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Sample records for 31p mas nmr

  1. 31P MAS-NMR of human erythrocytes: independence of cell volume from angular velocity.

    PubMed

    Kuchel, P W; Bubb, W A; Ramadan, S; Chapman, B E; Philp, D J; Coen, M; Gready, J E; Harvey, P J; McLean, A J; Hook, J

    2004-09-01

    31P magic angle spinning NMR (MAS-NMR) spectra were obtained from suspensions of human red blood cells (RBCs) that contained the cell-volume-sensitive probe molecule, dimethyl methylphosphonate (DMMP). A mathematical representation of the spectral-peak shape, including the separation and width-at-half-height in the 31P NMR spectra, as a function of rotor speed, enabled us to explore the extent to which a change in cell volume would be reflected in the spectra if it occurred. We concluded that a fractional volume change in excess of 3% would have been detected by our experiments. Thus, the experiments indicated that the mean cell volume did not change by this amount even at the highest spinning rate of 7 kHz. The mean cell volume and intracellular 31P line-width were independent of the packing density of the cells and of the initial cell volume. The relationship of these conclusions to other non-NMR studies of pressure effects on cells is noted. PMID:15334588

  2. Decomposition of adsorbed VX on activated carbons studied by {sup 31}P MAS NMR

    SciTech Connect

    Ishay Columbus; Daniel Waysbort; Liora Shmueli; Ido Nir; Doron Kaplan

    2006-06-15

    The fate of the persistent OP nerve agent O-ethyl S-(2-(diisopropylamino)ethyl) methylphosphonothioate (VX) on granular activated carbons that are used for gas filtration was studied by means of 31P magic angle spinning (MAS) NMR spectroscopy. Four types of activated carbon were used, including coal-based BPL. VX as vapor or liquid was adsorbed on carbon granules, and MAS NMR spectra were recorded periodically. The results show that at least 90% of the adsorbed VX decomposes within 20 days or less to the nontoxic ethyl methylphosphonic acid (EMPA) and bis(S-2-diisopropylaminoethane) ((DES){sub 2}). Decomposition occurred irrespective of the phase from which VX was loaded, the presence of metal impregnation on the carbon surface, and the water content of the carbon. Theoretical and practical aspects of the degradation are discussed. 17 refs., 6 figs., 3 tabs.

  3. Decomposition of adsorbed VX on activated carbons studied by 31P MAS NMR.

    PubMed

    Columbus, Ishay; Waysbort, Daniel; Shmueli, Liora; Nir, Ido; Kaplan, Doron

    2006-06-15

    The fate of the persistent OP nerve agent O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX) on granular activated carbons that are used for gas filtration was studied by means of 31P magic angle spinning (MAS) NMR spectroscopy. VX as vapor or liquid was adsorbed on carbon granules, and MAS NMR spectra were recorded periodically. The results show that at least 90% of the adsorbed VX decomposes within 20 days or less to the nontoxic ethyl methylphosphonic acid (EMPA) and bis(S-2-diisopropylaminoethane) {(DES)2}. Decomposition occurred irrespective of the phase from which VX was loaded, the presence of metal impregnation on the carbon surface, and the water content of the carbon. Theoretical and practical aspects of the degradation are discussed. PMID:16830567

  4. Molybdenum modified phosphate glasses studied by 31P MAS NMR and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Szumera, Magdalena

    2015-02-01

    Glasses have been synthesized in the system P2O5sbnd SiO2sbnd K2Osbnd MgOsbnd CaO modified by addition of MoO3. Glasses were prepared by conventional fusion method from 40 g batches. The influence of Mo-cations on the analysed glass structure was investigated by means of Raman and 31P MAS-NMR techniques. It has been found that molybdate units can form Mo[MoO4/MoO6]sbnd Osbnd P and/or Mo[MoO4/MoO6]sbnd Osbnd Si bonds with non-bridging oxygens atoms of Q2 methaphosphate units, resulting in the transformation of chain methaphosphate structure into pyrophosphate and finally into orthophosphate structure. It has been also found that increasing amount of MoO3 in the structure of investigated glasses causes their gradual depolymerization and molybdenum ions in the analysed glass matrix act as modifying cations.

  5. Incorporation of phosphorus guest ions in the calcium silicate phases of Portland cement from 31P MAS NMR spectroscopy.

    PubMed

    Poulsen, Søren L; Jakobsen, Hans J; Skibsted, Jørgen

    2010-06-21

    Portland cements may contain small quantities of phosphorus (typically below 0.5 wt % P(2)O(5)), originating from either the raw materials or alternative sources of fuel used to heat the cement kilns. This work reports the first (31)P MAS NMR study of anhydrous and hydrated Portland cements that focuses on the phase and site preferences of the (PO(4))(3-) guest ions in the main clinker phases and hydration products. The observed (31)P chemical shifts (10 to -2 ppm), the (31)P chemical shift anisotropy, and the resemblance of the lineshapes in the (31)P and (29)Si MAS NMR spectra strongly suggest that (PO(4))(3-) units are incorporated in the calcium silicate phases, alite (Ca(3)SiO(5)) and belite (Ca(2)SiO(4)), by substitution for (SiO(4))(4-) tetrahedra. This assignment is further supported by a determination of the spin-lattice relaxation times for (31)P in alite and belite, which exhibit the same ratio as observed for the corresponding (29)Si relaxation times. From simulations of the intensities, observed in inversion-recovery spectra for a white Portland cement, it is deduced that 1.3% and 2.1% of the Si sites in alite and belite, respectively, are replaced by phosphorus. Charge balance may potentially be achieved to some extent by a coupled substitution mechanism where Ca(2+) is replaced by Fe(3+) ions, which may account for the interaction of the (31)P spins with paramagnetic Fe(3+) ions as observed for the ordinary Portland cements. A minor fraction of phosphorus may also be present in the separate phase Ca(3)(PO(4))(2), as indicated by the observation of a narrow resonance at delta((31)P) = 3.0 ppm for two of the studied cements. (31)P{(1)H} CP/MAS NMR spectra following the hydration of a white Portland cement show that the resonances from the hydrous phosphate species fall in the same spectral range as observed for (PO(4))(3-) incorporated in alite. This similarity and the absence of a large (31)P chemical shift ansitropy indicate that the hydrous (PO(4

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

    PubMed Central

    Magusin, P C; Hemminga, M A

    1994-01-01

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

  7. Solid state 31P MAS NMR spectroscopy and conductivity measurements on NbOPO4 and H3PO4 composite materials

    NASA Astrophysics Data System (ADS)

    Risskov Sørensen, Daniel; Nielsen, Ulla Gro; Skou, Eivind M.

    2014-11-01

    A systematic study of composite powders of niobium oxide phosphate (NbOPO4) and phosphoric acid (H3PO4) has been performed in order to characterize the material's ability to perform as an electrolyte material in medium temperature fuel cells and electrolyzers. Powders of H3PO4 contents between 13.1 and 74.2 M% were produced and characterized with powder X-ray diffraction, 31P MAS NMR and impedance spectroscopy. NMR revealed that a significant degree of dehydration and vaporization of H3PO4 takes place above 200 °C, and increases with temperature. At 500 °C the NbOPO4 and H3PO4 has reacted to form niobium pyrophosphate (Nb2P4O15). Impedance spectroscopy showed an increase in conductivity with increasing acid concentration, whereas the conductivity decreased slightly with increasing temperature. The highest conductivity measured was 2.5·10-3 S/cm for a sample containing 74.2 M% of H3PO4. Lastly, it was shown that NbOPO4 has no significant conductivity of its own.

  8. Solid state {sup 31}P MAS NMR spectroscopy and conductivity measurements on NbOPO{sub 4} and H{sub 3}PO{sub 4} composite materials

    SciTech Connect

    Risskov Sørensen, Daniel; Nielsen, Ulla Gro; Skou, Eivind M.

    2014-11-15

    A systematic study of composite powders of niobium oxide phosphate (NbOPO{sub 4}) and phosphoric acid (H{sub 3}PO{sub 4}) has been performed in order to characterize the material's ability to perform as an electrolyte material in medium temperature fuel cells and electrolyzers. Powders of H{sub 3}PO{sub 4} contents between 13.1 and 74.2 M% were produced and characterized with powder X-ray diffraction, {sup 31}P MAS NMR and impedance spectroscopy. NMR revealed that a significant degree of dehydration and vaporization of H{sub 3}PO{sub 4} takes place above 200 °C, and increases with temperature. At 500 °C the NbOPO{sub 4} and H{sub 3}PO{sub 4} has reacted to form niobium pyrophosphate (Nb{sub 2}P{sub 4}O{sub 15}). Impedance spectroscopy showed an increase in conductivity with increasing acid concentration, whereas the conductivity decreased slightly with increasing temperature. The highest conductivity measured was 2.5·10{sup −3} S/cm for a sample containing 74.2 M% of H{sub 3}PO{sub 4}. Lastly, it was shown that NbOPO{sub 4} has no significant conductivity of its own. - Graphical abstract: Conductivity of NbOPO{sub 4}/H{sub 3}PO{sub 4} composites as a function of equivalent P{sub 2}O{sub 5} content. The conductivity is insignificant for pure NbOPO{sub 4}. - Highlights: • Composites have been made from NbOPO{sub 4} and H{sub 3}PO{sub 4}. • The composites composition has been investigated with solid state NMR. • The composites have shown clear signs of acid dehydration upon heating. • The conductivity of the composites increases for increasing acid content. • NbOPO{sub 4} has no significant conductivity of its own.

  9. Structural investigations of silicate-phosphate glasses containing MoO3 by FTIR, Raman and 31P MAS NMR spectroscopies.

    PubMed

    Szumera, M

    2014-09-15

    Molybdenum is a transition metal (refers to the "d" block of the periodic table) whose atom has an incomplete d sub-shell. It is known that in silicate glasses molybdenum may exist under four oxidation states: Mo6+, Mo5+, Mo4+ and Mo3+, simultaneously molybdenum cations, depending on their content in the glass network, may either be a glass forming component, or act as a modifier. The contemporary literature data show studies conducted mostly on the structure of silicate, phosphate, borate and borosilicate glasses containing molybdenum ions, but not silicate-phosphate glasses. Therefore, the author has undertaken detailed studies using FTIR, Raman and 31P MAS NMR techniques in order to examine the effect of MoO3 addition into the structure of silicate-phosphate glasses from SiO2P2O5K2OCaOMgO system. On the basis of obtained results it was concluded that molybdenum ions in the analysed glasses act as a modifier, which follows from the gradual breakage of oxygen bridges, i.e. POP, SiOSi, and SiOP, and the following formation of connections such as Mo[MoO4]OSi and/or Mo[MoO4]OP. In summary, it is concluded that the increase of MoO3 content (up to 4.4 mol.%) in the structure of glasses of SiO2P2O5K2OMgOCaO system results in weakening of the structure and gradual increase of the degree of silico-oxygen and phosphor-oxygen frameworks depolymerisation. PMID:24759778

  10. 31P MAS-NMR study of flux-grown rare-earth element orthophosphate (monazite/xenotime) solid solutions: Evidence of random cation distribution from paramagnetically shifted NMR resonances

    SciTech Connect

    Palke, A. C.; Stebbins, J. F.; Boatner, Lynn A

    2013-01-01

    We present 31P magic angle spinning nuclear magnetic resonance (MAS-NMR) spectra of flux-grown solid solutions of La1-xCexPO4 ( x between 0.027 and 0.32) having the monoclinic monazite structure, and of Y1-xMxPO4 (M = Vn+, Ce3+, Nd3+, 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 Vn+, Ce3+, and Nd3+ in the diamagnetic LaPO4 or YPO4. As a first-order observation, the number and relative intensity of these peaks is 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 La3+ or Y3+ with the paramagnetic substitutional species Ce3+ and Nd3+. The increased resolution given by the paramagnetic interactions also leads to the observation of splitting of specific resonances in the 31P NMR spectra that may be caused by local, small-scale distortions from the substitution of ions having dissimilar ionic radii.

  11. Modeling Ti/Ge Distribution in LiTi2-xGex(PO4)3 NASICON Series by (31)P MAS NMR and First-Principles DFT Calculations.

    PubMed

    Diez-Gómez, Virginia; Arbi, Kamel; Sanz, Jesús

    2016-08-01

    Ti/Ge distribution in rhombohedral LiTi2-xGex(PO4)3 NASICON series has been analyzed by (31)P magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy and first-principles density functional theory (DFT) calculations. Nuclear magnetic resonance is an excellent probe to follow Ti/Ge disorder, as it is sensitive to the atomic scale environment without long-range periodicity requirements. In the samples considered here, PO4 units are surrounded by four Ti/Ge octahedra, and then, five different components ascribed to P(OTi)4, P(OTi)3(OGe), P(OTi)2(OGe)2, P(OTi)(OGe)3, and P(OGe)4 environments are expected in (31)P MAS NMR spectra of R3̅c NASICON samples. However, (31)P MAS NMR spectra of analyzed series display a higher number of signals, suggesting that, although the overall symmetry remains R3̅c, partial substitution causes a local decrement in symmetry. With the aid of first-principles DFT calculations, 10 detected (31)P NMR signals have been assigned to different Ti4-nGen arrangements in the R3 subgroup symmetry. In this assignment, the influence of octahedra of the same or different R2(PO4)3 structural units has been considered. The influence of bond distances, angles and atom charges on (31)P NMR chemical shieldings has been discussed. Simulation of the LiTi2-xGex(PO4)3 series suggests that detection of 10 P environments is mainly due to the existence of two oxygen types, O1 and O2, whose charges are differently affected by Ge and Ti occupation of octahedra. From the quantitative analysis of detected components, a random Ti/Ge distribution has been deduced in next nearest neighbor (NNN) sites that surround tetrahedral PO4 units. This random distribution was supported by XRD data displaying Vegard's law. PMID:27373306

  12. Solid State FT-IR and (31)P NMR Spectral Features of Phosphate Compounds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Solid-state spectroscopic techniques, including Fourier transform infrared (FT-IR) and solid-state 31P magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopies, are powerful tools for evaluating metal speciation and transformation mechanisms of P compounds in the environment. Studie...

  13. Supramolecular self-organisation and conformational isomerism of a binuclear O,O'-dipropyl dithiophosphate gold(I) complex, [Au2{S2P(OC3H7)2}2]: Synthesis, (13)C and (31)P CP/MAS NMR spectroscopy, single-crystal X-ray diffraction study and thermal behaviour.

    PubMed

    Rodina, Tatyana A; Korneeva, Eugenia V; Antzutkin, Oleg N; Ivanov, Alexander V

    2015-10-01

    Crystalline one-dimensional polymeric catena-poly[bis(μ2-O,O'-dipropyldithiophosphato-S,S')digold(I)] (Au-Au) (1) was prepared and studied using (13)C and (31)P CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. To elucidate the structural function of Dtph ligands in crystalline gold(I) O,O'-dipropyl dithiophosphate, the chemical shift anisotropy parameters (δaniso and η) were calculated from spinning sideband manifolds in (31)P MAS NMR spectra. A novel structure of the gold(I) compound comprises two isomeric, non-centrosymmetric binuclear molecules of [Au2{S2P(OC3H7)2}2] (isomers 'A' and 'B'), whose four Dtph groups display structural inequivalence. In each isomeric binuclear molecule of 1, a pair of μ2-bridging dipropyl Dtph ligands almost symmetrically links two neighbouring gold atoms, forming an extensive eight-membered metallocycle [Au2S4P2], while the intramolecular aurophilic Au⋯Au bond additionally stabilises this central cyclic moiety. At the supramolecular level of complex 1, intermolecular aurophilic Au⋯Au bonds yield almost linear infinite polymeric chains (⋯'A'⋯'B'⋯'A'⋯'B'⋯)n. The thermal behaviour of this compound was studied by the simultaneous thermal analysis (STA) technique (a combination of TG and DSC) under an argon atmosphere. PMID:26004097

  14. Accurate calculation of (31)P NMR chemical shifts in polyoxometalates.

    PubMed

    Pascual-Borràs, Magda; López, Xavier; Poblet, Josep M

    2015-04-14

    We search for the best density functional theory strategy for the determination of (31)P nuclear magnetic resonance (NMR) chemical shifts, δ((31)P), in polyoxometalates. Among the variables governing the quality of the quantum modelling, we tackle herein the influence of the functional and the basis set. The spin-orbit and solvent effects were routinely included. To do so we analysed the family of structures α-[P2W18-xMxO62](n-) with M = Mo(VI), V(V) or Nb(V); [P2W17O62(M'R)](n-) with M' = Sn(IV), Ge(IV) and Ru(II) and [PW12-xMxO40](n-) with M = Pd(IV), Nb(V) and Ti(IV). The main results suggest that, to date, the best procedure for the accurate calculation of δ((31)P) in polyoxometalates is the combination of TZP/PBE//TZ2P/OPBE (for NMR//optimization step). The hybrid functionals (PBE0, B3LYP) tested herein were applied to the NMR step, besides being more CPU-consuming, do not outperform pure GGA functionals. Although previous studies on (183)W NMR suggested that the use of very large basis sets like QZ4P were needed for geometry optimization, the present results indicate that TZ2P suffices if the functional is optimal. Moreover, scaling corrections were applied to the results providing low mean absolute errors below 1 ppm for δ((31)P), which is a step forward in order to confirm or predict chemical shifts in polyoxometalates. Finally, via a simplified molecular model, we establish how the small variations in δ((31)P) arise from energy changes in the occupied and virtual orbitals of the PO4 group. PMID:25738630

  15. MAS NMR of HIV-1 protein assemblies

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    The negative global impact of the AIDS pandemic is well known. In this perspective article, the utility of magic angle spinning (MAS) NMR spectroscopy to answer pressing questions related to the structure and dynamics of HIV-1 protein assemblies is examined. In recent years, MAS NMR has undergone major technological developments enabling studies of large viral assemblies. We discuss some of these evolving methods and technologies and provide a perspective on the current state of MAS NMR as applied to the investigations into structure and dynamics of HIV-1 assemblies of CA capsid protein and of Gag maturation intermediates.

  16. MAS NMR of HIV-1 protein assemblies.

    PubMed

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

    2015-04-01

    The negative global impact of the AIDS pandemic is well known. In this perspective article, the utility of magic angle spinning (MAS) NMR spectroscopy to answer pressing questions related to the structure and dynamics of HIV-1 protein assemblies is examined. In recent years, MAS NMR has undergone major technological developments enabling studies of large viral assemblies. We discuss some of these evolving methods and technologies and provide a perspective on the current state of MAS NMR as applied to the investigations into structure and dynamics of HIV-1 assemblies of CA capsid protein and of Gag maturation intermediates. PMID:25797001

  17. Determination of coordination modes and estimation of the 31P-31P distances in heterogeneous catalyst by solid state double quantum filtered 31P NMR spectroscopy.

    PubMed

    Zhang, Si-Yong; Wang, Mei-Tao; Liu, Qing-Hua; Hu, Bing-Wen; Chen, Qun; Li, He-Xing; Amoureux, Jean-Paul

    2011-04-01

    To overcome the separation difficulty of the palladium-based homogeneous catalyst, the palladium complex can be anchored on various supports such as silica. However, it is difficult to determine the amounts of the two coordination modes of the Pd nucleus, that is, Pd coordinates with one phosphorus atom and Pd coordinates with two phosphorus atoms. Here a (31)P double-quantum filtered (DQ-filtered) method in solid-state NMR is introduced for the palladium-based heterogenous catalyst system. With the DQ-filtered method, we can not only determine the amounts of the two different kinds of palladium coordination modes, we can also estimate the interatomic distance of two (31)P nuclei bonded to a palladium nucleus. With the help of this method, we can quickly estimate interatomic distances in our designed system and accurately re-design the palladium system to accommodate either one (31)P or two (31)P. PMID:21301702

  18. Exploring new Routes for Identifying Phosphorus Species in Terrestrial and Aquatic Ecosystems with 31P NMR

    NASA Astrophysics Data System (ADS)

    Vestergren, Johan; Persson, Per; Sundman, Annelie; Ilstedt, Ulrik; Giesler, Reiner; Schleucher, Jürgen; Gröbner, Gerhard

    2014-05-01

    develop a new method to retrieve and characterize P components in water. By utilizing passive sampling with ion-exchange resin and subsequent analysis with solid state 31P MAS NMR we could identify various P-species extracted from the aquatic systems. By using this approach we can also study the dynamics of the absorption process at the resin as a function of P-species and temperature. This even enabled us to extract the fraction of bound versus free P as a function of temperature for different model P-components (manuscript in preparation). REFERENCES: Gilbert N. Nature 461 716-718 (2009) Vincent AG. et al., Biogeochemistry, 10.1007/s10533-011-9612-0 (2011). Vestergren J et al., Environ. Sci. Technol, 46, 3950-3956, (2012). Vincent AG et al., Plant Soil, 367, 149-162, (2013). Laudon H., et al., Water Resour. Res., 49, 7154-7158, (2013).

  19. 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.

  20. Functional group analysis in coal by sup 31 P NMR spectroscopy

    SciTech Connect

    Verkade, J.G.

    1989-05-01

    The purpose of this research is to determine the labile-hydrogen functional group composition of coal and coal-derived materials by the nmr spectroscopy of their derivatives made with reagents containing the nmr-active nuclei {sup 31}P, {sup 119}Sn, or {sup 205}Tl. 7 refs.

  1. A 13C{31P} REDOR NMR Investigation of the Role of Glutamic Acid Residues in Statherin-Hydroxyapatite Recognition

    PubMed Central

    Ndao, Moise; Ash, Jason T.; Breen, Nicholas F.; Goobes, Gil; Stayton, Patrick S.; Drobny, Gary P.

    2011-01-01

    The side chain carboxyl groups of acidic proteins found in the extra-cellular matrix (ECM) of mineralized tissues play a key role in promoting or inhibiting the growth of minerals such as hydroxyapatite (HAP), the principal mineral component of bone and teeth. Among the acidic proteins found in the saliva is statherin, a 43-residue tyrosine-rich peptide that is a potent lubricant in the salivary pellicle and an inhibitor of both HAP crystal nucleation and growth. Three acidic amino acids – D1, E4, and E5 – are located in the N-terminal 15 amino acid segment, with a fourth amino acid, E26, located outside the N-terminus. We have utilized 13C{31P} REDOR NMR to analyze the role played by acidic amino acids in the binding mechanism of statherin to the HAP surface by measuring the distance between the δ-carboxyl 13C spins of the three glutamic acid side chains of statherin (residues E4, E5, E26) and 31P spins of the phosphate groups at the HAP surface. 13C{31P} REDOR studies of glutamic-5-13C acid incorporated at positions E4 and E26 indicate a 13C–31P distance of more than 6.5 Å between the side chain carboxyl 13C spin of E4 and the closest 31P in the HAP surface. In contrast, the carboxyl 13C spin at E5 has a much shorter 13C–31P internuclear distance of 4.25±0.09 Å, indicating that the carboxyl group of this side chain interacts directly with the surface. 13C T1ρ and slow-spinning MAS studies indicate that the motions of the side chains of E4 and E5 are more restricted than that of E26. Together, these results provide further insight into the molecular interactions of statherin with HAP surfaces. PMID:19678690

  2. sup 31 P NMR analysis of coal moieties bearing -OH, -NH, and -SH functions

    SciTech Connect

    Verkade, J.G.

    1991-08-31

    NMR reagents for the speciation and quantitation of labile-hydrogen functional groups and sulfur groups in coal ligands have been synthesized and evaluated. These reagents, which contain the NMR-active nuclei {sup 31}p, {sup 119}Sn or {sup 195}pt, were designed to possess improved chemical shift resolution over reagents reported in the literature. Our efforts were successful in the case of the new {sup 31}p and {sup 119}Sn reagents we developed, but the {sup 195}pt work on sulfur groups was only partially successful in as much as the grant came to a close and was not renewed. Our success with {sup 31}P and {sup 119}Sn NMR reagents came to the attention of Amoco and they have recently expressed interest in further supporting that work. A further measure of the success of our efforts can be seen in the nine publications supported by this grant which are cited in the reference list.

  3. Comparison of phosphorus forms in three extracts of dairy feces by solution 31P NMR analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Using solution 31P NMR spectroscopy, we compared three extractants, deionized water, sodium acetate buffer (pH 5.0) with fresh sodium dithionite (NaAc-SD), and 0.25 M NaOH-0.05 M EDTA (NaOH-EDTA), for the profile of P compounds in two dairy fecal samples. Phosphorus extracted was 35% for water, and...

  4. Structure and motion of phospholipids in human plasma lipoproteins. A sup 31 P NMR study

    SciTech Connect

    Fenske, D.B.; Chana, R.S.; Parmar, Y.I.; Treleaven, W.D.; Cushley, R.J. )

    1990-04-24

    The structure and motion of phospholipids in human plasma lipoproteins have been studied by using {sup 31}P NMR. Lateral diffusion coefficients, D{sub T}, obtained from the viscosity dependence of the {sup 31}P NMR line widths, were obtained for very low density lipoprotein (VLDL), low-density lipoprotein (LDL), high-density lipoproteins (HDL{sub 2}, HDL{sub 3}), and egg PC/TO microemulsions at 25{degree}C, for VLDL at 40{degree}C, and for LDL at 45{degree}C. In order to prove the orientation and/or order of the phospholipid head-group, estimates of the residual chemical shift anistropy, {Delta}{sigma}, have been obtained for all the lipoproteins and the microemulsions from the viscosity and field dependence for the {sup 31}P NMR line widths. These results suggest differences in the orientation and/or ordering of the head-group in the HDLs. The dynamic behavior of the phosphate moiety in LDL and HDL{sub 3} has been obtained from the temperature dependence of the {sup 31}P spin-lattice relaxation rates. Values of the correlation time for phosphate group reorientation and the activation energy for the motion are nearly identical in LDL and HDL{sub 3} and are similar to values obtained for phospholipid bilayers. This argues against long-lived protein-lipid interactions being the source of either the slow diffusion in LDL or the altered head-group orientation in the HDLs.

  5. sup 31 P NMR analysis of coal moieties bearing -OH, -NH, and -SH functions

    SciTech Connect

    Verkade, J.G.

    1991-01-01

    The purpose of this research is to develop a convenient, reliable and rapid NMR method for the determination of labile-hydrogen functional groups and organic sulfur compounds which are components of coal and coal-derived materials. For this purpose, the former functional groups, including water molecules, are derivatized with reagents containing NMR-active nuclei such as {sup 31}P or {sup 119}Sn, while sulfur groups are derivatized with {sup 195}Pt NMR tagging reagents. Knowledge of the heteroatom composition of coals is necessary for the development of increasingly sophisticated coal processing technologies.

  6. FTIR and {sup 31}P-NMR spectroscopic analyses of surface species in phosphate-catalyzed lactic acid conversion

    SciTech Connect

    Gunter, G.C.; Tam, M.S.; Miller, D.J.

    1996-11-01

    The surface species present on silica/alumina-supported sodium phosphates, active catalysts for the conversion of lactic acid to acrylic acid and 2,3-pentanedione, are examined by pre- and postreaction MAS {sup 31}P-NMR and FTIR spectroscopies. Species present following lactic acid conversion are identified by transmission FTIR of phosphates supported on silicon disks (as a model catalyst system) and verified by {sup 31}P-NMR and diffuse reflectance IR spectroscopy of actual catalysts used in reaction. Monosodium phosphate (NaH{sub 2}PO{sub 4}) condenses to a mixture of sodium polyphosphate (NaPO{sub 3}){sub n} and sodium trimetaphosphate (Na{sub 3}P{sub 3}O{sub 9}), which exhibit little catalytic activity for converting lactic acid to desired products. Disodium phosphate (Na{sub 2}HPO{sub 4}) condenses to tetrasodium pyrophosphate (Na{sub 4}P{sub 2}O{sub 7}), and proton transfer from lactic acid to pyrophosphate results in the formation of sodium lactate. Trisodium phosphate (Na{sub 3}PO{sub 4}) accepts a proton from lactic acid to form sodium lactate and disodium phosphate, which condenses to pyrophosphate. The presence of pyrophosphate and sodium lactate on supported disodium and trisodium phosphates explains their similar catalytic properties; the larger quantity of sodium lactate present on trisodium phosphate leads to higher conversions at lower temperatures. 40 refs., 14 figs., 2 tabs.

  7. Evaluation of Phosphorus Characterization in Ileal Digesta, Manure, and Litter Samples: 31P-NMR vs. HPLC

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Using 31-Phosphorus Nuclear Magnetic Resosonance Spectroscopy (31P-NMR) to characterize phosphorus (P) in manures and litter has become prevalent in the area of nutrient management. To date, there has been no published work evaluating P quantification in manure/litter samples with 31P-NMR compared ...

  8. Evaluation of Phosphorus Characterization in Broiler Ileal Digesta, Manure, and Litter Samples: 31P-NMR vs. HPLC

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Using 31-Phosphorus Nuclear Magnetic Resosonance Spectroscopy (31P-NMR) to characterize phosphorus (P) in manures and litter has become prevalent in the area of nutrient management. To date, there has been no published work evaluating P quantification in manure/litter samples with 31P-NMR compared t...

  9. Local structure of spin Peierls compound TiPO4: 47/49Ti and 31P NMR study

    NASA Astrophysics Data System (ADS)

    Stern, Raivo; Heinmaa, Ivo; Leitmäe, Alexander; Joon, Enno; Tsirlin, Alexander; Kremer, Reinhard; Glaum, Robert

    TiPO4 structure is made of slightly corrugated TiO2 ribbon chains of edge-sharing TiO6 octahedra. The almost perfect 1D spin 1/2 Ti3 + chains are well separated by PO4 tetrahedra. By magnetic susceptibility and MAS-NMR measurements [1] it was shown that TiPO4 has nonmagnetic singlet ground state with remarkably high Spin-Peierls (SP) transition temperature. The high-T magnetic susceptibility of TiPO4 follows well that of a S =1/2 Heisenberg chain with very strong nearest-neighbor AF spin-exchange coupling constant of J =965K. On cooling TiPO4 shows two successive phase transitions at 111K and 74K, with incommensurate (IC) SP phase between them. We studied local structure and dynamics in TiPO4 single crystal using 47/49Ti and 31P NMR in the temperature range 40K to 300K, and determined the principal values and orientation of the magnetic shift tensors for 31P and 47,49Ti nuclei. Since 47,49Ti (S =5/2 and S =7/2, respectively) have quadrupolar moments, we also found the principal axis values and orientations of the electric field gradient (efg) tensor in SP phase and at 295K. In SP phase the structure contains 2 magnetically inequivalent P sites and only one Ti site. From the T-dependence of the relaxation rate of 31P and 47Ti nuclei we determined activation energy Ea = 550 K for spin excitations in SP phase. J. Law et al ., PRB 83, 180414(R) (2011).

  10. CD and 31P NMR studies of tachykinin and MSH neuropeptides in SDS and DPC micelles

    NASA Astrophysics Data System (ADS)

    Schneider, Sydney C.; Brown, Taylor C.; Gonzalez, Javier D.; Levonyak, Nicholas S.; Rush, Lydia A.; Cremeens, Matthew E.

    2016-02-01

    Secondary structural characteristics of substance P (SP), neurokinin A (NKA), neurokinin B (NKB), α-melanocyte stimulating hormone peptide (α-MSH), γ1-MSH, γ2-MSH, and melittin were evaluated with circular dichroism in phosphite buffer, DPC micelles, and SDS micelles. CD spectral properties of γ1-MSH and γ2-MSH as well as 31P NMR of DPC micelles with all the peptides are reported for the first time. Although, a trend in the neuropeptide/micelle CD data appears to show increased α-helix content for the tachykinin peptides (SP, NKA, NKB) and increased β-sheet content for the MSH peptides (α-MSH, γ1-MSH, γ2-MSH) with increasing peptide charge, the lack of perturbed 31P NMR signals for all neuropeptides could suggest that the reported antimicrobial activity of SP and α-MSH might not be related to a membrane disruption mode of action.

  11. Pyrolysis temperature affects phosphorus transformation in biochar: Chemical fractionation and (31)P NMR analysis.

    PubMed

    Xu, Gang; Zhang, You; Shao, Hongbo; Sun, Junna

    2016-11-01

    Phosphorus (P) recycling or reuse by pyrolyzing crop residue has recently elicited increased research interest. However, the effects of feedstock and pyrolysis conditions on P species have not been fully understood. Such knowledge is important in identifying the agronomic and environmental uses of biochar. Residues of three main Chinese agricultural crops and the biochars (produced at 300°C-600°C) derived from these crops were used to determine P transformations during pyrolysis. Hedley sequential fractionation and (31)P NMR analyses were used in the investigation. Our results showed that P transformation in biochar was significantly affected by pyrolysis temperature regardless of feedstock (Wheat straw, maize straw and peanut husk). Pyrolysis treatment transformed water soluble P into a labile (NaHCO3-Pi) or semi-labile pool (NaOH-Pi) and into a stable pool (Dil. HCl P and residual-P). At the same time, organic P was transformed into inorganic P fractions which was identified by the rapid decomposition of organic P detected with solution (31)P NMR. The P transformation during pyrolysis process suggested more stable P was formed at a higher pyrolysis temperature. This result was also evidenced by the presence of less soluble or stable P species, such as such as poly-P, crandallite (CaAl3(OH)5(PO4)2) and Wavellite (Al3(OH)3(PO4)2·5H2O), as detected by solid-state (31)P NMR in biochars formed at a higher pyrolysis temperature. Furthermore, a significant proportion of less soluble pyrophosphate was identified by solution (2%-35%) and solid-state (8%-53%) (31)P NMR, which was also responsible for the stable P forms at higher pyrolysis temperature although their solubility or stability requires further investigation. Results suggested that a relatively lower pyrolysis temperature retains P availability regardless of feedstock during pyrolysis process. PMID:27343937

  12. [sup 31]P NMR study of immobilized artificial membrane surfaces. Structure and dynamics of immobilized phospholipids

    SciTech Connect

    Qiu, X.; Pidgeon, C. )

    1993-11-25

    Chromatography surfaces were prepared by immobilizing a single-chain ether phospholipid at approximately a monolayer density on silica particles. The chromatography particles are denoted as [sup ether]IAM.PC[sup C10/C3], and they are stable to all solvents. The structure and dynamics of the interphase created by immobilizing phospholipids on silica particles were studied by [sup 31]P NMR methods. [sup ether]IAM.PC[sup C10/C3] spontaneously wets when suspended in both aqueous and organic solvents, and [sup 31]P NMR spectra were obtained in water, methanol, chloroform, acetonitrile, and acetone. [sup 31]P NMR spectra were subjected to line-shape analysis. From line-shape analysis, the correlation times for rapid internal motion ([tau]-PLL) and wobbling ([tau]-PRP) of the phospholipid headgroup were calculated for each solvent. Immobilized phospholipid headgroups comprising the IAM interfacial region undergo rapid reorientation similar to the case of the phospholipids forming liposome membranes with [tau]-PLL approximately 1 ns. Phospholipids in liposome membranes exhibit slower wobbling motion ([tau]-PRP approximately 1 ms) in the plane of the membrane. However, the immobilized phospholipids on [sup ether]IAM.PC[sup C10/C3] surfaces wobble with correlation times [tau]-PRP that depend on the solvent bathing the [sup ether]IAM.PC[sup C10/C3] surface. 41 refs., 9 figs., 2 tabs.

  13. Direct Speciation of Phosphorus in Alum-Amended Poultry Litter: Solid-State 31P NMR Investigation

    SciTech Connect

    Hunger, Stefan; Cho, Herman M.; Sims, James T.; Sparks, Donald L.

    2004-02-01

    Amending poultry litter (PL) with aluminum sulfate (alum) has proven to be effective in reducing water-soluble phosphorus (P) in the litter and in runoff from fields that have received PL applications; it has therefore been suggested as a best management practice. Although its effectiveness has been demonstrated on a macroscopic scale in the field, little is known about P speciation in either alumamended or unamended litter. This knowledge is important for the evaluation of the long-term stability and bioavailability of P, which is a necessary prerequisite for the assessment of the sustainability of intensive poultry operations. Both solid state MAS and CP-MAS {sup 31}P NMR as well as {sup 31}P({sup 27}Al) TRAPDOR were used to investigate P speciation in alumamended and unamended PL. The results indicate the presence of a complex mixture of organic and inorganic orthophosphate phases. A calcium phosphate phase, probably a surface precipitate on calcium carbonate, could be identified in both unamended and alum-amended PL, as well as physically bound HPO{sub 4}{sup 2-}. Phosphate associated with Al was found in the alum-amended PL, most probably a mixture of a poorly ordered wavellite and phosphate surface complexes on aluminum hydroxide that had been formed by the hydrolysis of alum. However, a complex mixture of organic and inorganic phosphate species could not be resolved. Phosphate associated with Al comprised on average 40{+-}14% of the total P in alum-amended PL, whereas calcium phosphate phases comprised on average 7{+-}4% in the alum-amended PL and 14{+-}5% in the unamended PL.

  14. Structural biology applications of solid state MAS DNP NMR.

    PubMed

    Akbey, Ümit; Oschkinat, Hartmut

    2016-08-01

    Dynamic Nuclear Polarization (DNP) has long been an aim for increasing sensitivity of nuclear magnetic resonance (NMR) spectroscopy, delivering spectra in shorter experiment times or of smaller sample amounts. In recent years, it has been applied in magic angle spinning (MAS) solid-state NMR to a large range of samples, including biological macromolecules and functional materials. New research directions in structural biology can be envisaged by DNP, facilitating investigations on very large complexes or very heterogeneous samples. Here we present a summary of state of the art DNP MAS NMR spectroscopy and its applications to structural biology, discussing the technical challenges and factors affecting DNP performance. PMID:27095695

  15. Structural biology applications of solid state MAS DNP NMR

    NASA Astrophysics Data System (ADS)

    Akbey, Ümit; Oschkinat, Hartmut

    2016-08-01

    Dynamic Nuclear Polarization (DNP) has long been an aim for increasing sensitivity of nuclear magnetic resonance (NMR) spectroscopy, delivering spectra in shorter experiment times or of smaller sample amounts. In recent years, it has been applied in magic angle spinning (MAS) solid-state NMR to a large range of samples, including biological macromolecules and functional materials. New research directions in structural biology can be envisaged by DNP, facilitating investigations on very large complexes or very heterogeneous samples. Here we present a summary of state of the art DNP MAS NMR spectroscopy and its applications to structural biology, discussing the technical challenges and factors affecting DNP performance.

  16. Surface coil localization of /sup 31/P NMR signals from orthotopic human kidney and liver

    SciTech Connect

    Jue, T.; Rothman, D.L.; Lohman, J.A.B.; Hughes, E.W.; Hanstock, C.C.; Shulman, R.G.

    1988-02-01

    By incorporating the hyperbolic secant inversion pulses with the image-selected in vivo spectroscopy localization technique and by applying a gradient-echo imaging method, the authors have selected only the /sup 31/P NMR signals from orthotopic human kidney and liver, using a single concentric /sup 1/H//sup 31/P surface coil. Corresponding to the experimental results on animal studies, the phosphocreatine signal is dramatically reduced in the localized spectra. The localization strategy also allows them to shim easily on the well-defined volume of interest and leads to high-resolution spectra that exhibit multiplet structure. The results indicate that they can obtain localized signals from deep small organs and point the way for other human metabolism studies.

  17. In vivo 31P-NMR spectroscopy of right ventricle in pigs.

    PubMed

    Schwartz, G G; Steinman, S K; Weiner, M W; Matson, G B

    1992-06-01

    The energy metabolism of the right ventricle (RV) in vivo has been largely unexplored. The goal of this study was to develop and implement techniques for in vivo 31P nuclear magnetic resonance (NMR) spectroscopy of the RV free wall. A two-turn, crossover-design elliptical surface coil was constructed to provide high sensitivity across the thin RV wall but minimal sensitivity in the blood-filled RV cavity. In 36 open-chest, anesthetized pigs, 31P spectroscopy of the RV free wall was performed with this coil at a field strength of 2 Tesla. Spectra were obtained from 800 acquisitions in 24 min with an average signal-to-noise ratio of 13.2 for phosphocreatine (PCr). The PCr-to-ATP (PCr/ATP) ratio of porcine RV was 1.42 +/- 0.05 (mean +/- SE), uncorrected for saturation at a repetition time of 1.8 s. With the use of literature values of the time constant of longitudinal relaxation (T1) to correct for partial saturation, the RV PCr/ATP was estimated to lie between 1.7 and 2.3. Decreased RV PCr/ATP was observed during RV ischemia and pressure overload. Thus in vivo 31P spectroscopy of the RV is readily accomplished with an appropriate surface coil and can provide new information about RV energy metabolism. PMID:1621852

  18. Detoxification of organophosphorus pesticides and nerve agents through RSDL: efficacy evaluation by (31)P NMR spectroscopy.

    PubMed

    Elsinghorst, Paul W; Worek, Franz; Koller, Marianne

    2015-03-01

    Intoxication by organophosphorus compounds, especially by pesticides, poses a considerable risk to the affected individual. Countermeasures involve both medical intervention by means of antidotes as well as external decontamination to reduce the risk of dermal absorption. One of the few decontamination options available is Reactive Skin Decontamination Lotion (RSDL), which was originally developed for military use. Here, we present a (31)P NMR spectroscopy based methodology to evaluate the detoxification efficacy of RSDL with respect to a series of organophosphorus pesticides and nerve agents. Kinetic analysis of the obtained NMR data provided degradation half-lives proving that RSDL is also reasonably effective against organophosphorus pesticides. Unexpected observations of different RSDL degradation patterns are presented in view of its reported oximate-catalyzed mechanism of action. PMID:25597861

  19. MAS PFG NMR Studies of Mixtures in Porous Materials

    NASA Astrophysics Data System (ADS)

    Gratz, Marcel; Hertel, Stefan; Wehring, Markus; Schlayer, Stefan; Stallmach, Frank; Galvosas, Petrik

    2011-03-01

    Pulsed field gradient (PFG) and magic angle spinning (MAS) NMR techniques have been successfully combined for the study of mixture diffusion in porous materials. Using a modular setup of commercially available components, gradient pulses of up to ±2.6 T/m can be applied coinciding with fast sample rotation at the magic angle. Methods for the proper alignment of all components are presented along with protocols for MAS PFG NMR experiments. Finally, first diffusion measurements of n-hexane and benzene being adsorbed together in the metal-organic framework MOF-5 are presented.

  20. In vivo 31P-NMR spectroscopy of chronically stimulated canine skeletal muscle.

    PubMed

    Clark, B J; Acker, M A; McCully, K; Subramanian, H V; Hammond, R L; Salmons, S; Chance, B; Stephenson, L W

    1988-02-01

    Chronic stimulation converts skeletal muscle of mixed fiber type to a uniform muscle made up of type I, fatigue-resistant fibers. Here, the bioenergetic correlates of fatigue resistance in conditioned canine latissimus dorsi are assessed with in vivo phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy. After chronic electrical stimulation, five dogs underwent 31P-NMR spectroscopic and isometric tension measurements on conditioned and contralateral control muscle during stimulation for 200, 300, 500, and 800 ms of an 1,100-ms duty cycle. With stimulation, phosphocreatine (PCr) fell proportional to the degree of stimulation in both conditioned and control muscle but fell significantly less in conditioned muscle at all but the least intense stimulation period (200 ms). Isometric tension, expressed as a tension time index per gram muscle, was significantly greater in the conditioned muscle at the two longest stimulation periods. The overall small change in PCr and the lack of a plateau in tension observed in the conditioned muscle are similar to that seen in cardiac muscle during increased energy demand. This study indicates that the conditioned muscle's markedly enhanced resistance to fatigue is in part the result of its increased capacity for oxidative phosphorylation. PMID:3348365

  1. In vivo sup 31 P-NMR spectroscopy of chronically stimulated canine skeletal muscle

    SciTech Connect

    Clark, B.J. III; McCully, A.K.; Subramanian, H.V.; Hammond, R.L.; Salmons, S.; Chance, B.; Stephenson, L.W. Univ. of Pennsylvania School of Medicine, Philadelphia Univ. of Birmingham )

    1988-02-01

    Chronic stimulation converts skeletal muscle of mixed fiber type to a uniform muscle made up of type I, fatigue-resistant fibers. Here, the bioenergetic correlates of fatigue resistance in conditioned canine latissimus dorsi are assessed with in vivo phosphorus-31 nuclear magnetic resonance ({sup 31}P-NMR) spectroscopy. After chronic electrical stimulation, five dogs underwent {sup 31}P-NMR spectroscopic and isometric tension measurements on conditioned and contralateral control muscle during stimulation for 200, 300, 500, and 800 ms of an 1,100-ms duty cycle. With stimulation, phosphocreatine (PCr) fell proportional to the degree of stimulation in both conditioned and control muscle but fell significantly less in conditioned muscle at all the least intense stimulation period (200 ms). Isometric tension, expressed as a tension time index per gram muscle, was significantly greater in the conditioned muscle at the two longest stimulation periods. The overall small change in PCr and the lack of a plateau in tension observed in the conditioned muscle are similar to that seen in cardiac muscle during increased energy demand. This study indicates that the conditioned muscle's markedly enhanced resistance to fatigue is in part the result of its increased capacity for oxidative phosphorylation.

  2. In vivo 31P and multilabel 13C NMR measurements for evaluation of plant metabolic pathways.

    PubMed

    Rijhwani, S K; Ho, C H; Shanks, J V

    1999-01-01

    Reliable measurements of intracellular metabolites are useful for effective plant metabolic engineering. This study explored the application of in situ 31P and 13C NMR spectroscopy for long-term measurements of intracellular pH and concentrations of several metabolites in glycolysis, glucan synthesis, and central carbon metabolic pathways in plant tissues. An NMR perfusion reactor system was designed to allow Catharanthus roseus hairy root cultures to grow for 3-6 weeks, during which time NMR spectroscopy was performed. Constant cytoplasmic pH (7.40+/-0.06), observed during the entire experiment, indicated adequate oxygenation. 13C NMR spectroscopy was performed on hairy root cultures grown in solutions containing 1-13C-, 2-13C-, and 3-13C-labeled glucose in separate experiments and the flow of label was monitored. Activities of pentose phosphate pathways, nonphotosynthetic CO2 fixation, and glucan synthesis pathways were evident from the experimental results. Scrambling of label in glucans also indicated recycling of triose phosphate and their subsequent conversion to hexose phosphates. PMID:10935751

  3. Metabolic engineering applications of in vivo sup 31 P and sup 13 C NMR studies of Saccharomyces cerevisiae

    SciTech Connect

    Shanks, J.V.

    1989-01-01

    With intent to quantify NMR measurements as much as possible, analysis techniques of the in vivo {sup 31}P NMR spectrum are developed. A systematic procedure is formulated for estimating the relative intracellular concentrations of the sugar phosphates in S. cerevisiae from the {sup 31}P NMR spectrum. In addition, in vivo correlation of inorganic phosphate chemical shift with the chemical shifts of 3-phosphoglycerate, {beta}-fructose 1,6-diphosphate, fructose 6-phosphate, and glucose 6-phosphate are determined. Also, a method was developed for elucidation of the cytoplasmic and vacuolar components of inorganic phosphate in the {sup 31}P NMR spectrum of S. cerevisiae. An in vivo correlation relating the inorganic phosphate chemical shift of the vacuole with the chemical shift of the resonance for pyrophosphate and the terminal phosphate of polyphosphate (PP{sub 1}) is established. Transient measurements provided by {sup 31}P NMR are applied to reg1 mutant and standard strains. {sup 31}P and {sup 13}C NMR measurements are used to analyze the performance of recombinant strains in which the glucose phosphorylation step had been altered.

  4. 31P NMR Study of Filled Skutterudite CeOs4P12

    NASA Astrophysics Data System (ADS)

    Magishi, K.; Sugawara, H.; Saito, T.; Koyama, K.

    2012-12-01

    We report the results of the electrical resistivity ρ(T) and the 31P-NMR measurements on filled skutterudite CeOs4P12 in order to investigate the magnetic properties at low temperatures from a microscopic point of view. For the polycrystalline sample synthesized under high pressure (HP), ρ(T) increases with decreasing temperature. On the other hand, for the single crystal (SC), ρ(T) reveals a positive temperature dependence between room temperature and 200 K, and increases with decreasing temperature below 200 K. Also, 1/T1 obeys the activated temperature dependence 1/T1 propto exp(-Δ/kBT) above 160 K with an energy gap Δ/fB ~ 500 K and 540 K for the HP and the SC samples, which are slightly larger than that of a previous report.

  5. Physiologic significance of the phosphorylation potential in isolated perfused rat hearts (31-P NMR)

    SciTech Connect

    Watters, T.; Wikman-Coffelt, J.; Wu, S.; Wendland, M.; James, T.; Sievers, R.; Botvinick, E.; Parmley, W.

    1986-03-05

    The authors assessed the metabolic and mechanical effects of changes in coronary perfusion pressure (CPP) and afterload (A) in isolated working apex-ejecting rat hearts perfused with Krebs-Henseleit solution containing an excess of O/sub 2/ and substrate. Log (phosphorylation potential) or log (ATP)/(ADP)x (Pi), designated (L), and log (PCR)/(Pi), designated (L*), were calculated from HPLC measurements after rapid freeze-clamping. Increasing CPP from 80-140 cm H/sub 2/O caused an increase in coronary flow (flow), developed pressure (DevP), O/sub 2/ consumption (VO/sub 2/), L, L*, and CO. L and L* were directly related to VO/sub 2/ and CO. Increasing A from 80-140 cm H/sub 2/O caused an increase in DevP and VO/sub 2/, but a decrease in L, L*, and CO. L and L* were inversely linearly related to VO/sub 2/ but were directly linearly related to CO. In both experiments, L and L* are directly related to CO, suggesting that determination of L* (which can be done with 31-P NMR spectroscopy) may be a useful non-invasive method for determining cardiac pump function curves. L and L* may be related to the Frank-Starling mechanism. In a separate experiment using 31-P NMR spectroscopy of isovolumic (left ventricular balloon) perfused rat hearts, increasing CPP caused a direct linear increase in flow, DevP, and L*, confirming the L* results reported above with CPP experiments using the rapid freeze-clamp technique.

  6. Physiologic significance of the phosphorylation potential in isolated perfused rat hearts (/sup 31/P NMR)

    SciTech Connect

    Watters, T.; Wikman-Coffelt, J.; Wu, S.; Wendland, M.; James, T.; Sievers, R.; Botvinick, E.; Parmley, W.

    1986-03-05

    The authors assessed the metabolic and mechanical effects of changes in coronary perfusion pressure (CPP) and afterload (A) in isolated working apex-ejecting rat hearts perfused with Krebs-Henseleit solution containing an excess of O/sub 2/ and substrate. Log(phosphorylation potential) or log (ATP)/(ADP)x (Pi), designated (L), and log (PCR)/(Pi), designated (L*), were calculated from HPLC measurements after rapid freeze-clamping. Increasing CPP from 80-140 cm H/sub 2/O caused an increase in coronary flow(flow), developed pressure(DevP), O/sub 2/ consumption (VO/sub 2/), L, L*, and CO. L and L* were directly related to VO/sub 2/ and CO. Increasing A from 80-140 cm H/sub 2/O caused an increase in DevP and VO/sub 2/, but a decrease in L, L*, and CO. L and L* were inversely linearly related to VO/sub 2/ but were directly linearly related to CO. In both experiments, L and L* are directly related to CO, suggesting that determination of L* (which can be done with /sup 31/P NMR spectroscopy) may be a useful non-invasive method for determining cardiac pump function curves. L and L* may be related to the Frank-Starling mechanism. In a separate experiment using /sup 31/P NMR spectroscopy of isovolumic (left ventricular balloon) perfused rat hearts, increasing CPP caused a direct linear increase in flow, DevP, and L*, confirming the L* results reported above with CPP experiments using the rapid freeze-clamp technique.

  7. Composition of phosphorus in wetland soils determined by SMT and solution 31P-NMR analyses.

    PubMed

    Zhang, Wenqiang; Jin, Xin; Ding, Yuekui; Zhu, Xiaolei; Rong, Nan; Li, Jie; Shan, Baoqing

    2016-05-01

    In Eastern China, wetlands are common in the lower reaches of catchments or in coastal zones. Wetlands are at risk from eutrophication because of the large quantities of phosphorus (P) they receive from rivers. They are also decreasing in size. In this contribution, we present information about the composition of P in wetland soils, obtained using the Standards, Measurements, and Testing (SMT) protocol and (31)P-nuclear magnetic resonance (NMR) spectroscopy. Average P concentrations varied in the different wetland soils and, in four of the five wetlands sampled, exceeded 500 mg∙kg(-1). HCl-inorganic P (Pi) was the main Pi fraction in wetland soils. The percentage contribution of Pi (89.7 %) to total P was the highest in the Yangtze River estuary wetland. Six P components were detected by (31)P-NMR analysis. Mono-P was the main organic P (Po) in wetland soils. Orthophosphate (Ortho-P) was positively and negatively related to NaOH-Pi (R (2) = 0.957, p < 0.001) and HCl-Pi (R (2) = -0.689, p < 0.001), respectively. Orthophosphate monoesters (Mono-P) were positively related to Po (R (2) = 0.617, p < 0.001) and ortho-P (R (2) = 0.624, p < 0.001), respectively. The main Po component was Mono-P, and it may be mineralized to ortho-P under the frequently changing redox conditions in wetland soils. The information from this study will support the development of robust scientific and effective policy for P management in wetlands. PMID:26832861

  8. Phosphate ions in bone: identification of a calcium-organic phosphate complex by 31P solid-state NMR spectroscopy at early stages of mineralization.

    PubMed

    Wu, Y; Ackerman, J L; Strawich, E S; Rey, C; Kim, H-M; Glimcher, M J

    2003-05-01

    Previous 31P cross-polarization and differential cross-polarization magic angle spinning (CP/MAS and DCP/MAS) solid-state NMR spectroscopy studies of native bone and of the isolated crystals of the calcified matrix synthesized by osteoblasts in cell culture identified and characterized the major PO(-3)(4) phosphate components of the mineral phase. The isotropic and anisotropic chemical shift parameters of the minor HPO(-2)(4) component in bone mineral and in mineral deposited in osteoblast cell cultures were found to differ significantly from those of brushite, octacalcium phosphate, and other synthetic calcium phosphates. However, because of in vivo and in vitro evidence that phosphoproteins may play a significant role in the nucleation of the solid mineral phase of calcium phosphate in bone and other vertebrate calcified tissues, the focus of the current solid-state 31P NMR experiments was to detect the possible presence of and characterize the phosphoryl groups of phosphoproteins in bone at the very earliest stages of bone mineralization, as well as the possible presence of calcium-phosphoprotein complexes. The present study demonstrates that by far the major phosphate components identified by solid-state 31P NMR in the very earliest stages of mineralization are protein phosphoryl groups which are not complexed with calcium. However, very small amounts of calcium-complexed protein phosphoryl groups as well as even smaller, trace amounts of apatite crystals were also present at the earliest phases of mineralization. These data support the hypothesis that phosphoproteins complexed with calcium play a significant role in the initiation of bone calcification. PMID:12724829

  9. {sup 31}P NMR analysis of coal moieties bearing -OH, -NH, and -SH functions. Final technical report

    SciTech Connect

    Verkade, J.G.

    1991-08-31

    NMR reagents for the speciation and quantitation of labile-hydrogen functional groups and sulfur groups in coal ligands have been synthesized and evaluated. These reagents, which contain the NMR-active nuclei {sup 31}p, {sup 119}Sn or {sup 195}pt, were designed to possess improved chemical shift resolution over reagents reported in the literature. Our efforts were successful in the case of the new {sup 31}p and {sup 119}Sn reagents we developed, but the {sup 195}pt work on sulfur groups was only partially successful in as much as the grant came to a close and was not renewed. Our success with {sup 31}P and {sup 119}Sn NMR reagents came to the attention of Amoco and they have recently expressed interest in further supporting that work. A further measure of the success of our efforts can be seen in the nine publications supported by this grant which are cited in the reference list.

  10. 31P NMR spectroscopy of rat organs, in situ, using chronically implanted radiofrequency coils.

    PubMed Central

    Koretsky, A P; Wang, S; Murphy-Boesch, J; Klein, M P; James, T L; Weiner, M W

    1983-01-01

    A technique for making 31P NMR spectroscopic measurements in rat kidney, heart, and liver in vivo is presented. Two-turn solenoid coils were surgically implanted around the organ sufficiently in advance of NMR experiments to allow recovery of the animal. These chronically implanted coils allowed acquisition of high-resolution spectra at 40.5 and 97.3 MHz. No resolution improvement occurred at the higher field. Spectra were stable for up to 24 hr, during which time a variety of experiments could be performed. By accumulating spectra at 10-min intervals, the effects of intraperitoneal fructose injections were monitored; in kidney and liver, a rapid increase in sugar phosphates at the expense of Pi and ATP resulted. Fructose had no effect on heart metabolite levels. Spectra from the heart in vivo were obtained at systole and diastole by gating the spectrometer to the aortic pressure wave; no differences in phosphate metabolites were detected. Finally, saturation transfer techniques were used to monitor the rate of ATP synthesis in the kidney. The unidirectional rate constant for the conversion of Pi to ATP was 0.12 +/- 0.03 sec-1. Images PMID:6584867

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

    NASA Astrophysics Data System (ADS)

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

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

  12. Chemical shift referencing in MAS solid state NMR

    NASA Astrophysics Data System (ADS)

    Morcombe, Corey R.; Zilm, Kurt W.

    2003-06-01

    Solid state 13C magic angle spinning (MAS) NMR spectra are typically referenced externally using a probe which does not incorporate a field frequency lock. Solution NMR shifts on the other hand are more often determined with respect to an internal reference and using a deuterium based field frequency lock. Further differences arise in solution NMR of proteins and nucleic acids where both 13C and 1H shifts are referenced by recording the frequency of the 1H resonance of DSS (sodium salt of 2,2-dimethyl-2-silapentane-5-sulphonic acid) instead of TMS (tetramethylsilane). In this note we investigate the difficulties in relating shifts measured relative to TMS and DSS by these various approaches in solution and solids NMR, and calibrate adamantane as an external 13C standard for solids NMR. We find that external chemical shift referencing of magic angle spinning spectra is typically quite reproducible and accurate, with better than ±0.03 ppm accuracy being straight forward to achieve. Solid state and liquid phase NMR shifts obtained by magic angle spinning with external referencing agree with those measured using typical solution NMR hardware with the sample tube aligned with the applied field as long as magnetic susceptibility corrections and solvent shifts are taken into account. The DSS and TMS reference scales for 13C and 1H are related accurately using MAS NMR. Large solvent shifts for the 13C resonance in TMS in either deuterochloroform or methanol are observed, being +0.71 ppm and -0.74 ppm from external TMS, respectively. The ratio of the 13C resonance frequencies for the two carbons in solid adamantane to the 1H resonance of TMS is reported.

  13. Chemical shift referencing in MAS solid state NMR.

    PubMed

    Morcombe, Corey R; Zilm, Kurt W

    2003-06-01

    Solid state 13C magic angle spinning (MAS) NMR spectra are typically referenced externally using a probe which does not incorporate a field frequency lock. Solution NMR shifts on the other hand are more often determined with respect to an internal reference and using a deuterium based field frequency lock. Further differences arise in solution NMR of proteins and nucleic acids where both 13C and 1H shifts are referenced by recording the frequency of the 1H resonance of DSS (sodium salt of 2,2-dimethyl-2-silapentane-5-sulphonic acid) instead of TMS (tetramethylsilane). In this note we investigate the difficulties in relating shifts measured relative to TMS and DSS by these various approaches in solution and solids NMR, and calibrate adamantane as an external 13C standard for solids NMR. We find that external chemical shift referencing of magic angle spinning spectra is typically quite reproducible and accurate, with better than +/-0.03 ppm accuracy being straight forward to achieve. Solid state and liquid phase NMR shifts obtained by magic angle spinning with external referencing agree with those measured using typical solution NMR hardware with the sample tube aligned with the applied field as long as magnetic susceptibility corrections and solvent shifts are taken into account. The DSS and TMS reference scales for 13C and 1H are related accurately using MAS NMR. Large solvent shifts for the 13C resonance in TMS in either deuterochloroform or methanol are observed, being +0.71 ppm and -0.74 ppm from external TMS, respectively. The ratio of the 13C resonance frequencies for the two carbons in solid adamantane to the 1H resonance of TMS is reported. PMID:12810033

  14. Mapping hypoxia-induced bioenergetic rearrangements and metabolic signaling by 18O-assisted 31P NMR and 1H NMR spectroscopy.

    PubMed

    Pucar, Darko; Dzeja, Petras P; Bast, Peter; Gumina, Richard J; Drahl, Carmen; Lim, Lynette; Juranic, Nenad; Macura, Slobodan; Terzic, Andre

    2004-01-01

    Brief hypoxia or ischemia perturbs energy metabolism inducing paradoxically a stress-tolerant state, yet metabolic signals that trigger cytoprotection remain poorly understood. To evaluate bioenergetic rearrangements, control and hypoxic hearts were analyzed with 18O-assisted 31P NMR and 1H NMR spectroscopy. The 18O-induced isotope shift in the 31P NMR spectrum of CrP, betaADP and betaATP was used to quantify phosphotransfer fluxes through creatine kinase and adenylate kinase. This analysis was supplemented with determination of energetically relevant metabolites in the phosphomonoester (PME) region of 31P NMR spectra, and in both aromatic and aliphatic regions of 1H NMR spectra. In control conditions, creatine kinase was the major phosphotransfer pathway processing high-energy phosphoryls between sites of ATP consumption and ATP production. In hypoxia, creatine kinase flux was dramatically reduced with a compensatory increase in adenylate kinase flux, which supported heart energetics by regenerating and transferring beta- and gamma-phosphoryls of ATP. Activation of adenylate kinase led to a build-up of AMP, IMP and adenosine, molecules involved in cardioprotective signaling. 31P and 1H NMR spectral analysis further revealed NADH and H+ scavenging by alpha-glycerophosphate dehydrogenase (alphaGPDH) and lactate dehydrogenase contributing to maintained glycolysis under hypoxia. Hypoxia-induced accumulation of alpha-glycerophosphate and nucleoside 5'-monophosphates, through alphaGPDH and adenylate kinase reactions, respectively, was mapped within the increased PME signal in the 31P NMR spectrum. Thus, 18O-assisted 31P NMR combined with 1H NMR provide a powerful approach in capturing rearrangements in cardiac bioenergetics, and associated metabolic signaling that underlie the cardiac adaptive response to stress. PMID:14977188

  15. Chemical Characterization and Water Content Determination of Bio-Oils Obtained from Various Biomass Species using 31P NMR Spectroscopy

    SciTech Connect

    David, K.; Ben, H.; Muzzy, J.; Feik, C.; Iisa, K.; Ragauskas, A.

    2012-03-01

    Pyrolysis is a promising approach to utilize biomass for biofuels. One of the key challenges for this conversion is how to analyze complicated components in the pyrolysis oils. Water contents of pyrolysis oils are normally analyzed by Karl Fischer titration. The use of 2-chloro-4,4,5,5,-tetramethyl-1,3,2-dioxaphospholane followed by {sup 31}P NMR analysis has been used to quantitatively analyze the structure of hydroxyl groups in lignin and whole biomass. Results: {sup 31}P NMR analysis of pyrolysis oils is a novel technique to simultaneously characterize components and analyze water contents in pyrolysis oils produced from various biomasses. The water contents of various pyrolysis oils range from 16 to 40 wt%. The pyrolysis oils obtained from Loblolly pine had higher guaiacyl content, while that from oak had a higher syringyl content. Conclusion: The comparison with Karl Fischer titration shows that {sup 31}P NMR could also reliably be used to measure the water content of pyrolysis oils. Simultaneously with analysis of water content, quantitative characterization of hydroxyl groups, including aliphatic, C-5 substituted/syringyl, guaiacyl, p-hydroxyl phenyl and carboxylic hydroxyl groups, could also be provided by {sup 31}P NMR analysis.

  16. [ 31P]NMR measurements of hexokinase activity in intact red blood cells with 2-deoxyglucose as substrate

    NASA Astrophysics Data System (ADS)

    Halabi, F.; Seguin, J. P.; Fonroget, J.; Goethals, G.

    [ 31P] NMR spectroscopy is demonstrated to be a suitable tool to follow the time course of 2-deoxyglucose-6-phosphate in intact human erythrocytes incubated with 2-deoxyglucose. It allowed to determine hexokinase Vmax and K m in near physiological conditions.

  17. Ab initio and DFT study of 31P-NMR chemical shifts of sphingomyelin and dihydrosphingomyelin lipid molecule

    NASA Astrophysics Data System (ADS)

    Sugimori, K.; Kawabe, H.; Nagao, H.; Nishikawa, K.

    One of the phospholipids, sphingomyelin (SM, N-acyl-sphingosine-1-phosphorylcholine) is the most abundant component of mammalian membranes in brain, nervous tissues, and human ocular lens. It plays an important role for apoptosis, aging, and signal transduction. Recently, Yappert and coworkers have shown that human lens sphingomyelin and its hydrogenated derivative, dihydrosphingomyelin (DHSM) are interacted with Ca2+ ions to develop human cataracts. Previously, we have investigated conformational differences between an isolated SM/DHSM molecule and Ca2+-coordinated form by using density functional theory (DFT) for geometry optimization and normal mode analysis. As a result, one of stable conformers of SMs has a hydrogen bonding between hydroxyl group and phosphate group, whereas another conformer has a hydrogen bonding between hydroxyl and phosphate amide group. In this study, 31P-Nuclear Magnetic Resonance (NMR) shielding constants of the obtained conformers are investigated by using ab initio and DFT with NMR-gauge invariant atomic orbitals (NMR-GIAO) calculations. The experimental 31P-NMR chemical shifts of SMs and DHSMs have significant small value around 0.1 ppm. We consider the relative conformational changes between SMs and DHSMs affect the slight deviations of 31P-NMR chemical shifts, and discuss intramolecular hydrogen bondings and the solvent effect in relation to NMR experimental reference.

  18. (31)P NMR phospholipid profiling of soybean emulsion recovered from aqueous extraction.

    PubMed

    Yao, Linxing; Jung, Stephanie

    2010-04-28

    The quantity and composition of phospholipids in full-fat soybean flour, flakes, and extruded flakes and in the cream fraction recovered after aqueous extraction (AEP) and enzyme-assisted aqueous extraction (EAEP) of these substrates were studied with (31)P NMR. Extruded flakes had significantly more phosphatidic acid (PA) than flakes and flour prior to aqueous extraction. The PA content of the cream recovered after AEP and EAEP of extruded flakes was similar to that of the starting material, whereas the PA content of the creams from flour and flakes significantly increased. Changes in the PA content could be explained by the action of phospholipase D during the processing step and aqueous extraction. Total phospholipids in the oil recovered from the creams varied from 0.09 to 0.75%, and free oil yield, which is an indicator of cream stability, varied from 6 to 78%. Total phospholipid did not correlate with emulsion stability when it was lower than 0.20%. Inactivation of phospholipase D prior to aqueous extraction of flour resulted in a cream emulsion less stable toward enzymatic demulsification and containing less PA and total phospholipids than untreated flour. The phospholipid distributions in the cream, skim, and insolubles obtained from AEP flour were 7, 51, and 42%, respectively. PMID:20329795

  19. 31P-NMR studies of isolated adult heart cells: effect of myoglobin inactivation.

    PubMed

    Gupta, R K; Wittenberg, B A

    1991-10-01

    31P nuclear magnetic resonance (NMR) studies of isolated adult rat heart cells revealed that the cells maintained high-energy phosphates for up to 6 h in polyamide hollow fibers perfused with well-oxygenated nutrient medium. Glucose plus pyruvate superfused heart cells maintained [phosphocreatine]/[ATP] at 1.4 +/- 0.1, internal pH at 7.09 +/- 0.04 (external pH = 7.25), and intracellular free Mg2+ at 0.51 +/- 0.04 mM. In glucose-containing media, hypoxia was accompanied by a reversible decrease in intracellular ATP and phosphocreatine of approximately 50% and 80%, respectively, while the intracellular free Mg2+ was reversibly increased by 40%. However, inhibition of glycolysis by iodoacetate in aerobic pyruvate-containing medium did not significantly alter high-energy phosphate content. Inactivation of intracellular myoglobin with 1-2 mM sodium nitrite, which reduces the steady-state respiratory oxygen consumption rate by 30%, caused a significant (30%) decrease in intracellular phosphocreatine peak, which was reversed upon removal of sodium nitrite. The nitrite-induced decrease in phosphocreatine was also observed in iodoacetate-treated myocytes but not in oligomycin-treated cells. These results indicate that functional myoglobin enhances high-energy phosphate synthesis in well-oxygenated myocytes. PMID:1928397

  20. Crystallinity and compositional changes in carbonated apatites: Evidence from {sup 31}P solid-state NMR, Raman, and AFM analysis

    SciTech Connect

    McElderry, John-David P.; Zhu, Peizhi; Mroue, Kamal H.; Xu, Jiadi; Pavan, Barbara; Fang, Ming; Zhao, Guisheng; McNerny, Erin; Kohn, David H.; Franceschi, Renny T.; Holl, Mark M.Banaszak; Tecklenburg, Mary M.J.; Ramamoorthy, Ayyalusamy; Morris, Michael D.

    2013-10-15

    Solid-state (magic-angle spinning) NMR spectroscopy is a useful tool for obtaining structural information on bone organic and mineral components and synthetic model minerals at the atomic-level. Raman and {sup 31}P NMR spectral parameters were investigated in a series of synthetic B-type carbonated apatites (CAps). Inverse {sup 31}P NMR linewidth and inverse Raman PO{sub 4}{sup 3−}ν{sub 1} bandwidth were both correlated with powder XRD c-axis crystallinity over the 0.3–10.3 wt% CO{sub 3}{sup 2−} range investigated. Comparison with bone powder crystallinities showed agreement with values predicted by NMR and Raman calibration curves. Carbonate content was divided into two domains by the {sup 31}P NMR chemical shift frequency and the Raman phosphate ν{sub 1} band position. These parameters remain stable except for an abrupt transition at 6.5 wt% carbonate, a composition which corresponds to an average of one carbonate per unit cell. This near-binary distribution of spectroscopic properties was also found in AFM-measured particle sizes and Ca/P molar ratios by elemental analysis. We propose that this transition differentiates between two charge-balancing ion-loss mechanisms as measured by Ca/P ratios. These results define a criterion for spectroscopic characterization of B-type carbonate substitution in apatitic minerals. - Graphical abstract: Carbonated apatite shows an abrupt change in spectral (NMR, Raman) and morphological (AFM) properties at a composition of about one carbonate substitution per unit cell. Display Omitted - Highlights: • Crystallinity (XRD), particle size (AFM) of carbonated apatites and bone mineral. • Linear relationships among crystallinity, {sup 31}P NMR and Raman inverse bandwidths. • Low and high carbonated apatites use different charge-balancing ion-loss mechanism.

  1. MAS-NMR study of lithium zinc silicate glasses and glass-ceramics with various ZnO content

    SciTech Connect

    Goswami, Madhumita; Kothiyal, Govind P.; Montagne, Lionel Delevoye, Laurent

    2008-02-15

    Lithium zinc silicate glasses of composition (mol%): 17.5Li{sub 2}O-(72-x)SiO{sub 2}-xZnO-5.1Na{sub 2}O-1.3P{sub 2}O{sub 5}-4.1B{sub 2}O{sub 3}, 5.5{<=}x{<=}17.7, were prepared by conventional melt-quenched technique and converted to glass-ceramic by controlled crystallization process. {sup 29}Si and {sup 31}P MAS-NMR was used to characterize the structure of both glass and glass-ceramic samples. Despite the complex glass composition, Q{sup 2}, Q{sup 3} and Q{sup 4} sites are identified from {sup 29}Si MAS-NMR, which relative intensities are found to vary with the ZnO content, indicating a network depolymerization by ZnO. Moreover, well separated Q{sup 3} and Q{sup 4} resonances for low ZnO content indicates the occurrence of phase separation. From {sup 31}P MAS-NMR, it is seen that phosphorus is mainly present in the form of ortho-(Q{sup 0}) and pyro-phosphate (Q{sup 1}) structural units and variation of ZnO content did not have much effect on these resonances, which provides an additional evidence for phase separation in the glass. On conversion to glass-ceramics, lithium disilicate (Li{sub 2}Si{sub 2}O{sub 5}), lithium zinc ortho-silicate (Li{sub 3}Zn{sub 0.5}SiO{sub 4}), tridymite (SiO{sub 2}) and cristobalite (SiO{sub 2}) were identified as major silicate crystalline phases. Using {sup 29}Si MAS-NMR, quantification of these silicate crystalline phases is carried out and correlated with the ZnO content in the glass-ceramics samples. In addition, {sup 31}P spectra unambiguously revealed the presence of crystalline Li{sub 3}PO{sub 4} and (Na,Li){sub 3}PO{sub 4} in the glass-ceramics. - Graphical abstract: {sup 29}Si and {sup 31}P MAS-NMR analyses were carried out on multi-component Li{sub 2}O-SiO{sub 2}-ZnO-Na{sub 2}O-P{sub 2}O{sub 5}-B{sub 2}O{sub 3} glasses and glass-ceramics developed for sealing application. Structural data are reported, including phase separation process and quantification of amorphous and crystalline phases.

  2. Trimethylphosphine-Assisted Surface Fingerprinting of Metal Oxide Nanoparticle by (31)P Solid-State NMR: A Zinc Oxide Case Study.

    PubMed

    Peng, Yung-Kang; Ye, Lin; Qu, Jin; Zhang, Li; Fu, Yingyi; Teixeira, Ivo F; McPherson, Ian James; He, Heyong; Tsang, Shik Chi Edman

    2016-02-24

    Nano metal oxides are becoming widely used in industrial, commercial and personal products (semiconductors, optics, solar cells, catalysts, paints, cosmetics, sun-cream lotions, etc.). However, the relationship of surface features (exposed planes, defects and chemical functionalities) with physiochemical properties is not well studied primarily due to lack of a simple technique for their characterization. In this study, solid state (31)P MAS NMR is used to map surfaces on various ZnO samples with the assistance of trimethylphosphine (TMP) as a chemical probe. As similar to XRD giving structural information on a crystal, it is demonstrated that this new surface-fingerprint technique not only provides qualitative (chemical shift) but also quantitative (peak intensity) information on the concentration and distribution of cations and anions, oxygen vacancies and hydroxyl groups on various facets from a single deconvoluted (31)P NMR spectrum. On the basis of this technique, a new mechanism for photocatalytic •OH radical generation from direct surface-OH oxidation is revealed, which has important implications regarding the safety of using nano oxides in personal care products. PMID:26812527

  3. Structural analysis of molybdo-zinc-phosphate glasses: Neutron scattering, FTIR, Raman scattering, MAS NMR studies

    NASA Astrophysics Data System (ADS)

    Renuka, C.; Shinde, A. B.; Krishna, P. S. R.; Reddy, C. Narayana

    2016-08-01

    Vitreous samples were prepared in the xMoO3-17ZnO-(83-x) NaPO3 with 35 ≥ x ≥ 55 glass forming system by energy efficient microwave heating method. Structural evolution of the vitreous network was monitored as a function of composition by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), Raman scattering, Magic Angle Spin Nuclear magnetic resonance (MAS NMR) and Neutron scattering. Addition of MoO3 to the ZnO-NaPO3 glass leads to a pronounced increase in glass transition temperature (Tg) suggesting a significant increase in network connectivity and strength. In order to analyze FTIR and Raman scattering, a simple structural model is presented to rationalize the experimental observations. A number of structural units are formed due to network modification, and the resulting glass may be characterized by a network polyhedral with different numbers of unshared corners. 31P MAS NMR confirms a clear distinction between structural species having 3, 2, 1, 0 bridging oxygens (BOs). Further, Neutron scattering studies were used to probe the structure of these glasses. The result suggests that all the investigated glasses have structures based on chains of four coordinated phosphate and six coordinated molybdate units, besides, two different lengths of P-O bonds in tetrahedral phosphate units that are assigned to bonds of the P-atom with terminal and bridging oxygen atoms.

  4. 31P NMR study of erythrocytes from a patient with hereditary pyrimidine-5'-nucleotidase deficiency.

    PubMed Central

    Swanson, M S; Angle, C R; Stohs, S J; Wu, S T; Salhany, J M; Eliot, R S; Markin, R S

    1983-01-01

    The composition of phosphate metabolites and the intracellular pH in erythrocytes from a patient with hereditary pyrimidine-5'-nucleotidase deficiency were examined using 31P NMR spectroscopy. Several resonances were identified in spectra from intact cells and from extracts. The 2,3-bisphosphoglycerate line intensities were normal but the NTP resonances were about twice normal due to the presence of millimolar quantities of pyrimidine phosphates. Several intense resonances were also observed in the diphosphodiester region of the spectrum. One compound contributing to these lines has been identified as cytidine diphosphocholine. The resonances of NTPs were in a position indicating that the additional triphosphates were also bound by Mg2+. Direct measurement shows that there is a nearly proportional increase in total cell Mg2+ in the patient's cells, in agreement with the interpretation of the spectra. The intracellular pH was about 0.2 unit lower in the patient's erythrocytes. This lower pH is due to the elevation in intracellular fixed negative charges and the shift in permeable anions consequent to the Donnan equilibrium. We suggest that the lower intracellular pH may explain the lower oxygen affinity of these cells in the presence of otherwise normal 2,3-bisphosphoglycerate levels and the increased Mg2+ triphosphates level, because the Mg2+ form of NTPs is known not to alter the oxygen affinity of hemoglobin under physiologic conditions. Furthermore, the lower intracellular pH can also explain the abnormalities in glycolytic intermediates observed for these cells. PMID:6296865

  5. Application of (31P) NMR in analyzing the degradation efficiency of organic phosphorus degrading-bacteria.

    PubMed

    Lu, Yang; Sun, Xin; Ji, Si-Yao; Wang, Jian-Feng; Huang, Yao-Jian; Zhao, Yu-Fen; Xu, Peng-Xiang

    2007-07-01

    HPLC and HPLC-MS are the fastest and most accurate techniques for analysis of organic phosphorus pesticide (OPP) at the present time. Using these techniques, 14 strains of methamidopho (MAP) degrading-bacteria from the area contaminated with MAP have been identified. The results from HPLC and HPLC-MS analyses showed that the highest degradation rate was 73% after 7 days. In order to determine what metabolites will be formed after degradation, a key issue that has been neglected for a long time, we used ((31)P) NMR to track the degradation process. The results showed that different strains produced different metabolites. Ten strains were divided into three groups (groups A, B and C) by their metabolic profiling. Strains in group A degraded MAP into phosphor acid by breaking down all P-N, P-O and P-S bonds in 7 days. Strains in groups B and C had only broken down partially P-N and P-S bonds at the same time. Therefore, the bacterial strains in group A had a greater application potential than the other two groups. In addition, most metal phosphates are unsolvable in water. The analysis of X-ray showed, that the phosphate radicals generated by bacterial degradation induce crystallogenesis of heavy metal salts in water phase and also cause the chemical sedimentation of their crystals. Furthermore, these crystals are hydrogen phosphates. The results suggested that the MAP-degrading bacteria could be used for cleaning up not only the organic phosphorous pesticide contamination but also the phosphorous and heavy metal contamination in water environment simultaneously. PMID:17072553

  6. Distinguishing Bicontinuous Lipid Cubic Phases from Isotropic Membrane Morphologies Using 31P Solid-State NMR Spectroscopy

    PubMed Central

    Yang, Yu; Yao, Hongwei

    2015-01-01

    Nonlamellar lipid membranes are frequently induced by proteins that fuse, bend, and cut membranes. Understanding the mechanism of action of these proteins requires the elucidation of the membrane morphologies that they induce. While hexagonal phases and lamellar phases are readily identified by their characteristic solid-state NMR lineshapes, bicontinuous lipid cubic phases are more difficult to discern, since the static NMR spectra of cubic-phase lipids consist of an isotropic 31P or 2H peak, indistinguishable from the spectra of isotropic membrane morphologies such as micelles and small vesicles. To date, small-angle X-ray scattering is the only method to identify bicontinuous lipid cubic phases. To explore unique NMR signatures of lipid cubic phases, we first describe the orientation distribution of lipid molecules in cubic phases and simulate the static 31P chemical shift lineshapes of oriented cubic-phase membranes in the limit of slow lateral diffusion. We then show that 31P T2 relaxation times differ significantly between isotropic micelles and cubic-phase membranes: the latter exhibit two-orders-of magnitude shorter T2 relaxation times. These differences are explained by the different timescales of lipid lateral diffusion on the cubic-phase surface versus the timescales of micelle tumbling. Using this relaxation NMR approach, we investigated a DOPE membrane containing the transmembrane domain (TMD) of a viral fusion protein. The static 31P spectrum of DOPE shows an isotropic peak, whose T2 relaxation times correspond to that of a cubic phase. Thus, the viral fusion protein TMD induces negative Gaussian curvature, which is an intrinsic characteristic of cubic phases, to the DOPE membrane. This curvature induction has important implications to the mechanism of virus-cell fusion. This study establishes a simple NMR diagnostic probe of lipid cubic phases, which is expected to be useful for studying many protein-induced membrane remodeling phenomena in biology

  7. 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.

  8. Protein analysis by 31p NMR spectroscopy in ionic liquid: quantitative determination of enzymatically created cross-links.

    PubMed

    Monogioudi, Evanthia; Permi, Perttu; Filpponen, Ilari; Lienemann, Michael; Li, Bin; Argyropoulos, Dimitris; Buchert, Johanna; Mattinen, Maija-Liisa

    2011-02-23

    Cross-linking of β-casein by Trichoderma reesei tyrosinase (TrTyr) and Streptoverticillium mobaraense transglutaminase (Tgase) was analyzed by (31)P nuclear magnetic resonance (NMR) spectroscopy in ionic liquid (IL). According to (31)P NMR, 91% of the tyrosine side chains were cross-linked by TrTyr at high dosages. When Tgase was used, no changes were observed because a different cross-linking mechanism was operational. However, this verified the success of the phosphitylation of phenolics within the protein matrix in the IL. Atomic force microscopy (AFM) in solid state showed that disk-shaped nanoparticles were formed in the reactions with average diameters of 80 and 20 nm for TrTyr and Tgase, respectively. These data further advance the current understanding of the action of tyrosinases on proteins on molecular and chemical bond levels. Quantitative (31)P NMR in IL was shown to be a simple and efficient method for the study of protein modification. PMID:21218836

  9. /sup 31/P NMR saturation-transfer and /sup 13/C NMR kinetic studies of glycolytic regulation during anaerobic and aerobic glycolysis

    SciTech Connect

    Campbell-Burk, S.L.; den Hollander, J.A.; Alger, J.R.; Shulman, R.G.

    1987-11-17

    /sup 31/P NMR saturation-transfer techniques have been employed in glucose-gown derepressed yeast to determine unidirectional fluxes in the upper part of the Embden-Meyerhof-Parnas pathway. The experiments were performed during anaerobic and aerobic glycolysis by saturating the ATP/sub ..gamma../ resonances and monitoring changes in the phosphomonoester signals from glucose 6-phosphate and fructose 1,6-bisphosphate. These experiments were supplemented with /sup 13/C NMR measurements of glucose utilization rates and /sup 13/C NMR label distribution studies. Combined with data obtained previously from radioisotope measurement, these /sup 31/P and /sup 13/C NMR kinetic studies allowed estimation of the net glycolytic flow in addition to relative flows through phosphofructokinase (PFK) and Fru-1,6-P/sub 2/ase during anaerobic and aerobic glycolysis. The /sup 31/P NMR saturation-transfer results are consistent with previous results obtained from measurements of metabolite levels, radioisotope data, and /sup 13/C NMR studies, providing additional support for in vivo measurement of the flows during glycolysis.

  10. Intracellular pH of perfused single frog skin: combined 19F- and 31P-NMR analysis.

    PubMed

    Civan, M M; Lin, L E; Peterson-Yantorno, K; Taylor, J; Deutsch, C

    1984-11-01

    Intracellular pH (pHc) has been determined in frog skin by applying two different methods of pH measurement, 19F and 31P nuclear magnetic resonance (NMR) analysis, to the same tissues. Results from both NMR approaches confirm an observation by Lin, Shporer, and Civan [Am. J. Physiol. 248 (Cell Physiol. 17): 1985] that acidification of the extracellular medium reverses the sign of the pH gradient present under baseline conditions. The fluorinated probe, alpha-(difluoromethyl)-alanine methyl ester, was introduced into the epithelial cells by preincubating skins for 4.7-10.4 h at room temperature in Ringer solutions containing 1 mM ester. The free amino acid was subsequently released by intracellular esterase activity, thus providing a high enough probe concentration for NMR analysis to be practicable. From measurements of short-circuit current and transepithelial resistance under base-line and experimental conditions and the appearance of phosphocreatine (PCr) in the 31P spectrum of preloaded tissues, the fluorinated probe appears to be nontoxic to frog skin. Measurement of the chemical shift of methylphosphonate relative to PCr permitted calculation of extracellular pH. Estimation of the intracellular pH was performed both by measurement of the chemical shift of inorganic phosphate (Pi) relative to PCr and by measurement of the central peak spacing of the 19F spectrum. From four direct comparisons of the two techniques in two experiments, the difference in the estimated pH was only 0.03 +/- 0.07 pH units, supporting the concept that 31P-NMR analysis is a valid method of measuring pH in this tissue. PMID:6496729

  11. 31P NMR study of magnetic phase transitions of MnP single crystal under 2 GPa pressure

    NASA Astrophysics Data System (ADS)

    Fan, GuoZhi; Zhao, Bo; Wu, Wei; Zheng, Ping; Luo, JianLin

    2016-05-01

    Superconductivity on the border of the long-range magnetic order has been discovered in MnP under high pressures. In order to investigate the nature of the magnetic properties adjacent to the superconducting state, we performed zero-field 31P NMR for MnP single crystal under ambient and hydrostatic pressure of 2 GPa, respectively. Radio frequency power level was used to determine whether NMR signal originates from a helical state or not. When 2 GPa pressure was applied, the signal from helical state exists even above 160 K, while that from the ferromagnetic phase was not observed. Our NMR results indicate that the magnetic phase which is adjacent to the superconducting state is in a helical magnetic structure.

  12. 2D 31P solid state NMR spectroscopy, electronic structure and thermochemistry of PbP7

    NASA Astrophysics Data System (ADS)

    Benndorf, Christopher; Hohmann, Andrea; Schmidt, Peer; Eckert, Hellmut; Johrendt, Dirk; Schäfer, Konrad; Pöttgen, Rainer

    2016-03-01

    Phase pure polycrystalline PbP7 was prepared from the elements via a lead flux. Crystalline pieces with edge-lengths up to 1 mm were obtained. The assignment of the previously published 31P solid state NMR spectrum to the seven distinct crystallographic sites was accomplished by radio-frequency driven dipolar recoupling (RFDR) experiments. As commonly found in other solid polyphosphides there is no obvious correlation between the 31P chemical shift and structural parameters. PbP7 decomposes incongruently under release of phosphorus forming liquid lead as remainder. The thermal decomposition starts at T>550 K with a vapor pressure almost similar to that of red phosphorus. Electronic structure calculations reveal PbP7 as a semiconductor according to the Zintl description and clearly shows the stereo-active Pb-6s2 lone pairs in the electron localization function ELF.

  13. Time course of myocardial sodium accumulation after burn trauma: a (31)P- and (23)Na-NMR study.

    PubMed

    Sikes, P J; Zhao, P; Maass, D L; Horton, J W

    2001-12-01

    In this study, (23)Na- and (31)P- nuclear magnetic resonance (NMR) spectra were examined in perfused rat hearts harvested 1, 2, 4, and 24 h after 40% total body surface area burn trauma and lactated Ringer resuscitation, 4 ml. kg(-1). %(-1) burn. (23)Na-NMR spectroscopy monitored myocardial intracellular Na+ using the paramagnetic shift reagent thulium 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetra(methylenephosphonic acid). Left ventricular function, cardiac high-energy phosphates (ATP/PCr), and myocyte intracellular pH were studied by using (31)P NMR spectroscopy to examine the hypothesis that burn-mediated acidification of cardiomyocytes contributes to subsequent Na+ accumulation by this cell population. Intracellular Na+ accumulation was confirmed by sodium-binding benzofuran isophthalate loading and fluorescence spectroscopy in cardiomyocytes isolated 1, 2, 4, 8, 12, 18, and 24 h postburn. This myocyte Na+ accumulation as early as 2 h postburn occurred despite no changes in cardiac ATP/PCr and intracellular pH. Left ventricular function progressively decreased after burn trauma. Cardiomyocyte Na+ accumulation paralleled cardiac contractile dysfunction, suggesting that myocardial Na+ overload contributes, in part, to the progressive postburn decrease in ventricular performance. PMID:11717236

  14. Using 31P-NMR to investigate dynamics of soil phosphorus compounds in the Rothamsted Long Term Experiments

    NASA Astrophysics Data System (ADS)

    Blackwell, Martin; Turner, Ben; Granger, Steve; Hooper, Tony; Darch, Tegan; Hawkins, Jane; Yuan, Huimin; McGrath, Steve

    2015-04-01

    The technique of 31P-NMR spectroscopy has done more to advance the knowledge of phosphorus forms (especially organic phosphorus) in environmental samples than any other method. The technique has advanced such that specific compounds can be identified where previously only broad categories such as orthophosphate monoesters and diesters were distinguishable. The Soil Archive and Long Term Experiments at Rothamsted Research, UK, potentially provides an unequalled opportunity to use this technique to observe changes in soil phosphorus compounds with time and under different treatments, thereby enhancing our understanding of phosphorus cycling and use by plants. Some of the earliest work using this technique on soils was carried out by Hawkes et al. in 1984 and this used soils from two of the oldest Rothamsted Long Term Experiments, namely Highfield and Park Grass. Here we revisit the samples studied in this early work and reanalyse them using current methodology to demonstrate how the 31P-NMR technique has advanced. We also present results from a study on the phosphorus chemistry in soils along the Hoosfield acid strip (Rothamsted, UK), where a pH gradient from 3.7 to 7.8 occurs in a single soil with little variation in total phosphorus (mean ± standard deviation 399 ± 27 mg P kg-1). Soil pH was found to be an important factor in determining the proportion of phosphomonoesters and phosphodiesters in the soil organic phosphorus, although total organic phosphorus concentrations were a relatively consistent proportion of the total soil phosphorus (36 ± 2%) irrespective of soil pH. Key words. 31P-NMR, soil organic phosphorus, long term experiments, Hoosfield acid strip

  15. Assessment of membrane protection by /sup 31/P-NMR effects of lidocaine on calcium-paradox in myocardium

    SciTech Connect

    Sakai, Hirosumi; Yoshiyama, Minoru; Teragaki, Masakazu; Takeuchi, Kazuhide; Takeda, Takeda; Ikata, Mari; Ishikawa, Makoto; Miura, Iwao

    1989-01-01

    In studying calcium paradox, perfused rat hearts were used to investigate the myocardial protective effects of lidocaine. Intracellular contents of phosphates were measured using the /sup 31/P-NMR method. In hearts reexposed to calcium, following 3 minute calcium-free perfusion, a rapid contracture occurred, followed by rapid and complete disappearance of intracellular phosphates with no resumption of cardiac function. In hearts where lidocaine was administered from the onset of the calcium-free perfusion until 2 minutes following the onset of reexposure to calcium, both intracellular phosphates and cardiac contractility were maintained. Therefore, it can be said that cell membranes were protected by lidocaine.

  16. [sup 31]P and [sup 27]Al NMR investigations of highly acidic, aqueous solutions containing aluminum and phosphorus

    SciTech Connect

    Mortlock, R.F.; Bell, A.T.; Radke, C.J. Univ. of California, Berkeley )

    1993-01-21

    [sup 31]P and [sup 27]Al NMR spectroscopies have been used to characterize acidic, aqueous solutions of orthophosphoric acid, aluminum chloride, and tetramethylammonium (TMA) hydroxide. The final compositions of the solutions range from 0.1 to 1 mol % P, 0.0 to 20 mol % HCl, P/Al = 0.1 to 20, and P/(TMA)[sub 2]O = 2 to 20. Soluble aluminophosphate cations form reactions of hexaaqua Al monomeric cations, [Al(H[sub 2]O)[sub 6

  17. 2D exchange 31P NMR spectroscopy of bacteriophage M13 and tobacco mosaic virus.

    PubMed Central

    Magusin, P C; Hemminga, M A

    1995-01-01

    Two-dimensional (2D) exchange 31P nuclear magnetic resonance spectroscopy is used to study the slow overall motion of the rod-shaped viruses M13 and tobacco mosaic virus in concentrated gels. Even for short mixing times, observed diagonal spectra differ remarkably from projection spectra and one-dimensional spectra. Our model readily explains this to be a consequence of the T2e anisotropy caused by slow overall rotation of the viruses about their length axis. 2D exchange spectra recorded for 30% (w/w) tobacco mosaic virus with mixing times < 1 s do not show any off-diagonal broadening, indicating that its overall motion occurs in the sub-Hz frequency range. In contrast, the exchange spectra obtained for 30% M13 show significant off-diagonal intensity for mixing times of 0.01 s and higher. A log-gaussian distribution around 25 Hz of overall diffusion coefficients mainly spread between 1 and 10(3) Hz faithfully reproduces the 2D exchange spectra of 30% M13 recorded at various mixing times in a consistent way. A small but notable change in diagonal spectra at increasing mixing time is not well accounted for by our model and is probably caused by 31P spin diffusion. PMID:7756532

  18. Intrauterine fetal brain NMR spectroscopy: 1H and 31P studies in rats

    SciTech Connect

    Nakada, T.; Kwee, I.L.; Suzuki, N.; Houkin, K. )

    1989-11-01

    Fetal brain metabolism was investigated in utero noninvasively using multinuclear nuclear magnetic resonance spectroscopy in rats at two representative prenatal stages: early (17-18 days) and late (20-21 days) stages. Phosphorus-31 (31P) spectroscopy revealed that phosphocreatine is significantly lower in the early stage and increases to the level of early neonates by the late prenatal stage. Intracellular pH at the early stage was found to be strikingly high (7.52 +/- 0.21) and decreased to a level similar to that of neonates by the late stage (7.29 +/- 0.07). Phosphomonoester levels at both stages were similar to the values reported for early neonates. Water-suppressed proton (1H) spectroscopy demonstrated a distinctive in vivo fetal brain spectral pattern characterized by low levels of N-acetyl aspartate and high levels of taurine. High-resolution proton spectroscopy and homonuclear chemical-shift correlate spectroscopy of brain perchloric acid extracts confirmed these in vivo findings. In vitro 31P spectroscopy of acidified chloroform methanol extracts showed the characteristic membrane phospholipid profiles of fetal brain. The phosphatidylethanolamine (PE)-to-phosphatidylcholine (PC) ratio (PE/PC) did not show significant changes between the two stages at 0.40 +/- 0.11, a value similar to that of early neonates.

  19. A solid-state 31P-NMR investigation of the allosteric transition in glycogen phosphorylase b.

    PubMed Central

    Challoner, R; McDowell, C A; Stirtan, W; Withers, S G

    1993-01-01

    The catalytic role of the cofactor phosphate moiety at the active site of glycogen phosphorylase has been the subject of many investigations including solution-state high-resolution 31P-NMR studies. In this study the pyridoxal phosphate moiety in both the inactive and active forms of microcrystalline phosphorylase b has been investigated by high-resolution 31P magic-angle spinning NMR. The symmetry of the shielding tensor in model compounds at varying degrees of ionization is investigated and the results indicate a marked difference between the dianionic and monoanionic model compounds. Consequently the observed similarity in the principal tensor components describing the shielding tensor of the phosphorus nuclei present at the active site of both the R- and T-state conformations suggests that there is no change in ionization site upon activation in contrast to suggestions based upon isotropic shifts. Since previous relaxation measurements have pointed to the need to consider motional influences in such systems, several plausible models are considered. Subject to the assumption of congruency between the principal axis system describing the shielding interaction and molecular frame determined by the molecular symmetry axes, we conclude that the phosphate cofactor is dianionic in both forms. PMID:8457672

  20. The intact muscle lipid composition of bulls: an investigation by MALDI-TOF MS and 31P NMR.

    PubMed

    Dannenberger, Dirk; Süss, Rosmarie; Teuber, Kristin; Fuchs, Beate; Nuernberg, Karin; Schiller, Jürgen

    2010-02-01

    The analysis of beef lipids is normally based on chromatographic techniques and/or gas chromatography in combination with mass spectrometry (GC/MS). Modern techniques of soft-ionization MS were so far scarcely used to investigate the intact lipids in muscle tissues of beef. The objective of the study was to investigate whether matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) mass spectrometry and (31)P nuclear magnetic resonance (NMR) spectroscopy are useful tools to study the intact lipid composition of beef. For the MALDI-TOF MS and (31)P NMR investigations muscle samples were selected from a feeding experiment with German Simmental bulls fed different diets. Beside the triacylglycerols (TAGs), phosphatidylethanolamine (PE), phosphatidylcholine (PC) and phosphatidylinositol (PI) species the MALDI-TOF mass spectra of total muscle lipids gave also intense signals of cardiolipin (CL) species. The application of different matrix compounds, 2,5-dihydroxybenzoic acid (DHB) and 9-aminoacridine (9-AA), leads to completely different mass spectra: 9-AA is particularly useful for the detection of (polar) phospholipids, whereas apolar lipids, such as cholesterol and triacylglycerols, are exclusively detected if DHB is used. Finally, the quality of the negative ion mass spectra is much higher if 9-AA is used. PMID:19900429

  1. /sup 31/P NMR analysis of membrane phospholipid organization in viable, reversibly electropermeabilized Chinese hamster ovary cells

    SciTech Connect

    Lopez, A.; Rols, M.P.; Teissie, J.

    1988-02-23

    Chinese hamster ovary (CHO) cells were reversibly permeabilized by submitting them to short, high-intensity, square wave pulses (1.8 kV/cm, 100 ..mu..s). The cells remained in a permeable state without loss of viability for several hours at 4/sup 0/C. A new anisotropic peak with respect to control cells was observed on /sup 31/P NMR spectroscopic analysis of the phospholipid components. This peak is only present when the cells are permeable, and normal anisotropy is recovered after resealing. Taking into account the fusogenicity of electropermeabilized cells, comparative studies were performed on 5% poly(ethylene glycol) treated cells. The /sup 31/P NMR spectra of the phospholipids displayed the same anisotropic peak as in the case of the electropermeabilized cells. In the two cases, this anisotropic peak was located downfield from the main peak associated to the phospholipids when organized in bilayers. The localization of this anisotropic peak is very different from the one of a hexagonal phase. The authors proposed a reorganization of the polar head group region leading to a weakening of the hydration layer to account for these observations. This was also thought to explain the electric field induced fusogenicity of these cells.

  2. Phosphide oxides RE2AuP2O (RE = La, Ce, Pr, Nd): synthesis, structure, chemical bonding, magnetism, and 31P and 139La solid state NMR.

    PubMed

    Bartsch, Timo; Wiegand, Thomas; Ren, Jinjun; Eckert, Hellmut; Johrendt, Dirk; Niehaus, Oliver; Eul, Matthias; Pöttgen, Rainer

    2013-02-18

    Polycrystalline samples of the phosphide oxides RE(2)AuP(2)O (RE = La, Ce, Pr, Nd) were obtained from mixtures of the rare earth elements, binary rare earth oxides, gold powder, and red phosphorus in sealed silica tubes. Small single crystals were grown in NaCl/KCl fluxes. The samples were studied by powder X-ray diffraction, and the structures were refined from single crystal diffractometer data: La(2)AuP(2)O type, space group C2/m, a = 1515.2(4), b = 424.63(8), c = 999.2(2) pm, β = 130.90(2)°, wR2 = 0.0410, 1050 F(2) values for Ce(2)AuP(2)O, and a = 1503.6(4), b = 422.77(8), c = 993.0(2) pm, β = 130.88(2)°, wR2 = 0.0401, 1037 F(2) values for Pr(2)AuP(2)O, and a = 1501.87(5), b = 420.85(5), c = 990.3(3) pm, β = 131.12(1)°, wR2 = 0.0944, 1143 F(2) values for Nd(2)AuP(2)O with 38 variables per refinement. The structures are composed of [RE(2)O](4+) polycationic chains of cis-edge-sharing ORE(4/2) tetrahedra and polyanionic strands [AuP(2)](4-), which contain gold in almost trigonal-planar phosphorus coordination by P(3-) and P(2)(4-) entities. The isolated phosphorus atoms and the P(2) pairs in La(2)AuP(2)O could clearly be distinguished by (31)P solid state NMR spectroscopy and assigned on the basis of a double quantum NMR technique. Also, the two crystallographically inequivalent La sites could be distinguished by static (139)La NMR in conjunction with theoretical electric field gradient calculations. Temperature-dependent magnetic susceptibility measurements show diamagnetic behavior for La(2)AuP(2)O. Ce(2)AuP(2)O and Pr(2)AuP(2)O are Curie-Weiss paramagnets with experimental magnetic moments of 2.35 and 3.48 μ(B) per rare earth atom, respectively. Their solid state (31)P MAS NMR spectra are strongly influenced by paramagnetic interactions. Ce(2)AuP(2)O orders antiferromagnetically at 13.1(5) K and shows a metamagnetic transition at 11.5 kOe. Pr(2)AuP(2)O orders ferromagnetically at 7.0 K. PMID:23374070

  3. Sealed rotors for in situ high temperature high pressure MAS NMR

    DOE PAGESBeta

    Hu, Jian Z.; Hu, Mary Y.; Zhao, Zhenchao; Xu, Souchang; Vjunov, Aleksei; Shi, Hui; Camaioni, Donald M.; Peden, Charles H. F.; Lercher, Johannes A.

    2015-07-06

    Magic angle spinning (MAS) nuclear magnetic resonance (NMR) investigations on heterogeneous samples containing solids, semi-solids, liquid and gases or a mixture of them under non-conventional conditions of a combined high pressure and high temperature, or cold temperature suffer from the unavailability of a perfectly sealed rotor. Here, we report the design of reusable and perfectly-sealed all-zircornia MAS rotors. The rotors are easy to use and are suitable for operation temperatures from below 0 to 250 °C and pressures up to 100 bar. As an example of potential applications we performed in situ MAS NMR investigations of AlPO₄-5 molecular sieve crystallization,more » a kinetic study of the cyclohexanol dehydration reaction using 13C MAS NMR, and an investigation of the metabolomics of intact biological tissue at low temperature using 1H HR-MAS NMR spectroscopy. The in situ MAS NMR experiments performed using the reported rotors allowed reproduction of the results from traditional batch reactions, while offering more detailed quantitative information at the molecular level, as demonstrated for the molecular sieve synthesis and activation energy measurements for cyclohexanol dehydration. The perfectly sealed rotor also shows promising application for metabolomics studies using 1H HR-MAS NMR.« less

  4. Sealed rotors for in situ high temperature high pressure MAS NMR

    SciTech Connect

    Hu, Jian Z.; Hu, Mary Y.; Zhao, Zhenchao; Xu, Souchang; Vjunov, Aleksei; Shi, Hui; Camaioni, Donald M.; Peden, Charles H. F.; Lercher, Johannes A.

    2015-07-06

    Magic angle spinning (MAS) nuclear magnetic resonance (NMR) investigations on heterogeneous samples containing solids, semi-solids, liquid and gases or a mixture of them under non-conventional conditions of a combined high pressure and high temperature, or cold temperature suffer from the unavailability of a perfectly sealed rotor. Here, we report the design of reusable and perfectly-sealed all-zircornia MAS rotors. The rotors are easy to use and are suitable for operation temperatures from below 0 to 250 °C and pressures up to 100 bar. As an example of potential applications we performed in situ MAS NMR investigations of AlPO₄-5 molecular sieve crystallization, a kinetic study of the cyclohexanol dehydration reaction using 13C MAS NMR, and an investigation of the metabolomics of intact biological tissue at low temperature using 1H HR-MAS NMR spectroscopy. The in situ MAS NMR experiments performed using the reported rotors allowed reproduction of the results from traditional batch reactions, while offering more detailed quantitative information at the molecular level, as demonstrated for the molecular sieve synthesis and activation energy measurements for cyclohexanol dehydration. The perfectly sealed rotor also shows promising application for metabolomics studies using 1H HR-MAS NMR.

  5. Coal liquefaction process streams characterization and evaluation: Estimation of total phenol concentrations in coal liquefaction resids by [sup 31]P NMR spectroscopy

    SciTech Connect

    Mohan, J.T.; Verkade, J.G. )

    1992-11-01

    In this study, Iowa State University researchers used [sub 31]P-tagged reagents to derivatize the labile hydrogen functional groups in the THF-soluble portion of 850[degrees]F[sup +] distillation resid materials and the THF-soluble portion of process oils derived from direct coal liquefaction.[sup 31]P-NMR was used to analyze the derivatized samples. NMR peak assignments can be made by comparison to model compounds similarly derivatized. Species can be quantified by integration of the NMR signals. Different [sup 31]P-NMR tagged reagents can be used to produce different degrees of peak resolution in the NMR spectrum. This, in turn, partially dictates the degree of speciation and/or quantification of species, or classes of compounds, that can be accomplished. Iowa State chose a [sup 31]P-tagged reagent (ClPOCMe[sub 2]CMe[sub 2]O) which was shown previously to be particularly useful in the derivatization of phenols. The derivatized samples all exhibited a small group of peaks attributed to amines and a broad group of peaks in the phenol region. The presence of paramagnetic species in the samples caused the NMR signals to broaden. Electron paramagnetic resonance (EPR) spectra confirmed the presence of paramagnetic organic free radicals in selected samples. Various methods were employed to process the NMR data. The complexity and broadness of the phenol peak, however, made speciation of the phenols impractical.

  6. Coal liquefaction process streams characterization and evaluation: Estimation of total phenol concentrations in coal liquefaction resids by {sup 31}P NMR spectroscopy

    SciTech Connect

    Mohan, J.T.; Verkade, J.G.

    1992-11-01

    In this study, Iowa State University researchers used {sub 31}P-tagged reagents to derivatize the labile hydrogen functional groups in the THF-soluble portion of 850{degrees}F{sup +} distillation resid materials and the THF-soluble portion of process oils derived from direct coal liquefaction.{sup 31}P-NMR was used to analyze the derivatized samples. NMR peak assignments can be made by comparison to model compounds similarly derivatized. Species can be quantified by integration of the NMR signals. Different {sup 31}P-NMR tagged reagents can be used to produce different degrees of peak resolution in the NMR spectrum. This, in turn, partially dictates the degree of speciation and/or quantification of species, or classes of compounds, that can be accomplished. Iowa State chose a {sup 31}P-tagged reagent (ClPOCMe{sub 2}CMe{sub 2}O) which was shown previously to be particularly useful in the derivatization of phenols. The derivatized samples all exhibited a small group of peaks attributed to amines and a broad group of peaks in the phenol region. The presence of paramagnetic species in the samples caused the NMR signals to broaden. Electron paramagnetic resonance (EPR) spectra confirmed the presence of paramagnetic organic free radicals in selected samples. Various methods were employed to process the NMR data. The complexity and broadness of the phenol peak, however, made speciation of the phenols impractical.

  7. 31P NMR study of daunorubicin-d(CGTACG) complex in solution. Evidence of the intercalation sites.

    PubMed

    Ragg, E; Mondelli, R; Battistini, C; Garbesi, A; Colonna, F P

    1988-08-15

    The interaction of daunorubicin with the self-complementary DNA fragment d(CGTACG) was studied by 31P NMR spectroscopy. The individual phosphates have been assigned for the nucleotide and the complex and signals from bound and free species in slow exchange at 19 degrees C were detected. In solution, the hexanucleotide binds two molecules of daunorubicin, which intercalate in the d(CG) sequence at both ends of the helix. Evidence for local deformations of the backbone at the sites of C5pG6, C1pG2 and G2pT3 phosphates is given. The binding constants for the stepwise equilibrium and the rate of dissociation of the intercalated duplex were also determined. PMID:3402614

  8. An efficient 1H/31P double-resonance solid-state NMR probe that utilizes a scroll coil

    PubMed Central

    Grant, Christopher V.; Sit, Siu-Ling; De Angelis, Anna A.; Khuong, Kelli S.; Wu, Chin H.; Plesniak, Leigh A.; Opella, Stanley J.

    2007-01-01

    The construction and performance of a scroll coil double-resonance probe for solid-state NMR on stationary samples is described. The advantages of the scroll coil at the high resonance frequencies of 1H and 31P include: high efficiency, minimal perturbations of tuning by a wide range of samples, minimal RF sample heating of high dielectric samples of biopolymers in aqueous solution, and excellent RF homogeneity. The incorporation of a cable tie cinch for mechanical stability of the scroll coil is described. Experimental results obtained on a Hunter Killer Peptide 1 (HKP1) interacting with phospholipid bilayers of varying lipid composition demonstrate the capabilities of this probe on lossy aqueous samples. PMID:17719813

  9. An efficient (1)H/(31)P double-resonance solid-state NMR probe that utilizes a scroll coil.

    PubMed

    Grant, Christopher V; Sit, Siu-Ling; De Angelis, Anna A; Khuong, Kelli S; Wu, Chin H; Plesniak, Leigh A; Opella, Stanley J

    2007-10-01

    The construction and performance of a scroll coil double-resonance probe for solid-state NMR on stationary samples is described. The advantages of the scroll coil at the high resonance frequencies of (1)H and (31)P include: high efficiency, minimal perturbations of tuning by a wide range of samples, minimal RF sample heating of high dielectric samples of biopolymers in aqueous solution, and excellent RF homogeneity. The incorporation of a cable tie cinch for mechanical stability of the scroll coil is described. Experimental results obtained on a Hunter Killer Peptide 1 (HKP1) interacting with phospholipid bilayers of varying lipid composition demonstrate the capabilities of this probe on lossy aqueous samples. PMID:17719813

  10. /sup 31/P NMR probes of sipunculan erythrocytes containing the O/sub 2/-carying protein hemerythrin

    SciTech Connect

    Robitaille, P.M.L.; Kurtz, D.M. Jr

    1988-06-14

    Reported are the first examinations by /sup 31/P NMR of erythrocytes containing the non-heme iron O/sub 2/ carrying protein hemerythrin (Hr). Intact coelomic erythrocytes from the sipunculids Phascolopsis gouldii and Themiste zostericola were shown by /sup 31/P NMR to contain O-phosphorylethanolamine and 2-amino-ethylphosphonate as the major soluble phosphorus metabolites. This combination of major metabolites appears to be unique to sipunculan erythrocytes. Nucleoside triphosphates and mannose 1-phosphate were present in lower concentrations. The concentration of O-phosphorylethanolamine within P. gouldii erythrocytes was established to be > 20 mM. T. zostericola erythrocytes contained relatively high levels of 2-amino-ethylphosphonate and lower levels of O-phosphorylethanolamine compared with those of P. gouldii. For P. gouldii and T. zostericola the intracellular pHs were determined to be 7.2 +/- 0.1 and 7.1 +/- 0.1, respectively, in air-equilibrated erythrocytes, and 6.5 +/- 0.1 in anaerobic P. gouldii erythrocytes. O-Phosphorylethanolamine was found to bind weakly to P. gouldii metHr. This interaction is best characterized by either negative cooperativity or nonspecific binding. O-phosphorylethanolamine strongly inhibits azide binding to the iron site of P. gouldii metHr at pH 7.2. The rate of azide binding decreases by approx. 85-fold in the presence of 0.33 M O-phosphorylethanolamine. However, neither O-phosphorylethanolamine nor 2-aminoethylphosphonate at 0.33 M was found to have any significant effect on O/sub 2/ affinity of P. gouldii deoxyHr. Alternative functions for the two metabolites are suggested.

  11. Determination of neo- and D-chiro-inositol hexakisphosphate in soils by solution 31P NMR spectroscopy.

    PubMed

    Turner, Benjamin L; Cheesman, Alexander W; Godage, H Yasmin; Riley, Andrew M; Potter, Barry V L

    2012-05-01

    The inositol phosphates are an abundant but poorly understood group of organic phosphorus compounds found widely in the environment. Four stereoisomers of inositol hexakisphosphate (IP(6)) occur, although for three of these (scyllo, neo, and D-chiro) the origins, dynamics, and biological function remain unknown, due in large part to analytical limitations in their measurement in environmental samples. We synthesized authentic neo- and D-chiro-IP(6) and used them to identify signals from these compounds in three soils from the Falkland Islands. Both compounds resisted hypobromite oxidation and gave quantifiable (31)P NMR signals at δ = 6.67 ppm (equatorial phosphate groups of the 4-equatorial/2-axial conformer of neo-IP(6)) and δ = 6.48 ppm (equatorial phosphate groups of the 2-equatorial/4-axial conformer of D-chiro-IP(6)) in soil extracts. Inositol hexakisphosphate accounted for 46-54% of the soil organic phosphorus, of which the four stereoisomers constituted, on average, 55.9% (myo), 32.8% (scyllo), 6.1% (neo), and 5.2% (D-chiro). Reappraisal of the literature based on the new signal assignments revealed that neo- and D-chiro-IP(6) occur widely in both terrestrial and aquatic ecosystems. These results confirm that the inositol phosphates can constitute a considerable fraction of the organic phosphorus in soils and reveal the prevalence of neo- and D-chiro-IP(6) in the environment. The hypobromite oxidation and solution (31)P NMR spectroscopy procedure allows the simultaneous quantification of all four IP(6) stereoisomers in environmental samples and provides a platform for research into the origins and ecological significance of these enigmatic compounds. PMID:22489788

  12. Citron and lemon under the lens of HR-MAS NMR spectroscopy.

    PubMed

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

    2013-12-01

    High Resolution Magic Angle Spinning (HR-MAS) is an NMR technique that can be applied to semi-solid samples. Flavedo, albedo, pulp, seeds, and oil gland content of lemon and citron were studied through HR-MAS NMR spectroscopy, which was used directly on intact tissue specimens without any physicochemical manipulation. HR-MAS NMR proved to be a very suitable technique for detecting terpenes, sugars, organic acids, aminoacids and osmolites. It is valuable in observing changes in sugars, principal organic acids (mainly citric and malic) and ethanol contents of pulp specimens and this strongly point to its use to follow fruit ripening, or commercial assessment of fruit maturity. HR-MAS NMR was also used to derive the molar percentage of fatty acid components of lipids in seeds, which can change depending on the Citrus species and varieties. Finally, this technique was employed to elucidate the metabolic profile of mold flavedo. PMID:23871074

  13. /sup 31/P NMR studies of ATP synthesis and hydrolysis kinetics in the intact myocardium

    SciTech Connect

    Kingsley-Hickman, P.B.; Sako, E.Y.; Mohanakrishnan, P.; Robitaille, P.M.L.; From, A.H.L.; Foker, J.E.; Ugurbil, K.

    1987-11-17

    The origin of the nuclear magnetic resonance (NMR)-measurable ATP in equilibrium P/sub i/ exchange and whether it can be used to determine net oxidative ATP synthesis rates in the intact myocardium were examined by detailed measurements of ATP in equilibrium P/sub i/ exchange rates in both directions as a function of the myocardial oxygen consumption rate (MVO/sub 2/) in (1) glucose-perfused, isovolumic rat hearts with normal glycolytic activity and (2) pyruvate-perfused hearts where glycolytic activity was reduced or eliminated either by depletion of their endogenous glycogen or by use of the inhibitor iodoacetate. In glucose-perfused hearts, the P/sub i/ ..-->.. ATP rate measured by the conventional two-site saturation transfer (CST) technique remained constant while MVO2 was increased approximately 2-fold. When the glycolytic activity was reduced, the P/sub i/ ..-->.. ATP rate decreased significantly, demonstrating the existence of a significant glycolytic contribution. The ATP ..-->.. P/sub i/ rates and rate:MVO ratios measured by the multiple-site saturation transfer method at two MVO/sub 2/ levels were equal to the corresponding P/sub i/..-->.. ATP rates and rate:MVO ratios obtained in the absence of a glycolytic contribution. The following conclusions are drawn from these studies: (1) unless the glycolytic contribution to the ATP in equilibrium P/sub i/ exchange is inhibited or is specifically shown not to exist, the myocardial P/sub i/ in equilibrium ATP exchange due to oxidative phosphorylation cannot be studied by NMR; (2) at moderate MVO/sub 2/ levels, the reaction catalyzed by the two glycolytic enzymes glyceraldehyde-3-phosphate dehydrogenase and 3-phosphoglycerate kinase is near equilibrium; (3) the ATP synthesis by the mitochondrial H/sup +/-ATPase occurs unidirectionally (i.e., the reaction is far out of equilibrium); (4) the operative P:O ratio in the intact myocardium under our conditions is significantly less than the canonically accepted value

  14. sup 13 C and sup 31 P NMR studies of myocardial metabolism

    SciTech Connect

    Laughlin, M.R.

    1988-01-01

    The fluxes through two enzyme systems have been measured in perfused or in in vivo heart using NMR: phosphocreatine kinase, and glycogen synthase and phosphorylase. The rates of synthesis and degradation of glycogen were monitored in vivo in fed, fasted, and diabetic rat heart during infusions of {sup 13}C-1-glucose and insulin using proton-decoupled {sup 13}C-NMR at 1.9 and 4.7 tesla. The enzyme activities of glycogen synthase and glycogen phosphorylase were also measured in this tissue which had been freeze clamped at the end of the experiment, for comparison with the synthetic rates. For normal fed, fasted, and diabetic animals, synthesis rates were 0.28, 0.16, and 0.15 {mu}mol/min.gww respectively. Glycogen synthase i activity was 0.23, 0.14, and 0.14 {mu}mol/min.gww in these hearts at the end of the experiment, when measured at appropriate substrate and activator concentrations, and follow activation time courses that are consistent with being the main rate determinant for net synthesis in all cases. Turnover of glycogen was studied by observing the preformed {sup 13}C-1-glycogen signal during infusion of {sup 12}C-glucose and insulin, and was found to be close to zero. Extracted phosphorylase a activity was approximately ten times that of synthase i under these circumstances. In order to fully interpret the turnover studies, glycogenolysis of preformed {sup 13}C-glycogen was observed after a bolus of glucagon. The glycogen had either been synthesized from {sup 13}C-1-glucose for a single hour, or during an hour of {sup 13}C-glucose and a subsequent hour of {sup 12}C-glucose infusion. The author observed that breakdown follows an exponential time course related to the phosphorylase a activation state and that the last synthesized glycogen breaks down at the rate of 2.5 {mu}mol/min.gww, five times faster than that synthesized an hour earlier.

  15. A software framework for analysing solid-state MAS NMR data.

    PubMed

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

    2011-12-01

    Solid-state magic-angle-spinning (MAS) NMR of proteins has undergone many rapid methodological developments in recent years, enabling detailed studies of protein structure, function and dynamics. Software development, however, has not kept pace with these advances and data analysis is mostly performed using tools developed for solution NMR which do not directly address solid-state specific issues. Here we present additions to the CcpNmr Analysis software package which enable easier identification of spinning side bands, straightforward analysis of double quantum spectra, automatic consideration of non-uniform labelling schemes, as well as extension of other existing features to the needs of solid-state MAS data. To underpin this, we have updated and extended the CCPN data model and experiment descriptions to include transfer types and nomenclature appropriate for solid-state NMR experiments, as well as a set of experiment prototypes covering the experiments commonly employed by solid-sate MAS protein NMR spectroscopists. This work not only improves solid-state MAS NMR data analysis but provides a platform for anyone who uses the CCPN data model for programming, data transfer, or data archival involving solid-state MAS NMR data. PMID:21953355

  16. (31)P Solid-State NMR study of the chemical setting process of a dual-paste injectable brushite cements.

    PubMed

    Legrand, A P; Sfihi, H; Lequeux, N; Lemaître, J

    2009-10-01

    The composition and evolution of a brushite-type calcium phosphate cement was investigated by Solid-State NMR and X-ray during the setting process. The cement is obtained by mixing beta-tricalcium phosphate [Ca(3)(PO(4))(2), beta-TCP] and monocalcium phosphate monohydrate [Ca(H(2)PO(4))(2).H(2)O, MCPM] in presence of water, with formation of dicalcium phosphate dihydrate or brushite [CaHPO(2).2H(2)O, DCPD]. Analysis of the initial beta-TCP paste has shown the presence of beta-calcium pyrophosphate [Ca(2)P(2)O(7), beta-CPy] and that of the initial MCPM a mixture of MCPM and dicalcium phosphate [CaHPO(4), DCP]. Follow-up of the chemical composition by (31)P Solid-State NMR enables to show that the chemical setting process appeared to reach an end after 20 min. The constant composition observed at the end of the process was similarly determined. PMID:19365821

  17. Hetergeneous tumour response to photodynamic therapy assessed by in vivo localised 31P NMR spectroscopy.

    PubMed Central

    Ceckler, T. L.; Gibson, S. L.; Kennedy, S. D.; Hill, R.; Bryant, R. G.

    1991-01-01

    Photodynamic therapy (PDT) is efficacious in the treatment of small malignant lesions when all cells in the tumour receive sufficient drug, oxygen and light to induce a photodynamic effect capable of complete cytotoxicity. In large tumours, only partial effectiveness is observed presumably because of insufficient light penetration into the tissue. The heterogeneity of the metabolic response in mammary tumours following PDT has been followed in vivo using localised phosphorus NMR spectroscopy. Alterations in nucleoside triphosphates (NTP), inorganic phosphate (Pi) and pH within localised regions of the tumour were monitored over 24-48 h following PDT irradiation of the tumour. Reduction of NTP and increases in Pi were observed at 4-6 h after PDT irradiation in all regions of treated tumours. The uppermost regions of the tumours (those nearest the skin surface and exposed to the greatest light fluence) displayed the greatest and most prolonged reduction of NTP and concomitant increase in Pi resulting in necrosis. The metabolite concentrations in tumour regions located towards the base of the tumour returned a near pre-treatment levels by 24-48 h after irradiation. The ability to follow heterogeneous metabolic responses in situ provides one means to assess the degree of metabolic inhibition which subsequently leads to tumour necrosis. Images Figure 4 PMID:1829953

  18. Temperature-dependent interconversion of phosphoramidite-Cu complexes detected by combined diffusion studies, 31P NMR, and low-temperature NMR spectroscopy.

    PubMed

    Schober, Katrin; Zhang, Hongxia; Gschwind, Ruth M

    2008-09-17

    For copper-catalyzed enantioselective conjugate additions, knowledge about the precatalytic and catalytic complexes has not yet been sufficiently developed to understand the strong influence of different temperatures on these famous reactions. Therefore, NMR experiments with four Cu(I) salts and two phosphoramidite ligands have been performed to elucidate the temperature dependence and the low-temperature structures of these copper complexes. The existence of the precatalytic binuclear complex with a mixed trigonal/tetrahedral coordination on copper is for the first time proven with direct NMR spectroscopic methods. Below 200 K, intermolecular interactions between free ligands and [Cu2X2L3] complexes induce binuclear [Cu2X2L4] complexes similar to the crystal structures. By combining diffusion experiments and (31)P integrals at different temperatures, it is for the first time possible to follow the formation of stoichiometrically different complexes, even under experimental conditions in which the (31)P signals of the complexes are spectroscopically not resolved due to exchange processes. This allows a first correlation between the complex species observed and the synthetic conditions reported. Furthermore, different preferences to build homo- or heterochiral complexes are detected for binaphthol and biphenol phosphoramidite complexes. PMID:18717560

  19. 31P NMR spectroscopy of hypertrophied rat heart: effect of graded global ischemia.

    PubMed

    Clarke, K; Sunn, N; Willis, R J

    1989-12-01

    To investigate the cause for the greater susceptibility of hypertrophied hearts to ischemic injury, we determined the interrelations of total work output, contractile function and energy metabolism in isolated, perfused normal and hypertrophied rat hearts subjected to graded global ischemia. Cardiac hypertrophy was induced by giving rats seven daily injections of either triiodothyronine (0.2 mg/kg) or isoproterenol (5 mg/kg). All hearts were perfused at an aortic pressure of 100 mmHg in the isovolumic mode in an NMR spectrometer (7.05 Tesla). Heart rate, developed pressure, and coronary flow were monitored simultaneously with changes in pH, creatine phosphate, ATP and inorganic phosphate. During pre-ischemic perfusion, the total work output (rate-pressure product) of hyperthyroid hearts was 28% higher than that of control hearts, whereas hearts from isoproterenol-treated animals showed no difference. However, when related to unit muscle mass, work was normal in hyperthyroid hearts and 26% lower after isoproterenol. Contractile function per unit myocardium (developed pressure/g wet weight) was lower in the hypertrophied hearts. ATP content was the same in all groups. Creatine phosphate decreased 41% after triiodothyronine and 25% after isoproterenol. Inorganic phosphate levels and intracellular pH were similar in control and isoproterenol-treated rat hearts, but were higher in the hyperthyroid rat hearts. The phosphorylation potential and the free energy change of ATP hydrolysis were lowered by hypertrophy, the levels correlating with the depressed contractile function. At each ischemic flow rate, both work and contractile function per unit myocardium were the same for all hearts, but the relations between flow and phosphorylation potential were different for each type of heart. Thus, at low flow rates, hypertrophied hearts perform the same amount of work and have the same contractile function as control hearts, but with abnormal changes in energy metabolism

  20. Investigation of domain size in polymer membranes using double quantum filtered spin diffusion MAS NMR.

    SciTech Connect

    Fujimoto, Cy H.; Alam, Todd Michael; Cherry, Brian Ray; Cornelius, Christopher James

    2005-02-01

    Solid-state {sup 1}H magic angle spinning (MAS) NMR was used to investigate sulfonated Diels-Alder poly(phenlylene) polymer membranes. Under high spinning speed {sup 1}H MAS conditions, the proton environments of the sulfonic acid and phenylene polymer backbone are resolved. A double-quantum (DQ) filter using the rotor-synchronized back-to-back (BABA) NMR multiple-pulse sequence allowed the selective suppression of the sulfonic proton environment in the {sup 1}H MAS NMR spectra. This DQ filter in conjunction with a spin diffusion NMR experiment was then used to measure the domain size of the sulfonic acid component within the membrane. In addition, the temperature dependence of the sulfonic acid spin-spin relaxation time (T{sub 2}) was determined, providing an estimate of the activation energy for the proton dynamics of the dehydrated membrane.

  1. Interactions of ciprofloxacin with DPPC and DPPG: fluorescence anisotropy, ATR-FTIR and 31P NMR spectroscopies and conformational analysis.

    PubMed

    Bensikaddour, Hayet; Snoussi, Karim; Lins, Laurence; Van Bambeke, Françoise; Tulkens, Paul M; Brasseur, Robert; Goormaghtigh, Erik; Mingeot-Leclercq, Marie-Paule

    2008-11-01

    The interactions between a drug and lipids may be critical for the pharmacological activity. We previously showed that the ability of a fluoroquinolone antibiotic, ciprofloxacin, to induce disorder and modify the orientation of the acyl chains is related to its propensity to be expelled from a monolayer upon compression [1]. Here, we compared the binding of ciprofloxacin on DPPC and DPPG liposomes (or mixtures of phospholipids [DOPC:DPPC], and [DOPC:DPPG]) using quasi-elastic light scattering and steady-state fluorescence anisotropy. We also investigated ciprofloxacin effects on the transition temperature (T(m)) of lipids and on the mobility of phosphate head groups using Attenuated Total Reflection Fourier Transform Infrared-Red Spectroscopy (ATR-FTIR) and (31)P Nuclear Magnetic Resonance (NMR) respectively. In the presence of ciprofloxacin we observed a dose-dependent increase of the size of the DPPG liposomes whereas no effect was evidenced for DPPC liposomes. The binding constants K(app) were in the order of 10(5) M(-1) and the affinity appeared dependent on the negative charge of liposomes: DPPG>DOPC:DPPG (1:1; M:M)>DPPC>DOPC:DPPC (1:1; M:M). As compared to the control samples, the chemical shift anisotropy (Deltasigma) values determined by (31)P NMR showed an increase of 5 and 9 ppm for DPPC:CIP (1:1; M:M) and DPPG:CIP (1:1; M:M) respectively. ATR-FTIR experiments showed that ciprofloxacin had no effect on the T(m) of DPPC but increased the order of the acyl chains both below and above this temperature. In contrast, with DPPG, ciprofloxacin induced a marked broadening effect on the transition with a decrease of the acyl chain order below its T(m) and an increase above this temperature. Altogether with the results from the conformational analysis, these data demonstrated that the interactions of ciprofloxacin with lipids depend markedly on the nature of their phosphate head groups and that ciprofloxacin interacts preferentially with anionic lipid compounds

  2. 31P-NMR analysis of congestive heart failure in the SHHF/Mcc-facp rat heart.

    PubMed

    Michael O'Donnell, J; Narayan, P; Bailey, M Q; Abduljalil, A M; Altschuld, R A; McCune, S A; Robitaille, P M

    1998-02-01

    31P-NMR was used to monitor myocardial bioenergetics in compensated and failing SHHF/MCC-fa(cp) (SHF) rat hearts. The SHHF/Mcc-fa(cp) (spontaneous hypertension and heart failure) rat is a relatively new genetic model in which all individuals spontaneously develop congestive heart failure, most during the second year of life. Failing SHF rat hearts displayed a pronounced decrease in resting PCr:ATP ratios (P<0.001), which was explained by a significant (P<0. 0001) drop in total creatine (47.2+/-3.1 nmol/mg protein) v age matched controls (106+/-3 nmol/mg protein). In end stage failure, NMR determined PCr was 2.9+/-0.1 micro mol/g wet weight under basal conditions. In contrast, 6- and 20-month-old controls and compensated SHFs had PCr values of 5.3+/-0.1, and 5.1+/-0.5 and 5. 1+/-0.2 micro mol/g wet weight. Both compensated and failing SHF hearts were metabolically compromised when the rate pressure product (RPP) was increased, as evidenced by an increase in Pi and a drop in PCr. Compensated SHF hearts, however, were able to increase rate pressure products (RRP, mmHg X beats/min) from 44.5+/-1.4 to 66.6+/-3. 4 K with dobutamine infusion, whereas hearts in end-stage failure were able to increase their RPP from baseline values of 27+/-4 K to only 37+/-7 K. The data indicate that a pronounced decline in PCr and total creatine signals the transition from compensatory hypertrophy to decompensation and failure in the SHF rat model of hypertensive cardiomyopathy. PMID:9515000

  3. Effect of Ca:Mg ratio on precipitated P species identified using 31P solid state NMR

    NASA Astrophysics Data System (ADS)

    Manimel Wadu, M.

    2009-04-01

    M.C.W. Manimel Wadu1, O.O Akinremi1, S. Kroeker2 1Department of Soil Science, University of Manitoba, Winnipeg, R3T 2N2, Canada 2Department of Chemistry, University of Manitoba, Winnipeg, R3T 2N2, Canada Agronomic efficiency of added P fertilizer is reduced by the precipitation reactions with the exchangeable Ca and Mg in calcareous soils. We hypothesized that the ratio of Ca to Mg on the soil exchange complex will affect the species of P that is precipitated and its solubility in the soil. A laboratory experiment was conducted using a model calcareous soil system which was composed of resin (Amberlite IRP69) and sand coated with CaCO3 packed into a column. The resin was pre saturated with Ca and Mg in order to achieve five different saturation ratios of Ca:Mg approximately as 100:0, 70:30, 50:50, 30:70 and 0:100. Monoammonium Phosphate was applied to the soil surface to simulate one-dimensional diffusive transport. The column was then incubated for 2 weeks. Chemical analysis for water and acid soluble P, pH, NH4, Ca and Mg was performed on 2mm sections of the soil to a depth of 10 cm. This paper will present and discuss the distribution of P along the soil column. Unlike similar studies that have speculated on the precipitation of P, this study will identify and quantify the P species that is formed using 31P solid state NMR technique. Such knowledge will be helpful in understanding the effect of Ca and Mg on P availability in calcareous system and the role of each cation on P precipitation. Key words: P fertilizers, Ca, Mg, model system, solid state NMR

  4. Modulation of 2,3-diphosphoglycerate 31P-NMR resonance positions by red cell membrane shape.

    PubMed

    Fossel, E T; Solomon, A K

    1976-06-17

    Na+ transport in the red cells of the dog is dependent on cell volume, a 20% change in cell volume leading to a 25-fold increase in apparent Na+ flux; the effect is dependent upon metabolic energy. We have found that swelling and shrinking dog red cells causes a shift in the 31P-NMR peak of 2,3-diphosphoglycerate, which is present in dog red cells at 5.5 mM. Control experiments indicate that the 2,3-diphosphoglycerate resonance peak shifts may not be attributed to: interaction with hemoglobin, changes in cell pH, ionic strength, diamagnetic susceptibility or small changes in the Mg2+/2,3-diphosphoglycerate ratio. Experiments with chlorpromazine and pentanol which alter red cell membrane area by a mechanism different from osmotic swelling suggest that 2,3-diphosphoglycerate interacts with a binding site in the cell that is dependent upon the physical condition of the dog red cell membrane. PMID:1276226

  5. Phospholipid fingerprints of milk from different mammalians determined by 31P NMR: towards specific interest in human health.

    PubMed

    Garcia, Cyrielle; Lutz, Norbert W; Confort-Gouny, Sylviane; Cozzone, Patrick J; Armand, Martine; Bernard, Monique

    2012-12-01

    Our objective was to identify and quantify phospholipids in milk from different species (human HM, cow CoM, camel CaM, and mare MM) using an optimised (31)P NMR spectroscopy procedure. The phospholipid fingerprints were species-specific with a broader variety of classes found in HM and MM; HM and CaM were richer in sphingomyelin (78.3 and 117.5μg/ml) and plasmalogens (27.3 and 24μg/ml), possibly important for infant development. Total phospholipid content was higher in CaM (0.503mM) and lower in MM (0.101mM) compared to HM (0.324mM) or CoM (0.265mM). Our optimised method showed good sensitivity, high resolution, and easy sample preparation with minimal loss of target molecules. It is suitable for determining the accurate composition of a large number of bioactive phospholipids with putative health benefits, including plasmalogens, and should aid in selecting appropriate ingredient sources for infant milk substitutes or fortifiers, and for functional foods dedicated to adults. PMID:22953921

  6. 13C/31P NMR studies on the role of glucose transport/phosphorylation in human glycogen supercompensation.

    PubMed

    Price, T B; Laurent, D; Petersen, K F

    2003-05-01

    This study measured muscle glycogen during a 7-day carbohydrate loading protocol. Twenty healthy subjects (12 male, 8 female) performed 1 hr treadmill/toe-raise exercise immediately before a 3-day low carbohydrate (LoCHO) diet (20 % carbohydrate, 60 % fat, 20 % protein). On day 3 they repeated the exercise and began a 4-day high carbohydrate (HiCHO) diet (90 % carbohydrate, 2 % fat, 8 % protein). The order of administration of the diet was reversed in a subpopulation (n = 3). Interleaved natural abundance 13C/ 31P NMR spectra were obtained before and immediately after exercise, and each day during the controlled diets in order to determine concentrations of glycogen (GLY), glucose-6-phosphate (G6P), and muscle pH. Following exercise, muscle GLY and pH were reduced (p < 0.001) while muscle G6P was elevated (p

  7. ¹¹³Cd NMR experiments reveal an unusual metal cluster in the solution structure of the yeast splicing protein Bud31p.

    PubMed

    van Roon, Anne-Marie M; Yang, Ji-Chun; Mathieu, Daniel; Bermel, Wolfgang; Nagai, Kiyoshi; Neuhaus, David

    2015-04-13

    Establishing the binding topology of structural zinc ions in proteins is an essential part of their structure determination by NMR spectroscopy. Using (113)Cd NMR experiments with (113)Cd-substituted samples is a useful approach but has previously been limited mainly to very small protein domains. Here we used (113)Cd NMR spectroscopy during structure determination of Bud31p, a 157-residue yeast protein containing an unusual Zn3Cys9 cluster, demonstrating that recent hardware developments make this approach feasible for significantly larger systems. PMID:25703931

  8. 113Cd NMR Experiments Reveal an Unusual Metal Cluster in the Solution Structure of the Yeast Splicing Protein Bud31p**

    PubMed Central

    van Roon, Anne-Marie M; Yang, Ji-Chun; Mathieu, Daniel; Bermel, Wolfgang; Nagai, Kiyoshi; Neuhaus, David

    2015-01-01

    Establishing the binding topology of structural zinc ions in proteins is an essential part of their structure determination by NMR spectroscopy. Using 113Cd NMR experiments with 113Cd-substituted samples is a useful approach but has previously been limited mainly to very small protein domains. Here we used 113Cd NMR spectroscopy during structure determination of Bud31p, a 157-residue yeast protein containing an unusual Zn3Cys9 cluster, demonstrating that recent hardware developments make this approach feasible for significantly larger systems. PMID:25703931

  9. {sup 31}P NMR analysis of coal moieties bearing -OH, -NH, and -SH functions. Quarterly report, June 1, 1991--August 31, 1991

    SciTech Connect

    Verkade, J.G.

    1991-12-31

    The purpose of this research is to develop a convenient, reliable and rapid NMR method for the determination of labile-hydrogen functional groups and organic sulfur compounds which are components of coal and coal-derived materials. For this purpose, the former functional groups, including water molecules, are derivatized with reagents containing NMR-active nuclei such as {sup 31}P or {sup 119}Sn, while sulfur groups are derivatized with {sup 195}Pt NMR tagging reagents. Knowledge of the heteroatom composition of coals is necessary for the development of increasingly sophisticated coal processing technologies.

  10. 29Si and 27Al MAS NMR spectra of mullites from different kaolinites.

    PubMed

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

    2004-04-01

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

  11. Advanced instrumentation for DNP-enhanced MAS NMR for higher magnetic fields and lower temperatures

    NASA Astrophysics Data System (ADS)

    Matsuki, Yoh; Idehara, Toshitaka; Fukazawa, Jun; Fujiwara, Toshimichi

    2016-03-01

    Sensitivity enhancement of MAS NMR using dynamic nuclear polarization (DNP) is gaining importance at moderate fields (B0 < 9 T) and temperatures (T > 90 K) with potential applications in chemistry and material sciences. However, considering the ever-increasing size and complexity of the systems to be studied, it is crucial to establish DNP under higher field conditions, where the spectral resolution and the basic NMR sensitivity tend to improve. In this perspective, we overview our recent efforts on hardware developments, specifically targeted on improving DNP MAS NMR at high fields. It includes the development of gyrotrons that enable continuous frequency tuning and rapid frequency modulation for our 395 GHz-600 MHz and 460 GHz-700 MHz DNP NMR spectrometers. The latter 700 MHz system involves two gyrotrons and a quasi-optical transmission system that combines two independent sub-millimeter waves into a single dichromic wave. We also describe two cryogenic MAS NMR probe systems operating, respectively, at T ∼100 K and ∼30 K. The latter system utilizes a novel closed-loop helium recirculation mechanism, achieving cryogenic MAS without consuming any cryogen. These instruments altogether should promote high-field DNP toward more efficient, reliable and affordable technology. Some experimental DNP results obtained with these instruments are presented.

  12. Advanced instrumentation for DNP-enhanced MAS NMR for higher magnetic fields and lower temperatures.

    PubMed

    Matsuki, Yoh; Idehara, Toshitaka; Fukazawa, Jun; Fujiwara, Toshimichi

    2016-03-01

    Sensitivity enhancement of MAS NMR using dynamic nuclear polarization (DNP) is gaining importance at moderate fields (B0<9T) and temperatures (T>90K) with potential applications in chemistry and material sciences. However, considering the ever-increasing size and complexity of the systems to be studied, it is crucial to establish DNP under higher field conditions, where the spectral resolution and the basic NMR sensitivity tend to improve. In this perspective, we overview our recent efforts on hardware developments, specifically targeted on improving DNP MAS NMR at high fields. It includes the development of gyrotrons that enable continuous frequency tuning and rapid frequency modulation for our 395 GHz-600 MHz and 460 GHz-700 MHz DNP NMR spectrometers. The latter 700 MHz system involves two gyrotrons and a quasi-optical transmission system that combines two independent sub-millimeter waves into a single dichromic wave. We also describe two cryogenic MAS NMR probe systems operating, respectively, at T ∼ 100K and ∼ 30K. The latter system utilizes a novel closed-loop helium recirculation mechanism, achieving cryogenic MAS without consuming any cryogen. These instruments altogether should promote high-field DNP toward more efficient, reliable and affordable technology. Some experimental DNP results obtained with these instruments are presented. PMID:26920836

  13. sup 31 P NMR saturation-transfer study of the in situ kinetics of the mitochondrial adenine nucleotide translocase

    SciTech Connect

    Masiakos, P.T.; Williams, G.D.; Berkich, D.A.; Smith, M.B.; LaNoue, K.F. )

    1991-08-27

    The exchange of intramitochondrial ATP (ATP{sub in}) for extramitochondrial ATP (ATP{sub out}) was measured by using {sup 31}P NMR spectroscopy over a range of temperatures in isolated rat liver mitochondria oxidizing glutamate and succinate in the presence of external ATP but no added ADP (state 4). The rate of this exchange is more than an order of magnitude faster than rates reported previously that were determined by using isotopic techniques in the presence of oligomycin, the potent ATPase inhibitor. Differences are ascribed in part to the low levels of matrix ATP present in oligomycin-treated mitochondrial. Intramitochondrial ATP content regulates the rate of the ATP{sub in}/ATP{sub out} exchange. At 18C, the concentration of internal ATP that produces half-maximal transport rate is 6.6{plus minus}0.12 nmol/mg of mitochondrial protein. The relationship between substrate concentration and flux is sigmoidal and is 90% saturated at 11.3{plus minus}0.18 nmol/mg of mitochondrial protein. Since the measured rates of exchange of ATP{sub in} for ATP{sub out} are almost 10 times faster than the ATP synthase (ATP/P{sub i}) exchange rates, the translocase cannot limit net ATP/P{sub i} exchange in state 4. It may, nonetheless, limit net synthesis of ATP under other conditions when matrix ATP concentration is lower than in state 4 and when external ADP is present at higher concentrations than in these experiments.

  14. The effect of ethanol on hydroxyl and carbonyl groups in biopolyol produced by hydrothermal liquefaction of loblolly pine: (31)P-NMR and (19)F-NMR analysis.

    PubMed

    Celikbag, Yusuf; Via, Brian K; Adhikari, Sushil; Buschle-Diller, Gisela; Auad, Maria L

    2016-08-01

    The goal of this study was to investigate the role of ethanol and temperature on the hydroxyl and carbonyl groups in biopolyol produced from hydrothermal liquefaction of loblolly pine (Pinus spp.) carried out at 250, 300, 350 and 390°C for 30min. Water and water/ethanol mixture (1/1, wt/wt) were used as liquefying solvent in the HTL experiments. HTL in water and water/ethanol is donated as W-HTL and W/E-HTL, respectively. It was found that 300°C and water/ethanol solvent was the optimum liquefaction temperature and solvent, yielding up to 68.1wt.% bio-oil and 2.4wt.% solid residue. (31)P-NMR analysis showed that biopolyol produced by W-HTL was rich in phenolic OH while W/E-HTL produced more aliphatic OH rich biopolyols. Moreover, biopolyols with higher hydroxyl concentration were produced by W/E-HTL. Carbonyl groups were analyzed by (19)F-NMR, which showed that ethanol reduced the concentration of carbonyl groups. PMID:27126078

  15. {sup 31}P NMR study of the complexation of TBP with lanthanides and actinides in solution and in a clay matrix

    SciTech Connect

    Hartzell, C.J.

    1994-07-24

    Goal was to use NMR to study TBP/lanthanide complexes in the interlayer or on edge sites of clays. Work in this laboratory yielded details of the complexation of Eu(NO{sub 3}){sub 3} and Pr(NO{sub 3}){sub 3} with TBP in hexane solution; this information is crucial to interpretation of results of NMR studies of the complexes exchanged into clays. The solution {sup 31}P-chemical shift values were improved by repeating the studies on the lanthanide salts dissolved directly into neat TBP. NMR studies of these neat solutions of the Eu(NO{sub 3}){sub 3}{lg_bullet}3TBP-complex and the Pr(NO{sub 3}){sub 3}{lg_bullet}3TBP-complex show that the {sup 31}P chemical shift remains relatively constant for TBP: lanthanide ratios below 3: 1. At higher ratios, the chemical shift approaches that of free TBP, indicating rapid exchange of TBP between the free and complexed state. Exchange of these complexes into the clay hectorite yielded discrete {sup 31}P-NMR signals for the Eu{lg_bullet}TBP complex at -190 ppm and free TBP at -6 ppm. Adsorption of the Pr{lg_bullet}TBP complex yielded broad signals at 76 ppm for the complex and -6 ppm for free TBP. There was no evidence of exchange between the incorporated complex and the free TBP.

  16. Structural investigations of Pu{sup III} phosphate by X-ray diffraction, MAS-NMR and XANES spectroscopy

    SciTech Connect

    Popa, Karin; Raison, Philippe E.; Martel, Laura; Martin, Philippe M.; Solari, Pier L.; Bouëxière, Daniel; Konings, Rudy J.M.; Somers, Joseph

    2015-10-15

    PuPO{sub 4} was prepared by a solid state reaction method and its crystal structure at room temperature was solved by powder X-ray diffraction combined with Rietveld refinement. High resolution XANES measurements confirm the +III valence state of plutonium, in agreement with valence bond derivation. The presence of the americium (as β{sup −} decay product of plutonium) in the +III oxidation state was determined based on XANES spectroscopy. High resolution solid state {sup 31}P NMR agrees with the XANES results and the presence of a solid-solution. - Graphical abstract: A full structural analysis of PuPO{sub 4} based on Rietveld analysis of room temperature X-ray diffraction data, XANES and MAS NMR measurements was performed. - Highlights: • The crystal structure of PuPO{sub 4} monazite is solved. • In PuPO{sub 4} plutonium is strictly trivalent. • The presence of a minute amount of Am{sup III} is highlighted. • We propose PuPO{sub 4} as a potential reference material for spectroscopic and microscopic studies.

  17. Structural characterization of chemical warfare agent degradation products in decontamination solutions with proton band-selective (1)H-(31)P NMR spectroscopy.

    PubMed

    Koskela, Harri; Hakala, Ullastiina; Vanninen, Paula

    2010-06-15

    Decontamination solutions, which are usually composed of strong alkaline chemicals, are used for efficient detoxification of chemical warfare agents (CWAs). The analysis of CWA degradation products directly in decontamination solutions is challenging due to the nature of the matrix. Furthermore, occasionally an unforeseen degradation pathway can result in degradation products which could be eluded to in standard analyses. Here, we present the results of the application of proton band-selective (1)H-(31)P NMR spectroscopy, i.e., band-selective 1D (1)H-(31)P heteronuclear single quantum coherence (HSQC) and band-selective 2D (1)H-(31)P HSQC-total correlation spectroscopy (TOCSY), for ester side chain characterization of organophosphorus nerve agent degradation products in decontamination solutions. The viability of the approach is demonstrated with a test mixture of typical degradation products of nerve agents sarin, soman, and VX. The proton band-selective (1)H-(31)P NMR spectroscopy is also applied in characterization of unusual degradation products of VX in GDS 2000 solution. PMID:20507069

  18. Line shapes in CP/MAS NMR spectra of half-integer quadrupolar nuclei

    NASA Astrophysics Data System (ADS)

    Hayashi, Shigenobu; Hayamizu, Kikuko

    1993-02-01

    Cross polarization (CP) from 1H to quadrupolar nuclei with S = 3/2 has been carried out under magic-angle-spinning (MAS) conditions for powder samples of Na 2B 4O 7·10H 2O and H 3BO 3. The line shapes in the CP/MAS NMR spectra are different from those in the spectra measured with the single pulse sequence combined with 1H dipolar decoupling. Furthermore, the line shapes are found to be dependent on the measuring conditions such as the pulse amplitude for the quadrupolar nuclei. The spin-locking experiments demonstrate that line shapes in CP/MAS NMR spectra are largely dependent on the spin-locking efficiency.

  19. Assessment of Preparation Methods for Organic Phosphorus Analysis in Phosphorus-Polluted Fe/Al-Rich Haihe River Sediments Using Solution 31P-NMR

    PubMed Central

    Zhang, Wenqiang; Shan, Baoqing; Zhang, Hong; Tang, Wenzhong

    2013-01-01

    Fe/Al-rich river sediments that were highly polluted with phosphorus (P) were used in tests to determine the optimum preparation techniques for measuring organic P (Po) using solution 31P nuclear magnetic resonance spectroscopy (31P-NMR). The optimum pre-treatment, extraction time, sediment to solution ratio and sodium hydroxide-ethylenediaminetetraacetic acid (NaOH-EDTA) extractant solution composition were determined. The total P and Po recovery rates were higher from freeze- and air-dried samples than from fresh samples. An extraction time of 16 h was adequate for extracting Po, and a shorter or longer extraction time led to lower recoveries of total P and Po, or led to the degradation of Po. An ideal P recovery rate and good-quality NMR spectra were obtained at a sediment:solution ratio of 1∶10, showing that this ratio is ideal for extracting Po. An extractant solution of 0.25 M NaOH and 50 mM EDTA was found to be more appropriate than either NaOH on its own, or a more concentrated NaOH-EDTA mixture for 31P-NMR analysis, as this combination minimized interference from paramagnetic ions and was appropriate for the detected range of Po concentrations. The most appropriate preparation method for Po analysis, therefore, was to extract the freeze-dried and ground sediment sample with a 0.25 M NaOH and 50 mM EDTA solution at a sediment:solution ratio of 1∶10, for 16 h, by shaking. As lyophilization of the NaOH-EDTA extracts proved to be an optimal pre-concentration method for Po analysis in the river sediment, the extract was lyophilized as soon as possible, and analyzed by 31P-NMR. PMID:24143192

  20. Phosphorus speciation in agro-industrial byproducts: sequential fractionation, solution (31)P NMR, and P K- and L(2,3)-edge XANES spectroscopy.

    PubMed

    Negassa, Wakene; Kruse, Jens; Michalik, Dirk; Appathurai, Narayana; Zuin, Lucia; Leinweber, Peter

    2010-03-15

    Little is known about P species in agro-industrial byproducts from developing countries, which may be either pollutants or valuable soil amendments. The present study speciated P in dry (COD) and wet (COW) coffee, sisal (SIS), barley malt (BEB) and sugar cane processing (FIC) byproducts, and filter cakes of linseed (LIC) and niger seed (NIC)with sequential fractionation, solution (31)P nuclear magnetic resonance (NMR) spectroscopy, and P K- and L(2,3)-edge X-ray absorption near-edge structure (XANES) spectroscopy. The sequential P fractionation recovered 59% to almost 100% of total P (P(t)), and more than 50% of P(t) was extracted by H(2)O and NaHCO(3) in five out of seven samples. Similarly, the NaOH + EDTA extraction for solution (31)P NMR recovered 48-94% of P(t). The (31)P NMR spectra revealed orthophosphate (6-81%), pyrophosphate (0-10%), and orthophosphate monoesters (6-94%). Orthophosphate predominated in COD, COW, SIS, and FIC, whereas BEB, UC, and NIC were rich in orthophosphate monoesters. The concentrations of P(i), and P(o) determined in the sequential and NaOH + EDTA extractions and (31)P NMR spectra were strongly and positively correlated (r = 0.88-1.00). Furthermore, the P K- and L(2,3)-edge XANES confirmed the H(2)SO(4)--P(i) detected in the sequential fractionation by unequivocal identification of Ca--P phases in a few samples. The results indicate that the combined use of all four analytical methods is crucial for comprehensive P speciation in environmental samples and the application of these byproducts to soil. PMID:20146464

  1. Vacuolar glyphosate-sequestration correlates with glyphosate resistance in ryegrass (Lolium spp.) from Australia, South America, and Europe: a 31P NMR investigation.

    PubMed

    Ge, Xia; d'Avignon, D André; Ackerman, Joseph J H; Collavo, Alberto; Sattin, Maurizio; Ostrander, Elizabeth L; Hall, Erin L; Sammons, R Douglas; Preston, Christopher

    2012-02-01

    Lolium spp., ryegrass, variants from Australia, Brazil, Chile, and Italy showing differing levels of glyphosate resistance were examined by (31)P NMR. Extents of glyphosate (i) resistance (LD(50)), (ii) inhibition of 5-enopyruvyl-shikimate-3-phosphate synthase (EPSPS) activity (IC(50)), and (iii) translocation were quantified for glyphosate-resistant (GR) and glyphosate-sensitive (GS) Lolium multiflorum Lam. variants from Chile and Brazil. For comparison, LD(50) and IC(50) data for Lolium rigidum Gaudin variants from Italy were also analyzed. All variants showed similar cellular uptake of glyphosate by (31)P NMR. All GR variants showed glyphosate sequestration within the cell vacuole, whereas there was minimal or no vacuole sequestration in the GS variants. The extent of vacuole sequestration correlated qualitatively with the level of resistance. Previous (31)P NMR studies of horseweed ( Conyza canadensis (L.) Cronquist) revealed that glyphosate sequestration imparted glyphosate resistance. Data presented herein suggest that glyphosate vacuolar sequestration is strongly contributing, if not the major contributing, resistance mechanism in ryegrass as well. PMID:22224711

  2. Development of a CP 31P NMR broadline simulation methodology for studying the interactions of antihypertensive AT1 antagonist losartan with phospholipid bilayers.

    PubMed

    Fotakis, Charalambos; Christodouleas, Dionisios; Chatzigeorgiou, Petros; Zervou, Maria; Benetis, Nikolas-Ploutarch; Viras, Kyriakos; Mavromoustakos, Thomas

    2009-03-18

    A cross-polarization (CP) (31)P NMR broadline simulation methodology was developed for studying the effects of drugs in phospholipids bilayers. Based on seven-parameter fittings, this methodology provided information concerning the conformational changes and dynamics effects of losartan in the polar region of the dipalmitoylphosphatidylcholine bilayers. The test molecule for this study was losartan, an antihypertensive drug known to exert its effect on AT(1) transmembrane receptors. The results were complemented and compared with those of differential scanning calorimetry, solid-state (13)C NMR spectroscopy, Raman spectroscopy, and electron spin resonance. More specifically, these physical chemical methodologies indicated that the amphipathic losartan molecule interacts with the hydrophilic-head zone of the lipid bilayers. The CP (31)P NMR broadline simulations showed that the lipid molecules in the bilayers containing losartan displayed greater collective tilt compared to the tilt displayed by the load-free bilayers, indicating improved packing. The Raman results displayed a decrease in the trans/gauche ratio and increased intermolecular interactions of the acyl chains in the liquid crystalline phase. Additional evidence, suggesting that losartan possibly anchors in the realm of the headgroup, was derived from upfield shift of the average chemical shift sigma(iso) of the (31)P signal in the presence of losartan and from shift of the observed peak at 715 cm(-1) attributed to C-N stretching in the Raman spectra. PMID:19289049

  3. Interaction of Lipopolysaccharide and Phospholipid in Mixed Membranes: Solid-State 31P-NMR Spectroscopic and Microscopic Investigations

    PubMed Central

    Nomura, Kaoru; Inaba, Takehiko; Morigaki, Kenichi; Brandenburg, Klaus; Seydel, Ulrich; Kusumoto, Shoichi

    2008-01-01

    Lipopolysaccharide (LPS), which constitutes the outermost layer of Gram-negative bacterial cells as a typical component essential for their life, induces the first line defense system of innate immunity of higher animals. To understand the basic mode of interaction between bacterial LPS and phospholipid cell membranes, distribution patterns were studied by various physical methods of deep rough mutant LPS (ReLPS) of Escherichia coli incorporated in phospholipid bilayers as simple models of cell membranes. Solid-state 31P-NMR spectroscopic analysis suggested that a substantial part of ReLPS is incorporated into 1,2-dimyristoyl-sn-glycero-3-phosphocholine lipid bilayers when multilamellar vesicles were prepared from mixtures of these. In egg L-α-phosphatidylcholine (egg-PC)-rich membranes, ReLPS undergoes micellization. In phosphatidylethanolamine-rich membranes, however, micellization was not observed. We studied by microscopic techniques the location of ReLPS in membranes of ReLPS/egg-PC (1:10 M/M) and ReLPS/egg-PC/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG) (1:9:1 M/M/M). The influence of ReLPS on the physicochemical properties of the membranes was studied as well. Microscopic images of both giant unilamellar vesicles and supported planar lipid bilayers showed that LPS was uniformly incorporated in the egg-PC lipid bilayers. In the egg-PC/POPG (9:1 M/M) lipid bilayers, however, ReLPS is only partially incorporated and becomes a part of the membrane in a form of aggregates (or as mixed aggregates with the lipids) on the bilayer surface. The lipid lateral diffusion coefficient measurements at various molar ratios of ReLPS/egg-PC/POPG indicated that the incorporated ReLPS reduces the diffusion coefficients of the phospholipids in the membrane. The retardation of diffusion became more significant with increasing POPG concentrations in the membrane at high ReLPS/phospholipid ratios. This work demonstrated that the phospholipid composition has critical

  4. Characteristics and degradation of carbon and phosphorus from aquatic macrophytes in lakes: Insights from solid-state (13)C NMR and solution (31)P NMR spectroscopy.

    PubMed

    Liu, Shasha; Zhu, Yuanrong; Meng, Wei; He, Zhongqi; Feng, Weiying; Zhang, Chen; Giesy, John P

    2016-02-01

    Water extractable organic matter (WEOM) derived from macrophytes plays an important role in biogeochemical cycling of nutrients, including carbon (C), nitrogen (N) and phosphorus (P) in lakes. However, reports of their composition and degradation in natural waters are scarce. Therefore, compositions and degradation of WEOM derived from six aquatic macrophytes species of Tai Lake, China, were investigated by use of solid-state (13)C NMR and solution (31)P NMR spectroscopy. Carbohydrates were the predominant constituents of WEOM fractions, followed by carboxylic acid. Orthophosphate (ortho-P) was the dominant form of P (78.7% of total dissolved P) in the water extracts, followed by monoester P (mono-P) (20.6%) and little diester P (0.65%). The proportion of mono-P in total P species increased with the percentage of O-alkyl and O-C-O increasing in the WEOM, which is likely due to degradation and dissolution of biological membranes and RNA from aquatic plants. Whereas the proportion of mono-P decreased with alkyl-C, NCH/OCH3 and COO/N-C=O increasing, which may be owing to the insoluble compounds including C functional groups of alkyl-C, NCH/OCH3 and COO/N-C=O, such as aliphatic biopolymers, lignin and peptides. Based on the results of this study and information in the literature about water column and sediment, we propose that WEOM, dominated by polysaccharides, are the most labile and bioavailable component in debris of macrophytes. Additionally, these WEOMs would also be a potential source for bioavailable organic P (e.g., RNA, DNA and phytate) for lakes. PMID:26624522

  5. [31P-NMR analysis of high energy phosphorous compounds (ATP and phosphocreatine) in the living rat brain--effects of halothane anesthesia and a hypoxic condition].

    PubMed

    Yuasa, T; Miyatake, T; Kuwabara, T; Umeda, M; Eguchi, K

    1983-11-01

    31phosphorus nuclear magnetic resonance (31P-NMR) measurements have provided new and valuable insights for studying the metabolism of living systems. The aim of this paper is to introduce a technique of application of 31P-NMR measurements using a surface coil method, and to discuss the effects of halothane anesthesia and hypoxic hypoxia on the energetic metabolism of intact rat brains. All measurements were made using a JEOL FX 270 spectrometer with a super conducting magnet of 54-mm bore diameter. The magnetic field intensity of this machine is 6.3 tesla, and the resonance frequency used for 31P was 109.14 MHz. We remodelled an ordinary probe to take a live rat, and the animals were made to inhale anesthetic halothane or mixture of oxygen and nitrogen at various concentrations controlled by a flow regulator. The best conditions for measurements with our surface coil method were determined in this study as follows: (1) 90 degrees pulse width and selectivity, Fig. 1 shows signal selectivity in depthwise direction changed with 90 degrees pulse width, which was set to 20 microseconds. (2) Sensitivity and resolution; To obtain a spectrum of 31P-NMR from a rat brain 500 accumulations of free induction decays were considered suitable for both time and space resolution. Fig. 2 shows variations of signal intensity with pulse repetition time, which was set to 2 sec. It took about 17 min for averaging to get a spectrogram. (3) Quantitative accuracy and qualification; As shown in Fig. 3, a linear relationship was found between the signal intensity of beta-phosphate of ATP and the concentration of ATP solutions, thus proving the quantitative accuracy of our systems.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:6661335

  6. Optimized multiple quantum MAS lineshape simulations in solid state NMR

    NASA Astrophysics Data System (ADS)

    Brouwer, William J.; Davis, Michael C.; Mueller, Karl T.

    2009-10-01

    /Linux Operating system: UNIX/Linux Has the code been vectorised or parallelized?: Yes RAM: Example: (1597 powder angles) × (200 Samples) × (81 F2 frequency pts) × (31 F1 frequency points) = 3.5M, SMP AMD opteron Classification: 2.3 External routines: OCTAVE ( http://www.gnu.org/software/octave/), GNU Scientific Library ( http://www.gnu.org/software/gsl/), OPENMP ( http://openmp.org/wp/) Nature of problem: The optimal simulation and modeling of multiple quantum magic angle spinning NMR spectra, for general systems, especially those with mild to significant disorder. The approach outlined and implemented in C and OCTAVE also produces model parameter error estimates. Solution method: A model for each distinct chemical site is first proposed, for the individual contribution of crystallite orientations to the spectrum. This model is averaged over all powder angles [1], as well as the (stochastic) parameters; isotropic chemical shift and quadrupole coupling constant. The latter is accomplished via sampling from a bi-variate Gaussian distribution, using the Box-Muller algorithm to transform Sobol (quasi) random numbers [2]. A simulated annealing optimization is performed, and finally the non-linear jackknife [3] is applied in developing model parameter error estimates. Additional comments: The distribution contains a script, mqmasOpt.m, which runs in the OCTAVE language workspace. Running time: Example: (1597 powder angles) × (200 Samples) × (81 F2 frequency pts) × (31 F1 frequency points) = 58.35 seconds, SMP AMD opteron. References:S.K. Zaremba, Annali di Matematica Pura ed Applicata 73 (1966) 293. H. Niederreiter, Random Number Generation and Quasi-Monte Carlo Methods, SIAM, 1992. T. Fox, D. Hinkley, K. Larntz, Technometrics 22 (1980) 29.

  7. Analysis of electron donors in photosystems in oxygenic photosynthesis by photo-CIDNP MAS NMR.

    PubMed

    Najdanova, M; Janssen, G J; de Groot, H J M; Matysik, J; Alia, A

    2015-11-01

    Both photosystem I and photosystem II are considerably similar in molecular architecture but they operate at very different electrochemical potentials. The origin of the different redox properties of these RCs is not yet clear. In recent years, insight was gained into the electronic structure of photosynthetic cofactors through the application of photochemically induced dynamic nuclear polarization (photo-CIDNP) with magic-angle spinning NMR (MAS NMR). Non-Boltzmann populated nuclear spin states of the radical pair lead to strongly enhanced signal intensities that allow one to observe the solid-state photo-CIDNP effect from both photosystem I and II from isolated reaction center of spinach (Spinacia oleracea) and duckweed (Spirodela oligorrhiza) and from the intact cells of the cyanobacterium Synechocystis by (13)C and (15)N MAS NMR. This review provides an overview on the photo-CIDNP MAS NMR studies performed on PSI and PSII that provide important ingredients toward reconstruction of the electronic structures of the donors in PSI and PSII. PMID:26282679

  8. Deuterium and lithium-6 MAS NMR studies of manganese oxide electrode materials

    NASA Astrophysics Data System (ADS)

    Paik, Younkee

    Electrolytic manganese dioxide (EMD) is used world wide as the cathode materials in both lithium and alkaline primary (non-rechargeable) batteries. We have developed deuterium and lithium MAS NMR techniques to study EMD and related manganese oxides and hydroxides, where diffraction techniques are of limited value due to a highly defective nature of the structures. Deuterons in EMD, manganite, groutite, and deuterium-intercalated pyrolusite and ramsdellite were detected by NMR, for the first time, and their locations and motions in the structures were analyzed by applying variable temperature NMR techniques. Discharge mechanisms of EMD in alkaline (aqueous) electrolytes were studied, in conjunction with step potential electrochemical spectroscopic (SPECS) method, and five distinctive discharge processes were proposed. EMD is usually heat-treated at about 300--400°C to remove water to be used in lithium batteries. Details of the effects of heat-treatment, such as structural and compositional changes as a function of heat-treatment temperature, were studied by a combination of MAS NMR, XRD, and thermogravimetric analysis. Lithium local environments in heat-treated EMD (HEMD) that were discharged in lithium cells, were described in terms of related environments found in model compounds pyrolusite and ramsdellite where specific Li + sites were detected by MAS NMR and the hyperfine shift scale method of Grey et al. Acid-leaching of Li2MnO3 represents an approach for synthesizing new or modified manganese oxide electrode materials for lithium rechargeable batteries. Progressive removal of lithium from specific crystallographic sites, followed by a gradual change of the crystal structure, was monitored by a combination of NMR and XRD techniques.

  9. Tetrahedral site ordering in synthetic gallium albite: A 29Si MAS NMR study

    NASA Astrophysics Data System (ADS)

    Sherriff, Barbara L.; Fleet, Michael E.; Burns, Peter C.

    1991-09-01

    The ordering of Si in the tetrahedral sites of gallium albite (NaGaSi 3O 8) has been studied by MAS NMR and Rietveld structure refinement of X-ray powder diffraction data. Low structural state (ordered) material was annealed at about 800°C under a load pressure of 1 kbar, and by Rietveld refinement has tetrahedral-site occupancies for Si of T1O = 0.24(3), T1m = 0.89(2), T2O = 0.98(2), and T2m = 0.89(2), respectively. Corresponding Si occupancies for high structural state (disordered) material are 0.71(2), 0.78(1), 0.76(2), and 0.74(2), respectively. The 29Si MAS NMR spectra of low gallium albite is equivalent to the three-peak spectrum of natural (Amelia) albite, with resonances at -89.6, -96.4, and -104.2 ppm but with relative peak areas of 0.79:1.0:0.77. The tetrahedral-site occupancies derived from the MAS NMR spectrum are in good agreement with those obtained by Rietveld refinement and, in particular, indicate that the -96.4 ppm peak must correspond to Si in T2O. This is the first independent assignment of the 29Si peak at -96 ppm in the spectrum of ordered albite to the T2O site. A peak at -96 ppm is also resolved in the spectrum of high gallium albite. The systematic differences in peak position between the 29Si MAS NMR spectra of low gallium albite and those of Amelia albite cannot be explained simply by the direct replacement of Al by Ga, without a change in angle at the bridging oxygen atoms.

  10. Interfacial enzyme kinetics of a membrane bound kinase analyzed by real-time MAS-NMR.

    PubMed

    Ullrich, Sandra J; Hellmich, Ute A; Ullrich, Stefan; Glaubitz, Clemens

    2011-05-01

    The simultaneous observation of interdependent reactions within different phases as catalyzed by membrane-bound enzymes is still a challenging task. One such enzyme, the Escherichia coli integral membrane protein diacylglycerol kinase (DGK), is a key player in lipid regulation. It catalyzes the generation of phosphatidic acid within the membrane through the transfer of the γ-phosphate from soluble MgATP to membrane-bound diacylglycerol. We demonstrate that time-resolved (31)P magic angle spinning NMR offers a unique opportunity to simultaneously and directly detect both ATP hydrolysis and diacylglycerol phosphorylation. This experiment demonstrates that solid-state NMR provides a general approach for the kinetic analysis of coupled reactions at the membrane interface regardless of their compartmentalization. The enzymatic activity of DGK was probed with different lipid substrates as well as ATP analogs. Our data yield conclusions about intersubunit cooperativity, reaction stoichiometries and phosphoryl transfer mechanism and are discussed in the context of known structural data. PMID:21423170

  11. Phosphatidylinositol-specific phospholipase C from Bacillus cereus combines intrinsic phosphotransferase and cyclic phosphodiesterase activities: A sup 31 P NMR study

    SciTech Connect

    Shashidhar, M.S.; Kuppe, A. ); Volwerk, J.J.; Griffith, O.H.

    1990-09-04

    The inositol phosphate products formed during the cleavage of phosphatidylinositol by phosphatidylinositol-specific phospholipase C from Bacillus cereus were analyzed by {sup 31}P NMR. {sup 31}P NMR spectroscopy can distinguish between the inositol phosphate species and phosphatidylinositol. Chemical shift values (with reference to phosphoric acid) observed are {minus}0.41, 3.62, 4.45, and 16.30 ppm for phosphatidylinositol, myo-inositol 1-monophosphate, myo-inositol 2-monophosphate, and myo-inositol 1,2-cyclic monophosphate, respectively. It is shown that under a variety of experimental conditions this phospholipase C cleaves phosphatidylinositol via an intramolecular phosphotransfer reaction producing diacylglycerol and D-myo-inositol 1,2-cyclic monophosphate. The authors also report the new and unexpected observation that the phosphatidylinositol-specific phospholipase C from B. cereus is able to hydrolyze the inositol cyclic phosphate to form D-myo-inositol 1-monophosphate. The enzyme, therefore, possesses phosphotransferase and cyclic phosphodiesterase activities. The second reaction requires thousandfold higher enzyme concentrations to be observed by {sup 31}P NMR. This reaction was shown to be regiospecific in that only the 1-phosphate was produced and stereospecific in that only D-myo-inositol 1,2-cyclic monophosphate was hydrolyzed. Inhibition with a monoclonal antibody specific for the B.cereus phospholipase C showed that the cyclic phosphodiesterase activity is intrinsic to the bacterial enzyme. They propose a two-step mechanism for the phosphatidyl-inositol-specific phospholipase C from B. cereus involving sequential phosphotransferase and cyclic phosphodiesterase activities. This mechanism bears a resemblance to the well-known two-step mechanism of pancreatic ribonuclease, RNase A.

  12. (11)B MAS NMR and First-Principles Study of the [OBO3] Pyramids in Borates.

    PubMed

    Zhou, Bing; Sun, Wei; Zhao, Biao-Chun; Mi, Jin-Xiao; Laskowski, Robert; Terskikh, Victor; Zhang, Xi; Yang, Lingyun; Botis, Sanda M; Sherriff, Barbara L; Pan, Yuanming

    2016-03-01

    Borates are built from the [Bϕ3] planar triangles and the [Bϕ4] tetrahedral groups, where ϕ denotes O or OH. However, the [Bϕ4] groups in some borates are highly distorted to include three normal B-O bonds and one anomalously long B-O bond and, therefore, are best described as the [OBO3] pyramids. Four synthetic borates of the boracite-type structures (Mg3B7O13Br, Cu3B7O13Br, Zn3B7O13Cl, and Mg3B7O13Cl) containing a range of [OBO3] pyramids were investigated by multifield (7.05, 14.1, and 21.1 T) (11)B magic-angle spinning nuclear magnetic resonance (MAS NMR), triple quantum (3Q) MAS NMR experiments, as well as density functional theory calculations. The high-resolution (11)B MAS NMR spectra supported by theoretical predictions show that the [OBO3] pyramids are characterized by isotropic chemical shifts δiso((11)B) from 1.4(1) to 4.9(1) ppm and nuclear quadrupole parameters CQ((11)B) up to 1.3(1) MHz, both significantly different from those of the [BO4] and [BO3] groups in borates. These δiso((11)B) and CQ((11)B) values indicate that the [OBO3] pyramids represent an intermediate state between the [BO4] tetrahedra and [BO3] triangles and demonstrate that the (11)B NMR parameters of four-coordinate boron oxyanions are sensitive to local structural environments. The orientation of the calculated unique electronic field gradient tensor element Vzz of the [OBO3] pyramids is aligned approximately along the direction of the anomalously long B-O bond, corresponding to B-2pz with the lowest electron density. PMID:26914372

  13. Effects of decreased pH on membrane structural organization of Escherichia coli grown in different fatty acid-supplemented media: a 31P NMR study.

    PubMed

    Ianzini, F; Guidoni, L; Simone, G; Viti, V; Yatvin, M B

    1990-04-01

    Total membranes from Escherichia coli cells grown in different fatty acid-supplemented media have been examined by 31P NMR at different pH values. The isolated inner and outer membranes were also studied and compared to the liposomes formed with the corresponding extracted lipids. While the liposomes show structures that are correlated with lipid composition, degree of fatty acid unsaturation, and pH, the membrane structure is mainly bilayer. The presence of two bilayer phases characterized by different chemical shift anisotropy values (delta nu csa) is detectable at neutral pH; a perturbation of the bilayer phase characterized by the smallest delta nu csa is produced by low pH. Moreover, an isotropic peak is always present in the membrane NMR spectra: its attribution to cardiolipin molecules is discussed on the basis of digestion experiments with phospholipase C. PMID:2181934

  14. Hydration behaviour of POPC/C(12)-Bet mixtures investigated by sorption gravimetry, (31)P NMR spectroscopy and X-ray diffraction.

    PubMed

    Pfeiffer, H; Weichert, H; Klose, G; Heremans, K

    2012-02-01

    The hydration behaviour of mixtures of the zwitterionic phospholipid 1-palmitoyl-2-oleolyl-sn-glycero-3-phosphocholine (POPC) and the zwitterionic surfactant N,N-dimethyl-N-dodecyl-betain (C(12)-Bet) was investigated by sorption gravimetry, solid-state (31)P NMR-spectroscopy and small angle X-ray diffraction (SAXD). Negative excess hydration (dehydration) was found for almost all hydration degrees investigated. This behaviour is explained by the formation of an inner salt between the dipoles of phospholipid and surfactant headgroups that show a reverse sequence of partial charges with respect to the hydrocarbon backbone. The formation of an inner-salt most probably reduces potential water binding sites. Moreover, NMR data suggest that the incorporation of the zwitterionic surfactant into the phospholipid membrane is correlated with reorientation of the phosphate axis towards the membrane director as well as with reduced lateral and wobbling diffusion. PMID:22285958

  15. Combined (Super 31)P and (Super 1)H NMR Experiments in the Structural Elucidation of Polynuclear Thiolate Complexes

    ERIC Educational Resources Information Center

    Cerrada, Elena; Laguna, Mariano

    2005-01-01

    A facile synthesis of two gold(I) complexes with 1,2-benzenedithiolate ligand and two different bidentate phosphines are described. A detailed sequence of NMR experiments is suggested to determine the structure of the compounds.

  16. Studies of uptake and suppresion of Mn/sup 2 +/ migration in highly vacuolated sycamore (Acer pseudoplatanus L) cells by /sup 31/P NMR

    SciTech Connect

    Roby, C.; Bligny, R.; Douce, R.; Pfeffer, P.E.

    1987-04-01

    Recent /sup 31/P NMR studies have demonstrated that Mn/sup 2 +/ appears to invade the cells of heterogeneous excised tissue of corn root tips sequentially, first entering the cytoplasmic compartment, where it complexes with nucleotides and P/sub i/. Under aerobic conditions, further migration across the tonoplast, followed by vacoule trapping was visualized through paramagnetic broadening of the vacoular P/sub i/ resonance. Cultured cells such as Acer pseudoplatanus L offer better opportunities for studying cellular activity by /sup 31/P NMR because of their homogeneity and uniformly rapid response to various metabolic disturbances. In contrast to excised root tissue, Mn/sup 2 +/ showed no measurable accumulation in the cytoplasmic compartments of these cells under aerobic conditions. However, a rapid crossing of the large tonoplast resulted in immediate vacuolar metal ion sequestration. Anoxia did not foster leakage of Mn/sup 2 +/ from the vacuole to the cytoplasm, while hypoxia completely halted all movement of Mn/sup 2 +/ across the plasmalema. This disparity in terms of cell and tissue morphology, membrane permeability and possible tissue trapping of metal ions will be discussed.

  17. 31P NMR characterization and efficiency of new types of water-insoluble phosphate fertilizers to supply plant-available phosphorus in diverse soil types.

    PubMed

    Erro, Javier; Baigorri, Roberto; Yvin, Jean-Claude; Garcia-Mina, Jose M

    2011-03-01

    Hydroponic plant experiments demonstrated the efficiency of a type of humic acid-based water-insoluble phosphate fertilizers, named rhizosphere controlled fertilizers (RCF), to supply available phosphorus (P) to different plant species. This effect was well correlated to the root release of specific organic acids. In this context, the aims of this study are (i) to study the chemical nature of RCF using solid-state (31)P NMR and (ii) to evaluate the real efficiency of RCF matrix as a source of P for wheat plants cultivated in an alkaline and acid soil in comparison with traditional water-soluble (simple superphosphate, SSP) and water-insoluble (dicalcium phosphate, DCP) P fertilizers. The (31)P NMR study revealed the formation of multimetal (double and triple, MgZn and/or MgZnCa) phosphates associated with chelating groups of the humic acid through the formation of metal bridges. With regard to P fertilizer efficiency, the results obtained show that the RCF matrix produced higher plant yields than SSP in both types of soil, with DCP and the water-insoluble fraction from the RCF matrix (WI) exhibiting the best results in the alkaline soil. By contrast, in the acid soil, DCP showed very low efficiency, WI performed on a par with SSP, and RCF exhibited the highest efficiency, thus suggesting a protector effect of humic acid from soil fixation. PMID:21254775

  18. Coupling of Li motion and structural distortions in olivine LiMnPO4 from 7Li and 31P NMR

    NASA Astrophysics Data System (ADS)

    Rudisch, Christian; Grafe, Hans-Joachim; Geck, Jochen; Partzsch, Sven; Zimmermann, M. v.; Wizent, Nadja; Klingeler, Rüdiger; Büchner, Bernd

    2013-08-01

    We present a detailed 7Li- and 31P-NMR study on single crystalline LiMnPO4 in the paramagnetic and antiferromagnetic phase (AFM, TN˜34 K). This allows us to determine the spin directions in the field-induced spin-flop phase. In addition, the anisotropic dipolar hyperfine coupling tensor of the 7Li and 31P nuclei is also fully determined by orientation and temperature-dependent NMR experiments and compared to the calculated values from crystal structure data. Deviations of the experimental values from the theoretical ones are discussed in terms of Mn disorder which is induced by Li disorder. In fact, the disorder in the Mn sublattice is directly revealed by diffuse x-ray scattering data. The present results provide experimental evidence for the Li diffusion strongly coupling to structural distortions within the MnPO4 host, which is expected to significantly affect the Li mobility as well as the performance of batteries based on this material.

  19. The contribution of magnetic susceptibility effects to transmembrane chemical shift differences in the 31P NMR spectra of oxygenated erythrocyte suspensions.

    PubMed

    Kirk, K; Kuchel, P W

    1988-01-01

    Triethyl phosphate, dimethyl methylphosphonate, and the hypophosphite ion all contain the phosphoryl functional group. When added to an oxygenated erythrocyte suspension, the former compound gives rise to a single 31P NMR resonance, whereas the latter compounds give rise to separate intra- and extracellular 31P NMR resonances. On the basis of experiments with intact oxygenated cell suspensions (in which the hematocrit was varied) and with oxygenated cell lysates (in which the lysate concentration was varied), it was concluded that the chemical shifts of the intra- and extracellular populations of triethyl phosphate differ as a consequence of the diamagnetic susceptibility of intracellular oxyhemoglobin but that this difference is averaged by the rapid exchange of the compound across the cell membrane. The difference in the magnetic susceptibility of the intra- and extracellular compartments contributes to the observed separation of the intra- and extracellular resonances of dimethyl methylphosphonate and hypophosphite. The magnitude of this contribution is, however, substantially less than that calculated using a simple two-compartment model and varies with the hematocrit of the suspension. Furthermore, it is insufficient to fully account for the transmembrane chemical shift differences observed for dimethyl methylphosphonate and hypophosphite. An additional effect is operating to move the intracellular resonances of these compounds to a lower chemical shift. The effect is mediated by an intracellular component, and the magnitude of the resultant chemical shift variations depends upon the chemical structure of the phosphoryl compound involved. PMID:3275636

  20. On the use of 31P NMR for the quantification of hydrosoluble phosphorus-containing compounds in coral host tissues and cultured zooxanthellae

    NASA Astrophysics Data System (ADS)

    Godinot, Claire; Gaysinski, Marc; Thomas, Olivier P.; Ferrier-Pagès, Christine; Grover, Renaud

    2016-02-01

    31P Nuclear Magnetic Resonance (NMR) was assessed to investigate the phosphorus-containing compounds present in the tissues of the scleractinian coral Stylophora pistillata as well as of cultured zooxanthellae (CZ). Results showed that phosphorus-containing compounds observed in CZ were mainly phosphate and phosphate esters. Phosphate accounted for 19 ± 2% of the total phosphorus compounds observed in CZ maintained under low P-levels (0.02 μM). Adding 5 mM of dissolved inorganic phosphorus (KH2PO4) to the CZ culture medium led to a 3.1-fold increase in intracellular phosphate, while adding 5 mM of dissolved organic phosphorus led to a reduction in the concentration of phosphorus compounds, including a 2.5-fold intracellular phosphate decrease. In sharp contrast to zooxanthellae, the host mainly contained phosphonates, and to a lesser extent, phosphate esters and phosphate. Two-months of host starvation decreased the phosphate content by 2.4 fold, while bleaching of fed corals did not modify this content. Based on 31P NMR analyses, this study highlights the importance of phosphonates in the composition of coral host tissues, and illustrates the impact of phosphorus availability on the phosphorus composition of host tissues and CZ, both through feeding of the host and inorganic phosphorus enrichment of the CZ.

  1. On the use of 31P NMR for the quantification of hydrosoluble phosphorus-containing compounds in coral host tissues and cultured zooxanthellae.

    PubMed

    Godinot, Claire; Gaysinski, Marc; Thomas, Olivier P; Ferrier-Pagès, Christine; Grover, Renaud

    2016-01-01

    (31)P Nuclear Magnetic Resonance (NMR) was assessed to investigate the phosphorus-containing compounds present in the tissues of the scleractinian coral Stylophora pistillata as well as of cultured zooxanthellae (CZ). Results showed that phosphorus-containing compounds observed in CZ were mainly phosphate and phosphate esters. Phosphate accounted for 19 ± 2% of the total phosphorus compounds observed in CZ maintained under low P-levels (0.02 μM). Adding 5 mM of dissolved inorganic phosphorus (KH2PO4) to the CZ culture medium led to a 3.1-fold increase in intracellular phosphate, while adding 5 mM of dissolved organic phosphorus led to a reduction in the concentration of phosphorus compounds, including a 2.5-fold intracellular phosphate decrease. In sharp contrast to zooxanthellae, the host mainly contained phosphonates, and to a lesser extent, phosphate esters and phosphate. Two-months of host starvation decreased the phosphate content by 2.4 fold, while bleaching of fed corals did not modify this content. Based on (31)P NMR analyses, this study highlights the importance of phosphonates in the composition of coral host tissues, and illustrates the impact of phosphorus availability on the phosphorus composition of host tissues and CZ, both through feeding of the host and inorganic phosphorus enrichment of the CZ. PMID:26902733

  2. Formations of hydroxyapatite and inositol hexakisphosphate in poultry litter during the composting period: sequential fractionation, P K-edge XANES and solution (31)P NMR investigations.

    PubMed

    Hashimoto, Yohey; Takamoto, Akira; Kikkawa, Ren; Murakami, Keiichi; Yamaguchi, Noriko

    2014-05-20

    Little is known about how the solubility and chemical speciation of phosphorus (P) in poultry litters are altered during the composting period. This study investigated the quantitative and qualitative changes in organic P (Po) and inorganic P (Pi) compositions in poultry litters during the seven-day composting period using sequential extraction in combination with P K-edge X-ray absorption near-edge structure (XANES) and solution (31)P nuclear magnetic resonance (NMR) spectroscopy. The result of sequential extraction illustrated that the significant decrease of H2O-P by 55% in poultry litters occurred concomitantly with the increase of HCl-Pi and HCl-Po during the composting period (p < 0.05). X-ray diffraction results for poultry litter samples showed three distinct peaks indicative of hydroxyapatite. Phosphorus K-edge XANES confirmed the increase of hydroxyapatite during the composting period, corresponding to the increase of HCl-Pi determined by the sequential extraction. The NaOH-EDTA extraction for solution (31)P NMR revealed that myo-inositol hexakisphosphate (IHP) constituted about 80% of phosphate monoesters and was increased from 16 to 28% in the poultry litter during the composting period. The combined applications of chemical extraction and molecular-spectroscopic techniques determined that water-soluble P in poultry litter was transformed into less soluble phases, primarily hydroxyapatite and IHP, during the composting period. PMID:24735189

  3. On the use of 31P NMR for the quantification of hydrosoluble phosphorus-containing compounds in coral host tissues and cultured zooxanthellae

    PubMed Central

    Godinot, Claire; Gaysinski, Marc; Thomas, Olivier P.; Ferrier-Pagès, Christine; Grover, Renaud

    2016-01-01

    31P Nuclear Magnetic Resonance (NMR) was assessed to investigate the phosphorus-containing compounds present in the tissues of the scleractinian coral Stylophora pistillata as well as of cultured zooxanthellae (CZ). Results showed that phosphorus-containing compounds observed in CZ were mainly phosphate and phosphate esters. Phosphate accounted for 19 ± 2% of the total phosphorus compounds observed in CZ maintained under low P-levels (0.02 μM). Adding 5 mM of dissolved inorganic phosphorus (KH2PO4) to the CZ culture medium led to a 3.1-fold increase in intracellular phosphate, while adding 5 mM of dissolved organic phosphorus led to a reduction in the concentration of phosphorus compounds, including a 2.5-fold intracellular phosphate decrease. In sharp contrast to zooxanthellae, the host mainly contained phosphonates, and to a lesser extent, phosphate esters and phosphate. Two-months of host starvation decreased the phosphate content by 2.4 fold, while bleaching of fed corals did not modify this content. Based on 31P NMR analyses, this study highlights the importance of phosphonates in the composition of coral host tissues, and illustrates the impact of phosphorus availability on the phosphorus composition of host tissues and CZ, both through feeding of the host and inorganic phosphorus enrichment of the CZ. PMID:26902733

  4. Contribution of magnetic susceptibility effects to transmembrane chemical shift differences in the /sup 31/P NMR spectra of oxygenated erythrocyte suspensions

    SciTech Connect

    Kirk, K.; Kuchel, P.W.

    1988-01-05

    Triethyl phosphate, dimethyl methylphosphonate, and the hypophosphite ion all contain the phosphoryl functional group. When added to an oxygenated erythrocyte suspension, the former compound gives rise to a single /sup 31/P NMR resonance, whereas the latter compounds give rise to separate intra- and extracellular /sup 31/P NMR resonances. On the basis of experiments with intact oxygenated cell suspensions (in which the hematocrit was varied) and with oxygenated cell lysates (in which the lysate concentration was varied) it was concluded that the chemical shifts of the intra- and extracellular populations of triethyl phosphate differ as a consequence of the diamagnetic susceptibility of intracellular oxyhemoglobin but that this difference is averaged by the rapid exchange of the compound across the cell membrane. The difference is the magnetic susceptibility of the intra- and extracellular compartments contributes to the observed separation of the intra- and extracellular resonances of dimethyl methylphosphonate and hypophosphite. The magnitude of this contribution is, however, substantially less than that calculated using a simple two-compartment model and varies with the hematocrit of the suspension. Furthermore, it is insufficient to fully account for the transmembrane chemical shift differences observed for dimethyl methylphosphonate and hypophosphite. An additional effect is operating to move the intracellular resonances of these compounds to a lower chemical shift. The effect is mediated by an intracellular component, and the magnitude of the resultant chemical shift variations depends upon the chemical structure of the phosphoryl compound involved.

  5. Carbon-13, sup 15 N, and sup 31 P NMR studies on 6-hydroxy-L-nicotine oxidase from Arthrobacter oxidans

    SciTech Connect

    Pust, S.; Vervoort, J.; Decker, K.; Bacher, A.; Mueller, F. )

    1989-01-24

    The interaction between the apoprotein of 6-hydroxy-L-nicotine oxidase from Arthrobacter oxidans and the prosthetic group FAD has been investigated by {sup 13}C, {sup 15}N and {sup 31}P NMR techniques. The FAD prosthetic group was selectively enriched in {sup 13}C and {sup 15}N isotopes by adding isotopically labeled riboflavin derivatives to the growth medium of riboflavin-requiring mutant cells. In the oxidized state the chemical shift of the C(7) and C(8) atoms indicates that the xylene moiety of the isoalloxazine ring is embedded in a hydrophobic environment. The binding of the competitive inhibitor, 6-hydroxy-D-nicotine, influences the resonances of the C(4a) and the N(5) atom strongly. It is suggested that these shifts are due to a strong hydrogen-bonding interaction between the N(5) atom and the inhibitor. On reduction all resonances, except those of the C(10a) and the N(1) atoms, shift upfield, indicating the increased electron density in the ring system. It can unambiguously be concluded from the chemical shift of the N(1) atom that the reduced flavin is anionic. The doublet character of the N(3) and N(5) resonances suggests that bulk water has no access to the active center. The strong downfield shift of the N(1) position indicates that this atom is embedded in a polar environment, but it does not indicate the presence of a positively charged residue. The {sup 31}P NMR spectra show that the resonances of the pyrophosphate group of the bound FAD differ slightly from those of free FAD. Besides the {sup 31}P resonances from FAD, four peaks around 0 ppm are observed that belongs to bound phosphorus residues. The residues are not located close to the isoalloxazine ring.

  6. Ammonia Vapor Removal by Cu3(BTC)2 and Its Characterization by MAS NMR

    PubMed Central

    Peterson, Gregory W.; Wagner, George W.; Balboa, Alex; Mahle, John; Sewell, Tara; Karwacki, Christopher J.

    2009-01-01

    Adsorption equilibria and NMR experiments were performed to study the adsorption and interactions of ammonia with metal-organic framework (MOF) HKUST-1, or Cu3(BTC)2 (BTC = 1,3,5-benzenetricarboxylate). Ammonia capacities determined from chemical breakthrough measurements show significantly higher uptake capacities than from adsorption alone, suggesting a stronger interaction involving a potential reaction with the Cu3(BTC)2 framework. Indeed, 1H MAS NMR reveals that a major disruption of the relatively simple spectrum of Cu3(BTC)2 occurs to generate a composite spectrum consistent with Cu(OH)2 and (NH4)3BTC species under humid conditions—the anticipated products of a copper(II) carboxylate reacted with limited ammonia. These species are not detected under dry conditions; however, reaction stoichiometry combined with XRD results suggests the partial formation of an indeterminate diammine copper (II) complex with some residual Cu3(BTC)2 structure retained. Cu(II)-induced paramagnetic shifts exhibited by various species in 1H and 13C MAS NMR spectra are consistent with model compounds and previous literature. Although results show extensive ammonia capacity of Cu3(BTC)2, much of the capacity is due to reaction with the structure itself, causing a permanent loss in porosity and structural integrity. PMID:20161144

  7. Investigation of multiaxial molecular dynamics by 2H MAS NMR spectroscopy.

    PubMed

    Kristensen, J H; Hoatson, G L; Vold, R L

    1998-11-01

    The technique of 2H MAS NMR spectroscopy is presented for the investigation of multiaxial molecular dynamics. To evaluate the effects of discrete random reorientation a Lie algebraic formalism based on the stochastic Liouville-von Neumann equation is developed. The solution to the stochastic Liouville-von Neumann equation is obtained both in the presence and absence of rf irradiation. This allows effects of molecular dynamics to be evaluated during rf pulses and extends the applicability of the formalism to arbitrary multiple pulse experiments. Theoretical methods are presented for the description of multiaxial dynamics with particular emphasis on the application of vector parameters to represent molecular rotations. Numerical time and powder integration algorithms are presented that are both efficient and easy to implement computationally. The applicability of 2H MAS NMR spectroscopy for investigating molecular dynamics is evaluated from theoretical spectra. To demonstrate the potential of the technique the dynamics of thiourea-2H4 is investigated experimentally. From a series of variable temperature MAS and quadrupole echo spectra it has been found that the dynamics can be described by composite rotation about the CS and CN bonds. Both experiments are sensitive to the fast CS rotation which is shown to be described by the Arrhenius parameters E(CS) = 46.4 +/- 2.3 kJ mol(-1) and ln(A(CS))= 32.6 +/- 0.9. The MAS experiment represents a significant improvement by simultaneously allowing the dynamics of the slow CN rotation to be fully characterized in terms of E(CN) = 56.3 +/- 3.4 kJ mol(-1) and ln(A(CN)) = 25.3 +/- 1.1. PMID:9875600

  8. Cation disorder determined by MAS {sup 27}Al NMR in high dose neutron irradiated spinel

    SciTech Connect

    Cooper, E.A.; Sickafus, K.E.; Hughes, C.D.; Earl, W.L.; Hollenberg, G.W.; Garner, F.A.; Bradt, R.C.

    1995-12-31

    Spinel (MgAl{sub 2}O{sub 4}) single crystals which had been neutron irradiated to high doses (53-250 dpa) were examined using {sup 27}Al magic angle spinning (MAS) nuclear magnetic resonance (NMR). The sensitivity of this procedure to a specific cation (Al) residing in different crystallographic environments allowed one to determine the distribution of the Al between the two cation sites in the spinel structure. The samples were irradiated at two different temperatures (400 and 750{degrees}C) and various doses. These results indicate that the Al was nearly fully disordered over the two lattice sites after irradiation.

  9. Effect of Oxygen Concentration on Viability and Metabolism in a Fluidized-Bed Bioartificial Liver Using 31P and 13C NMR Spectroscopy

    PubMed Central

    Jeffries, Rex E.; Gamcsik, Michael P.; Keshari, Kayvan R.; Pediaditakis, Peter; Tikunov, Andrey P.; Young, Gregory B.; Lee, Haakil; Watkins, Paul B.

    2013-01-01

    Many oxygen mass-transfer modeling studies have been performed for various bioartificial liver (BAL) encapsulation types; yet, to our knowledge, there is no experimental study that directly and noninvasively measures viability and metabolism as a function of time and oxygen concentration. We report the effect of oxygen concentration on viability and metabolism in a fluidized-bed NMR-compatible BAL using in vivo 31P and 13C NMR spectroscopy, respectively, by monitoring nucleotide triphosphate (NTP) and 13C-labeled nutrient metabolites, respectively. Fluidized-bed bioreactors eliminate the potential channeling that occurs with packed-bed bioreactors and serve as an ideal experimental model for homogeneous oxygen distribution. Hepatocytes were electrostatically encapsulated in alginate (avg. diameter, 500 μm; 3.5×107 cells/mL) and perfused at 3 mL/min in a 9-cm (inner diameter) cylindrical glass NMR tube. Four oxygen treatments were tested and validated by an in-line oxygen electrode: (1) 95:5 oxygen:carbon dioxide (carbogen), (2) 75:20:5 nitrogen:oxygen:carbon dioxide, (3) 60:35:5 nitrogen:oxygen:carbon dioxide, and (4) 45:50:5 nitrogen:oxygen:carbon dioxide. With 20% oxygen, β-NTP steadily decreased until it was no longer detected at 11 h. The 35%, 50%, and 95% oxygen treatments resulted in steady β-NTP levels throughout the 28-h experimental period. For the 50% and 95% oxygen treatment, a 13C NMR time course (∼5 h) revealed 2-13C-glycine and 2-13C-glucose to be incorporated into [2-13C-glycyl]glutathione (GSH) and 2-13C-lactate, respectively, with 95% having a lower rate of lactate formation. 31P and 13C NMR spectroscopy is a noninvasive method for determining viability and metabolic rates. Modifying tissue-engineered devices to be NMR compatible is a relatively easy and inexpensive process depending on the bioreactor shape. PMID:22835003

  10. High-resolution multiple quantum MAS NMR spectroscopy of half-integer quadrupolar nuclei

    NASA Astrophysics Data System (ADS)

    Wu, Gang; Rovnyank, David; Sun, Boqin; Griffin, Robert G.

    1996-02-01

    We demonstrate the utility of a two-pulse sequence in obtaining high-resolution solid state NMR spectra of half-integer quadrupolar nuclei with magic-angle-spinning (MAS). The experiment, which utilizes multiple/single-quantum correlation, was first described in a different form by Frydman and Harwood [J. Am. Chem. Soc. 117 (1995) 5367] and yields high-resolution isotropic NMR spectra where shifts are determined by the sum of resonance offset (chemical shift) and second-order quadrupolar effects. The two-pulse sequence described here is shown to provide a higher and more uniform excitation of multiple-quantum coherence than the three-pulse sequence used previously.

  11. Characterizing phosphorus speciation of Chesapeake Bay sediments using chemical extraction, 31P NMR, and X-ray absorption fine structure spectroscopy.

    PubMed

    Li, Wei; Joshi, Sunendra R; Hou, Guangjin; Burdige, David J; Sparks, Donald L; Jaisi, Deb P

    2015-01-01

    Nutrient contamination has been one of the lingering issues in the Chesapeake Bay because the bay restoration is complicated by temporally and seasonally variable nutrient sources and complex interaction between imported and regenerated nutrients. Differential reactivity of sedimentary phosphorus (P) pools in response to imposed biogeochemical conditions can record past sediment history and therefore a detailed sediment P speciation may provide information on P cycling particularly the stability of a P pool and the formation of one pool at the expense of another. This study examined sediment P speciation from three sites in the Chesapeake Bay: (i) a North site in the upstream bay, (ii) a middle site in the central bay dominated by seasonally hypoxic bottom water, and (iii) a South site at the bay-ocean boundary using a combination of sequential P extraction (SEDEX) and spectroscopic techniques, including (31)P NMR, P X-ray absorption near edge structure spectroscopy (XANES), and Fe extended X-ray absorption fine structure (EXAFS). Results from sequential P extraction reveal that sediment P is composed predominantly of ferric Fe-bound P and authigenic P, which was further confirmed by solid-state (31)P NMR, XANES, and EXAFS analyses. Additionally, solution (31)P NMR results show that the sediments from the middle site contain high amounts of organic P such as monoesters and diesters, compared to the other two sites, but that these compounds rapidly decrease with sediment depth indicating remineralized P could have precipitated as authigenic P. Fe EXAFS enabled to identify the changes in Fe mineral composition and P sinks in response to imposed redox condition in the middle site sediments. The presence of lepidocrocite, vermiculite, and Fe smectite in the middle site sediments indicates that some ferric Fe minerals can still be present along with pyrite and vivianite, and that ferric Fe-bound P pool can be a major P sink in anoxic sediments. These results provide

  12. Immobilization of soluble protein complexes in MAS solid-state NMR: Sedimentation versus viscosity.

    PubMed

    Sarkar, Riddhiman; Mainz, Andi; Busi, Baptiste; Barbet-Massin, Emeline; Kranz, Maximilian; Hofmann, Thomas; Reif, Bernd

    2016-01-01

    In recent years, MAS solid-state NMR has emerged as a technique for the investigation of soluble protein complexes. It was found that high molecular weight complexes do not need to be crystallized in order to obtain an immobilized sample for solid-state NMR investigations. Sedimentation induced by sample rotation impairs rotational diffusion of proteins and enables efficient dipolar coupling based cross polarization transfers. In addition, viscosity contributes to the immobilization of the molecules in the sample. Natural Deep Eutectic Solvents (NADES) have very high viscosities, and can replace water in living organisms. We observe a considerable amount of cross polarization transfers for NADES solvents, even though their molecular weight is too low to yield significant sedimentation. We discuss how viscosity and sedimentation both affect the quality of the obtained experimental spectra. The FROSTY/sedNMR approach holds the potential to study large protein complexes, which are otherwise not amenable for a structural characterization using NMR. We show that using this method, backbone assignments of the symmetric proteasome activator complex (1.1MDa), and high quality correlation spectra of non-symmetric protein complexes such as the prokaryotic ribosome 50S large subunit binding to trigger factor (1.4MDa) are obtained. PMID:27017576

  13. One- and two-dimensional exchange J-resolved CP-MAS NMR spectrum of adamantane

    NASA Astrophysics Data System (ADS)

    Takegoshi, K.; McDowell, C. A.

    1986-02-01

    A combined technique of 1D and 2D exchange NMR and J-resolved CP-MAS NMR of dilute spins in solids and its application to study a spin exchange process of abundant spins in solids is described, and demonstrated for powdered adamantane. A high-resolution J-resolved NMR spectrum of a 13C nucleus obtained by applying homonuclear decoupling and magic angle sample spinning is employed to label the spin states of 1H spins bonded to the 13C nucleus. Perspective 2D exchange spectra are employed to map out connectivity between the proton spin states, and the rate constants for the 1H spin exchange involved are determined by 1D exchange NMR techniques. Discussions based on the total energy conservation enable us to conclude that the observed spin exchange processes are to be ascribed mainly to the flip-flop motion of 1H spins; the spin-lattice process is negligible. The rate constant for the flip-flop motion of the proton spins is determined to be (7±2)×103 s-1 at room temperature.

  14. The effect of biradical concentration on the performance of DNP-MAS-NMR

    NASA Astrophysics Data System (ADS)

    Lange, Sascha; Linden, Arne H.; Akbey, Ümit; Trent Franks, W.; Loening, Nikolaus M.; van Rossum, Barth-Jan; Oschkinat, Hartmut

    2012-03-01

    With the technique of dynamic nuclear polarization (DNP) signal intensity in solid-state MAS-NMR experiments can be enhanced by 2-3 orders of magnitude. DNP relies on the transfer of electron spin polarization from unpaired electrons to nuclear spins. For this reason, stable organic biradicals such as TOTAPOL are commonly added to samples used in DNP experiments. We investigated the effects of biradical concentration on the relaxation, enhancement, and intensity of NMR signals, employing a series of samples with various TOTAPOL concentrations and uniformly 13C, 15N labeled proline. A considerable decrease of the NMR relaxation times (T1, T2∗, and T1ρ) is observed with increasing amounts of biradical due to paramagnetic relaxation enhancement (PRE). For nuclei in close proximity to the radical, decreasing T1ρ reduces cross-polarization efficiency and decreases in T2∗ broaden the signal. Additionally, paramagnetic shifts of 1H signals can cause further line broadening by impairing decoupling. On average, the combination of these paramagnetic effects (PE; relaxation enhancement, paramagnetic shifts) quenches NMR-signals from nuclei closer than 10 Å to the biradical centers. On the other hand, shorter T1 times allow the repetition rate of the experiment to be increased, which can partially compensate for intensity loss. Therefore, it is desirable to optimize the radical concentration to prevent additional line broadening and to maximize the signal-to-noise observed per unit time for the signals of interest.

  15. In vivo /sup 31/P NMR studies of corn root tissue and its uptake of toxic metals. [Zea mays L

    SciTech Connect

    Pfeffer, P.E.; Tu, S.I.; Gerasimowicz, W.V.; Cavanaugh, J.R.

    1986-01-01

    Excised corn root tissue has been evaluated for its viability, integrity of compartmentation, intracellular pH gradients, total mobile phosphorus content and nucleotide concentrations under different levels of acidity, and mineral stresses using in vivo /sup 31/P nuclear magnetic resonance spectroscopy at 21 to 23/sup 0/C. Perfusion with Al/sup 3 +/ ion at low pH (4.0) for 20 hours caused the overall concentration of nucleotides in the cytoplasm to decrease significantly relative to the control. Respiratory activity as measured by O/sub 2/ uptake decreased by a comparable amount over this time period. The addition of glucose to the Al-containing perfusate negated the inhibitory effects on the respiratory system. Treatment of the tissue with paramagnetic manganese ion while perfusing in the presence of O/sub 2/ allowed for the observation of the sequence of events leading to the irreversible trapping of Mn/sup 2 +/ in the vacuole. Pretreatment of the roots with Mg/sup 2 +/ prevented Mn/sup 2 +/ migration to the vacuole over the time period of this experiment. Hypoxia prevented all but a limited uptake of Mn/sup 2 +/ into the cytoplasm of the root tips. No evidence of Mn/sup 2 +/ complexation of either cytoplasmic or vacuole Pi suggests that the energy derived from O/sub 2/ consuming processes is necessary for the facilitated movement of this divalent cation.

  16. Combining solid-state and solution-state 31P NMR to study in vivo phosphorus metabolism.

    PubMed Central

    Cholli, A L; Yamane, T; Jelinski, L W

    1985-01-01

    Otherwise unavailable information concerning the distribution of phosphorylated compounds in biological systems is obtained by a combined solid-state/solution-state NMR approach, illustrated here for oocytes from Rana pipiens. General methodology is developed, and further extensions are proposed. The following conclusions pertain to the specific system under examination. (i) Nucleoside phosphates can be observed by magic-angle sample spinning of the lyophilized material. (ii) The solid-state NMR technique of dipolar decoupling provides no additional resolution of the phospholipid and phosphoprotein components of the yolk. However, cellular death produces sufficient pH changes to cause the phospholipid and protein phosphate peaks to become resolvable. The concentration of nucleoside phosphates also decreases. (iii) The phospholipid and phosphoprotein components are shown by computer simulation to be present in a ratio of 40:60, respectively. (iv) The amounts of inorganic phosphate, nucleoside phosphates, and sugar phosphates are determined by solution-state NMR observation of the perchloric acid extract of the oocytes. PMID:3871524

  17. Molecular orientational dynamics in C70S48: Investigation by 13C MAS NMR

    NASA Astrophysics Data System (ADS)

    Grell, A.-S.; Talyzin, A.; Pirotte, P.; Masin, F.

    2001-11-01

    At room temperature the MAS 13C NMR spectrum of C70S48 is identical to that of pure C70 above 323 K, except that the 13C line is shifted by 1.7 ppm compared to that of pure C70. From these results, we deduce that our system is mainly of the van der Waals type. A simulation of the low speed MAS spectrum shows that C70 molecules in C70S48 undergo a uniaxial rotation as in pure C70. This new result contradicts what had been previously published. The chemical shift of the 13C line does not vary with temperature, however the rotation of C70 slows down as the temperature is decreased and stops at ca. 150 K. Moreover the 13C spin-lattice relaxation time, T1, can be described by a single correlation time that follows an Arrhenius law with a 900 K activation energy. By NMR no phase transition is observed at 245 K contrary to dielectric relaxation measurements.

  18. SLOW-MAS NMR METHODS TO STUDY METABOLIC PROCESSES IN VIVO AND IN VITRO

    SciTech Connect

    Wind, Robert A.; Bertram, Hanne Christine; Hu, Jian Zhi

    2005-09-25

    In vitro and in vivo 1H NMR spectroscopy is widely used to measure metabolic profiles in cells, tissues, animals, and humans and to use them, e.g., for diagnosis and therapy response evaluations. However, the spectra often suffer from poor resolution due to variations in the isotropic bulk magnetic susceptibility present in biological objects, resulting in a broadening of the NMR lines. In principle this broadening can be averaged to zero by the technique of magic angle spinning (MAS), where the sample is rotated about an axis making an angle of 54o44’ relative to the external magnetic field. However, a problem is that in a standard MAS experiment spinning speeds of a kHz or more are required in order to avoid the occurrence of spinning sidebands (SSBs) in the spectra, which renders analysis of the spectra difficult again. At these spinning speeds the large centrifugal forces cause severe structural damage in larger biological objects, so that this method cannot be used to study metabolic processes in intact samples. In solid state NMR several methods have been developed where slow MAS is combined with special radio frequency pulse sequences to eliminate spinning side bands or separate them from the isotropic spectrum so that a SSB-free high-resolution isotropic spectrum is obtained. It has been shown recently that two methods, phase-adjusted spinning sidebands (PASS) and phase-corrected magic angle turning (PHORMAT), can successfully be modified for applications in biological materials (1, 2). With PASS MAS speeds as low as 40 Hz can be employed, allowing non or minimally invasive in vitro studies of excised tissues and organs. This method was used, amongst other things, to study post mortem changes in the proton metabolite spectra in excised rabbit muscle tissue (3). With PHORMAT the NMR sensitivity is reduced and longer measuring times are required, but with this methodology the MAS speed can be reduced to ~1 Hz. This makes PHORMAT amenable for in vivo

  19. Lipid Bilayer-Bound Conformation of an Integral Membrane Beta Barrel Protein by Multidimensional MAS NMR

    PubMed Central

    Eddy, Matthew T.; Su, Yongchao; Silvers, Robert; Andreas, Loren; Clark, Lindsay; Wagner, Gerhard; Pintacuda, Guido; Emsley, Lyndon; Griffin, Robert G.

    2015-01-01

    The human voltage dependent anion channel 1 (VDAC) is a 32 kDa β-barrel integral membrane protein that controls the transport of ions across the outer mitochondrial membrane. Despite the determination of VDAC solution and diffraction structures, a structural basis for the mechanism of its function is not yet fully understood. Biophysical studies suggest VDAC requires a lipid bilayer to achieve full function, motivating the need for atomic resolution structural information of VDAC in a membrane environment. Here we report an essential step toward that goal: extensive assignments of backbone and side chain resonances for VDAC in DMPC lipid bilayers via magic angle spinning nuclear magnetic resonance (MAS NMR). VDAC reconstituted into DMPC lipid bilayers spontaneously forms 2-dimensional lipid crystals, showing remarkable spectral resolution (0.5–0.3 ppm for 13C line width and less than 0.5 ppm 15N line widths at 750 MHz). In addition to the benefits of working in a lipid bilayer, several distinct advantages are observed with the lipid crystalline preparation. First, the strong signals and sharp line widths facilitated extensive NMR resonance assignments for an integral membrane β-barrel protein in lipid bilayers by MAS NMR. Second, a large number of residues in loop regions were readily observed and assigned, which can be challenging in detergent-solubilized membrane proteins where loop regions are often not detected due to line broadening from conformational exchange. Third, complete backbone and side chain chemical shift assignments could be obtained for the first 25 residues, which comprise the functionally important N-terminus. The reported assignments allow us to compare predicted torsion angles for VDAC prepared in DMPC 2D lipid crystals, DMPC liposomes, and LDAO-solubilized samples to address the possible effects of the membrane mimetic environment on the conformation of the protein. Concluding, we discuss the strengths and weaknesses of the reported

  20. Lipid bilayer-bound conformation of an integral membrane beta barrel protein by multidimensional MAS NMR.

    PubMed

    Eddy, Matthew T; Su, Yongchao; Silvers, Robert; Andreas, Loren; Clark, Lindsay; Wagner, Gerhard; Pintacuda, Guido; Emsley, Lyndon; Griffin, Robert G

    2015-04-01

    The human voltage dependent anion channel 1 (VDAC) is a 32 kDa β-barrel integral membrane protein that controls the transport of ions across the outer mitochondrial membrane. Despite the determination of VDAC solution and diffraction structures, a structural basis for the mechanism of its function is not yet fully understood. Biophysical studies suggest VDAC requires a lipid bilayer to achieve full function, motivating the need for atomic resolution structural information of VDAC in a membrane environment. Here we report an essential step toward that goal: extensive assignments of backbone and side chain resonances for VDAC in DMPC lipid bilayers via magic angle spinning nuclear magnetic resonance (MAS NMR). VDAC reconstituted into DMPC lipid bilayers spontaneously forms two-dimensional lipid crystals, showing remarkable spectral resolution (0.5-0.3 ppm for (13)C line widths and <0.5 ppm (15)N line widths at 750 MHz). In addition to the benefits of working in a lipid bilayer, several distinct advantages are observed with the lipid crystalline preparation. First, the strong signals and sharp line widths facilitated extensive NMR resonance assignments for an integral membrane β-barrel protein in lipid bilayers by MAS NMR. Second, a large number of residues in loop regions were readily observed and assigned, which can be challenging in detergent-solubilized membrane proteins where loop regions are often not detected due to line broadening from conformational exchange. Third, complete backbone and side chain chemical shift assignments could be obtained for the first 25 residues, which comprise the functionally important N-terminus. The reported assignments allow us to compare predicted torsion angles for VDAC prepared in DMPC 2D lipid crystals, DMPC liposomes, and LDAO-solubilized samples to address the possible effects of the membrane mimetic environment on the conformation of the protein. Concluding, we discuss the strengths and weaknesses of the reported

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

    PubMed

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

    2013-10-01

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

  2. 31P NMR analysis of intracellular pH of Swiss Mouse 3T3 cells: effects of extracellular Na+ and K+ and mitogenic stimulation.

    PubMed

    Civan, M M; Williams, S R; Gadian, D G; Rozengurt, E

    1986-01-01

    Swiss mouse 3T3 cells grown on microcarrier beads were superfused with electrolyte solution during continuous NMR analysis. Conventional 31P and 19F probes of intracellular pH (pHc) were found to be impracticable. Cells were therefore superfused with 1 to 4 mM 2-deoxyglucose, producing a large intracellular, pH-sensitive signal of 2-deoxyglucose phosphate (2DGP). The intracellular incorporation of 2DGP inhibited the Embden-Meyerhof pathway. However, intracellular ATP was at least in part retained and the cellular responsivity to changes in extracellular ionic composition and to the application of growth factors proved intact. Transient replacement of external Na+ with choline or K+ reversibly acidified the intracellular fluids. Quiescent cells and mitogenically stimulated cells displayed the same dependence of shifts in pHc on external Na+ concentration (CoNa). PHc also depended on intracellular Na+ concentration (CcNa). Increasing ccNa by withdrawing external K+ (thereby inhibiting the Na,K-pump) caused reversible intracellular acidification; subsequently reducing CoNa produced a larger acid shift in pHc than with external K+ present. Comparison of separate preparations indicated that pHc was higher in stimulated than in quiescent cells. Transient administration of mitogens also reversibly alkalinized quiescent cells studied continuously. This study documents the feasibility of monitoring pHc of Swiss mouse 3T3 cells using 31P NMR analysis of 2DGP. The results support the concept of a Na/H antiport operative in these cells, both in quiescence and after mitogenic stimulation. The data document by an independent technique that cytoplasmic alkalinization is an early event in mitogenesis, and that full activity of the Embden-Meyerhof pathway is not required for the expression of this event. PMID:3543375

  3. Roles of Arginine and Lysine Residues in the Translocation of a Cell-Penetrating Peptide from 13C, 31P and 19F Solid-State NMR

    PubMed Central

    Su, Yongchao; Doherty, Tim; Waring, Alan J.; Ruchala, Piotr; Hong, Mei

    2009-01-01

    Cell-penetrating peptides (CPPs) are small cationic peptides that cross the cell membrane while carrying macromolecular cargoes. We use solid-state NMR to investigate the structure and lipid interaction of two cationic residues, Arg10 and Lys13, in the CPP penetratin. 13C chemical shifts indicate that Arg10 adopts a rigid β-strand conformation in the liquid-crystalline state of anionic lipid membranes. This behavior contrasts with all other residues observed so far in this peptide, which adopt a dynamic β-turn conformation with coil-like chemical shifts at physiological temperature. Low-temperature 13C-31P distances between the peptide and the lipid phosphates indicate that both the Arg10 guanidinium Cζ and the Lys13 Cε lie in close proximity to the lipid 31P (4.0 - 4.2 Å), proving the existence of charge-charge interaction for both Arg10 and Lys13 in the gel-phase membrane. However, since lysine substitution in CPPs are known to reduce their translocation ability, we propose that low temperature stabilizes both lysine and arginine interactions with the phosphates, whereas at high temperature the lysine-phosphate interaction is much weaker than the arginine-phosphate interaction. This is supported by the unusually high rigidity of the Arg10 sidechain and its β-strand conformation at high temperature. The latter is proposed to be important for ion pair formation by allowing close approach of the lipid headgroups to guanidinium sidechains. 19F and 13C spin diffusion experiments indicate that penetratin is oligomerized into β-sheets in gel-phase membranes. These solid-state NMR data indicate that guanidinium-phosphate interactions exist in penetratin, and guanidinium groups play a stronger structural role than ammonium groups in the lipid-assisted translocation of CPPs across liquid-crystalline cell membranes. PMID:19364134

  4. 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.

  5. 1H, 13C MAS NMR and GIAO-CPHF calculations of chloramphenicol, thiamphenicol and their pyrrole analogues

    NASA Astrophysics Data System (ADS)

    Żołek, Teresa; Paradowska, Katarzyna; Krajewska, Dorota; Różański, Andrzej; Wawer, Iwona

    2003-02-01

    The 13C CP MAS and 1H MAS NMR and ab initio (GIAO-CPHF) calculations were used to obtain structural information on two known antibiotics: chloramphenicol, and thiamphenicol, and two new analogues: DL- threo-1-(1-methyl-4-nitro-pyrrole-2-yl)-2-dichloroacetamidopropane-1,3-diol and DL- threo-1-(1-methylsulfonylpyrrole-3-yl)-2-dichloroacetamidopropane-1,3-diol.

  6. Use of superfused rat skeletal muscle for metabolic studies: assessment of pH by 31P n.m.r.

    PubMed Central

    Meynial-Denis, D; Mignon, M; Foucat, L; Bonnet, Y; Bielicki, G; Renou, J P; Lacourt, P; Lacourt, A; Arnal, M

    1993-01-01

    We developed a muscle superfusion system suitable for metabolic studies of small isolated rat muscle ex vivo in real time and in a non-destructive manner by n.m.r. spectroscopy. In order to determine biochemical stability of superfused extensor digitorum longus (EDL) muscle (from fasted 45 and 100 g rats), the energy state and the pH of muscle were continuously monitored by 31P n.m.r. spectroscopy. ATP and phosphocreatine remained stable during 2 h whatever the muscle size (20 or 45 mg). Neither metabolite was a sensitive probe of possible metabolic compartmentation within muscle under our experimental conditions. By contrast, the chemical shift of Pi by its sensitivity to pH was a discriminant factor in the assessment of muscle stability. Indeed, heterogeneity of pH was observed only in the 45 mg EDL muscle resulting from a core region with loss of glycogen. Together, these observations suggest deviations of energy metabolism to supply ATP. Consequently, pH may be considered as a new real-time criterion for monitoring a metabolic heterogeneity due to changes in energy metabolism of muscle preparations ex vivo. Images Figure 1 PMID:8343121

  7. Studies of vanadium-phosphorus-oxygen selective oxidation catalysts by sup 31 P and sup 51 V NMR spin-echo and volume susceptibility measurements

    SciTech Connect

    Li, Juan.

    1991-10-01

    The purpose of this work is to characterize the vanadium-phosphorous oxide (V-P-O) catalysts for the selective oxidation of n-butane and 1-butene to maleic anhydride. The utility of solid state nuclear magnetic resonance as an analytical tool in this investigation lies in its sensitivity to the electronic environment surrounding the phosphorous and vanadium nuclei, and proximity of paramagnetic species. Spin-echo mapping NMR of {sup 31}p and {sup 51}v and volume magnetic susceptibility measurements were used as local microscopic probes of the presence of V{sup 5+}, V{sup 4+}, V{sup 3+} species in the model compounds: {beta}-VOPO{sub 4}, {beta}-VOPO{sub 4} treated with n-butane/1-butene, (VO){sub 2}P{sub 2}O{sub 7} treated with n-butane/1-butene; and industrial catalysts with P/V (phosphorus to vanadium) ratio of 0.9, 1.0 and 1.1, before and after treatment with n-butane and 1-butene. The NMR spectra provide a picture of how the oxidation states of vanadium are distributed in these catalysts. 73 refs., 32 figs., 8 tabs.

  8. Singlet-triplet separations measured by [sup 31]P[l brace][sup 1]H[r brace] NMR: Applications to quadruply bonded dimolybdenum and ditungsten complexes

    SciTech Connect

    Cotton, F.A.; Eglin, J.L.; Bo Hong; James, C.A. )

    1993-05-12

    A series of quadruply bonded dimolybdenum and ditungsten compounds M[sub 2]X[sub 4](PP)[sub 2] (M = Mo, W; PP = bidentate phosphine ligands; X = Cl, Br, I) with internal rotational angles [chi] varying from 0.0 to 69.4[degrees] have been studied. Their [sup 31]P[l brace][sup 1]H[r brace] NMR spectra are characterized by their temperature-dependent shifts and line widths that broaden with increasing temperature. A nonlinear, least-squares fit of this temperature dependence of the paramagnetic shifts for their NMR signals allows the evaluation of the singlet-triplet energy separation ([minus]2J), the diamagnetic shift (H[sub dia]), and the electron-nucleus hyperfine coupling constant (A). The singlet-triplet energy separations for all the compounds investigated are found to be in the range 1200-3000 cm[sup [minus]1]. It is now clearly established that the ground state remains [sup 1]A[sub 1g] ([delta][sup 2]) even at [chi] = 45[degrees], where [sup 3]A[sub 2u] ([delta][delta]*) lies 1230 cm[sup [minus]1] above it. The [delta]-bond energy and electronic [delta]-barrier can also be experimentally estimated as 13.8[+-]0.5 kcal mol[sup [minus]1] and 10.3[+-]0.5 kcal mol[sup [minus]1], respectively. 32 refs., 3 figs., 1 tab.

  9. Assessing the fate and transformation of plant residues in the terrestrial environment using HR-MAS NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Kelleher, Brian P.; Simpson, Myrna J.; Simpson, Andre J.

    2006-08-01

    Plant litter decomposition plays a fundamental role in carbon and nitrogen cycles, provides key nutrients to the soil environment and represents a potentially large positive feedback to atmospheric CO 2. However, the full details of decomposition pathways and products are unknown. Here we present the first application of HR-MAS NMR spectroscopy on 13C and 15N labeled plant materials, and apply this approach in a preliminary study to monitor the environmental degradation of the pine and wheatgrass residues over time. In HR-MAS, is it possible to acquire very high resolution NMR data of plant biomass, and apply the vast array of multidimensional experiments available in conventional solution-state NMR. High levels of isotopic enrichment combined with HR-MAS significantly enhance the detection limits, and provide a wealth of information that is unattainable by any other method. Diffusion edited HR-MAS NMR data reveal the rapid loss of carbohydrate structures, while two-dimensional (2-D) HR-MAS NMR spectra demonstrate the relatively fast loss of both hydrolysable and condensed tannin structures from all plant tissues studied. Aromatic (partially lignin) and aliphatic components (waxes, cuticles) tend to persist, along with a small fraction of carbohydrate, and become highly functionalized over time. While one-dimensional (1-D) 13C HR-MAS NMR spectra of fresh plant tissue reflect compositional differences between pine and grass, these differences become negligible after decomposition suggesting that recalcitrant carbon may be similar despite the plant source. Two-dimensional 1H- 15N HR-MAS NMR analysis of the pine residue suggests that nitrogen from specific peptides is either selectively preserved or used for the synthesis of what appears to be novel structures. The amount of relevant data generated from plant components in situ using HR-MAS NMR is highly encouraging, and demonstrates that complete assignment will yield unprecedented structural knowledge of plant cell

  10. Molecular degradation of ancient documents revealed by 1H HR-MAS NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Corsaro, Carmelo; Mallamace, Domenico; Łojewska, Joanna; Mallamace, Francesco; Pietronero, Luciano; Missori, Mauro

    2013-10-01

    For centuries mankind has stored its knowledge on paper, a remarkable biomaterial made of natural cellulose fibers. However, spontaneous cellulose degradation phenomena weaken and discolorate paper over time. The detailed knowledge of products arising from cellulose degradation is essential in understanding deterioration pathways and in improving durability of cultural heritage. In this study, for the first time, products of cellulose degradation were individually detected in solid paper samples by means of an extremely powerful proton HR-MAS NMR set-up, in combination to a wise use of both ancient and, as reference, artificially aged paper samples. Carboxylic acids, in addition to more complex dicarboxylic and hydroxy-carboxylic acids, were found in all samples studied. Since these products can catalyze further degradation, their knowledge is fundamental to improve conservation strategies of historical documents. Furthermore, the identification of compounds used in ancient production techniques, also suggests for artifacts dating, authentication and provenance.

  11. Structural models for covalent non-oxidic glasses: Atomic distribution and local order in CdGeAs2-xPx glasses studied by use of 31P and 113Cd spin-echo and 31-113Cd spin-echo double-resonance NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Franke, Deanna; Maxwell, Robert; Lathrop, David; Banks, Kesha; Eckert, Hellmut

    1992-10-01

    The structure of glasses in the system CdGeAs2-xPx is discussed on the basis of complementary solid-state NMR experiments, including 31P and 113Cd magic-angle spinning (MAS) and spin-echo techniques, as well as 31-113Cd spin-echo double resonance (SEDOR) NMR. Computer simulations of atomic distribution models and experimental studies on crystalline model systems are used to quantify the results. The analysis reveals striking differences in the short-range order between the glassy and the stoichiometrically analogous crystalline materials. The structure of glasses in the system CdGeAs2-xPx is characterized by the presence of a substantial fraction of homopolar pnictogen-pnictogen bonds and by a distribution of cadmium relative to phosphorus that is close to random. These results lend credence to the bond-switching model invoked for the structural description of amorphous tetrahedral semiconductors.

  12. Higher Order Amyloid Fibril Structure by MAS NMR and DNP Spectroscopy

    PubMed Central

    Debelouchina, Galia T.; Bayro, Marvin J.; Fitzpatrick, Anthony W.; Ladizhansky, Vladimir; Colvin, Michael T.; Caporini, Marc A.; Jaroniec, Christopher P.; Bajaj, Vikram S.; Rosay, Melanie; MacPhee, Cait E.; Vendruscolo, Michele; Maas, Werner E.; Dobson, Christopher M.; Griffin, Robert G.

    2014-01-01

    Protein magic angle spinning (MAS) NMR spectroscopy has generated structural models of several amyloid fibril systems, thus providing valuable information regarding the forces and interactions that confer the extraordinary stability of the amyloid architecture. Despite these advances, however, obtaining atomic resolution information describing the higher levels of structural organization within the fibrils remains a significant challenge. Here, we detail MAS NMR experiments and sample labeling schemes designed specifically to probe such higher order amyloid structure and we have applied them to the fibrils formed by an eleven-residue segment of the amyloidogenic protein transthyretin (TTR(105-115)). These experiments have allowed us to define unambiguously not only the arrangement of the peptide β-strands into β-sheets but also the β-sheet interfaces within each protofilament, and in addition to identify the nature of the protofilament-to-protofilament contacts that lead to the formation of the complete fibril. Our efforts have resulted in 111 quantitative distance and torsion angle restraints (10 per residue) that describe the various levels of structure organization. The experiments benefited extensively from the use of dynamic nuclear polarization (DNP), which in some cases allowed us to shorten the data acquisition time from days to hours and to improve significantly the signal-to-noise ratios of the spectra. The β-sheet interface and protofilament interactions identified here revealed local variations in the structure that result in multiple peaks for the exposed N- and C-termini of the peptide and in inhomogeneous line-broadening for the side-chains buried within the interior of the fibrils. PMID:24304221

  13. Sensitivity enhancement using paramagnetic relaxation in MAS solid-state NMR of perdeuterated proteins

    NASA Astrophysics Data System (ADS)

    Linser, Rasmus; Chevelkov, Veniamin; Diehl, Anne; Reif, Bernd

    2007-12-01

    Previously, Ishii et al., could show that chelated paramagnetic ions can be employed to significantly decrease the recycle delay of a MAS solid-state NMR experiment [N.P. Wickramasinghe, M. Kotecha, A. Samoson, J. Past, Y. Ishii, Sensitivity enhancement in C-13 solid-state NMR of protein microcrystals by use of paramagnetic metal ions for optimizing H-1 T-1 relaxation, J. Magn. Reson. 184 (2007) 350-356]. Application of the method is limited to very robust samples, for which sample stability is not compromised by RF induced heating. In addition, probe integrity might be perturbed in standard MAS PRE experiments due to the use of very short duty cycles. We show that these deleterious effects can be avoided if perdeuterated proteins are employed that have been re-crystallized from D 2O:H 2O = 9:1 containing buffer solutions. The experiments are demonstrated using the SH3 domain of chicken α-spectrin as a model system. The labeling scheme allows to record proton detected 1H, 15N correlation spectra with very high resolution in the absence of heteronuclear dipolar decoupling. Cu-edta as a doping reagent yields a reduction of the recycle delay by up to a factor of 15. In particular, we find that the 1H T1 for the bulk H N magnetization is reduced from 4.4 s to 0.3 s if the Cu-edta concentration is increased from 0 mM to 250 mM. Possible perturbations like chemical shift changes or line broadening due to the paramagnetic chelate complex are minimal. No degradation of our samples was observed in the course of the experiments.

  14. Dynamic Nuclear Polarization Enhanced MAS NMR Spectroscopy for Structural Analysis of HIV-1 Protein Assemblies.

    PubMed

    Gupta, Rupal; Lu, Manman; Hou, Guangjin; Caporini, Marc A; Rosay, Melanie; Maas, Werner; Struppe, Jochem; Suiter, Christopher; Ahn, Jinwoo; Byeon, In-Ja L; Franks, W Trent; Orwick-Rydmark, Marcella; Bertarello, Andrea; Oschkinat, Hartmut; Lesage, Anne; Pintacuda, Guido; Gronenborn, Angela M; Polenova, Tatyana

    2016-01-21

    Mature infectious HIV-1 virions contain conical capsids composed of CA protein, generated by the proteolytic cleavage cascade of the Gag polyprotein, termed maturation. The mechanism of capsid core formation through the maturation process remains poorly understood. We present DNP-enhanced MAS NMR studies of tubular assemblies of CA and Gag CA-SP1 maturation intermediate and report 20-64-fold sensitivity enhancements due to DNP at 14.1 T. These sensitivity enhancements enabled direct observation of spacer peptide 1 (SP1) resonances in CA-SP1 by dipolar-based correlation experiments, unequivocally indicating that the SP1 peptide is unstructured in assembled CA-SP1 at cryogenic temperatures, corroborating our earlier results. Furthermore, the dependence of DNP enhancements and spectral resolution on magnetic field strength (9.4-18.8 T) and temperature (109-180 K) was investigated. Our results suggest that DNP-based measurements could potentially provide residue-specific dynamics information by allowing for the extraction of the temperature dependence of the anisotropic tensorial or relaxation parameters. With DNP, we were able to detect multiple well-resolved isoleucine side-chain conformers; unique intermolecular correlations across two CA molecules; and functionally relevant conformationally disordered states such as the 14-residue SP1 peptide, none of which are visible at ambient temperatures. The detection of isolated conformers and intermolecular correlations can provide crucial constraints for structure determination of these assemblies. Overall, our results establish DNP-based MAS NMR spectroscopy as an excellent tool for the characterization of HIV-1 assemblies. PMID:26709853

  15. 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

  16. Outcome-related metabolomic patterns from 1H/31P NMR after mild hypothermia treatments of oxygen–glucose deprivation in a neonatal brain slice model of asphyxia

    PubMed Central

    Liu, Jia; Litt, Lawrence; Segal, Mark R; Kelly, Mark J S; Yoshihara, Hikari A I; James, Thomas L

    2011-01-01

    Human clinical trials using 72 hours of mild hypothermia (32°C–34°C) after neonatal asphyxia have found substantially improved neurologic outcomes. As temperature changes differently modulate numerous metabolite fluxes and concentrations, we hypothesized that 1H/31P nuclear magnetic resonance (NMR) spectroscopy of intracellular metabolites can distinguish different insults, treatments, and recovery stages. Three groups of superfused neonatal rat brain slices underwent 45 minutes oxygen–glucose deprivation (OGD) and then were: treated for 3 hours with mild hypothermia (32°C) that began with OGD, or similarly treated with hypothermia after a 15-minute delay, or not treated (normothermic control group, 37°C). Hypothermia was followed by 3 hours of normothermic recovery. Slices collected at different predetermined times were processed, respectively, for 14.1 Tesla NMR analysis, enzyme-linked immunosorbent assay (ELISA) cell-death quantification, and superoxide production. Forty-nine NMR-observable metabolites underwent a multivariate analysis. Separated clustering in scores plots was found for treatment and outcome groups. Final ATP (adenosine triphosphate) levels, severely decreased at normothermia, were restored equally by immediate and delayed hypothermia. Cell death was decreased by immediate hypothermia, but was equally substantially greater with normothermia and delayed hypothermia. Potentially important biomarkers in the 1H spectra included PCr-1H (phosphocreatine in the 1H spectrum), ATP-1H (adenosine triphosphate in the 1H spectrum), and ADP-1H (adenosine diphosphate in the 1H spectrum). The findings suggest a potential role for metabolomic monitoring during therapeutic hypothermia. PMID:20717124

  17. Outcome-related metabolomic patterns from 1H/31P NMR after mild hypothermia treatments of oxygen-glucose deprivation in a neonatal brain slice model of asphyxia.

    PubMed

    Liu, Jia; Litt, Lawrence; Segal, Mark R; Kelly, Mark J S; Yoshihara, Hikari A I; James, Thomas L

    2011-02-01

    Human clinical trials using 72 hours of mild hypothermia (32°C-34°C) after neonatal asphyxia have found substantially improved neurologic outcomes. As temperature changes differently modulate numerous metabolite fluxes and concentrations, we hypothesized that (1)H/(31)P nuclear magnetic resonance (NMR) spectroscopy of intracellular metabolites can distinguish different insults, treatments, and recovery stages. Three groups of superfused neonatal rat brain slices underwent 45 minutes oxygen-glucose deprivation (OGD) and then were: treated for 3 hours with mild hypothermia (32°C) that began with OGD, or similarly treated with hypothermia after a 15-minute delay, or not treated (normothermic control group, 37°C). Hypothermia was followed by 3 hours of normothermic recovery. Slices collected at different predetermined times were processed, respectively, for 14.1 Tesla NMR analysis, enzyme-linked immunosorbent assay (ELISA) cell-death quantification, and superoxide production. Forty-nine NMR-observable metabolites underwent a multivariate analysis. Separated clustering in scores plots was found for treatment and outcome groups. Final ATP (adenosine triphosphate) levels, severely decreased at normothermia, were restored equally by immediate and delayed hypothermia. Cell death was decreased by immediate hypothermia, but was equally substantially greater with normothermia and delayed hypothermia. Potentially important biomarkers in the (1)H spectra included PCr-(1)H (phosphocreatine in the (1)H spectrum), ATP-(1)H (adenosine triphosphate in the (1)H spectrum), and ADP-(1)H (adenosine diphosphate in the (1)H spectrum). The findings suggest a potential role for metabolomic monitoring during therapeutic hypothermia. PMID:20717124

  18. 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.

  19. Broadband inversion for MAS NMR with single-sideband-selective adiabatic pulses

    NASA Astrophysics Data System (ADS)

    Pell, Andrew J.; Kervern, Gwendal; Emsley, Lyndon; Deschamps, Michaël; Massiot, Dominique; Grandinetti, Philip J.; Pintacuda, Guido

    2011-01-01

    We explain how and under which conditions it is possible to obtain an efficient inversion of an entire sideband family of several hundred kHz using low-power, sideband-selective adiabatic pulses, and we illustrate with some experimental results how this framework opens new avenues in solid-state NMR for manipulating spin systems with wide spinning-sideband (SSB) manifolds. This is achieved through the definition of the criteria of phase and amplitude modulation for designing an adiabatic inversion pulse for rotating solids. In turn, this is based on a framework for representing the Hamiltonian of the spin system in an NMR experiment under magic angle spinning (MAS). Following earlier ideas from Caravatti et al. [J. Magn. Reson. 55, 88 (1983)], the so-called "jolting frame" is used, which is the interaction frame of the anisotropic interaction giving rise to the SSB manifold. In the jolting frame, the shift modulation affecting the nuclear spin is removed, while the Hamiltonian corresponding to the RF field is frequency modulated and acquires a spinning-sideband pattern, specific for each crystallite orientation.

  20. Investigations of Li-containing SiCN(O) ceramics via 7Li MAS NMR.

    PubMed

    Gumann, Sina; Nestle, Nikolaus; Liebau-Kunzmann, Verena; Riedel, Ralf

    2007-04-01

    Lithium-containing silicon (oxy)carbonitride ceramics (SiCN(O):Li) were synthesized via precursor-to-ceramic-transformation of Li-containing (poly)silazanes. The precursors were obtained by lithiation of 2,4,6-trimethyl-2,4,6-trivinylcyclotrisilazane with n-butyllithium and by reaction of a commercial poly(organosilazane) VL20 with metallic lithium. The annealing treatment was carried out at temperatures between 200 and 1400 degrees C in argon (DeltaT=200 degrees C) and yielded Li-containing silicon (oxy)carbonitride. X-ray powder diffraction revealed that the resulting SiCN(O):Li ceramics were basically amorphous up to temperatures of 1000 degrees C and formed LiSi(2)N(3), graphite and silicon carbide as crystalline phases at higher temperatures. (7)Li MAS NMR spectroscopy was carried out to investigate the structure of the Li-containing phases and to study the reaction path of metallic Li with polysilazane. Based on the NMR spectra, there is almost no difference found in the chemical shift of the SiCN(O):Li ceramics obtained at different temperatures. Accordingly, Li is assigned to be mainly coordinated to N and O present as contaminant element. Relaxation time measurements showed that the most mobile Li(+) species seems to be present in the product obtained in the pyrolysis temperature range between 600 and 1000 degrees C. PMID:17418540

  1. Low Temperature 1H MAS NMR Spectroscopy Studies of Proton Motion in Zeolite

    SciTech Connect

    Huo, H.; Peng, L; Grey, C

    2009-01-01

    Low temperature {sup 1}H MAS NMR spectroscopy is used to study protonic motion in zeolite HZSM-5 in both samples that have been dried using procedures that are standard in the literature and samples that have been more carefully dehydrated. A significant enhancement of proton mobility is seen for the ''standard'' dehydrated HZSM-5 sample in comparison to that seen for the much drier sample. This is ascribed to a vehicle-hopping mechanism involving the residual water that is present in these zeolites. A gradual change of the framework structure is observed on cooling to approximately 213 K, as monitored via the change in {sup 1}H chemical shift values of the Broensted acid resonances and by X-ray diffraction. A more sudden change in structure is seen by differential scanning calorimetry and NMR at approximately 220?230 K, which is associated with changes in both the mobility and the modes of binding of the residual water to the Broensted acid sites and the zeolite framework.

  2. Comparison of the 1H NMR analysis of solids by the CRAMPS and MAS-only techniques

    NASA Astrophysics Data System (ADS)

    Dec, Steven F.; Bronnimann, Charles E.; Wind, Robert A.; Maciel, Gary E.

    1H NMR spectra are reported on eight representative solid samples, including pure powdered crystalline samples, synthetic organic polymers, a silica gel, HY zeolite, and a lignite. Spectra were obtained by the following three approaches: (1) single pulse on a static sample, (2) CRAMPS, and (3) single pulse with magic-angle spinning (MAS-only). The MAS-only results were obtained as a function of MAS speed. Although the MAS-only technique is capable of achieving a significant degree of line narrowing, even with modest MAS speeds, MAS-only spectra of the general quality of the apparently undistorted high-resolution 1H spectra obtained by the CRAMPS technique are not obtained at the highest MAS speeds examined (21 kHz for a polymethylmethacrylate sample), unless the 1H- 1H dipolar interactions in the sample are rather weak, as with silica gel or a zeolite. Thus, caution should be exercised in interpreting 1H MAS-only spectra, especially if CRAMPS results are not available as a calibration.

  3. Characterization of cation environments in polycrystalline forsterite by Mg-25 MAS, MQMAS, and QCPMG NMR

    SciTech Connect

    Davis, Michael C.; Brouwer, William J.; Lipton, Andrew S.; Gan, Zhehong; Mueller, Karl T.

    2010-11-01

    Forsterite (Mg2SiO4) is a silicate mineral frequently studied in the Earth sciences as it has a simple crystal structure and fast dissolution kinetics (elemental release rates under typical conditions on the order of 10-7 mol/m2/s1). During the dissolution process, spectroscopic techniques are often utilized to augment solution chemical analysis and to provide data for determining reaction mechanisms. Nuclear magnetic resonance (NMR) is able to interrogate the local bonding arrangement and coordination of a particular nuclide to obtain in structural information. Although previous NMR studies have focused on the silicon and oxygen environments in forsterite, studies focusing on the two nonequivalent magnesium environments in forsterite are limited to a few single-crystal studies. In this study, we present the results of 25Mg MAS, MQMAS, and static QCMG experiments performed on a powdered sample of pure synthetic forsterite. We also present spectral fits obtained from simulation software packages, which directly provide quadrupolar parameters for 25Mg nuclei occupying each of the two nonequivalent magnesium sites in the forsterite structure. These results are compared to calculations of the electric field gradient tenor conducted in previous ab initio studies to make definitive assignments correlating each peak to their respective magnesium site in the forsterite structure. Although previous NMR investigations of forsterite have focused on single-crystal samples, we have focused on powdered forsterite as the increased surface area of powdered samples makes them more amenable to laboratory-scale dissolution studies and, ultimately, the products from chemical weathering may be monitored an quantified.

  4. {207}Pb MAS NMR and conductivity identified anomalous phase transition in nanostructured PbF {2}

    NASA Astrophysics Data System (ADS)

    Thangadurai, P.; Ramasamy, S.; Manoharan, P. T.

    2004-02-01

    Lead fluoride, a superionic conductor was prepared in its nanostructured form by Inert Gas Condensation Technique (IGCT) using an Ultra High Vacuum (UHV) chamber. The average grain size was found to be in the range 9 to 43 nm. The existence of mixed phases (α and β-PbF2) was identified using XRD. Solid state 207Pb MAS NMR was carried to average out the dipolar interaction and the resultant isotropic peaks were assigned to the corresponding phases. At high spinning frequencies, one isotropic peak emerged from the contribution of the grain boundary region. The relative intensity of this peak is reduced as the grain size is increased, independent of the concentration of the phases. This is related to the fact that the volume fraction of grain boundary atoms in nanostructured materials increases with the reduction of grain size. The width of the NMR resonance peak is found to be reduced as the grain size goes down. The structural phase transformations were identified at two different temperature regions. The first phase transformation from β to α phase in the annealing temperature range 573 K to 623 K is attributed to some anomalies related to the material microstructure and this has not been reported in earlier literatures. The second phase transformation from α to β in the temperature range 623 K to 673 K is similar to the already reported transformation. Electrical conductivity σ , of the samples was obtained from the complex impedance spectroscopy studies. Conduction species was identified as F- ion through anion vacancies. The magnitude of the conductivity varied according to the dominant phase available when the grain size is higher. But at lower grain sizes below 20 nm, it shows enhanced conductivity that is attributed to the grain size effect. The NMR and conductivity data have jointly supported the anomalous phase transition at the annealing temperature of 623 K.

  5. An FTIR Calibration for Structural Hydrogen in Feldspars Using 1H MAS NMR

    NASA Astrophysics Data System (ADS)

    Johnson, E. A.; Rossman, G. R.

    2002-05-01

    It is important to know how to determine the speciation and concentration of H in feldspars because this information could be used to determine primary magmatic water activity or to estimate the degree of hydrothermal alteration in igneous rocks. FTIR spectroscopy is sensitive to changes in speciation of hydrogen, and can be calibrated for quantitative determination of H concentration using 1H MAS (magic-angle spinning) NMR spectroscopy. Three pegmatitic albites, one metamorphic albite, three volcanic plagioclases (albite, andesine, and anorthite) and one pegmatite oligoclase were used in this study to provide a range of plagioclase compositions. Two pegmatitic microclines and one sanidine were also studied. Polarized infrared spectra were obtained in the three principal optical directions for each specimen. Samples were prepared for 1H MAS NMR experiments at 12 kHz spinning speed in a dry box, without the use of a liquid grinding aid. A spectrum from anhydrous synthetic corundum was used as a baseline for feldspar NMR spectra. The pegmatitic and metamorphic albites are transparent, but contain submicroscopic fluid inclusions as evidenced by a broad band at 3400 cm-1 and an asymmetric band at 5200 cm-1 in the IR spectra that shift to bands characteristic of ice upon cooling to 77 K. These albites have a very sharp band at 4.7 ppm (relative to TMS) in their NMR spectra consistent with fluid inclusion water. In addition to the broad fluid inclusion band, the pegmatitic albites have sharp bands in the mid-IR similar the OH bands found in quartz. All other plagioclases have broad, anisotropic bands around 3200 cm-1 in the mid-IR and MOH combination stretch-bend bands near 4500 cm-1 in the near-IR, indicative of structural OH. The NMR spectra of these plagioclases have a broad band at 4.7 to 4.9 ppm TMS. The OH vector in plagioclases is preferentially aligned parallel to the a crystallographic axis. The concentration of structural OH in the plagioclases ranges from 50

  6. /sup 31/P NMR saturation-transfer measurements in Saccharomyces cerevisiae: characterization of phosphate exchange reactions by iodoacetate and antimycin A inhibition

    SciTech Connect

    Campbell-Burk, S.L.; Jones, K.A.; Shulman, R.G.

    1987-11-17

    /sup 31/P nuclear magnetic resonance (NMR) saturation-transfer (ST) techniques have been used to measure steady-state flows through phosphate-adenosine 5'-triphosphate (ATP) exchange reactions in glucose-grown derepressed yeast. The results have revealed that the reactions catalyzed by glyceraldehyde-3-phosphate dehydrogenase/phosphoglycerate kinase (GAPDH/PGK) and by the mitochondrial ATPase contribute to the observed ST. Contributions from these reactions were evaluated by performing ST studies under various metabolic conditions in the presence and absence of either iodoacetate, a specific inhibitor of GAPDH, or the respiratory chain inhibitor antimycin A. Intracellular phosphate (P/sub i/) longitudinal relaxation times were determined by performing inversion recovery experiments during steady-state ATP/sub lambda/ saturation and were used in combination with ST data to determine P/sub i/ consumption rates. /sup 13/C NMR and O/sub 2/ electrode measurements were also conducted to monitor changes in rates of glucose consumption and O/sub 2/ consumption, respectively, under the various metabolic conditions examined. The results suggest that GAPDH/PGK-catalyzed P/sub i/-ATP exchange is responsible for antimycin-resistant saturation transfer observed in anaerobic and aerobic glucose-fed yeast. Kinetics through GAPDH/PGK were found to depend on metabolic conditions. The coupled system appears to operate in a unidirectional manner during anaerobic glucose metabolism and bidirectionally when the cells are respiring on exogenously supplied ethanol. Additionally, mitochondrial ATPase activity appears to be responsible for the transfer observed in iodoacetate-treated aerobic cells supplied with either glucose or ethanol, with synthesis of ATP occurring unidirectionally.

  7. Skeletal muscle intracellular pH and levels of high energy phosphates during hypercapnia in intact lizards by /sup 31/P NMR

    SciTech Connect

    Johnson, D.C.; Hitzig, B.M.; Elmden, K.; McFarland, E.; Koutcher, J.; Kazemi, H.

    1986-03-05

    Lizards have been shown to reduce ventilation during CO/sub 2/ breathing. This is thought to be detrimental to the maintenance of intracellular pH (pHi) and levels of high energy phosphates. The authors subjected chameleons (n=4) to 5% CO/sub 2/ breathing and made serial measurements of tail (skeletal) muscle pHi, levels of phosphocreatine (PCr), and ATP utilizing high resolution /sup 31/P NMR. pHi was unchanged from controls (7.27 +/- 0.06 units) (mean +/- SE) during 30 minutes of hypercapnia (7.19 +/- 0.09 units) (p>.2) demonstrating effective regulation of skeletal muscle pHi; however, there were significant decreases in the PCr/ATP ratios to 65% +/- 5% (p<.05) of control. The reduced PCr/ATP ratio does not appear due to decreased O/sub 2/ availability because there were no increases in the levels of glycolytic intermediates and inorganic phosphate which would indicate tissue hypoxia. It is possible that an active process requiring ATP is required for the maintenance of pHi in the presence of hypercapnia and that the reduction of PCr/ATP ratio is a reflection of an increased utilization of ATP.

  8. Uptake of metal ions by a new chelating ion exchange resin. Part 3: Protonation constants via potentiometric titration and solid state [sup 31]P NMR spectroscopy

    SciTech Connect

    Nash, K.L.; Rickert, P.G.; Muntean, J.V.; Alexandratos, S.D.

    1994-01-01

    A new chelating ion exchange resin which incorporates methylenediphosphonate, carboxylate, and sulfonate functional groups in a polystyrene-divinylbenzene matrix has been prepared. This resin exhibits exceptionally high affinity for polyvalent cations even from moderately acidic aqueous media. Metal ion coordination occurs primarily at the diphosphonate group with the secondary binding sites contributing to charge neutralization when necessary and possible, and to increasing hydrophilicity of the resin pores. In the present investigation, the protonation equilibria of the phosphonate groups in the resin are investigated via potentiometric titration and solid-state [sup 31]P NMR spectroscopy of the resin. Intrinsic equilibrium constants for the first two diphosphonate protonation reactions are pK[sub 4] = 10.47 and pK[sub 3] = 7.24. The last two protons added to the diphosphonate group are acidic having pK[sub a] values less than 2.5. These protonation constants are consistent with those reported previously for monomer analog 1,1-diphosphonic acids. This result implies that thermodynamic data available in the literature can be used to predict the relative affinity of the resin for polyvalent cations. 17 refs., 2 figs., 3 tabs.

  9. Thin-layer chromatography combined with MALDI-TOF-MS and 31P-NMR to study possible selective bindings of phospholipids to silica gel.

    PubMed

    Teuber, Kristin; Riemer, Thomas; Schiller, Jürgen

    2010-12-01

    High-performance thin-layer chromatography (HPTLC) is a highly established separation method in the field of lipid and (particularly) phospholipid (PL) research. HPTLC is not only used to identify certain lipids in a mixture but also to isolate lipids (preparative TLC). To do this, the lipids are separated and subsequently re-eluted from the silica gel. Unfortunately, it is not yet known whether all PLs are eluted to the same extent or whether some lipids bind selectively to the silica gel. It is also not known whether differences in the fatty acyl compositions affect the affinities to the stationary phase. We have tried to clarify these questions by using a readily available extract from hen egg yolk as a selected example of a lipid mixture. After separation, the complete lanes or selected spots were eluted from the silica gel and investigated by a combination of MALDI-TOF MS and (31)P NMR spectroscopy. The data obtained were compared with the composition of the total extract (without HPTLC). Although there were significant, solvent-dependent losses in the amount of each lipid, the relative composition of the mixture remained constant; there were also only very slight changes in the fatty acyl compositions of the individual PL classes. Therefore, lipid isolation by TLC may be used without any risk of major sample alterations. PMID:20694807

  10. [sup 31]P and [sup 27]Al NMR investigations of the effects of pH on aqueous solutions containing aluminum and phosphorus

    SciTech Connect

    Mortlock, R.F.; Bell, A.T.; Radke, C.J. Univ. of California, Berkeley )

    1993-01-21

    [sup 31]P and [sup 27]Al NMR spectroscopies are used to characterize the distribution of soluble aluminophosphate species in aqueous solutions of tetramethylammonium (TMA) hydroxide, phosphoric acid, and aluminum chloride. Solution compositions range from 0.1 to 1 mol % P, P/Al = 0.1-5, P/(TMA)[sub 2]O = 0.37-10. For solutions of 1 mol % P, a phase diagram is constructed for various concentrations of TMAOH and Al. The phase diagram is divided into three regions: a high-pH region (pH [ge] 6), a medium-pH range (2 [le] pH [le] 10) in which stable solid phases exist, and a low-pH region (pH [le] 2). In the low-pH region, soluble aluminophosphate complexes form between P species (H[sub 3]PO[sub 4] acid dimers, H[sub 3]PO[sub 4] molecules, and H[sub 2]PO[sub 4][sup [minus

  11. Early estrogen-induced metabolic changes and their inhibition by actinomycin D and cycloheximide in human breast cancer cells: sup 31 P and sup 13 C NMR studies

    SciTech Connect

    Neeman, M.; Degani, H. )

    1989-07-01

    Metabolic changes following estrogen stimulation and the inhibition of these changes in the presence of actinomycin D and cycloheximide were monitored continuously in perfused human breast cancer T47D clone 11 cells with {sup 31}P and {sup 13}C NMR techniques. The experiments were performed by estrogen rescue of tamoxifen-treated cells. Immediately after perfusion with estrogen-containing medium, a continuous enhancement in the rates of glucose consumption, lactate production by glycolysis, and glutamate synthesis by the Krebs cycle occurred with a persistent 2-fold increase at 4 hr. Pretreatment with either actinomycin D or cycloheximide, at concentrations known to inhibit mRNA and protein synthesis, respectively, and simultaneous treatment with estrogen and each inhibitor prevented the estrogen-induced changes in glucose metabolism. This suggested that the observed estrogen stimulation required synthesis of mRNA and protein. These inhibitors also modulated several metabolic activities that were not related to estrogen stimulation. The observed changes in the in vivo kinetics of glucose metabolism may provide a means for the early detection of the response of human breast cancer cells to estrogen versus tamoxifen treatment.

  12. Neutral zinc(II) O,O-di-alkyldithiopho- sphates-variable temperature 31P NMR and quantum chemical study of the ZDDP monomer-dimer equilibrium.

    PubMed

    Harrison, J J; Chan, C Y; Onopchenko, A; Pradhan, A R; Petersen, M

    2008-02-01

    A full line-shape analysis of the VT 31P NMR spectra was carried out for the monomer-dimer equilibrium of neutral ZDDP. The energy surface and the energetics of the monomer-dimer equilibrium (DeltaH degrees , DeltaG degrees , Ea, DeltaH(not equal), and DeltaG(not equal)) are reported for three variants wherein the alkyl groups in the ZDDP are 2-ethylhexyl, isopropyl, and isobutyl. We explored a reaction pathway between the monomer and dimer form by means of density functional theory (DFT). The linear combination of atomic orbitals (LCAO) code DMol3 was used together with a synchronous transient method to effectively locate transition states. Vibrational eigenmodes of all intermediates were computed to capture finite temperature effects. Methyl and ethyl were considered as alkyl groups. Two novel intermediates were located-a four-membered ring and a six-membered ring intermediate along the reaction coordinate. Comparison of the experimentally derived and computed energy surfaces was carried out. PMID:18098153

  13. Effect of sugars on headgroup mobility in freeze-dried dipalmitoylphosphatidylcholine bilayers: solid-state 31P NMR and FTIR studies.

    PubMed

    Tsvetkova, N M; Phillips, B L; Crowe, L M; Crowe, J H; Risbud, S H

    1998-12-01

    The effect of the carbohydrates trehalose, glucose, and hydroxyethyl starch (HES) on the motional properties of the phosphate headgroup of freeze-dried dipalmitoylphosphatidylcholine (DPPC) liposomes was studied by means of 31P NMR, Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The results show that trehalose, which is a strong glass former (Tg = 115 degreesC), elevates the onset of the lipid headgroup rotations and preserves some rotational mobility of the phosphate headgroups after cooling from the liquid-crystalline state. Glucose (Tg = 30 degreesC), a very effective depressant of the phase transition temperature of freeze-dried DPPC, markedly elevates the initiation of the temperature of headgroup rotations. On the other hand, the monosaccharide does not preserve the headgroup disordering when cooled from the liquid-crystalline state. These effects are consistent with formation of hydrogen bonds between the OH groups of the sugar and the polar headgroups of DPPC. They show, however, that hydrogen bonding is not sufficient for preservation of the dynamic properties of freeze-dried DPPC. HES, although a very good glass former (Tg > 110 degreesC), does not depress the phase transition temperature and affects only slightly the rotational properties of freeze-dried DPPC. This lack of effect of HES is associated with the absence of direct interactions with the lipid phosphates, as evidenced by the FTIR results. These data show that vitrification of the additive is not sufficient to affect the dynamic properties of dried DPPC. PMID:9826615

  14. 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.

  15. Proton chemical shift tensors determined by 3D ultrafast MAS double-quantum NMR spectroscopy

    SciTech Connect

    Zhang, Rongchun; Mroue, Kamal H.; Ramamoorthy, Ayyalusamy

    2015-10-14

    Proton NMR spectroscopy in the solid state has recently attracted much attention owing to the significant enhancement in spectral resolution afforded by the remarkable advances in ultrafast magic angle spinning (MAS) capabilities. In particular, proton chemical shift anisotropy (CSA) has become an important tool for obtaining specific insights into inter/intra-molecular hydrogen bonding. However, even at the highest currently feasible spinning frequencies (110–120 kHz), {sup 1}H MAS NMR spectra of rigid solids still suffer from poor resolution and severe peak overlap caused by the strong {sup 1}H–{sup 1}H homonuclear dipolar couplings and narrow {sup 1}H chemical shift (CS) ranges, which render it difficult to determine the CSA of specific proton sites in the standard CSA/single-quantum (SQ) chemical shift correlation experiment. Herein, we propose a three-dimensional (3D) {sup 1}H double-quantum (DQ) chemical shift/CSA/SQ chemical shift correlation experiment to extract the CS tensors of proton sites whose signals are not well resolved along the single-quantum chemical shift dimension. As extracted from the 3D spectrum, the F1/F3 (DQ/SQ) projection provides valuable information about {sup 1}H–{sup 1}H proximities, which might also reveal the hydrogen-bonding connectivities. In addition, the F2/F3 (CSA/SQ) correlation spectrum, which is similar to the regular 2D CSA/SQ correlation experiment, yields chemical shift anisotropic line shapes at different isotropic chemical shifts. More importantly, since the F2/F1 (CSA/DQ) spectrum correlates the CSA with the DQ signal induced by two neighboring proton sites, the CSA spectrum sliced at a specific DQ chemical shift position contains the CSA information of two neighboring spins indicated by the DQ chemical shift. If these two spins have different CS tensors, both tensors can be extracted by numerical fitting. We believe that this robust and elegant single-channel proton-based 3D experiment provides useful atomistic

  16. Hepatic lipid profiling of deer mice fed ethanol using {sup 1}H and {sup 31}P NMR spectroscopy: A dose-dependent subchronic study

    SciTech Connect

    Fernando, Harshica; Bhopale, Kamlesh K.; Boor, Paul J.; Ansari, G.A. Shakeel; Kaphalia, Bhupendra S.

    2012-11-01

    Chronic alcohol abuse is a 2nd major cause of liver disease resulting in significant morbidity and mortality. Alcoholic liver disease (ALD) is characterized by a wide spectrum of pathologies starting from fat accumulation (steatosis) in early reversible stage to inflammation with or without fibrosis and cirrhosis in later irreversible stages. Previously, we reported significant steatosis in the livers of hepatic alcohol dehydrogenase (ADH)-deficient (ADH{sup −}) vs. hepatic ADH-normal (ADH{sup +}) deer mice fed 4% ethanol daily for 2 months [Bhopale et al., 2006, Alcohol 39, 179–188]. However, ADH{sup −} deer mice fed 4% ethanol also showed a significant mortality. Therefore, a dose-dependent study was conducted to understand the mechanism and identify lipid(s) involved in the development of ethanol-induced fatty liver. ADH{sup −} and ADH{sup +} deer mice fed 1, 2 or 3.5% ethanol daily for 2 months and fatty infiltration in the livers were evaluated by histology and by measuring dry weights of extracted lipids. Lipid metabolomic changes in extracted lipids were determined by proton ({sup 1}H) and {sup 31}phosphorus ({sup 31}P) nuclear magnetic resonance (NMR) spectroscopy. The NMR data was analyzed by hierarchical clustering (HC) and principle component analysis (PCA) for pattern recognition. Extensive vacuolization by histology and significantly increased dry weights of total lipids found only in the livers of ADH{sup −} deer mice fed 3.5% ethanol vs. pair-fed controls suggest a dose-dependent formation of fatty liver in ADH{sup −} deer mouse model. Analysis of NMR data of ADH{sup −} deer mice fed 3.5% ethanol vs. pair-fed controls shows increases for total cholesterol, esterified cholesterol, fatty acid methyl esters (FAMEs), triacylglycerides and unsaturation, and decreases for free cholesterol, phospholipids and allylic and diallylic protons. Certain classes of neutral lipids (cholesterol esters, fatty acyl chain (-COCH{sub 2}-) and FAMEs) were

  17. Hydration properties of regioselectively etherified celluloses monitored by 2H and 13C solid-state MAS NMR spectroscopy.

    PubMed

    Larsen, Flemming H; Schöbitz, Michael; Schaller, Jens

    2012-06-20

    The hydration properties of 2,3-O-hydroxypropylcellulose (HPC) and 2,3-O-hydroxyethylcellulose (HEC) were analyzed by multi-nuclear solid-state MAS NMR spectroscopy. By 13C single-pulse (SP) MAS and cross-polarization (CP) MAS NMR, differences between the immobile regions and all parts of the polysaccharides were detected as a function of hydration. Complementary information about the water environments was observed by 2H MAS NMR. By this approach it was demonstrated that side chains in 2,3-O-HPC and 2,3-O-HEC were easier to hydrate than the cellulose backbone. Furthermore the motion of water was more restricted (slower) in 2,3-O-HPC than in 2,3-O-HEC. For both polysaccharides the hydration could be explained by a two-step process: in step one increased ordering of the immobile regions occurs after which the entire polymer is hydrated in step two. PMID:24750769

  18. 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

  19. Structural investigations of borosilicate glasses containing MoO 3 by MAS NMR and Raman spectroscopies

    NASA Astrophysics Data System (ADS)

    Caurant, D.; Majérus, O.; Fadel, E.; Quintas, A.; Gervais, C.; Charpentier, T.; Neuville, D.

    2010-01-01

    High molybdenum concentration in glass compositions may lead to alkali and alkaline-earth molybdates crystallization during melt cooling that must be controlled particularly during the preparation of highly radioactive nuclear glassy waste forms. To understand the effect of molybdenum addition on the structure of a simplified nuclear glass and to know how composition changes can affect molybdates crystallization tendency, the structure of two glass series belonging to the SiO 2-B 2O 3-Na 2O-CaO-MoO 3 system was studied by 29Si, 11B, 23Na MAS NMR and Raman spectroscopies by increasing MoO 3 or B 2O 3 concentrations. Increasing MoO 3 amount induced an increase of the silicate network reticulation but no significant effect was observed on the proportion of BO4- units and on the distribution of Na + cations in glass structure. By increasing B 2O 3 concentration, a strong evolution of the distribution of Na + cations was observed that could explain the evolution of the nature of molybdate crystals (CaMoO 4 or Na 2MoO 4) formed during melt cooling.

  20. DNP-Enhanced MAS NMR of Bovine Serum Albumin Sediments and Solutions

    PubMed Central

    2015-01-01

    Protein sedimentation sans cryoprotection is a new approach to magic angle spinning (MAS) and dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) spectroscopy of proteins. It increases the sensitivity of the experiments by a factor of ∼4.5 in comparison to the conventional DNP sample preparation and circumvents intense background signals from the cryoprotectant. In this paper, we investigate sedimented samples and concentrated frozen solutions of natural abundance bovine serum albumin (BSA) in the absence of a glycerol-based cryoprotectant. We observe DNP signal enhancements of ε ∼ 66 at 140 GHz in a BSA pellet sedimented from an aqueous solution containing the biradical polarizing agent TOTAPOL and compare this with samples prepared using the conventional protocol (i.e., dissolution of BSA in a glycerol/water cryoprotecting mixture). The dependence of DNP parameters on the radical concentration points to the presence of an interaction between TOTAPOL and BSA, so much so that a frozen solution sans cryoprotectant still gives ε ∼ 50. We have studied the interaction of BSA with another biradical, SPIROPOL, that is more rigid than TOTAPOL and has been reported to give higher enhancements. SPIROPOL was also found to interact with BSA, and to give ε ∼ 26 close to its maximum achievable concentration. Under the same conditions, TOTAPOL gives ε ∼ 31, suggesting a lesser affinity of BSA for SPIROPOL with respect to TOTAPOL. Altogether, these results demonstrate that DNP is feasible in self-cryoprotecting samples. PMID:24460530

  1. High-temperature behavior of NH4H2PO4 studied by single-crystal and MAS NMR

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran; Lee, Kwang-Sei

    2013-07-01

    To confirm a high-temperature behavior of NH4H2PO4, the temperature dependences of the line-width, resonance frequency, and spin-lattice relaxation times in the laboratory frame, T1, and in the rotating frame, T1ρ, were investigated using a Fourier transform NMR spectrometer. The hydrogen bonds both in O-H-O between two PO4 groups and in N-H-O between NH4 and PO4 were distinguished, and the T1 values of both types of hydrogen-bond proton and 31P ions were described by the Bloembergen-Purcell-Pound theory. In addition, the T1ρ values of both types of hydrogen-bond proton and of 31P ions exhibited strong temperature dependences at high temperature; the changes in T1ρ at high temperature were related to variations in the symmetry.

  2. Characterization of soil phosphorus in a fire-affected forest Cambisol by chemical extractions and (31)P-NMR spectroscopy analysis.

    PubMed

    Turrion, María-Belén; Lafuente, Francisco; Aroca, María-José; López, Olga; Mulas, Rafael; Ruipérez, Cesar

    2010-07-15

    This study was conducted to investigate the long-term effects of fire on soil phosphorus (P) and to determine the efficiency of different procedures in extracting soil P forms. Different P forms were determined: labile forms (Olsen-P, Bray-P, and P extracted by anion exchange membranes: AEM-P); moderately labile inorganic and organic P, obtained by NaOH-EDTA extraction after removing the AEM-P fraction; and total organic and inorganic soil P. (31)P-NMR spectroscopy was used to characterize the structure of alkali-soluble P forms (orthophosphate, monoester, pyrophosphate, and DNA). The studied area was a Pinus pinaster forest located at Arenas de San Pedro (southern Avila, Spain). The soils were Dystric Cambisols over granites. Soil samples were collected at 0-2 cm, 2-5 cm, and 10-15 cm depths, two years after a fire in the burned area and in an adjacent unburned forest area. Fire increased the total N, organic C, total P, and organic and inorganic P content in the surface soil layer. In burned soil, the P extracted by the sequential procedure (AEM and NaOH+EDTA) was about 95% of the total P. Bray extraction revealed a fire-induced increase in the sorption surfaces. Analysis by chemical methods overestimated the organic P fraction in the EDTA-NaOH extract in comparison with the determination by ignition procedure. This overestimation was more important in the burned than unburned soil samples, probably due to humification promoted by burning, which increased P sorption by soil particles. The fire-induced changes on the structure of alkali-soluble P were an increase in orthophosphate-P and a decrease in monoester-P and DNA-P. PMID:20452650

  3. 31P NMR lineshapes of beta-P (ATP) in the presence of Mg2+ and Ca2+: estimate of exchange rates.

    PubMed

    Vasavada, K V; Ray, B D; Nageswara Rao, B D

    1984-08-01

    The 31P NMR chemical shift of beta-P of adenosine triphosphate (ATP) undergoes a substantial change (approximately 2-3 ppm) upon chelation of divalent ions such as Mg2+ or Ca2+. In the presence of nonsaturating amounts of Mg2+ or Ca2+, the lineshape of this resonance depends on the characteristic association and dissociation rates of these metal-ATP complexes. A procedure for computer simulation of this lineshape is outlined. A comparison of computer-simulated lineshapes with the experimental lineshapes obtained at 121 MHz was used to determine the following dissociation rate of Mg2+ and Ca2+ from their ATP complexes at 20 degrees C and pH 8.0: Ca2+, greater than 3 X 10(5) s-1 (Hepes buffer); Mg2+, 1200 s-1 (no buffer), 1000 s-1 (Tris buffer) and 2100 s-1 (Hepes buffer). The limits of error are +/- 10% in these values. For the Mg2+ complexes, the rates were determined as a function of temperature to obtain activation energies (with a maximum deviation of 10% in the least-squares fit): 8.1 Kcal/mole (no buffer and Hepes buffer) and 6.8 kcal/mole (Tris buffer). Lineshapes of the beta-P resonance simulated as a function of Mg2+ concentration, using 2100 s-1 for the dissociation rate, are also presented. The computer simulation of lineshapes offers a reliable and straightforward method for the determination of exchange rates of diamagnetic cations from their ATP complexes, under a variety of sample conditions. PMID:6332879

  4. Influence of muscle temperature during fatiguing work with the first dorsal interosseous muscle in man: a 31P-NMR spectroscopy study.

    PubMed

    Wade, A J; Broadhead, M W; Cady, E B; Llewelyn, M E; Tong, H N; Newham, D J

    2000-02-01

    Six healthy subjects rapidly lifted and lowered a small (250 g) weight with the first dorsal interosseous muscle (FDI) of one hand while the work performed was recorded continuously until fatigue (defined as losing the ability to continue lifting). Work was recorded in units of chart recorder trace displacement from baseline (centimeters) as an isotonic transducer followed the movement of the weight. In all experiments, the temperature of the hand was first adjusted by immersion in a controlled-temperature water bath. In the warmest condition, the skin surface temperature over the FDI was 30.5(0.30) degrees C [mean (SE)]. After moderate cooling, this surface temperature was 21.5(0.16) degrees C. Cooling significantly reduced the time taken to reach fatigue and more than halved the work capacity. An intermediate degree of cooling was also used in four subjects, showing that most of the effects seen were changing incrementally. Before work, and at fatigue, intracellular metabolic conditions in the FDI were studied by phosphorus nuclear magnetic resonance (31P-NMR) spectroscopy, with occlusion of the blood flow maintained during measurements. The mean intracellular pH of the FDI was also calculated. The changes observed were all consistent with the fact that intense work requires energy which must be derived largely from intracellular stores of phosphocreatine and glycogen. Less work made less demand upon reserves, and created lower concentrations of waste products and by-products. The observations did not, however, allow us to explain why fatigue occurred at a particular point or why work capacity was reduced by cooling. PMID:10638378

  5. Rapid identification of osmolytes in tropical microalgae and cyanobacteria by (1)H HR-MAS NMR spectroscopy.

    PubMed

    Zea Obando, Claudia; Linossier, Isabelle; Kervarec, Nelly; Zubia, Mayalen; Turquet, Jean; Faÿ, Fabienne; Rehel, Karine

    2016-06-01

    In this study, we report the chemical characterization of 47 tropical microalgae and cyanobacteria by HR-MAS. The generated data confirm the interest of HR-MAS as a rapid screening technique with the major advantage of its easiness. The sample is used as powder of freeze-dried microalgae without any extraction process before acquisition. The spectral fingerprints of strains are then tested as variables for a chemotaxonomy study to discriminate cyanobacteria and dinoflagellates. The individual factor map generated by PCA analysis succeeds in separating the two groups, essentially thanks to the presence of specific carbohydrates. Furthermore, more resolved signals enable to identify many osmolytes. More precisely the characteristics δ of 2-O-alpha-D-glucosylglycerol (GG) are observed in all 21 h-MAS spectra of tropical cyanobacteria. After specific extraction, complementary analysis by 1D and 2D-NMR spectroscopies validates the identification of this osmolyte. PMID:27130130

  6. DRIFT and HR MAS NMR characterization of humic substances from a soil treated with different organic and mineral fertilizers

    NASA Astrophysics Data System (ADS)

    Ferrari, Erika; Francioso, Ornella; Nardi, Serenella; Saladini, Monica; Ferro, Nicola Dal; Morari, Francesco

    2011-07-01

    In this study, using DRIFT and HR MAS NMR, we analyzed the humic substances isolated from a soil treated, over 40 years, with different organic, mineral and organic plus mineral treatments and cultivated with maize as the main crop. As expected, the structure of humic substances was very complex but by combining both techniques (DRIFT and HR MAS NMR) additional information was obtained on aromatic and aliphatic components, the most recalcitrant parts of these macromolecules. In so doing we wanted to investigate the relationship between HS structure and long-term management practices. An elevated content of lignin, aminoacids, peptides and proteins was observed mainly for farmyard manure treatments with respect to mineral or liquid manure amendments; this supports how the different management practices have greatly influenced the humification process of cultivated soils.

  7. Thermal maturity of type II kerogen from the New Albany Shale assessed by13C CP/MAS NMR

    USGS Publications Warehouse

    Werner-Zwanziger, U.; Lis, G.; Mastalerz, Maria; Schimmelmann, A.

    2005-01-01

    Thermal maturity of oil and gas source rocks is typically quantified in terms of vitrinite reflectance, which is based on optical properties of terrestrial woody remains. This study evaluates 13C CP/MAS NMR parameters in kerogen (i.e., the insoluble fraction of organic matter in sediments and sedimentary rocks) as proxies for thermal maturity in marine-derived source rocks where terrestrially derived vitrinite is often absent or sparse. In a suite of samples from the New Albany Shale (Middle Devonian to the Early Mississippian, Illinois Basin) the abundance of aromatic carbon in kerogen determined by 13C CP/MAS NMR correlates linearly well with vitrinite reflectance. ?? 2004 Elsevier Inc. All rights reserved.

  8. Structural investigations of PuIII phosphate by X-ray diffraction, MAS-NMR and XANES spectroscopy

    NASA Astrophysics Data System (ADS)

    Popa, Karin; Raison, Philippe E.; Martel, Laura; Martin, Philippe M.; Prieur, Damien; Solari, Pier L.; Bouëxière, Daniel; Konings, Rudy J. M.; Somers, Joseph

    2015-10-01

    PuPO4 was prepared by a solid state reaction method and its crystal structure at room temperature was solved by powder X-ray diffraction combined with Rietveld refinement. High resolution XANES measurements confirm the +III valence state of plutonium, in agreement with valence bond derivation. The presence of the americium (as β- decay product of plutonium) in the +III oxidation state was determined based on XANES spectroscopy. High resolution solid state 31P NMR agrees with the XANES results and the presence of a solid-solution.

  9. Conversion of propan-2-ol on zeolites LaNaY and HY investigated by gas chromatography and in situ MAS NMR spectroscopy under continuous-flow conditions

    SciTech Connect

    Hunger, M.; Horvath, T.

    1997-04-01

    The conversion of propan-2-ol on zeolites HY and LaNaY has been investigated by gas chromatography (GC) and in situ {sup 1}H and {sup 13}C MAS NMR spectroscopy under continuous-flow conditions using a new MAS NMR microreactor with cylindrical catalyst bed. At reaction temperatures of T = 373 K and T = 393 K a propan-2-ol conversion of 50 and 100%, respectively, and the formation of propene, diisopropyl. ether, and small amounts of acetone was determined by GC. Applying in situ {sup 1}H and {sup 13}C MAS NMR spectroscopy, the initial step of the reaction was found to be the physisorption of propan-2-ol on Bronsted acid sites. A formation of isopropoxy species could be excluded by {sup 13}C MAS NMR spectroscopy. {sup 1}H MAS NMR spectroscopy indicated that the Bronsted acid sites of the zeolites LaNaY and HY were hydrated by water molecules in the first part of the induction period. These water molecules were formed in result of the propan-2-ol dehydration. The strong low-field shift of the {sup 1}H MAS NMR signals of the hydrated Bronsted acid sites is due to a partial protonation of adsorbed water molecules. At T = 393 K, a significant {sup 13}C MAS NMR signal of strongly bonded acetone molecules appeared at 220 ppm in the spectra of zeolites LaNaY and HY. As demonstrated by propan-2-ol conversion on a partially dealuminated zeolite HY, this by-reaction is promoted by extra-framework aluminium species. The formation of coke precursors which caused {sup 13}C MAS NMR signals at 10-50 ppm is explained by an oligomerization of propene. In situ {sup 13}C MAS NMR experiments carried out under a continuous flow of propene showed that the above-mentioned coke precursors are also formed on partially rehydrated zeolite HY. 25 refs., 14 figs., 1 tab.

  10. Characterization of solid polymer dispersions of active pharmaceutical ingredients by 19F MAS NMR and factor analysis

    NASA Astrophysics Data System (ADS)

    Urbanova, Martina; Brus, Jiri; Sedenkova, Ivana; Policianova, Olivia; Kobera, Libor

    In this contribution the ability of 19F MAS NMR spectroscopy to probe structural variability of poorly water-soluble drugs formulated as solid dispersions in polymer matrices is discussed. The application potentiality of the proposed approach is demonstrated on a moderately sized active pharmaceutical ingredient (API, Atorvastatin) exhibiting extensive polymorphism. In this respect, a range of model systems with the API incorporated in the matrix of polvinylpyrrolidone (PVP) was prepared. The extent of mixing of both components was determined by T1(1H) and T1ρ(1H) relaxation experiments, and it was found that the API forms nanosized domains. Subsequently it was found out that the polymer matrix induces two kinds of changes in 19F MAS NMR spectra. At first, this is a high-frequency shift reaching 2-3 ppm which is independent on molecular structure of the API and which results from the long-range polarization of the electron cloud around 19F nucleus induced by electrostatic fields of the polymer matrix. At second, this is broadening of the signals and formation of shoulders reflecting changes in molecular arrangement of the API. To avoid misleading in the interpretation of the recorded 19F MAS NMR spectra, because both the contributions act simultaneously, we applied chemometric approach based on multivariate analysis. It is demonstrated that factor analysis of the recorded spectra can separate both these spectral contributions, and the subtle structural differences in the molecular arrangement of the API in the nanosized domains can be traced. In this way 19F MAS NMR spectra of both pure APIs and APIs in solid dispersions can be directly compared. The proposed strategy thus provides a powerful tool for the analysis of new formulations of fluorinated pharmaceutical substances in polymer matrices.

  11. 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).

  12. Molecular dynamics of spider dragline silk fiber investigated by 2H MAS NMR.

    PubMed

    Shi, Xiangyan; Holland, Gregory P; Yarger, Jeffery L

    2015-03-01

    The molecular dynamics of the proteins that comprise spider dragline silk were investigated with solid-state (2)H magic angle spinning (MAS) NMR line shape and spin-lattice relaxation time (T1) analysis. The experiments were performed on (2)H/(13)C/(15)N-enriched N. clavipes dragline silk fibers. The silk protein side-chain and backbone dynamics were probed for Ala-rich regions (β-sheet and 31-helical domains) in both native (dry) and supercontracted (wet) spider silk. In native (dry) silk fibers, the side chains in all Ala containing regions undergo similar fast methyl rotations (>10(9) s(-1)), while the backbone remains essentially static (<10(2) s(-1)). When the silk is wet and supercontracted, the presence of water initiates fast side-chain and backbone motions for a fraction of the β-sheet region and 31-helicies. β-Sheet subregion 1 ascribed to the poly(Ala) core exhibits slower dynamics, while β-sheet subregion 2 present in the interfacial, primarily poly(Gly-Ala) region that links the β-sheets to disordered 31-helical motifs, exhibits faster motions when the silk is supercontracted. Particularly notable is the observation of microsecond backbone motions for β-sheet subregion 2 and 31-helicies. It is proposed that these microsecond backbone motions lead to hydrogen-bond disruption in β-sheet subregion 2 and helps to explain the decrease in silk stiffness when the silk is wet and supercontracted. In addition, water mobilizes and softens 31-helical motifs, contributing to the increased extensibility observed when the silk is in a supercontracted state. The present study provides critical insight into the supercontraction mechanism and corresponding changes in mechanical properties observed for spider dragline silks. PMID:25619304

  13. Effects of fluoride on in vitro enamel demineralization analyzed by ¹⁹F MAS-NMR.

    PubMed

    Mohammed, N R; Kent, N W; Lynch, R J M; Karpukhina, N; Hill, R; Anderson, P

    2013-01-01

    The mechanistic action of fluoride on inhibition of enamel demineralization was investigated using (19)F magic angle spinning nuclear magnetic resonance (MAS-NMR). The aim of this study was to monitor the fluoride-mineral phase formed on the enamel as a function of the concentration of fluoride ions [F(-)] in the demineralizing medium. The secondary aim was to investigate fluorapatite formation on enamel in the mechanism of fluoride anti-caries efficacy. Enamel blocks were immersed into demineralization solutions of 0.1 M acetic acid (pH 4) with increasing concentrations of fluoride up to 2,262 ppm. At and below 45 ppm [F(-)] in the solution, (19)F MAS-NMR showed fluoride-substituted apatite formation, and above 45 ppm, calcium fluoride (CaF2) formed in increasing proportions. Further increases in [F(-)] caused no further reduction in demineralization, but increased the proportion of CaF2 formed. Additionally, the combined effect of strontium and fluoride on enamel demineralization was also investigated using (19)F MAS-NMR. The presence of 43 ppm [Sr(2+)] in addition to 45 ppm [F(-)] increases the fraction of fluoride-substituted apatite, but delays formation of CaF2 when compared to the demineralization of enamel in fluoride-only solution. PMID:23712030

  14. Transport Properties of Ibuprofen Encapsulated in Cyclodextrin Nanosponge Hydrogels: A Proton HR-MAS NMR Spectroscopy Study.

    PubMed

    Ferro, Monica; Castiglione, Franca; Punta, Carlo; Melone, Lucio; Panzeri, Walter; Rossi, Barbara; Trotta, Francesco; Mele, Andrea

    2016-01-01

    The chemical cross-linking of β-cyclodextrin (β-CD) with ethylenediaminetetraacetic dianhydride (EDTA) led to branched polymers referred to as cyclodextrin nanosponges (CDNSEDTA). Two different preparations are described with 1:4 and 1:8 CD-EDTA molar ratios. The corresponding cross-linked polymers were contacted with 0.27 M aqueous solution of ibuprofen sodium salt (IP) leading to homogeneous, colorless, drug loaded hydrogels. The systems were characterized by high resolution magic angle spinning (HR-MAS) NMR spectroscopy. Pulsed field gradient spin echo (PGSE) NMR spectroscopy was used to determine the mean square displacement (MSD) of IP inside the polymeric gel at different observation times td. The data were further processed in order to study the time dependence of MSD: MSD = f(td). The proposed methodology is useful to characterize the different diffusion regimes that, in principle, the solute may experience inside the hydrogel, namely normal or anomalous diffusion. The full protocols including the polymer preparation and purification, the obtainment of drug-loaded hydrogels, the NMR sample preparation, the measurement of MSD by HR-MAS NMR spectroscopy and the final data processing to achieve the time dependence of MSD are here reported and discussed. The presented experiments represent a paradigmatic case and the data are discussed in terms of innovative approach to the characterization of the transport properties of an encapsulated guest within a polymeric host of potential application for drug delivery. PMID:27585291

  15. Determination of the structural changes by Raman and {sup 13}C CP/MAS NMR spectroscopy on native corn starch with plasticizers

    SciTech Connect

    Cozar, O.; Filip, C.; Tripon, C.; Cioica, N.; Coţa, C.; Nagy, E. M.

    2013-11-13

    The plasticizing - antiplasticizing effect of water and glycerol contents on native corn starch samples is investigated by FT-Raman and {sup 13}C CP/MAS NMR spectroscopy. The presence of both amorphous and crystalline structural phases was evidenced in pure native corn starch and also in the samples containing plasticizers. Among the crystalline starch structures, the A- and V- types were suggested by CP/MAS NMR spectra.

  16. Solid-state dynamics in the closo-carboranes: a (11)B MAS NMR and molecular dynamics study.

    PubMed

    Ahumada, Hernán; Kurkiewicz, Teresa; Thrippleton, Michael J; Wimperis, Stephen

    2015-03-19

    This work explores the dynamic behavior of the three closo-carborane isomers (formula C2B10H12) using modern solid-state magic angle spinning (MAS) NMR techniques and relates the experimental measurements to theoretical results obtained using molecular dynamics simulations. At high temperatures and at B0 = 9.4 T, the (11)B MAS line widths are narrow (40-90 Hz) for the three isomers. The rotational correlation times (τc) calculated by molecular dynamics are on the picosecond time scale, showing a quasi-isotropic rotation at these temperatures, typical for liquid systems. For all three isomers, the values of the (11)B spin-lattice relaxation times (T1) show discontinuities as the temperature is decreased, confirming the phase changes reported in the literature. At low temperatures, the (11)B MAS spectra of all three isomers exhibit much broader lines. The simulations showed that the molecular reorientation was anisotropic around different symmetry axes for each isomer, and this was supported by the values of the reduced quadrupolar parameter PQ(eff) derived from "dynamic shift" measurements using (11)B MQMAS NMR spectroscopy. The behavior of PQ(eff) as a function of temperature for p-carborane suggests that molecular reorientation is about the C5 symmetry axis of the molecule at low temperatures, and this was supported by the molecular dynamics simulations. PMID:25710751

  17. Conformation analysis and molecular mobility of ethylene and tetrafluoroethylene copolymer using solid-state 19F MAS and 1H --> 19F CP/MAS NMR spectroscopy.

    PubMed

    Aimi, Keitaro; Ando, Shinji

    2004-07-01

    The changes in the conformation and molecular mobility accompanied by a phase transition in the crystalline domain were analyzed for ethylene (E) and tetrafluoroethylene (TFE) copolymer, ETFE, using variable-temperature (VT) solid-state 19F magic angle spinning (MAS) and 1H --> 19F cross-polarization (CP)/MAS NMR spectroscopy. The shifts of the signals for fluorines in TFE units to higher frequency and the continuing decrease and increase in the T1rho(F) values suggest that conformational exchange motions exist in the crystalline domain between 42 and 145 degrees C. Quantum chemical calculations of magnetic shielding constants showed that the high-frequency shift of TFE units should be induced by trans to gauche conformational changes at the CH2-CF2 linkage in the E-TFE unit. Although the 19F signals of the crystalline domain are substantially overlapped with those of the amorphous domain at ambient probe temperature (68 degrees C), they were successfully distinguished by using the dipolar filter and spin-lock pulse sequences at 145 degrees C. The dipolar coupling constants for the crystalline domain, which can be estimated by fitting the dipolar oscillation behaviors in the 1H --> 19F CP curve, showed a significant decrease with increasing temperature from 42 to 145 degrees C. This is due to the averaging of 1H-19F dipolar interactions originating from the molecular motion in the crystalline domain. The increase in molecular mobility in the crystalline domain was clearly shown by VT T1rho(F) and 1H --> 19F CP measurements in the phase transition temperature range. PMID:15181627

  18. Interaction Study of an Amorphous Solid Dispersion of Cyclosporin A in Poly-Alpha-Cyclodextrin with Model Membranes by 1H-, 2H-, 31P-NMR and Electron Spin Resonance

    PubMed Central

    Debouzy, Jean-Claude; Bourbon, Fréderic; Lahiani-Skiba, Malika; Skiba, Mohamed

    2014-01-01

    The properties of an amorphous solid dispersion of cyclosporine A (ASD) prepared with the copolymer alpha cyclodextrin (POLYA) and cyclosporine A (CYSP) were investigated by 1H-NMR in solution and its membrane interactions were studied by 1H-NMR in small unilamellar vesicles and by 31P 2H NMR in phospholipidic dispersions of DMPC (dimyristoylphosphatidylcholine) in comparison with those of POLYA and CYSP alone. 1H-NMR chemical shift variations showed that CYSP really interacts with POLYA, with possible adduct formation, dispersion in the solid matrix of the POLYA, and also complex formation. A coarse approach to the latter mechanism was tested using the continuous variations method, indicating an apparent 1 : 1 stoichiometry. Calculations gave an apparent association constant of log Ka = 4.5. A study of the interactions with phospholipidic dispersions of DMPC showed that only limited interactions occurred at the polar head group level (31P). Conversely, by comparison with the expected chain rigidification induced by CYSP, POLYA induced an increase in the fluidity of the layer while ASD formation led to these effects almost being overcome at 298 K. At higher temperature, while the effect of CYSP seems to vanish, a resulting global increase in chain fluidity was found in the presence of ASD. PMID:24883210

  19. 1H HR-MAS NMR Spectroscopy and the Metabolite Determination of Typical Foods in Mediterranean Diet

    PubMed Central

    Corsaro, Carmelo; Mallamace, Domenico; Vasi, Sebastiano; Ferrantelli, Vincenzo; Dugo, Giacomo; Cicero, Nicola

    2015-01-01

    NMR spectroscopy has become an experimental technique widely used in food science. The experimental procedures that allow precise and quantitative analysis on different foods are relatively simple. For a better sensitivity and resolution, NMR spectroscopy is usually applied to liquid sample by means of extraction procedures that can be addressed to the observation of particular compounds. For the study of semisolid systems such as intact tissues, High-Resolution Magic Angle Spinning (HR-MAS) has received great attention within the biomedical area and beyond. Metabolic profiling and metabolism changes can be investigated both in animal organs and in foods. In this work we present a proton HR-MAS NMR study on the typical vegetable foods of Mediterranean diet such as the Protected Geographical Indication (PGI) cherry tomato of Pachino, the PGI Interdonato lemon of Messina, several Protected Designation of Origin (PDO) extra virgin olive oils from Sicily, and the Traditional Italian Food Product (PAT) red garlic of Nubia. We were able to identify and quantify the main metabolites within the studied systems that can be used for their characterization and authentication. PMID:26495154

  20. MAS-NMR studies of lithium aluminum silicate (LAS) glasses and glass-ceramics having different Li{sub 2}O/Al{sub 2}O{sub 3} ratio

    SciTech Connect

    Ananthanarayanan, A.; Kothiyal, G.P.; Montagne, L.; Revel, B.

    2010-01-15

    Emergence of phases in lithium aluminum silicate (LAS) glasses of composition (wt%) xLi{sub 2}O-71.7SiO{sub 2}-(17.7-x)Al{sub 2}O{sub 3}-4.9K{sub 2}O-3.2B{sub 2}O{sub 3}-2.5P{sub 2}O{sub 5} (5.1<=x<=12.6) upon heat treatment were studied. {sup 29}Si, {sup 27}Al, {sup 31}P and {sup 11}B MAS-NMR were employed for structural characterization of both LAS glasses and glass-ceramics. In glass samples, Al is found in tetrahedral coordination, while P exists mainly in the form of orthophosphate units. B exists as BO{sub 3} and BO{sub 4} units. {sup 27}Al NMR spectra show no change with crystallization, ruling out the presence of any Al containing phase. Contrary to X-ray diffraction studies carried out, {sup 11}B (high field 18.8 T) and {sup 29}Si NMR spectra clearly indicate the unexpected crystallization of a borosilicate phase (Li,K)BSi{sub 2}O{sub 6}, whose structure is similar to the aluminosilicate virgilite. Also, lithium disilicate (Li{sub 2}Si{sub 2}O{sub 5}), lithium metasilicate (Li{sub 2}SiO{sub 3}) and quartz (SiO{sub 2}) were identified in the {sup 29}Si NMR spectra of the glass-ceramics. {sup 31}P NMR spectra of the glass-ceramics revealed the presence of Li{sub 3}PO{sub 4} and a mixed phase (Li,K){sub 3}PO{sub 4} at low alkali concentrations. - Graphical Abstract: The {sup 11}B MAS-NMR spectra of lithium aluminum silicate (LAS) glass-ceramics indicating the formation of Li/KBSiO{sub 6} phase. This phase is isostructural with virgilite and cannot be distinguished in X-ray diffractograms.

  1. Slow motions in microcrystalline proteins as observed by MAS-dependent 15N rotating-frame NMR relaxation

    NASA Astrophysics Data System (ADS)

    Krushelnitsky, Alexey; Zinkevich, Tatiana; Reif, Bernd; Saalwächter, Kay

    2014-11-01

    15N NMR relaxation rate R1ρ measurements reveal that a substantial fraction of residues in the microcrystalline chicken alpha-spectrin SH3 domain protein undergoes dynamics in the μs-ms timescale range. On the basis of a comparison of 2D site-resolved with 1D integrated 15N spectral intensities, we demonstrate that the significant fraction of broad signals in the 2D spectrum exhibits the most pronounced slow mobility. We show that 15N R1ρ's in proton-diluted protein samples are practically free from the coherent spin-spin contribution even at low MAS rates, and thus can be analysed quantitatively. Moderate MAS rates (10-30 kHz) can be more advantageous in comparison with the rates >50-60 kHz when slow dynamics are to be identified and quantified by means of R1ρ experiments.

  2. Slow-MAS NMR: A New Technology for In Vivo Metabolomic Studies

    SciTech Connect

    Wind, Robert A.; Hu, Jian Zhi; Majors, Paul D.

    2005-08-01

    Improvements in the ability to obtain detailed in vivo metabolic information have been identified as key elements of better understanding the efficacy and toxicity of new therapies. A new NMR technology called LOCMAT is discussed that yields substantially increased spectral resolution of spatially localized in vivo 1H NMR metabolite spectra, as illustrated by measurements in the liver and heart of a live mouse. Thus, LOCMAT promises to significantly enhance the utility of NMR spectroscopy for biomedical research.

  3. Residual methyl protonation in perdeuterated proteins for multi-dimensional correlation experiments in MAS solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Agarwal, Vipin; Reif, Bernd

    2008-09-01

    NMR studies involving perdeuterated proteins focus in general on exchangeable amide protons. However, non-exchangeable sites contain as well a small amount of protons as the employed precursors for protein biosynthesis are not completely proton depleted. The degree of methyl group protonation is in the order of 9% for CD 2H using >97% deuterium enriched glucose. We show in this manuscript that this small amount of residual protonation is sufficient to perform 2D and 3D MAS solid-state NMR experiments. In particular, we suggest a HCCH-TOBSY type experiment which we successfully employ to assign the methyl resonances in aliphatic side chains in a perdeuterated sample of the SH3 domain of chicken α-spectrin.

  4. 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.

  5. Sealed rotors for in situ high temperature high pressure MAS NMR.

    PubMed

    Hu, Jian Zhi; Hu, Mary Y; Zhao, Zhenchao; Xu, Suochang; Vjunov, Aleksei; Shi, Hui; Camaioni, Donald M; Peden, Charles H F; Lercher, Johannes A

    2015-09-11

    Here we present the design of reusable and perfectly sealed all-zirconia MAS rotors. The rotors are used to study AlPO4-5 molecular sieve crystallization under hydrothermal conditions, high temperature high pressure cyclohexanol dehydration reaction, and low temperature metabolomics of intact biological tissue. PMID:26171928

  6. Characteristics and assessment of biogenic phosphorus in sediments from the multi-polluted Haihe River, China, using phosphorus fractionation and phosphorus-31 nuclear magnetic resonance (31P-NMR)

    NASA Astrophysics Data System (ADS)

    Zhang, W. Q.; Zhang, H.; Tang, W. Z.; Shan, B. Q.

    2013-10-01

    We studied the phosphorus (P) pollution, as described by concentrations, distribution and transformation potential, of sediments of the water scarce and heavily polluted Fuyang River, a tributary of the Haihe River, using P fractionation and phosphorus-31 nuclear magnetic resonance (31P-NMR).The sediments of the Fuyang River accumulate significant amounts of inorganic phosphorus (Pi) and organic phosphorus (Po) from industrial and domestic wastewater and agricultural non-point pollution. In terms of their contribution to total phosphorus, the rank order of the P fractions was as follows: H2SO4-P > NaOH-Pi > Res-P > NaOH-Po > KCl-P and their average relative proportions were 69.7:47.5:15.9:2.9:1.0 (the proportion was based on the average proportion of the KCl-P). Seven P compounds were detected by the 31P-NMR analysis. Orthophosphate (Ortho-P: 45.2-92.4%) and orthophosphate monoesters (mono-P: 6.6-45.7%) were the dominant forms. Smaller amounts of pyrophosphates (pyro-P: 0.1-6.6%), deoxyribonucleic acid (DNA-P: 0.3-3.9%), phosphonates (phon-P: 0-3.3%), phospholipids (lipids-P: 0-2.7%) and polyphosphate (poly-P: 0-0.04%) were observed in the sediments. Results of P fractionation and 31P-NMR analysis showed that 35% of Pi was labile P, including KCl-P and NaOH-Pi (Fe-P and Al-P). Biogenic-P accounted for 24% of P in the sediments. Analysis of the relationships between P species and water quality indicated that the Po compounds would mineralize to form ortho-P and would be potentially bioavailable for recycling to surface water, supporting further growth of phytoplankton and leading to algal blooms.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  8. Recognition of Membrane Sterols by Polyene Antifungals Amphotericin B and Natamycin, A 13C MAS NMR Study

    PubMed Central

    Ciesielski, Filip; Griffin, David C.; Loraine, Jessica; Rittig, Michael; Delves-Broughton, Joss; Bonev, Boyan B.

    2016-01-01

    The molecular action of polyene macrolides with antifungal activity, amphotericin B and natamycin, involves recognition of sterols in membranes. Physicochemical and functional studies have contributed details to understanding the interactions between amphotericin B and ergosterol and, to a lesser extent, with cholesterol. Fewer molecular details are available on interactions between natamycin with sterols. We use solid state 13C MAS NMR to characterize the impact of amphotericin B and natamycin on mixed lipid membranes of DOPC/cholesterol or DOPC/ergosterol. In cholesterol-containing membranes, amphotericin B addition resulted in marked increase in both DOPC and cholesterol 13C MAS NMR linewidth, reflecting membrane insertion and cooperative perturbation of the bilayer. By contrast, natamycin affects little either DOPC or cholesterol linewidth but attenuates cholesterol resonance intensity preferentially for sterol core with lesser impact on the chain. Ergosterol resonances, attenuated by amphotericin B, reveal specific interactions in the sterol core and chain base. Natamycin addition selectively augmented ergosterol resonances from sterol core ring one and, at the same time, from the end of the chain. This puts forward an interaction model similar to the head-to-tail model for amphotericin B/ergosterol pairing but with docking on opposite sterol faces. Low toxicity of natamycin is attributed to selective, non-cooperative sterol engagement compared to cooperative membrane perturbation by amphotericin B. PMID:27379235

  9. CaCl 2 -Accelerated Hydration of Tricalcium Silicate: A STXM Study Combined with 29 Si MAS NMR

    DOE PAGESBeta

    Li, Qinfei; Ge, Yong; Geng, Guoqing; Bae, Sungchul; Monteiro, Paulo J. M.

    2015-01-01

    Tmore » he effect of calcium chloride (CaCl 2 ) on tricalcium silicate (C 3 S) hydration was investigated by scanning transmission X-ray microscopy (STXM) with Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra and 29 Si MAS NMR. STXM is demonstrated to be a powerful tool for studying the chemical composition of a cement-based hydration system.he Ca L 3,2 -edge NEXAFS spectra obtained by examining C 3 S hydration in the presence of CaCl 2 showed that this accelerator does not change the coordination of calcium in the calcium silicate hydrate (C-S-H), which is the primary hydration product. O K-edge NEXAFS is also very useful in distinguishing the chemical components in hydrated C 3 S. Based on the Ca L 3,2 -edge spectra and chemical component mapping, we concluded that CaCl 2 prefers to coexist with unhydrated C 3 S instead of C-S-H. In Si K-edge NEXAFS analysis, CaCl 2 increases the degree of silicate polymerization of C-S-H in agreement with the 29 Si CP/MAS NMR results, which show that the presence of CaCl 2 in hydrated C 3 S considerably accelerates the formation of middle groups ( Q 2 ) and branch sites ( Q 3 ) in the silicate chains of C-S-H gel at 1-day hydration.« less

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

    PubMed

    Lindh, E L; Stilbs, P; Furó, I

    2016-07-01

    We investigate a way one can achieve good spectral resolution in (2)H MAS NMR experiments. The goal is to be able to distinguish between and study sites in various deuterated materials with small chemical shift dispersion. We show that the (2)H MAS NMR spectra recorded during a spin-relaxation experiment are amenable to spectral decomposition because of the different evolution of spectral components during the relaxation delay. We verify that the results are robust by global least-square fitting of the spectral series both under the assumption of specific line shapes and without such assumptions (COmponent-REsolved spectroscopy, CORE). In addition, we investigate the reliability of the developed protocol by analyzing spectra simulated with different combinations of spectral parameters. The performance is demonstrated in a model material of deuterated poly(methacrylic acid) that contains two (2)H spin populations with similar chemical shifts but different quadrupole splittings. In (2)H-exchanged cellulose containing two (2)H spin populations with very similar chemical shifts and quadrupole splittings, the method provides new site-selective information about the molecular dynamics. PMID:27152833

  11. {sup 29}Si MAS-NMR study of the short-range order in potassium borosilicate glasses

    SciTech Connect

    Martin, S.W.; Bhatnagar, A.; Parameswar, C.; Feller, S.; MacKenzie, J.

    1995-04-01

    Potassium borosilicate glasses were prepared in families having the general formula of RK{sub 2}O{center_dot}B{sub 2}O{sub 3}{center_dot}NSiO{sub 2}, where R is the ratio of potassium oxide to boron oxide and N is the ratio of silicon dioxide to boron oxide. The glasses were prepared for values of R ranging from 0 to 7.0 in the families N = 0.5, 1.0, 2.0, and 4.0. {sup 29}Si MAS-NMR measurements were performed on these glasses to determine the short-range order around the silicon atom. A model of proportional sharing of the added potassium oxide between the silicate and the borate groups was suggested. This model was tested against other suggested models where proportional sharing begins after a minimum amount of potassium oxide, R{sub 0}, and was observed to provide a better fit to the {sup 29}Si chemical shifts obtained. As was observed in the {sup 29}Si MAS-NMR studies of the RLi{sub 2}O{center_dot}B{sub 2}O{sub 3}{center_dot}NSiO{sub 2} glasses, the proportional sharing model with R{sub 0} = 0 is in stark disagreement with that proposed by the {sup 11}B NMR studies of the alkali borosilicate glasses. This problem is as yet not understood. Since K{sub 2}CO{sub 3} was used as the starting material for K{sub 2}O, it was observed that at large R values, R > R{sub CO{sub 2}}, where R{sub CO{sub 2}} = 2.3 for N = 1, R{sub CO{sub 2}} = 4.0 for N = 2, and R{sub CO{sub 2}} = 5.0 for N = 4, CO{sub 2} was retained in the melt in the fashion similar to that observed for other high-alkali borate and silicate glasses. The N = 0.5 family did not exhibit retention at the compositions studied. {sup 29}Si MAS-NMR could be used to determine where CO{sub 2} retention began in composition and the proportion of K{sub 2}O/K{sub 2}CO{sub 3} in the melt (glass).

  12. 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

  13. 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

  14. Phase Cycling Schemes for finite-pulse-RFDR MAS Solid State NMR Experiments

    PubMed Central

    Zhang, Rongchun; Nishiyama, Yusuke; Sun, Pingchuan; Ramamoorthy, Ayyalusamy

    2015-01-01

    The finite-pulse radio frequency driven dipolar recoupling (fp-RFDR) pulse sequence is used in 2D homonuclear chemical shift correlation experiments under magic angle spinning (MAS). A recent study demonstrated the advantages of using a short phase cycle, XY4, and its super-cycle, XY414, for the fp-RFDR pulse sequence employed in 2D 1H/1H single-quantum/single-quantum correlation experiments under ultrafast MAS conditions. In this study, we report a comprehensive analysis on the dipolar recoupling efficiencies of XY4, XY412, XY413, XY414, and XY814 phase cycles under different spinning speeds ranging from 10 to 100 kHz. The theoretical calculations reveal the presence of second-order terms (T10T2,±2, T1,±1T2,±1, etc.) in the recoupled homonuclear dipolar coupling Hamiltonian only when the basic XY4 phase cycle is utilized, making it advantageous for proton-proton magnetization transfer under ultrafast MAS conditions. It is also found that the recoupling efficiency of fp-RFDR is quite dependent on the duty factor (τ180/τR) as well as on the strength of homonuclear dipolar couplings. The rate of longitudinal magnetization transfer increases linearly with the duty factor of fp-RFDR for all the XY-based phase cycles investigated in this study. Examination of the performances of different phase cycles against chemical shift offset and RF field in homogeneity effects revealed that XY414 is the most tolerant phase cycle, while the shortest phase cycle XY4 suppressed the RF field inhomogeneity effects most efficiently under slow spinning speeds. Our results suggest that the difference in the fp-RFDR recoupling efficiencies decreases with the increasing MAS speed, while ultrafast (>60 kHz) spinning speed is advantageous as it recouples a large amount of homonuclear dipolar couplings and therefore enable fast magnetization exchange. The effects of higher-order terms and cross terms between various interactions in the effective Hamiltonian of fp-RFDR are also analyzed

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

    PubMed

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

    2014-07-01

    Reducing the data collection time without affecting the signal intensity and spectral resolution is one of the major challenges for the widespread application of multidimensional nuclear magnetic resonance (NMR) spectroscopy, especially in experiments conducted on complex heterogeneous biological systems such as bone. In most of these experiments, the NMR data collection time is ultimately governed by the proton spin-lattice relaxation times (T1). For over two decades, gadolinium(III)-DTPA (Gd-DTPA, DTPA=Diethylene triamine pentaacetic acid) has been one of the most widely used contrast-enhancement agents in magnetic resonance imaging (MRI). In this study, we demonstrate that Gd-DTPA can also be effectively used to enhance the longitudinal relaxation rates of protons in solid-state NMR experiments conducted on bone without significant line-broadening and chemical-shift-perturbation side effects. Using bovine cortical bone samples incubated in different concentrations of Gd-DTPA complex, the (1)H T1 values were calculated from data collected by (1)H spin-inversion recovery method detected in natural-abundance (13)C cross-polarization magic angle spinning (CPMAS) NMR experiments. Our results reveal that the (1)H T1 values can be successfully reduced by a factor of 3.5 using as low as 10mM Gd-DTPA without reducing the spectral resolution and thus enabling faster data acquisition of the (13)C CPMAS spectra. These results obtained from (13)C-detected CPMAS experiments were further confirmed using (1)H-detected ultrafast MAS experiments on Gd-DTPA doped bone samples. This approach considerably improves the signal-to-noise ratio per unit time of NMR experiments applied to bone samples by reducing the experimental time required to acquire the same number of scans. PMID:24881032

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  17. Acceleration of Natural-Abundance Solid-State MAS NMR Measurements on Bone by Paramagnetic Relaxation from Gadolinium-DTPA

    PubMed Central

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

    2014-01-01

    Reducing the data collection time without affecting the signal intensity and spectral resolution is one of the major challenges for the widespread application of multidimensional nuclear magnetic resonance (NMR) spectroscopy, especially in experiments conducted on complex heterogeneous biological systems such as bone. In most of these experiments, the NMR data collection time is ultimately governed by the proton spin-lattice relaxation times (T1). For over two decades, gadolinium(III)-DTPA (Gd-DTPA, DTPA = Diethylenetriamine pentaacetic acid) has been one of the most widely used contrast-enhancement agents in magnetic resonance imaging (MRI). In this study, we demonstrate that Gd-DTPA can also be effectively used to enhance the longitudinal relaxation rates of protons in solid-state NMR experiments conducted on bone without significant line-broadening and chemical-shift-perturbation side effects. Using bovine cortical bone samples incubated in different concentrations of Gd-DTPA complex, the 1H T1 values were calculated from data collected by 1H spin-inversion recovery method detected in natural-abundance 13C cross-polarization magic angle spinning (CPMAS) NMR experiments. Our results reveal that the 1H T1 values can be successfully reduced by a factor of 3.5 using as low as 10 mM Gd-DTPA without reducing the spectral resolution and thus enabling faster data acquisition of the 13C CPMAS spectra. These results obtained from 13C-detected CPMAS experiments were further confirmed using 1H-detected ultrafast MAS experiments on Gd-DTPA doped bone samples. This approach considerably improves the signal-to-noise ratio per unit time of NMR experiments applied to bone samples by reducing the experimental time required to acquire the same number of scans. PMID:24881032

  18. Magnetic susceptibility effects on 13C MAS NMR spectra of carbon materials and graphite.

    PubMed

    Freita, J C; Emmerich, F G; Cernicchiaro, G R; Sampaio, L C; Bonagamba, T J

    2001-01-01

    13C high-resolution solid-state nuclear magnetic resonance (NMR) was employed to study carbon materials prepared through the thermal decomposition of four different organic precursors (rice hulls, endocarp of babassu coconut, peat, and PVC). For heat treatment temperatures (HTTs) above about 600 C, all materials presented 13C NMR spectra composed of a unique resonance line associated with carbon atoms in aromatic planes. With increasing HTT a continuous broadening of this resonance and a diamagnetic shift in its central frequency were verified for all samples. The evolution of the magnitude and anisotropy of the magnetic susceptibility of the heat-treated carbon samples with HTT explains well these findings. It is shown that these results are better understood when a comparison is made with the features of the 13C NMR spectrum of polycrystalline graphite, for which the magnetic susceptibility effect is also present and is much more pronounced. PMID:11529420

  19. A sup 31 P NMR study of mitochondrial inorganic phosphate visibility: Effects of Ca sup 2+ , Mn sup 2+ , and the pH gradient

    SciTech Connect

    Hutson, S.M.; Williams, G.D.; Berkich, D.A.; LaNoue, K.F.; Briggs, R.W. )

    1992-02-11

    The effects of external pH, temperature, and Ca{sup 2+} and Mn{sup 2+} concentrations on the compartmentation and NMR visibility of inorganic phosphate (P{sub i}) were studied in isolated rat liver mitochondria respiring on succinate and glutamate. Mitochondrial matrix P{sub i} is totally visible by NMR at 8C and at low external concentrations of P{sub i}. However, when the external P{sub i} concentration is increased above 7 mM, the pH gradient decreases, the amount of matrix P{sub i} increases, and the fraction not observed by NMR increases. Raising the temperature to 25C also decreases the pH gradient and the P{sub i} fraction observed by NMR. At physiologically relevant concentrations, Ca{sup 2+} and Mn{sup 2+} do not seem to play a major role in matrix P{sub i} NMR invisibility. For Ca{sup 2+} concentrations above 30 nmol/mg of protein, formation of insoluble complexes will cause loss of P{sub i} signal intensity. For Mn{sup 2+} concentrations above 2 nmol/mg of protein, the P{sub i} peak can be broadened sufficiently to preclude detection of a high-resolution signal. The results indicate that mitochondrial matrix P{sub i} should be mostly observable up to 25C by high-resolution NMR. While the exact nature of the NMR-invisible phosphate in perfused or in vivo liver is yet to be determined, better success at detecting and resolving both P{sub i} pools by NMR is indicated at high field, low temperature, and optimized pulsing conditions.

  20. 1H and 31P NMR and HPLC studies of mouse L1210 leukemia cell extracts: the effect of Au(I) and Cu(I) diphosphine complexes on the cell metabolism.

    PubMed

    Berners-Price, S J; Sant, M E; Christopherson, R I; Kuchel, P W

    1991-03-01

    The effect of the antitumor complex [Au(dppe)2]Cl (where dppe is Ph2P(CH2)2PPh2) on the overall metabolism of cultured mouse L1210 leukemia cells was investigated by comparing 1H and 31P NMR spectra of perchloric acid extracts of cells incubated for 1 h in the presence and absence of 2 microM [Au(dppe)2]Cl. There were marked (ca. two-fold) increases in the levels of lactate and almost all detectable amino acids suggesting a drug-induced increase in the rate of glycolysis and inhibition of protein synthesis. The levels of taurine and phosphorylcholine were significantly decreased and 31P NMR spectra revealed a depletion of nucleoside triphosphates (NTP). The effect on nucleotide metabolism was investigated further by separating purine and pyrimidine nucleotides and precursors by anion-exchange HPLC. NTP levels were depleted by ca. 70-90% and there was a ca. three- to four-fold increase in nucleoside di- and monophosphates. The effect is postulated to be the result of uncoupling of mitochondrial oxidative phosphorylation. The Cu(I) complex [Cu(Ph2PCH = CHPPh2)2]Cl produced a similar effect on the cellular metabolism but was more potent. The water-soluble complex [Cu(Ph2P(CH2)PEt2)2]Cl caused the accumulation of cellular amino acids at a concentration that did not significantly deplete ATP levels. PMID:2062226

  1. Multiple Antiferromagnetic Spin Fluctuations and Novel Evolution of Tc in Iron-Based Superconductors LaFe(As1‑xPx)(O1‑yFy) Revealed by 31P-NMR Studies

    NASA Astrophysics Data System (ADS)

    Shiota, Takayoshi; Mukuda, Hidekazu; Uekubo, Masahiro; Engetsu, Fuko; Yashima, Mitsuharu; Kitaoka, Yoshio; Lai, Kwing To; Usui, Hidetomo; Kuroki, Kazuhiko; Miyasaka, Shigeki; Tajima, Setsuko

    2016-05-01

    We report on 31P-NMR studies of LaFe(As1‑xPx)(O1‑yFy) over wide compositions for 0 ≤ x ≤ 1 and 0 ≤ y ≤ 0.14, which provide clear evidence that antiferromagnetic spin fluctuations (AFMSFs) are one of the indispensable elements for enhancing Tc. Systematic 31P-NMR measurements revealed two types of AFMSFs in the temperature evolution, that is, one is the AFMSFs that develop rapidly down to Tc with low-energy characteristics, and the other, with relatively higher energy than the former, develops gradually upon cooling from high temperature. The low-energy AFMSFs in low y (electron doping) over a wide x (pnictogen height suppression) range are associated with the two orbitals of dxz/yz, whereas the higher-energy ones for a wide y region around low x originate from the three orbitals of dxy and dxz/yz. We remark that the nonmonotonic variation of Tc as a function of x and y in LaFe(As1‑xPx)(O1‑yFy) is attributed to these multiple AFMSFs originating from degenerated multiple 3d orbitals inherent to Fe-pnictide superconductors.

  2. Imaging of the B1 distribution and background signal in a MAS NMR probehead using inhomogeneous B0 and B1 fields.

    PubMed

    Odedra, Smita; Wimperis, Stephen

    2013-06-01

    Several widely used methods for suppressing the "background" signal in (1)H magic angle spinning (MAS) NMR spectroscopy are based on the assumption of a significant difference between the B1 radiofrequency field experienced by the sample (within the MAS rotor) and that felt by static components of the probehead (where the background signal is believed to originate). In this work, a two-dimensional correlation experiment employing inhomogeneous B0 and B1 fields is used to image the B1 distribution in a MAS NMR probehead. The experiment, which can be performed on any spectrometer, allows the distribution of the B1 field to be measured and also correlated with the spatial location of the NMR signal within the probehead. The method can also readily be combined with various "depth pulse" techniques for background suppression, allowing their performances to be more rigorously evaluated. PMID:23644349

  3. Application of (119)Sn CPMG MAS NMR for Fast Characterization of Sn Sites in Zeolites with Natural (119)Sn Isotope Abundance.

    PubMed

    Kolyagin, Yury G; Yakimov, Alexander V; Tolborg, Søren; Vennestrøm, Peter N R; Ivanova, Irina I

    2016-04-01

    (119)Sn CPMG MAS NMR is demonstrated to be a fast and efficient method for characterization of Sn-sites in Sn-containing zeolites. Tuning of the CPMG echo-train sequence decreases the experimental time by a factor of 5-40 in the case of as-synthesized and hydrated Sn-BEA samples and by 3 orders of magnitude in the case of dehydrated Sn-BEA samples as compared to conventional methods. In the latter case, the reconstruction of the quantitative spectrum without the loss of sensitivity is shown to be possible. The method proposed allows obtaining (119)Sn MAS NMR spectra with improved resolution for Sn-BEA zeolites with natural (119)Sn isotope abundance using conventional MAS NMR equipment. PMID:26978430

  4. Real time HR-MAS NMR: application in reaction optimization, mechanism elucidation and kinetic analysis for heterogeneous reagent catalyzed small molecule chemistry.

    PubMed

    Roy, Abhijeet Deb; Jayalakshmi, K; Dasgupta, Somnath; Roy, Raja; Mukhopadhyay, Balaram

    2008-12-01

    A novel application of in situ (1)H high-resolution magic angle spinning (HR-MAS) NMR technique for real-time monitoring of H(2)SO(4)-silica promoted formation of 2, 2-disubstituted quinozolin-4(3H)-ones is reported. The detailed NMR spectroscopic data led to elucidation of the mechanism, reaction optimization, kinetics and quantitative analysis of the product accurately and efficiently. The translation of the optimized parameters obtained by (1)H HR-MAS NMR in the wet laboratory provided similar results. It is proposed that (1)H HR-MAS has a potential utility for optimization of various organic transformations in solid supported catalyzed reactions. PMID:18853391

  5. SCAM-STMAS: satellite-transition MAS NMR of quadrupolar nuclei with self-compensation for magic-angle misset

    NASA Astrophysics Data System (ADS)

    Ashbrook, Sharon E.; Wimperis, Stephen

    2003-06-01

    Several methods are available for the acquisition of high-resolution solid-state NMR spectra of quadrupolar nuclei with half-integer spin quantum number. Satellite-transition MAS (STMAS) offers an approach that employs only conventional MAS hardware and can yield substantial signal enhancements over the widely used multiple-quantum MAS (MQMAS) experiment. However, the presence of the first-order quadrupolar interaction in the satellite transitions imposes the requirement of a high degree of accuracy in the setting of the magic angle on the NMR probehead. The first-order quadrupolar interaction is only fully removed if the sample spinning angle, χ, equals cos-1(1/ 3) exactly and rotor synchronization is performed. The required level of accuracy is difficult to achieve experimentally, particularly when the quadrupolar interaction is large. If the magic angle is not set correctly, the first-order splitting is reintroduced and the spectral resolution is severely compromised. Recently, we have demonstrated a novel STMAS method (SCAM-STMAS) that is self-compensated for angle missets of up to ±1° via coherence transfer between the two different satellite transitions ST +( mI=+3/2↔+1/2) and ST -( mI=-1/2↔-3/2) midway through the t1 period. In this work we describe in more detail the implementation of SCAM-STMAS and demonstrate its wider utility through 23Na ( I=3/2), 87Rb ( I=3/2), 27Al ( I=5/2), and 59Co ( I=7/2) NMR. We discuss linewidths in SCAM-STMAS and the limits over which angle-misset compensation is achieved and we demonstrate that SCAM-STMAS is more tolerant of temporary spinning rate fluctuations than STMAS, resulting in less " t1 noise" in the two-dimensional spectrum. In addition, alternative correlation experiments, for example involving the use of double-quantum coherences, that similarly display self-compensation for angle misset are investigated. The use of SCAM-STMAS is also considered in systems where other high-order interactions, such as third

  6. 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

  7. Determination of nuclear distances and chemical-shift anisotropy from 1H MAS NMR sideband patterns of surface OH groups

    NASA Astrophysics Data System (ADS)

    Fenzke, Dieter; Hunger, Michael; Pfeifer, Harry

    A procedure is described which allows a separate determination of the proton-aluminum distance and of the chemical-shift anisotropy for the bridging OH groups of crystalline molecular sieves from their 'H MAS NMR sideband patterns. For the bridging OH groups which point into the 6-rings of the framework (line "c"), the 1H- 27Al distance could be determined to be 0.237 ± 0.004 and 0.234 ± 0.004 nm for molecular sieves of type H-Y and SAPO-5, respectively. In contrast, for the bridging OH groups of the 12-rings (line "b"), the corresponding distances are equal and distinctly larger, 0.248 ± 0.004 nm. Within the limits of error, the values of the chemical-shift anisotropy are equal (about 19 ± 2 ppm) except for line b of SAPO-5, which exhibits a much smaller value of 14.5 ± 2 ppm.

  8. 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

  9. 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

  10. 31P NMR 2D Mapping of Creatine Kinase Forward Flux Rate in Hearts with Postinfarction Left Ventricular Remodeling in Response to Cell Therapy.

    PubMed

    Gao, Ling; Cui, Weina; Zhang, Pengyuan; Jang, Albert; Zhu, Wuqiang; Zhang, Jianyi

    2016-01-01

    Utilizing a fast 31P magnetic resonance spectroscopy (MRS) 2-dimensional chemical shift imaging (2D-CSI) method, this study examined the heterogeneity of creatine kinase (CK) forward flux rate of hearts with postinfarction left ventricular (LV) remodeling. Immunosuppressed Yorkshire pigs were assigned to 4 groups: 1) A sham-operated normal group (SHAM, n = 6); 2) A 60 minutes distal left anterior descending coronary artery ligation and reperfusion (MI, n = 6); 3) Open patch group; ligation injury plus open fibrin patch over the site of injury (Patch, n = 6); and 4) Cell group, hiPSCs-cardiomyocytes, -endothelial cells, and -smooth muscle cells (2 million, each) were injected into the injured myocardium pass through a fibrin patch (Cell+Patch, n = 5). At 4 weeks, the creatine phosphate (PCr)/ATP ratio, CK forward flux rate (Flux PCr→ATP), and k constant of CK forward flux rate (kPCr→ATP) were severely decreased at border zone myocardium (BZ) adjacent to MI. Cell treatment results in significantly increase of PCr/ATP ratio and improve the value of kPCr→ATP and Flux PCr→ATP in BZ myocardium. Moreover, the BZ myocardial CK total activity and protein expression of CK mitochondria isozyme and CK myocardial isozyme were significantly reduced, but recovered in response to cell treatment. Thus, cell therapy results in improvement of BZ bioenergetic abnormality in hearts with postinfarction LV remodeling, which is accompanied by significantly improvements in BZ CK activity and CK isozyme expression. The fast 2D 31P MR CSI mapping can reliably measure the heterogeneity of bioenergetics in hearts with post infarction LV remodeling. PMID:27606901

  11. Solid-state 109Ag CP/MAS NMR spectroscopy of some diammine silver(I) complexes.

    PubMed

    Bowmaker, Graham A; Harris, Robin K; Assadollahzadeh, Behnam; Apperley, David C; Hodgkinson, Paul; Amornsakchai, Pornsawan

    2004-09-01

    Solid-state cross-polarization magic-angle spinning (CP/MAS) NMR spectra were recorded for the compounds [Ag(NH3)2]2SO4, [Ag(NH3)2]2SeO4 and [Ag(NH3))]NO3, all of which contain the linear or nearly linear two-coordinate [Ag(NH3)2]+ ion. The 109Ag CP/MAS NMR spectra show centrebands and associated spinning sideband manifolds typical for systems with moderately large shielding anisotropy, and splittings due to indirect 1J(109Ag,14N) spin-spin coupling. Spinning sideband analysis was used to determine the 109Ag shielding anisotropy and asymmetry parameters Deltasigma and eta from these spectra, yielding anisotropies in the range 1500-1600 ppm and asymmetry parameters in the range 0-0.3. Spectra were also recorded for 15N and (for the selenate) 77Se. In all cases the number of resonances observed is as expected for the crystallographic asymmetric units. The crystal structure of the selenate is reported for the first time. One-bond (107, 109Ag,15N) coupling constants are found to have magnitudes in the range 60-65 Hz. Density functional calculations of the Ag shielding tensor for model systems yield results that are in good agreement with the experimentally determined shielding parameters, and suggest that in the solid compounds Deltasigma and eta are reduced and increased, respectively, from the values calculated for the free [Ag(NH3)2]+ ion (1920 ppm and 0, respectively), primarily as a result of cation-cation interactions, for which there is evidence from the presence of metal-over-metal stacks of [Ag(NH3)2]+ ions in the solid-state structures of these compounds. PMID:15307067

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

    SciTech Connect

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

    2014-04-22

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

  13. Acetylation of raw cotton for oil spill cleanup application: an FTIR and 13C MAS NMR spectroscopic investigation.

    PubMed

    Adebajo, Moses O; Frost, Ray L

    2004-08-01

    Fourier transform infrared (FTIR) and 13C MAS NMR spectroscopy have been used to investigate the acetylation of raw cotton samples with acetic anhydride without solvents in the presence of different amounts of 4-dimethylaminopyridine (DMAP) catalyst. This is a continuation of our previous investigation of acetylation of commercial cotton in an effort to develop hydrophobic, biodegradable, cellulosic sorbent materials for cleaning up oil spills. The FTIR data have again provided a clear evidence for successful acetylation. The NMR results further confirm the successful acetylation. The extent of acetylation was quantitatively determined using the weight percent gain (WPG) due to acetylation and by calculating the ratio R between the intensity of the acetyl C=O stretching band at 1740-1745 cm(-1) and the intensity of C-O stretching vibration of the cellulose backbone at about 1020-1040 cm(-1). The FTIR technique was found to be highly sensitive and reliable for the determination of the extent of acetylation. The level of acetylation of the raw cotton samples was found to be much higher than that of cotton fabrics and the previously studied commercial cotton. The variation of the R and WPG with reaction time, amount of DMAP catalyst and different samples of raw cotton is discussed. PMID:15249021

  14. Proton-detected scalar coupling based assignment strategies in MAS solid-state NMR spectroscopy applied to perdeuterated proteins

    NASA Astrophysics Data System (ADS)

    Linser, Rasmus; Fink, Uwe; Reif, Bernd

    2008-07-01

    Assignment of proteins in MAS (magic angle spinning) solid-state NMR relies so far on correlations among heteronuclei. This strategy is based on well dispersed resonances in the 15N dimension. In many complex cases like membrane proteins or amyloid fibrils, an additional frequency dimension is desirable in order to spread the amide resonances. We show here that proton detected HNCO, HNCA, and HNCACB type experiments can successfully be implemented in the solid-state. Coherences are sufficiently long lived to allow pulse schemes of a duration greater than 70 ms before incrementation of the first indirect dimension. The achieved resolution is comparable to the resolution obtained in solution-state NMR experiments. We demonstrate the experiments using a triply labeled sample of the SH3 domain of chicken α-spectrin, which was re-crystallized in H 2O/D 2O using a ratio of 1/9. We employ paramagnetic relaxation enhancement (PRE) using EDTA chelated Cu II to enable rapid data acquisition.

  15. Red coralline algae assessed as marine pH proxies using 11B MAS NMR

    NASA Astrophysics Data System (ADS)

    Cusack, M.; Kamenos, N. A.; Rollion-Bard, C.; Tricot, G.

    2015-02-01

    Reconstructing pH from biogenic carbonates using boron isotopic compositions relies on the assumption that only borate, and no boric acid, is present. Red coralline algae are frequently used in palaeoenvironmental reconstruction due to their widespread distribution and regular banding frequency. Prior to undertaking pH reconstructions using red coralline algae we tested the boron composition of the red coralline alga Lithothamnion glaciale using high field NMR. In bulk analysed samples, thirty percent of boron was present as boric acid. We suggest that prior to reconstructing pH using coralline algae 1) species-specific boron compositions and 2) within-skeleton special distributions of boron are determined for multiple species. This will enable site selective boron analyses to be conducted validating coralline algae as palaeo-pH proxies based on boron isotopic compositions.

  16. 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.

  17. Red coralline algae assessed as marine pH proxies using 11B MAS NMR.

    PubMed

    Cusack, M; Kamenos, N A; Rollion-Bard, C; Tricot, G

    2015-01-01

    Reconstructing pH from biogenic carbonates using boron isotopic compositions relies on the assumption that only borate, and no boric acid, is present. Red coralline algae are frequently used in palaeoenvironmental reconstruction due to their widespread distribution and regular banding frequency. Prior to undertaking pH reconstructions using red coralline algae we tested the boron composition of the red coralline alga Lithothamnion glaciale using high field NMR. In bulk analysed samples, thirty percent of boron was present as boric acid. We suggest that prior to reconstructing pH using coralline algae 1) species-specific boron compositions and 2) within-skeleton special distributions of boron are determined for multiple species. This will enable site selective boron analyses to be conducted validating coralline algae as palaeo-pH proxies based on boron isotopic compositions. PMID:25640229

  18. Heteronuclear decoupling in MAS NMR in the intermediate to fast sample spinning regime

    NASA Astrophysics Data System (ADS)

    Equbal, Asif; Bjerring, Morten; Sharma, Kshama; Madhu, P. K.; Nielsen, Niels Chr.

    2016-01-01

    Heteronuclear spin decoupling in solid-state magic-angle spinning NMR is investigated to present methods overcoming interferences between rf irradiation and sample spinning in the intermediate to fast spinning regime. We demonstrate that a recent phase-alternated variant of refocused CW irradiation (rCWApA) provides efficient and robust decoupling in this regime. An extensive experimental and numerical comparison is presented for rCWApA and PISSARRO (phase-inverted supercycled sequence for attenuation of rotary resonance), previously introduced to quench rotary-resonance recoupling effects, under conditions with spinning frequencies between 30 and 60 kHz. Simulations are used to identify the effect of decoupling for various nuclear spin interactions.

  19. Quantitative {sup 29}Si MAS NMR spectroscopy of cement and silica fume containing paramagnetic impurities

    SciTech Connect

    Hilbig, H. . E-mail: hilbig@cbm.bv.tum.de; Koehler, F.H.; Schiessl, P.

    2006-02-15

    The low natural abundance and the long spin lattice relaxation time of {sup 29}Si lead to long measurement times and/or low signal-to-noise ratios using {sup 29}Si magic angle spinning NMR spectroscopy. By contrast, samples containing paramagnetic iron ions have much shorter relaxation times, making measurements up to seven times more efficient, but at the same time making quantitative analysis unreliable. To solve the problem, the spin-lattice relaxation times of ordinary Portland cement (opc) and silica fume with and without iron content has been determined with inversion recovery experiments. The effect of varying the spectrum repetition time on the quantitative analysis is demonstrated for mixtures of opc with silica fume. For opc and silica fume with iron impurities repetition times as short as 5 s has permitted accurate quantitative analysis of the silicates present in these materials.

  20. Red coralline algae assessed as marine pH proxies using 11B MAS NMR

    PubMed Central

    Cusack, M.; Kamenos, N. A.; Rollion-Bard, C.; Tricot, G.

    2015-01-01

    Reconstructing pH from biogenic carbonates using boron isotopic compositions relies on the assumption that only borate, and no boric acid, is present. Red coralline algae are frequently used in palaeoenvironmental reconstruction due to their widespread distribution and regular banding frequency. Prior to undertaking pH reconstructions using red coralline algae we tested the boron composition of the red coralline alga Lithothamnion glaciale using high field NMR. In bulk analysed samples, thirty percent of boron was present as boric acid. We suggest that prior to reconstructing pH using coralline algae 1) species-specific boron compositions and 2) within-skeleton special distributions of boron are determined for multiple species. This will enable site selective boron analyses to be conducted validating coralline algae as palaeo-pH proxies based on boron isotopic compositions. PMID:25640229

  1. Following Solid-Acid-Catalyzed Reactions by MAS NMR Spectroscopy in Liquid Phase -Zeolite-Catalyzed Conversion of Cyclohexanol in Water

    SciTech Connect

    Vjunov, Aleksei; Hu, Mary Y.; Feng, Ju; Camaioni, Donald M.; Mei, Donghai; Hu, Jian Z.; Zhao, Chen; Lercher, Johannes A.

    2014-01-07

    The catalytic conversion of cyclohexanol on zeolite HBEA in hot liquid water leads to dehydration as well as alkylation products. A novel micro autoclave suitable for application in MAS NMR at high temperatures and pressures is developed and successfully applied to obtain new insight into the mechanistic pathway leading to an understanding of the reactions under selected experimental conditions.

  2. High-resolution solid-state 13C CP MAS NMR spectra of some β-cyclodextrin inclusion complexes with nitriles

    NASA Astrophysics Data System (ADS)

    Okazaki, M.; McDowell, C. A.

    1983-11-01

    β-cyclodextrin inclusion complexes of 3-aminobenzonitrile, 4-aminobenzonitrile, and adamantane-1-carbonitrile were studied by means of high-resolution solid-state CP MAS 13C NMR spectroscopy. The interactions between the host and guest molecules are discussed.

  3. Electrochemical lithiation/delithiation of SnP2O7 observed by in situ XRD and ex situ(7)Li/(31)P NMR, and (119)Sn Mössbauer spectroscopy.

    PubMed

    Bezza, Ilham; Kaus, Maximilian; Riekehr, Lars; Pfaffmann, Lukas; Doyle, Stephen; Indris, Sylvio; Ehrenberg, Helmut; Solhy, Abderrahim; Saadoune, Ismael

    2016-04-21

    SnP2O7 was prepared by a sol-gel route. The structural changes of tin pyrophosphate during the electrochemical lithiation were followed by using in situ XRD measurements that reveal the existence of a crystalline phase at the beginning of the discharge process. Nevertheless, it becomes amorphous after the full discharge as a result of a conversion reaction leading to the formation of LixSny alloys. The electrochemical tests show a high capacity with high retention upon cycling. To better understand the reaction mechanism of SnP2O7 with Li, several techniques were applied, such as ex situ(119)Sn Mössbauer and ex situ(7)Li and (31)P NMR spectroscopies with which we can follow the changes in the local environment of each element during cycling. PMID:27029601

  4. Mechanochemical and solution synthesis, X-ray structure and IR and 31P solid state NMR spectroscopic studies of copper(I) thiocyanate adducts with bulky monodentate tertiary phosphine ligands.

    PubMed

    Bowmaker, Graham A; Hanna, John V; Hart, Robert D; Healy, Peter C; King, Scott P; Marchetti, Fabio; Pettinari, Claudio; Skelton, Brian W; Tabacaru, Aurel; White, Allan H

    2012-07-01

    A number of adducts of copper(I) thiocyanate with bulky tertiary phosphine ligands, and some nitrogen-base solvates, were synthesized and structurally and spectroscopically characterised. CuSCN:PCy3 (1:2), as crystallized from pyridine, is shown by a single crystal X-ray study to be a one-dimensional polymer ...(Cy3P)2CuSCN(Cy3P)2CuSCN... (1) with the four-coordinate copper atoms linked end-on by S-SCN-N bridging thiocyanate groups. A second form (2), obtained from acetonitrile, was also identified and shown by IR and 31P CPMAS NMR spectroscopy to be mononuclear, with the magnitude of the dν(Cu) parameter measured from the 31P CPMAS and the ν(CN) value from the IR clearly establishing this compound as three-coordinate [(Cy3P)2CuNCS]. Two further CuSCN/PCy3 compounds CuSCN:PCy3 (1:1) (3), and CuSCN:PCy3:py (1:1:1) (4) were also characterized spectroscopically, with the dν(Cu) parameters indicating three- and four-coordinate copper sites, respectively. Attempts to obtain a 1:2 adduct with tri-t-butylphosphine have yielded, from pyridine, the 1:1 adduct as a dimer [(Bu(t)3P)((SCN)(NCS))Cu(PBu(t)3)] (5), while similar attempts with tri-o-tolylphosphine (from acetonitrile and pyridine (= L)) resulted in solvated 1:1:1 CuSCN:P(o-tol)3:L forms as dimeric [{(o-tol)3P}LCu((SCN)(NCS))CuL{P(o-tol)3}] (6 and 8). The solvent-free 1:1 CuSCN:P(o-tol)3 adduct (7), obtained by desolvation of 6, was characterized spectroscopically and dν(Cu) measurements from the 31P CPMAS NMR data are consistent with the decrease in coordination number of the copper atom from four (for 6) (P,N(MeCN)Cu,S,N) to three (for 7) (PCuS,N) upon loss of the acetonitrile of solvation. These results are compared with those previously reported for mononuclear and binuclear PPh3 adducts which demonstrate a clear tendency for the copper centre to remain four-coordinate. The IR spectroscopic measurements on these compounds show that bands in the far-IR spectra provide a much more definitive criterion for

  5. Dynamic effects in MAS and MQMAS NMR spectra of half-integer quadrupolar nuclei: calculations and an application to the double perovskite cryolite.

    PubMed

    Kotecha, Mrignayani; Chaudhuri, Santanu; Grey, Clare P; Frydman, Lucio

    2005-11-30

    Dynamic processes such as chemical exchange or rotations between inequivalent orientations can affect the magic-angle spinning (MAS) and the multiple-quantum (MQ) MAS NMR spectra of half-integer quadrupolar nuclei. The present paper discusses such dynamic multisite MAS and MQMAS effects and applies them to study the dynamic processes that occur in the double perovskite cryolite, Na3AlF6. Dynamic line shape simulations invoking a second-order broadening of the central transition and relying on the semiclassical Bloch-McConnell formalism for chemical exchange were performed for a variety of exchange models possessing different symmetries. Fitting experimental variable-temperature cryolite 23Na NMR data with this formalism revealed that the two inequivalent sodium sites in this mineral undergo an exchange characterized by a broad distribution of rates. To further assess this dynamic process a variety of 27Al and 19F MAS NMR studies were also undertaken; quantitative 27Al-19F dipolar coupling measurements then revealed a dynamic motion of the AlF6 octahedra that were qualitatively consistent with predictions stemming from molecular dynamic simulations on this double perovskite. PMID:16305261

  6. 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.

  7. Intermolecular (119)Sn,(31)P Through-Space Spin-Spin Coupling in a Solid Bivalent Tin Phosphido Complex.

    PubMed

    Arras, Janet; Eichele, Klaus; Maryasin, Boris; Schubert, Hartmut; Ochsenfeld, Christian; Wesemann, Lars

    2016-05-01

    A bivalent tin complex [Sn(NP)2] (NP = [(2-Me2NC6H4)P(C6H5)](-)) was prepared and characterized by X-ray diffraction and solution and solid-state nuclear magnetic resonance (NMR) spectroscopy. In agreement with the X-ray structures of two polymorphs of the molecule, (31)P and (119)Sn CP/MAS NMR spectra revealed one crystallographic phosphorus and tin site with through-bond (1)J((117/119)Sn,(31)P) and through-space (TS)J((117/119)Sn,(31)P) spin-spin couplings. Density functional theory (DFT) calculations of the NMR parameters confirm the experimental data. The observation of through-space (TS)J((117/119)Sn,(31)P) couplings was unexpected, as the distances of the phosphorus atoms of one molecule and the tin atom of the neighboring molecule (>4.6 Å) are outside the sum of the van der Waals radii of the atoms P and Sn (4.32 Å). The intermolecular Sn···P separations are clearly too large for bonding interactions, as supported by a natural bond orbital (NBO) analysis. PMID:27071033

  8. CP-MAS 207Pb with 19F decoupling NMR spectroscopy: medium range investigation in fluoride materials.

    PubMed

    Bureau, B; Silly, G; Buzaré, J Y

    1999-11-01

    The isotropic chemical shift of 207Pb is used to perform structural investigations of crystalline fluoride compounds (PbF2, Pb2ZnF6, PbGaF5, Pb3Ga2F12 and Pb9Ga2F24) and transition metal fluoride glasses (TMFG) of the PZG family (PbF2-ZnF2-GaF3). Using 207Pb Cross Polarisation Magic Angle Spinning (CP-MAS) NMR with 19F decoupling, it is shown that the isotropic chemical shift of 207Pb varies on a large scale (1000 ppm) and that the main changes of its value are not due to the nearest neighbour fluorines but may be related to the number of next nearest neighbour (nnn) Pb2+ ions. In this way, it is demonstrated that 207Pb chemical shift is an interesting probe to investigate medium range order in either crystalline or glassy fluoride systems. The 207Pb delta(iso) parameter has been linearly correlated to the number of nnn Pb2+ ions. PMID:10670899

  9. Hydrogen concentration dependence of 1H Knight shift in NbH x studied by 1H MAS NMR

    NASA Astrophysics Data System (ADS)

    Ueda, Takahiro; Hayashi, Shigenobu; Hayamizu, Kikuko

    1993-08-01

    Hydrogen concentration dependence of the Knight shift of protons in NbH x(0.05≤×≤1.05) has been studied by means of 1H MAS (magic angle sample spinning) NMR. In the mixed-phase samples of the α and β phases (0.05<×≤0.7), it is found that the 1H Knight shift of β-NbH x depends on the phase fraction. The shift variation in the β phase can be correlated with the unit cell volume, being explained by the variation of the density of electronic states at the Fermi level N(0) due to the compression of the crystal lattice. On the other hand, in the single β-phase samples (0.7<×≤1.05), the 1H Knight shift becomes smaller as the hydrogen concentration increases. This variation can be explained by increase in the number of electrons in the unit cell with the hydrogen concentration, resulting in the N(0) increase.

  10. N Photo-CIDNP MAS NMR To Reveal Functional Heterogeneity in Electron Donor of Different Plant Organisms.

    PubMed

    Janssen, Geertje J; Roy, Esha; Matysik, Jörg; Alia, A

    2012-02-01

    In plants and cyanobacteria, two light-driven electron pumps, photosystems I and II (PSI, PSII), facilitate electron transfer from water to carbon dioxide with quantum efficiency close to unity. While similar in structure and function, the reaction centers of PSI and PSII operate at widely different potentials with PSI being the strongest reducing agent known in living nature. Photochemically induced dynamic nuclear polarization (photo-CIDNP) in magic-angle spinning (MAS) nuclear magnetic resonance (NMR) measurements provides direct excess to the heart of large photosynthetic complexes (A. Diller, Alia, E. Roy, P. Gast, H.J. van Gorkom, J. Zaanen, H.J.M. de Groot, C. Glaubitz, J. Matysik, Photosynth. Res. 84, 303-308, 2005; Alia, E. Roy, P. Gast, H.J. van Gorkom, H.J.M. de Groot, G. Jeschke, J. Matysik, J. Am. Chem. Soc. 126, 12819-12826, 2004). By combining the dramatic signal increase obtained from the solid-state photo-CIDNP effect with (15)N isotope labeling of PSI, we were able to map the electron spin density in the active cofactors of PSI and study primary charge separation at atomic level. We compare data obtained from two different PSI proteins, one from spinach (Spinacia oleracea) and other from the aquatic plant duckweed (Spirodella oligorrhiza). Results demonstrate a large flexibility of the PSI in terms of its electronic architecture while their electronic ground states are strictly conserved. PMID:22303078

  11. Catalytic mechanism of α-phosphate attack in dUTPase is revealed by X-ray crystallographic snapshots of distinct intermediates, 31P-NMR spectroscopy and reaction path modelling

    PubMed Central

    Barabás, Orsolya; Németh, Veronika; Bodor, Andrea; Perczel, András; Rosta, Edina; Kele, Zoltán; Zagyva, Imre; Szabadka, Zoltán; Grolmusz, Vince I.; Wilmanns, Matthias; Vértessy, Beáta G.

    2013-01-01

    Enzymatic synthesis and hydrolysis of nucleoside phosphate compounds play a key role in various biological pathways, like signal transduction, DNA synthesis and metabolism. Although these processes have been studied extensively, numerous key issues regarding the chemical pathway and atomic movements remain open for many enzymatic reactions. Here, using the Mason–Pfizer monkey retrovirus dUTPase, we study the dUTPase-catalyzed hydrolysis of dUTP, an incorrect DNA building block, to elaborate the mechanistic details at high resolution. Combining mass spectrometry analysis of the dUTPase-catalyzed reaction carried out in and quantum mechanics/molecular mechanics (QM/MM) simulation, we show that the nucleophilic attack occurs at the α-phosphate site. Phosphorus-31 NMR spectroscopy (31P-NMR) analysis confirms the site of attack and shows the capability of dUTPase to cleave the dUTP analogue α,β-imido-dUTP, containing the imido linkage usually regarded to be non-hydrolyzable. We present numerous X-ray crystal structures of distinct dUTPase and nucleoside phosphate complexes, which report on the progress of the chemical reaction along the reaction coordinate. The presently used combination of diverse structural methods reveals details of the nucleophilic attack and identifies a novel enzyme–product complex structure. PMID:23982515

  12. Catalytic mechanism of α-phosphate attack in dUTPase is revealed by X-ray crystallographic snapshots of distinct intermediates, 31P-NMR spectroscopy and reaction path modelling.

    PubMed

    Barabás, Orsolya; Németh, Veronika; Bodor, Andrea; Perczel, András; Rosta, Edina; Kele, Zoltán; Zagyva, Imre; Szabadka, Zoltán; Grolmusz, Vince I; Wilmanns, Matthias; Vértessy, Beáta G

    2013-12-01

    Enzymatic synthesis and hydrolysis of nucleoside phosphate compounds play a key role in various biological pathways, like signal transduction, DNA synthesis and metabolism. Although these processes have been studied extensively, numerous key issues regarding the chemical pathway and atomic movements remain open for many enzymatic reactions. Here, using the Mason-Pfizer monkey retrovirus dUTPase, we study the dUTPase-catalyzed hydrolysis of dUTP, an incorrect DNA building block, to elaborate the mechanistic details at high resolution. Combining mass spectrometry analysis of the dUTPase-catalyzed reaction carried out in and quantum mechanics/molecular mechanics (QM/MM) simulation, we show that the nucleophilic attack occurs at the α-phosphate site. Phosphorus-31 NMR spectroscopy ((31)P-NMR) analysis confirms the site of attack and shows the capability of dUTPase to cleave the dUTP analogue α,β-imido-dUTP, containing the imido linkage usually regarded to be non-hydrolyzable. We present numerous X-ray crystal structures of distinct dUTPase and nucleoside phosphate complexes, which report on the progress of the chemical reaction along the reaction coordinate. The presently used combination of diverse structural methods reveals details of the nucleophilic attack and identifies a novel enzyme-product complex structure. PMID:23982515

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  14. Effect of aging on phosphate metabolites of rat brain as revealed by the in vivo and in vitro sup 31 P NMR measurements

    SciTech Connect

    Liu, Hsiuchih; Chi, Chinwen; Liu, Tsungyun; Liu, Lianghui ); Luh, Wenming; Hsieh, Changhuain; Wu, Wenguey )

    1991-01-01

    Changes of phosphate metabolism in brains of neonate, weaning and adult rats were compared using both in vivo and in vitro nuclear magnetic resonance spectra. Ratios of phosphocreatine/nucleoside triphosphate (PCr/NTP) were the same in neonatal brain in both in vivo and in vitro studies, but not in weaning and adult brains. This discrepancy may have resulted from extended cerebral hypoxia due to slowed freezing of the brain by the increased skull thickness and brain mass in the weaning and adult rats. Variations of in vitro extraction condition for this age-related study may lead to systematic errors in the adult rats. Nevertheless, the phosphomonoester/nucleoside triphosphate (PME/NTP) ratios in extracts of brain from neonatal rats were higher than those obtained in vivo. In addition, the glycerophosphorylethanolamine plus glycerophosphorylcholine/nucleoside triphosphate (GPE+GPC/NTP) ratios, which were not measurable in vivo, showed age-dependent increase in extracts of rat brain. Some of the phosphomonoester and phosphodiester molecules in rat brain may be undetectable in in vivo NMR analysis because of their interaction with cellular components. The total in vitro GPE and GPC concentration in brain from neonatal rat was estimated to be 0.34 mmole/g wet tissue.

  15. Interplay between Fe 3d and Ce 4f magnetism and Kondo interaction in CeFeAs(1-x)P(x)O probed by 75As and 31P NMR.

    PubMed

    Sarkar, R; Baenitz, M; Jesche, A; Geibel, C; Steglich, F

    2012-04-01

    A detailed (31)P (I = 1/2) and (75)As (I = 3/2) NMR study on polycrystalline CeFeAs(1-x)P(x)O alloys is presented. The magnetism of CeFeAsO changes drastically upon P substitution on the As site. CeFePO is a heavy fermion system without long-range order whereas CeFeAsO exhibits an Fe 3d SDW type of ordering accompanied by a structural transition from tetragonal (TT) to orthorhombic (OT) structure. Furthermore, Ce 4f(1) orders antiferromagnetically (AFM) at low temperature. At the critical concentration where the Fe magnetism is diminished the Ce-Ce interaction changes to a ferromagnetic (FM) type of ordering. Three representative samples of the CeFeAs(1-x)P(x)O (x = 0.05, 0.3 and 0.9) series are systematically investigated. (1) For the x = 0.05 alloy a drastic change of the linewidth at 130 K indicates the AFM-SDW type of ordering of Fe and the structural change from the TT to the OT phase. The linewidth roughly measures the internal field in the ordered state and the transition is most likely first order. The small and nearly constant shift from (31)P and (75)As NMR suggests the presence of competing hyperfine interactions between the nuclear spins and the 4f and 3d ions of Ce and Fe. (2) For the x = 0.3 alloy, the evolution of the Fe-SDW type of order takes place at around 70 K corroborating the results of bulk measurement and μSR. Here we found evidence for phase separation of paramagnetic and magnetic SDW phases. (3) In contrast to the heavy fermion CeFePO for the x = 0.9 alloy a phase transition is found at 2 K. The field-dependent NMR shift gives evidence of FM ordering. Above the ordering the spin-lattice relaxation rate (31)(1/T(1)) shows unconventional, non-Korringa-like behaviour which indicates a complex interplay of Kondo and FM fluctuations. PMID:22407024

  16. The Effect of a C-Terminal Peptide of Surfactant Protein B (SP-B) on Oriented Lipid Bilayers, Characterized by Solid-State 2H- and 31P-NMR

    PubMed Central

    Yang, Tran-Chin; McDonald, Mark; Morrow, Michael R.; Booth, Valerie

    2009-01-01

    SP-BCTERM, a cationic, helical peptide based on the essential lung surfactant protein B (SP-B), retains a significant fraction of the function of the full-length protein. Solid-state 2H- and 31P-NMR were used to examine the effects of SP-BCTERM on mechanically oriented lipid bilayer samples. SP-BCTERM modified the multilayer structure of bilayers composed of POPC, POPG, POPC/POPG, or bovine lipid extract surfactant (BLES), even at relatively low peptide concentrations. The 31P spectra of BLES, which contains ∼1% SP-B, and POPC/POPG with 1% SP-BCTERM, look very similar, supporting a similarity in lipid interactions of SP-BCTERM and its parent protein, full-length SP-B. In the model systems, although the peptide interacted with both the oriented and unoriented fractions of the lipids, it interacted differently with the two fractions, as demonstrated by differences in lipid headgroup structure induced by the peptide. On the other hand, although SP-BCTERM induced similar disruptions in overall bilayer orientation in BLES, there was no evidence of lipid headgroup conformational changes in either the oriented or the unoriented fractions of the BLES samples. Notably, in the model lipid systems the peptide did not induce the formation of small, rapidly tumbling lipid structures, such as micelles, or of hexagonal phases, the observation of which would have provided support for functional mechanisms involving peptide-induced lipid flip-flop or stabilization of curved lipid structures, respectively. PMID:19413982

  17. Identification of Li-Ion Battery SEI Compounds through (7)Li and (13)C Solid-State MAS NMR Spectroscopy and MALDI-TOF Mass Spectrometry.

    PubMed

    Huff, Laura A; Tavassol, Hadi; Esbenshade, Jennifer L; Xing, Wenting; Chiang, Yet-Ming; Gewirth, Andrew A

    2016-01-13

    Solid-state (7)Li and (13)C MAS NMR spectra of cycled graphitic Li-ion anodes demonstrate SEI compound formation upon lithiation that is followed by changes in the SEI upon delithiation. Solid-state (13)C DPMAS NMR shows changes in peaks associated with organic solvent compounds (ethylene carbonate and dimethyl carbonate, EC/DMC) upon electrochemical cycling due to the formation of and subsequent changes in the SEI compounds. Solid-state (13)C NMR spin-lattice (T1) relaxation time measurements of lithiated Li-ion anodes and reference poly(ethylene oxide) (PEO) powders, along with MALDI-TOF mass spectrometry results, indicate that large-molecular-weight polymers are formed in the SEI layers of the discharged anodes. MALDI-TOF MS and NMR spectroscopy results additionally indicate that delithiated anodes exhibit a larger number of SEI products than is found in lithiated anodes. PMID:26653886

  18. 1H and 23Na MAS NMR spectroscopy of cationic species in CO2 selective alkaline earth metal porous silicoaluminophosphates prepared via liquid and solid state ion exchange

    NASA Astrophysics Data System (ADS)

    Arévalo-Hidalgo, Ana G.; Dugar, Sneha; Fu, Riqiang; Hernández-Maldonado, Arturo J.

    2012-07-01

    The location of extraframework cations in Sr2+ and Ba2+ ion-exchanged SAPO-34 was estimated by means of 1H and 23Na MAS NMR spectroscopy and spectral deconvolution. Incorporation of the alkaline earth metal cations onto the SAPO framework was achieved via liquid state ion exchange, coupled partial detemplation/solid-state ion exchange, and combination of both techniques. MAS NMR revealed that the level of ion exchange was limited by the presence of protons and sodium cations near hexagonal prisms (site SI), which are relatively difficult to exchange with the alkaline earth metal due to steric and charge repulsion criteria. In addition, the presence of ammonium cations in the supercages facilitated the exchange of otherwise tenacious hydrogen as corroborated by unit cell compositional data as well as enhanced CO2 adsorption at low partial pressures. The extraframework ammonium species were produced from partial detemplation of the structure-directing agent employed for the SAPO-34 synthesis, tetraethylammonium.

  19. The metabolic profile of lemon juice by proton HR-MAS NMR: the case of the PGI Interdonato Lemon of Messina.

    PubMed

    Cicero, Nicola; Corsaro, Carmelo; Salvo, Andrea; Vasi, Sebastiano; Giofré, Salvatore V; Ferrantelli, Vincenzo; Di Stefano, Vita; Mallamace, Domenico; Dugo, Giacomo

    2015-01-01

    We have studied by means of High Resolution Magic Angle Spinning Nuclear Magnetic Resonance (HR-MAS NMR) the metabolic profile of the famous Sicilian lemon known as 'Interdonato Lemon of Messina PGI'. The PGI Interdonato Lemon of Messina possesses high organoleptic and healthy properties and is recognised as one of the most nutrient fruits. In particular, some of its constituents are actively studied for their chemo-preventive and therapeutic properties. In this paper, we have determined by means of HR-MAS NMR spectroscopy the molar concentration of the main metabolites constituent the juice of PGI Interdonato Lemon of Messina in comparison with that of the not-PGI Interdonato Lemon of Turkey. Our aim is to develop an analytical technique, in order to determine a metabolic fingerprint able to reveal commercial frauds in national and international markets. PMID:25702767

  20. Cumulative “roof effect” in high-resolution in vivo 31P NMR spectra of human calf muscle and the Clebsch Gordan coefficients of ATP at 1.5 T

    NASA Astrophysics Data System (ADS)

    Schröder, Leif; Schmitz, Christian; Bachert, Peter

    2005-05-01

    NMR spectra of non-weakly coupled spin systems exhibit asymmetries in line intensities known as "roof effect" in 1D spectroscopy. Due to limited spectral resolution, this effect has not been paid much attention so far in in vivo spectroscopy. But when high-quality spectra are obtained, this effect should be taken into account to explain the quantum-mechanical fine structure of the system. Adenosine 5'-triphosphate (ATP) represents a 31P spin system with multiple line splittings which are caused by J-couplings of medium strength at 1.5 T. We analyzed the ATP roof effect in vivo, especially for the β-ATP multiplet. The intensities of its outer resonances deviate by ca. 12.5% from a symmetrical triplet. As this asymmetry reflects the transition from Paschen-Back to Zeeman effect with total spin that is largely broken up, the Clebsch-Gordan coefficients of the system can be indicated in analogy to the hyperfine structure of hydrogen. Taking the roof effect into account, the χ2 of fitting in vivo ATP resonances is reduced by ca. 9% ( p < 0.005).

  1. Enhancement of superconducting transition temperature due to antiferromagnetic spin fluctuations in iron pnictides LaFe(As1-xPx)(O1-yFy): 31P-NMR studies

    NASA Astrophysics Data System (ADS)

    Mukuda, H.; Engetsu, F.; Yamamoto, K.; Lai, K. T.; Yashima, M.; Kitaoka, Y.; Takemori, A.; Miyasaka, S.; Tajima, S.

    2014-02-01

    Systematic 31P-NMR studies on LaFe(As1-xPx)(O1-yFy) with y =0.05 and 0.1 have revealed that the antiferromagnetic spin fluctuations (AFMSFs) at low energies are markedly enhanced around x =0.6 and 0.4, respectively, and as a result, Tc exhibits respective peaks at 24 and 27 K against the P substitution for As. This result demonstrates that the AFMSFs are responsible for the increase in Tc for LaFe(As1-xPx)(O1-yFy) as a primary mediator of the Cooper pairing. From a systematic comparison of AFMSFs with a series of (La1-zYz)FeAsOδ compounds in which Tc reaches 50 K for z =0.95, we remark that a moderate development of AFMSFs causes Tc to increase up to 50 K under the condition that the local lattice parameters of the FeAs tetrahedron approach those of the regular tetrahedron. We propose that Tc of Fe-pnictides exceeding 50 K is maximized under an intimate collaboration of the AFMSFs and other factors originating from the optimization of the local structure.

  2. Measurement of the lateral diffusion of dipalmitoylphosphatidylcholine adsorbed on silica beads in the absence and presence of melittin: a 31P two-dimensional exchange solid-state NMR study.

    PubMed Central

    Picard, F; Paquet, M J; Dufourc, E J; Auger, M

    1998-01-01

    31P two-dimensional exchange solid-state NMR spectroscopy was used to measure the lateral diffusion, D(L), in the fluid phase of dipalmitoylphosphatidylcholine (DPPC) in the presence and absence of melittin. The use of a spherical solid support with a radius of 320 +/- 20 nm, on which lipids and peptides are adsorbed together, and a novel way of analyzing the two-dimensional exchange patterns afforded a narrow distribution of D(L) centered at a value of (8.8 +/- 0.5) x 10(-8) cm2/s for the pure lipid system and a large distribution of D(L) spanning 1 x 10(-8) to 10 x 10(-8) cm2/s for the lipids in the presence of melittin. In addition, the determination of D(L) for nonsupported DPPC multilamellar vesicles (MLVs) suggests that the support does not slow down the lipid diffusion and that the radii of the bilayers vary from 300 to 800 nm. Finally, the DPPC-melittin complex is stabilized at the surface of the silica beads in the gel phase, opening the way to further study of the interaction between melittin and DPPC. PMID:9533697

  3. NMR studies of bond arrangements in alkali phosphate glasses

    SciTech Connect

    Alam, T.M.; Brow, R.K.

    1998-01-01

    Solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy has become a powerful tool for the investigation of local structure and medium range order in glasses. Previous {sup 31}P MAS NMR studies have detailed the local structure for a series of phosphate glasses. Phosphate tetrahedra within the glass network are commonly described using the Q{sup n} notation, where n = 0, 1, 2, 3 and represents the number of bridging oxygens attached to the phosphate. Using {sup 31}P MAS NMR different phosphate environments are readily identified and quantified. In this paper, the authors present a brief description of recent one dimensional (1D) {sup 6}Li, {sup 7}Li and {sup 31}P MAS experiments along with two-dimensional (2D) {sup 31}P exchange NMR experiments for a series of lithium ultraphosphate glasses. From the 2D exchange experiments the connectivities between different Q{sup n} phosphate tetrahedra were directly measured, while the 1D experiments provided a measure of the P-O-P bond angle distribution and lithium coordination number as a function of Li{sub 2}O concentration.

  4. A spectrometer designed for 6.7 and 14.1 T DNP-enhanced solid-state MAS NMR using quasi-optical microwave transmission.

    PubMed

    Pike, Kevin J; Kemp, Thomas F; Takahashi, Hiroki; Day, Robert; Howes, Andrew P; Kryukov, Eugeny V; MacDonald, James F; Collis, Alana E C; Bolton, David R; Wylde, Richard J; Orwick, Marcella; Kosuga, Kosuke; Clark, Andrew J; Idehara, Toshitaka; Watts, Anthony; Smith, Graham M; Newton, Mark E; Dupree, Ray; Smith, Mark E

    2012-02-01

    A Dynamic Nuclear Polarisation (DNP) enhanced solid-state Magic Angle Spinning (MAS) NMR spectrometer operating at 6.7 T is described and demonstrated. The 187 GHz TE(13) fundamental mode of the FU CW VII gyrotron is used as the microwave source for this magnetic field strength and 284 MHz (1)H DNP-NMR. The spectrometer is designed for use with microwave frequencies up to 395 GHz (the TE(16) second-harmonic mode of the gyrotron) for DNP at 14.1T (600 MHz (1)H NMR). The pulsed microwave output from the gyrotron is converted to a quasi-optical Gaussian beam using a Vlasov antenna and transmitted to the NMR probe via an optical bench, with beam splitters for monitoring and adjusting the microwave power, a ferrite rotator to isolate the gyrotron from the reflected power and a Martin-Puplett interferometer for adjusting the polarisation. The Gaussian beam is reflected by curved mirrors inside the DNP-MAS-NMR probe to be incident at the sample along the MAS rotation axis. The beam is focussed to a ~1 mm waist at the top of the rotor and then gradually diverges to give much more efficient coupling throughout the sample than designs using direct waveguide irradiation. The probe can be used in triple channel HXY mode for 600 MHz (1)H and double channel HX mode for 284 MHz (1)H, with MAS sample temperatures ≥85 K. Initial data at 6.7 T and ~1 W pulsed microwave power are presented with (13)C enhancements of 60 for a frozen urea solution ((1)H-(13)C CP), 16 for bacteriorhodopsin in purple membrane ((1)H-(13)C CP) and 22 for (15)N in a frozen glycine solution ((1)H-(15)N CP) being obtained. In comparison with designs which irradiate perpendicular to the rotation axis the approach used here provides a highly efficient use of the incident microwave beam and an NMR-optimised coil design. PMID:22218011

  5. A spectrometer designed for 6.7 and 14.1 T DNP-enhanced solid-state MAS NMR using quasi-optical microwave transmission

    NASA Astrophysics Data System (ADS)

    Pike, Kevin J.; Kemp, Thomas F.; Takahashi, Hiroki; Day, Robert; Howes, Andrew P.; Kryukov, Eugeny V.; MacDonald, James F.; Collis, Alana E. C.; Bolton, David R.; Wylde, Richard J.; Orwick, Marcella; Kosuga, Kosuke; Clark, Andrew J.; Idehara, Toshitaka; Watts, Anthony; Smith, Graham M.; Newton, Mark E.; Dupree, Ray; Smith, Mark E.

    2012-02-01

    A Dynamic Nuclear Polarisation (DNP) enhanced solid-state Magic Angle Spinning (MAS) NMR spectrometer operating at 6.7 T is described and demonstrated. The 187 GHz TE13 fundamental mode of the FU CW VII gyrotron is used as the microwave source for this magnetic field strength and 284 MHz 1H DNP-NMR. The spectrometer is designed for use with microwave frequencies up to 395 GHz (the TE16 second-harmonic mode of the gyrotron) for DNP at 14.1 T (600 MHz 1H NMR). The pulsed microwave output from the gyrotron is converted to a quasi-optical Gaussian beam using a Vlasov antenna and transmitted to the NMR probe via an optical bench, with beam splitters for monitoring and adjusting the microwave power, a ferrite rotator to isolate the gyrotron from the reflected power and a Martin-Puplett interferometer for adjusting the polarisation. The Gaussian beam is reflected by curved mirrors inside the DNP-MAS-NMR probe to be incident at the sample along the MAS rotation axis. The beam is focussed to a ˜1 mm waist at the top of the rotor and then gradually diverges to give much more efficient coupling throughout the sample than designs using direct waveguide irradiation. The probe can be used in triple channel HXY mode for 600 MHz 1H and double channel HX mode for 284 MHz 1H, with MAS sample temperatures ⩾85 K. Initial data at 6.7 T and ˜1 W pulsed microwave power are presented with 13C enhancements of 60 for a frozen urea solution (1H-13C CP), 16 for bacteriorhodopsin in purple membrane (1H-13C CP) and 22 for 15N in a frozen glycine solution (1H-15N CP) being obtained. In comparison with designs which irradiate perpendicular to the rotation axis the approach used here provides a highly efficient use of the incident microwave beam and an NMR-optimised coil design.

  6. (sup 6)Li and (sup 7)MAS NMR and In Situ X-Ray Diffraction Studies of Lithium Manganate Cathode Materials

    SciTech Connect

    Lee, Young Joo; Wang, Francis; Grey, Clare P.; Mukerjee, Sanjeev; McBreen, James

    1998-11-30

    {sup 6}Li MAS NMR spectra of lithium manganese oxides with differing manganese oxidation states (LiMn{sub 2}O{sub 4}, Li{sub 4}Mn{sub 5}O{sub 12}, Li{sub 2}Mn{sub 4}O{sub 9}, and Li{sub 2}Mn{sub 2}O{sub 4}) are presented. Improved understanding of the lithium NMR spectra of these model compounds is used to interpret the local structure of the Li{sub x}Mn{sub 2}O{sub 4} cathode materials following electrochemical Li{sup +} deintercalation to various charging levels. In situ x-ray diffraction patterns of the same material during charging are also reported for comparison. Evidence for two-phase behavior for x <0.4 (Li{sub x}Mn{sub 2}O{sub 4}) is seen by both NMR and diffraction.

  7. Constraints on the structure and dynamics of the β-cristobalite polymorphs of SiO2 and AlPO4 from 31P, 27Al and 29Si NMR spectroscopy to 770 K

    NASA Astrophysics Data System (ADS)

    Phillips, Brian L.; Thompson, John G.; Xiao, Yuehui; Kirkpatrick, R. James

    1993-10-01

    Nuclear magnetic resonance spectroscopic data are presented for the cristobalite polymorphs of AlPO4 and SiO2 from RT to 770 K, through their respective α- β transitions. The nuclear magnetic resonance (NMR) data include chemical shifts for 31P, 27Al, and 29Si, 27Al quadrupole coupling parameters, and 31P and 27Al spin-lattice relaxation rates. Also presented are electron diffraction patterns of β-cristobalite AlPO4 that show diffuse scattering similar to that reported previously for SiO2. For the α-phases of both AlPO4 and SiO2, the chemical shifts decrease approximately linearly with increasing temperature from RT to Tc and discontinuously by -2 to -3 ppm from α to β. This result is consistent with a small, continuous increase in the mean T-O-T angle (<θ>) of the α-phases with increasing T and an increase of <θ> by about 4° across the α- β transition for both cristobalite and its AlPO4 analogue. Based on the 29Si chemical shifts, the mean Si-O-Si angle for β-cristobalite is 152.7±1° near Tc. For AlPO4-cristobalite, the 27Al nuclear quadrupole coupling constant (CQ) decreases approximately linearly from 1.2 MHz at RT to 0.94 MHz near Tc (493±10 K). At the α- β transition the 27Al CQ approaches zero, in agreement with the cubic average structure observed by diffraction. The satellite transitions retain a small frequency distribution above the α- β transition from electric field gradients attributed to defects. The short-range cubic symmetry of the Al-site and non-linear Al-O-P angle support a dynamically disordered model of the β-cristobalite structure. Complete averaging of the 27Al quadrupole coupling in the β-phase indicates that the lifetime of any short-range ordered domains must be shorter than about 1 μs.

  8. Theoretical Studies on the Fe-M Interactions and 31P NMR in Fe(CO)3(EtPhPpy)2MX2 (X = NCS, SCN, Cl; M = Zn, Cd, Hg)

    NASA Astrophysics Data System (ADS)

    Huang, Xiao-xuan; Xu, Xuan; Xie, Mei-xiang

    2008-10-01

    To study the Fe-M interactions and their effects on 31P NMR, the structures of Fe(CO)3(EtPhPpy)2 1, Fe(CO)3(EtPhPpy)2M(NCS)2 (2: M = Zn, 3: M = Cd, 4: M = Hg) and Fe(CO)3(EtPhPpy)2CdX2 (5: X = C1, 6: X = SCN) were investigated by density functional theory (DFT) PBE0 method. The stabilities S of complexes follow S(2)>S(3)>S(4) and S(3)approxS(6)>S(5), indicating that 6 is stable and may be synthesized. The complexes with thiocyanate are more stable than that with chloride in Fe(CO)3(EtPhPpy)2CdX2. The strength / of Fe-M interactions follows I(2)approxI(3)31P chemical shifts are caused (compared with mononuclear complex 1).

  9. 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

  10. The guest ordering and dynamics in urea inclusion compounds studied by solid-state 1H and 13C MAS NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Yang, Xiaorong; Müller, Klaus

    2011-12-01

    Urea inclusion compounds with different guest species were studied by 13C CP MAS and 1H MAS NMR spectroscopy. It is possible to arrange the asymmetric guest species in three different ways: head-head, head-tail and tail-tail. 13C CP MAS NMR studies indicate that the preference arrangement is determined by the interaction strength of the end functional groups. 13C relaxation experiments are used to study the dynamic properties of urea inclusion compounds. 13C relaxation studies on urea inclusion compounds with n-alkane or decanoic acid show that the 13C T1 and 13C T1ρ values exhibit the position dependence towards the center of the chain, indicating internal chain mobility. The analysis of variable-temperature 13C T1ρ experiments on urea inclusion compounds with hexadecane and pentadecane, for the first time, suggests that chain fluctuations and lateral motion of n-alkane guests may contribute to the 13C T1ρ relaxation.

  11. Pr 2Sn 2O 7 and Sm 2Sn 2O 7 as High-Temperature Shift Thermometers in Variable-Temperature 119Sn MAS NMR

    NASA Astrophysics Data System (ADS)

    Vanmoorsel, G. J. M. P.; Vaneck, E. R. H.; Grey, C. P.

    Two shift thermometers have been developed in order to determine the exact sample temperature at elevated temperatures in MAS NMR. The probe was calibrated for different temperatures and bearing pressures using the structural phase transition NMR spectra of carbon tetrabromide (319.86 K), DABCO (351.08 K), rubidium nitrate (437 K), and lithium sodium sulfate (791 K). Temperature-dependent 119Sn MAS NMR spectra of Pr 2Sn 2O 7 and Sm 2Sn 2O 7 were then recorded. The temperature dependence is caused by the hyperfine interaction between the paramagnetic electron spin and the 119Sn nucleus. Pr 2Sn 2O 7 proved to be an extremely sensitive linear high-temperature shift thermometer: its sensitivity is 14.1 ppm/K at room temperature and 2.7 ppm/K at 790 K. Sm 2Sn 2O 7 also proved to be very sensitive to temperature, although its dependence was not linear. At room temperature its sensitivity is 1.1 ppm/K. The temperature dependence of the shift can be fitted to an equation derived from the Van Vleck equation, taking into account the ground and the first excited states of Sm 3+.

  12. Obtaining aluminas from the thermal decomposition of their different precursors: An {sup 27}Al MAS NMR and X-ray powder diffraction studies

    SciTech Connect

    Chagas, L.H.; De Carvalho, G.S.G.; San Gil, R.A.S.; Chiaro, S.S.X.; Leitão, A.A.; Diniz, R.

    2014-01-01

    Graphical abstract: - Highlights: • We synthesized three precursors of alumina from different methods. • The calcination of the precursors generated several alumina polymorphs. • XRD and NMR were used for structural investigation of the polymorphs. • The synthesis route determines the structural and textural properties of the solids. - Abstract: A commercial sample of Boehmite was used as precursor of alumina polymorphs. For comparison, three other precursors were synthesized from different methods. Particularly, the use of excess of urea promoted a very crystalline form of basic aluminum carbonate. The characteristics of the four precursors were investigated by thermal, vibrational and X-ray powder diffraction (XRD) analysis. Additionally, the nuclear magnetic resonance, with magic angle spinning ({sup 27}Al MAS NMR), was used to verify the coordination of aluminum cations. Each precursor was calcined at various temperatures generating alumina polymorphs, which were structurally analyzed by XRD and {sup 27}Al MAS NMR. Due to interest in catalysis supports, special attention was given to the γ-Al{sub 2}O{sub 3} phase, which in addition to structural investigation was subjected to textural analysis. The results showed that, from different synthesis procedures and common route of calcination, one can obtain materials with the same composition but with different structural and textural properties, which in turn can significantly influence the performance of a supported catalyst.

  13. Solid state structure by X-ray and 13C CP/MAS NMR of new 5-[2-(N,N-dimethylamino)ethoxy]-4,7-dimethylcoumarins

    NASA Astrophysics Data System (ADS)

    Ostrowska, Kinga; Maciejewska, Dorota; Dobrzycki, Łukasz; Socha, Pawel

    2016-05-01

    5-[2-(N,N-dimethylamino)ethoxy]-4,7-dimethylcoumarin (1) and 6-acetyl-5-[2-(N,N-dimethylamino)ethoxy]-4,7-dimethylcoumarin (2), structurally related, were synthesized using both conventional and microwave-assisted approach. An impact of acetyl groups on the molecular structure of coumarin derivatives has been examined. Crystals of 2 were investigated using single crystal and powder X-ray diffraction techniques. Compound 2 crystallizes forming two polymorphs (denoted as 2_1 and 2_2), both belonging to P21/c space group. Both polymorphs are comparably stable and can be formed simultaneously during crystallization process. The solid state structure was also analysed using the fully resolved 13C CP/MAS NMR. The double signals with the intensity ratio of about 1:1 which were observed in the 13C CP/MAS NMR spectrum of compound 1 must arise due to the presence of two conformers of 1. In contrast, NMR spectrum recorded for powder mixture of two polymorphs of compound 2 displays no signal splitting. This is related to structural similarities of molecules in both polymorphs.

  14. Direct evidence for a role of intramitochondrial Ca2+ in the regulation of oxidative phosphorylation in the stimulated rat heart. Studies using 31P n.m.r. and ruthenium red.

    PubMed Central

    Unitt, J F; McCormack, J G; Reid, D; MacLachlan, L K; England, P J

    1989-01-01

    1. The concentrations of free ATP, phosphocreatine (PCr), Pi, H+ and ADP (calculated) were monitored in perfused rat hearts by 31P n.m.r. before and during positive inotropic stimulation. Data were accumulated in 20 s blocks. 2. Administration of 0.1 microM-(-)-isoprenaline resulted in no significant changes in ATP, transient decreases in PCr, and transient increases in ADP and Pi. However, the concentrations of all of these metabolites returned to pre-stimulated values within 1 min, whereas cardiac work and O2 uptake remained elevated. 3. In contrast, in hearts perfused continuously with Ruthenium Red (2.5 micrograms/ml), a potent inhibitor of mitochondrial Ca2+ uptake, administration of isoprenaline caused significant decreases in ATP, and also much larger and more prolonged changes in the concentrations of ADP, PCr and Pi. In this instance values did not fully return to pre-stimulated concentrations. Administration of Ruthenium Red alone to unstimulated hearts had minor effects. 4. It is proposed that, in the absence of Ruthenium Red, the transmission of changes in cytoplasmic Ca2+ across the mitochondrial inner membrane is able to maintain the phosphorylation potential of the heart during positive inotropic stimulation, through activation of the Ca2+-sensitive intramitochondrial dehydrogenases (pyruvate, NAD+-isocitrate and 2-oxoglutarate dehydrogenases) leading to enhanced NADH production. 5. This mechanism is unavailable in the presence of Ruthenium Red, and oxidative phosphorylation must be stimulated primarily by a fall in phosphorylation potential, in accordance with the classical concept of respiratory control. However, the full oxidative response of the heart to stimulation may not be achievable under such circumstances. PMID:2479373

  15. Magnetism of the spin-trimer compound CaNi 3(P 2O 7)2: Microscopic insight from combined 31P NMR and first-principles studies

    NASA Astrophysics Data System (ADS)

    Majumder, M.; Kanungo, S.; Ghoshray, A.; Ghosh, M.; Ghoshray, K.

    2015-03-01

    Magnetization, 31P nuclear magnetic resonance study, and first-principles electronic structure calculations have been performed in the spin-1 trimer chain compound CaNi3(P2O7 )2. Two separate spectra arising from magnetically and crystallographically inequivalent P sites are observed. In the ordered state, the resonance lines for both the P sites (P1 and P2) are found to be split into two, which is clear microscopic evidence of the development of two-sublattice AFM order below TM. A nonnegligible contribution of ferromagnetic hyperfine field and dipolar field have also been seen in the ordered state. The first-principles calculations show that the intratrimer (J1) and intertrimer interactions (J2) are of weak ferromagnetic type with the values 2.85 and 1.49 meV, respectively, whereas the interchain interaction (J3) is of strong antiferromagnetic type with a value of 5.63 meV. The anisotropy of the imaginary part of dynamical spin susceptibility around TM along with the exponential decrement of 1 /T1 below TM indicate the probable participation of the Ni -3 d electron's orbital degrees of freedom in the ferrimagnetic transition. The dominance of orbital fluctuations over the spin fluctuations seems to be responsible for showing low value of the binding energy u of the local spin configuration (estimated from local spin models) and an unusually weak exponent in the power-law behavior of 1 /T1 below 50 K, in the paramagnetic state. Electronic structure calculations also reveal the importance of orbital degrees of freedom of Ni -3 d moments, which is consistent with our NMR data analysis.

  16. The solubilisation of boar sperm membranes by different detergents - a microscopic, MALDI-TOF MS, 31P NMR and PAGE study on membrane lysis, extraction efficiency, lipid and protein composition

    PubMed Central

    2009-01-01

    Background Detergents are often used to isolate proteins, lipids as well as "detergent-resistant membrane domains" (DRMs) from cells. Different detergents affect different membrane structures according to their physico-chemical properties. However, the effects of different detergents on membrane lysis of boar spermatozoa and the lipid composition of DRMs prepared from the affected sperm membranes have not been investigated so far. Results Spermatozoa were treated with the selected detergents Pluronic F-127, sodium cholate, CHAPS, Tween 20, Triton X-100 and Brij 96V. Different patterns of membrane disintegration were observed by light and electron microscopy. In accordance with microscopic data, different amounts of lipids and proteins were released from the cells by the different detergents. The biochemical methods to assay the phosphorus and cholesterol contents as well as 31P NMR to determine the phospholipids were not influenced by the presence of detergents since comparable amounts of lipids were detected in the organic extracts from whole cell suspensions after exposure to each detergent. However, matrix-assisted laser desorption and ionization time-of-flight mass spectrometry applied to identify phospholipids was essentially disturbed by the presence of detergents which exerted particular suppression effects on signal intensities. After separation of the membrane fractions released by detergents on a sucrose gradient only Triton X-100 and sodium cholate produced sharp turbid DRM bands. Only membrane solubilisation by Triton X-100 leads to an enrichment of cholesterol, sphingomyelin, phosphatidylinositol and phosphatidylethanolamine in a visible DRM band accompanied by a selective accumulation of proteins. Conclusion The boar sperm membranes are solubilised to a different extent by the used detergents. Particularly, the very unique DRMs isolated after Triton X-100 exposure are interesting candidates for further studies regarding the architecture of sperm. PMID

  17. The study of a monocotyledon abscission zone using microscopic, chemical, enzymatic and solid state 13C CP/MAS NMR analyses.

    PubMed

    Henderson, J; Davies, H A; Heyes, S J; Osborne, D J

    2001-01-01

    We have investigated distinguishing features in cells of the abscission zone of a monocotyledon fruit, the oil palm Elaeis guineensis. The cell walls of the abscission zone and the subtending mesocarp and pedicel have been analysed by light and transmission electron microscopy, by chemical methods and by solid state 13C CP/MAS NMR spectroscopy. Results show that these abscission zone cells have specific characteristics which include high levels of unmethylated pectin in the walls and an inducible (x35) polygalacturonase enzyme expression. Together these findings help to explain the localised precision of cell separation events. PMID:11219806

  18. 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.

  19. Identification by stopped-exchange solution /sup 31/P NMR spectroscopy of the stepwise formation of (AgL/sub n/)PF/sub 6/ (n = 1-4). Comparison of metal-phosphorus coupling constants for triphenylphosphine and 5-phenyldibenzophosphole

    SciTech Connect

    Alyea, E.C.; Malito, J.; Nelson, J.H.

    1987-12-16

    The coordination properties of 5-phenyldibenzophosphate (PhDBP) have been studied extensively. The stepwise formation of (L/sub n/Ag)/sup +/PF/sub 6//sup -/ (n = 1-4) for L = PhDBP and PhP/sub 3/ observed in situ by stopped-exchange solution /sup 31/P NMR spectroscopy is reported herein. The relative coordinating properties of PhDBP and PhP/sub 3/ are compared. 21 references, 1 figure, 2 tables.

  20. Bonding Preferences of Non-Bridging Oxygens in Calcium Aluminosilicate Glass: Evidence from O-17 MAS and 3QMAS NMR on Calcium Aluminate Glass

    NASA Astrophysics Data System (ADS)

    Allwardt, J. R.; Lee, S.; Stebbins, J.

    2001-12-01

    Non-bridging oxygens (NBO's) play a significant role in the thermodynamic and transport properties in glasses and silicate melts. Previous oxygen-17 (O-17) triple quantum magic angle spinning (3QMAS NMR) data have shown the presence of NBO's in several calcium aluminosilicate (CAS) glasses on the CaAl2O4-SiO2 join (Stebbins and Xu 1997). The observed chemical shifts of these glasses are similar to those for the NBO in calcium silicate glasses (Stebbins et al. 1997 and Stebbins et al 1999); however, a recent O-17 MAS NMR study of crystalline CaAl2O4 showed that the NBO peak in an associated impurity phase is shifted to a higher frequency by 30 to 40 ppm from that of CAS and Ca-silicate glasses (Stebbins et al. in press). This finding suggests that Si is the preferred network cation for NBO's in aluminosilicate glasses and melts at the glass transition temperature. The preference for Si over that of Al as the network cation host for NBO's has also been suggested by Raman and other spectroscopic techniques (Mysen 1988). To investigate this apparent preference for Si-NBO, O-17 3QMAS and MAS experiments were conducted to examine the location of the NBO peak in the spectra of a calcium aluminate glass. Since the CaAl2O4 glass is difficult to make by conventional cooling methods, the binary eutectic composition (63CaO-37Al2O3) was chosen. The resulting O-17 MAS spectrum shows an intense, relatively narrow peak centered at 72 ppm, which nearly coincides with the peak location and width of the Al-O-Al peak in the crystalline Ca-aluminates (Stebbins et al. in press.) (70 ppm). There is a broader, less intense peak centered at 155 ppm that is assigned to the Al-NBO peak. This peak is in approximately the same location as that for a Ca-aluminate phase reported by Stebbins et al. (in press) (137 ppm). In addition, our 3QMAS data show that the peak maximum of the NBO in the Ca-aluminate (-85 and 150 ppm in isotropic and MAS dimensions, respectively) differs significantly from

  1. {sup 13}C chemical shift anisotropies for carbonate ions in cement minerals and the use of {sup 13}C, {sup 27}Al and {sup 29}Si MAS NMR in studies of Portland cement including limestone additions

    SciTech Connect

    Sevelsted, Tine F.; Herfort, Duncan

    2013-10-15

    {sup 13}C isotropic chemical shifts and chemical shift anisotropy parameters have been determined for a number of inorganic carbonates relevant in cement chemistry from slow-speed {sup 13}C MAS or {sup 13}C({sup 1}H) CP/MAS NMR spectra (9.4 T or 14.1 T) for {sup 13}C in natural abundance. The variation in the {sup 13}C chemical shift parameters is relatively small, raising some doubts that different carbonate species in Portland cement-based materials may not be sufficiently resolved in {sup 13}C MAS NMR spectra. However, it is shown that by combining {sup 13}C MAS and {sup 13}C({sup 1}H) CP/MAS NMR carbonate anions in anhydrous and hydrated phases can be distinguished, thereby providing valuable information about the reactivity of limestone in cement blends. This is illustrated for three cement pastes prepared from an ordinary Portland cement, including 0, 16, and 25 wt.% limestone, and following the hydration for up to one year. For these blends {sup 29}Si MAS NMR reveals that the limestone filler accelerates the hydration for alite and also results in a smaller fraction of tetrahedrally coordinated Al incorporated in the C-S-H phase. The latter result is more clearly observed in {sup 27}Al MAS NMR spectra of the cement–limestone blends and suggests that dissolved aluminate species in the cement–limestone blends readily react with carbonate ions from the limestone filler, forming calcium monocarboaluminate hydrate. -- Highlights: •{sup 13}C chemical shift anisotropies for inorganic carbonates from {sup 13}C MAS NMR. •Narrow {sup 13}C NMR chemical shift range (163–171 ppm) for inorganic carbonates. •Anhydrous and hydrated carbonate species by {sup 13}C MAS and {sup 13}C({sup 1}H) CP/MAS NMR. •Limestone accelerates the hydration for alite in Portland – limestone cements. •Limestone reduces the amount of aluminium incorporated in the C-S-H phase.

  2. Low-power broadband homonuclear dipolar recoupling in MAS NMR by two-fold symmetry pulse schemes for magnetization transfers and double-quantum excitation

    NASA Astrophysics Data System (ADS)

    Teymoori, Gholamhasan; Pahari, Bholanath; Edén, Mattias

    2015-12-01

    We provide an experimental, numerical, and high-order average Hamiltonian evaluation of an open-ended series of homonuclear dipolar recoupling sequences, SR2 2p 1 with p = 1, 2, 3, … . While operating at a very low radio-frequency (rf) power, corresponding to a nutation frequency of 1/2 of the magic-angle spinning (MAS) rate (ωnut =ωr / 2), these recursively generated double-quantum (2Q) dipolar recoupling schemes offer a progressively improved compensation to resonance offsets and rf inhomogeneity for increasing pulse-sequence order p. The excellent recoupling robustness to these experimental obstacles, as well as to CSA, is demonstrated for 2Q filtering (2QF) experiments and for driving magnetization transfers in 2D NMR correlation spectroscopy, where the sequences may provide either double or zero quantum dipolar Hamiltonians during mixing. Experimental and numerical demonstrations, which mostly target conditions of "ultra-fast" MAS (≳50 kHz) and high magnetic fields, are provided for recoupling of 13C across a wide range of isotropic and anisotropic chemical shifts, as well as dipolar coupling constants, encompassing [2,3-13C2 ]alanine, [1,3-13C2 ]alanine, diammonium [1,4-13C2 ]fumarate, and [U-13 C]tyrosine. When compared at equal power levels, a superior performance is observed for the SR2p 1 sequences with p ⩾ 3 relative to existing and well-established 2Q recoupling techniques. At ultra-fast MAS, proton decoupling is redundant during the homonuclear dipolar recoupling of dilute spins in organic solids, which renders the family of SR2p 1 schemes the first efficient 2Q recoupling option for general applications, such as 2Q-1Q correlation NMR and high-order multiple-quantum excitation, under truly low-power rf conditions.

  3. Low-power broadband homonuclear dipolar recoupling in MAS NMR by two-fold symmetry pulse schemes for magnetization transfers and double-quantum excitation.

    PubMed

    Teymoori, Gholamhasan; Pahari, Bholanath; Edén, Mattias

    2015-12-01

    We provide an experimental, numerical, and high-order average Hamiltonian evaluation of an open-ended series of homonuclear dipolar recoupling sequences, SR [Formula: see text] with p=1,2,3,…. While operating at a very low radio-frequency (rf) power, corresponding to a nutation frequency of 1/2 of the magic-angle spinning (MAS) rate (ωnut=ωr/2), these recursively generated double-quantum (2Q) dipolar recoupling schemes offer a progressively improved compensation to resonance offsets and rf inhomogeneity for increasing pulse-sequence order p. The excellent recoupling robustness to these experimental obstacles, as well as to CSA, is demonstrated for 2Q filtering (2QF) experiments and for driving magnetization transfers in 2D NMR correlation spectroscopy, where the sequences may provide either double or zero quantum dipolar Hamiltonians during mixing. Experimental and numerical demonstrations, which mostly target conditions of "ultra-fast" MAS (≳50kHz) and high magnetic fields, are provided for recoupling of (13)C across a wide range of isotropic and anisotropic chemical shifts, as well as dipolar coupling constants, encompassing [2,3-(13)C2]alanine, [1,3-(13)C2]alanine, diammonium [1,4-(13)C2]fumarate, and [U-(13)C]tyrosine. When compared at equal power levels, a superior performance is observed for the SR [Formula: see text] sequences with p⩾3 relative to existing and well-established 2Q recoupling techniques. At ultra-fast MAS, proton decoupling is redundant during the homonuclear dipolar recoupling of dilute spins in organic solids, which renders the family of SR [Formula: see text] schemes the first efficient 2Q recoupling option for general applications, such as 2Q-1Q correlation NMR and high-order multiple-quantum excitation, under truly low-power rf conditions. PMID:26515279

  4. 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

  5. Constant-time 2D and 3D through-bond correlation NMR spectroscopy of solids under 60 kHz MAS

    NASA Astrophysics Data System (ADS)

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2016-01-01

    Establishing connectivity and proximity of nuclei is an important step in elucidating the structure and dynamics of molecules in solids using magic angle spinning (MAS) NMR spectroscopy. Although recent studies have successfully demonstrated the feasibility of proton-detected multidimensional solid-state NMR experiments under ultrafast-MAS frequencies and obtaining high-resolution spectral lines of protons, assignment of proton resonances is a major challenge. In this study, we first re-visit and demonstrate the feasibility of 2D constant-time uniform-sign cross-peak correlation (CTUC-COSY) NMR experiment on rigid solids under ultrafast-MAS conditions, where the sensitivity of the experiment is enhanced by the reduced spin-spin relaxation rate and the use of low radio-frequency power for heteronuclear decoupling during the evolution intervals of the pulse sequence. In addition, we experimentally demonstrate the performance of a proton-detected pulse sequence to obtain a 3D 1H/13C/1H chemical shift correlation spectrum by incorporating an additional cross-polarization period in the CTUC-COSY pulse sequence to enable proton chemical shift evolution and proton detection in the incrementable t1 and t3 periods, respectively. In addition to through-space and through-bond 13C/1H and 13C/13C chemical shift correlations, the 3D 1H/13C/1H experiment also provides a COSY-type 1H/1H chemical shift correlation spectrum, where only the chemical shifts of those protons, which are bonded to two neighboring carbons, are correlated. By extracting 2D F1/F3 slices (1H/1H chemical shift correlation spectrum) at different 13C chemical shift frequencies from the 3D 1H/13C/1H spectrum, resonances of proton atoms located close to a specific carbon atom can be identified. Overall, the through-bond and through-space homonuclear/heteronuclear proximities determined from the 3D 1H/13C/1H experiment would be useful to study the structure and dynamics of a variety of chemical and biological

  6. Constant-time 2D and 3D through-bond correlation NMR spectroscopy of solids under 60 kHz MAS.

    PubMed

    Zhang, Rongchun; Ramamoorthy, Ayyalusamy

    2016-01-21

    Establishing connectivity and proximity of nuclei is an important step in elucidating the structure and dynamics of molecules in solids using magic angle spinning (MAS) NMR spectroscopy. Although recent studies have successfully demonstrated the feasibility of proton-detected multidimensional solid-state NMR experiments under ultrafast-MAS frequencies and obtaining high-resolution spectral lines of protons, assignment of proton resonances is a major challenge. In this study, we first re-visit and demonstrate the feasibility of 2D constant-time uniform-sign cross-peak correlation (CTUC-COSY) NMR experiment on rigid solids under ultrafast-MAS conditions, where the sensitivity of the experiment is enhanced by the reduced spin-spin relaxation rate and the use of low radio-frequency power for heteronuclear decoupling during the evolution intervals of the pulse sequence. In addition, we experimentally demonstrate the performance of a proton-detected pulse sequence to obtain a 3D (1)H/(13)C/(1)H chemical shift correlation spectrum by incorporating an additional cross-polarization period in the CTUC-COSY pulse sequence to enable proton chemical shift evolution and proton detection in the incrementable t1 and t3 periods, respectively. In addition to through-space and through-bond (13)C/(1)H and (13)C/(13)C chemical shift correlations, the 3D (1)H/(13)C/(1)H experiment also provides a COSY-type (1)H/(1)H chemical shift correlation spectrum, where only the chemical shifts of those protons, which are bonded to two neighboring carbons, are correlated. By extracting 2D F1/F3 slices ((1)H/(1)H chemical shift correlation spectrum) at different (13)C chemical shift frequencies from the 3D (1)H/(13)C/(1)H spectrum, resonances of proton atoms located close to a specific carbon atom can be identified. Overall, the through-bond and through-space homonuclear/heteronuclear proximities determined from the 3D (1)H/(13)C/(1)H experiment would be useful to study the structure and dynamics of

  7. Conformations of solid 2-methyl-4-( p-X-phenylazo)imidazoles by 13C CP MAS NMR spectroscopy and PM3 semi-empirical calculations

    NASA Astrophysics Data System (ADS)

    Maciejewska, Dorota

    1999-03-01

    Solid 2-methyl-4-( p-X-phenylazo)imidazoles form hydrogen bonded chains with N-H⋯N bonds and C-H⋯O or C-H⋯N interaction. Depending on the nature and orientation of the substituents X it was possible to identify one tautomer if XH ( 2), Br ( 3), NO 2 ( 4) and the two, a- and b-tautomers in the crystal unit if XOCH 3 ( 1). The 13C CP MAS NMR spectra of ( 4) indicate the presence of phenyl ring dynamics. A preferred structure present in the solid state is that with different lengths of C1'-N and C4-N bonds and with higher dipole moment.

  8. A study of structure and dynamics of poly(aspartic acid) sodium/poly(vinyl alcohol) blends by 13C CP/MAS NMR

    NASA Astrophysics Data System (ADS)

    Wang, P.; Ando, I.

    1999-09-01

    Solid state 13C CP/MAS NMR measurements have been carried out on poly(aspartic acid) sodium (PAANa)/poly(vinyl alcohol) (PVA) blends over a wide range of temperatures. From these experimental results, it is found that the main-chain conformations of PAANa in PAANa/PVA blends take the α-helix form over a wide range of blend ratios, and, in contrast, the conformation and dynamics of the side chains of PAANa are strongly influenced by the formation of an intermolecular hydrogen bond between the carboxyl group of the side chains and the hydroxyl group of PVA. The behavior of the proton spin-lattice relaxation times in the rotating frame ( T1 ρ(H)) and the laboratory frame ( T1(H)) indicates that when the blend ratio of PAANa and PVA is 1:1, they are miscible.

  9. Resolution and measurement of heteronuclear dipolar couplings of a noncrystalline protein immobilized in a biological supramolecular assembly by proton-detected MAS solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Park, Sang Ho; Yang, Chen; Opella, Stanley J.; Mueller, Leonard J.

    2013-12-01

    Two-dimensional 15N chemical shift/1H chemical shift and three-dimensional 1H-15N dipolar coupling/15N chemical shift/1H chemical shift MAS solid-state NMR correlation spectra of the filamentous bacteriophage Pf1 major coat protein show single-site resolution in noncrystalline, intact-phage preparations. The high sensitivity and resolution result from 1H detection at 600 MHz under 50 kHz magic angle spinning using ∼0.5 mg of perdeuterated and uniformly 15N-labeled protein in which the exchangeable amide sites are partially or completely back-exchanged (reprotonated). Notably, the heteronuclear 1H-15N dipolar coupling frequency dimension is shown to select among 15N resonances, which will be useful in structural studies of larger proteins where the resonances exhibit a high degree of overlap in multidimensional chemical shift correlation spectra.

  10. Solid state structure of new 5-[2-(N,N-diethylamino)ethoxy]-4,7-dimethylcoumarins by X-ray and 13C CP/MAS NMR

    NASA Astrophysics Data System (ADS)

    Ostrowska, Kinga; Hejchman, Elżbieta; Dobrzycki, Łukasz; Maciejewska, Dorota

    2015-05-01

    5-[2-(N,N-diethylamino)ethoxy]-4,7-dimethylcoumarin (1) and 6-acetyl-5-[2-(N,N-diethylamino)ethoxy]-4,7-dimethylcoumarin (2) were synthesized in a traditional way and microwave-assisted synthesis. Crystals of 2 in form of hydrochloride salt (3) were investigated using single crystal X-ray diffraction technique. In the crystal lattice of 3 there is only one type of strong hydrogen bond present involving protonated amino group and chloride anion. The whole structure is dominated by weak C-H…Cl-, C-H…O contacts. There is also visible aggregation of cations in stacks due to π-π interactions. The solid state structures of 1 and 2 derived from 13C CP/MAS NMR spectra were also proposed.

  11. Selective detection and complete identification of triglycerides in cortical bone by high-resolution (1)H MAS NMR spectroscopy.

    PubMed

    Mroue, Kamal H; Xu, Jiadi; Zhu, Peizhi; Morris, Michael D; Ramamoorthy, Ayyalusamy

    2016-07-28

    Using (1)H-based magic angle spinning solid-state NMR spectroscopy, we report an atomistic-level characterization of triglycerides in compact cortical bone. By suppressing contributions from immobile molecules present in bone, we show that a (1)H-based constant-time uniform-sign cross-peak (CTUC) two-dimensional COSY-type experiment that correlates the chemical shifts of protons can selectively detect a mobile triglyceride layer as the main component of small lipid droplets embedded on the surface of collagen fibrils. High sensitivity and resolution afforded by this NMR approach could be potentially utilized to investigate the origin of triglycerides and their pathological roles associated with bone fractures, diseases, and aging. PMID:27374353

  12. (14)N overtone NMR under MAS: signal enhancement using symmetry-based sequences and novel simulation strategies.

    PubMed

    Haies, Ibraheem M; Jarvis, James A; Bentley, Harry; Heinmaa, Ivo; Kuprov, Ilya; Williamson, Philip T F; Carravetta, Marina

    2015-03-01

    Overtone (14)N NMR spectroscopy is a promising route for the direct detection of (14)N signals with good spectral resolution. Its application is currently limited, however, by the absence of efficient polarization techniques for overtone signal enhancement and the lack of efficient numerical simulation techniques to aid in both the development of new methods and the analysis and interpretation of experimental data. In this paper we report a novel method for the transfer of polarization from (1)H to the (14)N overtone using symmetry-based R-sequences that overcome many of the limitations of adiabatic approaches that have worked successfully on static samples. Refinement of these sequences and the analysis of the resulting spectra have been facilitated through the development of an efficient simulation strategy for (14)N overtone NMR spectroscopy of spinning samples, using effective Hamiltonians on top of Floquet and Fokker-Planck equations. PMID:25662410

  13. Two-dimensional MAS NMR correlation protocols involving double-quantum filtering of quadrupolar spin-pairs.

    PubMed

    Edén, Mattias

    2010-05-01

    Three two-dimensional (2D) NMR homonuclear correlation techniques invoking double-quantum (2Q) filtration of the central transitions of half-integer spins are evaluated numerically and experimentally. They correlate directly detected single-quantum (1Q) coherences in the t(2) domain with either of 1Q, two-spin 2Q or single-spin multiple-quantum coherence-evolutions in the indirect (t(1)) dimension. We employ experimental (23)Na and (27)Al NMR on sodium sulfite and the natural mineral sillimanite (SiAl(2)O(5)), in conjunction with simulated 2D spectra from pairs of dipolar-recoupled spins-3/2 and 5/2 at different external magnetic fields, to compare the correlation strategies from the viewpoints of 2D spectral resolution, signal sensitivity, implementational aspects and their relative merits for establishing internuclear proximities and quadrupolar tensor orientations. PMID:20202872

  14. Composite-180° pulse-based symmetry sequences to recouple proton chemical shift anisotropy tensors under ultrafast MAS solid-state NMR spectroscopy.

    PubMed

    Pandey, Manoj Kumar; Malon, Michal; Ramamoorthy, Ayyalusamy; Nishiyama, Yusuke

    2015-01-01

    There is considerable interest in the measurement of proton ((1)H) chemical shift anisotropy (CSA) tensors to obtain deeper insights into H-bonding interactions which find numerous applications in chemical and biological systems. However, the presence of strong (1)H/(1)H dipolar interaction makes it difficult to determine small size (1)H CSAs from the homogeneously broadened NMR spectra. Previously reported pulse sequences for (1)H CSA recoupling are prone to the effects of radio frequency field (B1) inhomogeneity. In the present work we have carried out a systematic study using both numerical and experimental approaches to evaluate γ-encoded radio frequency (RF) pulse sequences based on R-symmetries that recouple (1)H CSA in the indirect dimension of a 2D (1)H/(1)H anisotropic/isotropic chemical shift correlation experiment under ultrafast magic angle spinning (MAS) frequencies. The spectral resolution and sensitivity can be significantly improved in both frequency dimensions of the 2D (1)H/(1)H correlation spectrum without decoupling (1)H/(1)H dipolar couplings but by using ultrafast MAS rates up to 70 kHz. We successfully demonstrate that with a reasonable RF field requirement (<200 kHz) a set of symmetry-based recoupling sequences, with a series of phase-alternating 270°0-90°180 composite-180° pulses, are more robust in combating B1 inhomogeneity effects. In addition, our results show that the new pulse sequences render remarkable (1)H CSA recoupling efficiency and undistorted CSA lineshapes. Experimental results on citric acid and malonic acid comparing the efficiencies of these newly developed pulse sequences with that of previously reported CSA recoupling pulse sequences are also reported under ultrafast MAS conditions. PMID:25497846

  15. Nucleotide-type chemical shift assignment of the encapsulated 40 kbp dsDNA in intact bacteriophage T7 by MAS solid-state NMR.

    PubMed

    Abramov, Gili; Goldbourt, Amir

    2014-08-01

    The icosahedral bacteriophage T7 is a 50 MDa double-stranded DNA (dsDNA) virus that infects Escherichia coli. Although there is substantial information on the physical and morphological properties of T7, structural information, based mostly on Raman spectroscopy and cryo-electron microscopy, is limited. Here, we apply the magic-angle spinning (MAS) solid-state NMR (SSNMR) technique to study a uniformly (13)C and (15)N labeled wild-type T7 phage. We describe the details of the large-scale preparation and purification of an isotopically enriched phage sample under fully hydrated conditions, and show a complete (13)C and a near-complete (15)N nucleotide-type specific assignment of the sugar and base moieties in the 40 kbp dsDNA of T7 using two-dimensional (13)C-(13)C and (15)N-(13)C correlation experiments. The chemical shifts are interpreted as reporters of a B-form conformation of the encapsulated dsDNA. While MAS SSNMR was found to be extremely useful in determining the structures of proteins in native-like environments, its application to nucleic acids has lagged behind, leaving a missing (13)C and (15)N chemical shift database. This work therefore expands the (13)C and (15)N database of real B-form DNA systems, and opens routes to characterize more complex nucleic acid systems by SSNMR. PMID:24875850

  16. Correlations between 11B NMR parameters and structural characters in borate and borosilicate minerals investigated by high-resolution MAS NMR and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Zhou, Bing; Sun, Zhaohua; Yao, Yefeng; Pan, Yuanming

    2012-05-01

    Borates consisting of diverse fundamental building blocks (FBB) formed from complex polymerization of planar triangular [Bϕ3] groups and tetrahedral [Bϕ4] groups, where ϕ = O and OH, provide an excellent opportunity for investigation of correlations between the NMR parameters and local structures. However, previous studies suggested that the 11B NMR parameters in borates are insensitive to local structural environments other than the B coordination number, in contrast to those documented for 29Si, 23Na and 27Al in silicates, and no correlation between 11B chemical shifts and the sum of bond valences has been established for borate minerals with hydroxyl groups or molecular water in the structures. In this study, high-resolution NMR spectra have been acquired at the ultra high field of 21 T as well as at 14 T for selected borate and borosilicate minerals, and have been used to extract high-precision NMR parameters by using combined ab initio theoretical calculations and spectral simulations. These new NMR parameters reveal subtle correlations with various structural characters, especially the effects of the 11B chemical shifts from the bridging oxygen atom(s), site symmetry, symmetry of FBB, the sum of bond valences, as well as the next-nearest-neighbor cations and hydrogen bonding. Also, these results provide new insights into the shielding mechanism for 11B in borate and borosilicate minerals. In particular, this study demonstrates that the small variation in 11B chemical shifts can still be used to probe the local structural environments and that the established correlations can be used to investigate the structural details in borates and amorphous materials.

  17. Boron isotopes as pH proxy: A new look at boron speciation in deep-sea corals using 11B MAS NMR and EELS

    NASA Astrophysics Data System (ADS)

    Rollion-Bard, Claire; Blamart, Dominique; Trebosc, Julien; Tricot, Grégory; Mussi, Alexandre; Cuif, Jean-Pierre

    2011-02-01

    Dissolved boron in modern seawater occurs in the form of two species, trigonal boric acid B(OH) 3 and tetrahedral borate ion B(OH)4-. One of the key assumption in the use of boron isotopic compositions of carbonates as pH proxy is that only borate ions, B(OH)4-, are incorporated into the carbonate. Here, we investigate the speciation of boron in deep-sea coral microstructures ( Lophelia pertusa specimen) by using high field magic angle spinning nuclear magnetic resonance ( 11B MAS NMR) and electron energy-loss spectroscopy (EELS). We observe both boron coordination species, but in different proportions depending on the coral microstructure, i.e. centres of calcification versus fibres. These results suggest that careful sampling is necessary before performing boron isotopic measurements in deep-sea corals. By combining the proportions of B(OH) 3 and B(OH)4- determined by NMR and our previous ion microprobe boron isotope measurements, we propose a new equation for the relation between seawater pH and boron isotopic composition in deep-sea corals.

  18. Investigation of the Structure and Active Sites of TiO2 Nanorod Supported VOx Catalysts by High-Field and Fast-Spinning 51V MAS NMR

    SciTech Connect

    Hu, Jian Z.; Xu, Suochang; Li, Weizhen; Hu, Mary Y.; Deng, Xuchu; Dixon, David A.; Vasiliu, Monica; Craciun, Raluca; Wang, Yong; Bao, Xinhe; Peden, Charles HF

    2015-07-02

    Supported VOx/TiO2-Rod catalysts were studied by 51V MAS NMR at high field using a sample spinning rate of 55 kHz. The superior spectral resolution allows for the observation of at least five vanadate species. The assignment of these vanadate species was carried out by quantum mechanical calculations of 51V NMR chemical shifts of model V-surface structures. Methanol oxidative dehydrogenation (ODH) was used to establish the correlation between the reaction rate and the various surface V-sites. It is found that monomeric V-species dominated the catalyst at low vanadium loadings with two peaks observed at about -502 and -529 ppm. V-dimers with two bridged oxygen appeare at about -555 ppm. Vanadate dimers and polyvanadates connected by one bridged oxygen atom between two adjacent V atoms resonate at about -630 ppm. A positive correlation is found between the V-dimers related to the -555 ppm peak and the ODH rate while a better correlation is obtained by including monomeric contributions. This result indicates that surface V-dimers related to the -555 ppm peak are the major active sites for ODH reaction despite mono-V species are more catalytic active but their relative ratios are decreased dramatically at high V-loadings. Furthermore, a portion of the V-species is found invisible. In particular, the level of such invisibility increases with decreased level of V-loading, suggesting the existence of paramagnetic V-species at the surface.

  19. Analysis of mercerization process based on the intensity change of deconvoluted resonances of (13)C CP/MAS NMR: Cellulose mercerized under cooling and non-cooling conditions.

    PubMed

    Miura, Kento; Nakano, Takato

    2015-08-01

    The area intensity change of C1, C4, and C6 in spectrum obtained by (13)C CP/MAS NMR and the mutual relationship between their changes were examined for cellulose samples treated with various concentrations of aqueous NaOH solutions under non-cooling and cooling conditions. The area intensity of C1-up and C6-down changed cooperatively with that of C4-down which corresponds to the crystallinity of samples: "-up" and "-down" are the up- and down- field component in a splitting peak of NMR spectrum, respectively. The intensity change of C1-up starts to decrease with decreasing in that of C4-down after that of C6-down is almost complete. These changes were more clearly observed for samples treated under cooling condition. It can be suggested that their characteristic change relates closely to the change in conformation of cellulose chains by induced decrystallization and the subsequent crystallization of cellulose II, and presumed that their changes at microscopic level relate to the macroscopic morphological changes such as contraction along the length of cellulose chains and recovery along the length. PMID:26042706

  20. Characterization of phosphorus in sludges and sludge amended soils using /sup 31/P nuclear magnetic resonance spectroscopy

    SciTech Connect

    Hinedi, Z.R.

    1987-01-01

    /sup 31/P NMR spectroscopy was an effective tool in the characterization of phosphorus (P) in municipal sewage sludges and sludge amended soils. Waste activated and aerobically digested sludges contained higher percentages of organic P than anaerobically digested sludges. The /sup 31/P Cross Polarization Magic Angle Spinning (/sup 31/P CP MAS) spectrum of an aerobically digested sludge indicated the presence of a significant organic P fraction over the inorganic P fraction. The /sup 31/P NMR spectra of sludge-borne phospholipids dissolved in cholate, to which a complexing agent was added, were found to be better resolved than those dissolved in chloroform. Phytic acid and ribonucleic acid were shown to be constituents of organic P in sludges based upon their susceptibility to different phosphoric ester hydrolases. Sludge amended soils were incubated to examine the transformations of sludge-borne P in soils. It was found that soil pH affected the biodegradation of organic P as well as that of pyrophosphate. Phosphorus-monoesters and pyrophosphates hydrolyzed after 70 days of incubation under alkaline soil condition while they persisted beyond 140 days of incubation under acid soil condition. The P-diesters completely hydrolyzed after 28 days of incubation under acid and alkaline soil conditions. The solubility study showed that the P in a sludge amended soil was undersaturated with respect to Ca-P, Fe-P and Al-P minerals considered. The finding suggested that the activity of the P solid phase under study might be less than unity which would be indicative of a coprecipitated solid solution.

  1. Al speciation in tropical podzols of the upper Amazon Basin: A solid-state 27Al MAS and MQMAS NMR study

    NASA Astrophysics Data System (ADS)

    Bardy, Marion; Bonhomme, Christian; Fritsch, Emmanuel; Maquet, Jocelyne; Hajjar, Redouane; Allard, Thierry; Derenne, Sylvie; Calas, Georges

    2007-07-01

    In the upper Amazon Basin, aluminum previously accumulated in lateritic formations is massively remobilised in soils by podzolization and exported in waters. We have investigated the speciation of aluminum in the clay-size fractions of eight horizons of waterlogged podzols lying in a depression of a plateau. The horizons illustrate the main steps involved in the podzolization of laterites. They belong to eluviated topsoil A horizons and illuviated subsoil Bhs, Bh and 2BCs horizons of weakly and better-expressed podzols located at the margin and centre of the depression. For the first time, aluminum speciation is quantitatively assessed in soils by spectroscopic methods, namely FTIR, 27Al magic angle spinning (MAS) and multiple-quantum magic angle spinning (MQMAS), nuclear magnetic resonance (NMR). The results thus obtained are compared to chemical extraction data. Solid-state 27Al MAS NMR spectra enable to distinguish Al bound to organic compounds from that incorporated in secondary mineral phases detected by FTIR. MQMAS experiments additionally show that both chemical shifts and quadrupolar constants are distributed for Al nuclei linked with organic compounds. Similar amounts of chelated Al are obtained from NMR spectra and chemical extractions. The study enables to highlight three major steps in the fate of aluminum. (i) Aluminum is first released by mineral weathering, feeds complexing sites of organic matter and accumulates in subsurface Bhs horizons of weakly expressed podzols (acidocomplexolysis). (ii) Complexes of aluminum with organic matter (Al-OM) then migrate downwards in sandy horizons of better-expressed podzols and accumulate at depth in less permeable 2BCs horizons. (iii) The minor amounts of aluminum present in the 2BCs horizon of the downslope podzol show that aluminum is eventually exported towards the river network, either complexed with organic matter or as Al 3+ ions after desorption from organic compounds, due to decreasing pH or

  2. sup 31 P and sup 1 H NMR studies of the structure of enzyme-bound substrate complexes of lobster muscle arginine kinase: Relaxation measurements with Mn(II) and Co(II)

    SciTech Connect

    Jarori, G.K.; Ray, B.D.; Rao, B.D.N. )

    1989-11-28

    The paramagnetic effects of Mn(II) and Co(II) on the spin-lattice relaxation rates of {sup 31}P nuclei of ATP and ADP and of Mn(II) on the spin-lattice relaxation rate of the {delta} protons of arginine bound to arginine kinase from lobster tail muscle have been measured. Temperature variation of {sup 31}P relaxation rates in E-MnADP and E-MnATP yields activation energies ({Delta}E) in the range 6-10 kcal/mol. Thus, the {sup 31}P relaxation rates in these complexes are exchange limited and cannot provide structural information. However, the relaxation rates in E-CoADP and E-CoATP exhibit frequency dependence and {Delta}E values in the range 1-2 kcal/mol; i.e., these rates depend upon {sup 31}P-Co(II) distances. These distances were calculated to be in the range 3.2-4.5 {angstrom}, appropriate for direct coordination between Co(II) and the phosphoryl groups. The paramagnetic effect of Mn(II) on the {sup 1}H spin-lattice relaxation rate of the {delta} protons of arginine in the E-MnADP-Arg complex was also measured at three frequencies. From the frequency dependence of the relaxation rate an effective {tau}{sub C} of 0.6 ns has also been calculated, which is most likely to be the electron spin relaxation rate ({tau}{sub S1}) for Mn(II) in this complex. The distance estimated on the basis of the reciprocal sixth root of the average relaxation rate of the {delta} protons was 10.9 {plus minus} 0.3 {angstrom}.

  3. Proton-detected MAS NMR experiments based on dipolar transfers for backbone assignment of highly deuterated proteins

    NASA Astrophysics Data System (ADS)

    Chevelkov, Veniamin; Habenstein, Birgit; Loquet, Antoine; Giller, Karin; Becker, Stefan; Lange, Adam

    2014-05-01

    Proton-detected solid-state NMR was applied to a highly deuterated insoluble, non-crystalline biological assembly, the Salmonella typhimurium type iii secretion system (T3SS) needle. Spectra of very high resolution and sensitivity were obtained at a low protonation level of 10-20% at exchangeable amide positions. We developed efficient experimental protocols for resonance assignment tailored for this system and the employed experimental conditions. Using exclusively dipolar-based interspin magnetization transfers, we recorded two sets of 3D spectra allowing for an almost complete backbone resonance assignment of the needle subunit PrgI. The additional information provided by the well-resolved proton dimension revealed the presence of two sets of resonances in the N-terminal helix of PrgI, while in previous studies employing 13C detection only a single set of resonances was observed.

  4. Hybridizing cross-polarization with NOE or refocused-INEPT enhances the sensitivity of MAS NMR spectroscopy.

    PubMed

    Zhang, Rongchun; Mroue, Kamal H; Ramamoorthy, Ayyalusamy

    2016-05-01

    Heteronuclear cross polarization (CP) has been commonly used to enhance the sensitivity of dilute low-γ nuclei in almost all solid-state NMR experiments. However, CP relies on heteronuclear dipolar couplings, and therefore the magnetization transfer efficiency becomes inefficient when the dipolar couplings are weak, as is often the case for mobile components in solids. Here, we demonstrate methods that combine CP with heteronuclear Overhauser effect (referred to as CP-NOE) or with refocused-INEPT (referred to as CP-RINEPT) to overcome the efficiency limitation of CP and enhance the signal-to-noise ratio (S/N) for mobile components. Our experimental results reveal that, compared to the conventional CP, significant S/N ratio enhancement can be achieved for resonances originating from mobile components, whereas the resonance signals associated with rigid groups are not significantly affected due to their long spin-lattice relaxation times. In fact, the S/N enhancement factor is also dependent on the temperature, CP contact time as well as on the system under investigation. Furthermore, we also demonstrate that CP-RINEPT experiment can be successfully employed to independently detect mobile and rigid signals in a single experiment without affecting the data collection time. However, the resolution of CP spectrum obtained from the CP-RINEPT experiment could be slightly compromised by the mandatory use of continuous wave (CW) decoupling during the acquisition of signals from rigid components. In addition, CP-RINEPT experiment can be used for spectral editing utilizing the difference in dynamics of different regions of a molecule and/or different components present in the sample, and could also be useful for the assignment of resonances from mobile components in poorly resolved spectra. Therefore, we believe that the proposed approaches are beneficial for the structural characterization of multiphase and heterogeneous systems, and could be used as a building block in

  5. Hybridizing cross-polarization with NOE or refocused-INEPT enhances the sensitivity of MAS NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Rongchun; Mroue, Kamal H.; Ramamoorthy, Ayyalusamy

    2016-05-01

    Heteronuclear cross polarization (CP) has been commonly used to enhance the sensitivity of dilute low-γ nuclei in almost all solid-state NMR experiments. However, CP relies on heteronuclear dipolar couplings, and therefore the magnetization transfer efficiency becomes inefficient when the dipolar couplings are weak, as is often the case for mobile components in solids. Here, we demonstrate methods that combine CP with heteronuclear Overhauser effect (referred to as CP-NOE) or with refocused-INEPT (referred to as CP-RINEPT) to overcome the efficiency limitation of CP and enhance the signal-to-noise ratio (S/N) for mobile components. Our experimental results reveal that, compared to the conventional CP, significant S/N ratio enhancement can be achieved for resonances originating from mobile components, whereas the resonance signals associated with rigid groups are not significantly affected due to their long spin-lattice relaxation times. In fact, the S/N enhancement factor is also dependent on the temperature, CP contact time as well as on the system under investigation. Furthermore, we also demonstrate that CP-RINEPT experiment can be successfully employed to independently detect mobile and rigid signals in a single experiment without affecting the data collection time. However, the resolution of CP spectrum obtained from the CP-RINEPT experiment could be slightly compromised by the mandatory use of continuous wave (CW) decoupling during the acquisition of signals from rigid components. In addition, CP-RINEPT experiment can be used for spectral editing utilizing the difference in dynamics of different regions of a molecule and/or different components present in the sample, and could also be useful for the assignment of resonances from mobile components in poorly resolved spectra. Therefore, we believe that the proposed approaches are beneficial for the structural characterization of multiphase and heterogeneous systems, and could be used as a building block in

  6. Studies of rare-earth stannates by sup 119 Sn MAS NMR. The use of paramagnetic shift probes in the solid state

    SciTech Connect

    Grey, C.P.; Dobson, C.M.; Cheetham, A.K.; Jakeman, R.J.B. )

    1989-01-18

    {sup 119}Sn MAS NMR spectra have been obtained from members of a series of rare-earth stannates Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = La, Pr, Nd, Sm, Eu, Tm, Yb, Lu, and Y), all of which adopt the pyrochlore structure. Apart from La{sub 2}Sn{sub 2}O{sub 7}, Lu{sub 2}Sn{sub 2}O{sub 7}, and Y{sub 2}Sn{sub 2}O{sub 7}, these compounds are paramagnetic and exhibit a very large variation in {sup 119}Sn chemical shifts (from approximately +5,400 to {minus}4,200 ppm), which can be attributed principally to a Fermi contact shift mechanism. The spectra from the paramagnetic samples have large overall line widths associated with the substantial anisotropy of the shift, but the individual peaks within the spinning sideband manifolds remain sharp. Several tin pyrochlore solid solutions have also been studied (namely Y{sub 2-y}Ln{sub y}Sn{sub 2}O{sub 7} where Ln = Sm, Nd, Pr, and Eu and La{sub 2-y}Nd{sub y}Sn{sub 2}O{sub u}) by {sup 119}Sn MAS NMR. When the short relaxation times of nuclei close to paramagnetic centers were exploited, a series of peaks were observed, associated with the substitution of paramagnetic for diamagnetic lanthanide ions in the local coordination around a tin atom. For Y{sub 2-y}Sm{sub y}Sn{sub 2}O{sub 7} the composition of the solid solution could be determined from the intensities of these peaks. In the solid solutions the {sup 119}Sn nuclei were found to be sensitive not only to neighboring paramagnetic ions but also to paramagnetic ions in the second and third coordination spheres. The shifts induced in these cases arise primarily from a through-space dipolar pseudocontact mechanism and can be interpreted with a model for the site symmetry based on the crystal structure. 30 refs., 8 figs., 3 tabs.

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

    NASA Astrophysics Data System (ADS)

    Dou, S.

    2009-04-01

    The humified SOM or humic substances (HS) composed of humic acid (HA), fulvic acid (FA) and humin (HM) represent the most microbially recalcitrant and stable reservoir of organic carbon in soil (Piccolo et al., 2004). OM applications can influence the amount and structural characteristics of HS(Dou et al., 2008). During the past few decades, there has been much research on HS, but their chemical structure is still not fully understood (Dong, 2006).CP-MAS-13C-NMR spectroscopy was considered as an effective method to study structures of HS without dissolving problem compared with liquid 13C-NMR (Conte et al., 1997; Dou et al., 2008). It can directly measure the carbon framework and reflect the nature of HS transformation after OM application (Spaccini et al., 2000). For that reason, this method was applied in this study. The objective of this paper was to clarify the effect of long term OM application on the changes of structural characteristics in HAs, which provided new information for improving soil fertility by OM application. The experiment was carried out on a brown soil (Paleudalf in USDA Soil Taxonomy) at Shenyang Agricultural University, Liaoning province, China (N41°48'-E123°25'). The experiment included 3 treatments: zero-treatment (CKbr), and two pig manure (PM) treatments (O1 and O2) at the rates of 0.9 t ha-1 and 1.8 t ha-1 of organic carbon, respectively. The samples of the HA fraction were extracted, separated and purified according to the method described by Dou et al. (1991). Elemental composition, Differential thermal analysis (DTA), -lgK value, FT-IR and CP-MAS- 13C-NMR of HAs were performed. Effects on the contents of orgaic carbon and its composition. The contents of TOC were from 8.77 g kg-1 to 12.25 g kg-1. The relative contents in TOC for WSS, HA, and FA were 6.87%, 14.2% and 19.8%. Comparing the CKbr, the contents of WSS, HA and FA for O1 and O2 increased, but relative contents of WSS and FA decreased. The content of the HA increased after

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

    NASA Astrophysics Data System (ADS)

    Dou, S.

    2009-04-01

    The humified SOM or humic substances (HS) composed of humic acid (HA), fulvic acid (FA) and humin (HM) represent the most microbially recalcitrant and stable reservoir of organic carbon in soil (Piccolo et al., 2004). OM applications can influence the amount and structural characteristics of HS(Dou et al., 2008). During the past few decades, there has been much research on HS, but their chemical structure is still not fully understood (Dong, 2006).CP-MAS-13C-NMR spectroscopy was considered as an effective method to study structures of HS without dissolving problem compared with liquid 13C-NMR (Conte et al., 1997; Dou et al., 2008). It can directly measure the carbon framework and reflect the nature of HS transformation after OM application (Spaccini et al., 2000). For that reason, this method was applied in this study. The objective of this paper was to clarify the effect of long term OM application on the changes of structural characteristics in HAs, which provided new information for improving soil fertility by OM application. The experiment was carried out on a brown soil (Paleudalf in USDA Soil Taxonomy) at Shenyang Agricultural University, Liaoning province, China (N41°48'-E123°25'). The experiment included 3 treatments: zero-treatment (CKbr), and two pig manure (PM) treatments (O1 and O2) at the rates of 0.9 t ha-1 and 1.8 t ha-1 of organic carbon, respectively. The samples of the HA fraction were extracted, separated and purified according to the method described by Dou et al. (1991). Elemental composition, Differential thermal analysis (DTA), -lgK value, FT-IR and CP-MAS- 13C-NMR of HAs were performed. Effects on the contents of orgaic carbon and its composition. The contents of TOC were from 8.77 g kg-1 to 12.25 g kg-1. The relative contents in TOC for WSS, HA, and FA were 6.87%, 14.2% and 19.8%. Comparing the CKbr, the contents of WSS, HA and FA for O1 and O2 increased, but relative contents of WSS and FA decreased. The content of the HA increased after

  9. Solution (31)P NMR Study of the Acid-Catalyzed Formation of a Highly Charged {U24Pp12} Nanocluster, [(UO2)24(O2)24(P2O7)12](48-), and Its Structural Characterization in the Solid State Using Single-Crystal Neutron Diffraction.

    PubMed

    Dembowski, Mateusz; Olds, Travis A; Pellegrini, Kristi L; Hoffmann, Christina; Wang, Xiaoping; Hickam, Sarah; He, Junhong; Oliver, Allen G; Burns, Peter C

    2016-07-13

    The first neutron diffraction study of a single crystal containing uranyl peroxide nanoclusters is reported for pyrophosphate-functionalized Na44K6[(UO2)24(O2)24(P2O7)12][IO3]2·140H2O (1). Relative to earlier X-ray studies, neutron diffraction provides superior information concerning the positions of H atoms and lighter counterions. Hydrogen positions have been assigned and reveal an extensive network of H-bonds; notably, most O atoms present in the anionic cluster accept H-bonds from surrounding H2O molecules, and none of the surface-bound O atoms are protonated. The D4h symmetry of the cage is consistent with the presence of six encapsulated K cations, which appear to stabilize the lower symmetry variant of this cluster. (31)P NMR measurements demonstrate retention of this symmetry in solution, while in situ (31)P NMR studies suggest an acid-catalyzed mechanism for the assembly of 1 across a wide range of pH values. PMID:27322657

  10. Pyridoxal phosphate binding sites are similar in human heme-dependent and yeast heme-independent cystathionine beta-synthases. Evidence from 31P NMR and pulsed EPR spectroscopy that heme and PLP cofactors are not proximal in the human enzyme.

    PubMed

    Kabil, O; Toaka, S; LoBrutto, R; Shoemaker, R; Banerjee, R

    2001-06-01

    Two classes of cystathionine beta-synthases have been identified in eukaryotes, the heme-independent enzyme found in yeast and the heme-dependent form found in mammals. Both classes of enzymes catalyze a pyridoxal phosphate (PLP)-dependent condensation of serine and homocysteine to produce cystathionine. The role of the heme in the human enzyme and its location relative to the PLP in the active site are unknown. (31)P NMR spectroscopy revealed that spin-lattice relaxation rates of the phosphorus nucleus in PLP are similar in both the paramagnetic ferric (T(1) = 6.34 +/- 0.01 s) and the diamagnetic ferrous (T(1) = 5.04 +/- 0.06 s) enzyme, suggesting that the two cofactors are not proximal to each other. This is also supported by pulsed EPR studies that do not provide any evidence for strong or weak coupling between the phosphorus nucleus and the ferric iron. However, the (31)P signal in the reduced enzyme moved from 5.4 to 2.2 ppm, and the line width decreased from 73 to 16 Hz, providing the first structural evidence for transmission to the active site of an oxidation state change in the heme pocket. These results are consistent with a regulatory role for the heme as suggested by previous biochemical studies from our laboratory. The (31)P chemical shifts of the resting forms of the yeast and human enzymes are similar, suggesting that despite the difference in their heme content, the microenvironment of the PLP is similar in the two enzymes. The addition of the substrate, serine, resulted in an upfield shift of the phosphorus resonance in both enzymes, signaling formation of reaction intermediates. The resting enzyme spectra were recovered following addition of excess homocysteine, indicating that both enzymes retained catalytic activity during the course of the NMR experiment. PMID:11278994

  11. 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).

  12. 1H HR-MAS NMR Based Metabolic Profiling of Cells in Response to Treatment with a Hexacationic Ruthenium Metallaprism as Potential Anticancer Drug

    PubMed Central

    Vermathen, Martina; Paul, Lydia E. H.; Diserens, Gaëlle

    2015-01-01

    1H high resolution magic angle spinning (HR-MAS) NMR spectroscopy was applied in combination with multivariate statistical analyses to study the metabolic response of whole cells to the treatment with a hexacationic ruthenium metallaprism [1]6+ as potential anticancer drug. Human ovarian cancer cells (A2780), the corresponding cisplatin resistant cells (A2780cisR), and human embryonic kidney cells (HEK-293) were each incubated for 24 h and 72 h with [1]6+ and compared to untreated cells. Different responses were obtained depending on the cell type and incubation time. Most pronounced changes were found for lipids, choline containing compounds, glutamate and glutathione, nucleotide sugars, lactate, and some amino acids. Possible contributions of these metabolites to physiologic processes are discussed. The time-dependent metabolic response patterns suggest that A2780 cells on one hand and HEK-293 cells and A2780cisR cells on the other hand may follow different cell death pathways and exist in different temporal stages thereof. PMID:26024484

  13. 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.

  14. A (1)H HR-MAS NMR-Based Metabolomic Study for Metabolic Characterization of Rice Grain from Various Oryza sativa L. Cultivars.

    PubMed

    Song, Eun-Hye; Kim, Hyun-Ju; Jeong, Jaesik; Chung, Hyun-Jung; Kim, Han-Yong; Bang, Eunjung; Hong, Young-Shick

    2016-04-20

    Rice grain metabolites are important for better understanding of the plant physiology of various rice cultivars and thus for developing rice cultivars aimed at providing diverse processed products. However, the variation of global metabolites in rice grains has rarely been explored. Here, we report the identification of intra- or intercellular metabolites in rice (Oryza sativa L.) grain powder using a (1)H high-resolution magic angle spinning (HR-MAS) NMR-based metabolomic approach. Compared with nonwaxy rice cultivars, marked accumulation of lipid metabolites such as fatty acids, phospholipids, and glycerophosphocholine in the grains of waxy rice cultivars demonstrated the distinct metabolic regulation and adaptation of each cultivar for effective growth during future germination, which may be reflected by high levels of glutamate, aspartate, asparagine, alanine, and sucrose. Therefore, this study provides important insights into the metabolic variations of diverse rice cultivars and their associations with environmental conditions and genetic backgrounds, with the aim of facilitating efficient development and the improvement of rice grain quality through inbreeding with genetic or chemical modification and mutation. PMID:27030107

  15. A sequential assignment procedure for proteins that have intermediate line widths in MAS NMR spectra: amyloid fibrils of human CA150.WW2.

    PubMed

    Becker, Johanna; Ferguson, Neil; Flinders, Jeremy; van Rossum, Barth-Jan; Fersht, Alan R; Oschkinat, Hartmut

    2008-08-11

    The second WW domain (WW2) of CA150, a human transcriptional activator, forms amyloid fibrils in vitro under physiological conditions. Based on experimental constraints from MAS NMR spectroscopy experiments, alanine scanning and electron microscopy, a structural model of CA150.WW2 amyloid fibrils was calculated earlier. Here, the assignment strategy is presented and suggested as a general approach for proteins that show intermediate line width. The (13)C,(13)C correlation experiments were recorded on fully or partially (13)C-labelled fibrils. The earlier (13)C assignment (26 residues) was extended to 34 of the 40 residues by direct (13)C-excitation experiments by using a deuterated sample that showed strongly improved line width. A 3D HNC-TEDOR (transferred-echo double-resonance) experiment with deuterated CA150.WW2 fibrils yielded 14 amide nitrogen and proton resonance assignments. The obtained chemical shifts were compared with the chemical shifts determined with the natively folded WW domain. TALOS (Torsion angle likelihood obtained from shift and sequence similarity) predictions confirmed that, under physiological conditions, the fibrillar form of CA150.WW2 adopts a significantly different beta structure than the native WW-domain fold. PMID:18642254

  16. 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.

  17. 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

  18. {sup 1}H and {sup 23}Na MAS NMR spectroscopy of cationic species in CO{sub 2} selective alkaline earth metal porous silicoaluminophosphates prepared via liquid and solid state ion exchange

    SciTech Connect

    Arevalo-Hidalgo, Ana G.; Dugar, Sneha; Fu, Riqiang; Hernandez-Maldonado, Arturo J.

    2012-07-15

    The location of extraframework cations in Sr{sup 2+} and Ba{sup 2+} ion-exchanged SAPO-34 was estimated by means of {sup 1}H and {sup 23}Na MAS NMR spectroscopy and spectral deconvolution. Incorporation of the alkaline earth metal cations onto the SAPO framework was achieved via liquid state ion exchange, coupled partial detemplation/solid-state ion exchange, and combination of both techniques. MAS NMR revealed that the level of ion exchange was limited by the presence of protons and sodium cations near hexagonal prisms (site SI), which are relatively difficult to exchange with the alkaline earth metal due to steric and charge repulsion criteria. In addition, the presence of ammonium cations in the supercages facilitated the exchange of otherwise tenacious hydrogen as corroborated by unit cell compositional data as well as enhanced CO{sub 2} adsorption at low partial pressures. The extraframework ammonium species were produced from partial detemplation of the structure-directing agent employed for the SAPO-34 synthesis, tetraethylammonium. - Graphical abstract: MAS NMR was used to elucidate the position the cationic species in alkaline earth metal exchanged silicoaluminophosphates. These species played a significant role during the ion exchange process and, therefore, the materials ultimate CO{sub 2} adsorption performance. Highlights: Black-Right-Pointing-Pointer Location of extraframework Sr{sup 2+} or Ba{sup 2+} cations was estimated by means of {sup 1}H and {sup 23}Na MAS NMR. Black-Right-Pointing-Pointer Level of Sr{sup 2+} or Ba{sup 2+} ion exchange was limited by the presence of protons and sodium cations. Black-Right-Pointing-Pointer Presence of ammonium cations in the supercages facilitated the exchange. Black-Right-Pointing-Pointer Sr{sup 2+} and Ba{sup 2+} ion exchanged SAPOs are outstanding CO{sub 2} adsorbents.

  19. Pseudo-symmetry, rotation- and inversion-twinning of a structure with dinuclear and trinuclear Cd complexes. CP-MAS-NMR and IR spectroscopies characterisation

    NASA Astrophysics Data System (ADS)

    Soudani, Sarra; Zeller, Matthias; Wenger, Emmanuel; Jelsch, Christian; Lefebvre, Frédéric; Nasr, Cherif Ben

    2014-10-01

    The structure of the complex [C18H30Cd3Cl6N18S12·2(C18H30Cd2Cl3N18S12)·CdCl4], or [L6Cd3Cl6·2(L6Cd2Cl3)·CdCl4], with L being 2-amino-5-(methylthio)-1,3,4-thiadiazole, C3H5N3S2, crystallizes in the trigonal polar space group R3. The crystal packing features three chemically distinct cadmium complex species with eight crystallographically independent Cd(II) ions distributed over two types of L ligand complexes with two and three Cd(II) centers, respectively, and a tetrachlorocadmate(II) ion. The coordination environment of the cadmium ions in the dinuclear and trinuclear complexes is a distorted octahedron. The tetrachlorocadmate(II) is disordered around a crystallographic threefold rotation axis, which is, in turn, inducing disorder onto the two methyl-thio groups in closest proximity to a CdCl4 anion. The crystal under investigation was found to be twinned by rotational and inversion merohedry. In the higher symmetry setting, the trinuclear complex would feature exact inversion symmetry, and the two binuclear cationic complexes would be inversion counterparts of each other. The R3bar symmetry is broken by a mismatch of less than 1 Å between one pair of ligands L between the dinuclear cations, which feature slightly different rotational angles around the Cd ion in the otherwise symmetry equivalent complexes. This compound is also investigated by FT-IR and solid-state 13CCP-MAS NMR spectroscopies.

  20. Direct and simultaneous quantification of ATP, ADP and AMP by (1)H and (31)P Nuclear Magnetic Resonance spectroscopy.

    PubMed

    Lian, Yakun; Jiang, Hua; Feng, Jinzhou; Wang, Xiaoyan; Hou, Xiandeng; Deng, Pengchi

    2016-04-01

    ATP, ADP and AMP are energy substances with vital biological significance. Based on the structural differences, a simple, rapid and comprehensive method has been established by (1)H and (31)P Nuclear Magnetic Resonance ((1)H-NMR and (31)P-NMR) spectroscopies. Sodium 3-(trimethylsilyl) propionate-2,2,3,3-d4 (TMSP) and anhydrous disodium hydrogen phosphate (Na2HPO4) were selected as internal standards for (1)H-NMR and (31)P-NMR, respectively. Those three compounds and corresponding internal standards can be easily distinguished both by (1)H-NMR and (31)P-NMR. In addition, they all have perfect linearity in a certain range: 0.1-100mM for (1)H-NMR and 1-75mM for (31)P-NMR. To validate the precision of this method, mixed samples of different concentrations were measured. Recovery experiments were conducted in serum (91-113% by (1)H-NMR and 89-113% by (31)P-NMR). PMID:26838434

  1. Direct observation of ¹⁷O-¹⁸⁵/¹⁸⁷Re ¹J-coupling in perrhenates by solid-state ¹⁷O VT MAS NMR: temperature and self-decoupling effects.

    PubMed

    Jakobsen, Hans J; Bildsøe, Henrik; Brorson, Michael; Gan, Zhehong; Hung, Ivan

    2013-05-01

    (17)O MAS NMR spectra recorded at 14.1T and room temperature (RT) for (17)O-enriched samples of the two perrhenates, KReO4 and NH4ReO4, exhibit very similar overall appearances of the manifold of spinning sidebands (ssbs) for the satellite transitions (STs) and the central transition (CT). These overall appearances of the spectra are easily simulated in terms of the usual quadrupole coupling and chemical shift interaction parameters. However, a detailed inspection of the line shapes for the individual ssbs of the STs and, in particular, for the CT in the spectrum of KReO4 reveals line-shape features, which to our knowledge have not before been observed experimentally in 1D MAS NMR spectra for any quadrupolar nucleus, nor emerged from simulations for any combination of second-order quadrupolar interaction and chemical shift anisotropy. In contrast, such line-shape features are not observed for the corresponding ssbs (STs and CT) in the 14.1T RT (17)O MAS NMR spectrum of NH4ReO4. Considering the additional interaction of a combination of residual heteronuclear (17)O-(185/)(187)Re dipolar and scalar J coupling between this spin pair of two quadrupolar nuclei, spectral simulations for KReO4 show that these interactions are able to account for the observed line shapes, although the expected (1)J((17)O-(185/)(187)Re) six-line spin-spin splittings are not resolved. Low-temperature, high-field (21.1T) (17)O VT MAS NMR spectra of both KReO4 and NH4ReO4 show that full resolution into six-line multiplets for the centerbands are achieved at -90°C and -138°C, respectively. This allows determination of (1)J((17)O-(187)Re)=-268Hz and -278Hz for KReO4 and NH4ReO4, respectively, i.e., an isotropic (1)J coupling and its sign between two quadrupolar nuclei, observed for the first time directly from solid-state one-pulse 1D MAS NMR spectra, without resort to additional 1D or 2D experiments. Determination of T1((187)Re) spin-lattice relaxation times, observed indirectly through a 2D

  2. Investigation of relative metabolic changes in the organs and plasma of rats exposed to X-ray radiation using HR-MAS (1) H NMR and solution (1) H NMR.

    PubMed

    Jang, Won Gyo; Park, Ju Yeon; Lee, Jueun; Bang, Eunjung; Kim, So Ra; Lee, Eun Kyeong; Yun, Hyun Jin; Kang, Chang-Mo; Hwang, Geum-Sook

    2016-04-01

    Excess exposure to ionizing radiation generates reactive oxygen species and increases the cellular inflammatory response by modifying various metabolic pathways. However, an investigation of metabolic perturbations and organ-specific responses based on the amount of radiation during the acute phase has not been conducted. In this study, high-resolution magic-angle-spinning (HR-MAS) NMR and solution NMR-based metabolic profiling were used to investigate dose-dependent metabolic changes in multiple organs and tissues - including the jejunum, spleen, liver, and plasma - of rats exposed to X-ray radiation. The organs, tissues, and blood samples were obtained 24, 48, and 72 h after exposure to low-dose (2 Gy) and high-dose (6 Gy) X-ray radiation and subjected to metabolite profiling and multivariate analyses. The results showed the time course of the metabolic responses, and many significant changes were detected in the high-dose compared with the low-dose group. Metabolites with antioxidant properties showed acute responses in the jejunum and spleen after radiation exposure. The levels of metabolites related to lipid and protein metabolism were decreased in the jejunum. In addition, amino acid levels increased consistently at all post-irradiation time points as a consequence of activated protein breakdown. Consistent with these changes, plasma levels of tricarboxylic acid cycle intermediate metabolites decreased. The liver did not appear to undergo remarkable metabolic changes after radiation exposure. These results may provide insight into the major metabolic perturbations and mechanisms of the biological systems in response to pathophysiological damage caused by X-ray radiation. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26871685

  3. Modification of olefin polymerization catalysts. III. A sup 13 C CP-MAS NMR study of adsorption of silyl ethers on MgCl sub 2 -supported Ziegler-Natta catalysts

    SciTech Connect

    Pakkanen, T.T.; Vaehaesarja, E.; Pakkanen, T.A. ); Iiskola, E.; Sormunen, P. )

    1990-02-01

    A {sup 13}C CP-MAS NMR and elemental analysis study of adsorption and interaction of silyl ethers, RSi(OMe){sub 3} (R = Et, Ph, OMe), as internal and external electron donors with MgCl{sub 2}-supported Ziegler-Natta catalyst has been carried out. A chemical activation of anhydrous MgCl{sub 2} with EtOH and AlEt{sub 3} produces a high-surface-area support stabilized by an organoaluminum compound, AlEt{sub 2}(OEt). In a treatment of the aluminum-modified MgCl{sub 2} support with silyl ether, the aluminum surface complex is retained and silyl ether is almost totally incorporated into the support. {sup 13}C CP-MAS NMR data of the methoxy region indicate that a mobile liquid-like silyl ether species dominates, except in the case of Si(OMe){sub 4}, where a more strongly bound species is also present on the support. TiCl{sub 4} treatment removes the weakly adsorbed silyl ether species, leaving a species which is attributed to an aluminum-bound silyl ether surface complex. No evidence of titanium-bound silyl ether species was found in the solid state or in solution where TiCl{sub 4} undergoes with silyl ethers an exchange reaction forming a yellow solid identified as (TiCl{sub 2}(OMe){sub 2}){sub x}. Activation of the catalyst with AlEt{sub 3} at a high Al:Ti ratio produces a material with a low silyl ether coverage showing a weak methoxy signal in {sup 13}C CP-MAS. The linewidths of the observed signals in {sup 13}C CP-MAS NMR are in the range 5-10 ppm at every stage of preparation of the catalyst, indicating heterogeneity of the coordination sites on the surface of chemically activated MgCl{sub 2}.

  4. Phosphorus speciation by (31)P NMR spectroscopy in bracken (Pteridium aquilinum (L.) Kuhn) and bluebell (Hyacinthoides non-scripta (L.) Chouard ex Rothm.) dominated semi-natural upland soil.

    PubMed

    Ebuele, Victor O; Santoro, Anna; Thoss, Vera

    2016-10-01

    Access to P species is a driver for plant community composition based on nutrient acquisition. Here we investigated the distribution and accumulation of soil inorganic P (Pi) and organic P (Po) forms in a bracken and bluebell dominated upland soil for the period between bluebell above ground dominance until biomass is formed from half bluebells and half bracken. Chemical characterisation and (31)P Nuclear Magnetic Resonance spectroscopy was used to determine the organic and inorganic P species. Total P concentration in soils was 0.87gkg(-1), while in plants (above- and below-ground parts) total P ranged between 0.84-4.0gkg(-1) and 0.14-2.0gkg(-1) for bluebell and bracken, respectively. The P speciation in the plant samples was reflected in the surrounding soil. The main forms of inorganic P detected in the NaOH-EDTA soil extracts were orthophosphate (20.0-31.5%), pyrophosphate (0.6-2.5%) and polyphosphate (0.4-7.0%). Phytate (myo-IP6) was the most dominant organic P form (23.6-40.0%). Other major peaks were scyllo-IP6 and α- and β- glycerophosphate (glyP). In bluebells and bracken the main P form detected was orthophosphate ranging from (21.7-80.4%) and 68.5-81.1%, in above-ground and below-ground biomass, respectively. Other detected forms include α-glyP (4.5-14.4%) and β-glyP (0.9-7.7%) in bluebell, while in bracken they were detected only in stripe and blade in ranges of 2.5-5.5% and 4.4-9.6%, respectively. Pyrophosphate, polyphosphate, scyllo-IP6, phosphonates, found in soil samples, were not detected in any plant parts. In particular, the high abundance of phytate in the soil and in bluebell bulbs, may be related to a mechanism through which bluebells create a recalcitrant phosphorus store which form a key part of their adaptation to nutrient poor conditions. PMID:27288285

  5. 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.

  6. Nuclear magnetic resonance characterization of a paramagnetic DNA-drug complex with high spin cobalt; assignment of the 1H and 31P NMR spectra, and determination of electronic, spectroscopic and molecular properties.

    PubMed

    Gochin, M

    1998-08-01

    The proton NMR spectrum of the ternary complex between the octamer duplex d(TTGGCCAA)2, two molecules of the drug chromomycin-A3, and a divalent cobalt ion has been assigned. Assignment procedures used standard two-dimensional techniques and relied upon the expected NOE contacts observed in the equivalent diamagnetic complex containing zinc. The magnetic susceptibility tensor for the cobalt was determined and used to calculate shifts for all nuclei, aiding in the assignment process and verification. Relaxation, susceptibility, temperature and field dependence studies of the paramagnetic spectrum enabled determination of electronic properties of the octahedral cobalt complex. The electronic relaxation tau(s) was determined to be 2.5 +/- 1.5 ps; the effective isotropic g value was found to be 2.6 +/- 0.2, indicating strong spin-orbit coupling. The magnetic susceptibility tensor was determined to be chi(xx) = 8.9 x 10(-3) cm3/mol, chi(yy) = 9.5 x 10(-3) cm3/mol, chi(zz) = 12.8 * 10(-3) cm3/mol. A tentative rotational correlation time of 8 ns was obtained for the complex. Both macroscopic and microscopic susceptibility measurements revealed deviations from Curie behavior over the temperature range accessible in the study. Non-selective relaxation rates were found to be inaccurate for defining distances from the metal center. However, pseudocontact shifts could be calculated with high accuracy using the dipolar shift equation. Isotropic hyperfine shifts were factored into contact and dipolar terms, revealing that the dipolar shift predominates and that contact shifts are relatively small. PMID:9751997

  7. 31P NMR studies of enzyme-bound substrate complexes of yeast 3-phosphoglycerate kinase: III. Two ADP binding sites and their Mg(II) affinity; effects of vanadate and arsenate on enzymic complexes with ADP and 3-P-glycerate.

    PubMed

    Ray, B D; Moore, J M; Rao, B D

    1990-09-01

    31P nuclear magnetic resonance (NMR) measurements (at 121.5 MHz and 5 degrees C) were made on complexes of 3-phosphoglycerate kinase with ADP and 3-P-glycerate. Addition of Mg(II) to E.ADP shifts the alpha-P signal downfield by 3.8 ppm such that the alpha-P signal superimposes that for beta-P(E.MgADP). Such a shift is atypical among the Mg(II)-nucleotide complexes with other ATP-utilizing enzymes. This shift allowed the determination that enzyme bound ADP is saturated with Mg(II) for [Mg(II)]/[ADP] = 3.0--similar to that reported for ATP complexes with this enzyme (B.D. Ray and B.D. Nageswara Rao, Biochemistry 27, 5574 (1988]. This parallel behavior suggests that ADP binds at two sites on the enzyme as does ATP with disparate Mg(II) affinities. 31P relaxation times in E.MnADP.vanadate.3-P-glycerate and E.CoADP.vanadate.3-P-glycerate complexes indicate that these are long-lived, tightly bound complexes. 31P chemical shift measurements on diamagnetic complexes (with Mg(II] revealed three signals in the 2-5 ppm region (attributable to 3-P-glycerate) only upon addition of all the components necessary to form the E.MgADP.vanadate.3-P-glycerate complex. Subsequent sequestration of Mg(II) from the complex with excess EDTA reversed the Mg(II) induced effects on the ADP signals but did not cause coalescence of the three signals seen in the 2-5 ppm region. Addition of excess sulfate to dissociate these complexes from the enzyme resulted in a single resonance of 3-P-glycerate. The use of arsenate in place of vanadate yielded very similar results. These results suggest that, in the presence of MgADP, vanadate or arsenate, and 3-P-glycerate, the enzyme catalyzed the formation of multiple structurally distinguishable complexes that are stable on the enzyme and labile off the enzyme. PMID:2283509

  8. Efficient and facile Ar-Si bond cleavage by montmorillonite KSF: synthetic and mechanistic aspects of solvent-free protodesilylation studied by solution and solid-state MAS NMR.

    PubMed

    Zafrani, Yossi; Gershonov, Eytan; Columbus, Ishay

    2007-08-31

    A facile and efficient method for the cleavage of the Ar-Si bond of various aryl trimethyl silanes is described. When adsorbed on montmorillonite KSF (mont KSF), these arylsilanes readily undergo a solvent-free protodesilylation to the corresponding arenes at room temperature in excellent yields. This approach seems to be superior to the traditional mild methods (i.e., desilylation by TFA, TBAF, CsF), in terms of reaction yield, rate, and environmentally benign conditions. Some mechanistic studies using both solution and solid-state magic-angle spinning (SS MAS) (1)H NMR are also presented. PMID:17676903

  9. Feasibility Evaluation of Detecting Hydroxymethylphosphine Oxide In Vivo by (31)P-MRS.

    PubMed

    Doblas, Sabrina; Pathuri, Gopal; Towner, Rheal A; Gali, Hariprasad

    2010-09-01

    Application of organophosphorus compounds in biomedicine is attractive because the (31)P nucleus is very amenable to study by nuclear magnetic resonance (NMR) techniques, particularly, by in vivo (31)P magnetic resonance spectroscopy ((31)P-MRS). The water-soluble organophosphorus compounds that are non-toxic, exhibit metabolic stability, and show a unique resonance peak in (31)P NMR spectroscopy, which could be ideal to be used as probes for (31)P-MRS. Here we evaluated the in vivo feasibility of potentially using a hydroxymethylphosphine oxide as a novel probe for (31)P-MRS studies using tris (hydroxymethyl) phosphine oxide (THPO) as an example. THPO was synthesized, injected in the normal CF1 mice, and (31)P spectra were acquired before and after injection with the coil located on the regions of interest. The NMR signal from the region of interest appeared within one minute of THPO injection. The compound was stable in vivo as no metabolites of THPO were observed. No toxicity was observed after THPO injection in mice. The peak concentrations of THPO in liver and kidney were reached within 15 min and 60 min respectively. THPO was excreted exclusively in urine without undergoing any metabolism indicating that it is very stable under in vivo conditions. These initial studies in normal CF1 mice clearly demonstrate that THPO possess the essential characteristics required for a potential MRS probe. Based on the current preliminary results, we suggest that HMPs, when incorporated into targeted drugs (peptides, proteins, antibodies, etc.), may serve as novel (31)P probes for monitoring the drug distribution in vivo by MRS. PMID:23675197

  10. Monitoring changes of paramagnetically-shifted 31P signals in phospholipid vesicles

    NASA Astrophysics Data System (ADS)

    Joyce, Rebecca E.; Williams, Thomas L.; Serpell, Louise C.; Day, Iain J.

    2016-03-01

    Phospholipid vesicles are commonly used as biomimetics in the investigation of the interaction of various species with cell membranes. In this letter we present a 31P NMR investigation of a simple vesicle system using a paramagnetic shift reagent to probe the inner and outer layers of the lipid bilayer. Time-dependent changes in the 31P NMR signal are observed, which differ whether the paramagnetic species is inside or outside the vesicle, and on the choice of buffer solution used. An interpretation of these results is given in terms of the interaction of the paramagnetic shift reagent with the lipids.

  11. Posttranslational modification of Klebsiella pneumoniae flavodoxin by covalent attachment of coenzyme A, shown by sup 31 P NMR and electrospray mass spectrometry, prevents electron transfer from the nifJ protein to nitrogenase. A possible new regulatory mechanism for biological nitrogen fixation

    SciTech Connect

    Thorneley, R.N.F.; Ashby, G.A.; Drummond, M.H.; Eady, R.R.; Huff, S.; Macdonald, C.J. ); Abell, C.; Schneier, A. )

    1992-02-04

    A strain of Escherichia coli (71-18) that produces ca. 15% of its soluble cytoplasmic protein as a flavodoxin, the Klebsiella pneumoniae nifF gene product, has been constructed. The flavodoxin was purified using FPLC and resolved into two forms, designated KpFldI and KpFldII, which were shown to have identical N-terminal amino acid sequences (30 residues) in agreement with that predicted by the K. pneumoniae nifF DNA sequence. {sup 31}P NMR, electrospray mass spectrometry, UV-visible spectra, and thiol group estimations showed that the single cysteine residue (position 68) of KpFldI is posttranslationally modified in KpFldII by the covalent, mixed disulfide, attachment of coenzyme A. KpFldII was inactive as an electron carrier between the K. pneumoniae nifJ product (a pyruvate-flavodoxin oxidoreductase) and K. pneumoniae nifH product (the Fe-protein of nitrogenase). This novel posttranslational modification of a flavodoxin is discussed in terms of the regulation of nitrogenase activity in vivo in response to the level of dissolved O{sub 2} and the carbon status of diazotrophic cultures.

  12. Compatibility of Superparamagnetic Iron Oxide Nanoparticle Labeling for 1H MRI Cell Tracking with 31P MRS for Bioenergetic Measurements

    PubMed Central

    Zhang, Zhuoli; Hancock, Brynne; Leen, Stephanie; Ramaswamy, Sharan; Sollott, Steven J.; Boheler, Kenneth R.; Juhaszova, Magdalena; Lakatta, Edward G.; Spencer, Richard G.; Fishbein, Kenneth W.

    2011-01-01

    Labeling of cells with superparamagnetic iron oxide nanoparticles permits cell tracking by 1H MRI while 31P MRS allows non-invasive evaluation of cellular bioenergetics. We evaluated the compatibility of these two techniques by obtaining 31P NMR spectra of iron-labeled and unlabeled immobilized C2C12 myoblast cells in vitro. Broadened but usable 31P spectra were obtained, and peak area ratios of resonances corresponding to intracellular metabolites showed no significant differences between labeled and unlabeled cell populations. We conclude that 31P NMR spectra can be obtained from cells labeled with sufficient iron to permit visualization by 1H imaging protocols and that these spectra have sufficient quality to be used in assessing metabolic status. This result introduces the possibility of using localized 31P MRS to evaluate the viability of iron-labeled therapeutic cells as well as surrounding host tissue in vivo. PMID:20853523

  13. New adamantane-like mercury-chalcogen cages. Synthetic and multinuclear (/sup 31/P, /sup 77/Se, /sup 199/Hg) NMR study of ((. mu. -ER)/sub 6/(HgL)/sub 4/)/sup 2 +/ (E = S or Se; L = tertiary phosphine or arsine) and related species with mixed ligands

    SciTech Connect

    Dean, P.A.W.; Vittal, J.J.; Trattner, M.H.

    1987-12-16

    Reaction between HgL/sub 2/(ClO/sub 4/)/sub 2/, Hg(ER)/sub 2/, and L in a 1:3:2 ratio produces the isolable salts ((..mu..-ER)/sub 6/(HgL)/sub 4/)(ClO/sub 4/)/sub 2/ (L = PPh/sub 3/, ER = SePh, SPh, SMe, or SEt; L = AsPh/sub 3/, ER = SPh; L = PEt/sub 3/, ER = SePh or SPh). Multinuclear (/sup 31/P, /sup 77/Se, /sup 199/Hg) NMR was used to demonstrate the adamantanoid structure of the cations in these salts as well as in those with L = PPh/sub 3/ and ER = S-n-Pr, S-n-Bu, or S-n-C/sub 5/H/sub 11/, which were studied in situ. To confirm that the new cations contain the hitherto unobserved (..mu..-ER)/sub 6/Hg/sub 4/ core, several series of clusters with mixed ligands were investigated (as ClO/sub 4//sup -/ salts) by the multinuclear NMR technique also. The systems ((..mu..-ER)/sub 6/(HgL)/sub 4/)/sup 2 +/-((..mu..-ER)/sub 6/(HgL')/sub 4/)/sup 2 +/ (ER = SePh, L = PPh/sub 3/, L' = PEt/sub 3/; ER = SPh, L = PPh/sub 3/, L' = PEt/sub 3/ or AsPh/sub 3/) give the series ((..mu..-ER)/sub 6/(HgL)/sub 4-n/(HgL')/sub n/)/sup 2 +/ (n = 0-4). The related species ((..mu..-SPh)/sub 6/(HgPPh/sub 3/)/sub 4-n/(HgSbPh/sub 3/)/sub n/)/sup 2 +/ (n = 0-2 and possibly 3) were produced from Hg(PPhh/sub 3/)/sub 2/(ClO/sub 4/)/sub 2/, Hg(SPh)/sub 2/, and SbPh/sub 3/. From the notably rich /sup 31/P and /sup 199/Hg NMR spectra of the system ((..mu..-SPh)/sub 6/(HgPPh/sub 3/)/sub 4/)/sup 2 +/-((..mu..-SePh)/sub 6/(HgPPh/sub 3/)/sub 4/)/sup 2 +/ it was possible to demonstrate the existence of every possible mixed-chalcogen core in the series ((..mu..-SPh)/sub 6-m/(..mu..-SePh)/sub m/(HgPPh/sub 3/)/sub 4/)/sup 2 +/ (m = 0-6). The new (..mu..-SR)/sub 6/Hg/sub 4/ cages are possible models for the proposed Hg/sub 4/(Cys)/sub 11/ cluster in Hg/sub 7/-metallothionein. 46 references, 3 figures, 2 tables.

  14. Solid-State NMR Characterization of Mixed Phosphonic Acid Ligand Binding and Organization on Silica Nanoparticles.

    PubMed

    Davidowski, Stephen K; Holland, Gregory P

    2016-04-01

    As ligand functionalization of nanomaterials becomes more complex, methods to characterize the organization of multiple ligands on surfaces is required. In an effort to further the understanding of ligand-surface interactions, a combination of multinuclear ((1)H, (29)Si, (31)P) and multidimensional solid-state nuclear magnetic resonance (NMR) techniques was utilized to characterize the phosphonic acid functionalization of fumed silica nanoparticles using methylphosphonic acid (MPA) and phenylphosphonic acid (PPA). (1)H → (29)Si cross-polarization (CP)-magic angle spinning (MAS) solid-state NMR was used to selectively detect silicon atoms near hydrogen atoms (primarily surface species); these results indicate that geminal silanols are preferentially depleted during the functionalization with phosphonic acids. (1)H → (31)P CP-MAS solid-state NMR measurements on the functionalized silica nanoparticles show three distinct resonances shifted upfield (lower ppm) and broadened compared to the resonances of the crystalline ligands. Quantitative (31)P MAS solid-state NMR measurements indicate that ligands favor a monodentate binding mode. When fumed silica nanoparticles were functionalized with an equal molar ratio of MPA and PPA, the MPA bound the nanoparticle surface preferentially. Cross-peaks apparent in the 2D (1)H exchange spectroscopy (EXSY) NMR measurements of the multiligand sample at short mixing times indicate that the MPA and PPA are spatially close (≤5 Å) on the surface of the nanostructure. Furthermore, (1)H-(1)H double quantum-single quantum (DQ-SQ) back-to-back (BABA) 2D NMR spectra further confirmed that MPA and PPA are strongly dipolar coupled with observation of DQ intermolecular contacts between the ligands. DQ experimental buildup curves and simulations indicate that the average distance between MPA and PPA is no further than 4.2 ± 0.2 Å. PMID:26914738

  15. Solid-state NMR investigations of bulk and nanocrystalline indium phosphide

    NASA Astrophysics Data System (ADS)

    de Graw, David Thomas

    Second-rank indirect couplings in bulk InP. The heteronuclear J-coupling tensor between nearest neighbor 31P and 113In spins in undoped InP is investigated by means of 113 In → 31P polarization transfer under rapid magic angle spinning (MAS). The scalar contribution can be measured directly and is found to have the value |Jiso(31 P-113,115In)| = (225 +/- 10) Hz. The principal value of the traceless anisotropic J-coupling tensor (pseudodipolar coupling) is determined to be Janiso(31P- 113,115In) = 2/3(J∥|(31P- 113,115In)-J⊥(31P- 113,115In)) = (813 +/- 50) Hz or (1733 +/- 50) Hz, assuming axial symmetry with the principal axis parallel to the In-P bond. Our values deviate from those reported previously (Phys. Rev. B 5, 3395, 1972), (based on a moment analysis of the 31P resonance |J iso(31P-113,115In)| = 350 Hz and Janiso(31P-113,115 In) = 1273 Hz), but confirm the that the nearest neighbor 31P-113,115In magnetic dipolar and pseudodipolar interactions are of the same order of magnitude and partially cancel each other out. Surface structure and size effects in nanocrystalline InP. The assignment of 31P NMR spectra on trioctylphosphine oxide (TOPO) passivated InP quantum dots is made using 2D correlation and multinuclear (1H → 13C → 31P) polarization transfer techniques. The spectra show distinct surface-capping sites as well as two crystallite In31P surface components, implying a manifold of crystal-ligand bonding configurations and electronic environments. In a previous NMR study (Phys. Rev. Lett. 60, 2673, 1988) on Cd 77Se nanocrystals it was shown that the first moment of the resonance line showed an upfield shift with decreasing particle size. However, the resonance line also displayed a significant amount of inhomogeneous broadening. We have shown that with decreasing size, the nanocrystal core resonance displays an increasing upfield chemical shift related to the overall size dependence of the InP electronic structure.

  16. The Local Structural State of Aluminosilicate Garnet Solid Solutions: An Investigation of Grospydite Garnet from the Roberts Victor Kimberlite Using Paramagnetically Shifted 27Al and 29Si MAS NMR Resonances

    NASA Astrophysics Data System (ADS)

    Geiger, C. A.; Palke, A. C.; Stebbins, J. F.

    2014-12-01

    Most rock-forming silicates are substitutional solid solutions. Over the years extensive research has been done to determine their structural and crystal chemical properties. Here, the distribution of cations, or order-disorder behavior, is of central importance. In the case of aluminosilicate garnet solid solutions (X3Al2Si3O12 with X = Mg, Fe2+, Mn2+ and Ca) it has been shown that both synthetic and natural crystals have random long-range X-cation disorder in space group Ia-3d, as given by X-ray single-crystal diffraction measurements. However, the structural state of natural garnets at the local scale is not known. Garnet from a grospydite xenolith from the Roberts Victor kimberlite, South Africa, was studied by 27Al and 29Si MAS NMR spectroscopy. The research thrust was placed on measuring and analyzing paramagnetically shifted resonances to determine the local (short range) structural state of the X-cations in a grossular-rich ternary aluminosilicate garnet solid solution. The garnet crystals are compositionally homogeneous based on microprobe analysis, showing no measurable zoning, and have the formula Grs46.7Prp30.0Alm23.3. The garnet is cubic with the standard garnet space group Ia-3d. The 27Al MAS NMR spectrum shows a very broad asymmetric resonance located between about 100 and -50 ppm. It consists of a number of individual overlapping paramagnetically shifted resonances, which are difficult to analyze quantitatively. The 29Si MAS NMR spectrum, showing better resolution, has two observable resonances termed S0 and S4. S0 is located between about -60 ppm and -160 ppm and S4 is centered at roughly 95 ppm. Both S0 and S4 are composite resonances in nature containing many overlapping individual peaks. S0 contains information on local cation configurations whereby an isolated SiO4 group in the garnet structure does not have an edge-shared Fe2+-containing dodecahedron. S4 involves local configurations where there is one edge-shared dodecahedron containing Fe2

  17. 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

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

    PubMed

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

    2016-09-14

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

  19. 13C and 15N—Chemical Shift Anisotropy of Ampicillin and Penicillin-V Studied by 2D-PASS and CP/MAS NMR

    NASA Astrophysics Data System (ADS)

    Antzutkin, Oleg N.; Lee, Young K.; Levitt, Malcolm H.

    1998-11-01

    The principal values of the chemical shift tensors of all13C and15N sites in two antibiotics, ampicillin and penicillin-V, were determined by 2-dimensionalphaseadjustedspinningsideband (2D-PASS) and conventional CP/MAS experiments. The13C and15N chemical shift anisotropies (CSA), and their confidence limits, were evaluated using a Mathematica program. The CSA values suggest a revised assignment of the 2-methyl13C sites in the case of ampicillin. We speculate on a relationship between the chemical shift principal values of many of the13C and15N sites and the β-lactam ring conformation.

  20. 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).

  1. Characterization of the wound-induced material in Citrus paradisi fruit peel by carbon-13 CP-MAS solid state NMR spectroscopy.

    PubMed

    Lai, Simona; Lai, Adolfo; Stange, Richard R; McCollum, T Greg; Schirra, Mario

    2003-05-01

    Grapefruit, Citrus paradisi, were injured, inoculated with Penicillium digitatum and incubated under conditions favourable for the accumulation of defence related material. Histochemical examination revealed that tissues adjacent to inoculated injuries contained phloroglucinol-HCl (PG-HCl) reactive material. Solvent washed cell wall preparations of intact and injured-inoculated peel were further purified using a mixture of cell wall degrading enzymes. Samples from injured inoculated tissue contained PG-HCl reactive globular material in addition to the fragments of xylem and cuticle found in controls. The principal chemical moieties of the material that accumulates in grapefruit injuries during wound-healing were studied by solid state 13C cross-polarization magic angle spinning NMR. A complete assignment of the NMR signals was made. From the analysis evidence was found that cellulose and hemicellulose are the biopolymers present in the intact peel samples, in addition, relevant quantities of cutin were found in the residues of enzyme digest. The NMR difference spectrum intact- wounded peels showed resonances which were attributed to all major functional groups of the aromatic-aliphatic suberin polyester of new material produced by the wounds. Information on the latter polyester was obtained by analyzing the T(1)rho (1H) relaxation. PMID:12711139

  2. Interface Induced Growth and Transformation of Polymer-Conjugated Proto-Crystalline Phases in Aluminosilicate Hybrids: A Multiple-Quantum (23)Na-(23)Na MAS NMR Correlation Spectroscopy Study.

    PubMed

    Brus, Jiri; Kobera, Libor; Urbanova, Martina; Doušová, Barbora; Lhotka, Miloslav; Koloušek, David; Kotek, Jiří; Čuba, Pavel; Czernek, Jiri; Dědeček, Jiří

    2016-03-22

    Nanostructured materials typically offer enhanced physicochemical properties because of their large interfacial area. In this contribution, we present a comprehensive structural characterization of aluminosilicate hybrids with polymer-conjugated nanosized zeolites specifically grown at the organic-inorganic interface. The inorganic amorphous Al-O-Si framework is formed by alkali-activated low-temperature transformation of metakaoline, whereas simultaneous copolymerization of organic comonomers creates a secondary epoxide network covalently bound to the aluminosilicate matrix. This secondary epoxide phase not only enhances the mechanical integrity of the resulting hybrids but also introduces additional binding sites accessible for compensating negative charge on the aluminosilicate framework. This way, the polymer network initiates growth and subsequent transformation of protocrystalline short-range ordered zeolite domains that are located at the organic-inorganic interface. By applying an experimental approach based on 2D (23)Na-(23)Na double-quantum (DQ) MAS NMR spectroscopy, we discovered multiple sodium binding sites in these protocrystalline domains, in which immobilized Na(+) ions form pairs or small clusters. It is further demonstrated that these sites, the local geometry of which allows for the pairing of sodium ions, are preferentially occupied by Pb(2+) ions during the ion exchange. The proposed synthesis protocol thus allows for the preparation of a novel type of geopolymer hybrids with polymer-conjugated zeolite phases suitable for capturing and storage of metal cations. The demonstrated (23)Na-(23)Na DQ MAS NMR combined with DFT calculations represents a suitable approach for understanding the role of Na(+) ions in aluminositicate solids and related inorganic-organic hybrids, particularly their specific arrangement and clustering at interfacial areas. PMID:26931131

  3. NMR spectroscopic study of organic phosphate esters coprecipitated with calcite

    NASA Astrophysics Data System (ADS)

    Phillips, Brian L.; Zhang, Zelong; Kubista, Laura; Frisia, Silvia; Borsato, Andrea

    2016-06-01

    Organic phosphorus incorporated in calcite during laboratory precipitation experiments and in natural cave deposits was investigated by solid-state NMR spectroscopy. For calcite precipitated in the presence of organic phosphoesters of varying size and functionality, solid-state 31P{1H} CP/MAS NMR shows that the phosphoesters were incorporated intact into the solid. Systematic changes in the 31P NMR chemical shift of the phosphate group were observed between the solid phosphoester and that incorporated in the solid precipitate, yielding 31P NMR chemical shifts of the coprecipitates in the range of +1.8 to -2.2 ppm. These chemical shifts are distinct from that of similarly prepared calcite coprecipitated with inorganic phosphate, 3.5 ppm. Only minor changes were noted in the phosphoester 31P chemical shift anisotropy (CSA) which suggests no significant change in the local structure of the phosphate group, which is dominated by C-O-P bonding. Close spatial proximity of the organic phosphate group to calcite structural components was revealed by 31P/13C rotational echo double resonance (REDOR) experiments for coprecipitates prepared with 13C-labeled carbonate. All coprecipitates showed significant 31P dephasing effects upon 13C-irradiation, signaling atomic-scale proximity to carbonate carbon. The dephasing rate for smaller organophosphate molecules is similar to that observed for inorganic phosphate, whereas much slower dephasing was observed for larger molecules having long and/or bulky side-chains. This result suggests that small organic molecules can be tightly enclosed within the calcite structure, whereas significant structural disruption required to accommodate the larger organic molecules leads to longer phosphate-carbonate distances. Comparison of 31P NMR spectroscopic data from the synthetic coprecipitates with those from calcite moonmilk speleothems indicates that phosphorus occurs mainly as inorganic orthophosphate in the natural deposits, although small

  4. Carbonation of C–S–H and C–A–S–H samples studied by {sup 13}C, {sup 27}Al and {sup 29}Si MAS NMR spectroscopy

    SciTech Connect

    Sevelsted, Tine F.; Skibsted, Jørgen

    2015-05-15

    Synthesized calcium silicate hydrate (C–S–H) samples with Ca/Si ratios of 0.66, 1.0, and 1.5 have been exposed to atmospheric CO{sub 2} at room temperature and high relative humidity and studied after one to 12 weeks. {sup 29}Si NMR reveals that the decomposition of C–S–H caused by carbonation involves two steps and that the decomposition rate decreases with increasing Ca/Si ratio. The first step is a gradual decalcification of the C–S–H where calcium is removed from the interlayer and defect sites in the silicate chains until Ca/Si = 0.67 is reached, ideally corresponding to infinite silicate chains. In the seconds step, calcium from the principal layers is consumed, resulting in the final decomposition of the C–S–H and the formation of an amorphous silica phase composed of Q{sup 3} and Q{sup 4} silicate tetrahedra. The amount of solid carbonates and of carbonate ions in a hydrous environment increases with increasing Ca/Si ratio for the C–S–H, as shown by {sup 13}C NMR. For C–A–S–H samples with Ca/Si = 1.0 and 1.5, {sup 27}Al NMR demonstrates that all aluminium sites associated with the C–S–H are consumed during the carbonation reactions and incorporated mainly as tetrahedral Al(–OSi){sub 4} units in the amorphous silica phase. A small amount of penta-coordinated Al sites has also been identified in the silica phase.

  5. Direct Observation of Lattice Aluminum Environments in Li Ion Cathodes LiNi1-y-zCoyAlzO2 and Al-Doped LiNixMnyCozO2 via (27)Al MAS NMR Spectroscopy.

    PubMed

    Dogan, Fulya; Vaughey, John T; Iddir, Hakim; Key, Baris

    2016-07-01

    Direct observations of local lattice aluminum environments have been a major challenge for aluminum-bearing Li ion battery materials, such as LiNi1-y-zCoyAlzO2 (NCA) and aluminum-doped LiNixMnyCozO2 (NMC). (27)Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy is the only structural probe currently available that can qualitatively and quantitatively characterize lattice and nonlattice (i.e., surface, coatings, segregation, secondary phase etc.) aluminum coordination and provide information that helps discern its effect in the lattice. In the present study, we use NMR to gain new insights into transition metal (TM)-O-Al coordination and evolution of lattice aluminum sites upon cycling. With the aid of first-principles DFT calculations, we show direct evidence of lattice Al sites, nonpreferential Ni/Co-O-Al ordering in NCA, and the lack of bulk lattice aluminum in aluminum-"doped" NMC. Aluminum coordination of the paramagnetic (lattice) and diamagnetic (nonlattice) nature is investigated for Al-doped NMC and NCA. For the latter, the evolution of the lattice site(s) upon cycling is also studied. A clear reordering of lattice aluminum environments due to nickel migration is observed in NCA upon extended cycling. PMID:27299505

  6. Elemental and structural analysis of silicon forms in herbal drugs using silicon-29 MAS NMR and WD-XRF spectroscopic methods.

    PubMed

    Pajchel, L; Nykiel, P; Kolodziejski, W

    2011-12-01

    The objective of this work was to study concentration of silicon and its structural forms present in herbal drugs. Equisetum arvense and Urtica dioica L. from teapot bags, dietary supplements (tablets and capsules) containing those herbs, dry extract obtained from a teapot bag of E. arvense, and samples of the latter herb harvested in wild habitat over four months were studied using wavelength dispersive X-ray spectroscopy (WD-XRF) and high-resolution solid-state (29)Si NMR. The highest concentration of Si, ca. 27mg/g, was found in the herbal material from the teapot bags containing E. arvense. The Si content in natural E. arvense (whole plants) increased from May to August by ca. 7mg/g, reaching value 26mg/g. Three different silicon forms were detected in the studied herbal samples: Si(OSi)4 (Q(4)), Si(OH)(OSi)3 (Q(3)) and Si(OH)2(OSi)2 (Q(2)). Those sites were populated in E. arvense in the following order: Q(4)≫Q(3)>Q(2). A dramatic, ca. 50-fold decrease of the Si concentration during the infusion process was observed. The infusion process and the subsequent drying procedure augmented population of the Q(4) sites at the cost of the Q(2) sites. The WD-XRF and (29)Si NMR methods occurred useful and complementary in the study of herbal materials. PMID:21813258

  7. Correlations between lithium local structure and electrochemistry of layered LiCo(1-2x)Ni(x)Mn(x)O2 oxides: 7Li MAS NMR and EPR studies.

    PubMed

    Stoyanova, Radostina; Ivanova, Svetlana; Zhecheva, Ekaterina; Samoson, Ago; Simova, Svetlana; Tzvetkova, Pavleta; Barra, Anne-Laure

    2014-02-14

    Advanced (7)Li MAS NMR technologies and high frequency EPR are combined to identify structural motifs and their relation to electrochemical properties of layered lithium-cobalt-nickel-manganese oxides LiCo1-2xNixMnxO2 (0 < x ≤ 0.5) used as cathode materials in lithium ion batteries. Structural-chemical shift regularities were established by systematic variation of the ratio of diamagnetic Co(3+) to paramagnetic Ni/Mn ions with variable valences. While EPR allows identifying the oxidation state of transition metal ions inside the layers, (7)Li NMR probes the local structure of Li with respect to transition metal ions located in two adjacent layers. For assignment of the lithium chemical shifts, we examine first magnetically diluted LiCo1-2xNixMnxO2 with x = 0.02, where paramagnetic ions are stabilized only in Mn(4+) and Ni(3+) form. Then the studies are extended towards the intermediate compositions with x = 0.10 and 0.33, containing simultaneously paramagnetic Mn(4+), Ni(3+) and Ni(2+) ions and diamagnetic Co(3+) ions. The benefit of using NMR with ultrafast spinning rates is demonstrated for the end composition LiNi0.5Mn0.5O2 having only paramagnetic Ni(2+) and Mn(2+) ions. The local structure of Li is quantified in respect of the number of Ni(2+) and Mn(4+) neighbors. It has been demonstrated that Ni(2+) and Mn(4+) are non-randomly distributed around Li and their distribution depends on the method of synthesis. The extent of local cationic order and its effect on the electrochemical properties of LiNi0.5Mn0.5O2 are discussed. PMID:24356075

  8. The Amblygonite (LiAlPO{sub 4}F)-Montebrasite (LiAlPO{sub 4}OH) Solid Solution: A Combined powder and single-crystal neutron diffraction and solid-state {sup 6}Li MAS, CP MAS, and REDOR NMR study

    SciTech Connect

    Groat, Lee A.; Chakoumakos, Bryan C.; Brouwer, Darren H.; Hoffman, Christina M.; Fyfe, Colin A.; Morell, Heiko; Schultz, Arthur J.

    2003-01-01

    The amblygonite-montebrasite series of minerals, common constituents of granitic pegmatites and topaz-bearing granites, show complete solid solution with ideal composition LiAlPO{sub 4}(F, OH). These compounds are ideal for studying F {leftrightarrow} OH solid solution in minerals because natural members of the series generally show little deviation from the ideal composition. In this study, we used powder and single-crystal neutron diffraction and solid-state {sup 6}Li MAS, CP MAS, and REDOR NMR techniques to study the effect of F {leftrightarrow} OH substitution on the series. Lattice parameters refined from single-crystal neutron diffraction data show increasing b and decreasing a, c, and V with increasing F/(F + OH). The volume is highest for the OH end-member because of the presence of an additional atom (H). The a and c parameters decrease with increasing F/(F + OH) because the O-H vector is close to the a-c plane and the Al-OH/F vectors are approximately parallel to c. Lattice parameters refined from neutron powder diffraction patterns collected at lower T show that thermal contraction increases with F/(F + OH), presumably because the F anion takes up less space than the OH molecule. The results show that the OH/F position is always fully occupied. The H displacement ellipsoid shows little change with occupancy, which obviously corresponds negatively with increasing F/(F + OH). However, the Li displacement ellipsoid becomes extremely large and anisotropic with increasing F fraction. Most of the distortion is associated with the U{sub 3} eigenvalue, which lies between the c and c* directions. U{sub eq} values corresponding to the Li atom show a greater reduction with decreasing temperature than the other atoms. The temperature dependence of Li is the same regardless of F content. Even when extrapolated to absolute zero the Li displacement ellipsoid is very large, which implies a large static disorder.

  9. MAS NMR Study of the Metastable Solid Solutions Found in the LiFePO4/FePO4 System

    SciTech Connect

    Cabana, Jordi; Shirakawa, Junichi; Chen, Guoying; Richardson, Thomas; Grey, Clare P.

    2009-10-09

    Li and 3IP NMR experiments were conducted on a series of single- or two-phase samples in the LiFePCvFePCM system with different overall lithium contents, and containing the two end-members and/or two metastable solid solution hases, Lio.6FeP04 or Lio.34FeP04. These experiments were carried out at different temperatures in order to search for vacancy/charge ordering and ion/electron mobility in the metastable phases. Evidence for Li+-Fe2+ interactions was bserved for both Lio.6FeP04 and Lio.34FePC>4. The strength of this interaction leads to the formation of LiFePCvlike clusters in the latter, as shown by the room temperature data. Different motional processes are proposed to exist as the temperature is increased and various scenarios are discussed. While concerted lithium-electron hopping and/or correlations explains the data below 125C, evidence for some uncorrelated motion is found at higher temperatures, together with the onset of phase mixing.

  10. 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

  11. Following solid-acid-catalyzed reactions by MAS NMR spectroscopy in liquid phase--zeolite-catalyzed conversion of cyclohexanol in water.

    PubMed

    Vjunov, Aleksei; Hu, Mary Y; Feng, Ju; Camaioni, Donald M; Mei, Donghai; Hu, Jian Z; Zhao, Chen; Lercher, Johannes A

    2014-01-01

    A microautoclave magic angle spinning NMR rotor is developed enabling in situ monitoring of solid-liquid-gas reactions at high temperatures and pressures. It is used in a kinetic and mechanistic study of the reactions of cyclohexanol on zeolite HBEA in 130 °C water. The (13) C spectra show that dehydration of 1-(13) C-cyclohexanol occurs with significant migration of the hydroxy group in cyclohexanol and the double bond in cyclohexene with respect to the (13) C label. A simplified kinetic model shows the E1-type elimination fully accounts for the initial rates of 1-(13) C-cyclohexanol disappearance and the appearance of the differently labeled products, thus suggesting that the cyclohexyl cation undergoes a 1,2-hydride shift competitive with rehydration and deprotonation. Concurrent with the dehydration, trace amounts of dicyclohexyl ether are observed, and in approaching equilibrium, a secondary product, cyclohexyl-1-cyclohexene is formed. Compared to phosphoric acid, HBEA is shown to be a more active catalyst exhibiting a dehydration rate that is 100-fold faster per proton. PMID:24282024

  12. A generalized theoretical framework for the description of spin decoupling in solid-state MAS NMR: Offset effect on decoupling performance.

    PubMed

    Tan, Kong Ooi; Agarwal, Vipin; Meier, Beat H; Ernst, Matthias

    2016-09-01

    We present a generalized theoretical framework that allows the approximate but rapid analysis of residual couplings of arbitrary decoupling sequences in solid-state NMR under magic-angle spinning conditions. It is a generalization of the tri-modal Floquet analysis of TPPM decoupling [Scholz et al., J. Chem. Phys. 130, 114510 (2009)] where three characteristic frequencies are used to describe the pulse sequence. Such an approach can be used to describe arbitrary periodic decoupling sequences that differ only in the magnitude of the Fourier coefficients of the interaction-frame transformation. It allows a ∼100 times faster calculation of second-order residual couplings as a function of pulse sequence parameters than full spin-dynamics simulations. By comparing the theoretical calculations with full numerical simulations, we show the potential of the new approach to examine the performance of decoupling sequences. We exemplify the usefulness of this framework by analyzing the performance of commonly used high-power decoupling sequences and low-power decoupling sequences such as amplitude-modulated XiX (AM-XiX) and its super-cycled variant SC-AM-XiX. In addition, the effect of chemical-shift offset is examined for both high- and low-power decoupling sequences. The results show that the cross-terms between the dipolar couplings are the main contributions to the line broadening when offset is present. We also show that the SC-AM-XIX shows a better offset compensation. PMID:27608994

  13. (29)Si, (47)Ti, (49)Ti and (195)Pt solid state MAS NMR spectroscopic investigations of ternary silicides TPtSi, germanides TPtGe (T = Ti, Zr, Hf) and stannide TiPtSn.

    PubMed

    Benndorf, Christopher; Eckert, Hellmut; Pöttgen, Rainer

    2016-05-10

    Eight ternary tetrelides TPtX (T = Ti, Zr, Hf; X = Si, Ge, Sn) were synthesized from the elements by arc-melting and subsequent annealing. TiPtSi, ZrPtSi, ZrPtGe, HfPtSi and HfPtGe crystallize with the orthorhombic TiNiSi type structure, in the space group Pnma. The structures of HfPtSi (a = 654.44(9), b = 387.97(6), c = 750.0(1) pm, wR2 = 0.0592, 411 F(2) values, 20 variables) and HfPtGe (a = 660.36(7), b = 395.18(4), c = 763.05(8) pm, wR2 = 0.0495, 430 F(2) values, 20 variables) were refined from single crystal X-ray diffractometer data. TiPtSn adopts the cubic MgAgAs type. TiPtGe is dimorphic with a TiNiSi type high-temperature modification which transforms to cubic LT-TiPtGe (MgAgAs type). All phases were investigated by high resolution (29)Si, (47)Ti, (49)Ti and (195)Pt solid state MAS NMR spectroscopy. In the cubic compounds, the (47/49)Ti NMR signals are easily detected owing to the absence of quadrupolar broadening effects. The (195)Pt resonances of the orthorhombic compounds are characterized by strongly negative isotropic Knight shifts and large Knight shift anisotropies, whereas positive isotropic Knight shifts and no anisotropies are observed for the cubic compounds. These results indicate that the phase transition in TiPtGe is associated with dramatic changes in the electronic properties. Within each group of isotypic compounds the isotropic (29)Si, (47/49)Ti and (195)Pt Knight shifts show systematic dependences on the transition metal or tetrel atomic number, suggesting that the numerical values are influenced by the electronegativities of the metallic (or metalloid) neighbours. PMID:27097719

  14. Examination of the structure in solid state of amino analogs of 4,4‧-[1,5-pentanediylbis(oxy)]bisbenzonitrile by means of X-ray diffraction, 13C CP/MAS NMR, and theoretical calculations

    NASA Astrophysics Data System (ADS)

    Maciejewska, Dorota; Wolska, Irena; Żabiński, Jerzy

    2008-05-01

    A single crystal of X-ray diffraction structures is presented for 4,4'-[1,5-(3-oxapentanediylbis(amino))]bisbenzonitrile 2 and 4,4'-[1,5-( N-methyl-3-azapentane-diylbis(oxy))]bisbenzonitrile 3. The molecular structures of these derivatives differ especially in conformations of the central linker: in 2 this linker adopts a trans/ gauche conformation, whereas in 3 - a fully extended conformation. The N atoms in various positions of the aliphatic linker change dramatically the molecular packing mode of both bisnitriles. But in both cases the nitrile groups take part in intermolecular hydrogen bonds: a type of N sbnd H···N in 2 and of C sbnd H···N in 3. Various conformations of both molecules were reflected in 13C CP/MAS NMR spectra in solid state as single and double resonance patterns for 2 and 3, respectively. A preliminary anticancer assay against 60 cell lines of 3 reveals strong growth inhibition of leukemia, melanoma, and renal cancer cells.

  15. /sup 31/P nuclear magnetic resonance measurements of intracellular pH in giant barnacle muscle

    SciTech Connect

    Hamm, J.R.; Yue, G.M.

    1987-01-01

    The accuracy of intracellular pH (pH/sub i/) measurements by /sup 31/P nuclear magnetic resonance (NMR) spectroscopy was examined in single muscle fibers from the giant barnacle, Balanus nubilis. The pH/sub i/ was derived from the chemical shifts of 2-deoxy-D-glucose-6-phosphate and inorganic phosphate. In fibers superfused with sea water at pH 7.7, pH/sub i/ = 7.30 +/- 0.02 at 20/sup 0/C. Experimentally induced pH/sub i/ changes were followed with a time resolution of 3 min. Intracellular alkalinization was induced by exposure to NH/sub 3/Cl and intracellular acidification followed when NH/sub 3/ was removed. Then acid extrusion was stimulated by exposure to bicarbonate containing sea water. In single muscle fibers /sup 31/P NMR results were in excellent agreement with microelectrode studies over the pH range of 6.5 to 8.0. The initial acid extrusion rate was 1.7 +/- 0.3 mmol x 1/sup -1/ x min/sup -1/ at pH/sub i/ 6.75. The authors results showed that /sup 31/P NMR is a reliable in vivo pH probe.

  16. 31P nuclear magnetic resonance measurements of intracellular pH in giant barnacle muscle.

    PubMed

    Hamm, J R; Yue, G M

    1987-01-01

    The accuracy of intracellular pH (pHi) measurements by 31P nuclear magnetic resonance (NMR) spectroscopy was examined in single muscle fibers from the giant barnacle, Balanus nubilis. The pHi was derived from the chemical shifts of 2-deoxy-D-glucose-6-phosphate and inorganic phosphate. In fibers superfused with sea water at pH 7.7, pHi = 7.30 +/- 0.02 at 20 degrees C. Experimentally induced pHi changes were followed with a time resolution of 3 min. Intracellular alkalinization was induced by exposure to NH4Cl and intracellular acidification followed when NH3 was removed. Then acid extrusion was stimulated by exposure to bicarbonate containing sea water. In single muscle fibers 31P NMR results were in excellent agreement with microelectrode studies over the pH range of 6.5 to 8.0. The initial acid extrusion rate was 1.7 +/- 0.3 mmol X l-1 X min-1 at pHi 6.75. Our results showed that 31P NMR is a reliable in vivo pH probe. PMID:3812665

  17. Optimized 31P MRS in the human brain at 7 T with a dedicated RF coil setup

    PubMed Central

    van de Bank, Bart L.; Orzada, Stephan; Smits, Frits; Lagemaat, Miriam W.; Rodgers, Christopher T.; Bitz, Andreas K.

    2015-01-01

    The design and construction of a dedicated RF coil setup for human brain imaging (1H) and spectroscopy (31P) at ultra‐high magnetic field strength (7 T) is presented. The setup is optimized for signal handling at the resonance frequencies for 1H (297.2 MHz) and 31P (120.3 MHz). It consists of an eight‐channel 1H transmit–receive head coil with multi‐transmit capabilities, and an insertable, actively detunable 31P birdcage (transmit–receive and transmit only), which can be combined with a seven‐channel receive‐only 31P array. The setup enables anatomical imaging and 31P studies without removal of the coil or the patient. By separating transmit and receive channels and by optimized addition of array signals with whitened singular value decomposition we can obtain a sevenfold increase in SNR of 31P signals in the occipital lobe of the human brain compared with the birdcage alone. These signals can be further enhanced by 30 ± 9% using the nuclear Overhauser effect by B 1‐shimmed low‐power irradiation of water protons. Together, these features enable acquisition of 31P MRSI at high spatial resolutions (3.0 cm3 voxel) in the occipital lobe of the human brain in clinically acceptable scan times (~15 min). © 2015 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd. PMID:26492089

  18. 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.

  19. Aggregation of [Au(CN)4]- anions: examination by crystallography and 15N CP-MAS NMR and the structural factors influencing intermolecular Au···N interactions.

    PubMed

    Geisheimer, Andrew R; Wren, John E C; Michaelis, Vladimir K; Kobayashi, Masayuki; Sakai, Ken; Kroeker, Scott; Leznoff, Daniel B

    2011-02-21

    To investigate the factors influencing the formation of intermolecular Au···NC interactions between [Au(CN)(4)](-) units, a series of [cation](n+)[Au(CN)(4)](n) double salts was synthesized, structurally characterized and probed by IR and (15)N{(1)H} CP-MAS NMR spectroscopy. Thus, [(n)Bu(4)N][Au(CN)(4)], [AsPh(4)][Au(CN)(4)], [N(PPh(3))(2)][Au(CN)(4)], [Co(1,10-phenanthroline)(3)][Au(CN)(4)](2), and [Mn(2,2';6',2''-terpyridine)(2)][Au(CN)(4)](2) show [Au(CN)(4)](-) anions that are well-separated from one another; no Au-Au or Au···NC interactions are present. trans-[Co(1,2-diaminoethane)(2)Cl(2)][Au(CN)(4)] forms a supramolecular structure, where trans-[Co(en)(2)Cl(2)](+) and [Au(CN)(4)](-) ions are found in separate layers connected by Au-CN···H-N hydrogen-bonding; weak Au···NC coordinate bonds complete octahedral Au(III) centers, and support a 2-D (4,4) network motif of [Au(CN)(4)](-)-units. A similar structure-type is formed by [Co(NH(3))(6)][Au(CN)(4)](3)·(H(2)O)(4). In [Ni(1,2-diaminoethane)(3)][Au(CN)(4)](2), intermolecular Au···NC interactions facilitate formation of 1-D chains of [Au(CN)(4)](-) anions in the supramolecular structure, which are separated from one another by [Ni(en)(3)](2+) cations. In [1,4-diazabicyclo[2.2.2]octane-H][Au(CN)(4)], the monoprotonated amine cation forms a hydrogen-bond to the [Au(CN)(4)](-) unit on one side, while coordinating to the axial sites of the gold(III) center through the unprotonated amine on the other, thereby generating a 2-D (4,4) net of cations and anions; an additional, uncoordinated [Au(CN)(4)](-)-unit lies in the central space of each grid. This body of structural data indicates that cations with hydrogen-bonding groups can induce intermolecular Au···NC interactions, while the cationic charge, shape, size, and aromaticity have little effect. While the ν(CN) values are poor indicators of the presence or absence of N-cyano bridging between [Au(CN)(4)](-)-units (partly because of the very low

  20. {sup 27}Al and {sup 23}Na MAS NMR and powder x-ray diffraction studies of sodium aluminate speciation and the mechanistics of aluminum hydroxide precipitation upon acid hydrolysis

    SciTech Connect

    Bradley, S.M.; Hanna, J.V.

    1994-08-24

    {sup 27}Al and {sup 23}Na MAS NMR, powder X-ray diffraction, and infrared spectroscopic investigations of freeze-dried sodium aluminates and aluminum hydroxides formed through acid hydrolysis have been undertaken, with OH/Al hydrolysis ratios between 5.3 and 2.8 being analyzed. Numerous {sup 27}AlNMR resonances were observed, the intensities of which vary as a function of OH/Al ratio, and these have been assigned to four-, five-, and six-coordinate aluminum species constituting a variety of structural moieties. The dominant species at an OH/Al ratio above 4.4 appears to be a Q{sup o}Na[Al(OH);{sub 4}] salt, as indicated by a {sup 27}Al resonance at 86.6 ppm. In addition, a second, broader resonance at 71.3 ppm demonstrates the simultaneous existence of further four-coordinate aluminum species linked thorough oxo bonds to other four-coordinate aluminums (e.g., Q{sup 2} [Al(OH);{sub 2}(OAl){sub 2}];{sup x-}). At an OH/Al ratio between 4.4 and 4.1, a water-soluble phase forms that contains both four- and six-coordinate aluminum. At OH/Al ratios fo 4.0 and below, a water-soluble phase forms that contains both four-and six-coordinate aluminum. AT OH/Al ratios of 4.0 and below, a water-insoluble phase exists possessing four-, five-, and six-coordinate aluminum. At OH/Al{le}3.9 range exhibits {sup 27}Al chemical shifts similar to those reported for transitional aluminas such as {gamma}-, {eta}-, and 0-Al{sub 2}O{sub 3} and an infrared spectrum similar to pseudo-spinel gels, suggesting that a pseudo-spinel intermediate is the first phase involved in the crystallization of gibbsite. The resonance assigned to five-coordinate aluminum probably results from species involved in the transformation of the pseudo-spinal phase to pseudo-boehmite. The formation of gibbssite on the acid hydrolysis of alkaline sodium aluminate solutions thus appears to follow the pathway pseudo-spinel {r_arrow} pseudo-boehmite {r_arrow} bayerite {r_arrow} gibbsite. 82 refs., 7 figs., 3 tabs.

  1. Experimental (X-ray, (13)C CP/MAS NMR, IR, RS, INS, THz) and Solid-State DFT Study on (1:1) Co-Crystal of Bromanilic Acid and 2,6-Dimethylpyrazine.

    PubMed

    Łuczyńska, Katarzyna; Drużbicki, Kacper; Lyczko, Krzysztof; Dobrowolski, Jan Cz

    2015-06-01

    A combined structural, vibrational spectroscopy, and solid-state DFT study of the hydrogen-bonded complex of bromanilic acid with 2,6-dimethylpyrazine is reported. The crystallographic structure was determined by means of low-temperature single-crystal X-ray diffraction, which reveals the molecular units in their native protonation states, forming one-dimensional infinite nets of moderate-strength O···H-N hydrogen bonds. The nature of the crystallographic forces, stabilizing the studied structure, has been drawn by employing the noncovalent interactions analysis. It was found that, in addition to the hydrogen bonding, the intermolecular forces are dominated by stacking interactions and C-H···O contacts. The thermal and calorimetric analysis was employed to probe stability of the crystal phase. The structural analysis was further supported by a computationally assisted (13)C CP/MAS NMR study, providing a complete assignment of the recorded resonances. The vibrational dynamics was explored by combining the optical (IR, Raman, TDs-THz) and inelastic neutron scattering (INS) spectroscopy techniques with the state-of-the-art solid-state density functional theory (DFT) computations. Despite the quasi-harmonic approximation assumed throughout the study, an excellent agreement between the theoretical and experimental data was achieved over the entire spectral range, allowing for a deep and possibly thorough understanding of the vibrational characteristics of the system. Particularly, the significant influence of the long-range dipole coupling on the IR spectrum has been revealed. On the basis of a wealth of information gathered, the recent implementation of a dispersion-corrected linear-response scheme has been extensively examined. PMID:25961154

  2. Erythrocytes in muscular dystrophy. Investigation with 31P nuclear magnetic resonance spectroscopy

    SciTech Connect

    Sarpel, G.; Lubansky, H.J.; Danon, M.J.; Omachi, A.

    1981-05-01

    Phosphorus 31 nuclear magnetic resonance (31P NMR) signals were recorded from intact human erythrocytes for 16 hours. Total phosphate concentration, which was estimated as the sum of the individual 31P signals, was 25% lower in erythrocytes from men with myotonic dystrophy than in control erythrocytes. The inorganic-phosphate fraction contained the highest average phosphate concentration over the 16-hour period, and made the major contribution to the difference in total phosphate between the two groups. This result was not observed in erythrocytes from either women with myotonic dystrophy or patients with Duchenne's dystrophy and may be due to a change in cell membrane permeability to inorganic phosphate, which lead to lower steady-state concentrations of the intracellular phosphates.

  3. Erythrocytes in muscular dystrophy. Investigation with /sup 31/P nuclear magnetic resonance spectroscopy

    SciTech Connect

    Sarpel, G.; Lubansky, H.J.; Danon, M.J.; Omachi, A.

    1981-05-01

    Phosphorus 31 nuclear magnetic resonance (/sup 31/P NMR) signals were recorded from intact human erythrocytes for 16 hours. Total phosphate concentration, which was estimated as the sum of the individual /sup 31/P signals, was 25% lower in erythrocytes from men with myotonic dystrophy than in control erythrocytes. The inorganic-phosphate fraction contained the highest average phosphate concentration over the 16-hour period, and made the major contribution to the difference in total phosphate between the two groups. This result was not observed in erythrocytes from either women with myotonic dystrophy or patients with Duchenne's dystrophy and may be due to a change in cell membrane permeability to inorganic phosphate, which leads to lower steady-state concentrations of the intracellular phosphates.

  4. Solid-state NMR in the analysis of drugs and naturally occurring materials.

    PubMed

    Paradowska, Katarzyna; Wawer, Iwona

    2014-05-01

    This article presents some of the solid-state NMR (SSNMR) techniques used in the pharmaceutical and biomedical research. Solid-state magic angle spinning (MAS) NMR provides structural information on powder amorphous solids for which single-crystal diffraction structures cannot be obtained. NMR is non-destructive; the powder sample may be used for further studies. Quantitative results can be obtained, although solid-state NMR spectra are not normally quantitative. As compared with other techniques, MAS NMR is insensitive and requires a significant amount of the powder sample (2-100mg) to fill the 1.3-7 mm ZrO2 rotor. This is its main drawback, since natural compounds isolated from plants, microorganisms or cell cultures are difficult to obtain in quantities higher than a few milligrams. Multinuclear MAS NMR routinely uses (1)H and (13)C nuclei, less frequently (15)N, (19)F, (31)P, (77)Se, (29)Si, (43)Ca or (23)Na. The article focuses on the pharmaceutical applications of SSNMR, the studies were aimed to control over manufacturing processes (e.g. crystallization and milling) investigation of chemical and physical stability of solid forms both as pure drug and in a formulated product. SSNMR is used in combination with some other analytical methods (DSC, XRD, FT-IR) and theoretical calculations of NMR parameters. Biologically active compounds, such as amino acids and small peptides, steroids and flavonoids were studied by SSNMR methods (part 4) providing valuable structural information. The SSNMR experiments performed on biopolymers and large natural products like proteins, cellulose and lipid layers are commented upon briefly in part 5. PMID:24173236

  5. Prediction of 31P nuclear magnetic resonance chemical shifts for phosphines

    NASA Astrophysics Data System (ADS)

    Tong, Jianbo; Liu, Shuling; Zhang, Shengwan; Li, Shengshi Z.

    2007-07-01

    Quantitative relationships of the 31P NMR chemical shifts of the phosphorus atoms in 291 phosphines with the atomic ionicity index (INI) and stereoscopic effect parameters ( ɛα, ɛβ, ɛγ) were primarily investigated in this paper for modeling some fundamental quantitative structure-spectroscopy relationships (QSSR). The results indicated that the 31P NMR chemical shifts of phosphines can be described as the quantitative equation by multiple linear regression (MLR): δp (ppm) = -174.0197 - 2.6724 INI + 40.4755 ɛα + 15.1141 ɛβ - 3.1858 ɛγ, correlation coefficient R = 0.9479, root mean square error (rms) = 13.9, and cross-validated predictive correlation coefficient was found by using the leave-one-out procedure to be Q2 = 0.8919. Furthermore, through way of random sampling, the estimative stability and the predictive power of the proposed MLR model were examined by constructing data set randomly into both the internal training set and external test set of 261 and 30 compounds, respectively, and then the chemical shifts were estimated and predicted with the training correlation coefficient R = 0.9467 and rms = 13.4 and the external predicting correlation coefficient Qext = 0.9598 and rms = 10.8. A partial least square model was developed that produced R = 0.9466, Q = 0.9407 and Qext = 0.9599, respectively. Those good results provided a new, simple, accurate and efficient methodology for calculating 31P NMR chemical shifts of phosphines.

  6. 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

  7. In Vivo 31P Echo-Planar Spectroscopic Imaging of Human Calf Muscle

    NASA Astrophysics Data System (ADS)

    Wilhelm, Thomas; Bachert, Peter

    2001-03-01

    Localized phosphorus-31 NMR spectra of human calf muscle in vivo were obtained by means of echo-planar spectroscopic imaging (EPSI) with a 1.5-T whole-body scanner. The technique permits the measurement of two-dimensional 31P SI data at a minimum acquisition time of 2.4 s (8×8 voxels, TR=300 ms). With 9.4 min measurement time (TR=1100 ms, 64 averages) and 25×25×40 mm spatial resolution in vivo the 31P NMR signal-to-noise ratio (S/N) of the phosphocreatine (PCr) resonance was about 45; the multiplets of nucleoside 5‧-triphosphates were resolved. Spectral quality permits quantitative assessment of the PCr signal in a measurement time that is shorter by a factor of 2 or more than the minimum measurement time feasible with chemical-shift imaging. In a functional EPSI study with a time resolution of 20.5 s on the calf muscle of volunteers, spectra showed a 40% decrease of the PCr signal intensity (at rest: S/N≅12) upon exertion of the muscle.

  8. Hypophosphite ion as a 31P nuclear magnetic resonance probe of membrane potential in erythrocyte suspensions.

    PubMed Central

    Kirk, K; Kuchel, P W; Labotka, R J

    1988-01-01

    Hypophosphorus acid has a single pKa of 1.1 and at physiological pH values it is therefore present almost entirely as the univalent hypophosphite ion. When added to a red cell suspension the ion crosses the cell membrane rapidly, via the anion exchange protein, and the intra- and extracellular populations of the ion give rise to separate 31P NMR resonances. From a single 31P NMR spectrum it was possible to determine the relative amounts of hypophosphite in the intra- and extracellular compartments and thereby estimate the corresponding concentrations. The ratio of intracellular to extracellular hypophosphite concentration was independent of the total hypophosphite concentration for cells suspended in NaCl solutions and was independent of hematocrit. The hypophosphite distribution ratio increased as extracellular NaCl was replaced iso-osmotically with citrate or sucrose, through it remained very similar to the corresponding hydrogen ion distribution ratio. Incorporation of the hypophosphite distribution ratio into the Nernst equation yielded an estimate of the membrane potential. For cells suspended in NaCl solutions the estimated potential was consistently around -10 mV. PMID:3207824

  9. Ultra-low temperature MAS-DNP.

    PubMed

    Lee, Daniel; Bouleau, Eric; Saint-Bonnet, Pierre; Hediger, Sabine; De Paëpe, Gaël

    2016-03-01

    Since the infancy of NMR spectroscopy, sensitivity and resolution have been the limiting factors of the technique. Regular essential developments on this front have led to the widely applicable, versatile, and powerful spectroscopy that we know today. However, the Holy Grail of ultimate sensitivity and resolution is not yet reached, and technical improvements are still ongoing. Hence, high-field dynamic nuclear polarization (DNP) making use of high-frequency, high-power microwave irradiation of electron spins has become very promising in combination with magic angle sample spinning (MAS) solid-state NMR experiments. This is because it leads to a transfer of the much larger polarization of these electron spins under suitable irradiation to surrounding nuclei, greatly increasing NMR sensitivity. Currently, this boom in MAS-DNP is mainly performed at minimum sample temperatures of about 100K, using cold nitrogen gas to pneumatically spin and cool the sample. This Perspective deals with the desire to improve further the sensitivity and resolution by providing "ultra"-low temperatures for MAS-DNP, using cryogenic helium gas. Different designs on how this technological challenge has been overcome are described. It is shown that stable and fast spinning can be attained for sample temperatures down to 30K using a large cryostat developed in our laboratory. Using this cryostat to cool a closed-loop of helium gas brings the additional advantage of sample spinning frequencies that can greatly surpass those achievable with nitrogen gas, due to the differing fluidic properties of these two gases. It is shown that using ultra-low temperatures for MAS-DNP results in substantial experimental sensitivity enhancements and according time-savings. Access to this temperature range is demonstrated to be both viable and highly pertinent. PMID:26920837

  10. Ultra-low temperature MAS-DNP

    NASA Astrophysics Data System (ADS)

    Lee, Daniel; Bouleau, Eric; Saint-Bonnet, Pierre; Hediger, Sabine; De Paëpe, Gaël

    2016-03-01

    Since the infancy of NMR spectroscopy, sensitivity and resolution have been the limiting factors of the technique. Regular essential developments on this front have led to the widely applicable, versatile, and powerful spectroscopy that we know today. However, the Holy Grail of ultimate sensitivity and resolution is not yet reached, and technical improvements are still ongoing. Hence, high-field dynamic nuclear polarization (DNP) making use of high-frequency, high-power microwave irradiation of electron spins has become very promising in combination with magic angle sample spinning (MAS) solid-state NMR experiments. This is because it leads to a transfer of the much larger polarization of these electron spins under suitable irradiation to surrounding nuclei, greatly increasing NMR sensitivity. Currently, this boom in MAS-DNP is mainly performed at minimum sample temperatures of about 100 K, using cold nitrogen gas to pneumatically spin and cool the sample. This Perspective deals with the desire to improve further the sensitivity and resolution by providing "ultra"-low temperatures for MAS-DNP, using cryogenic helium gas. Different designs on how this technological challenge has been overcome are described. It is shown that stable and fast spinning can be attained for sample temperatures down to 30 K using a large cryostat developed in our laboratory. Using this cryostat to cool a closed-loop of helium gas brings the additional advantage of sample spinning frequencies that can greatly surpass those achievable with nitrogen gas, due to the differing fluidic properties of these two gases. It is shown that using ultra-low temperatures for MAS-DNP results in substantial experimental sensitivity enhancements and according time-savings. Access to this temperature range is demonstrated to be both viable and highly pertinent.

  11. Human cardiac 31P magnetic resonance spectroscopy at 7 tesla

    PubMed Central

    Rodgers, Christopher T; Clarke, William T; Snyder, Carl; Vaughan, J Thomas; Neubauer, Stefan; Robson, Matthew D

    2014-01-01

    Purpose Phosphorus magnetic resonance spectroscopy (31P-MRS) affords unique insight into cardiac energetics but has a low intrinsic signal-to-noise ratio (SNR) in humans. Theory predicts an increased 31P-MRS SNR at 7T, offering exciting possibilities to better investigate cardiac metabolism. We therefore compare the performance of human cardiac 31P-MRS at 7T to 3T, and measure T1s for 31P metabolites at 7T. Methods Matched 31P-MRS data were acquired at 3T and 7T, on nine normal volunteers. A novel Look-Locker CSI acquisition and fitting approach was used to measure T1s on six normal volunteers. Results T1s in the heart at 7T were: phosphocreatine (PCr) 3.05 ± 0.41s, γ-ATP 1.82 ± 0.09s, α-ATP 1.39 ± 0.09s, β-ATP 1.02 ± 0.17s and 2,3-DPG (2,3-diphosphoglycerate) 3.05 ± 0.41s (N = 6). In the field comparison (N = 9), PCr SNR increased 2.8× at 7T relative to 3T, the Cramer-Ráo uncertainty (CRLB) in PCr concentration decreased 2.4×, the mean CRLB in PCr/ATP decreased 2.7× and the PCr/ATP SD decreased 2×. Conclusion Cardiac 31P-MRS at 7T has higher SNR and the spectra can be quantified more precisely than at 3T. Cardiac 31P T1s are shorter at 7T than at 3T. We predict that 7T will become the field strength of choice for cardiac 31P-MRS. Magn Reson Med 72:304–315, 2014. © 2013 The Authors. Magnetic Resonance in Medicine Published by Wiley Periodicals, Inc. on behalf of International Society of Medicine in Resonance. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited. PMID:24006267

  12. Solid-state NMR strategies for the structural characterization of paramagnetic NO adducts of Frustrated Lewis Pairs (FLPs).

    PubMed

    Wiegand, Thomas; Sajid, Muhammad; Kehr, Gerald; Erker, Gerhard; Eckert, Hellmut

    2014-01-01

    By N,N addition of NO to the norbonane annulated borane-phosphane Frustrated Lewis pair (FLP) 1 a five-membered heterocyclic persistent aminoxyl radical 2 and its diamagnetic hydroxylamine reduction product 3 are prepared, and the comprehensive multinuclear solid state NMR characterization ((1)H, (11)B, (19)F, (31)P) of these FLP adducts is reported. Signal quantification experiments using a standard addition method reveal that the (11)B and (31)P NMR signals observed in 2 actually arise from molecular impurities of 3 embedded in the paramagnetic crystal. In contrast analogous quantification experiments reveal that the (1)H and (19)F MAS-NMR spectra originate from spin-carrying molecules. Peak assignments are based on DFT-calculated Mulliken spin densities, which lead to the surprising result that the largest paramagnetic shift affecting a proton NMR resonance in 2 originates from intermolecular interactions. For the (19)F nuclei, experiments and calculations indicate that paramagnetic shift effects are very small. In this case, assignments are based on DFT chemical shift calculations carried out on diamagnetic 3 and (19)F((11)B) Rotational Echo Adiabatic Passage DOuble Resonance (REAPDOR) experiments. The set of experiments described here defines an efficient strategy for the structural analysis of paramagnetic FLP adducts. PMID:24815176

  13. Probing the calcium and sodium local environment in bones and teeth using multinuclear solid state NMR and X-ray absorption spectroscopy.

    PubMed

    Laurencin, Danielle; Wong, Alan; Chrzanowski, Wojciech; Knowles, Jonathan C; Qiu, Dong; Pickup, David M; Newport, Robert J; Gan, Zhehong; Duer, Melinda J; Smith, Mark E

    2010-02-01

    Despite the numerous studies of bone mineral, there are still many questions regarding the exact structure and composition of the mineral phase, and how the mineral crystals become organised with respect to each other and the collagen matrix. Bone mineral is commonly formulated as hydroxyapatite, albeit with numerous substitutions, and has previously been studied by (31)P and (1)H NMR, which has given considerable insight into the complexity of the mineral structure. However, to date, there has been no report of an NMR investigation of the other major component of bone mineral, calcium, nor of common minority cations like sodium. Here, direct analysis of the local environment of calcium in two biological apatites, equine bone (HB) and bovine tooth (CT), was carried out using both (43)Ca solid state NMR and Ca K-edge X-ray absorption spectroscopy, revealing important structural information about the calcium coordination shell. The (43)Ca delta(iso) in HB and CT is found to correlate with the average Ca-O bond distance measured by Ca K-edge EXAFS, and the (43)Ca NMR linewidths show that there is a greater distribution in chemical bonding around calcium in HB and CT, compared to synthetic apatites. In the case of sodium, (23)Na MAS NMR, high resolution 3Q-MAS NMR, as well as (23)Na{(31)P} REDOR and (1)H{(23)Na} R(3)-HMQC correlation experiments give the first direct evidence that some sodium is located inside the apatite phase in HB and CT, but with a greater distribution of environments compared to a synthetic sodium substituted apatite (Na-HA). PMID:20094673

  14. Nuclear Spin Polarization of Phosphorus Donors in Silicon. Direct Evidence from 31P-Nuclear Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Gumann, Patryk; Ramanathan, Chandrasekhar; Patange, Om; Moussa, Osama; Thewalt, Mike; Riemann, Helge; Abrosimov, Nikolay; Becker, Peter; Pohl, Hans-Joachim; Itoh, Kohei; Cory, David G.

    2014-03-01

    We experimentally demonstrate the optical hyperpolarization and coherent control of 31P, nuclear spins in single crystal silicon via the inductive readout of the nuclear magnetic resonance (NMR) signal of 31P at a concentration of 1.5 x 1015 cc-1. The obtained polarization is sufficient the 31P spin polarization of 1.17 x 1015 in a 10 mm x 10 mm sample, observed in one FID with signal-to-noise ration of 113. The linewidth is 800 Hz. The Hahn echo pulse sequence reveals a 31P T2 time of 0.42 s at 1.6 K, which was extended by the Carr Purcell cycle to 1.2 s at the same temperature. The maximum build-up of the nuclear polarization was achieved within ~577 seconds, at 4.2 K, in 6.7 T, using optical excitations provided by an infra-red laser. This work has been supported by CERC Canada.

  15. Probing spin density and local structure in the Prussian blue analogues CsCd[Fe/Co(CN)6]·0.5H2O and Cd3[Fe/Co(CN)6]2·15H2O with solid-state MAS NMR spectroscopy.

    PubMed

    Flambard, Alexandrine; Köhler, Frank H; Lescouëzec, Rodrigue; Revel, Bertrand

    2011-10-01

    Magic-angle spinning (MAS) NMR spectroscopy is used to study the local structure and spin delocalisation in Prussian blue analogues (PBAs). We selected two common archetypes of PBAs (A(I)M(II)[M(III)(CN)(6)]·xH(2)O and M(II)(3)[M(III)(CN)(6)](2)·xH(2)O, in which A(I) is an alkali ion, and M(II) and M(III) are transition-metal ions) that exhibit similar cubic frameworks but different microscopic structures. Whereas the first type of PBA contains interstitial alkali ions and does not exhibit any [M(III)(CN)(6)](3-) vacancies, the second type of PBA exhibits [M(III)(CN)(6)](3-) vacancies, but does not contain inserted alkali ions. In this study, we selected Cd(II) as a divalent metal in order to use the (113)Cd nuclei (I=1/2) as a probe of the local structure. Here, we present a complete MAS NMR study on two series of PBAs of the formulas Cd(II)(3)[Fe(III)(x)Co(III)(1-x)(CN)(6)](2)·15H(2)O with x=0 (1), 0.25 (2), 0.5 (3), 0.75 (4) and 1 (5), and CsCd(II)[Fe(III)(x)Co(III)(1-x)(CN)(6)]·0.5H(2)O with x=0 (6), 0.25 (7), 0.5 (8), 0.75 (9) and 1 (10). Interestingly, the presence of Fe(III) magnetic centres in the vicinity of the cadmium sites has a magnifying-glass effect on the NMR spectrum: it induces a striking signal spread such that the resolution is notably improved compared to that achieved for the diamagnetic PBAs. By doping the sample with varying amounts of diamagnetic Co(III) and comparing the NMR spectra of both types of PBAs, we have been able to give a view of the structure which is complementary to that usually obtained from X-ray diffraction studies. In particular, this study has shown that the vacancies are not randomly distributed in the mesoporous PBAs. Moreover the cadmium chemical shift, which is a measure of the hyperfine coupling, allows the estimation of the spin density on the cadmium nucleus, and consequently, the elucidation of the spin delocalisation mechanism in these compounds along with its dependency on structural parameters. PMID

  16. 14N overtone NMR under MAS: signal enhancement using symmetry-based sequences and novel simulation strategies† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c4cp03994g Click here for additional data file.

    PubMed Central

    Haies, Ibraheem M.; Jarvis, James A.; Bentley, Harry; Heinmaa, Ivo; Kuprov, Ilya; Williamson, Philip T. F.

    2015-01-01

    Overtone 14N NMR spectroscopy is a promising route for the direct detection of 14N signals with good spectral resolution. Its application is currently limited, however, by the absence of efficient polarization techniques for overtone signal enhancement and the lack of efficient numerical simulation techniques to aid in both the development of new methods and the analysis and interpretation of experimental data. In this paper we report a novel method for the transfer of polarization from 1H to the 14N overtone using symmetry-based R-sequences that overcome many of the limitations of adiabatic approaches that have worked successfully on static samples. Refinement of these sequences and the analysis of the resulting spectra have been facilitated through the development of an efficient simulation strategy for 14N overtone NMR spectroscopy of spinning samples, using effective Hamiltonians on top of Floquet and Fokker–Planck equations. PMID:25662410

  17. Structural investigation of BaOsbnd B2O3sbnd P2O5 glasses by NMR and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Koudelka, Ladislav; Kalenda, Petr; Mošner, Petr; Černošek, Zdeněk; Montagne, Lionel; Revel, Bertrand

    2016-09-01

    Glasses of the ternary system BaOsbnd B2O3sbnd P2O5 were prepared and studied in broad concentration limits covering the whole vitrification domain: 20-50 mol% BaO, 0-40 mol% B2O3 and 20-60 mol% P2O5. Their structure was studied with combinations of Raman spectroscopy, 31P MAS NMR spectroscopy and 11B MAS NMR spectroscopy. The obtained results are discussed in several compositional lines A: (100-x)Ba(PO3)2sbnd xB2O3, B: 40BaOsbnd yB2O3sbnd (60-y)P2O5, C: (50-z)BaOsbnd zB2O3sbnd 50P2O5, D: (60-w)BaOsbnd wB2O3sbnd 40P2O5 and E: uBaOsbnd 40B2O3sbnd (60-u)P2O5. Boron oxide incorporates into the phosphate network in the form of BO4 and BO3 groups and increases their glass transition temperature. Nevertheless, the increase in Tg is only steep within the region of 0-20 mol% B2O3 reaching a maximum at the glasses with ∼30 mol% B2O3. In the lines A, B and E a decrease in the P2O5 and an increase of B2O3 content results in the shortening of phosphate chains with decreasing P2O5 content; these changes are most pronounced in line B with a constant BaO content. In lines C and D with a constant P2O5 content a decrease in the BaO content results, in contrast, in the reverse transformation of phosphate structural units in the direction Q1 → Q2 → Q3 as detected from Raman spectra and 31P MAS NMR spectra. 11B MAS NMR spectra revealed that only BO4 units are present in the glasses with 0-20 mol% B2O3. In the glasses of the E series the fraction of BO3 units increases with a decreasing P2O5 content. By the decomposition of the 11B MAS NMR spectra it is possible to estimate the fractions of basic structural units formed by boron - B(OP)3O, B(OP)2O2 and BO3 in all the glasses of the glass forming region.

  18. Determination of relative orientation between (1)H CSA tensors from a 3D solid-state NMR experiment mediated through (1)H/(1)H RFDR mixing under ultrafast MAS.

    PubMed

    Pandey, Manoj Kumar; Nishiyama, Yusuke

    2015-09-01

    To obtain piercing insights into inter and intramolecular H-bonding, and π-electron interactions measurement of (1)H chemical shift anisotropy (CSA) tensors is gradually becoming an obvious choice. While the magnitude of CSA tensors provides unique information about the local electronic environment surrounding the nucleus, the relative orientation between these tensors can offer further insights into the spatial arrangement of interacting nuclei in their respective three-dimensional (3D) space. In this regard, we present a 3D anisotropic/anisotropic/isotropic proton chemical shift (CSA/CSA/CS) correlation experiment mediated through (1)H/(1)H radio frequency-driven recoupling (RFDR) which enhances spin diffusion through recoupled (1)H-(1)H dipolar couplings under ultrafast magic angle spinning (MAS) frequency (70kHz). Relative orientation between two interacting 1H CSA tensors is obtained by fitting two-interacting (1)H CSA tensors by fitting two-dimensional (2D) (1)H/(1)H CSA/CSA spectral slices through extensive numerical simulations. To recouple (1)H CSAs in the indirect frequency dimensions of a 3D experiment we have employed γ-encoded radio frequency (RF) pulse sequence based on R-symmetry (R188(7)) with a series of phase-alternated 2700(°)-90180(°) composite-180° pulses on citric acid sample. Due to robustness of applied (1)H CSA recoupling sequence towards the presence of RF field inhomogeneity, we have successfully achieved an excellent (1)H/(1)H CSA/CSA cross-correlation efficiency between H-bonded sites of citric acid. PMID:26065628

  19. Fusogenic Alzheimer’s peptide fragment Aβ (29–42) in interaction with lipid bilayers: Secondary structure, dynamics, and specific interaction with phosphatidyl ethanolamine polar heads as revealed by solid-state NMR

    PubMed Central

    Ravault, Stéphanie; Soubias, Olivier; Saurel, Olivier; Thomas, Annick; Brasseur, Robert; Milon, Alain

    2005-01-01

    The interaction of the native Alzheimer’s peptide C-terminal fragment Aβ (29–42), and two mutants (G33A and G37A) with neutral lipid bilayers made of POPC and POPE in a 9:1 molar ratio was investigated by solid-state NMR. This fragment and the lipid composition were selected because they represent the minimum requirement for the fusogenic activity of the Alzheimer’s peptide. The chemical shifts of alanine methyl isotropic carbon were determined by MAS NMR, and they clearly demonstrated that the major form of the peptide equilibrated in membrane is not in a helical conformation. 2H NMR, performed with acyl chain deuterated POPC, demonstrated that there is no perturbation of the acyl chain’s dynamics and of the lipid phase transition temperature. 2H NMR, performed with alanine methyl-deuterated peptide demonstrated that the peptide itself has a limited mobility below and above the lipid phase transition temperature (molecular order parameter equal to 0.94). MAS 31P NMR revealed a specific interaction with POPE polar head as seen by the enhancement of POPE phosphorus nuclei T2 relaxation. All these results are in favor of a β-sheet oligomeric association of the peptide at the bilayer interface, preferentially recruiting phosphatidyl ethanolamine polar heads. PMID:15840826

  20. Differential cross sections measurement of 31P(p,pγ1)31P reaction for PIGE applications

    NASA Astrophysics Data System (ADS)

    Jokar, A.; Kakuee, O.; Lamehi-Rachti, M.

    2016-09-01

    Differential cross sections of proton induced gamma-ray emission from the 31P(p,pγ1)31P (Eγ = 1266 keV) nuclear reaction were measured in the proton energy range of 1886-3007 keV at the laboratory angle of 90°. For these measurements a thin Zn3P2 target evaporated onto a self-supporting C film was used. The gamma-rays and backscattered protons were detected simultaneously. An HPGe detector placed at an angle of 90° with respect to the beam direction was employed to collect gamma-rays while an ion implanted Si detector placed at a scattering angle of 165° was used to detect backscattered protons. Simultaneous collection of gamma-rays and RBS spectra is a great advantage of this approach which makes differential cross-section measurements independent on the collected beam charge. The obtained cross-sections were compared with the previously only measured data in the literature. The validity of the measured differential cross sections was verified through a thick target benchmarking experiment. The overall systematic uncertainty of cross section values was estimated to be better than ±9%.

  1. Inter- and intramolecular spin transfer in molecular magnetic materials. Solid-state NMR spectroscopy of paramagnetic metallocenium ions.

    PubMed

    Heise, Henrike; Köhler, Frank H; Herker, Martin; Hiller, Wolfgang

    2002-09-11

    To shed light on the interaction in molecule-based magnetic materials, the decamethylmetallocenium hexafluorophosphates, [(C(5)Me(5))(2)M](+) [PF(6)](-) with M = Cr, Mn, Fe, Co, and Ni, as well as the tetracyanoethenides, [(C(5)Me(5))(2)M](+) [TCNE](-) with M = Cr, Mn, Fe, and Co, have been investigated in the solid state by using (1)H, (13)C, (19)F, and (31)P NMR spectroscopy under magic angle spinning (MAS). The isotropic (13)C and (1)H NMR signals cover ranges of about 1300 and 500 ppm, respectively. From the shift anisotropies of the ring carbon signal of the [(C(5)Me(5))(2)M](+) cations, the total unpaired electron spin density in the ligand pi orbitals has been calculated; it amounts up to 36% (M = Ni) and is negative for M = Cr, Mn, and Fe. The radical anion of [(C(5)Me(5))(2)M](+) [TCNE](-) shifts the (13)C NMR signals of all [(C(5)Me(5))(2)M](+) cations to high frequency, which establishes transfer of positive spin density from the anions to the cations. The (19)F and (31)P NMR signals of the paramagnetic salts [(C(5)Me(5))(2)M](+) [PF(6)](-) are shifted up to 13.5 ppm relative to diamagnetic [(C(5)Me(5))(2)Co](+) [PF(6)](-). The signs of these shifts are the same as those of the pi spin density in [(C(5)Me(5))(2)M](+). After consideration of interionic ligand- and metal-centered dipolar shifts, this establishes cation-anion spin delocalization. The mixed crystals [(C(5)Me(5))(2)M(x)Co(1-x)](+)[PF(6)](-) have been prepared for M = Cr and Ni. They are isostructural with [(C(5)Me(5))(2)Co](+) [PF(6)](-) whose single-crystal structure has been determined by X-ray diffraction. The (13)C, (19)F, and (31)P MAS NMR spectra of the mixed crystals show that the respective two closest paramagnetic ions in the lattice delocalize spin density to [(C(5)Me(5))(2)Co](+), [(C(5)Me(5))(2)Ni](+), and [PF(6)](-). In [(C(5)Me(5))(2)M](+), about 10(-4) au per carbon atom are transferred. PMID:12207538

  2. 31P magnetization transfer measurements of Pi→ATP flux in exercising human muscle

    PubMed Central

    Savage, David B.; Williams, Guy B.; Porter, David; Carpenter, T. Adrian; Brindle, Kevin M.; Kemp, Graham J.

    2016-01-01

    Fundamental criticisms have been made over the use of 31P magnetic resonance spectroscopy (MRS) magnetization transfer estimates of inorganic phosphate (Pi)→ATP flux (VPi-ATP) in human resting skeletal muscle for assessing mitochondrial function. Although the discrepancy in the magnitude of VPi-ATP is now acknowledged, little is known about its metabolic determinants. Here we use a novel protocol to measure VPi-ATP in human exercising muscle for the first time. Steady-state VPi-ATP was measured at rest and over a range of exercise intensities and compared with suprabasal oxidative ATP synthesis rates estimated from the initial rates of postexercise phosphocreatine resynthesis (VATP). We define a surplus Pi→ATP flux as the difference between VPi-ATP and VATP. The coupled reactions catalyzed by the glycolytic enzymes GAPDH and phosphoglycerate kinase (PGK) have been shown to catalyze measurable exchange between ATP and Pi in some systems and have been suggested to be responsible for this surplus flux. Surplus VPi-ATP did not change between rest and exercise, even though the concentrations of Pi and ADP, which are substrates for GAPDH and PGK, respectively, increased as expected. However, involvement of these enzymes is suggested by correlations between absolute and surplus Pi→ATP flux, both at rest and during exercise, and the intensity of the phosphomonoester peak in the 31P NMR spectrum. This peak includes contributions from sugar phosphates in the glycolytic pathway, and changes in its intensity may indicate changes in downstream glycolytic intermediates, including 3-phosphoglycerate, which has been shown to influence the exchange between ATP and Pi catalyzed by GAPDH and PGK. PMID:26744504

  3. 31P MRSI and 1H MRS at 7 T: initial results in human breast cancer.

    PubMed

    Klomp, Dennis W J; van de Bank, Bart L; Raaijmakers, Alexander; Korteweg, Mies A; Possanzini, Cecilia; Boer, Vincent O; van de Berg, Cornelius A T; van de Bosch, Maurice A A J; Luijten, Peter R

    2011-12-01

    This study demonstrates the feasibility of the noninvasive determination of important biomarkers of human (breast) tumor metabolism using high-field (7-T) MRI and MRS. (31) P MRSI at this field strength was used to provide a direct method for the in vivo detection and quantification of endogenous biomarkers. These encompass phospholipid metabolism, phosphate energy metabolism and intracellular pH. A double-tuned, dual-element transceiver was designed with focused radiofrequency fields for unilateral breast imaging and spectroscopy tuned for optimized sensitivity at 7 T. T(1) -weighted three-dimensional MRI and (1) H MRS were applied for the localization and quantification of total choline compounds. (31) P MRSI was obtained within 20 min per subject and mapped in three dimensions over the breast with pixel volumes of 10 mL. The feasibility of monitoring in vivo metabolism was demonstrated in two patients with breast cancer during neoadjuvant chemotherapy, validated by ex vivo high-resolution magic angle spinning NMR and compared with data from an age-matched healthy volunteer. Concentrations of total choline down to 0.4 mM could be detected in the human breast in vivo. Levels of adenosine and other nucleoside triphosphates, inorganic phosphate, phosphocholine, phosphoethanolamine and their glycerol diesters detected in glandular tissue, as well as in tumor, were mapped over the entire breast. Altered levels of these compounds were observed in patients compared with an age-matched healthy volunteer; modulation of these levels occurred in breast tumors during neoadjuvant chemotherapy. To our knowledge, this is the first comprehensive MRI and MRS study in patients with breast cancer, which reveals detailed information on the morphology and phospholipid metabolism from volumes as small as 10 mL. This endogenous metabolic information may provide a new method for the noninvasive assessment of prognostic and predictive biomarkers in breast cancer treatment. PMID

  4. 31P-NMR study of different hypothyroid states in rat leg muscle.

    PubMed

    Kaminsky, P; Klein, M; Robin-Lherbier, B; Walker, P; Escanye, J M; Brunotte, F; Robert, J; Duc, M

    1991-12-01

    Using phosphorus nuclear magnetic resonance spectroscopy, this study was undertaken to determine the effects of experimental hypothyroidism on muscle bioenergetics. The peaks of phosphocreatine (PCr), Pi, phosphodiesters (PDE), sugar phosphomonoesters, and ATP were obtained at rest, during a 2-Hz hindleg muscle stimulation, and during a subsequent recovery period from four groups of anesthetized rats as follows: one control and three hypothyroid (HT) groups treated by propylthyouracil during 2, 4, and 6 wk, respectively. Resting spectra showed a significant rise in Pi by 30% and decreased intracellular pH and PCr/Pi in all three HT groups. PDE progressively increased to 200% of its initial value with hypothyroidism duration. Muscle stimulation did not lead to significant differences in PCr depletion. The percentage of PCr recovery is less in HT muscle than in control muscle. An abnormal H+ metabolism is obvious in all three HT groups. These results indicate abnormal bioenergetics in HT muscle and suggest an impairment of mitochondrial metabolism and of the H+ efflux. They also evoke a high sensitivity of cellular energetics to thyroid deficiency. PMID:1767830

  5. A Wet-Lab Approach to Stereochemistry Using [superscript 31]P NMR Spectroscopy

    ERIC Educational Resources Information Center

    Fenton, Owen S.; Sculimbrene, Bianca R.

    2011-01-01

    Understanding stereochemistry is an important and difficult task for students to master in organic chemistry. In both introductory and advanced courses, students are encouraged to explore the spatial relationships between molecules, but this exploration is often limited either to the lecture hall or the confines of the library. As such, we sought…

  6. Phosphitylation and Quantitative 31P-NMR Analysis of Partially Substituted Biodiesel Glycerols

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is a constant need for new and improved analytical techniques to monitor the quality of incoming feedstocks and their respective conversion products in the biofuels industry. Current analytical methods in the biodiesel industry include high performance liquid chromatography, gas chromatography...

  7. In vivo effects of photosynthesis inhibitors in Synechococcus as determined by /sup 31/P NMR spectroscopy

    SciTech Connect

    Thoma, W.J.; Gleason, F.K.

    1987-05-05

    Phosphorus-31 nuclear magnetic resonance spectra were obtained from darkened cells of the unicellular cyanobacterium Synechococcus sp. Resonance peaks were assigned to intracellular pools of sugar-phosphates, inorganic phosphate (P/sub i/), nucleotides, and polyphosphate. An internal pH of 7.2 was estimated from the chemical shift of the P/sub i/ resonance. Cells were then illuminated at 1600 ..mu..E m/sup -2/ s/sup -1/ photosynthetically active radiation by a fiber optic cable immersed in the cell sample. Spectra obtained after approximately 15 min of illumination showed an increase in nucleotide pools and an increase in the cytoplasmic pH to 7.6. In the presence of 0.3 mM dinitrophenol (DNP), an uncoupler of phosphorylation, spectra of illuminated cells showed an immediate decline in nucleotide pools while sugar-phosphate levels remained constant. Addition of the photosystem II (PS II) electron-transport inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) (7.2 ..mu..M) did not affect nucleotide levels in the cells during the time course of the experiment (15-30 min). However, an abrupt rise in the resonance in the sugar-phosphate region was noted. Spectra of DCMU-treated cells extracts indicated that one metabolite was principally responsible for the change in pool size. The metabolite was identified as 3-phosphoglyceric acid. Spectra of illuminated cells were also obtained in the presence of the natural herbicide cyanobacterin. Unlike results obtained with DNP or DCMU, spectra of cyanobacterin-treated cells showed no major changes in nucleotide or sugar-phosphate resonances. A slow decline in cytoplasmic pH was seen in the presence of cyanobacterin, indicating that the natural product affects the proton pumping mechanism in PS II.

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

    NASA Astrophysics Data System (ADS)

    Sarkar, Gautam

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

  9. Contraction and recovery of living muscles studied by 31p nuclear magnetic resonance

    PubMed Central

    Gadian, D. G.; Dawson, M. Joan; Wilkie, D. R.

    1977-01-01

    1. Phosphorus nuclear magnetic resonance (31P NMR) can be used to measure the concentrations of phosphorus-containing metabolites within living tissue. We have developed methods for maintaining muscles in physiological condition, stimulating them and recording tension while at the same time accumulating their 31P NMR spectra. Experiments were performed on frog sartorii and frog and toad gastrocnemii at 4° C. 2. The NMR signals from 31P (the naturally occurring phosphorus) is weak, and signal averaging is required. In order to follow the time course of reactions it is necessary to maintain the muscles in a steady state for many hours while they are undergoing repeated contractions. Signals were accumulated in separate computer bins according to time after initiation of contraction. By these means spectra were obtained which corresponded to the different intervals during the contraction and recovery cycle. 3. In the absence of stimulation, the spectra of frog sartorius muscles and of their extracts indicated concentrations of adenosine triphosphate (ATP), phosphoryl creatine (PCr), inorganic orthophosphate (Pi) and sugar phosphates (sugar P) which are in reasonable agreement with the values obtained by chemical analysis. 4. We have confirmed that unidentified resonances representing unknown compounds appear in the spectra of both frog and toad muscle; one of these is much larger in spectra from toad than from frog. We have found an additional small, unidentified resonance which appears to be specific to toad muscle. 5. Spectra accumulated during actual contractions (1 s tetani every 2 min) did not differ dramatically from those accumulated throughout the 2 min cycle of contraction and partial recovery. 6. Following 25 s tetanii, approximately 20% of the PCr had been hydrolysed; it was then rebuilt exponentially with a half-time of about 10 min. The increase in [Pi] immediately after contraction and the time course of its disappearance corresponded to the changes in

  10. Measurement of delta(1)J((199)Hg, (31)P) in [HgPCy3(OAc)2]2 and relativistic ZORA DFT investigations of mercury-phosphorus coupling tensors.

    PubMed

    Bryce, David L; Courchesne, Noémie Manuelle Dorval; Perras, Frédéric A

    2009-12-01

    Using 31P solid-state NMR spectroscopy, anisotropy in the indirect 199Hg-31P spin-spin coupling tensor (DeltaJ) for powdered [HgPCy3(OAc)2]2 (1) has been measured as 4700 +/- 300 Hz. Zeroth-order regular approximation (ZORA) density functional theory (DFT) calculations, including scalar and spin-orbit relativistic effects, performed on 1 and a series of other related compounds show that DeltaJ(199Hg, (31)P) arises entirely from the ZORA Fermi-contact-spin-dipolar cross term. The calculations validate assumptions made in the spectral analysis of 1 and in previous determinations of DeltaJ in powder samples, namely that J is axially symmetric and shares its principal axis system with the direct dipolar coupling tensor (D). Agreement between experiment and theory for various 199Hg, 31P spin-spin coupling anisotropies is reasonable; however, experimental values of 1J(199Hg, 31P)(iso) are significantly underestimated by the calculations. The most important improvements in the agreement were obtained as a result of including more of the crystal lattice in the model used for the calculations, e.g., a change of 43% was noted for 1J(199Hg, 31P)(iso) in [HgPPh3(NO3)2]2 depending on whether the two or three nearest nitrate ions are included in the model. Finally, we have written a computer program to simulate the effects of non-axial symmetry in J and of non-coincidence of the J and D on powder NMR spectra. Simulations clearly show that both of these effects have a pronounced impact on the 31P NMR spectrum of 199Hg-31P spin pairs, suggesting that the effects should be observable experimentally if a suitable compound can be identified. PMID:20056396

  11. Impact of structural differences in carcinopreventive agents indole-3-carbinol and 3,3'-diindolylmethane on biological activity. An X-ray, ¹H-¹⁴N NQDR, ¹³C CP/MAS NMR, and periodic hybrid DFT study.

    PubMed

    Latosińska, Jolanta Natalia; Latosińska, Magdalena; Szafrański, Marek; Seliger, Janez; Žagar, Veselko; Burchardt, Dorota V

    2015-09-18

    Three experimental techniques (1)H-(14)N NQDR, (13)C CP/MAS NMR and X-ray and Density Functional Theory (GGA/BLYP with PBC) and Hirshfeld surfaces were applied for the structure-activity oriented studies of two phyto-antioxidants and anticarcinogens: indole-3-carbinol, I3C, and 3,3'-diindolylmethane, DIM, (its bioactive metabolite). One set of (14)N NQR frequencies for DIM (2.310, 2.200 and 0.110 MHz at 295K) and I3C (2.315, 1.985 and 0.330 MHz at 160K) was recorded. The multiplicity of NQR lines recorded at RT revealed high symmetry (chemical and physical equivalence) of both methyl indazole rings of DIM. Carbonyl (13)C CSA tensor components were calculated from the (13)C CP/MAS solid state NMR spectrum of I3C recorded under fast and slow spinning. At room temperature the crystal structure of I3C is orthorhombic: space group Pca21, Z=4, a=5.78922(16), b=15.6434(7) and c=8.4405(2)Å. The I3C molecules are aggregated into ribbons stacked along [001]. The oxygen atomsare disorderedbetween the two sites of different occupancy factors. It implies that the crystal is built of about 70% trans and 30% gauche conformers, and apart from the weak OH⋯O hydrogen bonds (O⋯O=3.106Å) the formation of alternative O'H⋯O bonds (O'⋯O=2.785Å) is possible within the 1D ribbons. The adjacent ribbons are further stabilised by O'H⋯O bonds (O'⋯O=2.951Å). The analysis of spectra and intermolecular interactions pattern by experimental techniques was supported by solid (periodic) DFT calculations. The knowledge of the topology and competition of the interactions in crystalline state shed some light on the preferred conformations of CH2OH in I3C and steric hindrance of methyl indole rings in DIM. A comparison of the local environment in gas phase and solid permitted drawing some conclusions on the nature of the interactions required for effective processes of recognition and binding of a given anticarcinogen to the protein or nucleic acid. PMID:26066413

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

    PubMed

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

    2015-01-28

    Disordered sol-gel prepared calcium silicate biomaterials show significant, composition dependent ability to bond with bone. Bone bonding is attributed to rapid hydroxycarbonate apatite (HCA) formation on the glass surface after immersion in body fluid (or implantation). Atomic scale details of the development of the structure of (CaO)x(SiO2)1-x (x = 0.2, 0.3 and 0.5) under heat treatment and subsequent dissolution in simulated body fluid (SBF) are revealed through a multinuclear solid state NMR approach using one-dimensional (17)O, (29)Si, (31)P and (1)H. Central to this study is the combination of conventional static and magic angle spinning (MAS) and two-dimensional (2D) triple quantum (3Q) (17)O NMR experiments that can readily distinguish and quantify the bridging (BOs) and non-bridging (NBOs) oxygens in the silicate network. Although soluble calcium is present in the sol, the (17)O NMR results reveal that the sol-gel produced network structure is initially dominated by BOs after gelation, aging and drying (e.g. at 120 °C), indicating a nanoscale mixture of the calcium salt and a predominantly silicate network. Only once the calcium salt is decomposed at elevated temperatures do the Ca(2+) ions become available to break BO. Apatite forming ability in SBF depends strongly on the surface OH and calcium content. The presence of calcium aids HCA formation via promotion of surface hydration and the ready availability of Ca(2+) ions. (17)O NMR shows the rapid loss of NBOs charge balanced by calcium as it is leached into the SBF. The formation of nanocrystalline, partially ordered HCA can be detected via(31)P NMR. This data indicates the importance of achieving the right balance of BO/NBO for optimal biochemical response and network properties. PMID:25494341

  13. Quantitative NMR Analysis of Partially Substituted Biodiesel Glycerols

    SciTech Connect

    Nagy, M.; Alleman, T. L.; Dyer, T.; Ragauskas, A. J.

    2009-01-01

    Phosphitylation of hydroxyl groups in biodiesel samples with 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane followed by 31P-NMR analysis provides a rapid quantitative analytical technique for the determination of substitution patterns on partially esterified glycerols. The unique 31P-NMR chemical shift data was established with a series mono and di-substituted fatty acid esters of glycerol and then utilized to characterize an industrial sample of partially processed biodiesel.

  14. BaBa-xy16: Robust and broadband homonuclear DQ recoupling for applications in rigid and soft solids up to the highest MAS frequencies

    NASA Astrophysics Data System (ADS)

    Saalwächter, Kay; Lange, Frank; Matyjaszewski, Krzysztof; Huang, Chih-Feng; Graf, Robert

    2011-09-01

    We here present a substantially improved version of the popular Back-to-Back (BaBa) homonuclear double-quantum (DQ) MAS recoupling pulse sequence. By combining the original pulse sequence with a virtual π pulse train with xy-16 phase cycling along with time-reversed DQ reconversion, a truly broadband and exceptionally robust pulse sequence is obtained. The sequence has moderate radio-frequency power requirements, amounting to only one 360° nutation per rotor cycle, it is robust with respect to rf power and tune-up errors, and its broadband performance increases with increasing spinning frequency, here tested up to 63 kHz. The experiment can be applied to many spin-1/2 nuclei in rigid solids with substantial frequency offsets and CSAs, which is demonstrated on the example of 31P NMR of a magnesium ultraphosphate, comparing experimental data with multi-spin simulations, and we also show simulations addressing the performance in 13C NMR of bio(macro)molecules. 1H-based studies of polymer dynamics are highlighted for the example of a rigid solid with strongly anisotropic mobility, represented by a polymer inclusion compound, and for the example of soft materials with weak residual dipole-dipole couplings, represented by homogeneous and inhomogeneous elastomers. We advocate the use of normalized (relaxation-corrected) DQ build-up curves for a quantitative assessment of weak average dipole-dipole couplings and even distributions thereof.

  15. Quantitative study of atomic ordering in Ga0.5In0.5P thin films by 31P nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Tycko, Robert; Dabbagh, Gary; Kurtz, Sarah R.; Goral, John P.

    1992-06-01

    We use 31P nuclear-magnetic-resonance (NMR) spectra to measure the degree of cation ordering in thin films of the semiconductor alloy Ga0.5In0.5P grown by organometallic vapor-phase epitaxy. We show that the five possible GanIn4-nP clusters in GaxIn1-xP give rise to resolved NMR lines under magic-angle spinning, allowing a determination of the degree of cation ordering from the relative areas of the five lines. The ordering is shown to be weak (order parameter <=0.6) even in films that appear highly ordered in transmission electron microscopy.

  16. Understanding structure-property relationships in lithium metal phosphates and oxide electrode materials: X-ray/neutron diffraction and lithium-7 MAS-NMR coupled with lithium-ion electrochemistry

    NASA Astrophysics Data System (ADS)

    Yin, Shih-Chieh

    Li-ion rechargeable battery has emerged as one of the most important portable energy carriers in the last decade. While LiCoO2 has been used as the cathode for a decade because of the good capacity and cycle retentions, tremendous efforts have been devoted to search other low cost and environmentally viable materials. Some of the promising materials such as LiFePO4, Li3V2(PO4)3, and LiNi1/3 Mn1/3Co1/3O2 were studied in this thesis. New lithium metal fluorophosphates were also discovered as potential cathode materials. The use of an aqueous solution synthesis route employing nanosized oxidized carbon black particles to inhibit LiFePO4 crystal growth was demonstrated. The resultant particle size of about 100 nm is reduced by 20 times compared to the solution synthesis method alone. Electron diffraction patterns and high resolution images from TEM experiments confirmed the single olivine phase nature of the material and the very small crystallite sizes. The 100 nm crystallites of LiFePO4-OCB showed vastly improved capacity (0.7 Li, 125mAh/g) compared to the 2mum particle. This improvement is due to contributions of decreased Li diffusion paths and improved contact with conductive carbon particles. Electrochemical PITT experiments coupled with ex-situ X-ray diffraction studies revealed the structural similarities of the delithiated monoclinic single phase compositions of LixV2(PO 4)3. (x = 2, 1, 0) From Le Bail refinements of XRD patterns, monoclinic Li3V2(PO4)3 shows only 7% volume variation upon delithiation which demonstrates its excellent intercalation characteristics. Structures of delithiated single phase compositions were further studied by both powder neutron diffraction and 7Li solid state NMR. From the structure solutions, each plateau in the V vs x curve corresponds to a two-phase transition involving the reorganization of electrons and Li ions within the lattice. The existence of charge ordering in Li2V2(PO4)3 demonstrates the electrons are pinned on both

  17. 4 T Actively detuneable double-tuned 1H/31P head volume coil and four-channel 31P phased array for human brain spectroscopy.

    PubMed

    Avdievich, N I; Hetherington, H P

    2007-06-01

    Typically 31P in vivo magnetic resonance spectroscopic studies are limited by SNR considerations. Although phased arrays can improve the SNR; to date 31P phased arrays for high-field systems have not been combined with 31P volume transmit coils. Additionally, to provide anatomical reference for the 31P studies, without removal of the coil or patient from the magnet, double-tuning (31P/1H) of the volume coil is required. In this work we describe a series of methods for active detuning and decoupling enabling use of phased arrays with double-tuned volume coils. To demonstrate these principles we have built and characterized an actively detuneable 31P/1H TEM volume transmit/four-channel 31P phased array for 4 T magnetic resonance spectroscopic imaging (MRSI) of the human brain. The coil can be used either in volume-transmit/array-receive mode or in TEM transmit/receive mode with the array detuned. Threefold SNR improvement was obtained at the periphery of the brain using the phased array as compared to the volume coil. PMID:17379554

  18. Transport of phosphocholine in higher plant cells: sup 31 P nuclear magnetic resonance studies

    SciTech Connect

    Gout, E.; Bligny, R.; Roby, C.; Douce, R. )

    1990-06-01

    Phosphocholine (PC) is an abundant primary form of organic phosphate that is transported in plant xylem sap. Addition of PC to the perfusate of compressed P{sub i}-starved sycamore cells monitored by {sup 31}P NMR spectroscopy resulted in an accumulation of PC and all the other phosphate esters in the cytoplasmic compartment. Addition of hemicholinium-3, an inhibitor of choline uptake, to the perfusate inhibited PC accumulation but not inorganic phosphate (P{sub i}). When the P{sub i}-starved cells were perfused with a medium containing either P{sub i} or PC, the resulting P{sub i} distribution in the cell was the same. Addition of choline instead of PC to the perfusate of compressed cells resulted in an accumulation of PC in the cytoplasmic compartment from choline kinase activity. In addition, PC phosphatase activity has been discovered associated with the cell wall. These results indicate that PC was rapidly hydrolyzed outside the cell and that choline and P{sub i} entered the cytosolic compartment where choline kinase re-forms PC.

  19. 31P-nuclear magnetic resonance studies of chronic myocardial ischemia in the Yucatan micropig.

    PubMed

    Rath, D P; Bailey, M; Zhang, H; Jiang, Z; Abduljalil, A M; Weisbrode, S; Hamlin, R L; Robitaille, P M

    1995-01-01

    In this work, an x-irradiation/high fat/high cholesterol diet-induced atherogenic model was invoked to examine the effects of severe diffuse atherosclerosis on myocardial metabolism in the in vivo porcine heart. This model was studied using spatially localized 31P-nuclear magnetic resonance (NMR) to monitor pH and the levels of inorganic phosphate, phosphomonoesters, creatine phosphate, and adenosine triphosphate as a function of workload transmurally in control swine and in animals suffering from chronic ischemic heart disease. These preliminary studies revealed that the development of severe atherosclerosis and the accompanying chronically diseased state produce changes in high energy phosphates and that increases in rate pressure products result in demonstrable signs of ischemia in the myocardium which span the entire left ventricular wall. Ischemic changes include a global increase in inorganic phosphate and corresponding decreases in creatine phosphate, ATP, and pH. Importantly, changes in intracellular pH are noted with even the slightest increase in workload suggesting that these diseased hearts display elevated glycolytic activity. By challenging these animals with increased cardiac workload, we directly visualize how the chronically compromised heart responds to severe oxygen challenges in a clinically relevant model of this situation. PMID:7814609

  20. 31P-nuclear magnetic resonance studies of chronic myocardial ischemia in the Yucatan micropig.

    PubMed Central

    Rath, D P; Bailey, M; Zhang, H; Jiang, Z; Abduljalil, A M; Weisbrode, S; Hamlin, R L; Robitaille, P M

    1995-01-01

    In this work, an x-irradiation/high fat/high cholesterol diet-induced atherogenic model was invoked to examine the effects of severe diffuse atherosclerosis on myocardial metabolism in the in vivo porcine heart. This model was studied using spatially localized 31P-nuclear magnetic resonance (NMR) to monitor pH and the levels of inorganic phosphate, phosphomonoesters, creatine phosphate, and adenosine triphosphate as a function of workload transmurally in control swine and in animals suffering from chronic ischemic heart disease. These preliminary studies revealed that the development of severe atherosclerosis and the accompanying chronically diseased state produce changes in high energy phosphates and that increases in rate pressure products result in demonstrable signs of ischemia in the myocardium which span the entire left ventricular wall. Ischemic changes include a global increase in inorganic phosphate and corresponding decreases in creatine phosphate, ATP, and pH. Importantly, changes in intracellular pH are noted with even the slightest increase in workload suggesting that these diseased hearts display elevated glycolytic activity. By challenging these animals with increased cardiac workload, we directly visualize how the chronically compromised heart responds to severe oxygen challenges in a clinically relevant model of this situation. Images PMID:7814609

  1. Centerband-only analysis of rotor-unsynchronized spin echo for measurement of lipid (31) P chemical shift anisotropy.

    PubMed

    Umegawa, Yuichi; Yamaguchi, Toshiyuki; Murata, Michio; Matsuoka, Shigeru

    2015-07-01

    Structural diversity and molecular flexibility of phospholipids are essential for biological membranes to play key roles in numerous cellular processes. Uncovering the behavior of individual lipids in membrane dynamics is crucial for understanding the molecular mechanisms underlying biological functions of cell membranes. In this paper, we introduce a simple method to investigate dynamics of lipid molecules in multi-component systems by measuring the (31) P chemical shift anisotropy (CSA) under magic angle spinning (MAS) conditions. For achieving both signal separation and CSA determination, we utilized a centerband-only analysis of rotor-unsynchronized spin echo (COARSE). This analysis is based on the curve fitting of periodic modulation of centerband intensity along the interpulse delay time in rotor-unsynchronized spin-echo experiments. The utility of COARSE was examined by using phospholipid vesicles, a three-component lipid raft model system, and archaeal purple membranes. We found that the apparent advantages of this method are high resolution and high sensitivity given by the moderate MAS speed and the one-dimensional acquisition with short spin-echo delays. COARSE provides an alternative method for CSA measurement that is effective in the investigation of lipid polymorphologies. PMID:26017552

  2. 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.

  3. Solid-State NMR Reveals the Hydrophobic-Core Location of Poly(amidoamine) Dendrimers in Biomembranes

    PubMed Central

    Smith, Pieter E. S.; Brender, Jeffrey R.; Dürr, Ulrich H. N.; Xu, Jiadi; Mullen, Douglas G.; Banaszak Holl, Mark M.; Ramamoorthy, Ayyalusamy

    2010-01-01

    Poly(amidoamine) (PAMAM) dendrimer nanobiotechnology shows great promise in targeted drug delivery and gene therapy. Because of the involvement of cell membrane lipids with the pharmacological activity of dendrimer nanomedicines, the interactions between dendrimers and lipids are of particular relevance to the pharmaceutical applications of dendrimers. In this study, solid-state NMR was used to obtain a molecular image of the complex of generation 5 PAMAM dendrimer with the lipid bilayer. Using 1H radio frequency driven dipolar recoupling (RFDR) and 1H magic angle spinning (MAS) nuclear Overhauser effect spectroscopy (NOESY) techniques, we show that dendrimers are thermodynamically stable when inserted into zwitterionic lipid bilayers. 14N and 31P NMR experiments on static samples and measurements of the mobility of C–H bonds using a 2D proton detected local field protocol under MAS corroborate these results. The localization of dendrimers in the hydrophobic core of lipid bilayers restricts the motion of bilayer lipid tails, with the smaller G5 dendrimer having more of an effect than the larger G7 dendrimer. Fragmentation of the membrane does not occur at low dendrimer concentrations in zwitterionic membranes. Because these results show that the amphipathic dendrimer molecule can be stably incorporated in the interior of the bilayer (as opposed to electrostatic binding at the surface), they are expected to be useful in the design of dendrimer-based nanobiotechnologies. PMID:20481633

  4. Characterization of phosphorus forms in lake macrophytes and algae by solution (31)P nuclear magnetic resonance spectroscopy.

    PubMed

    Feng, Weiying; Zhu, Yuanrong; Wu, Fengchang; Meng, Wei; Giesy, John P; He, Zhongqi; Song, Lirong; Fan, Mingle

    2016-04-01

    Debris from aquatic macrophytes and algae are important recycling sources of phosphorus (P), which can result in continuing blooms of algae by recycling bioavailable P in the eutrophic lakes. However, knowledge of forms of P in aquatic macrophytes and algae and their contribution to internal loads of P in lakes is limited. Without such knowledge, it is difficult to develop appropriate strategies to remediate and or restore aquatic ecosystems that have become eutrophic. Therefore, in this work, P was extracted from six types of aquatic macrophytes and algae collected from Tai Lake of China and characterized by use of solution (31)P-nuclear magnetic resonance (NMR) spectroscopy. When extracted by 0.5 M NaOH-25 mM EDTA, extraction recovery of total P(TP) and organic P(Po) exceeded 90 %. Concentrations of Po in algae and aquatic macrophytes were 5552 mg kg(-1) and 1005 mg kg(-1) and accounted for 56.0 and 47.2 % of TP, respectively. When Po, including condensed P, was characterized by solution (31)P-NMR Po in algae included orthophosphate monoesters (79.8 %), pyrophosphate (18.2 %), and orthophosphate diester (2.0 %), and Po in aquatic macrophytes included orthophosphate monoesters (90.3 %), pyrophosphate (4.2 %), and orthophosphate diester (5.5 %). Additionally, orthophosphate monoesters in algal debris mainly included β-glycerophosphate (44.1 %), α-glycerophosphate (13.5 %), and glucose 6-phosphate (13.5 %). Orthophosphate monoesters in aquatic macrophytes mainly included β-glycerophosphate (27.9 %), α-glycerophosphate (24.6 %), and adenosine 5' monophosphate (8.2 %). Results derived from this study will be useful in better understanding nutrient cycling, relevant eutrophication processes, and pollution control for freshwater lakes. PMID:26681323

  5. Comparison of phytate and other organic P forms in Mehlich-3 and Alkaline-EDTA matrices by ICP, NMR and mass spectrometry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The favored method of organic P identification over the last few decades has been 31P NMR. While this technique has the distinct advantage of speciating the organic P fraction, it has a relatively poor detection threshold (0.05 mg/ml), which typically limits 31P NMR to qualitative or confirmative ap...

  6. Comparison of (31)P saturation and inversion magnetization transfer in human liver and skeletal muscle using a clinical MR system and surface coils.

    PubMed

    Buehler, Tania; Kreis, Roland; Boesch, Chris

    2015-02-01

    (31)P MRS magnetization transfer ((31)P-MT) experiments allow the estimation of exchange rates of biochemical reactions, such as the creatine kinase equilibrium and adenosine triphosphate (ATP) synthesis. Although various (31)P-MT methods have been successfully used on isolated organs or animals, their application on humans in clinical scanners poses specific challenges. This study compared two major (31)P-MT methods on a clinical MR system using heteronuclear surface coils. Although saturation transfer (ST) is the most commonly used (31)P-MT method, sequences such as inversion transfer (IT) with short pulses might be better suited for the specific hardware and software limitations of a clinical scanner. In addition, small NMR-undetectable metabolite pools can transfer MT to NMR-visible pools during long saturation pulses, which is prevented with short pulses. (31)P-MT sequences were adapted for limited pulse length, for heteronuclear transmit-receive surface coils with inhomogeneous B1 , for the need for volume selection and for the inherently low signal-to-noise ratio (SNR) on a clinical 3-T MR system. The ST and IT sequences were applied to skeletal muscle and liver in 10 healthy volunteers. Monte-Carlo simulations were used to evaluate the behavior of the IT measurements with increasing imperfections. In skeletal muscle of the thigh, ATP synthesis resulted in forward reaction constants (k) of 0.074 ± 0.022 s(-1) (ST) and 0.137 ± 0.042 s(-1) (IT), whereas the creatine kinase reaction yielded 0.459 ± 0.089 s(-1) (IT). In the liver, ATP synthesis resulted in k = 0.267 ± 0.106 s(-1) (ST), whereas the IT experiment yielded no consistent results. ST results were close to literature values; however, the IT results were either much larger than the corresponding ST values and/or were widely scattered. To summarize, ST and IT experiments can both be implemented on a clinical body scanner with heteronuclear transmit-receive surface coils; however, ST results are

  7. Scalar and anisotropic J interactions in undoped InP: A triple-resonance NMR study

    NASA Astrophysics Data System (ADS)

    Tomaselli, Marco; Degraw, David; Yarger, Jeffery L.; Augustine, Matthew P.; Pines, Alexander

    1998-10-01

    The heteronuclear J-coupling tensor between nearest neighbor 31P and 113In spins in undoped InP is investigated by means of 113In-->31P polarization transfer under rapid magic angle spinning (MAS). The scalar contribution can be measured directly and is found to have the value \\|Jiso(31P-113,115In)\\|=(225+/-10) Hz. The principal value of the traceless anisotropic J-coupling tensor (pseudodipolar coupling) is determined to be Janiso(31P-113,115In)=2/3[J||(31P-113,115In)-J⊥(31P-113,115In)]=(813+/-50) or (1733+/-50) Hz, assuming axial symmetry with the principal axis parallel to the In-P bond. Our values deviate from those reported previously [M. Engelsberg and R. E. Norberg, Phys. Rev. B 5, 3395 (1972)] [based on a moment analysis of the 31P resonance \\|Jiso(31P-113,115In)\\|=350 Hz and Janiso(31P-113,115In)=1273 Hz], but confirm the postulate that the nearest neighbor 31P-113,115In magnetic dipolar and pseudodipolar interactions are of the same order of magnitude and partially cancel each other.

  8. Solid-State NMR, Crystallographic, and Computational Investigation of Bisphosphonates and Farnesyl Diphosphate Synthase-Bisphosphonate Complexes

    SciTech Connect

    Mao,J.; Mukherjee, S.; Zhang, Y.; Cao, R.; Sanders, J.; Song, Y.; Zhang, Y.; Meints, G.; Gao, Y.; et al.

    2006-01-01

    Bisphosphonates are a class of molecules in widespread use in treating bone resorption diseases and are also of interest as immunomodulators and anti-infectives. They function by inhibiting the enzyme farnesyl diphosphate synthase (FPPS), but the details of how these molecules bind are not fully understood. Here, we report the results of a solid-state {sup 13}C, {sup 15}N, and {sup 31}P magic-angle sample spinning (MAS) NMR and quantum chemical investigation of several bisphosphonates, both as pure compounds and when bound to FPPS, to provide information about side-chain and phosphonate backbone protonation states when bound to the enzyme. We then used computational docking methods (with the charges assigned by NMR) to predict how several bisphosphonates bind to FPPS. Finally, we used X-ray crystallography to determine the structures of two potent bisphosphonate inhibitors, finding good agreement with the computational results, opening up the possibility of using the combination of NMR, quantum chemistry and molecular docking to facilitate the design of other, novel prenytransferase inhibitors.

  9. Characterization of the phosphoserine of pepsinogen using /sup 31/P nuclear magnetic resonance: corroboration of X-ray crystallographic results

    SciTech Connect

    Williams, S.P.; Bridger, W.A.; James, M.N.G.

    1986-10-21

    The endogenous phosphoserine residue in porcine pepsinogen has been titrated with use of phosphorus-31 nuclear magnetic resonance (/sup 31/P NMR). It has an observed pK/sub a/sub 2// of 6.7 and a narrow line width (approx. =10 Hz). The phosphate can be readily removed by an acid phosphatase from potato; however, it is resistant to hydrolysis by several alkaline phosphatases. The X-ray crystal structure of porcine pepsinogen at 1.8-A resolution shows a rather weak and diffuse region of electron density in the vicinity of the phosphorylated serine residue. This suggests considerable dynamic mobility or conformational disorder of the phosphate. In order to define more fully this behavior the NMR data have been used to corroborate these crystallographic results. All these physical data are consistent with a highly mobile phosphoserine residue on the surface of the zymogen and freely exposed to solvent. In addition, certain properties of this phosphoserine moiety on pepsinogen are similar to those of one of the phosphorylated residues of ovalbumin. The possible significance of this is discussed.

  10. The effects of pregnancy and parturition on phosphorus metabolites in rat uterus studied by 31P nuclear magnetic resonance.

    PubMed Central

    Dawson, M J; Wray, S

    1985-01-01

    Concentrations of phosphorus metabolites and intracellular pH have been measured in non-pregnant, late-pregnant and post-partum rat uterus using 31P nuclear magnetic resonance (31P n.m.r.). Intact uterine tissue was superfused with oxygenated de-Jalon solution at 4, 20 or 37 degrees C while inside the n.m.r. spectrometer. The phosphocreatine concentration [PCr], was higher and the inorganic phosphate concentration [Pi], lower than values determined by chemical analysis of extracts from both pregnant and non-pregnant rat uterus. [PCr] was 1.4-fold greater in late-pregnant than in non-pregnant rat uterus. Following parturition, large changes were observed in [PCr], [Pi] and in an unidentified metabolite in the phosphomonoester (PME) region of the n.m.r. spectrum. The time course of the recovery of these metabolites to prepregnant values was determined. The [PCr] remained below the non-pregnant value for at least 1 week post-partum and the [Pi] was elevated, compared to the non-pregnant value, during this period. More rapid changes were seen in the [PME], which doubled on day 0 post-partum but almost returned to its non-pregnant value on day 1 post-partum. No significant difference was observed between intracellular pH values in late-pregnant and non-pregnant rat uterus; however, there was a large acid shift following parturition. Intracellular pH depended upon the temperature at which the tissue was maintained. The effect of muscular work during parturition was investigated by comparing Caesarian-sectioned uteri with uteri which had undergone normal parturition. Uteri examined 1 day after Caesarian operation showed no differences in metabolite levels from normal, 1 day post-partum uteri. We conclude that concentrations of phosphorus metabolites depend upon the physiological state of the uterus. We suggest that the changes following parturition are not a consequence of the mechanical work performed by the uterus, but must be caused by some other event associated with

  11. Local structure and lithium mobility in intercalated Li3Al(x)Ti(2-x)(PO4)3 NASICON type materials: a combined neutron diffraction and NMR study.

    PubMed

    Arbi, K; Hoelzel, M; Kuhn, A; García-Alvarado, F; Sanz, J

    2014-09-14

    The structural features of intercalated Li3AlxTi2-x(PO4)3 compounds, with x = 0 and 0.2, have been deduced by Rietveld analysis of neutron diffraction (ND) patterns recorded between 100 and 500 K. The Li insertion decreases the symmetry from R3̄c to R3̄ in analyzed compounds. In pristine Li1+xAlxTi2-x(PO4)3 samples, Li occupies mainly six-fold M1 sites at ternary axes; but in lithiated Li3AlxTi2-x(PO4)3 samples, Li is located near M2 positions at M3/M3' four-fold coordinated sites. In both cases, Li arrangement minimizes electrostatic Li-Li repulsions. The insertion of lithium resulted in the reduction of Ti(4+) to Ti(3+) that shifts (7)Li, (27)Al and (31)P MAS-NMR resonances towards more positive chemical shifts, improving the resolution of different sites. The detection of twelve components in (7)Li MAS-NMR spectra recorded at room temperature suggests the location of Li(+) ions at three-oxygen faces that define M2 cavities. From (7)Li MAS-NMR spectra, the occupancy of sites and mobility of lithium were investigated in the temperature range 100-500 K. The correlation between structural information, deduced by neutron diffraction, and lithium mobility, deduced by NMR spectroscopy, provides new insights into structural factors that affect lithium mobility in materials with NASICON structure. PMID:25070935

  12. Bone Mineral 31P and Matrix-Bound Water Densities Measured by Solid-State 1H and 31P MRI

    PubMed Central

    Seifert, Alan C.; Li, Cheng; Rajapakse, Chamith S.; Bashoor- Zadeh, Mahdieh; Bhagat, Yusuf A.; Wright, Alexander C.; Zemel, Babette S.; Zavaliangos, Antonios; Wehrli, Felix W.

    2014-01-01

    Bone is a composite material consisting of mineral and hydrated collagen fractions. MRI of bone is challenging due to extremely short transverse relaxation times, but solid-state imaging sequences exist that can acquire the short-lived signal from bone tissue. Previous work to quantify bone density via MRI used powerful experimental scanners. This work seeks to establish the feasibility of MRI-based measurement on clinical scanners of bone mineral and collagen-bound water densities, the latter as a surrogate of matrix density, and to examine the associations of these parameters with porosity and donors’ age. Mineral and matrix-bound water images of reference phantoms and cortical bone from 16 human donors, ages 27-97 years, were acquired by zero-echo-time 31P and 1H MRI on whole body 7T and 3T scanners, respectively. Images were corrected for relaxation and RF inhomogeneity to obtain density maps. Cortical porosity was measured by micro-CT, and apparent mineral density by pQCT. MRI-derived densities were compared to x-ray-based measurements by least-squares regression. Mean bone mineral 31P density was 6.74±1.22 mol/L (corresponding to 1129±204 mg/cc mineral), and mean bound water 1H density was 31.3±4.2 mol/L (corresponding to 28.3±3.7 %v/v). Both 31P and bound water (BW) densities were correlated negatively with porosity (31P: R2 = 0.32, p < 0.005; BW: R2 = 0.63, p < 0.0005) and age (31P: R2 = 0.39, p < 0.05; BW: R2 = 0.70, p < 0.0001), and positively with pQCT density (31P: R2 = 0.46, p < 0.05; BW: R2 = 0.50, p < 0.005). In contrast, the bone mineralization ratio (expressed here as the ratio of 31P density to bound water density), which is proportional to true bone mineralization, was found to be uncorrelated with porosity, age, or pQCT density. This work establishes the feasibility of image-based quantification of bone mineral and bound water densities using clinical hardware. PMID:24846186

  13. 31P-nuclear magnetic resonance spectroscopy in vivo of six human melanoma xenograft lines: tumour bioenergetic status and blood supply.

    PubMed Central

    Lyng, H.; Olsen, D. R.; Southon, T. E.; Rofstad, E. K.

    1993-01-01

    Six human melanoma xenograft lines grown s.c. in BALB/c-nu/nu mice were subjected to 31P-nuclear magnetic resonance (31P-NMR) spectroscopy in vivo. The following resonances were detected: phosphomonoesters (PME), inorganic phosphate (Pi), phosphodiesters (PDE), phosphocreatine (PCr) and nucleoside triphosphate gamma, alpha and beta (NTP gamma, alpha and beta). The main purpose of the work was to search for possible relationships between 31P-NMR resonance ratios and tumour pH on the one hand and blood supply per viable tumour cell on the other. The latter parameter was measured by using the 86Rb uptake method. Tumour bioenergetic status [the (PCr + NTP beta)/Pi resonance ratio], tumour pH and blood supply per viable tumour cell decreased with increasing tumour volume for five of the six xenograft lines. The decrease in tumour bioenergetic status was due to a decrease in the (PCr + NTP beta)/total resonance ratio as well as an increase in the Pi/total resonance ratio. The decrease in the (PCr + NTP beta)/total resonance ratio was mainly a consequence of a decrease in the PCr/total resonance ratio for two lines and mainly a consequence of a decrease in the NTP beta/total resonance ratio for three lines. The magnitude of the decrease in the (PCr + NTP beta)/total resonance ratio and the magnitude of the decrease in tumour pH were correlated to the magnitude of the decrease in blood supply per viable tumour cell. Tumour pH decreased with decreasing tumour bioenergetic status, and the magnitude of this decrease was larger for the tumour lines showing a high than for those showing a low blood supply per viable tumour cell. No correlations across the tumour lines were found between tumour pH and tumour bioenergetic status or any other resonance ratio on the one hand and blood supply per viable tumour cell on the other. The differences in the 31P-NMR spectrum between the tumour lines were probably caused by differences in the intrinsic biochemical properties of the tumour

  14. Advancement of 31P Magnetic Resonance Spectroscopy Using GRAPPA Reconstruction on a 3D Volume

    NASA Astrophysics Data System (ADS)

    Clevenger, Tony

    The overall objective of this research is to improve currently available metabolic imaging techniques for clinical use in monitoring and predicting treatment response to radiation therapy in liver cancer. Liver metabolism correlates with inflammatory and neoplastic liver diseases, which alter the intracellular concentration of phosphorus- 31 (31P) metabolites [1]. It is assumed that such metabolic changes occur prior to physical changes of the tissue. Therefore, information on regional changes of 31P metabolites in the liver, obtained by Magnetic Resonance Spectroscopic Imaging (MRSI) [1,2], can help in diagnosis and follow-up of various liver diseases. Specifically, there appears to be an immediate need of this technology for both the assessment of tumor response in patients with Hepatocellular Carcinoma (HCC) treated with Stereotactic Body Radiation Therapy (SBRT) [3--5], as well as assessment of radiation toxicity, which can result in worsening liver dysfunction [6]. Pilot data from our lab has shown that 31P MRSI has the potential to identify treatment response five months sooner than conventional methods [7], and to assess the biological response of liver tissue to radiation 24 hours post radiation therapy [8]. While this data is very promising, commonly occurring drawbacks for 31P MRSI are patient discomfort due to long scan times and prone positioning within the scanner, as well as reduced data quality due to patient motion and respiration. To further advance the full potential of 31P MRSI as a clinical diagnostic tool in the management of liver cancer, this PhD research project had the following aims: I) Reduce the long acquisition time of 3D 31P MRS by formulating and imple- menting an appropriate GRAPPA undersampling scheme and reconstruction on a clinical MRI scanner II) Testing and quantitative validation of GRAPPA reconstruction on 3D 31P MRSI on developmental phantoms and healthy volunteers At completion, this work should considerably advance 31P MRSI

  15. Rotation of Lipids in Membranes: Molecular Dynamics Simulation, 31P Spin-Lattice Relaxation, and Rigid-Body Dynamics

    PubMed Central

    Klauda, Jeffery B.; Roberts, Mary F.; Redfield, Alfred G.; Brooks, Bernard R.; Pastor, Richard W.

    2008-01-01

    Molecular dynamics simulations and 31P-NMR spin-lattice (\\documentclass[10pt]{article} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{pmc} \\usepackage[Euler]{upgreek} \\pagestyle{empty} \\oddsidemargin -1.0in \\begin{document} \\begin{equation*}R_{1}\\end{equation*}\\end{document}) relaxation rates from 0.022 to 21.1 T of fluid phase dipalmitoylphosphatidylcholine bilayers are compared. Agreement between experiment and direct prediction from simulation indicates that the dominant slow relaxation (correlation) times of the dipolar and chemical shift anisotropy spin-lattice relaxation are ∼10 ns and 3 ns, respectively. Overall reorientation of the lipid body, consisting of the phosphorus, glycerol, and acyl chains, is well described within a rigid-body model. Wobble, with \\documentclass[10pt]{article} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{pmc} \\usepackage[Euler]{upgreek} \\pagestyle{empty} \\oddsidemargin -1.0in \\begin{document} \\begin{equation*}D_{{\\bot}}=\\end{equation*}\\end{document} 1–2 × 108 s−1, is the primary component of the 10 ns relaxation; this timescale is consistent with the tumbling of a lipid-sized cylinder in a medium with the viscosity of liquid hexadecane. The value for \\documentclass[10pt]{article} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{pmc} \\usepackage[Euler]{upgreek} \\pagestyle{empty} \\oddsidemargin -1.0in \\begin{document} \\begin{equation*}D_{{\\Vert}},\\end{equation*}\\end{document} the diffusion constant for rotation about the long axis of the lipid body, is difficult to determine precisely because of averaging by fast motions and wobble; it is tentatively estimated to be 1 × 107 s−1. The resulting D‖/D⊥

  16. Application of solids MAS nuclear magnetic resonance to study of diagenetic processes

    SciTech Connect

    Sommer, S.E.; Woessner, D.E.

    1984-04-01

    Magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR) provides the opportunity to probe composition of and ordering in minerals involved in the formation and alteration of sediments. MAS-NMR has the capability to detect a large number of elements, including aluminum, silicon, boron, oxygen, and magnesium. The chemical state, structural location, and with cross polarization, hydration character and surface proximity can also be determined using this method. Although MAS-NMR is relatively new and quantitative methodology is still being developed, a variety of geologic processes have been clarified through its application. Use of /sup 27/Al NMR allows detailed determination of the smectite-illite transformation by monitoring the movements of aluminum into tetrahedral positions and resultant cation ordering. Because /sup 27/Al is detectable to low ppm levels, clay mineral components can be determined well below XRD detection levels. The /sup 29/Si and /sup 27/Al MAS-NMR have sufficient resolution to discriminate between minerals in a natural assemblage but not with the resolution of XRD. Quadrupolar nuclei such as /sup 27/Al have relatively poor spectral resolution as compared to nonquadrupolar nuclei such as /sup 29/Si. However, modern high field instrumentation can discriminate between most aluminum-containing minerals including aluminum oxides, hydroxides, oxyhydroxides, clays, and feldspars, as well as trace aluminum levels in quartz, cristobalite, and tridymite. The combination of /sup 27/Al and /sup 29/Si NMR (and availability of other nuclei) provide a powerful aid to the resolution of exploration and production problems including determination of minor to trace amorphous components, hydration state of elements in cherts and clays, and formation damage.

  17. Ionothermal synthesis, crystal structure and solid-state NMR spectroscopy of a new organically templated gallium oxalatophosphate: (H2TMPD)0.5[Ga3(C2O4)0.5(PO4)3] (TMPD=N,N,N',N'-tetramethyl-1,3-propanediamine).

    PubMed

    Tang, Ming-Feng; Liu, Yi-Hui; Chang, Pai-Ching; Liao, Yi-Chen; Kao, Hsien-Ming; Lii, Kwang-Hwa

    2007-10-28

    A new organically templated gallium oxalatophosphate, (C7H20N2)0.5[Ga3(C2O4)0.5(PO4)3], has been synthesized by using a low-melting-point eutectic mixture of choline chloride and oxalic acid as a solvent and characterized by single-crystal X-ray diffraction, thermogravimetric analysis and solid-state NMR spectroscopy. It is the first example of ionothermal synthesis of organically templated metal oxalatophosphate. The structure contains double 6-ring units of the composition Ga6(PO4)6 which are connected by oxalate ligands and P-O-Ga bonds to form a 3-D framework. The charge-compensating organic ammonium cations which are disordered over two positions are located at the intersections of two types of 8-ring channels. 1H MAS and 13C CPMAS NMR studies confirm the presence of N,N,N',N'-tetramethyl-1,3-propanediammonium cation. The 71Ga and 31P MAS NMR spectra are also consistent with the crystal structure analysis results. PMID:17928909

  18. An NMR crystallographic approach to monitoring cation substitution in the aluminophosphate STA-2.

    PubMed

    Seymour, Valerie R; Eschenroeder, Eike C V; Wright, Paul A; Ashbrook, Sharon E

    2015-02-01

    The substitution of the divalent cations Mg(2+) and Zn(2+) into the aluminophosphate (AlPO) framework of STA-2 has been studied using an "NMR crystallographic" approach, combining multinuclear solid-state NMR spectroscopy, X-ray diffraction and first-principles calculations. Although the AlPO framework itself is inherently neutral, the positive charge of the organocation template in an as-made material is usually balanced either by the coordination to the framework of anions from the synthesis solution, such as OH(-) or F(-), and/or by the substitution of aliovalent cations. However, the exact position and distribution of the substituted cations can be difficult to determine, but can have a significant impact upon the catalytic properties a material exhibits once calcined. For as-made Mg substituted STA-2, the positive charge of the organocation template is balanced by the substitution of Mg(2+) for Al(3+) and, where required, by hydroxide anions coordinated to the framework [27] Al MAS NMR spectra show that Al is present in both tetrahedral and five-fold coordination, with the latter dependent on the amount of substituted cations, and confirms the bridging nature of the hydroxyl groups, while high-resolution MQMAS spectra are able to show that Mg appears to preferentially substitute on the Al1 site. This conclusion is also supported by first-principles calculations. The calculations also show that (31)P chemical shifts depend not only on the topologically-distinct site in the SAT framework, but also on the number of next-nearest-neighbour Mg species, and the exact nature of the coordinated hydroxyls (whether the P atom forms part of a six-membered ring, P(OAl)2OH, where OH bridges between two Al atoms). The calculations demonstrate a strong correlation between the (31)P isotropic chemical shift and the average 〈P-O-M〉 bond angle. In contrast, for Zn substituted STA-2, both X-ray diffraction and NMR spectroscopy show less preference for substitution onto Al1 or

  19. Solid state NMR investigation of intact human bone quality: balancing issues and insight into the structure at the organic-mineral interface

    PubMed Central

    Nikel, Ondrej; Laurencin, Danielle; Bonhomme, Christian; Sroga, Grażyna E.; Besdo, Silke; Lorenz, Anna; Vashishth, Deepak

    2012-01-01

    Age-related bone fragility fractures present a significant problem for public health. Measures of bone quality are increasingly recognized to complement the conventional bone mineral density (BMD) based assessment of fracture risk. The ability to probe and understand bone quality at the molecular level is desirable in order to unravel how the structure of organic matrix and its association with mineral contribute to the overall mechanical properties. The 13C{31P} REDOR MAS NMR (Rotational Echo Double Resonance Magic Angle Spinning Nuclear Magnetic Resonance) technique is uniquely suited for the study of the structure of the organic-mineral interface in bone. For the first time, we have applied it successfully to analyze the structure of intact (non-powdered) human cortical bone samples, from young healthy and old osteoporotic donors. Loading problems associated with the rapid rotation of intact bone were solved using a Finite Element Analysis (FEA) approach, and a method allowing osteoporotic samples to be balanced and spun reproducibly is described. REDOR NMR parameters were set to allow insight into the arrangement of the amino acids at the mineral interface to be accessed, and SVD (Singular Value Decomposition) was applied to enhance the signal to noise ratio and enable a better analysis of the data. From the REDOR data, it was found that carbon atoms belonging to citrate/glucosaminoglycans (GAGs) are closest to the mineral surface regardless of age or site. In contrast, the arrangement of the collagen backbone at the interface varied with site and age. The relative proximity of two of the main amino acids in bone matrix proteins, hydroxyproline and alanine, with respect to the mineral phase was analyzed in more detail, and discussed in view of glycation measurements which were carried out on the tissues. Overall, this work shows that the 13C{31P} REDOR NMR approach could be used as a complementary technique to assess a novel aspect of bone quality, the organic

  20. Moving NMR

    NASA Astrophysics Data System (ADS)

    Blümich, Bernhard; Casanova, Federico; Danieli, Ernesto; Gong, Qingxia; Greferath, Marcus; Haber, Agnes; Kolz, Jürgen; Perlo, Juan

    2008-12-01

    Initiated by the use of NMR for well logging, portable NMR instruments are being developed for a variety of novel applications in materials testing and process analysis and control. Open sensors enable non-destructive testing of large objects, and small, cup-size magnets become available for high throughput analysis by NMR relaxation and spectroscopy. Some recent developments of mobile NMR are reviewed which delineate the direction into which portable NMR is moving.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  2. High-frequency dynamic nuclear polarization in MAS spectra of membrane and soluble proteins.

    PubMed

    Rosay, Melanie; Lansing, Jonathan C; Haddad, Kristin C; Bachovchin, William W; Herzfeld, Judith; Temkin, Richard J; Griffin, Robert G

    2003-11-12

    One of the principal promises of solid-state NMR (SSNMR) magic angle spinning (MAS) experiments has been the possibility of determining the structures of molecules in states that are not accessible via X-ray or solution NMR experiments-e.g., membrane or amyloid proteins. However, the low sensitivity of SSNMR often restricts structural studies to small-model compounds and precludes many higher-dimensional solid-state MAS experiments on such systems. To address the sensitivity problem, we have developed experiments that utilize dynamic nuclear polarization (DNP) to enhance sensitivity. In this communication, we report the successful application of MAS DNP to samples of cryoprotected soluble and membrane proteins. In particular, we have observed DNP signal enhancements of up to 50 in 15N MAS spectra of bacteriorhodopsin (bR) and alpha-lytic protease (alpha-LP). The spectra were recorded at approximately 90 K where MAS is experimentally straightforward, and the results suggest that the described protocol will be widely applicable. PMID:14599177

  3. Decreased energy requirement of toad retina during light adaptation as demonstrated by 31P nuclear magnetic resonance.

    PubMed Central

    Apte, D V; Ebrey, T G; Dawson, M J

    1993-01-01

    1. The effect of light and dark adaptation on the levels of phosphorus metabolites (nucleotide di- and triphosphates, phosphocreatine, pyridine nucleotide, inorganic phosphate, phosphodiesters, phosphomonoesters, and uridine diphosphate-glucose) in the toad (Bufo marinus) retina and retinal extracts was studied by 31P nuclear magnetic resonance (NMR) spectroscopy. 2. Spectra were acquired using an NMR probe specifically designed for superfusion and illumination of a single retina. Retinae were maintained at a steady state for up to 10 h in an electrolyte solution containing 10 mM Hepes buffer and bubbled with 98% O2-2% CO2, pH 7.8 at 20 degrees C. 3. The intracellular concentrations of the phosphorus metabolites were measured in total darkness or during prolonged exposure to light. The concentration of nucleoside triphosphates (NTP) in the dark-adapted retina was about 1.5 mM and that of phosphocreatine (PCr) was about 0.7 mM. 4. In saturating levels of light, 6.0 x 10(11) or 1.5 x 10(13) quanta s-1 cm-2 at 520 nm, the levels of PCr and phosphomonoesters rose, the levels of NTP and protons (pH) were maintained, and the levels of pyridine nucleotides and nucleotide diphosphates (NDP) fell. 5. A rise in the level of PCr in the presence of an unchanged level of NTP in the light-adapted retina indicates that the energy consumption of the retina is greater in the dark. 6. These results are in agreement with the results of oxygen consumption, glucose dependence, and electrophysiological studies which also indicate that the metabolic energy requirement of the retina decreases in light. PMID:8229802

  4. Fluid flow dynamics in MAS systems

    NASA Astrophysics Data System (ADS)

    Wilhelm, Dirk; Purea, Armin; Engelke, Frank

    2015-08-01

    The turbine system and the radial bearing of a high performance magic angle spinning (MAS) probe with 1.3 mm-rotor diameter has been analyzed for spinning rates up to 67 kHz. We focused mainly on the fluid flow properties of the MAS system. Therefore, computational fluid dynamics (CFD) simulations and fluid measurements of the turbine and the radial bearings have been performed. CFD simulation and measurement results of the 1.3 mm-MAS rotor system show relatively low efficiency (about 25%) compared to standard turbo machines outside the realm of MAS. However, in particular, MAS turbines are mainly optimized for speed and stability instead of efficiency. We have compared MAS systems for rotor diameter of 1.3-7 mm converted to dimensionless values with classical turbomachinery systems showing that the operation parameters (rotor diameter, inlet mass flow, spinning rate) are in the favorable range. This dimensionless analysis also supports radial turbines for low speed MAS probes and diagonal turbines for high speed MAS probes. Consequently, a change from Pelton type MAS turbines to diagonal turbines might be worth considering for high speed applications. CFD simulations of the radial bearings have been compared with basic theoretical values proposing considerably smaller frictional loss values. The discrepancies might be due to the simple linear flow profile employed for the theoretical model. Frictional losses generated inside the radial bearings result in undesired heat-up of the rotor. The rotor surface temperature distribution computed by CFD simulations show a large temperature gradient over the rotor.

  5. Fluid flow dynamics in MAS systems.

    PubMed

    Wilhelm, Dirk; Purea, Armin; Engelke, Frank

    2015-08-01

    The turbine system and the radial bearing of a high performance magic angle spinning (MAS) probe with 1.3mm-rotor diameter has been analyzed for spinning rates up to 67kHz. We focused mainly on the fluid flow properties of the MAS system. Therefore, computational fluid dynamics (CFD) simulations and fluid measurements of the turbine and the radial bearings have been performed. CFD simulation and measurement results of the 1.3mm-MAS rotor system show relatively low efficiency (about 25%) compared to standard turbo machines outside the realm of MAS. However, in particular, MAS turbines are mainly optimized for speed and stability instead of efficiency. We have compared MAS systems for rotor diameter of 1.3-7mm converted to dimensionless values with classical turbomachinery systems showing that the operation parameters (rotor diameter, inlet mass flow, spinning rate) are in the favorable range. This dimensionless analysis also supports radial turbines for low speed MAS probes and diagonal turbines for high speed MAS probes. Consequently, a change from Pelton type MAS turbines to diagonal turbines might be worth considering for high speed applications. CFD simulations of the radial bearings have been compared with basic theoretical values proposing considerably smaller frictional loss values. The discrepancies might be due to the simple linear flow profile employed for the theoretical model. Frictional losses generated inside the radial bearings result in undesired heat-up of the rotor. The rotor surface temperature distribution computed by CFD simulations show a large temperature gradient over the rotor. PMID:26073599

  6. Accuracy and precision of quantitative 31P-MRS measurements of human skeletal muscle mitochondrial function.

    PubMed

    Layec, Gwenael; Gifford, Jayson R; Trinity, Joel D; Hart, Corey R; Garten, Ryan S; Park, Song Y; Le Fur, Yann; Jeong, Eun-Kee; Richardson, Russell S

    2016-08-01

    Although theoretically sound, the accuracy and precision of (31)P-magnetic resonance spectroscopy ((31)P-MRS) approaches to quantitatively estimate mitochondrial capacity are not well documented. Therefore, employing four differing models of respiratory control [linear, kinetic, and multipoint adenosine diphosphate (ADP) and phosphorylation potential], this study sought to determine the accuracy and precision of (31)P-MRS assessments of peak mitochondrial adenosine-triphosphate (ATP) synthesis rate utilizing directly measured peak respiration (State 3) in permeabilized skeletal muscle fibers. In 23 subjects of different fitness levels, (31)P-MRS during a 24-s maximal isometric knee extension and high-resolution respirometry in muscle fibers from the vastus lateralis was performed. Although significantly correlated with State 3 respiration (r = 0.72), both the linear (45 ± 13 mM/min) and phosphorylation potential (47 ± 16 mM/min) models grossly overestimated the calculated in vitro peak ATP synthesis rate (P < 0.05). Of the ADP models, the kinetic model was well correlated with State 3 respiration (r = 0.72, P < 0.05), but moderately overestimated ATP synthesis rate (P < 0.05), while the multipoint model, although being somewhat less well correlated with State 3 respiration (r = 0.55, P < 0.05), most accurately reflected peak ATP synthesis rate. Of note, the PCr recovery time constant (τ), a qualitative index of mitochondrial capacity, exhibited the strongest correlation with State 3 respiration (r = 0.80, P < 0.05). Therefore, this study reveals that each of the (31)P-MRS data analyses, including PCr τ, exhibit precision in terms of mitochondrial capacity. As only the multipoint ADP model did not overstimate the peak skeletal muscle mitochondrial ATP synthesis, the multipoint ADP model is the only quantitative approach to exhibit both accuracy and precision. PMID:27302751

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

    ERIC Educational Resources Information Center

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

    2004-01-01

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

  8. A theoretical study of rotational diffusion models for rod-shaped viruses. The influence of motion on 31P nuclear magnetic resonance lineshapes and transversal relaxation.

    PubMed Central

    Magusin, P C; Hemminga, M A

    1993-01-01

    Information about the interaction between nucleic acids and coat proteins in intact virus particles may be obtained by studying the restricted backbone dynamics of the incapsulated nucleic acids using 31P nuclear magnetic resonance (NMR) spectroscopy. In this article, simulations are carried out to investigate how reorientation of a rod-shaped virus particle as a whole and isolated nucleic acid motions within the virion influence the 31P NMR lineshape and transversal relaxation dominated by the phosphorus chemical shift anisotropy. Two opposite cases are considered on a theoretical level. First, isotropic rotational diffusion is used as a model for mobile nucleic acids that are loosely or partially bound to the protein coat. The effect of this type of diffusion on lineshape and transversal relaxation is calculated by solving the stochastic Liouville equation by an expansion in spherical functions. Next, uniaxial rotational diffusion is assumed to represent the mobility of phosphorus in a virion that rotates as a rigid rod about its length axis. This type of diffusion is approximated by an exchange process among discrete sites. As turns out from these simulations, the amplitude and the frequency of the motion can only be unequivocally determined from experimental data by a combined analysis of the lineshape and the transversal relaxation. In the fast motional region both the isotropic and the uniaxial diffusion model predict the same transversal relaxation as the Redfield theory. For very slow motion, transversal relaxation resembles the nonexponential relaxation as observed for water molecules undergoing translational diffusion in a magnetic field gradient. In this frequency region T2e is inversely proportional to the cube root of the diffusion coefficient. In addition to the isotropic and uniaxial diffusion models, a third model is presented, in which fast restricted nucleic acid backbone motions dominating the lineshape are superimposed on a slow rotation of the

  9. Is solid-state NMR enhanced by dynamic nuclear polarization?

    PubMed

    Lee, Daniel; Hediger, Sabine; De Paëpe, Gaël

    2015-01-01

    The recent trend of high-field (~5-20 T), low-temperature (~100 K) ssNMR combined with dynamic nuclear polarization (DNP) under magic angle spinning (MAS) conditions is analyzed. A brief overview of the current theory of hyperpolarization for so-called MAS-DNP experiments is given, along with various reasons why the DNP-enhancement, the ratio of the NMR signal intensities obtained in the presence and absence of microwave irradiation suitable for hyperpolarization, should not be used alone to gauge the value of performing MAS-DNP experiments relative to conventional ssNMR. This is demonstrated through a dissection of the current conditions required for MAS-DNP with particular attention to resulting absolute sensitivities and spectral resolution. Consequently, sample preparation methods specifically avoiding the surplus of glass-forming solvents so as to improve the absolute sensitivity and resolution are discussed, as are samples that are intrinsically pertinent for MAS-DNP studies (high surface area, amorphous, and porous). Owing to their pertinence, examples of recent applications on these types of samples where chemically-relevant information has been obtained that would have been impossible without the sensitivity increases bestowed by MAS-DNP are also detailed. Additionally, a promising further implementation for MAS-DNP is exampled, whereby the sensitivity improvements shown for (correlation) spectroscopy of nuclei at low natural isotopic abundance, facilitate internuclear distance measurements, especially for long distances (absence of dipolar truncation). Finally, we give some speculative perspectives for MAS-DNP. PMID:25779337

  10. 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

  11. Ab Initio Calculation of Nuclear Magnetic Resonance Chemical Shift Anisotropy Tensors 1. Influence of Basis Set on the Calculation of 31P Chemical Shifts

    SciTech Connect

    Alam, T.M.

    1998-09-01

    The influence of changes in the contracted Gaussian basis set used for ab initio calculations of nuclear magnetic resonance (NMR) phosphorous chemical shift anisotropy (CSA) tensors was investigated. The isotropic chemical shitl and chemical shift anisotropy were found to converge with increasing complexity of the basis set at the Hartree-Fock @IF) level. The addition of d polarization function on the phosphorous nucIei was found to have a major impact of the calculated chemical shi~ but diminished with increasing number of polarization fimctions. At least 2 d polarization fimctions are required for accurate calculations of the isotropic phosphorous chemical shift. The introduction of density fictional theory (DFT) techniques through tie use of hybrid B3LYP methods for the calculation of the phosphorous chemical shift tensor resulted in a poorer estimation of the NMR values, even though DFT techniques result in improved energy and force constant calculations. The convergence of the W parametem with increasing basis set complexity was also observed for the DFT calculations, but produced results with consistent large deviations from experiment. The use of a HF 6-31 l++G(242p) basis set represents a good compromise between accuracy of the simulation and the complexity of the calculation for future ab initio calculations of 31P NMR parameters in larger complexes.

  12. Excitation functions for actinides produced in the interactions of sup 31 P with sup 248 Cm

    SciTech Connect

    Leyba, J.D.; Henderson, R.A.; Hall, H.L.; Czerwinski, K.R.; Kadkhodayan, B.A.; Kreek, S.A.; Brady, E.K.; Gregorich, K.E.; Lee, D.M.; Nurmia, M.J.; Hoffman, D.C. Nuclear Science Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California )

    1991-11-01

    Excitation functions have been measured for the production of various isotopes of Bk, Cf, Es, and Fm from the interactions of 174- and 239-MeV {sup 31}P projectiles with {sup 248}Cm. The isotopic distributions were symmetric and displayed full widths at half maximum of 2.5, 2.5, and 2.25 mass units for Bk, Cf, and Fm, respectively. The maxima of the isotopic distributions occur for those reaction channels which involve the exchange of the fewest number of nucleons between the target and projectile for which the calculated excitation energy is a positive quantity. The maxima of the excitation functions occur at those projectile energies which are consistent with the calculated reaction barriers based upon a binary reaction mechanism. The effects of the odd proton in the {sup 31}P projectile on the final isotopic distributions are discussed.

  13. Dietary fat modulation of mammary tumor growth and metabolism demonstrated by /sup 31/P-nuclear magnetic resonance

    SciTech Connect

    Erickson, K.L.; Buckman, D.K.; Hubbard, N.E.; Ross, B.

    1986-03-05

    The relationship of dietary fat concentration and saturation on the growth and metabolic activity of line 168 was studied using syngeneic mice fed 6 experimental diets before and during tumor growth. Tumor latency was significantly greater for mice fed a diet containing the minimum of essential fatty acids (EFA, 0.5% corn oil) or 8% coconut oil (SF) than for mice fed 8 or 20% safflower oil (PUF) or 20% SF. Changes in dietary fat resulted in alterations of tumor cell and serum fatty acid composition but not the number of inflammatory cells infiltrating the tumor. /sup 31/P-surface coil NMR was used to measure possible changes in tumor metabolism in vivo. Although pH decreased from 7.2 to 6.6 as the tumor volume increased, there was no difference in pH among dietary groups. There was an inverse relationship between both sugar phosphate (SP)/Pi and ATP/Pi ratios and tumor volume; those ratios for mice fed an EFA deficient or minimal EFA diet decreased at a different rate than ratios for mice fed diets with additional fat. Tumors of mice fed diets containing no or a low level (0.3%) of 18:2 had higher SP/ATP ratios than mice fed diets containing a moderate level (approx. 4%) of 18:2. Thus, high levels of dietary fat had a significant effect on promotion of mammary tumors during early stages of tumor growth. Differences in tumor volume associated with dietary fat may be related to changes in the levels of high energy phosphate metabolites.

  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. Optimized (31)P MRS in the human brain at 7 T with a dedicated RF coil setup.

    PubMed

    van de Bank, Bart L; Orzada, Stephan; Smits, Frits; Lagemaat, Miriam W; Rodgers, Christopher T; Bitz, Andreas K; Scheenen, Tom W J

    2015-11-01

    The design and construction of a dedicated RF coil setup for human brain imaging ((1)H) and spectroscopy ((31)P) at ultra-high magnetic field strength (7 T) is presented. The setup is optimized for signal handling at the resonance frequencies for (1)H (297.2 MHz) and (31)P (120.3 MHz). It consists of an eight-channel (1)H transmit-receive head coil with multi-transmit capabilities, and an insertable, actively detunable (31)P birdcage (transmit-receive and transmit only), which can be combined with a seven-channel receive-only (31)P array. The setup enables anatomical imaging and (31)P studies without removal of the coil or the patient. By separating transmit and receive channels and by optimized addition of array signals with whitened singular value decomposition we can obtain a sevenfold increase in SNR of (31)P signals in the occipital lobe of the human brain compared with the birdcage alone. These signals can be further enhanced by 30 ± 9% using the nuclear Overhauser effect by B1-shimmed low-power irradiation of water protons. Together, these features enable acquisition of (31)P MRSI at high spatial resolutions (3.0 cm(3)  voxel) in the occipital lobe of the human brain in clinically acceptable scan times (~15 min). PMID:26492089

  17. NMR studies on polyphosphide Ce6Ni6P17

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  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. Mas' Making and Pedagogy: Imagined Possibilities

    ERIC Educational Resources Information Center

    Fournillier, Janice B.

    2009-01-01

    In this article I draw on an ethnographic case study that examined mas' makers' perceptions of the learning/teaching practices at work in the production of costumes for Trinidad and Tobago's annual Carnival celebrations. During the 2005 Carnival season I spent four months in the field, my country of birth, and collected data through participant…

  20. Chromatographic NMR in NMR solvents

    NASA Astrophysics Data System (ADS)

    Carrara, Caroline; Viel, Stéphane; Delaurent, Corinne; Ziarelli, Fabio; Excoffier, Grégory; Caldarelli, Stefano

    2008-10-01

    Recently, it was demonstrated that pseudo-chromatographic NMR experiments could be performed using typical chromatographic solids and solvents. This first setup yielded improved separation of the spectral components of the NMR spectra of mixtures using PFG self-diffusion measurements. The method (dubbed Chromatographic NMR) was successively shown to possess, in favorable cases, superior resolving power on non-functionalized silica, compared to its LC counterpart. To further investigate the applicability of the method, we studied here the feasibility of Chromatographic NMR in common deuterated solvents. Two examples are provided, using deuterated chloroform and water, for homologous compounds soluble in these solvents, namely aromatic molecules and alcohols, respectively.

  1. Characteristics and degradation of carbon and phosphorus from aquatic macrophytes in lakes: insights from solid-state 13C NMR and solution 31P NMR spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Water extractable organic matter (WEOM) derived from macrophytes plays an important role in biogeochemical cycling of nutrients, including carbon (C), nitrogen (N) and phosphorus (P) in lakes. However, reports of their composition and degradation in natural waters are scarce. Therefore, compositions...

  2. 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.

  3. 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.

  4. Whole-body radiofrequency coil for (31) P MRSI at 7 T.

    PubMed

    Löring, J; van der Kemp, W J M; Almujayyaz, S; van Oorschot, J W M; Luijten, P R; Klomp, D W J

    2016-06-01

    Widespread use of ultrahigh-field (31) P MRSI in clinical studies is hindered by the limited field of view and non-uniform radiofrequency (RF) field obtained from surface transceivers. The non-uniform RF field necessitates the use of high specific absorption rate (SAR)-demanding adiabatic RF pulses, limiting the signal-to-noise ratio (SNR) per unit of time. Here, we demonstrate the feasibility of using a body-sized volume RF coil at 7 T, which enables uniform excitation and ultrafast power calibration by pick-up probes. The performance of the body coil is examined by bench tests, and phantom and in vivo measurements in a 7-T MRI scanner. The accuracy of power calibration with pick-up probes is analyzed at a clinical 3-T MR system with a close to identical (1) H body coil integrated at the MR system. Finally, we demonstrate high-quality three-dimensional (31) P MRSI of the human body at 7 T within 5 min of data acquisition that includes RF power calibration. Copyright © 2016 John Wiley & Sons, Ltd. PMID:27037615

  5. Nuclear spin decoherence of neutral 31P donors in silicon: Effect of environmental 29Si nuclei

    NASA Astrophysics Data System (ADS)

    Petersen, Evan S.; Tyryshkin, A. M.; Morton, J. J. L.; Abe, E.; Tojo, S.; Itoh, K. M.; Thewalt, M. L. W.; Lyon, S. A.

    2016-04-01

    Spectral diffusion arising from 29Si nuclear spin flip-flops, known to be a primary source of electron spin decoherence in silicon, is also predicted to limit the coherence times of neutral donor nuclear spins in silicon. Here, the impact of this mechanism on 31P nuclear spin coherence is measured as a function of 29Si concentration using X -band pulsed electron nuclear double resonance. The 31P nuclear spin echo decays show that decoherence is controlled by 29Si flip-flops resulting in both fast (exponential) and slow (nonexponential) spectral diffusion processes. The decay times span a range from 100 ms in crystals containing 50% 29Si to 3 s in crystals containing 1% 29Si. These nuclear spin echo decay times for neutral donors are orders of magnitude longer than those reported for ionized donors in natural silicon. The electron spin of the neutral donors "protects" the donor nuclear spins by suppressing 29Si flip-flops within a "frozen core," as a result of the detuning of the 29Si spins caused by their hyperfine coupling to the electron spin.

  6. Review of NMR characterization of pyrolysis oils

    DOE PAGESBeta

    Hao, Naijia; Ben, Haoxi; Yoo, Chang Geun; Adhikari, Sushil; Ragauskas, Arthur J.

    2016-08-24

    Here, pyrolysis of renewable biomass has been developed as a method to produce green fuels and chemicals in response to energy security concerns as well as to alleviate environmental issues incurred with fossil fuel usage. However, pyrolysis oils still have limited commercial application, mainly because unprocessed oils cannot be readily blended with current petroleum-based transportation fuels. To better understand these challenges, researchers have applied diverse characterization techniques in the development of bio-oil studies. In particular, nuclear magnetic resonance (NMR) is a key spectroscopic characterization method through analysis of bio-oil components. This review highlights the NMR strategies for pyrolysis oil characterizationmore » and critically discusses the applications of 1H, 13C, 31P, 19F, and two-dimensional (2-D NMR) analyses such as heteronuclear single quantum correlation (HSQC) in representative pyrolysis oil studies.« less

  7. The A31P missense mutation in cardiac myosin binding protein C alters protein structure but does not cause haploinsufficiency.

    PubMed

    van Dijk, Sabine J; Bezold Kooiker, Kristina; Mazzalupo, Stacy; Yang, Yuanzhang; Kostyukova, Alla S; Mustacich, Debbie J; Hoye, Elaine R; Stern, Joshua A; Kittleson, Mark D; Harris, Samantha P

    2016-07-01

    Mutations in MYBPC3, the gene encoding cardiac myosin binding protein C (cMyBP-C), are a major cause of hypertrophic cardiomyopathy (HCM). While most mutations encode premature stop codons, missense mutations causing single amino acid substitutions are also common. Here we investigated effects of a single proline for alanine substitution at amino acid 31 (A31P) in the C0 domain of cMyBP-C, which was identified as a natural cause of HCM in cats. Results using recombinant proteins showed that the mutation disrupted C0 structure, altered sensitivity to trypsin digestion, and reduced recognition by an antibody that preferentially recognizes N-terminal domains of cMyBP-C. Western blots detecting A31P cMyBP-C in myocardium of cats heterozygous for the mutation showed a reduced amount of A31P mutant protein relative to wild-type cMyBP-C, but the total amount of cMyBP-C was not different in myocardium from cats with or without the A31P mutation indicating altered rates of synthesis/degradation of A31P cMyBP-C. Also, the mutant A31P cMyBP-C was properly localized in cardiac sarcomeres. These results indicate that reduced protein expression (haploinsufficiency) cannot account for effects of the A31P cMyBP-C mutation and instead suggest that the A31P mutation causes HCM through a poison polypeptide mechanism that disrupts cMyBP-C or myocyte function. PMID:26777460

  8. Optical hyperpolarization and inductive readout of 31P donor nuclei in natural abundance single crystal 29Si

    NASA Astrophysics Data System (ADS)

    Alexander, Thomas; Haas, Holger; Deshpande, Rahul; Gumann, Patryk; Cory, David

    2016-05-01

    We optically polarize and inductively detect 31P donor nuclei in single crystal silicon at high magnetic fields (6 . 7T). Samples include both natural abundance 29Si and an isotopically purified 28Si sample. We observe dipolar order in the 29Si nuclear spins through a spin-locking measurement. This provides a means of characterizing spin transport in the vicinity of the 31P donors.

  9. Homonuclear and Heteronuclear NMR Studies of a Statherin Fragment Bound to Hydroxyapatite Crystals

    SciTech Connect

    Raghunathan, Vinodhkumar; Gibson, James M.; Goobes, Gil; Popham, Jennifer M.; Louie, Elizabeth; Stayton, Patrick; Drobny, Gary P.

    2006-05-11

    Acidic proteins found in mineralized tissues act as nature's crystal engineers, where they play a key role in promoting or inhibiting the growth of minerals such as hydroxyapatite (HAP), Ca10(PO4)6(OH)2, the main mineral component of bone and teeth. Key to understanding the structural basis of protein-crystal recognition and protein control of hard tissue growth is the nature of interactions between the protein side chains and the crystal surface. In an earlier work we have measured the proximity of the lysine (K6) side chain in an SN-15 peptide fragment of the salivary protein statherin adsorbed to the Phosphorus-rich surface of HAP using solid-state NMR recoupling experiments. 15N(31P) rotational echo double resonance (REDOR) NMR data on the side-chain nitrogen in K6 gave rise to three different models of protein-surface interaction to explain the experimental data acquired. In this work we extend the analysis of the REDOR data by examining the contribution of interactions between surface phosphorus atoms to the observed 15N REDOR decay. We performed 31P-31P recoupling experiments in HAP and (NH4)2HPO4 (DHP) to explore the nature of dipolar coupled 31P spin networks. These studies indicate that extensive networks of dipolar coupled 31P spins can be represented as stronger effective dipolar couplings, the existence of which must be included in the analysis of REDOR data. We carried out 15N(31P) REDOR in the case of DHP to determine how the size of the dephasing spin network influences the interpretation of the REDOR data. Although use of an extended 31P coupled spin network simulates the REDOR data well, a simplified 31P dephasing system composed of two spins with a larger dipolar coupling also simulates the REDOR data and only perturbs the heteronuclear couplings very slightly. The 31P-31P dipolar couplings between phosphorus nuclei in HAP can be replaced by an effective dipolar interaction of 600 Hz between two 31P spins. We incorporated this coupling and

  10. Characterizing mixed phosphonic acid ligand capping on CdSe/ZnS quantum dots using ligand exchange and NMR spectroscopy.

    PubMed

    Davidowski, Stephen K; Lisowski, Carmen E; Yarger, Jeffery L

    2016-03-01

    The ligand capping of phosphonic acid functionalized CdSe/ZnS core-shell quantum dots (QDs) was investigated with a combination of solution and solid-state (31) P nuclear magnetic resonance (NMR) spectroscopy. Two phosphonic acid ligands were used in the synthesis of the QDs, tetradecylphosphonic acid and ethylphosphonic acid. Both alkyl phosphonic acids showed broad liquid and solid-state (31) P NMR resonances for the bound ligands, indicative of heterogeneous binding to the QD surface. In order to quantify the two ligand populations on the surface, ligand exchange facilitated by phenylphosphonic acid resulted in the displacement of the ethylphosphonic acid and tetradecylphosphonic acid and allowed for quantification of the free ligands using (31) P liquid-state NMR. After washing away the free ligand, two broad resonances were observed in the liquids' (31) P NMR corresponding to the alkyl and aromatic phosphonic acids. The washed samples were analyzed via solid-state (31) P NMR, which confirmed the ligand populations on the surface following the ligand exchange process. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26639792

  11. Na/Ca Intermixing around Silicate and Phosphate Groups in Bioactive Phosphosilicate Glasses Revealed by Heteronuclear Solid-State NMR and Molecular Dynamics Simulations.

    PubMed

    Mathew, Renny; Stevensson, Baltzar; Edén, Mattias

    2015-04-30

    We characterize the intermixing of network-modifying Na(+)/Ca(2+) ions around the silicate (QSi(n)) and phosphate (QP(n)) tetrahedra in a series of 16 Na2O–CaO–SiO2–P2O5 glasses, whose P content and silicate network connectivity were varied independently. The set includes both bioactive and bioinactive compositions and also encompasses two soda-lime-silicate members devoid of P, as well as two CaO–SiO2 glasses and one Na2O–SiO2–P2O5 glass. The various Si/P↔Na/Ca contacts were probed by molecular dynamics (MD) simulations together with heteronuclear magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) experimentation utilizing (23)Na{(31)P} and (23)Na{(29)Si} REDOR, as well as (31)P{ (23)Na} and (29)Si{(23)Na} REAPDOR. We introduce an approach for quantifying the extent of Na(+)/Ca(2+) ordering around a given QP(n) or QSi(n) group, encoded by the preference factor 0⩽ PM ⩽ 1 conveying the relative weights of a random cation intermixing (PM = 0) and complete preference/ordering (PM = 1) for one of the species M, which represents either Na(+) or Ca(2+). The MD-derived preference factors reveal phosphate and silicate species surrounded by Na(+)/Ca(2+) ions intermixed nearly randomly (PM ≲ 0.15), except for the QSi(4) and QSi(1) groups, which manifest more significant cation ordering with preference for Na+ and Ca2+, respectively. The overall weak preferences are essentially independent of the Si and P contents of the glass, whereas PM primarily correlates with the total amount of network modifiers: as the latter is increased, the Na/Ca distribution around the {QP(0), QSi(1), QSi(2)} groups with preference for Ca2(+ )tend to randomize (i.e., PCa decreases), while the PNa-values grow slightly for the {QP(1), QSi(3), QSi(4)} species already preferring coordination of Na. The set of experimental preference factors {PCa} for the orthophosphate (QP(0)) groups extracted from (31)P{(23)Na} REAPDOR NMR-derived M2(P–Na) dipolar second moments agrees

  12. Moderate MAS enhances local 1H spin exchange and spin diffusion

    NASA Astrophysics Data System (ADS)

    Roos, Matthias; Micke, Peter; Saalwächter, Kay; Hempel, Günter

    2015-11-01

    Proton NMR spin-diffusion experiments are often combined with magic-angle spinning (MAS) to achieve higher spectral resolution of solid samples. Here we show that local proton spin diffusion can indeed become faster at low (<10 kHz) spinning rates as compared to static conditions. Spin diffusion under static conditions can thus be slower than the often referred value of 0.8 nm2/ms, which was determined using slow MAS (Clauss et al., 1993). The enhancement of spin diffusion by slow MAS relies on the modulation of the orientation-dependent dipolar couplings during sample rotation and goes along with transient level crossings in combination with dipolar truncation. The experimental finding and its explanation is supported by density matrix simulations, and also emphasizes the sensitivity of spin diffusion to the local coupling topology. The amplification of spin diffusion by slow MAS cannot be explained by any model based on independent spin pairs; at least three spins have to be considered.

  13. Complex Mixture Analysis of Organic Compounds in Yogurt by NMR Spectroscopy

    PubMed Central

    Lu, Yi; Hu, Fangyu; Miyakawa, Takuya; Tanokura, Masaru

    2016-01-01

    NMR measurements do not require separation and chemical modification of samples and therefore rapidly and directly provide non-targeted information on chemical components in complex mixtures. In this study, one-dimensional (1H, 13C, and 31P) and two-dimensional (1H-13C and 1H-31P) NMR s