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Sample records for nmr spin-hamiltonian parameters

  1. Effect of glass structure on spin Hamiltonian parameters: Cu doped tellurite glasses

    International Nuclear Information System (INIS)

    Cu-doped glasses with compositions [(70TeO2−(30−x)ZnO−xPbO)0.98− (CuO)0.02] (x = 5, 10, 15, 20) were prepared using the melt quenching technique and characterized by EPR. Cu2+ ions are found to be in distorted oxygen octahedral cage and their corresponding spin Hamiltonian (splitting) parameters are deduced for all glasses as a function of increasing PbO. Finally, effect of the matrix on spin Hamiltonian parameters of Cu2+ ions are correlated with the help of EPR and earlier Raman analysis

  2. Optical spectra and spin-Hamiltonian parameters of trivalent ytterbium in lead tungstate

    Indian Academy of Sciences (India)

    W-L Feng; X-M Li

    2011-01-01

    By using crystal-field theory, the optical spectra and spin-Hamiltonian parameters (abbr. SH parameters, i.e. the anisotropic factors $g_{\\|} g_{⊥}$, and hyperfine structure constants $A_{\\|}, A_{⊥}$) of 171Yb3+ and 173Yb3+ isotopes in the tetragonal PbWO4 are calculated. The theoretical results agree well with the experimental values. The crystal-field parameters and the signs of the hyperfine structure constants for both 171Yb3+ and 173Yb3+ isotopes are determined. The validities of the theoretical results are discussed.

  3. Studies of the optical spectra and spin-Hamiltonian parameters for the trivalent ytterbium ions in lithium yttrium fluoride crystals

    Science.gov (United States)

    Feng, W. L.; Han, Z.; Zhong, Y. C.

    In this paper, the crystal field (CF) levels and spin-Hamiltonian (SH) parameters (g factors g∥ and g⊥ and hyperfine structure constants A∥ and A⊥) of the rare-earth ion Yb3+ in lithium yttrium fluoride crystals are calculated under D2d point symmetry assumption. Two main methods are used in the calculation to study the SH parameters: one is the perturbation theory method and the other is the complete diagonalization (energy matrix) method (CDM). Comparing the calculated results with the experimental data, we can see that the CDM is more effective to calculate the SH parameters. In addition, the CF J-mixing of all excited-state multiplets into the ground-state multiplet 2F7/2 is considered. The validity of the calculated results is discussed.

  4. Theoretical studies of the local structure and spin Hamiltonian parameters for Rh{sup 2+}:ZnWO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Chang-Chun, E-mail: ccding626@163.com; Wu, Shao-Yi; Kuang, Min-Quan; Cheng, Yong-Kun; Zhang, Li-Juan

    2014-10-15

    By establishing the perturbation formulas of the spin Hamiltonian parameters (anisotropic g factors and hyperfine structure constants) for a rhombically compressed 4d{sup 7} cluster, the EPR spectra and local structure are theoretically investigated for Rh{sup 2+}:ZnWO{sub 4}. Due to the Jahn–Teller effect, the impurity center shows slight axial compression of about 0.002 nm along the Z-axis and the perpendicular angular variation of about 6° for the planar impurity–ligand bonds. These lattice deformations transform the significant elongation (by about 0.031 nm) of host Zn{sup 2+} site into slight compression in the impurity center. The local distortion of the Jahn–Teller nature is discussed.

  5. Local structure distortion and spin Hamiltonian parameters of oxide-diluted magnetic semiconductor Mn-doped ZnO

    Institute of Scientific and Technical Information of China (English)

    Yang Zi-Yuan

    2009-01-01

    The local structure distortion, the spin Hamiltonian (SH) parameters, and the electric fine structure of the ground state for Mn2+(3d5) ion in ZnO crystals are systematically investigated, where spin-spin (SS), spin-other-orbit (SOO) and orbit-orbit (OO) magnetic interactions, besides the well-known spin-orbit (SO) coupling, are taken into account for the first time, by using the complete diagonalization method. The theoretical results of the second-order zero-field splitting (ZFS) parameter D, the fourth-order ZFS parameter (a-F), the Zeeman p-factors: g// and g⊥ and the energy differences of the ground state: δ1 and δ2 for Mn2+ in Mn2+: ZnO are in good agreement with experimental measurements when the three O2- ions below the Mn2+ ion rotate by 1.085° away from the [111]-axis. Hence, the local structure distortion effect plays an important role in explaining the spectroscopic properties of Mn2+ ions in Mn2+: ZnO crystals. It is found for Mn2+ ions in Mn2+: ZnO crystals that although the SO mechanism is the most important one, the contributions to the SH parameters, made by other four mechanisms, i.e. SS, SOO, OO, and SO~SS~SOO~OO mechanisms, are significant and should not be omitted, especially for calculating ZFS parameter D.

  6. Theoretical Studies of the Spin Hamiltonian Parameters and Local Distortions for Cu2+ in Alkaline Earth Lead Zinc Phosphate Glasses

    Science.gov (United States)

    Wang, Bo-Kun; Wu, Shao-Yi; Yuan, Zi-Yi; Liu, Zi-Xuan; Jiang, Shi-Xin; Liu, Zheng; Yao, Zi-Jian; Teng, Bao-Hua; Wu, Ming-He

    2016-08-01

    The spin Hamiltonian parameters and local structures are theoretically studied for Cu2+-doped alkaline earth lead zinc phosphate (RPPZ, R=Mg, Ca, Sr, and Ba) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d9 cluster. The relative elongation ratios are found to be ρ≈3.2%, 4.4%, 4.6%, and 3.3% for R=Mg, Ca, Sr, and Ba, respectively, because of the Jahn-Teller effect. The whole decreasing crystal-field strength Dq and orbital reduction factor k from Mg to Sr are ascribed to the weakening electrostatic coulombic interactions and the increasing probability of productivity of nonbridge oxygen (and hence increasing Cu2+-O2- electron cloud admixtures) under PbO addition, respectively, with increasing alkali earth ionic radius. The anomalies (the largest Dq and the next highest k among the systems) for R=Ba are attributed to the cross linkage of this large cation in the network. The overall increasing order (Mg≤Bacontaining copper dopants.

  7. Theoretical evaluation of the electron paramagnetic resonance spin Hamiltonian parameters for the impurity displacements for Fe3+ and Ru3+ in corundum

    Indian Academy of Sciences (India)

    Q Fu; S Y Wu; J Z Lin; J S Yao

    2007-03-01

    The impurity displacements for Fe3+ and Ru3+ in corundum (Al2O3) are theoretically studied using the perturbation formulas of the spin Hamiltonian parameters (zero-field splitting and anisotropic factors) for a 3d5 (with high spin = 5/2) and a 4d5 (with low spin = 1/2) ion in trigonal symmetry, respectively. According to the investigations, the nd5 ( = 3 and 4) impurity ions may not locate at the ideal Al3+ site but undergo axial displacements by about 0.132 Å and 0.170 Å for Fe3+ and Ru3+, respectively, away from the center of the ligand octahedron along the C3 axis. The calculated spin Hamiltonian parameters based on the above axial displacements show good agreement with the observed values. The validity of the results is discussed.

  8. Theoretical calculations of spin-Hamiltonian parameters for the square planer CuCl4 2 - cluster in Cs2ZrCl6 crystal

    Science.gov (United States)

    Liu, Gang; Mei, Yang; Zhang, Xin-Xin; Zheng, Wen-Chen

    2015-05-01

    The high-order perturbation formulas based on a two-mechanism model (where in addition to the contributions from the crystal-field (CF) mechanism in the usually-applied CF theory, those from the generally-neglected charge-transfer (CT) mechanism are also contained) are employed to calculate the spin-Hamiltonian parameters (g factors g//, g⊥ and the hyperfine structure constants A//, A⊥) of the square planar CuCl4 2 - clusters in Cs2ZrCl6 crystal. The needed CF energy levels in the calculations are obtained from the observed optical spectra. The calculated results show reasonable agreement with the experimented values. The negative sign of A// and positive sign of A⊥ are proposed from the calculations. The calculations also suggest that one should take account of the contributions due to both the CF and CT mechanisms for the exact and rational calculations of spin-Hamiltonian parameters of Cu2+-Cl- combination in crystals.

  9. Studies on the Local Angular Distortion and Spin Hamiltonian Parameters for the Trigonal Co2+ Center in MgCl2

    Science.gov (United States)

    Hu, Xian-Fen; Wu, Shao-Yi; Kuang, Min-Quan; Li, Guo-Liang

    2014-11-01

    The local angular distortion and spin Hamiltonian parameters (g factors g||, g⊥ and the hyperfine structure constants) for the trigonal Co2+ center in MgCl2 are theoretically studied by diagonalizing the 6×6 energy matrix of ground 4T1 state for a trigonally distorted octahedral 3d7 cluster. Based on the cluster approach, the contributions from the admixtures of various J (= 1/2;3/2;5/2) states and the ligand orbital and spin-orbit coupling interactions are taken into account in a uniform way. The local impurity-ligand bond angle in the Co2+ center is found to be about 3.44° larger than the host metal-ligand bond angle in the pure crystal due to substitution of smaller Mg2+ by bigger Co2+, inducing a further compressed ligand octahedron. The calculated spin Hamiltonian parameters using the above local angular distortion are in good agreement with the experimental data. The present studies on the local structure and the spin Hamiltonian parameters for Co2+ in MgCl2 are tentatively extended to a more general case by comparing the relevant impurity behaviours for Co2+ in various trigonal environments.

  10. Research on the optical band positions, spin-Hamiltonian parameters and atom-position parameter of Co{sup 2+} ion in CdSe crystal

    Energy Technology Data Exchange (ETDEWEB)

    Mei, Yang [School of Physics & Electronic Engineering, Mianyang Normal University, Mianyang 621000 (China); Research Center of Computational Physics, Mianyang Normal University, Mianyang 621000 (China); Zheng, Wen-Chen, E-mail: zhengwc1@163.com [Department of Material Science, Sichuan University, Chengdu 610064 (China); Peng, Ren-Ming; Wei, Cheng-Fu [School of Physics & Electronic Engineering, Mianyang Normal University, Mianyang 621000 (China)

    2015-10-01

    The optical band positions and EPR (or spin-Hamiltonian) parameters (g factors g{sub //}, g{sub ⊥} and zero-field splitting D) of Co{sup 2+} ion in the trigonally-distorted tetrahedral Cd{sup 2+} site of CdSe crystal are calculated simultaneously from the complete diagonalization (of energy matrix) method (CDM) based on the two-spin–orbit-parameter model. This model contains the contributions to the spectral data from both the spin–orbit parameters of central d{sup n} ion (i.e., one-spin–orbit-parameter model) in the conventional crystal-field theory and that of ligand ions via covalence effect. The calculated 12 optical band positions and three spin-Hamiltonian parameters using four adjustable parameters show reasonable agreement with the experimental values. The local atom-position parameter u{sub loc} (where the corresponding parameter u in the host CdSe crystal is unlikely) in the Co{sup 2+} center is also estimated from the calculations. The calculations of these spectral data from the CDM based on the conventional one-spin–orbit parameter model are also made for comparison. It is found that the calculated optical band positions are also close to the experimental values, but the calculated spin-Hamiltonian parameters are in poor agreement with the observed values. So, for the unified and reasonable calculations of optical and EPR data of d{sup n} ions in crystals (in particular, in the cases of ligand with large spin–orbit parameter), the CDM based on the two-spin–orbit-parameter model should be applied. - Highlights: • Fifteen optical and EPR data of Co{sup 2+} center in CdSe are calculated together. • Calculation is using the complete diagonalization (of energy matrix) method (CDM). • The CDM based on the two-spin–orbit-parameter model is more reasonable. • Local atom-position parameter in Co{sup 2+} center in CdSe is obtained from calculation.

  11. Local structure distortion and spin Hamiltonian parameters for Cr3+-VZn tetragonal defect centre in Cr3+ doped KZnF3 crystal

    Institute of Scientific and Technical Information of China (English)

    Yang Zi-Yuan

    2011-01-01

    The quantitative relationship between the spin Hamiltonian parameters (D,g1l,Og) and the crystal structure parameters for the Cr3+-VZ,,tetragonal defect centre in a Cr3+:KZnF3 crystal is established by using the superposition model. On the above basis,the local structure distortion and the spin Hamiltonian parameter for the Cr3+-VZn tetragonal defect centre in the KZnF3 crystal are systematically investigated using the complete diagonalization method.It is found that the Vzn vacancy and the differences in mass,radius and charge between the Cr3+ and the Zn2+ ions induce the local lattice distortion of the Cr3+ centre ions in the KZnF3 crystal. The local lattice distortion is shown to give rise to the tetragonal crystal field,which in turn results in the tetragonal zero-field splitting parameter D and the anisotropic g factor △g. We find that the ligand F-ion along [001]and the other five F-ions move towards the central Cr3+ by distances of △l=0.0121 nm and △2=0.0026 nm,respectively. Our approach takes into account the spin-orbit interaction as well as the spin-spin,spin-other-orbit,and orbit-orbit interactions omitted in the previous studies. It is found that for the Cr3+ ions in the Cr3+:KZnF3 crystal,although the spin-orbit mechanism is the most important one,the contribution to the spin Hamiltonian parameters from the other three mechanisms,including spin-spin,spin-other-orbit,and orbit-orbit magnetic interactions,is appreciable and should not be omitted,especially for the zero-field splitting (ZFS) parameter D.

  12. Theoretical studies of the spin-Hamiltonian parameters for the orthorhombic Pr4+ centers in Sr2CeO4 crystals

    Indian Academy of Sciences (India)

    Wen-Lin Feng

    2008-04-01

    Theoretical studies of spin-Hamiltonian (SH) parameters associated with Pr4+ in Sr2CeO4 single crystals have been made by using the complete diagonalizing energy matrix method (CDM) for the 41 electronic configuration. The calculated results are in excellent agreement with the experimental data. The negative signs of the anisotropic -factors and hyperfine structure constants (where = || or ⊥) for the orthorhombic Pr4+ ion in Sr2CeO4 are suggested from the calculations. By comparing the results obtained by the CDM with the experimental data, one finds it is valid to interpret the SH parameters for 41 ions in crystals. The results are discussed.

  13. Theoretical research of the spin-Hamiltonian parameters for two rhombic W5+ centers in KTiOPO4 (KTP) crystal through a two-mechanism model

    Science.gov (United States)

    Mei, Yang; Chen, Bo-Wei; Wei, Chen-Fu; Zheng, Wen-Chen

    2016-09-01

    The high-order perturbation formulas based on the two-mechanism model are employed to calculate the spin-Hamiltonian parameters (g factors gi and hyperfine structure constants Ai, where i=x, y, z) for two approximately rhombic W5+ centers in KTiOPO4 (KTP) crystal. In the model, both the widely-applied crystal-field (CF) mechanism concerning the interactions of CF excited states with the ground state and the generally-neglected charge-transfer (CT) mechanism concerning the interactions of CT excited states with the ground state are included. The calculated results agree with the experimental values, and the signs of constants Ai are suggested. The calculations indicate that (i) for the high valence state dn ions in crystals, the contributions to spin-Hamiltonian parameters should take into account both the CF and CT mechanisms and (ii) the large g-shifts |Δgi | (=|gi-ge |, where ge≈ 2.0023) for W5+ centers in crystals are due to the large spin-orbit parameter of free W5+ ion.

  14. Theoretical research on the spin-Hamiltonian parameters of the rhombic W5+ centers in CaWO4:Y3+ crystal

    Science.gov (United States)

    Mei, Yang; Wei, Cheng-Fu; Zheng, Wen-Chen

    2016-02-01

    Detailed theoretical calculations for the spin-Hamiltonian parameters (g factors gi and hyperfine structure constants Ai, where i=x, y, z) of the rhombic W5+ center in CaWO4:Y3+ crystal are performed by using the high-order perturbation formulas for d1 ions in rhombic tetrahedral clusters with the ground state |dz2>. These formulas consist of the contributions from two mechanisms, the crystal-field (CF) mechanism connected with CF excited states in the vastly-used CF theory and the frequently-neglected charge-transfer (CT) mechanism related to CT excited states. The calculated results agree well with the experimental values. The calculations indicate that for W5+ ion (or other high valence state dn ions) in crystals, the model calculations of spin-Hamiltonian parameters should take both the CF and CT mechanisms into account. The signs of hyperfine structure constants Ai are suggested and the forming (or defect model) of rhombic W5+ center in CaWO4:Y3+ crystal is confirmed from the calculations.

  15. Theoretical studies on the spin Hamiltonian parameters and local environment of Mn{sup 2+} in ZnO nanocrystal and bulk

    Energy Technology Data Exchange (ETDEWEB)

    Li, Guo-Liang, E-mail: liguolianglq@163.com [Department of Applied Physics, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); School of Physics and Engineering, Xingyi Normal University for Nationalities, Xingyi 562400 (China); Wu, Shao-Yi; Hu, Xian-Fen; Kuang, Min-Quan [Department of Applied Physics, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2015-06-15

    By employing the perturbation calculations, the spin Hamiltonian parameters (SHPs) and local structures are uniformly explored for Mn{sup 2+} in the ZnO nanocrystal and bulk. The EPR spectra are satisfactorily explained for both the systems, and the defect structure information is obtained, i.e., the substitutional impurity Mn{sup 2+} may undergo the axial displacements of 0.036 and 0.042 Å away from the oxygen triangles along the C{sub 3} axis in the ZnO nanocrystal and bulk, respectively. The similar SHPs for Mn{sup 2+} in the nanocrystal and bulk can be illustrated as the approximately identical covalency (equal covalency factor N) as well as the smaller axial displacement, the stronger crystal–field (CF) interactions (larger cubic CF parameter Dq) and Mn{sup 2+} 3d–3s orbital admixture (larger core polarization constant κ) in the former.

  16. An Investigation for the Spin Hamiltonian sParameters and the Local Structure for Co2+ in ZnWO4

    Directory of Open Access Journals (Sweden)

    Ding Chang-Chun

    2016-01-01

    Full Text Available Based on the perturbation formulae of the spin Hamiltonian parameters (SHPs, i,e,. g factors gx, gy, gz, and hyperfine structure constants Ax, Ay, Az, for a 3d7 ion in rhombically distorted octahedra, the defect structure and the experimental EPR spectra are theoretically investigated for the rhombic Co2+ centre in ZnWO4. Due to the Jahn-Teller effect, the impurity ion Co2+ on host Zn2+ site is found to undergo the local rhombic elongation distortion, characterized by the axial elongation ΔZ (≈ 0.157 Å of the impurity-ligand bonds and the perpendicular distortion angle Δф (≈ 3.5° related to an ideal octahedron. Compared with host Zn2+ site in ZnWO4, the Co2+ centre exhibits a more regular oxygen octahedron. All the calculated SHPs show good agreement with the observed values. The present work may be helpful to understand the local structures and properties of metal tungstate with transition-metal dopants.

  17. Theoretical investigations on the defect structures and spin Hamiltonian parameters for various orthorhombic Rh2+ centres in KTiOPO4 and KTiOAsO4

    Science.gov (United States)

    Ding, Chang-Chun; Wu, Shao-Yi; Zhang, Li-Juan; Li, Guo-Liang; Zhang, Zhi-Hong

    2015-12-01

    The defect structures and spin Hamiltonian parameters (SHPs) for three Rh2+ centres (denoted C1 in KTiOAsO4 and C2 and C3 in KTiOPO4) are theoretically investigated by utilising the perturbation formulae for a 4d7 ion under orthorhombically (D2h) elongated octahedra. The defect structures are characterized by the axial elongation ratios of 4.91%, 4.93% and 4.90% along the Z axis and the planar bond length variation ratios of 0.05%, 0.01% and 0.04% for centres C1, C2 and C3, respectively, owing to the Jahn-Teller effect. The nearly identical moderate axial elongation ratios and the slightly different tiny planar bond length variation ratios may suitably account for the comparable moderate axial g anisotropies ∆g (≈0.6087, 0.6124 and 0.6067) and the slightly dissimilar tiny perpendicular g anisotropies δg (≈0.0649, 0.0097 and 0.0509) of the three centres, respectively. All centres demonstrate similar strong crystal-field interactions and moderate covalence arising from the comparable short impurity-ligand distances.

  18. Theoretical calculations of spin-Hamiltonian parameters for the (MoOX{sub 5}){sup 2−} (X=Cl, Br) metallic complexes in solution or frozen-glass

    Energy Technology Data Exchange (ETDEWEB)

    Mei, Yang [School of Physics and Electronic Engineering, Mianyang Normal University, Mianyang 621000 (China); Research Center of Laser Fusion, CAEP, Mianyang 621900 (China); Research Center of Computational Physics, Mianyang Normal University, Mianyang 621000 (China); Zheng, Wen-Chen, E-mail: zhengwc1@163.com [Department of Material Science, Sichuan University, Chengdu 610064 (China); Zhang, Lin [Research Center of Laser Fusion, CAEP, Mianyang 621900 (China); Chen, Bo-Wei [School of Physics and Electronic Engineering, Mianyang Normal University, Mianyang 621000 (China); Research Center of Laser Fusion, CAEP, Mianyang 621900 (China); Research Center of Computational Physics, Mianyang Normal University, Mianyang 621000 (China)

    2014-11-01

    The spin-Hamiltonian parameters (g factors g{sub //}, g{sub ⊥} and hyperfine structure constants A{sub //}, A{sub ⊥}) of the (MoOX{sub 5}){sup 2−} (X=Cl, Br) metallic complexes in solution or frozen-glass are calculated from the high-order perturbation formulas based on the two-mechanism model. In these formulas, the contributions to spin-Hamiltonian parameters due to both the widely-applied crystal-field (CF) mechanism and the charge-transfer (CT) mechanism (which is neglected in CF theory) are taken into account, and the needed CF and CT energy levels are obtained from the optical spectra. The calculated results with two adjustable parameters are in reasonable agreement with the experimental values. The calculations show that (i) the relative importance of CT mechanism in (MoOBr{sub 5}){sup 2−} metallic complexes is larger than that in (MoOCl{sub 5}){sup 2−} ones because of the stronger covalence of Mo{sup 5+}–Br{sup −} combination, and (ii) in both (MoOCl{sub 5}){sup 2−} and (MoOBr{sub 5}){sup 2−} metallic complexes, the contributions to spin-Hamiltonian parameters due to CT mechanism should also be taken into account because of the high valence state of Mo{sup 5+} ion.

  19. Investigations on the local structure and the spin-Hamiltonian parameters for the tetragonal $Cu^{2+}$ centre in $ZnGeF_{6}·6H_{2}O$ crystal

    Indian Academy of Sciences (India)

    LI CHAO-YING; HUANG YING; ZHENG XUE MEI

    2016-08-01

    The spin-Hamiltonian parameters ($g$ factors $g_{||}, g{|perp}$ and hyperfine structure constants $A_{||}$, $A{|perp}$) and the local structure for the tetragonal $Cu^{2+}$ centre in trigonal $ZnGeF_{6}·6H_{2}O$ crystal are theoretically studied using the perturbation formulae of these parameters for a 3d9 ion in tetragonally elongated octahedra. In the calculations, the contributions to the spin-Hamiltonian parameters from ligand orbital and spin-orbit coupling are included on the basis of the cluster approach in view of moderate covalency of the studied systems, and the required crystal field parameters are obtained using the superposition model and the local structures of the studied $[Cu(H_{2}O)_{6}]^{2+}$ cluster. According to the calculations, the ligand octahedra around $Cu^{2+}$ suffer relative elongation$\\tau{\\sim 0.085 \\AA) along the [0 0 1] (or $C_4$) axis for the tetragonal $Cu^{2+}$ centres in $ZnGeF_{6}·6H_{2}O$ crystal, due to the Jahn--Teller effect. The calculated results show good agreement with the experimental data.

  20. Assignments of the optical band positions and theoretical calculations of the spin-Hamiltonian parameters for the tetragonal W{sup 5+} octahedral clusters in tungsten oxide (WO{sub 3})-based glasses

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Ren-Ming [School of Physics & Electronic Engineering, Mianyang Normal University, Mianyang 621000 (China); Mei, Yang [School of Physics & Electronic Engineering, Mianyang Normal University, Mianyang 621000 (China); Research Center of Computational Physics, Mianyang Normal University, Mianyang 621000 (China); Zheng, Wen-Chen, E-mail: zhengwc1@163.com [Department of Material Science, Sichuan University, Chengdu 610064 (China); Wei, Cheng-Fu [School of Physics & Electronic Engineering, Mianyang Normal University, Mianyang 621000 (China)

    2015-03-15

    The optical band positions of W{sup 5+} octahedral clusters (WO{sub 6}){sup 7−} in tungsten oxide (WO{sub 3})-based glasses are reassigned and suggested. Based on this, the spin-Hamiltonian parameters (g factors g{sub //}, g{sub ⊥} and hyperfine structure constants A{sub //}, A{sub ⊥}) of these W{sup 5+} clusters are calculated from the high-order perturbation formulas based on the two-mechanism model. In the model, besides the contributions due to crystal-field (CF) mechanism in the extensively-used CF theory, the contributions owing to charge-transfer (CT) mechanism (which are often omitted) are also included. The calculated results are in reasonable agreement with the experimental values and the signs of hyperfine structure constants A{sub i} are suggested. The results are discussed.

  1. Studies on the spin Hamiltonian parameters and local angular distortions for the tetragonal Cu{sup 2+} centers in the ZnX (X=O and S) nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Li, Guo-Liang, E-mail: liguolianglq@163.com [Department of Applied Physics, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); School of Physics and Engineering, Xingyi Normal University for Nationalities, Xingyi 562400 (China); Wu, Shao-Yi; Zhang, Zhi-Hong; Ding, Chang-Chun; Hu, Xian-Fen [Department of Applied Physics, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2015-01-15

    The spin Hamiltonian parameters (g factors and hyperfine structure constants) and local structures are theoretically studied for the tetragonal Cu{sup 2+} centers in the ZnX (X=O and S) nanocrystals from the perturbation formulas of these parameters for a 3d{sup 9} ion in tetragonally distorted tetrahedra. The ligand orbital and spin–orbit coupling contributions are considered in view of strong covalency. Due to the Jahn–Teller effect, the local Cu{sup 2+}‒X{sup 2−} bond angles between the four equivalent impurity-ligand bonds and the four-fold axis are found to be about 2.47° and 1.68° larger than that (≈54.74°) for an ideal tetrahedron. This induces tetragonally compressed [CuX{sub 4}]{sup 6−} clusters on tetrahedral substitutional Zn{sup 2+} sites, different from the assignments (i.e., Cu{sup 2+} on tetragonally elongated octahedral and tetrahedral substitutional sites in the ZnO and ZnS nanocrystals, respectively) in the previous works. The calculated g factors for both systems and the parallel component of the hyperfine structure constants for the ZnS:Cu{sup 2+} nanocrystals based on the above local angular distortions are in good agreement with the observed values. The validity of the present assignments for the local structures of the Cu{sup 2+} centers is analyzed.

  2. EPR study of Gd3+-doped RbR(SO4)2·4H2O (R=Pr,Nd,Sm,Eu) single crystals: Phase transitions and spin-Hamiltonian parameters

    International Nuclear Information System (INIS)

    Extensive EPR measurements were carried out in the temperature range 100 endash 300 K. The room-temperature data indicate that Gd3+ ions substitute equally for R3+ ions at the two magnetically inequivalent sites in the unit cell, and that the site symmetry of the Gd3+ ion is monoclinic. The Gd3+ room-temperature spin-Hamiltonian parameters and linewidths were estimated. The phase transition temperatures (Tc) were determined to be 175±1K (first order) in RbPr(SO4)2·4H2O, 178.5±1K (first order) in RbNd(SO4)2·4H2O, 232±0.5K (second order) in RbSm(SO4)2·4H2O, and 230.5±0.5K (second order) in RbEu(SO4)2·4H2O. In RbPr(SO4)2·4H2O and RbNd(SO4)2·4H2O, the occurrence of the first-order phase transitions was deduced from abrupt changes in the behavior of the linewidth, zero-field splitting, and line positions, and coexistence of lines observed below and above Tc. In addition, there were observed occurrences of two more phase transitions second order in nature in RbPr(SO4)2·4H2O (Tc1=261K, Tc2=207.5K) and in RbNd(SO4)2·4H2O (Tc1=250K, Tc2=219.5K); these were not as sharply defined as the preceding ones. Below Tc, for all the crystals, the symmetry of the crystals was found to be lower than monoclinic, the four ions in the unit cell becoming magnetically inequivalent from each other. The observed second-order phase transitions in the four crystals were found to be in agreement with Landau theory of second-order phase transitions; the critical exponent was determined to be β congruent 0.51. copyright 1997 The American Physical Society

  3. Gravitational spin Hamiltonians from the S matrix

    CERN Document Server

    Vaidya, Varun

    2014-01-01

    We utilize generalized unitarity and recursion relations combined with effective field theory(EFT) techniques to compute spin dependent interaction terms for inspiralling binary systems in the post newtonian(PN) approximation. Using these methods offers great computational advantage over traditional techniques involving feynman diagrams, especially at higher orders in the PN expansion. As a specific example, we reproduce the spin-orbit interaction up to 2.5 PN order as also the leading order $S^2$(3PN) hamiltonian for an arbitrary massive object. We also obtain the unknown $S^3$(3.5PN) spin hamiltonian for an arbitrary massive object in terms of its low frequency linear response to gravitational perturbations, which was till now known only for a black hole. Furthermore, we derive the missing $S^4$ Hamiltonian at leading order(4PN) for an arbitrary massive object and establish that a minimal coupling of a massive elementary particle to gravity leads to a black hole structure. Finally, the Kerr metric is obtain...

  4. Construction of Giant-Spin Hamiltonians from Many-Spin Hamiltonians by Third-Order Perturbation Theory and Application to an Fe3 Cr Single-Molecule Magnet.

    Science.gov (United States)

    Tabrizi, Shadan Ghassemi; Arbuznikov, Alexei V; Kaupp, Martin

    2016-05-10

    A general giant-spin Hamiltonian (GSH) describing an effective spin multiplet of an exchange-coupled metal cluster with dominant Heisenberg interactions was derived from a many-spin Hamiltonian (MSH) by treating anisotropic interactions at the third order of perturbation theory. Going beyond the existing second-order perturbation treatment allows irreducible tensor operators of rank six (or corresponding Stevens operator equivalents) in the GSH to be obtained. Such terms were found to be of crucial importance for the fitting of high-field EPR spectra of a number of single-molecule magnets (SMMs). Also, recent magnetization measurements on trigonal and tetragonal SMMs have found the inclusion of such high-rank axial and transverse terms to be necessary to account for experimental data in terms of giant-spin models. While mixing of spin multiplets by local zero-field splitting interactions was identified as the major origin of these contributions to the GSH, a direct and efficient microscopic explanation had been lacking. The third-order approach developed in this work is used to illustrate the mapping of an MSH onto a GSH for an S=6 trigonal Fe3 Cr complex that was recently investigated by high-field EPR spectroscopy. Comparisons between MSH and GSH consider the simulation of EPR data with both Hamiltonians, as well as locations of diabolical points (conical intersections) in magnetic-field space. The results question the ability of present high-field EPR techniques to determine high-rank zero-field splitting terms uniquely, and lead to a revision of the experimental GSH parameters of the Fe3 Cr SMM. Indeed, a bidirectional mapping between MSH and GSH effectively constrains the number of free parameters in the GSH. This notion may in the future facilitate spectral fitting for highly symmetric SMMs.

  5. Construction of Giant-Spin Hamiltonians from Many-Spin Hamiltonians by Third-Order Perturbation Theory and Application to an Fe3 Cr Single-Molecule Magnet.

    Science.gov (United States)

    Tabrizi, Shadan Ghassemi; Arbuznikov, Alexei V; Kaupp, Martin

    2016-05-10

    A general giant-spin Hamiltonian (GSH) describing an effective spin multiplet of an exchange-coupled metal cluster with dominant Heisenberg interactions was derived from a many-spin Hamiltonian (MSH) by treating anisotropic interactions at the third order of perturbation theory. Going beyond the existing second-order perturbation treatment allows irreducible tensor operators of rank six (or corresponding Stevens operator equivalents) in the GSH to be obtained. Such terms were found to be of crucial importance for the fitting of high-field EPR spectra of a number of single-molecule magnets (SMMs). Also, recent magnetization measurements on trigonal and tetragonal SMMs have found the inclusion of such high-rank axial and transverse terms to be necessary to account for experimental data in terms of giant-spin models. While mixing of spin multiplets by local zero-field splitting interactions was identified as the major origin of these contributions to the GSH, a direct and efficient microscopic explanation had been lacking. The third-order approach developed in this work is used to illustrate the mapping of an MSH onto a GSH for an S=6 trigonal Fe3 Cr complex that was recently investigated by high-field EPR spectroscopy. Comparisons between MSH and GSH consider the simulation of EPR data with both Hamiltonians, as well as locations of diabolical points (conical intersections) in magnetic-field space. The results question the ability of present high-field EPR techniques to determine high-rank zero-field splitting terms uniquely, and lead to a revision of the experimental GSH parameters of the Fe3 Cr SMM. Indeed, a bidirectional mapping between MSH and GSH effectively constrains the number of free parameters in the GSH. This notion may in the future facilitate spectral fitting for highly symmetric SMMs. PMID:27062248

  6. Spin Hamiltonian Spectroscopy in PRASEODYMIUM(3):LANTHANUM Trifluoride.

    Science.gov (United States)

    Otto, Frederick William

    An optically detected anticrossing in solid state laser spectroscopy produced by cross-relaxation is reported. Spin -spin cross-relaxation between the ^{141 }Pr and ^{19}F spin reservoirs in Pr^{+3}:LaF _3 and its influence on the ^{141}Pr NMR spectrum is observed. The detection technique employed combines optical pumping and hole burning with either an external magnetic field sweep or rf resonance saturation producing slow transient changes in resonant laser transmission. At a certain value of the external magnetic field, where the energy level splittings of Pr and F spins match, a level repulsion and discontinuity of the Pr^{+3} NMR lines is observed. This effect is interpreted as the "anticrossing" of the combined Pr-F spin-spin reservoir energy states. The Zeeman - Quadrupole Hamiltonian spectrum of the lowest hyperfine optical ground state manifold of Pr^ {+3}:LaF_3 is mapped out over a wide range of Zeeman magnetic fields. A new method is proposed for dynamically polarizing nuclei by means of optical pumping, using resonant cross-relaxation between rare spins and spin reservoirs.

  7. The dynamics of a spinning particle in a linear in spin Hamiltonian approximation

    CERN Document Server

    Lukes-Gerakopoulos, Georgios; Patsis, Panos A; Seyrich, Jonathan

    2016-01-01

    We investigate for order and chaos the dynamical system of a spinning test particle of mass $m$ moving in the spacetime background of a Kerr black hole of mass M. This system is approximated in our investigation by the linear in spin Hamiltonian function provided in [E. Barausse, and A. Buonanno, Phys.Rev. D 81, 084024 (2010)]. We study the corresponding phase space by using 2D projections on a surface of section and the method of color and rotation on a 4D Poincar\\'e section. Various topological structures coming from the non-integrability of the linear in spin Hamiltonian are found and discussed. Moreover, an interesting result is that from the value of the dimensionless spin $S/(m M)=10^{-4}$ of the particle and below, the impact of the non-integrability of the system on the motion of the particle seems to be negligible.

  8. Understanding visual map formation through vortex dynamics of spin Hamiltonian models

    CERN Document Server

    Cho, M W; Cho, Myoung Won; Kim, Seunghwan

    2003-01-01

    We introduce a general method for cerebral cortical map generation and apply it to pattern formation in orientation and ocular dominance columns of the brain. From a known cortical structure, we build spin Hamiltonian models with long-range interactions of the Mexican hat type. These Hamiltonian models allow a coherent interpretation of the diverse phenomena in the map formation in the visual cortex with the help of relaxation dynamics of spins. In particular, we predict various phenomena of self-organization in orientation and ocular map formation including the pinwheel annihilation and its dependency on the columnar wave vector and boundary conditions.

  9. Solid-state NMR of inorganic semiconductors.

    Science.gov (United States)

    Yesinowski, James P

    2012-01-01

    Studies of inorganic semiconductors by solid-state NMR vary widely in terms of the nature of the samples investigated, the techniques employed to observe the NMR signal, and the types of information obtained. Compared with the NMR of diamagnetic non-semiconducting substances, important differences often result from the presence of electron or hole carriers that are the hallmark of semiconductors, and whose theoretical interpretation can be involved. This review aims to provide a broad perspective on the topic for the non-expert by providing: (1) a basic introduction to semiconductor physical concepts relevant to NMR, including common crystal structures and the various methods of making samples; (2) discussions of the NMR spin Hamiltonian, details of some of the NMR techniques and strategies used to make measurements and theoretically predict NMR parameters, and examples of how each of the terms in the Hamiltonian has provided useful information in bulk semiconductors; (3) a discussion of the additional considerations needed to interpret the NMR of nanoscale semiconductors, with selected examples. The area of semiconductor NMR is being revitalized by this interest in nanoscale semiconductors, the great improvements in NMR detection sensitivity and resolution that have occurred, and the current interest in optical pumping and spintronics-related studies. Promising directions for future research will be noted throughout. PMID:21898208

  10. Higher-order Zeeman and spin terms in the electron paramagnetic resonance spin Hamiltonian; their description in irreducible form using Cartesian, tesseral spherical tensor and Stevens' operator expressions.

    Science.gov (United States)

    McGavin, Dennis G; Tennant, W Craighead

    2009-06-17

    In setting up a spin Hamiltonian (SH) to study high-spin Zeeman and high-spin nuclear and/or electronic interactions in electron paramagnetic resonance (EPR) experiments, it is argued that a maximally reduced SH (MRSH) framed in tesseral combinations of spherical tensor operators is necessary. Then, the SH contains only those terms that are necessary and sufficient to describe the particular spin system. The paper proceeds then to obtain interrelationships between the parameters of the MRSH and those of alternative SHs expressed in Cartesian tensor and Stevens operator-equivalent forms. The examples taken, initially, are those of Cartesian and Stevens' expressions for high-spin Zeeman terms of dimension BS(3) and BS(5). Starting from the well-known decomposition of the general Cartesian tensor of second rank to three irreducible tensors of ranks 0, 1 and 2, the decomposition of Cartesian tensors of ranks 4 and 6 are treated similarly. Next, following a generalization of the tesseral spherical tensor equations, the interrelationships amongst the parameters of the three kinds of expressions, as derived from equivalent SHs, are determined and detailed tables, including all redundancy equations, set out. In each of these cases the lowest symmetry, [Formula: see text] Laue class, is assumed and then examples of relationships for specific higher symmetries derived therefrom. The validity of a spin Hamiltonian containing mixtures of terms from the three expressions is considered in some detail for several specific symmetries, including again the lowest symmetry. Finally, we address the application of some of the relationships derived here to seldom-observed low-symmetry effects in EPR spectra, when high-spin electronic and nuclear interactions are present. PMID:21693947

  11. Spin Hamiltonian of hyper-kagome Na{sub 4}Ir{sub 3}O{sub 8}.

    Energy Technology Data Exchange (ETDEWEB)

    Micklitz, T.; Norman, M. R.; Materials Science Division; Freie Univ.

    2010-01-01

    We derive the spin Hamiltonian for the quantum spin liquid Na{sub 4}Ir{sub 3}O{sub 8}, and then estimate the direct and superexchange contributions between near neighbor iridium ions using a tight-binding parametrization of the electronic structure. We find a magnitude of the exchange interaction comparable to experiment for a reasonable value of the on-site Coulomb repulsion. For one of the two tight-binding parametrizations we have studied, the direct exchange term, which is isotropic, dominates the total exchange. This provides support for those theories proposed to describe this quantum spin liquid that assume an isotropic Heisenberg model.

  12. Rovibrational and temperature effects in theoretical studies of NMR parameters

    DEFF Research Database (Denmark)

    Faber, Rasmus; Kaminsky, Jakub; Sauer, Stephan P. A.

    2016-01-01

    The demand for high precision calculations of NMR shieldings (or their related values, chemical shifts δ) and spin-spin coupling constants facilitating and supporting detailed interpretations of NMR spectra increases hand in hand with the development of computational techniques and hardware resou...

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

    Directory of Open Access Journals (Sweden)

    Paige Lacy

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

  14. Ground-State Analysis for an Exactly Solvable Coupled-Spin Hamiltonian

    Directory of Open Access Journals (Sweden)

    Eduardo Mattei

    2013-11-01

    Full Text Available We introduce a Hamiltonian for two interacting su(2 spins. We use a mean-field analysis and exact Bethe ansatz results to investigate the ground-state properties of the system in the classical limit, defined as the limit of infinite spin (or highest weight. Complementary insights are provided through investigation of the energy gap, ground-state fidelity, and ground-state entanglement, which are numerically computed for particular parameter values. Despite the simplicity of the model, a rich array of ground-state features are uncovered. Finally, we discuss how this model may be seen as an analogue of the exactly solvable p+ip pairing Hamiltonian.

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

    Science.gov (United States)

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

    2012-01-01

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

  16. Quantum model of a solid-state spin qubit: Ni cluster on a silicon surface by the generalized spin Hamiltonian and X-ray absorption spectroscopy investigations

    Energy Technology Data Exchange (ETDEWEB)

    Farberovich, Oleg V. [School of Physics and Astronomy, Beverly and Raymond Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 69978 (Israel); Research Center for Nanoscale Structure of Matter, Southern Federal University, Zorge 5, 344090 Rostov-on-Don (Russian Federation); Voronezh State University, Voronezh 394000 (Russian Federation); Mazalova, Victoria L., E-mail: mazalova@sfedu.ru [Research Center for Nanoscale Structure of Matter, Southern Federal University, Zorge 5, 344090 Rostov-on-Don (Russian Federation); Soldatov, Alexander V. [Research Center for Nanoscale Structure of Matter, Southern Federal University, Zorge 5, 344090 Rostov-on-Don (Russian Federation)

    2015-11-15

    We present here the quantum model of a Ni solid-state electron spin qubit on a silicon surface with the use of a density-functional scheme for the calculation of the exchange integrals in the non-collinear spin configurations in the generalized spin Hamiltonian (GSH) with the anisotropic exchange coupling parameters linking the nickel ions with a silicon substrate. In this model the interaction of a spin qubit with substrate is considered in GSH at the calculation of exchange integrals J{sub ij} of the nanosystem Ni{sub 7}–Si in the one-electron approach taking into account chemical bonds of all Si-atoms of a substrate (environment) with atoms of the Ni{sub 7}-cluster. The energy pattern was found from the effective GSH Hamiltonian acting in the restricted spin space of the Ni ions by the application of the irreducible tensor operators (ITO) technique. In this paper we offer the model of the quantum solid-state N-spin qubit based on the studying of the spin structure and the spin-dynamics simulations of the 3d-metal Ni clusters on the silicon surface. The solution of the problem of the entanglement between spin states in the N-spin systems is becoming more interesting when considering clusters or molecules with a spectral gap in their density of states. For quantifying the distribution of the entanglement between the individual spin eigenvalues (modes) in the spin structure of the N-spin system we use the density of entanglement (DOE). In this study we have developed and used the advanced high-precision numerical techniques to accurately assess the details of the decoherence process governing the dynamics of the N-spin qubits interacting with a silicon surface. We have studied the Rabi oscillations to evaluate the N-spin qubits system as a function of the time and the magnetic field. We have observed the stabilized Rabi oscillations and have stabilized the quantum dynamical qubit state and Rabi driving after a fixed time (0.327 μs). The comparison of the energy

  17. Determination of Kinetic Parameters within a Single Nonisothermal On-Flow Experiment by Nanoliter NMR Spectroscopy.

    Science.gov (United States)

    Gomez, M Victoria; Rodriguez, Antonio M; de la Hoz, Antonio; Jimenez-Marquez, Francisco; Fratila, Raluca M; Barneveld, Peter A; Velders, Aldrik H

    2015-10-20

    Conventional methods to determine the kinetic parameters for a certain reaction require multiple, separate isothermal experiments, resulting in time- and material-consuming processes. Here, an approach to determine the kinetic information within a single nonisothermal on-flow experiment is presented, consuming less than 10 μmol of reagents and having a total measuring time of typically 10 min. This approach makes use of a microfluidic NMR chip hyphenated to a continuous-flow microreactor and is based on the capabilities of the NMR chip to analyze subnanomole quantities of material in the 25 nL detection volume. Importantly, useful data are acquired from the microreactor platform in specific isothermal and nonisothermal frames. A model fitting the experimental data enables rapid determination of kinetic parameters, as demonstrated for a library of isoxazole and pyrazole derivatives. PMID:26383715

  18. Ab initio determination of spin Hamiltonians with anisotropic exchange interactions: The case of the pyrochlore ferromagnet Lu2V2O7

    Science.gov (United States)

    Riedl, Kira; Guterding, Daniel; Jeschke, Harald O.; Gingras, Michel J. P.; Valentí, Roser

    2016-07-01

    We present a general framework for deriving effective spin Hamiltonians of correlated magnetic systems based on a combination of relativistic ab initio density functional theory calculations, exact diagonalization of a generalized Hubbard Hamiltonian on finite clusters, and spin projections onto the low-energy subspace. A key motivation is to determine anisotropic bilinear exchange couplings in materials of interest. As an example, we apply this method to the pyrochlore Lu2V2O7 where the vanadium ions form a lattice of corner-sharing spin-1/2 tetrahedra. In this compound, anisotropic Dzyaloshinskii-Moriya interactions (DMIs) play an essential role in inducing a magnon Hall effect. We obtain quantitative estimates of the nearest-neighbor Heisenberg exchange, the DMI, and the symmetric part of the anisotropic exchange tensor. Finally, we compare our results with experimental ones on the Lu2V2O7 compound.

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

    Science.gov (United States)

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

    2016-07-01

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

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

    Science.gov (United States)

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

    1984-04-01

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

  1. Thermal and solvent effects on NMR spectroscopy parameters of a prototypical Chagas disease drug

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-07-01

    understood on the basis of semiclassical physics, J-coupling is a purely quantum- mechanical phenomenon. The present results provide evidence that hyperconjugative effects in solute molecules are not due to changes in geometric parameters upon solvation, but arise from the direct response of the electronic wave function to the presence of the solvent, which can be represented by discrete molecules and/or the dielectric bulk. We believe that our findings may be helpful to rationalize the relation between NMR parameters and the interactions in hydrogen-bonded complexes. Further applications along these lines are in progress. (author)

  2. Relationships between 1H NMR Relaxation Data and Some Technological Parameters of Meat: A Chemometric Approach

    Science.gov (United States)

    Brown, Robert J. S.; Capozzi, Francesco; Cavani, Claudio; Cremonini, Mauro A.; Petracci, Massimiliano; Placucci, Giuseppe

    2000-11-01

    In this paper chemometrics (ANOVA and PCR) is used to measure unbiased correlations between NMR spin-echo decays of pork M. Longissimus dorsi obtained through Carr-Purcell-Meiboom-Gill (CPMG) experiments at low frequency (20 MHz) and the values of 14 technological parameters commonly used to assess pork meat quality. On the basis of the ANOVA results, it is also found that the CPMG decays of meat cannot be best interpreted with a "discrete" model (i.e., by expanding the decays in a series of a discrete number of exponential components, each with a different transverse relaxation time), but rather with a "continuous" model, by which a continuous distribution of T2's is allowed. The latter model also agrees with literature histological results.

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

    Science.gov (United States)

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

    2012-03-14

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

  4. Solid state NMR and bioequivalence comparison of the pharmacokinetic parameters of two formulations of clindamycin

    KAUST Repository

    Al-Talla, Zeyad

    2011-01-01

    Objective: The purpose of this study was to compare the pharmacokinetic parameters and determine the bioequivalence of a generic formulation of clindamycin that is sold in the local markets in the Middle East (Clindox® 150 mg capsule; test) with a reference formulation (Dalacin C® 150 mg capsule) in healthy adult male volunteers. Methods: A single-dose, open-label, 2-period crossover study was conducted. Healthy male volunteers were randomly assigned to oral administration of a single treatment of the reference and test formulations. The same groups were given the alternate formulation. After dosing, serial blood samples were withdrawn for a period of 24 h. Serum harvested from the blood samples was analyzed for clindamycin by high performance liquid chromatography (HPLC) with ultraviolet detection. Pharmacokinetic parameters, including AUC0-∞, AUC 0-t, Cmax, Ke, tmax and t 1/2 were determined from the serum concentrations for both formulations (test and reference). The products were tested for bioequivalence after log-transformation of the data. Results: 24 healthy adult male volunteers from Jordan (mean [SD] age, 28.8 (7.7) years (range 19-45 years); height, 175.8 (10.6) cm (range 159.0-192.0 cm); weight, 75.6 (11.0) kg (range 58-101 kg); and body mass index, 24.4 (1.8) kg/m2 (range 21.3-28 kg/m2)) were enrolled in and completed the study. The 13C NMR spectra for both Dalacin C® and Clindox® showed 18 distinct lines associated with the 18 different carbon atoms. Conclusion: The statistical comparison suggested that Clindox® capsules are bioequivalent to Dalacin C® capsules. The 13C CPMAS results confirmed that the two drugs exhibit typical clindamycin spectra. ©2011 Dustri-Verlag Dr. K. Feistle.

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

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Qing; Shi, Chaowei [Hefei National Laboratory for Physical Sciences at The Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026 (China); Yu, Lu [Hefei National Laboratory for Physical Sciences at The Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026 (China); High Magnetic Field Laboratory, Chinese Academy of Science, Hefei, Anhui, 230031 (China); Zhang, Longhua [Hefei National Laboratory for Physical Sciences at The Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026 (China); Xiong, Ying, E-mail: yxiong73@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at The Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026 (China); Tian, Changlin, E-mail: cltian@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at The Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, 230026 (China); High Magnetic Field Laboratory, Chinese Academy of Science, Hefei, Anhui, 230031 (China)

    2015-02-13

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

  6. Temperature Dependence of NMR Parameters Calculated from Path Integral Molecular Dynamics Simulations.

    Science.gov (United States)

    Dračínský, Martin; Bouř, Petr; Hodgkinson, Paul

    2016-03-01

    The influence of temperature on NMR chemical shifts and quadrupolar couplings in model molecular organic solids is explored using path integral molecular dynamics (PIMD) and density functional theory (DFT) calculations of shielding and electric field gradient (EFG) tensors. An approach based on convoluting calculated shielding or EFG tensor components with probability distributions of selected bond distances and valence angles obtained from DFT-PIMD simulations at several temperatures is used to calculate the temperature effects. The probability distributions obtained from the quantum PIMD simulations, which includes nuclear quantum effects, are significantly broader and less temperature dependent than those obtained with conventional DFT molecular dynamics or with 1D scans through the potential energy surface. Predicted NMR observables for the model systems were in excellent agreement with experimental data. PMID:26857802

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

    Directory of Open Access Journals (Sweden)

    Asoodeh Mojtaba

    2015-06-01

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

  8. The effects of some parameters on the calculated 1H NMR relaxation times of cell water

    International Nuclear Information System (INIS)

    The effect of some parameters on the longitudinal and transverse relaxation times is calculated and a comparison between the calculated relaxation times with the results of different measurements is made. (M.S.)

  9. Quantifying Lipari-Szabo modelfree parameters from 13CO NMR relaxation experiments

    International Nuclear Information System (INIS)

    It is proposed to obtain effective Lipari-Szabo order parameters and local correlation times for relaxation vectors of protein 13CO nuclei by carrying out a 13CO-R1 auto relaxation experiment, a transverse 13CO CSA/13CO-13C CSA/dipolar cross correlation and a transverse 13CO CSA/13CO-15N CSA/dipolar cross correlation experiment. Given the global rotational correlation time from 15N relaxation experiments, a new program COMFORD (CO-Modelfree Fitting Of Relaxation Data) is presented to fit the 13CO data to an effective order parameter SCO2, an effective local correlation time and the orientation of the CSA tensor with respect to the molecular frame. It is shown that the effective SCO2 is least sensitive to rotational fluctuations about an imaginary Cα-Cα axis and most sensitive to rotational fluctuations about an imaginary axis parallel to the NH bond direction. As such, the SCO2 information is fully complementary to the 15N relaxation order parameter, which is least sensitive to fluctuations about the NH axis and most sensitive to fluctuations about the Cα-Cα axis. The new paradigm is applied on data of Ca2+ saturated Calmodulin, and on available literature data for Ubiquitin. Our data indicate that the SCO2 order parameters rapport on slower, and sometimes different, motions than the 15N relaxation order parameters. The CO local correlation times correlate well with the calmodulin's secondary structure

  10. Dynamics, NMR parameters and hyperfine coupling constants of the Fe3O4(1 0 0)-water interface: Implications for MRI probes

    Science.gov (United States)

    Gonçalves, Mateus A.; Peixoto, Fernando C.; da Cunha, Elaine F. F.; Ramalho, Teodorico C.

    2014-08-01

    Magnetite is an iron oxide widely used as contrast agent in MRI, receiving considerable interest from nanoscience and nanotechnology. In this work, the face 1 0 0 of the magnetite structure was studied with water in order to obtain 1H hyperfine coupling constants (HFCCs). Molecular dynamics (MD) calculations were performed using the ReaxFF program and for statistical inefficiency, structures were selected for HFCC and NMR calculations. From our theoretical findings, the magnetite in solution considerably increases the 1H HFCC of water molecules. From our results, it is essential to incorporate the dynamics and solvent effects into NMR calculations of relaxation parameters.

  11. Study of correlations in molecular motion by multiple quantum NMR

    International Nuclear Information System (INIS)

    Nuclear magnetic resonance is a very useful tool for characterizing molecular configurations through the measurement of transition frequencies and dipolar couplings. The measurement of spectral lineshapes, spin-lattice relaxation times, and transverse relaxation times also provide us with valuable information about correlations in molecular motion. The new technique of multiple quantum nuclear magnetic resonance has numerous advantages over the conventional single quantum NMR techniques in obtaining information about static and dynamic interactions of coupled spin systems. In the first two chapters, the theoretical background of spin Hamiltonians and the density matrix formalism of multiple quantum NMR is discussed. The creation and detection of multiple quantum coherence by multiple pulse sequence are discussed. Prototype multiple quantum spectra of oriented benzene are presented. Redfield relaxation theory and the application of multiple quantum NMR to the study of correlations in fluctuations are presented. A specific example of an oriented methyl group relaxed by paramagnetic impurities is studied in detail. The study of possible correlated motion between two coupled methyl groups by multiple quantum NMR is presented. For a six spin system it is shown that the four-quantum spectrum is sensitive to two-body correlations, and serves a ready test of correlated motion. The study of the spin-lattice dynamics of orienting or tunneling methyl groups (CH3 and CD3) at low temperatures is presented. The anisotropic spin-lattice relaxation of deuterated hexamethylbenzene, caused by the sixfold reorientation of the molecules, is investigated, and the NMR spectrometers and other experimental details are discussed

  12. Compact NMR

    Energy Technology Data Exchange (ETDEWEB)

    Bluemich, Bernhard; Haber-Pohlmeier, Sabina; Zia, Wasif [RWTH Aachen Univ. (Germany). Inst. fuer Technische und Makromolekulare Chemie (ITMC)

    2014-06-01

    Nuclear Magnetic Resonance (NMR) spectroscopy is the most popular method for chemists to analyze molecular structures, while Magnetic Resonance Imaging (MRI) is a non-invasive diagnostic tool for medical doctors that provides high-contrast images of biological tissue. In both applications, the sample (or patient) is positioned inside a large, superconducting magnet to magnetize the atomic nuclei. Interrogating radio-frequency pulses result in frequency spectra that provide the chemist with molecular information, the medical doctor with anatomic images, and materials scientist with NMR relaxation parameters. Recent advances in magnet technology have led to a variety of small permanent magnets to allow compact and low-cost instruments. The goal of this book is to provide an introduction to the practical use of compact NMR at a level nearly as basic as the operation of a smart phone.

  13. Compact NMR

    International Nuclear Information System (INIS)

    Nuclear Magnetic Resonance (NMR) spectroscopy is the most popular method for chemists to analyze molecular structures, while Magnetic Resonance Imaging (MRI) is a non-invasive diagnostic tool for medical doctors that provides high-contrast images of biological tissue. In both applications, the sample (or patient) is positioned inside a large, superconducting magnet to magnetize the atomic nuclei. Interrogating radio-frequency pulses result in frequency spectra that provide the chemist with molecular information, the medical doctor with anatomic images, and materials scientist with NMR relaxation parameters. Recent advances in magnet technology have led to a variety of small permanent magnets to allow compact and low-cost instruments. The goal of this book is to provide an introduction to the practical use of compact NMR at a level nearly as basic as the operation of a smart phone.

  14. Calculation of average molecular parameters, functional groups, and a surrogate molecule for heavy fuel oils using 1H and 13C NMR spectroscopy

    KAUST Repository

    Abdul Jameel, Abdul Gani

    2016-04-22

    Heavy fuel oil (HFO) is primarily used as fuel in marine engines and in boilers to generate electricity. Nuclear Magnetic Resonance (NMR) is a powerful analytical tool for structure elucidation and in this study, 1H NMR and 13C NMR spectroscopy were used for the structural characterization of 2 HFO samples. The NMR data was combined with elemental analysis and average molecular weight to quantify average molecular parameters (AMPs), such as the number of paraffinic carbons, naphthenic carbons, aromatic hydrogens, olefinic hydrogens, etc. in the HFO samples. Recent formulae published in the literature were used for calculating various derived AMPs like aromaticity factor 〖(f〗_a), C/H ratio, average paraffinic chain length (¯n), naphthenic ring number 〖(R〗_N), aromatic ring number〖 (R〗_A), total ring number〖 (R〗_T), aromatic condensation index (φ) and aromatic condensation degree (Ω). These derived AMPs help in understanding the overall structure of the fuel. A total of 19 functional groups were defined to represent the HFO samples, and their respective concentrations were calculated by formulating balance equations that equate the concentration of the functional groups with the concentration of the AMPs. Heteroatoms like sulfur, nitrogen, and oxygen were also included in the functional groups. Surrogate molecules were finally constructed to represent the average structure of the molecules present in the HFO samples. This surrogate molecule can be used for property estimation of the HFO samples and also serve as a surrogate to represent the molecular structure for use in kinetic studies.

  15. Correlations between (51)V solid-state NMR parameters and chemical structure of vanadium (V) complexes as models for related metalloproteins and catalysts.

    Science.gov (United States)

    Fenn, Annika; Wächtler, Maria; Gutmann, Torsten; Breitzke, Hergen; Buchholz, Axel; Lippold, Ines; Plass, Winfried; Buntkowsky, Gerd

    2009-12-01

    The parameters describing the quadrupolar and CSA interactions of 51V solid-state MAS NMR investigations of model complexes mimicking vanadoenzymes as well as vanadium containing catalysts and enzyme complexes are interpreted with respect to the chemical structure. The interpretation is based on the data of 15 vanadium complexes including two new complexes with previously unpublished data and 13 complexes with data previously published by us. Correlations between the chemical structure and the 51V solid-state NMR data of this class of compounds have been established. Especially for the isotropic chemical shift delta(iso) and the chemical shift anisotropy delta(sigma), correlations with specific structural features like the coordination number of the vanadium atom, the number of coordinating nitrogens, the number of oxygen atoms and the chemical surrounding of the complex could be established for these compounds. Moreover, quantitative correlations between the solid-state NMR parameters and specific bond angles and bond lengths have been obtained. Our results can be of particular interest for future investigations concerning the structure and the mode of action of related vanadoenzymes and vanadate protein assemblies, including the use of vanadate adducts as transition state analogs for phosphate metabolizing systems.

  16. Gravitational spin Hamiltonians from the S matrix

    OpenAIRE

    Vaidya, Varun

    2014-01-01

    We utilize generalized unitarity and recursion relations combined with effective field theory(EFT) techniques to compute spin dependent interaction terms for inspiralling binary systems in the post newtonian(PN) approximation. Using these methods offers great computational advantage over traditional techniques involving feynman diagrams, especially at higher orders in the PN expansion. As a specific example, we reproduce the spin-orbit interaction up to 2.5 PN order as also the leading order ...

  17. Mechanical analogues of spin Hamiltonians and dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Harjeet, E-mail: harjeet_kaur17@yahoo.com [Department of Physics, Guru Nanak Dev University, Amritsar 143 005 (India); Jain, Sudhir R. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Malik, Sham S. [Department of Physics, Guru Nanak Dev University, Amritsar 143 005 (India)

    2014-01-17

    Bloch et al. mapped the precession of the spin-half in a magnetic field of variable magnitude and direction to the rotations of a rigid sphere rolling on a curved surface utilizing SU(2)–SO(3) isomorphism. This formalism is extended to study the behaviour of spin–orbit interactions and the mechanical analogy for Rashba–Dresselhauss spin–orbit interaction in two dimensions is presented by making its spin states isomorphic to the rotations of a rigid sphere rolling on a ring. The change in phase of spin is represented by the angle of rotation of sphere after a complete revolution. In order to develop the mechanical analogy for the spin filter, we find that perfect spin filtration of down spin makes the sphere to rotate at some unique angles and the perfect spin filtration of up spin causes the rotations with certain discrete frequencies.

  18. Choosing the best pulse sequences, acquisition parameters, postacquisition processing strategies, and probes for natural product structure elucidation by NMR spectroscopy.

    Science.gov (United States)

    Reynolds, William F; Enríquez, Raúl G

    2002-02-01

    The relative merits of different pairs of two-dimensional NMR pulse sequences (COSY-90 vs COSY-45, NOESY vs T-ROESY, HSQC vs HMQC, HMBC vs CIGAR, etc.) are compared and recommendations are made for the preferred choice of sequences for natural product structure elucidation. Similar comparisons are made between different selective 1D sequences and the corresponding 2D sequences. Many users of 2D NMR use longer than necessary relaxation delays and neglect to use forward linear prediction processing. It is shown that using shorter relaxation delays in combination with forward linear prediction allows one to get better resolved spectra in less time. The relative merits of different probes and likely future probe developments are also discussed.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ross, J.B.A.; Schwartz, G.P.; Laws, W.R. (Mount Sinai, New York, NY (United States)); Wyssbrod, H.R.; Porter, R.A. (Univ. of Louisville, KY (United States)); Michaels, C.A. (Swarthmore Coll., PA (United States))

    1992-02-18

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

  20. Vibrational studies, NMR analysis, modeling of electronic and thermodynamical parameters of 1,3-bis(4-benzamido)triazene

    Science.gov (United States)

    Ghalebsaz-Jeddi, N.; Vessally, E.

    2016-07-01

    The optimized geometry, vibrational wavenumbers, 1H and 13C chemical shift values of 1,3-bis(4-benzamido)triazene, BBT, in the ground state were computed with the Hartree-Fock (HF) and density functional theory method (PBE1PBE) with 6-311+G(2 d, p) basis set. The harmonic vibrational wavenumbers of BBT were calculated and the scaled values were compared with the experimental FT-IR spectra. A detailed interpretation of the NMR spectra of BBT was reported. The calculated data are in reasonably good agreement with experimental measurements. Moreover, the log P value was estimated with ChemBioOffice Ultra 11.0, ACD/LogP, and ALOGPS programs.

  1. Experimental investigation of the EPR parameters and molecular orbital bonding coefficients for VO2+ ion in NaH2PO4·2H2O single crystals

    Science.gov (United States)

    Kalfaoğlu, Emel; Karabulut, Bünyamin

    2016-09-01

    Electron paramagnetic resonance (EPR) spectra of VO2+ ions in NaH2PO4·2H2O single crystal have been studied. The spin-Hamiltonian parameters and molecular orbital bonding coefficients were calculated. The angular variation of the EPR spectra shows two different VO2+ complexes. These are located in different chemical environment and each environment contains four magnetically inequivalent VO2+ sites. The crystal field around VO2+ ion is approximately axially symmetric since a strong V=O bond distorts the crystal lattice. Spin Hamiltonian parameters and molecular orbital bonding coefficients were calculated from the EPR data and the nature of bonding in the complex was discussed together.

  2. Study of correlations in molecular motion by multiple quantum NMR

    Energy Technology Data Exchange (ETDEWEB)

    Tang, J.H.

    1981-11-01

    Nuclear magnetic resonance is a very useful tool for characterizing molecular configurations through the measurement of transition frequencies and dipolar couplings. The measurement of spectral lineshapes, spin-lattice relaxation times, and transverse relaxation times also provide us with valuable information about correlations in molecular motion. The new technique of multiple quantum nuclear magnetic resonance has numerous advantages over the conventional single quantum NMR techniques in obtaining information about static and dynamic interactions of coupled spin systems. In the first two chapters, the theoretical background of spin Hamiltonians and the density matrix formalism of multiple quantum NMR is discussed. The creation and detection of multiple quantum coherence by multiple pulse sequence are discussed. Prototype multiple quantum spectra of oriented benzene are presented. Redfield relaxation theory and the application of multiple quantum NMR to the study of correlations in fluctuations are presented. A specific example of an oriented methyl group relaxed by paramagnetic impurities is studied in detail. The study of possible correlated motion between two coupled methyl groups by multiple quantum NMR is presented. For a six spin system it is shown that the four-quantum spectrum is sensitive to two-body correlations, and serves a ready test of correlated motion. The study of the spin-lattice dynamics of orienting or tunneling methyl groups (CH/sub 3/ and CD/sub 3/) at low temperatures is presented. The anisotropic spin-lattice relaxation of deuterated hexamethylbenzene, caused by the sixfold reorientation of the molecules, is investigated, and the NMR spectrometers and other experimental details are discussed.

  3. Accurate determination of order parameters from 1H,15N dipolar couplings in MAS solid-state NMR experiments.

    Science.gov (United States)

    Chevelkov, Veniamin; Fink, Uwe; Reif, Bernd

    2009-10-01

    A reliable site-specific estimate of the individual N-H bond lengths in the protein backbone is the fundamental basis of any relaxation experiment in solution and in the solid-state NMR. The N-H bond length can in principle be influenced by hydrogen bonding, which would result in an increased N-H distance. At the same time, dynamics in the backbone induces a reduction of the experimental dipolar coupling due to motional averaging. We present a 3D dipolar recoupling experiment in which the (1)H,(15)N dipolar coupling is reintroduced in the indirect dimension using phase-inverted CP to eliminate effects from rf inhomogeneity. We find no variation of the N-H dipolar coupling as a function of hydrogen bonding. Instead, variations in the (1)H,(15)N dipolar coupling seem to be due to dynamics of the protein backbone. This is supported by the observed correlation between the H(N)-N dipolar coupling and the amide proton chemical shift. The experiment is demonstrated for a perdeuterated sample of the alpha-spectrin SH3 domain. Perdeuteration is a prerequisite to achieve high accuracy. The average error in the analysis of the H-N dipolar couplings is on the order of +/-370 Hz (+/-0.012 A) and can be as small as 150 Hz, corresponding to a variation of the bond length of +/-0.005 A.

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

    Science.gov (United States)

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

    2015-01-01

    The (1)H NMR signal of the methyl group of sodium acetate is shown to be a triplet in the anisotropic environment of stretched gelatin gel. The multiplet structure of the signal is due to the intra-methyl residual dipolar couplings. The relaxation properties of the spin system were probed by recording steady-state irradiation envelopes ('z-spectra'). A quantum-mechanical model based on irreducible spherical tensors formed by the three magnetically equivalent spins of the methyl group was used to simulate and fit experimental z-spectra. The multiple parameter values of the relaxation model were estimated by using a Bayesian-based Markov chain Monte Carlo algorithm. PMID:25486634

  5. Benford distributions in NMR

    CERN Document Server

    Bhole, Gaurav; Mahesh, T S

    2014-01-01

    Benford's Law is an empirical law which predicts the frequency of significant digits in databases corresponding to various phenomena, natural or artificial. Although counter intuitive at the first sight, it predicts a higher occurrence of digit 1, and decreasing occurrences to other larger digits. Here we report the Benford analysis of various NMR databases and draw several interesting inferences. We observe that, in general, NMR signals follow Benford distribution in time-domain as well as in frequency domain. Our survey included NMR signals of various nuclear species in a wide variety of molecules in different phases, namely liquid, liquid-crystalline, and solid. We also studied the dependence of Benford distribution on NMR parameters such as signal to noise ratio, number of scans, pulse angles, and apodization. In this process we also find that, under certain circumstances, the Benford analysis can distinguish a genuine spectrum from a visually identical simulated spectrum. Further we find that chemical-sh...

  6. NMR实验参数对IBP-血浆相互作用个性化差异研究的影响%Effects of NMR Parameters on Study of Individual Variations of Plasma-Ibuprofen Interactions

    Institute of Scientific and Technical Information of China (English)

    杜媛媛; 纪竹生; 刘买利

    2012-01-01

    药物与血浆蛋白相互作用强弱是影响药物分布代谢与药效的关键因素之一.本研究小组已报道用扩散加权谱、弛豫加权谱结合主成分分析(PCA)方法研究布洛芬(IBP)与血浆蛋白相互作用的个体差异性.该文则研究核磁共振实验参数的设置对血浆与药物相互作用个体差异性研究的影响.以对照血浆样品组与加入布洛芬血浆组为模型,改变扩散时间、梯度强度、回波时间这3种实验参数,采集了27套不同实验设置的扩散加权谱与10套不同回波时间的弛豫加权谱.结果表明,扩散时间为0.1s~0.14s且梯度强度为1.52×10-3T/cm~1.90×10-3T/cm时采集的扩散加权谱或回波时间为70 ms~110 ms时采集的弛豫加权谱更适合用来研究血浆与布洛芬相互作用的个性化差异.%The interactions between drug and plasma proteins play a major role in drug absorption, metabolism and its efficacy. Previous reports demonstrated that diffusion-and relaxation-weighted NMR combined with principal components analysis (PCA) could be used to characterize individual variations of plasma-drug interactions. In this research, using plasma with/without drug ibuprofen (IBP) as model, the NMR parameters including diffusion time, gradient strength for diffusion-weighted NMR and echo time for relaxation-weighted NMR were optimized. The results showed that gradient strength of 1. 52 X l0T-3T/cm~l. 90 X 10~3T/cm under diffusion time of 0. 1 s~0. 14 s for diffusion-weighted NMR and echo time of 70 ms~110 ms for relaxation-weighted NMR are optimal for characterizing individual variations of plasma-drug interactions.

  7. Targeted and nontargeted wine analysis by (1)h NMR spectroscopy combined with multivariate statistical analysis. Differentiation of important parameters: grape variety, geographical origin, year of vintage.

    Science.gov (United States)

    Godelmann, Rolf; Fang, Fang; Humpfer, Eberhard; Schütz, Birk; Bansbach, Melanie; Schäfer, Hartmut; Spraul, Manfred

    2013-06-12

    The authenticity, the grape variety, the geographical origin, and the year of vintage of wines produced in Germany were investigated by (1)H NMR spectroscopy in combination with several steps of multivariate data analysis including principal component analysis (PCA), linear discrimination analysis (LDA), and multivariate analysis of variance (MANOVA) together with cross-validation (CV) embedded in a Monte Carlo resampling approach (MC) and others. A total of about 600 wines were selected and carefully collected from five wine-growing areas in the southern and southwestern parts of Germany. Simultaneous saturation of the resonances of water and ethanol by application of a low-power eight-frequency band irradiation using shaped pulses allowed for high receiver gain settings and hence optimized signal-to-noise ratios. Correct prediction of classification of the grape varieties of Pinot noir, Lemberger, Pinot blanc/Pinot gris, Müller-Thurgau, Riesling, and Gewürztraminer of 95% in the wine panel was achieved. The classification of the vintage of all analyzed wines resulted in correct predictions of 97 and 96%, respectively, for vintage 2008 (n = 318) and 2009 (n = 265). The geographic origin of all wines from the largest German wine-producing regions, Rheinpfalz, Rheinhessen, Mosel, Baden, and Württemberg, could be predicted 89% correctly on average. Each NMR spectrum could be regarded as the individual "fingerprint" of a wine sample, which includes information about variety, origin, vintage, physiological state, technological treatment, and others.

  8. Rheo-NMR - how nuclear magnetic resonance is providing new insight regarding complex fluid rheology

    International Nuclear Information System (INIS)

    Over the past five decades, NMR has revolutionised chemistry, and has found widespread application in condensed matter physics, in molecular biology, in medicine and in food technology. Most recently NMR has made a significant impact in chemical engineering, where it is being extensively used for the non-invasive study of dispersion and flow in porous media. One of the most recent applications of NMR in materials science concerns its use in the study of the mechanical properties of complex fluids. This particular aspect of NMR has been extensively developed in research carried out at Massey University in New Zealand. In this short article, some of the ideas behind this work and the applications which have resulted, will be described. These examples provide a glimpse of possible applications of Nuclear Magnetic Resonance to the study of complex fluid rheology. While this is a very new field of research in which only a handful of groups presently participate, the potential exists for a substantial increase in Rheo-NMR research activity. Systems studied to date include polymer melts and semi-dilute solutions, thermotropic and lyotropic liquid crystals and liquid crystalline polymers, micellar solutions, food materials and colloidal suspensions. Rheo-NMR suffers in a number of respects by comparison with optical methods. It is expensive, it is difficult to use, it suffers from poor signal-to-noise ratios and the effective interpretation of spectra often depends on familiarity with the nuclear spin Hamiltonian and the associated effects of spin dynamics. Nonetheless NMR offers some unique advantages, including the ability to work with opaque materials, the ability to combine velocimetry with localised spectroscopy, and the ability to access a wide range of molecular properties relating to organisation, orientation and dynamics. Rheo-NMR has been able to provide a direct window on a variety of behaviours, including slip, shear-thinning, shear banding, yield stress

  9. Methyl tunnelling sidebands in the low-field NMR spectrum of 3-pentanone: Driving A-E transitions using rf irradiation.

    Science.gov (United States)

    Zhang, Bo; Horsewill, Anthony J

    2015-09-01

    Using magnetic field-cycling at cryogenic temperatures, low-field dipole-dipole driven NMR spectra have been recorded on 3-pentanone (CH3CH2C(O)CH2CH3). The spectra are characterised by tunnelling sidebands arising from the quantum dynamics of the methyl (CH3) rotors. From the sideband frequencies, the CH3 tunnelling frequency is determined to be νt=3.05±0.01MHz. The tunnelling sidebands are characterised by A-E transitions in nuclear spin-symmetry, involving simultaneous changes in tunnelling and nuclear spin states. To gain further insight, a theoretical analysis of the spin Hamiltonian matrix has been used to calculate the sideband transition probabilities. These are subsequently used in a thermodynamic model to simulate the low-field NMR spectrum which is compared with experiment. The level-crossings encountered as part of the magnetic field-cycling NMR sequence are found to play an essential role in determining the tunnelling sideband intensities. PMID:26183303

  10. On domain wall boundary conditions for the XXZ spin Hamiltonian

    DEFF Research Database (Denmark)

    Orlando, Domenico; Reffert, Susanne; Reshetikhin, Nicolai

    In this note, we derive the spectrum of the infinite quantum XXZ spin chain with domain wall boundary conditions. The eigenstates are constructed as limits of Bethe states for the finite XXZ spin chain with quantum sl(2) invariant boundary conditions.......In this note, we derive the spectrum of the infinite quantum XXZ spin chain with domain wall boundary conditions. The eigenstates are constructed as limits of Bethe states for the finite XXZ spin chain with quantum sl(2) invariant boundary conditions....

  11. Theoretical prediction of structural, vibrational and NMR parameters of plastic optical fiber (POF) material precursors. Cis and trans perhydro- and perfluoro-2-methylene-4,5-dimethyl-1,3-dioxolanes.

    Science.gov (United States)

    Nozirov, Farhod; Kupka, Teobald; Stachów, Michał

    2014-07-01

    Density functional theory (DFT) prediction of cis and trans perhydro- and perfluoro-2-methylene-4,5-dimethyl-1,3-dioxolanes structure, supported by vibrational analysis and calculation of multinuclear isotropic nuclear magnetic resonance (NMR) shieldings and indirect spin-spin couplings (SSCCs) was performed. The performance of the used methodology was verified on 1,3-dioxolane selected as model compound. The structures of hydrogenated and fluorinated monomers of POF materials were calculated using B3LYP and BLYP density functionals combined with 6-311++G(3df,2pd) basis set. The BLYP/6-311++G(3df,2pd) level of theory was suggested for vibrational analysis. Gauge independent atomic orbitals (GIAO) calculations were applied to distinguish between cis and trans isomers of the title 1,3-dioxolanes. For obtaining both accurate nuclear shieldings and individual spin-spin coupling constants the BHandH/aug-pcJ-2 level of theory was chosen. The protocol used for the calculations nicely showed remarkable differences in vibrational spectra and NMR parameters of cis and trans isomers of the studied 1,3-dioxolane derivatives before and after fluorination.

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

    Science.gov (United States)

    Kutateladze, Andrei G; Mukhina, Olga A

    2015-05-15

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

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

    Science.gov (United States)

    Kutateladze, Andrei G; Mukhina, Olga A

    2015-05-15

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

  14. NMR espectroscopic parameters of HX and Si (Sn)X{sub 4} (X = H, F, Cl, Br and I) and SnBr{sub 4-n}I{sub n} model compounds

    Energy Technology Data Exchange (ETDEWEB)

    Maldonado, Alejandro F.; Gimenez, Carlos A. [Physics Department, Natural and Exact Science Faculty, Northeastern University of Argentina and Institute of Modelling and Innovation on Technology, IMIT Avda Libertad 5460, W3404AAS Corrientes (Argentina); Aucar, Gustavo A., E-mail: gaa@unne.edu.ar [Physics Department, Natural and Exact Science Faculty, Northeastern University of Argentina and Institute of Modelling and Innovation on Technology, IMIT Avda Libertad 5460, W3404AAS Corrientes (Argentina)

    2012-02-20

    Graphical abstract: Optimized fully relativistic calculations of NMR J-couplings (HBr, HI), chemical shifts (Si, Sn) and absolute shielding for reference compounds of heavy atoms (Si, Sn) are given. Highlights: Black-Right-Pointing-Pointer In this article we show a procedure to get accurate NMR {sigma}{sup Ref} of Si and Sn. Black-Right-Pointing-Pointer Calculations of {sigma} on more than three heavy-atom-containing molecules are given. Black-Right-Pointing-Pointer Our results are closer to {delta}{sup exp} than previous calculations for SnX{sub 4} (X = H, Cl, Br, I). Black-Right-Pointing-Pointer Optimized basis sets were considered for full R and NR calculations of NMR J and {sigma}. Black-Right-Pointing-Pointer Relativistic effects enlarge electron correlation effects on J-couplings. - Abstract: The NMR spectroscopic parameters are largely influenced by relativistic effects. They are highly dependent on the electronic behavior inside the spatial regions occupied by nuclei. Full relativistic calculations of indirect nuclear spin-spin couplings at random phase level of approach (RPA) in the title compounds with reoptimized Dyall cVTZ basis sets are given. A comparison with the results of calculations with other basis sets that are mostly used within the non-relativistic (NR) domain is presented. We analyzed the dependence of that couplings with the speed of light over the whole range of values, from the full relativistic to the NR regimes. Within this last regime, calculations at the second-order level of approach (SOPPA) indicated that electron correlation effects may not be as important for nuclear magnetic shieldings, but they must be included with care for J-coupling calculations. From these calculations, we determined that relativity enlarges the electron correlation effects of the J-couplings of HBr and HI. Because the results of nuclear magnetic shielding calculations within polarization propagators at the RPA level were reliable, we were able to show a new

  15. NMR and dynamics of biopolymers

    Energy Technology Data Exchange (ETDEWEB)

    Lian, L.Y.; Barsukov, I.L. [Leicester Univ. (United Kingdom)

    1994-12-31

    Several basic experimental analytical NMR techniques that are frequently used for the qualitative and quantitative analysis of dynamic and exchange processes, focusing on proteins systems, are described: chemical exchange (slow exchange, fast exchange, intermediate exchange), heteronuclear relaxation measurements (relaxation parameters, strategy of relaxation data analysis, experimental results and examples, motional model interpretation of relaxation data, homonuclear relaxation); slow large-scale exchange and hydrogen-deuterium exchange are also studied: mechanisms of hydrogen exchange in a native protein, methods for measuring amide exchange rates by NMR, interpretation of amide exchange rates. 9 fig., 3 tab., 56 ref.

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

    Science.gov (United States)

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

    2015-10-01

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

  17. NMR analysis of biodiesel

    Science.gov (United States)

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

  18. NMR studies of multiphase flows II

    Energy Technology Data Exchange (ETDEWEB)

    Altobelli, S.A.; Caprihan, A.; Fukushima, E. [Lovelace Institutes, Albuquerque, NM (United States)] [and others

    1995-12-31

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

  19. An introduction to biological NMR spectroscopy

    International Nuclear Information System (INIS)

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

  20. Theoretical studies of the local structure and electron paramagnetic resonance parameters for tetragonal VO{sup 2+} in C{sub 6}H{sub 7}KO{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Ping [Chongqing Jiaotong Univ. (China). School of Science; Li, Ling [Sichuan University of Arts and Science, Dazhou (China). Dept. of Maths and Finance-Economics

    2015-07-01

    The optical spectra, electron paramagnetic resonance parameters (i.e., the spin Hamiltonian parameters, including paramagnetic g factors and the hyperfine structure constants A{sub i}) and the local distortion structure for the tetragonal VO{sup 2+} in C{sub 6}H{sub 7}KO{sub 7} are theoretically studied based on the crystal-field theory and three-order perturbation formulas of a 3d{sup 1} centre in tetragonal site. The magnitude of orbital reduction factor, core polarisation constant κ, and local structure parameters are obtained by fitting the calculated optical spectra and electron paramagnetic resonance parameters to the experimental values. The theoretical results are in reasonable agreement with the experimental values.

  1. NMR at 900 MHz

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    @@ An important factor in the development of solutionstate NMR has always been th e ability to produce stable and homogeneous magnetic fields. As higher and higher field strengths are reached the pressure is growing on manufacturers to produce NMR systems with greatly improved spectral resolution and signal to noise ratio. The introduction of the Varian 900 MHz INOVA system in August 2000 featuring Oxford Instruments 21.1 T magnet represents the latest pioneering development in NMR technology.

  2. Lectures on pulsed NMR

    Energy Technology Data Exchange (ETDEWEB)

    Pines, A.

    1986-09-01

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

  3. NMR studies of metalloproteins.

    Science.gov (United States)

    Li, Hongyan; Sun, Hongzhe

    2012-01-01

    Metalloproteins represent a large share of the proteomes, with the intrinsic metal ions providing catalytic, regulatory, and structural roles critical to protein functions. Structural characterization of metalloproteins and identification of metal coordination features including numbers and types of ligands and metal-ligand geometry, and mapping the structural and dynamic changes upon metal binding are significant for understanding biological functions of metalloproteins. NMR spectroscopy has long been used as an invaluable tool for structure and dynamic studies of macromolecules. Here we focus on the application of NMR spectroscopy in characterization of metalloproteins, including structural studies and identification of metal coordination spheres by hetero-/homo-nuclear metal NMR spectroscopy. Paramagnetic NMR as well as (13)C directly detected protonless NMR spectroscopy will also be addressed for application to paramagnetic metalloproteins. Moreover, these techniques offer great potential for studies of other non-metal binding macromolecules.

  4. Instrumentation in NMR/NMR imaging; Instrumentation en RMN/IRM

    Energy Technology Data Exchange (ETDEWEB)

    Favre, B.; Desgoutte, P.; Marguet, Ch. [Universite Claude Bernard, Lab. de Resonance Magnetique Nuleaire, 69 - Villeurbanne (France)

    1999-07-01

    Nuclear Magnetic Resonance (NMR) is largely used in medical imaging and in spectroscopy for the chemistry. The equipment is complex and explosive, and is not easily accessible for teaching. The didactic machine presented here allows, thanks to an extreme simplification, to approach essential notions of NMR with a cost and a space-factor reduced. It allows to visualize the phenomenon of NMR, to illustrate its main applications, and to measure main parameters concerning the magnetic field or the sample. In addition, it can be used to study signal acquisition and processing, fundamental digital and analog electronic circuits, programming... (authors)

  5. Optimization and practical implementation of ultrafast 2D NMR experiments

    Directory of Open Access Journals (Sweden)

    Luiz H. K. Queiroz Júnior

    2013-01-01

    Full Text Available Ultrafast 2D NMR is a powerful methodology that allows recording of a 2D NMR spectrum in a fraction of second. However, due to the numerous non-conventional parameters involved in this methodology its implementation is no trivial task. Here, an optimized experimental protocol is carefully described to ensure efficient implementation of ultrafast NMR. The ultrafast spectra resulting from this implementation are presented based on the example of two widely used 2D NMR experiments, COSY and HSQC, obtained in 0.2 s and 41 s, respectively.

  6. Optimization and practical implementation of ultrafast 2D NMR experiments

    Energy Technology Data Exchange (ETDEWEB)

    Queiroz Junior, Luiz H. K., E-mail: professorkeng@gmail.com [Universidade Federal de Sao Carlos (UFSC), SP (Brazil). Departamento de Quimica; Universidade Federal de Goias (UFGO), Goiania, GO (Brazil). Inst. de Quimica; Ferreira, Antonio G. [Universidade Federal de Sao Carlos (UFSC), SP (Brazil). Departamento de Quimica; Giraudeau, Patrick [Universite de Nantes (France). CNRS, Chimie et Interdisciplinarite: Synthese, Analyse, Modelisation

    2013-09-01

    Ultrafast 2D NMR is a powerful methodology that allows recording of a 2D NMR spectrum in a fraction of second. However, due to the numerous non-conventional parameters involved in this methodology its implementation is no trivial task. Here, an optimized experimental protocol is carefully described to ensure efficient implementation of ultrafast NMR. The ultrafast spectra resulting from this implementation are presented based on the example of two widely used 2D NMR experiments, COSY and HSQC, obtained in 0.2 s and 41 s, respectively. (author)

  7. Rapid prediction of multi-dimensional NMR data sets

    Energy Technology Data Exchange (ETDEWEB)

    Gradmann, Sabine; Ader, Christian [Utrecht University, Faculty of Science, Bijvoet Center for Biomolecular Research (Netherlands); Heinrich, Ines [Max Planck Institute for Molecular Physiology, Department of Physical Biochemistry (Germany); Nand, Deepak [Utrecht University, Faculty of Science, Bijvoet Center for Biomolecular Research (Netherlands); Dittmann, Marc [Max Planck Institute for Molecular Physiology, Department of Physical Biochemistry (Germany); Cukkemane, Abhishek; Dijk, Marc van; Bonvin, Alexandre M. J. J. [Utrecht University, Faculty of Science, Bijvoet Center for Biomolecular Research (Netherlands); Engelhard, Martin [Max Planck Institute for Molecular Physiology, Department of Physical Biochemistry (Germany); Baldus, Marc, E-mail: m.baldus@uu.nl [Utrecht University, Faculty of Science, Bijvoet Center for Biomolecular Research (Netherlands)

    2012-12-15

    We present a computational environment for Fast Analysis of multidimensional NMR DAta Sets (FANDAS) that allows assembling multidimensional data sets from a variety of input parameters and facilitates comparing and modifying such 'in silico' data sets during the various stages of the NMR data analysis. The input parameters can vary from (partial) NMR assignments directly obtained from experiments to values retrieved from in silico prediction programs. The resulting predicted data sets enable a rapid evaluation of sample labeling in light of spectral resolution and structural content, using standard NMR software such as Sparky. In addition, direct comparison to experimental data sets can be used to validate NMR assignments, distinguish different molecular components, refine structural models or other parameters derived from NMR data. The method is demonstrated in the context of solid-state NMR data obtained for the cyclic nucleotide binding domain of a bacterial cyclic nucleotide-gated channel and on membrane-embedded sensory rhodopsin II. FANDAS is freely available as web portal under WeNMR (http://www.wenmr.eu/services/FANDAShttp://www.wenmr.eu/services/FANDAS).

  8. Rapid prediction of multi-dimensional NMR data sets

    International Nuclear Information System (INIS)

    We present a computational environment for Fast Analysis of multidimensional NMR DAta Sets (FANDAS) that allows assembling multidimensional data sets from a variety of input parameters and facilitates comparing and modifying such “in silico” data sets during the various stages of the NMR data analysis. The input parameters can vary from (partial) NMR assignments directly obtained from experiments to values retrieved from in silico prediction programs. The resulting predicted data sets enable a rapid evaluation of sample labeling in light of spectral resolution and structural content, using standard NMR software such as Sparky. In addition, direct comparison to experimental data sets can be used to validate NMR assignments, distinguish different molecular components, refine structural models or other parameters derived from NMR data. The method is demonstrated in the context of solid-state NMR data obtained for the cyclic nucleotide binding domain of a bacterial cyclic nucleotide-gated channel and on membrane-embedded sensory rhodopsin II. FANDAS is freely available as web portal under WeNMR (http://www.wenmr.eu/services/FANDAShttp://www.wenmr.eu/services/FANDAS).

  9. Molecular dynamics simulations on PGLa using NMR orientational constraints

    Energy Technology Data Exchange (ETDEWEB)

    Sternberg, Ulrich, E-mail: ulrich.sternberg@partner.kit.edu; Witter, Raiker [Tallinn University of Technology, Technomedicum (Estonia)

    2015-11-15

    NMR data obtained by solid state NMR from anisotropic samples are used as orientational constraints in molecular dynamics simulations for determining the structure and dynamics of the PGLa peptide within a membrane environment. For the simulation the recently developed molecular dynamics with orientational constraints technique (MDOC) is used. This method introduces orientation dependent pseudo-forces into the COSMOS-NMR force field. Acting during a molecular dynamics simulation these forces drive molecular rotations, re-orientations and folding in such a way that the motional time-averages of the tensorial NMR properties are consistent with the experimentally measured NMR parameters. This MDOC strategy does not depend on the initial choice of atomic coordinates, and is in principle suitable for any flexible and mobile kind of molecule; and it is of course possible to account for flexible parts of peptides or their side-chains. MDOC has been applied to the antimicrobial peptide PGLa and a related dimer model. With these simulations it was possible to reproduce most NMR parameters within the experimental error bounds. The alignment, conformation and order parameters of the membrane-bound molecule and its dimer were directly derived with MDOC from the NMR data. Furthermore, this new approach yielded for the first time the distribution of segmental orientations with respect to the membrane and the order parameter tensors of the dimer systems. It was demonstrated the deuterium splittings measured at the peptide to lipid ratio of 1/50 are consistent with a membrane spanning orientation of the peptide.

  10. Molecular dynamics simulations on PGLa using NMR orientational constraints

    International Nuclear Information System (INIS)

    NMR data obtained by solid state NMR from anisotropic samples are used as orientational constraints in molecular dynamics simulations for determining the structure and dynamics of the PGLa peptide within a membrane environment. For the simulation the recently developed molecular dynamics with orientational constraints technique (MDOC) is used. This method introduces orientation dependent pseudo-forces into the COSMOS-NMR force field. Acting during a molecular dynamics simulation these forces drive molecular rotations, re-orientations and folding in such a way that the motional time-averages of the tensorial NMR properties are consistent with the experimentally measured NMR parameters. This MDOC strategy does not depend on the initial choice of atomic coordinates, and is in principle suitable for any flexible and mobile kind of molecule; and it is of course possible to account for flexible parts of peptides or their side-chains. MDOC has been applied to the antimicrobial peptide PGLa and a related dimer model. With these simulations it was possible to reproduce most NMR parameters within the experimental error bounds. The alignment, conformation and order parameters of the membrane-bound molecule and its dimer were directly derived with MDOC from the NMR data. Furthermore, this new approach yielded for the first time the distribution of segmental orientations with respect to the membrane and the order parameter tensors of the dimer systems. It was demonstrated the deuterium splittings measured at the peptide to lipid ratio of 1/50 are consistent with a membrane spanning orientation of the peptide

  11. Dynamics of a truncated prion protein, PrP(113–231), from 15N NMR relaxation: Order parameters calculated and slow conformational fluctuations localized to a distinct region

    OpenAIRE

    O'Sullivan, Denis B D; Jones, Christopher E; Abdelraheim, Salama R; Brazier, Marcus W; Toms, Harold; Brown, David R; Viles, John H.

    2009-01-01

    Prion diseases are associated with the misfolding of the prion protein (PrPC) from a largely α-helical isoform to a β-sheet rich oligomer (PrPSc). Flexibility of the polypeptide could contribute to the ability of PrPC to undergo the conformational rearrangement during PrPC–PrPSc interactions, which then leads to the misfolded isoform. We have therefore examined the molecular motions of mouse PrPC, residues 113–231, in solution, using 15N NMR relaxation measurements. A truncated fragment has b...

  12. NMR imaging technique

    International Nuclear Information System (INIS)

    This invention provides a method that can be adapted to existing NMR tomographic scanners of producing spectra of any given point in the image of the specimen slice, the intensity distribution of a selected resonance within an area of the image of the specimen slice, or an entire NMR spectrum of the given area. The method comprises acquiring n projections of the specimen slice, where n is greater than 1. Each of the projections is then shifted by Δ f for the point (the frequency offset of the signal arising from the point, from the true chemical shift)

  13. A hybrid inversion method of (T2 ,D) 2D NMR logging and observation parameters effects%(T2,D)二维核磁共振测井混合反演方法与参数影响分析

    Institute of Scientific and Technical Information of China (English)

    谭茂金; 邹友龙

    2012-01-01

    一维核磁共振(1D NMR)测井技术在流体识别中具有一定的局限性.二维核磁共振(2D NMR)测井能同时测量到多孔介质中横向弛豫时间(T2)和扩散系数(D)等信息,利用这两个参数区分流体性质,较一维核磁共振测井技术具有明显的优越性.针对梯度场下的2D NMR测井弛豫机理和数学模型,提出了适用于求解大型稀疏矩阵方程的反演方法—基于非负最小二乘法(LSQR)和截断奇异值分解(TSVD)法的混合算法.为验证方法的有效性,先根据多回波观测模式合成回波串数据,然后再用混合反演算法进行反演,反演得到横向弛豫时间(T2)和扩散系数(D),并构建T2-D二维谱图.结果对比表明,该混合反演算法得到的T2-D二维谱与流体模型一致性好,计算精度均比单一反演方法有较大改善,表明该混合反演方法可用于油气储集层2D NMR测井的反演和流体识别.此外,分别对油水同层和气水同层模型进行了正演模拟和反演实验,系统考察了不同磁场梯度、不同回波间隔组合对反演效果的影响,为2D NMR参数设计提供依据.%One dimensional nuclear magnetic resonance (ID NMR) logging technology is limited for fluid typing. Two dimensional nuclear magnetic resonance (2D NMR) logging can provide more parameters including transverse relaxation time (T2) and diffusion coefficient (D) in multi-pore media, and the fluid typing is realized successfully according to the fluid properties of NMR. So, 2D NMR logging is more advantageous than ID NMR logging. Point to the relaxation mechanism of 2D NMR at gradient field, the echo simulation and inversion of 2D NMR are discussed in detail. And a hybrid inversion algorithm is proposed, which is based on a dampingleast squares method (LSQR) and truncated singular value decomposition (TSVD). For verifying the hybrid inversion method, a series of spin echo trains in an ideal fluid model are firstly simulated with multiple echo spacing

  14. International symposium on NMR spectroscopy

    International Nuclear Information System (INIS)

    The publication consists of 32 papers and presentations from the field of NMR spectroscopy applications submitted to the International Symposium on NMR Spectroscopy held at Smolenice between 29 Sep and 3 Oct, 1980. (B.S.)

  15. NMR, Water and Plants

    NARCIS (Netherlands)

    As, van H.

    1982-01-01

    This Thesis describes the application of a non-destructive pulsed proton NMR method mainly to measure water transport in the xylem vessels of plant stems and in some model systems. The results are equally well applicable to liquid flow in other biological objects than plants, e.g. flow of blood and

  16. Soils, Pores, and NMR

    Science.gov (United States)

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

    2010-05-01

    Within Cluster A, Partial Project A1, the pore space exploration by means of Nuclear Magnetic Resonance (NMR) plays a central role. NMR is especially convenient since it probes directly the state and dynamics of the substance of interest: water. First, NMR is applied as relaxometry, where the degree of saturation but also the pore geometry controls the NMR signature of natural porous systems. Examples are presented where soil samples from the Selhausen, Merzenhausen (silt loams), and Kaldenkirchen (sandy loam) test sites are investigated by means of Fast Field Cycling Relaxometry at different degrees of saturation. From the change of the relaxation time distributions with decreasing water content and by comparison with conventional water retention curves we conclude that the fraction of immobile water is characterized by T1 samples (Haber-Pohlmeier et al. 2010). Third, relaxometric information forms the basis of understanding magnetic resonance imaging (MRI) results. The general difficulty of imaging in soils are the inherent fast T2 relaxation times due to i) the small pore sizes, ii) presence of paramagnetic ions in the solid matrix, and iii) diffusion in internal gradients. The last point is important, since echo times can not set shorter than about 1ms for imaging purposes. The way out is either the usage of low fields for imaging in soils or special ultra-short pulse sequences, which do not create echoes. In this presentation we will give examples on conventional imaging of macropore fluxes in soil cores (Haber-Pohlmeier et al. 2010), and the combination with relaxometric imaging, as well as the advantages and drawbacks of low-field and ultra-fast pulse imaging. Also first results on the imaging of soil columns measured by SIP in Project A3 are given. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Waterflow Monitored by Tracer Transport in Natural Porous Media Using MRI." Vadose Zone J.: submitted. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Relaxation in a

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

    Energy Technology Data Exchange (ETDEWEB)

    George J. Hirasaki; Kishore K. Mohanty

    2005-09-05

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

  18. NMR of unfolded proteins

    Indian Academy of Sciences (India)

    Amarnath Chtterjee; Ashutosh Kumar; Jeetender Chugh; Sudha Srivastava; Neel S Bhavesh; Ramakrishna V Hosur

    2005-01-01

    In the post-genomic era, as more and more genome sequences are becoming known and hectic efforts are underway to decode the information content in them, it is becoming increasingly evident that flexibility in proteins plays a crucial role in many of the biological functions. Many proteins have intrinsic disorder either wholly or in specific regions. It appears that this disorder may be important for regulatory functions of the proteins, on the one hand, and may help in directing the folding process to reach the compact native state, on the other. Nuclear magnetic resonance (NMR) has over the last two decades emerged as the sole, most powerful technique to help characterize these disordered protein systems. In this review, we first discuss the significance of disorder in proteins and then describe the recent developments in NMR methods for their characterization. A brief description of the results obtained on several disordered proteins is presented at the end.

  19. NMR, water and plants

    International Nuclear Information System (INIS)

    This thesis describes the application of a non-destructive pulsed proton NMR method mainly to measure water transport in the xylem vessels of plant stems and in some model systems. The results are equally well applicable to liquid flow in other biological objects than plants, e.g. flow of blood and other body fluids in human and animals. The method is based on a pulse sequence of equidistant π pulses in combination with a linear magnetic field gradient. (Auth.)

  20. Some exercises in quantitative NMR imaging

    International Nuclear Information System (INIS)

    The articles represented in this thesis result from a series of investigations that evaluate the potential of NMR imaging as a quantitative research tool. In the first article the possible use of proton spin-lattice relaxation time T1 in tissue characterization, tumor recognition and monitoring tissue response to radiotherapy is explored. The next article addresses the question whether water proton spin-lattice relaxation curves of biological tissues are adequately described by a single time constant T1, and analyzes the implications of multi-exponentiality for quantitative NMR imaging. In the third article the use of NMR imaging as a quantitative research tool is discussed on the basis of phantom experiments. The fourth article describes a method which enables unambiguous retrieval of sign information in a set of magnetic resonance images of the inversion recovery type. The next article shows how this method can be adapted to allow accurate calculation of T1 pictures on a pixel-by-pixel basis. The sixth article, finally, describes a simulation procedure which enables a straightforward determination of NMR imaging pulse sequence parameters for optimal tissue contrast. (orig.)

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

    Energy Technology Data Exchange (ETDEWEB)

    Hirasaki, George J.; Mohanty, Kishore K.

    2003-02-10

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

  2. Spectroscopic techniques and cyclic voltammetry with synthesis: Manganese(II) coordination stability and its ligand field parameters effect on macrocyclic ligands

    Science.gov (United States)

    Kumar, Rajiv; Chandra, Sulekh

    2007-05-01

    Manganese(II) macrocyclic complexes are prepared with different macrocyclic ligands, containing cyclic skeleton bearing organic components which have different chromospheres like N, O and S donor atoms and stereochemistry. Thus, six macrocyclic ligands, were prepared and their capacity to retain the manganese(II) ion in solid as well as in aqueous solution was determined and characterized by elemental analyses, molar conductance measurements, magnetic susceptibility measurements, mass, 1H NMR, IR, electronic spectral and cyclic voltammetric studies. The electronic spectrum of this system showed a dependence that may be consistent with the formation of stable complexes and coordination behaviour of the ions. ESR spectra of all the complexes are recorded in solid as well as solution, which show the oxidation state of the manganese(II). Spin Hamiltonian manganese(II), which can be defined as the magnetic field vector (ℋ): ℋ=gβHS+DSz2-{35}/{12}+E[Sz2-Sy2]+ASI+ 1/6 a Sx4+Sy4+Sz4-{707}/{16}+ 1/180 F{35Sz2-475}/{2Sz2+3255/10} Significant distortion of the manganese(II) ion in observed geometry is evident from the angle subtended by the different membered chelate rings and the angles spanned by trans donor atoms octahedral geometry. Cyclic voltammetric studies indicate that complexes with all ligands undergoes one electron oxidation from manganese(II) to manganese(III) followed by a further oxidation to manganese(IV) at a significantly more positive potential.

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

    Energy Technology Data Exchange (ETDEWEB)

    Konuma, Tsuyoshi [Icahn School of Medicine at Mount Sinai, Department of Structural and Chemical Biology (United States); Harada, Erisa [Suntory Foundation for Life Sciences, Bioorganic Research Institute (Japan); Sugase, Kenji, E-mail: sugase@sunbor.or.jp, E-mail: sugase@moleng.kyoto-u.ac.jp [Kyoto University, Department of Molecular Engineering, Graduate School of Engineering (Japan)

    2015-12-15

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

  4. Magic Angle Spinning NMR Metabolomics

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jian Z.

    2016-05-31

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

  5. DNA oligonucleotide conformations: high resolution NMR studies

    International Nuclear Information System (INIS)

    The present work describes a DNA double-helix model, which is well comparable with the models derived from fibre-diffraction studies. The model has a mononucleotide repeat with torsion angles in accordance with average geometries as derived from 1H NMR studies. Special attention was paid to reduce the number of short H-H nonbonding contacts, which are abundantly present in the 'classical' fibre-diffraction models. Chapter 3 describes the first complete assignment of a 1H NMR spectrum of a DNA tetramer, d(TAAT). Preliminary conformational data derived from the spectral parameters recorded at 27 0C are given. A more detailed analysis employing temperature-dependence studies is given in Chapter 4. (Auth.)

  6. Fully automated system for pulsed NMR measurements

    International Nuclear Information System (INIS)

    A system is described which places many of the complex, tedious operations for pulsed NMR experiments under computer control. It automatically optimizes the experiment parameters of pulse length and phase, and precision, accuracy, and measurement speed are improved. The hardware interface between the computer and the NMR instrument is described. Design features, justification of the choices made between alternative design strategies, and details of the implementation of design goals are presented. Software features common to all the available experiments are discussed. Optimization of pulse lengths and phases is performed via a sequential search technique called Uniplex. Measurements of the spin-lattice and spin-spin relaxation times and of diffusion constants are automatic. Options for expansion of the system are explored along with some of the limitations of the system

  7. Some nitrogen-14 NMR studies in solids

    International Nuclear Information System (INIS)

    The first order quadrupolar perturbation of the 14N NMR spectrum yields information regarding the static and dynamic properties of the surrounding electronic environment. Signal to noise problems caused by long 14N longitudinal relaxation times (T1) and small equilibrium polarizations are reduced by rotating frame cross polarization (CP) experiments between 14N and 1H. Using quadrupolar echo and CP techniques, the 14N quadrupolar coupling constants (e2qQ/h) and asymmetry parameters (eta) have been obtained for a variety of tetraalkylammonium compounds by observation of their quadrupolar powder patterns at various temperatures. For choline chloride and iodide the 14N NMR powder patterns exhibit the effects of anisotropic molecular motion, while choline bromide spectra show no such effects

  8. NMR Studies of 3-Acylcamphor

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    NMR studies of some chiral 3-acyclcamphor were conducted.A complete assignment was given to 3-(4-pyridyl)carbonylcamphor by the 2D NMR technology.Assignments were also given to other b -diketones.The results showed that those 3-acylcamphors exist in the enol forms,while 2-benzoyl menthone exists in diketon form.

  9. NMR in pulsed magnetic field

    KAUST Repository

    Abou-Hamad, Edy

    2011-09-01

    Nuclear magnetic resonance (NMR) experiments in pulsed magnetic fields up to 30.4 T focused on 1H and 93Nb nuclei are reported. Here we discuss the advantage and limitation of pulsed field NMR and why this technique is able to become a promising research tool. © 2011 Elsevier Inc. All Rights Reserved.

  10. Fundamentals of Protein NMR Spectroscopy

    CERN Document Server

    Rule, Gordon S

    2006-01-01

    NMR spectroscopy has proven to be a powerful technique to study the structure and dynamics of biological macromolecules. Fundamentals of Protein NMR Spectroscopy is a comprehensive textbook that guides the reader from a basic understanding of the phenomenological properties of magnetic resonance to the application and interpretation of modern multi-dimensional NMR experiments on 15N/13C-labeled proteins. Beginning with elementary quantum mechanics, a set of practical rules is presented and used to describe many commonly employed multi-dimensional, multi-nuclear NMR pulse sequences. A modular analysis of NMR pulse sequence building blocks also provides a basis for understanding and developing novel pulse programs. This text not only covers topics from chemical shift assignment to protein structure refinement, as well as the analysis of protein dynamics and chemical kinetics, but also provides a practical guide to many aspects of modern spectrometer hardware, sample preparation, experimental set-up, and data pr...

  11. Structural Biology: Practical NMR Applications

    CERN Document Server

    Teng, Quincy

    2005-01-01

    This textbook begins with an overview of NMR development and applications in biological systems. It describes recent developments in instrument hardware and methodology. Chapters highlight the scope and limitation of NMR methods. While detailed math and quantum mechanics dealing with NMR theory have been addressed in several well-known NMR volumes, chapter two of this volume illustrates the fundamental principles and concepts of NMR spectroscopy in a more descriptive manner. Topics such as instrument setup, data acquisition, and data processing using a variety of offline software are discussed. Chapters further discuss several routine stategies for preparing samples, especially for macromolecules and complexes. The target market for such a volume includes researchers in the field of biochemistry, chemistry, structural biology and biophysics.

  12. Two dimensional solid state NMR

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2016-01-01

    Nuclear magnetic resonance (NMR) logging provides a new means of estimating the hydraulic conductivity (K) of unconsolidated aquifers. The estimation of K from the measured NMR parameters can be performed using the Schlumberger-Doll Research (SDR) equation, which is based on the Kozeny-Carman equation and initially developed for obtaining permeability from NMR logging in petroleum reservoirs. The SDR equation includes empirically determined constants. Decades of research for petroleum applications have resulted in standard values for these constants that can provide accurate estimates of permeability in consolidated formations. The question we asked: Can standard values for the constants be defined for hydrogeologic applications that would yield accurate estimates of K in unconsolidated aquifers? Working at 10 locations at three field sites in Kansas and Washington, USA, we acquired NMR and K data using direct-push methods over a 10- to 20-m depth interval in the shallow subsurface. Analysis of pairs of NMR and K data revealed that we could dramatically improve K estimates by replacing the standard petroleum constants with new constants, optimal for estimating K in the unconsolidated materials at the field sites. Most significant was the finding that there was little change in the SDR constants between sites. This suggests that we can define a new set of constants that can be used to obtain high resolution, cost-effective estimates of K from NMR logging in unconsolidated aquifers. This significant result has the potential to change dramatically the approach to determining K for hydrogeologic applications. PMID:25810149

  14. Annual reports on NMR spectroscopy

    CERN Document Server

    Webb, Graham A; McCarthy, M J

    1995-01-01

    Over recent years, no other technique has grown to such importance as that of NMR spectroscopy. It is used in all branches of science where precise structural determination is required and where the nature of interactions and reactions in solution is being studied. Annual Reports on NMR Spectroscopy has established itself as a means for the specialist and non-specialist alike to become familiar with new applications of the technique in all branches of chemistry, including biochemistry, and pharmaceutics. This volume focuses on theoretical aspects of NMR nuclear shielding and on applications of

  15. NMR for chemists and biologists

    CERN Document Server

    Carbajo, Rodrigo J

    2013-01-01

    This book intends to be an easy and concise introduction to the field of nuclear magnetic resonance or NMR, which has revolutionized life sciences in the last twenty years. A significant part of the progress observed in scientific areas like Chemistry, Biology or Medicine can be ascribed to the development experienced by NMR in recent times. Many of the books currently available on NMR deal with the theoretical basis and some of its main applications, but they generally demand a strong background in Physics and Mathematics for a full understanding. This book is aimed to a wide scientific audie

  16. Flow units from integrated WFT and NMR data

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-08-01

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

  17. Cation-π versus anion-π interactions: A theoretical NMR study

    Science.gov (United States)

    Ebrahimi, Ali; Khorassani, Mostafa Habibi; Masoodi, Hamid Reza

    2011-03-01

    The influences of cation-π and anion-π interactions on NMR data have been investigated in complexes of cations and anions with 1,3,5-trifluorobenzene (TFB). Cation-π interaction increases 1JC-F, 1JC-H and the chemical shifts of hydrogen and fluorine while it decreases 1JC-C. The changes are in reverse direction in the presence of anion-π interaction. The role of geometry and electronic effects on the NMR data was considered. The distance dependence of NMR parameters has been studied in these complexes. The NMR data have been investigated in isoelectronic complexes.

  18. Integrative NMR for biomolecular research.

    Science.gov (United States)

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

    2016-04-01

    NMR spectroscopy is a powerful technique for determining structural and functional features of biomolecules in physiological solution as well as for observing their intermolecular interactions in real-time. However, complex steps associated with its practice have made the approach daunting for non-specialists. We introduce an NMR platform that makes biomolecular NMR spectroscopy much more accessible by integrating tools, databases, web services, and video tutorials that can be launched by simple installation of NMRFAM software packages or using a cross-platform virtual machine that can be run on any standard laptop or desktop computer. The software package can be downloaded freely from the NMRFAM software download page ( http://pine.nmrfam.wisc.edu/download_packages.html ), and detailed instructions are available from the Integrative NMR Video Tutorial page ( http://pine.nmrfam.wisc.edu/integrative.html ). PMID:27023095

  19. Optical pumping and xenon NMR

    Energy Technology Data Exchange (ETDEWEB)

    Raftery, M.D.

    1991-11-01

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

  20. Optical pumping and xenon NMR

    Energy Technology Data Exchange (ETDEWEB)

    Raftery, M.D.

    1991-11-01

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

  1. Optical pumping and xenon NMR

    International Nuclear Information System (INIS)

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

  2. NMR characterization of thin films

    Science.gov (United States)

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

    2008-11-25

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

  3. 25 T high resolution NMR magnet program and technology

    Energy Technology Data Exchange (ETDEWEB)

    Markiewicz, W.D.; Dixon, I.R.; Eyssa, Y.M.; Schwartz, J.; Swenson, C.A.; Van Sciver, S.; Schneider-Muntau, H.J. [National High Magnetic Field Lab., Tallahassee, FL (United States)

    1996-07-01

    The program at the National High Magnetic Field Laboratory for the design and development of 1 GHz class NMR magnets is described. The parameters are given for a 1.066 GHz magnet incorporating an HTS inner coil. The design of the related wide bore 900 MHz conventional superconductor magnet is described. Aspects of the technology development program supporting these designs are presented.

  4. Carbon-13 NMR studies of liquid crystals

    International Nuclear Information System (INIS)

    High resolution, proton decoupled 13C nmr are observed for a series of neat nematic liquid crystals, the p-alkoxyazoxybenzenes, and a smectic-A liquid crystal, diethylazoxydibenzoate in a magnetic field of 23 kG. The (uniaxial) order parameters S = less than P2(costheta) greater than are found to be about 0.4 and 0.9 for the nematic and smectic-A phase respectively at the clearing points. The order parameter increases with decreasing temperature in the nematic phase but is constant, or nearly so, with temperature in the smectic-A phase. In the nematic series studied, the ordering exhibits an even-odd alternation along the series and qualitative agreement with a recent theory due to Marcelja is found. In both phases, the spectra show that the molecule rotates rapidly about its long axis. Tentative conclusions about molecular conformational motion and 14N spin relaxation are presented for both nematic and smectic-A phases. In the smectic-A phase, the sample is rotated about an axis perpendicular to H0 and the resulting spectra are dicusssed. The theory of observed chemical shifts in liquid crystals is discussed and equations are derived which relate the nmr spectra of liquid-crystals to the order parameters. A model for the smectic-C phase due to Luz and Meiboom and Doane is described and lineshapes are determined on the basis of this model for special cases. The dependence of the order parameters on the molecular potential which give rise to the various degrees of order in the different liquid crystalline phases is examined. To a good approximation the functional dependence of the order parameters on the molecular potential is shown to be a simple one in the limit of small tilt angle in the smectic-C phase

  5. EPR OF Mn2+ IMPURITIES IN CALCITE: A DETAILED STUDY PERTINENT TO MARBLE PROVENANCE DETERMINATION

    DEFF Research Database (Denmark)

    Weihe, H.; Piligkos, S.; Barra, A.L.;

    2009-01-01

    We demonstrate that the electron paramagnetic resonance spectrum of Mn2+ impurities in calcite, and therefore also in marble, may be accurately reproduced by a traditional spin Hamiltonian formalism. The success of such a treatment, however, very much depends on the spin Hamiltonian parameters ha...

  6. Epr of Mn2+ Impurities in Calcite: A Detailed Study Pertinent to Marble Provenance Determination

    DEFF Research Database (Denmark)

    Weihe, H.; Piligkos, S.; Barra, A.L.;

    2009-01-01

    We demonstrate that the electron paramagnetic resonance spectrum of Mn2+ impurities in calcite, and therefore also in marble, may be accurately reproduced by a traditional spin Hamiltonian formalism. The success of such a treatment, however, very much depends on the spin Hamiltonian parameters ha...

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

    Energy Technology Data Exchange (ETDEWEB)

    Matwiyoff, N.A.

    1983-01-01

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

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

    International Nuclear Information System (INIS)

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

  9. Deriving NMR surface relaxivities, pore size distributions and water retention curves by NMR relaxation experiments on partially de-saturated rocks

    Science.gov (United States)

    Mohnke, O.; Nordlund, C. L.; Klitzsch, N.

    2013-12-01

    Nuclear magnetic resonance (NMR) is a method used over a wide field of geophysical applications to non-destructively determine transport and storage properties of rocks and soils. In NMR relaxometry signal amplitudes correspond directly to the rock's fluid (water, oil) content. On the other hand the NMR relaxation behavior, i.e. the longitudinal (T1) and transverse (T2) NMR relaxation times, can be used to derive pore sizes and permeability as it is linearly linked to the pore's surface-to-volume-ratio and physiochemical properties of the rock-fluid interface by the surface relaxivity ρ_s This parameter, however, is dependent on the type and mineral constituents of the investigated rock sample and thus has to be determined and calibrated prior to estimating pore sizes from NMR relaxometry measurements. Frequently used methods to derive surface relaxivity to calibrate NMR pore sizes comprise mercury injection, pulsed field gradients (PFG-NMR) or grain size analysis. This study introduces an alternative approach to jointly estimate NMR surface relaxivity and pore radii distributions using NMR relaxation data obtained from partially de-saturated rocks. In this, inverse modeling is carried on a linked Young Laplace equation for capillary bundles and the Brownstein and Tarr equations. Subsequently, this approach is used to predict water retention curves of the investigated rocks. The method was tested and validated on simulated and laboratory transverse NMR data. Calculated inverse models are generally in a good agreement with results obtained from mercury injection and drainage measurements. Left: Measured and predicted water retention (pF) curves. Center: NMR relaxometry data, fit and error. Right: Mercury injection data (HgPor, dashed line) and jointly derived pore radii distributions and surface relaxivity by joint inverse modelling

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

    Science.gov (United States)

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

    2016-08-01

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

  11. Variable-temperature NMR and conformational analysis of Oenothein B

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Suzana C.; Carvalho, Ariadne G.; Fortes, Gilmara A.C.; Ferri, Pedro H.; Oliveira, Anselmo E. de, E-mail: suzana.quimica.ufg@hotmail.com [Universidade Federal de Goias (UFGO), Goiania, GO (Brazil). Instituto de Quimica

    2014-02-15

    Oenothein B is a dimeric hydrolyzable tannin with a wide range of biological activities, such as antitumour, anti-inflammatory and antiviral. Its nuclear magnetic resonance (NMR) at room temperature show duplications and broadening of signals. Experiments of 1D and 2D NMR at lower temperatures were useful for the complete NMR assignments of all hydrogens and carbons. The 3D structure of the most stable conformer was determined for the first time by nuclear Overhauser effect spectroscopy (NOESY) experiment (-20 deg C) and density functional theory (DFT)(B3LYP/6-31G)/ polarizable continuum model (PCM) quantum chemical calculations. The favoured conformation showed a highly compacted geometry and a lack of symmetry, in which the two valoneoyl groups showed distinct conformational parameters and stabilities. (author)

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

    Science.gov (United States)

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

    2016-08-01

    NMRFx Processor is a new program for the processing of NMR data. Written in the Java programming language, NMRFx Processor is a cross-platform application and runs on Linux, Mac OS X and Windows operating systems. The application can be run in both a graphical user interface (GUI) mode and from the command line. Processing scripts are written in the Python programming language and executed so that the low-level Java commands are automatically run in parallel on computers with multiple cores or CPUs. Processing scripts can be generated automatically from the parameters of NMR experiments or interactively constructed in the GUI. A wide variety of processing operations are provided, including methods for processing of non-uniformly sampled datasets using iterative soft thresholding. The interactive GUI also enables the use of the program as an educational tool for teaching basic and advanced techniques in NMR data analysis. PMID:27457481

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

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, V V

    2005-04-26

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

  14. NMR Dynamic Studies in Living Systems

    Institute of Scientific and Technical Information of China (English)

    闫永彬; 范明杰; 罗雪春; 张日清

    2002-01-01

    Nuclear magnetic resonance (NMR) can noninvasively monitor the intracellular concentrations and kinetic properties of numerous inorganic and organic compounds. These characteristics have made NMR a useful tool for dynamic studies of living systems. Applications of NMR to living systems have successfully extended to many areas, including studies of metabolic regulation, ion transport, and intracellular reaction rates in vivo. The major purpose of this review is to summarize the results that can be obtained by modern NMR techniques in living systems. With the advances of new techniques, NMR measurements of various nuclides have been performed for specific physiological purposes. Although some technical problems still remain and there are still discrepancies between NMR and traditional biochemical results, the abundant and unique information obtained from NMR spectra suggests that NMR will be more extensively applied in future studies of living systems. The fast development of these new techniques is providing many new NMR applications in living systems, as well as in structural biology.

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

    Science.gov (United States)

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

    2011-08-01

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

  16. NMR Methods for Characterization of RNA Secondary Structure.

    Science.gov (United States)

    Kennedy, Scott D

    2016-01-01

    Knowledge of RNA secondary structure is often sufficient to identify relationships between the structure of RNA and processing pathways, and the design of therapeutics. Nuclear magnetic resonance (NMR) can identify types of nucleotide base pairs and the sequence, thus limiting possible secondary structures. Because NMR experiments, like chemical mapping, are performed in solution, not in single crystals, experiments can be initiated as soon as the biomolecule is expressed and purified. This chapter summarizes NMR methods that permit rapid identification of RNA secondary structure, information that can be used as supplements to chemical mapping, and/or as preliminary steps required for 3D structure determination. The primary aim is to provide guidelines to enable a researcher with minimal knowledge of NMR to quickly extract secondary structure information from basic datasets. Instrumental and sample considerations that can maximize data quality are discussed along with some details for optimal data acquisition and processing parameters. Approaches for identifying base pair types in both unlabeled and isotopically labeled RNA are covered. Common problems, such as missing signals and overlaps, and approaches to address them are considered. Programs under development for merging NMR data with structure prediction algorithms are briefly discussed. PMID:27665604

  17. NMR-based milk metabolomics

    DEFF Research Database (Denmark)

    Sundekilde, Ulrik; Larsen, Lotte Bach; Bertram, Hanne Christine S.

    2013-01-01

    Milk is a key component in infant nutrition worldwide and, in the Western parts of the world, also in adult nutrition. Milk of bovine origin is both consumed fresh and processed into a variety of dairy products including cheese, fermented milk products, and infant formula. The nutritional quality...... compounds. Furthermore, metabolomics applications elucidating how the differential regulated genes affects milk composition are also reported. This review will highlight the recent advances in NMR-based metabolomics on milk, as well as give a brief summary of when NMR spectroscopy can be useful for gaining...

  18. Advanced NMR characterization of zeolite catalysts

    Science.gov (United States)

    Welsh, L. B.

    1985-04-01

    The program discussed in this report is a two-year two-phase joint UOP-University of Illinois study of the application of improved high resolution solid state nuclear magnetic resonance (NMR) techniques to the characterization of zeolite catalysts. During the first phase of this program very pure, and in some cases isotopically enriched faujasites will be prepared and studied by magic angle sample spinning NMR (MASS NMR) and variable engine sample spinning NMR (VASS NMR) on 500 and 360 MHz (proton frequency) NMR spectrometers. The NMR techniques that will be emphasized are the measurement and analysis of the (17)O NMR properties, (27)Al NMR intensity quantitation, and (27)Al and (29)Si NMR relaxation rates. During the second phase of this program these NMR techniques will be used to study the effects of impurity concentration, dealumination treatments and cation exchange on the NMR properties of faujasites. The initial emphasis of this program during Phase I is on the preparation and measurement of the NMR properties of (17)O enriched Na-Y faujasties.

  19. Pulsed zero field NMR of solids and liquid crystals

    International Nuclear Information System (INIS)

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

  20. Dynamic NMR of nano- and microstructured materials

    Energy Technology Data Exchange (ETDEWEB)

    Olaru, Maria Alexandra

    2013-07-01

    double quantum filtered SD experiments and including a series of bonds for and minimizing uncertainties in the estimation of essential parameters. Recently developed cement-in-polymer dispersions (c/p) with different compositions and cement to polymer ratios are investigated in Chapters 3 and 4, by a vast array of NMR techniques, that probe, on different length scales, the structure of the investigated specimens, as well as the dynamics of water transport inside the materials. Chapter 3 presents the results obtained using multinuclear solid state magic angle spinning NMR to probe, at nanometer level, the structure of cement-in-polymer dispersions. The hydration effects and crystallization of the inorganic matrix are probed by {sup 29}Si NMR while the chemical reactions of the organic phase are quantified by {sup 13}C cross-polarization; the results are correlated with data offered by other analysis techniques. The study of hydrated c/p is continued in Chapter 4, where proton NMR imaging is employed to obtain information about the microstructural changes which take place upon exposure to water at different temperatures. The water transport in the c/p matrix is monitored on line and the hydration phenomenon, together with information about the physical suffered by the samples are discussed with regard to polymer type, amount and curing conditions. A simple mathematical model of diffusion in a cylindrical system, involving time dependent diffusion coefficients and variable surface concentrations, is used to predict the manner in which the water amount inside the organic/cementitious pastes evolves in time. Further on, the effects of diffusive and advective transport in model and natural porous media are systematically investigated in Chapters 5 and 6. NMR exchange relaxometry is known as a very powerful tool for probing the structure and dynamics of fully or partially hydrated porous systems, but, until know, no information existed on how the effects of slow advective

  1. Radiofrequency and magnet technology in medical NMR

    International Nuclear Information System (INIS)

    Nuclear magnetic resonance (NMR) is briefly described, particularly its rf and magnet aspects. Particular attention is given to the duplexer, the rf coils, and new kinds of magnets for remote sensing NMR

  2. Push-through Direction Injectin NMR Automation

    Science.gov (United States)

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

  3. High resolution NMR theory and chemical applications

    CERN Document Server

    Becker, Edwin D

    1969-01-01

    High Resolution NMR: Theory and Chemical Applications focuses on the applications of nuclear magnetic resonance (NMR), as well as chemical shifts, lattices, and couplings. The book first offers information on the theory of NMR, including nuclear spin and magnetic moment, spin lattice relaxation, line widths, saturation, quantum mechanical description of NMR, and ringing. The text then ponders on instrumentation and techniques and chemical shifts. Discussions focus on the origin of chemical shifts, reference compounds, empirical correlations of chemical shifts, modulation and phase detection,

  4. NMR relaxation times of trabecular bone—reproducibility, relationships to tissue structure and effects of sample freezing

    Science.gov (United States)

    Prantner, Viktória; Isaksson, Hanna; Närväinen, Johanna; Lammentausta, Eveliina; Nissi, Mikko J.; Avela, Janne; Gröhn, Olli H. J.; Jurvelin, Jukka S.

    2010-12-01

    Nuclear magnetic resonance (NMR) spectroscopy provides a potential tool for non-invasive evaluation of the trabecular bone structure. The objective of this study was to determine the reproducibility of the NMR relaxation parameters (T2, Carr-Purcel-T2, T1ρ) for fat and water and relate those to the structural parameters obtained by micro-computed tomography (μCT). Especially, we aimed to evaluate the effect of freezing on the relaxation parameters. For storing bone samples, freezing is the standard procedure during which the biochemical and cellular organization of the bone marrow may be affected. Bovine trabecular bone samples were stored at -20 °C for 7 days and measured by NMR spectroscopy before and after freezing. The reproducibility of NMR relaxation parameters, as expressed by the coefficient of variation, ranged from 3.1% to 27.9%. In fresh samples, some correlations between NMR and structural parameters (Tb.N, Tb.Sp) were significant (e.g. the relaxation rate for T2 of fat versus Tb.Sp: r = -0.716, p NMR relaxation times but the correlations between relaxation parameters and the μCT structural parameters were not statistically significant after freezing, suggesting some nonsystematic alterations of the marrow structure. Therefore, the use of frozen bone samples for NMR relaxation studies may provide inferior information about the trabecular bone structure.

  5. Exploring abiotic stress on asynchronous protein metabolism in single kernels of wheat studied by NMR spectroscopy and chemometrics

    DEFF Research Database (Denmark)

    Winning, H.; Viereck, N.; Wollenweber, B.;

    2009-01-01

    at the vegetative growth stage had little effect on the parameters investigated. For the first time, H-1 HR-MAS NMR spectra of grains taken during grain-filling were analysed by an advanced multiway model. In addition to the results from the chemical protein analysis and the H-1 HR-MAS NMR spectra of single kernels...

  6. Study of a Conformational Equilibrium of Lisinopril by HPLC, NMR, and DFT

    Directory of Open Access Journals (Sweden)

    Sondes Bouabdallah

    2014-01-01

    Full Text Available The isomerization of lisinopril has been investigated using chromatographic, NMR spectroscopic, and theoretical calculations. The NMR data, particularly the NOEDIFF experiments, show that the major species that was eluted first is the trans form. The proportion was 77% and 23% for the trans and cis, respectively. The thermodynamic parameters (ΔH, ΔS, and ΔG were determined by varying the temperature in the NMR experiments. The interpretations of the experimental data were further supported by DFT/B3LYP calculations.

  7. NMR Studies of Inclusion Compounds

    OpenAIRE

    Nikkhou Aski, Sahar

    2008-01-01

    This thesis presents the application of some of the NMR methods in studying host-guest complexes, mainly in solution. The general focus of the work is on investigating the reorientational dynamics of some small molecules that are bound inside cavities of larger moieties. In the current work, these moieties belong to two groups: cryptophanes and cyclodextrins. Depending on the structure of the cavities, properties of the guest molecules and the formed complexes vary. Chloroform and dichloromet...

  8. NMR-Based Milk Metabolomics

    Directory of Open Access Journals (Sweden)

    Hanne C. Bertram

    2013-04-01

    Full Text Available Milk is a key component in infant nutrition worldwide and, in the Western parts of the world, also in adult nutrition. Milk of bovine origin is both consumed fresh and processed into a variety of dairy products including cheese, fermented milk products, and infant formula. The nutritional quality and processing capabilities of bovine milk is closely associated to milk composition. Metabolomics is ideal in the study of the low-molecular-weight compounds in milk, and this review focuses on the recent nuclear magnetic resonance (NMR-based metabolomics trends in milk research, including applications linking the milk metabolite profiling with nutritional aspects, and applications which aim to link the milk metabolite profile to various technological qualities of milk. The metabolite profiling studies encompass the identification of novel metabolites, which potentially can be used as biomarkers or as bioactive compounds. Furthermore, metabolomics applications elucidating how the differential regulated genes affects milk composition are also reported. This review will highlight the recent advances in NMR-based metabolomics on milk, as well as give a brief summary of when NMR spectroscopy can be useful for gaining a better understanding of how milk composition is linked to nutritional or quality traits.

  9. NMR-Based Milk Metabolomics.

    Science.gov (United States)

    Sundekilde, Ulrik K; Larsen, Lotte B; Bertram, Hanne C

    2013-01-01

    Milk is a key component in infant nutrition worldwide and, in the Western parts of the world, also in adult nutrition. Milk of bovine origin is both consumed fresh and processed into a variety of dairy products including cheese, fermented milk products, and infant formula. The nutritional quality and processing capabilities of bovine milk is closely associated to milk composition. Metabolomics is ideal in the study of the low-molecular-weight compounds in milk, and this review focuses on the recent nuclear magnetic resonance (NMR)-based metabolomics trends in milk research, including applications linking the milk metabolite profiling with nutritional aspects, and applications which aim to link the milk metabolite profile to various technological qualities of milk. The metabolite profiling studies encompass the identification of novel metabolites, which potentially can be used as biomarkers or as bioactive compounds. Furthermore, metabolomics applications elucidating how the differential regulated genes affects milk composition are also reported. This review will highlight the recent advances in NMR-based metabolomics on milk, as well as give a brief summary of when NMR spectroscopy can be useful for gaining a better understanding of how milk composition is linked to nutritional or quality traits. PMID:24957988

  10. RECENT PROGRESS IN BIOMOLECULAR NMR

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    @@ Structural genomics and proteomics were born from the understanding that functions of a protein are dictated by its 3D structure and dynamics. To understand protein functions on a genomic scale, we must know protein structures on a genomic scale. High resolution NMR can be used for this purpose. Traditional multidimensional NMR structure determination protocols become ineffective for structural genomics since to obtain a structure of a small protein of 15kD requires many months of painstaking spectral analysis and modeling. Recent advances in magnet and probe technology and in experimental methods have expanded the range of proteins amenable to structure determination and make the large scale structure determination possible. These advances are (1) effective expression systems for protein production, (2) introduction of cryoprobe, (3) structure determination with the use of the minimal amount of structural restraints obtained from the chemical shifts, residual dipolar couplings, NOEs, and computer modeling. In this talk,Iwill briefly outline these developments and related works done in our NMR lab.

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

    Science.gov (United States)

    Harter, Andrew

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

  12. Application progress of solid 29Si, 27Al NMR in the research of cement-based materials

    International Nuclear Information System (INIS)

    Background: The solid-state Nuclear Magnetic Resonance (NMR) is an effective method for the research of cement-based materials. Now it focuses on using solid 29Si and 27Al NMR to research the hydration structure of the cement-based materials in cement chemistry. Purpose: A theoretical guidance is proposed for solid 29Si and 27Al NMR technology used in cement chemistry research. Methods: We reviewed the application of solid 29Si and 27Al NMR in the cement-based materials and analyzed the problem among the researches. Results: This paper introduced an fundamental, relevant-conditions and basic parameters of NMR, and studied the technical parameters of solid 29Si and 27Ai NMR together with the relationship among the hydration structure of cement based material. Moreover, this paper reviewed the related domestic and overseas achievements in the research of hydration structure of the cement-based materials using solid 29Si and 27Al NMR. Conclusion: There were some problems in the research on cement-based materials by technology of solid 29Si and 27Al NMR. NMR will promote the Hydration theory of cement-based material greatly. (authors)

  13. Measurements of Boar Spermatozoa Motility Using PFG NMR Method

    International Nuclear Information System (INIS)

    The evaluation of spermatozoa motility, viability and morphology is an essential parameter in the examination of sperm quality and in the establishment of correlations between sperm quality and fertility. Until now, assessment of sperm quality has been based on subjective evaluation of parameters, such as motility and viability, and on objective parameters, such as semen concentration and morphology abnormalities. When subjective optical microscopic evaluation was used in humans and animals, variations of 30 to 60% have been reported in the estimation of the motility parameters of the same ejaculates. To overcome this variability, different systems have been proposed such as turbidimetry, laser-Doppler spectroscopy, and photometric methods. Other accurate techniques, such as flow cytometry, which allows the evaluation of concentration, and cellulose-acetate/nitrate filter measure only a single semen parameter. The more recent track semen analysis system, based on individual spermatozoon evaluation, offers an accurate calculation of different semen parameters. Although some interesting results have already been obtained, many questions remain, which have to be answered to allow for further development in veterinary medicine, clinical fertility settings, physiological, and toxicology research activities. Pulsed field gradient nuclear magnetic resonance (PFG NMR) techniques have been presented demonstrating the potential to study flow and transport processes in complex systems. By PFG NMR, the molecular displacement can be measured that occurs during a time interval D, between two consecutive magnetic field gradient pulses. In this poster we present the results of PFG-NMR obtained for a number of samples of boar spermatozoa with varying motility and discuss whether this method can be useful for fast and reliable spermatozoa motility evaluation. (author)

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

    Science.gov (United States)

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

    2011-01-01

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

  15. Insight into sodium silicate glass structural organization by multinuclear NMR combined with first-principles calculations

    International Nuclear Information System (INIS)

    Short and medium range order of silica and sodium silicate glasses have been investigated from a quantitative analysis of 29Si MAS NMR and 23Na, 17O MQMAS NMR spectra. The method described enables the extraction of the underlying 17O NMR parameter distributions of bridging oxygens (BOs) and non-bridging oxygens (NBOs), and yields site populations which are confirmed by 29Si NMR data. The extracted NMR parameter distributions and their variations with respect to the glass chemical composition can then be analyzed in terms of local structural features (bond angles and bond lengths, coordination numbers) with the help of molecular dynamics simulations combined with first-principles calculations of NMR parameters. Correlations of relevant structural parameters with 23Na, 29Si and 17O NMR interactions (isotropic chemical shift δ(iso), quadrupolar coupling constant C(Q) and quadrupolar asymmetry parameter ηQ are re-examined and their applicability is discussed. These data offer better insights into the structural organization of the glass network, including both chemical and topological disorder. Adding sodium to pure silica significantly diminishes the Si-O-Si bond angles and leads to a longer mean Si-O bond length with a slight decrease of the mean Na-O bond length. Moreover, the present data are in favor of a homogeneous distribution of Na around both oxygen species in the silicate network. Finally, our approach was found to be sensitive enough to investigate the effect of addition of a small quantity of molybdenum oxide (about 1 mol%) on the 17O MAS spectrum, opening new possibilities for investigating the Mo environment in silicate glasses. (authors)

  16. EPR spectroscopy of a family of Cr(III) 7M(II) (M = Cd, Zn, Mn, Ni) "wheels": studies of isostructural compounds with different spin ground states

    DEFF Research Database (Denmark)

    Piligkos, Stergios; Weihe, Høgni; Bill, Eckhard;

    2009-01-01

    Spinning wheels: The presented highly resolved multifrequency continuous wave EPR spectra (e.g., see figure) of the heterooctametalic "wheels" Cr(7)M provide rare examples of high nuclearity polymetallic systems where detailed information on the spin-Hamiltonian parameters of the ground and excit...... to 10(5) by use of the Davidson algorithm. We show that transferability of spin-Hamiltonian parameters across complexes of the Cr(7)M family is possible and that the spin-Hamiltonian parameters of Cr(7)M do not have sharply defined values, but are rather distributed around a mean value....

  17. NMR investigation of Ag nanoparticles

    Science.gov (United States)

    Son, Kwanghyo; Jang, Zeehoon

    2013-01-01

    109Ag nuclear magnetic resonance (NMR) and relaxation measurements have been performed on two powder samples of Ag nanoparticles with average sizes of 20 nm and 80 nm. The measurements have been done in an external field of 9.4 T and in the temperature range 10 K Knight shift ( K) and the nuclear spin-lattice relaxation rate (1/ T 1) are observed to be almost identical to the values reported for the bulk Ag metal, whereby the Korringa ratio R(= K 2 T 1 T/S) is found to be 2.0 for both samples in the investigated temperature range.

  18. NMR spectroscopy and imaging of hyperpolarized gases

    OpenAIRE

    Zänker, Paul-Philipp

    2007-01-01

    Since the discovery of the nuclear magnetic resonance (NMR) phenomenon, countless NMR techniques have been developed that are today indispensable tools in physics, chemistry, biology, and medicine. As one of the main obstacles in NMR is its notorious lack of sensitivity, different hyperpolarization (HP) methods have been established to increase signals up to several orders of magnitude. In this work, different aspects of magnetic resonance, using HP noble gases, are studied, hereby combining ...

  19. Applications of NMR in Dairy Research

    Directory of Open Access Journals (Sweden)

    Anthony D. Maher

    2014-03-01

    Full Text Available NMR is a robust analytical technique that has been employed to investigate the properties of many substances of agricultural relevance. NMR was first used to investigate the properties of milk in the 1950s and has since been employed in a wide range of studies; including properties analysis of specific milk proteins to metabolomics techniques used to monitor the health of dairy cows. In this brief review, we highlight the different uses of NMR in the dairy industry.

  20. NMR INVESTIGATIONS OF HYDROGENATED AMORPHOUS SILICON

    OpenAIRE

    J. Reimer

    1981-01-01

    A review is presented of the N.M.R. (Nuclear Magnetic Resonance) studies to date of hydrogenated amorphous silicon-hydrogen films. Structural features of proton N.M.R. lineshapes, dynamics of hydrogen containing defect sites, and the promise of quantitative determinations of local silicon-hydrogen bonding environments are discussed in detail. Finally, some comments are given on future directions for N.M.R. studies of hydrogenated thin films.

  1. An Inversion Recovery NMR Kinetics Experiment

    OpenAIRE

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

    2011-01-01

    A convenient laboratory experiment is described in which NMR magnetization transfer by inversion recovery is used to measure the kinetics and thermochemistry of amide bond rotation. The experiment utilizes Varian spectrometers with the VNMRJ 2.3 software, but can be easily adapted to any NMR platform. The procedures and sample data sets in this article will enable instructors to use inversion recovery as a laboratory activity in applied NMR classes and provide research students with a conveni...

  2. Computational Analysis of Solvent Effects in NMR Spectroscopy.

    Science.gov (United States)

    Dračínský, Martin; Bouř, Petr

    2010-01-12

    Solvent modeling became a standard part of first principles computations of molecular properties. However, a universal solvent approach is particularly difficult for the nuclear magnetic resonance (NMR) shielding and spin-spin coupling constants that in part result from collective delocalized properties of the solute and the environment. In this work, bulk and specific solvent effects are discussed on experimental and theoretical model systems comprising solvated alanine zwitterion and chloroform molecules. Density functional theory computations performed on larger clusters indicate that standard dielectric continuum solvent models may not be sufficiently accurate. In some cases, more reasonable NMR parameters were obtained by approximation of the solvent with partial atomic charges. Combined cluster/continuum models yielded the most reasonable values of the spectroscopic parameters, provided that they are dynamically averaged. The roles of solvent polarizability, solvent shell structure, and bulk permeability were investigated. NMR shielding values caused by the macroscopic solvent magnetizability exhibited the slowest convergence with respect to the cluster size. For practical computations, however, inclusion of the first solvation sphere provided satisfactory corrections of the vacuum values. The simulations of chloroform chemical shifts and CH J-coupling constants were found to be very sensitive to the molecular dynamics model used to generate the cluster geometries. The results show that computationally efficient solvent modeling is possible and can reveal fine details of molecular structure, solvation, and dynamics. PMID:26614339

  3. Fourier Analysis and Structure Determination. Part II: Pulse NMR and NMR Imaging.

    Science.gov (United States)

    Chesick, John P.

    1989-01-01

    Uses simple pulse NMR experiments to discuss Fourier transforms. Studies the generation of spin echoes used in the imaging procedure. Shows that pulse NMR experiments give signals that are additions of sinusoids of differing amplitudes, frequencies, and phases. (MVL)

  4. NMR studies of isotopically labeled RNA

    Energy Technology Data Exchange (ETDEWEB)

    Pardi, A. [Univ. of Colorado, Boulder, CO (United States)

    1994-12-01

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

  5. Spin-Exchange Pumped NMR Gyros

    CERN Document Server

    Walker, Thad G

    2016-01-01

    We present the basic theory governing spin-exchange pumped NMR gyros. We review the basic physics of spin-exchange collisions and relaxation as they pertain to precision NMR. We present a simple model of operation as an NMR oscillator and use it to analyze the dynamic response and noise properties of the oscillator. We discuss the primary systematic errors (differential alkali fields, quadrupole shifts, and offset drifts) that limit the bias stability, and discuss methods to minimize them. We give with a brief overview of a practical implementation and performance of an NMR gyro built by Northrop-Grumman Corporation, and conclude with some comments about future prospects.

  6. NMR exposure sensitizes tumor cells to apoptosis.

    Science.gov (United States)

    Ghibelli, L; Cerella, C; Cordisco, S; Clavarino, G; Marazzi, S; De Nicola, M; Nuccitelli, S; D'Alessio, M; Magrini, A; Bergamaschi, A; Guerrisi, V; Porfiri, L M

    2006-03-01

    NMR technology has dramatically contributed to the revolution of image diagnostic. NMR apparatuses use combinations of microwaves over a homogeneous strong (1 Tesla) static magnetic field. We had previously shown that low intensity (0.3-66 mT) static magnetic fields deeply affect apoptosis in a Ca2+ dependent fashion (Fanelli et al., 1999 FASEBJ., 13;95-102). The rationale of the present study is to examine whether exposure to the static magnetic fields of NMR can affect apoptosis induced on reporter tumor cells of haematopoietic origin. The impressive result was the strong increase (1.8-2.5 fold) of damage-induced apoptosis by NMR. This potentiation is due to cytosolic Ca2+ overload consequent to NMR-promoted Ca2+ influx, since it is prevented by intracellular (BAPTA-AM) and extracellular (EGTA) Ca2+ chelation or by inhibition of plasma membrane L-type Ca2+ channels. Three-days follow up of treated cultures shows that NMR decrease long term cell survival, thus increasing the efficiency of cytocidal treatments. Importantly, mononuclear white blood cells are not sensitised to apoptosis by NMR, showing that NMR may increase the differential cytotoxicity of antitumor drugs on tumor vs normal cells. This strong, differential potentiating effect of NMR on tumor cell apoptosis may have important implications, being in fact a possible adjuvant for antitumor therapies. PMID:16528477

  7. Advance reservoir evaluation by using NMR logging

    International Nuclear Information System (INIS)

    Based on brief explanation of the measurement principle for nuclear magnetic resonance (NMR) logging, this paper illustrates the importance of NMR logging in reservoir evaluation through typical case examples. These case examples include: Reservoir characterization and productivity evaluation by using NMR logging, determination of reservoir porosity in complex lithology, identification of oil, water and gas zones under complex reservoir conditions where resistivity log data give poor indication, guiding the implementation of completion and drilling programs, etc. Excellent application results indicate that NMR logging has its special features and advantages in comparison with conventional logging techniques. It is a very practical and very promising logging technology

  8. A theoretical study of the stationary structures of the methane surface with special emphasis on NMR properties

    Science.gov (United States)

    Alkorta, Ibon; Elguero, José

    2010-04-01

    The seven stationary points of the methane hypersurface were first explored concerning geometries and energies to check previous data. On these geometries, absolute 1H and 13C NMR shieldings as well as 1J(CH) and 2J(HH) coupling constants were calculated. The results show important variations in the NMR parameters depending on the stationary point considered. Relationships have been found between the 1H and 13C shieldings and between these NMR parameters and the relative energy of the different species.

  9. One- and two-dimensional high-resolution solid-state NMR investigation of zeolite structures. [NMR (nuclear magnetic resonance)

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Y.

    1991-01-01

    The work reported in this thesis describes for the first time the application of two-dimensional [sup 29]Si high-resolution solid state NMR experiments to the investigation of the three-dimensional Si-O-Si bonding connectivities in zeolites. 2D COSY type, INADEQUATE type and spin-diffusion experiments are discussed and evaluated, the INADEQUATE experiments being particularly successful in this work. By preparing highly crystalline, highly siliceous samples of zeolites and careful optimization of all experimental parameters, it is possible to directly observe [sup 29]Si-O-[sup 29]Si J couplings in these experiments. The three-dimensional lattice connectivities obtained from this work for [sup 29]Si enriched zeolite ZSM-39 and natural abundance ZSM-12 and ZSM-22 are in excellent agreement with the lattice structures determined by XRD techniques. In the case of a [sup 29]Si enriched sample of zeolite DD3R, the [sup 29]Si 2D NMR results indicate that the structure is of lower symmetry than has been postulated from diffraction studies. Zeolite ZSM-5, which has the most complex three-dimensional framework of all the known zeolites, was extensively studied in its room temperature phase by 2D NMR spectroscopy. In addition, the effects of temperature and the presence of sorbed p-xylene and p-dichlorobenzene on the phase behavior of ZSM-5 were also investigated. The [sup 29]Si 2D NMR data on ZSM-11 at high temperature are in good agreement with the known structure, 14m2. Low temperature 2D experiments on ZSM-11 gave the assignment of space group symmetry 14 to the structure which was previously unknown. Finally, [sup 29]Si 2D NMR results on ZSM-23 reveal that there are 12 independent T-sites in the structure which is not consistent with the space groups proposed in the literature which have 7 crystallographically inequivalent T-sites.

  10. Using 2D NMR to determine the degree of branching of complicated hyperbranched polymers

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Degree of branching (DB) is a crucial structure parameter of hyperbranched polymers, which can be determined by 1H NMR, quantitative 13C NMR, degradative method, etc. However, for complicated hy-perbranched polymers, intricate structure and severe overlap of spectral signals hinder the determina-tion of DB using traditional methods. In this work, the architecture of complicated hyperbranched polymers has been elucidated with the help of 2D NMR techniques. Using such a method, overlapped NMR signals can be well separated into a two-dimensional space, and additional structural information is also available. Correspondingly, quantitative analysis for complicated systems can be realized. De-termination of DBs for three types of complicated hyperbranched polymers synthesized from step-polymerization, self-condensation vinyl polymerization and self-condensation ring-opening po-lymerization is shown as examples.

  11. NMR Spectroscopy and Its Value: A Primer

    Science.gov (United States)

    Veeraraghavan, Sudha

    2008-01-01

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

  12. An Inversion Recovery NMR Kinetics Experiment

    Science.gov (United States)

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

    2011-01-01

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

  13. Using Cloud Storage for NMR Data Distribution

    Science.gov (United States)

    Soulsby, David

    2012-01-01

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

  14. Carbon-13 NMR spectroscopy of biological systems

    CERN Document Server

    Beckmann, Nicolau

    1995-01-01

    This book is intended to provide an in-depth understanding of 13C NMR as a tool in biological research. 13C NMR has provided unique information concerning complex biological systems, from proteins and nucleic acids to animals and humans. The subjects addressed include multidimensional heteronuclear techniques for structural studies of molecules in the liquid and solid states, the investigation of interactions in model membranes, the elucidation of metabolic pathwaysin vitro and in vivo on animals, and noninvasive metabolic studies performed on humans. The book is a unique mix of NMR methods and biological applications which makes it a convenient reference for those interested in research in this interdisciplinary area of physics, chemistry, biology, and medicine.Key Features* An interdisciplinary text with emphasis on both 13C NMR methodology and the relevant biological and biomedical issues* State-of-the-art 13C NMR techniques are described; Whenever possible, their advantages over other approaches are empha...

  15. Preprocessing of NMR metabolomics data.

    Science.gov (United States)

    Euceda, Leslie R; Giskeødegård, Guro F; Bathen, Tone F

    2015-05-01

    Metabolomics involves the large scale analysis of metabolites and thus, provides information regarding cellular processes in a biological sample. Independently of the analytical technique used, a vast amount of data is always acquired when carrying out metabolomics studies; this results in complex datasets with large amounts of variables. This type of data requires multivariate statistical analysis for its proper biological interpretation. Prior to multivariate analysis, preprocessing of the data must be carried out to remove unwanted variation such as instrumental or experimental artifacts. This review aims to outline the steps in the preprocessing of NMR metabolomics data and describe some of the methods to perform these. Since using different preprocessing methods may produce different results, it is important that an appropriate pipeline exists for the selection of the optimal combination of methods in the preprocessing workflow.

  16. Tacrine derivatives-acetylcholinesterase interaction: 1H NMR relaxation study.

    Science.gov (United States)

    Delfini, Maurizio; Di Cocco, Maria Enrica; Piccioni, Fabiana; Porcelli, Fernando; Borioni, Anna; Rodomonte, Andrea; Del Giudice, Maria Rosaria

    2007-06-01

    Two acetylcholinesterase (AChE) inhibitors structurally related to Tacrine, 6-methoxytacrine (1a) and 9-heptylamino-6-methoxytacrine (1b), and their interaction with Electrophorus Electricus AChE were investigated. The complete assignment of the 1H and 13C NMR spectra of 1a and 1b was performed by mono-dimensional and homo- and hetero-correlated two-dimensional NMR experiments. This study was undertaken to elucidate the interaction modes between AChE and 1a and 1b in solution, using NMR. The interaction between the two inhibitors and AChE was studied by the analysis of the motional parameters non-selective and selective spin-lattice relaxation times, thereby allowing the motional state of 1a and 1b, both free and bound with AChE, to be defined. The relaxation data pointed out the ligands molecular moiety most involved in the binding with AChE. The relevant ligand/enzyme interaction constants were also evaluated for both compounds and resulted to be 859 and 5412M(-1) for 1a and1b, respectively.

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

    Science.gov (United States)

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

    2016-08-18

    The structure and dynamics of the bound water in barium chlorate monohydrate were studied with (17)O nuclear magnetic resonance (NMR) spectroscopy in samples that are stationary and spinning at the magic-angle in magnetic fields ranging from 14.1 to 21.1 T. (17)O NMR parameters of the water were determined, and the effects of torsional oscillations of the water molecule on the (17)O quadrupolar coupling constant (CQ) were delineated with variable temperature MAS NMR. With decreasing temperature and reduction of the librational motion, we observe an increase in the experimentally measured CQ explaining the discrepancy between experiments and predictions from density functional theory. In addition, at low temperatures and in the absence of (1)H decoupling, we observe a well-resolved (1)H-(17)O dipole splitting in the spectra, which provides information on the structure of the H2O molecule. The splitting arises because of the homogeneous nature of the coupling between the two (1)H-(17)O dipoles and the (1)H-(1)H dipole. PMID:27454747

  18. Microscale simulations of NMR relaxation in porous media

    Science.gov (United States)

    Mohnke, Oliver; Klitzsch, Norbert

    2010-05-01

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

  19. Parameter Estimation

    DEFF Research Database (Denmark)

    Sales-Cruz, Mauricio; Heitzig, Martina; Cameron, Ian;

    2011-01-01

    In this chapter the importance of parameter estimation in model development is illustrated through various applications related to reaction systems. In particular, rate constants in a reaction system are obtained through parameter estimation methods. These approaches often require the application...... of optimisation techniques coupled with dynamic solution of the underlying model. Linear and nonlinear approaches to parameter estimation are investigated. There is also the application of maximum likelihood principles in the estimation of parameters, as well as the use of orthogonal collocation to...... generate a set of algebraic equations as the basis for parameter estimation.These approaches are illustrated using estimations of kinetic constants from reaction system models....

  20. NMR in solid ionic and nanoionics

    International Nuclear Information System (INIS)

    Full text: Nuclear Magnetic Resonance (NMR) is a spectroscopic technique which employs magnetic nuclei to study, among others, the dynamics of condensed matter at the atomic level. Thus, NMR has been and still is a successful instrument in the research field of solid electrolytes also known as solid ionics. This paper presents the typical NMR experiments performed in solid ionics together with some examples from nanoionics. The experiments to be discussed comprise: (i) measurements of the diffusion coefficient employing the pulsed-field gradient and the static fringe-field method; (ii) the experimentally related NMR imaging; (iii) double resonance experiments like spin-echo double resonance (SEDOR) and two-dimensional Fourier transform NMR (2D-FT NMR); (iv) various types of nuclear relaxation, in particular spin-lattice relaxation. The NMR techniques yield information on topics like the following: type and number of mobile atoms and defects, diffusion pathways (e.g. dimensionality restrictions), atomic jump frequencies, activation energy and activation volume of these movements, diffusion coefficient with activation energy and prefactor, correlation effects in atomic movements, space correlation factor, cooperative phenomena, symmetry of atomic sites, behavior at phase transitions. These applications will be illustrated by giving examples from crystals, glasses, and polymers. (author)

  1. Theoretical and experimental NMR studies on muscimol from fly agaric mushroom (Amanita muscaria)

    Science.gov (United States)

    Kupka, Teobald; Wieczorek, Piotr P.

    2016-01-01

    In this article we report results of combined theoretical and experimental NMR studies on muscimol, the bioactive alkaloid from fly agaric mushroom (Amanita muscaria). The assignment of 1H and 13C NMR spectra of muscimol in DMSO-d6 was supported by additional two-dimensional heteronuclear correlated spectra (2D NMR) and gauge independent atomic orbital (GIAO) NMR calculations using density functional theory (DFT). The effect of solvent in theoretical calculations was included via polarized continuum model (PCM) and the hybrid three-parameter B3LYP density functional in combination with 6-311++G(3df,2pd) basis set enabled calculation of reliable structures of non-ionized (neutral) molecule and its NH and zwitterionic forms in the gas phase, chloroform, DMSO and water. GIAO NMR calculations, using equilibrium and rovibrationally averaged geometry, at B3LYP/6-31G* and B3LYP/aug-cc-pVTZ-J levels of theory provided muscimol nuclear magnetic shieldings. The theoretical proton and carbon chemical shifts were critically compared with experimental NMR spectra measured in DMSO. Our results provide useful information on its structure in solution. We believe that such data could improve the understanding of basic features of muscimol at atomistic level and provide another tool in studies related to GABA analogs.

  2. Scalar operators in solid-state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Boqin

    1991-11-01

    Selectivity and resolution of solid-state NMR spectra are determined by dispersion of local magnetic fields originating from relaxation effects and orientation-dependent resonant frequencies of spin nuclei. Theoretically, the orientation-dependent resonant frequencies can be represented by a set of irreducible tensors. Among these tensors, only zero rank tensors (scalar operators) are capable of providing high resolution NMR spectra. This thesis presents a series of new developments in high resolution solid-state NMR concerning the reconstruction of various scalar operators motion in solid C{sub 60} is analyzed.

  3. Graphical programming for pulse automated NMR experiments

    Energy Technology Data Exchange (ETDEWEB)

    Belmonte, S.B. [Universidade do Estado, Rio de Janeiro, RJ (Brazil); Oliveira, I.S.; Guimaraes, A.P. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)

    1999-01-01

    We describe a software program designed to control a broadband pulse Nuclear Magnetic Resonance (NMR) spectrometer used in zero-field NMR studies of magnetic metals. The software is written in the graphical language LabVIEW. This type of programming allows modifications and the inclusion of new routines to be easily made by the non-specialist, without changing the basic structure of the program. The program corrects for differences in the gain of the two acquisition channels [U (phase) and V (quadrature)], and automatic baseline subtraction. We present examples of measurements of NMR spectra, spin-echo decay (T{sub 2}), and quadrupolar oscillations, performed in magnetic intermetallic compounds. (author)

  4. Oriented solid-state NMR spectrosocpy

    DEFF Research Database (Denmark)

    Bertelsen, Kresten

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

  5. Solid-state NMR of polymers

    Energy Technology Data Exchange (ETDEWEB)

    Mirau, P

    2001-07-01

    Nuclear magnetic resonance (NMR) spectroscopy has emerged as one of the most important methods for the solid-state characterisation of polymers. The popularity of NMR is due to the fact that many molecular level features can be measured from the NMR spectra, including the polymer chain conformation, the morphology and the dynamics. The spectral features and relaxation times are affected by local interactions, so they provide information about the structure of polymers on a length scale (2-200 A) that is difficult to measure by other methods. In favourable cases, the NMR experiments provide a molecular-level explanation for the transitions observed by differential scanning calorimetry (DSC) and other methods, and the NMR properties can often be related to the bulk properties. Solid-state NMR has long been of interest in polymer science, and the first solid-state NMR studies of polymers were reported approximately a year after the discovery of nuclear resonance in bulk matter. It was reported in this initial study that the proton line width for natural rubber at room temperature is more like that of a mobile liquid than of a solid, but that the resonance broadens near the glass transition temperature (T{sub g}). This was recognised as being related to a change in chain dynamics above and below the T{sub g}. NMR methods developed rapidly after these initial observations, first for polymers in solution and, more recently, for polymers in the solid-state. Solid-state NMR studies of polymers were developed more slowly than their solution-state counterparts because solid-state NMR requires more specialised equipment. Solid-state NMR is now such an important tool that most modern spectrometers are capable of performing these studies. The interest in the NMR of solid polymers is due in part to the fact that most polymers are used in the solid state, and in many cases the NMR properties can be directly related to the macroscopic properties. Polymers have restricted mobility

  6. NMR data-driven structure determination using NMR-I-TASSER in the CASD-NMR experiment

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Richard [Huazhong University of Science and Technology, School of Software Engineering (China); Wang, Yan [Huazhong University of Science and Technology, School of Life Science and Technology (China); Xue, Zhidong, E-mail: zdxue@hust.edu.cn [Huazhong University of Science and Technology, School of Software Engineering (China); Zhang, Yang, E-mail: zhng@umich.edu [University of Michigan, Department of Computational Medicine and Bioinformatics (United States)

    2015-08-15

    NMR-I-TASSER, an adaption of the I-TASSER algorithm combining NMR data for protein structure determination, recently joined the second round of the CASD-NMR experiment. Unlike many molecular dynamics-based methods, NMR-I-TASSER takes a molecular replacement-like approach to the problem by first threading the target through the PDB to identify structural templates which are then used for iterative NOE assignments and fragment structure assembly refinements. The employment of multiple templates allows NMR-I-TASSER to sample different topologies while convergence to a single structure is not required. Retroactive and blind tests of the CASD-NMR targets from Rounds 1 and 2 demonstrate that even without using NOE peak lists I-TASSER can generate correct structure topology with 15 of 20 targets having a TM-score above 0.5. With the addition of NOE-based distance restraints, NMR-I-TASSER significantly improved the I-TASSER models with all models having the TM-score above 0.5. The average RMSD was reduced from 5.29 to 2.14 Å in Round 1 and 3.18 to 1.71 Å in Round 2. There is no obvious difference in the modeling results with using raw and refined peak lists, indicating robustness of the pipeline to the NOE assignment errors. Overall, despite the low-resolution modeling the current NMR-I-TASSER pipeline provides a coarse-grained structure folding approach complementary to traditional molecular dynamics simulations, which can produce fast near-native frameworks for atomic-level structural refinement.

  7. A HTS dc SQUID-NMR: fabrication of the SQUID and application to low-field NMR for fruit quality detection

    Science.gov (United States)

    Isingizwe Nturambirwe, J. Frédéric; Perold, Willem J.; Opara, Linus U.

    2014-06-01

    Superconducting Quantum Interference Devices (SQUIDs) have made the detection of low-field (LF) and ultra-low field nuclear magnetic resonance (ULF-NMR) a reality. The latter has been proven to be a potential tool for non-destructive quality testing of horticultural products, amongst many other applications. High-Temperature Superconductor (HTS) dc SQUIDS are likely to allow for the development of not only low-cost NMR systems but also prototypes that are mobile and easily maintainable. A HTS dc SQUID was manufactured on an YBCO thin film, using a novel laser based lithography method. The lithography was implemented by a new laser system developed in-house, as a model of low-cost lithography systems. The junctions of the dc SQUID were tested and displayed normal I-V characteristics in the acceptable range for the application. In order to determine the viability of low-field NMR for non-destructive quality measurement of horticultural products, a commercial HTS dc SQUID-NMR system was used to measure quality parameters of banana during ripening. The trend of color change and sugar increase of the banana during ripening were the most highly correlated attributes to the SQUID-NMR measured parameter, average T1 (spin-lattice relaxation time). Further studies were done, that involved processing of the NMR signal into relaxation time resolved spectra. A spectral signature of banana was obtained, where each peak is a T1 value corresponding to a proton pool, and is reported here. These results will potentially lead to deeper understanding of the quality of the samples under study.

  8. Imaging of complex NMR spectra.

    Science.gov (United States)

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

    1985-01-01

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

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

    DEFF Research Database (Denmark)

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

    2015-01-01

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

  10. Median Modified Wiener Filter for nonlinear adaptive spatial denoising of protein NMR multidimensional spectra

    KAUST Repository

    Cannistraci, Carlo Vittorio

    2015-01-26

    Denoising multidimensional NMR-spectra is a fundamental step in NMR protein structure determination. The state-of-the-art method uses wavelet-denoising, which may suffer when applied to non-stationary signals affected by Gaussian-white-noise mixed with strong impulsive artifacts, like those in multi-dimensional NMR-spectra. Regrettably, Wavelet\\'s performance depends on a combinatorial search of wavelet shapes and parameters; and multi-dimensional extension of wavelet-denoising is highly non-trivial, which hampers its application to multidimensional NMR-spectra. Here, we endorse a diverse philosophy of denoising NMR-spectra: less is more! We consider spatial filters that have only one parameter to tune: the window-size. We propose, for the first time, the 3D extension of the median-modified-Wiener-filter (MMWF), an adaptive variant of the median-filter, and also its novel variation named MMWF*. We test the proposed filters and the Wiener-filter, an adaptive variant of the mean-filter, on a benchmark set that contains 16 two-dimensional and three-dimensional NMR-spectra extracted from eight proteins. Our results demonstrate that the adaptive spatial filters significantly outperform their non-adaptive versions. The performance of the new MMWF* on 2D/3D-spectra is even better than wavelet-denoising. Noticeably, MMWF* produces stable high performance almost invariant for diverse window-size settings: this signifies a consistent advantage in the implementation of automatic pipelines for protein NMR-spectra analysis.

  11. NMR spectroscopy assists synthetic fuels research

    Energy Technology Data Exchange (ETDEWEB)

    Cookson, D.J.; Smith, B.E.

    1983-01-01

    NMR spectroscopy has proved to be a useful and versatile technique for the study of synthetic fuels feedstocks, catalysts, process intermediates and final products. Some applications of the technique to coal and gas conversion research are illustrated and discussed.

  12. Interfaces in polymer nanocomposites - An NMR study

    Science.gov (United States)

    Böhme, Ute; Scheler, Ulrich

    2016-03-01

    Nuclear Magnetic Resonance (NMR) is applied for the investigation of polymer nanocomposites. Solid-state NMR is applied to study the modification steps to compatibilize layered double hydroxides with non-polar polymers. 1H relaxation NMR gives insight on the polymer dynamics over a wide range of correlation times. For the polymer chain dynamics the transverse relaxation time T2 is most suited. In this presentation we report on two applications of T2 measurements under external mechanical stress. In a low-field system relaxation NMR studies are performed in-situ under uniaxial stress. High-temperature experiments in a Couette cell permit the investigation of the polymer dynamics in the melt under shear flow.

  13. Bayesian Peak Picking for NMR Spectra

    KAUST Repository

    Cheng, Yichen

    2014-02-01

    Protein structure determination is a very important topic in structural genomics, which helps people to understand varieties of biological functions such as protein-protein interactions, protein–DNA interactions and so on. Nowadays, nuclear magnetic resonance (NMR) has often been used to determine the three-dimensional structures of protein in vivo. This study aims to automate the peak picking step, the most important and tricky step in NMR structure determination. We propose to model the NMR spectrum by a mixture of bivariate Gaussian densities and use the stochastic approximation Monte Carlo algorithm as the computational tool to solve the problem. Under the Bayesian framework, the peak picking problem is casted as a variable selection problem. The proposed method can automatically distinguish true peaks from false ones without preprocessing the data. To the best of our knowledge, this is the first effort in the literature that tackles the peak picking problem for NMR spectrum data using Bayesian method.

  14. NMR studies of cerebral metabolism in vivo

    International Nuclear Information System (INIS)

    The nature and extent of the potential synergism between PET and NMR methods is not yet well appreciated in the biomedical community. The long-range interest of medical neurobiology will be well served by efforts of PET and NMR scientists to follow each others' work so that opportunities for productive interchange can be efficiently exploited. Appreciation of the synergism by the rest of the biomedical community will follow naturally. PET is said by the people doing it to be still in its infancy, for they are more concerned with advancing their discipline than with admiring its already impressive achievements. On the scale of the same developmental metaphor, many NMR methods for studying the living human brain are still in utero. The best way to provide the reader a sense of the current status and future course of NMR research in medical neurobiology is by discussion of published in vivo studies. Such a discussion, adapted from another article is what follows

  15. Numerical simulation of ( T 2, T 1) 2D NMR and fluid responses

    Science.gov (United States)

    Tan, Mao-Jin; Zou, You-Long; Zhang, Jin-Yan; Zhao, Xin

    2012-12-01

    One-dimensional nuclear magnetic resonance (1D NMR) logging technology is limited for fluid typing, while two-dimensional nuclear magnetic resonance (2D NMR) logging can provide more parameters including longitudinal relaxation time ( T 1) and transverse relaxation time ( T 2) relative to fluid types in porous media. Based on the 2D NMR relaxation mechanism in a gradient magnetic field, echo train simulation and 2D NMR inversion are discussed in detail. For 2D NMR inversion, a hybrid inversion method is proposed based on the damping least squares method (LSQR) and an improved truncated singular value decomposition (TSVD) algorithm. A series of spin echoes are first simulated with multiple waiting times ( T W s) in a gradient magnetic field for given fluid models and these synthesized echo trains are inverted by the hybrid method. The inversion results are consistent with given models. Moreover, the numerical simulation of various fluid models such as the gas-water, light oil-water, and vicious oil-water models were carried out with different echo spacings ( T E s) and T W s by this hybrid method. Finally, the influences of different signal-to-noise ratios (SNRs) on inversion results in various fluid models are studied. The numerical simulations show that the hybrid method and optimized observation parameters are applicable to fluid typing of gas-water and oil-water models.

  16. CoNSEnsX: an ensemble view of protein structures and NMR-derived experimental data

    Directory of Open Access Journals (Sweden)

    Perczel András

    2010-10-01

    Full Text Available Abstract Background In conjunction with the recognition of the functional role of internal dynamics of proteins at various timescales, there is an emerging use of dynamic structural ensembles instead of individual conformers. These ensembles are usually substantially more diverse than conventional NMR ensembles and eliminate the expectation that a single conformer should fulfill all NMR parameters originating from 1016 - 1017 molecules in the sample tube. Thus, the accuracy of dynamic conformational ensembles should be evaluated differently to that of single conformers. Results We constructed the web application CoNSEnsX (Consistency of NMR-derived Structural Ensembles with eXperimental data allowing fast, simple and convenient assessment of the correspondence of the ensemble as a whole with diverse independent NMR parameters available. We have chosen different ensembles of three proteins, human ubiquitin, a small protease inhibitor and a disordered subunit of cGMP phosphodiesterase 5/6 for detailed evaluation and demonstration of the capabilities of the CoNSEnsX approach. Conclusions Our results present a new conceptual method for the evaluation of dynamic conformational ensembles resulting from NMR structure determination. The designed CoNSEnsX approach gives a complete evaluation of these ensembles and is freely available as a web service at http://consensx.chem.elte.hu.

  17. Frontiers of NMR in Molecular Biology

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-08-25

    NMR spectroscopy is expanding the horizons of structural biology by determining the structures and describing the dynamics of blobular proteins in aqueous solution, as well as other classes of proteins including membrane proteins and the polypeptides that form the aggregates diagnostic of prion and amyloid diseases. Significant results are also emerging on DNA and RNA oligomers and their complexes with proteins. This meeting focused attention on key structural questions emanating from molecular biology and how NMR spectroscopy can be used to answer them.

  18. NMR of Membrane Proteins: Beyond Crystals.

    Science.gov (United States)

    Rajesh, Sundaresan; Overduin, Michael; Bonev, Boyan B

    2016-01-01

    Membrane proteins are essential for the flow of signals, nutrients and energy between cells and between compartments of the cell. Their mechanisms can only be fully understood once the precise structures, dynamics and interactions involved are defined at atomic resolution. Through advances in solution and solid state NMR spectroscopy, this information is now available, as demonstrated by recent studies of stable peripheral and transmembrane proteins. Here we highlight recent cases of G-protein coupled receptors, outer membrane proteins, such as VDAC, phosphoinositide sensors, such as the FAPP-1 pleckstrin homology domain, and enzymes including the metalloproteinase MMP-12. The studies highlighted have resulted in the determination of the 3D structures, dynamical properties and interaction surfaces for membrane-associated proteins using advanced isotope labelling strategies, solubilisation systems and NMR experiments designed for very high field magnets. Solid state NMR offers further insights into the structure and multimeric assembly of membrane proteins in lipid bilayers, as well as into interactions with ligands and targets. Remaining challenges for wider application of NMR to membrane structural biology include the need for overexpression and purification systems for the production of isotope-labelled proteins with fragile folds, and the availability of only a few expensive perdeuterated detergents.Step changes that may transform the field include polymers, such as styrene maleic acid, which obviate the need for detergent altogether, and allow direct high yield purification from cells or membranes. Broader demand for NMR may be facilitated by MODA software, which instantly predicts membrane interactive residues that can subsequently be validated by NMR. In addition, recent developments in dynamic nuclear polarization NMR instrumentation offer a remarkable sensitivity enhancement from low molarity samples and cell surfaces. These advances illustrate the current

  19. NMR of Membrane Proteins: Beyond Crystals.

    Science.gov (United States)

    Rajesh, Sundaresan; Overduin, Michael; Bonev, Boyan B

    2016-01-01

    Membrane proteins are essential for the flow of signals, nutrients and energy between cells and between compartments of the cell. Their mechanisms can only be fully understood once the precise structures, dynamics and interactions involved are defined at atomic resolution. Through advances in solution and solid state NMR spectroscopy, this information is now available, as demonstrated by recent studies of stable peripheral and transmembrane proteins. Here we highlight recent cases of G-protein coupled receptors, outer membrane proteins, such as VDAC, phosphoinositide sensors, such as the FAPP-1 pleckstrin homology domain, and enzymes including the metalloproteinase MMP-12. The studies highlighted have resulted in the determination of the 3D structures, dynamical properties and interaction surfaces for membrane-associated proteins using advanced isotope labelling strategies, solubilisation systems and NMR experiments designed for very high field magnets. Solid state NMR offers further insights into the structure and multimeric assembly of membrane proteins in lipid bilayers, as well as into interactions with ligands and targets. Remaining challenges for wider application of NMR to membrane structural biology include the need for overexpression and purification systems for the production of isotope-labelled proteins with fragile folds, and the availability of only a few expensive perdeuterated detergents.Step changes that may transform the field include polymers, such as styrene maleic acid, which obviate the need for detergent altogether, and allow direct high yield purification from cells or membranes. Broader demand for NMR may be facilitated by MODA software, which instantly predicts membrane interactive residues that can subsequently be validated by NMR. In addition, recent developments in dynamic nuclear polarization NMR instrumentation offer a remarkable sensitivity enhancement from low molarity samples and cell surfaces. These advances illustrate the current

  20. Metabolic flux in carbohydrate biosynthesis. New methods using stable isotopes, mass spectrometry, and NMR

    Science.gov (United States)

    Structural analysis of carbohydrates involves three parameters: composition, linkage, and conformation, and tends to rely on the various forms of two techniques; mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy. These techniques are enhanced and extended by the use of stable...

  1. A new laboratory approach to shale analysis using NMR relaxometry

    Science.gov (United States)

    Washburn, Kathryn E.; Birdwell, Justin E.

    2013-01-01

    kerogen, thermally degraded kerogen, and char. Integrated peak areas from the LF-NMR results representative of kerogen and bitumen were found to be well correlated with S1 and S2 parameters from Rock-Eval programmed pyrolysis. This study demonstrates that LFNMR relaxometry can provide a wide range of information on shales and other reservoir rocks that goes well beyond porosity and pore-fluid analysis.

  2. 33S NMR cryogenic probe for taurine detection

    Science.gov (United States)

    Hobo, Fumio; Takahashi, Masato; Maeda, Hideaki

    2009-03-01

    With the goal of a S33 nuclear magnetic resonance (NMR) probe applicable to in vivo NMR on taurine-biological samples, we have developed the S33 NMR cryogenic probe, which is applicable to taurine solutions. The NMR sensitivity gain relative to a conventional broadband probe is as large as 3.5. This work suggests that improvements in the preamplifier could allow NMR measurements on 100 μM taurine solutions, which is the level of sensitivity necessary for biological samples.

  3. 1H NMR spectroscopic determination of deterioration marker compounds in fats and oils

    OpenAIRE

    Skiera, Christina

    2013-01-01

    In food and pharmaceutical analysis, the classical indices peroxide value (PV), acid value (AV) and p-anisidine value (ANV) still play an important role as quality and authenticity control parameters of fats and oils. These indices are sum parameters for certain deterioration products (PV for hydroperoxides, AV for free fatty acids, ANV for aldehydes) and are obtained using volumetric or UV/VIS spectroscopic analytical approaches. 1H NMR spectroscopy provides a fast and simple alternative to ...

  4. Synergistic Applications of MD and NMR for the Study of Biological Systems

    Directory of Open Access Journals (Sweden)

    Olivier Fisette

    2012-01-01

    same time, theoretical and computational approaches gain in reliability and their field of application widens. In this short paper, we discuss recent advances in the areas of solution nuclear magnetic resonance (NMR spectroscopy and molecular dynamics (MD simulations that were made possible by the combination of both methods, that is, through their synergistic use. We present the main NMR observables and parameters that can be computed from simulations, and how they are used in a variety of complementary applications, including dynamics studies, model-free analysis, force field validation, and structural studies.

  5. Grape juice quality control by means of ¹H nmr spectroscopy and chemometric analyses

    Directory of Open Access Journals (Sweden)

    Caroline Werner Pereira da Silva Grandizoli

    2014-01-01

    Full Text Available This work shows the application of ¹H NMR spectroscopy and chemometrics for quality control of grape juice. A wide range of quality assurance parameters were assessed by single ¹H NMR experiments acquired directly from juice. The investigation revealed that conditions and time of storage should be revised and indicated on all labels. The sterilization process of homemade grape juices was efficient, making it possible to store them for long periods without additives. Furthermore, chemometric analysis classified the best commercial grape juices to be similar to homemade grape juices, indicating that this approach can be used to determine the authenticity after adulteration.

  6. Validation of quantitative 1H NMR method for the analysis of pharmaceutical formulations

    International Nuclear Information System (INIS)

    The need for effective and reliable quality control in products from pharmaceutical industries renders the analyses of their active ingredients and constituents of great importance. This study presents the theoretical basis of ¹H NMR for quantitative analyses and an example of the method validation according to Resolution RE N. 899 by the Brazilian National Health Surveillance Agency (ANVISA), in which the compound paracetamol was the active ingredient. All evaluated parameters (selectivity, linearity, accuracy, repeatability and robustness) showed satisfactory results. It was concluded that a single NMR measurement provides structural and quantitative information of active components and excipients in the sample. (author)

  7. Molecular dynamics of solid cortisol studied by NMR

    Science.gov (United States)

    Andrew, E. R.

    Polycrystalline cortisol (hydrocortisone; 11β,17α,21-trihydroxy-4-preg- nene-3,20-dione; C21H30O5) has been investigated by continuous and pulse proton NMR methods between 78 and 400 K at Larmor frequencies of 7, 25 and 60 MHz. A reduced value of second moment was found above 90 K and is ascribed to reorientation of two methyl groups. A single asymmetric minimum was found in the temperature dependence of the spin-lattice relaxation times and this also is attributed to reorientation of two methyl groups. The asymmetry suggests an asymmetric distribution of correlation times of the motion. Using the Cole-Davidson distribution, the best computer fit yields the following parameters characterizing the motion: Ea = 11ṡ8 ± 0ṡ1 kJ mol-1, τ0 = 4ṡ6 ± 0ṡ4) x 10-13s, distribution parameter δ = 0ṡ62.

  8. Uniform procedure of (1)H NMR analysis of rat urine and toxicometabonomics Part II: comparison of NMR profiles for classification of hepatotoxicity.

    Science.gov (United States)

    Schoonen, Willem G E J; Kloks, Cathelijne P A M; Ploemen, Jan-Peter H T M; Smit, Martin J; Zandberg, Pieter; Horbach, G Jean; Mellema, Jan-Remt; Thijssen-Vanzuylen, Carol; Tas, Albert C; van Nesselrooij, Joop H J; Vogels, Jack T W E

    2007-07-01

    A procedure of nuclear magnetic resonance (NMR) urinalysis using pattern recognition is proposed for early detection of toxicity of investigational compounds in rats. The method is applied to detect toxicity upon administration of 13 toxic reference compounds and one nontoxic control compound (mianserine) in rats. The toxic compounds are expected to induce necrosis (bromobenzene, paracetamol, carbon tetrachloride, iproniazid, isoniazid, thioacetamide), cholestasis (alpha-naphthylisothiocyanate (ANIT), chlorpromazine, ethinylestradiol, methyltestosterone, ibuprofen), or steatosis (phenobarbital, tetracycline). Animals were treated daily for 2 or 4 days except for paracetamol and bromobenzene (1 and 2 days) and carbon tetrachloride (1 day only). Urine was collected 24 h after the first and second treatment. The animals were sacrificed 24 h after the last treatment, and NMR data were compared with liver histopathology as well as blood and urine biochemistry. Pathology and biochemistry showed marked toxicity in the liver at high doses of bromobenzene, paracetamol, carbon tetrachloride, ANIT, and ibuprofen. Thioacetamide and chlorpromazine showed less extensive changes, while the influences of iproniazid, isoniazid, phenobarbital, ethinylestradiol, and tetracycline on the toxic parameters were marginal or for methyltestosterone and mianserine negligible. NMR spectroscopy revealed significant changes upon dosing in 88 NMR biomarker signals preselected with the Procrustus Rotation method on principal component discriminant analysis (PCDA) plots. Further evaluation of the specific changes led to the identification of biomarker patterns for the specific types of liver toxicity. Comparison of our rat NMR PCDA data with histopathological changes reported in humans and/or rats suggests that rat NMR urinalysis can be used to predict hepatotoxicity. PMID:17420222

  9. AEM and NMR: Tools for the Future of Groundwater Management

    Science.gov (United States)

    Abraham, J. D.; Cannia, J. C.; Lawrie, K.

    2012-12-01

    Within the world, understanding groundwater resources and their management are growing in importance to society as groundwater resources are stressed by drought and continued development. To minimize conflicts, tools and techniques need to be applied to support knowledge-based decisions and management. Airborne electromagnetic (AEM) surveys provide high-quality subsurface data not available from any other source for building the complex hydrogeologic frameworks needed by water-resource managers for effective groundwater management. Traditionally, point data, such as borehole logs, borehole geophysics, surface geophysics, and aquifer tests were interpolated over long distances to create hydrogeologic frameworks. These methods have enjoyed a long history of being the best available technology to inform our understanding of groundwater and how it moves. The AEM techniques proivde pathway for geoscientists to follow to develop more accurate descriptions of the hydrogeological framework. However, the critical and challenging measurements in characterizing aquifers include effective porosity and hydraulic conductivity. These parameters are not reliable derived from AEM. Typically, values for effective porosity and hydraulic conductivity are derived by lithological comparisons with published data; direct measurements of hydraulic conductivity acquired by a few constant head aquifer tests or slug tests; and expensive and time consuming laboratory measurements of cores which can be biased by sampling and the difficulty of making measurements on unconsolidated materials. Aquifer tests are considered to be the best method to gather information on hydraulic conductivity but are rare because of cost and difficult logistics. Also they are unique in design and interpretation from site to site. Nuclear Magnetic Resonance (NMR) can provide a direct measurement of the presence of water in the pore space of aquifer materials. Detection and direct measurement is possible due to the

  10. Dynamic Nuclear Polarization (DNP) solid-state NMR spectroscopy, a new approach to study humic material?

    Science.gov (United States)

    Knicker, Heike; Lange, Sascha; van Rossum, Barth; Oschkinat, Hartmut

    2016-04-01

    Compared to solution NMR spectroscopy, solid-state NMR spectra suffer from broad resonance lines and low resolution. This could be overcome by the use of 2-dimenstional solid-state NMR pulse sequences. Until recently, this approach has been unfeasible as a routine tool in soil chemistry, mainly because of the low NMR sensitivity of the respective samples. A possibility to circumvent those sensitivity problems represents high-field Dynamic Nuclear Polarization (DNP) solid-state NMR spectroscopy (Barnes et al., 2008), allowing considerable signal enhancements (Akbey et al., 2010). This is achieved by a microwave-driven transfer of polarization from a paramagnetic center to nuclear spins. Application of DNP to MAS spectra of biological systems (frozen solutions) showed enhancements of the factor 40 to 50 (Hall et al., 1997). Enhancements of this magnitude, thus may enable the use of at least some of the 2D solid-state NMR techniques that are presently already applied for pure proteins but are difficult to apply to soil peptides in their complex matrix. After adjusting the required acquisition parameters to the system "soil organic matter", lower but still promising enhancement factors were achieved. Additional optimization was performed and allowed the acquisition of 2D 13C and 15N solid-state NMR spectra of humified 13C and 15N enriched plant residues. Within the present contribution, the first solid-state DNP NMR spectra of humic material are presented. Those data demonstrate the great potential of this approach which certainly opens new doors for a better understanding of biochemical processes in soils, sediments and water. Akbey, Ü., Franks, W.T., Linden, A., Lange, S., Griffin, R.G., van Rossum, B.-J., Oschkinat, H., 2010. Dynamic nuclear polarization of deuterated proteins. Angewandte Chemie International Edition 49, 7803-7806. Barnes, A.B., De Paëpe, G., van der Wel, P.C.A., Hu, K.N., Joo, C.G., Bajaj, V.S., Mak-Jurkauskas, M.L., Sirigiri, J.R., Herzfeld, J

  11. BOOK REVIEW: NMR Imaging of Materials

    Science.gov (United States)

    Blümich, Bernhard

    2003-09-01

    Magnetic resonance imaging (MRI) of materials is a field of increasing importance. Applications extend from fundamental science like the characterization of fluid transport in porous rock, catalyst pellets and hemodialysers into various fields of engineering for process optimization and product quality control. While the results of MRI imaging are being appreciated by a growing community, the methods of imaging are far more diverse for materials applications than for medical imaging of human beings. Blümich has delivered the first book in this field. It was published in hardback three years ago and is now offered as a paperback for nearly half the price. The text provides an introduction to MRI imaging of materials covering solid-state NMR spectroscopy, imaging methods for liquid and solid samples, and unusual MRI in terms of specialized approaches to spatial resolution such as an MRI surface scanner. The book represents an excellent and thorough treatment which will help to grow research in materials MRI. Blümich developed the treatise over many years for his research students, graduates in chemistry, physics and engineering. But it may also be useful for medical students looking for a less formal discussion of solid-state NMR spectroscopy. The structure of this book is easy to perceive. The first three chapters cover an introduction, the fundamentals and methods of solid-state NMR spectroscopy. The book starts at the ground level where no previous knowledge about NMR is assumed. Chapter 4 discusses a wide variety of transformations beyond the Fourier transformation. In particular, the Hadamard transformation and the 'wavelet' transformation are missing from most related books. This chapter also includes a description of noise-correlation spectroscopy, which promises the imaging of large objects without the need for extremely powerful radio-frequency transmitters. Chapters 5 and 6 cover basic imaging methods. The following chapter about the use of relaxation and

  12. Solid-state NMR in the analysis of drugs and naturally occurring materials.

    Science.gov (United States)

    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

  13. Nuclear magnetic resonance (NMR): principles and applications

    International Nuclear Information System (INIS)

    The basis for the phenomenon of nuclear magnetic resonance (NMR) is the ability of certain nuclei possessing both intrinsic angular momentum or ''spin'' I and magnetic moment to absorb electromagnetic energy in the radio frequency range. In principle, there are approximately 200 nuclei which may be investigated using the NMR technique. The NMR spectrum consists of intensity peaks along an axis calibrated in terms of the steady magnetic field or the frequency of the radiofrequency electromagnetic radiation. Analysis of the number, spacing, position and intensity of the lines in an NMR spectrum consists of intensity peaks along an axis calibrated in terms of the steady magnetic field or the frequency of the radiofrequency electromagnetic radiation. Analysis of the number, spacing, position and intensity of the lines in an NMR spectrum provides a variety of qualitative and quantitative analytical applications. The most obvious applications consist of the measurements of nuclear properties, such as spin number and nuclear magnetic moment. In liquids, the fine structure of resonance spectra provides a tool for chemical identification and molecular structure analysis. Other applications include the measurements of self-diffusion coefficients, magnetic fields and field homogeneity, inter-nuclear distances, and, in some cases, the water content of biological materials. (author)

  14. Primjena spektroskopije NMR u analizi biodizela

    Directory of Open Access Journals (Sweden)

    Jelena Parlov Vuković

    2016-01-01

    Full Text Available U ovome preglednom radu opisane su najznačajnije i najčešće primjenjivane jednodimenzijske i dvodimenzijske tehnike NMR u analizi biodizela. Biodizel je ekološki prihvatljivo alternativno gorivo koje se sastoji od zasićenih i nezasićenih metilnih estera masnih kiselina. Budući da analiza kemijskog sastava i proučavanje svojstava biodizela i ostalih biogoriva analitičarima predstavlja izazov, sve više se razvijaju nove i učinkovitije analitičke metode. Spektroskopija NMR jedna je od takvih metoda koja može dati niz informacija o sastavu i strukturi biodizela. Nadalje, analiza spektara NMR pruža vrijedne podatke i o sirovinama iz kojih nastaje biodizel te o procesu esterifikacije. Isto tako primjenom tehnika 1H i 13C NMR može se odrediti sastav aditiva koji se dodaju za sprječavanje rasta mikroorganizama i sastav smjese acetilglicerola i sličnih nusproizvoda sinteze biodizela. U tu svrhu se osim spektara 1H i 13C analiziraju i spektri 31P. U radu su dani karakteristični spektri biodizela, dizela, biljnog ulja tretiranog vodikom te reprezentativan spektar jednog od uzoraka biocida snimljeni u Laboratoriju za spektroskopiju NMR u INA d. d.

  15. Targeted natural product isolation guided by HPLC-SPE-NMR: Constituents of Hubertia species

    DEFF Research Database (Denmark)

    Sprogoe, K.; Staek, D.; Jager, A.K.;

    2007-01-01

    The hyphenated technique, high-performance liquid chromatography-solid-phase extraction-nuclear magnetic resonance spectroscopy (HPLC-SPE-NMR), has been applied for rapid identification of novel natural products in crude extracts of Hubertia ambavilla and Hubertia tomentosa. The technique allowed...... full or partial identification of all major extract constituents and demonstrated the presence of unusual quinic acid derivatives containing the (1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetyl residue that exhibit strongly coupled ABXY patterns, the parameters of which were obtained by spin simulations....... Using homo- and heteronuclear 2D NMR data acquired in the HPLC-SPE-NMR mode, complete structure determination of three new natural products, i.e., 3,5-di-O-caffeoyl-4-O-[(1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetyl]quini c acid (1), its 2-hydroxy derivative (2), and 3,5-di-O-caffeoyl-4-O-[(4...

  16. Identifying Stereoisomers by ab-initio Calculation of Secondary Isotope Shifts on NMR Chemical Shieldings

    Directory of Open Access Journals (Sweden)

    Karl-Heinz Böhm

    2014-04-01

    Full Text Available We present ab-initio calculations of secondary isotope effects on NMR chemical shieldings. The change of the NMR chemical shift of a certain nucleus that is observed if another nucleus is replaced by a different isotope can be calculated by computing vibrational corrections on the NMR parameters using electronic structure methods. We demonstrate that the accuracy of the computational results is sufficient to even distinguish different conformers. For this purpose, benchmark calculations for fluoro(2-2Hethane in gauche and antiperiplanar conformation are carried out at the HF, MP2 and CCSD(T level of theory using basis sets ranging from double- to quadruple-zeta quality. The methodology is applied to the secondary isotope shifts for 2-fluoronorbornane in order to resolve an ambiguity in the literature on the assignment of endo- and exo-2-fluoronorbornanes with deuterium substituents in endo-3 and exo-3 positions, also yielding insight into mechanistic details of the corresponding synthesis.

  17. NMR-Based Multi Parametric Quality Control of Fruit Juices: SGF Profiling

    Directory of Open Access Journals (Sweden)

    Fang Fang

    2009-11-01

    Full Text Available With SGF Profiling™ we introduce an NMR-based screening method for the quality control of fruit juices. This method has been developed in a joint effort by Bruker BioSpin GmbH and SGF International e.V. The system is fully automated with respect to sample transfer, measurement, data analysis and reporting and is set up on an Avance 400 MHz flow-injection NMR spectrometer. For each fruit juice a multitude of parameters related to quality and authenticity are evaluated simultaneously from a single data set acquired within a few minutes. This multimarker/multi-aspect NMR screening approach features low cost-per-sample and is highly competitive with conventional and targeted fruit juice quality control methods.

  18. NMR Studies on the Internal Structure of High- T c Superconductors and Other Anorganic Compounds

    Science.gov (United States)

    Kumagai, K.; Kakuyanagi, K.; Saitoh, M.; Matsuda, Y.; Hasegawa, M.; Takashima, S.; Nohara, M.; Takagi, H.

    2004-12-01

    Spatially-resolved NMR is used to probe internal structures in highly correlated superconductors of optimally-doped {text{Tl}}2 {text{Ba}}2 {text{CuO}}_{{6 + δ }} ( T c = 85 K) and a heavy fermion superconductor CeCoIn5 ( T c = 2.3 K). The characteristic change of the properties of 205Tl-NMR in the vortex state provides a clear evidence of the antiferromagnetic order in the vortex cores below 20 K in {text{Tl}}2 {text{Ba}}2 {text{CuO}}_{{6 + δ }} . We also obtain anomalous 115In-NMR spectra of CeCoIn5, which provides a microscopic evidence for the occurrence of a spatially-modulated superconducting order parameter expected in a Fulde Ferrel Larkin Ovchinnkov (FFLO) state.

  19. NMR studies of phase behaviour in polyacrylonitrile solutions

    Energy Technology Data Exchange (ETDEWEB)

    Golightly, J.A

    1998-10-01

    semi-infinite diffusion framework. The fitting parameters represented the diffusion coefficients of the water molecules in the solution /coagulated PAN network, and in the bulk non-solvent /solvent. PAN films were cast at a range of temperatures in non-solvent baths. This was a scaling up of the dimensions of the fibre spinning process and was used to investigate the range of morphologies which can be formed in the wet-spinning of acrylic fibres. Before any drying processes, water molecules were confined in the porous structure of the saturated films, and their NMR relaxation and self diffusion behaviour was investigated. Parameters describing the pore size and the tortuosity were derived from these studies and scanning electron microscopy was used as a comparative technique. The pore sizes predicted from the NMR data span a smaller spatial range than those observed from SEM. This is explained by the fundamental differences between the two techniques. (author)

  20. NMR Evidence for the Topologically Nontrivial Nature in a Family of Half-Heusler Compounds

    Science.gov (United States)

    Zhang, Xiaoming; Hou, Zhipeng; Wang, Yue; Xu, Guizhou; Shi, Chenglong; Liu, Enke; Xi, Xuekui; Wang, Wenhong; Wu, Guangheng; Zhang, Xi-Xiang

    2016-03-01

    Spin-orbit coupling (SOC) is expected to partly determine the topologically nontrivial electronic structure of heavy half-Heusler ternary compounds. However, to date, attempts to experimentally observe either the strength of SOC or how it modifies the bulk band structure have been unsuccessful. By using bulk-sensitive nuclear magnetic resonance (NMR) spectroscopy combined with first-principles calculations, we reveal that 209Bi NMR isotropic shifts scale with relativity in terms of the strength of SOC and average atomic numbers, indicating strong relativistic effects on NMR parameters. According to first-principles calculations, we further claim that nuclear magnetic shieldings from relativistic p1/2 states and paramagnetic contributions from low-lying unoccupied p3/2 states are both sensitive to the details of band structures tuned by relativity, which explains why the hidden relativistic effects on band structure can be revealed by 209Bi NMR isotropic shifts in topologically nontrivial half-Heusler compounds. Used in complement to surface-sensitive methods, such as angle resolved photon electron spectroscopy and scanning tunneling spectroscopy, NMR can provide valuable information on bulk electronic states.

  1. NMR Evidence for the Topologically Nontrivial Nature in a Family of Half-Heusler Compounds

    KAUST Repository

    Zhang, Xiaoming

    2016-03-16

    Spin-orbit coupling (SOC) is expected to partly determine the topologically nontrivial electronic structure of heavy half-Heusler ternary compounds. However, to date, attempts to experimentally observe either the strength of SOC or how it modifies the bulk band structure have been unsuccessful. By using bulk-sensitive nuclear magnetic resonance (NMR) spectroscopy combined with first-principles calculations, we reveal that 209Bi NMR isotropic shifts scale with relativity in terms of the strength of SOC and average atomic numbers, indicating strong relativistic effects on NMR parameters. According to first-principles calculations, we further claim that nuclear magnetic shieldings from relativistic p1/2 states and paramagnetic contributions from low-lying unoccupied p3/2 states are both sensitive to the details of band structures tuned by relativity, which explains why the hidden relativistic effects on band structure can be revealed by 209Bi NMR isotropic shifts in topologically nontrivial half-Heusler compounds. Used in complement to surface-sensitive methods, such as angle resolved photon electron spectroscopy and scanning tunneling spectroscopy, NMR can provide valuable information on bulk electronic states.

  2. Spin Choreography: Basic Steps in High Resolution NMR (by Ray Freeman)

    Science.gov (United States)

    Minch, Michael J.

    1998-02-01

    There are three orientations that NMR courses may take. The traditional molecular structure course focuses on the interpretation of spectra and the use of chemical shifts, coupling constants, and nuclear Overhauser effects (NOE) to sort out subtle details of structure and stereochemistry. Courses can also focus on the fundamental quantum mechanics of observable NMR parameters and processes such a spin-spin splitting and relaxation. More recently there are courses devoted to the manipulation of nuclear spins and the basic steps of one- and two-dimensional NMR experiments. Freeman's book is directed towards the latter audience. Modern NMR methods offer a myriad ways to extract information about molecular structure and motion by observing the behavior of nuclear spins under a variety of conditions. In Freeman's words: "We can lead the spins through an intricate dance, carefully programmed in advance, to enhance, simplify, correlate, decouple, edit or assign NMR spectra." This is a carefully written, well-illustrated account of how this dance is choreographed by pulse programming, double resonance, and gradient effects. Although well written, this book is not an easy read; every word counts. It is recommended for graduate courses that emphasize the fundamentals of magnetic resonance. It is not a text on interpretation of spectra.

  3. Wine analysis to check quality and authenticity by fully-automated 1H-NMR

    Directory of Open Access Journals (Sweden)

    Spraul Manfred

    2015-01-01

    Full Text Available Fully-automated high resolution 1H-NMR spectroscopy offers unique screening capabilities for food quality and safety by combining non-targeted and targeted screening in one analysis (15–20 min from acquisition to report. The advantage of high resolution 1H-NMR is its absolute reproducibility and transferability from laboratory to laboratory, which is not equaled by any other method currently used in food analysis. NMR reproducibility allows statistical investigations e.g. for detection of variety, geographical origin and adulterations, where smallest changes of many ingredients at the same time must be recorded. Reproducibility and transferability of the solutions shown are user-, instrument- and laboratory-independent. Sample prepara- tion, measurement and processing are based on strict standard operation procedures which are substantial for this fully automated solution. The non-targeted approach to the data allows detecting even unknown deviations, if they are visible in the 1H-NMR spectra of e.g. fruit juice, wine or honey. The same data acquired in high-throughput mode are also subjected to quantification of multiple compounds. This 1H-NMR methodology will shortly be introduced, then results on wine will be presented and the advantages of the solutions shown. The method has been proven on juice, honey and wine, where so far unknown frauds could be detected, while at the same time generating targeted parameters are obtained.

  4. Optimization of CPMG sequences for NMR borehole measurements

    Directory of Open Access Journals (Sweden)

    M. Ronczka

    2012-07-01

    Full Text Available Nuklear Magnetic Resonance (NMR can provide key information such as porosity and permeability for hydrological characterization of geological material. Especially the NMR transverse relaxation time T2 is used to estimate permeability since it reflects a pore-size dependent relaxation process. The measurement sequence (CPMG usually used consists of several thousands of electromagnetic pulses to densely record the relaxation process. These pulses are equidistantly spaced by a time constant τ. In NMR borehole applications the use of CPMG sequences for measuring the transverse relaxation time T2 is limited due to requirements on energy consumption. It is state of the art to conduct at least two sequences with different echo spacings (τ for recording fast and slow relaxing processes that correspond to different pore-sizes. For the purpose to reduce the amount of energy used for conducting CPMG sequences and to obtain both, slow and fast, decaying components within one sequence we tested the usage of CPMG sequences with an increasing τ and a decreasing number of pulses. A synthetic study as well as laboratory measurements on samples of glass beads and granulate of different grain size spectra were conducted to evaluate the effects of of an increasing τ spacing, e.g. an enhanced relaxation due to diffusion processes. The results are showing broadened T2 distributions if the number of pulses is decreasing and the mean grain size is increasing, which is mostly an effect of a significantly shortened acquisition time. The shift of T2 distributions to small decay times in dependence of the τ spacing and the mean grain size distribution is observable. We found that it is possible to conduct CPMG sequences with an increased τ spacing. According to the acquisition time and enhanced diffusion the sequence parameters (number of pulses and τmax has to be chosen carefully. Otherwise the underestimated relaxation time (T2 will lead to misinterpretations.

  5. NMR Spectroscopy: Processing Strategies (by Peter Bigler)

    Science.gov (United States)

    Mills, Nancy S.

    1998-06-01

    Peter Bigler. VCH: New York, 1997. 249 pp. ISBN 3-527-28812-0. $99.00. This book, part of a four-volume series planned to deal with all aspects of a standard NMR experiment, is almost the exact book I have been hoping to find. My department has acquired, as have hundreds of other undergraduate institutions, high-field NMR instrumentation and the capability of doing extremely sophisticated experiments. However, the training is often a one- or two-day experience in which the material retained by the faculty trained is garbled and filled with holes, not unlike the information our students seem to retain. This text, and the accompanying exercises based on data contained on a CD-ROM, goes a long way to fill in the gaps and clarify misunderstandings about NMR processing.

  6. Characterization by NMR of ozonized methyl linoleate

    Energy Technology Data Exchange (ETDEWEB)

    Diaz, Maritza F. [National Center for Scientific Research, Havana (Cuba). Ozone Research Center. Dept. of Ozonized Substances]. E-mail: maritza.diaz@cnic.edu.cu; Gavin, Jose A. [University of the Laguna, Tenerife (Spain)

    2007-07-01

    In the present study ozonized methyl linoleate with peroxide index of 1,800 mmol-equiv kg{sup -1} was chemically characterized. Ozonation of methyl linoleate produced hydroperoxides, ozonides and aldehydes which were identified by {sup 1}H and {sup 13}C NMR two-dimensional. The standard methyl linoleate and ozonized methyl linoleate shown very similar {sup 1}H NMR spectra except for the signals at {delta} 9.7 and {delta} 9.6 that correspond to aldehydic hydrogen, {delta} 5.7 and {delta} 5.5 (olefinic signals from hydroperoxides) and {delta} 5.2 ppm (multiplet from ozonides methynic hydrogen). Other resonance assignments are based on the connectivities provided by the hydrogen scalar coupling constants. These results indicate that NMR spectroscopy can provide valuable information about the amount of formed oxygenated compounds in the ozonized methyl linoleate in order to use it to follow up ozone therapy and chemistry of ozonized vegetable oil. (author)

  7. Remote tuning of NMR probe circuits.

    Science.gov (United States)

    Kodibagkar, V D; Conradi, M S

    2000-05-01

    There are many circumstances in which the probe tuning adjustments cannot be located near the rf NMR coil. These may occur in high-temperature NMR, low-temperature NMR, and in the use of magnets with small diameter access bores. We address here circuitry for connecting a fixed-tuned probe circuit by a transmission line to a remotely located tuning network. In particular, the bandwidth over which the probe may be remotely tuned while keeping the losses in the transmission line acceptably low is considered. The results show that for all resonant circuit geometries (series, parallel, series-parallel), overcoupling of the line to the tuned circuit is key to obtaining a large tuning bandwidth. At equivalent extents of overcoupling, all resonant circuit geometries have nearly equal remote tuning bandwidths. Particularly for the case of low-loss transmission line, the tuning bandwidth can be many times the tuned circuit's bandwidth, f(o)/Q. PMID:10783273

  8. Deuterium NMR, induced and intrinsic cholesteric lyomesophases

    International Nuclear Information System (INIS)

    Induced and intrinsic cholesteric lyotropic mesophases were studied. Induced cholesteric lyomesophases based on potassium laurate (KL) system, with small amounts of cholesterol added, were studied by deuterium NMR and by polarizing microscopy. Order profiles obtained from deuterium NMR of KL perdenderated chains in both induced cholesteric and normal mesophases were compared. The intrinsic cholesteric lyotropic mesophases were based on the amphiphile potassium N-lauroyl serinate (KLNS) in the resolved levo form. The study of the type I intrinsic cholesteric mesophase was made by optical microscopy under polarized light and the type II intrinsic cholesteric lyomesophase was characterized by deuterium NMR. The new texture was explained by the use of the theory of disclinations developed for thermotropic liquid crystals, specially for cholesteric type. (M.J.C.)

  9. Early non-destructive biofouling detection in spiral wound RO Membranes using a mobile earth's field NMR

    KAUST Repository

    Fridjonsson, E.O.

    2015-04-20

    We demonstrate the use of Earth\\'s field (EF) Nuclear Magnetic Resonance (NMR) to provide early non-destructive detection of active biofouling of a commercial spiral wound reverse osmosis (RO) membrane module. The RO membrane module was actively biofouled to different extents, by the addition of biodegradable nutrients to the feed stream, as revealed by a subtle feed-channel pressure drop increase. Easily accessible EF NMR parameters (signal relaxation parameters T1, T2 and the total NMR signal modified to be sensitive to stagnant fluid only) were measured and analysed in terms of their ability to detect the onset of biofouling. The EF NMR showed that fouling near the membrane module entrance significantly distorted the flow field through the whole membrane module. The total NMR signal is shown to be suitable for non-destructive early biofouling detection of spiral wound membrane modules, it was readily deployed at high (operational) flow rates, was particularly sensitive to flow field changes due to biofouling and could be deployed at any position along the membrane module axis. In addition to providing early fouling detection, the mobile EF NMR apparatus could also be used to (i) evaluate the production process of spiral wound membrane modules, and (ii) provide an in-situ determination of module cleaning process efficiency.

  10. NMR Microscopy - Micron-Level Resolution.

    Science.gov (United States)

    Kwok, Wing-Chi Edmund

    1990-01-01

    Nuclear Magnetic Resonance Imaging (MRI) has been developed into a powerful and widely used diagnostic tool since the invention of techniques using linear magnetic field gradients in 1973. The variety of imaging contrasts obtainable in MRI, such as spin density, relaxation times and flow rate, gives MRI a significant advantage over other imaging techniques. For common diagnostic applications, image resolutions have been in the order of millimeters with slice thicknesses in centimeters. For many research applications, however, resolutions in the order of tens of microns or smaller are needed. NMR Imaging in these high resolution disciplines is known as NMR microscopy. Compared with conventional microscopy, NMR microscopy has the advantage of being non-invasive and non-destructive. The major obstacles of NMR microscopy are low signal-to-noise ratio and effects due to spin diffusion. To overcome these difficulties, more sensitive RF probes and very high magnetic field gradients have to be used. The most effective way to increase sensitivity is to build smaller probes. Microscope probes of different designs have been built and evaluated. Magnetic field gradient coils that can produce linear field gradients up to 450 Gauss/cm were also assembled. In addition, since microscope probes often employ remote capacitors for RF tuning, the associated signal loss in the transmission line was studied. Imaging experiments have been carried out in a 2.1 Tesla small bore superconducting magnet using the typical two-dimensional spin warp imaging technique. Images have been acquired for both biological and non-biological samples. The highest resolution was obtained in an image of a nerve bundle from the spinal cord of a racoon and has an in-plane resolution of 4 microns. These experiments have demonstrated the potential application of NMR microscopy to pathological research, nervous system study and non -destructive testings of materials. One way to further improve NMR microscopy is

  11. Conventions and nomenclature for double diffusion encoding NMR and MRI.

    Science.gov (United States)

    Shemesh, Noam; Jespersen, Sune N; Alexander, Daniel C; Cohen, Yoram; Drobnjak, Ivana; Dyrby, Tim B; Finsterbusch, Jurgen; Koch, Martin A; Kuder, Tristan; Laun, Fredrik; Lawrenz, Marco; Lundell, Henrik; Mitra, Partha P; Nilsson, Markus; Özarslan, Evren; Topgaard, Daniel; Westin, Carl-Fredrik

    2016-01-01

    Stejskal and Tanner's ingenious pulsed field gradient design from 1965 has made diffusion NMR and MRI the mainstay of most studies seeking to resolve microstructural information in porous systems in general and biological systems in particular. Methods extending beyond Stejskal and Tanner's design, such as double diffusion encoding (DDE) NMR and MRI, may provide novel quantifiable metrics that are less easily inferred from conventional diffusion acquisitions. Despite the growing interest on the topic, the terminology for the pulse sequences, their parameters, and the metrics that can be derived from them remains inconsistent and disparate among groups active in DDE. Here, we present a consensus of those groups on terminology for DDE sequences and associated concepts. Furthermore, the regimes in which DDE metrics appear to provide microstructural information that cannot be achieved using more conventional counterparts (in a model-free fashion) are elucidated. We highlight in particular DDE's potential for determining microscopic diffusion anisotropy and microscopic fractional anisotropy, which offer metrics of microscopic features independent of orientation dispersion and thus provide information complementary to the standard, macroscopic, fractional anisotropy conventionally obtained by diffusion MR. Finally, we discuss future vistas and perspectives for DDE. PMID:26418050

  12. NMR and Mushrooms : imaging post harvest senescence

    NARCIS (Netherlands)

    Donker, H.C.W.

    1999-01-01

    The objective of the study described in this thesis was to explore the potentials of NMR for the study of water relations in harvested mushrooms ( Agaricus bisporus ). Since harvested mushrooms tend to continue their growth after harvest, their morphogenesis is heavily influenced by the external cli

  13. Responsibilities of NMR application in research

    International Nuclear Information System (INIS)

    NMR investigations in clinical and/or scientific studies may be covered by different radiation protection regulations and legal liability responsibilities. The following topics are discussed: incidental findings, applicability to the situation in radiological hospitals, explicit abandonment of probands/patients, liability of the clinic, liability with respect to contrast agent administration, creation of additional imaging, attendance of radiologists, information requirements.

  14. Hyperpolarized NMR Probes for Biological Assays

    Directory of Open Access Journals (Sweden)

    Sebastian Meier

    2014-01-01

    Full Text Available During the last decade, the development of nuclear spin polarization enhanced (hyperpolarized molecular probes has opened up new opportunities for studying the inner workings of living cells in real time. The hyperpolarized probes are produced ex situ, introduced into biological systems and detected with high sensitivity and contrast against background signals using high resolution NMR spectroscopy. A variety of natural, derivatized and designed hyperpolarized probes has emerged for diverse biological studies including assays of intracellular reaction progression, pathway kinetics, probe uptake and export, pH, redox state, reactive oxygen species, ion concentrations, drug efficacy or oncogenic signaling. These probes are readily used directly under natural conditions in biofluids and are often directly developed and optimized for cellular assays, thus leaving little doubt about their specificity and utility under biologically relevant conditions. Hyperpolarized molecular probes for biological NMR spectroscopy enable the unbiased detection of complex processes by virtue of the high spectral resolution, structural specificity and quantifiability of NMR signals. Here, we provide a survey of strategies used for the selection, design and use of hyperpolarized NMR probes in biological assays, and describe current limitations and developments.

  15. SQUID detected NMR in microtesla magnetic fields

    Science.gov (United States)

    Matlachov, Andrei N.; Volegov, Petr L.; Espy, Michelle A.; George, John S.; Kraus, Robert H.

    2004-09-01

    We have built an NMR system that employs a superconducting quantum interference device (SQUID) detector and operates in measurement fields of 2-25 μT. The system uses a pre-polarizing field from 4 to 30 mT generated by simple room-temperature wire-wound coils that are turned off during measurements. The instrument has an open geometry with samples located outside the cryostat at room-temperature. This removes constraints on sample size and allows us to obtain signals from living tissue. We have obtained 1H NMR spectra from a variety of samples including water, mineral oil, and a live frog. We also acquired gradient encoded free induction decay (FID) data from a water-plastic phantom in the μT regime, from which simple projection images were reconstructed. NMR signals from samples inside metallic containers have also been acquired. This is possible because the penetration skin depth is much greater at the low operating frequencies of this system than for conventional systems. Advantages to ultra-low field NMR measurements include lower susceptibility artifacts caused by high strength polarizing and measurement fields, and negligible line width broadening due to measurement field inhomogeneity, reducing the burden of producing highly homogeneous fields.

  16. Structural Studies of Biological Solids Using NMR

    Science.gov (United States)

    Ramamoorthy, Ayyalusamy

    2011-03-01

    High-resolution structure and dynamics of biological molecules are important in understanding their function. While studies have been successful in solving the structures of water-soluble biomolecules, it has been proven difficult to determine the structures of membrane proteins and fibril systems. Recent studies have shown that solid-state NMR is a promising technique and could be highly valuable in studying such non-crystalline and non-soluble biosystems. I will present strategies to study the structures of such challenging systems and also about the applications of solid-state NMR to study the modes of membrane-peptide interactions for a better assessment of the prospects of antimicrobial peptides as substitutes to antibiotics in the control of human disease. Our studies on the mechanism of membrane disruption by LL-37 (a human antimicrobial peptide), analogs of the naturally occurring antimicrobial peptide magainin2 extracted from the skin of the African frog Xenopus Laevis, and pardaxin will be presented. Solid-state NMR experiments were used to determine the secondary structure, dynamics and topology of these peptides in lipid bilayers. Similarities and difference in the cell-lysing mechanism, and their dependence on the membrane composition, of these peptides will be discussed. Atomic-level resolution NMR structures of amyloidogenic proteins revealing the misfolding pathway and early intermediates that play key roles in amyloid toxicity will also be presented.

  17. NMR of porous Bio-systems

    NARCIS (Netherlands)

    Snaar, E.J.M.

    2002-01-01

    The structure and dynamics of water diffusion and -transport at a microscale in heterogeneous porous media have been investigated using various 1H NMR techniques. In particular in biological porous media the dynamics are usually very complex since it is intimately related to th

  18. Progress in NMR Applications to Well Logging and Formation Evaluation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    @@ Since its discovery in 1946, NMR has become a valuable tool in physics, chemistry, biology, and medicine. With the invention of NMR logging tools that take the medical MRI or laboratory NMR equipment and turn it inside-out, the application of sophisticated laboratory techniques to determine formation properties in situ is now available. The capability has opened a new era in formation evaluation just as the introduction of NMR has revolutionized the other scientific areas.

  19. Solid-state NMR studies of supercapacitors.

    Science.gov (United States)

    Griffin, John M; Forse, Alexander C; Grey, Clare P

    2016-01-01

    Electrochemical double-layer capacitors, or 'supercapacitors' are attracting increasing attention as high-power energy storage devices for a wide range of technological applications. These devices store charge through electrostatic interactions between liquid electrolyte ions and the surfaces of porous carbon electrodes. However, many aspects of the fundamental mechanism of supercapacitance are still not well understood, and there is a lack of experimental techniques which are capable of studying working devices. Recently, solid-state NMR has emerged as a powerful tool for studying the local environments and behaviour of electrolyte ions in supercapacitor electrodes. In this Trends article, we review these recent developments and applications. We first discuss the basic principles underlying the mechanism of supercapacitance, as well as the key NMR observables that are relevant to the study of supercapacitor electrodes. We then review some practical aspects of the study of working devices using ex situ and in situ methodologies and explain the key advances that these techniques have allowed on the study of supercapacitor charging mechanisms. NMR experiments have revealed that the pores of the carbon electrodes contain a significant number of electrolyte ions in the absence of any charging potential. This has important implications for the molecular mechanisms of supercapacitance, as charge can be stored by different ion adsorption/desorption processes. Crucially, we show how in situ NMR experiments can be used to quantitatively study and characterise the charging mechanism, with the experiments providing the most detailed picture of charge storage to date, offering the opportunity to design enhanced devices. Finally, an outlook for future directions for solid-state NMR in supercapacitor research is offered. PMID:26974032

  20. Performance of the WeNMR CS-Rosetta3 web server in CASD-NMR

    Energy Technology Data Exchange (ETDEWEB)

    Schot, Gijs van der [Uppsala University, Laboratory of Molecular Biophysics, Department of Cell and Molecular Biology (Sweden); Bonvin, Alexandre M. J. J., E-mail: a.m.j.j.bonvin@uu.nl [Utrecht University, Faculty of Science – Chemistry, Bijvoet Center for Biomolecular Research (Netherlands)

    2015-08-15

    We present here the performance of the WeNMR CS-Rosetta3 web server in CASD-NMR, the critical assessment of automated structure determination by NMR. The CS-Rosetta server uses only chemical shifts for structure prediction, in combination, when available, with a post-scoring procedure based on unassigned NOE lists (Huang et al. in J Am Chem Soc 127:1665–1674, 2005b, doi: 10.1021/ja047109h 10.1021/ja047109h ). We compare the original submissions using a previous version of the server based on Rosetta version 2.6 with recalculated targets using the new R3FP fragment picker for fragment selection and implementing a new annotation of prediction reliability (van der Schot et al. in J Biomol NMR 57:27–35, 2013, doi: 10.1007/s10858-013-9762-6 10.1007/s10858-013-9762-6 ), both implemented in the CS-Rosetta3 WeNMR server. In this second round of CASD-NMR, the WeNMR CS-Rosetta server has demonstrated a much better performance than in the first round since only converged targets were submitted. Further, recalculation of all CASD-NMR targets using the new version of the server demonstrates that our new annotation of prediction quality is giving reliable results. Predictions annotated as weak are often found to provide useful models, but only for a fraction of the sequence, and should therefore only be used with caution.

  1. Performance of the WeNMR CS-Rosetta3 web server in CASD-NMR

    International Nuclear Information System (INIS)

    We present here the performance of the WeNMR CS-Rosetta3 web server in CASD-NMR, the critical assessment of automated structure determination by NMR. The CS-Rosetta server uses only chemical shifts for structure prediction, in combination, when available, with a post-scoring procedure based on unassigned NOE lists (Huang et al. in J Am Chem Soc 127:1665–1674, 2005b, doi: 10.1021/ja047109h 10.1021/ja047109h ). We compare the original submissions using a previous version of the server based on Rosetta version 2.6 with recalculated targets using the new R3FP fragment picker for fragment selection and implementing a new annotation of prediction reliability (van der Schot et al. in J Biomol NMR 57:27–35, 2013, doi: 10.1007/s10858-013-9762-6 10.1007/s10858-013-9762-6 ), both implemented in the CS-Rosetta3 WeNMR server. In this second round of CASD-NMR, the WeNMR CS-Rosetta server has demonstrated a much better performance than in the first round since only converged targets were submitted. Further, recalculation of all CASD-NMR targets using the new version of the server demonstrates that our new annotation of prediction quality is giving reliable results. Predictions annotated as weak are often found to provide useful models, but only for a fraction of the sequence, and should therefore only be used with caution

  2. Several Applications of NMR in Organic Chemistry Research

    Institute of Scientific and Technical Information of China (English)

    CUI yuxin; LIU xuehui; XU hao

    2001-01-01

    @@ Modem NMR techniques, especially 2D-NMR have presented their powerful application in organic chemistry. Not only in structural determination, mechanism investigation, but also in solution conformation study for natural products. In this paper, various pulse field gradient NMR techniques such as COSY, NOESY, HMBC and HMQC were combined to study these problems.

  3. Study of NMR porosity for terrestrial formation in China

    Institute of Scientific and Technical Information of China (English)

    WANG Xiaowen; XIAO Lizhi; XIE Ranhong; ZHANG Yuanzhong

    2006-01-01

    NMR logging is an effective method for porosity measurement. NMR-derived porosity only comes from the pore fluid and is, in principle, not affected by rock matrix. However, it is found that the difference between NMR-derived and conventional log-derived porosities is often between 2 to 6 pu, which is unacceptable, in terrestrial formation in China. In the paper, the theory of NMR porosity was reviewed. The influence factors on NMR porosity error were analyzed based on NMR core measurements. More than 30 core samples with a wide range of porosities including sandstone, limestone and artificial ceramic were chosen for the conventional and NMR porosity measurements. The current NMR data acquisition method was studied based on laboratory NMR core measurements and found to be not good for terrestrial formation. A new NMR data acquisition method suiting for terrestrial formation in China was proposed and much improved the accuracy of NMR porosity measurement. It is suggested that the analysis of core samples from different regions should be carried out before logging in order to obtain accurate NMR porosity.

  4. Several Applications of NMR in Organic Chemistry Research

    Institute of Scientific and Technical Information of China (English)

    CUI; yuxin; XU; hao

    2001-01-01

    Modem NMR techniques, especially 2D-NMR have presented their powerful application in organic chemistry. Not only in structural determination, mechanism investigation, but also in solution conformation study for natural products. In this paper, various pulse field gradient NMR techniques such as COSY, NOESY, HMBC and HMQC were combined to study these problems.  ……

  5. e-NMR gLite grid enabled infrastructure

    NARCIS (Netherlands)

    Ferreira, N.L.; Wassenaar, T.A.; de Vries, S.J.; van Dijk, M.; van der Schot, G.; van der Zwan, J.; Boelens, R.; Bonvin, A.M.J.J.; Giachetti, A.; Carotenuto, D.; Rosato, A.; Bertini, I.; Herrmann, T.; Bagaria, A.; Zharavin, V.; Jonker, H.R.A.; Güntert, P.; Schwalbe, H.; Vranken, W.F.

    2010-01-01

    The e-NMR project is an European e-infrastructure that aims at providing the bio-NMR community with a software platform integrating and streamlining computational approaches necessary for NMR data analysis. The infrastructure is grid enabled with fteen gLite based partners sharing computational reso

  6. Lithological control on gas hydrate saturation as revealed by signal classification of NMR logging data

    Science.gov (United States)

    Bauer, Klaus; Kulenkampff, Johannes; Henninges, Jan; Spangenberg, Erik

    2015-09-01

    In this paper, nuclear magnetic resonance (NMR) downhole logging data are analyzed with a new strategy to study gas hydrate-bearing sediments in the Mackenzie Delta (NW Canada). In NMR logging, transverse relaxation time (T2) distribution curves are usually used to determine single-valued parameters such as apparent total porosity or hydrocarbon saturation. Our approach analyzes the entire T2 distribution curves as quasi-continuous signals to characterize the rock formation. We apply self-organizing maps, a neural network clustering technique, to subdivide the data set of NMR curves into classes with a similar and distinctive signal shape. The method includes (1) preparation of data vectors, (2) unsupervised learning, (3) cluster definition, and (4) classification and depth mapping of all NMR signals. Each signal class thus represents a specific pore size distribution which can be interpreted in terms of distinct lithologies and reservoir types. A key step in the interpretation strategy is to reconcile the NMR classes with other log data not considered in the clustering analysis, such as gamma ray, hydrate saturation, and other logs. Our results defined six main lithologies within the target zone. Gas hydrate layers were recognized by their low signal amplitudes for all relaxation times. Most importantly, two subtypes of hydrate-bearing shaly sands were identified. They show distinct NMR signals and differ in hydrate saturation and gamma ray values. An inverse linear relationship between hydrate saturation and clay content was concluded. Finally, we infer that the gas hydrate is not grain coating, but rather, pore filling with matrix support is the preferred growth habit model for the studied formation.

  7. From crystalline to glassy gallium fluoride materials: an NMR study of 69Ga and 71Ga quadrupolar nuclei.

    Science.gov (United States)

    Bureau, B; Silly, G; Buzaré, J Y; Legein, C; Massiot, D

    1999-11-01

    Owing to the implementation of acquisition techniques specific for nuclei with very large quadrupolar interaction (full shifted echo and variable offset cumulative spectra (VOCS)), NMR spectra of 69Ga and 71Ga are obtained in crystallised (PbGaF5, Pb3Ga2F12, Pb9Ga2F24 and CsZnGaF6) and glassy (PbF2-ZnF2-GaF3) gallium fluorides. Simulations of both static (full echo or VOCS) and 15 kHz MAS spectra allow to obtain consistent determinations of isotropic chemical shifts and very large quadrupolar parameters (nuQ up to 14 MHz). In the crystalline compounds whose structures are unknown, the number and the local symmetry of the different gallium sites are tentatively worked out. For the glassy systems, a continuous Czjzek's distribution of the NMR quadrupolar parameters accounts for the particular shape of the NMR spectrum. PMID:10670905

  8. NMR CHARACTERIZATIONS OF PROPERTIES OF HETEROGENEOUS MEDIA

    Energy Technology Data Exchange (ETDEWEB)

    C.T. Philip Chang; Changho Choi; Jeromy T. Hollenshead; Rudi Michalak; Jack Phan; Ramon Saavedra; John C. Slattery; Jinsoo Uh; Randi Valestrand; A. Ted Watson; Song Xue

    2005-01-01

    A critical and long-standing need within the petroleum industry is the specification of suitable petrophysical properties for mathematical simulation of fluid flow in petroleum reservoirs (i.e., reservoir characterization). The development of accurate reservoir characterizations is extremely challenging. Property variations may be described on many scales, and the information available from measurements reflect different scales. In fact, experiments on laboratory core samples, well-log data, well-test data, and reservoir-production data all represent information potentially valuable to reservoir characterization, yet they all reflect information about spatial variations of properties at different scales. Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) provide enormous potential for developing new descriptions and understandings of heterogeneous media. NMR has the rare capability to probe permeable media non-invasively, with spatial resolution, and it provides unique information about molecular motions and interactions that are sensitive to morphology. NMR well-logging provides the best opportunity ever to resolve permeability distributions within petroleum reservoirs. We develop MRI methods to determine, for the first time, spatially resolved distributions of porosity and permeability within permeable media samples that approach the intrinsic scale: the finest resolution of these macroscopic properties possible. To our knowledge, this is the first time that the permeability is actually resolved at a scale smaller than the sample. In order to do this, we have developed a robust method to determine of relaxation distributions from NMR experiments and a novel implementation and analysis of MRI experiments to determine the amount of fluid corresponding to imaging regions, which are in turn used to determine porosity and saturation distributions. We have developed a novel MRI experiment to determine velocity distributions within flowing experiments, and

  9. Direct 13C NMR Detection in HPLC Hyphenation Mode

    DEFF Research Database (Denmark)

    Wubshet, Sileshi Gizachew; Johansen, Kenneth; Nyberg, Nils;

    2012-01-01

    Solid phase extraction (SPE) was introduced as a crucial step in the HPLC-SPE-NMR technique to enable online analyte enrichment from which proton-detected NMR experiments on submicrogram amounts from complex mixtures were possible. However, the significance of direct-detected (13)C NMR experiments...... application of HPLC-SPE-NMR analysis using direct-detected (13)C NMR spectra. HPLC column loading, accumulative SPE trappings, and the effect of different elution solvents were evaluated and optimized. A column loading of approximately 600 mug of a prefractionated triterpenoid mixture, six trappings...

  10. Solid state NMR of biopolymers and synthetic polymers

    Energy Technology Data Exchange (ETDEWEB)

    Jelinski, Lynn W. [Cornell Univ., Geneva, NY (United States)

    1995-12-31

    Solid state NMR has been invaluable in evaluating the structure, phase separation, and dynamics of polymers. Because polymers are generally used in the solid state, solid state NMR is especially powerful because it provides information about the materials in their native state. This review gives a general overview of solid state NMR, concentrating on solid state {sup 13} C and {sup 2} H NMR. It then focuses on two examples: the biopolymer spider silka and the engineering material polyurethane. It illustrates how solid state NMR can provide new information about synthetic and bio-polymers. (author) 11 refs., 5 figs., 3 tabs.

  11. Solution conformation and dynamics of a tetrasaccharide related to the Lewis{sup X} antigen deduced by NMR relaxation measurements

    Energy Technology Data Exchange (ETDEWEB)

    Poveda, Ana [Universidad Autonoma de Madrid, Servicio Interdepartamental de Investigacion (Spain); Asensio, Juan Luis; Martin-Pastor, Manuel; Jimenez-Barbero, Jesus [Instituto de Quimica Organica, CSIC, Grupo de Carbohidratos (Spain)

    1997-07-15

    {sup 1}H-NMR cross-relaxation rates and nonselective longitudinal relaxation times have been obtained at two magnetic fields (7.0 and 11.8 T) and at a variety of temperatures for the branched tetrasaccharide methyl 3-O-{alpha}-N-acetyl-galactosaminyl-{beta}-galactopyranosyl-(1{sup {yields}}4)[3-O-{alpha}-fucosyl] -glucopyranoside (1), an inhibitor of astrocyte growth. In addition, {sup 13}C-NMR relaxation data have also been recorded at both fields. The {sup 1}H-NMR relaxation data have been interpreted using different motional models to obtain proton-proton correlation times. The results indicate that the GalNAc and Fuc rings display more extensive local motion than the two inner Glc and Gal moieties, since those present significantly shorter local correlation times. The{sup 13}C-NMR relaxation parameters have been interpreted in terms of the Lipari-Szabo model-free approach. Thus, order parameters and internal motion correlation times have been deduced. As obtained for the{sup 1}H-NMR relaxation data, the two outer residues possess smaller order parameters than the two inner rings. Internal correlation times are in the order of 100 ps. The hydroxymethyl groups have also different behaviour,with the exocyclic carbon on the glucopyranoside unit showing the highestS{sup 2}. Molecular dynamics simulations using a solvated system have also been performed and internal motion correlation functions have been deduced from these calculations. Order parameters and interproton distances have been compared to those inferred from the NMR measurements. The obtained results are in fair agreement with the experimental data.

  12. Nuclear spin noise in NMR revisited

    Energy Technology Data Exchange (ETDEWEB)

    Ferrand, Guillaume; Luong, Michel [Laboratoire d’Ingénierie des Systèmes Accélérateurs et des Hyperfréquences, SACM, CEA, Université Paris-Saclay, CEA/Saclay, F-91191 Gif-sur-Yvette (France); Huber, Gaspard; Desvaux, Hervé, E-mail: herve.desvaux@cea.fr [Laboratoire Structure et Dynamique par Résonance Magnétique, NIMBE, CEA, CNRS, Université Paris-Saclay, CEA/Saclay, F-91191 Gif-sur-Yvette (France)

    2015-09-07

    The theoretical shapes of nuclear spin-noise spectra in NMR are derived by considering a receiver circuit with finite preamplifier input impedance and a transmission line between the preamplifier and the probe. Using this model, it becomes possible to reproduce all observed experimental features: variation of the NMR resonance linewidth as a function of the transmission line phase, nuclear spin-noise signals appearing as a “bump” or as a “dip” superimposed on the average electronic noise level even for a spin system and probe at the same temperature, pure in-phase Lorentzian spin-noise signals exhibiting non-vanishing frequency shifts. Extensive comparisons to experimental measurements validate the model predictions, and define the conditions for obtaining pure in-phase Lorentzian-shape nuclear spin noise with a vanishing frequency shift, in other words, the conditions for simultaneously obtaining the spin-noise and frequency-shift tuning optima.

  13. Nuclear spin noise in NMR revisited

    International Nuclear Information System (INIS)

    The theoretical shapes of nuclear spin-noise spectra in NMR are derived by considering a receiver circuit with finite preamplifier input impedance and a transmission line between the preamplifier and the probe. Using this model, it becomes possible to reproduce all observed experimental features: variation of the NMR resonance linewidth as a function of the transmission line phase, nuclear spin-noise signals appearing as a “bump” or as a “dip” superimposed on the average electronic noise level even for a spin system and probe at the same temperature, pure in-phase Lorentzian spin-noise signals exhibiting non-vanishing frequency shifts. Extensive comparisons to experimental measurements validate the model predictions, and define the conditions for obtaining pure in-phase Lorentzian-shape nuclear spin noise with a vanishing frequency shift, in other words, the conditions for simultaneously obtaining the spin-noise and frequency-shift tuning optima

  14. Nuclear spin noise in NMR revisited

    Science.gov (United States)

    Ferrand, Guillaume; Huber, Gaspard; Luong, Michel; Desvaux, Hervé

    2015-09-01

    The theoretical shapes of nuclear spin-noise spectra in NMR are derived by considering a receiver circuit with finite preamplifier input impedance and a transmission line between the preamplifier and the probe. Using this model, it becomes possible to reproduce all observed experimental features: variation of the NMR resonance linewidth as a function of the transmission line phase, nuclear spin-noise signals appearing as a "bump" or as a "dip" superimposed on the average electronic noise level even for a spin system and probe at the same temperature, pure in-phase Lorentzian spin-noise signals exhibiting non-vanishing frequency shifts. Extensive comparisons to experimental measurements validate the model predictions, and define the conditions for obtaining pure in-phase Lorentzian-shape nuclear spin noise with a vanishing frequency shift, in other words, the conditions for simultaneously obtaining the spin-noise and frequency-shift tuning optima.

  15. Nuclear spin noise in NMR revisited

    CERN Document Server

    Ferrand, Guillaume; Luong, Michel; Desvaux, Hervé

    2015-01-01

    The theoretical shapes of nuclear spin-noise spectra in NMR are derived by considering a receiver circuit with finite, preamplifier input impedance and a transmission line between the preamplifier and the probe. Using this model, it becomes possible to reproduce all observed experimental features: variation of the NMR resonance linewidth as a function of the transmission line phase, nuclear spin-noise signals appearing as a "bump" or as a "dip" superimposed on the average electronic noise level even for a spin system and probe at the same temperature, pure in-phase Lorentzian spin-noise signals exhibiting non-vanishing frequency shifts. Extensive comparison to experimental measurements validate the model predictions, and define the conditions for obtaining pure in-phase Lorentzian-shape nuclear spin noise with a vanishing frequency shift, in other words, the conditions for simultaneously obtaining the Spin-Noise and Frequency-Shift Tuning Optima.

  16. NMR with excitation modulated by Frank sequences.

    Science.gov (United States)

    Blümich, Bernhard; Gong, Qingxia; Byrne, Eimear; Greferath, Marcus

    2009-07-01

    Miniaturized NMR is of growing importance in bio-, chemical, and -material sciences. Other than the magnet, bulky components are the radio-frequency power amplifier and the power supply or battery pack. We show that constant flip-angle excitation with phase modulation following a particular type of polyphase perfect sequences results in low peak excitation power at high response peak power. It has ideal power distribution in both the time domain and the frequency domain. A savings in peak excitation power of six orders of magnitude has been realized compared to conventionally pulsed excitation. Among others, the excitation promises to be of use for button-cell operated miniature NMR devices as well as for complying with specific-absorption-rate regulations in high-field medical imaging. PMID:19386525

  17. NMR-Based Diffusion Lattice Imaging

    CERN Document Server

    Laun, Frederik Bernd

    2013-01-01

    Nuclear magnetic resonance (NMR) diffusion experiments are widely employed as they yield information about structures hindering the diffusion process, e.g. about cell membranes. While it has been shown in recent articles, that these experiments can be used to determine the exact shape of closed pores averaged over a volume of interest, it is still an open question how much information can be gained in open systems. In this theoretical work, we show that the full structure information of periodic open systems is accessible. To this end, the so-called 'SEquential Rephasing by Pulsed field-gradient Encoding N Time-intervals' (SERPENT) sequence is used, which employs several diffusion weighting gradient pulses with different amplitudes. The structural information is obtained by an iterative technique relying on a Gaussian envelope model of the diffusion propagator. Two solid matrices that are surrounded by an NMR-visible medium are considered: a hexagonal lattice of cylinders and a cubic lattice of triangles.

  18. Exploring the limits to spatially resolved NMR

    Energy Technology Data Exchange (ETDEWEB)

    Gaedke, Achim; Nestle, Nikolaus [TU Darmstadt, Institute of Condensed Matter Physics (Germany)

    2010-07-01

    Recent advances in MRI have demonstrated resolutions down to 1 {mu}m. Magnetic resonance force microscopy has the potential to reach sensitivity for single nuclear spins. Given these numbers, in vivo imaging of single cells or even biomacromolecules may seem possible. However, for in vivo applications, there are fundamental differences in the contrast mechanisms compared to MRI at macroscopic scales as the length scale of of molecular self-diffusion exceeds that of the spatial resolution on the NMR time scale. Those effects - which are fundamentally different from the echo attenuation in field gradient NMR - even may lead to general limitations on the spatial resolution achievable in aqueous systems with high water content. In our contribution, we explore those effects on a model system in a high-resolution stray-field imaging setup. In addition to experimental results, simulations based on the Bloch-Torrey equation are presented.

  19. NMR-based diffusion lattice imaging.

    Science.gov (United States)

    Laun, Frederik Bernd; Müller, Lars; Kuder, Tristan Anselm

    2016-03-01

    Nuclear magnetic resonance (NMR) diffusion experiments are widely employed as they yield information about structures hindering the diffusion process, e.g., about cell membranes. While it has been shown in recent articles that these experiments can be used to determine the shape of closed pores averaged over a volume of interest, it is still an open question how much information can be gained in open well-connected systems. In this theoretical work, it is shown that the full structure information of connected periodic systems is accessible. To this end, the so-called "SEquential Rephasing by Pulsed field-gradient Encoding N Time intervals" (SERPENT) sequence is used, which employs several diffusion encoding gradient pulses with different amplitudes. Two two-dimensional solid matrices that are surrounded by an NMR-visible medium are considered: a hexagonal lattice of cylinders and a rectangular lattice of isosceles triangles. PMID:27078384

  20. NMR studies of nucleic acid dynamics

    Science.gov (United States)

    Al-Hashimi, Hashim M.

    2013-12-01

    Nucleic acid structures have to satisfy two diametrically opposite requirements; on one hand they have to adopt well-defined 3D structures that can be specifically recognized by proteins; on the other hand, their structures must be sufficiently flexible to undergo very large conformational changes that are required during key biochemical processes, including replication, transcription, and translation. How do nucleic acids introduce flexibility into their 3D structure without losing biological specificity? Here, I describe the development and application of NMR spectroscopic techniques in my laboratory for characterizing the dynamic properties of nucleic acids that tightly integrate a broad set of NMR measurements, including residual dipolar couplings, spin relaxation, and relaxation dispersion with sample engineering and computational approaches. This approach allowed us to obtain fundamental new insights into directional flexibility in nucleic acids that enable their structures to change in a very specific functional manner.

  1. NMR spectral analysis using prior knowledge

    Science.gov (United States)

    Kasai, Takuma; Nagata, Kenji; Okada, Masato; Kigawa, Takanori

    2016-03-01

    Signal assignment is a fundamental step for analyses of protein structure and dynamics with nuclear magnetic resonance (NMR). Main-chain signal assignment is achieved with a sequential assignment method and/or an amino-acid selective stable isotope labeling (AASIL) method. Combinatorial selective labeling (CSL) methods, as well as our labeling strategy, stable isotope encoding (SiCode), were developed to reduce the required number of labeled samples, since one of the drawbacks of AASIL is that many samples are needed. Signal overlapping in NMR spectra interferes with amino-acid determination by CSL and SiCode. Since spectral deconvolution by peak fitting with a gradient method cannot resolve closely overlapped signals, we developed a new method to perform both peak fitting and amino acid determination simultaneously, with a replica exchange Monte Carlo method, incorporating prior knowledge of stable-isotope labeling ratios and the amino-acid sequence of the protein.

  2. NMR-based diffusion lattice imaging

    Science.gov (United States)

    Laun, Frederik Bernd; Müller, Lars; Kuder, Tristan Anselm

    2016-03-01

    Nuclear magnetic resonance (NMR) diffusion experiments are widely employed as they yield information about structures hindering the diffusion process, e.g., about cell membranes. While it has been shown in recent articles that these experiments can be used to determine the shape of closed pores averaged over a volume of interest, it is still an open question how much information can be gained in open well-connected systems. In this theoretical work, it is shown that the full structure information of connected periodic systems is accessible. To this end, the so-called "SEquential Rephasing by Pulsed field-gradient Encoding N Time intervals" (SERPENT) sequence is used, which employs several diffusion encoding gradient pulses with different amplitudes. Two two-dimensional solid matrices that are surrounded by an NMR-visible medium are considered: a hexagonal lattice of cylinders and a rectangular lattice of isosceles triangles.

  3. An NMR study on shale wettability

    Energy Technology Data Exchange (ETDEWEB)

    Odusina, Elijah; Sondergeld, Carl; Rai, Chandra [University of Oklahoma (United States)

    2011-07-01

    In recent years, the importance of shales as unconventional gas resources has grown significantly. It is therefore important to reach a better understanding of their petrophysical properties. One of the important rock properties that is directly linked to successful hydrocarbon recovery is wettability. This paper presents a study on shale wettability using nuclear magnetic resonance (NMR) to monitor sequential imbibition of brine and oil. Due to the presence of mineralogical variations, low permeability and viscosity, and complex pore structure, the interpretation of wettability using conventional approaches becomes complex. Samples that included 21 core plugs from the Eagle Ford shale, 12 from the Barnett, 11 from the Floyd, and 10 from the Woodford shale were analyzed. The NMR study confirmed the water-wet behavior of Berea sandstone. From the study, it was seen that the Woodford shale showed more affinity for dodecane than did the other shales.

  4. Lithological controls on gas hydrate saturation: Insights from signal classification of NMR downhole data

    Science.gov (United States)

    Bauer, Klaus; Kulenkampff, Johannes; Henninges, Jan; Spangenberg, Erik

    2016-04-01

    Nuclear magnetic resonance (NMR) downhole data are analyzed with a new strategy to study gas hydrate-bearing sediments in the Mackenzie Delta (NW Canada). NMR logging is a powerful tool to study geological reservoir formations. The measurements are based on interactions between the magnetic moments of protons in geological formation water and an external magnetic field. Inversion of the measured raw data provides so-called transverse relaxation time (T2) distribution curves or spectra. Different parts of the T2 curve are related with distinct pore radii and corresponding fluid components. A common practice in the analysis of T2 distribution curves is to extract single-valued parameters such as apparent total porosity. Moreover, the derived total NMR apparent porosity and the gamma-gamma density log apparent porosity can be combined to estimate gas hydrate saturation in hydrate-bearing sediments. To avoid potential loss of information, in our new approach we analyze the entire T2 distribution curves as quasi-continuous signals to characterize the rock formation. The approach is applied to NMR data measured in gas hydrate research well Mallik 5L-38. We use self-organizing maps, a neural network clustering technique, to subdivide the data set of NMR T2 distribution curves into classes with a similar and distinctive signal shape. The method includes (1) preparation of data vectors, (2) unsupervised learning, (3) cluster definition, and (4) classification and depth mapping of all NMR signals. Each signal class thus represents a specific pore size distribution which can be interpreted in terms of distinct lithologies and reservoir types. A key step in the interpretation strategy is to reconcile the NMR classes with other log data not considered in the clustering analysis, such as gamma ray, photo-electric factor, hydrate saturation, and other logs. Our results defined six main lithologies within the target zone. Gas hydrate layers were recognized by their low signal

  5. The stoichiometry of synthetic alunite as a function of hydrothermal aging investigated by solid-state NMR spectroscopy, powder X-ray diffraction and infrared spectroscopy

    DEFF Research Database (Denmark)

    Grube, Elisabeth; Nielsen, Ulla Gro

    2015-01-01

    angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The 1H MAS NMR spectra recorded at high magnetic field (21.1 T, 900 MHz) allowed for a clear separation of the different proton environments and for quantitative determination of the aluminum vacancy concentration as a function of time....... The concentration of structural defects determined from, i.e., aluminum vacancies was reduced from 4 to 1 %, as the reaction time was extended from one to 31 days based on 1H MAS NMR. This was further supported by an increase of the unit cell parameter c, which is indicative of the relative concentration...

  6. NMR investigations of G-quadruplex structures

    OpenAIRE

    Bessi, Irene

    2016-01-01

    This thesis deals with the NMR characterization of the structure and the folding dynamics of DNA G quadruplexes as potential therapeutic target in cancer therapy and building block for DNA based nanotechnology. The first part of this thesis (Chapters 1-5) introduces the reader to the world of G quadruplexes. The main features of the classic Watson Crick double helix and alternative non B DNA structures are illustrated in Chapter 1. Many different base pairing schemes are possible, besid...

  7. Funktionelle NMR-Mikroskopie an Pflanzenwurzeln

    OpenAIRE

    Kaufmann, Ilja

    2009-01-01

    Als nicht-invasive Methode bietet die magnetische Kernspinresonanztomographie durch ihre Vielzahl an messbaren Größen wie Wassergehalt und Flussgeschwindigkeiten gute Voraussetzungen, um funktionelle Abläufe in Pflanzen und insbesondere Pflanzenwurzeln zu untersuchen. Für funktionelle NMR-Mikroskopie notwendige Hardware und Methoden wurden in dieser Arbeit entwickelt und angewendet. Aufgrund der starken Suszeptibilitätsunterschiede in den Proben und der notwendigen Zeitauflösung für funktione...

  8. Structure of high-resolution NMR spectra

    CERN Document Server

    Corio, PL

    2012-01-01

    Structure of High-Resolution NMR Spectra provides the principles, theories, and mathematical and physical concepts of high-resolution nuclear magnetic resonance spectra.The book presents the elementary theory of magnetic resonance; the quantum mechanical theory of angular momentum; the general theory of steady state spectra; and multiple quantum transitions, double resonance and spin echo experiments.Physicists, chemists, and researchers will find the book a valuable reference text.

  9. NMR Structural Studies on Alamethicin Dimers

    Institute of Scientific and Technical Information of China (English)

    李星

    2003-01-01

    15N labeled alamethicin dimer was synthesized. The structure and dynamics of alamethicin dimers were studied with nuclear magnetic resonance (NMR) spectroscopy. The data from 15N-labeled alamethicin dimer suggest little differences in conformation between the dimer and monomer in the Aib1-Pro14 region. Significant difference in the conformation of the C-terminus are manifest in the NH chemical shifts in the Val15-Pho20 region.

  10. Physiological parameters

    International Nuclear Information System (INIS)

    The physiological characteristics of man depend on the intake, metabolism and excretion of stable elements from food, water, and air. The physiological behavior of natural radionuclides and radionuclides from nuclear weapons testing and from the utilization of nuclear energy is believed to follow the pattern of stable elements. Hence information on the normal physiological processes occurring in the human body plays an important role in the assessment of the radiation dose received by man. Two important physiological parameters needed for internal dose determination are the pulmonary function and the water balance. In the Coordinated Research Programme on the characterization of Asian population, five participants submitted data on these physiological characteristics - China, India, Japan, Philippines and Viet Nam. During the CRP, data on other pertinent characteristics such as physical and dietary were simultaneously being collected. Hence, the information on the physiological characteristics alone, coming from the five participants were not complete and are probably not sufficient to establish standard values for the Reference Asian Man. Nonetheless, the data collected is a valuable contribution to this research programme

  11. Principles of high resolution NMR in solids

    CERN Document Server

    Mehring, Michael

    1983-01-01

    The field of Nuclear Magnetic Resonance (NMR) has developed at a fascinating pace during the last decade. It always has been an extremely valuable tool to the organic chemist by supplying molecular "finger print" spectra at the atomic level. Unfortunately the high resolution achievable in liquid solutions could not be obtained in solids and physicists and physical chemists had to live with unresolved lines open to a wealth of curve fitting procedures and a vast amount of speculations. High resolution NMR in solids seemed to be a paradoxon. Broad structure­ less lines are usually encountered when dealing with NMR in solids. Only with the recent advent of mUltiple pulse, magic angle, cross-polarization, two-dimen­ sional and multiple-quantum spectroscopy and other techniques during the last decade it became possible to resolve finer details of nuclear spin interactions in solids. I have felt that graduate students, researchers and others beginning to get involved with these techniques needed a book which trea...

  12. Multispectral dual isotope and NMR image analysis

    International Nuclear Information System (INIS)

    Dual isotope scintigraphy and nuclear magnetic resonance imaging produce image data that is intrinsically multispectral. That is multiple images of the same anatomic region are generated with different gray scale distribution and morphologic content that is largely redundant. Image processing technology, originally developed by NASA for satellite imaging, is available for multispectral analysis. These methods have been applied to provide tissue characterization. Tissue specific information encoded in the grapy scale data from dual isotope and NMR studies may be extracted using multispectral pattern recognition methods. The authors used table lookup minimum distance, maximum likelihood and cluster analysis techniques with data sets from Ga-67 / Tc-99m, 1-131 labeled antibodies / Tc-99m, Tc-99m perfusion / Xe-133 ventilation, and NMR studies. The results show; tissue characteristic signatures exist in dual isotope and NMR imaging, and these spectral signatures are identifiable using multispectral image analysis and provide tissue classification maps with scatter diagrams that facilitate interpretation and assist in elucidating subtle changes

  13. Cutoff-Free Traveling Wave NMR

    CERN Document Server

    Tang, Joel A; Sodickson, Daniel K; Jerschow, Alexej

    2011-01-01

    Recently, the concept of traveling-wave NMR/MRI was introduced by Brunner et al. (Nature 457, 994-992 (2009)), who demonstrated MR images acquired using radio frequency (RF) waves propagating down the bore of an MR scanner. One of the significant limitations of this approach is that each bore has a specific cutoff frequency, which can be higher than most Larmor frequencies of at the magnetic field strengths commonly in use for MR imaging and spectroscopy today. We overcome this limitation by using a central conductor in the waveguide and thereby converting it to a transmission line (TL), which has no cutoff frequency. Broadband propagation of waves through the sample thus becomes possible. NMR spectra and images with such an arrangement are presented and genuine traveling wave behavior is demonstrated. In addition to facilitating NMR spectroscopy and imaging in smaller bores via traveling waves, this approach also allows one to perform multinuclear traveling wave experiments (an example of which is shown), an...

  14. NMR measurement of bitumen at different temperatures.

    Science.gov (United States)

    Yang, Zheng; Hirasaki, George J

    2008-06-01

    Heavy oil (bitumen) is characterized by its high viscosity and density, which is a major obstacle to both well logging and recovery. Due to the lost information of T2 relaxation time shorter than echo spacing (TE) and interference of water signal, estimation of heavy oil properties from NMR T2 measurements is usually problematic. In this work, a new method has been developed to overcome the echo spacing restriction of NMR spectrometer during the application to heavy oil (bitumen). A FID measurement supplemented the start of CPMG. Constrained by its initial magnetization (M0) estimated from the FID and assuming log normal distribution for bitumen, the corrected T2 relaxation time of bitumen sample can be obtained from the interpretation of CPMG data. This new method successfully overcomes the TE restriction of the NMR spectrometer and is nearly independent on the TE applied in the measurement. This method was applied to the measurement at elevated temperatures (8-90 degrees C). Due to the significant signal-loss within the dead time of FID, the directly extrapolated M0 of bitumen at relatively lower temperatures ( or = 60 degrees C), the M0 value of bitumen at lower temperatures (Curie's Law. Consequently, some important petrophysical properties of bitumen, such as hydrogen index (HI), fluid content and viscosity were evaluated by using corrected T2. PMID:18387325

  15. Discrete analysis of stochastic NMR.II

    Science.gov (United States)

    Wong, S. T. S.; Rods, M. S.; Newmark, R. D.; Budinger, T. F.

    Stochastic NMR is an efficient technique for high-field in vivo imaging and spectroscopic studies where the peak RF power required may be prohibitively high for conventional pulsed NMR techniques. A stochastic NMR experiment excites the spin system with a sequence of RF pulses where the flip angles or the phases of the pulses are samples of a discrete stochastic process. In a previous paper the stochastic experiment was analyzed and analytic expressions for the input-output cross-correlations, average signal power, and signal spectral density were obtained for a general stochastic RF excitation. In this paper specific cases of excitation with random phase, fixed flip angle, and excitation with two random components in quadrature are analyzed. The input-output cross-correlation for these two types of excitations is shown to be Lorentzian. Line broadening is the only spectral distortion as the RF excitation power is increased. The systematic noise power is inversely proportional to the number of data points N used in the spectral reconstruction. The use of a complete maximum length sequence (MLS) may improve the signal-to-systematic-noise ratio by 20 dB relative to random binary excitation, but peculiar features in the higher-order autocorrelations of MLS cause noise-like distortion in the reconstructed spectra when the excitation power is high. The amount of noise-like distortion depends on the choice of the MLS generator.

  16. NMR methodologies for studying mitochondrial bioenergetics.

    Science.gov (United States)

    Alves, Tiago C; Jarak, Ivana; Carvalho, Rui A

    2012-01-01

    Nuclear magnetic resonance (NMR) spectroscopy is a technique with an increasing importance in the study of metabolic diseases. Its initial important role in the determination of chemical structures (1, 2) has been considerably overcome by its potential for the in vivo study of metabolism (3-5). The main characteristic that makes this technique so attractive is its noninvasiveness. Only nuclei capable of transitioning between energy states, in the presence of an intense and constant magnetic field, are studied. This includes abundant nuclei such as proton ((1)H) and phosphorous ((31)P), as well as stable isotopes such as deuterium ((2)H) and carbon 13 ((13)C). This allows a wide range of applications that vary from the determination of water distribution in tissues (as obtained in a magnetic resonance imaging scan) to the calculation of metabolic fluxes under ex vivo and in vivo conditions without the need to use radioactive tracers or tissue biopsies (as in a magnetic resonance spectroscopy (MRS) scan). In this chapter, some technical aspects of the methodology of an NMR/MRS experiment as well as how it can be used to study mitochondrial bioenergetics are overviewed. Advantages and disadvantages of in vivo MRS versus high-resolution NMR using proton high rotation magic angle spinning (HRMAS) of tissue biopsies and tissue extracts are also discussed. PMID:22057574

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

    Science.gov (United States)

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

    2013-08-22

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

  18. Guiding automated NMR structure determination using a global optimization metric, the NMR DP score

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yuanpeng Janet, E-mail: yphuang@cabm.rutgers.edu; Mao, Binchen; Xu, Fei; Montelione, Gaetano T., E-mail: gtm@rutgers.edu [Rutgers, The State University of New Jersey, Department of Molecular Biology and Biochemistry, Center for Advanced Biotechnology and Medicine, and Northeast Structural Genomics Consortium (United States)

    2015-08-15

    ASDP is an automated NMR NOE assignment program. It uses a distinct bottom-up topology-constrained network anchoring approach for NOE interpretation, with 2D, 3D and/or 4D NOESY peak lists and resonance assignments as input, and generates unambiguous NOE constraints for iterative structure calculations. ASDP is designed to function interactively with various structure determination programs that use distance restraints to generate molecular models. In the CASD–NMR project, ASDP was tested and further developed using blinded NMR data, including resonance assignments, either raw or manually-curated (refined) NOESY peak list data, and in some cases {sup 15}N–{sup 1}H residual dipolar coupling data. In these blinded tests, in which the reference structure was not available until after structures were generated, the fully-automated ASDP program performed very well on all targets using both the raw and refined NOESY peak list data. Improvements of ASDP relative to its predecessor program for automated NOESY peak assignments, AutoStructure, were driven by challenges provided by these CASD–NMR data. These algorithmic improvements include (1) using a global metric of structural accuracy, the discriminating power score, for guiding model selection during the iterative NOE interpretation process, and (2) identifying incorrect NOESY cross peak assignments caused by errors in the NMR resonance assignment list. These improvements provide a more robust automated NOESY analysis program, ASDP, with the unique capability of being utilized with alternative structure generation and refinement programs including CYANA, CNS, and/or Rosetta.

  19. STUDY ON THE SEQUENCE STRUCTURE OF SBR BY 13C- NMR METHOD Ⅰ. ASSIGNMENT FOR UNSATURATED CARBONS SPECTRA

    Institute of Scientific and Technical Information of China (English)

    JIAO Shuke; CHEN Xiaonong; HU Liping; YAN Baozhen

    1990-01-01

    The sequence structures of emulsion- processed SBR and solution- processed ( by lithium catalyst )SBR were investigated by 13C- NMR spectroscopy. Seventeen peaks within unsaturated carbon region were recorded under the adopted experimental conditions. Assignments for these peaks were made by empirical- parameter- evaluation method.

  20. STUDY ON THE SEQUENCE STRUCTURE OF SBR BY 13C- NMR METHOD Ⅱ . PEAK ASSIGNMENT FOR ALIPHATIC CARBONS SPECTRA

    Institute of Scientific and Technical Information of China (English)

    JIAO Shuke; CHEN Xiaonong; HU Liping; YAN Baozhen

    1990-01-01

    The study on 13C-NMR spectra of aliphatic carbon region of emulsion-processed and solution-processed ( by lithium catalyst ) SBR was carried out. The assignments for more than thirty odd peaks observed experimentally were made by using " corresponding analysis " method, combined with the empirical parameters reported in literature. The peak intensities were calculated based on Bernoullian statistic assumption.

  1. Toward cardiac electrophysiological mapping based on micro-Tesla NMR: a novel modality for localizing the cardiac reentry

    OpenAIRE

    Kiwoong Kim

    2012-01-01

    Matching the proton magnetic resonance frequency to the frequency of a periodic electrophysiological excitation of myocardium enables direct localization of the cardiac reentry by magnetic resonance imaging techniques. The feasibility of this new idea has been demonstrated by conducting a numerical simulation based on a realistic heart model and experimental parameters in SQUID-based micro-Tesla NMR.

  2. Toward cardiac electrophysiological mapping based on micro-Tesla NMR: a novel modality for localizing the cardiac reentry

    Science.gov (United States)

    Kim, Kiwoong

    2012-06-01

    Matching the proton magnetic resonance frequency to the frequency of a periodic electrophysiological excitation of myocardium enables direct localization of the cardiac reentry by magnetic resonance imaging techniques. The feasibility of this new idea has been demonstrated by conducting a numerical simulation based on a realistic heart model and experimental parameters in SQUID-based micro-Tesla NMR.

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

    Science.gov (United States)

    Jacob, Daniel; Deborde, Catherine; Moing, Annick

    2013-06-01

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

  4. Molecular mobility in Medicago truncatula seed during early stage of germination: Neutron scattering and NMR investigations

    International Nuclear Information System (INIS)

    Highlights: • Neutron scattering and NMR approaches were used to characterize seed germination. • A parallel between macromolecular motions and water dynamics was established. • Freezing/thawing cycle revealed a hysteresis connected to the seed hydration level. - Abstract: First hours of Medicago truncatula (MT) seeds germination were investigated using elastic incoherent neutron scattering (EINS) and nuclear magnetic resonance (NMR), to follow respectively how macromolecular motions and water mobility evolve when water permeates into the seed. From EINS results, it was shown that there is an increase in macromolecular mobility with the water uptake. Changes in NMR relaxation parameters reflected microstructural changes associated with the recovery of the metabolic processes. The EINS investigation of the effect of temperature on macromolecular motions showed that there is a relationship between the amount of water in the seeds and the effect of freezing–thawing cycle. The NMR relaxometry results obtained at 253 K allowed establishing possible link between the freezing of water molecules tightly bound to macromolecules and their drastic motion restriction around 250 K, as observed with EINS at the highest water content

  5. NMR imaging and spectroscopy of the mammalian central nervous system after heavy ion radiation

    Energy Technology Data Exchange (ETDEWEB)

    Richards, T.

    1984-09-01

    NMR imaging, NMR spectroscopic, and histopathologic techniques were used to study the proton relaxation time and related biochemical changes in the central nervous system after helium beam in vivo irradiation of the rodent brain. The spectroscopic observations reported in this dissertation were made possible by development of methods for measuring the NMR parameters of the rodent brain in vivo and in vitro. The methods include (1) depth selective spectroscopy using an optimization of rf pulse energy based on a priori knowledge of N-acetyl aspartate and lipid spectra of the normal brain, (2) phase-encoded proton spectroscopy of the living rodent using a surface coil, and (3) dual aqueous and organic tissue extraction technique for spectroscopy. Radiation induced increases were observed in lipid and p-choline peaks of the proton spectrum, in vivo. Proton NMR spectroscopy measurements on brain extracts (aqueous and organic solvents) were made to observe chemical changes that could not be seen in vivo. Radiation-induced changes were observed in lactate, GABA, glutamate, and p-choline peak areas of the aqueous fraction spectra. In the organic fraction, decreases were observed in peak area ratios of the terminal-methyl peaks, the N-methyl groups of choline, and at a peak at 2.84 ppM (phosphatidyl ethanolamine and phosphatidyl serine resonances) relative to TMS. With histology and Evans blue injections, blood-brain barrier alternations were seen as early as 4 days after irradiation. 83 references, 53 figures.

  6. Real-time reaction monitoring by ultrafast 2D NMR on a benchtop spectrometer.

    Science.gov (United States)

    Gouilleux, Boris; Charrier, Benoît; Danieli, Ernesto; Dumez, Jean-Nicolas; Akoka, Serge; Felpin, François-Xavier; Rodriguez-Zubiri, Mireia; Giraudeau, Patrick

    2015-12-01

    Reaction monitoring is widely used to follow chemical processes in a broad range of application fields. Recently, the development of robust benchtop NMR spectrometers has brought NMR under the fume hood, making it possible to monitor chemical reactions in a safe and accessible environment. However, these low-field NMR approaches suffer from limited resolution leading to strong peak overlaps, which can limit their application range. Here, we propose an approach capable of recording ultrafast 2D NMR spectra on a compact spectrometer and of following in real time reactions in the synthetic chemistry laboratory. This approach--whose potential is shown here on a Heck-Matsuda reaction--is highly versatile; the duration of the measurement can be optimized to follow reactions whose time scale ranges from between a few tens of seconds to a few hours. It makes it possible to monitor complex reactions in non-deuterated solvents, and to confirm in real time the molecular structure of the compounds involved in the reaction while giving access to relevant kinetic parameters. PMID:26501887

  7. NMR characterization of membrane protein-detergent micelle solutions by use of microcoil equipment.

    Science.gov (United States)

    Stanczak, Pawel; Horst, Reto; Serrano, Pedro; Wüthrich, Kurt

    2009-12-30

    Using microcoil NMR technology, the uniformly (2)H,(15)N-labeled integral membrane protein OmpX, and the phosphocholine derivative detergent Fos-10 (n-decylphosphocholine), we investigated solutions of mixed protein-detergent micelles to determine the influence of the detergent concentration on the NMR spectra of the protein. In a first step, we identified key parameters that influence the composition of the micelle solutions, which resulted in a new protocol for the preparation of well-defined concentrated protein solutions. This led to the observation that high-quality 2D [(15)N,(1)H]-transverse relaxation-optimized spectroscopy (TROSY) spectra of OmpX reconstituted in mixed micelles with Fos-10 were obtained only in a limited range of detergent concentrations. Outside of this range from about 90-180 mM, we observed a significant decrease of the average peak intensity. Relaxation-optimized NMR measurements of the rotational and translational diffusion coefficients of the OmpX/Fos-10 mixed micelles, D(r) and D(t), respectively, then showed that the stoichiometry and the effective hydrodynamic radius of the protein-containing micelles are not significantly affected by high Fos-10 concentrations and that the deterioration of NMR spectra is due to the increased viscosity at high detergent concentrations. The paper thus provides a basis for refined guidelines on the preparation of integral membrane proteins for structural studies.

  8. Refinement of the protein backbone angle {psi} in NMR structure calculations

    Energy Technology Data Exchange (ETDEWEB)

    Sprangers, R.; Bottomley, M.J.; Linge, J.P.; Schultz, J.; Nilges, M.; Sattler, M. [European Molecular Biology Laboratory (Germany)

    2000-01-15

    Cross-correlated relaxation rates involving the C{sup {alpha}}-H{sup {alpha}} dipolar interaction and the carbonyl (C') chemical shift anisotropy (CSA) have been measured using two complementary 3D experiments. We show that the protein backbone angle {psi} can be directly refined against such cross-correlated relaxation rates ({gamma}{sup H{alpha}}{sup C{alpha}}{sup ,C'}) and the three-bond H/D isotope effect on the C{sup {alpha}} chemical shifts ({sup 3}{delta}C{sup {alpha}}{sub (ND)}). By simultaneously using both experimental parameters as restraints during NMR structure calculations, a unique value for the backbone angle {psi} is defined. We have applied the new refinement method to the {alpha}-Spectrin SH3 domain (a {beta}-sheet protein) and to the Sgs1p HRDC domain (an {alpha}-helical protein) and show that the quality of the NMR structures is substantially improved, judging from the atomic coordinate precision and the Ramachandran map. In addition, the {psi}-refined NMR structures of the SH3 domain deviate less from the 1.8 A crystal structure, suggesting an improved accuracy. The proposed refinement method can be used to significantly improve the quality of NMR structures and will be applicable to larger proteins.

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

    Science.gov (United States)

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

    2014-11-28

    The electronic and coordination environment of minerals surfaces, as calcite, are very difficult to characterize experimentally. This is mainly due to the fact that there are relatively few spectroscopic techniques able to detect Ca(2+). Since calcite is a major constituent of sedimentary rocks in oil reservoir, a more detailed characterization of the interaction between hydrocarbon molecules and mineral surfaces is highly desirable. Here we perform a first principles study on the adsorption of hydrocarbon molecules on calcite surface (CaCO3 (101¯4)). The simulations were based on Density Functional Theory with Solid State Nuclear Magnetic Resonance (SS-NMR) calculations. The Gauge-Including Projector Augmented Wave method was used to compute mainly SS-NMR parameters for (43)Ca, (13)C, and (17)O in calcite surface. It was possible to assign the peaks in the theoretical NMR spectra for all structures studied. Besides showing different chemical shifts for atoms located on different environments (bulk and surface) for calcite, the results also display changes on the chemical shift, mainly for Ca sites, when the hydrocarbon molecules are present. Even though the interaction of the benzene molecule with the calcite surface is weak, there is a clearly distinguishable displacement of the signal of the Ca sites over which the hydrocarbon molecule is located. A similar effect is also observed for hexane adsorption. Through NMR spectroscopy, we show that aromatic and alkane hydrocarbon molecules adsorbed on carbonate surfaces can be differentiated.

  10. Layered structure of room-temperature ionic liquids in microemulsions by multinuclear NMR spectroscopic studies.

    Science.gov (United States)

    Falcone, R Dario; Baruah, Bharat; Gaidamauskas, Ernestas; Rithner, Christopher D; Correa, N Mariano; Silber, Juana J; Crans, Debbie C; Levinger, Nancy E

    2011-06-01

    Microemulsions form in mixtures of polar, nonpolar, and amphiphilic molecules. Typical microemulsions employ water as the polar phase. However, microemulsions can form with a polar phase other than water, which hold promise to diversify the range of properties, and hence utility, of microemulsions. Here microemulsions formed by using a room-temperature ionic liquid (RTIL) as the polar phase were created and characterized by using multinuclear NMR spectroscopy. (1)H, (11)B, and (19)F NMR spectroscopy was applied to explore differences between microemulsions formed by using 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)]) as the polar phase with a cationic surfactant, benzylhexadecyldimethylammonium chloride (BHDC), and a nonionic surfactant, Triton X-100 (TX-100). NMR spectroscopy showed distinct differences in the behavior of the RTIL as the charge of the surfactant head group varies in the different microemulsion environments. Minor changes in the chemical shifts were observed for [bmim](+) and [BF(4)](-) in the presence of TX-100 suggesting that the surfactant and the ionic liquid are separated in the microemulsion. The large changes in spectroscopic parameters observed are consistent with microstructure formation with layering of [bmim](+) and [BF(4)](-) and migration of Cl(-) within the BHDC microemulsions. Comparisons with NMR results for related ionic compounds in organic and aqueous environments as well as literature studies assisted the development of a simple organizational model for these microstructures. PMID:21547960

  11. NMR imaging and spectroscopy of the mammalian central nervous system after heavy ion radiation

    International Nuclear Information System (INIS)

    NMR imaging, NMR spectroscopic, and histopathologic techniques were used to study the proton relaxation time and related biochemical changes in the central nervous system after helium beam in vivo irradiation of the rodent brain. The spectroscopic observations reported in this dissertation were made possible by development of methods for measuring the NMR parameters of the rodent brain in vivo and in vitro. The methods include (1) depth selective spectroscopy using an optimization of rf pulse energy based on a priori knowledge of N-acetyl aspartate and lipid spectra of the normal brain, (2) phase-encoded proton spectroscopy of the living rodent using a surface coil, and (3) dual aqueous and organic tissue extraction technique for spectroscopy. Radiation induced increases were observed in lipid and p-choline peaks of the proton spectrum, in vivo. Proton NMR spectroscopy measurements on brain extracts (aqueous and organic solvents) were made to observe chemical changes that could not be seen in vivo. Radiation-induced changes were observed in lactate, GABA, glutamate, and p-choline peak areas of the aqueous fraction spectra. In the organic fraction, decreases were observed in peak area ratios of the terminal-methyl peaks, the N-methyl groups of choline, and at a peak at 2.84 ppM (phosphatidyl ethanolamine and phosphatidyl serine resonances) relative to TMS. With histology and Evans blue injections, blood-brain barrier alternations were seen as early as 4 days after irradiation. 83 references, 53 figures

  12. Non-destructive characterization of materials by single-sided NMR

    Energy Technology Data Exchange (ETDEWEB)

    Goga, Nicolae-Octavian

    2007-08-20

    The experiments conducted in this work demonstrate the efficiency and sensitivity of single-sided NMR for investigating macromolecular materials on large time and length scales. Elastomers can readily be characterized by unilateral NMR of protons in terms of a variety of parameters, which correlate with the overall molecular mobility. In this way information about the cross-link density, state of cure and strain, the effects of aging and product heterogeneity can obtained. For these purposes, the NMR-MOUSE was used to optimize product development and to monitor product and production quality on-line. The sensor is also suitable for nondestructive probing of the mechanical deformation in cross-linked elastomers. A special magnet design that fits a stress-strain device has been used for complementary investigation of a series of different rubber stripes during mechanical testing. The profile NMR-MOUSE was found to be a unique tool for the characterization of changes induced by the UV irradiation in natural rubber. The aging profiles were interpreted for the first time based on a novel model in which the radiation absorption coefficient depends on the depth in the sample. (orig.)

  13. Non-destructive characterization of materials by single-sided NMR

    International Nuclear Information System (INIS)

    The experiments conducted in this work demonstrate the efficiency and sensitivity of single-sided NMR for investigating macromolecular materials on large time and length scales. Elastomers can readily be characterized by unilateral NMR of protons in terms of a variety of parameters, which correlate with the overall molecular mobility. In this way information about the cross-link density, state of cure and strain, the effects of aging and product heterogeneity can obtained. For these purposes, the NMR-MOUSE was used to optimize product development and to monitor product and production quality on-line. The sensor is also suitable for nondestructive probing of the mechanical deformation in cross-linked elastomers. A special magnet design that fits a stress-strain device has been used for complementary investigation of a series of different rubber stripes during mechanical testing. The profile NMR-MOUSE was found to be a unique tool for the characterization of changes induced by the UV irradiation in natural rubber. The aging profiles were interpreted for the first time based on a novel model in which the radiation absorption coefficient depends on the depth in the sample. (orig.)

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

    Science.gov (United States)

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

    2014-11-28

    The electronic and coordination environment of minerals surfaces, as calcite, are very difficult to characterize experimentally. This is mainly due to the fact that there are relatively few spectroscopic techniques able to detect Ca(2+). Since calcite is a major constituent of sedimentary rocks in oil reservoir, a more detailed characterization of the interaction between hydrocarbon molecules and mineral surfaces is highly desirable. Here we perform a first principles study on the adsorption of hydrocarbon molecules on calcite surface (CaCO3 (101¯4)). The simulations were based on Density Functional Theory with Solid State Nuclear Magnetic Resonance (SS-NMR) calculations. The Gauge-Including Projector Augmented Wave method was used to compute mainly SS-NMR parameters for (43)Ca, (13)C, and (17)O in calcite surface. It was possible to assign the peaks in the theoretical NMR spectra for all structures studied. Besides showing different chemical shifts for atoms located on different environments (bulk and surface) for calcite, the results also display changes on the chemical shift, mainly for Ca sites, when the hydrocarbon molecules are present. Even though the interaction of the benzene molecule with the calcite surface is weak, there is a clearly distinguishable displacement of the signal of the Ca sites over which the hydrocarbon molecule is located. A similar effect is also observed for hexane adsorption. Through NMR spectroscopy, we show that aromatic and alkane hydrocarbon molecules adsorbed on carbonate surfaces can be differentiated. PMID:25429955

  15. Phase Structures of Nascent Polyethylene Powder Studied by Wideline Proton NMR

    Institute of Scientific and Technical Information of China (English)

    YAN,Xiao-Wei; WANG,Jing-Dai; REN,Xiao-Hong; YANG,Yong-Rong; JIANG,Bin-Bo; VODA,Mihai Adrian; BERTMER,Marko; STAFF,Siegfried

    2007-01-01

    The wideline proton NMR spectra of polyethylene powder samples were analyzed in terms of contributions from three components: (1) a rigid part with immobile chains, (2) a soft region with liquid-like character which produces a Lorentzian contribution to the spectrum, and (3) an intermediate region in which the rotation of me-thylene groups about C-C bonds is partially hindered. The relative mass fractions as well as chain mobilities varied greatly among samples produced by different polymerization techniques. The NMR crystallinity agreed well with that estimated by WAXD and was much higher than DSC crystallinity, indicating an inclusion of the contribution from a crystalline-amorphous interphase. The crystalline defects in the rigid part could be significantly affected by processing parameters when employing the same type of polymerization technique. The intermediate region in the NMR spectra was analyzed according to the comparison between bimodal high density polyethylene and corresponding linear unimodal one. It was found that the mass fraction of the NMR interphase could be an indication of the percentage of tie molecules between crystalline lamellae and thus may significantly affect the mechanical properties of polymeric material.

  16. Comparative study of inversion methods of three-dimensional NMR and sensitivity to fluids

    Science.gov (United States)

    Tan, Maojin; Wang, Peng; Mao, Keyu

    2014-04-01

    Three-dimensional nuclear magnetic resonance (3D NMR) logging can simultaneously measure transverse relaxation time (T2), longitudinal relaxation time (T1), and diffusion coefficient (D). These parameters can be used to distinguish fluids in the porous reservoirs. For 3D NMR logging, the relaxation mechanism and mathematical model, Fredholm equation, are introduced, and the inversion methods including Singular Value Decomposition (SVD), Butler-Reeds-Dawson (BRD), and Global Inversion (GI) methods are studied in detail, respectively. During one simulation test, multi-echo CPMG sequence activation is designed firstly, echo trains of the ideal fluid models are synthesized, then an inversion algorithm is carried on these synthetic echo trains, and finally T2-T1-D map is built. Futhermore, SVD, BRD, and GI methods are respectively applied into a same fluid model, and the computing speed and inversion accuracy are compared and analyzed. When the optimal inversion method and matrix dimention are applied, the inversion results are in good aggreement with the supposed fluid model, which indicates that the inversion method of 3D NMR is applieable for fluid typing of oil and gas reservoirs. Additionally, the forward modeling and inversion tests are made in oil-water and gas-water models, respectively, the sensitivity to the fluids in different magnetic field gradients is also examined in detail. The effect of magnetic gradient on fluid typing in 3D NMR logging is stuied and the optimal manetic gradient is choosen.

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

    Energy Technology Data Exchange (ETDEWEB)

    Bevilaqua, Rochele C. A.; Miranda, Caetano R. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, UFABC, Santo André, SP (Brazil); Rigo, Vagner A. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, UFABC, Santo André, SP (Brazil); Universidade Tecnológica Federal do Paraná, UTFPR, Cornélio Procópio, PR (Brazil); Veríssimo-Alves, Marcos [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, UFABC, Santo André, SP (Brazil); Departamento de Física, ICEx, Universidade Federal Fluminense, UFF, Volta Redonda, RJ (Brazil)

    2014-11-28

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

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

    International Nuclear Information System (INIS)

    The electronic and coordination environment of minerals surfaces, as calcite, are very difficult to characterize experimentally. This is mainly due to the fact that there are relatively few spectroscopic techniques able to detect Ca2+. Since calcite is a major constituent of sedimentary rocks in oil reservoir, a more detailed characterization of the interaction between hydrocarbon molecules and mineral surfaces is highly desirable. Here we perform a first principles study on the adsorption of hydrocarbon molecules on calcite surface (CaCO3 (101¯4)). The simulations were based on Density Functional Theory with Solid State Nuclear Magnetic Resonance (SS-NMR) calculations. The Gauge-Including Projector Augmented Wave method was used to compute mainly SS-NMR parameters for 43Ca, 13C, and 17O in calcite surface. It was possible to assign the peaks in the theoretical NMR spectra for all structures studied. Besides showing different chemical shifts for atoms located on different environments (bulk and surface) for calcite, the results also display changes on the chemical shift, mainly for Ca sites, when the hydrocarbon molecules are present. Even though the interaction of the benzene molecule with the calcite surface is weak, there is a clearly distinguishable displacement of the signal of the Ca sites over which the hydrocarbon molecule is located. A similar effect is also observed for hexane adsorption. Through NMR spectroscopy, we show that aromatic and alkane hydrocarbon molecules adsorbed on carbonate surfaces can be differentiated

  19. Molecular mobility in Medicago truncatula seed during early stage of germination: Neutron scattering and NMR investigations

    Energy Technology Data Exchange (ETDEWEB)

    Falourd, Xavier [UR1268 Biopolymères Interactions Assemblages, INRA, F-44316 Nantes (France); Natali, Francesca [CNR-IOM-OGG, c/o Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9 (France); Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9 (France); Peters, Judith [Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9 (France); Université Joseph Fourier UFR PhITEM, BP 53, 38041 Grenoble Cedex 9 (France); Institut de Biologie Structurale, 41 rue Jules Horowitz, 38027 Grenoble Cedex 1 (France); Foucat, Loïc, E-mail: Loic.Foucat@nantes.inra.fr [UR1268 Biopolymères Interactions Assemblages, INRA, F-44316 Nantes (France)

    2014-01-15

    Highlights: • Neutron scattering and NMR approaches were used to characterize seed germination. • A parallel between macromolecular motions and water dynamics was established. • Freezing/thawing cycle revealed a hysteresis connected to the seed hydration level. - Abstract: First hours of Medicago truncatula (MT) seeds germination were investigated using elastic incoherent neutron scattering (EINS) and nuclear magnetic resonance (NMR), to follow respectively how macromolecular motions and water mobility evolve when water permeates into the seed. From EINS results, it was shown that there is an increase in macromolecular mobility with the water uptake. Changes in NMR relaxation parameters reflected microstructural changes associated with the recovery of the metabolic processes. The EINS investigation of the effect of temperature on macromolecular motions showed that there is a relationship between the amount of water in the seeds and the effect of freezing–thawing cycle. The NMR relaxometry results obtained at 253 K allowed establishing possible link between the freezing of water molecules tightly bound to macromolecules and their drastic motion restriction around 250 K, as observed with EINS at the highest water content.

  20. From NMR chemical shifts to amino acid types: Investigation of the predictive power carried by nuclei

    International Nuclear Information System (INIS)

    An approach to automatic prediction of the amino acid type from NMR chemical shift values of its nuclei is presented here, in the frame of a model to calculate the probability of an amino acid type given the set of chemical shifts. The method relies on systematic use of all chemical shift values contained in the BioMagResBank (BMRB). Two programs were designed, one (BMRB stats) for extracting statistical chemical shift parameters from the BMRB and another one (RESCUE2) for computing the probabilities of each amino acid type, given a set of chemical shifts. The Bayesian prediction scheme presented here is compared to other methods already proposed: PROTYP (Grzesiek and Bax, J. Biomol. NMR, 3, 185-204, 1993) RESCUE (Pons and Delsuc, J. Biomol. NMR, 15, 15-26, 1999) and PLATON (Labudde et al., J. Biomol. NMR, 25, 41-53, 2003) and is found to be more sensitive and more specific. Using this scheme, we tested various sets of nuclei. The two nuclei carrying the most information are Cβ and Hβ, in agreement with observations made in Grzesiek and Bax, 1993. Based on four nuclei: Hβ, Cβ, Cα and C', it is possible to increase correct predictions to a rate of more than 75%. Taking into account the correlations between the nuclei chemical shifts has only a slight impact on the percentage of correct predictions: indeed, the largest correlation coefficients display similar features on all amino acids

  1. Acquisition strategy to obtain quantitative diffusion NMR data

    Science.gov (United States)

    Barrère, Caroline; Thureau, Pierre; Thévand, André; Viel, Stéphane

    2012-03-01

    Pulsed Gradient Spin Echo (PGSE) diffusion NMR experiments constitute a powerful tool for analyzing complex mixtures because they can in principle separate the NMR spectra of each mixture component. However, because these experiments intrinsically rely on spin echoes, they are traditionally regarded as non-quantitative, due to the signal attenuation caused by longitudinal (T1) and transverse (T2) nuclear magnetic relaxation during the rather long delays of the pulse sequence. Alternatively to the quantitative Direct Exponential Curve Resolution Algorithm (qDECRA) approach proposed by Antalek (J. Am. Chem. Soc. 128 (2006) 8402-8403), this work presents an acquisition strategy that renormalizes this relaxation attenuation using estimates of the T1 and T2 relaxation times for all the nuclei in the mixture, as obtained directly with the pulse sequence used to record the PGSE experiment. More specifically, it is shown that only three distinct PGSE experiments need to be recorded, each with a specific set of acquisition parameters. For small- and medium-sized molecules, only T1 is required for obtaining accurate quantification. For larger molecular weight species, which typically exhibit short T2 values, estimates of T2 must also be included but only a rough estimation is required. This appears fortunate because these data are especially hard to obtain with good accuracy when analyzing homonuclear scalar-coupled systems. Overall, the proposed methodology is shown to yield a quantification accuracy of ±5%, both in the absence and in the presence of spectral overlap, giving rise - at least, in our hands - to results that superseded those achieved by qDECRA, while requiring substantially less experimental time.

  2. Studies of Lung Micromechanics via Hyperpolarized Helium-3 Diffusion NMR

    Science.gov (United States)

    Hajari, Adam James

    While high quality MR Images of lungs are difficult to obtain with conventional proton MRI due to the organ's low tissue density, the advent of techniques in noble gas polarization have enabled MR investigations of the lung's more abundant air space rather than its tissue. In addition to high-resolution images of lung ventilation, lung morphometry via gas diffusion NMR provides information about the size and shape of the microscopic airways that account for over 95% of the lung's airspace. Consequently, gas diffusion NMR provides an important new tool for investigating changes in lung microstructure during macroscopic changes in lung volume. Despite decades of research into the mechanisms of lung inflation and deflation, there is little consensus about whether macroscopic changes in lung volume occur due to changes in the size and/or shape of alveoli and alveolar ducts or by alveolar recruitment and derecruitment. In this dissertation lung morphometry is performed via 3He diffusion MRI in order to measure the average alveolar depth and alveolar duct radius at multiple levels of both inspiration and expiration in in vivo human subjects and in explanted human and canine lungs. Average alveolar volume, surface area, and the total number of alveoli at each lung volume are calculated from the 3He morphometric parameters. The results suggest that human lungs inflate/deflate primarily by recruitment/derecruitment of alveoli, and that individual alveolar ducts in both human and canine lungs increase in volume non-isotropically by accordion-like extension. The results further suggest that this change in alveolar duct volume is the primary mechanism of lung volume change in canine lungs but is secondary to alveolar recruitment/derecruitment in humans.

  3. Fast automated protein NMR data collection and assignment by ADAPT-NMR on Bruker spectrometers

    Science.gov (United States)

    Lee, Woonghee; Hu, Kaifeng; Tonelli, Marco; Bahrami, Arash; Neuhardt, Elizabeth; Glass, Karen C.; Markley, John L.

    2013-11-01

    ADAPT-NMR (Assignment-directed Data collection Algorithm utilizing a Probabilistic Toolkit in NMR) supports automated NMR data collection and backbone and side chain assignment for [U-13C, U-15N]-labeled proteins. Given the sequence of the protein and data for the orthogonal 2D 1H-15N and 1H-13C planes, the algorithm automatically directs the collection of tilted plane data from a variety of triple-resonance experiments so as to follow an efficient pathway toward the probabilistic assignment of 1H, 13C, and 15N signals to specific atoms in the covalent structure of the protein. Data collection and assignment calculations continue until the addition of new data no longer improves the assignment score. ADAPT-NMR was first implemented on Varian (Agilent) spectrometers [A. Bahrami, M. Tonelli, S.C. Sahu, K.K. Singarapu, H.R. Eghbalnia, J.L. Markley, PLoS One 7 (2012) e33173]. Because of broader interest in the approach, we present here a version of ADAPT-NMR for Bruker spectrometers. We have developed two AU console programs (ADAPT_ORTHO_run and ADAPT_NMR_run) that run under TOPSPIN Versions 3.0 and higher. To illustrate the performance of the algorithm on a Bruker spectrometer, we tested one protein, chlorella ubiquitin (76 amino acid residues), that had been used with the Varian version: the Bruker and Varian versions achieved the same level of assignment completeness (98% in 20 h). As a more rigorous evaluation of the Bruker version, we tested a larger protein, BRPF1 bromodomain (114 amino acid residues), which yielded an automated assignment completeness of 86% in 55 h. Both experiments were carried out on a 500 MHz Bruker AVANCE III spectrometer equipped with a z-gradient 5 mm TCI probe. ADAPT-NMR is available at http://pine.nmrfam.wisc.edu/ADAPT-NMR in the form of pulse programs, the two AU programs, and instructions for installation and use.

  4. The (1) H NMR spectrum of pyrazole in a nematic phase.

    Science.gov (United States)

    Provasi, Patricio; Jimeno, María Luisa; Alkorta, Ibon; Reviriego, Felipe; Elguero, José; Jokisaari, Jukka

    2016-08-01

    The experimental (1) H nuclear magnetic resonance (NMR) spectrum of 1H-pyrazole was recorded in thermotropic nematic liquid crystal N-(p-ethoxybenzylidene)-p-butylaniline (EBBA) within the temperature range of 299-308 K. Two of three observable dipolar DHH -couplings appeared to be equal at each temperature because of fast prototropic tautomerism. Analysis of the Saupe orientational order parameters using fixed geometry determined by computations and experimental dipolar couplings results in a situation in which the molecular orientation relative to the magnetic field (and the liquid crystal director) can be described exceptionally by a single parameter. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26947581

  5. Lipid Dynamics Studied by Calculation of 31P Solid-State NMR Spectra Using Ensembles from Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Hansen, Sara Krogh; Vestergaard, Mikkel; Thøgersen, Lea;

    2014-01-01

    We present a method to calculate 31P solid-state NMR spectra based on the dynamic input from extended molecular dynamics (MD) simulations. The dynamic information confered by MD simulations is much more comprehensive than the information provided by traditional NMR dynamics models based on......, for example, order parameters. Therefore, valuable insight into the dynamics of biomolecules may be achieved by the present method. We have applied this method to study the dynamics of lipid bilayers containing the antimicrobial peptide alamethicin, and we show that the calculated 31P spectra obtained...

  6. Direct Comparison of 19F qNMR and 1H qNMR by Characterizing Atorvastatin Calcium Content

    Directory of Open Access Journals (Sweden)

    Yang Liu

    2016-01-01

    Full Text Available Quantitative nuclear magnetic resonance (qNMR is a powerful tool in measuring drug content because of its high speed, sensitivity, and precision. Most of the reports were based on proton qNMR (1H qNMR and only a few fluorine qNMR (19F qNMR were reported. No research has been conducted to directly compare the advantage and disadvantage between these two methods. In the present study, both 19F and 1H qNMR were performed to characterize the content of atorvastatin calcium with the same internal standard. Linearity, precision, and results from two methods were compared. Results showed that 19F qNMR has similar precision and sensitivity to 1H qNMR. Both methods generate similar results compared to mass balance method. Major advantage from 19F qNMR is that the analyte signal is with less or no interference from impurities. 19F qNMR is an excellent approach to quantify fluorine-containing analytes.

  7. NMR study of magnetism and superparamagnetism

    Science.gov (United States)

    Yuan, Shaojie

    The research described in this dissertation is concerned with two different types of magnetic materials. Both types of systems involve competing interactions between transition metal ions. New approaches involving magnetic resonance in the large hyperfine fields at nuclear sites have been developed. The interactions responsible for the properties that have been investigated in the materials studied are geometric frustration in an insulator and ferromagnetic and antiferromagnetic interactions in a metal alloy. Further details are given below. The extended kagome frustrated system YBaCo4O7 has 2D kagome and triangular lattices of Co ions stacked along the c-axis. Antiferromagnetic (AF) ordering accompanied by a structural transition has been reported in the literature. From a zero field (ZF) NMR single crystal rotation experiment, we have obtained the Co spin configurations for both the kagome and triangular layers. A 'spin-flop' configuration between the spins on the kagome layer and the spins on the triangular layer is indicated by our results. Our NMR findings are compared with neutron scattering results for this intriguing frustrated AF spin system. The non-stoichiometric oxygenated sister compound YBaCo4O7.1 has application potential for oxygen storage. While, its' magnetic properties are quite different from those of the stoichiometric compound, in spite of their similar structures of alternating kagome and triangular Co layers. Various techniques, including ZF NMR have been used to investigate the spin dynamics and spin configuration in a single crystal of YBaCo4O7.1. A magnetic transition at 80 K is observed, which is interpreted as the freezing out of spins in the triangular layers. At low temperatures (below 50 K), the spin dynamics persists and a fraction of spins in the kagome layers form a viscous spin liquid. Below 10 K, a glass-like spin structure forms and a large distribution of spin correlation times are suggested by nuclear spin lattice relaxation

  8. Isotope labeling for NMR studies of macromolecular structure and interactions

    Energy Technology Data Exchange (ETDEWEB)

    Wright, P.E. [Scripps Research Institute, La Jolla, CA (United States)

    1994-12-01

    Implementation of biosynthetic methods for uniform or specific isotope labeling of proteins, coupled with the recent development of powerful heteronuclear multidimensional NMR methods, has led to a dramatic increase in the size and complexity of macromolecular systems that are now amenable to NMR structural analysis. In recent years, a new technology has emerged that combines uniform {sup 13}C, {sup 15}N labeling with heteronuclear multidimensional NMR methods to allow NMR structural studies of systems approaching 25 to 30 kDa in molecular weight. In addition, with the introduction of specific {sup 13}C and {sup 15}N labels into ligands, meaningful NMR studies of complexes of even higher molecular weight have become feasible. These advances usher in a new era in which the earlier, rather stringent molecular weight limitations have been greatly surpassed and NMR can begin to address many central biological problems that involve macromolecular structure, dynamics, and interactions.

  9. The Expanding Role of NMR in Drug Discovery and Development

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    @@ The role of NMR in the pharmaceutical industry has changed dramatically over the last decade. Once thought of as an analytical technique used primarily to support synthetic chemistry, NMR now has an important role in the investigation of biochemical changes involved in clinical diseases and drug toxicity. It is also used extensively to elucidate the structures of drug metabolites. Data obtained using LC NMR MS and 19F NMR will be used to illustrate the utility of hyphenated methods in identifying xenobiotic metabolites as part of a drug development program. The application of NMR to the study of potential drug toxicity will also be described using the cationic, amphiphilic drugs chloroquine and amiodarone. These drugs are known to induce phospholipidosis characterized by lysosomal lamellar bodies and drug accumulation. Using a metabonomic approach, NMR spectroscopy of urine allowed the identification of a combination of urinary biomarkers of phospholipidosis.

  10. Action of the multifunctional peptide BP100 on native biomembranes examined by solid-state NMR

    Energy Technology Data Exchange (ETDEWEB)

    Misiewicz, Julia [Karlsruhe Institute of Technology (KIT), Institute of Organic Chemistry (Germany); Afonin, Sergii; Grage, Stephan L.; Berg, Jonas van den; Strandberg, Erik; Wadhwani, Parvesh [Karlsruhe Institute of Technology (KIT), Institute of Biological Interfaces (IBG-2) (Germany); Ulrich, Anne S., E-mail: anne.ulrich@kit.edu [Karlsruhe Institute of Technology (KIT), Institute of Organic Chemistry (Germany)

    2015-04-15

    Membrane composition is a key factor that regulates the destructive activity of antimicrobial peptides and the non-leaky permeation of cell penetrating peptides in vivo. Hence, the choice of model membrane is a crucial aspect in NMR studies and should reflect the biological situation as closely as possible. Here, we explore the structure and dynamics of the short multifunctional peptide BP100 using a multinuclear solid-state NMR approach. The membrane alignment and mobility of this 11 amino acid peptide was studied in various synthetic lipid bilayers with different net charge, fluidity, and thickness, as well as in native biomembranes harvested from prokaryotic and eukaryotic cells. {sup 19}F-NMR provided the high sensitivity and lack of natural abundance background that are necessary to observe a labelled peptide even in protoplast membranes from Micrococcus luteus and in erythrocyte ghosts. Six selectively {sup 19}F-labeled BP100 analogues gave remarkably similar spectra in all of the macroscopically oriented membrane systems, which were studied under quasi-native conditions of ambient temperature and full hydration. This similarity suggests that BP100 has the same surface-bound helical structure and high mobility in the different biomembranes and model membranes alike, independent of charge, thickness or cholesterol content of the system. {sup 31}P-NMR spectra of the phospholipid components did not indicate any bilayer perturbation, so the formation of toroidal wormholes or micellarization can be excluded as a mechanism of its antimicrobial or cell penetrating action. However, {sup 2}H-NMR analysis of the acyl chain order parameter profiles showed that BP100 leads to considerable membrane thinning and thereby local destabilization.

  11. Stroke, evolution of NMR imaging characteristics

    International Nuclear Information System (INIS)

    This study evaluates the NMR imaging characteristics of stroke and temporal evolution of these features. Patients with acute stroke clinically had NMR imaging (prototype 0.15T resistive imager, Technicare, Inc.) acutely (n=37), at approximately 2 weeks (n=31) and 3 months (n=10). Patients with old (> 1 yr.) stroke were also imaged (n=7). Partial saturation sequences were used employing echo time (T/sub E/) of 30, 60 and 120 msec, as well as inversion recovery (TR) sequences. Partial saturation images displayed a homogeneous increase in signal at lesion sites in both bland and hemorrhagic infarcts, reflection prolongation of spin-spin relaxation (T/sub 2/) due to increased tissue water content, blood and edema being indistinguishable. IR images recovered low signal from bland infarcts due to prolongation of spinlattice relaxation (T/sub 1/) by tissue edema, hemorrhagic lesions and short (T/sub 1/) centrally (blood) with moderate or increased IR signal, and low signal peripherally (edema). On follow-up IR imaging, hematomas developed low signal centres, possibly reflection cavitation, with short T/sub 2/ rims, possibly indicating the presence of iron-laden macrophages. In 2 patients with hemorrhagic infarcts an area of increased signal (prolonged T/sub 2/) was seen on initial partial saturation images in the homologous portion of the other hemisphere (normal by CT). This may reflect a local alteration of blood volume or velocity. In 5 patients with old infarcts, a rim of prolonged T/sub 2/ was seen at the periphery of old lesions, possibly reflecting a local chronic increase in extravascular or intravascular water, slowing of blood velocity, or a zone of neuronal dropout. Detailed pathophysiologic correlation is required to understand the basis of these NMR findings

  12. Stroke, evolution of NMR imaging characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Nicholson, R.L.; Carr, T.; Kertesz, A.; Black, S.; Cooper, P.; Stewart, S.

    1984-01-01

    This study evaluates the NMR imaging characteristics of stroke and temporal evolution of these features. Patients with acute stroke clinically had NMR imaging (prototype 0.15T resistive imager, Technicare, Inc.) acutely (n=37), at approximately 2 weeks (n=31) and 3 months (n=10). Patients with old (> 1 yr.) stroke were also imaged (n=7). Partial saturation sequences were used employing echo time (T/sub E/) of 30, 60 and 120 msec, as well as inversion recovery (TR) sequences. Partial saturation images displayed a homogeneous increase in signal at lesion sites in both bland and hemorrhagic infarcts, reflection prolongation of spin-spin relaxation (T/sub 2/) due to increased tissue water content, blood and edema being indistinguishable. IR images recovered low signal from bland infarcts due to prolongation of spinlattice relaxation (T/sub 1/) by tissue edema, hemorrhagic lesions and short (T/sub 1/) centrally (blood) with moderate or increased IR signal, and low signal peripherally (edema). On follow-up IR imaging, hematomas developed low signal centres, possibly reflection cavitation, with short T/sub 2/ rims, possibly indicating the presence of iron-laden macrophages. In 2 patients with hemorrhagic infarcts an area of increased signal (prolonged T/sub 2/) was seen on initial partial saturation images in the homologous portion of the other hemisphere (normal by CT). This may reflect a local alteration of blood volume or velocity. In 5 patients with old infarcts, a rim of prolonged T/sub 2/ was seen at the periphery of old lesions, possibly reflecting a local chronic increase in extravascular or intravascular water, slowing of blood velocity, or a zone of neuronal dropout. Detailed pathophysiologic correlation is required to understand the basis of these NMR findings.

  13. Measurement of vorticity diffusion by NMR microscopy.

    Science.gov (United States)

    Brown, Jennifer R; Callaghan, Paul T

    2010-05-01

    In a Newtonian fluid, vorticity diffuses at a rate determined by the kinematic viscosity. Here we use rapid NMR velocimetry, based on a RARE sequence, to image the time-dependent velocity field on startup of a fluid-filled cylinder and therefore measure the diffusion of vorticity. The results are consistent with the solution to the vorticity diffusion equation where the angular velocity on the outside surface of the fluid, at the cylinder's rotating wall, is fixed. This method is a means of measuring kinematic viscosity for low viscosity fluids without the need to measure stress. PMID:20189854

  14. Analysis of multiple pulse NMR in solids

    Science.gov (United States)

    Rhim, W.-K.; Elleman, D. D.; Vaughan, R. W.

    1973-01-01

    The general problems associated with the removal of the effects of dipolar broadening from solid-state NMR spectra are analyzed. The effects of finite pulse width and H sub 1 inhomogeneity are shown to have limited the resolution of previous pulse cycles, and a new eight-pulse cycle designed to minimize these problems is discussed. Spectra for F-19 in CaF2 taken with this cycle are presented which show residual linewidth near 10 Hz. The feasibility of measuring proton chemical shift tensors is discussed.

  15. Dynamic NMR cardiac imaging in a piglet

    Energy Technology Data Exchange (ETDEWEB)

    Doyle, M.; Rzedzian, R.; Mansfield, P. (Nottingham Univ. (UK). Dept. of Physics); Coupland, R.E. (Nottingham Univ. (UK). Queen' s Medical Centre)

    1983-12-01

    NMR echo-planar imaging (EPI) has been used in a real-time mode to visualise the thorax of a live piglet. Moving pictures are available on an immediate image display system which demonstrates dynamic cardiac function. Frame rates vary from one per cardiac cycle in a prospective stroboscopic mode with immediate visual output to a maximum of 10 frames per second yielding up to six looks in one piglet heart cycle, but using a visual playback mode. A completely new system has been used to obtain these images, features of which include a probe assembly with 22 cm access and an AP400 array processor for real-time data processing.

  16. Structural study of pyrones by NMR

    International Nuclear Information System (INIS)

    Extracts of two species of Aniba, designed Aniba-SA (light petroleum extract) and Aniba-SB (benzene extract), afforded by chromatographic fraccionation some compounds. The isolated compounds were identified using spectrometric data and C13-NMR coupled and decompled spectra of pyrones were registered. Measurement of the heteronuclear residual coupling by irradiation proton frequency off-resonance was used for distinguish C-5, C-7 and C-8 carbons of the pyrones SB-1, SB-3, SB-4 and SB-5. (M.J.C.)

  17. A NMR characterisation of a banded sandstone.

    Science.gov (United States)

    Bolam, A C; Packer, K J

    1998-01-01

    1H-nuclear magnetic resonance (NMR) measurements have been carried out on a banded sandstone to investigate the effects of structural inhomogeneities on the fluid dynamics of the sample as a whole. The results obtained from average propagator measurements (the probability of a displacement z in a time delta or P delta (z)) using pulsed-field-gradient techniques have been compared to those obtained from a study of a homogeneous sandstone. Relaxation has been used to derive the pore sizes for the differing bands and have been found to correlate with flow velocities within the bands.

  18. Quenched Hydrogen Exchange NMR of Amyloid Fibrils.

    Science.gov (United States)

    Alexandrescu, Andrei T

    2016-01-01

    Amyloid fibrils are associated with a number of human diseases. These aggregatively misfolded intermolecular β-sheet assemblies constitute some of the most challenging targets in structural biology because to their complexity, size, and insolubility. Here, protocols and controls are described for experiments designed to study hydrogen-bonding in amyloid fibrils indirectly, by transferring information about amide proton occupancy in the fibrils to the dimethyl sulfoxide-denatured state. Since the denatured state is amenable to solution NMR spectroscopy, the method can provide residue-level-resolution data on hydrogen exchange for the monomers that make up the fibrils.

  19. Studies on irradiation stability of polystyrene by NMR

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xin; SUN Wan-Fu; XIE Cheng-Xi

    2004-01-01

    The irradiation stability of polystyrene (PS) was studied by 13C and 1H NMR spectra, Nuclear Overhauser Relaxation (NOE) and 13C NMR spin-lattice relaxation time (T1). The results indicate that 13C and 1H NMR chemical shifts, NOE and T1 were almost invariant with the increase of irradiation dose. This shows that polystyrene is particularly stable within 2.5 kGy doses and the mechanism of its stability is discussed.

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

    Energy Technology Data Exchange (ETDEWEB)

    Hirasaki, George J.; Mohanty, Kishore K.

    2003-02-10

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

  1. Classical model for bulk-ensemble NMR quantum computation

    OpenAIRE

    Schack, R.; Caves, C. M.

    1999-01-01

    We present a classical model for bulk-ensemble NMR quantum computation: the quantum state of the NMR sample is described by a probability distribution over the orientations of classical tops, and quantum gates are described by classical transition probabilities. All NMR quantum computing experiments performed so far with three quantum bits can be accounted for in this classical model. After a few entangling gates, the classical model suffers an exponential decrease of the measured signal, whe...

  2. On the sensitivity of running-fluid NMR magnetometers

    Science.gov (United States)

    Davydov, V. V.; Dudkin, V. I.; Petrov, A. A.; Myazin, N. S.

    2016-07-01

    A new procedure for determining the sensitivity of running-fluid NMR magnetometers is considered. The procedure is based on mathematical processing of experimental data that are related to measuring the gradient of a nutation-line slope at the point at which an inverted NMR signal crosses zero. The procedure allows one to determine the sensitivity of running-fluid NMR magnetometers for resonance frequencies of magnetic-field measurements within a range of 0.5 Hz to 840 MHz.

  3. A Covariance NMR Toolbox for MATLAB and OCTAVE

    OpenAIRE

    Short, Timothy; Alzapiedi, Leigh; Brüschweiler, Rafael; Snyder, David

    2010-01-01

    The Covariance NMR Toolbox is a new software suite that provides a streamlined implementation of covariance-based analysis of multi-dimensional NMR data. The Covariance NMR Toolbox uses the MATLAB or, alternatively, the freely available GNU OCTAVE computer language, providing a user-friendly environment in which to apply and explore covariance techniques. Covariance methods implemented in the toolbox described here include direct and indirect covariance processing, 4D covariance, generalized ...

  4. Fractional order analysis of Sephadex gel structures: NMR measurements reflecting anomalous diffusion

    Science.gov (United States)

    Magin, Richard L.; Akpa, Belinda S.; Neuberger, Thomas; Webb, Andrew G.

    2011-12-01

    We report the appearance of anomalous water diffusion in hydrophilic Sephadex gels observed using pulse field gradient (PFG) nuclear magnetic resonance (NMR). The NMR diffusion data was collected using a Varian 14.1 Tesla imaging system with a home-built RF saddle coil. A fractional order analysis of the data was used to characterize heterogeneity in the gels for the dynamics of water diffusion in this restricted environment. Several recent studies of anomalous diffusion have used the stretched exponential function to model the decay of the NMR signal, i.e., exp[-( bD) α], where D is the apparent diffusion constant, b is determined the experimental conditions (gradient pulse separation, durations and strength), and α is a measure of structural complexity. In this work, we consider a different case where the spatial Laplacian in the Bloch-Torrey equation is generalized to a fractional order model of diffusivity via a complexity parameter, β, a space constant, μ, and a diffusion coefficient, D. This treatment reverts to the classical result for the integer order case. The fractional order decay model was fit to the diffusion-weighted signal attenuation for a range of b-values (0 < b < 4000 s mm -2). Throughout this range of b values, the parameters β, μ and D, were found to correlate with the porosity and tortuosity of the gel structure.

  5. Computer-intensive simulation of solid-state NMR experiments using SIMPSON

    Science.gov (United States)

    Tošner, Zdeněk; Andersen, Rasmus; Stevensson, Baltzar; Edén, Mattias; Nielsen, Niels Chr.; Vosegaard, Thomas

    2014-09-01

    Conducting large-scale solid-state NMR simulations requires fast computer software potentially in combination with efficient computational resources to complete within a reasonable time frame. Such simulations may involve large spin systems, multiple-parameter fitting of experimental spectra, or multiple-pulse experiment design using parameter scan, non-linear optimization, or optimal control procedures. To efficiently accommodate such simulations, we here present an improved version of the widely distributed open-source SIMPSON NMR simulation software package adapted to contemporary high performance hardware setups. The software is optimized for fast performance on standard stand-alone computers, multi-core processors, and large clusters of identical nodes. We describe the novel features for fast computation including internal matrix manipulations, propagator setups and acquisition strategies. For efficient calculation of powder averages, we implemented interpolation method of Alderman, Solum, and Grant, as well as recently introduced fast Wigner transform interpolation technique. The potential of the optimal control toolbox is greatly enhanced by higher precision gradients in combination with the efficient optimization algorithm known as limited memory Broyden-Fletcher-Goldfarb-Shanno. In addition, advanced parallelization can be used in all types of calculations, providing significant time reductions. SIMPSON is thus reflecting current knowledge in the field of numerical simulations of solid-state NMR experiments. The efficiency and novel features are demonstrated on the representative simulations.

  6. Perspectives of Deuteron Field-Cycling NMR Relaxometry for Probing Molecular Dynamics in Soft Matter.

    Science.gov (United States)

    Flämig, M; Becher, M; Hofmann, M; Körber, T; Kresse, B; Privalov, A F; Willner, L; Kruk, D; Fujara, F; Rössler, E A

    2016-08-11

    Due to the single-particle character of the quadrupolar interaction in molecular systems, (2)H NMR poses a unique method for probing reorientational dynamics. Spin-lattice relaxation gives access to the spectral density, and its frequency dependency can be monitored by field-cycling (FC) techniques. However, most FC NMR studies employ (1)H; the use of (2)H is still rare. We report on the application of (2)H FC NMR for investigating the dynamics in molecular liquids and polymers. Commercial as well as home-built relaxometers are employed accessing a frequency range from 30 Hz to 6 MHz. Due to low gyromagnetic ratio, high coupling constants, and finite FC switching times, current (2)H FC NMR does not reach the dispersion region in liquids (toluene and glycerol), yet good agreement with the results from conventional high-field (HF) relaxation studies is demonstrated. The pronounced difference at low frequencies between (2)H and (1)H FC NMR data shows the relevance of intermolecular relaxation in the case of (1)H NMR. In the case of the polymers polybutadiene and poly(ethylene-alt-propylene), very similar relaxation dispersion is observed and attributed to Rouse and entanglement dynamics. Combination with HF (2)H relaxation data via applying frequency-temperature superposition allows the reconstruction of the full spectral density reflecting both polymer as well as glassy dynamics. Transformation into the time domain yields the reorientational correlation function C2(t) extending over nine decades in time with a long-time power law, C2(t) ∝ t(-0.45±0.05), which does not conform to the prediction of the tube-reptation model, for which ∝ t(-0.25) is expected. Entanglement sets in below C2(t = τe) ≅ S(2) = 0.001, where τe is the entanglement time and S the corresponding order parameter. Finally, we discuss the future prospects of the (2)H FC NMR technique. PMID:27420118

  7. Crystallographic and dynamic aspects of solid-state NMR calibration compounds: towards ab initio NMR crystallography

    DEFF Research Database (Denmark)

    Li, Xiaozhou; Tapmeyer, Lukas; Bolte, Michael;

    2016-01-01

    The excellent results of dispersion-corrected density functional theory (DFT-D) calculations for static systems have been well established over the past decade. The introduction of dynamics into DFT-D calculations is a target, especially for the field of molecular NMR crystallography. Four 13C ss...

  8. Touch NMR: An NMR Data Processing Application for the iPad

    Science.gov (United States)

    Li, Qiyue; Chen, Zhiwei; Yan, Zhiping; Wang, Cheng; Chen, Zhong

    2014-01-01

    Nuclear magnetic resonance (NMR) spectroscopy has become one of the most powerful technologies to aid research in numerous scientific disciplines. With the development of consumer electronics, mobile devices have played increasingly important roles in our daily life. However, there is currently no application available for mobile devices able to…

  9. A primer to nutritional metabolomics by NMR spectroscopy and chemometrics

    DEFF Research Database (Denmark)

    Savorani, Francesco; Rasmussen, Morten Arendt; Mikkelsen, Mette Skau;

    2013-01-01

    This paper outlines the advantages and disadvantages of using high throughput NMR metabolomics for nutritional studies with emphasis on the workflow and data analytical methods for generation of new knowledge. The paper describes one-by-one the major research activities in the interdisciplinary...... metabolomics platform and highlights the opportunities that NMR spectra can provide in future nutrition studies. Three areas are emphasized: (1) NMR as an unbiased and non-destructive platform for providing an overview of the metabolome under investigation, (2) NMR for providing versatile information and data...

  10. Rotational Doppler Effect and Barnett Field in Spinning NMR

    Science.gov (United States)

    Chudo, Hiroyuki; Harii, Kazuya; Matsuo, Mamoru; Ieda, Jun'ichi; Ono, Masao; Maekawa, Sadamichi; Saitoh, Eiji

    2015-04-01

    We report the observation of the rotational Doppler effect using nuclear magnetic resonance (NMR). We have developed a coil-spinning technique that enables measurements by rotating a detector and fixing a sample. We found that the rotational Doppler effect gives rise to NMR frequency shifts equal to the rotation frequency. We formulate the rotational Doppler effect and the Barnett field using a vector model for the nuclear magnetic moment. This formulation reveals that, with just the sample rotating, both effects cancel each other, thereby explaining the absence of an NMR frequency shift in conventional sample-spinning NMR measurements.

  11. Synthesis and biological characterization of new amino-phosphonates for mitochondrial pH determination by 31P NMR spectroscopy

    International Nuclear Information System (INIS)

    A series of mitochondria targeted α-amino-phosphonates combining a diethoxy-phosphoryl group and an alkyl chain-connected triphenylphosphonium bromide tail were designed and synthesized, and their pH-sensitive 31P NMR properties and biological activities in vitro and in vivo were evaluated. The results showed a number of these mitoaminophosphonates exhibiting pKa values fitting the mitochondrial pH range, short relaxation, and chemical shift parameters compatible with sensitive 31P NMR detection, and low cytotoxicity on green algae and murine fibroblasts cell cultures. Of these, two selected compounds demonstrated to distribute at NMR detectable levels within the cytosolic and mitochondrial sites following their perfusion to isolated rat livers, with no detrimental effects on cell energetics and aerobic respiration. This study provided a new molecular scaffold for further development of in situ spectroscopic real-time monitoring of mitochondrion/cytosol pH gradients. (authors)

  12. NMR Studies on the Internal Structure of High-T{sub c} Superconductors and Other Anorganic Compounds

    Energy Technology Data Exchange (ETDEWEB)

    Kumagai, K., E-mail: kumagai@phys.sci.hokudai.ac.jp; Kakuyanagi, K.; Saitoh, M. [Hokkaido University, Division of Physics, Graduate School of Science (Japan); Matsuda, Y. [University of Tokyo, Institute for Solid State Physics (Japan); Hasegawa, M. [Tohoku University, Institute of Material Research (Japan); Takashima, S.; Nohara, M.; Takagi, H. [University of Tokyo, Department of Advanced Materials Science (Japan)

    2004-12-15

    Spatially-resolved NMR is used to probe internal structures in highly correlated superconductors of optimally-doped Tl{sub 2}Ba{sub 2}CuO{sub 6+{delta}} (T{sub c} 85 K) and a heavy fermion superconductor CeCoIn{sub 5} (T{sub c} = 2.3 K). The characteristic change of the properties of {sup 205}Tl-NMR in the vortex state provides a clear evidence of the antiferromagnetic order in the vortex cores below 20 K in Tl{sub 2}Ba{sub 2}CuO{sub 6+{delta}}. We also obtain anomalous {sup 115}In-NMR spectra of CeCoIn{sub 5}, which provides a microscopic evidence for the occurrence of a spatially-modulated superconducting order parameter expected in a Fulde-Ferrel-Larkin-Ovchinnkov (FFLO) state.

  13. Fast and global authenticity screening of honey using ¹H-NMR profiling.

    Science.gov (United States)

    Spiteri, Marc; Jamin, Eric; Thomas, Freddy; Rebours, Agathe; Lees, Michèle; Rogers, Karyne M; Rutledge, Douglas N

    2015-12-15

    An innovative analytical approach was developed to tackle the most common adulterations and quality deviations in honey. Using proton-NMR profiling coupled to suitable quantification procedures and statistical models, analytical criteria were defined to check the authenticity of both mono- and multi-floral honey. The reference data set used was a worldwide collection of more than 800 honeys, covering most of the economically significant botanical and geographical origins. Typical plant nectar markers can be used to check monofloral honey labeling. Spectral patterns and natural variability were established for multifloral honeys, and marker signals for sugar syrups were identified by statistical comparison with a commercial dataset of ca. 200 honeys. Although the results are qualitative, spiking experiments have confirmed the ability of the method to detect sugar addition down to 10% levels in favorable cases. Within the same NMR experiments, quantification of glucose, fructose, sucrose and 5-HMF (regulated parameters) was performed. Finally markers showing the onset of fermentation are described.

  14. Wettability testing of unconsolidated oil sands using low field NMR technology

    Energy Technology Data Exchange (ETDEWEB)

    Ji, X.; Kantzas, A.; Bryan, J. [University of Calgary/TIPM Laboratory (Canada)

    2011-07-01

    In an oil field it is important to understand wettability within the reservoir as it has an important impact on several parameters. However it is difficult to measure wettability in oil sands since conventional Amott/USBM testing cannot be applied. The aim of this paper is to develop protocols to assess wettability from NMR spectra in heavy oil reservoirs. Research was conducted on water wet and oil wet conditions; 3 sets of experiments were carried out with oil phases of different viscosity. Results showed that the signal from oil is insensitive to the location of the oil when viscosity increases but that water relaxation times are linked to the presence of water so water peak shifts can be used to determine different wettability states. This study determined that using water phase NMR relaxation presents several advantages to extract wettability information in unconsolidated sand systems and a technique was developed to interpret wettability.

  15. New generation NMR bioreactor coupled with high-resolution NMR spectroscopy leads to novel discoveries in Moorella thermoaceticum metabolic profiles

    Energy Technology Data Exchange (ETDEWEB)

    Xue, Junfeng; Isern, Nancy G.; Ewing, R James; Liyu, Andrey V.; Sears, Jesse A.; Knapp, Harlan; Iversen, Jens; Sisk, Daniel R.; Ahring, Birgitte K.; Majors, Paul D.

    2014-06-20

    An in-situ nuclear magnetic resonance (NMR) bioreactor was developed and employed to monitor microbial metabolism under batch-growth conditions in real time. We selected Moorella thermoacetica ATCC 49707 as a test case. M. thermoacetica (formerly Clostridium thermoaceticum) is a strictly anaerobic, thermophilic, acetogenic, gram-positive bacterium with potential for industrial production of chemicals. The metabolic profiles of M. thermoacetica were characterized during growth in batch mode on xylose (a component of lignocellulosic biomass) using the new generation NMR bioreactor in combination with high-resolution, high sensitivity NMR (HR-NMR) spectroscopy. In-situ NMR measurements were performed using water-suppressed H-1 NMR spectroscopy at an NMR frequency of 500 MHz, and aliquots of the bioreactor contents were taken for 600 MHz HR-NMR spectroscopy at specific intervals to confirm metabolite identifications and expand metabolite coverage. M. thermoacetica demonstrated the metabolic potential to produce formate, ethanol and methanol from xylose, in addition to its known capability of producing acetic acid. Real-time monitoring of bioreactor conditions showed a temporary pH decrease, with a concomitant increase in formic acid during exponential growth. Fermentation experiments performed outside of the magnet showed that the strong magnetic field employed for NMR detection did not significantly affect cell metabolism. Use of the in-situ NMR bioreactor facilitated monitoring of the fermentation process in real time, enabling identification of intermediate and end-point metabolites and their correlation with pH and biomass produced during culture growth. Real-time monitoring of culture metabolism using the NMR bioreactor in combination with the HR-NMR spectroscopy will allow optimization of the metabolism of microorganisms producing valuable bioproducts.

  16. The D0 solenoid NMR magnetometer

    Energy Technology Data Exchange (ETDEWEB)

    Sten Uldall Hansen Terry Kiper, Tom Regan, John Lofgren et al.

    2002-11-20

    A field monitoring system for the 2 Tesla Solenoid of the D0 detector is described. It is comprised of a very small NMR probe cabled to a DSP based signal processing board. The design magnetic field range is from 1.0 to 2.2 Tesla, corresponding to an RF frequency range of 42.57 to 93.67 MHz. The desired an accuracy is one part in 10{sup 5}. To minimize material in the interaction region of the D0 detector, the overall thickness of the NMR probe is 4 mm, including its mounting plate, and its width is 10 mm. To minimize cable mass, 4mm diameter IMR-100A cables are used for transmitting the RF signals from a nearby patch panel 25 meters to each of four probes mounted within the bore of the solenoid. RG213U cables 45 meters long are used to send the RF from the movable counting house to the patch panel. With this setup, the detector signal voltage at the moving counting room is in the range of 250-400 mV.

  17. In vivo NMR spectroscopy of ripening avocado

    International Nuclear Information System (INIS)

    Ripening of avocado fruit is associated with a dramatic increase in respiration. Previous studies have indicated that the increase in respiration is brought about by activation of the glycolytic reaction catalyzing the conversion of fructose-6-phosphate to fructose 1,6-bisphosphate. The authors reinvestigated the proposed role of glycolytic regulation in the respiratory increase using in vivo 31P nuclear magnetic resonance (NMR) spectroscopy using an external surface coil and analysis of phosphofructokinase (PFK), phosphofructophosphotransferase (PFP), and fructose 2,6-bisphosphate (fru 2,6-P2) levels in ripening avocado fruit. In vivo 31P NMR spectroscopy revealed large increases in ATP levels accompanying the increase in respiration. Both glycolytic enzymes, PFK and PFP, were present in avocado fruit, with the latter activity being highly stimulated by fru 2,6-P2. Fructose 2,6-bisphosphate levels increased approximately 90% at the onset of ripening, indicating that the respiratory increase in ripening avocado may be regulated by the activation of PFP brought about by an increase in fru 2,6-P2

  18. Automated Control of the Organic and Inorganic Composition of Aloe vera Extracts Using (1)H NMR Spectroscopy.

    Science.gov (United States)

    Monakhova, Yulia B; Randel, Gabriele; Diehl, Bernd W K

    2016-09-01

    Recent classification of Aloe vera whole-leaf extract by the International Agency for Research and Cancer as a possible carcinogen to humans as well as the continuous adulteration of A. vera's authentic material have generated renewed interest in controlling A. vera. The existing NMR spectroscopic method for the analysis of A. vera, which is based on a routine developed at Spectral Service, was extended. Apart from aloverose, glucose, malic acid, lactic acid, citric acid, whole-leaf material (WLM), acetic acid, fumaric acid, sodium benzoate, and potassium sorbate, the quantification of Mg(2+), Ca(2+), and fructose is possible with the addition of a Cs-EDTA solution to sample. The proposed methodology was automated, which includes phasing, baseline-correction, deconvolution (based on the Lorentzian function), integration, quantification, and reporting. The NMR method was applied to 41 A. vera preparations in the form of liquid A. vera juice and solid A. vera powder. The advantages of the new NMR methodology over the previous method were discussed. Correlation between the new and standard NMR methodologies was significant for aloverose, glucose, malic acid, lactic acid, citric acid, and WLM (P < 0.0001, R(2) = 0.99). NMR was found to be suitable for the automated simultaneous quantitative determination of 13 parameters in A. vera. PMID:27413027

  19. Determination of free fatty acids in pharmaceutical lipids by ¹H NMR and comparison with the classical acid value.

    Science.gov (United States)

    Skiera, Christina; Steliopoulos, Panagiotis; Kuballa, Thomas; Diehl, Bernd; Holzgrabe, Ulrike

    2014-05-01

    Indices like acid value, peroxide value, and saponification value play an important role in quality control and identification of lipids. Requirements on these parameters are given by the monographs of the European pharmacopeia. (1)H NMR spectroscopy provides a fast and simple alternative to these classical approaches. In the present work a new (1)H NMR approach to determine the acid value is described. The method was validated using a statistical approach based on a variance components model. The performance under repeatability and in-house reproducibility conditions was assessed. We applied this (1)H NMR assay to a wide range of different fatty oils. A total of 305 oil and fat samples were examined by both the classical and the NMR method. Except for hard fat, the data obtained by the two methods were in good agreement. The (1)H NMR method was adapted to analyse waxes and oleyloleat. Furthermore, the effect of solvent and in the case of castor oil the effect of the oil matrix on line broadening and chemical shift of the carboxyl group signal are discussed.

  20. NMR doesn't lie or how solid-state NMR spectroscopy contributed to a better understanding of the nature and function of soil organic matter (Philippe Duchaufour Medal Lecture)

    Science.gov (United States)

    Knicker, Heike

    2016-04-01

    "Nuclear magnetic resonance (NMR) does not lie". More than anything else, this statement of a former colleague and friend has shaped my relation to solid-state NMR spectroscopy. Indeed, if this technique leads to results which contradict the expectations, it is because i) some parts of the instrument are broken, ii) maladjustment of the acquisition parameters or iii) wrong preparation or confusion of samples. However, it may be even simpler, namely that the expectations were wrong. Of course, for researchers, the latter is the most interesting possibility since it forces to reassess accepted views and to search for new explanations. As my major analytical tool, NMR spectroscopy has confronted me with this challenge often enough to turn this issue into the main subject of my talk and to share with the audience how it formed my understanding of function and nature of soil organic matter (SOM). Already shortly after its introduction into soil science in the 1980's, the data obtained with solid-state 13C NMR spectroscopy opened the stage for ongoing discussions, since they showed that in humified SOM aromatic carbon is considerably less important than previously thought. This finding had major implications regarding the understanding of the origin of SOM and the mechanisms by which it is formed. Certainly, the discrepancy between the new results and previous paradigms contributed to mistrust in the reliability of solid-state NMR techniques. The respective discussion has survived up to our days, although already in the 1980's and 1990's fundamental studies could demonstrate that quantitative solid-state NMR data can be obtained if i) correct acquisition parameters are chosen, ii) the impact of paramagnetic compounds is reduced and iii) the presence of soot in soils can be excluded. On the other hand, this mistrust led to a detailed analysis of the impact of paramagnetics on the NMR behavior of C groups which then improved our understanding of the role of carbohydrates

  1. SPE-NMR metabolite sub-profiling of urine

    NARCIS (Netherlands)

    Jacobs, D.M.; Spiesser, L.; Garnier, M.; Roo, de N.; Dorsten, van F.; Hollebrands, B.; Velzen, van E.; Draijer, R.; Duynhoven, van J.P.M.

    2012-01-01

    NMR-based metabolite profiling of urine is a fast and reproducible method for detection of numerous metabolites with diverse chemical properties. However, signal overlap in the (1)H NMR profiles of human urine may hamper quantification and identification of metabolites. Therefore, a new method has b

  2. Facing and Overcoming Sensitivity Challenges in Biomolecular NMR Spectroscopy

    DEFF Research Database (Denmark)

    Ardenkjær-Larsen, Jan Henrik; Boebinger, Gregory S.; Comment, Arnaud;

    2015-01-01

    In the Spring of 2013, NMR spectroscopists convened at the Weizmann Institute in Israel to brainstorm on approaches to improve the sensitivity of NMR experiments, particularly when applied in biomolecular settings. This multi‐author interdisciplinary Review presents a state‐of‐the‐art description...

  3. Current progress and future prospects in NMR imaging

    International Nuclear Information System (INIS)

    Future prospects in NMR imaging will depend not only on the extent to which images of diagnostic quality can be obtained in reasonable short times, but, more importantly, on whether the whole range of NMR measurements and techniques can be applied to achieve a useful degree of tissue characterization and the measurement of blood flow in vivo. (orig./VJ)

  4. Characterizing RNA ensembles from NMR data with kinematic models

    DEFF Research Database (Denmark)

    Fonseca, Rasmus; Pachov, Dimitar V.; Bernauer, Julie;

    2014-01-01

    the conformational landscapes of 3D RNA encoded by NMR proton chemical shifts. KGSrna resolves motionally averaged NMR data into structural contributions; when coupled with residual dipolar coupling data, a KGSrna ensemble revealed a previously uncharacterized transient excited state of the HIV-1 trans...

  5. Realization of quantum discrete Fourier transform with NMR

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The pulse sequences of the logic operations used in quantum discrete Fourier transform are designed for the experiment of nuclear magnetic resonance(NMR), and 2-qubit discrete Fourier transforms are implemented experimentally with NMR. The experimental errors are examined and methods for reducing the errors are proposed.

  6. The Characterization of Comblike Polymer Electrolyte by Means of NMR

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The comblike polymers based on poly (styrene-co-maleic anhydride) backbone with poly (ethylene glycol) methyl ether as side chains were synthesized and characterized by 1H NMR, with the result compared with that of IR.It is found that it is both feasible and simple to synthesize this kind of compounds with the help of 1H NMR.

  7. Chemical Equilibrium in Supramolecular Systems as Studied by NMR Spectrometry

    Science.gov (United States)

    Gonzalez-Gaitano, Gustavo; Tardajos, Gloria

    2004-01-01

    Undergraduate students are required to study the chemical balance in supramolecular assemblies constituting two or more interacting species, by using proton NMR spectrometry. A good knowledge of physical chemistry, fundamentals of chemical balance, and NMR are pre-requisites for conducting this study.

  8. Heteronuclear Multidimensional Protein NMR in a Teaching Laboratory

    Science.gov (United States)

    Wright, Nathan T.

    2016-01-01

    Heteronuclear multidimensional NMR techniques are commonly used to study protein structure, function, and dynamics, yet they are rarely taught at the undergraduate level. Here, we describe a senior undergraduate laboratory where students collect, process, and analyze heteronuclear multidimensional NMR experiments using an unstudied Ig domain (Ig2…

  9. New generation NMR bioreactor coupled with high-resolution NMR spectroscopy leads to novel discoveries in Moorella thermoacetica metabolic profiles.

    Science.gov (United States)

    Xue, Junfeng; Isern, Nancy G; Ewing, R James; Liyu, Andrei V; Sears, Jesse A; Knapp, Harlan; Iversen, Jens; Sisk, Daniel R; Ahring, Birgitte K; Majors, Paul D

    2014-10-01

    An in situ nuclear magnetic resonance (NMR) bioreactor was developed and employed to monitor microbial metabolism under batch growth conditions in real time. We selected Moorella thermoacetica ATCC 49707 as a test case. M. thermoacetica (formerly Clostridium thermoaceticum) is a strictly anaerobic, thermophilic, acetogenic, gram-positive bacterium with potential for industrial production of chemicals. The metabolic profiles of M. thermoacetica were characterized during growth in batch mode on xylose (a component of lignocellulosic biomass) using the new generation NMR bioreactor in combination with high-resolution NMR (HR-NMR) spectroscopy. In situ NMR measurements were performed using water-suppressed H-1 NMR spectroscopy at 500 MHz, and aliquots of the bioreactor contents were taken for 600-MHz HR-NMR spectroscopy at specific intervals to confirm metabolite identifications and expand metabolite coverage. M. thermoacetica demonstrated the metabolic potential to produce formate, ethanol, and methanol from xylose, in addition to its known capability of producing acetic acid. Real-time monitoring of bioreactor conditions showed a temporary pH decrease, with a concomitant increase in formic acid during exponential growth. Fermentation experiments performed outside of the magnet showed that the strong magnetic field employed for NMR detection did not significantly affect cell metabolism. Use of the in situ NMR bioreactor facilitated monitoring of the fermentation process, enabling identification of intermediate and endpoint metabolites and their correlation with pH and biomass produced during culture growth. Real-time monitoring of culture metabolism using the NMR bioreactor in combination with HR-NMR spectroscopy will allow optimization of the metabolism of microorganisms producing valuable bioproducts.

  10. New generation NMR bioreactor coupled with high-resolution NMR spectroscopy leads to novel discoveries in Moorella thermoacetica metabolic profiles.

    Science.gov (United States)

    Xue, Junfeng; Isern, Nancy G; Ewing, R James; Liyu, Andrei V; Sears, Jesse A; Knapp, Harlan; Iversen, Jens; Sisk, Daniel R; Ahring, Birgitte K; Majors, Paul D

    2014-10-01

    An in situ nuclear magnetic resonance (NMR) bioreactor was developed and employed to monitor microbial metabolism under batch growth conditions in real time. We selected Moorella thermoacetica ATCC 49707 as a test case. M. thermoacetica (formerly Clostridium thermoaceticum) is a strictly anaerobic, thermophilic, acetogenic, gram-positive bacterium with potential for industrial production of chemicals. The metabolic profiles of M. thermoacetica were characterized during growth in batch mode on xylose (a component of lignocellulosic biomass) using the new generation NMR bioreactor in combination with high-resolution NMR (HR-NMR) spectroscopy. In situ NMR measurements were performed using water-suppressed H-1 NMR spectroscopy at 500 MHz, and aliquots of the bioreactor contents were taken for 600-MHz HR-NMR spectroscopy at specific intervals to confirm metabolite identifications and expand metabolite coverage. M. thermoacetica demonstrated the metabolic potential to produce formate, ethanol, and methanol from xylose, in addition to its known capability of producing acetic acid. Real-time monitoring of bioreactor conditions showed a temporary pH decrease, with a concomitant increase in formic acid during exponential growth. Fermentation experiments performed outside of the magnet showed that the strong magnetic field employed for NMR detection did not significantly affect cell metabolism. Use of the in situ NMR bioreactor facilitated monitoring of the fermentation process, enabling identification of intermediate and endpoint metabolites and their correlation with pH and biomass produced during culture growth. Real-time monitoring of culture metabolism using the NMR bioreactor in combination with HR-NMR spectroscopy will allow optimization of the metabolism of microorganisms producing valuable bioproducts. PMID:24946863

  11. Ligand exchange and complex formation kinetics studied by NMR exemplified on fac-[(CO)3M(H2O)]+ (M = Mn, Tc, Re)

    OpenAIRE

    Helm, Lothar

    2008-01-01

    In this review ligand exchange and complex formation reactions on fac-[(CO)3M(H2O)3]+ (M = Mn, Tc, Re) and on fac-[(CO)2(NO)Re(H2O)3]2+ are presented. A variety of experimental NMR techniques are described and it is shown that sometimes combinations of techniques applied at variable temperature or variable pressure allowed to measure exchange rate constants and their activation parameters as well as thermodynamic parameters. Furthermore, the use of uncommon nuclei for NMR like 17O or 99Tc ext...

  12. Diffusional properties of methanogenic granular sludge: 1H-NMR Characterisation

    NARCIS (Netherlands)

    Lens, P.N.L.; Gastesi, R.; Vergeldt, F.; Aelst, van A.C.; Pisabarro, G.; As, van H.

    2003-01-01

    The diffusive properties of anaerobic methanogenic and sulfidogenic aggregates present in wastewater treatment bioreactors were studied using diffusion analysis by relaxation time-separated pulsed-field gradient nuclear magnetic resonance (NMR) spectroscopy and NMR imaging. NMR spectroscopy measurem

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

    Science.gov (United States)

    Frydman, Lucio; Scherf, Tali; Lupulescu, Adonis

    2002-01-01

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

  14. $\\beta$-NMR of copper isotopes in ionic liquids

    CERN Multimedia

    We propose to test the feasibility of spin-polarization and $\\beta$-NMR studies on several short-lived copper isotopes, $^{58}$ Cu, $^{74}$Cu and $^{75}$Cu in crystals and liquids. The motivation is given by biological studies of Cu with $\\beta$-NMR in liquid samples, since Cu is present in a large number of enzymes involved in electron transfer and activation of oxygen. The technique is based on spin-polarization via optical pumping in the new VITO beamline. We will use the existing lasers, NMR magnet and NMR chambers and we will prepare a new optical pumping system. The studies will be devoted to tests of achieved $\\beta$-asymmetry in solid hosts, the behaviour of asymmetry when increasing vacuum, and finally NMR scans in ionic liquids. The achieved spin polarization will be also relevant for the plans to measure with high precision the magnetic moments of neutron-rich Cu isotopes.

  15. NMR chemical shift as analytical derivative of the Helmholtz free energy

    CERN Document Server

    Heuvel, Willem Van den

    2012-01-01

    We present a theory for the temperature-dependent nuclear magnetic shielding tensor of molecules with arbitrary electronic structure. The theory is a generalization of Ramsey's theory for closed-shell molecules. The shielding tensor is defined as a second derivative of the Helmholtz free energy of the electron system in equilibrium with the applied magnetic field and the nuclear magnetic moments. This derivative is analytically evaluated and expressed as a sum over states formula. Special consideration is given to a system with an isolated degenerate ground state for which the size of the degeneracy and the composition of the wave functions are arbitrary. In this case the paramagnetic part of the shielding tensor is expressed in terms of the $g$ and $A$ tensors of the EPR spin Hamiltonian of the degenerate state. As an illustration of the proposed theory, we provide an explicit formula for the paramagnetic shift of the central lanthanide ion in endofullerenes Ln@C$_{60}$, with Ln=Ce$^{3+}$, Nd$^{3+}$, Sm$^{3+...

  16. NMR studies of polysaccharides from brown seaweeds

    Energy Technology Data Exchange (ETDEWEB)

    Noseda, M.D.; Tisher, C.A.; Gorin, P.A.J.; Duarte, M.E.R. [Parana Univ., Curitiba, PR (Brazil). Dept. de Bioquimica; Cerezo, A.S. [Buenos Aires Univ. Nacional (Argentina). Dept. de Quimica Organica

    1997-12-31

    Alginic acid is the major intercellular polysaccharide serving as matrix in the brown algae and is comprised of an unbranched chain of (1->4)-linked {beta}-D-mannuronic acid (M) and {alpha}-L-guluronic acid (G), arranged in a blockwise fashion. The composition of the monomer residues and the block structure varies depending on the source of the polymer. The selective binding of cations to alginate accounts for its ability to form gels, which is dependent on the number and lenght of the G-blocks. They are widely used industrially for their ability to retain water, and for their gelling, viscosifying and stabilizing properties (Smidsrod and draget, 1996). In this study, alginate composition and block structure in Sargassum stenophyllum has been determined by chemical methods and NMR spectroscopic analysis. (author) 4 refs., 3 figs.

  17. Experimental implementation of a NMR entanglement witness

    CERN Document Server

    Filgueiras, J G; Auccaise, R E; Vianna, R O; Sarthour, R S; Oliveira, I S

    2012-01-01

    Entanglement witnesses (EW) allow the detection of entanglement in a quantum system, from the measurement of some few observables. They do not require the complete determination of the quantum state, which is regarded as a main advantage. On this paper it is experimentally analyzed an entanglement witness recently proposed in the context of Nuclear Magnetic Resonance (NMR) experiments to test it in some Bell-diagonal states. We also propose some optimal entanglement witness for Bell-diagonal states. The efficiency of the two types of EW's are compared to a measure of entanglement with tomographic cost, the generalized robustness of entanglement. It is used a GRAPE algorithm to produce an entangled state which is out of the detection region of the EW for Bell-diagonal states. Upon relaxation, the results show that there is a region in which both EW fails, whereas the generalized robustness still shows entanglement, but with the entanglement witness proposed here with a better performance.

  18. Solid state NMR of sulfa-drugs

    CERN Document Server

    Portieri, A

    2001-01-01

    deducted. Exact positions of the hydrogen has proved to be essential as well in order to improve the calculations. Finally a case study for the REDOR pulse sequence has been carried out. Different attempts to understand the effects influencing this particular experiment have been carried out on 20% and 99% doubly enriched glycine, as well as on a particular sample, doubly enriched BRL55834, but the internuclear distances measured with this technique still displayed some uncertainties that made results not thoroughly reliable. This work has been a study of systems, mostly of sulfa-drugs, showing polymorphic behaviour. Using different means as solid state NMR, X-ray analysis, * and theoretical calculations, we have seen how it is possible to understand results obtained from the different techniques, proving how the study of polymorphic systems needs cooperative advice from the different techniques that are able to detect polymorphic differences. Within the sulfa-drugs I have been mostly concentrating on sulfani...

  19. NMR applications to low porosity carbonate stones.

    Science.gov (United States)

    Alesiani, M; Capuani, S; Maraviglia, B

    2003-09-01

    The purpose of this paper is to investigate NMR applications to porous materials widely employed in artistic and historical monuments and largely studied in the Cultural Heritage conservation field. Carrara marble, Candoglia marble and travertine samples were studied and data from relaxation times measurements were compared. Very interesting results from treated samples are reported and explained under the structure related spin lattice relaxation time point of view. Images of Carrara marble aged sample (XIX century), coming from the Florence Cathedral obtained for short absorption time of water by capillary rise and for relatively small thickness slices together show the fluid's spatial distribution within the stone. Comparative images showing untreated sample with the treated ones were obtained suggesting very useful applications for the determination of treatment effectiveness. PMID:14559345

  20. In situ deuteron NMR investigations of sheared liquid crystalline polymers.

    Science.gov (United States)

    Siebert, Hartmut; Becker, Patrick; Quijada-Garrido, Isabel; Grabowski, David A; Schmidt, Claudia

    2002-01-01

    The flow behavior of nematic liquid crystalline polysiloxanes of the side-chain type is studied by in situ 2H NMR spectroscopy on samples under shear in a cone-and-plate cell. The director orientation as a function of applied shear rate is determined from the quadrupole splitting of the spectra. The data analysis yields the two Leslie viscosity coefficients alpha2 and alpha3 and the flow-alignment parameter lambda = -(alpha3 + alpha2)/(alpha3 - alpha2). The values of lambda were determined for several homopolymers with only one type of side chain and random copolymers containing two different side chains. The results show that the flow behavior is related to the phase structure of the polymers, which varies with their composition. Only polymers with large amounts of smectic clusters in the nematic state show the tumbling instability (absolute value(lambda) polymers are flow aligning (absolute value(lambda) > or = 1). For some polymers, a transition from tumbling at low temperature to flow aligning at high temperatures was observed. PMID:12469817

  1. Non-uniform sampling of NMR relaxation data

    Energy Technology Data Exchange (ETDEWEB)

    Linnet, Troels E.; Teilum, Kaare, E-mail: kaare.teilum@bio.ku.dk [University of Copenhagen, SBiNLab and the Linderstrøm-Lang Centre for Protein Science, Department of Biology (Denmark)

    2016-02-15

    The use of non-uniform sampling of NMR spectra may give significant reductions in the data acquisition time. For quantitative experiments such as the measurement of spin relaxation rates, non-uniform sampling is however not widely used as inaccuracies in peak intensities may lead to errors in the extracted dynamic parameters. By systematic reducing the coverage of the Nyquist grid of {sup 15}N Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion datasets for four different proteins and performing a full data analysis of the resulting non-uniform sampled datasets, we have compared the performance of the multi-dimensional decomposition and iterative re-weighted least-squares algorithms in reconstructing spectra with accurate peak intensities. As long as a single fully sampled spectrum is included in a series of otherwise non-uniform sampled two-dimensional spectra, multi-dimensional decomposition reconstructs the non-uniform sampled spectra with high accuracy. For two of the four analyzed datasets, a coverage of only 20 % results in essentially the same results as the fully sampled data. As exemplified by other data, such a low coverage is in general not enough to produce reliable results. We find that a coverage level not compromising the final results can be estimated by recording a single full two-dimensional spectrum and reducing the spectrum quality in silico.

  2. Non-uniform sampling of NMR relaxation data

    International Nuclear Information System (INIS)

    The use of non-uniform sampling of NMR spectra may give significant reductions in the data acquisition time. For quantitative experiments such as the measurement of spin relaxation rates, non-uniform sampling is however not widely used as inaccuracies in peak intensities may lead to errors in the extracted dynamic parameters. By systematic reducing the coverage of the Nyquist grid of 15N Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion datasets for four different proteins and performing a full data analysis of the resulting non-uniform sampled datasets, we have compared the performance of the multi-dimensional decomposition and iterative re-weighted least-squares algorithms in reconstructing spectra with accurate peak intensities. As long as a single fully sampled spectrum is included in a series of otherwise non-uniform sampled two-dimensional spectra, multi-dimensional decomposition reconstructs the non-uniform sampled spectra with high accuracy. For two of the four analyzed datasets, a coverage of only 20 % results in essentially the same results as the fully sampled data. As exemplified by other data, such a low coverage is in general not enough to produce reliable results. We find that a coverage level not compromising the final results can be estimated by recording a single full two-dimensional spectrum and reducing the spectrum quality in silico

  3. Variations of NMR signals by hyperpolarization and ultrasound; Variation von NMR-Signalen durch Hyperpolarisation und Ultraschall

    Energy Technology Data Exchange (ETDEWEB)

    Engelbertz, A.

    2006-07-01

    In this thesis it is described how p-NMR can be applied to metals with verlo low hydrogen concentrations and how a combination of ultrasound and NMR can lead to an improvement of the measureing method. As examples measurements on H{sub 2}O and ethanol are described. (HSI)

  4. NMR study of hyper-polarized 129Xe and applications to liquid-phase NMR experiments

    International Nuclear Information System (INIS)

    In liquid samples where both nuclear polarization and spin density are strong, the magnetization dynamics, which can be analysed by NMR (nuclear magnetic resonance) methods, is deeply influenced by the internal couplings induced by local dipolar fields. The present thesis describes some of the many consequences associated to the presence in the sample of concentrated xenon hyper-polarized by an optical pumping process. First, we deal with the induced modifications in frequency and line width of the proton and xenon spectra, then we present the results of SPIDER, a coherent polarization transfer experiment designed to enhance the polarization of protons, in order to increase their NMR signal level. A third part is dedicated to the description of the apparition of repeated chaotic maser emissions by un unstable xenon magnetization coupled to the detection coil tuned at the xenon Larmor frequency (here 138 MHz). In the last part, we present a new method allowing a better tuning of any NMR detection probe and resulting in sensible gains in terms of sensitivity and signal shaping. Finally, we conclude with a partial questioning of the classical relaxation theory in the specific field of highly polarized and concentrated spin systems in a liquid phase. (author)

  5. NMR Relaxation in Systems with Magnetic Nanoparticles: A Temperature Study

    Science.gov (United States)

    Issa, Bashar; Obaidat, Ihab M.; Hejasee, Rola H.; Qadri, Shahnaz; Haik, Yousef

    2013-01-01

    Purpose To measure and model NMR relaxation enhancement due to the presence of Gd substituted Zn-Mn ferrite magnetic nanoparticles at different temperatures. Materials and Methods Relaxation rates were measured at 1.5 T using FSE sequences in samples of agarose gel doped with uncoated and polyethylene glycol (PEG) coated Mn0.5Zn0.5Gd0.02Fe1.98O4 nanoparticles over the temperature range 8 to 58°C. Physical characterization of the magnetic nanoparticles synthesized using chemical co-precipitation included scanning (SEM) and transmission (TEM) electron microscopy, inductively coupled plasma (ICP), dynamic light scattering (DLS), and magnetometry. Results Relaxivity (in s−1 mM−1 Fe) for the uncoated and coated particles, respectively, increased as follows: from 2.5 to 3.2 and 0.4 to 0.7 for T1, while for T2 it increased from 162.3 to 253.7 and 59.7 to 82.2 over the temperature range 8 to 58°C. T2 data was fitted to the echo limited motional regime using one fitting parameter that reflects the degree of agglomeration of particles into a cluster. This parameter was found to increase linearly with temperature and was larger for the PEG coated particles than the uncoated ones. Conclusion The increase of 1/T2 with temperature is modeled successfully using echo limited motional regime where both diffusion of the protons and nanoparticle cluster size increase with temperature. Both transverse and longitudinal relaxation efficiencies are reduced by PEG coating at all temperatures. If prediction of relaxation rates under different particle concentrations and operating temperatures is possible then the use of MNP in temperature monitoring and hyperthermia applications may be achieved. PMID:23720101

  6. Communication: Molecular dynamics and {sup 1}H NMR of n-hexane in liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Adrian C. J., E-mail: WeberA@BrandonU.CA [Chemistry Department, Brandon University, 270-18th Street, Brandon, Manitoba R7A 6A9 (Canada); Burnell, E. Elliott, E-mail: elliott.burnell@ubc.ca [Chemistry Department, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1 (Canada); Meerts, W. Leo, E-mail: leo.meerts@science.ru.nl [Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135, NL-6525 AJ Nijmegen (Netherlands); Atomic, Molecular and Laser Physics, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam (Netherlands); Lange, Cornelis A. de, E-mail: c.a.de.lange@vu.nl [Atomic, Molecular and Laser Physics, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam (Netherlands); Dong, Ronald Y., E-mail: rondong@phas.ubc.ca [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia V6T 1Z1 (Canada); Muccioli, Luca, E-mail: Luca.Muccioli@unibo.it; Pizzirusso, Antonio, E-mail: Antonio.Pizzirusso80@gmail.com; Zannoni, Claudio, E-mail: Claudio.Zannoni@unibo.it [Dipartimento di Chimica Industriale “Toso Montanari,” Università di Bologna and INSTM, viale Risorgimento 4, 40136 Bologna (Italy)

    2015-07-07

    The NMR spectrum of n-hexane orientationally ordered in the nematic liquid crystal ZLI-1132 is analysed using covariance matrix adaptation evolution strategy (CMA-ES). The spectrum contains over 150 000 transitions, with many sharp features appearing above a broad, underlying background signal that results from the plethora of overlapping transitions from the n-hexane as well as from the liquid crystal. The CMA-ES requires initial search ranges for NMR spectral parameters, notably the direct dipolar couplings. Several sets of such ranges were utilized, including three from MD simulations and others from the modified chord model that is specifically designed to predict hydrocarbon-chain dipolar couplings. In the end, only inaccurate dipolar couplings from an earlier study utilizing proton-proton double quantum 2D-NMR techniques on partially deuterated n-hexane provided the necessary estimates. The precise set of dipolar couplings obtained can now be used to investigate conformational averaging of n-hexane in a nematic environment.

  7. Communication: Molecular dynamics and 1H NMR of n-hexane in liquid crystals

    Science.gov (United States)

    Weber, Adrian C. J.; Burnell, E. Elliott; Meerts, W. Leo; de Lange, Cornelis A.; Dong, Ronald Y.; Muccioli, Luca; Pizzirusso, Antonio; Zannoni, Claudio

    2015-07-01

    The NMR spectrum of n-hexane orientationally ordered in the nematic liquid crystal ZLI-1132 is analysed using covariance matrix adaptation evolution strategy (CMA-ES). The spectrum contains over 150 000 transitions, with many sharp features appearing above a broad, underlying background signal that results from the plethora of overlapping transitions from the n-hexane as well as from the liquid crystal. The CMA-ES requires initial search ranges for NMR spectral parameters, notably the direct dipolar couplings. Several sets of such ranges were utilized, including three from MD simulations and others from the modified chord model that is specifically designed to predict hydrocarbon-chain dipolar couplings. In the end, only inaccurate dipolar couplings from an earlier study utilizing proton-proton double quantum 2D-NMR techniques on partially deuterated n-hexane provided the necessary estimates. The precise set of dipolar couplings obtained can now be used to investigate conformational averaging of n-hexane in a nematic environment.

  8. Communication: Molecular dynamics and 1H NMR of n-hexane in liquid crystals

    International Nuclear Information System (INIS)

    The NMR spectrum of n-hexane orientationally ordered in the nematic liquid crystal ZLI-1132 is analysed using covariance matrix adaptation evolution strategy (CMA-ES). The spectrum contains over 150 000 transitions, with many sharp features appearing above a broad, underlying background signal that results from the plethora of overlapping transitions from the n-hexane as well as from the liquid crystal. The CMA-ES requires initial search ranges for NMR spectral parameters, notably the direct dipolar couplings. Several sets of such ranges were utilized, including three from MD simulations and others from the modified chord model that is specifically designed to predict hydrocarbon-chain dipolar couplings. In the end, only inaccurate dipolar couplings from an earlier study utilizing proton-proton double quantum 2D-NMR techniques on partially deuterated n-hexane provided the necessary estimates. The precise set of dipolar couplings obtained can now be used to investigate conformational averaging of n-hexane in a nematic environment

  9. Advanced Structural Determination of Diterpene Esters Using Molecular Modeling and NMR Spectroscopy.

    Science.gov (United States)

    Nothias-Scaglia, Louis-Félix; Gallard, Jean-François; Dumontet, Vincent; Roussi, Fanny; Costa, Jean; Iorga, Bogdan I; Paolini, Julien; Litaudon, Marc

    2015-10-23

    Three new jatrophane esters (1-3) were isolated from Euphorbia amygdaloides ssp. semiperfoliata, including an unprecedented macrocyclic jatrophane ester bearing a hemiketal substructure, named jatrohemiketal (3). The chemical structures of compounds 1-3 and their relative configurations were determined by spectroscopic analysis. The absolute configuration of compound 3 was determined unambiguously through an original strategy combining NMR spectroscopy and molecular modeling. Conformational search calculations were performed for the four possible diastereomers 3a-3d differing in their C-6 and C-9 stereocenters, and the lowest energy conformer was used as input structure for geometry optimization. The prediction of NMR parameters ((1)H and (13)C chemical shifts and (1)H-(1)H coupling constants) by density functional theory (DFT) calculations allowed identifying the most plausible diastereomer. Finally, the stereostructure of 3 was solved by comparison of the structural features obtained by molecular modeling for 3a-3d with NMR-derived data (the values of dihedral angles deduced from the vicinal proton-proton coupling constants ((3)JHH) and interproton distances determined by ROESY). The methodology described herein provides an efficient way to solve or confirm structural elucidation of new macrocyclic diterpene esters, in particular when no crystal structure is available.

  10. Characterization of the insertase BamA in three different membrane mimetics by solution NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Morgado, Leonor; Zeth, Kornelius; Burmann, Björn M.; Maier, Timm; Hiller, Sebastian, E-mail: sebastian.hiller@unibas.ch [University of Basel, Biozentrum (Switzerland)

    2015-04-15

    The insertase BamA is the central protein of the Bam complex responsible for outer membrane protein biogenesis in Gram-negative bacteria. BamA features a 16-stranded transmembrane β-barrel and five periplasmic POTRA domains, with a total molecular weight of 88 kDa. Whereas the structure of BamA has recently been determined by X-ray crystallography, its functional mechanism is not well understood. This mechanism comprises the insertion of substrates from a dynamic, chaperone-bound state into the bacterial outer membrane, and NMR spectroscopy is thus a method of choice for its elucidation. Here, we report solution NMR studies of different BamA constructs in three different membrane mimetic systems: LDAO micelles, DMPC:DiC{sub 7}PC bicelles and MSP1D1:DMPC nanodiscs. The impact of biochemical parameters on the spectral quality was investigated, including the total protein concentration and the detergent:protein ratio. The barrel of BamA is folded in micelles, bicelles and nanodiscs, but the N-terminal POTRA5 domain is flexibly unfolded in the absence of POTRA4. Measurements of backbone dynamics show that the variable insertion region of BamA, located in the extracellular lid loop L6, features high local flexibility. Our work establishes biochemical preparation schemes for BamA, which will serve as a platform for structural and functional studies of BamA and its role within the Bam complex by solution NMR spectroscopy.

  11. Ultrafast double-quantum NMR spectroscopy with optimized sensitivity for the analysis of mixtures.

    Science.gov (United States)

    Rouger, Laetitia; Gouilleux, Boris; Pourchet-Gellez, Mariane; Dumez, Jean-Nicolas; Giraudeau, Patrick

    2016-03-01

    Ultrafast (UF) 2D NMR enables the acquisition of 2D spectra within a single-scan. This methodology has become a powerful analytical tool, used in a large array of applications. However, UF NMR spectroscopy still suffers from the need to compromise between sensitivity, spectral width and resolution. With the commonly used UF-COSY pulse sequence, resolution issues are compounded by the presence of strong auto-correlation signals, particularly in the case of samples with high dynamic ranges. The recently proposed concept of UF Double Quantum Spectroscopy (DQS) allows a better peak separation as it provides a lower spectral peak density. This paper presents the detailed investigation of this new NMR tool in an analytical chemistry context. Theoretical calculations and numerical simulations are used to characterize the modulation of peak intensities as a function of pulse-sequence parameters, and thus enable a significant enhancement of the sensitivity. The analytical comparison of UF-COSY and UF-DQS shows similar performances, however the ultrafast implementation of the DQS approach is found to have some sensitivity advantages over its conventional counterpart. The analytical performance of the pulse sequence is illustrated by the quantification of taurine in complex mixtures (homemade and commercial energy drinks). The results demonstrate the high potential of this experiment, which forms a valuable alternative to UF-COSY spectra when the latter are characterized by strong overlaps and high dynamic ranges. PMID:26865359

  12. Improving the accuracy of pulsed field gradient NMR diffusion experiments: Correction for gradient non-uniformity

    Science.gov (United States)

    Connell, Mark A.; Bowyer, Paul J.; Adam Bone, P.; Davis, Adrian L.; Swanson, Alistair G.; Nilsson, Mathias; Morris, Gareth A.

    2009-05-01

    Pulsed field gradient NMR is a well-established technique for the determination of self-diffusion coefficients. However, a significant source of systematic error exists in the spatial variation of the applied pulsed field gradient. Non-uniform pulsed field gradients cause the decay of peak amplitudes to deviate from the expected exponential dependence on gradient squared. This has two undesirable effects: the apparent diffusion coefficient will deviate from the true value to an extent determined by the choice of experimental parameters, and the error estimated by the nonlinear least squares fitting will contain a significant systematic contribution. In particular, the apparent diffusion coefficient determined by exponential fitting of the diffusional attenuation of NMR signals will depend both on the exact pulse widths used and on the range of gradient amplitudes chosen. These problems can be partially compensated for if experimental attenuation data are fitted to a function corrected for the measured spatial dependence of the gradient and signal strength. This study describes a general alternative to existing methods for the calibration of NMR diffusion measurements. The dominant longitudinal variation of the pulsed field gradient amplitude and the signal strength are mapped by measuring pulsed field gradient echoes in the presence of a weak read gradient. These data are then used to construct a predicted signal decay function for the whole sample, which is parameterised as the exponential of a power series. Results are presented which compare diffusion coefficients obtained using the new calibration method with previous literature values.

  13. Experimental and NMR theoretical methodology applied to geometric analysis of the bioactive clerodane trans-dehydrocrotonin

    Energy Technology Data Exchange (ETDEWEB)

    Soares, Breno Almeida; Firme, Caio Lima, E-mail: firme.caio@gmail.com, E-mail: caiofirme@quimica.ufrn.br [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Instituto de Quimica; Maciel, Maria Aparecida Medeiros [Universidade Potiguar, Natal, RN (Brazil). Programa de Pos-graduacao em Biotecnologia; Kaiser, Carlos R. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Instituto de Quimica; Schilling, Eduardo; Bortoluzzi, Adailton J. [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Departamento de Quimica

    2014-04-15

    trans-Dehydrocrotonin (t-DCTN) a bioactive 19-nor-diterpenoid clerodane type isolated from Croton cajucara Benth, is one of the most investigated clerodane in the current literature. In this work, a new approach joining X-ray diffraction data, nuclear magnetic resonance (NMR) data and theoretical calculations was applied to the thorough characterization of t-DCTN. For that, the geometry of t-DCTN was reevaluated by X-ray diffraction as well as {sup 1}H and {sup 13}C NMR data, whose geometrical parameters where compared to those obtained from B3LYP/6-311G++(d,p) level of theory. From the evaluation of both calculated and experimental values of {sup 1}H and {sup 13}C NMR chemical shifts and spin-spin coupling constants, it was found very good correlations between theoretical and experimental magnetic properties of t-DCTN. Additionally, the delocalization indexes between hydrogen atoms correlated accurately with theoretical and experimental spin-spin coupling constants. An additional topological analysis from quantum theory of atoms in molecules (QTAIM) showed intramolecular interactions for t-DCTN. (author)

  14. Time-resolved CIDNP: an NMR way to determine the EPR parameters of elusive radicals.

    Science.gov (United States)

    Morozova, Olga B; Ivanov, Konstantin L; Kiryutin, Alexey S; Sagdeev, Renad Z; Köchling, Talea; Vieth, Hans-Martin; Yurkovskaya, Alexandra V

    2011-04-14

    Chemically Induced Dynamic Nuclear Polarization (CIDNP) of the diamagnetic products of radical reactions is exploited for the purpose of determination of the hyperfine coupling constants (HFCCs) of the radical intermediates. A simple proportionality relation between geminate CIDNP of a nucleus and its HFCC at the radical stage is established. The applicability range of this relation is determined: the relation is fulfilled in the case of a large difference in g-factor between the radicals involved and for the situation where the number of magnetic nuclei in the system is sufficiently large. The validity of the relation was confirmed by CIDNP experiments on radical pairs with precisely known HFCCs. Using the proportionality relation we were able to measure the HFCCs in various short-lived radicals of the amino acids histidine and tryptophan and of the S-N-centered cyclic radical of methionine derived from the methionine-glycine dipeptide in aqueous solution.

  15. Origin of the conformational modulation of the 13C NMR chemical shift of methoxy groups in aromatic natural compounds.

    Science.gov (United States)

    Toušek, Jaromír; Straka, Michal; Sklenář, Vladimír; Marek, Radek

    2013-01-24

    The interpretation of nuclear magnetic resonance (NMR) parameters is essential to understanding experimental observations at the molecular and supramolecular levels and to designing new and more efficient molecular probes. In many aromatic natural compounds, unusual (13)C NMR chemical shifts have been reported for out-of-plane methoxy groups bonded to the aromatic ring (~62 ppm as compared to the typical value of ~56 ppm for an aromatic methoxy group). Here, we analyzed this phenomenon for a series of aromatic natural compounds using Density Functional Theory (DFT) calculations. First, we checked the methodology used to optimize the structure and calculate the NMR chemical shifts in aromatic compounds. The conformational effects of the methoxy group on the (13)C NMR chemical shift then were interpreted by the Natural Bond Orbital (NBO) and Natural Chemical Shift (NCS) approaches, and by excitation analysis of the chemical shifts, breaking down the total nuclear shielding tensor into the contributions from the different occupied orbitals and their magnetic interactions with virtual orbitals. We discovered that the atypical (13)C NMR chemical shifts observed are not directly related to a different conjugation of the lone pair of electrons of the methoxy oxygen with the aromatic ring, as has been suggested. Our analysis indicates that rotation of the methoxy group induces changes in the virtual molecular orbital space, which, in turn, correlate with the predominant part of the contribution of the paramagnetic deshielding connected with the magnetic interactions of the BD(CMet-H)→BD*(CMet-OMet) orbitals, resulting in the experimentally observed deshielding of the (13)C NMR resonance of the out-of-plane methoxy group.

  16. Can NMR solve some significant challenges in metabolomics?

    Science.gov (United States)

    Nagana Gowda, G. A.; Raftery, Daniel

    2015-11-01

    The field of metabolomics continues to witness rapid growth driven by fundamental studies, methods development, and applications in a number of disciplines that include biomedical science, plant and nutrition sciences, drug development, energy and environmental sciences, toxicology, etc. NMR spectroscopy is one of the two most widely used analytical platforms in the metabolomics field, along with mass spectrometry (MS). NMR's excellent reproducibility and quantitative accuracy, its ability to identify structures of unknown metabolites, its capacity to generate metabolite profiles using intact bio-specimens with no need for separation, and its capabilities for tracing metabolic pathways using isotope labeled substrates offer unique strengths for metabolomics applications. However, NMR's limited sensitivity and resolution continue to pose a major challenge and have restricted both the number and the quantitative accuracy of metabolites analyzed by NMR. Further, the analysis of highly complex biological samples has increased the demand for new methods with improved detection, better unknown identification, and more accurate quantitation of larger numbers of metabolites. Recent efforts have contributed significant improvements in these areas, and have thereby enhanced the pool of routinely quantifiable metabolites. Additionally, efforts focused on combining NMR and MS promise opportunities to exploit the combined strength of the two analytical platforms for direct comparison of the metabolite data, unknown identification and reliable biomarker discovery that continue to challenge the metabolomics field. This article presents our perspectives on the emerging trends in NMR-based metabolomics and NMR's continuing role in the field with an emphasis on recent and ongoing research from our laboratory.

  17. Dispersion Properties of NMR Relaxation for Crude Oil

    Institute of Scientific and Technical Information of China (English)

    Xie Ranhong; Xiao Lizhi

    2007-01-01

    Special requirements for design of tools used for wireline NMR logging and NMR logging while drilling and for interpretation model are demanded due to the dispersion properties of NMR relaxation for crude oil.NMR longitudinal relaxation time (T1) and transverse relaxation time (T2) of the dead oil samples with different viscosities were measured by NMR spectrometers with a Larmor frequency of 2 MHz and 23 MHz at five different temperatures respectively.The results showed that T1 was obviously dependent on the Larmor frequency of NMR spectrometer.The degree of T1 dispersion became stronger with the increasing crude oil viscosity,Larmor frequency and the viscosity/temperature ratio.T2 was independent of NMR spectrometer measuring frequency.It is suggested that the resonance frequency should be selected lower than 2 MHz when measuring T1 in logging while-drilling and that T1 dispersion should be corrected when Larmor frequency is higher than 2 MHz.

  18. Theoretical Modeling of (99)Tc NMR Chemical Shifts.

    Science.gov (United States)

    Hall, Gabriel B; Andersen, Amity; Washton, Nancy M; Chatterjee, Sayandev; Levitskaia, Tatiana G

    2016-09-01

    Technetium-99 (Tc) displays a rich chemistry due to its wide range of accessible oxidation states (from -I to +VII) and ability to form coordination compounds. Determination of Tc speciation in complex mixtures is a major challenge, and (99)Tc nuclear magnetic resonance (NMR) spectroscopy is widely used to probe chemical environments of Tc in odd oxidation states. However, interpretation of (99)Tc NMR data is hindered by the lack of reference compounds. Density functional theory (DFT) calculations can help to fill this gap, but to date few computational studies have focused on (99)Tc NMR of compounds and complexes. This work evaluates the effectiveness of both pure generalized gradient approximation and their corresponding hybrid functionals, both with and without the inclusion of scalar relativistic effects, to model the (99)Tc NMR spectra of Tc(I) carbonyl compounds. With the exception of BLYP, which performed exceptionally well overall, hybrid functionals with inclusion of scalar relativistic effects are found to be necessary to accurately calculate (99)Tc NMR spectra. The computational method developed was used to tentatively assign an experimentally observed (99)Tc NMR peak at -1204 ppm to fac-Tc(CO)3(OH)3(2-). This study examines the effectiveness of DFT computations for interpretation of the (99)Tc NMR spectra of Tc(I) coordination compounds in high salt alkaline solutions. PMID:27518482

  19. Can NMR solve some significant challenges in metabolomics?

    Science.gov (United States)

    Nagana Gowda, G A; Raftery, Daniel

    2015-11-01

    The field of metabolomics continues to witness rapid growth driven by fundamental studies, methods development, and applications in a number of disciplines that include biomedical science, plant and nutrition sciences, drug development, energy and environmental sciences, toxicology, etc. NMR spectroscopy is one of the two most widely used analytical platforms in the metabolomics field, along with mass spectrometry (MS). NMR's excellent reproducibility and quantitative accuracy, its ability to identify structures of unknown metabolites, its capacity to generate metabolite profiles using intact bio-specimens with no need for separation, and its capabilities for tracing metabolic pathways using isotope labeled substrates offer unique strengths for metabolomics applications. However, NMR's limited sensitivity and resolution continue to pose a major challenge and have restricted both the number and the quantitative accuracy of metabolites analyzed by NMR. Further, the analysis of highly complex biological samples has increased the demand for new methods with improved detection, better unknown identification, and more accurate quantitation of larger numbers of metabolites. Recent efforts have contributed significant improvements in these areas, and have thereby enhanced the pool of routinely quantifiable metabolites. Additionally, efforts focused on combining NMR and MS promise opportunities to exploit the combined strength of the two analytical platforms for direct comparison of the metabolite data, unknown identification and reliable biomarker discovery that continue to challenge the metabolomics field. This article presents our perspectives on the emerging trends in NMR-based metabolomics and NMR's continuing role in the field with an emphasis on recent and ongoing research from our laboratory. PMID:26476597

  20. NMR data visualization, processing, and analysis on mobile devices.

    Science.gov (United States)

    Cobas, Carlos; Iglesias, Isaac; Seoane, Felipe

    2015-08-01

    Touch-screen computers are emerging as a popular platform for many applications, including those in chemistry and analytical sciences. In this work, we present our implementation of a new NMR 'app' designed for hand-held and portable touch-controlled devices, such as smartphones and tablets. It features a flexible architecture formed by a powerful NMR processing and analysis kernel and an intuitive user interface that makes full use of the smart devices haptic capabilities. Routine 1D and 2D NMR spectra acquired in most NMR instruments can be processed in a fully unattended way. More advanced experiments such as non-uniform sampled NMR spectra are also supported through a very efficient parallelized Modified Iterative Soft Thresholding algorithm. Specific technical development features as well as the overall feasibility of using NMR software apps will also be discussed. All aspects considered the functionalities of the app allowing it to work as a stand-alone tool or as a 'companion' to more advanced desktop applications such as Mnova NMR.

  1. High-resolution NMR spectroscopy under the fume hood.

    Science.gov (United States)

    Küster, Simon K; Danieli, Ernesto; Blümich, Bernhard; Casanova, Federico

    2011-08-01

    This work reports the possibility to acquire high-resolution (1)H NMR spectra with a fist-sized NMR magnet directly installed under the fume hood. The small NMR sensor based on permanent magnets was used to monitor the trimerization of propionaldehyde catalyzed by indium trichloride in real time by continuously circulating the reaction mixture through the magnet bore in a closed loop with the help of a peristaltic pump. Thanks to the chemical selectivity of NMR spectroscopy the progress of the reaction can be monitored on-line by determining the concentrations of both reactant and product from the area under their respective lines in the NMR spectra as a function of time. This in situ measurement demonstrates that NMR probes can be used in chemistry laboratories, e.g. for reaction optimization, or installed at specific points of interest along industrial process lines. Therefore, it will open the door for the implementation of feedback control based on spectroscopic NMR data. PMID:21698335

  2. Quantum Mechanical Nature in Liquid NMR Quantum Computing

    Institute of Scientific and Technical Information of China (English)

    LONGGui-Lu; YANHai-Yang; 等

    2002-01-01

    The quantum nature of bulk ensemble NMR quantum computing-the center of recent heated debate,is addressed.Concepts of the mixed state and entanglement are examined,and the data in a two-qubit liquid NMR quantum computation are analyzed.the main points in this paper are;i) Density matrix describes the "state" of an average particle in an ensemble.It does not describe the state of an individual particle in an ensemble;ii) Entanglement is a property of the wave function of a microscopic particle(such as a molecule in a liquid NMR sample),and separability of the density matrix canot be used to measure the entanglement of mixed ensemble;iii) The state evolution in bulkensemble NMR quantum computation is quantum-mechanical;iv) The coefficient before the effective pure state density matrix,ε,is a measure of the simultaneity of the molecules in an ensemble,It reflets the intensity of the NMR signal and has no significance in quantifying the entanglement in the bulk ensemble NMR system.The decomposition of the density matrix into product states is only an indication that the ensemble can be prepared by an ensemble with the particles unentangeld.We conclude that effective-pure-state NMR quantum computation is genuine,not just classical simulations.

  3. From NMR chemical shifts to amino acid types: Investigation of the predictive power carried by nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Marin, Antoine; Malliavin, Therese E. [Institut de Biologie Physico-Chimique, Laboratoire de Biochimie Theorique, CNRS UPR 9080 (France)], E-mail: therese.malliavin@ibpc.fr; Nicolas, Pierre; Delsuc, Marc-Andre [INRA - Domaine de Vilvert, Unite Mathematique Informatique et Genome (France)

    2004-09-15

    An approach to automatic prediction of the amino acid type from NMR chemical shift values of its nuclei is presented here, in the frame of a model to calculate the probability of an amino acid type given the set of chemical shifts. The method relies on systematic use of all chemical shift values contained in the BioMagResBank (BMRB). Two programs were designed, one (BMRB stats) for extracting statistical chemical shift parameters from the BMRB and another one (RESCUE2) for computing the probabilities of each amino acid type, given a set of chemical shifts. The Bayesian prediction scheme presented here is compared to other methods already proposed: PROTYP (Grzesiek and Bax, J. Biomol. NMR, 3, 185-204, 1993) RESCUE (Pons and Delsuc, J. Biomol. NMR, 15, 15-26, 1999) and PLATON (Labudde et al., J. Biomol. NMR, 25, 41-53, 2003) and is found to be more sensitive and more specific. Using this scheme, we tested various sets of nuclei. The two nuclei carrying the most information are C{sub {beta}} and H{sub {beta}}, in agreement with observations made in Grzesiek and Bax, 1993. Based on four nuclei: H{sub {beta}}, C{sub {beta}}, C{sub {alpha}} and C', it is possible to increase correct predictions to a rate of more than 75%. Taking into account the correlations between the nuclei chemical shifts has only a slight impact on the percentage of correct predictions: indeed, the largest correlation coefficients display similar features on all amino acids.

  4. GUARDD: user-friendly MATLAB software for rigorous analysis of CPMG RD NMR data.

    Science.gov (United States)

    Kleckner, Ian R; Foster, Mark P

    2012-01-01

    Molecular dynamics are essential for life, and nuclear magnetic resonance (NMR) spectroscopy has been used extensively to characterize these phenomena since the 1950s. For the past 15 years, the Carr-Purcell Meiboom-Gill relaxation dispersion (CPMG RD) NMR experiment has afforded advanced NMR labs access to kinetic, thermodynamic, and structural details of protein and RNA dynamics in the crucial μs-ms time window. However, analysis of RD data is challenging because datasets are often large and require many non-linear fitting parameters, thereby confounding assessment of accuracy. Moreover, novice CPMG experimentalists face an additional barrier because current software options lack an intuitive user interface and extensive documentation. Hence, we present the open-source software package GUARDD (Graphical User-friendly Analysis of Relaxation Dispersion Data), which is designed to organize, automate, and enhance the analytical procedures which operate on CPMG RD data ( http://code.google.com/p/guardd/). This MATLAB-based program includes a graphical user interface, permits global fitting to multi-field, multi-temperature, multi-coherence data, and implements χ (2)-mapping procedures, via grid-search and Monte Carlo methods, to enhance and assess fitting accuracy. The presentation features allow users to seamlessly traverse the large amount of results, and the RD Simulator feature can help design future experiments as well as serve as a teaching tool for those unfamiliar with RD phenomena. Based on these innovative features, we expect that GUARDD will fill a well-defined gap in service of the RD NMR community.

  5. GUARDD: user-friendly MATLAB software for rigorous analysis of CPMG RD NMR data

    International Nuclear Information System (INIS)

    Molecular dynamics are essential for life, and nuclear magnetic resonance (NMR) spectroscopy has been used extensively to characterize these phenomena since the 1950s. For the past 15 years, the Carr-Purcell Meiboom-Gill relaxation dispersion (CPMG RD) NMR experiment has afforded advanced NMR labs access to kinetic, thermodynamic, and structural details of protein and RNA dynamics in the crucial μs-ms time window. However, analysis of RD data is challenging because datasets are often large and require many non-linear fitting parameters, thereby confounding assessment of accuracy. Moreover, novice CPMG experimentalists face an additional barrier because current software options lack an intuitive user interface and extensive documentation. Hence, we present the open-source software package GUARDD (Graphical User-friendly Analysis of Relaxation Dispersion Data), which is designed to organize, automate, and enhance the analytical procedures which operate on CPMG RD data (http://code.google.com/p/guardd/http://code.google.com/p/guardd/). This MATLAB-based program includes a graphical user interface, permits global fitting to multi-field, multi-temperature, multi-coherence data, and implements χ2-mapping procedures, via grid-search and Monte Carlo methods, to enhance and assess fitting accuracy. The presentation features allow users to seamlessly traverse the large amount of results, and the RD Simulator feature can help design future experiments as well as serve as a teaching tool for those unfamiliar with RD phenomena. Based on these innovative features, we expect that GUARDD will fill a well-defined gap in service of the RD NMR community.

  6. GUARDD: user-friendly MATLAB software for rigorous analysis of CPMG RD NMR data

    Energy Technology Data Exchange (ETDEWEB)

    Kleckner, Ian R., E-mail: ian.kleckner@gmail.com [Biophysics Program, Ohio State University (United States); Foster, Mark P., E-mail: Foster.281@osu.edu [Ohio State University, Biochemistry Department (United States)

    2012-01-15

    Molecular dynamics are essential for life, and nuclear magnetic resonance (NMR) spectroscopy has been used extensively to characterize these phenomena since the 1950s. For the past 15 years, the Carr-Purcell Meiboom-Gill relaxation dispersion (CPMG RD) NMR experiment has afforded advanced NMR labs access to kinetic, thermodynamic, and structural details of protein and RNA dynamics in the crucial {mu}s-ms time window. However, analysis of RD data is challenging because datasets are often large and require many non-linear fitting parameters, thereby confounding assessment of accuracy. Moreover, novice CPMG experimentalists face an additional barrier because current software options lack an intuitive user interface and extensive documentation. Hence, we present the open-source software package GUARDD (Graphical User-friendly Analysis of Relaxation Dispersion Data), which is designed to organize, automate, and enhance the analytical procedures which operate on CPMG RD data (http://code.google.com/p/guardd/http://code.google.com/p/guardd/). This MATLAB-based program includes a graphical user interface, permits global fitting to multi-field, multi-temperature, multi-coherence data, and implements {chi}{sup 2}-mapping procedures, via grid-search and Monte Carlo methods, to enhance and assess fitting accuracy. The presentation features allow users to seamlessly traverse the large amount of results, and the RD Simulator feature can help design future experiments as well as serve as a teaching tool for those unfamiliar with RD phenomena. Based on these innovative features, we expect that GUARDD will fill a well-defined gap in service of the RD NMR community.

  7. NMR-based metabolomics in human disease diagnosis: Applications, limitations, and recommendations

    KAUST Repository

    Emwas, Abdul-Hamid M.

    2013-04-03

    Metabolomics is a dynamic and emerging research field, similar to proteomics, transcriptomics and genomics in affording global understanding of biological systems. It is particularly useful in functional genomic studies in which metabolism is thought to be perturbed. Metabolomics provides a snapshot of the metabolic dynamics that reflect the response of living systems to both pathophysiological stimuli and/or genetic modification. Because this approach makes possible the examination of interactions between an organism and its diet or environment, it is particularly useful for identifying biomarkers of disease processes that involve the environment. For example, the interaction of a high fat diet with cardiovascular disease can be studied via such a metabolomics approach by modeling the interaction between genes and diet. The high reproducibility of NMR-based techniques gives this method a number of advantages over other analytical techniques in large-scale and long-term metabolomic studies, such as epidemiological studies. This approach has been used to study a wide range of diseases, through the examination of biofluids, including blood plasma/serum, urine, blister fluid, saliva and semen, as well as tissue extracts and intact tissue biopsies. However, complicating the use of NMR spectroscopy in biomarker discovery is the fact that numerous variables can effect metabolic composition including, fasting, stress, drug administration, diet, gender, age, physical activity, life style and the subject\\'s health condition. To minimize the influence of these variations in the datasets, all experimental conditions including sample collection, storage, preparation as well as NMR spectroscopic parameters and data analysis should be optimized carefully and conducted in an identical manner as described by the local standard operating protocol. This review highlights the potential applications of NMR-based metabolomics studies and gives some recommendations to improve sample

  8. Structural investigation of molten fluorides of nuclear interest by NMR and XAFS spectroscopies

    International Nuclear Information System (INIS)

    In the frame of the renewal of the different nuclear plans, the molten salt reactor is one of the six concepts of reactors of 4. generation. This reactor has the particularity to use a liquid fuel based on LiF-ThF4 mixtures. In order to develop and to optimize this concept, it is important to characterize the structure of the melt and to describe its physical and chemical properties. Our work has been based on the study of the system MF-ZrF4 (M = Li, Na, K) selected as a model of ThF4 based systems. We have combined two spectroscopic techniques, the Nuclear Magnetic Resonance and the X-ray Absorption at high temperature, with molecular dynamics calculations. We particularly focused on the local environments of the fluorine and the zirconium. In order to interpret the NMR data obtain in the molten state, we performed a preliminary study on zirconium halides and rare earth and alkali fluoro zirconates using the 91Zr solid-state NMR at very high magnetic fields. New correlations between structural parameters and NMR data have been established. At high temperature, in MF-ZrF4 melts we have shown the coexistence of three different kind of Zr-based complexes with different proportions depending on the amount of ZrF4 and on the nature of the alkali. Depending on the ZrF4 content, three kinds of fluorine have been characterized: form free fluorines at low amount of zirconium fluorides, fluorines involved in Zr-based complexes and bridging fluorines at higher ZrF4 content. This original and innovative approach of molten fluorides mixtures, combining NMR and EXAFS at high temperature with molecular dynamics calculations, is very efficient to describe their speciation and thus their fluoro-acidity. (author)

  9. Understanding NMR relaxometry of partially water-saturated rocks

    Directory of Open Access Journals (Sweden)

    O. Mohnke

    2014-11-01

    Full Text Available Nuclear Magnetic Resonance (NMR relaxometry measurements are commonly used to characterize the storage and transport properties of water-saturated rocks. These assessments are based on the proportionality of NMR signal amplitude and relaxation time to porosity (water content and pore size, respectively. The relationship between pore size and NMR relaxation time depends on pore shape, which is usually assumed to be spherical or cylindrical. However, the NMR response at partial water saturation for natural sediments and rocks differs strongly from the response calculated for spherical or cylindrical pores, because these pore shapes cannot account for water menisci remaining in the corners of de-saturated angular pores. Therefore, we consider a bundle of pores with triangular cross-sections. We introduce analytical solutions of the NMR equations at partial saturation of these pores, which account for water menisci of de-saturated pores. After developing equations that describe the water distribution inside the pores, we calculate the NMR response at partial saturation for imbibition and drainage based on the deduced water distributions. For this pore model, NMR amplitude and NMR relaxation time at partial water saturation strongly depend on pore shape even so the NMR relaxation time at full saturation only depends on the surface to volume ratio of the pore. The pore-shape-dependence at partial saturation arises from the pore shape and capillary pressure dependent water distribution in pores with triangular cross-sections. Moreover, we show the qualitative agreement of the saturation dependent relaxation time distributions of our model with those observed for rocks and soils.

  10. 1H NMR investigation of self-association of vanillin in aqueous solution

    International Nuclear Information System (INIS)

    A self-association of vanillin have been studied by 1H NMR spectroscopy using the analysis of proton chemical shifts changes in aqueous solution as a function of concentration. The experimental results have been analysed using indefinite non-cooperative and cooperative models of molecular self-association, enabling the determination of equilibrium constants, parameters of cooperativity and the limiting values of vanillin proton chemical shifts in the complex. It was found that the dimer formation creates energetically favourable conditions for subsequent molecular association.

  11. 1H NMR investigation of self-association of vanillin in aqueous solution

    Science.gov (United States)

    Bogdan, Mircea; Floare, Calin G.; Pîrnau, Adrian

    2009-08-01

    A self-association of vanillin have been studied by 1H NMR spectroscopy using the analysis of proton chemical shifts changes in aqueous solution as a function of concentration. The experimental results have been analysed using indefinite non-cooperative and cooperative models of molecular self-association, enabling the determination of equilibrium constants, parameters of cooperativity and the limiting values of vanillin proton chemical shifts in the complex. It was found that the dimer formation creates energetically favourable conditions for subsequent molecular association.

  12. {sup 1}H NMR investigation of self-association of vanillin in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Bogdan, Mircea; Floare, Calin G; PIrnau, Adrian, E-mail: mircea.bogdan@itim-cj.r [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania)

    2009-08-01

    A self-association of vanillin have been studied by {sup 1}H NMR spectroscopy using the analysis of proton chemical shifts changes in aqueous solution as a function of concentration. The experimental results have been analysed using indefinite non-cooperative and cooperative models of molecular self-association, enabling the determination of equilibrium constants, parameters of cooperativity and the limiting values of vanillin proton chemical shifts in the complex. It was found that the dimer formation creates energetically favourable conditions for subsequent molecular association.

  13. Perturbed Angular Correlation (PAC)/NMR spectroscopic properties and dynamics of compounds containing metal ions

    DEFF Research Database (Denmark)

    Arcisauskaité, Vaida

    199mHg PAC and 199Hg NMR spectroscopic properties, nuclear quadrupole coupling constants, Q, asymmetry parameters, , and chemical shifts, , respectively, are the fingerprint of the local molecular and electronic structure, at the probed Hg nuclei. For this reason, these spectroscopic techniques......, these studies did not provide the insight into the microscopic nature of the water exchange mechanism. The aim of this study was to provide this insight using a computational chemistry approach. In this respect, in our work presented in Section 6.6 we first equilibrated the Zn(II) + 64 H2O system using a Car...

  14. NMR studies on polyphosphide Ce6Ni6P17

    Science.gov (United States)

    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.

  15. Molecular dynamics computer simulations based on NMR data

    International Nuclear Information System (INIS)

    In the work described in this thesis atom-atom distance information obtained from two-dimensional cuclear magnetic resonance is combined with molecular dynamics simulaitons. The simulation is used to improve the accuracy of a structure model constructed on the basis of NMR data. During the MD refinement the crude NMR structure is simultaneously optimized with respect to the atomic interaction function and to the set of atom-atom distances or other NMR information. This means that insufficient experimental data is completed with theoretical knowledge and the combination will lead to more reliable structures than would be obtained from one technique alone. (author). 191 refs.; 17 figs.; 12 schemes; 22 tabs

  16. Room temperature chiral discrimination in paramagnetic NMR spectroscopy

    CERN Document Server

    Soncini, Alessandro

    2016-01-01

    A recently proposed theory of chiral discrimination in NMR spectroscopy based on the detection of a molecular electric polarization $\\mathbf{P}$ rotating in a plane perpendicular to the NMR magnetic field [A. D. Buckingham, J. Chem. Phys. $\\mathbf{140}$, 011103 (2014)], is here generalized to paramagnetic systems. Our theory predicts new contributions to $\\mathbf{P}$, varying as the square of the inverse temperature. Ab initio calculations for ten Dy$^{3+}$ complexes, at 293K, show that in strongly anisotropic paramagnetic molecules $\\mathbf{P}$ can be more than 1000 times larger than in diamagnetic molecules, making paramagnetic NMR chiral discrimination amenable to room temperature detection.

  17. Developments of RF Coil for P in vivo NMR Spectroscopy .

    Directory of Open Access Journals (Sweden)

    S. Khushu

    1993-07-01

    Full Text Available RF receiver coils are very important parts of an NMR System. The design of these coils is very critical and has a dramatic effect on the SNR of the NMR signal and are generally developed in TRA/REC mode. This paper reports the developments of a 3.5 cm TRA/REC 26 MHz RF coil for P spectroscopy of small organs like thyroid. The coil is small in size, fits well in the neck for thyroid spectroscopy and is successfully working with the 1.5 tesla whole body Superconducting NMR System available at INMAS.

  18. Developments of RF Coil for P in vivo NMR Spectroscopy .

    OpenAIRE

    S. Khushu; S.B. Mehta; Sushil Chandra; A Jena

    1993-01-01

    RF receiver coils are very important parts of an NMR System. The design of these coils is very critical and has a dramatic effect on the SNR of the NMR signal and are generally developed in TRA/REC mode. This paper reports the developments of a 3.5 cm TRA/REC 26 MHz RF coil for P spectroscopy of small organs like thyroid. The coil is small in size, fits well in the neck for thyroid spectroscopy and is successfully working with the 1.5 tesla whole body Superconducting NMR System availab...

  19. A simple low-cost single-crystal NMR setup

    Science.gov (United States)

    Vinding, Mads S.; Kessler, Tommy O.; Vosegaard, Thomas

    2016-08-01

    A low-cost single-crystal NMR kit is presented along with a web-based post-processing software. The kit consists of a piezo-crystal motor and a goniometer for the crystal, both embedded in a standard wide-bore NMR probe with a 3D printed scaffold. The NMR pulse program controls the angle setting automatically, and the post-processing software incorporates a range of orientation-angle discrepancies present in the kit and other single-crystal setups. Results with a NaNO3 single-crystal show a high degree of reproducibility and excellent agreement with previous findings for the anisotropic quadrupolar interaction.

  20. Structural biology applications of solid state MAS DNP NMR

    Science.gov (United States)

    Akbey, Ümit; Oschkinat, Hartmut

    2016-08-01

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

  1. Calculations of NMR properties for sI and sII clathrate hydrates of methane, ethane and propane.

    Science.gov (United States)

    Siuda, Paweł; Sadlej, Joanna

    2014-12-01

    Calculations of NMR parameters (the absolute shielding constants and the spin-spin coupling constants) for 5(12), 5(12)6(2) and 5(12)6(4) cages enclathrating CH4, C2H6 and C3H8 molecules are presented. The DFT/B3LYP/HuzIII-su3 level of theory was employed. The (13)C shielding constants of guest molecules are close to available experimental data. In two cases (the ethane in 5(12) and the propane in 5(12)6(2) cages) the (13)C shielding constants are reported for the first time. Inversion of the methyl/methylene (13)C and (1)H shielding constants order is found for propane in the 5(12)6(2) cage. Topological criteria are used to interpret the changes of values of NMR parameters of water molecules and they establish a connection between single cages and bulk crystal.

  2. NMR Methods, Applications and Trends for Groundwater Evaluation and Management

    Science.gov (United States)

    Walsh, D. O.; Grunewald, E. D.

    2011-12-01

    Nuclear magnetic resonance (NMR) measurements have a tremendous potential for improving groundwater characterization, as they provide direct detection and measurement of groundwater and unique information about pore-scale properties. NMR measurements, commonly used in chemistry and medicine, are utilized in geophysical investigations through non-invasive surface NMR (SNMR) or downhole NMR logging measurements. Our recent and ongoing research has focused on improving the performance and interpretation of NMR field measurements for groundwater characterization. Engineering advancements have addressed several key technical challenges associated with SNMR measurements. Susceptibility of SNMR measurements to environmental noise has been dramatically reduced through the development of multi-channel acquisition hardware and noise-cancellation software. Multi-channel instrumentation (up to 12 channels) has also enabled more efficient 2D and 3D imaging. Previous limitations in measuring NMR signals from water in silt, clay and magnetic geology have been addressed by shortening the instrument dead-time from 40 ms to 4 ms, and increasing the power output. Improved pulse sequences have been developed to more accurately estimate NMR relaxation times and their distributions, which are sensitive to pore size distributions. Cumulatively, these advancements have vastly expanded the range of environments in which SNMR measurements can be obtained, enabling detection of groundwater in smaller pores, in magnetic geology, in the unsaturated zone, and nearby to infrastructure (presented here in case studies). NMR logging can provide high-resolution estimates of bound and mobile water content and pore size distributions. While NMR logging has been utilized in oil and gas applications for decades, its use in groundwater investigations has been limited by the large size and high cost of oilfield NMR logging tools and services. Recently, engineering efforts funded by the US Department of

  3. NMR study of oligonucleotides containing base pair mismatches and a human growth hormone peptide for the determination of solution structures

    International Nuclear Information System (INIS)

    Formation of unusual basepairs in DNA for random mutations in DNA was proposed in the sixties. These mismatches arise due to errors in replication, and from deamination of the 5-methylcytosine. The author's interest in studying mismatches and other oligonucleotides has been two fold. One is related to 31P chemical shifts and the backbone structure of oligonucleotides. He wanted to find out the significance of the dispersion of 31p chemical shifts in oligonucleotides. He wished to address whether this dispersion in 31P chemical shifts is related to global structural parameters of oligonucleotides like helix twist and whether he can prove the relationship between 31P chemical shifts and the backbone torsional angles epsilon and zeta. How does a mismatch affect 31P chemical shifts and the backbone torsional angle? The second interest is related to solving the three dimensional structure of these biopolymers by using NMR data (NOESY distances) and computer simulations. His major study of these mismatches has been in the assignments of the protons resonances and the phosphorus resonances by 2D NMR. He has also tried to answer the question about the relationships between 31P chemical shifts and global parameters for DNA such as the helix twist. He has made substantial progress in determination of J(H3'-P) coupling constants by 2D NMR and also in determining the relationship between the SIP chemical shifts and the backbone torsional angles by using the mismatch dodecamer sequences and the tetradecamer sequences. The 2D NMR data for the GG and GT mismatch have been used to determine three dimensional structures by using distance restrained molecular dynamics. The second project involved studying a 28 residue synthetic peptide by NMR

  4. Resolution-by-proxy: a simple measure for assessing and comparing the overall quality of NMR protein structures

    Energy Technology Data Exchange (ETDEWEB)

    Berjanskii, Mark; Zhou Jianjun; Liang Yongjie; Lin Guohui; Wishart, David S., E-mail: david.wishart@ualberta.ca [University of Alberta, Department of Computing Science (Canada)

    2012-07-15

    In protein X-ray crystallography, resolution is often used as a good indicator of structural quality. Diffraction resolution of protein crystals correlates well with the number of X-ray observables that are used in structure generation and, therefore, with protein coordinate errors. In protein NMR, there is no parameter identical to X-ray resolution. Instead, resolution is often used as a synonym of NMR model quality. Resolution of NMR structures is often deduced from ensemble precision, torsion angle normality and number of distance restraints per residue. The lack of common techniques to assess the resolution of X-ray and NMR structures complicates the comparison of structures solved by these two methods. This problem is sometimes approached by calculating 'equivalent resolution' from structure quality metrics. However, existing protocols do not offer a comprehensive assessment of protein structure as they calculate equivalent resolution from a relatively small number (<5) of protein parameters. Here, we report a development of a protocol that calculates equivalent resolution from 25 measurable protein features. This new method offers better performance (correlation coefficient of 0.92, mean absolute error of 0.28 A) than existing predictors of equivalent resolution. Because the method uses coordinate data as a proxy for X-ray diffraction data, we call this measure 'Resolution-by-Proxy' or ResProx. We demonstrate that ResProx can be used to identify under-restrained, poorly refined or inaccurate NMR structures, and can discover structural defects that the other equivalent resolution methods cannot detect. The ResProx web server is available at http://www.resprox.cahttp://www.resprox.ca.

  5. A multinuclear static NMR study of geopolymerisation

    Energy Technology Data Exchange (ETDEWEB)

    Favier, Aurélie, E-mail: aurelie.favier@epfl.ch [Univ Paris-Est, IFSTTAR, Materials Department, 14-20 bd Newton, F-77447 Marne la Vallée Cedex 2 (France); Habert, Guillaume [Institute for Construction and Infrastructure Management, ETH Zurich, CH-8093 Zurich (Switzerland); Roussel, Nicolas [Univ Paris-Est, IFSTTAR, Materials Department, 14-20 bd Newton, F-77447 Marne la Vallée Cedex 2 (France); D' Espinose de Lacaillerie, Jean-Baptiste [Ecole Supérieure de Physique et de Chimie Indusrtrielles de la Ville de Paris (ESPCI), ParisTech, PSL Research University, Soft Matter Sciences and Engineering Laboratory SIMM, CNRS UMR 7615, 10 rue Vauquelin, F-75005 Paris (France)

    2015-09-15

    Geopolymers are inorganic binders obtained by alkali activation of aluminosilicates. While the structure of geopolymers is now well understood, the details of the geopolymerisation reaction and their impact on the rheology of the paste remain uncertain. In this work, we follow the elastic properties of a paste made with metakaolin and sodium silicate solution. After the first sharp increase of elastic modulus occurring a few hundred of seconds after mixing and related to the heterogeneous formation of an alumina–silicate gel with a molar ratio Si/Al < 4 located at the grains boundaries, we focus on the progressive increase in elastic modulus on a period of few hours during the setting of the geopolymer. In this study, we combine the study of rheological properties of the paste with {sup 23}Na, {sup 27}Al and {sup 29}Si static NMR measurement in order to better understand the origin of this second increase in elastic modulus. Our results show that, after a few hours, Al and Na evolution in the liquid phase are concomitant. This suggests the precipitation of an aluminosilicate phase where Al is in tetrahedral position and Na compensates the charge. Furthermore, Si speciation confirms this result and allows us to identify the precipitation of a product, which has a chemical composition close to the final composition of geopolymer. This study provides strong evidence for a heterogeneous formation of an aluminosilicate glass directly from the first gel and the silicate solution without the need for a reorganisation of Gel 1 into Gel 2.

  6. The Doppler effect in NMR spectroscopy.

    Science.gov (United States)

    Guéron, Maurice

    2003-02-01

    An NMR sample may be subject to motions, such as those due to sample spinning or to liquid flow. Is the spectrum of such a sample affected by the Doppler effect? The question arises because, instrumental dimensions being much shorter than the wavelength, it is the near-field of the precessing magnetic moment which couples to the receiver coil, rather than the radiated far-field. We expand the near-field into plane propagating waves. For each such wave there is another one with the same amplitude, propagating in the opposite direction. The Doppler shifts are therefore equal and opposite. In the model case of a small fluid sample moving with constant velocity, this leads to a distribution of Doppler shifts which is symmetrical with respect to the unshifted frequency: there is no net spectral shift. We examine the possibility of observing the Doppler distribution in this case. We also consider the case of thermal motion of a gas. We draw attention to the resolved Doppler splitting of molecular rotational transitions in a supersonic burst as observed in a microwave resonator. We also mention briefly the Doppler effect in molecular beam spectroscopy.

  7. Studies on metabolic regulation using NMR spectroscopy.

    Science.gov (United States)

    Bachelard, H; Badar-Goffer, R; Ben-Yoseph, O; Morris, P; Thatcher, N

    1993-01-01

    The effects of hypoxia and hypoglycaemia on cerebral metabolism and calcium have been studied using multinuclear magnetic resonance spectroscopy. 13C MRS showed that severe hypoxia did not cause any further increase in metabolic flux into lactate seen in mild hypoxia, but there was a further increase in 13C labelling of alanine and glycerol 3-phosphate. These results are discussed in terms of the ability of lactate dehydrogenase to maintain normal levels of NADH in mild hypoxia, but not in severe hypoxia. We conclude that glycerol 3-phosphate and alanine may provide novel means of monitoring severe hypoxia whereas lactate is a reliable indicator only of mild hypoxia. 19F- and 31P NMR spectroscopy showed that neither hypoxia nor hypoglycaemia alone caused any significant change in [Ca2+]i. Combined sequential insults (hypoxia, followed by hypoxia plus hypoglycaemia), or vice versa, produced a 100% increase in [Ca2+]i, whereas immediate exposure to the combined insult (hypoxia plus hypoglycaemia) resulted in a large 5-fold increase in [Ca2+]i, with severe irreversible effects on the energy state. These results are discussed in terms of metabolic adaptation to the single type of insult, which renders the tissue less vulnerable to the combined insult. The effects of this combined insult are far more severe than those caused by glutamate or NMDA, which throws doubt on the current excitoxic hypothesis of cell damage.

  8. Analysis of human urine metabolites using SPE and NMR spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Nuclear magnetic resonance (NMR) spectroscopic analysis of metabonome/metabolome has widespread applications in biomedical science researches. However, most of NMR resonances for urinary metabolites remain to be fully assigned. In the present study, human urine samples from two healthy volunteers were pre-treated with C18 solid-phase extraction and the resultant 5 sub-fractions were subjected to one- and two-dimensional NMR studies, including 1H J-Resolved, 1H-1H COSY, 1H-1H TOCSY, 1H-13C HSQC, and HMBC 2D NMR. More than 70 low molecular weight metabolites were identified, and complete assignments of 1H and 13C resonances including many complex coupled spin systems were obtained.

  9. NMR methods for the investigation of structure and transport

    Energy Technology Data Exchange (ETDEWEB)

    Hardy, Edme H. [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. fuer Mechanische Verfahrenstechnik und Mechanik

    2012-07-01

    Extensive derivations of required fundamental relations for readers with engineering background New applications based on MRI, PGSE-NMR, and low-field NMR New concepts in quantitative data evaluation and image analysis Methods of nuclear magnetic resonance (NMR) are increasingly applied in engineering sciences. The book summarizes research in the field of chemical and process engineering performed at the Karlsruhe Institute of Technology (KIT). Fundamentals of the methods are exposed for readers with an engineering background. Applications cover the fields of mechanical process engineering (filtration, solid-liquid separation, powder mixing, rheometry), chemical process engineering (trickle-bed reactor, ceramic sponges), bioprocess engineering (biofilm growth), and food process engineering (microwave heating, emulsions). Magnetic Resonance Imaging (MRI) as well as low-field NMR are covered with notes on hardware. Emphasis is placed on quantitative data analysis and image processing. (orig.)

  10. Mobile NMR for geophysical analysis and materials testing

    Institute of Scientific and Technical Information of China (English)

    BLUMICH Bernhard; MAULER Jǒrg; HABER Agnes; PERLO Juan; DANIELI Ernesto; CASANOVA Federico

    2009-01-01

    Initiated by well logging NMR, portable NMR instruments are being developed for a variety of novel applications in materials testing, process analysis and control, which provides new opportunities for geophysical investigations. Small-diameter cylindrical sensors can probe short distances into the walls of slim-line logging holes, and single-sided sensors enable non-destructive testing of large objects. Both sensors are characterized by small sensitive volumes. Barrel-shaped magnets that accommodate the sample in their center have higher sensitivity due to a larger sensitive volume but can accommodate only samples like drill cores, which fit in size to the diameter of the magnet bore. Both types of magnets can be scaled down to the size of a coffee mug to arrive at sub-compact NMR equipment. Portable NMR magnets are reviewed in the context of applications related to geophysics.

  11. 31P NMR Study on Some Phosphorus-Containing Compounds

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    31P NMR has become a widely applied spectroscopic probe of the structure of phosphorus-containing compounds. Meanwhile, the application of 31P NMR has been rapidly expanded to biochemistry and medicinal chemistry of phosphorus-containing compounds because the growing importance of the phosphorus compounds is now widely realized. We report here the results of 31P NMR study on some phosphorus-containing compounds, namely, O-alkyl O-4-nitrophenyl methyl phosphonates with different alkyl chain-length (MePO-n), 4-nitrophenyl alkylphenylphosphinates with different alkyl chain-length (PhP-n), diethyl phosphono- acetonitrile anion and diethyl phosphite anion . Our results indicate that 31P NMR can not only be applied to not only the study of the hydrolytic reactions of MePO-8 and PhP-8 but also be applied to the study of the presence of the anions of diethylphosphonoacetonitrile and diethyl phosphite in nucleophilic reactions.

  12. NMR study of some coumarins and furocoumarins methylated

    Science.gov (United States)

    Miranda, R.; Santana, L.; Uriarte, E.; Zagotto, G.

    1994-01-01

    The 1H and 13C NMR spectra of various methylcoumarins and methylfurocoumarins are reported. All signals were assigned and the influence on chemical shifts of methylation at various positions was determined.

  13. Optical analogue of 2D heteronuclear double-quantum NMR

    CERN Document Server

    Tollerud, Jonathan

    2016-01-01

    Heteronuclear multi-quantum spectroscopy is a powerful part of the NMR toolbox, commonly used to identify specific sequences of atoms in complex pulse sequences designed to determine the structure of complex molecules, including proteins. Optical coherent multidimensional spectroscopy (CMDS) is analogous to multidimensional NMR and many of the techniques of NMR have been adapted for application in the optical regime. This has been highly successful, with CMDS being used to understand energy transfer in photosynthesis and many body effects in semiconductor nanostructures amongst many other scientific breakthroughs. Experimental challenges have, however, prevented the translation of heteronuclear multi-quantum NMR to the optical regime, where capabilities to isolate signals in otherwise congested spectra, reduce acquisition times and enable more incisive probes of multi-particle correlations and complex electronic systems would have great benefit. Here we utilise a diffraction based pulseshaper to impose the tw...

  14. Dihydroflavanonols from Cedrus deodara, A (13)C NMR study.

    Science.gov (United States)

    Agrawal, P K; Agarwal, S K; Rastogi, R P; Osterdahal, B G

    1981-09-01

    High resolution (13)C NMR study of taxifolin, cedeodarin, cedrin and their methyl ethers allowed unambiguous placement of the Me in 5,7-dihydroxyflavanonol nucleus, besides providing other valuable information on the substitution pattern in the molecule.

  15. Predicting ESR Peaks in Copper (II Chelates Having Quadrupolar Coordinating Sites by NMR, ESR and NQR Techniques: A DFT Study

    Directory of Open Access Journals (Sweden)

    Harminder Singh

    2015-06-01

    Full Text Available Computational chemistry was helpful in predicting the number of ESR peaks in Cu (II complexes having a large number of spatially different NMR and ESR active nuclei. The presence of the large Jahn-Teller effect and the high value of spin-orbit coupling constant of the metal ion made the experimental determination of the exact number of ESR peaks quite difficult in such complexes. Fourteen distorted poly-dentate chelating Cu(II complexes included in this study were of two types such as [Cu(gly2] , [Cu(edta]4-,[Cu(tpyX2] (X= Cl, Br, I, NCS and [Cu(en2]2+, [Cu(teta]2+, Cu(tepa]2+ ,[Cu(peha]2+, [Cu(detaX2] (X= Cl, Br, I, NCS.The latter eight complexes belonged to an important class of ligands called polyethylene polyamines. Density functional theory implemented in ADF: 2010.02 was applied. Three parameters of both the ESR (A ten and NQR (NQCC, for the Cu(II and the coordinating atoms of the ligands were obtained from “ESR/EPR program” and two NMR parameters namely the shielding constants (σ and chemical shifts (δ were obtained from “NMR/EPR program” after optimization of the complexes. The species having the same values of these 5 parameters were expected to be spatially equivalent to undergo the same hyperfine interaction with Cu (II.

  16. Study of multi-site chemical exchange in solution state by NMR: 1D experiments with multiply selective excitation

    Indian Academy of Sciences (India)

    Samanwita Pal

    2010-07-01

    Chemical exchange in solution state has been investigated traditionally by both 1D and 2D NMR, permitting the extraction of kinetic parameters (e.g. the spin-lattice relaxation time 1, the exchange rate constant and the activation parameters). This work demonstrates a simple 1D NMR approach employing multiply selective excitation to study multi-site exchange processes in solution, applying it to systems that exhibit three-site exchange. This approach involves simultaneous excitation of all - or a chosen subset of - the exchanging sites by using an appropriately modulated shaped radiofrequency pulse. The pulse sequence, as well as analysis is summarized. Significant features of the experiment, which relies on sign labelling of the exchanging sites, include considerably shorter experiment time compared to standard 2D exchange work, clear definition of the exchange time window and uniform pulse non-ideality effects for all the exchanging sites. Complete kinetic information is reported in the study of dynamic processes in superacid solutions of two weak bases, studied by 1H NMR. An analytical solution, leading to the determination of four rate parameters, is presented for proton exchange studies on these systems, which involve a mixture of two weak bases in arbitrary concentration ratio, and stoichiometric excess of the superacid.

  17. Application and Reliability of Solid-State NMR in Environmental Sciences

    Science.gov (United States)

    Knicker, Heike

    2010-05-01

    For the characterization of soil organic matter, a suite of analytical approaches are available. Chemical degradative methods involve an extraction scheme with which the soluble part of the mixture is isolated and analyzed by colorimetrical or chromatographic means. Macromolecular structures can be subjected to thermolytic or combined thermochemolytic degradation. Because secondary reactions (rearrangement, cracking, hydrogenation and polymerization) in a heterogeneous mixture cannot be excluded, it is obvious that conclusions regarding the original structure in the macromolecular phase have to be drawn with caution. A powerful alternative represents solid-state nuclear magnetic resonance (NMR) spectroscopy, allowing the examination of the bulk sample without major pre-treatment In environmental sciences, this technique mostly involves the isotope 13C to study the chemical composition of organic matter in soils, sediments or compost to study the temporal development of humic material or chemical alterations due to variation in environmental parameters. Due to its low sensibility solid-state 15N NMR studies on such samples are only found occasionally. The emphasis of solid-state NMR spectroscopy is not only to determine the gross chemical composition of the material under study via a chemical shift assignment but also a quantitative correlation between the different signal intensities and the relative contribution of the respective C or N types to the total organic C or N content. However, despite increasing popularity, this approach is still viewed as mysterious techniques, in particular with respect to quantification. Accordingly, the purpose of this review is to give a short overview on the possibilities and limitations of this technique in environmental science and in particular for the study of soil organic matter. In general, solid-state 13C NMR spectra of soil organic matter are obtained with the cross polarization magic angle spinning (CPMAS) technique. This

  18. Solid state NMR coal science. Final progress report

    Energy Technology Data Exchange (ETDEWEB)

    Zilm, K.W.

    1986-08-01

    This report covers the final work on this project and summarizes the accomplishments of the project. The dipolar shift correlated 2D NMR method described in previous reports has been applied to a whole coal successfully. The theory necessary for semi-quantitative interpretation of this data has also been worked out and implemented computationally. Several interesting structural features in coal seen by the 2D dipolar shift experiment not previously observed by other NMR methods are discussed. 4 figs.

  19. Rapid characterization of molecular diffusion by NMR spectroscopy.

    Science.gov (United States)

    Pudakalakatti, Shivanand M; Chandra, Kousik; Thirupathi, Ravula; Atreya, Hanudatta S

    2014-11-24

    An NMR-based approach for rapid characterization of translational diffusion of molecules has been developed. Unlike the conventional method of acquiring a series of 2D (13)C and (1)H spectra, the proposed approach involves a single 2D NMR spectrum, which can be acquired in minutes. Using this method, it was possible to detect the presence of intermediate oligomeric species of diphenylalanine in solution during the process of its self-assembly to form nanotubular structures. PMID:25331210

  20. Manifestations of nuclear anapole moments in solid state NMR

    CERN Document Server

    Mukhamedjanov, T N; Cadogan, J M

    2004-01-01

    We suggest to use insulating garnets doped by rare earth ions for measurements of nuclear anapole moments. A parity violating shift of the NMR frequency arises due to the combined effect of the lattice crystal field and the anapole moment of the rare-earth nucleus. We show that there are two different observable effects related to frequency: 1) A shift of the NMR frequency in an external electric field applied to the solid. The value of the shift is about \\Delta \

  1. ¹³C solid-state NMR analysis of the most common pharmaceutical excipients used in solid drug formulations Part II: CP kinetics and relaxation analysis.

    Science.gov (United States)

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

    2016-04-15

    Excipients used in the solid drug formulations differ in their NMR relaxation and (13)C cross-polarization (CP) kinetics parameters. Therefore, experimental parameters like contact time of cross-polarization and repetition time have a major impact on the registered solid state NMR spectra and in consequence on the results of the NMR analysis. In this work the CP kinetics and relaxation of the most common pharmaceutical excipients: anhydrous α-lactose, α-lactose monohydrate, mannitol, sucrose, sorbitol, sodium starch glycolate type A and B, starch of different origin, microcrystalline cellulose, hypromellose, ethylcellulose, methylcellulose, hydroxyethylcellulose, sodium alginate, magnesium stearate, sodium laurilsulfate and Kollidon(®) were analyzed. The studied excipients differ significantly in their optimum repetition time (from 5 s to 1200 s) and T(1ρ)(I) parameters (from 2 ms to 73 ms). The practical use of those differences in the excipients composition analysis was demonstrated on the example of commercially available tablets containing indapamide as an API. The information presented in this article will help to choose the correct acquisition parameters and also will save the time and effort needed for their optimization in the NMR analysis of the solid drug formulations.

  2. Identification and quantification of the main organic components of vinegars by high resolution {sup 1}H NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Caligiani, A. [Dipartimento di Chimica Organica e Industriale, Universita degli Studi di Parma, Via Usberti 17A, 43100-Parma (Italy)]. E-mail: augusta.caligiani@unipr.it; Acquotti, D. [Centro Interfacolta Misure, Universita degli Studi di Parma, Via Usberti 23A, 43100-Parma (Italy); Palla, G. [Dipartimento di Chimica Organica e Industriale, Universita degli Studi di Parma, Via Usberti 17A, 43100-Parma (Italy); Bocchi, V. [Dipartimento di Chimica Organica e Industriale, Universita degli Studi di Parma, Via Usberti 17A, 43100-Parma (Italy)

    2007-02-28

    A detailed analysis of the proton high-field NMR spectra of vinegars (in particular of Italian balsamic vinegars) is reported. A large number of organic substances belonging to different classes, such as carbohydrates, alcohols, organic acids, volatile compounds and amino acids, were assigned. The possibility of quantification of the substances identified in the whole vinegar sample, without extraction or pre-concentration steps, was also tested. The data validity was demonstrated in terms of precision, accuracy, repeatability and inter-day reproducibility. The effects of the most critical experimental parameters (sample concentration, water suppression and relaxation time) on the analysis response were also discussed. {sup 1}H NMR results were compared with those obtained by traditional techniques (GC-MS, titrations), and good correlations were obtained. The results showed that {sup 1}H NMR with water suppression allows a rapid, simultaneous determination of carbohydrates (glucose and fructose), organic acids (acetic, formic, lactic, malic, citric, succinic and tartaric acids), alcohols and polyols (ethanol, acetoin, 2,3-butanediol, hydroxymethylfurfural), and volatile substances (ethyl acetate) in vinegar samples. On the contrary, the amino acid determination without sample pre-concentration was critical. The {sup 1}H NMR method proposed was applied to different samples of vinegars, allowing, in particular, the discrimination of vinegars and balsamic vinegars.

  3. Chemical Origins of Permanent Set in a Peroxide Cured Filled Silicone Elastomer - Tensile and 1H NMR Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Chinn, S; Deteresa, S; Shields, A; Sawvel, A; Balazs, B; Maxwell, R S

    2004-10-29

    The aging of a commercial filled siloxane polymeric composite in states of high stress and Co-60 {gamma}-radiation exposure has been studied. DC-745 is a commercially available silicone elastomer consisting of dimethyl, methyl-phenyl, and vinyl-methyl siloxane monomers crosslinked with a peroxide vinyl specific curing agent. It is filled with {approx}30 wt.% mixture of high and low surface area silicas. This filled material is shown to be subject to permanent set if exposed to radiation while under tensile stress. Tensile modulus measurements show that the material gets marginally softer with combined radiation exposure and tensile strain as compared to material exposed to radiation without tensile strain. In addition, the segmental dynamics as measured by both uniaxial NMR relaxometry and Multiple Quantum NMR methods indicate that the material is undergoes radiatively-induced crosslinking in the absence of tensile strain and a combination of crosslinking and strain dependent increase in dynamic order parameter for the network chains. The MQ-NMR also suggests a small change in the number of polymer chains associated with the silica filler surface. Comparison of the prediction of the relative change in crosslink density from the NMR data as well as solvent swelling data and from that predicted from the Tobolsky model suggest that degradation leads to a deviation from Gaussian chain statistics and the formation of increased numbers of elastically ineffective network chains.

  4. Recommendations and Standardization of Biomarker Quantification Using NMR-based Metabolomics with Particular Focus on Urinary Analysis

    KAUST Repository

    Emwas, Abdul-Hamid M.

    2016-01-08

    NMR-based metabolomics has shown considerable promise in disease diagnosis and biomarker discovery because it allows one to non-destructively identify and quantify large numbers of novel metabolite biomarkers in both biofluids and tissues. Indeed, precise metabolite quantification is a necessary prerequisite to move any chemical biomarker or biomarker panel from the lab into the clinic. Among the many biofluids (urine, serum, plasma, cerebrospinal fluid and saliva) commonly used for disease diagnosis and prognosis, urine has several advantages. It is abundant, sterile, easily obtained, needs little sample preparation and does not require any invasive medical procedures for collection. Furthermore, urine captures and concentrates many “unwanted” or “undesirable” compounds throughout the body, thereby providing a rich source of potentially useful disease biomarkers. However, the incredible variation in urine chemical concentrations due to effects such as gender, age, diet, life style, health conditions, and physical activity make the analysis of urine and the identification of useful urinary biomarkers by NMR quite challenging. In this review, we discuss a number of the most significant issues regarding NMR-based urinary metabolomics with a specific emphasis on metabolite quantification for disease biomarker applications. We also propose a number of data collection and instrumental recommendations regarding NMR pulse sequences, acceptable acquisition parameter ranges, relaxation effects on quantitation, proper handling of instrumental differences, as well as recommendations regarding sample preparation and biomarker assessment.

  5. Structure and dynamics of silicone networks as investigated by {sup 1}H low field double-quantum NMR

    Energy Technology Data Exchange (ETDEWEB)

    Chasse, Walter; Saalwachter, Kay [Martin-Luther-Universitaet Halle-Wittenberg, Halle (Germany). Institut fuer Physik

    2008-07-01

    The existence of cross-links and other topological restrictions lead to non-isotropic fast segmental fluctuations, and therefore some residual dipolar couplings persist, which are directly related to the crosslink density. Based on this principle, we have used static {sup 1}H double-quantum NMR spectroscopy to measure quantitatively these residual dipolar couplings and their distribution{sup 1}. Usually the easiest method to study network structure (crosslink density) is the swelling experiment based on Flory-Rehner-Theory. In this view we have compared the molecular weight between cross-links MC obtained from DQ-NMR with results of as well performed swelling experiments for PDMS networks with different topologies. Independently of this, the crosslink density can also be taken from {sup 1}H MAS experiments. With these results, we obtained information not only about the network structure of the rubber but also about the validity of the model used to analyze the DQ-NMR data, thermodynamics of swelling (polymer solvent interaction parameter {chi}), and the influence of network heterogenuities in that process. In conclusion we could show that DQ-NMR in combination with swelling experiments is a powerful method to characterize structure and dynamics of rubber.

  6. Identification and quantification of the main organic components of vinegars by high resolution 1H NMR spectroscopy.

    Science.gov (United States)

    Caligiani, A; Acquotti, D; Palla, G; Bocchi, V

    2007-02-28

    A detailed analysis of the proton high-field NMR spectra of vinegars (in particular of Italian balsamic vinegars) is reported. A large number of organic substances belonging to different classes, such as carbohydrates, alcohols, organic acids, volatile compounds and amino acids, were assigned. The possibility of quantification of the substances identified in the whole vinegar sample, without extraction or pre-concentration steps, was also tested. The data validity was demonstrated in terms of precision, accuracy, repeatability and inter-day reproducibility. The effects of the most critical experimental parameters (sample concentration, water suppression and relaxation time) on the analysis response were also discussed. (1)H NMR results were compared with those obtained by traditional techniques (GC-MS, titrations), and good correlations were obtained. The results showed that (1)H NMR with water suppression allows a rapid, simultaneous determination of carbohydrates (glucose and fructose), organic acids (acetic, formic, lactic, malic, citric, succinic and tartaric acids), alcohols and polyols (ethanol, acetoin, 2,3-butanediol, hydroxymethylfurfural), and volatile substances (ethyl acetate) in vinegar samples. On the contrary, the amino acid determination without sample pre-concentration was critical. The (1)H NMR method proposed was applied to different samples of vinegars, allowing, in particular, the discrimination of vinegars and balsamic vinegars. PMID:17386654

  7. Dynamics of the time dependent Bloch NMR equations for complex rFB1(t) magnetic field

    International Nuclear Information System (INIS)

    This study examines the dynamical changes produced by a complex time-dependent rFB1(t) magnetic field in an initially unperturbed magnetic resonance system. The analysis uses the Green's function algorithm as a tool to solve the transverse component of the time-dependent Bloch NMR equations with complex rFB1(t) field. The time development of the system is studied in the Hersenberg picture in which the operators are subject to unitary transformation as the applied rFB1(t) field changes the state of the NMR system from its initial ground state into another coherent state. The detailed features of the rFB1(t) field essentially affect the evolution of the state during its application. The state of the system after the complete cessation of the radio-frequency field is determined exclusively by a Fourier component which is in resonance with the NMR system. The unitary operator allows us to determine all the physically relevant information about the system in terms of a NMR relaxation parameter. (author)

  8. NMRbot: Python scripts enable high-throughput data collection on current Bruker BioSpin NMR spectrometers.

    Science.gov (United States)

    Clos, Lawrence J; Jofre, M Fransisca; Ellinger, James J; Westler, William M; Markley, John L

    2013-06-01

    To facilitate the high-throughput acquisition of nuclear magnetic resonance (NMR) experimental data on large sets of samples, we have developed a simple and straightforward automated methodology that capitalizes on recent advances in Bruker BioSpin NMR spectrometer hardware and software. Given the daunting challenge for non-NMR experts to collect quality spectra, our goal was to increase user accessibility, provide customized functionality, and improve the consistency and reliability of resultant data. This methodology, NMRbot, is encoded in a set of scripts written in the Python programming language accessible within the Bruker BioSpin TopSpin™ software. NMRbot improves automated data acquisition and offers novel tools for use in optimizing experimental parameters on the fly. This automated procedure has been successfully implemented for investigations in metabolomics, small-molecule library profiling, and protein-ligand titrations on four Bruker BioSpin NMR spectrometers at the National Magnetic Resonance Facility at Madison. The investigators reported benefits from ease of setup, improved spectral quality, convenient customizations, and overall time savings. PMID:23678341

  9. NMRbot: Python scripts enable high-throughput data collection on current Bruker BioSpin NMR spectrometers.

    Science.gov (United States)

    Clos, Lawrence J; Jofre, M Fransisca; Ellinger, James J; Westler, William M; Markley, John L

    2013-06-01

    To facilitate the high-throughput acquisition of nuclear magnetic resonance (NMR) experimental data on large sets of samples, we have developed a simple and straightforward automated methodology that capitalizes on recent advances in Bruker BioSpin NMR spectrometer hardware and software. Given the daunting challenge for non-NMR experts to collect quality spectra, our goal was to increase user accessibility, provide customized functionality, and improve the consistency and reliability of resultant data. This methodology, NMRbot, is encoded in a set of scripts written in the Python programming language accessible within the Bruker BioSpin TopSpin™ software. NMRbot improves automated data acquisition and offers novel tools for use in optimizing experimental parameters on the fly. This automated procedure has been successfully implemented for investigations in metabolomics, small-molecule library profiling, and protein-ligand titrations on four Bruker BioSpin NMR spectrometers at the National Magnetic Resonance Facility at Madison. The investigators reported benefits from ease of setup, improved spectral quality, convenient customizations, and overall time savings.

  10. Ultrafast 2D NMR: An Emerging Tool in Analytical Spectroscopy

    Science.gov (United States)

    Giraudeau, Patrick; Frydman, Lucio

    2014-06-01

    Two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy is widely used in chemical and biochemical analyses. Multidimensional NMR is also witnessing increased use in quantitative and metabolic screening applications. Conventional 2D NMR experiments, however, are affected by inherently long acquisition durations, arising from their need to sample the frequencies involved along their indirect domains in an incremented, scan-by-scan nature. A decade ago, a so-called ultrafast (UF) approach was proposed, capable of delivering arbitrary 2D NMR spectra involving any kind of homo- or heteronuclear correlation, in a single scan. During the intervening years, the performance of this subsecond 2D NMR methodology has been greatly improved, and UF 2D NMR is rapidly becoming a powerful analytical tool experiencing an expanded scope of applications. This review summarizes the principles and main developments that have contributed to the success of this approach and focuses on applications that have been recently demonstrated in various areas of analytical chemistry—from the real-time monitoring of chemical and biochemical processes, to extensions in hyphenated techniques and in quantitative applications.

  11. The eigenmode perspective of NMR spin relaxation in proteins

    Energy Technology Data Exchange (ETDEWEB)

    Shapiro, Yury E., E-mail: shapiro@nmrsgi4.ls.biu.ac.il, E-mail: eva.meirovitch@biu.ac.il; Meirovitch, Eva, E-mail: shapiro@nmrsgi4.ls.biu.ac.il, E-mail: eva.meirovitch@biu.ac.il [The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900-02 (Israel)

    2013-12-14

    We developed in recent years the two-body (protein and probe) coupled-rotator slowly relaxing local structure (SRLS) approach for elucidating protein dynamics from NMR spin relaxation. So far we used as descriptors the set of physical parameters that enter the SRLS model. They include the global (protein-related) diffusion tensor, D{sub 1}, the local (probe-related) diffusion tensor, D{sub 2}, and the local coupling/ordering potential, u. As common in analyzes based on mesoscopic dynamic models, these parameters have been determined with data-fitting techniques. In this study, we describe structural dynamics in terms of the eigenmodes comprising the SRLS time correlation functions (TCFs) generated by using the best-fit parameters as input to the Smoluchowski equation. An eigenmode is a weighted exponential with decay constant given by an eigenvalue of the Smoluchowski operator, and weighting factor determined by the corresponding eigenvector. Obviously, both quantities depend on the SRLS parameters as determined by the SRLS model. Unlike the set of best-fit parameters, the eigenmodes represent patterns of motion of the probe-protein system. The following new information is obtained for the typical probe, the {sup 15}N−{sup 1}H bond. Two eigenmodes, associated with the protein and the probe, dominate when the time scale separation is large (i.e., D{sub 2} ≫ D{sub 1}), the tensorial properties are simple, and the local potential is either very strong or very weak. When the potential exceeds these limits while the remaining conditions are preserved, new eigenmodes arise. The multi-exponentiality of the TCFs is associated in this case with the restricted nature of the local motion. When the time scale separation is no longer large, the rotational degrees of freedom of the protein and the probe become statistically dependent (coupled dynamically). The multi-exponentiality of the TCFs is associated in this case with the restricted nature of both the local and the

  12. Methodological NMR imaging developments to measure cerebral perfusion

    International Nuclear Information System (INIS)

    This work focuses on acquisition techniques and physiological models that allow characterization of cerebral perfusion by MRI. The arterial input function (AIF), on which many models are based, is measured by a technique of optical imaging at the carotid artery in rats. The reproducibility and repeatability of the AIF are discussed and a model function is proposed. Then we compare two techniques for measuring the vessel size index (VSI) in rats bearing a glioma. The reference technique, using a USPIO contrast agent (CA), faces the dynamic approach that estimates this parameter during the passage of a bolus of Gd. This last technique has the advantage of being used clinically. The results obtained at 4.7 T by both approaches are similar and use of VSI in clinical protocols is strongly encouraged at high field. The mechanisms involved (R1 and R2* relaxivities) were then studied using a multi gradient -echoes approach. A multi-echoes spiral sequence is developed and a method that allows the refocusing between each echo is presented. This sequence is used to characterize the impact of R1 effects during the passage of two successive injections of Gd. Finally, we developed a tool for simulating the NMR signal on a 2D geometry taking into account the permeability of the BBB and the CA diffusion in the interstitial space. At short TE, the effect of diffusion on the signal is negligible. In contrast, the effects of diffusion and permeability may be separated at long echo time. Finally we show that during the extravasation of the CA, the local magnetic field homogenization due to the decrease of the magnetic susceptibility difference at vascular interfaces is quickly balanced by the perturbations induced by the increase of the magnetic susceptibility difference at the cellular interfaces in the extravascular compartment. (author)

  13. Conformational analysis of amide extractants by NMR in organic phase

    International Nuclear Information System (INIS)

    This study deals with nuclear fuel reprocessing. We have essentially used NMR spectroscopy. We want to understand which kind of conformational parameters control selectivity and efficiency of amide extractant. The symmetric monoamides used are DOBA (C3H7 CON (CH2 CH(C2H5) C4H9)2), DOiBA ((CH3)2 CCHON (CH2CH(C2H5)C4H9)2) and DOTA ((CH3)3 CCH2CON(CH2CH(C2H5)C4H9)2). Each gives two quasi equivalent conformers (cis and trans) in organic phases. The selected malonamide DMDBTDMA ((C4H9 (CH3)NCO)2 CHC14H29) has four conformers because of its twice disymmetric amide functions. Weak interactions between monoamides which yield to dimer formation. The malonamide also gives dimers but forms aggregates too. Nitric acid extraction is due to the competitive formation of six species L, L2, L2(HNO3), L(HNO3), L(HNO3)2, L(HNO3)3 (L: monoamide). Complexation between lanthanides (III) and monoamides yields to the stoichiometries L3Ln(NO3)3 and L2Ln(NO3)3. Their ratio depend of steric hindrance on the carbonyl and the metal ionic radius. The same thing is observed of Pu4+ and Th4+ extraction in non acidic media. L2An(NO3)4 is the main stoichiometric except for the Th4+ - DOBA system where the species (DOBA)3 Th(NO3)4 appear. Exchange rates between the ligand and the complex are pointed out. The monoamide conformations obtained with lanthanide and plutonium nitrate can explain the difference in extracting power of this molecule between An4+ and Ln3+. (author). 162 refs., 87 figs., 44 tabs., 7 annexes

  14. Amide-Exchange-Rate-Edited NMR (AERE-NMR) Experiment:A Novel Method for Resolving Overlapping Resonances

    Institute of Scientific and Technical Information of China (English)

    LIU Xue-Hui; LIN Dong-Hai

    2007-01-01

    This paper describes an amide-exchange-rate-edited (AERE) NMR method that can effectively alleviate the problem of resonance overlap for proteins and peptides. This method exploits the diversity of amide proton exchange rates and consists of two complementary experiments: (1) SEA (solvent exposed amide)-type NMR experiments to map exchangeable surface residues whose amides are not involved in hydrogen bonding, and (2) presat-type NMR experiments to map solvent inaccessibly buried residues or nonexchangeable residues located in hydrogen-bonded secondary structures with properly controlled saturation transfer via amide proton exchanges with the solvent. This method separates overlapping resonances in a spectrum into two complementary spectra. The AERE-NMR method was demonstrated with a sample of 15N/13C/2H(70%) labeled ribosome-inactivating protein trichosanthin of 247 residues.

  15. (13)C NMR assignments of regenerated cellulose from solid-state 2D NMR spectroscopy.

    Science.gov (United States)

    Idström, Alexander; Schantz, Staffan; Sundberg, Johan; Chmelka, Bradley F; Gatenholm, Paul; Nordstierna, Lars

    2016-10-20

    From the assignment of the solid-state (13)C NMR signals in the C4 region, distinct types of crystalline cellulose, cellulose at crystalline surfaces, and disordered cellulose can be identified and quantified. For regenerated cellulose, complete (13)C assignments of the other carbon regions have not previously been attainable, due to signal overlap. In this study, two-dimensional (2D) NMR correlation methods were used to resolve and assign (13)C signals for all carbon atoms in regenerated cellulose. (13)C-enriched bacterial nanocellulose was biosynthesized, dissolved, and coagulated as highly crystalline cellulose II. Specifically, four distinct (13)C signals were observed corresponding to conformationally different anhydroglucose units: two signals assigned to crystalline moieties and two signals assigned to non-crystalline species. The C1, C4 and C6 regions for cellulose II were fully examined by global spectral deconvolution, which yielded qualitative trends of the relative populations of the different cellulose moieties, as a function of wetting and drying treatments. PMID:27474592

  16. Accessible surface area from NMR chemical shifts

    International Nuclear Information System (INIS)

    Accessible surface area (ASA) is the surface area of an atom, amino acid or biomolecule that is exposed to solvent. The calculation of a molecule’s ASA requires three-dimensional coordinate data and the use of a “rolling ball” algorithm to both define and calculate the ASA. For polymers such as proteins, the ASA for individual amino acids is closely related to the hydrophobicity of the amino acid as well as its local secondary and tertiary structure. For proteins, ASA is a structural descriptor that can often be as informative as secondary structure. Consequently there has been considerable effort over the past two decades to try to predict ASA from protein sequence data and to use ASA information (derived from chemical modification studies) as a structure constraint. Recently it has become evident that protein chemical shifts are also sensitive to ASA. Given the potential utility of ASA estimates as structural constraints for NMR we decided to explore this relationship further. Using machine learning techniques (specifically a boosted tree regression model) we developed an algorithm called “ShiftASA” that combines chemical-shift and sequence derived features to accurately estimate per-residue fractional ASA values of water-soluble proteins. This method showed a correlation coefficient between predicted and experimental values of 0.79 when evaluated on a set of 65 independent test proteins, which was an 8.2 % improvement over the next best performing (sequence-only) method. On a separate test set of 92 proteins, ShiftASA reported a mean correlation coefficient of 0.82, which was 12.3 % better than the next best performing method. ShiftASA is available as a web server ( http://shiftasa.wishartlab.com http://shiftasa.wishartlab.com ) for submitting input queries for fractional ASA calculation

  17. Monitoring prion protein stability by NMR.

    Science.gov (United States)

    Julien, Olivier; Graether, Steffen P; Sykes, Brian D

    2009-01-01

    Prion diseases, or transmissible spongiform encephalopathies (TSE), are a group of fatal neurological diseases that affect both humans and animals. At the end of the 20th century, bovine spongiform encephalopathy (BSE), better known as mad cow disease, was shown to be transmissible to humans. This resulted in considerable concern for public health and a number of questions for scientists. The first question answered was the possible source of the disease, which appears to be the prion protein (PrP). There are two major forms of this protein: the native, noninfectious form (PrP(C)), and the misfolded infectious form (PrP(Sc)). PrP(C) is mainly alpha-helical in structure, whereas PrP(Sc) aggregates into an assembly of beta-sheets, forming amyloid fibrils. Since the first solution structure of the noninfectious form of the mouse prion protein, about 30 structures of the globular portion of PrP(C) have been characterized from different organisms. However, only a few minor differences are observed when comparing one PrP(C) structure to another. The key to understanding prion formation may then be not in the structure of PrP(C), but in the mechanism underlying PrP(C) unfolding and then conversion into a misfolded fibril state. To identify the possible region(s) of PrP(C) responsible for initiating the conversion into the amyloid fibril formation, nuclear magnetic resonance (NMR) was applied to characterize the stability and structure of PrP(C) and intermediate states during the conversion from PrP(C) to PrP(Sc). Subsequently urea was used to induce unfolding, and data analysis revealed region-specific structural stabilities that may bring insights into the mechanisms underlying conversion of protein into an infectious prion. PMID:19697241

  18. NMR Investigations of Structure and Dynamics in Polymers for Energy Storage Applications

    Science.gov (United States)

    Greenbaum, Steven

    Materials innovation is needed to realize major progress in energy storage capacity for lithium batteries and capacitors. Polymers hold considerable promise as ion conducting media in batteries and electrochemical capacitors and as dielectrics in thin film capacitors. Structural studies of materials utilized in lithium battery technology are hampered by the lack of long-range order found in well-defined crystalline phases. Powder x-ray diffraction yields structural parameters that have been averaged over hundreds of lattice sites, and is unable to provide structural information about amorphous phases. Our laboratory uses solid state nuclear magnetic resonance (NMR) methods to investigate structural and chemical aspects of lithium ion cathodes, anodes, electrolytes, interfaces and interphases. NMR is element- (nuclear-) specific and sensitive to small variations in the immediate environment of the ions being probed, for example Li+, and in most cases is a reliably quantitative spectroscopy in that the integrated intensity of a particular spectral component is directly proportional to the number of nuclei in the corresponding material phase. NMR is also a powerful tool for probing ionic and molecular motion in lithium battery electrolytes with a dynamic range spanning some ten orders of magnitude through spin-lattice relaxation and self-diffusion measurements. Broadband relaxometry based on Fast Field Cycling NMR (FFCNMR) methods can span three to four of these orders of magnitude in a single set of measurements. Results of several recent NMR investigations performed on our lab will be presented. We explore the ion transport mechanism in polyether-based and lithium polymer electrolytes and those based on other base polymers, in particular, the extent to which ionic motion is coupled to polymer segmental motion. Polycarbonates are being considered as a possible replacement for polypropylene in high power thin film capacitors due to their favorable dielectric

  19. A new method of evaluating tight gas sands pore structure from nuclear magnetic resonance (NMR) logs

    Science.gov (United States)

    Xiao, Liang; Mao, Zhi-qiang; Xie, Xiu-hong

    2016-04-01

    Tight gas sands always display such characteristics of ultra-low porosity, permeability, high irreducible water, low resistivity contrast, complicated pore structure and strong heterogeneity, these make that the conventional methods are invalid. Many effective gas bearing formations are considered as dry zones or water saturated layers, and cannot be identified and exploited. To improve tight gas sands evaluation, the best method is quantitative characterizing rock pore structure. The mercury injection capillary pressure (MICP) curves are advantageous in predicting formation pore structure. However, the MICP experimental measurements are limited due to the environment and economy factors, this leads formation pore structure cannot be consecutively evaluated. Nuclear magnetic resonance (NMR) logs are considered to be promising in evaluating rock pore structure. Generally, to consecutively quantitatively evaluate tight gas sands pore structure, the best method is constructing pseudo Pc curves from NMR logs. In this paper, based on the analysis of lab experimental results for 20 core samples, which were drilled from tight gas sandstone reservoirs of Sichuan basin, and simultaneously applied for lab MICP and NMR measurements, the relationships of piecewise power function between nuclear magnetic resonance (NMR) transverse relaxation T2 time and pore-throat radius Rc are established. A novel method, which is used to transform NMR reverse cumulative curve as pseudo capillary pressure (Pc) curve is proposed, and the corresponding model is established based on formation classification. By using this model, formation pseudo Pc curves can be consecutively synthesized. The pore throat radius distribution, and pore structure evaluation parameters, such as the average pore throat radius (Rm), the threshold pressure (Pd), the maximum pore throat radius (Rmax) and so on, can also be precisely extracted. After this method is extended into field applications, several tight gas

  20. The theoretic design of NMR pulses program of arbitrary N-qubit Grover's algorithm and the NMR experiment proof

    Institute of Scientific and Technical Information of China (English)

    杨晓冬; 缪希茄

    2002-01-01

    Grover's quantum searching algorithm is most widely studied in the current quantum computation research, and has been implemented experimentally by NMR (Nuclear Magnetic Resonance) technique. In this article, we design arbitrary N-qubit NMR pulses program of Grover's algorithm based on the multiple-quantum operator algebra theory and demonstrate 2-qubit pulses program experimentally. The result also proves the validity of the multiple-quantum operator algebra theory.

  1. Condition Monitoring of a Thermally Aged HTPB/IPDI Elastomer by NMR CP Recovery Times

    Energy Technology Data Exchange (ETDEWEB)

    ASSINK,ROGER A.; LANG,DAVID; CELINA,MATHIAS C.

    2000-07-24

    A hydroxy-terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) elastomer is commonly used as propellant binder material. The thermal degradation of the binder is believed to be an important parameter governing the performance of the propellant. The aging of these binders can be monitored by mechanical property measurements such as modulus or tensile elongation. These techniques, however, are not easily adapted to binder agents that are dispersed throughout a propellant. In this paper the authors investigated solid state NMR relaxation times as a means to predict the mechanical properties of the binder as a function of aging time. {sup 1}H spin-lattice and spin-spin relaxation times were found to be insensitive to the degree of thermal degradation of the elastomer. Apparently these relaxation times depend on localized motions that are only weakly correlated with mechanical properties. A strong correlation was found between the {sup 13}C cross-polarization (CP) NMR time constant, T{sub cp}, and the tensile elongation at break of the elastomer as a function of aging time. A ramped-amplitude CP experiment was shown to be less sensitive to imperfections in setting critical instrumental parameters for this mobile material.

  2. The quantitative in vivo analysis of the muscle degeneration in Duchenne type muscular dystrophy using NMR-CT

    International Nuclear Information System (INIS)

    In order to develop a simple noninvasive method to determine progressive stages of Duchenne type muscular dystrophy (DMD), we proposed two muscular degeneration parameters calculated from NMR-CT data. The parameters are W.C.P. (water concentration parameter) and F.C.P. (fat concentration parameter). We examined 15 normal male and 10 normal female volunteers, 19 carrier females and 21 DMD patients. The normal value indicated 0 to 30 % F.C.P., while the results of DMD patients showed abnormally high W.C.P. at the early stage and increased F.C.P. corresponding to the clinical stages (Ueda's disability stages). But there was not any difference between the DMD carrier's data and the control data. The present study suggested the possibilities of clinical stagings and early detection of DMD with the parameters. (author)

  3. Estimation of Permeability from NMR Logs Based on Formation Classification Method in Tight Gas Sands

    Science.gov (United States)

    Wei, Deng-Feng; Liu, Xiao-Peng; Hu, Xiao-Xin; Xu, Rui; Zhu, Ling-Ling

    2015-10-01

    The Schlumberger Doll Research (SDR) model and cross plot of porosity versus permeability cannot be directly used in tight gas sands. In this study, the HFU approach is introduced to classify rocks, and determine the involved parameters in the SDR model. Based on the difference of FZI, 87 core samples, drilled from tight gas sandstones reservoirs of E basin in northwest China and applied for laboratory NMR measurements, were classified into three types, and the involved parameters in the SDR model are calibrated separately. Meanwhile, relationships of porosity versus permeability are also established. The statistical model is used to calculate consecutive FZI from conventional logs. Field examples illustrate that the calibrated SDR models are applicable in permeability estimation; models established from routine core analyzed results are effective in reservoirs with permeability lower than 0.3 mD, while the unified SDR model is only valid in reservoirs with permeability ranges from 0.1 to 0.3 mD.

  4. Lumped-parameter models

    Energy Technology Data Exchange (ETDEWEB)

    Ibsen, Lars Bo; Liingaard, M.

    2006-12-15

    A lumped-parameter model represents the frequency dependent soil-structure interaction of a massless foundation placed on or embedded into an unbounded soil domain. In this technical report the steps of establishing a lumped-parameter model are presented. Following sections are included in this report: Static and dynamic formulation, Simple lumped-parameter models and Advanced lumped-parameter models. (au)

  5. Accurate, fully-automated NMR spectral profiling for metabolomics.

    Directory of Open Access Journals (Sweden)

    Siamak Ravanbakhsh

    Full Text Available Many diseases cause significant changes to the concentrations of small molecules (a.k.a. metabolites that appear in a person's biofluids, which means such diseases can often be readily detected from a person's "metabolic profile"-i.e., the list of concentrations of those metabolites. This information can be extracted from a biofluids Nuclear Magnetic Resonance (NMR spectrum. However, due to its complexity, NMR spectral profiling has remained manual, resulting in slow, expensive and error-prone procedures that have hindered clinical and industrial adoption of metabolomics via NMR. This paper presents a system, BAYESIL, which can quickly, accurately, and autonomously produce a person's metabolic profile. Given a 1D 1H NMR spectrum of a complex biofluid (specifically serum or cerebrospinal fluid, BAYESIL can automatically determine the metabolic profile. This requires first performing several spectral processing steps, then matching the resulting spectrum against a reference compound library, which contains the "signatures" of each relevant metabolite. BAYESIL views spectral matching as an inference problem within a probabilistic graphical model that rapidly approximates the most probable metabolic profile. Our extensive studies on a diverse set of complex mixtures including real biological samples (serum and CSF, defined mixtures and realistic computer generated spectra; involving > 50 compounds, show that BAYESIL can autonomously find the concentration of NMR-detectable metabolites accurately (~ 90% correct identification and ~ 10% quantification error, in less than 5 minutes on a single CPU. These results demonstrate that BAYESIL is the first fully-automatic publicly-accessible system that provides quantitative NMR spectral profiling effectively-with an accuracy on these biofluids that meets or exceeds the performance of trained experts. We anticipate this tool will usher in high-throughput metabolomics and enable a wealth of new applications of

  6. Transient protein-protein interactions visualized by solution NMR.

    Science.gov (United States)

    Liu, Zhu; Gong, Zhou; Dong, Xu; Tang, Chun

    2016-01-01

    Proteins interact with each other to establish their identities in cell. The affinities for the interactions span more than ten orders of magnitude, and KD values in μM-mM regimen are considered transient and are important in cell signaling. Solution NMR including diamagnetic and paramagnetic techniques has enabled atomic-resolution depictions of transient protein-protein interactions. Diamagnetic NMR allows characterization of protein complexes with KD values up to several mM, whereas ultraweak and fleeting complexes can be modeled with the use of paramagnetic NMR especially paramagnetic relaxation enhancement (PRE). When tackling ever-larger protein complexes, PRE can be particularly useful in providing long-range intermolecular distance restraints. As NMR measurements are averaged over the ensemble of complex structures, structural information for dynamic protein-protein interactions besides the stereospecific one can often be extracted. Herein the protein interaction dynamics are exemplified by encounter complexes, alternative binding modes, and coupled binding/folding of intrinsically disordered proteins. Further integration of NMR with other biophysical techniques should allow better visualization of transient protein-protein interactions. In particular, single-molecule data may facilitate the interpretation of ensemble-averaged NMR data. Though same structures of proteins and protein complexes were found in cell as in diluted solution, we anticipate that the dynamics of transient protein protein-protein interactions be different, which awaits awaits exploration by NMR. This article is part of a Special Issue entitled: Physiological Enzymology and Protein Functions. This article is part of a Special Issue entitled: Physiological Enzymology and Protein Functions. PMID:25896389

  7. GEL-STATE NMR OF BALL-MILLED WHOLE CELL WALLS IN DMSO-d6 USING 2D SOLUTION-STATE NMR SPECTROSCOPY

    Science.gov (United States)

    Plant cell walls were used for obtaining 2D solution-state NMR spectra without actual solubilization or structural modification. Ball-milled whole cell walls were swelled directly in the NMR tube with DMSO-d6 where they formed a gel. There are relatively few gel-state NMR studies. Most have involved...

  8. Use of NMR logging to obtain estimates of hydraulic conductivity in the High Plains aquifer, Nebraska, USA

    Science.gov (United States)

    Dlubac, Katherine; Knight, Rosemary; Song, Yi-Qiao; Bachman, Nate; Grau, Ben; Cannia, Jim; Williams, John

    2013-01-01

    Hydraulic conductivity (K) is one of the most important parameters of interest in groundwater applications because it quantifies the ease with which water can flow through an aquifer material. Hydraulic conductivity is typically measured by conducting aquifer tests or wellbore flow (WBF) logging. Of interest in our research is the use of proton nuclear magnetic resonance (NMR) logging to obtain information about water-filled porosity and pore space geometry, the combination of which can be used to estimate K. In this study, we acquired a suite of advanced geophysical logs, aquifer tests, WBF logs, and sidewall cores at the field site in Lexington, Nebraska, which is underlain by the High Plains aquifer. We first used two empirical equations developed for petroleum applications to predict K from NMR logging data: the Schlumberger Doll Research equation (KSDR) and the Timur-Coates equation (KT-C), with the standard empirical constants determined for consolidated materials. We upscaled our NMR-derived K estimates to the scale of the WBF-logging K(KWBF-logging) estimates for comparison. All the upscaled KT-C estimates were within an order of magnitude of KWBF-logging and all of the upscaled KSDR estimates were within 2 orders of magnitude of KWBF-logging. We optimized the fit between the upscaled NMR-derived K and KWBF-logging estimates to determine a set of site-specific empirical constants for the unconsolidated materials at our field site. We conclude that reliable estimates of K can be obtained from NMR logging data, thus providing an alternate method for obtaining estimates of K at high levels of vertical resolution.

  9. An EPR study of the phase transitions and Gd3+ zero-field splitting parameters in RbR(SO4)2.4H2O (R = Er, Dy, Pr, Nd, Sm, Eu)

    International Nuclear Information System (INIS)

    X-band (∼9.6 GHz) electron paramagnetic resonance measurements were carried out on Gd3+-doped RbEr(SO4)2.4H2O and RbDy(SO4)2.4H2O single crystals in the 4.2-295 K temperature range, and on Gd3+-doped RbPr(SO4)2.4H2O, RbNd(SO4)2.4H2O, RbSm(SO4)2.4H2O and RbEu(SO4)2.4H2O single crystals in the 4.2-110 K range. Gd3+ room-temperature spin-Hamiltonian parameters were estimated in RbR(SO4)2.4H2O samples with R = Er, Dy. The following phase transitions undergone by the various host crystals were found to occur: three second-order phase transitions in RbDy(SO4)2.4H2O at 260.3 K, 226.9 K and 65.4 K, and second-order and first-order phase transitions in RbEr(SO4)2.4H2O at 228.1 and 68.8 K, respectively. In addition, there were observed first-order phase transitions in each of RbNd(SO4)2.4H2O (at 72.1 K), RbSm(SO4)2.4H2O (at 70.3 K) and RbEu(SO4)2.4H2O (at 79.4 K), and two in RbPr(SO4)2.4H2O (at 71.4 and 9.7 K) crystals, in the 4.2-110 K range, in addition to those reported previously in the 110-295 K range. Systematics of the various phase transitions occurring in RbR(SO4)2.4H2O (R = Pr, Nd, Sm, Er, Dy, Eu) single crystals in the temperature range 4.2-295 K, and those of Gd3+ zero-field splitting parameters at room temperature, have been deduced. (author)

  10. Affecting factors of NMR data and correction%影响核磁测井质量的因素及校正

    Institute of Scientific and Technical Information of China (English)

    宋公仆; 张向林

    2013-01-01

    本文从数学和物理模型的基础推导出了核磁测井仪器天线的数据关系式,同时分析了各参数影响,并利用地层流体含氢的特性与实验室纯水中刻度的比值进行孔隙度的校正,用该方法对几种核磁测井数据进行处理并与常规测井处理得出的结论进行对比,符合的很好,证明了该方法有很好的效果,可提升核磁解释的准确性.%Parameters obtained from NMR logging technology can be used to evaluate the total porosity,effective porosity,clay-bound water,capillary-bound water,permeability,pore-size distribution,movable fluid,mobile water saturation and bound water saturation of the reservoir.It is well known that rock physical information of reservoirs is got by measuring the NMR phenomena of hydrogen nucleus in formation fluids,such as water,brine,oil or gas.Sametimes,porosity obtained from NMR logging data is different from that from other logging data or no disagreement with real porosity of reservoirfor some reasons.The composed functions of probe of NMR logging tool are introduced briefly in this paper,and effect factors of NMR tool probe are discussed at the same time.NMR signal can be significant affected by the Hydrogen nucleus in rock reservoirs,tool factor,temperature and tool frequency.The analysis of the functions shows porous error caused by hydrogen nucleus in formation fluids.Hydrogen nucleus in oil,gas or brine in same porosity of reservoir is different because of temperature and pressure inflation.To eliminate Hydrogen nucleus effect and correct porous error,fisrt,NMR tool's data is got in water in lab,it is used to as standard to calibrate NMR logging data,then,ratio of HI in fluid-saturated rocks is obtained to correct NMR logging porosity.The results indicate that Porosity obtained from several NMR tools data processed with the method given in this arctic is agreed with porosity from conventional instrument.Advantages of this method are presented.

  11. Mechanisms of Action of (Methacrylates in Hemolytic Activity, in Vivo Toxicity and Dipalmitoylphosphatidylcholine (DPPC Liposomes Determined Using NMR Spectroscopy

    Directory of Open Access Journals (Sweden)

    Seiichiro Fujisawa

    2012-01-01

    Full Text Available We investigated the quantitative structure-activity relationships between hemolytic activity (log 1/H50 or in vivo mouse intraperitoneal (ip LD50 using reported data for α,β-unsaturated carbonyl compounds such as (methacrylate monomers and their 13C-NMR β-carbon chemical shift (δ. The log 1/H50 value for methacrylates was linearly correlated with the δCβ value. That for (methacrylates was linearly correlated with log P, an index of lipophilicity. The ipLD50 for (methacrylates was linearly correlated with δCβ but not with log P. For (methacrylates, the δCβ value, which is dependent on the π-electron density on the β-carbon, was linearly correlated with PM3-based theoretical parameters (chemical hardness, η; electronegativity, χ; electrophilicity, ω, whereas log P was linearly correlated with heat of formation (HF. Also, the interaction between (methacrylates and DPPC liposomes in cell membrane molecular models was investigated using 1H-NMR spectroscopy and differential scanning calorimetry (DSC. The log 1/H50 value was related to the difference in chemical shift (ΔδHa (Ha: H (trans attached to the β-carbon between the free monomer and the DPPC liposome-bound monomer. Monomer-induced DSC phase transition properties were related to HF for monomers. NMR chemical shifts may represent a valuable parameter for investigating the biological mechanisms of action of (methacrylates.

  12. Magic-angle spinning NMR of cold samples.

    Science.gov (United States)

    Concistrè, Maria; Johannessen, Ole G; Carignani, Elisa; Geppi, Marco; Levitt, Malcolm H

    2013-09-17

    Magic-angle-spinning solid-state NMR provides site-resolved structural and chemical information about molecules that complements many other physical techniques. Recent technical advances have made it possible to perform magic-angle-spinning NMR experiments at low temperatures, allowing researchers to trap reaction intermediates and to perform site-resolved studies of low-temperature physical phenomena such as quantum rotations, quantum tunneling, ortho-para conversion between spin isomers, and superconductivity. In examining biological molecules, the improved sensitivity provided by cryogenic NMR facilitates the study of protein assembly or membrane proteins. The combination of low-temperatures with dynamic nuclear polarization has the potential to boost sensitivity even further. Many research groups, including ours, have addressed the technical challenges and developed hardware for magic-angle-spinning of samples cooled down to a few tens of degrees Kelvin. In this Account, we briefly describe these hardware developments and review several recent activities of our group which involve low-temperature magic-angle-spinning NMR. Low-temperature operation allows us to trap intermediates that cannot be studied under ambient conditions by NMR because of their short lifetime. We have used low-temperature NMR to study the electronic structure of bathorhodopsin, the primary photoproduct of the light-sensitive membrane protein, rhodopsin. This project used a custom-built NMR probe that allows low-temperature NMR in the presence of illumination (the image shows the illuminated spinner module). We have also used this technique to study the behavior of molecules within a restricted environment. Small-molecule endofullerenes are interesting molecular systems in which molecular rotors are confined to a well-insulated, well-defined, and highly symmetric environment. We discuss how cryogenic solid state NMR can give information on the dynamics of ortho-water confined in a fullerene

  13. Development of a superconducting bulk magnet for NMR and MRI

    Science.gov (United States)

    Nakamura, Takashi; Tamada, Daiki; Yanagi, Yousuke; Itoh, Yoshitaka; Nemoto, Takahiro; Utumi, Hiroaki; Kose, Katsumi

    2015-10-01

    A superconducting bulk magnet composed of six vertically stacked annular single-domain c-axis-oriented Eu-Ba-Cu-O crystals was energized to 4.74 T using a conventional superconducting magnet for high-resolution NMR spectroscopy. Shim coils, gradient coils, and radio frequency coils for high resolution NMR and MRI were installed in the 23 mm-diameter room-temperature bore of the bulk magnet. A 6.9 ppm peak-to-peak homogeneous region suitable for MRI was achieved in the central cylindrical region (6.2 mm diameter, 9.1 mm length) of the bulk magnet by using a single layer shim coil. A 21 Hz spectral resolution that can be used for high resolution NMR spectroscopy was obtained in the central cylindrical region (1.3 mm diameter, 4 mm length) of the bulk magnet by using a multichannel shim coil. A clear 3D MR image dataset of a chemically fixed mouse fetus with (50 μm)3 voxel resolution was obtained in 5.5 h. We therefore concluded that the cryogen-free superconducting bulk magnet developed in this study is useful for high-resolution desktop NMR, MRI and mobile NMR device.

  14. GFT projection NMR spectroscopy for proteins in the solid state

    International Nuclear Information System (INIS)

    Recording of four-dimensional (4D) spectra for proteins in the solid state has opened new avenues to obtain virtually complete resonance assignments and three-dimensional (3D) structures of proteins. As in solution state NMR, the sampling of three indirect dimensions leads per se to long minimal measurement time. Furthermore, artifact suppression in solid state NMR relies primarily on radio-frequency pulse phase cycling. For an n-step phase cycle, the minimal measurement times of both 3D and 4D spectra are increased n times. To tackle the associated 'sampling problem' and to avoid sampling limited data acquisition, solid state G-Matrix Fourier Transform (SS GFT) projection NMR is introduced to rapidly acquire 3D and 4D spectral information. Specifically, (4,3)D (HA)CANCOCX and (3,2)D (HACA)NCOCX were implemented and recorded for the 6 kDa protein GB1 within about 10% of the time required for acquiring the conventional congeners with the same maximal evolution times and spectral widths in the indirect dimensions. Spectral analysis was complemented by comparative analysis of expected spectral congestion in conventional and GFT NMR experiments, demonstrating that high spectral resolution of the GFT NMR experiments enables one to efficiently obtain nearly complete resonance assignments even for large proteins.

  15. High resolution deuterium NMR studies of bacterial metabolism

    Energy Technology Data Exchange (ETDEWEB)

    Aguayo, J.B.; Gamcsik, M.P.; Dick, J.D.

    1988-12-25

    High resolution deuterium NMR spectra were obtained from suspensions of five bacterial strains: Escherichia coli, Clostridium perfringens, Klebsiella pneumoniae, Proteus mirabilis, and Staphylococcus aureus. Deuterium-labeled D-glucose at C-1, C-2, and C-6 was used to monitor dynamically anaerobic metabolism. The flux of glucose through the various bacterial metabolic pathways could be determined by following the disappearance of glucose and the appearance of the major end products in the 2H NMR spectrum. The presence of both labeled and unlabeled metabolites could be detected using 1H NMR spectroscopy since the proton resonances in the labeled species are shifted upfield due to an isotopic chemical shift effect. The 1H-1H scalar coupling observed in both the 2H and 1H NMR spectra was used to assign definitively the resonances of labeled species. An increase in the intensity of natural abundance deuterium signal of water can be used to monitor pathways in which a deuteron is lost from the labeled metabolite. The steps in which label loss can occur are outlined, and the influence these processes have on the ability of 2H NMR spectroscopy to monitor metabolism are assessed.

  16. NMR characterization of a novel bile acid sequestrant, DMP 504.

    Science.gov (United States)

    Lerke, S A; Nemeth, G; Schubert, E; Hovsepian, P K

    2001-02-01

    DMP 504, a potential bile acid sequestrant for the treatment of hypercholesterolemia, is a highly insoluble, cross-linked polymer which does not lend itself to ordinary means of characterization used for drug substances in the pharmaceutical industry. Therefore, alternative characterization techniques have been sought. As part of an effort into extensive characterization of DMP 504 drug substance, nuclear magnetic resonance (NMR) was employed to provide insight into details of the DMP 504 polymer structure. The primary motivation for determining the structure of the polymer chain is to relate the DMP 504 structure to its performance properties as a bile acid sequestrant. Characterization of the polymer chain and understanding of the structural basis of its properties is essential in optimizing and controlling the manufacture of reproducible drug substance. NMR has proven a versatile tool for the description of polymer structure and dynamics because of the wide range of nuclear interactions affecting the NMR signal. This allows the design of experiments to elicit information about specific polymer interactions or properties. The methods of sample preparation utilized to obtain NMR spectra of the insoluble polymer, as well as a discussion and comparison of results for the characterization of DMP 504 obtained using several different NMR techniques will be presented.

  17. Recovering Invisible Signals by Two-Field NMR Spectroscopy.

    Science.gov (United States)

    Cousin, Samuel F; Kadeřávek, Pavel; Haddou, Baptiste; Charlier, Cyril; Marquardsen, Thorsten; Tyburn, Jean-Max; Bovier, Pierre-Alain; Engelke, Frank; Maas, Werner; Bodenhausen, Geoffrey; Pelupessy, Philippe; Ferrage, Fabien

    2016-08-16

    Nuclear magnetic resonance (NMR) studies have benefited tremendously from the steady increase in the strength of magnetic fields. Spectacular improvements in both sensitivity and resolution have enabled the investigation of molecular systems of rising complexity. At very high fields, this progress may be jeopardized by line broadening, which is due to chemical exchange or relaxation by chemical shift anisotropy. In this work, we introduce a two-field NMR spectrometer designed for both excitation and observation of nuclear spins in two distinct magnetic fields in a single experiment. NMR spectra of several small molecules as well as a protein were obtained, with two dimensions acquired at vastly different magnetic fields. Resonances of exchanging groups that are broadened beyond recognition at high field can be sharpened to narrow peaks in the low-field dimension. Two-field NMR spectroscopy enables the measurement of chemical shifts at optimal fields and the study of molecular systems that suffer from internal dynamics, and opens new avenues for NMR spectroscopy at very high magnetic fields.

  18. Quantum Mechanical Nature in Liquid NMR Quantum Computing

    Institute of Scientific and Technical Information of China (English)

    LONG Gui-Lu; YAN Hai-Yang; LI Yan-Song; TU Chang-Cun; ZHU Sheng-Jiang; RUAN Dong; SUN Yang; TAO Jia-Xun; CHEN Hao-Ming

    2002-01-01

    The quantum nature of bulk ensemble NMR quantum computing the center of recent heated debate,is addressed. Concepts of the mixed state and entanglement are examined, and the data in a two-qubit liquid NMRquantum computation are analyzed. The main points in this paper are: i) Density matrix describes the "state" of anaverage particle in an ensemble. It does not describe the state of an individual particle in an ensemble; ii) Entanglementis a property of the wave function of a microscopic particle (such as a molecule in a liquid NMR sample), and separabilityof the density matrix cannot be used to measure the entanglement of mixed ensemble; iii) The state evolution in bulk-ensemble NMRquantum computation is quantum-mechanical; iv) The coefficient before the effective pure state densitymatrix, e, is a measure of the simultaneity of the molecules in an ensemble. It reflects the intensity of the NMR signaland has no significance in quantifying the entanglement in the bulk ensemble NMR system. The decomposition of thedensity matrix into product states is only an indication that the ensemble can be prepared by an ensemble with theparticles unentangled. We conclude that effective-pure-state NMR quantum computation is genuine, not just classicalsimulations.

  19. General method of preparation of uniformly {sup 13}C, {sup 15}N-labeled DNA fragments for NMR analysis of DNA structures

    Energy Technology Data Exchange (ETDEWEB)

    Rene, Brigitte; Masliah, Gregoire; Zargarian, Loussine; Mauffret, Olivier; Fermandjian, Serge [UMR 8113 CNRS - LBPA Ecole Normale Superieure de Cachan, Institut Gustave Roussy, Departement de Biologie et Pharmacologie Structurales (France)], E-mail: sfermand@igr.fr

    2006-11-15

    Summary{sup 13}C, {sup 15}N labeling of biomolecules allows easier assignments of NMR resonances and provides a larger number of NMR parameters, which greatly improves the quality of DNA structures. However, there is no general DNA-labeling procedure, like those employed for proteins and RNAs. Here, we describe a general and widely applicable approach designed for preparation of isotopically labeled DNA fragments that can be used for NMR studies. The procedure is based on the PCR amplification of oligonucleotides in the presence of labeled deoxynucleotides triphosphates. It allows great flexibility thanks to insertion of a short DNA sequence (linker) between two repeats of DNA sequence to study. Size and sequence of the linker are designed as to create restriction sites at the junctions with DNA of interest. DNA duplex with desired sequence and size is released upon enzymatic digestion of the PCR product. The suitability of the procedure is validated through the preparation of two biological relevant DNA fragments.

  20. Investigation of the energy barrier to the rotation of amide CN bonds in ACE inhibitors by NMR, dynamic HPLC and DFT.

    Science.gov (United States)

    Bouabdallah, S; Ben Dhia, M T; Driss, M R; Touil, S

    2016-09-01

    The isomerizations of Enalapril, Perindopril, Enalaprilat and Lisinopril have been investigated using NMR spectroscopic, dynamic chromatographic, unified equation and DFT theoretical calculations. The thermodynamic parameters (ΔH, ΔS and ΔG) were determined by varying the temperature in the NMR experiments. At the coalescence temperature, we can evaluate the isomerization barrier to the rotation (ΔG(≠)) around the amide bond. Using dynamics chromatography and an unified equation introduced by Trap, we can determine isomerization rate constants and Gibbs activation energies. Molecular mechanics calculations also provided evidence for the presence of low energy conformers for the ACE due to restricted amide rotation. With the value of barriers (ΔE) between them of the order of (20kJmol(-1)), which is in agreement with the dynamic NMR results and DFT calculations. PMID:27344631

  1. Investigation of the energy barrier to the rotation of amide CN bonds in ACE inhibitors by NMR, dynamic HPLC and DFT.

    Science.gov (United States)

    Bouabdallah, S; Ben Dhia, M T; Driss, M R; Touil, S

    2016-09-01

    The isomerizations of Enalapril, Perindopril, Enalaprilat and Lisinopril have been investigated using NMR spectroscopic, dynamic chromatographic, unified equation and DFT theoretical calculations. The thermodynamic parameters (ΔH, ΔS and ΔG) were determined by varying the temperature in the NMR experiments. At the coalescence temperature, we can evaluate the isomerization barrier to the rotation (ΔG(≠)) around the amide bond. Using dynamics chromatography and an unified equation introduced by Trap, we can determine isomerization rate constants and Gibbs activation energies. Molecular mechanics calculations also provided evidence for the presence of low energy conformers for the ACE due to restricted amide rotation. With the value of barriers (ΔE) between them of the order of (20kJmol(-1)), which is in agreement with the dynamic NMR results and DFT calculations.

  2. Ligands turning around in the midst of protein conformers: the origin of ligand-protein mating. A NMR view.

    Science.gov (United States)

    Pertinhez, T A; Spisni, A

    2011-01-01

    Protein-ligand binding is a puzzling process. Many theories have been devised since the pioneering key-and-lock hypothesis based on the idea that both the protein and the ligand have a rigid single conformation. Indeed, molecular motion is the essence of the universe. Consequently, not only proteins are characterized by an extraordinary conformational freedom, but ligands too can fluctuate in a rather vast conformational space. In this scenario, the quest to understand how do they match is fascinating. Recognizing that the inherent dynamics of molecules is the key factor controlling the success of the binding and, subsequently, their chemical/biological function, here we present a view of this process from the NMR stand point. A description of the most relevant NMR parameters that can provide insights, at atomic level, on the mechanisms of protein-ligand binding is provided in the final section. PMID:20939791

  3. XRD, NMR, and EPR study of polycrystalline micro- and nano-diamonds prepared by a shock wave compression method

    Energy Technology Data Exchange (ETDEWEB)

    Shames, Alexander I.; Panich, Alexander M. [Department of Physics, Ben-Gurion University of the Negev, Be' er Sheva (Israel); Mogilyansky, Dmitry [Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Be' er-Sheva (Israel); Sergeev, Nikolay A.; Olszewski, Marcin [Institute of Physics, University of Szczecin (Poland); Boudou, Jean-Paul [Laboratoire Aime Cotton, CNRS, Universite Paris-Sud et ENS Cachan, Orsay (France); Osipov, Vladimir Yu. [Ioffe Physical-Technical Institute, St. Petersburg (Russian Federation)

    2015-11-15

    We report on XRD, NMR, and EPR study of commercial micro- and nano-diamonds of the SSX series fabricated by a shock wave compression method. XRD data analysis shows that SSX samples consist of nanometer cubic diamond domains intermixing with stacking faults and twins. We show that as-received samples reveal a graphitic component, which may be removed by additional purification. Crushing the initial microdiamond powder into submicron and nanometer sizes does not result in noticeable variations of the XRD, NMR, and EPR parameters. This finding is explained by the fact that SSX diamonds are polycrystalline aggregates consisting of numerous nanocrystallites of ∝20-25 nm in size. Therefore, soft crushing of these aggregates diminishes their size, but leaves constituting nanocrystallites and their intrinsically facet surfaces mainly untreated. With that some modification of the outer nanocrystallite surface on crushing is observed. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. XRD, NMR, and EPR study of polycrystalline micro- and nano-diamonds prepared by a shock wave compression method

    International Nuclear Information System (INIS)

    We report on XRD, NMR, and EPR study of commercial micro- and nano-diamonds of the SSX series fabricated by a shock wave compression method. XRD data analysis shows that SSX samples consist of nanometer cubic diamond domains intermixing with stacking faults and twins. We show that as-received samples reveal a graphitic component, which may be removed by additional purification. Crushing the initial microdiamond powder into submicron and nanometer sizes does not result in noticeable variations of the XRD, NMR, and EPR parameters. This finding is explained by the fact that SSX diamonds are polycrystalline aggregates consisting of numerous nanocrystallites of ∝20-25 nm in size. Therefore, soft crushing of these aggregates diminishes their size, but leaves constituting nanocrystallites and their intrinsically facet surfaces mainly untreated. With that some modification of the outer nanocrystallite surface on crushing is observed. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Polyphosphates as a source of enhanced P fluxes in marine sediments overlain by anoxic waters: Evidence from 31P NMR

    Directory of Open Access Journals (Sweden)

    Ingall Ellery

    2005-06-01

    Full Text Available Sedimentary phosphorus (P composition was investigated in Effingham Inlet, a fjord located on the west coast of Vancouver Island in Barkley Sound. Solid-state 31P nuclear magnetic resonance (NMR spectroscopy was applied to demineralized sediment samples from sites overlain by oxic and anoxic bottom waters. The two sites were similar in terms of key diagenetic parameters, including the mass accumulation rate, integrated sulfate reduction rate, and bulk sediment organic carbon content. In contrast, P benthic fluxes were much higher at the anoxic site. 31P NMR results show that P esters and phosphonates are the major organic P species present at the surface and at depth in sediments at both sites. Polyphosphates were only found in the surface sediment of the site overlain by oxic waters. The varying stability of polyphosphates in microorganisms under different redox conditions may, in part, explain their distribution as well as differences in P flux between the two sites.

  6. Analysis of the mechanical properties and characterization by solid state 13C NMR of recycled EVA copolymer/silica composites

    Directory of Open Access Journals (Sweden)

    Giovanni Chaves Stael

    2005-09-01

    Full Text Available The incorporation of micrometer sized silica particles on poly (ethylene-co-vinyl acetate - EVA - residues from the footwear industry was evaluated. The effects of the processing parameters - temperature and mixing ratio - on the mechanical behavior of molded plates of neat recycled EVA and EVA/silica composites were also investigated. The mechanical properties measured by the tensile test, the fractographic analysis by scanning electron microscopy (SEM, and the 13C Nuclear Magnetic Resonance (NMR showed a reduced EVA to silica compatibility. Therefore, incorporation of untreated silica to recycled EVA copolymer produced a slight decrease on the mechanical performance of EVA/silica composites in respect to neat EVA copolymer. The NMR analysis also shows that the crosslinking process on recycled EVA may be occurring at the carbonyl group.

  7. Analysis of the mechanical properties and characterization by solid state 13 C NMR of recycled EVA copolymer/silica composites

    International Nuclear Information System (INIS)

    The incorporation of micrometer sized silica particles on poly (ethylene-co-vinyl acetate) - EVA - residues from the footwear industry was evaluated. The effects of the processing parameters - temperature and mixing ratio - on the mechanical behavior of molded plates of neat recycled EVA and EVA/silica composites were also investigated. The mechanical properties measured by the tensile test, the fractographic analysis by scanning electron microscopy (SEM), and the 13 C Nuclear Magnetic Resonance (NMR) showed a reduced EVA to silica compatibility. Therefore, incorporation of untreated silica to recycled EVA copolymer produced a slight decrease on the mechanical performance of EVA/silica composites in respect to neat EVA copolymer. The NMR analysis also shows that the crosslinking process on recycled EVA may be occurring at the carbonyl group. (author)

  8. Molecular structure and spectroscopic analysis of homovanillic acid and its sodium salt - NMR, FT-IR and DFT studies

    Science.gov (United States)

    Samsonowicz, M.; Kowczyk-Sadowy, M.; Regulska, E.; Lewandowski, W.

    2014-01-01

    The estimation of the electronic charge distribution in metal complex or salt allows to predict what kind of deformation of the electronic system of ligand would undergo during complexation. It also permits to make more precise interpretation of mechanism by which metals affect the biochemical properties of ligands. The influence of sodium cation on the electronic system of homovanillic acid was studied in this paper. Optimized geometrical structures of studied compounds were calculated by B3LYP/6-311++G** method. Mulliken, MK and ChelpG atomic charges were analyzed. The theoretical NMR and IR spectra were obtained. 1H and 13C NMR as well as FT-IR and FT-Raman spectra of studied compounds were also recorded and analyzed. The calculated parameters are compared with experimental characteristics of these molecules.

  9. A portable NMR sensor to measure dynamic changes in the amount of water in living stems or fruit and its potential to measure sap flow.

    Science.gov (United States)

    Windt, Carel W; Blümler, Peter

    2015-04-01

    Nuclear magnetic resonance (NMR) and NMR imaging (magnetic resonance imaging) offer the possibility to quantitatively and non-invasively measure the presence and movement of water. Unfortunately, traditional NMR hardware is expensive, poorly suited for plants, and because of its bulk and complexity, not suitable for use in the field. But does it need to be? We here explore how novel, small-scale portable NMR devices can be used as a flow sensor to directly measure xylem sap flow in a poplar tree (Populus nigra L.), or in a dendrometer-like fashion to measure dynamic changes in the absolute water content of fruit or stems. For the latter purpose we monitored the diurnal pattern of growth, expansion and shrinkage in a model fruit (bean pod, Phaseolus vulgaris L.) and in the stem of an oak tree (Quercus robur L.). We compared changes in absolute stem water content, as measured by the NMR sensor, against stem diameter variations as measured by a set of conventional point dendrometers, to test how well the sensitivities of the two methods compare and to investigate how well diurnal changes in trunk absolute water content correlate with the concomitant diurnal variations in stem diameter. Our results confirm the existence of a strong correlation between the two parameters, but also suggest that dynamic changes in oak stem water content could be larger than is apparent on the basis of the stem diameter variation alone. PMID:25595754

  10. 87Sr solid-state NMR as a structurally sensitive tool for the investigation of materials: antiosteoporotic pharmaceuticals and bioactive glasses.

    Science.gov (United States)

    Bonhomme, Christian; Gervais, Christel; Folliet, Nicolas; Pourpoint, Frédérique; Diogo, Cristina Coelho; Lao, Jonathan; Jallot, Edouard; Lacroix, Joséphine; Nedelec, Jean-Marie; Iuga, Dinu; Hanna, John V; Smith, Mark E; Xiang, Ye; Du, Jincheng; Laurencin, Danielle

    2012-08-01

    Strontium is an element of fundamental importance in biomedical science. Indeed, it has been demonstrated that Sr(2+) ions can promote bone growth and inhibit bone resorption. Thus, the oral administration of Sr-containing medications has been used clinically to prevent osteoporosis, and Sr-containing biomaterials have been developed for implant and tissue engineering applications. The bioavailability of strontium metal cations in the body and their kinetics of release from materials will depend on their local environment. It is thus crucial to be able to characterize, in detail, strontium environments in disordered phases such as bioactive glasses, to understand their structure and rationalize their properties. In this paper, we demonstrate that (87)Sr NMR spectroscopy can serve as a valuable tool of investigation. First, the implementation of high-sensitivity (87)Sr solid-state NMR experiments is presented using (87)Sr-labeled strontium malonate (with DFS (double field sweep), QCPMG (quadrupolar Carr-Purcell-Meiboom-Gill), and WURST (wideband, uniform rate, and smooth truncation) excitation). Then, it is shown that GIPAW DFT (gauge including projector augmented wave density functional theory) calculations can accurately compute (87)Sr NMR parameters. Last and most importantly, (87)Sr NMR is used for the study of a (Ca,Sr)-silicate bioactive glass of limited Sr content (only ~9 wt %). The spectrum is interpreted using structural models of the glass, which are generated through molecular dynamics (MD) simulations and relaxed by DFT, before performing GIPAW calculations of (87)Sr NMR parameters. Finally, changes in the (87)Sr NMR spectrum after immersion of the glass in simulated body fluid (SBF) are reported and discussed. PMID:22738329

  11. Improved reliability, accuracy and quality in automated NMR structure calculation with ARIA

    Energy Technology Data Exchange (ETDEWEB)

    Mareuil, Fabien [Institut Pasteur, Cellule d' Informatique pour la Biologie (France); Malliavin, Thérèse E.; Nilges, Michael; Bardiaux, Benjamin, E-mail: bardiaux@pasteur.fr [Institut Pasteur, Unité de Bioinformatique Structurale, CNRS UMR 3528 (France)

    2015-08-15

    In biological NMR, assignment of NOE cross-peaks and calculation of atomic conformations are critical steps in the determination of reliable high-resolution structures. ARIA is an automated approach that performs NOE assignment and structure calculation in a concomitant manner in an iterative procedure. The log-harmonic shape for distance restraint potential and the Bayesian weighting of distance restraints, recently introduced in ARIA, were shown to significantly improve the quality and the accuracy of determined structures. In this paper, we propose two modifications of the ARIA protocol: (1) the softening of the force field together with adapted hydrogen radii, which is meaningful in the context of the log-harmonic potential with Bayesian weighting, (2) a procedure that automatically adjusts the violation tolerance used in the selection of active restraints, based on the fitting of the structure to the input data sets. The new ARIA protocols were fine-tuned on a set of eight protein targets from the CASD–NMR initiative. As a result, the convergence problems previously observed for some targets was resolved and the obtained structures exhibited better quality. In addition, the new ARIA protocols were applied for the structure calculation of ten new CASD–NMR targets in a blind fashion, i.e. without knowing the actual solution. Even though optimisation of parameters and pre-filtering of unrefined NOE peak lists were necessary for half of the targets, ARIA consistently and reliably determined very precise and highly accurate structures for all cases. In the context of integrative structural biology, an increasing number of experimental methods are used that produce distance data for the determination of 3D structures of macromolecules, stressing the importance of methods that successfully make use of ambiguous and noisy distance data.

  12. Optimization of CPMG sequences to measure NMR transverse relaxation time T2 in borehole applications

    Directory of Open Access Journals (Sweden)

    M. Ronczka

    2012-11-01

    Full Text Available Nuclear Magnetic Resonance (NMR can provide key information such as porosity and permeability for hydrological characterization of geological material. In particular the NMR transverse relaxation time T2 is used to estimate permeability since it reflects a pore-size dependent relaxation process. The measurement sequence (CPMG usually consists of several thousands of electromagnetic pulses to densely record the relaxation process and to avoid relaxation processes that are due to diffusion. These pulses are equidistantly spaced by a time constant tE. In NMR borehole applications the use of CPMG sequences for measuring the transverse relaxation time T2 is limited due to requirements on energy consumption. For measuring T2, it is state-of-the-art to conduct at least two sequences with different echo spacings (tE for recording fast and slow relaxing processes that correspond to different pore-sizes. We focus on conducting only a single CPMG sequence and reducing the amount of energy while obtaining both slow and fast decaying components and minimizing the influence of relaxation due to diffusion. Therefore, we tested the usage of CPMG sequences with an increasing tE and a decreasing number of pulses. A synthetic study as well as laboratory measurements on samples of glass beads and granulate material of different grain size spectra were conducted to evaluate the effects of an increasing tE. We show that T2 distributions are broadened if the number of pulses is decreasing and the mean grain size is increasing, which is mostly an effect of a significantly shortened acquisition time. The shift of T2 distributions to small decay times as a function of tE and the mean grain size distribution is observed. We found that it is possible to conduct CPMG sequences with an increased tE. According to the acquisition time and increasing influence of relaxation due to diffusion, the sequence parameters need to be chosen carefully to avoid misinterpretations.

  13. The Influence of Plant Litter on Soil Water Repellency: Insight from 13C NMR Spectroscopy.

    Directory of Open Access Journals (Sweden)

    Gaspare Cesarano

    Full Text Available Soil water repellency (SWR, i.e. reduced affinity for water owing to the presence of organic hydrophobic coatings on soil particles has relevant hydrological implications because low rates of infiltration enhance water runoff, and untargeted diffusion of fertilizers and pesticides. Previous studies investigated the occurrence of SWR in ecosystems with different vegetation cover but did not clarify its relationships with litter biochemical quality. Here, we investigated the capability of different plant litter types to induce SWR by using fresh and decomposed leaf materials from 12 species, to amend a model sandy soil over a year-long microcosm experiment. Water repellency, measured by the Molarity of an Ethanol Droplet (MED test, was tested for the effects of litter species and age, and compared with litter quality assessed by 13C-CPMAS NMR in solid state and elemental chemical parameters. All litter types were highly water repellent, with MED values of 18% or higher. In contrast, when litter was incorporated into the soil, only undecomposed materials induced SWR, but with a large variability of onset and peak dynamics among litter types. Surprisingly, SWR induced by litter addition was unrelated to the aliphatic fraction of litter. In contrast, lignin-poor but labile C-rich litter, as defined by O-alkyl C and N-alkyl and methoxyl C of 13C-CPMAS NMR spectral regions, respectively, induced a stronger SWR. This study suggests that biochemical quality of plant litter is a major controlling factor of SWR and, by defining litter quality with 13C-CPMAS NMR, our results provide a significant novel contribution towards a full understanding of the relationships between plant litter biochemistry and SWR.

  14. 13C and 31P NMR [Nuclear Magnetic Resonance] studies of prostate tumor metabolism

    International Nuclear Information System (INIS)

    The current research on prostate cancer by NMR spectroscopy and microscopy will most significantly contribute to tumor diagnosis and characterization only if sound biochemical models of tumor metabolism are established and tested. Prior searches focused on universal markers of malignancy, have to date, revealed no universal markers by any method. It is unlikely that NMRS will succeed where other methods have failed, however, NMR spectroscopy does provide a non-invasive means to analyze multiple compounds simultaneously in vivo. In order to fully evaluate the ability of NMRS to differentiate non-malignant from malignant tissues it is necessary to determine sufficient multiple parameters from specific, well-diagnosed, histological tumor types that, in comparison to normal tissue and non-neoplastic, non-normal pathologies from which the given neoplasm must be differentiated, one has enough degrees of freedom to make a mathematically and statistically significant determination. Confounding factors may consist of tumor heterogeneity arising from regional variations in differentiation, ischemia, necrosis, hemorrhage, inflammation and the presence of intermingled normal tissue. One related aspect of our work is the development of {13C}-1H metabolic imaging of 13C for metabolic characterization, with enhanced spatial localization (46). This should markedly extend the range of potential clinical NMR uses because the spatial variation in prostate metabolism may prove to be just as important in tumor diagnoses as bulk (volume-averaged) properties themselves. It is our hope that NMRS and spectroscopic imaging will reveal a sound correlation between prostate metabolism and tumor properties that will be clinically straightforward and useful for diagnosis

  15. NMR-Metabolic Methodology in the Study of GM Foods

    Directory of Open Access Journals (Sweden)

    Irene D’Amico

    2010-01-01

    Full Text Available The 1H-NMR methodology used in the study of genetically modified (GM foods is discussed. Transgenic lettuce (Lactuca sativa cv "Luxor" over-expressing the Arabidopsis KNAT1 gene is presented as a case study. Twenty-two water-soluble metabolites (amino acids, organic acids, sugars present in leaves of conventional and GM lettuce were monitored by NMR and quantified at two developmental stages. The NMR spectra did not reveal any difference in metabolite composition between the GM lettuce and the wild type counterpart. Statistical analyses of metabolite variables highlighted metabolism variation as a function of leaf development as well as the transgene. A main effect of the transgene was in altering sugar metabolism.

  16. In-Cell Protein Structures from 2D NMR Experiments.

    Science.gov (United States)

    Müntener, Thomas; Häussinger, Daniel; Selenko, Philipp; Theillet, Francois-Xavier

    2016-07-21

    In-cell NMR spectroscopy provides atomic resolution insights into the structural properties of proteins in cells, but it is rarely used to solve entire protein structures de novo. Here, we introduce a paramagnetic lanthanide-tag to simultaneously measure protein pseudocontact shifts (PCSs) and residual dipolar couplings (RDCs) to be used as input for structure calculation routines within the Rosetta program. We employ this approach to determine the structure of the protein G B1 domain (GB1) in intact Xenopus laevis oocytes from a single set of 2D in-cell NMR experiments. Specifically, we derive well-defined GB1 ensembles from low concentration in-cell NMR samples (∼50 μM) measured at moderate magnetic field strengths (600 MHz), thus offering an easily accessible alternative for determining intracellular protein structures. PMID:27379949

  17. Deuterium NMR Studies of the Structure and Dynamics of Gramicidin.

    Science.gov (United States)

    Hing, Andrew William

    1990-01-01

    The structure and dynamics of the membrane peptide gramicidin are investigated by deuterium NMR. A specific structural and dynamical question about the peptide backbone of gramicidin is investigated by deuterating the alpha carbon of the third alanine residue. Deuterium NMR experiments performed on this analog in oriented lipid bilayers indicate that the c_alpha- ^2H bond makes an angle relative to the helical axis that is in agreement with the bond angle predicted by the beta^{6.3} helical model. A second structural and dynamical question about the peptide backbone of gramicidin is investigated by deuterating the formyl group of two different analogs. Deuterium NMR experiments performed on these analogs show that the spectra of the two analogs are very similar. However, the analog possessing D-leucine as the second residue also appears to exist in a second, minor conformation which does not seem to exist for the analog possessing glycine as the second residue.

  18. Multidimensional NMR Inversion without Kronecker Products: Multilinear Inversion

    CERN Document Server

    Medellín, David; Torres-Verdín, Carlos

    2016-01-01

    Multidimensional NMR inversion using Kronecker products poses several challenges. First, kernel compression is only possible when the kernel matrices are separable, and in recent years, there has been an increasing interest in NMR sequences with non-separable kernels. Second, in three or more dimensions, the singular value decomposition is not unique; therefore kernel compression is not well-defined for higher dimensions. Without kernel compression, the Kronecker product yields matrices that require large amounts of memory, making the inversion intractable for personal computers. Finally, incorporating arbitrary regularization terms is not possible using the Lawson-Hanson (LH) or the Butler-Reeds-Dawson (BRD) algorithms. We develop a minimization-based inversion method that circumvents the above problems by using multilinear forms to perform multidimensional NMR inversion without using kernel compression or Kronecker products. The new method is memory efficient, requiring less than 0.1% of the memory required...

  19. Computer systems for laboratory networks and high-performance NMR.

    Science.gov (United States)

    Levy, G C; Begemann, J H

    1985-08-01

    Modern computer technology is significantly enhancing the associated tasks of spectroscopic data acquisition and data reduction and analysis. Distributed data processing techniques, particularly laboratory computer networking, are rapidly changing the scientist's ability to optimize results from complex experiments. Optimization of nuclear magnetic resonance spectroscopy (NMR) and magnetic resonance imaging (MRI) experimental results requires use of powerful, large-memory (virtual memory preferred) computers with integrated (and supported) high-speed links to magnetic resonance instrumentation. Laboratory architectures with larger computers, in order to extend data reduction capabilities, have facilitated the transition to NMR laboratory computer networking. Examples of a polymer microstructure analysis and in vivo 31P metabolic analysis are given. This paper also discusses laboratory data processing trends anticipated over the next 5-10 years. Full networking of NMR laboratories is just now becoming a reality. PMID:3840171

  20. NMR structure improvement: A structural bioinformatics & visualization approach

    Science.gov (United States)

    Block, Jeremy N.

    The overall goal of this project is to enhance the physical accuracy of individual models in macromolecular NMR (Nuclear Magnetic Resonance) structures and the realism of variation within NMR ensembles of models, while improving agreement with the experimental data. A secondary overall goal is to combine synergistically the best aspects of NMR and crystallographic methodologies to better illuminate the underlying joint molecular reality. This is accomplished by using the powerful method of all-atom contact analysis (describing detailed sterics between atoms, including hydrogens); new graphical representations and interactive tools in 3D and virtual reality; and structural bioinformatics approaches to the expanded and enhanced data now available. The resulting better descriptions of macromolecular structure and its dynamic variation enhances the effectiveness of the many biomedical applications that depend on detailed molecular structure, such as mutational analysis, homology modeling, molecular simulations, protein design, and drug design.

  1. Application of Multi-Exponential Inversion Method to NMR Measurements

    Institute of Scientific and Technical Information of China (English)

    XiaoLizhi; WangZhongdong; LiuTangyan

    2004-01-01

    A new multi-exponential inversion method for NMR relaxation signals is presented and tested, which is based on a solid iteration rebuild technique (SIRT). The T2 spectra inversed by the new method are compared with MAP-Ⅱ results. The T1 and T2 inversion results with different pre-assigned relaxation times and different SNR show that 16 to 64 logarithm equal spaced time constants is better obviously than MAP-Ⅱ. And in particular, it can ensure the relaxation time distribution when the SNR of the measured signal is very low. The new algorithm has been applied in rock core NMR analysis and NMR logging data process and interpretation.

  2. Suppression of radiation damping for high precision quantitative NMR

    Science.gov (United States)

    Bayle, Kevin; Julien, Maxime; Remaud, Gérald S.; Akoka, Serge

    2015-10-01

    True quantitative analysis of concentrated samples by 1H NMR is made very difficult by Radiation Damping. A novel NMR sequence (inspired by the WET NMR sequence and by Outer Volume Saturation methods) is therefore proposed to suppress this phenomenon by reducing the spatial area and consequently the number of spins contributing to the signal detected. The size of the detected volume can be easily chosen in a large range and line shape distortions are avoided thanks to a uniform signal suppression of the outer volume. Composition of a mixture can as a result be determined with very high accuracy (precision and trueness) at the per mille level whatever the concentrations and without hardware modification.

  3. Toroid cavity/coil NMR multi-detector

    Science.gov (United States)

    Gerald, II, Rex E.; Meadows, Alexander D.; Gregar, Joseph S.; Rathke, Jerome W.

    2007-09-18

    An analytical device for rapid, non-invasive nuclear magnetic resonance (NMR) spectroscopy of multiple samples using a single spectrometer is provided. A modified toroid cavity/coil detector (TCD), and methods for conducting the simultaneous acquisition of NMR data for multiple samples including a protocol for testing NMR multi-detectors are provided. One embodiment includes a plurality of LC resonant circuits including spatially separated toroid coil inductors, each toroid coil inductor enveloping its corresponding sample volume, and tuned to resonate at a predefined frequency using a variable capacitor. The toroid coil is formed into a loop, where both ends of the toroid coil are brought into coincidence. Another embodiment includes multiple micro Helmholtz coils arranged on a circular perimeter concentric with a central conductor of the toroid cavity.

  4. Solid-state NMR on defects in lead titanates

    International Nuclear Information System (INIS)

    Failure of ferroelectrics is not well understood. In our approach, we employ various solid-state NMR techniques to characterize and quantify chemical structures that arise from crystallographic defects. Especially, the existence and distributions of 1H as water or other species is a primary goal in our research. 1H spectra are known to be often of low resolution due to the strong homonuclear dipolar coupling. With sophisticated NMR techniques, e. g. echo methods and multiple quantum transitions, we want to get more insight into the defect structures. This enables both improvement in spectral resolution as well as to obtain information about the dynamics of present chemical structures such as water. Additionally, all nuclei present in lead titanates are accessible by NMR with different degree of sensitivity. Especially, with self-built equipment we are able to increase the abundance of the 17O nuclei and therefore allow for detection

  5. Mobile sensor for high resolution NMR spectroscopy and imaging

    Science.gov (United States)

    Danieli, Ernesto; Mauler, Jörg; Perlo, Juan; Blümich, Bernhard; Casanova, Federico

    2009-05-01

    In this work we describe the construction of a mobile NMR tomograph with a highly homogeneous magnetic field. Fast MRI techniques as well as NMR spectroscopy measurements were carried out. The magnet is based on a Halbach array built from identical permanent magnet blocks generating a magnetic field of 0.22 T. To shim the field inhomogeneities inherent to magnet arrays constructed from these materials, a shim strategy based on the use of movable magnet blocks is employed. With this approach a reduction of the line-width from ˜20 kHz to less than 0.1 kHz was achieved, that is by more than two orders of magnitude, in a volume of 21 cm 3. Implementing a RARE sequence, 3D images of different objects placed in this volume were obtained in short experimental times. Moreover, by reducing the sample size to 1 cm 3, sub ppm resolution is obtained in 1H NMR spectra.

  6. MetAssimulo:Simulation of Realistic NMR Metabolic Profiles

    Directory of Open Access Journals (Sweden)

    De Iorio Maria

    2010-10-01

    Full Text Available Abstract Background Probing the complex fusion of genetic and environmental interactions, metabolic profiling (or metabolomics/metabonomics, the study of small molecules involved in metabolic reactions, is a rapidly expanding 'omics' field. A major technique for capturing metabolite data is 1H-NMR spectroscopy and this yields highly complex profiles that require sophisticated statistical analysis methods. However, experimental data is difficult to control and expensive to obtain. Thus data simulation is a productive route to aid algorithm development. Results MetAssimulo is a MATLAB-based package that has been developed to simulate 1H-NMR spectra of complex mixtures such as metabolic profiles. Drawing data from a metabolite standard spectral database in conjunction with concentration information input by the user or constructed automatically from the Human Metabolome Database, MetAssimulo is able to create realistic metabolic profiles containing large numbers of metabolites with a range of user-defined properties. Current features include the simulation of two groups ('case' and 'control' specified by means and standard deviations of concentrations for each metabolite. The software enables addition of spectral noise with a realistic autocorrelation structure at user controllable levels. A crucial feature of the algorithm is its ability to simulate both intra- and inter-metabolite correlations, the analysis of which is fundamental to many techniques in the field. Further, MetAssimulo is able to simulate shifts in NMR peak positions that result from matrix effects such as pH differences which are often observed in metabolic NMR spectra and pose serious challenges for statistical algorithms. Conclusions No other software is currently able to simulate NMR metabolic profiles with such complexity and flexibility. This paper describes the algorithm behind MetAssimulo and demonstrates how it can be used to simulate realistic NMR metabolic profiles with

  7. NMR of geophysical drill cores with a mobile Halbach scanner

    International Nuclear Information System (INIS)

    This thesis is devoted to a mobile NMR with an improved Halbach scanner. This is a lightweight tube-shaped magnet with sensitive volume larger and a homogeneity of the magnetic field higher than the previous prototype version. The improved Halbach scanner is used for analysis of water-saturated drill cores and plugs with diameters up to 60 mm. To provide the analysis, the standard 1D technique with the CPMG sequence as well as 2D correlation experiments were successfully applied and adapted to study properties of fluid-saturated sediments. Afterwards the Halbach scanner was calibrated to fast non-destructive measurements of porosity, relaxation time distributions, and estimation of permeability. These properties can be calculated directly from the NMR data using the developed methodology. Any independent measurements of these properties with other methods are not needed. One of the main results of this work is the development of a new NMR on-line core scanner for measurements of porosity in long cylindrical and semi cylindrical drill cores. Also dedicated software was written to operate the NMR on-line core scanner. The physical background of this work is the study of the diffusion influence on transverse relaxation. The diffusion effect in the presence of internal gradients in porous media was probed by 1D and 2D experiments. The transverse relaxation time distributions obtained from 1D and from 2D experiments are comparable but different in fine details. Two new methodologies were developed based on the results of this study. First is the methodology quantifying the influence of diffusion in the internal gradients of water-saturated sediments on transverse relaxation from 2D correlation experiments. The second one is the correction of the permeability estimation from the NMR data taking in account the influence of the diffusion. Furthermore, PFG NMR technique was used to study restricted diffusion in the same kind of samples. Preliminary results are reported

  8. NMR of geophysical drill cores with a mobile Halbach scanner

    Energy Technology Data Exchange (ETDEWEB)

    Talnishnikh, E.

    2007-08-21

    This thesis is devoted to a mobile NMR with an improved Halbach scanner. This is a lightweight tube-shaped magnet with sensitive volume larger and a homogeneity of the magnetic field higher than the previous prototype version. The improved Halbach scanner is used for analysis of water-saturated drill cores and plugs with diameters up to 60 mm. To provide the analysis, the standard 1D technique with the CPMG sequence as well as 2D correlation experiments were successfully applied and adapted to study properties of fluid-saturated sediments. Afterwards the Halbach scanner was calibrated to fast non-destructive measurements of porosity, relaxation time distributions, and estimation of permeability. These properties can be calculated directly from the NMR data using the developed methodology. Any independent measurements of these properties with other methods are not needed. One of the main results of this work is the development of a new NMR on-line core scanner for measurements of porosity in long cylindrical and semi cylindrical drill cores. Also dedicated software was written to operate the NMR on-line core scanner. The physical background of this work is the study of the diffusion influence on transverse relaxation. The diffusion effect in the presence of internal gradients in porous media was probed by 1D and 2D experiments. The transverse relaxation time distributions obtained from 1D and from 2D experiments are comparable but different in fine details. Two new methodologies were developed based on the results of this study. First is the methodology quantifying the influence of diffusion in the internal gradients of water-saturated sediments on transverse relaxation from 2D correlation experiments. The second one is the correction of the permeability estimation from the NMR data taking in account the influence of the diffusion. Furthermore, PFG NMR technique was used to study restricted diffusion in the same kind of samples. Preliminary results are reported

  9. Structural properties of carbon nanotubes derived from 13C NMR

    KAUST Repository

    Abou-Hamad, E.

    2011-10-10

    We present a detailed experimental and theoretical study on how structural properties of carbon nanotubes can be derived from 13C NMR investigations. Magic angle spinning solid state NMR experiments have been performed on single- and multiwalled carbon nanotubes with diameters in the range from 0.7 to 100 nm and with number of walls from 1 to 90. We provide models on how diameter and the number of nanotube walls influence NMR linewidth and line position. Both models are supported by theoretical calculations. Increasing the diameter D, from the smallest investigated nanotube, which in our study corresponds to the inner nanotube of a double-walled tube to the largest studied diameter, corresponding to large multiwalled nanotubes, leads to a 23.5 ppm diamagnetic shift of the isotropic NMR line position δ. We show that the isotropic line follows the relation δ = 18.3/D + 102.5 ppm, where D is the diameter of the tube and NMR line position δ is relative to tetramethylsilane. The relation asymptotically tends to approach the line position expected in graphene. A characteristic broadening of the line shape is observed with the increasing number of walls. This feature can be rationalized by an isotropic shift distribution originating from different diamagnetic shielding of the encapsulated nanotubes together with a heterogeneity of the samples. Based on our results, NMR is shown to be a nondestructive spectroscopic method that can be used as a complementary method to, for example, transmission electron microscopy to obtain structural information for carbon nanotubes, especially bulk samples.

  10. NMR imaging of fluid dynamics in reservoir core.

    Science.gov (United States)

    Baldwin, B A; Yamanashi, W S

    1988-01-01

    A medical NMR imaging instrument has been modified to image water and oil in reservoir rocks by the construction of a new receiving coil. Both oil and water inside the core produced readily detectable proton NMR signals, while the rock matrix produced no signal. Because of similar T2 NMR relaxation times, the water was doped with a paramagnetic ion, Mn+2, to reduce its T2 relaxation time. This procedure enhanced the separation between the oil and water phases in the resulting images. Sequential measurements, as water imbibed into one end and oil was expelled from the other end of a core plug, produced a series of images which showed the dynamics of the fluids. For water-wet Berea Sandstone a flood front was readily observed, but some of the oil was apparently left behind in small, isolated pockets which were larger than individual pores. After several additional pore volumes of water flowed through the plug the NMR image indicated a homogeneous distribution of oil. The amount of residual oil, as determined from the ratio of NMR intensities, closely approximated the residual oil saturation of fully flooded Berea samples measured by Dean-Stark extraction. A Berea sandstone core treated to make it partially oil-wet, did not show a definitive flood front, but appeared to channel the water around the perimeter of the core plug. The relative ease with which these images were made indicates that NMR imaging can be a useful technique to follow the dynamics of oil and water through a core plug for a variety of production processes.

  11. A survey on quantitative analysis of organic compounds by nuclear magnetic resonance (NMR) spectroscopy

    International Nuclear Information System (INIS)

    Nuclear Magnetic Resonance (NMR) spectroscopy is known as a powerful analytical technique, which is used to determine the structure of small and macro organic compounds. In recent years, 1H NMR is being recognized more and more as a quantitative analytical method, which is based on the principle where the area under a 1H NMR signal peak in solution state is proportional to the number of nuclei contributing to the peak. In this report, the basic concepts, developmental history and current state of the quantitative 1H NMR (qNMR) method are described. Furthermore, future prospect of the qNMR method is presented. (author)

  12. Booster parameter list

    Energy Technology Data Exchange (ETDEWEB)

    Parsa, Z.

    1986-10-01

    The AGS Booster is designed to be an intermediate synchrotron injector for the AGS, capable of accelerating protons from 200 MeV to 1.5 GeV. The parameters listed include beam and operational parameters and lattice parameters, as well as parameters pertaining to the accelerator's magnets, vacuum system, radio frequency acceleration system, and the tunnel. 60 refs., 41 figs. (LEW)

  13. NMR Based Diffusion Pore Imaging by Double Wave Vector Measurements

    CERN Document Server

    Kuder, Tristan Anselm

    2012-01-01

    In porous material research, one main interest of nuclear magnetic resonance (NMR) diffusion experiments is the determination of the exact shape of pores. It has been a longstanding ques-tion if this is achievable in principle. In this work, we present a method using short diffusion gradient pulses only, which is able to reveal the shape of arbitrary closed pores without rely-ing on a priori knowledge. In comparison to former approaches, the method has reduced de-mands on relaxation times and allows for a more flexible NMR sequence design, since, for example, stimulated echoes can be used.

  14. NMR investigation of intermetallic compound FeΛ2Sc

    International Nuclear Information System (INIS)

    Structure, macro- and microscopic magnetic properties of Fe12Sc intermetallides are studied. The structure of compounds has been determined roentgenographically using FeKsub(α) irradiation. NMR measurements have been carried out at 4.2 77 and 293 K and structure measurements - at 293 K. Fe2Sc samples magnetation, measured with the help of vibrational manometer in the 9 kOe field and in the temperature range from 293-1000 K, is equal to approximately 400 Gs (measurement accuracy approximately 3%). Curie temperature for Fe2Sc is determined according to the point of magnetization curve decay bend at high temperatures. Analysis of NMR spectra is carried out

  15. Applications of NMR in the characterization of pharmaceutical microemulsions.

    Science.gov (United States)

    Hathout, Rania M; Woodman, Timothy J

    2012-07-10

    Microemulsions have successfully proven themselves as useful vehicles for drugs through the different routes of administration because they can confer on drugs greater water solubility and bioavailability. The ability to understand the structural aspects of these important drug delivery systems is essential to the progress of this science. The use of NMR techniques in pharmaceutical and drug delivery science is increasing especially in the characterization field. This review demonstrates the major and novel NMR methods and techniques used in understanding and characterizing the different microemulsion components, types and structures. PMID:22579644

  16. Localized double-quantum-filtered 1H NMR spectroscopy

    Science.gov (United States)

    Thomas, M. A.; Hetherington, H. P.; Meyerhoff, D. J.; Twieg, D. B.

    The image-guided in vivo spectroscopic (ISIS) pulse sequence has been combined with a double-quantum-filter scheme in order to obtain localized and water-suppressed 1H NMR spectra of J-coupled metabolites. The coherence-transfer efficiency associated with the DQ filter for AX and A 3X spin systems is described. Phantom results of carnosine, alanine, and ethanol in aqueous solution are presented. For comparison, the 1H NMR spectrum of alanine in aqueous solution with the binomial (1331, 2662) spin-echo sequence is also shown.

  17. NMR Meets Tau: Insights into Its Function and Pathology.

    Science.gov (United States)

    Lippens, Guy; Landrieu, Isabelle; Smet, Caroline; Huvent, Isabelle; Gandhi, Neha S; Gigant, Benoît; Despres, Clément; Qi, Haoling; Lopez, Juan

    2016-01-01

    In this review, we focus on what we have learned from Nuclear Magnetic Resonance (NMR) studies on the neuronal microtubule-associated protein Tau. We consider both the mechanistic details of Tau: the tubulin relationship and its aggregation process. Phosphorylation of Tau is intimately linked to both aspects. NMR spectroscopy has depicted accurate phosphorylation patterns by different kinases, and its non-destructive character has allowed functional assays with the same samples. Finally, we will discuss other post-translational modifications of Tau and its interaction with other cellular factors in relationship to its (dys)function. PMID:27338491

  18. ISOLATION AND NMR SPECTRAL ASSIGNMENTS OF STEVIOLBIOSIDE AND STEVIOSIDE

    Directory of Open Access Journals (Sweden)

    Venkata Sai Prakash Chaturvedula

    2011-04-01

    Full Text Available The complete 1H and 13C NMR assignments of the two diterpene glycosides, 13-[(2-O--D-glucopyranosyl--D-glucopyranosyloxy]-ent-kaur-16-en-19-oic acid (steviolbioside and 3-[(2-O--D-glucopyranosyl--D-glucopyranosyloxy]-ent-kaur-16-en-19-oic acid β-D-glucopyranosyl ester (stevioside isolated from Stevia rebaudiana were achieved on the basis of extensive NMR (1H and 13C, COSY, HMQC, HMBC and MS spectral data. The structures of steviolbioside and stevioside were further supported by acid and enzymatic hydrolysis studies by identifying their corresponding aglycone and sugar residues.

  19. Handbook of proton-NMR spectra and data index

    CERN Document Server

    Asahi Research Center Co, Ltd

    2013-01-01

    Handbook of Proton-NMR Spectra and Data: Index to Volumes 1-10 compiles four types of indexes used in charting the proton-NMR spectral database -Chemical Name Index, Molecular Formula Index, Substructure Index, and Chemical Shift Index. The Chemical Name Index compiles all chemical names in alphabetical order, followed by a spectrum number. When the desired organic compound cannot be found in the Chemical Name Index or its nomenclature is unclear, it becomes necessary to look for a compound by means of its molecular formula, hence the Molecular Formula Index. A unique notation system for repre

  20. Mapping protein conformational energy landscapes using NMR and molecular simulation

    International Nuclear Information System (INIS)

    Nuclear magnetic resonance (NMR) spectroscopy provides detailed understanding of the nature and extent of protein dynamics on physiologically important timescales. We present recent advances in the combination of NMR with state-of-the art molecular simulation that are providing unique new insight into the motions on timescales from nanoseconds to milliseconds. In particular, we focus on methods based on residual dipolar couplings (RDCs) that allow for detailed mapping of the protein conformational energy landscape. A novel combination of RDCs with accelerated molecular dynamics allows for the development of ensemble representations of the underlying Boltzmann ensemble. (authors)