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Sample records for 17o nmr spectra

  1. 17O NMR and Raman spectra of water with different calcium salts

    NASA Astrophysics Data System (ADS)

    Yan, Ying; Ou, Xiao-xia; Zhang, Hui-ping

    2014-09-01

    17O NMR and Raman spectra of water with different calcium salts have been measured. Different water samples were prepared by adding nano-materials, calcium gluconate, calcium citrate and calcium chloride into distilled water. Both 17O NMR and Raman spectra of different water samples were recorded. The effects of temperature and time on 17O NMR line-width of different water samples were analyzed as well. The experimental results showed that Raman spectra of water with these four calcium salts were almost the same as those for distilled water when the temperature increased to 40 °C. The 17O NMR line-width of distilled water decreased from 76.8 Hz to 46.9 Hz and 65.8 Hz after nano-materials and calcium chloride were added, respectively. Besides, the 17O NMR line-width of distilled water increased from 76.8 Hz to 131.6 Hz after calcium citrate was added, while the 17O NMR line-width of distilled water increased from 76.8 Hz to 77.2 Hz after calcium gluconate was added. The 17O NMR line-width of water with calcium chloride increased while the other three water samples were nearly stable as the temperature increased from 30 °C to 85 °C. The 17O NMR line-width of water with nano-materials kept steady while the 17O NMR line-width of the other three water samples all increased in 42 days.

  2. 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.

  3. Natural-abundance 17O NMR of monosaccharides

    NASA Astrophysics Data System (ADS)

    Gerothanassis, Ioannis P.; Lauterwein, Jürgen; Sheppard, Norman

    Natural-abundance "high-resolution" 17O NMR spectra of D-glucose, D-mannose, D-galactose, and some methoxy derivatives of D-glucose were recorded in aqueous solution. The sensitivity and spectral resolution was improved by optimizing the accumulation and manipulation of data. The water solvent peak was suppressed through use of 17O-depleted water or displaced by addition of paramagnetic shift reagents. With Dy 3+ the 17O NMR spectrum of D-glucose remained unaltered; however, the water peak was shifted outside the carbohydrate spectral region. The 17O NMR resonances were assigned from earlier data for some specifically 17O-enriched monosaccharide derivatives. The anomeric hydroxyl resonances could also be located because of their exchange with the 17O-depleted water. Although the chemical shifts of the monosacharides generally parallel the sequence of chemical shifts for simple primary and secondary alcohols and substituted ethers, several exceptions were found and discussed in terms of steric and electrostatic repulsive forces between oxygens.

  4. (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. PMID:27454747

  5. (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.

  6. {sup 17}O NMR investigation of oxidative degradation in polymers under gamma-irradiation

    SciTech Connect

    ALAM,TODD M.; CELINA,MATHIAS C.; ASSINK,ROGER A.; CLOUGH,ROGER LEE; GILLEN,KENNETH T.

    2000-03-08

    The {gamma}-irradiated-oxidation of pentacontane (C{sub 50}H{sub 102}) and the polymer polyisoprene was investigated as a function of oxidation level using {sup 17}O nuclear magnetic resonance (NMR) spectroscopy. It is demonstrated that by using {sup 17}O labeled O{sub 2} gas during the {gamma}-irradiation process, details about the oxidative degradation mechanisms can be directly obtained from the analysis of the {sup 17}O NMR spectra. Production of carboxylic acids is the primary oxygen-containing functionality during the oxidation of pentacontane, while ethers and alcohols are the dominant oxidation product observed for polyisoprene. The formation of ester species during the oxidation process is very minor for both materials, with water also being produced in significant amounts during the radiolytic oxidation of polyisoprene. The ability to focus on the oxidative component of the degradation process using {sup 17}O NMR spectroscopy demonstrates the selectivity of this technique over more conventional approaches.

  7. 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

  8. Understanding the symmetric line shape in the 17O MAS spectra for hexagonal ice

    NASA Astrophysics Data System (ADS)

    Yamada, Kazuhiko; Oki, Shinobu; Deguchi, Kenzo; Shimizu, Tadashi

    2016-06-01

    Solid-state 17O Magic-Angle Spinning (MAS) nuclear magnetic resonance (NMR) spectra of 17O-enriched hexagonal ice, [17O]-Ih, between 173 and 253 K were presented. Marked changes in the line shape were clearly observed, indicating water molecular reorientation in the crystal structure. At 173 K, molecular motions were considered to be frozen and analysis of the 1D MAS spectrum yielded the following parameters: quadrupole coupling constant (CQ) = 6.6 ± 0.2 MHz and asymmetry parameter (ηQ) = 0.95 ± 0.05. At 232 K and above, contrary to the conventional explanation, pseudo-symmetric line shapes appeared in the 17O MAS NMR spectra arising from the contribution of second-order quadrupole interactions. As a chemical exchange model to describe these isotropic 17O MAS NMR spectra, a modified Ratcliffe model, which consider the effects of proton disorder, was proposed, and the resulting theoretical spectra could well reproduce the experimental spectra.

  9. 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.

  10. Dynamic NMR of low-sensitivity fast-relaxing nuclei: (17)O NMR and DFT study of acetoxysilanes.

    PubMed

    Fusaro, Luca; Mameli, Giulia; Mocci, Francesca; Luhmer, Michel; Cerioni, Giovanni

    2012-02-01

    (17)O NMR is not routinely used for structure characterization, and kinetic studies of fluxional organic compounds are seldom undertaken because poor sensitivity and fast quadrupole relaxation are frequently regarded as intractable issues. This work shows how, nowadays, quantitative (17)O dynamic NMR studies on small organic molecules are feasible without enrichment being needed. It reports on acetoxysilanes, a class of fluxional compounds whose structure and dynamics were to be clarified. Natural abundance (17)O NMR spectra were recorded over a wide range of temperatures using standard instrumentation. The analysis relies on simple linewidth measurements and directly provides the activation parameters. The activation enthalpy is found to decrease with increasing number of acetoxy groups bound to silicon. Density functional theory calculations properly predict this trend and show that a single oxygen atom of the acetoxy group is bound to silicon, excluding chelation as binding mode, and that the dynamic process involves the shift of the silicon atom between the two oxygen atoms of the acetoxy group.

  11. 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.

  12. 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

  13. Natural abundant (17) O NMR in a 1.5-T Halbach magnet.

    PubMed

    Sørensen, Morten K; Bakharev, Oleg N; Jensen, Ole; Nielsen, Niels Chr

    2016-06-01

    We present mobile, low-field (17) O NMR as a means for monitoring oxygen in liquids. Whereas oxygen is one of the most important elements, oxygen NMR is limited by a poor sensitivity related to low natural abundance and gyro-magnetic ratio of the NMR active (17) O isotope. Here, we demonstrate (17) O NMR detection at a Larmor frequency of 8.74 MHz in a 1.5-T Halbach neodymium magnet with a home-built digital NMR instrument suitable for large-scale production and in-line monitoring applications. The proposed (17) O NMR sensor may be applied for direct, noninvasive measurements of water content in, for example, oil, manure, or food in automated quality or process control. Copyright © 2015 John Wiley & Sons, Ltd. PMID:25641664

  14. (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.

  15. (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. PMID:27461881

  16. Characterizing Oxygen Local Environments in Paramagnetic Battery Materials via (17)O NMR and DFT Calculations.

    PubMed

    Seymour, Ieuan D; Middlemiss, Derek S; Halat, David M; Trease, Nicole M; Pell, Andrew J; Grey, Clare P

    2016-08-01

    Experimental techniques that probe the local environment around O in paramagnetic Li-ion cathode materials are essential in order to understand the complex phase transformations and O redox processes that can occur during electrochemical delithiation. While Li NMR is a well-established technique for studying the local environment of Li ions in paramagnetic battery materials, the use of (17)O NMR in the same materials has not yet been reported. In this work, we present a combined (17)O NMR and hybrid density functional theory study of the local O environments in Li2MnO3, a model compound for layered Li-ion batteries. After a simple (17)O enrichment procedure, we observed five resonances with large (17)O shifts ascribed to the Fermi contact interaction with directly bonded Mn(4+) ions. The five peaks were separated into two groups with shifts at 1600 to 1950 ppm and 2100 to 2450 ppm, which, with the aid of first-principles calculations, were assigned to the (17)O shifts of environments similar to the 4i and 8j sites in pristine Li2MnO3, respectively. The multiple O environments in each region were ascribed to the presence of stacking faults within the Li2MnO3 structure. From the ratio of the intensities of the different (17)O environments, the percentage of stacking faults was found to be ca. 10%. The methodology for studying (17)O shifts in paramagnetic solids described in this work will be useful for studying the local environments of O in a range of technologically interesting transition metal oxides. PMID:27404908

  17. 17O and 29Si NMR parameters of MgSiO3 phases from high-resolution solid-state NMR spectroscopy and first-principles calculations.

    PubMed

    Ashbrook, Sharon E; Berry, Andrew J; Frost, Daniel J; Gregorovic, Alan; Pickard, Chris J; Readman, Jennifer E; Wimperis, Stephen

    2007-10-31

    The 29Si and 17O NMR parameters of six polymorphs of MgSiO3 were determined through a combination of high-resolution solid-state NMR and first-principles gauge including projector augmented wave (GIPAW) formalism calculations using periodic boundary conditions. MgSiO3 is an important component of the Earth's mantle that undergoes structural changes as a function of pressure and temperature. For the lower pressure polymorphs (ortho-, clino-, and protoenstatite), all oxygen species in the 17O high-resolution triple-quantum magic angle spinning (MAS) NMR spectra were resolved and assigned. These assignments differ from those tentatively suggested in previous work on the basis of empirical experimental correlations. The higher pressure polymorphs of MgSiO3 (majorite, akimotoite, and perovskite) are stabilized at pressures corresponding to the Earth's transition zone and lower mantle, with perovskite being the major constituent at depths >660 km. We present the first 17O NMR data for these materials and confirm previous 29Si work in the literature. The use of high-resolution multiple-quantum MAS (MQMAS) and satellite-transition MAS (STMAS) experiments allows us to resolve distinct oxygen species, and full assignments are suggested. The six polymorphs exhibit a wide variety of structure types, providing an ideal opportunity to consider the variation of NMR parameters (both shielding and quadrupolar) with local structure, including changes in coordination number, local geometry (bond distances and angles), and bonding. For example, we find that, although there is a general correlation of increasing 17O chemical shift with increasing Si-O bond length, the shift observed also depends upon the exact coordination environment.

  18. Predicting (17)O NMR chemical shifts of polyoxometalates using density functional theory.

    PubMed

    Sharma, Rupali; Zhang, Jie; Ohlin, C André

    2016-03-21

    We have investigated the computation of (17)O NMR chemical shifts of a wide range of polyoxometalates using density functional theory. The effects of basis sets and exchange-correlation functionals are explored, and whereas pure DFT functionals generally predict the chemical shifts of terminal oxygen sites quite well, hybrid functionals are required for the prediction of accurate chemical shifts in conjunction with linear regression. By using PBE0/def2-tzvp//PBE0/cc-pvtz(H-Ar), lanl2dz(K-) we have computed the chemical shifts of 37 polyoxometalates, corresponding to 209 (17)O NMR signals. We also show that at this level of theory the protonation-induced pH dependence of the chemical shift of the triprotic hexaniobate Lindqvist anion, [HxNb6O19]((8-x)), can be reproduced, which suggests that hypotheses regarding loci of protonation can be confidently tested. PMID:26925832

  19. 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. PMID:26670708

  20. 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.

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

    DOE PAGES

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

    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

  2. Onset of Superconductivity in YBCO in Very High Fields from ^17O and ^63Cu NMR

    NASA Astrophysics Data System (ADS)

    Halperin, William

    2000-03-01

    We have used NMR to study the onset of superconductivity in near optimally doped YBCO in fields from 1 to 27 T. We have compared Knight shift(^17O), spin-spin relaxation measurements(^17O), and spin lattice relaxation measurements (^63Cu and ^17O). The measurements have been performed as a function of temperature above and below the transition region. The Knight shift can be measured with considerable precision directly giving the Pauli spin susceptibility. We show that the onset of superconductivity in a magnetic field is really a crossover region from normal state behavior to a vortex liquid for which we determine a H-T phase diagram up to high field. The relaxation measurements show clear evidence for the opening of a pseudo gap near 100 K in the transition region. The different NMR experiments are sensitive to the susceptibility dependence on wave vector from different regions of the Brillouin zone indicating possible origins of such a gap including superconducting fluctuations or a gap in the spin excitation spectrum. Magnetic field dependence of the data allows discrimination. Intercomparison between samples near optimal doping as well as the work from other laboratories will be made. This work was performed in collaboration with V. F. Mitović, H. N. Bachman, E. E. Sigmund, M. Eschrig, J. A. Sauls, A. P. Reyes, P. Kuhns, and W. G. Moulton. Work at Northwestern University is supported by the NSF (DMR 91-20000) through the Science and Technology Center for Superconductivity. The NHMFL is supported through the NSF and the state of Florida.

  3. 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)].

  4. 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). PMID:26107984

  5. 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).

  6. 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

  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. PMID:27538437

  8. /sup 17/O NMR spectroscopy: torsion angle relationships in aryl carboxylic esters, acids, and amides

    SciTech Connect

    Baumstark, A.L.; Balakrishnan, P.; Dotrong, M.; McCloskey, C.J.; Oakley, M.G.; Boykin, D.W.

    1987-02-18

    /sup 1/ /sup 7/O NMR spectroscopic data (natural abundance in acetonitrile at 75/sup 0/C) were obtained for the following series of electronically similar, sterically hindered compounds: aromatic methyl esters, aromatic carboxylic acids, and aromatic amides. Torsional angles were calculated by the molecular mechanics (MM2) method. Linear regression analysis of the estimated torsion angles and the /sup 17/O chemical shift data for each series yielded the following results (series, slope delta/degree, correlation coefficient): esters (C=O), 0.70, 0.997; esters (-0-), 0.43, 0.992; acids (-CO/sub 2/H), 0.56, 0.994; amides (C=O), 0.84, 0.942; N,N-dimethylamides (C=O), 0.6, 0.991. The results are discussed in terms of minimization of repulsive van der Waals interactions by rotation of the functional group out of the plane of the aromatic ring.

  9. Vortex Lattice Formation in High Magnetic Fields in an Underdoped Single Crystal of Hg1201 from 17O NMR

    NASA Astrophysics Data System (ADS)

    Lee, Jeongseop; Xin, Yizhou; Halperin, W. P.; Reyes, A. P.; Kuhns, P. L.

    The vortex lattice in HgBa2CuO4+δ forms at a vortex melting temperature, Tv, typically ~40K for underdoped crystals with a hole doping ~ 0.11. We present our results from 17O NMR for investigation of the vortex lattice as a function of external magnetic field up to 30 T and temperature as low as 5 K. The vortex contribution to the NMR linewidth can be separated from inhomogeneous broadening by deconvolution of the normal state spectra which was measured separately above, Tv. The vortex melting temperature was measured for two underdoped samples marked by the onset of extra linewidth broadening due to the inhomogeneous magnetic field distribution from the solid vortex lattice consistent with transverse relaxation measurements. We have found evidence for a change in the vortex lattice symmetry as a function of external fields. This work was supported by the DOE BES under Grant No. DE-FG02-05ER46248 and the NHMFL through the NSF and State of Florida.

  10. First-principles calculation of the 17O NMR parameters in Ca oxide and Ca aluminosilicates: the partially covalent nature of the Ca-O bond, a challenge for density functional theory.

    PubMed

    Profeta, Mickaël; Benoit, Magali; Mauri, Francesco; Pickard, Chris J

    2004-10-01

    We apply density functional theory (DFT) to the calculation of the (17)O NMR parameters in Ca and Mg oxides and aluminosilicates. We study the accuracy of the Perdew, Burke, and Ernzerhof (PBE) generalized-gradient approximation to DFT in the description of these systems and the origin of the experimentally observed large dependence of the (17)O chemical shift on the alkaline earth ion. We find that (i) the partially covalent nature of the Ca-O bond has a huge impact on the O chemical shifts. The Ca-O covalence alone explains why in Ca oxides and aluminosilicates the (17)O chemical shifts are much more deshielded than those of the corresponding Mg compounds. (ii) The Ca-O covalence is overestimated by the PBE functional. Thus PBE-DFT is not able to reproduce the measured (17)O NMR parameters in Ca oxide and Ca aluminosilicates. (iii) It is possible to correct for the PBE-DFT deficiency in a simple and transferable way and to predict very accurate (17)O NMR parameters. Such accuracy allows us to assign the (17)O NMR spectra of two important model systems: the grossite aluminate (CaAl(4)O(7)) and the wollastonite (CaSiO(3)) silicate.

  11. 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

  12. 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.

  13. Solid-state (17)O NMR as a sensitive probe of keto and gem-diol forms of alpha-keto acid derivatives.

    PubMed

    Zhu, Jianfeng; Geris, Amanda J; Wu, Gang

    2009-08-28

    We have used solid-state (17)O NMR experiments to measure the (17)O quadrupole coupling (QC) and chemical shift (CS) tensors for two alpha-keto acids: sodium [2-(17)O]pyruvate and lithium [2,2'-(17)O(2)]pyruvate. In the solid state, sodium [2-(17)O]pyruvate is in the keto form (-C(double bond (17)O)-) whereas lithium [2,2'-(17)O(2)]pyruvate takes the gem-diol form (-C((17)OH)(2)-). This study represents the first time that a full set of (17)O NMR tensors are experimentally determined for alpha-keto acids in these two different tautomeric forms. We have found that the two forms exhibit drastically different (17)O QC and CS tensors: for the keto form, delta(iso) = 543 +/- 1 ppm, C(Q) = 10.8 +/- 0.2 MHz, eta(Q) = 0.48 +/- 0.05, delta(11) = 1020 +/- 10, delta(22) = 640 +/- 10, delta(33) = -40 +/- 10 ppm, alpha = 80 +/- 5 degrees, beta = 90 +/- 2 degrees, and gamma = 83 +/- 2 degrees; for the gem-diol form, delta(iso) = 62 +/- 1 ppm, C(Q) = 8.5 +/- 0.5 MHz, eta(Q) = 1.0 +/- 0.05, delta(11) = 140 +/- 5, delta(22) = 45 +/- 5, delta(33) = 0 +/- 5 ppm, alpha = 55 +/- 5 degrees, beta = 90 +/- 5 degrees, and gamma = 80 +/- 2 degrees. The (17)O chemical shift tensor observed for the gem-diol functional group also represents the first such measurement for any -ol functional group (e.g., alcohols, phenols, carbohydrates, etc.) Using these accurate experimental (17)O NMR tensors, we were able to evaluate the accuracy of quantum chemical calculations. Our results showed that quantum chemical calculations using the crystal lattice approach are in much better agreement with the experimental solid-state (17)O NMR data than those calculated using the molecular cluster approach. Quantum chemical calculations have also provided information about the sign of the (17)O quadrupolar coupling constants and about the (17)O NMR tensor orientations in the molecular frame of reference. Our findings suggest that solid-state (17)O NMR may be useful in probing the tautomeric form of the alpha

  14. 17O NMR study of the doped electrons in lightly oxygen-deficient cubic SrMnO3 -x

    NASA Astrophysics Data System (ADS)

    Trokiner, A.; Verkhovskii, S.; Volkova, Z.; Gerashenko, A.; Mikhalev, K.; Germov, A.; Yakubovskii, A.; Korolev, A.; Dabrowski, B.; Tyutyunnik, A.

    2016-05-01

    The spin susceptibility of the localized Mn (t2 g) electrons, χs, and the spatially distributed spin density of the doped electrons were investigated by 17O nuclear magnetic resonance (NMR) in the paramagnetic (PM) and antiferromagnetic (AF) phases of electron-doped SrMnO3 -x ceramics with the cubic structure. Three lightly doped samples (2 x <0.015 ) were studied with TN=220 K-240 K. In the PM state χs increases gradually from TN and reaches a broad maximum above ˜1.5 TN . The gapped behavior of χs indicates a low-dimensional short-range spin order persisting above TN. These short-range one-dimensional correlations are consistent with 17O NMR results obtained at room temperature, which show that Mn magnetic moments are aligned along the edges of the cubic unit cell. Above 350 K all doped electrons are fast-moving eg electrons. They provide the uniform polarization of the localized spins which increases χs and the increasing doping shifts the oxygen-deficient SrMnO3 -x oxide towards a ferromagnetic (FM) metallic state. At lower T the doped electrons are heterogeneously distributed in the oxide: The fraction of the fast-moving electrons diminishes and vanishes below 100 K, while the remaining doped electrons slow down their hopping and each of them creates a FM domain. These FM domains which are detected below 10 K by 55Mn NMR can be considered as small-size magnetic polarons. Their T -activated hopping in the G-type AF lattice was probed by 17O spin-echo experiments. The energy barrier of hopping shows a trend to grow with increasing doping, indicating that the de Gennes metallic ground state cannot be achieved in oxygen-deficient SrMnO3 -x oxides, probably due to detrimental oxygen vacancy defects.

  15. Direct measurement of the Mn(II) hydration state in metal complexes and metalloproteins through 17O NMR line widths.

    PubMed

    Gale, Eric M; Zhu, Jiang; Caravan, Peter

    2013-12-11

    Here we describe a simple method to estimate the inner-sphere hydration state of the Mn(II) ion in coordination complexes and metalloproteins. The line width of bulk H2(17)O is measured in the presence and absence of Mn(II) as a function of temperature, and transverse (17)O relaxivities are calculated. It is demonstrated that the maximum (17)O relaxivity is directly proportional to the number of inner-sphere water ligands (q). Using a combination of literature data and experimental data for 12 Mn(II) complexes, we show that this method provides accurate estimates of q with an uncertainty of ±0.2 water molecules. The method can be implemented on commercial NMR spectrometers working at fields of 7 T and higher. The hydration number can be obtained for micromolar Mn(II) concentrations. We show that the technique can be extended to metalloproteins or complex:protein interactions. For example, Mn(II) binds to the multimetal binding site A on human serum albumin with two inner-sphere water ligands that undergo rapid exchange (1.06 × 10(8) s(-1) at 37 °C). The possibility of extending this technique to other metal ions such as Gd(III) is discussed.

  16. 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

  17. NMR spectra of androstane analogs of brassinosteroids

    NASA Astrophysics Data System (ADS)

    Baranovskii, A. V.; Litvinovskaya, R. P.; Aver'kova, M. A.; Khripach, N. B.; Khripach, V. A.

    2007-09-01

    We have used two-dimensional NMR spectroscopy to make a complete assignment of signals from the nuclei of hydrogen and carbon atoms in the spectra of brassinosteroids in the androstane series. We have confirmed the stereochemistry of the chiral centers and the structure of the molecules. We have studied the effect of the configuration of the 2,3-diol groups in the A ring of the steroids on the chemical shift of adjacent atoms in the 13C and 1H NMR spectra.

  18. Water permeability of polyunsaturated lipid membranes measured by 17O NMR.

    PubMed

    Huster, D; Jin, A J; Arnold, K; Gawrisch, K

    1997-08-01

    Diffusion-controlled water permeation across bilayers of polyunsaturated phospholipids was measured by 17O nuclear magnetic resonance. In 100-nm extruded liposomes containing 50 mM MnCl2, water exchange between internal and external solutions was monitored via changes in the linewidth of the 17O water resonance of external water. Liposome size and shape were characterized by light scattering methods and determination of liposome trapped volume. At 25 degrees C, the following water permeability coefficients were determined: 18:0-18:1n-9 PC, 155 +/- 24 microns/s; 18:0-18:3n-3 PC, 330 +/- 88 microns/s; and 18:0-22:6n-3 PC, 412 +/- 91 microns/s. The addition of 1 M ethanol reduced permeability coefficients to 66 +/- 15 microns/s for 18:0-18:1n-9 PC and to 239 +/- 67 microns/s for 18:0-22:6n-3 PC. Furthermore, the addition of 50 mol% 18:1n-9-18:1n-9 PE reduced the water permeability from 122 +/- 21 microns/s for pure 18:1n-9-18:1n-9 PC to 74 +/- 15 microns/s for the mixture. The significant increase in water permeation for membranes with polyunsaturated hydrocarbon chains correlates with looser packing of polyunsaturated lipids at the lipid-water interface and the suggested deeper penetration of water into these bilayers. Ethanol may block water diffusion pathways by occupying points of water entry into bilayers at the interface. The addition of dioleoylphosphatidylethanolamine increases lipid packing density and, consequently, reduces permeation rates.

  19. Imaging of complex NMR spectra.

    PubMed

    Harrison, C G; Adams, D F; Kramer, P B

    1985-01-01

    The Point Spread Function (PSF) in NMR imaging is the result of both the line broadening due to magnet field inhomogeneity and the intrinsic spectrum of the nucleus at resonance. In the case of proton imaging, the line broadening dominates the small chemical shifts and the spectral lines are not resolved. This is not generally the case with other nuclei having strong chemical shifts and the PSF then has a complex structure. During imaging, the complex PSF is convolved with the spatial distribution of the nucleus at resonance and this leads to halo artifacts which are dependent on the imaging technique employed. The images due to the ensemble of spectral lines can be separated in principle by deconvolution of the data with the PSF before reconstruction. In the special case where the complex PSF is spatially independent, it can be obtained from the Free Induction Decay (FID) data produced in the absence of a spatially encoding gradient field. This technique has been successfully applied to in-vivo imaging of exogenous perfluorocarbon material. PMID:3988470

  20. Effects of the degree of polymerization on the structure of sodium silicate and aluminosilicate glasses and melts: An 17O NMR study

    NASA Astrophysics Data System (ADS)

    Lee, Sung Keun; Stebbins, Jonathan F.

    2009-02-01

    Revealing the atomic structure and disorder in oxide glasses, including sodium silicates and aluminosilicates, with varying degrees of polymerization, is a challenging problem in high-temperature geochemistry as well as glass science. Here, we report 17O MAS and 3QMAS NMR spectra for binary sodium silicate and ternary sodium aluminosilicate glasses with varying degrees of polymerization (Na 2O/SiO 2 ratio and Na 2O/Al 2O 3 ratio), revealing in detail the extent of disorder (network connectivity and topological disorder) and variations of NMR parameters with the glass composition. In binary sodium silicate glasses [Na 2O- k(SiO 2)], the fraction of non-bridging oxygens (NBOs, Na-O-Si) increases with the Na 2O/SiO 2 ratio ( k), as predicted from the composition. The 17O isotropic chemical shifts ( 17O δiso) for both bridging oxygen (BO) and NBO increase by about 10-15 ppm with the SiO 2 content (for k = 1-3). The quadrupolar coupling products of BOs and NBOs also increase with the SiO 2 content. These trends suggest that both NBOs and BOs strongly interact with Na; therefore, the Na distributions around BOs and NBOs are likely to be relatively homogenous for the glass compositions studied here, placing some qualitative limits on the extent of segregation of alkali channels from silica-enriched regions as suggested by modified random-network models. The peak width (in the isotropic dimension) and thus bond angle and length distributions of Si-O-Si and Na-O-Si increase with the SiO 2 content, indicating an increase in the topological disorder with the degree of polymerization. In the ternary aluminosilicate glasses [Na 2O] x[Al 2O 3] 1-xSiO 2, the NBO fraction decreases while the Al-O-Si and Al-O-Al fractions apparently increase with increasing Al 2O 3 content. The variation of oxygen cluster populations suggests that deviation from "Al avoidance" is more apparent near the charge-balanced join (Na/Al = 1). The Si-O-Si fraction, which is closely related to the activity

  1. Toward Relatively General and Accurate Quantum Chemical Predictions of Solid-State 17O NMR Chemical Shifts in Various Biologically Relevant Oxygen-containing Compounds

    PubMed Central

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

    2015-01-01

    Oxygen is an important element in most biologically significant molecules and experimental solid-state 17O NMR studies have provided numerous useful structural probes to study these systems. However, computational predictions of solid-state 17O NMR chemical shift tensor properties are still challenging in many cases and in particular each of the prior computational work is basically limited to one type of oxygen-containing systems. This work provides the first systematic study of the effects of geometry refinement, method and basis sets for metal and non-metal 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 17O NMR chemical shifts in organic and organometallic compounds. A number of computational factors towards relatively general and accurate predictions of 17O NMR chemical shifts were studied to provide helpful and detailed suggestions for future work. For the studied various kinds of oxygen-containing compounds, the best computational approach results in a theory-versus-experiment correlation coefficient R2 of 0.9880 and mean absolute deviation of 13 ppm (1.9% of the experimental range) for isotropic NMR shifts and R2 of 0.9926 for all shift tensor properties. These results shall facilitate future computational studies of 17O NMR chemical shifts in many biologically relevant systems, and the high accuracy may also help refinement and determination of active-site structures of some oxygen-containing substrate bound proteins. PMID:26274812

  2. 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

    2015-09-01

    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.

  3. 17O solid-state NMR and first-principles calculations of sodium trimetaphosphate (Na3P3O9), tripolyphosphate (Na5P3O10), and pyrophosphate (Na4P2O7).

    PubMed

    Vasconcelos, Filipe; Cristol, Sylvain; Paul, Jean-Francois; Tricot, Grégory; Amoureux, Jean-Paul; Montagne, Lionel; Mauri, Francesco; Delevoye, Laurent

    2008-08-18

    The assignment of high-field (18.8 T) (17)O MAS and 3QMAS spectra has been completed by use of first-principles calculations for three crystalline sodium phosphates, Na 3P 3O 9, Na 5P 3O 10, and Na 4P 2O 7. In Na 3P 3O 9, the calculated parameters, quadrupolar constant ( C Q), quadrupolar asymmetry (eta Q), and the isotropic chemical shift (delta cs) correspond to those deduced experimentally, and the calculation is mandatory to achieve a complete assignment. For the sodium tripolyphosphate Na 5P 3O 10, the situation is more complex because of the free rotation of the end-chain phosphate groups. The assignment obtained with ab initio calculations can however be confirmed by the (17)O{ (31)P} MAS-J-HMQC spectrum. Na 4P 2O 7 (17)O MAS and 3QMAS spectra show a complex pattern in agreement with the computed NMR parameters, which indicate that all of the oxygens exhibit very similar values. These results are related to structural data to better understand the influence of the oxygen environment on the NMR parameters. The findings are used to interpret those results observed on a binary sodium phosphate glass. PMID:18642900

  4. 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)].

  5. Preparation and Tungsten-183 NMR Characterization of [alpha-1-P(2)W(17)O(61)](10)(-), [alpha-1-Zn(H(2)O)P(2)W(17)O(61)](8)(-), and [alpha-2-Zn(H(2)O)P(2)W(17)O(61)](8)(-).

    PubMed

    Bartis, Judit; Kunina, Yuliya; Blumenstein, Michael; Francesconi, Lynn C.

    1996-03-13

    The preparation of the alpha-1 and alpha-2 isomers of the Wells-Dawson 17 tungsto derivatives by standard methods is accompanied by a significant proportion of the other isomer present as an impurity. In this study, the alpha-1 and alpha-2 isomers of [Zn(H(2)O)P(2)W(17)O(61)](8)(-) have been prepared in >98% purity by reacting isomerically pure K(9)Li[alpha-1-P(2)W(17)O(61)] and K(10)[alpha-2-P(2)W(17)O(61)], respectively, with ZnCl(2), while rigorously controlling the pH at 4.7. The molecules were isolated as potassium salts. For (183)W NMR and (31)P NMR characterization, both molecules were ion exchanged by cation-exchange chromatography, maintaining the pH at 4.7, to obtain the lithium salts. Removal of water and isolation of a solid sample of [alpha-1-Zn(H(2)O)P(2)W(17)O(61)](8)(-) was achieved by lyophilization at -40 degrees C. The chemical shift data from (31)P and (183)W NMR spectroscopy of the isolated [alpha-1-Zn(H(2)O)P(2)W(17)O(61)](8)(-) and [alpha-2-Zn(H(2)O)P(2)W(17)O(61)](8)(-) isomers are consistent with a mixture of the alpha-1 and alpha-2 isomers reported previously;(1) the molecules have the expected C(1) and C(s)() symmetry, respectively. The [alpha-1-Zn(H(2)O)P(2)W(17)O(61)](8)(-) isomer is stable in the pH range of 4.6-6 at temperatures <35 degrees C. Using the same ion exchange and lyophilization techniques, the lacunary [alpha-1-P(2)W(17)O(61)](10)(-) isomer was isolated as the lithium salt; characterization by (183)W NMR spectroscopy confirms the C(1) symmetry.

  6. Magnetic Field-Independent ^17O and ^63, 65Cu Normal State Spin Lattice Relaxation as Inferred by ^17O T2 NMR up to 28 T in YBa_2Cu_3O_7

    NASA Astrophysics Data System (ADS)

    Mitrovic, V. F.; Bachman, H. N.; Halperin, W. P.

    1998-03-01

    ^17O spin-spin relaxation NMR (T_2) is a powerful probe of vortex fluctuations in high Tc cuprates.(H. N. Bachman et al)., Bull. Am. Phys. Soc., 41, 467 (1996). It is important to understand the normal state T2 relaxation in order to extract the vortex field fluctuations.^1,(C. H. Recchia et al)., Phys. Rev. Lett. 78, 3543 (1997). The study of T2 in YBCO has shown that, in the normal state, copper and oxygen spin fluctuations (T1 processes) dominate the time scales for T_2, the spin-echo height decay. Thus, measurements of T2 as a function of magnetic field are an indicator of ^17O and ^63, 65Cu T1 behavior. We report new T2 measurements taken in the normal state from 3.2 T up to 28.2 T in which the spin-spin relaxation rate is observed to be completely field independent. By comparison with the predicted spin echo height decay given by the Gaussian Phase Approximation model we show that T1 of ^63, 65Cu and ^17O must not deviate from their published low-field values, within experimental error, over the entire magnetic field range. Work at Northwestern University is supported by the NSF (DMR 91-20000) through the Science and Technology Center for Superconductivity. The NHMFL is supported through the NSF and the state of Florida.

  7. 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

  8. 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. PMID:25854521

  9. 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

  10. 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

  11. 13C NMR spectra of pyridine chalcone analogs

    NASA Astrophysics Data System (ADS)

    Jovanović, B. Ž.; Mišić-Vuković, M.; Marinković, A. D.; Csanádi, J.

    1999-05-01

    13C NMR spectra of two series of pyridine chalcone analogs were determined in deuterated dimethylsulphoxide (DMSO-d 6). It was established that these compounds were in more stable E-configurations except for the 4-pyridalacetophenone which was in Z-configuration. On the basis of the Hammett correlations of 13C NMR chemical shifts of the ethylenic bond carbon atoms and the σ values for the pyridine "aza" groups, the polarization of ethylenic bonds were discussed. It was established that the opposite effect of the pyridine substituents at the electronic density distribution in pyridalacetophenone and cinnamoylpyridines depends on its direct bonding to the ethylenic carbon or the transmission electronic effects via the carbonyl group, respectively.

  12. {sup 13}C and {sup 17}O NMR binding constant studies of uranyl carbonate complexes in near-neutral aqueous solution. Yucca Mountain Project Milestone Report 3351

    SciTech Connect

    Clark, D.L.; Newton, T.W.; Palmer, P.D.; Zwick, B.D.

    1995-01-01

    Valuable structural information, much of it unavailable by other methods, can be obtained about complexes in solution through NMR spectroscopy. From chemical shift and intensity measurements of complexed species, NMR can serve as a species-specific structural probe for molecules in solution and can be used to validate thermodynamic constants used in geochemical modeling. Fourier-transform nuclear magnetic resonance (FT-NMR) spectroscopy has been employed to study the speciation of uranium(VI) ions in aqueous carbonate solutions as a function of pH, ionic strength, carbonate concentration, uranium concentration, and temperature. Carbon-13 and oxygen-17 NMR spectroscopy were used to monitor the fractions, and hence thermodynamic binding constants of two different uranyl species U0{sub 2}(CO{sub 3}){sub 3}{sup 4{minus}} and (UO{sub 2}){sub 3}(CO{sub 3}){sub 6}{sup 6{minus}} in aqueous solution. Synthetic buffer solutions were prepared under the ionic strength conditions used in the NMR studies in order to obtain an accurate measure of the hydrogen ion concentration, and a discussion of pH = {minus}log(a{sub H}{sup +}) versus p[H] = {minus}log[H+] is provided. It is shown that for quantitative studies, the quantity p[H] needs to be used. Fourteen uranium(VI) binding constants recommended by the OECD NEA literature review were corrected to the ionic strengths employed in the NMR study using specific ion interaction theory (SIT), and the predicted species distributions were compared with the actual species observed by multinuclear NMR. Agreement between observed and predicted stability fields is excellent. This establishes the utility of multinuclear NMR as a species-specific tool for the study of the actinide carbonate complexation constants, and serves as a means for validating the recommendations provided by the OECD NEA.

  13. Total lineshape analysis of high-resolution NMR spectra powered by simulated annealing

    NASA Astrophysics Data System (ADS)

    Cheshkov, D. A.; Sinitsyn, D. O.; Sheberstov, K. F.; Chertkov, V. A.

    2016-11-01

    The novel algorithm for a total lineshape analysis of high-resolution NMR spectra has been developed. A global optimization by simulated annealing has been applied that has allowed to overcome the main trouble of common approaches which had frequently returned solutions for local minima rather than for global ones. The algorithm has been verified for the four-spin test systems ABCD, and has been successfully used for analysis of experimental NMR spectra of proline. The approach has allowed to avoid a sophisticated manual setup of initial parameters and to conduct the analysis of complicated high-resolution NMR spectra nearly automatically.

  14. Access to experimentally infeasible spectra by pure-shift NMR covariance

    NASA Astrophysics Data System (ADS)

    Fredi, André; Nolis, Pau; Cobas, Carlos; Parella, Teodor

    2016-09-01

    Covariance processing is a versatile processing tool to generate synthetic NMR spectral representations without the need to acquire time-consuming experimental datasets. Here we show that even experimentally prohibited NMR spectra can be reconstructed by introducing key features of a reference 1D CHn-edited spectrum into standard 2D spectra. This general procedure is illustrated with the calculation of experimentally infeasible multiplicity-edited pure-shift NMR spectra of some very popular homonuclear (ME-psCOSY and ME-psTOCSY) and heteronuclear (ME-psHSQC-TOCSY and ME-psHMBC) experiments.

  15. Access to experimentally infeasible spectra by pure-shift NMR covariance.

    PubMed

    Fredi, André; Nolis, Pau; Cobas, Carlos; Parella, Teodor

    2016-09-01

    Covariance processing is a versatile processing tool to generate synthetic NMR spectral representations without the need to acquire time-consuming experimental datasets. Here we show that even experimentally prohibited NMR spectra can be reconstructed by introducing key features of a reference 1D CHn-edited spectrum into standard 2D spectra. This general procedure is illustrated with the calculation of experimentally infeasible multiplicity-edited pure-shift NMR spectra of some very popular homonuclear (ME-psCOSY and ME-psTOCSY) and heteronuclear (ME-psHSQC-TOCSY and ME-psHMBC) experiments.

  16. The acquisition of multidimensional NMR spectra within a single scan

    PubMed Central

    Frydman, Lucio; Scherf, Tali; Lupulescu, Adonis

    2002-01-01

    A scheme enabling the complete sampling of multidimensional NMR domains within a single continuous acquisition is introduced and exemplified. Provided that an analyte's signal is sufficiently strong, the acquisition time of multidimensional NMR experiments can thus be shortened by orders of magnitude. This could enable the characterization of transient events such as proteins folding, 2D NMR experiments on samples being chromatographed, bring the duration of higher dimensional experiments (e.g., 4D NMR) into the lifetime of most proteins under physiological conditions, and facilitate the incorporation of spectroscopic 2D sequences into in vivo imaging investigations. The protocol is compatible with existing multidimensional pulse sequences and can be implemented by using conventional hardware; its performance is exemplified here with a variety of homonuclear 2D NMR acquisitions. PMID:12461169

  17. Proton NMR Spectra: Deceptively Simple and Deceptively Complex Examples.

    ERIC Educational Resources Information Center

    Gurst, J. E.; And Others

    1985-01-01

    Describes relatively simple nuclear magnetic resonance (NMR) experiments that demonstrate unexpected results of the deceptively simple and deceptively complex types. Background information, experimental procedures, and typical results obtained are included. (JN)

  18. Enrichment of H(2)(17)O from tap water, characterization of the enriched water, and properties of several (17)O-labeled compounds.

    PubMed

    Prasad, Brinda; Lewis, Andrew R; Plettner, Erika

    2011-01-01

    A low-abundance form of water, H(2)(17)O, was enriched from 0.04% to ∼90% by slow evaporation and fractional distillation of tap water. The density and refractive index for H(2)(17)O are reported. Gas chromatography-mass spectrometry (GC-MS) of (16)O- and (17)O-1-hexanols and their trimethyl silyl ethers and of (16)O- and (17)O-hexamethyl disiloxanes was used to determine the percentage of (17)O enrichment in the H(2)(17)O. Furthermore, the chemical shifts of labeled and nonlabeled water dissolved in CDCl(3) differed sufficiently that we could verify the enrichment of H(2)(17)O. (17)O hexanol was synthesized by the reaction of iodohexane with Na(17)OH. (17)O-Labeled trimethylsilanol and (17)O-labeled hexamethyldisiloxane were prepared by the reaction of H(2)(17)O with bis(trimethylsilyl)trifluoroacetamide (BSTFA). To generate standards for (17)O NMR, H(2)(17)O(2), and (17)O camphor were prepared. H(2)(17)O was electrolyzed to form (17)O-labeled hydrogen peroxide which was quantified using two colorimetric assays. (17)O-Labeled camphor was prepared by exchanging the ketone oxygen of camphor using H(2)(17)O. The (17)O-labeled compounds were characterized using (17)O, (1)H, and (13)C NMR and GC-MS. While we were characterizing the labeled camphor, we also detected an unexpected oxygen exchange reaction of primary alcohols, catalyzed by electrophilic ketones such as camphor. The reaction is a displacement of the alcohol OH group by water. This is an example of the usefulness of (17)O NMR in the study of a reaction mechanism that has not been noticed previously. PMID:21128590

  19. Quantification of in vivo ³¹P NMR brain spectra using LCModel.

    PubMed

    Deelchand, Dinesh Kumar; Nguyen, Tra-My; Zhu, Xiao-Hong; Mochel, Fanny; Henry, Pierre-Gilles

    2015-06-01

    Quantification of (31)P NMR spectra is commonly performed using line-fitting techniques with prior knowledge. Currently available time- and frequency-domain analysis software includes AMARES (in jMRUI) and CFIT respectively. Another popular frequency-domain approach is LCModel, which has been successfully used to fit both (1)H and (13)C in vivo NMR spectra. To the best of our knowledge LCModel has not been used to fit (31)P spectra. This study demonstrates the feasibility of using LCModel to quantify in vivo (31)P MR spectra, provided that adequate prior knowledge and LCModel control parameters are used. Both single-voxel and MRSI data are presented, and similar results are obtained with LCModel and with AMARES. This provides a new method for automated, operator-independent analysis of (31)P NMR spectra. PMID:25871439

  20. High-resolution 2D NMR spectra in inhomogeneous fields via 3D acquisition

    NASA Astrophysics Data System (ADS)

    Lin, Yanqin; Wei, Zhiliang; Zhang, Liandi; Lin, Liangjie; Chen, Zhong

    2014-04-01

    High-resolution nuclear magnetic resonance (NMR) spectroscopy plays an important role in chemical studies. Here, a pulse sequence, based on coherence transfer module of tracking differences of precession frequencies of two spins and spin echo module, is proposed to obtain two dimension (2D) high-resolution NMR spectra via 3D acquisition under large field inhomogeneity. The proposed scheme composes of simple hard pulses and rectangle gradients. Resulting 2D spectra exhibit chemical shift differences and J coupling splittings in two orthogonal dimensions. The method developed here may offer a promising way for in situ high-resolution NMR studies on combinatorial chemistry.

  1. Vibrational spectra, NMR and theoretical studies of the enantiomers and rotamers of alpha-cypermethrin.

    PubMed

    Jubert, Alicia H; Alegre, María L; Diez, Reinaldo Pis; Pomilio, Alicia B; Szewczuk, Víctor D

    2007-04-01

    NMR, infrared and Raman vibrational spectra of alpha-cypermethrin have been measured at room temperature. Infrared spectra were also recorded to low temperature. The spectra were analyzed by means of ab initio calculations. The conformational space of both enantiomers and some rotamers A, B and C of alpha-cypermethrin has been scanned using molecular dynamics and complemented with functional density calculations that optimize the geometry of the lowest-energy conformers of each species as obtained in the simulations. The vibrational frequencies and the 1H and 13C NMR chemical shifts were assigned using functional density calculations. The molecular electrostatic potential maps were obtained and analyzed.

  2. Vibrational spectra, NMR and theoretical studies of the enantiomers and rotamers of alpha-cypermethrin

    NASA Astrophysics Data System (ADS)

    Jubert, Alicia H.; Alegre, María L.; Diez, Reinaldo Pis; Pomilio, Alicia B.; Szewczuk, Víctor D.

    2007-04-01

    NMR, infrared and Raman vibrational spectra of alpha-cypermethrin have been measured at room temperature. Infrared spectra were also recorded to low temperature. The spectra were analyzed by means of ab initio calculations. The conformational space of both enantiomers and some rotamers A, B and C of alpha-cypermethrin has been scanned using molecular dynamics and complemented with functional density calculations that optimize the geometry of the lowest-energy conformers of each species as obtained in the simulations. The vibrational frequencies and the 1H and 13C NMR chemical shifts were assigned using functional density calculations. The molecular electrostatic potential maps were obtained and analyzed.

  3. 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

  4. Computer aided evaluation of two-dimensional NMR spectra of proteins.

    PubMed

    Neidig, K P; Bodenmueller, H; Kalbitzer, H R

    1984-12-28

    A computer program for the automatic evaluation of two-dimensional NMR spectra of peptides and proteins has been developed. The used strategy is described, the advantages and limits of this approach are discussed. The program was successfully tested on a COSY-spectrum of the neuropeptide Glp-Pro-Pro-Gly-Gly-Ser-Lys-Val-Ile-Leu-Phe from hydra, resulting in a drastic reduction of the time needed for the evaluation of two-dimensional NMR data.

  5. RUBIDIUM, a program for computer-aided assignment of two-dimensional NMR spectra of polypeptides.

    PubMed

    Yu, C; Hwang, J F; Chen, T B; Soo, V W

    1992-01-01

    Taking advantage of the rule-based expert system technology, a program named RUBIDIUM (Rule-Based Identification In 2D NMR Spectrum) was developed to accomplish the automatic 1H NMR resonance assignments of polypeptides. Besides noise elimination and peak selection capabilities, RUBIDIUM detects the cross-peak patterns of amino acid residues in the COSY spectrum, assigning these patterns to amino acid types, performing sequential assignments using combined COSY/NOESY spectra, and finally, achieving the total assignment of the 1H NMR spectrum.

  6. An efficient spectra processing method for metabolite identification from 1H-NMR metabolomics data.

    PubMed

    Jacob, Daniel; Deborde, Catherine; Moing, Annick

    2013-06-01

    The spectra processing step is crucial in metabolomics approaches, especially for proton NMR metabolomics profiling. During this step, noise reduction, baseline correction, peak alignment and reduction of the 1D (1)H-NMR spectral data are required in order to allow biological information to be highlighted through further statistical analyses. Above all, data reduction (binning or bucketing) strongly impacts subsequent statistical data analysis and potential biomarker discovery. Here, we propose an efficient spectra processing method which also provides helpful support for compound identification using a new data reduction algorithm that produces relevant variables, called buckets. These buckets are the result of the extraction of all relevant peaks contained in the complex mixture spectra, rid of any non-significant signal. Taking advantage of the concentration variability of each compound in a series of samples and based on significant correlations that link these buckets together into clusters, the method further proposes automatic assignment of metabolites by matching these clusters with the spectra of reference compounds from the Human Metabolome Database or a home-made database. This new method is applied to a set of simulated (1)H-NMR spectra to determine the effect of some processing parameters and, as a proof of concept, to a tomato (1)H-NMR dataset to test its ability to recover the fruit extract compositions. The implementation code for both clustering and matching steps is available upon request to the corresponding author. PMID:23525538

  7. Bayesian deconvolution and quantification of metabolites in complex 1D NMR spectra using BATMAN.

    PubMed

    Hao, Jie; Liebeke, Manuel; Astle, William; De Iorio, Maria; Bundy, Jacob G; Ebbels, Timothy M D

    2014-01-01

    Data processing for 1D NMR spectra is a key bottleneck for metabolomic and other complex-mixture studies, particularly where quantitative data on individual metabolites are required. We present a protocol for automated metabolite deconvolution and quantification from complex NMR spectra by using the Bayesian automated metabolite analyzer for NMR (BATMAN) R package. BATMAN models resonances on the basis of a user-controllable set of templates, each of which specifies the chemical shifts, J-couplings and relative peak intensities for a single metabolite. Peaks are allowed to shift position slightly between spectra, and peak widths are allowed to vary by user-specified amounts. NMR signals not captured by the templates are modeled non-parametrically by using wavelets. The protocol covers setting up user template libraries, optimizing algorithmic input parameters, improving prior information on peak positions, quality control and evaluation of outputs. The outputs include relative concentration estimates for named metabolites together with associated Bayesian uncertainty estimates, as well as the fit of the remainder of the spectrum using wavelets. Graphical diagnostics allow the user to examine the quality of the fit for multiple spectra simultaneously. This approach offers a workflow to analyze large numbers of spectra and is expected to be useful in a wide range of metabolomics studies.

  8. 13C-NMR spectra and contact time experiment for Skjervatjern fulvic and humic acids

    USGS Publications Warehouse

    Malcolm, R.L.

    1992-01-01

    The T(CP) and T(1p) time constants for Skjervatjern fulvic and humic acids were determined to be short with T(CP) values ranging from 0.14 ms to 0.53 ms and T(1p) values ranging from 3.3 ms to 5.9 ms. T(CP) or T(1p) time constants at a contact time of 1 ms are favorable for quantification of 13C-NMR spectra. Because of the short T(CP) values, correction factors for signal intensity for various regions of the 13C-NMR spectra would be necessary at contact times greater than 1.1 ms or less than 0.9 ms. T(CP) and T(1p) values have a limited non-homogeneity within Skjervatjern fulvic and humic acids. A pulse delay or repeat time of 700 ms is more than adequate for quantification of these 13C-NMR spectra. Paramagnetic effects in these humic substances are precluded due to low inorganic ash contents, low contents of Fe, Mn, and Co, and low organic free-radical contents. The observed T(CP) values suggest that all the carbon types in Skjervatjern fulvic and humic acids are fully cross-polarized before significant proton relaxation occurs. The 13C-NMR spectra for Skjervatjern fulvic acid is similar to most aquatic fulvic acids as it is predominantly aliphatic, low in aromaticity (fa1 = 24), low in phenolic content, high in carboxyl content, and has no resolution of a methoxyl peak. The 13C-NMR spectra for Skjervatjern humic acid is also similar to most other aquatic humic acids in that it is also predominantly aliphatic, high in aromaticity (fa1 = 38), moderate in phenolic content, moderate in carboxyl content, and has a clear resolution of a methoxyl carbon region. After the consideration of the necessary 13C-NMR experimental conditions, these spectra are considered to be quantitative. With careful consideration of the previously determined 13C-NMR experimental conditions, quantitative spectra can be obtained for humic substances in the future from the HUMEX site. Possible changes in humic substances due to acidification should be determined from 13C-NMR data.

  9. In Vivo potassium-39 NMR spectra by the burg maximum-entropy method

    NASA Astrophysics Data System (ADS)

    Uchiyama, Takanori; Minamitani, Haruyuki

    The Burg maximum-entropy method was applied to estimate 39K NMR spectra of mung bean root tips. The maximum-entropy spectra have as good a linearity between peak areas and potassium concentrations as those obtained by fast Fourier transform and give a better estimation of intracellular potassium concentrations. Therefore potassium uptake and loss processes of mung bean root tips are shown to be more clearly traced by the maximum-entropy method.

  10. Bulk magnetization and 1H NMR spectra of magnetically heterogeneous model systems

    SciTech Connect

    Levin, E M; Bud' ko, S L

    2011-04-28

    Bulk magnetization and ¹H static and magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of two magnetically heterogeneous model systems based on laponite (LAP) layered silicate or polystyrene (PS) with low and high proton concentration, respectively, and ferrimagnetic Fe₂O₃ nano- or micro-particles have been studied. In LAP+Fe₂O₃, a major contribution to the NMR signal broadening is due to the dipolar coupling between the magnetic moments of protons and magnetic particles. In PS+Fe₂O₃, due to the higher proton concentration in polystyrene and stronger proton–proton dipolar coupling, an additional broadening is observed, i.e. ¹H MAS NMR spectra of magnetically heterogeneous systems are sensitive to both proton–magnetic particles and proton–proton dipolar couplings. An increase of the volume magnetization by ~1 emu/cm³ affects the ¹H NMR signal width in a way that is similar to an increase of the proton concentration by ~2×10²²/cm³. ¹H MAS NMR spectra, along with bulk magnetization measurements, allow the accurate determination of the hydrogen concentration in magnetically heterogeneous systems.

  11. Molecular Structures from [superscript 1]H NMR Spectra: Education Aided by Internet Programs

    ERIC Educational Resources Information Center

    Debska, Barbara; Guzowska-Swider, Barbara

    2007-01-01

    The article presents the way in which freeware Internet programs can be applied to teach [superscript 1]H NMR spectroscopy. The computer programs described in this article are part of the educational curriculum that explores spectroscopy and spectra interpretation. (Contains 6 figures.)

  12. Improving the chemical shift dispersion of multidimensional NMR spectra of intrinsically disordered proteins.

    PubMed

    Bermel, Wolfgang; Bruix, Marta; Felli, Isabella C; Kumar M V, Vasantha; Pierattelli, Roberta; Serrano, Soraya

    2013-03-01

    Intrinsically disordered proteins (IDPs) have recently attracted the attention of the scientific community challenging the well accepted structure-function paradigm. In the characterization of the dynamic features of proteins nuclear magnetic resonance spectroscopy (NMR) is a strategic tool of investigation. However the peculiar properties of IDPs, with the lack of a unique 3D structure and their high flexibility, have a strong impact on NMR observables (low chemical shift dispersion, efficient solvent exchange broadening) and thus on the quality of NMR spectra. Key aspects to be considered in the design of new NMR experiments optimized for the study of IDPs are discussed. A new experiment, based on direct detection of (13)C(α), is proposed.

  13. Differential Analysis of 2D NMR Spectra: New Natural Products from a Pilot-Scale Fungal Extract Library

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Using a newly developed protocol for the differential analysis of arrays of 2D NMR spectra, we were able to rapidly identify two previously unreported indole alkaloids from a library of unfractionated fungal extracts. Differential analyses of NMR spectra thus constitute an effective tool for the non...

  14. HyperBIRD: a sensitivity-enhanced approach to collecting homonuclear-decoupled proton NMR spectra.

    PubMed

    Donovan, Kevin J; Frydman, Lucio

    2015-01-01

    Samples prepared following dissolution dynamic nuclear polarization (DNP) enable the detection of NMR spectra from low-γ nuclei with outstanding sensitivity, yet have limited use for the enhancement of abundant species like (1)H nuclei. Small- and intermediate-sized molecules, however, show strong heteronuclear cross-relaxation effects: spontaneous processes with an inherent isotopic selectivity, whereby only the (13)C-bonded protons receive a polarization enhancement. These effects are here combined with a recently developed method that delivers homonuclear-decoupled (1)H spectra in natural abundance samples based on heteronuclear couplings to these same, (13)C-bonded nuclei. This results in the HyperBIRD methodology; a single-shot combination of these two effects that can simultaneously simplify and resolve complex, congested (1)H NMR spectra with many overlapping spin multiplets, while achieving 50-100 times sensitivity enhancements over conventional thermal counterparts. PMID:25256418

  15. Solid-state NMR spectra of lipid-anchored proteins under magic angle spinning.

    PubMed

    Nomura, Kaoru; Harada, Erisa; Sugase, Kenji; Shimamoto, Keiko

    2014-03-01

    Solid-state NMR is a promising tool for elucidating membrane-related biological phenomena. We achieved the measurement of high-resolution solid-state NMR spectra for a lipid-anchored protein embedded in lipid bilayers under magic angle spinning (MAS). To date, solid-state NMR measurements of lipid-anchored proteins have not been accomplished due to the difficulty in supplying sufficient amount of stable isotope labeled samples in the overexpression of lipid-anchored proteins requiring complex posttranslational modification. We designed a pseudo lipid-anchored protein in which the protein component was expressed in E. coli and attached to a chemically synthesized lipid-anchor mimic. Using two types of membranes, liposomes and bicelles, we demonstrated different types of insertion procedures for lipid-anchored protein into membranes. In the liposome sample, we were able to observe the cross-polarization and the (13)C-(13)C chemical shift correlation spectra under MAS, indicating that the liposome sample can be used to analyze molecular interactions using dipolar-based NMR experiments. In contrast, the bicelle sample showed sufficient quality of spectra through scalar-based experiments. The relaxation times and protein-membrane interaction were capable of being analyzed in the bicelle sample. These results demonstrated the applicability of two types of sample system to elucidate the roles of lipid-anchors in regulating diverse biological phenomena.

  16. 29Si and 27Al MAS NMR spectra of mullites from different kaolinites.

    PubMed

    He, Hongping; Guo, Jiugao; Zhu, Jianxi; Yuan, Peng; Hu, Cheng

    2004-04-01

    Mullites synthesized from four kaolinites with different random defect densities have been studied by 27Al and 29Si magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) and X-ray diffraction (XRD). All these mullites show the same XRD pattern. However, 29Si and 27Al MAS NMR spectra reveal that the mullites derived from kaolinites with high defect densities, have a sillimanite-type Al/Si ordering scheme and are low in silica, whereas those mullites derived from kaolinites with low defect densities, consist of both sillimanite- and mullite-type Al/Si ordering schemes and are rich in silica. PMID:15084323

  17. Intelligent Automated Correction of Baseplane and Systematic Noise in Two-Dimensional NMR Spectra

    NASA Astrophysics Data System (ADS)

    Levy, G. C.; Jeong, G. W.; Yu, J. Q.; Wang, K.

    A computer program useful for 2D NMR data is described that provides automatic two-dimensional baseplane correction and subsequent tl and t2 ridge suppression. The algorithm per forms combined correction of smooth baseplane distortions and sharp ridges in 2D NMR spectra through five steps: (1) identification of resonance peaks and ridges, (2) extraction of initial, putative global baseplane, (3) window filtering of the corresponding time domain, (4) construction of a 2D spectrum free of baseplane distortion, and (5) suppression of ridges, The optimal parameters for baseplane and ridge correction are automatically decided by the program, yielding a greatly improved spectrum, together with more accurate spectral information.

  18. Rapid assignment of solution 31P NMR spectra of large proteins by solid-state spectroscopy.

    PubMed

    Iuga, Adriana; Spoerner, Michael; Ader, Christian; Brunner, Eike; Kalbitzer, Hans Robert

    2006-07-21

    The application of the (31)P NMR spectroscopy to large proteins or protein complexes in solution is hampered by a relatively low intrinsic sensitivity coupled with large line widths. Therefore, the assignment of the phosphorus signals by two-dimensional NMR methods in solution is often extremely time consuming. In contrast, the quality of solid-state NMR spectra is not dependent on the molecular mass and the solubility of the protein. For the complex of Ras with the GTP-analogue GppCH(2)p we show solid-state (31)P NMR methods to be more sensitive by almost one order of magnitude than liquid-state NMR. Thus, solid-state NMR seems to be the method of choice for obtaining the resonance assignment of the phosphorus signals of protein complexes in solution. Experiments on Ras.GDP complexes show that the microcrystalline sample can be substituted by a precipitate of the sample and that unexpectedly the two structural states observed earlier in solution are present in crystals as well.

  19. Disentangling Complex Mixtures of Compounds with Near-Identical (1) H and (13) C NMR Spectra using Pure Shift NMR Spectroscopy.

    PubMed

    Castañar, Laura; Roldán, Raquel; Clapés, Pere; Virgili, Albert; Parella, Teodor

    2015-05-18

    The thorough analysis of highly complex NMR spectra using pure shift NMR experiments is described. The enhanced spectral resolution obtained from modern 2D HOBS experiments incorporating spectral aliasing in the (13) C indirect dimension enables the distinction of similar compounds exhibiting near-identical (1) H and (13) C NMR spectra. It is shown that a complete set of extremely small Δδ((1) H) and Δδ((13) C) values, even below the natural line width (1 and 5 ppb, respectively), can be simultaneously determined and assigned.

  20. Measurement of longitudinal relaxation times in crowded 1H NMR spectra using one- and two-dimensional maximum quantum (MAXY) NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Maili; Ye, Chaohui; Farrant, R. Duncan; Nicholson, Jeremy K.; Lindon, John C.

    Methods for measuring longitudinal relaxation times of protons in heavily overlapped 1H NMR spectra are introduced and exemplified using a solution of cholesteryl acetate. The methods are based on 1-dimensional and 2-dimensional maximum quantum NMR spectroscopy (MAXY), which makes possible the selective detection of CH, CH2 and CH31H NMR resonances. A modification of the BIRD pulse sequence to achieve selective inversion of protons bonded to either 12C or 13C is given. The approach should find application in studies of molecular dynamics where isotopic enrichment is not possible and the level of available sample dictates the use of 1H NMR spectroscopy.

  1. TCA Cycle Turnover And Serum Glucose Sources By Automated Bayesian Analysis Of NMR Spectra

    SciTech Connect

    Merritt, Matthew E.; Burgess, Shawn; Jeffrey, F. Mark; Sherry, A. Dean; Malloy, Craig; Bretthorst, G. Larry

    2004-04-21

    Changes in sources of serum glucose are indicative of a variety of pathological metabolic states. It is possible to measure the sources of serum glucose by the administration of deuterated water to a subject followed by analysis of the 2H enrichment levels in glucose extracted from plasma from a single blood draw by 2H NMR. Markov Chain Monte Carlo simulations of the posterior probability densities may then be used to evaluate the contribution of glycogenolysis, glycerol, and the Kreb's cycle to serum glucose. Experiments with simulated NMR spectra show that in spectra with a S/N of 20 to 1, the resulting metabolic information may be evaluated with an accuracy of about 4 percent.

  2. TCA Cycle Turnover And Serum Glucose Sources By Automated Bayesian Analysis Of NMR Spectra

    NASA Astrophysics Data System (ADS)

    Merritt, Matthew E.; Burgess, Shawn; Jeffrey, F. Mark; Sherry, A. Dean; Malloy, Craig; Bretthorst, G. Larry

    2004-04-01

    Changes in sources of serum glucose are indicative of a variety of pathological metabolic states. It is possible to measure the sources of serum glucose by the administration of deuterated water to a subject followed by analysis of the 2H enrichment levels in glucose extracted from plasma from a single blood draw by 2H NMR. Markov Chain Monte Carlo simulations of the posterior probability densities may then be used to evaluate the contribution of glycogenolysis, glycerol, and the Kreb's cycle to serum glucose. Experiments with simulated NMR spectra show that in spectra with a S/N of 20 to 1, the resulting metabolic information may be evaluated with an accuracy of about 4 percent.

  3. Interpreting C-13 NMR spectra of technical lignins based on ionization chemical shifts

    SciTech Connect

    Akim, L.G.; Fedulina, T.G.; Shevchenko, S.M.

    1996-10-01

    Newly developed technique of C-13 NMR spectroscopy of ionized lignins in aqueous alkali has been applied to analysis of the chemical structure of technical lignins. Ionization of phenolic and carboxylic hydroxyl groups has a strong effect on the electronic structure of lignin and leads to significant changes in C-13 NMR spectra of the polymer. Comparative analysis of the spectra of organosolv and alkali lignins in neutral organic and aqueous alkaline media based on the data obtained for lignin model compounds demonstrated the usefulness and scope of applicability of the method. This method was especially useful when applied to a highly degraded alkaline lignin, enhancing our ability to analyze the poorly resolved spectrum. A technique is developed that permits the user to analyze a lignin spectrum in an aqueous alkaline solution without the accompanying spectrum in an organic solution. The research described was made possible by Grant No. NWFOOO from the International Science Foundation.

  4. Experimental and calculated 1H, 13C, 15N NMR spectra of famotidine

    NASA Astrophysics Data System (ADS)

    Barańska, M.; Czarniecki, K.; Proniewicz, L. M.

    2001-05-01

    Famotidine, 3-[[[2-[(aminoiminomethyl)amino]-4-thiazolyl]methyl]thio]- N-(aminosulfonyl), is a histamine H 2-receptor blocker that has been used mainly for the treatment of peptic ulcers and the Zollinger-Ellison syndrome. Its NMR spectra in different solvents were reported earlier; however, detailed interpretation has not been done thus far. In this work, experimental 1H, 13C and 15N NMR spectra of famotidine dissolved in DMSO-d 6 are shown. The assignment of observed chemical shifts is based on quantum chemical calculation at the Hartree-Fock/6-31G ∗ level. The geometry optimization of the famotidine molecule with two internal hydrogen bonds, i.e. [N(3)-H(23)⋯N(9) and N(3)⋯H(34)-N(20)], is done by using the B3LYP method with the 6-31G ∗ basis set.

  5. Sensitivity enhancement of MQMAS NMR spectra of spin 3/2 nuclei using hyperbolic secant pulses

    NASA Astrophysics Data System (ADS)

    Siegel, Renée; Nakashima, Thomas T.; Wasylishen, Roderick E.

    2005-02-01

    The use of hyperbolic secant (HS) pulses to enhance the intensity of the central transition in MQMAS experiments for spin 3/2 quadrupolar nuclei is investigated by examining 87Rb NMR spectra of a powder sample of RbNO 3. The application of HS pulses prior to the triple-quantum (3Q) excitation provides sensitivity enhancements in MQMAS spectra that are superior to those previously reported. For the conversion of 3Q to single-quantum (1Q) observables, the HS pulses have an efficiency similar to that reported for double frequency sweeps (DFS) but greater than that of the fast amplitude modulation (FAM) technique.

  6. Deuteron and triton magnetic moments from NMR spectra of the hydrogen molecule

    NASA Astrophysics Data System (ADS)

    Puchalski, Mariusz; Komasa, Jacek; Pachucki, Krzysztof

    2015-08-01

    We present a theory and calculations of the nuclear magnetic shielding with finite nuclear mass effects and determine the magnetic moments of deuteron and triton using the known NMR spectra of HD and HT molecules. The results μd=0.857 438 234 6 (53 ) μN and μt=2.978 962 471 (10 ) μN are more accurate and in good agreement with the currently accepted values.

  7. Fast acquisition of multidimensional NMR spectra of solids and mesophases using alternative sampling methods.

    PubMed

    Lesot, Philippe; Kazimierczuk, Krzysztof; Trébosc, Julien; Amoureux, Jean-Paul; Lafon, Olivier

    2015-11-01

    Unique information about the atom-level structure and dynamics of solids and mesophases can be obtained by the use of multidimensional nuclear magnetic resonance (NMR) experiments. Nevertheless, the acquisition of these experiments often requires long acquisition times. We review here alternative sampling methods, which have been proposed to circumvent this issue in the case of solids and mesophases. Compared to the spectra of solutions, those of solids and mesophases present some specificities because they usually display lower signal-to-noise ratios, non-Lorentzian line shapes, lower spectral resolutions and wider spectral widths. We highlight herein the advantages and limitations of these alternative sampling methods. A first route to accelerate the acquisition time of multidimensional NMR spectra consists in the use of sparse sampling schemes, such as truncated, radial or random sampling ones. These sparsely sampled datasets are generally processed by reconstruction methods differing from the Discrete Fourier Transform (DFT). A host of non-DFT methods have been applied for solids and mesophases, including the G-matrix Fourier transform, the linear least-square procedures, the covariance transform, the maximum entropy and the compressed sensing. A second class of alternative sampling consists in departing from the Jeener paradigm for multidimensional NMR experiments. These non-Jeener methods include Hadamard spectroscopy as well as spatial or orientational encoding of the evolution frequencies. The increasing number of high field NMR magnets and the development of techniques to enhance NMR sensitivity will contribute to widen the use of these alternative sampling methods for the study of solids and mesophases in the coming years.

  8. Distinguishing Vaccinium species by chemical fingerprinting based on NMR spectra, validated with spectra collected in different laboratories.

    PubMed

    Markus, Michelle A; Ferrier, Jonathan; Luchsinger, Sarah M; Yuk, Jimmy; Cuerrier, Alain; Balick, Michael J; Hicks, Joshua M; Killday, K Brian; Kirby, Christopher W; Berrue, Fabrice; Kerr, Russell G; Knagge, Kevin; Gödecke, Tanja; Ramirez, Benjamin E; Lankin, David C; Pauli, Guido F; Burton, Ian; Karakach, Tobias K; Arnason, John T; Colson, Kimberly L

    2014-06-01

    A method was developed to distinguish Vaccinium species based on leaf extracts using nuclear magnetic resonance spectroscopy. Reference spectra were measured on leaf extracts from several species, including lowbush blueberry (Vaccinium angustifolium), oval leaf huckleberry (Vaccinium ovalifolium), and cranberry (Vaccinium macrocarpon). Using principal component analysis, these leaf extracts were resolved in the scores plot. Analysis of variance statistical tests demonstrated that the three groups differ significantly on PC2, establishing that the three species can be distinguished by nuclear magnetic resonance. Soft independent modeling of class analogies models for each species also showed discrimination between species. To demonstrate the robustness of nuclear magnetic resonance spectroscopy for botanical identification, spectra of a sample of lowbush blueberry leaf extract were measured at five different sites, with different field strengths (600 versus 700 MHz), different probe types (cryogenic versus room temperature probes), different sample diameters (1.7 mm versus 5 mm), and different consoles (Avance I versus Avance III). Each laboratory independently demonstrated the linearity of their NMR measurements by acquiring a standard curve for chlorogenic acid (R(2) = 0.9782 to 0.9998). Spectra acquired on different spectrometers at different sites classifed into the expected group for the Vaccinium spp., confirming the utility of the method to distinguish Vaccinium species and demonstrating nuclear magnetic resonance fingerprinting for material validation of a natural health product. PMID:24963620

  9. Distinguishing Vaccinium species by chemical fingerprinting based on NMR spectra, validated with spectra collected in different laboratories.

    PubMed

    Markus, Michelle A; Ferrier, Jonathan; Luchsinger, Sarah M; Yuk, Jimmy; Cuerrier, Alain; Balick, Michael J; Hicks, Joshua M; Killday, K Brian; Kirby, Christopher W; Berrue, Fabrice; Kerr, Russell G; Knagge, Kevin; Gödecke, Tanja; Ramirez, Benjamin E; Lankin, David C; Pauli, Guido F; Burton, Ian; Karakach, Tobias K; Arnason, John T; Colson, Kimberly L

    2014-06-01

    A method was developed to distinguish Vaccinium species based on leaf extracts using nuclear magnetic resonance spectroscopy. Reference spectra were measured on leaf extracts from several species, including lowbush blueberry (Vaccinium angustifolium), oval leaf huckleberry (Vaccinium ovalifolium), and cranberry (Vaccinium macrocarpon). Using principal component analysis, these leaf extracts were resolved in the scores plot. Analysis of variance statistical tests demonstrated that the three groups differ significantly on PC2, establishing that the three species can be distinguished by nuclear magnetic resonance. Soft independent modeling of class analogies models for each species also showed discrimination between species. To demonstrate the robustness of nuclear magnetic resonance spectroscopy for botanical identification, spectra of a sample of lowbush blueberry leaf extract were measured at five different sites, with different field strengths (600 versus 700 MHz), different probe types (cryogenic versus room temperature probes), different sample diameters (1.7 mm versus 5 mm), and different consoles (Avance I versus Avance III). Each laboratory independently demonstrated the linearity of their NMR measurements by acquiring a standard curve for chlorogenic acid (R(2) = 0.9782 to 0.9998). Spectra acquired on different spectrometers at different sites classifed into the expected group for the Vaccinium spp., confirming the utility of the method to distinguish Vaccinium species and demonstrating nuclear magnetic resonance fingerprinting for material validation of a natural health product.

  10. Distinguishing Vaccinium Species by Chemical Fingerprinting Based on NMR Spectra, Validated with Spectra Collected in Different Laboratories

    PubMed Central

    Markus, Michelle A.; Ferrier, Jonathan; Luchsinger, Sarah M.; Yuk, Jimmy; Cuerrier, Alain; Balick, Michael J.; Hicks, Joshua M.; Killday, K. Brian; Kirby, Christopher W.; Berrue, Fabrice; Kerr, Russell G.; Knagge, Kevin; Gödecke, Tanja; Ramirez, Benjamin E.; Lankin, David C.; Pauli, Guido F.; Burton, Ian; Karakach, Tobias K.; Arnason, John T.; Colson, Kimberly L.

    2014-01-01

    A method was developed to distinguish Vaccinium species based on leaf extracts using nuclear magnetic resonance spectroscopy. Reference spectra were measured on leaf extracts from several species, including lowbush blueberry (Vaccinium angustifolium), oval leaf huckleberry (Vaccinium ovalifolium), and cranberry (Vaccinium macrocarpon). Using principal component analysis, these leaf extracts were resolved in the scores plot. Analysis of variance statistical tests demonstrated that the three groups differ significantly on PC2, establishing that the three species can be distinguished by nuclear magnetic resonance. Soft independent modeling of class analogies models for each species also showed discrimination between species. To demonstrate the robustness of nuclear magnetic resonance spectroscopy for botanical identification, spectra of a sample of lowbush blueberry leaf extract were measured at five different sites, with different field strengths (600 versus 700 MHz), different probe types (cryogenic versus room temperature probes), different sample diameters (1.7 mm versus 5 mm), and different consoles (Avance I versus Avance III). Each laboratory independently demonstrated the linearity of their NMR measurements by acquiring a standard curve for chlorogenic acid (R2 = 0.9782 to 0.9998). Spectra acquired on different spectrometers at different sites classifed into the expected group for the Vaccinium spp., confirming the utility of the method to distinguish Vaccinium species and demonstrating nuclear magnetic resonance fingerprinting for material validation of a natural health product. PMID:24963620

  11. Exploring the use of Generalized Indirect Covariance to reconstruct pure shift NMR spectra: Current Pros and Cons.

    PubMed

    Fredi, André; Nolis, Pau; Cobas, Carlos; Martin, Gary E; Parella, Teodor

    2016-05-01

    The current Pros and Cons of a processing protocol to generate pure chemical shift NMR spectra using Generalized Indirect Covariance are presented and discussed. The transformation of any standard 2D homonuclear and heteronuclear spectrum to its pure shift counterpart by using a reference DIAG spectrum is described. Reconstructed pure shift NMR spectra of NOESY, HSQC, HSQC-TOCSY and HSQMBC experiments are reported for the target molecule strychnine.

  12. 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.

  13. (129) Xe and (131) Xe nuclear magnetic dipole moments from gas phase NMR spectra.

    PubMed

    Makulski, Włodzimierz

    2015-04-01

    (3) He, (129) Xe and (131) Xe NMR measurements of resonance frequencies in the magnetic field B0=11.7586 T in different gas phase mixtures have been reported. Precise radiofrequency values were extrapolated to the zero gas pressure limit. These results combined with new quantum chemical values of helium and xenon nuclear magnetic shielding constants were used to determine new accurate nuclear magnetic moments of (129) Xe and (131) Xe in terms of that of the (3) He nucleus. They are as follows: μ((129) Xe) = -0.7779607(158)μN and μ((131) Xe) = +0.6918451(70)μN . By this means, the new 'helium method' for estimations of nuclear dipole moments was successfully tested. Gas phase NMR spectra demonstrate the weak intermolecular interactions observed on the (3) He and (129) Xe and (131) Xe shielding in the gaseous mixtures with Xe, CO2 and SF6 .

  14. Predicting the spin state of paramagnetic iron complexes by DFT calculation of proton NMR spectra.

    PubMed

    Borgogno, Andrea; Rastrelli, Federico; Bagno, Alessandro

    2014-07-01

    Many transition-metal complexes easily change their spin state S in response to external perturbations (spin crossover). Determining such states and their dynamics can play a central role in the understanding of useful properties such as molecular magnetism or catalytic behavior, but is often far from straightforward. In this work we demonstrate that, at a moderate computational cost, density functional calculations can predict the correct ground spin state of Fe(ii) and Fe(iii) complexes and can then be used to determine the (1)H NMR spectra of all spin states. Since the spectral features are remarkably different according to the spin state, calculated (1)H NMR resonances can be used to infer the correct spin state, along with supporting the structure elucidation of numerous paramagnetic complexes.

  15. Achievement of 1020MHz NMR.

    PubMed

    Hashi, Kenjiro; Ohki, Shinobu; Matsumoto, Shinji; Nishijima, Gen; Goto, Atsushi; Deguchi, Kenzo; Yamada, Kazuhiko; Noguchi, Takashi; Sakai, Shuji; Takahashi, Masato; Yanagisawa, Yoshinori; Iguchi, Seiya; Yamazaki, Toshio; Maeda, Hideaki; Tanaka, Ryoji; Nemoto, Takahiro; Suematsu, Hiroto; Miki, Takashi; Saito, Kazuyoshi; Shimizu, Tadashi

    2015-07-01

    We have successfully developed a 1020MHz (24.0T) NMR magnet, establishing the world's highest magnetic field in high resolution NMR superconducting magnets. The magnet is a series connection of LTS (low-Tc superconductors NbTi and Nb3Sn) outer coils and an HTS (high-Tc superconductor, Bi-2223) innermost coil, being operated at superfluid liquid helium temperature such as around 1.8K and in a driven-mode by an external DC power supply. The drift of the magnetic field was initially ±0.8ppm/10h without the (2)H lock operation; it was then stabilized to be less than 1ppb/10h by using an NMR internal lock operation. The full-width at half maximum of a (1)H spectrum taken for 1% CHCl3 in acetone-d6 was as low as 0.7Hz (0.7ppb), which was sufficient for solution NMR. On the contrary, the temporal field stability under the external lock operation for solid-state NMR was 170ppb/10h, sufficient for NMR measurements for quadrupolar nuclei such as (17)O; a (17)O NMR measurement for labeled tri-peptide clearly demonstrated the effect of high magnetic field on solid-state NMR spectra. PMID:25978708

  16. 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.

  17. Determination of orientational order parameters from 2H NMR spectra of magnetically partially oriented lipid bilayers.

    PubMed Central

    Schäfer, H; Mädler, B; Sternin, E

    1998-01-01

    The partial orientation of multilamellar vesicles (MLVs) in high magnetic fields is known to affect the shape of 2H NMR spectra. There are numerical methods for extracting either the orientational order parameters of lipid molecules for a random distribution of domain orientations in the sample, or the distribution of orientations for a known set of spectral anisotropies. A first attempt at determining the orientational order parameters in the presence of an unknown nonrandom distribution of orientations is presented. The numerical method is based on the Tikhonov regularization algorithm. It is tested using simulated partially oriented spectra. An experimental spectrum of a phospholipid-ether mixture in water is analyzed as an example. The experimental spectrum is consistent with an ellipsoidal shape of MLVs with a ratio of semiaxes of approximately 3.4. PMID:9533713

  18. Spectral investigations of 2,5-difluoroaniline by using mass, electronic absorption, NMR, and vibrational spectra

    NASA Astrophysics Data System (ADS)

    Kose, Etem; Karabacak, Mehmet; Bardak, Fehmi; Atac, Ahmet

    2016-11-01

    One of the most significant aromatic amines is aniline, a primary aromatic amine replacing one hydrogen atom of a benzene molecule with an amino group (NH2). This study reports experimental and theoretical investigation of 2,5-difluoroaniline molecule (2,5-DFA) by using mass, ultraviolet-visible (UV-vis), 1H and 13C nuclear magnetic resonance (NMR), Fourier transform infrared and Raman (FT-IR and FT-Raman) spectra, and supported with theoretical calculations. Mass spectrum (MS) of 2,5-DFA is presented with their stabilities. The UV-vis spectra of the molecule are recorded in the range of 190-400 nm in water and ethanol solvents. The 1H and 13C NMR chemical shifts are recorded in CDCl3 solution. The vibrational spectra are recorded in the region 4000-400 cm-1 (FT-IR) and 4000-10 cm-1 (FT-Raman), respectively. Theoretical studies are underpinned the experimental results as described below; 2,5-DFA molecule is optimized by using B3LYP/6-311++G(d,p) basis set. The mass spectrum is evaluated and possible fragmentations are proposed based on the stable structure. The electronic properties, such as excitation energies, oscillator strengths, wavelengths, frontier molecular orbitals (FMO), HOMO and LUMO energies, are determined by time-dependent density functional theory (TD-DFT). The electrostatic potential surface (ESPs), density of state (DOS) diagrams are also prepared and evaluated. In addition to these, reduced density gradient (RDG) analysis is performed, and thermodynamic features are carried out theoretically. The NMR spectra (1H and 13C) are calculated by using the gauge-invariant atomic orbital (GIAO) method. The vibrational spectra of 2,5-DFA molecule are obtained by using DFT/B3LYP method with 6-311++G(d,p) basis set. Fundamental vibrations are assigned based on the potential energy distribution (PED) of the vibrational modes. The nonlinear optical properties (NLO) are also investigated. The theoretical and experimental results give a detailed description of

  19. Sorting signals from protein NMR spectra: SPI, a Bayesian protocol for uncovering spin systems.

    PubMed

    Grishaev, Alexander; Llinás, Miguel

    2002-11-01

    Grouping of spectral peaks into J-connected spin systems is essential in the analysis of macromolecular NMR data as it provides the basis for disentangling chemical shift degeneracies. It is a mandatory step before resonance and NOESY cross-peak identities can be established. We have developed SPI, a computational protocol that scrutinizes peak lists from homo- and hetero-nuclear multidimensional NMR spectra and progressively assembles sets of resonances into consensus J- and/or NOE-connected spin systems. SPI estimates the likelihood of nuclear spin resonances appearing at defined frequencies given sets of cross-peaks measured from multi-dimensional experiments. It quantifies spin system matching probabilities via Bayesian inference. The protocol takes advantage of redundancies in the number of connectivities revealed by suites of diverse NMR experiments, systematically tracking the adequacy of each grouping hypothesis. SPI was tested on 2D homonuclear and 2D/3D(15)N-edited data recorded from two protein modules, the col 2 domain of matrix metalloproteinase-2 (MMP-2) and the kringle 2 domain of plasminogen, of 60 and 83 amino acid residues, respectively. For these protein domains SPI identifies approximately 95% unambiguous resonance frequencies, a relatively good performance vis-à-vis the reported 'manual' (interactive) analyses. Abbreviations and Acronyms: SPI, SPin Identification; BMRB, BioMagResBank (Madison, WI).

  20. Structures of Si-Carbohydrate Aqueous Complexes: Comparison of NMR Spectra and Molecular Orbital Results

    NASA Astrophysics Data System (ADS)

    Kubicki, J. D.; Heaney, P. J.

    2002-12-01

    Researchers recently have made the discovery that hypercoordinate Si-sorbitol complexes will readily form in biologically relevant fluids, and they have reported the first evidence for a transient organosilicon complex generated within the life cycle of an organism. These interpretations are based upon peak assignments of Si-29 NMR spectra that invoke Si-polyol complexes with Si in five- and six-fold coordination states. However, ab initio analyses of the proposed organosilicon structures do not reproduce the experimentally observed chemical shifts. We have successfully modeled one of the observed Si-29 chemical shifts with a 5-fold Si-disorbitol complex involving 5-membered ring configurations (i.e., Si-O-C-C-O), which yielded Si-29 chemical shifts that closely matched the observed values in the -100 to -102 ppm range. Likewise, Si-29 NMR peaks near -144 ppm were well fit by a model in which a 6-fold Si was complexed to three sorbitol molecules in a 5-membered ring configuration. The ability to simulate observed NMR signals using molecular orbital calculations provides strong support for the controversial role of hypercoordinate organosilicon species in the uptake and transport of silica by biological systems. The existence of such complexes in turn may explain other puzzles in Si biogeochemistry, such as the persistence of monomeric silica in concentrated biological fluids and the biofractionation of Si isotopes and Ge.

  1. Quantification of Human Brain Metabolites from in Vivo1H NMR Magnitude Spectra Using Automated Artificial Neural Network Analysis

    NASA Astrophysics Data System (ADS)

    Hiltunen, Yrjö; Kaartinen, Jouni; Pulkkinen, Juhani; Häkkinen, Anna-Maija; Lundbom, Nina; Kauppinen, Risto A.

    2002-01-01

    Long echo time (TE=270 ms) in vivo proton NMR spectra resembling human brain metabolite patterns were simulated for lineshape fitting (LF) and quantitative artificial neural network (ANN) analyses. A set of experimental in vivo1H NMR spectra were first analyzed by the LF method to match the signal-to-noise ratios and linewidths of simulated spectra to those in the experimental data. The performance of constructed ANNs was compared for the peak area determinations of choline-containing compounds (Cho), total creatine (Cr), and N-acetyl aspartate (NAA) signals using both manually phase-corrected and magnitude spectra as inputs. The peak area data from ANN and LF analyses for simulated spectra yielded high correlation coefficients demonstrating that the peak areas quantified with ANN gave similar results as LF analysis. Thus, a fully automated ANN method based on magnitude spectra has demonstrated potential for quantification of in vivo metabolites from long echo time spectroscopic imaging.

  2. Quantum Mechanical Calculations to Interpret Vibrational and NMR Spectra of Organic Compounds Adsorbed onto Mineral Surfaces

    NASA Astrophysics Data System (ADS)

    Kubicki, J. D.

    2008-12-01

    Vibrational (e.g., ATR FTIR and Raman) and nuclear magnetic resonance (NMR) spectroscopies provide excellent information on the bonding and atomic environment of adsorbed organic compounds. However, interpretation of observed spectra collected for organic compounds adsorbed onto mineral surfaces can be complicated by the lack of comparable analogs of known structure and uncertainties about the mineral surface structure. Quantum mechanical calculations provide a method for testing interpretations of observed spectra because models can be built to mimic predicted structures, and the results are independent of experimental parameters (i.e., no fitting to data is necessary). In this talk, methodologies for modeling vibrational frequencies and NMR chemical shifts of adsorbed organic compounds are discussed. Examples included salicylic acid (as an analog for important binding functional groups in humic acids) adsorbed onto aluminum oxides, organic phosphoryl compounds that represent herbicides and bacterial extracellular polymeric substances (EPS), and ofloxacin (a common agricultural antibiotic). The combination of the ability of quantum mechanical calculations to predict structures, spectroscopic parameters and energetics of adsorption with experimental data on these same properties allows for more definitive construction of surface complex models.

  3. Assignment of congested NMR spectra: Carbonyl backbone enrichment via the Entner Doudoroff pathway

    NASA Astrophysics Data System (ADS)

    Goldbourt, Amir; Day, Loren A.; McDermott, Ann E.

    2007-12-01

    In NMR spectra of complex proteins, sparse isotope enrichment can be important, in that the removal of many 13C- 13C homonuclear J-couplings can narrow the lines and thereby facilitate the process of spectral assignment and structure elucidation. We present a simple scheme for selective yet extensive isotopic enrichment applicable for production of proteins in organisms utilizing the Entner-Doudoroff (ED) metabolic pathway. An enrichment scheme so derived is demonstrated in the context of a magic-angle spinning solid-state NMR (MAS SSNMR) study of Pf1 bacteriophage, the host of which is Pseudomonas aeruginosa, strain K (PAK), an organism that uses the ED pathway for glucose catabolism. The intact and infectious Pf1 phage in this study was produced by infected PAK cells grown on a minimal medium containing 1- 13C D-glucose ( 13C in position 1) as the sole carbon source, as well as 15NH 4Cl as the only nitrogen source. The 37 MDa Pf1 phage consists of about 93% major coat protein, 1% minor coat proteins, and 6% single-stranded, circular DNA. As a consequence of this composition and the enrichment scheme, the resonances in the MAS SSNMR spectra of the Pf1 sample were almost exclusively due to carbonyl carbons in the major coat protein. Moreover, 3D heteronuclear NCOCX correlation experiments also show that the amino acids leucine, serine, glycine, and tyrosine were not isotopically enriched in their carbonyl positions (although most other amino acids were), which is as expected based upon considerations of the ED metabolic pathway. 3D NCOCX NMR data and 2D 15N- 15N data provided strong verification of many previous assignments of 15N amide and 13C carbonyl shifts in this highly congested spectrum; both the semi-selective enrichment patterns and the narrowed linewidths allowed for greater certainty in the assignments as compared with use of uniformly enriched samples alone.

  4. MATCAKE: a flexible toolbox for 2D NMR spectra integration by CAKE algorithm

    NASA Astrophysics Data System (ADS)

    Romano, Rocco; Acernese, Fausto; Vilasi, Silvia; Paris, Debora; Motta, Andrea; Barone, Fabrizio

    2011-04-01

    MatCAKE (www.cake.unisa.it) is a toolbox for integrating 2D NMR spectra by the CAKE (Monte CArlo peaK volume Estimation)1 algorithm within the Matlab environment (www.mathworks.com). Quantitative information from multidimensional NMR experiments can be obtained by peak volume integration. The standard procedure (selection of a region around the chosen peak and addition of all values) is often biased by poor peak definition because of peak overlap. CAKE is a simple algorithm designed for volume integration of (partially) overlapping peaks. Assuming the axial symmetry of two-dimensional NMR peaks, as it occurs in NOESY and TOCSY when Lorentz-Gauss transformation of the signals is carried out, CAKE estimates the peak volume by multiplying a volume fraction by a factor R. It represents a proportionality ratio between the total and the fractional volume, which is identified as a slice in an exposed region of the overlapping peaks. The volume fraction is obtained via Monte Carlo Hit-or-Miss technique, which proved to be the most efficient because of the small region and the limited number of points within the selected area. Due to the large number of software packages available for processing nuclear magnetic resonance data, MatCAKE is designed just for implementing the new CAKE algorithm. In MatCAKe, in fact, only already processed bidimensional spectra are imported and, at the moment, the only volume integration (by CAKE and by the most simple standard procedure) are allowed. MatCAKE is a free software at disposal for the scientific community and can be obtained on line at the web address cake.unisa.it.

  5. Cu-NMR spectra in UCu4Ni uncover site disorder

    NASA Astrophysics Data System (ADS)

    Bernal, O. O.; Rose, D. A.; Wu, Hsin-Ju; Chiang, M.; MacLaughlin, D. E.; Stewart, G. R.; Kim, J. S.

    2012-12-01

    Cu-NMR measurements in a random powder of UCu4Ni reveal two types of spectral lines for each of the two isotopes of naturally abundant Cu in the material. These lines, which we label L1 and L2, point to the existence of two inequivalent Cu sites in the sample. We present a study of the NMR line shape in UCu4Ni at three different frequencies (in the range from 40-70 MHz) and two temperature values (10 K and 150 K), that allow us to assign the lines to particular Cu sites. L1 is strongly broadened as the frequency decreases, but changes less with increasing temperature. In contrast, the width of L2 grows in proportion to frequency and decreases noticeably with increasing temperature. This behavior indicates that the crystallographic site corresponding to L1 is exposed to electric field gradients and has lower point symmetry than the site corresponding to L2, which displays some anisotropy but no discernible quadrupole effects. By comparison with the Cu-NMR spectra in UCu4Pd, where only one type of Cu-NMR line has been observed clearly, we can associate L1 with Cu(16e) nuclei: Cu nuclei sitting at the 16e site (Wyckoff notation) in the AuBe5 structure of the parent compound UCu5. This leaves L2 as originating from Cu(4c) nuclei; i.e., those sitting at the 4c site of the same structure. Unlike in UCu4Pd, the appearance of signal from Cu(4c) nuclei in the Ni compound is clear evidence of site disorder in UCu4Ni.

  6. Automated data evaluation and modelling of simultaneous (19) F-(1) H medium-resolution NMR spectra for online reaction monitoring.

    PubMed

    Zientek, Nicolai; Laurain, Clément; Meyer, Klas; Paul, Andrea; Engel, Dirk; Guthausen, Gisela; Kraume, Matthias; Maiwald, Michael

    2016-06-01

    Medium-resolution nuclear magnetic resonance spectroscopy (MR-NMR) currently develops to an important analytical tool for both quality control and process monitoring. In contrast to high-resolution online NMR (HR-NMR), MR-NMR can be operated under rough environmental conditions. A continuous re-circulating stream of reaction mixture from the reaction vessel to the NMR spectrometer enables a non-invasive, volume integrating online analysis of reactants and products. Here, we investigate the esterification of 2,2,2-trifluoroethanol with acetic acid to 2,2,2-trifluoroethyl acetate both by (1) H HR-NMR (500 MHz) and (1) H and (19) F MR-NMR (43 MHz) as a model system. The parallel online measurement is realised by splitting the flow, which allows the adjustment of quantitative and independent flow rates, both in the HR-NMR probe as well as in the MR-NMR probe, in addition to a fast bypass line back to the reactor. One of the fundamental acceptance criteria for online MR-MNR spectroscopy is a robust data treatment and evaluation strategy with the potential for automation. The MR-NMR spectra are treated by an automated baseline and phase correction using the minimum entropy method. The evaluation strategies comprise (i) direct integration, (ii) automated line fitting, (iii) indirect hard modelling (IHM) and (iv) partial least squares regression (PLS-R). To assess the potential of these evaluation strategies for MR-NMR, prediction results are compared with the line fitting data derived from the quantitative HR-NMR spectroscopy. Although, superior results are obtained from both IHM and PLS-R for (1) H MR-NMR, especially the latter demands for elaborate data pretreatment, whereas IHM models needed no previous alignment. Copyright © 2015 John Wiley & Sons, Ltd.

  7. Spatially encoded pulse sequences for the acquisition of high resolution NMR spectra in inhomogeneous fields

    NASA Astrophysics Data System (ADS)

    Shapira, Boaz; Frydman, Lucio

    2006-09-01

    We have recently proposed a protocol for retrieving nuclear magnetic resonance (NMR) spectra based on a spatially-dependent encoding of the MR interactions. It has also been shown that the spatial selectivity with which spins are manipulated during such encoding opens up new avenues towards the removal of magnetic field inhomogeneities; not by demanding extreme Bo field uniformities, but rather by compensating for the dephasing effects introduced by the field distribution at a radiofrequency excitation and/or refocusing level. The present study discusses in further detail a number of strategies deriving from this principle, geared at acquiring both uni- as well as multi-dimensional spectroscopic data at high resolution conditions. Different variants are presented, tailored according to the relative sensitivity and chemical nature of the spin system being explored. In particular a simple multi-scan experiment is discussed capable of affording substantial improvements in the spectral resolution, at nearly no sensitivity or scaling penalties. This new compensation scheme is therefore well-suited for the collection of high-resolution data in low-field systems possessing limited signal-to-noise ratios, where magnetic field heterogeneities might present a serious obstacle. Potential areas of applications of these techniques include high-field in vivo NMR studies in regions near tissue/air interfaces, clinical low field MR spectroscopy on relatively large off-center volumes difficult to shim, and ex situ NMR. The principles of the different compensation methods are reviewed and experimentally demonstrated for one-dimensional inhomogeneities; further improvements and extensions are briefly discussed.

  8. Characterization of Paramagnetic Reactive Intermediates: Predicting the NMR Spectra of Iron(IV)-Oxo Complexes by DFT.

    PubMed

    Borgogno, Andrea; Rastrelli, Federico; Bagno, Alessandro

    2015-09-01

    The relative energies of spin states of several iron(IV)-oxo complexes and related species have been calculated with DFT methods by employing the B3LYP* functional. We show that such calculations can predict the correct ground spin state of Fe(IV) complexes and can then be used to determine the (1) H NMR spectra of all spin states; the spectral features are remarkably different, hence calculated paramagnetic (1) H NMR spectra can be used to support the structure elucidation of numerous paramagnetic complexes. Applications to a number of stable and reactive iron(IV)-oxo species are described.

  9. Investigation of broad resonances in 31P NMR spectra of the human brain in vivo.

    PubMed

    McNamara, R; Arias-Mendoza, F; Brown, T R

    1994-08-01

    Broad resonances that lie underneath the familiar small molecule profile of in vivo 31P NMR spectra can make accurate spectral integration of these mobile phosphates difficult. The two major broad components are the phosphate contained in the hydroxyapatite in cranial bone and the phosphodiester moiety in partially mobile membrane phospholipids. They can be removed with post-acquisition processing but this results in distortion of lineshapes and intensities and interferes with accurate quantitation. We have employed an off-resonance saturation procedure to eliminate the bone resonance and isolate the signal from the membrane phospholipids by subtraction. Selective saturation of the phospholipid resonance increases the clarity of the sharp peaks downfield from the phosphocreatine peak. Selective saturation 3-D chemical shift imaging techniques were used to create a localized phospholipid profile of the entire brain simultaneously. Monitoring localized phospholipid concentration may be important in studying demyelinating diseases. PMID:7848814

  10. An analytical derivation of a popular approximation of the Voigt function for quantification of NMR spectra.

    PubMed

    Bruce, S D; Higinbotham, J; Marshall, I; Beswick, P H

    2000-01-01

    The approximation of the Voigt line shape by the linear summation of Lorentzian and Gaussian line shapes of equal width is well documented and has proved to be a useful function for modeling in vivo (1)H NMR spectra. We show that the error in determining peak areas is less than 0.72% over a range of simulated Voigt line shapes. Previous work has concentrated on empirical analysis of the Voigt function, yielding accurate expressions for recovering the intrinsic Lorentzian component of simulated line shapes. In this work, an analytical approach to the approximation is presented which is valid for the range of Voigt line shapes in which either the Lorentzian or Gaussian component is dominant. With an empirical analysis of the approximation, the direct recovery of T(2) values from simulated line shapes is also discussed. PMID:10617435

  11. Fractional volume integration in two-dimensional NMR spectra: CAKE, a Monte Carlo approach.

    PubMed

    Romano, Rocco; Paris, Debora; Acernese, Fausto; Barone, Fabrizio; Motta, Andrea

    2008-06-01

    Quantitative information from multi-dimensional NMR experiments can be obtained by peak volume integration. The standard procedure (selection of a region around the chosen peak and addition of all values) is often biased by poor peak definition because of peak overlap. Here we describe a simple method, called CAKE, for volume integration of (partially) overlapping peaks. Assuming the axial symmetry of two-dimensional NMR peaks, as it occurs in NOESY and TOCSY when Lorentz-Gauss transformation of the signals is carried out, CAKE estimates the peak volume by multiplying a volume fraction by a factor R. It represents a proportionality ratio between the total and the fractional volume, which is identified as a slice in an exposed region of the overlapping peaks. The volume fraction is obtained via Monte Carlo Hit-or-Miss technique, which proved to be the most efficient because of the small region and the limited number of points within the selected area. Tests on simulated and experimental peaks, with different degrees of overlap and signal-to-noise ratios, show that CAKE results in improved volume estimates. A main advantage of CAKE is that the volume fraction can be flexibly chosen so as to minimize the effect of overlap, frequently observed in two-dimensional spectra. PMID:18396078

  12. Fractional volume integration in two-dimensional NMR spectra: CAKE, a Monte Carlo approach

    NASA Astrophysics Data System (ADS)

    Romano, Rocco; Paris, Debora; Acernese, Fausto; Barone, Fabrizio; Motta, Andrea

    2008-06-01

    Quantitative information from multi-dimensional NMR experiments can be obtained by peak volume integration. The standard procedure (selection of a region around the chosen peak and addition of all values) is often biased by poor peak definition because of peak overlap. Here we describe a simple method, called CAKE, for volume integration of (partially) overlapping peaks. Assuming the axial symmetry of two-dimensional NMR peaks, as it occurs in NOESY and TOCSY when Lorentz-Gauss transformation of the signals is carried out, CAKE estimates the peak volume by multiplying a volume fraction by a factor R. It represents a proportionality ratio between the total and the fractional volume, which is identified as a slice in an exposed region of the overlapping peaks. The volume fraction is obtained via Monte Carlo Hit-or-Miss technique, which proved to be the most efficient because of the small region and the limited number of points within the selected area. Tests on simulated and experimental peaks, with different degrees of overlap and signal-to-noise ratios, show that CAKE results in improved volume estimates. A main advantage of CAKE is that the volume fraction can be flexibly chosen so as to minimize the effect of overlap, frequently observed in two-dimensional spectra.

  13. Fractional volume integration in two-dimensional NMR spectra: CAKE, a Monte Carlo approach

    NASA Astrophysics Data System (ADS)

    Romano, Rocco; Acernese, Fausto; Paris, Debora; Motta, Andrea; Barone, Fabrizio

    2009-03-01

    Quantitative information from multidimensional NMR experiments can be obtained by peak volume integration. The standard procedure (selection of a region around the chosen peak and addition of all values) is often biased by poor peak definition because of peak overlap. Here we describe a simple method, called CAKE, for volume integration of (partially) overlapping peaks. Assuming the axial symmetry of two-dimensional NMR peaks, as it occurs in NOESY and TOCSY when Lorentz-Gauss transformation of the signals is carried out, CAKE estimates the peak volume by multiplying a volume fraction by a factor R. It represents a proportionality ratio between the total and the fractional volume, which is identified as a slice in an exposed region of the overlapping peaks. The volume fraction is obtained via Monte Carlo Hit-or-Miss technique, which proved to be the most efficient because of the small region and the limited number of points within the selected area. Tests on simulated and experimental peaks, with different degrees of overlap and signal-to-noise ratios, show that CAKE results in improved volume estimates. A main advantage of CAKE is that the volume fraction can be flexibly chosen so as to minimize the effect of overlap, frequently observed in two-dimensional spectra.

  14. Spatially localized sup 1 H NMR spectra of metabolites in the human brain

    SciTech Connect

    Hanstock, C.C. ); Rothman, D.L.; Jue, T.; Shulman, R.G. ); Prichard, J.W. )

    1988-03-01

    Using a surface coil, the authors have obtained {sup 1}H NMR spectra from metabolites in the human brain. Localization was achieved by combining depth pulses with image-selected in vivo spectroscopy magnetic field gradient methods. {sup 1}H spectra in which total creatine (3.03 ppm) has a signal/noise ratio of 95:1 were obtained in 4 min from 14 ml of brain. A resonance at 2.02 ppm consisting predominantly of N-acetylaspartate was measured relative to the creatine peak in gray and white matter, and the ratio was lower in the white matter. The spin-spin relaxation times of N-acetylaspartate and creatine were measured in white and gray matter and while creatine relaxation times were the same in both, the N-acetylaspartate relaxation time was longer in white matter. Lactate was detected in the normoxic brain and the average of three measurements was {approx}0.5 mM from comparison with the creatine plus phosphocreatine peak, which was assumed to be 10.5 mM.

  15. 1H NMR spectra of humic and fulvic acids and their peracetic oxidation products

    NASA Astrophysics Data System (ADS)

    Ruggiero, P.; Interesse, F. S.; Cassidei, L.; Sciacovelli, O.

    1980-04-01

    1H NMR spectra of humic (HA) and fulvic (FA) acids and their oxidative degradation products are reported. The HA shows the presence of -( CH2) n - CH3 ( n > 6) chemical fragments belonging to n-alkanes and/or n-fatty acids physically adsorbed onto the macromolecule structure. These fragments are absent in the FA fraction. Both humic fractions reveal the presence of similar amounts of aromatic protons which partly undergo exchange phenomena. The importance of this experimental observation is discussed. Oxidative degradation seems to cause partial cleavage of aromatic rings, more pronounced in the FA than in the HA. The degraded FA shows a higher total acidity and a higher phenolic OH content than the degraded HA. Both degraded fractions display some sharp singlet signals at 1.9 and 3.9 ppm arising from protons belonging to repetitive chemical fragments probably formed during the oxidation reaction. Tentative assignments of these signals are given. A general analysis of the HA and FA degraded spectra seems to indicate that the chemical fragments which undergo peracetic oxidation are substantially similar. The extent of oxidation of the two humic fractions is different. The HA degradation products reveal the presence of oligomeric structures, whereas the degraded FA appears less resistant to the oxidizing agent.

  16. Separation and complete analyses of the overlapped and unresolved 1H NMR spectra of enantiomers by spin selected correlation experiments.

    PubMed

    Prabhu, Uday Ramesh; Baishya, Bikash; Suryaprakash, N

    2008-06-26

    NMR spectroscopic discrimination of optical enantiomers is most often carried out using (2)H and (13)C spectra of chiral molecules aligned in a chiral liquid crystalline solvent. The use of proton NMR for such a purpose is severely hindered due to the spectral complexity and the significant loss of resolution arising from numerous short- and long-distance couplings and the indistinguishable overlap of spectra from both R and S enantiomers. The determination of all the spectral parameters by the analyses of such intricate NMR spectra poses challenges, such as, unraveling of the resonances for each enantiomer, spectral resolution, and simplification of the multiplet pattern. The present study exploits the spin state selection achieved by the two-dimensional (1)H NMR correlation of selectively excited isolated coupled spins (Soft-COSY) of the molecules to overcome these problems. The experiment provides the relative signs and magnitudes of all of the proton-proton couplings, which are otherwise not possible to determine from the broad and featureless one-dimensional (1)H spectra. The utilization of the method for quantification of enantiomeric excess has been demonstrated. The studies on different chiral molecules, each having a chiral center, whose spectral complexity increases with the increasing number of interacting spins, and the advantages and limitations of the method over SERF and DQ-SERF experiments have been reported in this work.

  17. Complete assignment of (1)H and (13)C NMR spectra of standard neo-iota-carrabiose oligosaccharides.

    PubMed

    Jouanneau, Diane; Boulenguer, Patrick; Mazoyer, Jacques; Helbert, William

    2010-02-26

    Standard Eucheuma denticulatum iota-carrageenan was degraded with the Alteromonas fortis iota-carrageenase. The most abundant products, the neo-iota-carratetraose and neo-iota-carrahexaose were purified by permeation gel chromatography, and their corresponding (1)H and (13)C NMR spectra were fully assigned. PMID:20038459

  18. Method for determining molar concentrations of metabolites in complex solutions from two-dimensional 1H-13C NMR spectra.

    PubMed

    Lewis, Ian A; Schommer, Seth C; Hodis, Brendan; Robb, Kate A; Tonelli, Marco; Westler, William M; Sussman, Michael R; Markley, John L

    2007-12-15

    One-dimensional (1D) (1)H nuclear magnetic resonance (NMR) spectroscopy is used extensively for high-throughput analysis of metabolites in biological fluids and tissue extracts. Typically, such spectra are treated as multivariate statistical objects rather than as collections of quantifiable metabolites. We report here a two-dimensional (2D) (1)H-(13)C NMR strategy (fast metabolite quantification, FMQ, by NMR) for identifying and quantifying the approximately 40 most abundant metabolites in biological samples. To validate this technique, we prepared mixtures of synthetic compounds and extracts from Arabidopsis thaliana, Saccharomyces cerevisiae, and Medicago sativa. We show that accurate (technical error 2.7%) molar concentrations can be determined in 12 min using our quantitative 2D (1)H-(13)C NMR strategy. In contrast, traditional 1D (1)H NMR analysis resulted in 16.2% technical error under nearly ideal conditions. We propose FMQ by NMR as a practical alternative to 1D (1)H NMR for metabolomics studies in which 50-mg (extract dry weight) samples can be obtained. PMID:17985927

  19. Method for determining molar concentrations of metabolites in complex solutions from two-dimensional 1H-13C NMR spectra.

    PubMed

    Lewis, Ian A; Schommer, Seth C; Hodis, Brendan; Robb, Kate A; Tonelli, Marco; Westler, William M; Sussman, Michael R; Markley, John L

    2007-12-15

    One-dimensional (1D) (1)H nuclear magnetic resonance (NMR) spectroscopy is used extensively for high-throughput analysis of metabolites in biological fluids and tissue extracts. Typically, such spectra are treated as multivariate statistical objects rather than as collections of quantifiable metabolites. We report here a two-dimensional (2D) (1)H-(13)C NMR strategy (fast metabolite quantification, FMQ, by NMR) for identifying and quantifying the approximately 40 most abundant metabolites in biological samples. To validate this technique, we prepared mixtures of synthetic compounds and extracts from Arabidopsis thaliana, Saccharomyces cerevisiae, and Medicago sativa. We show that accurate (technical error 2.7%) molar concentrations can be determined in 12 min using our quantitative 2D (1)H-(13)C NMR strategy. In contrast, traditional 1D (1)H NMR analysis resulted in 16.2% technical error under nearly ideal conditions. We propose FMQ by NMR as a practical alternative to 1D (1)H NMR for metabolomics studies in which 50-mg (extract dry weight) samples can be obtained.

  20. 13C NMR spectra of 1,3-dipyridyl- and pyridylphenylthioureas. Chemical shift assignments and conformational implications

    NASA Astrophysics Data System (ADS)

    Sudha, L. V.; Sathyanarayana, D. N.; Manogaran, S.

    The 13C NMR spectra of a series of 1,3-dipyridyl- and pyridylphenylthioureas have been obtained. Complete analyses of the experimental spectra have provided the chemical shifts and coupling constants. The spectra of dipyridylthioureas over a temperature range showed important changes which could be attributed to an intramolecular conversion between the two equivalent E,Z and Z,E conformations. The coalescence temperature of the 13C signals leads to a Δ G* of ˜ 58.0 kJ mol -1 for the dynamic process involved. The results show that pyridylphenyl thioureas exist in a single conformation at ambient temperature.

  1. Observation of the Second-Order Quadrupolar Interaction as a Dominating NMR Relaxation Mechanism in Liquids: The Ultraslow Regime of Motion.

    PubMed

    Shen, Jiahui; Terskikh, Victor; Wu, Gang

    2016-09-01

    We report variable-temperature (VT) (17)O NMR spectra of [5-(17)O]-d-glucose in an aqueous solution and in glycerol at 14.1 and 21.1 T. The VT (17)O NMR data cover a wide range of motion for which the molecular rotational correlation time (τc) of glucose changes more than 5 orders of magnitude. The observed line width of the (17)O NMR signal for [5-(17)O]-d-glucose displays a maximum at ω0τc ≈ 1 and a minimum at ω0τc ≈ 150, where ω0 is the angular Larmor frequency of (17)O. Under the ultraslow motion condition (i.e., ω0τc > 150), the line width of the observed (17)O NMR signal increases drastically with τc, suggesting that the second-order quadrupolar interaction becomes the predominant relaxation mechanism. While this relaxation mechanism has long been predicted by theory, the current study reports the first experimental observation of such a phenomenon. The implications of this new relaxation mechanism on the spectral resolution limit in liquid-state NMR spectroscopy for half-integer spins are discussed. PMID:27525537

  2. Vibrational and multinuclear NMR spectra of anionic mercuriomethanes [CH 4-n(HgX) n] n-

    NASA Astrophysics Data System (ADS)

    Breitinger, D. K.; Krumphanzl, U.; Moll, M.

    1990-03-01

    Vibrational spectra of solid sodium sulfitomercuriomethanates Na n[CH 4-n(HgSO 3) n]·nH 2O (2 ≤ and ≤ 4) exhibit high frequencies of the valence vibrations ν as(SO 3) > ν s(SO 3) (average 1057 cm -1) with big differences ν as - ν s (mean 104 cm -1), and ν(HgS) vibrations in the 200 to 230 cm -1 range, thus indicating S-coordinated sulfite ligands. Force field calculations for the ion [C(HgSO 3) 4] 4- yield high force constants K(S-O) = 605 N/m, K(Hg-S) = 258 N/m, and even K(C-Hg) = 181 N/m.- For thiosulfatomercuriomethanates [CH 4-n(HgS 2O 3] n- (1 ≤ n ≤ 4) in aqueous solutions Raman spectra suggest S-coordination with high ν as(SO 3) and ν s(SO 3) (average 1130 cm -1), and low ν(S-S) (˜420 cm -1) frequencies, and strong ν(Hg-S) bands (˜250 cm -1). From 1H, 13C and 199Hg NMR data is concluded that the CHg bond strengths in the series decrease on a lower level than in other mercuriomethanes.- On the whole, the electronic properties of the peripheral ligands X in the mercuriomethanes CH 4-n(HgX) n seem to be more important for the CHg bond strengths than the total charge.

  3. Resolution Improvements in in Vivo1H NMR Spectra with Increased Magnetic Field Strength

    NASA Astrophysics Data System (ADS)

    Gruetter, Rolf; Weisdorf, Sally A.; Rajanayagan, Vasantham; Terpstra, Melissa; Merkle, Hellmut; Truwit, Charles L.; Garwood, Michael; Nyberg, Scott L.; Ugurbil, Kâmil

    1998-11-01

    The measurement of cerebral metabolites using highly homologous localization techniques and similar shimming methods was performed in the human brain at 1.5 and 4 T as well as in the dog and rat brain at 9.4 T. In rat brain, improved resolution was achieved by shimming all first- and second-order shim coils using a fully adiabatic FASTMAP sequence. The spectra showed a clear improvement in spectral resolution for all metabolite resonances with increased field strength. Changes in cerebral glutamine content were clearly observed at 4 T compared to 1.5 T in patients with hepatic encephalopathy. At 9.4 T, glutamine H4 at 2.46 ppm was fully resolved from glutamate H4 at 2.37 ppm, as was the potential resonance from γ-amino-butyric acid at 2.30 ppm and N-acetyl-aspartyl-glutamate at 2.05 ppm. Singlet linewidths were found to be as low as 6 Hz (0.015 ppm) at 9.4 T, indicating a substantial decrease in ppm linewidth with field strength. Furthermore, the methylene peak of creatine was partially resolved from phosphocreatine, indicating a close to 1:1 relationship in gray matter. We conclude that increasing the magnetic field strength increases spectral resolution also for1H NMR, which can lead to more than linear sensitivity gains.

  4. Atomic structure of icosahedral B4C boron carbide from a first principles analysis of NMR spectra.

    PubMed

    Mauri, F; Vast, N; Pickard, C J

    2001-08-20

    Density functional theory is demonstrated to reproduce the 13C and 11B NMR chemical shifts of icosahedral boron carbides with sufficient accuracy to extract previously unresolved structural information from experimental NMR spectra. B4C can be viewed as an arrangement of 3-atom linear chains and 12-atom icosahedra. According to our results, all the chains have a CBC structure. Most of the icosahedra have a B11C structure with the C atom placed in a polar site, and a few percent have a B (12) structure or a B10C2 structure with the two C atoms placed in two antipodal polar sites.

  5. Variations of pH as an additional tool in the analysis of crowded NMR spectra of fucosylated chondroitin sulfates.

    PubMed

    Ustyuzhanina, Nadezhda E; Dmitrenok, Andrey S; Bilan, Maria I; Shashkov, Alexander S; Gerbst, Alexey G; Usov, Anatolii I; Nifantiev, Nikolay E

    2016-03-24

    The influence of pH variation on chemical shift values in NMR spectra of fucosylated chondroitin sulfates was studied using polysaccharides isolated from three sea cucumber species Apostichopus japonicus, Actinopyga mauritiana and Cucumaria japonica. The signals of glucuronic acid residues were found to be the most sensitive to pH changes in comparison to the chemical shifts of the sulfated galactosamine and fucosyl units, most of which were altered insignificantly. It was shown that in the presence of imidazole-HCl buffer (pH 7.2) NMR spectra of the polysaccharides from A. japonicus and A. mauritiana were sufficiently resolved, whereas under acidic conditions their (1)H NMR spectra were complicated by overlapping of H-1 signals of GlcA and GalNAc. In the case of polysaccharide from C. japonica bearing 3-O-fucosylated and 3-O-sulfated glucuronic acid residues in the backbone, acidification of the medium led to separation of H-1 signals of GlcA3S and GalNAc. Therefore, the combination of data obtained at different pH values may be useful for interpretation of overcrowded spectra of fucosylated chondroitin sulfates. PMID:26895544

  6. Variations of pH as an additional tool in the analysis of crowded NMR spectra of fucosylated chondroitin sulfates.

    PubMed

    Ustyuzhanina, Nadezhda E; Dmitrenok, Andrey S; Bilan, Maria I; Shashkov, Alexander S; Gerbst, Alexey G; Usov, Anatolii I; Nifantiev, Nikolay E

    2016-03-24

    The influence of pH variation on chemical shift values in NMR spectra of fucosylated chondroitin sulfates was studied using polysaccharides isolated from three sea cucumber species Apostichopus japonicus, Actinopyga mauritiana and Cucumaria japonica. The signals of glucuronic acid residues were found to be the most sensitive to pH changes in comparison to the chemical shifts of the sulfated galactosamine and fucosyl units, most of which were altered insignificantly. It was shown that in the presence of imidazole-HCl buffer (pH 7.2) NMR spectra of the polysaccharides from A. japonicus and A. mauritiana were sufficiently resolved, whereas under acidic conditions their (1)H NMR spectra were complicated by overlapping of H-1 signals of GlcA and GalNAc. In the case of polysaccharide from C. japonica bearing 3-O-fucosylated and 3-O-sulfated glucuronic acid residues in the backbone, acidification of the medium led to separation of H-1 signals of GlcA3S and GalNAc. Therefore, the combination of data obtained at different pH values may be useful for interpretation of overcrowded spectra of fucosylated chondroitin sulfates.

  7. NMR Spectra Transformed by Electron-Nuclear Coupling as Indicator of Structural Peculiarities of Magnetically Active Molecular Systems.

    PubMed

    Voronov, Vladimir K

    2016-09-01

    The peculiarities of nuclear spin relaxation in the paramagnetic systems have been analyzed taking into account the exchange processes. The analysis is based on the modified Solomon-Bloembergen equations. In this line, the conditions of detecting of the NMR signals of samples are discussed depending on resonance frequency of the NMR spectrometer and characteristic relaxation time. On this basis, (1)H NMR spectra of cobalt semiquinolate complex have been analyzed. It has been shown that the satellite signals observed in the spectrum are caused by hyperfine coupling of the tert-butyl group protons with α and β states (localized on pz orbital of the aromatic carbon) of unpaired electron spin. The relaxation process of the resonance protons is controlled by paramagnetic dipole-dipole coupling. The contact hyperfine coupling does not contribute to the paramagnetic broadening. A mechanism involving paramagnetic molecular structures, which are responsible for intramolecular exchange processes in the cobalt semiquinolate complex, is given. PMID:27513208

  8. A general method for diagonal peak suppression in homonuclear correlated NMR spectra by spatially and frequency selective pulses☆

    PubMed Central

    Glanzer, Simon; Schrank, Evelyne; Zangger, Klaus

    2013-01-01

    Homonuclear two- and multidimensional NMR spectra are standard experiments for the structure determination of small to medium-sized molecules. In the large majority of homonuclear correlated spectra the diagonal contains the most intense peaks. Cross-peaks near the diagonal could overlap with huge tails of diagonal peaks and can therefore be easily overlooked. Here we present a general method for the suppression of peaks along the diagonal in homonuclear correlated spectra. It is based on a spatially selective excitation followed by the suppression of magnetization which has not changed the frequency during the mixing process. In addition to the auto correlation removal, these experiments are also less affected by magnetic field inhomogeneities due to the slice selective excitation, which on the other side leads to a reduced intensity compared to regular homonuclear correlated spectra. PMID:23665403

  9. Resistively detected NMR spectra of the crystal states of the two-dimensional electron gas in a quantizing magnetic field

    NASA Astrophysics Data System (ADS)

    Côté, R.; Simoneau, Alexandre M.

    2016-02-01

    Transport experiments on the two-dimensional electron gas (2DEG) confined into a semiconductor quantum well and subjected to a quantizing magnetic field have uncovered a rich variety of uniform and nonuniform phases such as the Laughlin liquids, the Wigner, bubble, and Skyrme crystals, and the quantum Hall stripe state. Optically pumped nuclear magnetic resonance (OP-NMR) has also been extremely useful in studying the magnetization and dynamics of electron solids with exotic spin textures such as the Skyrme crystal. Recently, it has been demonstrated that a related technique, resistively-detected nuclear magnetic resonance (RD-NMR), could be a good tool to study the topography of the electron solids in the fractional and integer quantum Hall regimes. In this work, we compute theoretically the RD-NMR line shapes of various crystal phases of the 2DEG and study the relation between their spin density and texture and their NMR spectra. This allows us to evaluate the ability of the RD-NMR to discriminate between the various types of crystal states.

  10. Experimental and theoretical studies on compositions, structures, and IR and NMR spectra of functionalized protic ionic liquids.

    PubMed

    Cui, Yingna; Yin, Jingmei; Li, Changping; Li, Shenmin; Wang, Ailing; Yang, Guang; Jia, Yingping

    2016-07-20

    The compositions and structures of amine-based functionalized protic ionic liquids (PILs), namely N,N-dimethyl(cyanoethyl)ammonium propionate (DMCEAP) and N,N-dimethyl(hydroxyethyl)ammonium propionate (DMEOAP) have been investigated systematically by IR and (1)H NMR spectroscopy and density functional theory (DFT) calculations. Analysis of the IR spectra suggests that both DMCEAP and DMEOAP are composed of neutral and ionized species in the liquid phase, the former one mainly existing in the state of precursor molecules, and the latter mainly as ion-pairs. The ratio of precursor molecules to ion-pairs in the liquid phase depends on the types of precursors, especially the functional groups of cations. (1)H NMR spectra indicate that there is a dynamic equilibrium between the neutral and ionized species, probably due to the formation of some intermediates in the PILs. The DFT calculations have been carried out to reveal the conformation, and obtain the corresponding IR and (1)H NMR spectra of the neutral and ionized species, so that the theoretical support to the experimental results can be provided. The present study will help understand the properties of PILs and provide guidance for further applications of PILs. PMID:27385035

  11. Vibrational spectra, monomer, dimer, NBO, HOMO, LUMO and NMR analyses of trans-4-hydroxy-L-proline

    NASA Astrophysics Data System (ADS)

    Xavier, R. John; Dinesh, P.

    2014-07-01

    This work presents the characterization of trans-4-hydroxy-L-proline (abbreviated as THLP) by quantum chemical calculations and spectral techniques. The spectroscopic properties were investigated by FT-IR, FT-Raman and 1H and 13C nuclear magnetic resonance (NMR) techniques. The FT-IR (4000-400 cm-1) and FT-Raman (3500-10 cm-1) spectra in the solid phase were recorded for THLP. The 1H and 13C NMR spectra were recorded in DMSO solution. The energies of THLP are obtained for all the eight conformers form density functional theory (DFT) with 6-311++G(d,p) basis set calculations. From the computational results, C1 conformer is identified as the most stable conformer of THLP. The theoretical wavenumbers were scaled and compared with experimental FT-IR and FT-Raman spectra. The complete assignments were performed on the basis of the experimental results and potential energy distribution (PED) of the vibrational modes, calculated with scaled quantum mechanical (SQM) method in terms of fundamental modes. The values of the total dipole moment (μ) and the first order hyperpolarizability (β) of the investigated compound were computed using B3LYP/6-311++G(d,p) calculations. The calculated HOMO-LUMO energies reveal charges transfer occurs within the molecule. The isotropic chemical shift computed by 1H and 13C NMR chemical shifts of the THLF, calculated using the gauge invariant atomic orbital (GIAO) method also shows good agreement with experimental observations.

  12. Near-silence of isothiocyanate carbon in (13)C NMR spectra: a case study of allyl isothiocyanate.

    PubMed

    Glaser, Rainer; Hillebrand, Roman; Wycoff, Wei; Camasta, Cory; Gates, Kent S

    2015-05-01

    (1)H and (13)C NMR spectra of allyl isothiocyanate (AITC) were measured, and the exchange dynamics were studied to explain the near-silence of the ITC carbon in (13)C NMR spectra. The dihedral angles α = ∠(C1-C2-C3-N4) and β = ∠(C2-C3-N4-C5) describe the conformational dynamics (conformation change), and the bond angles γ = ∠(C3-N4-C5) and ε = ∠(N4-C5-S6) dominate the molecular dynamics (conformer flexibility). The conformation space of AITC contains three minima, Cs-M1 and enantiomers M2 and M2'; the exchange between conformers is very fast, and conformational effects on (13)C chemical shifts are small (νM1 - νM2 < 3 ppm). Isotropic chemical shifts, ICS(γ), were determined for sp, sp(x), and sp(2) N-hybridization, and the γ dependencies of δ(N4) and δ(C5) are very large (10-33 ppm). Atom-centered density matrix propagation trajectories show that every conformer can access a large region of the potential energy surface AITC(γ,ε,...) with 120° < γ < 180° and 155° < ε < 180°. Because the extreme broadening of the (13)C NMR signal of the ITC carbon is caused by the structural flexibility of every conformer of AITC, the analysis provides a general explanation for the near-silence of the ITC carbon in (13)C NMR spectra of organic isothiocyanates.

  13. Singular spectrum analysis for an automated solvent artifact removal and baseline correction of 1D NMR spectra

    NASA Astrophysics Data System (ADS)

    De Sanctis, Silvia; Malloni, Wilhelm M.; Kremer, Werner; Tomé, Ana M.; Lang, Elmar W.; Neidig, Klaus-Peter.; Kalbitzer, Hans Robert

    2011-06-01

    NMR spectroscopy in biology and medicine is generally performed in aqueous solutions, thus in 1H NMR spectroscopy, the dominant signal often stems from the partly suppressed solvent and can be many orders of magnitude larger than the resonances of interest. Strong solvent signals lead to a disappearance of weak resonances of interest close to the solvent artifact and to base plane variations all over the spectrum. The AUREMOL-SSA/ALS approach for automated solvent artifact removal and baseline correction has been originally developed for multi-dimensional NMR spectroscopy. Here, we describe the necessary adaptations for an automated application to one-dimensional NMR spectra. Its core algorithm is still based on singular spectrum analysis (SSA) applied on time domain signals (FIDs) and it is still combined with an automated baseline correction (ALS) in the frequency domain. However, both steps (SSA and ALS) have been modified in order to achieve optimal results when dealing with one-dimensional spectra. The performance of the method has been tested on one-dimensional synthetic and experimental spectra including the back-calculated spectrum of HPr protein and an experimental spectrum of a human urine sample. The latter has been recorded with the typically used NOESY-type 1D pulse sequence including water pre-saturation. Furthermore, the fully automated AUREMOL-SSA/ALS procedure includes the managing of oversampled, digitally filtered and zero-filled data and the correction of the frequency domain phase shift caused by the group delay time shift from the digital finite response filtering.

  14. Matrix-dependent modulation of anisotropic effects on NMR spectra from 7Li+ and 23Na+ encapsulated in cryptands.

    PubMed

    Naumann, Christoph; Kuchel, Philip W

    2013-01-01

    (7)Li and (23)Na NMR spectra of the respective cations in gelatin and ι-carrageenan gels containing cryptand-[2.1.1] (for Li(+)) or cryptand-[2.2.2] (for Na(+)) displayed two transitions: the one at higher frequency corresponded to the cation surrounded by gel, the other to cation inside its appropriately sized cryptand. While binding to cryptands yielded much broader lines and shorter T (1) relaxation times, anisotropic splitting in first order (7)Li or (23)Na NMR spectra was not detected. Stretching the gels resulted in increasing the anisotropic electric field gradient tensor; thus, the NMR transitions of the cation in the gel were split (removal of degeneracy) to display its characteristic 3:4:3 triplet for spin = 3/2 nuclei. The transitions of the cryptand-bound cations (Li(+)-cryptand-[2.1.1] and Na(+)-cryptand-[2.2.2]) showed different extents of interaction with the electric field gradient tensor depending on the composition of the gel matrix. The NMR signal for (7)Li(+)-cryptand-[2.1.1] in stretched gelatin gel showed a five-fold increased splitting as compared to the (7)Li(+) signal in the reference gel. In stretched ι-carrageenan gels, no anisotropic splitting from the cryptand-bound Li(+) was recorded. Steady-state irradiation envelopes or z-spectra showed evidence of Li(+) exchange between isotropic (cryptand) and anisotropic (gel) sites only at higher temperatures (55 °C). For Na(+) bound to the cryptand-[2.2.2], anisotropic splitting (three-fold smaller compared with the (23)Na signal in the reference gel) was only recorded in stretched ι-carrageenan gels, whereas gelatin gels showed only anisotropic splitting for the (23)Na signal in the reference gel.

  15. Analysis of the electronic, IR, and 1H NMR spectra of conjugated oligomers based on 4,4'-triphenylamine vinylene

    NASA Astrophysics Data System (ADS)

    Baryshnikov, G. V.; Minaeva, V. A.; Minaev, B. F.; Sun, V.-H.; Grigoras, M.

    2016-09-01

    Two types of conjugated oligomers based on 4,4'-triphenylamine vinylene have been synthesized and characterized by the methods of IR, UV-visible, and 1H NMR spectroscopy. The corresponding spectra have also been simulated theoretically at the density functional theory level with application of the B3LYP and BMK hybrid exchange-correlation functionals. A comparative analysis of the experimental and theoretical spectra of polymers and oligomers has revealed regularities of the manifestation of spectral signals depending on the conjugation chain length and the presence of a substituent in the triphenylamine core. It has been established, in particular, that the absolute intensity of IR bands satisfies a linear dependence with increase in the degree of polymerization; however, no frequency shift is observed at the same time. The position of the main peak in electron absorption spectra demonstrates the bathochromic shift with an increase in the oligomeric chain length due to the narrowing of the energy gap between the boundary molecular orbitals. Based on the theoretical estimation of the hydrogen atoms chemical shifts, the signals of various protons types in the strongly broadened experimental 1H NMR spectra of the bis-(4-iodine phenyl)-phenylamine and N,N-bis-(4-iodine phenyl)-4'-(phenylethynyl)-phenylamine polymerization products have also been identified.

  16. Biaxial Q-shearing of 27Al 3QMAS NMR spectra: insight into the structural disorder of framework aluminosilicates.

    PubMed

    Kobera, Libor; Brus, Jiri; Klein, Petr; Dedecek, Jiri; Urbanova, Martina

    2014-01-01

    In this contribution, we present the application potentiality of biaxial Q-shearing of (27)Al 3QMAS NMR spectra in the analysis of structural defects of aluminium units in aluminosilicates. This study demonstrates that the combination of various shearing transformations of the recorded (27)Al 3QMAS NMR spectra enables an understanding of the broadening processes of the correlation signals of disordered framework aluminosilicates, for which a wide distribution of (27)Al MAS NMR chemical shifts and quadrupolar parameters (i.e., second-order quadrupolar splitting and quadrupole-induced chemical shifts) can be expected. By combining the suitably selected shearing transformation procedures, the mechanisms of the formation of local defects in aluminosilicate frameworks, including Al/Si substitution effects in the next-nearest neighbouring T-sites, variations in bond angles, and/or variations in the physicochemical nature of charge-balancing counter-ions, can be identified. The proposed procedure has been extensively tested on a range of model aluminosilicate materials (kyanite, γ-alumina, metakaolin, analcime, chabazite, natrolite, phillipsite, mordenite, zeolite A, and zeolite Y).

  17. Spatially resolved NMR spectra for the Swiss cheese model in heavy fermion PuCoGa5 superconductor

    NASA Astrophysics Data System (ADS)

    Das, Tanmoy; Zhu, Jian-Xin; Balatsky, A. V.; Graf, M. J.

    2011-03-01

    Spatially resolved NMR experiments, which probe the local electronic excitations, play a vital role for studying the pairing symmetry of unconventional superconductors. Here we calculate the spatial modulation of the NMR spin-lattice relaxation rate (1/T1) for the Swiss cheese model as a function of impurity concentration in PuCoGa5 superconductor. The local suppression of the superconducting order parameter due to impurities is related to the number of holes in the Swiss cheese model. Our results indicate that Friedel-like oscillations,as seen in the local-density of states near an impurity, are also present in the behavior of 1/T1 as one moves away from the impurity site. We demonstrate that the gap nodes, which are filled by disorder, can be probed by NMR through the local information encoded in the spectra. The advantage of spatially resolved NMR compared to STM measurements is that the former probe is not sensitive to surface states. Work is supported by US DOE.

  18. Ab initio study of 59Co NMR spectra in Co2FeAl1-xSix Heusler alloys

    NASA Astrophysics Data System (ADS)

    Nishihara, H.; Sato, K.; Akai, H.; Takiguchi, C.; Geshi, M.; Kanomata, T.; Sakon, T.; Wada, T.

    2015-05-01

    Ab initio electronic structure calculation of a series of Co2FeAl1-xSix Heusler alloys has been performed, using the Korringa-Kohn-Rostoker-coherent potential approximation method to explain experimental 59Co NMR spectra. Two prominent features are explained semi-quantitatively-a global shift of the 59Co resonance line due to alloying with Al and Si atoms in Co2FeAl1-xSix, and the effect of local disorder in creating distinct satellite lines of 59Co NMR in Co2FeAl. The importance is stressed of the positive contribution to the 59Co hyperfine field from valence electron polarization, which emerges from the half-metallic band structure inherent in Co-based Heusler alloys.

  19. Vibrational spectra, monomer, dimer, NBO, HOMO, LUMO and NMR analyses of trans-4-hydroxy-L-proline.

    PubMed

    Xavier, R John; Dinesh, P

    2014-07-15

    This work presents the characterization of trans-4-hydroxy-L-proline (abbreviated as THLP) by quantum chemical calculations and spectral techniques. The spectroscopic properties were investigated by FT-IR, FT-Raman and (1)H and (13)C nuclear magnetic resonance (NMR) techniques. The FT-IR (4000-400 cm(-1)) and FT-Raman (3500-10 cm(-1)) spectra in the solid phase were recorded for THLP. The (1)H and (13)C NMR spectra were recorded in DMSO solution. The energies of THLP are obtained for all the eight conformers form density functional theory (DFT) with 6-311++G(d,p) basis set calculations. From the computational results, C1 conformer is identified as the most stable conformer of THLP. The theoretical wavenumbers were scaled and compared with experimental FT-IR and FT-Raman spectra. The complete assignments were performed on the basis of the experimental results and potential energy distribution (PED) of the vibrational modes, calculated with scaled quantum mechanical (SQM) method in terms of fundamental modes. The values of the total dipole moment (μ) and the first order hyperpolarizability (β) of the investigated compound were computed using B3LYP/6-311++G(d,p) calculations. The calculated HOMO-LUMO energies reveal charges transfer occurs within the molecule. The isotropic chemical shift computed by (1)H and (13)C NMR chemical shifts of the THLF, calculated using the gauge invariant atomic orbital (GIAO) method also shows good agreement with experimental observations. PMID:24657468

  20. Fast and simple acquisition of solid-state 14N NMR spectra with signal enhancement via population transfer.

    PubMed

    O'Dell, Luke A; Schurko, Robert W

    2009-05-20

    A new approach for the acquisition of static, wideline (14)N NMR powder patterns is outlined. The method involves the use of frequency-swept pulses which serve two simultaneous functions: (1) broad-band excitation of magnetization and (2) signal enhancement via population transfer. The signal enhancement mechanism is described using numerical simulations and confirmed experimentally. This approach, which we call DEISM (Direct Enhancement of Integer Spin Magnetization), allows high-quality (14)N spectra to be acquired at intermediate field strengths in an uncomplicated way and in a fraction of the time required for previously reported methods.

  1. Automatic phase correction of fourier transform NMR spectra based on the dispersion versus absorption (DISPA) lineshape analysis

    NASA Astrophysics Data System (ADS)

    Sotak, Christopher H.; Dumoulin, Charles L.; Newsham, Mark D.

    A method for automatic phase correction of Fourier transform NMR spectra bused on the dispersion versus absorption (DISPA) lineshape analysis is described. The DISPA display of a single misphased Lorentzian line gives a unit circle which has been rotated about the origin (relative to its "reference circle") by a number of degrees equal to the phase misadjustment. This rotation, Φ, is a combination of the zero- and first-order phase angles at the frequency of the resonance. Calculation of Φ for two or more resonances allows the spectral phasing parameters to be determined and applied to correct the spectrum. This approach has been implemented in both automatic and "semi-automatic" modes.

  2. Tendencies of 31P chemical shifts changes in NMR spectra of nucleotide derivatives.

    PubMed

    Lebedev, A V; Rezvukhin, A I

    1984-07-25

    31P NMR chemical shifts of the selected mono- and oligonucleotide derivatives, including the compounds with P-N, P-C, P-S bonds and phosphite nucleotide analogues have been presented. The influence of substituents upon 31P chemical shifts has been discussed. The concrete examples of 31P chemical shifts data application in the field of nucleotide chemistry have been considered.

  3. HiFSA Fingerprinting Applied to Isomers with Near-Identical NMR Spectra: The Silybin/Isosilybin Case

    PubMed Central

    Napolitano, José G.; Lankin, David C.; Graf, Tyler N.; Friesen, J. Brent; Chen, Shao-Nong; McAlpine, James B.; Oberlies, Nicholas H.; Pauli, Guido F.

    2013-01-01

    This study demonstrates how regio- and diastereo-isomers with near-identical NMR spectra can be distinguished and unambiguously assigned using quantum mechanical driven, 1H iterative Full Spin Analysis (HiFSA). The method is illustrated with four natural products, the flavonolignans silybin A, silybin B, isosilybin A, and isosilybin B, which exhibit extremely similar coupling patterns and chemical shift differences well below the commonly reported level of accuracy of 0.01 ppm. The HiFSA approach generated highly reproducible 1H NMR fingerprints that enable distinction of all four isomers at 1H frequencies from 300 to 900 MHz. Furthermore, it is demonstrated that the underlying numeric 1H NMR profiles, combined with iterative computational analysis, allow parallel quantification of all four isomers, even in difficult to characterize reference materials and mixtures. The results shed new light on the historical challenges to the qualitative and quantitative analysis of these therapeutically relevant flavonolignans and open new opportunities to explore hidden diversity in the chemical space of organic molecules. PMID:23461697

  4. {sup 139}La NMR in lanthanum manganites: Indication of the presence of magnetic polarons from spectra and nuclear relaxations

    SciTech Connect

    Allodi, G.; De Renzi, R.; Guidi, G.

    1998-01-01

    We present {sup 139}La NMR experiments on five powder samples of lanthanum manganites, with a Mn{sup 4+} concentration ranging from the antiferromagnetic-insulator (AFM) to the ferromagnetic-conducting (FM) region of the phase diagram. We measure a positive hyperfine coupling C=0.13 T/{mu}{sub B}. A signal from nuclei in a FM environment is present at all compositions, as evidenced by a hyperfine frequency in zero-field experiments, by a positive hyperfine shift in NMR experiments below T{sub c}, and by a paramagnetic frequency shift following Curie-Weiss law. A signal from nuclei in an AFM environment is identified by a similar negative intercept Curie-Weiss law. The NMR spectra reveal a large temperature dependent fraction of static spin defects below T{sub c} in the FM domains. Nuclear relaxation indicates that the FM regions are influenced by diffusing, AFM-correlated excitations, while the AFM regions probe spin fluctuations from diffusing, FM correlated excitations. These results are interpreted in terms of electronic inhomogeneities due to the presence of a magnetic small polaron. {copyright} {ital 1998} {ital The American Physical Society}

  5. HiFSA fingerprinting applied to isomers with near-identical NMR spectra: the silybin/isosilybin case.

    PubMed

    Napolitano, José G; Lankin, David C; Graf, Tyler N; Friesen, J Brent; Chen, Shao-Nong; McAlpine, James B; Oberlies, Nicholas H; Pauli, Guido F

    2013-04-01

    This study demonstrates how regio- and diastereo-isomers with near-identical NMR spectra can be distinguished and unambiguously assigned using quantum mechanical driven (1)H iterative Full Spin Analysis (HiFSA). The method is illustrated with four natural products, the flavonolignans silybin A, silybin B, isosilybin A, and isosilybin B, which exhibit extremely similar coupling patterns and chemical shift differences well below the commonly reported level of accuracy of 0.01 ppm. The HiFSA approach generated highly reproducible (1)H NMR fingerprints that enable distinction of all four isomers at (1)H frequencies from 300 to 900 MHz. Furthermore, it is demonstrated that the underlying numeric (1)H NMR profiles, combined with iterative computational analysis, allow parallel quantification of all four isomers, even in difficult to characterize reference materials and mixtures. The results shed new light on the historical challenges to the qualitative and quantitative analysis of these therapeutically relevant flavonolignans and open new opportunities to explore hidden diversity in the chemical space of organic molecules. PMID:23461697

  6. The structure elucidation of mequindox and 1,4-bisdesoxymequindox: NMR analyses, FT-IR spectra, DFT calculations and thermochemical studies

    NASA Astrophysics Data System (ADS)

    Zhang, Jiaheng; He, Xin; Gao, Haixiang

    2011-10-01

    In the current work, we report a combined experimental and theoretical study on the molecular conformation, vibrational spectra, and nuclear magnetic resonance (NMR) spectra of mequindox (MEQ) and 1,4-bisdesoxymequindox (1,4-BDM). The geometric structure and vibrational frequencies of MEQ and 1,4-BDM have been calculated by density functional theory employing the B3LYP functional and 6-311++G(d,p) basis set. The 1H and 13C NMR chemical shifts have been calculated by gauge-including atomic orbital method with B3LYP 6-311++G(2df,2pd) approach. The calculation results have been applied to simulate the infrared and NMR spectra of the compounds. The theoretical results agree well with the observed spectra. The bond dissociation enthalpy of MEQ and the heat of formation of MEQ and 1,4-BDM have also been computed.

  7. A Global Approach to Accurate and Automatic Quantitative Analysis of NMR Spectra by Complex Least-Squares Curve Fitting

    NASA Astrophysics Data System (ADS)

    Martin, Y. L.

    The performance of quantitative analysis of 1D NMR spectra depends greatly on the choice of the NMR signal model. Complex least-squares analysis is well suited for optimizing the quantitative determination of spectra containing a limited number of signals (<30) obtained under satisfactory conditions of signal-to-noise ratio (>20). From a general point of view it is concluded, on the basis of mathematical considerations and numerical simulations, that, in the absence of truncation of the free-induction decay, complex least-squares curve fitting either in the time or in the frequency domain and linear-prediction methods are in fact nearly equivalent and give identical results. However, in the situation considered, complex least-squares analysis in the frequency domain is more flexible since it enables the quality of convergence to be appraised at every resonance position. An efficient data-processing strategy has been developed which makes use of an approximate conjugate-gradient algorithm. All spectral parameters (frequency, damping factors, amplitudes, phases, initial delay associated with intensity, and phase parameters of a baseline correction) are simultaneously managed in an integrated approach which is fully automatable. The behavior of the error as a function of the signal-to-noise ratio is theoretically estimated, and the influence of apodization is discussed. The least-squares curve fitting is theoretically proved to be the most accurate approach for quantitative analysis of 1D NMR data acquired with reasonable signal-to-noise ratio. The method enables complex spectral residuals to be sorted out. These residuals, which can be cumulated thanks to the possibility of correcting for frequency shifts and phase errors, extract systematic components, such as isotopic satellite lines, and characterize the shape and the intensity of the spectral distortion with respect to the Lorentzian model. This distortion is shown to be nearly independent of the chemical species

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  9. Pulse Electron Double Resonance Detected Multinuclear NMR Spectra of Distant and Low Sensitivity Nuclei and Its Application to the Structure of Mn(II) Centers in Organisms.

    PubMed

    Bruch, Eduardo M; Warner, Melissa T; Thomine, Sébastien; Tabares, Leandro C; Un, Sun

    2015-10-29

    The ability to characterize the structure of metal centers beyond their primary ligands is important to understanding their chemistry. High-magnetic-field pulsed electron double resonance detected NMR (ELDOR-NMR) is shown to be a very sensitive approach to measuring the multinuclear NMR spectra of the nuclei surrounding Mn(II) ions. Resolved spectra of intact organisms with resonances arising from (55)Mn, (31)P, (1)H, (39)K, (35)Cl, (23)Na, and (14)N nuclei surrounding Mn(2+) centers were obtained. Naturally abundant cellular (13)C could be routinely measured as well. The amplitudes of the (14)N and (2)H ELDOR-NMR spectra were found to be linearly dependent on the number of nuclei in the ligand sphere. The evolution of the Mn(II) ELDOR-NMR spectra as a function of excitation time was found to be best described by a saturation phenomenon rather than a coherently driven process. Mn(II) ELDOR-NMR revealed details about not only the immediate ligands to the Mn(II) ions but also more distant nuclei, providing a view of their extended structures. This will be important for understanding the speciation and chemistry of the manganese complexes as well as other metals found in organisms.

  10. Metabonomics classifies pathways affected by bioactive compounds. Artificial neural network classification of NMR spectra of plant extracts.

    PubMed

    Ott, Karl-Heinz; Araníbar, Nelly; Singh, Bijay; Stockton, Gerald W

    2003-03-01

    The biochemical mode-of-action (MOA) for herbicides and other bioactive compounds can be rapidly and simultaneously classified by automated pattern recognition of the metabonome that is embodied in the 1H NMR spectrum of a crude plant extract. The ca. 300 herbicides that are used in agriculture today affect less than 30 different biochemical pathways. In this report, 19 of the most interesting MOAs were automatically classified. Corn (Zea mays) plants were treated with various herbicides such as imazethapyr, glyphosate, sethoxydim, and diuron, which represent various biochemical modes-of-action such as inhibition of specific enzymes (acetohydroxy acid synthase [AHAS], protoporphyrin IX oxidase [PROTOX], 5-enolpyruvylshikimate-3-phosphate synthase [EPSPS], acetyl CoA carboxylase [ACC-ase], etc.), or protein complexes (photosystems I and II), or major biological process such as oxidative phosphorylation, auxin transport, microtubule growth, and mitosis. Crude isolates from the treated plants were subjected to 1H NMR spectroscopy, and the spectra were classified by artificial neural network analysis to discriminate the herbicide modes-of-action. We demonstrate the use and refinement of the method, and present cross-validated assignments for the metabolite NMR profiles of over 400 plant isolates. The MOA screen also recognizes when a new mode-of-action is present, which is considered extremely important for the herbicide discovery process, and can be used to study deviations in the metabolism of compounds from a chemical synthesis program. The combination of NMR metabolite profiling and neural network classification is expected to be similarly relevant to other metabonomic profiling applications, such as in drug discovery. PMID:12590124

  11. Tendencies of 31P chemical shifts changes in NMR spectra of nucleotide derivatives.

    PubMed

    Lebedev, A V; Rezvukhin, A I

    1984-07-25

    31P NMR chemical shifts of the selected mono- and oligonucleotide derivatives, including the compounds with P-N, P-C, P-S bonds and phosphite nucleotide analogues have been presented. The influence of substituents upon 31P chemical shifts has been discussed. The concrete examples of 31P chemical shifts data application in the field of nucleotide chemistry have been considered. PMID:6087290

  12. Improving sensitivity and resolution of MQMAS spectra: A 45Sc-NMR case study of scandium sulphate pentahydrate

    NASA Astrophysics Data System (ADS)

    Chandran, C. Vinod; Cuny, Jérôme; Gautier, Régis; Le Pollès, Laurent; Pickard, Chris J.; Bräuniger, Thomas

    2010-04-01

    To efficiently obtain multiple-quantum magic-angle spinning (MQMAS) spectra of the nuclide 45Sc ( I = 7/2), we have combined several previously suggested techniques to enhance the signal-to-noise ratio and to improve spectral resolution for the test sample, scandium sulphate pentahydrate (ScSPH). Whereas the 45Sc-3QMAS spectrum of ScSPH does not offer sufficient resolution to clearly distinguish between the 3 scandium sites present in the crystal structure, these sites are well-resolved in the 5QMAS spectrum. The loss of sensitivity incurred by using MQMAS with 5Q coherence order is partly compensated for by using fast-amplitude modulated (FAM) sequences to improve the efficiency of both 5Q coherence excitation and conversion. Also, heteronuclear decoupling is employed to minimise dephasing of the 45Sc signal during the 5Q evolution period due to dipolar couplings with the water protons in the ScSPH sample. Application of multi-pulse decoupling schemes such as TPPM and SPINAL results in improved sensitivity and resolution in the F1 (isotropic) dimension of the 5QMAS spectrum, the best results being achieved with the recently suggested SW f-TPPM sequence. By numerical fitting of the 45Sc-NMR spectra of ScSPH from 3QMAS, 5QMAS and single-quantum MAS at magnetic fields B0 = 9.4 T and 17.6 T, the isotropic chemical shift δiso, the quadrupolar coupling constant χ, and the asymmetry parameter η were obtained. Averaging over all experiments, the NMR parameters determined for the 3 scandium sites, designated (a), (b) and (c) are: δiso( a) = -15.5 ± 0.5 ppm, χ( a) = 5.60 ± 0.10 MHz, η( a) = 0.06 ± 0.05; δiso( b) = -12.9 ± 0.5 ppm, χ( b) = 4.50 ± 0.10 MHz, η( b) = 1.00 ± 0.00; and δiso( c) = -4.7 ± 0.2 ppm, χ( c) = 4.55 ± 0.05 MHz, η( c) = 0.50 ± 0.02. The NMR scandium species were assigned to the independent crystallographic sites by evaluating their experimental response to proton decoupling, and by density functional theory (DFT) calculations using

  13. Optical detection of NMR J-spectra at zero magnetic field

    NASA Astrophysics Data System (ADS)

    Ledbetter, M. P.; Crawford, C. W.; Pines, A.; Wemmer, D. E.; Knappe, S.; Kitching, J.; Budker, D.

    2009-07-01

    Scalar couplings of the form JI1 · I2 between nuclei impart valuable information about molecular structure to nuclear magnetic-resonance spectra. Here we demonstrate direct detection of J-spectra due to both heteronuclear and homonuclear J-coupling in a zero-field environment where the Zeeman interaction is completely absent. We show that characteristic functional groups exhibit distinct spectra with straightforward interpretation for chemical identification. Detection is performed with a microfabricated optical atomic magnetometer, providing high sensitivity to samples of microliter volumes. We obtain 0.1 Hz linewidths and measure scalar-coupling parameters with 4-mHz statistical uncertainty. We anticipate that the technique described here will provide a new modality for high-precision "J spectroscopy" using small samples on microchip devices for multiplexed screening, assaying, and sample identification in chemistry and biomedicine.

  14. Modified Prony Method to Resolve and Quantify in Vivo31P NMR Spectra of Tumors

    NASA Astrophysics Data System (ADS)

    Barone, P.; Guidoni, L.; Ragona, R.; Viti, V.; Furman, E.; Degani, H.

    Prony's method, successfully used in processing NMR signals, performs poorly at low signal-to-noise ratios. To overcome this problem, a statistical approach has been adopted by using Prony's method as a sampling device from the distribution associated with the true spectrum. Specifically, Prony's method is applied for each regression order p and number of data points n, both considered in a suitable range, and the estimates of frequencies, amplitudes, and decay factors are pooled separately. A histogram of the pooled frequencies is computed and, looking at the histogram, a lower and an upper frequency bound for each line of interest is determined. All frequency estimates in each of the determined intervals as well as associated decay factors and amplitudes are considered to be independent normal variates. A mean value and a corresponding 95% confidence interval are computed for each parameter. 31P NMR signals from MCF7 human breast cancer cells, inoculated into athymic mice and which developed into tumors, have been processed with traditional methods and with this modified Prony's method. The main components of the phosphomonoester peak, namely those deriving from phosphorylcholine and phosphorylethanolamine, are always well resolved with this new approach and their relative amplitudes can be consequently evaluated. Peak intensities of these two signals show different behavior during treatment of tumors with the antiestrogenic drug tamoxifen. The results of this new approach are compared with those obtainable with traditional techniques.

  15. Pulsed field gradients in simulations of one- and two-dimensional NMR spectra.

    PubMed

    Meresi, G H; Cuperlovic, M; Palke, W E; Gerig, J T

    1999-03-01

    A method for the inclusion of the effects of z-axis pulsed field gradients in computer simulations of an arbitrary pulsed NMR experiment with spin (1/2) nuclei is described. Recognizing that the phase acquired by a coherence following the application of a z-axis pulsed field gradient bears a fixed relation to its order and the spatial position of the spins in the sample tube, the sample is regarded as a collection of volume elements, each phase-encoded by a characteristic, spatially dependent precession frequency. The evolution of the sample's density matrix is thus obtained by computing the evolution of the density matrix for each volume element. Following the last gradient pulse, these density matrices are combined to form a composite density matrix which evolves through the rest of the experiment to yield the observable signal. This approach is implemented in a program which includes capabilities for rigorous inclusion of spin relaxation by dipole-dipole, chemical shift anisotropy, and random field mechanisms, plus the effects of arbitrary RF fields. Mathematical procedures for accelerating these calculations are described. The approach is illustrated by simulations of representative one- and two-dimensional NMR experiments.

  16. A novel approach to the rapid assignment of (13)C NMR spectra of major components of vegetable oils such as avocado, mango kernel and macadamia nut oils.

    PubMed

    Retief, Liezel; McKenzie, Jean M; Koch, Klaus R

    2009-09-01

    Assignment of (13)C nuclear magnetic resonance (NMR) spectra of major fatty acid components of South African produced vegetable oils was attempted using a method in which the vegetable oil was spiked with a standard triacylglycerol. This proved to be inadequate and therefore a new rapid and potentially generic graphical linear correlation method is proposed for assignment of the (13)C NMR spectra of major fatty acid components of apricot kernel, avocado pear, grapeseed, macadamia nut, mango kernel and marula vegetable oils. In this graphical correlation method, chemical shifts of fatty acids present in a known standard triacylglycerol is plotted against the corresponding chemical shifts of fatty acids present in the vegetable oils. This new approach (under carefully defined conditions and concentrations) was found especially useful for spectrally crowded regions where significant peak overlap occurs and was validated with the well-known (13)C NMR spectrum of olive oil which has been extensively reported in the literature. In this way, a full assignment of the (13)C{1H} NMR spectra of the vegetable oils, as well as tripalmitolein was readily achieved and the resonances belonging to the palmitoleic acid component of the triacylglycerols in the case of macadamia nut and avocado pear oil resonances were also assigned for the first time in the (13)C NMR spectra of these oils.

  17. A novel approach to the rapid assignment of (13)C NMR spectra of major components of vegetable oils such as avocado, mango kernel and macadamia nut oils.

    PubMed

    Retief, Liezel; McKenzie, Jean M; Koch, Klaus R

    2009-09-01

    Assignment of (13)C nuclear magnetic resonance (NMR) spectra of major fatty acid components of South African produced vegetable oils was attempted using a method in which the vegetable oil was spiked with a standard triacylglycerol. This proved to be inadequate and therefore a new rapid and potentially generic graphical linear correlation method is proposed for assignment of the (13)C NMR spectra of major fatty acid components of apricot kernel, avocado pear, grapeseed, macadamia nut, mango kernel and marula vegetable oils. In this graphical correlation method, chemical shifts of fatty acids present in a known standard triacylglycerol is plotted against the corresponding chemical shifts of fatty acids present in the vegetable oils. This new approach (under carefully defined conditions and concentrations) was found especially useful for spectrally crowded regions where significant peak overlap occurs and was validated with the well-known (13)C NMR spectrum of olive oil which has been extensively reported in the literature. In this way, a full assignment of the (13)C{1H} NMR spectra of the vegetable oils, as well as tripalmitolein was readily achieved and the resonances belonging to the palmitoleic acid component of the triacylglycerols in the case of macadamia nut and avocado pear oil resonances were also assigned for the first time in the (13)C NMR spectra of these oils. PMID:19544589

  18. Analysis of 31P MAS NMR spectra and transversal relaxation of bacteriophage M13 and tobacco mosaic virus.

    PubMed Central

    Magusin, P C; Hemminga, M A

    1994-01-01

    Phosphorus magic angle spinning nuclear magnetic resonance (NMR) spectra and transversal relaxation of M13 and TMV are analyzed by use of a model, which includes both local backbone motions of the encapsulated nucleic acid molecules and overall rotational diffusion of the rod-shaped virions about their length axis. Backbone motions influence the sideband intensities by causing a fast restricted reorientation of the phosphodiesters. To evaluate their influence on the observed sideband patterns, we extend the model that we used previously to analyze nonspinning 31P NMR lineshapes (Magusin, P.C.M.M., and M. A. Hemminga. 1993a. Biophys. J. 64:1861-1868) to magic angle spinning NMR experiments. Backbone motions also influence the conformation of the phosphodiesters, causing conformational averaging of the isotropic chemical shift, which offers a possible explanation for the various linewidths of the centerband and the sidebands observed for M13 gels under various conditions. The change of the experimental lineshape of M13 as a function of temperature and hydration is interpreted in terms of fast restricted fluctuation of the dihedral angles between the POC and the OCH planes on both sides of the 31P nucleus in the nucleic acid backbone. Backbone motions also seem to be the main cause of transversal relaxation measured at spinning rates of 4 kHz or higher. At spinning rates less than 2 kHz, transversal relaxation is significantly faster. This effect is assigned to slow, overall rotation of the rod-shaped M13 phage about its length axis. Equations are derived to simulate the observed dependence of T2e on the spinning rate. PMID:8038391

  19. Structure of dimethylphenyl betaine hydrochloride studied by X-ray diffraction, DFT calculation, NMR and FTIR spectra

    NASA Astrophysics Data System (ADS)

    Szafran, M.; Katrusiak, A.; Dega-Szafran, Z.; Kowalczyk, I.

    2013-01-01

    The structure of dimethylphenyl betaine hydrochloride (1) has been studied by X-ray diffraction, DFT calculations, NMR and FTIR spectra. The crystals are monoclinic, space group P21/c. In the crystal, the Cl- anion is connected with protonated betaine through the O-H⋯Cl- hydrogen bond of 2.943(2) Å. The structures in the gas phase (2) and water solution (3) have been optimized by the B3LYP/6-311++G(d,p) approach and the geometrical results have been compared with the X-ray data of 1. The FTIR spectrum of the solid compound is consistent with the X-ray results. The probable assignments of the anharmonic experimental vibrational frequencies of the investigated chloride (1) based on the calculated harmonic frequencies in water solution (3) are proposed. The correlations between the experimental 1H and 13C NMR chemical shifts (δexp) of 1 in D2O and the magnetic isotropic shielding constants (σcalc) calculated by the GIAO/B3LYP/6-311G++(d,p) approach, using the screening solvation model (COSMO), δexp = a + b σcalc, for optimized molecule 3 in water solution are linear and correctly reproduce the experimental chemical shifts.

  20. The effect of sample hydration on 13C CPMAS NMR spectra of fulvic acids

    USGS Publications Warehouse

    Hatcher, P.G.; Wilson, M.A.

    1991-01-01

    Three fulvic acids, two of which have been well studied by a number of other groups (Armadale and Suwannee river fulvic acids) have been examined by high resolution solid-state 13C-NMR techniques to delineate the effect of absorbed water. Two main effects of absorbed water were observed: (1) changes in spin lattice relaxation times in the rotating frame and cross polarization times and (2) total loss of signal so that some fulvic acid is effectively in solution. These results suggest that discrepancies in the literature concerning observed relative signal intensities from different structural groups are due to absorbed water and emphasize the necessity for proper precautionary drying before spectroscopic analysis. ?? 1991.

  1. Evaluation of standard and advanced preprocessing methods for the univariate analysis of blood serum 1H-NMR spectra.

    PubMed

    De Meyer, Tim; Sinnaeve, Davy; Van Gasse, Bjorn; Rietzschel, Ernst-R; De Buyzere, Marc L; Langlois, Michel R; Bekaert, Sofie; Martins, José C; Van Criekinge, Wim

    2010-10-01

    Proton nuclear magnetic resonance ((1)H-NMR)-based metabolomics enables the high-resolution and high-throughput assessment of a broad spectrum of metabolites in biofluids. Despite the straightforward character of the experimental methodology, the analysis of spectral profiles is rather complex, particularly due to the requirement of numerous data preprocessing steps. Here, we evaluate how several of the most common preprocessing procedures affect the subsequent univariate analyses of blood serum spectra, with a particular focus on how the standard methods perform compared to more advanced examples. Carr-Purcell-Meiboom-Gill 1D (1)H spectra were obtained for 240 serum samples from healthy subjects of the Asklepios study. We studied the impact of different preprocessing steps--integral (standard method) and probabilistic quotient normalization; no, equidistant (standard), and adaptive-intelligent binning; mean (standard) and maximum bin intensity data summation--on the resonance intensities of three different types of metabolites: triglycerides, glucose, and creatinine. The effects were evaluated by correlating the differently preprocessed NMR data with the independently measured metabolite concentrations. The analyses revealed that the standard methods performed inferiorly and that a combination of probabilistic quotient normalization after adaptive-intelligent binning and maximum intensity variable definition yielded the best overall results (triglycerides, R = 0.98; glucose, R = 0.76; creatinine, R = 0.70). Therefore, at least in the case of serum metabolomics, these or equivalent methods should be preferred above the standard preprocessing methods, particularly for univariate analyses. Additional optimization of the normalization procedure might further improve the analyses.

  2. A method based on covariance and pattern recognition for improving resolutions of spatially encoded NMR spectra.

    PubMed

    Qiu, Wenqi; Chen, Youhe; Wei, Zhiliang; Yang, Jian; Lin, Yulan; Chen, Zhong

    2015-11-01

    The spatially encoded technique enables the fast acquisition of two-dimensional (2D) nuclear magnetic resonance spectrum within a single scan, serving as a powerful tool for studying various systems and phenomena in short time scales. In spatially encoded spectroscopy, the resolution in the direct dimension can be enhanced by increasing effective acquisition times. However, spectral widths and resolutions in indirect dimensions are no longer independent of each other with wider spectral widths yielding lower resolution. The covariance method, which has achieved success in enhancing resolutions in the indirect dimensions of conventional 2D spectroscopy, is employed here to improve resolutions in the spatially encoded dimension. Moreover, an algorithm is developed based on pattern recognition to eliminate artifacts arising from the employment of the covariance method and experimental imperfections in recording the spatially encoded spectra. Therefore, high-resolution homonuclear 2D correlated spectra are obtained. Experiments are performed to show the feasibility and effectiveness of this proposed method in providing high-resolution spectra within greatly shortened times.

  3. 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.

  4. Vibrational spectra, molecular structure, NBO, UV, NMR, first order hyperpolarizability, analysis of 4-Methoxy-4'-Nitrobiphenyl by density functional theory.

    PubMed

    Govindarasu, K; Kavitha, E

    2014-03-25

    In this study, geometrical optimization, spectroscopic analysis, electronic structure and nuclear magnetic resonance studies of 4-Methoxy-4'-Nitrobiphenyl (abbreviated as 4M4'NBPL) were investigated by utilizing HF and DFT/B3LYP with 6-31G(d,p) as basis set. The equilibrium geometry, vibrational wavenumbers and the first order hyperpolarizability of the 4M4'NBPL have been calculated with the help of density functional theory computations. The FT-IR and FT-Raman spectra were recorded in the region 4000-400 cm(-1) and 3500-50 cm(-1) respectively. Natural Bond Orbital (NBO) analysis is also used to explain the molecular stability. The UV-Vis absorption spectra of the title compound dissolved in chloroform were recorded in the range of 200-800 cm(-1). The HOMO-LUMO energy gap explains the charge interaction taking place within the molecule. Good correlation between the experimental (1)H and (13)C NMR chemical shifts in chloroform solution and calculated GIAO shielding tensors were found. The dipole moment, linear polarizability and first order hyperpolarizability values were also computed. The linear polarizability and first order hyperpolarizability of the studied molecule indicate that the compound is a good candidate of nonlinear optical materials. The chemical reactivity and thermodynamic properties of 4M4'NBPL at different temperature are calculated. In addition, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis were investigated using theoretical calculations.

  5. Sensitivity Gains, Linearity, and Spectral Reproducibility in Nonuniformly Sampled Multidimensional MAS NMR Spectra of High Dynamic Range.

    SciTech Connect

    Suiter, Christopher L.; Paramasivam, Sivakumar; Hou, Guangjin; Sun, Shangjin; Rice, David M.; Hoch, Jeffrey C.; Rovnyak, David S.; Polenova, Tatyana E.

    2014-04-22

    Recently, we have demonstrated that considerable inherent sensitivity gains are attained in MAS NMR spectra acquired by nonuniform sampling (NUS) and introduced maximum entropy interpolation (MINT) processing that assures the linearity of transformation between the time and frequency domains. In this report, we examine the utility of the NUS/MINT approach in multidimensional datasets possessing high dynamic range, such as homonuclear 13C–13C correlation spectra. We demonstrate on model compounds and on 1–73-(U-13C,15N)/74–108-(U-15N) E. coli thioredoxin reassembly, that with appropriately constructed 50 % NUS schedules inherent sensitivity gains of 1.7–2.1-fold are readily reached in such datasets. We show that both linearity and line width are retained under these experimental conditions throughout the entire dynamic range of the signals. Furthermore, we demonstrate that the reproducibility of the peak intensities is excellent in the NUS/MINT approach when experiments are repeated multiple times and identical experimental and processing conditions are employed. Finally, we discuss the principles for design and implementation of random exponentially biased NUS sampling schedules for homonuclear 13C–13C MAS correlation experiments that yield high quality artifact-free datasets.

  6. Sensitivity gains, linearity, and spectral reproducibility in nonuniformly sampled multidimensional MAS NMR spectra of high dynamic range

    PubMed Central

    Suiter, Christopher L.; Paramasivam, Sivakumar; Hou, Guangjin; Sun, Shangjin; Rice, David; Hoch, Jeffrey C.; Rovnyak, David

    2014-01-01

    Recently, we have demonstrated that considerable inherent sensitivity gains are attained in MAS NMR spectra acquired by nonuniform sampling (NUS) and introduced maximum entropy interpolation (MINT) processing that assures the linearity of transformation between the time and frequency domains. In this report, we examine the utility of the NUS/MINT approach in multidimensional datasets possessing high dynamic range, such as homonuclear 13C–13C correlation spectra. We demonstrate on model compounds and on 1–73-(U-13C, 15N)/74–108-(U-15N) E. coli thioredoxin reassembly, that with appropriately constructed 50 % NUS schedules inherent sensitivity gains of 1.7–2.1-fold are readily reached in such datasets. We show that both linearity and line width are retained under these experimental conditions throughout the entire dynamic range of the signals. Furthermore, we demonstrate that the reproducibility of the peak intensities is excellent in the NUS/MINT approach when experiments are repeated multiple times and identical experimental and processing conditions are employed. Finally, we discuss the principles for design and implementation of random exponentially biased NUS sampling schedules for homonuclear 13C–13C MAS correlation experiments that yield high-quality artifact-free datasets. PMID:24752819

  7. Relativistic force field: parametric computations of proton-proton coupling constants in (1)H NMR spectra.

    PubMed

    Kutateladze, Andrei G; Mukhina, Olga A

    2014-09-01

    Spin-spin coupling constants in (1)H NMR carry a wealth of structural information and offer a powerful tool for deciphering molecular structures. However, accurate ab initio or DFT calculations of spin-spin coupling constants have been very challenging and expensive. Scaling of (easy) Fermi contacts, fc, especially in the context of recent findings by Bally and Rablen (Bally, T.; Rablen, P. R. J. Org. Chem. 2011, 76, 4818), offers a framework for achieving practical evaluation of spin-spin coupling constants. We report a faster and more precise parametrization approach utilizing a new basis set for hydrogen atoms optimized in conjunction with (i) inexpensive B3LYP/6-31G(d) molecular geometries, (ii) inexpensive 4-31G basis set for carbon atoms in fc calculations, and (iii) individual parametrization for different atom types/hybridizations, not unlike a force field in molecular mechanics, but designed for the fc's. With the training set of 608 experimental constants we achieved rmsd <0.19 Hz. The methodology performs very well as we illustrate with a set of complex organic natural products, including strychnine (rmsd 0.19 Hz), morphine (rmsd 0.24 Hz), etc. This precision is achieved with much shorter computational times: accurate spin-spin coupling constants for the two conformers of strychnine were computed in parallel on two 16-core nodes of a Linux cluster within 10 min.

  8. Relativistic force field: parametric computations of proton-proton coupling constants in (1)H NMR spectra.

    PubMed

    Kutateladze, Andrei G; Mukhina, Olga A

    2014-09-01

    Spin-spin coupling constants in (1)H NMR carry a wealth of structural information and offer a powerful tool for deciphering molecular structures. However, accurate ab initio or DFT calculations of spin-spin coupling constants have been very challenging and expensive. Scaling of (easy) Fermi contacts, fc, especially in the context of recent findings by Bally and Rablen (Bally, T.; Rablen, P. R. J. Org. Chem. 2011, 76, 4818), offers a framework for achieving practical evaluation of spin-spin coupling constants. We report a faster and more precise parametrization approach utilizing a new basis set for hydrogen atoms optimized in conjunction with (i) inexpensive B3LYP/6-31G(d) molecular geometries, (ii) inexpensive 4-31G basis set for carbon atoms in fc calculations, and (iii) individual parametrization for different atom types/hybridizations, not unlike a force field in molecular mechanics, but designed for the fc's. With the training set of 608 experimental constants we achieved rmsd <0.19 Hz. The methodology performs very well as we illustrate with a set of complex organic natural products, including strychnine (rmsd 0.19 Hz), morphine (rmsd 0.24 Hz), etc. This precision is achieved with much shorter computational times: accurate spin-spin coupling constants for the two conformers of strychnine were computed in parallel on two 16-core nodes of a Linux cluster within 10 min. PMID:25158224

  9. Towards high resolution ^1H NMR spectra of tannin colloidal aggregates

    NASA Astrophysics Data System (ADS)

    Mirabel, M.; Glories, Y.; Pianet, I.; Dufourc, E. J.

    1999-10-01

    The time dependent colloidal formation of tannins in hydro-alcoholic medium has been studied by 1H-NMR. Line broadening observed with time can be cancelled by making use of magic angle sample spinning (MASS) thus yielding sharp lines that allow structural studies. We used as an example catechin, a constitutive monomer of Bordeaux young red wine tannins. Chemical shift variations of polyphenol protons allow monitoring the time course of aggregation. La formation de tanins colloïdaux au cours du temps, en milieu hydroalcoolique, a été suivie par RMN-^1H. Un élargissement marqué des résonances est observé et peut être supprimé par la rotation de l'échantillon à l'angle magique ce qui ouvre tout un champ d'études structurales sur ces composés colloïdaux. L'exemple proposé est celui de la catéchine, monomère constitutif de tannins présents en grande quantité dans les vins rouges jeunes de Bordeaux. Des variations du déplacement chimique de certains protons polyphénoliques permettent de suivre l'évolution temporelle de l'agrégation.

  10. A specialized database manager for interpretation of NMR spectra of synthetic glucides: JPD

    NASA Astrophysics Data System (ADS)

    Czaplicki, J.; Ponthus, C.

    1998-02-01

    The current communication presents a program, written specifically to create and handle a specialized database, containing NMR spectral patterns of various monosaccharidic units. The program's database format is compatible with that of the Aurelia/Amix Bruker software package. The software facilitates the search for J patterns included in the database and their comparison with an experimental spectrum, in order to identify the components of the studied system, including the contaminants. Nous présentons ici un logiciel écrit spécifiquement pour créer et gérer une base de données spécialisées, contenant les motifs du couplage J des unités monosaccharidiques différentes. Le format de la base de données est compatible avec le format utilisé par le logiciel Aurelia/Amix de Bruker. Le logiciel facilite la recherche des motifs J inclus dans la base de données de leurs comparaisons avec un spectre expérimental, afin d'identifier les constituants de l'échantillon étudié, et ses éventuelles impuretés.

  11. Macroscopic orientation effects in broadline NMR-spectra of model membranes at high magnetic field strength: A method preventing such effects.

    PubMed

    Brumm, T; Möps, A; Dolainsky, C; Brückner, S; Bayerl, T M

    1992-04-01

    The partial orientation of multilamellar vesicles (MLV) in high magnetic fields has been studied and a method to prevent such effects is herewith proposed. The orientation effect was measured with (2)H-, (31)P-NMR and electron microscopy on MLVs of dipalmitoyl phosphatidylcholine with 30 mol% cholesterol. We present the first freeze-etch electron microscopy data obtained from MLV samples that were frozen directly in the NMR magnet at a field strength of 9.4 Tesla. These experiments clearly show that the MLVs adopt an ellipsoidal (but not a cylindrical) shape in the magnetic field. Best fit (31)P-NMR lineshape calculations assuming an ellipsoidal distribution of molecular director axes to the experimentally obtained spectra provide a quantitative measure of the average semiaxis ratio of the ellipsoidal MLVs and its change with temperature. The application of so-called spherical supported vesicles (SSV) is found to prevent any partial orientation effects so that undistorted NMR powder pattern of the bilayer can be measured independently of magnetic field strength and temperature.The usefulness of SSVs is further demonstrated by a direct comparison of spectral data such as (31)P-and (2)H-NMR lineshapes and relaxation times as well as (2)H-NMR dePaked spectra obtained for both model systems. These experiments show that spectral data obtained from partially oriented MLVs are not unambiguous to interpret, in particular, if an external parameter such as temperature is varied.

  12. Gas-phase NMR spectra of cyclohexene are consistent with a barrier to ring inversion of less than 30 kJ mol -1

    NASA Astrophysics Data System (ADS)

    Suarez, Cristina; Tafazzoli, Mohsen; True, Nancy S.

    1992-08-01

    1H NMR spectra of gaseous cyclohexene at 7.05 T and 195 K do not show line broadening attributable to axial-equatorial proton exchange, indicating that the Gibbs energy of activation, Δ G‡, is less than 30 kJ mol -1, considerably lower than the 43 kJ mol -1 barrier recently determined from a vibrational analysis.

  13. Quantitative analysis of ³¹P NMR spectra of soil extracts--dealing with overlap of broad and sharp signals.

    PubMed

    Doolette, Ashlea L; Smernik, Ronald J

    2015-09-01

    Solution (31)P NMR analysis following extraction with a mixture of sodium hydroxide and ethylenediaminetetraacetic acid is the most widely used method for detailed characterization of soil organic P. However, quantitative analysis of the (31)P NMR spectra is complicated by severe spectral overlap in the monoester region. Various deconvolution procedures have been developed for the task, yet none of these are widely accepted or implemented. In this mini-review, we first describe and compare these varying approaches. We then review approaches to similar issues of spectral overlap in biomedical science applications including NMR-based metabolic profiling and analyzing (31)P magnetic resonance spectra of ex vivo and in vivo intact tissues. The greater maturity and resourcing of this biomedical research means that a wider variety of approaches has been developed. Of particular relevance are approaches to dealing with overlap of broad and sharp signals. Although the existence of this problem is still debated in the context of soil analyses, not only is it well-recognized in biomedical applications, but multiple approaches have been developed to deal with it, including T2 editing and time-domain fitting. Perhaps the most transferable concept is the incorporation of 'prior knowledge' in the fitting of spectra. This is well established in biomedical applications but barely touched in soil analyses. We argue that shortcuts to dealing with overlap in the monoester region (31)P NMR soil spectra are likely to be found in the biomedical literature, although some degree of adaptation will be necessary. PMID:25854619

  14. Quantitative analysis of ³¹P NMR spectra of soil extracts--dealing with overlap of broad and sharp signals.

    PubMed

    Doolette, Ashlea L; Smernik, Ronald J

    2015-09-01

    Solution (31)P NMR analysis following extraction with a mixture of sodium hydroxide and ethylenediaminetetraacetic acid is the most widely used method for detailed characterization of soil organic P. However, quantitative analysis of the (31)P NMR spectra is complicated by severe spectral overlap in the monoester region. Various deconvolution procedures have been developed for the task, yet none of these are widely accepted or implemented. In this mini-review, we first describe and compare these varying approaches. We then review approaches to similar issues of spectral overlap in biomedical science applications including NMR-based metabolic profiling and analyzing (31)P magnetic resonance spectra of ex vivo and in vivo intact tissues. The greater maturity and resourcing of this biomedical research means that a wider variety of approaches has been developed. Of particular relevance are approaches to dealing with overlap of broad and sharp signals. Although the existence of this problem is still debated in the context of soil analyses, not only is it well-recognized in biomedical applications, but multiple approaches have been developed to deal with it, including T2 editing and time-domain fitting. Perhaps the most transferable concept is the incorporation of 'prior knowledge' in the fitting of spectra. This is well established in biomedical applications but barely touched in soil analyses. We argue that shortcuts to dealing with overlap in the monoester region (31)P NMR soil spectra are likely to be found in the biomedical literature, although some degree of adaptation will be necessary.

  15. A Discovery-Based Hydrochlorination of Carvone Utilizing a Guided-Inquiry Approach to Determine the Product Structure from [superscript 13]C NMR Spectra

    ERIC Educational Resources Information Center

    Pelter, Michael W.; Walker, Natalie M.

    2012-01-01

    This experiment describes a discovery-based method for the regio- and stereoselective hydrochlorination of carvone, appropriate for a 3-h second-semester organic chemistry laboratory. The product is identified through interpretation of the [superscript 13]C NMR and DEPT spectra are obtained on an Anasazi EFT-60 at 15 MHz as neat samples. A…

  16. A General Method for Extracting Individual Coupling Constants from Crowded (1)H NMR Spectra.

    PubMed

    Sinnaeve, Davy; Foroozandeh, Mohammadali; Nilsson, Mathias; Morris, Gareth A

    2016-01-18

    Couplings between protons, whether scalar or dipolar, provide a wealth of structural information. Unfortunately, the high number of (1)H-(1)H couplings gives rise to complex multiplets and severe overlap in crowded spectra, greatly complicating their measurement. Many different methods exist for disentangling couplings, but none approaches optimum resolution. Here, we present a general new 2D J-resolved method, PSYCHEDELIC, in which all homonuclear couplings are suppressed in F2, and only the couplings to chosen spins appear, as simple doublets, in F1. This approaches the theoretical limit for resolving (1)H-(1)H couplings, with close to natural linewidths and with only chemical shifts in F2. With the same high sensitivity and spectral purity as the parent PSYCHE pure shift experiment, PSYCHEDELIC offers a robust method for chemists seeking to exploit couplings for structural, conformational, or stereochemical analyses.

  17. Communication: Permanent dipoles contribute to electric polarization in chiral NMR spectra

    SciTech Connect

    Buckingham, A. David

    2014-01-07

    Nuclear magnetic resonance spectroscopy is blind to chirality because the spectra of a molecule and its mirror image are identical unless the environment is chiral. However, precessing nuclear magnetic moments in chiral molecules in a strong magnetic field induce an electric polarization through the nuclear magnetic shielding polarizability. This effect is equal and opposite for a molecule and its mirror image but is small and has not yet been observed. It is shown that the permanent electric dipole moment of a chiral molecule is partially oriented through the antisymmetric part of the nuclear magnetic shielding tensor, causing the electric dipole to precess with the nuclear magnetic moment and producing a much larger temperature-dependent electric polarization with better prospects of detection.

  18. Communication: Permanent dipoles contribute to electric polarization in chiral NMR spectra

    NASA Astrophysics Data System (ADS)

    Buckingham, A. David

    2014-01-01

    Nuclear magnetic resonance spectroscopy is blind to chirality because the spectra of a molecule and its mirror image are identical unless the environment is chiral. However, precessing nuclear magnetic moments in chiral molecules in a strong magnetic field induce an electric polarization through the nuclear magnetic shielding polarizability. This effect is equal and opposite for a molecule and its mirror image but is small and has not yet been observed. It is shown that the permanent electric dipole moment of a chiral molecule is partially oriented through the antisymmetric part of the nuclear magnetic shielding tensor, causing the electric dipole to precess with the nuclear magnetic moment and producing a much larger temperature-dependent electric polarization with better prospects of detection.

  19. A General Method for Extracting Individual Coupling Constants from Crowded 1H NMR Spectra

    PubMed Central

    Foroozandeh, Mohammadali; Nilsson, Mathias; Morris, Gareth A.

    2015-01-01

    Abstract Couplings between protons, whether scalar or dipolar, provide a wealth of structural information. Unfortunately, the high number of 1H‐1H couplings gives rise to complex multiplets and severe overlap in crowded spectra, greatly complicating their measurement. Many different methods exist for disentangling couplings, but none approaches optimum resolution. Here, we present a general new 2D J‐resolved method, PSYCHEDELIC, in which all homonuclear couplings are suppressed in F 2, and only the couplings to chosen spins appear, as simple doublets, in F 1. This approaches the theoretical limit for resolving 1H‐1H couplings, with close to natural linewidths and with only chemical shifts in F 2. With the same high sensitivity and spectral purity as the parent PSYCHE pure shift experiment, PSYCHEDELIC offers a robust method for chemists seeking to exploit couplings for structural, conformational, or stereochemical analyses. PMID:26636773

  20. X-ray and DFT studies of the structure, vibrational and NMR spectra of 2-amino-pyridine betaine hydrochloride

    NASA Astrophysics Data System (ADS)

    Szafran, M.; Kowalczyk, I.; Koput, J.; Katrusiak, A.

    2005-06-01

    The effect of hydrogen bonding, inter- and intramolecular electrostatic interactions on the conformation of 2-amino-pyridine betaine hydrochloride (1-carboxymethyl-2-amino-pyridinium chloride), 2-NH 2PBH⋯Cl(c), in the crystal and its isolated molecules has been studied by X-ray diffraction, FT-IR, Raman, 1H and 13C NMR spectroscopies, and by DFT calculations. In the crystal, the Cl - anion is connected with protonated betaine via hydrogen bond, O-H⋯Cl -= 2.975(2) Å, two N(12)-H⋯Cl - hydrogen bonds and two N(1) H⋯Cl - intermolecular electrostatic interactions. Two minima are located in the potential energy surface at the B3LYP/6-31G(d,p) level, 2-NH 2PBH⋯Cl(t) and 2-NH 2PB⋯HCl(c), with the latter being 20,7 kcal/mol higher in energy. The optimized bond lengths and angles of 2-NH 2PBH⋯Cl(t) at B3LYP level of theory are in good agreement with X-ray data, except for the conformation of the COOH group, which is cis ( syn) in the crystal and trans ( anti) in the single molecule. The probable assignments for the anharmonic experimental solid state vibrational spectra of 2-NH 2PBH⋯Cl(c) and 2-ND 2PBD⋯Cl(c) based on the calculated B3LYP/6-31G(d,p) harmonic frequencies have been made. 1H and 13C NMR screening constants for both single molecules have been calculated in the GIAO/B3LYP/6-31G(d,p) approach. Linear correlation between the calculated and experimental 1H chemical shifts holds only for cis conformer. The lack of such a correlation for trans conformer indicates that it is absent in D 2O solution.

  1. Automated assignment of NMR chemical shifts based on a known structure and 4D spectra.

    PubMed

    Trautwein, Matthias; Fredriksson, Kai; Möller, Heiko M; Exner, Thomas E

    2016-08-01

    Apart from their central role during 3D structure determination of proteins the backbone chemical shift assignment is the basis for a number of applications, like chemical shift perturbation mapping and studies on the dynamics of proteins. This assignment is not a trivial task even if a 3D protein structure is known and needs almost as much effort as the assignment for structure prediction if performed manually. We present here a new algorithm based solely on 4D [(1)H,(15)N]-HSQC-NOESY-[(1)H,(15)N]-HSQC spectra which is able to assign a large percentage of chemical shifts (73-82 %) unambiguously, demonstrated with proteins up to a size of 250 residues. For the remaining residues, a small number of possible assignments is filtered out. This is done by comparing distances in the 3D structure to restraints obtained from the peak volumes in the 4D spectrum. Using dead-end elimination, assignments are removed in which at least one of the restraints is violated. Including additional information from chemical shift predictions, a complete unambiguous assignment was obtained for Ubiquitin and 95 % of the residues were correctly assigned in the 251 residue-long N-terminal domain of enzyme I. The program including source code is available at https://github.com/thomasexner/4Dassign . PMID:27484442

  2. Automated Quantification of Human Brain Metabolites by Artificial Neural Network Analysis from in VivoSingle-Voxel 1H NMR Spectra

    NASA Astrophysics Data System (ADS)

    Kaartinen, Jouni; Mierisová, Šarka; Oja, Joni M. E.; Usenius, Jukka-Pekka; Kauppinen, Risto A.; Hiltunen, Yrjö

    1998-09-01

    A real-time automated way of quantifying metabolites fromin vivoNMR spectra using an artificial neural network (ANN) analysis is presented. The spectral training and test sets for ANN containing peaks at the chemical shift ranges resembling long echo time proton NMR spectra from human brain were simulated. The performance of the ANN constructed was compared with an established lineshape fitting (LF) analysis using both simulated and experimental spectral data as inputs. The correspondence between the ANN and LF analyses showed correlation coefficients of order of 0.915-0.997 for spectra with large variations in both signal-to-noise and peak areas. Water suppressed1H NMR spectra from 24 healthy subjects were collected and choline-containing compounds (Cho), total creatine (Cr), and N-acetyl aspartate (NAA) were quantified with both methods. The ANN quantified these spectra with an accuracy similar to LF analysis (correlation coefficients of 0.915-0.951). These results show that LF and ANN are equally good quantifiers; however, the ANN analyses are more easily automated than LF analyses.

  3. Unusual effects in variable temperature powder NMR spectra of the methyl group protons in 9,10-dimethyltriptycene-d₁₂.

    PubMed

    Bernatowicz, P; Ratajczyk, T; Kalicki, P; Szymanski, S

    2014-01-01

    Variable temperature (1)H wide line NMR spectra of polycrystalline 9,10-dimethyltriptycene-d12 deuterated in the aromatic positions were studied. The spectra show different patterns in an unrepeatable dependence on the way of preparation of the powdered samples. Simultaneously, no anomalies were seen in the MAS and CPMAS proton-decoupled room-temperature (13)C spectra as well as in powder X-ray diffraction patterns. The effects observed in the (1)H spectra are tentatively explained in terms of a phenomenological model. For one of the examined samples it afforded a consistent interpretation of the entire series of temperature dependent spectra in terms of structural non uniformity of the solid material studied. Quantum character of the stochastic dynamics of the methyl groups in the investigated compound was confirmed, although these dynamics are close to the classical limit where the familiar random jump model applies. PMID:24656571

  4. MetaboID: a graphical user interface package for assignment of 1H NMR spectra of bodyfluids and tissues.

    PubMed

    MacKinnon, Neil; Somashekar, Bagganahalli S; Tripathi, Pratima; Ge, Wencheng; Rajendiran, Thekkelnaycke M; Chinnaiyan, Arul M; Ramamoorthy, Ayyalusamy

    2013-01-01

    Nuclear magnetic resonance based measurements of small molecule mixtures continues to be confronted with the challenge of spectral assignment. While multi-dimensional experiments are capable of addressing this challenge, the imposed time constraint becomes prohibitive, particularly with the large sample sets commonly encountered in metabolomic studies. Thus, one-dimensional spectral assignment is routinely performed, guided by two-dimensional experiments on a selected sample subset; however, a publicly available graphical interface for aiding in this process is currently unavailable. We have collected spectral information for 360 unique compounds from publicly available databases including chemical shift lists and authentic full resolution spectra, supplemented with spectral information for 25 compounds collected in-house at a proton NMR frequency of 900 MHz. This library serves as the basis for MetaboID, a Matlab-based user interface designed to aid in the one-dimensional spectral assignment process. The tools of MetaboID were built to guide resonance assignment in order of increasing confidence, starting from cursory compound searches based on chemical shift positions to analysis of authentic spike experiments. Together, these tools streamline the often repetitive task of spectral assignment. The overarching goal of the integrated toolbox of MetaboID is to centralize the one dimensional spectral assignment process, from providing access to large chemical shift libraries to providing a straightforward, intuitive means of spectral comparison. Such a toolbox is expected to be attractive to both experienced and new metabolomic researchers as well as general complex mixture analysts.

  5. The infrared, Raman, NMR and UV spectra, ab initio calculations and spectral assignments of 2-amino-4-chloro-6-methoxypyrimidine

    NASA Astrophysics Data System (ADS)

    Cinar, Z.; Karabacak, M.; Cinar, M.; Kurt, M.; Chinna babu, P.; Sundaraganesan, N.

    2013-12-01

    The 2-amino-4-chloro-6-methoxypyrimidine abbreviated as ACMP have been investigated by both the experimental and theoretical methods; through this work we provide the essential fact about the structural and vibrational insights. The optimized molecular structure, atomic charges, vibrational frequencies and ultraviolet spectral interpretation of ACMP have been studied by performing DFT/B3LYP/6-311++G(df,pd) level of theory. The FT-IR, FT-Raman spectra were recorded in the region 4000-400 cm-1 and 4000-50 cm-1 respectively. The UV absorption spectrum of the compound that dissolved in ethanol and water solution were recorded in the range of 200-400 nm. The scaled wavenumbers are compared with the experimental values. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. Based on the UV spectrum and TD-DFT calculations, the electronic structure and the assignments of the absorption bands were carried out. The 1H, 13C and DEPT 135 nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated using with the Gauge Including Atomic Orbital (GIAO) method and compared with experimental results. Besides, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis were investigated using theoretical calculations.

  6. Study of molecular structure, vibrational, electronic and NMR spectra of oncocalyxone A using DFT and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Joshi, Bhawani Datt; Srivastava, Anubha; Honorato, Sara Braga; Tandon, Poonam; Pessoa, Otília Deusdênia Loiola; Fechine, Pierre Basílio Almeida; Ayala, Alejandro Pedro

    2013-09-01

    Oncocalyxone A (C17H18O5) is the major secondary metabolite isolated from ethanol extract from the heartwood of Auxemma oncocalyx Taub popularly known as “pau branco”. Oncocalyxone A (Onco A) has many pharmaceutical uses such as: antitumor, analgesic, antioxidant and causative of inhibition of platelet activation. We have performed the optimized geometry, total energy, conformational study, molecular electrostatic potential mapping, frontier orbital energy gap and vibrational frequencies of Onco A employing ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) method with 6-311++G(d, p) basis set. Stability of the molecule arising from hyperconjugative interactions and/or charge delocalization has been analyzed using natural bond orbital (NBO) analysis. UV-vis spectrum of the compound was recorded in DMSO and MeOH solvent. The TD-DFT calculations have been performed to explore the influence of electronic absorption spectra in the gas phase, as well as in solution environment using IEF-PCM and 6-31G basis set. The 13C NMR chemical shifts have been calculated with the B3LYP/6-311++G(d, p) basis set and compared with the experimental values. These methods have been used as tools for structural characterization of Onco A.

  7. An approach to the simultaneous quantitative analysis of metabolites in table wines by (1)H NMR self-constructed three-dimensional spectra.

    PubMed

    Li, Bao Qiong; Xu, Min Li; Wang, Xue; Zhai, Hong Lin; Chen, Jing; Liu, Jin Jin

    2017-02-01

    Wine consists of several hundred components with different concentrations, including water, ethanol, glycerol, organic acids and sugars. Accurate quantification of target compounds in such complex samples is a difficult task based on conventional (1)H NMR spectra due to some challenges. In this paper, the three-dimensional spectrum was constructed firstly by simply repeating (1)H NMR spectrum itself so as to extract the features of target compounds by Tchebichef moment method. A proof-of-concept model system, the determination of five metabolites in wines was utilized to evaluate the performance of the proposed strategy. The results indicate that the proposed approach can provide accurate and reliable concentration predictions, probably the best results ever achieved using PLS and interval-PLS methods. Our novel strategy has not only good performance but also does not require laborious multi-step and subjective pretreatments. Therefore, it is expected that the proposed method could extend the application of conventional (1)H NMR. PMID:27596391

  8. Quantitative (13)C Solid-State NMR Spectra by Multiple-Contact Cross-polarization for Drug Delivery: From Active Principles to Excipients and Drug Carriers.

    PubMed

    Saïdi, Fadila; Taulelle, Francis; Martineau, Charlotte

    2016-08-01

    In this contribution, we present an analysis of the main parameters influencing the efficiency of the (1)H → (13)C multiple-contact cross-polarization nuclear magnetic resonance (NMR) experiment in the context of solid pharmaceutical materials. Using the optimum experimental conditions, quantitative (13)C NMR spectra are then obtained for porous metal-organic frameworks (potential drug carriers) and for components present in drug formulations (active principle ingredient and excipients, amorphous or crystalline). Finally, we show that mixtures of components can also be quantified with this method and, hence, that it represents an ideal tool for quantification of pharmaceutical formulations by (13)C cross-polarization under magic-angle spinning NMR in the industry as it is robust and easy to set up, much faster than direct (13)C polarization and is efficient for samples at natural abundance. PMID:27372550

  9. Evaluation of the reliability of the maximum entropy method for reconstructing 3D and 4D NOESY-type NMR spectra of proteins.

    PubMed

    Shigemitsu, Yoshiki; Ikeya, Teppei; Yamamoto, Akihiro; Tsuchie, Yuusuke; Mishima, Masaki; Smith, Brian O; Güntert, Peter; Ito, Yutaka

    2015-02-01

    Despite their advantages in analysis, 4D NMR experiments are still infrequently used as a routine tool in protein NMR projects due to the long duration of the measurement and limited digital resolution. Recently, new acquisition techniques for speeding up multidimensional NMR experiments, such as nonlinear sampling, in combination with non-Fourier transform data processing methods have been proposed to be beneficial for 4D NMR experiments. Maximum entropy (MaxEnt) methods have been utilised for reconstructing nonlinearly sampled multi-dimensional NMR data. However, the artefacts arising from MaxEnt processing, particularly, in NOESY spectra have not yet been clearly assessed in comparison with other methods, such as quantitative maximum entropy, multidimensional decomposition, and compressed sensing. We compared MaxEnt with other methods in reconstructing 3D NOESY data acquired with variously reduced sparse sampling schedules and found that MaxEnt is robust, quick and competitive with other methods. Next, nonlinear sampling and MaxEnt processing were applied to 4D NOESY experiments, and the effect of the artefacts of MaxEnt was evaluated by calculating 3D structures from the NOE-derived distance restraints. Our results demonstrated that sufficiently converged and accurate structures (RMSD of 0.91Å to the mean and 1.36Å to the reference structures) were obtained even with NOESY spectra reconstructed from 1.6% randomly selected sampling points for indirect dimensions. This suggests that 3D MaxEnt processing in combination with nonlinear sampling schedules is still a useful and advantageous option for rapid acquisition of high-resolution 4D NOESY spectra of proteins.

  10. A study of the molecular conformations and the vibrational, 1H and 13C NMR spectra of the anticancer drug tamoxifen and triphenylethylene

    NASA Astrophysics Data System (ADS)

    Badawi, Hassan M.; Khan, Ibrahim

    2016-08-01

    The structural stability and the vibrational spectra of the anticancer drug tamoxifen and triphenylethylene were investigated by the DFT B3LYP/6-311G (d,p) calculations. Tamoxifen and triphenylethylene were predicted to exist predominantly as non-planar structures. The vibrational frequencies and the 1H and 13C NMR chemical shifts of the low energy structures of tamoxifen and triphenylethylene were computed at the DFT B3LYP level of theory. Complete vibrational assignments were provided by combined theoretical and experimental data of tamoxifen and triphenylethylene. The 1H and 13C NMR spectra of both molecules were interpreted by experimental and DFT calculated chemical shifts of the two molecules. The RMSD between experimental and theoretical 1H and 13C chemical shifts for tamoxifen is 0.29 and 4.72 ppm, whereas for triphenylethylene, it is 0.16 and 2.70 ppm, respectively.

  11. Systematic Comparison of Sets of 13C NMR Spectra That Are Potentially Identical. Confirmation of the Configuration of a Cuticular Hydrocarbon from the Cane Beetle Antitrogus parvulus

    PubMed Central

    2015-01-01

    A systematic process is introduced to compare 13C NMR spectra of two (or more) candidate samples of known structure to a natural product sample of unknown structure. The process is designed for the case where the spectra involved can reasonably be expected to be very similar, perhaps even identical. It is first validated by using published 13C NMR data sets for the natural product 4,6,8,10,16,18-hexamethyldocosane. Then the stereoselective total syntheses of two candidate isomers of the related 4,6,8,10,16-pentamethyldocosane natural product are described, and the process is applied to confidently assign the configuration of the natural product as (4S,6R,8R,10S,16S). This is accomplished even though the chemical shift differences between this isomer and its (16R)-epimer are only ±5–10 ppb (±0.005–0.01 ppm). PMID:25019530

  12. Cellobiose as a model system to reveal cellulose dissolution mechanism in acetate-based ionic liquids: Density functional theory study substantiated by NMR spectra.

    PubMed

    Cao, Bobo; Du, Jiuyao; Du, Dongmei; Sun, Haitao; Zhu, Xiao; Fu, Hui

    2016-09-20

    Cellulose dissolution mechanism in acetate-based ionic liquids was systematically studied in Nuclear Magnetic Resonance (NMR) spectra and Density Functional Theory (DFT) methods by using cellobiose and 1-butyl-3-methylimidazolium acetate (BmimAc) as a model system. The solubility of cellulose in ionic liquid increased with temperature increase in the range of 90-140°C. NMR spectra suggested OAc(-) preferred to form stronger hydrogen bonds with hydrogen of hydroxyl in cellulose. Electrostatic potential method was employed to predict the most possible reaction sites and locate the most stable configuration. Atoms in molecules (AIM) theory was used to study the features of bonds at bond critical points and the variations of bond types. Simultaneously, noncovalent interactions were characterized and visualized by employing reduced density gradient analysis combined with Visual Molecular Dynamics (VMD) program. Natural bond orbital (NBO) theory was applied to study the noncovalent nature and characterize the orbital interactions between cellobiose and Bmim[OAc]. PMID:27261759

  13. Cellobiose as a model system to reveal cellulose dissolution mechanism in acetate-based ionic liquids: Density functional theory study substantiated by NMR spectra.

    PubMed

    Cao, Bobo; Du, Jiuyao; Du, Dongmei; Sun, Haitao; Zhu, Xiao; Fu, Hui

    2016-09-20

    Cellulose dissolution mechanism in acetate-based ionic liquids was systematically studied in Nuclear Magnetic Resonance (NMR) spectra and Density Functional Theory (DFT) methods by using cellobiose and 1-butyl-3-methylimidazolium acetate (BmimAc) as a model system. The solubility of cellulose in ionic liquid increased with temperature increase in the range of 90-140°C. NMR spectra suggested OAc(-) preferred to form stronger hydrogen bonds with hydrogen of hydroxyl in cellulose. Electrostatic potential method was employed to predict the most possible reaction sites and locate the most stable configuration. Atoms in molecules (AIM) theory was used to study the features of bonds at bond critical points and the variations of bond types. Simultaneously, noncovalent interactions were characterized and visualized by employing reduced density gradient analysis combined with Visual Molecular Dynamics (VMD) program. Natural bond orbital (NBO) theory was applied to study the noncovalent nature and characterize the orbital interactions between cellobiose and Bmim[OAc].

  14. Simplification of the 1H NMR spectra of enantiomers dissolved in chiral liquid crystals, combining variable angle sample spinning and selective refocusing experiments.

    PubMed

    Beguin, Laetitia; Courtieu, Jacques; Ziani, Latifa; Merlet, Denis

    2006-12-01

    This work presents a technique to simplify overcrowded proton spectra in chiral liquid crystal solvents using rotation of the sample near the magic angle, VASS, combined with homonuclear selective refocusing 2D NMR experiments, SERF. This methodology provides a powerful tool to visualise enantiomers out of unresolved proton spectra. A modified SERF sequence is presented where the resulting 2D spectrum can be phased to increase the resolution. Accurate enantiomeric excesses are determined that are not possible to measure on static samples. Two examples are presented.

  15. A Simple Approach for Obtaining High Resolution, High Sensitivity ¹H NMR Metabolite Spectra of Biofluids with Limited Mass Supply

    SciTech Connect

    Hu, Jian Zhi; Rommereim, Donald N.; Wind, Robert A.; Minard, Kevin R.; Sears, Jesse A.

    2006-11-01

    A simple approach is reported that yields high resolution, high sensitivity ¹H NMR spectra of biofluids with limited mass supply. This is achieved by spinning a capillary sample tube containing a biofluid at the magic angle at a frequency of about 80Hz. A 2D pulse sequence called ¹H PASS is then used to produce a high-resolution ¹H NMR spectrum that is free from magnetic susceptibility induced line broadening. With this new approach a high resolution ¹H NMR spectrum of biofluids with a volume less than 1.0 µl can be easily achieved at a magnetic field strength as low as 7.05T. Furthermore, the methodology facilitates easy sample handling, i.e., the samples can be directly collected into inexpensive and disposable capillary tubes at the site of collection and subsequently used for NMR measurements. In addition, slow magic angle spinning improves magnetic field shimming and is especially suitable for high throughput investigations. In this paper first results are shown obtained in a magnetic field of 7.05T on urine samples collected from mice using a modified commercial NMR probe.

  16. Synthesis and NMR Spectral Analysis of Amine Heterocycles: The Effect of Asymmetry on the [superscript 1]H and [superscript 13]C NMR Spectra of N,O-Acetals

    ERIC Educational Resources Information Center

    Saba, Shahrokh; Ciaccio, James A.; Espinal, Jennifer; Aman, Courtney E.

    2007-01-01

    The stereochemical investigation is conducted to give students the combined experience of chemical synthesis of amines and N-heterocycles and structural stereochemical analysis using NMR spectroscopy. Students are introduced to the concept of topicity-stereochemical relationships between ligands within a molecule by synthesizing N,O-acetals.

  17. 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.

  18. Noninvasive Recognition and Biomarkers of Early Allergic Asthma in Cats Using Multivariate Statistical Analysis of NMR Spectra of Exhaled Breath Condensate

    PubMed Central

    Fulcher, Yan G.; Fotso, Martial; Chang, Chee-Hoon; Rindt, Hans; Reinero, Carol R.

    2016-01-01

    Asthma is prevalent in children and cats, and needs means of noninvasive diagnosis. We sought to distinguish noninvasively the differences in 53 cats before and soon after induction of allergic asthma, using NMR spectra of exhaled breath condensate (EBC). Statistical pattern recognition was improved considerably by preprocessing the spectra with probabilistic quotient normalization and glog transformation. Classification of the 106 preprocessed spectra by principal component analysis and partial least squares with discriminant analysis (PLS-DA) appears to be impaired by variances unrelated to eosinophilic asthma. By filtering out confounding variances, orthogonal signal correction (OSC) PLS-DA greatly improved the separation of the healthy and early asthmatic states, attaining 94% specificity and 94% sensitivity in predictions. OSC enhancement of multi-level PLS-DA boosted the specificity of the prediction to 100%. OSC-PLS-DA of the normalized spectra suggest the most promising biomarkers of allergic asthma in cats to include increased acetone, metabolite(s) with overlapped NMR peaks near 5.8 ppm, and a hydroxyphenyl-containing metabolite, as well as decreased phthalate. Acetone is elevated in the EBC of 74% of the cats with early asthma. The noninvasive detection of early experimental asthma, biomarkers in EBC, and metabolic perturbation invite further investigation of the diagnostic potential in humans. PMID:27764146

  19. Conformational and isomerizational studies of 3- N, N-dimethylhydrazino-2-methylsulfonyl propenenitrile using NMR and vibrational spectra, X-ray analysis and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Gróf, M.; Gatial, A.; Milata, V.; Prónayová, N.; Kožíšek, J.; Breza, M.; Matějka, P.

    2008-11-01

    The IR, Raman and NMR spectra of 3- N, N-dimethylhydrazino-2-methylsulfonyl propenenitrile (DMHSP) [(H 3C) 2N sbnd NH sbnd CH dbnd C(CN) (SO 2CH 3)] as a solid and in different solvents were measured. The spectra and X-ray analysis revealed that DMHSP was prepared as a pure E-isomer and E- syn conformer with the syn orientation of N, N-dimethylhydrazino group towards the C dbnd C double bond in the solid state. Due to the low barrier practically free isomerization process occurred in solutions at room temperature. DMHSP exists in more polar solvents as pure E-isomer in conformational equilibrium between E- syn and E- anti but in a less polar solvent the presence of Z-isomer was observed as well. From the IR and NMR temperature dependence spectra in polar solvents the energy difference between E- anti and E- syn of Δ H = 2.3 ± 0.9 kJ/mol and Δ H = 3.2 ± 0.4 kJ/mol, respectively, was estimated with the syn one being more stable. The geometries and relative energies of possible conformers of DMHSP were evaluated using ab initio MP2 and B3LYP density functional methods in 6-31G ∗∗ basis set and compared with the X-ray data. The interpretation of NMR spectra was supported by ab initio MP2 calculations. The influence of solvent polarity on the conformational equilibrium is discussed with respect to the SCRF solvent effect calculations using PCM model. In addition, the observed IR and Raman bands were compared also with harmonic vibrational frequencies, calculated on the same levels of theory, and assigned on the base of potential energy distribution.

  20. Orphan spin operators enable the acquisition of multiple 2D and 3D magic angle spinning solid-state NMR spectra

    PubMed Central

    Gopinath, T.; Veglia, Gianluigi

    2013-01-01

    We propose a general method that enables the acquisition of multiple 2D and 3D solid-state NMR spectra for U-13C, 15N-labeled proteins. This method, called MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), makes it possible to detect four coherence transfer pathways simultaneously, utilizing orphan (i.e., neglected) spin operators of nuclear spin polarization generated during 15N-13C cross polarization (CP). In the MEIOSIS experiments, two phase-encoded free-induction decays are decoded into independent nuclear polarization pathways using Hadamard transformations. As a proof of principle, we show the acquisition of multiple 2D and 3D spectra of U-13C, 15N-labeled microcrystalline ubiquitin. Hadamard decoding of CP coherences into multiple independent spin operators is a new concept in solid-state NMR and is extendable to many other multidimensional experiments. The MEIOSIS method will increase the throughput of solid-state NMR techniques for microcrystalline proteins, membrane proteins, and protein fibrils. PMID:23676036

  1. Orphan spin operators enable the acquisition of multiple 2D and 3D magic angle spinning solid-state NMR spectra

    NASA Astrophysics Data System (ADS)

    Gopinath, T.; Veglia, Gianluigi

    2013-05-01

    We propose a general method that enables the acquisition of multiple 2D and 3D solid-state NMR spectra for U-13C, 15N-labeled proteins. This method, called MEIOSIS (Multiple ExperIments via Orphan SpIn operatorS), makes it possible to detect four coherence transfer pathways simultaneously, utilizing orphan (i.e., neglected) spin operators of nuclear spin polarization generated during 15N-13C cross polarization (CP). In the MEIOSIS experiments, two phase-encoded free-induction decays are decoded into independent nuclear polarization pathways using Hadamard transformations. As a proof of principle, we show the acquisition of multiple 2D and 3D spectra of U-13C, 15N-labeled microcrystalline ubiquitin. Hadamard decoding of CP coherences into multiple independent spin operators is a new concept in solid-state NMR and is extendable to many other multidimensional experiments. The MEIOSIS method will increase the throughput of solid-state NMR techniques for microcrystalline proteins, membrane proteins, and protein fibrils.

  2. Infrared spectroscopy of 17O- and 18O-enriched carbon dioxide: Line positions and intensities in the 4681-5337 cm-1 region

    NASA Astrophysics Data System (ADS)

    Borkov, Yu. G.; Jacquemart, D.; Lyulin, O. M.; Tashkun, S. A.; Perevalov, V. I.

    2015-07-01

    The line positions and intensities of carbon dioxide isotopologues have been retrieved in the 4681-5337 cm-1 spectral range from Fourier transform spectra of carbon dioxide recorded in LADIR (Paris, France) with the Bruker IFS 125-HR [Jacquemart D, et al., J Quant Spectrosc Radiat Transf 2012;113:961-975]. In total 6386 line positions and intensities of 89 bands of 12 isotopologues 16O12C16O, 16O13C16O, 16O12C18O, 16O12C17O, 16O13C18O, 16O13C17O, 18O12C18O, 17O12C18O, 17O12C17O, 18O13C18O, 17O13C18O, and 17O13C17O have been retrieved. 23 bands were newly assigned. All studied bands belong to the ΔP=7 series of transitions, where P = 2V1 +V2 + 3V3 is the polyad number (Vi are vibrational quantum numbers). The accuracy of the line position measurement is about 0.3×10-3 cm-1 for the unblended and not very weak lines. The accuracy of the line intensities varies from 4% to 15% depending on the isotopologue, on the intensity of the line and on the extent of the line overlapping. The observed intensities were used to fit the effective dipole moment parameters for the ΔP=7 series of transitions in 16O12C18O, 16O12C17O, 12C17O2, 17O12C18O, 16O13C17O, 13C17O2 and 17O13C18O isotopologues of carbon dioxide.

  3. Separation of small metabolites and lipids in spectra from biopsies by diffusion-weighted HR-MAS NMR: a feasibility study.

    PubMed

    Diserens, G; Vermathen, M; Precht, C; Broskey, N T; Boesch, C; Amati, F; Dufour, J-F; Vermathen, P

    2015-01-01

    High Resolution Magic Angle Spinning (HR-MAS) NMR allows metabolic characterization of biopsies. HR-MAS spectra from tissues of most organs show strong lipid contributions that are overlapping metabolite regions, which hamper metabolite estimation. Metabolite quantification and analysis would benefit from a separation of lipids and small metabolites. Generally, a relaxation filter is used to reduce lipid contributions. However, the strong relaxation filter required to eliminate most of the lipids also reduces the signals for small metabolites. The aim of our study was therefore to investigate different diffusion editing techniques in order to employ diffusion differences for separating lipid and small metabolite contributions in the spectra from different organs for unbiased metabonomic analysis. Thus, 1D and 2D diffusion measurements were performed, and pure lipid spectra that were obtained at strong diffusion weighting (DW) were subtracted from those obtained at low DW, which include both small metabolites and lipids. This subtraction yielded almost lipid free small metabolite spectra from muscle tissue. Further improved separation was obtained by combining a 1D diffusion sequence with a T2-filter, with the subtraction method eliminating residual lipids from the spectra. Similar results obtained for biopsies of different organs suggest that this method is applicable in various tissue types. The elimination of lipids from HR-MAS spectra and the resulting less biased assessment of small metabolites have potential to remove ambiguities in the interpretation of metabonomic results. This is demonstrated in a reproducibility study on biopsies from human muscle.

  4. Molecular structure, vibrational spectra, HOMO, LUMO and NMR studies of 2,3,4,5,6-penta bromo toluene and bromo durene based on density functional calculations.

    PubMed

    Krishna Kumar, V; Suganya, S; Mathammal, R

    2014-05-01

    This work deals with the vibrational spectra of 2,3,4,5,6-Penta Bromo Toluene (PBT) and Bromo Durene (BD) by quantum chemical calculations. The solid phase FTIR and FT-Raman spectra of the title compounds were recorded in the regions 4000-400 cm(-1) and 4000-50 cm(-1), respectively. The spectra were interpreted with the aid of normal coordinate analysis based on density functional theory (DFT) using B3LYP/6-31G* level and basis set combinations and was scaled using various scale factors yielding a good agreement between observed and calculated frequencies. The infrared and Raman spectra were also predicted from the calculated intensities. Comparison of the simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. The HOMO and LUMO energies were calculated within the molecule. (13)C and (1)H NMR chemical shifts results were also calculated and compared with the experimental values. Thermodynamical properties like entropy heat capacity, zero point energy have been calculated for the title molecules.

  5. 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.

  6. The conformational stability, solvation and the assignments of the experimental infrared, Raman, 1H and 13C NMR spectra of the local anesthetic drug lidocaine

    NASA Astrophysics Data System (ADS)

    Badawi, Hassan M.; Förner, Wolfgang; Ali, Shaikh A.

    2015-05-01

    The structure, vibrational and 1H and 13C NMR spectra of the local anesthetic drug lidocaine were investigated by the B3LYP/6-311G∗∗ calculations. The molecule was predicted to have the non-planar cis (NCCN ∼ 0°) structures being about 2-6 kcal/mol lower in energy than the corresponding trans (NCCN ∼ 180°) forms. The calculated NCCN (9.6°) and CNCC (-132.2°) torsional angles were in a good qualitative agreement with the reported X-ray angles (3.1 and 13.0°, -102.67 and -77.9°, respectively, for H-bonded dimers). The Gibbs energy of solution of lidocaine in formamide, water, dimethylsulfoxide, acetonitrile, methanol, ethanol and chloroform solutions was estimated at the B3LYP level. The predicted affinity of lidocaine toward the alcohols, acetonitrile and chloroform solutions was in excellent agreement with the reported experimental solubility of the drug in organic solvents. The analysis of the observed vibrational spectra is consistent with the presence of lidocaine in only one conformation at room temperature. The 1H and 13C NMR spectra of lidocaine were interpreted by experimental and DFT calculated chemical shifts of the drug. The RMSD between experimental and theoretical 1H and 13C chemical shifts for lidocaine is 0.47 and 8.26 ppm, respectively.

  7. N-15 NMR spectra of naturally abundant nitrogen in soil and aquatic natural organic matter samples of the International Humic Substances Society

    USGS Publications Warehouse

    Thorn, K.A.; Cox, L.G.

    2009-01-01

    The naturally abundant nitrogen in soil and aquatic NOM samples from the International Humic Substances Society has been characterized by solid state CP/MAS 15N NMR. Soil samples include humic and fulvic acids from the Elliot soil, Minnesota Waskish peat and Florida Pahokee peat, as well as the Summit Hill soil humic acid and the Leonardite humic acid. Aquatic samples include Suwannee River humic, fulvic and reverse osmosis isolates, Nordic humic and fulvic acids and Pony Lake fulvic acid. Additionally, Nordic and Suwannee River XAD-4 acids and Suwannee River hydrophobic neutral fractions were analyzed. Similar to literature reports, amide/aminoquinone nitrogens comprised the major peaks in the solid state spectra of the soil humic and fulvic acids, along with heterocyclic and amino sugar/terminal amino acid nitrogens. Spectra of aquatic samples, including the XAD-4 acids, contain resolved heterocyclic nitrogen peaks in addition to the amide nitrogens. The spectrum of the nitrogen enriched, microbially derived Pony Lake, Antarctica fulvic acid, appeared to contain resonances in the region of pyrazine, imine and/or pyridine nitrogens, which have not been observed previously in soil or aquatic humic substances by 15N NMR. Liquid state 15N NMR experiments were also recorded on the Elliot soil humic acid and Pony Lake fulvic acid, both to examine the feasibility of the techniques, and to determine whether improvements in resolution over the solid state could be realized. For both samples, polarization transfer (DEPT) and indirect detection (1H-15N gHSQC) spectra revealed greater resolution among nitrogens directly bonded to protons. The amide/aminoquinone nitrogens could also be observed by direct detection experiments.

  8. N-15 NMR spectra of naturally abundant nitrogen in soil and aquatic natural organic matter samples of the International Humic Substances Society

    SciTech Connect

    Thorn, Kevin A.; Cox, Larry G.

    2009-02-28

    The naturally abundant nitrogen in soil and aquatic NOM samples from the International Humic Substances Society has been characterized by solid state CP/MAS ¹⁵N NMR. Soil samples include humic and fulvic acids from the Elliot soil, Minnesota Waskish peat and Florida Pahokee peat, as well as the Summit Hill soil humic acid and the Leonardite humic acid. Aquatic samples include Suwannee River humic, fulvic and reverse osmosis isolates, Nordic humic and fulvic acids and Pony Lake fulvic acid. Additionally, Nordic and Suwannee River XAD-4 acids and Suwannee River hydrophobic neutral fractions were analyzed. Similar to literature reports, amide/aminoquinone nitrogens comprised the major peaks in the solid state spectra of the soil humic and fulvic acids, along with heterocyclic and amino sugar/terminal amino acid nitrogens. Spectra of aquatic samples, including the XAD-4 acids, contain resolved heterocyclic nitrogen peaks in addition to the amide nitrogens. The spectrum of the nitrogen enriched, microbially derived Pony Lake, Antarctica fulvic acid, appeared to contain resonances in the region of pyrazine, imine and/or pyridine nitrogens, which have not been observed previously in soil or aquatic humic substances by ¹⁵N NMR. Liquid state ¹⁵N NMR experiments were also recorded on the Elliot soil humic acid and Pony Lake fulvic acid, both to examine the feasibility of the techniques, and to determine whether improvements in resolution over the solid state could be realized. For both samples, polarization transfer (DEPT) and indirect detection (¹H–¹⁵N gHSQC) spectra revealed greater resolution among nitrogens directly bonded to protons. The amide/aminoquinone nitrogens could also be observed by direct detection experiments.

  9. Toward an in Vivo Neurochemical Profile: Quantification of 18 Metabolites in Short-Echo-Time 1H NMR Spectra of the Rat Brain

    NASA Astrophysics Data System (ADS)

    Pfeuffer, Josef; Tkáč , Ivan; Provencher, Stephen W.; Gruetter, Rolf

    1999-11-01

    Localized in vivo1H NMR spectroscopy was performed with 2-ms echo time in the rat brain at 9.4 T. Frequency domain analysis with LCModel showed that the in vivo spectra can be explained by 18 metabolite model solution spectra and a highly structured background, which was attributed to resonances with fivefold shorter in vivo T1 than metabolites. The high spectral resolution (full width at half maximum approximately 0.025 ppm) and sensitivity (signal-to-noise ratio approximately 45 from a 63-μL volume, 512 scans) was used for the simultaneous measurement of the concentrations of metabolites previously difficult to quantify in 1H spectra. The strongly represented signals of N-acetylaspartate, glutamate, taurine, myo-inositol, creatine, phosphocreatine, glutamine, and lactate were quantified with Cramér-Rao lower bounds below 4%. Choline groups, phosphorylethanolamine, glucose, glutathione, γ-aminobutyric acid, N-acetylaspartylglutamate, and alanine were below 13%, whereas aspartate and scyllo-inositol were below 22%. Intra-assay variation was assessed from a time series of 3-min spectra, and the coefficient of variation was similar to the calculated Cramér-Rao lower bounds. Interassay variation was determined from 31 pooled spectra, and the coefficient of variation for total creatine was 7%. Tissue concentrations were found to be in very good agreement with neurochemical data from the literature.

  10. Experimental and theoretical investigation of the molecular structure, conformational stability, hyperpolarizability, electrostatic potential, thermodynamic properties and NMR spectra of pharmaceutical important molecule: 4'-methylpropiophenone.

    PubMed

    Karunakaran, V; Balachandran, V

    2014-07-15

    Combined experimental and theoretical studies have been performed on the structure and vibrational spectra (IR and Raman spectra) of 4'-methylpropiophenone (MPP). The FT-IR and FT-Raman spectra of 4'-methylpropiophenone (MPP) have been recorded in the region 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR and FT-Raman spectra. A detailed interpretation of the infrared and Raman spectra of MPP are also reported based on total energy distribution (TED). The observed and the calculated frequencies are found to be in good agreement. The (1)H and (13)C NMR chemical shifts have been calculated by Gauge-Independent Atomic Orbital (GIAO) method with B3LYP/6-311++G(d,p). The natural bond orbital (NBO), natural hybrid orbital (NHO) analysis and electronic properties, such as HOMO and LUMO energies, were performed by DFT approach. The calculated HOMO and LUMO energies show that charge transfer occurs within molecule. The first order hyperpolarizability (β0) of the novel molecular system and related properties (βtot, α0 and Δα) of MPP are calculated using DFT/6-311++G(d,p) method on the finite-field approach. The Mulliken charges, the values of electric dipole moment (μ) of the molecule were computed using DFT calculations. The thermodynamic functions of the title compound were also performed at the above method and basis set.

  11. Ultrafast Magic-Angle Spinning: Benefits for the Acquisition of Ultrawide-Line NMR Spectra of Heavy Spin-1/2 Nuclei.

    PubMed

    Pöppler, Ann-Christin; Demers, Jean-Philippe; Malon, Michal; Singh, Amit Pratap; Roesky, Herbert W; Nishiyama, Yusuke; Lange, Adam

    2016-03-16

    The benefits of the ultrafast magic-angle spinning (MAS) approach for the acquisition of ultrawide-line NMR spectra-spectral simplification, increased mass sensitivity allowing the fast study of small amounts of material, efficient excitation, and application to multiple heavy nuclei-are demonstrated for tin(II) oxide (SnO) and the tin complex [(LB)Sn(II) Cl](+) [Sn(II) Cl3 ](-) [LB=2,6-diacetylpyridinebis(2,6-diisopropylanil)] containing two distinct tin environments. The ultrafast MAS experiments provide optimal conditions for the extraction of the chemical-shift anisotropy tensor parameters, anisotropy, and asymmetry for heavy spin-1/2 nuclei.

  12. Influence of inner-sphere processes on the paramagnetic shifts in the {sup 1}H NMR spectra of some mixed-ligand complexes of rare-earth elements

    SciTech Connect

    Khachatryan, A.S.; Vashchuk, A.V.; Panyushkin, V.T.

    1995-12-20

    Concentration dependences of the observed chemical shifts in the NMR spectra of 1:1:1 and 1:2:1 mixed-ligand complexes of rare-earth elements with acetylacetone and acrylic, methacrylic, maleic, and fumaric acids were analyzed. The complexes undergo inner-sphere structural transformations involving different modes of coordination of the unsaturated acid, which is capable of coordination to the central ion through both the carboxylic group and {pi} electrons of the double bond. The possibility of determining equilibrium constants and limiting chemical shifts of the isomeric forms of the complexes was demonstrated. 9 refs., 4 figs.

  13. Absolute nutrient concentration measurements in cell culture media: (1)H q-NMR spectra and data to compare the efficiency of pH-controlled protein precipitation versus CPMG or post-processing filtering approaches.

    PubMed

    Goldoni, Luca; Beringhelli, Tiziana; Rocchia, Walter; Realini, Natalia; Piomelli, Daniele

    2016-09-01

    The NMR spectra and data reported in this article refer to the research article titled "A simple and accurate protocol for absolute polar metabolite quantification in cell cultures using q-NMR" [1]. We provide the (1)H q-NMR spectra of cell culture media (DMEM) after removal of serum proteins, which show the different efficiency of various precipitating solvents, the solvent/DMEM ratios, and pH of the solution. We compare the data of the absolute nutrient concentrations, measured by PULCON external standard method, before and after precipitation of serum proteins and those obtained using CPMG (Carr-Purcell-Meiboom-Gill) sequence or applying post-processing filtering algorithms to remove, from the (1)H q-NMR spectra, the proteins signal contribution. For each of these approaches, the percent error in the absolute value of every measurement for all the nutrients is also plotted as accuracy assessment. PMID:27331118

  14. Using a Problem Solving-Cooperative Learning Approach to Improve Students' Skills for Interpreting [Superscript 1]H NMR Spectra of Unknown Compounds in an Organic Spectroscopy Course

    ERIC Educational Resources Information Center

    Angawi, Rihab F.

    2014-01-01

    To address third- and fourth-year chemistry students' difficulties with the challenge of interpreting [superscript 1]H NMR spectra, a problem solving-cooperative learning technique was incorporated in a Spectra of Organic Compounds course. Using this approach helped students deepen their understanding of the basics of [superscript 1]H NMR…

  15. Combined experimental (FT-IR, UV-visible spectra, NMR) and theoretical studies on the molecular structure, vibrational spectra, HOMO, LUMO, MESP surfaces, reactivity descriptor and molecular docking of Phomarin

    NASA Astrophysics Data System (ADS)

    Kumar, Abhishek; Srivastava, Ambrish Kumar; Gangwar, Shashi; Misra, Neeraj; Mondal, Avijit; Brahmachari, Goutam

    2015-09-01

    Phomarin is an important natural product belonging to anthraquinone series of compounds. The equilibrium geometry of phomarin has been determined and analyzed at DFT method employing B3LYP/6-311++G(d,p) level of computation. The reactivity of molecule using various descriptors such as Fukui functions, local softness, electrophilicity, electronegativity, Hardness, HOMO-LUMO gap are calculated and discussed. The infrared and UV-vis spectra of phomarin are calculated and compared with the experimentally observed ones. Moreover, 1H and 13C NMR spectra have been calculated by using the gauge independent atomic orbital method. We also notice that phomarin shows remarkable biological activities against malaria parasite. The study suggests further investigation on phomarin for their pharmacological importance.

  16. On the Δ17O budget of atmospheric O2

    NASA Astrophysics Data System (ADS)

    Young, Edward D.; Yeung, Laurence Y.; Kohl, Issaku E.

    2014-06-01

    We modeled the Δ17O of atmospheric O2 using 27 ordinary differential equations comprising a box model composed of the stratosphere, troposphere, geosphere, hydrosphere and biosphere. Results show that 57% of the deficit in 17O in O2 relative to a reference water fractionation line is the result of kinetic isotope fractionation attending the Dole effect, 33% balances the positive Δ17O of O(1D) in the stratosphere, and 10% is from evapotranspiration. The predicted Δ‧17O O2 relative to waters is -0.410‰ as measured at the δ18O of air. The value for Δ‧17O O2 varies at fixed δ18O with the concentration of atmospheric CO2, gross primary production, and net primary production as well as with reaction rates in the stratosphere. Our model prediction is consistent with our measurements of the oxygen isotopic composition of air O2 compared with rocks if rocks define a fractionation line with an intercept in δ‧17O = 103ln(δ17O/103 + 1) vs. δ‧18O = 103ln(δ18O/103 + 1) space less than SMOW but more positive than some recent measurements imply. The predicted Δ17O is less negative than that obtained from recent measurements of O2 directly against SMOW. Underestimation of Δ‧17O O2 can only be ameliorated if the integrated (bulk) Δ‧17O for stratospheric CO2 is significantly greater than measurements currently allow. Our results underscore the need for high-precision comparisons of the 17O/16O and 18O/16O ratios of atmospheric O2, VSMOW, and rocks.

  17. Conformational and isomerizational studies of 3- N, N-dimethylhydrazino-2-acetyl propenenitrile using X-ray analysis, NMR and vibrational spectra, and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Gróf, M.; Gatial, A.; Milata, V.; Prónayová, N.; Kožíšek, J.; Breza, M.; Matějka, P.

    2009-12-01

    The IR, Raman and NMR spectra of 3- N, N-dimethylhydrazino-2-acetyl propenenitrile (DMHAP) [(H 3C) 2N sbnd NH sbnd CH dbnd C(CN)(COCH 3)] were measured. X-ray analysis revealed that DMHAP exists in solid state as ZZa conformer. Vibrational and NMR spectra confirmed the existence of only one ZZa conformer with an intramolecular hydrogen bond in less polar solvents and next two EZa and EZs conformers of E-isomer with Z-orientation of acetyl group and anti and syn orientation of dimethylhydrazino group in more polar environments. The observed IR and Raman bands were compared with harmonic vibrational frequencies, calculated using ab initio MP2 and DFT/B3LYP methods in 6-31G∗∗ basis set, and assigned on the basis of potential energy distribution. In addition, the geometries and relative energies of the possible isomers and conformers of DMHAP were also evaluated on the same levels and compared with the X-ray data. The influence of environment polarity on this conformational equilibrium is discussed with respect to the SCRF solvent effect calculations using IEFPCM model.

  18. IR and NMR spectra, intramolecular hydrogen bonding and conformations of para-tert-butyl-aminothiacalix[4]arene in solid state and chloroform solution

    NASA Astrophysics Data System (ADS)

    Zvereva, Elena E.; Katsyuba, Sergey A.; Vandyukov, Alexander E.; Chernova, Alla V.; Kovalenko, Valery I.; Solovieva, Svetlana E.; Antipin, Igor S.; Konovalov, Alexander I.

    2010-02-01

    It is demonstrated that dissolution of aminothiacalix[4]arene in chloroform results in transformation of 1,3-alternate conformation, adopted in single-crystal and bulk polycrystalline solids, to the pinched-cone form. This conformer is stabilised by the intramolecular hydrogen bonds of two distal amino-groups acting as H-donors with another two amino moieties that appear as H-acceptors. The H-bonds cause quite small (ca. 10-20 cm -1) red shift of the IR bands of the NH 2 stretching vibrations, which suggests rather weak NH⋯N hydrogen bonding. This latter is sufficient to stabilize the pinched-cone conformation in the chloroform solution, but the energy gap between the pinched-cone and other conformations is small, and solid-state intermolecular forces easily overcome it, leading to realisation of the 1,3-alternate conformer. The comparison of the DFT computed and experimental vibrational and NMR spectra demonstrates good quality of present quantum-chemical computations, allows complete interpretation of the spectra and reveals simple IR and NMR spectroscopic markers of the conformers of aminothiacalix[4]arenes.

  19. Anomalous peaks in NMR spectra of iron-containing silicate minerals: pseudo-contact shifts and the potential for mapping the distributions of transition metal ions

    NASA Astrophysics Data System (ADS)

    Stebbins, J. F.; Kelsey, K. E.

    2009-04-01

    High-resolution nuclear magnetic resonance (NMR) spectroscopy has now been applied to problems of mineral structure for more than 25 years. Early attempts to collect MAS spectra on natural minerals rich in iron (or other cations with unpaired electron spins, e.g. more than a few % FeO) showed serious peak broadening, loss of signal, and thus loss of structural information. Spectroscopists have thus largely avoided such materials and have worked either with low-Fe natural minerals (e.g. zeolites) or with Fe-free synthetic compositions. While this problem remains, it has recently become apparent that in silicates with minor contents of such elements (100's to 1000's of ppm), or, in special cases, with much higher contents (at least 4% FeO), NMR spectra of nuclides such as Si-29 and Al-27 may indeed provide interesting and useful structural information that may eventually reveal new details of cation distribution, ordering, clustering, etc. Here we report on the early stages of this new application. In a recent report (Stebbins, Panero, Smyth and Frost, Am. Min. in press) we noted the presence of a variety of tiny "extra" peaks in Si-29 spectra of forsterite and wadsleyite, both containing 10's to 1000's of ppm of transition metal impurities. Some of these have chemical shifts well outside the known range for diamagnetic silicates, and were hypothesized to result from "pseudo-contact" interactions with unpaired electrons, which depend strongly on local structure. Peak shifts of this type have long been known in Sn-119 and Y-89 spectra for oxides such as rare-earth stannates (Grey et al.), but have apparently not been previously reported for silicates. New data on Si-29 and Al-27 NMR of synthetic pyrope (0.6 % CoO) and natural pyropes from the Dora Maira massif (1.5 to 3.5 wt % FeO) also show "anomalous" resonances, some of which again fall well outside the range of normal chemical shifts (e.g. +140 ppm in a Si-29 spectrum, 70 and 35 ppm in the Al-27 spectrum of a

  20. Improving the efficiency of branch-and-bound complete-search NMR assignment using the symmetry of molecules and spectra.

    PubMed

    Bernal, Andrés; Castillo, Andrés M; González, Fabio; Patiny, Luc; Wist, Julien

    2015-02-21

    Nuclear magnetic resonance (NMR) assignment of small molecules is presented as a typical example of a combinatorial optimization problem in chemical physics. Three strategies that help improve the efficiency of solution search by the branch and bound method are presented: 1. reduction of the size of the solution space by resort to a condensed structure formula, wherein symmetric nuclei are grouped together; 2. partitioning of the solution space based on symmetry, that becomes the basis for an efficient branching procedure; and 3. a criterion of selection of input restrictions that leads to increased gaps between branches and thus faster pruning of non-viable solutions. Although the examples chosen to illustrate this work focus on small-molecule NMR assignment, the results are generic and might help solving other combinatorial optimization problems. PMID:25701998

  1. Rapid measurement of multidimensional 1H solid-state NMR spectra at ultra-fast MAS frequencies

    NASA Astrophysics Data System (ADS)

    Ye, Yue Qi; Malon, Michal; Martineau, Charlotte; Taulelle, Francis; Nishiyama, Yusuke

    2014-02-01

    A novel method to realize rapid repetition of 1H NMR experiments at ultra-fast MAS frequencies is demonstrated. The ultra-fast MAS at 110 kHz slows the 1H-1H spin diffusion, leading to variations of 1H T1 relaxation times from atom to atom within a molecule. The different relaxation behavior is averaged by applying 1H-1H recoupling during relaxation delay even at ultra-fast MAS, reducing the optimal relaxation delay to maximize the signal to noise ratio. The way to determine optimal relaxation delay for arbitrary relaxation curve is shown. The reduction of optimal relaxation delay by radio-frequency driven recoupling (RFDR) was demonstrated on powder samples of glycine and ethenzamide with one and multi-dimensional NMR measurements.

  2. Improving the efficiency of branch-and-bound complete-search NMR assignment using the symmetry of molecules and spectra

    NASA Astrophysics Data System (ADS)

    Bernal, Andrés; Castillo, Andrés M.; González, Fabio; Patiny, Luc; Wist, Julien

    2015-02-01

    Nuclear magnetic resonance (NMR) assignment of small molecules is presented as a typical example of a combinatorial optimization problem in chemical physics. Three strategies that help improve the efficiency of solution search by the branch and bound method are presented: 1. reduction of the size of the solution space by resort to a condensed structure formula, wherein symmetric nuclei are grouped together; 2. partitioning of the solution space based on symmetry, that becomes the basis for an efficient branching procedure; and 3. a criterion of selection of input restrictions that leads to increased gaps between branches and thus faster pruning of non-viable solutions. Although the examples chosen to illustrate this work focus on small-molecule NMR assignment, the results are generic and might help solving other combinatorial optimization problems.

  3. Improving the efficiency of branch-and-bound complete-search NMR assignment using the symmetry of molecules and spectra

    SciTech Connect

    Bernal, Andrés; Patiny, Luc; Castillo, Andrés M.; González, Fabio; Wist, Julien

    2015-02-21

    Nuclear magnetic resonance (NMR) assignment of small molecules is presented as a typical example of a combinatorial optimization problem in chemical physics. Three strategies that help improve the efficiency of solution search by the branch and bound method are presented: 1. reduction of the size of the solution space by resort to a condensed structure formula, wherein symmetric nuclei are grouped together; 2. partitioning of the solution space based on symmetry, that becomes the basis for an efficient branching procedure; and 3. a criterion of selection of input restrictions that leads to increased gaps between branches and thus faster pruning of non-viable solutions. Although the examples chosen to illustrate this work focus on small-molecule NMR assignment, the results are generic and might help solving other combinatorial optimization problems.

  4. Effects of T2-relaxation in MAS NMR spectra of the satellite transitions for quadrupolar nuclei: a 27Al MAS and single-crystal NMR study of alum KAl(SO 4) 2 · 12H 2O

    NASA Astrophysics Data System (ADS)

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

    2005-04-01

    Asymmetries in the manifold of spinning sidebands (ssbs) from the satellite transitions have been observed in variable-temperature 27Al MAS NMR spectra of alum (KAl(SO 4) 2 · 12H 2O), recorded in the temperature range from -76 to 92 °C. The asymmetries decrease with increasing temperature and reflect the fact that the ssbs exhibit systematically different linewidths for different spectral regions of the manifold. From spin-echo 27Al NMR experiments on a single-crystal of alum, it is demonstrated that these variations in linewidth originate from differences in transverse ( T2) relaxation times for the two inner ( m = 1/2 ↔ m = 3/2 and m = -1/2 ↔ m = -3/2) and correspondingly for the two outer ( m = 3/2 ↔ m = 5/2 and m = -3/2 ↔ m = -5/2) satellite transitions. T2 relaxation times in the range 0.5-3.5 ms are observed for the individual satellite transitions at -50 °C and 7.05 T, whereas the corresponding T1 relaxation times, determined from similar saturation-recovery 27Al NMR experiments, are almost constant ( T1 = 0.07-0.10 s) for the individual satellite transitions. The variation in T2 values for the individual 27Al satellite transitions for alum is justified by a simple theoretical approach which considers the cross-correlation of the local fluctuating fields from the quadrupolar coupling and the heteronuclear ( 27Al- 1H) dipolar interaction on the T2 relaxation times for the individual transitions. This approach and the observed differences in T2 values indicate that a single random motional process modulates both the quadrupolar and heteronuclear dipolar interactions for 27Al in alum at low temperatures.

  5. 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

  6. 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.

  7. A comparative study of the conformational equilibria, vibrational, 1H and 13C NMR spectra of isobutyranilide and its derivative the anticancer drug flutamide

    NASA Astrophysics Data System (ADS)

    Badawi, Hassan M.; Förner, Wolfgang; Ali, Shaikh A.

    2014-10-01

    The molecular structure of isobutyranilide and flutamide were investigated by DFT-B3LYP/6-311G** and MP2/6-311G** calculations. Isobutyranilide was predicted to exist predominantly in a planar cis conformation, while flutamide in non-planar structures with the CF3 and the NO2 groups adopting an out of the phenyl-plane configuration. The vibrational frequencies of the low energy structures of the two molecules were computed at the DFT-B3LYP level of theory. From the calculated Gibb's free energies, isobutyranilide is estimated to have an equilibrium mixture of 91% cis and 9% trans structures, while flutamide is calculated to have a mixture of 65% cis-cis and 28% trans-cis structures at 298.15 K. The analysis of the observed vibrational spectra supports the presence of isobutyranilide in only one conformation at room temperature. From a 1:1 acetonitrile solvent experiment flutamide is determined to exist in more than one conformation at ambient temperature. Complete vibrational assignments of the normal modes of isobutyranilide and flutamide were provided on the basis of combined normal coordinate calculations and experimental Infrared and Raman spectra. The 1H and 13C NMR spectra of isobutyranilide were measured and their chemical shifts were compared to the corresponding ones of flutamide.

  8. Molecular dynamics and information on possible sites of interaction of intramyocellular metabolites in vivo from resolved dipolar couplings in localized 1H NMR spectra

    NASA Astrophysics Data System (ADS)

    Schröder, Leif; Schmitz, Christian; Bachert, Peter

    2004-12-01

    Proton NMR resonances of the endogenous metabolites creatine and phosphocreatine ((P)Cr), taurine (Tau), and carnosine (Cs, β-alanyl- L-histidine) were studied with regard to residual dipolar couplings and molecular mobility. We present an analysis of the direct 1H- 1H interaction that provides information on motional reorientation of subgroups in these molecules in vivo. For this purpose, localized 1H NMR experiments were performed on m. gastrocnemius of healthy volunteers using a 1.5-T clinical whole-body MR scanner. We evaluated the observable dipolar coupling strength SD0 ( S = order parameter) of the (P)Cr-methyl triplet and the Tau-methylene doublet by means of the apparent line splitting. These were compared to the dipolar coupling strength of the (P)Cr-methylene doublet. In contrast to the aliphatic protons of (P)Cr and Tau, the aromatic H2 ( δ = 8 ppm) and H4 ( δ = 7 ppm) protons of the imidazole ring of Cs exhibit second-order spectra at 1.5 T. This effect is the consequence of incomplete transition from Zeeman to Paschen-Back regime and allows a determination of SD0 from H2 and H4 of Cs as an alternative to evaluating the multiplet splitting which can be measured directly in high-resolution 1H NMR spectra. Experimental data showed striking differences in the mobility of the metabolites when the dipolar coupling constant D0 (calculated with the internuclear distance known from molecular geometry in the case of complete absence of molecular dynamics and motion) is used for comparison. The aliphatic signals involve very small order parameters S ≈ (1.4 - 3) × 10 -4 indicating rapid reorientation of the corresponding subgroups in these metabolites. In contrast, analysis of the Cs resonances yielded S ≈ (113 - 137) × 10 -4. Thus, the immobilization of the Cs imidazole ring owing to an anisotropic cellular substructure in human m. gastrocnemius is much more effective than for (P)Cr and Tau subgroups. Furthermore, 1H NMR experiments on aqueous model

  9. Determination of glucan phosphorylation using heteronuclear 1H, 13C double and 1H, 13C, 31P triple-resonance NMR spectra.

    PubMed

    Schmieder, Peter; Nitschke, Felix; Steup, Martin; Mallow, Keven; Specker, Edgar

    2013-10-01

    Phosphorylation and dephosphorylation of starch and glycogen are important for their physicochemical properties and also their physiological functions. It is therefore desirable to reliably determine the phosphorylation sites. Heteronuclear multidimensional NMR-spectroscopy is in principle a straightforward analytical approach even for complex carbohydrate molecules. With heterogeneous samples from natural sources, however, the task becomes more difficult because a full assignment of the resonances of the carbohydrates is impossible to obtain. Here, we show that the combination of heteronuclear (1) H,(13) C and (1) H,(13) C,(31) P techniques and information derived from spectra of a set of reference compounds can lead to an unambiguous determination of the phosphorylation sites even in heterogeneous samples. PMID:23913630

  10. Determination of glucan phosphorylation using heteronuclear 1H, 13C double and 1H, 13C, 31P triple-resonance NMR spectra.

    PubMed

    Schmieder, Peter; Nitschke, Felix; Steup, Martin; Mallow, Keven; Specker, Edgar

    2013-10-01

    Phosphorylation and dephosphorylation of starch and glycogen are important for their physicochemical properties and also their physiological functions. It is therefore desirable to reliably determine the phosphorylation sites. Heteronuclear multidimensional NMR-spectroscopy is in principle a straightforward analytical approach even for complex carbohydrate molecules. With heterogeneous samples from natural sources, however, the task becomes more difficult because a full assignment of the resonances of the carbohydrates is impossible to obtain. Here, we show that the combination of heteronuclear (1) H,(13) C and (1) H,(13) C,(31) P techniques and information derived from spectra of a set of reference compounds can lead to an unambiguous determination of the phosphorylation sites even in heterogeneous samples.

  11. Frequency-Selective Heteronuclear Dephasing and Selective Carbonyl Labeling to Deconvolute Crowded Spectra of Membrane Proteins By Magic Angle Spinning NMR

    PubMed Central

    Traaseth, Nathaniel J.; Veglia, Gianluigi

    2011-01-01

    We present a new method that combines carbonyl-selective labeling with frequency-selective heteronuclear recoupling to resolve the spectral overlap of magic angle spinning (MAS) NMR spectra of membrane proteins in fluid lipid membranes with broad lines and high redundancy in the primary sequence. We implemented this approach in both heteronuclear 15N-13Cα and homonuclear 13C-13C dipolar assisted rotational resonance (DARR) correlation experiments. We demonstrate its efficacy for the membrane protein phospholamban reconstituted in fluid PC/PE/PA lipid bilayers. The main advantage of this method is to discriminate overlapped 13Cα resonances by strategically labeling the preceding residue. This method is highly complementary to 13C′i-1-15Ni-13Cαi and 13Cαi-1-15Ni-1-13C′i experiments to discriminate inter-residue spin systems at a minimal cost to signal-to-noise. PMID:21482162

  12. Indole-containing new types of dyes and their UV-vis and NMR spectra and electronic structures: Experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Kuzu, Burak; Menges, Nurettin

    2016-06-01

    Indole containing dyes were synthesized via a simple method with high yield. These molecules have different colors and UV-vis spectra of them were recorded. Impact of solvents on absorbances was investigated and it was observed that basic solvent such as DMF and pyridine have blue shift. TD-DFT calculations were done and results were compared with experimental data. NMR data of molecules were analyzed and tautomeric forms of colorants and their ratio were determined. It was find out that two tautomers might be formed in solution, called indole and indolenine form. HOMO-LUMO and energy gaps were calculated and plotted. Furthermore, molecular electrostatic potentials were simulated to find out electrophilic and nucleophilic regions.

  13. Indole-containing new types of dyes and their UV-vis and NMR spectra and electronic structures: Experimental and theoretical study.

    PubMed

    Kuzu, Burak; Menges, Nurettin

    2016-06-01

    Indole containing dyes were synthesized via a simple method with high yield. These molecules have different colors and UV-vis spectra of them were recorded. Impact of solvents on absorbances was investigated and it was observed that basic solvent such as DMF and pyridine have blue shift. TD-DFT calculations were done and results were compared with experimental data. NMR data of molecules were analyzed and tautomeric forms of colorants and their ratio were determined. It was find out that two tautomers might be formed in solution, called indole and indolenine form. HOMO-LUMO and energy gaps were calculated and plotted. Furthermore, molecular electrostatic potentials were simulated to find out electrophilic and nucleophilic regions.

  14. Pure shift NMR.

    PubMed

    Zangger, Klaus

    2015-04-01

    Although scalar-coupling provides important structural information, the resulting signal splittings significantly reduce the resolution of NMR spectra. Limited resolution is a particular problem in proton NMR experiments, resulting in part from the limited proton chemical shift range (∼10 ppm) but even more from the splittings due to scalar coupling to nearby protons. "Pure shift" NMR spectroscopy (also known as broadband homonuclear decoupling) has been developed for disentangling overlapped proton NMR spectra. The resulting spectra are considerably simplified as they consist of single lines, reminiscent of proton-decoupled C-13 spectra at natural abundance, with no multiplet structure. The different approaches to obtaining pure shift spectra are reviewed here and several applications presented. Pure shift spectra are especially useful for highly overlapped proton spectra, as found for example in reaction mixtures, natural products and biomacromolecules.

  15. Demystifying fluorine chemical shifts: electronic structure calculations address origins of seemingly anomalous (19)F-NMR spectra of fluorohistidine isomers and analogues.

    PubMed

    Kasireddy, Chandana; Bann, James G; Mitchell-Koch, Katie R

    2015-11-11

    Fluorine NMR spectroscopy is a powerful tool for studying biomolecular structure, dynamics, and ligand binding, yet the origins of (19)F chemical shifts are not well understood. Herein, we use electronic structure calculations to describe the changes in (19)F chemical shifts of 2F- and 4F-histidine/(5-methyl)-imidazole upon acid titration. While the protonation of the 2F species results in a deshielded chemical shift, protonation of the 4F isomer results in an opposite, shielded chemical shift. The deshielding of 2F-histidine/(5-methyl)-imidazole upon protonation can be rationalized by concomitant decreases in charge density on fluorine and a reduced dipole moment. These correlations do not hold for 4F-histidine/(5-methyl)-imidazole, however. Molecular orbital calculations reveal that for the 4F species, there are no lone pair electrons on the fluorine until protonation. Analysis of a series of 4F-imidazole analogues, all with delocalized fluorine electron density, indicates that the deshielding of (19)F chemical shifts through substituent effects correlates with increased C-F bond polarity. In summary, the delocalization of fluorine electrons in the neutral 4F species, with gain of a lone pair upon protonation may help explain the difficulty in developing a predictive framework for fluorine chemical shifts. Ideas debated by chemists over 40 years ago, regarding fluorine's complex electronic effects, are shown to have relevance for understanding and predicting fluorine NMR spectra.

  16. Facilitating quality control for spectra assignments of small organic molecules: nmrshiftdb2--a free in-house NMR database with integrated LIMS for academic service laboratories.

    PubMed

    Kuhn, Stefan; Schlörer, Nils E

    2015-08-01

    nmrshiftdb2 supports with its laboratory information management system the integration of an electronic lab administration and management into academic NMR facilities. Also, it offers the setup of a local database, while full access to nmrshiftdb2's World Wide Web database is granted. This freely available system allows on the one hand the submission of orders for measurement, transfers recorded data automatically or manually, and enables download of spectra via web interface, as well as the integrated access to prediction, search, and assignment tools of the NMR database for lab users. On the other hand, for the staff and lab administration, flow of all orders can be supervised; administrative tools also include user and hardware management, a statistic functionality for accounting purposes, and a 'QuickCheck' function for assignment control, to facilitate quality control of assignments submitted to the (local) database. Laboratory information management system and database are based on a web interface as front end and are therefore independent of the operating system in use. PMID:25998807

  17. Crystal structure and theoretical study of IR and 1H and 13C NMR spectra of cordatin, a natural product with antiulcerogenic activity

    NASA Astrophysics Data System (ADS)

    Brasil, Davi S. B.; Alves, Cláudio N.; Guilhon, Giselle M. S. P.; Muller, Adolfo H.; Secco, Ricardo De S.; Peris, Gabriel; Llusar, Rosa

    Cordatin is a furan diterpenoid with a clerodane skeleton isolated from Croton palanostigma Klotzsch (Euphorbiaceae). This natural product shows significant antiulcerogenic activity, similar to cimetidine (Tagamet®), a compound used for the treatment of peptic ulcers. The crystal structure of cordatin was obtained by X-ray diffraction and its geometrical parameters were compared with theoretical calculations at the B3LYP theory level. The IR and NMR (1H and 13C chemical shifts and coupling constants) spectra were obtained and compared with the theoretical calculations. The B3LYP theory level, with the 6-31G(d,p) and 6-311G(d,p) basis set, provided IR absorption values close to the experimental data. Moreover, theoretical NMR parameters obtained in both gas phase and chloroform solvent at the B3PW91/DGDZVP, B3LYP/6-311+G(2d,p), and B3PW91/6-311+G(2d,p) levels showed good correlations with the experimental results.

  18. FT-IR, FT-Raman, NMR and UV-Vis spectra and DFT calculations of 5-bromo-2-ethoxyphenylboronic acid (monomer and dimer structures).

    PubMed

    Sas, E B; Kose, E; Kurt, M; Karabacak, M

    2015-02-25

    In this study, the Fourier Transform Infrared (FT-IR) and Fourier Transform Raman (FT-Raman) spectra of 5-bromo-2-ethoxyphenylboronic acid (5Br2EPBA) are recorded in the solid phase in the region 4000-400 cm(-1) and 3500-10 cm(-1), respectively. The (1)H, (13)C and DEPT nuclear magnetic resonance (NMR) spectra are recorded in DMSO solution. The UV-Vis absorption spectrum of 5Br2EPBA is saved in the range of 200-400 nm in ethanol and water. The following theoretical calculations for monomeric and dimeric structures are supported by experimental results. The molecular geometry and vibrational frequencies in the ground state are calculated by using DFT methods with 6-31G(d,p) and 6-311G(d,p) basis sets. There are four conformers for the present molecule. The computational results diagnose the most stable conformer of 5Br2EPBA as Trans-Cis (TC) form. The complete assignments are performed on the basis of the total energy distribution (TED) of vibrational modes, calculated with scaled quantum mechanics (SQM) method in parallel quantum solutions (PQS) program. The (1)H and (13)C NMR chemical shifts of 5Br2EPBA molecule are calculated by using the Gauge Invariant Atomic Orbital (GIAO) method in DMSO and gas phase for monomer and dimer structures of the most stable conformer. Moreover, electronic properties, such as the HOMO and LUMO energies (by TD-DFT and CIS methods) and molecular electrostatic potential surface (MEPs) are investigated. Stability of the molecule arising from hyper-conjugative interactions, charge delocalization is analyzed using natural bond orbital (NBO) analysis. Nonlinear optical (NLO) properties and thermodynamic features are presented. All calculated results are compared with the experimental data of the title molecule. The correlation of theoretical and experimental results provides a detailed description of the structural and physicochemical properties of the title molecule.

  19. FT-IR, FT-Raman, NMR and UV-Vis spectra and DFT calculations of 5-bromo-2-ethoxyphenylboronic acid (monomer and dimer structures).

    PubMed

    Sas, E B; Kose, E; Kurt, M; Karabacak, M

    2015-02-25

    In this study, the Fourier Transform Infrared (FT-IR) and Fourier Transform Raman (FT-Raman) spectra of 5-bromo-2-ethoxyphenylboronic acid (5Br2EPBA) are recorded in the solid phase in the region 4000-400 cm(-1) and 3500-10 cm(-1), respectively. The (1)H, (13)C and DEPT nuclear magnetic resonance (NMR) spectra are recorded in DMSO solution. The UV-Vis absorption spectrum of 5Br2EPBA is saved in the range of 200-400 nm in ethanol and water. The following theoretical calculations for monomeric and dimeric structures are supported by experimental results. The molecular geometry and vibrational frequencies in the ground state are calculated by using DFT methods with 6-31G(d,p) and 6-311G(d,p) basis sets. There are four conformers for the present molecule. The computational results diagnose the most stable conformer of 5Br2EPBA as Trans-Cis (TC) form. The complete assignments are performed on the basis of the total energy distribution (TED) of vibrational modes, calculated with scaled quantum mechanics (SQM) method in parallel quantum solutions (PQS) program. The (1)H and (13)C NMR chemical shifts of 5Br2EPBA molecule are calculated by using the Gauge Invariant Atomic Orbital (GIAO) method in DMSO and gas phase for monomer and dimer structures of the most stable conformer. Moreover, electronic properties, such as the HOMO and LUMO energies (by TD-DFT and CIS methods) and molecular electrostatic potential surface (MEPs) are investigated. Stability of the molecule arising from hyper-conjugative interactions, charge delocalization is analyzed using natural bond orbital (NBO) analysis. Nonlinear optical (NLO) properties and thermodynamic features are presented. All calculated results are compared with the experimental data of the title molecule. The correlation of theoretical and experimental results provides a detailed description of the structural and physicochemical properties of the title molecule. PMID:25305625

  20. FT-IR, FT-Raman, NMR and UV-Vis spectra and DFT calculations of 5-bromo-2-ethoxyphenylboronic acid (monomer and dimer structures)

    NASA Astrophysics Data System (ADS)

    Sas, E. B.; Kose, E.; Kurt, M.; Karabacak, M.

    2015-02-01

    In this study, the Fourier Transform Infrared (FT-IR) and Fourier Transform Raman (FT-Raman) spectra of 5-bromo-2-ethoxyphenylboronic acid (5Br2EPBA) are recorded in the solid phase in the region 4000-400 cm-1 and 3500-10 cm-1, respectively. The 1H, 13C and DEPT nuclear magnetic resonance (NMR) spectra are recorded in DMSO solution. The UV-Vis absorption spectrum of 5Br2EPBA is saved in the range of 200-400 nm in ethanol and water. The following theoretical calculations for monomeric and dimeric structures are supported by experimental results. The molecular geometry and vibrational frequencies in the ground state are calculated by using DFT methods with 6-31G(d,p) and 6-311G(d,p) basis sets. There are four conformers for the present molecule. The computational results diagnose the most stable conformer of 5Br2EPBA as Trans-Cis (TC) form. The complete assignments are performed on the basis of the total energy distribution (TED) of vibrational modes, calculated with scaled quantum mechanics (SQM) method in parallel quantum solutions (PQS) program. The 1H and 13C NMR chemical shifts of 5Br2EPBA molecule are calculated by using the Gauge Invariant Atomic Orbital (GIAO) method in DMSO and gas phase for monomer and dimer structures of the most stable conformer. Moreover, electronic properties, such as the HOMO and LUMO energies (by TD-DFT and CIS methods) and molecular electrostatic potential surface (MEPs) are investigated. Stability of the molecule arising from hyper-conjugative interactions, charge delocalization is analyzed using natural bond orbital (NBO) analysis. Nonlinear optical (NLO) properties and thermodynamic features are presented. All calculated results are compared with the experimental data of the title molecule. The correlation of theoretical and experimental results provides a detailed description of the structural and physicochemical properties of the title molecule.

  1. Spectrally edited 2D 13Csbnd 13C NMR spectra without diagonal ridge for characterizing 13C-enriched low-temperature carbon materials

    NASA Astrophysics Data System (ADS)

    Johnson, Robert L.; Anderson, Jason M.; Shanks, Brent H.; Fang, Xiaowen; Hong, Mei; Schmidt-Rohr, Klaus

    2013-09-01

    Two robust combinations of spectral editing techniques with 2D 13Csbnd 13C NMR have been developed for characterizing the aromatic components of 13C-enriched low-temperature carbon materials. One method (exchange with protonated and nonprotonated spectral editing, EXPANSE) selects cross peaks of protonated and nearby nonprotonated carbons, while the other technique, dipolar-dephased double-quantum/single-quantum (DQ/SQ) NMR, selects signals of bonded nonprotonated carbons. Both spectra are free of a diagonal ridge, which has many advantages: Cross peaks on the diagonal or of small intensity can be detected, and residual spinning sidebands or truncation artifacts associated with the diagonal ridge are avoided. In the DQ/SQ experiment, dipolar dephasing of the double-quantum coherence removes protonated-carbon signals; this approach also eliminates the need for high-power proton decoupling. The initial magnetization is generated with minimal fluctuation by combining direct polarization, cross polarization, and equilibration by 13C spin diffusion. The dipolar dephased DQ/SQ spectrum shows signals from all linkages between aromatic rings, including a distinctive peak from polycondensed aromatics. In EXPANSE NMR, signals of protonated carbons are selected in the first spectral dimension by short cross polarization combined with dipolar dephasing difference. This removes ambiguities of peak assignment to overlapping signals of nonprotonated and protonated aromatic carbons, e.g. near 125 ppm. Spin diffusion is enhanced by dipolar-assisted rotational resonance. Before detection, Csbnd H dipolar dephasing by gated decoupling is applied, which selects signals of nonprotonated carbons. Thus, only cross peaks due to magnetization originating from protonated C and ending on nearby nonprotonated C are retained. Combined with the chemical shifts deduced from the cross-peak position, this double spectral editing defines the bonding environment of aromatic, COO, and Cdbnd O carbons

  2. NMR of 133Cs+ in stretched hydrogels: One-dimensional, z- and NOESY spectra, and probing the ion's environment in erythrocytes

    NASA Astrophysics Data System (ADS)

    Kuchel, Philip W.; Shishmarev, Dmitry; Puckeridge, Max; Levitt, Malcolm H.; Naumann, Christoph; Chapman, Bogdan E.

    2015-12-01

    133Cs nuclear magnetic resonance (NMR) spectroscopy was conducted on 133Cs+ in gelatin hydrogels that were either relaxed or stretched. Stretching generated a septet from this spin-7/2 nucleus, and its nuclear magnetic relaxation was studied via z-spectra, and two-dimensional nuclear Overhauser (NOESY) spectroscopy. Various spectral features were well simulated by using Mathematica and the software package SpinDynamica. Spectra of CsCl in suspensions of human erythrocytes embedded in gelatin gel showed separation of the resonances from the cation inside and outside the cells. Upon stretching the sample, the extracellular 133Cs+ signal split into a septet, while the intracellular peak was unchanged, revealing different alignment/ordering properties of the environment inside and around the cells. Differential interference contrast light microscopy confirmed that the cells were stretched when the overall sample was elongated. Analysis of the various spectral features of 133Cs+ reported here opens up applications of this K+ congener for studies of cation-handling by metabolically-active cells and tissues in aligned states.

  3. NMR spectra and potentiometry studies of aluminum(III) binding with coenzyme NAD+ in acidic aqueous solutions.

    PubMed

    Yang, Xiaodi; Bi, Shuping; Yang, Xiaoliang; Yang, Li; Hu, Jun; Liu, Jian; Yang, Zhengbiao

    2003-06-01

    Complexation and conformational studies of coenzyme NAD+ with aluminum were conducted in acidic aqueous solutions (pH 2-5) by means of potentiometry as well as multinuclear (1H, 13C, 31P, 27Al) and two-dimensional (1H, 1H-NOESY) NMR spectroscopy. These led to the following results: (1) Al could coordinate with NAD+ through the following binding sites: N7' of adenine and pyrophosphate free oxygen (O(A)1, O(N)1,O(A)2) to form various mononuclear 1:1 (AlLH23+, AlLH2+) and 2:1 (AlL2-) species, and dinuclear 2:2 (Al2L22+) species. (2) The conformations of NAD+ and Al-NAD+ depended on the solvents and different species in the complexes. The results suggest the occurrence of an Al-linked complexation, which causes structural changes at the primary recognition sites and secondary conformational alterations for coenzymes. This finding will help us to understand role of Al in biological enzyme reaction systems.

  4. Structure of 1-methyl-6-oxyquinolinium betaine dihydrate studied by X-ray diffraction, DFT calculations, vibrational and NMR spectra

    NASA Astrophysics Data System (ADS)

    Barczyński, P.; Ratajczak-Sitarz, M.; Katrusiak, A.; Szafran, M.

    2010-07-01

    The crystals of 1-methyl-6-oxyquinolinium betaine dihydrate, 6QB·2H 2O, are triclinic, space group P1¯. The oxygen atom of 6QB exhibits an extremely rare capability of accepting four hydrogen bonds. It is engaged in four hydrogen bonds to water molecules of the 2.823, 2.825, 2.833 and 2.849 Å; each water molecule interacts with two neighbouring 6QB molecules linking them into infinite sheets. Differences in geometrical parameters between the X-ray and calculated molecules reflect changes in their structures between zwitterion and quinonoid forms. The probable assignments of the experimental FTIR solid spectrum have been made on the basis of B3LYP/6-311G(d,p) calculated frequencies in vacuum. Both 1H and 13C chemical shifts are solvent dependent. Linear correlations between the experimental 1H and 13C NMR chemical shifts of 6QB·2H 2O in solutions and the GIAO/B3LYP/6-311G(d,p) calculated magnetic isotropic shielding tensors ( σcal) using the screening solvation model, δexp = a + bσcal, are reported.

  5. Ab Initio Molecular Dynamics Simulations and GIPAW NMR Calculations of a Lithium Borate Glass Melt.

    PubMed

    Ohkubo, Takahiro; Tsuchida, Eiji; Takahashi, Takafumi; Iwadate, Yasuhiko

    2016-04-14

    The atomic structure of a molten 0.3Li2O-0.7B2O3 glass at 1250 K was investigated using ab initio molecular dynamics (AIMD) simulations. The gauge including projector augmented wave (GIPAW) method was then employed for computing the chemical shift and quadrupolar coupling constant of (11)B, (17)O, and (7)Li from 764 AIMD derived structures. The chemical shift and quadrupolar coupling constant distributions were directly estimated from the dynamical structure of the molten glass. (11)B NMR parameters of well-known structural units such as the three-coordinated ring, nonring, and four-coordinated tetrahedron were found to be in good agreement with the experimental results. In this study, more detailed classification of B units was presented based on the number of O species bonded to the B atoms. This highlights the limitations of (11)B NMR sensitivity for resolving (11)B local environment using the experimentally obtained spectra only. The (17)O NMR parameter distributions can theoretically resolve the bridging and nonbridging O atoms with different structural units such as nonring, single boroxol ring, and double boroxol ring. Slight but clear differences in the number of bridging O atoms surrounding Li that have not been reported experimentally were observed in the theoretically obtained (7)Li NMR parameters. PMID:27010637

  6. A Comparison of NMR Spectra Obtained for Solid-Phase-Synthesis Resins Using Conventional High-Resolution, Magic-Angle-Spinning, and High-Resolution Magic-Angle-Spinning Probes

    NASA Astrophysics Data System (ADS)

    Keifer, Paul A.; Baltusis, Laima; Rice, David M.; Tymiak, Adrienne A.; Shoolery, James N.

    It has recently been shown that high-resolution 1H NMR spectra can be obtained for samples covalently bound to polystyrene-based (Tentagel) solid-phase-synthesis resins by the use of magic-angle spinning (MAS) combined with high-resolution-probe technology. The attainable spectral resolution in the 1H and 13C NMR spectra of these resins is affected by molecular mobility and magnetic-susceptibility mismatches, both within the sample and in the probe itself. Using new high-resolution MAS probes called Nano·nmr probes, the importance of magnetic-susceptibility matching in the construction of these probes is demonstrated, and the limitations of using MAS alone to generate line narrowing in both 1H and 13C NMR are explored using a solvent-swollen functionalized Wang resin. The effects of presaturation, temperature, spin rate, and different solvents upon spectral quality have also been investigated, and advanced 1D- and 2D-experimental capability is demonstrated. This ability to generate high-resolution NMR spectra of samples still bound to the resins is expected to be of extreme interest in not only solid-phase synthesis, but also in the rapidly growing field of combinatorial chemistry.

  7. Technical aspects of fast magic-angle turning NMR for dilute spin-1/2 nuclei with broad spectra.

    PubMed

    Hu, Y-Y; Schmidt-Rohr, K

    2011-09-01

    For obtaining sideband-free spectra of high-Z spin-1/2 nuclei with large (>1000 ppm) chemical-shift anisotropies and broad isotropic-shift dispersion, we recently identified Gan's modified five-pulse magic-angle turning (MAT) experiment as the best available broadband pulse sequence, and adapted it to fast magic-angle spinning. Here, we discuss technical aspects such as pulse timings that compensate for off-resonance effects and are suitable for large CSAs over a range of 1.8γB(1); methods to minimize the duration of z-periods by cyclic decrementation; shearing without digitization artifacts, by sharing between channels (points); and maximizing the sensitivity by echo-matched full-Gaussian filtering. The method is demonstrated on a model sample of mixed amino acids and its large bandwidth is highlighted by comparison with the multiple-π-pulse PASS technique. Applications to various tellurides are shown; these include GeTe, Sb(2)Te(3) and Ag(0.53)Pb(18)Sb(1.2)Te(20), with spectra spanning up to 190 kHz, at 22 kHz MAS. We have also determined the (125)Te chemical shift anisotropies from the intensities of the spinning sidebands resolved by isotropic-shift separation. PMID:21782396

  8. Ultra-wide bore 900 MHz high-resolution NMR at the National High Magnetic Field Laboratory

    NASA Astrophysics Data System (ADS)

    Fu, R.; Brey, W. W.; Shetty, K.; Gor'kov, P.; Saha, S.; Long, J. R.; Grant, S. C.; Chekmenev, E. Y.; Hu, J.; Gan, Z.; Sharma, M.; Zhang, F.; Logan, T. M.; Brüschweller, R.; Edison, A.; Blue, A.; Dixon, I. R.; Markiewicz, W. D.; Cross, T. A.

    2005-11-01

    Access to an ultra-wide bore (105 mm) 21.1 T magnet makes possible numerous advances in NMR spectroscopy and MR imaging, as well as novel applications. This magnet was developed, designed, manufactured and tested at the National High Magnetic Field Laboratory and on July 21, 2004 it was energized to 21.1 T. Commercial and unique homebuilt probes, along with a standard commercial NMR console have been installed and tested with many science applications to develop this spectrometer as a user facility. Solution NMR of membrane proteins with enhanced resolution, new pulse sequences for solid state NMR taking advantage of narrowed proton linewidths, and enhanced spatial resolution and contrast leading to improved animal imaging have been documented. In addition, it is demonstrated that spectroscopy of single site 17O labeled macromolecules in a hydrated lipid bilayer environment can be recorded in a remarkably short period of time. 17O spectra of aligned samples show the potential for using this data for orientational restraints and for characterizing unique details of cation binding properties to ion channels. The success of this NHMFL magnet illustrates the potential for using a similar magnet design as an outsert for high temperature superconducting insert coils to achieve an NMR magnet with a field >25 T.

  9. 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.

  10. FTIR, FT-RAMAN, NMR, spectra, normal co-ordinate analysis, NBO, NLO and DFT calculation of N,N-diethyl-4-methylpiperazine-1-carboxamide molecule.

    PubMed

    Muthu, S; Elamurugu Porchelvi, E

    2013-11-01

    The Fourier Transform Infrared (FT-IR) and FT-Raman of N,N-diethyl-4-methylpiperazine-1-carboxamide (NND4MC) have been recorded and analyzed. The structure of the compound was optimized and the structural characteristics were determined by density functional theory (DFT) using B3LYP method with 6-31G(d,p) and 6-311G(d,p) basis sets. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The theoretically predicted FT-IR and FT-Raman spectra of the title molecule have been constructed. The detailed interpretation of the vibrational spectra has been carried out with aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that electron density (ED) in the σ(*) and π(*) antibonding orbitals and second order delocalization energies (E2) confirm the occurrence of intramolecular charge transfer (ICT) within the molecule. The electronic dipole moment (μD) and the first hyperpolarizability (βtot) values of the investigated molecule were computed using Density Functional Theory (DFT/B3LYP) with 6-31G(d,p) and 6-311G(d,p) basis sets. The calculated results also show that the NND4MC molecule may have microscopy nonlinear optical (NLO) behavior with non zero values. Mulliken atomic charges of NND4MC were calculated. The (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. The UV-Vis spectrum of the compound was recorded. The theoretical electronic absorption spectra have been calculated by using CIS, TD-DFT methods. A study on the electronic properties, such as HOMO and LUMO energies, molecular electrostatic potential (MEP) were also performed.

  11. Probing the influential factors of NMR T1-T2 spectra in the characterization of the kerogen by numerical simulation

    NASA Astrophysics Data System (ADS)

    Ge, Xinmin; Fan, Yiren; Chen, Hua; Deng, Shaogui; Cao, Yingchang; Zahid, Muhammad Aleem

    2015-11-01

    The low field nuclear magnetic resonance (NMR) spectroscopy has been widely used to characterize the longitudinal and transversal relaxation (T1-T2) spectrum of unconventional resources such as shale gas and tight oil containing significant proportions of kerogen and bitumen. However, it requires exquisite design of the acquisition model and the inversion algorithm due to the fast relaxation nature of the kerogen and bitumen. A new direct two dimensional (2D) inversion algorithm combined the iterative truncated singular value decomposition (TSVD) and the Akaiake Information Criterion (AIC) is presented to perform the data inversion efficiently. The fluid component decomposition (FCD) is applied to construct the forward T1-T2 model of the kerogen, and numerical simulations are conducted to investigate factors which may influence inversion results including echo spacing, recovery time series, signal to noise ratio (SNR), and the maximal iteration time. Results show that the T2 component is heavily impaired by the echo spacing, whereas the T1 component is influenced by the recovery time series but with limited effects. The inversion precision is greatly affected by the quality of the data. The inversed spectrum deviates from the model seriously when the SNR of the artificial noise is lower than 50, and the T2 component is more sensitive to the noise than the T1 component. What's more, the maximal iteration time can also affect the inversion result, especially when the maximal iteration time is smaller than 500. Proper acquisition and inversion parameters for the characterization of the kerogen are obtained considering the precision and the computational cost.

  12. Probing the influential factors of NMR T1-T2 spectra in the characterization of the kerogen by numerical simulation.

    PubMed

    Ge, Xinmin; Fan, Yiren; Chen, Hua; Deng, Shaogui; Cao, Yingchang; Zahid, Muhammad Aleem

    2015-11-01

    The low field nuclear magnetic resonance (NMR) spectroscopy has been widely used to characterize the longitudinal and transversal relaxation (T1-T2) spectrum of unconventional resources such as shale gas and tight oil containing significant proportions of kerogen and bitumen. However, it requires exquisite design of the acquisition model and the inversion algorithm due to the fast relaxation nature of the kerogen and bitumen. A new direct two dimensional (2D) inversion algorithm combined the iterative truncated singular value decomposition (TSVD) and the Akaiake Information Criterion (AIC) is presented to perform the data inversion efficiently. The fluid component decomposition (FCD) is applied to construct the forward T1-T2 model of the kerogen, and numerical simulations are conducted to investigate factors which may influence inversion results including echo spacing, recovery time series, signal to noise ratio (SNR), and the maximal iteration time. Results show that the T2 component is heavily impaired by the echo spacing, whereas the T1 component is influenced by the recovery time series but with limited effects. The inversion precision is greatly affected by the quality of the data. The inversed spectrum deviates from the model seriously when the SNR of the artificial noise is lower than 50, and the T2 component is more sensitive to the noise than the T1 component. What's more, the maximal iteration time can also affect the inversion result, especially when the maximal iteration time is smaller than 500. Proper acquisition and inversion parameters for the characterization of the kerogen are obtained considering the precision and the computational cost. PMID:26397220

  13. Automated feature extraction for the classification of human in vivo 13C NMR spectra using statistical pattern recognition and wavelets.

    PubMed

    Tate, A R; Watson, D; Eglen, S; Arvanitis, T N; Thomas, E L; Bell, J D

    1996-06-01

    If magnetic resonance spectroscopy (MRS) is to become a useful tool in clinical medicine, it will be necessary to find reliable methods for analyzing and classifying MRS data. Automated methods are desirable because they can remove user bias and can deal with large amounts of data, allowing the use of all the available information. In this study, techniques for automatically extracting features for the classification of MRS in vivo data are investigated. Among the techniques used were wavelets, principal component analysis, and linear discriminant function analysis. These techniques were tested on a set of 75 in vivo 13C spectra of human adipose tissue from subjects from three different dietary groups (vegan, vegetarian, and omnivore). It was found that it was possible to assign automatically 94% of the vegans and omnivores to their correct dietary groups, without the need for explicit identification or measurement of peaks.

  14. Assignment of the sup 1 H and sup 15 N NMR spectra of Rhodobacter capsulatus ferrocytochrome c sub 2

    SciTech Connect

    Gooley, P.R.; Caffrey, M.S.; Cusanovich, M.A.; MacKenzie, N.E. )

    1990-03-06

    The peptide resonances of the {sup 1}H and {sup 15}N nuclear magnetic resonance spectra of ferrocytochrome c{sub 2} from Rhodobacter capsulatus are sequentially assigned by a combination of 2D {sup 1}H-{sup 1}H and {sup 1}H-{sup 15}N spectroscopy, the latter performed on {sup 15}N-enriched protein. Short-range nuclear Overhauser effect (NOE) data show {alpha}-helices from residues 3-17, 55-65, 69-88, and 103-115. Within the latter two {alpha}-helices, there are three single 3{sub 10} turns, 70-72, 76-78, and 107-109. In addition {alpha}H-NH{sub i+1} and {alpha}H-NH{sub i+2} NOEs indicate that the N-terminal helix (3-17) is distorted. Compared to horse or tuna cytochrome c and cytochrome c{sub 2} of Rhodospirillium rubrum, there is a 6-residue insertion at residues 23-29 in R. capsulatus cytochrome c{sub 2}. The NOE data show that this insertion forms a loop, probably an {Omega} loop. {sup 1}H-{sup 15}N heteronuclear multiple quantum correlation experiments are used to follow NH exchange over a period of 40 h. As the 2D spectra are acquired in short time periods (30 min), rates for intermediate exchanging protons can be measured. Comparison of the NH exchange data for the N-terminal helix of cytochrome c{sub 2} of R. capsulatus with the highly homologous horse heart cytochrome c shows that this helix is less stable in cytochrome c{sub 2}.

  15. Advanced NMR characterization of zeolite catalysts

    NASA Astrophysics Data System (ADS)

    Welsh, L. B.

    1985-04-01

    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 magic angle sample spinning NMR (MASS NMR) and variable engine sample spinning NMR (VASS NMR) on 500 and 360 MHz (proton frequency) NMR spectrometers. The NMR techniques that will be emphasized are the measurement and analysis of the (17)O NMR properties, (27)Al NMR intensity quantitation, and (27)Al and (29)Si NMR relaxation rates. 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 (17)O enriched Na-Y faujasties.

  16. 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.

  17. Fingerprints of molecular structure and hydrogen bonding effects in the /sup 13/C NMR spectra of monosaccharides with partially deuterated hydroxyls

    SciTech Connect

    Reuben, J.

    1984-10-17

    A new NMR approach to structure elucidation of carbohydrates in solution is presented. Examined in detail are the isotopic multiplets in /sup 13/C NMR spectra that result from partial deuteration of the hydroxyls for a series of monosaccharides and some of their deoxy and methyl glycoside derivatives in Me/sub 2/SO-d/sub 6/ solutions. Chemical shift and isotope effect data are presented for the pyranose and furanose forms of aldopentoses, aldohexoses, and ketohexoses. The results show that the magnitude of the ..gamma.. effect resulting from deuteration of a hydroxyl on a vicinal carbon atoms is sensitive to the relative geometric relationship, cis or trans, of the hydroxyls in vicinal diol arrays. Thus, the multiplet pattern for carbons 3 and 4 of the pyranose ring can serve as a fingerprint of molecular structure at the pentopyranose level. The aldopentoses and ketohexoses are amenable to structural analysis by this simple approach. Ambiguity will arise for pairs of aldohexoses related to each other by epimerization at C5. Intramolecular hydrogen bonding between the hydroxyls at C2 and C4 in ..cap alpha..-D-talopyranose gives rise to some unusual effects. A mechanism involving isotopic perturbation of the equilibrium between the hydrogen-bonded structures O4-H...O2-H and O2-H...O4-H is suggested as the possible source of these effects. Similarly, the extra splitting observed in the /sup 13/C resonance of C3 of ..beta..-D-fucofuranose are rationalized in terms of an equilibrium between the hydrogen-bonded structures C5-O5-H...O3-H and Cl-O1-H...O3-H. The approach of isotopic multiplets appears to be uniquely suited for the study of such structures.

  18. Apparatus for rapid adjustment of the degree of alignment of NMR samples in aqueous media: verification with residual quadrupolar splittings in (23)Na and (133)Cs spectra.

    PubMed

    Kuchel, Philip W; Chapman, Bogdan E; Müller, Norbert; Bubb, William A; Philp, David J; Torres, Allan M

    2006-06-01

    NMR spectra of (23)Na(+) and (133)Cs(+) in gelatine in a silicone rubber tube that was stretched to various extents showed remarkably reproducible resonance multiplicity. The relative intensities of the components of the split peaks had ratios, 3:4:3, and 7:12:15:16:15:12:7, respectively, that conformed with those predicted using a Mathematica program. The silicone-rubber tube was sealed at its lower end by a small rubber stopper and placed inside a thick-walled glass tube. Gelatine was injected in solution into the silicone tube and 'set' by cooling below 30 degrees C. A plastic thumb-screw held the silicone tube at various degrees of extension, up to approximately 2-fold. After constituting the gel in buffers containing NaCl and CsCl, both (23)Na and (133)Cs NMR spectroscopy revealed that after stretching the initial single Lorentzian line was split into a well-resolved triplet and a heptet, respectively. This was interpreted as being due to coupling between the electric quadrupoles of the nuclei and the average electric field gradient tensor of the collagen molecules of gelatine; these molecules became progressively more aligned in the direction of the main magnetic field, B(0), of the vertical bore magnet, as the gel was stretched. This apparatus provides a simple way of demonstrating fundamental physical characteristics of quadrupolar cations, some characteristics of gelatine under stretching, and a way to invoke static distortion of red blood cells. It should be useful with these and other cell types, for studies of metabolic and membrane transport characteristics that may change when the cells are distorted, and possibly for structural studies of macromolecules.

  19. Apparatus for rapid adjustment of the degree of alignment of NMR samples in aqueous media: Verification with residual quadrupolar splittings in 23Na and 133Cs spectra

    NASA Astrophysics Data System (ADS)

    Kuchel, Philip W.; Chapman, Bogdan E.; Müller, Norbert; Bubb, William A.; Philp, David J.; Torres, Allan M.

    2006-06-01

    NMR spectra of 23Na + and 133Cs + in gelatine in a silicone rubber tube that was stretched to various extents showed remarkably reproducible resonance multiplicity. The relative intensities of the components of the split peaks had ratios, 3:4:3, and 7:12:15:16:15:12:7, respectively, that conformed with those predicted using a Mathematica program. The silicone-rubber tube was sealed at its lower end by a small rubber stopper and placed inside a thick-walled glass tube. Gelatine was injected in solution into the silicone tube and 'set' by cooling below 30 °C. A plastic thumb-screw held the silicone tube at various degrees of extension, up to ˜2-fold. After constituting the gel in buffers containing NaCl and CsCl, both 23Na and 133Cs NMR spectroscopy revealed that after stretching the initial single Lorentzian line was split into a well-resolved triplet and a heptet, respectively. This was interpreted as being due to coupling between the electric quadrupoles of the nuclei and the average electric field gradient tensor of the collagen molecules of gelatine; these molecules became progressively more aligned in the direction of the main magnetic field, B0, of the vertical bore magnet, as the gel was stretched. This apparatus provides a simple way of demonstrating fundamental physical characteristics of quadrupolar cations, some characteristics of gelatine under stretching, and a way to invoke static distortion of red blood cells. It should be useful with these and other cell types, for studies of metabolic and membrane transport characteristics that may change when the cells are distorted, and possibly for structural studies of macromolecules.

  20. Bayesian reconstruction of projection reconstruction NMR (PR-NMR).

    PubMed

    Yoon, Ji Won

    2014-11-01

    Projection reconstruction nuclear magnetic resonance (PR-NMR) is a technique for generating multidimensional NMR spectra. A small number of projections from lower-dimensional NMR spectra are used to reconstruct the multidimensional NMR spectra. In our previous work, it was shown that multidimensional NMR spectra are efficiently reconstructed using peak-by-peak based reversible jump Markov chain Monte Carlo (RJMCMC) algorithm. We propose an extended and generalized RJMCMC algorithm replacing a simple linear model with a linear mixed model to reconstruct close NMR spectra into true spectra. This statistical method generates samples in a Bayesian scheme. Our proposed algorithm is tested on a set of six projections derived from the three-dimensional 700 MHz HNCO spectrum of a protein HasA. PMID:25218584

  1. Correcting human heart 31P NMR spectra for partial saturation. Evidence that saturation factors for PCr/ATP are homogeneous in normal and disease states

    NASA Astrophysics Data System (ADS)

    Bottomley, Paul A.; Hardy, Christopher J.; Weiss, Robert G.

    Heart PCr/ATP ratios measured from spatially localized 31P NMR spectra can be corrected for partial saturation effects using saturation factors derived from unlocalized chest surface-coil spectra acquired at the heart rate and approximate Ernst angle for phosphor creatine (PCr) and again under fully relaxed conditions during each 31P exam. To validate this approach in studies of normal and disease states where the possibility of heterogeneity in metabolite T1 values between both chest muscle and heart and normal and disease states exists, the properties of saturation factors for metabolite ratios were investigated theoretically under conditions applicable in typical cardiac spectroscopy exams and empirically using data from 82 cardiac 31P exams in six study groups comprising normal controls ( n = 19) and patients with dilated ( n = 20) and hypertrophic ( n = 5) cardiomyopathy, coronary artery disease ( n = 16), heart transplants ( n = 19), and valvular heart disease ( n = 3). When TR ≪ T1,(PCr), with T1(PCr) ⩾ T1(ATP), the saturation factor for PCr/ATP lies in the range 1.5 ± 0.5, regardless of the T1 values. The precise value depends on the ratio of metabolite T1 values rather than their absolute values and is insensitive to modest changes in TR. Published data suggest that the metabolite T1 ratio is the same in heart and muscle. Our empirical data reveal that the saturation factors do not vary significantly with disease state, nor with the relative fractions of muscle and heart contributing to the chest surface-coil spectra. Also, the corrected myocardial PCr/ATP ratios in each normal or disease state bear no correlation with the corresponding saturation factors nor the fraction of muscle in the unlocalized chest spectra. However, application of the saturation correction (mean value, 1.36 ± 0.03 SE) significantly reduced scatter in myocardial PCr/ATP data by 14 ± 11% (SD) ( p ⩽ 0.05). The findings suggest that the relative T1 values of PCr and ATP are

  2. HOMO-LUMO, UV, NLO, NMR and vibrational analysis of 3-methyl-1-phenylpyrazole using FT-IR, FT-RAMAN FT-NMR spectra and HF-DFT computational methods.

    PubMed

    Carthigayan, K; Xavier, S; Periandy, S

    2015-05-01

    In this paper, the spectral analysis of 3-methyl-1-phenylpyrazole is carried out using the FT-IR, FT Raman, FT NMR and UV-Vis spectra with the help of quantum mechanical computations using HF and density functional theories. The different conformers of the compound and their minimum energies are studied using B3LYP functional with 6-311+G (d,p) basis set and the most stable conformer with minimum energy was identified and the same conformer was used for further computations. The computed wave numbers from different methods are scaled so as to agree with the experimental values and the scaling factors are reported. All the modes of vibrations are assigned and the structure the molecule is analyzed in terms of parameters like bond length, bond angle and dihedral angle predicted by both HF and B3LYP methods with 6-311+G (d,p) and 6-311++G (d,p) basis sets. The values of dipole moment (μ), polarizability (α) and hyperpolarizability (β) of the molecule are reported, using which the non-linear property of the molecule is discussed. The HOMO-LUMO mappings are reported which reveals the different charge transfer possibilities within the molecule. The isotropic chemical shifts predicted for (1)H and (13)C atoms using gauge invariant atomic orbital (GIAO) theory show good agreement with experimental shifts. NBO analysis is carried out to picture the charge transfer between the localized bonds and lone pairs. The thermodynamic properties (heat capacity, entropy and enthalpy) at different temperatures are also calculated. PMID:25710893

  3. HOMO-LUMO, UV, NLO, NMR and vibrational analysis of 3-methyl-1-phenylpyrazole using FT-IR, FT-RAMAN FT-NMR spectra and HF-DFT computational methods.

    PubMed

    Carthigayan, K; Xavier, S; Periandy, S

    2015-05-01

    In this paper, the spectral analysis of 3-methyl-1-phenylpyrazole is carried out using the FT-IR, FT Raman, FT NMR and UV-Vis spectra with the help of quantum mechanical computations using HF and density functional theories. The different conformers of the compound and their minimum energies are studied using B3LYP functional with 6-311+G (d,p) basis set and the most stable conformer with minimum energy was identified and the same conformer was used for further computations. The computed wave numbers from different methods are scaled so as to agree with the experimental values and the scaling factors are reported. All the modes of vibrations are assigned and the structure the molecule is analyzed in terms of parameters like bond length, bond angle and dihedral angle predicted by both HF and B3LYP methods with 6-311+G (d,p) and 6-311++G (d,p) basis sets. The values of dipole moment (μ), polarizability (α) and hyperpolarizability (β) of the molecule are reported, using which the non-linear property of the molecule is discussed. The HOMO-LUMO mappings are reported which reveals the different charge transfer possibilities within the molecule. The isotropic chemical shifts predicted for (1)H and (13)C atoms using gauge invariant atomic orbital (GIAO) theory show good agreement with experimental shifts. NBO analysis is carried out to picture the charge transfer between the localized bonds and lone pairs. The thermodynamic properties (heat capacity, entropy and enthalpy) at different temperatures are also calculated.

  4. Effect of organic matter application on CP-MAS-13C-NMR spectra of humic acids from a brown soil

    NASA Astrophysics Data System (ADS)

    Dou, S.

    2009-04-01

    -MAS-13C-NMR spectrum of HA. The CP-MAS- 13C-NMR spectra of the HA were quite similar to each other. These spectra exhibited signals for alkyl (0~50 ppm), O-alkyl (50~110 ppm), aromatic (110~160 ppm) and carbonyl (160~200 ppm) regions. The signals in carbonyl C region concentrated between 172 ppm and 173 ppm, and with a small signal occurred in the region of 190~200 ppm, indicating that there was carbonyl C of carboxylic acid, ester and amide, but a little amount carbonyl C of ketonic compounds. In the region of aromatic C, the most obvious peaks were the absorption at 131~133 ppm and 114~117 ppm. The former was mainly the aromatic C substituted by -COOH or -COOMe and the unsubstituted aromatic meta to carbons bearing an oxygen or nitrogen atom; the latter was mainly the unsubstituted aromatic C ortho and para to carbons bearing an oxygen and nitrogen atom. There was a small peak at 152-154ppm, which was the signal of phenolic OH. The signal at 55~56 ppm was methoxyl C. The signals at 71~73 ppm were due to the -CH(OH)- in carbohydrate. The peak at 102~103 ppm was generally assigned to double oxygen-C in polysaccharide (possibly acetal). The maximum absorption at 30 ppm was the contribution of the polymethylene chain -(CH2)n- in saturated hydrocarbons (Wilson, 1981). After OM application, the contents of alkyl C and O-alkyl C increased and the contents of aromatic C and carbonxyl C except to 1986 decreased. Compared with 1986, the contents of O-alkyl C increased and the contents of alkyl C decreased for the same treatment CKbr and O2. Aromaticity decreased significantly in OM treatments, indicating that the OM decreased the content of aromatic C and was simplified the molecular structure. The relative content of O-alkyl C increased indicating that OM application increased the content of methoxyl C and -CH(OH)- in carbohydrate. Alkyl C was probably derived from compounds of plants with high resistance to degradation, such as cutin and suberin (Baldock et al., 1992; Preston

  5. Ferroelastic phase transitions by 14N NMR spectra in [N(CH3)4]2CoCl4 and [N(CH3)4]2ZnCl4 single crystals

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2016-09-01

    Changes in the structural geometry of [N(CH3)4]2BCl4 (B=Co and Zn) crystals near the phase transition temperatures were studied by analyzing the 14N nuclear magnetic resonance (NMR) spectra. Two physically inequivalent a-N(1)(CH3)4 and b-N(2)(CH3)4 groups were observed in these spectra. Abrupt changes in the resonance frequency and splitting of 14N NMR signals near the phase transition temperatures were attributed to structural phase transitions, and the primary mechanism of these phase transitions exhibited ferroelastic characteristics. In addition, ferroelasticity of [N(CH3)4]2BCl4 was identified at low temperatures using optical polarizing microscopy.

  6. Quantum-chemical simulation of 1H NMR spectra. 2. Comparison of DFT-based procedures for computing proton-proton coupling constants in organic molecules.

    PubMed

    Bally, Thomas; Rablen, Paul R

    2011-06-17

    The performance of 250 different computational protocols (combinations of density functionals, basis sets and methods) was assessed on a set of 165 well-established experimental (1)H-(1)H nuclear coupling constants (J(H-H)) from 65 molecules spanning a wide range of "chemical space". Thereby we found that, if one uses core-augmented basis sets and allows for linear scaling of the raw results, calculations of only the Fermi contact term yield more accurate predictions than calculations where all four terms that contribute to J(H-H) are evaluated. It turns out that B3LYP/6-31G(d,p)u+1s is the best (and, in addition, one of the most economical) of all tested methods, yielding predictions of J(H-H) with a root-mean-square deviation from experiment of less than 0.5 Hz for our test set. Another method that does similarly well, without the need for additional 1s basis functions, is B3LYP/cc-pVTZ, which is, however, ca. 8 times more "expensive" in terms of CPU time. A selection of the better methods was tested on a probe set comprising 61 J(H-H) values from 37 molecules. In this set we also included five molecules where conformational averaging is required. The rms deviations were better than or equal to those with the training set, which indicates that the method we recommend is generally applicable for organic molecules. We give instructions on how to carry out calculations of (1)H chemical shifts and J(H-H) most economically and provide scripts to extract the relevant information from the outputs of calculations with the Gaussian program in clearly arranged form, e.g., to feed them into programs for simulating entire (1)H NMR spectra.

  7. Alterations in the natural abundance /sup 13/C NMR spectra of skeletal muscle membranes depending on the extraction medium of muscle

    SciTech Connect

    Barany, M.; Arus, C.; Anderson, J.A.; Marotta, S.F.

    1986-03-01

    Minced rat muscles were extracted with NaCl solution with additions: 1) 10 mM EDTA, or 2) 2 mM MgCl/sub 2/, or 3) None (final ionic strength equivalent to 150 mM NaCl, pH 7.0). The total muscle membranes were pelleted between 1500 and 252,000 x g. All membranes were washed several times by homogenization with 0.05 M NaCl, pH 6.1, and centrifugation at 252,000 x g. The final pellets were suspended in /sup 2/H/sub 2/O to contain 150 mg membrane protein/ml in 30% /sup 2/H/sub 2/O. /sup 13/C NMR spectra were recorded at 50.3 MHz, under fully relaxed conditions. The spectral pattern varied according to the extraction medium of muscle: Relative to None addition, EDTA caused a decrease in the intensity of the polyunsaturated carbon resonance (128.6 ppm), whereas with MgCl/sub 2/ the opposite effect was found. Metal analysis, after combustion of the membranes, showed 1.1-1.6 mol Ca/sup 2 +/ per 10/sup 5/ g protein in None and Mgcl/sub 2/ membranes, and 1000-times less Ca/sup 2 +/ in EDTA membranes. The Mg/sup 2 +/ content of the membranes was not affected by EDTA, however, it was increased 5-fold when MgCl/sub 2/ was present in the extraction medium. Thus, the results indicate that membrane-bound Ca/sup 2 +/ and Mg/sup 2 +/ alter the conformation of membrane-phospholipis.

  8. Effect of organic matter application on CP-MAS-13C-NMR spectra of humic acids from a brown soil

    NASA Astrophysics Data System (ADS)

    Dou, S.

    2009-04-01

    -MAS-13C-NMR spectrum of HA. The CP-MAS- 13C-NMR spectra of the HA were quite similar to each other

  9. Hydrogen Burning of {sup 17}O in Classical Novae

    SciTech Connect

    Chafa, A.; Ouichaoui, S.; Tatischeff, V.; Coc, A.; Garrido, F.; Kiener, J.; Lefebvre-Schuhl, A.; Thibaud, J.-P.; Aguer, P.; Barhoumi, S.; Hernanz, M.; Jose, J.; Sereville, N. de

    2005-07-15

    We report on the observation of a previously unknown resonance at E{sub R}{sup lab}=194.1{+-}0.6 keV in the {sup 17}O(p,{alpha}){sup 14}N reaction, with a measured resonance strength {omega}{gamma}{sub p{alpha}}=1.6{+-}0.2 meV. We studied in the same experiment the {sup 17}O(p,{gamma}){sup 18}F reaction by an activation method and the resonance-strength ratio was found to be {omega}{gamma}{sub p{alpha}}/{omega}{gamma}{sub p{gamma}}=470{+-}50. The corresponding excitation energy in the {sup 18}F compound nucleus was determined to be 5789.8{+-}0.3 keV by {gamma}-ray measurements using the {sup 14}N({alpha},{gamma}){sup 18}F reaction. These new resonance properties have important consequences for {sup 17}O nucleosynthesis and {gamma}-ray astronomy of classical novae.

  10. 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

  11. The interstellar C18O/C17O ratio in the solar neighbourhood: The ρ Ophiuchus cloud

    NASA Astrophysics Data System (ADS)

    Wouterloot, J. G. A.; Brand, J.; Henkel, C.

    2005-02-01

    Observations of up to ten carbon monoxide (CO and isotopomers) transitions are presented to study the interstellar C18O/C17O ratio towards 21 positions in the nearby (d˜140 pc) low-mass star forming cloud ρ Oph. A map of the C18O J=1-0 distribution of parts of the cloud is also shown. An average 12C18O/12C17O isotopomeric ratio of 4.11 ± 0.14, reflecting the 18O/17O isotope ratio, is derived from Large Velocity Gradient (LVG) calculations. From LTE column densities we derive a ratio of 4.17±0.26. These calculations also show that the kinetic temperature decreases from about 30 K in the cloud envelope to about 10 K in the cloud cores. This decrease is accompanied by an increase of the average molecular hydrogen density from 104 cm-3 to ⪆105 cm-3. Towards some lines of sight C18O optical depths reach values of order unity. Based on observations collected with the Swedish/ESO Submillimeter Telescope (SEST) at the European Southern Observatory, Chile (ESO 62.I-0752). All spectra (some of which are shown in Fig. \\ref{spectra}) are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/430/549

  12. 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

    2016-02-01

    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. PMID:26730889

  13. 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

    2016-02-01

    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.

  14. 19F high magnetic field NMR study of beta-ZrF4 and CeF4: from spectra reconstruction to correlation between fluorine sites and 19F isotropic chemical shifts.

    PubMed

    Legein, C; Fayon, F; Martineau, C; Body, M; Buzaré, J-Y; Massiot, D; Durand, E; Tressaud, A; Demourgues, A; Péron, O; Boulard, B

    2006-12-25

    High magnetic field and high spinning frequency one- and two-dimensional one-pulse MAS 19F NMR spectra of beta-ZrF4 and CeF4 were recorded and reconstructed allowing the accurate determination of the 19F chemical shift tensor parameters for the seven different crystallographic fluorine sites of each compound. The attributions of the NMR resonances are performed using the superposition model for 19F isotropic chemical shift calculation initially proposed by Bureau et al. (Bureau, B.; Silly, G.; Emery, J.; Buzaré, J.-Y. Chem. Phys. 1999, 249, 85-104). A satisfactory reliability is reached with a root-mean-square (rms) deviation between calculated and measured isotropic chemical shift values equal to 1.5 and 3.5 ppm for beta-ZrF4 and CeF4, respectively. PMID:17173418

  15. FT-IR, FT-Raman, UV, NMR spectra and molecular structure investigation of (E)-2-(3-chloropyrazin-2-yl)-1-(3-ethyl-2, 6-diphenyl piperidin-4-ylidene) hydrazine: A combined experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Therasa Alphonsa, A.; Loganathan, C.; Athavan Alias Anand, S.; Kabilan, S.

    2015-11-01

    This work presents the characterization of (E)-2-(3-chloropyrazin-2-yl)-1-(3-ethyl-2, 6-diphenyl piperidin-4-ylidene) hydrazine (HDE) by quantum chemical calculations and spectral techniques. The structure was investigated by FT-IR, FT-Raman, UV-vis and NMR techniques. The geometrical parameters and energies have been obtained from Density functional theory (DFT) B3LYP (6-31G (d, p)) basis set calculations. The geometry of the molecule was fully optimized, vibrational spectra were calculated and fundamental vibrations were assigned on the basis of total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. 1H and 13C NMR chemical shifts of the molecule were calculated using Gauge-independent atomic orbital method (GIAO). The electronic properties such as excitation energies, wavelength, HOMO, LUMO energies performed by Time dependent density functional theory (TD-DFT) results complements with the experimental findings. NBO analysis has been performed for analyzing charge delocalization throughout the molecule. The calculation results were applied to simulate spectra of the title compound, which show excellent agreement with observed spectra. To provide information about the interactions between human cytochrome protein and the novel compound theoretically, docking studies were carried out using Schrödinger software.

  16. PIC microcontroller based external fast analog to digital converter to acquire wide-lined solid NMR spectra by BRUKER DRX and Avance-I spectrometers.

    PubMed

    Koczor, Bálint; Rohonczy, János

    2015-01-01

    Concerning many former liquid or hybrid liquid/solid NMR consoles, the built in Analog-to-Digital Converters (ADCs) are incapable of digitizing the fids at sampling rates in the MHz range. Regarding both strong anisotropic interactions in the solid state and wide chemical shift dispersion nuclei in solution phase such as (195)Pt, (119)Sn, (207)Pb etc., the spectrum range of interest might be in the MHz range. As determining the informative tensor components of anisotropic NMR interactions requires nonlinear fitting over the whole spectrum including the asymptotic baseline, it is prohibited by low sampling rates of the ADCs. Wide spectrum width is also useful in solution NMR, since windowing of wide chemical shift ranges is avoidable. We built an external analog to digital converter with 10 MHz maximal sampling rate, which can work simultaneously with the built in ADC of the spectrometer. The ADC was tested on both Bruker DRX and Avance-I NMR consoles. In addition to the analog channels it only requires three external digital lines of the NMR console. The ADC sends data to PC via USB. The whole process is controlled by software written in JAVA which is implemented under TopSpin.

  17. Pulsed EPR investigations of systems modeling molybdenum enzymes: hyperfine and quadrupole parameters of oxo-17O in [Mo 17O(SPh)4]-.

    PubMed

    Astashkin, Andrei V; Neese, Frank; Raitsimring, Arnold M; Cooney, J Jon A; Bultman, Eric; Enemark, John H

    2005-11-30

    Ka band ESEEM spectroscopy was used to determine the hyperfine (hfi) and nuclear quadrupole (nqi) interaction parameters for the oxo-17O ligand in [Mo 17O(SPh)4]-, a spectroscopic model of the oxo-Mo(V) centers of enzymes. The isotropic hfi constant of 6.5 MHz found for the oxo-17O is much smaller than the values of approximately 20-40 MHz typical for the 17O nucleus of an equatorial OH(2) ligand in molybdenum enzymes. The 17O nqi parameter (e2qQ/h = 1.45 MHz, eta approximately = 0) is the first to be obtained for an oxo group in a metal complex. The parameters of the oxo-17O ligand, as well as other magnetic resonance parameters of [Mo 17O(SPh)4]- predicted by quasi-relativistic DFT calculations, were in good agreement with those obtained in experiment. From the electronic structure of the complex revealed by DFT, it follows that the SOMO is almost entirely molybdenum d(xy) and sulfur p, while the spin density on the oxo-17O is negative, determined by spin polarization mechanisms. The results of this work will enable direct experimental identification of the oxo ligand in a variety of chemical and biological systems.

  18. 17O-Decoupled 1H Spectroscopy and Imaging with a Surface Coil: STEAM Decoupling

    NASA Astrophysics Data System (ADS)

    Charagundla, Sridhar R.; Duvvuri, Umamaheswar; Noyszewski, Elizabeth A.; Dandora, Rahul; Stolpen, Alan H.; Leigh, J. S.; Reddy, Ravinder

    2000-03-01

    17O-decoupled 1H spin-echo imaging has been reported as a means of indirect 17O detection, with potential application to measurement of blood flow and metabolism. In its current form, 17O decoupling requires large RF amplitudes and a 180° refocusing pulse, complicating its application in volume and surface coils, respectively. To overcome this problem, we have developed an 17O-decoupled proton stimulated echo sequence ("STEAM decoupling") to allow 17O detection with a surface coil. A high B1 amplitude is easily generated, allowing complete decoupling of 17O and 1H. Slice-selective, 17O-decoupled 1H imaging is readily performed and the sequence is easily adapted for localized spectroscopy. Intrinsic correction for variations in B1 and further compensation for B1 inhomogeneity are discussed.

  19. NBO, HOMO-LUMO, UV, NLO, NMR and vibrational analysis of veratrole using FT-IR, FT-Raman, FT-NMR spectra and HF-DFT computational methods.

    PubMed

    Suvitha, A; Periandy, S; Gayathri, P

    2015-03-01

    This work deals with FT-IR, FT-Raman and FT-NMR spectral analysis and NBO, NLO, HOMO-LUMO and electronic transitions studies on veratrole. The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands were interpreted with the aid of structure optimizations and geometrical parameter calculations based on Hartree-Fock (HF) and density functional theory (DFT) method with 6-311++G(d, p) basis set. A study on the electronic properties, such as HOMO and LUMO energies were performed by time independent DFT approach. In addition, molecular electrostatic potential (MEP), Natural Bond-Orbital (NBO) analysis and thermodynamic properties were performed. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by gauge independent atomic orbital (GIAO) method and compared with experimental chemical shift.

  20. Dynamic nuclear polarization of 17O: direct polarization.

    PubMed

    Michaelis, Vladimir K; Corzilius, Björn; Smith, Albert A; Griffin, Robert G

    2013-12-01

    Dynamic nuclear polarization of (17)O was studied using four different polarizing agents: the biradical TOTAPOL and the monoradicals trityl and SA-BDPA, as well as a mixture of the latter two. Field profiles, DNP mechanisms, and enhancements were measured to better understand and optimize directly polarizing this low-gamma quadrupolar nucleus using both mono- and biradical polarizing agents. Enhancements were recorded at <88 K and were >100 using the trityl (OX063) radical and <10 with the other polarizing agents. The >10,000-fold savings in acquisition time enabled a series of biologically relevant small molecules to be studied with small sample sizes and the measurement of various quadrupolar parameters. The results are discussed with comparison to room temperature studies and GIPAW quantum chemical calculations. These experimental results illustrate the strength of high field DNP and the importance of radical selection for studying low-gamma nuclei.

  1. Vibrational (FT-IR and FT-Raman), electronic (UV-Vis), NMR (1H and 13C) spectra and reactivity analyses of 4,5-dimethyl-o-phenylenediamine.

    PubMed

    Atac, Ahmet; Karaca, Caglar; Gunnaz, Salih; Karabacak, Mehmet

    2014-09-15

    The structure of 4,5-dimethyl-o-phenylenediamine (C8H12N2, DMPDA) was investigated on the basis of spectroscopic data and theoretical calculations. The sterochemical structure was determined by FT-IR, FT-Raman, UV, 1H and 13C NMR spectra. An experimental study and a theoretical analysis were associated by using the B3LYP method with Gaussian09 package program. FT-IR and FT-Raman spectra were recorded in the region of 4000-400 cm(-1) and 4000-10 cm(-1), respectively. The vibrational spectra were calculated by DFT method and the fundamental vibrations were assigned on the basis of the total energy distribution (TED), calculated with scaled quantum mechanics (SQM) method with Parallel Quantum Solutions (PQS) program. The UV absorption spectrum of the compound that dissolved in ethanol solution were recorded in the range of 190-400 nm. Total density of state (TDOS) and partial density of state (PDOS) of the DMPDA in terms of HOMOs and LUMOs were calculated and analyzed. Chemical shifts were reported in ppm relative to tetramethylsilane (TMS) for 1H and 13C NMR spectra. The compound was dissolved in dimethyl sulfoxide (DMSO). Also, 1H and 13C chemical shifts calculated using the gauge independent atomic orbital (GIAO) method. Mullikan atomic charges and other thermo-dynamical parameters were investigated with the help of B3LYP (DFT) method using 6-311++G** basis set. On the basis of the thermodynamic properties of the title compound at different temperatures have been carried out, revealing the correlations between heat capacity (C), entropy (S), enthalpy changes (H) and temperatures. The optimized bond lengths, bond angles, chemical shifts and vibrational wavenumbers showed the best agreement with the experimental results.

  2. Vibrational (FT-IR and FT-Raman), electronic (UV-Vis), NMR (1H and 13C) spectra and reactivity analyses of 4,5-dimethyl-o-phenylenediamine.

    PubMed

    Atac, Ahmet; Karaca, Caglar; Gunnaz, Salih; Karabacak, Mehmet

    2014-09-15

    The structure of 4,5-dimethyl-o-phenylenediamine (C8H12N2, DMPDA) was investigated on the basis of spectroscopic data and theoretical calculations. The sterochemical structure was determined by FT-IR, FT-Raman, UV, 1H and 13C NMR spectra. An experimental study and a theoretical analysis were associated by using the B3LYP method with Gaussian09 package program. FT-IR and FT-Raman spectra were recorded in the region of 4000-400 cm(-1) and 4000-10 cm(-1), respectively. The vibrational spectra were calculated by DFT method and the fundamental vibrations were assigned on the basis of the total energy distribution (TED), calculated with scaled quantum mechanics (SQM) method with Parallel Quantum Solutions (PQS) program. The UV absorption spectrum of the compound that dissolved in ethanol solution were recorded in the range of 190-400 nm. Total density of state (TDOS) and partial density of state (PDOS) of the DMPDA in terms of HOMOs and LUMOs were calculated and analyzed. Chemical shifts were reported in ppm relative to tetramethylsilane (TMS) for 1H and 13C NMR spectra. The compound was dissolved in dimethyl sulfoxide (DMSO). Also, 1H and 13C chemical shifts calculated using the gauge independent atomic orbital (GIAO) method. Mullikan atomic charges and other thermo-dynamical parameters were investigated with the help of B3LYP (DFT) method using 6-311++G** basis set. On the basis of the thermodynamic properties of the title compound at different temperatures have been carried out, revealing the correlations between heat capacity (C), entropy (S), enthalpy changes (H) and temperatures. The optimized bond lengths, bond angles, chemical shifts and vibrational wavenumbers showed the best agreement with the experimental results. PMID:24813280

  3. Vibrational (FT-IR and FT-Raman), electronic (UV-Vis), NMR (1H and 13C) spectra and reactivity analyses of 4,5-dimethyl-o-phenylenediamine

    NASA Astrophysics Data System (ADS)

    Atac, Ahmet; Karaca, Caglar; Gunnaz, Salih; Karabacak, Mehmet

    2014-09-01

    The structure of 4,5-dimethyl-o-phenylenediamine (C8H12N2, DMPDA) was investigated on the basis of spectroscopic data and theoretical calculations. The sterochemical structure was determined by FT-IR, FT-Raman, UV, 1H and 13C NMR spectra. An experimental study and a theoretical analysis were associated by using the B3LYP method with Gaussian09 package program. FT-IR and FT-Raman spectra were recorded in the region of 4000-400 cm-1 and 4000-10 cm-1, respectively. The vibrational spectra were calculated by DFT method and the fundamental vibrations were assigned on the basis of the total energy distribution (TED), calculated with scaled quantum mechanics (SQM) method with Parallel Quantum Solutions (PQS) program. The UV absorption spectrum of the compound that dissolved in ethanol solution were recorded in the range of 190-400 nm. Total density of state (TDOS) and partial density of state (PDOS) of the DMPDA in terms of HOMOs and LUMOs were calculated and analyzed. Chemical shifts were reported in ppm relative to tetramethylsilane (TMS) for 1H and 13C NMR spectra. The compound was dissolved in dimethyl sulfoxide (DMSO). Also, 1H and 13C chemical shifts calculated using the gauge independent atomic orbital (GIAO) method. Mullikan atomic charges and other thermo-dynamical parameters were investigated with the help of B3LYP (DFT) method using 6-311++G** basis set. On the basis of the thermodynamic properties of the title compound at different temperatures have been carried out, revealing the correlations between heat capacity (C), entropy (S), enthalpy changes (H) and temperatures. The optimized bond lengths, bond angles, chemical shifts and vibrational wavenumbers showed the best agreement with the experimental results.

  4. 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.

  5. 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. PMID:24158053

  6. Exploiting periodic first-principles calculations in NMR spectroscopy of disordered solids.

    PubMed

    Ashbrook, Sharon E; Dawson, Daniel M

    2013-09-17

    -bearing radioactive waste. In a second example, we discuss how (17)O NMR can be used to probe the dynamic disorder of H in hydroxyl-humite minerals (nMg2SiO4·Mg(OH)2), and how (19)F NMR can be used to understand F substitution in these systems. The combination of first-principles calculations and multinuclear NMR spectroscopy facilitates the investigation of local structure, disorder, and dynamics in solids. We expect that applications will undoubtedly become more widespread with further advances in computational and experimental methods. Insight into the atomic-scale environment is a crucial first step in understanding the structure-property relationships in solids, and it enables the efficient design of future materials for a range of end uses.

  7. Peptide bond hydrolysis catalyzed by the Wells-Dawson Zr(α2-P2W17O61)2 polyoxometalate.

    PubMed

    Absillis, Gregory; Parac-Vogt, Tatjana N

    2012-09-17

    In this paper we report the first example of peptide hydrolysis catalyzed by a polyoxometalate complex. A series of metal-substituted Wells-Dawson polyoxometalates were synthesized, and their hydrolytic activity toward the peptide bond in glycylglycine (GG) was examined. Among these, the Zr(IV)- and Hf(IV)-substituted ones were the most reactive. Detailed kinetic studies were performed with the Zr(IV)-substituted Wells-Dawson type polyoxometalate K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O which was shown to act as a catalyst for the hydrolysis of the peptide bond in GG. The speciation of K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O which is highly dependent on the pD, concentration, and temperature of the solution, was fully determined with the help of (31)P NMR spectroscopy and its influence on the GG hydrolysis rate was examined. The highest reaction rate (k(obs) = 9.2 (±0.2) × 10(-5) min(-1)) was observed at pD 5.0 and 60 °C. A 10-fold excess of GG was hydrolyzed in the presence of K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O proving the principles of catalysis. (13)C NMR data suggested the coordination of GG to the Zr(IV) center in K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O via its N-terminal amine group and amide carbonyl oxygen. These findings were confirmed by the inactivity of K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O toward the N-blocked analogue acetamidoglycylglycinate and the inhibitory effect of oxalic, malic, and citric acid. Triglycine, tetraglycine, and pentaglycine were also fully hydrolyzed in the presence of K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O yielding glycine as the final product of hydrolysis. K(15)H[Zr(α(2)-P(2)W(17)O(61))(2)]·25H(2)O also exhibited hydrolytic activity toward a series of other dipeptides.

  8. NMR characterization of hydrocarbon adsorption on calcite surfaces: a first principles study.

    PubMed

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

    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(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 (CaCO3 (101¯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 (43)Ca, (13)C, and (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.

  9. 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.

  10. NMR characterization of hydrocarbon adsorption on calcite surfaces: a first principles study.

    PubMed

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

    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(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 (CaCO3 (101¯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 (43)Ca, (13)C, and (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. PMID:25429955

  11. Molecular structure, vibrational and 13C NMR spectra of two ent-kaurenes spirolactone type diterpenoids rabdosinate and rabdosin B: A combined experimental and density functional methods

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Wang, Xueliang

    2015-01-01

    The title compounds, rabdosinate and rabdosin B, were isolated from the leaves of Isodon japonica, and characterized by IR-NMR spectroscopy. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO-13C) chemical shift values of the title compounds have been calculated by using DFT/B3LYP method with 6-311++G(d,p) basis set. In addition, obtained results were related to the linear regression of experimental 13C NMR chemical shifts values. The integral equation formalism polarized continuum model (IEFPCM) was used in treating chloroform solvation effects on optimized structural parameters and 13C chemical shifts. Besides, molecular electrostatic potential (MEP), HOMO-LUMO analysis were performed by the B3LYP method.

  12. Molecular structure, vibrational and 13C NMR spectra of two ent-kaurenes spirolactone type diterpenoids rabdosinate and rabdosin B: a combined experimental and density functional methods.

    PubMed

    Wang, Tao; Wang, Xueliang

    2015-01-25

    The title compounds, rabdosinate and rabdosin B, were isolated from the leaves of Isodon japonica, and characterized by IR-NMR spectroscopy. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO-13C) chemical shift values of the title compounds have been calculated by using DFT/B3LYP method with 6-311++G(d,p) basis set. In addition, obtained results were related to the linear regression of experimental 13C NMR chemical shifts values. The integral equation formalism polarized continuum model (IEFPCM) was used in treating chloroform solvation effects on optimized structural parameters and 13C chemical shifts. Besides, molecular electrostatic potential (MEP), HOMO-LUMO analysis were performed by the B3LYP method. PMID:25123947

  13. Molecular structure, vibrational and 13C NMR spectra of two ent-kaurenes spirolactone type diterpenoids rabdosinate and rabdosin B: a combined experimental and density functional methods.

    PubMed

    Wang, Tao; Wang, Xueliang

    2015-01-25

    The title compounds, rabdosinate and rabdosin B, were isolated from the leaves of Isodon japonica, and characterized by IR-NMR spectroscopy. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO-13C) chemical shift values of the title compounds have been calculated by using DFT/B3LYP method with 6-311++G(d,p) basis set. In addition, obtained results were related to the linear regression of experimental 13C NMR chemical shifts values. The integral equation formalism polarized continuum model (IEFPCM) was used in treating chloroform solvation effects on optimized structural parameters and 13C chemical shifts. Besides, molecular electrostatic potential (MEP), HOMO-LUMO analysis were performed by the B3LYP method.

  14. Experimental determination of the {sup 17}O(p,{alpha}){sup 14}N and {sup 17}O(p,{gamma}){sup 18}F reaction rates

    SciTech Connect

    Chafa, A.; Ouichaoui, S.; Tatischeff, V.; Coc, A.; Garrido, F.; Kiener, J.; Lefebvre-Schuhl, A.; Thibaud, J.-P.; Aguer, P.; Barhoumi, S.; Hernanz, M.; Jose, J.; Sereville, N. de

    2007-03-15

    The {sup 17}O(p,{alpha}){sup 14}N and {sup 17}O(p,{gamma}){sup 18}F reactions are of major importance to hydrogen-burning nucleosynthesis in a number of different stellar sites. In particular, {sup 17}O and {sup 18}F nucleosynthesis in classical novae is strongly dependent on the thermonuclear rates of these two reactions. The previously estimated rate for {sup 17}O(p,{alpha}){sup 14}N carries very large uncertainties in the temperature range of classical novae (T=0.01-0.4 GK), whereas a recent measurement has reduced the uncertainty of the {sup 17}O(p,{gamma}){sup 18}F rate. We report on the observation of a previously undiscovered resonance at E{sub c.m.}=183.3 keV in the {sup 17}O(p,{alpha}){sup 14}N reaction, with a measured resonance strength {omega}{gamma}{sub p{alpha}}=(1.6{+-}0.2)x10{sup -3} eV. We studied in the same experiment the {sup 17}O(p,{gamma}){sup 18}F reaction by an activation method, and the resonance strength was found to amount to {omega}{gamma}{sub p{gamma}}=(2.2{+-}0.4)x10{sup -6} eV. The excitation energy of the corresponding level in {sup 18}F was determined to be 5789.8{+-}0.3 keV in a Doppler shift attenuation method measurement, which yielded a value of {tau}<2.6 fs for the level lifetime. The {sup 17}O(p,{alpha}){sup 14}N and {sup 17}O(p,{gamma}){sup 18}F reaction rates were calculated using the measured resonance properties and reconsidering some previous analyses of the contributions of other levels or processes. The {sup 17}O(p,{alpha}){sup 14}N rate is now well established below T=1.5 GK, with uncertainties reduced by orders of magnitude in the temperature range T=0.1-0.4 GK. The uncertainty in the {sup 17}O(p,{gamma}){sup 18}F rate is somewhat larger because of remaining obscurities in the knowledge of the direct capture process. These new resonance properties have important consequences for {sup 17}O nucleosynthesis and {gamma}-ray emission of classical novae.

  15. 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.

  16. Benchmark fragment-based (1)H, (13)C, (15)N and (17)O chemical shift predictions in molecular crystals.

    PubMed

    Hartman, Joshua D; Kudla, Ryan A; Day, Graeme M; Mueller, Leonard J; Beran, Gregory J O

    2016-08-21

    The performance of fragment-based ab initio(1)H, (13)C, (15)N and (17)O chemical shift predictions is assessed against experimental NMR chemical shift data in four benchmark sets of molecular crystals. Employing a variety of commonly used density functionals (PBE0, B3LYP, TPSSh, OPBE, PBE, TPSS), we explore the relative performance of cluster, two-body fragment, and combined cluster/fragment models. The hybrid density functionals (PBE0, B3LYP and TPSSh) generally out-perform their generalized gradient approximation (GGA)-based counterparts. (1)H, (13)C, (15)N, and (17)O isotropic chemical shifts can be predicted with root-mean-square errors of 0.3, 1.5, 4.2, and 9.8 ppm, respectively, using a computationally inexpensive electrostatically embedded two-body PBE0 fragment model. Oxygen chemical shieldings prove particularly sensitive to local many-body effects, and using a combined cluster/fragment model instead of the simple two-body fragment model decreases the root-mean-square errors to 7.6 ppm. These fragment-based model errors compare favorably with GIPAW PBE ones of 0.4, 2.2, 5.4, and 7.2 ppm for the same (1)H, (13)C, (15)N, and (17)O test sets. Using these benchmark calculations, a set of recommended linear regression parameters for mapping between calculated chemical shieldings and observed chemical shifts are provided and their robustness assessed using statistical cross-validation. We demonstrate the utility of these approaches and the reported scaling parameters on applications to 9-tert-butyl anthracene, several histidine co-crystals, benzoic acid and the C-nitrosoarene SnCl2(CH3)2(NODMA)2. PMID:27431490

  17. 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.

  18. Experimental Study of 17O(p,{alpha})14N and 17O(p,{gamma})18F for Classical Nova Nucleosynthesis

    SciTech Connect

    Chafa, A.; Ouichaoui, S.; Tatischeff, V.; Coc, A.; Garrido, F.; Kiener, J.; Lefebvre-Schuhl, A.; Thibaud, J.-P.; Aguer, P.; Barhoumi, S.; Hernanz, M.; Jose, J.; Sereville, N. de

    2006-04-26

    We investigated the proton-capture reactions on 17O occurring in classical nova explosions. We observed a previously undiscovered resonance at E{sub R}{sup lab}=194.1{+-}0.6 keV in the 17O(p,{alpha})14N reaction, with a measured resonance strength {omega}{gamma}p{alpha}=1.6{+-}0.2 meV. We studied in the same experiment the 17O(p,{gamma})18F reaction by an activation method and the resonance-strength ratio was found to be {omega}{gamma}p{alpha}/{omega}{gamma}p{gamma}=470{+-}50. The corresponding excitation energy in the 18F compound nucleus was determined to be 5789.8{+-}0.3 keV by {gamma}-ray measurements using the 14N({alpha},{gamma})18F reaction. These new resonance properties have important consequences for 17O nucleosynthesis and {gamma}-ray astronomy of classical novae.

  19. Measurement of δ18O, δ17O, and 17O-excess in water by off-axis integrated cavity output spectroscopy and isotope ratio mass spectrometry.

    PubMed

    Berman, Elena S F; Levin, Naomi E; Landais, Amaelle; Li, Shuning; Owano, Thomas

    2013-11-01

    Stable isotopes of water have long been used to improve understanding of the hydrological cycle, catchment hydrology, and polar climate. Recently, there has been increasing interest in measurement and use of the less-abundant (17)O isotope in addition to (2)H and (18)O. Off-axis integrated cavity output spectroscopy (OA-ICOS) is demonstrated for accurate and precise measurements δ(18)O, δ(17)O, and (17)O-excess in liquid water. OA-ICOS involves no sample conversion and has a small footprint, allowing measurements to be made by researchers collecting the samples. Repeated (514) high-throughput measurements of the international isotopic reference water standard Greenland Ice Sheet Precipitation (GISP) demonstrate the precision and accuracy of OA-ICOS: δ(18)OVSMOW-SLAP = -24.74 ± 0.07‰ (1σ) and δ(17)OVSMOW-SLAP = -13.12 ± 0.05‰ (1σ). For comparison, the International Atomic Energy Agency (IAEA) value for δ(18)OVSMOW-SLAP is -24.76 ± 0.09‰ (1σ) and an average of previously reported values for δ(17)OVSMOW-SLAP is -13.12 ± 0.06‰ (1σ). Multiple (26) high-precision measurements of GISP provide a (17)O-excessVSMOW-SLAP of 23 ± 10 per meg (1σ); an average of previously reported values for (17)O-excessVSMOW-SLAP is 22 ± 11 per meg (1σ). For all these OA-ICOS measurements, precision can be further enhanced by additional averaging. OA-ICOS measurements were compared with two independent isotope ratio mass spectrometry (IRMS) laboratories and shown to have comparable accuracy and precision as the current fluorination-IRMS techniques in δ(18)O, δ(17)O, and (17)O-excess. The ability to measure accurately δ(18)O, δ(17)O, and (17)O-excess in liquid water inexpensively and without sample conversion is expected to increase vastly the application of δ(17)O and (17)O-excess measurements for scientific understanding of the water cycle, atmospheric convection, and climate modeling among others. PMID:24032448

  20. 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.

  1. Theoretical investigation of 5-(2-acetoxyethyl)-6-methylpyrimidin-2,4-dione: conformational study, NBO and NLO analysis, molecular structure and NMR spectra.

    PubMed

    Pir, Hacer; Günay, Nergin; Tamer, Ömer; Avcı, Davut; Atalay, Yusuf

    2013-08-01

    Structural and conformational, natural bond orbital (NBO) and nonlinear optical (NLO) analysis was performed, and (1)H and (13)C NMR chemical shifts values of 5-(2-Acetoxyethyl)-6-methylpyrimidin-2,4-dione [C9H12N2O4] in the ground state were calculated by using Density Functional Theory (DFT-B3LYP/6-311++G(d,p)) and Hartree-Fock (HF/6-311++G(d,p)) methods. The NMR data were calculated by means of the GIAO, CSGT, and IGAIM methods. In addition, the molecular frontier orbital energies, thermodynamic parameters (in the range of 200-700 K), molecular surfaces, Mulliken charges and atomic polar tensor-based charges were investigated. Besides, the analysis of all possible conformational of the title compound, a detailed potential energy curve for τ1(C8O3C10O4), τ2 (C8O3C10C11) and τ3 (C5C7C8O3) dihedral angles were performed in steps of 10° from 0° to 360°, and depicted to find the most stable form. Finally, the calculated HOMO and LUMO energies show that charge transfer occurs within the title compound.

  2. Elucidation of the CCR1- and CCR5-binding modes of MIP-1α by application of an NMR spectra reconstruction method to the transferred cross-saturation experiments.

    PubMed

    Yoshiura, Chie; Ueda, Takumi; Kofuku, Yutaka; Matsumoto, Masahiko; Okude, Junya; Kondo, Keita; Shiraishi, Yutaro; Shimada, Ichio

    2015-12-01

    C-C chemokine receptor 1 (CCR1) and CCR5 are involved in various inflammation and immune responses, and regulate the progression of the autoimmune diseases differently. However, the number of residues identified at the binding interface was not sufficient to clarify the differences in the CCR1- and CCR5-binding modes to MIP-1α, because the NMR measurement time for CCR1 and CCR5 samples was limited to 24 h, due to their low stability. Here we applied a recently developed NMR spectra reconstruction method, Conservation of experimental data in ANAlysis of FOuRier, to the amide-directed transferred cross-saturation experiments of chemokine receptors, CCR1 and CCR5, embedded in lipid bilayers of the reconstituted high density lipoprotein, and MIP-1α. Our experiments revealed that the residues on the N-loop and β-sheets of MIP-1α are close to both CCR1 and CCR5, and those in the C-terminal helix region are close to CCR5. These results suggest that the genetic influence of the single nucleotide polymorphisms of MIP-1α that accompany substitution of residues in the C-terminal helix region, E57 and V63, would provide clues toward elucidating how the CCR5-MIP-1α interaction affects the progress of autoimmune diseases.

  3. 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.

  4. NMR Studies of the original magnetic properties of the cuprates: influence of impurities and defects.

    NASA Astrophysics Data System (ADS)

    Alloul, Henri

    1998-03-01

    The cuprates display original magnetic properties, both in their insulating and metallic phases. In underdoped metallic systems, a pseudo gap in the density of magnetic q=3D0 excitations is observed from local susceptibility measurements, as well as from specific heat and transport properties. A pseudo spin-gap in the AF excitations at the AF wave vector is detected both by NMR and inelastic neutron scattering. From the NMR measurements it can be concluded that these magnetic anomalies are quite similar in single layer(J. Bobroff, H.. Alloul, P. Mendels, V. Viallet, J. F. Marucco and D. Colson, Phys. Rev. Letters 78, 3757 (1997).), bilayer and trilayer underdoped cuprates. The modifications of magnetic properties induced by substitutions or defects in the planes, which do not modify appreciably the charge transfer have been studied. The spatial dependence of the spin susceptibility \\chi ' (r) of the pure material can be directly probed through the study of the modifications of the NMR spectra of various nuclei (^89Y, ^17O, ^63Cu) induced by such localised magnetic impurities. Large qualitative differences between the underdoped and slightly overdoped YBCO are evidenced from ^17O NMR line broadening in Ni substituted YBCO. This allows us to propose a quite powerful method for studying the q and T dependence of the static magnetic susceptibility (J. Bobroff et al, Phys. Rev. Letters 78, 3757 (1997).). The impurity magnetic state also directly reflects the occurence of electronic correlations in the metallic state. The case of Zn will be examined in some detail. ^89Y NMR has revealed that the substitution of this 3d^10 non magnetic atom on a Cu site induces a Curie like contribution to the local susceptibility on the near neighbour coppers ( A. V. Mahajan, H. Alloul, G. Collin and J. F. Marucco, Physical Review Letters 72, 3100 (1994).). The effective induced moment decreases with hole doping and becomes rather weak, but is still present for optimal doping

  5. {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.

  6. Vibrational analysis using FT-IR, FT-Raman spectra and HF-DFT methods and NBO, NLO, NMR, HOMO-LUMO, UV and electronic transitions studies on 2,2,4-trimethyl pentane.

    PubMed

    Suvitha, A; Periandy, S; Govindarajan, M; Gayathri, P

    2015-03-01

    In this work, the vibrational spectral analysis was carried out by using Raman and infrared spectroscopy in the range 100-4000cm(-1)and 50-4000cm(-1), respectively, for 2,2,4-Trimethyl Pentane, TMP (C8H18) molecule. The molecular structure, fundamental vibrational frequencies and intensity of the vibrational bands are interpreted with the aid of structure optimizations and geometrical parameter calculations based on Hartree Fock (HF) and density functional theory (DFT) method with 6-311++G(d,p) basis set. The scaled B3LYP/6-311++G(d,p) results shows the best agreement with the experimental values over the other method. The calculated HOMO and LUMO energies shows that charge transfer within the molecule. The physical reactions of single bond hydrocarbon TMP were investigated. The results of the calculations were applied to simulate spectra of the title compound, which shows the excellent agreement with observed spectra. Besides, Mulliken atomic charges, UV, frontier molecular orbital (FMO), MEP, NLO activity, Natural Bond-Orbital (NBO) analysis, NMR and thermodynamic properties of title molecule were also performed.

  7. Relaxation times of spin states of all ranks and orders of quadrupolar nuclei estimated from NMR z-spectra: Markov chain Monte Carlo analysis applied to 7Li+ and 23Na+ in stretched hydrogels.

    PubMed

    Kuchel, Philip W; Naumann, Christoph; Puckeridge, Max; Chapman, Bogdan E; Szekely, David

    2011-09-01

    The NMR z-spectra of 7Li+ and 23Na+ in stretched hydrogels contain five minima, or critical values, with a sharp "dagger" on the central dip. The mathematical representation of such z-spectra from spin-3/2 nuclei contains nine distinct (the total is 15 but there is redundancy of the ±order-numbers) relaxation rate constants that are unique for each of the spin states, up to rank 3, order 3. We present an approach to multiple-parameter-value estimation that exploits the high level of separability of the effects of each of the relaxation rate constants on the features of the z-spectrum. The Markov chain Monte Carlo (MCMC) method is computationally demanding but it yielded statistically robust estimates (low coefficients of variation) of the parameter values. We describe the implementation of the MCMC analysis (in the present context) and posit that it can obviate the need for using multiple-quantum filtered RF-pulse sequences to estimate all relaxation rate constants/times under experimentally favorable, but readily achievable, circumstances.

  8. Hydrothermal synthesis, X-ray structure refinement, 31P NMR spectra and vibrational study of NaLa(HPO4)2

    NASA Astrophysics Data System (ADS)

    Ben Hassen, C.; Boujelbene, M.; Mhiri, T.

    2013-10-01

    NaLa(HPO4)2 was obtained by hydrothermal synthesis. The structure of NaLa(HPO4)2 was determined by X-ray powder diffraction methods. The results of Rietveld refinement revealed a space group P21/c (No. 14), with lattice parameters of a = 9.7151(17) Å, b = 8.320(12) Å, c = 9.83(2) Å, beta = 114.65(17)°, V = 722 (8) Å3 and Z = 4. Final refinement led to RF = 4.86% and RB = 12.35%.The existence of bound O-H and bound P-O in the structure has been confirmed by IR and Raman spectroscopy. The existence of two crystallographically independent phosphorus atoms in the structure has been confirmed by NMR spectrum. The structure is characterized by LaO6 octahedra which are solely connected to six adjacent HPO4 tetrahedra via common O-corners. This structure contains twelve- and four-membered rings forming channels along [1 1¯ 1]. The cross sections of the channels are given by twelve-membered rings consisting of four lanthanum coordination octahedral and eight hydrogenphosphate groups as well as four-membered rings consisting of two lanthanum coordination octahedra and two hydrogenphosphate tetrahedra. Sodium ions are located within those channels of the twelve-membered rings.

  9. Minimalist Relativistic Force Field: Prediction of Proton-Proton Coupling Constants in (1)H NMR Spectra Is Perfected with NBO Hybridization Parameters.

    PubMed

    Kutateladze, Andrei G; Mukhina, Olga A

    2015-05-15

    We previously developed a reliable method for multiparametric scaling of Fermi contacts to achieve fast and accurate prediction of proton-proton spin-spin coupling constants (SSCC) in (1)H NMR. We now report that utilization of NBO hybridization coefficients for carbon atoms in the involved C-H bonds allows for a significant simplification of this parametric scheme, requiring only four general types of SSCCs: geminal, vicinal, 1,3-, and long-range constants. The method is optimized for inexpensive B3LYP/6-31G(d) molecular geometries. A new DU8 basis set, based on a training set of 475 experimental spin-spin coupling constants, is developed for hydrogen and common non-hydrogen atoms (Li, B, C, N, O, F, Si, P, S, Cl, Se, Br, I) to calculate Fermi contacts. On a test set of 919 SSCCs from a diverse collection of natural products and complex synthetic molecules the method gave excellent accuracy of 0.29 Hz (rmsd) with the maximum unsigned error not exceeding 1 Hz.

  10. Analysis of NAD 2D-NMR spectra of saturated fatty acids in polypeptide aligning media by experimental and modeling approaches.

    PubMed

    Serhan, Zeinab; Borgogno, Andrea; Billault, Isabelle; Ferrarini, Alberta; Lesot, Philippe

    2012-01-01

    The overall and detailed elucidation (including the stereochemical aspects) of enzymatic mechanisms requires the access to all reliable information related to the natural isotopic fractionation of both precursors and products. Natural abundance deuterium (NAD) 2D-NMR experiments in polypeptide liquid-crystalline solutions are a new, suitable tool for analyzing site-specific deuterium isotopic distribution profiles. Here this method is utilized for analyzing saturated C14 to C18 fatty acid methyl esters (FAMEs), which are challenging because of the crowding of signals in a narrow spectral region. Experiments in achiral and chiral oriented solutions were performed. The spectral analysis is supplemented by the theoretical prediction of quadrupolar splittings as a function of the geometry and flexibility of FAMEs, based on a novel computational methodology. This allows us to confirm the spectral assignments, while providing insights into the mechanism of solute ordering in liquid-crystalline polypeptide solutions. This is found to be dominated by steric repulsions between FAMEs and polypeptides.

  11. Insight into dissolution mechanism of cellulose in [C4mim][CH3COO]/DMSO solvent by 13C NMR spectra

    NASA Astrophysics Data System (ADS)

    Xu, Airong; Zhang, Yibo

    2015-05-01

    Recently, it has been reported that 1-butyl-3-methylimidazolium acetate/dimethyl sulfoxide ([C4mim][CH3COO]/DMSO) can efficiently dissolve cellulose at room temperature. In the present study, 13C NMR measurements of 1-butyl-3-methylimidazolium acetate [C4mim][CH3COO] and cellulose were carried out in [C4mim][CH3COO]/DMSO-d6 (Deuterated dimethyl sulfoxide)/cellulose solution to directly reveal the possible dissolution mechanism of cellulose in true [C4mim][CH3COO]/DMSO solvent. The results indicate that both cation and anion of [C4mim][CH3COO] in [C4mim][CH3COO]/DMSO solvent dominate cellulose dissolution, and DMSO mainly serves to dissociate the ion pairs in [C4mim][CH3COO] into solvated cations and anions. Moreover, the hydrogen bonding interaction of anion of [C4mim][CH3COO] with cellulose hydroxyl proton is much stronger than that of cation of [C4mim][CH3COO] with cellulose hydroxyl oxygen.

  12. Minimalist Relativistic Force Field: Prediction of Proton-Proton Coupling Constants in (1)H NMR Spectra Is Perfected with NBO Hybridization Parameters.

    PubMed

    Kutateladze, Andrei G; Mukhina, Olga A

    2015-05-15

    We previously developed a reliable method for multiparametric scaling of Fermi contacts to achieve fast and accurate prediction of proton-proton spin-spin coupling constants (SSCC) in (1)H NMR. We now report that utilization of NBO hybridization coefficients for carbon atoms in the involved C-H bonds allows for a significant simplification of this parametric scheme, requiring only four general types of SSCCs: geminal, vicinal, 1,3-, and long-range constants. The method is optimized for inexpensive B3LYP/6-31G(d) molecular geometries. A new DU8 basis set, based on a training set of 475 experimental spin-spin coupling constants, is developed for hydrogen and common non-hydrogen atoms (Li, B, C, N, O, F, Si, P, S, Cl, Se, Br, I) to calculate Fermi contacts. On a test set of 919 SSCCs from a diverse collection of natural products and complex synthetic molecules the method gave excellent accuracy of 0.29 Hz (rmsd) with the maximum unsigned error not exceeding 1 Hz. PMID:25885091

  13. Broad levels in 17O and their relevance for the astrophysical s process

    NASA Astrophysics Data System (ADS)

    Faestermann, T.; Mohr, P.; Hertenberger, R.; Wirth, H.-F.

    2015-11-01

    Levels in 17O affect the astrophysical s process in two opposite ways. The neutron production is enhanced by resonances in the 13C(α ,n )16O reaction at excitation energies around 7 MeV in 17O, and the number of available neutrons is reduced by low-lying resonances in the 16O(n ,γ )17O reaction corresponding to levels in 17O with excitation energies of 4 -5 MeV . The present work uses the 19F(d ,α )17O reaction to determine absolute widths of the relevant levels in 17O. The results improve the uncertainties of the previously adopted values and resolve a discrepancy between recent studies for the 1 /2+ level close to the threshold of the 13C(α ,n )16O reaction. In addition, improved excitation energies and widths are provided for several states in 17O up to excitation energies close to 8 MeV.

  14. NBO, NMR, UV, FT-IR, FT-Raman spectra and molecular structure (monomeric and dimeric structures) investigation of 4-Chloro-3,5-Xylenol: a combined experimental and theoretical study.

    PubMed

    Arivazhagan, M; Gayathri, R

    2013-12-01

    In this work, a joint experimental (FTIR and FT-Raman) and theoretical (DFT and ab initio) study on the structure and the vibrations of 4-Chloro-3,5-Xylenol (CXL) are compared and analyzed. CXL is a chlorinated phenolic antiseptic which is a bactericide against most gram-positive bacteria. The first hyperpolarizability (β0) of this novel molecular system and related non-linear properties of CXL are calculated using HF/6-311++G(d,p) method on the finite-field approach. The energy and oscillator strength calculated using absorption spectra (UV-Vis spectrum), this spectral analysis confirms the charge transfer of the molecule. The theoretical (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by Gauge Including Atomic Orbital (GIAO) method, to analyze the molecular environment as well as the delocalization activities of electron clouds. The directly calculated ionization potential (IP), electron affinity (EA), electronegativity (χ), chemical hardness (η), first electron excitation energy (τ) and electrophilicity index (ω) as well as local reactivity (S) analyzed using HOMO and LUMO energies; the energy band gap are also determined. NBO analysis shows that charge in electron density(ED) in the σ(*) and π(*) antibonding orbitals and E((2)) energies confirms the occurrence of ICT (Intramolecular Charge Transfer) within the molecule. Inter molecular hydrogen bonds exist between -OH group, give the evidence for the formation of dimer entities in the title molecule. The influences of chlorine atom, hydroxyl group and methyl group on the geometry of benzene and its normal modes of vibrations (monomer and dimer of CXL) have also been discussed. Finally the calculated results were applied to simulate Infrared and Raman spectra of the title molecule which show good agreement with observed spectra.

  15. NBO, NMR, UV, FT-IR, FT-Raman spectra and molecular structure (monomeric and dimeric structures) investigation of 4-Chloro-3,5-Xylenol: A combined experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Arivazhagan, M.; Gayathri, R.

    2013-12-01

    In this work, a joint experimental (FTIR and FT-Raman) and theoretical (DFT and ab initio) study on the structure and the vibrations of 4-Chloro-3,5-Xylenol (CXL) are compared and analyzed. CXL is a chlorinated phenolic antiseptic which is a bactericide against most gram-positive bacteria. The first hyperpolarizability (β0) of this novel molecular system and related non-linear properties of CXL are calculated using HF/6-311++G(d,p) method on the finite-field approach. The energy and oscillator strength calculated using absorption spectra (UV-Vis spectrum), this spectral analysis confirms the charge transfer of the molecule. The theoretical 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by Gauge Including Atomic Orbital (GIAO) method, to analyze the molecular environment as well as the delocalization activities of electron clouds. The directly calculated ionization potential (IP), electron affinity (EA), electronegativity (χ), chemical hardness (η), first electron excitation energy (τ) and electrophilicity index (ω) as well as local reactivity (S) analyzed using HOMO and LUMO energies; the energy band gap are also determined. NBO analysis shows that charge in electron density(ED) in the σ* and π* antibonding orbitals and E(2) energies confirms the occurrence of ICT (Intramolecular Charge Transfer) within the molecule. Inter molecular hydrogen bonds exist between -OH group, give the evidence for the formation of dimer entities in the title molecule. The influences of chlorine atom, hydroxyl group and methyl group on the geometry of benzene and its normal modes of vibrations (monomer and dimer of CXL) have also been discussed. Finally the calculated results were applied to simulate Infrared and Raman spectra of the title molecule which show good agreement with observed spectra.

  16. δ17O and Δ47—The Heavens can Wait.

    NASA Astrophysics Data System (ADS)

    Olack, G.; Colman, A. S.

    2015-12-01

    Most terrestrial systems fall on or close to the Global Meteoric Water Line, GMWL, for 17O and 18O isotopes. Luz and Barken (2010) recently discussed variations from the GMWL, and typically the differences were in the 50 per meg, or 0.05‰, 17O excess. Landais et al. also looked at water from a Vostok ice core, covering the past 150,000 years, and see differences from GMWL on the order of 45 per meg 17O excess. Carbonate samples are analyze for their 13C and 18O to help understand paleo-climate, water sources, and by looking at clumped isotopes, Δ47, the excess of 13C-18O bonds measured by mass spectroscopy on m/z 47. Those samples will also carry thru the 17O-excess in their waters of formation. We modeled the effect of 17O excess on Δ47 and basically there is little effect in the 50 per meg 17O excess range. We also looked at what would happen with 18O spiked samples, presuming the spike does not add 17O. In that case, a 100 ‰ shift in 18O would give rise to -49‰ 17O excess anomaly. That shows a significant effect, a 1.8 ‰ shift in Δ47 and even a 3.5 ‰ shift in the δ13C reading. So spiked samples are not good candidates for clumped isotope analysis, terrestrial samples probably will not have enough of a 17O excess to affect Δ47 measurements, and extra-terrestrial samples will have to be checked.

  17. Axial ligand modulation of the electronic structures of binuclear copper sites: analysis of paramagnetic 1H NMR spectra of Met160Gln Cu(A).

    PubMed

    Fernández, C O; Cricco, J A; Slutter, C E; Richards, J H; Gray, H B; Vila, A J

    2001-11-28

    Cu(A) is an electron-transfer copper center present in heme-copper oxidases and N2O reductases. The center is a binuclear unit, with two cysteine ligands bridging the metal ions and two terminal histidine residues. A Met residue and a peptide carbonyl group are located on opposite sides of the Cu2S2 plane; these weaker ligands are fully conserved in all known Cu(A) sites. The Met160Gln mutant of the soluble subunit II of Thermus thermophilus ba3 oxidase has been studied by NMR spectroscopy. In its oxidized form, the binuclear copper is a fully delocalized mixed-valence pair, as are all natural Cu(A) centers. The faster nuclear relaxation in this mutant suggests that a low-lying excited state has shifted to higher energies compared to that of the wild-type protein. The introduction of the Gln residue alters the coordination mode of His114 but does not affect His157, thereby confirming the proposal that the axial ligand-to-copper distances influence the copper-His interactions (Robinson, H.; Ang, M. C.; Gao, Y. G.; Hay, M. T.; Lu, Y.; Wang, A. H. Biochemistry 1999, 38, 5677). Changes in the hyperfine coupling constants of the Cys beta-CH2 groups are attributed to minor geometrical changes that affect the Cu-S-C(beta)-H(beta) dihedral angles. These changes, in addition, shift the thermally accessible excited states, thus influencing the spectral position of the Cys beta-CH2 resonances. The Cu-Cys bonds are not substantially altered by the Cu-Gln160 interaction, in contrast to the situation found in the evolutionarily related blue copper proteins. It is possible that regulatory subunits in the mitochondrial oxidases fix the relative positions of thermally accessible Cu(A) excited states by tuning axial ligand interactions.

  18. 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.

  19. 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 spectral…

  20. Exploring Chromophore-Binding Pocket: High-Resolution Solid-State H-C Interfacial Correlation NMR Spectra with Windowed PMLG Scheme.

    PubMed

    Song, Chen; Lang, Christina; Mailliet, Jo; Hughes, Jon; Gärtner, Wolfgang; Matysik, Jörg

    2012-02-01

    High-resolution two-dimensional (2D) (1)H-(13)C heteronuclear correlation spectra are recorded for selective observation of interfacial 3-5.5 Å contacts of the uniformly (13)C-labeled phycocyanobilin (PCB) chromophore with its unlabeled binding pocket. The experiment is based on a medium- and long-distance heteronuclear correlation (MELODI-HETCOR) method. For improving (1)H spectral resolution, a windowed phase-modulated Lee-Goldburg (wPMLG) decoupling scheme is applied during the t(1) evolution period. Our approach allows for identification of chromophore-protein interactions, in particular for elucidation of the hydrogen-bonding networks and charge distributions within the chromophore-binding pocket. The resulting pulse sequence is tested on the cyanobacterial (Cph1) phytochrome sensory module (residues 1-514, Cph1Δ2) containing uniformly (13)C- and (15)N-labeled PCB chromophore (u-[(13)C,(15)N]-PCB-Cph1Δ2) at 17.6 T. PMID:22303079

  1. Simulations of molecular dynamics in solid-state NMR spectra of spin-1 nuclei including effects of CSA- and EFG-terms up to second order.

    PubMed

    Larsen, Flemming H

    2007-04-01

    By numerical simulations MAS and QCPMG methods for acquiring spectra of spin-1 nuclei were compared in order to determine the most sensitive experiment for analysis of molecular dynamics. To comply with the large quadrupolar constants for 14N and the CSA reported for 6Li both of these interactions are included up to second order. For 2H and 6Li both QCPMG and single-pulse MAS experiments were suitable for dynamics studies whereas the single-pulse MAS experiment were the method of choice for investigation of 14N dynamics for C(Q)'s larger than 750kHz at 14.1T. This property prohibits excitation of the 14N lineshape using either single hard or softer composite rf-pulses. Focusing on 14N it was demonstrated that the centerband lineshape is sensitive toward both off-MAS and CSA effects. In addition, excitation by real-time pulses showed that proper lineshapes corresponding to a site with a C(Q) of 3MHz may be excited by a very short pulse. PMID:17418539

  2. 17O(p, α) 14N study at the LUNA accelerator

    NASA Astrophysics Data System (ADS)

    Scott, D. A.; Bruno, C.; Caciolli, A.; LUNA Collaboration

    2013-08-01

    Hydrogen burning of 17O sensitively influences nucleosynthesis in a number of stellar sites, including red giants, asymptotic giant branch (AGB) stars, massive stars, and classical novae. In particular, the ratio between reaction rates of 17O(p, α) 14N (Q=1.2 MeV) and 17O(p, γ) 18F (Q=5.6 MeV) channels on 17O is one of the most important parameters for the galactic synthesis of 17O, the stellar production of radioactive 18F, and for predicted O isotopic ratios in premolar grains. Now the LUNA collaboration is preparing a new effort to study the (p, α) channel on 17O at astrophysical energies. To reach this goal a new chamber has been constructed which allows to place 8 silicons detectors in backward directions. The setup improves the efficiency which is a crucial parameter in measuring nuclear reaction at such low energies. Aluminum foils are placed on the silicon in order to stop the elastic backscattered protons which otherwise produce non-negligible background on the silicons.

  3. Improvement of the high-accuracy 17O(p ,α )14N reaction-rate measurement via the Trojan Horse method for application to 17O nucleosynthesis

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    The 17O(p ,α )14N and 17O(p ,γ )18F reactions are of paramount importance for the nucleosynthesis in a number of stellar sites, including red giants (RGs), asymptotic giant branch (AGB) stars, massive stars, and classical novae. In particular, they govern the destruction of 17O and the formation of the short-lived radioisotope 18F, which is of special interest for γ -ray astronomy. At temperatures typical of the above-mentioned astrophysical scenario, T =0.01 -0.1 GK for RG, AGB, and massive stars and T =0.1 -0.4 GK for a classical nova explosion, the 17O(p ,α )14N reaction cross section is dominated by two resonances: one at about ERc m=65 keV above the 18F proton threshold energy, corresponding to the EX=5.673 MeV level in 18F, and another one at ERc m=183 keV (EX=5.786 MeV). We report on the indirect study of the 17O(p ,α )14N reaction via the Trojan Horse method by applying the approach recently developed for extracting the strength of narrow resonance at ultralow energies. The mean value of the strengths obtained in the two measurements was calculated and compared with the direct data available in literature. This value was used as input parameter for reaction-rate determination and its comparison with the result of the direct measurement is also discussed in the light of the electron screening effect.

  4. Spatial Distribution of 17O-excess of Tap Waters in the Conterminous United States

    NASA Astrophysics Data System (ADS)

    Li, S.; Levin, N. E.; Chesson, L. A.

    2011-12-01

    17O-excess is the deviation from the average relationship between δ18O and δ17O values in meteoric waters. This parameter is similar to d-excess in that it is sensitive to relative humidity during evaporation, but unlike d-excess it is largely insensitive to temperature. Therefore, 17O-excess may be used to provide independent information on relative humidity during evaporative processes in hydrological and climatic models. Here we report the first national-level survey of 17O-excess of tap waters collected from 92 localities across the conterminous United States (US). Since tap water primarily originates from rivers, reservoirs and groundwater, our results should approximate the seasonally integrated 17O-excess of precipitation at any given locality. The average of these 17O-excess values for measured US tap waters is 0.028±0.005%, which is consistent with the global average (0.033±0.005%). The spatial distributions of the measured 17O-excess values are likely controlled by the effects of evaporation in two different types of settings: (1) evaporation in oceanic regions that vary in relative humidity, which results in air masses carrying moisture with distinct 17O-excess values, and (2) evaporation of water either during or after precipitation events. To first order, we observed high 17O-excess values (0.036±0.005 to 0.065±0.005%) in tap waters from the Appalachian Mountains, the Rocky Mountains, west of the Great Plains and the Mississippi Delta region; whereas low 17O-excess values (-0.015±0.005 to 0.010±0.005%) are observed in the majority of the states bordering the Gulf of Mexico. These data suggest that the high 17O-excess values may be the results of moisture from relatively dry oceanic sources, while the low 17O-excess values may be due to moisture from a relatively humid source such as the Gulf of Mexico. We also found some second-order features in the 17O-excess distribution of the tap waters, which could be attributed to the local evaporation

  5. An experimental and theoretical investigation of Acenaphthene-5-boronic acid: conformational study, NBO and NLO analysis, molecular structure and FT-IR, FT-Raman, NMR and UV spectra.

    PubMed

    Karabacak, Mehmet; Sinha, Leena; Prasad, Onkar; Asiri, Abdullah M; Cinar, Mehmet

    2013-11-01

    The solid state Fourier transform infrared (FT-IR) and FT-Raman spectra of Acenaphthene-5-boronic acid (AN-5-BA), have been recorded in the range 4000-400cm(-1) and 4000-10cm(-1), respectively. Density functional theory (DFT), with the B3LYP functional was used for the optimization of the ground state geometry and simulation of the infrared and Raman spectra of the molecule. The vibrational wave numbers and their assignments were examined theoretically using the Gaussian 09 set of quantum chemistry codes and the normal modes were assigned by a scaled quantum mechanical (SQM) force field approach. Hydrogen-bonded dimer of AN-5-BA, optimized by counterpoise correction, has also been studied by B3LYP at the 6-311++G(d,p) level and the effects of molecular association through O-H⋯O hydrogen bonding have been discussed. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by Gauge-Including Atomic Orbital (GIAO) method. Natural bond orbital (NBO) analysis has been applied to study stability of the molecule arising from charge delocalization. UV spectrum of the title compound was also recorded and the electronic properties, such as frontier orbitals, and band gap energies were measured by TD-DFT approach. The first order hyperpolarizability 〈β〉, its components and associated properties such as average polarizability and anisotropy of the polarizability (α and Δα) of AN-5-BA was calculated using the finite-field approach. PMID:23892116

  6. An experimental and theoretical investigation of Acenaphthene-5-boronic acid: Conformational study, NBO and NLO analysis, molecular structure and FT-IR, FT-Raman, NMR and UV spectra

    NASA Astrophysics Data System (ADS)

    Karabacak, Mehmet; Sinha, Leena; Prasad, Onkar; Asiri, Abdullah M.; Cinar, Mehmet

    2013-11-01

    The solid state Fourier transform infrared (FT-IR) and FT-Raman spectra of Acenaphthene-5-boronic acid (AN-5-BA), have been recorded in the range 4000-400 cm-1 and 4000-10 cm-1, respectively. Density functional theory (DFT), with the B3LYP functional was used for the optimization of the ground state geometry and simulation of the infrared and Raman spectra of the molecule. The vibrational wave numbers and their assignments were examined theoretically using the Gaussian 09 set of quantum chemistry codes and the normal modes were assigned by a scaled quantum mechanical (SQM) force field approach. Hydrogen-bonded dimer of AN-5-BA, optimized by counterpoise correction, has also been studied by B3LYP at the 6-311++G(d,p) level and the effects of molecular association through O-H⋯O hydrogen bonding have been discussed. The 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by Gauge-Including Atomic Orbital (GIAO) method. Natural bond orbital (NBO) analysis has been applied to study stability of the molecule arising from charge delocalization. UV spectrum of the title compound was also recorded and the electronic properties, such as frontier orbitals, and band gap energies were measured by TD-DFT approach. The first order hyperpolarizability <β>, its components and associated properties such as average polarizability and anisotropy of the polarizability (α and Δα) of AN-5-BA was calculated using the finite-field approach.

  7. 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

  8. Disentangling scalar coupling patterns by real-time SERF NMR.

    PubMed

    Gubensäk, Nina; Fabian, Walter M F; Zangger, Klaus

    2014-10-21

    Scalar coupling constants and signal splitting patterns in NMR spectra contain a wealth of short-range structural information. The extraction of these parameters from (1)H NMR spectra is often prohibited by simultaneous scalar coupling interactions with several other protons. Here we present a high-resolution NMR experiment where scalar coupling to only one selected signal is visible. All other couplings are removed from the spectrum. This real-time selectively refocused NMR experiment is achieved by spatially selective homonuclear broadband decoupling combined with selective refocusing during acquisition. It allows the unperturbed extraction of scalar coupling constants from the highly resolved acquisition dimension of NMR spectra.

  9. 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.

  10. Protonated hydronium dication, H/sub 4/O/sup 2 +/. Hydrogen-deuterium exchange of D/sub 2/H/sup 17/O/sup +/ in HF:SbF/sub 5/ and DH/sub 2//sup 17/O/sup +/ in DF:SbF/sub 5/ and theoretical calculations

    SciTech Connect

    Olah, G.A.; Prakash, G.K.S.; Barzaghi, M.; Lammertsma, K.; von R. Schleyer, P.; Pople, J.A.

    1986-03-05

    Isotopic hydronium ions D/sub 2/H/sup 17/O/sup +/ and DH/sub 2//sup 17/O/sup +/ in 1:1 (molar) HF:SbF/sub 5//SO/sub 2/ and DF:SbF/sub 2/SO/sub 2/ solutions, respectively, at -15/sup 0/C undergo slow hydrogen-deuterium exchange as monitored by /sup 17/O NMR spectroscopy. The rate of such exchange increases with the increase in the acidity of the fluoroantimonic acid medium (1:2 molar composition). The previously observed lack of exchange of isotopic hydronium ions in the somewhat weaker Magic Acid, FSO/sub 3/H:SbF/sub 5/, medium (H/sub 0/ approx. -21.5) suggests that in the stronger HF:SbF/sub 5/ medium (H/sub 0/ approx. -25 to -28), the exchange occurs through the intermediacy of protonated hydronium dication. Consequently, the structure and stability of protonated hydronium dication has been probed by ab initio theory. The T/sub d/ symmetry structure was found to be the minimum energy structure at the HF/6.31G* level. At the HF/6.31G* level this structure is thermodynamically unstable (dissociation preferred by 59.2 kcal/mol), it seems to have significant kinetic stability (deprotonation barrier 39.4 kcal/mol). 20 references, 1 table.

  11. Measurments and Modeling of Δ 17O Vatiations in Atmospheric Nitrate

    NASA Astrophysics Data System (ADS)

    Michalski, G. M.; Thiemens, M. H.

    2002-12-01

    The estimated doubling of HNO3 production in the atmosphere in the next 50 years is important from both an ecological and an atmospheric chemistry perspective. The removal of NO-{3 atm} (HNO3 + aerosol nitrate) by dry and wet deposition can initiate serious environmental consequences including soil acidification, forest decline, the alteration of native plant diversity, and the promotion of eutrophication and toxic algae blooms in coastal waters. A reliable, quantitative, tracer of NO-{3 atm} deposition, particularly in regions with multiple nitrate sources and heavy nitrogen cycling is still lacking. In the atmosphere, HNO3 production is the primary sink for NOx, which via direct and catalytic production of ozone regulates the oxidative capacity of the troposphere. The impact heterogeneous versus homogenous HNO3 production exert on global O3 and OH steady state concentrations has also been demonstrated in Global 3-D chemical models. Yet, the extent that anthroprogenic activities have impacted heterogeneous and homogenous production, and how these pathways varied on ancient time scales is also unknown. Nitrate aerosols were collected in La Jolla, Ca. for a one-year period and their oxygen isotopic composition were analyzed (δ 18O and δ 17O). A large Δ 17O17O = δ 17O - 0.515 δ 18O ) was observed and this isotopic signature exhibited a strong seasonal amplitude. The variability in Δ 17O is attributed to variability in HOx and O3 oxidation rates and the seasonal variation of homogeneous versus heterogeneous nitric acid formation reactions. An isotopic model coupled to a photochemical box model reproduced the observed Δ 17O with good precision. Implications for the use of Δ 17O in nitrate as an investigative tool for NOx related chemistry in both present day atmosphere and in ancient atmospheres is discussed. The magnitude of the Δ 17O signature also has implications as a tracer of atmospheric nitrogen deposition. Both the increased detection sensitivity

  12. Isotope separation of {sup 17}O by photodissociation of ozone with near-infrared laser irradiation

    SciTech Connect

    Hayashida, Shigeru; Kambe, Takashi; Sato, Tetsuya; Igarashi, Takehiro; Kuze, Hiroaki

    2012-04-01

    Oxygen-17 is a stable oxygen isotope useful for various diagnostics in both engineering and medical applications. Enrichment of {sup 17}O, however, has been very costly due to the lack of appropriate methods that enable efficient production of {sup 17}O on an industrial level. In this paper, we report the first {sup 17}O-selective photodissociation of ozone at a relatively high pressure, which has been achieved by irradiating a gas mixture of 10 vol% O{sub 3}-90 vol% CF{sub 4} with narrowband laser. The experiment was conducted on a pilot-plant scale. A total laser power of 1.6 W was generated by external-cavity diode lasers with all the laser wavelengths fixed at the peak of an absorption line of {sup 16}O{sup 16}O{sup 17}O around 1 {mu}m. The beams were introduced into a 25 -m long photoreaction cell under the sealed-off condition with a total pressure of 20 kPa. Lower cell temperature reduced the background decomposition of ozone, and at the temperature of 158 K, an {sup 17}O enrichment factor of 2.2 was attained.

  13. CRDS of 17O enriched water between 5850 and 6671 cm-1: More than 1000 energy levels of H217O and HD17O newly determined

    NASA Astrophysics Data System (ADS)

    Mikhailenko, S. N.; Leshchishina, O.; Karlovets, E. V.; Mondelain, D.; Kassi, S.; Campargue, A.

    2016-07-01

    The room temperature absorption spectrum of water vapor highly enriched in 17O has been recorded by Cavity Ring Down Spectroscopy (CRDS) between 5850 and 6671 cm-1. Two series of recordings were performed with pressure values of 1.0 and 12.0 Torr. The investigated spectral region corresponds to the important 1.55 μm transparency window of the atmosphere where water absorption is very weak. The high sensitivity of the recordings (αmin ~ 5×10-11 cm-1) allows detecting lines with intensity spanning six orders of magnitude (1.4×10-30-3.6×10-24 cm/molecule at room temperature). The experimental list includes more than 10,300 lines. The assignments of water lines were performed using known experimental energy levels as well as calculated line lists based on the results of Partridge and Schwenke. More than 8500 lines were assigned to 9619 transitions of six water isotopologues (H216O, H217O, H218O, HD16O, HD17O and HD18O). All but four transitions of the 16O and 18O isotopologues were assigned using known experimental energy levels. More than half of the assigned H217O and HD17O transitions correspond to new (or corrected) upper energy levels. About 1000 new H217O transitions associated with upper states of the second triad and of the first hexad were identified. Most of the newly assigned HD17O transitions belong to the ν1+ν3 and 2ν2+ν3 bands. The assigned transitions allowed to newly determine or correct 20 highly excited rotational levels of the vibrational ground state of this isotopologue. Overall 791 and 266 energy levels are newly determined for H217O and HD17O, respectively. A few additional levels were corrected compared to literature values. The obtained experimental results are compared to the spectroscopic parameters provided by the HITRAN database and to the empirical energy levels recommended by an IUPAC task group.

  14. CRDS of 17O enriched water between 5850 and 6671 cm-1: More than 1000 energy levels of H217O and HD17O newly determined

    NASA Astrophysics Data System (ADS)

    Mikhailenko, S. N.; Leshchishina, O.; Karlovets, E. V.; Mondelain, D.; Kassi, S.; Campargue, A.

    2016-07-01

    The room temperature absorption spectrum of water vapor highly enriched in 17O has been recorded by Cavity Ring Down Spectroscopy (CRDS) between 5850 and 6671 cm-1. Two series of recordings were performed with pressure values of 1.0 and 12.0 Torr. The investigated spectral region corresponds to the important 1.55 μm transparency window of the atmosphere where water absorption is very weak. The high sensitivity of the recordings (αmin ~ 5×10-11 cm-1) allows detecting lines with intensity spanning six orders of magnitude (1.4×10-30-3.6×10-24 cm/molecule at room temperature). The experimental list includes more than 10,300 lines. The assignments of water lines were performed using known experimental energy levels as well as calculated line lists based on the results of Partridge and Schwenke. More than 8500 lines were assigned to 9619 transitions of six water isotopologues (H216O, H217O, H218O, HD16O, HD17O and HD18O). All but four transitions of the 16O and 18O isotopologues were assigned using known experimental energy levels. More than half of the assigned H217O and HD17O transitions correspond to new (or corrected) upper energy levels. About 1000 new H217O transitions associated with upper states of the second triad and of the first hexad were identified. Most of the newly assigned HD17O transitions belong to the ν1+ν3 and 2ν2+ν3 bands. The assigned transitions allowed to newly determine or correct 20 highly excited rotational levels of the vibrational ground state of this isotopologue. Overall 791 and 266 energy levels are newly determined for H217O and HD17O, respectively. A few additional levels were corrected compared to literature values. The obtained experimental results are compared to the spectroscopic parameters provided by the HITRAN database and to the empirical energy levels recommended by an IUPAC task group.

  15. Overcoming the overlap problem in the assignment of 1H NMR spectra of larger proteins by use of three-dimensional heteronuclear 1H-15N Hartmann-Hahn-multiple quantum coherence and nuclear Overhauser-multiple quantum coherence spectroscopy: application to interleukin 1 beta.

    PubMed

    Marion, D; Driscoll, P C; Kay, L E; Wingfield, P T; Bax, A; Gronenborn, A M; Clore, G M

    1989-07-25

    The application of three-dimensional (3D) heteronuclear NMR spectroscopy to the sequential assignment of the 1H NMR spectra of larger proteins is presented, using uniformly labeled (approximately 95%) [15N]interleukin 1 beta, a protein of 153 residues and molecular mass of 17.4 kDa, as an example. The two-dimensional (2D) 600-MHz spectra of interleukin 1 beta are too complex for complete analysis, owing to extensive cross-peak overlap and chemical shift degeneracy. We show that the combined use of 3D 1H-15N Hartmann-Hahn-multiple quantum coherence (HOHAHA-HMQC) and nuclear Overhauser-multiple quantum coherence (NOESY-HMQC) spectroscopy, designed to provide the necessary through-bond and through-space correlations for sequential assignment, provides a practical general-purpose method for resolving ambiguities which severely limit the analysis of conventional 2D NMR spectra. The absence of overlapping cross-peaks in these 3D spectra allows the unambiguous identification of C alpha H(i)-NH(i+1) and NH(i)-NH(i+1) through-space nuclear Overhauser connectivities necessary for connecting a particular C alpha H(i)-NH(i) through-bond correlation with its associated through-space sequential cross-peak The problem of amide NH chemical shift degeneracy in the 1H NMR spectrum is therefore effectively removed, and the assignment procedure simply involves inspecting a series of 2D 1H-1H slices edited by the chemical shift of the directly bonded 15N atom. Connections between residues can be identified almost without any knowledge of the spin system types involved, though this type of information is clearly required for the eventual placement of the connected residues within the primary sequence.

  16. 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.

  17. 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)

  18. Automated protein NMR resonance assignments.

    PubMed

    Wan, Xiang; Xu, Dong; Slupsky, Carolyn M; Lin, Guohui

    2003-01-01

    NMR resonance peak assignment is one of the key steps in solving an NMR protein structure. The assignment process links resonance peaks to individual residues of the target protein sequence, providing the prerequisite for establishing intra- and inter-residue spatial relationships between atoms. The assignment process is tedious and time-consuming, which could take many weeks. Though there exist a number of computer programs to assist the assignment process, many NMR labs are still doing the assignments manually to ensure quality. This paper presents (1) a new scoring system for mapping spin systems to residues, (2) an automated adjacency information extraction procedure from NMR spectra, and (3) a very fast assignment algorithm based on our previous proposed greedy filtering method and a maximum matching algorithm to automate the assignment process. The computational tests on 70 instances of (pseudo) experimental NMR data of 14 proteins demonstrate that the new score scheme has much better discerning power with the aid of adjacency information between spin systems simulated across various NMR spectra. Typically, with automated extraction of adjacency information, our method achieves nearly complete assignments for most of the proteins. The experiment shows very promising perspective that the fast automated assignment algorithm together with the new score scheme and automated adjacency extraction may be ready for practical use. PMID:16452794

  19. 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

  20. 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.

  1. Width of the 3841-keV level in 17O

    NASA Astrophysics Data System (ADS)

    Moreh, R.; Beck, O.; Kneissl, U.; Margraf, J.; Maser, H.; Pitz, H. H.; Herzberg, R.-D.; Pietralla, N.; Zilges, A.

    1994-10-01

    The width of 3841-keV level in 17O was precisely measured in nuclear resonance fluorescence experiments performed at the Stuttgart Dynamitron facility. The result of Γ(3841 keV)=(92+/-6) meV is compared with upper limits quoted in the literature. Possible particle-hole configurations of the 3841-keV level are discussed.

  2. Solar 18O/17O and the Setting for Solar Birth

    NASA Astrophysics Data System (ADS)

    Clayton, D. D.

    2004-03-01

    The burst of star formation during the gaeous merger of the Milky Way with a low-metallicity dwarf galaxy created not only the Si-isotope correlation in mainstream SiC grains but also the anomalously large ^18O/^17O ratio in the sun.

  3. ISOTOPIC RATIOS OF {sup 18}O/{sup 17}O IN THE GALACTIC CENTRAL REGION

    SciTech Connect

    Zhang, J. S.; Sun, L. L.; Riquelme, D.; Henkel, C.; Lu, D. R.; Zhang, Y.; Wang, J. Z.; Li, J.; Wang, M.

    2015-08-15

    The {sup 18}O/{sup 17}O isotopic ratio of oxygen is a crucial measure of the secular enrichment of the interstellar medium by ejecta from high-mass versus intermediate-mass stars. So far, however, there is a lack of data, particularly from the Galactic center (GC) region. Therefore, we have mapped typical molecular clouds in this region in the J = 1–0 lines of C{sup 18}O and C{sup 17}O with the Delingha 13.7 m telescope (DLH). Complementary pointed observations toward selected positions throughout the GC region were obtained with the IRAM 30 m and Mopra 22 m telescopes. C{sup 18}O/C{sup 17}O abundance ratios reflecting the {sup 18}O/{sup 17}O isotope ratios were obtained from integrated intensity ratios of C{sup 18}O and C{sup 17}O. For the first time, C{sup 18}O/C{sup 17}O abundance ratios are determined for Sgr C (V ∼ −58 km s{sup −1}), Sgr D (V ∼ 80 km s{sup −1}), and the 1.°3 complex (V ∼ 80 km s{sup −1}). Through our mapping observations, abundance ratios are also obtained for Sgr A (∼0 and ∼50 km s{sup −1} component) and Sgr B2 (∼60 km s{sup −1}), which are consistent with the results from previous single-point observations. Our frequency-corrected abundance ratios of the GC clouds range from 2.58 ± 0.07 (Sgr D, V ∼ 80 km s{sup −1}, DLH) to 3.54 ± 0.12 (Sgr A, ∼50 km s{sup −1}). In addition, strong narrow components (line width less than 5 km s{sup −1}) from the foreground clouds are detected toward Sgr D (−18 km s{sup −1}), the 1.°3 complex (−18 km s{sup −1}), and M+5.3−0.3 (22 km s{sup −1}), with a larger abundance ratio around 4.0. Our results show a clear trend of lower C{sup 18}O/C{sup 17}O abundance ratios toward the GC region relative to molecular clouds in the Galactic disk. Furthermore, even inside the GC region, ratios appear not to be uniform. The low GC values are consistent with an inside-out formation scenario for our Galaxy.

  4. 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.

  5. NMR characterization of shocked quartz

    SciTech Connect

    Boslough, M.B.; Cygan, R.T.; Assink, R.A.; Kirkpatrick, R.J.

    1994-03-01

    We have characterized experimentally and naturally-shocked quartz (both synthetic and natural samples) by solid state nuclear magnetic resonance (NMR) spectroscopy. Relaxation analysis of experimentally-shocked samples provides a means for quantitative characterization of the amorphous/disordered silica component NMR spectra demonstrate that magnetization in both the amorphous and crystalline components follows power-law behavior as a function of recycle time. This observation is consistent with the relaxation of nuclear spins by paramagnetic impurities. A fractal dimension can be extracted from the power-law exponent associated with each phase, and relative abundances can be extracted from integrated intensities of deconvolved peaks. NMR spectroscopy of naturally-shocked sandstone from Meteor Crater, Arizona (USA) led to the discovery of a new amorphous hydroxylated silica phase. Solid state NMR spectra of both experimentally and naturally shocked quartz were unexpectedly rich in microstructural information, especially when combined with relaxation analysis and cross-polarization studies. We suggest solid state NMR as a potentially useful tool for examining shock-induced microstructural changes in other inorganic compounds, with possible implications for shock processing of structural ceramics.

  6. 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.

  7. Using NMR to study full intact wine bottles

    NASA Astrophysics Data System (ADS)

    Weekley, A. J.; Bruins, P.; Sisto, M.; Augustine, M. P.

    2003-03-01

    A nuclear magnetic resonance (NMR) probe and spectrometer capable of investigating full intact wine bottles is described and used to study a series of Cabernet Sauvignons with high resolution 1H NMR spectroscopy. Selected examples of full bottle 13C NMR spectra are also provided. The application of this full bottle NMR method to the measurement of acetic acid content, the detection of complex sugars, phenols, and trace elements in wine is discussed.

  8. 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

  9. Measurements and Modeling of 16O12C17O Spectroscopic Parameters at 2 μm

    NASA Astrophysics Data System (ADS)

    Jacquemart, David; Sung, Keeyoon; Brown, Linda; Coleman, Max; Mantz, Arlan; Smith, Mary Ann H.

    2014-06-01

    Nearly 1000 line intensities of 16O12C17O between 4604 and 5126 wn were measured using an isotopically-enriched mixture sample having 40 % (determined by mass spectrometry). Spectra were recorded at 0.0056 wn resolution with a Fourier transform spectrometer (Bruker IFS-125HR at JPL) configured to a Herriott cell with a 20.946 m absorption path. Since collisional narrowing effects were observed, the Rautian profile was systematically applied (instead of the Voigt profile) using a multispectrum retrieval procedure. Transition dipole moments and Herman-Wallis factors were derived for 15 bands, and a global comparison with theoretical calculations and predictions was obtained. Accuracies for the line intensities ranged between 2 - 3 % for strong bands and 6 - 30 % for weak bands. Retrieved line positions were calibrated using CO, HCl and some well-known 16O12C16O transitions. For both measured and calculated line positions, the accuracies fell between 0.1 - 1×10-3 wn. Self-broadening was also obtained for a few bands. Complete line lists were generated to support atmospheric remote sensing of the Earth (e.g., OCO-2 mission), Mars and Venus. Research described in this paper was performed at Connecticut College, the Jet Propulsion Laboratory, and California Institute of Technology, and NASA Langley Research Center, under contracts and cooperative agreements with the National Aeronautics and Space Administration.

  10. FTS Studies of the 17O Enriched Isotopologues of CO_2 Toward Creating a Complete and Highly Accurate Reference Standard

    NASA Astrophysics Data System (ADS)

    Elliott, Ben; Sung, Keeyoon; Brown, Linda; Miller, Charles

    2014-06-01

    The proliferation and increased abilities of remote sensing missions for the monitoring of planetary atmospheric gas species has spurred the need for complete and accurate spectroscopic reference standards. As a part of our ongoing effort toward creating a global carbon dioxide (CO2) frequency reference standard, we report new FTS measurements of the 17O enriched isotopologues of CO2. The first measurements were taken in the ν3 region (2200 - 2450 cm-1, 65 - 75 THz), have absolute calibration accuracies of 100 kHz (3E-6 cm-1), comparable to the uncertainties for typical sub-millimeter/THz spectroscopy. Such high absolute calibration accuracy has become regular procedure for the cases of linear molecules such as CO2 and CO for FTS measurements at JPL, and enables us to produce measured transition frequencies for entire bands with accuracies that rival those of early heterodyne measurements for individual beat notes. Additionally, by acquiring spectra of multiple carbon dioxide isotopologues simultaneously, we have begun to construct a self-consistent frequency grid based on CO2 that extends from 20 - 200 THz. These new spectroscopic reference standards are a significant step towards minimizing CO2 retrieval errors from remote sensing applications, especially those involving targets with predominantly CO2 atmospheres such as Mars, Venus and candidate terrestrial exoplanets where minor isotopologues will make significant contributions to the radiance signals.

  11. 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.

  12. 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

  13. 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.

  14. Optically detected magnetic resonance studies of photoexcited /sup 17/O-benzophenone. Orbital rotation in the lowest triplet state

    SciTech Connect

    Waeckerle, G.; Baer, M.; Zimmermann, H.; Dinse, K.H.; Yamauchi, S.; Kashmar, R.J.; Pratt, D.W.

    1982-03-01

    The magnetically active isotope of oxygen /sup 17/O has been used to probe the changes in the electron charge and spin density distributions in oxygen valence orbitals which occur when benzophenone is excited to its lowest triplet state. The data obtained include the optically detected magnetic resonance (ODMR) and electron-nuclear double resonance spectra at both zero and high magnetic fields. New methods of analysis of zero-field ODMR spectra, appropriate when the second-order hyperfine splitting exceeds the quadrupole coupling, are described. This analysis yields the principal values of the electron fine-structure (D), oxygen hyperfine (A), and oxygen quadrupole (Q) tensors, and the orientation of their principal axes with respect to the molecular frame. It is found, consistent with expectations for an n..pi..( state, that the direction of the largest component of Q is different from that of the ground state. It is also found, by two independent methods, that the principal transverse axes of A and Q do not conform to the local C/sub 2v/ symmetry axes of the carbonyl group. This result is interpreted to mean that the axis of the n-type oxygen 2p orbital is rotated out of the carbonyl plane, a rotation which appears to be direct consequence of n..pi..(/..pi pi..( configurational mixing. In agreement with this, the principal values of D, A, and Q are different from those expected for a ''pure'' n..pi..( state. Other consequences of n..pi..(/..pi pi..( mixing, not only in benzophenone but also in the lowest triplet states of other aromatic carbonyls, are discussed briefly.

  15. New opportunities for high-resolution solid-state NMR spectroscopy of oxide materials at 21.1- and 18.8-T fields.

    PubMed

    Stebbins, J; Du, Lin-Shu; Kroeker, S; Neuhoff, P; Rice, D; Frye, J; Jakobsen, H J

    2002-01-01

    We present here high-resolution solid state NMR spectra of several oxide and silicate materials that illustrate the improvements obtainable with very high external fields (18.8 and 21.1 T), with probes capable of tuning to a wide frequency range that allow observations of nuclides from high to low magnetogyric ratio. We discuss 27Al MAS spectra for the zeolite scolecite (CaAl2Si3O10 x 3H2O), 17O MAS data for analcime (NaAlSi2O6 x H2O), calcium monoaluminate (CaAI2O4), and titanite (CaTiSiO5), 39K spin-echo spectra for leucite (KAlSi2O6), microline (KAlSiO8), muscovite (KAl2(AlSi3O10)(OH2) and a potassium aluminosolicate glass, and preliminary 73Ge spin-echo MAS spectra for crystalline and glassy germanium dioxide (GeO2).

  16. Review of advances in coupling electrochemistry and liquid state NMR.

    PubMed

    Bussy, Ugo; Boujtita, Mohammed

    2015-05-01

    The coupling of electrochemistry and NMR spectroscopy (EC-NMR) may present an interesting approach in the environmental oxidative degradation or metabolism studies. This review presents experimental advances in the field of EC-NMR and highlights the main advantages and drawbacks of in situ and on line of NMR spectroelectrochemistry. The analysis of NMR spectra recorded in situ or on line EC-NMR permits to elucidate the reaction pathway of the electrochemical oxidation reactions and could constitute a fast way for monitoring unstable species as for instance quinone and quinone imine structures without using any coupling agents. The use of 1D and 2D NMR coupled with electrochemistry may leads to the elucidation of the major species produced from the electrochemical oxidation process. The present review gives an overview about the development of the electrochemical cells which can operate on line or in situ with NMR measurements. Future developments and potential applications of EC-NMR are also discussed.

  17. Structural Studies of the Molybdenum Center of the Pathogenic R160Q Mutant of Human Sulfite Oxidase by Pulsed EPR Spectroscopy and 17O and 33S Labeling

    PubMed Central

    Astashkin, Andrei V.; Johnson-Winters, Kayunta; Klein, Eric L.; Feng, Changjian; Wilson, Heather L.; Rajagopalan, K. V.; Raitsimring, Arnold M.; Enemark, John H.

    2009-01-01

    Electron paramagnetic resonance (EPR) investigation of the Mo(V) center of the pathogenic R160Q mutant of human sulfite oxidase (hSO) confirms the presence of three distinct species whose relative abundances depend upon pH. Species 1 is exclusively present at pH ≤ 6, and remains in significant amounts even at pH 8. Variable-frequency electron spin echo envelope modulation (ESEEM) studies of this species prepared with 33S-labeled sulfite clearly show the presence of coordinated sulfate, as has previously been found for the “blocked” form of Arabidopsis thaliana at low pH (Astashkin, A. V.; Johnson-Winters, K.; Klein, E. L.; Byrne, R. S.; Hille, R.; Raitsimring, A. M.; Enemark, J. H. J. Am. Chem. Soc. 2007, 129, 14800). The ESEEM spectra of Species 1 prepared in 17O-enriched water show both strongly and weakly magnetically coupled 17O atoms that can be assigned to an equatorial sulfate ligand and the axial oxo ligand, respectively. The nuclear quadrupole interaction (nqi) of the axial oxo ligand is substantially stronger than those found for other oxo-Mo(V) centers studied previously. Additionally, pulsed electron–nuclear double resonance (ENDOR) measurements reveal a nearby weakly coupled exchangeable proton. The structure for Species 1 proposed from the pulsed EPR results using isotopic labeling is a six-coordinate Mo(V) center with an equatorial sulfate ligand that is hydrogen bonded to an exchangeable proton. Six-coordination is supported by the 17O nqi parameters for the axial oxo group of the model compound, (dttd)Mo17O(17Otms), where H2dttd = 2,3:8,9-dibenzo-1,4,7,10-tetrathiadecane; tms = trimethylsilyl. Reduction of R160Q to Mo(V) with Ti(III) gives primarily Species 2, another low pH form, whereas reduction with sulfite at higher pH values gives a mixture of Species 1 and 2, as well as the “primary” high pH form of wild-type SO. The occurrence of significant amounts of the “sulfate-blocked” form of R160Q (Species 1) at physiological p

  18. Assigning the NMR Spectrum of Glycidol: An Advanced Organic Chemistry Exercise

    ERIC Educational Resources Information Center

    Helms, Eric; Arpaia, Nicholas; Widener, Melissa

    2007-01-01

    Various one- and two-dimensional NMR experiments have been found to be extremely useful for assigning the proton and carbon NMR spectra of glycidol. The technique provides extremely valuable information aiding in the complete assignment of the peaks.

  19. 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.

  20. NMR of fd coat protein.

    PubMed

    Cross, T A; Opella, S J

    1979-01-01

    The conformations of the major coat protein of a filamentous bacteriophage can be described by nuclear magnetic resonance spectroscopy of the protein and the virus. The NMR experiments involve detection of the 13C and 1H nuclei of the coat protein. Both the 13C and 1H nuclear magnetic resonance (NMR) spectra show that regions of the polypeptide chain have substantially more motion than a typical globular protein. The fd coat protein was purified by gel chromatography of the SDA solubilized virus. Natural abundance 13C NMR spectra at 38 MHz resolve all of the nonprotonated aromatic carbons from the three phenylalanines, two tyrosines, and one tryptophan of the coat protein. The alpha carbons of the coat protein show at least two different classes of relaxation behavior, indicative of substantial variation in the motion of the backbone carbons in contrast to the rigidity of the alpha carbons of globular proteins. The 1H spectrum at 360 MHz shows all of the aromatic carbons and many of the amide protons. Titration of a 1H spectra gives the pKas for the tyrosines.

  1. Synthesis and x-ray structural characterization of binuclear iridium(I) and rhodium(I) hydroxypyridinate complexes. 1. Complete assignment of the /sup 1/H NMR spectra by two-dimensional and NOE techniques. The nature of inside and outside /sup 1/H chemical shift differences

    SciTech Connect

    Rodman, G.S.; Mann, K.R.

    1988-09-21

    Six new d/sup 8/-d/sup 8/ complexes, (Ir(COD)(..mu..-hp))/sub 2/, (Ir(COD)(..mu..-mhp))/sub 2/, (Ir(COD)(..mu..-chp))/sub 2/, (Ir(COD)(..mu..-2hq))/sub 2/, (Rh(COD)(..mu..-hp))/sub 2/, and (Rh(COD)(..mu..-mhp))/sub 2/ (hp = 2-hydroxyphridinate, mhp = 6-methyl-2-hydroxypyridinate, chp = 6-chloro-2-hydroxypyridinate, 2hq = 2-hydroxyquinolate, COD = 1,5-cyclooctadiene), were synthesized and characterized by /sup 1/H NMR, /sup 13/C NMR, and IR spectroscopy and FAB mass spectrometry. X-ray crystallographic analyses of the isostructural (M(COD)(..mu..-mhp))/sub 2/ (M = Ir and Rh) complexes confirmed the binuclear nature of the complexes. The complete assignment of the /sup 1/H NMR spectrum of (Ir(COD)(..mu..-hp))/sub 2/ (and by analogy, the spectra of the other five complexes) was carried out with selective decoupling, nuclear Overhauser effect (NOE), and two-dimensional NMR techniques. The NOE observed between hp proton H5 and COD proton H15 allowed the precise assignment of all 12 COD resonances. Olefinic proton H12 (trans to N and outside) resonates downfield of olefinic proton H11 (trans to N and inside). Olefininc proton H15 (trans to O and outside) resonates upfield of olefinic proton H16 (trans to O and inside). The endo methylene protons resonate upfield of the exo methylene protons. The inside/outside chemical shift differences observed for these compounds are ascribed to steric and magnetic anisotropy effects. The crystallographic data are presented. The molecular structure of the complexes is discussed in detail. 39 references, 5 figures, 9 tables.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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. PMID:25870269

  7. 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.

  8. Site connectivities in sodium aluminoborate glasses: multinuclear and multiple quantum NMR results.

    PubMed

    Du, Lin-Shu; Stebbins, Jonathan F

    2005-01-01

    In a series of sodium aluminoborate glasses, we have applied triple-quantum magic-angle spinning (3QMAS) 17O NMR to obtain high-resolution information about the connections among various network structural units, to explore the mixing of aluminum and boron species. Oxygen-17 3QMAS spectra reveal changes in connectivities between AlO4 ([4]Al), AlO5 and AlO6 ([5,6]Al), BO3 ([3]B) and BO4 ([4]B) units, by quantifying populations of bridging oxygens such as Al-O-Al, Al-O-B and B-O-B and of non-bridging oxygens. Several linkages such as [4]Al-O-[4]Al and three-coordinated oxygen associated with [5,6]Al in Al-O-Al, [4]Al-O-[4]B, [4]Al-O-[3]B and [5,6]Al-O-[3]B in Al-O-B as well as [4]B-O-[3]B and [3]B-O-[3]B in B-O-B can be distinguished for the first time. The fractions of these linkages were calculated from models of random mixing and of mixing with maximum avoidance of tetrahedral-tetrahedral linkages. The results suggest that the structure of all of glasses in this study is well approximated by the latter model. However, the energetic "penalty" for formation of [4]Al-O-[4]B may be somewhat less than for [4]Al-O-[4]Al and [4]B-O-[4]B. In general, the new results presented here are similar to those obtained on glasses in this system by 27Al{11B} REDOR NMR (J. Phys. Chem. B 104 (2000) 6541), but provide considerably more detail on network connectivity and ordering schemes.

  9. GEL-STATE NMR OF BALL-MILLED WHOLE CELL WALLS IN DMSO-d6 USING 2D SOLUTION-STATE NMR SPECTROSCOPY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plant cell walls were used for obtaining 2D solution-state NMR spectra without actual solubilization or structural modification. Ball-milled whole cell walls were swelled directly in the NMR tube with DMSO-d6 where they formed a gel. There are relatively few gel-state NMR studies. Most have involved...

  10. Pygmy dipole resonance in 140Ce via inelastic scattering of 17O

    NASA Astrophysics Data System (ADS)

    Krzysiek, M.; Kmiecik, M.; Maj, A.; Bednarczyk, P.; Bracco, A.; Crespi, F. C. L.; Lanza, E. G.; Litvinova, E.; Paar, N.; Avigo, R.; Bazzacco, D.; Benzoni, G.; Birkenbach, B.; Blasi, N.; Bottoni, S.; Brambilla, S.; Camera, F.; Ceruti, S.; Ciemała, M.; de Angelis, G.; Désesquelles, P.; Eberth, J.; Farnea, E.; Gadea, A.; Giaz, A.; Görgen, A.; Gottardo, A.; Grebosz, J.; Hess, H.; Isocarte, R.; Jungclaus, A.; Leoni, S.; Ljungvall, J.; Lunardi, S.; Mazurek, K.; Menegazzo, R.; Mengoni, D.; Michelagnoli, C.; Milion, B.; Morales, A. I.; Napoli, D. R.; Nicolini, R.; Pellegri, L.; Pullia, A.; Quintana, B.; Recchia, F.; Reiter, P.; Rosso, D.; Salsac, M. D.; Siebeck, B.; Siem, S.; Söderström, P.-A.; Ur, C.; Valiente-Dobon, J. J.; Wieland, O.; Ziebliński, M.

    2016-04-01

    The γ decay from the high-lying states of 140Ce excited via inelastic scattering of 17O at a bombarding energy of 340 MeV was measured using the high-resolution AGATA-demonstrator array in coincidence with scattered ions detected in two segmented Δ E -E silicon detectors. Angular distributions of scattered ions and emitted γ rays were measured, as well as their differential cross sections. The excitation of 1- states below the neutron separation energy is similar to the one obtained in reactions with the α isoscalar probe. The comparison between the experimental differential cross sections and the corresponding predictions using the distorted-wave Born approximation allowed us to extract the isoscalar component of identified 1- pygmy states. For this analysis the form factor obtained by folding microscopically calculated transition densities and optical potentials was used.

  11. The 871 keV gamma ray from 17O and the identification of plutonium oxide

    NASA Astrophysics Data System (ADS)

    Peurrung, Anthony; Arthur, Richard; Elovich, Robert; Geelhood, Bruce; Kouzes, Richard; Pratt, Sharon; Scheele, Randy; Sell, Richard

    2001-12-01

    Disarmament agreements and discussions between the United States and the Russian Federation for reducing the number of stockpiled nuclear weapons require verification of the origin of materials as having come from disassembled weapons. This has resulted in the identification of measurable "attributes" that characterize such materials. It has been proposed that the 871 keV gamma ray of 17O can be observed as an indicator of the unexpected presence of plutonium oxide, as opposed to plutonium metal, in such materials. We have shown that the observation of the 871 keV gamma ray is not a specific indicator of the presence of the oxide, but rather indicates the presence of nitrogen.

  12. The impact of anthropogenic emissions on atmospheric sulfate production pathways, oxidants, and ice core Δ17O(SO42-)

    NASA Astrophysics Data System (ADS)

    Sofen, E. D.; Alexander, B.; Kunasek, S. A.

    2011-04-01

    We use a global three-dimensional chemical transport model to quantify the influence of anthropogenic emissions on atmospheric sulfate production mechanisms and oxidant concentrations constrained by observations of the oxygen isotopic composition (Δ17O = &delta17O-0.52 × &delta18O) of sulfate in Greenland and Antarctic ice cores and aerosols. The oxygen isotopic composition of non-sea salt sulfate (Δ17O(SO42-)) is a function of the relative importance of each oxidant (e.g. O3, OH, H2O2, and O2) during sulfate formation, and can be used to quantify sulfate production pathways. Due to its dependence on oxidant concentrations, Δ17O(SO42-) has been suggested as a proxy for paleo-oxidant levels. However, the oxygen isotopic composition of sulfate from both Greenland and Antarctic ice cores shows a trend opposite to that expected from the known increase in the concentration of tropospheric O3 since the preindustrial period. The model simulates a significant increase in the fraction of sulfate formed via oxidation by O2 catalyzed by transition metals in the present-day Northern Hemisphere troposphere (from 11% to 22%), offset by decreases in the fractions of sulfate formed by O3 and H2O2. There is little change, globally, in the fraction of tropospheric sulfate produced by gas-phase oxidation (from 23% to 27%). The model-calculated change in Δ17O(SO42-) since preindustrial times (1850 CE) is consistent with Arctic and Antarctic observations. The model simulates a 42% increase in the concentration of global mean tropospheric O3, a 10% decrease in OH, and a 58% increase in H2O2 between the preindustrial period and present. Model results indicate that the observed decrease in the Arctic Δ17O(SO42-) - in spite of increasing tropospheric O3 concentrations - can be explained by the combined effects of increased sulfate formation by O2 catalyzed by anthropogenic transition metals and increased cloud water acidity, rendering Δ17O(SO42-) insensitive to changing oxidant

  13. MetaboQuant: a tool combining individual peak calibration and outlier detection for accurate metabolite quantification in 1D (1)H and (1)H-(13)C HSQC NMR spectra.

    PubMed

    Klein, Matthias S; Oefner, Peter J; Gronwald, Wolfram

    2013-05-01

    Solution nuclear magnetic resonance (NMR) spectroscopy is widely used to analyze complex mixtures of organic compounds such as biological fluids and tissue extracts. Targeted profiling approaches with reliable compound quantitifcation are hampered, however, by signal overlap and other interferences. Here, we present a tool named MetaboQuant for automated compound quantification from pre-processed 1D and 2D heteronuclear single quantum coherence (HSQC) NMR spectral data and concomitant validation of results. Performance of MetaboQuant was tested on a urinary spike-in data set and compared with other quantification strategies. The use of individual calibration factors in combination with the validation algorithms of MetaboQuant raises the reliability of the quantification results. MetaboQuant can be downloaded at http://genomics.uni-regensburg.de/site/institute/software/metaboquant/ as stand-alone software for Windows or run on other operating systems from within Matlab. Separate software for peak fitting and integration is necessary in order to use MetaboQuant. PMID:23662895

  14. 17O excess traces atmospheric nitrate in paleo-groundwater of the Saharan desert

    NASA Astrophysics Data System (ADS)

    Dietzel, M.; Leis, A.; Abdalla, R.; Savarino, J.; Morin, S.; Böttcher, M. E.; Köhler, S.

    2014-06-01

    Saharan paleo-groundwater from the Hasouna area of Libya contains up to 1.8 mM of nitrate, which exceeds the World Health Organization limit for drinking water, but the origin is still disputed. Herein we show that a positive 17O excess in NO3- (Δ17ONO3 = Δ17ONO3 - 0.52 δ18ONO3) is preserved in the paleo-groundwater. The 17O excess provides an excellent tracer of atmospheric NO3-, which is caused by the interaction of ozone with NOx via photochemical reactions, coupled with a non-mass-dependent isotope fractionation. Our Δ17ONO3 data from 0.4 to 5.0 ‰ (n = 28) indicate that up to 20 mol % of total dissolved NO3- originated from the Earth's atmosphere (x[NO3-]atm), where the remaining NO3- refers to microbially induced nitrification in soils. High Δ17ONO3 values correspond to soils that are barren in dry periods, while low Δ17ONO3 values correspond to more fertile soils. Coupled high Δ17ONO3 and high x[NO3-]atm values are caused by a sudden wash-out of accumulated disposition of atmospheric NO3- on plants, soil surfaces and in vadose zones within humid-wet cycles. The individual isotope and chemical composition of the Hasouna groundwater can be followed by a binary mixing approach using the lowest and highest mineralised groundwater as end members without considering evaporation. Using the δ34SSO4 and δ18OSO4 isotope signature of dissolved SO42-, no indication is found for a superimposition by denitrification, e.g. involving pyrite minerals within the aquifers. It is suggested that dissolved SO42- originates from the dissolution of CaSO4 minerals during groundwater evolution.

  15. 17O-excess traces atmospheric nitrate in paleo groundwater of the Saharan desert

    NASA Astrophysics Data System (ADS)

    Dietzel, M.; Leis, A.; Abdalla, R.; Savarino, J.; Morin, S.; Böttcher, M. E.; Köhler, S.

    2013-12-01

    Saharan paleo groundwater from the Hasouna area of Libya contains up to 1.8 mM of nitrate, the origin of which is still disputed. Herein we show that a positive 17O-excess in NO3- (Δ17ONO3 = δ17ONO3 - 0.52 δ18ONO3) is preserved in the paleo groundwater. The 17O-excess provides an excellent tracer of atmospheric NO3-, which is caused by the interaction of ozone with NOx via photochemical reactions, coupled with a non-mass dependent isotope fractionation. Our Δ17ONO3 data from 0.4 to 5.0‰ (n = 28) indicate that up to x [NO3-]atm = 20 mol % of total dissolved NO3- originated from the Earth's atmosphere. High Δ17ONO3 values correspond to soils that are barren in dry periods, while low Δ17ONO3 values correspond to more fertile soils. Coupled high Δ17ONO3 and high x [NO3-]atm values are caused by a sudden wash out of dry deposition of atmospheric NO3- on plant or soil surfaces within humid-wet cycles. The individual isotope and chemical composition of the Hasouna groundwater can be followed by a binary mixing approach using the lowest and highest mineralized groundwater as end-members without considering evaporation. Using the δ34SSO4 and δ18OSO4 isotope signature of dissolved sulfate, no indication is found for a superimposition by denitrification, e.g. involving pyrite minerals within the aquifers. It is suggested that dissolved sulfate originates from the dissolution of calcium sulfate minerals during groundwater evolution.

  16. 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.

  17. 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

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

    PubMed

    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

  19. Preparation, electrochemistry and crystal structure of a derivative of 18-tungstophosphate with Dawson structure: K 16H[Yb(α-2-P 2W 17O 61) 2]·44H 2O

    NASA Astrophysics Data System (ADS)

    Niu, Jingyang; Zhao, Junwei; Guo, Dongjie; Wang, Jingping

    2004-04-01

    The heteropolyanion [Yb(α-2-P 2W 17O 61) 2] 17- has been isolated as a potassium salt in ˜30% yield by five-day decreasing temperature-programmed from 60 °C to room temperature, in a potassium acetate buffer, formed by reaction of K 6P 2W 18O 62·10H 2O with Yb(NO 3) 3 and characterized by IR, UV spectra. Single crystal X-ray structural analysis of K 16H[Yb(α-2-P 2W 17O 61) 2]·44H 2O (triclinic, space group PI a=14.499(3), b=22.433(5), c=24.505(5) Å, α=95.36(3), β=102.67(3), γ=100.06(3)°, Z=2, 24,089 independent reflections, R1=0.0497) reveals that two chemically identical [α-2-P 2W 17O 61] 10- moieties are connected through one Yb atom, which is in a square antiprismatic coordination environment with eight oxygen atoms, four from each of the two [α-2-P 2W 17O 61] 10- moieties. The Yb(III) ion substitutes for two [W=O] 4+ units in the 'cap' regions of the tungsten-oxygen frameworks of the two parent Wells-Dawson ions. The point group symmetry of the title polyanion is C 2. In the extensive pH region from 10.5 to 1.60, the cyclic voltammograms for the title compound in the presence of 0.5 M NaCl aqueous solution as supporting electrolyte mainly illustrate nearly reversible one-electron reduction processes. The results of the thermogravimetric analysis of the title compound show one one-step slow weight loss and the framework decomposition of the polyanion in the title compound is at 560.0 °C.

  20. Evidence for intrinsic impurities in the high-temperature superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} from {sup 17}O nuclear magnetic resonance.

    SciTech Connect

    Chen, B.; Mukhopadhyay, S.; Halperin, W. P.; Guptasarma, P.; Hinks, D. G.; Materials Science Division; Northwestern Univ.; Univ. of Wisconsin at Milwaukee

    2008-02-01

    We have found that high quality crystals of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} (Bi-2212) have intrinsic magnetic defects that depend on oxygen doping. Our {sup 17}O nuclear magnetic resonance spectra provide evidence that local moments form in the CuO{sub 2} plane in both normal and superconducting states. We suggest that these magnetic impurities are related to the electronic disorder that scanning tunneling microscopy experiments identify with the oxygen dopant atoms.

  1. 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. PMID:26789115

  2. 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.

  3. 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.

  4. Isotopic Water Analyzer for Highly Precise Measurements of δ2H, δ18O, and δ17O

    NASA Astrophysics Data System (ADS)

    Berman, E. S.; Fortson, S.; Snaith, S.; Gupta, M.

    2012-12-01

    Measurements of the stable isotope ratios (δ2H, δ18O and δ17O) of both liquid water and water vapor are widely used in hydrology, atmospheric sciences, and biogeochemistry to determine the migration of water through an ecosystem. Previously, discrete samples were collected (or condensed) and transported to an isotope ratio mass spectrometer for characterization. Due to the expense and labor associated with such sampling, isotope studies were generally limited in scope and in temporal resolution. We report on the continued development of a field-portable Isotopic Water Analyzer that exploits cavity-enhanced absorption spectrometry (e.g. Off-Axis ICOS) to accurately and rapidly quantify δ2H, δ18O and δ17O of both liquid water and water vapor. The instrument is thermally-controlled to better than ±8 mK and is capable of measuring over 90 liquid samples/day with δ2H, δ18O and δ17O precisions exceeding ±0.2 ‰, ±0.05 ‰, and ±0.06 ‰ respectively. Subsequent averaging yields δ2H, δ18O and δ17O precisions exceeding ±0.077 ‰, ±0.023 ‰, and ±0.03 ‰ respectively with over 22 samples/day. The accuracy of the liquid analyzer was confirmed over a very wide dynamic range (δ2H = -455 to +671 ‰ with comparable δ18O and δ17O values) by direct comparison to isotope ratio mass spectrometry. Moreover, the ability to directly measure 17O-excess, vapor samples, and unnatural waters (e.g. plant water, soil water, urine, blood, saliva…) will also be presented.

  5. 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.

  6. 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.

  7. 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

  8. 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...

  9. SEnD NMR: Sensitivity Enhanced n-Dimensional NMR

    PubMed Central

    Gledhill, John M.; Wand, A. Joshua

    2009-01-01

    Sparse sampling offers tremendous potential for overcoming the time limitations imposed by traditional Cartesian sampling of indirectly detected dimensions of multidimensional NMR data. However, in many instances sensitivity rather than time remains of foremost importance when collecting data on protein samples. Here we explore how to optimize the collection of radial sampled multidimensional NMR data to achieve maximal signal-to-noise. A method is presented that exploits a rigorous definition of the minimal set of radial sampling angles required to resolve all peaks of interest in combination with a fundamental statistical property of radial sampled data. The approach appears general and can achieve a substantial sensitivity advantage over Cartesian sampling for the same total data acquisition time. Termed Sensitivity Enhanced n-Dimensional or SEnD NMR, the method involves three basic steps. First, data collection is optimized using routines to determine a minimal set of radial sampling angles required to resolve frequencies in the radially sampled chemical shift evolution dimensions. Second, appropriate combinations of experimental parameters (transients and increments) are defined by simple statistical considerations in order to optimize signal-to-noise in single angle frequency domain spectra. Finally, the data is processed with a direct multidimensional Fourier transform and a statistical artifact and noise removal step is employed. PMID:20004602

  10. NMR system and method having a permanent magnet providing a rotating magnetic field

    DOEpatents

    Schlueter, Ross D [Berkeley, CA; Budinger, Thomas F [Berkeley, CA

    2009-05-19

    Disclosed herein are systems and methods for generating a rotating magnetic field. The rotating magnetic field can be used to obtain rotating-field NMR spectra, such as magic angle spinning spectra, without having to physically rotate the sample. This result allows magic angle spinning NMR to be conducted on biological samples such as live animals, including humans.

  11. Organic Spectroscopy Laboratory: Utilizing IR and NMR in the Identification of an Unknown Substance

    ERIC Educational Resources Information Center

    Glagovich, Neil M.; Shine, Timothy D.

    2005-01-01

    A laboratory experiment that emphasizes the interpretation of both infrared (IR) and nuclear magnetic resonance (NMR) spectra in the elucidation of the structure of an unknown compound was developed. The method helps students determine [to the first power]H- and [to the thirteenth power]C-NMR spectra from the structures of compounds and to…

  12. Hyperpolarized NMR of plant and cancer cell extracts at natural abundance.

    PubMed

    Dumez, Jean-Nicolas; Milani, Jonas; Vuichoud, Basile; Bornet, Aurélien; Lalande-Martin, Julie; Tea, Illa; Yon, Maxime; Maucourt, Mickaël; Deborde, Catherine; Moing, Annick; Frydman, Lucio; Bodenhausen, Geoffrey; Jannin, Sami; Giraudeau, Patrick

    2015-09-01

    Natural abundance (13)C NMR spectra of biological extracts are recorded in a single scan provided that the samples are hyperpolarized by dissolution dynamic nuclear polarization combined with cross polarization. Heteronuclear 2D correlation spectra of hyperpolarized breast cancer cell extracts can also be obtained in a single scan. Hyperpolarized NMR of extracts opens many perspectives for metabolomics. PMID:26215673

  13. 17O(n,α)14C cross section from 25 meV to approximately 1 MeV

    NASA Astrophysics Data System (ADS)

    Koehler, P. E.; Graff, S. M.

    1991-12-01

    We have measured the 17O(n,α)14C cross section from thermal energy to approximately 1 MeV. A bump in the data near 3 keV could be fitted by a state whose properties are consistent with a known subthreshold J π=1- level at Ex=8.039 MeV. The cause of the 1/v cross section near thermal energy could not be determined although the known 2+ state at 8.213 MeV was found to be too narrow to contribute much to the thermal cross section. Our data are compared to measurements made via the inverse reaction. There are many differences between the two sets of data. The astrophysical reaction rate was calculated from the measured cross section. This reaction plays a role in the nucleosynthesis of heavy elements in nonstandard big-bang models. At big-bang temperatures, the experimental rate was found to be in fair agreement with the rate estimated from the previously known properties of states of 18O in this region. Furthermore, using the available information from experiments, it was estimated that the 17O(n,α)14C rate is approximately a factor of 103-104 times larger than the 17O(n,γ)18O rate at big-bang temperatures. As a result, there may be significant cycling between 14C and 17O resulting in a reduction of heavy-element nucleosynthesis.

  14. Synthesis of 5α-androstane-3α,17β-diol 17-O-glucuronide histaminyl conjugate for immunoassays.

    PubMed

    Vinš, Petr; Černý, Ivan; Mikšátková, Petra; Drašar, Pavel

    2016-05-01

    Simple method of preparation of 5α-androstane-3α,17β-diol 17-O-glucuronide N-histaminyl amide was developed for the construction of immunoanalytical kit. Improved method of glucuronide derivative synthesis was used, followed by hydroxybenzotriazole-dicyclohexylcarbodiimide coupling with histamine. PMID:26898541

  15. 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.

  16. Solid-State NMR Study of Paramagnetic Bis(alaninato-κ(2)N,O)copper(II) and Bis(1-amino(cyclo)alkane-1-carboxylato-κ(2)N,O)copper(II) Complexes: Reflection of Stereoisomerism and Molecular Mobility in (13)C and (2)H Fast Magic Angle Spinning Spectra.

    PubMed

    Szalontai, Gábor; Csonka, Róbert; Speier, Gábor; Kaizer, József; Sabolović, Jasmina

    2015-05-18

    Solid-state stereochemistry and mobility of paramagnetic copper(II) complexes formed by aliphatic amino acids (l-alanine, d,l-alanine, 1-amino-2-methyl-alanine) and 1-amino(cyclo)alkane-1-carboxylic acids (alkane = propane, butane, pentane, hexane) as bidentate ligands has been studied by (13)C and (2)H solid-state fast magic angle spinning (MAS) NMR spectroscopy. We examined the prospective method to characterize solid-state paramagnetic compounds in a routine way. Both (13)C and (2)H MAS spectra can distinguish d,l and l,l diastereomers of natural and polydeuterated bis([Dn]alaninato)copper(II) (n = 0, 2, 8) complexes with axial and/or equatorial methyl positions (conformations) primarily due to different Fermi-contact (FC) contributions. The three-bond hyperfine couplings clearly show Karplus-like dependence on the torsional angles which turned out to be a useful assignment aid. Density functional theory calculations of the FC term and crystal structures were also used to aid the final assignments. The correlations obtained for bis(alaninato-κ(2)N,O)copper(II) complexes were successfully used to characterize other complexes. The usefulness of the (2)H MAS spectra of the deuterated complexes was underlined. Even the spectra of the easily exchangeable amine protons contained essential stereochemical information. In the case of a dimer structure of bis(1-aminohexane-1-carboxylato-κ(2)N,O)copper(II) both the (13)C and (2)H resolutions were good enough to confirm the presence of the cis and trans forms in the asymmetric unit. With regard to the internal solid-state motions in the crystal lattice, the obtained quadrupolar tensor parameters were similar for the d,l- and l,l-alaninato isomers and also for the cis-trans forms suggesting similar crystal packing effects, static amine deuterons involved in hydrogen bonding, and fast rotating methyl groups.

  17. Picoliter 1H NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Minard, Kevin R.; Wind, Robert A.

    2002-02-01

    In this study, a 267-μm-diameter solenoid transceiver is used to acquire localized 1H NMR spectra and the measured signal-to-noise ratio (SNR) at 500 MHz is shown to be within 20-30% of theoretical limits formulated by considering only its resistive losses. This is illustrated using a 100-μm-diameter globule of triacylglycerols (∼900 mM) that may be an oocyte precursor in young Xenopus laevis frogs and a water sample containing choline at a concentration often found in live mammalian cells (∼33 mM). In chemical shift imaging (CSI) experiments performed using a few thousand total scans, the choline methyl line is shown to have an acceptable SNR in resolved volume elements containing only 50 pL of sample, and localized spectra are resolved from just 5 pL in the Xenopus globule. These findings demonstrate the feasibility of performing 1H NMR on picoliter-scale sample volumes in biological cells and tissues and illustrate how the achieved SNR in spectroscopic images can be predicted with reasonable accuracy at microscopic spatial resolutions.

  18. 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.

  19. Theoretical Modeling of (99)Tc NMR Chemical Shifts.

    PubMed

    Hall, Gabriel B; Andersen, Amity; Washton, Nancy M; Chatterjee, Sayandev; Levitskaia, Tatiana G

    2016-09-01

    Technetium-99 (Tc) displays a rich chemistry due to its wide range of accessible oxidation states (from -I to +VII) and ability to form coordination compounds. Determination of Tc speciation in complex mixtures is a major challenge, and (99)Tc nuclear magnetic resonance (NMR) spectroscopy is widely used to probe chemical environments of Tc in odd oxidation states. However, interpretation of (99)Tc NMR data is hindered by the lack of reference compounds. Density functional theory (DFT) calculations can help to fill this gap, but to date few computational studies have focused on (99)Tc NMR of compounds and complexes. This work evaluates the effectiveness of both pure generalized gradient approximation and their corresponding hybrid functionals, both with and without the inclusion of scalar relativistic effects, to model the (99)Tc NMR spectra of Tc(I) carbonyl compounds. With the exception of BLYP, which performed exceptionally well overall, hybrid functionals with inclusion of scalar relativistic effects are found to be necessary to accurately calculate (99)Tc NMR spectra. The computational method developed was used to tentatively assign an experimentally observed (99)Tc NMR peak at -1204 ppm to fac-Tc(CO)3(OH)3(2-). This study examines the effectiveness of DFT computations for interpretation of the (99)Tc NMR spectra of Tc(I) coordination compounds in high salt alkaline solutions. PMID:27518482

  20. 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.

  1. 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. PMID:25494341

  2. Use of 17O/16O to trace atmospherically-deposited sulfate in surface waters: A case study in alpine watersheds in the Rocky Mountains

    USGS Publications Warehouse

    Johnson, C.A.; Mast, M.A.; Kester, C.L.

    2001-01-01

    Building on the discovery of excess 17O in atmospheric sulfate by Lee et al. (2001), we have carried out a case study to determine whether 17O might provide a new tool for quantifying the impact of atmospheric deposition on surface-water sulfate loads. In Rocky Mountain alpine regions, excess 17O was found to be characteristics of atmospheric sulfate deposited in snow. Excess 17O was also evident in stream sulfate in one of two high-elevation watersheds where analyses were made. Isotope mass balance calculations gave surprizingly low atmospheric contributions to stream sulfate suggesting that (1) despite abundant outcrop and sparse soil in these areas, significant sulfate may be taken up and released by soil microbes before being exported in streams, and (2) surface waters can carry multiple non-atmospheric sulfate types, some possibly anthropogenic. Measurements of 17O may prove very useful in studies of sulfate behavior in a variety of surficial environments.

  3. HIGH-PRECISION C{sup 17}O, C{sup 18}O, AND C{sup 16}O MEASUREMENTS IN YOUNG STELLAR OBJECTS: ANALOGUES FOR CO SELF-SHIELDING IN THE EARLY SOLAR SYSTEM

    SciTech Connect

    Smith, Rachel L.; Young, Edward D.; Pontoppidan, Klaus M.; Morris, Mark R.; Van Dishoeck, Ewine F. E-mail: pontoppi@gps.caltech.edu E-mail: morris@astro.ucla.edu

    2009-08-10

    Using very high resolution ({lambda}/{delta}{lambda} {approx} 95 000) 4.7 {mu}m fundamental and 2.3 {mu}m overtone rovibrational CO absorption spectra obtained with the Cryogenic Infrared Echelle Spectrograph infrared spectrometer on the Very Large Telescope (VLT), we report detections of four CO isotopologues-C{sup 16}O, {sup 13}CO, C{sup 18}O, and the rare species, C{sup 17}O-in the circumstellar environment of two young protostars: VV CrA, a binary T Tauri star in the Corona Australis molecular cloud, and Reipurth 50, an intermediate-mass FU Ori star in the Orion Molecular Cloud. We argue that the observed CO absorption lines probe a protoplanetary disk in VV CrA, and a protostellar envelope in Reipurth 50. All CO line profiles are spectrally resolved, with intrinsic line widths of {approx}3-4 km s{sup -1} (FWHM), permitting direct calculation of CO oxygen isotopologue ratios with 5%-10% accuracy. The rovibrational level populations for all species can be reproduced by assuming that CO absorption arises in two temperature regimes. In the higher temperature regime, in which the column densities are best determined, the derived oxygen isotope ratios in VV CrA are: [C{sup 16}O]/[C{sup 18}O] =690 {+-} 30; [C{sup 16}O]/[C{sup 17}O] =2800 {+-} 300, and [C{sup 18}O]/[C{sup 17}O]=4.1 {+-} 0.4. For Reipurth 50, we find [C{sup 16}O]/[C{sup 18}O] =490 {+-} 30; [C{sup 16}O]/[C{sup 17}O] =2200 {+-} 150, [C{sup 18}O]/[C{sup 17}O] = 4.4 {+-} 0.2. For both objects, {sup 12}C/{sup 13}C are on the order of 100, nearly twice the expected interstellar medium (ISM) ratio. The derived oxygen abundance ratios for the VV CrA disk show a significant mass-independent deficit of C{sup 17}O and C{sup 18}O relative to C{sup 16}O compared to ISM baseline abundances. The Reipurth 50 envelope shows no clear differences in oxygen CO isotopologue ratios compared with the local ISM. A mass-independent fractionation can be interpreted as being due to selective photodissociation of CO in the disk

  4. 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.

  5. Conformational NMR Study of Bistriazolyl Anion Receptors.

    PubMed

    Makuc, Damjan; Merckx, Tamara; Dehaen, Wim; Plavec, Janez

    2016-01-01

    Conformational features of pyridine- and pyrimidine-based bistriazolyl anion receptors dissolved in acetonitrile-d3 were assessed by multidimensional, heteronuclear NMR spectroscopy. NOESY correlation signals suggested preorganization of both host molecules in solution in the absence of anions. In addition, only a single set of signals was observed in the 1H NMR spectra, which suggested a symmetrical conformation of anion receptors or their conformational exchange that is fast on the NMR time-scale. Furthermore, the predominant conformations of the pyridine- and pyrimidine-based anion receptors are preserved upon addition of chloride, bromide, and acetate anions. Chemical shift changes observed upon addition of anions showed that the NH (thio)urea and triazole protons are involved in anion-receptor interactions through hydrogen bonding. PMID:27640375

  6. 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.

  7. High precision delta(17)O isotope measurements of oxygen from silicates and other oxides: method and applications.

    PubMed

    Miller; Franchi; Sexton; Pillinger

    1999-07-01

    The use of infrared laser-assisted fluorination to release oxygen from milligram quantities of silicates or other oxide mineral grains is a well-established technique. However, relatively few studies have reported the optimisation of this procedure for oxygen-17 isotope measurements. We describe here details of an analytical system using infrared (10 µm) laser-assisted fluorination, in conjunction with a dual inlet mass spectrometer of high resolving power ( approximately 250) to provide (17)O and (18)O oxygen isotope measurements from 0.5-2 mg of silicates or other oxide mineral grains. Respective precisions (1) of typically 0.08 and 0.04 per thousand are obtained for the complete analytical procedure. Departures from the mass-dependent oxygen isotope fractionation line are quantified by Delta(17)O; our precision (1) of such measurements on individual samples is shown to be +/-0.024 per thousand. In turn, this permits the offset between parallel, mass-dependent fractionation lines to be characterised to substantially greater precision than has been possible hitherto. Application of this system to investigate the (17)O versus (18)O relationship for numerous terrestrial whole-rock and mineral samples, of diverse geological origins and age, indicates that the complete data set may be described by a single, mass-dependent fractionation line of slope 0.5244+/- 0.00038 (standard error). Copyright 1999 John Wiley & Sons, Ltd.

  8. 15N and13C NMR investigation of hydroxylamine-derivatized humic substances

    USGS Publications Warehouse

    Thorn, K.A.; Arterburn, J.B.; Mikita, M.A.

    1992-01-01

    Five fulvic and humic acid samples of diverse origins were derivatized with 15N-labeled hydroxylamine and analyzed by liquid-phase 15N NMR spectrometry. The 15N NMR spectra indicated that hydroxylamine reacted similarly with all samples and could discriminate among carbonyl functional groups. Oximes were the major derivatives; resonances attributable to hydroxamic acids, the reaction products of hydroxylamine with esters, and resonances attributable to the tautomeric equilibrium position between the nitrosophenol and monoxime derivatives of quinones, the first direct spectroscopic evidence for quinones, also were evident. The 15N NMR spectra also suggested the presence of nitriles, oxazoles, oxazolines, isocyanides, amides, and lactams, which may all be explained in terms of Beckmann reactions of the initial oxime derivatives. INEPT and ACOUSTIC 15N NMR spectra provided complementary information on the derivatized samples. 13C NMR spectra of derivatized samples indicated that the ketone/quinone functionality is incompletely derivatized with hydroxylamine. ?? 1991 American Chemical Society.

  9. Ultra-wideline solid-state NMR spectroscopy.

    PubMed

    Schurko, Robert W

    2013-09-17

    Although solid-state NMR (SSNMR) provides rich information about molecular structure and dynamics, the small spin population differences between pairs of spin states that give rise to NMR transitions make it an inherently insensitive spectroscopic technique in terms of signal acquisition. Scientists have continuously addressed this issue via improvements in NMR hardware and probes, increases in the strength of the magnetic field, and the development of innovative pulse sequences and acquisition methodologies. As a result, researchers can now study NMR-active nuclides previously thought to be unobservable or too unreceptive for routine examination via SSNMR. Several factors can make it extremely challenging to detect signal or acquire spectra using SSNMR: (i) low gyromagnetic ratios (i.e., low Larmor frequencies), (ii) low natural abundances or dilution of the nuclide of interest (e.g., metal nuclides in proteins or in organometallic catalysts supported on silica), (iii) inconvenient relaxation characteristics (e.g., very long longitudinal or very short transverse relaxation times), and/or (iv) extremely broad powder patterns arising from large anisotropic NMR interactions. Our research group has been particularly interested in efficient acquisition of broad NMR powder patterns for a variety of spin-1/2 and quadrupolar (spin > 1/2) nuclides. Traditionally, researchers have used the term "wideline" NMR to refer to experiments yielding broad (1)H and (2)H SSNMR spectra ranging from tens of kHz to ∼250 kHz in breadth. With modern FT NMR hardware, uniform excitation in these spectral ranges is relatively easy, allowing for the acquisition of high quality spectra. However, spectra that range in breadth from ca. 250 kHz to tens of MHz cannot be uniformly excited with conventional, high-power rectangular pulses. Rather, researchers must apply special methodologies to acquire such spectra, which have inherently low S/N because the signal intensity is spread across such

  10. 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.

  11. 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.

  12. 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.

  13. NMR studies of metalloproteins.

    PubMed

    Li, Hongyan; Sun, Hongzhe

    2012-01-01

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

  14. Detection of Taurine in Biological Tissues by 33S NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Musio, Roberta; Sciacovelli, Oronzo

    2001-12-01

    The potential of 33S NMR spectroscopy for biochemical investigations on taurine (2-aminoethanesulfonic acid) is explored. It is demonstrated that 33S NMR spectroscopy allows the selective and unequivocal identification of taurine in biological samples. 33S NMR spectra of homogenated and intact tissues are reported for the first time, together with the spectrum of a living mollusc. Emphasis is placed on the importance of choosing appropriate signal processing methods to improve the quality of the 33S NMR spectra of biological tissues.

  15. Chemical analysis using J-coupling multiplets in zero-field NMR

    NASA Astrophysics Data System (ADS)

    Theis, Thomas; Blanchard, John W.; Butler, Mark C.; Ledbetter, Micah P.; Budker, Dmitry; Pines, Alexander

    2013-08-01

    Zero-field nuclear magnetic resonance (NMR) spectroscopy is emerging as a new, potentially portable, and cost-effective NMR modality with the ability to provide information-rich, high-resolution spectra. We present simple rules for analysis of zero-field NMR spectra based on first-order perturbation theory and the addition of angular momenta. These rules allow for the prediction of observed spectral lines without numerical simulation. Results are presented for a few small organic molecules with characteristic spin topologies, demonstrating unambiguous assignment of peaks, highlighting the potential of zero-field NMR as a tool for chemical identification.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. NMR methods in combinatorial chemistry.

    PubMed

    Shapiro, M J; Wareing, J R

    1998-06-01

    The use of NMR spectroscopy in combinatorial chemistry has provided a versatile tool for monitoring combinatorial chemistry reactions and for assessing ligand-receptor interactions. The application of magic angle spinning NMR is widespread and has allowed structure determination to be performed on compounds attached to solid supports. A variety of two-dimensional NMR techniques have been applied to enhance the usability of the magic angle spinning NMR data. New developments for solution NMR analysis include high performance liquid chromatography, NMR, mass spectroscopy and flow NMR. NMR based methods currently being investigated may prove valuable as compound screening tools.

  18. A review of blind source separation in NMR spectroscopy.

    PubMed

    Toumi, Ichrak; Caldarelli, Stefano; Torrésani, Bruno

    2014-08-01

    Fourier transform is the data processing naturally associated to most NMR experiments. Notable exceptions are Pulse Field Gradient and relaxation analysis, the structure of which is only partially suitable for FT. With the revamp of NMR of complex mixtures, fueled by analytical challenges such as metabolomics, alternative and more apt mathematical methods for data processing have been sought, with the aim of decomposing the NMR signal into simpler bits. Blind source separation is a very broad definition regrouping several classes of mathematical methods for complex signal decomposition that use no hypothesis on the form of the data. Developed outside NMR, these algorithms have been increasingly tested on spectra of mixtures. In this review, we shall provide an historical overview of the application of blind source separation methodologies to NMR, including methods specifically designed for the specificity of this spectroscopy. PMID:25142734

  19. 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

  20. Structural biology applications of solid state MAS DNP NMR

    NASA Astrophysics Data System (ADS)

    Akbey, Ümit; Oschkinat, Hartmut

    2016-08-01

    Dynamic Nuclear Polarization (DNP) has long been an aim for increasing sensitivity of nuclear magnetic resonance (NMR) spectroscopy, delivering spectra in shorter experiment times or of smaller sample amounts. In recent years, it has been applied in magic angle spinning (MAS) solid-state NMR to a large range of samples, including biological macromolecules and functional materials. New research directions in structural biology can be envisaged by DNP, facilitating investigations on very large complexes or very heterogeneous samples. Here we present a summary of state of the art DNP MAS NMR spectroscopy and its applications to structural biology, discussing the technical challenges and factors affecting DNP performance.

  1. NMR studies on polyphosphide Ce6Ni6P17

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  2. Solid-State ¹⁷O NMR studies of organic and biological molecules: Recent advances and future directions.

    PubMed

    Wu, Gang

    2016-02-01

    This Trends article highlights the recent advances published between 2012 and 2015 in solid-state (17)O NMR for organic and biological molecules. New developments in the following areas are described: (1) new oxygen-containing functional groups, (2) metal organic frameworks, (3) pharmaceuticals, (4) probing molecular motion in organic solids, (5) dynamic nuclear polarization, and (6) paramagnetic coordination compounds. For each of these areas, the author offers his personal views on important problems to be solved and possible future directions.

  3. Monoterpene Unknowns Identified Using IR, [to the first power]H-NMR, [to the thirteenth power]C-NMR, DEPT, COSY, and HETCOR

    ERIC Educational Resources Information Center

    Alty, Lisa T.

    2005-01-01

    A study identifies a compound from a set of monoterpenes using infrared (IR) and one-dimensional (1D) nuclear magnetic resonance (NMR) techniques. After identifying the unknown, each carbon and proton signal can be interpreted and assigned to the structure using the information in the two-dimensional (2D) NMR spectra, correlation spectroscopy…

  4. NMR data visualization, processing, and analysis on mobile devices.

    PubMed

    Cobas, Carlos; Iglesias, Isaac; Seoane, Felipe

    2015-08-01

    Touch-screen computers are emerging as a popular platform for many applications, including those in chemistry and analytical sciences. In this work, we present our implementation of a new NMR 'app' designed for hand-held and portable touch-controlled devices, such as smartphones and tablets. It features a flexible architecture formed by a powerful NMR processing and analysis kernel and an intuitive user interface that makes full use of the smart devices haptic capabilities. Routine 1D and 2D NMR spectra acquired in most NMR instruments can be processed in a fully unattended way. More advanced experiments such as non-uniform sampled NMR spectra are also supported through a very efficient parallelized Modified Iterative Soft Thresholding algorithm. Specific technical development features as well as the overall feasibility of using NMR software apps will also be discussed. All aspects considered the functionalities of the app allowing it to work as a stand-alone tool or as a 'companion' to more advanced desktop applications such as Mnova NMR. PMID:25924947

  5. NMR data visualization, processing, and analysis on mobile devices.

    PubMed

    Cobas, Carlos; Iglesias, Isaac; Seoane, Felipe

    2015-08-01

    Touch-screen computers are emerging as a popular platform for many applications, including those in chemistry and analytical sciences. In this work, we present our implementation of a new NMR 'app' designed for hand-held and portable touch-controlled devices, such as smartphones and tablets. It features a flexible architecture formed by a powerful NMR processing and analysis kernel and an intuitive user interface that makes full use of the smart devices haptic capabilities. Routine 1D and 2D NMR spectra acquired in most NMR instruments can be processed in a fully unattended way. More advanced experiments such as non-uniform sampled NMR spectra are also supported through a very efficient parallelized Modified Iterative Soft Thresholding algorithm. Specific technical development features as well as the overall feasibility of using NMR software apps will also be discussed. All aspects considered the functionalities of the app allowing it to work as a stand-alone tool or as a 'companion' to more advanced desktop applications such as Mnova NMR.

  6. 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.

  7. Computer compensation for NMR quantitative analysis of trace components

    SciTech Connect

    Nakayama, T.; Fujiwara, Y.

    1981-07-22

    A computer program has been written that determines trace components and separates overlapping components in multicomponent NMR spectra. This program uses the Lorentzian curve as a theoretical curve of NMR spectra. The coefficients of the Lorentzian are determined by the method of least squares. Systematic errors such as baseline/phase distortion are compensated and random errors are smoothed by taking moving averages, so that there processes contribute substantially to decreasing the accumulation time of spectral data. The accuracy of quantitative analysis of trace components has been improved by two significant figures. This program was applied to determining the abundance of 13C and the saponification degree of PVA.

  8. 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.

  9. 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.

  10. Dicobalt-μ-oxo polyoxometalate compound, [(α(2)-P2W17O61Co)2O](14-): a potent species for water oxidation, C-H bond activation, and oxygen transfer.

    PubMed

    Barats-Damatov, Delina; Shimon, Linda J W; Weiner, Lev; Schreiber, Roy E; Jiménez-Lozano, Pablo; Poblet, Josep M; de Graaf, Coen; Neumann, Ronny

    2014-02-01

    High-valent oxo compounds of transition metals are often implicated as active species in oxygenation of hydrocarbons through carbon-hydrogen bond activation or oxygen transfer and also in water oxidation. Recently, several examples of cobalt-catalyzed water oxidation have been reported, and cobalt(IV) species have been suggested as active intermediates. A reactive species, formally a dicobalt(IV)-μ-oxo polyoxometalate compound [(α2-P2W17O61Co)2O](14-), [(POMCo)2O], has now been isolated and characterized by the oxidation of a monomeric [α2-P2W17O61Co(II)(H2O)](8-), [POMCo(II)H2O], with ozone in water. The crystal structure shows a nearly linear Co-O-Co moiety with a Co-O bond length of ∼1.77 Å. In aqueous solution [(POMCo)2O] was identified by (31)P NMR, Raman, and UV-vis spectroscopy. Reactivity studies showed that [(POMCo)2O]2O] is an active compound for the oxidation of H2O to O2, direct oxygen transfer to water-soluble sulfoxides and phosphines, indirect epoxidation of alkenes via a Mn porphyrin, and the selective oxidation of alcohols by carbon-hydrogen bond activation. The latter appears to occur via a hydrogen atom transfer mechanism. Density functional and CASSCF calculations strongly indicate that the electronic structure of [(POMCo)2O]2O] is best defined as a compound having two cobalt(III) atoms with two oxidized oxygen atoms.

  11. An NMR Study of Microvoids in Polymers

    NASA Technical Reports Server (NTRS)

    Toy, James; Mattrix, Larry

    1996-01-01

    An understanding of polymer defect structures, like microvoids in polymeric matrices, is most crucial to their fabrication and application potential. In this project guest atoms are introduced into the microvoids in PMR-15 and NMR is used to determine microvoid sizes and locations. Xenon is a relatively inert probe that would normally not be found naturally in polymer or in NMR probe materials. There are two NMR active Xenon isotopes, Xe-129 and Xe-131. The Xe atom has a very high polarizability, which makes it sensitive to the intracrystalline environment of polymers. Interactions between the Xe atoms and the host matrix perturb and Xe electron cloud, deshielding the nuclei, and thereby expanding the range of the observed NMR chemical shifts. This chemical shift range which may be as large as 5000 ppm, permits subtle structural and chemical effects to be studied with high sensitivity. The Xe-129-NMR line shape has been found to vary in response to changes in the pore symmetry of the framework hosts in Zeolites and Clathrasil compounds. Before exposure to Xe gas, the PMR-15 samples were dried in a vacuum oven at 150 C for 48 hours. The samples were then exposed to Xe gas at 30 psi for 72 hours and sealed in glass tubes with 1 atmosphere of Xenon gas. Xenon gas at 1 atmosphere was used to tune up the spectrometer and to set up the appropriate NMR parameters. A series of spectra were obtained interspersed with applications of vacuum and heating to drive out the adsorbed Xe and determine the role of Xe-Xe interactions in the observed chemical shift.

  12. Experimental and theoretical study of the intramolecular C-H···N and C-H···S hydrogen bonding effects in the 1H and 13C NMR spectra of the 2-(alkylsulfanyl)-5-amino-1-vinylpyrroles: a particular state of amine nitrogen.

    PubMed

    Afonin, Andrei V; Pavlov, Dmitry V; Albanov, Alexander I; Tarasova, Ol'ga A; Nedolya, Nina A

    2013-07-01

    In the (1)H NMR spectra of the 1-vinylpyrroles with amino- and alkylsulfanyl groups in 5 and 2 positions, an extraordinarily large difference between resonance positions of the HA and HB terminal methylene protons of the vinyl group is discovered. Also, the one-bond (1)J(C(β),H(B)) coupling constant is surprisingly greater than the (1)J(C(β),H(A)) coupling constant in pyrroles under investigation, while in all known cases, there was a reverse relationship between these coupling constants. These spectral anomalies are substantiated by quantum chemical calculations. The calculations show that the amine nitrogen lone pair is removed from the conjugation with the π-system of the pyrrole ring so that it is directed toward the HB hydrogen. These factors are favorable to the emergence of the intramolecular C-HB •••N hydrogen bonding in the s-cis(N) conformation. On the other hand, the spatial proximity of the sulfur to the HB hydrogen provides an opportunity of the intramolecular C-HB •••S hydrogen bonding in the s-cis(S) conformation. Presence of the hydrogen bond critical points as well as ring critical point for corresponding chelate ring revealed by a quantum theory of atoms in molecules (QTAIM) approach confirms the existence of the weak intramolecular C-H•••N and C-H•••S hydrogen bonding. Therefore, an unusual high-frequency shift of the HB signal and the increase in the (1)J(C(β),H(B)) coupling constant can be explained by the effects of hydrogen bonding. PMID:23695830

  13. Ultrafast multidimensional Laplace NMR for a rapid and sensitive chemical analysis.

    PubMed

    Ahola, Susanna; Zhivonitko, Vladimir V; Mankinen, Otto; Zhang, Guannan; Kantola, Anu M; Chen, Hsueh-Ying; Hilty, Christian; Koptyug, Igor V; Telkki, Ville-Veikko

    2015-09-18

    Traditional nuclear magnetic resonance (NMR) spectroscopy relies on the versatile chemical information conveyed by spectra. To complement conventional NMR, Laplace NMR explores diffusion and relaxation phenomena to reveal details on molecular motions. Under a broad concept of ultrafast multidimensional Laplace NMR, here we introduce an ultrafast diffusion-relaxation correlation experiment enhancing the resolution and information content of corresponding 1D experiments as well as reducing the experiment time by one to two orders of magnitude or more as compared with its conventional 2D counterpart. We demonstrate that the method allows one to distinguish identical molecules in different physical environments and provides chemical resolution missing in NMR spectra. Although the sensitivity of the new method is reduced due to spatial encoding, the single-scan approach enables one to use hyperpolarized substances to boost the sensitivity by several orders of magnitude, significantly enhancing the overall sensitivity of multidimensional Laplace NMR.

  14. Ultrafast multidimensional Laplace NMR for a rapid and sensitive chemical analysis

    PubMed Central

    Ahola, Susanna; Zhivonitko, Vladimir V; Mankinen, Otto; Zhang, Guannan; Kantola, Anu M.; Chen, Hsueh-Ying; Hilty, Christian; Koptyug, Igor V.; Telkki, Ville-Veikko

    2015-01-01

    Traditional nuclear magnetic resonance (NMR) spectroscopy relies on the versatile chemical information conveyed by spectra. To complement conventional NMR, Laplace NMR explores diffusion and relaxation phenomena to reveal details on molecular motions. Under a broad concept of ultrafast multidimensional Laplace NMR, here we introduce an ultrafast diffusion-relaxation correlation experiment enhancing the resolution and information content of corresponding 1D experiments as well as reducing the experiment time by one to two orders of magnitude or more as compared with its conventional 2D counterpart. We demonstrate that the method allows one to distinguish identical molecules in different physical environments and provides chemical resolution missing in NMR spectra. Although the sensitivity of the new method is reduced due to spatial encoding, the single-scan approach enables one to use hyperpolarized substances to boost the sensitivity by several orders of magnitude, significantly enhancing the overall sensitivity of multidimensional Laplace NMR. PMID:26381101

  15. Ultrafast multidimensional Laplace NMR for a rapid and sensitive chemical analysis

    NASA Astrophysics Data System (ADS)

    Ahola, Susanna; Zhivonitko, Vladimir V.; Mankinen, Otto; Zhang, Guannan; Kantola, Anu M.; Chen, Hsueh-Ying; Hilty, Christian; Koptyug, Igor V.; Telkki, Ville-Veikko

    2015-09-01

    Traditional nuclear magnetic resonance (NMR) spectroscopy relies on the versatile chemical information conveyed by spectra. To complement conventional NMR, Laplace NMR explores diffusion and relaxation phenomena to reveal details on molecular motions. Under a broad concept of ultrafast multidimensional Laplace NMR, here we introduce an ultrafast diffusion-relaxation correlation experiment enhancing the resolution and information content of corresponding 1D experiments as well as reducing the experiment time by one to two orders of magnitude or more as compared with its conventional 2D counterpart. We demonstrate that the method allows one to distinguish identical molecules in different physical environments and provides chemical resolution missing in NMR spectra. Although the sensitivity of the new method is reduced due to spatial encoding, the single-scan approach enables one to use hyperpolarized substances to boost the sensitivity by several orders of magnitude, significantly enhancing the overall sensitivity of multidimensional Laplace NMR.

  16. Multinuclear NMR studies of relaxor ferroelectrics

    NASA Astrophysics Data System (ADS)

    Zhou, Donghua

    Multinuclear NMR of 93Nb, 45Sc, and 207Pb has been carried out to study the structure, disorder, and dynamics of a series of important solid solutions: perovskite relaxor ferroelectric materials (1-x) Pb(Mg1/3Nb 2/3)O3-x Pb(Sc1/2Nb1/2)O 3 (PMN-PSN). 93Nb NMR investigations of the local structure and cation order/disorder are presented as a function of PSN concentration, x. The superb fidelity and accuracy of 3QMAS allows us to make clear and consistent assignments of spectral intensities to the 28 possible nearest B-site neighbor (nBn) configurations, (NMg, NSc, NNb), where each number ranges from 0 to 6 and their sum is 6. For most of the 28 possible nBn configurations, isotropic chemical shifts and quadrupole product constants have been extracted from the data. The seven configurations with only larger cations, Mg 2+ and Sc3+ (and no Nb5+) are assigned to the seven observed narrow peaks, whose deconvoluted intensities facilitate quantitative evaluation of, and differentiation between, different models of B-site (chemical) disorder. The "completely random" model is ruled out and the "random site" model is shown to be in qualitative agreement with the NMR experiments. To obtain quantitative agreement with observed NMR intensities, the random site model is slightly modified by including unlike-pair interaction energies. To date, 45Sc studies have not been as fruitful as 93Nb NMR because the resolution is lower in the 45Sc spectra. The lower resolution of 45Sc spectra is due to a smaller span of isotropic chemical shift (40 ppm for 45Sc vs. 82 ppm for 93Nb) and to the lack of a fortuitous mechanism that simplifies the 93Nb spectra; for 93Nb the overlap of the isotropic chemical shifts of 6-Sc and 6-Nb configurations results in the alignment of all the 28 configurations along only seven quadrupole distribution axes. Finally we present variable temperature 207Pb static, MAS, and 2D-PASS NMR studies. Strong linear correlations between isotropic and anisotropic chemical

  17. Gadolinium heteropoly complex K 17[Gd(P 2W 17O 61) 2] as a potential MRI contrast agent

    NASA Astrophysics Data System (ADS)

    Sun, Guoying; Feng, Jianghua; Wu, Huifeng; Pei, Fengkui; Fang, Ke; Lei, Hao

    2004-10-01

    Gadolinium heteropoly complex K17[Gd(P2W17O61)2] has been evaluated by in vitro and in vivo experiments as a potential contrast agent for magnetic resonance imaging (MRI). The thermal analysis and conductivity study indicate that this complex has good thermal stability and wide pH stability range. The T1 relaxivity is 7.59 mM-1 s-1 in aqueous solution and 7.97 mM-1 s-1 in 0.725 mmol l-1 bovine serum albumin (BSA) solution at 25 °C and 9.39 T, respectively. MR imaging of three male Sprague-Dawley rats showed remarkable enhancement in rat liver after intravenous injection, which persisted longer than with Gd-DTPA. The signal intensity increased by 57.1±16.9% during the whole imaging period at 0.082 mmol kg-1dose. Our preliminary in vitro and in vivo studies indicate that K17[Gd(P2W17O61)2] is a potential liver-specific MRI contrast agent.

  18. RNA Secondary Structure Determination by NMR.

    PubMed

    Chen, Jonathan L; Bellaousov, Stanislav; Turner, Douglas H

    2016-01-01

    Dynamic programming methods for predicting RNA secondary structure often use thermodynamics and experimental restraints and/or constraints to limit folding space. Chemical mapping results typically restrain certain nucleotides not to be in AU or GC pairs. Two-dimensional nuclear magnetic resonance (NMR) spectra can reveal the order of AU, GC, and GU pairs in double helixes. This chapter describes a program, NMR-assisted prediction of secondary structure and chemical shifts (NAPSS-CS), that constrains possible secondary structures on the basis of the NMR determined order and 5'-3' direction of AU, GC, and GU pairs in helixes. NAPSS-CS minimally requires input of the order of base pairs as determined from nuclear Overhauser effect spectroscopy (NOESY) of imino protons. The program deduces the 5'-3' direction of the base pairs if certain chemical shifts are also input. Secondary structures predicted by the program provide assignments of input chemical shifts to particular nucleotides in the sequence, thus facilitating an important step for determination of the three dimensional structure by NMR. The method is particularly useful for revealing pseudoknots and an example is provided. The method may also allow determination of secondary structures when a sequence folds into two structures that exchange slowly. PMID:27665599

  19. BOOK REVIEW: NMR Imaging of Materials

    NASA Astrophysics Data System (ADS)

    Blümich, Bernhard

    2003-09-01

    spectroscopic methods to weight or filter the spin signals represents the core of the book. This is a subject where Blümich is deeply involved with substantial contributions. The chapter includes a lot of ideas to provide MR contrast between different regions based on their mobility, diffusion, spin couplings or NMR spectra. After describing NMR imaging methods for solids with broad lines, Blümich spends time on applications in the last two chapters of the book. This part is really fun to read. It underlines the effort to bring NMR into many kinds of manufacturing. Car tyres and high-voltage cables are just two such areas. Elastomeric materials, green-state ceramics and food science represent other interesting fields of applications. This part of the book represents a personal but nevertheless extensive compilation of modern applications. As a matter of course the MOUSE is presented, a portable permanent-magnet based NMR developed by Blümich and his co-workers. Thus the book is not only of interest to NMR spectroscopists but also to people in material science and chemical engineering. The bibliography and indexing are excellent and may serve as an attractive reference source for NMR spectroscopists. The book is the first on the subject and likely to become the standard text for NMR imaging of materials as the books by Abragam, Slicher and Ernst et al are for NMR spectroscopy. The purchase of this beautiful book for people dealing with NMR spectroscopy or medical MRI is highly recommended. Ralf Ludwig

  20. 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;…

  1. Experimental Determination of pK[subscript a] Values by Use of NMR Chemical Shifts, Revisited

    ERIC Educational Resources Information Center

    Gift, Alan D.; Stewart, Sarah M.; Bokashanga, Patrick Kwete

    2012-01-01

    This laboratory experiment, using proton NMR spectroscopy to determine the dissociation constant for heterocyclic bases, has been modified from a previously described experiment. A solution of a substituted pyridine is prepared using deuterium oxide (D[subscript 2]O) as the solvent. The pH of the solution is adjusted and proton NMR spectra are…

  2. Complete assignments of 1H and 13C NMR data for ten phenylpiperazine derivatives.

    PubMed

    Xiao, Zhihui; Yuan, Mu; Zhang, Si; Wu, Jun; Qi, Shuhua; Li, Qingxin

    2005-10-01

    Ten phenylpiperazine derivatives were designed and synthesized. The first complete assignments of (1)H and (13)C NMR chemical shifts for these phenylpiperazine derivatives were achieved by means of 1D and 2D NMR techniques, including (1)H-(1)H COSY, HSQC and HMBC spectra.

  3. Complete assignments of 1H and 13C NMR data for 10 phenylethanoid glycosides.

    PubMed

    Wu, Jun; Huang, Jianshe; Xiao, Qiang; Zhang, Si; Xiao, Zhihui; Li, Qingxin; Long, Lijuan; Huang, Liangmin

    2004-07-01

    Ten phenylethanoid glycosides, including two new ones, isolated from the aerial parts of the mangrove plant Acanthus ilicifolius were identified. The first complete assignments of the 1H and 13C NMR chemical shifts for these glycosides were achieved by means of 2D NMR techniques, including 1H-1H COSY, TOCSY, HSQC and HMBC spectra.

  4. NMR at cryogenic temperatures: A {sup 13}C NMR study of ferrocene

    SciTech Connect

    Orendt, A.M.; Facelli, J.C.; Jiang, Y.J.; Grant, D.M.

    1998-09-24

    A new cryogenic apparatus is described that can be used to obtain NMR spectra at temperatures down to 8--10 K. The static solid {sup 13}C NMR spectrum of ferrocene is recorded at that temperature. Spectra recorded at higher temperatures show that ferrocene is still freely rotating about its 5-fold symmetry axis on the {sup 13}C NMR time scale at 45--50 K. A comparison of the principal values of the {sup 13}C chemical-shift tensor obtained from the room- and low-temperature spectra of ferrocene indicates that the lowest frequency chemical shift principal component, {delta}{sub 33}, is tilted off this symmetry axis by approximately 12{degree}. Quantum chemical calculations of the chemical-shift tensor, completed on structures of ferrocene from the literature as well as on optimized structures with the cyclopentadienyl rings locked in both the staggered and eclipsed arrangements, predict the angle between the {delta}{sub 33} direction and the rotation axis to be between 11 and 15{degree}, depending upon the geometry used in the calculation. The calculations also predict the sign of the angular perturbation, information not obtained from the experiment. An explanation of this angular change in the {delta}{sub 33} direction is provided by the composition of the molecular orbitals.

  5. Storm Spectra

    NASA Technical Reports Server (NTRS)

    2007-01-01

    portion is defined by the day/night boundary (known as the terminator).

    These two images illustrate only a small fraction of the information contained in a single LEISA scan, highlighting just one aspect of the power of infrared spectra for atmospheric studies.

  6. 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.''

  7. High-Resolution NMR Studies of Human Tissue Factor

    PubMed Central

    Nuzzio, Kristin M.; Watt, Eric D.; Boettcher, John M.; Gajsiewicz, Joshua M.; Morrissey, James H.; Rienstra, Chad M.

    2016-01-01

    In normal hemostasis, the blood clotting cascade is initiated when factor VIIa (fVIIa, other clotting factors are named similarly) binds to the integral membrane protein, human tissue factor (TF). The TF/fVIIa complex in turn activates fX and fIX, eventually concluding with clot formation. Several X-ray crystal structures of the soluble extracellular domain of TF (sTF) exist; however, these structures are missing electron density in functionally relevant regions of the protein. In this context, NMR can provide complementary structural information as well as dynamic insights into enzyme activity. The resolution and sensitivity for NMR studies are greatly enhanced by the ability to prepare multiple milligrams of protein with various isotopic labeling patterns. Here, we demonstrate high-yield production of several isotopically labeled forms of recombinant sTF, allowing for high-resolution NMR studies both in the solid and solution state. We also report solution NMR spectra at sub-mM concentrations of sTF, ensuring the presence of dispersed monomer, as well as the first solid-state NMR spectra of sTF. Our improved sample preparation and precipitation conditions have enabled the acquisition of multidimensional NMR data sets for TF chemical shift assignment and provide a benchmark for TF structure elucidation. PMID:27657719

  8. 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.

  9. 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.

  10. NMR spectral analysis using prior knowledge

    NASA Astrophysics Data System (ADS)

    Kasai, Takuma; Nagata, Kenji; Okada, Masato; Kigawa, Takanori

    2016-03-01

    Signal assignment is a fundamental step for analyses of protein structure and dynamics with nuclear magnetic resonance (NMR). Main-chain signal assignment is achieved with a sequential assignment method and/or an amino-acid selective stable isotope labeling (AASIL) method. Combinatorial selective labeling (CSL) methods, as well as our labeling strategy, stable isotope encoding (SiCode), were developed to reduce the required number of labeled samples, since one of the drawbacks of AASIL is that many samples are needed. Signal overlapping in NMR spectra interferes with amino-acid determination by CSL and SiCode. Since spectral deconvolution by peak fitting with a gradient method cannot resolve closely overlapped signals, we developed a new method to perform both peak fitting and amino acid determination simultaneously, with a replica exchange Monte Carlo method, incorporating prior knowledge of stable-isotope labeling ratios and the amino-acid sequence of the protein.

  11. NMR and NQR study of the thermodynamically stable quasicrystals

    SciTech Connect

    Shastri, A.

    1995-02-10

    {sup 27}Al and {sup 61,65}Cu NMR measurements are reported for powder samples of stable AlCuFe and AlCuRu icosahedral quasicrystals and their crystalline approximants, and for a AlPdMn single grain quasicrystal. Furthermore, {sup 27}Al NQR spectra at 4.2 K have been observed in the AlCuFe and AlCuRu samples. From the quadrupole perturbed NMR spectra at different magnetic fields, and from the zero field NQR spectra, a wide distribution of local electric field gradient (EFG) tensor components and principal axis system orientations was found at the Al site. A model EFG calculation based on a 1/1 AlCuFe approximant was successful in explaining the observed NQR spectra. It is concluded that the average local gradient is largely determined by the p-electron wave function at the Al site, while the width of the distribution is due to the lattice contribution to the EFG. Comparison of {sup 63}Cu NMR with {sup 27}Al NMR shows that the EFG distribution at the two sites is similar, but that the electronic contribution to the EFG is considerably smaller at the Cu site, in agreement with a more s-type wave function of the conduction electrons.

  12. NMR observation of rotory conformers in flexible-chain polymers

    SciTech Connect

    Sadykov, R.K.; Makhiyanov, N.; Kurbatov, V.A.; Savel'ev, V.S.; Kirpichnikov, P.A.

    1987-08-01

    The authors conduct a comprehensive line analysis of the NMR spectra of a number of polymers, including cis-1,4-polyisoprenes, cis-1-4-polybutadiene, polyisobutylene, and polyethylene, in a deuterated benzene solvent. Data are given on hyperfine structure and spin-spin coupling constants along with conformational behavior and a negative Overhauser effect observed in the isomers.

  13. Quantitative calibration of radiofrequency NMR Stark effects

    NASA Astrophysics Data System (ADS)

    Tarasek, Matthew R.; Kempf, James G.

    2011-10-01

    Nuclear magnetic resonance (NMR) Stark responses can occur in quadrupolar nuclei for an electric field oscillating at twice the usual NMR frequency (2ω0). Calibration of responses to an applied E field is needed to establish nuclear spins as probes of native E fields within material and molecular systems. We present an improved approach and apparatus for accurate measurement of quadrupolar Stark effects. Updated values of C14 (the response parameter in cubic crystals) were obtained for both 69Ga and 75As in GaAs. Keys to improvement include a modified implementation of voltage dividers to assess the 2ω0 amplitude, |E|, and the stabilization of divider response by reduction of stray couplings in 2ω0 circuitry. Finally, accuracy was enhanced by filtering sets of |E| through a linear response function that we established for the radiofrequency amplifier. Our approach is verified by two types of spectral results. Steady-state 2ω0 excitation to presaturate NMR spectra yielded C14 = (2.59 ± 0.06) × 1012 m-1 for 69Ga at room-temperature and 14.1 T. For 75As, we obtained (3.1 ± 0.1) × 1012 m-1. Both values reconcile with earlier results from 77 K and below 1 T, whereas current experiments are at room temperature and 14.1 T. Finally, we present results where few-microsecond pulses of the 2ω0 field induced small (tens of Hz) changes in high-resolution NMR line shapes. There too, spectra collected vs |E| agree with the model for response, further establishing the validity of our protocols to specify |E|.

  14. Dual Species NMR Oscillator

    NASA Astrophysics Data System (ADS)

    Weber, Joshua; Korver, Anna; Thrasher, Daniel; Walker, Thad

    2016-05-01

    We present progress towards a dual species nuclear magnetic oscillator using synchronous spin exchange optical pumping. By applying the bias field as a sequence of alkali 2 π pulses, we generate alkali polarization transverse to the bias field. The alkali polarization is then modulated at the noble gas resonance so that through spin exchange collisions the noble gas becomes polarized. This novel method of NMR suppresses the alkali field frequency shift by at least a factor of 2500 as compared to longitudinal NMR. We will present details of the apparatus and measurements of dual species co-magnetometry using this method. Research supported by the NSF and Northrop-Grumman Corp.

  15. {sup 17}O Knight shift study of the superconducting state of Sr{sub 2}RuO{sub 4}

    SciTech Connect

    Mukuda, H.; Ishida, K.; Kitaoka, Y.; Mao, Z.; Mori, Y.; Maeno, Y.

    1999-12-01

    {sup 17}O Knight shift measurements in Sr{sub 2}RuO{sub 4} were performed over the wide range of magnetic field 3.2--11.4kOe parallel to the basal RuO{sub 2} planes. The spin susceptibility is totally unchanged through its T{prime}{sub c}, evidencing that the spin-triplet superconducting state is realized in Sr{sub 2}RuO{sub 4}. The results indicates that the Cooper pairs consist of the parallel spin pairs {vert{underscore}bar}{up{underscore}arrow}{up{underscore}arrow}> and {vert{underscore}bar}{down{underscore}arrow}{down{underscore}arrow}> with their quantization axis perpendicular to the c-axis direction. The in-plane 2D nearly ferromagnetic spin fluctuations may play a role for the stabilization of this state among various representations of spin-triplet order parameter.

  16. Magnetic isotope effects in the photolysis of dibenzyl ketone on porous silica. /sup 13/C and /sup 17/O enrichments

    SciTech Connect

    Turro, N.J.; Cheng, C.C.; Wan, P.; Chung, C.; Mahler, W.

    1985-04-25

    The photolysis of dibenzyl ketone (DBK) on porous silica has been investigated. Both /sup 13/C and /sup 17/O isotopic enrichment in the ketone remaining after partial photolysis is demonstrated. The efficiency of /sup 13/C enrichment was found to be relatively insensitive to the average pore diameter of the silica host, to the percent coverage by DBK, and to the application of an external magnetic field. A significant dependence of /sup 13/C enrichment with temperature, with a maximum in the enrichment-temperature profile, was observed. The results are interpreted in terms of the competition between pathways available to the triplet C/sub 6/H/sub 5/CH/sub 2/COCH/sub 2/C/sub 6/H/sub 5/ radical pair produced by photolysis of DBK.

  17. Continuous-flow IRMS technique for determining the 17O excess of CO2 using complete oxygen isotope exchange with cerium oxide

    NASA Astrophysics Data System (ADS)

    Mrozek, D. J.; van der Veen, C.; Kliphuis, M.; Kaiser, J.; Wiegel, A. A.; Röckmann, T.

    2015-02-01

    This paper presents an analytical system for analysis of all single substituted isotopologues (12C16O17O, 12C16O18O, 13C16O16O) in nanomolar quantities of CO2 extracted from stratospheric air samples. CO2 is separated from bulk air by gas chromatography and CO2 isotope ratio measurements (ion masses 45 / 44 and 46 / 44) are performed using isotope ratio mass spectrometry (IRMS). The 17O excess (Δ17O) is derived from isotope measurements on two different CO2 aliquots: unmodified CO2 and CO2 after complete oxygen isotope exchange with cerium oxide (CeO2) at 700 °C. Thus, a single measurement of Δ17O requires two injections of 1 mL of air with a CO2 mole fraction of 390 μmol mol-1 at 293 K and 1 bar pressure (corresponding to 16 nmol CO2 each). The required sample size (including flushing) is 2.7 mL of air. A single analysis (one pair of injections) takes 15 minutes. The analytical system is fully automated for unattended measurements over several days. The standard deviation of the 17O excess analysis is 1.7‰. Multiple measurements on an air sample reduce the measurement uncertainty, as expected for the statistical standard error. Thus, the uncertainty for a group of 10 measurements is 0.58‰ for Δ 17O in 2.5 h of analysis. 100 repeat analyses of one air sample decrease the standard error to 0.20‰. The instrument performance was demonstrated by measuring CO2 on stratospheric air samples obtained during the EU project RECONCILE with the high-altitude aircraft Geophysica. The precision for RECONCILE data is 0.03‰ (1σ) for δ13C, 0.07‰ (1σ) for δ18O and 0.55‰ (1σ) for δ17O for a sample of 10 measurements. This is sufficient to examine stratospheric enrichments, which at altitude 33 km go up to 12‰ for δ17O and up to 8‰ for δ18O with respect to tropospheric CO2 : δ17O ~ 21‰ Vienna Standard Mean Ocean Water (VSMOW), δ18O ~ 41‰ VSMOW (Lämmerzahl et al., 2002). The samples measured with our analytical technique agree with available data for

  18. 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.

  19. 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.

  20. Nontarget analysis of Murchison soluble organic matter by high-field NMR spectroscopy and FTICR mass spectrometry.

    PubMed

    Hertkorn, N; Harir, M; Schmitt-Kopplin, Ph

    2015-09-01

    High-field NMR spectra of Murchison meteorite methanolic extracts revealed primarily aliphatic extraterrestrial organic matter (EOM) with near statistical branching of commonly C(3-5) units separated by heteroatoms and aromatic units. The ratios of CCH, OCH and C(sp2)H units were 89 : 8 : 3, whereas carbon-based aliphatic chain termination was in the order methyl >  -COOH >  -CH(CH3)COOH. Aliphatic methine carbon was abundant, but its weak NMR signatures were primarily deduced from JRES (J-resolved) NMR spectra. Carbon NMR spectra were dominated by methylene and methyl carbon; strong apodization revealed methine carbon, of which about 20% was aromatic. Extrapolation provided 5-7% aromatic carbon present in Murchison soluble EOM. Compositional heterogeneity in Murchison methanolic extracts was visible in NMR and Fourier transform ion cyclotron (FTICR) mass spectra obtained from a few cubic millimeters of solid Murchison meteorite; increasing sample size enhanced uniformity of NMR spectra. Intrinsic chemical diversity and pH-dependent chemical shift variance contributed to the disparity of NMR spectra. FTICR mass spectra provided distinct clustering of CHO/CHOS and CHNO/CHNOS molecular series and confirmed the prevalence of aliphatic/alicyclic (73%) over single aromatic (21%) and polyaromatic (6%) molecular compositions, suggesting extensive aliphatic substitution of aromatic units as proposed by NMR. Murchison soluble EOM molecules feature a center with enhanced aromatic and heteroatom content, which provides rather diffuse and weak NMR signatures resulting from a huge overall chemical diversity. The periphery of Murchison EOM molecules comprises flexible branched aliphatic chains and aliphatic carboxylic acids. These project on narrow ranges of chemical shift, facilitating observation in one-dimensional and two-dimensional NMR spectra. The conformational entropy provided by these flexible surface moieties facilitates the solubility of EOM. PMID

  1. Nontarget analysis of Murchison soluble organic matter by high-field NMR spectroscopy and FTICR mass spectrometry.

    PubMed

    Hertkorn, N; Harir, M; Schmitt-Kopplin, Ph

    2015-09-01

    High-field NMR spectra of Murchison meteorite methanolic extracts revealed primarily aliphatic extraterrestrial organic matter (EOM) with near statistical branching of commonly C(3-5) units separated by heteroatoms and aromatic units. The ratios of CCH, OCH and C(sp2)H units were 89 : 8 : 3, whereas carbon-based aliphatic chain termination was in the order methyl >  -COOH >  -CH(CH3)COOH. Aliphatic methine carbon was abundant, but its weak NMR signatures were primarily deduced from JRES (J-resolved) NMR spectra. Carbon NMR spectra were dominated by methylene and methyl carbon; strong apodization revealed methine carbon, of which about 20% was aromatic. Extrapolation provided 5-7% aromatic carbon present in Murchison soluble EOM. Compositional heterogeneity in Murchison methanolic extracts was visible in NMR and Fourier transform ion cyclotron (FTICR) mass spectra obtained from a few cubic millimeters of solid Murchison meteorite; increasing sample size enhanced uniformity of NMR spectra. Intrinsic chemical diversity and pH-dependent chemical shift variance contributed to the disparity of NMR spectra. FTICR mass spectra provided distinct clustering of CHO/CHOS and CHNO/CHNOS molecular series and confirmed the prevalence of aliphatic/alicyclic (73%) over single aromatic (21%) and polyaromatic (6%) molecular compositions, suggesting extensive aliphatic substitution of aromatic units as proposed by NMR. Murchison soluble EOM molecules feature a center with enhanced aromatic and heteroatom content, which provides rather diffuse and weak NMR signatures resulting from a huge overall chemical diversity. The periphery of Murchison EOM molecules comprises flexible branched aliphatic chains and aliphatic carboxylic acids. These project on narrow ranges of chemical shift, facilitating observation in one-dimensional and two-dimensional NMR spectra. The conformational entropy provided by these flexible surface moieties facilitates the solubility of EOM.

  2. 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…

  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. Photochemical pump and NMR probe: chemically created NMR coherence on a microsecond time scale.

    PubMed

    Torres, Olga; Procacci, Barbara; Halse, Meghan E; Adams, Ralph W; Blazina, Damir; Duckett, Simon B; Eguillor, Beatriz; Green, Richard A; Perutz, Robin N; Williamson, David C

    2014-07-16

    We report pump-probe experiments employing laser-synchronized reactions of para-hydrogen (para-H2) with transition metal dihydride complexes in conjunction with nuclear magnetic resonance (NMR) detection. The pump-probe experiment consists of a single nanosecond laser pump pulse followed, after a precisely defined delay, by a single radio frequency (rf) probe pulse. Laser irradiation eliminates H2 from either Ru(PPh3)3(CO)(H)2 1 or cis-Ru(dppe)2(H)2 2 in C6D6 solution. Reaction with para-H2 then regenerates 1 and 2 in a well-defined nuclear spin state. The rf probe pulse produces a high-resolution, single-scan (1)H NMR spectrum that can be recorded after a pump-probe delay of just 10 μs. The evolution of the spectra can be followed as the pump-probe delay is increased by micro- or millisecond increments. Due to the sensitivity of this para-H2 experiment, the resulting NMR spectra can have hydride signal-to-noise ratios exceeding 750:1. The spectra of 1 oscillate in amplitude with frequency 1101 ± 3 Hz, the chemical shift difference between the chemically inequivalent hydrides. The corresponding hydride signals of 2 oscillate with frequency 83 ± 5 Hz, which matches the difference between couplings of the hydrides to the equatorial (31)P nuclei. We use the product operator formalism to show that this oscillatory behavior arises from a magnetic coherence in the plane orthogonal to the magnetic field that is generated by use of the laser pulse without rf initialization. In addition, we demonstrate how chemical shift imaging can differentiate the region of laser irradiation thereby distinguishing between thermal and photochemical reactivity within the NMR tube.

  5. Operation of a 500 MHz high temperature superconducting NMR: towards an NMR spectrometer operating beyond 1 GHz.

    PubMed

    Yanagisawa, Y; Nakagome, H; Tennmei, K; Hamada, M; Yoshikawa, M; Otsuka, A; Hosono, M; Kiyoshi, T; Takahashi, M; Yamazaki, T; Maeda, H

    2010-04-01

    We have begun a project to develop an NMR spectrometer that operates at frequencies beyond 1 GHz (magnetic field strength in excess of 23.5 T) using a high temperature superconductor (HTS) innermost coil. As the first step, we developed a 500 MHz NMR with a Bi-2223 HTS innermost coil, which was operated in external current mode. The temporal magnetic field change of the NMR magnet after the coil charge was dominated by (i) the field fluctuation due to a DC power supply and (ii) relaxation in the screening current in the HTS tape conductor; effect (i) was stabilized by the 2H field-frequency lock system, while effect (ii) decreased with time due to relaxation of the screening current induced in the HTS coil and reached 10(-8)(0.01 ppm)/h on the 20th day after the coil charge, which was as small as the persistent current mode of the NMR magnet. The 1D (1)H NMR spectra obtained by the 500 MHz LTS/HTS magnet were nearly equivalent to those obtained by the LTS NMR magnet. The 2D-NOESY, 3D-HNCO and 3D-HNCACB spectra were achieved for ubiquitin by the 500 MHz LTS/HTS magnet; their quality was closely equivalent to that achieved by a conventional LTS NMR. Based on the results of numerical simulation, the effects of screening current-induced magnetic field changes are predicted to be harmless for the 1.03 GHz NMR magnet system.

  6. Operation of a 500 MHz high temperature superconducting NMR: towards an NMR spectrometer operating beyond 1 GHz.

    PubMed

    Yanagisawa, Y; Nakagome, H; Tennmei, K; Hamada, M; Yoshikawa, M; Otsuka, A; Hosono, M; Kiyoshi, T; Takahashi, M; Yamazaki, T; Maeda, H

    2010-04-01

    We have begun a project to develop an NMR spectrometer that operates at frequencies beyond 1 GHz (magnetic field strength in excess of 23.5 T) using a high temperature superconductor (HTS) innermost coil. As the first step, we developed a 500 MHz NMR with a Bi-2223 HTS innermost coil, which was operated in external current mode. The temporal magnetic field change of the NMR magnet after the coil charge was dominated by (i) the field fluctuation due to a DC power supply and (ii) relaxation in the screening current in the HTS tape conductor; effect (i) was stabilized by the 2H field-frequency lock system, while effect (ii) decreased with time due to relaxation of the screening current induced in the HTS coil and reached 10(-8)(0.01 ppm)/h on the 20th day after the coil charge, which was as small as the persistent current mode of the NMR magnet. The 1D (1)H NMR spectra obtained by the 500 MHz LTS/HTS magnet were nearly equivalent to those obtained by the LTS NMR magnet. The 2D-NOESY, 3D-HNCO and 3D-HNCACB spectra were achieved for ubiquitin by the 500 MHz LTS/HTS magnet; their quality was closely equivalent to that achieved by a conventional LTS NMR. Based on the results of numerical simulation, the effects of screening current-induced magnetic field changes are predicted to be harmless for the 1.03 GHz NMR magnet system. PMID:20149698

  7. 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

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

    SciTech Connect

    Guardo, G. L.; Lamia, L.; Spitaleri, C.; Cherubini, S.; Rapisarda, G. G.; Sergi, M. L.; Gulino, M.; Tang, X. D.; Bucher, B.; Couder, M.; Davies, P.; Boer, R. de; Fang, X.; Lamm, L.; Ma, C.; Notani, M.; OBrien, S.; Roberson, D.; Tan, W.; Wiescher, M.; and others

    2014-05-02

    The experimental study of the {sup 17}O(n,α){sup 14}C 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 {sup 17}O(n,α){sup 14}C reaction has been studied using the quasi-free {sup 2}H({sup 17}O,α{sup 14}C){sup 1}H 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, J{sup π}=5{sup −}), absent in the available direct measurements because of centrifugal suppression effects.

  9. Dynamic NMR under nonstationary conditions: Theoretical model, numerical calculation, and potential of application.

    PubMed

    Babailov, S P; Purtov, P A; Fomin, E S

    2016-08-01

    An expression has been derived for the time dependence of the NMR line shape for systems with multi-site chemical exchange in the absence of spin-spin coupling, in a zero saturation limit. The dynamics of variation of the NMR line shape with time is considered in detail for the case of two-site chemical exchange. Mathematical programs have been designed for numerical simulation of the NMR spectra of chemical exchange systems. The analytical expressions obtained are useful for NMR line shape simulations for systems with photoinduced chemical exchange.

  10. Dynamic NMR under nonstationary conditions: Theoretical model, numerical calculation, and potential of application.

    PubMed

    Babailov, S P; Purtov, P A; Fomin, E S

    2016-08-01

    An expression has been derived for the time dependence of the NMR line shape for systems with multi-site chemical exchange in the absence of spin-spin coupling, in a zero saturation limit. The dynamics of variation of the NMR line shape with time is considered in detail for the case of two-site chemical exchange. Mathematical programs have been designed for numerical simulation of the NMR spectra of chemical exchange systems. The analytical expressions obtained are useful for NMR line shape simulations for systems with photoinduced chemical exchange. PMID:27497554

  11. Enhancing NMR of insensitive nuclei by transfer of SABRE spin hyperpolarization

    NASA Astrophysics Data System (ADS)

    Pravdivtsev, Andrey N.; Yurkovskaya, Alexandra V.; Zimmermann, Herbert; Vieth, Hans-Martin; Ivanov, Konstantin L.

    2016-09-01

    We describe the performance of methods for enhancing NMR (Nuclear Magnetic Resonance) signals of "insensitive", but important NMR nuclei, which are based on the SABRE (Signal Amplification By Reversible Exchange) technique, i.e., on spin order transfer from parahydrogen (H2 molecule in its nuclear singlet spin state) to a substrate in a transient organometallic complex. Here such transfer is performed at high magnetic fields by INEPT-type NMR pulse sequences, modified for SABRE. Signal enhancements up to three orders of magnitude are obtained for 15N nuclei; the possibility of sensitive detection of 2D-NMR 1H-15N spectra of SABRE complexes and substrates is demonstrated.

  12. Analysis of Radiation Induced Degradation in FPC-461 Fluoropolymers by Variable Temperature Multinuclear NMR

    SciTech Connect

    Chinn, S C; Wilson, T S; Maxwell, R S

    2004-10-27

    Solid state nuclear magnetic resonance techniques have been used to investigate aging mechanisms in a vinyl chloride:chlorotrifluoroethylene copolymer, FPC-461, due to exposure to {gamma}-radiation. Solid state {sup 1}H MAS NMR spectra revealed structural changes of the polymer upon irradiation under both air and nitrogen atmospheres. Considerable degradation is seen with {sup 1}H NMR in the vinyl chloride region of the polymer, particularly in the samples irradiated in air. {sup 19}F MAS NMR was used to investigate speciation in the chlorotrifluoroethylene blocks, though negligible changes were seen. {sup 1}H and {sup 19}F NMR at elevated temperature revealed increased segmental mobility and decreased structural heterogeneity within the polymer, yielding significant resolution enhancement over room temperature solid state detection. The effects of multi-site exchange are manifest in both the {sup 1}H and {sup 19}F NMR spectra as a line broadening and change in peak position as a function of temperature.

  13. Experimental estimation of postmortem interval using multivariate analysis of proton NMR metabolomic data.

    PubMed

    Hirakawa, Keiko; Koike, Kaoru; Uekusa, Kyoko; Nihira, Makoto; Yuta, Kohtaro; Ohno, Youkichi

    2009-04-01

    Nuclear magnetic resonance (NMR) spectroscopy has recently been applied to metabolic studies. In particular, metabolic profiles of tissues or of the whole body can easily be acquired through multivariate analysis of NMR spectra. The present study investigates metabolic changes after death in rat femoral muscles using pattern recognition of proton NMR spectra. Rats were killed by suffocation, cocaine overdose and induced respiratory failure, and then low molecular weight metabolites extracted using perchlorate from excised tissues were measured using proton NMR. All spectral data were processed and assessed by multivariate analysis to obtain metabolic profiles of the tissues. The results of principal component analysis (PCA) score plots soon after death showed that the metabolic profiles of the tissues differed according to the mode of death. The principal component (PC) scores of the data varied hourly and correlated with postmortem interval. The present results showed that NMR-based metabolic profiling could provide useful information with which to estimate postmortem intervals and causes of death.

  14. Characterization of nitrogen compound types in shale oils using /sup 1/H NMR and high resolution mass spectral analyses

    SciTech Connect

    Thompson, L.F.; Netzel, D.A.

    1984-12-01

    The /sup 1/H nuclear magnetic resonance (NMR) spectra were obtained for nitrogen compound-type fractions from a Geokinetics shale oil distillate and a Caribou intermediately refined oil obtained during catalytic hydroprocessing of the Geokinetics distillate. These fractions were generated using alumina and silica chromatography. The NMR spectra of the fractions were analyzed for hydrogen types and for individual compounds and the results compared with mass spectral data. The observed differences in resonance intensities in the /sup 1/H NMR spectra of the nitrogen fractions from the distillate and intermediately refined oil are also discussed in relationship to hydroprocessing. 17 refs., 17 figs., 5 tabs.

  15. 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.

  16. NMR/MS Translator for the Enhanced Simultaneous Analysis of Metabolomics Mixtures by NMR Spectroscopy and Mass Spectrometry: Application to Human Urine.

    PubMed

    Bingol, Kerem; Brüschweiler, Rafael

    2015-06-01

    A novel metabolite identification strategy is presented for the combined NMR/MS analysis of complex metabolite mixtures. The approach first identifies metabolite candidates from 1D or 2D NMR spectra by NMR database query, which is followed by the determination of the masses (m/z) of their possible ions, adducts, fragments, and characteristic isotope distributions. The expected m/z ratios are then compared with the MS(1) spectrum for the direct assignment of those signals of the mass spectrum that contain information about the same metabolites as the NMR spectra. In this way, the mass spectrum can be assigned with very high confidence, and it provides at the same time validation of the NMR-derived metabolites. The method was first demonstrated on a model mixture, and it was then applied to human urine collected from a pool of healthy individuals. A number of metabolites could be detected that had not been reported previously, further extending the list of known urine metabolites. The new analysis approach, which is termed NMR/MS Translator, is fully automated and takes only a few seconds on a computer workstation. NMR/MS Translator synergistically uses the power of NMR and MS, enhancing the accuracy and efficiency of the identification of those metabolites compiled in databases. PMID:25881480

  17. Extrinsic Proton NMR Studies of Mg(OH)2 and Ca(OH)2

    NASA Astrophysics Data System (ADS)

    Itoh, Yutaka; Isobe, Masahiko

    2016-03-01

    We studied narrow 1H NMR spectra of Mg(OH)2 and Ca(OH)2 powders at 100-355 K and 42-59 MHz using pulsed NMR techniques. The Fourier transformed NMR spectra of the proton free-induction signals show the superposition of broad and narrow components, which can be assigned to immobile protons and extrinsic mobile protons, respectively. We found that a narrow spectrum develops on heating above about Tc = 260 K and widens above a Larmor frequency of about νc = 50 MHz for Mg(OH)2. The temperature-induced NMR spectrum and the characteristic frequency νc of 50 MHz are the noteworthy features of the nuclear spin fluctuation spectra of the extrinsic protons.

  18. Metabolic discrimination of mango juice from various cultivars by band-selective NMR spectroscopy.

    PubMed

    Koda, Masanori; Furihata, Kazuo; Wei, Feifei; Miyakawa, Takuya; Tanokura, Masaru

    2012-02-01

    NMR-based metabolic analysis of foods has been widely applied in food science. In this study, we performed discrimination of five different mango cultivars, Awin, Carabao, Keitt, Kent, and Nam Dok Mai, using metabolic analysis with band-selective excitation NMR spectra. A combination of unsupervised principal component analysis (PCA) with low-field region (1)H NMR spectra obtained by band-selective excitation provided a good discriminant model of the five mango cultivars. Using F(2)-selective 2D NMR spectra, we also identified various minor components in the mango juice. Signal assignment of the minor components facilitated the interpretation of the loading plot, and it was found that arginine, histidine, phenylalanine, glutamine, shikimic acid, and trigonelline were important for classification of the five mango cultivars.

  19. Determination of NMR chemical shifts for cholesterol crystals from first-principles

    NASA Astrophysics Data System (ADS)

    Kucukbenli, Emine; de Gironcoli, Stefano

    2011-03-01

    Solid State Nuclear Magnetic Resonance (NMR) is a powerful tool in crystallography when combined with theoretical predictions. So far, empirical calculations of spectra have been employed for an unambiguous identification. However, many complex systems are outside the scope of these methods. Our implementation of ultrasoft and projector augmented wave pseudopotentials within ab initio gauge including projector augmented plane wave (GIPAW) method in Quantum Espresso simulation package allows affordable calculations of NMR spectra for systems of thousands of electrons. We report here the first ab initio determination of NMR spectra for several crystal structures of cholesterol. Cholesterol crystals, the main component of human gallstones, are of interest to medical research as their structural properties can shed light on the pathologies of gallbladder. With our application we show that ab initio calculations can be employed to aid NMR crystallography.

  20. High resolution deuterium NMR studies of bacterial metabolism

    SciTech Connect

    Aguayo, J.B.; Gamcsik, M.P.; Dick, J.D.

    1988-12-25

    High resolution deuterium NMR spectra were obtained from suspensions of five bacterial strains: Escherichia coli, Clostridium perfringens, Klebsiella pneumoniae, Proteus mirabilis, and Staphylococcus aureus. Deuterium-labeled D-glucose at C-1, C-2, and C-6 was used to monitor dynamically anaerobic metabolism. The flux of glucose through the various bacterial metabolic pathways could be determined by following the disappearance of glucose and the appearance of the major end products in the 2H NMR spectrum. The presence of both labeled and unlabeled metabolites could be detected using 1H NMR spectroscopy since the proton resonances in the labeled species are shifted upfield due to an isotopic chemical shift effect. The 1H-1H scalar coupling observed in both the 2H and 1H NMR spectra was used to assign definitively the resonances of labeled species. An increase in the intensity of natural abundance deuterium signal of water can be used to monitor pathways in which a deuteron is lost from the labeled metabolite. The steps in which label loss can occur are outlined, and the influence these processes have on the ability of 2H NMR spectroscopy to monitor metabolism are assessed.

  1. Monitoring the Electrochemical Processes in the Lithium–Air Battery by Solid State NMR Spectroscopy

    PubMed Central

    2013-01-01

    A multi-nuclear solid-state NMR approach is employed to investigate the lithium–air battery, to monitor the evolution of the electrochemical products formed during cycling, and to gain insight into processes affecting capacity fading. While lithium peroxide is identified by 17O solid state NMR (ssNMR) as the predominant product in the first discharge in 1,2-dimethoxyethane (DME) based electrolytes, it reacts with the carbon cathode surface to form carbonate during the charging process. 13C ssNMR provides evidence for carbonate formation on the surface of the carbon cathode, the carbonate being removed at high charging voltages in the first cycle, but accumulating in later cycles. Small amounts of lithium hydroxide and formate are also detected in discharged cathodes and while the hydroxide formation is reversible, the formate persists and accumulates in the cathode upon further cycling. The results indicate that the rechargeability of the battery is limited by both the electrolyte and the carbon cathode stability. The utility of ssNMR spectroscopy in directly detecting product formation and decomposition within the battery is demonstrated, a necessary step in the assessment of new electrolytes, catalysts, and cathode materials for the development of a viable lithium–oxygen battery. PMID:24489976

  2. 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.

  3. Live cell NMR.

    PubMed

    Freedberg, Darón I; Selenko, Philipp

    2014-01-01

    Ever since scientists realized that cells are the basic building blocks of all life, they have been developing tools to look inside them to reveal the architectures and mechanisms that define their biological functions. Whereas "looking into cells" is typically said in reference to optical microscopy, high-resolution in-cell and on-cell nuclear magnetic resonance (NMR) spectroscopy is a powerful method that offers exciting new possibilities for structural and functional studies in and on live cells. In contrast to conventional imaging techniques, in- and on-cell NMR methods do not provide spatial information on cellular biomolecules. Instead, they enable atomic-resolution insights into the native cell states of proteins, nucleic acids, glycans, and lipids. Here we review recent advances and developments in both fields and discuss emerging concepts that have been delineated with these methods.

  4. NMR Studies of Cartilage Dynamics, Diffusion, Degradation

    NASA Astrophysics Data System (ADS)

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

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

  5. Discrete analysis of stochastic NMR.II

    NASA Astrophysics Data System (ADS)

    Wong, S. T. S.; Rods, M. S.; Newmark, R. D.; Budinger, T. F.

    Stochastic NMR is an efficient technique for high-field in vivo imaging and spectroscopic studies where the peak RF power required may be prohibitively high for conventional pulsed NMR techniques. A stochastic NMR experiment excites the spin system with a sequence of RF pulses where the flip angles or the phases of the pulses are samples of a discrete stochastic process. In a previous paper the stochastic experiment was analyzed and analytic expressions for the input-output cross-correlations, average signal power, and signal spectral density were obtained for a general stochastic RF excitation. In this paper specific cases of excitation with random phase, fixed flip angle, and excitation with two random components in quadrature are analyzed. The input-output cross-correlation for these two types of excitations is shown to be Lorentzian. Line broadening is the only spectral distortion as the RF excitation power is increased. The systematic noise power is inversely proportional to the number of data points N used in the spectral reconstruction. The use of a complete maximum length sequence (MLS) may improve the signal-to-systematic-noise ratio by 20 dB relative to random binary excitation, but peculiar features in the higher-order autocorrelations of MLS cause noise-like distortion in the reconstructed spectra when the excitation power is high. The amount of noise-like distortion depends on the choice of the MLS generator.

  6. The NMR phased array.

    PubMed

    Roemer, P B; Edelstein, W A; Hayes, C E; Souza, S P; Mueller, O M

    1990-11-01

    We describe methods for simultaneously acquiring and subsequently combining data from a multitude of closely positioned NMR receiving coils. The approach is conceptually similar to phased array radar and ultrasound and hence we call our techniques the "NMR phased array." The NMR phased array offers the signal-to-noise ratio (SNR) and resolution of a small surface coil over fields-of-view (FOV) normally associated with body imaging with no increase in imaging time. The NMR phased array can be applied to both imaging and spectroscopy for all pulse sequences. The problematic interactions among nearby surface coils is eliminated (a) by overlapping adjacent coils to give zero mutual inductance, hence zero interaction, and (b) by attaching low input impedance preamplifiers to all coils, thus eliminating interference among next nearest and more distant neighbors. We derive an algorithm for combining the data from the phased array elements to yield an image with optimum SNR. Other techniques which are easier to implement at the cost of lower SNR are explored. Phased array imaging is demonstrated with high resolution (512 x 512, 48-cm FOV, and 32-cm FOV) spin-echo images of the thoracic and lumbar spine. Data were acquired from four-element linear spine arrays, the first made of 12-cm square coils and the second made of 8-cm square coils. When compared with images from a single 15 x 30-cm rectangular coil and identical imaging parameters, the phased array yields a 2X and 3X higher SNR at the depth of the spine (approximately 7 cm). PMID:2266841

  7. 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.

  8. 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.

  9. In-cell NMR of intrinsically disordered proteins in prokaryotic cells.

    PubMed

    Ito, Yutaka; Mikawa, Tsutomu; Smith, Brian O

    2012-01-01

    In-cell NMR, i.e., the acquisition of heteronuclear multidimensional NMR of biomacromolecules inside living cells, is, to our knowledge, the only method for investigating the three-dimensional structure and dynamics of proteins at atomic detail in the intracellular environment. Since the inception of the method, intrinsically disordered proteins have been regarded as particular targets for in-cell NMR, due to their expected sensitivity to the molecular crowding in the intracellular environment. While both prokaryotic and eukaryotic cells can be used as host cells for in-cell NMR, prokaryotic in-cell NMR, particularly employing commonly used protein overexpression systems in Escherichia coli cells, is the most accessible approach. In this chapter we describe general procedures for obtaining in-cell NMR spectra in E. coli cells.

  10. Protein interaction patterns in different cellular environments are revealed by in-cell NMR

    PubMed Central

    Barbieri, Letizia; Luchinat, Enrico; Banci, Lucia

    2015-01-01

    In-cell NMR allows obtaining atomic-level information on biological macromolecules in their physiological environment. Soluble proteins may interact with the cellular environment in different ways: either specifically, with their functional partners, or non-specifically, with other cellular components. Such behaviour often causes the disappearance of the NMR signals. Here we show that by introducing mutations on the human protein profilin 1, used here as a test case, the in-cell NMR signals can be recovered. In human cells both specific and non-specific interactions are present, while in bacterial cells only the effect of non-specific interactions is observed. By comparing the NMR signal recovery pattern in human and bacterial cells, the relative contribution of each type of interaction can be assessed. This strategy allows detecting solution in-cell NMR spectra of soluble proteins without altering their fold, thus extending the applicability of in-cell NMR to a wider range of proteins. PMID:26399546

  11. beta-Ureidopropionase deficiency: a novel inborn error of metabolism discovered using NMR spectroscopy on urine.

    PubMed

    Moolenaar, S H; Göhlich-Ratmann, G; Engelke, U F; Spraul, M; Humpfer, E; Dvortsak, P; Voit, T; Hoffmann, G F; Bräutigam, C; van Kuilenburg, A B; van Gennip, A; Vreken, P; Wevers, R A

    2001-11-01

    In this work, NMR investigations that led to the discovery of a new inborn error of metabolism, beta-ureidopropionase (UP) deficiency, are reported. 1D (1)H-NMR experiments were performed using a patient's urine. 3-Ureidopropionic acid was observed in elevated concentrations in the urine spectrum. A 1D (1)H-(1)H total correlation spectroscopy (TOCSY) and two heteronuclear 2D NMR techniques (heteronuclear multiple bond correlation (HMBC) and heteronuclear single-quantum correlation (HSQC)) were used to identify the molecular structure of the compound that caused an unknown doublet resonance at 1.13 ppm. Combining the information from the various NMR spectra, this resonance could be assigned to 3-ureidoisobutyric acid. These observations suggested a deficiency of UP. With 1D (1)H-NMR spectroscopy, UP deficiency can be easily diagnosed. The (1)H-NMR spectrum can also be used to diagnose patients suffering from other inborn errors of metabolism in the pyrimidine degradation pathway.

  12. NMR measurements in solutions of dialkylimidazolium haloaluminates

    SciTech Connect

    Takahashi, S.; Saboungi, M.L.; Klingler, R.J.; Chen, M.J.; Rathke, J.W.

    1992-06-01

    {sup 27}Al and {sup 35}Cl NMR spectra of AlCl{sub 3}-1-ethyl-3-methyl imidazolium chloride (EMIC) melts were measured for initial compositions ranging from 50 to 67 mol % AlCl{sub 3} at various temperatures. It was shown by changing the preaquisition delay time (DE value) that the dominant aluminum species are AlCl{sub 4}{sup {minus}} in the melt formed by mixing 50 mol % with EMIC and Al{sub 2}Cl{sub 7}{sup {minus}} in the 67 mol % AlCl{sub 3} melt. In the equimolar mixture, the chemical shift of {sup 27}Al NMR spectrum is 103.28 ppm and the line width is 22.83Hz. In the 67 mol % AlCl{sub 3} mixture, the chemical shift is 103.41 ppm and the line width is 2624Hz. A third species observed at 97 ppm in the {sup 27}Al spectra for the 55 and 60 mol % AlCl{sub 3} mixtures is identified to be a product of the reaction with residual water. The relaxation rates for each species in the melts were determined.

  13. In situ NMR analysis of fluids contained in sedimentary rock

    PubMed

    de Swiet TM; Tomaselli; Hurlimann; Pines

    1998-08-01

    Limitations of resolution and absorption in standard chemical spectroscopic techniques have made it difficult to study fluids in sedimentary rocks. In this paper, we show that a chemical characterization of pore fluids may be obtained in situ by magic angle spinning (MAS) nuclear magnetic resonance (NMR), which is normally used for solid samples. 1H MAS-NMR spectra of water and crude oil in Berea sandstone show sufficient chemical shift resolution for a straightforward determination of the oil/water ratio. Copyright 1998 Academic Press.

  14. Protein folding on the ribosome studied using NMR spectroscopy

    PubMed Central

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

    2013-01-01

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

  15. The development of solid-state NMR of membrane proteins

    PubMed Central

    Opella, Stanley J.

    2014-01-01

    Most biological functions are carried out in supramolecular assemblies. As a result of their slow reorientation in solution, these assemblies have been resistant to the widely employed solution NMR approaches. The development of solid-state NMR to first of all overcome the correlation time problem and then obtain informative high-resolution spectra of proteins in supramolecular assemblies, such as virus particles and membranes, is described here. High resolution solid-state NMR is deeply intertwined with the history of NMR, and the seminal paper was published in 1948. Although the general principles were understood by the end of the 1950s, it has taken more than fifty years for instrumentation and experimental methods to become equal to the technical problems presented by the biological assemblies of greatest interest. It is now possible to obtain atomic resolution structures of viral coat proteins in virus particles and membrane proteins in phospholipid bilayers by oriented sample solid-state NMR methods. The development of this aspect of the field of solid-state NMR is summarized in this review article. PMID:26069880

  16. Ultrafast 2D NMR: an emerging tool in analytical spectroscopy.

    PubMed

    Giraudeau, Patrick; Frydman, Lucio

    2014-01-01

    Two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy is widely used in chemical and biochemical analyses. Multidimensional NMR is also witnessing increased use in quantitative and metabolic screening applications. Conventional 2D NMR experiments, however, are affected by inherently long acquisition durations, arising from their need to sample the frequencies involved along their indirect domains in an incremented, scan-by-scan nature. A decade ago, a so-called ultrafast (UF) approach was proposed, capable of delivering arbitrary 2D NMR spectra involving any kind of homo- or heteronuclear correlation, in a single scan. During the intervening years, the performance of this subsecond 2D NMR methodology has been greatly improved, and UF 2D NMR is rapidly becoming a powerful analytical tool experiencing an expanded scope of applications. This review summarizes the principles and main developments that have contributed to the success of this approach and focuses on applications that have been recently demonstrated in various areas of analytical chemistry--from the real-time monitoring of chemical and biochemical processes, to extensions in hyphenated techniques and in quantitative applications. PMID:25014342

  17. Protein folding on the ribosome studied using NMR spectroscopy.

    PubMed

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

    2013-10-01

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

  18. 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

  19. Spatial distribution of 17O-excess in surface snow along a traverse from Zhongshan station to Dome A, East Antarctica

    NASA Astrophysics Data System (ADS)

    Pang, Hongxi; Hou, Shugui; Landais, Amaelle; Masson-Delmotte, Valérie; Prie, Frederic; Steen-Larsen, Hans Christian; Risi, Camille; Li, Yuansheng; Jouzel, Jean; Wang, Yetang; He, Jing; Minster, Bénédicte; Falourd, Sonia

    2015-03-01

    The influence of temperature on the triple isotopic composition of oxygen in water is still an open question and limits the interpretation of water isotopic profiles in Antarctic ice cores. The main limitation arises from the lack of 17O-excess measurements in surface snow and especially for remote regions characterized by low temperature and accumulation rate. In this study, we present new 17<