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Sample records for 13c cross-polarization magic-angle-spinning

  1. Comparisons of lipid dynamics and packing in fully interdigitated monoarachidoylphosphatidylcholine and non-interdigitated dipalmitoylphosphatidylcholine bilayers: cross polarization/magic angle spinning 13C-NMR studies.

    PubMed

    Wu, W G; Chi, L M

    1990-07-24

    13C-NMR spectra have been obtained at 50.3 MHz for monoarachidoylphosphatidylcholine (MAPC) and dipalmitoylphosphatidylcholine (DPPC) dispersions from 25 degrees C to 55 degrees C and for DPPC polycrystals at 25 degrees C using the cross polarization/magic angle spinning technique. Differential scanning calorimetric studies on DPPC and MAPC dispersions show comparable lipid phase transitions with transition temperatures at 41 degrees C and 45 degrees C, respectively, and thus enable the comparison of thermal, structural and dynamic differences between these two systems at corresponding temperatures. Conformational-dependent 13C chemical shift studies on DPPC dispersions demonstrate not only the coexistence of the tilted gel (L beta') and liquid-crystalline (L alpha) phases in the rippled gel (P beta') phase, but also the presence of an intermediate third microscopic phase as evidenced by three resolvable peaks for omega - 1 methylene carbon signals at the temperature interval between Tp and Tm. By comparing chemical shifts of MAPC in the hydrocarbon chain region with those of DPPC at similar reduced temperatures, it can be concluded that the packings are perturbed markedly in the middle segment of the fatty acyl chain during the lamellar to micellar transition. However, terminal methylene and methyl groups of interdigitated MAPC lamellae were found to be more ordered than those of non-interdigitated DPPC bilayers in the gel state. Interestingly, the terminal methyl groups of MAPC in the micelles remain to be relatively ordered; in fact, they are more ordered than the corresponding acyl chain end of DPPC in the liquid-crystalline state. Analysis of data obtained from rotating frame proton spin-lattice relaxation measurements shows a highly mobile phosphocholine headgroup, a rigid carbonyl group and an ordered hydrocarbon chain for lamellar MAPC in the interdigitated state. Furthermore, results suggest that free rotations of the glycerol C2-C3 bond within MAPC

  2. Spin-locking and cross-polarization under magic-angle spinning of uniformly labeled solids.

    PubMed

    Hung, Ivan; Gan, Zhehong

    2015-07-01

    Spin-locking and cross-polarization under magic-angle spinning are investigated for uniformly (13)C and (15)N labeled solids. In particular, the interferences from chemical shift anisotropy, and (1)H heteronuclear and (13)C homonuclear dipolar couplings are identified. The physical origin of these interferences provides guidelines for selecting the best (13)C and (15)N polarization transfer rf fields. Optimal settings for both the zero- and double-quantum cross-polarization transfer mechanisms are recommended. PMID:25965280

  3. Spin-locking and cross-polarization under magic-angle spinning of uniformly labeled solids

    NASA Astrophysics Data System (ADS)

    Hung, Ivan; Gan, Zhehong

    2015-07-01

    Spin-locking and cross-polarization under magic-angle spinning are investigated for uniformly 13C and 15N labeled solids. In particular, the interferences from chemical shift anisotropy, and 1H heteronuclear and 13C homonuclear dipolar couplings are identified. The physical origin of these interferences provides guidelines for selecting the best 13C and 15N polarization transfer rf fields. Optimal settings for both the zero- and double-quantum cross-polarization transfer mechanisms are recommended.

  4. A study of conformational stability of poly(L-alanine), poly(L-valine), and poly(L-alanine)/poly(L-valine) blends in the solid state by (13)C cross-polarization/magic angle spinning NMR.

    PubMed

    Murata, Katsuyoshi; Kuroki, Shigeki; Kimura, Hideaki; Ando, Isao

    2002-06-01

    13C cross-polarization/magic angle spinning (CP/MAS) NMR and (1)H T(1rho) experiments of poly(L-alanine) (PLA), poly(L-valine) (PLV), and PLA/PLV blends have been carried out in order to elucidate the conformational stability of the polypeptides in the solid state. These were prepared by adding a trifluoroacetic acid (TFA) solution of the polymer with a 2.0 wt/wt % of sulfuric acid (H(2)SO(4)) to alkaline water. From these experimental results, it is clarified that the conformations of PLA and PLV in their blends are strongly influenced by intermolecular hydrogen-bonding interactions that cause their miscibility at the molecular level. PMID:11948439

  5. Stochastic molecular motions in the nematic, smectic-A, and solid phases of p,p{sup '}-di-n-heptyl-azoxybenzene as seen by quasielastic neutron scattering and {sup 13}C cross-polarization magic-angle-spinning NMR

    SciTech Connect

    ZajaPc, Wojciech; Urban, Stanislaw; Domenici, Valentina; Geppi, Marco; Veracini, Carlo Alberto; Telling, Mark T. F.; Gabrys, Barbara J.

    2006-05-15

    Molecular rotational dynamics in p,p{sup '}-di-n-heptyl-azoxybenzene was studied by means of quasielastic neutron scattering (QENS) and {sup 13}C cross-polarization magic-angle-spinning (CPMAS) NMR. Fast reorientation of the hydrogen nuclei was observed by QENS in the two liquid crystalline (LC) phases nematic and smectic A, as well as in the crystalline phase. The latter could not be restricted to the -CH{sub 3} rotations alone, and a clear indication was found of some other reorientation motions persisting in the crystal. Two Lorentz-type components convoluted with the resolution function gave an excellent fit to the QENS spectra in both LC phases. The narrow (slow) component was attributed to the reorientation of the whole molecule around the long axis. The corresponding characteristic time of {approx}130 ps agreed well with the values obtained in recent dielectric relaxation and {sup 2}H NMR studies. The full width at half maximum of the broader (fast) component shows a quadratic Q dependence (Q is the momentum transfer). Hence the corresponding motions could be described by a stretched exponential correlation function and were interpreted as various ''crankshaft-type'' motions within the alkyl tails. The {sup 13}C CPMAS experiments fully corroborated the QENS results, sometimes considered ambiguous in complex systems.

  6. Stochastic molecular motions in the nematic, smectic-A, and solid phases of p,p'-di-n-heptyl-azoxybenzene as seen by quasielastic neutron scattering and 13C cross-polarization magic-angle-spinning NMR.

    PubMed

    Zajac, Wojciech; Urban, Stanisław; Domenici, Valentina; Geppi, Marco; Veracini, Carlo Alberto; Telling, Mark T F; Gabryś, Barbara J

    2006-05-01

    Molecular rotational dynamics in p,p'-di-n-heptyl-azoxybenzene was studied by means of quasielastic neutron scattering (QENS) and 13C cross-polarization magic-angle-spinning (CPMAS) NMR. Fast reorientation of the hydrogen nuclei was observed by QENS in the two liquid crystalline (LC) phases nematic and smectic A, as well as in the crystalline phase. The latter could not be restricted to the -CH3 rotations alone, and a clear indication was found of some other reorientation motions persisting in the crystal. Two Lorentz-type components convoluted with the resolution function gave an excellent fit to the QENS spectra in both LC phases. The narrow (slow) component was attributed to the reorientation of the whole molecule around the long axis. The corresponding characteristic time of approximately 130 ps agreed well with the values obtained in recent dielectric relaxation and 2H NMR studies. The full width at half maximum of the broader (fast) component shows a quadratic Q dependence (Q is the momentum transfer). Hence the corresponding motions could be described by a stretched exponential correlation function and were interpreted as various "crankshaft-type" motions within the alkyl tails. The 13C CPMAS experiments fully corroborated the QENS results, sometimes considered ambiguous in complex systems. PMID:16802951

  7. Exploring the conformational energy landscape of glassy disaccharides by cross polarization magic angle spinning 13C nuclear magnetic resonance and numerical simulations. II. Enhanced molecular flexibility in amorphous trehalose

    NASA Astrophysics Data System (ADS)

    Lefort, Ronan; Bordat, Patrice; Cesaro, Attilio; Descamps, Marc

    2007-01-01

    This paper uses chemical shift surfaces to simulate experimental C13 cross polarization magic angle spinning spectra for amorphous solid state disaccharides, paying particular attention to the glycosidic linkage atoms in trehalose, sucrose, and lactose. The combination of molecular mechanics with density functional theory/gauge invariant atomic orbital ab initio methods provides reliable structural information on the conformational distribution in the glass. The results are interpreted in terms of an enhanced flexibility that trehalose possesses in the amorphous solid state, at least on the time scale of C13 nuclear magnetic resonance measurements. Implications of these findings for the fragility of trehalose glass and bioprotectant action are discussed.

  8. Study of lignification by noninvasive techniques in growing maize internodes. An investigation by Fourier transform infrared cross-polarization-magic angle spinning 13C-nuclear magnetic resonance spectroscopy and immunocytochemical transmission electron microscopy.

    PubMed

    Joseleau, J P; Ruel, K

    1997-07-01

    Noninvasive techniques were used for the study in situ of lignification in the maturing cell walls of the maize (Zea mays L.) stem. Within the longitudinal axis of a developing internode all of the stages of lignification can be found. The synthesis of the three types of lignins, p-hydroxyphenylpropane (H), guaiacyl (G), and syringyl (S), was investigated in situ by cross-polarization-magic angle spinning 13C-solid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, and immunocytochemical electron microscopy. The first lignin appearing in the parenchyma is of the G-type preceeding the incorporation of S nuclei in the later stages. However, in vascular bundles, typical absorption bands of S nuclei are visible in the Fourier transform infrared spectra at the earliest stage of lignification. Immunocytochemical determination of the three types of lignin in transmission electron microscopy was possible thanks to the use of antisera prepared against synthetic H, G, and the mixed GS dehydrogenative polymers (K. Ruel, O. Faix, J.P. Joseleau [1994] J Trace Microprobe Tech 12: 247-265). The specificity of the immunological probes demonstrated that there are differences in the relative temporal synthesis of the H, G, and GS lignins in the different tissues undergoing lignification. Considering the intermonomeric linkages predominating in the antigens used for the preparation of the immunological probes, the relative intensities of the labeling obtained provided, for the first time to our knowledge, information about the macromolecular nature of lignins (condensed versus noncondensed) in relation to their ultrastructural localization and development stage. PMID:9232887

  9. Tailored low-power cross-polarization under fast magic-angle spinning

    NASA Astrophysics Data System (ADS)

    Demers, Jean-Philippe; Vijayan, Vinesh; Becker, Stefan; Lange, Adam

    2010-08-01

    High static magnetic fields and very fast magic-angle spinning (MAS) promise to improve resolution and sensitivity of solid-state NMR experiments. The fast MAS regime has permitted the development of low-power cross-polarization schemes, such as second-order cross-polarization (SOCP), which prevent heat deposition in the sample. Those schemes are however limited in bandwidth, as weak radio-frequency (RF) fields only cover a small chemical shift range for rare nuclei (e.g. 13C). Another consideration is that the efficiency of cross-polarization is very sensitive to magnetization decay that occurs during the spin-lock pulse on the abundant nuclei (e.g. 1H). Having characterized this decay in glutamine at 60 kHz MAS, we propose two complementary strategies to tailor cross-polarization to desired spectral regions at low RF power. In the case of multiple sites with small chemical shift dispersion, a larger bandwidth for SOCP is obtained by slightly increasing the RF power while avoiding recoupling conditions that lead to fast spin-lock decay. In the case of two spectral regions with large chemical shift offset, an extension of the existing low-power schemes, called MOD-CP, is introduced. It consists of a spin-lock on 1H and an amplitude-modulated spin-lock on the rare nucleus. The range of excited chemical shifts is assessed by experimental excitation profiles and numerical simulation of an I 2S spin system. All SOCP-based schemes exhibit higher sensitivity than high-power CP schemes, as demonstrated on solid (glutamine) and semi-solid (hydrated, micro-crystalline ubiquitin) samples.

  10. High-resolution magic-angle spinning (13)C spectroscopy of brain tissue at natural abundance.

    PubMed

    Yang, Yongxia; Chen, Lei; Gao, Hongchang; Zeng, Danlin; Yue, Yong; Liu, Maili; Lei, Hao; Deng, Feng; Ye, Chaohui

    2006-03-01

    High-resolution magic-angle spinning (MAS) (1)H and (13)C magnetic resonance spectroscopy (MRS) has recently been applied to study the metabolism in intact biological tissue samples. Because of the low natural abundance and the low gyromagnetic ratio of the (13)C nuclei, signal enhancement techniques such as cross-polarization (CP) and distortionless enhancement by polarization transfer (DEPT) are often employed in MAS (13)C MRS to improve the detection sensitivity. In this study, several sensitivity enhancement techniques commonly used in liquid- and solid-state NMR, including CP, DEPT and nuclear Overhauser enhancement (NOE), were combined with MAS to acquire high-resolution (13)C spectra on intact rat brain tissue at natural abundance, and were compared for their performances. The results showed that different signal enhancement techniques are sensitive to different classes of molecules/metabolites, depending on their molecular weights and mobility. DEPT was found to enhance the signals of low-molecular weight metabolites exclusively, while the signals of lipids, which often are associated with membranes and have relatively lower mobility, were highly sensitive to CP enhancement. PMID:16477685

  11. Rotary resonance recoupling of 13C- 1H dipolar interactions in magic angle spinning 13C NMR of dynamic solids

    NASA Astrophysics Data System (ADS)

    Kitchin, Simon J.; Harris, Kenneth D. M.; Aliev, Abil E.; Apperley, David C.

    2000-06-01

    Rotary resonance recoupling of heteronuclear 13C- 1H dipolar interactions in magic angle spinning solid state 13C NMR spectra (recorded under conditions of 1H decoupling at frequency ν1 and magic angle spinning at frequency νr) has been studied for three examples of molecular solids (adamantane, ferrocene and hexamethylbenzene) in which substantial molecular motion is known to occur. It is shown that when rotary resonance conditions are satisfied (i.e. ν1/νr= n, for n=1 or 2), the recoupling can lead to motionally averaged Pake-like powder patterns from which information on 13C- 1H internuclear distances and/or molecular motion can be derived.

  12. (1)H and (13)C magic-angle spinning nuclear magnetic resonance studies of the chicken eggshell.

    PubMed

    Pisklak, Dariusz Maciej; Szeleszczuk, Lukasz; Wawer, Iwona

    2012-12-19

    The chicken eggshell, a product of biomineralization, contains inorganic and organic substances whose content changes during the incubation process. Bloch-decay (BD) (1)H, (13)C, and cross-polarization (CP) (13)C nuclear magnetic resonance (NMR) spectra of chicken eggshells were acquired under magic-angle spinning (MAS). Variable contact time (13)C CP MAS NMR experiments revealed the signals of carbonyl groups from organic and inorganic compounds. In the (13)C BD NMR spectra, a single peak at 168.1 ppm was detected, whereas in the (1)H BD spectra, the signals from water and the bicarbonate ion were assigned. A simultaneous decrease of the water signal in the (1)H MAS NMR spectra and an increase of the carbonate ion signal in the (13)C CP MAS NMR spectra of eggshells collected during the incubation period indicate the substitution of calcium ions by hydrogen ions in the calcium carbonate crystalline phase during the incubation of an egg. PMID:23157303

  13. Two-dimensional (13)C-(13)C correlation spectroscopy with magic angle spinning and dynamic nuclear polarization.

    PubMed

    Rosay, Melanie; Weis, Volker; Kreischer, Kenneth E; Temkin, Richard J; Griffin, Robert G

    2002-04-01

    The sensitivity of solid-state NMR experiments can be enhanced with dynamic nuclear polarization (DNP), a technique that transfers the high Boltzmann polarization of unpaired electrons to nuclei. Signal enhancements of up to 23 have been obtained for magic angle spinning (MAS) experiments at 5 T and 85-90 K using a custom-designed high-power gyrotron. The extended stability of MAS/DNP experiments at low temperature is demonstrated with (1)H-driven (13)C spin-diffusion experiments on the amino acid proline. These (13)C-(13)C chemical shift correlation spectra are the first two-dimensional MAS/DNP experiments performed at high field (>1.4 T). PMID:11916398

  14. Cross-polarization/magic-angle spinning NMR studies of polymorphism: Cortisone acetate

    NASA Astrophysics Data System (ADS)

    Harris, Robin K.; Kenwright, Alan M.; Say, Barry J.; Yeung, Race R.; Fletton, Richard A.; Lancaster, Robert W.; Hardgrove, George L.

    13C CPMAS spectra have been recorded for nine samples of cortisone acetate (21-acetoxy-17α-hydroxy-4-pregnene-3,11,20-trione, C 23H 30O 6) and the observed resonances are attributed to six crystalline forms. Two of these forms are novel. The spectra of all six are entirely distinct. The resonances are assigned to individual carbon atoms on the basis of previously-determined solution-state spectra together with dipolar dephasing experiments and observations of shielding anisotropies as reflected in spinning sideband manifolds. The results are interpreted in relation to known crystal structures. The value of solid-state NMR for analysis of polymorph mixtures is emphasized.

  15. Carbon-13 cross-polarization magic-angle-spinning nuclear magnetic resonance investigation of the interactions between maleic anhydride grafted polypropylene and wood polymers.

    PubMed

    Rude, Erica; Laborie, Marie-Pierre G

    2008-05-01

    The chemical interactions between maleic anhydride grafted polypropylene (MAPP) and wood were studied with solid-state carbon-13 cross-polarization magic-angle-spinning nuclear magnetic resonance ((13)C CPMAS NMR) spectroscopy. MAPP was synthesized with 100% (13)C enrichment at the C(1) and C(4) carbons to allow detection of the [1,4-(13)C(2)]MAPP functional groups and was melt blended with cellulose, lignin, and maple wood. In the cellulose/MAPP blend, changes in (13)C CPMAS NMR corrected signal intensities for the anhydride and dicarboxylic maleic acid functionalities suggested that esterification may have occurred predominantly from the more numerous diacid carbons. A single proton longitudinal relaxation in the rotating frame, (H)T(1rho), for the MAPP and the cellulose carbons in the blend suggested that they were spin coupled, i.e., homogeneous on a 10-200 Angstrom scale. Esterification was also suggested in the lignin/MAPP blend. Furthermore, the more significant changes in the intensities of the carbonyl signals and (H)T(1rho) values suggested that lignin may be more reactive to MAPP than cellulose. Finally, when maple was melt blended with MAPP, the same trends in the (13)C CP-MAS NMR spectra and (H)T(1rho) behavior were observed as when MAPP was blended with cellulose or lignin. This study therefore clarifies that during melt compounding of wood with MAPP, esterification occurs with wood polymers, preferentially with lignin. Understanding the interactions of MAPP with wood is of significance for the development of natural-fiber-reinforced thermoplastic composites. PMID:18498698

  16. Characterization of high-tannin fractions from humus by carbon-13 cross-polarization and magic-angle spinning nuclear magnetic resonance.

    PubMed

    Lorenz, Klaus; Preston, Caroline M

    2002-01-01

    Condensed tannins can be found in various parts of many plants. Unlike lignin there has been little study of their fate as they enter the soil organic matter pool and their influence on nutrient cycling, especially through their protein-binding properties. We extracted and characterized tannin-rich fractions from humus collected in 1998 from a black spruce [Picea mariana (Mill.) Britton et al.] forest in Canada where a previous study (1995) showed high levels (3.8% by weight) of condensed tannins. A reference tannin purified from black spruce needles was characterized by solution 13C nuclear magnetic resonance (NMR) as a pure procyanidin with mainly cis stereochemistry and an average chain length of four to five units. The colorimetric proanthocyanidin (PA) assay, standardized against the black spruce tannin, showed that both extracted humus fractions had higher tannin contents than the original humus (2.84% and 11.17% vs. 0.08%), and accounted for 32% of humus tannin content. Consistent with the results from the chemical assay, the aqueous fraction showed higher tannin signals in the 13C cross-polarization and magic-angle spinning (CPMAS) NMR spectrum than the emulsified one. As both tannin-rich humus fractions were depleted in N and high in structures derived from lignin and cutin, they did not have properties consistent with recaldtrant tannin-protein complexes proposed as a mechanism for N sequestration in humus. Further studies are needed to establish if tannin-protein structures in humus can be detected or isolated, or if tannins contribute to forest management problems observed in these ecosystems by binding to and slowing down the activity of soil enzymes. PMID:11931430

  17. Measurements of 13C multiple-quantum coherences in amyloid fibrils under magic-angle spinning.

    PubMed

    Chou, Fang-Chieh; Tsai, Tim W T; Cheng, Hsin-Mei; Chan, Jerry C C

    2012-06-21

    The excitation and detection of high-order multiple quantum coherences among (13)C nuclear spins are demonstrated in the samples of [1-(13)C]-L-alanine and (13)C labeled amyloid fibrils at a spinning frequency of 20 kHz. The technique is based on the double-quantum average Hamiltonian prepared by the DRAMA-XY4 pulse sequence. Empirically, we find that multiple supercycles are required to suppress the higher-order effects for real applications. Measurements for the fibril samples formed by the polypeptides of PrP(113-127) provide the first solid-state NMR evidence for the stacking of multiple β-sheet layers at the structural core of amyloid fibrils. PMID:22632418

  18. The mobility of chondroitin sulfate in articular and artificial cartilage characterized by 13C magic-angle spinning NMR spectroscopy.

    PubMed

    Scheidt, Holger A; Schibur, Stephanie; Magalhães, Alvicler; de Azevedo, Eduardo R; Bonagamba, Tito J; Pascui, Ovidiu; Schulz, Ronny; Reichert, Detlef; Huster, Daniel

    2010-06-01

    We have studied the molecular dynamics of one of the major macromolecules in articular cartilage, chondroitin sulfate. Applying (13)C high-resolution magic-angle spinning NMR techniques, the NMR signals of all rigid macromolecules in cartilage can be suppressed, allowing the exclusive detection of the highly mobile chondroitin sulfate. The technique is also used to detect the chondroitin sulfate in artificial tissue-engineered cartilage. The tissue-engineered material that is based on matrix producing chondrocytes cultured in a collagen gel should provide properties as close as possible to those of the natural cartilage. Nuclear relaxation times of the chondroitin sulfate were determined for both tissues. Although T(1) relaxation times are rather similar, the T(2) relaxation in tissue-engineered cartilage is significantly shorter. This suggests that the motions of chondroitin sulfate in natural and artificial cartilage are different. The nuclear relaxation times of chondroitin sulfate in natural and tissue-engineered cartilage were modeled using a broad distribution function for the motional correlation times. Although the description of the microscopic molecular dynamics of the chondroitin sulfate in natural and artificial cartilage required the identical broad distribution functions for the correlation times of motion, significant differences in the correlation times of motion that are extracted from the model indicate that the artificial tissue does not fully meet the standards of the natural ideal. This could also be confirmed by macroscopic biomechanical elasticity measurements. Nevertheless, these results suggest that NMR is a useful tool for the investigation of the quality of artificially engineered tissue. PMID:20091673

  19. Cross-polarization magic-angle spinning nuclear magnetic resonance study of platinum complexes containing the cis-P2PtC2 fragment.

    PubMed

    Challoner, R; Sebald, A

    1995-01-01

    31P and 195Pt cross-polarization magic-angle spinning nuclear magnetic resonance (CP-MAS NMR) spectra of three platinum complexes of formal oxidation state Pt(0) and Pt(II), respectively, are reported. All three complexes, (Ph3P)2Pt(C2H4) (1), (Et2P-CH2-CH2-PEt2)Pt(C identical to C-H)2 (2) and (Ph2P-CH2-CH2-PPh2)Pt(C identical to C-C(CH3)=CH2)2 (3) contain the square-planar cis-P2PtC2 fragment and show unusual NMR spectroscopic properties insofar that the 195Pt shielding patterns are fairly narrow in relation to what one would generally have to expect for 195Pt in square-planar coordination. Another unexpected NMR property of the cis-P2PtC2 fragment in 1-3 is the absence of spinning frequency-dependent second-order effects in this solid-state ABX spin system. PMID:7894980

  20. Multidimensional High-Resolution Magic Angle Spinning and Solution-State NMR Characterization of (13)C-labeled Plant Metabolites and Lignocellulose.

    PubMed

    Mori, Tetsuya; Tsuboi, Yuuri; Ishida, Nobuhiro; Nishikubo, Nobuyuki; Demura, Taku; Kikuchi, Jun

    2015-01-01

    Lignocellulose, which includes mainly cellulose, hemicellulose, and lignin, is a potential resource for the production of chemicals and for other applications. For effective production of materials derived from biomass, it is important to characterize the metabolites and polymeric components of the biomass. Nuclear magnetic resonance (NMR) spectroscopy has been used to identify biomass components; however, the NMR spectra of metabolites and lignocellulose components are ambiguously assigned in many cases due to overlapping chemical shift peaks. Using our (13)C-labeling technique in higher plants such as poplar samples, we demonstrated that overlapping peaks could be resolved by three-dimensional NMR experiments to more accurately assign chemical shifts compared with two-dimensional NMR measurements. Metabolites of the (13)C-poplar were measured by high-resolution magic angle spinning NMR spectroscopy, which allows sample analysis without solvent extraction, while lignocellulose components of the (13)C-poplar dissolved in dimethylsulfoxide/pyridine solvent were analyzed by solution-state NMR techniques. Using these methods, we were able to unambiguously assign chemical shifts of small and macromolecular components in (13)C-poplar samples. Furthermore, using samples of less than 5 mg, we could differentiate between two kinds of genes that were overexpressed in poplar samples, which produced clearly modified plant cell wall components. PMID:26143886

  1. Multidimensional High-Resolution Magic Angle Spinning and Solution-State NMR Characterization of 13C-labeled Plant Metabolites and Lignocellulose

    PubMed Central

    Mori, Tetsuya; Tsuboi, Yuuri; Ishida, Nobuhiro; Nishikubo, Nobuyuki; Demura, Taku; Kikuchi, Jun

    2015-01-01

    Lignocellulose, which includes mainly cellulose, hemicellulose, and lignin, is a potential resource for the production of chemicals and for other applications. For effective production of materials derived from biomass, it is important to characterize the metabolites and polymeric components of the biomass. Nuclear magnetic resonance (NMR) spectroscopy has been used to identify biomass components; however, the NMR spectra of metabolites and lignocellulose components are ambiguously assigned in many cases due to overlapping chemical shift peaks. Using our 13C-labeling technique in higher plants such as poplar samples, we demonstrated that overlapping peaks could be resolved by three-dimensional NMR experiments to more accurately assign chemical shifts compared with two-dimensional NMR measurements. Metabolites of the 13C-poplar were measured by high-resolution magic angle spinning NMR spectroscopy, which allows sample analysis without solvent extraction, while lignocellulose components of the 13C-poplar dissolved in dimethylsulfoxide/pyridine solvent were analyzed by solution-state NMR techniques. Using these methods, we were able to unambiguously assign chemical shifts of small and macromolecular components in 13C-poplar samples. Furthermore, using samples of less than 5 mg, we could differentiate between two kinds of genes that were overexpressed in poplar samples, which produced clearly modified plant cell wall components. PMID:26143886

  2. Recoupling of chemical shift anisotropies in solid-state NMR under high-speed magic-angle spinning and in uniformly 13C-labeled systems

    NASA Astrophysics Data System (ADS)

    Chan, Jerry C. C.; Tycko, Robert

    2003-05-01

    We demonstrate the possibility of recoupling chemical shift anisotropy (CSA) interactions in solid-state nuclear magnetic resonance (NMR) under high-speed magic-angle spinning (MAS) while retaining a static CSA powder pattern line shape and simultaneously attenuating homonuclear dipole-dipole interactions. CSA recoupling is accomplished by a rotation-synchronized radio-frequency pulse sequence with symmetry properties that permit static CSA line shapes to be obtained. We suggest a specific recoupling sequence, which we call ROCSA, for which the scaling factors for CSA and homonuclear dipole-dipole interactions are 0.272 and approximately 0.05, respectively. This sequence is suitable for high-speed 13C MAS NMR experiments on uniformly 13C-labeled organic compounds, including biopolymers. We demonstrate the ROCSA sequence experimentally by measuring the 13C CSA patterns of the uniformly labeled, polycrystalline compounds L-alanine and N-acetyl-D,L-valine at MAS frequencies of 11 and 20 kHz. We also present experimental data for amyloid fibrils formed by a 15-residue fragment of the β-amyloid peptide associated with Alzheimer's disease, in which four amino acid residues are uniformly labeled, demonstrating the applicability to biochemical systems of high molecular weight and significant complexity. Analysis of the CSA patterns in the amyloid fibril sample demonstrates the utility of ROCSA measurements as probes of peptide and protein conformation in noncrystalline solids.

  3. Conformational dynamics of phenylene rings in poly(p-phenylene vinylene) as revealed by 13C magic-angle-spinning exchange nuclear magnetic resonance experiments

    NASA Astrophysics Data System (ADS)

    deAzevedo, E. R.; Franco, R. W. A.; Marletta, A.; Faria, R. M.; Bonagamba, T. J.

    2003-08-01

    Poly(p-phenylene vinylene) (PPV) has shown a great potential for electro-optical applications due to its electroluminescent and semiconducting properties. Such properties are directly related with the polymer chain conformation and dynamics. Then, it is important to understand in detail the local chain motions. In this work, three 13C solid-state magic-angle-spinning (MAS) exchange NMR techniques were used to study conformational dynamics of phenylene rings in PPV. The standard 2D MAS exchange experiment was used to identify exchange processes between equivalent and nonequivalent sites. Centerband-only detection of exchange (CODEX) experiments were applied to determine the amplitude of the phenylene ring flips and small-angle oscillations. Additionally, a new version of the CODEX technique, which allows for the selective observation of segments executing exchange between non-equivalent sites, is demonstrated and applied to determine the flipping fractions and the activation energies of the phenylene ring rotations. It was found that, at -15 °C, (26±3)% of the rings undergo 180° flips in the millisecond time scale, with average imprecision of (30±5)° and activation energies of (23±3) kJ/mol. Other (31±10)% of the rings perform only small-angle oscillations with an average amplitude of (9±2)°. These results corroborate previous experimental data and agree with recent ab initio calculations of potential energies barriers in phenylenevinylene oligomers.

  4. Spinning-frequency-dependent linewidths in 1H-decoupled 13C magic-angle spinning NMR spectra

    NASA Astrophysics Data System (ADS)

    Nakai, Toshihito; McDowell, Charles A.

    1994-09-01

    The broadenings observed in 13C MAS NMR spectra, which depend on the sample-spinning speed, were studied, using polycrystalline adamantane. Not only was a monotonic increase of the linewidths with the increase of the spinning frequency observed, but also a novel resonant feature was found. The phenomena were interpreted as originating from rotary-resonance 13C 1H recoupling.

  5. Mesoporous Silica Nanoparticles Loaded with Surfactant: Low Temperature Magic Angle Spinning 13C and 29Si NMR Enhanced by Dynamic Nuclear Polarization

    SciTech Connect

    Lafon, Olivier; Thankamony, Aany S. Lilly; Kokayashi, Takeshi; Carnevale, Diego; Vitzthum, Veronika; Slowing, Igor I.; Kandel, Kapil; Vezin, Herve; Amoureux, Jean-Paul; Bodenhausen, Geoffrey; Pruski, Marek

    2012-12-21

    We show that dynamic nuclear polarization (DNP) can be used to enhance NMR signals of 13C and 29Si nuclei located in mesoporous organic/inorganic hybrid materials, at several hundreds of nanometers from stable radicals (TOTAPOL) trapped in the surrounding frozen disordered water. The approach is demonstrated using mesoporous silica nanoparticles (MSN), functionalized with 3-(N-phenylureido)propyl (PUP) groups, filled with the surfactant cetyltrimethylammonium bromide (CTAB). The DNP-enhanced proton magnetization is transported into the mesopores via 1H–1H spin diffusion and transferred to rare spins by cross-polarization, yielding signal enhancements εon/off of around 8. When the CTAB molecules are extracted, so that the radicals can enter the mesopores, the enhancements increase to εon/off ≈ 30 for both nuclei. A quantitative analysis of the signal enhancements in MSN with and without surfactant is based on a one-dimensional proton spin diffusion model. The effect of solvent deuteration is also investigated.

  6. Photo-CIDNP 13C magic angle spinning NMR on bacterial reaction centres: exploring the electronic structure of the special pair and its surroundings.

    PubMed

    Matysik, J; Schulten, E; Alia; Gast, P; Raap, J; Lugtenburg, J; Hoff, A J; de Groot, H J

    2001-08-01

    Photochemically induced dynamic nuclear polarisation (photo-CIDNP) in intact bacterial reaction centres has been observed by 13C-solid state NMR under continuous illumination with white light. Strong intensity enhancement of 13C NMR signals of the aromatic rings allows probing the electronic ground state of the two BChl cofactors of the special pair at the molecular scale with atomic selectivity. Differences between the two BChl cofactors are discussed. Several aliphatic 13C atoms of cofactors, as well as 13C atoms of the imidazole ring of histidine residue(s), show nuclear-spin polarisation to the same extent as the aromatic nuclei of the cofactors. Mechanisms and applications of polarisation transfer are discussed. PMID:11592409

  7. {sup 13}C, {sup 1}H, {sup 6}Li magic-angle spinning nuclear magnetic resonance, electron paramagnetic resonance, and Fourier transform infrared study of intercalation electrodes based in ultrasoft carbons obtained below 3100 K

    SciTech Connect

    Alcantara, R.; Madrigal, F.J.F.; Lavela, P.; Tirado, J.L.; Mateos, J.M.J.; Stoyanova, R.; Zhecheva, E.

    1999-01-01

    The past decade has seen an important development of materials for high-performance energy storage systems. Particularly, the field of electrode materials for advanced lithium batteries has attracted the interest of numerous researchers. Petroleum coke samples of different origins and heat treated at different temperatures below 3100 K have been studied by spectroscopic and electrochemical procedures. According to {sup 13}C and {sup 1}H magic-angle spinning (MAS) nuclear magnetic resonance (NMR), infrared (IR), and electron paramagnetic resonance (EPR) data, aromatic compounds and surface OH groups are present in green coke samples. The preparation of CMB (combustible) sample from 1673 K leads to a low-temperature graphitization process, as shown by the occurrence of multiphase products containing both turbostatic and graphitized solid. This process is accompanied by the loss of aromatic compounds and surface hydroxyls. The optimization of the lithium intercalation electrodes based in the green coke materials was carried out by thermal treatment at 1023 K under dynamic vacuum conditions. Such pretreatment of the electrode material leads to marked enhancement of reversible capacities without the higher temperatures usually required for other soft carbon materials. Finally, the results of {sup 6}Li MAS NMR and EPR have been correlated with the experimental determination of lithium diffusion coefficients and surface properties. On the basis of these results, spin resonance spectroscopies are found to be a powerful tool to discern between the different petroleum coke samples to select the active electrode material with best performance.

  8. In Situ 13C and 23Na Magic Angle Spinning NMR Investigation of Supercritical CO2 Incorporation in Smectite-Natural Organic Matter Composites

    SciTech Connect

    Bowers, Geoffrey M.; Hoyt, David W.; Burton, Sarah D.; Ferguson, Brennan O.; Varga, Tamas; Kirkpatrick, Robert J.

    2014-01-29

    This paper presents an in situ NMR study of clay-natural organic polymer systems (a hectoritehumic acid [HA] composite) under CO2 storage reservoir conditions (90 bars CO2 pressure, 50°C). The 13C and 23Na NMR data show that supercritical CO2 interacts more strongly with the composite than with the base clay and does not react to form other C-containing species over several days at elevated CO2. With and without organic matter, the data suggest that CO2 enters the interlayer space of Na-hectorite equilibrated at 43% relative humidity. The presence of supercritical CO2 also leads to increased 23Na signal intensity, reduced line width at half height, increased basal width, more rapid 23Na T1 relaxation rates, and a shift to more positive resonance frequencies. Larger changes are observed for the hectorite-HA composite than for the base clay. In light of recently reported MD simulations of other polymer-Na-smectite composites, we interpret the observed changes as an increase in the rate of Na+ site hopping in the presence of supercritical CO2, the presence of potential new Na+ sorption sites when the humic acid is present, and perhaps an accompanying increase in the number of Na+ ions actively involved in site hopping. The results suggest that the presence of organic material either in clay interlayers or on external particle surfaces can significantly affect the behavior of supercritical CO2 and the mobility of metal ions in reservoir rocks.

  9. 1H-13C/1H-15N Heteronuclear Dipolar Recoupling by R-Symmetry Sequences Under Fast Magic Angle Spinning for Dynamics Analysis of Biological and Organic Solids

    PubMed Central

    Hou, Guangjin; Byeon, In-Ja L.; Ahn, Jinwoo; Gronenborn, Angela M.; Polenova, Tatyana

    2011-01-01

    Fast magic angle spinning (MAS) NMR spectroscopy is becoming increasingly important in structural and dynamics studies of biological systems and inorganic materials. Superior spectral resolution due to the efficient averaging of the dipolar couplings can be attained at MAS frequencies of 40 kHz and higher with appropriate decoupling techniques, while proton detection gives rise to significant sensitivity gains, therefore making fast MAS conditions advantageous across the board compared with the conventional slow- and moderate-MAS approaches. At the same time, many of the dipolar recoupling approaches that currently constitute the basis for structural and dynamics studies of solid materials and that are designed for MAS frequencies of 20 kHz and below, fail above 30 kHz. In this report, we present an approach for 1H-13C/1H-15N heteronuclear dipolar recoupling under fast MAS conditions using R-type symmetry sequences, which is suitable even for fully protonated systems. A series of rotor-synchronized R-type symmetry pulse schemes are explored for the determination of structure and dynamics in biological and organic systems. The investigations of the performance of the various RNnv-symmetry sequences at the MAS frequency of 40 kHz experimentally and by numerical simulations on [U-13C,15N]-alanine and [U-13C,15N]-N-acetyl-valine, revealed excellent performance for sequences with high symmetry number ratio (N/2n > 2.5). Further applications of this approach are presented for two proteins, sparsely 13C/uniformly 15N enriched CAP-Gly domain of dynactin and U-13C,15N-Tyr enriched C-terminal domain of HIV-1 CA protein. 2D and 3D R1632-based DIPSHIFT experiments carried out at the MAS frequency of 40 kHz, yielded site-specific 1H-13C/1H-15N heteronuclear dipolar coupling constants for CAP-Gly and CTD CA, reporting on the dynamic behavior of these proteins on time scales of nano- to microseconds. The R-symmetry based dipolar recoupling under fast MAS is expected to find

  10. Determination of methyl 13C-15N dipolar couplings in peptides and proteins by three-dimensional and four-dimensional magic-angle spinning solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Helmus, Jonathan J.; Nadaud, Philippe S.; Höfer, Nicole; Jaroniec, Christopher P.

    2008-02-01

    We describe three- and four-dimensional semiconstant-time transferred echo double resonance (SCT-TEDOR) magic-angle spinning solid-state nuclear magnetic resonance (NMR) experiments for the simultaneous measurement of multiple long-range N15-Cmethyl13 dipolar couplings in uniformly C13, N15-enriched peptides and proteins with high resolution and sensitivity. The methods take advantage of C13 spin topologies characteristic of the side-chain methyl groups in amino acids alanine, isoleucine, leucine, methionine, threonine, and valine to encode up to three distinct frequencies (N15-Cmethyl13 dipolar coupling, N15 chemical shift, and Cmethyl13 chemical shift) within a single SCT evolution period of initial duration ˜1/JCC1 (where JCC1≈35Hz, is the one-bond Cmethyl13-C13 J-coupling) while concurrently suppressing the modulation of NMR coherences due to C13-C13 and N15-C13 J-couplings and transverse relaxation. The SCT-TEDOR schemes offer several important advantages over previous methods of this type. First, significant (approximately twofold to threefold) gains in experimental sensitivity can be realized for weak N15-Cmethyl13 dipolar couplings (corresponding to structurally interesting, ˜3.5Å or longer, distances) and typical Cmethyl13 transverse relaxation rates. Second, the entire SCT evolution period can be used for Cmethyl13 and/or N15 frequency encoding, leading to increased spectral resolution with minimal additional coherence decay. Third, the experiments are inherently "methyl selective," which results in simplified NMR spectra and obviates the use of frequency-selective pulses or other spectral filtering techniques. Finally, the N15-C13 cross-peak buildup trajectories are purely dipolar in nature (i.e., not influenced by J-couplings or relaxation), which enables the straightforward extraction of N15-Cmethyl13 distances using an analytical model. The SCT-TEDOR experiments are demonstrated on a uniformly C13, N15-labeled peptide, N-acetyl-valine, and a 56

  11. 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

  12. Optimized Spectral Editing of 13C MAS NMR Spectra of Rigid Solids Using Cross-Polarization Methods

    NASA Astrophysics Data System (ADS)

    Sangill, R.; Rastrupandersen, N.; Bildsoe, H.; Jakobsen, H. J.; Nielsen, N. C.

    Combinations of 13C magic-angle spinning (MAS) NMR experiments employing cross polarization (CP), cross polarization-depolarization (CPD), and cross polarization-depolarization-repolarization are analyzed quantitatively to derive simple and general procedures for optimized spectral editing of 13C CP/MAS NMR spectra of rigid solids by separation of the 13C resonances into CH n subspectra ( n = 0, 1, 2, and 3). Special attention is devoted to a differentiation by CPD/MAS of CH and CH 2 resonances since these groups behave quite similarly during spin lock under Hartmann-Hahn match and are therefore generally difficult to distinguish unambiguously. A general procedure for the design of subexperiments and linear combinations of their spectra to provide optimized signal-to-noise ratios for the edited subspectra is described. The technique is illustrated by a series of edited 13C CP/MAS spectra for a number of rigid solids ranging from simple organic compounds (sucrose and l-menthol) to complex pharmaceutical products (calcipotriol monohydrate and vitamin D 3) and polymers (polypropylene, polyvinyl alcohol, polyvinyl chloride, and polystyrene).

  13. Protonation of carbon single-walled nanotubes studied using 13C and 1H-13C cross polarization nuclear magnetic resonance and Raman spectroscopies.

    PubMed

    Engtrakul, Chaiwat; Davis, Mark F; Gennett, Thomas; Dillon, Anne C; Jones, Kim M; Heben, Michael J

    2005-12-14

    The reversible protonation of carbon single-walled nanotubes (SWNTs) in sulfuric acid and Nafion was investigated using solid-state nuclear magnetic resonance (NMR) and Raman spectroscopies. Magic-angle spinning (MAS) was used to obtain high-resolution 13C and 1H-13C cross polarization (CP) NMR spectra. The 13C NMR chemical shifts are reported for bulk SWNTs, H2SO4-treated SWNTs, SWNT-Nafion polymer composites, SWNT-AQ55 polymer composites, and SWNTs in contact with water. Protonation occurs without irreversible oxidation of the nanotube substrate via a charge-transfer process. This is the first report of a chemically induced change in a SWNT 13C resonance brought about by a reversible interaction with an acidic proton, providing additional evidence that carbon nanotubes behave as weak bases. Cross polarization was found to be a powerful technique for providing an additional contrast mechanism for studying nanotubes in contact with other chemical species. The CP studies confirmed polarization transfer from nearby protons to nanotube carbon atoms. The CP technique was also applied to investigate water adsorbed on carbon nanotube surfaces. Finally, the degree of bundling of the SWNTs in Nafion films was probed with the 1H-13C CP-MAS technique. PMID:16332107

  14. Quantitative solid-state 13C NMR with signal enhancement by multiple cross polarization

    NASA Astrophysics Data System (ADS)

    Johnson, Robert L.; Schmidt-Rohr, Klaus

    2014-02-01

    A simple new method is presented that yields quantitative solid-state magic-angle spinning (MAS) 13C NMR spectra of organic materials with good signal-to-noise ratios. It achieves long (>10 ms) cross polarization (CP) from 1H without significant magnetization losses due to relaxation and with a moderate duty cycle of the radio-frequency irradiation, by multiple 1-ms CP periods alternating with 1H spin-lattice relaxation periods that repolarize the protons. The new method incorporates previous techniques that yield less distorted CP/MAS spectra, such as a linear variation (“ramp”) of the radio-frequency field strength, and it overcomes their main limitation, which is T1ρ relaxation of the spin-locked 1H magnetization. The ramp of the radio-frequency field strength and the asymptotic limit of cross polarization makes the spectral intensity quite insensitive to the exact field strengths used. The new multiCP pulse sequence is a “drop-in” replacement for previous CP methods and produces no additional data-processing burden. Compared to the only reliable quantitative 13C NMR method for unlabeled solids previously available, namely direct-polarization NMR, the measuring time is reduced by more than a factor of 50, enabling higher-throughput quantitative NMR studies. The new multiCP technique is validated with 14-kHz MAS on amino-acid derivatives, plant matter, a highly aromatic humic acid, and carbon materials made by low-temperature pyrolysis.

  15. High resolution structural characterization of Aβ42 amyloid fibrils by magic angle spinning NMR.

    PubMed

    Colvin, Michael T; Silvers, Robert; Frohm, Birgitta; Su, Yongchao; Linse, Sara; Griffin, Robert G

    2015-06-17

    The presence of amyloid plaques composed of amyloid beta (Aβ) fibrils is a hallmark of Alzheimer's disease (AD). The Aβ peptide is present as several length variants with two common alloforms consisting of 40 and 42 amino acids, denoted Aβ1-40 and Aβ1-42, respectively. While there have been numerous reports that structurally characterize fibrils of Aβ1-40, very little is known about the structure of amyloid fibrils of Aβ1-42, which are considered the more toxic alloform involved in AD. We have prepared isotopically (13)C/(15)N labeled AβM01-42 fibrils in vitro from recombinant protein and examined their (13)C-(13)C and (13)C-(15)N magic angle spinning (MAS) NMR spectra. In contrast to several other studies of Aβ fibrils, we observe spectra with excellent resolution and a single set of chemical shifts, suggesting the presence of a single fibril morphology. We report the initial structural characterization of AβM01-42 fibrils utilizing (13)C and (15)N shift assignments of 38 of the 43 residues, including the backbone and side chains, obtained through a series of cross-polarization based 2D and 3D (13)C-(13)C, (13)C-(15)N MAS NMR experiments for rigid residues along with J-based 2D TOBSY experiments for dynamic residues. We find that the first ∼5 residues are dynamic and most efficiently detected in a J-based TOBSY spectrum. In contrast, residues 16-42 are easily observed in cross-polarization experiments and most likely form the amyloid core. Calculation of ψ and φ dihedral angles from the chemical shift assignments indicate that 4 β-strands are present in the fibril's secondary structure. PMID:26001057

  16. Magic Angle Spinning NMR of Viruses

    PubMed Central

    Quinn, Caitlin; Lu, Manman; Suiter, Christopher L.; Hou, Guangjin; Zhang, Huilan; Polenova, Tatyana

    2015-01-01

    Viruses, relatively simple pathogens, are able to replicate in many living organisms and to adapt to various environments. Conventional atomic-resolution structural biology techniques, X-ray crystallography and solution NMR spectroscopy provided abundant information on the structures of individual proteins and nucleic acids comprising viruses; however, viral assemblies are not amenable to analysis by these techniques because of their large size, insolubility, and inherent lack of long-range order. In this article, we review the recent advances in magic angle spinning NMR spectroscopy that enabled atomic-resolution analysis of structure and dynamics of large viral systems and give examples of several exciting case studies. PMID:25919197

  17. Functional groups identified by solid state 13C NMR spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Animal manure is generally high in organic matter intensity so it is well suitable for 13C nuclear magnetic resonance (NMR) analysis. Solid-state 13C NMR techniques used in characterizing organic matter and its components include, but are not limited to, cross-polarization /magic angle spinning (CP...

  18. High Resolution Structural Characterization of Aβ42 Amyloid Fibrils by Magic Angle Spinning NMR

    PubMed Central

    2015-01-01

    The presence of amyloid plaques composed of amyloid beta (Aβ) fibrils is a hallmark of Alzheimer’s disease (AD). The Aβ peptide is present as several length variants with two common alloforms consisting of 40 and 42 amino acids, denoted Aβ1–40 and Aβ1–42, respectively. While there have been numerous reports that structurally characterize fibrils of Aβ1–40, very little is known about the structure of amyloid fibrils of Aβ1–42, which are considered the more toxic alloform involved in AD. We have prepared isotopically 13C/15N labeled AβM01–42 fibrils in vitro from recombinant protein and examined their 13C–13C and 13C–15N magic angle spinning (MAS) NMR spectra. In contrast to several other studies of Aβ fibrils, we observe spectra with excellent resolution and a single set of chemical shifts, suggesting the presence of a single fibril morphology. We report the initial structural characterization of AβM01–42 fibrils utilizing 13C and 15N shift assignments of 38 of the 43 residues, including the backbone and side chains, obtained through a series of cross-polarization based 2D and 3D 13C–13C, 13C–15N MAS NMR experiments for rigid residues along with J-based 2D TOBSY experiments for dynamic residues. We find that the first ∼5 residues are dynamic and most efficiently detected in a J-based TOBSY spectrum. In contrast, residues 16–42 are easily observed in cross-polarization experiments and most likely form the amyloid core. Calculation of ψ and φ dihedral angles from the chemical shift assignments indicate that 4 β-strands are present in the fibril’s secondary structure. PMID:26001057

  19. ¹³C cross-polarization magic-angle spinning nuclear magnetic resonance analysis of the solid drug forms with low concentration of an active ingredient-propranolol case.

    PubMed

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

    2014-05-01

    Solid State NMR is a method that could be widely used for analyzing solid state forms of drugs in their original formulations. However, when the concentration of the active pharmaceutical ingredient (API) in the final drug form is low, (13)C CP MAS NMR methods using standard parameters are not efficient. An example of this situation is propranolol, an important drug from the group of beta-blockers whose concentration in the final drug form is low (below 10%). Basing on the differences in the CP kinetics and relaxation parameters for propranolol and the excipients the authors suggest the proper set of the CP MAS experimental parameters that would allow one to analyze API even in small concentrations in the solid drug formulations. PMID:23911072

  20. Simultaneous cross polarization to 13C and 15N with 1H detection at 60 kHz MAS solid-state NMR

    NASA Astrophysics Data System (ADS)

    Das, Bibhuti B.; Opella, Stanley J.

    2016-01-01

    We describe high resolution MAS solid-state NMR experiments that utilize 1H detection with 60 kHz magic angle spinning; simultaneous cross-polarization from 1H to 15N and 13C nuclei; bidirectional cross-polarization between 13C and 15N nuclei; detection of both amide nitrogen and aliphatic carbon 1H; and measurement of both 13C and 15N chemical shifts through multi-dimensional correlation experiments. Three-dimensional experiments correlate amide 1H and alpha 1H selectively with 13C or 15N nuclei in a polypeptide chain. Two separate three-dimensional spectra correlating 1Hα/13Cα/1HN and 1HN/15N/1Hα are recorded simultaneously in a single experiment, demonstrating that a twofold savings in experimental time is potentially achievable. Spectral editing using bidirectional coherence transfer pathways enables simultaneous magnetization transfers between 15N, 13Cα(i) and 13C‧(i-1), facilitating intra- and inter-residue correlations for sequential resonance assignment. Non-uniform sampling is integrated into the experiments, further reducing the length of experimental time.

  1. Solid state nuclear magnetic resonance with magic-angle spinning and dynamic nuclear polarization below 25 K

    NASA Astrophysics Data System (ADS)

    Thurber, Kent R.; Potapov, Alexey; Yau, Wai-Ming; Tycko, Robert

    2013-01-01

    We describe an apparatus for solid state nuclear magnetic resonance (NMR) with dynamic nuclear polarization (DNP) and magic-angle spinning (MAS) at 20-25 K and 9.4 Tesla. The MAS NMR probe uses helium to cool the sample space and nitrogen gas for MAS drive and bearings, as described earlier [1], but also includes a corrugated waveguide for transmission of microwaves from below the probe to the sample. With a 30 mW circularly polarized microwave source at 264 GHz, MAS at 6.8 kHz, and 21 K sample temperature, greater than 25-fold enhancements of cross-polarized 13C NMR signals are observed in spectra of frozen glycerol/water solutions containing the triradical dopant DOTOPA-TEMPO when microwaves are applied. As demonstrations, we present DNP-enhanced one-dimensional and two-dimensional 13C MAS NMR spectra of frozen solutions of uniformly 13C-labeled L-alanine and melittin, a 26-residue helical peptide that we have synthesized with four uniformly 13C-labeled amino acids.

  2. Solid state nuclear magnetic resonance with magic-angle spinning and dynamic nuclear polarization below 25 K

    PubMed Central

    Thurber, Kent R.; Potapov, Alexey; Yau, Wai-Ming; Tycko, Robert

    2012-01-01

    We describe an apparatus for solid state nuclear magnetic resonance (NMR) with dynamic nuclear polarization (DNP) and magic-angle spinning (MAS) at 20–25 K and 9.4 Tesla. The MAS NMR probe uses helium to cool the sample space and nitrogen gas for MAS drive and bearings, as described earlier (Thurber et al., J. Magn. Reson. 2008) [1], but also includes a corrugated waveguide for transmission of microwaves from below the probe to the sample. With a 30 mW circularly polarized microwave source at 264 GHz, MAS at 6.8 kHz, and 21 K sample temperature, greater than 25-fold enhancements of cross-polarized 13C NMR signals are observed in spectra of frozen glycerol/water solutions containing the triradical dopant DOTOPA-TEMPO when microwaves are applied. As demonstrations, we present DNP-enhanced one-dimensional and two-dimensional 13C MAS NMR spectra of frozen solutions of uniformly 13C-labeled L-alanine and melittin, a 26-residue helical peptide that we have synthesized with four uniformly 13C-labeled amino acids. PMID:23238592

  3. High-pressure magic angle spinning nuclear magnetic resonance.

    PubMed

    Hoyt, David W; Turcu, Romulus V F; Sears, Jesse A; Rosso, Kevin M; Burton, Sarah D; Felmy, Andrew R; Hu, Jian Zhi

    2011-10-01

    A high-pressure magic angle spinning (MAS) NMR capability, consisting of a reusable high-pressure MAS rotor, a high-pressure rotor loading/reaction chamber for in situ sealing and re-opening of the high-pressure MAS rotor, and a MAS probe with a localized RF coil for background signal suppression, is reported. The unusual technical challenges associated with development of a reusable high-pressure MAS rotor are addressed in part by modifying standard ceramics for the rotor sleeve by abrading the internal surface at both ends of the cylinder. In this way, not only is the advantage of ceramic cylinders for withstanding very high-pressure utilized, but also plastic bushings can be glued tightly in place so that other removable plastic sealing mechanisms/components and O-rings can be mounted to create the desired high-pressure seal. Using this strategy, sealed internal pressures exceeding 150 bars have been achieved and sustained under ambient external pressure with minimal loss of pressure for 72 h. As an application example, in situ(13)C MAS NMR studies of mineral carbonation reaction intermediates and final products of forsterite (Mg(2)SiO(4)) reacted with supercritical CO(2) and H(2)O at 150 bar and 50°C are reported, with relevance to geological sequestration of carbon dioxide. PMID:21862372

  4. High-pressure magic angle spinning nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Hoyt, David W.; Turcu, Romulus V. F.; Sears, Jesse A.; Rosso, Kevin M.; Burton, Sarah D.; Felmy, Andrew R.; Hu, Jian Zhi

    2011-10-01

    A high-pressure magic angle spinning (MAS) NMR capability, consisting of a reusable high-pressure MAS rotor, a high-pressure rotor loading/reaction chamber for in situ sealing and re-opening of the high-pressure MAS rotor, and a MAS probe with a localized RF coil for background signal suppression, is reported. The unusual technical challenges associated with development of a reusable high-pressure MAS rotor are addressed in part by modifying standard ceramics for the rotor sleeve by abrading the internal surface at both ends of the cylinder. In this way, not only is the advantage of ceramic cylinders for withstanding very high-pressure utilized, but also plastic bushings can be glued tightly in place so that other removable plastic sealing mechanisms/components and O-rings can be mounted to create the desired high-pressure seal. Using this strategy, sealed internal pressures exceeding 150 bars have been achieved and sustained under ambient external pressure with minimal loss of pressure for 72 h. As an application example, in situ13C MAS NMR studies of mineral carbonation reaction intermediates and final products of forsterite (Mg 2SiO 4) reacted with supercritical CO 2 and H 2O at 150 bar and 50 °C are reported, with relevance to geological sequestration of carbon dioxide.

  5. Low-temperature dynamic nuclear polarization with helium-cooled samples and nitrogen-driven magic-angle spinning

    NASA Astrophysics Data System (ADS)

    Thurber, Kent; Tycko, Robert

    2016-03-01

    We describe novel instrumentation for low-temperature solid state nuclear magnetic resonance (NMR) with dynamic nuclear polarization (DNP) and magic-angle spinning (MAS), focusing on aspects of this instrumentation that have not been described in detail in previous publications. We characterize the performance of an extended interaction oscillator (EIO) microwave source, operating near 264 GHz with 1.5 W output power, which we use in conjunction with a quasi-optical microwave polarizing system and a MAS NMR probe that employs liquid helium for sample cooling and nitrogen gas for sample spinning. Enhancement factors for cross-polarized 13C NMR signals in the 100-200 range are demonstrated with DNP at 25 K. The dependences of signal amplitudes on sample temperature, as well as microwave power, polarization, and frequency, are presented. We show that sample temperatures below 30 K can be achieved with helium consumption rates below 1.3 l/h. To illustrate potential applications of this instrumentation in structural studies of biochemical systems, we compare results from low-temperature DNP experiments on a calmodulin-binding peptide in its free and bound states.

  6. Low-temperature dynamic nuclear polarization with helium-cooled samples and nitrogen-driven magic-angle spinning.

    PubMed

    Thurber, Kent; Tycko, Robert

    2016-03-01

    We describe novel instrumentation for low-temperature solid state nuclear magnetic resonance (NMR) with dynamic nuclear polarization (DNP) and magic-angle spinning (MAS), focusing on aspects of this instrumentation that have not been described in detail in previous publications. We characterize the performance of an extended interaction oscillator (EIO) microwave source, operating near 264 GHz with 1.5 W output power, which we use in conjunction with a quasi-optical microwave polarizing system and a MAS NMR probe that employs liquid helium for sample cooling and nitrogen gas for sample spinning. Enhancement factors for cross-polarized (13)C NMR signals in the 100-200 range are demonstrated with DNP at 25K. The dependences of signal amplitudes on sample temperature, as well as microwave power, polarization, and frequency, are presented. We show that sample temperatures below 30K can be achieved with helium consumption rates below 1.3 l/h. To illustrate potential applications of this instrumentation in structural studies of biochemical systems, we compare results from low-temperature DNP experiments on a calmodulin-binding peptide in its free and bound states. PMID:26920835

  7. Measurement of nuclear magnetic dipole—dipole couplings in magic angle spinning NMR

    NASA Astrophysics Data System (ADS)

    Tycko, Robert; Dabbagh, Gary

    1990-10-01

    We describe a method for measuring nuclear magnetic dipole—dipole couplings in NMR spectra of solids undergoing rapid magic angle spinning (MAS). We show in theory, simulations, and experiments that the couplings, which are averaged out by MAS alone, can be recovered by applying simple resonant radiofrequency pulse sequences in synchrony with the sample rotation. Experimental 13C dipolar powder pattern spectra of polycrystalline ( 13CH 3) 2C(OH)SO 3Na obtained in a two-dimensional experiment based on this method are presented. The method provides a means of determining internuclear distances in polycrystalline and noncrystalline solids while retaining the high resolution and sensitivity afforded by MAS.

  8. Magic-angle-spinning NMR studies of zeolite SAPO-5

    NASA Astrophysics Data System (ADS)

    Freude, D.; Ernst, H.; Hunger, M.; Pfeifer, H.; Jahn, E.

    1988-01-01

    SAPO-5 was synthesized using triethylamine as template. Magic-angle-spinning (MAS) NMR of 1H, 27Al, 29Si and 31P was used to study the silicon incorporation into the framework and the nature of the Brønsted sites. 1H MAS NMR shows two types of bridging hydroxyl groups. 29Si MAS NMR indicates that silicon substitutes mostly for phosphorus and that there is a small amount of crystalline SiO 2 in the zeolite powder.

  9. Broadband "Infinite-Speed" Magic-Angle Spinning NMR Spectroscopy

    SciTech Connect

    Hu, Yan-Yan; Levin, E.M; Schmidt-Rohr, Klaus

    2009-06-02

    High-resolution magic-angle spinning NMR of high-Z spin- 1/2 nuclei such as {sup 125}Te, {sup 207}Pb, {sup 119}Sn, {sup 113}Cd, and {sup 195}Pt is often hampered by large (>1000 ppm) chemical-shift anisotropies, which result in strong spinning sidebands that can obscure the centerbands of interest. In various tellurides with applications as thermoelectrics and as phase-change materials for data storage, even 22-kHz magic-angle spinning cannot resolve the center- and sidebands broadened by chemical-shift dispersion, which precludes peak identification or quantification. For sideband suppression over the necessary wide spectral range (up to 200 kHz), radio frequency pulse sequences with few, short pulses are required. We have identified Gan's two-dimensional magic-angle-turning (MAT) experiment with five 90{sup o} pulses as a promising broadband technique for obtaining spectra without sidebands. We have adapted it to broad spectra and fast magic-angle spinning by accounting for long pulses (comparable to the dwell time in t{sub 1}) and short rotation periods. Spectral distortions are small and residual sidebands negligible even for spectra with signals covering a range of 1.5 {gamma}B{sub 1}, due to a favorable disposition of the narrow ranges containing the signals of interest in the spectral plane. The method is demonstrated on various technologically interesting tellurides with spectra spanning up to 170 kHz, at 22 kHz MAS.

  10. Efficient dipolar double quantum filtering under magic angle spinning without a 1H decoupling field

    NASA Astrophysics Data System (ADS)

    Courtney, Joseph M.; Rienstra, Chad M.

    2016-08-01

    We present a systematic study of dipolar double quantum (DQ) filtering in 13C-labeled organic solids over a range of magic-angle spinning rates, using the SPC-n recoupling sequence element with a range of n symmetry values from 3 to 11. We find that efficient recoupling can be achieved for values n ⩾ 7, provided that the 13C nutation frequency is on the order of 100 kHz or greater. The decoupling-field dependence was investigated and explicit heteronuclear decoupling interference conditions identified. The major determinant of DQ filtering efficiency is the decoupling interference between 13C and 1H fields. For 13C nutation frequencies greater than 75 kHz, optimal performance is observed without an applied 1H field. At spinning rates exceeding 20 kHz, symmetry conditions as low as n = 3 were found to perform adequately.

  11. Efficient dipolar double quantum filtering under magic angle spinning without a (1)H decoupling field.

    PubMed

    Courtney, Joseph M; Rienstra, Chad M

    2016-08-01

    We present a systematic study of dipolar double quantum (DQ) filtering in (13)C-labeled organic solids over a range of magic-angle spinning rates, using the SPC-n recoupling sequence element with a range of n symmetry values from 3 to 11. We find that efficient recoupling can be achieved for values n⩾7, provided that the (13)C nutation frequency is on the order of 100kHz or greater. The decoupling-field dependence was investigated and explicit heteronuclear decoupling interference conditions identified. The major determinant of DQ filtering efficiency is the decoupling interference between (13)C and (1)H fields. For (13)C nutation frequencies greater than 75kHz, optimal performance is observed without an applied (1)H field. At spinning rates exceeding 20kHz, symmetry conditions as low as n=3 were found to perform adequately. PMID:27314744

  12. Study of the ferroelastic phase transition in the tetraethylammonium compound [N(C2H5)4]2ZnBr4 by magic-angle spinning and static NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2016-03-01

    The ferroelastic phase transition of tetraethylammonium compound [N(C2H5)4]2ZnBr4 at the phase transition temperature (TC) = 283 K was characterized by magic-angle spinning (MAS) and static nuclear magnetic resonance (NMR), and confirmed by optical polarizing spectroscopy. The structural geometry near TC was studied in terms of the chemical shifts and the spin-lattice relaxation times T1ρ in the rotating frame for 1H MAS NMR and 13C cross-polarization (CP)/MAS NMR. The two inequivalent ethyl groups were distinguishable in the 13C NMR spectrum, and the T1ρ results indicate that they undergo tumbling motion above TC in a coupled manner. From the 14N NMR results, the two nitrogen nuclei in the N(C2H5)4+ ions were distinguishable above TC, and the splitting in the spectra below TC was related to the ferroelastic domains with different orientations.

  13. Double-quantum homonuclear rotary resonance: Efficient dipolar recovery in magic-angle spinning nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Nielsen, N. C.; Bildsøe, H.; Jakobsen, H. J.; Levitt, M. H.

    1994-08-01

    We describe an efficient method for the recovery of homonuclear dipole-dipole interactions in magic-angle spinning NMR. Double-quantum homonuclear rotary resonance (2Q-HORROR) is established by fulfilling the condition ωr=2ω1, where ωr is the sample rotation frequency and ω1 is the nutation frequency around an applied resonant radio frequency (rf) field. This resonance can be used for double-quantum filtering and measurement of homonuclear dipolar interactions in the presence of magic-angle spinning. The spin dynamics depend only weakly on crystallite orientation allowing good performance for powder samples. Chemical shift effects are suppressed to zeroth order. The method is demonstrated for singly and doubly 13C labeled L-alanine.

  14. Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves

    SciTech Connect

    Thurber, Kent R. Tycko, Robert

    2014-05-14

    We report solid state {sup 13}C and {sup 1}H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, {sup 1}H and cross-polarized {sup 13}C NMR signals from {sup 15}N,{sup 13}C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T{sub 1e} is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations.

  15. Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves

    PubMed Central

    Thurber, Kent R.; Tycko, Robert

    2014-01-01

    We report solid state 13C and 1H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, 1H and cross-polarized 13C NMR signals from 15N,13C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T1e is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations. PMID:24832263

  16. Rapid proton-detected NMR assignment for proteins with fast magic angle spinning.

    PubMed

    Barbet-Massin, Emeline; Pell, Andrew J; Retel, Joren S; Andreas, Loren B; Jaudzems, Kristaps; Franks, W Trent; Nieuwkoop, Andrew J; Hiller, Matthias; Higman, Victoria; Guerry, Paul; Bertarello, Andrea; Knight, Michael J; Felletti, Michele; Le Marchand, Tanguy; Kotelovica, Svetlana; Akopjana, Inara; Tars, Kaspars; Stoppini, Monica; Bellotti, Vittorio; Bolognesi, Martino; Ricagno, Stefano; Chou, James J; Griffin, Robert G; Oschkinat, Hartmut; Lesage, Anne; Emsley, Lyndon; Herrmann, Torsten; Pintacuda, Guido

    2014-09-01

    Using a set of six (1)H-detected triple-resonance NMR experiments, we establish a method for sequence-specific backbone resonance assignment of magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of 5-30 kDa proteins. The approach relies on perdeuteration, amide (2)H/(1)H exchange, high magnetic fields, and high-spinning frequencies (ωr/2π ≥ 60 kHz) and yields high-quality NMR data, enabling the use of automated analysis. The method is validated with five examples of proteins in different condensed states, including two microcrystalline proteins, a sedimented virus capsid, and two membrane-embedded systems. In comparison to contemporary (13)C/(15)N-based methods, this approach facilitates and accelerates the MAS NMR assignment process, shortening the spectral acquisition times and enabling the use of unsupervised state-of-the-art computational data analysis protocols originally developed for solution NMR. PMID:25102442

  17. Magic-angle-spinning NMR studies of acid sites in zeolite H-ZSM-5

    SciTech Connect

    Brunner, E.; Ernst, H.; Freude, D.; Froehlich, T.; Hunger, M.; Pfeifer, H. )

    1991-01-01

    {sup 1}H, {sup 13}C, {sup 27}Al, and {sup 29}Si magic-angle-spinning (MAS) NMR was used to elucidate the nature of the catalytic activity of zeolite H-ZSM-5. {sup 1}H MAS NMR of sealed samples after mild hydrothermal dealumination shows that the enhanced activity for n-hexane cracking is not due to an enhanced Bronstead acidity. The concentrations of the various OH groups and aluminous species suggest that the reason for the enhanced catalytic activity is the interaction of the n-hexane molecule with a bridging hydroxyl group and with extra-framework aluminium species, which give rise to the enhanced activity, cannot be easily removed from their positions, and are therefore immobilized by the zeolitic framework.

  18. Selective excitation enables assignment of proton resonances and (1)H-(1)H distance measurement in ultrafast magic angle spinning solid state NMR spectroscopy.

    PubMed

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2015-07-21

    Remarkable developments in ultrafast magic angle spinning (MAS) solid-state NMR spectroscopy enabled proton-based high-resolution multidimensional experiments on solids. To fully utilize the benefits rendered by proton-based ultrafast MAS experiments, assignment of (1)H resonances becomes absolutely necessary. Herein, we propose an approach to identify different proton peaks by using dipolar-coupled heteronuclei such as (13)C or (15)N. In this method, after the initial preparation of proton magnetization and cross-polarization to (13)C nuclei, transverse magnetization of desired (13)C nuclei is selectively prepared by using DANTE (Delays Alternating with Nutations for Tailored Excitation) sequence and then, it is transferred to bonded protons with a short-contact-time cross polarization. Our experimental results demonstrate that protons bonded to specific (13)C atoms can be identified and overlapping proton peaks can also be assigned. In contrast to the regular 2D HETCOR experiment, only a few 1D experiments are required for the complete assignment of peaks in the proton spectrum. Furthermore, the finite-pulse radio frequency driven recoupling sequence could be incorporated right after the selection of specific proton signals to monitor the intensity buildup for other proton signals. This enables the extraction of (1)H-(1)H distances between different pairs of protons. Therefore, we believe that the proposed method will greatly aid in fast assignment of peaks in proton spectra and will be useful in the development of proton-based multi-dimensional solid-state NMR experiments to study atomic-level resolution structure and dynamics of solids. PMID:26203019

  19. Selective excitation enables assignment of proton resonances and 1H-1H distance measurement in ultrafast magic angle spinning solid state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2015-07-01

    Remarkable developments in ultrafast magic angle spinning (MAS) solid-state NMR spectroscopy enabled proton-based high-resolution multidimensional experiments on solids. To fully utilize the benefits rendered by proton-based ultrafast MAS experiments, assignment of 1H resonances becomes absolutely necessary. Herein, we propose an approach to identify different proton peaks by using dipolar-coupled heteronuclei such as 13C or 15N. In this method, after the initial preparation of proton magnetization and cross-polarization to 13C nuclei, transverse magnetization of desired 13C nuclei is selectively prepared by using DANTE (Delays Alternating with Nutations for Tailored Excitation) sequence and then, it is transferred to bonded protons with a short-contact-time cross polarization. Our experimental results demonstrate that protons bonded to specific 13C atoms can be identified and overlapping proton peaks can also be assigned. In contrast to the regular 2D HETCOR experiment, only a few 1D experiments are required for the complete assignment of peaks in the proton spectrum. Furthermore, the finite-pulse radio frequency driven recoupling sequence could be incorporated right after the selection of specific proton signals to monitor the intensity buildup for other proton signals. This enables the extraction of 1H-1H distances between different pairs of protons. Therefore, we believe that the proposed method will greatly aid in fast assignment of peaks in proton spectra and will be useful in the development of proton-based multi-dimensional solid-state NMR experiments to study atomic-level resolution structure and dynamics of solids.

  20. Selective excitation enables assignment of proton resonances and {sup 1}H-{sup 1}H distance measurement in ultrafast magic angle spinning solid state NMR spectroscopy

    SciTech Connect

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2015-07-21

    Remarkable developments in ultrafast magic angle spinning (MAS) solid-state NMR spectroscopy enabled proton-based high-resolution multidimensional experiments on solids. To fully utilize the benefits rendered by proton-based ultrafast MAS experiments, assignment of {sup 1}H resonances becomes absolutely necessary. Herein, we propose an approach to identify different proton peaks by using dipolar-coupled heteronuclei such as {sup 13}C or {sup 15}N. In this method, after the initial preparation of proton magnetization and cross-polarization to {sup 13}C nuclei, transverse magnetization of desired {sup 13}C nuclei is selectively prepared by using DANTE (Delays Alternating with Nutations for Tailored Excitation) sequence and then, it is transferred to bonded protons with a short-contact-time cross polarization. Our experimental results demonstrate that protons bonded to specific {sup 13}C atoms can be identified and overlapping proton peaks can also be assigned. In contrast to the regular 2D HETCOR experiment, only a few 1D experiments are required for the complete assignment of peaks in the proton spectrum. Furthermore, the finite-pulse radio frequency driven recoupling sequence could be incorporated right after the selection of specific proton signals to monitor the intensity buildup for other proton signals. This enables the extraction of {sup 1}H-{sup 1}H distances between different pairs of protons. Therefore, we believe that the proposed method will greatly aid in fast assignment of peaks in proton spectra and will be useful in the development of proton-based multi-dimensional solid-state NMR experiments to study atomic-level resolution structure and dynamics of solids.

  1. Solid-state 13C NMR study of banana liquid crystals - 3: Alkyl-tail-group packing environments of an acute-angle bent-core molecule in the hexagonal columnar and cubic phases

    NASA Astrophysics Data System (ADS)

    Kurosu, Hiromichi; Endo, Yumi; Kimura, Saori; Hashimoto, Tomoko; Harada, Motoi; Lee, Eun-Woo; Sone, Masato; Watanabe, Junji; Kang, Sungmin

    2016-02-01

    Solid-state 13C nuclear magnetic resonance (NMR) measurements were performed on the hexagonal columnar and cubic phases of an acute-angle banana-shaped molecule, N(1,7)-S30. In the hexagonal columnar phase, three peaks appear at the NMR chemical shifts assigned to the internal methylene carbons of alkyl tails, indicating that the two alkyl tails have different packing structures, and one of the tails has two different conformations within a single molecule. Combined cross-polarization/magic-angle spinning and pulse saturation transfer/magic-angle spinning measurements show that one of the alkyl chains is located inside and the other is located outside the columnar structure. In the cubic phase, pulse saturation transfer/magic-angle spinning measurement shows that only one peak appears at the NMR chemical shifts assigned to the internal methylene carbons of alkyl tails, indicating that both of the alkyl chains are located outside the cubic structure.

  2. Recoupling of chemical shift anisotropy by R-symmetry sequences in magic angle spinning NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Hou, Guangjin; Byeon, In-Ja L.; Ahn, Jinwoo; Gronenborn, Angela M.; Polenova, Tatyana

    2012-10-01

    13C and 15N chemical shift (CS) interaction is a sensitive probe of structure and dynamics in a wide variety of biological and inorganic systems, and in the recent years several magic angle spinning NMR approaches have emerged for residue-specific measurements of chemical shift anisotropy (CSA) tensors in uniformly and sparsely enriched proteins. All of the currently existing methods are applicable to slow and moderate magic angle spinning (MAS) regime, i.e., MAS frequencies below 20 kHz. With the advent of fast and ultrafast MAS probes capable of spinning frequencies of 40-100 kHz, and with the superior resolution and sensitivity attained at such high frequencies, development of CSA recoupling techniques working under such conditions is necessary. In this work, we present a family of R-symmetry based pulse sequences for recoupling of 13C/15N CSA interactions that work well in both natural abundance and isotopically enriched systems. We demonstrate that efficient recoupling of either first-rank (σ1) or second-rank (σ2) spatial components of CSA interaction is attained with appropriately chosen γ-encoded RNnv symmetry sequences. The advantage of these γ-encoded RNnv-symmetry based CSA (RNCSA) recoupling schemes is that they are suitable for CSA recoupling under a wide range of MAS frequencies, including fast MAS regime. Comprehensive analysis of the recoupling properties of these RNnv symmetry sequences reveals that the σ1-CSA recoupling symmetry sequences exhibit large scaling factors; however, the partial homonuclear dipolar Hamiltonian components are symmetry allowed, which makes this family of sequences suitable for CSA measurements in systems with weak homonuclear dipolar interactions. On the other hand, the γ-encoded symmetry sequences for σ2-CSA recoupling have smaller scaling factors but they efficiently suppress the homonuclear dipole-dipole interactions. Therefore, the latter family of sequences is applicable for measurements of CSA parameters in

  3. Intermolecular structure determination of amyloid fibrils with magic-angle spinning and dynamic nuclear polarization NMR

    PubMed Central

    Bayro, Marvin J.; Debelouchina, Galia T.; Eddy, Matthew T.; Birkett, Neil R.; MacPhee, Catherine E.; Rosay, Melanie; Maas, Werner E.; Dobson, Christopher M.

    2011-01-01

    We describe magic-angle spinning NMR experiments designed to elucidate the interstrand architecture of amyloid fibrils. Three methods are introduced for this purpose, two being based on the analysis of long-range 13C-13C correlation spectra and a third based on the identification of intermolecular interactions in 13C-15N spectra. We show, in studies of fibrils formed by the 86-residue SH3 domain of PI3 kinase (PI3-SH3), that efficient 13C-13C correlation spectra display a resonance degeneracy that establishes a parallel, in-register alignment of the proteins in the amyloid fibrils. In addition, this degeneracy can be circumvented to yield direct intermolecular constraints. The 13C-13C experiments are corroborated by 15N-13C correlation spectrum obtained from a mixed [15N,12C]/[14N,13C] sample which directly quantifies interstrand distances. Furthermore, when the spectra are recorded with signal enhancement provided by dynamic nuclear polarization (DNP) at 100 K, we demonstrate a dramatic increase (from 23 to 52) in the number of intermolecular 15N-13C constraints present in the spectra. The increase in the information content is due to the enhanced signal intensities and to the fact that dynamic processes, leading to spectral intensity losses, are quenched at low temperatures. Thus, acquisition of low temperature spectra addresses a problem that is frequently encountered in MAS spectra of proteins. In total the experiments provide 111 intermolecular 13C-13C and 15N-13C constraints that establish that the PI3-SH3 protein strands are aligned in a parallel, in-register arrangement within the amyloid fibril. PMID:21774549

  4. Structure of a protein determined by solid-state magic-angle-spinning NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Castellani, Federica; van Rossum, Barth; Diehl, Annette; Schubert, Mario; Rehbein, Kristina; Oschkinat, Hartmut

    2002-11-01

    The determination of a representative set of protein structures is a chief aim in structural genomics. Solid-state NMR may have a crucial role in structural investigations of those proteins that do not easily form crystals or are not accessible to solution NMR, such as amyloid systems or membrane proteins. Here we present a protein structure determined by solid-state magic-angle-spinning (MAS) NMR. Almost complete 13C and 15N resonance assignments for a micro-crystalline preparation of the α-spectrin Src-homology 3 (SH3) domain formed the basis for the extraction of a set of distance restraints. These restraints were derived from proton-driven spin diffusion (PDSD) spectra of biosynthetically site-directed, labelled samples obtained from bacteria grown using [1,3-13C]glycerol or [2-13C]glycerol as carbon sources. This allowed the observation of long-range distance correlations up to ~7Å. The calculated global fold of the α-spectrin SH3 domain is based on 286 inter-residue 13C-13C and six 15N-15N restraints, all self-consistently obtained by solid-state MAS NMR. This MAS NMR procedure should be widely applicable to small membrane proteins that can be expressed in bacteria.

  5. Variable-effective-field cross polarization. An approach to broadband Hartmann-Hahn matching in MAS NMR

    NASA Astrophysics Data System (ADS)

    Kolbert, Andrew C.; Gann, Sheryl L.

    1994-07-01

    A method for broadening the Hartmann-Hahn matching condition for cross polarization under magic angle spinning is presented. Variable-effective-field cross polarization (VEFCP) employs different effective raido-frequency (rf) fields on the 1H channel during mixing, while the 13C rf field remains constant. VEFCP is shown to result in both a broader matching condition, and a more rapid polarization transfer than ordinary cross polarization at the Hartmann-Hahn match. Experimental results on both adamantane and polycarbonate are discussed.

  6. High-pressure magic angle spinning nuclear magnetic resonance

    SciTech Connect

    Hoyt, David W.; Turcu, Romulus V. F.; Sears, Jesse A.; Rosso, Kevin M.; Burton, Sarah D.; Felmy, Andrew R.; Hu, Jian Zhi

    2011-10-01

    A high-pressure magic angle spinning (MAS) NMR capability, consisting of a reusable high-pressure MAS rotor, a high-pressure rotor loading/reaction chamber for in situ sealing and re-opening of the high-pressure MAS rotor, and a MAS probe with a localized RF coil for background signal suppression, is reported. The unusual technical challenges associated with development of a reusable high-pressure MAS rotor are addressed in part by modifying standard ceramics for the rotor sleeve by abrading the internal surface at both ends of the cylinder. In this way, not only is the advantage of ceramic cylinders for withstanding very high-pressure utilized, but also plastic bushings can be glued tightly in place so that other removable plastic sealing mechanisms/components and O-rings can be mounted to create the desired high-pressure seal. Using this strategy, sealed internal pressures exceeding 150 bars have been achieved and sustained under ambient external pressure with minimal loss of pressure for 72 h. Finally, as an application example, in situ13C MAS NMR studies of mineral carbonation reaction intermediates and final products of forsterite (Mg2SiO4) reacted with supercritical CO2 and H2O at 150 bar and 50 °C are reported, with relevance to geological sequestration of carbon dioxide.

  7. Solid effect in magic angle spinning dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Corzilius, Björn; Smith, Albert A.; Griffin, Robert G.

    2012-08-01

    For over five decades, the solid effect (SE) has been heavily utilized as a mechanism for performing dynamic nuclear polarization (DNP). Nevertheless, it has not found widespread application in contemporary, high magnetic field DNP experiments because SE enhancements display an ω _0 ^{ - 2} field dependence. In particular, for nominally forbidden zero and double quantum SE transitions to be partially allowed, it is necessary for mixing of adjacent nuclear spin states to occur, and this leads to the observed field dependence. However, recently we have improved our instrumentation and report here an enhancement of ɛ = 91 obtained with the organic radical trityl (OX063) in magic angle spinning experiments performed at 5 T and 80 K. This is a factor of 6-7 higher than previous values in the literature under similar conditions. Because the solid effect depends strongly on the microwave field strength, we attribute this large enhancement to larger microwave field strengths inside the sample volume, achieved with more efficient coupling of the gyrotron to the sample chamber. In addition, we develop a theoretical model to explain the dependence of the buildup rate of enhanced nuclear polarization and the steady-state enhancement on the microwave power. Buildup times and enhancements were measured as a function of 1H concentration for both trityl and Gd-DOTA. Comparison of the results indicates that for trityl the initial polarization step is the slower, rate-determining step. However, for Gd-DOTA the spread of nuclear polarization via homonuclear 1H spin diffusion is rate-limiting. Finally, we discuss the applicability of the solid effect at fields > 5 T and the requirements to address the unfavorable field dependence of the solid effect.

  8. Solid effect in magic angle spinning dynamic nuclear polarization

    PubMed Central

    Corzilius, Björn; Smith, Albert A.; Griffin, Robert G.

    2012-01-01

    For over five decades, the solid effect (SE) has been heavily utilized as a mechanism for performing dynamic nuclear polarization (DNP). Nevertheless, it has not found widespread application in contemporary, high magnetic field DNP experiments because SE enhancements display an \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}\\omega _0 ^{ - 2}\\end{equation*} \\end{document}ω0−2 field dependence. In particular, for nominally forbidden zero and double quantum SE transitions to be partially allowed, it is necessary for mixing of adjacent nuclear spin states to occur, and this leads to the observed field dependence. However, recently we have improved our instrumentation and report here an enhancement of ɛ = 91 obtained with the organic radical trityl (OX063) in magic angle spinning experiments performed at 5 T and 80 K. This is a factor of 6-7 higher than previous values in the literature under similar conditions. Because the solid effect depends strongly on the microwave field strength, we attribute this large enhancement to larger microwave field strengths inside the sample volume, achieved with more efficient coupling of the gyrotron to the sample chamber. In addition, we develop a theoretical model to explain the dependence of the buildup rate of enhanced nuclear polarization and the steady-state enhancement on the microwave power. Buildup times and enhancements were measured as a function of 1H concentration for both trityl and Gd-DOTA. Comparison of the results indicates that for trityl the initial polarization step is the slower, rate-determining step. However, for Gd-DOTA the spread of nuclear polarization via homonuclear 1H spin diffusion is rate-limiting. Finally, we discuss the applicability of the solid effect at fields > 5 T and the requirements

  9. Solid effect in magic angle spinning dynamic nuclear polarization.

    PubMed

    Corzilius, Björn; Smith, Albert A; Griffin, Robert G

    2012-08-01

    For over five decades, the solid effect (SE) has been heavily utilized as a mechanism for performing dynamic nuclear polarization (DNP). Nevertheless, it has not found widespread application in contemporary, high magnetic field DNP experiments because SE enhancements display an ω(0)(-2) field dependence. In particular, for nominally forbidden zero and double quantum SE transitions to be partially allowed, it is necessary for mixing of adjacent nuclear spin states to occur, and this leads to the observed field dependence. However, recently we have improved our instrumentation and report here an enhancement of ε = 91 obtained with the organic radical trityl (OX063) in magic angle spinning experiments performed at 5 T and 80 K. This is a factor of 6-7 higher than previous values in the literature under similar conditions. Because the solid effect depends strongly on the microwave field strength, we attribute this large enhancement to larger microwave field strengths inside the sample volume, achieved with more efficient coupling of the gyrotron to the sample chamber. In addition, we develop a theoretical model to explain the dependence of the buildup rate of enhanced nuclear polarization and the steady-state enhancement on the microwave power. Buildup times and enhancements were measured as a function of (1)H concentration for both trityl and Gd-DOTA. Comparison of the results indicates that for trityl the initial polarization step is the slower, rate-determining step. However, for Gd-DOTA the spread of nuclear polarization via homonuclear (1)H spin diffusion is rate-limiting. Finally, we discuss the applicability of the solid effect at fields > 5 T and the requirements to address the unfavorable field dependence of the solid effect. PMID:22894339

  10. Magic-angle-spinning NMR of the drug resistant S31N M2 proton transporter from influenza A.

    PubMed

    Andreas, Loren B; Eddy, Matthew T; Chou, James J; Griffin, Robert G

    2012-05-01

    We report chemical shift assignments of the drug-resistant S31N mutant of M2(18-60) determined using 3D magic-angle-spinning (MAS) NMR spectra acquired with a (15)N-(13)C ZF-TEDOR transfer followed by (13)C-(13)C mixing by RFDR. The MAS spectra reveal two sets of resonances, indicating that the tetramer assembles as a dimer of dimers, similar to the wild-type channel. Helicies from the two sets of chemical shifts are shown to be in close proximity at residue H37, and the assignments reveal a difference in the helix torsion angles, as predicted by TALOS+, for the key resistance residue N31. In contrast to wild-type M2(18-60), chemical shift changes are minimal upon addition of the inhibitor rimantadine, suggesting that the drug does not bind to S31N M2. PMID:22480220

  11. Theoretical aspects of Magic Angle Spinning - Dynamic Nuclear Polarization

    NASA Astrophysics Data System (ADS)

    Mentink-Vigier, Frederic; Akbey, Ümit; Oschkinat, Hartmut; Vega, Shimon; Feintuch, Akiva

    2015-09-01

    Magic Angle Spinning (MAS) combined with Dynamic Nuclear Polarization (DNP) has been proven in recent years to be a very powerful method for increasing solid-state NMR signals. Since the advent of biradicals such as TOTAPOL to increase the nuclear polarization new classes of radicals, with larger molecular weight and/or different spin properties have been developed. These have led to unprecedented signal gain, with varying results for different experimental parameters, in particular the microwave irradiation strength, the static field, and the spinning frequency. Recently it has been demonstrated that sample spinning imposes DNP enhancement processes that differ from the active DNP mechanism in static samples as upon sample spinning the DNP enhancements are the results of energy level anticrossings occurring periodically during each rotor cycle. In this work we present experimental results with regards to the MAS frequency dependence of the DNP enhancement profiles of four nitroxide-based radicals at two different sets of temperature, 110 and 160 K. In fact, different magnitudes of reduction in enhancement are observed with increasing spinning frequency. Our simulation code for calculating MAS-DNP powder enhancements of small model spin systems has been improved to extend our studies of the influence of the interaction and relaxation parameters on powder enhancements. To achieve a better understanding we simulated the spin dynamics of a single three-spin system {ea -eb - n } during its steady state rotor periods and used the Landau-Zener formula to characterize the influence of the different anti-crossings on the polarizations of the system and their necessary action for reaching steady state conditions together with spin relaxation processes. Based on these model calculations we demonstrate that the maximum steady state nuclear polarization cannot become larger than the maximum polarization difference between the two electrons during the steady state rotor cycle

  12. Theoretical aspects of Magic Angle Spinning - Dynamic Nuclear Polarization.

    PubMed

    Mentink-Vigier, Frederic; Akbey, Ümit; Oschkinat, Hartmut; Vega, Shimon; Feintuch, Akiva

    2015-09-01

    Magic Angle Spinning (MAS) combined with Dynamic Nuclear Polarization (DNP) has been proven in recent years to be a very powerful method for increasing solid-state NMR signals. Since the advent of biradicals such as TOTAPOL to increase the nuclear polarization new classes of radicals, with larger molecular weight and/or different spin properties have been developed. These have led to unprecedented signal gain, with varying results for different experimental parameters, in particular the microwave irradiation strength, the static field, and the spinning frequency. Recently it has been demonstrated that sample spinning imposes DNP enhancement processes that differ from the active DNP mechanism in static samples as upon sample spinning the DNP enhancements are the results of energy level anticrossings occurring periodically during each rotor cycle. In this work we present experimental results with regards to the MAS frequency dependence of the DNP enhancement profiles of four nitroxide-based radicals at two different sets of temperature, 110 and 160K. In fact, different magnitudes of reduction in enhancement are observed with increasing spinning frequency. Our simulation code for calculating MAS-DNP powder enhancements of small model spin systems has been improved to extend our studies of the influence of the interaction and relaxation parameters on powder enhancements. To achieve a better understanding we simulated the spin dynamics of a single three-spin system {ea-eb-n} during its steady state rotor periods and used the Landau-Zener formula to characterize the influence of the different anti-crossings on the polarizations of the system and their necessary action for reaching steady state conditions together with spin relaxation processes. Based on these model calculations we demonstrate that the maximum steady state nuclear polarization cannot become larger than the maximum polarization difference between the two electrons during the steady state rotor cycle. This

  13. A LOW-E MAGIC ANGLE SPINNING PROBE FOR BIOLOGICAL SOLID STATE NMR AT 750 MHz

    PubMed Central

    McNeill, Seth A.; Gor’kov, Peter L.; Shetty, Kiran; Brey, William W.; Long, Joanna R.

    2009-01-01

    Crossed-coil NMR probes are a useful tool for reducing sample heating for biological solid state NMR. In a crossed-coil probe, the higher frequency 1H field, which is the primary source of sample heating in conventional probes, is produced by a separate low-inductance resonator. Because a smaller driving voltage is required, the electric field across the sample and the resultant heating is reduced. In this work we describe the development of a magic angle spinning (MAS) solid state NMR probe utilizing a dual resonator. This dual resonator approach, referred to as “Low-E,” was originally developed to reduce heating in samples of mechanically aligned membranes. The study of inherently dilute systems, such as proteins in lipid bilayers, via MAS techniques requires large sample volumes at high field to obtain spectra with adequate signal-to-noise ratio under physiologically relevant conditions. With the Low-E approach, we are able to obtain homogeneous and sufficiently strong radiofrequency fields for both 1H and 13C frequencies in a 4 mm probe with a 1H frequency of 750 MHz. The performance of the probe using windowless dipolar recoupling sequences is demonstrated on model compounds as well as membrane embedded peptides. PMID:19138870

  14. Molecular orientational dynamics in solid C70: Investigation by one- and two-dimensional magic angle spinning nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Tycko, R.; Dabbagh, G.; Vaughan, G. B. M.; Heiney, P. A.; Strongin, R. M.; Cichy, M. A.; Smith, A. B., III

    1993-11-01

    We present the results of 13C nuclear magnetic resonance (NMR) measurements that probe molecular orientational dynamics in solid C70 in the temperature range 223-343 K. Orientational dynamics affect the NMR line shapes and spin-lattice relaxation rates by modulating the 13C chemical shift anisotropy (CSA). Motionally averaged CSA line shapes, determined from both one-dimensional and two-dimensional magic angle spinning NMR spectra, and relaxation rates are determined for each of the five inequivalent carbon sites in the C70 molecule. Comparisons of the results for the five sites provide evidence for rapid uniaxial molecular reorientation in the monoclinic (T≤280 K) and rhombohedral (280≤T≤330 K) phases and rapid isotropic reorientation in the face-centered cubic (T≥330 K) phase. The orientational correlation time is roughly 2 ns at 250 K and of the order of 5 ps at 340 K.

  15. Microwave field distribution in a magic angle spinning dynamic nuclear polarization NMR probe

    NASA Astrophysics Data System (ADS)

    Nanni, Emilio A.; Barnes, Alexander B.; Matsuki, Yoh; Woskov, Paul P.; Corzilius, Björn; Griffin, Robert G.; Temkin, Richard J.

    2011-05-01

    We present a calculation of the microwave field distribution in a magic angle spinning (MAS) probe utilized in dynamic nuclear polarization (DNP) experiments. The microwave magnetic field (B 1 S) profile was obtained from simulations performed with the High Frequency Structure Simulator (HFSS) software suite, using a model that includes the launching antenna, the outer Kel-F stator housing coated with Ag, the RF coil, and the 4 mm diameter sapphire rotor containing the sample. The predicted average B 1 S field is 13 μT/W 1/2, where S denotes the electron spin. For a routinely achievable input power of 5 W the corresponding value is γSB 1 S = 0.84 MHz. The calculations provide insights into the coupling of the microwave power to the sample, including reflections from the RF coil and diffraction of the power transmitted through the coil. The variation of enhancement with rotor wall thickness was also successfully simulated. A second, simplified calculation was performed using a single pass model based on Gaussian beam propagation and Fresnel diffraction. This model provided additional physical insight and was in good agreement with the full HFSS simulation. These calculations indicate approaches to increasing the coupling of the microwave power to the sample, including the use of a converging lens and fine adjustment of the spacing of the windings of the RF coil. The present results should prove useful in optimizing the coupling of microwave power to the sample in future DNP experiments. Finally, the results of the simulation were used to predict the cross effect DNP enhancement ( ɛ) vs. ω1 S/(2 π) for a sample of 13C-urea dissolved in a 60:40 glycerol/water mixture containing the polarizing agent TOTAPOL; very good agreement was obtained between theory and experiment.

  16. Rotor Design for High Pressure Magic Angle Spinning Nuclear Magnetic Resonance

    SciTech Connect

    Turcu, Romulus V.F.; Hoyt, David W.; Rosso, Kevin M.; Sears, Jesse A.; Loring, John S.; Felmy, Andrew R.; Hu, Jian Z.

    2013-01-01

    High pressure magic angle spinning (MAS) nuclear magnetic resonance (NMR) with a sample spinning rate exceeding 2.1 kHz and pressure greater than 165 bar has never been realized. In this work, a new sample cell design is reported, suitable for constructing cells of different sizes. Using a 7.5 mm high pressure MAS rotor as an example, internal pressure as high as 200 bar at a sample spinning rate of 6 kHz is achieved. The new high pressure MAS rotor is re-usable and compatible with most commercial NMR set-ups, exhibiting low 1H and 13C NMR background and offering maximal NMR sensitivity. As an example of its many possible applications, this new capability is applied to determine reaction products associated with the carbonation reaction of a natural mineral, antigorite ((Mg,Fe2+)3Si2O5(OH)4), in contact with liquid water in water-saturated supercritical CO2 (scCO2) at 150 bar and 50 deg C. This mineral is relevant to the deep geologic disposal of CO2, but its iron content results in too many sample spinning sidebands at low spinning rate. Hence, this chemical system is a good case study to demonstrate the utility of the higher sample spinning rates that can be achieved by our new rotor design. We expect this new capability will be useful for exploring solid-state, including interfacial, chemistry at new levels of high-pressure in a wide variety of fields.

  17. Rotor design for high pressure magic angle spinning nuclear magnetic resonance.

    PubMed

    Turcu, Romulus V F; Hoyt, David W; Rosso, Kevin M; Sears, Jesse A; Loring, John S; Felmy, Andrew R; Hu, Jian Zhi

    2013-01-01

    High pressure magic angle spinning (MAS) nuclear magnetic resonance (NMR) with a sample spinning rate exceeding 2.1 kHz and pressure greater than 165 bar has never been realized. In this work, a new sample cell design is reported, suitable for constructing cells of different sizes. Using a 7.5 mm high pressure MAS rotor as an example, internal pressure as high as 200 bar at a sample spinning rate of 6 kHz is achieved. The new high pressure MAS rotor is re-usable and compatible with most commercial NMR set-ups, exhibiting low (1)H and (13)C NMR background and offering maximal NMR sensitivity. As an example of its many possible applications, this new capability is applied to determine reaction products associated with the carbonation reaction of a natural mineral, antigorite ((Mg,Fe(2+))(3)Si(2)O(5)(OH)(4)), in contact with liquid water in water-saturated supercritical CO(2) (scCO(2)) at 150 bar and 50°C. This mineral is relevant to the deep geologic disposal of CO(2), but its iron content results in too many sample spinning sidebands at low spinning rate. Hence, this chemical system is a good case study to demonstrate the utility of the higher sample spinning rates that can be achieved by our new rotor design. We expect this new capability will be useful for exploring solid-state, including interfacial, chemistry at new levels of high-pressure in a wide variety of fields. PMID:23220181

  18. Rotor design for high pressure magic angle spinning nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Turcu, Romulus V. F.; Hoyt, David W.; Rosso, Kevin M.; Sears, Jesse A.; Loring, John S.; Felmy, Andrew R.; Hu, Jian Zhi

    2013-01-01

    High pressure magic angle spinning (MAS) nuclear magnetic resonance (NMR) with a sample spinning rate exceeding 2.1 kHz and pressure greater than 165 bar has never been realized. In this work, a new sample cell design is reported, suitable for constructing cells of different sizes. Using a 7.5 mm high pressure MAS rotor as an example, internal pressure as high as 200 bar at a sample spinning rate of 6 kHz is achieved. The new high pressure MAS rotor is re-usable and compatible with most commercial NMR set-ups, exhibiting low 1H and 13C NMR background and offering maximal NMR sensitivity. As an example of its many possible applications, this new capability is applied to determine reaction products associated with the carbonation reaction of a natural mineral, antigorite ((Mg,Fe2+)3Si2O5(OH)4), in contact with liquid water in water-saturated supercritical CO2 (scCO2) at 150 bar and 50 °C. This mineral is relevant to the deep geologic disposal of CO2, but its iron content results in too many sample spinning sidebands at low spinning rate. Hence, this chemical system is a good case study to demonstrate the utility of the higher sample spinning rates that can be achieved by our new rotor design. We expect this new capability will be useful for exploring solid-state, including interfacial, chemistry at new levels of high-pressure in a wide variety of fields.

  19. Microwave field distribution in a magic angle spinning dynamic nuclear polarization NMR probe.

    PubMed

    Nanni, Emilio A; Barnes, Alexander B; Matsuki, Yoh; Woskov, Paul P; Corzilius, Björn; Griffin, Robert G; Temkin, Richard J

    2011-05-01

    We present a calculation of the microwave field distribution in a magic angle spinning (MAS) probe utilized in dynamic nuclear polarization (DNP) experiments. The microwave magnetic field (B(1S)) profile was obtained from simulations performed with the High Frequency Structure Simulator (HFSS) software suite, using a model that includes the launching antenna, the outer Kel-F stator housing coated with Ag, the RF coil, and the 4mm diameter sapphire rotor containing the sample. The predicted average B(1S) field is 13μT/W(1/2), where S denotes the electron spin. For a routinely achievable input power of 5W the corresponding value is γ(S)B(1S)=0.84MHz. The calculations provide insights into the coupling of the microwave power to the sample, including reflections from the RF coil and diffraction of the power transmitted through the coil. The variation of enhancement with rotor wall thickness was also successfully simulated. A second, simplified calculation was performed using a single pass model based on Gaussian beam propagation and Fresnel diffraction. This model provided additional physical insight and was in good agreement with the full HFSS simulation. These calculations indicate approaches to increasing the coupling of the microwave power to the sample, including the use of a converging lens and fine adjustment of the spacing of the windings of the RF coil. The present results should prove useful in optimizing the coupling of microwave power to the sample in future DNP experiments. Finally, the results of the simulation were used to predict the cross effect DNP enhancement (ϵ) vs. ω(1S)/(2π) for a sample of (13)C-urea dissolved in a 60:40 glycerol/water mixture containing the polarizing agent TOTAPOL; very good agreement was obtained between theory and experiment. PMID:21382733

  20. Microwave Field Distribution in a Magic Angle Spinning Dynamic Nuclear Polarization NMR Probe

    PubMed Central

    Nanni, Emilio A.; Barnes, Alexander B.; Matsuki, Yoh; Woskov, Paul P.; Corzilius, Björn; Griffin, Robert G.; Temkin, Richard J.

    2011-01-01

    We present a calculation of the microwave field distribution in a magic angle spinning (MAS) probe utilized in dynamic nuclear polarization (DNP) experiments. The microwave magnetic field (B1S) profile was obtained from simulations performed with the High Frequency Structure Simulator (HFSS) software suite, using a model that includes the launching antenna, the outer Kel-F stator housing coated with Ag, the RF coil, and the 4 mm diameter sapphire rotor containing the sample. The predicted average B1S field is 13µT/W1/2, where S denotes the electron spin. For a routinely achievable input power of 5 W the corresponding value is γ SB1S = 0.84 MHz. The calculations provide insights into the coupling of the microwave power to the sample, including reflections from the RF coil and diffraction of the power transmitted through the coil. The variation of enhancement with rotor wall thickness was also successfully simulated. A second, simplified calculation was performed using a single pass model based on Gaussian beam propagation and Fresnel diffraction. This model provided additional physical insight and was in good agreement with the full HFSS simulation. These calculations indicate approaches to increasing the coupling of the microwave power to the sample, including the use of a converging lens and fine adjustment of the spacing of the windings of the RF coil. The present results should prove useful in optimizing the coupling of microwave power to the sample in future DNP experiments. Finally, the results of the simulation were used to predict the cross effect DNP enhancement (ε) vs. ω1S/(2π) for a sample of 13C-urea dissolved in a 60:40 glycerol/water mixture containing the polarizing agent TOTAPOL; very good agreement was obtained between theory and experiment. PMID:21382733

  1. Sealed magic angle spinning nuclear magnetic resonance probe and process for spectroscopy of hazardous samples

    DOEpatents

    Cho, Herman M.; Washton, Nancy M.; Mueller, Karl T.; Sears, Jr., Jesse A.; Townsend, Mark R.; Ewing, James R.

    2016-06-14

    A magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) probe is described that includes double containment enclosures configured to seal and contain hazardous samples for analysis. The probe is of a modular design that ensures containment of hazardous samples during sample analysis while preserving spin speeds for superior NMR performance and convenience of operation.

  2. Devices and process for high-pressure magic angle spinning nuclear magnetic resonance

    DOEpatents

    Hoyt, David W; Sears, Jr., Jesse A; Turcu, Romulus V.F.; Rosso, Kevin M; Hu, Jian Zhi

    2014-04-08

    A high-pressure magic angle spinning (MAS) rotor is detailed that includes a high-pressure sample cell that maintains high pressures exceeding 150 bar. The sample cell design minimizes pressure losses due to penetration over an extended period of time.

  3. HYDROGEN AND DEUTERIUM NMR OF SOLIDS BY MAGIC ANGLE SPINNING

    SciTech Connect

    Eckman, R.R.

    1982-10-01

    The nuclear magnetic resonance of solids has long been characterized by very large spectral broadening which arises from internuclear dipole-dipole coupling or the nuclear electric quadrupole interaction. These couplings can obscure the smaller chemical shift interaction and make that information unavailable. Two important and difficult cases are that of hydrogen and deuterium. For example, the homonuclear dipolar broadening, HD, for hydrogen is usually several tens of kilohertz. For deuterium, HD is relatively small; however, the quadrupole interaction causes a broadening which can be hundreds of kilohertz in polycrystalline or amorphous solids. The development of cross polarization, heteronuclear radiofrequency decoupling, and coherent averaging of nuclear spin interactions has provided measurement of chemical shift tensors in solids. Recently, double quantum NMR and double quantum decoupling have led to measurement of deuterium and proton chemical shift tensors, respectively. A general problem of these experiments is the overlapping of the tensor powder pattern spectra of magnetically distinct sites which cannot be resolved. In this work, high resolution NMR of hydrogen and deuterium in solids is demonstrated. For both nuclei, the resonances are narrowed to obtain liquid-like isotropic spectra by high frequency rotation of the sample about an axis inclined at the magic angle, {beta}{sub m} = Arccos(3{sup -1/2}), with respect to the direction of the external magnetic field. Two approaches have been developed for each nucleus. For deuterium, the powder spectra were narrowed by over three orders of magnitude by magic angle rotation with precise control of {beta}. A second approach was the observation of deuterium double quantum transitions under magic angle rotation. For hydrogen, magic angle rotation alone could be applied to obtain the isotropic spectrum when H{sub D} was small. This often occurs naturally when the nuclei are semi-dilute or involved in internal

  4. Excitation of multiple quantum transitions under magic angle spinning conditions: Adamantane

    NASA Astrophysics Data System (ADS)

    Meier, B. H.; Earl, William L.

    1986-11-01

    A pulse sequence designed for the excitation of multiple quantum transitions in magic angle spinning solid state NMR spectroscopy is presented. It is shown that under the action of the standard time-reversal pulse sequence, the change in the sign of the dipole coupling (which is used to generate the multiple quantum coherences) upon rotation causes the multiple quantum intensity to vanish after each rotor period. This effect is demonstrated both in calculations and in experimental 1H spectra of adamantane. A modification of the time-reversal pulse sequence, which involves switching the phase of the rf pulses every half-rotor period causes the spin part of the Hamiltonian to switch sign in synchrony with the modulation of the spacial part. This allows the creation of multiple quantum coherences in solids with magic angle spinning. The effectiveness of this pulse sequence is demonstrated through calculations and experiments.

  5. Excitation of multiple quantum transitions under magic angle spinning conditions: Adamantane

    SciTech Connect

    Meier, B.H.; Earl, W.L.

    1986-11-01

    A pulse sequence designed for the excitation of multiple quantum transitions in magic angle spinning solid state NMR spectroscopy is presented. It is shown that under the action of the standard time-reversal pulse sequence, the change in the sign of the dipole coupling (which is used to generate the multiple quantum coherences) upon rotation causes the multiple quantum intensity to vanish after each rotor period. This effect is demonstrated both in calculations and in experimental /sup 1/H spectra of adamantane. A modification of the time-reversal pulse sequence, which involves switching the phase of the rf pulses every half-rotor period causes the spin part of the Hamiltonian to switch sign in synchrony with the modulation of the spacial part. This allows the creation of multiple quantum coherences in solids with magic angle spinning. The effectiveness of this pulse sequence is demonstrated through calculations and experiments.

  6. NMR high-resolution magic angle spinning rotor design for quantification of metabolic concentrations

    NASA Astrophysics Data System (ADS)

    Holly, R.; Damyanovich, A.; Peemoeller, H.

    2006-05-01

    A new high-resolution magic angle spinning nuclear magnetic resonance technique is presented to obtain absolute metabolite concentrations of solutions. The magnetic resonance spectrum of the sample under investigation and an internal reference are acquired simultaneously, ensuring both spectra are obtained under the same experimental conditions. The robustness of the technique is demonstrated using a solution of creatine, and it is shown that the technique can obtain solution concentrations to within 7% or better.

  7. Solid-state proton multiple-quantum NMR spectroscopy with fast magic angle spinning

    NASA Astrophysics Data System (ADS)

    Geen, Helen; Titman, Jeremy J.; Gottwald, Johannes; Spiess, Hans W.

    1994-09-01

    The feasibility of multiple-quantum NMR spectroscopy with high resolution for protons in solids is explored. A new multiple-quantum excitation sequence suitable for use with fast magic angle spinning is described, and its performance is compared to that of both static and slow-spinning multiple-quantum methods. Modified sequences with scale the rate of development of the multiple-quantum coherences are also demonstrated, and two-dimensional double-quantum spectra of adamantane and polycarbonate are presented.

  8. Recent developments in solid-state magic-angle spinning, nuclear magnetic resonance of fully and significantly isotopically labelled peptides and proteins.

    PubMed Central

    Straus, Suzana K

    2004-01-01

    In recent years, a large number of solid-state nuclear magnetic resonance (NMR) techniques have been developed and applied to the study of fully or significantly isotopically labelled ((13)C, (15)N or (13)C/(15)N) biomolecules. In the past few years, the first structures of (13)C/(15)N-labelled peptides, Gly-Ile and Met-Leu-Phe, and a protein, Src-homology 3 domain, were solved using magic-angle spinning NMR, without recourse to any structural information obtained from other methods. This progress has been made possible by the development of NMR experiments to assign solid-state spectra and experiments to extract distance and orientational information. Another key aspect to the success of solid-state NMR is the advances made in sample preparation. These improvements will be reviewed in this contribution. Future prospects for the application of solid-state NMR to interesting biological questions will also briefly be discussed. PMID:15306412

  9. Magic-Angle Spinning Solid-State NMR Spectroscopy of Nanodisc– Embedded Human CYP3A4†

    PubMed Central

    Kijac, Aleksandra; Li, Ying; Sligar, Stephen G.; Rienstra, Chad M.

    2008-01-01

    Cytochrome P450 (CYP) 3A4 contributes to the metabolism of approximately 50% of commercial drugs by oxidizing a large number of structurally diverse substrates. Like other endoplasmic reticulum-localized P450s, CYP3A4 contains a membrane-anchoring N-terminal helix and a significant number of hydrophobic domains, important for the interaction between CYP3A4 and the membrane. Although the membrane affects specificity of CYP3A4 ligand binding, the structural details of the interaction have not been revealed so far because x-ray crystallography studies are available only for the soluble domain of CYP3A4. Here we report sample preparation and initial magic-angle spinning (MAS) solid-state NMR (SSNMR) of CYP3A4 (Δ3−12) embedded in a nanoscale membrane bilayer, or Nanodisc. The growth protocol yields ∼2.5 mg of the enzymatically active, uniformly 13C, 15N-enriched CYP3A4 from a liter of growth medium. Polyethylene glycol 3350-precipitated CYP3A4 in Nanodiscs yields spectra of high resolution and sensitivity, consistent with a folded, homogeneous protein. CYP3A4 in Nanodiscs remains enzymatically active throughout the precipitation protocol as monitored by bromocriptine binding. The 13C line widths measured from 13C-13C 2D chemical shift correlation spectra are ∼0.5 ppm. The secondary structure distribution within several amino acid types determined from 13C chemical shifts is consistent with the ligand-free x-ray structures. These results demonstrate that MAS SSNMR can be performed on Nanodisc-embedded membrane proteins in a folded, active state. The combination of SSNMR and Nanodisc methodologies opens up new possibilities for obtaining structural information on CYP3A4 and other integral membrane proteins with full retention of functionality. PMID:17985934

  10. Tethered or adsorbed supported lipid bilayers in nanotubes characterized by deuterium magic angle spinning NMR spectroscopy.

    PubMed

    Wattraint, Olivier; Warschawski, Dror E; Sarazin, Catherine

    2005-04-12

    2H solid-state NMR experiments were performed under magic angle spinning on lipid bilayers oriented into nanotubes arrays, as a new method to assess the geometrical arrangement of the lipids. Orientational information is obtained from the intensities of the spinning sidebands. The lipid bilayers are formed by fusion of small unilamellar vesicles of DMPC-d54 inside a nanoporous anodic aluminum oxide, either by direct adsorption on the support or by tethering through a streptavidin/biotin linker. The results support that the quality of the lipid bilayers alignment is clearly in favor of the tethering rather than an adsorbed strategy. PMID:15807556

  11. An efficient amplification pulse sequence for measuring chemical shift anisotropy under fast magic-angle spinning.

    PubMed

    Hung, Ivan; Gan, Zhehong

    2011-12-01

    A two-dimensional experiment for measuring chemical shift anisotropy (CSA) under fast magic-angle spinning (MAS) is presented. The chemical shift anisotropy evolution is amplified by a sequence of π-pulses that repetitively interrupt MAS averaging. The amplification generates spinning sideband manifolds in the indirect dimension separated by the isotropic shift along the direct dimension. The basic unit of the pulse sequence is designed based on the magic-angle turning experiment and can be concatenated for larger amplification factors. PMID:21962909

  12. High-resolution magic-angle-spinning NMR spectroscopy of intact tissue.

    PubMed

    Giskeødegård, Guro F; Cao, Maria D; Bathen, Tone F

    2015-01-01

    High-resolution magic-angle-spinning (HR-MAS) NMR spectroscopy is a nondestructive technique that is used to obtain the metabolite profile of a tissue sample. This method requires minimal sample preparation. However, it is important to handle the sample with care and keep it frozen during preparation to minimize degradation. Here, we describe a typical protocol for HR-MAS analysis of intact tissue. We also include examples of typical pulse sequence programs and quantification methods that are used today. PMID:25677145

  13. High resolution 11B NMR of magnesium diboride using cryogenic magic angle spinning

    NASA Astrophysics Data System (ADS)

    Beckett, Peter; Denning, Mark S.; Heinmaa, Ivo; Dimri, Mukesh C.; Young, Edward A.; Stern, Raivo; Carravetta, Marina

    2012-09-01

    Static and magic-angle spinning 11B nuclear magnetic resonance (NMR) data at 4.7 T and 8.5 T have been obtained under cryogenic conditions on a diluted sample of magnesium diboride powder in the normal and superconducting state. The data provide accurate information on the magnetic shift and longitudinal relaxation time down to a temperature of 8 K, with a resolution improvement over the entire temperature range. The onset of superconductivity is unaffected by the sample rotation, as revealed by a steep variation of the magnetic shift just below the critical temperature.

  14. Instrumentation for solid-state dynamic nuclear polarization with magic angle spinning NMR

    NASA Astrophysics Data System (ADS)

    Rosay, Melanie; Blank, Monica; Engelke, Frank

    2016-03-01

    Advances in dynamic nuclear polarization (DNP) instrumentation and methodology have been key factors in the recent growth of solid-state DNP NMR applications. We review the current state of the art of solid-state DNP NMR instrumentation primarily based on available commercial platforms. We start with a general system overview, including options for microwave sources and DNP NMR probes, and then focus on specific developments for DNP at 100 K with magic angle spinning (MAS). Gyrotron microwave sources, passive components to transmit microwaves, the DNP MAS probe, a cooling device for low-temperature MAS, and sample preparation procedures including radicals for DNP are considered.

  15. Instrumentation for solid-state dynamic nuclear polarization with magic angle spinning NMR.

    PubMed

    Rosay, Melanie; Blank, Monica; Engelke, Frank

    2016-03-01

    Advances in dynamic nuclear polarization (DNP) instrumentation and methodology have been key factors in the recent growth of solid-state DNP NMR applications. We review the current state of the art of solid-state DNP NMR instrumentation primarily based on available commercial platforms. We start with a general system overview, including options for microwave sources and DNP NMR probes, and then focus on specific developments for DNP at 100K with magic angle spinning (MAS). Gyrotron microwave sources, passive components to transmit microwaves, the DNP MAS probe, a cooling device for low-temperature MAS, and sample preparation procedures including radicals for DNP are considered. PMID:26920834

  16. A practical guide for the setup of a 1H-31P-13C double cross-polarization (DCP) experiment.

    PubMed

    Ciesielski, Wlodzimierz; Kassassir, Hassan; Potrzebowski, Marek J

    2011-01-01

    O-phospho-L-threonine is a convenient sample to setup a (1)H-(31)P-(13)C double cross-polarization (DCP) Hartmann-Hahn match. The (1)H-(31)P-(13)C technique is extremely sensitive to the rate of the sample spinning. Both zero-quantum (ZQ) and double-quantum (DQ) cross-polarization operate at an average spinning rate (6-7 kHz). At higher spinning rates (10 kHz), the DQCP mechanism dominates and leads to a reduction of signal intensity, in particular for lower (31)P RF field strength. The application of two shape pulses during the second cross-polarization greatly improves the signal to noise ratio allowing the recording of better quality spectra. (31)P-(13)C spectrally induced filtering in combination with cross-polarization (SPECIFIC-CP) experiments can be carried out under ZQCP and DQCP conditions if careful attention is paid to the choice of RF field amplitudes and carriers Ω. Application of 1D and 2D (1)H-(31)P-(13)C experiments is demonstrated on model samples; disodium ATP hydrate and O-phospho-L-tyrosine. PMID:21440422

  17. Magic-angle-spinning NMR on solid biological systems. Analysis Of the origin of the spectral linewidths

    NASA Astrophysics Data System (ADS)

    Hemminga, M. A.; de Jager, P. A.; Krüse, J.; Lamerichs, R. M. J. N.

    Magic-angle-spinning (MAS) high-power 1H-decoupled 13C and 31P NMR has been applied to solid biological materials to obtain information about the mechanisms that determine the spectral linewidths. The line broadening in MAS 31P NMR spectra of solid tobacco mosaic virus (TMV) has been investigated by selective saturation and T2 measurements. About 90 Hz stems from homogeneous effects, whereas the inhomogeneous contribution is approximately 100 Hz. The inhomogeneous line broadening is assigned to macroscopic inhomogeneities in the sample and not to variations in the nucleotide bases along the RNA strand in TMV. It is concluded that sample preparation is of vital importance for obtaining well-resolved spectra. Under optimal preparation techniques the isotropic values of the chemical shift of the different 31P sites have been determined to obtain information about the secondary structure of the viral RNA. The chemical shift anisotropy has been determined from the relative intensities of the spinning side bands in the spectra. The chemical shift information is used to make a tentative assignment of the resonance in terms of the three structurally distinguishable phosphate groups in TMV. The origin of the linewidths in MAS NMR has been examined further by 13C NMR of approximately 10% 13C-enriched coat protein of cowpea chlorotic mottle virus, using selective excitation and saturation techniques, as well as measurements of the relaxation times T1 γ and T2. The CO resonance in the spectrum is composed of an inhomogeneous and homogeneous part with a total linewidth of 700 Hz. The homogeneous linewidth, contributing with 200 Hz, is found to arise from slow molecular motions in the solid on a millisecond timescale.

  18. Magic-Angle-Spinning NMR Magnet Development: Field Analysis and Prototypes

    PubMed Central

    Voccio, John; Hahn, Seungyong; Park, Dong Keun; Ling, Jiayin; Kim, Youngjae; Bascuñán, Juan; Iwasa, Yukikazu

    2013-01-01

    We are currently working on a program to complete a 1.5 T/75 mm RT bore magic-angle-spinning nuclear magnetic resonance magnet. The magic-angle-spinning magnet comprises a z-axis 0.866-T solenoid and an x-axis 1.225-T dipole, each to be wound with NbTi wire and operated at 4.2 K in persistent mode. A combination of the fields creates a 1.5-T field pointed at 54.74 degrees (magic angle) from the rotation (z) axis. In the first year of this 3-year program, we have completed magnetic analysis and design of both coils. Also, using a winding machine of our own design and fabrication, we have wound several prototype dipole coils with NbTi wire. As part of this development, we have repeatedly made successful persistent NbTi-NbTi joints with this multifilamentary NbTi wire. PMID:24058275

  19. Sensitivity and resolution enhanced solid-state NMR for paramagnetic systems and biomolecules under very fast magic angle spinning.

    PubMed

    Parthasarathy, Sudhakar; Nishiyama, Yusuke; Ishii, Yoshitaka

    2013-09-17

    Recent research in fast magic angle spinning (MAS) methods has drastically improved the resolution and sensitivity of NMR spectroscopy of biomolecules and materials in solids. In this Account, we summarize recent and ongoing developments in this area by presenting (13)C and (1)H solid-state NMR (SSNMR) studies on paramagnetic systems and biomolecules under fast MAS from our laboratories. First, we describe how very fast MAS (VFMAS) at the spinning speed of at least 20 kHz allows us to overcome major difficulties in (1)H and (13)C high-resolution SSNMR of paramagnetic systems. As a result, we can enhance both sensitivity and resolution by up to a few orders of magnitude. Using fast recycling (∼ms/scan) with short (1)H T1 values, we can perform (1)H SSNMR microanalysis of paramagnetic systems on the microgram scale with greatly improved sensitivity over that observed for diamagnetic systems. Second, we discuss how VFMAS at a spinning speed greater than ∼40 kHz can enhance the sensitivity and resolution of (13)C biomolecular SSNMR measurements. Low-power (1)H decoupling schemes under VFMAS offer excellent spectral resolution for (13)C SSNMR by nominal (1)H RF irradiation at ∼10 kHz. By combining the VFMAS approach with enhanced (1)H T1 relaxation by paramagnetic doping, we can achieve extremely fast recycling in modern biomolecular SSNMR experiments. Experiments with (13)C-labeled ubiquitin doped with 10 mM Cu-EDTA demonstrate how effectively this new approach, called paramagnetic assisted condensed data collection (PACC), enhances the sensitivity. Lastly, we examine (13)C SSNMR measurements for biomolecules under faster MAS at a higher field. Our preliminary (13)C SSNMR data of Aβ amyloid fibrils and GB1 microcrystals acquired at (1)H NMR frequencies of 750-800 MHz suggest that the combined use of the PACC approach and ultrahigh fields could allow for routine multidimensional SSNMR analyses of proteins at the 50-200 nmol level. Also, we briefly discuss the

  20. Mineral Carbonation in Wet Supercritical CO2: An in situ High-Pressure Magic Angle Spinning Nuclear Magnetic Resonance Study

    NASA Astrophysics Data System (ADS)

    Turcu, R. V.; Hoyt, D. H.; Sears, J. A.; Rosso, K. M.; Felmy, A. R.; Hu, J. Z.

    2011-12-01

    Understanding the mechanisms and kinetics of mineral carbonation reactions relevant to sequestering carbon dioxide as a supercritical fluid (scCO2) in geologic formations is crucial for accurately predicting long-term storage risks. In situ probes that provide molecular-level information at geologically relevant temperatures and pressures are highly desirable and challenging to develop. Magic angle spinning nuclear magnetic resonance (MAS NMR) is a powerful tool for obtaining detailed molecular structure and dynamics information of a system regardless whether the system is in a solid, a liquid, a gaseous, a supercritical state, or a mixture thereof. However, MAS NMR under scCO2 conditions has never been realized due to the tremendous technical difficulties of achieving and maintaining high pressure within a fast spinning MAS sample rotor. In this work, we report development of a unique high pressure MAS NMR capability capable of handling fluid pressure exceeding 170 bars and temperatures up to 80°C, and its application to mineral carbonation in scCO2 under geologically relevant temperatures and pressures. Mineral carbonation reactions of the magnesium silicate mineral forsterite and the magnesium hydroxide brucite reacted with scCO2 (up to 170 bar) and containing variable content of H2O (at, below, and above saturation in scCO2) were investigated at 50 to 70°C. In situ 13C MAS NMR spectra show peaks corresponding to the reactants, intermediates, and the magnesium carbonation products in a single spectrum. For example, Figure 1 shows the reaction dynamics, i.e., the formation and conversion of reaction intermediates, i.e., HCO3- and nesquehonite, to magnesite as a function of time at 70°C. This capability offers a significant advantage over traditional ex situ 13C MAS experiments on similar systems, where, for example, CO2 and HCO3- are not directly observable.

  1. In situ structural characterization of a recombinant protein in native Escherichia coli membranes with solid-state magic-angle-spinning NMR.

    PubMed

    Fu, Riqiang; Wang, Xingsheng; Li, Conggang; Santiago-Miranda, Adriana N; Pielak, Gary J; Tian, Fang

    2011-08-17

    The feasibility of using solid-state magic-angle-spinning NMR spectroscopy for in situ structural characterization of the LR11 (sorLA) transmembrane domain (TM) in native Escherichia coli membranes is presented. LR11 interacts with the human amyloid precursor protein (APP), a central player in the pathology of Alzheimer's disease. The background signals from E. coli lipids and membrane proteins had only minor effects on the LR11 TM resonances. Approximately 50% of the LR11 TM residues were assigned by using (13)C PARIS data. These assignments allowed comparisons of the secondary structure of the LR11 TM in native membrane environments and commonly used membrane mimics (e.g., micelles). In situ spectroscopy bypasses several obstacles in the preparation of membrane proteins for structural analysis and offers the opportunity to investigate how membrane heterogeneity, bilayer asymmetry, chemical gradients, and macromolecular crowding affect the protein structure. PMID:21774553

  2. Magic-angle spinning NMR of intact bacteriophages: Insights into the capsid, DNA and their interface

    NASA Astrophysics Data System (ADS)

    Abramov, Gili; Morag, Omry; Goldbourt, Amir

    2015-04-01

    Bacteriophages are viruses that infect bacteria. They are complex macromolecular assemblies, which are composed of multiple protein subunits that protect genomic material and deliver it to specific hosts. Various biophysical techniques have been used to characterize their structure in order to unravel phage morphogenesis. Yet, most bacteriophages are non-crystalline and have very high molecular weights, in the order of tens of MegaDaltons. Therefore, complete atomic-resolution characterization on such systems that encompass both capsid and DNA is scarce. In this perspective article we demonstrate how magic-angle spinning solid-state NMR has and is used to characterize in detail bacteriophage viruses, including filamentous and icosahedral phage. We discuss the process of sample preparation, spectral assignment of both capsid and DNA and the use of chemical shifts and dipolar couplings to probe the capsid-DNA interface, describe capsid structure and dynamics and extract structural differences between viruses.

  3. Magic-angle spinning NMR of intact bacteriophages: insights into the capsid, DNA and their interface.

    PubMed

    Abramov, Gili; Morag, Omry; Goldbourt, Amir

    2015-04-01

    Bacteriophages are viruses that infect bacteria. They are complex macromolecular assemblies, which are composed of multiple protein subunits that protect genomic material and deliver it to specific hosts. Various biophysical techniques have been used to characterize their structure in order to unravel phage morphogenesis. Yet, most bacteriophages are non-crystalline and have very high molecular weights, in the order of tens of MegaDaltons. Therefore, complete atomic-resolution characterization on such systems that encompass both capsid and DNA is scarce. In this perspective article we demonstrate how magic-angle spinning solid-state NMR has and is used to characterize in detail bacteriophage viruses, including filamentous and icosahedral phage. We discuss the process of sample preparation, spectral assignment of both capsid and DNA and the use of chemical shifts and dipolar couplings to probe the capsid-DNA interface, describe capsid structure and dynamics and extract structural differences between viruses. PMID:25797007

  4. The magnetic field dependence of cross-effect dynamic nuclear polarization under magic angle spinning

    SciTech Connect

    Mance, Deni; Baldus, Marc; Gast, Peter; Huber, Martina; Ivanov, Konstantin L.

    2015-06-21

    We develop a theoretical description of Dynamic Nuclear Polarization (DNP) in solids under Magic Angle Spinning (MAS) to describe the magnetic field dependence of the DNP effect. The treatment is based on an efficient scheme for numerical solution of the Liouville-von Neumann equation, which explicitly takes into account the variation of magnetic interactions during the sample spinning. The dependence of the cross-effect MAS-DNP on various parameters, such as the hyperfine interaction, electron-electron dipolar interaction, microwave field strength, and electron spin relaxation rates, is analyzed. Electron spin relaxation rates are determined by electron paramagnetic resonance measurements, and calculations are compared to experimental data. Our results suggest that the observed nuclear magnetic resonance signal enhancements provided by MAS-DNP can be explained by discriminating between “bulk” and “core” nuclei and by taking into account the slow DNP build-up rate for the bulk nuclei.

  5. The magnetic field dependence of cross-effect dynamic nuclear polarization under magic angle spinning

    NASA Astrophysics Data System (ADS)

    Mance, Deni; Gast, Peter; Huber, Martina; Baldus, Marc; Ivanov, Konstantin L.

    2015-06-01

    We develop a theoretical description of Dynamic Nuclear Polarization (DNP) in solids under Magic Angle Spinning (MAS) to describe the magnetic field dependence of the DNP effect. The treatment is based on an efficient scheme for numerical solution of the Liouville-von Neumann equation, which explicitly takes into account the variation of magnetic interactions during the sample spinning. The dependence of the cross-effect MAS-DNP on various parameters, such as the hyperfine interaction, electron-electron dipolar interaction, microwave field strength, and electron spin relaxation rates, is analyzed. Electron spin relaxation rates are determined by electron paramagnetic resonance measurements, and calculations are compared to experimental data. Our results suggest that the observed nuclear magnetic resonance signal enhancements provided by MAS-DNP can be explained by discriminating between "bulk" and "core" nuclei and by taking into account the slow DNP build-up rate for the bulk nuclei.

  6. High-resolution NMR spectroscopy of biological tissues usingprojected Magic Angle Spinning

    SciTech Connect

    Martin, Rachel W.; Jachmann, Rebecca C.; Sakellariou, Dimitris; Nielsen, Ulla Gro; Pines, Alexander

    2005-01-27

    High-resolution NMR spectra of materials subject toanisotropic broadening are usually obtained by rotating the sample aboutthe magic angle, which is 54.7 degrees to the static magnetic field. Inprojected Magic Angle Spinning (p-MAS), the sample is spun about twoangles, neither of which is the magic angle. This provides a method ofobtaining isotropic spectra while spinning at shallow angles. The p-MASexperiment may be used in situations where spinning the sample at themagic angle is not possible due to geometric or other constraints,allowing the choice of spinning angle to be determined by factors such asthe shape of the sample, rather than by the spin physics. The applicationof this technique to bovine tissue samples is demonstrated as a proof ofprinciple for future biological or medical applications.

  7. Magic angle spinning solid-state NMR experiments for structural characterization of proteins.

    PubMed

    Shi, Lichi; Ladizhansky, Vladimir

    2012-01-01

    Solid-state nuclear magnetic resonance (SSNMR) has become a prominent method in biology and is suitable for the characterization of insoluble proteins and protein aggregates such as amyloid fibrils, membrane-lipid complexes, and precipitated proteins. Often, the initial and the most critical step is to obtain spectroscopic assignments, that is, to determine chemical shifts of individual atoms. The procedures for SSNMR spectroscopic assignments are now well established for small microcrystalline proteins, where high signal-to-noise can be obtained. The sensitivity of the experiments and spectral resolution decrease with the increasing molecular weight, which makes setting SSNMR experiments in large proteins a much more challenging and demanding procedure. Here, we describe the protocol for the most common set of 3D magic angle spinning (MAS) SSNMR experiments. While the procedures described in the text are well known to SSNMR practitioners, we hope they will be of interest to scientists interested in extending their repertoire of biophysical techniques. PMID:22760319

  8. Forensic examination of electrical tapes using high resolution magic angle spinning ¹H NMR spectroscopy.

    PubMed

    Schoenberger, Torsten; Simmross, Ulrich; Poppe, Christian

    2016-01-01

    The application of high resolution magic angle spinning (HR-MAS) (1)H NMR spectroscopy is ideally suited for the differentiation of plastics. In addition to the actual material composition, the different types of polymer architectures and tacticity provide characteristic signals in the fingerprint of the (1)H NMR spectra. The method facilitates forensic comparison, as even small amounts of insoluble but swellable plastic particles are utilized. The performance of HR-MAS NMR can be verified against other methods that were recently addressed in various articles about forensic tape comparison. In this study samples of the 90 electrical tapes already referenced by the FBI laboratory were used. The discrimination power of HR-MAS is demonstrated by the fact that more tape groups can be distinguished by NMR spectroscopy than by using the combined evaluation of several commonly used analytical techniques. An additional advantage of this robust and quick method is the very simple sample preparation. PMID:26558760

  9. Spin dynamics in the modulation frame: application to homonuclear recoupling in magic angle spinning solid-state NMR.

    PubMed

    De Paëpe, Gaël; Lewandowski, Józef R; Griffin, Robert G

    2008-03-28

    We introduce a family of solid-state NMR pulse sequences that generalizes the concept of second averaging in the modulation frame and therefore provides a new approach to perform magic angle spinning dipolar recoupling experiments. Here, we focus on two particular recoupling mechanisms-cosine modulated rotary resonance (CMpRR) and cosine modulated recoupling with isotropic chemical shift reintroduction (COMICS). The first technique, CMpRR, is based on a cosine modulation of the rf phase and yields broadband double-quantum (DQ) (13)C recoupling using >70 kHz omega(1,C)/2pi rf field for the spinning frequency omega(r)/2=10-30 kHz and (1)H Larmor frequency omega(0,H)/2pi up to 900 MHz. Importantly, for p>or=5, CMpRR recouples efficiently in the absence of (1)H decoupling. Extension to lower p values (3.513)C recoupling and (1)H decoupling. The second technique, COMICS, involves low power (13)C irradiation that induces simultaneous recoupling of the (13)C DQ dipolar and isotropic chemical shift terms. In contrast to CMpRR, where the DQ bandwidth (approximately 30 kHz at omega(0,H)/2pi=750 MHz) covers the entire (13)C spectral width, COMICS recoupling, through the reintroduction of the isotropic chemical shift, is selective with respect to the carrier frequency, having a typical bandwidth of approximately 100 Hz. This approach is intended as a general frequency selective method circumventing dipolar truncation (supplementary to R(2) experiments). These new gamma-encoded sequences with attenuated rf requirements extend the applicability of homonuclear recoupling techniques to new regimes--high spinning and Larmor frequencies--and therefore should be of major

  10. High-resolution paramagnetically enhanced solid-state NMR spectroscopy of membrane proteins at fast magic angle spinning.

    PubMed

    Ward, Meaghan E; Wang, Shenlin; Krishnamurthy, Sridevi; Hutchins, Howard; Fey, Michael; Brown, Leonid S; Ladizhansky, Vladimir

    2014-01-01

    Magic angle spinning nuclear magnetic resonance (MAS NMR) is well suited for the study of membrane proteins in membrane mimetic and native membrane environments. These experiments often suffer from low sensitivity, due in part to the long recycle delays required for magnetization and probe recovery, as well as detection of low gamma nuclei. In ultrafast MAS experiments sensitivity can be enhanced through the use of low power sequences combined with paramagnetically enhanced relaxation times to reduce recycle delays, as well as proton detected experiments. In this work we investigate the sensitivity of (13)C and (1)H detected experiments applied to 27 kDa membrane proteins reconstituted in lipids and packed in small 1.3 mm MAS NMR rotors. We demonstrate that spin diffusion is sufficient to uniformly distribute paramagnetic relaxation enhancement provided by either covalently bound or dissolved CuEDTA over 7TM alpha helical membrane proteins. Using paramagnetic enhancement and low power decoupling in carbon detected experiments we can recycle experiments ~13 times faster than under traditional conditions. However, due to the small sample volume the overall sensitivity per unit time is still lower than that seen in the 3.2 mm probe. Proton detected experiments, however, showed increased efficiency and it was found that the 1.3 mm probe could achieve sensitivity comparable to that of the 3.2 mm in a given amount of time. This is an attractive prospect for samples of limited quantity, as this allows for a reduction in the amount of protein that needs to be produced without the necessity for increased experimental time. PMID:24338448

  11. Magic Angle Spinning NMR Spectroscopy: A Versatile Technique for Structural and Dynamic Analysis of Solid-Phase Systems

    PubMed Central

    Polenova, Tatyana; Gupta, Rupal; Goldbourt, Amir

    2016-01-01

    Magic Angle Spinning (MAS) NMR spectroscopy is a powerful method for analysis of a broad range of systems, including inorganic materials, pharmaceuticals, and biomacromolecules. The recent developments in MAS NMR instrumentation and methodologies opened new vistas to atomic-level characterization of a plethora of chemical environments previously inaccessible to analysis, with unprecedented sensitivity and resolution. PMID:25794311

  12. Cross-polarization phenomena in the NMR of fast spinning solids subject to adiabatic sweeps

    SciTech Connect

    Wi, Sungsool E-mail: lucio.frydman@weizmann.ac.il; Gan, Zhehong; Schurko, Robert; Frydman, Lucio E-mail: lucio.frydman@weizmann.ac.il

    2015-02-14

    Cross-polarization magic-angle spinning (CPMAS) experiments employing frequency-swept pulses are explored within the context of obtaining broadband signal enhancements for rare spin S = 1/2 nuclei at very high magnetic fields. These experiments employ adiabatic inversion pulses on the S-channel ({sup 13}C) to cover a wide frequency offset range, while simultaneously applying conventional spin-locking pulse on the I-channel ({sup 1}H). Conditions are explored where the adiabatic frequency sweep width, Δν, is changed from selectively irradiating a single magic-angle-spinning (MAS) spinning centerband or sideband, to sweeping over multiple sidebands. A number of new physical features emerge upon assessing the swept-CP method under these conditions, including multiple zero- and double-quantum CP transfers happening in unison with MAS-driven rotary resonance phenomena. These were examined using an average Hamiltonian theory specifically designed to tackle these experiments, with extensive numerical simulations, and with experiments on model compounds. Ultrawide CP profiles spanning frequency ranges of nearly 6⋅γB{sub 1}{sup s} were predicted and observed utilizing this new approach. Potential extensions and applications of this extremely broadband transfer conditions are briefly discussed.

  13. Cross-polarization phenomena in the NMR of fast spinning solids subject to adiabatic sweeps.

    PubMed

    Wi, Sungsool; Gan, Zhehong; Schurko, Robert; Frydman, Lucio

    2015-02-14

    Cross-polarization magic-angle spinning (CPMAS) experiments employing frequency-swept pulses are explored within the context of obtaining broadband signal enhancements for rare spin S = 1/2 nuclei at very high magnetic fields. These experiments employ adiabatic inversion pulses on the S-channel ((13)C) to cover a wide frequency offset range, while simultaneously applying conventional spin-locking pulse on the I-channel ((1)H). Conditions are explored where the adiabatic frequency sweep width, Δν, is changed from selectively irradiating a single magic-angle-spinning (MAS) spinning centerband or sideband, to sweeping over multiple sidebands. A number of new physical features emerge upon assessing the swept-CP method under these conditions, including multiple zero- and double-quantum CP transfers happening in unison with MAS-driven rotary resonance phenomena. These were examined using an average Hamiltonian theory specifically designed to tackle these experiments, with extensive numerical simulations, and with experiments on model compounds. Ultrawide CP profiles spanning frequency ranges of nearly 6⋅γB1 (s) were predicted and observed utilizing this new approach. Potential extensions and applications of this extremely broadband transfer conditions are briefly discussed. PMID:25681899

  14. Unexpected effects of third-order cross-terms in heteronuclear spin systems under simultaneous radio-frequency irradiation and magic-angle spinning NMR

    NASA Astrophysics Data System (ADS)

    Tatton, Andrew S.; Frantsuzov, Ilya; Brown, Steven P.; Hodgkinson, Paul

    2012-02-01

    We recently noted [R. K. Harris, P. Hodgkinson, V. Zorin, J.-N. Dumez, B. Elena, L. Emsley, E. Salager, and R. Stein, Magn. Reson. Chem. 48, S103 (2010), 10.1002/mrc.2636] anomalous shifts in apparent 1H chemical shifts in experiments using 1H homonuclear decoupling sequences to acquire high-resolution 1H NMR spectra for organic solids under magic-angle spinning (MAS). Analogous effects were also observed in numerical simulations of model 13C,1H spin systems under homonuclear decoupling and involving large 13C,1H dipolar couplings. While the heteronuclear coupling is generally assumed to be efficiently suppressed by sample spinning at the magic angle, we show that under conditions typically used in solid-state NMR, there is a significant third-order cross-term from this coupling under the conditions of simultaneous MAS and homonuclear decoupling for spins directly bonded to 1H. This term, which is of the order of 100 Hz under typical conditions, explains the anomalous behaviour observed on both 1H and 13C spins, including the fast dephasing observed in 13C{1H} heteronuclear spin-echo experiments under 1H homonuclear decoupling. Strategies for minimising the impact of this effect are also discussed.

  15. Quantitative neuropathology by high resolution magic angle spinning proton magnetic resonance spectroscopy

    PubMed Central

    Cheng, L. L.; Ma, M. J.; Becerra, L.; Ptak, T.; Tracey, I.; Lackner, A.; González, R. G.

    1997-01-01

    We describe a method that directly relates tissue neuropathological analysis to medical imaging. Presently, only indirect and often tenuous relationships are made between imaging (such as MRI or x-ray computed tomography) and neuropathology. We present a biochemistry-based, quantitative neuropathological method that can help to precisely quantify information provided by in vivo proton magnetic resonance spectroscopy (1HMRS), an emerging medical imaging technique. This method, high resolution magic angle spinning (HRMAS) 1HMRS, is rapid and requires only small amounts of unprocessed samples. Unlike chemical extraction or other forms of tissue processing, this method analyzes tissue directly, thus minimizing artifacts. We demonstrate the utility of this method by assessing neuronal damage using multiple tissue samples from differently affected brain regions in a case of Pick disease, a human neurodegenerative disorder. Among different regions, we found an excellent correlation between neuronal loss shown by traditional neurohistopathology and decrease of the neuronal marker N-acetylaspartate measured by HRMAS 1HMRS. This result demonstrates for the first time, to our knowledge, a direct, quantitative link between a decrease in N-acetylaspartate and neuronal loss in a human neurodegenerative disease. As a quantitative method, HRMAS 1HMRS has potential applications in experimental and clinical neuropathologic investigations. It should also provide a rational basis for the interpretation of in vivo 1HMRS studies of human neurological disorders. PMID:9177231

  16. MATPASS/CPMG: a sensitivity enhanced magic-angle spinning sideband separation experiment for disordered solids.

    PubMed

    Hung, Ivan; Edwards, Trenton; Sen, Sabyasachi; Gan, Zhehong

    2012-08-01

    A Carr-Purcell Meiboom-Gill (CPMG) sensitivity-enhanced spinning sideband separation experiment is presented. The experiment combines the idea of magic-angle turning and phase-adjusted sideband separation (MATPASS), allowing for isotropic/anisotropic chemical shift separation of disordered solids with line widths far greater than the magic-angle spinning frequency. The use of CPMG enhances the sensitivity of the wide-line spectra by an order of magnitude via multiple-echo acquisition. The MATPASS/CPMG protocol involves acquisition of time-domain data using a MAT/CPMG pulse sequence followed by f(1) shearing during data processing to arrive at the PASS representation. Such a protocol has √2 higher sensitivity than the conventional PASS method because all CPMG echo signals are used for the final PASS spectrum. Application of this method is demonstrated using a GeSe₄ glass sample with both ⁷⁷Se isotropic line widths and chemical shift anisotropy that far exceed the spinning frequency. The sideband separation allows for the measurement of chemical shift anisotropy of the disordered solids. PMID:22750637

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

    PubMed

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

    2016-06-14

    Orders of magnitude decrease of (207)Pb and (199)Hg NMR longitudinal relaxation times T1 upon magic-angle-spinning (MAS) are observed and systematically investigated in solid lead and mercury halides MeX2 (Me = Pb, Hg and X = Cl, Br, I). In lead(ii) halides, the most dramatic decrease of T1 relative to that in a static sample is in PbI2, while it is smaller but still significant in PbBr2, and not detectable in PbCl2. The effect is magnetic-field dependent but independent of the spinning speed in the range 200-15 000 Hz. The observed relaxation enhancement is explained by laboratory-frame heteronuclear polarization exchange due to crossing between energy levels of spin-1/2 metal nuclei and adjacent quadrupolar-spin halogen nuclei. The enhancement effect is also present in lead-containing organometal halide perovskites. Our results demonstrate that in affected samples, it is the relaxation data recorded under non-spinning conditions that characterize the local properties at the metal sites. A practical advantage of fast relaxation at slow MAS is that spectral shapes with orientational chemical shift anisotropy information well retained can be acquired within a shorter experimental time. PMID:27306000

  18. High-resolution magic angle spinning 1H MRS in prostate cancer.

    PubMed

    Decelle, Emily A; Cheng, Leo L

    2014-01-01

    Prostate cancer (PCa) is the most frequently diagnosed malignancy in men worldwide, largely as a result of the increased use of the annual serum prostate-specific antigen (PSA) screening test for detection. PSA screening has saved lives, but it has also resulted in the overtreatment of many patients with PCa because of a limited ability to accurately localize and characterize PCa lesions through imaging. High-resolution magic angle spinning (HRMAS) (1)H MRS has proven to be a strong potential clinical tool for PCa diagnosis and prognosis. The HRMAS technique allows valuable metabolic information to be obtained from ex vivo intact tissue samples and also enables the performance of histopathology on the same tissue specimens. Studies have found that the quantification of individual metabolite levels and metabolite ratios, as well as metabolomic profiles, shows strong potential to improve accuracy in PCa detection, diagnosis and monitoring. Ex vivo HRMAS is also a valuable tool for the interpretation of in vivo results, including the localization of tumors, and thus has the potential to improve in vivo diagnostic tests used in the clinic. Here, we primarily review publications of HRMAS (1)H MRS and its use for the study of intact human prostate tissue. PMID:23529951

  19. Magic-angle spinning solid-state multinuclear NMR on low-field instrumentation

    NASA Astrophysics Data System (ADS)

    Sørensen, Morten K.; Bakharev, Oleg; Jensen, Ole; Jakobsen, Hans J.; Skibsted, Jørgen; Nielsen, Niels Chr.

    2014-01-01

    Mobile and cost-effective NMR spectroscopy exploiting low-field permanent magnets is a field of tremendous development with obvious applications for arrayed large scale analysis, field work, and industrial screening. So far such demonstrations have concentrated on relaxation measurements and lately high-resolution liquid-state NMR applications. With high-resolution solid-state NMR spectroscopy being increasingly important in a broad variety of applications, we here introduce low-field magic-angle spinning (MAS) solid-state multinuclear NMR based on a commercial ACT 0.45 T 62 mm bore Halbach magnet along with a homebuilt FPGA digital NMR console, amplifiers, and a modified standard 45 mm wide MAS probe for 7 mm rotors. To illustrate the performance of the instrument and address cases where the low magnetic field may offer complementarity to high-field NMR experiments, we demonstrate applications for 23Na MAS NMR with enhanced second-order quadrupolar coupling effects and 31P MAS NMR where reduced influence from chemical shift anisotropy at low field may facilitate determination of heteronuclear dipole-dipole couplings.

  20. A unified heteronuclear decoupling strategy for magic-angle-spinning solid-state NMR spectroscopy

    SciTech Connect

    Equbal, Asif; Bjerring, Morten; Nielsen, Niels Chr. E-mail: ncn@inano.au.dk; Madhu, P. K. E-mail: ncn@inano.au.dk

    2015-05-14

    A unified strategy of two-pulse based heteronuclear decoupling for solid-state magic-angle spinning nuclear magnetic resonance is presented. The analysis presented here shows that different decoupling sequences like two-pulse phase-modulation (TPPM), X-inverse-X (XiX), and finite pulse refocused continuous wave (rCW{sup A}) are basically specific solutions of a more generalized decoupling scheme which incorporates the concept of time-modulation along with phase-modulation. A plethora of other good decoupling conditions apart from the standard, TPPM, XiX, and rCW{sup A} decoupling conditions are available from the unified decoupling approach. The importance of combined time- and phase-modulation in order to achieve the best decoupling conditions is delineated. The consequences of different indirect dipolar interactions arising from cross terms comprising of heteronuclear and homonuclear dipolar coupling terms and also those between heteronuclear dipolar coupling and chemical-shift anisotropy terms are presented in order to unfold the effects of anisotropic interactions under different decoupling conditions. Extensive numerical simulation results are corroborated with experiments on standard amino acids.

  1. Magnetization transfer magic-angle-spinning z-spectroscopy of excised tissues

    NASA Astrophysics Data System (ADS)

    Avni, Reut; Mangoubi, Oren; Bhattacharyya, Rangeet; Degani, Hadassa; Frydman, Lucio

    2009-07-01

    NMR experiments devised to aid in analyses of tissues include magnetization transfer (MT), which can highlight the signals of biological macromolecules through cross-relaxation and/or chemical exchange processes with the bulk 1H water resonance, and high-resolution magic-angle-spinning (HRMAS) methods, akin to those used in solid-state NMR to introduce additional spectral resolution via the averaging of spin anisotropies. This paper explores the result of combining these methodologies, and reports on MT "z-spectroscopy" between water and cell components in excised tissues under a variety of HRMAS conditions. Main features arising from the resulting 1H "MTMAS" experiments include strong spinning sideband manifolds centered at the liquid water shift, high-resolution isotropic features coinciding with aliphatic and amide proton resonances, and a second sideband manifold arising as spinning speeds are increased. Interpretations are given for the origin of these various features, including simulations shedding further light onto the nature of MT NMR signals observed for tissue samples. Concurrently, histological examinations are reported validating the limits of HRMAS NMR procedures to the analysis of tissue samples preserved in a number of different ways.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  3. Structure of fully protonated proteins by proton-detected magic-angle spinning NMR.

    PubMed

    Andreas, Loren B; Jaudzems, Kristaps; Stanek, Jan; Lalli, Daniela; Bertarello, Andrea; Le Marchand, Tanguy; Cala-De Paepe, Diane; Kotelovica, Svetlana; Akopjana, Inara; Knott, Benno; Wegner, Sebastian; Engelke, Frank; Lesage, Anne; Emsley, Lyndon; Tars, Kaspars; Herrmann, Torsten; Pintacuda, Guido

    2016-08-16

    Protein structure determination by proton-detected magic-angle spinning (MAS) NMR has focused on highly deuterated samples, in which only a small number of protons are introduced and observation of signals from side chains is extremely limited. Here, we show in two fully protonated proteins that, at 100-kHz MAS and above, spectral resolution is high enough to detect resolved correlations from amide and side-chain protons of all residue types, and to reliably measure a dense network of (1)H-(1)H proximities that define a protein structure. The high data quality allowed the correct identification of internuclear distance restraints encoded in 3D spectra with automated data analysis, resulting in accurate, unbiased, and fast structure determination. Additionally, we find that narrower proton resonance lines, longer coherence lifetimes, and improved magnetization transfer offset the reduced sample size at 100-kHz spinning and above. Less than 2 weeks of experiment time and a single 0.5-mg sample was sufficient for the acquisition of all data necessary for backbone and side-chain resonance assignment and unsupervised structure determination. We expect the technique to pave the way for atomic-resolution structure analysis applicable to a wide range of proteins. PMID:27489348

  4. Alignment of high resolution magic angle spinning magnetic resonance spectra using warping methods.

    PubMed

    Giskeødegård, Guro F; Bloemberg, Tom G; Postma, Geert; Sitter, Beathe; Tessem, May-Britt; Gribbestad, Ingrid S; Bathen, Tone F; Buydens, Lutgarde M C

    2010-12-17

    The peaks of magnetic resonance (MR) spectra can be shifted due to variations in physiological and experimental conditions, and correcting for misaligned peaks is an important part of data processing prior to multivariate analysis. In this paper, five warping algorithms (icoshift, COW, fastpa, VPdtw and PTW) are compared for their feasibility in aligning spectral peaks in three sets of high resolution magic angle spinning (HR-MAS) MR spectra with different degrees of misalignments, and their merits are discussed. In addition, extraction of information that might be present in the shifts is examined, both for simulated data and the real MR spectra. The generic evaluation methodology employs a number of frequently used quality criteria for evaluation of the alignments, together with PLS-DA to assess the influence of alignment on the classification outcome. Peak alignment greatly improved the internal similarity of the data sets. Especially icoshift and COW seem suitable for aligning HR-MAS MR spectra, possibly because they perform alignment segment-wise. The choice of reference spectrum can influence the alignment result, and it is advisable to test several references. Information from the peak shifts was extracted, and in one case cancer samples were successfully discriminated from normal tissue based on shift information only. Based on these findings, general recommendations for alignment of HR-MAS MRS data are presented. Where possible, observations are generalized to other data types (e.g. chromatographic data). PMID:21094376

  5. Frequency-stepped acquisition in nuclear magnetic resonance spectroscopy under magic angle spinning

    NASA Astrophysics Data System (ADS)

    Pell, Andrew J.; Clément, Raphaële J.; Grey, Clare P.; Emsley, Lyndon; Pintacuda, Guido

    2013-03-01

    The nuclear magnetic resonance of paramagnetic solids is usually characterized by the presence of large chemical shifts and shift anisotropies due to hyperfine interactions. Frequently the resulting spectra cover a frequency range of several megahertz, which is greater than the bandwidth of commercially available radio-frequency (RF) probes, making it impossible to acquire the whole spectrum in a single experiment. In these cases it common to record a series of spectra, in which the probe is tuned to a different frequency for each, and then sum the results to give the "true" spectrum. While this method is very widely used on static samples, the application of frequency stepping under magic-angle spinning (MAS) is less common, owing to the increased complexity of the spin dynamics when describing the interplay of the RF irradiation with the mechanical rotation of the shift tensor. In this paper, we present a theoretical description, based on the jolting frame formalism of Caravatti et al. [J. Magn. Reson. 55, 88 (1983), 10.1016/0022-2364(83)90279-2], for describing the spin dynamics of a powder sample under MAS when subjected to a selective pulse of low RF-field amplitude. The formalism is used to describe the frequency stepping method under MAS, and under what circumstances the true spectrum is reproduced. We also present an experimental validation of the methodology under ultra-fast MAS with the paramagnetic materials LiMnPO4 and TbCsDPA.

  6. Deuterium magic angle spinning studies of substrates bound to cytochrome P450.

    PubMed

    Lee, H; Ortiz de Montellano, P R; McDermott, A E

    1999-08-17

    We report solid-state deuterium magic angle spinning NMR spectra of perdeuterated adamantane bound to the active site of microcrystalline cytochrome P450cam (CP450cam) in its resting state. CP450cam contains a high-spin ferric (Fe3+) heme in the resting state; the isotropic shift was displaced from the diamagnetic value and varied with temperature consistent with Curie-law dependence. A nondeuterated competitive tighter binding ligand, camphor, was used to displace the adamantane-bound species. This addition resulted in the disappearance of the hyperfine-shifted signal associated with a perdeuterated adamantane bound to CP450cam, while signals presumably associated with adamantane bound to other cavities persisted. We simulated the deuterium spinning side-band intensities for the enzyme-bound species using dipolar hyperfine coupling as the only anisotropic interaction; the deuterium quadrupolar interaction was apparently averaged due to a fast high-symmetry motion. These data provide direct support for previous proposals that substrates are conformationally mobile on the time scale of enzymatic turnover. The simulations suggested that the adamantane binds with an average metal-deuterium distance of 6.2 (+/-0.2) A, corresponding to a dipolar coupling constant of 6.5 (+/-0.5) kHz. PMID:10451377

  7. Molecular dynamics in paramagnetic materials as studied by magic-angle spinning 2H NMR spectra.

    PubMed

    Mizuno, Motohiro; Suzuki, You; Endo, Kazunaka; Murakami, Miwa; Tansho, Masataka; Shimizu, Tadashi

    2007-12-20

    A magic-angle spinning (MAS) 2H NMR experiment was applied to study the molecular motion in paramagnetic compounds. The temperature dependences of 2H MAS NMR spectra were measured for paramagnetic [M(H2O)6][SiF6] (M=Ni2+, Mn2+, Co2+) and diamagnetic [Zn(H2O)6][SiF6]. The paramagnetic compounds exhibited an asymmetric line shape in 2H MAS NMR spectra because of the electron-nuclear dipolar coupling. The drastic changes in the shape of spinning sideband patterns and in the line width of spinning sidebands due to the 180 degrees flip of water molecules and the reorientation of [M(H2O)6]2+ about its C3 axis were observed. In the paramagnetic compounds, paramagnetic spin-spin relaxation and anisotropic g-factor result in additional linebroadening of each of the spinning sidebands. The spectral simulation of MAS 2H NMR, including the effects of paramagnetic shift and anisotropic spin-spin relaxation due to electron-nuclear dipolar coupling and anisotropic g-factor, was performed for several molecular motions. Information about molecular motions in the dynamic range of 10(2) s(-1)

  8. Dynamic nuclear polarization at 40 kHz magic angle spinning.

    PubMed

    Chaudhari, Sachin R; Berruyer, Pierrick; Gajan, David; Reiter, Christian; Engelke, Frank; Silverio, Daniel L; Copéret, Christophe; Lelli, Moreno; Lesage, Anne; Emsley, Lyndon

    2016-04-21

    DNP-enhanced solid-state NMR spectroscopy under magic angle spinning (MAS) is rapidly developing into a powerful analytical tool to investigate the structure of a wide range of solid materials, because it provides unsurpassed sensitivity gains. Most developments and applications of DNP MAS NMR were so far reported at moderate spinning frequencies (up to 14 kHz using 3.2 mm rotors). Here, using a 1.3 mm MAS DNP probe operating at 18.8 T and ∼100 K, we show that signal amplification factors can be increased by up to a factor two when using smaller volume rotors as compared to 3.2 mm rotors, and report enhancements of around 60 over a range of sample spinning rates from 10 to 40 kHz. Spinning at 40 kHz is also shown to increase (29)Si coherence lifetimes by a factor three as compared to 10 kHz, substantially increasing sensitivity in CPMG type experiments. The contribution of quenching effects to the overall sensitivity gain at very fast MAS is evaluated, and applications are reported on a functionalised mesostructured organic-inorganic material. PMID:27035630

  9. Cryogenic sample exchange NMR probe for magic angle spinning dynamic nuclear polarization

    PubMed Central

    Barnes, Alexander B.; Mak-Jurkauskas, Melody L.; Matsuki, Yoh; Bajaj, Vikram S.; van der Wel, Patrick C. A.; DeRocher, Ronald; Bryant, Jeffrey; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Lugtenburg, Johan; Herzfeld, Judith; Griffin, Robert G.

    2009-01-01

    We describe a cryogenic sample exchange system that dramatically improves the efficiency of magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments by reducing the time required to change samples and by improving long-term instrument stability. Changing samples in conventional cryogenic MAS DNP/NMR experiments involves warming the probe to room temperature, detaching all cryogenic, RF, and microwave connections, removing the probe from the magnet, replacing the sample, and reversing all the previous steps, with the entire cycle requiring a few hours. The sample exchange system described here — which relies on an eject pipe attached to the front of the MAS stator and a vacuum jacketed dewar with a bellowed hole — circumvents these procedures. To demonstrate the excellent sensitivity, resolution, and stability achieved with this quadruple resonance sample exchange probe, we have performed high precision distance measurements on the active site of the membrane protein bacteriorhodopsin. We also include a spectrum of the tripeptide N-f-MLF-OH at 100 K which shows 30 Hz linewidths. PMID:19356957

  10. Advanced slow-magic angle spinning probe for magnetic resonance imaging and spectroscopy

    DOEpatents

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

    2006-01-24

    The present invention relates to a probe and processes useful for magnetic resonance imaging and spectroscopy instruments. More particularly, the invention relates to a MR probe and processes for obtaining resolution enhancements of fluid objects, including live specimens, using an ultra-slow (magic angle) spinning (MAS) of the specimen combined with a modified phase-corrected magic angle turning (PHORMAT) pulse sequence. Proton NMR spectra were measured of the torso and the top part of the belly of a female BALBc mouse in a 2T field, while spinning the animal at a speed of 1.5 Hz. Results show that even in this relatively low field with PHORMAT, an isotropic spectrum is obtained with line widths that are a factor 4.6 smaller than those obtained in a stationary mouse. Resolution of 1H NMR metabolite spectra are thus significantly enhanced. Results indicate that PHORMAT has the potential to significantly increase the utility of 1H NMR spectroscopy for in vivo biochemical, biomedical and/or medical applications involving large-sized biological objects such as mice, rats and even humans within a hospital setting. For small-sized objects, including biological objects, such as excised tissues, organs, live bacterial cells, and biofilms, use of PASS at a spinning rate of 30 Hz and above is preferred.

  11. Correlating high-resolution magic angle spinning NMR spectroscopy and gene analysis in osteoarthritic cartilage.

    PubMed

    Tufts, Lauren; Shet Vishnudas, Keerthi; Fu, Eunice; Kurhanewicz, John; Ries, Michael; Alliston, Tamara; Li, Xiaojuan

    2015-05-01

    Osteoarthritis (OA) is a common multifactorial and heterogeneous degenerative joint disease, and biochemical changes in cartilage matrix occur during the early stages of OA before morphological changes occur. Thus, it is desired to measure regional biochemical changes in the joint. High-resolution magic angle spinning (HRMAS) NMR spectroscopy is a powerful method of observing cartilaginous biochemical changes ex vivo, including the concentrations of alanine and N-acetyl, which are markers of collagen and total proteoglycan content, respectively. Previous studies have observed significant changes in chondrocyte metabolism of OA cartilage via the altered gene expression profiles of ACAN, COL2A1 and MMP13, which encode aggrecan, type II collagen and matrix metalloproteinase 13 (a protein crucial in the degradation of type II collagen), respectively. Employing HRMAS, this study aimed to elucidate potential relationships between N-acetyl and/or alanine and ACAN, COL2A1 and/or MMP13 expression profiles in OA cartilage. Thirty samples from the condyles of five subjects undergoing total knee arthroplasty to treat OA were collected. HRMAS spectra were obtained at 11.7 T for each sample. RNA was subsequently extracted to determine gene expression profiles. A significant negative correlation between N-acetyl metabolite and ACAN gene expression levels was observed; this provides further evidence of N-acetyl as a biomarker of cartilage degeneration. The alanine doublet was distinguished in the spectra of 15 of the 30 specimens of this study. Alanine can only be detected with HRMAS NMR spectroscopy when the collagen framework has been degraded such that alanine is sufficiently mobile to form a distinguished peak in the spectrum. Thus, HRMAS NMR spectroscopy may provide unique localized measurements of collagenous degeneration in OA cartilage. The identification of imaging markers that could provide a link between OA pathology and chondrocyte metabolism will facilitate the

  12. Spinning-sideband patterns in multiple-quantum magic-angle spinning NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Friedrich, Ulli

    1998-12-01

    Recent interest has focused on solid-state NMR experiments which excite multiple-quantum (MQ) coherences in the presence of magic-angle spinning (MAS). Such experiments have been applied to both dipolar-coupled spin Ι = 1/2 and half-integer quadrupolar systems. A feature common to both cases is the observation of interesting spinning sideband patterns in the indirect (MQ) dimension. In this paper, the origin of these patterns is reviewed in terms of two distinct mechanisms: first, rotor encoding of the dipolar or quadrupolar interaction caused by the change in the Hamiltonian active during the MQ reconversion period relative to the excitation period (reconversion rotor encoding, RRE); and, second, rotor modulation of the interaction during the evolution of the MQ coherences in the t1 dimension (evolution rotor modulation, ERM). Only the first mechanism is present for total spin coherences, while for lower-order MQ coherences both mechanisms contribute to the pattern. For dipolar and quadrupolar model systems, i.e., the three protons of a methyl group and quadrupolar nuclei with spin Ι = 3/2 and Ι = 5/2 and axially symmetric first-order quadrupolar interactions, analytical expressions are derived for all orders of MQ MAS signals. Simulations based on these analytical expressions and numerical density matrix simulations are compared with experimental spectra. Additional perturbing influences, such as the heteronuclear dipolar coupling between a quadrupolar and a spin Ι = 1/2 nucleus, are taken into account. The effect of dipolar couplings on a quadrupolar MQ spectrum is found to be enhanced by the order of the observed MQ coherence.

  13. Pulsed field gradient magic angle spinning NMR self-diffusion measurements in liquids.

    PubMed

    Viel, Stéphane; Ziarelli, Fabio; Pagès, Guilhem; Carrara, Caroline; Caldarelli, Stefano

    2008-01-01

    Several investigations have recently reported the combined use of pulsed field gradient (PFG) with magic angle spinning (MAS) for the analysis of molecular mobility in heterogeneous materials. In contrast, little attention has been devoted so far to delimiting the role of the extra force field induced by sample rotation on the significance and reliability of self-diffusivity measurements. The main purpose of this work is to examine this phenomenon by focusing on pure liquids for which its impact is expected to be largest. Specifically, we show that self-diffusion coefficients can be accurately determined by PFG MAS NMR diffusion measurements in liquids, provided that specific experimental conditions are met. First, the methodology to estimate the gradient uniformity and to properly calibrate its absolute strength is briefly reviewed and applied on a MAS probe equipped with a gradient coil aligned along the rotor spinning axis, the so-called 'magic angle gradient' coil. Second, the influence of MAS on the outcome of PFG MAS diffusion measurements in liquids is investigated for two distinct typical rotors of different active volumes, 12 and 50 microL. While the latter rotor led to totally unreliable results, especially for low viscosity compounds, the former allowed for the determination of accurate self-diffusion coefficients both for fast and slowly diffusing species. Potential implications of this work are the possibility to measure accurate self-diffusion coefficients of sample-limited mixtures or to avoid radiation damping interferences in NMR diffusion measurements. Overall, the outlined methodology should be of interest to anyone who strives to improve the reliability of MAS diffusion studies, both in homogeneous and heterogeneous media. PMID:18006344

  14. Nuclear depolarization and absolute sensitivity in magic-angle spinning cross effect dynamic nuclear polarization.

    PubMed

    Mentink-Vigier, Frédéric; Paul, Subhradip; Lee, Daniel; Feintuch, Akiva; Hediger, Sabine; Vega, Shimon; De Paëpe, Gaël

    2015-09-14

    Over the last two decades solid state Nuclear Magnetic Resonance has witnessed a breakthrough in increasing the nuclear polarization, and thus experimental sensitivity, with the advent of Magic Angle Spinning Dynamic Nuclear Polarization (MAS-DNP). To enhance the nuclear polarization of protons, exogenous nitroxide biradicals such as TOTAPOL or AMUPOL are routinely used. Their efficiency is usually assessed as the ratio between the NMR signal intensity in the presence and the absence of microwave irradiation εon/off. While TOTAPOL delivers an enhancement εon/off of about 60 on a model sample, the more recent AMUPOL is more efficient: >200 at 100 K. Such a comparison is valid as long as the signal measured in the absence of microwaves is merely the Boltzmann polarization and is not affected by the spinning of the sample. However, recent MAS-DNP studies at 25 K by Thurber and Tycko (2014) have demonstrated that the presence of nitroxide biradicals combined with sample spinning can lead to a depolarized nuclear state, below the Boltzmann polarization. In this work we demonstrate that TOTAPOL and AMUPOL both lead to observable depolarization at ≈110 K, and that the magnitude of this depolarization is radical dependent. Compared to the static sample, TOTAPOL and AMUPOL lead, respectively, to nuclear polarization losses of up to 20% and 60% at a 10 kHz MAS frequency, while Trityl OX63 does not depolarize at all. This experimental work is analyzed using a theoretical model that explains how the depolarization process works under MAS and gives new insights into the DNP mechanism and into the spin parameters, which are relevant for the efficiency of a biradical. In light of these results, the outstanding performance of AMUPOL must be revised and we propose a new method to assess the polarization gain for future radicals. PMID:26235749

  15. 13C NMR spectroscopy of the insoluble carbon of carbonaceous chondrites

    NASA Technical Reports Server (NTRS)

    Cronin, J. R.; Pizzarello, S.; Frye, J. S.

    1987-01-01

    13C NMR spectra have been obtained of the insoluble carbon residues resulting from HF-digestion of three carbonaceous chondrites, Orgueil (C1), Murchison (CM2), and Allende (CV3). Spectra obtained using the cross polarization magic-angle spinning technique show two major features attributable respectively to carbon in aliphatic/olefinic structures. The spectrum obtained from the Allende sample was weak, presumably as a consequence of its low hydrogen content. Single pulse excitation spectra, which do not depend on 1H-13C polarization transfer for signal enhancement were also obtained. These spectra, which may be more representative of the total carbon in the meteorite samples, indicate a greater content of carbon in aromatic/olefinic structures. These results suggest that extensive polycyclic aromatic sheets are important structural features of the insoluble carbon of all three meteorites. The Orgueil and Murchison materials contain additional hydrogenated aromatic/olefinic and aliphatic groups.

  16. Characterization of lithium coordination sites with magic-angle spinning NMR

    NASA Astrophysics Data System (ADS)

    Haimovich, A.; Goldbourt, A.

    2015-05-01

    Lithium, in the form of lithium carbonate, is one of the most common drugs for bipolar disorder. Lithium is also considered to have an effect on many other cellular processes hence it possesses additional therapeutic as well as side effects. In order to quantitatively characterize the binding mode of lithium, it is required to identify the interacting species and measure their distances from the metal center. Here we use magic-angle spinning (MAS) solid-state NMR to study the binding site of lithium in complex with glycine and water (LiGlyW). Such a compound is a good enzyme mimetic since lithium is four-coordinated to one water molecule and three carboxylic groups. Distance measurements to carbons are performed using a 2D transferred echo double resonance (TEDOR) MAS solid-state NMR experiment, and water binding is probed by heteronuclear high-resolution proton-lithium and proton-carbon correlation (wPMLG-HETCOR) experiments. Both HETCOR experiments separate the main complex from impurities and non-specifically bound lithium species, demonstrating the sensitivity of the method to probe the species in the binding site. Optimizations of the TEDOR pulse scheme in the case of a quadrupolar nucleus with a small quadrupole coupling constant show that it is most efficient when pulses are positioned on the spin-1/2 (carbon-13) nucleus. Since the intensity of the TEDOR signal is not normalized, careful data analysis that considers both intensity and dipolar oscillations has to be performed. Nevertheless we show that accurate distances can be extracted for both carbons of the bound glycine and that these distances are consistent with the X-ray data and with lithium in a tetrahedral environment. The lithium environment in the complex is very similar to the binding site in inositol monophosphatase, an enzyme associated with bipolar disorder and the putative target for lithium therapy. A 2D TEDOR experiment applied to the bacterial SuhB gene product of this enzyme was designed

  17. Proton-detected solid-state NMR spectroscopy of fully protonated proteins at slow to moderate magic-angle spinning frequencies

    NASA Astrophysics Data System (ADS)

    Mote, Kaustubh R.; Madhu, Perunthiruthy K.

    2015-12-01

    1H -detection offers a substitute to the sensitivity-starved experiments often used to characterize biomolecular samples using magic-angle spinning solid-state NMR spectroscopy (MAS-ssNMR). To mitigate the effects of the strong 1H -1H dipolar coupled network that would otherwise severely broaden resonances, high MAS frequencies (>40 kHz) are often employed. Here, we have explored the alternative of stroboscopic 1H -detection at moderate MAS frequencies of 5-30 kHz using windowed version of supercycled-phase-modulated Lee-Goldburg homonuclear decoupling. We show that improved resolution in the 1H dimension, comparable to that obtainable at high spinning frequencies of 40-60 kHz without homonuclear decoupling, can be obtained in these experiments for fully protonated proteins. Along with detailed analysis of the performance of the method on the standard tri-peptide f-MLF, experiments on micro-crystalline GB1 and amyloid- β aggregates are used to demonstrate the applicability of these pulse-sequences to challenging biomolecular systems. With only two parameters to optimize, broadbanded performance of the homonuclear decoupling sequence, linear dependence of the chemical-shift scaling factor on resonance offset and a straightforward implementation under experimental conditions currently used for many biomolecular studies (viz. spinning frequencies and radio-frequency amplitudes), we expect these experiments to complement the current 13C -detection based methods in assignments and characterization through chemical-shift mapping.

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

    PubMed

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

    2016-09-01

    Transverse relaxation rate measurements in magic-angle spinning solid-state nuclear magnetic resonance provide information about molecular motions occurring on nanosecond-to-millisecond (ns-ms) time scales. The measurement of heteronuclear ((13)C, (15)N) relaxation rate constants in the presence of a spin-lock radiofrequency field (R1ρ relaxation) provides access to such motions, and an increasing number of studies involving R1ρ relaxation in proteins have been reported. However, two factors that influence the observed relaxation rate constants have so far been neglected, namely, (1) the role of CSA/dipolar cross-correlated relaxation (CCR) and (2) the impact of fast proton spin flips (i.e., proton spin diffusion and relaxation). We show that CSA/D CCR in R1ρ experiments is measurable and that the CCR rate constant depends on ns-ms motions; it can thus provide insight into dynamics. We find that proton spin diffusion attenuates this CCR due to its decoupling effect on the doublet components. For measurements of dynamics, the use of R1ρ rate constants has practical advantages over the use of CCR rates, and this article reveals factors that have so far been disregarded and which are important for accurate measurements and interpretation. PMID:27500976

  19. A Monte Carlo/Simulated Annealing Algorithm for Sequential Resonance Assignment in Solid State NMR of Uniformly Labeled Proteins with Magic-Angle Spinning

    PubMed Central

    Tycko, Robert; Hu, Kan-Nian

    2010-01-01

    We describe a computational approach to sequential resonance assignment in solid state NMR studies of uniformly 15N,13C-labeled proteins with magic-angle spinning. As input, the algorithm uses only the protein sequence and lists of 15N/13Cα crosspeaks from 2D NCACX and NCOCX spectra that include possible residue-type assignments of each crosspeak. Assignment of crosspeaks to specific residues is carried out by a Monte Carlo/simulated annealing algorithm, implemented in the program MC_ASSIGN1. The algorithm tolerates substantial ambiguity in residue-type assignments and coexistence of visible and invisible segments in the protein sequence. We use MC_ASSIGN1 and our own 2D spectra to replicate and extend the sequential assignments for uniformly labeled HET-s(218-289) fibrils previously determined manually by Siemer et al. (J. Biomolec. NMR, vol. 34, pp. 75-87, 2006) from a more extensive set of 2D and 3D spectra. Accurate assignments by MC_ASSIGN1 do not require data that are of exceptionally high quality. Use of MC_ASSIGN1 (and its extensions to other types of 2D and 3D data) is likely to alleviate many of the difficulties and uncertainties associated with manual resonance assignments in solid state NMR studies of uniformly labeled proteins, where spectral resolution and signal-to-noise are often sub-optimal. PMID:20547467

  20. Magic angle spinning nuclear magnetic resonance characterization of voltage-dependent anion channel gating in two-dimensional lipid crystalline bilayers.

    PubMed

    Eddy, Matthew T; Andreas, Loren; Teijido, Oscar; Su, Yongchao; Clark, Lindsay; Noskov, Sergei Y; Wagner, Gerhard; Rostovtseva, Tatiana K; Griffin, Robert G

    2015-02-01

    The N-terminus of the voltage-dependent anion channel (VDAC) has been proposed to contain the mechanistically important gating helices that modulate channel opening and closing. In this study, we utilize magic angle spinning nuclear magnetic resonance (MAS NMR) to determine the location and structure of the N-terminus for functional channels in lipid bilayers by measuring long-range (13)C-(13)C distances between residues in the N-terminus and other domains of VDAC reconstituted into DMPC lipid bilayers. Our structural studies show that the distance between A14 Cβ in the N-terminal helix and S193 Cβ is ∼4-6 Å. Furthermore, VDAC phosphorylation by a mitochondrial kinase at residue S193 has been claimed to delay mitochondrial cell death by causing a conformational change that closes the channel, and a VDAC-Ser193Glu mutant has been reported to show properties very similar to those of phosphorylated VDAC in a cellular context. We expressed VDAC-S193E and reconstituted it into DMPC lipid bilayers. Two-dimensional (13)C-(13)C correlation experiments showed chemical shift perturbations for residues located in the N-terminus, indicating possible structural perturbations to that region. However, electrophysiological data recorded on VDAC-S193E showed that channel characteristics were identical to those of wild type samples, indicating that phosphorylation of S193 does not directly affect channel gating. The combination of NMR and electrophysiological results allows us to discuss the validity of proposed gating models. PMID:25545271

  1. High Resolution Magic Angle Spinning 1H-NMR Metabolic Profiling of Nanoliter Biological Tissues at High Magnetic Field

    SciTech Connect

    Feng, Ju; Hu, Jian Z.; Burton, Sarah D.; Hoyt, David W.

    2013-03-05

    It is demonstrated that a high resolution magic angle spinning 1H-NMR spectrum of biological tissue samples with volumes as small as 150 nanoliters, or 0.15 mg in weight, can be acquired in a few minutes at 21.1 T magnetic field using a commercial 1.6 mm fast-MAS probe with minor modification of the MAS rotor. The strategies of sealing the samples inside the MAS rotor to avoid fluid leakage as well as the ways of optimizing the signal to noise are discussed.

  2. High-pressure, high-temperature magic angle spinning nuclear magnetic resonance devices and processes for making and using same

    DOEpatents

    Hu, Jian Zhi; Hu, Mary Y.; Townsend, Mark R.; Lercher, Johannes A.; Peden, Charles H. F.

    2015-10-06

    Re-usable ceramic magic angle spinning (MAS) NMR rotors constructed of high-mechanic strength ceramics are detailed that include a sample compartment that maintains high pressures up to at least about 200 atmospheres (atm) and high temperatures up to about least about 300.degree. C. during operation. The rotor designs minimize pressure losses stemming from penetration over an extended period of time. The present invention makes possible a variety of in-situ high pressure, high temperature MAS NMR experiments not previously achieved in the prior art.

  3. 13C Nuclear magnetic resonance studies of kerogen from Cretaceous black shales thermally altered by basaltic intrusions and laboratory simulations

    USGS Publications Warehouse

    Dennis, L.W.; Maciel, G.E.; Hatcher, P.G.; Simoneit, B.R.T.

    1982-01-01

    Cretaceous black shales from DSDP Leg 41, Site 368 in the Eastern Atlantic Ocean were thermally altered during the Miocene by an intrusive basalt. The sediments overlying and underlying the intrusive body were subjected to high temperatures (up to ~ 500??C) and, as a result, their kerogen was significantly altered. The extent of this alteration has been determined by examination by means of 13C nuclear magnetic resonance, using cross polarization/magic-angle spinning (CP/MAS). Results indicate that the kerogen becomes progressively more aromatic in the vicinity of the intrusive body. Laboratory heating experiments, simulating the thermal effects of the basaltic intrusion, produced similar results on unaltered shale from the drill core. The 13C CP/MAS results appear to provide a good measure of thermal alteration. ?? 1982.

  4. Bonding in hard and elastic amorphous carbon nitride films investigated using 15N, 13C, and 1H NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Gammon, W. J.; Hoatson, G. L.; Holloway, B. C.; Vold, R. L.; Reilly, A. C.

    2003-11-01

    The nitrogen bonding in hard and elastic amorphous carbon nitride (a-CNx) films is examined with 15N, 13C, and 1H nuclear magnetic resonance (NMR) spectroscopy. Films were deposited by dc magnetron sputtering, in a pure nitrogen discharge on Si(001) substrates at 300 °C. Nanoindentation tests revealed an elastic recovery of 80%, a hardness of 5 GPa, and an elastic modulus of 47 GPa. The NMR results show that nitrogen bonding in this material is consistent with sp2 hybridized nitrogen incorporated in an aromatic carbon environment. The data also indicate that the a-CNx prepared for this study has very low hydrogen content and is hydrophilic. Specifically, analysis of 15N and 13C cross polarization magic angle spinning and 1H NMR experiments suggests that water preferentially protonates nitrogen sites.

  5. Dynamics of cross polarization in solid state nuclear magnetic resonance experiments of amorphous and heterogeneous natural organic substances.

    PubMed

    Conte, Pellegrino; Berns, Anne E

    2008-09-01

    Nuclear magnetic resonance (NMR) experiments on carbon-13 in the solid state were done with cross polarization (CP) and magic angle spinning (MAS) in order to overcome the low NMR sensitivity of (13)C and the chemical shift anisotropy, respectively. In the present research, CPMAS (13)C-NMR spectra were collected by modulating the contact time needed for cross polarization (variable contact times experiments, VCT) on two different humic acids (a soil-HA and a coal-HA). VCT data were fitted by a model containing either a monotonic or a non-monotonic cross polarization term. The non-monotonic model, which fitted the experimental results better than the monotonic one, provided two cross-polarization rates, thereby suggesting that two different mechanisms for the energy transfer from protons to carbons arise in amorphous and heterogeneous humic substances. The first mechanism was a fast proton-to-carbon energy transfer due to protons directly bound to carbons. The second mechanism was related to a slow transfer mediated by local segmental motions. Different domains in the humic acids were identified. Soil-HA was made of rigid domains, containing mainly aromatic and carboxylic moieties, and fast moving domains, containing alkyl, C-O and C-O groups. Coal-HA showed a rigid aromatic domain that was differentiated from a very mobile domain made of alkyl and COOH groups. PMID:18781033

  6. Lipid bilayer preparations of membrane proteins for oriented and magic-angle spinning solid-state NMR samples

    PubMed Central

    Das, Nabanita; Murray, Dylan T; Cross, Timothy A

    2014-01-01

    Solid-state NMR spectroscopy has been used successfully for characterizing the structure and dynamics of membrane proteins as well as their interactions with other proteins in lipid bilayers. such an environment is often necessary for achieving native-like structures. sample preparation is the key to this success. Here we present a detailed description of a robust protocol that results in high-quality membrane protein samples for both magic-angle spinning and oriented-sample solid-state NMR. the procedure is demonstrated using two proteins: CrgA (two transmembrane helices) and rv1861 (three transmembrane helices), both from Mycobacterium tuberculosis. the success of this procedure relies on two points. First, for samples for both types of NMR experiment, the reconstitution of the protein from a detergent environment to an environment in which it is incorporated into liposomes results in ‘complete’ removal of detergent. second, for the oriented samples, proper dehydration followed by rehydration of the proteoliposomes is essential. By using this protocol, proteoliposome samples for magic-angle spinning NMR and uniformly aligned samples (orientational mosaicity of <1°) for oriented-sample NMR can be obtained within 10 d. PMID:24157546

  7. Magic Angle Spinning Nuclear Magnetic Resonance Characterization of Voltage-Dependent Anion Channel Gating in Two-Dimensional Lipid Crystalline Bilayers

    PubMed Central

    2015-01-01

    The N-terminus of the voltage-dependent anion channel (VDAC) has been proposed to contain the mechanistically important gating helices that modulate channel opening and closing. In this study, we utilize magic angle spinning nuclear magnetic resonance (MAS NMR) to determine the location and structure of the N-terminus for functional channels in lipid bilayers by measuring long-range 13C–13C distances between residues in the N-terminus and other domains of VDAC reconstituted into DMPC lipid bilayers. Our structural studies show that the distance between A14 Cβ in the N-terminal helix and S193 Cβ is ∼4–6 Å. Furthermore, VDAC phosphorylation by a mitochondrial kinase at residue S193 has been claimed to delay mitochondrial cell death by causing a conformational change that closes the channel, and a VDAC-Ser193Glu mutant has been reported to show properties very similar to those of phosphorylated VDAC in a cellular context. We expressed VDAC-S193E and reconstituted it into DMPC lipid bilayers. Two-dimensional 13C–13C correlation experiments showed chemical shift perturbations for residues located in the N-terminus, indicating possible structural perturbations to that region. However, electrophysiological data recorded on VDAC-S193E showed that channel characteristics were identical to those of wild type samples, indicating that phosphorylation of S193 does not directly affect channel gating. The combination of NMR and electrophysiological results allows us to discuss the validity of proposed gating models. PMID:25545271

  8. Indirectly detected chemical shift correlation NMR spectroscopy in solids under fast magic angle spinning

    SciTech Connect

    Mao, Kanmi

    2011-01-01

    The development of fast magic angle spinning (MAS) opened up an opportunity for the indirect detection of insensitive low-γ nuclei (e.g., 13C and 15N) via the sensitive high-{gamma} nuclei (e.g., 1H and 19F) in solid-state NMR, with advanced sensitivity and resolution. In this thesis, new methodology utilizing fast MAS is presented, including through-bond indirectly detected heteronuclear correlation (HETCOR) spectroscopy, which is assisted by multiple RF pulse sequences for 1H-1H homonuclear decoupling. Also presented is a simple new strategy for optimization of 1H-1H homonuclear decoupling. As applications, various classes of materials, such as catalytic nanoscale materials, biomolecules, and organic complexes, are studied by combining indirect detection and other one-dimensional (1D) and two-dimensional (2D) NMR techniques. Indirectly detected through-bond HETCOR spectroscopy utilizing refocused INEPT (INEPTR) mixing was developed under fast MAS (Chapter 2). The time performance of this approach in 1H detected 2D 1H{l_brace}13C{r_brace} spectra was significantly improved, by a factor of almost 10, compared to the traditional 13C detected experiments, as demonstrated by measuring naturally abundant organic-inorganic mesoporous hybrid materials. The through-bond scheme was demonstrated as a new analytical tool, which provides complementary structural information in solid-state systems in addition to through-space correlation. To further benefit the sensitivity of the INEPT transfer in rigid solids, the combined rotation and multiple-pulse spectroscopy (CRAMPS) was implemented for homonuclear 1H decoupling under fast MAS (Chapter 3). Several decoupling schemes (PMLG5m$\\bar{x}$, PMLG5mm$\\bar{x}$x and SAM3) were analyzed to maximize the performance of through-bond transfer based

  9. Floquet-Magnus expansion for general N-coupled spins systems in magic-angle spinning nuclear magnetic resonance spectra

    NASA Astrophysics Data System (ADS)

    Mananga, Eugene Stephane; Charpentier, Thibault

    2015-04-01

    In this paper we present a theoretical perturbative approach for describing the NMR spectrum of strongly dipolar-coupled spin systems under fast magic-angle spinning. Our treatment is based on two approaches: the Floquet approach and the Floquet-Magnus expansion. The Floquet approach is well known in the NMR community as a perturbative approach to get analytical approximations. Numerical procedures are based on step-by-step numerical integration of the corresponding differential equations. The Floquet-Magnus expansion is a perturbative approach of the Floquet theory. Furthermore, we address the " γ -encoding" effect using the Floquet-Magnus expansion approach. We show that the average over " γ " angle can be performed for any Hamiltonian with γ symmetry.

  10. Development of a magic-angle spinning nuclear magnetic resonance probe with a cryogenic detection system for sensitivity enhancement

    NASA Astrophysics Data System (ADS)

    Mizuno, Takashi; Hioka, Katsuya; Fujioka, Koji; Takegoshi, K.

    2008-04-01

    A novel nuclear magnetic resonance (NMR) probe for high-resolution solid-state NMR has been developed. In this probe, temperature of the detection coil is kept at cryogenic temperature (˜12K) for sensitivity enhancement, which is achieved not only by suppression of thermal noise but also by increment of a Q factor of the coil. A marked feature of this probe is that a sample rotating at magic angle is thermally isolated from the cryogenic system in order to realize high-resolution solid-state NMR measurement at various sample temperatures. We call this system as cryocoil magic-angle spinning (cryocoil MAS). H1 MAS NMR with the coil temperature of ˜20K was successfully observed for solid adamantane rotating at room temperature, and signal-to-noise increment due to this cryocoil approach was confirmed.

  11. Magic angle spinning NMR investigation of influenza A M2(18-60): support for an allosteric mechanism of inhibition.

    PubMed

    Andreas, Loren B; Eddy, Matthew T; Pielak, Rafal M; Chou, James; Griffin, Robert G

    2010-08-18

    The tetrameric M2 proton channel from influenza A virus conducts protons at low pH and is inhibited by aminoadamantyl drugs such as amantadine and rimantadine (Rmt). We report magic angle spinning NMR spectra of POPC and DPhPC membrane-embedded M2(18-60), both apo and in the presence of Rmt. Similar line widths in the spectra of apo and bound M2 indicate that Rmt does not have a significant impact on the dynamics or conformational heterogeneity of this construct. Substantial chemical shift changes for many residues in the transmembrane region support an allosteric mechanism of inhibition. An Rmt titration supports a binding stoichiometry of >1 Rmt molecule per channel and shows that nonspecific binding or changes in membrane composition are unlikely sources of the chemical shift changes. In addition, doubling of spectral lines in all of the observed samples provides evidence that the channel assembles with twofold symmetry. PMID:20698642

  12. Magic-angle spinning NMR studies of molecular organization in multibilayers formed by 1-octadecanoyl-2-decanoyl-sn-glycero-3-phosphocholine.

    PubMed Central

    Halladay, H N; Stark, R E; Ali, S; Bittman, R

    1990-01-01

    Magic-angle spinning 1H and 13C nuclear magnetic resonance (NMR) have been employed to study 50%-by-weight aqueous dispersions of 1-octadecanoyl-2-decanoyl-sn-glycero-3-phosphocholine (C[18]:C[10]PC) and 1-octadecanoyl-2-d19-decanoyl-PC (C[18]:C[10]PC-d19), mixed-chain phospholipids which can form interdigitated multibilayers. The 1H NMR linewidth for methyl protons of the choline headgroup has been used to monitor the liquid crystalline-to-gel (LC-to-G) phase transition and confirm variations between freezing and melting temperatures. Both 1H and 13C spin-lattice relaxation times indicate unusual restrictions on segmental reorientation at megahertz frequencies for C(18):C(10)PC as compared with symmetric-chain species in the LC state; nevertheless each chemical moiety of the mixed-chain phospholipid exhibits motional behavior that may be classified as liquidlike. Two-dimensional nuclear Overhauser spectroscopy (NOESY) on C(18):C(10)PC and C(18):C(10)PC-d19 reveals cross-peaks between the omega-methyl protons of the C18 chain and the N-methyl protons of the phosphocholine headgroup, and several experimental and theoretical considerations argue against an interpretation based on spin diffusion. Using NMR relaxation times and NOESY connectivities along with a computational formalism for four-spin systems (Keepers, J. W., and T. L. James. 1984. J. Magn. Reson. 57:404-426), an estimate of 3.5 A is obtained for the average distance between the omega-methyl protons of the C18 chain and the N-methyl protons of the phosphocholine headgroup. This finding is consistent with a degree of interdigitation similar to that proposed for organized assemblies of gel-state phosphatidylcholine molecules with widely disparate acyl-chain lengths (Hui, S. W., and C.-H. Huang. 1986. Biochemistry. 25:1330-1335); however, acyl-chain bendback or other intermolecular interactions may also contribute to the NOESY results. For multibilayers of C(18):C(10)PC in the gel phase, 13C chemical

  13. 13C MAS NMR studies of the effects of hydration on the cell walls of potatoes and Chinese water chestnuts.

    PubMed

    Tang, H; Belton, P S; Ng, A; Ryden, P

    1999-02-01

    13C NMR with magic angle spinning (MAS) has been employed to investigate the cell walls of potatoes and Chinese water chestnuts over a range of hydration levels. Both single-pulse excitation (SPEMAS) and cross-polarization (CPMAS) experiments were carried out. Hydration led to a substantial increase in signal intensities of galactan and galacturonan in the SPEMAS spectra and a decrease in line width, implying mobilization in the backbone and side chains of pectin. In CPMAS spectra of both samples, noncellulose components showed signal loss as hydration increased. However, the signals of some galacturonan in the 3(1) helix configuration remained in the spectra even when the water content was as high as 110%. Cellulose was unaffected. It is concluded that the pectic polysaccharides experience a distribution of molecular conformations and mobility, whereas cellulose remained as typical rigid solid. PMID:10563925

  14. Glycerin-Induced Conformational Changes in Bombyx mori Silk Fibroin Film Monitored by (13)C CP/MAS NMR and ¹H DQMAS NMR.

    PubMed

    Asakura, Tetsuo; Endo, Masanori; Hirayama, Misaki; Arai, Hiroki; Aoki, Akihiro; Tasei, Yugo

    2016-01-01

    In order to improve the stiff and brittle characteristics of pure Bombyx mori (B. mori) silk fibroin (SF) film in the dry state, glycerin (Glyc) has been used as a plasticizer. However, there have been very limited studies on the structural characterization of the Glyc-blended SF film. In this study, (13)C Cross Polarization/Magic Angle Spinning nuclear magnetic resonance (CP/MAS NMR) was used to monitor the conformational changes in the films by changing the Glyc concentration. The presence of only 5 wt % Glyc in the film induced a significant conformational change in SF where Silk I* (repeated type II β-turn and no α-helix) newly appeared. Upon further increase in Glyc concentration, the percentage of Silk I* increased linearly up to 9 wt % Glyc and then tended to be almost constant (30%). This value (30%) was the same as the fraction of Ala residue within the Silk I* form out of all Ala residues of SF present in B. mori mature silkworm. The ¹H DQMAS NMR spectra of Glyc-blended SF films confirmed the appearance of Silk I* in the Glyc-blended SF film. A structural model of Glyc-SF complex including the Silk I* form was proposed with the guidance of the Molecular Dynamics (MD) simulation using ¹H-¹H distance constraints obtained from the ¹H Double-Quantum Magic Angle Spinning (DQMAS) NMR spectra. PMID:27618034

  15. Distortion-free {sup 13}C NMR spectroscopy in coal: {sup 1}H rotating-frame dynamic nuclear polarization and {sup 1}H-{sup 13}C cross-polarization

    SciTech Connect

    Wind, R.A.

    1993-12-31

    A {sup 1}H-{sup 13}C cross-polarization (CP) experiment is described in which the {sup 1}H magnetization, used in CP, is obtained via dynamic nuclear polarization (DNP) in the proton rotating frame (RF DNP). This experiment can be carried out in coal and other solids containing unpaired electrons. In this so-called RF DNP-CP experiment, interplay effects between the {sup 1}H-{sup 13}C polarization-transfer times and the {sup 1}H rotating-frame relaxation time are avoided; thus {sup 13}C spectral distortions due to these effects are prevented. Moreover, multiple-contact RF DNP-CP experiments are possible, and these experiments reduce the measuring time of a {sup 13}C spectrum. An application of the RF DNP-CP technique in a low-volatile bituminous coal is given. 25 refs., 3 figs.

  16. Pf1 bacteriophage hydration by magic angle spinning solid-state NMR

    NASA Astrophysics Data System (ADS)

    Sergeyev, Ivan V.; Bahri, Salima; Day, Loren A.; McDermott, Ann E.

    2014-12-01

    High resolution two- and three-dimensional heteronuclear correlation spectroscopy (1H-13C, 1H-15N, and 1H-13C-13C HETCOR) has provided a detailed characterization of the internal and external hydration water of the Pf1 virion. This long and slender virion (2000 nm × 7 nm) contains highly stretched DNA within a capsid of small protein subunits, each only 46 amino acid residues. HETCOR cross-peaks have been unambiguously assigned to 25 amino acids, including most external residues 1-21 as well as residues 39-40 and 43-46 deep inside the virion. In addition, the deoxyribose rings of the DNA near the virion axis are in contact with water. The sets of cross-peaks to the DNA and to all 25 amino acid residues were from the same hydration water 1H resonance; some of the assigned residues do not have exchangeable side-chain protons. A mapping of the contacts onto structural models indicates the presence of water "tunnels" through a highly hydrophobic region of the capsid. The present results significantly extend and modify results from a lower resolution study, and yield a comprehensive hydration surface map of Pf1. In addition, the internal water could be distinguished from external hydration water by means of paramagnetic relaxation enhancement. The internal water population may serve as a conveniently localized magnetization reservoir for structural studies.

  17. Nano-Mole Scale Side-Chain Signal Assignment by 1H-Detected Protein Solid-State NMR by Ultra-Fast Magic-Angle Spinning and Stereo-Array Isotope Labeling

    PubMed Central

    Nishiyama, Yusuke; Endo, Yuki; Nemoto, Takahiro; Yamauchi, Kazuo; Asakura, Tetsuo; Takeda, Mitsuhiro; Terauchi, Tsutomu; Kainosho, Masatsune; Ishii, Yoshitaka

    2015-01-01

    We present a general approach in 1H-detected 13C solid-state NMR (SSNMR) for side-chain signal assignments of 10-50 nmol quantities of proteins using a combination of a high magnetic field, ultra-fast magic-angle spinning (MAS) at ~80 kHz, and stereo-array-isotope-labeled (SAIL) proteins [Kainosho M. et al., Nature 440, 52–57, 2006]. First, we demonstrate that 1H indirect detection improves the sensitivity and resolution of 13C SSNMR of SAIL proteins for side-chain assignments in the ultra-fast MAS condition. 1H-detected SSNMR was performed for micro-crystalline ubiquitin (~55 nmol or ~0.5mg) that was SAIL-labeled at seven isoleucine (Ile) residues. Sensitivity was dramatically improved by 1H-detected 2D 1H/13C SSNMR by factors of 5.4-9.7 and 2.1-5.0, respectively, over 13C-detected 2D 1H/13C SSNMR and 1D 13C CPMAS, demonstrating that 2D 1H-detected SSNMR offers not only additional resolution but also sensitivity advantage over 1D 13C detection for the first time. High 1H resolution for the SAIL-labeled side-chain residues offered reasonable resolution even in the 2D data. A 1H-detected 3D 13C/13C/1H experiment on SAIL-ubiquitin provided nearly complete 1H and 13C assignments for seven Ile residues only within ~2.5 h. The results demonstrate the feasibility of side-chain signal assignment in this approach for as little as 10 nmol of a protein sample within ~3 days. The approach is likely applicable to a variety of proteins of biological interest without any requirements of highly efficient protein expression systems. PMID:25856081

  18. Nano-mole scale side-chain signal assignment by 1H-detected protein solid-state NMR by ultra-fast magic-angle spinning and stereo-array isotope labeling.

    PubMed

    Wang, Songlin; Parthasarathy, Sudhakar; Nishiyama, Yusuke; Endo, Yuki; Nemoto, Takahiro; Yamauchi, Kazuo; Asakura, Tetsuo; Takeda, Mitsuhiro; Terauchi, Tsutomu; Kainosho, Masatsune; Ishii, Yoshitaka

    2015-01-01

    We present a general approach in 1H-detected 13C solid-state NMR (SSNMR) for side-chain signal assignments of 10-50 nmol quantities of proteins using a combination of a high magnetic field, ultra-fast magic-angle spinning (MAS) at ~80 kHz, and stereo-array-isotope-labeled (SAIL) proteins [Kainosho M. et al., Nature 440, 52-57, 2006]. First, we demonstrate that 1H indirect detection improves the sensitivity and resolution of 13C SSNMR of SAIL proteins for side-chain assignments in the ultra-fast MAS condition. 1H-detected SSNMR was performed for micro-crystalline ubiquitin (~55 nmol or ~0.5mg) that was SAIL-labeled at seven isoleucine (Ile) residues. Sensitivity was dramatically improved by 1H-detected 2D 1H/13C SSNMR by factors of 5.4-9.7 and 2.1-5.0, respectively, over 13C-detected 2D 1H/13C SSNMR and 1D 13C CPMAS, demonstrating that 2D 1H-detected SSNMR offers not only additional resolution but also sensitivity advantage over 1D 13C detection for the first time. High 1H resolution for the SAIL-labeled side-chain residues offered reasonable resolution even in the 2D data. A 1H-detected 3D 13C/13C/1H experiment on SAIL-ubiquitin provided nearly complete 1H and 13C assignments for seven Ile residues only within ~2.5 h. The results demonstrate the feasibility of side-chain signal assignment in this approach for as little as 10 nmol of a protein sample within ~3 days. The approach is likely applicable to a variety of proteins of biological interest without any requirements of highly efficient protein expression systems. PMID:25856081

  19. Magic angle spinning nuclear magnetic resonance apparatus and process for high-resolution in situ investigations

    DOEpatents

    Hu, Jian Zhi; Sears, Jr., Jesse A.; Hoyt, David W.; Mehta, Hardeep S.; Peden, Charles H. F.

    2015-11-24

    A continuous-flow (CF) magic angle sample spinning (CF-MAS) NMR rotor and probe are described for investigating reaction dynamics, stable intermediates/transition states, and mechanisms of catalytic reactions in situ. The rotor includes a sample chamber of a flow-through design with a large sample volume that delivers a flow of reactants through a catalyst bed contained within the sample cell allowing in-situ investigations of reactants and products. Flow through the sample chamber improves diffusion of reactants and products through the catalyst. The large volume of the sample chamber enhances sensitivity permitting in situ .sup.13C CF-MAS studies at natural abundance.

  20. Hydrogen and deuterium NMR of solids by magic-angle spinning

    SciTech Connect

    Eckman, R.R.

    1982-10-01

    The nuclear magnetic resonance of solids has long been characterized by very large specral broadening which arises from internuclear dipole-dipole coupling or the nuclear electric quadrupole interaction. These couplings can obscure the smaller chemical shift interaction and make that information unavailable. Two important and difficult cases are that of hydrogen and deuterium. The development of cross polarization, heteronuclear radiofrequency decoupling, and coherent averaging of nuclear spin interactions has provided measurement of chemical shift tensors in solids. Recently, double quantum NMR and double quantum decoupling have led to measurement of deuterium and proton chemical shift tensors, respectively. A general problem of these experiments is the overlapping of the tensor powder pattern spectra of magnetically distinct sites which cannot be resolved. In this work, high resolution NMR of hydrogen and deuterium in solids is demonstrated. For both nuclei, the resonances are narrowed to obtain liquid-like isotropic spectra by high frequency rotation of the sample about an axis inclined at the magic angle, ..beta../sub m/ = Arccos (3/sup -1/2/), with respect to the direction of the external magnetic field. For deuterium, the powder spectra were narrowed by over three orders of magnitude by magic angle rotation with precise control of ..beta... A second approach was the observation of deuterium double quantum transitions under magic angle rotation. For hydrogen, magic angle rotation alone could be applied to obtain the isotropic spectrum when H/sub D/ was small. This often occurs naturally when the nuclei are semi-dilute or involved in internal motion. In the general case of large H/sub D/, isotropic spectra were obtained by dilution of /sup 1/H with /sup 2/H combined with magic angle rotation. The resolution obtained represents the practical limit for proton NMR of solids.

  1. Pf1 bacteriophage hydration by magic angle spinning solid-state NMR

    SciTech Connect

    Sergeyev, Ivan V.; Bahri, Salima; McDermott, Ann E.; Day, Loren A.

    2014-12-14

    High resolution two- and three-dimensional heteronuclear correlation spectroscopy ({sup 1}H–{sup 13}C, {sup 1}H–{sup 15}N, and {sup 1}H–{sup 13}C–{sup 13}C HETCOR) has provided a detailed characterization of the internal and external hydration water of the Pf1 virion. This long and slender virion (2000 nm × 7 nm) contains highly stretched DNA within a capsid of small protein subunits, each only 46 amino acid residues. HETCOR cross-peaks have been unambiguously assigned to 25 amino acids, including most external residues 1–21 as well as residues 39–40 and 43–46 deep inside the virion. In addition, the deoxyribose rings of the DNA near the virion axis are in contact with water. The sets of cross-peaks to the DNA and to all 25 amino acid residues were from the same hydration water {sup 1}H resonance; some of the assigned residues do not have exchangeable side-chain protons. A mapping of the contacts onto structural models indicates the presence of water “tunnels” through a highly hydrophobic region of the capsid. The present results significantly extend and modify results from a lower resolution study, and yield a comprehensive hydration surface map of Pf1. In addition, the internal water could be distinguished from external hydration water by means of paramagnetic relaxation enhancement. The internal water population may serve as a conveniently localized magnetization reservoir for structural studies.

  2. Discrimination of Basal Cell Carcinoma from Normal Skin Tissue Using High-Resolution Magic Angle Spinning 1H NMR Spectroscopy

    PubMed Central

    Mun, Je-Ho; Lee, Heonho; Yoon, Dahye; Kim, Byung-Soo; Kim, Moon-Bum; Kim, Shukmann

    2016-01-01

    High-resolution magic angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy is a useful tool for investigating the metabolism of various cancers. Basal cell carcinoma (BCC) is the most common skin cancer. However, to our knowledge, data on metabolic profiling of BCC have not been reported in the literature. The objective of the present study was to investigate the metabolic profiling of cutaneous BCC using HR-MAS 1H NMR spectroscopy. HR-MAS 1H NMR spectroscopy was used to analyze the metabolite profile and metabolite intensity of histopathologically confirmed BCC tissues and normal skin tissue (NST) samples. The metabolic intensity normalized to the total spectral intensities in BCC and NST was compared, and multivariate analysis was performed with orthogonal partial least-squares discriminant analysis (OPLS-DA). P values < 0.05 were considered statistically significant. Univariate analysis revealed 9 metabolites that showed statistically significant difference between BCC and NST. In multivariate analysis, the OPLS-DA models built with the HR-MAS NMR metabolic profiles revealed a clear separation of BCC from NST. The receiver operating characteristic curve generated from the results revealed an excellent discrimination of BCC from NST with an area under the curve (AUC) value of 0.961. The present study demonstrated that the metabolite profile and metabolite intensity differ between BCC and NST, and that HR-MAS 1H NMR spectroscopy can be a valuable tool in the diagnosis of BCC. PMID:26934749

  3. Evaluation of Cancer Metabolomics Using ex vivo High Resolution Magic Angle Spinning (HRMAS) Magnetic Resonance Spectroscopy (MRS)

    PubMed Central

    Fuss, Taylor L.; Cheng, Leo L.

    2016-01-01

    According to World Health Organization (WHO) estimates, cancer is responsible for more deaths than all coronary heart disease or stroke worldwide, serving as a major public health threat around the world. High resolution magic angle spinning (HRMAS) magnetic resonance spectroscopy (MRS) has demonstrated its usefulness in the identification of cancer metabolic markers with the potential to improve diagnosis and prognosis for the oncology clinic, due partially to its ability to preserve tissue architecture for subsequent histological and molecular pathology analysis. Capable of the quantification of individual metabolites, ratios of metabolites, and entire metabolomic profiles, HRMAS MRS is one of the major techniques now used in cancer metabolomic research. This article reviews and discusses literature reports of HRMAS MRS studies of cancer metabolomics published between 2010 and 2015 according to anatomical origins, including brain, breast, prostate, lung, gastrointestinal, and neuroendocrine cancers. These studies focused on improving diagnosis and understanding patient prognostication, monitoring treatment effects, as well as correlating with the use of in vivo MRS in cancer clinics. PMID:27011205

  4. Variable temperature system using vortex tube cooling and fiber optic temperature measurement for low temperature magic angle spinning NMR.

    PubMed

    Martin, Rachel W; Zilm, Kurt W

    2004-06-01

    We describe the construction and operation of a variable temperature (VT) system for a high field fast magic angle spinning (MAS) probe. The probe is used in NMR investigations of biological macromolecules, where stable setting and continuous measurement of the temperature over periods of several days are required in order to prevent sample overheating and degradation. The VT system described is used at and below room temperature. A vortex tube is used to provide cooling in the temperature range of -20 to 20 degrees C, while a liquid nitrogen-cooled heat exchanger is used below -20 degrees C. Using this arrangement, the lowest temperature that is practically achievable is -140 degrees C. Measurement of the air temperature near the spinning rotor is accomplished using a fiber optic thermometer that utilizes the temperature dependence of the absorption edge of GaAs. The absorption edge of GaAs also has a magnetic field dependence that we have measured and corrected for. This dependence was calibrated at several field strengths using the well-known temperature dependence of the (1)H chemical shift difference of the protons in methanol. PMID:15140428

  5. Resonance Assignments and Secondary Structure Analysis of Dynein Light Chain 8 by Magic-angle Spinning NMR Spectroscopy

    SciTech Connect

    Sun, Shangjin; Butterworth, Andrew H.; Paramasivam, Sivakumar; Yan, Si; Lightcap, Christine M.; Williams, John C.; Polenova, Tatyana E.

    2011-08-04

    Dynein light chain LC8 is the smallest subunit of the dynein motor complex and has been shown to play important roles in both dynein-dependent and dynein-independent physiological functions via its interaction with a number of its binding partners. It has also been linked to pathogenesis including roles in viral infections and tumorigenesis. Structural information for LC8-target proteins is critical to understanding the underlying function of LC8 in these complexes. However, some LC8-target interactions are not amenable to structural characterization by conventional structural biology techniques owing to their large size, low solubility, and crystallization difficulties. Here, we report magic-angle spinning (MAS) NMR studies of the homodimeric apo-LC8 protein as a first effort in addressing more complex, multi-partner, LC8-based protein assemblies. We have established site-specific backbone and side-chain resonance assignments for the majority of the residues of LC8, and show TALOS+-predicted torsion angles ø and ψ in close agreement with most residues in the published LC8 crystal structure. Data obtained through these studies will provide the first step toward using MAS NMR to examine the LC8 structure, which will eventually be used to investigate protein–protein interactions in larger systems that cannot be determined by conventional structural studies.

  6. Closed-cycle cold helium magic-angle spinning for sensitivity-enhanced multi-dimensional solid-state NMR

    NASA Astrophysics Data System (ADS)

    Matsuki, Yoh; Nakamura, Shinji; Fukui, Shigeo; Suematsu, Hiroto; Fujiwara, Toshimichi

    2015-10-01

    Magic-angle spinning (MAS) NMR is a powerful tool for studying molecular structure and dynamics, but suffers from its low sensitivity. Here, we developed a novel helium-cooling MAS NMR probe system adopting a closed-loop gas recirculation mechanism. In addition to the sensitivity gain due to low temperature, the present system has enabled highly stable MAS (vR = 4-12 kHz) at cryogenic temperatures (T = 35-120 K) for over a week without consuming helium at a cost for electricity of 16 kW/h. High-resolution 1D and 2D data were recorded for a crystalline tri-peptide sample at T = 40 K and B0 = 16.4 T, where an order of magnitude of sensitivity gain was demonstrated versus room temperature measurement. The low-cost and long-term stable MAS strongly promotes broader application of the brute-force sensitivity-enhanced multi-dimensional MAS NMR, as well as dynamic nuclear polarization (DNP)-enhanced NMR in a temperature range lower than 100 K.

  7. Direct determination of phosphate sugars in biological material by (1)H high-resolution magic-angle-spinning NMR spectroscopy.

    PubMed

    Diserens, Gaëlle; Vermathen, Martina; Gjuroski, Ilche; Eggimann, Sandra; Precht, Christina; Boesch, Chris; Vermathen, Peter

    2016-08-01

    The study aim was to unambiguously assign nucleotide sugars, mainly UDP-X that are known to be important in glycosylation processes as sugar donors, and glucose-phosphates that are important intermediate metabolites for storage and transfer of energy directly in spectra of intact cells, as well as in skeletal muscle biopsies by (1)H high-resolution magic-angle-spinning (HR-MAS) NMR. The results demonstrate that sugar phosphates can be determined quickly and non-destructively in cells and biopsies by HR-MAS, which may prove valuable considering the importance of phosphate sugars in cell metabolism for nucleic acid synthesis. As proof of principle, an example of phosphate-sugar reaction and degradation kinetics after unfreezing the sample is shown for a cardiac muscle, suggesting the possibility to follow by HR-MAS NMR some metabolic pathways. Graphical abstract Glucose-phosphate sugars (Glc-1P and Glc-6P) detected in muscle by 1H HR-MAS NMR. PMID:27271261

  8. Closed-cycle cold helium magic-angle spinning for sensitivity-enhanced multi-dimensional solid-state NMR.

    PubMed

    Matsuki, Yoh; Nakamura, Shinji; Fukui, Shigeo; Suematsu, Hiroto; Fujiwara, Toshimichi

    2015-10-01

    Magic-angle spinning (MAS) NMR is a powerful tool for studying molecular structure and dynamics, but suffers from its low sensitivity. Here, we developed a novel helium-cooling MAS NMR probe system adopting a closed-loop gas recirculation mechanism. In addition to the sensitivity gain due to low temperature, the present system has enabled highly stable MAS (vR=4-12 kHz) at cryogenic temperatures (T=35-120 K) for over a week without consuming helium at a cost for electricity of 16 kW/h. High-resolution 1D and 2D data were recorded for a crystalline tri-peptide sample at T=40 K and B0=16.4 T, where an order of magnitude of sensitivity gain was demonstrated versus room temperature measurement. The low-cost and long-term stable MAS strongly promotes broader application of the brute-force sensitivity-enhanced multi-dimensional MAS NMR, as well as dynamic nuclear polarization (DNP)-enhanced NMR in a temperature range lower than 100 K. PMID:26302269

  9. Concentration Profiling in Rat Tissue by High-Resolution Magic-Angle Spinning NMR Spectroscopy: Investigation of a Model Drug

    PubMed Central

    Lucas, Laura H.; Wilson, Sarah F.; Lunte, Craig E.; Larive, Cynthia K.

    2008-01-01

    The utility of high-resolution magic-angle spinning (HR-MAS) NMR for studying drug delivery in whole tissues was explored by dosing female Sprague–Dawley rats with topical or injectable benzoic acid (BA). In principle, HR-MAS NMR permits the detection of both intra- and extracellular compounds. This is an advantage over the previous detection of topically applied BA using microdialysis coupled to HPLC/UV as microdialysis samples only the extracellular space. Skin and muscle samples were analyzed by 1H HR-MAS NMR, and BA levels were determined using an external standard solution added to the sample rotor. One to two percent of the BA topical dose was detected in the muscle, showing that BA penetrated through the dermal and subcutaneous layers. Since BA was not detected in the muscle in the microdialysis studies, the NMR spectra revealed the intracellular localization of BA. The amount of BA detected in muscle after subcutaneous injection correlated with the distance from the dosing site. Overall, the results suggest that HR-MAS NMR can distinguish differences in the local concentration of BA varying with tissue type, dosage method, and tissue proximity to the dosing site. The results illustrate the potential of this technique for quantitative analysis of drug delivery and distribution and the challenges to be addressed as the method is refined. PMID:15859619

  10. Order-selective multiple-quantum excitation in magic-angle spinning NMR: creating triple-quantum coherences with a trilinear Hamiltonian

    NASA Astrophysics Data System (ADS)

    Edén, Mattias

    2002-12-01

    Order-selective multiple-quantum excitation in magic-angle spinning nuclear magnetic resonance is explored using a class of symmetry-based pulse sequences, denoted S Mχ. Simple rules are presented that aid the design of S Mχ schemes with certain desirable effective Hamiltonians. They are applied to construct sequences generating trilinear effective dipolar Hamiltonians, suitable for efficient excitation of triple-quantum coherences in rotating solids. The new sequences are investigated numerically and demonstrated by 1H experiments on adamantane.

  11. Site-resolved multiple-quantum filtered correlations and distance measurements by magic-angle spinning NMR: Theory and applications to spins with weak to vanishing quadrupolar couplings.

    PubMed

    Eliav, U; Haimovich, A; Goldbourt, A

    2016-01-14

    We discuss and analyze four magic-angle spinning solid-state NMR methods that can be used to measure internuclear distances and to obtain correlation spectra between a spin I = 1/2 and a half-integer spin S > 1/2 having a small quadrupolar coupling constant. Three of the methods are based on the heteronuclear multiple-quantum and single-quantum correlation experiments, that is, high rank tensors that involve the half spin and the quadrupolar spin are generated. Here, both zero and single-quantum coherence of the half spins are allowed and various coherence orders of the quadrupolar spin are generated, and filtered, via active recoupling of the dipolar interaction. As a result of generating coherence orders larger than one, the spectral resolution for the quadrupolar nucleus increases linearly with the coherence order. Since the formation of high rank tensors is independent of the existence of a finite quadrupolar interaction, these experiments are also suitable to materials in which there is high symmetry around the quadrupolar spin. A fourth experiment is based on the initial quadrupolar-driven excitation of symmetric high order coherences (up to p = 2S, where S is the spin number) and subsequently generating by the heteronuclear dipolar interaction higher rank (l + 1 or higher) tensors that involve also the half spins. Due to the nature of this technique, it also provides information on the relative orientations of the quadrupolar and dipolar interaction tensors. For the ideal case in which the pulses are sufficiently strong with respect to other interactions, we derive analytical expressions for all experiments as well as for the transferred echo double resonance experiment involving a quadrupolar spin. We show by comparison of the fitting of simulations and the analytical expressions to experimental data that the analytical expressions are sufficiently accurate to provide experimental (7)Li-(13)C distances in a complex of lithium, glycine, and water. Discussion

  12. Metabolic profiling of a Schistosoma mansoni infection in mouse tissues using magic angle spinning-nuclear magnetic resonance spectroscopy.

    PubMed

    Li, Jia V; Holmes, Elaine; Saric, Jasmina; Keiser, Jennifer; Dirnhofer, Stephan; Utzinger, Jürg; Wang, Yulan

    2009-04-01

    In order to enhance our understanding of physiological and pathological consequences of a patent Schistosoma mansoni infection in the mouse, we examined the metabolic responses of different tissue samples recovered from the host animal using a metabolic profiling strategy. Ten female NMRI mice were infected with approximately 80 S. mansoni cercariae each, and 10 uninfected age- and sex-matched animals served as controls. At day 74 post infection (p.i.), mice were killed and jejunum, ileum, colon, liver, spleen and kidney samples were removed. We employed (1)H magic angle spinning-nuclear magnetic resonance spectroscopy to generate tissue-specific metabolic profiles. The spectral data were analyzed using multivariate modelling methods including an orthogonal signal corrected-projection to latent structure analysis and hierarchical principal component analysis to assess the differences and/or similarities in metabolic responses between infected and non-infected control mice. Most tissues obtained from S. mansoni-infected mice were characterized by high levels of amino acids, such as leucine, isoleucine, lysine, glutamine and asparagine. High levels of membrane phospholipid metabolites, including glycerophosphoryl choline and phosphoryl choline were found in the ileum, colon, liver and spleen of infected mice. Additionally, low levels of energy-related metabolites, including lipids, glucose and glycogen were observed in ileum, spleen and liver samples of infected mice. Energy-related metabolites in the jejunum, liver and renal medulla were found to be positively correlated with S. mansoni worm burden upon dissection. These findings show that a patent S. mansoni infection causes clear disruption of metabolism in a range of tissues at a molecular level, which can be interpreted in relation to the previously reported signature in a biofluid (i.e. urine), giving further evidence of the global effect of the infection. PMID:19068218

  13. Distortional binding of transition state analogs to human purine nucleoside phosphorylase probed by magic angle spinning solid-state NMR.

    PubMed

    Vetticatt, Mathew J; Itin, Boris; Evans, Gary B; Schramm, Vern L

    2013-10-01

    Transition state analogs mimic the geometry and electronics of the transition state of enzymatic reactions. These molecules bind to the active site of the enzyme much tighter than substrate and are powerful noncovalent inhibitors. Immucillin-H (ImmH) and 4'-deaza-1'-aza-2'-deoxy-9-methylene Immucillin-H (DADMe-ImmH) are picomolar inhibitors of human purine nucleoside phosphorylase (hPNP). Although both molecules are electronically similar to the oxocarbenium-like dissociative hPNP transition state, DADMe-ImmH is more potent than ImmH. DADMe-ImmH captures more of the transition state binding energy by virtue of being a closer geometric match to the hPNP transition state than ImmH. A consequence of these similarities is that the active site of hPNP exerts greater distortional forces on ImmH than on DADMe-ImmH to "achieve" the hPNP transition state geometry. By using magic angle spinning solid-state NMR to investigate stable isotope-labeled ImmH and DADMe-ImmH, we have explored the difference in distortional binding of these two inhibitors to hPNP. High-precision determinations of internuclear distances from NMR recoupling techniques, rotational echo double resonance, and rotational resonance, have provided unprecedented atomistic insight into the geometric changes that occur upon binding of transition state analogs. We conclude that hPNP stabilizes conformations of these chemically distinct analogs having distances between the cation and leaving groups resembling those of the known transition state. PMID:24043827

  14. Live-cell high resolution magic angle spinning magnetic resonance spectroscopy for in vivo analysis of Pseudomonas aeruginosa metabolomics.

    PubMed

    Righi, Valeria; Constantinou, Caterina; Kesarwani, Meenu; Rahme, Laurence G; Tzika, Aria A

    2013-09-01

    Pseudomonas aeruginosa (PA) is a pathogenic gram-negative bacterium that is widespread in nature, inhabiting soil, water, plants and animals. PA is a prevalent cause of deleterious human infections, particularly in patients whose host defense mechanisms have been compromised. Metabolomics is an important tool used to study host-pathogen interactions and to identify novel therapeutic targets and corresponding compounds. The aim of the present study was to report the metabolic profile of live PA bacteria using in vivo high-resolution magic angle spinning (HRMAS) nuclear magnetic resonance spectroscopy (NMR), in combination with 1- and 2-dimensional HRMAS NMR. This methodology provides a new and powerful technique to rapidly interrogate the metabolome of intact bacterial cells and has several advantages over traditional techniques that identify metabolome components from disrupted cells. Furthermore, application of multidimensional HRMAS NMR, in combination with the novel technique total through-Bond correlation Spectroscopy (TOBSY), is a promising approach that may be used to obtain in vivo metabolomics information from intact live bacterial cells and can mediate such analyses in a short period of time. Moreover, HRMAS (1)H NMR enables the investigation of the associations between metabolites and cell processes. In the present study, we detected and quantified several informative metabolic molecules in live PA cells, including N-acetyl, betaine, citrulline, alanine and glycine, which are important in peptidoglycan synthesis. The results provided a complete metabolic profile of PA for future studies of PA clinical isolates and mutants. In addition, this in vivo NMR biomedical approach might have clinical utility and should prove useful in gene function validation, the study of pathogenetic mechanisms, the classification of microbial strains into functional/clinical groups, the testing of anti-bacterial agents and the determination of metabolic profiles of bacterial

  15. Characterization of metabolites in infiltrating gliomas using ex vivo ¹H high-resolution magic angle spinning spectroscopy.

    PubMed

    Elkhaled, Adam; Jalbert, Llewellyn; Constantin, Alexandra; Yoshihara, Hikari A I; Phillips, Joanna J; Molinaro, Annette M; Chang, Susan M; Nelson, Sarah J

    2014-05-01

    Gliomas are routinely graded according to histopathological criteria established by the World Health Organization. Although this classification can be used to understand some of the variance in the clinical outcome of patients, there is still substantial heterogeneity within and between lesions of the same grade. This study evaluated image-guided tissue samples acquired from a large cohort of patients presenting with either new or recurrent gliomas of grades II-IV using ex vivo proton high-resolution magic angle spinning spectroscopy. The quantification of metabolite levels revealed several discrete profiles associated with primary glioma subtypes, as well as secondary subtypes that had undergone transformation to a higher grade at the time of recurrence. Statistical modeling further demonstrated that these metabolomic profiles could be differentially classified with respect to pathological grading and inter-grade conversions. Importantly, the myo-inositol to total choline index allowed for a separation of recurrent low-grade gliomas on different pathological trajectories, the heightened ratio of phosphocholine to glycerophosphocholine uniformly characterized several forms of glioblastoma multiforme, and the onco-metabolite D-2-hydroxyglutarate was shown to help distinguish secondary from primary grade IV glioma, as well as grade II and III from grade IV glioma. These data provide evidence that metabolite levels are of interest in the assessment of both intra-grade and intra-lesional malignancy. Such information could be used to enhance the diagnostic specificity of in vivo spectroscopy and to aid in the selection of the most appropriate therapy for individual patients. PMID:24596146

  16. Application of High-Resolution Magic-Angle Spinning NMR Spectroscopy to Define the Cell Uptake of MRI Contrast Agents

    NASA Astrophysics Data System (ADS)

    Calabi, Luisella; Alfieri, Goffredo; Biondi, Luca; De Miranda, Mario; Paleari, Lino; Ghelli, Stefano

    2002-06-01

    A new method, based on proton high-resolution magic-angle spinning ( 1H HR-MAS) NMR spectroscopy, has been employed to study the cell uptake of magnetic resonance imaging contrast agents (MRI-CAs). The method was tested on human red blood cells (HRBC) and white blood cells (HWBC) by using three gadolinium complexes, widely used in diagnostics, Gd-BOPTA, Gd-DTPA, and Gd-DOTA, and the analogous complexes obtained by replacing Gd(III) with Dy(III), Nd(III), and Tb(III) (i.e., complexes isostructural to the ones of gadolinium but acting as shift agents). The method is based on the evaluation of the magnetic effects, line broadening, or induced lanthanide shift (LIS) caused by these complexes on NMR signals of intra- and extracellular water. Since magnetic effects are directly linked to permeability, this method is direct. In all the tests, these magnetic effects were detected for the extracellular water signal only, providing a direct proof that these complexes are not able to cross the cell membrane. Line broadening effects (i.e., the use of gadolinium complexes) only allow qualitative evaluations. On the contrary, LIS effects can be measured with high precision and they can be related to the concentration of the paramagnetic species in the cellular compartments. This is possible because the HR-MAS technique provides the complete elimination of bulk magnetic susceptibility (BMS) shift and the differentiation of extra- and intracellular water signals. Thus with this method, the rapid quantification of the MRI-CA amount inside and outside the cells is actually feasible.

  17. 19F Magic angle spinning NMR reporter molecules: empirical measures of surface shielding, polarisability and H-bonding.

    PubMed

    Budarin, Vitaliy L; Clark, James H; Deswarte, Fabien E I; Mueller, Karl T; Tavener, Stewart J

    2007-06-14

    Magic Angle Spinning (MAS) (19)F NMR spectra have been obtained and chemical shifts measured for 37 molecules in the gas phase and adsorbed on the surfaces of six common materials: octadecyl- and octyl-functionalised chromatography silicas, Kieselgel 100 silica, Brockmann neutral alumina, Norit activated charcoal and 3-(1-piperidino)propyl functionalised silica. From these six surfaces, octadecyl-silica is selected as a non-polar reference to which the others are compared. The change in chemical shift of a fluorine nucleus within a molecule on adsorption to a surface from the gas phase, Deltadelta(gas)(surface), is described by the empirical relationship: Deltadelta(gas)(surface) = delta(s) + (alpha(s)+pi(s))/alpha(r) (Deltadelta(gas)(reference) - delta(r)) + delta(HBA) + delta(HBD), where delta(s) and delta(r) are constants that describe the chemical shift induced by the electromagnetic field of the surface under investigation and reference surface, alpha(s) and alpha(r) are the relative surface polarisability for the surface and reference, pi(s) is an additional contribution to the surface polarisabilities due to its ability to interact with aromatic molecules, and delta(HBA) and delta(HBD) are measurements of the hydrogen acceptor and donor properties of the surface. These empirical parameters are measured for the surfaces under study. Silica and alumina are found to undergo specific interactions with aromatic reporter molecules and both accept and donate H-bonds. Activated charcoal was found to have an extreme effect on shielding but no specific interactions with the adsorbed molecules. 3-(1-Piperidino)propyl functionalised silica exhibits H-bond acceptor ability, but does not donate H-bonds. PMID:17487325

  18. Intratumoral Agreement of High-Resolution Magic Angle Spinning Magnetic Resonance Spectroscopic Profiles in the Metabolic Characterization of Breast Cancer

    PubMed Central

    Park, Vivian Youngjean; Yoon, Dahye; Koo, Ja Seung; Kim, Eun-Kyung; Kim, Seung Il; Choi, Ji Soo; Park, Seho; Park, Hyung Seok; Kim, Suhkmann; Kim, Min Jung

    2016-01-01

    Abstract High-resolution magic angle spinning (HR-MAS) magnetic resonance (MR) spectroscopy data may serve as a biomarker for breast cancer, with only a small volume of tissue sample required for assessment. However, previous studies utilized only a single tissue sample from each patient. The aim of this study was to investigate whether intratumoral location and biospecimen type affected the metabolic characterization of breast cancer assessed by HR-MAS MR spectroscopy This prospective study was approved by the institutional review board and informed consent was obtained. Preoperative core-needle biopsies (CNBs), central, and peripheral surgical tumor specimens were prospectively collected under ultrasound (US) guidance in 31 patients with invasive breast cancer. Specimens were assessed with HR-MAS MR spectroscopy. The reliability of metabolite concentrations was evaluated and multivariate analysis was performed according to intratumoral location and biospecimen type. There was a moderate or higher agreement between the relative concentrations of 94.3% (33 of 35) of metabolites in the center and periphery, 80.0% (28 of 35) of metabolites in the CNB and central surgical specimens, and 82.9% (29 of 35) of metabolites between all 3 specimen types. However, there was no significant agreement between the concentrations of phosphocholine (PC) and phosphoethanolamine (PE) in the center and periphery. The concentrations of several metabolites (adipate, arginine, fumarate, glutamate, PC, and PE) had no significant agreement between the CNB and central surgical specimens. In conclusion, most HR-MAS MR spectroscopic data do not differ based on intratumoral location or biospecimen type. However, some metabolites may be affected by specimen-related variables, and caution is recommended in decision-making based solely on metabolite concentrations, particularly PC and PE. Further validation through future studies is needed for the clinical implementation of these biomarkers based

  19. Complete protocol for slow-spinning high-resolution magic-angle spinning NMR analysis of fragile tissues.

    PubMed

    André, Marion; Dumez, Jean-Nicolas; Rezig, Lamya; Shintu, Laetitia; Piotto, Martial; Caldarelli, Stefano

    2014-11-01

    High-resolution magic-angle spinning (HR-MAS) nuclear magnetic resonance (NMR) is an essential tool to characterize a variety of semisolid systems, including biological tissues, with virtually no sample preparation. The "non-destructive" nature of NMR is typically compromised, however, by the extreme centrifugal forces experienced under conventional HR-MAS frequencies of several kilohertz. These features limit the usefulness of current HR-MAS approaches for fragile samples. Here, we introduce a full protocol for acquiring high-quality HR-MAS NMR spectra of biological tissues at low spinning rates (down to a few hundred hertz). The protocol first consists of a carefully designed sample preparation, which yields spectra without significant spinning sidebands at low spinning frequency for several types of sample holders, including the standard disposable inserts classically used in HR-MAS NMR-based metabolomics. Suppression of broad spectral features is then achieved using a modified version of the recently introduced PROJECT experiment with added water suppression and rotor synchronization, which deposits limited power in the sample and which can be suitably rotor-synchronized at low spinning rates. The performance of the slow HR-MAS NMR procedure is demonstrated on conventional (liver tissue) and very delicate (fish eggs) samples, for which the slow-spinning conditions are shown to preserve the structural integrity and to minimize intercompartmental leaks of metabolites. Taken together, these results expand the applicability and reliability of HR-MAS NMR spectroscopy. These results have been obtained at 400 and 600 MHz and suggest that high-quality slow HR-MAS spectra can be expected at higher magnetic fields using the described protocol. PMID:25286333

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

    PubMed

    Kempgens, Pierre; Britton, Jonathan

    2016-05-01

    Some metal nitrides (TiN, ZrN, InN, GaN, Ca3 N2 , Mg3 N2 , and Ge3 N4 ) have been studied by powder X-ray diffraction (XRD) and (14) N magic angle-spinning (MAS) solid-state NMR spectroscopy. For Ca3 N2 , Mg3 N2 , and Ge3 N4 , no (14) N NMR signal was observed. Low speed (νr  = 2 kHz for TiN, ZrN, and GaN; νr  = 1 kHz for InN) and 'high speed' (νr  = 15 kHz for TiN; νr  = 5 kHz for ZrN; νr  = 10 kHz for InN and GaN) MAS NMR experiments were performed. For TiN, ZrN, InN, and GaN, powder-XRD was used to identify the phases present in each sample. The number of peaks observed for each sample in their (14) N MAS solid-state NMR spectrum matches perfectly well with the number of nitrogen-containing phases identified by powder-XRD. The (14) N MAS solid-state NMR spectra are symmetric and dominated by the quadrupolar interaction. The envelopes of the spinning sidebands manifold are Lorentzian, and it is concluded that there is a distribution of the quadrupolar coupling constants Qcc 's arising from structural defects in the compounds studied. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26687421

  1. Shortening spin-lattice relaxation using a copper-chelated lipid at low-temperatures - A magic angle spinning solid-state NMR study on a membrane-bound protein.

    PubMed

    Yamamoto, Kazutoshi; Caporini, Marc A; Im, Sangchoul; Waskell, Lucy; Ramamoorthy, Ayyalusamy

    2013-12-01

    Inherent low sensitivity of NMR spectroscopy has been a major disadvantage, especially to study biomolecules like membrane proteins. Recent studies have successfully demonstrated the advantages of performing solid-state NMR experiments at very low and ultralow temperatures to enhance the sensitivity. However, the long spin-lattice relaxation time, T1, at very low temperatures is a major limitation. To overcome this difficulty, we demonstrate the use of a copper-chelated lipid for magic angle spinning solid-state NMR measurements on cytochrome-b5 reconstituted in multilamellar vesicles. Our results on multilamellar vesicles containing as small as 0.5mol% of a copper-chelated lipid can significantly shorten T1 of protons, which can be used to considerably reduce the data collection time or to enhance the signal-to-noise ratio. We also monitored the effect of slow cooling on the resolution and sensitivity of (13)C and (15)N signals from the protein and (13)C signals from lipids. PMID:24246881

  2. Shortening Spin-lattice Relaxation Using a Copper-Chelated lipid at Low-Temperatures – A Magic Angle Spinning Solid-State NMR Study on a Membrane-Bound Protein

    PubMed Central

    Yamamoto, Kazutoshi; Caporini, Marc; Im, Sangchoul; Waskell, Lucy; Ramamoorthy, Ayyalusamy

    2013-01-01

    Inherent low sensitivity of NMR spectroscopy has been a major disadvantage, especially to study biomolecules like membrane proteins. Recent studies have successfully demonstrated the advantages of performing solid-state NMR experiments at very low and ultralow temperatures to enhance the sensitivity. However, the long spin-lattice relaxation time, T1, at very low temperatures is a major limitation. To overcome this difficulty, we demonstrate the use of a copper-chelated lipid for magic angle spinning solid-state NMR measurements on cytochrome-b5 reconstituted in multilamellar vesicles. Our results on multilamellar vesicles containing as small as 0.5 mole % of a copper-chelated lipid can significantly shorten T1 of protons, which can be used to considerably reduce the data collection time or to enhance the signal-to-noise ratio. We also monitored the effect of slow cooling on the resolution and sensitivity of 13C and 15N signals from the protein and 13C signals from lipids. PMID:24246881

  3. Study of chemically inequivalent N(CH3)4 ions in [N(CH3)4]2ZnBr4 near the phase transition temperature using 1H MAS NMR, 13C CP/MAS NMR, and 14N NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2016-02-01

    The temperature dependences of the chemical shifts and intensities of 1H, 13C, and 14N nuclei in tetramethylammonium tetrabromozincate, [N(CH3)4]2ZnBr4, were investigated using single-crystal nuclear magnetic resonance (NMR) and magic angle spinning (MAS) NMR spectroscopy to elucidate the structural geometry near the phase transition temperature. Based on the analysis of the 13C cross-polarization (CP)/MAS NMR and 14N NMR spectra, the two chemically inequivalent N(1) (CH3)4 and N(2) (CH3)4 ions were distinguished. Furthermore, the 14N NMR spectrum at the phase transition temperature indicated the existence of the ferroelastic characteristics of the N(CH3)4 ions.

  4. Characterization of a Mixture of CO2 Adsorption Products in Hyperbranched Aminosilica Adsorbents by (13)C Solid-State NMR.

    PubMed

    Moore, Jeremy K; Sakwa-Novak, Miles A; Chaikittisilp, Watcharop; Mehta, Anil K; Conradi, Mark S; Jones, Christopher W; Hayes, Sophia E

    2015-11-17

    Hyperbranched amine polymers (HAS) grown from the mesoporous silica SBA-15 (hereafter "SBA-15-HAS") exhibit large capacities for CO2 adsorption. We have used static in situ and magic-angle spinning (MAS) ex situ (13)C nuclear magnetic resonance (NMR) to examine the adsorption of CO2 by SBA-15-HAS. (13)C NMR distinguishes the signal of gas-phase (13)CO2 from that of the chemisorbed species. HAS polymers possess primary, secondary, and tertiary amines, leading to multiple chemisorption reaction outcomes, including carbamate (RnNCOO(-)), carbamic acid (RnNCOOH), and bicarbonate (HCO3(-)) moieties. Carbamates and bicarbonate fall within a small (13)C chemical shift range (162-166 ppm), and a mixture was observed including carbamic acid and carbamate, the former disappearing upon evacuation of the sample. By examining the (13)C-(14)N dipolar coupling through low-field (B0 = 3 T) (13)C{(1)H} cross-polarization MAS NMR, carbamate is confirmed through splitting of the (13)C resonance. A third species that is either bicarbonate or a second carbamate is evident from bimodal T2 decay times of the ∼163 ppm peak, indicating the presence of two species comprising that single resonance. The mixture of products suggests that (1) the presence of amines and water leads to bicarbonate being present and/or (2) the multiple types of amine sites in HAS permit formation of chemically distinct carbamates. PMID:26477882

  5. Molecular structure of crude beeswax studied by solid-state 13C NMR

    PubMed Central

    Kameda, Tsunenori

    2004-01-01

    13C Solid-state NMR experiments were performed to investigate the structure of beeswax in the native state (crude beeswax) for the first time. From quantitative direct polarization 13C MAS NMR spectrum, it was found that the fraction of internal-chain methylene (int-(CH2)) component compared to other components of crude beeswax was over 95%. The line shape of the int-(CH2) carbon resonance region was comprehensively analyzed in terms of NMR chemical shift. The 13C broad peak component covering from 31 to 35ppm corresponds to int-(CH2) carbons with trans conformation in crystalline domains, whereas the sharp signal at 30.3 ppm corresponds to gauche conformation in the non-crystalline domain. From peak deconvolution of the aliphatic region, it was found that over 85% of the int-(CH2) has a crystal structure and several kinds of molecular packing for int-(CH2), at least three, exist in the crystalline domain. Abbreviation: NMR nuclear magnetic resonance int-(CH2) internal-chain methylene CP cross-polarization MAS magic angle spinning PMID:15861244

  6. Advanced CPMAS-13C NMR techniques for molecular characterization of size-separated fractions from a soil humic acid.

    PubMed

    Conte, Pellegrino; Spaccini, Riccardo; Piccolo, Alessandro

    2006-09-01

    A humic acid extracted from a volcanic soil was subjected to preparative high-performance size-exclusion chromatography (HPSEC) to reduce its molecular complexity and eleven different size fractions were obtained. Cross-polarization magic-angle spinning 13C NMR (CPMAS 13C NMR) analysis performed with variable contact-time (VCT) pulse sequences showed that the largest molecular-size fractions contained aromatic, alkyl, and carbohydrate-like components. The carbohydrate-like content and the alkyl chain length seemed to decrease with decreasing molecular size. Progressive reduction of aromatic carbon atoms was also observed with decreasing molecular size of the separated fractions. Mathematical treatment of the results from VCT experiments enabled cross polarization (T (CH)) and proton spin-lattice relaxation (T(1rho)(H)) times to be related to structural differences among the size fractions. The conformational distribution indicated that the eleven size fractions could be allocated to two main groups. The first group, with larger nominal molecular sizes, was characterized by molecular domains with slower local molecular motion. The second group of size fractions, with smaller nominal molecular sizes, was characterized by a larger number of molecular domains with faster local molecular motion. The T (CH) and (T(1rho)(H)) values suggested that either condensed or strongly associated aromatic systems were predominant in the size fractions with the largest apparent molecular dimensions. PMID:16896626

  7. A suite of pulse sequences based on multiple sequential acquisitions at one and two radiofrequency channels for solid-state magic-angle spinning NMR studies of proteins.

    PubMed

    Sharma, Kshama; Madhu, Perunthiruthy K; Mote, Kaustubh R

    2016-08-01

    One of the fundamental challenges in the application of solid-state NMR is its limited sensitivity, yet a majority of experiments do not make efficient use of the limited polarization available. The loss in polarization in a single acquisition experiment is mandated by the need to select out a single coherence pathway. In contrast, sequential acquisition strategies can encode more than one pathway in the same experiment or recover unused polarization to supplement a standard experiment. In this article, we present pulse sequences that implement sequential acquisition strategies on one and two radiofrequency channels with a combination of proton and carbon detection to record multiple experiments under magic-angle spinning. We show that complementary 2D experiments such as [Formula: see text] and [Formula: see text] or DARR and [Formula: see text], and 3D experiments such as [Formula: see text] and [Formula: see text], or [Formula: see text] and [Formula: see text]  can be combined in a single experiment to ensure time savings of at least 40 %. These experiments can be done under fast or slow-moderate magic-angle spinning frequencies aided by windowed [Formula: see text] acquisition and homonulcear decoupling. The pulse sequence suite is further expanded by including pathways that allow the recovery of residual polarization, the so-called 'afterglow' pathways, to encode a number of pulse sequences to aid in assignments and chemical-shift mapping. PMID:27364976

  8. Electrical and ionic conductivity effects on magic-angle spinning nuclear magnetic resonance parameters of CuI

    NASA Astrophysics Data System (ADS)

    Yesinowski, James P.; Ladouceur, Harold D.; Purdy, Andrew P.; Miller, Joel B.

    2010-12-01

    We investigate experimentally and theoretically the effects of two different types of conductivity, electrical and ionic, upon magic-angle spinning NMR spectra. The experimental demonstration of these effects involves 63Cu, 65Cu, and 127I variable temperature MAS-NMR experiments on samples of γ-CuI, a Cu+-ion conductor at elevated temperatures as well as a wide bandgap semiconductor. We extend previous observations that the chemical shifts depend very strongly upon the square of the spinning-speed as well as the particular sample studied and the magnetic field strength. By using the 207Pb resonance of lead nitrate mixed with the γ-CuI as an internal chemical shift thermometer we show that frictional heating effects of the rotor do not account for the observations. Instead, we find that spinning bulk CuI, a p-type semiconductor due to Cu+ vacancies in nonstoichiometric samples, in a magnetic field generates induced AC electric currents from the Lorentz force that can resistively heat the sample by over 200 °C. These induced currents oscillate along the rotor spinning axis at the spinning speed. Their associated heating effects are disrupted in samples containing inert filler material, indicating the existence of macroscopic current pathways between micron-sized crystallites. Accurate measurements of the temperature-dependence of the 63Cu and 127I chemical shifts in such diluted samples reveal that they are of similar magnitude (ca. 0.27 ppm/K) but opposite sign (being negative for 63Cu), and appear to depend slightly upon the particular sample. This relationship is identical to the corresponding slopes of the chemical shifts versus square of the spinning speed, again consistent with sample heating as the source of the observed large shift changes. Higher drive-gas pressures are required to spin samples that have higher effective electrical conductivities, indicating the presence of a braking effect arising from the induced currents produced by rotating a

  9. Electrical and ionic conductivity effects on magic-angle spinning nuclear magnetic resonance parameters of CuI.

    PubMed

    Yesinowski, James P; Ladouceur, Harold D; Purdy, Andrew P; Miller, Joel B

    2010-12-21

    We investigate experimentally and theoretically the effects of two different types of conductivity, electrical and ionic, upon magic-angle spinning NMR spectra. The experimental demonstration of these effects involves (63)Cu, (65)Cu, and (127)I variable temperature MAS-NMR experiments on samples of γ-CuI, a Cu(+)-ion conductor at elevated temperatures as well as a wide bandgap semiconductor. We extend previous observations that the chemical shifts depend very strongly upon the square of the spinning-speed as well as the particular sample studied and the magnetic field strength. By using the (207)Pb resonance of lead nitrate mixed with the γ-CuI as an internal chemical shift thermometer we show that frictional heating effects of the rotor do not account for the observations. Instead, we find that spinning bulk CuI, a p-type semiconductor due to Cu(+) vacancies in nonstoichiometric samples, in a magnetic field generates induced AC electric currents from the Lorentz force that can resistively heat the sample by over 200 °C. These induced currents oscillate along the rotor spinning axis at the spinning speed. Their associated heating effects are disrupted in samples containing inert filler material, indicating the existence of macroscopic current pathways between micron-sized crystallites. Accurate measurements of the temperature-dependence of the (63)Cu and (127)I chemical shifts in such diluted samples reveal that they are of similar magnitude (ca. 0.27 ppm/K) but opposite sign (being negative for (63)Cu), and appear to depend slightly upon the particular sample. This relationship is identical to the corresponding slopes of the chemical shifts versus square of the spinning speed, again consistent with sample heating as the source of the observed large shift changes. Higher drive-gas pressures are required to spin samples that have higher effective electrical conductivities, indicating the presence of a braking effect arising from the induced currents produced by

  10. Amino-acid selective experiments on uniformly 13C and 15N labeled proteins by MAS NMR: Filtering of lysines and arginines

    NASA Astrophysics Data System (ADS)

    Jehle, Stefan; Rehbein, Kristina; Diehl, Anne; van Rossum, Barth-Jan

    2006-12-01

    Amino-acid selective magic-angle spinning (MAS) NMR experiments can aid the assignment of ambiguous cross-peaks in crowded spectra of solid proteins. In particular for larger proteins, data analysis can be hindered by severe resonance overlap. In such cases, filtering techniques may provide a good alternative to site-specific spin-labeling to obtain unambiguous assignments that can serve as starting points in the assignment procedure. In this paper we present a simple pulse sequence that allows selective excitation of arginine and lysine residues. To achieve this, we make use of a combination of specific cross-polarization for selective excitation [M. Baldus, A.T. Petkova, J. Herzfeld, R.G. Griffin, Cross polarization in the tilted frame: assignment and spectral simplification in heteronuclear spin systems, Mol. Phys. 95 (1998) 1197-1207.] and spin diffusion for transfer along the amino-acid side-chain. The selectivity of the filter is demonstrated with the excitation of lysine and arginine side-chain resonances in a uniformly 13C and 15N labeled protein preparation of the α-spectrin SH3 domain. It is shown that the filter can be applied as a building block in a 13C- 13C lysine-only correlation experiment.

  11. Solid-State Selective 13C Excitation and Spin Diffusion NMR to Resolve Spatial Dimensions in Plant Cell Walls

    SciTech Connect

    Foston, M.; Katahira, R.; Gjersing, E.; Davis, M. F.; Ragauskas, A. J.

    2012-02-15

    The average spatial dimensions between major biopolymers within the plant cell wall can be resolved using a solid-state NMR technique referred to as a {sup 13}C cross-polarization (CP) SELDOM (selectively by destruction of magnetization) with a mixing time delay for spin diffusion. Selective excitation of specific aromatic lignin carbons indicates that lignin is in close proximity to hemicellulose followed by amorphous and finally crystalline cellulose. {sup 13}C spin diffusion time constants (T{sub SD}) were extracted using a two-site spin diffusion theory developed for {sup 13}C nuclei under magic angle spinning (MAS) conditions. These time constants were then used to calculate an average lower-limit spin diffusion length between chemical groups within the plant cell wall. The results on untreated {sup 13}C enriched corn stover stem reveal that the lignin carbons are, on average, located at distances {approx}0.7-2.0 nm from the carbons in hemicellulose and cellulose, whereas the pretreated material had larger separations.

  12. {sup 129}Xe magic-angle spinning spectra of xenon in zeolite NaA direct observation of mixed clusters of co-adsorbed species.

    SciTech Connect

    Jameson, A. K.; Jameson, C. J.; de Dios, A. C.; Oldfield, E.; Gerald, R. E., II; Turner, G. L.; Chemical Engineering; Loyola Univ.; Univ. of Illinois at Chicago; Univ. of Illinois; Spectral Data Services, Inc.

    1995-01-01

    We present the first demonstration that the individual {sup 129}Xe resonances corresponding to Xe{sub n} (n = 1-8) clusters inside the {alpha}-cages of zeolite NaA can be narrowed under magic-angle spinning (MAS). Under these high-resolution conditions we also observe upon addition of Kr the individual peaks corresponding to mixed clusters, Xe{sub n}Kr{sub m}, inside the a-cages, which will allow the first direct determination of the distribution of co-adsorbates in a microporous solid. Under MAS the chemical shifts of the Xe{sub n} clusters are shown to be highly sensitive to 'disorder' in the zeolite and provides new, quantitative information about the presence of {alpha}-cages of several types.

  13. Two-Dimensional NMR Study of a Liquid-Crystal Solution under Magic-Angle Spinning. Conformation of Carboxylic Ionophore Lasalocid A Dissolved in a Lyotropic Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Kimura, Atsuomi; Kano, Tetsushi; Fujiwara, Hideaki

    1996-07-01

    The conformation of a carboxylic ionophore, lasalocid A, has been determined in a lyotropic liquid crystal by means of magic-angle spinning (MAS) and two-dimensional NMR experiments. The information extracted from ROESY spectra measured under MAS was analyzed according to the distance-geometry algorithm. The liquid crystal used for the solvent is cesium perfluorooctanoate dissolved in D2O, and the resulting structure of lasalocid A is a cyclic one, indicating cation complexation within a hydrophobic region of the liquid crystal. In this way, the two-dimensional MAS NMR experiment is proved to be a useful technique in conformational studies of complex molecules dissolved in lyotropic liquid crystal which may be regarded as offering a membrane-like environment.

  14. Crocus sativus Petals: Waste or Valuable Resource? The Answer of High-Resolution and High-Resolution Magic Angle Spinning Nuclear Magnetic Resonance.

    PubMed

    Righi, Valeria; Parenti, Francesca; Tugnoli, Vitaliano; Schenetti, Luisa; Mucci, Adele

    2015-09-30

    Intact Crocus sativus petals were studied for the first time by high-resolution magic angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy, revealing the presence of kinsenoside (2) and goodyeroside A (3), together with 3-hydroxy-γ-butyrolactone (4). These findings were confirmed by HR-NMR analysis of the ethanol extract of fresh petals and showed that, even though carried out rapidly, partial hydrolysis of glucopyranosyloxybutanolides occurs during extraction. On the other hand, kaempferol 3-O-sophoroside (1), which is "NMR-silent" in intact petals, is present in extracts. These results suggest to evaluate the utilization of saffron petals for phytopharmaceutical and nutraceutical purposes to exploit a waste product of massive production of commercial saffron and point to the application of HR-MAS NMR for monitoring bioactive compounds directly on intact petals, avoiding the extraction procedure and the consequent hydrolysis reaction. PMID:26367873

  15. Satellite transitions acquired in real time by magic angle spinning (STARTMAS): ``Ultrafast'' high-resolution MAS NMR spectroscopy of spin I =3/2 nuclei

    NASA Astrophysics Data System (ADS)

    Thrippleton, Michael J.; Ball, Thomas J.; Wimperis, Stephen

    2008-01-01

    The satellite transitions acquired in real time by magic angle spinning (STARTMAS) NMR experiment combines a train of pulses with sample rotation at the magic angle to refocus the first- and second-order quadrupolar broadening of spin I =3/2 nuclei in a series of echoes, while allowing the isotropic chemical and quadrupolar shifts to evolve. The result is real-time isotropic NMR spectra at high spinning rates using conventional MAS equipment. In this paper we describe in detail how STARTMAS data can be acquired and processed with ease on commercial equipment. We also discuss the advantages and limitations of the approach and illustrate the discussion with numerical simulations and experimental data from four different powdered solids.

  16. Caught in the act: ATP hydrolysis of an ABC-multidrug transporter followed by real-time magic angle spinning NMR.

    PubMed

    Hellmich, Ute A; Haase, Winfried; Velamakanni, Saroj; van Veen, Hendrik W; Glaubitz, Clemens

    2008-10-15

    The ATP binding cassette (ABC) transporter LmrA from Lactococcus lactis transports cytotoxic molecules at the expense of ATP. Molecular and kinetic details of LmrA can be assessed by solid-state nuclear magnetic resonance (ssNMR), if functional reconstitution at a high protein-lipid ratio can be achieved and the kinetic rate constants are small enough. In order to follow ATP hydrolysis directly by 31P-magic angle spinning (MAS) nuclear magnetic resonance (NMR), we generated such conditions by reconstituting LmrA-dK388, a mutant with slower ATP turnover rate, at a protein-lipid ration of 1:150. By analysing time-resolved 31P spectra, protein activity has been directly assessed. These data demonstrate the general possibility to perform ssNMR studies on a fully active full length ABC transporter and also form the foundation for further kinetic studies on LmrA by NMR. PMID:18817774

  17. An NMR thermometer for cryogenic magic-angle spinning NMR: The spin-lattice relaxation of 127I in cesium iodide

    NASA Astrophysics Data System (ADS)

    Sarkar, Riddhiman; Concistrè, Maria; Johannessen, Ole G.; Beckett, Peter; Denning, Mark; Carravetta, Marina; al-Mosawi, Maitham; Beduz, Carlo; Yang, Yifeng; Levitt, Malcolm H.

    2011-10-01

    The accurate temperature measurement of solid samples under magic-angle spinning (MAS) is difficult in the cryogenic regime. It has been demonstrated by Thurber et al. (J. Magn. Reson., 196 (2009) 84-87) [10] that the temperature dependent spin-lattice relaxation time constant of 79Br in KBr powder can be useful for measuring sample temperature under MAS over a wide temperature range (20-296 K). However the value of T1 exceeds 3 min at temperatures below 20 K, which is inconveniently long. In this communication, we show that the spin-lattice relaxation time constant of 127I in CsI powder can be used to accurately measure sample temperature under MAS within a reasonable experimental time down to 10 K.

  18. Homonuclear dipolar recoupling under ultra-fast magic-angle spinning: probing 19F-19F proximities by solid-state NMR.

    PubMed

    Wang, Qiang; Hu, Bingwen; Lafon, Olivier; Trébosc, Julien; Deng, Feng; Amoureux, Jean-Paul

    2010-03-01

    We describe dipolar recoupling methods that accomplish, at high magic-angle spinning (MAS) frequencies, the excitation of double-quantum (DQ) coherences between spin-1/2 nuclei. We employ rotor-synchronized symmetry-based pulse sequences which are either gamma-encoded or non-gamma-encoded. The sensitivity and the robustness to both chemical-shift anisotropy and offset are examined. We also compare different techniques to avoid signal folding in the indirect dimension of two-dimensional double-quantum<-->single-quantum (DQ-SQ) spectra. This comprehensive analysis results in the identification of satisfactory conditions for dipolar (19)F-(19)F recoupling at high magnetic fields and high MAS frequencies. The utility of these recoupling methods is demonstrated with high-resolution DQ-SQ NMR spectra, which allow probing (19)F-(19)F proximities in powered fluoroaluminates. PMID:20044288

  19. High-Speed Magic-Angle Spinning 13C MAS NMR Spectra of Adamantane: Self-Decoupling of the Heteronuclear Scalar Interaction and Proton Spin Diffusion

    NASA Astrophysics Data System (ADS)

    Ernst, Matthias; Verhoeven, Aswin; Meier, Beat H.

    1998-02-01

    We have investigated the carbon line shape of solid adamantane under high-speed magic-angle sample spinning (MAS) acquired without proton decoupling. The CH-group shows a spinning-speed-dependent line broadening while the CH2-group consists of a spinning-speed-independent sharp component and a spinning-speed-dependent broader part. These phenomena can be explained by self-decoupling of theJ-interaction due to proton spin diffusion. Such a self-decoupling process can be described by a magnetization exchange process between the multiplet lines. Changing the spin-diffusion rate constant by off-resonance irradiation of the protons allows us to observe the full range from slow exchange to coalescence to fast exchange of the carbon spectra. One of the multiplet components in the CH2-group corresponds to a group spin of the protons of zero and therefore does not couple to the other protons. This gives rise to the sharp central line. The magnetization exchange rate constant between the different multiplet lines can be determined from the spectra and is a measure for the spinning-speed-dependent proton spin-diffusion rate constant. Even at an MAS speed of 30 kHz, proton spin diffusion is still observable despite the relatively weak intermolecular proton dipolar-coupling network in adamantane which results in a static proton line width of only 14 kHz (full width at half height).

  20. 13C Solid State Nuclear Magnetic Resonance and µ-Raman Spectroscopic Characterization of Sicilian Amber.

    PubMed

    Barone, Germana; Capitani, Donatella; Mazzoleni, Paolo; Proietti, Noemi; Raneri, Simona; Longobardo, Ugo; Di Tullio, Valeria

    2016-08-01

    (13)C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) and µ-Raman spectroscopy were applied to characterize Sicilian amber samples. The main goal of this work was to supply a complete study of simetite, highlighting discriminating criteria useful to distinguish Sicilian amber from fossil resins from other regions and laying the foundations for building a spectroscopic database of Sicilian amber. With this aim, a private collection of unrefined simetite samples and fossil resins from the Baltic region and Dominican Republic was analyzed. Overall, the obtained spectra permitted simetite to be distinguished from the other resins. In addition, principal component analysis (PCA) was applied to the spectroscopic data, allowing the clustering of simetite samples with respect to the Baltic and Dominican samples and to group the simetite samples in two sets, depending on their maturity. Finally, the analysis of loadings allowed for a better understanding of the spectral features that mainly influenced the discriminating characteristics of the investigated ambers. PMID:27340217

  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. Multi-dimensional 1H- 13C HETCOR and FSLG-HETCOR NMR study of sphingomyelin bilayers containing cholesterol in the gel and liquid crystalline states

    NASA Astrophysics Data System (ADS)

    Holland, Gregory P.; Alam, Todd M.

    2006-08-01

    13C cross polarization magic angle spinning (CP-MAS) and 1H MAS NMR spectra were collected on egg sphingomyelin (SM) bilayers containing cholesterol above and below the liquid crystalline phase transition temperature ( Tm). Two-dimensional (2D) dipolar heteronuclear correlation (HETCOR) spectra were obtained on SM bilayers in the liquid crystalline ( Lα) state for the first time and display improved resolution and chemical shift dispersion compared to the individual 1H and 13C spectra and significantly aid in spectral assignment. In the gel ( Lβ) state, the 1H dimension suffers from line broadening due to the 1H- 1H homonuclear dipolar coupling that is not completely averaged by the combination of lipid mobility and MAS. This line broadening is significantly suppressed by implementing frequency switched Lee-Goldburg (FSLG) homonuclear 1H decoupling during the evolution period. In the liquid crystalline ( Lα) phase, no improvement in line width is observed when FSLG is employed. All of the observed resonances are assignable to cholesterol and SM environments. This study demonstrates the ability to obtain 2D heteronuclear correlation experiments in the gel state for biomembranes, expands on previous SM assignments, and presents a comprehensive 1H/ 13C NMR assignment of SM bilayers containing cholesterol. Comparisons are made to a previous report on cholesterol chemical shifts in dimyristoylphosphatidylcholine (DMPC) bilayers. A number of similarities and some differences are observed and discussed.

  3. A Novel High-Resolution and Sensitivity-Enhanced Three-Dimensional Solid-State NMR Experiment Under Ultrafast Magic Angle Spinning Conditions.

    PubMed

    Zhang, Rongchun; Pandey, Manoj Kumar; Nishiyama, Yusuke; Ramamoorthy, Ayyalusamy

    2015-01-01

    Although magic angle spinning (MAS) solid-state NMR is a powerful technique to obtain atomic-resolution insights into the structure and dynamics of a variety of chemical and biological solids, poor sensitivity has severely limited its applications. In this study, we demonstrate an approach that suitably combines proton-detection, ultrafast-MAS and multiple frequency dimensions to overcome this limitation. With the utilization of proton-proton dipolar recoupling and double quantum (DQ) coherence excitation/reconversion radio-frequency pulses, very high-resolution proton-based 3D NMR spectra that correlate single-quantum (SQ), DQ and SQ coherences of biological solids have been obtained successfully for the first time. The proposed technique requires a very small amount of sample and does not need multiple radio-frequency (RF) channels. It also reveals information about the proximity between a spin and a certain other dipolar-coupled pair of spins in addition to regular SQ/DQ and SQ/SQ correlations. Although (1)H spectral resolution is still limited for densely proton-coupled systems, the 3D technique is valuable to study dilute proton systems, such as zeolites, small molecules, or deuterated samples. We also believe that this new methodology will aid in the design of a plethora of multidimensional NMR techniques and enable high-throughput investigation of an exciting class of solids at atomic-level resolution. PMID:26138791

  4. Microanisotropy imaging: quantification of microscopic diffusion anisotropy and orientational order parameter by diffusion MRI with magic-angle spinning of the q-vector

    NASA Astrophysics Data System (ADS)

    Lasič, Samo; Szczepankiewicz, Filip; Eriksson, Stefanie; Nilsson, Markus; Topgaard, Daniel

    2014-02-01

    Diffusion tensor imaging (DTI) is the method of choice for non-invasive investigations of the structure of human brain white matter. The results are conventionally reported as maps of the fractional anisotropy (FA), which is a parameter related to microstructural features such as axon density, diameter, and myelination. The interpretation of FA in terms of microstructure becomes ambiguous when there is a distribution of axon orientations within the image voxel. In this paper, we propose a procedure for resolving this ambiguity by determining a new parameter, the microscopic fractional anisotropy (µFA), which corresponds to the FA without the confounding influence of orientation dispersion. In addition, we suggest a method for measuring the orientational order parameter (OP) for the anisotropic objects. The experimental protocol is capitalizing on a recently developed diffusion NMR pulse sequence based on magic-angle spinning of the q-vector. Proof-of-principle experiments are carried out on microimaging and clinical MRI equipment using lyotropic liquid crystals and plant tissues as model materials with high µFA and low FA on account of orientation dispersion. We expect the presented method to be especially fruitful in combination with DTI and high angular resolution acquisition protocols for neuroimaging studies of grey and white matter.

  5. Systematic evaluation of heteronuclear spin decoupling in solid-state NMR at the rotary-resonance conditions in the regime of fast magic-angle spinning

    NASA Astrophysics Data System (ADS)

    Sharma, Kshama; Madhu, P. K.; Agarwal, Vipin

    2016-09-01

    The performance of heteronuclear spin decoupling sequences in solid-state NMR severely degrades when the proton radiofrequency (RF) nutation frequencies (ν1) are close to or at multiples of magic-angle spinning (MAS) frequency (νr) that are referred to as rotary-resonance recoupling conditions (ν1 = n · νr). Recently, two schemes, namely, PISSARRO and rCWApA, have been shown to be less affected by the problem of MAS and RF interference, specifically at the n = 2 rotary-resonance recoupling condition, especially in the fast MAS regime. Here, we systematically evaluate the loss in intensity of several heteronuclear spin decoupling sequences at the n = 1, 2 conditions compared to high-power decoupling in the fast-MAS regime. We propose that in the fast-MAS regime (above 40 kHz) the entire discussion about RF and MAS interference can be avoided by using appropriate low-power decoupling sequences which give comparable performance to decoupling sequences with high-power 1H irradiation of ca.195 kHz.

  6. Metabolomics by Proton High-Resolution Magic-Angle-Spinning Nuclear Magnetic Resonance of Tomato Plants Treated with Two Secondary Metabolites Isolated from Trichoderma.

    PubMed

    Mazzei, Pierluigi; Vinale, Francesco; Woo, Sheridan Lois; Pascale, Alberto; Lorito, Matteo; Piccolo, Alessandro

    2016-05-11

    Trichoderma fungi release 6-pentyl-2H-pyran-2-one (1) and harzianic acid (2) secondary metabolites to improve plant growth and health protection. We isolated metabolites 1 and 2 from Trichoderma strains, whose different concentrations were used to treat seeds of Solanum lycopersicum. The metabolic profile in the resulting 15 day old tomato leaves was studied by high-resolution magic-angle-spinning nuclear magnetic resonance (HRMAS NMR) spectroscopy directly on the whole samples without any preliminary extraction. Principal component analysis (PCA) of HRMAS NMR showed significantly enhanced acetylcholine and γ-aminobutyric acid (GABA) content accompanied by variable amount of amino acids in samples treated with both Trichoderma secondary metabolites. Seed germination rates, seedling fresh weight, and the metabolome of tomato leaves were also dependent upon doses of metabolites 1 and 2 treatments. HRMAS NMR spectroscopy was proven to represent a rapid and reliable technique for evaluating specific changes in the metabolome of plant leaves and calibrating the best concentration of bioactive compounds required to stimulate plant growth. PMID:27088924

  7. Quantification of microheterogeneity in glioblastoma multiforme with ex vivo high-resolution magic-angle spinning (HRMAS) proton magnetic resonance spectroscopy.

    PubMed Central

    Cheng, L. L.; Anthony, D. C.; Comite, A. R.; Black, P. M.; Tzika, A. A.; Gonzalez, R. G.

    2000-01-01

    Microheterogeneity is a routinely observed neuropathologic characteristic in brain tumor pathology. Although microheterogeneity is readily documented by routine histologic techniques, these techniques only measure tumor status at the time of biopsy or surgery and do not indicate likely tumor progression. A biochemical screening technique calibrated against pathologic standards would greatly assist in predicting tumor progression from its biological activity. Here we demonstrate for the first time that proton magnetic resonance spectroscopy (1H MRS) with high-resolution magic-angle spinning (HRMAS), a technique introduced in 1997, can preserve tissue histopathologic features while producing well-resolved spectra of cellular metabolites in the identical intact tissue specimens. Observed biochemical alterations and tumor histopathologic characteristics can thus be correlated for the same surgical specimen, obviating the problems caused by tumor microheterogeneity. We analyzed multiple specimens of a single human glioblastoma multiforme surgically removed from a 44-year-old patient. Each specimen was first measured with HRMAS 1H MRS to determine tumor metabolites, then evaluated by quantitative histopathology. The concentrations of lactate and mobile lipids measured with HRMAS linearly reflected the percentage of tumor necrosis. Moreover, metabolic ratios of phosphorylcholine to choline correlated linearly with the percentage of the highly cellular malignant glioma. The quantification of tumor metabolic changes with HRMAS 1H MRS, in conjunction with subsequent histopathology of the same tumor specimen, has the potential to further our knowledge of the biochemistry of tumor heterogeneity during development, and thus ultimately to improve our accuracy in diagnosing, characterizing, and evaluating tumor progression. PMID:11303625

  8. Atomic-resolution structure of the CAP-Gly domain of dynactin on polymeric microtubules determined by magic angle spinning NMR spectroscopy.

    PubMed

    Yan, Si; Guo, Changmiao; Hou, Guangjin; Zhang, Huilan; Lu, Xingyu; Williams, John Charles; Polenova, Tatyana

    2015-11-24

    Microtubules and their associated proteins perform a broad array of essential physiological functions, including mitosis, polarization and differentiation, cell migration, and vesicle and organelle transport. As such, they have been extensively studied at multiple levels of resolution (e.g., from structural biology to cell biology). Despite these efforts, there remain significant gaps in our knowledge concerning how microtubule-binding proteins bind to microtubules, how dynamics connect different conformational states, and how these interactions and dynamics affect cellular processes. Structures of microtubule-associated proteins assembled on polymeric microtubules are not known at atomic resolution. Here, we report a structure of the cytoskeleton-associated protein glycine-rich (CAP-Gly) domain of dynactin motor on polymeric microtubules, solved by magic angle spinning NMR spectroscopy. We present the intermolecular interface of CAP-Gly with microtubules, derived by recording direct dipolar contacts between CAP-Gly and tubulin using double rotational echo double resonance (dREDOR)-filtered experiments. Our results indicate that the structure adopted by CAP-Gly varies, particularly around its loop regions, permitting its interaction with multiple binding partners and with the microtubules. To our knowledge, this study reports the first atomic-resolution structure of a microtubule-associated protein on polymeric microtubules. Our approach lays the foundation for atomic-resolution structural analysis of other microtubule-associated motors. PMID:26604305

  9. Recoupling of native homonuclear dipolar couplings in magic-angle-spinning solid-state NMR by the double-oscillating field technique

    NASA Astrophysics Data System (ADS)

    Straasø, Lasse Arnt; Nielsen, Niels Chr.

    2010-08-01

    A new solid-state NMR method, the double-oscillating field technique (DUO), that under magic-angle-spinning conditions produces an effective Hamiltonian proportional to the native high-field homonuclear dipole-dipole coupling operator is presented. The method exploits one part of the radio frequency (rf) field to recouple the dipolar coupling interaction with a relatively high scaling factor and to eliminate offset effects over a reasonable bandwidth while in the recoupling frame, the other part gives rise to a sufficiently large longitudinal component of the residual rf field that averages nonsecular terms and in addition ensures stability toward rf inhomogeneity and rf miscalibration. The capability of the DUO experiment to mediate transfer of polarization is described theoretically and compared numerically and experimentally with finite pulse rf driven recoupling and experimentally with dipolar-assisted rotational resonance. Two-dimensional recoupling experiments were performed on antiparallel amyloid fibrils of the decapeptide SNNFGAILSS with the FGAIL fragment uniformly labeled with C13 and N15.

  10. Trifluoroethanol and 19F magic angle spinning nuclear magnetic resonance as a basic surface hydroxyl reactivity probe for zirconium(IV) hydroxide structures.

    PubMed

    DeCoste, Jared B; Glover, T Grant; Mogilevsky, Gregory; Peterson, Gregory W; Wagner, George W

    2011-08-01

    A novel technique for determining the relative accessibility and reactivity of basic surface hydroxyl sites by reacting various zirconium(IV) hydroxide materials with 2,2,2-trifluoroethanol (TFE) and characterizing the resulting material using (19)F magic angle spinning (MAS) nuclear magnetic resonance (NMR) is presented here. Studied here are three zirconium hydroxide samples, two unperturbed commercial materials, and one commercial material that is crushed by a pellet press. Factors, such as the ratio of bridging/terminal hydroxyls, surface area, and pore size distribution, are examined and found to affect the ability of the zirconium(IV) hydroxide to react with TFE. X-ray diffraction, nitrogen isotherms, and (1)H MAS NMR were used to characterize the unperturbed materials, while thermogravitric analysis with gas chromatography and mass spectrometry along with the (19)F MAS NMR were used to characterize the materials that were reacted with TFE. Zirconium hydroxide materials with a high surface area and a low bridging/terminal hydroxyl ratio were found to react TFE in the greatest amounts. PMID:21699226

  11. Magic Angle Spinning NMR Reveals Sequence-Dependent Structural Plasticity, Dynamics, and the Spacer Peptide 1 Conformation in HIV-1 Capsid Protein Assemblies

    SciTech Connect

    Han, Yun; Hou, Guangjin; Suiter, Christopher L.; Ahn, Jinwoo; Byeon, In-Ja L.; Lipton, Andrew S.; Burton, Sarah D.; Hung, Ivan; Gorkov, Peter L.; Gan, Zhehong; Brey, William W.; Rice, David M.; Gronenborn, Angela M.; Polenova, Tatyana E.

    2013-11-27

    Maturation of HIV-1 virus into an infectious virion requires cleavage of the Gag polyprotein into its constituent domains and formation of a conical capsid core that encloses viral RNA and a small complement of proteins for replication. The final step of this process is the cleavage of the SP1 peptide from the CA-SP1 maturation intermediate, which triggers the condensation of the CA protein into a conical capsid. The mechanism of this step, including the conformation of the SP1 peptide in CA-SP1, is under intense debate. In this report, we examine the tubular assemblies of CA and the CA-SP1 maturation intermediate using Magic Angle Spinning NMR spectroscopy. At the magnetic fields of 19.9 T and above, tubular CA and CA-SP1 assemblies yield outstanding-quality 2D and 3D MAS NMR spectra, which are amenable to resonance assignments and detailed structural characterization. Dipolar- and scalar-based correlation experiments unequivocally indicate that SP1 peptide is in a random coil conformation and mobile in the assembled CA-SP1. Analysis of two sequence variants reveals that remarkably, the conformation of SP1 tail, of the functionally important CypA loop, and of the loop preceding helix 8 are sequence dependent and modulated by the residue variations at distal sites. These findings challenge the role of SP1 as a conformational switch in the maturation process and establish sequence-dependent conformational plasticity in CA.

  12. Systematic evaluation of heteronuclear spin decoupling in solid-state NMR at the rotary-resonance conditions in the regime of fast magic-angle spinning.

    PubMed

    Sharma, Kshama; Madhu, P K; Agarwal, Vipin

    2016-09-01

    The performance of heteronuclear spin decoupling sequences in solid-state NMR severely degrades when the proton radiofrequency (RF) nutation frequencies (ν1) are close to or at multiples of magic-angle spinning (MAS) frequency (νr) that are referred to as rotary-resonance recoupling conditions (ν1=n·νr). Recently, two schemes, namely, PISSARRO and rCW(ApA), have been shown to be less affected by the problem of MAS and RF interference, specifically at the n=2 rotary-resonance recoupling condition, especially in the fast MAS regime. Here, we systematically evaluate the loss in intensity of several heteronuclear spin decoupling sequences at the n=1, 2 conditions compared to high-power decoupling in the fast-MAS regime. We propose that in the fast-MAS regime (above 40kHz) the entire discussion about RF and MAS interference can be avoided by using appropriate low-power decoupling sequences which give comparable performance to decoupling sequences with high-power (1)H irradiation of ca.195kHz. PMID:27472380

  13. A nuclear magnetic resonance spectrometer concept for hermetically sealed magic angle spinning investigations on highly toxic, radiotoxic, or air sensitive materials

    NASA Astrophysics Data System (ADS)

    Martel, L.; Somers, J.; Berkmann, C.; Koepp, F.; Rothermel, A.; Pauvert, O.; Selfslag, C.; Farnan, I.

    2013-05-01

    A concept to integrate a commercial high-resolution, magic angle spinning nuclear magnetic resonance (MAS-NMR) probe capable of very rapid rotation rates (70 kHz) in a hermetically sealed enclosure for the study of highly radiotoxic materials has been developed and successfully demonstrated. The concept centres on a conventional wide bore (89 mm) solid-state NMR magnet operating with industry standard 54 mm diameter probes designed for narrow bore magnets. Rotor insertion and probe tuning take place within a hermetically enclosed glovebox, which extends into the bore of the magnet, in the space between the probe and the magnet shim system. Oxygen-17 MAS-NMR measurements demonstrate the possibility of obtaining high quality spectra from small sample masses (˜10 mg) of highly radiotoxic material and the need for high spinning speeds to improve the spectral resolution when working with actinides. The large paramagnetic susceptibility arising from actinide paramagnetism in (Th1-xUx)O2 solid solutions gives rise to extensive spinning sidebands and poor resolution at 15 kHz, which is dramatically improved at 55 kHz. The first 17O MAS-NMR measurements on NpO2+x samples spinning at 55 kHz are also reported. The glovebox approach developed here for radiotoxic materials can be easily adapted to work with other hazardous or even air sensitive materials.

  14. Structure of (NH4)3GaF6 investigated by multinuclear magic-angle spinning NMR spectroscopy in comparison with rietveld refinement.

    PubMed

    Krahl, Thoralf; Ahrens, Mike; Scholz, Gudrun; Heidemann, Detlef; Kemnitz, Erhard

    2008-01-21

    The structure of ammonium gallium cryolite (NH(4))(3)GaF(6) was investigated by (19)F and (69,71)Ga magic-angle spinning (MAS) NMR in comparison with X-ray powder diffraction followed by Rietveld refinement. In agreement with previous thermodynamic measurements, NMR experiments on (NH(4))(3)GaF(6) support the model of rigid GaF(6) octahedra. At high spinning speeds (30 kHz), the scalar coupling between the six equivalent (19)F nuclei and (69,71)Ga can be directly observed in the powder spectra. The coupling constants are J(19)F(69)Ga = 197 Hz and J(19)F(71)Ga = 264 Hz. To explain the (71)Ga spectra recorded at 3 kHz a small distribution of quadrupolar frequencies has to be included. The spread of the spinning sidebands hints to a largest nu(Q) value of 28 kHz for (71)Ga. This can be explained by the occurrence of highly symmetric GaF(6) octahedra, which are tilted against the surrounding atoms. In addition, the incomplete motional excitation does not average out the quadrupolar effects. NMR findings are in discrepancy to those of Rietveld refinement. As result it appears that X-ray diffraction is not sensitive enough to deliver proper results. PMID:18069821

  15. Theory for cross effect dynamic nuclear polarization under magic-angle spinning in solid state nuclear magnetic resonance: The importance of level crossings

    PubMed Central

    Thurber, Kent R.; Tycko, Robert

    2012-01-01

    We present theoretical calculations of dynamic nuclear polarization (DNP) due to the cross effect in nuclear magnetic resonance under magic-angle spinning (MAS). Using a three-spin model (two electrons and one nucleus), cross effect DNP with MAS for electron spins with a large g-anisotropy can be seen as a series of spin transitions at avoided crossings of the energy levels, with varying degrees of adiabaticity. If the electron spin-lattice relaxation time T1e is large relative to the MAS rotation period, the cross effect can happen as two separate events: (i) partial saturation of one electron spin by the applied microwaves as one electron spin resonance (ESR) frequency crosses the microwave frequency and (ii) flip of all three spins, when the difference of the two ESR frequencies crosses the nuclear frequency, which transfers polarization to the nuclear spin if the two electron spins have different polarizations. In addition, adiabatic level crossings at which the two ESR frequencies become equal serve to maintain non-uniform saturation across the ESR line. We present analytical results based on the Landau-Zener theory of adiabatic transitions, as well as numerical quantum mechanical calculations for the evolution of the time-dependent three-spin system. These calculations provide insight into the dependence of cross effect DNP on various experimental parameters, including MAS frequency, microwave field strength, spin relaxation rates, hyperfine and electron-electron dipole coupling strengths, and the nature of the biradical dopants. PMID:22938251

  16. Theory for cross effect dynamic nuclear polarization under magic-angle spinning in solid state nuclear magnetic resonance: the importance of level crossings.

    PubMed

    Thurber, Kent R; Tycko, Robert

    2012-08-28

    We present theoretical calculations of dynamic nuclear polarization (DNP) due to the cross effect in nuclear magnetic resonance under magic-angle spinning (MAS). Using a three-spin model (two electrons and one nucleus), cross effect DNP with MAS for electron spins with a large g-anisotropy can be seen as a series of spin transitions at avoided crossings of the energy levels, with varying degrees of adiabaticity. If the electron spin-lattice relaxation time T(1e) is large relative to the MAS rotation period, the cross effect can happen as two separate events: (i) partial saturation of one electron spin by the applied microwaves as one electron spin resonance (ESR) frequency crosses the microwave frequency and (ii) flip of all three spins, when the difference of the two ESR frequencies crosses the nuclear frequency, which transfers polarization to the nuclear spin if the two electron spins have different polarizations. In addition, adiabatic level crossings at which the two ESR frequencies become equal serve to maintain non-uniform saturation across the ESR line. We present analytical results based on the Landau-Zener theory of adiabatic transitions, as well as numerical quantum mechanical calculations for the evolution of the time-dependent three-spin system. These calculations provide insight into the dependence of cross effect DNP on various experimental parameters, including MAS frequency, microwave field strength, spin relaxation rates, hyperfine and electron-electron dipole coupling strengths, and the nature of the biradical dopants. PMID:22938251

  17. Biochemical classification of kidney carcinoma biopsy samples using magic-angle-spinning 1H nuclear magnetic resonance spectroscopy.

    PubMed

    Moka, D; Vorreuther, R; Schicha, H; Spraul, M; Humpfer, E; Lipinski, M; Foxall, P J; Nicholson, J K; Lindon, J C

    1998-05-01

    High resolution 1H nuclear magnetic resonance (NMR) spectra using spinning at the magic angle (1H MAS NMR) have been obtained on intact normal and pathological kidney tissue samples from patients undergoing surgery for renal cell carcinoma (RCC). The spectra were measured on ca. 80 mg samples and provided high resolution 1H NMR spectra in which effects of dipolar couplings, chemical shift anisotropy and magnetic susceptibility differences are minimised thus yielding high spectral resolution. Conventional one-dimensional and spin-echo spectra and two-dimensional J-resolved, TOCSY and 1H-13C HMQC spectra were also measured on selected samples and these allowed the assignment of resonances of endogenous substances comprising both cytosolic and membrane components. The tumour tissues were characterised principally by an increased lipid content. These are the first reported results on human tumour tissues using this technique and the approach offers potential for the rapid classification of different types of tumour tissue. PMID:9608434

  18. Fundamental Science Tools for Geologic Carbon Sequestration and Mineral Carbonation Chemistry: In Situ Magic Angle Spinning (MAS) Nuclear Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Hoyt, D. W.; Turcu, R. V.; Sears, J. A.; Rosso, K. M.; Burton, S. D.; Kwak, J.; Felmy, A. R.; Hu, J.

    2010-12-01

    GCS is one of the most promising ways of mitigating atmospheric greenhouse gases. Mineral carbonation reactions are potentially important to the long-term sealing effectiveness of caprock but remain poorly predictable, particularly reactions occurring in low-water supercritical CO2(scCO2)-dominated environments where the chemistry has not been adequately explored. In situ probes that provide molecular-level information is desirable for investigating mechanisms and rates of GCS mineral carbonation reactions. MAS-NMR is a powerful tool for obtaining detailed molecular structure and dynamics information of a system regardless whether the system is in a solid, a liquid, a gaseous, or a supercritical state, or a mixture thereof. However, MAS NMR under scCO2 conditions has never been realized due to the tremendous technical difficulties of achieving and maintaining high pressure within a fast spinning MAS rotor. In this work, we report development of a unique high pressure MAS NMR capability, and its application to mineral carbonation chemistry in scCO2 under geologically relevant temperatures and pressures. Our high pressure MAS rotor has successfully maintained scCO2 conditions with minimal leakage over a period of 72 hours. Mineral carbonation reactions of a model magnesium silicate (forsterite) reacted with 96 bars scCO2 containing varying amounts of H2O (both below and above saturation of the scCO2) were investigated at 50○C. Figure 1 shows typical in situ 13C MAS NMR spectra demonstrating that the peaks corresponding to the reactants, intermediates, and the magnesium carbonation products are all observed in a single spectrum. For example, the scCO2 peak is located at 126.1 ppm. Reaction intermediates include the aqueous species HCO3-(160 ppm), partially hydrated/hydroxylated magnesium carbonates(166-168 ppm), and can easily be distinguished from final product magnesite(170 ppm). The new capability and this model mineral carbonation process will be overviewed in

  19. Investigation of the Curvature Induction and Membrane Localization of the Influenza Virus M2 Protein Using Static and Off-Magic-Angle Spinning Solid-State NMR of Oriented Bicelles

    PubMed Central

    Wang, Tuo; Hong, Mei

    2015-01-01

    A wide variety of membrane proteins induce membrane curvature for function, thus it is important to develop new methods to simultaneously determine membrane curvature and protein binding sites in membranes with multiple curvatures. We introduce solid-state NMR methods based on magnetically oriented bicelles and off-magic-angle spinning (OMAS) to measure membrane curvature and the binding site of proteins in mixed-curvature membranes. We demonstrate these methods on the influenza virus M2 protein, which not only acts as a proton channel but also mediates virus assembly and membrane scission. An M2 peptide encompassing the transmembrane (TM) domain and an amphipathic helix, M2(21-61), was studied and compared with the TM peptide (M2TM). Static 31P NMR spectra of magnetically oriented DMPC/DHPC bicelles exhibit a temperature-independent isotropic chemical shift in the presence of M2(21-61) but not M2TM, indicating that the amphipathic helix confers the peptide with the ability to generate a high-curvature phase. 2D 31P spectra indicate that this high-curvature phase is associated with the DHPC bicelle edges, suggestive of the structure of budding viruses from the host cell. 31P- and 13C-detected 1H relaxation times of the lipids indicate that the majority of M2(21-61) is bound to the high-curvature phase. Using OMAS experiments, we resolved the 31P signals of lipids with identical headgroups based on their distinct chemical shift anisotropies. Based on this resolution, 2D 1H-31P correlation spectra show that the amide protons in M2(21-61) correlate with the DMPC but not the DHPC 31P signal of the bicelle, indicating that a small percentage of M2(21-61) partitions into the planar region of the bicelles. These results show that the M2 amphipathic helix induces high membrane curvature and localizes the protein to this phase, in excellent agreement with the membrane-scission function of the protein. These bicelle-based relaxation and OMAS solid-state NMR techniques are

  20. Quantitative solid-state 13C nuclear magnetic resonance spectrometric analyses of wood xylen: effect of increasing carbohydrate content

    USGS Publications Warehouse

    Bates, A.L.; Hatcher, P.G.

    1992-01-01

    Isolated lignin with a low carbohydrate content was spiked with increasing amounts of alpha-cellulose, and then analysed by solid-state 13C nuclear magnetic resonance (NMR) using cross-polarization with magic angle spinning (CPMAS) and dipolar dephasing methods in order to assess the quantitative reliability of CPMAS measurement of carbohydrate content and to determine how increasingly intense resonances for carbohydrate carbons affect calculations of the degree of lignin's aromatic ring substitution and methoxyl carbon content. Comparisons were made of the carbohydrate content calculated by NMR with carbohydrate concentrations obtained by phenol-sulfuric acid assay and by the calculation from the known amounts of cellulose added. The NMR methods used in this study yield overestimates for carbohydrate carbons due to resonance area overlap from the aliphatic side chain carbons of lignin. When corrections are made for these overlapping resonance areas, the NMR results agree very well with results obtained by other methods. Neither the calculated methoxyl carbon content nor the degree of aromatic ring substitution in lignin, both calculated from dipolar dephasing spectra, change with cellulose content. Likewise, lignin methoxyl content does not correlate with cellulose abundance when measured by integration of CPMAS spectra. ?? 1992.

  1. Residue specific hydration of primary cell wall potato pectin identified by solid-state 13C single-pulse MAS and CP/MAS NMR spectroscopy.

    PubMed

    Larsen, Flemming H; Byg, Inge; Damager, Iben; Diaz, Jerome; Engelsen, Søren B; Ulvskov, Peter

    2011-05-01

    Hydration of rhamnogalacturonan-I (RG-I) derived from potato cell wall was analyzed by (13)C single-pulse (SP) magic-angle-spinning (MAS) and (13)C cross-polarization (CP) MAS nuclear magnetic resonance (NMR) and supported by (2)H SP/MAS NMR experiments. The study shows that the arabinan side chains hydrate more readily than the galactan side chains and suggests that the overall hydration properties can be controlled by modifying the ratio of these side chains. Enzymatic modification of native (NA) RG-I provided samples with reduced content of arabinan (sample DA), galactan (sample DG), or both side chains (sample DB). Results of these samples suggested that hydration properties were determined by the length and character of the side chains. NA and DA exhibited similar hydration characteristics, whereas DG and DB were difficult to hydrate because of the less hydrophilic properties of the rhamnose-galacturonic acid (Rha-GalA) backbone in RG-I. Potential food ingredient uses of RG-I by tailoring of its structure are discussed. PMID:21462966

  2. Analysis of metabolic characteristics in a rat model of chronic pancreatitis using high-resolution magic-angle spinning nuclear magnetic resonance spectroscopy.

    PubMed

    Tian, Bing; Ma, Chao; Wang, Jian; Pan, Chun-Shu; Yang, Gen-Jin; Lu, Jian-Ping

    2015-01-01

    Pathological and metabolic alterations co-exist and co-develop in the progression of chronic pancreatitis (CP). The aim of the present study was to investigate the metabolic characteristics and disease severity of a rat model of CP in order to determine associations in the observed pathology and the metabolites of CP using high-resolution magic-angle spinning nuclear magnetic resonance spectroscopy (HR-MAS NMR). Wistar rats (n=36) were randomly assigned into 6 groups (n=6 per group). CP was established by administering dibutyltin dichloride solution into the tail vein. After 0, 7, 14, 21, 28 and 35 days, the pancreatic tissues were collected for pathological scoring or for HR-MAS NMR. Correlation analyses between the major pathological scores and the integral areas of the major metabolites were determined. The most representative metabolites, aspartate, betaine and fatty acids, were identified as possessing the greatest discriminatory significance. The Spearman's rank correlation coefficients between the pathology and metabolites of the pancreatic tissues were as follows: Betaine and fibrosis, 0.454 (P=0.044); betaine and inflammatory cell infiltration, 0.716 (P=0.0001); aspartate and fibrosis, -0.768 (P=0.0001); aspartate and inflammatory cell infiltration, -0.394 (P=0.085); fatty acid and fibrosis, -0.764 (P=0.0001); and fatty acid and inflammatory cell infiltration, -0.619 (P=0.004). The metabolite betaine positively correlated with fibrosis and inflammatory cell infiltration in CP. In addition, aspartate negatively correlated with fibrosis, but exhibited no significant correlation with inflammatory cell infiltration. Furthermore, the presence of fatty acids negatively correlated with fibrosis and inflammatory cell infiltration in CP. HR-MAS NMR may be used to analyze metabolic characteristics in a rat model of different degrees of chronic pancreatitis. PMID:25338744

  3. Assessment of a 1H high-resolution magic angle spinning NMR spectroscopy procedure for free sugars quantification in intact plant tissue.

    PubMed

    Delgado-Goñi, Teresa; Campo, Sonia; Martín-Sitjar, Juana; Cabañas, Miquel E; San Segundo, Blanca; Arús, Carles

    2013-08-01

    In most plants, sucrose is the primary product of photosynthesis, the transport form of assimilated carbon, and also one of the main factors determining sweetness in fresh fruits. Traditional methods for sugar quantification (mainly sucrose, glucose and fructose) require obtaining crude plant extracts, which sometimes involve substantial sample manipulation, making the process time-consuming and increasing the risk of sample degradation. Here, we describe and validate a fast method to determine sugar content in intact plant tissue by using high-resolution magic angle spinning nuclear magnetic resonance spectroscopy (HR-MAS NMR). The HR-MAS NMR method was used for quantifying sucrose, glucose and fructose in mesocarp tissues from melon fruits (Cucumis melo var. reticulatus and Cucumis melo var. cantalupensis). The resulting sugar content varied among individual melons, ranging from 1.4 to 7.3 g of sucrose, 0.4-2.5 g of glucose; and 0.73-2.83 g of fructose (values per 100 g fw). These values were in agreement with those described in the literature for melon fruit tissue, and no significant differences were found when comparing them with those obtained using the traditional, enzymatic procedure, on melon tissue extracts. The HR-MAS NMR method offers a fast (usually <30 min) and sensitive method for sugar quantification in intact plant tissues, it requires a small amount of tissue (typically 50 mg fw) and avoids the interferences and risks associated with obtaining plant extracts. Furthermore, this method might also allow the quantification of additional metabolites detectable in the plant tissue NMR spectrum. PMID:23824526

  4. High-resolution magic angle spinning and 1H magnetic resonance spectroscopy reveal significantly altered neuronal metabolite profiles in CLN1 but not in CLN3.

    PubMed

    Sitter, Beathe; Autti, Taina; Tyynelä, Jaana; Sonnewald, Ursula; Bathen, Tone F; Puranen, Johanna; Santavuori, Pirkko; Haltia, Matti J; Paetau, Anders; Polvikoski, Tuomo; Gribbestad, Ingrid S; Häkkinen, Anna-Maija

    2004-09-01

    The neuronal ceroid lipofuscinoses (NCLs) are among the most severe inherited progressive neurodegenerative disorders of children. The purpose of this study was to compare the in vivo 1.5-T 1H magnetic resonance (MR) and ex vivo 14.3-T high-resolution (HR) magic angle spinning (MAS) 1H MR brain spectra of patients with infantile (CLN1) and juvenile (CLN3) types of NCL, to obtain detailed information about the alterations in the neuronal metabolite profiles in these diseases and to test the suitability of the ex vivo HR MAS (1)H MRS technique in analysis of autopsy brain tissue. Ex vivo spectra from CLN1 autopsy brain tissue (n = 9) significantly differed from those of the control (n = 9) and CLN3 (n = 5) groups, although no differences were found between the CLN3 and the control groups. Principal component analysis of ex vivo data showed that decreased levels of N-acetylaspartate (NAA), gamma-aminobutyric acid (GABA), glutamine, and glutamate as well as increased levels of inositols characterized the CLN1 spectra. Also, the intensity ratio of lipid methylene/methyl protons was decreased in spectra of CLN1 brain tissue compared with CLN3 and control brain tissue. In concordance with the ex vivo data, the in vivo spectra of late-stage patients with CLN1 (n = 3) revealed a dramatic decrease of NAA and a proportional increase of myo-inositol and lipids compared with control subjects. Again, the spectra of patients with CLN3 (n = 13) did not differ from those of controls (n = 15). In conclusion, the ex vivo and in vivo spectroscopic findings were in good agreement within all analyzed groups and revealed significant alterations in metabolite profiles in CLN1 brain tissue but not in CLN3 compared with controls. Furthermore, HR MAS 1H MR spectra facilitated refined detection of neuronal metabolites, including GABA, and composition of lipids in the autopsy brain tissue of NCL patients. PMID:15352223

  5. Enhanced sensitivity and resolution in (1)H solid-state NMR spectroscopy of paramagnetic complexes under very fast magic angle spinning.

    PubMed

    Wickramasinghe, Nalinda P; Shaibat, Medhat; Ishii, Yoshitaka

    2005-04-27

    High-resolution NMR spectroscopy for paramagnetic complexes in solids has been rarely performed because of its limited sensitivity and resolution due to large paramagnetic shifts and associated technical difficulties. The present study demonstrates that magic angle spinning (MAS) at speeds exceeding 20 kHz provides unusually high sensitivity and excellent resolution in 1H solid-state NMR (SSNMR) for paramagnetic systems. Spinning-speed dependence of 1H MAS spectra showed that very fast MAS (VFMAS) at 24-28 kHz enhanced sensitivity by a factor of 12-18, compared with the sensitivity of 1H SSNMR spectra under moderate MAS at 10 kHz, for Cu(dl-alanine)2.H2O and Mn(acac)3, for which the spectral ranges due to 1H paramagnetic shifts reach 200 and 1000 ppm, respectively. It was theoretically and experimentally confirmed that the absolute sensitivity of 1H VFMAS for small paramagnetic complexes such as Cu(dl-alanine)2 can be an order of magnitude higher than that of equimolar diamagnetic ligands because of short 1H T1 ( approximately 1 ms) of the paramagnetic systems and improved sensitivity under VFMAS. On the basis of this demonstrated high sensitivity, 1H SSNMR micro analysis of paramagnetic systems in a nanomole scale is proposed. Applications were performed on two polymorphs of Cu(II)(8-quinolinol)2, which is a suppressor of human cancer cells. It was demonstrated that 1H VFMAS SSNMR spectra accumulated for 20 nmol of the polycrystalline samples in 10 min enabled one to distinguish alpha- and beta-forms of Cu(II)(8-quinolinol)2 on the basis of shift positions and line widths. PMID:15839671

  6. Application of the Floquet theory to multiple quantum NMR of dipolar-coupled multi-spin systems under magic angle spinning

    NASA Astrophysics Data System (ADS)

    Filip, Claudiu; Bertmer, Marko; Demco, Dan E.; Blümich, Bernhard

    A new analytical Liouville-space representation of the time-propagator under magic angle spinning (MAS) is introduced using the formalized quantum Floquet theory. This approach has the advantage that it is applicable to the analysis of any type of NMR experiment where MAS is combined with multiple-pulse excitation. General relationships describing the spectral parameters in multiple-quantum (MQ) MAS spectra are derived in this representation. Their use is illustrated with an application to double-quantum (DQ) NMR spectra of dipolarcoupled multi-spin systems. Corresponding to the separation of the MAS time-propagator into a rotor modulated and a dephasing component, two distinct mechanisms for DQ excitation are identified. One of them exploits the rotor-modulated component to excite DQ coherences through dipolar-recoupling techniques, which are familiar for spin pairs. Analytical expressions of the integral intensities and linewidths in the resulting DQ sideband pattern are derived in the form of power series expansions of the inverse rotor frequency, of which coefficients depend on structural parameters. In a multi-spin system they can most reliably be extracted in the fast spinning regime. The other mechanism exploits the dephasing component, which is characteristic to multi-spin systems only. This is shown to give rise to DQ coherences by free evolution at full rotor periods. The possibility to exploit it for selective excitation of higher order MQ coherences is discussed. In either case, the dephasing component also leads to residual broadening. The main results of the theoretical developments are demonstrated experimentally on adamantane.

  7. Magic-angle spinning NMR study of deuterium site occupancy and dynamics in ZrNiD1.0 and ZrNiD3.0

    NASA Astrophysics Data System (ADS)

    Adolphi, Natalie L.; Badola, Sharwari; Browder, Lisa A.; Bowman, R. C.

    2002-01-01

    Both static and magic-angle spinning (MAS) 2H nuclear magnetic resonance spectroscopy indicate that two inequivalent sites are occupied in ZrNiD3.0, in a 2:1 ratio, in agreement with previous work. The sites occupied in the trihydride phase have been previously identified as Zr3Ni and Zr3Ni2. In ZrNiD1.0, two well-resolved lines of equal intensity are observed in the MAS spectrum at temperatures<220 K, indicating that two other inequivalent sites are occupied in a 1:1 ratio, in contrast with previous reports that only one type of site (Zr4Ni2) is occupied in the monohydride (β) phase at room temperature and above. The temperature dependences of both MAS and static ZrNiD1.0 spectra indicate that no phase transitions occur over the entire temperature range studied, 160-500 K. The deuterium hopping rate in ZrNiD1.0 is determined from characteristic changes in the MAS spectra as a function of temperature; the motion is consistent with an activation energy Ea≅0.44 eV assuming a rate prefactor 1/τ0~1013 s-1. In ZrNiD3.0, the rate of deuterium motion is determined from signatures of motion in the static and MAS spectra. The motion in ZrNiD3.0 is consistent with an activation energy Ea≅0.62 eV assuming a rate prefactor of ~1013 s-1.

  8. Nanostructures of Mg0.65Ti0.35Dx studied with x-ray diffraction, neutron diffraction, and magic-angle-spinning H2 NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Srinivasan, S.; Magusin, P. C. M. M.; Kalisvaart, W. P.; Notten, P. H. L.; Cuevas, F.; Latroche, M.; van Santen, R. A.

    2010-02-01

    Magnesium transition-metal alloys have a high hydrogen-storage capacity and show improved hydrogen-uptake and -release kinetics compared to magnesium alone. In the present study we have investigated the structure of bulk magnesium-titanium deuteride Mg0.65Ti0.35Dx prepared via mechanical alloying and gas-phase deuterium absorption by combined use of x-ray diffraction (XRD), neutron diffraction, and magic-angle-spinning H2 nuclear magnetic resonance (NMR). The initial ball-milled alloy has two XRD-distinct Mg and Ti fcc phases. Even after prolonged exposure to deuterium gas at 75 bar and 175°C the materials with and without palladium catalyst are only partly deuterated. Deuterium loading causes the formation of, on the one hand, bct (rutile) MgD2 nanodomains with interdispersed TiDy layers and, on the other hand, a separate fcc (fluorite) TiDz phase. The TiDy phase is XRD invisible, but shows clearly up at a H2 NMR shift of -43ppm between the shift of MgD2 (3 ppm) and the Knight shift of the TiDz phase (-143ppm) . Exchange NMR indicates complete deuterium exchange at 25°C between the MgD2 and TiDy phase within 1 s, as consistent with intimate contacts between these phases. Combined analysis of the XRD and NMR peak areas suggests that the deuterium concentrations y and z in the TiDy and TiDz domains are about 1.5 and 2.0, respectively. Comparing the intrinsic cell parameters of rutile MgH2 and fluorite TiH2 , we propose that stabilization of the mixed nanocomposite may arise from a coherent coupling between the crystal structures of the rutile MgD2 nanodomains and the thin layers of fcc TiDy .

  9. [Characterization of biochar by X-ray photoelectron spectroscopy and 13C nuclear magnetic resonance].

    PubMed

    Xu, Dong-yu; Jin, Jie; Yan, Yu; Han, Lan-fang; Kang, Ming-jie; Wang, Zi-ying; Zhao, Ye; Sun, Ke

    2014-12-01

    The wood (willow branch) and grass (rice straw) materials were pyrolyzed at different temperatures (300, 450 and 600 °C) to obtain the biochars used in the present study. The biochars were characterized using elementary analysis, X-ray photoelectron spectroscopy (XPS) and solid state 13C cross-polarization and magic angle spinning nuclear magnetic resonance spectroscopy (13C NMR) to illuminate the structure and composition of the biochars which were derived from the different thermal temperatures and biomass. The results showed that the H/C, O/C and (O+N)/C ratios of the biochars decreased with the increase in the pyrolysis temperatures. The surface polarity and ash content of the grass-derived biochars were higher than those of the wood-derived biochars. The minerals of the wood-derived biochars were mainly covered by the organic matter; in contrast, parts of the mineral surfaces of the grass-derived biochars were not covered by organic matter? The 13C NMR of the low temperature-derived biochars revealed a large contribution of aromatic carbon, aliphatic carbon, carboxyl and carbonyl carbon, while the high temperature-derived biochars contained a large amount of aromatic carbon. Moreover, the wood-derived biochars produced at low heat treatment temperatures contained more lignin residues than grass-derived ones, probably due to the existence of high lignin content in the feedstock soures of wood-derived biochars. The results of the study would be useful for environmental application of biochars. PMID:25881450

  10. The structural properties of the transmembrane segment of the integral membrane protein phospholamban utilizing (13)C CPMAS, (2)H, and REDOR solid-state NMR spectroscopy.

    PubMed

    Karp, Ethan S; Tiburu, Elvis K; Abu-Baker, Shadi; Lorigan, Gary A

    2006-06-01

    Solid-state NMR spectroscopic techniques were used to investigate the secondary structure of the transmembrane peptide phospholamban (TM-PLB), a sarcoplasmic Ca(2+) regulator. (13)C cross-polarization magic angle spinning spectra of (13)C carbonyl-labeled Leu39 of TM-PLB exhibited two peaks in a pure 1-palmitoyl-2-oleoyl-phosphocholine (POPC) bilayer, each due to a different structural conformation of phospholamban as characterized by the corresponding (13)C chemical shift. The addition of a negatively charged phospholipid (1-palmitoyl-2-oleoylphosphatidylglycerol (POPG)) to the POPC bilayer stabilized TM-PLB to an alpha-helical conformation as monitored by an enhancement of the alpha-helical carbonyl (13)C resonance in the corresponding NMR spectrum. (13)C-(15)N REDOR solid-state NMR spectroscopic experiments revealed the distance between the (13)C carbonyl carbon of Leu39 and the (15)N amide nitrogen of Leu42 to be 4.2+/-0.2A indicating an alpha-helical conformation of TM-PLB with a slight deviation from an ideal 3.6 amino acid per turn helix. Finally, the quadrupolar splittings of three (2)H labeled leucines (Leu28, Leu39, and Leu51) incorporated in mechanically aligned DOPE/DOPC bilayers yielded an 11 degrees +/-5 degrees tilt of TM-PLB with respect to the bilayer normal. In addition to elucidating valuable TM-PLB secondary structure information, the solid-state NMR spectroscopic data indicates that the type of phospholipids and the water content play a crucial role in the secondary structure and folding of TM-PLB in a phospholipid bilayer. PMID:16839519

  11. Sensitivity enhanced (14)N/(14)N correlations to probe inter-beta-sheet interactions using fast magic angle spinning solid-state NMR in biological solids.

    PubMed

    Pandey, Manoj Kumar; Amoureux, Jean-Paul; Asakura, Tetsuo; Nishiyama, Yusuke

    2016-08-10

    (14)N/(14)N correlations are vital for structural studies of solid samples, especially those in which (15)N isotopic enrichment is challenging, time-consuming and expensive. Although (14)N nuclei have high isotopic abundance (99.6%), there are inherent difficulties in observing (14)N/(14)N correlations due to limited resolution and sensitivity related to: (i) low (14)N gyromagnetic ratio (γ), (ii) large (14)N quadrupolar couplings, (iii) integer (14)N spin quantum number (I = 1), and (iv) very weak (14)N-(14)N dipolar couplings. Previously, we demonstrated a proton-detected 3D (14)N/(14)N/(1)H correlation experiment at fast magic angle spinning (MAS) on l-histidine·HCl·H2O utilizing a through-bond (J) and residual dipolar-splitting (RDS) based heteronuclear multiple quantum correlation (J-HMQC) sequence mediated through (1)H/(1)H radio-frequency driven recoupling (RFDR). As an extension of our previous work, in this study we show the utility of dipolar-based HMQC (D-HMQC) in combination with (1)H/(1)H RFDR mixing to obtain sensitivity enhanced (14)N/(14)N correlations in more complex biological solids such as a glycyl-l-alanine (Gly-l-Ala) dipeptide, and parallel (P) and antiparallel (AP) β-strand alanine tripeptides (P-(Ala)3 and AP-(Ala)3, respectively). These systems highlight the mandatory necessity of 3D (14)N/(14)N/(1)H measurements to get (14)N/(14)N correlations when the amide proton resonances are overlapped. Moreover, the application of long selective (14)N pulses, instead of short hard ones, is shown to improve the sensitivity. Globally, we demonstrate that replacing J-scalar with dipolar interaction and hard- with selective-(14)N pulses allows gaining a factor of ca. 360 in experimental time. On the basis of intermolecular NH/NH distances and (14)N quadrupolar tensor orientations, (14)N/(14)N correlations are effectively utilized to make a clear distinction between the parallel and antiparallel arrangements of the β-strands in (Ala)3 through the

  12. Structures and thermal and hydrothermal stabilities of sulfonated poly(organosiloxanes) by /sup 29/Si and /sup 13/C CP/MAS NMR

    SciTech Connect

    Suzuki, S.; Ono, Y.; Nakata, S.; Asaoka, S.

    1987-03-12

    High-resolution /sup 29/Si and /sup 13/C cross polarization/magic-angle spinning (CP/MAS) NMR spectroscopies have been applied to poly((sulfophenyl)siloxane) and poly((sulfopropyl)siloxane) in order to examine their thermal and hydrothermal stability. The effects of the treatments on the catalytic activity for the alcohol dehydration were also studied. Under nonsteaming conditions, both siloxanes have much higher thermal stability than Amberlyst-15. Thermal stability is in a decreasing order, poly((sulfophenyl)siloxane) (573 K) > poly((sulfopropyl)siloxane) (543 K) > Amberlyst-15 (468 K), while the thermal stability under steaming conditions is in the order of poly((sulfopropyl)siloxane) (543 K) > poly((sulfophenyl)siloxane) = Amberlyst-15 (468 K). The thermal degradation of the poly((sulfophenyl)siloxane) mainly occurs by the rupture of the C-Si bonds between the benzene ring and the siloxane chain. The steam greatly affects the thermal stability of poly((sulfophenyl)siloxane). Thus, under steaming conditions, thermal degradation occurred at much lower temperatures than under nonsteaming conditions. The thermal degradation of the poly((sulfopropyl)siloxane) mainly occurs at the C-C bond in the sulfopropyl groups. Steam does not affect the thermal stability of poly((sulfopropyl)siloxane).

  13. 13C, 2h NMR studies of structural and dynamical modifications of glucose-exposed porcine aortic elastin.

    PubMed

    Silverstein, Moshe C; Bilici, Kübra; Morgan, Steven W; Wang, Yunjie; Zhang, Yanhang; Boutis, Gregory S

    2015-04-01

    Elastin, the principal component of the elastic fiber of the extracellular matrix, imparts to vertebrate tissues remarkable resilience and longevity. This work focuses on elucidating dynamical and structural modifications of porcine aortic elastin exposed to glucose by solid-state NMR spectroscopic and relaxation methodologies. Results from macroscopic stress-strain tests are also presented and indicate that glucose-treated elastin is mechanically stiffer than the same tissue without glucose treatment. These measurements show a large hysteresis in the stress-strain behavior of glucose-treated elastin-a well-known signature of viscoelasticity. Two-dimensional relaxation NMR methods were used to investigate the correlation time, distribution, and population of water in these samples. Differences are observed between the relative populations of water, whereas the measured correlation times of tumbling motion of water across the samples were similar. (13)C magic-angle-spinning NMR methods were applied to investigate structural and dynamical modifications after glucose treatment. Although some overall structure is preserved, the process of glucose exposure results in more heterogeneous structures and slower mobility. The correlation times of tumbling motion of the (13)C-(1)H internuclear vectors in the glucose-treated sample are larger than in untreated samples, pointing to their more rigid structure. The (13)C cross-polarization spectra reveal a notably increased α-helical character in the alanine motifs after glucose exposure. Results from molecular dynamics simulations are provided that add further insight into dynamical and structural changes of a short repeat, [VPGVG]5, an alanine pentamer, desmosine, and isodesmosine sites with and without glucose. The simulations point to changes in the entropic and energetic contributions in the retractive forces of VPGVG and AAAAA motifs. The most notable change is the increase of the energetic contribution in the retractive

  14. 13C, 2H NMR Studies of Structural and Dynamical Modifications of Glucose-Exposed Porcine Aortic Elastin

    PubMed Central

    Silverstein, Moshe C.; Bilici, Kübra; Morgan, Steven W.; Wang, Yunjie; Zhang, Yanhang; Boutis, Gregory S.

    2015-01-01

    Elastin, the principal component of the elastic fiber of the extracellular matrix, imparts to vertebrate tissues remarkable resilience and longevity. This work focuses on elucidating dynamical and structural modifications of porcine aortic elastin exposed to glucose by solid-state NMR spectroscopic and relaxation methodologies. Results from macroscopic stress-strain tests are also presented and indicate that glucose-treated elastin is mechanically stiffer than the same tissue without glucose treatment. These measurements show a large hysteresis in the stress-strain behavior of glucose-treated elastin—a well-known signature of viscoelasticity. Two-dimensional relaxation NMR methods were used to investigate the correlation time, distribution, and population of water in these samples. Differences are observed between the relative populations of water, whereas the measured correlation times of tumbling motion of water across the samples were similar. 13C magic-angle-spinning NMR methods were applied to investigate structural and dynamical modifications after glucose treatment. Although some overall structure is preserved, the process of glucose exposure results in more heterogeneous structures and slower mobility. The correlation times of tumbling motion of the 13C-1H internuclear vectors in the glucose-treated sample are larger than in untreated samples, pointing to their more rigid structure. The 13C cross-polarization spectra reveal a notably increased α-helical character in the alanine motifs after glucose exposure. Results from molecular dynamics simulations are provided that add further insight into dynamical and structural changes of a short repeat, [VPGVG]5, an alanine pentamer, desmosine, and isodesmosine sites with and without glucose. The simulations point to changes in the entropic and energetic contributions in the retractive forces of VPGVG and AAAAA motifs. The most notable change is the increase of the energetic contribution in the retractive force

  15. - and Cross-Polarization 13C NMR Evidence of Alterations in Molecular Composition of Humic Substances Following Afforestation with Eucalypt in Distinct Brazilian Biomes

    NASA Astrophysics Data System (ADS)

    Silva, I. R.; Soares, E. M.; Schmidt-Rohr, K.; Novais, R.; Barros, N.; Fernandes, S.

    2010-12-01

    The effect of planting fast growing tree species on SOM quality in tropical regions has been overlooked. In the present study 13C-NMR approaches were used to evaluate the impact of eucalypt cultivation on humic and fulvic acids molecular composition. The results indicate that the replacement of native vegetation by eucalypt plantations increased the relative contribution of aliphatic groups in HA from soils previously under Atlantic Forest, Grassland, and the Cerrado (Curvelo site only). The same trend was observed for FA, except in the Curvelo site. A trend for degradation and smaller contribution of O-alkyl C (carbohydrates) in HA was observed in soils under eucalyptus in Atlantic Forest and Cerrado. For FA such decreases were seen in Cerrado and Grassland biomes after eucalypt planting. In the area cultivated with pasture in the Atlantic Forest biome and in the Grassland soil, the largest contributions of lignin-derived compounds were detected in HA. The HA from the Cerrado at the Curvelo site, where the woody vegetation is virtually devoid of grassy species, showed the lowest intensity of lignin signal then those from the Cerrado sensu stricto in Itacambira, where grass species are more abundant. At our study sites, charred material are most likely derived from burning of the native vegetation, as naturally occurs in the Cerrado region, or anthropogenic fires in the Grassland biome. Burning of harvest residues in eucalypt fields was also a common practice in the early rotations. The replacement of native vegetation by eucalypt plantations increases the relative contribution of nonpolar alkyl groups in HA from soils previously under Atlantic Forest, Grassland, and the Cerrado (Curvelo site only) biomes. There is evidence of substantial contribution of lignin-derived C to HA and FA, especially in sites planted with Brachiaria sp pastures. Eucalypt introduction decreases the relative contribution of carbohydrates in HA and FA. 13C DP/MAS NMR functional groups in

  16. Polydisperse methyl β-cyclodextrin–epichlorohydrin polymers: variable contact time 13C CP-MAS solid-state NMR characterization

    PubMed Central

    Mallard, Isabelle; Baudelet, Davy; Castiglione, Franca; Ferro, Monica; Panzeri, Walter; Ragg, Enzio

    2015-01-01

    Summary The polymerization of partially methylated β-cyclodextrin (CRYSMEB) with epichlorohydrin was carried out in the presence of a known amount of toluene as imprinting agent. Three different preparations (D1, D2 and D3) of imprinted polymers were obtained and characterized by solid-state 13C NMR spectroscopy under cross-polarization magic angle spinning (CP-MAS) conditions. The polymers were prepared by using the same synthetic conditions but with different molar ratios of imprinting agent/monomer, leading to morphologically equivalent materials but with different absorption properties. The main purpose of the work was to find a suitable spectroscopic descriptor accounting for the different imprinting process in three homogeneous polymeric networks. The polymers were characterized by studying the kinetics of the cross-polarization process. This approach is based on variable contact time CP-MAS spectra, referred to as VCP-MAS. The analysis of the VCP-MAS spectra provided two relaxation parameters: T CH (the CP time constant) and T 1ρ (the proton spin-lattice relaxation time in the rotating frame). The results and the analysis presented in the paper pointed out that T CH is sensitive to the imprinting process, showing variations related to the toluene/cyclodextrin molar ratio used for the preparation of the materials. Conversely, the observed values of T 1ρ did not show dramatic variations with the imprinting protocol, but rather confirmed that the three polymers are morphologically similar. Thus the combined use of T CH and T 1ρ can be helpful for the characterization and fine tuning of imprinted polymeric matrices. PMID:26877800

  17. Polydisperse methyl β-cyclodextrin-epichlorohydrin polymers: variable contact time (13)C CP-MAS solid-state NMR characterization.

    PubMed

    Mallard, Isabelle; Baudelet, Davy; Castiglione, Franca; Ferro, Monica; Panzeri, Walter; Ragg, Enzio; Mele, Andrea

    2015-01-01

    The polymerization of partially methylated β-cyclodextrin (CRYSMEB) with epichlorohydrin was carried out in the presence of a known amount of toluene as imprinting agent. Three different preparations (D1, D2 and D3) of imprinted polymers were obtained and characterized by solid-state (13)C NMR spectroscopy under cross-polarization magic angle spinning (CP-MAS) conditions. The polymers were prepared by using the same synthetic conditions but with different molar ratios of imprinting agent/monomer, leading to morphologically equivalent materials but with different absorption properties. The main purpose of the work was to find a suitable spectroscopic descriptor accounting for the different imprinting process in three homogeneous polymeric networks. The polymers were characterized by studying the kinetics of the cross-polarization process. This approach is based on variable contact time CP-MAS spectra, referred to as VCP-MAS. The analysis of the VCP-MAS spectra provided two relaxation parameters: T CH (the CP time constant) and T 1ρ (the proton spin-lattice relaxation time in the rotating frame). The results and the analysis presented in the paper pointed out that T CH is sensitive to the imprinting process, showing variations related to the toluene/cyclodextrin molar ratio used for the preparation of the materials. Conversely, the observed values of T 1ρ did not show dramatic variations with the imprinting protocol, but rather confirmed that the three polymers are morphologically similar. Thus the combined use of T CH and T 1ρ can be helpful for the characterization and fine tuning of imprinted polymeric matrices. PMID:26877800

  18. Solid-state distortions of nominally square-planar palladium and platinum (R sub 3 P) sub 2 MX sub 2 complexes as determined by a combination of sup 13 C( sup 1 H) and sup 31 P( sup 31 H) NMR spectroscopy

    SciTech Connect

    Rahn, J.A.; Nelson, J.H. ); O'Donnell, D.J.; Pamer, A.R. )

    1989-06-28

    Phosphorus-31 and carbon-13 NMR spectra have been obtained for a series of 20 (R{sub 3}P){sub 2}MX{sub 2} complexes (R{sub 3}P = MePh{sub 2}P and Me{sub 2}PhP; M = Pd, Pt; X = Cl, Br, I, CN, N{sub 3}) in the solid state by cross-polarization and magic-angle-spinning (CP/MAS) techniques. Comparison of these data with spectral data obtained at 300 K in CDCl{sub 3} solutions was made in order to investigate the influence of local symmetry on {sup 31}P and {sup 13}C chemical shifts in the solid state. It was found that most of these compounds, which have regular square-planar geometries in solution, are distorted in the solid state. The solid-state distortions are evidenced by additional {sup 31}P and {sup 13}C resonances in the CP/MAS spectra as compared to the solution spectra. The nature and degree of these distortions are discussed. 25 refs., 2 figs., 6 tabs.

  19. 27Al magic-angle spinning nuclear magnetic resonance satellite transition spectroscopy of glasses in the system K2O-Al2O3-SiO2.

    PubMed

    Mundus, C; Müller-Warmuth, W

    1995-10-01

    27Al magic-angle spinning nuclear magnetic resonance satellite transition spectroscopy at 78 MHz has been applied to determine (true) chemical shift and quadrupole coupling parameters of glasses in the system K2O-Al2O3-SiO2 with 60-80 mol% SiO2 and K2O concentrations between 0 and 24 mol%. The powdered crystalline aluminosilicates andalusite and sillimanite have also been examined. In the glasses, all Al appears to be tetrahedrally bound in the aluminosilicate network unless x = mol% K2O:mol% Al2O3 becomes extremely small. Upon decreasing x the distortion of the tetrahedral Al(OSi)4 units increases in steps, and possible explanations are discussed. Six-coordinated aluminum observed for x < 0.2 is connected with the occurrence of interstitial Al3+ ions which charge-compensate the AlO4 units in addition to K+. PMID:8748646

  20. /sup 13/C spin diffusion of adamantane

    SciTech Connect

    Bronniman, C.E.; Szeverenyi, N.M.; Maciel, G.E.

    1983-10-15

    Two-dimensional exchange spectroscopy of natural abundance /sup 13/C--/sup 13/C spin diffusion in solid adamantane illustrates the influence that /sup 13/C--/sup 1/H dipole--dipole coupling exerts on /sup 13/C spin diffusion by determining spectral overlap in the /sup 13/C system. 2D /sup 13/C spectra were obtained for several values of mixing time tau/sub m/ and compared with spectra calculated in the limit of nearest-neighbor coupling. Good agreement is obtained for short tau/sub m/, during which the equilibration of neighboring spins dominates. For longer tau/sub m/, slower spin diffusion that is not acounted for by the simple model is seen; after nearest-neighbor spins equilibrate, communication over larger distances produces further mixing. It is possible to modify spin diffusion rates by altering experimental conditions, e.g., magic-angle spinning, low-power /sup 1/H decoupling, or spin locking /sup 13/C in the rotating frame during tau/sub m/.

  1. Determination of the Orientation and Dynamics of Ergosterol in Model Membranes Using Uniform 13C Labeling and Dynamically Averaged 13C Chemical Shift Anisotropies as Experimental Restraints

    PubMed Central

    Soubias, O.; Jolibois, F.; Massou, S.; Milon, A.; Réat, V.

    2005-01-01

    A new strategy was established to determine the average orientation and dynamics of ergosterol in dimyristoylphosphatidylcholine model membranes. It is based on the analysis of chemical shift anisotropies (CSAs) averaged by the molecular dynamics. Static 13C CSA tensors were computed by quantum chemistry, using the gauge-including atomic-orbital approach within Hartree-Fock theory. Uniformly 13C-labeled ergosterol was purified from Pichia pastoris cells grown on labeled methanol. After reconstitution into dimyristoylphosphatidylcholine lipids, the complete 1H and 13C assignment of ergosterol's resonances was performed using a combination of magic-angle spinning two-dimensional experiments. Dynamically averaged CSAs were determined by standard side-band intensity analysis for isolated 13C resonances (C3 and ethylenic carbons) and by off-magic-angle spinning experiments for other carbons. A set of 18 constraints was thus obtained, from which the sterol's molecular order parameter and average orientation could be precisely defined. The validity of using computed CSAs in this strategy was verified on cholesterol model systems. This new method allowed us to quantify ergosterol's dynamics at three molar ratios: 16 mol % (Ld phase), 30 mol % (Lo phase), and 23 mol % (mixed phases). Contrary to cholesterol, ergosterol's molecular diffusion axis makes an important angle (14°) with the inertial axis of the rigid four-ring system. PMID:15923221

  2. Mechanism of Solid-State Thermolysis of Ammonia Boraine: 15N NMR Study Using Fast Magic-Angle Spinning and Dynamic Nuclear Polarization

    SciTech Connect

    Kobayashi, Takeshi; Gupta, Shalabh; Caporini, Marc A; Pecharsky, Vitalij K; Pruski, Marek

    2014-08-28

    The solid-state thermolysis of ammonia borane (NH3BH3, AB) was explored using state-of-the-art 15N solid-state NMR spectroscopy, including 2D indirectly detected 1H{15N} heteronuclear correlation and dynamic nuclear polarization (DNP)-enhanced 15N{1H} cross-polarization experiments as well as 11B NMR. The complementary use of 15N and 11B NMR experiments, supported by density functional theory calculations of the chemical shift tensors, provided insights into the dehydrogenation mechanism of AB—insights that have not been available by 11B NMR alone. Specifically, highly branched polyaminoborane derivatives were shown to form from AB via oligomerization in the “head-to-tail” manner, which then transform directly into hexagonal boron nitride analog through the dehydrocyclization reaction, bypassing the formation of polyiminoborane.

  3. 13C SPE MAS measurement of ligand concentration in compressible chromatographic beads

    PubMed Central

    Elwinger, Fredrik; Dvinskikh, Sergey V.

    2015-01-01

    A method for measuring the ligand concentration in heterogeneous materials like chromatography media is described. In this method, 13C single pulse excitation magic angle spinning NMR experiment with broadband 1H decoupling is used to determine the peak integrals for a butyl ligand in the spectrum of a dried chromatography medium. Within a carefully controlled protocol, those integrals compared with that of the internal reference compound dimethyl sulfone provide the required volume concentration with an accuracy of ca 2%. The effects of temperature, degree of hydration, and other experimental parameters are discussed. Copyright © 2015 The Authors. Magnetic Resonance in Chemistry published by John Wiley & Sons Ltd. PMID:26053054

  4. Study of wheat high molecular weight 1Dx5 subunit by (13)C and (1)H solid-state NMR. II. Roles of nonrepetitive terminal domains and length of repetitive domain.

    PubMed

    Alberti, Enrica; Gilbert, Simon M; Tatham, Arthur S; Shewry, Peter R; Naito, Akira; Okuda, Kanna; Saitô, Hazime; Gil, Ana M

    2002-10-15

    This work follows a previous article that addressed the role of disulfide bonds in the behavior of the 1Dx5 subunit upon hydration. Here the roles of nonrepetitive terminal domains present and the length of the central repetitive domain in the hydration of 1Dx5 are investigated. This was achieved by comparing the hydration behavior of suitable model samples determined by (13)C- and (1)H-NMR: an alkylated 1Dx5 subunit (alk1Dx5), a recombinant 58-kDa peptide corresponding to the central repetitive domain of 1Dx5 (i.e., lacking the terminal domains), and two synthetic peptides (with 6 and 21 amino acid residues) based on the consensus repeat motifs of the central domain. The (13)C cross-polarization and magic angle spinning (MAS) experiments recorded as a function of hydration gave information about the protein or peptide fractions resisting plasticization. Conversely, (13)C single pulse excitation and (1)H-MAS gave information on the more plasticized segments. The results are consistent with the previous proposal of a hydrated network held by hydrogen-bonded glutamines and possibly hydrophobic interactions. The nonrepetitive terminal domains were found to induce water insolubility and a generally higher network hindrance. Shorter chain lengths were shown to increase plasticization and water solubility. However, at low water contents, the 21-mer peptide was characterized by higher hindrance in the megahertz and kilohertz frequency ranges compared to the longer peptide; and a tendency for a few hydrogen-bonded glutamines and hydrophobic residues to remain relatively hindered was still observed, as for the protein and large peptide. It is suggested that this ability is strongly dependent on the peptide primary structure. PMID:12209466

  5. (13) C-TmDOTA as versatile thermometer compound for solid-state NMR of hydrated lipid bilayer membranes.

    PubMed

    Umegawa, Yuichi; Tanaka, Yuya; Nobuaki, Matsumori; Murata, Michio

    2016-03-01

    Recent advances in solid-state nuclear magnetic resonance (NMR) techniques, such as magic angle spinning and high-power decoupling, have dramatically increased the sensitivity and resolution of NMR. However, these NMR techniques generate extra heat, causing a temperature difference between the sample in the rotor and the variable temperature gas. This extra heating is a particularly crucial problem for hydrated lipid membrane samples. Thus, to develop an NMR thermometer that is suitable for hydrated lipid samples, thulium-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (TmDOTA) was synthesized and labeled with (13) C (i.e., (13) C-TmDOTA) to increase the NMR sensitivity. The complex was mixed with a hydrated lipid membrane, and the system was subjected to solid-state NMR and differential scanning calorimetric analyses. The physical properties of the lipid bilayer and the quality of the NMR spectra of the membrane were negligibly affected by the presence of (13) C-TmDOTA, and the (13) C chemical shift of the complex exhibited a large-temperature dependence. The results demonstrated that (13) C-TmDOTA could be successfully used as a thermometer to accurately monitor temperature changes induced by (1) H decoupling pulses and/or by magic angle spinning and the temperature distribution of the sample inside the rotor. Thus, (13) C-TmDOTA was shown to be a versatile thermometer for hydrated lipid assemblies. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26460094

  6. Accurate measurement of heteronuclear dipolar couplings by phase-alternating R-symmetry (PARS) sequences in magic angle spinning NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Hou, Guangjin; Lu, Xingyu; Vega, Alexander J.; Polenova, Tatyana

    2014-09-01

    We report a Phase-Alternating R-Symmetry (PARS) dipolar recoupling scheme for accurate measurement of heteronuclear 1H-X (X = 13C, 15N, 31P, etc.) dipolar couplings in MAS NMR experiments. It is an improvement of conventional C- and R-symmetry type DIPSHIFT experiments where, in addition to the dipolar interaction, the 1H CSA interaction persists and thereby introduces considerable errors in the dipolar measurements. In PARS, phase-shifted RN symmetry pulse blocks applied on the 1H spins combined with π pulses applied on the X spins at the end of each RN block efficiently suppress the effect from 1H chemical shift anisotropy, while keeping the 1H-X dipolar couplings intact. Another advantage over conventional DIPSHIFT experiments, which require the signal to be detected in the form of a reduced-intensity Hahn echo, is that the series of π pulses refocuses the X chemical shift and avoids the necessity of echo formation. PARS permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons. The performance of PARS is tested on two model systems, [15N]-N-acetyl-valine and [U-13C,15N]-N-formyl-Met-Leu-Phe tripeptide. The application of PARS for site-resolved measurement of accurate 1H-15N dipolar couplings in the context of 3D experiments is presented on U-13C,15N-enriched dynein light chain protein LC8.

  7. A Large Sample Volume Magic Angle Spinning Nuclear Magnetic Resonance Probe for In-Situ Investigations with Constant Flow of Reactants

    SciTech Connect

    Hu, Jian Z.; Sears, Jesse A.; Mehta, Hardeep S.; Ford, Joseph J.; Kwak, Ja Hun; Zhu, Kake; Wang, Yong; Liu, Jun; Hoyt, David W.; Peden, Charles HF

    2012-02-21

    A large-sample-volume constant-flow magic angle sample spinning (CF-MAS) NMR probe is reported for in-situ studies of the reaction dynamics, stable intermediates/transition states, and mechanisms of catalytic reactions. In our approach, the reactants are introduced into the catalyst bed using a fixed tube at one end of the MAS rotor while a second fixed tube, linked to a vacuum pump, is attached at the other end of the rotor. The pressure difference between both ends of the catalyst bed inside the sample cell space forces the reactants flowing through the catalyst bed, which improves the diffusion of the reactants and products. This design allows the use of a large sample volume for enhanced sensitivity and thus permitting in-situ 13C CF-MAS studies at natural abundance. As an example of application, we show that reactants, products and reaction transition states associated with the 2-butanol dehydration reaction over a mesoporous silicalite supported heteropoly acid catalyst (HPA/meso-silicalite-1) can all be detected in a single 13C CF-MAS NMR spectrum at natural abundance. Coke products can also be detected at natural 13C abundance and under the stopped flow condition. Furthermore, 1H CF-MAS NMR is used to identify the surface functional groups of HPA/meso-silicalite-1 under the condition of in-situ drying . We also show that the reaction dynamics of 2-butanol dehydration using HPA/meso-silicalite-1 as a catalyst can be explored using 1H CF-MAS NMR.

  8. Accurate measurement of heteronuclear dipolar couplings by phase-alternating R-symmetry (PARS) sequences in magic angle spinning NMR spectroscopy

    SciTech Connect

    Hou, Guangjin E-mail: tpolenov@udel.edu; Lu, Xingyu E-mail: lexvega@comcast.net; Vega, Alexander J. E-mail: lexvega@comcast.net; Polenova, Tatyana E-mail: tpolenov@udel.edu

    2014-09-14

    We report a Phase-Alternating R-Symmetry (PARS) dipolar recoupling scheme for accurate measurement of heteronuclear {sup 1}H-X (X = {sup 13}C, {sup 15}N, {sup 31}P, etc.) dipolar couplings in MAS NMR experiments. It is an improvement of conventional C- and R-symmetry type DIPSHIFT experiments where, in addition to the dipolar interaction, the {sup 1}H CSA interaction persists and thereby introduces considerable errors in the dipolar measurements. In PARS, phase-shifted RN symmetry pulse blocks applied on the {sup 1}H spins combined with π pulses applied on the X spins at the end of each RN block efficiently suppress the effect from {sup 1}H chemical shift anisotropy, while keeping the {sup 1}H-X dipolar couplings intact. Another advantage over conventional DIPSHIFT experiments, which require the signal to be detected in the form of a reduced-intensity Hahn echo, is that the series of π pulses refocuses the X chemical shift and avoids the necessity of echo formation. PARS permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons. The performance of PARS is tested on two model systems, [{sup 15}N]-N-acetyl-valine and [U-{sup 13}C,{sup 15}N]-N-formyl-Met-Leu-Phe tripeptide. The application of PARS for site-resolved measurement of accurate {sup 1}H-{sup 15}N dipolar couplings in the context of 3D experiments is presented on U-{sup 13}C,{sup 15}N-enriched dynein light chain protein LC8.

  9. In vivo high-resolution magic angle spinning magnetic resonance spectroscopy of Drosophila melanogaster at 14.1 T shows trauma in aging and in innate immune-deficiency is linked to reduced insulin signaling

    PubMed Central

    RIGHI, VALERIA; APIDIANAKIS, YIORGOS; MINTZOPOULOS, DIONYSSIOS; ASTRAKAS, LOUKAS; RAHME, LAURENCE G.; TZIKA, A. ARIA

    2010-01-01

    In vivo magnetic resonance spectroscopy (MRS), a non-destructive biochemical tool for investigating live organisms, has yet to be used in the fruit fly Drosophila melanogaster, a useful model organism for investigating genetics and physiology. We developed and implemented a high-resolution magic-angle-spinning (HRMAS) MRS method to investigate live Drosophila at 14.1 T. We demonstrated, for the first time, the feasibility of using HRMAS MRS for molecular characterization of Drosophila with a conventional MR spectrometer equipped with an HRMAS probe. We showed that the metabolic HRMAS MRS profiles of injured, aged wild-type (wt) flies and of immune deficient (imd) flies were more similar to chico flies mutated at the chico gene in the insulin signaling pathway, which is analogous to insulin receptor substrate 1–4 (IRS1–4) in mammals and less to those of adipokinetic hormone receptor (akhr) mutant flies, which have an obese phenotype. We thus provide evidence for the hypothesis that trauma in aging and in innate immune-deficiency is linked to insulin signaling. This link may explain the mitochondrial dysfunction that accompanies insulin resistance and muscle wasting that occurs in trauma, aging and immune system deficiencies, leading to higher susceptibility to infection. Our approach advances the development of novel in vivo non-destructive research approaches in Drosophila, suggests biomarkers for investigation of biomedical paradigms, and thus may contribute to novel therapeutic development. PMID:20596596

  10. Broadband homonuclear correlation spectroscopy driven by combined R2(n)(v) sequences under fast magic angle spinning for NMR structural analysis of organic and biological solids.

    PubMed

    Hou, Guangjin; Yan, Si; Trébosc, Julien; Amoureux, Jean-Paul; Polenova, Tatyana

    2013-07-01

    We recently described a family of experiments for R2n(v) Driven Spin Diffusion (RDSD) spectroscopy suitable for homonuclear correlation experiments under fast MAS conditions [G. Hou, S. Yan, S.J. Sun, Y. Han, I.J. Byeon, J. Ahn, J. Concel, A. Samoson, A.M. Gronenborn, T. Polenova, Spin diffusion drive by R-symmetry sequencs: applications to homonuclear correlation spectroscopy in MAS NMR of biological and organic solids, J. Am. Chem. Soc. 133 (2011) 3943-3953]. In these RDSD experiments, since the broadened second-order rotational resonance conditions are dominated by the radio frequency field strength and the phase shifts, as well as the size of reintroduced dipolar couplings, the different R2n(v) sequences display unique polarization transfer behaviors and different recoupling frequency bandwidths. Herein, we present a series of modified R2n(v) sequences, dubbed COmbined R2n(v)-Driven (CORD), that yield broadband homonuclear dipolar recoupling and give rise to uniform distribution of cross peak intensities across the entire correlation spectrum. We report NMR experiments and numerical simulations demonstrating that these CORD spin diffusion sequences are suitable for broadband recoupling at a wide range of magnetic fields and MAS frequencies, including fast-MAS conditions (νr=40 kHz and above). Since these CORD sequences are largely insensitive to dipolar truncation, they are well suited for the determination of long-range distance constraints, which are indispensable for the structural characterization of a broad range of systems. Using U-(13)C,(15)N-alanine and U-(13)C,(15)N-histidine, we show that under fast-MAS conditions, the CORD sequences display polarization transfer efficiencies within broadband frequency regions that are generally higher than those offered by other existing spin diffusion pulse schemes. A 89-residue U-(13)C,(15)N-dynein light chain (LC8) protein has also been used to demonstrate that the CORD sequences exhibit uniformly high cross peak

  11. Application of (13)C ramp CPMAS NMR with phase-adjusted spinning sidebands (PASS) for the quantitative estimation of carbon functional groups in natural organic matter.

    PubMed

    Ikeya, Kosuke; Watanabe, Akira

    2016-01-01

    The composition of carbon (C) functional groups in natural organic matter (NOM), such as dissolved organic matter, soil organic matter, and humic substances, is frequently estimated using solid-state (13)C NMR techniques. A problem associated with quantitative analysis using general cross polarization/magic angle spinning (CPMAS) spectra is the appearance of spinning side bands (SSBs) split from the original center peaks of sp (2) hybridized C species (i.e., aromatic and carbonyl C). Ramp CP/phase-adjusted side band suppressing (PASS) is a pulse sequence that integrates SSBs separately and quantitatively recovers them into their inherent center peaks. In the present study, the applicability of ramp CP/PASS to NOM analysis was compared with direct polarization (DPMAS), another quantitative method but one that requires a long operation time, and/or a ramp CP/total suppression side band (ramp CP/TOSS) technique, a popular but non-quantitative method for deleting SSBs. The test materials were six soil humic acid samples with various known degrees of aromaticity and two fulvic acids. There were no significant differences in the relative abundance of alkyl C, O-alkyl C, and aromatic C between the ramp CP/PASS and DPMAS methods, while the signal intensities corresponding to aromatic C in the ramp CP/TOSS spectra were consistently less than the values obtained in the ramp CP/PASS spectra. These results indicate that ramp CP/PASS can be used to accurately estimate the C composition of NOM samples. PMID:26522329

  12. Chemical structures of coal lithotypes before and after CO2 adsorption as investigated by advanced solid-state 13C nuclear magnetic resonance spectroscopy

    USGS Publications Warehouse

    Cao, X.; Mastalerz, Maria; Chappell, M.A.; Miller, L.F.; Li, Y.; Mao, J.

    2011-01-01

    Four lithotypes (vitrain, bright clarain, clarain, and fusain) of a high volatile bituminous Springfield Coal from the Illinois Basin were characterized using advanced solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. The NMR techniques included quantitative direct polarization/magic angle spinning (DP/MAS), cross polarization/total sideband suppression (CP/TOSS), dipolar dephasing, CHn selection, and recoupled C-H long-range dipolar dephasing techniques. The lithotypes that experienced high-pressure CO2 adsorption isotherm analysis were also analyzed to determine possible changes in coal structure as a result of CO2 saturation at high pressure and subsequent evacuation. The main carbon functionalities present in original vitrain, bright clarain, clarain and fusain were aromatic carbons (65.9%-86.1%), nonpolar alkyl groups (9.0%-28.9%), and aromatic C-O carbons (4.1%-9.5%). Among these lithotypes, aromaticity increased in the order of clarain, bright clarain, vitrain, and fusain, whereas the fraction of alkyl carbons decreased in the same order. Fusain was distinct from other three lithotypes in respect to its highest aromatic composition (86.1%) and remarkably small fraction of alkyl carbons (11.0%). The aromatic cluster size in fusain was larger than that in bright clarain. The lithotypes studied responded differently to high pressure CO2 saturation. After exposure to high pressure CO2, vitrain and fusain showed a decrease in aromaticity but an increase in the fraction of alkyl carbons, whereas bright clarain and clarain displayed an increase in aromaticity but a decrease in the fraction of alkyl carbons. Aromatic fused-rings were larger for bright clarain but smaller for fusain in the post-CO2 adsorption samples compared to the original lithotypes. These observations suggested chemical CO2-coal interactions at high pressure and the selectivity of lithotypes in response to CO2 adsorption. ?? 2011 Elsevier B.V.

  13. 2H-DNP-enhanced 2H–13C solid-state NMR correlation spectroscopy

    PubMed Central

    Maly, Thorsten; Andreas, Loren B.; Smith, Albert A.

    2015-01-01

    Perdeuteration of biological macromolecules for magic angle spinning solid-state NMR spectroscopy can yield high-resolution 2H–13C correlation spectra and the method is therefore of great interest for the structural biology community. Here we demonstrate that the combination of sample deuteration and dynamic nuclear polarization yields resolved 2H–13C correlation spectra with a signal enhancement of ε ≥ 700 compared to a spectrum recorded with microwaves off and otherwise identical conditions. To our knowledge, this is the first time that 2H-DNP has been employed to enhance MAS-NMR spectra of a biologically relevant system. The DNP process is studied using several polarizing agents and the technique is applied to obtain 2H–13C correlation spectra of U-[2H, 13C] proline. PMID:20458422

  14. A 23Na magic angle spinning nuclear magnetic resonance, XANES, and high-temperature X-ray diffraction study of NaUO3, Na4UO5, and Na2U2O7.

    PubMed

    Smith, A L; Raison, P E; Martel, L; Charpentier, T; Farnan, I; Prieur, D; Hennig, C; Scheinost, A C; Konings, R J M; Cheetham, A K

    2014-01-01

    The valence state of uranium has been confirmed for the three sodium uranates NaU(V)O3/[Rn](5f(1)), Na4U(VI)O5/[Rn](5f(0)), and Na2U(VI)2O7/[Rn](5f(0)), using X-ray absorption near-edge structure (XANES) spectroscopy. Solid-state (23)Na magic angle spinning nuclear magnetic resonance (MAS NMR) measurements have been performed for the first time, yielding chemical shifts at -29.1 (NaUO3), 15.1 (Na4UO5), and -14.1 and -19 ppm (Na1 8-fold coordinated and Na2 7-fold coordinated in Na2U2O7), respectively. The [Rn]5f(1) electronic structure of uranium in NaUO3 causes a paramagnetic shift in comparison to Na4UO5 and Na2U2O7, where the electronic structure is [Rn]5f(0). A (23)Na multi quantum magic angle spinning (MQMAS) study on Na2U2O7 has confirmed a monoclinic rather than rhombohedral structure with evidence for two distinct Na sites. DFT calculations of the NMR parameters on the nonmagnetic compounds Na4UO5 and Na2U2O7 have permitted the differentiation between the two Na sites of the Na2U2O7 structure. The linear thermal expansion coefficients of all three compounds have been determined using high-temperature X-ray diffraction: αa = 22.7 × 10(-6) K(-1), αb = 12.9 × 10(-6) K(-1), αc = 16.2 × 10(-6) K(-1), and αvol = 52.8 × 10(-6) K(-1) for NaUO3 in the range 298-1273 K; αa = 37.1 × 10(-6) K(-1), αc = 6.2 × 10(-6) K(-1), and αvol = 81.8 × 10(-6) K(-1) for Na4UO5 in the range 298-1073 K; αa = 6.7 × 10(-6) K(-1), αb = 14.4 × 10(-6) K(-1), αc = 26.8 × 10(-6) K(-1), αβ = -7.8 × 10(-6) K(-1), and αvol = -217.6 × 10(-6) K(-1) for Na2U2O7 in the range 298-573 K. The α to β phase transition reported for the last compound above about 600 K was not observed in the present studies, either by high-temperature X-ray diffraction or by differential scanning calorimetry. PMID:24350659

  15. 31P magic angle spinning NMR study of flux-grown rare-earth element orthophosphate (monazite/xenotime) solid solutions: evidence of random cation distribution from paramagnetically shifted NMR resonances.

    PubMed

    Palke, Aaron C; Stebbins, Jonathan F; Boatner, Lynn A

    2013-11-01

    We present (31)P magic angle spinning nuclear magnetic resonance spectra of flux-grown solid solutions of La(1-x)Ce(x)PO4 (x between 0.027 and 0.32) having the monoclinic monazite structure, and of Y(1-x)M(x)PO4 (M = V(n+), Ce(3+), Nd(3+), x between 0.001 and 0.014) having the tetragonal zircon structure. Paramagnetically shifted NMR resonances are observed in all samples due to the presence of paramagnetic V(n+), Ce(3+), and Nd(3+) in the diamagnetic LaPO4 or YPO4. As a first-order observation, the number and relative intensities of these peaks are related to the symmetry and structure of the diamagnetic host phase. The presence of paramagnetic shifts allows for increased resolution between NMR resonances for distinct atomic species which leads to the observation of low intensity peaks related to PO4 species having more than one paramagnetic neighbor two or four atomic bonds away. Through careful analysis of peak areas and comparison with predictions for simple models, it was determined that solid solutions in the systems examined here are characterized by complete disorder (random distribution) of diamagnetic La(3+) or Y(3+) with the paramagnetic substitutional species Ce(3+) and Nd(3+). The increased resolution given by the paramagnetic interactions also leads to the observation of splitting of specific resonances in the (31)P NMR spectra that may be caused by local, small-scale distortions from the substitution of ions having dissimilar ionic radii. PMID:24131129

  16. The Role of High-Resolution Magic Angle Spinning 1H Nuclear Magnetic Resonance Spectroscopy for Predicting the Invasive Component in Patients with Ductal Carcinoma In Situ Diagnosed on Preoperative Biopsy.

    PubMed

    Chae, Eun Young; Shin, Hee Jung; Kim, Suhkmann; Baek, Hyeon-Man; Yoon, Dahye; Kim, Siwon; Shim, Ye Eun; Kim, Hak Hee; Cha, Joo Hee; Choi, Woo Jung; Lee, Jeong Hyun; Shin, Ji Hoon; Lee, Hee Jin; Gong, Gyungyub

    2016-01-01

    The purpose of this study was to evaluate the role of high-resolution magic angle spinning (HR-MAS) 1H nuclear magnetic resonance (NMR) spectroscopy in patients with ductal carcinoma in situ (DCIS) diagnosed on preoperative biopsy. We investigated whether the metabolic profiling of tissue samples using HR-MAS 1H NMR spectroscopy could be used to distinguish between DCIS lesions with or without an invasive component. Our institutional review board approved this combined retrospective and prospective study. Tissue samples were collected from 30 patients with pure DCIS and from 30 with DCIS accompanying invasive carcinoma. All patients were diagnosed with DCIS by preoperative core-needle biopsy and underwent surgical resection. The metabolic profiling of tissue samples was performed by HR-MAS 1H NMR spectroscopy. All observable metabolite signals were identified and quantified in all tissue samples. Metabolite intensity normalized by total spectral intensities was compared according to the tumor type using the Mann-Whitney test. Multivariate analysis was performed with orthogonal projections to latent structure-discriminant analysis (OPLS-DA). By univariate analysis, the metabolite concentrations of choline-containing compounds obtained with HR-MAS 1H NMR spectroscopy did not differ significantly between the pure DCIS and DCIS accompanying invasive carcinoma groups. However, the GPC/PC ratio was higher in the pure DCIS group than in the DCIS accompanying invasive carcinoma group (p = 0.004, Bonferroni-corrected p = 0.064), as well as the concentration of myo-inositol and succinate. By multivariate analysis, the OPLS-DA models built with HR-MAS MR metabolic profiles could clearly discriminate between pure DCIS and DCIS accompanying invasive carcinoma. Our preliminary results suggest that HR-MAS MR metabolomics on breast tissue may be able to distinguish between DCIS lesions with or without an invasive component. PMID:27560937

  17. The Role of High-Resolution Magic Angle Spinning 1H Nuclear Magnetic Resonance Spectroscopy for Predicting the Invasive Component in Patients with Ductal Carcinoma In Situ Diagnosed on Preoperative Biopsy

    PubMed Central

    Chae, Eun Young; Kim, Suhkmann; Baek, Hyeon-Man; Yoon, Dahye; Kim, Siwon; Shim, Ye Eun; Kim, Hak Hee; Cha, Joo Hee; Choi, Woo Jung; Lee, Jeong Hyun; Shin, Ji Hoon; Lee, Hee Jin; Gong, Gyungyub

    2016-01-01

    The purpose of this study was to evaluate the role of high-resolution magic angle spinning (HR-MAS) 1H nuclear magnetic resonance (NMR) spectroscopy in patients with ductal carcinoma in situ (DCIS) diagnosed on preoperative biopsy. We investigated whether the metabolic profiling of tissue samples using HR-MAS 1H NMR spectroscopy could be used to distinguish between DCIS lesions with or without an invasive component. Our institutional review board approved this combined retrospective and prospective study. Tissue samples were collected from 30 patients with pure DCIS and from 30 with DCIS accompanying invasive carcinoma. All patients were diagnosed with DCIS by preoperative core-needle biopsy and underwent surgical resection. The metabolic profiling of tissue samples was performed by HR-MAS 1H NMR spectroscopy. All observable metabolite signals were identified and quantified in all tissue samples. Metabolite intensity normalized by total spectral intensities was compared according to the tumor type using the Mann-Whitney test. Multivariate analysis was performed with orthogonal projections to latent structure-discriminant analysis (OPLS-DA). By univariate analysis, the metabolite concentrations of choline-containing compounds obtained with HR-MAS 1H NMR spectroscopy did not differ significantly between the pure DCIS and DCIS accompanying invasive carcinoma groups. However, the GPC/PC ratio was higher in the pure DCIS group than in the DCIS accompanying invasive carcinoma group (p = 0.004, Bonferroni-corrected p = 0.064), as well as the concentration of myo-inositol and succinate. By multivariate analysis, the OPLS-DA models built with HR-MAS MR metabolic profiles could clearly discriminate between pure DCIS and DCIS accompanying invasive carcinoma. Our preliminary results suggest that HR-MAS MR metabolomics on breast tissue may be able to distinguish between DCIS lesions with or without an invasive component. PMID:27560937

  18. Luminescence dynamics and {sup 13}C NMR characteristics of dinuclear complexes exhibiting coupled lanthanide(III) cation pairs

    SciTech Connect

    Matthews, K.D.; Bailey-Folkes, S.A.; Kahwa, I.A.

    1992-08-20

    Luminescence and cross-polarization magic angle spinning (CP-MAS) {sup 13}C NMR properties of lanthanide dinuclear macrocyclic complexes of a compartmental Schiff base chelate (1) derived from the condensation of 2,6-diformyl-p-cresol and 3,6-dioxa-1,8-octanediamine are reported. The Schiff base chromophore in 1 is a strong light absorber and an efficient sensitizer for intense Tb{sup 3+}({sup 5}D{sub 4}) and Eu{sup 3+}({sup 5}D{sub 0})(T < 110 K ) emission which does not exhibit self-quenching effects. Emission from Tb{sup 3+} is sensitized by the ligand singlet state; in striking contrast, Eu{sup 3+} emission is sensitized by the triplet state and reveals an unusual nonradiative quenching process at T > 110 K with a thermal barrier of {approx} 2300 cm{sup {minus}1}. Weak emission is observed from Dy{sup 3+}({sup 4}F{sub 9/2}), Sm{sup 3+}({sup 4}G{sub 5/2}), and Pr{sup 3+}({sup 1}D{sub 2}) diluted in Gd{sup 3+} (i.e., from Gd{sup 3+}-Ln{sup 3+} heteropairs, Ln = Pr, Sm, Dy). Intramolecular metal-metal (Ln-Ln = 4 {Angstrom}) interactions account for the greatly quenched emission from Sm{sup 3+}-Sm{sup 3+} and Dy{sup 3+}-Dy{sup 3+} homopairs compared to Gd{sup 3+}-Ln heteropairs (Ln = Sm, Dy). Gd{sup 3+}-Ln{sup 3+} emission lifetimes at 77 K are 1610 (Tb{sup 3+}), 890 (Eu{sup 3+}), 14 (Dy{sup 3+}) and {approx} 13 {mu}s (Sm{sup 3+}). Nonradiative relaxation processes at 77 K in dilute Ln{sup 3+}:Gd{sub 2}1(NO{sub 3}){sub 4}{center_dot}H{sub 2}O, being temperature independent for Sm{sup 3+} and Eu{sup 3+} but temperature dependent for Tb{sup 3+}, follow the energy gap law with {alpha} {approx} - 10{sup {minus}3} cm and B {approx} 2 x 10{sup 8} s{sup {minus}1}. CP-MAS data show paramagnetic broadening of {sup 13}C resonances which increases with the magnetic moment of Ln{sup 3+}. Surprisingly, no significant shifts in resonance positions corresponding to the changing nature of paramagnetic Ln{sup 3+} ions are observed. 43 refs., 8 figs., 2 tabs.

  19. Metabolomics of Breast Cancer Using High-Resolution Magic Angle Spinning Magnetic Resonance Spectroscopy: Correlations with 18F-FDG Positron Emission Tomography-Computed Tomography, Dynamic Contrast-Enhanced and Diffusion-Weighted Imaging MRI

    PubMed Central

    Yoon, Haesung; Yoon, Dahye; Yun, Mijin; Choi, Ji Soo; Park, Vivian Youngjean; Kim, Eun-Kyung; Jeong, Joon; Koo, Ja Seung; Yoon, Jung Hyun; Moon, Hee Jung; Kim, Suhkmann; Kim, Min Jung

    2016-01-01

    Purpose Our goal in this study was to find correlations between breast cancer metabolites and conventional quantitative imaging parameters using high-resolution magic angle spinning (HR-MAS) magnetic resonance spectroscopy (MRS) and to find breast cancer subgroups that show high correlations between metabolites and imaging parameters. Materials and methods Between August 2010 and December 2013, we included 53 female patients (mean age 49.6 years; age range 32–75 years) with a total of 53 breast lesions assessed by the Breast Imaging Reporting and Data System. They were enrolled under the following criteria: breast lesions larger than 1 cm in diameter which 1) were suspicious for malignancy on mammography or ultrasound (US), 2) were pathologically confirmed to be breast cancer with US-guided core-needle biopsy (CNB) 3) underwent 3 Tesla MRI with dynamic contrast-enhanced (DCE) and diffusion-weighted imaging (DWI) and positron emission tomography-computed tomography (PET-CT), and 4) had an attainable immunohistochemistry profile from CNB. We acquired spectral data by HR-MAS MRS with CNB specimens and expressed the data as relative metabolite concentrations. We compared the metabolites with the signal enhancement ratio (SER), maximum standardized FDG uptake value (SUV max), apparent diffusion coefficient (ADC), and histopathologic prognostic factors for correlation. We calculated Spearman correlations and performed a partial least squares-discriminant analysis (PLS-DA) to further classify patient groups into subgroups to find correlation differences between HR-MAS spectroscopic values and conventional imaging parameters. Results In a multivariate analysis, the PLS-DA models built with HR-MAS MRS metabolic profiles showed visible discrimination between high and low SER, SUV, and ADC. In luminal subtype breast cancer, compared to all cases, high SER, ADV, and SUV were more closely clustered by visual assessment. Multiple metabolites were correlated with SER and SUV in

  20. Structure of amantadine-bound M2 transmembrane peptide of influenza A in lipid bilayers from magic-angle-spinning solid-state NMR: the role of Ser31 in amantadine binding.

    PubMed

    Cady, Sarah D; Mishanina, Tatiana V; Hong, Mei

    2009-01-30

    The M2 proton channel of influenza A is the target of the antiviral drugs amantadine and rimantadine, whose effectiveness has been abolished by a single-site mutation of Ser31 to Asn in the transmembrane domain of the protein. Recent high-resolution structures of the M2 transmembrane domain obtained from detergent-solubilized protein in solution and crystal environments gave conflicting drug binding sites. We present magic-angle-spinning solid-state NMR results of Ser31 and a number of other residues in the M2 transmembrane peptide (M2TMP) bound to lipid bilayers. Comparison of the spectra of the membrane-bound apo and complexed M2TMP indicates that Ser31 is the site of the largest chemical shift perturbation by amantadine. The chemical shift constraints lead to a monomer structure with a small kink of the helical axis at Gly34. A tetramer model is then constructed using the helix tilt angle and several interhelical distances previously measured on unoriented bilayer samples. This tetramer model differs from the solution and crystal structures in terms of the openness of the N-terminus of the channel, the constriction at Ser31, and the side-chain conformations of Trp41, a residue important for channel gating. Moreover, the tetramer model suggests that Ser31 may interact with amantadine amine via hydrogen bonding. While the apo and drug-bound M2TMP have similar average structures, the complexed peptide has much narrower linewidths at physiological temperature, indicating drug-induced changes of the protein dynamics in the membrane. Further, at low temperature, several residues show narrower lines in the complexed peptide than the apo peptide, indicating that amantadine binding reduces the conformational heterogeneity of specific residues. The differences of the current solid-state NMR structure of the bilayer-bound M2TMP from the detergent-based M2 structures suggest that the M2 conformation is sensitive to the environment, and care must be taken when interpreting

  1. High-resolution {sup 13}C nuclear magnetic resonance evidence of phase transition of Rb,Cs-intercalated single-walled nanotubes

    SciTech Connect

    Bouhrara, M.; Saih, Y.; Waagberg, T.; Goze-Bac, C.; Abou-Hamad, E.

    2011-09-01

    We present 13 C high-resolution magic-angle-turning (MAT) and magic angle spinning nuclear magnetic resonance data of Cs and Rb intercalated single walled carbon nanotubes. We find two distinct phases at different intercalation levels. A simple charge transfer is applicable at low intercalation level. The new phase at high intercalation level is accompanied by a hybridization of alkali (s) orbitals with the carbon (sp2) orbitals of the single walled nanotubes, which indicate bundle surface sites is the most probable alkali site.

  2. Measuring (13)C/(15)N chemical shift anisotropy in [(13)C,(15)N] uniformly enriched proteins using CSA amplification.

    PubMed

    Hung, Ivan; Ge, Yuwei; Liu, Xiaoli; Liu, Mali; Li, Conggang; Gan, Zhehong

    2015-11-01

    Extended chemical shift anisotropy amplification (xCSA) is applied for measuring (13)C/(15)N chemical shift anisotropy (CSA) of uniformly labeled proteins under magic-angle spinning (MAS). The amplification sequence consists of a sequence of π-pulses that repetitively interrupt MAS averaging of the CSA interaction. The timing of the pulses is designed to generate amplified spinning sideband manifolds which can be fitted to extract CSA parameters. The (13)C/(13)C homonuclear dipolar interactions are not affected by the π-pulses due to the bilinear nature of the spin operators and are averaged by MAS in the xCSA experiment. These features make the constant evolution-time experiment suitable for measuring CSA of uniformly labeled samples. The incorporation of xCSA with multi-dimensional (13)C/(15)N correlation is demonstrated with a GB1 protein sample as a model system for measuring (13)C/(15)N CSA of all backbone (15)NH, (13)CA and (13)CO sites. PMID:26404770

  3. Analysis of Hydroperoxides in Solid Polyethylene by MAS (13)C NMR and EPR

    SciTech Connect

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

    1999-11-19

    {sup 13}C-enriched polyethylene was subjected to {gamma}-irradiation in the presence of air at 25 and 80 C for total doses ranging from 71 to 355 kGy. Significant quantities of hydroperoxides were detected in the 25 C irradiated sample by {sup 13}C magic angle spinning NMR spectroscopy. This method of detection was performed on the solid polymer and required no chemical derivatization or addition of solvent. The chemical stability and subsequent products of the hydroperoxide species were studied by annealing the irradiated samples in air at temperatures ranging from 22 to 110 C. A time-temperature superposition analysis provided an activation energy of 108 kJ/mol for the hydroperoxide decomposition process. The primary products of hydroperoxide decomposition were ketones and secondary alcohols with lesser amounts of acids and esters. EPR measurements suggest that the reactive hydroperoxide species reside in the amorphous phase of polyethylene, consistent with degradation occurring in the amorphous phase.

  4. Solid state 13C NMR characterisation study on fourth generation Ziegler-Natta catalysts.

    PubMed

    Heikkinen, Harri; Liitiä, Tiina; Virkkunen, Ville; Leinonen, Timo; Helaja, Tuulamari; Denifl, Peter

    2012-01-01

    In this study, solid state (13)C NMR spectroscopy was utilised to characterize and identify the metal-ester coordination in active fourth generation (phthalate) Ziegler-Natta catalysts. It is known that different donors affect the active species in ZN catalysts. However, there is still limited data available of detailed molecular information how the donors and the active species are interplaying. One of the main goals of this work was to get better insight into the interactions of donor and active species. Based on the anisotropy tensor values (δ(11), δ(22), δ(33)) from low magic-angle spinning (MAS) (13)C NMR spectra in combination with chemical shift anisotropy (CSA) calculations (δ(aniso) and η), both the coordinative metal (Mg/Ti) and the symmetry of this interaction between metal and the internal donor in the active catalyst (MgCl(2)/TiCl(4)/electron donor) system could be identified. PMID:22425229

  5. 1H to 13C Energy Transfer in Solid State NMR Spectroscopy of Natural Organic Systems

    NASA Astrophysics Data System (ADS)

    Berns, Anne E.; Conte, Pellegrino

    2010-05-01

    Cross polarization (CP) magic angle spinning (MAS) 13C-NMR spectroscopy is a solid state NMR technique widely used to study chemical composition of organic materials with low or no solubility in the common deuterated solvents used to run liquid state NMR experiments. Based on the magnetization transfer from abundant nuclei (with spin of 1 -2) having a high gyromagnetic ratio (γ), such as protons, to the less abundant 13C nuclei with low γ values, 13C-CPMAS NMR spectroscopy is often applied in environmental chemistry to obtain quantitative information on the chemical composition of natural organic matter (NOM) (Conte et al., 2004), although its quantitative assessment is still matter of heavy debates. Many authors (Baldock et al., 1997; Conte et al., 1997, 2002; Dria et al., 2002; Kiem et al., 2000; Kögel-Knabner, 2000; Preston, 2001), reported that the application of appropriate instrument setup as well as the use of special pulse sequences and correct spectra elaboration may provide signal intensities that are directly proportional to the amount of nuclei creating a NMR signal. However, many other papers dealt with the quantitative unsuitability of 13C-CPMAS NMR spectroscopy. Among those, Mao et al. (2000), Smernik and Oades (2000 a,b), and Preston (2001) reported that cross-polarized NMR techniques may fail in a complete excitation of the 13C nuclei. In fact, the amount of observable carbons via 13C-CPMAS NMR spectroscopy appeared, in many cases, lower than that measured by a direct observation of the 13C nuclei. As a consequence, cross-polarized NMR techniques may provide spectra where signal distribution may not be representative of the quantitative distribution of the different natural organic matter components. Cross-polarization is obtained after application of an initial 90° x pulse on protons and a further spin lock pulse (along the y axis) having a fixed length (contact time) for both nuclei (1H and 13C) once the Hartmann-Hahn condition is matched

  6. I: Low Frequency NMR and NQR Using a dc SQUID. II: Variable-temperature 13C CP/MAS of Organometallics

    SciTech Connect

    Ziegeweid, M.A.

    1995-11-29

    NMR and NQR at low frequencies are difficult prospects due to small nuclear spin polarization. Furthermore, the sensitivity'of the inductive pickup circuitry of standard spectrometers is reduced as the frequency is lowered. I have used a cw-SQUID (Superconducting QUantum Interference Device) spectrometer, which has no such frequency dependence, to study the local atomic environment of {sup 14}N via the quadrupolar interaction. Because {sup 14}N has spin I = 1 and a 0-6 MHz frequency range, it is not possible to obtain well-resolved spectra in high magnetic fields. I have used a technique to observe {sup 14}N NQR resonances via their effect on neighboring protons mediated by the heteronuclear dipolar interaction to study peptides and narcotics. The sensitivity of the SQUID is not enough to measure low-frequency surface (or other low spin density) systems. The application of spin-polarized xenon has been previously used to enhance polarization in conventional NMR experiments. Because xenon only polarizes spins with which it is in contact, it is surface selective. While differences in chemical shifts between surface and bulk spins are not large, it is expected that the differences in quadrupole coupling constant should be very large due to the drastic change of the electric field gradient surrounding spins at the surface. With this in mind, I have taken preliminary steps to measure SQUID detected polarization transfer from Xe to another spin species at 4.2 K and in small magnetic fields (<50 G). In this regime, the spin-lattice relaxation of xenon is dependent on the applied magnetic field. The results of our efforts to characterize the relaxation of xenon are presented. The final section describes the solid-state variable-temperature (VT) one- and two-dimensional {sup 13}C cross polarization (CP)/magic angle spinning (MAS) NMR of Hf({eta}{sup 5}-C{sub 5}H{sub 5}){sub 2}({eta}{sup 1}-C{sub 5}H{sub 5}){sub 2}, Zr({eta}{sup 5}-C{sub 5}H{sub 5}){sub 3}({eta}{sup 1}-C

  7. Accurate measurements of {sup 13}C-{sup 13}C distances in uniformly {sup 13}C-labeled proteins using multi-dimensional four-oscillating field solid-state NMR spectroscopy

    SciTech Connect

    Straasø, Lasse Arnt; Nielsen, Jakob Toudahl; Bjerring, Morten; Nielsen, Niels Chr.; Khaneja, Navin

    2014-09-21

    Application of sets of {sup 13}C-{sup 13}C internuclear distance restraints constitutes a typical key element in determining the structure of peptides and proteins by magic-angle-spinning solid-state NMR spectroscopy. Accurate measurements of the structurally highly important {sup 13}C-{sup 13}C distances in uniformly {sup 13}C-labeled peptides and proteins, however, pose a big challenge due to the problem of dipolar truncation. Here, we present novel two-dimensional (2D) solid-state NMR experiments capable of extracting distances between carbonyl ({sup 13}C′) and aliphatic ({sup 13}C{sub aliphatic}) spins with high accuracy. The method is based on an improved version of the four-oscillating field (FOLD) technique [L. A. Straasø, M. Bjerring, N. Khaneja, and N. C. Nielsen, J. Chem. Phys. 130, 225103 (2009)] which circumvents the problem of dipolar truncation, thereby offering a base for accurate extraction of internuclear distances in many-spin systems. The ability to extract reliable accurate distances is demonstrated using one- and two-dimensional variants of the FOLD experiment on uniformly {sup 13}C,{sup 15}N-labeled-L-isoleucine. In a more challenging biological application, FOLD 2D experiments are used to determine a large number of {sup 13}C′-{sup 13}C{sub aliphatic} distances in amyloid fibrils formed by the SNNFGAILSS fibrillating core of the human islet amyloid polypeptide with uniform {sup 13}C,{sup 15}N-labeling on the FGAIL fragment.

  8. Characterisation of black carbon-rich samples by 13C solid-state nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Novotny, Etelvino H.; Hayes, Michael H. B.; Deazevedo, Eduardo R.; Bonagamba, Tito J.

    2006-09-01

    There are difficulties in quantifying and characterising the organic matter (OM) in soils that contain significant amounts of partially oxidised char or charcoal materials. The anthropogenic black carbon (BC), such as that found in the Terra Preta de Índio soils of the Amazon region, is a good example of the OM that is difficult to analyse in such soils. 13C direct polarisation/magic angle spinning (DP/MAS) at high MAS frequency, 1H-13C cross polarisation (CP)/MAS with total suppression of spinning sidebands (TOSS), and chemical shift anisotropy (CSA) filter nuclear magnetic resonance techniques have been applied successfully for quantifying the different components of OM. However, because pyrogenic materials present strong local magnetic susceptibility heterogeneities, the use of CSA-filter and TOSS make the pulse sequences very sensitive to imperfections in the π pulses. In this study, the DP/MAS pulse sequence was replaced by a CP with a radio frequency ramp—variable amplitude CP (VACP)—VACP/MAS pulse sequence, and composite π pulses were used in the CSA-filter and TOSS pulse sequences. In that way, the component functionalities in a humic acid from a BC soil were successfully determined. The spectrometer time needed was greatly decreased by employing this VACP/MAS technique. This development provides an accurate method for characterising BC-rich samples from different origins.

  9. Characterisation of black carbon-rich samples by (13)C solid-state nuclear magnetic resonance.

    PubMed

    Novotny, Etelvino H; Hayes, Michael H B; Deazevedo, Eduardo R; Bonagamba, Tito J

    2006-09-01

    There are difficulties in quantifying and characterising the organic matter (OM) in soils that contain significant amounts of partially oxidised char or charcoal materials. The anthropogenic black carbon (BC), such as that found in the Terra Preta de Indio soils of the Amazon region, is a good example of the OM that is difficult to analyse in such soils. (13)C direct polarisation/magic angle spinning (DP/MAS) at high MAS frequency, (1)H-(13)C cross polarisation (CP)/MAS with total suppression of spinning sidebands (TOSS), and chemical shift anisotropy (CSA) filter nuclear magnetic resonance techniques have been applied successfully for quantifying the different components of OM. However, because pyrogenic materials present strong local magnetic susceptibility heterogeneities, the use of CSA-filter and TOSS make the pulse sequences very sensitive to imperfections in the pi pulses. In this study, the DP/MAS pulse sequence was replaced by a CP with a radio frequency ramp--variable amplitude CP (VACP)--VACP/MAS pulse sequence, and composite pi pulses were used in the CSA-filter and TOSS pulse sequences. In that way, the component functionalities in a humic acid from a BC soil were successfully determined. The spectrometer time needed was greatly decreased by employing this VACP/MAS technique. This development provides an accurate method for characterising BC-rich samples from different origins. PMID:16688435

  10. Observation of 1H-13C and 1H-1H proximities in a paramagnetic solid by NMR at high magnetic field under ultra-fast MAS.

    PubMed

    Li, Shenhui; Trébosc, Julien; Lafon, Olivier; Zhou, Lei; Shen, Ming; Pourpoint, Frédérique; Amoureux, Jean-Paul; Deng, Feng

    2015-02-01

    The assignment of NMR signals in paramagnetic solids is often challenging since: (i) the large paramagnetic shifts often mask the diamagnetic shifts specific to the local chemical environment, and (ii) the hyperfine interactions with unpaired electrons broaden the NMR spectra and decrease the coherence lifetime, thus reducing the efficiency of usual homo- and hetero-nuclear NMR correlation experiments. Here we show that the assignment of (1)H and (13)C signals in isotopically unmodified paramagnetic compounds with moderate hyperfine interactions can be facilitated by the use of two two-dimensional (2D) experiments: (i) (1)H-(13)C correlations with (1)H detection and (ii) (1)H-(1)H double-quantum↔single-quantum correlations. These methods are experimentally demonstrated on isotopically unmodified copper (II) complex of l-alanine at high magnetic field (18.8 T) and ultra-fast Magic Angle Spinning (MAS) frequency of 62.5 kHz. Compared to (13)C detection, we show that (1)H detection leads to a 3-fold enhancement in sensitivity for (1)H-(13)C 2D correlation experiments. By combining (1)H-(13)C and (1)H-(1)H 2D correlation experiments with the analysis of (13)C longitudinal relaxation times, we have been able to assign the (1)H and (13)C signals of each l-alanine ligand. PMID:25557861

  11. Benzenium ion chemistry on solid metal halide superacids: in situ {sup 13}C NMR experiments and theoretical calculations

    SciTech Connect

    Xu, T.; Barich, D.H.; Torres, P.D.; Haw, J.F.

    1997-01-15

    The benzenium, toluenium, and ethylbenzenium ions were synthesized on aluminium bromide by coadsorption of the precursors with either HBr or alkyl bromide. Principal components of the {sup 13}C chemical shift tensors for the ring carbons of these species were measured from magic angle spinning spectra. The benzenium ion was static at 77 K but underwent both proton scrambling and anisotropic rotation at 298 K as well as oligomerization at higher loadings. The para form of the toluenium ion was the dominant isomer at 77 K, but a temperature-dependent equilibrium between the para and ortho isomers was observed at 273 K. The energy calculations at MP4(fc,sdq)/ 6-311+G{sup *}//MP2/6-311+G{sup *} with thermal corrections resulted in good agreement between calculated and measured proton affinities for benzene, toluene, and ethylbenzene. For toluenium ion, the energies of the ortho and meta isomers were 1.2 and 5.4 kcal/mol, respectively, above the para isomer, consistent with the temperature-dependent {sup 13}C NMR spectra in the solid state. {sup 13}C chemical shift tensors calculated at the GIAO-MP2/tzp/dz//MP2/ 6-311+G{sup *} and GIAO-MP2/tzp/dz//B3LYP/6-311+G{sup *} levels of theory were in very close agreement with each other and generally in satisfactory agreement with experimental principal components. 64 refs., 8 figs., 4 tabs.

  12. Large structure rearrangement of colicin ia channel domain after membrane binding from 2D 13C spin diffusion NMR.

    PubMed

    Luo, Wenbin; Yao, Xiaolan; Hong, Mei

    2005-05-01

    One of the main mechanisms of membrane protein folding is by spontaneous insertion into the lipid bilayer from the aqueous environment. The bacterial toxin, colicin Ia, is one such protein. To shed light on the conformational changes involved in this dramatic transfer from the polar to the hydrophobic milieu, we carried out 2D magic-angle spinning (13)C NMR experiments on the water-soluble and membrane-bound states of the channel-forming domain of colicin Ia. Proton-driven (13)C spin diffusion spectra of selectively (13)C-labeled protein show unequivocal attenuation of cross-peaks after membrane binding. This attenuation can be assigned to distance increases but not reduction of the diffusion coefficient. Analysis of the statistics of the interhelical and intrahelical (13)C-(13)C distances in the soluble protein structure indicates that the observed cross-peak reduction is well correlated with a high percentage of short interhelical contacts in the soluble protein. This suggests that colicin Ia channel domain becomes open and extended upon membrane binding, thus lengthening interhelical distances. In comparison, cross-peaks with similar intensities between the two states are dominated by intrahelical contacts in the soluble state. This suggests that the membrane-bound structure of colicin Ia channel domain may be described as a "molten globule", in which the helical secondary structure is retained while the tertiary structure is unfolded. This study demonstrates that (13)C spin diffusion NMR is a valuable tool for obtaining qualitative long-range distance constraints on membrane protein folding. PMID:15853348

  13. NMR cross polarization in solids using multipulse irradiation

    NASA Astrophysics Data System (ADS)

    Quiroga, L.; Virlet, J.

    1984-12-01

    A double resonance NMR scheme (MPSLCP) is presented in which a WHH-4 type multipulse irradiation of the abundant spins I is applied during cross polarization. When using the HW-8 sequence, the locking Hamiltonian for the I spins is provided by the average pulse length error Hamiltonian. Double resonance is obtained with a weak pulse irradiation of the rare spin S, whose amplitude matches (Hartmann-Hahn condition) the average pulse error field. Experimental results on 13C-1H in powdered adamantane are presented. Owing to the high symmetry of both the crystal and the molecular reorientations, the 13C multipulse cross-polarization rise is described by considering one carbon coupled to N equivalent protons and applying the calculations of L. Muller and R. R. Ernst [Mol. Phys. 38, 963 (1979)] for an SIN system with, here N=196 (or better N=235). Such a cross-polarization scheme (MPSLCP) is shown to be applicable to rigid organic solids. For S spins with very low gyromagnetic ratio and/or far from I spins, MPSLCP (i) is selective; (ii) increases the rate of polarization (it is suggested that this might help for quantitative analysis purposes); (iii) provides a very important rf power saving (104 here for adamantane) at the S spin frequency.

  14. Proton-detected 3D 1H/13C/1H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz

    NASA Astrophysics Data System (ADS)

    Zhang, Rongchun; Nishiyama, Yusuke; Ramamoorthy, Ayyalusamy

    2015-10-01

    A proton-detected 3D 1H/13C/1H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of 13C-1H connectivities, and proximities of 13C-1H and 1H-1H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including 1H-1H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) 1H/1H and 2D 13C/1H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of 1H-1H proximity and 13C-1H connectivity. In addition, the 2D (F1/F2) 1H/13C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of 1H-1H dipolar couplings, enables the measurement of proximities between 13C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of 1H-1H-13C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ṡ H2O ṡ HCl demonstrate the efficiency of the 3D experiment.

  15. Cross polarization compatible dialysis chip.

    PubMed

    Kornreich, Micha; Heymann, Michael; Fraden, Seth; Beck, Roy

    2014-10-01

    We visualize birefringence in microliter sample volumes using a microfluidic dialysis chip optimized for cross polarization microscopy. The chip is composed of two overlapping polydimethylsiloxane (PDMS) channels separated by a commercial cellulose ester membrane. Buffer exchange in the sample chamber is achieved within minutes by dialyzing under continuous reservoir flow. Using fd virus as a birefringent model system, we monitor the fd virus isotropic to liquid crystal phase transition as a function of ionic strength. We show that the reorientation of the fd virus spans a few tens of seconds, indicative of fast ion exchange across the membrane. Complete phase separation reorganization takes minutes to hours as it involves diffusive virus mass transport within the storage chamber. PMID:25105977

  16. In situ measurement of magnesium carbonate formation from CO2 using static high-pressure and -temperature 13C NMR.

    PubMed

    Surface, J Andrew; Skemer, Philip; Hayes, Sophia E; Conradi, Mark S

    2013-01-01

    We explore a new in situ NMR spectroscopy method that possesses the ability to monitor the chemical evolution of supercritical CO(2) in relevant conditions for geological CO(2) sequestration. As a model, we use the fast reaction of the mineral brucite, Mg(OH)(2), with supercritical CO(2) (88 bar) in aqueous conditions at 80 °C. The in situ conversion of CO(2) into metastable and stable carbonates is observed throughout the reaction. After more than 58 h of reaction, the sample was depressurized and analyzed using in situ Raman spectroscopy, where the laser was focused on the undisturbed products through the glass reaction tube. Postreaction, ex situ analysis was performed on the extracted and dried products using Raman spectroscopy, powder X-ray diffraction, and magic-angle spinning (1)H-decoupled (13)C NMR. These separate methods of analysis confirmed a spatial dependence of products, possibly caused by a gradient of reactant availability, pH, and/or a reaction mechanism that involves first forming hydroxy-hydrated (basic, hydrated) carbonates that convert to the end-product, anhydrous magnesite. This carbonation reaction illustrates the importance of static (unmixed) reaction systems at sequestration-like conditions. PMID:22676479

  17. Area per Lipid and Cholesterol Interactions in Membranes from Separated Local-Field 13C NMR Spectroscopy

    PubMed Central

    Leftin, Avigdor; Molugu, Trivikram R.; Job, Constantin; Beyer, Klaus; Brown, Michael F.

    2014-01-01

    Investigations of lipid membranes using NMR spectroscopy generally require isotopic labeling, often precluding structural studies of complex lipid systems. Solid-state 13C magic-angle spinning NMR spectroscopy at natural isotopic abundance gives site-specific structural information that can aid in the characterization of complex biomembranes. Using the separated local-field experiment DROSS, we resolved 13C-1H residual dipolar couplings that were interpreted with a statistical mean-torque model. Liquid-disordered and liquid-ordered phases were characterized according to membrane thickness and average cross-sectional area per lipid. Knowledge of such structural parameters is vital for molecular dynamics simulations, and provides information about the balance of forces in membrane lipid bilayers. Experiments were conducted with both phosphatidylcholine (dimyristoylphosphatidylcholine (DMPC) and palmitoyloleoylphosphatidylcholine (POPC)) and egg-yolk sphingomyelin (EYSM) lipids, and allowed us to extract segmental order parameters from the 13C-1H residual dipolar couplings. Order parameters were used to calculate membrane structural quantities, including the area per lipid and bilayer thickness. Relative to POPC, EYSM is more ordered in the ld phase and experiences less structural perturbation upon adding 50% cholesterol to form the lo phase. The loss of configurational entropy is smaller for EYSM than for POPC, thus favoring its interaction with cholesterol in raftlike lipid systems. Our studies show that solid-state 13C NMR spectroscopy is applicable to investigations of complex lipids and makes it possible to obtain structural parameters for biomembrane systems where isotope labeling may be prohibitive. PMID:25418296

  18. Photochemically Induced Dynamic Nuclear Polarization Observed by Solid-State NMR in a Uniformly (13)C-Isotope-Labeled Photosynthetic Reaction Center.

    PubMed

    Paul, Shubhajit; Bode, Bela E; Matysik, Jörg; Alia, A

    2015-10-29

    A sample of solubilized and quinone-depleted reaction centers from the purple bacterium Rhodobacter (R.) sphaeroides wild type has been prepared entirely (13)C and (15)N isotope labeled at all positions of the protein as well as of the cofactors. In this sample, the occurrence of the solid-state photo-CIDNP (photochemically induced dynamic nuclear polarization) effect has been probed by (13)C solid-state magic-angle spinning NMR under illumination. Under continuous illumination, signal intensities are modified by the three-spin mixing (TSM) mechanism. Time-resolved illumination experiments reveal the occurrence of light-induced nuclear polarization on the time scale of hundreds of microseconds, initially dominated by the transient polarization of the singlet branch of the radical-pair mechanism. A first kinetic analysis shows that the lifetime of the polarization from the singlet branch, indicated by the enhanced absorptive intensities of the signals from aliphatic carbons, is significantly extended. Upon arrival of the polarization from the triplet decay branch, emissive polarization caused by the TSM mechanism is observed. Also, this arrival is significantly delayed. The decay of TSM polarization occurs in two steps, assigned to intra- and intermolecular spin diffusion. PMID:26110356

  19. Quantitative comparison of structure and dynamics of elastin following three isolation schemes by 13C solid state NMR and MALDI mass spectrometry

    PubMed Central

    Papaioannou, A.; Louis, M.; Dhital, B.; Ho, H. P.; Chang, E. J.

    2015-01-01

    Methods for isolating elastin from fat, collagen, and muscle, commonly used in the design of artificial elastin based biomaterials, rely on exposing tissue to harsh pH levels and temperatures that usually denature many proteins. At present, a quantitative measurement of the modifications to elastin following isolation from other extracellular matrix constituents has not been reported. Using magic angle spinning 13C NMR spectroscopy and relaxation methodologies, we have measured the modification in structure and dynamics following three known purification protocols. Our experimental data reveal that the 13C spectra of the hydrated samples appear remarkably similar across the various purification methods. Subtle differences in the half maximum widths were observed in the backbone carbonyl suggesting possible structural heterogeneity across the different methods of purification. Additionally, small differences in the relative signal intensities were observed between purified samples. Lyophilizing the samples results in a reduction of backbone motion and reveals additional differences across the purification methods studied. These differences were most notable in the alanine motifs indicating possible changes in cross-linking or structural rigidity. The measured correlation times of glycine and proline moieties are observed to also vary considerably across the different purification methods, which may be related to peptide bond cleavage. Lastly, the relative concentration of desmosine cross-links in the samples quantified by MALDI mass spectrometry is reported. PMID:25592991

  20. Global Fold of Human Cannabinoid Type 2 Receptor Probed by Solid-State 13C-, 15N-MAS NMR and Molecular Dynamics Simulations

    PubMed Central

    Kimura, Tomohiro; Vukoti, Krishna; Lynch, Diane L.; Hurst, Dow P.; Grossfield, Alan; Pitman, Michael C.; Reggio, Patricia H.; Yeliseev, Alexei A.; Gawrisch, Klaus

    2014-01-01

    The global fold of human cannabinoid type 2 (CB2) receptor in the agonist-bound active state in lipid bilayers was investigated by solid-state 13C- and 15N magic-angle spinning (MAS) NMR, in combination with chemical-shift prediction from a structural model of the receptor obtained by microsecond-long molecular dynamics (MD) simulations. Uniformly 13C-, and 15N-labeled CB2 receptor was expressed in milligram quantities by bacterial fermentation, purified, and functionally reconstituted into liposomes. 13C MAS NMR spectra were recorded without sensitivity enhancement for direct comparison of Cα, Cβ, and C=O bands of superimposed resonances with predictions from protein structures generated by MD. The experimental NMR spectra matched the calculated spectra reasonably well indicating agreement of the global fold of the protein between experiment and simulations. In particular, the 13C chemical shift distribution of Cα resonances was shown to be very sensitive to both the primary amino acid sequence and the secondary structure of CB2. Thus the shape of the Cα band can be used as an indicator of CB2 global fold. The prediction from MD simulations indicated that upon receptor activation a rather limited number of amino acid residues, mainly located in the extracellular loop 2 and the second half of intracellular loop 3, change their chemical shifts significantly (≥1.5 ppm for carbons and ≥5.0 ppm for nitrogens). Simulated two-dimensional 13Cα(i)-13C=O(i) and 13C=O(i)-15NH(i+1) dipolar-interaction correlation spectra provide guidance for selective amino-acid labeling and signal assignment schemes to study the molecular mechanism of activation of CB2 by solid-state MAS NMR. PMID:23999926

  1. Proton-detected 3D {sup 1}H/{sup 13}C/{sup 1}H correlation experiment for structural analysis in rigid solids under ultrafast-MAS above 60 kHz

    SciTech Connect

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy; Nishiyama, Yusuke

    2015-10-28

    A proton-detected 3D {sup 1}H/{sup 13}C/{sup 1}H chemical shift correlation experiment is proposed for the assignment of chemical shift resonances, identification of {sup 13}C-{sup 1}H connectivities, and proximities of {sup 13}C-{sup 1}H and {sup 1}H-{sup 1}H nuclei under ultrafast magic-angle-spinning (ultrafast-MAS) conditions. Ultrafast-MAS is used to suppress all anisotropic interactions including {sup 1}H-{sup 1}H dipolar couplings, while the finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used to recouple dipolar couplings among protons and the insensitive nuclei enhanced by polarization transfer technique is used to transfer magnetization between heteronuclear spins. The 3D experiment eliminates signals from non-carbon-bonded protons and non-proton-bonded carbons to enhance spectral resolution. The 2D (F1/F3) {sup 1}H/{sup 1}H and 2D {sup 13}C/{sup 1}H (F2/F3) chemical shift correlation spectra extracted from the 3D spectrum enable the identification of {sup 1}H-{sup 1}H proximity and {sup 13}C-{sup 1}H connectivity. In addition, the 2D (F1/F2) {sup 1}H/{sup 13}C chemical shift correlation spectrum, incorporated with proton magnetization exchange via the fp-RFDR recoupling of {sup 1}H-{sup 1}H dipolar couplings, enables the measurement of proximities between {sup 13}C and even the remote non-carbon-bonded protons. The 3D experiment also gives three-spin proximities of {sup 1}H-{sup 1}H-{sup 13}C chains. Experimental results obtained from powder samples of L-alanine and L-histidine ⋅ H{sub 2}O ⋅ HCl demonstrate the efficiency of the 3D experiment.

  2. Multidimensional solid-state NMR studies of the structure and dynamics of pectic polysaccharides in uniformly 13C-labeled Arabidopsis primary cell walls

    SciTech Connect

    Dick-Perez, Marilu; Wang, Tuo; Salazar, Andre; Zabotina, Olga A.; Hong, Mei

    2012-07-08

    Plant cell wall (CW) polysaccharides are responsible for the mechanical strength and growth of plant cells; however, the high-resolution structure and dynamics of the CW polysaccharides are still poorly understood because of the insoluble nature of these molecules. Here, we use 2D and 3D magic-angle-spinning (MAS) solid-state NMR (SSNMR) to investigate the structural role of pectins in the plant CW. Intact and partially depectinated primary CWs of Arabidopsis thaliana were uniformly labeled with 13C and their NMR spectra were compared. Recent 13C resonance assignment of the major polysaccharides in Arabidopsis thaliana CWs allowed us to determine the effects of depectination on the intermolecular packing and dynamics of the remaining wall polysaccharides. 2D and 3D correlation spectra show the suppression of pectin signals, confirming partial pectin removal by chelating agents and sodium carbonate. Importantly, higher cross peaks are observed in 2D and 3D 13C spectra of the depectinated CW, suggesting higher rigidity and denser packing of the remaining wall polysaccharides compared with the intact CW. 13C spin–lattice relaxation times and 1H rotating-frame spin–lattice relaxation times indicate that the polysaccharides are more rigid on both the nanosecond and microsecond timescales in the depectinated CW. Taken together, these results indicate that pectic polysaccharides are highly dynamic and endow the polysaccharide network of the primary CW with mobility and flexibility, which may be important for pectin functions. This study demonstrates the capability of multidimensional SSNMR to determine the intermolecular interactions and dynamic structures of complex plant materials under near-native conditions. Copyright © 2012 John Wiley & Sons, Ltd.

  3. Cross Polarization for 1H NMR Image Contrast in Solids

    NASA Astrophysics Data System (ADS)

    Nakai, Toshihito; Fukunaga, Yasuhiro; Nonaka, Masayuki; Matsui, Shigeru; Inouye, Tamon

    1998-09-01

    A novel1H imaging method for solids, yielding images reflecting1H-13C dipolar interactions through cross relaxation timeTIS, is presented. Phase-alternating multiple-contact cross polarization (PAMC CP) was incorporated into the magic-echo frequency-encoding imaging scheme; the PAMC CP sequence may partly but efficiently destroy the initial1H magnetization depending on theTISvalues. A theory describing the effects of the PAMC CP sequence was developed, which was used for the assessment of the sequence as well as the analysis for the experimental results. It was demonstrated that theTIS-weighted1H image and theTISmapping for a phantom, constituted of adamantane and ferrocene, can distinguish these compounds clearly.

  4. Optically enhanced nuclear cross polarization in acridine-doped fluorene

    SciTech Connect

    Oshiro, C.M.

    1982-06-01

    The objective of this work has been to create large polarizations of the dilute /sup 13/C nuclei in the solid state. The idea was to create /sup 1/H polarizations larger than Boltzmann and to use the proton enhanced nuclear induction spectroscopy cross polarization technique to then transfer this large polarization to the /sup 13/C spin system. Optical Nuclear Polarization (ONP) of acridine-doped fluorene single crystals was studied. In addition, ONP of powdered samples of the acridine-doped fluorene was studied. In general, many compounds do not crystallize easily or do not form large crystals suitable for NMR experiments. Powdered, amorphous and randomly dispersed samples are generally far more readily available than single crystals. One objective of this work has been to (first) create large /sup 1/H polarizations. Although large optical proton polarizations in single crystals have been reported previously, optically generated polarizations in powdered samples have not been reported. For these reasons, ONP studies of powdered samples of the acridine-doped fluorene were also undertaken. Using ONP in combination with the proton enhanced nuclear induction spectroscopy experiment, large /sup 13/C polarizations have been created in fluorene single crystals. These large /sup 13/C polarizations have permitted the determination of the seven incongruent chemical shielding tensors of the fluorene molecule. Part 2 of this thesis describes the proton enhanced nuclear induction spectroscopy experiment. Part 3 describes the ONP experiment. Part 4 is a description of the experimental set-up. Part 5 describes the data analysis for the determination of the chemical shielding tensors. Part 6 presents the results of the ONP experiments performed in this work and the chemical shielding tensors determined.

  5. Cross-polarized excitons in carbon nanotubes.

    PubMed

    Kilina, Svetlana; Tretiak, Sergei; Doorn, Stephen K; Luo, Zhengtang; Papadimitrakopoulos, Fotios; Piryatinski, Andrei; Saxena, Avadh; Bishop, Alan R

    2008-05-13

    Polarization of low-lying excitonic bands in finite-size semiconducting single-walled carbon nanotubes (SWNTs) is studied by using quantum-chemical methodologies. Our calculations elucidate properties of cross-polarized excitons, which lead to the transverse optical absorption of nanotubes and presumably couple to intermediate-frequency modes recently observed in resonance Raman excitation spectroscopy. We identify up to 12 distinct excitonic transitions below the second fundamental band associated with the E(22) van Hove singularity. Calculations for several chiral SWNTs distinguish the optically active "bright" excitonic band polarized parallel to the tube axis and several optically "weak" cross-polarized excitons. The rest are optically (near) forbidden "dark" transitions. An analysis of the transition density matrices related to excitonic bands provides detailed information about delocalization of excitonic wavefunction along the tube. Utilization of the natural helical coordinate system accounting for the tube chirality allows one to disentangle longitudinal and circumferential components. The distribution of the transition density matrix along a tube axis is similar for all excitons. However, four parallel-polarized excitons associated with the E(11) transition are more localized along the circumference of a tube, compared with others related to the E(12) and E(21) cross-polarized transitions. Calculated splitting between optically active parallel- and cross-polarized transitions increases with tube diameter, which compares well with experimental spectroscopic data. PMID:18463293

  6. Cross-polarized excitons in carbon nanotubes

    PubMed Central

    Kilina, Svetlana; Tretiak, Sergei; Doorn, Stephen K.; Luo, Zhengtang; Papadimitrakopoulos, Fotios; Piryatinski, Andrei; Saxena, Avadh; Bishop, Alan R.

    2008-01-01

    Polarization of low-lying excitonic bands in finite-size semiconducting single-walled carbon nanotubes (SWNTs) is studied by using quantum-chemical methodologies. Our calculations elucidate properties of cross-polarized excitons, which lead to the transverse optical absorption of nanotubes and presumably couple to intermediate-frequency modes recently observed in resonance Raman excitation spectroscopy. We identify up to 12 distinct excitonic transitions below the second fundamental band associated with the E22 van Hove singularity. Calculations for several chiral SWNTs distinguish the optically active “bright” excitonic band polarized parallel to the tube axis and several optically “weak” cross-polarized excitons. The rest are optically (near) forbidden “dark” transitions. An analysis of the transition density matrices related to excitonic bands provides detailed information about delocalization of excitonic wavefunction along the tube. Utilization of the natural helical coordinate system accounting for the tube chirality allows one to disentangle longitudinal and circumferential components. The distribution of the transition density matrix along a tube axis is similar for all excitons. However, four parallel-polarized excitons associated with the E11 transition are more localized along the circumference of a tube, compared with others related to the E12 and E21 cross-polarized transitions. Calculated splitting between optically active parallel- and cross-polarized transitions increases with tube diameter, which compares well with experimental spectroscopic data. PMID:18463293

  7. Solid-state NMR studies of theophylline co-crystals with dicarboxylic acids.

    PubMed

    Pindelska, Edyta; Sokal, Agnieszka; Szeleszczuk, Lukasz; Pisklak, Dariusz Maciej; Kolodziejski, Waclaw

    2014-11-01

    In this work, three polycrystalline materials containing co-crystals of theophylline with malonic, maleic, and glutaric acids were studied using (13)C, (15)N and (1)H solid-state NMR and FT-IR spectroscopy. The NMR assignments were supported by gauge including projector augmented waves (GIPAW) calculations of chemical shielding, performed using X-ray determined geometry. The experimental (13)C cross polarization/magic angle spinning (CP/MAS) NMR results and the calculated isotropic chemical shifts were in excellent agreement. A rapid and convenient method for theophylline co-crystals crystal structure analysis has been proposed for co-crystals, which are potentially new APIs. PMID:25194346

  8. Combining Nuclear Magnetic Resonance Spectroscopy and Density Functional Theory Calculations to Characterize Carvedilol Polymorphs.

    PubMed

    Rezende, Carlos A; San Gil, Rosane A S; Borré, Leandro B; Pires, José Ricardo; Vaiss, Viviane S; Resende, Jackson A L C; Leitão, Alexandre A; De Alencastro, Ricardo B; Leal, Katia Z

    2016-09-01

    The experiments of carvedilol form II, form III, and hydrate by (13)C and (15)N cross-polarization magic-angle spinning (CP MAS) are reported. The GIPAW (gauge-including projector-augmented wave) method from DFT (density functional theory) calculations was used to simulate (13)C and (15)N chemical shifts. A very good agreement was found for the comparison between the global results of experimental and calculated nuclear magnetic resonance (NMR) chemical shifts for carvedilol polymorphs. This work aims a comprehensive understanding of carvedilol crystalline forms employing solution and solid-state NMR as well as DFT calculations. PMID:26372719

  9. Quantitative 13C NMR of whole and fractionated Iowa Mollisols for assessment of organic matter composition

    NASA Astrophysics Data System (ADS)

    Fang, Xiaowen; Chua, Teresita; Schmidt-Rohr, Klaus; Thompson, Michael L.

    2010-01-01

    Both the concentrations and the stocks of soil organic carbon vary across the landscape. Do the amounts of recalcitrant components of soil organic matter (SOM) vary with landscape position? To address this question, we studied four Mollisols in central Iowa, two developed in till and two developed in loess. Two of the soils were well drained and two were poorly drained. We collected surface-horizon samples and studied organic matter in the particulate organic matter (POM) fraction, the clay fractions, and the whole, unfractionated samples. We treated the soil samples with 5 M HF at ambient temperature or at 60 °C for 30 min to concentrate the SOM. To assess the composition of the SOM, we used solid-state nuclear magnetic resonance (NMR) spectroscopy, in particular, quantitative 13C DP/MAS (direct-polarization/magic-angle spinning), with and without recoupled dipolar dephasing. Spin counting by correlation of the integral NMR intensity with the C concentration by elemental analysis showed that NMR was ⩾85% quantitative for the majority of the samples studied. For untreated whole-soil samples with <2.5 wt.% C, which is considerably less than in most previous quantitative NMR analyses of SOM, useful spectra that reflected ⩾65% of all C were obtained. The NMR analyses allowed us to conclude (1) that the HF treatment (with or without heat) had low impact on the organic C composition in the samples, except for protonating carboxylate anions to carboxylic acids, (2) that most organic C was observable by NMR even in untreated soil materials, (3) that esters were likely to compose only a minor fraction of SOM in these Mollisols, and (4) that the aromatic components of SOM were enriched to ˜53% in the poorly drained soils, compared with ˜48% in the well drained soils; in plant tissue and particulate organic matter (POM) the aromaticities were ˜18% and ˜32%, respectively. Nonpolar, nonprotonated aromatic C, interpreted as a proxy for charcoal C, dominated the

  10. Thermodynamic evaluation of aromatic CH/π interactions and rotational entropy in a molecular rotor.

    PubMed

    Pérez-Estrada, Salvador; Rodríguez-Molina, Braulio; Xiao, Leilei; Santillan, Rosa; Jiménez-Osés, Gonzalo; Houk, K N; Garcia-Garibay, Miguel A

    2015-02-18

    A molecular rotor built with a stator formed by two rigid 9β-mestranol units having a 90° bent angle linked to a central phenylene rotator has an ideal structure to examine aromatic CH/π interactions. Energies and populations of the multiple solution conformations from quantum-mechanical calculations and molecular dynamics simulations were combined with variable-temperature (VT) (1)H NMR data to establish the enthalpy of this interaction and the entropy associated with rotation about a single bond. Rotational dynamics in the solid state were determined via VT cross-polarization magic-angle spinning (13)C NMR spectroscopy. PMID:25635355

  11. Crystal Structures and Vibrational and Solid-State (CPMAS) NMR Spectroscopy of Some Bis(triphenylphosphine)silver(I) Sulfate, Selenate and Phosphate Systems.

    SciTech Connect

    Bowmaker, Graham A.; Hanna, John V.; Rickard, Clifton E.; Lipton, Andrew S.

    2001-01-01

    The complexes [Ag2(PPh3)4EO4].2H2O(E=S, Se) (1,2), [Ag(PPh3)2HEO4].H2O (E=S, Se)(3,4) and [Ag9PPh3)2H2PO4].2EtOH (5) have been prepared and studied by X-ray crystallography and by infrared and solid-state 13C and 31 P cross-polarization, magic-angle-spinning (CPMAS) NMR spectroscopy.

  12. Ultra-broadband perfect cross polarization conversion metasurface

    NASA Astrophysics Data System (ADS)

    Dong, Guoxiang; Shi, Hongyu; Xia, Song; Zhang, Anxue; Xu, Zhuo; Wei, Xiaoyong

    2016-04-01

    We propose a metasurface with multiple plasmon resonances that achieves an ultra-broadband perfect cross polarization conversion. The metasurface is composed of an array of unit resonators, three plasmon resonances are excited in the unit resonator, which leads to an ultra-broadband perfect cross polarization conversion. The cross polarization conversion efficiency is higher than 99%, and the bandwidth of the converter is 53.7% of the central wavelength. Both numerical and experimental results were used to validate the ultra-broadband perfect cross polarization converter presented here.

  13. Low-temperature cross polarization in view of enhancing dissolution Dynamic Nuclear Polarization in NMR

    NASA Astrophysics Data System (ADS)

    Jannin, Sami; Bornet, Aurélien; Colombo, Sonia; Bodenhausen, Geoffrey

    2011-12-01

    Dynamic Nuclear Polarization (DNP) induced by saturation of ESR transitions of TEMPO at 1.2 K and 3.35 T is characterized by build-up rates that are typically 5 times faster for protons than for the carboxylic carbon-13 in acetate. We show that cross polarization from protons to carbon-13 allows one to achieve a polarization P( 13C) >20% in less than 10 min, twice as much as has been previously reported, in one-fifth of the time. This should open the way to an unprecedented improvement in the efficiency of dissolution DNP.

  14. Metabolite localization in living drosophila using High Resolution Magic Angle Spinning NMR

    PubMed Central

    Sarou-Kanian, Vincent; Joudiou, Nicolas; Louat, Fanny; Yon, Maxime; Szeremeta, Frédéric; Même, Sandra; Massiot, Dominique; Decoville, Martine; Fayon, Franck; Beloeil, Jean-Claude

    2015-01-01

    We have developed new methods enabling in vivo localization and identification of metabolites through their 1H NMR signatures, in a drosophila. Metabolic profiles in localized regions were obtained using HR-MAS Slice Localized Spectroscopy and Chemical Shift Imaging at high magnetic fields. These methods enabled measurement of metabolite contents in anatomic regions of the fly, demonstrated by a decrease in β-alanine signals in the thorax of flies showing muscle degeneration. PMID:25892587

  15. Metabolite localization in living drosophila using High Resolution Magic Angle Spinning NMR.

    PubMed

    Sarou-Kanian, Vincent; Joudiou, Nicolas; Louat, Fanny; Yon, Maxime; Szeremeta, Frédéric; Même, Sandra; Massiot, Dominique; Decoville, Martine; Fayon, Franck; Beloeil, Jean-Claude

    2015-01-01

    We have developed new methods enabling in vivo localization and identification of metabolites through their (1)H NMR signatures, in a drosophila. Metabolic profiles in localized regions were obtained using HR-MAS Slice Localized Spectroscopy and Chemical Shift Imaging at high magnetic fields. These methods enabled measurement of metabolite contents in anatomic regions of the fly, demonstrated by a decrease in β-alanine signals in the thorax of flies showing muscle degeneration. PMID:25892587

  16. Protein fold determined by paramagnetic magic-angle spinning solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Sengupta, Ishita; Nadaud, Philippe S.; Helmus, Jonathan J.; Schwieters, Charles D.; Jaroniec, Christopher P.

    2012-05-01

    Biomacromolecules that are challenging for the usual structural techniques can be studied with atomic resolution by solid-state NMR spectroscopy. However, the paucity of distance restraints >5 Å, traditionally derived from measurements of magnetic dipole-dipole couplings between protein nuclei, is a major bottleneck that hampers such structure elucidation efforts. Here, we describe a general approach that enables the rapid determination of global protein fold in the solid phase via measurements of nuclear paramagnetic relaxation enhancements (PREs) in several analogues of the protein of interest containing covalently attached paramagnetic tags, without the use of conventional internuclear distance restraints. The method is demonstrated using six cysteine-EDTA-Cu2+ mutants of the 56-residue B1 immunoglobulin-binding domain of protein G, for which ~230 longitudinal backbone 15N PREs corresponding to distances of ~10-20 Å were obtained. The mean protein fold determined in this manner agrees with the X-ray structure with a backbone atom root-mean-square deviation of 1.8 Å.

  17. Quadrupolar magic angle spinning NMR spectra fitted using the Pearson IV function.

    PubMed

    Mironenko, Roman M; Belskaya, Olga B; Talsi, Valentin P; Likholobov, Vladimir A

    2014-01-01

    The Pearson IV function was used to fit the asymmetric solid-state (27)Al NMR spectra of alumina based catalysts. A high convergence (correlation coefficient is no less than 0.997) between experimental and simulated spectra was achieved. The decomposition of the (27)Al NMR spectra of zinc/aluminum mixed oxides with different Zn/Al molar ratio revealed an increased fraction (6-9%) of pentacoordinated aluminum atoms in these oxides as compared to γ-Al2O3. As the Zn/Al ratio is raised, the fraction of [AlO6] octahedral units decreases, while the fraction of [AlO4] tetrahedra increases. PMID:25454293

  18. IN SITU MAGIC ANGLE SPINNING NMR FOR STUDYING GEOLOGICAL CO(2) SEQUESTRATION

    SciTech Connect

    Hoyt, David W.; Turcu, Romulus VF; Sears, Jesse A.; Rosso, Kevin M.; Burton, Sarah D.; Kwak, Ja Hun; Felmy, Andrew R.; Hu, Jian Z.

    2011-03-27

    Geological carbon sequestration (GCS) is one of the most promising ways of mitigating atmospheric greenhouse gases (1-3). Mineral carbonation reactions are potentially important to the long-term sealing effectiveness of caprock but remain poorly predictable, particularly in low-water supercritical CO2 (scCO2)-dominated environments where the chemistry has not been adequately explored. In situ probes that provide molecular-level information is desirable for investigating mechanisms and rates of GCS mineral carbonation reactions. MAS-NMR is a powerful tool for obtaining detailed molecular structure and dynamics information of a system regardless whether the system is in a solid, a liquid, a gaseous, or a supercritical state, or a mixture thereof (4,5). However, MAS NMR under scCO2 conditions has never been realized due to the tremendous technical difficulties of achieving and maintaining high pressure within a fast spinning MAS rotor (6,7), where non-metal materials must be used. In this work, we report development of a unique high pressure MAS NMR capability, and its application to mineral carbonation chemistry in scCO2 under geologically relevant temperatures and pressures.

  19. Compensated DRAMA sequence for homonuclear dipolar recoupling under magic-angle spinning.

    PubMed

    Chou, Fang-Chieh; Tsai, Tim W T; Lee, Hsin-Kuan; Chan, Jerry C C

    2009-12-01

    The DRAMA sequence has been considered as the milestone in the development of homonuclear dipolar recoupling. Although it has a high efficiency for double-quantum excitation in spin 1/2 systems, it is seldom used today for real applications because of its susceptibility to the deteriorating effects of chemical shift anisotropy and resonance offsets. We show in this work that the practicability of DRAMA can be greatly enhanced by incorporating four pi pulses with XY-4 phases into the basic DRAMA cycles. Average Hamiltonian theory is used to evaluate the performance of the resulting pulse sequence with respect to the compensation of chemical shift anisotropy. Numerical simulations and experimental measurements on hydroxyapatite indeed show that the performance of DRAMA-XY4 is very satisfying for 31P DQ excitation, provided that the resonance offset is within the range of [-4, 4]kHz. PMID:19962863

  20. 51V solid-state magic angle spinning NMR spectroscopy of vanadium chloroperoxidase.

    PubMed

    Pooransingh-Margolis, Neela; Renirie, Rokus; Hasan, Zulfiqar; Wever, Ron; Vega, Alexander J; Polenova, Tatyana

    2006-04-19

    We report 51V solid-state NMR spectroscopy of the 67.5-kDa vanadium chloroperoxidase, at 14.1 T. We demonstrate that, despite the low concentration of vanadium sites in the protein (one per molecule, 1 mumol of vanadium spins in the entire sample), the spinning sideband manifold spanning the central and the satellite transitions is readily detectable. The quadrupolar and chemical shift anisotropy tensors have been determined by numerical simulations of the spinning sideband envelopes and the line shapes of the individual spinning sidebands corresponding to the central transition. The observed quadrupolar coupling constant C(Q) of 10.5 +/- 1.5 MHz and chemical shift anisotropy delta(sigma) of -520 +/- 13 ppm are sensitive reporters of the geometric and electronic structure of the vanadium center. Density functional theory calculations of the NMR spectroscopic observables for an extensive series of active site models indicate that the vanadate cofactor is most likely anionic with one axial hydroxo- group and an equatorial plane consisting of one hydroxo- and two oxo- groups. The work reported in this manuscript is the first example of 51V solid-state NMR spectroscopy applied to probe the vanadium center in a protein directly. This approach yields the detailed coordination environment of the metal unavailable from other experimental measurements and is expected to be generally applicable for studies of diamagnetic vanadium sites in metalloproteins. PMID:16608356

  1. Pulsed Field Gradient Selection in Two-Dimensional Magic Angle Spinning NMR Spectroscopy of Dipolar Solids

    NASA Astrophysics Data System (ADS)

    Fritzhanns, Tilo; Hafner, Siegfried; Demco, Dan E.; Spiess, Hans W.; Laukien, Frank H.

    1998-10-01

    The utility of gradient selection in MAS spectroscopy of dipolar solids is explored in two examples. In the first, rotor-synchronized gradients of appropriate strength and duration are applied to select1H double-quantum coherences. The resulting DQ MAS spectrum of adamantane is compared with that acquired by the corresponding phase-cycling technique. As a second example, a1H 2D exchange MAS experiment is performed on an elastomer sample. In this experiment, a gradient is applied to remove undesired coherences that would otherwise distort the spectrum for short mixing times. The diagonal-peak intensities in the resulting spectrum show a linear decrease with increasing mixing time indicating cross-relaxation by slow chain motions as the relevant process. Both types of experiments demonstrate the potential of gradient-selection techniques for MAS spectroscopy of dipolar solids.

  2. Protein fold determined by paramagnetic magic-angle spinning solid-state NMR spectroscopy.

    PubMed

    Sengupta, Ishita; Nadaud, Philippe S; Helmus, Jonathan J; Schwieters, Charles D; Jaroniec, Christopher P

    2012-05-01

    Biomacromolecules that are challenging for the usual structural techniques can be studied with atomic resolution by solid-state NMR spectroscopy. However, the paucity of distance restraints >5 Å, traditionally derived from measurements of magnetic dipole-dipole couplings between protein nuclei, is a major bottleneck that hampers such structure elucidation efforts. Here, we describe a general approach that enables the rapid determination of global protein fold in the solid phase via measurements of nuclear paramagnetic relaxation enhancements (PREs) in several analogues of the protein of interest containing covalently attached paramagnetic tags, without the use of conventional internuclear distance restraints. The method is demonstrated using six cysteine-EDTA-Cu(2+) mutants of the 56-residue B1 immunoglobulin-binding domain of protein G, for which ~230 longitudinal backbone (15)N PREs corresponding to distances of ~10-20 Å were obtained. The mean protein fold determined in this manner agrees with the X-ray structure with a backbone atom root-mean-square deviation of 1.8 Å. PMID:22522262

  3. Gel synthesis of magnesium silicates: A 29Si magic angle spinning NMR study

    NASA Astrophysics Data System (ADS)

    Hartman, J. Stephen; Millard, Roberta L.

    1990-01-01

    The formation of the magnesium silicate minerals forsterite, enstatite, and roedderite by heating of amorphous “protosilicate” gels precipitated from aqueous solution has been studied by 29Si MAS nmr. Gentle drying of the hydrogels at 110° C gives materials with broad nmr signals that do not differ appreciably with preparation conditions, but the minerals formed by heating at 750° C or higher are greatly dependent on the precipitation and washing conditions of the original gel. The rare mineral roedderite, best known from studies of unequilibrated enstatite chondrite meteorites, becomes a major species along with forsterite when the hydrogels are washed with sodium hydroxide solution before drying and heating to 750° C.

  4. Investigation of different apple cultivars by high resolution magic angle spinning NMR. A feasibility study.

    PubMed

    Vermathen, Martina; Marzorati, Mattia; Baumgartner, Daniel; Good, Claudia; Vermathen, Peter

    2011-12-28

    (1)H HR-MAS NMR spectroscopy was applied to apple tissue samples deriving from 3 different cultivars. The NMR data were statistically evaluated by analysis of variance (ANOVA), principal component analysis (PCA), and partial least-squares-discriminant analysis (PLS-DA). The intra-apple variability of the compounds was found to be significantly lower than the inter-apple variability within one cultivar. A clear separation of the three different apple cultivars could be obtained by multivariate analysis. Direct comparison of the NMR spectra obtained from apple tissue (with HR-MAS) and juice (with liquid-state HR NMR) showed distinct differences in some metabolites, which are probably due to changes induced by juice preparation. This preliminary study demonstrates the feasibility of (1)H HR-MAS NMR in combination with multivariate analysis as a tool for future chemometric studies applied to intact fruit tissues, e.g. for investigating compositional changes due to physiological disorders, specific growth or storage conditions. PMID:22084979

  5. Performance evaluation of quantitative adiabatic (13)C NMR pulse sequences for site-specific isotopic measurements.

    PubMed

    Thibaudeau, Christophe; Remaud, Gérald; Silvestre, Virginie; Akoka, Serge

    2010-07-01

    (2)H/(1)H and (13)C/(12)C site-specific isotope ratios determined by NMR spectroscopy may be used to discriminate pharmaceutically active ingredients based on the synthetic process used in production. Extending the Site-specific Natural Isotope Fractionation NMR (SNIF-NMR) method to (13)C is highly beneficial for complex organic molecules when measurements of (2)H/(1)H ratios lead to poorly defined molecular fingerprints. The current NMR methodology to determine (13)C/(12)C site-specific isotope ratios suffers from poor sensitivity and long experimental times. In this work, several NMR pulse sequences based on polarization transfer were evaluated and optimized to measure precise quantitative (13)C NMR spectra within a short time. Adiabatic 180 degrees (1)H and (13)C pulses were incorporated into distortionless enhancement by polarization transfer (DEPT) and refocused insensitive nuclei enhanced by polarization transfer (INEPT) to minimize the influence of 180 degrees pulse imperfections and of off-resonance effects on the precision of the measured (13)C peak areas. The adiabatic DEPT sequence was applied to draw up a precise site-specific (13)C isotope profile of ibuprofen. A modified heteronuclear cross-polarization (HCP) experiment featuring (1)H and (13)C spin-locks with adiabatic 180 degrees pulses is also introduced. This sequence enables efficient magnetization transfer across a wide (13)C frequency range although not enough for an application in quantitative (13)C isotopic analysis. PMID:20527737

  6. Cross polarization in beam waveguide-fed Cassegrain reflector antennas

    NASA Astrophysics Data System (ADS)

    Houshmand, Bijan

    1991-02-01

    The sensitivity of the cross-polarization level to a deviation from the geometrical condition derived by Mizusawa and Kitsuregawa (1973) for different geometrical configurations is studied. This condition restricts the number of possible beam waveguide configurations for beam waveguide-fed Cassegrain reflector (BFCR) antennas. For a symmetrical feed, this condition results in a symmetrical aperture distribution with no cross-polarized component. By examining a number of beam waveguide configurations satisfying the condition, it was observed that for linearly polarized feed, the cross-polarization level is very sensitive to a deviation from this condition. For circularly polarized feed, deviation from this condition does not increase the cross-polarization level; however, it results in the squinting of the beam for BFCRs.

  7. Reducing Cross-Polarized Radiation From A Microstrip Antenna

    NASA Technical Reports Server (NTRS)

    Huang, John

    1991-01-01

    Change in configuration of feed of nominally linearly polarized microstrip-patch transmitting array antenna reduces cross-polarized component of its radiation. Patches fed on opposing sides, in opposite phases. Combination of spatial symmetry and temporal asymmetry causes copolarized components of radiation from fundamental modes of patches to reinforce each other and cross-polarized components of radiation from higher-order modes to cancel each other.

  8. Dynamic nuclear polarization-enhanced 1H-13C double resonance NMR in static samples below 20 K

    NASA Astrophysics Data System (ADS)

    Potapov, Alexey; Thurber, Kent R.; Yau, Wai-Ming; Tycko, Robert

    2012-08-01

    We demonstrate the feasibility of one-dimensional and two-dimensional 1H-13C double resonance NMR experiments with dynamic nuclear polarization (DNP) at 9.4 T and temperatures below 20 K, including both 1H-13C cross-polarization and 1H decoupling, and discuss the effects of polarizing agent type, polarizing agent concentration, temperature, and solvent deuteration. We describe a two-channel low-temperature DNP/NMR probe, capable of carrying the radio-frequency power load required for 1H-13C cross-polarization and high-power proton decoupling. Experiments at 8 K and 16 K reveal a significant T2 relaxation of 13C, induced by electron spin flips. Carr-Purcell experiments and numerical simulations of Carr-Purcell dephasing curves allow us to determine the effective correlation time of electron flips under our experimental conditions. The dependence of the DNP signal enhancement on electron spin concentration shows a maximum near 80 mM. Although no significant difference in the absolute DNP enhancements for triradical (DOTOPA-TEMPO) and biradical (TOTAPOL) dopants was found, the triradical produced greater DNP build-up rates, which are advantageous for DNP experiments. Additionally the feasibility of structural measurements on 13C-labeled biomolecules was demonstrated with a two-dimensional 13C-13C exchange spectrum of selectively 13C-labeled β-amyloid fibrils.

  9. Efficient cross-polarization using a composite 0° pulse for NMR studies on static solids

    NASA Astrophysics Data System (ADS)

    Fukuchi, Masashi; Ramamoorthy, Ayyalusamy; Takegoshi, K.

    2009-02-01

    In most solid-state NMR experiments, cross-polarization is an essential step to detect low-γ nuclei such as 13C and 15N. In this study, we present a new cross-polarization scheme using spin-locks composed of composite 0° pulses in the RF channels of high-γ and low-γ nuclei to establish the Hartmann-Hahn match. The composite 0° pulses with no net nutation-angle{(2 π) X - (2 π) -X - (2 π) Y - (2 π) -Y -} n applied simultaneously to both high-γ ( I) and low-γ ( S) nuclei create an effective heteronuclear dipolar Hamiltonian Hd(0)={d}/{2}(2IZSZ+IXSX+IYSY), which is capable of transferring the Z-component of the I spin magnetization to the Z-component of the S spin magnetization. It also retains a homonuclear dipolar coupling Hamiltonian that enables the flip-flop transfer among abundant spins. While our experimental results indicate that the new pulse sequence, called composite zero cross- polarization (COMPOZER-CP) performs well on adamantane, it is expected to be more valuable to study semi-solids like liquid crystalline materials and model lipid membranes. Theoretical analysis of COMPOZER-CP is presented along with experimental results. Our experimental results demonstrate that COMPOZER-CP overcomes the RF field inhomogeneity and Hartmann-Hahn mismatch for static solids. Experimental results comparing the performance of COMPOZER-CP with that of the traditional constant-amplitude CP and rampCP sequences are also presented in this paper.

  10. Fracture Flow Channel Imaging Using Cross-Polarized GPR Signals

    NASA Astrophysics Data System (ADS)

    Tsoflias, G. P.; Perll, C.; Baker, M.; Becker, M.

    2014-12-01

    Fractures control the flow of fluids in rocks with important implications for groundwater resources, contaminant transport, geothermal resources, sequestration of carbon dioxide, and the development of unconventional hydrocarbon resources. Ground penetrating radar (GPR) can be used to image fractured rock and monitor the flow of fluids in the subsurface. Conventional GPR imaging uses single-polarization, co-polarized signals. Changes in reflected signal amplitude result from changes in fracture aperture and changes in fluid electrical properties introduced by tracers or contaminants. Recent research has also shown changes in radar reflected signal phase resulting from changes in fluid electrical conductivity. However, the radar response is dependent on the polarization of EM waves. This study investigates the use of cross-polarized GPR signals for imaging flow channeling at a discrete horizontal fracture. Numerical modeling demonstrated that cross-polarized GPR data are able to image fracture channels when the axis of the channel is oriented obliquely to the EM wavefield orientation. Summation of the cross-polarized and co-polarized components results in an accurate representation of the total scattered energy from the channel. Multipolarization, time-lapse 3D GPR field data were used investigate GPR imaging of flow channeling in a discrete subhorizontal fracture. The GPR surveys were conducted during background fresh fracture water conditions and during six varying orientation dipole flow saline tracer tests. The cross-polarized data revealed flow channeling which is in agreement with the co-polarized GPR data and with independent hydraulic tests. In addition, the cross-polarized components showed changes in flow channeling as a result of changing dipole flow orientation and position. This study demonstrates that cross-polarized GPR signals can be used to enhance imaging of flow in fractured rock.

  11. Coherent Backscattering in the Cross-Polarized Channel

    NASA Technical Reports Server (NTRS)

    Mischenko, Michael I.; Mackowski, Daniel W.

    2011-01-01

    We analyze the asymptotic behavior of the cross-polarized enhancement factor in the framework of the standard low-packing-density theory of coherent backscattering by discrete random media composed of spherically symmetric particles. It is shown that if the particles are strongly absorbing or if the smallest optical dimension of the particulate medium (i.e., the optical thickness of a plane-parallel slab or the optical diameter of a spherically symmetric volume) approaches zero, then the cross-polarized enhancement factor tends to its upper-limit value 2. This theoretical prediction is illustrated using direct computer solutions of the Maxwell equations for spherical volumes of discrete random medium.

  12. A Cross-Polarization Based Rotating-Frame Separated-Local-Field NMR Experiment Under Ultrafast MAS Conditions

    PubMed Central

    Zhang, Rongchun; Damron, Joshua; Vosegaard, Thomas

    2014-01-01

    Rotating-frame separated-local-field solid-state NMR experiments measure highly resolved heteronuclear dipolar couplings which, in turn, provide valuable interatomic distances for structural and dynamic studies of molecules in the solid-state. Though many different rotating-frame SLF sequences have been put forth, recent gains in ultrafast MAS technology have considerably simplified pulse sequence requirements due to the suppression of proton-proton dipolar interactions. In this study we revisit a simple two-dimensional 1H-13C dipolar coupling/chemical shift correlation experiment using 13C detected Cross-Polarization with a Variable Contact time (CPVC) and systematically study the conditions for its optimal performance at 60 kHz MAS. In addition, we demonstrate the feasibility of a proton-detected version of the CPVC experiment. The theoretical analysis of the CPVC pulse sequence under different Hartmann-Hahn matching conditions confirms that it performs optimally under the ZQ (w1H-w1C=±wr) condition for polarization transfer. The limits of the cross polarization process are explored and precisely defined as a function of offset and Hartmann-Hahn mismatch via spin dynamics simulation and experiments on a powder sample of uniformly 13C-labeled L-isoleucine. Our results show that the performance of the CPVC sequence and subsequent determination of 1H-13C dipolar couplings are insensitive to 1H/13C frequency offset frequency when high RF fields are used on both RF channels. Conversely, the CPVC sequence is quite sensitive to the Hartmann-Hahn mismatch, particularly for systems with weak heteronuclear dipolar couplings. We demonstrate the use of the CPVC based SLF experiment as a tool to identify different carbon groups, and hope to motivate the exploration of more sophisticated 1H detected avenues for ultrafast MAS. PMID:25486635

  13. Dynamic nuclear polarization-enhanced 1H–13C double resonance NMR in static samples below 20 K

    PubMed Central

    Potapov, Alexey; Thurber, Kent R.; Yau, Wai-Ming; Tycko, Robert

    2012-01-01

    We demonstrate the feasibility of one-dimensional and two-dimensional 1H–13C double resonance NMR experiments with dynamic nuclear polarization (DNP) at 9.4 T and temperatures below 20 K, including both 1H–13C cross-polarization and 1H decoupling, and discuss the effects of polarizing agent type, polarizing agent concentration, temperature, and solvent deuteration. We describe a two-channel low-temperature DNP/NMR probe, capable of carrying the radio-frequency power load required for 1H–13C cross-polarization and high-power proton decoupling. Experiments at 8 K and 16 K reveal a significant T2 relaxation of 13C, induced by electron spin flips. Carr–Purcell experiments and numerical simulations of Carr–Purcell dephasing curves allow us to determine the effective correlation time of electron flips under our experimental conditions. The dependence of the DNP signal enhancement on electron spin concentration shows a maximum near 80 mM. Although no significant difference in the absolute DNP enhancements for triradical (DOTOPA-TEMPO) and biradical (TOTAPOL) dopants was found, the triradical produced greater DNP build-up rates, which are advantageous for DNP experiments. Additionally the feasibility of structural measurements on 13C-labeled biomolecules was demonstrated with a two-dimensional 13C–13C exchange spectrum of selectively 13C-labeled β-amyloid fibrils. PMID:22743540

  14. Spatio-Temporal Dynamics of Cross Polarized Wave Generation

    NASA Astrophysics Data System (ADS)

    Adams, Daniel; Squier, Jeff; Durfee, Charles

    2009-10-01

    We use time-domain Spatially and Spectrally Resolved Interferometry (SSRI) to investigate cross-polarized wave (XPW) generation in barium fluoride. We find that the XPW pulse is √3 smaller than the input in the spatiotemporal domain regardless of the input chirp. Additionally, we calculate a temporally dependent focal length resulting from the nonlinear interaction, and discuss its implications.

  15. Interactions between Nafion resin and protonated dodecylamine modified montmorillonite: a solid state NMR study.

    PubMed

    Zhang, Limin; Xu, Jun; Hou, Guangjin; Tang, Huiru; Deng, Feng

    2007-07-01

    A series of nanocomposites have been prepared from perfluorosulfonylfluoride copolymer resin (Nafion) and layered montmorillonite (MMT) modified with protonated dodecylamine by conventional sol-gel intercalation. The structure of these nanocomposite materials have been characterized using FT-IR, elemental analysis, XRD and solid state NMR techniques, including 19F magic-angle spinning (MAS) NMR, 19F NMR relaxation time measurements, 29Si MAS, 1H MAS, 1H-13C cross-polarization magic-angle spinning (CPMAS), and 1H-13C heteronuclear correlation (HETCOR) 2D NMR. The results showed that thermal stability of Nafion was improved moderately by the addition of dodecylamine modified MMT without intercalation. FT-IR and 29Si MAS NMR results indicated that dodecylamine modification did not result in obvious changes in the MMT lattice structure. The XRD results showed that the protonated dodecylamine has been embedded and intercalated into the MMT interlayers, whereas Nafion was not. Elemental analysis results also suggested that some dodecylamine was adsorbed on the surface of MMT. 1H-13C HETCOR 2D NMR experiment clearly indicated that strong electrostatic interactions were present between the NH+3 group of dodecylamine and the fluorine-containing groups (CF3, OCF2, and SCF2) of Nafion resin. Such electrostatic interactions are probably the major contributors for the improved thermal stability of the resultant composite materials. PMID:17382953

  16. The 'Nuts and Bolts' of 13C NMR Spectroscopy at Elevated-Pressures and -Temperatures for Monitoring In Situ CO2 Conversion to Metal Carbonates

    NASA Astrophysics Data System (ADS)

    Moore, J. K.; Surface, J. A.; Skemer, P. A.; Conradi, M. S.; Hayes, S. E.

    2013-12-01

    We will present details of newly-constructed specialized NMR designed to conduct in situ elevated-pressure, elevated-temperature 13C NMR studies on unmixed slurries of minerals in the presence of CO2 or other gases. This static probe is capable of achieving 300 bar, 300C conditions, and it is designed to spectroscopically examine 13C signals in mixtures of solids, liquids, gases, and supercritical fluids. Ultimately, our aim is to monitor CO2 uptake in both ultramafic rocks and in more porous geological materials to understand the mechanisms of chemisorption as a function of temperature, pressure and pH. We will give details of the hardware setup, and we will show a variety of static in situ NMR, as well as ex situ 'magic-angle spinning' NMR to show the analyses that are possible of minerals in pure form and in mixtures. In addition, specific NMR pulse sequences, techniques, and modeling will be described in detail. In this in situ NMR probe, we are able to simulate processes at geologically relevant fluid pressures and temperatures, monitoring the kinetics of CO2 conversion to carbonates. The in situ NMR experiments consist of heterogeneous mixtures of rock, salty brine solution, and moderate pressure CO2 gas at elevated temperatures. The purpose of studying these reactions is to determine conditions that affect the efficacy of carbonate formation in various targeted geological reservoirs (i.e., peroditite, or others). Via 13C NMR, we have spectroscopically characterized and quantified the conversion of CO2 to magnesium carbonate and calcium carbonate minerals, including metastable intermediates (such as hydromagnesite, or dypingite in the case of magnesium carbonate species, or vaterite in the case of calcium carbonate species). Such species are distinguishable from a combination of the 13C isotropic chemical shift, the static 13C lineshape, and changes in spin-lattice (T1) relaxation times. We will demonstrate that NMR can be used for quantitative

  17. Aging Studies of Filled and Unfilled VCE

    SciTech Connect

    Letant, S; Herberg, J; Alviso, C; Small, W; Mulcahy, H; Pearson, M; Wilson, T; Chinn, S; Maxwell, R

    2009-11-10

    This report presents data on the effects of temperature and gamma radiation on the chemical and structural properties of both filled and unfilled VCE material produced by the Kansas City Plant using WR-qualified processes. Thermal effects up to 300 C and gamma irradiation doses of 1 MRad and 25 MRad were investigated under atmospheric conditions. Characterization techniques used in the study comprise Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Tensile Testing, Solid Phase MicroExtraction - Gas Chromatography/Mass Spectrometry (SPME-GC/MS), phenol extraction followed by HPLC, and various Nuclear Magnetic Resonance (NMR) techniques including: {sup 13}C, {sup 13}C {l_brace}{sup 1}H{r_brace} cross polarization (CP), {sup 1}H magic angle spinning (MAS), 13C{l_brace}{sup 1}H{r_brace} Wide-line-Separation (2D-WISE) and development of Center band-Only Detection of Exchange (CODEX).

  18. Study on ethyl groups with two different orientations in [N(C2H5)4]2CuBr4

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2016-06-01

    The crystal structure and phase transition temperature of [N(C2H5)4]2CuBr4 are studied using X-ray diffraction and differential scanning calorimetry (DSC); measurements revealed a tetragonal structure and the two phase transition temperatures TC of 204 K and 255.5 K. The structural geometry near TC is discussed in terms of the chemical shifts for 1H magic angle spinning (MAS) nuclear magnetic resonance (NMR) and 13C cross-polarization (CP)/MAS NMR. The two inequivalent ethyl groups are distinguishable by the 13C NMR spectrum. The molecular motions are discussed in terms of the spin-lattice relaxation times T1ρ in the rotating frame for 1H MAS NMR and 13C CP/MAS NMR. The T1ρ results reveal that the ethyl groups undergo tumbling motion, and furthermore that the ethyl groups are highly mobile.

  19. Theoretical description of RESPIRATION-CP

    NASA Astrophysics Data System (ADS)

    Nielsen, Anders B.; Tan, Kong Ooi; Shankar, Ravi; Penzel, Susanne; Cadalbert, Riccardo; Samoson, Ago; Meier, Beat H.; Ernst, Matthias

    2016-02-01

    We present a quintuple-mode operator-based Floquet approach to describe arbitrary amplitude modulated cross polarization experiments under magic-angle spinning (MAS). The description is used to analyze variants of the RESPIRATION approach (RESPIRATIONCP) where recoupling conditions and the corresponding first-order effective Hamiltonians are calculated, validated numerically and compared to experimental results for 15N-13C coherence transfer in uniformly 13C,15N-labeled alanine and in uniformly 2H,13C,15N-labeled (deuterated and 100% back-exchanged) ubiquitin at spinning frequencies of 16.7 and 90.9 kHz. Similarities and differences between different implementations of the RESPIRATIONCP sequence using either CW irradiation or small flip-angle pulses are discussed.

  20. Roles of chemically inequivalent N(CH3)4 ions in phase transition temperatures in [N(CH3)4]2CoCl4 by single-crystal NMR and MAS NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2014-06-01

    The temperature dependences of the 1H and 13C spin-lattice relaxation time in the laboratory frame, T1, and in the rotating frame, T1ρ, in [N(CH3)4]2CoCl4 were measured by static nuclear magnetic resonance (NMR) and magic angle spinning (MAS) NMR. In the ferroelastic phase, 1H T1ρ underwent molecular motion according to the Bloembergen-Purcell-Pound theory. Two inequivalent ions, a-N(CH3)4 and b-N(CH3)4, were identified by 13C cross polarization (CP)/MAS NMR. On the basis of the 13C NMR results, the existence of two chemically inequivalent a-N(CH3)4 and b-N(CH3)4 ions in the ferroelectric phase and the existence of the ferroelastic twin structure of the N(CH3)4 ions in the ferroelastic phase were discussed.

  1. Cross polarization with long delayed contact in rotating solids

    NASA Astrophysics Data System (ADS)

    Ding, Shangwu; McDowell, Charles A.

    1996-06-01

    The cross polarization NMR spectra and cross relaxation rates of polycrystalline hexamethylbenzene and adamantane were obtained by employing a long delay before contact for samples spinning at, and off, the magic angle with respect to the static magnetic field. The results are compared with those obtained by using the conventional cross polarization pulse sequence. The results support the memory effect explanation of origin of the SPEDA spectra in contrast with the assumptions that the high resolution SPEDA spectra arising either, from the nearly isotropic motion of a very small fraction, or a pool of highly thermo-activated molecules, or from special spin pairs within the crystallites which are orientated at the magic angle with respect to the static magnetic field.

  2. Study of conformation and dynamic of surfactant molecules in graphite oxide via NMR

    NASA Astrophysics Data System (ADS)

    Ai, X. Q.; Ma, L. G.

    2016-08-01

    The conformation and dynamic of surfactant in graphite oxide (GO) was investigated by solid-state 13C magic-angle-spinning NMR and 1H-13C cross-polarization/magic-angle-spinning NMR spectra. The conformation ordering of the alkyl chains in the confined system shows strong dependence on its orientation. While the alkyl chains parallel to the GO layer in lateral monolayer arrangement are in gauche conformation in addition to a small amount of all-trans conformation, those with orientation radiating away from the GO in paraffin bilayer arrangement is in all-trans conformation in addition to some gauche conformation even though high-order diffraction peaks appears. NMR results suggest that the least mobile segment is located at the GO-surfactant interface corresponding to the N-methylene group. Further from it, the mobility of the alkyl chain increases. The terminal methyl and N-methyl carbon groups have the highest mobile. The chains in all-trans conformational state are characterized as more rigid than chains with gauche conformation; each segment of the confined alkyl chains with the lateral monolayer arrangement exhibits less mobility as compared to that with the paraffin bilayer arrangement.

  3. 13C NMR Metabolomics: INADEQUATE Network Analysis

    PubMed Central

    Clendinen, Chaevien S.; Pasquel, Christian; Ajredini, Ramadan; Edison, Arthur S.

    2015-01-01

    The many advantages of 13C NMR are often overshadowed by its intrinsically low sensitivity. Given that carbon makes up the backbone of most biologically relevant molecules, 13C NMR offers a straightforward measurement of these compounds. Two-dimensional 13C-13C correlation experiments like INADEQUATE (incredible natural abundance double quantum transfer experiment) are ideal for the structural elucidation of natural products and have great but untapped potential for metabolomics analysis. We demonstrate a new and semi-automated approach called INETA (INADEQUATE network analysis) for the untargeted analysis of INADEQUATE datasets using an in silico INADEQUATE database. We demonstrate this approach using isotopically labeled Caenorhabditis elegans mixtures. PMID:25932900

  4. Solid-state (13)C NMR and synchrotron SAXS/WAXS studies of uniaxially-oriented polyethylene.

    PubMed

    Afeworki, Mobae; Brant, Pat; Lustiger, Arnold; Norman, Alexander

    2015-11-01

    We report solid-state (13)C NMR and synchrotron wide-and small-angle X-ray scattering experiments (WAXS, SAXS) on metallocene linear low density polyethylene films (e.g., Exceed™ 1018 mLLDPE; nominally 1MI, 0.918 density ethylene-hexene metallocene copolymer) as a function of uniaxial draw ratio, λ. Combined, these experiments provide an unambiguous, quantitative molecular view of the orientation of both the crystalline and amorphous phases in the samples as a function of draw. Together with previously reported differential scanning calorimetry (DSC), gas transport measurements, transmission electron microscopy (TEM), optical birefringence, small angle X-ray scattering (SAXS) as well as other characterization techniques, this study of the state of orientation in both phases provides insight concerning the development of unusually high barrier properties of the most oriented samples (λ=10). In this work, static (non-spinning) solid-state NMR measurements indicate that in the drawn Exceed(TM) films both the crystalline and amorphous regions are highly oriented. In particular, chemical shift data show the amorphous phase is comprised increasingly of so-called "taut tie chains" (or tie chains under any state of tautness) in the mLLDPE with increasing draw ratio - the resonance lines associated with the amorphous phase shift to where the crystalline peaks are observed. In the sample with highest total draw (λ=10), virtually all of the chains in the non-crystalline region have responded and aligned in the machine (draw) direction. Both monoclinic and orthorhombic crystalline peaks are observed in high-resolution, solid-state magic-angle spinning (MAS) NMR measurements of the oriented PE films. The orientation is comparable to that obtained for ultra-high molecular weight HDPE fibers described as "ultra-oriented" in the literature. Furthermore, the presence of a monoclinic peak in cold-drawn samples suggests that there is an appreciable internal stress associated

  5. Advanced solid-state NMR characterization of marine dissolved organic matter isolated using the coupled reverse osmosis/electrodialysis method.

    PubMed

    Mao, Jingdong; Kong, Xueqian; Schmidt-Rohr, Klaus; Pignatello, Joseph J; Perdue, E Michael

    2012-06-01

    Advanced (13)C solid-state techniques were employed to investigate the major structural characteristics of two surface-seawater dissolved organic matter (DOM) samples isolated using the novel coupled reverse osmosis/electrodialysis method. The NMR techniques included quantitative (13)C direct polarization/magic angle spinning (DP/MAS) and DP/MAS with recoupled dipolar dephasing, (13)C cross-polarization/total sideband suppression (CP/TOSS), (13)C chemical shift anisotropy filter, CH, CH(2), and CH(n) selection, two-dimensional (1)H-(13)C heteronuclear correlation NMR (2D HETCOR), 2D HETCOR combined with dipolar dephasing, and (15)N cross-polarization/magic angle spinning (CP/MAS). The two samples (Coastal and Marine DOM) were collected at the mouth of the Ogeechee River and in the Gulf Stream, respectively. The NMR results indicated that they were structurally distinct. Coastal DOM contained significantly more aromatic and carbonyl carbons whereas Marine DOM was markedly enriched in alkoxy carbon (e.g., carbohydrate-like moieties). Both samples contained significant amide N, but Coastal DOM had nitrogen bonded to aromatic carbons. Our dipolar-dephased spectra indicated that a large fraction of alkoxy carbons were not protonated. For Coastal DOM, our NMR results were consistent with the presence of the major structural units of (1) carbohydrate-like moieties, (2) lignin residues, (3) peptides or amino sugars, and (4) COO-bonded alkyls. For Marine DOM, they were (1) carbohydrate-like moieties, (2) peptides or amino sugars, and (3) COO-bonded alkyls. In addition, both samples contained significant amounts of nonpolar alkyl groups. The potential sources of the major structural units of DOM were discussed in detail. Nonprotonated O-alkyl carbon content was proposed as a possible index of humification. PMID:22553962

  6. Tunable graphene-based dual-frequency cross polarization converters

    NASA Astrophysics Data System (ADS)

    Ding, Jun; Arigong, Bayaner; Ren, Han; Shao, Jin; Zhou, Mi; Lin, Yuankun; Zhang, Hualiang

    2015-03-01

    In this paper, we proposed a novel cross-polarization converter that simultaneously works at two frequencies in the reflection mode, which is constructed of an L-shape perforated graphene sheet printed on a dielectric spacer backed by a gold layer. For the normal incidence, the optical rotation at these two working frequencies originates from the simultaneous excitation of both eigenmodes characterized as the localized surface plasmon resonances. In addition, both working frequencies can be tuned within a large frequency range by varying the Fermi energy of the graphene, which opens up tremendous opportunities to develop voltage-controlled tunable devices at mid-IR frequencies.

  7. Cross-polarized interferometry of a Jovian decametric radio storm

    NASA Astrophysics Data System (ADS)

    Phillips, J. A.; Carr, T. D.; Greenman, W. B.; Levy, J.

    1987-09-01

    Observations of an 18-MHz Io-A storm have been conducted using a 46 km cross-polarized interferometer at the University of Florida. The pre- and postdetection correlation properties of LH and RH elliptically polarized L bursts have been studied. Fringe visibility measurements suggest that two discrete and independent sources are sometimes simultaneously active, the polarization sense of one being LH and that of the other RH. A scintillation analysis supports the conclusion that two or more sources were active in such cases.

  8. Initial Aging Studies of Unfilled VCE

    SciTech Connect

    Letant, S E; Herberg, J L; Wilson, T S; Alviso, C T; Chinn, S C; Maxwell, R S

    2008-10-09

    This report presents initial data on the effects of temperature, oxygen, and radiation on the chemical and structural properties of newly formulated, unfilled VCE. This initial effort focused on a pristine sample, and a replicate sample irradiated in air at a dose of 25MR. Thermal degradation was investigated by performing Thermogravimetric Analysis (TGA), and radiation-induced degradation was investigated using Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Solid Phase MicroExtraction--Gas Chromatography/Mass Spectrometry (SPME-GC/MS), as well as various Nuclear Magnetic Resonance (NMR) techniques including: {sup 13}C, {sup 13}C {sup 1}H cross polarization (CP), and {sup 1}H magic angle spinning (MAS) NMR.

  9. Metal ion uptake from aqueous solution by olive stones: a carbon-13 solid-state nuclear magnetic resonance and potentiometric study.

    PubMed

    Nurchi, Valeria Marina; Floris, Costantino; Pinna, Rosalba; Fiol, Núria; Villaescusa, Isabel

    2007-10-01

    The use of biomasses that result from the agriculture and food industries in removing heavy metals from wastewaters is attracting increasing interest. We present a joined potentiometric and cross polarization magic angle spinning (CP-MAS) carbon-13 (13C) nuclear magnetic resonance (NMR) study on the interaction of olive stones with copper(II), nickel(II), and cadmium(II). The potentiometric measurements allow both to distinguish two kind of basic sites in the olive stones and to postulate the coordination models for the three studied metals. The NMR spectral analysis allows the attribution of the different signals to the components of the olive stone matrix. A comparison of CP-MAS 13C NMR spectra of the samples after metal treatment suggests a specific complexation between metal ions and hydroxyl groups on guaiacyl and syringyl moieties. PMID:17966704

  10. Limitations in the use of commercial humic acids in water and soil research

    USGS Publications Warehouse

    Malcolm, R.L.; MacCarthy, P.

    1986-01-01

    Seven samples of commercial "humic acids", purchased from five different suppliers, were studied, and their characteristics were compared with humic and fulvic acids isolated from streams, soils, peat, leonardite, and a dopplerite sample. Cross-polarization and magic-angle spinning 13C NMR spectroscopy clearly shows pronounced differences between the commercial materials and all other samples. Elemental and infrared spectroscopic data do not show such clear-cut differences but can be used as supportive evidence, with the 13C NMR data, to substantiate the above distinctions. As a result of these differences and due to the general lack of information relating to the source, method of isolation, or other pretreatment of the commercial materials, these commercial products are not considered to be appropriate for use as analogues of true soil and water humic substances, in experiments designed to evaluate the nature and reactivity of humic substances in natural waters and soils.

  11. Characterization and compaction behaviour of nimesulide crystal forms.

    PubMed

    Di Martino, Piera; Censi, Roberta; Barthélémy, Christine; Gobetto, Roberto; Joiris, Etienne; Masic, Admir; Odou, Pascal; Martelli, Sante

    2007-09-01

    Nimesulide is a typical nonsteroidal anti-inflammatory drug (NSAID), widely used in solid oral formulations. By crystallizing nimesulide from an ethanol solution a crystalline form was obtained, different from the reference sample, as confirmed by X-ray powder diffraction (XRPD), Differential Scanning Calorimetry (DSC) and solid cross polarization-magic angle spinning ((13)C-CPMAS) NMR. Moreover, when crystallized from dioxane nimesulide forms a solvate. The solvate was characterized by XRPD, IR-spectrometry, DSC, thermo-gravimetric analysis (TGA) and by (13)C-CPMAS NMR. In particular, through this technique, the presence of several conformational isomers was demonstrated. In addition to the physico-chemical characterization, the technological properties of nimesulide, namely densification and tableting, were evaluated. Contrarily to the other forms that are affected by capping phenomena at increasing compression pressures, the form obtained by desolvation of dioxane solvate has positive effect on tableting properties, increasing both compressibility and tabletability of nimesulide. PMID:17583450

  12. Nuclear magnetic resonance study of the ferroelastic phase transition of order-disorder type in [N(C2H5)4]2CdCl4

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran; Kim, Min Soo; Lim, Kye-Young

    2016-08-01

    This study uses nuclear magnetic resonance (NMR) techniques to examine the detailed changes in [N(C2H5)4]2CdCl4 around its phase transition at the temperature TC = 284 K. The chemical shifts and spin-lattice relaxation times in the rotating frame (T1ρ) were determined from 1H magic angle spinning (MAS) NMR and 13C cross-polarization (CP)/MAS NMR spectra. The two sets of inequivalent 1H and 13C nuclei in CH3 and CH2 were distinguished. A ferroelastic phase transition was observed at TC, without structural symmetry change. The phase transition is mainly attributed to the orientational ordering of the [N(C2H5)4]+ cations, and the spectral splitting at low temperature is associated with different ferroelastic domains.

  13. Limitations in the use of commercial humic acids in water and soil research

    SciTech Connect

    Malcolm, R.L.; MacCarthy, P.

    1986-09-01

    Seven samples of commercial humic acids, purchased from five different suppliers, were studied, and their characteristics were compared with humic and fulvic acids isolated from streams, soils, peat, leonardite, and a dopplerite sample. Cross-polarization and magic-angle spinning /sup 13/C NMR spectroscopy clearly shows pronounced differences between the commercial materials and all other samples. Elemental and infrared spectroscopic data do not show such clear-cut differences but can be used as supportive evidence, with the /sup 13/C NMR data, to substantiate the above distinctions. As a result of these differences and due to the general lack of information relating to the source, method of isolation, or other pretreatment of the commercial materials, these commercial products are not considered to be appropriate for use as analogues of true soil and water humic substances, in experiments designed to evaluate the nature and reactivity of humic substances in natural waters and soils.

  14. New guidelines for δ13C measurements

    USGS Publications Warehouse

    Coplen, Tyler B.; Brand, Willi A.; Gehre, Matthias; Groning, Manfred; Meijer, Harro A. J.; Toman, Blaza; Verkouteren, R. Michael

    2006-01-01

    Consistency of δ13C measurements can be improved 39−47% by anchoring the δ13C scale with two isotopic reference materials differing substantially in 13C/12C. It is recommended thatδ13C values of both organic and inorganic materials be measured and expressed relative to VPDB (Vienna Peedee belemnite) on a scale normalized by assigning consensus values of −46.6‰ to L-SVEC lithium carbonate and +1.95‰ to NBS 19 calcium carbonate. Uncertainties of other reference material values on this scale are improved by factors up to two or more, and the values of some have been notably shifted:  the δ13C of NBS 22 oil is −30.03%.

  15. Cross-polarization for dissolution dynamic nuclear polarization.

    PubMed

    Batel, Michael; Däpp, Alexander; Hunkeler, Andreas; Meier, Beat H; Kozerke, Sebastian; Ernst, Matthias

    2014-10-21

    Dynamic nuclear polarization (DNP) in combination with subsequent dissolution of the sample allows the detection of low-γ nuclei in the solution state with a signal gain of up to tens of thousand times compared to experiments starting from Boltzmann conditions. The long polarization build-up times of typically more than one hour are a drawback of this technique. The combination of dissolution DNP with cross-polarization (CP) in the solid state was shown to have the potential to overcome this disadvantage. In this article we discuss the cross-polarization step under dissolution DNP conditions in more detail. We show that adiabatic half-passage pulses allow us to enhance the CP efficiency in power-limited DNP probes. As a low-power alternative to Hartmann-Hahn CP we also demonstrate the applicability of frequency-swept de- and re-magnetization pulses for polarization transfer via dipolar order. We investigate the implications and restrictions of the common solid-state DNP mechanisms to the DNP-CP technique and apply a spin-thermodynamic model based on the thermal-mixing mechanism. The model allows us to investigate the dynamics of the polarization levels in a system with two nuclear Zeeman reservoirs and explains the enhanced DNP efficiency upon solvent deuteration within a spin-thermodynamic picture. PMID:25182534

  16. Multiple acquisition/multiple observation separated local field/chemical shift correlation solid-state magic angle spinning NMR spectroscopy.

    PubMed

    Das, Bibhuti B; Opella, Stanley J

    2014-08-01

    Multiple acquisition spectroscopy (MACSY) experiments that enable multiple free induction decays to be recorded during individual experiments are demonstrated. In particular, the experiments incorporate separated local field spectroscopy into homonuclear and heteronuclear correlation spectroscopy. The measured heteronuclear dipolar couplings are valuable in structure determination as well as in enhancing resolution by providing an additional frequency axis. In one example four different three-dimensional spectra are obtained in a single experiment, demonstrating that substantial potential saving in experimental time is available when multiple multi-dimensional spectra are required as part of solid-state NMR studies. PMID:25023566

  17. Multiple Acquisition/Multiple Observation Separated Local Field/Chemical Shift Correlation Solid-state Magic Angle Spinning NMR Spectroscopy

    PubMed Central

    Das, Bibhuti B.; Opella, Stanley J.

    2014-01-01

    Multiple acquisition spectroscopy (MACSY) experiments that enable multiple free induction decays to be recorded during individual experiments are demonstrated. In particular, the experiments incorporate separated local field spectroscopy into homonuclear and heteronuclear correlation spectroscopy. The measured heteronuclear dipolar couplings are valuable in structure determination as well as in enhancing resolution by providing an additional frequency axis. In one example four different three-dimensional spectra are obtained in a single experiment, demonstrating that substantial potential saving in experimental time is available when multiple multi-dimensional spectra are required as part of solid-state NMR studies. PMID:25023566

  18. Phase separation, clustering, and fractal characteristics in glass: A magic-angle-spinning NMR spin-lattice relaxation study

    NASA Astrophysics Data System (ADS)

    Sen, S.; Stebbins, J. F.

    1994-07-01

    A comparative study of the 29Si spin-lattice relaxation behavior (induced by trace amounts of paramagnetic dopants in the glass) in phase-separated Li2Si4O9 and monophasic Li2Si2O5 and Na2Si2O5 glasses has been made in order to understand the nature of clustering and the resulting intermediate-range ordering. Optically clear tetrasilicate and disilicate glasses were prepared with 500 to 2000 ppm of Gd2O3, a paramagnetic dopant. The constituent structural units (Q3 and Q4 species) in all tetrasilicate glasses show strong differential relaxation following a power-law behavior. This is due to preferential partitioning of Gd3+ into the lower silica (Q3-rich) regions of these glasses, indicating the presence of Q species clusters too small to produce optical opalescence (a few nm to perhaps tens of nm). Preliminary results on 6Li spin-lattice relaxation in these glasses support this hypothesis. Differential relaxation becomes more pronounced on annealing due to growth of such clusters. No such differential relaxation was observed in the monophase disilicate glasses. For spin-lattice relaxation induced by direct dipolar coupling to paramagnetic ions, the recovery of magnetization is proportional to time as M(t)~tα where α is a function of the dimensionality D of mass distribution of the constituent Q species around the Gd3+ paramagnetic centers in the glass. For tetrasilicate glasses D~=2.62+/-0.22 and the system behaves as a mass fractal up to a length scale of 2 to 3 nm. D is thus equal to, within error, the theoretical value of 2.6 for an infinite percolation cluster of one type of Q species in another. For disilicate glasses, D~=3.06+/-0.18 which indicates a three-dimensional (and thus nonfractal) mass distribution of the constituent Q species over the same length scale.

  19. Experimental study of resolution of proton chemical shifts in solids: Combined multiple pulse NMR and magic-angle spinning

    SciTech Connect

    Ryan, L.M.; Taylor, R.E.; Paff, A.J.; Gerstein, B.C.

    1980-01-01

    High-resolution nuclear magnetic resonance spectra of protons in rigid, randomly oriented solids have been measured using combined homonuclear dipolar decoupling (via multiple pulse techniques) and attenuation of chemical shift anisotropies (via magic-angle sample spinning). Under those conditions, isotropic proton chemical shifts were recorded for a variety of chemical species, with individual linewidths varying from about 55 to 110 Hz (1--2 ppm). Residual line broadening was due predominately to (i) magnetic-field instability and inhomogeneity, (ii) unresolved proton--proton spin couplings, (iii) chemical shift dispersion, (iv) residual dipolar broadening, and (v) lifetime broadening under the multiple pulse sequences used. The magnitudes of those effects and the current limits of resolution for this experiment in our spectrometer have been investigated. The compounds studied included organic solids (4, 4'-dimethylbenzophenone, 2, 6-dimethylbenzoic acid, and aspirin), polymers (polystyrene and polymethylmethacrylate), and the vitrain portion of a bituminous coal.

  20. Time displacement rotational echo double resonance: Heteronuclear dipolar recoupling with suppression of homonuclear interaction under fast magic-angle spinning

    NASA Astrophysics Data System (ADS)

    Tsai, Tim W. T.; Mou, Yun; Chan, Jerry C. C.

    2012-01-01

    We have developed a novel variant of REDOR which is applicable to multiple-spin systems without proton decoupling. The pulse sequence is constructed based on a systematic time displacement of the pi pulses of the conventional REDOR sequence. This so-called time displacement REDOR (td-REDOR) is insensitive to the effect of homonuclear dipole-dipole interaction when the higher order effects are negligible. The validity of td-REDOR has been verified experimentally by the P-31{C-13} measurements on glyphosate at a spinning frequency of 25 kHz. The experimental dephasing curve is in favorable agreement with the simulation data without considering the homonuclear dipole-dipole interactions.

  1. In vivo13C spectroscopy in the rat brain using hyperpolarized [1- 13C]pyruvate and [2- 13C]pyruvate

    NASA Astrophysics Data System (ADS)

    Marjańska, Małgorzata; Iltis, Isabelle; Shestov, Alexander A.; Deelchand, Dinesh K.; Nelson, Christopher; Uğurbil, Kâmil; Henry, Pierre-Gilles

    2010-10-01

    The low sensitivity of 13C spectroscopy can be enhanced using dynamic nuclear polarization. Detection of hyperpolarized [1- 13C]pyruvate and its metabolic products has been reported in kidney, liver, and muscle. In this work, the feasibility of measuring 13C signals of hyperpolarized 13C metabolic products in the rat brain in vivo following the injection of hyperpolarized [1- 13C]pyruvate and [2- 13C]pyruvate is investigated. Injection of [2- 13C]pyruvate led to the detection of [2- 13C]lactate, but no other downstream metabolites such as TCA cycle intermediates were detected. Injection of [1- 13C]pyruvate enabled the detection of both [1- 13C]lactate and [ 13C]bicarbonate. A metabolic model was used to fit the hyperpolarized 13C time courses obtained during infusion of [1- 13C]pyruvate and to determine the values of VPDH and VLDH.

  2. Cross-Polar Aircraft Trajectory Optimization and Potential Climate Impact

    NASA Technical Reports Server (NTRS)

    Sridhar, Banavar; Chen, Neil; Ng, Hok

    2011-01-01

    Cross-Polar routes offer new opportunities for air travel markets. Transpolar flights reduce travel times, fuel burns, and associated environmental emissions by flying direct paths between many North American and Asian cities. This study evaluates the potential benefits of flying wind-optimal polar routes and assessed their potential impact on climate change. An optimization algorithm is developed for transpolar flights to generate wind-optimal trajectories that minimize climate impact of aircraft, in terms of global warming potentials (relative to warming by one kg of CO2) of several types of emissions, while avoiding regions of airspace that facilitate persistent contrail formation. Estimations of global warming potential are incorporated into the objective function of the optimization algorithm to assess the climate impact of aircraft emissions discharged at a given location and altitude. The regions of airspace with very low ambient temperature and areas favorable to persistent contrail formation are modeled as undesirable regions that aircraft should avoid and are formulated as soft state constraints. The fuel burn and climate impact of cross-polar air traffic flying various types of trajectory including flightplan, great circle, wind-optimal, and contrail-avoidance are computed for 15 origin-destination pairs between major international airports in the U.S. and Asia. Wind-optimal routes reduce average fuel burn of flight plan routes by 4.4% on December 4, 2010 and 8.0% on August 7, 2010, respectively. The tradeoff between persistent contrail formation and additional global warming potential of aircraft emissions is investigated with and without altitude optimization. Without altitude optimization, the reduction in contrail travel times is gradual with increase in total fuel consumption. When altitude is optimized, a one percent increase in additional global warming potential, a climate impact equivalent to that of 4070kg and 4220kg CO2 emission, reduces 135

  3. Analysing Groundwater Using the 13C Isotope

    NASA Astrophysics Data System (ADS)

    Awad, Sadek

    The stable isotope of the carbon atom (13C) give information about the type of the mineralisation of the groundwater existing during the water seepage and about the recharge conditions of the groundwater. The concentration of the CO2(aq.) dissolved during the infiltration of the water through the soil's layers has an effect on the mineralisation of this water. The type of the photosynthesis's cycle (C-3 or C-4 carbon cycle) can have a very important role to determine the conditions (closed or open system) of the mineralisation of groundwater. The isotope 13C of the dissolved CO2 in water give us a certain information about the origin and the area of pollution of water. The proportion of the biogenic carbon and its percentage in the mineralisation of groundwater is determined by using the isotope 13C.

  4. States of 13C with abnormal radii

    NASA Astrophysics Data System (ADS)

    Demyanova, A. S.; Ogloblin, A. A.; Danilov, A. N.; Goncharov, S. A.; Belyaeva, T. L.; Sobolev, Yu. G.; Khlebnikov, S. V.; Burtebaev, N.; Trzaska, W.; Heikkinen, P.; Tyurin, G. P.; Janseitov, D.; Gurov, Yu. B.

    2016-05-01

    Differential cross-sections of the elastic and inelastic 13C + α scattering were measured at E(α) = 90 MeV. The root mean-square radii() of 13C nucleus in the states: 8.86 (1/2-), 3.09 (1/2+) and 9.90 (3/2-) MeV were determined by the Modified diffraction model (MDM). The radii of the first two levels are enhanced compared to that of the ground state of 13C, confirming the suggestion that the 8.86 MeV state is an analogue of the Hoyle state in 12C and the 3.09 MeV state has a neutron halo. Some indications to the abnormally small size of the 9.90 MeV state were obtained.

  5. Organic-inorganic hybrid gels for the selective absorption of oils from water.

    PubMed

    Ozan Aydin, Gulsah; Bulbul Sonmez, Hayal

    2016-06-01

    Organic-inorganic hybrid gels were synthesized by the condensation of a linear aliphatic diol (1,8-octanediol) and altering the chain length of the alkyltriethoxysilanes (from ethyltriethoxysilane to hexadecyltrimethoxysilane) through a bulk polymerization process without using any initiator, activator, catalyst, or solvent for the selective removal of oils from water. Fourier transform infrared spectroscopy (FTIR) and solid-state (13)C and (29)Si cross-polarization magic-angle spinning nuclear magnetic resonance (CPMAS NMR) were used for the structural analysis of hybrid gels. Thermal properties of the hybrid gels were determined by thermogravimetric analysis (TGA). Oil absorbency of organic-inorganic hybrid gels was determined by oil absorption tests. The results showed that hybrid gels have high and fast absorption capacities and excellent reusability. Good selectivity, high thermal stability, low density, and excellent recyclability for the oil removal give the material potential applications. PMID:26939691

  6. Fulleretic Well-Defined Scaffolds: Donor-Fullerene Alignment Through Metal Coordination and Its Effect on Photophysics.

    PubMed

    Williams, Derek E; Dolgopolova, Ekaterina A; Godfrey, Danielle C; Ermolaeva, Evgeniya D; Pellechia, Perry J; Greytak, Andrew B; Smith, Mark D; Avdoshenko, Stanislav M; Popov, Alexey A; Shustova, Natalia B

    2016-07-25

    Herein, we report the first example of a crystalline metal-donor-fullerene framework, in which control of the donor-fullerene mutual orientation was achieved through chemical bond formation, in particular, by metal coordination. The (13) C cross-polarization magic-angle spinning NMR spectroscopy, X-ray diffraction, and time-resolved fluorescence spectroscopy were performed for comprehensive structural analysis and energy-transfer (ET) studies of the fulleretic donor-acceptor scaffold. Furthermore, in combination with photoluminescence measurements, the theoretical calculations of the spectral overlap function, Förster radius, excitation energies, and band structure were employed to elucidate the photophysical and ET processes in the prepared fulleretic material. We envision that the well-defined fulleretic donor-acceptor materials could contribute not only to the basic science of fullerene chemistry but would also be used towards effective development of organic photovoltaics and molecular electronics. PMID:27265385

  7. Rapid and accurate determination of the lignin content of lignocellulosic biomass by solid-state NMR

    PubMed Central

    Fu, Li; McCallum, Scott A.; Miao, Jianjun; Hart, Courtney; Tudryn, Gregory J.; Zhang, Fuming; Linhardt, Robert J.

    2014-01-01

    Biofuels and biomaterials, produced from lignocellulosic feedstock, require facile access to cellulose and hemicellulose to be competitive with petroleum processing and sugar-based fermentation. Physical-chemical barriers resulting from lignin complicates the hydrolysis biomass into fermentable sugars. Thus, the amount of lignin within a substrate is critical in determining biomass processing. The application of 13C cross-polarization, magic-angle spinning, and solid-state nuclear magnetic resonance for the direct quantification of lignin content in biomass is examined. Using a standard curve constructed from pristine lignin and cellulose, the lignin content of a biomass sample is accurately determined through direct measurement without chemical or enzymatic pre-treatment. PMID:25404762

  8. Characterization of woody and herbaceous biomasses lignin composition with 1064 nm dispersive multichannel Raman spectroscopy.

    PubMed

    Lupoi, Jason S; Smith, Emily A

    2012-08-01

    Biomass representing different classes of bioenergy feedstocks, including woody and herbaceous species, was measured with 1064 nm Raman spectroscopy. Pine, oak, poplar, kenaf, miscanthus, pampas grass, switchgrass, alfalfa, orchard grass, and red clover were included in this study. Spectral differences have been identified with an emphasis on lignin guaiacyl and syringyl monomer content and carotenoid compounds. The interpretation of the Raman spectra was correlated with (13)C-nuclear magnetic resonance cross-polarization/magic-angle spinning spectra of select biomass samples. Thioacidolysis quantification of guaiacyl and syringyl monomer composition and the library of Raman spectra were used as a training set to develop a principal component analysis model for classifying plant samples and a principal component regression model for quantifying lignin guaiacyl and syringyl composition. Raman spectroscopy with 1064 nm excitation offers advantages over alternative techniques for biomass characterization, including low spectral backgrounds, higher spectral resolution, short analysis times, and nondestructive analyses. PMID:22800567

  9. Comparison of bridged polysilsesquioxane xerogels prepared from methoxy-, ethoxy-, and propoxy-silyl monomers

    SciTech Connect

    Baugher, B.M.; Loy, D.A.

    1996-10-01

    Hydrocarbon-bridged polysilsesquioxanes are prepared by the sol-gel polymerization of monomers with more than one trialkoxysilyl groups attached directly to the bridging group by Si-C bonds. While the effects of varying the length of the bridging group (length, rigidity, etc.), monomer concentration, and type of catalyst have been studied, the effect of different alkoxy ligands on the silicon atoms has not been investigated. For this study, 1, 6-bis(triethoxysilyl)hexane 1, 1,6-bis(trimethoxysilyl)hexane 2, and 1,6-bis(tripropoxysilyl)hexane 3 were polymerized under acidic and basic conditions in ethanol, methanol, and n-propanol respectively as well as tetrahydrofuran (THF). The resulting gels were processed to afford xerogels that were characterized by SEM, solid state {sup 13}C and {sup 29}Si Cross Polarization Magic Angle Spinning (CP MAS) NMR spectroscopy, nitrogen and CO{sub 2} sorption porosimetry.

  10. Comparison of bridged polysilsesquioxane xerogels prepared from methoxy- and ethoxy-silyl monomers

    SciTech Connect

    Loy, D.A.; Baugher, B.; Assink, R.A.; Prabakar, S.; Shea, K.J.

    1994-12-31

    Hydrocarbon-bridged polysilsesquioxanes are prepared by the sol-gel polymerization of monomers with more than one trialkoxysilyl group attached directly to the bridging group by Si-C bonds. While the effects of varying the identity of the bridging group (length, rigidity, etc.), monomer concentration, and type of catalyst have been studied, the effect of different alkoxy ligands on the silicon atoms has not been investigated. For this study, 1, 6-- bis(triethoxysilyl)hexane 1 and 1, 6-bis(trimethoxysilyl)hexane 2 were polymerized under acidic and basic conditions in ethanol and methanol, respectively, and in tetrahydrofuran (THF). The resulting gels were processed to afford xerogels that were characterized by SEM, solid state {sup 13}C and {sup 29}Si Cross Polarization Magic Angle Spinning (CP MAS) NMR spectroscopy, and nitrogen sorption porosimetry.

  11. Photoluminescence and quantum yields of organic/inorganic hybrids prepared through formic acid solvolysis

    NASA Astrophysics Data System (ADS)

    Fu, Lianshe; Sá Ferreira, R. A.; Fernandes, M.; Nunes, S. C.; de Zea Bermudez, V.; Hungerford, Graham; Rocha, J.; Carlos, L. D.

    2008-03-01

    Three undoped di-urea cross-linked poly(oxyethylene) (POE)/siloxane hybrid matrices, classed as di-ureasils, incorporating POE segments with different lengths were prepared through the carboxylic acid solvolysis sol-gel method using formic acid. The resulting hybrids were characterized by X-ray diffraction, Fourier transform mid-infrared spectroscopy, 29Si and cross-polarization 13C magic-angle spinning nuclear magnetic resonance and photoluminescence spectroscopy. The hybrids' structure is essentially independent of the polymer chain length and the materials are room temperature white-light emitters with emission quantum yields of ˜10 ± 1% and lifetime average values between 2 and 4 ns. For the di-ureasil host with short polymer chains the solvolysis method favours the increase of the PL quantum yields relatively to conventional sol-gel route.

  12. Fulleretic Well-Defined Scaffolds: Donor–Fullerene Alignment Through Metal Coordination and Its Effect on Photophysics

    PubMed Central

    Williams, Derek E.; Dolgopolova, Ekaterina A.; Godfrey, Danielle C.; Ermolaeva, Evgeniya D.; Pellechia, Perry J.; Greytak, Andrew B.; Smith, Mark D.; Avdoshenko, Stanislav M.; Popov, Alexey A.; Shustova, Natalia B.

    2016-01-01

    Herein, we report the first example of a crystalline metal–donor–fullerene framework, in which control of the donor–fullerene mutual orientation was achieved through chemical bond formation, in particular, by metal coordination. The 13C cross-polarization magic-angle spinning NMR spectroscopy, X-ray diffraction, and time-resolved fluorescence spectroscopy were performed for comprehensive structural analysis and energy-transfer (ET) studies of the fulleretic donor–acceptor scaffold. Furthermore, in combination with photoluminescence measurements, the theoretical calculations of the spectral overlap function, Förster radius, excitation energies, and band structure were employed to elucidate the photophysical and ET processes in the prepared fulleretic material. We envision that the well-defined fulleretic donor–acceptor materials could contribute not only to the basic science of fullerene chemistry but would also be used towards effective development of organic photovoltaics and molecular electronics. PMID:27265385

  13. The influence of structural features of marine humic substances on the accumulation rates of cadmium by a blue mussel Mytilus edulis

    SciTech Connect

    Pempkowiak, J.; Kozuch, J. ); Southon, T. )

    1994-01-01

    Laboratory experiments revealed that both concentration and origin of humic substances (HS) influence the accumulation rates of cadmium by the blue mussel Mytilus edulis. In the concentration of humic substances typical of seawater, the increase is about 60% and 100%, respectively, for aquatic and sedimentary humic substances. The phenomenon was attributed to the stimulation of cadmium uptake due to complexing properties of the substances toward cadmium. Complexing capacity of sedimentary humic substances was found to be 0.57 [mu]g/mg HS, that of aquatic substances 0.41 [mu]g/mg HS. Cross Polarization Magic Angle Spinning (CP/MAS) [sup 13]C NMR of the investigated humic substances revealed differences in the spectra at about 175, 100, 55 and 32 ppm. This was attributed to the varying content of oxygen containing functional groups involved in formation of complexes with metal ions. 8 refs., 4 figs., 3 tabs.

  14. A 4-mm Probe for C-13 CP/MAS NMR of Solids at 21.15 T

    SciTech Connect

    Jakobsen, Hans J.; Daugaard, P; Hald, E; Rice, D; Kupce, Eriks; Ellis, Paul D. )

    2002-05-31

    With the recent announcement of a persistent 21.15 Tesla (i.e., 900 MHz for 1H NMR) narrow-bore (54 mm bore) superconducting magnet by Oxford Instruments and the associated Unity INOVA-900 console by Varian Inc. we were challenged with the task of designing a double-resonance broadband solid-state magic-angle spinning (MAS) NMR probe in particular for evaluating the 13C-{1H} cross-polarization (CP) MAS NMR experiment on this magnet and spectrometer system. In this communication we report the successful construction of an efficient X-1H/19F double resonance multinuclear MAS probe for this purpose along with our preliminary results on its performance at the 900 MHz spectrometer.

  15. Background suppression in MAS NMR

    NASA Astrophysics Data System (ADS)

    White, Jeffery L.; Beck, Larry W.; Ferguson, David B.; Haw, James F.

    Pulse sequences for suppressing background signals from spinning modules used in magic-angle spinning NMR are described. These pulse sequences are based on spatially selective composite 90° pulses originally reported by Bax, which provide for no net excitation of spins outside the homogeneous region of the coil. We have achieved essentially complete suppression of background signals originating from our Vespel spinning module (which uses a free-standing coil) in both 1H and 13C spectra without notable loss in signal intensity. Successful modification of both Bloch decay and cross-polarization pulse sequences to include spatially selective pulses was essential to acquire background-free spectra for weak samples. Background suppression was also found to be particularly valuable for both T1 and T1 ϱ, relaxation measurements.

  16. Solid-state NMR study of intercalated species in poly(epsilon-caprolactone)/clay nanocomposites.

    PubMed

    Hrobarikova, J; Robert, J-L; Calberg, C; Jérôme, R; Grandjean, J

    2004-10-26

    The structure and dynamics of surfactant and polymer chains in intercalated poly(epsilon-caprolactone)/clay nanocomposites are characterized by (31)P magic-angle spinning (MAS) and (13)C cross-polarization MAS NMR techniques. To obtain hybrid materials with the low polymer content required for this study, in situ intercalative polymerization was performed by adapting a published procedure. After nanocomposite formation, the chain motion of the surfactant is enhanced in the saponite-based materials but reduced in the Laponite ones. Compared to the starting clay, the trans conformer population of the surfactant hydrocarbon chain in the nanocomposite decreases for the saponite systems. Mobility of the polymer chain is higher in the nanocomposites than in the bulk phase. The charge of the modified saponite does not significantly influence chain mobility in the nanocomposites. PMID:15491221

  17. NMR characterization and sorption behavior of agricultural and forest soil humic substances

    NASA Astrophysics Data System (ADS)

    Li, Chengliang; Berns, Anne E.; Séquaris, Jean-Marie; Klumpp, Erwin

    2010-05-01

    Humic substances are the predominant components of the organic matter in the terrestrial system, which are not only important for the physicochemical properties of soil but are also dominant factors for controlling the environmental behaviors and fates of some organic contaminants, such as hydrophobic compounds. Nonylphenol [4-(1-ethyl-1, 3 dimethylpentyl) phenol] (NP), a ubiquitous hydrophobic pollutant, has recently focused the attention owing to its endocrine disruptors property. Sorption behavior of NP on humic substances, which were isolated from agricultural and forest soils, was investigated by using the dialysis technique at room temperature. 14C-labeled NP was used to quantify the partitioning behavior. Humic substances were characterized by 13C Cross-Polarization/Magic-Angle-Spinning Nuclear Magnetic Resonance (CP/MAS NMR). The results showed that the partition parameters of NP on various humic acids were slightly different. Relationships between partition coefficients and the functional groups of humic substances identified by CP/MAS NMR were analyzed.

  18. Rapid and accurate determination of the lignin content of lignocellulosic biomass by solid-state NMR.

    PubMed

    Fu, Li; McCallum, Scott A; Miao, Jianjun; Hart, Courtney; Tudryn, Gregory J; Zhang, Fuming; Linhardt, Robert J

    2015-02-01

    Biofuels and biomaterials, produced from lignocellulosic feedstock, require facile access to cellulose and hemicellulose to be competitive with petroleum processing and sugar-based fermentation. Physical-chemical barriers resulting from lignin complicates the hydrolysis biomass into fermentable sugars. Thus, the amount of lignin within a substrate is critical in determining biomass processing. The application of (13)C cross-polarization, magic-angle spinning, and solid-state nuclear magnetic resonance for the direct quantification of lignin content in biomass is examined. Using a standard curve constructed from pristine lignin and cellulose, the lignin content of a biomass sample is accurately determined through direct measurement without chemical or enzymatic pre-treatment. PMID:25404762

  19. Synthesis Of [2h, 13c] And [2h3, 13c]Methyl Aryl Sulfides

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.

    2004-03-30

    The present invention is directed to labeled compounds, [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfides wherein the .sup.13 C methyl group attached to the sulfur of the sulfide includes exactly one, two or three deuterium atoms and the aryl group is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, and R.sub.5 are each independently, hydrogen, a C.sub.1 -C.sub.4 lower alkyl, a halogen, an amino group from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each a C.sub.1 -C.sub.4 lower alkyl, a phenyl, or an alkoxy group. The present invention is also directed to processes of preparing [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2,.sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfides wherein the .sup.13 C methyl group attached to the sulfur of the sulfide includes exactly one, two or three deuterium atoms. The present invention is also directed to the labeled compounds of [.sup.2 H.sub.1, .sup.13 C]methyl iodide and [.sup.2 H.sub.2, .sup.13 C]methyl iodide.

  20. A Close Look at 13C CPMAS Linewidths in Solids for Rigid, Strongly Coupled Carbons under CW Proton Decoupling

    NASA Astrophysics Data System (ADS)

    VanderHart, D. L.; Campbell, G. C.

    1998-09-01

    Ambient-temperature13C linewidth (LW) and transverse relaxation (TC2) data are presented for the natural-abundance crystalline carbons of linear polyethylene (LPE) under CW proton decoupling conditions and magic angle spinning (MAS). This linewidth behavior typifies that seen for rigid methylene carbons whose attached protons are also strongly coupled to other protons. These data are presented for two LPE samples (unoriented, melt-crystallized and uniaxially oriented, extruded) as a function of several parameters including static field (1.4 T 13C-bonded protons. The difference in sensitivities of LW(ORPI) to νrfor the off-resonance and the on-resonance cases is traced back, respectively, to the

  1. Use of solid-state 13C NMR in structural studies of humic acids and humin from Holocene sediments

    USGS Publications Warehouse

    Hatcher, P.G.; VanderHart, D.L.; Earl, W.L.

    1980-01-01

    13C NMR spectra of solid humic substances in Holocene sediments have been obtained using cross polarization with magic-angle sample spinning techniques. The results demonstrate that this technique holds great promise for structural characterizations of complex macromolecular substances such as humin and humic acids. Quantifiable distinctions can be made between structural features of aquatic and terrestrial humic substances. The aliphatic carbons of the humic substances are dominant components suggestive of input from lipid-like materials. An interesting resemblance is also noted between terrestrial humic acid and humin spectra. ?? 1980.

  2. 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

  3. 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.

  4. 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.

  5. Analysis of organic matter at the soil-water interface by NMR spectroscopy: Implications for contaminant sorption processes

    NASA Astrophysics Data System (ADS)

    Simpson, M.; Simpson, A.

    2009-05-01

    Contaminant sorption to soil organic matter (OM) is the main fate of nonionic, hydrophobic organic contaminants in terrestrial environments and a number of studies have suggested that both soil OM structure and physical conformation (as regulated by the clay mineral phase) govern contaminant sorption processes. To investigate this further, a number of soil samples were characterized by both solid-state 13 C Cross Polarization Magic Angle Spinning (CPMAS) NMR and 1H High Resolution Magic Angle Spinning (HR- MAS) NMR. HR-MAS NMR is an innovative NMR method that allows one to examine samples that are semi- solid using liquid state NMR methods (ie: observe 1H which is more sensitive than 13C). With HR-MAS NMR, only those structures that are in contact with the solvent are NMR visible thus one can probe different components within a mixture using different solvents. The 1H HR-MAS NMR spectrum of a grassland soil swollen in water (D2O) is dominated by signals from alkyl and O-alkyl structures but signals from aromatic protons are negligible (the peak at ~8.2ppm is attributed to formic acid). When the soil is swollen in DMSO-d6, a solvent which is more penetrating and capable of breaking hydrogen bonds, aromatic signals are visible suggesting that the aromatic structures are buried within the soil matrix and do not exist at the soil-water interface. The 13C solid-state NMR data confirms that aromatic carbon is present in substantial amounts (estimated at ~40% of the total 13C signal) therefore, the lack of 1H aromatic signals in the HR-MAS NMR spectrum indicates that aromatic structures are buried and that the soil-water interface is dominated by aliphatic chains, carbohydrates, and peptides. The NMR data indicates that the mineral component of soils governs the physical conformation of OM at the soil-water interface.

  6. Cross polarization optical coherence tomography for diagnosis of oral soft tissues

    NASA Astrophysics Data System (ADS)

    Gladkova, Natalia; Karabut, Maria; Kiseleva, Elena; Robakidze, Natalia; Muraev, Alexander; Fomina, Julia

    2011-03-01

    We consider the capabilities of cross-polarization OCT (CP OCT) focused on comparison of images resulting from cross-polarization and co-polarization scattering simultaneously for diagnosis of oral soft tissues. CP OCT was done for 35 patients with dental implants and 30 patients with inflammatory intestine diseases. Our study showed good diagnostic capabilities of CP OCT for detecting soft tissue pathology in the oral cavity. The cross-polarized images demonstrate the ability of tissue to depolarize. CP OCT demonstrates clinical capabilities for early diagnosis of inflammatory intestine diseases by the state of oral cavity mucosa and for early detection of gingivitis in patients above implant.

  7. Accurate determinations of one-bond 13C-13C couplings in 13C-labeled carbohydrates

    NASA Astrophysics Data System (ADS)

    Azurmendi, Hugo F.; Freedberg, Darón I.

    2013-03-01

    Carbon plays a central role in the molecular architecture of carbohydrates, yet the availability of accurate methods for 1DCC determination has not been sufficiently explored, despite the importance that such data could play in structural studies of oligo- and polysaccharides. Existing methods require fitting intensity ratios of cross- to diagonal-peaks as a function of the constant-time (CT) in CT-COSY experiments, while other methods utilize measurement of peak separation. The former strategies suffer from complications due to peak overlap, primarily in regions close to the diagonal, while the latter strategies are negatively impacted by the common occurrence of strong coupling in sugars, which requires a reliable assessment of their influence in the context of RDC determination. We detail a 13C-13C CT-COSY method that combines a variation in the CT processed with diagonal filtering to yield 1JCC and RDCs. The strategy, which relies solely on cross-peak intensity modulation, is inspired in the cross-peak nulling method used for JHH determinations, but adapted and extended to applications where, like in sugars, large one-bond 13C-13C couplings coexist with relatively small long-range couplings. Because diagonal peaks are not utilized, overlap problems are greatly alleviated. Thus, one-bond couplings can be determined from different cross-peaks as either active or passive coupling. This results in increased accuracy when more than one determination is available, and in more opportunities to measure a specific coupling in the presence of severe overlap. In addition, we evaluate the influence of strong couplings on the determination of RDCs by computer simulations. We show that individual scalar couplings are notably affected by the presence of strong couplings but, at least for the simple cases studied, the obtained RDC values for use in structural calculations were not, because the errors introduced by strong couplings for the isotropic and oriented phases are very

  8. Ice Shelf Modeling: A Cross-Polar Bayesian Statistical Approach

    NASA Astrophysics Data System (ADS)

    Kirchner, N.; Furrer, R.; Jakobsson, M.; Zwally, H. J.

    2010-12-01

    Ice streams interlink glacial terrestrial and marine environments: embedded in a grounded inland ice such as the Antarctic Ice Sheet or the paleo ice sheets covering extensive parts of the Eurasian and Amerasian Arctic respectively, ice streams are major drainage agents facilitating the discharge of substantial portions of continental ice into the ocean. At their seaward side, ice streams can either extend onto the ocean as floating ice tongues (such as the Drygalsky Ice Tongue/East Antarctica), or feed large ice shelves (as is the case for e.g. the Siple Coast and the Ross Ice Shelf/West Antarctica). The flow behavior of ice streams has been recognized to be intimately linked with configurational changes in their attached ice shelves; in particular, ice shelf disintegration is associated with rapid ice stream retreat and increased mass discharge from the continental ice mass, contributing eventually to sea level rise. Investigations of ice stream retreat mechanism are however incomplete if based on terrestrial records only: rather, the dynamics of ice shelves (and, eventually, the impact of the ocean on the latter) must be accounted for. However, since floating ice shelves leave hardly any traces behind when melting, uncertainty regarding the spatio-temporal distribution and evolution of ice shelves in times prior to instrumented and recorded observation is high, calling thus for a statistical modeling approach. Complementing ongoing large-scale numerical modeling efforts (Pollard & DeConto, 2009), we model the configuration of ice shelves by using a Bayesian Hiearchial Modeling (BHM) approach. We adopt a cross-polar perspective accounting for the fact that currently, ice shelves exist mainly along the coastline of Antarctica (and are virtually non-existing in the Arctic), while Arctic Ocean ice shelves repeatedly impacted the Arctic ocean basin during former glacial periods. Modeled Arctic ocean ice shelf configurations are compared with geological spatial

  9. Cross-polarization level in radiation from a microstrip dipole antenna

    NASA Astrophysics Data System (ADS)

    Hoorfar, Ahmad; Gupta, Kuldip C.; Chang, David C.

    1988-09-01

    A description is given of the cross-polarization level in radiation from a small horizontal electric dipole (HED) on a flat grounded dielectric substrate. The study is directed toward the design of a very low cross-polarization level in a linear array of microstrip antenna elements. Field expressions for a copolarized and crosspolarized microstrip HED for any arbitrary dipole orientation and array direction are derived.

  10. Dual-band cross polarization converter in bi-layered complementary chiral metamaterial

    NASA Astrophysics Data System (ADS)

    Ma, Xiaolong; Xiao, Zhongyin; Liu, Dejun

    2016-05-01

    In this article, a new chiral metamaterial with giant optical activity (90°) around 225 and 285 THz has been proposed which can be acted as a dual-band cross polarization converter (CPC). During the frequency range of proposed CPC, the maximum transmission coefficient and cross polarization conversion efficiency are up to 0.55 and 0.998, respectively. Importantly, the corresponding ellipticities are almost zero at 225 and 285 THz.

  11. Quantification of cross polarization with relaxation compensated reciprocity relation in NMR

    NASA Astrophysics Data System (ADS)

    Shu, Jie; Chen, Qun; Zhang, Shanmin

    2008-09-01

    The reciprocity relation in solid state NMR has been extended to include the effects of spin-lattice relaxation in the rotating frame. This method was successfully applied to the experiments of Hartmann-Hahn cross polarization, making the originally non-quantified NMR spectra quantitative. In addition, it provides detailed dynamics of cross polarization that is often obscured by spin-lattice relaxation in the rotating frame and by some other effects.

  12. Optoacoustic 13C-breath test analyzer

    NASA Astrophysics Data System (ADS)

    Harde, Hermann; Helmrich, Günther; Wolff, Marcus

    2010-02-01

    The composition and concentration of exhaled volatile gases reflects the physical ability of a patient. Therefore, a breath analysis allows to recognize an infectious disease in an organ or even to identify a tumor. One of the most prominent breath tests is the 13C-urea-breath test, applied to ascertain the presence of the bacterium helicobacter pylori in the stomach wall as an indication of a gastric ulcer. In this contribution we present a new optical analyzer that employs a compact and simple set-up based on photoacoustic spectroscopy. It consists of two identical photoacoustic cells containing two breath samples, one taken before and one after capturing an isotope-marked substrate, where the most common isotope 12C is replaced to a large extent by 13C. The analyzer measures simultaneously the relative CO2 isotopologue concentrations in both samples by exciting the molecules on specially selected absorption lines with a semiconductor laser operating at a wavelength of 2.744 μm. For a reliable diagnosis changes of the 13CO2 concentration of 1% in the exhaled breath have to be detected at a concentration level of this isotope in the breath of about 500 ppm.

  13. Towards hyperpolarized 13C-succinate imaging of brain cancer

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Pratip; Chekmenev, Eduard Y.; Perman, William H.; Harris, Kent C.; Lin, Alexander P.; Norton, Valerie A.; Tan, Chou T.; Ross, Brian D.; Weitekamp, Daniel P.

    2007-05-01

    We describe a novel 13C enriched precursor molecule, sodium 1- 13C acetylenedicarboxylate, which after hydrogenation by PASADENA (Parahydrogen and Synthesis Allows Dramatically Enhanced Nuclear Alignment) under controlled experimental conditions, becomes hyperpolarized 13C sodium succinate. Fast in vivo 3D FIESTA MR imaging demonstrated that, following carotid arterial injection, the hyperpolarized 13C-succinate appeared in the head and cerebral circulation of normal and tumor-bearing rats. At this time, no in vivo hyperpolarized signal has been localized to normal brain or brain tumor. On the other hand, ex vivo samples of brain harvested from rats bearing a 9L brain tumor, 1 h or more following in vivo carotid injection of hyperpolarized 13C sodium succinate, contained significant concentrations of the injected substrate, 13C sodium succinate, together with 13C maleate and succinate metabolites 1- 13C-glutamate, 5- 13C-glutamate, 1- 13C-glutamine and 5- 13C-glutamine. The 13C substrates and products were below the limits of NMR detection in ex vivo samples of normal brain consistent with an intact blood-brain barrier. These ex vivo results indicate that hyperpolarized 13C sodium succinate may become a useful tool for rapid in vivo identification of brain tumors, providing novel biomarkers in 13C MR spectral-spatial images.

  14. Synthesis Of 2h- And 13c-Substituted Dithanes

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.

    2004-05-04

    The present invention is directed to labeled compounds, [2-.sup.13 C]dithane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to processes of preparing [2-.sup.13 C]dithane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to labeled compounds, e.g., [.sup.2 H.sub.1-2, .sup.13 C]methanol (arylthio)-, acetates wherein the .sup.13 C atom is directly bonded to exactly one or two deuterium atoms.

  15. Synthesis of 2H- and 13C-substituted dithanes

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.

    2003-01-01

    The present invention is directed to labeled compounds, [2-.sup.13 C]dithiane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to processes of preparing [2-.sup.13 C]dithiane wherein the .sup.13 C atom is directly bonded to one or two deuterium atoms. The present invention is also directed to labeled compounds, e.g., [.sup.2 H.sub.1-2, .sup.13 C]methanol (arylthio)-, acetates wherein the .sup.13 C atom is directly bonded to exactly one or two deuterium atoms.

  16. Dipolar-coupling-mediated total correlation spectroscopy in solid-state 13C NMR: Selection of individual 13C- 13C dipolar interactions

    NASA Astrophysics Data System (ADS)

    Spano, Justin; Wi, Sungsool

    2010-06-01

    Herein is described a useful approach in solid-state NMR, for selecting homonuclear 13C- 13C spin pairs in a multiple- 13C homonuclear dipolar coupled spin system. This method builds upon the zero-quantum (ZQ) dipolar recoupling method introduced by Levitt and coworkers (Marin-Montesinos et al., 2006 [30]) by extending the originally introduced one-dimensional (1D) experiment into a two-dimensional (2D) method with selective irradiation scheme, while moving the 13C- 13C mixing scheme from the transverse to the longitudinal mode, together with a dramatic improvement in the proton decoupling efficiency. Selective spin-pair recoupling experiments incorporating Gaussian and cosine-modulated Gaussian pulses for inverting specific spins were performed, demonstrating the ability to detect informative, simplified/individualized, long-range 13C- 13C homonuclear dipolar coupling interactions more accurately by removing less informative, stronger, short-range 13C- 13C interactions from 2D correlation spectra. The capability of this new approach was demonstrated experimentally on uniformly 13C-labeled Glutamine and a tripeptide sample, GAL.

  17. In vivo dynamic turnover of cerebral 13C isotopomers from [U- 13C]glucose

    NASA Astrophysics Data System (ADS)

    Xu, Su; Shen, Jun

    2006-10-01

    An INEPT-based 13C MRS method and a cost-effective and widely available 11.7 Tesla 89-mm bore vertical magnet were used to detect dynamic 13C isotopomer turnover from intravenously infused [U- 13C]glucose in a 211 μL voxel located in the adult rat brain. The INEPT-based 1H → 13C polarization transfer method is mostly adiabatic and therefore minimizes signal loss due to B 1 inhomogeneity of the surface coils used. High quality and reproducible data were acquired as a result of combined use of outer volume suppression, ISIS, and the single-shot three-dimensional localization scheme built in the INEPT pulse sequence. Isotopomer patterns of both glutamate C4 at 34.00 ppm and glutamine C4 at 31.38 ppm are dominated first by a doublet originated from labeling at C4 and C5 but not at C3 (with 1JC4C5 = 51 Hz) and then by a quartet originated from labeling at C3, C4, and C5 (with 1JC3C4 = 35 Hz). A lag in the transition of glutamine C4 pattern from doublet-dominance to quartet dominance as compared to glutamate C4 was observed, which provides an independent verification of the precursor-product relationship between neuronal glutamate and glial glutamine and a significant intercompartmental cerebral glutamate-glutamine cycle between neurons and glial cells.

  18. Calculation of total meal d13C from individual food d13C.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Variations in the isotopic signature of carbon in biological samples can be used to distinguish dietary patterns and monitor shifts in metabolism. But for these variations to have meaning, the isotopic signature of the diet must be known. We sought to determine if knowledge of the 13C isotopic abund...

  19. High-contrast coherent population trapping based on crossed polarizers method.

    PubMed

    Yano, Yuichiro; Goka, Shigeyoshi

    2014-12-01

    A method based on crossed polarizers to observe high-contrast coherent population trapping (CPT) resonance has been developed. Because crossed polarizers have a simple optical system, our method is suitable for chip-scale atomic clocks (CSACs). In CPT, the Faraday rotation in a linearly polarized light field (lin||lin) was calculated using two pairs of Λ-system models; the spectrum of the Faraday rotation is also estimated. After measuring the contrast and linewidth with the crossed-polarizer method, a comparison of the theoretical model and experimental data showed they were in good agreement. Moreover, the experimental results showed that a high contrast (88.4%) and narrow linewidth (1.15 kHz) resonance could be observed using a Cs gas cell and D1-line verticalcavity surface-emitting laser (VCSEL). PMID:25474771

  20. Broadband cross polarization converter using plasmon hybridizations in a ring/disk cavity.

    PubMed

    Shi, Hongyu; Li, Jianxing; Zhang, Anxue; Wang, Jiafu; Xu, Zhuo

    2014-08-25

    In this paper, we report on the design, fabrication and subsequent investigation of a broad band cross polarization converter based on a C2-symmetric ring/disk cavity. Different plasmon hybridization modes are excited in the ring/disk cavity and enable the polarization manipulations. The designed cross polarization converter can convert the x or y polarized incident wave to its cross polarized wave in the frequency range from 9.65 to 14.16 GHz with a bandwidth of ~38% of the central wavelength and an efficiency higher than 80%. At 9.25 GHz and 14.35 GHz, the x (y) polarized incident wave is converted to a left (right) handed and right (left) handed circularly polarized wave, respectively. PMID:25321298

  1. The cluster and single-particle states in 13C (α,α)13C reactions

    NASA Astrophysics Data System (ADS)

    Mynbayev, N. A.; Nurmukhanbetova, A. K.; Goldberg, V. Z.; Rogachev, G. V.; Golovkov, M. S.; Koloberdin, M.; Ivanov, I.; Nauruzbayev, D. K.; Berdibek, Sh S.; Rakhymzhanov, A. M.; Tribble, R. E.

    2016-06-01

    The excitation functions of elastic scattering of 13C on alpha particle have been measured using the thick-target inverse kinematic method at the heavy ion DC-60 cyclotron. The helium gas was used as a target and also as a degrader to stop the beam. New data (including 180°degree) of the resonances close to the threshold in 17O have been obtained.

  2. A Low Cross-Polarization Smooth-Walled Horn with Improved Bandwidth

    NASA Technical Reports Server (NTRS)

    Zeng, Lingzhen; Bennett, Charles L.; Chuss, David T.; Wollack, Edward J.

    2009-01-01

    Corrugated feed horns offer excellent beam symmetry, main beam efficiency, and cross-polar response over wide bandwidths, but can be challenging to fabricate. An easier-to-manufacture smooth-walled feed is explored that approximates these properties over a finite bandwidth. The design, optimization and measurement of a monotonically-profiled, smooth-walled scalar feedhorn with a diffraction-limited approximately 7 degrees full width at half maximum (FWHM) is presented. The feed was demonstrated to have low cross polarization (<-30 dB) across the frequency range 33-45 GHz (30% fractional bandwidth). A return loss better than -28 dB was measured across the band.

  3. Cross polarization caused by perturbed circular cross sections of waveguides and horn antennas

    NASA Astrophysics Data System (ADS)

    Lier, Erik

    1987-03-01

    The cross polarization caused by a perturbed cross section of the conical hybrid-mode horn is analyzed. The perturbed cross section is assumed to be slightly elliptical. The theory of Lier and Bergh (1986) for cross polarization in a smooth-walled waveguide supporting the TE11-mode is referred and applied to the HE11 mode as well. Simple analytical formulas which are sufficiently accurate for small ellipticites of the cross-section ellipse are presented. These show that the tolerances on the waveguide diameter are extremely strong, typically on the order of 0.02-0.04 mm in the horn throat for typical horn geometries at 12 GHz.

  4. A Low Cross-Polarization Smooth-Walled Horn with Improved Bandwidth

    NASA Technical Reports Server (NTRS)

    Zeng, Lingzhen; Bennette, Charles L.; Chuss, David T.; Wollack, Edward J.

    2009-01-01

    Corrugated feed horns offer excellent beam symmetry, main beam efficiency, and cross-polar response over wide bandwidths, but can be challenging to fabricate. An easier-to-manufacture smooth-walled feed is explored that approximates these properties over a finite bandwidth. The design, optimization and measurement of a monotonically-profiled, smooth-walled scalar feedhorn with a diffraction-limited approx. 14deg FWHM beam is presented. The feed was demonstrated to have low cross polarization (<-30 dB) across the frequency range 33-45 GHz (30% fractional bandwidth). A power reflection below -28 dB was measured across the band.

  5. CARBON-13 NUCLEAR MAGNETIC RESONANCE. 13C CHEMICAL SHIFTS AND 13C-199HG COUPLING CONSTANTS FOR SOME ORGANOMERCURY COMPOUNDS

    EPA Science Inventory

    The (13)C shieldings and (13)C-(199)Hg coupling constants of fourteen phenyl- and seven alkyl- and alkenyl-mercury compounds have been obtained. Substituent effects on the (13)C shieldings are similar to those in nonmercurated phenyl compounds, with a similar relationship between...

  6. Coherence selection in double CP MAS NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Yang, Jen-Hsien; Chou, Fang-Chieh; Tzou, Der-Lii M.

    2008-11-01

    Applications of double cross-polarization (CP) magic-angle spinning (MAS) NMR spectroscopy, via 1H/ 15N and then 15N/ 13C coherence transfers, for 13C coherence selection are demonstrated on a 15N/ 13C-labeled N-acetyl-glucosamine (GlcNAc) compound. The 15N/ 13C coherence transfer is very sensitive to the settings of the experimental parameters. To resolve explicitly these parameter dependences, we have systematically monitored the 13C{ 15N/ 1H} signal as a function of the rf field strength and the MAS frequency. The data reveal that the zero-quantum coherence transfer, with which the 13C effective rf field is larger than that of the 15N by the spinning frequency, would give better signal sensitivity. We demonstrate in one- and two-dimensional double CP experiments that spectral editing can be achieved by tailoring the experimental parameters, such as the rf field strengths and/or the MAS frequency.

  7. 13C and 31P chemical shielding tensors of a single crystal of dipotassium α- D-glucose-1-phosphate dihydrate. An application of a 13C-{ 1H, 31P} triple-resonance technique

    NASA Astrophysics Data System (ADS)

    McDowell, C. A.; Naito, A.; Sastry, D. L.; Takegoshi, K.

    The 13C NMR spectra of a single crystal of dipotassium α- D-glucose-l-phosphate dehydrate for different orientations in the external magnetic field, were recorded by using 1H and 31P double nuclear decoupling. To overcome difficulties encountered because of the high 13C RF power required to achieve the Hartmann-Hahn condition, a new cross-polarization method (K. Takegoshi and C. A. McDowell, J. Magn. Reson.67, 356 (1986)) was used. The directions of the most shielded principal value of the 13C chemical shielding tensors for the C2-C6 carbon nuclei in the glucose group were along the CO bond, and that for the CI carbon nucleus made an angle of 42† with the C1-O5 bond direction in the O1-C1-O5 plane. The 31P chemical shielding tensors are axially symmetric and the direction of the least shielded principal value is almost parallel to the P-O1(R) bond, which is the longest among the four PO bonds in the phosphate moiety.

  8. Cross-polarized wave generation by effective cubic nonlinear optical interaction.

    PubMed

    Petrov, G I; Albert, O; Etchepare, J; Saltiel, S M

    2001-03-15

    A new cubic nonlinear optical effect in which a linearly polarized wave propagating in a single quadratic medium is converted into a wave that is cross polarized to the input wave is observed in BBO crystal. The effect is explained by cascading of two different second-order processes: second-harmonic generation and difference frequency mixing. PMID:18040322

  9. On the cross-polarization characteristics of crooked wire antennas designed by genetic-algorithms

    NASA Technical Reports Server (NTRS)

    Rengarajan, S. R.; Rahmat-Samii, Y.

    2002-01-01

    In many modern communication applications there is a need for simple circularly polarized antennas for hemispherical coverage with good axial ratio or low value of cross polarization. We revisited the crooked wire antenna because of its simplicity. This paper presents results of our investigation on the crooked wire antennas and other elements.

  10. Synthesis Of [2h, 13c]M [2h2m 13c], And [2h3,, 13c] Methyl Aryl Sulfones And Sulfoxides

    DOEpatents

    Martinez, Rodolfo A.; Alvarez, Marc A.; Silks, III, Louis A.; Unkefer, Clifford J.; Schmidt, Jurgen G.

    2004-07-20

    The present invention is directed to labeled compounds, [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfones and [.sup.2 H.sub.1, .sup.13 C], [.sup.2 H.sub.2, .sup.13 C] and [.sup.2 H.sub.3, .sup.13 C]methyl aryl sulfoxides, wherein the .sup.13 C methyl group attached to the sulfur of the sulfone or sulfoxide includes exactly one, two or three deuterium atoms and the aryl group is selected from the group consisting of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently, hydrogen, a C.sub.1 -C.sub.4 lower alkyl, a halogen, an amino group from the group consisting of NH.sub.2, NHR and NRR' where R and R' are each a C.sub.1 -C.sub.4 lower alkyl, a phenyl, or an alkoxy group. The present invention is also directed to processes of preparing methyl aryl sulfones and methyl aryl sulfoxides.

  11. Circularly Polarized Microwave Antenna Element with Very Low Off-Axis Cross-Polarization

    NASA Technical Reports Server (NTRS)

    Greem. David; DuToit, Cornelis

    2013-01-01

    The goal of this work was to improve off-axis cross-polarization performance and ease of assembly of a circularly polarized microwave antenna element. To ease assembly, the initial design requirement of Hexweb support for the internal circuit part, as well as the radiating disks, was eliminated. There is a need for different plating techniques to improve soldering. It was also desirable to change the design to eliminate soldering as well as the need to use the Hexweb support. Thus, a technique was developed to build the feed without using solder, solving the lathing and soldering issue. Internal parts were strengthened by adding curvature to eliminate Hexweb support, and in the process, the new geometries of the internal parts opened the way for improving the off-axis cross-polarization performance as well. The radiating disks curvatures were increased for increased strength, but it was found that this also improved crosspolarization. Optimization of the curvatures leads to very low off-axis cross-polarization. The feed circuit was curved into a cylinder for improved strength, eliminating Hexweb support. An aperture coupling feed mechanism eliminated the need for feed pins to the disks, which would have required soldering. The aperture coupling technique also improves cross-polarization performance by effectively exciting the radiating disks very close to the antenna s central axis of symmetry. Because of the shape of the parts, it allowed for an all-aluminum design bolted together and assembled with no solder needed. The advantage of a solderless design is that the reliability is higher, with no single-point failure (solder), and no need for special plating techniques in order to solder the unit together. The shapes (curved or round) make for a more robust build without extra support materials, as well as improved offaxis cross-polarization.

  12. /sup 13/C nuclear magnetic resonance studies of cardiac metabolism

    SciTech Connect

    Seeholzer, S.H.

    1985-01-01

    The last decade has witnessed the increasing use of Nuclear Magnetic Resonance (NMR) techniques for following the metabolic fate of compounds specifically labeled with /sup 13/C. The goals of the present study are: (1) to develop reliable quantitative procedures for measuring the /sup 13/C enrichment of specific carbon sites in compounds enriched by the metabolism of /sup 13/C-labeled substrates in rat heart, and (2) to use these quantitative measurements of fractional /sup 13/C enrichment within the context of a mathematical flux model describing the carbon flow through the TCA cycle and ancillary pathways, as a means for obtaining unknown flux parameters. Rat hearts have been perfused in vitro with various combinations of glucose, acetate, pyruvate, and propionate to achieve steady state flux conditions, followed by perfusion with the same substrates labeled with /sup 13/C in specific carbon sites. The hearts were frozen at different times after addition of /sup 13/C-labeled substrates and neutralized perchloric acid extracts were used to obtain high resolution proton-decoupled /sup 13/C NMR spectra at 90.55 MHz. The fractional /sup 13/C enrichment (F.E.) of individual carbon sites in different metabolites was calculated from the area of the resolved resonances after correction for saturation and nuclear Overhauser effects. These F.E. measurements by /sup 13/C NMR were validated by the analysis of /sup 13/C-/sup 1/H scalar coupling patterns observed in /sup 1/H NMR spectra of the extracted metabolites. The results obtained from perfusion of hearts glucose plus either (2-/sup 13/C) acetate or (3-/sup 13/C) pyruvate are similar to those obtained by previous investigators using /sup 14/C-labeled substrates.

  13. Solid-state NMR study of fluorinated steroids.

    PubMed

    Yang, Kai-Jay; Lin, Su-Ching; Huang, Shing-Jong; Ching, Wei-Min; Hung, Chen-Hsiung; Tzou, Der-Lii M

    2014-02-01

    Solid-state {(1)H}(13)C cross-polarization/magic angle spinning (CP/MAS) NMR spectroscopy was performed to analyze two fluorinated steroids, i.e., betamethasone (BMS) and fludrocortisone acetate (FCA), that have fluorine attached to C9, as well as two non-fluorinated analogs, i.e., prednisolone (PRD) and hydrocortisone 21-acetate (HCA). The (13)C signals of BMS revealed multiplet patterns with splittings of 16-215Hz, indicating multiple ring conformations, whereas the (13)C signals of FCA, HCA, and PRD exhibited only singlet patterns, implying a unique conformation. In addition, BMS and FCA exhibited substantial deviation (>3.5ppm) in approximately half of the (13)C signals and significant deviation (>45ppm) in the (13)C9 signal compared to PRD and HCA, respectively. In this study, we demonstrate that fluorinated steroids, such as BMS and FCA, have steroidal ring conformation(s) that are distinct from non-fluorinated analogs, such as PRD and HCA. PMID:24316163

  14. Non-stationary (13)C-metabolic flux ratio analysis.

    PubMed

    Hörl, Manuel; Schnidder, Julian; Sauer, Uwe; Zamboni, Nicola

    2013-12-01

    (13)C-metabolic flux analysis ((13)C-MFA) has become a key method for metabolic engineering and systems biology. In the most common methodology, fluxes are calculated by global isotopomer balancing and iterative fitting to stationary (13)C-labeling data. This approach requires a closed carbon balance, long-lasting metabolic steady state, and the detection of (13)C-patterns in a large number of metabolites. These restrictions mostly reduced the application of (13)C-MFA to the central carbon metabolism of well-studied model organisms grown in minimal media with a single carbon source. Here we introduce non-stationary (13)C-metabolic flux ratio analysis as a novel method for (13)C-MFA to allow estimating local, relative fluxes from ultra-short (13)C-labeling experiments and without the need for global isotopomer balancing. The approach relies on the acquisition of non-stationary (13)C-labeling data exclusively for metabolites in the proximity of a node of converging fluxes and a local parameter estimation with a system of ordinary differential equations. We developed a generalized workflow that takes into account reaction types and the availability of mass spectrometric data on molecular ions or fragments for data processing, modeling, parameter and error estimation. We demonstrated the approach by analyzing three key nodes of converging fluxes in central metabolism of Bacillus subtilis. We obtained flux estimates that are in agreement with published results obtained from steady state experiments, but reduced the duration of the necessary (13)C-labeling experiment to less than a minute. These results show that our strategy enables to formally estimate relative pathway fluxes on extremely short time scale, neglecting cellular carbon balancing. Hence this approach paves the road to targeted (13)C-MFA in dynamic systems with multiple carbon sources and towards rich media. PMID:23860906

  15. Magic angle Lee-Goldburg frequency offset irradiation improves the efficiency and selectivity of SPECIFIC-CP in triple-resonance MAS solid-state NMR

    PubMed Central

    Wu, C.H.; De Angelis, Anna A.; Opella, Stanley J.

    2014-01-01

    The efficiency and selectivity of SPECIFIC-CP, a widely used method for selective double cross-polarization in triple-resonance magic angle spinning solid-state NMR, is improved by performing the tangential-shaped 13C irradiation at an offset frequency that meets the Lee-Goldburg condition (LG-SPECIFIC-CP). This is demonstrated on polycrystalline samples of uniformly 13C, 15N labeled N-acetyl-leucine and N-formyl-Met-Leu-Phe-OH (MLF) at 700 MHz and 900 MHz 1H resonance frequencies, respectively. For the single 13Cα of N-acetyl-leucine, relative to conventional broad band cross-polarization, the SPECIFIC-CP signal has 47% of the intensity. Notably, the LG-SPECIFIC-CP signal has 72% of the intensity, essentially the theoretical maximum. There were no other changes in the experimental parameters. The three 13Cα signals in MLF show some variation in intensities, reflecting the relatively narrow bandwidth of a frequency-offset procedure, and pointing to future developments for this class of experiment. PMID:25051542

  16. Tri-band transparent cross-polarization converters using a chiral metasurface

    NASA Astrophysics Data System (ADS)

    Shi, Hong-Yu; Li, Jian-Xing; Zhang, An-Xue; Wang, Jia-Fu; Xu, Zhuo

    2014-11-01

    A chiral metasurface is proposed to realize a tri-band polarization angle insensitive cross-polarization converter. The unit cell of the chiral metamaterial is composed by four twisted anisotropic structure pairs in four-fold rotation symmetry. The simulation results show that this device can work at 9.824 GHz, 11.39 GHz, and 13.37 GHz with low loss and a high polarization conversion ratio (PCR) of more than 99%. The proposed design can transmit the co-polarization wave at 14.215 GHz, like a frequency selective surface. The study of the current and electric fields distributions indicates that the cross-polarization transmission is due to electric dipole coupling.

  17. Wideband tunable mid-infrared cross polarization converter using rectangle-shape perforated graphene.

    PubMed

    Yang, Chen; Luo, Yi; Guo, Jiaxin; Pu, Yang; He, De; Jiang, Yadong; Xu, Jimmy; Liu, Zhijun

    2016-07-25

    The strong plasmonic response and wide electrostatic tunability of graphene make it a promising material for developing infrared optoelectronic components. In this paper, we present a mid-infrared wideband tunable cross polarization converter using periodically perforated graphene. The polarization converter consists of a metal ground plane, an insulator layer, and a rectangle-shape periodically perforated graphene sheet. By superimposing two localized surface plasmon modes, the polarization converter transforms a linear polarization to its cross polarization over a bandwidth as wide as ~5% of the central frequency (46.8THz) with a peak conversion ratio exceeding 90%. The polarization conversion performance is maintained over a wide range of incident angles up to 50°, and is highly tunable by electrostatic tuning of the graphene Fermi energy. Our proposed device enables the manipulation of light polarization for potential mid-infrared applications. PMID:27464143

  18. Ergodicity and efficiency of cross-polarization in NMR of static solids

    NASA Astrophysics Data System (ADS)

    Nevzorov, Alexander A.

    2011-04-01

    Cross-polarization transfer is employed in virtually every solid-state NMR experiment to enhance magnetization of low-gamma spins. Theory and experiment is used to assess the magnitude of the final quasistationary magnetization amplitude. The many-body density matrix equation is solved for relatively large (up to N = 14) spin systems without the spin-temperature assumption for the final spin states. Simulations show that about 13% of the thermodynamic limit is still retained within the proton bath. To test this theoretical prediction, a combination of a reverse cross-polarization experiment and multiple contacts is employed to show that the thermodynamic limit of magnetization cannot be transferred from high- to low-gamma nuclei in a single contact. Multiple contacts, however, fully transfer the maximum magnetization. A simple diffusion on a cone model shows that slow dynamics can affect the build up profile for the transferred magnetization.

  19. Ergodicity and efficiency of cross-polarization in NMR of static solids.

    PubMed

    Nevzorov, Alexander A

    2011-04-01

    Cross-polarization transfer is employed in virtually every solid-state NMR experiment to enhance magnetization of low-gamma spins. Theory and experiment is used to assess the magnitude of the final quasistationary magnetization amplitude. The many-body density matrix equation is solved for relatively large (up to N=14) spin systems without the spin-temperature assumption for the final spin states. Simulations show that about 13% of the thermodynamic limit is still retained within the proton bath. To test this theoretical prediction, a combination of a reverse cross-polarization experiment and multiple contacts is employed to show that the thermodynamic limit of magnetization cannot be transferred from high- to low-gamma nuclei in a single contact. Multiple contacts, however, fully transfer the maximum magnetization. A simple diffusion on a cone model shows that slow dynamics can affect the build up profile for the transferred magnetization. PMID:21296016

  20. Surface configuration as an explanation for lithology-related cross-polarized radar image anomalies

    NASA Technical Reports Server (NTRS)

    Mccauley, J. R.

    1973-01-01

    One problem that has persisted since the development of multipolarized radar is the cause or causes of differential depolarization which is expressed as tonal reversals between like- and cross-polarized images of certain outcrops. Rocks producing anomalously low returns on the cross-polarized image could be classed into three general types: (1) certain geologically recent lava flows (late Pleistocene and Holocene), (2) some tertiary volcanics and (3) certain massive sandstones. Differential depolarization has been produced by volcanic rocks of various compositions including rhyolite, rhyodacite, dacite, andesite, and basalt. This has led to the conclusion that differential depolarization is not directly caused by any compositional factor. However, the study of aerial photos and subsequent field observation have led to the conclusion that the weathering and other surface characteristics of the outcrops are responsible for their appearance on multipolarized imagery.

  1. Unidirectional cross polarization rotator with enhanced broadband transparency by cascading twisted nanobars

    NASA Astrophysics Data System (ADS)

    Wang, Ying-Hua; Shao, Jian; Li, Jie; Zhu, Ming-Jie; Li, Jiaqi; Dong, Zheng-Gao

    2016-05-01

    We demonstrate the optical activity for linear polarization by twisting cascading multilayer nanobars, for which the x- (y-)polarized light is significantly transformed to a y- (x-)polarized one with enhanced transmittance in a unidirectional manner, and the bandwidth can be broadened by increasing the cascading number of layers. The polarization conversion rate reaches nearly 100% with a maximum cross-polarization transmission coefficient larger than 0.95. This phenomenon is attributed to the chiral structural arrangement and anisotropic resonance of nanobars, which consequently leads to different cross-polarization conversions between forward and backward incident lights, and thus the unidirectional transmission with an extinction ratio up to 103. These characteristics show application potential in optical nano-devices.

  2. Optical cross-polarization converter with an octave bandwidth based on anisotropic plasmonic meta-surfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Liang; Song, Zhengyong; Huo Liu, Qing

    2015-07-01

    We show that the linear polarization state of electromagnetic waves can be efficiently rotated to its orthogonal direction by an alternative design of anisotropic plasmonic meta-surfaces. Numerical results demonstrate that the reflection coefficient converting to cross-polarization after reflection is larger than 71% within an octave frequency band from ∼232 \\text{THz} to ∼490 \\text{THz} . The designed system is much thinner than conventional geometric-optics devices, and takes favorable advantage of little energy loss.

  3. Nonlinear spectral cleaning of few-cycle pulses via cross-polarized wave (XPW) generation

    NASA Astrophysics Data System (ADS)

    Jullien, A.; Durfee, C. G.; Trisorio, A.; Canova, L.; Rousseau, J.-P.; Mercier, B.; Antonucci, L.; Chériaux, G.; Albert, O.; Lopez-Martens, R.

    2009-08-01

    The characterization of a temporal filter based on cross-polarized wave generation working in the few-optical-cycle regime is presented. We show that this device dramatically improves the spectral quality of the ultrashort seed pulses, opening the way to the production of sub-10 fs pulses with high incoherent and coherent contrast. The dispersion compensation conditions for an optimized behavior of the process are experimentally and theoretically discussed.

  4. DESIGN AND PERFORMANCE OF A LOW-FREQUENCY CROSS-POLARIZED LOG-PERIODIC DIPOLE ANTENNA

    SciTech Connect

    Raja, K. Sasikumar; Kathiravan, C.; Ramesh, R.; Rajalingam, M.; Barve, Indrajit V.

    2013-07-01

    We report the design and performance of a cross-polarized log-periodic dipole (CLPD) antenna for observations of polarized radio emission from the solar corona at low frequencies. The measured isolation between the two mutually orthogonal log-periodic dipole antennas was as low as Almost-Equal-To - 43 dBm in the 65-95 MHz range. We carried out observations of the solar corona at 80 MHz with the above CLPD and successfully recorded circularly polarized emission.

  5. CTS attenuation and cross-polarization measurements at 11.7 GHz

    NASA Technical Reports Server (NTRS)

    Vogel, W. J.; Straiton, A. W.

    1977-01-01

    The results of data obtained 80 days preceding the solar eclipse shutdown of the CTS 11.7 GHz righthand circularly polarized beacon transmitter are presented. Attenuation and cross polarization isolation were measured. It was determined that depolarization presents a serious limitation to satellite system reliability when frequency reuse by polarization diversity is employed. A 27 db isolation margin would reduce reliability below 99.95%. For the same percentage the required fade margin was below 3 db.

  6. Distinct fungal and bacterial δ13C signatures can drive the increase in soil δ13C with depth

    NASA Astrophysics Data System (ADS)

    Kohl, Lukas; Laganièrea, Jérôme; Edwards, Kate A.; Billings, Sharon A.; Morrill, Penny L.; Van Biesen, Geert; Ziegler, Susan E.

    2015-04-01

    Soil microbial biomass is a key precursor of soil organic carbon (SOC), and the enrichment in 13C during SOC diagenesis has been purported to be driven by increasing proportions of microbially derived SOC. Yet, little is known about how the δ13C of soil microbial biomass - and by extension the δ13C of microbial inputs to SOC - vary in space, time, or with the composition of the microbial community. Phospholipid fatty acids (PLFA) can be analyzed to measure the variation of the natural abundance δ13C values of both individual groups of microorganisms and the microbial community as a whole. Here, we show how variations of δ13CPLFA within the soil profile provides insight into C fluxes in undisturbed soils and demonstrate that distinct δ13C of fungal and bacterial biomass and their relative abundance can drive the increase of bulk δ13CSOC with depth. We studied the variation in natural abundance δ13C signatures of PLFA in podzolic soil profiles from mesic boreal forests in Atlantic Canada. Samples from the organic horizons (L,F,H) and the mineral (B; top 10 cm) horizons were analyzed for δ13C values of PLFA specific to fungi, G+ bacteria, or G- bacteria as proxies for the δ13C of the biomass of these groups, and for δ13C values of PLFA produced by a wide range of microorganisms (e.g. 16:0) as a proxy for the δ13C value of microbial biomass as a whole. Results were compared to fungi:bacteria ratios (F:B) and bulk δ13CSOC values. The δ13C values of group-specific PLFA were driven by differences among source organisms, with fungal PLFA consistently depleted (2.1 to 6.4‰) relative to and G+ and G- bacterial PLFA in the same sample. All group-specific PLFA, however, exhibited nearly constant δ13C values throughout the soil profile, apparently unaffected by the over 2.8‰ increase in δ13CSOC with depth from the L to B horizons. This indicates that bulk SOC poorly represents the substrates actually consumed by soil microorganisms in situ. Instead, our

  7. Whole-core analysis by sup 13 C NMR

    SciTech Connect

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

    1991-06-01

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

  8. Accurate quantitative 13C NMR spectroscopy: repeatability over time of site-specific 13C isotope ratio determination.

    PubMed

    Caytan, Elsa; Botosoa, Eliot P; Silvestre, Virginie; Robins, Richard J; Akoka, Serge; Remaud, Gérald S

    2007-11-01

    The stability over time (repeatability) for the determination of site-specific 13C/12C ratios at natural abundance by quantitative 13C NMR spectroscopy has been tested on three probes: enriched bilabeled [1,2-13C2]ethanol; ethanol at natural abundance; and vanillin at natural abundance. It is shown in all three cases that the standard deviation for a series of measurements taken every 2-3 months over periods between 9 and 13 months is equal to or smaller than the standard deviation calculated from 5-10 replicate measurements made on a single sample. The precision which can be achieved using the present analytical 13C NMR protocol is higher than the prerequisite value of 1-2 per thousand for the determination of site-specific 13C/12C ratios at natural abundance (13C-SNIF-NMR). Hence, this technique permits the discrimination of very small variations in 13C/12C ratios between carbon positions, as found in biogenic natural products. This observed stability over time in 13C NMR spectroscopy indicates that further improvements in precision will depend primarily on improved signal-to-noise ratio. PMID:17900175

  9. State-of-the-Art Direct 13C and Indirect 1H-[13C] NMR Spectroscopy In Vivo

    PubMed Central

    de Graaf, Robin A.; Rothman, Douglas L.; Behar, Kevin L.

    2013-01-01

    Carbon-13 NMR spectroscopy in combination with 13C-labeled substrate infusion is a powerful technique to measure a large number of metabolic fluxes non-invasively in vivo. It has been used to quantify glycogen synthesis rates, establish quantitative relationships between energy metabolism and neurotransmission and evaluate the importance of different substrates. All measurements can, in principle, be performed through direct 13C NMR detection or via indirect 1H-[13C] NMR detection of the protons attached to 13C nuclei. The choice for detection scheme and pulse sequence depends on the magnetic field strength, whereas substrate selection depends on the metabolic pathways that are studied. 13C NMR spectroscopy remains a challenging technique that requires several non-standard hardware modifications, infusion of 13C-labeled substrates and sophisticated processing and metabolic modeling. Here the various aspects of direct 13C and indirect 1H-[13C] NMR are reviewed with the aim of providing a practical guide. PMID:21919099

  10. Sensitivity-enhanced IPAP experiments for measuring one-bond 13C '- 13C α and 13C α- 1H α residual dipolar couplings in proteins

    NASA Astrophysics Data System (ADS)

    Ding, Keyang; Gronenborn, Angela M.

    2004-04-01

    Sensitivity-enhanced 2D IPAP experiments using the accordion principle for measuring one-bond 13C '- 13C α and 1H α- 13C α dipolar couplings in proteins are presented. The resolution of the resulting spectra is identical to that of the decoupled HSQC spectra and the sensitivity of the corresponding 1D acquisitions are only slightly lower than those obtained with 3D HNCO and 3D HN(COCA)HA pulse sequences due to an additional delay 2 Δ. For cases of limited resolution in the 2D 15N- 1H N HSQC spectrum the current pulse sequences can easily be modified into 3D versions by introducing a poorly digitized third dimension, if so desired. The experiments described here are a valuable addition to the suites available for determination of residual dipolar couplings in biological systems.

  11. Biodegradation and Mineralization of Polystyrene by Plastic-Eating Mealworms: Part 1. Chemical and Physical Characterization and Isotopic Tests.

    PubMed

    Yang, Yu; Yang, Jun; Wu, Wei-Min; Zhao, Jiao; Song, Yiling; Gao, Longcheng; Yang, Ruifu; Jiang, Lei

    2015-10-20

    Polystyrene (PS) is generally considered to be durable and resistant to biodegradation. Mealworms (the larvae of Tenebrio molitor Linnaeus) from different sources chew and eat Styrofoam, a common PS product. The Styrofoam was efficiently degraded in the larval gut within a retention time of less than 24 h. Fed with Styrofoam as the sole diet, the larvae lived as well as those fed with a normal diet (bran) over a period of 1 month. The analysis of fecula egested from Styrofoam-feeding larvae, using gel permeation chromatography (GPC), solid-state (13)C cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) spectroscopy, and thermogravimetric Fourier transform infrared (TG-FTIR) spectroscopy, substantiated that cleavage/depolymerization of long-chain PS molecules and the formation of depolymerized metabolites occurred in the larval gut. Within a 16 day test period, 47.7% of the ingested Styrofoam carbon was converted into CO2 and the residue (ca. 49.2%) was egested as fecula with a limited fraction incorporated into biomass (ca. 0.5%). Tests with α (13)C- or β (13)C-labeled PS confirmed that the (13)C-labeled PS was mineralized to (13)CO2 and incorporated into lipids. The discovery of the rapid biodegradation of PS in the larval gut reveals a new fate for plastic waste in the environment. PMID:26390034

  12. Probing the nanostructure, interfacial interaction, and dynamics of chitosan-based nanoparticles by multiscale solid-state NMR.

    PubMed

    Wang, Fenfen; Zhang, Rongchun; Wu, Qiang; Chen, Tiehong; Sun, Pingchuan; Shi, An-Chang

    2014-12-10

    Chitosan-based nanoparticles (NPs) are widely used in drug and gene delivery, therapy, and medical imaging, but a molecular-level understanding of the internal morphology and nanostructure size, interface, and dynamics, which is critical for building fundamental knowledge for the precise design and efficient biological application of the NPs, remains a great challenge. Therefore, the availability of a multiscale (0.1-100 nm) and nondestructive analytical technique for examining such NPs is of great importance for nanotechnology. Herein, we present a new multiscale solid-state NMR approach to achieve this goal for the investigation of chitosan-poly(N-3-acrylamidophenylboronic acid) NPs. First, a recently developed (13)C multiple cross-polarization magic-angle spinning (MAS) method enabled fast quantitative determination of the NPs' composition and detection of conformational changes in chitosan. Then, using an improved (1)H spin-diffusion method with (13)C detection and theoretical simulations, the internal morphology and nanostructure size were quantitatively determined. The interfacial coordinated interaction between chitosan and phenylboronic acid was revealed by one-dimensional MAS and two-dimensional (2D) triple-quantum MAS (11)B NMR. Finally, dynamic-editing (13)C MAS and 2D (13)C-(1)H wide-line separation experiments provided details regarding the componential dynamics of the NPs in the solid and swollen states. On the basis of these NMR results, a model of the unique nanostructure, interfacial interaction, and componential dynamics of the NPs was proposed. PMID:25372426

  13. Quality assurance of PASADENA hyperpolarization for 13C biomolecules

    PubMed Central

    Hövener, Jan-Bernd; Chekmenev, Eduard Y.; Harris, Kent C.; Perman, William H.; Tran, Thao T.; Bhattacharya, Pratip

    2009-01-01

    Object Define MR quality assurance procedures for maximal PASADENA hyperpolarization of a biological 13C molecular imaging reagent. Materials and methods An automated PASADENA polarizer and a parahydrogen generator were installed. 13C enriched hydroxyethyl acrylate, 1-13C, 2,3,3-d3 (HEA), was converted to hyperpolarized hydroxyethyl propionate, 1-13C, 2,3,3-d3 (HEP) and fumaric acid, 1-13C, 2,3-d2 (FUM) to hyperpolarized succinic acid, 1-13C, 2,3-d2 (SUC), by reaction with parahydrogen and norbornadiene rhodium catalyst. Incremental optimization of successive steps in PASADENA was implemented. MR spectra and in vivo images of hyperpolarized 13C imaging agents were acquired at 1.5 and 4.7 T. Results Application of quality assurance (QA) criteria resulted in incremental optimization of the individual steps in PASADENA implementation. Optimal hyperpolarization of HEP of P = 20% was achieved by calibration of the NMR unit of the polarizer (B0 field strength ± 0.002 mT). Mean hyperpolarization of SUC, P = [15.3 ± 1.9]% (N = 16) in D2O, and P = [12.8 ± 3.1]% (N = 12) in H2O, was achieved every 5–8 min (range 13–20%). An in vivo 13C succinate image of a rat was produced. Conclusion PASADENA spin hyperpolarization of SUC to 15.3% in average was demonstrated (37,400 fold signal enhancement at 4.7 T). The biological fate of 13C succinate, a normally occurring cellular intermediate, might be monitored with enhanced sensitivity. PMID:19067009

  14. Study of Urban environmental quality through Isotopes δ13C

    NASA Astrophysics Data System (ADS)

    González-Sosa, E.; Mastachi-Loza, C.; Becerril-Piña, R.; Ramos-Salinas, N. M.

    2012-04-01

    Usually, trees with similar pH values on their bark develop epiphytes of similar species, the acidity to be a factor for growth. The aim of the study was evaluate the air quality through isotope δ13C in order to define the levels of environmental quality in the city of Queretaro, Mexico. In this work were collected at least 4 epiphytes positioned in trees of the species Prosopis Laevigata at 25 sites of Queretaro City. The samples were analyzed for trace elements with an inductively coupled plasma atomic emission spectroscopy (ICP). The collecting took place during dry period, in May and early rain June 2011 period, and on four sectors to identify the spatial distribution of pollution, using isotopic analysis of concentration of δ 13C. According with the results there are significant differences among the species in each of the sampled areas. The 5 February Avenue presented greater diversity and richness of δ13C, followed by those who were surveyed in the proximity of the UAQ and finally in the middle-east area. An average value of δ13C-17.92%, followed by those surveyed in the vicinity of the UAQ that correspond to sector I and II with an concentration of δ13C-17.55% and δ13C-17.22%, and finally the samples collected in trees scattered in the East-Sector II and IV with a value of δ13C-17.02% and δ13C-15.62%, respectively. Also were observed differences between the dry and wet period. It is likely that these results of δ 13C in moist period reflect the drag of the isotopes due to rain events that could mark a trend in the dilution of this element, however there is a trend in terms of abundance and composition of finding more impact in those species sampled in dry period, in May and early June 2011.

  15. Determination of NH proton chemical shift anisotropy with 14N-1H heteronuclear decoupling using ultrafast magic angle spinning solid-state NMR

    NASA Astrophysics Data System (ADS)

    Pandey, Manoj Kumar; Nishiyama, Yusuke

    2015-12-01

    The extraction of chemical shift anisotropy (CSA) tensors of protons either directly bonded to 14N nuclei (I = 1) or lying in their vicinity using rotor-synchronous recoupling pulse sequence is always fraught with difficulty due to simultaneous recoupling of 14N-1H heteronuclear dipolar couplings and the lack of methods to efficiently decouple these interactions. This difficulty mainly arises from the presence of large 14N quadrupolar interactions in comparison to the rf field that can practically be achieved. In the present work it is demonstrated that the application of on-resonance 14N-1H decoupling with rf field strength ∼30 times weaker than the 14N quadrupolar coupling during 1H CSA recoupling under ultrafast MAS (90 kHz) results in CSA lineshapes that are free from any distortions from recoupled 14N-1H interactions. With the use of extensive numerical simulations we have shown the applicability of our proposed method on a naturally abundant L-Histidine HCl·H2O sample.

  16. Application of 1H and 23Na magic angle spinning NMR spectroscopy to define the HRBC up-taking of MRI contrast agents

    NASA Astrophysics Data System (ADS)

    Calabi, Luisella; Paleari, Lino; Biondi, Luca; Linati, Laura; De Miranda, Mario; Ghelli, Stefano

    2003-09-01

    The up-take of Gd(III) complexes of BOPTA, DTPA, DOTA, EDTP, HPDO3A, and DOTP in HRBC has been evaluated by measuring the lanthanide induced shift (LIS) produced by the corresponding dysprosium complexes (DC) on the MAS-NMR resonances of water protons and free sodium ions. These complexes are important in their use as MRI contrast agents (MRI-CA) in diagnostics. 1H and 23Na MAS-NMR spectra of HRBC suspension, collected at 9.395 T, show only one signal due to extra- and intra-cellular water (or sodium). In MAS spectra, the presence of DC in a cellular compartment produces the LIS of only the nuclei (water proton or sodium) in that cellular compartment and this LIS can be related to the DC concentrations (by the experimental curves of LIS vs. DC concentrations) collected in the physiological solution. To obtain correct results about LIS, the use of MAS technique is mandatory, because it guarantees the only the nuclei staying in the same cellular compartment where the LC is present show the LIS. In all the cases considered, the addition of the DC to HRBC (100% hematocrit) produced a shift of only the extra-cellular water (or sodium) signal and the gradient of concentration ( GC) between extra- and intra-cellular compartments resulted greater than 100:1, when calculated by means of sodium signals. These high values of GC are direct proofs that none of the tested dysprosium complexes crosses the HRBC membrane. Since the DC are iso-structural to the gadolinium complexes the corresponding gadolinium ones (MRI-CA) do not cross the HRBC membrane and, consequently, they are not up-taken in HRBC. The GC values calculated by means of water proton signals resulted much lower than those obtained by sodium signals. This proves that the choice of the isotope is a crucial step in order to use this method in the best way. In fact, GC value depends on the lowest detectable LIS which, in turn, depends on the nature of the LC (lanthanide complex) and the observed isotopes.

  17. Relative merits of rCWA and XiX heteronuclear spin decoupling in solid-state magic-angle-spinning NMR spectroscopy: A bimodal Floquet analysis

    NASA Astrophysics Data System (ADS)

    Equbal, Asif; Leskes, Michal; Nielsen, Niels Chr.; Madhu, P. K.; Vega, Shimon

    2016-02-01

    We present a bimodal Floquet analysis of the recently introduced refocused continuous wave (rCW) solid-state NMR heteronuclear dipolar decoupling method and compare it with the similar looking X-inverse X (XiX) scheme. The description is formulated in the rf interaction frame and is valid for both finite and ideal π pulse rCW irradiation that forms the refocusing element in the rCW scheme. The effective heteronuclear dipolar coupling Hamiltonian up to first order is described. The analysis delineates the difference between the two sequences to different orders of their Hamiltonians for both diagonal and off-diagonal parts. All the resonance conditions observed in experiments and simulations have been characterised and their influence on residual line broadening is highlighted. The theoretical comparison substantiates the numerical simulations and experimental results to a large extent.

  18. Multiple Acquisition of Magic Angle Spinning Solid-State NMR Experiments Using One Receiver: Application to Microcrystalline and Membrane Protein Preparations

    PubMed Central

    Gopinath, T.; Veglia, Gianluigi

    2015-01-01

    Solid-State NMR spectroscopy of proteins is a notoriously low-throughput technique. Relatively low-sensitivity and poor resolution of protein samples require long acquisition times for multidimensional NMR experiments. To speed up data acquisition, we developed a family of experiments called Polarization Optimized Experiments (POE), in which we utilized the orphan spin operators that are discarded in classical multidimensional NMR experiments, recovering them to allow simultaneous acquisition of multiple 2D and 3D experiments, all while using conventional probes with spectrometers equipped with one receiver. POEs allow the concatenation of multiple 2D or 3D pulse sequences into a single experiment, thus potentially combining all of the aforementioned advances, boosting the capability of ssNMR spectrometers at least two-fold without the addition of any hardware. In this Perspective, we describe the first generation of POEs, such as dual acquisition MAS (or DUMAS) methods, and then illustrate the evolution of these experiments into MEIOSIS, a method that enables the simultaneous acquisition of multiple 2D and 3D spectra. Using these new pulse schemes for the solid-state NMR investigation of biopolymers makes it possible to obtain sequential resonance assignments, as well as distance restraints, in about half the experimental time. While designed for acquisition of heteronuclei, these new experiments can be easily implemented for proton detection and coupled with other recent advancements, such as dynamic polarization, to improve signal to noise. Finally, we illustrate the application of these methods to microcrystalline protein preparations as well as single and multi-span membrane proteins reconstituted in lipid membranes. PMID:25797011

  19. Studying the Conformation of a Silaffin-Derived Pentalysine Peptide Embedded in Bioinspired Silica using Solution and Dynamic Nuclear Polarization Magic-Angle Spinning NMR.

    PubMed

    Geiger, Yasmin; Gottlieb, Hugo E; Akbey, Ümit; Oschkinat, Hartmut; Goobes, Gil

    2016-05-01

    Smart materials are created in nature at interfaces between biomolecules and solid materials. The ability to probe the structure of functional peptides that engineer biogenic materials at this heterogeneous setting can be facilitated tremendously by use of DNP-enhanced solid-state NMR spectroscopy. This sensitive NMR technique allows simple and quick measurements, often without the need for isotope enrichment. Here, it is used to characterize a pentalysine peptide, derived from a diatom's silaffin protein. The peptide accelerates the formation of bioinspired silica and gets embedded inside the material as it is formed. Two-dimensional DNP MAS NMR of the silica-bound peptide and solution NMR of the free peptide are used to derive its secondary structure in the two states and to pinpoint some subtle conformational changes that the peptide undergoes in order to adapt to the silica environment. In addition, interactions between abundant lysine residues and silica surface are identified, and proximity of other side chains to silica and to neighboring peptide molecules is discussed. PMID:26451953

  20. Effect of organochlorine pesticides exposure on the maize root metabolome assessed using high-resolution magic-angle spinning (1)H NMR spectroscopy.

    PubMed

    Blondel, Claire; Khelalfa, Farid; Reynaud, Stéphane; Fauvelle, Florence; Raveton, Muriel

    2016-07-01

    (1)H-HRMAS NMR-based metabolomics was used to better understand the toxic effects on maize root tips of organochlorine pesticides (OCPs), namely lindane (γHCH) and chlordecone (CLD). Maize seedlings were exposed to 2.5 μM γHCH (mimicking basic environmental contaminations) for 7 days and compared to 2.5 μM CLD and 25 μM γHCH for 7 days (mimicking hot spot contaminations). The (1)H-HRMAS NMR-based metabolomic profiles provided details of the changes in carbohydrates, amino acids, tricarboxylic acid (TCA) cycle intermediates and fatty acids with a significant separation between the control and OCP-exposed root tips. First of all, alterations in the balance between glycolysis/gluconeogenesis were observed with sucrose depletion and with dose-dependent fluctuations in glucose content. Secondly, observations indicated that OCPs might inactivate the TCA cycle, with sizeable succinate and fumarate depletion. Thirdly, disturbances in the amino acid composition (GABA, glutamine/glutamate, asparagine, isoleucine) reflected a new distribution of internal nitrogen compounds under OCP stress. Finally, OCP exposure caused an increase in fatty acid content, concomitant with a marked rise in oxidized fatty acids which could indicate failures in cell integrity and vitality. Moreover, the accumulation of asparagine and oxidized fatty acids with the induction of LOX3 transcription levels under OCP exposure highlighted an induction of protein and lipid catabolism. The overall data indicated that the effect of OCPs on primary metabolism could have broader physiological consequences on root development. Therefore, (1)H-HRMAS NMR metabolomics is a sensitive tool for understanding molecular disturbances under OCP exposure and can be used to perform a rapid assessment of phytotoxicity. PMID:27131813

  1. In vivo and ex vivo high-resolution ¹H NMR in biological systems using low-speed magic angle spinning

    SciTech Connect

    Wind, Robert A.; Hu, Jian Zhi

    2006-11-30

    Metabolism refers to the network of interacting chemical processes that constitute (and define) cell life and provide the chemical energy and materials required for all work at the cellular and whole-organism levels. These processes take the form of metabolic pathways, an interdependent network of chemical reactions that is regulated by catalytic enzymes. Metabolites are chemical compounds that participate as reactants (substrates), intermediate compounds, or byproducts in a cellular metabolic pathway, and include carbon compounds with a molecular weight typically in the range 100-1000, which are usually present as solutes in the cytoplasm. Four broad classes of such metabolites can be distinguished [Alberts et al 1989]: sugars, the food molecules of the cell; fatty acids, present as droplets of triglyceride molecules in the cells and serving as energy resources, and as phospholipids present in the cell membranes; amino acids, the subunits of proteins; and nucleotides, the subunits of RNA and DNA, that can also act as carriers of chemical energy (adenosine triphosphate, i.e. ATP). Metabolomics involves characterizing the metabolic composition of a single cell type measured under defined physiological conditions and can be considered as analogous to genomics or proteomics [Lindon et al 2003]. Metabonomics involves quantitative studies of the changes in the metabolic profiles of living systems in response to patho-physiological stimuli or genetic modification [Nicholson et al 1999, Lindon 2003]. Metabolic changes are the earliest cellular response to environmental or physiological changes such as toxin exposure or disease state, so a snapshot of the various metabolite concentrations within cells, tissues, or biofluids, and how these concentrations change under different physiological, pharmacological and toxicological conditions provides valuable information that is complementary to gene expression and proteomic studies. Hence metabol(n)omics may be capable of, e.g., detecting and diagnosing a disease or evaluating the efficacy of therapy in an early stage, and provide powerful new tools for gaining insight into functional biology.

  2. Multiple acquisition of magic angle spinning solid-state NMR experiments using one receiver: Application to microcrystalline and membrane protein preparations

    NASA Astrophysics Data System (ADS)

    Gopinath, T.; Veglia, Gianluigi

    2015-04-01

    Solid-state NMR spectroscopy of proteins is a notoriously low-throughput technique. Relatively low-sensitivity and poor resolution of protein samples require long acquisition times for multidimensional NMR experiments. To speed up data acquisition, we developed a family of experiments called Polarization Optimized Experiments (POE), in which we utilized the orphan spin operators that are discarded in classical multidimensional NMR experiments, recovering them to allow simultaneous acquisition of multiple 2D and 3D experiments, all while using conventional probes with spectrometers equipped with one receiver. POE allow the concatenation of multiple 2D or 3D pulse sequences into a single experiment, thus potentially combining all of the aforementioned advances, boosting the capability of ssNMR spectrometers at least two-fold without the addition of any hardware. In this perspective, we describe the first generation of POE, such as dual acquisition MAS (or DUMAS) methods, and then illustrate the evolution of these experiments into MEIOSIS, a method that enables the simultaneous acquisition of multiple 2D and 3D spectra. Using these new pulse schemes for the solid-state NMR investigation of biopolymers makes it possible to obtain sequential resonance assignments, as well as distance restraints, in about half the experimental time. While designed for acquisition of heteronuclei, these new experiments can be easily implemented for proton detection and coupled with other recent advancements, such as dynamic nuclear polarization (DNP), to improve signal to noise. Finally, we illustrate the application of these methods to microcrystalline protein preparations as well as single and multi-span membrane proteins reconstituted in lipid membranes.

  3. Investigation of Mechanical Activation on Li-N-H Systems Using 6Li Magic Angle Spinning Nuclear Magnetic Resonance at Ultra-High Field

    SciTech Connect

    Hu, Jian Zhi; Kwak, Ja Hun; Yang, Zhenguo; Osborn, William; Markmaitree, Tippawan; Shaw, Leonard D.

    2008-07-15

    Abstract The significantly enhanced spectral resolution in the 6Li MAS NMR spectra of Li-N-H systems at ultra-high field of 21.1 tesla is exploited, for the first time, to study the detailed electronic and chemical environmental changes associated with mechanical activation of Li-N-H system using high energy balling milling. Complementary to ultra-high field studies, the hydrogen discharge dynamics are investigated using variable temperature in situ 1H MAS NMR at 7.05 tesla field. The significantly enhanced spectral resolution using ultra-high filed of 21.1 tesla was demonstrated along with several major findings related to mechanical activation, including the upfield shift of the resonances in 6Li MAS spectra induced by ball milling, more efficient mechanical activation with ball milling at liquid nitrogen temperature than with ball milling at room temperature, and greatly enhanced hydrogen discharge exhibited by the liquid nitrogen ball milled samples.

  4. Strategy for Enhancement of (13)C-Photo-CIDNP NMR Spectra by Exploiting Fractional (13)C-Labeling of Tryptophan.

    PubMed

    Eisenreich, Wolfgang; Joshi, Monika; Illarionov, Boris; Kacprzak, Sylwia; Lukaschek, Michail; Kothe, Gerd; Budisa, Nediljko; Fischer, Markus; Bacher, Adelbert; Weber, Stefan

    2015-10-29

    The photo-CIDNP effect has proven to be useful to strongly enhance NMR signals of photochemically active proteins simply by irradiation with light. The evolving characteristic patterns of enhanced absorptive and emissive NMR lines can be exploited to elucidate the photochemistry and photophysics of light-driven protein reactions. In particular, by the assignment of (13)C NMR resonances, redox-active amino acids may be identified and thereby electron-transfer pathways unraveled, in favorable cases, even with (13)C at natural abundance. If signal enhancement is weak, uniform (13)C isotope labeling is traditionally applied to increase the signal strength of protein (13)C NMR. However, this typically leads to cross relaxation, which transfers light-induced nuclear-spin polarization to adjacent (13)C nuclei, thereby preventing an unambiguous analysis of the photo-CIDNP effect. In this contribution, two isotope labeling strategies are presented; one leads to specific but ubiquitous (13)C labeling in tryptophan, and the other is based on fractional isotope labeling affording sets of isotopologs with low probability of next-neighbor isotope accumulation within individual tryptophan molecules. Consequently, cross relaxation is largely avoided while the signal enhancement by (13)C enrichment is preserved. This results in significantly simplified polarization patterns that are easier to analyze with respect to the generation of light-generated nuclear-spin polarization. PMID:26244593

  5. IRMS detection of testosterone manipulated with 13C labeled standards in human urine by removing the labeled 13C.

    PubMed

    Wang, Jingzhu; Yang, Rui; Yang, Wenning; Liu, Xin; Xing, Yanyi; Xu, Youxuan

    2014-12-10

    Isotope ratio mass spectrometry (IRMS) is applied to confirm testosterone (T) abuse by determining the carbon isotope ratios (δ(13)C value). However, (13)C labeled standards can be used to control the δ(13)C value and produce manipulated T which cannot be detected by the current method. A method was explored to remove the (13)C labeled atom at C-3 from the molecule of androsterone (Andro), the metabolite of T in urine, to produce the resultant (A-nor-5α-androstane-2,17-dione, ANAD). The difference in δ(13)C values between Andro and ANAD (Δδ(13)CAndro-ANAD, ‰) would change significantly in case manipulated T is abused. Twenty-one volunteers administered T manipulated with different (13)C labeled standards. The collected urine samples were analyzed with the established method, and the maximum value of Δδ(13)CAndro-ANAD post ingestion ranged from 3.0‰ to 8.8‰. Based on the population reference, the cut-off value of Δδ(13)CAndro-ANAD for positive result was suggested as 1.2‰. The developed method could be used to detect T manipulated with 3-(13)C labeled standards. PMID:25441891

  6. Detection of inflammatory cell function using 13C magnetic resonance spectroscopy of hyperpolarized [6-13C]-arginine

    PubMed Central

    Najac, Chloé; Chaumeil, Myriam M.; Kohanbash, Gary; Guglielmetti, Caroline; Gordon, Jeremy W.; Okada, Hideho; Ronen, Sabrina M.

    2016-01-01

    Myeloid-derived suppressor cells (MDSCs) are highly prevalent inflammatory cells that play a key role in tumor development and are considered therapeutic targets. MDSCs promote tumor growth by blocking T-cell-mediated anti-tumoral immune response through depletion of arginine that is essential for T-cell proliferation. To deplete arginine, MDSCs express high levels of arginase, which catalyzes the breakdown of arginine into urea and ornithine. Here, we developed a new hyperpolarized 13C probe, [6-13C]-arginine, to image arginase activity. We show that [6-13C]-arginine can be hyperpolarized, and hyperpolarized [13C]-urea production from [6-13C]-arginine is linearly correlated with arginase concentration in vitro. Furthermore we show that we can detect a statistically significant increase in hyperpolarized [13C]-urea production in MDSCs when compared to control bone marrow cells. This increase was associated with an increase in intracellular arginase concentration detected using a spectrophotometric assay. Hyperpolarized [6-13C]-arginine could therefore serve to image tumoral MDSC function and more broadly M2-like macrophages. PMID:27507680

  7. Biosynthetic uniform 13C,15N-labelling of zervamicin IIB. Complete 13C and 15N NMR assignment.

    PubMed

    Ovchinnikova, Tatyana V; Shenkarev, Zakhar O; Yakimenko, Zoya A; Svishcheva, Natalia V; Tagaev, Andrey A; Skladnev, Dmitry A; Arseniev, Alexander S

    2003-01-01

    Zervamicin IIB is a member of the alpha-aminoisobutyric acid containing peptaibol antibiotics. A new procedure for the biosynthetic preparation of the uniformly 13C- and 15N-enriched peptaibol is described This compound was isolated from the biomass of the fungus-producer Emericellopsis salmosynnemata strain 336 IMI 58330 obtained upon cultivation in the totally 13C, 15N-labelled complete medium. To prepare such a medium the autolysed biomass and the exopolysaccharides of the obligate methylotrophic bacterium Methylobacillus flagellatus KT were used. This microorganism was grown in totally 13C, 15N-labelled minimal medium containing 13C-methanol and 15N-ammonium chloride as the only carbon and nitrogen sources. Preliminary NMR spectroscopic analysis indicated a high extent of isotope incorporation (> 90%) and led to the complete 13C- and 15N-NMR assignment including the stereospecific assignment of Aib residues methyl groups. The observed pattern of the structurally important secondary chemical shifts of 1H(alpha), 13C=O and 13C(alpha) agrees well with the previously determined structure of zervamicin IIB in methanol solution. PMID:14658801

  8. Anomalous 13C enrichment in modern marine organic carbon

    USGS Publications Warehouse

    Arthur, M.A.; Dean, W.E.; Claypool, G.E.

    1985-01-01

    Marine organic carbon is heavier isotopically (13C enriched) than most land-plant or terrestrial organic C1. Accordingly, ??13C values of organic C in modern marine sediments are routinely interpreted in terms of the relative proportions of marine and terrestrial sources of the preserved organic matter2,3. When independent geochemical techniques are used to evaluate the source of organic matter in Cretaceous or older rocks, those rocks containing mostly marine organic C are found typically to have lighter (more-negative) ??13C values than rocks containing mostly terrestrial organic C. Here we conclude that marine photosynthesis in mid-Cretaceous and earlier oceans generally resulted in a greater fractionation of C isotopes and produced organic C having lighter ??13C values. Modern marine photosynthesis may be occurring under unusual geological conditions (higher oceanic primary production rates, lower PCO2) that limit dissolved CO2 availability and minimize carbon isotope fractionation4. ?? 1985 Nature Publishing Group.

  9. Field measurements of del13C in ecosystem respiration

    NASA Astrophysics Data System (ADS)

    van Asperen, Hella; Sabbatini, Simone; Nicolini, Giacomo; Warneke, Thorsten; Papale, Dario; Notholt, Justus

    2014-05-01

    Stable carbon isotope del13C-measurements are extensively used to study ecological and biogeochemical processes in ecosystems. Above terrestrial ecosystems, atmospheric del13C can vary largely due to photosynthetic fractionation. Photosynthetic processes prefer the uptake of the lighter isotope 12C (in CO2), thereby enriching the atmosphere in 13C and depleting the ecosystem carbon. At night, when ecosystem respiratory fluxes are dominant, 13C-depleted CO2 is respired and thereby depletes the atmospheric del13C-content. Different ecosystems and different parts of one ecosystem (type of plant, leaves, and roots) fractionate and respire with a different del13C-ratio signature. By determining the del13C-signature of ecosystem respiration in temporal and spatial scale, an analysis can be made of the composition of respiratory sources of the ecosystem. A field study at a dry cropland after harvest (province of Viterbo, Lazio, Italy) was performed in the summer of 2013. A FTIR (Fourier Transform Infrared Spectrometer) was set up to continuously measure CO2-, CH4-, N2O-, CO- and del13C-concentrations. The FTIR was connected to 2 different flux measurements systems: a Flux Gradient system (sampling every half hour at 1.3m and 4.2m) and 2 flux chambers (measured every hour), providing a continuous data set of the biosphere-atmosphere gas fluxes and of the gas concentrations at different heights. Keeling plot intercept values of respiratory CO2, measured by the Flux Gradient system at night, were determined to be between -25‰ and -20‰. Keeling plot intercept values of respiratory CO2, measured by the flux chamber system, varied between -24‰ and -29‰, and showed a clear diurnal pattern, suggesting different (dominant) respiratory processes between day and night.

  10. Abundance anomaly of the 13C species of CCH

    NASA Astrophysics Data System (ADS)

    Sakai, N.; Saruwatari, O.; Sakai, T.; Takano, S.; Yamamoto, S.

    2010-03-01

    Aims: We have observed the N = 1-0 lines of CCH and its 13C isotopic species toward a cold dark cloud, TMC-1 and a star-forming region, L1527, to investigate the 13C abundances and formation pathways of CCH. Methods: The observations have been carried out with the IRAM 30 m telescope. Results: We have successfully detected the lines of 13CCH and C13CH toward the both sources and found a significant intensity difference between the two 13C isotopic species. The [C13CH] /[13CCH] abundance ratios are 1.6 ± 0.4 (3σ) and 1.6 ± 0.1 (3σ) for TMC-1 and L1527, respectively. The abundance difference between C13CH and 13CCH means that the two carbon atoms of CCH are not equivalent in the formation pathway. On the other hand, the [CCH]/[C13CH] and [CCH]/[13CCH] ratios are evaluated to be larger than 170 and 250 toward TMC-1, and to be larger than 80 and 135 toward L1527, respectively. Therefore, both of the 13C species are significantly diluted in comparison with the interstellar 12C/13C ratio of 60. The dilution is discussed in terms of a behavior of 13C in molecular clouds.

  11. Single Shot Polarization Characterization of XUV FEL Pulses from Crossed Polarized Undulators

    PubMed Central

    Ferrari, E.; Allaria, E.; Buck, J.; De Ninno, G.; Diviacco, B.; Gauthier, D.; Giannessi, L.; Glaser, L.; Huang, Z.; Ilchen, M.; Lambert, G.; Lutman, A. A.; Mahieu, B.; Penco, G.; Spezzani, C.; Viefhaus, J.

    2015-01-01

    Polarization control is a key feature of light generated by short-wavelength free-electron lasers. In this work, we report the first experimental characterization of the polarization properties of an extreme ultraviolet high gain free-electron laser operated with crossed polarized undulators. We investigate the average degree of polarization and the shot-to-shot stability and we analyze aspects such as existing possibilities for controlling and switching the polarization state of the emitted light. The results are in agreement with predictions based on Gaussian beams propagation. PMID:26314764

  12. Characterization of atherosclerotic plaques by cross-polarization optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Gubarkova, Ekaterina V.; Dudenkova, Varvara V.; Feldchtein, Felix I.; Timofeeva, Lidia B.; Kiseleva, Elena B.; Kuznetsov, Sergei S.; Moiseev, Alexander A.; Gelikonov, Gregory V.; Vitkin, Alex I.; Gladkova, Natalia D.

    2016-02-01

    We combined cross-polarization optical coherence tomography (CP OCT) and non-linear microscopy based on second harmonic generation (SHG) and two-photon-excited fluorescence (2PEF) to assess collagen and elastin fibers in the development of the atherosclerotic plaque (AP). The study shows potential of CP OCT for the assessment of collagen and elastin fibers condition in atherosclerotic arteries. Specifically, the additional information afforded by CP OCT, related to birefringence and cross-scattering properties of arterial tissues, may improve the robustness and accuracy of assessment about the microstructure and composition of the plaque for different stages of atherosclerosis.

  13. Single shot polarization characterization of XUV FEL pulses from crossed polarized undulators

    DOE PAGESBeta

    Ferrari, E.; Allaria, E.; Buck, J.; De Ninno, G.; Diviacco, B.; Gauthier, D.; Giannessi, L.; Glaser, L.; Huang, Z.; Ilchen, M.; et al

    2015-08-28

    Polarization control is a key feature of light generated by short-wavelength free-electron lasers. In this work, we report the first experimental characterization of the polarization properties of an extreme ultraviolet high gain free-electron laser operated with crossed polarized undulators. We research the average degree of polarization and the shot-to-shot stability and we analyze aspects such as existing possibilities for controlling and switching the polarization state of the emitted light. The results are in agreement with predictions based on Gaussian beams propagation.

  14. Observation of solid-state 103Rh NMR by cross-polarization.

    PubMed

    Phillips, Brian L; Houston, Jacqueline R; Feng, Jian; Casey, William H

    2006-03-29

    Using 103Rh[1H] cross-polarization (CP) methods, we have obtained solid-state 103Rh NMR spectra for diamagnetic Rh(III) compounds. The isotropic chemical shift and chemical shift anisotropy (CSA) are reported for a crystalline form of the dihydroxy-bridged Rh(III) dimer and for a salt of the oxo-centered acetate-bridged Rh(III) trimer, from analysis of conventional CP/MAS spectra. Comparison of the CP kinetics of the dimer with new crystal structure data suggests a strategy for predicting 103Rh CP/MAS properties in solids. PMID:16551090

  15. Transport and imaging of brute-force (13)C hyperpolarization.

    PubMed

    Hirsch, Matthew L; Smith, Bryce A; Mattingly, Mark; Goloshevsky, Artem G; Rosay, Melanie; Kempf, James G

    2015-12-01

    We demonstrate transport of hyperpolarized frozen 1-(13)C pyruvic acid from its site of production to a nearby facility, where a time series of (13)C images was acquired from the aqueous dissolution product. Transportability is tied to the hyperpolarization (HP) method we employ, which omits radical electron species used in other approaches that would otherwise relax away the HP before reaching the imaging center. In particular, we attained (13)C HP by 'brute-force', i.e., using only low temperature and high-field (e.g., T<∼2K and B∼14T) to pre-polarize protons to a large Boltzmann value (∼0.4% (1)H polarization). After polarizing the neat, frozen sample, ejection quickly (<1s) passed it through a low field (B<100G) to establish the (1)H pre-polarization spin temperature on (13)C via the process known as low-field thermal mixing (yielding ∼0.1% (13)C polarization). By avoiding polarization agents (a.k.a. relaxation agents) that are needed to hyperpolarize by the competing method of dissolution dynamic nuclear polarization (d-DNP), the (13)C relaxation time was sufficient to transport the sample for ∼10min before finally dissolving in warm water and obtaining a (13)C image of the hyperpolarized, dilute, aqueous product (∼0.01% (13)C polarization, a >100-fold gain over thermal signals in the 1T scanner). An annealing step, prior to polarizing the sample, was also key for increasing T1∼30-fold during transport. In that time, HP was maintained using only modest cryogenics and field (T∼60K and B=1.3T), for T1((13)C) near 5min. Much greater time and distance (with much smaller losses) may be covered using more-complete annealing and only slight improvements on transport conditions (e.g., yielding T1∼5h at 30K, 2T), whereas even intercity transfer is possible (T1>20h) at reasonable conditions of 6K and 2T. Finally, it is possible to increase the overall enhancement near d-DNP levels (i.e., 10(2)-fold more) by polarizing below 100mK, where nanoparticle

  16. Transport and imaging of brute-force 13C hyperpolarization

    NASA Astrophysics Data System (ADS)

    Hirsch, Matthew L.; Smith, Bryce A.; Mattingly, Mark; Goloshevsky, Artem G.; Rosay, Melanie; Kempf, James G.

    2015-12-01

    We demonstrate transport of hyperpolarized frozen 1-13C pyruvic acid from its site of production to a nearby facility, where a time series of 13C images was acquired from the aqueous dissolution product. Transportability is tied to the hyperpolarization (HP) method we employ, which omits radical electron species used in other approaches that would otherwise relax away the HP before reaching the imaging center. In particular, we attained 13C HP by 'brute-force', i.e., using only low temperature and high-field (e.g., T < ∼2 K and B ∼ 14 T) to pre-polarize protons to a large Boltzmann value (∼0.4% 1H polarization). After polarizing the neat, frozen sample, ejection quickly (<1 s) passed it through a low field (B < 100 G) to establish the 1H pre-polarization spin temperature on 13C via the process known as low-field thermal mixing (yielding ∼0.1% 13C polarization). By avoiding polarization agents (a.k.a. relaxation agents) that are needed to hyperpolarize by the competing method of dissolution dynamic nuclear polarization (d-DNP), the 13C relaxation time was sufficient to transport the sample for ∼10 min before finally dissolving in warm water and obtaining a 13C image of the hyperpolarized, dilute, aqueous product (∼0.01% 13C polarization, a >100-fold gain over thermal signals in the 1 T scanner). An annealing step, prior to polarizing the sample, was also key for increasing T1 ∼ 30-fold during transport. In that time, HP was maintained using only modest cryogenics and field (T ∼ 60 K and B = 1.3 T), for T1(13C) near 5 min. Much greater time and distance (with much smaller losses) may be covered using more-complete annealing and only slight improvements on transport conditions (e.g., yielding T1 ∼ 5 h at 30 K, 2 T), whereas even intercity transfer is possible (T1 > 20 h) at reasonable conditions of 6 K and 2 T. Finally, it is possible to increase the overall enhancement near d-DNP levels (i.e., 102-fold more) by polarizing below 100 mK, where

  17. Synthesis and evaluation of nitroxide-based oligoradicals for low-temperature dynamic nuclear polarization in solid state NMR

    NASA Astrophysics Data System (ADS)

    Yau, Wai-Ming; Thurber, Kent R.; Tycko, Robert

    2014-07-01

    We describe the synthesis of new nitroxide-based biradical, triradical, and tetraradical compounds and the evaluation of their performance as paramagnetic dopants in dynamic nuclear polarization (DNP) experiments in solid state nuclear magnetic resonance (NMR) spectroscopy with magic-angle spinning (MAS). Under our experimental conditions, which include temperatures in the 25-30 K range, a 9.4 T magnetic field, MAS frequencies of 6.2-6.8 kHz, and microwave irradiation at 264.0 GHz from a 800 mW extended interaction oscillator source, the most effective compounds are triradicals that are related to the previously-described compound DOTOPA-TEMPO (see Thurber et al., 2010), but have improved solubility in glycerol/water solvent near neutral pH. Using these compounds at 30 mM total nitroxide concentration, we observe DNP enhancement factors of 92-128 for cross-polarized 13C NMR signals from 15N,13C-labeled melittin in partially protonated glycerol/water, and build-up times of 2.6-3.8 s for 1H spin polarizations. Net sensitivity enhancements with biradical and tetraradical dopants, taking into account absolute 13C NMR signal amplitudes and build-up times, are approximately 2-4 times lower than with the best triradicals.

  18. Investigation of a naphthalene pitch by high-resolution solid-state dynamic nuclear polarization.

    PubMed

    Zhou, J; Yang, B; Hu, J; Hu, H; Li, L; Qiu, J; Zeng, F; Ye, C

    1996-04-01

    The possibility of applying the dynamic nuclear polarization (DNP) technique to a study of char is explored with a naphthalene-derived pitch. It is shown that a 13C DNP enhancement factor of about 10(2) is obtained when the polarization is directly transferred from the unpaired electrons to the 13C nuclei. An undistorted spectrum with an enhancement factor of 8 is obtained by the DNP cross-polarization magic-angle spinning nuclear magnetic resonance (DNP-CP-MAS NMR) method. With such a high increase in S/N, it is possible to measure the 13C polarization time (Tp) and the spin-lattice relaxation time (T1) of the system in a reasonable experimental time. The resultant values are Tp = 19 s and T1 = 38 s, respectively. Based on the DNP enhancement as a function of the microwave frequency, it is found that the predominant DNP mechanism in the pitch is the solid-state effect. PMID:8784951

  19. Accelerating Nuclear Magnetic Resonance (NMR) Analysis of Soil Organic Matter with Dynamic Nuclear Polarization (DNP) Enhancement

    NASA Astrophysics Data System (ADS)

    Normand, A. E.; Smith, A. N.; Long, J. R.; Reddy, K. R.

    2014-12-01

    13C magic angle spinning (MAS) solid state Nuclear Magnetic Resonance (ssNMR) has become an essential tool for discerning the chemical composition of soil organic matter (SOM). However, the technique is limited due to the inherent insensitivity of NMR resulting in long acquisition times, especially for low carbon (C) soil. The pursuits of higher magnetic fields or concentrating C with hydrofluoric acid are limited solutions for signal improvement. Recent advances in dynamic nuclear polarization (DNP) have addressed the insensitivity of NMR. DNP utilizes the greater polarization of an unpaired electron in a given magnetic field and transfers that polarization to an NMR active nucleus of interest via microwave irradiation. Signal enhancements of up to a few orders of magnitude have been achieved for various DNP experiments. In this novel study, we conduct DNP 13C cross-polarization (CP) MAS ssNMR experiments of SOM varying in soil C content and chemical composition. DNP signal enhancements reduce the experiment run time allowing samples with low C to be analyzed in hours rather than days. We compare 13C CP MAS ssNMR of SOM with multiple magnetic field strengths, hydrofluoric acid treatment, and novel DNP approaches. We also explore DNP surface enhanced NMR Spectroscopy (SENP) to determine the surface chemistry of SOM. The presented results and future DNP MAS ssNMR advances will lead to further understanding of the nature and processes of SOM.

  20. Stable isotope ratios of carbon and nitrogen in pollen grains in order to characterize plant functional groups and photosynthetic pathway types.

    PubMed

    Descolas-Gros, Chantal; Schölzel, Christian

    2007-01-01

    Measurements of delta(13)C, delta(15)N and C : N ratios on modern pollen grains from temperate plants, including whole grains as well as extracted sporopollenin, were analysed in order to characterize physiological plant types at the pollen level and to determine the variation of these parameters in modern pollen grains of the same climatic area. Measurements are presented for 95 batches of whole modern pollen from 58 temperate species and on the stable fraction of modern pollen grains, chemically extracted sporopollenin, for two modern species. Fourier transform infrared (FTIR) and cross-polarization and magic-angle spinning (CP/MAS) sporopollenin spectra were conducted in parallel. C(3) and C(4) plants can be separated by delta(13)C measurements based on pollen. Probabilistic assignments to plant functional groups (herbaceous, deciduous woody, evergreen woody) of C(3) plants by the means of a discriminant analysis can be made for C : N ratios and for delta(13)C. The results are related to other studies on sporopollenin in order to use this method in future work on fossil samples. Stable isotope measurements on pollen allow improved pollen diagrams, including forms that cannot be differentiated at species level, increasing the accuracy and resolution of plant physiological type distribution in quaternary and older fossil sediments. PMID:17888118

  1. A 13C-NMR study of azacryptand complexes.

    PubMed

    Wild, Aljoscha A C; Fennell, Kevin; Morgan, Grace G; Hewage, Chandralal M; Malthouse, J Paul G

    2014-09-28

    An azacryptand has been solubilised in aqueous media containing 50% (v/v) dimethyl sulphoxide. (13)C-NMR has been used to determine how the azacryptand is affected by zinc binding at pH 10. Using (13)C-NMR and (13)C-enriched bicarbonate we have been able to observe the formation of 4 different carbamate derivatives of the azacryptand at pH 10. The azacryptand was shown to solubilise zinc or cadmium at alkaline pHs. Two moles of zinc are bound per mole of azacryptand and this complex binds 1 mole of carbonate. By replacing the zinc with cadmium-113 we have shown that the (13)C-NMR signal of the (13)C-enriched carbon of the bound carbonate is split into two triplets at 2.2 °C. This shows that two cadmium complexes are formed and in each of these complexes the carbonate group is bound by two magnetically equivalent metal ions. It also demonstrates that these cadmium complexes are not in fast exchange. From temperature studies we show that in the zinc complexes both complexes are in fast exchange with each other but are in slow exchange with free bicarbonate. HOESY is used to determine the position of the carbonate carbon in the complex. The solution and crystal structures of the zinc-carbonate-azacryptand complexes are compared. PMID:25091182

  2. Synthesis and applications of {sup 13}C glycerol

    SciTech Connect

    Stocking, E.; Khalsa, O.; Martinez, R.A.; Silks, L.A. III

    1994-12-01

    Due in part to the use of labeled glycerol for the {sup 13}C enrichment of biomolecules, we are currently developing new synthetic routes to various isotopomers of glycerol. Judging from our experience, traditional methods of glycerol synthesis are not easily adapted for isotopic enrichment and/or have poor overall yields (12 to 15%). Furthermore, the use of glycerol for enrichment can be prohibitively expensive and its availability is limited by the level of demand. We are presently developing a short de novo synthesis of glycerol from carbon dioxide ({approximately}53% overall yield for four steps) and are examining the feasibility of synthesizing site-specific {sup 13}C-labeled glycerol and dihydroxyacetone (DHA) from labeled methanol and carbon dioxide. One application of {sup 13}C glycerol we have examined is enzymatic conversion of glycerol to glyceraldehyde-3-monophosphate or dihydroxyacetone monophosphate (DHAP) with yields ranging from 25 to 50% (as determined by NMR spectroscopy). We are also pursuing the chemical conversion of {sup 13}C-labeled DHA to DHAP. We are especially interested in {sup 13}C-labeled DHAP because we are investigating its use as a chemo-enzymatic precursor for both labeled 2-deoxyribose and 2-deoxyribonucleic acids.

  3. A scientific workflow framework for (13)C metabolic flux analysis.

    PubMed

    Dalman, Tolga; Wiechert, Wolfgang; Nöh, Katharina

    2016-08-20

    Metabolic flux analysis (MFA) with (13)C labeling data is a high-precision technique to quantify intracellular reaction rates (fluxes). One of the major challenges of (13)C MFA is the interactivity of the computational workflow according to which the fluxes are determined from the input data (metabolic network model, labeling data, and physiological rates). Here, the workflow assembly is inevitably determined by the scientist who has to consider interacting biological, experimental, and computational aspects. Decision-making is context dependent and requires expertise, rendering an automated evaluation process hardly possible. Here, we present a scientific workflow framework (SWF) for creating, executing, and controlling on demand (13)C MFA workflows. (13)C MFA-specific tools and libraries, such as the high-performance simulation toolbox 13CFLUX2, are wrapped as web services and thereby integrated into a service-oriented architecture. Besides workflow steering, the SWF features transparent provenance collection and enables full flexibility for ad hoc scripting solutions. To handle compute-intensive tasks, cloud computing is supported. We demonstrate how the challenges posed by (13)C MFA workflows can be solved with our approach on the basis of two proof-of-concept use cases. PMID:26721184

  4. 13C NMR spectroscopy applications to brain energy metabolism

    PubMed Central

    Rodrigues, Tiago B.; Valette, Julien; Bouzier-Sore, Anne-Karine

    2013-01-01

    13C nuclear magnetic resonance (NMR) spectroscopy is the method of choice for studying brain metabolism. Indeed, the most convincing data obtained to decipher metabolic exchanges between neurons and astrocytes have been obtained using this technique, thus illustrating its power. It may be difficult for non-specialists, however, to grasp thefull implication of data presented in articles written by spectroscopists. The aim of the review is, therefore, to provide a fundamental understanding of this topic to facilitate the non-specialists in their reading of this literature. In the first part of this review, we present the metabolic fate of 13C-labeled substrates in the brain in a detailed way, including an overview of some general neurochemical principles. We also address and compare the various spectroscopic strategies that can be used to study brain metabolism. Then, we provide an overview of the 13C NMR experiments performed to analyze both intracellular and intercellular metabolic fluxes. More particularly, the role of lactate as a potential energy substrate for neurons is discussed in the light of 13C NMR data. Finally, new perspectives and applications offered by 13C hyperpolarization are described. PMID:24367329

  5. Impact of cross-polarization isolation on polarimetric target decomposition and target detection

    NASA Astrophysics Data System (ADS)

    Xu, Feng; Wang, Haipeng; Jin, Ya-Qiu; Liu, Xiuqing; Wang, Robert; Deng, Yunkai

    2015-04-01

    Cross-polarization isolation is one of the key engineering parameters for a polarimetric radar system. Previous studies focused more on the calibration of cross-talk contamination. This paper presents a numerical evaluation of the requirement for cross-polarization isolation from the data users' perspective, i.e., the quantitative impact of polarization cross talk on polarimetric target decomposition and the associated applications such as classification and detection. Sensitivity analyses of several commonly used target decomposition parameters suggest that a theoretical lower bound of -32 dB isolation level is preferred to avoid any significant impact on these parameters. Our analyses with both simulated and real synthetic aperture radar (SAR) data show that a level of -25 dB would be acceptable for general terrain surface classification. This requirement is also true for man-made target detection application. Using simulated SAR images of man-made targets in natural environment, sensitivity analyses on two polarimetric detectors, Yang and Marino, both suggest that target detection performance would break down rapidly if isolation deteriorates from -25 dB to -20 dB.

  6. Influence of dental resin material composition on cross-polarization-optical coherence tomography imaging

    PubMed Central

    Lammeier, Carmen; Li, YuPing; Lunos, Scott; Fok, Alex; Rudney, Joel

    2012-01-01

    Abstract. The purpose of this study was to investigate cross-polarization-optical coherence tomography (CP-OCT) signal attenuation through different resin material compositions. Four distinct composite systems were used: Filtek supreme ultra (FSU) (3M ESPE), IPS empress direct (EMD) (Ivoclar Vivadent), estelite sigma quick (SQK) (Tokuyama Dental), and Z100 (3M ESPE). Cross-sectional images of different composite-demineralized phantoms (n=108) were collected using a 1310-nm intraoral cross-polarization swept source OCT (CP-OCT) imaging system. %T quantified the CP-OCT signal attenuation. Scanning electron microscopy, transmission electron microscopy, and energy-dispersive x-ray spectrometer chemical analysis was utilized to determine how different matrix/filler compositions affected attenuation of the near infrared (NIR) signal. CP-OCT imaging of dental resin composites showed enormous variation in signal attenuation. For each of our composite systems, there was not a consistent attenuation difference in the NIR signal for A to D shades. The four composites had similar measured backscattering values but attenuated the overall signal to different degrees. When comparing the A2 shades between the four different composite systems, the order of highest to lowest of %T was EMD>Z100, FSU>SQK (ANOVA, Tukey, p<0.0001). As a result, we demonstrate the importance of understanding how the constituents of composite materials affect CP-OCT signal attenuation. PMID:23224001

  7. Monitoring tooth demineralization using a cross polarization optical coherence tomographic system with an integrated MEMS scanner

    NASA Astrophysics Data System (ADS)

    Fried, Daniel; Staninec, Michal; Darling, Cynthia; Kang, Hobin; Chan, Kenneth

    2012-01-01

    New methods are needed for the nondestructive measurement of tooth demineralization and remineralization to monitor the progression of incipient caries lesions (tooth decay) for effective nonsurgical intervention and to evaluate the performance of anti-caries treatments such as chemical treatments or laser irradiation. Studies have shown that optical coherence tomography (OCT) has great potential to fulfill this role since it can be used to measure the depth and severity of early lesions with an axial resolution exceeding 10-μm, it is easy to apply in vivo and it can be used to image the convoluted topography of tooth occlusal surfaces. In this paper we present early results using a new cross-polarization OCT system introduced by Santec. This system utilizes a swept laser source and a MEMS scanner for rapid acquisition of cross polarization images. Preliminary studies show that this system is useful for measurement of the severity of demineralization on tooth surfaces and for showing the spread of occlusal lesions under the dentinal-enamel junction.

  8. Evaluation of cross-polarized near infrared hyperspectral imaging for early detection of dental caries

    NASA Astrophysics Data System (ADS)

    Usenik, Peter; Bürmen, Miran; Fidler, Aleš; Pernuš, Franjo; Likar, Boštjan

    2012-01-01

    Despite major improvements in dental healthcare and oral hygiene, dental caries remains one of the most prevalent oral diseases and represents the primary cause of oral pain and tooth loss. The initial stages of dental caries are characterized by demineralization of enamel crystals and are difficult to diagnose. Near infrared (NIR) hyperspectral imaging is a new promising technique for detection of early changes in the surfaces of carious teeth. This noninvasive imaging technique can characterize and differentiate between the sound tooth surface and initial or advanced tooth caries. The absorbing and scattering properties of dental tissues reflect in distinct spectral features, which can be measured, quantified and used to accurately classify and map different dental tissues. Specular reflections from the tooth surface, which appear as bright spots, mostly located around the edges and the crests of the teeth, act as a noise factor which can significantly interfere with the spectral measurements and analysis of the acquired images, degrading the accuracy of the classification and diagnosis. Employing cross-polarized imaging setup can solve this problem, however has yet to be systematically evaluated, especially in broadband hyperspectral imaging setups. In this paper, we employ cross-polarized illumination setup utilizing state-of-the-art high-contrast broadband wire-grid polarizers in the spectral range from 900 nm to 1700 nm for hyperspectral imaging of natural and artificial carious lesions of various degrees.

  9. Inclusion of 13C and D in protonated acetylene

    NASA Astrophysics Data System (ADS)

    Fortenberry, Ryan C.; Roueff, Evelyne; Lee, Timothy J.

    2016-04-01

    The rovibrational spectrum of cyclic, protonated acetylene has been established. The improvement in modern telescopes coupled with the different branching ratios in reaction models welcomes study of 13C-substitution for C2H3+. Quartic force fields (QFFs) have been previously utilized to predict the antisymmetric HCCH stretch in standard c-C2H3+ to within 0.1 cm-1 of experiment and are employed here to generate rovibrational insights for the 13C isotopologues. The zero-point energies are also given for the cyclic and 'Y'-shaped isomers for both 13C and D substitutions. Vibrational intensities and the dipole moments are provided in order to characterize more fully this simple cation.

  10. {sup 13}C relaxation in an RNA hairpin

    SciTech Connect

    King, G.C. |; Akratos, C.; Xi, Z.; Michnica, M.J.

    1994-12-01

    This initial survey of {sup 13}C relaxation in the {triangle}TAR RNA element has generated a number of interesting results that should prove generally useful for future studies. The most readily comparable study in the literature monitored {sup 13}C relaxation of the methyl groups from unusual bases in tRNA{sup Phe}. The study, which used T{sub 1} and NOE data only, reported order parameters for the methyl group axis that ranged between 0.51 and 0.97-a range similar to that observed here. However, they reported a breakdown of the standard order parameter analysis at higher (118-MHz {sup 13}C) frequencies, which should serve to emphasize the need for a thorough exploration of suitable motional models.

  11. Magnetic Resonance Imaging with Hyperpolarized 13C Contrast Agents

    NASA Astrophysics Data System (ADS)

    Gordon, Jeremy W.

    Hyperpolarized 13C substrates offer the potential to non-invasively image metabolism and enzymatic activity. However, hyperpolarization introduces a number of difficulties, and imaging is hampered by non-equilibrium magnetization and the need for spectral encoding. There is therefore a need for fast and RF efficient spectral imaging techniques. This work presents a number of new methods that can be used to improve polarization, increase RF efficiency and improve modeling accuracy in hyperpolarized 13C experiments. In particular, a novel encoding and reconstruction algorithm is presented that can generate spatially and spectrally resolved images with a single RF excitation and echo time. This reconstruction framework increases data acquisition efficiency, enabling accelerated acquisition speed, preserved polarization, and/or improved temporal or spatial resolution. Overall, the methods enumerated in this dissertation have the potential to improve modeling accuracy and to mitigate the conventional tradeoffs between SNR, spatial resolution, and temporal resolution that govern image quality in hyperpolarized 13C experiments.

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

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

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

  13. Influence of 13C isotopic labeling location of 13C DNP of acetate using TEMPO free radical

    NASA Astrophysics Data System (ADS)

    Parish, Christopher; Niedbalski, Peter; Lumata, Lloyd

    2015-03-01

    Dynamic nuclear polarization (DNP) via the dissolution method enhances the liquid-state magnetic resonance (NMR or MRI) signals of insensitive nuclear spins by at least 10,000-fold. The basis for all these signal enhancements at room temperature is the polarization transfer from the electrons to nuclear spins at cryogenic temperature and high magnetic field. In this work, we have studied the influence of the location of 13C isotopic labeling on the DNP of sodium acetate at 3.35 T and 1.4 K using a wide ESR linewidth free radical 4-oxo-TEMPO. The carbonyl [1-13C]acetate spins produced a polarization level that is almost twice that of the methyl [2-13C]acetate spins. On the other hand, the polarization of the methyl 13C spins doubled to reach the level of [1-13C]acetate when the methyl group was deuterated. Meanwhile, the solid-state nuclear relaxation of these samples are the same and do not correlate with the polarization levels. These behavior implies that the nuclear relaxation for these samples is dominated by the contribution from the free radicals and the polarization levels can be explained by a thermodynamic picture of DNP.

  14. Measuring doubly 13C-substituted ethane by mass spectrometry

    NASA Astrophysics Data System (ADS)

    Clog, M.; Ling, C.; Eiler, J. M.

    2012-12-01

    Ethane (C2H6) is present in non-negligible amounts in most natural gas reservoirs and is used to produce ethylene for petrochemical industries. It is one of the by-products of lipid metabolism and is the arguably simplest molecule that can manifest multiple 13C substitutions. There are several plausible controls on the relative abundances of 13C2H6 in natural gases: thermodynamically controlled homogeneous isotope exchange reactions analogous to those behind carbonate clumped isotope thermometry; inheritance from larger biomolecules that under thermal degradation to produce natural gas; mixing of natural gases that differ markedly in bulk isotopic composition; or combinations of these and/or other, less expected fractionations. There is little basis for predicting which of these will dominate in natural samples. Here, we focus on an analytical techniques that will provide the avenue for exploring these phenomena. The method is based on high-resolution gas source isotope ratio mass spectrometry, using the Thermo 253-Ultra (a new prototype mass spectrometer). This instrument achieves the mass resolution (M/Δ M) up to 27,000, permitting separation of the isobaric interferences of potential contaminants and isotopologues of an analtye or its fragments which share a cardinal mass. We present techniques to analyze several isotopologues of molecular and fragment ions of C2H6. The critical isobaric separations for our purposes include: discrimination of 13C2H6 from 13C12CDH5 at mass 32 and separation of the 13CH3 fragment from 12CH4 at mass 16, both requiring at least a mass resolution of 20000 to make an adequate measurement. Other obvious interferences are either cleanly separated (e.g., O2, O) or accounted for by peak-stripping (CH3OH on mass 32 and NH2 on mass 16). We focus on a set of measurements which constrain: the doubly-substituted isotopologue, 13C2H6, and the 13CH3/12CH3 ratio of the methyl fragment, which constrains the bulk δ 13C. Similar methods can be

  15. Spectral editing for in vivo 13C magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Xiang, Yun; Shen, Jun

    2012-01-01

    In vivo detection of carboxylic/amide carbons is a promising technique for studying cerebral metabolism and neurotransmission due to the very low RF power required for proton decoupling. In the carboxylic/amide region, however, there is severe spectral overlap between acetate C1 and glutamate C5, complicating studies that use acetate as an astroglia-specific substrate. There are no known in vivo MRS techniques that can spectrally resolve acetate C1 and glutamate C5 singlets. In this study, we propose to spectrally separate acetate C1 and glutamate C5 by a two-step J-editing technique after introducing homonuclear 13C- 13C scalar coupling between carboxylic/amide carbons and aliphatic carbons. By infusing [1,2- 13C 2]acetate instead of [1- 13C]acetate the acetate doublet can be spectrally edited because of the large separation between acetate C2 and glutamate C4 in the aliphatic region. This technique can be applied to studying acetate transport and metabolism in brain in the carboxylic/amide region without spectral interference.

  16. Synthesis of 2-deoxy-(6-/sup 13/C)glucose

    SciTech Connect

    Walker, T.E.; Unkefer, C.J.; Ehler, D.S.

    1987-05-01

    The authors have prepared 2-deoxy-D-(6-/sup 13/C)glucose which will be used to test the stability of 2-deoxy-D-glucose-6-phosphate in brain tissue. They chose to label 2-deoxy-D-glucose at C-6 because of the large chemical shift difference between C-6 in the free sugar and C-6 in the 6-phosphate analog. Their synthetic scheme is similar to that used for the synthesis of D-(6-/sup 13/C)glucose which involves the removal of C-6 from D-glucose followed by its replacement with /sup 13/C. They first prepare the methyl ..cap alpha..-furanoside using trifluoroacetic acid in methanol. This product is then treated with periodate which cleaves only between C-5 and C-6 to form a hydrated aldehyde which is reacted directly with K/sup 13/CN to form a mixture of nitriles. The enriched nitriles are reduced with hydrogen to a mixture of 6-aldehydo sugars using a 5% Pd on carbon catalyst. These sugars are reduced with NaBH/sub 4/ to a mixture of labeled methyl furanosides. Acid hydrolysis followed by chromatography yields 2-deoxy-D-(6-/sup 13/C)glucose in an overall yield of 10% from K/sup 13/CN.

  17. Does the Shuram δ13C excursion record Ediacaran oxygenation?

    NASA Astrophysics Data System (ADS)

    Husson, J. M.; Maloof, A. C.; Schoene, B.; Higgins, J. A.

    2013-12-01

    The most negative carbon isotope excursion in Earth history is found in carbonate rocks of the Ediacaran Period (635-542 Ma). Known colloquially as the the 'Shuram' excursion, workers have long noted its tantalizing, broad concordance with the rise of abundant macro-scale fossils in the rock record, variously interpreted as animals, giant protists, macro-algae and lichen, and known as the 'Ediacaran Biota.' Thus, the Shuram excursion has been interpreted by many in the context of a dramatically changing redox state of the Ediacaran oceans - e.g., a result of methane cycling in a low O2 atmosphere, the final destruction of a large pool of recalcitrant dissolved organic carbon (DOC), and the step-wise oxidation of the Ediacaran oceans. More recently, diagenetic interpretations of the Shuram excursion - e.g. sedimentary in-growth of very δ13C depleted authigenic carbonates, meteoric alteration of Ediacaran carbonates, late-stage burial diagenesis - have challenged the various Ediacaran redox models. A rigorous geologic context is required to discriminate between these explanatory models, and determine whether the Shuram excursion can be used to evaluate terminal Neoproterozoic oxygenation. Here, we present chemo-stratigraphic data (δ13C, δ18O, δ44/42Ca and redox sensitive trace element abundances) from 12 measured sections of the Ediacaran-aged Wonoka Formation (Fm.) of South Australia that require a syn-depositional age for the extraordinary range of δ13C values (-12 to +4‰) observed in the formation. In some locations, the Wonoka Fm. is ~700 meters (m) of mixed shelf limestones and siliclastics that record the full 16 ‰ δ13C excursion in a remarkably consistent fashion across 100s of square kilometers of basin area. Fabric-altering diagenesis, where present, occurs at the sub-meter vertical scale, only results in sub-permil offsets in δ13C and cannot be used to explain the full δ13C excursion. In other places, the Wonoka Fm. is host to deep (1 km

  18. Optical hyperpolarization of 13C nuclear spins in nanodiamond ensembles

    NASA Astrophysics Data System (ADS)

    Chen, Q.; Schwarz, I.; Jelezko, F.; Retzker, A.; Plenio, M. B.

    2015-11-01

    Dynamical nuclear polarization holds the key for orders of magnitude enhancements of nuclear magnetic resonance signals which, in turn, would enable a wide range of novel applications in biomedical sciences. However, current implementations of DNP require cryogenic temperatures and long times for achieving high polarization. Here we propose and analyze in detail protocols that can achieve rapid hyperpolarization of 13C nuclear spins in randomly oriented ensembles of nanodiamonds at room temperature. Our protocols exploit a combination of optical polarization of electron spins in nitrogen-vacancy centers and the transfer of this polarization to 13C nuclei by means of microwave control to overcome the severe challenges that are posed by the random orientation of the nanodiamonds and their nitrogen-vacancy centers. Specifically, these random orientations result in exceedingly large energy variations of the electron spin levels that render the polarization and coherent control of the nitrogen-vacancy center electron spins as well as the control of their coherent interaction with the surrounding 13C nuclear spins highly inefficient. We address these challenges by a combination of an off-resonant microwave double resonance scheme in conjunction with a realization of the integrated solid effect which, together with adiabatic rotations of external magnetic fields or rotations of nanodiamonds, leads to a protocol that achieves high levels of hyperpolarization of the entire nuclear-spin bath in a randomly oriented ensemble of nanodiamonds even at room temperature. This hyperpolarization together with the long nuclear-spin polarization lifetimes in nanodiamonds and the relatively high density of 13C nuclei has the potential to result in a major signal enhancement in 13C nuclear magnetic resonance imaging and suggests functionalized and hyperpolarized nanodiamonds as a unique probe for molecular imaging both in vitro and in vivo.

  19. Synthesis of [1-.sup.13C]pyruvic acid], [2-.sup.13C]pyruvic acid], [3-.sup.13C]pyruvic acid] and combinations thereof

    DOEpatents

    Martinez, Rodolfo A.; Unkefer, Clifford J.; Alvarez, Marc A.

    2009-09-01

    The present invention is directed to labeled compounds, of the formulae ##STR00001## wherein C* is each independently selected from the group consisting of .sup.13C and .sup.12C with the proviso that at least one C* is .sup.13C, each hydrogen of the methylene group can independently be either hydrogen or deuterium, the methyl group includes either zero or three deuterium atoms, Q is from the group of sulfide, sulfinyl, and sulfone, Z is an aryl group from the group of 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, and phenyl groups with the structure ##STR00002## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently from the group of hydrogen, a C.sub.1-C.sub.4 lower alkyl, a halogen, and an amino group from the group of NH.sub.2, NHR and NRR' where R and R' are each independently from the group of a C.sub.1-C.sub.4 lower alkyl, a phenyl, and an alkoxy group, and the methyl group can include either zero or three deuterium atoms.

  20. Synthesis of [1-.sup.13C]pyruvic acid], [2-.sup.13C]pyruvic acid], [3-.sup.13C]pyruvic acid] and combinations thereof

    DOEpatents

    Martinez, Rodolfo A. , Unkefer; Clifford J. , Alvarez; Marc A.

    2012-06-12

    The present invention is directed to the labeled compounds, ##STR00001## wherein C* is each either .sup.13C and .sup.12C where at least one C* is .sup.13C, each hydrogen of the methylene group is hydrogen or deuterium, the methyl group includes either zero or three deuterium atoms, Q is sulfide, sulfinyl, or sulfone, Z is an aryl group such as 1-naphthyl, substituted 1-naphthyl, 2-naphthyl, substituted 2-naphthyl, or a phenyl group ##STR00002## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are each independently either hydrogen, a C.sub.1-C.sub.4 lower alkyl, a halogen, and an amino group such as NH.sub.2, NHR and NRR' where R and R' are each independently either a C.sub.1-C.sub.4 lower alkyl, a phenyl, and an alkoxy group, and the methyl group can include either zero or three deuterium atoms. The present invention is also directed to the labeled compounds ##STR00003##

  1. Nondestructive monitoring of the repair of natural occlusal lesions using cross polarization optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Kang, Hobin; Darling, Cynthia L.; Fried, Daniel

    2012-01-01

    Previous remineralization studies employing cross polarization sensitive optical coherence tomography (CP-OCT), have been limited to the repair of artificial enamel-like lesions. In this study we attempted to remineralize existing occlusal lesions on extracted teeth. Lesions were imaged before and after exposure to an acidic remineralization regimen and the integrated reflectivity and lesion depth was calculated. Automated integration routines worked well for assessing the integrated reflectivity for the lesion areas after remineralization. Polarized light microscopy was also used to examine the lesions areas after sectioning the teeth. An acidic remineralization solution was used to remineralize the lesions. The integrated reflectivity significantly increased after exposure to the remineralization solution which suggests that the acidic solution caused additional demineralization as opposed to the desired remineralization.

  2. Square-wave switching by crossed-polarization gain modulation in vertical-cavity semiconductor lasers

    SciTech Connect

    Mulet, J.; Giudici, M.; Javaloyes, J.; Balle, S.

    2007-10-15

    We study experimentally and theoretically the effects of crossed-polarization reinjection (XPR) on the output characteristics of a vertical-cavity semiconductor laser. We find a set of parameters values for which each polarization component develops a square-wave modulation at a period close to twice the reinjection delay. We analyze the regularity of this modulation in terms of the laser pumping current and of the reinjection level. These observations are numerically reproduced within the spin-flip model modified to account for XPR. In particular, the degradation of the square-wave switching is linked to the finite value of the spin-flip rate, and it occurs when the current approaches the boundaries of polarization bistability.

  3. Improving temporal contrast by cross-polarized wave generation at a sub-petawatt laser facility

    NASA Astrophysics Data System (ADS)

    Xie, Na; Wang, Xiaodong; Huang, Wanqing; Sun, Li; Guo, Yi; Li, Qing; Zhao, Runchang; Su, Jingqin

    2011-10-01

    Temporal contrast is an important factor affecting the application of ultraintense and ultrashort laser systems. In this paper, we employ cross-polarized wave (XPW) generation to improve the temporal contrast for ultraintense and ultrashort pulses in a 300 TW Ti:Sapphire laser facility, i.e. the super intense laser for experiment on the extremes (SILEX-I). We designed a double chirped-pulse amplification (CPA) system with an intermediate nonlinear temporal pulse filter based on XPW generation and the estimated output energy is more than 300 mJ for the new front-end system. The experimental results show that the output energy of the double CPA system is greater than 370 mJ. The amplified spontaneous emission (ASE) pedestal is suppressed significantly and the temporal contrast is improved by more than two orders of magnitude.

  4. The hat feed - A dual-mode rear-radiating waveguide antenna having low cross polarization

    NASA Astrophysics Data System (ADS)

    Kildal, Per-Simon

    1987-09-01

    The hat antenna is a new self-supported rear-radiating waveguide feed, related to existing feeds known as splashplate and waveguide cup antennas. An analytical model for the radiation pattern of the hat antenna, a model which includes the axial waveguide itself is presented. This model shows that by exciting the feed with two modes it is possible to use the waveguide constructively as one of the dominant radiating parts of the feed instead of having to live with it as an undesirable blockage effect. Thereby aperture efficiencies up to 81 percent and cross-polar sidelobes down to -30 dB are available. The results are confirmed by measurements on a practical model, but the bandwidth is narrow.

  5. Efficient cross polarized wave generation for compact, energy-scalable, ultrashort laser sources.

    PubMed

    Ramirez, L P; Papadopoulos, D N; Pellegrina, A; Georges, P; Druon, F; Monot, P; Ricci, A; Jullien, A; Chen, X; Rousseau, J P; Lopez-Martens, R

    2011-01-01

    The generation of high contrast and ultrashort laser pulses via a compact and energy-scalable cross polarized wave filter is presented. The setup incorporates a waveguide spatial filter into a single crystal XPW configuration, enabling high energy and high intensity transmission, efficient contrast enhancement and pulse shortening at the multi-mJ level. Excellent XPW conversion of up to 33% (global efficiency: 20%, intensity transmission: 40%) led to an output energy of 650 µJ for an input of 3.3 mJ. Additionally, efficient conversion under specific input phase conditions, allowed pulse shortening from 25 fs to 9.6 fs, indicating the prospective application of this setup as a high energy, ultrabroad laser source. PMID:21263545

  6. Low-cost label-free biosensors using photonic crystals embedded between crossed polarizers.

    PubMed

    Nazirizadeh, Yousef; Bog, Uwe; Sekula, Sylwia; Mappes, Timo; Lemmer, Uli; Gerken, Martina

    2010-08-30

    There is a strong need for low-cost biosensors to enable rapid, on-site analysis of biological, biomedical, or chemical substances. We propose a platform for label-free optical biosensors based on applying the analyte onto a surface-functionalized photonic crystal slab and performing a transmission measurement with two crossed polarization filters. This dark-field approach allows for efficient background suppression as only the photonic crystal guided-mode resonances interacting with the functionalized surface experience significant polarization rotation. We present a compact biosensor demonstrator using a low-cost light emitting diode and a simple photodiode capable of detecting the binding kinetics of a 2.5 nM solution of the protein streptavidin on a biotin-functionalized photonic crystal surface. PMID:20940807

  7. Remineralization of root caries monitored using cross polarization optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Darling, Cynthia L.; Staninec, Michal; Chan, Kenneth H.; Kang, Hobin; Fried, Daniel

    2012-01-01

    Previous studies have demonstrated that polarization sensitive optical coherence tomography (PS-OCT) can be used to image caries lesions in dentin, measure nondestructively the severity of dentin demineralization, and determine the efficacy of intervention with anticaries agents including fluoride and lasers. However, those studies were limited to artificial lesions on dentin and roots surfaces. The objective of this study is to determine if a cross polarization OCT system (CP-OCT) can be used to nondestructively measure a reduction in the reflectivity of natural root caries lesions after exposure to a remineralization solution. CPOCT images of 11 teeth with existing root lesions were acquired before and after exposure to a remineralizing solution for 20 days. The integrated reflectivity was calculated after integrating to a fixed depth of 200-μm. There was a significant decrease in the integrated reflectivity after exposure to the remineralizing solution.

  8. Ray Scattering by an Arbitrarily Oriented Spheroid: 2. Transmission and Cross-polarization Effects

    NASA Technical Reports Server (NTRS)

    Lock, James A.

    1996-01-01

    Transmission of an arbitrarily polarized plane wave by an arbitrarily oriented spheroid in the short-wavelength limit is considered in the context of ray theory. The transmitted electric field is added to the diffracted plus reflected ray-theory electric field that was previously derived to obtain an approximation to the far-zone scattered intensity in the forward hemisphere. Two different types of cross-polarization effects are found. These are: (a) a rotation of the polarization state of the transmitted rays from when they are referenced with respect to their entrance into the spheroid to when they are referenced with respect to their exit from it and (b) a rotation of the polarization state of the transmitted rays when they are referenced with respect to the polarization state of the diffracted plus reflected rays.

  9. Cross-Polar Aircraft Trajectory Optimization and the Potential Climate Impact

    NASA Technical Reports Server (NTRS)

    Ng, Hok K.; Sridhar, Banavar; Grabbe, Shon; Chen, Neil

    2011-01-01

    Cross-Polar routes offer new opportunities for air travel markets. Transpolar flights reduce travel times, fuel burns, and associated environmental emissions by flying direct paths between many North American and Asian cities. This study evaluates the potential benefits of flying wind-optimal polar routes and assessed their potential impact on climate change. An optimization algorithm is developed for transpolar flights to generate wind-optimal trajectories that minimize climate impact of aircraft, in terms of global warming potentials (relative to warming by one kg of CO2) of several types of emissions, while avoiding regions of airspace that facilitate persistent contrail formation. Estimations of global warming potential are incorporated into the objective function of the optimization algorithm to assess the climate impact of aircraft emissions discharged at a given location and altitude. The regions of airspace with very low ambient temperature and areas favorable to persistent contrail formation are modeled as undesirable regions that aircraft should avoid and are formulated as soft state constraints. The fuel burn and climate impact of cross-polar air traffic flying various types of trajectory including flight plan, great circle, wind-optimal, and contrail-avoidance are computed for 15 origin-destination pairs between major international airports in the U.S. and Asia. Wind-optimal routes reduce average fuel burn of flight plan routes by 4.4% on December 4, 2010 and 8.0% on August 7, 2010, respectively. The tradeoff between persistent contrail formation and additional global warming potential of aircraft emissions is investigated with and without altitude optimization. Without altitude optimization, the reduction in contrail travel times is gradual with increase in total fuel consumption. When altitude is optimized, a one percent increase in additional global warming potential, a climate impact equivalent to that of 4070kg and 4220kg CO2 emission, reduces 135

  10. A cross-polarized freeform illumination design for glare reduction in fruit quality inspection

    NASA Astrophysics Data System (ADS)

    Keresztes, Janos C.; Koshel, R. John; Chipman, Russel; Stover, John C.; Saeys, Wouter

    2015-09-01

    Common illumination systems in short wave infrared (SWIR) hyperspectral imaging (HSI) include direct or indirect tungsten halogen lights. While direct lights provide more radiation onto the samples than dome setups, thus being more energy efficient, the acquired images often suffer from specular reflections and gloss. Glare artifacts in images increase variability in the data limiting the accuracy of machine vision algorithms for defect detection and quality inspection, or even providing false positives. Although domes are known to provide a near Lambertian illumination and glare free images, glossy regions and heterogeneities may remain in the data in practice. More particularly, in the field of fruit and vegetable quality inspection, due to their waxy surface, it remains challenging to design an efficient realistic lighting system. This paper suggests a new approach to optimize the illumination of fruit and vegetables based on measurements of the bidirectional reflectance distribution function (BRDF), shape and Stokes parameters. From these measured values, a BRDF model is loaded into ray-tracing software for realistic illumination engineering in order to determine the most suitable illumination scheme. This concept is applied to apples and a cross polarizer (CP) with freeform optics (FO) optical configuration is proposed, which allows the FO to be optimized to maximize uniformity in the field of view of the imager and removes the parallel polarized gloss on the apples. The performance of this CP illumination system was determined experimentally for a set of apples. This cross polarized (CP) illumination system provided a uniformity (U) of 92% and an efficiency (ν) of 90%, while U = 87% and ν = 14% for an ideal dome configuration when illuminating a rectangular target. The simulated imaged apples with assigned optical properties performed better with CP (U=80%) than when using a dome (U=73%) by 7%. Finally, the sensitivity of the design for the light

  11. Realization of broadband cross-polarization conversion in transmission mode in the terahertz region using a single-layer metasurface.

    PubMed

    Liu, Wenwei; Chen, Shuqi; Li, Zhancheng; Cheng, Hua; Yu, Ping; Li, Jianxiong; Tian, Jianguo

    2015-07-01

    We present the design specifications and in-depth analysis of a terahertz (THz) broadband cross-polarization converter composed of a single-layer metasurface. This device can convert linearly polarized light into its cross-polarization in transmission mode. Different from other polarization conversion devices, this effect results from the suppression and enhancement for different electric components. The broadband characteristic is also achieved by specific partial symmetries designed in the structure. The proposed polarization converter can aid in the development of novel plasmonic polarization devices, and can help to overcome certain limitations of the customary designs that have been proposed thus far. PMID:26125398

  12. Single voxel localization for dynamic hyperpolarized 13C MR spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, Albert P.; Cunningham, Charles H.

    2015-09-01

    The PRESS technique has been widely used to achieve voxel localization for in vivo1H MRS acquisitions. However, for dynamic hyperpolarized 13C MRS experiments, the transition bands of the refocusing pulses may saturate the pre-polarized substrate spins flowing into the voxel. This limitation may be overcome by designing refocusing pulses that do not perturb the resonance of the hyperpolarized substrate, but selectively refocuses the spins of the metabolic products. In this study, a PRESS pulse sequence incorporating spectral-spatial refocusing pulses that have a stop band ('notch') at the substrate resonance is tested in vivo using hyperpolarized [1-13C]pyruvate. Higher metabolite SNR was observed in experiments using the spectral-spatial refocusing pulses as compared to conventional refocusing pulses.

  13. Single voxel localization for dynamic hyperpolarized (13)C MR spectroscopy.

    PubMed

    Chen, Albert P; Cunningham, Charles H

    2015-09-01

    The PRESS technique has been widely used to achieve voxel localization for in vivo(1)H MRS acquisitions. However, for dynamic hyperpolarized (13)C MRS experiments, the transition bands of the refocusing pulses may saturate the pre-polarized substrate spins flowing into the voxel. This limitation may be overcome by designing refocusing pulses that do not perturb the resonance of the hyperpolarized substrate, but selectively refocuses the spins of the metabolic products. In this study, a PRESS pulse sequence incorporating spectral-spatial refocusing pulses that have a stop band ('notch') at the substrate resonance is tested in vivo using hyperpolarized [1-(13)C]pyruvate. Higher metabolite SNR was observed in experiments using the spectral-spatial refocusing pulses as compared to conventional refocusing pulses. PMID:26232365

  14. Rotating phenyl rings as a guest-dependent switch in two-dimensional metal-organic frameworks.

    PubMed

    Murdock, Christopher R; McNutt, Nicholas W; Keffer, David J; Jenkins, David M

    2014-01-15

    A semirigid bis(1,2,4-triazole) ligand binds in a syn conformation between copper(I) chains to form a series of two-dimensional metal-organic frameworks that display a topology of fused one-dimensional metal-organic nanotubes. These anisotropic frameworks undergo two different transformations in the solid state as a function of solvation. The 2D sheet layers can expand or contract, or, more remarkably, the phenyl rings can rotate between two distinct positions. Rotation of the phenyl rings allows for the adjustment of the tube size, depending on the guest molecules present. This "gate" effect along the 1D tubes has been characterized through single-crystal X-ray diffraction. The transformations can also be followed by powder X-ray diffraction (PXRD) and solid-state (13)C cross-polarization magic-angle-spinning (CP-MAS) NMR. Whereas PXRD cannot differentiate between transformations, solid-state (13)C CP-MAS NMR can be employed to directly monitor phenyl rotation as a function of solvation, suggesting that this spectroscopic method is a powerful approach for monitoring breathing in this novel class of frameworks. Finally, simulations show that rotation of the phenyl ring from a parallel orientation to a perpendicular orientation occurs at the cost of framework-framework energy and that this energetic cost is offset by stronger framework-solvent interactions. PMID:24351165

  15. Microstructure elucidation of historic silk (Bombyx mori) by nuclear magnetic resonance.

    PubMed

    Zhu, Zhanyun; Gong, Decai; Liu, Liu; Wang, Yusong

    2014-04-01

    (1)H NMR cryoporometry and solid-state (13)C cross-polarization (CP) magic-angle spinning (MAS) NMR spectroscopy were used to characterize the microstructure of historic and fresh silk samples. Silk is a polymeric bicomponent material composed of fibroin and water located in micropores. According to the (1)H NMR cryoporometry method, the intensity of the water resonance as a function of the temperature was used to obtain the pore size distribution, which was strongly asymmetric with a well-defined maximum at 1.1 nm. Compared with the fresh silk samples, the volume of pores around 1.1 nm decreased distinctly in the historic silk, and more pores larger than 2 nm emerged accordingly. In addition, these results correlated well with solid-state (13)C CP/MAS NMR spectroscopy as the percentage of random coil in the historic silk sample was much less than that in the fresh silk samples. Therefore, it is suggested that the water-filled microvoids grow larger as the random coil conformation fades away in the degradation process. PMID:24535686

  16. Simultaneous recovery of organic and inorganic content of paper deinking residue through low-temperature microwave-assisted pyrolysis.

    PubMed

    Zhang, Zhanrong; Macquarrie, Duncan J; Aguiar, Pedro M; Clark, James H; Matharu, Avtar S

    2015-02-17

    Significant amounts of paper deinking residue (DIR) has been and is still being generated from paper deinking processes, representing both an economic and environmental burden for recycled paper mills. Our research on low-temperature (<200 °C) microwave-assisted (MW-assisted) pyrolysis of DIR allows for simultaneously efficient fast separation and recovery of the organic and inorganic content of DIR at relatively low temperature and within 15 min. Our study is the first highly detailed account of the use low-temperature MW-assisted pyrolysis to effect this change. The obtained liquid and solid products were characterized by a variety of analytical techniques (e.g., attenuated total reflection infrared, gas chromatography-mass spectrometry, liquid-state nuclear magnetic resonance (NMR), X-ray diffraction, solid-state cross-polarization/magic-angle spinning (13)C NMR, and Bloch-decay (13)C NMR). The results reveal that the process efficiently separates the inorganic minerals as microwave residue (mainly calcite and kaolinite) from organic matter, and hence the microwave residue could be reused to produce new paper/cardboard products. The organic fraction bio-oil generated is energy-densified and rich in carbohydrates and is a potential source for valuable aromatic compounds. PMID:25590264

  17. Chemical Makeup and Hydrophilic Behavior of Graphene Oxide Nanoribbons after Low-Temperature Fluorination.

    PubMed

    Romero Aburto, Rebeca; Alemany, Lawrence B; Weldeghiorghis, Thomas K; Ozden, Sehmus; Peng, Zhiwei; Lherbier, Aurélien; Botello Méndez, Andrés Rafael; Tiwary, Chandra Sekhar; Taha-Tijerina, Jaime; Yan, Zheng; Tabata, Mika; Charlier, Jean-Christophe; Tour, James M; Ajayan, Pulickel M

    2015-07-28

    Here we investigated the fluorination of graphene oxide nanoribbons (GONRs) using H2 and F2 gases at low temperature, below 200 °C, with the purpose of elucidating their structure and predicting a fluorination mechanism. The importance of this study is the understanding of how fluorine functional groups are incorporated in complex structures, such as GONRs, as a function of temperature. The insight provided herein can potentially help engineer application-oriented materials for several research and industrial sectors. Direct (13)C pulse magic angle spinning (MAS) nuclear magnetic resonance (NMR) confirmed the presence of epoxy, hydroxyl, ester and ketone carbonyl, tertiary alkyl fluorides, as well as graphitic sp(2)-hybridized carbon. Moreover, (19)F-(13)C cross-polarization MAS NMR with (1)H and (19)F decoupling confirmed the presence of secondary alkyl fluoride (CF2) groups in the fluorinated graphene oxide nanoribbon (FGONR) structures fluorinated above 50 °C. First-principles density functional theory calculations gained insight into the atomic arrangement of the most dominant chemical groups. The fluorinated GONRs present atomic fluorine percentages in the range of 6-35. Interestingly, the FGONRs synthesized up to 100 °C, with 6-19% of atomic fluorine, exhibit colloidal similar stability in aqueous environments when compared to GONRs. This colloidal stability is important because it is not common for materials with up to 19% fluorine to have a high degree of hydrophilicity. PMID:26020447

  18. Gas-Phase Synthesis and Characterization of CH4-Loaded Hydroquinone Clathrates

    SciTech Connect

    Lee, J.; Lee, Y; Takeya, S; Kawamura, T; Yamamoto, Y; Lee, Y; Yoon, J

    2010-01-01

    A CH{sub 4}-loaded hydroquinone (HQ) clathrate was synthesized via a gas-phase reaction using the {alpha}-form of crystalline HQ and CH{sub 4} gas at 12 MPa and room temperature. Solid-state {sup 13}C cross-polarization/magic angle spinning (CP/MAS) NMR and Raman spectroscopic measurements confirm the incorporation of CH{sub 4} molecules into the cages of the HQ clathrate framework. The chemical analysis indicates that about 69% of the cages are filled by CH{sub 4} molecules, that is, 0.69 CH{sub 4} per three HQ molecules. Rietveld refinement using synchrotron X-ray powder diffraction (XRD) data shows that the CH{sub 4}-loaded HQ clathrate adopts the {beta}-form of HQ clathrate in a hexagonal space group R3 with lattice parameters of a = 16.6191 {angstrom} and c = 5.5038 {angstrom}. Time-resolved synchrotron XRD and quadrupole mass spectroscopic measurements show that the CH{sub 4}-loaded HQ clathrate is stable up to 368 K and gradually transforms to the {alpha}-form by releasing the confined CH{sub 4} gases between 368-378 K. Using solid-state {sup 13}C CP/MAS NMR, the reaction kinetics between the {alpha}-form HQ and CH{sub 4} gas is qualitatively described in terms of the particle size of the crystalline HQ.

  19. Advanced NMR approaches in the characterization of coal. Final technical report, September 1, 1990--August 31, 1993

    SciTech Connect

    Maciel, G.E.

    1993-09-30

    This project addressed two main goals and one much smaller one. The main goals were (1) to improve the significance, reliability and information content in high-resolution NMR (nuclear magnetic resonance) characterization of coal samples and (2) to develop chemically informative NMR imaging techniques for coal. The minor goal was to explore advanced features of dynamic nuclear polarization (DNP) as a technique for coal characterization; this included the development of two DNP probes and the examination of DNP characteristics of various carbonaceous samples, including coals. {sup 13}C NMR advances for coal depended on large-sample MAS devices, employing either cross-polarization (CP) or direct polarization (DP) approaches. CP and DP spin dynamics and their relationships to quantitation and spin counting were elucidated. {sup 1}H NMR studies, based on CRAMPS, dipolar dephasing and saturation with perdeuteropyridine, led to a {sup 1}H NMR-based elucidation of chemical functionality in coal. {sup 1}H and {sup 13}C NMR imaging techniques, based on magic-angle spinning and rotating magnetic field gradients, were developed for introducing chemical shift information (hence, chemical detail) into the spatial imaging of coal. The TREV multiple-pulse sequence was found to be useful in the {sup 1}H CRAMPS imaging of samples like coal.

  20. Nuclear Overhauser effect as a probe of molecular structure, dynamics and order of axially reorienting molecules in membranes.

    PubMed

    Davis, James H; Komljenović, Ivana

    2016-02-01

    The location, orientation, order and dynamics of cholesterol in model membranes have been well characterized, therefore cholesterol is an ideal molecule for developing new methods for studying structured molecules undergoing rapid axially symmetric reorientation. The use of (13)C filtering via short contact cross polarization transfer to (1)H allows the recovery of the weak cholesterol (1)H magic angle spinning NMR signals from beneath the strong phospholipid background in bicelles composed of chain perdeuterated dimyristoyl phosphatidylcholine/dicaproyl phosphatidylcholine/[3,4-(13)C]-cholesterol. Measurements of the nuclear Overhauser enhancement for (1)H nuclei located in the first ring of cholesterol are interpreted in terms of a simple two motion model consisting of axial reorientation, with a correlation time τ∥, and a slower reorientation of the diffusion axis relative to the bilayer normal, with correlation time τ⊥. This approach can be extended to other molecules which undergo rapid axial reorientation such as small membrane associated peptides. PMID:26607012

  1. Hartmann-Hahn 2D-map to optimize the RAMP-CPMAS NMR experiment for pharmaceutical materials.

    PubMed

    Suzuki, Kazuko; Martineau, Charlotte; Fink, Gerhard; Steuernagel, Stefan; Taulelle, Francis

    2012-02-01

    Cross polarization-magic angle spinning (CPMAS) is the most used experiment for solid-state NMR measurements in the pharmaceutical industry, with the well-known variant RAMP-CPMAS its dominant implementation. The experimental work presented in this contribution focuses on the entangled effects of the main parameters of such an experiment. The shape of the RAMP-CP pulse has been considered as well as the contact time duration, and a particular attention also has been devoted to the radio-frequency (RF) field inhomogeneity. (13)C CPMAS NMR spectra have been recorded with a systematic variation of (13)C and (1)H constant radiofrequency field pair values and represented as a Hartmann-Hahn matching two-dimensional map. Such a map yields a rational overview of the intricate optimal conditions necessary to achieve an efficient CP magnetization transfer. The map also highlights the effects of sweeping the RF by the RAMP-CP pulse on the number of Hartmann-Hahn matches crossed and how RF field inhomogeneity helps in increasing the CP efficiency by using a larger fraction of the sample. In the light of the results, strategies for optimal RAMP-CPMAS measurements are suggested, which lead to a much higher efficiency than constant amplitude CP experiment. PMID:22367881

  2. NMR study of ferroelastic phase transition of tetramethylammonium tetrabromocobaltate

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran; Kim, Sun Ha

    2016-09-01

    Static and magic angle spinning (MAS) nuclear magnetic resonance (NMR) experiments were carried out on 1H, 13C, and 14N nuclei in order to understand the structural changes of the N(CH3)4 groups in [N(CH3)4]2CoBr4 near the ferroelastic phase transition temperature TC. The two chemically inequivalent N(CH3)4 groups were distinguished using 13C cross-polarization/(CP)MAS and 14N static NMR. The changes in chemical shifts, line intensities, and the spin-lattice relaxation time near TC can be correlated with the changing structural geometry, which underlies the phase transition. The 14N NMR spectra indicated a crystal symmetry change at TC, which is related to the ferroelastic domain with different orientations of the N(CH3)4 groups. The ferroelastic domain walls were confirmed by optical polarizing microscopy, and the wall orientations were described by the Sapriel theory. The transition to the ferroelastic phase was found to be related to the orientational ordering of the N(CH3)4 groups.

  3. Quantitative solid state NMR analysis of residues from acid hydrolysis of loblolly pine wood.

    PubMed

    Sievers, Carsten; Marzialetti, Teresita; Hoskins, Travis J C; Valenzuela Olarte, Mariefel B; Agrawal, Pradeep K; Jones, Christopher W

    2009-10-01

    The composition of solid residues from hydrolysis reactions of loblolly pine wood with dilute mineral acids is analyzed by (13)C Cross Polarization Magic Angle Spinning (CP MAS) NMR spectroscopy. Using this method, the carbohydrate and lignin fractions are quantified in less than 3h as compared to over a day using wet chemical methods. In addition to the quantitative information, (13)C CP MAS NMR spectroscopy provides information on the formation of additional extractives and pseudo lignin from the carbohydrates. Being a non-destructive technique, NMR spectroscopy provides unambiguous evidence of the presence of side reactions and products, which is a clear advantage over the wet chemical analytical methods. Quantitative results from NMR spectroscopy and proximate analysis are compared for the residues from hydrolysis of loblolly pine wood under 13 different conditions; samples were treated either at 150 degrees C or 200 degrees C in the presence of various acids (HCl, H(2)SO(4), H(3)PO(4), HNO(3) and TFA) or water. The lignin content determined by both methods differed on averaged by 2.9 wt% resulting in a standard deviation of 3.5 wt%. It is shown that solid degradation products are formed from saccharide precursors under harsh reaction conditions. These degradation reactions limit the total possible yield of monosaccharides from any subsequent reaction. PMID:19477123

  4. Effects of hemicellulose removal on cellulose fiber structure and recycling characteristics of eucalyptus pulp.

    PubMed

    Wan, JinQuan; Wang, Yan; Xiao, Qing

    2010-06-01

    Eucalyptus pulp fibers with large differences in cellulose and hemicellulose proportions but similar lignin contents were produced by partial removal of the hemicellulose and studied using Cross-Polarization Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance (CP/MAS (13)C NMR) in combination with spectral fitting, Atomic Force Microscopy (AFM), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). There were remarkable differences in both cellulose fibril structure, pore structure and cellulose supermolecular structure between the samples. CP/MAS (13)C NMR combined with spectral fitting demonstrated an increase in average fibril aggregate size (17.9-22.2 nm) with decreasing hemicellulose content. AFM observations revealed that when the hemicellulose content decreased from 27.62% to 19.80%, the average diameters of pores decreased by 12.53%, but increased by 13.55% when the hemicellulose content decreased from 19.80% to 9.09%. XRD and FTIR analysis indicated that cellulose crystallinity increased with decreasing hemicellulose content. The low and high hemicellulose-containing pulps had very different recycling characteristics, which may be explained by the changes observed at cellulose fiber structure level. Fibrils appear to aggregate and form a more compact structure when the hemicellulose is removed, which was caused by a coalescence of the cellulose microfibrils. The removal of hemicellulose had disadvantageous influence on the accessibility of fibers and enhanced fiber flattening during drying, leading to increased sheet density and increased hornification. PMID:20181478

  5. Degradation of carbohydrates during dilute sulfuric acid pretreatment can interfere with lignin measurements in solid residues.

    PubMed

    Katahira, Rui; Sluiter, Justin B; Schell, Daniel J; Davis, Mark F

    2013-04-01

    The lignin content measured after dilute sulfuric acid pretreatment of corn stover indicates more lignin than could be accounted for on the basis of the untreated corn stover lignin content. This phenomenon was investigated using a combination of (13)C cross-polarization/magic-angle spinning (CP/MAS) solid-state nuclear magnetic resonance (NMR) spectroscopy and lignin removal using acid chlorite bleaching. Only minimal contamination with carbohydrates and proteins was observed in the pretreated corn stover. Incorporating degradation products from sugars was also investigated using (13)C-labeled sugars. The results indicate that sugar degradation products are present in the pretreatment residue and may be intimately associated with the lignin. Studies comparing whole corn stover (CS) to extractives-free corn stover [CS(Ext)] clearly demonstrated that extractives are a key contributor to the high-lignin mass balance closure (MBC). Sugars and other low molecular weight compounds present in plant extractives polymerize and form solids during pretreatment, resulting in apparent Klason lignin measurements that are biased high. PMID:23428141

  6. Effects of low-temperature catalytic pretreatments on coal structure and reactivity in liquefaction

    SciTech Connect

    Song, C.; Saini, A.; Huang, L.; Wenzel, K.; Hatcher, P.G.; Schobert, H.H.

    1992-01-01

    Low-temperature catalytic pretreatment is a promising approach to the development of an improved liquefaction process. This work is a fundamental study on effects of pretreatments on coal structure and reactivity in liquefaction. The main objectives of this project are to study the coal structural changes induced by low-temperature catalytic and thermal pretreatments by using spectroscopic techniques; and to clarify the pretreatment-induced changes in reactivity or convertibility of coals in the subsequent liquefaction. This report describes the progress of our work during the first quarterly period. Substantial progress has been made in the spectroscopic characterization of fresh and THF-extracted samples of two subbituminous coals and fresh samples of three bituminous coals using cross-polarization magic angle spinning (CPMAS) solid state {sup 13}C NMR and pyrolysis-GC-MS techniques. CPMAS {sup 13}C NMR and pyrolysis-GC-MS provided important information on carbon distribution/functionality and molecular components/structural units, respectively, for these coal samples. Pyrolysis-GC-MS revealed that there are remarkable structural differences in structural units between the subbituminous coals and the bituminous coals. Furthermore, significant progress has been made in the pretreatments and spectroscopic characterization of catalytically and thermally pretreated as well as physically treated Wyodak subbituminous coal, and temperature-staged and temperature-programmed thermal and catalytic liquefaction of a Montana subbituminous coal.

  7. Effects of low-temperature catalytic pretreatments on coal structure and reactivity in liquefaction. Technical progress report, October 1991--December 1991

    SciTech Connect

    Song, C.; Saini, A.; Huang, L.; Wenzel, K.; Hatcher, P.G.; Schobert, H.H.

    1992-01-01

    Low-temperature catalytic pretreatment is a promising approach to the development of an improved liquefaction process. This work is a fundamental study on effects of pretreatments on coal structure and reactivity in liquefaction. The main objectives of this project are to study the coal structural changes induced by low-temperature catalytic and thermal pretreatments by using spectroscopic techniques; and to clarify the pretreatment-induced changes in reactivity or convertibility of coals in the subsequent liquefaction. This report describes the progress of our work during the first quarterly period. Substantial progress has been made in the spectroscopic characterization of fresh and THF-extracted samples of two subbituminous coals and fresh samples of three bituminous coals using cross-polarization magic angle spinning (CPMAS) solid state {sup 13}C NMR and pyrolysis-GC-MS techniques. CPMAS {sup 13}C NMR and pyrolysis-GC-MS provided important information on carbon distribution/functionality and molecular components/structural units, respectively, for these coal samples. Pyrolysis-GC-MS revealed that there are remarkable structural differences in structural units between the subbituminous coals and the bituminous coals. Furthermore, significant progress has been made in the pretreatments and spectroscopic characterization of catalytically and thermally pretreated as well as physically treated Wyodak subbituminous coal, and temperature-staged and temperature-programmed thermal and catalytic liquefaction of a Montana subbituminous coal.

  8. Interlobe communication in 13C-methionine-labeled human transferrin.

    PubMed

    Beatty, E J; Cox, M C; Frenkiel, T A; Tam, B M; Mason, A B; MacGillivray, R T; Sadler, P J; Woodworth, R C

    1996-06-18

    [1H, 13C] NMR investigations of metal-induced conformational changes in the blood serum protein transferrin (80 kDa) are reported. These are thought to play an important role in the recognition of this protein by its cellular receptors. [1H, 13C] NMR resonance assignments are presented for all nine methionine 13CH3 groups of recombinant deglycosylated human transferrin on the basis of studies of recombinant N-lobe (40 kDa, five Met residues), NOESY-relayed [1H, 13C] HMQC spectra, and structural considerations. The first specific assignments for C-lobe resonances of transferrin are presented. Using methionine 13CH3 resonances as probes, it is shown that, with oxalate as the synergistic anion, Ga3+ binds preferentially to the C-lobe and subsequently to the N-lobe. The NMR shifts of Met464, which is in the Trp460-centered hydrophobic patch of helix 5 in the C-lobe in contact with the anion and metal binding site, show that Ga3+ binding causes movement of side chains within this helix, as is also the case in the N-lobe. The C-lobe residue Met382, which contacts the N-lobe hinge region, is perturbed when Ga3+ binds to the N-lobe, indicative of interlobe communication, a feature which may control the recognition of fully-metallated transferrin by its receptor. These results demonstrate that selective 13C labeling is a powerful method for probing the structure and dynamics of high-molecular-mass proteins. PMID:8672464

  9. 13c Measurements On Air of Small Ice Samples

    NASA Astrophysics Data System (ADS)

    Eyer, M.; Leuenberger, M.

    We have developed a new method for 13C analysis for very small air amounts of less than 0.5 cc STP, corresponding to less than 10 gram of ice. It is based on the needle-crasher technique, which we routinely use for CO2 concentration measurements by infrared laser absorption. The extracted air is slowly expanded into a large volume through a water trap held at ­100°C. This sampled air is then carried by a high helium flux through a modified Precon system of Thermo-Finnigan to separate CO2 from the air and to inject the pure CO2 gas in a low helium stream via an open split device to a Delta Plus XL mass spectrometer. The overall precision based on replicates of standard air is significantly better than 0.1 for a single analysis and is further improved by a triplicate measurement of the same sample through a specially designed gas splitter. We have used this new method for investigations on polar ice cores. The 13C measurements are important for climate reconstructions, e.g. to reconstruct the evolution and its variability in the terrestrial and oceanic carbon sinks and to identify natural variations in the marine carbon cycle. During the industrialization atmospheric 13C decreased by about -2, mainly due to the anthropogenic release of biogenic CO2 by fossil fuel burning. Reconstructions of carbon and oxygen cycles of Joos at al. [1999] using a double deconvolution method show that between 1930 and 1950 the net terrestrial release is changing to a net terrestrial uptake of CO2. A highly resolved 13C dataset of this time window would replenish the documentation of this behaviour. Further, it would be interesting to compare such data with O2/N2 measurements, known as an other partitioning tool for carbon sources and sinks. At the EGS 2002 we will present a highly resolved 13C record from Antarctic ice covering this time period.

  10. Millimeter and submillimeter wave spectra of 13C methylamine

    NASA Astrophysics Data System (ADS)

    Motiyenko, R. A.; Margulès, L.; Ilyushin, V. V.; Smirnov, I. A.; Alekseev, E. A.; Halfen, D. T.; Ziurys, L. M.

    2016-03-01

    Context. Methylamine (CH3NH2) is a light molecule of astrophysical interest, which has an intensive rotational spectrum that extends in the submillimeter wave range and far beyond, even at temperatures characteristic for the interstellar medium. It is likely for 13C isotopologue of methylamine to be identified in astronomical surveys, but there is no information available for the 13CH3NH2 millimeter and submillimeter wave spectra. Aims: In this context, to provide reliable predictions of 13CH3NH2 spectrum in millimeter and submillimeter wave ranges, we have studied rotational spectra of the 13C methylamine isotopologue in the frequency range from 48 to 945 GHz. Methods: The spectrum of 13C methylamine was recorded using conventional absorption spectrometers. The analysis of the rotational spectrum of 13C methylamine in the ground vibrational state was performed on the basis of the group-theoretical high-barrier tunneling Hamiltonian that was developed for methylamine. The available multiple observations of the parent methylamine species toward Sgr B2(N) at 1, 2, and 3 mm using the Submillimeter Telescope and the 12 m antenna of the Arizona Radio Observatory were used to make a search for interstellar 13CH3NH2. Results: In the recorded spectra, we have assigned 2721 rotational transitions that belong to the ground vibrational state of the 13CH3NH2. These measurements were fitted to the Hamilt