuclei, 1H, 13C and 15N, are usually used for determination of protein structure. However, solution 17O-NMR application to proteins is extremely limited although oxygen is an essential element in biomolecules. Proteins are oxidized through cysteine residues by two types of oxidation. One is reversible oxidation such as disulphide bonding (Cys-S-S-Cys) and the other is irreversible oxidation to cysteine sulfinic acid (Cys-SO 2H) and cysteine sulfonic acid (Cys-SO 3H). Copper,Zinc-superoxide dismutase (SOD1) is a key enzyme in the protection of cells from the superoxide anion radical. The SH group at Cys 111 residue in human SOD1 is selectively oxidized to -SO 2H and -SO 3H with atmospheric oxygen, and this oxidized human SOD1 is also suggested to play an important role in the pathophysiology of various neurodegenerative diseases, probably mainly via protein aggregation. Therefore, information on the structural and the dynamics of the oxidized cysteine residue would be crucial for the understanding of protein aggregation mechanism. Although the -SO 3H group on proteins cannot be directly detected by conventional NMR techniques, we successfully performed the site-specific 17O-labeling of Cys 111 in SOD1 using ^{17}it {O}2 gas and the 17O-NMR analysis for the first time. We observed clear 17O signal derived from a protein molecule and show that 17O-NMR is a sensitive probe for studying the structure and dynamics of the 17O-labeled protein molecule. This novel and unique strategy can have great impact on many research fields in biology and chemistry.

  14. Synthesis and characterization of novel Wells-Dawson-type mono vanadium(V)-substituted tungsto-polyoxometalate isomers: 1- and 4-[S2VW17O62](5-).

    PubMed

    Ueda, Tadaharu; Ohnishi, Miho; Shiro, Motoo; Nambu, Jun-ichi; Yonemura, Toshiaki; Boas, John F; Bond, Alan M

    2014-05-19

    Two vanadium(V)-substituted tungsto-polyoxometalate isomers, 1- and 4-[S2VW17O62](5-), were prepared as their tetra-alkyl ammonium salts from a W(VI)-H2SO4-V(V) reaction mixture in aqueous CH3CN solution. X-ray crystallographic structural analysis revealed that both isomers have a Wells-Dawson-type structure with a higher occupancy of vanadium at polar sites and belt sites for 1- and 4-[S2VW17O62](5-), respectively. The isomers were also characterized by elemental analysis, infrared, Raman, UV-vis, and (51)V NMR spectroscopies as well as voltammetry, and the data obtained were compared with that derived from [S2W18O62](4-). Significantly, the reversible potentials for the vanadium(V/IV) couple for both 1- and 4-[S2VW17O62](5-) in CH3CN (0.1 M n-Bu4NPF6) are considerably more positive than the tungstate reduction process exhibited by the [S2W18O62](4-) framework, implying that the presence of vanadium should be useful in catalytic reactions. The one-electron-reduced [S2V(IV)W17O62](6-) forms of both isomers were prepared in solution by controlled potential bulk electrolysis and characterized by voltammetry and EPR spectroscopy.

  15. Elastic scattering of 17O ions from 58Ni at near-barrier energies

    NASA Astrophysics Data System (ADS)

    Torresi, D.; Strano, E.; Mazzocco, M.; Boiano, A.; Boiano, C.; Di Meo, P.; Guglielmetti, A.; La Commara, M.; Manea, C.; Nicoletto, M.; Parascandolo, C.; Parascandolo, L.; Pierroutsakou, D.; Sandoli, M.; Signorini, C.; Soramel, F.; Toniolo, N.; Grebosz, J.; Filipescu, D.; Gheorghe, A.; Glodariu, T.; Stroe, L.; Miyatake, H.; Watanabe, Y.; Jeong, S.; Kim, Y. H.; Pakou, A.; Sgouros, O.; Soukeras, V.; Zerva, K.

    2014-03-01

    Elastic scattering has been studied for the collisions induced by 17O on 58Ni target at energies around and above the Coulomb barrier. The elastic scattering angular distributions were measured for several energies and were analyzed within the framework of the optical model to obtain total reaction cross sections. The reaction cross-sections of the tightly bound 17O were compared with those of weakly bound 17F on the same targets in order to investigate the effects of the low binding energy in the reaction dynamics.

  16. High resolution δ17O-δ18O as a single mineral thermometer

    NASA Astrophysics Data System (ADS)

    Sharp, Z. D.; Sengupta, S.; Pack, A.

    2014-12-01

    The equilibrium relationship α17O/16Oa-b = (α18O/16Oa-b)θ makes the analysis of δ17O redundant for most terrestrial applications. However the θ term varies with temperature, so that ultra-high precision δ17O data provide additional information not available from δ18O alone. If the δ18O and δ17O values of formation water covary in a known way (e.g., meteoric water, ocean water), then a unique solution for both temperature and the δ18O of the formation fluids can be obtained from the combined δ18O-δ17O mineral values. The paired δ18O-δ17O values are in essence a single mineral thermometer. Unlike clumped isotopes or combined δ18O-δD data, the δ18O and δ17O values of a mineral have identical 'diagenetic potential', and will only be altered with a high F/R ratio. We have made an empirical determination of the temperature dependence on θ = -710/T2 + 0.5305 using Pleistocene diatom data from ODP Leg 177, Site 1093 (δ18O = 39.610, δ17O = 20.536‰), which is almost identical to Pack and Herwartz (EPSL, 2014). Application to ancient cherts gives the following results: The δ18O-δ17O values of cherts vary systematically with age, from Archean to Proterozoic to Phanerozoic. The Archean cherts are incompatible with modern seawater under any temperature conditions. Instead they have equilibrated with water of δ18O= -10±3 (‰ vs SMOW) at 50 to 70°C. These data support a lighter ocean in the Archean by ~5‰. Proterozoic cherts equilibrated at 35-50°C with meteoric water of -8±3‰ and Phanerozoic cherts equilibrated with mixed meteoric water/ocean water at similar temperatures and higher δ18O values (-3±3‰). The δ18O values of lacustrine diatoms from the Valles Caldera, NM, vary by over 20‰ between glacial and interglacial times. The combined δ18O-δ17O values of interglacial diatoms give T= ~12°C, δ18Ometeoric water = -9‰. A glacial age diatom sample gives T=<10°C, δ18Ometeoric water = -20‰. These data could not be obtained from the

  17. Mechanical Ventilator for Delivery of 17O2 in Brief Pulses

    PubMed Central

    Baumgardner, J.E; Mellon, E.A; Tailor, D.R; Mallikarjunarao, K; Borthakur, A; Reddy, R

    2008-01-01

    The 17O nucleus has been used recently by several groups for magnetic resonance (MR) imaging of cerebral metabolism. Inhalational delivery of 17O2 in very brief pulses could, in theory, have significant advantages for determination of the cerebral metabolic rate for oxygen (CMRO2) with MR imaging. Mechanical ventilators, however, are not typically capable of creating step changes in gas concentration at the airway. We designed a ventilator for large animal and human studies that provides mechanical ventilation to a subject inside an MR scanner through 25 feet of small-bore connecting tubing, and tested its capabilities using helium as a surrogate for 17O2. After switching the source gas from oxygen to helium, the 0-90% response time for helium concentration changes at the airway was 2.4 seconds. The capability for creating rapid step changes in gas concentration at the airway in large animal and human studies should facilitate the experimental testing of the delivery 17O2 in brief pulses, and its potential use in imaging CMRO2. PMID:19662118

  18. Anomalous 17O compositions in massive sulphate deposits on the Earth

    PubMed

    Bao, H; Thiemens, M H; Farquhar, J; Campbell, D A; Lee, C C; Heine, K; Loope, D B

    2000-07-13

    The variation of delta 18O that results from nearly all physical, biological and chemical processes on the Earth is approximately twice as large as the variation of delta 17O. This so-called 'mass-dependent' fractionation is well documented in terrestrial minerals. Evidence for 'mass-independent' fractionation (delta 17O = delta 17O-0.52 delta 18O), where deviation from this tight relationship occurs, has so far been found only in meteoritic material and a few terrestrial atmospheric substances. In the rock record it is thought that oxygen isotopes have followed a mass-dependent relationship for at least the past 3.7 billion years, and no exception to this has been encountered for terrestrial solids. Here, however, we report oxygen-isotope values of two massive sulphate mineral deposits, which formed in surface environments on the Earth but show large isotopic anomalies (delta 17O up to 4.6%). These massive sulphate deposits are gypcretes from the central Namib Desert and the sulphate-bearing Miocene volcanic ash-beds in North America. The source of this isotope anomaly might be related to sulphur oxidation reactions in the atmosphere and therefore enable tracing of such oxidation. These findings also support the possibility of a chemical origin of variable isotope anomalies on other planets, such as Mars.

  19. Hunting for hydrogen: random structure searching and prediction of NMR parameters of hydrous wadsleyite† †Electronic supplementary information (ESI) available: Further information on the structures generated by AIRSS, alternative structural models, supercell calculations, total enthalpies of all computed structures and further information on 1H/2H NMR parameters. Example input and all raw output files from AIRSS and CASTEP NMR calculations are also included. See DOI: 10.1039/c6cp01529h Click here for additional data file.

    PubMed Central

    Moran, Robert F.; McKay, David; Pickard, Chris J.; Berry, Andrew J.; Griffin, John M.

    2016-01-01

    The structural chemistry of materials containing low levels of nonstoichiometric hydrogen is difficult to determine, and producing structural models is challenging where hydrogen has no fixed crystallographic site. Here we demonstrate a computational approach employing ab initio random structure searching (AIRSS) to generate a series of candidate structures for hydrous wadsleyite (β-Mg2SiO4 with 1.6 wt% H2O), a high-pressure mineral proposed as a repository for water in the Earth's transition zone. Aligning with previous experimental work, we solely consider models with Mg3 (over Mg1, Mg2 or Si) vacancies. We adapt the AIRSS method by starting with anhydrous wadsleyite, removing a single Mg2+ and randomly placing two H+ in a unit cell model, generating 819 candidate structures. 103 geometries were then subjected to more accurate optimisation under periodic DFT. Using this approach, we find the most favourable hydration mechanism involves protonation of two O1 sites around the Mg3 vacancy. The formation of silanol groups on O3 or O4 sites (with loss of stable O1–H hydroxyls) coincides with an increase in total enthalpy. Importantly, the approach we employ allows observables such as NMR parameters to be computed for each structure. We consider hydrous wadsleyite (∼1.6 wt%) to be dominated by protonated O1 sites, with O3/O4–H silanol groups present as defects, a model that maps well onto experimental studies at higher levels of hydration (J. M. Griffin et al., Chem. Sci., 2013, 4, 1523). The AIRSS approach adopted herein provides the crucial link between atomic-scale structure and experimental studies. PMID:27020937

  20. Practice and applications of 17-O-excess measurements of water using novel laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Dennis, K. J.; Steig, E. J.; Vasileios, G.; Schauer, A. J.; Schoenemann, S. W.; Hoffnagle, J.

    2014-12-01

    17O-excess, defined as the deviation from the Global Meteoric Water Line (GMWL) in a plot of ln(δ18O+1) vs. ln(δ17O+1), is an evolving tool for understanding the modern water cycle and reconstructing past climate regimes. Because of competing effects between equilibrium and kinetic fractionation small variations in 17O-excess can be used, for example, to (i) infer changes in temperature and sea ice across glacial-interglacial cycles in Antarctica (Schoenemann et al., 2014), (ii) study the role of rain re-evaporation during convective events thereby improving the incorporation of isotopes into GCMs (Landais et al., 2010), and (iii) assess the role of stratospheric water vapor intrusions at high altitudes or in polar regions (Winkler et al., 2013). In natural waters, variability in 17O-excess is very small (on the order of tens of per meg, where 1 per meg is 0.001‰). Until recently, only measurements made via Isotope Ratio Mass Spectrometry (IRMS) could achieve the required precision, following time-consuming front-end chemistry that converted H2O into O2 for analysis of m/z+ 32, 33 and 34. Recent improvements in laser-based spectroscopy, e.g., Cavity Ring-Down Spectroscopy (CRDS), are enabling quicker and easier measurement of 17O-excess in water (Steig et al., 2013; 2014). The Picarro L2140-i is certified with a precision of ≤ 0.015‰; however implementation of best practices can result in an achievable precision of ≤ 0.008‰, thereby demonstrating comparable performance to IRMS. We will review our recommendations for achieving high-precision measurements of 17O-excess on the Picarro L2140-i, including how to calibrate the system, the frequency of standards analysis, the number of replicate injections and vials required, and approaches to dealing with sample-to-sample memory. We will also compare the external accuracy achieved by three distinct Picarro L2140-i analyzers for multiple waters with distinct isotopic composition.

  1. Controls on the Nitrogen and Oxygen Isotopic Composition (δ 15N, δ 18O, δ 17O) of Atmospheric Nitrate in Princeton, NJ

    NASA Astrophysics Data System (ADS)

    Hastings, M. G.; Malcolm, E.; Kaiser, J.; Sigman, D. M.

    2004-12-01

    .7 to 30.8‰ ), as a result of the interaction of NOx and ozone in the atmosphere prior to HNO3 deposition. Comparison of δ 17O and δ 18O of nitrate show the data falling along a mixing line between the oxygen isotopic composition of tropospheric ozone and that of hydroxy/peroxy radicals (i.e. water), which has also been observed in nitrate aerosol samples collected in La Jolla, CA [Michalski et al., 2003]. Although there is considerable scatter in the isotopic time series, a distinctive increase in the oxygen isotope ratios occurs in mid-September and continues through the end of December 2003. This aspect of the time series will be discussed in the context of changes in atmospheric chemistry based on seasonal variations in atmospheric transport patterns, meteorology, and NOx and ozone concentrations. In addition to these parameters, the nitrogen isotopic variations will also be interpreted in the context of changes in source contributions, e.g. coal burning in the Midwest, based on multiple chemical analyses including trace metals, mercury, and major ion concentrations.

  2. Simulating the budget and distribution of Δ17O in CO2 with a global atmosphere-biosphere model

    NASA Astrophysics Data System (ADS)

    Peters, Wouter; Schneider, Linda; Hofmann, Magdalena E. G.; van der Velde, Ivar; Röckmann, Thomas

    2015-04-01

    The isotope ratios of 16O, 17O and 18O in CO2 are referred to as the triple-oxygen isotope composition of CO2, and have long held promise to better understand terrestrial carbon cycling. However, measurement precision as well as an incomplete understanding of fractionation during equilibrium exchange and diffusion of CO2 have been a challenge, especially for the estimation of gross primary production (GPP) and respiration from measured δ17O and δ18O isotope ratios in CO2. The excess-17O in CO2 (Δ17O), defined as the deviation of the δ17O and δ18O ratios from an expected mass-dependent fractionation line, is in principle easier to interpret as many processes that simultaneously affect δ17O and δ18O are not reflected in Δ17O. Two global box model simulations suggest that atmospheric Δ17O is therefore mostly determined by transport of relatively δ17O enriched CO2 from the stratosphere, and its equilibration in leaf-water back to an excess of close to zero, following diffusion as part of photosynthetic CO2 uptake by vegetation. This makes Δ17O an interesting tracer for photosynthesis at the global scale, and the first decadal time series have recently been published that indeed suggest strong GPP-driven variations in atmospheric Δ17O. In this study, we expand the modeling of Δ17O beyond the current two global box model results published by explicitly simulating the global atmospheric Δ17O distribution over a five year period. We specifically are interested whether regional gradients in Δ17O in areas with large GPP such as Amazonia leave an imprint on Δ17O that can be measured with the rapidly improving measurement precision (10-40 permeg currently). Therefore, we used the SIBCASA biosphere model at 1x1 degrees globally to simulate hourly fluxes of Δ17O into and out of C3 and C4 vegetation as well as soils. These fluxes were then fed into the TM5 atmospheric transport model at 6x4 degrees horizontal resolution to simulate the hourly spatial gradients in

  3. Pygmy dipole resonance in 124Sn populated by inelastic scattering of 17O

    NASA Astrophysics Data System (ADS)

    Pellegri, L.; Bracco, A.; Crespi, F. C. L.; Leoni, S.; Camera, F.; Lanza, E. G.; Kmiecik, M.; Maj, A.; Avigo, R.; Benzoni, G.; Blasi, N.; Boiano, C.; Bottoni, S.; Brambilla, S.; Ceruti, S.; Giaz, A.; Million, B.; Morales, A. I.; Nicolini, R.; Vandone, V.; Wieland, O.; Bazzacco, D.; Bednarczyk, P.; Bellato, M.; Birkenbach, B.; Bortolato, D.; Cederwall, B.; Charles, L.; Ciemala, M.; De Angelis, G.; Désesquelles, P.; Eberth, J.; Farnea, E.; Gadea, A.; Gernhäuser, R.; Görgen, A.; Gottardo, A.; Grebosz, J.; Hess, H.; Isocrate, R.; Jolie, J.; Judson, D.; Jungclaus, A.; Karkour, N.; Krzysiek, M.; Litvinova, E.; Lunardi, S.; Mazurek, K.; Mengoni, D.; Michelagnoli, C.; Menegazzo, R.; Molini, P.; Napoli, D. R.; Pullia, A.; Quintana, B.; Recchia, F.; Reiter, P.; Salsac, M. D.; Siebeck, B.; Siem, S.; Simpson, J.; Söderström, P.-A.; Stezowski, O.; Theisen, Ch.; Ur, C.; Valiente Dobon, J. J.; Zieblinski, M.

    2014-11-01

    The γ decay from the high-lying states of 124Sn was measured using the inelastic scattering of 17O at 340 MeV. The emitted γ rays were detected with high resolution with the AGATA demonstrator array and the scattered ions were detected in two segmented ΔE- E silicon telescopes. The angular distribution was measured both for the γ rays and the scattered 17O ions. An accumulation of E1 strength below the particle threshold was found and compared with previous data obtained with (γ ,γ‧) and (α ,α‧ γ) reactions. The present results of elastic scattering, and excitation of E2 and E1 states were analysed using the DWBA approach. From this comprehensive description the isoscalar component of the 1- excited states was extracted. The obtained values are based on the comparison of the data with DWBA calculations including a form factor deduced using a microscopic transition density.

  4. 17O+58Ni scattering and reaction dynamics around the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Strano, E.; Torresi, D.; Mazzocco, M.; Keeley, N.; Boiano, A.; Boiano, C.; Di Meo, P.; Guglielmetti, A.; La Commara, M.; Molini, P.; Manea, C.; Parascandolo, C.; Pierroutsakou, D.; Signorini, C.; Soramel, F.; Filipescu, D.; Gheorghe, A.; Glodariu, T.; Grebosz, J.; Jeong, S.; Kim, Y. H.; Lay, J. A.; Miyatake, H.; Nicoletto, M.; Pakou, A.; Rusek, K.; Sgouros, O.; Soukeras, V.; Stroe, L.; Toniolo, N.; Vitturi, A.; Watanabe, Y.; Zerva, K.

    2016-08-01

    This work aims at investigating the projectile binding energy influence on the reaction dynamics, introducing new results and new data analysis methods in order to overcome some typically encountered problems, such as the identification of reaction products differing by few mass units and the discrimination of direct reaction processes. The 17O+58Ni collision was studied at five near-barrier energies employing a compact experimental setup consisting of four double-sided silicon strip detectors (DSSSDs). Different reaction processes, namely the elastic and inelastic scattering and the 1 n stripping, were discriminated by means of a detailed analysis of the experimental energy spectra based on Monte Carlo simulations. The elastic scattering angular distributions were investigated within the framework of the optical model using Woods-Saxon and double-folding potentials. The total reaction cross sections were extracted and the reduced cross sections compared with those obtained for 17F (Sp=0.600 MeV), the mirror nucleus of 17O (Sn=4.143 MeV), and for the tightly bound 16O projectile. The 17O+58Ni total reaction cross sections were larger than those for 16O on the same target at the lowest energies studied, becoming identical, within errors, as the incident energy increased above the Coulomb barrier. This behavior was related to a strong contribution from the 1 n -stripping channel at the lowest energies.

  5. Study of the soft dipole modes in 140Ce via inelastic scattering of 17O

    NASA Astrophysics Data System (ADS)

    Krzysiek, M.; Kmiecik, M.; Maj, A.; Bednarczyk, P.; Ciemała, M.; Fornal, B.; Grȩbosz, J.; Mazurek, K.; Mȩczyński, W.; Ziȩbliński, M.; Crespi, F. C. L.; Bracco, A.; Benzoni, G.; Blasi, N.; Boiano, C.; Bottoni, S.; Brambilla, S.; Camera, F.; Giaz, A.; Leoni, S.; Million, B.; Morales, A. I.; Nicolini, R.; Pellegri, L.; Riboldi, S.; Vandone, V.; Wieland, O.; De Angelis, G.; Napoli, D. R.; Valiente-Dobon, J. J.; Bazzacco, D.; Farnea, E.; Gottardo, A.; Lenzi, S.; Lunardi, S.; Mengoni, D.; Michelagnoli, C.; Recchia, F.; Ur, C.; Gadea, A.; Huyuk, T.; Barrientos, D.; Birkenbach, B.; Geibel, K.; Hess, H.; Reiter, P.; Steinbach, T.; Wiens, A.; Bürger, A.; Görgen, A.; Guttormsen, M.; Larsen, A. C.; Siem, S.

    2014-05-01

    The main aim of this study was a deeper understanding of the nuclear structure properties of the soft dipole modes in 140Ce, excited via inelastic scattering of weakly bound 17O projectiles. An important aim was to investigate the ‘splitting’ of the PDR into two parts: a low-energy isoscalar component dominated by neutron-skin oscillations and a higher-energy component lying on the tail of the giant dipole resonance of a rather isovector character. This was already observed for this nucleus, investigated in (α, α‧) and (γ, γ‧) experiments. The experiment was performed at Laboratori Nazionali di Legnaro, Italy. Inelastic scattering of 17O ion beam at 20 MeV A-1 was used to excite the resonance modes in the 140Ce target. Gamma-rays were registered by five triple clusters of AGATA-Demonstrator and nine large volume scintillators (LaBr3). The scattered 17O ions were identified by two ΔE - E Si telescopes of the TRACE array mounted inside the scattering chamber. The telescopes consisted of two segmented Si-pad detectors, each of 60 pixels. Very preliminary data have shown a strong domination of the E1 transitions in the ‘pygmy’ region with a character more similar to the one obtained in alpha scattering experiment.

  6. Kinetic 17O effects in the hydrologic cycle: Indirect evidence and implications

    SciTech Connect

    Angert, Alon; Cappa, Christopher D.; DePaolo, Donald J.

    2004-11-22

    The abundances of 18O and deuterium in the present and past hydrologic cycle have proven to be an important tool in Earth systems science. In contrast, the abundance of 17O in precipitation has thus far been assumed to carry no additional information to that of 18O. Here, we demonstrate, using known constraints on oxygen isotope abundances from the O2 cycle and existing data about the natural abundance of 17O in water, that the relationship between the discrimination against 17O and 18O in water may vary. This relationship, presented here as q = ln (17a)/ln (18a), is found to be 0.511 +- 0.005 for kinetic transport effects and 0.526 +- 0.001 for equilibrium effects, with very low temperature sensitivity. As a result, the 17D of precipitation is controlled primarily by kinetic effects during evaporation of the initial vapor and, in contrast to the deuterium excess, is independent of the temperature at the evaporation (and condensation) site. This makes 17D a unique tracer that complements 18O and deuterium, and may allow for a decoupling of changes in the temperature of the ocean, that serves as the vapor source, from changes in the relative humidity above it. In addition, the 17D of ice caps is influenced by the kinetic effects in ice formation, and therefore measurement of ice 17D can be used as an additional constraint for better understanding and parameterization of these effects.

  7. NMR Studies of Peroxidases.

    NASA Astrophysics Data System (ADS)

    Veitch, Nigel Charles

    Available from UMI in association with The British Library. Requires signed TDF. Peroxidases are a haem-containing group of enzymes with a wide diversity of function within biological systems. While a common characteristic is the ability to catalyse the conversion of hydrogen peroxide to water, it is the accompanying processes of hormone synthesis and degradation which have generated such a high level of interest. However, information at the molecular level is limited to a single well-resolved crystal structure, that of yeast cytochrome c peroxidase. This thesis presents a strategy for the investigation of peroxidase structure and function based on proton nuclear magnetic resonance spectroscopy, a technique which has the ability to address aspects of both protein structure and protein dynamics in solution. The application of one- and two-dimensional NMR techniques has been developed in the context of plant peroxidases, notably the isoenzyme HRP-C derived from the horseradish root. Characterisation of the proton NMR spectra of HRP -C in resting and ligated states provided new information enabling the structure of the binding site for aromatic donor molecules, such as indole-3-propionic, ferulic and benzhydroxamic acids, to be resolved. In order to overcome difficulties encountered with a protein of the complexity of peroxidase, additional information was obtained from chemical shift parameters and the use of peroxidase variants produced by site-directed mutagenesis. A comparative study using NMR spectroscopy was undertaken for wild-type recombinant HRP-C expressed in Escherichia coli, and two protein variants with substitutions made to residues located on the distal side of the haem pocket, Phe41 to Val and Arg38 to Lys. NMR analyses of a plant peroxidase from barley grains and the fungal peroxidase from Coprinus cinereus were also successful using methods conceived with HRP-C. Examination of three specifically constructed recombinant protein variants of C. cinereus

  8. Laser Fluorination of Meteorites--Small Sample Analysis of delta17O and delta18O

    NASA Astrophysics Data System (ADS)

    Franchi, I. A.; Akagi, T.; Pillinger, C. T.

    1992-07-01

    The importance of oxygen isotope analysis in the field of meteoritics has been firmly established over the past 15 to 20 years, almost exclusively by Clayton and co-workers at the University of Chicago. The ability of the now classical oxygen three isotope plot to distinguish between fractionation and mixing processes has meant that such analyses are particularly powerful in helping to establish the generic relationships between different classes of meteorites. Conventionally, oxygen gas is usually extracted from the samples in nickel, or similar, reaction bombs at temperatures up to 700 degrees C in the presence of a powerful oxidizing reagent. Due to the nature of these experiments relatively large samples are required (35 mg or more) and the maximum temperatures used make analyses of more refractory minerals difficult if not dangerous. In the past two years a number of laboratories have been developing laser fluorination techniques. Such a technique greatly helps to reduce the blank, allow higher reaction temperatures, and speed up the reaction times, resulting in smaller sample size requirements, and potentially in situ analysis. However, to date this has only been applied to delta^18O analyses where the oxygen is analysed as CO2. We report here the development of a laser fluorination technique capable of running small samples for delta^17O and delta^18O using oxygen gas. The laser used is a 25W CO2 laser (10.6 micrometer radiation) and the reagent is ClF3. The sample size requirements are currently 0.5 to 1.0 mg. Replicate analyses of NBS-28 quartz has yielded precision on delta^18O and delta^17O of +-0.15 and +-0.17o/oo respectively and with other terrestrial samples define the expected fractionation line. The results of the first application of this technique to meteorite samples are shown in the figures. The LL6 Appley Bridge has been analyzed four times (Fig. 1a) giving mean values for delta^17O and delta^18O of +3.94o/oo (+-0.14) and +4.99o/oo (+-0

  9. Solid-state NMR of inorganic semiconductors.

    PubMed

    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.

  10. Fourier-transform spectroscopy of 13C17O and deperturbation analysis of the A1Π (υ=0-3) levels

    NASA Astrophysics Data System (ADS)

    Hakalla, R.; Niu, M. L.; Field, R. W.; Heays, A. N.; Salumbides, E. J.; Stark, G.; Lyons, J. R.; Eidelsberg, M.; Lemaire, J. L.; Federman, S. R.; de Oliveira, N.; Ubachs, W.

    2017-03-01

    The high-resolution B1Σ+→A1Π (0, 0) and (0, 3) emission bands of the less-abundant 13C17O isotopologue have been investigated by Fourier-transform spectroscopy in the visible region using a Bruker IFS 125HR spectrometer at an accuracy 0.003 cm-1. These spectra are combined with high-resolution photoabsorption measurements of the 13C17O B1Σ+←X1Σ+ (0, 0), B1Σ+←X1Σ+ (1, 0) and C1Σ+←X1Σ+ (0, 0) bands recorded with an accuracy of 0.01 cm-1 using the vacuum ultraviolet Fourier-transform spectrometer, installed on the DESIRS beamline at the SOLEIL synchrotron. In the studied 17,950-22,500 cm-1 and 86,800-92,100 cm-1 regions, 480 transitions have been measured. These new experimental data were combined with data from the C→A and B→A systems, previously analyzed in 13C17O. The frequencies of 1003 transitions derived from 12 bands were used to analyze the perturbations between the A1Π (υ=0-3) levels and rovibrational levels of the d3Δi, e3Σ-, a'3Σ+, I1Σ- and D1Δ states as well as to a preliminary investigation of weak irregularities that appear in the B1Σ+ (υ=0) level. Deperturbed molecular constants and term values of the A1Π state were obtained. The spin-orbit and L-uncoupling interaction parameters as well as isotopologue-independent spin-orbit and rotation-electronic perturbation parameters were derived.

  11. Vibrational spectra, NBO analysis, first order hyperpolarizabilities, thermodynamic functions and NMR chemical shielding anisotropy (CSA) parameters of 5-nitro-2-furoic acid by ab initio HF and DFT calculations.

    PubMed

    Balachandran, V; Rajeswari, S; Lalitha, S

    2013-09-01

    In this work, FT-IR and FT-Raman spectra are recorded on the solid phase of 5-nitro-2-furoic acid (abbreviated as NFA) in the regions 4000-400 cm(-1) and 3500-100 cm(-1) respectively. The geometrical parameters, vibrational assignments, HOMO-LUMO energies and NBO calculations are obtained for the monomer and dimer of NFA from HF and DFT (B3LYP) with 6-311++G (d, p) basis set calculations. Second order perturbation energies and electron density (ED) transfer from filled lone pairs of Lewis base to unfilled Lewis acid sites of NFA are discussed on the basis of NBO analysis. Intermolecular hydrogen bonds exist through COOH groups; give the evidence for the formation of dimer entities in the title molecule. The theoretically calculated harmonic frequencies are scaled by common scale factor. The observed and the calculated frequencies are found to be in good agreement. The thermodynamic functions were obtained for the range of temperature 100-1000 K. The polarizability, first hyperpolarizability, anisotropy polarizability invariant has been computed using quantum chemical calculations. The chemical parameters were calculated from the HOMO and LUMO values. The NMR chemical shielding anisotropy (CSA) parameters were also computed for the title molecule.

  12. Changes in Precipitation Sources over Glacial/Interglacial MIS 11 and 12 Examined by Δ17O of SiO2 Obtained from Diatoms along the Valles Caldera Lake Core, NM

    NASA Astrophysics Data System (ADS)

    Gibbons, J.; Sharp, Z. D.; Fawcett, P. J.

    2015-12-01

    Quantitative estimates of the isotopic composition of paleo-lake water have been made using 18O/16O (ẟ18O) in diatom silica (Dodd and Sharp, GCA, 2010). Post-mortem diatom silica equilibrates with ambient lake water within six months, chronicling the bulk oxygen isotope composition of the lake and resulting in silica that is near the quartz-water fractionation line (Dodd et al, GGG, 2012). The δ18O values of lacustrine diatoms from the Valles Caldera, NM, vary by ~25‰ between glacial and interglacial periods and suggest a collapse of the summer monsoon that currently provides 50% of the modern precipitation in NM. Triple oxygen isotope measurements of diatom silica may serve as a proxy for the isotopic composition of the lake water and as an estimate of paleo-humidity over the precipitation source. The deuterium excess parameter (d= ẟD - 8 ẟ18O) has been used along ice cores as a source relative humidity index, but is difficult to make in lake sediments. Instead, high precision 17O-excess (∆17O) measurements (=ẟ17O - 0.528 ẟ18O) may provide paleo-humidity information. Landais et al. (GRL, 2008) found a ∆17O difference of 0.02‰ in the Vostok ice core between glacial and interglacial times, interpreted as a function of changing relative humidity of the precipitation source. A 0.03‰ change was observed in glacial (∆17O=-0.22‰) and interglacial (∆17O=-0.19‰) diatom silica along the Valles Caldera lake core. Further information regarding the δ18O value of meteoric water can be calculated from paired δ18O-δ17O measurements. The combined δ18O-δ17O values of interglacial diatoms suggest a δ18Ometeoric water value of -9‰. Modern δ18O value of monsoonal precipitation in NM is ~-10‰. The δ18O of glacial diatoms suggest a δ18Ometeoric water = -20‰. Modern δ18O value of winter precipitation in NM is ~-20‰. These results suggest that the seasonality of precipitation in New Mexico can be inferred based on changes in the relative

  13. International Conference on Quantum Chemical Calculations of NMR and EPR Parameters Held in Castle Smolenice, Slovak Republic on September 14-18 1998

    DTIC Science & Technology

    1998-10-21

    Density functional calculations of ESR parameters in the zero order regular approximation for relativis- tic effects Erik van Lenthe, Paul E.S. Wormer...which facilitates structural studies of 4anhydrothymidines REFERENCES 1. V. G. Malkin, 0. L. Malkina, L. A. Erikson , and R. D. Salahub, In Density...1332 Fax: +46-13-132-285 FAX: +358-8-553-1287 vahtras@ifm.liu.se jvaara@sun3.oulu.fi Erik van Lenthe Veronique van Speybroeck Scheikundig Laboratorium

  14. Microscopic multiphonon method for odd nuclei and its application to 17O

    NASA Astrophysics Data System (ADS)

    De Gregorio, G.; Knapp, F.; Lo Iudice, N.; Vesely, P.

    2016-12-01

    An equations of motion phonon method is extended to odd nuclei. It generates an orthonormal basis out of an odd particle coupled to n -phonon core states (n =0 ,1 ,2 ,⋯ ), built of Tamm-Dancoff phonons, and formulates the eigenvalue problem in such a multiphonon particle-core space. 17O is chosen as testing ground. An intrinsic chiral Hamiltonian is adopted in a large configuration space to perform a calculation using a Hartree-Fock (HF) basis in a space encompassing up to two and, under simplifying assumptions, three phonons. The impact of the different phonon components on spectrum, moments, transitions, and dipole cross section is discussed.

  15. Distal and proximal ligand interactions in heme proteins: Correlations between C-O and Fe-C vibrational frequencies, oxygen-17 and carbon-13 nuclear magnetic resonance chemical shifts, and oxygen-17 nuclear quadrupole coupling constants in C sup 17 O- and sup 13 CO-labeled species

    SciTech Connect

    Ki Deok Park; Guo, K.; Adebodun, F.; Chiu, M.L.; Sligar, S.G.; Oldfield, E. )

    1991-03-05

    The authors have obtained the oxygen-17 nuclear magnetic resonance (NMR) spectra of a variety of C{sup 17}O-labeled heme proteins, including sperm whale (Physeter catodon) myoglobin, two synthetic sperm whale myoglobin mutants (His E7 {yields} Val E7; His E7 {yields} Phe E7), adult human hemoglobin, rabbit (Oryctolagus cuniculus) hemoglobin, horseradish (Cochlearia armoracia) peroxidase isoenzymes A and C, and Caldariomyces fumago chloroperoxidase, in some cases as a function of pH, and have determined their isotropic {sup 17}O NMR chemical shifts, {delta}{sub i}, and spin-lattice relaxation times, T{sub 1}. They have also obtained similar results on a picket fence prophyrin. The results show an excellent correlation between the infrared C-O vibrational frequencies, {nu}(C-O), and {delta}{sub i}, between {nu}(C-O) and the {sup 17}O nuclear quadrupole coupling constant, and as expected between e{sup 2}qQ/h and {delta}{sub i}. The results suggest the IR and NMR measurements reflect the same interaction, which is thought to be primarily the degree of {pi}-back-bonding from Fe d to CO {pi}* orbitals, as outlined previously.

  16. The rotational spectra of HD17O and D217O: Experiment and quantum-chemical calculations

    NASA Astrophysics Data System (ADS)

    Puzzarini, Cristina; Cazzoli, Gabriele; Gauss, Jürgen

    2012-10-01

    Guided by theoretical predictions, the rotational spectrum of HD17O was recorded and assigned for the first time, while the measurements for D217O were extended up to the THz region. For both isotopic species, a large portion of the rotational spectrum, from 65 GHz (from 200 GHz for the bideuterated isotopologue) up to 1.6 THz, was investigated, thus allowing the accurate determination of the ground-state rotational and centrifugal-distortion constants. Considering that the rotational spectra of water isotopologues are characterized by a very low density of lines and strong centrifugal-distortion effects, the accurate quantum-chemical prediction of the relevant spectroscopic parameters played a crucial role in the line search and assignment as well as in supporting the fitting procedure. In addition to rotational and centrifugal-distortion constants, the knowledge of the oxygen quadrupole-coupling constants was essential, as the corresponding interaction leads to characteristic features (hyperfine structure) that enabled proper line assignments.

  17. Solution NMR conformation of glycosaminoglycans.

    PubMed

    Pomin, Vitor H

    2014-04-01

    Nuclear magnetic resonance (NMR) spectroscopy has been giving a pivotal contribution to the progress of glycomics, mostly by elucidating the structural, dynamical, conformational and intermolecular binding aspects of carbohydrates. Particularly in the field of conformation, NOE resonances, scalar couplings, residual dipolar couplings, and chemical shift anisotropy offsets have been the principal NMR parameters utilized. Molecular dynamics calculations restrained by NMR-data input are usually employed in conjunction to generate glycosidic bond dihedral angles. Glycosaminoglycans (GAGs) are a special class of sulfated polysaccharides extensively studied worldwide. Besides regulating innumerous physiological processes, these glycans are also widely explored in the global market as either clinical or nutraceutical agents. The conformational aspects of GAGs are key regulators to the quality of interactions with the functional proteins involved in biological events. This report discusses the solution conformation of each GAG type analyzed by one or more of the above-mentioned methods.

  18. Using dual-bacterial denitrification to improve δ15N determinations of nitrates containing mass-independent 17O

    USGS Publications Warehouse

    Coplen, T.B.; Böhlke, J.K.; Casciotti, K.L.

    2004-01-01

    The bacterial denitrification method for isotopic analysis of nitrate using N2O generated from Pseudomonas aureofaciens may overestimate ??15N values by as much as 1-2??? for samples containing atmospheric nitrate because of mass-independent 17O variations in such samples. By analyzing such samples for ??15N and ??18O using the denitrifier Pseudomonas chlororaphis, one obtains nearly correct ??15N values because oxygen in N 2O generated by P. chlororaphis is primarily derived from H 2O. The difference between the apparent ??15N value determined with P. aureofaciens and that determined with P. chlororaphis, assuming mass-dependent oxygen isotopic fractionation, reflects the amount of mass-independent 17O in a nitrate sample. By interspersing nitrate isotopic reference materials having substantially different ?? 18O values with samples, one can normalize oxygen isotope ratios and determine the fractions of oxygen in N2O derived from the nitrate and from water with each denitrifier. This information can be used to improve ??15N values of nitrates having excess 17O. The same analyses also yield estimates of the magnitude of 17O excess in the nitrate (expressed as ??17O) that may be useful in some environmental studies. The 1-?? uncertainties of ??15N, ??18O and ??17O measurements are ??0.2, ??0.3 and ??5???, respectively. Copyright ?? 2004 John Wiley & Sons, Ltd.

  19. Revealing the climate of snowball Earth from Δ17O systematics of hydrothermal rocks.

    PubMed

    Herwartz, Daniel; Pack, Andreas; Krylov, Dmitri; Xiao, Yilin; Muehlenbachs, Karlis; Sengupta, Sukanya; Di Rocco, Tommaso

    2015-04-28

    The oxygen isotopic composition of hydrothermally altered rocks partly originates from the interacting fluid. We use the triple oxygen isotope composition ((17)O/(16)O, (18)O/(16)O) of Proterozoic rocks to reconstruct the (18)O/(16)O ratio of ancient meteoric waters. Some of these waters have originated from snowball Earth glaciers and thus give insight into the climate and hydrology of these critical intervals in Earth history. For a Paleoproterozoic [∼2.3-2.4 gigayears ago (Ga)] snowball Earth, δ(18)O = -43 ± 3‰ is estimated for pristine meteoric waters that precipitated at low paleo-latitudes (≤35°N). Today, such low (18)O/(16)O values are only observed in central Antarctica, where long distillation trajectories in combination with low condensation temperatures promote extreme (18)O depletion. For a Neoproterozoic (∼0.6-0.7 Ga) snowball Earth, higher meltwater δ(18)O estimates of -21 ± 3‰ imply less extreme climate conditions at similar paleo-latitudes (≤35°N). Both estimates are single snapshots of ancient water samples and may not represent peak snowball Earth conditions. We demonstrate how (17)O/(16)O measurements provide information beyond traditional (18)O/(16)O measurements, even though all fractionation processes are purely mass dependent.

  20. Revealing the climate of snowball Earth from Δ17O systematics of hydrothermal rocks

    PubMed Central

    Herwartz, Daniel; Pack, Andreas; Krylov, Dmitri; Xiao, Yilin; Muehlenbachs, Karlis; Sengupta, Sukanya; Di Rocco, Tommaso

    2015-01-01

    The oxygen isotopic composition of hydrothermally altered rocks partly originates from the interacting fluid. We use the triple oxygen isotope composition (17O/16O, 18O/16O) of Proterozoic rocks to reconstruct the 18O/16O ratio of ancient meteoric waters. Some of these waters have originated from snowball Earth glaciers and thus give insight into the climate and hydrology of these critical intervals in Earth history. For a Paleoproterozoic [∼2.3–2.4 gigayears ago (Ga)] snowball Earth, δ18O = −43 ± 3‰ is estimated for pristine meteoric waters that precipitated at low paleo-latitudes (≤35°N). Today, such low 18O/16O values are only observed in central Antarctica, where long distillation trajectories in combination with low condensation temperatures promote extreme 18O depletion. For a Neoproterozoic (∼0.6–0.7 Ga) snowball Earth, higher meltwater δ18O estimates of −21 ± 3‰ imply less extreme climate conditions at similar paleo-latitudes (≤35°N). Both estimates are single snapshots of ancient water samples and may not represent peak snowball Earth conditions. We demonstrate how 17O/16O measurements provide information beyond traditional 18O/16O measurements, even though all fractionation processes are purely mass dependent. PMID:25870269

  1. Origin of meteoritic stardust unveiled by a revised proton-capture rate of 17O

    NASA Astrophysics Data System (ADS)

    Lugaro, M.; Karakas, A. I.; Bruno, C. G.; Aliotta, M.; Nittler, L. R.; Bemmerer, D.; Best, A.; Boeltzig, A.; Broggini, C.; Caciolli, A.; Cavanna, F.; Ciani, G. F.; Corvisiero, P.; Davinson, T.; Depalo, R.; di Leva, A.; Elekes, Z.; Ferraro, F.; Formicola, A.; Fülöp, Zs.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, Gy.; Imbriani, G.; Junker, M.; Menegazzo, R.; Mossa, V.; Pantaleo, F. R.; Piatti, D.; Prati, P.; Scott, D. A.; Straniero, O.; Strieder, F.; Szücs, T.; Takács, M. P.; Trezzi, D.

    2017-01-01

    Stardust grains recovered from meteorites provide high-precision snapshots of the isotopic composition of the stellar environment in which they formed 1 . Attributing their origin to specific types of stars, however, often proves difficult. Intermediate-mass stars of 4-8 solar masses are expected to have contributed a large fraction of meteoritic stardust 2,3 . Yet, no grains have been found with the characteristic isotopic compositions expected for such stars 4,5 . This is a long-standing puzzle, which points to serious gaps in our understanding of the lifecycle of stars and dust in our Galaxy. Here we show that the increased proton-capture rate of 17O reported by a recent underground experiment 6 leads to 17O/16O isotopic ratios that match those observed in a population of stardust grainsfor proton-burning temperatures of 60-80 MK. These temperatures are achieved at the base of the convective envelope during the late evolution of intermediate-mass stars of 4-8 solar masses 7-9 , which reveals them as the most likely site of origin of the grains. This result provides direct evidence that these stars contributed to the dust inventory from which the Solar System formed.

  2. Elastic scattering of 17O+208Pb at energies near the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Torresi, D.; Strano, E.; Mazzocco, M.; Boiano, A.; Boiano, C.; Di Meo, P.; La Commara, M.; Manea, C.; Nicoletto, M.; Grebosz, J.; Guglielmetti, A.; Molini, P.; Parascandolo, C.; Pierroutsakou, D.; Signorini, C.; Soramel, F.; Toniolo, N.; Filipescu, D.; Gheorghe, A.; Glodariu, T.; Jeong, S.; Kim, Y. H.; Lay, J. A.; Miyatake, H.; Pakou, A.; Sgouros, O.; Soukeras, V.; Stroe, L.; Vitturi, A.; Watanabe, Y.; Zerva, K.

    2016-05-01

    Within the frame of the commissioning of a new experimental apparatus EXPADES we undertook the measurement of the elastic scattering angular distribution for the system 17O+208Pb at energy around the Coulomb barrier. The reaction dynamics induced by loosely bound Radioactive Ion Beams is currently being extensively studied [4]. In particular the study of the elastic scattering process allows to obtain direct information on the total reaction cross section of the exotic nuclei. In order to understand the effect of the low binding energy on the reaction mechanism it is important to compare radioactive weakly bound nuclei with stable strongly-bound nuclei. In this framework the study of the 17O+208Pb elastic scattering can be considered to be complementary to a previous measurement of the total reaction cross section for the system 17F+208Pb at energies of 86, 90.4 MeV [5, 6]. The data will be compared with those obtained for the neighboring systems 16,18O+208Pb and others available in literature.

  3. 1- and 2+ discrete states in 90Zr populated via the (17O,'17Oγ ) reaction

    NASA Astrophysics Data System (ADS)

    Crespi, F. C. L.; Bracco, A.; Nicolini, R.; Lanza, E. G.; Vitturi, A.; Mengoni, D.; Leoni, S.; Benzoni, G.; Blasi, N.; Boiano, C.; Bottoni, S.; Brambilla, S.; Camera, F.; Corsi, A.; Giaz, A.; Million, B.; Pellegri, L.; Vandone, V.; Wieland, O.; Bednarczyk, P.; Ciemała, M.; Kmiecik, M.; Krzysiek, M.; Maj, A.; Bazzacco, D.; Bellato, M.; Birkenbach, B.; Bortolato, D.; Calore, E.; Cederwall, B.; de Angelis, G.; Désesquelles, P.; Eberth, J.; Farnea, E.; Gadea, A.; Görgen, A.; Gottardo, A.; Hess, H.; Isocrate, R.; Jolie, J.; Jungclaus, A.; Kempley, R. S.; Labiche, M.; Menegazzo, R.; Michelagnoli, C.; Molini, P.; Napoli, D. R.; Pullia, A.; Quintana, B.; Recchia, F.; Reiter, P.; Sahin, E.; Siem, S.; Söderström, P.-A.; Stezowski, O.; Theisen, Ch.; Ur, C.; Valiente-Dobón, J. J.

    2015-02-01

    2+ and 1- states in 90Zr were populated via the (17O,'17Oγ ) reaction at 340 MeV. The γ decay was measured with high resolution using the AGATA (advanced γ tracking array demonstrator array). Differential cross sections were obtained at few different angles for the scattered particle. The results of the elastic scattering and inelastic excitation of 2+,3-, and 1- states are compared with distorted-wave Born approximation (DWBA) calculations, using both the standard collective form factor and a form factor obtained by folding microscopically calculated transition densities. This allowed to extract the isoscalar component of the 1- state at 6.424 MeV. The comparison of the present (17O,'17Oγ ) data with existing (γ ,γ' ) and (p ,p' ) data in the corresponding region of the γ continuum (6-11 MeV), characterized by a large E 1 component, shows completely different behaviors of the cross section as a function of the nuclear excitation energy. The comparison of the data with DWBA calculations suggests a decrease of the isoscalar strength in the cross section with increasing excitation energy.

  4. Water dissolution in albite melts: - Constraints from ab initio NMR calculations

    NASA Astrophysics Data System (ADS)

    Liu, Yun; Nekvasil, Hanna; Long, Hongbo

    2002-12-01

    Hartree-Fock and B3LYP NMR calculations were performed at the 6-311+G(2df,p) level on cluster models representing albite glasses using B3LYP/6 to 31G* optimized geometries. Calculation results on several well-known crystalline materials, such as low albite and KHSi 2O 5, were used to check the accuracy of the calculation methods. Calculated 29Si-NMR results on clusters that model protonation of Al-O-Si linkages and the replacement of Na + by H + indicate a major increase in Si-O(H) bond length and a 5 ppm difference in δ iso for 29Si compared to that for anhydrous albite glass. The calculated δ iso of 27Al in such linkages agrees with the experimental data, but shows an increase in C q that cannot be fully diminished by H-bonding to additional water molecules. This protonation model is consistent with both experimental 17O NMR data and the major peak of 1H-NMR spectra. It cannot readily explain the existence of the small peak in the experimental 1H spectra around 1.5 ppm. Production of the depolymerized units Al [Q 3]-O-H upon the dissolution of water is not consistent with 27Al, 1H, or 17O NMR experimental results. Production of Si [Q 3]-O-H is consistent with all of the experimental 17O and 1H-NMR data; such units can produce both the major peak at 3.5 ppm and the small peak at 1.5 ppm in 1H spectra, either with or without hydrogen bonding. This species, however, cannot produce the main features of 29Si spectra. It is concluded that although neither protonation nor the production of Si [Q 3]-O-H alone is consistent with the available experimental data, the combination of these two processes is consistent with available experimental NMR data.

  5. Supplementation of antipsychotic treatment with sarcosine – GlyT1 inhibitor – causes changes of glutamatergic (1)NMR spectroscopy parameters in the left hippocampus in patients with stable schizophrenia.

    PubMed

    Strzelecki, Dominik; Podgórski, Michał; Kałużyńska, Olga; Gawlik-Kotelnicka, Oliwia; Stefańczyk, Ludomir; Kotlicka-Antczak, Magdalena; Gmitrowicz, Agnieszka; Grzelak, Piotr

    2015-10-08

    Glutamatergic system, the main stimulating system of the brain, plays an important role in the pathogenesis of schizophrenia. Hippocampus, a structure crucial for memory and cognitive functions and rich in glutamatergic neurons, is a natural object of interest in studies on psychoses. Sarcosine, a glycine transporter (GlyT-1) inhibitor influences the function of NMDA receptor and glutamate-dependent transmission. The aim of the study was to assess the effects of sarcosine on metabolism parameters in the left hippocampus in patients with schizophrenia. Assessments were performed using proton nuclear magnetic resonance ((1)H NMR) spectroscopy (1.5T). Fifty patients diagnosed with schizophrenia (DSM-IV-TR), with dominant negative symptoms, in stable clinical condition and stable antipsychotics doses were treated either with sarcosine (n=25) or placebo (n=25). Spectroscopic parameters were evaluated within groups and between two groups before and after 6-month intervention. All patients were also assessed with the Positive and Negative Syndrome Scale (PANSS). In the sarcosine group, after 6-month treatment, we found significant decrease in hippocampal Glx/Cr (Glx-complex of glutamate, glutamine and GABA, Cr-creatine) and Glx/Cho (Cho-choline), while N-acetylaspartate (NAA), myo-inositol (mI), Cr and Cho parameters remained stable along the study and also did not differ significantly between both groups. This is the first study showing that a pharmacological intervention in schizophrenia, particularly augmentation of the antypsychotic treatment with sarcosine, may reverse the pathological increase in glutamatergic transmission in the hippocampus. The results confirm involvement of glutamatergic system in the pathogenesis of schizophrenia and demonstrate beneficial effects of GlyT-1 inhibitor on the metabolism in the hippocampus and symptoms of schizophrenia.

  6. NMR analysis of biodiesel

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biodiesel is usually analyzed by the various methods called for in standards such as ASTM D6751 and EN 14214. Nuclear magnetic resonance (NMR) is not one of these methods. However, NMR, with 1H-NMR commonly applied, can be useful in a variety of applications related to biodiesel. These include monit...

  7. Evolution of the Proterozoic Earth System: Insights from the ∆17O Record of Sedimentary Sulfate Minerals

    NASA Astrophysics Data System (ADS)

    Crockford, P. W.; Hayles, J. A.; Halverson, G. P.; Bekker, A.; Rainbird, R.; Wing, B. A.

    2014-12-01

    Triple oxygen isotope ratios (18O/16O and 17O/16O) are a powerful tool to tease out interconnections within the Surface Earth System, both today and throughout Earth's history. This ability comes from the fact that stratospheric photochemistry imparts a negative ∆17O anomaly (∆17O = δ17O - 0.52×δ18O) to atmospheric oxygen whose magnitude is proportional to pCO2 levels and photosynthetic oxygen production. Atmospheric oxygen readily weathers continental sulfides and, as a result, the secular variations in atmospheric ∆17O values may be recorded in marine sulfate minerals (barite, gypsum and anhydrite). The largest ∆17O anomalies found in the rock record are from peculiar barite layers that immediately post-date the 635 Ma Marinoan Snowball Event. While these anomalies have been interpreted to result from a weak post-glacial photosynthetic O2 flux, the balance of other evidence (e.g., Zn isotope records of near-modern post-glacial productivity) suggests that they instead reflect the elevated CO2 levels thought to be required to exit a snowball state. As this situation illustrates, the ∆17O record by itself does not provide a unique solution between production of the anomaly by stratospheric reactions and its destruction by global biospheric productivity. In the context of additional geological and geochemical constraints, however, a marine sulfate ∆17O record has the potential to provide new insights into paleoatmospheres, paleoclimates, and paleoproductivity. We have produced new data (n ≈ 200) for Proterozoic evaporites that extend the sulfate ∆17O record from the Neoproterozoic to ~2.3 Ga. This data will be interpreted within our current understanding of Proterozoic Earth System Evolution on basinal to global scales and will address key questions that include: Were Paleoproterozoic glacial episodes terminated by elevated pCO2? Was the Great Oxidation Event accompanied by enhanced productivity? Does the lack of C isotope variability throughout

  8. Rapid Synthesis of Thin and Long Mo17O47 Nanowire-Arrays in an Oxygen Deficient Flame

    PubMed Central

    Allen, Patrick; Cai, Lili; Zhou, Lite; Zhao, Chenqi; Rao, Pratap M.

    2016-01-01

    Mo17O47 nanowire-arrays are promising active materials and electrically-conductive supports for batteries and other devices. While high surface area resulting from long, thin, densely packed nanowires generally leads to improved performance in a wide variety of applications, the Mo17O47 nanowire-arrays synthesized previously by electrically-heated chemical vapor deposition under vacuum conditions were relatively thick and short. Here, we demonstrate a method to grow significantly thinner and longer, densely packed, high-purity Mo17O47 nanowire-arrays with diameters of 20–60 nm and lengths of 4–6 μm on metal foil substrates using rapid atmospheric flame vapor deposition without any chamber or walls. The atmospheric pressure and 1000 °C evaporation temperature resulted in smaller diameters, longer lengths and order-of-magnitude faster growth rate than previously demonstrated. As explained by kinetic and thermodynamic calculations, the selective synthesis of high-purity Mo17O47 nanowires is achieved due to low oxygen partial pressure in the flame products as a result of the high ratio of fuel to oxidizer supplied to the flame, which enables the correct ratio of MoO2 and MoO3 vapor concentrations for the growth of Mo17O47. This flame synthesis method is therefore a promising route for the growth of composition-controlled one-dimensional metal oxide nanomaterials for many applications. PMID:27271194

  9. One-Proton Breakup of 18F and the 17O(p,γ)18F Reaction in Classical Novae

    NASA Astrophysics Data System (ADS)

    Isherwood, Bryan; Banu, A.; E491 Collaboration

    2013-10-01

    Classical nova studies are of considerable interest for understanding the chemical evolution of the Galaxy. They have been proposed as the most significant source for the nucleosynthesis of the isotopes 13C, 15N, and 17O in the Universe. Novae are also likely to synthesize the short-lived radioisotope 18F (T1/2 = 110 min), which is expected to be the most important contributor to the observed emission of 511 keV gamma radiation by space-based γ-ray telescopes. This emission is produced by electron-positron annihilation following the beta + decay of radioactive nuclei. A detection of these gamma rays could significantly constrain the nova simulation models. 18F nucleosynthesis in classical novae strongly depends on the thermonuclear rate of the 17O(p,γ)18F reaction, which is part of the CNO cycle. This work presents preliminary results toward determination of the 17O(p,γ)18F reaction cross section, which was measured by the indirect method of one-proton nuclear breakup at intermediate energies. The experiment was carried out at GANIL using a beam of 18F at 40 MeV/u impinging on a carbon target. Longitudinal momentum distributions of the 17O breakup fragments were measured in coincidence with γ-rays emitted by 17O residues.

  10. Rapid Synthesis of Thin and Long Mo17O47 Nanowire-Arrays in an Oxygen Deficient Flame

    NASA Astrophysics Data System (ADS)

    Allen, Patrick; Cai, Lili; Zhou, Lite; Zhao, Chenqi; Rao, Pratap M.

    2016-06-01

    Mo17O47 nanowire-arrays are promising active materials and electrically-conductive supports for batteries and other devices. While high surface area resulting from long, thin, densely packed nanowires generally leads to improved performance in a wide variety of applications, the Mo17O47 nanowire-arrays synthesized previously by electrically-heated chemical vapor deposition under vacuum conditions were relatively thick and short. Here, we demonstrate a method to grow significantly thinner and longer, densely packed, high-purity Mo17O47 nanowire-arrays with diameters of 20–60 nm and lengths of 4–6 μm on metal foil substrates using rapid atmospheric flame vapor deposition without any chamber or walls. The atmospheric pressure and 1000 °C evaporation temperature resulted in smaller diameters, longer lengths and order-of-magnitude faster growth rate than previously demonstrated. As explained by kinetic and thermodynamic calculations, the selective synthesis of high-purity Mo17O47 nanowires is achieved due to low oxygen partial pressure in the flame products as a result of the high ratio of fuel to oxidizer supplied to the flame, which enables the correct ratio of MoO2 and MoO3 vapor concentrations for the growth of Mo17O47. This flame synthesis method is therefore a promising route for the growth of composition-controlled one-dimensional metal oxide nanomaterials for many applications.

  11. Spectroscopic (FT-IR, FT-Raman and UV-Visible) investigations, NMR chemical shielding anisotropy (CSA) parameters of 2,6-Diamino-4-chloropyrimidine for dye sensitized solar cells using density functional theory.

    PubMed

    Gladis Anitha, E; Joseph Vedhagiri, S; Parimala, K

    2015-02-05

    The molecular structure, geometry optimization, vibrational frequencies of organic dye sensitizer 2,6-Diamino-4-chloropyrimidine (DACP) were studied based on Hartree-Fock (HF) and density functional theory (DFT) using B3LYP methods with 6-311++G(d,p) basis set. Ultraviolet-Visible (UV-Vis) spectrum was investigated by time dependent DFT (TD-DFT). Features of the electronic absorption spectrum in the UV-Visible regions were assigned based on TD-DFT calculation. The absorption bands are assigned to transitions. The interfacial electron transfer between semiconductor TiO2 electrode and dye sensitizer DACP is due to an electron injection process from excited dye to the semiconductor's conduction band. The observed and the calculated frequencies are found to be in good agreement. The energies of the frontier molecular orbitals (FMOS) have also been determined. The chemical shielding anisotropic (CSA) parameters are calculated from the NMR analysis, Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis.

  12. NMR reaction monitoring in flow synthesis

    PubMed Central

    Gomez, M Victoria

    2017-01-01

    Recent advances in the use of flow chemistry with in-line and on-line analysis by NMR are presented. The use of macro- and microreactors, coupled with standard and custom made NMR probes involving microcoils, incorporated into high resolution and benchtop NMR instruments is reviewed. Some recent selected applications have been collected, including synthetic applications, the determination of the kinetic and thermodynamic parameters and reaction optimization, even in single experiments and on the μL scale. Finally, software that allows automatic reaction monitoring and optimization is discussed. PMID:28326137

  13. Oxygen-17 dynamic nuclear polarisation enhanced solid-state NMR spectroscopy at 18.8 T.

    PubMed

    Brownbill, Nick J; Gajan, David; Lesage, Anne; Emsley, Lyndon; Blanc, Frédéric

    2017-02-23

    We report (17)O dynamic nuclear polarisation (DNP) enhanced solid-state NMR experiments at 18.8 T. Several formulations were investigated on the Mg(OH)2 compound. A signal enhancement factor of 17 could be obtained when the solid particles were incorporated into a glassy o-terphenyl matrix doped with BDPA using the Overhauser polarisation transfer scheme whilst the cross effect mechanism enabled by TEKPol yielded a slightly lower enhancement but more time efficient data acquisition.

  14. NMR studies of multiphase flows II

    SciTech Connect

    Altobelli, S.A.; Caprihan, A.; Fukushima, E.

    1995-12-31

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

  15. Resonance Strength Measurement at Astrophysical Energies: The 17O(p,α)14N Reaction Studied via THM

    NASA Astrophysics Data System (ADS)

    Sergi, M. L.; Spitaleri, C.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Rapisarda, G. G.; Mukhamedzhanov, A.; Irgaziev, B.; Tang, X. D.; Wischer, M.; Mrazek, J.; Kroha, V.

    2016-05-01

    In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on 17O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the 17O(p,α)14N reaction via the Trojan Horse Method by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. The mean value of the strengths obtained in the two measurements was calculated and compared with the direct data available in literature.

  16. Resonance strength measurement at astrophysical energies: The 17O(p,α)14N reaction studied via Trojan Horse Method

    NASA Astrophysics Data System (ADS)

    Sergi, M. L.; Spitaleri, C.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Rapisarda, G. G.; Mukhamedzhanov, A.; Irgaziev, B.; Tang, X. D.; Wiescher, M.; Mrazek, J.; Kroha, V.

    2015-10-01

    In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on 17O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the 17O(p,α)14N reaction via the THM by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. Two measurements will be described and the experimental THM cross sections will be shown for both experiments.

  17. An Introduction to Biological NMR Spectroscopy*

    PubMed Central

    Marion, Dominique

    2013-01-01

    NMR spectroscopy is a powerful tool for biologists interested in the structure, dynamics, and interactions of biological macromolecules. This review aims at presenting in an accessible manner the requirements and limitations of this technique. As an introduction, the history of NMR will highlight how the method evolved from physics to chemistry and finally to biology over several decades. We then introduce the NMR spectral parameters used in structural biology, namely the chemical shift, the J-coupling, nuclear Overhauser effects, and residual dipolar couplings. Resonance assignment, the required step for any further NMR study, bears a resemblance to jigsaw puzzle strategy. The NMR spectral parameters are then converted into angle and distances and used as input using restrained molecular dynamics to compute a bundle of structures. When interpreting a NMR-derived structure, the biologist has to judge its quality on the basis of the statistics provided. When the 3D structure is a priori known by other means, the molecular interaction with a partner can be mapped by NMR: information on the binding interface as well as on kinetic and thermodynamic constants can be gathered. NMR is suitable to monitor, over a wide range of frequencies, protein fluctuations that play a crucial role in their biological function. In the last section of this review, intrinsically disordered proteins, which have escaped the attention of classical structural biology, are discussed in the perspective of NMR, one of the rare available techniques able to describe structural ensembles. This Tutorial is part of the International Proteomics Tutorial Programme (IPTP 16 MCP). PMID:23831612

  18. An introduction to biological NMR spectroscopy.

    PubMed

    Marion, Dominique

    2013-11-01

    NMR spectroscopy is a powerful tool for biologists interested in the structure, dynamics, and interactions of biological macromolecules. This review aims at presenting in an accessible manner the requirements and limitations of this technique. As an introduction, the history of NMR will highlight how the method evolved from physics to chemistry and finally to biology over several decades. We then introduce the NMR spectral parameters used in structural biology, namely the chemical shift, the J-coupling, nuclear Overhauser effects, and residual dipolar couplings. Resonance assignment, the required step for any further NMR study, bears a resemblance to jigsaw puzzle strategy. The NMR spectral parameters are then converted into angle and distances and used as input using restrained molecular dynamics to compute a bundle of structures. When interpreting a NMR-derived structure, the biologist has to judge its quality on the basis of the statistics provided. When the 3D structure is a priori known by other means, the molecular interaction with a partner can be mapped by NMR: information on the binding interface as well as on kinetic and thermodynamic constants can be gathered. NMR is suitable to monitor, over a wide range of frequencies, protein fluctuations that play a crucial role in their biological function. In the last section of this review, intrinsically disordered proteins, which have escaped the attention of classical structural biology, are discussed in the perspective of NMR, one of the rare available techniques able to describe structural ensembles. This Tutorial is part of the International Proteomics Tutorial Programme (IPTP 16 MCP).

  19. Diethylstilbestrol can effectively accelerate estradiol-17-O-glucuronidation, while potently inhibiting estradiol-3-O-glucuronidation

    SciTech Connect

    Zhu, Liangliang; Xiao, Ling; Xia, Yangliu; Zhou, Kun; Wang, Huili; Huang, Minyi; Ge, Guangbo; Wu, Yan; Wu, Ganlin; Yang, Ling

    2015-03-01

    This in vitro study investigates the effects of diethylstilbestrol (DES), a widely used toxic synthetic estrogen, on estradiol-3- and 17-O- (E2-3/17-O) glucuronidation, via culturing human liver microsomes (HLMs) or recombinant UDP-glucuronosyltransferases (UGTs) with DES and E2. DES can potently inhibit E2-3-O-glucuronidation in HLM, a probe reaction for UGT1A1. Kinetic assays indicate that the inhibition follows a competitive inhibition mechanism, with the Ki value of 2.1 ± 0.3 μM, which is less than the possible in vivo level. In contrast to the inhibition on E2-3-O-glucuronidation, the acceleration is observed on E2-17-O-glucuronidation in HLM, in which cholestatic E2-17-O-glucuronide is generated. In the presence of DES (0–6.25 μM), K{sub m} values for E2-17-O-glucuronidation are located in the range of 7.2–7.4 μM, while V{sub max} values range from 0.38 to 1.54 nmol/min/mg. The mechanism behind the activation in HLM is further demonstrated by the fact that DES can efficiently elevate the activity of UGT1A4 in catalyzing E2-17-O-glucuronidation. The presence of DES (2 μM) can elevate V{sub max} from 0.016 to 0.81 nmol/min/mg, while lifting K{sub m} in a much lesser extent from 4.4 to 11 μM. Activation of E2-17-O-glucuronidation is well described by a two binding site model, with K{sub A}, α, and β values of 0.077 ± 0.18 μM, 3.3 ± 1.1 and 104 ± 56, respectively. However, diverse effects of DES towards E2-3/17-O-glucuronidation are not observed in liver microsomes from several common experimental animals. In summary, this study issues new potential toxic mechanisms for DES: potently inhibiting the activity of UGT1A1 and powerfully accelerating the formation of cholestatic E2-17-O-glucuronide by UGT1A4. - Highlights: • E2-3-O-glucuronidation in HLM is inhibited when co-incubated with DES. • E2-17-O-glucuronidation in HLM is stimulated when co-incubated with DES. • Acceleration of E2-17-O-glucuronidationin in HLM by DES is via activating the

  20. Report on neptunium speciation by NMR and optical spectroscopies

    SciTech Connect

    Tait, C.D.; Palmer, P.D.; Ekberg, S.A.; Clark, D.L.

    1995-11-01

    Hydrolysis and carbonate complexation reactions were examined for NpO{sub 2}{sup 2+} and NpO{sub 2}{sup +} ions by a variety of techniques including potentiometric titration, UV-Vis-NIR and NMR spectroscopy. The equilibrium constant for the reaction 3NpO{sub 2}(CO{sub 3}){sub 3}{sup 4{minus}} + 3H{sup +} {rightleftharpoons} (NpO{sub 2}){sub 3}(CO{sub 3}){sub 6}{sup 6{minus}} + 3HCO{sub 3}{sup {minus}} was determined to be logK = 19.7 ({plus_minus} 0.8) (I = 2.5 m). {sup 17}O NMR spectroscopy of NpO{sub 2}{sup n+} ions (n = 1,2) reveals a readily observable {sup 17}O resonance for n = 2, but not for n = 1. The first hydrolysis constant for NpO{sub 2}{sup +} was studied as a function of temperature, and the functional form for the temperature-dependent equilibrium constant for the reaction written as NpO{sub 2}{sup +} + H{sub 2}O {rightleftharpoons} NpO{sub 2}OH + H{sup +} was found to be logK = 2.28 {minus} 3780/T, where T is in {degree}K. Finally, the temperature dependence of neptunium(V) carbonate complexation constants was studied. For the first carbonate complexation constant, the appropriate functional form was found to be log{beta}{sub 01} = 1.47 + 786/T.

  1. Correction for the 17O interference in δ(13C) measurements when analyzing CO2 with stable isotope mass spectrometry

    USGS Publications Warehouse

    Coplen, Tyler B.; Brand, Willi A.; Assonov, Sergey S.

    2010-01-01

    Measurements of δ(13C) determined on CO2 with an isotope-ratio mass spectrometer (IRMS) must be corrected for the amount of 17O in the CO2. For data consistency, this must be done using identical methods by different laboratories. This report aims at unifying data treatment for CO2 IRMS by proposing (i) a unified set of numerical values, and (ii) a unified correction algorithm, based on a simple, linear approximation formula. Because the oxygen of natural CO2 is derived mostly from the global water pool, it is recommended that a value of 0.528 be employed for the factor λ, which relates differences in 17O and 18O abundances. With the currently accepted N(13C)/N(12C) of 0.011 180(28) in VPDB (Vienna Peedee belemnite) reevaluation of data yields a value of 0.000 393(1) for the oxygen isotope ratio N(17O)/N(16O) of the evolved CO2. The ratio of these quantities, a ratio of isotope ratios, is essential for the 17O abundance correction: [N(17O)/N(16O)]/[N(13C)/N(12C)] = 0.035 16(8). The equation [δ(13C) ≈ 45δVPDB-CO2 + 2 17R/13R (45δVPDB-CO2 – λ46δVPDB-CO2)] closely approximates δ(13C) values with less than 0.010 ‰ deviation for normal oxygen-bearing materials and no more than 0.026 ‰ in extreme cases. Other materials containing oxygen of non-mass-dependent isotope composition require a more specific data treatment. A similar linear approximation is also suggested for δ(18O). The linear approximations are easy to implement in a data spreadsheet, and also help in generating a simplified uncertainty budget.

  2. A multinuclear solid state NMR spectroscopic study of the structural evolution of disordered calcium silicate sol-gel biomaterials.

    PubMed

    Lin, Zhongjie; Jones, Julian R; Hanna, John V; Smith, Mark E

    2015-01-28

    Disordered sol-gel prepared calcium silicate biomaterials show significant, composition dependent ability to bond with bone. Bone bonding is attributed to rapid hydroxycarbonate apatite (HCA) formation on the glass surface after immersion in body fluid (or implantation). Atomic scale details of the development of the structure of (CaO)x(SiO2)1-x (x = 0.2, 0.3 and 0.5) under heat treatment and subsequent dissolution in simulated body fluid (SBF) are revealed through a multinuclear solid state NMR approach using one-dimensional (17)O, (29)Si, (31)P and (1)H. Central to this study is the combination of conventional static and magic angle spinning (MAS) and two-dimensional (2D) triple quantum (3Q) (17)O NMR experiments that can readily distinguish and quantify the bridging (BOs) and non-bridging (NBOs) oxygens in the silicate network. Although soluble calcium is present in the sol, the (17)O NMR results reveal that the sol-gel produced network structure is initially dominated by BOs after gelation, aging and drying (e.g. at 120 °C), indicating a nanoscale mixture of the calcium salt and a predominantly silicate network. Only once the calcium salt is decomposed at elevated temperatures do the Ca(2+) ions become available to break BO. Apatite forming ability in SBF depends strongly on the surface OH and calcium content. The presence of calcium aids HCA formation via promotion of surface hydration and the ready availability of Ca(2+) ions. (17)O NMR shows the rapid loss of NBOs charge balanced by calcium as it is leached into the SBF. The formation of nanocrystalline, partially ordered HCA can be detected via(31)P NMR. This data indicates the importance of achieving the right balance of BO/NBO for optimal biochemical response and network properties.

  3. Rotary echo nutation NMR

    NASA Astrophysics Data System (ADS)

    Janssen, R.; Tijink, G. A. H.; Veeman, W. S.

    1988-01-01

    A two-dimensional solid state NMR experiment which combines rotary echoes and nutation NMR is investigated and used to study different sodium sites in zeolite NaA. It is shown that with this technique sodium ions with different relaxation rates in the rotating frame can be distinguished.

  4. Lectures on pulsed NMR

    SciTech Connect

    Pines, A.

    1988-08-01

    These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 32 refs., 56 figs.

  5. Lectures on pulsed NMR

    SciTech Connect

    Pines, A.

    1986-09-01

    These lectures discuss some recent developments in pulsed NMR, emphasizing fundamental principles with selected illustrative applications. Major topics covered include multiple-quantum spectroscopy, spin decoupling, the interaction of spins with a quantized field, adiabatic rapid passage, spin temperature and statistics of cross-polarization, coherent averaging, and zero field NMR. 55 figs.

  6. NMR logging apparatus

    DOEpatents

    Walsh, David O; Turner, Peter

    2014-05-27

    Technologies including NMR logging apparatus and methods are disclosed. Example NMR logging apparatus may include surface instrumentation and one or more downhole probes configured to fit within an earth borehole. The surface instrumentation may comprise a power amplifier, which may be coupled to the downhole probes via one or more transmission lines, and a controller configured to cause the power amplifier to generate a NMR activating pulse or sequence of pulses. Impedance matching means may be configured to match an output impedance of the power amplifier through a transmission line to a load impedance of a downhole probe. Methods may include deploying the various elements of disclosed NMR logging apparatus and using the apparatus to perform NMR measurements.

  7. NMR quadruopole spectra of PZT from first-principles

    NASA Astrophysics Data System (ADS)

    Mao, Dandan; Walter, Eric J.; Krakauer, Henry

    2006-03-01

    High performance piezoelectric materials are disordered alloys, so it can be difficult to determine the local atomic geometry. Recently, high field NMR measurements have shown great promise as a microscopic probe of ABO3 perovskite-based alloys by their ability to resolve line-splittings due to nuclear quadrupolar coupling with the electric field gradient (EFG) at the nucleus. We report first-principles LDA calculations of the EFG's in monoclinic and tetragonal Pb(Zr0.5Ti0.5)O3 systems using the linear augmented planewave (LAPW) method, and we compute NMR static powder spectra for ^91Zr, ^47Ti, and ^17O atoms as a function of applied strain. With decreasing c/a ratio PZT converts from tetragonal to monoclinic symmetry. We observe that the calculated NMR spectra show dramatic deviations with decreasing c/a from that in tetragonal P4mm well before the electric polarization begins to rotate away from the [001] direction. This indicates that NMR measurements can be a very accurate probe of local structural changes in perovskite piezoelectrics. G. L. Hoatson, D. H. Zhou, F. Fayon, D. Massiot, and R. L. Vold, Phys. Rev. B, 66, 224103 (2002).

  8. Preparation of directionally solidified BaTi2O5-Ba6Ti17O40 eutectic by the floating zone method

    NASA Astrophysics Data System (ADS)

    Shiga, K.; Katsui, H.; Goto, T.

    2017-02-01

    The BaTi2O5-Ba6Ti17O40 eutectic (BaO-68.7 mol% TiO2) was directionally solidified by the floating zone (FZ) method and crystalline phases, microstructures and orientation were investigated. Ba6Ti17O40 with faceted rod-like shape was dispersed in the BaTi2O5 matrix. The growth directions of BaTi2O5 and Ba6Ti17O40 were parallel to the b and a axis, respectively, and the orientation relations were BaTi2O5 (010)//Ba6Ti17O40(60 2 ̅) and BaTi2O5 (001)//Ba6Ti17O40 (001).

  9. On the introduction of {sup 17}O+p reaction rates evaluated through the THM in AGB nucleosynthesis calculations

    SciTech Connect

    Palmerini, S.; Sergi, M. L.; La Cognata, M.; Pizzone, R. G.; Lamia, L.; Spitaleri, C.

    2014-05-09

    The rates for the {sup 17}O(p,αα{sup 14}N, {sup 17}O(p,α){sup 18}F and {sup 18}O(p,α){sup 15}N reactions deduced trough the Trojan Horse Method (THM) have been introduced into a state-of-the-art asymptotic giant branch (AGB) models for proton-capture nucleosynthesis and cool bottom process. The predicted abundances have been compared with isotopic compositions provided by geochemical analysis of presolar grains. As a result, an improved agreement is found between the models and the isotopic mix of oxide grains of AGB origins, whose composition is the signature of low-temperature proton-capture nucleosynthesis.

  10. Isospin character of low-lying pygmy dipole states in 208Pb via inelastic scattering of 17O ions.

    PubMed

    Crespi, F C L; Bracco, A; Nicolini, R; Mengoni, D; Pellegri, L; Lanza, E G; Leoni, S; Maj, A; Kmiecik, M; Avigo, R; Benzoni, G; Blasi, N; Boiano, C; Bottoni, S; Brambilla, S; Camera, F; Ceruti, S; Giaz, A; Million, B; Morales, A I; Vandone, V; Wieland, O; Bednarczyk, P; Ciemała, M; Grebosz, J; Krzysiek, M; Mazurek, K; Zieblinski, M; Bazzacco, D; Bellato, M; Birkenbach, B; Bortolato, D; Calore, E; Cederwall, B; Charles, L; de Angelis, G; Désesquelles, P; Eberth, J; Farnea, E; Gadea, A; Görgen, A; Gottardo, A; Isocrate, R; Jolie, J; Jungclaus, A; Karkour, N; Korten, W; Menegazzo, R; Michelagnoli, C; Molini, P; Napoli, D R; Pullia, A; Recchia, F; Reiter, P; Rosso, D; Sahin, E; Salsac, M D; Siebeck, B; Siem, S; Simpson, J; Söderström, P-A; Stezowski, O; Theisen, Ch; Ur, C; Valiente-Dobón, J J

    2014-07-04

    The properties of pygmy dipole states in 208Pb were investigated using the 208Pb(17O, 17O'γ) reaction at 340 MeV and measuring the γ decay with high resolution with the AGATA demonstrator array. Cross sections and angular distributions of the emitted γ rays and of the scattered particles were measured. The results are compared with (γ, γ') and (p, p') data. The data analysis with the distorted wave Born approximation approach gives a good description of the elastic scattering and of the inelastic excitation of the 2+ and 3- states. For the dipole transitions a form factor obtained by folding a microscopically calculated transition density was used for the first time. This has allowed us to extract the isoscalar component of the 1- excited states from 4 to 8 MeV.

  11. First analysis of the B1Σ+ (υ=1) Rydberg state in the lesser-abundant 12C17O isotopologue on the basis of the 1-υ″ progression of the Ångström band system

    NASA Astrophysics Data System (ADS)

    Hakalla, Rafał; Zachwieja, Mirosław; Szajna, Wojciech

    2014-06-01

    So far unobserved in the 12C17O isotopologue, the 1-υ″ progression of the Ångström (B1Σ+-A1Π) band system was recorded under high resolution in the 17,200-22,950 cm-1 spectral region as an emission spectrum using high-accuracy dispersive optical spectroscopy. The 12C17O molecules were formed and excited in two steps in a stainless steel hollow-cathode lamp with two anodes. The emission from the discharge was observed with a plane-grating spectrograph and recorded by a photomultiplier tube. In the studied region, the full rotational structure of the 1-1 and 1-5 bands of the B-A system was observed, in total 114 spectral emission lines up to J″=21. All those lines were precisely measured with an estimated accuracy of about 0.0030 cm-1, and rotationally analyzed. As a result, many molecular constants were determined for the B1Σ+ and A1Π states in the 12C17O isotopologue. In this paper we have also presented the results of calculations concerning RKR turning points, Franck-Condon factors, relative intensities, and r-centroids for the Ångström band system in the 12C17O molecule. We have also determined the value of the ΔG1/2 vibrational quantum, the isotope shifts, as well as the main, isotopically invariant parameters of the B1Σ+ Rydberg state in the CO molecule within the Born-Oppenheimer approximation. For the A1Π, υ=5 state, considerable irregularities of the rotational structure have been observed and analyzed in detail. Suspected candidates responsible for these perturbations have been identified. The B1Σ+, υ=1 state has been thoroughly analyzed in terms of possible perturbations and it emerged to be completely regular in the 12C17O molecule up to the observed maximum J value.

  12. NMR Stark Spectroscopy: New Methods to Calibrate NMR Sensitivity to Electric Fields

    NASA Astrophysics Data System (ADS)

    Tarasek, Matthew R.

    The influence of electrostatics on NMR parameters is well accepted. Thus, NMR is a promising route to probe electrical features within molecules and materials. However, applications of NMR Stark effects (E-field induced changes in spin energy levels) have been elusive. I have developed new approaches to resolve NMR Stark effects from an applied E field. This calibrates nuclear probes whose spectral response might later be used to evaluate internal E fields that are critical to function, such as those due to local charge distributions or sample structure. I will present two novel experimental approaches for direct calibration of NMR quadrupolar Stark effects (QSEs). In the first, steady-state (few-second) excitation by an E field at twice the NMR frequency (2ω 0) is used to saturate spin magnetization. The extent of saturation vs. E-field amplitude calibrates the QSE response rate, while measurements vs sample orientation determine tensorial character. The second method instead synchronizes short (few µs) pulses of the 2ω0 E field with a multiple-pulse NMR sequence. This, “POWER” (Perturbations Observed With Enhanced Resolution) approach enables more accurate measure of small QSEs (i.e. few Hz spectral changes). A 2nd key advantage is the ability to define tensorial response without reorienting the sample, but instead varying the phase of the 2ω0 field. I will describe these experiments and my home-built NMR “Stark probe”, employed on a conventional wide-bore solid-state NMR system. Results with GaAs demonstrate each method, while extensions to a wider array of molecular and material systems may now be possible using these methods.

  13. NMR imaging microscopy

    SciTech Connect

    Not Available

    1986-10-01

    In the past several years, proton nuclear magnetic resonance (NMR) imaging has become an established technique in diagnostic medicine and biomedical research. Although much of the work in this field has been directed toward development of whole-body imagers, James Aguayo, Stephen Blackband, and Joseph Schoeninger of the Johns Hopkins University School of Medicine working with Markus Hintermann and Mark Mattingly of Bruker Medical Instruments, recently developed a small-bore NMR microscope with sufficient resolution to image a single African clawed toad cell (Nature 1986, 322, 190-91). This improved resolution should lead to increased use of NMR imaging for chemical, as well as biological or physiological, applications. The future of NMR microscopy, like that of many other newly emerging techniques, is ripe with possibilities. Because of its high cost, however, it is likely to remain primarily a research tool for some time. ''It's like having a camera,'' says Smith. ''You've got a way to look at things at very fine levels, and people are going to find lots of uses for it. But it is a very expensive technique - it costs $100,000 to add imaging capability once you have a high-resolution NMR, which itself is at least a $300,000 instrument. If it can answer even a few questions that can't be answered any other way, though, it may be well worth the cost.''

  14. Distal and proximal ligand interactions in heme proteins: correlations between C-O and Fe-C vibrational frequencies, oxygen-17 and carbon-13 nuclear magnetic resonance chemical shifts, and oxygen-17 nuclear quadrupole coupling constants in C17O- and 13CO-labeled species.

    PubMed

    Park, K D; Guo, K M; Adebodun, F; Chiu, M L; Sligar, S G; Oldfield, E

    1991-03-05

    We have obtained the oxygen-17 nuclear magnetic resonance (NMR) spectra of a variety of C17O-labeled heme proteins, including sperm whale (Physeter catodon) myoglobin, two synthetic sperm whale myoglobin mutants (His E7----Val E7; His E7----Phe E7), adult human hemoglobin, rabbit (Oryctolagus cuniculus) hemoglobin, horseradish (Cochlearia armoracia) peroxidase (E.C. 1.11.1.7) isoenzymes A and C, and Caldariomyces fumago chloroperoxidase (E.C. 1.11.1.10), in some cases as a function of pH, and have determined their isotropic 17O NMR chemical shifts, delta i, and spin-lattice relaxation times, T1. We have also obtained similar results on a picket fence prophyrin, [5,10,15,20-tetrakis(alpha, alpha, alpha, alpha, alpha-pivalamidophenyl)porphyrinato]iron(II) (1-MeIm)CO, both in solution and in the solid state. Our results show an excellent correlation between the infrared C-O vibrational frequencies, v(C-O), and delta i, between v(C-O) and the 17O nuclear quadrupole coupling constant (e2qQ/h, derived from T1), and as expected between e2qQ/h and delta i. Taken together with the work of others on the 13C NMR of 13CO-labeled proteins, where we find an excellent correlation between delta i(13C) and v(Fe-C), our results suggest that IR and NMR measurements reflect the same interaction, which is thought to be primarily the degree of pi-back-bonding from Fe d to CO pi* orbitals, as outlined previously [Li, X.-Y., & Spiro, T.G. (1988) J. Am. Chem. Soc. 110, 6024]. The modulation of this interaction by the local charge field of the distal heme residue (histidine, glutamine, arginine, and possibly lysine) in a variety of species and mutants, as reflected in the NMR and IR measurements, is discussed, as is the effect of cysteine as the proximal heme ligand.

  15. NMR studies of cation transport across membranes

    SciTech Connect

    Shochet, N.R.

    1985-01-01

    /sup 23/Na NMR Studies of cation transport across membranes were conducted both on model and biological membranes. Two ionophores, the carrier monensin and the channel-former gramicidin, were chosen to induce cation transport in large unilamellar phosphatidylcholine vesicles. The distinction between the NMR signals arising from the two sides of the membrane was achieved by the addition of an anionic paramagnetic shift reagent to the outer solution. The kinetics of the cation transport across the membrane was observed simultaneously monitoring the changes in the /sup 23/Na NMR signals of both compartments. Two mathematical models were developed for the estimation of the transport parameters of the monensin- and gramicidin-induced cation transport. The models were able to fit the experimental data very well. A new method for the estimation of the volume trapped inside the vesicles was developed. The method uses the relative areas of the intra- and extravesicular NMR signals arising from a suspension of vesicles bathed in the same medium they contain, as a measure for the relative volumes of these compartments. Sodium transport across biological membranes was studied by /sup 23/ NMR, using suspensions of cultured nerve cells. The sodium influx through voltage-gated channels was studied using the channel modifier batrachotoxin in combination with scorpion toxin.

  16. Study of the γ decay of high-lying states in 208Pb via inelastic scattering of 17O ions

    NASA Astrophysics Data System (ADS)

    Crespi, F. C. L.; Kmiecik, M.; Bracco, A.; Leoni, S.; Maj, A.; Benzoni, G.; Blasi, N.; Boiano, C.; Bottoni, S.; Brambilla, S.; Camera, F.; Ceruti, S.; Giaz, A.; Million, B.; Morales, A. I.; Nicolini, R.; Pellegri, L.; Riboldi, S.; Vandone, V.; Wieland, O.; Bednarczyk, P.; Ciemala, M.; Grebosz, J.; Krzysiek, M.; Mazurek, K.; Zieblinski, M.; Bazzacco, D.; Bellato, M.; Birkenbach, B.; Bortolato, D.; Calore, E.; De Angelis, G.; Farnea, E.; Gadea, A.; Görgen, A.; Gottardo, A.; Isocrate, R.; Lenzi, S.; Lunardi, S.; Mengoni, D.; Michelagnoli, C.; Molini, P.; Napoli, D. R.; Recchia, F.; Sahin, E.; Siebeck, B.; Siem, S.; Ur, C.; Valiente Dobon, J. J.

    2014-03-01

    A measurement of the high-lying states in 208Pb has been made using 17O beams at 20 MeV/u. The gamma decay following inelastic excitation was measured with the detector system AGATA Demonstrator based on segmented HPGe detectors, coupled to an array of large volume LaBr3:Ce scintillators and to an array of Si detectors. Preliminary results in comparison with (γ,γ') data, for states in the 5-8 MeV energy interval, are presented.

  17. Optimizing Adiabaticity in NMR

    NASA Astrophysics Data System (ADS)

    Vandermause, Jonathan; Ramanathan, Chandrasekhar

    We demonstrate the utility of Berry's superadiabatic formalism for numerically finding control sequences that implement quasi-adiabatic unitary transformations. Using an iterative interaction picture, we design a shortcut to adiabaticity that reduces the time required to perform an adiabatic inversion pulse in liquid state NMR. We also show that it is possible to extend our scheme to two or more qubits to find adiabatic quantum transformations that are allowed by the control algebra, and demonstrate a two-qubit entangling operation in liquid state NMR. We examine the pulse lengths at which the fidelity of these adiabatic transitions break down and compare with the quantum speed limit.

  18. THM determination of the 65 keV resonance strength intervening in the {sup 17}O(p,α){sup 14}N reaction rate

    SciTech Connect

    Sergi, M. L.; La Cognata, M.; Pizzone, R. G.; Spitaleri, C.; Cherubini, S.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Burjan, S. V.; Hons, Z.; Kroha, V.; Coc, A.; Hammache, F.; Irgaziev, B.; Kiss, G. G.; Somorjai, E.; Lamia, L.; Mukhamedzhanov, A.; and others

    2015-02-24

    The {sup 17}O(p,α){sup 14}N reaction is of paramount importance for the nucleosynthesis in a number of stellar sites, including red giants (RG), asymptotic giant branch (AGB) stars, massive stars and classical novae. We report on the indirect study of the {sup 17}O(p,α){sup 14}N reaction via the Trojan Horse Method by applying the approach recently developed for extracting the resonance strength of the narrow resonance at E{sub c.m.}{sup R} = 65 keV (E{sub X} =5.673 MeV). The strength of the 65 keV resonance in the {sup 17}O(p,α){sup 14}N reaction, measured by means of the THM, has been used to renormalize the corresponding resonance strength in the {sup 17}O+p radiative capture channel.

  19. Oxygen Isotopes of Chondrules in the Queen Alexandra Range 99177 CR3 Chondrite: Further Evidence for Systematic Relationships Between Chondrule Mg# and Δ^1^7O and the Role of Ice During Chondrule Formation

    NASA Astrophysics Data System (ADS)

    Tenner, T. J.; Nakashima, D.; Ushikubo, T.; Kita, N. T.; Weisberg, M. K.

    2012-03-01

    QUE 99177 chondrules steadily rise in Δ^1^7O (-5 to -1 ‰) as Mg# decreases (99 to 97). Addition of +Δ1^7O H_2O ice to dry precursors could reduce chondrule Mg# (by oxidation during formation) while increasing Δ^1^7O. Estimated H_2O ice Δ^1^7O is 0.5 to 6‰.

  20. First-principles calculations of 17O nuclear magnetic resonance chemical shielding in Pb(Zr(1/2)Ti(1/2))O3 and Pb(Mg(1/3)Nb(2/3))O3: linear dependence on transition-metal/oxygen bond lengths.

    PubMed

    Pechkis, Daniel L; Walter, Eric J; Krakauer, Henry

    2011-09-21

    First-principles density functional theory oxygen chemical shift tensors were calculated for A(B,B')O(3) perovskite alloys Pb(Zr(1/2)Ti(1/2))O(3) (PZT) and Pb(Mg(1/3)Nb(2/3))O(3) (PMN). Quantum chemistry methods for embedded clusters and the gauge including projector augmented waves (GIPAW) method [C. J. Pickard and F. Mauri, Phys. Rev. B 63, 245101 (2001)] for periodic boundary conditions were used. Results from both methods are in good agreement for PZT and prototypical perovskites. PMN results were obtained using only GIPAW. Both isotropic δ(iso) and axial δ(ax) chemical shifts were found to vary approximately linearly as a function of the nearest-distance transition-metal/oxygen bond length, r(s). Using these results, we argue against Ti clustering in PZT, as conjectured from recent (17)O NMR magic-angle-spinning measurements. Our findings indicate that (17)O NMR measurements, coupled with first-principles calculations, can be an important probe of local structure in complex perovskite solid solutions.

  1. NMR studies of oriented molecules

    SciTech Connect

    Sinton, S.W.

    1981-11-01

    Deuterium and proton magnetic resonance are used in experiments on a number of compounds which either form liquid crystal mesophases themselves or are dissolved in a liquid crystal solvent. Proton multiple quantum NMR is used to simplify complicated spectra. The theory of nonselective multiple quantum NMR is briefly reviewed. Benzene dissolved in a liquid crystal are used to demonstrate several outcomes of the theory. Experimental studies include proton and deuterium single quantum (..delta..M = +-1) and proton multiple quantum spectra of several molecules which contain the biphenyl moiety. 4-Cyano-4'-n-pentyl-d/sub 11/-biphenyl (5CB-d/sub 11/) is studied as a pure compound in the nematic phase. The obtained chain order parameters and dipolar couplings agree closely with previous results. Models for the effective symmetry of the biphenyl group in 5CB-d/sub 11/ are tested against the experimental spectra. The dihedral angle, defined by the planes containing the rings of the biphenyl group, is found to be 30 +- 2/sup 0/ for 5DB-d/sub 11/. Experiments are also described for 4,4'-d/sub 2/-biphenyl, 4,4' - dibromo-biphenyl, and unsubstituted biphenyl.

  2. Theoretical Study of the Electrostatic and Steric Effects on the Spectroscopic Characteristics of the Metal-Ligand Unit of Heme Proteins. 2. C-O Vibrational Frequencies, 17O Isotropic Chemical Shifts, and Nuclear Quadrupole Coupling Constants

    PubMed Central

    Kushkuley, Boris; Stavrov, Solomon S.

    1997-01-01

    The quantum chemical calculations, vibronic theory of activation, and London-Pople approach are used to study the dependence of the C-O vibrational frequency, 17O isotropic chemical shift, and nuclear quadrupole coupling constant on the distortion of the porphyrin ring and geometry of the CO coordination, changes in the iron-carbon and iron-imidazole distances, magnitude of the iron displacement out of the porphyrin plane, and presence of the charged groups in the heme environment. It is shown that only the electrostatic interactions can cause the variation of all these parameters experimentally observed in different heme proteins, and the heme distortions could modulate this variation. The correlations between the theoretically calculated parameters are shown to be close to the experimentally observed ones. The study of the effect of the electric field of the distal histidine shows that the presence of the four C-O vibrational bands in the infrared absorption spectra of the carbon monoxide complexes of different myoglobins and hemoglobins can be caused by the different orientations of the different tautomeric forms of the distal histidine. The dependence of the 17O isotropic chemical shift and nuclear quadrupole coupling constant on pH and the distal histidine substitution can be also explained from the same point of view. PMID:9017215

  3. Modern NMR Spectroscopy.

    ERIC Educational Resources Information Center

    Jelinski, Lynn W.

    1984-01-01

    Discusses direct chemical information that can be obtained from modern nuclear magnetic resonance (NMR) methods, concentrating on the types of problems that can be solved. Shows how selected methods provide information about polymers, bipolymers, biochemistry, small organic molecules, inorganic compounds, and compounds oriented in a magnetic…

  4. Autonomous driving in NMR.

    PubMed

    Perez, Manuel

    2017-01-01

    The automatic analysis of NMR data has been a much-desired endeavour for the last six decades, as it is the case with any other analytical technique. This need for automation has only grown as advances in hardware; pulse sequences and automation have opened new research areas to NMR and increased the throughput of data. Full automatic analysis is a worthy, albeit hard, challenge, but in a world of artificial intelligence, instant communication and big data, it seems that this particular fight is happening with only one technique at a time (let this be NMR, MS, IR, UV or any other), when the reality of most laboratories is that there are several types of analytical instrumentation present. Data aggregation, verification and elucidation by using complementary techniques (e.g. MS and NMR) is a desirable outcome to pursue, although a time-consuming one if performed manually; hence, the use of automation to perform the heavy lifting for users is required to make the approach attractive for scientists. Many of the decisions and workflows that could be implemented under automation will depend on the two-way communication with databases that understand analytical data, because it is desirable not only to query these databases but also to grow them in as much of an automatic manner as possible. How these databases are designed, set up and the data inside classified will determine what workflows can be implemented. Copyright © 2016 John Wiley & Sons, Ltd.

  5. Simultaneously cycled NMR spectroscopy.

    PubMed

    Parish, David M; Szyperski, Thomas

    2008-04-09

    Simultaneously cycled (SC) NMR was introduced and exemplified by implementing a set of 2-D [1H,1H] SC exclusive COSY (E.COSY) NMR experiments, that is, rf pulse flip-angle cycled (SFC), rf pulse phase cycled (SPC), and pulsed field gradient (PFG) strength cycled (SGC) E.COSY. Spatially selective 1H rf pulses were applied as composite pulses such that all steps of the respective cycles were affected simultaneously in different slices of the sample. This increased the data acquisition speed for an n-step cycle n-fold. A high intrinsic sensitivity was achieved by defining the cycles in a manner that the receiver phase remains constant for all steps of the cycle. Then, the signal resulting from applying the cycle corresponded to the sum of the signals from all steps of the cycle. Hence, the detected free induction decay did not have to be separated into the contributions arising from different slices, and read-out PFGs, which not only greatly reduce sensitivity but also negatively impact lineshapes in the direct dimension, were avoided. The current implementation of SFC E.COSY reached approximately 65% of the intrinsic sensitivity of the conventional phase cycled congener, making this experiment highly attractive whenever conventional data acquisition is sampling limited. Highly resolved SC E.COSY yielding accurate 3J-coupling values was recorded for the 416 Da plant alkaloid tomatidine within 80 min, that is, 12 times faster than with conventional phase cycled E.COSY. SC NMR is applicable for a large variety of NMR experiments and thus promises to be a valuable addition to the arsenal of approaches for tackling the NMR sampling problem to avoid sampling limited data acquisition.

  6. Earth's field NMR flow meter: preliminary quantitative measurements.

    PubMed

    Fridjonsson, Einar O; Stanwix, Paul L; Johns, Michael L

    2014-08-01

    In this paper we demonstrate the use of Earth's field NMR (EF NMR) combined with a pre-polarising permanent magnet for measuring fast fluid velocities. This time of flight measurement protocol has a considerable history in the literature; here we demonstrate that it is quantitative when employing the Earth's magnetic field for signal detection. NMR signal intensities are measured as a function of flow rate (0-1m/s) and separation distance between the permanent magnet and the EF NMR signal detection. These data are quantitatively described by a flow model, ultimately featuring no free parameters, that accounts for NMR signal modulation due to residence time inside the pre-polarising magnet, between the pre-polarising magnet and the detection RF coil and inside the detection coil respectively. The methodology is subsequently demonstrated with a metallic pipe in the pre-polarising region.

  7. Fluid-Rock Characterization and Interactions in NMR Well Logging

    SciTech Connect

    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.

  8. NMR imaging of materials

    SciTech Connect

    Vinegar, H.J.; Rothwell, W.P.

    1988-03-01

    A method for obtaining at least one petrophysical property of a porous material containing therein at least one preselected fluid, is described, comprising: NMR imaging the material to generate signals dependent upon both M(0) and T/sub 1/ and M(0) and T/sub 2/, generating separate M(0), T/sub 1/ and T/sub 2/ images from the signals, and determining at least one petrophysical property from at least one of the images.

  9. β-NMR

    NASA Astrophysics Data System (ADS)

    Morris, Gerald D.

    2014-01-01

    The β-NMR facility at ISAC is constructed specifically for experiments in condensed matter physics with radioactive ion beams. Using co-linear optical pumping, a 8Li + ion beam having a large nuclear spin polarisation and low energy (nominally 30 keV) can be generated. When implanted into materials these ions penetrate to shallow depths comparable to length scales of interest in the physics of surfaces and interfaces between materials. Such low-energy ions can be decelerated with simple electrostatic optics to enable depth-resolved studies of near-surface phenomena over the range of about 2-200 nm. Since the β-NMR signal is extracted from the asymmetry intrinsic to beta-decay and therefore monitors the polarisation of the radioactive probe nuclear magnetic moments, this technique is fundamentally a probe of local magnetism. More generally though, any phenomena which affects the polarisation of the implanted spins by, for example, a change in resonance frequency, line width or relaxation rate can be studied. The β-NMR program at ISAC currently supports a number of experiments in magnetism and superconductivity as well as novel ultra-thin heterostructures exhibiting properties that cannot occur in bulk materials. The general purpose zero/low field and high field spectrometers are configured to perform CW and pulsed RF nuclear magnetic resonance and spin relaxation experiments over a range of temperatures (3-300 K) and magnetic fields (0-9 T).

  10. Xenon for NMR biosensing--inert but alert.

    PubMed

    Schröder, Leif

    2013-01-01

    NMR studies with hyperpolarized xenon as functionalized sensor or contrast agent recently made notable progress in developing a new approach for detecting molecular markers and parameters of biomedical interest. Combining spin polarization enhancement with novel indirect detection schemes easily enables a 10⁷-fold signal gain, thus having promising potential to solve the NMR sensitivity problem in many applications. Though an inert element, ¹²⁹Xe has exquisite NMR properties to sense molecular environments. This review summarizes recent developments in the production of hyperpolarized xenon and the design and detection schemes of xenon biosensors.

  11. Characterization of Atmospheric Nitrate Dynamics in a Sub-Alpine Watershed Using Δ17O and δ15N

    NASA Astrophysics Data System (ADS)

    Bourgeois, I.; Savarino, J. P.; Clement, J. C.

    2015-12-01

    Remote subalpine ecosystems are usually characterized by nutrient-poor soils (Körner, 2004; Seastedt et al., 2004), making them particularly susceptible to undergo changes due to increased atmospheric N deposition (Vitousek et al., 1997; Preunkert et al., 2003). Using Δ17O, a conserved tracer of atmospheric nitrate (NO3 atm) (Michalski et al., 2004; Tsunogai et al., 2010), and δ15N, indicator of NO3 biological sources (Kendall, 1998; Casciotti et al., 2009), we measured the seasonal variations of NO3 atm stable isotopic composition and concentration in several streams and soils originating from two sub-alpine watersheds in the French Alps. Our objective was to investigate whether or not NO3 atm impacts the soil N biogeochemical cycle by increasing nutrients availability for plants and bacteria. We coupled streams and soils measurements with snow-pits sampling and aerosols collection at the Lautaret Pass, to better emphasize the correlation between atmospheric deposition, soil retention and watersheds effluents response. Our results reveal that different temporal dynamics govern our study site: stream measurements show that in spring, snowmelt results in a NO3 atm impulse, accounting for ca. 31 % of the total stream NO3 budget; on the opposite in autumn, NO3 atm accounts only for ca. 3 % of the total stream NO3 budget, highlighting the presence of a NO3 bacterial pool (nitrification). We also inferred from the observed Δ17O variations two distinct phenomena in the spring/summer season: a fast snow run-off and a slower snow-water percolation. The later is believed to affect most the soil N cycle as it directly increases available NO3. Measured soil leachates and extracts confirm this hypothesis and point out the potential importance of anthropogenic N deposition as on average 7 to 10 % of the soil solutions NO3 derives directly from the atmosphere.

  12. Solid-state NMR for bacterial biofilms

    NASA Astrophysics Data System (ADS)

    Reichhardt, Courtney; Cegelski, Lynette

    2014-04-01

    Bacteria associate with surfaces and one another by elaborating an extracellular matrix to encapsulate cells, creating communities termed biofilms. Biofilms are beneficial in some ecological niches, but also contribute to the pathogenesis of serious and chronic infectious diseases. New approaches and quantitative measurements are needed to define the composition and architecture of bacterial biofilms to help drive the development of strategies to interfere with biofilm assembly. Solid-state nuclear magnetic resonance (NMR) is uniquely suited to the examination of insoluble and complex macromolecular and whole-cell systems. This article highlights three examples that implement solid-state NMR to deliver insights into bacterial biofilm composition and changes in cell-wall composition as cells transition to the biofilm lifestyle. Most recently, solid-state NMR measurements provided a total accounting of the protein and polysaccharide components in the extracellular matrix of an Escherichia coli biofilm and transformed our qualitative descriptions of matrix composition into chemical parameters that permit quantitative comparisons among samples. We present additional data for whole biofilm samples (cells plus the extracellular matrix) that complement matrix-only analyses. The study of bacterial biofilms by solid-state NMR is an exciting avenue ripe with many opportunities and we close the article by articulating some outstanding questions and future directions in this area.

  13. Fluid-Rock Characterization and Interactions in NMR Well Logging

    SciTech Connect

    Hirasaki, George J.; Mohanty, Kishore K.

    2003-02-10

    The objective of this project was to characterize the fluid properties and fluid-rock interactions which are needed for formation evaluation by NMR well logging. NMR well logging is finding wide use in formation evaluation. The formation parameters commonly estimated were porosity, permeability, and capillary bound water. Special cases include estimation of oil viscosity, residual oil saturation, location of oil/water contact, and interpretation on whether the hydrocarbon is oil or gas.

  14. Soils, Pores, and NMR

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    Within Cluster A, Partial Project A1, the pore space exploration by means of Nuclear Magnetic Resonance (NMR) plays a central role. NMR is especially convenient since it probes directly the state and dynamics of the substance of interest: water. First, NMR is applied as relaxometry, where the degree of saturation but also the pore geometry controls the NMR signature of natural porous systems. Examples are presented where soil samples from the Selhausen, Merzenhausen (silt loams), and Kaldenkirchen (sandy loam) test sites are investigated by means of Fast Field Cycling Relaxometry at different degrees of saturation. From the change of the relaxation time distributions with decreasing water content and by comparison with conventional water retention curves we conclude that the fraction of immobile water is characterized by T1 < 5 ms. Moreover, the dependence of the relaxation rate on magnetic field strength allows the identification of 2D diffusion at the interfaces as the mechanism which governs the relaxation process (Pohlmeier et al. 2009). T2 relaxation curves are frequently measured for the rapid characterization of soils by means of the CPMG echo train. Basically, they contain the same information about the pore systems like T1 curves, since mostly the overall relaxation is dominated by surface relaxivity and the surface/volume ratio of the pores. However, one must be aware that T2 relaxation is additionally affected by diffusion in internal gradients, and this can be overcome by using sufficiently short echo times and low magnetic fields (Stingaciu et al. 2009). Second, the logic continuation of conventional relaxation measurements is the 2-dimensional experiment, where prior to the final detection of the CPMG echo train an encoding period is applied. This can be T1-encoding by an inversion pulse, or T2 encoding by a sequence of 90 and 180° pulses. During the following evolution time the separately encoded signals can mix and this reveals information about

  15. NMR Investigation of Filler Effects of (Gamma) Irradiation in Polyurethane Adhesives

    SciTech Connect

    Chinn, S C; Gjersing, E L; Maxwell, R S; Cohenour, R

    2007-06-11

    Polyurethane and polyester elastomers have been used for decades in a wide variety of applications, from seat cushion foams to prosthetic materials to high performance adhesives. Adiprene LW-520 is a polyurethane-based adhesive used in a number of U. S. Department of Energy applications. Several investigations have been performed to determine aging properties of polyurethanes. For example, {sup 1}H nuclear magnetic resonance (NMR) relaxation times have been shown to be sensitive to thermal degradation in polyurethanes. Detailed information about the exact nature of the oxidative thermal degradation in related materials has also been obtained via {sup 17}O and {sup 13}C NMR, with additional insight into morphological changes being obtained using {sup 1}H spin diffusion experiments. Radiation has also been shown to change the physical and mechanical properties of the polymers; in fact many polyurethanes are cured using radiation to affect the isocyanate and free radical reactive groups, thus controlling the properties such as thermal or solvent resistance.

  16. The AGB star nucleosynthesis in the light of the recent 17O ( p ,α)14N and 18O ( p ,α)15N reaction rate determinations

    NASA Astrophysics Data System (ADS)

    Palmerini, S.; Sergi, M. L.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Spitaleri, C.

    2015-02-01

    Presolar grains form in the cold and dusty envelopes of Asymptotic Giant Branch (AGB) stars. These solides, once that have been ejected by stellar winds, come to us as inclusions in meteorites providing invaluable benchmarks and constraints for our knowledge of low temeperature H-burning in stars. The Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of the 17O ( p ,α)14N and 18O ( p ,α)15N reactions. Moreover, the strength of the 65 keV resonance in the 17O ( p ,α)14N reaction, measured by means of the THM, has been used to renormalize the corresponding resonance strength in the 17O + p radiative capture channel. The new estimates of the reaction rates have been introduced into calculations of AGB star nucleosynthesis and the results have been compared with geochemical analysis of "presolar" grains to determine their impact on astrophysical environments.

  17. Simple quantitative structure-property relationship (QSPR) modeling of 17O carbonyl chemical shifts in substituted benzaldehydes compared to DFT and empirical approaches.

    PubMed

    Kiralj, Rudolf; Ferreira, Márcia M C

    2008-07-10

    The geometry of 50 substituted benzaldehydes was optimized at the semiempirical PM3 level, and various electronic and steric descriptors accounting for properties of the benzene ring, aldehyde group, and their connecting carbon-carbon bond were calculated. Quantitative structure-property relationships (QSPR) between (17)O carbonyl chemical shifts and these descriptors were established using partial least-squares regression and principal component regression. These two parsimonious QSPR models were comparable with the literature empirical model and DFT (density functional theory) and capable of predicting (17)O chemical shifts for 10 benzaldehydes. Principal component analysis, hierarchical cluster analysis, and crystal structure data retrieved from the Cambridge Structural Database were additional methods for chemical verification of the regression models. The QSPR models are recommended as being more reliable than and superior to the empirical and DFT models due to the results of all validations, simplicity, and short time that regressions need for (17)O shift prediction.

  18. Atmospheric measurements of Δ17O in CO2 in Göttingen, Germany reveal a seasonal cycle driven by biospheric uptake

    NASA Astrophysics Data System (ADS)

    Hofmann, M. E. G.; Horváth, B.; Schneider, L.; Peters, W.; Schützenmeister, K.; Pack, A.

    2017-02-01

    The triple oxygen isotope composition of tropospheric CO2 might be a promising new tracer for terrestrial gross carbon fluxes. This notion is based on global box modeling of its abundance, and on highly challenging and therefore very sparse measurements of 16O, 17O and 18O in CO2 in the lower atmosphere. Here, we present additional high-precision triple oxygen isotope measurements of ambient air CO2 sampled in Göttingen (NW Germany) over the course of 2 years and of two air samples taken on top of the Brocken Mountain (1140 m, NW Germany). Göttingen differs from other locations where Δ17O was measured by its proximity to both urban sources of CO2, and to extensive uptake of CO2 by vegetation. In our analysis, we specifically try to discern this latter influence on our measurements, and to distinguish it from other known sources of variation in Δ17O. Our triple oxygen isotope data are reported as Δ17O values relative to a CO2-water equilibration line with Δ17O = ln (δ17O + 1) - 0.5229 × ln (δ18O + 1). We report an average of -0.02 ± 0.05‰ (SD) in the first year and -0.12 ± 0.04‰ (SD) in the second year of our measurements. This year-to-year difference is higher than expected based on other available Δ17O records, but careful scrutiny of our measurement approach did not reveal obvious analytical biases, leaving this aspect of our record unexplained. After removing the year-to-year trend, our time series shows a statistically robust seasonal cycle with maximum values in June/July and an amplitude (peak-to-trough) of 0.13 ± 0.02‰. We compare our observational data to a revised triple oxygen isotope mass balance ;box; model of tropospheric CO2 where we reconcile both 18O/16O and 17O/16O fractionation processes. We also compare them to Göttingen-specific output from a three-dimensional transport model simulation of Δ17O in CO2 performed with the Tracer Model 5 (TM5). Both the modeled isofluxes at the surface, and the modeled stratospheric, fossil

  19. High-Precision Measurement of The Oxygen Isotopic Composition of Tropospheric O2: Implications for Δ17O of air as a Biosignature

    NASA Astrophysics Data System (ADS)

    Young, E. D.; Ziegler, K.

    2006-05-01

    Here we present high-precision measurements of 18O/16O and 17O/16O in samples of tropospheric O2 using a standard calibrated with measurements of terrestrial and extraterrestrial rock samples. These new data provide a measure of Δ17O on an absolute scale that aids in the interpretation of the cause of the disparity in Δ17O between O2 in the troposphere and terrestrial rocks. We measured the isotopic composition of four separate aliquotes of ground-level air O2. Oxygen was isolated from air cryogenically using molecular sieve substrates. Correction was made for the influence of Ar scattered across the Faraday collectors (~0.06 per mil in δ17O) of the gas- source mass spectrometer. The reference gas used as an internal standard was calibrated against terrestrial rock samples and meteorites analyzed using infrared laser heating fluorination. All results are reported as linearized delta values (signified with a prime superscript symbol). With a mean terrestrial rock Δ17O'of 0.00 ‰ ± 0.02 we obtain Δ17O values of -0.25 ‰ ± 0.04 1σ, -0.22 ‰ ± 0.03, and -0.23 ‰ ± 0.05 for 5 mesosiderite meteorites, 7 pallasites, and 12 HED meteorites, respectively. The latter meteorite data are consistent with results from three other laboratories and serve to establish the absolute scale for the air O2 measurements. Our results for the O2 samples give a mean linearized δ18O' of 23.237 ‰ ± 0.008 1 std err (corresponding to a normal, non-linearized δ18O SMOW value of 23.509 ‰), a mean δ17O' of 11.922 ‰ ± 0.018, and a mean linearized Δ17O' of -0.347 ‰ ± 0.018 based on a rock-water terrestrial fractionation reference line with a slope (β) of 0.528. The latter is the exponent in a normal fractionation law described by the relation α17=(α18)β. This result can be reconciled with the suggestion by Young et al (2002) that the whole of the departure in Δ17O' of tropospheric O2 relative to terrestrial rocks can be attributed to respiration (a Δ17O Dole effect

  20. Study of the 17O(n,α)14C reaction: Extension of the Trojan Horse Method to neutron induced reactions

    NASA Astrophysics Data System (ADS)

    Guardo, G. L.; Lamia, L.; Spitaleri, C.; Gulino, M.; Tang, X. D.; Bucher, B.; Burjan, V.; Cherubini, S.; Couder, M.; Davies, P.; deBoer*, R.; Fang, X.; Goldberg, V. Z.; Hons, Z.; Kroha, V.; Lamm, L.; La Cognata, M.; Li, C.; Ma, C.; Mrazek, J.; Mukhamedzhanov, A. M.; Notani, M.; OBrien, S.; Pizzone, R. G.; Rapisarda, G. G.; Roberson, D.; Sergi, M. L.; Tan, W.; Thompson, I. J.; Wiescher, M.

    2014-05-01

    The experimental study of the 17O(n,α)14C reaction has been performed in the energy range 0-350 keV. This reaction could play an important role in explaining heavy elements (s-process) nucleosynthesis in various astrophysical scenario. To overcome the practical problems arising from the neutrons production, a new application of the Trojan Horse Method has been recently suggested. In more details, the 17O(n,α)14C reaction has been studied using the quasi-free 2H(17O,α14C)1H reaction, induced at an energy of 43.5 MeV. The measurement allows one to investigate the ℓ=3, 75 keV resonance (E*=8.125 MeV, Jπ=5-), absent in the available direct measurements because of centrifugal suppression effects.

  1. A Review of the Principles and Applications of the NMR Technique for Near-Surface Characterization

    NASA Astrophysics Data System (ADS)

    Behroozmand, Ahmad A.; Keating, Kristina; Auken, Esben

    2015-01-01

    This paper presents a comprehensive review of the recent advances in nuclear magnetic resonance (NMR) measurements for near-surface characterization using laboratory, borehole, and field technologies. During the last decade, NMR has become increasingly popular in near-surface geophysics due to substantial improvements in instrumentation, data processing, forward modeling, inversion, and measurement techniques. This paper starts with a description of the principal theory and applications of NMR. It presents a basic overview of near-surface NMR theory in terms of its physical background and discusses how NMR relaxation times are related to different relaxation processes occurring in porous media. As a next step, the recent and seminal near-surface NMR developments at each scale are discussed, and the limitations and challenges of the measurement are examined. To represent the growth of applications of near-surface NMR, case studies in a variety of different near-surface environments are reviewed and, as examples, two recent case studies are discussed in detail. Finally, this review demonstrates that there is a need for continued research in near-surface NMR and highlights necessary directions for future research. These recommendations include improving the signal-to-noise ratio, reducing the effective measurement dead time, and improving production rate of surface NMR (SNMR), reducing the minimum echo time of borehole NMR (BNMR) measurements, improving petrophysical NMR models of hydraulic conductivity and vadose zone parameters, and understanding the scale dependency of NMR properties.

  2. Resonance strength measurement at astrophysical energies: The {sup 17}O(p,α){sup 14}N reaction studied via Trojan Horse Method

    SciTech Connect

    Sergi, M. L. La Cognata, M.; Pizzone, R. G.; Spitaleri, C.; Lamia, L.; Rapisarda, G. G.; Mukhamedzhanov, A.; Irgaziev, B.; Tang, X. D.; Wiescher, M.; Mrazek, J.; Kroha, V.

    2015-10-15

    In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on {sup 17}O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the {sup 17}O(p,α){sup 14}N reaction via the THM by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. Two measurements will be described and the experimental THM cross sections will be shown for both experiments.

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

    PubMed

    Konuma, Tsuyoshi; Harada, Erisa; Sugase, Kenji

    2015-12-01

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

  4. Magic Angle Spinning NMR Metabolomics

    SciTech Connect

    Zhi Hu, Jian

    2016-01-01

    Nuclear Magnetic Resonance (NMR) spectroscopy is a non-destructive, quantitative, reproducible, untargeted and unbiased method that requires no or minimal sample preparation, and is one of the leading analytical tools for metabonomics research [1-3]. The easy quantification and the no need of prior knowledge about compounds present in a sample associated with NMR are advantageous over other techniques [1,4]. 1H NMR is especially attractive because protons are present in virtually all metabolites and its NMR sensitivity is high, enabling the simultaneous identification and monitoring of a wide range of low molecular weight metabolites.

  5. Benchmarking NMR experiments: A relational database of protein pulse sequences

    NASA Astrophysics Data System (ADS)

    Senthamarai, Russell R. P.; Kuprov, Ilya; Pervushin, Konstantin

    2010-03-01

    Systematic benchmarking of multi-dimensional protein NMR experiments is a critical prerequisite for optimal allocation of NMR resources for structural analysis of challenging proteins, e.g. large proteins with limited solubility or proteins prone to aggregation. We propose a set of benchmarking parameters for essential protein NMR experiments organized into a lightweight (single XML file) relational database (RDB), which includes all the necessary auxiliaries (waveforms, decoupling sequences, calibration tables, setup algorithms and an RDB management system). The database is interfaced to the Spinach library ( http://spindynamics.org), which enables accurate simulation and benchmarking of NMR experiments on large spin systems. A key feature is the ability to use a single user-specified spin system to simulate the majority of deposited solution state NMR experiments, thus providing the (hitherto unavailable) unified framework for pulse sequence evaluation. This development enables predicting relative sensitivity of deposited implementations of NMR experiments, thus providing a basis for comparison, optimization and, eventually, automation of NMR analysis. The benchmarking is demonstrated with two proteins, of 170 amino acids I domain of αXβ2 Integrin and 440 amino acids NS3 helicase.

  6. An oxygen-17 dynamic NMR study of the Pr-DOTA complex.

    PubMed

    Fusaro, Luca; Luhmer, Michel

    2014-01-21

    The complex between (17)O-enriched DOTA (tetraazacyclododecanetetraacetic acid) and praseodymium(III) (Pr(3+)) was studied in aqueous solution by variable-temperature (17)O NMR at 14.1 T. pH effects as well as the influence of metal ions free in solution were investigated. At low temperature, the so-called TSAP and SAP conformations give rise to distinct signals for the oxygen atoms coordinated to the metal ion (O2); coalescence occurs between 20 and 30 °C. In contrast, a single signal was detected for the noncoordinated oxygen atoms (O1) in the entire investigated temperature range, i.e. between -3 and 135 °C. At high temperature, the spectra exhibit signal broadening that reveals the interchange of the O1 and O2 oxygen atoms of the carboxylate groups. The linewidths measured for O1 were deconvolved into contributions from quadrupole relaxation and chemical exchange, allowing the corresponding activation barriers to be determined. The present (17)O dynamic NMR study provides the first quantitative experimental data characterizing the interchange of the oxygen atoms in a DOTA chelate of a lanthanide metal ion. The activation entropy of this process is negligible and the activation enthalpy is found to range between 66 and 77 kJ mol(-1), depending on the pH and the presence of free Pr(3+) ions in solution. These data support the results of a previous computational study according to which the exchange mechanism involves the internal rotation of the carboxylate groups.

  7. Some nitrogen-14 NMR studies in solids

    SciTech Connect

    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.

  8. Protein structure determination from NMR chemical shifts.

    PubMed

    Cavalli, Andrea; Salvatella, Xavier; Dobson, Christopher M; Vendruscolo, Michele

    2007-06-05

    NMR spectroscopy plays a major role in the determination of the structures and dynamics of proteins and other biological macromolecules. Chemical shifts are the most readily and accurately measurable NMR parameters, and they reflect with great specificity the conformations of native and nonnative states of proteins. We show, using 11 examples of proteins representative of the major structural classes and containing up to 123 residues, that it is possible to use chemical shifts as structural restraints in combination with a conventional molecular mechanics force field to determine the conformations of proteins at a resolution of 2 angstroms or better. This strategy should be widely applicable and, subject to further development, will enable quantitative structural analysis to be carried out to address a range of complex biological problems not accessible to current structural techniques.

  9. Jointly deriving NMR surface relaxivity and pore size distributions by NMR relaxation experiments on partially desaturated rocks

    NASA Astrophysics Data System (ADS)

    Mohnke, O.; Hughes, B.

    2014-06-01

    Nuclear magnetic resonance (NMR) relaxometry is a geophysical method widely used in borehole and laboratory applications to nondestructively infer transport and storage properties of rocks and soils as it is directly sensitive to the water/oil content and pore sizes. However, for inferring pore sizes, NMR relaxometry data need to be calibrated with respect to a surface interaction parameter, surface relaxivity, which depends on the type and mineral constituents of the investigated rock. This study introduces an inexpensive and quick alternative to the classical calibration methods, e.g., mercury injection, pulsed field gradient (PFG) NMR, or grain size analysis, which allows for jointly estimating NMR surface relaxivity and pore size distributions using NMR relaxometry data from partially desaturated rocks. Hereby, NMR relaxation experiments are performed on the fully saturated sample and on a sample partially drained at a known differential pressure. Based on these data, the (capillary) pore radius distribution and surface relaxivity are derived by joint optimization of the Brownstein-Tarr and the Young-Laplace equation assuming parallel capillaries. Moreover, the resulting pore size distributions can be used to predict water retention curves. This inverse modeling approach—tested and validated using NMR relaxometry data measured on synthetic porous borosilicate samples with known petrophysical properties (i.e., permeability, porosity, inner surfaces, pore size distributions)—yields consistent and reproducible estimates of surface relaxivity and pore radii distributions. Also, subsequently calculated water retention curves generally correlate well with measured water retention curves.

  10. Analysis and theoretical modeling of the 18O enriched carbon dioxide spectrum by CRDS near 1.35 μm: (I) 16O12C18O, 16O12C17O, 12C16O2 and 13C16O2

    NASA Astrophysics Data System (ADS)

    Kassi, S.; Karlovets, E. V.; Tashkun, S. A.; Perevalov, V. I.; Campargue, A.

    2017-01-01

    The room temperature absorption spectrum of 18O enriched carbon dioxide has been recorded by very high-sensitivity Cavity Ring Down spectroscopy between 6977 and 7918 cm-1 (1.43-1.26 μm). The achieved sensitivity (noise equivalent absorption αmin 8×10-11 cm-1) has allowed for the detection of more than 8600 lines belonging to 166 bands of eleven carbon dioxide isotopologues. Line intensities of the weakest observed transitions are on the order of 2×10-30 cm/molecule. In this first part, we present the results relative to the 16O12C18O, 16O12C17O, 12C16O2 and 13C16O2 isotopologues. Their absorption lines were rovibrationally assigned on the basis of the predictions of their respective effective Hamiltonian model. Overall 5476 lines were measured and assigned to 93 bands. Forty nine of them, all belonging to 16O12C18O and 16O12C17O, are reported for the first time. The studied spectral region is formed by ΔP=10-12 series of transitions, where P=2V1+V2+3V3 is the polyad number (Vi are vibrational quantum numbers). The spectroscopic parameters of 58 bands of 16O12C18O and 16O12C17O were determined from a fit of the measured line positions. An inter- and an intrapolyad resonance perturbation were identified and analyzed in the 16O12C18O spectrum. The comparison with the line positions and line intensities included in the AMES line list is discussed. Global fits of the line intensities were performed in order to (i) improve the ΔP=10 and 11 sets of the effective dipole moment parameters of 16O12C18O and the ΔP=11 set of parameters of 16O12C17O and (ii) derive for the first time the ΔP=10 and 12 parameters of 16O12C17O and 16O12C18O, respectively.

  11. THz Dynamic Nuclear Polarization NMR

    PubMed Central

    Nanni, Emilio A.; Barnes, Alexander B.; Griffin, Robert G.; Temkin, Richard J.

    2013-01-01

    Dynamic nuclear polarization (DNP) increases the sensitivity of nuclear magnetic resonance (NMR) spectroscopy by using high frequency microwaves to transfer the polarization of the electrons to the nuclear spins. The enhancement in NMR sensitivity can amount to a factor of well above 100, enabling faster data acquisition and greatly improved NMR measurements. With the increasing magnetic fields (up to 23 T) used in NMR research, the required frequency for DNP falls into the THz band (140–600 GHz). Gyrotrons have been developed to meet the demanding specifications for DNP NMR, including power levels of tens of watts; frequency stability of a few megahertz; and power stability of 1% over runs that last for several days to weeks. Continuous gyrotron frequency tuning of over 1 GHz has also been demonstrated. The complete DNP NMR system must include a low loss transmission line; an optimized antenna; and a holder for efficient coupling of the THz radiation to the sample. This paper describes the DNP NMR process and illustrates the THz systems needed for this demanding spectroscopic application. THz DNP NMR is a rapidly developing, exciting area of THz science and technology. PMID:24639915

  12. Observation and interpretation of Δ17O variations in terrestrial rocks - Response to the comment by Miller et al. on the paper by Pack & Herwartz (2014)

    NASA Astrophysics Data System (ADS)

    Pack, Andreas; Herwartz, Daniel

    2015-05-01

    There are four aspects of our paper that are criticized by Miller et al. (comment) that we attempt to clarify in this reply. Our first point is that δ17O of different materials (water, rocks, tropospheric and stratospheric O2, CO2 gas, meteorites, animal body water, biogenic carbonate, bioapatite, etc.) should be reported on the same scale. This requires that each laboratory calibrate its reference O2 (currently O2 is the gas of choice for high precision Δ17O studies) relative to O2 extracted from VSMOW water. The choice of water as standard has historical reasons and is somewhat arbitrary. Any other reference material could be chosen (e.g., San Carlos olivine, NBS-19 calcite, NBS-28 quartz, or tropospheric O2) as a scale for δ17O. VSMOW, however, is the accepted scale for δ18O and we suggest it should also be used as primary standard and a scale for δ17O, too.

  13. Improved Direct Measurement of the 64.5 keV Resonance Strength in the 17O (p ,α )14N Reaction at LUNA

    NASA Astrophysics Data System (ADS)

    Bruno, C. G.; Scott, D. A.; Aliotta, M.; Formicola, A.; Best, A.; Boeltzig, A.; Bemmerer, D.; Broggini, C.; Caciolli, A.; Cavanna, F.; Ciani, G. F.; Corvisiero, P.; Davinson, T.; Depalo, R.; Di Leva, A.; Elekes, Z.; Ferraro, F.; Fülöp, Zs.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, Gy.; Imbriani, G.; Junker, M.; Menegazzo, R.; Mossa, V.; Pantaleo, F. R.; Piatti, D.; Prati, P.; Somorjai, E.; Straniero, O.; Strieder, F.; Szücs, T.; Takács, M. P.; Trezzi, D.; LUNA Collaboration

    2016-09-01

    The 17O (p ,α ) 14N reaction plays a key role in various astrophysical scenarios, from asymptotic giant branch stars to classical novae. It affects the synthesis of rare isotopes such as 17O and 18F, which can provide constraints on astrophysical models. A new direct determination of the ER=64.5 keV resonance strength performed at the Laboratory for Underground Nuclear Astrophysics (LUNA) accelerator has led to the most accurate value to date ω γ =10.0 ±1. 4stat±0. 7syst neV , thanks to a significant background reduction underground and generally improved experimental conditions. The (bare) proton partial width of the corresponding state at Ex=5672 keV in 18F is Γp=35 ±5stat±3syst neV . This width is about a factor of 2 higher than previously estimated, thus leading to a factor of 2 increase in the 17O (p , α ) 14N reaction rate at astrophysical temperatures relevant to shell hydrogen burning in red giant and asymptotic giant branch stars. The new rate implies lower 17O/16O ratios, with important implications on the interpretation of astrophysical observables from these stars.

  14. Measurements of 18O18O and 17O18O in the atmosphere and the role of isotope-exchange reactions

    NASA Astrophysics Data System (ADS)

    Yeung, Laurence Y.; Young, Edward D.; Schauble, Edwin A.

    2012-09-01

    Of the six stable isotopic variants of O2, only three are measured routinely. Observations of natural variations in 16O18O/16O16O and 16O17O/16O16O ratios have led to insights in atmospheric, oceanographic, and paleoclimate research. Complementary measurements of the exceedingly rare 18O18O and 17O18O isotopic variants might therefore broaden our understanding of oxygen cycling. Here we describe a method to measure natural variations in these multiply substituted isotopologues of O2. Its accuracy is demonstrated by measuring isotopic effects for Knudsen diffusion and O2 electrolysis in the laboratory that are consistent with theoretical predictions. We then report the first measurements of 18O18O and 17O18O proportions relative to the stochastic distribution of isotopes (i.e., Δ36 and Δ35 values, respectively) in tropospheric air. Measured enrichments in 18O18O and 17O18O yield Δ36 = 2.05 ± 0.24‰ and Δ35 = 1.4 ± 0.5‰ (2σ). Based on the results of our electrolysis experiment, we suggest that autocatalytic O(3P) + O2 isotope exchange reactions play an important role in regulating the distribution of 18O18O and 17O18O in air. We constructed a box model of the atmosphere and biosphere that includes the effects of these isotope exchange reactions, and we find that the biosphere exerts only a minor influence on atmospheric Δ36 and Δ35 values. O(3P) + O2 isotope exchange in the stratosphere and troposphere is therefore expected to govern atmospheric Δ36 and Δ35 values on decadal timescales. These results suggest that the `clumped' isotopic composition of atmospheric O2in ice core records is sensitive to past variations in atmospheric dynamics and free-radical chemistry.

  15. Rotational analysis of the Ångström system (B1Σ+-A1Π) in the rare 13C17O isotopologue

    NASA Astrophysics Data System (ADS)

    Hakalla, Rafał; Zachwieja, Mirosław

    2012-02-01

    Although yet unobserved in the very rare 13C17O isotopologue, the Ångström system (B1Σ+-A1Π) was obtained under high resolution as an emission spectrum using a conventional spectroscopic technique. The emission from the discharge was observed with a plane grating spectrograph and recorded by a photomultiplier tube. In total, 192 transition wave numbers belonging to two bands (0-1 and 0-2) were precisely measured and rotationally analyzed. This method allowed us to determine the merged rotational constants B0 = 1.8131941(58) cm-1 and D0 = 5.5620(46) × 10-6 cm-1 and the individual molecular constant B1 = 1.471059(47) cm-1, D1 = 5.315(64) × 10-6 cm-1, B2 = 1.451762(13) cm-1, D2 = 7.812(16) × 10-6 cm-1 for the as yet unanalyzed 13C17O molecule B1Σ+ and A1Π states, respectively. The band origins σ of the Ångström system in the 13C17O molecule were also calculated. Numerous rotational perturbations observed in the A1Π state in 13C17O molecule have been identified and analyzed in detail. The suspected candidates responsible for these irregularities were indicated by means of a graph of the rovibronic levels of the neighboring states based on the estimated term value in the 13C17O molecule. The values of these perturbations have also been defined for both the e- and f-parity of the A1Π(v = 1 and 2) state. Simultaneously, the B1Σ+ state was observed to be quite regular up to the observed Jmax level.

  16. Protein NMR structures refined without NOE data.

    PubMed

    Ryu, Hyojung; Kim, Tae-Rae; Ahn, SeonJoo; Ji, Sunyoung; Lee, Jinhyuk

    2014-01-01

    The refinement of low-quality structures is an important challenge in protein structure prediction. Many studies have been conducted on protein structure refinement; the refinement of structures derived from NMR spectroscopy has been especially intensively studied. In this study, we generated flat-bottom distance potential instead of NOE data because NOE data have ambiguity and uncertainty. The potential was derived from distance information from given structures and prevented structural dislocation during the refinement process. A simulated annealing protocol was used to minimize the potential energy of the structure. The protocol was tested on 134 NMR structures in the Protein Data Bank (PDB) that also have X-ray structures. Among them, 50 structures were used as a training set to find the optimal "width" parameter in the flat-bottom distance potential functions. In the validation set (the other 84 structures), most of the 12 quality assessment scores of the refined structures were significantly improved (total score increased from 1.215 to 2.044). Moreover, the secondary structure similarity of the refined structure was improved over that of the original structure. Finally, we demonstrate that the combination of two energy potentials, statistical torsion angle potential (STAP) and the flat-bottom distance potential, can drive the refinement of NMR structures.

  17. The Carlisle Lakes-type chondrites: A new grouplet with high. Delta. sup 17 O and evidence for nebular oxidation

    SciTech Connect

    Weisberg, M.K. Brooklyn Coll., NY ); Prinz, M. ); Kojima, Hideyasu; Yanai, Keizo ); Clayton, R.N.; Mayeda, T.K. )

    1991-09-01

    Carlisle Lakes, ALH85151, and Y75302 are similar ungrouped chondrites which have petrologic and bulk compositional similarities to the ordinary chondrites, but are more oxidized; and their oxygen isotopic compositions differ. They represent a new grouplet which the authors call the Carlisle Lakes-type chondrites. They have the highest {Delta}{sup 17}O values (up to 2.91) measured to date. The whole chondrites and most of their chondrules plot on the same mass fractionation line on an oxygen 3-isotope diagram. They are olivine rich (>70 vol%), essentially metal free, and most olivine is FeO rich, equilibrated at Fa{sub 38}. Rare olivine and pyroxene grains in chondrules and fragments are zoned, and these are important in discerning the history of these chondrites. The zoning does not appear to have formed during crystallization from a melt droplet chondrule, but post-dated chondrule formation. Two hypotheses are postulated to explain the zoning: (1) parent-body thermal metamorphism and (2) nebular gas-solid exchange reactions accompanied by condensation of new FeO-rich olivine, utilizing existing olivine surfaces as nucleation sites. The occurrence of steep Fe-Mg compositional gradients of core-to-rim profiles, oscillatory zoning in olivine, fayalitic rims of Fa{sub 45} that exceed instead of approach the equilibrium composition of the matrix (Fa{sub 38}), and olivine-filled veins in zoned pyroxenes are more compatible with the nebular hypothesis. The Carlisle Lakes-type chondrites may have originally been derived from an ordinary chondrite-like precursor which was later oxidized, prior to its final lithification. However, the oxygen isotopic compositions of the whole chondrites and most of their chondrules suggest that the precursor probably formed in an oxygen isotopically distinct environment.

  18. Covalency in La2CuO4: A study of 17O hyperfine couplings in the paramagnetic phase

    NASA Astrophysics Data System (ADS)

    Walstedt, R. E.; Cheong, S.-W.

    2001-07-01

    17O nuclear magnetic resonance spectra from single crystals of La2CuO4 are reported for temperatures ranging from 285 to 800 K. Hyperfine tensor data for the planar sites are analyzed using a spin Hamiltonian model that includes spin-orbit coupling effects. The results show a 7.7% hybridization effect of the oxygen 2pσ orbital from a single copper neighbor, in good agreement with recent density-functional (DF) calculations by Hüsser et al. (HSSM). A large, positive isotropic shift component is also reported, presumably originating from the contact interaction with a hybridized 2s orbital component. First-order quadrupolar-splitting data lead to complete characterization of the electric-field gradient (EFG) tensor, which varies only slightly with temperature up to 800 K. EFG tensors for both doped and undoped La2CuO4 are fitted with a two-component model, which incorporates a substantial anisotropy in for the 2pσ wave functions, an effect that originated in the DF calculations of HSSM. This analysis reveals an increased charge density on the planar oxygens for the superconducting phase, in accord with the original Zhang-Rice model. However, the increase is found to correspond to only ~80% of the nominal doped-hole density, corroborating a similar conclusion reached recently by Hammel et al. Regarding the anomalous spin HF interaction reported in a previous paper for the weakly ferromagnetic state, the present results show that its effects extend all the way to and slightly beyond the orthorhombic-tetragonal phase boundary (TO-T~=550 K). Further, the predominant 2s contact HF interaction reported here supports the notion, suggested earlier, that a 2s admixture underlies the anomaly. However, the basic mechanism of the anomaly remains obscure.

  19. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1989-01-01

    This report covers the progress made on the title project during the past reporting period. Four major areas of inquiry are being pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines the authors are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. The authors have been reinvestigating the prospects of using zero field NMR types of techniques for two dimensional NMR structural analysis of complex organic solids such as coals. Currently MAS spin rates are not sufficiently high to permit zero field in high field NMR for protons in typical organic solids, however they are compatible with {sup 13}C-{sup 13}C dipolar couplings. In collaboration with Dr. Robert Tycko of AT T Bell Laboratories, inventor of the zero field in high field NMR method, the authors have performed the first zero field in high field {sup 13}C NMR experiments. These results are described. 9 refs., 2 figs.

  20. NMR Logging to Estimate Hydraulic Conductivity in Unconsolidated Aquifers.

    PubMed

    Knight, Rosemary; Walsh, David O; Butler, James J; Grunewald, Elliot; Liu, Gaisheng; Parsekian, Andrew D; Reboulet, Edward C; Knobbe, Steve; Barrows, Mercer

    2016-01-01

    Nuclear magnetic resonance (NMR) logging provides a new means of estimating the hydraulic conductivity (K) of unconsolidated aquifers. The estimation of K from the measured NMR parameters can be performed using the Schlumberger-Doll Research (SDR) equation, which is based on the Kozeny-Carman equation and initially developed for obtaining permeability from NMR logging in petroleum reservoirs. The SDR equation includes empirically determined constants. Decades of research for petroleum applications have resulted in standard values for these constants that can provide accurate estimates of permeability in consolidated formations. The question we asked: Can standard values for the constants be defined for hydrogeologic applications that would yield accurate estimates of K in unconsolidated aquifers? Working at 10 locations at three field sites in Kansas and Washington, USA, we acquired NMR and K data using direct-push methods over a 10- to 20-m depth interval in the shallow subsurface. Analysis of pairs of NMR and K data revealed that we could dramatically improve K estimates by replacing the standard petroleum constants with new constants, optimal for estimating K in the unconsolidated materials at the field sites. Most significant was the finding that there was little change in the SDR constants between sites. This suggests that we can define a new set of constants that can be used to obtain high resolution, cost-effective estimates of K from NMR logging in unconsolidated aquifers. This significant result has the potential to change dramatically the approach to determining K for hydrogeologic applications.

  1. Oxygen-17 NMR in solids by dynamic-angle spinning and double rotation

    NASA Astrophysics Data System (ADS)

    Chmelka, B. F.; Mueller, K. T.; Pines, A.; Stebbins, J.; Wu, Y.; Zwanziger, J. W.

    1989-05-01

    IT is widely lamented that despite its unqualified success with spin-1/2 nuclei such as 13C, 29Si and31P, the popular NMR technique of magic-angle spinning (MAS) has experienced a somewhat restricted applicability among quadrupolar nuclei such as 17O, 23Na and 27A1 (refs 1-3). The resolution in the central (1/2 lrarr-1/2) transition of these non-integer quadrupolar spins under MAS is thought to be limited primarily by second-order quadrupolar broadening. Such effects of second-order spatial anisotropy cannot be eliminated by rotation about a fixed axis or by multiple-pulse techniques4,5. More general mechanisms of sample reorientation (refs 6-8 and A. Samoson and A. Pines, manuscript in preparation) can, however, make high-resolution NMR of quadrupolar nuclei feasible. MAS is implemented by spinning a sample about a single axis so that second-rank spherical harmonics (which give rise to first-order broadening through anisotropy of electrical and magnetic interactions) are averaged away. But dynamic-angle-spinning (DAS) and double-rotation (DOR) NMR involve spinning around two axes, averaging away both the second- and fourth-rank spherical harmonics, which are responsible for second-order broadening. Here we present the application of these new techniques to 17O in two minerals, cristobalite (SiO2) and diopside (CaMgSi2O6). This work goes beyond previous results on 23Na (ref. 8) by showing the first experimental results using DAS and by demonstrating the application of DOR to the resolution of distinct oxygen sites in an important class of oxide materials.

  2. An Analysis of a Commercial Furniture Refinisher: A Comprehensive Introductory NMR Experiment.

    ERIC Educational Resources Information Center

    Markow, Peter G.; Cramer, John A.

    1983-01-01

    Describes a comprehensive nuclear magnetic resonance (NMR) experiment designed to introduce undergraduate organic chemistry students to measurement/interpretation of NMR parameters. Students investigate chemical shift analysis, spin-spin coupling, peak integrations, effect of deuterium oxide extraction, and comparisons with literature spectra;…

  3. Polarization transfer NMR imaging

    DOEpatents

    Sillerud, Laurel O.; van Hulsteyn, David B.

    1990-01-01

    A nuclear magnetic resonance (NMR) image is obtained with spatial information modulated by chemical information. The modulation is obtained through polarization transfer from a first element representing the desired chemical, or functional, information, which is covalently bonded and spin-spin coupled with a second element effective to provide the imaging data. First and second rf pulses are provided at first and second frequencies for exciting the imaging and functional elements, with imaging gradients applied therebetween to spatially separate the nuclei response for imaging. The second rf pulse is applied at a time after the first pulse which is the inverse of the spin coupling constant to select the transfer element nuclei which are spin coupled to the functional element nuclei for imaging. In a particular application, compounds such as glucose, lactate, or lactose, can be labeled with .sup.13 C and metabolic processes involving the compounds can be imaged with the sensitivity of .sup.1 H and the selectivity of .sup.13 C.

  4. Understanding NMR Chemical Shifts

    NASA Astrophysics Data System (ADS)

    Jameson, Cynthia J.

    1996-10-01

    The NMR chemical shift serves as a paradigm for molecular electronic properties. We consider the factors that determine the general magnitudes of the shifts, the state of the art in theoretical calculations, the nature of the shielding tensor, and the multidimensional shielding surface that describes the variation of the shielding with nuclear positions. We also examine the nature of the intermolecular shielding surface as a general example of a supermolecule property surface. The observed chemical shift in the zero-pressure limit is determined not only by the value of the shielding at the equilibrium geometry, but the dynamic average over the multidimensional shielding surface during rotation and vibration of the molecule. In the gas, solution, or adsorbed phase it is an average of the intermolecular shielding surface over all the configurations of the molecule with its neighbors. The temperature dependence of the chemical shift in the isolated molecule, the changes upon isotopic substitution, the changes with environment, are well characterized experimentally so that quantum mechanical descriptions of electronic structure and theories related to dynamics averaging of any electronic property can be subjected to stringent test.

  5. Oxygen isotopes in nitrate: New reference materials for 18O:17O:16O measurements and observations on nitrate-water equilibration

    USGS Publications Warehouse

    Böhlke, J.K.; Mroczkowski, S.J.; Coplen, T.B.

    2003-01-01

    Despite a rapidly growing literature on analytical methods and field applications of O isotope-ratio measurements of NO3- in environmental studies, there is evidence that the reported data may not be comparable because reference materials with widely varying ?? 18O values have not been readily available. To address this problem, we prepared large quantities of two nitrate salts with contrasting O isotopic compositions for distribution as reference materials for O isotope-ratio measurements: USGS34 (KNO3) with low ??18O and USGS35 (NaNO3) with high ??18O and 'mass-independent' ??17O. The procedure used to produce USGS34 involved equilibration of HNO3 with 18O-depleted meteoric water. Nitric acid equilibration is proposed as a simple method for producing laboratory NO3- reference materials with a range of ??18O values and normal (mass-dependent) 18O: 17O:16O variation. Preliminary data indicate that the equilibrium O isotope-fractionation factor (??) between [NO 3-] and H2O decreases with increasing temperature from 1.0215 at 22??C to 1.0131 at 100??C. USGS35 was purified from the nitrate ore deposits of the Atacama Desert in Chile and has a high 17O:18O ratio owing to its atmospheric origin. These new reference materials, combined with previously distributed NO3- isotopic reference materials IAEA-N3 (=IAEA-NO-3) and USGS32, can be used to calibrate local laboratory reference materials for determining offset values, scale factors, and mass-independent effects on N and O isotope-ratio measurements in a wide variety of environmental NO 3- samples. Preliminary analyses yield the following results (normalized with respect to VSMOW and SLAP, with reproducibilities of ??0.2-0.3???, 1??): IAEA-N3 has ??18O = +25.6??? and ??17O = +13.2??? USGS32 has ?? 18O = +25.7??? USGS34 has ??18O = -27. 9??? and ??17O = -14.8??? and USGS35 has ?? 18O = +57.5??? and ??17O = +51.5???.

  6. Measurement of the reaction 17O(α,n)20Ne and its impact on the s process in massive stars

    NASA Astrophysics Data System (ADS)

    Best, A.; Beard, M.; Görres, J.; Couder, M.; deBoer, R.; Falahat, S.; Güray, R. T.; Kontos, A.; Kratz, K.-L.; LeBlanc, P. J.; Li, Q.; O'Brien, S.; Özkan, N.; Pignatari, M.; Sonnabend, K.; Talwar, R.; Tan, W.; Uberseder, E.; Wiescher, M.

    2013-04-01

    Background: The ratio between the rates of the reactions 17O(α,n)20Ne and 17O(α,γ)21Ne determines whether 16O is an efficient neutron poison for the s process in massive stars, or if most of the neutrons captured by 16O(n,γ) are recycled into the stellar environment. This ratio is of particular relevance to constrain the s process yields of fast rotating massive stars at low metallicity.Purpose: Recent results on the (α,γ) channel have made it necessary to measure the (α,n) reaction more precisely and investigate the effect of the new data on s process nucleosynthesis in massive stars.Method: The 17O(α,n(0+1)) reaction has been measured with a moderating neutron detector. In addition, the (α,n1) channel has been measured independently by observation of the characteristic 1633 keV γ transition in 20Ne. The reaction cross section was determined with a simultaneous R-matrix fit to both channels. (α,n) and (α,γ) resonance strengths of states lying below the covered energy range were estimated using their known properties from the literature.Result: The reaction channels 17O(α,n0)20Ne and 17O(α,n1γ)20Ne were measured in the energy range Eα=800 keV to 2300 keV. A new 17O(α,n) reaction rate was deduced for the temperature range 0.1 GK to 10 GK. At typical He burning temperatures, the combination of the new (α,n) rate with a previously measured (α,γ) rate gives approximately the same ratio as current compilations. The influence on the nucleosynthesis of the s process in massive stars at low metallicity is discussed.Conclusions: It was found that in He burning conditions the (α,γ) channel is strong enough to compete with the neutron channel. This leads to a less efficient neutron recycling compared to a previous suggestion of a very weak (α,γ) channel. S process calculations using our rates confirm that massive rotating stars do play a significant role in the production of elements up to Sr, but they strongly reduce the s process contribution to

  7. Flow units from integrated WFT and NMR data

    SciTech Connect

    Kasap, E.; Altunbay, M.; Georgi, D.

    1997-08-01

    Reliable and continuous permeability profiles are vital as both hard and soft data required for delineating reservoir architecture. They can improve the vertical resolution of seismic data, well-to-well stratigraphic correlations, and kriging between the well locations. In conditional simulations, permeability profiles are imposed as the conditioning data. Variograms, covariance functions and other geostatistical indicators are more reliable when based on good quality permeability data. Nuclear Magnetic Resonance (NMR) logging and Wireline Formation Tests (WFT) separately generate a wealth of information, and their synthesis extends the value of this information further by providing continuous and accurate permeability profiles without increasing the cost. NMR and WFT data present a unique combination because WFTs provide discrete, in situ permeability based on fluid-flow, whilst NMR responds to the fluids in the pore space and yields effective porosity, pore-size distribution, bound and moveable fluid saturations, and permeability. The NMR permeability is derived from the T{sub 2}-distribution data. Several equations have been proposed to transform T{sub 2} data to permeability. Regardless of the transform model used, the NMR-derived permeabilities depend on interpretation parameters that may be rock specific. The objective of this study is to integrate WFT permeabilities with NMR-derived, T{sub 2} distribution-based permeabilities and thereby arrive at core quality, continuously measured permeability profiles. We outlined the procedures to integrate NMR and WFT data and applied the procedure to a field case. Finally, this study advocates the use of hydraulic unit concepts to extend the WFT-NMR derived, core quality permeabilities to uncored intervals or uncored wells.

  8. Compact orthogonal NMR field sensor

    DOEpatents

    Gerald, II, Rex E.; Rathke, Jerome W.

    2009-02-03

    A Compact Orthogonal Field Sensor for emitting two orthogonal electro-magnetic fields in a common space. More particularly, a replacement inductor for existing NMR (Nuclear Magnetic Resonance) sensors to allow for NMR imaging. The Compact Orthogonal Field Sensor has a conductive coil and a central conductor electrically connected in series. The central conductor is at least partially surrounded by the coil. The coil and central conductor are electrically or electro-magnetically connected to a device having a means for producing or inducing a current through the coil and central conductor. The Compact Orthogonal Field Sensor can be used in NMR imaging applications to determine the position and the associated NMR spectrum of a sample within the electro-magnetic field of the central conductor.

  9. Integrative NMR for biomolecular research.

    PubMed

    Lee, Woonghee; Cornilescu, Gabriel; Dashti, Hesam; Eghbalnia, Hamid R; Tonelli, Marco; Westler, William M; Butcher, Samuel E; Henzler-Wildman, Katherine A; Markley, John L

    2016-04-01

    NMR spectroscopy is a powerful technique for determining structural and functional features of biomolecules in physiological solution as well as for observing their intermolecular interactions in real-time. However, complex steps associated with its practice have made the approach daunting for non-specialists. We introduce an NMR platform that makes biomolecular NMR spectroscopy much more accessible by integrating tools, databases, web services, and video tutorials that can be launched by simple installation of NMRFAM software packages or using a cross-platform virtual machine that can be run on any standard laptop or desktop computer. The software package can be downloaded freely from the NMRFAM software download page ( http://pine.nmrfam.wisc.edu/download_packages.html ), and detailed instructions are available from the Integrative NMR Video Tutorial page ( http://pine.nmrfam.wisc.edu/integrative.html ).

  10. NMR study of strontium binding by a micaceous mineral.

    PubMed

    Bowers, Geoffrey M; Ravella, Ramesh; Komarneni, Sridhar; Mueller, Karl T

    2006-04-13

    The nature of strontium binding by soil minerals directly affects the transport and sequestration/remediation of radioactive strontium species released from leaking high-level nuclear waste storage tanks. However, the molecular-level structure of strontium binding sites has seldom been explored in phyllosilicate minerals by direct spectroscopic means and is not well-understood. In this work, we use solid-state NMR to analyze strontium directly and indirectly in a fully strontium-exchanged synthetic mica of nominal composition Na(4)Mg(6)Al(4)Si(4)O(20)F(4). Thermogravimetric analysis, X-ray diffraction analysis, and NMR evidence supports that heat treatment at 500 degrees C for 4 h fully dehydrates the mica, creating a hydrogen-free interlayer. Analysis of the strontium NMR spectrum of the heat-treated mica shows a single strontium environment with a quadrupolar coupling constant of 9.02 MHz and a quadrupolar asymmetry parameter of 1.0. These quadrupolar parameters are consistent with a highly distorted and asymmetric coordination environment that would be produced by strontium cations without water in the coordination sphere bound deep within the ditrigonal holes. Evidence for at least one additional strontium environment, where proton-strontium couplings may occur, was found via a (1)H-(87)Sr transfer of populations by double resonance NMR experiment. We conclude that the strontium cations in the proton-free interlayer are observable by (87)Sr NMR and bound through electrostatic interactions as nine coordinate inner-sphere complexes sitting in the ditrigonal holes. Partially hydrated strontium cations invisible to direct (87)Sr NMR are also present and located on the external mica surfaces, which are known to hydrate upon exposure to atmospheric moisture. These results demonstrate that modern pulsed NMR techniques and high fields can be used effectively to provide structural details of strontium binding by phyllosilicate minerals.

  11. NMR Study of Strontium Binding by a Micaceous Mineral

    SciTech Connect

    Bowers, Geoffrey M.; Ravella, Ramesh; Komarneni, S.; Mueller, Karl T.

    2006-04-13

    The nature of strontium binding by soil minerals directly affects the transport and sequestration/remediation of radioactive strontium species released from leaking high-level nuclear waste storage tanks. However, the molecular-level structure of strontium binding sites has seldom been explored in phyllosilicate minerals by direct spectroscopic means and is not well-understood. In this work, we use solid-state NMR to analyze strontium directly and indirectly in a fully strontium-exchanged synthetic mica of nominal composition Na4Mg6Al4Si4O20F4. Thermogravimetric analysis, X-ray diffraction analysis, and NMR evidence supports that heat treatment at 500 °C for 4 h fully dehydrates the mica, creating a hydrogen-free interlayer. Analysis of the strontium NMR spectrum of the heat-treated mica shows a single strontium environment with a quadrupolar coupling constant of 9.02 MHz and a quadrupolar asymmetry parameter of 1.0. These quadrupolar parameters are consistent with a highly distorted and asymmetric coordination environment that would be produced by strontium cations without water in the coordination sphere bound deep within the ditrigonal holes. Evidence for at least one additional strontium environment, where proton-strontium couplings may occur, was found via a 1H-87Sr transfer of populations by double resonance NMR experiment. We conclude that the strontium cations in the proton-free interlayer are observable by 87Sr NMR and bound through electrostatic interactions as nine coordinate inner-sphere complexes sitting in the ditrigonal holes. Partially hydrated strontium cations invisible to direct 87Sr NMR are also present and located on the external mica surfaces, which are known to hydrate upon exposure to atmospheric moisture. These results demonstrate that modern pulsed NMR techniques and high fields can be used effectively to provide structural details of strontium binding by phyllosilicate minerals.

  12. NMR characterization of thin films

    DOEpatents

    Gerald II, Rex E.; Klingler, Robert J.; Rathke, Jerome W.; Diaz, Rocio; Vukovic, Lela

    2010-06-15

    A method, apparatus, and system for characterizing thin film materials. The method, apparatus, and system includes a container for receiving a starting material, applying a gravitational force, a magnetic force, and an electric force or combinations thereof to at least the starting material, forming a thin film material, sensing an NMR signal from the thin film material and analyzing the NMR signal to characterize the thin film of material.

  13. Optical pumping and xenon NMR

    SciTech Connect

    Raftery, M.D.

    1991-11-01

    Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping {sup 129}Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the {sup 131}Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

  14. Optical pumping and xenon NMR

    SciTech Connect

    Raftery, M.D.

    1991-11-01

    Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping [sup 129]Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the [sup 131]Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

  15. Multispectral Analysis of NMR Imagery

    NASA Technical Reports Server (NTRS)

    Butterfield, R. L.; Vannier, M. W. And Associates; Jordan, D.

    1985-01-01

    Conference paper discusses initial efforts to adapt multispectral satellite-image analysis to nuclear magnetic resonance (NMR) scans of human body. Flexibility of these techniques makes it possible to present NMR data in variety of formats, including pseudocolor composite images of pathological internal features. Techniques do not have to be greatly modified from form in which used to produce satellite maps of such Earth features as water, rock, or foliage.

  16. NMR Imaging of Elastomeric Materials

    DTIC Science & Technology

    1990-11-30

    on ’everse if necessary and identify by block number) FIELD GROUP SUB-GROUP nuclear magnetic resonance , imaging, elastomers, tires, composites, porous...correspondence should be addressed 1i ABSTRACT Nuclear magnetic resonance images have been obtained for four porous glass disks of different porosities...INDEX HEADINGS: NMR imaging Porous materials Spin relaxation 2. I0J INTRODUCTION Nuclear magnetic resonance (NMR) imaging has seen increasing use in the

  17. Crystal structure and proton conductivity of BaSn0.6Sc0.4O3-δ : insights from neutron powder diffraction and solid-state NMR spectroscopy.

    PubMed

    Kinyanjui, Francis G; Norberg, Stefan T; Knee, Christopher S; Ahmed, Istaq; Hull, Stephen; Buannic, Lucienne; Hung, Ivan; Gan, Zhehong; Blanc, Frédéric; Grey, Clare P; Eriksson, Sten G

    2016-04-14

    The solid-state synthesis and structural characterisation of perovskite BaSn1-x Sc x O3-δ (x = 0.0, 0.1, 0.2, 0.3, 0.4) and its corresponding hydrated ceramics are reported. Powder and neutron X-ray diffractions reveal the presence of cubic perovskites (space group Pm3m) with an increasing cell parameter as a function of scandium concentration along with some indication of phase segregation. (119)Sn and (45)Sc solid-state NMR spectroscopy data highlight the existence of oxygen vacancies in the dry materials, and their filling upon hydrothermal treatment with D2O. It also indicates that the Sn(4+) and Sc(3+) local distribution at the B-site of the perovskite is inhomogeneous and suggests that the oxygen vacancies are located in the scandium dopant coordination shell at low concentrations (x ≤ 0.2) and in the tin coordination shell at high concentrations (x ≥ 0.3). (17)O NMR spectra on (17)O enriched BaSn1-x Sc x O3-δ materials show the existence of Sn-O-Sn, Sn-O-Sc and Sc-O-Sc bridging oxygen environments. A further room temperature neutron powder diffraction study on deuterated BaSn0.6Sc0.4O3-δ refines the deuteron position at the 24k crystallographic site (x, y, 0) with x = 0.579(3) and y = 0.217(3) which leads to an O-D bond distance of 0.96(1) Å and suggests tilting of the proton towards the next nearest oxygen. Proton conduction was found to dominate in wet argon below 700 °C with total conductivity values in the range 1.8 × 10(-4) to 1.1 × 10(-3) S cm(-1) between 300 and 600 °C. Electron holes govern the conduction process in dry oxidizing conditions, whilst in wet oxygen they compete with protonic defects leading to a wide mixed conduction region in the 200 to 600 °C temperature region, and a suppression of the conductivity at higher temperature.

  18. A consensus on protein structure accuracy in NMR?

    PubMed

    Billeter, Martin

    2015-02-03

    The precision of an NMR structure may be manipulated by calculation parameters such as calibration factors. Its accuracy is, however, a different issue. In this issue of Structure, Buchner and Güntert present "consensus structure bundles," where precision analysis allows estimation of accuracy.

  19. Identification and MS-assisted interpretation of genetically influenced NMR signals in human plasma

    PubMed Central

    2013-01-01

    Nuclear magnetic resonance spectroscopy (NMR) provides robust readouts of many metabolic parameters in one experiment. However, identification of clinically relevant markers in 1H NMR spectra is a major challenge. Association of NMR-derived quantities with genetic variants can uncover biologically relevant metabolic traits. Using NMR data of plasma samples from 1,757 individuals from the KORA study together with 655,658 genetic variants, we show that ratios between NMR intensities at two chemical shift positions can provide informative and robust biomarkers. We report seven loci of genetic association with NMR-derived traits (APOA1, CETP, CPS1, GCKR, FADS1, LIPC, PYROXD2) and characterize these traits biochemically using mass spectrometry. These ratios may now be used in clinical studies. PMID:23414815

  20. Elastic scattering measurement for the system 17O + 58Ni at Coulomb barrier energies with silicon strip detectors exploiting ASIC electronics

    NASA Astrophysics Data System (ADS)

    Signorini, C.; Mazzocco, M.; Molini, P.; Pierroutsakou, D.; Boiano, C.; Manea, C.; Strano, E.; Torresi, D.; Di Meo, P.; Nicoletto, M.; Boiano, A.; Glodariu, T.; Grebosz, J.; Guglielmetti, A.; La Commara, M.; Parascandolo, C.; Parascandolo, L.; Sandoli, M.; Soramel, F.; Stroe, L.; Toniolo, N.; Veronese, F.

    2013-03-01

    The quasi elastic scattering of a 17O projectile from a 58Ni target has been studied at beam energies ranging from 42.5 to 55.0 MeV in 2.5 MeV steps. The total reaction cross sections were derived from the measured angular distributions by using an optical model fit within the coupled-channel code FRESCO. These cross sections are very similar to those measured for 17F (loosely bound by 0.6 MeV), mirror nucleus of 17O (tightly bound by 4.14 MeV). This outcome points out that, in this energy range, the small binding energy of the 17F valence proton has negligible influence onto the reactivity of such a loosely bound projectile, contrary to simple expectations, and to what observed for other loosely bound nuclei. The reaction dynamics seems to be influenced mainly by the Coulomb interaction which is similar for both mirror projectiles.

  1. Electron paramagnetic resonance crystallography of 17O-enriched oxycobaltomyoglobin: Stereoelectronic structure of the cobalt dioxygen system

    PubMed Central

    Dickinson, L. Charles; Chien, James C. W.

    1980-01-01

    An electron paramagnetic resonance crystallographic study was made on oxycobaltomyoglobin with the dioxygen ligand enriched to 19.1% in 17O. There are two spectroscopically distinct cobalt dioxygen species. The less abundant species, II (40%), has nonequivalent oxygen atoms with superhyperfine tensors OAα = (5, -67.5, 22.4)G and OAβ = (5.4, -83.3, 30.3)G. Together with the previously reported 59Co hyperfine tensor [Chien, J. C. W. & Dickinson, L. C. (1972) Proc. Natl. Acad. Sci. USA 69, 2783-2787], the orbital spin densities are found to be Oα(pη) = 0.48, Oα(pζ) = -0.11, Oβ(pη) = 0.74, Oβ(pζ) = -0.16, Co(dxz) = -0.01, Co(dyz) = 0.06 for a total electron density of 1.01. The O—O axis is directed toward His-E7, suggesting a possible hydrogen bonding interaction which may contribute to the nonequivalency of the oxygen atoms; its projection approximately bisects N1—Fe—N2. The z axis of the CoA tensor is tilted at an angle of 28° from the heme normal, resulting in a Co—O—O angle of 120°. The more abundant species, I (60%), has equivalent oxygen atoms with OAγ = (12, -72.5, 20)G and orbital spin densities of Oγ(pη) = 0.54, Oγ(pζ) = -0.05, Co(dxz) = -0.02, Co(dyz) = 0.09 for a total spin density of 1.10. Although the direction cosines for this molecule cannot be precisely determined, the projection of its O—O axis approximately bisects N2—Fe—N3 and is parallel to the imidazole ring of His-F8. Increase of temperature changes g, CoA, and OA values, with the largest effect seen with OA. This temperature dependence indicates averaging of the two bond structures which are stabilized at 77 K. PMID:6246485

  2. Development of Cu1.3Mn1.7O4 spinel coating on ferritic stainless steel for solid oxide fuel cell interconnects

    NASA Astrophysics Data System (ADS)

    Hosseini, N.; Abbasi, M. H.; Karimzadeh, F.; Choi, G. M.

    2015-01-01

    To protect solid oxide fuel cells (SOFCs) from chromium poisoning and to improve area specific resistance (ASR), Cu1.3Mn1.7O4 is thermally grown on AISI 430 ferritic stainless steel. The samples are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy equipped with energy dispersive spectroscopy (FESEM-EDS) and 4-probe ASR tests. The results show that the coating not only decreases the ASR considerably, but also acts as a barrier to mitigate the sub-scale growth and to prevent chromium migration through the coating and the cathode. The EDS analysis reveals that a mixed spinel region is formed between the coating and oxide scale after 500 h oxidation at 750 °C causing a noticeable decrease in oxygen diffusivity through this layer and subsequent decline in sub-scale growth rate. The ASR of uncoated sample is measured to be 63.5 mΩ cm2 after 500 h oxidation, while the Cu1.3Mn1.7O4 spinel coated sample shows a value of 19.3 mΩ cm2 representing ∼70% reduction compared to the uncoated sample. It is proposed that the high electrical conductivity of Cu1.3Mn1.7O4 (140 S cm-1), reduction of oxide scale growth, and good bonding between the coating and substrate contribute to the substantial ASR reduction for the coated sample.

  3. Study of the 17O(n, α )14C Reaction: Extension of the Trojan Horse Method to the Neutrons Induced Reactions

    NASA Astrophysics Data System (ADS)

    Guardo, G. L.; Spitaleri, C.; Lamia, L.; Gulino, M.; Tang, X.; Bucher, B.; Burjan, V.; Couder, M.; Davies, P.; deBoer, R.; Fang, X.; Kroha, V.; La Cognata, M.; Ma, C.; Mrazek, J.; Mukhamedzhanov, A.; Notani, M.; Obrien, S.; Pizzone, R. G.; Rapisarda, G. G.; Roberson, D.; Sergi, M. L.; Tan, W.; Wiescher, M.

    The experimental study of the 17O(n, α )14C reaction has been performed in the energy range 0-350 keV. This reaction could play an important role in explaining heavy elements (s-process) nucleosynthesis in various astrophysical scenario. To overcome the practical problems arising from the neutrons production, a new application of the Trojan Horse Method has been recently suggested. In more details, the 17O(n, α )14C reaction has been studied using the quasi-free 2H(17O, α 14C)1H reaction, induced at an energy of 43.5 MeV. The measurement allows one to investigate the ℓ = 3, 75 keV resonance (E* = 8.125 MeV, Jπ = 5-), absent in the available direct measurements because of centrifugal suppression effects. Moreover, the results show that the contribution of the 166 and 236 keV resonances is in energy agreement with the available direct data. A clear contribution of the -7 keV subthreshold level is also present.

  4. Assessing the near threshold cross section of the 17O(n ,α )14C reaction by means of the Trojan horse method

    NASA Astrophysics Data System (ADS)

    Guardo, G. L.; Spitaleri, C.; Lamia, L.; Gulino, M.; La Cognata, M.; Tang, X.; deBoer, R.; Fang, X.; Goldberg, V.; Mrazek, J.; Mukhamedzhanov, A.; Notani, M.; Pizzone, R. G.; Rapisarda, G. G.; Sergi, M. L.; Wiescher, M.

    2017-02-01

    The study of the 17O(n ,α )14C reaction has been performed by means of the Trojan horse method (THM) applied to the quasifree 2H(17O,α 14C )1H reaction induced at a beam energy of 43.5 MeV. The THM allowed us to study the 8121-keV *18O resonant level, for which the previous THM investigation pointed out the ability of the method to overcome the centrifugal barrier suppression effects in the entrance channel. Here, in view of the developments of the method for resonant reactions, the detailed analysis of the performed experiment will be discussed, focusing on the extraction of the 8121-keV resonance strength for which no information is present in scientific literature. Moreover, the experimental results clearly show the excitation of the subthreshold level centered at -6 keV in the center-of-mass system, which is fundamental to determine the 17O(n ,α )14C reaction rate of astrophysical interest. Finally, a new recommended reaction rate is presented for future astrophysical application.

  5. 14N solid-state NMR: a sensitive probe of the local order in zeolites.

    PubMed

    Dib, Eddy; Mineva, Tzonka; Gaveau, Philippe; Alonso, Bruno

    2013-11-14

    Local order in as-synthesised zeolites templated by tetraalkylammonium cations is proven from solid-state (14)N NMR and related quadrupolar parameters, opening new perspectives in the study of porous materials.

  6. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1988-01-01

    This report covers the progress made on the title project during the current reporting period. Four major areas of inquiry are being pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines we are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. This quarter we have focused on variable temperature spin lattice relaxation measurements for several of the Argonne coals. 5 figs.

  7. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1988-01-01

    This report covers the progress made on the title project during the current reporting period. Four major areas of inquiry are being pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines we are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. This quarter we have focussed on spin lattice relaxation measurements for several of the Argonne coals. 2 figs., 1 tab.

  8. jsNMR: an embedded platform-independent NMR spectrum viewer.

    PubMed

    Vosegaard, Thomas

    2015-04-01

    jsNMR is a lightweight NMR spectrum viewer written in JavaScript/HyperText Markup Language (HTML), which provides a cross-platform spectrum visualizer that runs on all computer architectures including mobile devices. Experimental (and simulated) datasets are easily opened in jsNMR by (i) drag and drop on a jsNMR browser window, (ii) by preparing a jsNMR file from the jsNMR web site, or (iii) by mailing the raw data to the jsNMR web portal. jsNMR embeds the original data in the HTML file, so a jsNMR file is a self-transforming dataset that may be exported to various formats, e.g. comma-separated values. The main applications of jsNMR are to provide easy access to NMR data without the need for dedicated software installed and to provide the possibility to visualize NMR spectra on web sites.

  9. Medical applications of NMR imaging and NMR spectroscopy with stable isotopes. Summary

    SciTech Connect

    Matwiyoff, N.A.

    1983-01-01

    The current status of NMR imaging and NMR spectroscopy are summarized. For the most part examples from the March 1983 Puerto Rico symposium are used to illustrate the utility of NMR in medicine. 18 refs., 5 figs.

  10. NMR planar microcoil for microanalysis

    NASA Astrophysics Data System (ADS)

    Sorli, B.; Chateaux, J. F.; Quiquerez, L.; Bouchet-Fakri, L.; Briguet, A.; Morin, P.

    2006-11-01

    This article deals with the analysis of small sample volume by using a planar microcoil and a micromachined cavity. This microcoil is used as a nuclear magnetic resonance (NMR) radio frequency detection coil in order to perform in vitro NMR analysis of the sample introduced into the microcavity. It is a real challenging task to develop microsystem for NMR spectrum extraction for smaller and smaller sample volume. Moreover, it is advantageous that these microsystems could be integrated in a Micro Total Analysing System (μ -TAS) as an analysing tool. In this paper, NMR theory, description, fabrication process and electrical characterization of planar microcoils receiver are described. Results obtained on NMR microspectroscopy experiments have been performed on water and ethanol, using a 1 mm diameter planar coil. This microcoil is tuned and matched at 85.13 MHz which is the Larmor frequency of proton in a 2 T magnetic field. This paper has been presented at “3e colloque interdisciplinaire en instrumentation (C2I 2004)”, École Normale Supérieure de Cachan, 29 30 janvier 2004.

  11. Ligand screening by saturation-transfer difference (STD) NMR spectroscopy.

    SciTech Connect

    Krishnan, V V

    2005-04-26

    NMR based methods to screen for high-affinity ligands have become an indispensable tool for designing rationalized drugs, as these offer a combination of good experimental design of the screening process and data interpretation methods, which together provide unprecedented information on the complex nature of protein-ligand interactions. These methods rely on measuring direct changes in the spectral parameters, that are often simpler than the complex experimental procedures used to study structure and dynamics of proteins. The goal of this review article is to provide the basic details of NMR based ligand-screening methods, with particular focus on the saturation transfer difference (STD) experiment. In addition, we provide an overview of other NMR experimental methods and a practical guide on how to go about designing and implementing them.

  12. NMRFx Processor: a cross-platform NMR data processing program.

    PubMed

    Norris, Michael; Fetler, Bayard; Marchant, Jan; Johnson, Bruce A

    2016-08-01

    NMRFx Processor is a new program for the processing of NMR data. Written in the Java programming language, NMRFx Processor is a cross-platform application and runs on Linux, Mac OS X and Windows operating systems. The application can be run in both a graphical user interface (GUI) mode and from the command line. Processing scripts are written in the Python programming language and executed so that the low-level Java commands are automatically run in parallel on computers with multiple cores or CPUs. Processing scripts can be generated automatically from the parameters of NMR experiments or interactively constructed in the GUI. A wide variety of processing operations are provided, including methods for processing of non-uniformly sampled datasets using iterative soft thresholding. The interactive GUI also enables the use of the program as an educational tool for teaching basic and advanced techniques in NMR data analysis.

  13. Investigation of structure, vibrational and NMR spectra of oxycodone and naltrexone: A combined experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Tavakol, Hossein; Esfandyari, Maryam; Taheri, Salman; Heydari, Akbar

    2011-08-01

    In this work, two important opioid antagonists, naltrexone and oxycodone, were prepared from thebaine and were characterized by IR, 1H NMR and 13C NMR spectroscopy. Moreover, computational NMR and IR parameters were obtained using density functional theory (DFT) at B3LYP/6-311++G** level of theory. Complete NMR and vibrational assignment were carried out using the observed and calculated spectra. The IR frequencies and NMR chemical shifts, determined experimentally, were compared with those obtained theoretically from DFT calculations, showed good agreements. The RMS errors observed between experimental and calculated data for the IR absorptions are 85 and 105 cm -1, for the 1H NMR peaks are 0.87 and 0.17 ppm and for those of 13C NMR are 5.6 and 5.3 ppm, respectively for naltrexone and oxycodone.

  14. NMR-based analysis of protein-ligand interactions.

    PubMed

    Cala, Olivier; Guillière, Florence; Krimm, Isabelle

    2014-02-01

    Physiological processes are mainly controlled by intermolecular recognition mechanisms involving protein-protein and protein-ligand (low molecular weight molecules) interactions. One of the most important tools for probing these interactions is high-field solution nuclear magnetic resonance (NMR) through protein-observed and ligand-observed experiments, where the protein receptor or the organic compounds are selectively detected. NMR binding experiments rely on comparison of NMR parameters of the free and bound states of the molecules. Ligand-observed methods are not limited by the protein molecular size and therefore have great applicability for analysing protein-ligand interactions. The use of these NMR techniques has considerably expanded in recent years, both in chemical biology and in drug discovery. We review here three major ligand-observed NMR methods that depend on the nuclear Overhauser effect-transferred nuclear Overhauser effect spectroscopy, saturation transfer difference spectroscopy and water-ligand interactions observed via gradient spectroscopy experiments-with the aim of reporting recent developments and applications for the characterization of protein-ligand complexes, including affinity measurements and structural determination.

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

    NASA Astrophysics Data System (ADS)

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

    2006-01-01

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

  16. NMR study of mesomorphic solutions of cellulose derivatives

    SciTech Connect

    Dayan, S.; Fried, F.; Gilli, J.M.; Sixou, P.

    1983-01-01

    Highly concentrated solutions of hydroxypropylcellulose and cellulose acetate give mesomorphic phases in a precise range of temperatures and concentrations. The existence of an orientational anisotropy in such solutions induces typical parameters of the high-resolution NMR spectra (chemical shift, splitting) that are similar to those of liquid crystal spectra. In the present work, the high-resolution NMR spectra of nuclei belonging to the solute molecules (D/sub 2/O and trifluoroacetic acid) were recorded as a function of various physical parameters such as temperature, concentration, and temporal change of the solutions. The specific variation of the orientational degree of order for each mesophase is described. In the case of the cellulose acetate/trifluoroacetic acid solution, an order parameter is calculated and a model for the orientational organization of the solution is described. 34 references, 10 figures, 1 table.

  17. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1990-01-01

    This report covers the progress made on the title project and summarizes the accomplishments for the project period. Four major areas of inquiry have been pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines the authors are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. The authors have concentrated on a theoretical treatment of pairs of tightly coupled spin {1/2} nuclei under magic angle spinning conditions. The average Hamiltonian theory developed here is required for a quantitative understanding of two dimensional NMR experiments of such spin pairs in solids. These experiments in turn provide a means of determining connectivities between resonances in solid state NMR spectra. Development of these techniques will allow us to establish connectivities between functional components in coals. The complete description of these spin dynamics has turned out to be complex, and is necessary to provide a foundation upon which such experiments may be quantitatively interpreted in complex mixtures such as coals. 25 refs., 4 figs., 3 tabs.

  18. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1989-01-01

    This report covers the progress made on the title project and summarizes the accomplishments for the project period. Four major areas of inquiry have been pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concern how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coals model. Along the same lines we are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. During the last quarter the authors have concentrated on improvements in cross polarization (CP) sequences with a goal of making the CP process insensitive to experimental conditions such as the magic angle spinning (MAS) rate. In order to be able to use fields the order of 7.0 T or higher, CP efficiency must be maintained at MAS rates of over 10 kHz. The standard sequences have severe limitations at these rates which lead to intensity distortions in {sup 13}C CPMAS spectra. Thus in order to be able to take advantage of the increases in sensitivity and resolution that accompany high field operation, improvements in the NMR methods are required. The new sequences the authors are developing will be especially important for quantitative analysis of coal structure by {sup 13}C solid state NMR at high field strengths. 13 refs., 7 figs., 2 tabs.

  19. Computer Simulation of NMR Spectra.

    ERIC Educational Resources Information Center

    Ellison, A.

    1983-01-01

    Describes a PASCAL computer program which provides interactive analysis and display of high-resolution nuclear magnetic resonance (NMR) spectra from spin one-half nuclei using a hard-copy or monitor. Includes general and theoretical program descriptions, program capability, and examples of its use. (Source for program/documentation is included.)…

  20. Deuterium Exchange Kinetics by NMR.

    ERIC Educational Resources Information Center

    Roper, G. C.

    1985-01-01

    Describes a physical chemistry experiment which allows such concepts as kinetics, catalysis, isotope shifts, coupling constants, and the use of nuclear magnetic resonance (NMR) for quantitative work to be covered in the same exercise. Background information, experimental procedures used, and typical results obtained are included. (JN)

  1. Petrophysical applications of NMR imaging

    SciTech Connect

    Rothwell, W.P.; Vinegar, H.J.

    1985-12-01

    A system for obtaining high-resolution NMR images of oil field cores is described. Separate proton density and T/sub 2/ relaxation images are obtained to distinguish spatial variations of fluid-filled porosity and the physical nature of the pores. Results are presented for typical sandstones.

  2. Quantifying global atmospheric sulfate formation pathways utilizing observations and modeling of the oxygen isotopic composition (Δ17O) of sulfate aerosol (Invited)

    NASA Astrophysics Data System (ADS)

    Alexander, B.

    2010-12-01

    Sulfate is a major component of the atmospheric aerosol and drives the formation of new aerosol particles through nucleation. The implications for scattering of solar radiation and for cloud microphysics represent one of the largest uncertainties in current assessments of climate change. The specific formation pathway of secondary sulfate in the atmosphere has implications for climate, as only sulfate formed through gas-phase oxidation can nucleate new particles under favorable conditions, increasing aerosol number density. Sulfate produced in the aqueous phase is present in larger particles and does not lead to nucleation of new particles. The oxygen isotopic composition (Δ17O = δ17O - 0.52 x δ18O) of sulfate aerosol can be used as a means to quantify various sulfate production mechanisms in the atmosphere. Large-scale models of the atmosphere typically include sulfate production in the gas-phase by the hydroxyl radical (OH) and in cloud droplet by hydrogen peroxide (H2O2) and ozone (O3). Additional reaction pathways are considered minor and therefore neglected. While these models typically reproduce observations of sulfate aerosol concentration to within 20%, SO2 concentrations are overestimated by a factor of two or more. Here, I compare observations of the oxygen isotopic composition of sulfate aerosol collected at the surface at various locations around the world to calculated sulfate Δ17O in a global model. This model-measurement comparison is used to assess the global importance of sulfate production on alkaline sea-salt and dust aerosol, metal catalyzed oxidation by O2 in cloud droplets, and oxidation by halogen oxidizes. I will show how these additional sulfur oxidation pathways influence the global sulfur budget, to what degree they resolve the global model’s bias in SO2 concentrations, and how they influence the contribution of atmospheric sulfate produced in the gas-phase.

  3. Pulsed zero field NMR of solids and liquid crystals

    SciTech Connect

    Thayer, A.M.

    1987-02-01

    This work describes the development and applications to solids and liquid crystals of zero field nuclear magnetic resonance (NMR) experiments with pulsed dc magnetic fields. Zero field NMR experiments are one approach for obtaining high resolution spectra of amorphous and polycrystalline materials which normally (in high field) display broad featureless spectra. The behavior of the spin system can be coherently manipulated and probed in zero field with dc magnetic field pulses which are employed in a similar manner to radiofrequency pulses in high field NMR experiments. Nematic phases of liquid crystalline systems are studied in order to observe the effects of the removal of an applied magnetic field on sample alignment and molecular order parameters. In nematic phases with positive and negative magnetic susceptibility anisotropies, a comparison between the forms of the spin interactions in high and low fields is made. High resolution zero field NMR spectra of unaligned smectic samples are also obtained and reflect the symmetry of the liquid crystalline environment. These experiments are a sensitive measure of the motionally induced asymmetry in biaxial phases. Homonuclear and heteronuclear solute spin systems are compared in the nematic and smectic phases. Nonaxially symmetric dipolar couplings are reported for several systems. The effects of residual fields in the presence of a non-zero asymmetry parameter are discussed theoretically and presented experimentally. Computer programs for simulations of these and other experimental results are also reported. 179 refs., 75 figs.

  4. Optimal control in NMR spectroscopy: numerical implementation in SIMPSON.

    PubMed

    Tosner, Zdenek; Vosegaard, Thomas; Kehlet, Cindie; Khaneja, Navin; Glaser, Steffen J; Nielsen, Niels Chr

    2009-04-01

    We present the implementation of optimal control into the open source simulation package SIMPSON for development and optimization of nuclear magnetic resonance experiments for a wide range of applications, including liquid- and solid-state NMR, magnetic resonance imaging, quantum computation, and combinations between NMR and other spectroscopies. Optimal control enables efficient optimization of NMR experiments in terms of amplitudes, phases, offsets etc. for hundreds-to-thousands of pulses to fully exploit the experimentally available high degree of freedom in pulse sequences to combat variations/limitations in experimental or spin system parameters or design experiments with specific properties typically not covered as easily by standard design procedures. This facilitates straightforward optimization of experiments under consideration of rf and static field inhomogeneities, limitations in available or desired rf field strengths (e.g., for reduction of sample heating), spread in resonance offsets or coupling parameters, variations in spin systems etc. to meet the actual experimental conditions as close as possible. The paper provides a brief account on the relevant theory and in particular the computational interface relevant for optimization of state-to-state transfer (on the density operator level) and the effective Hamiltonian on the level of propagators along with several representative examples within liquid- and solid-state NMR spectroscopy.

  5. "Solvent Effects" in 1H NMR Spectroscopy.

    ERIC Educational Resources Information Center

    Cavaleiro, Jose A. S.

    1987-01-01

    Describes a simple undergraduate experiment in chemistry dealing with the "solvent effects" in nuclear magnetic resonance (NMR) spectroscopy. Stresses the importance of having students learn NMR spectroscopy as a tool in analytical chemistry. (TW)

  6. Protein-Inhibitor Interaction Studies Using NMR

    PubMed Central

    Ishima, Rieko

    2015-01-01

    Solution-state NMR has been widely applied to determine the three-dimensional structure, dynamics, and molecular interactions of proteins. The designs of experiments used in protein NMR differ from those used for small-molecule NMR, primarily because the information available prior to an experiment, such as molecular mass and knowledge of the primary structure, is unique for proteins compared to small molecules. In this review article, protein NMR for structural biology is introduced with comparisons to small-molecule NMR, such as descriptions of labeling strategies and the effects of molecular dynamics on relaxation. Next, applications for protein NMR are reviewed, especially practical aspects for protein-observed ligand-protein interaction studies. Overall, the following topics are described: (1) characteristics of protein NMR, (2) methods to detect protein-ligand interactions by NMR, and (3) practical aspects of carrying out protein-observed inhibitor-protein interaction studies. PMID:26361636

  7. Push-through Direction Injectin NMR Automation

    EPA Science Inventory

    Nuclear magnetic resonance (NMR) and mass spectrometry (MS) are the two major spectroscopic techniques successfully used in metabolomics studies. The non-invasive, quantitative and reproducible characteristics make NMR spectroscopy an excellent technique for detection of endogeno...

  8. Simultaneous analysis of 17O/16O, 18O/16O and 2H/1H of gypsum hydration water by cavity ring‐down laser spectroscopy

    PubMed Central

    Mather, Ian; Rolfe, James; Evans, Nicholas P.; Herwartz, Daniel; Staubwasser, Michael; Hodell, David A.

    2015-01-01

    Rationale The recent development of cavity ring‐down laser spectroscopy (CRDS) instruments capable of measuring 17O‐excess in water has created new opportunities for studying the hydrologic cycle. Here we apply this new method to studying the triple oxygen (17O/16O, 18O/16O) and hydrogen (2H/1H) isotope ratios of gypsum hydration water (GHW), which can provide information about the conditions under which the mineral formed and subsequent post‐depositional interaction with other fluids. Methods We developed a semi‐automated procedure for extracting GHW by slowly heating the sample to 400°C in vacuo and cryogenically trapping the evolved water. The isotopic composition (δ17O, δ18O and δ2H values) of the GHW is subsequently measured by CRDS. The extraction apparatus allows the dehydration of five samples and one standard simultaneously, thereby increasing the long‐term precision and sample throughput compared with previous methods. The apparatus is also useful for distilling brines prior to isotopic analysis. A direct comparison is made between results of 17O‐excess in GHW obtained by CRDS and fluorination followed by isotope ratio mass spectrometry (IRMS) of O2. Results The long‐term analytical precision of our method of extraction and isotopic analysis of GHW by CRDS is ±0.07‰ for δ17O values, ±0.13‰ for δ18O values and ±0.49‰ for δ2H values (all ±1SD), and ±1.1‰ and ±8 per meg for the deuterium‐excess and 17O‐excess, respectively. Accurate measurement of the 17O‐excess values of GHW, of both synthetic and natural samples, requires the use of a micro‐combustion module (MCM). This accessory removes contaminants (VOCs, H2S, etc.) from the water vapour stream that interfere with the wavelengths used for spectroscopic measurement of water isotopologues. CRDS/MCM and IRMS methods yield similar isotopic results for the analysis of both synthetic and natural gypsum samples within analytical error of the two methods. Conclusions We

  9. 95Mo nuclear magnetic resonance parameters of molybdenum hexacarbonyl from density functional theory: appraisal of computational and geometrical parameters.

    PubMed

    Cuny, Jérôme; Sykina, Kateryna; Fontaine, Bruno; Le Pollès, Laurent; Pickard, Chris J; Gautier, Régis

    2011-11-21

    Solid-state (95)Mo nuclear magnetic resonance (NMR) properties of molybdenum hexacarbonyl have been computed using density functional theory (DFT) based methods. Both quadrupolar coupling and chemical shift parameters were evaluated and compared with parameters of high precision determined using single-crystal (95)Mo NMR experiments. Within a molecular approach, the effects of major computational parameters, i.e. basis set, exchange-correlation functional, treatment of relativity, have been evaluated. Except for the isotropic parameter of both chemical shift and chemical shielding, computed NMR parameters are more sensitive to geometrical variations than computational details. Relativistic effects do not play a crucial part in the calculations of such parameters for the 4d transition metal, in particular isotropic chemical shift. Periodic DFT calculations were tackled to measure the influence of neighbouring molecules on the crystal structure. These effects have to be taken into account to compute accurate solid-state (95)Mo NMR parameters even for such an inorganic molecular compound.

  10. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1992-05-27

    This report covers the progress made on the title project for the project period. Four major areas of inquiry are being pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups that determine the reactivity of coals. Special attention is being paid to methods that are compatible with the very high magic angle sample spinning rates needed for operation at the high magnetic field strengths available today. Polarization inversion methods utilizing the difference in heat capacities of small groups of spins are particularly promising. Methods combining proton-proton spin diffusion with {sup 13}C CPMAS readout are being developed to determine the connectivity of functional groups in coals in a high sensitivity relay type of experiment. Additional work is aimed a delineating the role of methyl group rotation in the proton NMR relaxation behavior of coals.

  11. Two dimensional NMR and NMR relaxation studies of coal structure

    SciTech Connect

    Zilm, K.W.

    1989-01-01

    This report covers the progress made on the title project and summarizes the accomplishments for the project period. Four major areas of inquiry have been pursued. Advanced solid state NMR methods are being developed to assay the distribution of the various important functional groups in coals that determine the reactivity of coals. Other methods are being developed which will also determine how these functional groups are linked together. A third area of investigation concerns how molecular mobility in coals impacts NMR relaxation times, which is important for interpretation of such data in terms of the mobile phase in coal models. Along the same lines the author are also using these studies to establish protocols for obtaining the best quantitative response from coals in solid state C-13 NMR spectra. The effects of very high MAS rates (>10 kHz) on cross polarization dynamics are also being investigated for similar reasons. During the last quarter the authors has concentrated on improvements in cross polarization (CP) sequences with a goal of making the CP process insensitive to experimental conditions such as the Hartmann-Hahn mismatch. It has been found that the usual theories of CP are incorrect, and that the CP process is very heterogeneous in nature. This has significant implications on methods typically used in quantifying {sup 13}C CPMAS spectra of coals. 19 refs., 11 figs.

  12. Electrical properties of ferroelectric BaTi{sub 2}O{sub 5} and dielectric Ba{sub 6}Ti{sub 17}O{sub 40} ceramics

    SciTech Connect

    Beltran, Hector; Gomez, Beatriz; Maso, Nahum; Cordoncillo, Eloisa; Escribano, Purificacion; West, Anthony R.

    2005-04-15

    Single phase powders of BaTi{sub 2}O{sub 5} and Ba{sub 6}Ti{sub 17}O{sub 40} were made by a sol-gel method with final heating at 1100-1200 deg. C. Ceramic samples were prepared and fired at temperatures in the range 1100-1300 deg. C. Both sets were highly insulating, with conductivities of, e.g., 10{sup -6}-10{sup -7} S cm{sup -1} at 600 deg. C and activation energies for conduction in the range 1.75-1.86 eV. BaTi{sub 2}O{sub 5} compositions are ferroelectric with a permittivity maximum dependent on firing conditions: {epsilon}{sub max}{sup '}=122 at 450 deg. C on firing at 1100 deg. C; and {epsilon}{sub max}{sup '}=130 at 475 deg. C on firing at 1225 deg. C. Ba{sub 6}Ti{sub 17}O{sub 40} is a dielectric with {epsilon}{sup '}{approx}57-55 over the range 40-400 deg. C.

  13. Multichannel study of the {sup 13}C({alpha},n){sup 16}O and {sup 16}O(n,{gamma}){sup 17}O reactions

    SciTech Connect

    Dufour, M.; Descouvemont, P.

    2005-07-01

    The {sup 13}C({alpha},n){sup 16}O reaction is investigated in a microscopic two-cluster model with an effective interaction recently developed for transfer reactions. The wave functions are defined in the generator coordinate method. The basis includes all {sup 13}C+{alpha} and {sup 16}O+n channels with {sup 13}C and {sup 16}O described in the p shell. Particle-hole excitations in the sd shell are also taken into account in order to include the {sup 16}O(3{sup -})+n channel. The {sup 17}O spectroscopy is in good agreement with experiment. In particular, the width of the astrophysically relevant 1/2{sub 2}{sup +} state is well reproduced ({gamma}=121 keV as compared to the experimental value {gamma}=124{+-}12 keV). The calculation of the {sup 13}C({alpha},n){sup 16}O S factor shows the importance of the 3/2{sub 3}{sup +} resonance, and provides S(0.2 MeV)=2.1x10{sup 6} MeV b, slightly lower than the NACRE recommended value (2.5x10{sup 6} MeV b). The same model is applied to the {sup 16}O(n,{gamma}){sup 17}O radiative-capture reaction at thermal and astrophysical energies.

  14. Extended analysis of the Ångström band system (B1Σ+ - A1Π) in the rare 12C17O isotopologue

    NASA Astrophysics Data System (ADS)

    Hakalla, R.; Szajna, W.; Zachwieja, M.

    2012-11-01

    The Ångström band system (B1Σ+ - A1Π), so far unobserved in the rare 12C17O isotopologue, was obtained under high resolution as an emission spectrum using high accuracy dispersive optical spectroscopy. In total, 200 transition wave numbers belonging to the 0-1 and 0-2 bands were precisely measured and rotationally analysed. The obtained result was the merged rotational constants B0 = 1.898 8823(41) cm-1 and D0 = 6.4283(26) × 10-6 cm-1 for the B1Σ+ Rydberg state as well as the individual rotational constants B1 = 1.540 88(12) cm-1, D1 = 6.950(87) × 10-6 cm-1, B2 = 1.519 292(69) cm-1, D2 = 8.22(16) × 10-6 cm-1 for the A1Π state in the 12C17O isotopologue. The \\sigma _{0 - v^{\\prime \\prime }} band origins were also calculated. Numerous rotational perturbations observed in the A1Π state in this molecule have been identified. The observed perturbations were confronted with those predicted from theoretical calculations.

  15. Joint numerical microscale simulations of multi-phase flow and NMR relaxation behaviour in porous media

    NASA Astrophysics Data System (ADS)

    Mohnke, O.; Ahrenholz, B.

    2011-12-01

    Nuclear Magnetic Resonance (NMR) is a useful tool for analyzing gas (methane) and fluids (water, oil) in rock formations in order to derive transport and storage properties such as pore-size distributions or relative permeability. Even though there is considerable NMR data available about hydraulic properties of rock formations, this information is only empirical. Thus, the aim of this paper is to present joint NMR and multi-phase flow simulations in micro-scale pore systems derived from micro-CT images to quantify relationships between NMR parameters and transport and storage properties of partially saturated rocks. Hereby, the NMR differential equations were implemented using an advection/diffusion lattice-Boltzmann method (LBM) where the flow field is computed by a coupled LBM CFD solver. The results of numerical imbibition and drainage experiments quantitatively agree with laboratory experiments with regard to frequently found peak shifts and bimodal NMR decay time distributions related to residual water in films and corners as well as to fluids/gases trapped in large pores. This numerical framework enables one to quantitatively describe NMR surface and bulk relaxation processes, diffusive coupling along with the multi-phase flow properties of partially saturated porous systems. Furthermore, it is a viable alternative to the more time-consuming and less controllable laboratory experiments. Such virtual experimental setups can considerably help to benchmark and validate statistical network models to better understand hydraulic properties of partially saturated rocks by using experimentally obtained NMR data.

  16. Sorption isotherm measurements by NMR.

    PubMed

    Leisen, Johannes; Beckham, Haskell W; Benham, Michael

    2002-01-01

    An experimental setup is described for the automated recording of sorption isotherms by NMR experiments at precisely defined levels of relative humidity (RH). Implementation is demonstrated for a cotton fabric; Bloch decays. T1 and T2* relaxation times were measured at predefined steps of increasing and decreasing relative humidities (RHs) so that a complete isotherm of NMR properties was obtained. Bloch decays were analyzed by fitting to relaxation functions consisting or a slow- and a fast-relaxing component. The fraction of slow-relaxing component was greater than the fraction of sorbed moisture determined from gravimetric sorption data. The excess slow-relaxing component was attributed to plasticized segments of the formerly rigid cellulose matrix. T1 and T2* sorption isotherms exhibit hysteresis similar to gravimetric sorption isotherms. However, correlating RH to moisture content (MC) reveals that both relaxation constants depend only on MC, and not on the history of moisture exposure.

  17. Two-dimensional NMR spectrometry

    SciTech Connect

    Farrar, T.C.

    1987-06-01

    This article is the second in a two-part series. In part one (ANALYTICAL CHEMISTRY, May 15) the authors discussed one-dimensional nuclear magnetic resonance (NMR) spectra and some relatively advanced nuclear spin gymnastics experiments that provide a capability for selective sensitivity enhancements. In this article and overview and some applications of two-dimensional NMR experiments are presented. These powerful experiments are important complements to the one-dimensional experiments. As in the more sophisticated one-dimensional experiments, the two-dimensional experiments involve three distinct time periods: a preparation period, t/sub 0/; an evolution period, t/sub 1/; and a detection period, t/sub 2/.

  18. Recognition of lumbar disk herniation with NMR

    SciTech Connect

    Chafetz, N.I.; Genant, H.K.; Moon, K.L.; Helms, C.A.; Morris, J.M.

    1983-12-01

    Fifteen nuclear magnetic resonance (NMR) studies of 14 patients with herniated lumbar intervertebral disks were performed on the UCSF NMR imager. Computed tomographic (CT) scans done on a GE CT/T 8800 or comparable scanner were available at the time of NMR scan interpretation. Of the 16 posterior disk ruptures seen at CT, 12 were recognized on NMR. Diminished nucleus pulposus signal intensity was present in all ruptured disks. In one patient, NMR scans before and after chymopapain injection showed retraction of the protruding part of the disk and loss of signal intensity after chemonucleolysis. Postoperative fibrosis demonstrated by CT in one patient and at surgery in another showed intermediate to high signal intensity on NMR, easily distinguishing it from nearby thecal sac and disk. While CT remains the method of choice for evaluation of the patient with suspected lumbar disk rupture, the results of this study suggest that NMR may play a role in evaluating this common clinical problem.

  19. NMR analysis, protonation equilibria and decomposition kinetics of tolperisone.

    PubMed

    Orgován, Gábor; Tihanyi, Károly; Noszál, Béla

    2009-12-05

    The rate constants of spontaneous and hydroxide-catalyzed decomposition and the tautomer-specific protonation constants of tolperisone, a classical muscle relaxant were determined. A solution NMR method without any separation techniques was elaborated to quantitate the progress of decomposition. All the rate and equilibrium constants were determined at four different temperatures and the activation parameters were calculated. The molecular mechanism of decomposition is proposed.

  20. NMR Hyperpolarization Techniques for Biomedicine

    PubMed Central

    Nikolaou, Panayiotis; Goodson, Boyd M.

    2015-01-01

    Recent developments in NMR hyperpolarization have enabled a wide array of new in vivo molecular imaging modalities—ranging from functional imaging of the lungs to metabolic imaging of cancer. This Concept article explores selected advances in methods for the preparation and use of hyperpolarized contrast agents, many of which are already at or near the phase of their clinical validation in patients. PMID:25470566

  1. Hyperpolarized 131Xe NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Stupic, Karl F.; Cleveland, Zackary I.; Pavlovskaya, Galina E.; Meersmann, Thomas

    2011-01-01

    Hyperpolarized (hp) 131Xe with up to 2.2% spin polarization (i.e., 5000-fold signal enhancement at 9.4 T) was obtained after separation from the rubidium vapor of the spin-exchange optical pumping (SEOP) process. The SEOP was applied for several minutes in a stopped-flow mode, and the fast, quadrupolar-driven T1 relaxation of this spin I = 3/2 noble gas isotope required a rapid subsequent rubidium removal and swift transfer into the high magnetic field region for NMR detection. Because of the xenon density dependent 131Xe quadrupolar relaxation in the gas phase, the SEOP polarization build-up exhibits an even more pronounced dependence on xenon partial pressure than that observed in 129Xe SEOP. 131Xe is the only stable noble gas isotope with a positive gyromagnetic ratio and shows therefore a different relative phase between hp signal and thermal signal compared to all other noble gases. The gas phase 131Xe NMR spectrum displays a surface and magnetic field dependent quadrupolar splitting that was found to have additional gas pressure and gas composition dependence. The splitting was reduced by the presence of water vapor that presumably influences xenon-surface interactions. The hp 131Xe spectrum shows differential line broadening, suggesting the presence of strong adsorption sites. Beyond hp 131Xe NMR spectroscopy studies, a general equation for the high temperature, thermal spin polarization, P, for spin I⩾1/2 nuclei is presented.

  2. Hyperpolarized 131Xe NMR spectroscopy

    PubMed Central

    Stupic, Karl F.; Cleveland, Zackary I.; Pavlovskaya, Galina E.; Meersmann, Thomas

    2011-01-01

    Hyperpolarized (hp) 131Xe with up to 2.2% spin polarization (i.e., 5000-fold signal enhancement at 9.4 T) was obtained after separation from the rubidium vapor of the spin-exchange optical pumping (SEOP) process. The SEOP was applied for several minutes in a stopped-flow mode, and the fast, quadrupolar-driven T1 relaxation of this spin I = 3/2 noble gas isotope required a rapid subsequent rubidium removal and swift transfer into the high magnetic field region for NMR detection. Because of the xenon density dependent 131Xe quadrupolar relaxation in the gas phase, the SEOP polarization build-up exhibits an even more pronounced dependence on xenon partial pressure than that observed in 129Xe SEOP. 131Xe is the only stable noble gas isotope with a positive gyromagnetic ratio and shows therefore a different relative phase between hp signal and thermal signal compared to all other noble gases. The gas phase 131Xe NMR spectrum displays a surface and magnetic field dependent quadrupolar splitting that was found to have additional gas pressure and gas composition dependence. The splitting was reduced by the presence of water vapor that presumably influences xenon-surface interactions. The hp 131Xe spectrum shows differential line broadening, suggesting the presence of strong adsorption sites. Beyond hp 131Xe NMR spectroscopy studies, a general equation for the high temperature, thermal spin polarization, P, for spin I⩾1/2 nuclei is presented. PMID:21051249

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

    NASA Astrophysics Data System (ADS)

    Coston, Timothy Peter John

    Available from UMI in association with The British Library. This Thesis is primarily concerned with the quantitative study of fluxional processes in, predominantly platinum(IV) complexes, with the ligands 1,1,2,2-tetrakis(methylthio)ethane (MeS)_2CHCH(SMe)_2 , and 1,1,2,2-tetrakis(methylthio)ethene (MeS) _2C=C(SMe)_2. Quantitative information relating to the energetics of these processes has been obtained by a combination of one- and two-dimensional NMR techniques. Chapter One provides an introduction to the background of fluxional processes in transition metal complexes together with data concerning the energetics of the processes that have already been studied by NMR techniques. Chapter Two provides a thorough grounding in NMR techniques, in particular those concerned with the quantitative measurement of rates involved in chemical exchange processes. A description of the use of 2D EXSY NMR spectroscopy in obtaining rate data is given. The properties of the magnetic isotope of platinum are given in Chapter Three. A general survey is also given of some additional compounds that have already been studied by platinum-195 spectroscopy. Chapter Four is concerned with the quantitative study of low temperature (<293 K) fluxionality (sulphur inversion) in the complexes (PtXMe_3 (MeS)_2CHCH(SMe) _2) (X = Cl, Br, I). These complexes were studied by dynamic nuclear magnetic resonance and the information regarding the rates of sulphur inversion was obtained by complete band-shape analysis. Chapter Five is concerned with high temperature (>333 K) fluxionality, of the previous complexes, as studied by a combination of one- and two -dimensional NMR techniques. Aside from obtaining thermodynamic parameters for all the processes, a new novel mechanism is proposed. Chapter Six is primarily concerned with the NMR investigation of the new dinuclear complexes ((PtXMe _3)_2(MeS) _2CHCH(SMe)_2) (X = Cl, Br, I). The solution properties have been established and thermo-dynamic parameters

  4. Development and Use of a Virtual NMR Facility

    NASA Astrophysics Data System (ADS)

    Keating, Kelly A.; Myers, James D.; Pelton, Jeffrey G.; Bair, Raymond A.; Wemmer, David E.; Ellis, Paul D.

    2000-03-01

    We have developed a "virtual NMR facility" (VNMRF) to enhance access to the NMR spectrometers in Pacific Northwest National Laboratory's Environmental Molecular Sciences Laboratory (EMSL). We use the term virtual facility to describe a real NMR facility made accessible via the Internet. The VNMRF combines secure remote operation of the EMSL's NMR spectrometers over the Internet with real-time videoconferencing, remotely controlled laboratory cameras, real-time computer display sharing, a Web-based electronic laboratory notebook, and other capabilities. Remote VNMRF users can see and converse with EMSL researchers, directly and securely control the EMSL spectrometers, and collaboratively analyze results. A customized Electronic Laboratory Notebook allows interactive Web-based access to group notes, experimental parameters, proposed molecular structures, and other aspects of a research project. This paper describes our experience developing a VNMRF and details the specific capabilities available through the EMSL VNMRF. We show how the VNMRF has evolved during a test project and present an evaluation of its impact in the EMSL and its potential as a model for other scientific facilities. All Collaboratory software used in the VNMRF is freely available from http://www.emsl.pnl.gov:2080/docs/collab.

  5. NMR spin relaxation rates in the Heisenberg bilayer

    NASA Astrophysics Data System (ADS)

    Mendes, Tiago; Curro, Nicholas; Scalettar, Richard; Paiva, Thereza; Dos Santos, Raimundo R.

    One of the striking features of heavy fermions is the fact that in the vicinity of a quantum phase transition these systems exhibit the breakdown of Fermi-liquid behavior and superconductivity. Nuclear magnetic resonance (NMR) expirements play an important role in the study of these phenomena. Measurements of NMR spin relaxation rates and Knight shift, for instance, can be used to probe the electronic spin susceptibility of these systems. Here we studied the NMR response of the Heisenberg bilayer model. In this model, it is well known that the increase of the interplane coupling between the planes, Jperp, supresses the antiferromagnetic order at a quantum critical point (QCP). We use stochastic series expansion (SSE) and the maximum-entropy analytic continuation method to calculate the NMR spin lattice relaxation rate 1 /T1 and the spin echo decay 1 /T2 G as function of Jperp. The spin echo decay, T2 G increases for small Jperp, due to the increase of the order parameter, and then vanishes abruptly in the QCP. The effects of Jperp dilution disorder in the QCP and the relaxation rates are also discussed. This research was supported by the NNSA Grant Number DE-NA 0002908, and Ciência sem fronteiras program/CNPQ.

  6. (19) F DOSY diffusion-NMR spectroscopy of fluoropolymers.

    PubMed

    Xu, Chenglong; Wan, Yingbo; Chen, Dongxue; Gao, Chun; Yin, Hongnan; Fetherston, Daniel; Kupce, Eriks; Lopez, Gerald; Ameduri, Bruno; Twum, Eric B; Wyzgoski, Faith J; Li, Xiaohong; McCord, Elizabeth F; Rinaldi, Peter L

    2017-05-01

    A new pulse sequence for obtaining (19) F detected DOSY (diffusion ordered spectroscopy) spectra of fluorinated molecules is presented and used to study fluoropolymers based on vinylidene fluoride and chlorotrifluoroethylene. The performance of (19) F DOSY NMR experiments (and in general any type of NMR experiment) on fluoropolymers creates some unique complications that very often prevent detection of important signals. Factors that create these complications include: (1) the presence of many scalar couplings among (1) H, (19) F and (13) C; (2) the large magnitudes of many (19) F homonuclear couplings (especially (2) JFF ); (3) the large (19) F chemical shift range; and (4) the low solubility of these materials (which requires that experiments be performed at high temperatures). A systematic study of the various methods for collecting DOSY NMR data, and the adaptation of these methods to obtain (19) F detected DOSY data, has been performed using a mixture of low molecular weight, fluorinated model compounds. The best pulse sequences and optimal experimental conditions have been determined for obtaining (19) F DOSY spectra. The optimum pulse sequences for acquiring (19) F DOSY NMR data have been determined for various circumstances taking into account the spectral dispersion, number and magnitude of couplings present, and experimental temperature. Pulse sequences and experimental parameters for optimizing these experiments for the study of fluoropolymers have been studied. Copyright © 2016 John Wiley & Sons, Ltd.

  7. Microcoil NMR spectroscopy: a novel tool for biological high throughput NMR spectroscopy.

    PubMed

    Hopson, Russell E; Peti, Wolfgang

    2008-01-01

    Microcoil NMR spectroscopy is based on the increase of coil sensitivity for smaller coil diameters (approximately 1/d). Microcoil NMR probes deliver a remarkable mass-based sensitivity increase (8- to 12-fold) when compared with commonly used 5-mm NMR probes. Although microcoil NMR probes are a well established analytical tool for small molecule liquid-state NMR spectroscopy, after spectroscopy only recently have microcoil NMR probes become available for biomolecular NMR spectroscopy. This chapter highlights differences between commercially available microcoil NMR probes suitable for biomolecular NMR spectroscopy. Furthermore, it provides practical guidance for the use of microcoil probes and shows direct applications for structural biology and structural genomics, such as optimal target screening and structure determination, among others.

  8. On the Hydration State of Amino Acids and Their Derivatives at Different Ionization States: A Comparative Multinuclear NMR and Crystallographic Investigation

    PubMed Central

    Pappas, Charalampos G.; Tzakos, Andreas G.; Gerothanassis, Ioannis P.

    2012-01-01

    2D, 13C, 14N, and 17O NMR and crystallographic data from the literature were critically evaluated in order to provide a coherent hydration model of amino acids and selected derivatives at different ionization states. 17O shielding variations, longitudinal relaxation times (T1) of 2D and 13C and line widths (Δν1/2) of 14N and 17O, may be interpreted with the hypothesis that the cationic form of amino acids is more hydrated by 1 to 3 molecules of water than the zwitterionic form. Similar behaviour was also observed for N-acetylated derivatives of amino acids. An exhaustive search in crystal structure databases demonstrates the importance of six-membered hydrogen-bonded conjugated rings of both oxygens of the α-carboxylate group with a molecule of water in the vicinity. This type of hydrogen bond mode is absent in the case of the carboxylic groups. Moreover, a considerable number of structures was identified with the propensity to form intramolecular hydrogen bond both in the carboxylic acid (NH⋯O=C) and in the carboxylate (NH ⋯ O−) ionization state. In the presence of bound molecules of water this interaction is significantly reduced in the case of the carboxylate group whereas it is statistically negligible in the carboxylic group. PMID:22675607

  9. Stratospheric Air Sub-sampler (SAS) and its application to analysis of Δ17O(CO2) from small air samples collected with an AirCore

    NASA Astrophysics Data System (ADS)

    Janina Mrozek, Dorota; van der Veen, Carina; Hofmann, Magdalena E. G.; Chen, Huilin; Kivi, Rigel; Heikkinen, Pauli; Röckmann, Thomas

    2016-11-01

    We present the set-up and a scientific application of the Stratospheric Air Sub-sampler (SAS), a device to collect and to store the vertical profile of air collected with an AirCore (Karion et al., 2010) in numerous sub-samples for later analysis in the laboratory. The SAS described here is a 20 m long 1/4 inch stainless steel tubing that is separated by eleven valves to divide the tubing into 10 identical segments, but it can be easily adapted to collect smaller or larger samples. In the collection phase the SAS is directly connected to the outlet of an optical analyzer that measures the mole fractions of CO2, CH4 and CO from an AirCore sampler. The stratospheric part (or if desired any part of the AirCore air) is then directed through the SAS. When the SAS is filled with the selected air, the valves are closed and the vertical profile is maintained in the different segments of the SAS. The segments can later be analysed to retrieve vertical profiles of other trace gas signatures that require slower instrumentation. As an application, we describe the coupling of the SAS to an analytical system to determine the 17O excess of CO2, which is a tracer for photochemical processing of stratospheric air. For this purpose the analytical system described by Mrozek et al. (2015) was adapted for analysis of air directly from the SAS. The performance of the coupled system is demonstrated for a set of air samples from an AirCore flight in November 2014 near Sodankylä, Finland. The standard error for a 25 mL air sample at stratospheric CO2 mole fraction is 0.56 ‰ (1σ) for δ17O and 0.03 ‰ (1σ) for both δ18O and δ13C. Measured Δ17O(CO2) values show a clear correlation with N2O in agreement with already published data.

  10. Advanced NMR technology for bioscience and biotechnology

    SciTech Connect

    Hammel, P.C.; Hernandez, G.; Trewhella, J.; Unkefer, C.J.; Boumenthal, D.K.; Kennedy, M.A.; Moore, G.J.

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). NMR plays critical roles in bioscience and biotechnology in both imaging and structure determination. NMR is limited, however, by the inherent low sensitivity of the NMR experiment and the demands for spectral resolution required to study biomolecules. The authors addressed both of these issues by working on the development of NMR force microscopy for molecular imaging, and high field NMR with isotope labeling to overcome limitations in the size of biomolecules that can be studied using NMR. A novel rf coil design for NMR force microscopy was developed that increases the limits of sensitivity in magnetic resonance detection for imaging, and the authors demonstrated sub-surface spatial imaging capabilities. The authors also made advances in the miniaturization of two critical NMR force microscope components. They completed high field NMR and isotope labeling studies of a muscle protein complex which is responsible for regulating muscle contraction and is too large for study using conventional NMR approaches.

  11. Scalable NMR spectroscopy with semiconductor chips

    PubMed Central

    Ha, Dongwan; Paulsen, Jeffrey; Sun, Nan; Song, Yi-Qiao; Ham, Donhee

    2014-01-01

    State-of-the-art NMR spectrometers using superconducting magnets have enabled, with their ultrafine spectral resolution, the determination of the structure of large molecules such as proteins, which is one of the most profound applications of modern NMR spectroscopy. Many chemical and biotechnological applications, however, involve only small-to-medium size molecules, for which the ultrafine resolution of the bulky, expensive, and high-maintenance NMR spectrometers is not required. For these applications, there is a critical need for portable, affordable, and low-maintenance NMR spectrometers to enable in-field, on-demand, or online applications (e.g., quality control, chemical reaction monitoring) and co-use of NMR with other analytical methods (e.g., chromatography, electrophoresis). As a critical step toward NMR spectrometer miniaturization, small permanent magnets with high field homogeneity have been developed. In contrast, NMR spectrometer electronics capable of modern multidimensional spectroscopy have thus far remained bulky. Complementing the magnet miniaturization, here we integrate the NMR spectrometer electronics into 4-mm2 silicon chips. Furthermore, we perform various multidimensional NMR spectroscopies by operating these spectrometer electronics chips together with a compact permanent magnet. This combination of the spectrometer-electronics-on-a-chip with a permanent magnet represents a useful step toward miniaturization of the overall NMR spectrometer into a portable platform. PMID:25092330

  12. Multinuclear NMR spectroscopy for differentiation of molecular configurations and solvent properties between acetone and dimethyl sulfoxide

    NASA Astrophysics Data System (ADS)

    Wen, Yuan-Chun; Kuo, Hsiao-Ching; Jia, Hsi-Wei

    2016-04-01

    The differences in molecular configuration and solvent properties between acetone and dimethyl sulfoxide (DMSO) were investigated using the developed technique of 1H, 13C, 17O, and 1H self-diffusion liquid state nuclear magnetic resonance (NMR) spectroscopy. Acetone and DMSO samples in the forms of pure solution, ionic salt-added solution were used to deduce their active sites, relative dipole moments, dielectric constants, and charge separations. The NMR results suggest that acetone is a trigonal planar molecule with a polarized carbonyl double bond, whereas DMSO is a trigonal pyramidal-like molecule with a highly polarized S-O single bond. Both molecules use their oxygen atoms as the active sites to interact other molecules. These different molecular models explain the differences their physical and chemical properties between the two molecules and explain why DMSO is classified as an aprotic but highly dipolar solvent. The results are also in agreement with data obtained using X-ray diffraction, neutron diffraction, and theoretical calculations.

  13. Efficient design of multituned transmission line NMR probes: the electrical engineering approach.

    PubMed

    Frydel, J A; Krzystyniak, M; Pienkowski, D; Pietrzak, M; de Sousa Amadeu, N; Ratajczyk, T; Idzik, K; Gutmann, T; Tietze, D; Voigt, S; Fenn, A; Limbach, H H; Buntkowsky, G

    2011-01-01

    Transmission line-based multi-channel solid state NMR probes have many advantages regarding the cost of construction, number of RF-channels, and achievable RF-power levels. Nevertheless, these probes are only rarely employed in solid state-NMR-labs, mainly owing to the difficult experimental determination of the necessary RF-parameters. Here, the efficient design of multi-channel solid state MAS-NMR probes employing transmission line theory and modern techniques of electrical engineering is presented. As technical realization a five-channel ((1)H, (31)P, (13)C, (2)H and (15)N) probe for operation at 7 Tesla is described. This very cost efficient design goal is a multi port single coil transmission line probe based on the design developed by Schaefer and McKay. The electrical performance of the probe is determined by measuring of Scattering matrix parameters (S-parameters) in particular input/output ports. These parameters are compared to the calculated parameters of the design employing the S-matrix formalism. It is shown that the S-matrix formalism provides an excellent tool for examination of transmission line probes and thus the tool for a rational design of these probes. On the other hand, the resulting design provides excellent electrical performance. From a point of view of Nuclear Magnetic Resonance (NMR), calibration spectra of particular ports (channels) are of great importance. The estimation of the π/2 pulses length for all five NMR channels is presented.

  14. First application of the n - 9Be optical potential to the study of the 10Be continuum via the (18O,17O ) neutron-transfer reaction

    NASA Astrophysics Data System (ADS)

    Carbone, D.; Bondı, M.; Bonaccorso, A.; Agodi, C.; Cappuzzello, F.; Cavallaro, M.; Charity, R. J.; Cunsolo, A.; De Napoli, M.; Foti, A.

    2014-12-01

    The 9Be(18O,17O ) 10Be reaction has been studied at an incident energy of 84 MeV, and the ejectiles have been detected at forward angles. The 10Be excitation energy spectrum has been obtained up to about 18 MeV, and several known bound and resonant states of 10Be have been identified. Calculations that describe the interaction of the neutron removed from the 18O projectile with the 9Be target by means of an optical potential with a semiclassical approximation for the relative motion account for a significant part of the 10Be continuum. Two parametrizations of the optical-model potential for the system n - 9Be have been used and compared.

  15. Enhanced efficiency of solid-state NMR investigations of energy materials using an external automatic tuning/matching (eATM) robot

    NASA Astrophysics Data System (ADS)

    Pecher, Oliver; Halat, David M.; Lee, Jeongjae; Liu, Zigeng; Griffith, Kent J.; Braun, Marco; Grey, Clare P.

    2017-02-01

    We have developed and explored an external automatic tuning/matching (eATM) robot that can be attached to commercial and/or home-built magic angle spinning (MAS) or static nuclear magnetic resonance (NMR) probeheads. Complete synchronization and automation with Bruker and Tecmag spectrometers is ensured via transistor-transistor-logic (TTL) signals. The eATM robot enables an automated "on-the-fly" re-calibration of the radio frequency (rf) carrier frequency, which is beneficial whenever tuning/matching of the resonance circuit is required, e.g. variable temperature (VT) NMR, spin-echo mapping (variable offset cumulative spectroscopy, VOCS) and/or in situ NMR experiments of batteries. This allows a significant increase in efficiency for NMR experiments outside regular working hours (e.g. overnight) and, furthermore, enables measurements of quadrupolar nuclei which would not be possible in reasonable timeframes due to excessively large spectral widths. Additionally, different tuning/matching capacitor (and/or coil) settings for desired frequencies (e.g.7Li and 31P at 117 and 122 MHz, respectively, at 7.05 T) can be saved and made directly accessible before automatic tuning/matching, thus enabling automated measurements of multiple nuclei for one sample with no manual adjustment required by the user. We have applied this new eATM approach in static and MAS spin-echo mapping NMR experiments in different magnetic fields on four energy storage materials, namely: (1) paramagnetic 7Li and 31P MAS NMR (without manual recalibration) of the Li-ion battery cathode material LiFePO4; (2) paramagnetic 17O VT-NMR of the solid oxide fuel cell cathode material La2NiO4+δ; (3) broadband 93Nb static NMR of the Li-ion battery material BNb2O5; and (4) broadband static 127I NMR of a potential Li-air battery product LiIO3. In each case, insight into local atomic structure and dynamics arises primarily from the highly broadened (1-25 MHz) NMR lineshapes that the eATM robot is uniquely

  16. Enhanced efficiency of solid-state NMR investigations of energy materials using an external automatic tuning/matching (eATM) robot.

    PubMed

    Pecher, Oliver; Halat, David M; Lee, Jeongjae; Liu, Zigeng; Griffith, Kent J; Braun, Marco; Grey, Clare P

    2017-02-01

    We have developed and explored an external automatic tuning/matching (eATM) robot that can be attached to commercial and/or home-built magic angle spinning (MAS) or static nuclear magnetic resonance (NMR) probeheads. Complete synchronization and automation with Bruker and Tecmag spectrometers is ensured via transistor-transistor-logic (TTL) signals. The eATM robot enables an automated "on-the-fly" re-calibration of the radio frequency (rf) carrier frequency, which is beneficial whenever tuning/matching of the resonance circuit is required, e.g. variable temperature (VT) NMR, spin-echo mapping (variable offset cumulative spectroscopy, VOCS) and/or in situ NMR experiments of batteries. This allows a significant increase in efficiency for NMR experiments outside regular working hours (e.g. overnight) and, furthermore, enables measurements of quadrupolar nuclei which would not be possible in reasonable timeframes due to excessively large spectral widths. Additionally, different tuning/matching capacitor (and/or coil) settings for desired frequencies (e.g.(7)Li and (31)P at 117 and 122MHz, respectively, at 7.05 T) can be saved and made directly accessible before automatic tuning/matching, thus enabling automated measurements of multiple nuclei for one sample with no manual adjustment required by the user. We have applied this new eATM approach in static and MAS spin-echo mapping NMR experiments in different magnetic fields on four energy storage materials, namely: (1) paramagnetic (7)Li and (31)P MAS NMR (without manual recalibration) of the Li-ion battery cathode material LiFePO4; (2) paramagnetic (17)O VT-NMR of the solid oxide fuel cell cathode material La2NiO4+δ; (3) broadband (93)Nb static NMR of the Li-ion battery material BNb2O5; and (4) broadband static (127)I NMR of a potential Li-air battery product LiIO3. In each case, insight into local atomic structure and dynamics arises primarily from the highly broadened (1-25MHz) NMR lineshapes that the eATM robot is

  17. NMR characterization of pituitary tumors

    SciTech Connect

    Osbakken, M.; Gonzales, J.; Page, R.

    1984-01-01

    Twelve patients (5 male, 7 female, mean age 37.9 +- 20) with pituitary tumors were extensively evaluated with NMR imaging using a 1.5K gauss resistive magnet. Saturation recovery (SR), inversion recovery (IR) and spin echo (SE) pulse sequences were used for qualitative characterization of the lesions. T/sub 1/ calculations were also performed for brain and pituitary. Tumor histology and endocrine status were correlated with NMR data. All tumors were large with suprasellar extension (6 with prolactin secretion, 6 without). Pituitary T/sub 1/'s ranged from .2 to .64, the mean T/sub 1/ being longer than that of brain (Brain = .4 +- .04; Pit = .48 +- .14). 3 patients with histological evidence of homogeneous adenomas had long T/sub 1/'s (0.58 +- .05). 3 patients with evidence of recent or old hemorhage into the pituitary had much shorter T/sub 1/'s (0.29 +- .12). There was no relationship between prolactin secretion and T/sub 1/. Qualitative T/sub 1/ and T/sub 2/ information can be obtained by using a combination of SR, IR, and SE images. Using this method in the patients, homogeneous adenomas had similar T/sub 1/'s and longer T/sub 2/'s compared to the brain, while patients with bleeds had shorter T/sub 1/'s and T/sub 2/'s. Image T/sub 1/ characteristics correlated well with the calculated T/sub 1/ values. The range of T/sub 1/ (and potentially T/sub 2/) values which occur in apparently similar lesions are most likely due to anatomical and pathophysiological variations in these lesions. It may be ultimately possible to separate different types of pathological processes based on NMR image T/sub 1/ and T/sub 2/ characteristics after careful comparative studies of NMR and histological data are completed. The combination of calculated T/sub 1/ and T/sub 2/ with image T/sub 1/ and T/sub 2/ information may also be useful in further characterization of lesions.

  18. Improvements in Technique of NMR Imaging and NMR Diffusion Measurements in the Presence of Background Gradients.

    NASA Astrophysics Data System (ADS)

    Lian, Jianyu

    In this work, modification of the cosine current distribution rf coil, PCOS, has been introduced and tested. The coil produces a very homogeneous rf magnetic field, and it is inexpensive to build and easy to tune for multiple resonance frequency. The geometrical parameters of the coil are optimized to produce the most homogeneous rf field over a large volume. To avoid rf field distortion when the coil length is comparable to a quarter wavelength, a parallel PCOS coil is proposed and discussed. For testing rf coils and correcting B _1 in NMR experiments, a simple, rugged and accurate NMR rf field mapping technique has been developed. The method has been tested and used in 1D, 2D, 3D and in vivo rf mapping experiments. The method has been proven to be very useful in the design of rf coils. To preserve the linear relation between rf output applied on an rf coil and modulating input for an rf modulating -amplifying system of NMR imaging spectrometer, a quadrature feedback loop is employed in an rf modulator with two orthogonal rf channels to correct the amplitude and phase non-linearities caused by the rf components in the rf system. The modulator is very linear over a large range and it can generate an arbitrary rf shape. A diffusion imaging sequence has been developed for measuring and imaging diffusion in the presence of background gradients. Cross terms between the diffusion sensitizing gradients and background gradients or imaging gradients can complicate diffusion measurement and make the interpretation of NMR diffusion data ambiguous, but these have been eliminated in this method. Further, the background gradients has been measured and imaged. A dipole random distribution model has been established to study background magnetic fields Delta B and background magnetic gradients G_0 produced by small particles in a sample when it is in a B_0 field. From this model, the minimum distance that a spin can approach a particle can be determined by measuring

  19. Defects in doped LaGaO3 anionic conductors: linking NMR spectral features, local environments, and defect thermodynamics.

    PubMed

    Blanc, Frédéric; Middlemiss, Derek S; Gan, Zhehong; Grey, Clare P

    2011-11-09

    Doped lanthanum gallate perovskites (LaGaO(3)) constitute some of the most promising electrolyte materials for solid oxide fuel cells operating in the intermediate temperature regime. Here, an approach combining experimental multinuclear NMR spectroscopy with density functional theory total energy and GIPAW NMR calculations yields a comprehensive understanding of the structural and defect chemistries of Sr- and Mg-doped LaGaO(3) anionic conductors. The DFT energetics demonstrate that Ga-V(O)-Ga (V(O) = oxygen vacancy) environments are favored (vs Ga-V(O)-Mg, Mg-V(O)-Mg and Mg-O-Mg-V(O)-Ga) across a range y = 0.0625, 0.125, and 0.25 of fractional Mg contents in LaGa(1-y)Mg(y)O(3-y/2). The results are interpreted in terms of doping and mean phase formation energies (relative to binary oxides) and are compared with previous calculations and experimental calorimetry data. Experimental multinuclear NMR data reveal that while Mg sites remain six-fold coordinated across the range of phase stoichiometries, albeit with significant structural disorder, a stoichiometry-dependent minority of the Ga sites resonate at a shift consistent with Ga(V) coordination, demonstrating that O vacancies preferentially locate in the first anion coordination shell of Ga. The strong Mg-V(O) binding inferred by previous studies is not observed here. The (17)O NMR spectra reveal distinct resonances that can be assigned by using the GIPAW NMR calculations to anions occupying equatorial and axial positions with respect to the Ga(V)-V(O) axis. The disparate shifts displayed by these sites are due to the nature and extent of the structural distortions caused by the O vacancies.

  20. Quantitative 2D liquid-state NMR.

    PubMed

    Giraudeau, Patrick

    2014-06-01

    Two-dimensional (2D) liquid-state NMR has a very high potential to simultaneously determine the absolute concentration of small molecules in complex mixtures, thanks to its capacity to separate overlapping resonances. However, it suffers from two main drawbacks that probably explain its relatively late development. First, the 2D NMR signal is strongly molecule-dependent and site-dependent; second, the long duration of 2D NMR experiments prevents its general use for high-throughput quantitative applications and affects its quantitative performance. Fortunately, the last 10 years has witnessed an increasing number of contributions where quantitative approaches based on 2D NMR were developed and applied to solve real analytical issues. This review aims at presenting these recent efforts to reach a high trueness and precision in quantitative measurements by 2D NMR. After highlighting the interest of 2D NMR for quantitative analysis, the different strategies to determine the absolute concentrations from 2D NMR spectra are described and illustrated by recent applications. The last part of the manuscript concerns the recent development of fast quantitative 2D NMR approaches, aiming at reducing the experiment duration while preserving - or even increasing - the analytical performance. We hope that this comprehensive review will help readers to apprehend the current landscape of quantitative 2D NMR, as well as the perspectives that may arise from it.

  1. NMR studies of isotopically labeled RNA

    SciTech Connect

    Pardi, A.

    1994-12-01

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

  2. DFT calculations of quadrupolar solid-state NMR properties: Some examples in solid-state inorganic chemistry.

    PubMed

    Cuny, Jerome; Messaoudi, Sabri; Alonzo, Veronique; Furet, Eric; Halet, Jean-François; Le Fur, Eric; Ashbrook, Sharon E; Pickard, Chris J; Gautier, Regis; Le Polles, Laurent

    2008-10-01

    This article presents results of first-principles calculations of quadrupolar parameters measured by solid-state nuclear magnetic measurement (NMR) spectroscopy. Different computational methods based on density functional theory were used to calculate the quadrupolar parameters. Through a series of illustrations from different areas of solid state inorganic chemistry, it is shown how quadrupolar solid-state NMR properties can be tackled by a theoretical approach and can yield structural information.

  3. Recent advances in application of (27)Al NMR spectroscopy to materials science.

    PubMed

    Haouas, Mohamed; Taulelle, Francis; Martineau, Charlotte

    2016-05-01

    Valuable information about the local environment of the aluminum nucleus can be obtained through (27)Al Nuclear Magnetic Resonance (NMR) parameters like the isotropic chemical shift, scalar and quadrupolar coupling constants, and relaxation rate. With nearly 250 scientific articles per year dealing with (27)Al NMR spectroscopy, this analytical tool has become popular because of the recent progress that has made the acquisition and interpretation of the NMR data much easier. The application of (27)Al NMR techniques to various classes of compounds, either in solution or solid-state, has been shown to be extremely informative concerning local structure and chemistry of aluminum in its various environments. The development of experimental methodologies combined with theoretical approaches and modeling has contributed to major advances in spectroscopic characterization especially in materials sciences where long-range periodicity and classical local NMR probes are lacking. In this review we will present an overview of results obtained by (27)Al NMR as well as the most relevant methodological developments over the last 25years, concerning particularly on progress in the application of liquid- and solid-state (27)Al NMR to the study of aluminum-based materials such as aluminum polyoxoanions, zeolites, aluminophosphates, and metal-organic-frameworks.

  4. Picoliter H-1 NMR Spectroscopy

    SciTech Connect

    Minard, Kevin R. ); Wind, Robert A. )

    2002-02-01

    A RF probe that fits inside the bore of a small gradient coil package is described for routine 1H-NMR microscopy measurements on small samples. The probe operates at 500 MHz and houses a 267-um-diameter solenoid transceiver. When used in three dimensional chemical shift imaging (3D-CSI) experiments, the measured signal-to-noise ratio (SNR) is shown to be within 20-30 percent of theoretical limits formulated by only considering the solenoid's resistive losses. This is illustrated using a 100-um-diameter globule of triacylglycerols ({approx}900mM) that may be an oocyte precursor in young Xenopus Laevis frogs, and water sample containing choline at a concentration often found in live cells ({approx}33mM). In chemical shift images generated using a few thousand scans, the choline methyl line is found to have an acceptable SNR in resolved from just 5 picoliters in the Xenopus globule. It is concluded that the probe's sensitivity is sufficient for performing 1H-NMR on picoliter-scale volumes in biological cells and tissues.

  5. Measurements of intracellular volumes by 59Co and 2H/1H NMR and their physiological applications.

    PubMed

    Askenasy, Nadir; Navon, Gil

    2005-04-01

    Determination of the intracellular water volumes using NMR spectroscopy was performed using the NMR-visible nuclei: 59Co and 2H or 1H. Accurate measurement of intracellular water in cell suspensions and perfused organs is an important physiological parameter in the context of electrolyte homeostasis and energy metabolism, in particular when these parameters are monitored by non-invasive NMR spectroscopy. Furthermore, repeated or continuous monitoring of intracellular water provided significant insights into the physiology of cardiac muscle and sarcolemmal membrane permeability and integrity.

  6. Conformational analysis of small molecules: NMR and quantum mechanics calculations.

    PubMed

    Tormena, Cláudio F

    2016-08-01

    This review deals with conformational analysis in small organic molecules, and describes the stereoelectronic interactions responsible for conformational stability. Conformational analysis is usually performed using NMR spectroscopy through measurement of coupling constants at room or low temperature in different solvents to determine the populations of conformers in solution. Quantum mechanical calculations are used to address the interactions responsible for conformer stability. The conformational analysis of a large number of small molecules is described, using coupling constant measurements in different solvents and at low temperature, as well as recent applications of through-space and through-hydrogen bond coupling constants JFH as tools for the conformational analysis of fluorinated molecules. Besides NMR parameters, stereoelectronic interactions such as conjugative, hyperconjugative, steric and intramolecular hydrogen bond interactions involved in conformational preferences are discussed.

  7. Faster and cleaner real-time pure shift NMR experiments.

    PubMed

    Mauhart, Johannes; Glanzer, Simon; Sakhaii, Peyman; Bermel, Wolfgang; Zangger, Klaus

    2015-10-01

    Real-time pure shift experiments provide highly resolved proton NMR spectra which do not require any special processing. Although being more sensitive than their pseudo 2D counterparts, their signal intensities per unit time are still far below regular NMR spectra. In addition, scalar coupling evolution during the individual data chunks produces decoupling sidebands. Here we show that faster and cleaner real-time pure shift spectra can be obtained through the implementation of two parameter alterations. Variation of the FID chunk lengths between individual transients significantly suppresses decoupling sidebands for any kind of real-time pure shift spectra and thus allows for example the analysis of minor components in compound mixtures. Shifting the excitation frequency between individual scans of real-time slice-selective pure shift spectra increases their sensitivity obtainable in unit time by allowing faster repetitions of acquisitions.

  8. Access to NMR Spectroscopy for Two-Year College Students: The NMR Site at Trinity University

    ERIC Educational Resources Information Center

    Mills, Nancy S.; Shanklin, Michael

    2011-01-01

    Students at two-year colleges and small four-year colleges have often obtained their exposure to NMR spectroscopy through "canned" spectra because the cost of an NMR spectrometer, particularly a high-field spectrometer, is prohibitive in these environments. This article describes the design of a NMR site at Trinity University in which…

  9. Analytical Applications of NMR: Summer Symposium on Analytical Chemistry.

    ERIC Educational Resources Information Center

    Borman, Stuart A.

    1982-01-01

    Highlights a symposium on analytical applications of nuclear magnetic resonance spectroscopy (NMR), discussing pulse Fourier transformation technique, two-dimensional NMR, solid state NMR, and multinuclear NMR. Includes description of ORACLE, an NMR data processing system at Syracuse University using real-time color graphics, and algorithms for…

  10. Relationships between Greenland and lower latitude climate over the last glacial period from new high resolution measurements of 17O-excess and d-excess on the NorthGRIP ice core

    NASA Astrophysics Data System (ADS)

    Landais, Amaelle; Prie, Frederic; Minster, Benedicte; Masson-Delmotte, Valerie; Vinther, Bo; Popp, Trevor; Rhodes, Rachael; Dahl-Jensen, Dorther

    2016-04-01

    Greenland ice cores have long revealed the abrupt climatic variability characterizing the last glacial period (succession of Dansgaard-Oeschger events). Since then, many other continental and marine records have shown the northern hemispheric extent of these abrupt events with an associated signature in the southern hemisphere. While the water isotopic records (d18O or dD) records of Greenland ice cores have long been used as references for the northern hemisphere climatic variability, more and more pieces of evidence point to some decoupling between the climate variability in Greenland and the climate variability in lower latitudes. In particular, the Greenland temperature records derived from water and air isotopes do not exhibit any signature for the Heinrich events. We present here new high resolution measurements of 17O-excess and d-excess from the NorthGRIP ice core covering the abrupt climatic variability of the last deglaciation and the last glacial period. These second order parameters are particularly useful to decipher the local from the distant effect on the water isotopic records in polar ice cores since they are sensitive to climatic conditions at the oceanic evaporative regions and to the trajectories of the water mass toward the polar precipitation sites. These new measurements clearly highlight a decoupling between Greenland and lower latitudes between the cold phases (stadials) of the Dansgaard-Oeschger events that can be due to sea-ice extent or other modifications in the oceanic surface climatic conditions. A comparison between the d-excess records of the GRIP and NGRIP ice core highlight different behaviours in the trajectories of moisture toward different regions Greenland that can again be linked to regional differences in sea-ice extent. Finally, our new sets of data also exhibit a particular behavior of the Greenland vs lower latitude climate during very short Dansgaard-Oeschger events.

  11. Field Experiment Provides Ground Truth for Surface NMR Measurement

    NASA Astrophysics Data System (ADS)

    Knight, R. J.; Abraham, J. D.; Cannia, J. C.; Dlubac, K. I.; Grau, B.; Grunewald, E. D.; Irons, T.; Song, Y.; Walsh, D.

    2010-12-01

    Effective and sustainable long-term management of fresh water resources requires accurate information about the availability of water in groundwater aquifers. Proton Nuclear Magnetic Resonance (NMR) can provide a direct link to the presence of water in the pore space of geological materials through the detection of the nuclear magnetization of the hydrogen nuclei (protons) in the pore water. Of interest for groundwater applications is the measurement of the proton-NMR relaxation time constant, referred to as T2. This parameter is sensitive to the geometry of the water-filled pore space and can be related to the hydraulic conductivity. NMR logging instruments, which have been available since the 1980’s, provide direct measurements of T2 in boreholes. Surface NMR (SNMR) is a non-invasive geophysical method that uses a loop of wire on the surface to probe the NMR properties of groundwater aquifers to a depth of ~100 m, without the need for the drilling of boreholes. SNMR provides reliable measurements of a different NMR time constant referred to as T2*, that is related to, but not necessarily equivalent to, T2. The relationship between T2* and T2 is likely to depend upon the physical environment and the composition of the sampled material. In order to advance the use of SNMR as a non-invasive means of characterizing groundwater aquifers, we must answer the fundamental question: When probing a groundwater aquifer, what information is provided by T2*, the time constant measured with SNMR? Our approach was to conduct a field experiment in Nebraska, in an area underlain by the Quaternary Alluvium and Tertiary Ogallala aquifers. We first used SNMR to obtain a 1D profile of T2* to a depth of ~60 m. We then drilled a well inside the area of the SNMR loop, to a depth of ~150 m, and used the drill cuttings to describe the composition of the geologic material at the site. The borehole was kept open for 2 days to acquire logging NMR T2 measurements over the total depth. Three

  12. Microscale simulations of NMR relaxation in porous media

    NASA Astrophysics Data System (ADS)

    Mohnke, Oliver; Klitzsch, Norbert

    2010-05-01

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

  13. Microscale simulations of NMR relaxation in porous media

    NASA Astrophysics Data System (ADS)

    Mohnke, O.; Klitzsch, N.; Clauser, C.

    2009-12-01

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

  14. Frequency-domain method based on the singular value decomposition for frequency-selective NMR spectroscopy.

    PubMed

    Stoica, Petre; Sandgren, Niclas; Selén, Yngve; Vanhamme, Leentje; Van Huffel, Sabine

    2003-11-01

    In several applications of NMR spectroscopy the user is interested only in the components lying in a small frequency band of the spectrum. A frequency selective analysis deals precisely with this kind of NMR spectroscopy: parameter estimation of only those spectroscopic components that lie in a preselected frequency band of the NMR data spectrum, with as little interference as possible from the out-of-band components and in a computationally efficient way. In this paper we introduce a frequency-domain singular value decomposition (SVD)-based method for frequency selective spectroscopy that is computationally simple, statistically accurate, and which has a firm theoretical basis. To illustrate the good performance of the proposed method we present a number of numerical examples for both simulated and in vitro NMR data.

  15. Complete Measurement of Stable Isotopes in N2O (δ15N, δ15Nα, δ15Nβ, δ18O, δ17O) Using Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS)

    NASA Astrophysics Data System (ADS)

    Leen, J. B.; Gupta, M.

    2014-12-01

    Nitrate contamination in water is a worldwide environmental problem and source apportionment is critical to managing nitrate pollution. Fractionation caused by physical, chemical and biological processes alters the isotope ratios of nitrates (15N/14N, 18O/16O and 17O/16O) and biochemical nitrification and denitrification impart different intramolecular site preference (15N14NO vs. 14N15NO). Additionally, atmospheric nitrate is anomalously enriched in 17O compared to other nitrate sources. The anomaly (Δ17O) is conserved during fractionation processes, providing a tracer of atmospheric nitrate. All of these effects can be used to apportion nitrate in soil. Current technology for measuring nitrate isotopes is complicated and costly - it involves conversion of nitrate to nitrous oxide (N2O), purification, preconcentration and measurement by isotope ratio mass spectrometer (IRMS). Site specific measurements require a custom IRMS. There is a pressing need to make this measurement simpler and more accessible. Los Gatos Research has developed a next generation mid-infrared Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) analyzer to quantify all stable isotope ratios of N2O (δ15N, δ15Nα, δ15Nβ, δ18O, δ17O). We present the latest performance data demonstrating the precision and accuracy of the OA-ICOS based measurement. At an N2O concentration of 322 ppb, the analyzer quantifies [N2O], δ15N, δ15Na, δ15Nb, and δ18O with a precision of ±0.05 ppb, ±0.4 ‰, ±0.45 ‰, and ±0.6 ‰, and ±0.8 ‰ respectively (1σ, 100s; 1σ, 1000s for δ18O). Measurements of gas standards demonstrate accuracy better than ±1 ‰ for isotope ratios over a wide dynamic range (200 - 100,000 ppb). The measurement of δ17O requires a higher concentration (1 - 50 ppm), easily obtainable through conversion of nitrates in water. For 10 ppm of N2O, the instrument achieves a δ17O precision of ±0.05 ‰ (1σ, 1000s). This performance is sufficient to quantify atmospheric

  16. An Integrated Laboratory Project in NMR Spectroscopy.

    ERIC Educational Resources Information Center

    Hudson, Reggie L.; Pendley, Bradford D.

    1988-01-01

    Describes an advanced NMR project that can be done with a 60-MHz continuous-wave proton spectrometer. Points out the main purposes are to give students experience in second-order NMR analysis, the simplification of spectra by raising the frequency, and the effect of non-hydrogen nuclei on proton resonances. (MVL)

  17. A Guided Inquiry Approach to NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Parmentier, Laura E.; Lisensky, George C.; Spencer, Brock

    1998-04-01

    We present a novel way to introduce NMR spectroscopy into the general chemistry curriculum as part of a week-long aspirin project in our one-semester introductory course. Aspirin is synthesized by reacting salicylic acid and acetic anhydride. Purity is determined by titration and IR and NMR spectroscopy. Students compare IR and NMR spectra of their aspirin product to a series of reference spectra obtained by the class. Students are able to interpret the IR spectra of their aspirin using IR data from previous experiments. NMR is introduced by having students collect 1H NMR spectra of a series of reference compounds chosen to include some of the structural features of aspirin and compare spectra and structures of the reference compounds to develop a correlation chart for chemical shifts. This process is done in small groups using shared class data and is guided by a series of questions designed to relate the different kinds of hydrogen atoms to number and position of peaks in the NMR spectrum. Students then identify the peaks in the NMR spectrum of their aspirin product and relate percent purity by titration with spectral results and percent yield. This is an enjoyable project that combines the synthesis of a familiar material with a guided inquiry-based introduction to NMR spectroscopy.

  18. An Inversion Recovery NMR Kinetics Experiment

    ERIC Educational Resources Information Center

    Williams, Travis J.; Kershaw, Allan D.; Li, Vincent; Wu, Xinping

    2011-01-01

    A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this…

  19. Microslot NMR probe for metabolomics studies.

    PubMed

    Krojanski, Hans Georg; Lambert, Jörg; Gerikalan, Yilmaz; Suter, Dieter; Hergenröder, Roland

    2008-11-15

    A NMR microprobe based on microstrip technology suitable for investigations of volume-limited samples in the low nanoliter range was designed. NMR spectra of sample quantities in the 100 pmol range can be obtained with this probe in a few seconds. The planar geometry of the probe is easily adaptable to the size and geometry requirements of the samples.

  20. NMR Spectroscopy and Its Value: A Primer

    ERIC Educational Resources Information Center

    Veeraraghavan, Sudha

    2008-01-01

    Nuclear magnetic resonance (NMR) spectroscopy is widely used by chemists. Furthermore, the use of NMR spectroscopy to solve structures of macromolecules or to examine protein-ligand interactions is popular. Yet, few students entering graduate education in biological sciences have been introduced to this method or its utility. Over the last six…

  1. NMR-Profiles of Protein Solutions

    PubMed Central

    Pedrini, Bill; Serrano, Pedro; Mohanty, Biswaranjan; Geralt, Michael; Wüthrich, Kurt

    2014-01-01

    NMR-Profiles are quantitative one-dimensional presentations of two-dimensional [15N,1H]-correlation spectra used to monitor the quality of protein solutions prior to and during NMR structure determinations and functional studies. In our current use in structural genomics projects, a NMR-Profile is recorded at the outset of a structure determination, using a uniformly 15N-labeled micro-scale sample of the protein. We thus assess the extent to which polypeptide backbone resonance assignments can be achieved with given NMR techniques, for example, conventional triple resonance experiments or APSY-NMR. With the availability of sequence-specific polypeptide backbone resonance assignments in the course of the structure determination, an “Assigned NMR-Profile” is generated, which visualizes the variation of the 15N–1H correlation cross peak intensities along the sequence and thus maps the sequence locations of polypeptide segments for which the NMR line shapes are affected by conformational exchange or other processes. The Assigned NMR-Profile provides a guiding reference during later stages of the structure determination, and is of special interest for monitoring the protein during functional studies, where dynamic features may be modulated during physiological functions. PMID:23839514

  2. Using Cloud Storage for NMR Data Distribution

    ERIC Educational Resources Information Center

    Soulsby, David

    2012-01-01

    An approach using Google Groups as method for distributing student-acquired NMR data has been implemented. We describe how to configure NMR spectrometer software so that data is uploaded to a laboratory section specific Google Group, thereby removing bottlenecks associated with printing and processing at the spectrometer workstation. Outside of…

  3. Evaluation of algorithms for automated phase correction of NMR spectra.

    PubMed

    de Brouwer, Hans

    2009-12-01

    In our attempt to fully automate the data acquisition and processing of NMR analysis of dissolved synthetic polymers, phase correction was found to be the most challenging aspect. Several approaches in literature were evaluated but none of these was found to be capable of phasing NMR spectra with sufficient robustness and high enough accuracy to fully eliminate intervention by a human operator. Step by step, aspects from the process of manual/visual phase correction were translated into mathematical concepts and evaluated. This included area minimization, peak height maximization, negative peak minimization and baseline correction. It was found that not one single approach would lead to acceptable results but that a combination of aspects was required, in line again with the process of manual phase correction. The combination of baseline correction, area minimization and negative area penalization was found to give the desired results. The robustness was found to be 100% which means that the correct zeroth order and first order phasing parameters are returned independent of the position of the starting point of the search in this parameter space. When applied to high signal-to-noise proton spectra, the accuracy was such that the returned phasing parameters were within a distance of 0.1-0.4 degrees in the two dimensional parameter space which resulted in an average error of 0.1% in calculated properties such as copolymer composition and end groups.

  4. PFG NMR and Bayesian analysis to characterise non-Newtonian fluids

    NASA Astrophysics Data System (ADS)

    Blythe, Thomas W.; Sederman, Andrew J.; Stitt, E. Hugh; York, Andrew P. E.; Gladden, Lynn F.

    2017-01-01

    Many industrial flow processes are sensitive to changes in the rheological behaviour of process fluids, and there therefore exists a need for methods that provide online, or inline, rheological characterisation necessary for process control and optimisation over timescales of minutes or less. Nuclear magnetic resonance (NMR) offers a non-invasive technique for this application, without limitation on optical opacity. We present a Bayesian analysis approach using pulsed field gradient (PFG) NMR to enable estimation of the rheological parameters of Herschel-Bulkley fluids in a pipe flow geometry, characterised by a flow behaviour index n , yield stress τ0 , and consistency factor k , by analysis of the signal in q -space. This approach eliminates the need for velocity image acquisition and expensive gradient hardware. We investigate the robustness of the proposed Bayesian NMR approach to noisy data and reduced sampling using simulated NMR data and show that even with a signal-to-noise ratio (SNR) of 100, only 16 points are required to be sampled to provide rheological parameters accurate to within 2% of the ground truth. Experimental validation is provided through an experimental case study on Carbopol 940 solutions (model Herschel-Bulkley fluids) using PFG NMR at a 1H resonance frequency of 85.2 MHz; for SNR > 1000, only 8 points are required to be sampled. This corresponds to a total acquisition time of <60 s and represents an 88% reduction in acquisition time when compared to MR flow imaging. Comparison of the shear stress-shear rate relationship, quantified using Bayesian NMR, with non-Bayesian NMR methods demonstrates that the Bayesian NMR approach is in agreement with MR flow imaging to within the accuracy of the measurement. Furthermore, as we increase the concentration of Carbopol 940 we observe a change in rheological characteristics, probably due to shear history-dependent behaviour and the different geometries used. This behaviour highlights the need for

  5. NMR and MRI apparatus and method

    DOEpatents

    Clarke, John; Kelso, Nathan; Lee, SeungKyun; Moessle, Michael; Myers, Whittier; McDermott, Robert; ten Haken, Bernard; Pines, Alexander; Trabesinger, Andreas

    2007-03-06

    Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. Additional signal to noise benefits are obtained by use of a low noise polarization coil, comprising litz wire or superconducting materials. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

  6. Challenges and perspectives in quantitative NMR.

    PubMed

    Giraudeau, Patrick

    2017-01-01

    This perspective article summarizes, from the author's point of view at the beginning of 2016, the major challenges and perspectives in the field of quantitative NMR. The key concepts in quantitative NMR are first summarized; then, the most recent evolutions in terms of resolution and sensitivity are discussed, as well as some potential future research directions in this field. A particular focus is made on methodologies capable of boosting the resolution and sensitivity of quantitative NMR, which could open application perspectives in fields where the sample complexity and the analyte concentrations are particularly challenging. These include multi-dimensional quantitative NMR and hyperpolarization techniques such as para-hydrogen-induced polarization or dynamic nuclear polarization. Because quantitative NMR cannot be dissociated from the key concepts of analytical chemistry, i.e. trueness and precision, the methodological developments are systematically described together with their level of analytical performance. Copyright © 2016 John Wiley & Sons, Ltd.

  7. Robust, integrated computational control of NMR experiments to achieve optimal assignment by ADAPT-NMR.

    PubMed

    Bahrami, Arash; Tonelli, Marco; Sahu, Sarata C; Singarapu, Kiran K; Eghbalnia, Hamid R; Markley, John L

    2012-01-01

    ADAPT-NMR (Assignment-directed Data collection Algorithm utilizing a Probabilistic Toolkit in NMR) represents a groundbreaking prototype for automated protein structure determination by nuclear magnetic resonance (NMR) spectroscopy. With a [(13)C,(15)N]-labeled protein sample loaded into the NMR spectrometer, ADAPT-NMR delivers complete backbone resonance assignments and secondary structure in an optimal fashion without human intervention. ADAPT-NMR achieves this by implementing a strategy in which the goal of optimal assignment in each step determines the subsequent step by analyzing the current sum of available data. ADAPT-NMR is the first iterative and fully automated approach designed specifically for the optimal assignment of proteins with fast data collection as a byproduct of this goal. ADAPT-NMR evaluates the current spectral information, and uses a goal-directed objective function to select the optimal next data collection step(s) and then directs the NMR spectrometer to collect the selected data set. ADAPT-NMR extracts peak positions from the newly collected data and uses this information in updating the analysis resonance assignments and secondary structure. The goal-directed objective function then defines the next data collection step. The procedure continues until the collected data support comprehensive peak identification, resonance assignments at the desired level of completeness, and protein secondary structure. We present test cases in which ADAPT-NMR achieved results in two days or less that would have taken two months or more by manual approaches.

  8. An Experimental Study on What Controls the Ratios of 18O/16O and 17O/16O of O2 During Microbial Respiration

    NASA Astrophysics Data System (ADS)

    Stolper, D. A.; Ward, B. B.; Fischer, W. W.; Bender, M. L.

    2015-12-01

    18O/16O and 17O/16O ratios of atmospheric and dissolved oceanic O2 are key biogeochemical tracers of total photosynthesis and respiration on global to local length scales and glacial/interglacial time scales (Luz et al., 1999). Critical to the use of these ratios as biogeochemical tracers is knowledge of how they are affected by production, consumption, and transport of O2. We present new measurements of O2 respiration by E. coli and N. oceanus, an ammonia oxidizing bacterium, to test three assumptions of isotopically enabled models of the O2 cycle: (i) laboratory-measured respiratory 18O/16O isotope effects (18α) of microorganisms are constant under all experimental and natural conditions (e.g., temperature and growth rate); (ii) the respiratory 'mass law' relationship between 18O/16O and 17O/16O [17α = (18α)β] is universal; and (iii) 18α and β for aerobic ammonia and organic carbon oxidation are identical. For E. coli, we find that both 18α and β are variable. From 37°C to 15°C, 18α varies linearly with temperature from 17 to 14‰, and β varies linearly from 0.513 to 0.508. 18α and β do not appear to vary with growth rate (as tested using different carbon sources). Both 18α and β are lower than previous observations for bacteria: 18α = 17-20‰ (Kiddon et al., 1993) and β = 0.515 (Luz and Barkan, 2005). We were able to simulate the observed temperature dependence of 18α and β using a model of respiration with two isotopically discriminating steps: O2 binding to cytochrome bo oxidase (the respiratory enzyme) and reduction of O2 to H2O. Finally, initial results on N. oceanus suggest it has similar values for 18α and β as previously studied aerobic bacteria that consume organic carbon, providing the first support for assumption (iii). Based on these results, isotopically constrained biogeochemical models of O2 cycling may need to consider a temperature dependence for 18α and β for microbial respiration. For example, these results may

  9. Ternary complexes between cationic GdIII chelates and anionic metabolites in aqueous solution: an NMR relaxometric study.

    PubMed

    Botta, Mauro; Aime, Silvio; Barge, Alessandro; Bobba, Gabriella; Dickins, Rachel S; Parker, David; Terreno, Enzo

    2003-05-09

    The (1)H and (17)O NMR relaxometric properties of two cationic complexes formed by Gd(III) with a macrocyclic heptadentate triamide ligand, L(1), and its Nmethylated analogue, L(2), have been investigated in aqueous media as a function of pH, temperature and magnetic field strength. The complexes possess two water molecules in their inner coordination sphere for which the rate of exchange has been found to be sensibly faster for the Nmethylated derivative and explained in terms of electronic effects (decrease of the charge density at the metal center) and perturbation of the network of hydrogen-bonded water molecules in the outer hydration sphere. The proton relaxivity shows a marked dependence from pH and decreases of about six units in the pH range 6.5 to 9.0. This has been accounted for by the displacement of the two water molecules by dissolved carbonate which acts as a chelating anion. The formation of ternary complexes with lactate, malonate, citrate, acetate, fluoride and hydrogenphosphate has been monitored by (1)H NMR relaxometric titrations at 20 MHz and pH 6.3 and the value of the affinity constant, K, and of the relaxivity of the adducts could be obtained. Lactate, malonate and citrate interact strongly with the complexes (log K > or =3.7) and coordinate in a bidendate mode by displacing both water molecules. Larger affinity constants have been measured for GdL(2). Acetate, fluoride and hydrogenphosphate form monoaqua ternary complexes which were investigated in detail with regard to their relaxometric properties. The NMR dispersion (NMRD) profiles indicate a large contribution to the relaxivity of the adducts from water molecules belonging to the second hydration shell of the complexes and hydrogen-bonded to the anion. A VT (17)O NMR study has shown a marked increase of the rate of water exchange upon binding which is explained by coordination of the anion in an equatorial site, thus leaving the water molecule in an apical position, more accessible for

  10. Parsimony and goodness-of-fit in multi-dimensional NMR inversion

    NASA Astrophysics Data System (ADS)

    Babak, Petro; Kryuchkov, Sergey; Kantzas, Apostolos

    2017-01-01

    Multi-dimensional nuclear magnetic resonance (NMR) experiments are often used for study of molecular structure and dynamics of matter in core analysis and reservoir evaluation. Industrial applications of multi-dimensional NMR involve a high-dimensional measurement dataset with complicated correlation structure and require rapid and stable inversion algorithms from the time domain to the relaxation rate and/or diffusion domains. In practice, applying existing inverse algorithms with a large number of parameter values leads to an infinite number of solutions with a reasonable fit to the NMR data. The interpretation of such variability of multiple solutions and selection of the most appropriate solution could be a very complex problem. In most cases the characteristics of materials have sparse signatures, and investigators would like to distinguish the most significant relaxation and diffusion values of the materials. To produce an easy to interpret and unique NMR distribution with the finite number of the principal parameter values, we introduce a new method for NMR inversion. The method is constructed based on the trade-off between the conventional goodness-of-fit approach to multivariate data and the principle of parsimony guaranteeing inversion with the least number of parameter values. We suggest performing the inversion of NMR data using the forward stepwise regression selection algorithm. To account for the trade-off between goodness-of-fit and parsimony, the objective function is selected based on Akaike Information Criterion (AIC). The performance of the developed multi-dimensional NMR inversion method and its comparison with conventional methods are illustrated using real data for samples with bitumen, water and clay.

  11. Xe-129 NMR of xenon dissolved in biological media.

    NASA Astrophysics Data System (ADS)

    Mazitov, R. K.; Kuzma, N. N.; Happer, W.; Driehuys, B.; Merrill, G. F.

    2002-03-01

    The high solubility and large chemical shift of ^129Xe in various tissues makes it an ideal, non-invasive probe for pathological conditions such as cancer or atherosclerosis. To this end, we report NMR measurements of lineshapes, chemical shifts, and relaxation times of ^129Xe dissolved in the following biological tissues in vitro: heart, muscle, sinew, stomach(R.K. Mazitov, K. M. Enikeev, et al., Dokl. Akad. Nauk) 365, 396 (1999)., and the white and yolk of egg. NMR measurements of xenon dissolved in olive and sunflower oils are also reported. Tissues weighing 160--250 mg, not exposed to freezing, were studied in a 11.75 T field at the ^129Xe resonance frequency of 138.4 MHz; the pressure of xenon in the sealed-sample ampoules was ~20 bar. The influence of drugs and water content on tissues was studied. No xenon-water clathrates(J.A. Ripmeester and D.W. Davidson, J. Mol. Struct. ) 75, 67 (1981). were observed in the tissues, even at the high pressures used. The aim of this study is to establish possible correlations between the NMR parameters of dissolved xenon and the state of the tissue.

  12. The effect of the recent 17O(p,α)14N and 18O(p,α)15N fusion cross section measurements in the nucleosynthesis of AGB stars

    NASA Astrophysics Data System (ADS)

    Palmerini, S.; Sergi, M. L.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Spitaleri, C.

    2015-01-01

    The Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of the 17O(p,α)14N and 18O(p,α)15N fusion reactions and to extract the strengths of the resonances that more contribute to the reaction rates at astrophysical energies. Moreover, the strength of the 65 keV resonance in the 17O(p,α)14N reaction, measured by means of the THM, has been used to renormalize the corresponding resonance strength in the 17O + p radiative capture channel. Since, proton-induced fusion reactions on 17O and 18O belong to the CNO cycle network for H-burning in stars, the new estimates of the cross sections have been introduced into calculations of Asymptotic giant branch (AGB) star nucleosynthesis to determine their impact on astrophysical environments. Results of nucleosynthesis calculations have been compared with geochemical analysis of "presolar" grains. These solids form in the cold and dusty envelopes that surround AGB stars and once that have been ejected by stellar winds, come to us as inclusions in meteorites providing invaluable benchmarks and constraints for our knowledge of fusion reactions in astrophysical environments.

  13. A microcoil NMR probe for coupling microscale HPLC with on-line NMR spectroscopy.

    PubMed

    Subramanian, R; Kelley, W P; Floyd, P D; Tan, Z J; Webb, A G; Sweedler, J V

    1999-12-01

    An HPLC NMR system is presented that integrates a commercial microbore HPLC system using a 0.5-mm column with a 500-MHz proton NMR spectrometer using a custom NMR probe with an observe volume of 1.1 microL and a coil fill factor of 68%. Careful attention to capillary connections and NMR flow cell design allows on-line NMR detection with no significant loss in separation efficiency when compared with a UV chromatogram. HPLC NMR is performed on mixtures of amino acids and small peptides with analyte injection amounts as small as 750 ng; the separations are accomplished in less than 10 min and individual NMR spectra are acquired with 12 s time resolution. Stopped-flow NMR is achieved by diversion of the chromatographic flow after observation of the beginning of the analyte band within the NMR flow cell. Isolation of the compound of interest within the NMR detection cell allows multidimensional experiments to be performed. A stopped-flow COSY spectrum of the peptide Phe-Ala is acquired in 3.5 h with an injected amount of 5 micrograms.

  14. ADVANCED SOLIDS NMR STUDIES OF COAL STRUCTURE AND CHEMISTRY

    SciTech Connect

    1997-03-01

    This report covers the progress made on the title project for the project period. The study of coal chemical structure is a vital component of research efforts to develop better chemical utilization of coals, and for furthering our basic understanding of coal geochemistry. In this grant we are addressing several structural questions pertaining to coals with advances in state of the art solids NMR methods. Our goals are twofold. First, we are interested in developing new methods that will enable us to measure important structural parameters in whole coals not directly accessible by other techniques. In parallel with these efforts we will apply these NMR methods in a study of the chemical differences between gas-sourcing and oil-sourcing coals. The NMR methods work will specifically focus on determination of the number and types of methylene groups, determination of the number and types of methane groups, identification of carbons adjacent to nitrogen and sites with exchangeable protons, and methods to more finely characterize the distribution of hydrogen in coals. The motivation for investigating these specific structural features of coals arises from their relevance to the chemical reactivity of coals, and their suitability for possible correlations with the oil sourcing potential of some types of coals. The coals to be studied and contrasted include oil-prone coals from Australia and Indonesia, those comprising the Argonne Premium Coal Sample bank, and other relevant samples. In this report period we have focused our work on 1 segment of the program. Our last report outlined progress in using our NMR editing methods with higher field operation where higher magic angle spinning rates are required. Significant difficulties were identified, and these have been the main subject of study during the most recent granting period.

  15. An NMR determination of CO diffusion on platinum electrocatalysts.

    PubMed

    Kobayashi, Takeshi; Babu, Panakkattu K; Gancs, Lajos; Chung, Jong Ho; Oldfield, Eric; Wieckowski, Andrzej

    2005-10-19

    We report the first direct measurement of CO diffusion on nanoparticle Pt electrocatalysts at the solid/liquid interface, carried out using 13C nuclear magnetic resonance (NMR) with a spin-labeling pulse sequence. Diffusion parameters were measured in the temperature range of 253-293 K for CO adsorbed on commercial Pt-black under saturation coverage. 2H NMR of the same system indicates that the electrolyte remains in the liquid state at temperatures where the CO diffusion experiments were performed. The CO diffusion parameters follow typical Arrhenius behavior with an activation energy of 6.0 +/- 0.4 kcal/mol and a pre-exponential factor of (1.1 +/- 0.6) x 10-8 cm2/s. Exchange between different CO populations, driven by a chemical potential gradient, is suggested to be the main mechanism for CO diffusion. The presence of the electrolyte medium considerably slows down the diffusion of CO as compared to that seen on surfaces of bulk metals under UHV conditions. This work opens up a new approach to the study of surface diffusion of adsorbed molecules on nanoparticle electrode catalysts, including the possibility of correlating diffusion parameters to catalytic activity in real world applications of broad general interest.

  16. NMR analysis of base-pair opening kinetics in DNA.

    PubMed

    Szulik, Marta W; Voehler, Markus; Stone, Michael P

    2014-12-12

    Base pairing in nucleic acids plays a crucial role in their structure and function. Differences in the base-pair opening and closing kinetics of individual double-stranded DNA sequences or between chemically modified base pairs provide insight into the recognition of these base pairs by DNA processing enzymes. This unit describes how to quantify the kinetics for localized base pairs by observing changes in the imino proton signals by nuclear magnetic resonance spectroscopy. The determination of all relevant parameters using state-of-the art techniques and NMR instrumentation, including cryoprobes, is discussed.

  17. Scalar operators in solid-state NMR

    SciTech Connect

    Sun, Boqin

    1991-11-01

    Selectivity and resolution of solid-state NMR spectra are determined by dispersion of local magnetic fields originating from relaxation effects and orientation-dependent resonant frequencies of spin nuclei. Theoretically, the orientation-dependent resonant frequencies can be represented by a set of irreducible tensors. Among these tensors, only zero rank tensors (scalar operators) are capable of providing high resolution NMR spectra. This thesis presents a series of new developments in high resolution solid-state NMR concerning the reconstruction of various scalar operators motion in solid C{sub 60} is analyzed.

  18. An Inversion Recovery NMR Kinetics Experiment.

    PubMed

    Williams, Travis J; Kershaw, Allan D; Li, Vincent; Wu, Xinping

    2011-05-01

    A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this article will enable instructors to use inversion recovery as a laboratory activity in applied NMR classes and provide research students with a convenient template with which to acquire inversion recovery data on research samples.

  19. An Inversion Recovery NMR Kinetics Experiment

    PubMed Central

    Williams, Travis J.; Kershaw, Allan D.; Li, Vincent; Wu, Xinping

    2011-01-01

    A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this article will enable instructors to use inversion recovery as a laboratory activity in applied NMR classes and provide research students with a convenient template with which to acquire inversion recovery data on research samples. PMID:21552343

  20. MAS NMR of HIV-1 protein assemblies

    NASA Astrophysics Data System (ADS)

    Suiter, Christopher L.; Quinn, Caitlin M.; Lu, Manman; Hou, Guangjin; Zhang, Huilan; Polenova, Tatyana

    2015-04-01

    The negative global impact of the AIDS pandemic is well known. In this perspective article, the utility of magic angle spinning (MAS) NMR spectroscopy to answer pressing questions related to the structure and dynamics of HIV-1 protein assemblies is examined. In recent years, MAS NMR has undergone major technological developments enabling studies of large viral assemblies. We discuss some of these evolving methods and technologies and provide a perspective on the current state of MAS NMR as applied to the investigations into structure and dynamics of HIV-1 assemblies of CA capsid protein and of Gag maturation intermediates.

  1. N-H...F hydrogen bonds in fluorinated benzanilides: NMR and DFT study.

    PubMed

    Manjunatha Reddy, G N; Vasantha Kumar, M V; Guru Row, T N; Suryaprakash, N

    2010-10-28

    Using (19)F and (1)H-NMR (with (14)N decoupling) spectroscopic techniques together with density functional theoretical (DFT) calculations, we have investigated weak molecular interactions in isomeric fluorinated benzanilides. Simultaneous presence of through space nuclear spin-spin couplings ((1h)J(N-HF)) of diverse strengths and feeble structural fluctuations are detected as a function of site specific substitution of fluorine atoms within the basic identical molecular framework. The transfer of hydrogen bonding interaction energies through space is established by perturbing their strengths and monitoring the effect on NMR parameters. Multiple quantum (MQ) excitation, up to the highest possible MQ orders of coupled protons, is utilized as a tool for accurate (1)H assignments. Results of NMR studies and DFT calculations are compared with the relevant structural parameters taken from single crystal X-ray diffraction studies.

  2. The role of H⋯π interaction on some calculated NMR data

    NASA Astrophysics Data System (ADS)

    Ebrahimi, Ali; Habibi, Mostafa; Masoodi, Hamid Reza

    2009-08-01

    The effect of C-H⋯π and X-H⋯π interactions on some NMR data of haloacetylene⋯benzene, halomethane⋯benzene and hydrogen halide⋯benzene complexes has been studied at PBE0/6-311++G(d, p) and PBE1KCIS/6-311++G(d, p) levels of theory. The complexes were optimized by MP2 method using 6-311++G(d, p) and aug-cc-pVDZ basis sets. In addition to geometrical parameters and binding energies, topological properties of electron charge density calculated by atoms in molecules (AIM) method, and the results of natural bond orbital (NBO) analysis are in a good relationship with calculated NMR data. The consideration of these parameters aids in better understanding of NMR data in these complexes.

  3. Determination of the 15N/14N, 17O/16O, and 18O/16O ratios of nitrous oxide by using continuous-flow isotope-ratio mass spectrometry.

    PubMed

    Komatsu, Daisuke D; Ishimura, Toyoho; Nakagawa, Fumiko; Tsunogai, Urumu

    2008-05-01

    We developed a rapid, sensitive, and automated analytical system to determine the delta15N, delta18O, and Delta17O values of nitrous oxide (N2O) simultaneously in nanomolar quantities for a single batch of samples by continuous-flow isotope-ratio mass spectrometry (CF-IRMS) without any cumbersome and time-consuming pretreatments. The analytical system consisted of a vacuum line to extract and purify N2O, a gas chromatograph for further purification of N2O, an optional thermal furnace to decompose N2O to O2, and a CF-IRMS system. We also used pneumatic valves and pneumatic actuators in the system so that we could operate it automatically with timing software on a personal computer. The analytical precision was better than 0.12 per thousand for delta15N with >4 nmol N2O injections, 0.25 per thousand for delta18O with >4 nmol N2O injections, and 0.20 per thousand for Delta17O with >20 nmol N2O injections for a single measurement. We were also easily able to improve the precision (standard errors) to better than 0.05 per thousand for delta15N, 0.10 per thousand for delta18O, and 0.10 per thousand for Delta17O through multiple analyses with more than four repetitions with 190 nmol samples using the automated analytical system. Using the system, the delta15N, delta18O, and Delta17O values of N2O can be quantified not only for atmospheric samples, but also for other gas or liquid samples with low N2O content, such as soil gas or natural water. Here, we showed the first ever Delta17O measurements of soil N2O.

  4. HERSCHEL/HIFI SEARCH FOR H{sub 2}{sup 17}O AND H{sub 2}{sup 18}O IN IRC+10216: CONSTRAINTS ON MODELS FOR THE ORIGIN OF WATER VAPOR

    SciTech Connect

    Neufeld, David A.; Tolls, Volker; Melnick, Gary J.; Agundez, Marcelino; Gonzalez-Alfonso, Eduardo; Decin, Leen; Daniel, Fabien; Cernicharo, Jose; Schmidt, Miroslaw; Szczerba, Ryszard

    2013-04-10

    We report the results of a sensitive search for the minor isotopologues of water, H{sub 2}{sup 17}O and H{sub 2}{sup 18}O, toward the carbon-rich asymptotic giant branch star IRC+10216 (a.k.a. CW Leonis) using the HIFI instrument on the Herschel Space Observatory. This search was motivated by the fact that any detection of isotopic enhancement in the H{sub 2}{sup 17}O and H{sub 2}{sup 18}O abundances would have strongly implicated CO photodissociation as the source of the atomic oxygen needed to produce water in a carbon-rich circumstellar envelope. Our observations place an upper limit of 1/470 on the H{sub 2}{sup 17}O/H{sub 2}{sup 16}O abundance ratio. Given the isotopic {sup 17}O/{sup 16}O ratio of 1/840 inferred previously for the photosphere of IRC+10216, this result places an upper limit of a factor 1.8 on the extent of any isotope-selective enhancement of H{sub 2}{sup 17}O in the circumstellar material, and provides an important constraint on any model that invokes CO photodissociation as the source of O for H{sub 2}O production. In the context of the clumpy photodissociation model proposed previously for the origin of water in IRC+10216, our limit implies that {sup 12}C{sup 16}O (not {sup 13}C{sup 16}O or SiO) must be the dominant source of {sup 16}O for H{sub 2}O production, and that the effects of self-shielding can only have reduced the {sup 12}C{sup 16}O photodissociation rate by at most a factor {approx}2.

  5. Theoretical and experimental NMR studies on muscimol from fly agaric mushroom (Amanita muscaria)

    NASA Astrophysics Data System (ADS)

    Kupka, Teobald; Wieczorek, Piotr P.

    2016-01-01

    In this article we report results of combined theoretical and experimental NMR studies on muscimol, the bioactive alkaloid from fly agaric mushroom (Amanita muscaria). The assignment of 1H and 13C NMR spectra of muscimol in DMSO-d6 was supported by additional two-dimensional heteronuclear correlated spectra (2D NMR) and gauge independent atomic orbital (GIAO) NMR calculations using density functional theory (DFT). The effect of solvent in theoretical calculations was included via polarized continuum model (PCM) and the hybrid three-parameter B3LYP density functional in combination with 6-311++G(3df,2pd) basis set enabled calculation of reliable structures of non-ionized (neutral) molecule and its NH and zwitterionic forms in the gas phase, chloroform, DMSO and water. GIAO NMR calculations, using equilibrium and rovibrationally averaged geometry, at B3LYP/6-31G* and B3LYP/aug-cc-pVTZ-J levels of theory provided muscimol nuclear magnetic shieldings. The theoretical proton and carbon chemical shifts were critically compared with experimental NMR spectra measured in DMSO. Our results provide useful information on its structure in solution. We believe that such data could improve the understanding of basic features of muscimol at atomistic level and provide another tool in studies related to GABA analogs.

  6. Theoretical and experimental NMR studies on muscimol from fly agaric mushroom (Amanita muscaria).

    PubMed

    Kupka, Teobald; Wieczorek, Piotr P

    2016-01-15

    In this article we report results of combined theoretical and experimental NMR studies on muscimol, the bioactive alkaloid from fly agaric mushroom (Amanita muscaria). The assignment of (1)H and (13)C NMR spectra of muscimol in DMSO-d6 was supported by additional two-dimensional heteronuclear correlated spectra (2D NMR) and gauge independent atomic orbital (GIAO) NMR calculations using density functional theory (DFT). The effect of solvent in theoretical calculations was included via polarized continuum model (PCM) and the hybrid three-parameter B3LYP density functional in combination with 6-311++G(3df,2pd) basis set enabled calculation of reliable structures of non-ionized (neutral) molecule and its NH and zwitterionic forms in the gas phase, chloroform, DMSO and water. GIAO NMR calculations, using equilibrium and rovibrationally averaged geometry, at B3LYP/6-31G* and B3LYP/aug-cc-pVTZ-J levels of theory provided muscimol nuclear magnetic shieldings. The theoretical proton and carbon chemical shifts were critically compared with experimental NMR spectra measured in DMSO. Our results provide useful information on its structure in solution. We believe that such data could improve the understanding of basic features of muscimol at atomistic level and provide another tool in studies related to GABA analogs.

  7. NMR relaxometry as a versatile tool to study Li ion dynamics in potential battery materials.

    PubMed

    Kuhn, A; Kunze, M; Sreeraj, P; Wiemhöfer, H D; Thangadurai, V; Wilkening, M; Heitjans, P

    2012-04-01

    NMR spin relaxometry is known to be a powerful tool for the investigation of Li(+) dynamics in (non-paramagnetic) crystalline and amorphous solids. As long as significant structural changes are absent in a relatively wide temperature range, with NMR spin-lattice (as well as spin-spin) relaxation measurements information on Li self-diffusion parameters such as jump rates and activation energies are accessible. Diffusion-induced NMR relaxation rates are governed by a motional correlation function describing the ion dynamics present. Besides the mean correlation rate of the dynamic process, the motional correlation function (i) reflects deviations from random motion (so-called correlation effects) and (ii) gives insights into the dimensionality of the hopping process. In favorable cases, i.e., when temperature- and frequency-dependent NMR relaxation rates are available over a large dynamic range, NMR spin relaxometry is able to provide a comprehensive picture of the relevant Li dynamic processes. In the present contribution, we exemplarily present two recent variable-temperature (7)Li NMR spin-lattice relaxation studies focussing on Li(+) dynamics in crystalline ion conductors which are of relevance for battery applications, viz. Li(7) La(3)Zr(2)O(12) and Li(12)Si(7).

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  9. A ferromagnetic shim insert for NMR magnets - Towards an integrated gyrotron for DNP-NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Ryan, Herbert; van Bentum, Jan; Maly, Thorsten

    2017-04-01

    In recent years high-field Dynamic Nuclear Polarization (DNP) enhanced NMR spectroscopy has gained significant interest. In high-field DNP-NMR experiments (⩾400 MHz 1H NMR, ⩾9.4 T) often a stand-alone gyrotron is used to generate high microwave/THz power to produce sufficiently high microwave induced B1e fields at the position of the NMR sample. These devices typically require a second, stand-alone superconducting magnet to operate. Here we present the design and realization of a ferroshim insert, to create two iso-centers inside a commercially available wide-bore NMR magnet. This work is part of a larger project to integrate a gyrotron into NMR magnets, effectively eliminating the need for a second, stand-alone superconducting magnet.

  10. NMR Analysis of Unknowns: An Introduction to 2D NMR Spectroscopy

    ERIC Educational Resources Information Center

    Alonso, David E.; Warren, Steven E.

    2005-01-01

    A study combined 1D (one-dimensional) and 2D (two-dimensional) NMR spectroscopy to solve structural organic problems of three unknowns, which include 2-, 3-, and 4-heptanone. Results showed [to the first power]H NMR and [to the thirteenth power]C NMR signal assignments for 2- and 3-heptanone were more challenging than for 4-heptanone owing to the…

  11. A New Microcell Technique for NMR Analysis.

    ERIC Educational Resources Information Center

    Yu, Sophia J.

    1987-01-01

    Describes a new laboratory technique for working with small samples of compounds used in nuclear magnetic resonance (NMR) analysis. Demonstrates how microcells can be constructed for each experiment and samples can be recycled. (TW)

  12. Relaxation time estimation in surface NMR

    DOEpatents

    Grunewald, Elliot D.; Walsh, David O.

    2017-03-21

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

  13. Interfaces in polymer nanocomposites - An NMR study

    NASA Astrophysics Data System (ADS)

    Böhme, Ute; Scheler, Ulrich

    2016-03-01

    Nuclear Magnetic Resonance (NMR) is applied for the investigation of polymer nanocomposites. Solid-state NMR is applied to study the modification steps to compatibilize layered double hydroxides with non-polar polymers. 1H relaxation NMR gives insight on the polymer dynamics over a wide range of correlation times. For the polymer chain dynamics the transverse relaxation time T2 is most suited. In this presentation we report on two applications of T2 measurements under external mechanical stress. In a low-field system relaxation NMR studies are performed in-situ under uniaxial stress. High-temperature experiments in a Couette cell permit the investigation of the polymer dynamics in the melt under shear flow.

  14. NMR-Assisted Molecular Docking Methodologies.

    PubMed

    Sturlese, Mattia; Bellanda, Massimo; Moro, Stefano

    2015-08-01

    Nuclear magnetic resonance (NMR) spectroscopy and molecular docking are regularly being employed as helpful tools of drug discovery research. Molecular docking is an extremely rapid method to evaluate possible binders from a large chemical library in a fast and cheap manner. NMR techniques can directly detect a protein-ligand interaction, can determine the corresponding association constant, and can consistently identify the ligand binding cavity. Consequently, molecular docking and NMR techniques are naturally complementary techniques where the combination of the two has the potential to improve the overall efficiency of drug discovery process. In this review, we would like to summarize the state of the art of docking methods which have been recently bridged to NMR experiments to identify novel and effective therapeutic drug candidates.

  15. NMR Methods to Study Dynamic Allostery

    PubMed Central

    Grutsch, Sarina; Brüschweiler, Sven; Tollinger, Martin

    2016-01-01

    Nuclear magnetic resonance (NMR) spectroscopy provides a unique toolbox of experimental probes for studying dynamic processes on a wide range of timescales, ranging from picoseconds to milliseconds and beyond. Along with NMR hardware developments, recent methodological advancements have enabled the characterization of allosteric proteins at unprecedented detail, revealing intriguing aspects of allosteric mechanisms and increasing the proportion of the conformational ensemble that can be observed by experiment. Here, we present an overview of NMR spectroscopic methods for characterizing equilibrium fluctuations in free and bound states of allosteric proteins that have been most influential in the field. By combining NMR experimental approaches with molecular simulations, atomistic-level descriptions of the mechanisms by which allosteric phenomena take place are now within reach. PMID:26964042

  16. Median Modified Wiener Filter for nonlinear adaptive spatial denoising of protein NMR multidimensional spectra.

    PubMed

    Cannistraci, Carlo Vittorio; Abbas, Ahmed; Gao, Xin

    2015-01-26

    Denoising multidimensional NMR-spectra is a fundamental step in NMR protein structure determination. The state-of-the-art method uses wavelet-denoising, which may suffer when applied to non-stationary signals affected by Gaussian-white-noise mixed with strong impulsive artifacts, like those in multi-dimensional NMR-spectra. Regrettably, Wavelet's performance depends on a combinatorial search of wavelet shapes and parameters; and multi-dimensional extension of wavelet-denoising is highly non-trivial, which hampers its application to multidimensional NMR-spectra. Here, we endorse a diverse philosophy of denoising NMR-spectra: less is more! We consider spatial filters that have only one parameter to tune: the window-size. We propose, for the first time, the 3D extension of the median-modified-Wiener-filter (MMWF), an adaptive variant of the median-filter, and also its novel variation named MMWF*. We test the proposed filters and the Wiener-filter, an adaptive variant of the mean-filter, on a benchmark set that contains 16 two-dimensional and three-dimensional NMR-spectra extracted from eight proteins. Our results demonstrate that the adaptive spatial filters significantly outperform their non-adaptive versions. The performance of the new MMWF* on 2D/3D-spectra is even better than wavelet-denoising. Noticeably, MMWF* produces stable high performance almost invariant for diverse window-size settings: this signifies a consistent advantage in the implementation of automatic pipelines for protein NMR-spectra analysis.

  17. Median Modified Wiener Filter for nonlinear adaptive spatial denoising of protein NMR multidimensional spectra

    PubMed Central

    Cannistraci, Carlo Vittorio; Abbas, Ahmed; Gao, Xin

    2015-01-01

    Denoising multidimensional NMR-spectra is a fundamental step in NMR protein structure determination. The state-of-the-art method uses wavelet-denoising, which may suffer when applied to non-stationary signals affected by Gaussian-white-noise mixed with strong impulsive artifacts, like those in multi-dimensional NMR-spectra. Regrettably, Wavelet's performance depends on a combinatorial search of wavelet shapes and parameters; and multi-dimensional extension of wavelet-denoising is highly non-trivial, which hampers its application to multidimensional NMR-spectra. Here, we endorse a diverse philosophy of denoising NMR-spectra: less is more! We consider spatial filters that have only one parameter to tune: the window-size. We propose, for the first time, the 3D extension of the median-modified-Wiener-filter (MMWF), an adaptive variant of the median-filter, and also its novel variation named MMWF*. We test the proposed filters and the Wiener-filter, an adaptive variant of the mean-filter, on a benchmark set that contains 16 two-dimensional and three-dimensional NMR-spectra extracted from eight proteins. Our results demonstrate that the adaptive spatial filters significantly outperform their non-adaptive versions. The performance of the new MMWF* on 2D/3D-spectra is even better than wavelet-denoising. Noticeably, MMWF* produces stable high performance almost invariant for diverse window-size settings: this signifies a consistent advantage in the implementation of automatic pipelines for protein NMR-spectra analysis. PMID:25619991

  18. Frontiers of NMR in Molecular Biology

    SciTech Connect

    1999-08-25

    NMR spectroscopy is expanding the horizons of structural biology by determining the structures and describing the dynamics of blobular proteins in aqueous solution, as well as other classes of proteins including membrane proteins and the polypeptides that form the aggregates diagnostic of prion and amyloid diseases. Significant results are also emerging on DNA and RNA oligomers and their complexes with proteins. This meeting focused attention on key structural questions emanating from molecular biology and how NMR spectroscopy can be used to answer them.

  19. WHNMR--a universal NMR application package.

    PubMed

    Xiaodong, Z; Hongbin, H; Nian, H; Lianfang, S; Chaohui, Y

    1996-06-01

    A PC-based NMR off-line data processing system is developed and described in detail. With this software system, one-dimensional (1D), two-dimensional (2D), and NMR imaging (MRI) data can be processed easily, and give reliable results. By the applications of this system, a versatile software interface is set up to achieve data exchanging and integrated usage with other PC application software and aids the PC to become an effective and powerful workstation.

  20. Modern NMR spectroscopy: a guide for chemists

    SciTech Connect

    Sanders, J.K.M.; Hunter, B.K.

    1988-01-01

    The aim of the authors of Modern NMR Spectroscopy is to bridge the communication gap between the chemist and the spectroscopist. The approach is nonmathematical, descriptive, and pictorial. To illustrate the ideas introduced in the text, the authors provide original spectra obtained specially for this purpose. Examples include spectroscopy of protons, carbon, and less receptive nuclei of interest to inorganic chemists. The authors succeed in making high-resolution NMR spectroscopy comprehensible for the average student or chemist.

  1. Metabolic flux in carbohydrate biosynthesis. New methods using stable isotopes, mass spectrometry, and NMR

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Structural analysis of carbohydrates involves three parameters: composition, linkage, and conformation, and tends to rely on the various forms of two techniques; mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy. These techniques are enhanced and extended by the use of stable...

  2. An NMR Study of Isotope Effect on Keto-Enol Tautomerization: A Physical Organic Chemistry Experiment

    ERIC Educational Resources Information Center

    Atkinson, D.; Chechik, V.

    2004-01-01

    Isotope substitution often affects the rate of an organic reaction and can be used to reveal the underlying mechanism. A series of experiments that use (super 1)H NMR to determine primary and secondary isotope effects, activation parameters, and the regioselectivity of butanone enolization are described.

  3. Hypothesis driven assessment of an NMR curriculum

    NASA Astrophysics Data System (ADS)

    Cossey, Kimberly

    The goal of this project was to develop a battery of assessments to evaluate an undergraduate NMR curriculum at Penn State University. As a chemical education project, we sought to approach the problem of curriculum assessment from a scientific perspective, while remaining grounded in the education research literature and practices. We chose the phrase hypothesis driven assessment to convey this process of relating the scientific method to the study of educational methods, modules, and curricula. We began from a hypothesis, that deeper understanding of one particular analytical technique (NMR) will increase undergraduate students' abilities to solve chemical problems. We designed an experiment to investigate this hypothesis, and data collected were analyzed and interpreted in light of the hypothesis and several related research questions. The expansion of the NMR curriculum at Penn State was funded through the NSF's Course, Curriculum, and Laboratory Improvement (CCLI) program, and assessment was required. The goal of this project, as stated in the grant proposal, was to provide NMR content in greater depth by integrating NMR modules throughout the curriculum in physical chemistry, instrumental, and organic chemistry laboratory courses. Hands-on contact with the NMR spectrometer and NMR data and repeated exposure of the analytical technique within different contexts (courses) were unique factors of this curriculum. Therefore, we maintained a focus on these aspects throughout the evaluation process. The most challenging and time-consuming aspect of any assessment is the development of testing instruments and methods to provide useful data. After key variables were defined, testing instruments were designed to measure these variables based on educational literature (Chapter 2). The primary variables measured in this assessment were: depth of understanding of NMR, basic NMR knowledge, problem solving skills (HETCOR problem), confidence for skills used in class (within

  4. A new laboratory approach to shale analysis using NMR relaxometry

    USGS Publications Warehouse

    Washburn, Kathryn E.; Birdwell, Justin E.; Baez, Luis; Beeney, Ken; Sonnenberg, Steve

    2013-01-01

    kerogen, thermally degraded kerogen, and char. Integrated peak areas from the LF-NMR results representative of kerogen and bitumen were found to be well correlated with S1 and S2 parameters from Rock-Eval programmed pyrolysis. This study demonstrates that LFNMR relaxometry can provide a wide range of information on shales and other reservoir rocks that goes well beyond porosity and pore-fluid analysis.

  5. The Kinetics of Dissociations of Aluminum - Oxygen Bonds in Aqueous Complexes - An NMR Study

    SciTech Connect

    Dr. William Casey

    2003-09-03

    OAK B262 The Kinetics of Dissociations of Aluminum--Oxygen Bonds in Aqueous Complexes--An NMR Study. In this project we determined rates and mechanisms of Al(III)-O bond rupture at mineral surfaces and in dissolved aluminum complexes. We then compared the experimental results to simulations in an attempt to predict rate coefficients. Most of the low-temperature reactions that are geochemically important involve a bonded atom or molecule that is replaced with another. We probe these reactions at the most fundamental level in order to establish a model to predict rates for the wide range of reactions that cannot be experimentally studied. The chemistry of small aluminum cluster (Figure) provides a window into the hydrolytic processes that control rates of mineral formation and the transformation of adsorbates into extended structures. The molecule shown below as an example exposes several types of oxygens to the bulk solution including seven structurally distinct sets of bridging hydroxyls. This molecule is a rich model for the aqueous interface of aluminum (hydr)oxide minerals, since it approaches colloidal dimensions in size, yet is a dissolved complex with +18 charge. We have conducted both {sup 17}O- {sup 27}Al- and {sup 19}F-NMR experiments to identify the reactive sites and to determine the rates of isotopic exchange between these sites and the bulk solution. The research was enormously successful and led to a series of papers that are being used as touchstones for assessing the accuracy of computer models of bond ruptures in water.

  6. Molecular dynamics of solid cortisol studied by NMR

    NASA Astrophysics Data System (ADS)

    Andrew, E. R.

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

  7. Singular Hopf bifurcation to unstable periodic solutions in a NMR laser

    NASA Astrophysics Data System (ADS)

    Braza, Peter A.; Erneux, Thomas

    1989-09-01

    We apply recent developments in the study of singular Hopf bifurcations to describe the complete bifurcation diagram of a simple NMR laser with an injected signal. The branch of periodic solutions appears at a Hopf bifurcation point and may or may not disappear at a homoclinic point. The bifurcation is always subcritical, which suggests that the periodic solutions are all unstable. Our asymptotic analysis is based on the relative values of the fixed parameters in the problem. Our results complement earlier investigations by Holzner et al. [Phys. Rev. A 36, 1280 (1987)] and by Baugher, Hammack, and Lin [Phys. Rev. A 39, 1549 (1989)] on the subcritical Hopf bifurcation in a NMR laser.

  8. Temperature imaging by 1H NMR and suppression of convection in NMR probes

    PubMed

    Hedin; Furo

    1998-03-01

    A simple arrangement for suppressing convection in NMR probes is tested experimentally. Diffusion experiments are used to determine the onset of convection and 1H temperature imaging helps to rationalize the somewhat surprising results. A convenient new 1H NMR thermometer, CH2Br2 dissolved in a nematic thermotropic liquid crystal, is presented. Copyright 1998 Academic Press.

  9. Performance of the WeNMR CS-Rosetta3 web server in CASD-NMR.

    PubMed

    van der Schot, Gijs; Bonvin, Alexandre M J J

    2015-08-01

    We present here the performance of the WeNMR CS-Rosetta3 web server in CASD-NMR, the critical assessment of automated structure determination by NMR. The CS-Rosetta server uses only chemical shifts for structure prediction, in combination, when available, with a post-scoring procedure based on unassigned NOE lists (Huang et al. in J Am Chem Soc 127:1665-1674, 2005b, doi: 10.1021/ja047109h). We compare the original submissions using a previous version of the server based on Rosetta version 2.6 with recalculated targets using the new R3FP fragment picker for fragment selection and implementing a new annotation of prediction reliability (van der Schot et al. in J Biomol NMR 57:27-35, 2013, doi: 10.1007/s10858-013-9762-6), both implemented in the CS-Rosetta3 WeNMR server. In this second round of CASD-NMR, the WeNMR CS-Rosetta server has demonstrated a much better performance than in the first round since only converged targets were submitted. Further, recalculation of all CASD-NMR targets using the new version of the server demonstrates that our new annotation of prediction quality is giving reliable results. Predictions annotated as weak are often found to provide useful models, but only for a fraction of the sequence, and should therefore only be used with caution.

  10. Use of NMR and NMR Prediction Software to Identify Components in Red Bull Energy Drinks

    ERIC Educational Resources Information Center

    Simpson, Andre J.; Shirzadi, Azadeh; Burrow, Timothy E.; Dicks, Andrew P.; Lefebvre, Brent; Corrin, Tricia

    2009-01-01

    A laboratory experiment designed as part of an upper-level undergraduate analytical chemistry course is described. Students investigate two popular soft drinks (Red Bull Energy Drink and sugar-free Red Bull Energy Drink) by NMR spectroscopy. With assistance of modern NMR prediction software they identify and quantify major components in each…

  11. NMR Spectra through the Eyes of a Student: Eye Tracking Applied to NMR Items

    ERIC Educational Resources Information Center

    Topczewski, Joseph J.; Topczewski, Anna M.; Tang, Hui; Kendhammer, Lisa K.; Pienta, Norbert J.

    2017-01-01

    Nuclear magnetic resonance spectroscopy (NMR) plays a key role in introductory organic chemistry, spanning theory, concepts, and experimentation. Therefore, it is imperative that the instruction methods for NMR are both efficient and effective. By utilizing eye tracking equipment, the researchers were able to monitor how second-semester organic…

  12. Articulatory Parameters.

    ERIC Educational Resources Information Center

    Ladefoged, Peter

    1980-01-01

    Summarizes the 16 parameters hypothesized to be necessary and sufficient for linguistic phonetic specifications. Suggests seven parameters affecting tongue shapes, three determining the positions of the lips, one controlling the position of the velum, four varying laryngeal actions, and one controlling respiratory activity. (RL)

  13. Characterization of heroin samples by 1H NMR and 2D DOSY 1H NMR.

    PubMed

    Balayssac, Stéphane; Retailleau, Emmanuel; Bertrand, Geneviève; Escot, Marie-Pierre; Martino, Robert; Malet-Martino, Myriam; Gilard, Véronique

    2014-01-01

    Twenty-four samples of heroin from different illicit drug seizures were analyzed using proton Nuclear Magnetic Resonance ((1)H NMR) and two-dimensional diffusion-ordered spectroscopy (2D DOSY) (1)H NMR. A careful assignment and quantification of (1)H signals enabled a comprehensive characterization of the substances present in the samples investigated: heroin, its main related impurities (6-acetylmorphine, acetylcodeine, morphine, noscapine and papaverine) and cutting agents (caffeine and acetaminophen in nearly all samples as well as lactose, lidocaine, mannitol, piracetam in one sample only), and hence to establish their spectral signatures. The good agreement between the amounts of heroin, noscapine, caffeine and acetaminophen determined by (1)H NMR and gas chromatography, the reference method in forensic laboratories, demonstrates the validity of the (1)H NMR technique. In this paper, 2D DOSY (1)H NMR offers a new approach for a whole characterization of the various components of these complex mixtures.

  14. Nuclear magnetic resonance apparatus having semitoroidal rf coil for use in topical NMR and NMR imaging

    DOEpatents

    Fukushima, Eiichi; Roeder, Stephen B. W.; Assink, Roger A.; Gibson, Atholl A. V.

    1986-01-01

    An improved nuclear magnetic resonance (NMR) apparatus for use in topical magnetic resonance (TMR) spectroscopy and other remote sensing NMR applications includes a semitoroidal radio-frequency (rf) coil. The semitoroidal rf coil produces an effective alternating magnetic field at a distance from the poles of the coil, so as to enable NMR measurements to be taken from selected regions inside an object, particularly including human and other living subjects. The semitoroidal rf coil is relatively insensitive to magnetic interference from metallic objects located behind the coil, thereby rendering the coil particularly suited for use in both conventional and superconducting NMR magnets. The semitoroidal NMR coil can be constructed so that it emits little or no excess rf electric field associated with the rf magnetic field, thus avoiding adverse effects due to dielectric heating of the sample or to any other interaction of the electric field with the sample.

  15. Measurement of the cross section for the reaction {sup 20}Ne(n,{alpha}){sup 17}O in the neutron-energy between 4 and 7 MeV

    SciTech Connect

    Khryachkov, V. A.; Bondarenko, I. P.; Kuzminov, B. D.; Semenova, N. N.; Sergachev, A. I.

    2012-04-15

    The cross section for the reaction {sup 20}Ne(n, {alpha}){sup 17}O was measured in the neutron-energy range 4-7 MeV. An ionization chamber equipped with a Frisch grid combined with a pulse-shape digitizer was used as a detector. Gaseous neon that served as a target on which the reaction being studied proceeded was added to the gas filling the ionization chamber. The partial cross sections for the {alpha}{sub 0}, {alpha}{sub 1}, {alpha}{sub 2}, and {alpha}{sub 3} channels of the reaction {sup 20}Ne(n, {alpha}){sup 17}O were obtained for the first time.

  16. BOOK REVIEW: NMR Imaging of Materials

    NASA Astrophysics Data System (ADS)

    Blümich, Bernhard

    2003-09-01

    Magnetic resonance imaging (MRI) of materials is a field of increasing importance. Applications extend from fundamental science like the characterization of fluid transport in porous rock, catalyst pellets and hemodialysers into various fields of engineering for process optimization and product quality control. While the results of MRI imaging are being appreciated by a growing community, the methods of imaging are far more diverse for materials applications than for medical imaging of human beings. Blümich has delivered the first book in this field. It was published in hardback three years ago and is now offered as a paperback for nearly half the price. The text provides an introduction to MRI imaging of materials covering solid-state NMR spectroscopy, imaging methods for liquid and solid samples, and unusual MRI in terms of specialized approaches to spatial resolution such as an MRI surface scanner. The book represents an excellent and thorough treatment which will help to grow research in materials MRI. Blümich developed the treatise over many years for his research students, graduates in chemistry, physics and engineering. But it may also be useful for medical students looking for a less formal discussion of solid-state NMR spectroscopy. The structure of this book is easy to perceive. The first three chapters cover an introduction, the fundamentals and methods of solid-state NMR spectroscopy. The book starts at the ground level where no previous knowledge about NMR is assumed. Chapter 4 discusses a wide variety of transformations beyond the Fourier transformation. In particular, the Hadamard transformation and the 'wavelet' transformation are missing from most related books. This chapter also includes a description of noise-correlation spectroscopy, which promises the imaging of large objects without the need for extremely powerful radio-frequency transmitters. Chapters 5 and 6 cover basic imaging methods. The following chapter about the use of relaxation and

  17. Determination of the Substrate Binding Mode to the Active Site Iron of (S)-2-Hydroxypropylphosphonic Acid Epoxidase Using 17O-Enriched Substrates and Substrate Analogues†

    PubMed Central

    Yan, Feng; Moon, Sung-Ju; Liu, Pinghua; Zhao, Zongbao; Lipscomb, John D.; Liu, Aimin; Liu, Hung-wen

    2009-01-01

    (S)-2-hydroxypropylphosphonic acid epoxidase (HppE) is an O2-dependent, nonheme Fe(II)-containing oxidase that converts (S)-2-hydroxypropylphosphonic acid ((S)-HPP) to the regio-and enantiomerically specific epoxide, fosfomycin. Use of (R)-2-hydroxypropylphosphonic acid ((R)-HPP) yields the 2-keto-adduct rather than the epoxide. Here we report the chemical synthesis of a range of HPP analogs designed to probe the basis for this specificity. In past studies, NO has been used as an O2 surrogate to provide an EPR probe of the Fe(II) environment. These studies suggest that O2 binds to the iron, and substrates bind in a single orientation that strongly perturbs the iron environment. Recently, the X-ray crystal structure showed direct binding of the substrate to the iron, but both monodentate (via the phosphonate) and chelated (via the hydroxyl and phosphonate) orientations were observed. In the current study, hyperfine broadening of the homogeneous S = 3/2 EPR spectrum of the HppE-NO-HPP complex was observed when either the hydroxyl or the phosphonate group of HPP was enriched with 17O (I = 5/2). These results indicate that both functional groups of HPP bind to Fe(II) ion at the same time as NO, suggesting that the chelated substrate binding mode dominates in solution. (R)- and (S)-analog compounds that maintained the core structure of HPP but added bulky terminal groups were turned over to give products analogous to those from (R)- and (S)-HPP, respectively. In contrast, substrate analogs lacking either the phosphonate or hydroxyl group were not turned over. Elongation of the carbon chain between the hydroxyl and phosphonate allowed binding to the iron in a variety of orientations to give keto and diol products at positions determined by the hydroxyl substituent, but no stable epoxide was formed. These studies show the importance of the Fe(II)-substrate chelate structure to active antibiotic formation. This fixed orientation may align the substrate next to the iron

  18. Δ17O Isotopic Investigation of Nitrate Salts Found in Co-Occurrence with Naturally Formed Perchlorate in the Mojave Desert, California, USA and the Atacama Desert, Chile

    NASA Astrophysics Data System (ADS)

    Lybrand, R. A.; Parker, D.; Rech, J.; Prellwitz, J.; Michalski, G.

    2009-12-01

    Perchlorate is both a naturally occurring and manmade contaminant that has been identified in soil, groundwater and surface water. Perchlorate directly affects human health by interfering with iodide uptake in the thyroid gland, which may in turn lower the production of key hormones that are needed for proper growth and development. Until recently, the Atacama Desert, Chile was thought to be the only location where perchlorate salts formed naturally. Recent work has documented the occurrence of these salts in several semi-arid regions of the United States. This study identified putatively natural sources of perchlorate in the Mojave Desert of California. Soil samples were collected from six field sites varying in geologic age. The co-occurrence of perchlorate and nitrate in caliches from the Atacama Desert and soils from the Mojave Desert was also investigated. Although the former are richer in NO3-, near-ore-grade (~5%) deposits occur in the vicinity of Death Valley National Park. Weak but significant correlations exist between ClO4- and NO3- at both locations, but the perchlorate levels are much higher (up to 800 mg/kg) in the Chilean samples than in California (<25 mg/kg). Oxygen isotopes in the nitrate were examined to identify variation within the Mojave Desert field sites, and to compare with those in samples collected from the Atacama Desert. The Mojave Desert Δ17O values ranged from 7-13‰ and those from the Atacama were between 17-21‰. This isotopic analysis revealed a dominantly atmospheric origin for the Atacama nitrate salts, and a mixture between biological nitrate and atmospherically-derived nitrate for the Mojave samples. When corrected for the percentage of atmospheric nitrate measured in the Atacama samples, the Mojave samples still contain much lower perchlorate concentrations than would be expected if the occurrence of perchlorate correlated strictly with atmospherically derived nitrate. These results indicate that the variation in the

  19. Spin transition of Fe2+ in (Fe0.83Fe0.17)O in the multi anvil apparatus equipped with sintered diamond anvils

    NASA Astrophysics Data System (ADS)

    Ito, E.; Yoshino, T.; Yamazaki, D.; Shatsky, A.; Guo, X.; Shan, S.; Katsura, T.; Yoneda, A.; Higo, Y.; Funakoshi, K.

    2010-12-01

    We have improved performance of the Kawai-type multi anvil apparatus by adopting sintered diamond anvils with an edge length of 14 mm and a truncated corner of 1.0 mm. Most experiments have been carried out at synchrotron facility SPring-8 in Japan. The Kawai-cell (an assemblage of eight cubic anvils and an octahedral specimen) has been squeezed in the DIA-type apparatus installed on the beam line BL04B1. Sample mixed with pressure standard such as Au has been examined by in situ X-ray diffraction method, and the experimental pressure is simultaneously determined from measured volume of the standard material via its EoS. Recently maximum attainable pressure exceeded 95 GPa [Ito et al., 2010]. Based on the experimental innovation, we have investigated the high spin (HS) to low spin (LS) transition of Fe2+ in (Mg1-xFex) ferropericlase (Fp) under lower mantle conditions. Since the effective ionic radius of Fe2+ in LS state is substantially smaller than that in HS state, the spin transition brings about a definite volume contraction together with an increase in bulk modulus. The progressive transition in Fp solid solution with pressure causes a regime of mixed spin state at pressures between those of HS and LS states. The feature should be realized along a P-V compression curve [e.g., Lin and Tsuchiya, 2008]. We have acquired the P-V data of (Mg0.83Fe0.17)O Fp up to 90 GPa and at 300 and 700 K with errors less than ±0.006 Å3 in volume and ±0.4 GPa in pressure. Pressure determination is based on the Anderson et al’s [1989] Au scale. From detailed analysis of the data by fitting the 3rd order Birch-Murnaghan EoS, it has been concluded that the spin transition proceeds over pressure ranges from 50 to 70 GPa at 300 K and from 60 to 85 GPa.

  20. AEM and NMR: Tools for the Future of Groundwater Management

    NASA Astrophysics Data System (ADS)

    Abraham, J. D.; Cannia, J. C.; Lawrie, K.

    2012-12-01

    Within the world, understanding groundwater resources and their management are growing in importance to society as groundwater resources are stressed by drought and continued development. To minimize conflicts, tools and techniques need to be applied to support knowledge-based decisions and management. Airborne electromagnetic (AEM) surveys provide high-quality subsurface data not available from any other source for building the complex hydrogeologic frameworks needed by water-resource managers for effective groundwater management. Traditionally, point data, such as borehole logs, borehole geophysics, surface geophysics, and aquifer tests were interpolated over long distances to create hydrogeologic frameworks. These methods have enjoyed a long history of being the best available technology to inform our understanding of groundwater and how it moves. The AEM techniques proivde pathway for geoscientists to follow to develop more accurate descriptions of the hydrogeological framework. However, the critical and challenging measurements in characterizing aquifers include effective porosity and hydraulic conductivity. These parameters are not reliable derived from AEM. Typically, values for effective porosity and hydraulic conductivity are derived by lithological comparisons with published data; direct measurements of hydraulic conductivity acquired by a few constant head aquifer tests or slug tests; and expensive and time consuming laboratory measurements of cores which can be biased by sampling and the difficulty of making measurements on unconsolidated materials. Aquifer tests are considered to be the best method to gather information on hydraulic conductivity but are rare because of cost and difficult logistics. Also they are unique in design and interpretation from site to site. Nuclear Magnetic Resonance (NMR) can provide a direct measurement of the presence of water in the pore space of aquifer materials. Detection and direct measurement is possible due to the

  1. NMR methodologies in the analysis of blueberries.

    PubMed

    Capitani, Donatella; Sobolev, Anatoly P; Delfini, Maurizio; Vista, Silvia; Antiochia, Riccarda; Proietti, Noemi; Bubici, Salvatore; Ferrante, Gianni; Carradori, Simone; De Salvador, Flavio Roberto; Mannina, Luisa

    2014-06-01

    An NMR analytical protocol based on complementary high and low field measurements is proposed for blueberry characterization. Untargeted NMR metabolite profiling of blueberries aqueous and organic extracts as well as targeted NMR analysis focused on anthocyanins and other phenols are reported. Bligh-Dyer and microwave-assisted extractions were carried out and compared showing a better recovery of lipidic fraction in the case of microwave procedure. Water-soluble metabolites belonging to different classes such as sugars, amino acids, organic acids, and phenolic compounds, as well as metabolites soluble in organic solvent such as triglycerides, sterols, and fatty acids, were identified. Five anthocyanins (malvidin-3-glucoside, malvidin-3-galactoside, delphinidin-3-glucoside, delphinidin-3-galactoside, and petunidin-3-glucoside) and 3-O-α-l-rhamnopyranosyl quercetin were identified in solid phase extract. The water status of fresh and withered blueberries was monitored by portable NMR and fast-field cycling NMR. (1) H depth profiles, T2 transverse relaxation times and dispersion profiles were found to be sensitive to the withering.

  2. Radiation damping in microcoil NMR probes

    NASA Astrophysics Data System (ADS)

    Krishnan, V. V.

    2006-04-01

    Radiation damping arises from the field induced in the receiver coil by large bulk magnetization and tends to selectively drive this magnetization back to equilibrium much faster than relaxation processes. The demand for increased sensitivity in mass-limited samples has led to the development of microcoil NMR probes that are capable of obtaining high quality NMR spectra with small sample volumes (nL-μL). Microcoil probes are optimized to increase sensitivity by increasing either the sample-to-coil ratio (filling factor) of the probe or quality factor of the detection coil. Though radiation damping effects have been studied in standard NMR probes, these effects have not been measured in the microcoil probes. Here a systematic evaluation of radiation damping effects in a microcoil NMR probe is presented and the results are compared with similar measurements in conventional large volume samples. These results show that radiation-damping effects in microcoil probe is much more pronounced than in 5 mm probes, and that it is critically important to optimize NMR experiments to minimize these effects. As microcoil probes provide better control of the bulk magnetization, with good RF and B0 inhomogeneity, in addition to negligible dipolar field effects due to nearly spherical sample volumes, these probes can be used exclusively to study the complex behavior of radiation damping.

  3. Radiation damping in microcoil NMR probes.

    PubMed

    Krishnan, V V

    2006-04-01

    Radiation damping arises from the field induced in the receiver coil by large bulk magnetization and tends to selectively drive this magnetization back to equilibrium much faster than relaxation processes. The demand for increased sensitivity in mass-limited samples has led to the development of microcoil NMR probes that are capable of obtaining high quality NMR spectra with small sample volumes (nL-microL). Microcoil probes are optimized to increase sensitivity by increasing either the sample-to-coil ratio (filling factor) of the probe or quality factor of the detection coil. Though radiation damping effects have been studied in standard NMR probes, these effects have not been measured in the microcoil probes. Here a systematic evaluation of radiation damping effects in a microcoil NMR probe is presented and the results are compared with similar measurements in conventional large volume samples. These results show that radiation-damping effects in microcoil probe is much more pronounced than in 5 mm probes, and that it is critically important to optimize NMR experiments to minimize these effects. As microcoil probes provide better control of the bulk magnetization, with good RF and B0 inhomogeneity, in addition to negligible dipolar field effects due to nearly spherical sample volumes, these probes can be used exclusively to study the complex behavior of radiation damping.

  4. Magic angle spinning NMR of paramagnetic proteins.

    PubMed

    Knight, Michael J; Felli, Isabella C; Pierattelli, Roberta; Emsley, Lyndon; Pintacuda, Guido

    2013-09-17

    Metal ions are ubiquitous in biochemical and cellular processes. Since many metal ions are paramagnetic due to the presence of unpaired electrons, paramagnetic molecules are an important class of targets for research in structural biology and related fields. Today, NMR spectroscopy plays a central role in the investigation of the structure and chemical properties of paramagnetic metalloproteins, linking the observed paramagnetic phenomena directly to electronic and molecular structure. A major step forward in the study of proteins by solid-state NMR came with the advent of ultrafast magic angle spinning (MAS) and the ability to use (1)H detection. Combined, these techniques have allowed investigators to observe nuclei that previously were invisible in highly paramagnetic metalloproteins. In addition, these techniques have enabled quantitative site-specific measurement of a variety of long-range paramagnetic effects. Instead of limiting solid-state NMR studies of biological systems, paramagnetism provides an information-rich phenomenon that can be exploited in these studies. This Account emphasizes state-of-the-art methods and applications of solid-state NMR in paramagnetic systems in biological chemistry. In particular, we discuss the use of ultrafast MAS and (1)H-detection in perdeuterated paramagnetic metalloproteins. Current methodology allows us to determine the structure and dynamics of metalloenzymes, and, as an example, we describe solid-state NMR studies of microcrystalline superoxide dismutase, a 32 kDa dimer. Data were acquired with remarkably short times, and these experiments required only a few milligrams of sample.

  5. Dynamic Nuclear Polarization (DNP) solid-state NMR spectroscopy, a new approach to study humic material?

    NASA Astrophysics Data System (ADS)

    Knicker, Heike; Lange, Sascha; van Rossum, Barth; Oschkinat, Hartmut

    2016-04-01

    Compared to solution NMR spectroscopy, solid-state NMR spectra suffer from broad resonance lines and low resolution. This could be overcome by the use of 2-dimenstional solid-state NMR pulse sequences. Until recently, this approach has been unfeasible as a routine tool in soil chemistry, mainly because of the low NMR sensitivity of the respective samples. A possibility to circumvent those sensitivity problems represents high-field Dynamic Nuclear Polarization (DNP) solid-state NMR spectroscopy (Barnes et al., 2008), allowing considerable signal enhancements (Akbey et al., 2010). This is achieved by a microwave-driven transfer of polarization from a paramagnetic center to nuclear spins. Application of DNP to MAS spectra of biological systems (frozen solutions) showed enhancements of the factor 40 to 50 (Hall et al., 1997). Enhancements of this magnitude, thus may enable the use of at least some of the 2D solid-state NMR techniques that are presently already applied for pure proteins but are difficult to apply to soil peptides in their complex matrix. After adjusting the required acquisition parameters to the system "soil organic matter", lower but still promising enhancement factors were achieved. Additional optimization was performed and allowed the acquisition of 2D 13C and 15N solid-state NMR spectra of humified 13C and 15N enriched plant residues. Within the present contribution, the first solid-state DNP NMR spectra of humic material are presented. Those data demonstrate the great potential of this approach which certainly opens new doors for a better understanding of biochemical processes in soils, sediments and water. Akbey, Ü., Franks, W.T., Linden, A., Lange, S., Griffin, R.G., van Rossum, B.-J., Oschkinat, H., 2010. Dynamic nuclear polarization of deuterated proteins. Angewandte Chemie International Edition 49, 7803-7806. Barnes, A.B., De Paëpe, G., van der Wel, P.C.A., Hu, K.N., Joo, C.G., Bajaj, V.S., Mak-Jurkauskas, M.L., Sirigiri, J.R., Herzfeld, J

  6. Quantitative Analysis of STD-NMR Spectra of Reversibly Forming Ligand-Receptor Complexes

    NASA Astrophysics Data System (ADS)

    Krishna, N. Rama; Jayalakshmi, V.

    We describe our work on the quantitative analysis of STD-NMR spectra of reversibly forming ligand-receptor complexes. This analysis is based on the theory of complete relaxation and conformational exchange matrix analysis of saturation transfer (CORCEMA-ST) effects. As part of this work, we have developed two separate versions of the CORCEMA-ST program. The first version predicts the expected STD intensities for a given model of a ligand-protein complex, and compares them quantitatively with the experimental data. This version is very useful for rapidly determining if a model for a given ligand-protein complex is compatible with the STD-NMR data obtained in solution. It is also useful in determining the optimal experimental conditions for undertaking the STD-NMR measurements on a given complex by computer simulations. In the second version of the CORCEMA-ST program, we have implemented a torsion angle refinement feature for the bound ligand within the protein binding pocket. In this approach, the global minimum for the bound ligand conformation is obtained by a hybrid structure refinement protocol involving CORCEMA-ST calculation of intensities and simulated annealing refinement of torsion angles of the bound ligand using STD-NMR intensities as experimental constraints to minimize a pseudo-energy function. This procedure is useful in refining and improving the initial models based on crystallography, computer docking, or other procedures to generate models for the bound ligand within the protein binding pocket compatible with solution STD-NMR data. In this chapter we describe the properties of the STD-NMR spectra, including the dependence of the intensities on various parameters. We also describe the results of the CORCEMA-ST analyses of experimental STD-NMR data on some ligand-protein complexes to illustrate the quantitative analysis of the data using this method. This CORCEMA-ST program is likely to be useful in structure-based drug design efforts.

  7. NMR techniques in the study of cardiovascular structure and functions

    SciTech Connect

    Osbakken, M.; Haselgrove, J.

    1987-01-01

    The chapter titles of this book are: Introduction to NMR Techniques;Theory of NMR Probe Design;Overview of Magnetic Resonance Imaging to Study the Cardiovascular System;Vascular Anatomy and Physiology Studied with NMR Techniques;Assessment of Myocardial Ischemia and Infarction by Nuclear Magnetic Resonance Imaging;The Use of MRI in Congenital Heart Disease;Cardiomyopathies and Myocarditis Studied with NMR Techniques;Determination of Myocardial Mechanical Function with Magnetic Resonance Imaging Techniques;Determination of Flow Using NMR Techniques;The Use of Contrast Agents in Cardiac MRI;Can Cardiovascular Disease Be Effectively Evaluated with NMR Spectroscopy. NMR Studies of ATP Synthesis Reactions in the Isolated Heart;Studies of Intermediary Metabolism in the Heart by 13C NMR Spectroscopy;23Na and 39K NMR Spectroscopic Studies of the Intact Beating Heart;and Evaluation of Skeletal Muscle Metabolism in Patients with Congestive Heart Failure Using Phosphorus Nuclear Magnetic Resonance.

  8. The AGB star nucleosynthesis in the light of the recent {sup 17}O(p,α){sup 14}N and {sup 18}O(p,α){sup 15}N reaction rate determinations

    SciTech Connect

    Palmerini, S.; Sergi, M. L.; La Cognata, M.; Pizzone, R. G.; Lamia, L.; Spitaleri, C.

    2015-02-24

    Presolar grains form in the cold and dusty envelopes of Asymptotic Giant Branch (AGB) stars. These solides, once that have been ejected by stellar winds, come to us as inclusions in meteorites providing invaluable benchmarks and constraints for our knowledge of low temeperature H-burning in stars. The Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of the {sup 17}O(p,α){sup 14}N and {sup 18}O(p,α){sup 15}N reactions. Moreover, the strength of the 65 keV resonance in the {sup 17}O(p,α){sup 14}N reaction, measured by means of the THM, has been used to renormalize the corresponding resonance strength in the {sup 17}O+p radiative capture channel. The new estimates of the reaction rates have been introduced into calculations of AGB star nucleosynthesis and the results have been compared with geochemical analysis of 'presolar' grains to determine their impact on astrophysical environments.

  9. NMR-Based Multi Parametric Quality Control of Fruit Juices: SGF Profiling

    PubMed Central

    Spraul, Manfred; Schütz, Birk; Rinke, Peter; Koswig, Susanne; Humpfer, Eberhard; Schäfer, Hartmut; Mörtter, Monika; Fang, Fang; Marx, Ute C.; Minoja, Anna

    2009-01-01

    With SGF Profiling™ we introduce an NMR-based screening method for the quality control of fruit juices. This method has been developed in a joint effort by Bruker BioSpin GmbH and SGF International e.V. The system is fully automated with respect to sample transfer, measurement, data analysis and reporting and is set up on an Avance 400 MHz flow-injection NMR spectrometer. For each fruit juice a multitude of parameters related to quality and authenticity are evaluated simultaneously from a single data set acquired within a few minutes. This multimarker/multi-aspect NMR screening approach features low cost-per-sample and is highly competitive with conventional and targeted fruit juice quality control methods. PMID:22253974

  10. Proton-coupled 15N NMR spectra of neutral and protonated ethenoadenosine and ethenocytidine.

    PubMed Central

    Sierzputowska-Gracz, H; Wiewiórowski, M; Kozerski, L; von Philipsborn, W

    1984-01-01

    The 15N chemical shifts and 15N, 1H spin coupling constants were determined in the title compounds using the INEPT pulse sequence and assigned with the aid of selective proton decoupling. The delta/15N/ and J/N, H/ values are discussed in terms of involvement of the imidazole ring created by ethenobridging in the electronic structure of the whole molecule. Both spectral parameters indicate that the diligant nitrogen in this ring is the primary site of protonation in these modified nucleosides. It is concluded that 15N NMR of nucleoside bases can be largely a complementary method to 1H and 13C NMR studies and, in addition, can serve as a direct probe for studies of nitrogen environment in oligomeric fragments of nucleic acids even at moderately strong magnetic fields due to the higher spectral dispersion compared with 1H and 13C NMR spectra. PMID:6473107

  11. Probing acid-amide intermolecular hydrogen bonding by NMR spectroscopy and DFT calculations

    NASA Astrophysics Data System (ADS)

    Chaudhari, Sachin Rama; Suryaprakash, N.

    2012-05-01

    Benzene carboxylic acids and benzamide act as their self-complement in molecular recognition to form inter-molecular hydrogen bonded dimers between amide and carboxylic acid groups, which have been investigated by 1H, 13C and 15N NMR spectroscopy. Extensive NMR studies using diffusion ordered spectroscopy (DOSY), variable temperature 1D, 2D NMR, established the formation of heterodimers of benzamide with benzoic acid, salicylic acid and phenyl acetic acid in deuterated chloroform solution. Association constants for the complex formation in the solution state have been determined. The results are ascertained by X-ray diffraction in the solid state. Intermolecular interactions in solution and in solid state were found to be similar. The structural parameters obtained by X-ray diffraction studies are compared with those obtained by DFT calculations.

  12. Theoretical and experimental investigation of the 1H NMR spectrum of putrescine

    NASA Astrophysics Data System (ADS)

    Allouche, A. R.; Graveron-Demilly, D.; Fauvelle, F.; Aubert-Frécon, M.

    2008-12-01

    Chemical shifts δ and spin-spin coupling constants J have been calculated for the putrescine molecule, a polyamine present in prostate tissue, through a DFT/B3LYP/6-311++G(d,p)/PCM/(GIAO) approach, which has been shown to be accurate in previous work. From δ and J values, calculated for the first time for the isolated and the solvated putrescine, the 1H NMR spectra have been simulated. Comparisons between the calculated and the experimental NMR spectra at 400 MHz show a good agreement and allow to propose reliable values for the NMR spin Hamiltonian parameters of putrescine to be used as good starting values for further quantitation methods of metabolites in prostate tissue.

  13. NMR structural study of the prototropic equilibrium in solution of Schiff bases as model compounds.

    PubMed

    Ortegón-Reyna, David; Garcías-Morales, Cesar; Padilla-Martínez, Itzia; García-Báez, Efren; Aríza-Castolo, Armando; Peraza-Campos, Ana; Martínez-Martínez, Francisco

    2013-12-31

    An NMR titration method has been used to simultaneously measure the acid dissociation constant (pKa) and the intramolecular NHO prototropic constant ΔKNHO on a set of Schiff bases. The model compounds were synthesized from benzylamine and substituted ortho-hydroxyaldehydes, appropriately substituted with electron-donating and electron-withdrawing groups to modulate the acidity of the intramolecular NHO hydrogen bond. The structure in solution was established by 1H-, 13C- and 15N-NMR spectroscopy. The physicochemical parameters of the intramolecular NHO hydrogen bond (pKa, ΔKNHO and ΔΔG°) were obtained from 1H-NMR titration data and pH measurements. The Henderson-Hasselbalch data analysis indicated that the systems are weakly acidic, and the predominant NHO equilibrium was established using Polster-Lachmann δ-diagram analysis and Perrin model data linearization.

  14. Nondestructive Quantification of Local Plasticizer Concentration in PVC by (1)H NMR Relaxometry.

    PubMed

    Adams, Alina; Kwamen, Rance; Woldt, Benjamin; Graß, Michael

    2015-12-01

    The properties of plasticized poly(vinyl chloride) (PVC) , one of the most important polymers today, are strongly dictated by the concentration of plasticizer. Yet, it has been impossible to quantify this concentration at different positions inside a PVC product without its destruction because of a lack of suitable analytical methods. Thus, this paper introduces a simple, fast, and efficient way to determine truly nondestructively the concentration of plasticizer in PVC by single-sided nuclear magnetic resonance (NMR). With the help of correlation curves between the concentration of plasticizer inside nonaged PVC samples and the corresponding volume-averaged NMR parameters, single-sided NMR allows the quantification of the local concentration of plasticizer in aged PVC plates at different depths by spatially resolved relaxation measurements. The presented approach represents a fundamental step toward in situ characterization of plasticized PVC.

  15. The NMR study of biologically active metallated alkanol ammoinium ionic liquids

    NASA Astrophysics Data System (ADS)

    Ushakov, I. A.; Voronov, V. K.; Adamovich, S. N.; Mirskov, R. G.; Mirskova, A. N.

    2016-01-01

    The 1H, 13C, 15N, and 111Cd NMR spectra of a series of metallated alkanol ammonium ionic liquids (MAIL) series [n N(CH2CH2OH;)3M]+ · mX-, where M = Cd, Mg, Zn, Fe, Rh; X = Cl, OOCCH3, obtained in a wide range of temperatures of the studied samples, have been analyzed. It is found that, under biomimetic conditions (H2O, 25 °C), the compounds studied exist as mono- bi- and the tricyclic structures, which are in equilibrium. Shift of the equilibrium depends upon nature of a metal and effects all the parameters of the NMR spectra. Peculiarities of ligand exchange, typical for the studied compounds, have been studied in a wide range of temperatures. It is found that the NMR data can be used to control structure of the compounds formed in the course of synthesis.

  16. Review of NMR characterization of pyrolysis oils

    SciTech Connect

    Hao, Naijia; Ben, Haoxi; Yoo, Chang Geun; Adhikari, Sushil; Ragauskas, Arthur J.

    2016-08-24

    Here, pyrolysis of renewable biomass has been developed as a method to produce green fuels and chemicals in response to energy security concerns as well as to alleviate environmental issues incurred with fossil fuel usage. However, pyrolysis oils still have limited commercial application, mainly because unprocessed oils cannot be readily blended with current petroleum-based transportation fuels. To better understand these challenges, researchers have applied diverse characterization techniques in the development of bio-oil studies. In particular, nuclear magnetic resonance (NMR) is a key spectroscopic characterization method through analysis of bio-oil components. This review highlights the NMR strategies for pyrolysis oil characterization and critically discusses the applications of 1H, 13C, 31P, 19F, and two-dimensional (2-D NMR) analyses such as heteronuclear single quantum correlation (HSQC) in representative pyrolysis oil studies.

  17. Review of NMR characterization of pyrolysis oils

    DOE PAGES

    Hao, Naijia; Ben, Haoxi; Yoo, Chang Geun; ...

    2016-08-24

    Here, pyrolysis of renewable biomass has been developed as a method to produce green fuels and chemicals in response to energy security concerns as well as to alleviate environmental issues incurred with fossil fuel usage. However, pyrolysis oils still have limited commercial application, mainly because unprocessed oils cannot be readily blended with current petroleum-based transportation fuels. To better understand these challenges, researchers have applied diverse characterization techniques in the development of bio-oil studies. In particular, nuclear magnetic resonance (NMR) is a key spectroscopic characterization method through analysis of bio-oil components. This review highlights the NMR strategies for pyrolysis oil characterizationmore » and critically discusses the applications of 1H, 13C, 31P, 19F, and two-dimensional (2-D NMR) analyses such as heteronuclear single quantum correlation (HSQC) in representative pyrolysis oil studies.« less

  18. A modularized pulse programmer for NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Mao, Wenping; Bao, Qingjia; Yang, Liang; Chen, Yiqun; Liu, Chaoyang; Qiu, Jianqing; Ye, Chaohui

    2011-02-01

    A modularized pulse programmer for a NMR spectrometer is described. It consists of a networked PCI-104 single-board computer and a field programmable gate array (FPGA). The PCI-104 is dedicated to translate the pulse sequence elements from the host computer into 48-bit binary words and download these words to the FPGA, while the FPGA functions as a sequencer to execute these binary words. High-resolution NMR spectra obtained on a home-built spectrometer with four pulse programmers working concurrently demonstrate the effectiveness of the pulse programmer. Advantages of the module include (1) once designed it can be duplicated and used to construct a scalable NMR/MRI system with multiple transmitter and receiver channels, (2) it is a totally programmable system in which all specific applications are determined by software, and (3) it provides enough reserve for possible new pulse sequences.

  19. NMR Spectroscopy: Processing Strategies (by Peter Bigler)

    NASA Astrophysics Data System (ADS)

    Mills, Nancy S.

    1998-06-01

    Peter Bigler. VCH: New York, 1997. 249 pp. ISBN 3-527-28812-0. $99.00. This book, part of a four-volume series planned to deal with all aspects of a standard NMR experiment, is almost the exact book I have been hoping to find. My department has acquired, as have hundreds of other undergraduate institutions, high-field NMR instrumentation and the capability of doing extremely sophisticated experiments. However, the training is often a one- or two-day experience in which the material retained by the faculty trained is garbled and filled with holes, not unlike the information our students seem to retain. This text, and the accompanying exercises based on data contained on a CD-ROM, goes a long way to fill in the gaps and clarify misunderstandings about NMR processing.

  20. Spin Choreography: Basic Steps in High Resolution NMR (by Ray Freeman)

    NASA Astrophysics Data System (ADS)

    Minch, Michael J.

    1998-02-01

    There are three orientations that NMR courses may take. The traditional molecular structure course focuses on the interpretation of spectra and the use of chemical shifts, coupling constants, and nuclear Overhauser effects (NOE) to sort out subtle details of structure and stereochemistry. Courses can also focus on the fundamental quantum mechanics of observable NMR parameters and processes such a spin-spin splitting and relaxation. More recently there are courses devoted to the manipulation of nuclear spins and the basic steps of one- and two-dimensional NMR experiments. Freeman's book is directed towards the latter audience. Modern NMR methods offer a myriad ways to extract information about molecular structure and motion by observing the behavior of nuclear spins under a variety of conditions. In Freeman's words: "We can lead the spins through an intricate dance, carefully programmed in advance, to enhance, simplify, correlate, decouple, edit or assign NMR spectra." This is a carefully written, well-illustrated account of how this dance is choreographed by pulse programming, double resonance, and gradient effects. Although well written, this book is not an easy read; every word counts. It is recommended for graduate courses that emphasize the fundamentals of magnetic resonance. It is not a text on interpretation of spectra.

  1. Prediction of recrystallization behavior of troglitazone/polyvinylpyrrolidone solid dispersion by solid-state NMR.

    PubMed

    Ito, Atsutoshi; Watanabe, Tomoyuki; Yada, Shuichi; Hamaura, Takeshi; Nakagami, Hiroaki; Higashi, Kenjirou; Moribe, Kunikazu; Yamamoto, Keiji

    2010-01-04

    The purpose of this study was to elaborate the relationship between the (13)C CP/MAS NMR spectra and the recrystallization behavior during the storage of troglitazone solid dispersions. The solid dispersions were prepared by either the solvent method or by co-grinding. The recrystallization behavior under storage conditions at 40 degrees C/94% RH was evaluated by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation. Solid dispersions prepared by the solvent method or by prolonged grinding brought about inhibition of the nucleation and the nuclei growth at the same time. No differences in the PXRD profiles were found in the samples prepared by the co-grinding and solvent methods, however, (13)C CP/MAS NMR showed significant differences in the spectra. The correlation coefficients using partial least square regression analysis between the PXRD profiles and the apparent nuclei-growth constant or induction period to nucleation were 0.1305 or 0.6350, respectively. In contrast, those between the (13)C CP/MAS NMR spectra and the constant or the period were 0.9916 or 0.9838, respectively. The (13)C CP/MAS NMR spectra had good correlation with the recrystallization kinetic parameters evaluated by the KJMA equation. Consequently, solid-state NMR was judged to be a useful tool for the prediction of the recrystallization behavior of solid dispersions.

  2. Organic Chemistry Course Development in a Forensic Science Program: Use of FT-NMR

    NASA Astrophysics Data System (ADS)

    Callahan, Ronald; Kobilinsky, Lawrence; Rothchild, Robert

    1999-10-01

    The acquisition of a modern, multinuclear, medium-field (7 tesla) FT-NMR, with partial support from NSF-ILI, has made possible the introduction of a major special project for second-semester organic chemistry laboratory, within a forensic science program. The eight-week special project focuses on microscale syntheses of Diels-Alder adducts of phencyclone. Students synthesize a wide range of different N-substituted maleimides for use as dienophiles. The corresponding phencyclone adducts permit studies of: a) unusual hindered rotations of unsubsituted bridgehead phenyls, b) striking examples of magnetic anisotropic effects, and c) modern one- and two-dimensional NMR methods for structural characterization. Use of fluorine-containing dienophiles provides a basis for examining NMR spectra of three different NMR-active nuclei: proton, carbon-13, and fluorine-19. Variable-temperature NMR is also applicable to these compounds. Molecular modeling software has been introduced in the organic laboratory course for students to examine the geometry of these adducts, precursors, and simplified model compounds, and to evaluate geometric parameters in structures that are optimized by semi-empirical and ab initio calculations. References are included with the article and can be accessed via its PDF file.

  3. NMR Evidence for the Topologically Nontrivial Nature in a Family of Half-Heusler Compounds

    PubMed Central

    Zhang, Xiaoming; Hou, Zhipeng; Wang, Yue; Xu, Guizhou; Shi, Chenglong; Liu, EnKe; Xi, Xuekui; Wang, Wenhong; Wu, Guangheng; Zhang, Xi-xiang

    2016-01-01

    Spin-orbit coupling (SOC) is expected to partly determine the topologically nontrivial electronic structure of heavy half-Heusler ternary compounds. However, to date, attempts to experimentally observe either the strength of SOC or how it modifies the bulk band structure have been unsuccessful. By using bulk-sensitive nuclear magnetic resonance (NMR) spectroscopy combined with first-principles calculations, we reveal that 209Bi NMR isotropic shifts scale with relativity in terms of the strength of SOC and average atomic numbers, indicating strong relativistic effects on NMR parameters. According to first-principles calculations, we further claim that nuclear magnetic shieldings from relativistic p1/2 states and paramagnetic contributions from low-lying unoccupied p3/2 states are both sensitive to the details of band structures tuned by relativity, which explains why the hidden relativistic effects on band structure can be revealed by 209Bi NMR isotropic shifts in topologically nontrivial half-Heusler compounds. Used in complement to surface-sensitive methods, such as angle resolved photon electron spectroscopy and scanning tunneling spectroscopy, NMR can provide valuable information on bulk electronic states. PMID:26980406

  4. NMR Evidence for the Topologically Nontrivial Nature in a Family of Half-Heusler Compounds.

    PubMed

    Zhang, Xiaoming; Hou, Zhipeng; Wang, Yue; Xu, Guizhou; Shi, Chenglong; Liu, EnKe; Xi, Xuekui; Wang, Wenhong; Wu, Guangheng; Zhang, Xi-Xiang

    2016-03-16

    Spin-orbit coupling (SOC) is expected to partly determine the topologically nontrivial electronic structure of heavy half-Heusler ternary compounds. However, to date, attempts to experimentally observe either the strength of SOC or how it modifies the bulk band structure have been unsuccessful. By using bulk-sensitive nuclear magnetic resonance (NMR) spectroscopy combined with first-principles calculations, we reveal that (209)Bi NMR isotropic shifts scale with relativity in terms of the strength of SOC and average atomic numbers, indicating strong relativistic effects on NMR parameters. According to first-principles calculations, we further claim that nuclear magnetic shieldings from relativistic p1/2 states and paramagnetic contributions from low-lying unoccupied p3/2 states are both sensitive to the details of band structures tuned by relativity, which explains why the hidden relativistic effects on band structure can be revealed by (209)Bi NMR isotropic shifts in topologically nontrivial half-Heusler compounds. Used in complement to surface-sensitive methods, such as angle resolved photon electron spectroscopy and scanning tunneling spectroscopy, NMR can provide valuable information on bulk electronic states.

  5. Mechanical Behavior of Polymer Gels for RDCs and RCSAs Collection: NMR Imaging Study of Buckling Phenomena.

    PubMed

    Hellemann, Erich; Teles, Rubens R; Hallwass, Fernando; Barros, W; Navarro-Vázquez, Armando; Gil, Roberto R

    2016-11-07

    Anisotropic NMR parameters, such as residual dipolar couplings (RDCs), residual chemical shift anisotropies (RCSAs) and residual quadrupolar couplings (RQCs or ΔνQ ), appear in solution-state NMR when the molecules under study are subjected to a degree of order. The tunable alignment by reversible compression/relaxation of gels (PMMA and p-HEMA) is an easy, user-friendly, and very affordable method to measure them. When using this method, a fraction of isotropic NMR signals is observed in the NMR spectra, even at a maximum degree of compression. To explain the origin of these isotropic signals we decided to investigate their physical location inside the NMR tube using deuterium 1D imaging and MRI micro-imaging experiments. It was observed that after a certain degree of compression the gels start to buckle and they generate pockets of isotropic solvent, which are never eliminated. The amount of buckling depends on the amount of cross-linker and the length of the gel.

  6. NMR Evidence for the Topologically Nontrivial Nature in a Family of Half-Heusler Compounds

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoming; Hou, Zhipeng; Wang, Yue; Xu, Guizhou; Shi, Chenglong; Liu, Enke; Xi, Xuekui; Wang, Wenhong; Wu, Guangheng; Zhang, Xi-Xiang

    2016-03-01

    Spin-orbit coupling (SOC) is expected to partly determine the topologically nontrivial electronic structure of heavy half-Heusler ternary compounds. However, to date, attempts to experimentally observe either the strength of SOC or how it modifies the bulk band structure have been unsuccessful. By using bulk-sensitive nuclear magnetic resonance (NMR) spectroscopy combined with first-principles calculations, we reveal that 209Bi NMR isotropic shifts scale with relativity in terms of the strength of SOC and average atomic numbers, indicating strong relativistic effects on NMR parameters. According to first-principles calculations, we further claim that nuclear magnetic shieldings from relativistic p1/2 states and paramagnetic contributions from low-lying unoccupied p3/2 states are both sensitive to the details of band structures tuned by relativity, which explains why the hidden relativistic effects on band structure can be revealed by 209Bi NMR isotropic shifts in topologically nontrivial half-Heusler compounds. Used in complement to surface-sensitive methods, such as angle resolved photon electron spectroscopy and scanning tunneling spectroscopy, NMR can provide valuable information on bulk electronic states.

  7. Determination of 15N chemical shift anisotropy from a membrane-bound protein by NMR spectroscopy.

    PubMed

    Pandey, Manoj Kumar; Vivekanandan, Subramanian; Ahuja, Shivani; Pichumani, Kumar; Im, Sang-Choul; Waskell, Lucy; Ramamoorthy, Ayyalusamy

    2012-06-21

    Chemical shift anisotropy (CSA) tensors are essential in the structural and dynamic studies of proteins using NMR spectroscopy. Results from relaxation studies in biomolecular solution and solid-state NMR experiments on aligned samples are routinely interpreted using well-characterized CSA tensors determined from model compounds. Since CSA tensors, particularly the (15)N CSA, highly depend on a number of parameters including secondary structure, electrostatic interaction, and the amino acid sequence, there is a need for accurately determined CSA tensors from proteins. In this study, we report the backbone amide-(15)N CSA tensors for a 16.7-kDa membrane-bound and paramagnetic-heme containing protein, rabbit Cytochrome b(5) (cytb(5)), determined using the (15)N CSA/(15)N-(1)H dipolar transverse cross-correlation rates. The mean values of (15)N CSA determined for residues in helical, sheet, and turn regions are -187.9, -166.0, and -161.1 ppm, respectively, with an overall average value of -171.7 ppm. While the average CSA value determined from this study is in good agreement with previous solution NMR experiments on small globular proteins, the CSA value determined for residues in helical conformation is slightly larger, which may be attributed to the paramagnetic effect from Fe(III) of the heme unit in cytb(5). However, like in previous solution NMR studies, the CSA values reported in this study are larger than the values measured from solid-state NMR experiments. We believe that the CSA parameters reported in this study will be useful in determining the structure, dynamics, and orientation of proteins, including membrane proteins, using NMR spectroscopy.

  8. Contact replacement for NMR resonance assignment

    PubMed Central

    Xiong, Fei; Pandurangan, Gopal; Bailey-Kellogg, Chris

    2008-01-01

    Motivation: Complementing its traditional role in structural studies of proteins, nuclear magnetic resonance (NMR) spectroscopy is playing an increasingly important role in functional studies. NMR dynamics experiments characterize motions involved in target recognition, ligand binding, etc., while NMR chemical shift perturbation experiments identify and localize protein–protein and protein–ligand interactions. The key bottleneck in these studies is to determine the backbone resonance assignment, which allows spectral peaks to be mapped to specific atoms. This article develops a novel approach to address that bottleneck, exploiting an available X-ray structure or homology model to assign the entire backbone from a set of relatively fast and cheap NMR experiments. Results: We formulate contact replacement for resonance assignment as the problem of computing correspondences between a contact graph representing the structure and an NMR graph representing the data; the NMR graph is a significantly corrupted, ambiguous version of the contact graph. We first show that by combining connectivity and amino acid type information, and exploiting the random structure of the noise, one can provably determine unique correspondences in polynomial time with high probability, even in the presence of significant noise (a constant number of noisy edges per vertex). We then detail an efficient randomized algorithm and show that, over a variety of experimental and synthetic datasets, it is robust to typical levels of structural variation (1–2 AA), noise (250–600%) and missings (10–40%). Our algorithm achieves very good overall assignment accuracy, above 80% in α-helices, 70% in β-sheets and 60% in loop regions. Availability: Our contact replacement algorithm is implemented in platform-independent Python code. The software can be freely obtained for academic use by request from the authors. Contact: gopal@cs.purdue.edu; cbk@cs.dartmouth.edu PMID:18586716

  9. Binding modes of phosphonic acid derivatives adsorbed on TiO2 surfaces: Assignments of experimental IR and NMR spectra based on DFT/PBC calculations

    NASA Astrophysics Data System (ADS)

    Geldof, D.; Tassi, M.; Carleer, R.; Adriaensens, P.; Roevens, A.; Meynen, V.; Blockhuys, F.

    2017-01-01

    A DFT study on the adsorption of a series of phosphonic acids (PAs) on the TiO2 anatase (101) and (001) surfaces was performed. The adsorption energies and geometries of the most stable binding modes were compared to literature data and the effect of the inclusion of dispersion forces in the energy calculations was gauged. As the (101) surface is the most exposed surface of TiO2 anatase, the calculated chemical shifts and vibrational frequencies of PAs adsorbed on this surface were compared to experimental 31P and 17O NMR and IR data in order to assign the two possible binding modes (mono- and bidentate) to peaks and bands in these spectra; due to the corrugated nature of anatase (101) tridentate binding is not possible on this surface. Analysis of the calculated and experimental 31P chemical shifts indicates that both monodentate and bidentate binding modes are present. For the reactive (001) surface, the results of the calculations indicate that both bi- and tridentate binding modes result in stable systems. Due to the particular sensitivity of 17O chemical shifts to hydrogen bonding and solvent effects, the model used is insufficient to assign these spectra at present. Comparison of calculated and experimental IR spectra leads to the conclusion that IR spectroscopy is not suitable for the characterization of the different binding modes of the adsorption complexes.

  10. W-band ELDOR-detected NMR (EDNMR) spectroscopy as a versatile technique for the characterisation of transition metal-ligand interactions

    NASA Astrophysics Data System (ADS)

    Cox, Nicholas; Lubitz, Wolfgang; Savitsky, Anton

    2013-10-01

    ELDOR-detected NMR (EDNMR) spectra for a series of hydrated transition metal complexes: MnII(H2O)6, CuII(H2O)6 and VIVO(H2O)5 are reported. All EDNMR experiments were performed at W-band (94 GHz) employing two independent microwave frequencies. A purpose-built broadband microwave resonator (spectral range 300 MHz) was used, sufficient to detect all single quantum nuclear transitions of the three model systems. The EDNMR spectral lineshape observed is essentially the same as in conventional ENDOR (Electron-Nuclear Double Resonance). EDNMR presents two technical advantages over ENDOR for transition metal complexes: (i) enhanced sensitivity, reducing acquisition times by at least one order of magnitude; and (ii) simultaneous detection of transitions from all magnetic nuclei. This includes ligand (1H, 2H, 17O) and metal centred hyperfine couplings. For the latter, both isotropic couplings in the case of the 55Mn complex and highly anisotropic couplings in the case of 51V and 63,65Cu complexes could be resolved. By monitoring the intensity of the EDNMR lines as function of the amplitude of the pumping microwave pulse, transitions from non-equivalent nuclei can be differentiated. Double quantum transitions are also readily identified. In case of the MnII(H217O)6 complex, spectral lines involving the simultaneous pumping of both the 55Mn and 17O nuclear transitions are observed.

  11. Solid-state NMR of proteins sedimented by ultracentrifugation

    PubMed Central

    Bertini, Ivano; Luchinat, Claudio; Parigi, Giacomo; Ravera, Enrico; Reif, Bernd; Turano, Paola

    2011-01-01

    Relatively large proteins in solution, spun in NMR rotors for solid samples at typical ultracentrifugation speeds, sediment at the rotor wall. The sedimented proteins provide high-quality solid-state-like NMR spectra suitable for structural investigation. The proteins fully revert to the native solution state when spinning is stopped, allowing one to study them in both conditions. Transiently sedimented proteins can be considered a novel phase as far as NMR is concerned. NMR of transiently sedimented molecules under fast magic angle spinning has the advantage of overcoming protein size limitations of solution NMR without the need of sample crystallization/precipitation required by solid-state NMR. PMID:21670262

  12. Magic Angle Spinning NMR of Viruses

    PubMed Central

    Quinn, Caitlin; Lu, Manman; Suiter, Christopher L.; Hou, Guangjin; Zhang, Huilan; Polenova, Tatyana

    2015-01-01

    Viruses, relatively simple pathogens, are able to replicate in many living organisms and to adapt to various environments. Conventional atomic-resolution structural biology techniques, X-ray crystallography and solution NMR spectroscopy provided abundant information on the structures of individual proteins and nucleic acids comprising viruses; however, viral assemblies are not amenable to analysis by these techniques because of their large size, insolubility, and inherent lack of long-range order. In this article, we review the recent advances in magic angle spinning NMR spectroscopy that enabled atomic-resolution analysis of structure and dynamics of large viral systems and give examples of several exciting case studies. PMID:25919197

  13. New Designs for NMR Core Scanning

    NASA Astrophysics Data System (ADS)

    Bluemich, B.; Anferova, S.; Talnishnikh, E.; Arnold, J.; Clauser, C.

    2006-12-01

    Within the last ten years, mobile magnetic resonance has moved from the oil field to many new areas of application. While the focus of mobile NMR in the past was on single-sided or inside-out NMR, the advent of tube-shaped Halbach magnets has introduced the conventional outside-in NMR concept to mobile NMR where the object is inside a magnet. Our Halbach magnet is constructed from small magnet blocks at light weight and low cost with a magnetic field sufficiently homogeneous. To automatize NMR measurements, the Halbach magnet is mounted on a sliding table to scan long core sections without human interaction. In homogeneous magnetic fields, the longitudinal relaxation time T1 and even the transverse relaxation time T2 are proportional to the pore diameters of rocks. Hence, the T1 and T2 signals map the pore-size distribution of the studied rock cores. For fully saturated samples the integral of the distribution curve is proportional to porosity. The porosity values from NMR measurements with the Halbach magnet are used to estimate permability. The Halbach magnet can be used for certain sample geometries in combination with exchangeable radio frequency (rf) coils with different diameters from 24 mm up to 80 mm. To measure standard Ocean Drilling Program (ODP)/Integrated Ocean Drilling Program (IODP) cores, which have a standard diameter of 60 mm and are split lengthwise after recovery, we use a surface figure-8 rf coil with an inner diameter of 60 mm. Besides 1D T2 measurements, we perform relaxation-relaxation correlation experiments, where T1 and T2 are measured in parallel. In this way, the influence of diffusion on the shape of the T2 distribution function is probed. A gradient coil system was designed to perform Pulsed Field Gradients (PFG) experiments. As the gradient coils restrict the axial access to the magnet, only cylindrical core plugs with 20 mm in diameter can be analysed by PFG NMR methods. The homogeneity of the magnetic field in the sensitive volume

  14. Complete (1) H NMR assignment of cedranolides.

    PubMed

    Perez-Hernandez, Nury; Gordillo-Roman, Barbara; Arrieta-Baez, Daniel; Cerda-Garcia-Rojas, Carlos M; Joseph-Nathan, Pedro

    2017-03-01

    Complete and unambiguous (1) H NMR chemical shift assignment of α-cedrene (2) and cedrol (9), as well as for α-pipitzol (1), isocedrol (10), and the six related compounds 3-8 has been established by iterative full spin analysis using the PERCH NMR software (PERCH Solutions Ltd., Kuopio, Finland). The total sets of coupling constants are described and correlated with the conformational equilibria of the five-membered ring of 1-10, which were calculated using the complete basis set method. Copyright © 2015 John Wiley & Sons, Ltd.

  15. (13)C NMR Metabolomics: INADEQUATE Network Analysis.

    PubMed

    Clendinen, Chaevien S; Pasquel, Christian; Ajredini, Ramadan; Edison, Arthur S

    2015-06-02

    The many advantages of (13)C NMR are often overshadowed by its intrinsically low sensitivity. Given that carbon makes up the backbone of most biologically relevant molecules, (13)C NMR offers a straightforward measurement of these compounds. Two-dimensional (13)C-(13)C correlation experiments like INADEQUATE (incredible natural abundance double quantum transfer experiment) are ideal for the structural elucidation of natural products and have great but untapped potential for metabolomics analysis. We demonstrate a new and semiautomated approach called INETA (INADEQUATE network analysis) for the untargeted analysis of INADEQUATE data sets using an in silico INADEQUATE database. We demonstrate this approach using isotopically labeled Caenorhabditis elegans mixtures.

  16. The Quiet Renaissance of Protein NMR

    PubMed Central

    Barrett, Paul J.; Chen, Jiang; Cho, Min-Kyu; Kim, Ji-Hun; Lu, Zhenwei; Mathew, Sijo; Peng, Dungeng; Song, Yuanli; Van Horn, Wade D.; Zhuang, Tiandi; Sönnichsen, Frank D.; Sanders, Charles R.

    2013-01-01

    From roughly 1985 through the start of the new millennium, the cutting edge of solution protein nuclear magnetic resonance (NMR) spectroscopy was to a significant extent driven by the aspiration to determine structures. Here we survey recent advances in protein NMR that herald a renaissance in which a number of its most important applications reflect the broad problem-solving capability displayed by this method during its classical era during the 1970s and early 80s. “Without receivers fitted and kept in order, the air may tingle and thrill with the message, but it will not reach my spirit and consciousness.” Mary Slessor, Calabar, circa 1910 PMID:23368985

  17. An optical NMR spectrometer for Larmor-beat detection and high-resolution POWER NMR

    NASA Astrophysics Data System (ADS)

    Kempf, J. G.; Marohn, J. A.; Carson, P. J.; Shykind, D. A.; Hwang, J. Y.; Miller, M. A.; Weitekamp, D. P.

    2008-06-01

    Optical nuclear magnetic resonance (ONMR) is a powerful probe of electronic properties in III-V semiconductors. Larmor-beat detection (LBD) is a sensitivity optimized, time-domain NMR version of optical detection based on the Hanle effect. Combining LBD ONMR with the line-narrowing method of POWER (perturbations observed with enhanced resolution) NMR further enables atomically detailed views of local electronic features in III-Vs. POWER NMR spectra display the distribution of resonance shifts or line splittings introduced by a perturbation, such as optical excitation or application of an electric field, that is synchronized with a NMR multiple-pulse time-suspension sequence. Meanwhile, ONMR provides the requisite sensitivity and spatial selectivity to isolate local signals within macroscopic samples. Optical NMR, LBD, and the POWER method each introduce unique demands on instrumentation. Here, we detail the design and implementation of our system, including cryogenic, optical, and radio-frequency components. The result is a flexible, low-cost system with important applications in semiconductor electronics and spin physics. We also demonstrate the performance of our systems with high-resolution ONMR spectra of an epitaxial AlGaAs /GaAs heterojunction. NMR linewidths down to 4.1Hz full width at half maximum were obtained, a 103-fold resolution enhancement relative any previous optically detected NMR experiment.

  18. Combining (27)Al Solid-State NMR and First-Principles Simulations To Explore Crystal Structure in Disordered Aluminum Oxynitride.

    PubMed

    Tu, Bingtian; Liu, Xin; Wang, Hao; Wang, Weimin; Zhai, Pengcheng; Fu, Zhengyi

    2016-12-19

    The nuclear magnetic resonance (NMR) technique gives insight into the local information in a crystal structure, while Rietveld refinement of powder X-ray diffraction (PXRD) sketches out the framework of a crystal lattice. In this work, first-principles calculations were combined with the solid-state NMR technique and Rietveld refinement to explore the crystal structure of a disordered aluminum oxynitride (γ-alon). The theoretical NMR parameters (chemical shift, δiso, quadrupolar coupling constants, CQ, and asymmetry parameter, η) of Al22.5O28.5N3.5, predicted by the gauge-including projector augmented wave (GIPAW) algorithm, were used to facilitate the analytical investigation of the (27)Al magic-angle spinning (MAS) NMR spectra of the as-prepared sample, whose formula was confirmed to be Al2.811O3.565N0.435 by quantitative analysis. The experimental δiso, CQ, and η of (27)Al showed a small discrepancy compared with theoretical models. The ratio of aluminum located at the 8a to 16d sites was calculated to be 0.531 from the relative integration of peaks in the (27)Al NMR spectra. The occupancies of aluminum at the 8a and 16d positions were determined through NMR investigations to be 0.9755 and 0.9178, respectively, and were used in the Rietveld refinement to obtain the lattice parameter and anion parameter of Al2.811O3.565N0.435. The results from (27)Al NMR investigations and PXRD structural refinement complemented each other. This work provides a powerful and accessible strategy to precisely understand the crystal structure of novel oxynitride materials with multiple disorder.

  19. (1)H NMR spectra dataset and solid-state NMR data of cowpea (Vigna unguiculata).

    PubMed

    Alves Filho, Elenilson G; Silva, Lorena M A; Teofilo, Elizita M; Larsen, Flemming H; de Brito, Edy S

    2017-04-01

    In this article the NMR data from chemical shifts, coupling constants, and structures of all the characterized compounds were provided, beyond a complementary PCA evaluation for the corresponding manuscript (E.G. Alves Filho, L.M.A. Silva, E.M. Teofilo, F.H. Larsen, E.S. de Brito, 2017) [3]. In addition, a complementary assessment from solid-state NMR data was provided. For further chemometric analysis, numerical matrices from the raw (1)H NMR data were made available in Microsoft Excel workbook format (.xls).

  20. Engineered solubility tag for solution NMR of proteins.

    PubMed

    Ruschak, Amy M; Rose, Justine D; Coughlin, Michael P; Religa, Tomasz L

    2013-11-01

    The low solubility of many proteins hinders large scale expression and purification as well as biophysical measurements. Here, we devised a general strategy to solubilize a protein by conjugating it at a solvent-exposed position to a 6 kDa protein that was re-engineered to be highly soluble. We applied this method to the CARD domain of Apoptosis-associated speck-like protein containing a CARD (ASC), which represents one member of a class of proteins that are notoriously prone to aggregation. Attachment of the tag to a cysteine residue, introduced by site-directed mutagenesis at its self-association interface, improved the solubility of the ASC CARD over 50-fold under physiological conditions. Although it is not possible to use nuclear magnetic resonance (NMR) to obtain a high quality 2D correlation spectrum of the wild type domain under physiological conditions, we demonstrate that NMR relaxation parameters of the solubilized variant are sufficiently improved to facilitate virtually any demanding measurement. The method shown here represents a straightforward approach for dramatically increasing protein solubility, enabled by ease of labeling as well as flexibility in tag placement with minimal perturbation to the target.

  1. Protein Motions and Folding Investigated by NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Palmer, Arthur

    2002-03-01

    NMR spin relaxation spectroscopy is a powerful experimental approach for globally characterizing conformational dynamics of proteins in solution. Laboratory frame relaxation measurements are sensitive to overall rotational diffusion and internal motions on picosecond-nanosecond time scales, while rotating frame relaxation measurements are sensitive to chemical exchange processes on microsecond-millisecond time scales. The former approach is illustrated by ^15N laboratory-frame relaxation experiments as a function of temperature for the helical subdomain HP36 of the F-actin-binding headpiece domain of chicken villin. The data are analyzed using the model-free formalism to characterize order parameters and effective correlation times for intramolecular motions of individual ^15N sites. The latter approach is illustrated by ^13C Carr-Purcell-Meiboom-Gill relaxation measurements for the de novo designed α_2D protein and by ^15N rotating-frame relaxation measurements for the peripheral subunit-binding domain (PSBD) from the dihydrolopoamide acetyltransferase component of the pyruvate dehydrogenase multienzyme complex from Bacillus stearothermophilus. These experiments are used to determine the folding and unfolding kinetic rate constants for the two proteins. The results for HP36, α_2D, and PSBD illustrate the capability of current NMR methods for characterizing dynamic processes on multiple time scales in proteins.

  2. Theory of mirrored time domain sampling for NMR spectroscopy.

    PubMed

    Ghosh, Arindam; Wu, Yibing; He, Yunfen; Szyperski, Thomas

    2011-12-01

    A generalized theory is presented for novel mirrored hypercomplex time domain sampling (MHS) of NMR spectra. It is the salient new feature of MHS that two interferograms are acquired with different directionality of time evolution, that is, one is sampled forward from time t=0 to the maximal evolution time tmax, while the second is sampled backward from t=0 to -tmax. The sampling can be accomplished in a (semi) constant time or non constant-time manner. Subsequently, the two interferograms are linearly combined to yield a complex time domain signal. The manifold of MHS schemes considered here is defined by arbitrary settings of sampling phases ('primary phase shifts') and amplitudes of the two interferograms. It is shown that, for any two given primary phase shifts, the addition theorems of trigonometric functions yield the unique linear combination required to form the complex signal. In the framework of clean absorption mode (CAM) acquisition of NMR spectra being devoid of residual dispersive signal components, 'secondary phase shifts' represent time domain phase errors which are to be eliminated. In contrast, such secondary phase shifts may be introduced by experimental design in order to encode additional NMR parameters, a new class of NMR experiments proposed here. For generalization, it is further considered that secondary phase shifts may depend on primary phase shifts and/or sampling directionality. In order to compare with MHS theory, a correspondingly generalized theory is derived for widely used hypercomplex ('States') sampling (HS). With generalized theory it is shown, first, that previously introduced 'canonical' schemes, characterized by primary phases being multiples of π/4, afford maximal intensity of the desired absorptive signals in the absence of secondary phase shifts, and second, how primary phases can be adjusted to maximize the signal intensity provided that the secondary phase shifts are known. Third, it is demonstrated that theory enables

  3. 13C NMR of tunnelling methyl groups

    NASA Astrophysics Data System (ADS)

    Detken, A.

    The dipolar interactions between the protons and the central 13C nucleus of a 13CH3 group are used to study rotational tunnelling and incoherent dynamics of such groups in molecular solids. Single-crystal 13C NMR spectra are derived for arbitrary values of the tunnel frequency upsilon t. Similarities to ESR and 2H NMR are pointed out. The method is applied to three different materials. In the hydroquinone/acetonitrile clathrate, the unique features in the 13C NMR spectra which arise from tunnelling with a tunnel frequency that is much larger than the dipolar coupling between the methyl protons and the 13C nucleus are demonstrated, and the effects of incoherent dynamics are studied. The broadening of the 13C resonances is related to the width of the quasi-elastic line in neutron scattering. Selective magnetization transfer experiments for studying slow incoherent dynamics are proposed. For the strongly hindered methyl groups of L-alanine, an upper limit for upsilon is derived from the 13C NMR spectrum. In aspirinTM (acetylsalicylic acid), incoherent reorientations dominate the spectra down to the lowest temperatures studied; their rate apparently increases with decreasing temperature below 25K.

  4. Increasing the quantitative bandwidth of NMR measurements.

    PubMed

    Power, J E; Foroozandeh, M; Adams, R W; Nilsson, M; Coombes, S R; Phillips, A R; Morris, G A

    2016-02-18

    The frequency range of quantitative NMR is increased from tens to hundreds of kHz by a new pulse sequence, CHORUS. It uses chirp pulses to excite uniformly over very large bandwidths, yielding accurate integrals even for nuclei such as (19)F that have very wide spectra.

  5. Advanced Laboratory NMR Spectrometer with Applications.

    ERIC Educational Resources Information Center

    Biscegli, Clovis; And Others

    1982-01-01

    A description is given of an inexpensive nuclear magnetic resonance (NMR) spectrometer suitable for use in advanced laboratory courses. Applications to the nondestructive analysis of the oil content in corn seeds and in monitoring the crystallization of polymers are presented. (SK)

  6. Planar microcoil-based microfluidic NMR probes

    NASA Astrophysics Data System (ADS)

    Massin, C.; Vincent, F.; Homsy, A.; Ehrmann, K.; Boero, G.; Besse, P.-A.; Daridon, A.; Verpoorte, E.; de Rooij, N. F.; Popovic, R. S.

    2003-10-01

    Microfabricated small-volume NMR probes consisting of electroplated planar microcoils integrated on a glass substrate with etched microfluidic channels are fabricated and tested. 1H NMR spectra are acquired at 300 MHz with three different probes having observed sample volumes of respectively 30, 120, and 470 nL. The achieved sensitivity enables acquisition of an 1H spectrum of 160 μg sucrose in D 2O, corresponding to a proof-of-concept for on-chip NMR spectroscopy. Increase of mass-sensitivity with coil diameter reduction is demonstrated experimentally for planar microcoils. Models that enable quantitative prediction of the signal-to-noise ratio and of the influence of microfluidic channel geometry on spectral resolution are presented and successfully compared to the experimental data. The main factor presently limiting sensitivity for high-resolution applications is identified as being probe-induced static magnetic field distortions. Finally, based on the presented model and measured data, future performance of planar microcoil-based microfluidic NMR probes is extrapolated and discussed.

  7. Planar microcoil-based microfluidic NMR probes.

    PubMed

    Massin, C; Vincent, F; Homsy, A; Ehrmann, K; Boero, G; Besse, P-A; Daridon, A; Verpoorte, E; de Rooij, N F; Popovic, R S

    2003-10-01

    Microfabricated small-volume NMR probes consisting of electroplated planar microcoils integrated on a glass substrate with etched microfluidic channels are fabricated and tested. 1H NMR spectra are acquired at 300 MHz with three different probes having observed sample volumes of respectively 30, 120, and 470 nL. The achieved sensitivity enables acquisition of an 1H spectrum of 160 microg sucrose in D2O, corresponding to a proof-of-concept for on-chip NMR spectroscopy. Increase of mass-sensitivity with coil diameter reduction is demonstrated experimentally for planar microcoils. Models that enable quantitative prediction of the signal-to-noise ratio and of the influence of microfluidic channel geometry on spectral resolution are presented and successfully compared to the experimental data. The main factor presently limiting sensitivity for high-resolution applications is identified as being probe-induced static magnetic field distortions. Finally, based on the presented model and measured data, future performance of planar microcoil-based microfluidic NMR probes is extrapolated and discussed.

  8. Hyperpolarized NMR Probes for Biological Assays

    PubMed Central

    Meier, Sebastian; Jensen, Pernille R.; Karlsson, Magnus; Lerche, Mathilde H.

    2014-01-01

    During the last decade, the development of nuclear spin polarization enhanced (hyperpolarized) molecular probes has opened up new opportunities for studying the inner workings of living cells in real time. The hyperpolarized probes are produced ex situ, introduced into biological systems and detected with high sensitivity and contrast against background signals using high resolution NMR spectroscopy. A variety of natural, derivatized and designed hyperpolarized probes has emerged for diverse biological studies including assays of intracellular reaction progression, pathway kinetics, probe uptake and export, pH, redox state, reactive oxygen species, ion concentrations, drug efficacy or oncogenic signaling. These probes are readily used directly under natural conditions in biofluids and are often directly developed and optimized for cellular assays, thus leaving little doubt about their specificity and utility under biologically relevant conditions. Hyperpolarized molecular probes for biological NMR spectroscopy enable the unbiased detection of complex processes by virtue of the high spectral resolution, structural specificity and quantifiability of NMR signals. Here, we provide a survey of strategies used for the selection, design and use of hyperpolarized NMR probes in biological assays, and describe current limitations and developments. PMID:24441771

  9. Structural Studies of Biological Solids Using NMR

    NASA Astrophysics Data System (ADS)

    Ramamoorthy, Ayyalusamy

    2011-03-01

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

  10. Hydrate Shell Growth Measured Using NMR.

    PubMed

    Haber, Agnes; Akhfash, Masoumeh; Loh, Charles K; Aman, Zachary M; Fridjonsson, Einar O; May, Eric F; Johns, Michael L

    2015-08-18

    Benchtop nuclear magnetic resonance (NMR) pulsed field gradient (PFG) and relaxation measurements were used to monitor the clathrate hydrate shell growth occurring in water droplets dispersed in a continuous cyclopentane phase. These techniques allowed the growth of hydrate inside the opaque exterior shell to be monitored and, hence, information about the evolution of the shell's morphology to be deduced. NMR relaxation measurements were primarily used to monitor the hydrate shell growth kinetics, while PFG NMR diffusion experiments were used to determine the nominal droplet size distribution (DSD) of the unconverted water inside the shell core. A comparison of mean droplet sizes obtained directly via PFG NMR and independently deduced from relaxation measurements showed that the assumption of the shell model-a perfect spherical core of unconverted water-for these hydrate droplet systems is correct, but only after approximately 24 h of shell growth. Initially, hydrate growth is faster and heat-transfer-limited, leading to porous shells with surface areas larger than that of spheres with equivalent volumes. Subsequently, the hydrate growth rate becomes mass-transfer-limited, and the shells become thicker, spherical, and less porous.

  11. NMR characterization of polymers: Review and update

    Technology Transfer Automated Retrieval System (TEKTRAN)

    NMR spectroscopy is a major technique for the characterization and analysis of polymers. A large number of methodologies have been developed in both the liquid and the solid state, and the literature has grown considerably (1-5). The field now covers a broad spectrum of activities, including polym...

  12. Structural fidelity and NMR relaxation analysis in a prototype RNA hairpin.

    PubMed

    Giambaşu, George M; York, Darrin M; Case, David A

    2015-05-01

    RNA hairpins are widespread and very stable motifs that contribute decisively to RNA folding and biological function. The GTP1G2C3A4C5U6U7C8G9G10U11G12C13C14 construct (with a central UUCG tetraloop) has been extensively studied by solution NMR, and offers and excellent opportunity to evaluate the structure and dynamical description afforded by molecular dynamics (MD) simulations. Here, we compare average structural parameters and NMR relaxation rates estimated from a series of multiple independent explicit solvent MD simulations using the two most recent RNA AMBER force fields (ff99 and ff10). Predicted overall tumbling times are ∼20% faster than those inferred from analysis of NMR data and follow the same trend when temperature and ionic strength is varied. The Watson-Crick stem and the "canonical" UUCG loop structure are maintained in most simulations including the characteristic syn conformation along the glycosidic bond of G9, although some key hydrogen bonds in the loop are partially disrupted. Our analysis pinpoints G9-G10 backbone conformations as a locus of discrepancies between experiment and simulation. In general the results for the more recent force-field parameters (ff10) are closer to experiment than those for the older ones (ff99). This work provides a comprehensive and detailed comparison of state of the art MD simulations against a wide variety of solution NMR measurements.

  13. A mobile one-sided NMR sensor with a homogeneous magnetic field: the NMR-MOLE.

    PubMed

    Manz, B; Coy, A; Dykstra, R; Eccles, C D; Hunter, M W; Parkinson, B J; Callaghan, P T

    2006-11-01

    A new portable NMR sensor with a novel one-sided access magnet design, termed NMR-MOLE (MObile Lateral Explorer), has been characterised in terms of sensitivity and depth penetration. The magnet has been designed to be portable and create a volume with a relatively homogeneous magnetic field, 15,000 ppm over a region from 4 to 16 mm away from the probe, with maximum sensitivity at a depth of 10 mm. The proton NMR frequency is 3.3 MHz. We have demonstrated that with this approach a highly sensitive, portable, unilateral NMR sensor can be built. Such a design is especially suited for the characterisation of liquids in situations where unilateral or portable access is required.

  14. Solid-state NMR/NQR and first-principles study of two niobium halide cluster compounds.

    PubMed

    Perić, Berislav; Gautier, Régis; Pickard, Chris J; Bosiočić, Marko; Grbić, Mihael S; Požek, Miroslav

    2014-01-01

    Two hexanuclear niobium halide cluster compounds with a [Nb6X12](2+) (X=Cl, Br) diamagnetic cluster core, have been studied by a combination of experimental solid-state NMR/NQR techniques and PAW/GIPAW calculations. For niobium sites the NMR parameters were determined by using variable Bo field static broadband NMR measurements and additional NQR measurements. It was found that they possess large positive chemical shifts, contrary to majority of niobium compounds studied so far by solid-state NMR, but in accordance with chemical shifts of (95)Mo nuclei in structurally related compounds containing [Mo6Br8](4+) cluster cores. Experimentally determined δiso((93)Nb) values are in the range from 2,400 to 3,000 ppm. A detailed analysis of geometrical relations between computed electric field gradient (EFG) and chemical shift (CS) tensors with respect to structural features of cluster units was carried out. These tensors on niobium sites are almost axially symmetric with parallel orientation of the largest EFG and the smallest CS principal axes (Vzz and δ33) coinciding with the molecular four-fold axis of the [Nb6X12](2+) unit. Bridging halogen sites are characterized by large asymmetry of EFG and CS tensors, the largest EFG principal axis (Vzz) is perpendicular to the X-Nb bonds, while intermediate EFG principal axis (Vyy) and the largest CS principal axis (δ11) are oriented in the radial direction with respect to the center of the cluster unit. For more symmetrical bromide compound the PAW predictions for EFG parameters are in better correspondence with the NMR/NQR measurements than in the less symmetrical chlorine compound. Theoretically predicted NMR parameters of bridging halogen sites were checked by (79/81)Br NQR and (35)Cl solid-state NMR measurements.

  15. NMR Constraints Analyser: a web-server for the graphical analysis of NMR experimental constraints

    PubMed Central

    Heller, Davide Martin; Giorgetti, Alejandro

    2010-01-01

    Nuclear magnetic resonance (NMR) spectroscopy together with X-ray crystallography, are the main techniques used for the determination of high-resolution 3D structures of biological molecules. The output of an NMR experiment includes a set of lower and upper limits for the distances (constraints) between pairs of atoms. If the number of constraints is high enough, there will be a finite number of possible conformations (models) of the macromolecule satisfying the data. Thus, the more constraints are measured, the better defined these structures will be. The availability of a user-friendly tool able to help in the analysis and interpretation of the number of experimental constraints per residue, is thus of valuable importance when assessing the levels of structure definition of NMR solved biological macromolecules, in particular, when high-quality structures are needed in techniques such as, computational biology approaches, site-directed mutagenesis experiments and/or drug design. Here, we present a free publicly available web-server, i.e. NMR Constraints Analyser, which is aimed at providing an automatic graphical analysis of the NMR experimental constraints atom by atom. The NMR Constraints Analyser server is available from the web-page http://molsim.sci.univr.it/constraint PMID:20513646

  16. Continuous Flow 1H and 13C NMR Spectroscopy in Microfluidic Stripline NMR Chips

    PubMed Central

    2017-01-01

    Microfluidic stripline NMR technology not only allows for NMR experiments to be performed on small sample volumes in the submicroliter range, but also experiments can easily be performed in continuous flow because of the stripline’s favorable geometry. In this study we demonstrate the possibility of dual-channel operation of a microfluidic stripline NMR setup showing one- and two-dimensional 1H, 13C and heteronuclear NMR experiments under continuous flow. We performed experiments on ethyl crotonate and menthol, using three different types of NMR chips aiming for straightforward microfluidic connectivity. The detection volumes are approximately 150 and 250 nL, while flow rates ranging from 0.5 μL/min to 15 μL/min have been employed. We show that in continuous flow the pulse delay is determined by the replenishment time of the detector volume, if the sample trajectory in the magnet toward NMR detector is long enough to polarize the spin systems. This can considerably speed up quantitative measurement of samples needing signal averaging. So it can be beneficial to perform continuous flow measurements in this setup for analysis of, e.g., reactive, unstable, or mass-limited compounds. PMID:28194934

  17. NMR Constraints Analyser: a web-server for the graphical analysis of NMR experimental constraints.

    PubMed

    Heller, Davide Martin; Giorgetti, Alejandro

    2010-07-01

    Nuclear magnetic resonance (NMR) spectroscopy together with X-ray crystallography, are the main techniques used for the determination of high-resolution 3D structures of biological molecules. The output of an NMR experiment includes a set of lower and upper limits for the distances (constraints) between pairs of atoms. If the number of constraints is high enough, there will be a finite number of possible conformations (models) of the macromolecule satisfying the data. Thus, the more constraints are measured, the better defined these structures will be. The availability of a user-friendly tool able to help in the analysis and interpretation of the number of experimental constraints per residue, is thus of valuable importance when assessing the levels of structure definition of NMR solved biological macromolecules, in particular, when high-quality structures are needed in techniques such as, computational biology approaches, site-directed mutagenesis experiments and/or drug design. Here, we present a free publicly available web-server, i.e. NMR Constraints Analyser, which is aimed at providing an automatic graphical analysis of the NMR experimental constraints atom by atom. The NMR Constraints Analyser server is available from the web-page http://molsim.sci.univr.it/constraint.

  18. OPENCORE NMR: open-source core modules for implementing an integrated FPGA-based NMR spectrometer.

    PubMed

    Takeda, Kazuyuki

    2008-06-01

    A tool kit for implementing an integrated FPGA-based NMR spectrometer [K. Takeda, A highly integrated FPGA-based nuclear magnetic resonance spectrometer, Rev. Sci. Instrum. 78 (2007) 033103], referred to as the OPENCORE NMR spectrometer, is open to public. The system is composed of an FPGA chip and several peripheral boards for USB communication, direct-digital synthesis (DDS), RF transmission, signal acquisition, etc. Inside the FPGA chip have been implemented a number of digital modules including three pulse programmers, the digital part of DDS, a digital quadrature demodulator, dual digital low-pass filters, and a PC interface. These FPGA core modules are written in VHDL, and their source codes are available on our website. This work aims at providing sufficient information with which one can, given some facility in circuit board manufacturing, reproduce the OPENCORE NMR spectrometer presented here. Also, the users are encouraged to modify the design of spectrometer according to their own specific needs. A home-built NMR spectrometer can serve complementary roles to a sophisticated commercial spectrometer, should one comes across such new ideas that require heavy modification to hardware inside the spectrometer. This work can lower the barrier of building a handmade NMR spectrometer in the laboratory, and promote novel and exciting NMR experiments.

  19. OPENCORE NMR: Open-source core modules for implementing an integrated FPGA-based NMR spectrometer

    NASA Astrophysics Data System (ADS)

    Takeda, Kazuyuki

    2008-06-01

    A tool kit for implementing an integrated FPGA-based NMR spectrometer [K. Takeda, A highly integrated FPGA-based nuclear magnetic resonance spectrometer, Rev. Sci. Instrum. 78 (2007) 033103], referred to as the OPENCORE NMR spectrometer, is open to public. The system is composed of an FPGA chip and several peripheral boards for USB communication, direct-digital synthesis (DDS), RF transmission, signal acquisition, etc. Inside the FPGA chip have been implemented a number of digital modules including three pulse programmers, the digital part of DDS, a digital quadrature demodulator, dual digital low-pass filters, and a PC interface. These FPGA core modules are written in VHDL, and their source codes are available on our website. This work aims at providing sufficient information with which one can, given some facility in circuit board manufacturing, reproduce the OPENCORE NMR spectrometer presented here. Also, the users are encouraged to modify the design of spectrometer according to their own specific needs. A home-built NMR spectrometer can serve complementary roles to a sophisticated commercial spectrometer, should one comes across such new ideas that require heavy modification to hardware inside the spectrometer. This work can lower the barrier of building a handmade NMR spectrometer in the laboratory, and promote novel and exciting NMR experiments.

  20. First NMR Experiments in the Hybrid, 40T and beyond: A challenge to traditional NMR instrumentation

    NASA Astrophysics Data System (ADS)

    Reyes, Arneil P.

    2001-03-01

    The recent commissioning of the continuous 45T hybrid magnet at NHMFL has opened new horizon for science but carried with it new challenges that forced NMR spectroscopists to reevaluate the traditional approach to NMR instrumentation. Very recently, a world record frequency at 1.5GHz has been achieved, signaling the new era of NMR probe designs that may someday blur the distinction between the classic NMR and millimeter-wave spectroscopies. No longer can we ignore stray capacitances and exposed leads in the terrain where every millimeter of cable counts. The challenge brought about by ever increasing fields and consequently, frequency, requirements has stimulated ingenuity among scientists. This is eased by accelerated growth in RF communications and computing technologies that made available advanced devices with more speed, power, bandwidth, noise immunity, flexibility, and complexity in small space at very low costs. Utilization of these devices have been paramount consideration in cutting-edge designs at NHMFL for Condensed Matter NMR and will be described in this talk. I will also discuss a number of first >33T NMR experiments to date utilizing the strength of the field to expose, as well as to induce occurrence of, new physical phenomena in condensed matter and which resulted in better understanding of the physics of materials. This work has been a result of continuing collaboration with P. L Kuhns, W. G. Moulton, W. P. Halperin (NU), and W. G. Clark (UCLA). The NHMFL is supported through the National Science Foundation and the State of Florida.

  1. Continuous Flow (1)H and (13)C NMR Spectroscopy in Microfluidic Stripline NMR Chips.

    PubMed

    Oosthoek-de Vries, Anna Jo; Bart, Jacob; Tiggelaar, Roald M; Janssen, Johannes W G; van Bentum, P Jan M; Gardeniers, Han J G E; Kentgens, Arno P M

    2017-02-21

    Microfluidic stripline NMR technology not only allows for NMR experiments to be performed on small sample volumes in the submicroliter range, but also experiments can easily be performed in continuous flow because of the stripline's favorable geometry. In this study we demonstrate the possibility of dual-channel operation of a microfluidic stripline NMR setup showing one- and two-dimensional (1)H, (13)C and heteronuclear NMR experiments under continuous flow. We performed experiments on ethyl crotonate and menthol, using three different types of NMR chips aiming for straightforward microfluidic connectivity. The detection volumes are approximately 150 and 250 nL, while flow rates ranging from 0.5 μL/min to 15 μL/min have been employed. We show that in continuous flow the pulse delay is determined by the replenishment time of the detector volume, if the sample trajectory in the magnet toward NMR detector is long enough to polarize the spin systems. This can considerably speed up quantitative measurement of samples needing signal averaging. So it can be beneficial to perform continuous flow measurements in this setup for analysis of, e.g., reactive, unstable, or mass-limited compounds.

  2. Structural investigations on betacyanin pigments by LC NMR and 2D NMR spectroscopy.

    PubMed

    Stintzing, Florian C; Conrad, Jürgen; Klaiber, Iris; Beifuss, Uwe; Carle, Reinhold

    2004-02-01

    Four betacyanin pigments were analysed by LC NMR and subjected to extensive NMR characterisation after isolation. Previously, low pH values were applied for NMR investigations of betalains resulting in rapid degradation of the purified substances thus preventing extensive NMR studies. Consequently, up to now only one single (13)C NMR spectrum of a betalain pigment, namely that of neobetanin (=14,15-dehydrobetanin), was available. Because of its sufficient stability under highly acidic conditions otherwise detrimental for betacyanins, this pigment remained an exemption. Since betalains are most stable in the pH range of 5-7, a new solvent system has been developed allowing improved data acquisition through improved pigment stability at near neutral pH. Thus, not only (1)H, but for the first time also partial (13)C data of betanin, isobetanin, phyllocactin and hylocerenin isolated from red-purple pitaya [Hylocereus polyrhizus (Weber) Britton & Rose, Cactaceae] could be indirectly obtained by gHSQC- and gHMQC-NMR experiments.

  3. Advances in NMR-based biofluid analysis and metabolite profiling.

    PubMed

    Zhang, Shucha; Nagana Gowda, G A; Ye, Tao; Raftery, Daniel

    2010-07-01

    Significant improvements in NMR technology and methods have propelled NMR studies to play an important role in a rapidly expanding number of applications involving the profiling of metabolites in biofluids. This review discusses recent technical advances in NMR spectroscopy based metabolite profiling methods, data processing and analysis over the last three years.

  4. Superoxygenated Water as an Experimental Sample for NMR Relaxometry

    ERIC Educational Resources Information Center

    Nestle, Nikolaus; Dakkouri, Marwan; Rauscher, Hubert

    2004-01-01

    The increase in NMR relaxation rates as a result of dissolved paramagnetic species on the sample of superoxygenated drinking water is demonstrated. It is concluded that oxygen content in NMR samples is an important issue and can give rise to various problems in the interpretation of both spectroscopic and NMR imaging or relaxation experiments.

  5. Applications of Diffusion Ordered Spectroscopy (DOSY-NMR)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diffusion-ordered NMR (DOSY-NMR) is a powerful, but under-utilized, technique for the investigation of mixtures based on translational diffusion rates. DOSY spectra allow for determination by NMR of components that may differ in molecular weight, geometry or complexation. Typical applications coul...

  6. Genetic algorithms and solid state NMR pulse sequences

    NASA Astrophysics Data System (ADS)

    Bechmann, Matthias; Clark, John; Sebald, Angelika

    2013-03-01

    The use of genetic algorithms for the optimisation of magic angle spinning NMR pulse sequences is discussed. The discussion uses as an example the optimisation of the C721 dipolar recoupling pulse sequence, aiming to achieve improved efficiency for spin systems characterised by large chemical shielding anisotropies and/or small dipolar coupling interactions. The optimised pulse sequence is found to be robust over a wide range of parameters, requires only minimal a priori knowledge of the spin system for experimental implementations with buildup rates being solely determined by the magnitude of the dipolar coupling interaction, but is found to be less broadbanded than the original C721 pulse sequence. The optimised pulse sequence breaks the synchronicity between r.f. pulses and sample spinning.

  7. Basic facts and perspectives of Overhauser DNP NMR.

    PubMed

    Ravera, Enrico; Luchinat, Claudio; Parigi, Giacomo

    2016-03-01

    After the first surprisingly large (1)H DNP enhancements of the water signal in aqueous solutions of nitroxide radicals observed at high magnetic fields, Overhauser DNP is gaining increasing attention for a number of applications now flourishing, showing the potentialities of this mechanism in solution and solid state NMR as well as in MRI. Unexpected Overhauser DNP enhancements in insulating solids were recently measured at 100K, with a magnitude which increases with the applied magnetic field. We recapitulate here the theoretical premises of Overhauser DNP in solution and analyze the effects of the various parameters on the efficacy of the mechanism, underlining the link between the DNP enhancements and the field dependent relaxation properties. Promisingly, more effective DNP enhancements are expected by exploiting the potentialities offered by (13)C detection and the use of supercritical fluids.

  8. NMR microscopy of heavy metal absorption in calcium alginate beads

    SciTech Connect

    Nestle, N.; Kimmich, R.

    1996-01-01

    In recent years, heavy metal uptake by biopolymer gels, such as Cal-Alginate or chitosan, has been studied by various methods. This is of interest because such materials might be an alternative to synthetical ion-exchange resins in the treatment of industrial waste waters. Most of the work done in this field consisted of studies of equilibrium absorption of different heavy metal ions with dependence on various experimental parameters. In some publications, the kinetics of absorption were studied, too. However, no experiments on the spatial distribution of heavy metals during the absorption process are known to us. Using Cu as an example, it is demonstrated in this article that NMR microscopy is an appropriate tool for such studies. By the method presented here, it is possible to monitor the spatial distribution of heavy metal ions with a time resolution of about 5 min and a spatial resolution of 100 {mu}m or even better. 14 refs., 10 figs.

  9. Perspectives in enzymology of membrane proteins by solid-state NMR.

    PubMed

    Ullrich, Sandra J; Glaubitz, Clemens

    2013-09-17

    Membrane proteins catalyze reactions at the cell membrane and facilitate thetransport of molecules or signals across the membrane. Recently researchers have made great progress in understanding the structural biology of membrane proteins, mainly based on X-ray crystallography. In addition, the application of complementary spectroscopic techniques has allowed researchers to develop a functional understanding of these proteins. Solid-state NMR has become an indispensable tool for the structure-function analysis of insoluble proteins and protein complexes. It offers the possibility of investigating membrane proteins directly in their environment, which provides essential information about the intrinsic coupling of protein structure and functional dynamics within the lipid bilayer. However, to date, researchers have hardly explored the enzymology of mem-brane proteins. In this Account, we review the perspectives for investigating membrane-bound enzymes by solid-state NMR. Understanding enzyme mechanisms requires access to kinetic parameters, structural analysis of the catalytic center, knowledge of the 3D structure and methods to follow the structural dynamics of the enzyme during the catalytic cycle. In principle, solid-state NMR can address all of these issues. Researchers can characterize the enzyme kinetics by observing substrate turnover within the membrane or at the membrane interphase in a time-resolved fashion as shown for diacylglycerol kinase. Solid-state NMR has also provided a mechanistic understanding of soluble enzymes including triosephosphate isomerase (TIM) and different metal-binding proteins, which demonstrates a promising perspective also for membrane proteins. The increasing availability of high magnetic fields and the development of new experimental schemes and computational protocols have made it easier to determine 3D structure using solid-state NMR. Dynamic nuclear polarization, a key technique to boost sensitivity of solid-state NMR at low

  10. Probing cation and vacancy ordering in the dry and hydrated yttrium-substituted BaSnO3 perovskite by NMR spectroscopy and first principles calculations: implications for proton mobility.

    PubMed

    Buannic, Lucienne; Blanc, Frédéric; Middlemiss, Derek S; Grey, Clare P

    2012-09-05

    Hydrated BaSn(1-x)Y(x)O(3-x/2) is a protonic conductor that, unlike many other related perovskites, shows high conductivity even at high substitution levels. A joint multinuclear NMR spectroscopy and density functional theory (total energy and GIPAW NMR calculations) investigation of BaSn(1-x)Y(x)O(3-x/2) (0.10 ≤ x ≤ 0.50) was performed to investigate cation ordering and the location of the oxygen vacancies in the dry material. The DFT energetics show that Y doping on the Sn site is favored over doping on the Ba site. The (119)Sn chemical shifts are sensitive to the number of neighboring Sn and Y cations, an experimental observation that is supported by the GIPAW calculations and that allows clustering to be monitored: Y substitution on the Sn sublattice is close to random up to x = 0.20, while at higher substitution levels, Y-O-Y linkages are avoided, leading, at x = 0.50, to strict Y-O-Sn alternation of B-site cations. These results are confirmed by the absence of a "Y-O-Y" (17)O resonance and supported by the (17)O NMR shift calculations. Although resonances due to six-coordinate Y cations were observed by (89)Y NMR, the agreement between the experimental and calculated shifts was poor. Five-coordinate Sn and Y sites (i.e., sites next to the vacancy) were observed by (119)Sn and (89)Y NMR, respectively, these sites disappearing on hydration. More five-coordinated Sn than five-coordinated Y sites are seen, even at x = 0.50, which is ascribed to the presence of residual Sn-O-Sn defects in the cation-ordered material and their ability to accommodate O vacancies. High-temperature (119)Sn NMR reveals that the O ions are mobile above 400 °C, oxygen mobility being required to hydrate these materials. The high protonic mobility, even in the high Y-content materials, is ascribed to the Y-O-Sn cation ordering, which prevents proton trapping on the more basic Y-O-Y sites.

  11. NMR CHARACTERIZATIONS OF PROPERTIES OF HETEROGENEOUS MEDIA

    SciTech Connect

    C.T. Philip Chang; Changho Choi; Jeromy T. Hollenshead; Rudi Michalak; Jack Phan; Ramon Saavedra; John C. Slattery; Jinsoo Uh; Randi Valestrand; A. Ted Watson; Song Xue

    2005-01-01

    A critical and long-standing need within the petroleum industry is the specification of suitable petrophysical properties for mathematical simulation of fluid flow in petroleum reservoirs (i.e., reservoir characterization). The development of accurate reservoir characterizations is extremely challenging. Property variations may be described on many scales, and the information available from measurements reflect different scales. In fact, experiments on laboratory core samples, well-log data, well-test data, and reservoir-production data all represent information potentially valuable to reservoir characterization, yet they all reflect information about spatial variations of properties at different scales. Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) provide enormous potential for developing new descriptions and understandings of heterogeneous media. NMR has the rare capability to probe permeable media non-invasively, with spatial resolution, and it provides unique information about molecular motions and interactions that are sensitive to morphology. NMR well-logging provides the best opportunity ever to resolve permeability distributions within petroleum reservoirs. We develop MRI methods to determine, for the first time, spatially resolved distributions of porosity and permeability within permeable media samples that approach the intrinsic scale: the finest resolution of these macroscopic properties possible. To our knowledge, this is the first time that the permeability is actually resolved at a scale smaller than the sample. In order to do this, we have developed a robust method to determine of relaxation distributions from NMR experiments and a novel implementation and analysis of MRI experiments to determine the amount of fluid corresponding to imaging regions, which are in turn used to determine porosity and saturation distributions. We have developed a novel MRI experiment to determine velocity distributions within flowing experiments, and

  12. Sodium ion effect on silk fibroin conformation characterized by solid-state NMR and generalized 2D NMR NMR correlation

    NASA Astrophysics Data System (ADS)

    Ruan, Qing-Xia; Zhou, Ping

    2008-07-01

    In the present work, we investigated Na + ion effect on the silk fibroin (SF) conformation. Samples are Na +-involved regenerated silk fibroin films. 13C CP-MAS NMR demonstrates that as added [Na +] increases, partial silk fibroin conformation transit from helix-form to β-form at certain Na + ion concentration which is much higher than that in Bombyx mori silkworm gland. The generalized two-dimensional NMR-NMR correlation analysis reveals that silk fibroin undergoes several intermediate states during its conformation transition process as [Na +] increase. The appearance order of the intermediates is followed as: helix and/or random coil → helix-like → β-sheet-like → β-sheet, which is the same as that produced by pH decrease from 6.8 to 4.8 in the resultant regenerated silk fibroin films. The binding sites of Na + to silk fibroin might involve the carbonyl oxygen atom of certain amino acids sequence which could promote the formation of β-sheet conformation. Since the Na +sbnd O bond is weak, the ability of Na + inducing the secondary structure transition is weaker than those of Ca 2+, Cu 2+ and even K +. It is maybe a reason why the sodium content is much lower than potassium in the silkworm gland.

  13. Solid state and solution 43Ca NMR of calcium peroxides involved in the disproportionation of hydrogen peroxide by calcium hydroxide.

    PubMed

    Trokiner, Arlette; Bessière, Aurélie; Thouvenot, René; Hau, Damien; Marko, Jean; Nardello, Véronique; Pierlot, Christel; Aubry, Jean-Marie

    2004-06-01

    In order to get some insight into the mechanism of the disproportionation of hydrogen peroxide catalyzed by calcium hydroxide, 43Ca NMR spectra of enriched samples of calcium peroxides and of their precursors have been studied in both solution and solid state. This study demonstrates that no well-defined peroxidized calcium species are formed in solution, showing that the catalytic role of calcium is likely restricted to the solid state. Most of the calcium compounds that could be involved in the catalytic process have been investigated with solid state NMR. The shift and quadrupolar parameters of Ca(OH)2, CaO2.8H2O and CaO2.2H2O2 are reported for the first time. These parameters are different enough to allow the quantitative analysis of a complex mixture of these compounds by NMR.

  14. ABCs of FT NMR, (by John D. Roberts)

    NASA Astrophysics Data System (ADS)

    Shibata, John H.

    2002-11-01

    In summary, there are several good books on NMR that I have read and used in preparing lectures on NMR, and in comparison to these books, this would not be the first book that I would take from my bookshelf to learn NMR. It is an elementary book that does have explanations that may help clarify some topics. For that reason, it may be useful to have in a chemistry library collection. I could envision an NMR course based on this book, but not without using other books to supplement the course. To this end, this book has a very useful appendix that describes several excellent NMR books and journals.

  15. Squid detected NMR and MRI at ultralow fields

    DOEpatents

    Clarke, John; Pines, Alexander; McDermott, Robert F.; Trabesinger, Andreas H.

    2008-12-16

    Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

  16. Squid detected NMR and MRI at ultralow fields

    DOEpatents

    Clarke, John; McDermott, Robert; Pines, Alexander; Trabesinger, Andreas Heinz

    2007-05-15

    Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

  17. Squid detected NMR and MRI at ultralow fields

    DOEpatents

    Clarke, John; McDermott, Robert; Pines, Alexander; Trabesinger, Andreas Heinz

    2006-05-30

    Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

  18. SQUID detected NMR and MRI at ultralow fields

    DOEpatents

    Clarke, John; McDermott, Robert; Pines, Alexander; Trabesinger, Andreas Heinz

    2006-10-03

    Nuclear magnetic resonance (NMR) signals are detected in microtesla fields. Prepolarization in millitesla fields is followed by detection with an untuned dc superconducting quantum interference device (SQUID) magnetometer. Because the sensitivity of the SQUID is frequency independent, both signal-to-noise ratio (SNR) and spectral resolution are enhanced by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. MRI in ultralow magnetic field is based on the NMR at ultralow fields. Gradient magnetic fields are applied, and images are constructed from the detected NMR signals.

  19. Determination of carbon dioxide transport coefficients in liquids and polymers by NMR spectroscopy.

    PubMed

    Guzmán, Julio; Garrido, Leoncio

    2012-05-24

    In liquids and in polymeric membranes, a precise determination of their transport properties is of paramount importance. In this work, an NMR method to measure sequentially the solubility and diffusion coefficients of carbon dioxide in liquids (n-alkanes and 1-alkanols) and in polymer membranes (polyethylene, polybutadiene, and polycarbonate) is described. The results show that NMR measurements are very reproducible and in good agreement with those determined by other methods. Considering that the gas permeability is defined as the product of the solubility and diffusion coefficients, the method allows the determination of all transport parameters in an accurate manner. The influence of chain length, viscosity, and solubility parameters on the transport coefficients of [(13)C]O(2) in alkanes and 1-alkanols was also analyzed and compared to those measured in polyethylene.

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

    PubMed

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

    2013-10-09

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

  1. Intermolecular interactions in AST zeolites through (14)N NMR and DFT calculations.

    PubMed

    Dib, Eddy; Freire, Mélanie; Pralong, Valérie; Mineva, Tzonka; Alonso, Bruno

    2017-03-01

    The structure of the silica AST zeolites (octadecasil) synthesized in fluoride medium using tetramethylammonium (TMA) as the organic structure-directing agent has been reinvestigated using (14)N NMR quadrupolar parameters and DFT calculations. The value of the experimental (14)N quadrupolar coupling constant (CQ = 27 kHz) is larger than expected for a TMA cation possessing a high degree of motion. The analysis of a DFT-optimized octadecasil cluster along with the comparison between measured and calculated (14)N NMR parameters demonstrate the presence of weak C-H...O hydrogen bonds between the TMA in the [4(6)6(12)] cages and the silica skeleton. These intermolecular interactions can be related to the presence of Si...F tetrel bonds within the [4(6)] cages. These new results provide additional information with regard to the formation mechanisms and structure of the octadecasil zeolites.

  2. Dynamics of Reassembled Thioredoxin Studied by Magic Angle Spinning NMR: Snapshots from Different Timescales

    PubMed Central

    Yang, Jun; Tasayco, Maria Luisa; Polenova, Tatyana

    2014-01-01

    Solid-state NMR spectroscopy can be used to probe internal protein dynamics in the absence of the overall molecular tumbling. In this study, we report 15N backbone dynamics in differentially enriched 1-73(U-13C, 15N)/74-108(U-15N) reassembled thioredoxin on multiple timescales using a series of 2D and 3D MAS NMR experiments probing the backbone amide 15N longitudinal relaxation, 1H-15N dipolar order parameters, 15N chemical shift anisotropy (CSA), and signal intensities in the temperature-dependent and 1H T2′ -filtered NCA experiments. The spin-lattice relaxation rates R1(R1 = 1/T1) were observed in the range from 0.012 to 0.64 s-1 indicating large site-to-site variations in dynamics on pico- to nanosecond time scales. The 1H-15N dipolar order parameters, , and 15N CSA anisotropies, δσ reveal the backbone mobilities in reassembled thioredoxin, as reflected in the average = 0.89 ± 0.06 and δσ = 92.3 ± 5.2 ppm, respectively. From the aggregate of experimental data from different dynamics methods, some degree of correlation between the motions on the different time scales has been suggested. Analysis of the dynamics parameters derived from these solid-state NMR experiments indicates higher mobilities for the residues constituting irregular secondary structure elements than for those located in the α-helices and β-sheets, with no apparent systematic differences in dynamics between the α-helical and β-sheet residues. Remarkably, the dipolar order parameters derived from the solid-state NMR measurements and the corresponding solution NMR generalized order parameters display similar qualitative trends as a function of the residue number. The comparison of the solid-state dynamics parameters to the crystallographic B-factors has identified the contribution of static disorder to the B-factors. The combination of longitudinal relaxation, dipolar order parameter, and CSA line shape analyses employed in this study provides snapshots of dynamics and a new

  3. NMR shielding calculations across the periodic table: diamagnetic uranium compounds. 2. Ligand and metal NMR.

    PubMed

    Schreckenbach, Georg

    2002-12-16

    In this and a previous article (J. Phys. Chem. A 2000, 104, 8244), the range of application for relativistic density functional theory (DFT) is extended to the calculation of nuclear magnetic resonance (NMR) shieldings and chemical shifts in diamagnetic actinide compounds. Two relativistic DFT methods are used, ZORA ("zeroth-order regular approximation") and the quasirelativistic (QR) method. In the given second paper, NMR shieldings and chemical shifts are calculated and discussed for a wide range of compounds. The molecules studied comprise uranyl complexes, [UO(2)L(n)](+/-)(q); UF(6); inorganic UF(6) derivatives, UF(6-n)Cl(n), n = 0-6; and organometallic UF(6) derivatives, UF(6-n)(OCH(3))(n), n = 0-5. Uranyl complexes include [UO(2)F(4)](2-), [UO(2)Cl(4)](2-), [UO(2)(OH)(4)](2-), [UO(2)(CO(3))(3)](4-), and [UO(2)(H(2)O)(5)](2+). For the ligand NMR, moderate (e.g., (19)F NMR chemical shifts in UF(6-n)Cl(n)) to excellent agreement [e.g., (19)F chemical shift tensor in UF(6) or (1)H NMR in UF(6-n)(OCH(3))(n)] has been found between theory and experiment. The methods have been used to calculate the experimentally unknown (235)U NMR chemical shifts. A large chemical shift range of at least 21,000 ppm has been predicted for the (235)U nucleus. ZORA spin-orbit appears to be the most accurate method for predicting actinide metal chemical shifts. Trends in the (235)U NMR chemical shifts of UF(6-n)L(n) molecules are analyzed and explained in terms of the calculated electronic structure. It is argued that the energy separation and interaction between occupied and virtual orbitals with f-character are the determining factors.

  4. Nuclear spin noise in NMR revisited

    SciTech Connect

    Ferrand, Guillaume; Luong, Michel

    2015-09-07

    The theoretical shapes of nuclear spin-noise spectra in NMR are derived by considering a receiver circuit with finite preamplifier input impedance and a transmission line between the preamplifier and the probe. Using this model, it becomes possible to reproduce all observed experimental features: variation of the NMR resonance linewidth as a function of the transmission line phase, nuclear spin-noise signals appearing as a “bump” or as a “dip” superimposed on the average electronic noise level even for a spin system and probe at the same temperature, pure in-phase Lorentzian spin-noise signals exhibiting non-vanishing frequency shifts. Extensive comparisons to experimental measurements validate the model predictions, and define the conditions for obtaining pure in-phase Lorentzian-shape nuclear spin noise with a vanishing frequency shift, in other words, the conditions for simultaneously obtaining the spin-noise and frequency-shift tuning optima.

  5. High Resolution non-Markovianity in NMR

    PubMed Central

    Bernardes, Nadja K.; Peterson, John P. S.; Sarthour, Roberto S.; Souza, Alexandre M.; Monken, C. H.; Roditi, Itzhak; Oliveira, Ivan S.; Santos, Marcelo F.

    2016-01-01

    Memoryless time evolutions are ubiquitous in nature but often correspond to a resolution-induced approximation, i.e. there are correlations in time whose effects are undetectable. Recent advances in the dynamical control of small quantum systems provide the ideal scenario to probe some of these effects. Here we experimentally demonstrate the precise induction of memory effects on the evolution of a quantum coin (qubit) by correlations engineered in its environment. In particular, we design a collisional model in Nuclear Magnetic Resonance (NMR) and precisely control the strength of the effects by changing the degree of correlation in the environment and its time of interaction with the qubit. We also show how these effects can be hidden by the limited resolution of the measurements performed on the qubit. The experiment reinforces NMR as a test bed for the study of open quantum systems and the simulation of their classical counterparts. PMID:27669652

  6. Protein Dynamics from NMR and Computer Simulation

    NASA Astrophysics Data System (ADS)

    Wu, Qiong; Kravchenko, Olga; Kemple, Marvin; Likic, Vladimir; Klimtchuk, Elena; Prendergast, Franklyn

    2002-03-01

    Proteins exhibit internal motions from the millisecond to sub-nanosecond time scale. The challenge is to relate these internal motions to biological function. A strategy to address this aim is to apply a combination of several techniques including high-resolution NMR, computer simulation of molecular dynamics (MD), molecular graphics, and finally molecular biology, the latter to generate appropriate samples. Two difficulties that arise are: (1) the time scale which is most directly biologically relevant (ms to μs) is not readily accessible by these techniques and (2) the techniques focus on local and not collective motions. We will outline methods using ^13C-NMR to help alleviate the second problem, as applied to intestinal fatty acid binding protein, a relatively small intracellular protein believed to be involved in fatty acid transport and metabolism. This work is supported in part by PHS Grant GM34847 (FGP) and by a fellowship from the American Heart Association (QW).

  7. (129)Xe NMR of Mesoporous Silicas

    SciTech Connect

    Anderson, M.T.; Asink, R.A.; Kneller, J.M.; Pietrass, T.

    1999-04-23

    The porosities of three mesoporous silica materials were characterized with {sup 129}Xe NMR spectroscopy. The materials were synthesized by a sol-gel process with r = 0, 25, and 70% methanol by weight in an aqueous cetyltrimethylammonium bromide solution. Temperature dependent chemical shifts and spin lattice relaxation times reveal that xenon does not penetrate the pores of the largely disordered (r= 70%) silica. For both r = 0 and 25%, temperature dependent resonances corresponding to physisorbed xenon were observed. An additional resonance for the r = 25% sample was attributed to xenon between the disordered cylindrical pores. 2D NMR exchange experiments corroborate the spin lattice relaxation data which show that xenon is in rapid exchange between the adsorbed and the gas phase.

  8. High Resolution non-Markovianity in NMR

    NASA Astrophysics Data System (ADS)

    Bernardes, Nadja K.; Peterson, John P. S.; Sarthour, Roberto S.; Souza, Alexandre M.; Monken, C. H.; Roditi, Itzhak; Oliveira, Ivan S.; Santos, Marcelo F.

    2016-09-01

    Memoryless time evolutions are ubiquitous in nature but often correspond to a resolution-induced approximation, i.e. there are correlations in time whose effects are undetectable. Recent advances in the dynamical control of small quantum systems provide the ideal scenario to probe some of these effects. Here we experimentally demonstrate the precise induction of memory effects on the evolution of a quantum coin (qubit) by correlations engineered in its environment. In particular, we design a collisional model in Nuclear Magnetic Resonance (NMR) and precisely control the strength of the effects by changing the degree of correlation in the environment and its time of interaction with the qubit. We also show how these effects can be hidden by the limited resolution of the measurements performed on the qubit. The experiment reinforces NMR as a test bed for the study of open quantum systems and the simulation of their classical counterparts.

  9. NMR studies of nucleic acid dynamics

    NASA Astrophysics Data System (ADS)

    Al-Hashimi, Hashim M.

    2013-12-01

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

  10. The ambient hydration of the aluminophosphate JDF-2 to AlPO-53(A): insights from NMR crystallography.

    PubMed

    Dawson, Daniel M; Walton, Richard I; Wimperis, Stephen; Ashbrook, Sharon E

    2017-03-01

    The aluminophosphate (AlPO) JDF-2 is prepared hydrothermally with methylammonium hydroxide (MAH(+)·HO(-), MAH(+) = CH3NH3(+)), giving rise to a microporous AEN-type framework with occluded MAH(+) cations and extra-framework (Al-bound) HO(-) anions. Despite the presence of these species within its pores, JDF-2 can hydrate upon exposure to atmospheric moisture to give AlPO-53(A), an isostructural material whose crystal structure contains one molecule of H2O per formula unit. This hydration can be reversed by mild heating (such as the frictional heating from magic angle spinning). Previous work has shown good agreement between the NMR parameters obtained experimentally and those calculated from the (optimized) crystal structure of JDF-2. However, several discrepancies are apparent between the experimental NMR parameters for AlPO-53(A) and those calculated from the (optimized) crystal structure (e.g. four (13)C resonances are observed, rather than the expected two). The unexpected resonances appear and disappear reversibly with the respective addition and removal of H2O, so clearly arise from AlPO-53(A). We investigate the ambient hydration of JDF-2 using quantitative (31)P MAS NMR to follow the transformation over the course of ∼3 months. The structures of JDF-2 and AlPO-53(A) are also investigated using a combination of multinuclear solid-state NMR spectroscopy to characterize the samples, and first-principles density functional theory (DFT) calculations to evaluate a range of possible structural models in terms of calculated NMR parameters and energetics. The published structure of JDF-2 is shown to be a good representation of the dehydrated material, but modification of the published structure of AlPO-53(A) is required to provide calculated NMR parameters that are in better agreement with experiment. This modification includes reorientation of all the MAH(+) cations and partial occupancy of the H2O sites.

  11. Extending the scope of NMR spectroscopy with microcoil probes.

    PubMed

    Schroeder, Frank C; Gronquist, Matthew

    2006-11-06

    Capillary NMR (CapNMR) spectroscopy has emerged as a major breakthrough for increasing the mass-sensitivity of NMR spectroscopic analysis and enabling the combination of NMR spectroscopy with other analytical techniques. Not only is the acquisition of high-sensitivity spectra getting easier but the quality of CapNMR spectra obtained in many small-molecule applications exceeds what can be accomplished with conventional designs. This Minireview discusses current CapNMR technology and its applications for the characterization of mass-limited, small-molecule and protein samples, the rapid screening of small-molecule or protein libraries, as well as hyphenated techniques that combine CapNMR with other analytical methods.

  12. Multiecho scheme advances surface NMR for aquifer characterization

    NASA Astrophysics Data System (ADS)

    Grunewald, Elliot; Walsh, David

    2013-12-01

    nuclear magnetic resonance (NMR) is increasingly used as a method to noninvasively characterize aquifers. This technology follows a successful history of NMR logging, applied over decades to estimate hydrocarbon reservoir properties. In contrast to logging, however, surface methods have utilized relatively simple acquisition sequences, from which pore-scale properties may not be reliably and efficiently estimated. We demonstrate for the first time the capability of sophisticated multiecho measurements to rapidly record a surface NMR response that more directly reflects aquifer characteristics. Specifically, we develop an adaptation of the multipulse Carr-Purcell-Meiboom-Gill (CPMG) sequence, widely used in logging, to measure the T2 relaxation response in a single scan. We validate this approach in a field surface NMR data set and by direct comparison with an NMR log. Adoption of the CPMG marked a landmark advancement in the history of logging NMR; we have now realized this same advancement in the surface NMR method.

  13. Improved Characterization of Healthy and Malignant Tissue by NMR Line-Shape Relaxation Correlations

    PubMed Central

    Peemoeller, H.; Shenoy, R.K.; Pintar, M.M.; Kydon, D.W.; Inch, W.R.

    1982-01-01

    We performed a relaxation-line-shape correlation NMR experiment on muscle, liver, kidney, and spleen tissues of healthy mice and of mouse tumor tissue. In each tissue studied, five spin groups were resolved and characterized by their relaxation parameters. We report a previously uncharacterized semi-solid spin group and discuss briefly the value of this method for the identification of malignant tissues. PMID:7104438

  14. Hypoxia-sensitive NMR contrast agents

    SciTech Connect

    Swartz, H.M.; Chen, K.; Pals, M.; Sentjurc, M.; Morse, P.D. 2d.

    1986-02-01

    The rate of reduction of nitroxides is shown to be more rapid in hypoxic cells. The rate of reduction and the effect of hypoxia on the reduction rate vary for different nitroxides. These findings indicate that it may be feasible to develop in vivo NMR contrast agents that selectively will indicate areas of hypoxia and thereby aid in the detection of disease processes such as neoplasia, ischemia, and inflammation.

  15. NMR in Copper-Oxide Metals

    SciTech Connect

    Varma, C.M.

    1996-10-01

    The anomalous part of the NMR relaxation rate of copper nuclei in the normal state of copper-oxide metals is calculated using the orbital magnetic parts of the fluctuations derived in a recent theory to explain the long wavelength transport anomalies. Oxygen and yttrium reside on lattice sites at which the anomalous contribution is absent at all hole densities. The frequency, momentum dependence, and the form factor of the fluctuations is predicted. {copyright} {ital 1996 The American Physical Society.}

  16. NMR Characterizations of Properties of Heterogeneous Media

    SciTech Connect

    Watson, A. Ted; Phan, Jack; Uh, Jinsoo; Michalak, Rudi; Xue, Song

    2003-01-28

    The overall goal of this project was to develop reliable methods for resolving macroscopic properties important for describing the flow of one or more fluid phases in reservoirs from formation measurements. Completed the facilities to house our new NMR imager, the equipment has been delivered and installed. New experimental designs will provide for more reliable estimation of permeability distributions were evaluated. Designed and built a new core holder to incorporate one of the new experimental designs.

  17. NMR Studies of Dynamic Biomolecular Conformational Ensembles

    PubMed Central

    Torchia, Dennis A.

    2015-01-01

    Multidimensional heteronuclear NMR approaches can provide nearly complete sequential signal assignments of isotopically enriched biomolecules. The availability of assignments together with measurements of spin relaxation rates, residual spin interactions, J-couplings and chemical shifts provides information at atomic resolution about internal dynamics on timescales ranging from ps to ms, both in solution and in the solid state. However, due to the complexity of biomolecules, it is not possible to extract a unique atomic-resolution description of biomolecular motions even from extensive NMR data when many conformations are sampled on multiple timescales. For this reason, powerful computational approaches are increasingly applied to large NMR data sets to elucidate conformational ensembles sampled by biomolecules. In the past decade, considerable attention has been directed at an important class of biomolecules that function by binding to a wide variety of target molecules. Questions of current interest are: “Does the free biomolecule sample a conformational ensemble that encompasses the conformations found when it binds to various targets; and if so, on what time scale is the ensemble sampled?” This article reviews recent efforts to answer these questions, with a focus on comparing ensembles obtained for the same biomolecules by different investigators. A detailed comparison of results obtained is provided for three biomolecules: ubiquitin, calmodulin and the HIV-1 trans-activation response RNA. PMID:25669739

  18. BetaNMR Experiments on Liquid Samples

    NASA Astrophysics Data System (ADS)

    Gottberg, A.; Stachura, M.; Hemmingsen, L.; Macfarlane, W. A.; Bio-Beta-Nmr Collaboration; Collaps Collaboration

    2016-09-01

    In 2012 betaNMR spectroscopy was successfully applied on liquid samples; an achievement which opens new opportunities in the fields of chemistry and biochemistry. This project was motivated by the need for finding a new experimental approach to directly study biologically highly relevant metal ions, such as Mg(II), Cu(I), Ca(II), and Zn(II), which are silent in most spectroscopic techniques. The resonance spectrum recorded for Mg-31 implanted into an ionic liquid sample showed two resonances which originate from Mg ions occupying two different coordination geometries, illustrating that this technique can discriminate between different structures. This proof-of-principle result lays the foundation for studies of these metal ions at low concentrations and in environments of biological relevance where other methods are silent. The prototype chamber for bio-betaNMR allows for experiments not only on different samples such as: liquids, gels and solids, but also operates at different vacuum environments. In order to exploit the potential of betaNMR on liquid samples, tests with polarized beams of Mg-29 and Mg-31 have recently been performed at the ISAC facility at TRIUMF.

  19. NMR quantum computation with optically polarized molecules

    NASA Astrophysics Data System (ADS)

    Verhulst, Anne; Yannoni, Constantino; Sherwood, Mark; Pomerantz, Drew; Vandersypen, Lieven; Chuang, Isaac

    2000-03-01

    Current methods for bulk NMR quantum computation rely on nuclear spin polarization present at high temperature equilibrium. This presents a challenging obstacle as the probability to find a spin in a specific state decreases exponentially in the number of spins used as qubits, causing a corresponding decrease in the signal to noise ratio of the desired NMR signal. One way to address this problem is to provide an artificial source of high polarization, such as optically pumped ^129Xe. For comparison, thermal equilibrium polarizations are only about 10-3% for ^1H in a typical NMR experiment at room temperature and in a 10 Tesla magnetic field, but with ^129Xe polarizations as high as 18% have been achieved [Happer et. al., Chem.Phys.Lett., 284, p.87-92, Feb 1998]. Using this technique, we prepare hyperpolarized liquid Xe and use it as a solvent for chloroform molecules (CHCl_3). Cross polarization (SPINOE) between ^129Xe and ^1H results in measured enhancements of the proton signal of over 300%, and evidence of transfer to ^13C. These results provide hope for the scalability of quantum computation.

  20. In-cell NMR: a topical review

    PubMed Central

    Banci, Lucia

    2017-01-01

    Classical structural biology approaches allow structural characterization of biological macromolecules in vitro, far from their physiological context. Nowadays, thanks to the wealth of structural data available and to technological and methodological advances, the interest of the research community is gradually shifting from pure structural determination towards the study of functional aspects of biomolecules. Therefore, a cellular structural approach is ideally needed to characterize biological molecules, such as proteins, in their native cellular environment and the functional processes that they are involved in. In-cell NMR is a new application of high-resolution nuclear magnetic resonance spectroscopy that allows structural and dynamical features of proteins and other macromolecules to be analyzed directly in living cells. Owing to its challenging nature, this methodology has shown slow, but steady, development over the past 15 years. To date, several in-cell NMR approaches have been successfully applied to both bacterial and eukaryotic cells, including several human cell lines, and important structural and functional aspects have been elucidated. In this topical review, the major advances of in-cell NMR are summarized, with a special focus on recent developments in eukaryotic and mammalian cells. PMID:28250949

  1. Earth's field NMR; a surface moisture detector?

    NASA Astrophysics Data System (ADS)

    Fukushima, Eiichi; Altobelli, Stephen; McDowell, Andrew; Zhang, Tongsheng

    2012-10-01

    Earth's field NMR (EFNMR), being free of magnets, would be an ideal teaching medium as well as a mobile NMR technique except for its weak S/N. The common EFNMR apparatus uses a powerful prepolarization field to enhance the spin magnetization before the experiment. We introduce a coil design geared to larger but manageable samples with sufficient sensitivity without prepolarization to move EFNMR closer to routine use and to provide an inexpensive teaching tool. Our coil consists of parallel wires spread out on a plywood to form a current sheet with the current return wires separated so they will not influence the main part of the coil assembly. The sensitive region is a relatively thin region parallel to the coil and close to it. A single turn of the coil is wound to be topologically equivalent to a figure-8. The two crossing segments in the center of a figure-8 form two of the parallel wires of the flat coil. Thus, a two-turn figure-8 has four crossing wires so its topologically equivalent coil will have four parallel wires with currents in phase. Together with the excellent sensitivity, this coil offers outstanding interference rejection because of the figure-8 geometry. An example of such a coil has 328 parallel wires covering a ˜1 meter square plywood which yields a good NMR signal from 26 liters of water spread out roughly over the area of the coil in less than one minute in a nearby park.

  2. NMR studies of protein structure and dynamics

    NASA Astrophysics Data System (ADS)

    Kay, Lewis E.

    2011-12-01

    Recent advances in solution NMR spectroscopy have significantly extended the spectrum of problems that can now be addressed with this technology. In particular, studies of proteins with molecular weights on the order of 100 kDa are now possible at a level of detail that was previously reserved for much smaller systems. An example of the sort of information that is now accessible is provided in a study of malate synthase G, a 723 residue enzyme that has been a focal point of research efforts in my laboratory. Details of the labeling schemes that have been employed and optimal experiments for extraction of structural and dynamics information on this protein are described. NMR studies of protein dynamics, in principle, give insight into the relation between motion and function. A description of deuterium-based spin relaxation methods for the investigation of side chain dynamics is provided. Examples where millisecond (ms) time scale dynamics play an important role and where relaxation dispersion NMR spectroscopy has been particularly informative, including applications involving the membrane enzyme PagP and mutants of the Fyn SH3 domain that fold on a ms time scale, are presented.

  3. Lithological controls on gas hydrate saturation: Insights from signal classification of NMR downhole data

    NASA Astrophysics Data System (ADS)

    Bauer, Klaus; Kulenkampff, Johannes; Henninges, Jan; Spangenberg, Erik

    2016-04-01

    Nuclear magnetic resonance (NMR) downhole data are analyzed with a new strategy to study gas hydrate-bearing sediments in the Mackenzie Delta (NW Canada). NMR logging is a powerful tool to study geological reservoir formations. The measurements are based on interactions between the magnetic moments of protons in geological formation water and an external magnetic field. Inversion of the measured raw data provides so-called transverse relaxation time (T2) distribution curves or spectra. Different parts of the T2 curve are related with distinct pore radii and corresponding fluid components. A common practice in the analysis of T2 distribution curves is to extract single-valued parameters such as apparent total porosity. Moreover, the derived total NMR apparent porosity and the gamma-gamma density log apparent porosity can be combined to estimate gas hydrate saturation in hydrate-bearing sediments. To avoid potential loss of information, in our new approach we analyze the entire T2 distribution curves as quasi-continuous signals to characterize the rock formation. The approach is applied to NMR data measured in gas hydrate research well Mallik 5L-38. We use self-organizing maps, a neural network clustering technique, to subdivide the data set of NMR T2 distribution curves into classes with a similar and distinctive signal shape. The method includes (1) preparation of data vectors, (2) unsupervised learning, (3) cluster definition, and (4) classification and depth mapping of all NMR signals. Each signal class thus represents a specific pore size distribution which can be interpreted in terms of distinct lithologies and reservoir types. A key step in the interpretation strategy is to reconcile the NMR classes with other log data not considered in the clustering analysis, such as gamma ray, photo-electric factor, hydrate saturation, and other logs. Our results defined six main lithologies within the target zone. Gas hydrate layers were recognized by their low signal

  4. Crystallinity and compositional changes in carbonated apatites: Evidence from {sup 31}P solid-state NMR, Raman, and AFM analysis

    SciTech Connect

    McElderry, John-David P.; Zhu, Peizhi; Mroue, Kamal H.; Xu, Jiadi; Pavan, Barbara; Fang, Ming; Zhao, Guisheng; McNerny, Erin; Kohn, David H.; Franceschi, Renny T.; Holl, Mark M.Banaszak; Tecklenburg, Mary M.J.; Ramamoorthy, Ayyalusamy; Morris, Michael D.

    2013-10-15

    Solid-state (magic-angle spinning) NMR spectroscopy is a useful tool for obtaining structural information on bone organic and mineral components and synthetic model minerals at the atomic-level. Raman and {sup 31}P NMR spectral parameters were investigated in a series of synthetic B-type carbonated apatites (CAps). Inverse {sup 31}P NMR linewidth and inverse Raman PO{sub 4}{sup 3−}ν{sub 1} bandwidth were both correlated with powder XRD c-axis crystallinity over the 0.3–10.3 wt% CO{sub 3}{sup 2−} range investigated. Comparison with bone powder crystallinities showed agreement with values predicted by NMR and Raman calibration curves. Carbonate content was divided into two domains by the {sup 31}P NMR chemical shift frequency and the Raman phosphate ν{sub 1} band position. These parameters remain stable except for an abrupt transition at 6.5 wt% carbonate, a composition which corresponds to an average of one carbonate per unit cell. This near-binary distribution of spectroscopic properties was also found in AFM-measured particle sizes and Ca/P molar ratios by elemental analysis. We propose that this transition differentiates between two charge-balancing ion-loss mechanisms as measured by Ca/P ratios. These results define a criterion for spectroscopic characterization of B-type carbonate substitution in apatitic minerals. - Graphical abstract: Carbonated apatite shows an abrupt change in spectral (NMR, Raman) and morphological (AFM) properties at a composition of about one carbonate substitution per unit cell. Display Omitted - Highlights: • Crystallinity (XRD), particle size (AFM) of carbonated apatites and bone mineral. • Linear relationships among crystallinity, {sup 31}P NMR and Raman inverse bandwidths. • Low and high carbonated apatites use different charge-balancing ion-loss mechanism.

  5. Guiding automated NMR structure determination using a global optimization metric, the NMR DP score

    PubMed Central

    Huang, Yuanpeng Janet; Mao, Binchen; Xu, Fei; Montelione, Gaetano

    2016-01-01

    ASDP is an automated NMR NOE assignment program. It uses a distinct bottom-up topology-constrained network anchoring approach for NOE interpretation, with 2D, 3D and/or 4D NOESY peak lists and resonance assignments as input, and generates unambiguous NOE constraints for iterative structure calculations. ASDP is designed to function interactively with various structure determination programs that use distance restraints to generate molecular models. In the CASD-NMR project, ASDP was tested and further developed using blinded NMR data, including resonance assignments, either raw or manually-curated (refined) NOESY peak list data, and in some cases 15N-1H residual dipolar coupling data. In these blinded tests, in which the reference structure was not available until after structures were generated, the fully-automated ASDP program performed very well on all targets using both the raw and refined NOESY peak list data. Improvements of ASDP relative to its predecessor program for automated NOESY peak assignments, AutoStructure, were driven by challenges provided by these CASD-NMR data. These algorithmic improvements include 1) using a global metric of structural accuracy, the Discriminating Power (DP) score, for guiding model selection during the iterative NOE interpretation process, and 2) identifying incorrect NOESY cross peak assignments caused by errors in the NMR resonance assignment list. These improvements provide a more robust automated NOESY analysis program, ASDP, with the unique capability of being utilized with alternative structure generation and refinement programs including CYANA, CNS, and/or Rosetta. PMID:26081575

  6. CcpNmr AnalysisAssign: a flexible platform for integrated NMR analysis.

    PubMed

    Skinner, Simon P; Fogh, Rasmus H; Boucher, Wayne; Ragan, Timothy J; Mureddu, Luca G; Vuister, Geerten W

    2016-10-01

    NMR spectroscopy is an indispensably powerful technique for the analysis of biomolecules under ambient conditions, both for structural- and functional studies. However, in practice the complexity of the technique has often frustrated its application by non-specialists. In this paper, we present CcpNmr version-3, the latest software release from the Collaborative Computational Project for NMR, for all aspects of NMR data analysis, including liquid- and solid-state NMR data. This software has been designed to be simple, functional and flexible, and aims to ensure that routine tasks can be performed in a straightforward manner. We have designed the software according to modern software engineering principles and leveraged the capabilities of modern graphics libraries to simplify a variety of data analysis tasks. We describe the process of backbone assignment as an example of the flexibility and simplicity of implementing workflows, as well as the toolkit used to create the necessary graphics for this workflow. The package can be downloaded from www.ccpn.ac.uk/v3-software/downloads and is freely availabl