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Sample records for 2h nmr spectroscopy

  1. Natural abundance high-resolution solid state 2 H NMR spectroscopy

    NASA Astrophysics Data System (ADS)

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

    1994-08-01

    We report for the first time an approach for natural abundance solid state 2 H NMR spectroscopy involving magic angle sample spinning (MAS), high-power 1 H decoupling (HPPD) and 1 H- 2 H cross polarization (CP). Taking tetrakis(trimethylsilyl)silane (TTMSS), adamantane, 1-chloroadamantane, hexamethylbenzene (HMB), 2,2-dimethyl-1,3-propanediol (DMPD) and 2-hydroxymethyl-2-methyl-1,3-propanediol (HMPD) as examples, it has been shown that the combination of HPPD and MAS can be applied readily to study rotator phase solids, allowing isotropic peaks arising from chemically inequivalent 2 H nuclei to be resolved. For natural abundance samples of TTMSS and chloroadamantane, it has been shown that 2 H CP/HPPD/MAS NMR experiments, involving polarization transfer from 1 H to 2 H, may provide considerable sensitivity enhancement in comparison with single pulse experiments.

  2. Natural abundance high-resolution solid state 2 H NMR spectroscopy

    NASA Astrophysics Data System (ADS)

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

    1994-08-01

    We report for the first time an approach for natural abundance solid state 2H NMR spectroscopy involving magic angle sample spinning (MAS), high-power 1H decoupling (HPPD) and 1H- 2H cross polarization (CP). Taking tetrakis(trimethylsilyl)silane (TTMSS), adamantane, 1-chloroadamantane, hexamethylbenzene (HMB), 2,2-dimethyl-1,3-propanediol (DMPD) and 2-hydroxymethyl-2-methyl-1,3-propanediol (HMPD) as examples, it has been shown that the combination of HPPD and MAS can be applied readily to study rotator phase solids, allowing isotropic peaks arising from chemically inequivalent 2H nuclei to be resolved. For natural abundance samples of TTMSS and chloroadamantane, it has been shown that 2H CP/HPPD/MAS NMR experiments, involving polarization transfer from 1H to 2H, may provide considerable sensitivity enhancement in comparison with single pulse experiments.

  3. 2H-DNP-enhanced 2H–13C solid-state NMR correlation spectroscopy

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    1998-11-01

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

  5. Conformations of banana-shaped molecules studied by 2H NMR spectroscopy in liquid crystalline solvents.

    PubMed

    Calucci, Lucia; Forte, Claudia; Csorba, Katalin Fodor; Mennucci, Benedetta; Pizzanelli, Silvia

    2007-01-11

    ClPbis11BB and Pbis11BB, two banana-shaped mesogens differing by a chlorine substituent on the central phenyl ring, show a nematic and a B2 phase, respectively. To obtain information on the structural features responsible for their different mesomorphic behavior, a study of the preferred conformations of these mesogens has been performed by NMR spectroscopy in two nematic media (Phase IV and ZLI1167), which should mimic the environment of the molecules in their own mesophases, avoiding problems of sample alignment by a magnetic field. To this aim, 2H NMR experiments have been performed on selectively deuterated isotopomers of ClPbis11BB and Pbis11BB and of two parent molecules, ClPbisB and PbisB, assumed as models in previous theoretical and experimental conformational studies. We found that only a limited number of conformations is compatible with experimental data, often very different from those inferred from theoretical calculations in vacuo, indicating a strong influence of the liquid crystalline environment on molecular conformation. No significant differences between chlorinated and non-chlorinated molecules were found, this suggesting that chlorine does not change the molecular conformational equilibrium, as previously proposed. PMID:17201428

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

    PubMed

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

    2012-06-20

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

  7. Orientational ordering of a banana-shaped solute molecule in a nematic calamitic solvent by {sup 2}H-NMR spectroscopy: An indication of glasslike behavior

    SciTech Connect

    Cinacchi, Giorgio; Domenici, Valentina

    2006-09-15

    The Saupe ordering matrix of a banana-shaped mesogenic molecule as a solute in a common nematic calamitic solvent has been determined by {sup 2}H-NMR spectroscopy as a function of temperature. The temperature dependence of the Saupe ordering matrix element associated with the principal molecular axis is consistent with a glassy behavior in the reorientational motion of this particular solute molecule. The Haller expression, appropriately modified, provides a good fit to the experimental data.

  8. Phase Separation in Binary Mixtures of Bipolar and Monopolar Lipid Dispersions Revealed by 2H NMR Spectroscopy, Small Angle X-Ray Scattering, and Molecular Theory

    PubMed Central

    Brownholland, David P.; Longo, Gabriel S.; Struts, Andrey V.; Justice, Matthew J.; Szleifer, Igal; Petrache, Horia I.; Brown, Michael F.; Thompson, David H.

    2009-01-01

    Abstract Binary mixtures of C20BAS and POPC membranes were studied by solid-state 2H NMR spectroscopy and small angle x-ray scattering (SAXS) over a wide range of concentrations and at different temperatures. Three specifically deuterated C20BAS derivatives—[1′,1′,20′,20′-2H4]C20BAS, [2′,2′,19′,19′-2H4]C20BAS, and [10′,11′-2H2]C20BAS—combined with protiated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), as well as membranes containing POPC-d31 and fully protiated bolalipid, were used in NMR experiments to obtain structural information for the mixtures. The 2H NMR spectra of [10′,11′-2H2]C20BAS/POPC membrane dispersions reveal that the bolalipid is predominantly in the transmembrane conformation at high bolalipid concentrations (100, 90, and 70 mol %). At ≤50 mol % C20BAS, smaller quadrupolar couplings appear in the spectra, indicating the presence of U-shaped conformers. The proportion of U-shaped bolalipids increases as the amount of POPC in the membrane increases; however, the transmembrane component remains the dominant bolalipid conformation in the membrane even at 45°C and 10 mol % C20BAS, where it accounts for ∼50% of the bolalipid population. The large fraction of C20BAS transmembrane conformers, regardless of the C20BAS/POPC ratio, together with the findings from molecular mean-field theory calculations, suggests the coexistence of phase-separated bolalipid-rich domains and POPC-rich domains. A single lamellar repeat distance was observed in SAXS experiments corresponding to the average repeat spacing expected for C20BAS- and POPC-rich domains. These observations are consistent with the presence of microphase-separated domains in the mixed membrane samples that arise from POPC-C20BAS hydrophobic mismatch. PMID:19917223

  9. Diffusion Coefficient-Formula Weight (D-FW) Analysis of (2)H Diffusion-Ordered NMR Spectroscopy (DOSY).

    PubMed

    Guang, Jie; Hopson, Russell; Williard, Paul G

    2015-09-18

    We report extension of the D-FW analysis using referenced (2)H DOSY. This technique was developed in response to limitations due to peak overlay in (1)H DOSY spectra. We find a corresponding linear relationship (R(2) > 0.99) between log D and log FW as the basis of the D-FW analysis. The solution-state structure of THF solvated lithium diisopropyl amide (LDA) in hydrocarbon solvent was chosen to demonstrate the reliability of the methodology. We observe an equilibrium between monosolvated and disolvated dimeric LDA complexes at room temperature. Additionally we demonstrate the application of the (2)H D-FW analysis using a compound with an exchangeable proton that is readily labeled with (2)H. Hence, the (2)H DOSY D-FW analysis is shown to provide results consistent with the (1)H DOSY method, thereby greatly extending the applicability of the D-FW analysis. PMID:26318438

  10. Capturing Guest Dynamics in Metal-Organic Framework CPO-27-M (M = Mg, Zn) by (2)H Solid-State NMR Spectroscopy.

    PubMed

    Xu, Jun; Sinelnikov, Regina; Huang, Yining

    2016-06-01

    Metal-organic frameworks (MOFs) are promising porous materials for gas separation and storage as well as sensing. In particular, a series of isostructural MOFs with coordinately unsaturated metal centers, namely, CPO-27-M or M-MOF-74 (M = Mg, Zn, Mn, Fe, Ni, Co, Cu), have shown exceptional adsorption capacity and selectivity compared to those of classical MOFs that contain only fully coordinated metal sites. Although it is widely accepted that the interaction between guest molecules and exposed metal centers is responsible for good selectivity and large maximum uptake, the investigation of such guest-metal interaction is very challenging because adsorbed molecules are usually disordered in the pores and undergo rapid thermal motions. (2)H solid-state NMR (SSNMR) spectroscopy is one of the most extensively used techniques for capturing guest dynamics in porous materials. In this work, variable-temperature (2)H wide-line SSNMR experiments were performed on CPO-27-M (M = Mg, Zn) loaded with four prototypical guest molecules: D2O, CD3CN, acetone-d6, and C6D6. The results indicate that different guest molecules possess distinct dynamic behaviors inside the channel of CPO-27-M. For a given guest molecule, its dynamic behavior also depends on the nature of the metal centers. The binding strength of guest molecules is discussed on the basis of the (2)H SSNMR data. PMID:27183247

  11. Formation of Al2H7- anions--indirect evidence of volatile AlH3 on sodium alanate using solid-state NMR spectroscopy.

    PubMed

    Felderhoff, Michael; Zibrowius, Bodo

    2011-10-14

    After more than a decade of intense research on NaAlH(4) doped with transition metals as hydrogen storage material, the actual mechanism of the decomposition and rehydrogenation reaction is still unclear. Early on, monomeric AlH(3) was named as a possible transport shuttle for aluminium, but never observed experimentally. Here we report for the first time the trapping of volatile AlH(3) produced during the decomposition of undoped NaAlH(4) by an adduct of sodium alanate and crown ether. The resulting Al(2)H(7)(-) anion was identified by solid-state (27)Al NMR spectroscopy. Based on this indirect evidence of volatile alane, we present a simple description of the processes occurring during the reversible dehydrogenation of NaAlH(4). PMID:21879065

  12. Short hydrogen bonds in salts of dicarboxylic acids; structural correlations from solid-state 13C and 2H NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Kalsbeek, Nicoline; Schaumburg, Kjeld; Larsen, Sine

    1993-10-01

    Solid-state 13C and 2H NMR spectra are found to very suitable for characterizing the short Osbnd H...O hydrogen bonds observed in acid salts of dicarboxylic acids. The majority of the investigated compounds are acid salts of malonic, succinic and tartaric acid with monovalent cations derived from alkali metals and small aliphatic amines. They include systems with symmetric and asymmetric hydrogen bonds. Accurate structural information about their geometry is available from low-temperature X-ray diffraction data. The 13C chemical shifts of the C atoms in the different carboxy groups display a linear variation with the absolute difference between the two Csbnd O bond lengths. Theoretical ab initio calculations for model systems showed that the nuclear quadrupole coupling constant NQCC for 2H increases with increasing asymmetry of the hydrogen-bonded system. NQCC values for 2H in the short symmetric hydrogen-bonded systems are in the range 53-59 kHz compared with the larger values of up to 166kHz found in systems with longer asymmetric hydrogen bonds. The 2H NQCC values display a perfect linear dependence on the asymmetry of the hydrogen bond. 2H NQCC decreases with decreasing temperature in the symmetric hydrogen bonds showing that the corresponding potential has a single well.

  13. 2H NMR studies of supercooled and glassy aspirin

    NASA Astrophysics Data System (ADS)

    Nath, R.; Nowaczyk, A.; Geil, B.; Bohmer, R.

    2007-11-01

    Acetyl salicylic acid, deuterated at the methyl group, was investigated using 2H-NMR in its supercooled and glassy states. Just above the glass transition temperature the molecular reorientations were studied using stimulated-echo spectroscopy and demonstrated a large degree of similarity with other glass formers. Deep in the glassy phase the NMR spectra look similar to those reported for the crystal [A. Detken, P. Focke, H. Zimmermann, U. Haeberlen, Z. Olejniczak, Z. T. Lalowicz, Z. Naturforsch. A 50 (1995) 95] and below 20 K they are indicative for rotational tunneling with a relatively large tunneling frequency. Measurements of the spin-lattice relaxation times for temperatures below 150 K reveal a broad distribution of correlation times in the glass. The dominant energy barrier characterizing the slow-down of the methyl group is significantly smaller than the well defined barrier in the crystal.

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

    PubMed

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

    2006-06-01

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

  15. Effect of Saturated Very Long-Chain Fatty Acids on the Organization of Lipid Membranes: A Study Combining (2)H NMR Spectroscopy and Molecular Dynamics Simulations.

    PubMed

    Paz Ramos, Adrian; Lagüe, Patrick; Lamoureux, Guillaume; Lafleur, Michel

    2016-07-21

    Little is known about the interaction of very long-chain saturated fatty acids (VLCFAs) with biological membranes. However, this could play an important role on interleaflet interactions and signal transduction mechanisms in cells. The aim of this work is to determine how VLCFA structurally adapts in fluid phospholipid bilayers, since both species must exhibit a significant hydrophobic mismatch. The membrane organization has been described by means of (2)H NMR and molecular dynamics simulations. Our results show that the protonation state affects the position and order of free fatty acids (FFAs) in phospholipid membranes. It was shown that the protonated FFA-C24 carboxyl group is located slightly under the POPC head group and therefore its acyl chain can interact with the lipids of the opposite leaflet. This interdigitation of the end of the acyl chain causes a second plateau observed in SC-D profiles, a very unusual feature in lipid systems. PMID:27351151

  16. Two dimensional NMR spectroscopy

    SciTech Connect

    Schram, J.; Bellama, J.M.

    1988-01-01

    Two dimensional NMR represents a significant achievement in the continuing effort to increase solution in NMR spectroscopy. This book explains the fundamentals of this new technique and its analytical applications. It presents the necessary information, in pictorial form, for reading the ''2D NMR,'' and enables the practicing chemist to solve problems and run experiments on a commercial spectrometer by using the software provided by the manufacturer.

  17. Locations of local anesthetic dibucaine in model membranes and the interaction between dibucaine and a Na+ channel inactivation gate peptide as studied by 2H- and 1H-NMR spectroscopies.

    PubMed Central

    Kuroda, Y; Ogawa, M; Nasu, H; Terashima, M; Kasahara, M; Kiyama, Y; Wakita, M; Fujiwara, Y; Fujii, N; Nakagawa, T

    1996-01-01

    To study the molecular mechanisms of local anesthesia, locations of local anesthetic dibucaine in model membranes and the interactions of dibucaine with a Na+ channel inactivation gate peptide have been studied by 2H- and 1H-NMR spectroscopies. The 2H-NMR spectra of dibucaine-d9 and dibucaine-d1, which are deuterated at the butoxy group and at the 3 position in its quinoline ring, respectively, have been observed in multilamellar dispersions of the lipid mixture composed of phosphatidylcholine, phosphatidylserine, and phosphatidylethanolamine. 2H-NMR spectra of deuterated palmitic acids incorporated, as a probe, into the lipid mixture containing cholesterol have also been observed. An order parameter, SCD, for each carbon segment was calculated from the observed quadrupole splittings. Combining these results, we concluded that first, the butoxy group of dibucaine is penetrating between the acyl chains of lipids in the model membranes, and second, the quinoline ring of dibucaine is located at the polar region of lipids but not at the hydrophobic acyl chain moiety. These results mean that dibucaine is situated in a favorable position that permits it to interact with a cluster of hydrophobic amino acids (Ile-Phe-Met) within the intracellular linker between domains III and IV of Na+ channel protein, which functions as an inactivation gate. To confirm whether the dibucaine molecule at the surface region of lipids can really interact with the hydrophobic amino acids, we synthesized a model peptide that includes the hydrophobic amino acids (Ac-GGQDIFMTEEQK-OH, MP-1), the amino acid sequence of which corresponds to the linker part of rat brain type IIA Na+ channel, and the one in which Phe has been substituted by Gln (MP-2), and measured 1H-NMR spectra in both phosphate buffer and phosphatidylserine liposomes. It was found that the quinoline ring of dibucaine can interact with the aromatic ring of Phe by stacking of the rings; moreover, the interaction can be reinforced by

  18. Enantiodiscrimination by NMR spectroscopy.

    PubMed

    Uccello-Barretta, Gloria; Balzano, Federica; Salvadori, Piero

    2006-01-01

    The analysis of enantiorecognition processes involves the detection of enantiomeric species as well as the study of chiral discrimination mechanisms. In both fields Nuclear Magnetic Resonance (NMR) spectroscopy plays a fundamental role, providing several tools, based on the use of suitable chiral auxiliaries, for observing distinct signals of enantiomers and for investigating the complexation phenomena involved in enantiodiscrimination processes. PMID:17100610

  19. Hydration of DNA by tritiated water and isotope distribution: a study by /sup 1/H, /sup 2/H, and /sup 3/H NMR spectroscopy

    SciTech Connect

    Mathur-De Vre, R.; Grimee-Declerck, R.; Lejeune, P.; Bertinchamps, A.J.

    1982-06-01

    The hydration layer of DNA (0.75%) in tritiated water represents 3.5% of solvent /sup 3/HHO. The combined effects of temperature (-6 to -40/sup 0/C) and H/sub 2/O//sup 2/H/sub 2/O solvent composition on the spin-lattice relaxation times of water protons and deuterons suggest selective distribution of isotopes in the hydration layer. The ''hydration isotope'' effect and the localization of tritiated water molecules in the hydration layer of DNA have important implications in describing the radiobiological effects of tritiated water because the initial molecular damage caused by /sup 3/HHO (internal radiation source) localizes close to /sup 3/H due to the short range and low energy of /sup 3/H ..beta.. rays.

  20. Probing perturbation of bovine lung surfactant extracts by albumin using DSC and 2H-NMR.

    PubMed

    Nag, Kaushik; Keough, Kevin M W; Morrow, Michael R

    2006-05-15

    Lung surfactant (LS), a lipid-protein mixture, forms films at the lung air-water interface and prevents alveolar collapse at end expiration. In lung disease and injury, the surface activity of LS is inhibited by leakage of serum proteins such as albumin into the alveolar hypophase. Multilamellar vesicular dispersions of a clinically used replacement, bovine lipid extract surfactant (BLES), to which (2% by weight) chain-perdeuterated dipalmitoylphosphatidycholine (DPPG mixtures-d(62)) had been added, were studied using deuterium-NMR spectroscopy ((2)H-NMR) and differential scanning calorimetry (DSC). DSC scans of BLES showed a broad gel to liquid-crystalline phase transition between 10-35 degrees C, with a temperature of maximum heat flow (T(max)) around 27 degrees C. Incorporation of the DPPC-d(62) into BLES-reconstituted vesicles did not alter the T(max) or the transition range as observed by DSC or the hydrocarbon stretching modes of the lipids observed using infrared spectroscopy. Transition enthalpy change and (2)H-NMR order parameter profiles were not significantly altered by addition of calcium and cholesterol to BLES. (2)H-NMR spectra of the DPPC-d(62) probes in these samples were characteristic of a single average lipid environment at all temperatures. This suggested either continuous ordering of the bilayer through the transition during cooling or averaging of the DPPC-d(62) environment by rapid diffusion between small domains on a short timescale relative to that characteristic of the (2)H-NMR experiment. Addition of 10% by weight of soluble bovine serum albumin (1:0.1, BLES/albumin, dry wt/wt) broadened the transition slightly and resulted in the superposition of (2)H-NMR spectral features characteristic of coexisting fluid and ordered phases. This suggests the persistence of phase-separated domains throughout the transition regime (5-35 degrees C) of BLES with albumin. The study suggests albumin can cause segregation of protein bound-lipid domains in

  1. Recent advances in the analysis of the site-specific isotopic fractionation of metabolites such as fatty acids using anisotropic natural-abundance 2H NMR spectroscopy: application to conjugated linolenic methyl esters.

    PubMed

    Lesot, Philippe; Serhan, Zeinab; Billault, Isabelle

    2011-01-01

    The full elucidation of the enzymatic mechanisms leading to polyunsaturated ω-3 to ω-5 fatty acids (PUFAs) occurring in plants or microorganisms by analyzing their site-specific isotopic fractionation profiles is a challenging task. Isotropic SNIF-NMR® method is an historical, powerful tool for the determination of ((2)H/(1)H) ratios. However, the absence of accessible isotopic data on the enantiotopic hydrogen sites (CH(2) groups) prevents the study of the enzymatic reaction stereoselectivity. Natural-abundance deuterium (NAD) 2D NMR experiment using chiral liquid crystals (CLC) as solvent is a new tool in this field, overcoming this limitation. In this work, we have explored various possibilities for optimizing the enantio-discrimination properties of CLC by changing the nature of the polypeptide and/or increasing the polarity of the organic co-solvents. We report also the first applications of TMU as co-solvent for preparing enantio-discriminating, homogenous polypeptide mesophases. The various experimental NAD NMR results recorded at an optimal sample temperature are discussed and compared in terms of number of discriminated (2)H sites and magnitude of spectral separation for different PUFAs such as the linoleic and linolenic acids. The comparison of all NMR results shows that optimal results are obtained when CLC mixtures made of poly-γ-benzyl-L-glutamate (PBLG) and high polarity co-solvents are used. As new challenging examples of applications, we report the preliminary analytical results obtained from two ω-5 conjugated linolenic acids: the α-eleostearic acid (9Z, 11E, 13E) and the punicic acid (9Z, 11E, 13Z). NMR data are discussed in terms of molecular orientational ordering parameters and isotopic distribution. PMID:21107978

  2. Two-dimensional NMR spectroscopy

    SciTech Connect

    Croasmun, W.R.; Carlson, R.M.K.

    1987-01-01

    Written for chemists and biochemists who are not NMR spectroscopists, but who wish to use the new techniques of two-dimensional NMR spectroscopy, this book brings together for the first time much of the practical and experimental data needed. It also serves as information source for industrial, academic, and graduate student researchers who already use NMR spectroscopy, but not yet in two dimensions. The authors describe the use of 2-D NMR in a wide variety of chemical and biochemical fields, among them peptides, steroids, oligo- and poly-saccharides, nucleic acids, natural products (including terpenoids, alkaloids, and coal-derived heterocyclics), and organic synthetic intermediates. They consider throughout the book both the advantages and limitations of using 2-D NMR.

  3. Natural abundance 2H-ERETIC-NMR authentication of the origin of methyl salicylate.

    PubMed

    Le Grand, Flore; George, Gerard; Akoka, Serge

    2005-06-29

    Methyl salicylate is a compound currently used in the creation of many flavors. It can be obtained by synthesis or from two natural sources: essential oil of wintergreen and essential oil of sweet birch bark. Deuterium site-specific natural isotope abundance (A(i)) determination by NMR spectroscopy with the method of reference ERETIC ((2)H-ERETIC-NMR) has been applied to this compound. A(i) measurements have been performed on 19 samples of methyl salicylate from different origins, natural/synthetic and commercial/extracted. This study demonstrates that appropriate treatment performed on the data allows discrimination between synthetic and natural samples. Moreover, the representation of intramolecular ratios R(6/5) as a function of R(3/2) distinguishes between synthetics, wintergreen oils, and sweet birch bark oils. PMID:15969485

  4. Determination of muscle protein synthesis rates in fish using (2)H2O and (2)H NMR analysis of alanine.

    PubMed

    Marques, Cátia; Viegas, Filipa; Rito, João; Jones, John; Viegas, Ivan

    2016-09-15

    Following administration of deuterated water ((2)H2O), the fractional synthetic rate (FSR) of a given endogenous protein can be estimated by (2)H-enrichment quantification of its alanine residues. Currently, this is measured by mass spectrometry following a derivatization procedure. Muscle FSR was measured by (1)H/(2)H NMR analysis of alanine from seabass kept for 6 days in 5% (2)H-enriched saltwater, following acid hydrolysis and amino acid isolation by cation-exchange chromatography of muscle tissue. The analysis is simple and robust, and provides precise measurements of excess alanine (2)H-enrichment in the 0.1-0.4% range from 50 mmol of alanine recovered from muscle protein. PMID:27418547

  5. Modern NMR Spectroscopy.

    ERIC Educational Resources Information Center

    Jelinski, Lynn W.

    1984-01-01

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

  6. Sepsis does not alter red blood cell glucose metabolism or Na+ concentration: A 2H-, 23Na-NMR study

    SciTech Connect

    Hotchkiss, R.S.; Song, S.K.; Ling, C.S.; Ackerman, J.J.; Karl, I.E. )

    1990-01-01

    The effects of sepsis on intracellular Na+ concentration ((Na+)i) and glucose metabolism were examined in rat red blood cells (RBCs) by using 23Na- and 2H-nuclear magnetic resonance (NMR) spectroscopy. Sepsis was induced in 15 halothane-anesthetized female Sprague-Dawley rats by using the cecal ligation and perforation technique; 14 control rats underwent cecal manipulation without ligation. The animals were fasted for 36 h, but allowed free access to water. At 36 h postsurgery, RBCs were examined by 23Na-NMR by using dysprosium tripolyphosphate as a chemical shift reagent. Human RBCs from 17 critically ill nonseptic patients and from 7 patients who were diagnosed as septic were also examined for (Na+)i. Five rat RBC specimens had (Na+)i determined by both 23Na-NMR and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). For glucose metabolism studies, RBCs from septic and control rats were suspended in modified Krebs-Henseleit buffer containing (6,6-2H2)glucose and examined by 2H-NMR. No significant differences in (Na+)i or glucose utilization were found in RBCs from control or septic rats. There were no differences in (Na+)i in the two groups of patients. The (Na+)i determined by NMR spectroscopy agreed closely with measurements using ICP-AES and establish that 100% of the (Na+)i of the RBC is visible by NMR. Glucose measurements determined by 2H-NMR correlated closely (correlation coefficient = 0.93) with enzymatic analysis. These studies showed no evidence that sepsis disturbed RBC membrane function or metabolism.

  7. Measurement of regional cerebral blood flow in cat brain using intracarotid 2H2O and 2H NMR imaging

    SciTech Connect

    Detre, J.A.; Subramanian, V.H.; Mitchell, M.D.; Smith, D.S.; Kobayashi, A.; Zaman, A.; Leigh, J.S. Jr. )

    1990-05-01

    Cerebral blood flow (CBF) was measured in cat brain in vivo at 2.7 T using 2H NMR to monitor the washout of deuterated saline injected into both carotid arteries via the lingual arteries. In anesthetized cats, global CBF varied directly with PaCO{sub 2} over a range of 20-50 mm Hg, and the corresponding global CBF values ranged from 25 to 125 ml.100 g-1.min-1. Regional CBF was measured in a 1-cm axial section of cat brain using intracarotid deuterated saline and gradient-echo 2H NMR imaging. Blood flow images with a maximum pixel resolution of 0.3 x 0.3 x 1.0 cm were generated from the deuterium signal washout at each pixel. Image derived values for CBF agreed well with other determinations, and decreased significantly with hypocapnia.

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

    ERIC Educational Resources Information Center

    Cavaleiro, Jose A. S.

    1987-01-01

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

  9. Solid-State 2H NMR Shows Equivalence of Dehydration and Osmotic Pressures in Lipid Membrane Deformation

    PubMed Central

    Mallikarjunaiah, K.J.; Leftin, Avigdor; Kinnun, Jacob J.; Justice, Matthew J.; Rogozea, Adriana L.; Petrache, Horia I.; Brown, Michael F.

    2011-01-01

    Lipid bilayers represent a fascinating class of biomaterials whose properties are altered by changes in pressure or temperature. Functions of cellular membranes can be affected by nonspecific lipid-protein interactions that depend on bilayer material properties. Here we address the changes in lipid bilayer structure induced by external pressure. Solid-state 2H NMR spectroscopy of phospholipid bilayers under osmotic stress allows structural fluctuations and deformation of membranes to be investigated. We highlight the results from NMR experiments utilizing pressure-based force techniques that control membrane structure and tension. Our 2H NMR results using both dehydration pressure (low water activity) and osmotic pressure (poly(ethylene glycol) as osmolyte) show that the segmental order parameters (SCD) of DMPC approach very large values of ≈0.35 in the liquid-crystalline state. The two stresses are thermodynamically equivalent, because the change in chemical potential when transferring water from the interlamellar space to the bulk water phase corresponds to the induced pressure. This theoretical equivalence is experimentally revealed by considering the solid-state 2H NMR spectrometer as a virtual osmometer. Moreover, we extend this approach to include the correspondence between osmotic pressure and hydrostatic pressure. Our results establish the magnitude of the pressures that lead to significant bilayer deformation including changes in area per lipid and volumetric bilayer thickness. We find that appreciable bilayer structural changes occur with osmotic pressures in the range of 10−100 atm or lower. This research demonstrates the applicability of solid-state 2H NMR spectroscopy together with bilayer stress techniques for investigating the mechanism of pressure sensitivity of membrane proteins. PMID:21190661

  10. Rotational spectroscopy of 2H,3H-perfluoropentane

    NASA Astrophysics Data System (ADS)

    Duong, Chinh H.; Obenchain, Daniel A.; Cooke, S. A.; Novick, Stewart E.

    2016-06-01

    The structure of 2H,3H-perfluoropentane, CF3CHFCHFCF2CF3, has been determine by a combination of Chirp-pulsed Fourier transform microwave (CP-FTMW) spectroscopy and cavity FTMW spectroscopy. Of the four possible stereoisomers, only the enantiomeric pair (R,R)/(S,S) were observed experimentally; there was no spectroscopic evidence for the enantiomeric pair (R,S)/(S,R). The conformeric structure of the (R,R)/(S,S) stereoisomer(s) was that of partial helices with C-C-C-C dihedral angles of 12° (helical) and 1° (staggered).

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

    PubMed

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

    2007-12-20

    A magic-angle spinning (MAS) 2H NMR experiment was applied to study the molecular motion in paramagnetic compounds. The temperature dependences of 2H MAS NMR spectra were measured for paramagnetic [M(H2O)6][SiF6] (M=Ni2+, Mn2+, Co2+) and diamagnetic [Zn(H2O)6][SiF6]. The paramagnetic compounds exhibited an asymmetric line shape in 2H MAS NMR spectra because of the electron-nuclear dipolar coupling. The drastic changes in the shape of spinning sideband patterns and in the line width of spinning sidebands due to the 180 degrees flip of water molecules and the reorientation of [M(H2O)6]2+ about its C3 axis were observed. In the paramagnetic compounds, paramagnetic spin-spin relaxation and anisotropic g-factor result in additional linebroadening of each of the spinning sidebands. The spectral simulation of MAS 2H NMR, including the effects of paramagnetic shift and anisotropic spin-spin relaxation due to electron-nuclear dipolar coupling and anisotropic g-factor, was performed for several molecular motions. Information about molecular motions in the dynamic range of 10(2) s(-1)2H MAS NMR spectra when these paramagnetic effects are taken into account. PMID:18027914

  12. Hyperpolarized 131Xe NMR spectroscopy

    PubMed Central

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

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

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

    PubMed

    Lindh, E L; Stilbs, P; Furó, I

    2016-07-01

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

  15. Alcohol binding to liposomes by 2H NMR and radiolabel binding assays: does partitioning describe binding?

    PubMed Central

    Dubey, A K; Eryomin, V A; Taraschi, T F; Janes, N

    1996-01-01

    Implicit within the concept of membrane-buffer partition coefficients of solutes is a nonspecific solvation mechanism of solute binding. However, (2)H NMR studies of the binding of (2)H(6)-ethanol and [1-(2)H(2)] n-hexanol to phosphatidylcholine vesicles have been interpreted as evidence for two distinct alcohol binding modes. One binding mode was reported to be at the membrane surface. The second mode was reported to be within the bilayer interior. An examination of the (2)H NMR binding studies, together with direct radiolabel binding assays, shows that other interpretations of the data are more plausible. The results are entirely consistent with partitioning (nonspecific binding) as the sole mode of alcohol binding to liposomes, in accord with our previous thermodynamic interpretation of alcohol action in phosphatidylcholine liposomes. PMID:9172754

  16. 2H transmit-receive NMR probes for magnetic field monitoring in MRI.

    PubMed

    Sipilä, Pekka; Greding, Sebastian; Wachutka, Gerhard; Wiesinger, Florian

    2011-05-01

    Measuring image encoding fields in real time and applying the information in postprocessing offer improved image quality for MRI, particularly for applications that are intrinsically sensitive to gradient imperfections. For this task, a stand-alone magnetometer system based on multiple (2)H transmit-receive NMR probes has been developed. The conceptual advantages of changing to (2)H NMR probes for (1)H magnetic field monitoring are elucidated here, and the practical design of the probes is described. In comparison to previous (1)H NMR probe-based designs, (2)H probes are perfectly decoupled from standard (1)H imaging. Utilization of RF shielding or other nonoptimal decoupling schemes is therefore not needed. Probes based on (2)H nuclei are also more easily miniaturized for high-resolution imaging. This is particularly important for diffusion tensor and phase-contrast imaging, which rely on strong motion-sensitizing gradients. The presented (2)H NMR probes have been shown to fulfill the requirements for accurate (1)H imaging down to image resolutions of 0.2 mm. Using susceptibility matching techniques, the probe's B(0) inhomogeneity-induced signal dephasing is reduced and monitoring periods beyond 200 msec are achieved. The benefit of real time magnetic field monitoring is highlighted for phase-contrast and non-Cartesian multishot imaging. PMID:21254204

  17. NMR Spectroscopy and Its Value: A Primer

    ERIC Educational Resources Information Center

    Veeraraghavan, Sudha

    2008-01-01

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

  18. Modern NMR spectroscopy: a guide for chemists

    SciTech Connect

    Sanders, J.K.M.; Hunter, B.K.

    1988-01-01

    The aim of the authors of Modern NMR Spectroscopy is to bridge the communication gap between the chemist and the spectroscopist. The approach is nonmathematical, descriptive, and pictorial. To illustrate the ideas introduced in the text, the authors provide original spectra obtained specially for this purpose. Examples include spectroscopy of protons, carbon, and less receptive nuclei of interest to inorganic chemists. The authors succeed in making high-resolution NMR spectroscopy comprehensible for the average student or chemist.

  19. Scalable NMR spectroscopy with semiconductor chips

    PubMed Central

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

    2014-01-01

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

  20. Scalable NMR spectroscopy with semiconductor chips.

    PubMed

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

    2014-08-19

    State-of-the-art NMR spectrometers using superconducting magnets have enabled, with their ultrafine spectral resolution, the determination of the structure of large molecules such as proteins, which is one of the most profound applications of modern NMR spectroscopy. Many chemical and biotechnological applications, however, involve only small-to-medium size molecules, for which the ultrafine resolution of the bulky, expensive, and high-maintenance NMR spectrometers is not required. For these applications, there is a critical need for portable, affordable, and low-maintenance NMR spectrometers to enable in-field, on-demand, or online applications (e.g., quality control, chemical reaction monitoring) and co-use of NMR with other analytical methods (e.g., chromatography, electrophoresis). As a critical step toward NMR spectrometer miniaturization, small permanent magnets with high field homogeneity have been developed. In contrast, NMR spectrometer electronics capable of modern multidimensional spectroscopy have thus far remained bulky. Complementing the magnet miniaturization, here we integrate the NMR spectrometer electronics into 4-mm(2) silicon chips. Furthermore, we perform various multidimensional NMR spectroscopies by operating these spectrometer electronics chips together with a compact permanent magnet. This combination of the spectrometer-electronics-on-a-chip with a permanent magnet represents a useful step toward miniaturization of the overall NMR spectrometer into a portable platform. PMID:25092330

  1. NMR resonance splitting of urea in stretched hydrogels: proton exchange and (1)H/(2)H isotopologues.

    PubMed

    Kuchel, Philip W; Naumann, Christoph; Chapman, Bogdan E; Shishmarev, Dmitry; Håkansson, Pär; Bacskay, George; Hush, Noel S

    2014-10-01

    Urea at ∼12 M in concentrated gelatin gel, that was stretched, gave (1)H and (2)H NMR spectral splitting patterns that varied in a predictable way with changes in the relative proportions of (1)H2O and (2)H2O in the medium. This required consideration of the combinatorics of the two amide groups in urea that have a total of four protonation/deuteration sites giving rise to 16 different isotopologues, if all the atoms were separately identifiable. The rate constant that characterized the exchange of the protons with water was estimated by back-transformation analysis of 2D-EXSY spectra. There was no (1)H NMR spectral evidence that the chiral gelatin medium had caused in-equivalence in the protons bonded to each amide nitrogen atom. The spectral splitting patterns in (1)H and (2)H NMR spectra were accounted for by intra-molecular scalar and dipolar interactions, and quadrupolar interactions with the electric field gradients of the gelatin matrix, respectively. PMID:25241007

  2. A Guided Inquiry Approach to NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

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

    1998-04-01

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

  3. Probing Cancer Cell Metabolism Using NMR Spectroscopy.

    PubMed

    Hollinshead, Kate E R; Williams, Debbie S; Tennant, Daniel A; Ludwig, Christian

    2016-01-01

    Altered cellular metabolism is now accepted to be at the core of many diseases including cancer. Over the past 20 years, NMR has become a core technology to study these metabolic perturbations in detail. This chapter reviews current NMR-based methods for steady-state metabolism and, in particular, the use of non-radioactive stable isotope-enriched tracers. Opportunities and challenges for each method, such as 1D (1)H NMR spectroscopy and (13)C carbon-based NMR spectroscopic methods, are discussed. Ultimately, the combination of NMR and mass spectra as orthogonal technologies are required to compensate for the drawbacks of each technique when used singly are discussed. PMID:27325263

  4. QUANTITATIVE 15N NMR SPECTROSCOPY

    EPA Science Inventory

    Line intensities in 15N NMR spectra are strongly influenced by spin-lattice and spin-spin relaxation times, relaxation mechanisms and experimental conditions. Special care has to be taken in using 15N spectra for quantitative purposes. Quantitative aspects are discussed for the 1...

  5. Orientational landscapes of peptides in membranes: prediction of (2)H NMR couplings in a dynamic context.

    PubMed

    Esteban-Martín, Santi; Giménez, Diana; Fuertes, Gustavo; Salgado, Jesús

    2009-12-01

    Unlike soluble proteins, membrane polypeptides face an anisotropic milieu. This imposes restraints on their orientation and provides a reference that makes structure prediction tractable by minimalistic thermodynamic models. Here we use this framework to build orientational distributions of monomeric membrane-bound peptides and to predict their expected solid-state (2)H NMR quadrupolar couplings when labeled at specific side chain positions. Using a complete rigid-body sampling of configurations relative to an implicit lipid membrane, peptide free energy landscapes are calculated. This allows us to obtain probability distributions of the peptide tilt, azimuthal rotation, and depth of membrane insertion. The orientational distributions are broad and originate from an interplay among the three relevant rigid-body degrees of freedom, which allows population of multiple states in shallow free energy minima. Remarkably, only when the orientational distributions are taken into account do we obtain a close correlation between predicted (2)H NMR splittings and values measured in experiments. Such a good correlation is not seen with splittings calculated from single configurations, being either the averaged or the lowest free energy state, showing there are distributions, rather than single structures, that best define the peptide-membrane systems. Moreover, we propose that these distributions contribute to the understanding of the rigid-body dynamics of the system. PMID:19860438

  6. Mobility of Core Water in Bacillus subtilis Spores by 2H NMR

    NASA Astrophysics Data System (ADS)

    Kaieda, Shuji; Setlow, Barbara; Setlow, Peter; Halle, Bertil

    2013-11-01

    Bacterial spores in a metabolically dormant state can survive long periods without nutrients under extreme environmental conditions. The molecular basis of spore dormancy is not well understood, but the distribution and physical state of water within the spore is thought to play an important role. Two scenarios have been proposed for the spore's core region, containing the DNA and most enzymes. In the gel scenario, the core is a structured macromolecular framework permeated by mobile water. In the glass scenario, the entire core, including the water, is an amorphous solid and the quenched molecular diffusion accounts for the spore's dormancy and thermal stability. Here, we use $^2$H magnetic relaxation dispersion to selectively monitor water mobility in the core of Bacillus subtilis spores in the presence and absence of core Mn$^{2+}$ ions. We also report and analyze the solid-state $^2$H NMR spectrum from these spores. Our NMR data clearly support the gel scenario with highly mobile core water (~ 25 ps average rotational correlation time). Furthermore, we find that the large depot of manganese in the core is nearly anhydrous, with merely 1.7 % on average of the maximum sixfold water coordination.

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

    SciTech Connect

    Matwiyoff, N.A.

    1983-01-01

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

  8. Epitope mapping by solution NMR spectroscopy.

    PubMed

    Bardelli, M; Livoti, E; Simonelli, L; Pedotti, M; Moraes, A; Valente, A P; Varani, L

    2015-06-01

    Antibodies play an ever more prominent role in basic research as well as in the biotechnology and pharmaceutical sectors. Characterizing their epitopes, that is, the region that they recognize on their target molecule, is useful for purposes ranging from molecular biology research to vaccine design and intellectual property protection. Solution NMR spectroscopy is ideally suited to the atomic level characterization of intermolecular interfaces and, as a consequence, to epitope discovery. Here, we illustrate how NMR epitope mapping can be used to rapidly and accurately determine protein antigen epitopes. The basic concept is that differences in the NMR signal of an antigen free or bound by an antibody will identify epitope residues. NMR epitope mapping provides more detailed information than mutagenesis or peptide mapping and can be much more rapid than X-ray crystallography. Advantages and drawbacks of this technique are discussed together with practical considerations. PMID:25726811

  9. Picoliter H-1 NMR Spectroscopy

    SciTech Connect

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

    2002-02-01

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

  10. An Introduction to Biological NMR Spectroscopy*

    PubMed Central

    Marion, Dominique

    2013-01-01

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

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

    PubMed Central

    Schäfer, H; Mädler, B; Sternin, E

    1998-01-01

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

  12. Protein dynamics in the solid state from 2H NMR line shape analysis: a consistent perspective.

    PubMed

    Meirovitch, Eva; Liang, Zhichun; Freed, Jack H

    2015-02-19

    Deuterium line shape analysis of CD3 groups has emerged as a particularly useful tool for studying microsecond-millisecond protein motions in the solid state. The models devised so far consist of several independently conceived simple jump-type motions. They are comprised of physical quantities encoded in their simplest form; improvements are only possible by adding yet another simple motion, thereby changing the model. The various treatments developed are case-specific; hence comparison among the different systems is not possible. Here we develop a new methodology for (2)H NMR line shape analysis free of these limitations. It is based on the microscopic-order-macroscopic-disorder (MOMD) approach. In MOMD motions are described by diffusion tensors, spatial restrictions by potentials/ordering tensors, and geometric features by relative tensor orientations. Jump-type motions are recovered in the limit of large orientational potentials. Model improvement is accomplished by monitoring the magnitude, symmetry, and orientation of the various tensors. The generality of MOMD makes possible comparison among different scenarios. CD3 line shapes from the Chicken Villin Headpiece Subdomain and the Streptomyces Subtilisin Inhibitor are used as experimental examples. All of these spectra are reproduced by using rhombic local potentials constrained for simplicity to be given by the L = 2 spherical harmonics, and by axial diffusion tensors. Potential strength and rhombicity are found to be ca. 2-3 k(B)T. The diffusion tensor is tilted at 120° from the C-CD3 axis. The perpendicular (parallel) correlation times for local motion are 0.1-1.0 ms (3.3-30 μs). Activation energies in the 1.1-8.0 kcal/mol range are estimated. Future prospects include extension to the (2)H relaxation limit, application to the (15)N and (13)C NMR nuclei, and accounting for collective motions and anisotropic media. PMID:25594631

  13. Protein Dynamics in the Solid-State from 2H NMR Lineshape Analysis: a Consistent Perspective

    PubMed Central

    Meirovitch, Eva; Liang, Zhichun; Freed, Jack H.

    2015-01-01

    Deuterium lineshape analysis of CD3 groups has emerged as a particularly useful tool for studying μs - ms protein motions in the solid-state. The models devised so far consist of several independently conceived simple jump-type motions. They are comprised of physical quantities encoded in their simplest form; improvements are only possible by adding yet another simple motion, thereby changing the model. The various treatments developed are case-specific; hence comparison amongst the different systems is not possible. Here we develop a new methodology for 2H NMR lineshape analysis free of these limitations. It is based on the microscopic-order-macroscopic-disorder (MOMD) approach. In MOMD motions are described by diffusion tensors, spatial restrictions by potentials/ordering tensors, and geometric features by relative tensor orientations. Jump-type motions are recovered in the limit of large orientational potentials. Model-improvement is accomplished by monitoring the magnitude, symmetry and orientation of the various tensors. The generality of MOMD makes possible comparison amongst different scenarios. CD3 lineshapes from the Chicken Villin Headpiece Subdomain, and the Streptomyces Subtilisin Inhibitor, are used as experimental examples. All of these spectra are reproduced by using rhombic local potentials constrained for simplicity to be given by the L = 2 spherical harmonics, and axial diffusion tensors. Potential strength and rhombicity are found to be ca. 2 − 3 [kBT]. The diffusion tensor is tilted at 120° from the C−CD3 axis. The perpendicular (parallel) correlation times for local motion are 0.1 − 1.0 ms (3.3 − 30 μs). Activation energies in the 1.1 − 8.0 kcal/mol range are estimated. Future prospects include extension to the 2H relaxation limit, application to the 15N and 13C NMR nuclei, and accounting for collective motions and anisotropic media. PMID:25594631

  14. Multidimensional NMR spectroscopy in a single scan.

    PubMed

    Gal, Maayan; Frydman, Lucio

    2015-11-01

    Multidimensional NMR has become one of the most widespread spectroscopic tools available to study diverse structural and functional aspects of organic and biomolecules. A main feature of multidimensional NMR is the relatively long acquisition times that these experiments demand. For decades, scientists have been working on a variety of alternatives that would enable NMR to overcome this limitation, and deliver its data in shorter acquisition times. Counting among these methodologies is the so-called ultrafast (UF) NMR approach, which in principle allows one to collect arbitrary multidimensional correlations in a single sub-second transient. By contrast to conventional acquisitions, a main feature of UF NMR is a spatiotemporal manipulation of the spins that imprints the chemical shift and/or J-coupling evolutions being sought, into a spatial pattern. Subsequent gradient-based manipulations enable the reading out of this information and its multidimensional correlation into patterns that are identical to those afforded by conventional techniques. The current review focuses on the fundamental principles of this spatiotemporal UF NMR manipulation, and on a few of the methodological extensions that this form of spectroscopy has undergone during the years. PMID:26249041

  15. Tritiation methods and tritium NMR spectroscopy

    SciTech Connect

    Jaiswal, D.K.; Morimoto, H.; Salijoughian, M.; Williams, P.G.

    1991-09-01

    We have used a simple process for the production of highly tritiated water and characterized the product species by {sup 1}H and {sup 3}H NMR spectroscopy. The water is readily manipulated and used in subsequent reactions either as T{sub 2}O, CH{sub 3}COOT or CF{sub 3}COOT. Development of tritiated diimide has progressed to the point where cis-hydrogenated products at 1-20 Ci/mmole S.A. are possible. Tri-n-butyl tin tritide has been produced at >95% tritium content and well characterized by multinuclear NMR techniques. 27 refs., 3 figs.

  16. Hydration and Lateral Organization in Phospholipid Bilayers Containing Sphingomyelin: A 2H-NMR Study

    PubMed Central

    Steinbauer, Bernhard; Mehnert, Thomas; Beyer, Klaus

    2003-01-01

    Interfacial properties of lipid bilayers were studied by 2H nuclear magnetic resonance spectroscopy, with emphasis on a comparison between phosphatidylcholine and sphingomyelin. Spectral resolution and sensitivity was improved by macroscopic membrane alignment. The motionally averaged quadrupolar interaction of interlamellar deuterium oxide was employed to probe the interfacial polarity of the membranes. The D2O quadrupolar splittings indicated that the sphingomyelin lipid-water interface is less polar above the phase transition temperature Tm than below Tm. The opposite behavior was found in phosphatidylcholine bilayers. Macroscopically aligned sphingomyelin bilayers also furnished 2H-signals from the amide residue and from the hydroxyl group of the sphingosine moiety. The rate of water-hydroxyl deuteron exchange could be measured, whereas the exchange of the amide deuteron was too slow for the inversion-transfer technique employed, suggesting that the amide residue is involved in intermolecular hydrogen bonding. Order parameter profiles in mixtures of sphingomyelin and chain-perdeuterated phosphatidylcholine revealed an ordering effect as a result of the highly saturated chains of the sphingolipids. The temperature dependence of the 2H quadrupolar splittings was indicative of lateral phase separation in the mixed systems. The results are discussed with regard to interfacial structure and lateral organization in sphingomyelin-containing biomembranes. PMID:12885648

  17. Local structure and molecular motions in imidazolium hydrogen malonate crystal as studied by 2H and 13C NMR

    NASA Astrophysics Data System (ADS)

    Mizuno, M.; Chizuwa, M.; Umiyama, T.; Kumagai, Y.; Miyatou, T.; Ohashi, R.; Ida, T.; Tansho, M.; Shimizu, T.

    2015-04-01

    The local structure and molecular motion of the imidazolium hydrogen malonate crystal were investigated using solid-state 2H and 13C NMR. The imidazolium ion undergoes isotropic rotation, which is correlated with a defect in the crystal, as observed by 2H NMR broadline spectra above 263 K. A 180∘ flip of the imidazolium ion in the regular site was observed from 2H NMR quadrupole Carr-Purcell-Meiboom-Gill (QCPMG) spectra. The Grotthuss mechanism was accompanied by a 180∘ flip of the imidazolium ion in regular sites. Moreover, the proton transfer associated with the imidazolium ion of the defective crystal is important for proton conductivity of the imidazolium hydrogen malonate crystal.

  18. Water interactions with varying molecular states of bovine casein: 2H NMR relaxation studies

    SciTech Connect

    Kumosinski, T.F.; Pessen, H.; Prestrelski, S.J.; Farrell, H.M. Jr.

    1987-09-01

    The caseins occur in milk as spherical colloidal complexes of protein and salts with an average diameter of 1200 A, the casein micelles. Removal of Ca2+ is thought to result in their dissociation into smaller protein complexes stabilized by hydrophobic interactions and called submicelles. Whether these submicelles actually occur within the micelles as discrete particles interconnected by calcium phosphate salt bridges has been the subject of much controversy. A variety of physical measurements have shown that casein micelles contain an inordinately high amount of trapped water (2 to 7 g H/sub 2/O/g protein). With this in mind it was of interest to determine if NMR relaxation measurements could detect the presence of this trapped water within the micelles, and to evaluate whether it is a continuum with picosecond correlation times or is associated in part with discrete submicellar structures with nanosecond motions. For this purpose the variations in /sup 2/H NMR longitudinal and transverse relaxation rates of water with protein concentration were determined for bovine casein at various temperatures, under both submicellar and micellar conditions. D/sub 2/O was used instead of H/sub 2/O to eliminate cross-relaxation effects. From the protein concentration dependence of the relaxation rates, the second virial coefficient of the protein was obtained by nonlinear regression analysis. Using either an isotropic tumbling or an intermediate asymmetry model, degrees of hydration, v, and correlation times, tau c, were calculated for the caseins; from the latter parameter the Stokes radius, r, was obtained. Next, estimates of molecular weights were obtained from r and the partial specific volume. Values were in the range of those published from other methodologies for the submicelles.

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

    PubMed

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

    2015-03-01

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

  20. Ultra-wideline solid-state NMR spectroscopy.

    PubMed

    Schurko, Robert W

    2013-09-17

    Although solid-state NMR (SSNMR) provides rich information about molecular structure and dynamics, the small spin population differences between pairs of spin states that give rise to NMR transitions make it an inherently insensitive spectroscopic technique in terms of signal acquisition. Scientists have continuously addressed this issue via improvements in NMR hardware and probes, increases in the strength of the magnetic field, and the development of innovative pulse sequences and acquisition methodologies. As a result, researchers can now study NMR-active nuclides previously thought to be unobservable or too unreceptive for routine examination via SSNMR. Several factors can make it extremely challenging to detect signal or acquire spectra using SSNMR: (i) low gyromagnetic ratios (i.e., low Larmor frequencies), (ii) low natural abundances or dilution of the nuclide of interest (e.g., metal nuclides in proteins or in organometallic catalysts supported on silica), (iii) inconvenient relaxation characteristics (e.g., very long longitudinal or very short transverse relaxation times), and/or (iv) extremely broad powder patterns arising from large anisotropic NMR interactions. Our research group has been particularly interested in efficient acquisition of broad NMR powder patterns for a variety of spin-1/2 and quadrupolar (spin > 1/2) nuclides. Traditionally, researchers have used the term "wideline" NMR to refer to experiments yielding broad (1)H and (2)H SSNMR spectra ranging from tens of kHz to ∼250 kHz in breadth. With modern FT NMR hardware, uniform excitation in these spectral ranges is relatively easy, allowing for the acquisition of high quality spectra. However, spectra that range in breadth from ca. 250 kHz to tens of MHz cannot be uniformly excited with conventional, high-power rectangular pulses. Rather, researchers must apply special methodologies to acquire such spectra, which have inherently low S/N because the signal intensity is spread across such

  1. Anisotropic sup 2 H NMR spin-lattice relaxation in L sub. alpha. -phase cerebroside bilayers

    SciTech Connect

    Speyer, J.B.; Weber, R.T.; Gupta, S.K.D.; Griffin, R.G. )

    1989-12-12

    A series of {sup 2}H NMR inversion recovery experiments in the L{sub {alpha}} phase of the cerebroside N-palmitoylgalactosylsphingosine (NPGS) have been performed. In these liquid crystalline lipid bilayers the authors have observed substantial anisotropy in the spin-lattice relaxation of the CD{sub 2} groups in the acyl chains. The form and magnitude of the anisotropy varies with position in the chain, being positive in the upper region, decreasing to zero at the 4-position, and reversing sign at the lower chain positions. It is also shown that addition of cholesterol to the bilayer results in profound changes in the anisotropy. These observations are accounted for by a simple motional model of discrete hops among nine sites, which result from the coupling of two modes of motion - long-axis rotational diffusion and guache-trans isomerization. This model is employed in quantitative simulations of the spectral line shapes and permits determination of site populations and motional rates. These results, plus preliminary results in sphingomyelin and lecithin bilayers,illustrate the utility of T{sub 1} anisotropy measurements as a probe of dynamics in L{sub {alpha}}-phase bilayers.

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

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran

    2016-03-01

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

  3. Conformation-Specific Infrared Spectroscopy of γ2-PEPTIDE Foldamers: Ac-γ2-hPhe-γ2-hAla-NHMe and Ac-γ2-hAla-γ2-hPhe-NHMe

    NASA Astrophysics Data System (ADS)

    James, William H., III; Buchanan, Evan G.; Müller, Christian W.; Zwier, Timothy S.; Guo, Li; Gellman, Samuel H.

    2010-06-01

    IR/UV double-resonance spectroscopy has been used to study the intrinsic conformational preferences of naturally occurring and synthetic peptides. These studies demonstrated the power of double-resonance methods and highlighted the ability of even short peptide mimics to form a variety of intramolecular hydrogen bonded architectures. Currently, we are extending these studies to a series of model γ2-peptides, which differ from α-peptides by virtue of having two additional, substitutable methylene units separating amide groups in the peptide backbone. Initial studies centered on the conformation-specific infrared spectra of Ac-γ2-hPhe-NHMe, where three unique conformational isomers (two hydrogen-bonded and one intramolecular amide stacked) were observed under the isolated-molecule conditions of a jet-cooled environment. This talk will focus on on two larger γ2-peptides, Ac-γ2-hPhe-γ2-hAla-NHMe and Ac-γ2-hAla-γ2-hPhe-NHMe. Utilizing resonant ion-dip infrared spectroscopy, the single-conformation infrared spectra of eight resolved conformers of the two molecules were recorded in the amide NH stretch region. The resulting infrared spectra of the tri-amides contain evidence for structures comprised of one, two, and three intramolecular amide-amide hydrogen bonds, the last of which is unprecedented for a tri-amide. In an effort to make firm conformational assignments, the spectroscopic data will be compared to the results of harmonic vibrational frequency calculations using traditional DFT and dispersion-corrected DFT methods, the results of which will be discussed.

  4. Rapid solid-state NMR of deuterated proteins by interleaved cross-polarization from 1H and 2H nuclei

    NASA Astrophysics Data System (ADS)

    Bjerring, Morten; Paaske, Berit; Oschkinat, Hartmut; Akbey, Ümit; Nielsen, Niels Chr.

    2012-01-01

    We present a novel sampling strategy, interleaving acquisition of multiple NMR spectra by exploiting initial polarization subsequently from 1H and 2H spins, taking advantage of their different T1 relaxation times. Different 1H- and 2H-polarization based spectra are in this way simultaneously recorded improving either information content or sensitivity by adding spectra. The so-called Relaxation-optimized Acquisition of Proton Interleaved with Deuterium (RAPID) 1H → 13C/ 2H → 13C CP/MAS multiple-acquisition method is demonstrated by 1D and 2D experiments using a uniformly 2H, 15N, 13C-labeled α-spectrin SH3 domain sample with all or 30% back-exchanged labile 2H to 1H. It is demonstrated how 1D 13C CP/MAS or 2D 13C- 13C correlation spectra initialized with polarization from either 1H or 2H may be recorded simultaneously with flexibility to be added or used individually for spectral editing. It is also shown how 2D 13C- 13C correlation spectra may be recorded interleaved with 2H- 13C correlation spectra to obtain 13C- 13C correlations along with information about dynamics from 2H sideband patterns.

  5. Deuterium NMR of Val1...(2-2H)Ala3...gramicidin A in oriented DMPC bilayers.

    PubMed

    Hing, A W; Adams, S P; Silbert, D F; Norberg, R E

    1990-05-01

    Deuterium NMR is used to study the selectively labeled Val1...(2-2H)Ala3...gramicidin A molecule to investigate the structure and dynamics of the C alpha-2H bond in the Ala3 residue of gramicidin. Val1...(2-2H)Ala3...gramicidin A is synthesized, purified, and characterized and then incorporated into oriented bilayers of dimyristoylphosphatidylcholine sandwiched between glass coverslips. Phosphorus NMR line shapes obtained from this sample are consistent with the presence of the bilayer phase and indicate that no nonbilayer phases are present in significant amounts. Deuterium NMR line shapes obtained from this sample indicate that the motional axis of the gramicidin Ala3 residue is parallel to the coverslip normal, that the distribution of motional axis orientations has a width of 2 degrees, and that only one major conformational and dynamical state of the Ala3 C alpha-2H bond is observed on the NMR time scale. Furthermore, the Ala3 C alpha-2H bond angle relative to the motional axis is 19-20 degrees if fast axial rotation is assumed to be the only motion present but is less than or equal to 19-20 degrees in the absence of such an assumption. This result indicates that various double-stranded, helical dimer models are very unlikely to represent the structure of gramicidin in the sample studied but that the single-stranded, beta 6.3 helical dimer models are consistent with the experimental data. However, a definitive distinction between the left-handed, single-stranded, beta 6.3 helical dimer model and the right-handed, single-stranded, beta 6.3 helical dimer model cannot be made on the basis of the experimental data obtained in this study. PMID:1694457

  6. Models of stratum corneum intercellular membranes: 2H NMR of macroscopically oriented multilayers.

    PubMed Central

    Fenske, D B; Thewalt, J L; Bloom, M; Kitson, N

    1994-01-01

    Deuterium NMR was used to characterize model membrane systems approximating the composition of the intercellular lipid lamellae of mammalian stratum corneum (SC). The SC models, equimolar mixtures of ceramide:cholesterol:palmitic acid (CER:CHOL:PA) at pH 5.2, were contrasted with the sphingomyelin:CHOL:PA (SPM:CHOL:PA) system, where the SPM differs from the CER only in the presence of a phosphocholine headgroup. The lipids were prepared both as oriented samples and as multilamellar dispersions, and contained either perdeuterated palmitic acid (PA-d31) or [2,2,3,4,6-2H5]CHOL (CHOL-d5). SPM:CHOL:PA-d31 formed liquid-ordered membranes over a wide range of temperatures, with a maximum order parameter of approximately 0.4 at 50 degrees C for positions C3-C10 (the plateau region). The quadrupolar splitting at C2 was significantly smaller, suggesting an orientational change at this position, possibly because of hydrogen bonding with water and/or other surface components. A comparison of the longitudinal relaxation times obtained at theta = 0 degrees and 90 degrees (where theta is the angle between the normal to the glass plates and the magnetic field) revealed a significant T1Z anisotropy for all positions. In contrast to the behavior observed with the SPM system, lipid mixtures containing CER exhibited a complex polymorphism. Between 20 and 50 degrees C, a significant portion of the entire membrane (as monitored by both PA-d31 and CHOL-d5) was found to exist as a solid phase, with the remainder either a gel or liquid-ordered phase. The proportion of solid decreased as the temperature was increased and disappeared entirely above 50 degrees C. Between 50 and 70 degrees C, the membrane underwent a liquid-ordered to isotropic phase transition. These transitions were reversible but displayed considerable hysteresis, especially the conversion from a fluid phase to solid. The order profiles, relaxation behavior, and angular dependence of these parameters suggest strongly that

  7. Models of stratum corneum intercellular membranes: 2H NMR of macroscopically oriented multilayers.

    PubMed

    Fenske, D B; Thewalt, J L; Bloom, M; Kitson, N

    1994-10-01

    Deuterium NMR was used to characterize model membrane systems approximating the composition of the intercellular lipid lamellae of mammalian stratum corneum (SC). The SC models, equimolar mixtures of ceramide:cholesterol:palmitic acid (CER:CHOL:PA) at pH 5.2, were contrasted with the sphingomyelin:CHOL:PA (SPM:CHOL:PA) system, where the SPM differs from the CER only in the presence of a phosphocholine headgroup. The lipids were prepared both as oriented samples and as multilamellar dispersions, and contained either perdeuterated palmitic acid (PA-d31) or [2,2,3,4,6-2H5]CHOL (CHOL-d5). SPM:CHOL:PA-d31 formed liquid-ordered membranes over a wide range of temperatures, with a maximum order parameter of approximately 0.4 at 50 degrees C for positions C3-C10 (the plateau region). The quadrupolar splitting at C2 was significantly smaller, suggesting an orientational change at this position, possibly because of hydrogen bonding with water and/or other surface components. A comparison of the longitudinal relaxation times obtained at theta = 0 degrees and 90 degrees (where theta is the angle between the normal to the glass plates and the magnetic field) revealed a significant T1Z anisotropy for all positions. In contrast to the behavior observed with the SPM system, lipid mixtures containing CER exhibited a complex polymorphism. Between 20 and 50 degrees C, a significant portion of the entire membrane (as monitored by both PA-d31 and CHOL-d5) was found to exist as a solid phase, with the remainder either a gel or liquid-ordered phase. The proportion of solid decreased as the temperature was increased and disappeared entirely above 50 degrees C. Between 50 and 70 degrees C, the membrane underwent a liquid-ordered to isotropic phase transition. These transitions were reversible but displayed considerable hysteresis, especially the conversion from a fluid phase to solid. The order profiles, relaxation behavior, and angular dependence of these parameters suggest strongly that

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

    ERIC Educational Resources Information Center

    Mills, Nancy S.; Shanklin, Michael

    2011-01-01

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

  9. Exploring RNA polymerase regulation by NMR spectroscopy

    PubMed Central

    Drögemüller, Johanna; Strauß, Martin; Schweimer, Kristian; Wöhrl, Birgitta M.; Knauer, Stefan H.; Rösch, Paul

    2015-01-01

    RNA synthesis is a central process in all organisms, with RNA polymerase (RNAP) as the key enzyme. Multisubunit RNAPs are evolutionary related and are tightly regulated by a multitude of transcription factors. Although Escherichia coli RNAP has been studied extensively, only little information is available about its dynamics and transient interactions. This information, however, are crucial for the complete understanding of transcription regulation in atomic detail. To study RNAP by NMR spectroscopy we developed a highly efficient procedure for the assembly of active RNAP from separately expressed subunits that allows specific labeling of the individual constituents. We recorded [1H,13C] correlation spectra of isoleucine, leucine, and valine methyl groups of complete RNAP and the separately labeled β’ subunit within reconstituted RNAP. We further produced all RNAP subunits individually, established experiments to determine which RNAP subunit a certain regulator binds to, and identified the β subunit to bind NusE. PMID:26043358

  10. Spatially resolved spectroscopy using tapered stripline NMR

    NASA Astrophysics Data System (ADS)

    Tijssen, Koen C. H.; Bart, Jacob; Tiggelaar, Roald M.; Janssen, J. W. G. (Hans); Kentgens, Arno P. M.; van Bentum, P. Jan M.

    2016-02-01

    Magnetic field B0 gradients are essential in modern Nuclear Magnetic Resonance spectroscopy and imaging. Although RF/B1 gradients can be used to fulfill a similar role, this is not used in common practice because of practical limitations in the design of B1 gradient coils. Here we present a new method to create B1 gradients using stripline RF coils. The conductor-width of a stripline NMR chip and the strength of its radiofrequency field are correlated, so a stripline chip can be tapered to produce any arbitrary shaped B1 field gradient. Here we show the characterization of this tapered stripline configuration and demonstrate three applications: magnetic resonance imaging on samples with nL-μL volumes, reaction monitoring of fast chemical reactions (10-2-101 s) and the compensation of B0 field gradients to obtain high-resolution spectra in inhomogeneous magnetic fields.

  11. Grasping hydrogen adsorption and dynamics in metal-organic frameworks using (2)H solid-state NMR.

    PubMed

    Lucier, Bryan E G; Zhang, Yue; Lee, Kelly J; Lu, Yuanjun; Huang, Yining

    2016-06-18

    Record greenhouse gas emissions have spurred the search for clean energy sources such as hydrogen (H2) fuel cells. Metal-organic frameworks (MOFs) are promising H2 adsorption and storage media, but knowledge of H2 dynamics and adsorption strengths in these materials is lacking. Variable-temperature (VT) (2)H solid-state NMR (SSNMR) experiments targeting (2)H2 gas (i.e., D2) shed light on D2 adsorption and dynamics within six representative MOFs: UiO-66, M-MOF-74 (M = Zn, Mg, Ni), and α-M3(COOH)6 (M = Mg, Zn). D2 binding is relatively strong in Mg-MOF-74, Ni-MOF-74, α-Mg3(COOH)6, and α-Zn3(COOH)6, giving rise to broad (2)H SSNMR powder patterns. In contrast, D2 adsorption is weaker in UiO-66 and Zn-MOF-74, as evidenced by the narrow (2)H resonances that correspond to rapid reorientation of the D2 molecules. Employing (2)H SSNMR experiments in this fashion holds great promise for the correlation of MOF structural features and functional groups/metal centers to H2 dynamics and host-guest interactions. PMID:27181834

  12. From molecular complexes to complex metallic nanostructures--2H solid-state NMR studies of ruthenium-containing hydrogenation catalysts.

    PubMed

    Gutmann, Torsten; del Rosal, Iker; Chaudret, Bruno; Poteau, Romuald; Limbach, Hans-Heinrich; Buntkowsky, Gerd

    2013-09-16

    In the last years, the combination of (2)H solid-state NMR techniques with quantum-chemical calculations has evolved into a powerful spectroscopic tool for the characterization of the state of hydrogen on the surfaces of heterogeneous catalysts. In the present minireview, a brief summary of this development is given, in which investigations of the structure and dynamics of hydrogen in molecular complexes, clusters and nanoparticle systems are presented, aimed to understand the reaction mechanisms on the surface of hydrogenation catalysts. The surface state of deuterium/hydrogen is analyzed employing a combination of variable-temperature (2)H static and magic-angle spinning (MAS) solid-state NMR techniques, in which the dominant quadrupolar interactions of deuterium give information on the binding situation and local symmetry of deuterium/hydrogen on molecular species. Using a correlation database from molecular complexes and clusters, the possibility to distinguish between terminal Ru-D, bridged Ru2-D, three-fold Ru3-D, and interstitial Ru6-D is demonstrated. Combining these results with quantum-chemical density functional theory (DFT) calculations allows the interpretation of (2)H solid-state data of complex "real world" nanostructures, which yielded new insights into reaction pathways at the molecular level. PMID:23658058

  13. Quantitative C2H2 measurements in sooty flames using mid-infrared polarization spectroscopy

    NASA Astrophysics Data System (ADS)

    Sun, Z. W.; Li, Z. S.; Li, B.; Alwahabi, Z. T.; Aldén, M.

    2010-10-01

    Quantitative measurements of acetylene (C2H2) molecules as a combustion intermediate species in a series of rich premixed C2H4/air flames were non-intrusively performed, spatially resolved, using mid-infrared polarization spectroscopy (IRPS), by probing its fundamental ro-vibrational transitions. The flat sooty C2H4/air premixed flames with different equivalence ratios varying from 1.25 to 2.50 were produced on a 6 cm diameter porous-plug McKenna type burner at atmospheric pressure, and all measurements were performed at a height of 8.5 mm above the burner surface. IRPS excitation scans in different flame conditions were performed and rotational line-resolved spectra were recorded. Spectral features of acetylene molecules were readily recognized in the spectral ranges selected, with special attention to avoid the spectral interference from the large amount of coexisting hot water and other hydrocarbon molecules. On-line calibration of the optical system was performed in a laminar C2H2/N2 gas flow at ambient conditions. Using the flame temperatures measured by coherent anti-Stokes Raman spectroscopy in a previous work, C2H2 mole fractions in different flames were evaluated with collision effects and spectral overlap between molecular line and laser source being analyzed and taken into account. C2H2 IRPS signals in two different buffering gases, N2 and CO2, had been investigated in a tube furnace in order to estimate the spectral overlap coefficients and collision effects at different temperatures. The soot-volume fractions (SVF) in the studied flames were measured using a He-Ne laser-extinction method, and no obvious degrading of the IRPS technique due to the sooty environment has been observed in the flame with SVF up to ˜2×10-7. With the increase of flame equivalence ratios not only the SVF but also the C2H2 mole fractions increased.

  14. sup 2 H NMR study of molecular dynamics and organization in the system C sub 12 E sub 4 -water

    SciTech Connect

    Henriksson, U. ); Jonstroemer, M.; Olsson, U.; Soederman, O. ); Klose, G. )

    1991-05-02

    A sample containing 20 wt % of the nonionic surfactant tetraethylene glycol dodecyl ether (C{sub 12}E{sub 4}), specifically deuterated in the {alpha}-position, was investigated with {sup 2}H NMR relaxation in H{sub 2}O. From the frequency dependence of the longitudinal relaxation rate in the Larmor frequency range 2-55 MHz, it was concluded that the solution contains rodlike micelles. A slow motion in the microsecond time scale, as determined from the transverse relaxation rate, was interpreted taking the flexibility of the rodlike micelles explicitly into account.

  15. Double and zero quantum filtered 2H NMR analysis of D2O in intervertebral disc tissue

    NASA Astrophysics Data System (ADS)

    Ooms, Kristopher J.; Vega, Alexander J.; Polenova, Tatyana; Cannella, Marco; Marcolongo, Michele

    2015-09-01

    The analysis of double and zero quantum filtered 2H NMR spectra obtained from D2O perfused in the nucleus pulposus of human intervertebral disc tissue samples is reported. Fitting the spectra with a three-site model allows for residual quadrupolar couplings and T2 relaxation times to be measured. The analysis reveals changes in both the couplings and relaxation times as the tissue begins to show signs of degradation. The full analysis demonstrates that information about tissue hydration, water collagen interactions, and sample heterogeneity can be obtained and used to better understand the biochemical differences between healthy and degraded tissue.

  16. Fully automated high-quality NMR structure determination of small 2H-enriched proteins

    PubMed Central

    Tang, Yuefeng; Schneider, William M.; Shen, Yang; Raman, Srivatsan; Inouye, Masayori; Baker, David; Roth, Monica J.

    2010-01-01

    Determination of high-quality small protein structures by nuclear magnetic resonance (NMR) methods generally requires acquisition and analysis of an extensive set of structural constraints. The process generally demands extensive backbone and sidechain resonance assignments, and weeks or even months of data collection and interpretation. Here we demonstrate rapid and high-quality protein NMR structure generation using CS-Rosetta with a perdeuterated protein sample made at a significantly reduced cost using new bacterial culture condensation methods. Our strategy provides the basis for a high-throughput approach for routine, rapid, high-quality structure determination of small proteins. As an example, we demonstrate the determination of a high-quality 3D structure of a small 8 kDa protein, E. coli cold shock protein A (CspA), using <4 days of data collection and fully automated data analysis methods together with CS-Rosetta. The resulting CspA structure is highly converged and in excellent agreement with the published crystal structure, with a backbone RMSD value of 0.5 Å, an all atom RMSD value of 1.2 Å to the crystal structure for well-defined regions, and RMSD value of 1.1 Å to crystal structure for core, non-solvent exposed sidechain atoms. Cross validation of the structure with 15N- and 13C-edited NOESY data obtained with a perdeuterated 15N, 13C-enriched 13CH3 methyl protonated CspA sample confirms that essentially all of these independently-interpreted NOE-based constraints are already satisfied in each of the 10 CS-Rosetta structures. By these criteria, the CS-Rosetta structure generated by fully automated analysis of data for a perdeuterated sample provides an accurate structure of CspA. This represents a general approach for rapid, automated structure determination of small proteins by NMR. PMID:20734145

  17. NMR Analysis of Unknowns: An Introduction to 2D NMR Spectroscopy

    ERIC Educational Resources Information Center

    Alonso, David E.; Warren, Steven E.

    2005-01-01

    A study combined 1D (one-dimensional) and 2D (two-dimensional) NMR spectroscopy to solve structural organic problems of three unknowns, which include 2-, 3-, and 4-heptanone. Results showed [to the first power]H NMR and [to the thirteenth power]C NMR signal assignments for 2- and 3-heptanone were more challenging than for 4-heptanone owing to the…

  18. Crystal structure, NMR study, dc-conductivity and dielectric relaxation studies of a new compound [C2H10N2]Cd(SCN)2Cl2

    NASA Astrophysics Data System (ADS)

    Saidi, K.; Kamoun, S.; Ayedi, H. F.; Gargouri, M.

    2012-06-01

    The crystal structure, the solid NMR spectroscopy and the complex impedance study have been carried out on [C2H10N2]CdCl2(SCN)2. Characterization by single crystal X-ray crystallography shows that the cadmium atoms have à 2N2S2Cl hexa-coordination sphere, exhibiting pseudo-octahedral geometry. The cadmium atoms are bridged by two thiocyanate ions generating 1-D polymeric-chains. These chains are themselves interconnected by means of N-H…Cl(NCS) hydrogen bonds originating from the organic cation [(NH3)2(CH2)2]2+. 111Cd isotropic chemical shifts span a range of 268ppm. The cadmium atom exhibits multiplets that result from 111Cd-14N spin-spin coupling. Examination of 111Cd and 13C MAS line shapes shows direct measurement of the indirect spin-spin coupling constant 2J(111Cd, 14N) = 105Hz and the dipolar coupling constant of 1381Hz . Impedance spectroscopy measurements of [C2H10N2]CdCl2(SCN)2 have been studied from 209Hz to 5 MHz over the temperature range 300-370 K. The Cole-Cole (Z" versus Z') plots are fitted to two equivalent circuits models. The formalism of complex permittivity and impedance were employed to analyze the experimental data. The dc conductivity follows the Arrhenius relation with an activation energy Ea = 0.54 (3) eV.

  19. Multiplet-separated heteronuclear two-dimensional NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Levitt, Malcolm H.; Sørensen, O. W.; Ernst, R. R.

    1983-02-01

    Techniques are described for the identification and separation of peaks of different multiplicity in heteronuclear two-dimensional NMR spectroscopy. The methods are applied to the two-dimensional 13C- 1H shift correlation spectrum of menthol.

  20. An Integrated Laboratory Project in NMR Spectroscopy.

    ERIC Educational Resources Information Center

    Hudson, Reggie L.; Pendley, Bradford D.

    1988-01-01

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

  1. Importance of Tensor Asymmetry for the Analysis of 2H-NMR Spectra from Deuterated Aromatic Rings

    PubMed Central

    Pulay, Peter; Scherer, Erin M.; van der Wel, Patrick C. A.; Koeppe, Roger E.

    2008-01-01

    We have used ab initio calculations to compute all of the tensor elements of the electric field gradient for each carbon-deuterium bond in the ring of deuterated 3-methyl-indole. Previous analyses have ignored the smaller tensor elements perpendicular to principal component Vzz which is aligned with the C-2H bond (local bond z-axis). At each ring position, the smallest element Vxx is in the molecular plane and Vyy is normal to the plane of the ring. The asymmetry parameter η = (|Vyy|-|Vxx|)/|Vzz| ranges from 0.07 at C4 to 0.11 at C2. We used the perpendicular (off-bond) tensor elements, in concert with an improved understanding of the indole ring geometry1, to analyze prototype 2H-NMR spectra from well-oriented, hydrated peptide/lipid samples. For each of the 4 tryptophans of membrane-spanning gramicidin A (gA)2 channels, the inclusion of the perpendicular elements changes the deduced ring tilt by nearly 10° and increases the ring principal order parameter Szz for overall ‘wobble’ with respect to the membrane normal (molecular z-axis). With the improved analysis, the magnitude of Szz for the outermost indole rings of Trp13 and Trp15 is indistinguishable from that observed previously for backbone atoms (0.93 ± 0.03). For the Trp9 and Trp11 rings, which are slightly more buried within the membrane, Szz is slightly lower (0.86 ± 0.03). The results show that the perpendicular elements are important for the detailed analysis of 2H-NMR spectra from aromatic ring systems. PMID:16332101

  2. Fragment-Based Drug Discovery Using NMR Spectroscopy

    PubMed Central

    Harner, Mary J.; Frank, Andreas O.; Fesik, Stephen W.

    2013-01-01

    Nuclear magnetic resonance (NMR) spectroscopy has evolved into a powerful tool for fragment-based drug discovery over the last two decades. While NMR has been traditionally used to elucidate the three-dimensional structures and dynamics of biomacromolecules and their interactions, it can also be a very valuable tool for the reliable identification of small molecules that bind to proteins and for hit-to-lead optimization. Here, we describe the use of NMR spectroscopy as a method for fragment-based drug discovery and how to most effectively utilize this approach for discovering novel therapeutics based on our experience. PMID:23686385

  3. Facing and Overcoming Sensitivity Challenges in Biomolecular NMR Spectroscopy.

    PubMed

    Ardenkjaer-Larsen, Jan-Henrik; Boebinger, Gregory S; Comment, Arnaud; Duckett, Simon; Edison, Arthur S; Engelke, Frank; Griesinger, Christian; Griffin, Robert G; Hilty, Christian; Maeda, Hidaeki; Parigi, Giacomo; Prisner, Thomas; Ravera, Enrico; van Bentum, Jan; Vega, Shimon; Webb, Andrew; Luchinat, Claudio; Schwalbe, Harald; Frydman, Lucio

    2015-08-01

    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 of the primary approaches that were considered. Topics discussed included the future of ultrahigh-field NMR systems, emerging NMR detection technologies, new approaches to nuclear hyperpolarization, and progress in sample preparation. All of these are orthogonal efforts, whose gains could multiply and thereby enhance the sensitivity of solid- and liquid-state experiments. While substantial advances have been made in all these areas, numerous challenges remain in the quest of endowing NMR spectroscopy with the sensitivity that has characterized forms of spectroscopies based on electrical or optical measurements. These challenges, and the ways by which scientists and engineers are striving to solve them, are also addressed. PMID:26136394

  4. Studies of organic paint binders by NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Spyros, A.; Anglos, D.

    2006-06-01

    Nuclear magnetic resonance spectroscopy is applied to the study of aged binding media used in paintings, namely linseed oil, egg tempera and an acrylic medium. High resolution 1D and 2D NMR experiments establish the state of hydrolysis and oxidation of the linseed and egg tempera binders after five years of aging, by determining several markers sensitive to the hydrolytic and oxidative processes of the binder lipid fraction. The composition of the acrylic binder co-polymer is determined by 2D NMR spectroscopy, while the identification of a surfactant, poly(ethylene glycol), found in greater amounts in aged acrylic medium, is reported. The non-destructive nature of the proposed analytical NMR methodology, and minimization of the amount of binder material needed through the use of sophisticated cryoprobes and hyphenated LC-NMR techniques, make NMR attractive for the arts analyst, in view of its rapid nature and experimental simplicity.

  5. Proton zero-quantum 2D NMR of 2-propenenitrile aligned by an electric field. Determination of the 2H and 14N quadrupole coupling constants

    NASA Astrophysics Data System (ADS)

    Ruessink, B. H.; De Kanter, F. J. J.; MaClean, C.

    Zero-quantum NMR, selectively detected by 2D NMR, is applied to observe small 1H- 1H dipolar couplings in a polar liquid partially oriented by a strong electric field. The normal (single-quantum) 1H spectrum is severely broadened, which prevents the observation of small couplings. The results from the zero-quantum proton spectrum are used to calculate the 2H and 14N quadrupole coupling constants of 2-deutero-2-propenenitrile from the 2H and 14N NMR spectra.

  6. Solid-State NMR Spectroscopy for the Physical Chemistry Laboratory

    ERIC Educational Resources Information Center

    Kinnun, Jacob J.; Leftin, Avigdor; Brown, Michael F.

    2013-01-01

    Solid-state nuclear magnetic resonance (NMR) spectroscopy finds growing application to inorganic and organic materials, biological samples, polymers, proteins, and cellular membranes. However, this technique is often neither included in laboratory curricula nor typically covered in undergraduate courses. On the other hand, spectroscopy and…

  7. Characterization of proteins by in-cell NMR spectroscopy in cultured mammalian cells.

    PubMed

    Barbieri, Letizia; Luchinat, Enrico; Banci, Lucia

    2016-06-01

    In-cell NMR spectroscopy is a unique tool for characterizing biological macromolecules in their physiological environment at atomic resolution. Recent progress in NMR instruments and sample preparation methods allows functional processes, such as metal uptake, disulfide-bond formation and protein folding, to be analyzed by NMR in living, cultured human cells. This protocol describes the necessary steps to overexpress one or more proteins of interest inside human embryonic kidney 293T (HEK293T) cells, and it explains how to set up in-cell NMR experiments. The cDNA is transiently transfected as a complex with a cationic polymer (DNA:PEI (polyethylenimine)), and protein expression is carried on for 2-3 d, after which the NMR sample is prepared. (1)H and (1)H-(15)N correlation NMR experiments (for example, using band-selective optimized flip-angle short-transient heteronuclear multiple quantum coherence (SOFAST-HMQC)) can be carried out in <2 h, ensuring cell viability. Uniform (15)N labeling and amino-acid-specific (e.g., cysteine, methionine) labeling schemes are possible. The entire procedure takes 4 d from cell culture seeding to NMR data collection. PMID:27196722

  8. Selective {sup 2}H and {sup 13}C labeling in NMR analysis of solution protein structure and dynamics

    SciTech Connect

    LeMaster, D.M.

    1994-12-01

    Preparation of samples bearing combined isotope enrichment patterns has played a central role in the recent advances in NMR analysis of proteins in solution. In particular, uniform {sup 13}C, {sup 15}N enrichment has made it possible to apply heteronuclear multidimensional correlation experiments for the mainchain assignments of proteins larger than 30 KDa. In contrast, selective labeling approaches can offer advantages in terms of the directedness of the information provided, such as chirality and residue type assignments, as well as through enhancements in resolution and sensitivity that result from editing the spectral complexity, the relaxation pathways and the scalar coupling networks. In addition, the combination of selective {sup 13}C and {sup 2}H enrichment can greatly facilitate the determination of heteronuclear relaxation behavior.

  9. Tracing bacterial metabolism using multi-nuclear (1H, 2H, and 13C) Solid State NMR: Realizing an Idea Initiated by James Scott

    NASA Astrophysics Data System (ADS)

    Cody, G.; Fogel, M. L.; Jin, K.; Griffen, P.; Steele, A.; Wang, Y.

    2011-12-01

    Approximately 6 years ago, while at the Geophysical Laboratory, James Scott became interested in the application of Solid State Nuclear Magnetic Resonance Spectroscopy to study bacterial metabolism. As often happens, other experiments intervened and the NMR experiments were not pursued. We have revisited Jame's question and find that using a multi-nuclear approach (1H, 2H, and 13C Solid State NMR) on laboratory cell culture has some distinct advantages. Our experiments involved batch cultures of E. coli (MG1655) harvested at stationary phase. In all experiments the growth medium consisted of MOPS medium for enterobacteria, where the substrate is glucose. In one set of experiments, 10 % of the water was D2O; in another 10 % of the glucose was per-deuterated. The control experiment used both water and glucose at natural isotopic abundance. A kill control of dead E. coli immersed in pure D2O for an extended period exhibited no deuterium incorporation. In both deuterium enriched experiments, considerable incorporation of deuterium into E. coli's biomolecular constituents was detected via 2H Solid State NMR. In the case of the D2O enriched experiment, 58 % of the incorporated deuterium is observed in a sharp peak at a frequency of 0.31 ppm, consistent with D incorporation in the cell membrane lipids, the remainder is observed in a broad peak at a higher frequency (centered at 5.4 ppm, but spanning out to beyond 10 ppm) that is consistent with D incorporation into predominantly DNA and RNA. In the case of the D-glucose experiments, 61 % of the deuterium is observed in a sharp resonance peak at 0.34 ppm, also consistent with D incorporation into membrane lipids, the remainder of the D is observed at a broad resonance peak centered at 4.3 ppm, consistent with D enrichment in glycogen. Deuterium abundance in the E. coli cells grown in 10 % D2O is nearly 2X greater than that grown with 10 % D-glucose. Very subtle differences are observed in both the 1H and 13C solid

  10. Acyl chain length effects related to glycosphingolipid crypticity in phospholipid membranes: probed by 2H-NMR.

    PubMed

    Hamilton, K S; Briere, K; Jarrell, H C; Grant, C W

    1994-03-23

    Wideline 2H-NMR was used to consider the relationships amongst glycosphingolipid and phospholipid fatty acid chain length and glycosphingolipid receptor function, in a system classically associated with crypticity. Galactosyl ceramide (GalCer), having 18- or 24-carbon fatty acid, was deuterium labelled at the conformationally-restricted fatty acid alpha-carbon (C-2). 2H-NMR spectra of N-[2,2-2H2]stearoyl and N-[2,2-2H2]lignoceroyl GalCer (GalCer with 18-vs. 24-carbon selectively deuterated fatty acid) were then compared over a range of temperatures in phosphatidylcholine/cholesterol membranes in which the host phospholipid had dimyristoyl, dipalmitoyl, or distearoyl fatty acid composition. Findings were evaluated in the light of known sensitivity of antibody interaction with GalCer to temperature and to both glycolipid fatty acid chain length and host matrix fatty acid chain length. Under the conditions of experimentation, spectra were not obtainable for glycolipids having rigid body motions that were slow on the NMR timescale (10(-4)-10(-5) s)-i.e.. motions typical of non-fluid (gel phase) membranes. The systems, DPPC/cholesterol and DSPC/cholesterol, in which the original observation was made of increased antibody binding to GalCer with long fatty acid, proved to be characterised by receptor motions that were in this slow timescale for both 18:0 and 24:0 GalCer at 22-24 degrees C. Under conditions for which spectra could be obtained, those for GalCer with [2,2-2H2]lignoceroyl (24-carbon alpha-deuterated) fatty acid were qualitatively similar to those of its 18-carbon analogue in all (fluid) membranes examined. However, spectral splittings differed quantitatively between deuterated 18:0 and 24:0 GalCer at a given temperature, dependent upon host matrix. These differences were most marked at lower temperatures and in the longer chain (more ordered) matrices, DPPC/cholesterol and DSPC/cholesterol. This suggests that maximum effects of glycolipid chain length on

  11. A modularized pulse programmer for NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Mao, Wenping; Bao, Qingjia; Yang, Liang; Chen, Yiqun; Liu, Chaoyang; Qiu, Jianqing; Ye, Chaohui

    2011-02-01

    A modularized pulse programmer for a NMR spectrometer is described. It consists of a networked PCI-104 single-board computer and a field programmable gate array (FPGA). The PCI-104 is dedicated to translate the pulse sequence elements from the host computer into 48-bit binary words and download these words to the FPGA, while the FPGA functions as a sequencer to execute these binary words. High-resolution NMR spectra obtained on a home-built spectrometer with four pulse programmers working concurrently demonstrate the effectiveness of the pulse programmer. Advantages of the module include (1) once designed it can be duplicated and used to construct a scalable NMR/MRI system with multiple transmitter and receiver channels, (2) it is a totally programmable system in which all specific applications are determined by software, and (3) it provides enough reserve for possible new pulse sequences.

  12. Cell signaling, post-translational protein modifications and NMR spectroscopy

    PubMed Central

    Theillet, Francois-Xavier; Smet-Nocca, Caroline; Liokatis, Stamatios; Thongwichian, Rossukon; Kosten, Jonas; Yoon, Mi-Kyung; Kriwacki, Richard W.; Landrieu, Isabelle; Lippens, Guy

    2016-01-01

    Post-translationally modified proteins make up the majority of the proteome and establish, to a large part, the impressive level of functional diversity in higher, multi-cellular organisms. Most eukaryotic post-translational protein modifications (PTMs) denote reversible, covalent additions of small chemical entities such as phosphate-, acyl-, alkyl- and glycosyl-groups onto selected subsets of modifiable amino acids. In turn, these modifications induce highly specific changes in the chemical environments of individual protein residues, which are readily detected by high-resolution NMR spectroscopy. In the following, we provide a concise compendium of NMR characteristics of the main types of eukaryotic PTMs: serine, threonine, tyrosine and histidine phosphorylation, lysine acetylation, lysine and arginine methylation, and serine, threonine O-glycosylation. We further delineate the previously uncharacterized NMR properties of lysine propionylation, butyrylation, succinylation, malonylation and crotonylation, which, altogether, define an initial reference frame for comprehensive PTM studies by high-resolution NMR spectroscopy. PMID:23011410

  13. Membrane Protein Structure and Dynamics from NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hong, Mei; Zhang, Yuan; Hu, Fanghao

    2012-05-01

    We review the current state of membrane protein structure determination using solid-state nuclear magnetic resonance (NMR) spectroscopy. Multidimensional magic-angle-spinning correlation NMR combined with oriented-sample experiments has made it possible to measure a full panel of structural constraints of membrane proteins directly in lipid bilayers. These constraints include torsion angles, interatomic distances, oligomeric structure, protein dynamics, ligand structure and dynamics, and protein orientation and depth of insertion in the lipid bilayer. Using solid-state NMR, researchers have studied potassium channels, proton channels, Ca2+ pumps, G protein-coupled receptors, bacterial outer membrane proteins, and viral fusion proteins to elucidate their mechanisms of action. Many of these membrane proteins have also been investigated in detergent micelles using solution NMR. Comparison of the solid-state and solution NMR structures provides important insights into the effects of the solubilizing environment on membrane protein structure and dynamics.

  14. Combining solid-state NMR spectroscopy with first-principles calculations - a guide to NMR crystallography.

    PubMed

    Ashbrook, Sharon E; McKay, David

    2016-06-01

    Recent advances in the application of first-principles calculations of NMR parameters to periodic systems have resulted in widespread interest in their use to support experimental measurement. Such calculations often play an important role in the emerging field of "NMR crystallography", where NMR spectroscopy is combined with techniques such as diffraction, to aid structure determination. Here, we discuss the current state-of-the-art for combining experiment and calculation in NMR spectroscopy, considering the basic theory behind the computational approaches and their practical application. We consider the issues associated with geometry optimisation and how the effects of temperature may be included in the calculation. The automated prediction of structural candidates and the treatment of disordered and dynamic solids are discussed. Finally, we consider the areas where further development is needed in this field and its potential future impact. PMID:27117884

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

    DOE PAGESBeta

    Perras, Frédéric A.

    2016-01-01

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

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

    SciTech Connect

    Perras, Frederic A.

    2015-12-15

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

  17. New Views of Functionally Dynamic Proteins by Solution NMR Spectroscopy.

    PubMed

    Kay, Lewis E

    2016-01-29

    In the past several decades solution NMR spectroscopy has emerged as a powerful technique for the study of the structure and dynamics of proteins, providing detailed insights into biomolecular function. Herein, I provide a summary of two important areas of application, focusing on NMR studies of (i) supramolecular systems with aggregate molecular masses in the hundreds of kilodaltons and of (ii) sparsely populated and transiently formed protein states that are thermally accessible from populated ground-state conformers. The critical role of molecular dynamics in function is emphasized, highlighting the utility of the NMR technique in providing such often elusive information. PMID:26707200

  18. Analysis of experimentally shocked minerals by NMR spectroscopy

    SciTech Connect

    Cygan, R.T.; Boslough, M.B.

    1994-10-01

    The shock-loading of natural materials by an impact or explosion can result in the formation of modified and altered phases. In order to characterize the resulting material and to evaluate the extent of shock modification, the authors have used nuclear magnetic resonance (NMR) spectroscopy to examine several experimentally shocked minerals. In three related NMR studies, they have (1) examined shocked clinoptilolite, (2) performed a preliminary analysis of shocked quartz, and (3) reproduced shocked quartz results with detailed spectral deconvolutions, and extended it with NMR analysis of shocked feldspar powders.

  19. Nanoscale NMR spectroscopy and imaging of multiple nuclear species

    NASA Astrophysics Data System (ADS)

    Devience, Stephen J.; Pham, Linh M.; Lovchinsky, Igor; Sushkov, Alexander O.; Bar-Gill, Nir; Belthangady, Chinmay; Casola, Francesco; Corbett, Madeleine; Zhang, Huiliang; Lukin, Mikhail; Park, Hongkun; Yacoby, Amir; Walsworth, Ronald L.

    2015-02-01

    Nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) provide non-invasive information about multiple nuclear species in bulk matter, with wide-ranging applications from basic physics and chemistry to biomedical imaging. However, the spatial resolution of conventional NMR and MRI is limited to several micrometres even at large magnetic fields (>1 T), which is inadequate for many frontier scientific applications such as single-molecule NMR spectroscopy and in vivo MRI of individual biological cells. A promising approach for nanoscale NMR and MRI exploits optical measurements of nitrogen-vacancy (NV) colour centres in diamond, which provide a combination of magnetic field sensitivity and nanoscale spatial resolution unmatched by any existing technology, while operating under ambient conditions in a robust, solid-state system. Recently, single, shallow NV centres were used to demonstrate NMR of nanoscale ensembles of proton spins, consisting of a statistical polarization equivalent to ˜100-1,000 spins in uniform samples covering the surface of a bulk diamond chip. Here, we realize nanoscale NMR spectroscopy and MRI of multiple nuclear species (1H, 19F, 31P) in non-uniform (spatially structured) samples under ambient conditions and at moderate magnetic fields (˜20 mT) using two complementary sensor modalities.

  20. Two-dimensional NMR spectroscopy. Applications for chemists and biochemists

    SciTech Connect

    Croasmun, W.R.; Carlson, R.M.K.

    1987-01-01

    Two-dimensional nuclear magnetic resonance spectroscopy (2-D NMR) has become a very powerful class of experiments (in the hands of an adept scientist) with broad adaptability to new situations. It is the product of a happy marriage between modern pulse FT-NMR technology, with its large memory and high-speed computers, and the physicists and chemists who love to manipulate spin systems. Basic 2-D experiments are now a standard capability of modern NMR spectrometers, and this timely book intends to make 2-D NMR users of those who are familiar with normal 1-D NMR. The 2-D NMR goal is correlation of the lines of the observed NMR spectrum with other properties of the system. This book deals with applications to high-resolution spectrum analysis, utilizing either coupling between the NMR-active nuclei or chemical exchange to perform the correlation. The coupling can be scalar (through bonds) or direct through space (within 5 A). The coupling may be homonuclear (between like nuclei) or heteronuclear.

  1. CHARACTERIZATION OF METABOLITES IN SMALL FISH BIOFLUIDS AND TISSUES BY NMR SPECTROSCOPY

    EPA Science Inventory

    Nuclear magnetic resonance (NMR) spectroscopy has been utilized for assessing ecotoxicity in small fish models by means of metabolomics. Two fundamental challenges of NMR-based metabolomics are the detection limit and characterization of metabolites (or NMR resonance assignments...

  2. Protein folding on the ribosome studied using NMR spectroscopy

    PubMed Central

    Waudby, Christopher A.; Launay, Hélène; Cabrita, Lisa D.; Christodoulou, John

    2013-01-01

    NMR spectroscopy is a powerful tool for the investigation of protein folding and misfolding, providing a characterization of molecular structure, dynamics and exchange processes, across a very wide range of timescales and with near atomic resolution. In recent years NMR methods have also been developed to study protein folding as it might occur within the cell, in a de novo manner, by observing the folding of nascent polypeptides in the process of emerging from the ribosome during synthesis. Despite the 2.3 MDa molecular weight of the bacterial 70S ribosome, many nascent polypeptides, and some ribosomal proteins, have sufficient local flexibility that sharp resonances may be observed in solution-state NMR spectra. In providing information on dynamic regions of the structure, NMR spectroscopy is therefore highly complementary to alternative methods such as X-ray crystallography and cryo-electron microscopy, which have successfully characterized the rigid core of the ribosome particle. However, the low working concentrations and limited sample stability associated with ribosome–nascent chain complexes means that such studies still present significant technical challenges to the NMR spectroscopist. This review will discuss the progress that has been made in this area, surveying all NMR studies that have been published to date, and with a particular focus on strategies for improving experimental sensitivity. PMID:24083462

  3. Dual-laser absorption spectroscopy of C2H2 at 1.4 μ m

    NASA Astrophysics Data System (ADS)

    Fasci, E.; Odintsova, T. A.; Castrillo, A.; De Vizia, M. D.; Merlone, A.; Bertiglia, F.; Moretti, L.; Gianfrani, L.

    2016-04-01

    Spectroscopic parameters (line intensity factor, pressure self-broadening, and shifting coefficients) of C2H2 at 1.4 μ m were accurately measured using a dual-laser approach, based upon the technique of optical phase locking. This generated an absolute frequency scale underneath the absorption spectra. A pair of extended-cavity diode lasers was used. One of them, the probe laser, is forced to maintain a precise frequency offset from a reference laser, which is an optical frequency standard based on noise-immune cavity-enhanced optical heterodyne molecular spectroscopy. Laser-gas interaction takes place inside an isothermal multipass cell that is stabilized at the temperature of the triple point of water. The fidelity in the observation of the shape associated to the Pe(14) line of the 2 ν3+ν5 band allowed us to measure the spectroscopic parameters, with a global uncertainty for the line strength of 0.22%.

  4. Combined analysis of C-18 unsaturated fatty acids using natural abundance deuterium 2D NMR spectroscopy in chiral oriented solvents.

    PubMed

    Lesot, Philippe; Baillif, Vincent; Billault, Isabelle

    2008-04-15

    The quantitative determination of isotopic (2H/1H)i ratios at natural abundance using the SNIF-NMR protocol is a well-known method for understanding the enzymatic biosynthesis of metabolites. However, this approach is not always successful for analyzing large solutes and, specifically, is inadequate for prochiral molecules such as complete essential unsaturated fatty acids. To overcome these analytical limitations, we use the natural abundance deuterium 2D NMR (NAD 2D NMR) spectroscopy on solutes embedded in polypeptide chiral liquid crystals. This approach, recently explored for measuring (2H/1H)i ratios of small analytes (Lesot, P.; Aroulanda, C.; Billault, I. Anal. Chem. 2004, 76, 2827-2835), is a powerful way to separate the 2H signals of all nonequivalent enantioisotopomers on the basis both of the 2H quadrupolar interactions and of the 2H chemical shift. Two significant advances over our previous work are presented here and allow the complete isotopic analysis of four mono- and polyunsaturated fatty acid methyl esters: methyl oleate (1), methyl linoleate (2), methyl linolenate (3), and methyl vernoleate (4). The first consists of using NMR spectrometers operating at higher magnetic field strength (14.1 T) and equipped with a selective cryoprobe optimized for deuterium nuclei. The second is the development of Q-COSY Fz 2D NMR experiments able to produce phased 2H 2D maps after a double Fourier transformation. This combination of modern hardware and efficient NMR sequences provides a unique tool to analyze the (2H/1H)i ratios of large prochiral molecules (C-18) dissolved in organic solutions of poly(gamma-benzyl-L-glutamate) and requires smaller amounts of solute than previous study on fatty acids. For each compound (1-4), all 2H quadrupolar doublets visible in the 2D spectra have been assigned on the basis of 2H chemical shifts, isotopic data obtained from isotropic quantitative NAD NMR, and by an interspectral comparison of the anisotropic NAD spectra of four

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

    PubMed

    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

  6. MULTIVARIATE CURVE RESOLUTION OF NMR SPECTROSCOPY METABONOMIC DATA

    EPA Science Inventory

    Sandia National Laboratories is working with the EPA to evaluate and develop mathematical tools for analysis of the collected NMR spectroscopy data. Initially, we have focused on the use of Multivariate Curve Resolution (MCR) also known as molecular factor analysis (MFA), a tech...

  7. Order and dynamics in mixtures of membrane glucolipids from Acholeplasma laidlawii studied by sup 2 H NMR

    SciTech Connect

    Eriksson, P.O.; Rilfors, L.; Lundberg, A.; Lindblom, G.; Wieslander, A. )

    1991-05-21

    The two dominant glucolipids in Acholeplasma laidlawii, viz., 1,2-diacyl-3-O-({alpha}-D-glucopyranosyl)-sn-glycerol (MGlcDG) and 1,2-diacyl-3-O-({alpha}-D-glucopyranosyl-(1{yields}2)-O-{alpha}-D-glucopyranosyl)-sn-glycerol (DGlcDG), have markedly different phase behavior. MGlcDG has an ability to form nonlamellar phases, whereas DGlcDG only forms lamellar phases. For maintenance of a stable lipid bilayer, the polar headgroup composition in A. laidlawii is metabolically regulated in vivo, in response to changes in the growth conditions. To investigate the mechanism behind the lipid regulation the authors have here studied bilayers of mixtures of unsaturated MGlcDG and DGlcDG, containing a small fraction of biosynthetically incorporated per-deuterated palmitic acid, with {sup 2}H NMR. The order-parameter profile of the acyl chains and an apparent transverse spin relaxation rate (R{sub 2}) were determined from dePaked quadrupole-echo spectra. The variation of order with lipid composition is rationalized from simple packing constraints. The relaxation data indicate the presence of slow reorientational motions, such as collective bilayer fluctuations and/or lipid lateral diffusion over a curved bilayer surface. The variation of acyl-chain order and bilayer curvature and/or fluctuations with sample composition are discussed in relation to the tendency of MGlcDG to form nonlamellar phases in vitro and in relation to the lipid regulation in vivo.

  8. Recovering Invisible Signals by Two-Field NMR Spectroscopy.

    PubMed

    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. PMID:27417269

  9. Ultrafast 2D NMR: an emerging tool in analytical spectroscopy.

    PubMed

    Giraudeau, Patrick; Frydman, Lucio

    2014-01-01

    Two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy is widely used in chemical and biochemical analyses. Multidimensional NMR is also witnessing increased use in quantitative and metabolic screening applications. Conventional 2D NMR experiments, however, are affected by inherently long acquisition durations, arising from their need to sample the frequencies involved along their indirect domains in an incremented, scan-by-scan nature. A decade ago, a so-called ultrafast (UF) approach was proposed, capable of delivering arbitrary 2D NMR spectra involving any kind of homo- or heteronuclear correlation, in a single scan. During the intervening years, the performance of this subsecond 2D NMR methodology has been greatly improved, and UF 2D NMR is rapidly becoming a powerful analytical tool experiencing an expanded scope of applications. This review summarizes the principles and main developments that have contributed to the success of this approach and focuses on applications that have been recently demonstrated in various areas of analytical chemistry--from the real-time monitoring of chemical and biochemical processes, to extensions in hyphenated techniques and in quantitative applications. PMID:25014342

  10. Ultrafast 2D NMR: An Emerging Tool in Analytical Spectroscopy

    NASA Astrophysics Data System (ADS)

    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. Silver-109 NMR spectroscopy of inorganic solids.

    PubMed

    Penner, Glenn H; Li, Wenli

    2004-09-01

    In this study the (109)Ag NMR spectra of the following solid inorganic silver-containing compounds were investigated: AgNO(3), AgNO(2), Ag(2)SO(4), Ag(2)SO(3), AgCO(3), Ag(3)PO(4), AgCl, AgBr, AgI, AgSO(3)CH(3), silver p-toluenesulfonate, NaAg(CN)(2), KAg(CN)(2), K(3)Ag(CN)(4), Me(4)NAgCl(2), silver diethylthiocarbamate, silver lactate, silver acetate, silver citrate, and bis[(N,N(1)-di-tert-butylformamidinato)silver(I)]. The magic angle spinning (MAS) spectra of all compounds were obtained. In some cases, when protons were available, the (1)H to (109)Ag cross-polarization (CP) technique was used to enhance the signal and shorten the experimental relaxation delay. It was possible to obtain slow MAS (or CP/MAS) or nonspinning spectra for 10 samples, allowing the determination of the principal components of the (109)Ag chemical shift (CS) tensors. The isotropic chemical shifts and the CS tensors are discussed in light of the available crystal structures. The need for an accepted standard for referencing (109)Ag chemical shifts and the use of AgSO(3)CH(3) as a CP setup sample are also discussed. PMID:15332810

  12. Mobile sensor for high resolution NMR spectroscopy and imaging

    NASA Astrophysics Data System (ADS)

    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.

  13. RNA structure determination by solid-state NMR spectroscopy

    PubMed Central

    Marchanka, Alexander; Simon, Bernd; Althoff-Ospelt, Gerhard; Carlomagno, Teresa

    2015-01-01

    Knowledge of the RNA three-dimensional structure, either in isolation or as part of RNP complexes, is fundamental to understand the mechanism of numerous cellular processes. Because of its flexibility, RNA represents a challenge for crystallization, while the large size of cellular complexes brings solution-state NMR to its limits. Here, we demonstrate an alternative approach on the basis of solid-state NMR spectroscopy. We develop a suite of experiments and RNA labeling schemes and demonstrate for the first time that ssNMR can yield a RNA structure at high-resolution. This methodology allows structural analysis of segmentally labelled RNA stretches in high-molecular weight cellular machines—independent of their ability to crystallize— and opens the way to mechanistic studies of currently difficult-to-access RNA-protein assemblies. PMID:25960310

  14. Optical emission spectroscopy study of premixed C2H4/O2 and C2H4/C2H2/O2 flames for diamond growth with and without CO2 laser excitation

    NASA Astrophysics Data System (ADS)

    He, X. N.; Gebre, T.; Shen, X. K.; Xie, Z. Q.; Zhou, Y. S.; Lu, Y. F.

    2010-02-01

    Optical emission spectroscopy (OES) measurements were carried out to study premixed C2H4/O2 and C2H4/C2H2/O2 combustion flame for diamond deposition with and without a CO2 laser excitation. Strong emissions from radicals C2 and CH were observed in the visible range in all the OES spectra acquired. By adding a continuous-wave CO2 laser to irradiate the flame at a wavelength of 10.591 μm, the common CO2 laser wavelength, it was discovered that the emission intensities of the C2 and CH radicals were increased due to the laser beam induced excitation. OES measurements of the C2 and CH radicals were performed using different gas combinations and laser powers. The rotational temperatures in the flame were determined by analyzing the spectra of the R-branch of the A2Δ-->X2Π (0, 0) electronic transition near 430 nm (CH band head). Information obtained from the OES spectra, including the emission intensities of the C2 and CH radicals, the intensity ratios, and the rotational temperatures, was integrated into the study of diamond deposition on tungsten carbide substrates for mechanism analysis of the laser induced vibrational excitation and laser-assisted diamond deposition.

  15. 103Rh NMR spectroscopy and its application to rhodium chemistry.

    PubMed

    Ernsting, Jan Meine; Gaemers, Sander; Elsevier, Cornelis J

    2004-09-01

    Rhodium is used for a number of large processes that rely on homogeneous rhodium-catalyzed reactions, for instance rhodium-catalyzed hydroformylation of alkenes, carbonylation of methanol to acetic acid and hydrodesulfurization of thiophene derivatives (in crude oil). Many laboratory applications in organometallic chemistry and catalysis involve organorhodium chemistry and a wealth of rhodium coordination compounds is known. For these and other areas, 103Rh NMR spectroscopy appears to be a very useful analytical tool. In this review, most of the literature concerning 103Rh NMR spectroscopy published from 1989 up to and including 2003 has been covered. After an introduction to several experimental methods for the detection of the insensitive 103Rh nucleus, a discussion of factors affecting the transition metal chemical shift is given. Computational aspects and calculations of chemical shifts are also briefly addressed. Next, the application of 103Rh NMR in coordination and organometallic chemistry is elaborated in more detail by highlighting recent developments in measurement and interpretation of 103Rh NMR data, in relation to rhodium-assisted reactions and homogeneous catalysis. The dependence of the 103Rh chemical shift on the ligands at rhodium in the first coordination sphere, on the complex geometry, oxidation state, temperature, solvent and concentration is treated. Several classes of compounds and special cases such as chiral rhodium compounds are reviewed. Finally, a section on scalar coupling to rhodium is provided. PMID:15307053

  16. Molecular structure by two-dimensional NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Freeman, R.

    Two examples are presented of the use of two-dimensional NMR spectroscopy to solve molecular structure problems. The first is called correlation spectroscopy (COSY) and it allows us to disentangle a complex network of spin-spin couplings. By dispersing the NMR information in two frequency dimensions, it facilitates the analysis of very complex spectra of organic and biochemical molecules, normally too crowded to be tractable. The second application exploits the special properties of multiple-quantum coherence to explore the molecular framework one CC linkage at a time. The natural product panamine is used as a test example; with some supplementary evidence, the structure of this six-ringed heterocyclic molecule is elucidated from the double-quantum filtered two-dimensional spectrum.

  17. Single-sided sensor for high-resolution NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Perlo, J.; Casanova, F.; Blümich, B.

    2006-06-01

    The unavoidable spatial inhomogeneity of the static magnetic field generated by open sensors has precluded their use for high-resolution NMR spectroscopy. In fact, this application was deemed impossible because these field variations are usually orders of magnitude larger than those created by the microscopic structure of the molecules to be detected. Recently, chemical shift resolved NMR spectra were observed for the first time outside a portable single-sided magnet by implementing a method that exploits inhomogeneities in the rf field designed to reproduce variations of the static magnetic field [J. Perlo, V. Demas, F. Casanova, C.A. Meriles, J. Reimer, A. Pines, B. Blümich, High-resolution spectroscopy with a portable single-sided sensor, Science 308 (2005) 1279]. In this communication, we describe in detail the magnet system built from permanent magnets as well as the rf coil geometry used to compensate the static field variations.

  18. 2H and 27Al Solid-State NMR Study of the Local Environments in Al-Doped 2-Line Ferrihydrite, Goethite, and Lepidocrocite

    PubMed Central

    2015-01-01

    Although substitution of aluminum into iron oxides and oxyhydroxides has been extensively studied, it is difficult to obtain accurate incorporation levels. Assessing the distribution of dopants within these materials has proven especially challenging because bulk analytical techniques cannot typically determine whether dopants are substituted directly into the bulk iron oxide or oxyhydroxide phase or if they form separate, minor phase impurities. These differences have important implications for the chemistry of these iron-containing materials, which are ubiquitous in the environment. In this work, 27Al and 2H NMR experiments are performed on series of Al-substituted goethite, lepidocrocite, and 2-line ferrihydrite in order to develop an NMR method to track Al substitution. The extent of Al substitution into the structural frameworks of each compound is quantified by comparing quantitative 27Al MAS NMR results with those from elemental analysis. Magnetic measurements are performed for the goethite series to compare with NMR measurements. Static 27Al spin–echo mapping experiments are used to probe the local environments around the Al substituents, providing clear evidence that they are incorporated into the bulk iron phases. Predictions of the 2H and 27Al NMR hyperfine contact shifts in Al-doped goethite and lepidocrocite, obtained from a combined first-principles and empirical magnetic scaling approach, give further insight into the distribution of the dopants within these phases. PMID:26321790

  19. NMR spectroscopy to follow reaction progress in ionic liquids.

    PubMed

    Butler, Bradley J; Thomas, Donald S; Hook, James M; Harper, Jason B

    2016-06-01

    In order to understand reaction outcomes in ionic liquids, it is crucial to be able to follow the progress of these reactions. This review highlights the advantages of NMR spectroscopy over other analytical techniques in following reaction progress in ionic liquids, particularly addressing the practical aspects of the methodology and highlighting the range of processes that can be readily followed. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25287592

  20. NMR clinical imaging and spectroscopy: Its impact on nuclear medicine

    SciTech Connect

    Not Available

    1990-02-02

    This is a collection of four papers describing aspects of past and future use of nuclear magnetic resonance as a clinical diagnostic tool. The four papers are entitled (1) What Does NMR Offer that Nuclear Medicine Does Not by Jerry W. Froelich, (2) Oncological Imaging: Now, Future and Impact Jerry W. Froelich, (3) Magnetic Resonance Spectroscopy/Spectroscopic Imaging and Nuclear Medicine: Past, Present and Future by H. Cecil Charles, and (4) MR Cardiology: Now, Future and Impact by Robert J. Herfkens.

  1. NMR clinical imaging and spectroscopy: Its impact on nuclear medicine

    SciTech Connect

    Not Available

    1990-02-02

    This is a collection of four papers describing aspects of past and future use of nuclear magnetic resonance as a clinical diagnostic tool. The four papers are entitled (1) What Does NMR Offer that Nuclear Medicine Does Not? by Jerry W. Froelich, (2) Oncological Imaging: Now, Future and Impact Jerry W. Froelich, (3) Magnetic Resonance Spectroscopy/Spectroscopic Imaging and Nuclear Medicine: Past, Present and Future by H. Cecil Charles, and (4) MR Cardiology: Now, Future and Impact by Robert J. Herfkens.

  2. 1H- and 2H-NMR studies of a fragment of PMP1, a regulatory subunit associated with the yeast plasma membrane H(+)-ATPase. Conformational properties and lipid-peptide interactions.

    PubMed

    Beswick, V; Roux, M; Navarre, C; Coïc, Y M; Huynh-Dinh, T; Goffeau, A; Sanson, A; Neumann, J M

    1998-01-01

    PMP1 is a 38-residue polypeptide associated with the yeast plasma membrane H(+)-ATPase, found to regulate the enzyme activity. To investigate the molecular basis of the PMP1 biological function, the conformational properties of a synthetic PMP1 fragment, A18-F38, comprising the predicted C-terminal cytoplasmic domain and a part of the transmembrane anchor have been studied by 1H- and 2H-NMR spectroscopies. High resolution 1H-NMR experiments showed that, in deuterated DPC micelles, the A18-G34 segment adopts a well defined helix conformation. Our data suggest that the whole PMP1 molecule forms a unique helix whose axis might be slightly tilted with respect to the bilayer normal. Protonated DPC, DMPC and DMPS were incorporated in deuterated micelles containing the PMP1 fragment for studying lipid-peptide interactions. Unusually strong and selective intermolecular NOEs between lipid chain and peptide side chain protons, especially those of the unique Trp residue, were observed. Solid state 2H-NMR experiments performed on pure deuterated POPC and mixed deuterated POPC:POPS (5:1) bilayers revealed that the PMP1 fragment specifically interacts with negatively charged PS lipids. PMID:9782385

  3. In situ solid-state NMR spectroscopy of electrochemical cells: batteries, supercapacitors, and fuel cells.

    PubMed

    Blanc, Frédéric; Leskes, Michal; Grey, Clare P

    2013-09-17

    prevent dendrite formation. The in situ method was also applied to monitor (by (11)B NMR) electrochemical double-layer formation in supercapacitors in real time. Though this method is useful, it comes with challenges. The separation of the contributions from the different cell components in the NMR spectra is not trivial because of overlapping resonances. In addition, orientation-dependent NMR interactions, including the spatial- and orientation-dependent bulk magnetic susceptibility (BMS) effects, can lead to resonance broadening. Efforts to understand and mitigate these BMS effects are discussed in this Account. The in situ NMR investigation of fuel cells initially focused on the surface electrochemistry at the electrodes and the electrochemical oxidation of methanol and CO to CO2 on the Pt cathode. On the basis of the (13)C and (195)Pt NMR spectra of the adsorbates and electrodes, CO adsorbed on Pt and other reaction intermediates and complete oxidation products were detected and their mode of binding to the electrodes investigated. Appropriate design and engineering of the NMR hardware has allowed researchers to integrate intact direct methanol fuel cells into NMR probes. Chemical transformations of the circulating methanol could be followed and reaction intermediates could be detected in real time by either (2)H or (13)C NMR spectroscopy. By use of the in situ NMR approach, factors that control fuel cell performance, such as methanol cross over and catalyst performance, were identified. PMID:24041242

  4. Crystal structure, NMR study, dielectric relaxation and AC conductivity of a new compound [Cd3(SCN)2Br6(C2H9N2)2]n

    NASA Astrophysics Data System (ADS)

    Saidi, K.; Kamoun, S.; Ayedi, H. Ferid; Arous, M.

    2013-11-01

    The crystal structure, the 13C NMR spectroscopy and the complex impedance have been carried out on [Cd3(SCN)2Br6(C2H9N2)2]n. Crystal structure shows a 2D polymeric network built up of two crystallographically independent cadmium atoms with two different octahedral coordinations. This compound exhibits a phase transition at (T=355±2 K) which has been characterized by differential scanning calorimetry (DSC), X-rays powder diffraction, AC conductivity and dielectric measurements. Examination of 13C CP/MAS line shapes shows indirect spin-spin coupling (14N and 13C) with a dipolar coupling constant of 1339 Hz. The AC conductivity of this compound has been carried out in the temperature range 325-376 K and the frequency range from 10-2 Hz to 10 MHz. The impedance data were well fitted to two equivalent electrical circuits. The results of the modulus study reveal the presence of two distinct relaxation processes. One, at low frequency side, is thermally activated due to the ionic conduction of the crystal and the other, at higher frequency side, gradually disappears when temperature reaches 355 K which is attributed to the localized dipoles in the crystal. Moreover, the temperature dependence of DC-conductivity in both phases follows the Arrhenius law and the frequency dependence of σ(ω,T) follows Jonscher's universal law. The near values of activation energies obtained from the conductivity data and impedance confirm that the transport is through the ion hopping mechanism.

  5. Fluid Mechanical Matching of H+-ATP Synthase Subunit c-Ring with Lipid Membranes Revealed by 2H Solid-State NMR

    PubMed Central

    Kobayashi, Masatoshi; Struts, Andrey V.; Fujiwara, Toshimichi; Brown, Michael F.; Akutsu, Hideo

    2008-01-01

    The F1Fo-ATP synthase utilizes the transmembrane H+ gradient for the synthesis of ATP. Fo subunit c-ring plays a key role in transporting H+ through Fo in the membrane. We investigated the interactions of Escherichia coli subunit c with dimyristoylphosphatidylcholine (DMPC-d54) at lipid/protein ratios of 50:1 and 20:1 by means of 2H-solid-state NMR. In the liquid-crystalline state of DMPC, the 2H-NMR moment values and the order parameter (SCD) profile were little affected by the presence of subunit c, suggesting that the bilayer thickness in the liquid-crystalline state is matched to the transmembrane hydrophobic surface of subunit c. On the other hand, hydrophobic mismatch of subunit c with the lipid bilayer was observed in the gel state of DMPC. Moreover, the viscoelasticity represented by a square-law function of the 2H-NMR relaxation was also little influenced by subunit c in the fluid phase, in contrast with flexible nonionic detergents or rigid additives. Thus, the hydrophobic matching of the lipid bilayer to subunit c involves at least two factors, the hydrophobic length and the fluid mechanical property. These findings may be important for the torque generation in the rotary catalytic mechanism of the F1Fo-ATPse molecular motor. PMID:18310246

  6. Advancements in waste water characterization through NMR spectroscopy: review.

    PubMed

    Alves Filho, Elenilson G; Alexandre e Silva, Lorena M; Ferreira, Antonio G

    2015-09-01

    There are numerous organic pollutants that lead to several types of ecosystem damage and threaten human health. Wastewater treatment plants are responsible for the removal of natural and anthropogenic pollutants from the sewage, and because of this function, they play an important role in the protection of human health and the environment. Nuclear magnetic resonance (NMR) has proven to be a valuable analytical tool as a result of its versatility in characterizing both overall chemical composition as well as individual species in a wide range of mixtures. In addition, NMR can provide physical information (rigidity, dynamics, etc.) as well as permit in depth quantification. Hyphenation with other techniques such as liquid chromatography, solid phase extraction and mass spectrometry creates unprecedented capabilities for the identification of novel and unknown chemical species. Thus, NMR is widely used in the study of different components of wastewater, such as complex organic matter (fulvic and humic acids), sludge and wastewater. This review article summarizes the NMR spectroscopy methods applied in studies of organic pollutants from wastewater to provide an exhaustive review of the literature as well as a guide for readers interested in this topic. PMID:25280056

  7. 2H NMR study of phase transition and hydrogen dynamics in hydrogen bonded organic antiferroelectric 55DMBP-H2ca

    NASA Astrophysics Data System (ADS)

    Asaji, Tetsuo; Hara, Masamichi; Fujimori, Hiroki; Hagiwara, Shoko

    2016-12-01

    Hydrogen dynamics in one-dimensional hydrogen bonded organic antiferroelectric, co-crystal of 5,5'-dimethyl-2,2'-bipyridine (55DMBP) and chloranilic acid (H2ca), was investigated by use of 2H high resolution solid-state NMR. The two types of hydrogen bonds O-H …N and N+-H … O - in the antiferroelectric phase were clearly observed as the splitting of the side band of the 2H MAS NMR spectra of the acid-proton deuterated compound 55DMBP-D 2ca. The temperature dependence of the spin-lattice relaxation time was measured of the N+-H and O-H deuterons, respectively. It was suggested that the motion of the O-H deuteron is already in the antiferroelectric phase in the fast-motion regime in the NMR time scale, while that of the N+-H deuteron is a slow motion. In the high-temperature paraelectric phase, the both deuterons become equivalent and the fast motion of the deuterons in the NMR time scale is taking place with the activation energy of 7.9 kJ mol-1.

  8. NMR spectroscopy of proteins encapsulated in a positively charged surfactant.

    PubMed

    Lefebvre, Brian G; Liu, Weixia; Peterson, Ronald W; Valentine, Kathleen G; Wand, A Joshua

    2005-07-01

    Traditionally, large proteins, aggregation-prone proteins, and membrane proteins have been difficult to examine by modern multinuclear and multidimensional solution NMR spectroscopy. A major limitation presented by these protein systems is that their slow molecular reorientation compromises many aspects of the more powerful solution NMR methods. Several approaches have emerged to deal with the various spectroscopic difficulties arising from slow molecular reorientation. One of these takes the approach of actively seeking to increase the effective rate of molecular reorientation by encapsulating the protein of interest within the protective shell of a reverse micelle and dissolving the resulting particle in a low viscosity fluid. Since the encapsulation is largely driven by electrostatic interactions, the preparation of samples of acidic proteins suitable for NMR spectroscopy has been problematic owing to the paucity of suitable cationic surfactants. Here, it is shown that the cationic surfactant CTAB may be used to prepare samples of encapsulated anionic proteins dissolved in low viscosity solvents. In a more subtle application, it is further shown that this surfactant can be employed to encapsulate a highly basic protein, which is completely denatured upon encapsulation using an anionic surfactant. PMID:15949753

  9. Solid-State NMR Spectroscopy of Protein Complexes

    PubMed Central

    Sun, Shangjin; Han, Yun; Paramasivam, Sivakumar; Yan, Si; Siglin, Amanda E.; Williams, John C.; Byeon, In-Ja L.; Ahn, Jinwoo; Gronenborn, Angela M.; Polenova, Tatyana

    2016-01-01

    Protein-protein interactions are vital for many biological processes. These interactions often result in the formation of protein assemblies that are large in size, insoluble and difficult to crystallize, and therefore are challenging to study by structure biology techniques, such as single crystal X-ray diffraction and solution NMR spectroscopy. Solid-state NMR (SSNMR) spectroscopy is emerging as a promising technique for studies of such protein assemblies because it is not limited by molecular size, solubility or lack of long-range order. In the past several years, we have applied magic angle spinning SSNMR based methods to study several protein complexes. In this chapter, we discuss the general solid-state NMR methodologies employed for structural and dynamics analyses of protein complexes with specific examples from our work on thioredoxin reassemblies, HIV-1 capsid protein assemblies and microtubule-associated protein assemblies. We present protocols for sample preparation and characterization, pulse sequences, SSNMR spectra collection and data analysis. PMID:22167681

  10. Simulation of selective pulse techniques for localized NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Garwood, Michael; Schleich, Thomas; Robin Bendall, M.

    The results of a computer simulation investigation delineating the limits of resolution, sensitivity, and accuracy of the depth- resolved suface-coil spectroscopy (DRESS), volume-selective excitation (VSE), and image-selected in vivo spectroscopy (ISIS) methods for achieving spatially localized NMR spectroscopy are presented. A computer program, which numerically solves the Bloch equations for variable input parameters, is used to simulate the spatial localization afforded by each technique. Because the numerical solution of the Bloch equations describes the behavior of the bulk magnetization with great precision, the simulations provide an objective and realistic means of evaluating the performance of the individual localization schemes and reveal nuances and limitations not discussed in the original experimental papers. The results of this computer simulation study should encourage the optimization of localization methodology for use in specific applications.

  11. Perspectives on DNP-enhanced NMR spectroscopy in solutions

    NASA Astrophysics Data System (ADS)

    van Bentum, Jan; van Meerten, Bas; Sharma, Manvendra; Kentgens, Arno

    2016-03-01

    More than 60 years after the seminal work of Albert Overhauser on dynamic nuclear polarization by dynamic cross relaxation of coupled electron-nuclear spin systems, the quest for sensitivity enhancement in NMR spectroscopy is as pressing as ever. In this contribution we will review the status and perspectives for dynamic nuclear polarization in the liquid state. An appealing approach seems to be the use of supercritical solvents that may allow an extension of the Overhauser mechanism towards common high magnetic fields. A complementary approach is the use of solid state DNP on frozen solutions, followed by a rapid dissolution or in-situ melting step and NMR detection with substantially enhanced polarization levels in the liquid state. We will review recent developments in the field and discuss perspectives for the near future.

  12. Perspectives on DNP-enhanced NMR spectroscopy in solutions.

    PubMed

    van Bentum, Jan; van Meerten, Bas; Sharma, Manvendra; Kentgens, Arno

    2016-03-01

    More than 60 years after the seminal work of Albert Overhauser on dynamic nuclear polarization by dynamic cross relaxation of coupled electron-nuclear spin systems, the quest for sensitivity enhancement in NMR spectroscopy is as pressing as ever. In this contribution we will review the status and perspectives for dynamic nuclear polarization in the liquid state. An appealing approach seems to be the use of supercritical solvents that may allow an extension of the Overhauser mechanism towards common high magnetic fields. A complementary approach is the use of solid state DNP on frozen solutions, followed by a rapid dissolution or in-situ melting step and NMR detection with substantially enhanced polarization levels in the liquid state. We will review recent developments in the field and discuss perspectives for the near future. PMID:26920831

  13. Recombinant Kinase Production and Fragment Screening by NMR Spectroscopy.

    PubMed

    Han, Byeonggu; Ahn, Hee-Chul

    2016-01-01

    During the past decade fragment-based drug discovery (FBDD) has rapidly evolved and several drugs or drug candidates developed by FBDD approach are clinically in use or in clinical trials. For example, vemurafenib, a V600E mutated BRAF inhibitor, was developed by utilizing FBDD approach and approved by FDA in 2011. In FBDD, screening of fragments is the starting step for identification of hits and lead generation. Fragment screening usually relies on biophysical techniques by which the protein-bound small molecules can be detected. NMR spectroscopy has been extensively used to study the molecular interaction between the protein and the ligand, and has many advantages in fragment screening over other biophysical techniques. This chapter describes the practical aspects of fragment screening by saturation transfer difference NMR. PMID:26501900

  14. Infrared spectrum of the disilane cation (Si2H6+) from Ar-tagging spectroscopy.

    PubMed

    Savoca, Marco; George, Martin Andreas Robert; Langer, Judith; Dopfer, Otto

    2013-02-28

    The infrared spectrum of the disilane cation, Si(2)H(6)(+), in its (2)A(1g) ground state is inferred from photodissociation of cold Si(2)H(6)(+)-Ar(n) complexes (n = 1, 2). Vibrational analysis is consistent with a D(3d) symmetric structure of H(3)SiSiH(3)(+) generated by ionization from the bonding σ(SiSi) orbital. Structural, vibrational, and electronic properties of Si(2)H(6)((+)) and Si(2)H(6)(+)-Ar(1,2) are determined at the MP2/aug-cc-pVTZ and B3LYP/aug-cc-pVTZ levels. Ar ligands bind weakly at the C(3) axis on opposite sides to Si(2)H(6)(+) with only a minor impact on the Si(2)H(6)(+) properties. The calculations reveal a low-energy H(2)SiHSiH(3)(+) isomer with C(s) symmetry and a Si-H-Si bridge, which is only ~15 kJ mol(-1) above the D(3d) structure. PMID:23325390

  15. Maximum entropy signal processing in practical NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Sibisi, Sibusiso; Skilling, John; Brereton, Richard G.; Laue, Ernest D.; Staunton, James

    1984-10-01

    NMR spectroscopy is intrinsically insensitive, a frequently serious limitation especially in biochemical applications where sample size is limited and compounds may be too insoluble or unstable for data to be accumulated over long periods. Fourier transform (FT) NMR was developed by Ernst1 to speed up the accumulation of useful data, dramatically improving the quality of spectra obtained in a given observing time by recording the free induction decay (FID) data directly in time, at the cost of requiring numerical processing. Ernst also proposed that more information could be obtained from the spectrum if the FID was multiplied by a suitable apodizing function before being Fourier transformed. For example (see ref. 2), an increase in sensitivity can result from the use of a matched filter1, whereas an increase in resolution can be achieved by the use of gaussian multiplication1,3, application of sine bells4-8 or convolution difference9. These methods are now used routinely in NMR data processing. The maximum entropy method (MEM)10 is theoretically capable of achieving simultaneous enhancement in both respects11, and this has been borne out in practice in other fields where it has been applied. However, this technique requires relatively heavy computation. We describe here the first practical application of MEM to NMR, and we analyse 13C and 1H NMR spectra of 2-vinyl pyridine. Compared with conventional spectra, MEM gives considerable suppression of noise, accompanied by significant resolution enhancement. Multiplets in the 1H spectra are resolved better leading to improved visual clarity.

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

    SciTech Connect

    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.

  17. Synthesis, structure and NMR characterization of a new monomeric aluminophosphate [ dl-Co(en) 3] 2[Al(HPO 4) 2(H 1.5PO 4) 2(H 2PO 4) 2](H 3PO 4) 4 containing four different types of monophosphates

    NASA Astrophysics Data System (ADS)

    Chen, Peng; Li, Jiyang; Xu, Jun; Duan, Fangzheng; Deng, Feng; Xu, Ruren

    2009-03-01

    A new zero-dimensional (0D) aluminophosphate monomer [ dl-Co(en) 3] 2[Al(HPO 4) 2(H 1.5PO 4) 2(H 2PO 4) 2](H 3PO 4) 4 (designated AlPO-CJ38) with Al/P ratio of 1/6 has been solvothermally prepared by using racemic cobalt complex dl-Co(en) 3Cl 3 as the template. The Al atom is octahedrally linked to six P atoms via bridging oxygen atoms, forming a unique [Al(HPO 4) 2(H 1.5PO 4) 2(H 2PO 4) 2] 6- monomer. Notably, there exists intramolecular symmetrical O⋯H⋯O bonds, which results in pseudo-4-rings stabilized by the strong H-bonding interactions. The structure is also featured by the existence of four different types of monophosphates that have been confirmed by 31P NMR and 1H NMR spectra. The crystal data are as follows: AlPO-CJ38, [ dl-Co(en) 3] 2[Al(HPO 4) 2(H 1.5PO 4) 2(H 2PO 4) 2](H 3PO 4) 4, M = 1476.33, monoclinic, C2/ c (No. 15), a = 36.028(7) Å, b = 8.9877(18) Å, c = 16.006(3) Å, β = 100.68(3)°, U = 5093.2(18) Å 3,Z = 4, R1 = 0.0509 ( I > 2 σ( I)) and wR2 = 0.1074 (all data). CCDC number 689491.

  18. TOCCATA: a customized carbon total correlation spectroscopy NMR metabolomics database.

    PubMed

    Bingol, Kerem; Zhang, Fengli; Bruschweiler-Li, Lei; Brüschweiler, Rafael

    2012-11-01

    A customized metabolomics NMR database, TOCCATA, is introduced, which uses (13)C chemical shift information for the reliable identification of metabolites, their spin systems, and isomeric states. TOCCATA, whose information was derived from the BMRB and HMDB databases and the literature, currently contains 463 compounds and 801 spin systems, and it can be used through a publicly accessible web server. TOCCATA allows the identification of metabolites in the submillimolar concentration range from (13)C-(13)C total correlation spectroscopy experiments of complex mixtures, which is demonstrated for an Escherichia coli cell lysate, a carbohydrate mixture, and an amino acid mixture, all of which were uniformly (13)C-labeled. PMID:23016498

  19. Twist, tilt, and orientational order at the nematic to twist-bend nematic phase transition of 1″,9″-bis(4-cyanobiphenyl-4'-yl) nonane: A dielectric, 2H NMR, and calorimetric study

    NASA Astrophysics Data System (ADS)

    Robles-Hernández, Beatriz; Sebastián, Nerea; de la Fuente, M. Rosario; López, David O.; Diez-Berart, Sergio; Salud, Josep; Ros, M. Blanca; Dunmur, David A.; Luckhurst, Geoffrey R.; Timimi, Bakir A.

    2015-12-01

    The nature of the nematic-nematic phase transition in the liquid crystal dimer 1″,9″-bis(4-cyanobiphenyl-4'-yl) nonane (CB9CB) has been investigated using techniques of calorimetry, dynamic dielectric response measurements, and 2H NMR spectroscopy. The experimental results for CB9CB show that, like the shorter homologue CB7CB, the studied material exhibits a normal nematic phase, which on cooling undergoes a transition to the twist-bend nematic phase (NTB), a uniaxial nematic phase, promoted by the average bent molecular shape, in which the director tilts and precesses describing a conical helix. Modulated differential scanning calorimetry has been used to analyze the nature of the NTB-N phase transition, which is found to be weakly first order, but close to tricritical. Additionally broadband dielectric spectroscopy and 2H magnetic resonance studies have revealed information on the structural characteristics of the recently discovered twist-bend nematic phase. Analysis of the dynamic dielectric response in both nematic phases has provided an estimate of the conical angle of the heliconical structure for the NTB phase. Capacitance measurements of the electric-field realignment of the director in initially planar aligned cells have yielded values for the splay and bend elastic constants in the high temperature nematic phase. The bend elastic constant is small and decreases with decreasing temperature as the twist-bend phase is approached. This behavior is expected theoretically and has been observed in materials that form the twist-bend nematic phase. 2H NMR measurements characterize the chiral helical twist identified in the twist-bend nematic phase and also allow the determination of the temperature dependence of the conical angle and the orientational order parameter with respect to the director.

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

    PubMed

    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

  1. Zwitterionic phosphorylated quinines as chiral solvating agents for NMR spectroscopy.

    PubMed

    Rudzińska-Szostak, Ewa; Górecki, Łukasz; Berlicki, Łukasz; Ślepokura, Katarzyna; Mucha, Artur

    2015-10-01

    Because of their unique 3D arrangement, naturally occurring Cinchona alkaloids and their synthetic derivatives have found wide-ranging applications in chiral recognition. Recently, we determined the enantioselective properties of C-9-phosphate mixed triesters of quinine as versatile chiral solvating agents in nuclear magnetic resonance (NMR) spectroscopy. In the current study, we introduce new zwitterionic members of this class of molecules containing a negatively charged phosphate moiety (i.e., ethyl, n-butyl and phenyl hydrogen quininyl phosphate). An efficient approach for synthesizing these compounds is elaborated, and full characterization, including conformational and autoaggregation phenomena studies, was performed. Therefore, their ability to induce NMR anisochrony of selected enantiomeric substrates (i.e., primarily N-DNB-protected amino acids and their methyl esters) was analyzed compared to uncharged diphenyl quininyl phosphate and its positively charged quaternary ammonium hydrochloride salt. In addition, (1) H and (13) C NMR experiments revealed their enantiodiscrimination potential toward novel analytes, such as secondary amines and nonprotected amino acids. PMID:26415853

  2. 13C NMR spectroscopy applications to brain energy metabolism

    PubMed Central

    Rodrigues, Tiago B.; Valette, Julien; Bouzier-Sore, Anne-Karine

    2013-01-01

    13C nuclear magnetic resonance (NMR) spectroscopy is the method of choice for studying brain metabolism. Indeed, the most convincing data obtained to decipher metabolic exchanges between neurons and astrocytes have been obtained using this technique, thus illustrating its power. It may be difficult for non-specialists, however, to grasp thefull implication of data presented in articles written by spectroscopists. The aim of the review is, therefore, to provide a fundamental understanding of this topic to facilitate the non-specialists in their reading of this literature. In the first part of this review, we present the metabolic fate of 13C-labeled substrates in the brain in a detailed way, including an overview of some general neurochemical principles. We also address and compare the various spectroscopic strategies that can be used to study brain metabolism. Then, we provide an overview of the 13C NMR experiments performed to analyze both intracellular and intercellular metabolic fluxes. More particularly, the role of lactate as a potential energy substrate for neurons is discussed in the light of 13C NMR data. Finally, new perspectives and applications offered by 13C hyperpolarization are described. PMID:24367329

  3. Interaction of the replication terminator protein of Bacillus subtilis with DNA probed by NMR spectroscopy

    SciTech Connect

    Hastings, Adam F.; Otting, Gottfried; Folmer, Rutger H.A.; Duggin, Iain G.; Wake, R. Gerry; Wilce, Matthew C.J.; Wilce, Jacqueline A. . E-mail: Jackie.Wilce@med.monash.edu.au

    2005-09-23

    Termination of DNA replication in Bacillus subtilis involves the polar arrest of replication forks by a specific complex formed between the dimeric 29 kDa replication terminator protein (RTP) and DNA terminator sites. We have used NMR spectroscopy to probe the changes in {sup 1}H-{sup 15}N correlation spectra of a {sup 15}N-labelled RTP.C110S mutant upon the addition of a 21 base pair symmetrical DNA binding site. Assignment of the {sup 1}H-{sup 15}N correlations was achieved using a suite of triple resonance NMR experiments with {sup 15}N,{sup 13}C,70% {sup 2}H enriched protein recorded at 800 MHz and using TROSY pulse sequences. Perturbations to {sup 1}H-{sup 15}N spectra revealed that the N-termini, {alpha}3-helices and several loops are affected by the binding interaction. An analysis of this data in light of the crystallographically determined apo- and DNA-bound forms of RTP.C110S revealed that the NMR spectral perturbations correlate more closely to protein structural changes upon complex formation rather than to interactions at the protein-DNA interface.

  4. Report on neptunium speciation by NMR and optical spectroscopies

    SciTech Connect

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

    1995-11-01

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

  5. Labeling strategy and signal broadening mechanism of Protein NMR spectroscopy in Xenopus laevis oocytes.

    PubMed

    Ye, Yansheng; Liu, Xiaoli; Chen, Yanhua; Xu, Guohua; Wu, Qiong; Zhang, Zeting; Yao, Chendie; Liu, Maili; Li, Conggang

    2015-06-01

    We used Xenopus laevis oocytes, a paradigm for a variety of biological studies, as a eukaryotic model system for in-cell protein NMR spectroscopy. The small globular protein GB1 was one of the first studied in Xenopus oocytes, but there have been few reports since then of high-resolution spectra in oocytes. The scarcity of data is at least partly due to the lack of good labeling strategies and the paucity of information on resonance broadening mechanisms. Here, we systematically evaluate isotope enrichment and labeling methods in oocytes injected with five different proteins with molecular masses of 6 to 54 kDa. (19) F labeling is more promising than (15) N, (13) C, and (2) H enrichment. We also used (19) F NMR spectroscopy to quantify the contribution of viscosity, weak interactions, and sample inhomogeneity to resonance broadening in cells. We found that the viscosity in oocytes is only about 1.2 times that of water, and that inhomogeneous broadening is a major factor in determining line width in these cells. PMID:25965532

  6. Membrane Interactions of Phylloseptin-1, -2, and -3 Peptides by Oriented Solid-State NMR Spectroscopy

    PubMed Central

    Resende, Jarbas M.; Verly, Rodrigo M.; Aisenbrey, Christopher; Cesar, Amary; Bertani, Philippe; Piló-Veloso, Dorila; Bechinger, Burkhard

    2014-01-01

    Phylloseptin-1, -2, and -3 are three members of the family of linear cationic antimicrobial peptides found in tree frogs. The highly homologous peptides encompass 19 amino acids, and only differ in the amino acid composition and charge at the six most carboxy-terminal residues. Here, we investigated how such subtle changes are reflected in their membrane interactions and how these can be correlated to their biological activities. To this end, the three peptides were labeled with stable isotopes, reconstituted into oriented phospholipid bilayers, and their detailed topology determined by a combined approach using 2H and 15N solid-state NMR spectroscopy. Although phylloseptin-2 and -3 adopt perfect in-plane alignments, the tilt angle of phylloseptin-1 deviates by 8° probably to assure a more water exposed localization of the lysine-17 side chain. Furthermore, different azimuthal angles are observed, positioning the amphipathic helices of all three peptides with the charged residues well exposed to the water phase. Interestingly, our studies also reveal that two orientation-dependent 2H quadrupolar splittings from methyl-deuterated alanines and one 15N amide chemical shift are sufficient to unambiguously determine the topology of phylloseptin-1, where quadrupolar splittings close to the maximum impose the most stringent angular restraints. As a result of these studies, a strategy is proposed where the topology of a peptide structure can be determined accurately from the labeling with 15N and 2H isotopes of only a few amino acid residues. PMID:25140425

  7. Vanishing amplitude of backbone dynamics causes a true protein dynamical transition: 2H NMR studies on perdeuterated C-phycocyanin.

    PubMed

    Kämpf, Kerstin; Kremmling, Beke; Vogel, Michael

    2014-03-01

    Using a combination of H2 nuclear magnetic resonance (NMR) methods, we study internal rotational dynamics of the perdeuterated protein C-phycocyanin (CPC) in dry and hydrated states over broad temperature and dynamic ranges with high angular resolution. Separating H2 NMR signals from methyl deuterons, we show that basically all backbone deuterons exhibit highly restricted motion occurring on time scales faster than microseconds. The amplitude of this motion increases when a hydration shell exists, while it decreases upon cooling and vanishes near 175 K. We conclude that the vanishing of the highly restricted motion marks a dynamical transition, which is independent of the time window and of a fundamental importance. This conclusion is supported by results from experimental and computational studies of the proteins myoglobin and elastin. In particular, we argue based on findings in molecular dynamics simulations that the behavior of the highly restricted motion of proteins at the dynamical transition resembles that of a characteristic secondary relaxation of liquids at the glass transition, namely the nearly constant loss. Furthermore, H2 NMR studies on perdeuterated CPC reveal that, in addition to highly restricted motion, small fractions of backbone segments exhibit weakly restricted dynamics when temperature and hydration are sufficiently high. PMID:24730877

  8. In vivo two-dimensional NMR correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Kraft, Robert A.

    1999-10-01

    The poor resolution of in-vivo one- dimensional nuclear magnetic resonance spectroscopy (NMR) has limited its clinical potential. Currently, only the large singlet methyl resonances arising from N-acetyl aspartate (NAA), choline, and creatine are quantitated in a clinical setting. Other metabolites such as myo- inositol, glutamine, glutamate, lactate, and γ- amino butyric acid (GABA) are of clinical interest but quantitation is difficult due to the overlapping resonances and limited spectral resolution. To improve the spectral resolution and distinguish between overlapping resonances, a series of two- dimensional chemical shift correlation spectroscopy experiments were developed for a 1.5 Tesla clinical imaging magnet. Two-dimensional methods are attractive for in vivo spectroscopy due to their ability to unravel overlapping resonances with the second dimension, simplifying the interpretation and quantitation of low field NMR spectra. Two-dimensional experiments acquired with mix-mode line shape negate the advantages of the second dimension. For this reason, a new experiment, REVOLT, was developed to achieve absorptive mode line shape in both dimensions. Absorptive mode experiments were compared to mixed mode experiments with respect to sensitivity, resolution, and water suppression. Detailed theoretical and experimental calculations of the optimum spin lock and radio frequency power deposition were performed. Two-dimensional spectra were acquired from human bone marrow and human brain tissue. The human brain tissue spectra clearly reveal correlations among the coupled spins of NAA, glutamine, glutamate, lactate, GABA, aspartate and myo-inositol obtained from a single experiment of 23 minutes from a volume of 59 mL. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

  9. 13C, 2h NMR studies of structural and dynamical modifications of glucose-exposed porcine aortic elastin.

    PubMed

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

    2015-04-01

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

  10. 13C, 2H NMR Studies of Structural and Dynamical Modifications of Glucose-Exposed Porcine Aortic Elastin

    PubMed Central

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

    2015-01-01

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

  11. An Oil Spill in a Tube: An Accessible Approach for Teaching Environmental NMR Spectroscopy

    ERIC Educational Resources Information Center

    Simpson, Andre´ J.; Mitchell, Perry J.; Masoom, Hussain; Mobarhan, Yalda Liaghati; Adamo, Antonio; Dicks, Andrew P.

    2015-01-01

    NMR spectroscopy has great potential as an instrumental method for environmental chemistry research and monitoring but may be underused in teaching laboratories because of its complexity and the level of expertise required in operating the instrument and interpreting data. This laboratory experiment introduces environmental NMR spectroscopy to…

  12. Multiplicative or t1 Noise in NMR Spectroscopy

    SciTech Connect

    Granwehr, Josef

    2005-01-25

    The signal in an NMR experiment is highly sensitive to fluctuations of the environment of the sample. If, for example, the static magnetic field B{sub 0}, the amplitude and phase of radio frequency (rf) pulses, or the resonant frequency of the detection circuit are not perfectly stable and reproducible, the magnetic moment of the spins is altered and becomes a noisy quantity itself. This kind of noise not only depends on the presence of a signal, it is in fact proportional to it. Since all the spins at a particular location in a sample experience the same environment at any given time, this noise primarily affects the reproducibility of an experiment, which is mainly of importance in the indirect dimensions of a multidimensional experiment, when intense lines are suppressed with a phase cycle, or for difference spectroscopy techniques. Equivalently, experiments which are known to be problematic with regard to their reproducibility, like flow experiments or experiments with a mobile target, tend to be affected stronger by multiplicative noise. In this article it is demonstrated how multiplicative noise can be identified and characterized using very simple, repetitive experiments. An error estimation approach is developed to give an intuitive, yet quantitative understanding of its properties. The consequences for multidimensional NMR experiments are outlined, implications for data analysis are shown, and strategies for the optimization of experiments are summarized.

  13. Protein Motions and Folding Investigated by NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Palmer, Arthur

    2002-03-01

    NMR spin relaxation spectroscopy is a powerful experimental approach for globally characterizing conformational dynamics of proteins in solution. Laboratory frame relaxation measurements are sensitive to overall rotational diffusion and internal motions on picosecond-nanosecond time scales, while rotating frame relaxation measurements are sensitive to chemical exchange processes on microsecond-millisecond time scales. The former approach is illustrated by ^15N laboratory-frame relaxation experiments as a function of temperature for the helical subdomain HP36 of the F-actin-binding headpiece domain of chicken villin. The data are analyzed using the model-free formalism to characterize order parameters and effective correlation times for intramolecular motions of individual ^15N sites. The latter approach is illustrated by ^13C Carr-Purcell-Meiboom-Gill relaxation measurements for the de novo designed α_2D protein and by ^15N rotating-frame relaxation measurements for the peripheral subunit-binding domain (PSBD) from the dihydrolopoamide acetyltransferase component of the pyruvate dehydrogenase multienzyme complex from Bacillus stearothermophilus. These experiments are used to determine the folding and unfolding kinetic rate constants for the two proteins. The results for HP36, α_2D, and PSBD illustrate the capability of current NMR methods for characterizing dynamic processes on multiple time scales in proteins.

  14. Saturation in Deuteron Hadamard NMR Spectroscopy of Solids

    NASA Astrophysics Data System (ADS)

    Greferath, M.; Blumich, B.; Griffith, W. M.; Hoatson, G. L.

    Hadamard NMR was investigated for wide-line solid-state deuteron spectroscopy by numerical simulations and experiments on hexamethylbenzene. Similar signal-to-noise ratios were obtained at large filter bandwidths (500 kHz) by both the quadrupolar echo and the Hadamard methods, although the excitation power differs by up to four orders in magnitude. Increasing the excitation power leads to systematic, noise-like features in Hadamard spectra. In contrast to phase modulation, simulations indicate that for amplitude modulation of the pseudorandom excitation, the pulse sequence burns a saturation hole into the lineshape at the carrier frequency. Violation of the cyclicity requirement by introduction of a recycle delay between successive Hadamard scans results in a high-frequency noise contribution. Finite pulse widths are shown not to cause significant spectral distortions.

  15. 2H-NMR resolution of the methylenic isotopomers of ethanol applied to the study of stereospecific enzyme-catalysed exchange.

    PubMed

    Rabiller, C; Mesbahi, M; Martin, M L

    1990-01-01

    We have shown that site-specific natural isotope fractionation of hydrogen studied by NMR (SNIF-NMR) is an important source of information on the mechanistic and environmental effects which govern the photosynthesis of sugars and their fermentation into ethanol. Three isotope ratios associated with the methyl, methylene, and hydroxyl sites of ethanol are determined in achiral media. In this study we show that complementary information about possible stereospecific mechanisms involving the methylenic hydrogens is also rendered accessible by 2H-NMR enantiomeric resolution. The synthesis of mandelate esters enables exchange between the pro-R site of ethanol and water to be investigated. Simultaneous access to the three site-specific isotope ratios of the ethyl group is obtained at isotopic dilutions close to the natural ones. Mediation of the exchange by the enzymic system alcohol dehydrogenase-alpha-lipoyldehydrogenase and by the yeast Saccharomyces cerevisiae are compared. The progress of the reaction can be followed quantitatively as a function of time and the occurrence of glycolytic metabolism of endogeneous materials by yeast can be substantiated in a one-pot experiment. PMID:2205266

  16. High-resolution spectroscopy of Saturn at 3 microns: CH 4, CH 3D, C 2H 2, C 2H 6, PH 3, clouds, and haze

    NASA Astrophysics Data System (ADS)

    Kim, Joo Hyeon; Kim, Sang J.; Geballe, Thomas R.; Kim, Sungsoo S.; Brown, Linda R.

    2006-12-01

    We report observation and analysis of a high-resolution 2.87-3.54 μm spectrum of the southern temperate region of Saturn obtained with NIRSPEC at Keck II. The spectrum reveals absorption and emission lines of five molecular species as well as spectral features of haze particles. The ν+ν band of CH 3D is detected in absorption between 2.87 and 2.92 μm; and we derived from it a mixing ratio approximately consistent with the Infrared Space Observatory result. The ν band of C 2H 2 also is detected in absorption between 2.95 and 3.05 μm; analysis indicates a sudden drop in the C 2H 2 mixing ratio at 15 mbar (130 km above the 1 bar level), probably due to condensation in the low stratosphere. The presence of the ν+ν+ν band of C 2H 6 near 3.07 μm, first reported by Bjoraker et al. [Bjoraker, G.L., Larson, H.P., Fink, U., 1981. Astrophys. J. 248, 856-862], is confirmed, and a C 2H 6 condensation altitude of 10 mbar (140 km) in the low stratosphere is determined. We assign weak emission lines within the 3.3 μm band of CH 4 to the ν band of C 2H 6, and derive a mixing ratio of 9±4×10 for this species. Most of the C 2H 6 3.3 μm line emission arises in the altitude range 460-620 km (at ˜μbar pressure levels), much higher than the 160-370 km range where the 12 μm thermal molecular line emission of this species arises. At 2.87-2.90 μm the major absorber is tropospheric PH 3. The cloud level determined here and at 3.22-3.54 is 390-460 mbar (˜30 km), somewhat higher than found by Kim and Geballe [Kim, S.J., Geballe, T.R., 2005. Icarus 179, 449-458] from analysis of a low resolution spectrum. A broad absorption feature at 2.96 μm, which might be due to NH 3 ice particles in saturnian clouds, is also present. The effect of a haze layer at about 125 km (˜12 mbar level) on the 3.20-3.54 μm spectrum, which was not apparent in the low resolution spectrum, is clearly evident in the high resolution data, and the spectral properties of the haze particles suggest that

  17. Quantitative high-resolution on-line NMR spectroscopy in reaction and process monitoring.

    PubMed

    Maiwald, Michael; Fischer, Holger H; Kim, Young-Kyu; Albert, Klaus; Hasse, Hans

    2004-02-01

    On-line nuclear magnetic resonance spectroscopy (on-line NMR) is a powerful technique for reaction and process monitoring. Different set-ups for direct coupling of reaction and separation equipment with on-line NMR spectroscopy are described. NMR spectroscopy can be used to obtain both qualitative and quantitative information from complex reacting multicomponent mixtures for equilibrium or reaction kinetic studies. Commercial NMR probes can be used at pressures up to 35 MPa and temperatures up to 400 K. Applications are presented for studies of equilibria and kinetics of complex formaldehyde-containing mixtures as well as homogeneously and heterogeneously catalyzed esterification kinetics. Direct coupling of a thin-film evaporator is described as an example for the benefits of on-line NMR spectroscopy in process monitoring. PMID:14729025

  18. Detection of Taurine in Biological Tissues by 33S NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Musio, Roberta; Sciacovelli, Oronzo

    2001-12-01

    The potential of 33S NMR spectroscopy for biochemical investigations on taurine (2-aminoethanesulfonic acid) is explored. It is demonstrated that 33S NMR spectroscopy allows the selective and unequivocal identification of taurine in biological samples. 33S NMR spectra of homogenated and intact tissues are reported for the first time, together with the spectrum of a living mollusc. Emphasis is placed on the importance of choosing appropriate signal processing methods to improve the quality of the 33S NMR spectra of biological tissues.

  19. Nuclear Magnetic Resonance (NMR) Spectroscopy For Metabolic Profiling of Medicinal Plants and Their Products.

    PubMed

    Kumar, Dinesh

    2016-09-01

    NMR spectroscopy has multidisciplinary applications, including excellent impact in metabolomics. The analytical capacity of NMR spectroscopy provides information for easy qualitative and quantitative assessment of both endogenous and exogenous metabolites present in biological samples. The complexity of a particular metabolite and its contribution in a biological system are critically important for understanding the functional state that governs the organism's phenotypes. This review covers historical aspects of developments in the NMR field, its applications in chemical profiling, metabolomics, and quality control of plants and their derived medicines, foods, and other products. The bottlenecks of NMR in metabolic profiling are also discussed, keeping in view the future scope and further technological interventions. PMID:26575437

  20. Applications of Diffusion Ordered Spectroscopy (DOSY-NMR)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diffusion-ordered NMR (DOSY-NMR) is a powerful, but under-utilized, technique for the investigation of mixtures based on translational diffusion rates. DOSY spectra allow for determination by NMR of components that may differ in molecular weight, geometry or complexation. Typical applications coul...

  1. Deuterium dynamics in the icosahedral and amorphous phases of the Ti40Zr40Ni20 hydrogen-absorbing alloy studied by 2H NMR

    NASA Astrophysics Data System (ADS)

    Gradišek, A.; Kocjan, A.; McGuiness, P. J.; Apih, T.; Kim, Hae Jin; Dolinšek, J.

    2008-11-01

    The Ti40Zr40Ni20 hydrogen-absorbing alloy was prepared in the icosahedral and amorphous phases by controlling the rotation speed of the melt-spinning method of sample preparation, and the deuterium dynamics was investigated by 2H NMR dynamic lineshape and spin-lattice relaxation. The results were analysed by the lineshape and relaxation models that assume deuterium thermally activated hopping within a manifold of different chemical environments. The observed 8% larger activation energy for the deuterium hopping over the interstitial sites and the 10% larger static spectrum width of the amorphous phase, as compared to the icosahedral phase, can be accounted for by the larger deuterium content of the investigated amorphous sample. From the deuterium dynamics point of view, the icosahedral phase is not special with respect to the amorphous modification of the same material.

  2. Coherence selection in double CP MAS NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Yang, Jen-Hsien; Chou, Fang-Chieh; Tzou, Der-Lii M.

    2008-11-01

    Applications of double cross-polarization (CP) magic-angle spinning (MAS) NMR spectroscopy, via 1H/ 15N and then 15N/ 13C coherence transfers, for 13C coherence selection are demonstrated on a 15N/ 13C-labeled N-acetyl-glucosamine (GlcNAc) compound. The 15N/ 13C coherence transfer is very sensitive to the settings of the experimental parameters. To resolve explicitly these parameter dependences, we have systematically monitored the 13C{ 15N/ 1H} signal as a function of the rf field strength and the MAS frequency. The data reveal that the zero-quantum coherence transfer, with which the 13C effective rf field is larger than that of the 15N by the spinning frequency, would give better signal sensitivity. We demonstrate in one- and two-dimensional double CP experiments that spectral editing can be achieved by tailoring the experimental parameters, such as the rf field strengths and/or the MAS frequency.

  3. Three-Dimensional Maximum-Quantum Correlation HMQC NMR Spectroscopy (3D MAXY-HMQC)

    NASA Astrophysics Data System (ADS)

    Liu, Maili; Mao, Xi-An; Ye, Chaohui; Nicholson, Jeremy K.; Lindon, John C.

    1997-11-01

    The extension of two-dimensional maximum-quantum correlation spectroscopy (2D MAXY NMR), which can be used to simplify complex NMR spectra, to three dimensions (3D) is described. A new pulse sequence for 3D MAXY-HMQC is presented and exemplified using the steroid drug dexamethasone. The sensitivity and coherence transfer efficiency of the MAXY NMR approach has also been assessed in relation to other HMQC- and HSQC-based 3D methods.

  4. Development of a micro flow-through cell for high field NMR spectroscopy.

    SciTech Connect

    Alam, Todd Michael; McIntyre, Sarah K.

    2011-05-01

    A highly transportable micro flow-through detection cell for nuclear magnetic resonance (NMR) spectroscopy has been designed, fabricated and tested. This flow-through cell allows for the direct coupling between liquid chromatography (LC) and gel permeation chromatography (GPC) resulting in the possibility of hyphenated LC-NMR and GPC-NMR. The advantage of the present flow cell design is that it is independent and unconnected to the detection probe electronics, is compatible with existing commercial high resolution NMR probes, and as such can be easily implemented at any NMR facility. Two different volumes were fabricated corresponding to between {approx}3.8 and 10 {micro}L detection volume. Examples of the performance of the cell on different NMR instruments, and using different NMR detection probes were demonstrated.

  5. 2H NMR study of dynamics of benzene-d6 interacting with humic and fulvic acids.

    PubMed

    Eastman, Margaret A; Brothers, Lucinda A; Nanny, Mark A

    2011-05-01

    Samples of three humic acids and one fulvic acid with 1% loading of benzene-d(6) in sealed glass tubes have been studied with solid-state deuterium quadrupole-echo nuclear magnetic resonance spectroscopy. Calculated spectra combining three motional models, two isotropic models and a third more restricted small-angle wobble (SAW) motional model, are fit to the experimental spectra. One isotropic motion (ISO(v)) is assigned to vaporous benzene-d(6) due to the small line width, short T(1), and the loss of this component by about -25 °C when the temperature is lowered. The remaining two motional components, ISO(s) and SAW, are sorbed by the humic or fulvic acid. Benzene-d(6) slowly interacts with the humic substances, progressively filling SAW sites as ISO(s) motion diminishes. Both the sorption and increase in percentage of SAW motion are for the most part complete within 200 days but continue to a lesser extent over a period of a few years. For the SAW motion there are at least two and most likely a series of T(1) values, indicating more than one adsorption environment. Enthalpies of sorption, obtained from application of the van't Hoff equation to the percentages of the different motional models derived from a series of variable temperature spectra, are comparable in magnitude to the enthalpy of vaporization of benzene. In Leonardite humic acid, ΔH and ΔS for the ISO(s) to SAW transition change from positive to negative values with age, implying a transition in the driving force from an entropic effect associated with expansion and deformation in the molecular structure of the humic substance to accommodate benzene-d(6) to an enthalpic effect of strong benzene-d(6)-humic substance interactions. In contrast, at advanced ages, Suwannee River humic and fulvic acids have small positive or near zero ΔH and positive ΔS for the ISO(s) to SAW transition. PMID:21456559

  6. [Measurement of Trace C2H6 Based on Optical-Feedback Cavity-Enhanced Absorption Spectroscopy].

    PubMed

    Wan, Fu; Chen, Wei-gen; Gu, Zhao-liang; Zou, Jing-xin; DU, Ling-Ling; Qi, Wei; Zhou, Qu

    2015-10-01

    Ethane is one of major fault characteristic gases dissolved in power transformer, the detection of Ethane with high accuracy and sensitivity is the key of dissolved gas analysis. In this paper, based on optical feedback theory and cavity-enhanced absorption spectroscopy, combined with quantum cascade laser, a detection system for dissolved gas C2 H6 in transformer oil was built up. Based on the symmetry of the individual cavity modes, the phase matching of returning light in resonance with the cavity was achieved through LabVIEW codes. The optical feedback effect that the emitted light return to the laser cavity after a small delay time and lock to the resonance frequency of cavity, even and odd modes effect that the higher modes and lower modes structure will build up alternatively, and threshold current lowering effect of about 1.2 mA were studied and achieved. By cavity ring-down spectroscopy, the effective reflectivity of 99.978% and cavity finesse of 7 138.4 is obtained respectively. The frequency selectivity is 0.005 2 cm(-1). With an acquisition time of 1s, this optical system allows detection for the PQ3 band of C2 H6 with high accuracy of 95.72% ± 0.17% and detection limit of (1.97 ± 0.06) x 10(-3) μL x L(-1) at atmospheric pressure and temperature of 20 degrees C, which lays a foundation for fault diagnose from dissolved gas analysis. PMID:26904820

  7. Measurement of Solution Viscosity via Diffusion-Ordered NMR Spectroscopy (DOSY)

    ERIC Educational Resources Information Center

    Li, Weibin; Kagan, Gerald; Hopson, Russell; Williard, Paul G.

    2011-01-01

    Increasingly, the undergraduate chemistry curriculum includes nuclear magnetic resonance (NMR) spectroscopy. Advanced NMR techniques are often taught including two-dimensional gradient-based experiments. An investigation of intermolecular forces including viscosity, by a variety of methods, is often integrated in the undergraduate physical and…

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

    SciTech Connect

    Verkade, J.G.

    1989-05-01

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

  9. Mobility and Diffusion-Ordered Two-Dimensional NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Morris, Kevin Freeman

    Mobility and diffusion-ordered two-dimensional nuclear magnetic resonance spectroscopy experiments have been developed for the analysis of mixtures. In the mobility -ordered experiments, the full range of positive and negative electrophoretic mobilities is displayed in one dimension and chemical shifts are displayed in the other. A concentric cylindrical tube electrophoresis chamber was designed to reduce the effective pathlength for current and to provide unidirectional flow for ions of interest. Techniques based upon the reverse precession method were also implemented to recover the signs of the mobilities and improved resolution in the mobility dimension was obtained by replacing Fourier transformation of truncated data sets with a linear prediction analysis. In the diffusion-ordered two-dimensional NMR experiments, the conventional chemical shift spectrum is resolved in one dimension and spectra of diffusion rates or molecular radii are resolved in the other. Diffusion dependent pulsed field gradient NMR data sets were inverted by means of the computer programs SPLMOD or DISCRETE, when discrete diffusion coefficients were present, and CONTIN when continuous distributions were present. Since the inversion is ill -conditioned, it was necessary to introduce additional information to limit the range of the solutions. In addition to prior knowledge of the decay kernels and non-negativity of amplitudes and damping constants, a set of rejection criteria was constructed for the discrete analysis case that took into account physical limits on diffusion coefficients, experimentally accessible values, and variations in effective decay kernels resulting from instrumental non-linearities. Examples of analyses of simulated data and experimental data for mixtures are presented as well as two-dimensional spectra generated by CONTIN for polydisperse polymer samples. Also, resolution in the diffusion dimension was increased by performing experiments on hydrophobic molecules in

  10. High-resolution NMR of hydrogen in organic solids by DNP enhanced natural abundance deuterium spectroscopy

    NASA Astrophysics Data System (ADS)

    Rossini, Aaron J.; Schlagnitweit, Judith; Lesage, Anne; Emsley, Lyndon

    2015-10-01

    We demonstrate that high field (9.4 T) dynamic nuclear polarization (DNP) at cryogenic (∼100 K) sample temperatures enables the rapid acquisition of natural abundance 1H-2H cross-polarization magic angle spinning (CPMAS) solid-state NMR spectra of organic solids. Spectra were obtained by impregnating substrates with a solution of the stable DNP polarizing agent TEKPol in tetrachloroethane. Tetrachloroethane is a non-solvent for the solids, and the unmodified substrates are then polarized through spin diffusion. High quality natural abundance 2H CPMAS spectra of histidine hydrochloride monohydrate, glycylglycine and theophylline were acquired in less than 2 h, providing direct access to hydrogen chemical shifts and quadrupolar couplings. The spectral resolution of the 2H solid-state NMR spectra is comparable to that of 1H spectra obtained with state of the art homonuclear decoupling techniques.

  11. High-resolution NMR of hydrogen in organic solids by DNP enhanced natural abundance deuterium spectroscopy.

    PubMed

    Rossini, Aaron J; Schlagnitweit, Judith; Lesage, Anne; Emsley, Lyndon

    2015-10-01

    We demonstrate that high field (9.4 T) dynamic nuclear polarization (DNP) at cryogenic (∼100 K) sample temperatures enables the rapid acquisition of natural abundance (1)H-(2)H cross-polarization magic angle spinning (CPMAS) solid-state NMR spectra of organic solids. Spectra were obtained by impregnating substrates with a solution of the stable DNP polarizing agent TEKPol in tetrachloroethane. Tetrachloroethane is a non-solvent for the solids, and the unmodified substrates are then polarized through spin diffusion. High quality natural abundance (2)H CPMAS spectra of histidine hydrochloride monohydrate, glycylglycine and theophylline were acquired in less than 2h, providing direct access to hydrogen chemical shifts and quadrupolar couplings. The spectral resolution of the (2)H solid-state NMR spectra is comparable to that of (1)H spectra obtained with state of the art homonuclear decoupling techniques. PMID:26363582

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

    SciTech Connect

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

    2001-01-01

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  14. Characterization of protein hydration by solution NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Wand, Joshua

    A comprehensive understanding of the interactions between protein molecules and hydration water remains elusive. Solution nuclear magnetic resonance (NMR) spectroscopy has been proposed as a means to characterize these interactions but is plagued with artifacts when employed in bulk aqueous solution. Encapsulation of proteins in reverse micelles prepared in short chain alkane solvents can overcome these technical limitations. Application of this approach has revealed that the interaction of water with the surface of protein molecules is quite heterogeneous with some regions of the protein having long-lived interactions while other regions show relatively transient hydration. Results from several proteins will be presented including ubiquitin, staphylococcal nuclease, interleukin 1beta, hen egg white lysozyme (HEWL) and T4 lysozyme. Ubiquitin and interleukin 1beta are signaling proteins and interact with other proteins through formation of dry protein-protein interfaces. Interestingly, the protein surfaces of the free proteins show relatively slowed (restricted) motion at the surface, which is indicative of low residual entropy. Other regions of the protein surface have relatively high mobility water. These results are consistent with the idea that proteins have evolved to maximize the hydrophobic effect in optimization of binding with protein partners. As predicted by simulation and theory, we find that hydration of internal hydrophobic cavities of interleukin 1beta and T4 lysozyme is highly disfavored. In contrast, the hydrophilic polar cavity of HEWL is occupied by water. Initial structural correlations suggest that hydration of alpha helical structure is characterized by relatively mobile water while those of beta strands and loops are more ordered and slowed. These and other results from this set of proteins reveals that the dynamical and structural character of hydration of proteins is heterogeneous and complex. Supported by the National Science Foundation.

  15. PMP1 18-38, a yeast plasma membrane protein fragment, binds phosphatidylserine from bilayer mixtures with phosphatidylcholine: a (2)H-NMR study.

    PubMed

    Roux, M; Beswick, V; Coïc, Y M; Huynh-Dinh, T; Sanson, A; Neumann, J M

    2000-11-01

    PMP1 is a 38-residue plasma membrane protein of the yeast Saccharomyces cerevisiae that regulates the activity of the H(+)-ATPase. The cytoplasmic domain conformation results in a specific interfacial distribution of five basic side chains, thought to strongly interact with anionic phospholipids. We have used the PMP1 18-38 fragment to carry out a deuterium nuclear magnetic resonance ((2)H-NMR) study for investigating the interactions between the PMP1 cytoplasmic domain and phosphatidylserines. For this purpose, mixed bilayers of 1-palmitoyl, 2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl, 2-oleoyl-sn-glycero-3-phosphoserine (POPS) were used as model membranes (POPC/POPS 5:1, m/m). Spectra of headgroup- and chain-deuterated POPC and POPS phospholipids, POPC-d4, POPC-d31, POPS-d3, and POPS-d31, were recorded at different temperatures and for various concentrations of the PMP1 fragment. Data obtained from POPS deuterons revealed the formation of specific peptide-POPS complexes giving rise to a slow exchange between free and bound PS lipids, scarcely observed in solid-state NMR studies of lipid-peptide/protein interactions. The stoichiometry of the complex (8 POPS per peptide) was determined and its significance is discussed. The data obtained with headgroup-deuterated POPC were rationalized with a model that integrates the electrostatic perturbation induced by the cationic peptide on the negatively charged membrane interface, and a "spacer" effect due to the intercalation of POPS/PMP1f complexes between choline headgroups. PMID:11053135

  16. PMP1 18-38, a yeast plasma membrane protein fragment, binds phosphatidylserine from bilayer mixtures with phosphatidylcholine: a (2)H-NMR study.

    PubMed Central

    Roux, M; Beswick, V; Coïc, Y M; Huynh-Dinh, T; Sanson, A; Neumann, J M

    2000-01-01

    PMP1 is a 38-residue plasma membrane protein of the yeast Saccharomyces cerevisiae that regulates the activity of the H(+)-ATPase. The cytoplasmic domain conformation results in a specific interfacial distribution of five basic side chains, thought to strongly interact with anionic phospholipids. We have used the PMP1 18-38 fragment to carry out a deuterium nuclear magnetic resonance ((2)H-NMR) study for investigating the interactions between the PMP1 cytoplasmic domain and phosphatidylserines. For this purpose, mixed bilayers of 1-palmitoyl, 2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl, 2-oleoyl-sn-glycero-3-phosphoserine (POPS) were used as model membranes (POPC/POPS 5:1, m/m). Spectra of headgroup- and chain-deuterated POPC and POPS phospholipids, POPC-d4, POPC-d31, POPS-d3, and POPS-d31, were recorded at different temperatures and for various concentrations of the PMP1 fragment. Data obtained from POPS deuterons revealed the formation of specific peptide-POPS complexes giving rise to a slow exchange between free and bound PS lipids, scarcely observed in solid-state NMR studies of lipid-peptide/protein interactions. The stoichiometry of the complex (8 POPS per peptide) was determined and its significance is discussed. The data obtained with headgroup-deuterated POPC were rationalized with a model that integrates the electrostatic perturbation induced by the cationic peptide on the negatively charged membrane interface, and a "spacer" effect due to the intercalation of POPS/PMP1f complexes between choline headgroups. PMID:11053135

  17. Interpretation of combined 2H SNIF/NMR and 13C SIRA/MS analyses of fruit juices to detect added sugar.

    PubMed

    Martin, G G; Hanote, V; Lees, M; Martin, Y L

    1996-01-01

    The site-specific natural isotopic fractionation studied by nuclear magnetic resonance (SNIF/NMR) method measures site-specific isotope contents in a variety of organic compounds by deuterium nuclear magnetic resonance spectroscopy. This technique, together with SIRA/MS (stable isotope ratio analysis/mass spectrometry) provides a powerful tool for food authentication and characterization. By using the ethanol resulting from sugar fermentation as a molecular probe, SNIF/NMR (deuterium) and SIRA/MS (13C) have been used together for authentication of fruit juices. The influence of deuterium content of the fermentation water on the isotopic parameters is shown and a means for normalizing the results is proposed. A large number of authentic juices have been analyzed to define the variation of isotopic ratios in natural juices. On the basis of these data, a set of rules was designed to enable interpretation of isotopic parameters in terms of possible adulteration of fruit juices by sugar addition. Results of analyses of Florida orange juice are presented. Orange juice samples from Brazil and Israel are included as 2 extreme cases. Assignment limits for a sample of orange juice of unknown origin also are given. These assignment limits are also provided for apple and grapefruit juices. PMID:8620113

  18. [Non-invasive analysis of proteins in living cells using NMR spectroscopy].

    PubMed

    Tochio, Hidehito; Murayama, Shuhei; Inomata, Kohsuke; Morimoto, Daichi; Ohno, Ayako; Shirakawa, Masahiro

    2015-01-01

    NMR spectroscopy enables structural analyses of proteins and has been widely used in the structural biology field in recent decades. NMR spectroscopy can be applied to proteins inside living cells, allowing characterization of their structures and dynamics in intracellular environments. The simplest "in-cell NMR" approach employs bacterial cells; in this approach, live Escherichia coli cells overexpressing a specific protein are subjected to NMR. The cells are grown in an NMR active isotope-enriched medium to ensure that the overexpressed proteins are labeled with the stable isotopes. Thus the obtained NMR spectra, which are derived from labeled proteins, contain atomic-level information about the structure and dynamics of the proteins. Recent progress enables us to work with higher eukaryotic cells such as HeLa and HEK293 cells, for which a number of techniques have been developed to achieve isotope labeling of the specific target protein. In this review, we describe successful use of electroporation for in-cell NMR. In addition, (19)F-NMR to characterize protein-ligand interactions in cells is presented. Because (19)F nuclei rarely exist in natural cells, when (19)F-labeled proteins are delivered into cells and (19)F-NMR signals are observed, one can safely ascertain that these signals originate from the delivered proteins and not other molecules. PMID:25759048

  19. Perspectives of solution NMR spectroscopy for structural and functional studies of integral membrane proteins

    NASA Astrophysics Data System (ADS)

    Reckel, Sina; Hiller, Sebastian

    2013-04-01

    This article discusses future perspectives of solution NMR spectroscopy to study structures and functions of integral membrane proteins at atomic resolution, based on a review of recent progress in this area. Several selected examples of structure determinations, as well as functional studies of integral membrane proteins are highlighted. We expect NMR spectroscopy to make future key scientific contributions to understanding membrane protein function, in particular for large membrane protein systems with known three-dimensional structure. Such situations can benefit from the fact that functional NMR studies have substantially less limitations by molecular size than a full de novo structure determination. Therefore, the general potential for NMR spectroscopy to solve biologic key questions associated with integral membrane proteins is very promising.

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

    NASA Astrophysics Data System (ADS)

    Tarasek, Matthew R.

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

  1. NMR Spectroscopy for Thin Films by Magnetic Resonance Force Microscopy

    PubMed Central

    Won, Soonho; Saun, Seung-Bo; Lee, Soonchil; Lee, SangGap; Kim, Kiwoong; Han, Yunseok

    2013-01-01

    Nuclear magnetic resonance (NMR) is a fundamental research tool that is widely used in many fields. Despite its powerful applications, unfortunately the low sensitivity of conventional NMR makes it difficult to study thin film or nano-sized samples. In this work, we report the first NMR spectrum obtained from general thin films by using magnetic resonance force microscopy (MRFM). To minimize the amount of imaging information inevitably mixed into the signal when a gradient field is used, we adopted a large magnet with a flat end with a diameter of 336 μm that generates a homogeneous field on the sample plane and a field gradient in a direction perpendicular to the plane. Cyclic adiabatic inversion was used in conjunction with periodic phase inversion of the frequency shift to maximize the SNR. In this way, we obtained the 19F NMR spectrum for a 34 nm-thick CaF2 thin film. PMID:24217000

  2. Applications of high resolution /sup 3/H NMR spectroscopy

    SciTech Connect

    Williams, P.G.

    1987-10-01

    The advantages of tritium as an NMR nucleus are pointed out. Examples of its use are given, including labelled toluene, hydrogenation of ..beta..-methylstyrene, and maltose and its binding proteins. 7 refs., 2 figs. (DLC)

  3. Rapid characterization of molecular diffusion by NMR spectroscopy.

    PubMed

    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

  4. Conditions affecting the re-alignment of the antimicrobial peptide PGLa in membranes as monitored by solid state 2H-NMR.

    PubMed

    Tremouilhac, Pierre; Strandberg, Erik; Wadhwani, Parvesh; Ulrich, Anne S

    2006-09-01

    The cationic antimicrobial peptide PGLa is electrostatically attracted to bacterial membranes, binds as an amphiphilic alpha-helix, and is thus able to permeabilize the lipid bilayer. Using solid state (2)H-NMR of non-perturbing Ala-d(3) labels on the peptide, we have characterized the helix alignment under a range of different conditions. Even at a very high peptide-to-lipid ratio (1:20) and in the presence of negatively charged lipids, there was no indication of a toroidal wormhole structure. Instead, PGLa re-aligns from a surface-bound S-state to an obliquely tilted T-state, which is presumably dimeric. An intermediate structure half-way between the S- and T-state was observed in fully hydrated multilamellar DMPC vesicles at 1:50, suggesting a fast exchange between the two states on the time scale of >50 kHz. We demonstrate that this equilibrium is shifted from the S- towards the T-state either upon (i) increasing the peptide concentration, (ii) adding negatively charged DMPG, or (iii) decreasing the level of hydration. The threshold concentration for re-alignment in DMPC is found to be between 1:200 and 1:100 in oriented samples at 96% humidity. In fully hydrated multilamellar DMPC vesicles, it shifts to an effective peptide-to-lipid ratio of 1:50 as some peptides are able to escape into the bulk water phase. PMID:16716250

  5. Main chain and side chain dynamics of a heme protein: 15N and 2H NMR relaxation studies of R. capsulatus ferrocytochrome c2.

    PubMed

    Flynn, P F; Bieber Urbauer, R J; Zhang, H; Lee, A L; Wand, A J

    2001-06-01

    A detailed characterization of the main chain and side chain dynamics in R. capsulatus ferrocytochrome c(2) derived from (2)H NMR relaxation of methyl group resonances is presented. (15)N relaxation measurements confirm earlier results indicating that R. capsulatus ferrocytochrome c(2) exhibits minor rotational anisotropy in solution. The current study is focused on the use of deuterium relaxation in side chain methyl groups, which has been shown to provide a detailed and accurate measure of internal dynamics. Results obtained indicate that the side chains of ferrocytochrome c(2) exhibit a wide range of motional amplitudes, but are more rigid than generally found in the interior of nonprosthetic group bearing globular proteins. This unusual rigidity is ascribed to the interactions of the protein with the large heme prosthetic group. This observation has significant implications for the potential of the heme-protein interface to modulate the redox properties of the protein and also points to the need for great precision in the design and engineering of heme proteins. PMID:11380250

  6. Spin-spin coupling in the HD molecule determined from 1H and 2H NMR experiments in the gas-phase

    NASA Astrophysics Data System (ADS)

    Garbacz, Piotr

    2014-10-01

    The indirect spin-spin coupling of hydrogen deuteride, J(D, H), was determined from a series of 1H and 2H NMR spectra acquired at various densities of gaseous solvents (He, Ar, CO2, and N2O). The analysis of these spectra shows that accurate determination of J(D, H) from this experimental data requires careful examination of the effects of nuclear relaxation and of HD-solvent gas interactions on hydrogen deuteride line shapes. Particularly, it was found that the first-order corrections of the peak-to-peak separations between HD multiplet peaks due to weak van der Waals interactions are proportional to solvent gas density, while these corrections for nuclear relaxation of the proton and the deuteron are proportional to the second power of the inverse of the gas density. Analysis of the data indicates that J(D, H), obtained by correcting for the effects of nuclear relaxation and intermolecular interactions, is 43.136(7) Hz at 300 K.

  7. Functional genomics by NMR spectroscopy. Phenylacetate catabolism in Escherichia coli.

    PubMed

    Ismail, Wael; El-Said Mohamed, Magdy; Wanner, Barry L; Datsenko, Kirill A; Eisenreich, Wolfgang; Rohdich, Felix; Bacher, Adelbert; Fuchs, Georg

    2003-07-01

    Aerobic metabolism of phenylalanine in most bacteria proceeds via oxidation to phenylacetate. Surprisingly, the further metabolism of phenylacetate has not been elucidated, even in well studied bacteria such as Escherichia coli. The only committed step is the conversion of phenylacetate into phenylacetyl-CoA. The paa operon of E. coli encodes 14 polypeptides involved in the catabolism of phenylacetate. We have found that E. coli K12 mutants with a deletion of the paaF, paaG, paaH, paaJ or paaZ gene are unable to grow with phenylacetate as carbon source. Incubation of a paaG mutant with [U-13C8]phenylacetate yielded ring-1,2-dihydroxy-1,2-dihydrophenylacetyl lactone as shown by NMR spectroscopy. Incubation of the paaF and paaH mutants with phenylacetate yielded delta3-dehydroadipate and 3-hydroxyadipate, respectively. The origin of the carbon atoms of these C6 compounds from the aromatic ring was shown using [ring-13C6]phenylacetate. The paaG and paaZ mutants also converted phenylacetate into ortho-hydroxyphenylacetate, which was previously identified as a dead end product of phenylacetate catabolism. These data, in conjunction with protein sequence data, suggest a novel catabolic pathway via CoA thioesters. According to this, phenylacetyl-CoA is attacked by a ring-oxygenase/reductase (PaaABCDE proteins), generating a hydroxylated and reduced derivative of phenylacetyl-CoA, which is not re-oxidized to a dihydroxylated aromatic intermediate, as in other known aromatic pathways. Rather, it is proposed that this nonaromatic intermediate CoA ester is further metabolized in a complex reaction sequence comprising enoyl-CoA isomerization/hydration, nonoxygenolytic ring opening, and dehydrogenation catalyzed by the PaaG and PaaZ proteins. The subsequent beta-oxidation-type degradation of the resulting CoA dicarboxylate via beta-ketoadipyl-CoA to succinyl-CoA and acetyl-CoA appears to be catalyzed by the PaaJ, PaaF and PaaH proteins. PMID:12846838

  8. Determination of Dihydrobenzoacridinone Structures by NMR, IR, and UV Spectroscopy and Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Kozlov, N. G.; Zhiharko, Yu. D.; Skakovsky, E. D.; Baranovsky, A. V.; Ogorodnikova, M. M.; Basalaeva, L. I.

    2016-01-01

    Condensation of 2-naphthylamine, aromatic aldehydes, and dimedone was found to produce 9,10-dihydrobenzo[a] acridin-11-one derivatives according to PMR, 13C NMR, and IR spectroscopy and mass spectrometry. Correlation spectroscopy showed that the carbonyl in the synthesized dihydrobenzoacridinone derivatives was located on C11.

  9. Detection of urban O3, NO2, H2CO, and SO2 using Fourier transform spectroscopy

    NASA Astrophysics Data System (ADS)

    Vandaele, Ann Carine; Carleer, M.; Colin, R.; Simon, Paul C.

    1993-02-01

    Concentrations of SO2, NO2, H2CO, and O3 have been measured regularly since October 1990 at the urban site of the Campus of the Universite Libre de Bruxelles, using the differential optical absorption spectroscopy (DOAS) technique associated with a Fourier Transform Spectrometer. The experimental set up has already been described elsewhere (Vandaele et al., 1992). It consists of a source (either a high pressure xenon lamp or a tungsten filament) and an 800 m long path system. The spectra are recorded in the 26,000 - 38,000 cm-1 and 14,000 - 30,000 cm-1 spectral regions, at the dispersion of 7.7 cm-1. The analytical method of the DOAS technique is based on the fact that in atmospheric measurements, it is impossible to obtain an experimental blank spectrum. Therefore, the Beer-Lambert law has to be rewritten as: I equals I'oen(Delta (sigma) d) where I is the measured intensity, Io the measured intensity from which all absorption structures have been removed, n the concentration, d the optical path length, and (Delta) (sigma) the differential absorption cross section of the molecule. Numerous methods for determining I'o exist. Fourier transform filtering has been used in this work. This method defines I'o as the inverse Fourier transform of the lower frequencies portion of the power spectrum of the experimental data. A least squares procedure is then applied in order to determine the concentration of the desired molecules.

  10. GFT projection NMR spectroscopy for proteins in the solid state

    PubMed Central

    Franks, W. Trent; Atreya, Hanudatta S.; Szyperski, Thomas

    2011-01-01

    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. PMID:21052779

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

    SciTech Connect

    Krishnan, V V

    2005-04-26

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

  12. Quantitating Metabolites in Protein Precipitated Serum Using NMR Spectroscopy

    PubMed Central

    2015-01-01

    Quantitative NMR-based metabolite profiling is challenged by the deleterious effects of abundant proteins in the intact blood plasma/serum, which underscores the need for alternative approaches. Protein removal by ultrafiltration using low molecular weight cutoff filters thus represents an important step. However, protein precipitation, an alternative and simple approach for protein removal, lacks detailed quantitative assessment for use in NMR based metabolomics. In this study, we have comprehensively evaluated the performance of protein precipitation using methanol, acetonitrile, perchloric acid, and trichloroacetic acid and ultrafiltration approaches using 1D and 2D NMR, based on the identification and absolute quantitation of 44 human blood metabolites, including a few identified for the first time in the NMR spectra of human serum. We also investigated the use of a “smart isotope tag,” 15N-cholamine for further resolution enhancement, which resulted in the detection of a number of additional metabolites. 1H NMR of both protein precipitated and ultrafiltered serum detected all 44 metabolites with comparable reproducibility (average CV, 3.7% for precipitation; 3.6% for filtration). However, nearly half of the quantified metabolites in ultrafiltered serum exhibited 10–74% lower concentrations; specifically, tryptophan, benzoate, and 2-oxoisocaproate showed much lower concentrations compared to protein precipitated serum. These results indicate that protein precipitation using methanol offers a reliable approach for routine NMR-based metabolomics of human blood serum/plasma and should be considered as an alternative to ultrafiltration. Importantly, protein precipitation, which is commonly used by mass spectrometry (MS), promises avenues for direct comparison and correlation of metabolite data obtained from the two analytical platforms to exploit their combined strength in the metabolomics of blood. PMID:24796490

  13. Alkaline earth chloride hydrates: chlorine quadrupolar and chemical shift tensors by solid-state NMR spectroscopy and plane wave pseudopotential calculations.

    PubMed

    Bryce, David L; Bultz, Elijah B

    2007-01-01

    A series of alkaline earth chloride hydrates has been studied by solid-state (35/37)Cl NMR spectroscopy in order to characterize the chlorine electric field gradient (EFG) and chemical shift (CS) tensors and to relate these observables to the structure around the chloride ions. Chlorine-35/37 NMR spectra of solid powdered samples of pseudopolymorphs (hydrates) of magnesium chloride (MgCl(2).6H(2)O), calcium chloride (CaCl(2).2H(2)O), strontium chloride (SrCl(2), SrCl(2).2H(2)O, and SrCl(2).6H(2)O), and barium chloride (BaCl(2).2H(2)O) have been acquired under stationary and magic-angle spinning conditions in magnetic fields of 11.75 and 21.1 T. Powder X-ray diffraction was used as an additional tool to confirm the purity and identity of the samples. Chlorine-35 quadrupolar coupling constants (C(Q)) range from essentially zero in cubic anhydrous SrCl(2) to 4.26+/-0.03 MHz in calcium chloride dihydrate. CS tensor spans, Omega, are between 40 and 72 ppm, for example, Omega= 45+/-20 ppm for SrCl(2).6H(2)O. Plane wave-pseudopotential density functional theory, as implemented in the CASTEP program, was employed to model the extended solid lattices of these materials for the calculation of their chlorine EFG and nuclear magnetic shielding tensors, and allowed for the assignment of the two-site chlorine NMR spectra of barium chloride dihydrate. This work builds upon our current understanding of the relationship between chlorine NMR interaction tensors and the local molecular and electronic structure, and highlights the particular sensitivity of quadrupolar nucleus solid-state NMR spectroscopy to the differences between various pseudopolymorphic structures in the case of strontium chloride. PMID:17385204

  14. Localized double-quantum-filtered 1H NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    Schoenberger, Torsten; Simmross, Ulrich; Poppe, Christian

    2016-01-01

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

  16. High-Resolution 3D Structure Determination of Kaliotoxin by Solid-State NMR Spectroscopy

    PubMed Central

    Korukottu, Jegannath; Schneider, Robert; Vijayan, Vinesh; Lange, Adam; Pongs, Olaf; Becker, Stefan; Baldus, Marc; Zweckstetter, Markus

    2008-01-01

    High-resolution solid-state NMR spectroscopy can provide structural information of proteins that cannot be studied by X-ray crystallography or solution NMR spectroscopy. Here we demonstrate that it is possible to determine a protein structure by solid-state NMR to a resolution comparable to that by solution NMR. Using an iterative assignment and structure calculation protocol, a large number of distance restraints was extracted from 1H/1H mixing experiments recorded on a single uniformly labeled sample under magic angle spinning conditions. The calculated structure has a coordinate precision of 0.6 Å and 1.3 Å for the backbone and side chain heavy atoms, respectively, and deviates from the structure observed in solution. The approach is expected to be applicable to larger systems enabling the determination of high-resolution structures of amyloid or membrane proteins. PMID:18523586

  17. NMR spectroscopy of experimentally shocked single crystal quartz: A reexamination of the NMR shock barometer

    NASA Technical Reports Server (NTRS)

    Fiske, P. S.; Gratz, A. J.; Nellis, W. J.

    1993-01-01

    Cygan and others report a broadening of the Si-29 nuclear magnetic resonance (NMR) peak for synthetic quartz powders with increasing shock pressure which they propose as a shock wave barometer for natural systems. These results are expanded by studying single crystal quartz shocked to 12 and 33 GPa using the 6.5 m two-stage light-gas gun at Lawrence Livermore National Laboratories. Our NMR results differ substantially from those of Cygan and others and suggest that the proposed shock wave barometer may require refinement. The difference in results between this study and that of Cygan and others is most likely caused by different starting materials (single crystal vs. powder) and different shock loading histories. NMR results from single crystal studies may be more applicable to natural systems.

  18. Macromolecular NMR spectroscopy for the non-spectroscopist: beyond macromolecular solution structure determination.

    PubMed

    Bieri, Michael; Kwan, Ann H; Mobli, Mehdi; King, Glenn F; Mackay, Joel P; Gooley, Paul R

    2011-03-01

    A strength of NMR spectroscopy is its ability to monitor, on an atomic level, molecular changes and interactions. In this review, which is intended for non-spectroscopist, we describe major uses of NMR in protein science beyond solution structure determination. After first touching on how NMR can be used to quickly determine whether a mutation induces structural perturbations in a protein, we describe the unparalleled ability of NMR to monitor binding interactions over a wide range of affinities, molecular masses and solution conditions. We discuss the use of NMR to measure the dynamics of proteins at the atomic level and over a wide range of timescales. Finally, we outline new and expanding areas such as macromolecular structure determination in multicomponent systems, as well as in the solid state and in vivo. PMID:21214861

  19. 2H NMR and 13C-IRMS analyses of acetic acid from vinegar, 18O-IRMS analysis of water in vinegar: international collaborative study report.

    PubMed

    Thomas, Freddy; Jamin, Eric

    2009-09-01

    An international collaborative study of isotopic methods applied to control the authenticity of vinegar was organized in order to support the recognition of these procedures as official methods. The determination of the 2H/1H ratio of the methyl site of acetic acid by SNIF-NMR (site-specific natural isotopic fractionation-nuclear magnetic resonance) and the determination of the 13C/12C ratio, by IRMS (isotope ratio mass spectrometry) provide complementary information to characterize the botanical origin of acetic acid and to detect adulterations of vinegar using synthetic acetic acid. Both methods use the same initial steps to recover pure acetic acid from vinegar. In the case of wine vinegar, the determination of the 18O/16O ratio of water by IRMS allows to differentiate wine vinegar from vinegars made from dried grapes. The same set of vinegar samples was used to validate these three determinations. The precision parameters of the method for measuring delta13C (carbon isotopic deviation) were found to be similar to the values previously obtained for similar methods applied to wine ethanol or sugars extracted from fruit juices: the average repeatability (r) was 0.45 per thousand, and the average reproducibility (R) was 0.91 per thousand. As expected from previous in-house study of the uncertainties, the precision parameters of the method for measuring the 2H/1H ratio of the methyl site were found to be slightly higher than the values previously obtained for similar methods applied to wine ethanol or fermentation ethanol in fruit juices: the average repeatability was 1.34 ppm, and the average reproducibility was 1.62 ppm. This precision is still significantly smaller than the differences between various acetic acid sources (delta13C and delta18O) and allows a satisfactory discrimination of vinegar types. The precision parameters of the method for measuring delta18O were found to be similar to the values previously obtained for other methods applied to wine and

  20. NMR spectroscopy and perfusion of mammalian cells using surface microprobes.

    PubMed

    Ehrmann, Klaus; Pataky, Kristopher; Stettler, Matthieu; Wurm, Florian Maria; Brugger, Jürgen; Besse, Pierre-André; Popovic, Radivoje

    2007-03-01

    NMR spectra of mammalian cells are taken using surface microprobes that are based on microfabricated planar coils. The surface microprobe resembles a miniaturized Petri dish commonly used in biological research. The diameter of the planar coils is 1 mm. Chinese Hamster Ovaries are immobilized in a uniform layer on the microprobe surface or patterned by an ink-jet printer in the centre of the microcoil, where the rf-field of the planar microcoil is most uniform. The acquired NMR spectra show the prevalent metabolites found in mammalian cells. The volumes of the detected samples range from 25 nL to 1 nL (or 50,000 to 1800 cells). With an extended set-up that provides fluid inlets and outlets to the microprobe, the cells can be perfused within the NMR-magnet while constantly taking NMR spectra. Perfusion of the cells opens the way to increased cell viability for long acquisitions or to analysis of the cells' response to environmental change. PMID:17330170

  1. Alanine scan and (2)H NMR analysis of the membrane-active peptide BP100 point to a distinct carpet mechanism of action.

    PubMed

    Zamora-Carreras, Héctor; Strandberg, Erik; Mühlhäuser, Philipp; Bürck, Jochen; Wadhwani, Parvesh; Jiménez, M Ángeles; Bruix, Marta; Ulrich, Anne S

    2016-06-01

    The short membrane-active peptide BP100 [KKLFKKILKYL-NH2] is known as an effective antimicrobial and cell penetrating agent. For a functional alanine scan each of the 11 amino acids was replaced with deuterated Ala-d3, one at a time. MIC assays showed that a substitution of Lys did not affect the antimicrobial activity, but it decreased when a hydrophobic residue was replaced. In most cases, a reduction in hydrophobicity led to a decrease in hemolysis, and some peptide analogues had an improved therapeutic index. Circular dichroism showed that BP100 folds as an amphiphilic α-helix in a bilayer. Its alignment was determined from (2)H NMR in oriented membranes of different composition. The azimuthal rotation angle was the same under all conditions, but the average helix tilt angle and the dynamical behavior of the peptide varied in a systematic manner. In POPC/POPG bilayers, with a negative spontaneous curvature, the peptide was found to lie flat on the bilayer surface, and with little wobble. In DMPC/DMPG, with a positive spontaneous curvature, BP100 at higher concentrations became tilted obliquely into the membrane, with the uncharged C-terminus inserted more deeply into the lipid bilayer, experiencing significant fluctuations in tilt angle. In DMPC/DMPG/lyso-MPC, with a pronounced positive spontaneous curvature, the helix tilted even further and became even more mobile. The 11-mer BP100 is obviously too short to form transmembrane pores. We conclude that BP100 operates via a carpet mechanism, whereby the C-terminus gets inserted into the hydrophobic core of the bilayer, which leads to membrane perturbation and induces transient permeability. PMID:26975251

  2. Guanidinoacetate methyltransferase (GAMT) deficiency diagnosed by proton NMR spectroscopy of body fluids.

    PubMed

    Engelke, Udo F H; Tassini, Maria; Hayek, Joseph; de Vries, Maaike; Bilos, Appie; Vivi, Antonio; Valensin, Gianni; Buoni, Sabrina; Zannolli, Raffaella; Brussel, Wim; Kremer, Berry; Salomons, Gajja S; Veendrick-Meekes, Monique J B M; Kluijtmans, Leo A J; Morava, Eva; Wevers, Ron A

    2009-06-01

    In patients with guanidinoacetate methyltransferase (GAMT) deficiency several parameters may point towards the diagnosis of GAMT deficiency. These include the low levels of creatine and creatinine in urine, the high concentration of guanidinoacetic acid (GAA) in urine and the low levels of creatine and creatinine in the cerebrospinal fluid (CSF). In this study, body fluids from 10 GAMT deficient patients were analysed using (1)H NMR spectroscopy. The urine 1D (1)H NMR spectra of all the patients showed a doublet resonance at 3.98 ppm (pH 2.50) derived from GAA present in high concentration. For this compound, a good recovery and good correlation was found between an LC-MS/MS method and (1)H NMR spectroscopy. In CSF NMR spectra of these patients, the singlet resonances of creatine and creatinine (3.05 and 3.13 ppm, respectively) were absent (normally always present in (1)H NMR spectra of CSF). Due to overlap by other resonances, the doublet of GAA could not be observed. Our data demonstrate that (1)H NMR spectroscopy of urine and CSF can be used to diagnose patients with GAMT deficiency. PMID:19288536

  3. Coupled changes between lipid order and polypeptide conformation at the membrane surface. A sup 2 H NMR and Raman study of polylysine-phosphatidic acid systems

    SciTech Connect

    Laroche, G.; Pezolet, M. ); Dufourc, E.J.; Dufourcq, J. )

    1990-07-10

    Thermotropism and segmental chain order parameters of sn-2-perdeuteriated dimyristoylphosphatidic acid (DMPA)-water dispersions, with and without poly(L-lysine) (PLL) of different molecular weights, have been investigated by solid-state deuterium NMR spectroscopy. The segmental chain order parameter profile of this negatively charged lipid is similar to that already found for other lipids. Addition of long PLL increases the temperature, {Tc}, of the lipid gel-to-fluid phase transition, whereas short PLL has practically no effect on {Tc}. In the fluid phase both varieties of PLL increase the plateau character of segmental order parameters up to carbon position 10. At the same reduced temperature, long PLL more significantly increases the segmental ordering, especially at the methyl terminal position. This leads to the conclusion that polar head-group capping and charge neutralization by PLL induce severe changes in lipid chain ordering, even down to the bilayer core. The structure of PLL bound to the lipid bilayer surface was monitored by Raman spectroscopy, following the amide I bands. Results show that the lipid gel-to-fluid phase transition triggers a conformational transition from ordered {beta}-sheet to random structure of short PLL, while it does not affect the strongly stabilized {beta}-sheet structure of long PLL. It is concluded that both short and long PLL can efficiently cap and neutralize lipid head groups, whatever their structure, and that peptide length is a key parameter in whether lipids or peptides are the driving force in conformationally coupled changes of both partners in the membrane.

  4. DSP-based on-line NMR spectroscopy using an anti-Hebbian learning algorithm

    SciTech Connect

    Razazian, K.; Dieckman, S.L.; Raptis, A.C.; Bobis, J.P. |

    1995-07-01

    This paper describes a nuclear magnetic resonance (NMR) system that uses an adaptive algorithm to carry out real-time NMR spectroscopy. The system employs a digital signal processor (DSP) chip to regulate the transmitted and received signal together with spectral analysis of the received signal to determine free induction decay (FID). To implement such a signal-processing routine for detection of the desired signal, an adaptive line enhancer filter that uses an anti-Hebbian learning algorithm is applied to the FID spectra. The results indicate that the adaptive filter can be a reliable technique for on-line spectroscopy study.

  5. Genetic algorithm optimized triply compensated pulses in NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Manu, V. S.; Veglia, Gianluigi

    2015-11-01

    Sensitivity and resolution in NMR experiments are affected by magnetic field inhomogeneities (of both external and RF), errors in pulse calibration, and offset effects due to finite length of RF pulses. To remedy these problems, built-in compensation mechanisms for these experimental imperfections are often necessary. Here, we propose a new family of phase-modulated constant-amplitude broadband pulses with high compensation for RF inhomogeneity and heteronuclear coupling evolution. These pulses were optimized using a genetic algorithm (GA), which consists in a global optimization method inspired by Nature's evolutionary processes. The newly designed π and π / 2 pulses belong to the 'type A' (or general rotors) symmetric composite pulses. These GA-optimized pulses are relatively short compared to other general rotors and can be used for excitation and inversion, as well as refocusing pulses in spin-echo experiments. The performance of the GA-optimized pulses was assessed in Magic Angle Spinning (MAS) solid-state NMR experiments using a crystalline U-13C, 15N NAVL peptide as well as U-13C, 15N microcrystalline ubiquitin. GA optimization of NMR pulse sequences opens a window for improving current experiments and designing new robust pulse sequences.

  6. Computational Analysis of Solvent Effects in NMR Spectroscopy.

    PubMed

    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

  7. Genetic algorithm optimized triply compensated pulses in NMR spectroscopy.

    PubMed

    Manu, V S; Veglia, Gianluigi

    2015-11-01

    Sensitivity and resolution in NMR experiments are affected by magnetic field inhomogeneities (of both external and RF), errors in pulse calibration, and offset effects due to finite length of RF pulses. To remedy these problems, built-in compensation mechanisms for these experimental imperfections are often necessary. Here, we propose a new family of phase-modulated constant-amplitude broadband pulses with high compensation for RF inhomogeneity and heteronuclear coupling evolution. These pulses were optimized using a genetic algorithm (GA), which consists in a global optimization method inspired by Nature's evolutionary processes. The newly designed π and π/2 pulses belong to the 'type A' (or general rotors) symmetric composite pulses. These GA-optimized pulses are relatively short compared to other general rotors and can be used for excitation and inversion, as well as refocusing pulses in spin-echo experiments. The performance of the GA-optimized pulses was assessed in Magic Angle Spinning (MAS) solid-state NMR experiments using a crystalline U-(13)C, (15)N NAVL peptide as well as U-(13)C, (15)N microcrystalline ubiquitin. GA optimization of NMR pulse sequences opens a window for improving current experiments and designing new robust pulse sequences. PMID:26473327

  8. Discovering [superscript 13]C NMR, [superscript 1]H NMR, and IR Spectroscopy in the General Chemistry Laboratory through a Sequence of Guided-Inquiry Exercises

    ERIC Educational Resources Information Center

    Iler, H. Darrell; Justice, David; Brauer, Shari; Landis, Amanda

    2012-01-01

    This sequence of three guided-inquiry labs is designed for a second-semester general chemistry course and challenges students to discover basic theoretical principles associated with [superscript 13]C NMR, [superscript 1]H NMR, and IR spectroscopy. Students learn to identify and explain basic concepts of magnetic resonance and vibrational…

  9. Resonance Raman spectroscopy of 2H-labelled spheroidenes in petroleum ether and in the Rhodobacter sphaeroides reaction centre.

    PubMed

    Kok, P; Köhler, J; Groenen, E J; Gebhard, R; van der Hoef, I; Lugtenburg, J; Farhoosh, R; Frank, H A

    1997-03-01

    As a step towards the structural analysis of the carotenoid spheroidene in the Rhodobacter sphaeroides reaction centre, we present the resonance Raman spectra of 14-2H, 15-2H, 15'-2H, 14'-2H, 14,15'-2H2 and 15-15'-2H2 spheroidenes in petroleum ether and, except for 14,15'-2H2 spheroidene, in the Rb. sphaeroides R26 reaction center (RC). Analysis of the spectral changes upon isotopic substitution allows a qualitative assignment of most of the vibrational bands to be made. For the all-trans spheroidenes in solution the resonance enhancement of the Raman bands is determined by the participation of carbon carbon stretching modes in the centre of the conjugated chain, the C9 to C15' region. For the RC-bound 15,15'-cis spheroidenes, enhancement is determined by the participation of carbon-carbon stretching modes in the centre of the molecule, the C13 to C13' region. Comparison of the spectra in solution and in the RC reveals evidence for an out-of-plane distortion of the RC-bound spheroidene in the central C14 to C14' region of the carotenoid. The characteristic 1240 cm-1 band in the spectrum of the RC-bound spheroidene has been assigned to a normal mode that contains the coupled C12-C13 and C13'-C12' stretch vibrations. PMID:9177038

  10. Probing oxidative degradation in polymers using {sup 17}O NMR spectroscopy

    SciTech Connect

    Alam, T.M.; Click, C.A.; Assink, R.A.

    1997-09-01

    Understanding the mechanism of oxidative degradation remains an important goal in being able to predict the aging process in polymer materials. Nuclear magnetic resonance (NMR) spectroscopy has previously been utilized to investigate polymer degradation, including both proton ({sup 1}H) and carbon ({sup 13}C) studies. These previous NMR studies, as well as other spectroscopic investigations, are complicated by the almost overwhelming signal arising from the native undegraded polymer. This makes the identification and quantification of degradation species at small concentrations difficult. In this note we discuss recent investigation into the use of oxygen ({sup 17}O) NMR spectroscopy to probe the oxidative degradation process in polymers at a molecular level. Due to the low natural abundance (0.037%) and a nuclear spin of I=5/2 possessing an appreciable quadrupolar moment, the use of {sup 17}O NMR in polymer investigations has been limited. By utilizing synthetically enriched oxygen gas during the accelerated aging process, both the difficulties of low natural abundance and background interference signals are eliminated. For enriched samples {sup 17}O NMR spectra now provide a unique probe since all of the observed NMR resonances are the direct result of oxidative degradation.

  11. Simultaneous 19F-1H medium resolution NMR spectroscopy for online reaction monitoring

    NASA Astrophysics Data System (ADS)

    Zientek, Nicolai; Laurain, Clément; Meyer, Klas; Kraume, Matthias; Guthausen, Gisela; Maiwald, Michael

    2014-12-01

    Medium resolution nuclear magnetic resonance (MR-NMR) spectroscopy is currently a fast developing field, which has an enormous potential to become an important analytical tool for reaction monitoring, in hyphenated techniques, and for systematic investigations of complex mixtures. The recent developments of innovative MR-NMR spectrometers are therefore remarkable due to their possible applications in quality control, education, and process monitoring. MR-NMR spectroscopy can beneficially be applied for fast, non-invasive, and volume integrating analyses under rough environmental conditions. Within this study, a simple 1/16″ fluorinated ethylene propylene (FEP) tube with an ID of 0.04″ (1.02 mm) was used as a flow cell in combination with a 5 mm glass Dewar tube inserted into a benchtop MR-NMR spectrometer with a 1H Larmor frequency of 43.32 MHz and 40.68 MHz for 19F. For the first time, quasi-simultaneous proton and fluorine NMR spectra were recorded with a series of alternating 19F and 1H single scan spectra along the reaction time coordinate of a homogeneously catalysed esterification model reaction containing fluorinated compounds. The results were compared to quantitative NMR spectra from a hyphenated 500 MHz online NMR instrument for validation. Automation of handling, pre-processing, and analysis of NMR data becomes increasingly important for process monitoring applications of online NMR spectroscopy and for its technical and practical acceptance. Thus, NMR spectra were automatically baseline corrected and phased using the minimum entropy method. Data analysis schemes were designed such that they are based on simple direct integration or first principle line fitting, with the aim that the analysis directly revealed molar concentrations from the spectra. Finally, the performance of 1/16″ FEP tube set-up with an ID of 1.02 mm was characterised regarding the limit of detection (LOQ (1H) = 0.335 mol L-1 and LOQ (19F) = 0.130 mol L-1 for trifluoroethanol in

  12. Simultaneous (19)F-(1)H medium resolution NMR spectroscopy for online reaction monitoring.

    PubMed

    Zientek, Nicolai; Laurain, Clément; Meyer, Klas; Kraume, Matthias; Guthausen, Gisela; Maiwald, Michael

    2014-10-18

    Medium resolution nuclear magnetic resonance (MR-NMR) spectroscopy is currently a fast developing field, which has an enormous potential to become an important analytical tool for reaction monitoring, in hyphenated techniques, and for systematic investigations of complex mixtures. The recent developments of innovative MR-NMR spectrometers are therefore remarkable due to their possible applications in quality control, education, and process monitoring. MR-NMR spectroscopy can beneficially be applied for fast, non-invasive, and volume integrating analyses under rough environmental conditions. Within this study, a simple 1/16″ fluorinated ethylene propylene (FEP) tube with an ID of 0.04″ (1.02mm) was used as a flow cell in combination with a 5mm glass Dewar tube inserted into a benchtop MR-NMR spectrometer with a (1)H Larmor frequency of 43.32MHz and 40.68MHz for (19)F. For the first time, quasi-simultaneous proton and fluorine NMR spectra were recorded with a series of alternating (19)F and (1)H single scan spectra along the reaction time coordinate of a homogeneously catalysed esterification model reaction containing fluorinated compounds. The results were compared to quantitative NMR spectra from a hyphenated 500MHz online NMR instrument for validation. Automation of handling, pre-processing, and analysis of NMR data becomes increasingly important for process monitoring applications of online NMR spectroscopy and for its technical and practical acceptance. Thus, NMR spectra were automatically baseline corrected and phased using the minimum entropy method. Data analysis schemes were designed such that they are based on simple direct integration or first principle line fitting, with the aim that the analysis directly revealed molar concentrations from the spectra. Finally, the performance of 1/16″ FEP tube set-up with an ID of 1.02mm was characterised regarding the limit of detection (LOQ ((1)H)=0.335molL(-1) and LOQ ((19)F)=0.130molL(-1) for trifluoroethanol

  13. Theory of mirrored time domain sampling for NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Ghosh, Arindam; Wu, Yibing; He, Yunfen; Szyperski, Thomas

    2011-12-01

    A generalized theory is presented for novel mirrored hypercomplex time domain sampling (MHS) of NMR spectra. It is the salient new feature of MHS that two interferograms are acquired with different directionality of time evolution, that is, one is sampled forward from time t = 0 to the maximal evolution time tmax, while the second is sampled backward from t = 0 to - tmax. The sampling can be accomplished in a (semi) constant time or non constant-time manner. Subsequently, the two interferograms are linearly combined to yield a complex time domain signal. The manifold of MHS schemes considered here is defined by arbitrary settings of sampling phases ('primary phase shifts') and amplitudes of the two interferograms. It is shown that, for any two given primary phase shifts, the addition theorems of trigonometric functions yield the unique linear combination required to form the complex signal. In the framework of clean absorption mode (CAM) acquisition of NMR spectra being devoid of residual dispersive signal components, 'secondary phase shifts' represent time domain phase errors which are to be eliminated. In contrast, such secondary phase shifts may be introduced by experimental design in order to encode additional NMR parameters, a new class of NMR experiments proposed here. For generalization, it is further considered that secondary phase shifts may depend on primary phase shifts and/or sampling directionality. In order to compare with MHS theory, a correspondingly generalized theory is derived for widely used hypercomplex ('States') sampling (HS). With generalized theory it is shown, first, that previously introduced 'canonical' schemes, characterized by primary phases being multiples of π/4, afford maximal intensity of the desired absorptive signals in the absence of secondary phase shifts, and second, how primary phases can be adjusted to maximize the signal intensity provided that the secondary phase shifts are known. Third, it is demonstrated that theory

  14. Theory of mirrored time domain sampling for NMR spectroscopy.

    PubMed

    Ghosh, Arindam; Wu, Yibing; He, Yunfen; Szyperski, Thomas

    2011-12-01

    A generalized theory is presented for novel mirrored hypercomplex time domain sampling (MHS) of NMR spectra. It is the salient new feature of MHS that two interferograms are acquired with different directionality of time evolution, that is, one is sampled forward from time t=0 to the maximal evolution time tmax, while the second is sampled backward from t=0 to -tmax. The sampling can be accomplished in a (semi) constant time or non constant-time manner. Subsequently, the two interferograms are linearly combined to yield a complex time domain signal. The manifold of MHS schemes considered here is defined by arbitrary settings of sampling phases ('primary phase shifts') and amplitudes of the two interferograms. It is shown that, for any two given primary phase shifts, the addition theorems of trigonometric functions yield the unique linear combination required to form the complex signal. In the framework of clean absorption mode (CAM) acquisition of NMR spectra being devoid of residual dispersive signal components, 'secondary phase shifts' represent time domain phase errors which are to be eliminated. In contrast, such secondary phase shifts may be introduced by experimental design in order to encode additional NMR parameters, a new class of NMR experiments proposed here. For generalization, it is further considered that secondary phase shifts may depend on primary phase shifts and/or sampling directionality. In order to compare with MHS theory, a correspondingly generalized theory is derived for widely used hypercomplex ('States') sampling (HS). With generalized theory it is shown, first, that previously introduced 'canonical' schemes, characterized by primary phases being multiples of π/4, afford maximal intensity of the desired absorptive signals in the absence of secondary phase shifts, and second, how primary phases can be adjusted to maximize the signal intensity provided that the secondary phase shifts are known. Third, it is demonstrated that theory enables

  15. High pressure 2H-NMR study of the order and dynamics of selectively deuterated dipalmitoyl phosphatidylcholine in multilamellar aqueous dispersions.

    PubMed Central

    Peng, X.; Jonas, A.; Jonas, J.

    1995-01-01

    High pressure 2H multipulse NMR techniques were used to investigate the effects of pressure on the structure and dynamics of selectively deuterated 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) multilamellar aqueous dispersions. The samples were deuterated on both chains at positions 2, 9, or 13. The deuterium lineshapes, the spin-lattice relaxation times, T1, and the spin-spin relaxation times, T2, were measured as a function of pressure from 1 bar to 5 kbar at 50 degrees C for the three deuterated DPPC samples. This pressure range permitted us to explore the phase behavior of DPPC from the liquid-crystalline (LC) phase through various gel phases such as the Gel I (P beta), Gel II (L beta), Gel III, Gel X, and the interdigitated, Gel i, gel phase. Pressure had an ordering effect on all chain segments both in the LC phase and various high pressure gel phases as indicated by the increase in SCD bond order parameter and the first moment, M1, with pressure. Compared with the adjacent gel phases, the Gel i phase had the highest order. Also, in all gel phases the carbon-9 segment of the chains had the most restricted motions in contrast to the LC phase, where the carbon-2 segment was the most restricted. In the LC phase, T1 and T2 values for all segments decreased with pressure, indicative of the fast correlation time regime. Similarly, T1 decreased with pressure in the Gel I and the interdigitated Gel i gel phases but changed to the slow correlation time regime at the Gel i/Gel II phase transition. For T2, which reflects slow motions, the transition to the slow correlation time regime occurred already at LC/Gel I phase transition. Considering the various motions which contribute to relaxation, the behavior of T1 and T2 in the Gel 11 through Gel X phases showing discontinuities and slope changes at the phase transitions was, as expected, quite complex.In addition we found a straight line relationship for T-1 vs. S2D, and T-1 vs. S2CD for the deuterons in the 9

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

    PubMed

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

    2013-12-01

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

  17. Structural studies of PCU-hydrazones: NMR spectroscopy, X-ray diffractions, and DFT calculations

    NASA Astrophysics Data System (ADS)

    Veljković, Jelena; Šekutor, Marina; Molčanov, Krešimir; Lo, Rabindranath; Ganguly, Bishwajit; Mlinarić-Majerski, Kata

    2011-06-01

    In this article we present a detailed structural investigation for the configurational isomers of PCU-hydrazones. The structural characterization of these hydrazones was performed using NMR spectroscopy, X-ray diffraction analysis and theoretical calculations. The single crystal X-ray structures of PCU-hydrazones 6B and 6C have been solved and used to conclusively confirm the characterization obtained via NMR spectra of a particular isomer. Nuclear magnetic shielding values calculated for 6A-C using DFT calculations were correlated with the experimentally determined chemical shifts. The computed results were found to be in good agreement with the observed 13C NMR values. The computed NMR results helped to ascertain the isomers of PCU-hydrazones 4A-C.

  18. Automated sample preparation station for studying self-diffusion in porous solids with NMR spectroscopy

    SciTech Connect

    Hedin, Niklas; DeMartin, Gregory J.; Reyes, Sebastian C.

    2006-03-15

    In studies of gas diffusion in porous solids with nuclear magnetic resonance (NMR) spectroscopy the sample preparation procedure becomes very important. An apparatus is presented here that pretreats the sample ex situ and accurately sets the desired pressure and temperature within the NMR tube prior to its introduction in the spectrometer. The gas manifold that supplies the NMR tube is also connected to a microbalance containing another portion of the same sample, which is kept at the same temperature as the sample in the NMR tube. This arrangement permits the simultaneous measurement of the adsorption loading on the sample, which is required for the interpretation of the NMR diffusion experiments. Furthermore, to ensure a good seal of the NMR tube, a hybrid valve design composed of titanium, a Teflon registered seat, and Kalrez registered O-rings is utilized. A computer controlled algorithm ensures the accuracy and reproducibility of all the procedures, enabling the NMR diffusion experiments to be performed at well controlled conditions of pressure, temperature, and amount of gas adsorbed on the porous sample.

  19. Structure determination of helical filaments by solid-state NMR spectroscopy

    PubMed Central

    Ahmed, Mumdooh; Spehr, Johannes; König, Renate; Lünsdorf, Heinrich; Rand, Ulfert; Lührs, Thorsten; Ritter, Christiane

    2016-01-01

    The controlled formation of filamentous protein complexes plays a crucial role in many biological systems and represents an emerging paradigm in signal transduction. The mitochondrial antiviral signaling protein (MAVS) is a central signal transduction hub in innate immunity that is activated by a receptor-induced conversion into helical superstructures (filaments) assembled from its globular caspase activation and recruitment domain. Solid-state NMR (ssNMR) spectroscopy has become one of the most powerful techniques for atomic resolution structures of protein fibrils. However, for helical filaments, the determination of the correct symmetry parameters has remained a significant hurdle for any structural technique and could thus far not be precisely derived from ssNMR data. Here, we solved the atomic resolution structure of helical MAVSCARD filaments exclusively from ssNMR data. We present a generally applicable approach that systematically explores the helical symmetry space by efficient modeling of the helical structure restrained by interprotomer ssNMR distance restraints. Together with classical automated NMR structure calculation, this allowed us to faithfully determine the symmetry that defines the entire assembly. To validate our structure, we probed the protomer arrangement by solvent paramagnetic resonance enhancement, analysis of chemical shift differences relative to the solution NMR structure of the monomer, and mutagenesis. We provide detailed information on the atomic contacts that determine filament stability and describe mechanistic details on the formation of signaling-competent MAVS filaments from inactive monomers. PMID:26733681

  20. NMR difference spectroscopy with a dual saddle-coil difference probe.

    PubMed

    Macnaughtan, Megan A; Smith, Aaron P; Goldsbrough, Peter B; Santini, Robert E; Raftery, Daniel

    2004-03-01

    A new difference probe for nuclear magnetic resonance (NMR) spectroscopy is presented. The difference probe uses two saddle-shaped coils to excite and detect two samples simultaneously. The samples are held in a specially modified 3-mm NMR tube with an Ultem plastic disk to separate the samples. The probe's resonant circuit contains two crossed diodes that passively switch the relative phase of each coil during the NMR experiment. The result is a difference spectrum from the two samples. The degree of cancellation of common signals was determined to be approximately 90%, and the application of the probe to relaxation-edited difference spectroscopy for identifying protein-ligand interactions was demonstrated using glutathione and glutathione S-transferase binding protein. PMID:15214412

  1. Chiral Recognition Studies of α-(Nonafluoro-tert-butoxy)carboxylic Acids by NMR Spectroscopy.

    PubMed

    Nemes, Anikó; Csóka, Tamás; Béni, Szabolcs; Farkas, Viktor; Rábai, József; Szabó, Dénes

    2015-06-19

    Three chiral α-(nonafluoro-tert-butoxy)carboxylic acids (R)-1, (RS)-2, (R)-3 were synthesized to examine their application as chiral solvating agents with amines. As a model compound, first (S)- and/or (RS)-α-phenylethylamine was used, and their diastereomeric salts were investigated by (1)H and (19)F NMR and ECD spectroscopy. The NMR spectroscopic studies were carried out at room temperature using the slightly polar CDCl3 and apolar C6D6 as solvents in 5 mM and 54 mM concentrations. The difference of the chemical shifts (Δδ) in the diastereomeric complexes is comparable with other, well-known chiral derivatizing and solvating agents (e.g., Mosher's acid, Pirkle's alcohol). Diastereomeric salts of racemic acids (RS)-1 and (RS)-2 with biologically active amines (1R,2S)-ephedrine and (S)-dapoxetine were also investigated by (19)F NMR spectroscopy. PMID:26024423

  2. Probing acid-amide intermolecular hydrogen bonding by NMR spectroscopy and DFT calculations

    NASA Astrophysics Data System (ADS)

    Chaudhari, Sachin Rama; Suryaprakash, N.

    2012-05-01

    Benzene carboxylic acids and benzamide act as their self-complement in molecular recognition to form inter-molecular hydrogen bonded dimers between amide and carboxylic acid groups, which have been investigated by 1H, 13C and 15N NMR spectroscopy. Extensive NMR studies using diffusion ordered spectroscopy (DOSY), variable temperature 1D, 2D NMR, established the formation of heterodimers of benzamide with benzoic acid, salicylic acid and phenyl acetic acid in deuterated chloroform solution. Association constants for the complex formation in the solution state have been determined. The results are ascertained by X-ray diffraction in the solid state. Intermolecular interactions in solution and in solid state were found to be similar. The structural parameters obtained by X-ray diffraction studies are compared with those obtained by DFT calculations.

  3. Surface Binding of TOTAPOL Assists Structural Investigations of Amyloid Fibrils by Dynamic Nuclear Polarization NMR Spectroscopy.

    PubMed

    Nagaraj, Madhu; Franks, Trent W; Saeidpour, Siavash; Schubeis, Tobias; Oschkinat, Hartmut; Ritter, Christiane; van Rossum, Barth-Jan

    2016-07-15

    Dynamic nuclear polarization (DNP) NMR can enhance sensitivity but often comes at the price of a substantial loss of resolution. Two major factors affect spectral quality: low-temperature heterogeneous line broadening and paramagnetic relaxation enhancement (PRE) effects. Investigations by NMR spectroscopy, isothermal titration calorimetry (ITC), and EPR revealed a new substantial affinity of TOTAPOL to amyloid surfaces, very similar to that shown by the fluorescent dye thioflavin-T (ThT). As a consequence, DNP spectra with remarkably good resolution and still reasonable enhancement could be obtained at very low TOTAPOL concentrations, typically 400 times lower than commonly employed. These spectra yielded several long-range constraints that were difficult to obtain without DNP. Our findings open up new strategies for structural studies with DNP NMR spectroscopy on amyloids that can bind the biradical with affinity similar to that shown towards ThT. PMID:27147408

  4. Water Behavior in Bacterial Spores by Deuterium NMR Spectroscopy

    PubMed Central

    2015-01-01

    Dormant bacterial spores are able to survive long periods of time without nutrients, withstand harsh environmental conditions, and germinate into metabolically active bacteria when conditions are favorable. Numerous factors influence this hardiness, including the spore structure and the presence of compounds to protect DNA from damage. It is known that the water content of the spore core plays a role in resistance to degradation, but the exact state of water inside the core is a subject of discussion. Two main theories present themselves: either the water in the spore core is mostly immobile and the core and its components are in a glassy state, or the core is a gel with mobile water around components which themselves have limited mobility. Using deuterium solid-state NMR experiments, we examine the nature of the water in the spore core. Our data show the presence of unbound water, bound water, and deuterated biomolecules that also contain labile deuterons. Deuterium–hydrogen exchange experiments show that most of these deuterons are inaccessible by external water. We believe that these unreachable deuterons are in a chemical bonding state that prevents exchange. Variable-temperature NMR results suggest that the spore core is more rigid than would be expected for a gel-like state. However, our rigid core interpretation may only apply to dried spores whereas a gel core may exist in aqueous suspension. Nonetheless, the gel core, if present, is inaccessible to external water. PMID:24950158

  5. Characterization of animal manure using advanced solid-state C-13 NMR spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of chemical structure of animal manure is necessary for its effective utilization. However, characterization of animal manure is challenging since it is a complex mixture and partially soluble. Solid-state C-13 NMR (nuclear magnetic resonance) spectroscopy is regarded as the best tool to i...

  6. USING HIGH-RESOLUTION SOLUTION-STATE NMR SPECTROSCOPY TO INVESTIGATE PMDI REACTIONS WITH WOOD

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Solution-state NMR spectroscopy provides a powerful tool for understanding the formation of chemical bonds between wood components and adhesives. Finely ground cell wall (CW) material fully dissolves in a solvent system containing dimethylsulfoxide (DMSO-d6) and N-methyl¬imidazole (NMI-d6), keeping ...

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

    SciTech Connect

    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.

  8. Introducing High School Students to NMR Spectroscopy through Percent Composition Determination Using Low-Field Spectrometers

    ERIC Educational Resources Information Center

    Bonjour, Jessica L.; Pitzer, Joy M.; Frost, John A.

    2015-01-01

    Mole to gram conversions, density, and percent composition are fundamental concepts in first year chemistry at the high school or undergraduate level; however, students often find it difficult to engage with these concepts. We present a simple laboratory experiment utilizing portable nuclear magnetic resonance spectroscopy (NMR) to determine the…

  9. Structure Determination of Unknown Organic Liquids Using NMR and IR Spectroscopy: A General Chemistry Laboratory

    ERIC Educational Resources Information Center

    Pavel, John T.; Hyde, Erin C.; Bruch, Martha D.

    2012-01-01

    This experiment introduced general chemistry students to the basic concepts of organic structures and to the power of spectroscopic methods for structure determination. Students employed a combination of IR and NMR spectroscopy to perform de novo structure determination of unknown alcohols, without being provided with a list of possible…

  10. High-Resolution Solid-State NMR Spectroscopy: Characterization of Polymorphism in Cimetidine, a Pharmaceutical Compound

    ERIC Educational Resources Information Center

    Pacilio, Julia E.; Tokarski, John T.; Quiñones, Rosalynn; Iuliucci, Robbie J.

    2014-01-01

    High-resolution solid-state NMR (SSNMR) spectroscopy has many advantages as a tool to characterize solid-phase material that finds applications in polymer chemistry, nanotechnology, materials science, biomolecular structure determination, and others, including the pharmaceutical industry. The technology associated with achieving high resolution…

  11. NMR Spectroscopy of Aqueous Extracts of Fenugreek ( Trigonella foenum- graecum L.)

    NASA Astrophysics Data System (ADS)

    Skakovskii, E. D.; Tychinskaya, L. Yu.; Matveichuk, S. V.; Karankevich, E. G.; Agabalaeva, E. D.; Reshetnikov, V. N.

    2014-09-01

    The amino-acid and monosaccharide compositions of aqueous extracts of fenugreek herb were determined using PMR and 13C NMR spectroscopy. The content of identified extract constituents was >70 mol%, of which the dominant amino acid was 4-hydroxyisoleucine (26.5 mol%); the major carbohydrate, glucose (10.1 mol%).

  12. In situ measurement of molecular diffusion during catalytic reaction by pulsed-field gradient NMR spectroscopy

    SciTech Connect

    Hong, Y.; Kaerger, J.; Hunger, B. ); Feoktistova, N.N.; Zhdanov, S.P. )

    1992-09-01

    Pulsed-field gradient (PFG) NMR spectroscopy is applied to study the intracrystalline diffusivity of the reactant and product molecules during the conversion of cyclopropane to propene in Zeolite X. The diffusivities are found to be large enough that any influence of intracrystalline diffusion on the overall reaction in flow reactors may be excluded.

  13. Characterization of various fast pyrolysis bio-oils by NMR spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    NMR spectroscopy, including 1H, 13 C and DEPT spectra were used to characterize fast pyrolysis oil from numerous energy crops and other agricultural feedstocks. The bio-oils studied were produced from swithchgrass, alfalfa stems, corn stover, guayule (whole plant and latex extracted bagasse) and ch...

  14. (13)C NMR assignments of regenerated cellulose from solid-state 2D NMR spectroscopy.

    PubMed

    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

  15. NMR spectroscopy in studies of light-induced structural changes in mammalian rhodopsin: applicability of solution (19)F NMR.

    PubMed

    Klein-Seetharaman, J; Getmanova, E V; Loewen, M C; Reeves, P J; Khorana, H G

    1999-11-23

    We report high resolution solution (19)F NMR spectra of fluorine-labeled rhodopsin mutants in detergent micelles. Single cysteine substitution mutants in the cytoplasmic face of rhodopsin were labeled by attachment of the trifluoroethylthio (TET), CF(3)-CH(2)-S, group through a disulfide linkage. TET-labeled cysteine mutants at amino acid positions 67, 140, 245, 248, 311, and 316 in rhodopsin were thus prepared. Purified mutant rhodopsins (6-10 mg), in dodecylmaltoside, were analyzed at 20 degrees C by solution (19)F NMR spectroscopy. The spectra recorded in the dark showed the following chemical shifts relative to trifluoroacetate: Cys-67, 9.8 ppm; Cys-140, 10.6 ppm; Cys-245, 9.9 ppm; Cys-248, 9.5 ppm; Cys-311, 9.9 ppm; and Cys-316, 10.0 ppm. Thus, all mutants showed chemical shifts downfield that of free TET (6.5 ppm). On illumination to form metarhodopsin II, upfield changes in chemical shift were observed for (19)F labels at positions 67 (-0.2 ppm) and 140 (-0.4 ppm) and downfield changes for positions 248 (+0.1 ppm) and 316 (+0.1 ppm) whereas little or no change was observed at positions 311 and 245. On decay of metarhodopsin II, the chemical shifts reverted largely to those originally observed in the dark. The results demonstrate the applicability of solution (19)F NMR spectroscopy to studies of the tertiary structures in the cytoplasmic face of intact rhodopsin in the dark and on light activation. PMID:10570143

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  17. Kinetics of the Reaction C2H + O2 from 193 to 350 K Using Laser Flash Kinetic Infrared Absorption Spectroscopy

    NASA Technical Reports Server (NTRS)

    Opansky, Brian J.; Seakins, Paul W.; Pedersen, Jens Olaf P.; Leone, Stephen R.

    1993-01-01

    Rate coefficients for the reaction C2H + O2 are measured from 193 to 350 K by using transient absorption spectroscopy with an infrared color center laser. Ethynyl radicals are produced by pulsed laser photolysis of C2H2 in a temperature variable flow cell and a tunable color center laser probes the transient removal Of C2H ((bar-X(sup 2))Sigma(+))(0,0,0)) in absorption. The rate coefficient has a slight negative temperature dependence over the range 193-350 K which can be expressed as k(O2) = (1.5 +/- 0.3) x 10(exp -11) exp((230 +/- 36)/T) Cu cm/(Molecule.s). The lack of a pressure dependence under our experimental conditions strongly suggests that the HCCOO* complex is short lived with respect to encountering a collision and rapidly dissociates to products without competition from collisional stabilization to HCCOO or collisionally induced dissociation to reactants.

  18. Complex Mixture Analysis of Organic Compounds in Yogurt by NMR Spectroscopy

    PubMed Central

    Lu, Yi; Hu, Fangyu; Miyakawa, Takuya; Tanokura, Masaru

    2016-01-01

    NMR measurements do not require separation and chemical modification of samples and therefore rapidly and directly provide non-targeted information on chemical components in complex mixtures. In this study, one-dimensional (1H, 13C, and 31P) and two-dimensional (1H-13C and 1H-31P) NMR spectroscopy were conducted to analyze yogurt without any pretreatment. 1H, 13C, and 31P NMR signals were assigned to 10 types of compounds. The signals of α/β-lactose and α/β-galactose were separately observed in the 1H NMR spectra. In addition, the signals from the acyl chains of milk fats were also successfully identified but overlapped with many other signals. Quantitative difference spectra were obtained by subtracting the diffusion ordered spectroscopy (DOSY) spectra from the quantitative 1H NMR spectra. This method allowed us to eliminate interference on the overlaps; therefore, the correct intensities of signals overlapped with those from the acyl chains of milk fat could be determined directly without separation. Moreover, the 1H-31P HMBC spectra revealed for the first time that N-acetyl-d-glucosamine-1-phosphate is contained in yogurt. PMID:27322339

  19. New methods and applications in solid-state NMR spectroscopy of quadrupolar nuclei.

    PubMed

    Ashbrook, Sharon E; Sneddon, Scott

    2014-11-01

    Solid-state nuclear magnetic resonance (NMR) spectroscopy has long been established as offering unique atomic-scale and element-specific insight into the structure, disorder, and dynamics of materials. NMR spectra of quadrupolar nuclei (I > (1)/2) are often perceived as being challenging to acquire and to interpret because of the presence of anisotropic broadening arising from the interaction of the electric field gradient and the nuclear electric quadrupole moment, which broadens the spectral lines, often over several megahertz. Despite the vast amount of information contained in the spectral line shapes, the problems with sensitivity and resolution have, until very recently, limited the application of NMR spectroscopy of quadrupolar nuclei in the solid state. In this Perspective, we provide a brief overview of the quadrupolar interaction, describe some of the basic experimental approaches used for acquiring high-resolution NMR spectra, and discuss the information that these spectra can provide. We then describe some interesting recent examples to showcase some of the more exciting and challenging new applications of NMR spectra of quadrupolar nuclei in the fields of energy materials, microporous materials, Earth sciences, and biomaterials. Finally, we consider the possible directions that this highly informative technique may take in the future. PMID:25296129

  20. Complex Mixture Analysis of Organic Compounds in Yogurt by NMR Spectroscopy.

    PubMed

    Lu, Yi; Hu, Fangyu; Miyakawa, Takuya; Tanokura, Masaru

    2016-01-01

    NMR measurements do not require separation and chemical modification of samples and therefore rapidly and directly provide non-targeted information on chemical components in complex mixtures. In this study, one-dimensional (¹H, (13)C, and (31)P) and two-dimensional (¹H-(13)C and ¹H-(31)P) NMR spectroscopy were conducted to analyze yogurt without any pretreatment. ¹H, (13)C, and (31)P NMR signals were assigned to 10 types of compounds. The signals of α/β-lactose and α/β-galactose were separately observed in the ¹H NMR spectra. In addition, the signals from the acyl chains of milk fats were also successfully identified but overlapped with many other signals. Quantitative difference spectra were obtained by subtracting the diffusion ordered spectroscopy (DOSY) spectra from the quantitative ¹H NMR spectra. This method allowed us to eliminate interference on the overlaps; therefore, the correct intensities of signals overlapped with those from the acyl chains of milk fat could be determined directly without separation. Moreover, the ¹H-(31)P HMBC spectra revealed for the first time that N-acetyl-d-glucosamine-1-phosphate is contained in yogurt. PMID:27322339

  1. Solvation and crystal effects in bilirubin studied by NMR spectroscopy and density functional theory.

    PubMed

    Rohmer, Thierry; Matysik, Jörg; Mark, Franz

    2011-10-27

    The open-chain tetrapyrrole compound bilirubin was investigated in chloroform and dimethyl sulfoxide solutions by liquid-state NMR and as solid by (1)H, (13)C, and (15)N magic-angle spinning (MAS) solid-state NMR spectroscopy. Density functional theory (DFT) calculations were performed to interpret the data, using the B3LYP exchange-correlation functional to optimize geometries and to compute NMR chemical shieldings by the gauge-including atomic orbital method. The dependence of geometries and chemical shieldings on the size of the basis sets was investigated for the reference molecules tetramethylsilane, NH(3), and H(2)O, and for bilirubin as a monomer and in clusters consisting of up to six molecules. In order to assess the intrinsic errors of the B3LYP approximation in calculating NMR shieldings, complete basis set estimates were obtained for the nuclear shielding values of the reference molecules. The experimental liquid-state NMR data of bilirubin are well reproduced by a monomeric bilirubin molecule using the 6-311+G(2d,p) basis set for geometry optimization and for calculating chemical shieldings. To simulate the bilirubin crystal, a hexameric model was required. It was constructed from geometry-optimized monomers using information from the X-ray structure of bilirubin to fix the monomeric entities in space and refined by partial optimization. Combining experimental (1)H-(13)C and (1)H-(15)N NMR correlation spectroscopy and density functional theory, almost complete sets of (1)H, (13)C, and (15)N chemical shift assignments were obtained for both liquid and solid states. It is shown that monomeric bilirubin in chloroform solution is formed by 3-vinyl anti conformers, while bilirubin crystals are formed by 3-vinyl syn conformers. This conformational change leads to characteristic differences between the liquid- and solid-state NMR resonances. PMID:21846145

  2. Terahertz Spectroscopy of the Bending Vibrations of Acetylene 12C2H2 and 12C2D2

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Drouin, B.; Pearson, J.

    2009-12-01

    Several fundamental interstellar molecules, e.g., C2H2, CH4 and C3, are completely symmetric molecules and feature no permanent dipole moment and no pure rotation spectrum. As a result they have only previously been observed in the infrared. However, directly observing them with the rest of the molecular column especially when the source is spatially resolved would be very valuable in understanding chemical evolution. Vibrational difference bands provide a means to detect symmetric molecules with microwave precision using terahertz techniques. Herschel, SOFIA and ALMA have the potential to identify a number of vibrational difference bands of light symmetric species. This paper reports laboratory results on 12C2H2 and 12C2D2. Symmetric acetylene isotopologues have two bending modes, the trans bending and the cis bending. Their difference bands are allowed and occur in the microwave, terahertz, and far-infrared wavelengths, with band origins at 3500 GHz for 12C2H2 and 900 GHz for 12C2D2. Twenty 12C2H2 P branch high-J transitions and two hundred and fifty-one 12C2D2 P Q and R branch transitions have been measured in the 0.2 - 1.6 THz region with precision of 50 to 100 kHz. These lines were modeled together with prior data on the pure bending levels. Significantly improved molecular parameters were obtained for 12C2H2 and 12C2D2 with the combined data set, and new frequency and intensity predictions were made to support astrophysics applications. The research was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. S. Y. was supported by an appointment to the NASA Postdoctoral Program, administrated by Oak Ridge Associated Universities through a contract with NASA.

  3. High-resolution heteronuclear multi-dimensional NMR spectroscopy in magnetic fields with unknown spatial variations

    NASA Astrophysics Data System (ADS)

    Zhang, Zhiyong; Huang, Yuqing; Smith, Pieter E. S.; Wang, Kaiyu; Cai, Shuhui; Chen, Zhong

    2014-05-01

    Heteronuclear NMR spectroscopy is an extremely powerful tool for determining the structures of organic molecules and is of particular significance in the structural analysis of proteins. In order to leverage the method’s potential for structural investigations, obtaining high-resolution NMR spectra is essential and this is generally accomplished by using very homogeneous magnetic fields. However, there are several situations where magnetic field distortions and thus line broadening is unavoidable, for example, the samples under investigation may be inherently heterogeneous, and the magnet’s homogeneity may be poor. This line broadening can hinder resonance assignment or even render it impossible. We put forth a new class of pulse sequences for obtaining high-resolution heteronuclear spectra in magnetic fields with unknown spatial variations based on distant dipolar field modulations. This strategy’s capabilities are demonstrated with the acquisition of high-resolution 2D gHSQC and gHMBC spectra. These sequences’ performances are evaluated on the basis of their sensitivities and acquisition efficiencies. Moreover, we show that by encoding and decoding NMR observables spatially, as is done in ultrafast NMR, an extra dimension containing J-coupling information can be obtained without increasing the time necessary to acquire a heteronuclear correlation spectrum. Since the new sequences relax magnetic field homogeneity constraints imposed upon high-resolution NMR, they may be applied in portable NMR sensors and studies of heterogeneous chemical and biological materials.

  4. Binding of Sulfonamide Antibiotics to CTABr Micelles Characterized Using (1)H NMR Spectroscopy.

    PubMed

    Sarker, Ashish K; Cashin, Patrick J; Balakrishnan, Vimal K; Exall, Kirsten; Buncel, Erwin; Brown, R Stephen

    2016-08-01

    Interactions of nine sulfonamide antibiotics (sulfadoxine, sulfathiazole, sulfamethoxazole, sulfamerazine, sulfadiazine, sulfamethazine, sulfacetamide, sulfaguanidine, and sulfanilamide) with cetyltrimethylamonium bromide (CTABr) micelles were examined using (1)H NMR spectroscopy. Seven of the nine provided a significant change in the (1)H NMR chemical shift such that the magnitude and direction (upfield vs downfield) of the chemical shift could be used to propose a locus and orientation of the sulfonamide within the micelle structure. The magnitude of the chemical shift was used to estimate the binding constant for seven sulfonamides with CTABr micelles, providing values and an overall pattern consistent with previous studies of these sulfonamides. PMID:27391918

  5. Synthesis and Proton NMR Spectroscopy of Intra-Vesicular Gamma-Aminobutyric Acid (GABA)*

    PubMed Central

    Wang, Luke Y.-J.; Tong, Rong; Kohane, Daniel S.

    2014-01-01

    We report the synthesis of vesicles containing gamma-aminobutyric acid (GABA), and their proton nuclear magnetic resonance (1H NMR) spectra. These vesicles were constructed to more closely mimic the intracellular environment wherein GABA exists. For this study, these GABA-containing vesicles were examined under 1H NMR as a potential platform for future studies on the differences between aqueous phantoms, ex vivo brain extracts, and in vivo magnetic resonance spectroscopy results. We found that intra-vesicular GABA faithfully yielded the chemical shifts and J-coupling constants of free aqueous GABA, alongside the chemical shift signals of the vesicle wall. PMID:24109882

  6. High frequency volume coils for clinical NMR imaging and spectroscopy.

    PubMed

    Vaughan, J T; Hetherington, H P; Otu, J O; Pan, J W; Pohost, G M

    1994-08-01

    A tuned transmission line resonator has been developed in theory and in practical design for the clinical NMR volume coil application at 4.1 tesla. The distributed circuit transmission line resonator was designed for high frequency, large conductive volume applications where conventional lumped element coil designs perform less efficiently. The resonator design has made use of a resonant coaxial cavity, which could be variably tuned to the Larmor frequency of interest by tunable transmission line elements. Large head- and body-sized volumes, high efficiencies, and broad tuning ranges have been shown to be characteristic of the transmission line resonator to frequencies of 500 MHz. The B1 homogeneity of the resonator has been demonstrated to be a function of the electromagnetic properties of the load itself. By numerically solving Maxwell's equations for the fully time-dependent B1 field, coil homogeneity was predicted with finite-element models of anatomic structure, and inhomogeneities corrected for. A how-to exposition of coil design and construction has been included. Simple methods of quadrature driving and double tuning the transmission line resonator have also been presented. Human head images obtained with a tuned transmission line resonator at 175 MHz have clearly demonstrated uncompromised high field advantages of signal-to-noise and spatial resolution. PMID:7968443

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

    SciTech Connect

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

    2009-06-02

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

  8. Fundamental studies of supported bimetallic catalysts by NMR spectroscopy

    SciTech Connect

    Savargaonkar, N.

    1996-10-17

    Various hydrogenation reactions on transition metals are important commercially whereas certain hydrogenolysis reactions are useful from fundamental point of view. Understanding the hydrogen mobility and kinetics of adsorption-desorption of hydrogen is important in understanding the mechanisms of such reactions involving hydrogen. The kinetics of hydrogen chemisorption was studied by means of selective excitation NMR on silica supported Pt, Rh and Pt-Rh catalysts. The activation energy of hydrogen desorption was found to be lower on silica supported Pt catalysts as compared to Rh and Pt-Rh catalysts. It was found that the rates of hydrogen adsorption and desorption on Pt-Rh catalyst were similar to those on Rh catalyst and much higher as compared to Pt catalyst. The Ru-Ag bimetallic system is much simpler to study than the Pt-Rh system and serves as a model system to characterize more complicated systems such as the K/Ru system. Ag was found to decrease the amounts of adsorbed hydrogen and the hydrogen-to-ruthenium stoichiometry. Ag reduced the populations of states with low and intermediate binding energies of hydrogen on silica supported Ru catalyst. The rates of hydrogen adsorption and desorption were also lower on silica supported Ru-Ag catalyst as compared to Ru catalyst. This report contains introductory information, the literature review, general conclusions, and four appendices. An additional four chapters and one appendix have been processed separately for inclusion on the data base.

  9. Deuterium NMR spectroscopy of biosynthetically deuterated mammalian tissues

    SciTech Connect

    Curatolo, W.; Jungalwala, F.B.; Sears, B.; Tuck, L.; Neuringer, L.J.

    1985-07-30

    The choline-containing phospholipids of mammalian membranes have been biosynthetically deuterated by raising rats on a diet supplemented with (HOCH2CH2N(CD3)3) Cl or (HOCD2CH2N(CH3)3) Cl . Deuterium NMR spectra have been obtained from excised deuterated brain, sciatic nerve, heart, and lung, from isolated brain myelin and brain microsomes, and from aqueous dispersions of lipid extracts. Measurements of residual quadrupole splittings for excised deuterated neural tissues demonstrate that the orientational order of the choline head group is similar to that observed in model membranes. The spin-lattice relaxation time of the choline head group in deuterated neural tissue is indistinguishable from that observed in model membranes. These results support the proposal that the conformation and motional dynamics of the choline head groups of the bulk choline-containing lipids of neural tissue are similar to those in model membranes. Spectra of biosynthetically deuterated brain myelin and brain microsomes exhibit similar quadrupole splittings. Since these membranes have significantly different protein contents, these results indicate that no strong polar interactions exist between membrane proteins and the choline head groups of choline-containing membrane lipids. Spectra of intact deuterated heart and lung exhibit broad lines and a range of quadrupole splittings.

  10. Fractional deuteration applied to biomolecular solid-state NMR spectroscopy.

    PubMed

    Nand, Deepak; Cukkemane, Abhishek; Becker, Stefan; Baldus, Marc

    2012-02-01

    Solid-state Nuclear Magnetic Resonance can provide detailed insight into structural and dynamical aspects of complex biomolecules. With increasing molecular size, advanced approaches for spectral simplification and the detection of medium to long-range contacts become of critical relevance. We have analyzed the protonation pattern of a membrane-embedded ion channel that was obtained from bacterial expression using protonated precursors and D(2)O medium. We find an overall reduction of 50% in protein protonation. High levels of deuteration at H(α) and H(β) positions reduce spectral congestion in ((1)H,(13)C,(15)N) correlation experiments and generate a transfer profile in longitudinal mixing schemes that can be tuned to specific resonance frequencies. At the same time, residual protons are predominantly found at amino-acid side-chain positions enhancing the prospects for obtaining side-chain resonance assignments and for detecting medium to long-range contacts. Fractional deuteration thus provides a powerful means to aid the structural analysis of complex biomolecules by solid-state NMR. PMID:22105305

  11. TERAHERTZ SPECTROSCOPY OF THE BENDING VIBRATIONS OF ACETYLENE {sup 12}C{sub 2}H{sub 2}

    SciTech Connect

    Yu Shanshan; Drouin, Brian J.; Pearson, John C.

    2009-11-01

    Twenty P-branch transitions of {sup 12}C{sub 2}H{sub 2} have been measured in the 0.8-1.6 THz region of its bending vibrational difference band. The accuracy of these measurements is estimated to be 100 kHz. The {sup 12}C{sub 2}H{sub 2} molecules were generated under room temperature by passing 150 mTorr H{sub 2}O vapor through calcium carbide (CaC{sub 2}) powder. The observed transitions were modeled together with prior far-infrared data involving the bending levels with SIGMA{sub t}V{sub t} (t = 4,5)<=2. Frequency predictions of {sup 12}C{sub 2}H{sub 2} in the terahertz region have been greatly improved by adding the first data of 'microwave' precision. The new measurements and predictions reported here will facilitate the analyses of astronomical observations by the high spectral resolution telescopes such as Herschel, SOFIA, and ALMA.

  12. Evidence for a dipolar-coupled AM system in carnosine in human calf muscle from in vivo 1H NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Schröder, Leif; Bachert, Peter

    2003-10-01

    Spin systems with residual dipolar couplings such as creatine, taurine, and lactate in skeletal muscle tissue exhibit first-order spectra in in vivo 1H NMR spectroscopy at 1.5 T because the coupled protons are represented by (nearly) symmetrized eigenfunctions. The imidazole ring protons (H2, H4) of carnosine are suspected to form also a coupled system. The ring's stiffness could enable a connectivity between these anisochronous protons with the consequence of second-order spectra at low field strength. Our purpose was to study whether this deviation from the Paschen-Back condition can be used to detect the H2-H4 coupling in localized 1D 1H NMR spectra obtained at 1.5 T (64 MHz) from the human calf in a conventional whole-body scanner. As for the hydrogen hyperfine interaction, a Breit-Rabi equation was derived to describe the transition from Zeeman to Paschen-Back regime for two dipolar-coupled protons. The ratio of the measurable coupling strength ( Sk) and the difference in resonance frequencies of the coupled spins (Δ ω) induces quantum-state mixing of various degree upon definition of an appropriate eigenbase of the coupled spin system. The corresponding Clebsch-Gordan coefficients manifest in characteristic energy corrections in the Breit-Rabi formula. These additional terms were used to define an asymmetry parameter of the line positions as a function of Sk and Δ ω. The observed frequency shifts of the resonances were found to be consistent with this parameter within the accuracy achievable in in vivo NMR spectroscopy. Thus it was possible to identify the origin of satellite peaks of H2, H4 and to describe this so far not investigated type of residual dipolar coupling in vivo.

  13. Bis(pentamethylcyclopentadienyl)ytterbium: An investigation of weak interactions in solution using multinuclear NMR spectroscopy

    SciTech Connect

    Schwartz, D.J.

    1995-07-01

    NMR spectroscopy is ideal for studying weak interactions (formation enthalpy {le}20 kcal/mol) in solution. The metallocene bis(pentamethylcyclopentadienyl)ytterbium, Cp*{sub 2}Yb, is ideal for this purpose. cis-P{sub 2}PtH{sub 2}complexes (P = phosphine) were used to produce slow-exchange Cp*{sub 2}YbL adducts for NMR study. Reversible formation of (P{sub 2}PtH){sub 2} complexes from cis-P{sub 2}PtH{sub 2} complexes were also studied, followed by interactions of Cp*{sub 2}Yb with phosphines, R{sub 3}PX complexes. A NMR study was done on the interactions of Cp*{sub 2}Yb with H{sub 2}, CH{sub 4}, Xe, CO, silanes, stannanes, C{sub 6}H{sub 6}, and toluene.

  14. Target-based whole-cell screening by ¹H NMR spectroscopy.

    PubMed

    Ma, Junhe; Cao, Qing; McLeod, Sarah M; Ferguson, Keith; Gao, Ning; Breeze, Alexander L; Hu, Jun

    2015-04-13

    An NMR-based approach marries the two traditional screening technologies (phenotypic and target-based screening) to find compounds inhibiting a specific enzymatic reaction in bacterial cells. Building on a previous study in which it was demonstrated that hydrolytic decomposition of meropenem in living Escherichia coli cells carrying New Delhi metallo-β-lactamase subclass 1 (NDM-1) can be monitored in real time by NMR spectroscopy, we designed a cell-based NMR screening platform. A strong NDM-1 inhibitor was identified with cellular IC50 of 0.51 μM, which is over 300-fold more potent than captopril, a known NDM-1 inhibitor. This new screening approach has great potential to be applied to targets in other cell types, such as mammalian cells, and to targets that are only stable or functionally competent in the cellular environment. PMID:25693499

  15. Structures of larger proteins in solution: Three- and four-dimensional heteronuclear NMR spectroscopy

    SciTech Connect

    Gronenborn, A.M.; Clore, G.M.

    1994-12-01

    Complete understanding of a protein`s function and mechanism of action can only be achieved with a knowledge of its three-dimensional structure at atomic resolution. At present, there are two methods available for determining such structures. The first method, which has been established for many years, is x-ray diffraction of protein single crystals. The second method has blossomed only in the last 5 years and is based on the application of nuclear magnetic resonance (NMR) spectroscopy to proteins in solution. This review paper describes three- and four-dimensional NMR methods applied to protein structure determination and was adapted from Clore and Gronenborn. The review focuses on the underlying principals and practice of multidimensional NMR and the structural information obtained.

  16. Fast acquisition of high-resolution 2D NMR spectroscopy in inhomogeneous magnetic fields

    NASA Astrophysics Data System (ADS)

    Lin, Liangjie; Wei, Zhiliang; Zeng, Qing; Yang, Jian; Lin, Yanqin; Chen, Zhong

    2016-05-01

    High-resolution nuclear magnetic resonance (NMR) spectroscopy plays an important role in chemical and biological analyses. In this study, we combine the J-coupling coherence transfer module with the echo-train acquisition technique for fast acquisition of high-resolution 2D NMR spectra in magnetic fields with unknown spatial variations. The proposed method shows satisfactory performance on a 5 mM ethyl 3-bromopropionate sample, under a 5-kHz (10 ppm at 11.7 T) B0 inhomogeneous field, as well as under varying degrees of pulse-flip-angle deviations. Moreover, a simulative ex situ NMR measurement is also conducted to show the effectiveness of the proposed pulse sequence.

  17. Metabolomic differentiation of Cannabis sativa cultivars using 1H NMR spectroscopy and principal component analysis.

    PubMed

    Choi, Young Hae; Kim, Hye Kyong; Hazekamp, Arno; Erkelens, Cornelis; Lefeber, Alfons W M; Verpoorte, Robert

    2004-06-01

    The metabolomic analysis of 12 Cannabis sativa cultivars was carried out by 1H NMR spectroscopy and multivariate analysis techniques. Principal component analysis (PCA) of the 1H NMR spectra showed a clear discrimination between those samples by principal component 1 (PC1) and principal component 3 (PC3) in cannabinoid fraction. The loading plot of PC value obtained from all 1)H NMR signals shows that Delta9-tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA) are important metabolites to differentiate the cultivars from each other. The discrimination of the cultivars could also be obtained from a water extract containing carbohydrates and amino acids. The level of sucrose, glucose, asparagine, and glutamic acid are found to be major discriminating metabolites of these cultivars. This method allows an efficient differentiation between cannabis cultivars without any prepurification steps. PMID:15217272

  18. 33S NMR spectroscopy 3. Substituent effects on 33S NMR parameters in 2-substituted ethanesulfonates.

    PubMed

    Musio, Roberta; Sciacovelli, Oronzo

    2006-08-01

    33S NMR parameters (chemical shifts and linewidths) in 2-substituted sodium ethanesulfonates, XCH2CH2SO3Na (X = H, CH3, OH, SH, NH2, Cl, Br, NH3+) depend upon the electronic properties of substituents. To explain experimental results and obtain additional information on the origin of the observed substituent effect (SE), sulfur isotropic absolute shielding constants have been calculated at DFT level of theory (B3LYP/6-311++G(2d,p)) by gauge-including atomic orbitals (GIAO) method. Data have been interpreted with the aid of natural bond orbital (NBO) method and natural chemical shielding (NCS) analysis. It has been demonstrated that in the class of compounds considered the diamagnetic contribution to sulfur-shielding constant is constant and the observed upfield shift of 33S resonance induced by electron-withdrawing substituents (reverse chemical shift effect) can be related to variations of the paramagnetic contribution. Substituents with different electronic properties cause variations in the polarization of S-C and S-O bonds of the -C-SO3- moiety thus determining changes of the electron density at sulfur nucleus and consequently the expansion or contraction of 3p sulfur orbitals. Also oxygen lone-pairs and sulfur core 2p electrons can play an active role in determining the paramagnetic contribution to sulfur shielding. With regard to linewidth variations, they can be ascribed primarily to changes in the nuclear quadrupole coupling constant values. B3LYP/6-311++G(2d,p) method allows obtaining a good reproducibility of SE on the electric field gradient (EFG) at sulfur, although its values tend to be underestimated significantly. Moreover, 17O shielding constants have been calculated. PMID:16741982

  19. HRMAS-NMR spectroscopy and multivariate analysis meat characterisation.

    PubMed

    Ritota, Mena; Casciani, Lorena; Failla, Sebastiana; Valentini, Massimiliano

    2012-12-01

    ¹H-High resolution magic angle spinning-nuclear magnetic resonance spectroscopy was employed to gain the metabolic profile of longissimus dorsi and semitendinosus muscles of four different breeds: Chianina, Holstein Friesian, Maremmana and Buffalo. Principal component analysis, partial least squares projection to latent structure - discriminant analysis and orthogonal partial least squares projection to latent structure - discriminant analysis were used to build models capable of discriminating the muscle type according to the breed. Data analysis led to an excellent classification for Buffalo and Chianina, while for Holstein Friesian the separation was lower. In the case of Maremmana the use of intelligent bucketing was necessary due to some resonances shifting allowed improvement of the discrimination ability. Finally, by using the Variable Importance in Projection values the metabolites relevant for the classification were identified. PMID:22819725

  20. Direct analysis of δ2H and δ18O in natural and enriched human urine using laser-based, off-axis integrated cavity output spectroscopy.

    PubMed

    Berman, Elena S F; Fortson, Susan L; Snaith, Steven P; Gupta, Manish; Baer, Douglas S; Chery, Isabelle; Blanc, Stephane; Melanson, Edward L; Thomson, Peter J; Speakman, John R

    2012-11-20

    The stable isotopes of hydrogen (δ(2)H) and oxygen (δ(18)O) in human urine are measured during studies of total energy expenditure by the doubly labeled water method, measurement of total body water, and measurement of insulin resistance by glucose disposal among other applications. An ultrasensitive laser absorption spectrometer based on off-axis integrated cavity output spectroscopy was demonstrated for simple and inexpensive measurement of stable isotopes in natural isotopic abundance and isotopically enriched human urine. Preparation of urine for analysis was simple and rapid (approximately 25 samples per hour), requiring no decolorizing or distillation steps. Analysis schemes were demonstrated to address sample-to-sample memory while still allowing analysis of 45 natural or 30 enriched urine samples per day. The instrument was linear over a wide range of water isotopes (δ(2)H = -454 to +1702 ‰ and δ(18)O = -58.3 to +265 ‰). Measurements of human urine were precise to better than 0.65 ‰ 1σ for δ(2)H and 0.09 ‰ 1σ for δ(18)O for natural urines, 1.1 ‰ 1σ for δ(2)H and 0.13 ‰ 1σ for δ(18)O for low enriched urines, and 1.0 ‰ 1σ for δ(2)H and 0.08 ‰ 1σ for δ(18)O for high enriched urines. Furthermore, the accuracy of the isotope measurements of human urines was verified to better than ±0.81 ‰ in δ(2)H and ±0.13 ‰ in δ(18)O (average deviation) against three independent isotope-ratio mass spectrometry laboratories. The ability to immediately and inexpensively measure the stable isotopes of water in human urine is expected to increase the number and variety of experiments which can be undertaken. PMID:23075099

  1. Direct analysis of δ2H and δ18O in natural and enriched human urine using laser-based, Off-Axis Integrated Cavity Output Spectroscopy

    PubMed Central

    Berman, Elena S.F.; Fortsona, Susan L.; Snaith, Steven P.; Gupta, Manish; Baer, Douglas S.; Chery, Isabelle; Blanc, Stephane; Melanson, Edward L.; Thomson, Peter J; Speakman, John R.

    2012-01-01

    The stable isotopes of hydrogen (δ2H) and oxygen (δ18O) in human urine are measured during studies of total energy expenditure by the doubly labeled water method, measurement of total body water, and measurement of insulin resistance by glucose disposal among other applications. An ultrasensitive laser absorption spectrometer based on off-axis integrated cavity output spectroscopy was demonstrated for simple and inexpensive measurement of stable isotopes in natural isotopic abundance and isotopically enriched human urine. Preparation of urine for analysis was simple and rapid (approx. 25 samples per hour), requiring no decolorizing or distillation steps. Analysis schemes were demonstrated to address sample-to-sample memory while still allowing analysis of 45 natural or 30 enriched urine samples per day. The instrument was linear over a wide range of water isotopes (δ2H = −454 to +1702 ‰ and δ18O= −58.3 to +265 ‰). Measurements of human urine were precise to better than 0.65 ‰ 1σ for δ2H and 0.09 ‰ 1σ for δ18O for natural urines, 1.1 ‰ 1σ for δ2H and 0.13 ‰ 1σ for δ18O for low enriched urines, and 1.0 ‰ 1σ for δ2H and 0.08 ‰ 1σ for δ18O for high enriched urines. Furthermore, the accuracy of the isotope measurements of human urines was verified to better than ±0.81 ‰ in δ2H and ±0.13 ‰ in δ18O (average deviation) against three independent IRMS laboratories. The ability to immediately and inexpensively measure the stable isotopes of water in human urine is expected to increase the number and variety of experiments which can be undertaken. PMID:23075099

  2. Investigating brain metabolism at high fields using localized 13C NMR spectroscopy without 1H decoupling.

    PubMed

    Deelchand, Dinesh Kumar; Uğurbil, Kâmil; Henry, Pierre-Gilles

    2006-02-01

    Most in vivo 13C NMR spectroscopy studies in the brain have been performed using 1H decoupling during acquisition. Decoupling imposes significant constraints on the experimental setup (particularly for human studies at high magnetic field) in order to stay within safety limits for power deposition. We show here that incorporation of the 13C label from 13C-labeled glucose into brain amino acids can be monitored accurately using localized 13C NMR spectroscopy without the application of 1H decoupling. Using LCModel quantification with prior knowledge of one-bond and multiple-bond J(CH) coupling constants, the uncertainty on metabolites concentrations was only 35% to 91% higher (depending on the carbon resonance of interest) in undecoupled spectra compared to decoupled spectra in the rat brain at 9.4 Tesla. Although less sensitive, 13C NMR without decoupling dramatically reduces experimental constraints on coil setup and pulse sequence design required to keep power deposition within safety guidelines. This opens the prospect of safely measuring 13C NMR spectra in humans at varied brain locations (not only the occipital lobe) and at very high magnetic fields above 4 Tesla. PMID:16345037

  3. Characterisation of oxygen permeation into a microfluidic device for cell culture by in situ NMR spectroscopy.

    PubMed

    Yilmaz, Ali; Utz, Marcel

    2016-05-24

    A compact microfluidic device for perfusion culture of mammalian cells under in situ metabolomic observation by NMR spectroscopy is presented. The chip is made from poly(methyl methacrylate) (PMMA), and uses a poly(dimethyl siloxane) (PDMS) membrane to allow gas exchange. It is integrated with a generic micro-NMR detector developed recently by our group [J. Magn. Reson., 2016, 262, 73-80]. While PMMA is an excellent material in the context of NMR, PDMS is known to produce strong background signals. To mitigate this, the device keeps the PDMS away from the detection area. The oxygen permeation into the device is quantified using a flow chemistry approach. A solution of glucose is mixed on the chip with a solution of glucose oxidase, before flowing through the gas exchanger. The resulting concentration of gluconate is measured by (1)H NMR spectroscopy as a function of flow rate. An oxygen equilibration rate constant of 2.4 s(-1) is found for the device, which is easily sufficient to maintain normoxic conditions in a cell culture at low perfusion flow rates. PMID:27149932

  4. Differentiating and characterizing geminal silanols in silicas by (29)Si NMR spectroscopy.

    PubMed

    Murray, David K

    2010-12-01

    Single and geminal hydroxyl species in silicas have been characterized using solid-state (29)Si NMR spectroscopy. Differentiating hydroxyl types is important in understanding their roles in chemical toxicity mechanisms for inhaled crystalline silicas responsible for silicosis. (1)H-(29)Si cross polarization NMR spectroscopy has been employed to obtain (29)Si NMR chemical shift data and signal accrual and relaxation characteristics. Spectral deconvolution is used to examine relative single and geminal hydroxyl resonance areas for a series of representative silicas and silica gels. Silicon-containing materials examined include 1878a quartz, and 1879a cristobalite from the National Institute for Science and Technology, kaolin, and several widely used respirable silicas and silica gels. Geminal hydroxyls were observed in every case, with relative resonance areas accounting for 21-65% of total hydroxyl signals. Factors affecting relative areas measured as a function of contact time, relaxation, and surface area are discussed. Subsequent (29)Si and (31)P NMR studies of a silica coated with various sodium hydrogen phosphates show preferential single silanol-phosphate interaction for basic phosphates, and oligomerization products for acidic phosphates. Geminal hydroxyl resonance areas displayed significant error (4-17%) for low surface area silicas, limiting this method to studies exhibiting major changes in chemical or spectroscopic properties. PMID:20825948

  5. Membrane structure and conformational changes of the antibiotic heterodimeric peptide distinctin by solid-state NMR spectroscopy

    PubMed Central

    Resende, Jarbas M.; Moraes, Cléria Mendonça; Munhoz, Victor H. O.; Aisenbrey, Christopher; Verly, Rodrigo M.; Bertani, Philippe; Cesar, Amary; Piló-Veloso, Dorila; Bechinger, Burkhard

    2009-01-01

    The heterodimeric antimicrobial peptide distinctin is composed of 2 linear peptide chains of 22- and 25-aa residues that are connected by a single intermolecular S-S bond. This heterodimer has been considered to be a unique example of a previously unrecorded class of bioactive peptides. Here the 2 distinctin chains were prepared by chemical peptide synthesis in quantitative amounts and labeled with 15N, as well as 15N and 2H, at selected residues, respectively, and the heterodimer was formed by oxidation. CD spectroscopy indicates a high content of helical secondary structures when associated with POPC/POPG 3:1 vesicles or in membrane-mimetic environments. The propensity for helix formation follows the order heterodimer >chain 2 >chain 1, suggesting that peptide-peptide and peptide-lipid interactions both help in stabilizing this secondary structure. In a subsequent step the peptides were reconstituted into oriented phospholipid bilayers and investigated by 2H and proton-decoupled 15N solid-state NMR spectroscopy. Whereas chain 2 stably inserts into the membrane at orientations close to perfectly parallel to the membrane surface in the presence or absence of chain 1, the latter adopts a more tilted alignment, which further increases in the heterodimer. The data suggest that membrane interactions result in considerable conformational rearrangements of the heterodimer. Therefore, chain 2 stably anchors the heterodimer in the membrane, whereas chain 1 interacts more loosely with the bilayer. These structural observations are consistent with the antimicrobial activities when the individual chains are compared to the dimer. PMID:19805350

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

    PubMed

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

    2005-04-12

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

  7. Structural characterization of selenosubtilisin by sup 77 Se-NMR spectroscopy

    SciTech Connect

    House, K.L.; Dunlap, R.B.; Odom, J.D.; Wu, Z.P.; Hilvert. D. Research Inst. of Scripps Clinic, La Jolla, CA )

    1991-03-15

    Selenosubtilisin is an artificial enzyme containing an active site selenocysteine residue. In this environment the selenium atom is a valuable probe of structure-function relationships and also confers novel redox and hydrolytic properties to the original protease template. The authors have used {sup 77}Se NMR spectroscopy to characterize different oxidation states of {sup 77}Se isotopically enriched selenosubtilisin. The oxidized form of the enzyme exhibits a {sup 77}Se resonance at 1,189 ppm. This is in good agreement with the {sup 77}Se chemical shifts for model seleninic acids, confirming that the prosthetic group is in the seleninic acid oxidation state. On treatment of the oxidized enzyme with three equivalents of 3-carboxy-4-nitrobenzenethiol at pH 5.0, they observe the enzyme bound selenenyl sulfide at 388.5 ppm. This work demonstrates the utility of {sup 77}Se NMR spectroscopy for examining structure-function relationships of selenium containing proteins.

  8. Analysis and aging of unsaturated polyester resins in contemporary art installations by NMR spectroscopy.

    PubMed

    Stamatakis, Georgios; Knuutinen, Ulla; Laitinen, Kai; Spyros, Apostolos

    2010-12-01

    Two original art installations constructed from unsaturated polyester resins (UPR) and four different reference UPR products (before and after UVB aging) were analyzed by high-resolution 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. Breaking strain studies were also conducted for the four UPR model products before and after different aging procedures (moisture, UVB exposure, melt/freeze). NMR analysis of the chemical composition of the UPR resin extracts showed they contain several low MW organic compounds and oligomers rich in polar -OH groups that play a significant role in the degradation behavior of the composite UPR materials. Statistical analysis of the NMR compositional data showed that styrene and benzaldehyde contents can be used to differentiate between fresh and aged UPR samples. The phthalate and propylene glycol unit speciation (esterified, primary or secondary -OH) of the extracts provided evidence that UPR resin C was used in the construction of the two art installations, and direct comparison of (1)H and (13)C NMR spectra verified this compositional similarity. UPR resin C was shown by both NMR and breaking strain studies to be the reference UPR most susceptible to degradation by different aging procedures, a characteristic attributed to the lower styrene content of resin C. PMID:20922516

  9. Monitoring the Electrochemical Processes in the Lithium-Air Battery by Solid State NMR Spectroscopy.

    PubMed

    Leskes, Michal; Moore, Amy J; Goward, Gillian R; Grey, Clare P

    2013-12-27

    A multi-nuclear solid-state NMR approach is employed to investigate the lithium-air battery, to monitor the evolution of the electrochemical products formed during cycling, and to gain insight into processes affecting capacity fading. While lithium peroxide is identified by (17)O solid state NMR (ssNMR) as the predominant product in the first discharge in 1,2-dimethoxyethane (DME) based electrolytes, it reacts with the carbon cathode surface to form carbonate during the charging process. (13)C ssNMR provides evidence for carbonate formation on the surface of the carbon cathode, the carbonate being removed at high charging voltages in the first cycle, but accumulating in later cycles. Small amounts of lithium hydroxide and formate are also detected in discharged cathodes and while the hydroxide formation is reversible, the formate persists and accumulates in the cathode upon further cycling. The results indicate that the rechargeability of the battery is limited by both the electrolyte and the carbon cathode stability. The utility of ssNMR spectroscopy in directly detecting product formation and decomposition within the battery is demonstrated, a necessary step in the assessment of new electrolytes, catalysts, and cathode materials for the development of a viable lithium-oxygen battery. PMID:24489976

  10. Monitoring the Electrochemical Processes in the Lithium–Air Battery by Solid State NMR Spectroscopy

    PubMed Central

    2013-01-01

    A multi-nuclear solid-state NMR approach is employed to investigate the lithium–air battery, to monitor the evolution of the electrochemical products formed during cycling, and to gain insight into processes affecting capacity fading. While lithium peroxide is identified by 17O solid state NMR (ssNMR) as the predominant product in the first discharge in 1,2-dimethoxyethane (DME) based electrolytes, it reacts with the carbon cathode surface to form carbonate during the charging process. 13C ssNMR provides evidence for carbonate formation on the surface of the carbon cathode, the carbonate being removed at high charging voltages in the first cycle, but accumulating in later cycles. Small amounts of lithium hydroxide and formate are also detected in discharged cathodes and while the hydroxide formation is reversible, the formate persists and accumulates in the cathode upon further cycling. The results indicate that the rechargeability of the battery is limited by both the electrolyte and the carbon cathode stability. The utility of ssNMR spectroscopy in directly detecting product formation and decomposition within the battery is demonstrated, a necessary step in the assessment of new electrolytes, catalysts, and cathode materials for the development of a viable lithium–oxygen battery. PMID:24489976

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

    NASA Astrophysics Data System (ADS)

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

    1994-09-01

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

  12. Gyrotron FU CW VII for 300 MHz and 600 MHz DNP-NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Idehara, Toshitaka; Kosuga, Kosuke; Agusu, La; Ogawa, Isamu; Takahashi, Hiroki; Smith, Mark E.; Dupree, Ray

    2010-07-01

    Gyrotron FU CW VII, one of the FU CW Series Gyrotrons, has been designed, constructed and completed operational tests successfully in the Research Center for Development of Far Infrared Region, University of Fukui (FIR FU). The gyrotron operates at around 200 GHz for the fundamental cyclotron resonances and at around 400 GHz for the second harmonics. These radiation frequencies will be applied to 300 MHz and 600 MHz DNP enhanced NMR spectroscopy.

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

    NASA Astrophysics Data System (ADS)

    Berns, Anne E.; Conte, Pellegrino

    2010-05-01

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

  14. Distortion of ethyne on coordination to silver acetylide, C2H2⋅⋅⋅AgCCH, characterised by broadband rotational spectroscopy and ab initio calculations.

    PubMed

    Stephens, Susanna L; Zaleski, Daniel P; Mizukami, Wataru; Tew, David P; Walker, Nicholas R; Legon, Anthony C

    2014-03-28

    The rotational spectra of six isotopologues of a complex of ethyne and silver acetylide, C2H2⋅⋅⋅AgCCH, are measured by both chirped-pulse and Fabry-Perot cavity versions of Fourier-transform microwave spectroscopy. The complex is generated through laser ablation of a silver target in the presence of a gas sample containing 1% C2H2, 1% SF6, and 98% Ar undergoing supersonic expansion. Rotational, A0, B0, C0, and centrifugal distortion ΔJ and ΔJK constants are determined for all isotopologues of C2H2⋅⋅⋅AgCCH studied. The geometry is planar, C2v and T-shaped in which the C2H2 sub-unit comprises the bar of the "T" and binds to the metal atom through its π electrons. In the r0 geometry, the distance of the Ag atom from the centre of the triple bond in C2H2 is 2.2104(10) Å. The r(HC≡CH) parameter representing the bond distance separating the two carbon atoms and the angle, ∠(CCH), each defined within the C2H2 sub-unit, are determined to be 1.2200(24) Å and 186.0(5)°, respectively. This distortion of the linear geometry of C2H2 involves the hydrogen atoms moving away from the silver atom within the complex. The results thus reveal that the geometry of C2H2 changes measurably on coordination to AgCCH. A value of 59(4) N m(-1) is determined for the intermolecular force constant, kσ, confirming that the complex is significantly more strongly bound than hydrogen and halogen-bonded analogues. Ab initio calculations of the re geometry at the CCSD(T)(F12(*))/ACVTZ level of theory are consistent with the experimental results. The spectra of the (107)Ag(13)C(13)CH and (109)Ag(13)C(13)CH isotopologues of free silver acetylide are also measured for the first time allowing the geometry of the AgCCH monomer to be examined in greater detail than previously. PMID:24697444

  15. Single-shot diffusion trace (1)H NMR spectroscopy.

    PubMed

    de Graaf, R A; Braun, K P; Nicolay, K

    2001-05-01

    Ignoring diffusion anisotropy can severely hamper the quantitative determination of water and metabolite diffusion in complex tissues. The measurement of the trace of the diffusion tensor provides unambiguous and rotationally invariant ADC values, but usually requires three separate experiments. A single-shot technique developed earlier, originally designed for diffusion trace MR imaging (Mori and van Zijl, Magn Reson Med 1995;33:41-52), was improved and adapted for diffusion trace MR spectroscopy. A double spin-echo pulse sequence was incorporated with four pairs of bipolar gradients with specific predetermined relative signs in each of the three orthogonal directions. The combination of gradient directions leads to cancellation of all off-diagonal tensor elements while constructively adding the diagonal elements. Furthermore, the pulse scheme provides complete compensation for cross-terms between static magnetic field gradients and the applied diffusion gradients, while simultaneously avoiding cross-terms with localization gradients. The sequence was tested at 4.7 T in vivo on rat brain for MRI and on rat skeletal muscle and brain for MRS. It is shown that the average ADC as determined from the measurement of the ADCs in the three orthogonal directions is in close agreement with the ADC obtained along the trace of the diffusion tensor in a single acquisition, for both water and metabolite diffusion. The large differences in water and metabolite diffusion coefficients as measured in the individual orthogonal directions illustrate the need for diffusion trace measurements when accurate and rotationally invariant diffusion quantitation is required. The pulse scheme presented here may be applied for such purposes in MRS and MRI studies. PMID:11323799

  16. Methodology of 1H NMR Spectroscopy of the Human Brain at Very High Magnetic Fields

    PubMed Central

    Tkáč, I.; Gruetter, R.

    2009-01-01

    An ultrashort-echo-time stimulated echo-acquisition mode (STEAM) pulse sequence with interleaved outer volume suppression and VAPOR (variable power and optimized relaxation delays) water suppression was redesigned and optimized for human applications at 4 and 7 T, taking into account the specific requirements for spectroscopy at high magnetic fields and limitations of currently available hardware. In combination with automatic shimming, automated parameter adjustments and data processing, this method provided a user-friendly tool for routine 1H nuclear magnetic resonance (NMR) spectroscopy of the human brain at very high magnetic fields. Effects of first- and second-order shimming, single-scan averaging, frequency and phase corrections, and eddy currents were described. LCModel analysis of an in vivo 1H NMR spectrum measured from the human brain at 7 T allowed reliable quantification of more than fifteen metabolites noninvasively, illustrating the potential of high-field NMR spectroscopy. Examples of spectroscopic studies performed at 4 and 7 T demonstrated the high reproducibility of acquired spectra quality. PMID:20179773

  17. INVESTIGATION INTO HOW WOOD CELL WALLS INTERACT WITH SYNTHETIC ADHESIVES USING HIGH-RESOLUTION SOLUTION-STATE NMR SPECTROSCOPY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    With the continued growth of the wood adhesive industry and the need to create durable and environmentally friendly adhesive systems, it is still unclear whether covalent bonds contribute to wood adhesive bond strength. In order to investigate this question, solid-state NMR spectroscopy (NMR) has be...

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

    PubMed Central

    Polenova, Tatyana; Gupta, Rupal; Goldbourt, Amir

    2016-01-01

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

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

    PubMed Central

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

    2014-01-01

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

  20. Terahertz Spectroscopy and Global Analysis of the Bending Vibrations of ^{12}C_2H_2 and ^{12}C_2D_2

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Drouin, Brian J.; Pearson, John C.; Pickett, Herbert M.; Lattanzi, Valerio; Walters, Adam

    2009-06-01

    Symmetric molecules have no permanent dipole moment and are undetectable by rotational spectroscopy. Their interstellar observations have previously been limited to mid-infrared vibration-rotation spectroscopy. Although relatively weak, vibrational difference bands provide a means for detection of non polar molecules by terahertz techniques with microwave precision. Herschel, SOFIA, and ALMA have the potential to identify a number of difference bands of light symmetric species, e.g., C_2H_2, CH_4 and C_3. This paper reports the results of the laboratory study on ^{12}C_2H_2 and ^{12}C_2D_2. The symmetric isotopomers of acetylene have two bending modes, the trans bending ν_4 (^1{π}_g), and the cis bending ν_5 (^1{π}_u). For ^{12}C_2H_2, the two bending modes occur at 612 and 729 cm^{-1}, respectively. For ^{12}C_2D_2, the two bending modes occur at 511 and 538 cm^{-1}. The ν_5-ν_4 difference bands are allowed and occur in the microwave, terahertz, and far-infrared wavelengths, with band origins at 117 cm^{-1} (3500 GHz) for ^{12}C_2H_2 and 27 cm^{-1} (900 GHz) for ^{12}C_2D_2. Two hundred and fifty-one ^{12}C_2D_2 transitions, which are from ν_5-ν_4, (ν_5+ν_4)-2ν_4 and 2ν_5-(ν_5+ν_4) bands, have been measured in the 0.2-1.6 THz region, and 202 of them were observed for the first time. The precision of these measurements is estimated to be from 50 kHz to 100 kHz. A multistate analysis was carried out for the bending vibrational modes ν_4 and ν_5 of ^{12}C_2D_2, which includes the lines observed in this work and prior microwave, far-infrared and infrared data on the pure bending levels. Significantly improved molecular parameters were obtained for ^{12}C_2D_2 by adding the new measurements to the old data set which had only 10 lines with microwave measurement precision. The experiments on ^{12}C_2H_2 are in progress and ten P branch lines have been observed. We will present the ^{12}C_2H_2 results to date.

  1. Investigation of the dispersion and the effective masses of excitons in bulk 2 H -MoS2 using transition electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Habenicht, Carsten; Knupfer, Martin; Büchner, Bernd

    2015-06-01

    We have investigated the electronic excitations in bulk 2 H -MoS2 using electron energy-loss spectroscopy. The electron energy-loss spectra in the Γ M and Γ K directions were measured for various momentum transfer values. The results allow the identification of the A1 and B1 exciton peaks and in particular their energy-momentum dispersion. The dispersions exhibit approximately quadratic upward trends and slight anisotropies in the Γ M and Γ K directions. The fitted energy-momentum transfer functions allow the estimation of the effective masses of the excitons which are in close proximity to predicted values.

  2. Identifying metabolites related to nitrogen mineralisation using 1H NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    . T McDonald, Noeleen; Graham, Stewart; Watson, Catherine; Gordon, Alan; Lalor, Stan; Laughlin, Ronnie; Elliott, Chris; . P Wall, David

    2015-04-01

    Exploring new analysis techniques to enhance our knowledge of the various metabolites within our soil systems is imperative. Principally, this knowledge would allow us to link key metabolites with functional influences on critical nutrient processes, such as the nitrogen (N) mineralisation in soils. Currently there are few studies that utilize proton nuclear magnetic resonance spectroscopy (1H NMR) to characterize multiple metabolites within a soil sample. The aim of this research study was to examine the effectiveness of 1H NMR for isolating multiple metabolites that are related to the mineralizable N (MN) capacity across a range of 35 Irish grassland soils. Soils were measured for MN using the standard seven day anaerobic incubation (AI-7). Additionally, soils were also analysed for a range of physio-chemical properties [e.g. total N, total C, mineral N, texture and soil organic matter (SOM)]. Proton NMR analysis was carried on these soils by extracting with 40% methanol:water, lyophilizing and reconstituting in deuterium oxide and recording the NMR spectra on a 400MHz Bruker AVANCE III spectrometer. Once the NMR data were spectrally processed and analysed using multivariate statistical analysis, seven metabolites were identified as having significant relationships with MN (glucose, trimethylamine, glutamic acid, serine, aspartic acid, 4-aminohippuirc acid and citric acid). Following quantification, glucose was shown to explain the largest percentage variability in MN (72%). These outcomes suggest that sources of labile carbon are essential in regulating N mineralisation and the capacity of plant available N derived from SOM-N pools in these soils. Although, smaller in concentration, the amino acids; 4-aminohippuirc acid, glutamic acid and serine also significantly (P<0.05) explained 43%, 27% and 19% of the variability in MN, respectively. This novel study highlights the effectiveness of using 1H NMR as a practical approach to profile multiple metabolites in

  3. Submillimeter Spectroscopy of the Out-Of Bending State ν_{20} of C_2H_5CN

    NASA Astrophysics Data System (ADS)

    Pearson, John C.; Brauer, Carolyn S.; Yu, Shanshan; Drouin, Brian J.

    2009-06-01

    Propionitrile is a well known interstellar molecule that is a closely associated with warm dust near ultra compact H_{II} regions. In these regions the C_2H_5CN column can reach 10^{17} and the rotational temperature often equals the vibrational temperature and exceeds 200 K, populating all the low-lying vibrational states. The rotational spectrum of the third lowest excited vibrational state, the 378 cm^{-1} out-of-plane bending state, ν_{20}, of propionitrile, which was previously identified at millimeter wavelengths in both the laboratory and the interstellar medium, has been characterized to high angular momentum quantum numbers. This state is surprisingly isolated considering its proximity to the overtone of the in-plane bend, 2ν_{13}, the excited torsional state of the in-plane bend, ν_{13}+ν_{21}, and the second excited torsional state, 2ν_{21}, which lie approximately 35 cm^{-1} higher. The only surprising aspect is the presence of significantly larger torsional A-E splitting than observed in either the ground state or the ν_{13} in the absence of a resonance with ν_{21}. Because ν_{20} has been observed in high mass star forming cores in the millimeter, its higher angular momentum lines are known to be a major source of line confusion in high mass star forming cores. The spectrum, constants and determined barriers will be presented.

  4. Structure and properties of the (HCl)2H2O cluster observed by chirped-pulse Fourier transform microwave spectroscopy.

    PubMed

    Kisiel, Zbigniew; Lesarri, Alberto; Neill, Justin L; Muckle, Matt T; Pate, Brooks H

    2011-08-21

    The rotational spectrum of the cyclic (HCl)(2)H(2)O cluster has been identified for the first time in the chirped pulse, Fourier transform microwave spectrum of a supersonically expanded HCl/H(2)O/Ar mixture. The spectrum was measured at frequencies 6-18.5 GHz, and transitions in two inversion-tunneling states, at close to 1 : 3 relative intensity, have been assigned for the parent species. The two single (37)Cl isotopic species, and the double (37)Cl species have been assigned in the natural abundance sample, and the (18)O and HDO species of the cluster were identified in isotopically enriched samples. The rich nuclear quadrupole hyperfine structure due to the presence of two chlorine nuclei has been satisfactorily fitted and provided useful information on the nonlinearity of intermolecular bonds in the cluster. The r(s) heavy atom geometry of the cluster was determined and the strongest bond in the intermolecular cycle r(O···HCl) = 3.126(3) Å, is found to be intermediate in length between the values in H(2)O···HCl and (H(2)O)(2)HCl. The fitted spectroscopic constants and derived molecular properties are compared with ab initio predictions, and a discussion of complexation effects in these three clusters is made. PMID:21743896

  5. Membrane topology of a 14-mer model amphipathic peptide: a solid-state NMR spectroscopy study.

    PubMed

    Ouellet, Marise; Doucet, Jean-Daniel; Voyer, Normand; Auger, Michèle

    2007-06-01

    We have investigated the interaction between a synthetic amphipathic 14-mer peptide and model membranes by solid-state NMR. The 14-mer peptide is composed of leucines and phenylalanines modified by the addition of crown ethers and forms a helical amphipathic structure in solution and bound to lipid membranes. To shed light on its membrane topology, 31P, 2H, 15N solid-state NMR experiments have been performed on the 14-mer peptide in interaction with mechanically oriented bilayers of dilauroylphosphatidylcholine (DLPC), dimyristoylphosphatidylcholine (DMPC), and dipalmitoylphosphatidylcholine (DPPC). The 31P, 2H, and 15N NMR results indicate that the 14-mer peptide remains at the surface of the DLPC, DMPC, and DPPC bilayers stacked between glass plates and perturbs the lipid orientation relative to the magnetic field direction. Its membrane topology is similar in DLPC and DMPC bilayers, whereas the peptide seems to be more deeply inserted in DPPC bilayers, as revealed by the greater orientational and motional disorder of the DPPC lipid headgroup and acyl chains. 15N{31P} rotational echo double resonance experiments have also been used to measure the intermolecular dipole-dipole interaction between the 14-mer peptide and the phospholipid headgroup of DMPC multilamellar vesicles, and the results indicate that the 14-mer peptide is in contact with the polar region of the DMPC lipids. On the basis of these studies, the mechanism of membrane perturbation of the 14-mer peptide is associated to the induction of a positive curvature strain induced by the peptide lying on the bilayer surface and seems to be independent of the bilayer hydrophobic thickness. PMID:17487978

  6. Distinguishing Phosphate Structural Defects From Inclusions in Calcite and Aragonite by NMR Spectroscopy (Invited)

    NASA Astrophysics Data System (ADS)

    Phillips, B. L.; Mason, H. E.

    2010-12-01

    Variations in the concentration of minor and trace elements are being studied extensively for potential use as proxies to infer environmental conditions at the time of mineral deposition. Such proxies rely fundamentally on a relationship between the activities in the solution and in the solid that would seem to be simple only in the case that the species substitutes into the mineral structure. Other incorporation mechanisms are possible, including inclusions (both mineral and fluid) and occlusion of surface adsorbate complexes, that might be sensitive to other factors, such as crystallization kinetics, and difficult to distinguish analytically. For example, it is known from mineral adsorption studies that surface precipitates can be nanoscopic, and might not be apparent at resolutions typical of microchemical analysis. Techniques by which a structural relationship between the substituting element and the host mineral structure are needed to provide a sound basis for geochemical proxies. NMR spectroscopy offers methods for probing such spatial relationship. We are using solid-state NMR spectroscopy to investigate phosphate incorporation in calcium carbonate minerals, including calcite speleothems and coral skeletal aragonite, at concentrations of the order 100 μg P g -1. In 31P NMR spectra of most samples, narrow peaks arising from crystalline inclusions can be resolved, including apatite in coral aragonite and an unidentified phase in calcite. All samples studied yield also a broad 31P signal, centered near chemical shifts of +3 to +4 ppm, that could be assigned to phosphate defects in the host mineral and from which the fraction of P occurring in the carbonate mineral structure can be determined. To test this assignment we applied rotational-echo double-resonance (REDOR) NMR techniques that probe the molecular-scale proximity of carbonate groups to the phosphate responsible for the broad 31P peak. This method measures dipole-dipole coupling between 31P of

  7. Stereochemistry of 16a-hydroxyfriedelin and 3-Oxo-16-methylfriedel-16-ene established by 2D NMR spectroscopy.

    PubMed

    Duarte, Lucienir Pains; Silva de Miranda, Roqueline Rodrigues; Rodrigues, Salomão Bento Vasconcelos; de Fátima Silva, Grácia Divina; Vieira Filho, Sidney Augusto; Knupp, Vagner Fernandes

    2009-01-01

    Friedelin (1), 3beta-friedelinol (2), 28-hydroxyfriedelin (3), 16alpha-hydroxyfriedelin (4), 30-hydroxyfriedelin (5) and 16alpha,28-dihydroxyfriedelin (6) were isolated through fractionation of the hexane extract obtained from branches of Salacia elliptica. After a week in CDCl(3) solution, 16alpha-hydroxyfriedelin (4) reacted turning into 3-oxo-16-methylfriedel-16-ene (7). This is the first report of a dehydration followed by a Nametkin rearrangement of a pentacyclic triterpene in CDCl(3) solution occurring in the NMR tube. These seven pentacyclic triterpenes was identified through NMR spectroscopy and the stereochemistry of compound 4 and 7 was established by 2D NMR (NOESY) spectroscopy and mass spectrometry (GC-MS). It is also the first time that all the (13)C-NMR and 2D NMR spectral data are reported for compounds 4 and 7. PMID:19214150

  8. NMR spectroscopy as a tool to close the gap on metabolite characterization under MIST.

    PubMed

    Caceres-Cortes, Janet; Reily, Michael D

    2010-07-01

    Withdrawals from the market due to unforeseen adverse events have triggered changes in the way therapeutics are discovered and developed. This has resulted in an emphasis on truly understanding the efficacy and toxicity profile of new chemical entities (NCE) and the contributions of their metabolites to on-target pharmacology and off-target receptor-mediated toxicology. Members of the pharmaceutical industry, scientific community and regulatory agencies have held dialogues with respect to metabolites in safety testing (MIST); and both the US FDA and International Conference on Harmonisation have issued guidances with respect to when and how to characterize metabolites for human safety testing. This review provides a brief overview of NMR spectroscopy as applied to the structure elucidation and quantification of drug metabolites within the drug discovery and development process. It covers advances in this technique, including cryogenic cooling of detection circuitry for enhanced sensitivity, hyphenated LC-NMR techniques, improved dynamic range through new solvent-suppression pulse sequences and quantitation. These applications add to the already diverse NMR toolkit and further anchor NMR as a technique that is directly applicable to meeting the requirements of MIST guidelines. PMID:21083239

  9. Survey and qualification of internal standards for quantification by 1H NMR spectroscopy.

    PubMed

    Rundlöf, Torgny; Mathiasson, Marie; Bekiroglu, Somer; Hakkarainen, Birgit; Bowden, Tim; Arvidsson, Torbjörn

    2010-09-01

    In quantitative NMR (qNMR) selection of an appropriate internal standard proves to be crucial. In this study, 25 candidate compounds considered to be potent internal standards were investigated with respect to the ability of providing unique signal chemical shifts, purity, solubility, and ease of use. The (1)H chemical shift (delta) values, assignments, multiplicities and number of protons (for each signal), appropriateness (as to be used as internal standards) in four different deuterated solvents (D(2)O, DMSO-d(6), CD(3)OD, CDCl(3)) were studied. Taking into account the properties of these 25 internal standards, the most versatile eight compounds (2,4,6-triiodophenol, 1,3,5-trichloro-2-nitrobenzene, 3,4,5-trichloropyridine, dimethyl terephthalate, 1,4-dinitrobenzene, 2,3,5-triiodobenzoic acid, maleic acid and fumaric acid) were qualified using both differential scanning calorimetry (DSC) and NMR spectroscopy employing highly pure acetanilide as the reference standard. The data from these two methods were compared as well as utilized in the quality assessment of the compounds as internal standards. Finally, the selected internal standards were tested and evaluated in a real case of quantitative NMR analysis of a paracetamol pharmaceutical product. PMID:20207092

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

    DOE PAGESBeta

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

    2015-06-22

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

  11. Structure-Correlation NMR Spectroscopy for Macromolecules Using Repeated Bidirectional Photoisomerization of Azobenzene.

    PubMed

    Nagashima, Toshio; Ueda, Keisuke; Nishimura, Chiaki; Yamazaki, Toshio

    2015-11-17

    Control over macromolecular structure offers bright potentials for manipulation of macromolecular functions. We here present structure-correlation NMR spectroscopy to analyze the correlation between polymorphic macromolecular structures driven by photoisomerization of azobenzene. The structural conversion of azobenzene was induced within the mixing time of a NOESY experiment using a colored light source, and the reverse structural conversion was induced during the relaxation delay using a light source of another color. The correlation spectrum between trans- and cis-azobenzene was then obtained. To maximize the efficiency of the bidirectional photoisomerization of azobenzene-containing macromolecules, we developed a novel light-irradiation NMR sample tube and method for irradiating target molecules in an NMR radio frequency (rf) coil. When this sample tube was used for photoisomerization of an azobenzene derivative at a concentration of 0.2 mM, data collection with reasonable sensitivity applicable to macromolecules was achieved. We performed isomerization of an azobenzene-cross-linked peptide within the mixing time of a NOESY experiment that produced cross-peaks between helix and random-coil forms of the peptide. Thus, these results indicate that macromolecular structure manipulation can be incorporated into an NMR pulse sequence using an azobenzene derivative and irradiation with light of two types of wavelengths, providing a new method for structural analysis of metastable states of macromolecules. PMID:26479462

  12. In-situ unsaturated zone stable water isotope (2H and 18O) measurements in semi-arid environments using tunable off-axis integrated cavity output spectroscopy

    NASA Astrophysics Data System (ADS)

    Gaj, M.; Beyer, M.; Koeniger, P.; Wanke, H.; Hamutoko, J.; Himmelsbach, T.

    2015-06-01

    Stable isotopes (deuterium, 2H, and oxygen-18, 18O) of soil pore water were measured directly in the field using tunable off-axis integrated cavity output spectroscopy (OA-ICOS) and commercially available soil gas probes in a semi-arid region of the Cuvelai-Etosha-Basin, Namibia. High spatial and temporal resolution was achieved in the study area with reasonable accuracy and measurements were in agreement with laboratory-based cryogenic vacuum extraction and subsequent cavity ring down laser spectroscopic isotope analysis (CRDS). After drift correction of the isotope data, mean precision for over 140 measurements of two consecutive field campaigns in June and November 2014 were 1.8 and 0.46 ‰ for δ2H and 18O, respectively. Mean Accuracy using quality check standards was 5 and 0.3 ‰ for δ2H and δ18O, respectively. Results support the applicability of an in-situ measurement system for the determination of stable isotopes in soil pore water. Spatio-temporal variability could be deduced with the observed data in an extremely dry evaporation dominated environment which was sporadically affected by intermittent rainfall.

  13. The halogen bond between ethene and a simple perfluoroiodoalkane: C2H4\\ctdot ICF3 identified by broadband rotational spectroscopy

    NASA Astrophysics Data System (ADS)

    Stephens, Susanna L.; Mizukami, Wataru; Tew, David P.; Walker, Nicholas R.; Legon, Anthony C.

    2012-10-01

    An isolated complex of C2H4 and ICF3 has been generated in the gas phase and studied by chirped-pulse, Fourier transform microwave (CP-FTMW) spectroscopy. Ab initio calculations at the CCSD(T)(F12*)/VTZ level support the experimental work and further establish the dissociation energy, De, and dipole moment, μ, of the complex. Rotational constants, B0 and C0, the centrifugal distortion constant, ΔJ, nuclear quadrupole coupling constants, χaa (I) and (χbb(I)-χcc(I)) and the nuclear spin-rotation coupling constant Cbb(I) of the complex are determined from the experimental data. The iodine atom interacts with π-electrons on C2H4 resulting in the formation of a linear (∠(Csbnd I⋯*)) halogen bond (where * indicates the centre of the Cdbnd C bond) and a complex of Cs symmetry. The measured rotational constants allow the length of the halogen bond to be determined as 3.434(2) Å in the r0 geometry. The complex is formally an asymmetric top but with a very low barrier to internal rotation of C2H4 about the C3 axis defined by the CF3I sub-unit. Adopting an approach also used in a recent study of H2O⋯ICF3, other transitions are assigned using the Hamiltonian of a symmetric top molecule.

  14. pKa determination by ¹H NMR spectroscopy - an old methodology revisited.

    PubMed

    Bezençon, Jacqueline; Wittwer, Matthias B; Cutting, Brian; Smieško, Martin; Wagner, Bjoern; Kansy, Manfred; Ernst, Beat

    2014-05-01

    pKa values of acids and protonated bases have an essential impact on organic synthesis, medicinal chemistry, and material and food sciences. In drug discovery and development, they are of utmost importance for the prediction of pharmacokinetic and pharmacodynamic properties. To date, various methods for the determination of pKa values are available, including UV-spectroscopic, potentiometric, and capillary electrophoretic techniques. An additional option is provided by nuclear magnetic resonance (NMR) spectroscopy. The underlying principle is the alteration of chemical shifts of NMR-active nuclei (e.g., (13)C and (1)H) depending on the protonation state of adjacent acidic or basic sites. When these chemical shifts are plotted against the pH, the inflection point of the resulting sigmoidal curve defines the pKa value. Although pKa determinations by (1)H NMR spectroscopy are reported for numerous cases, the potential of this approach is not yet fully evaluated. We therefore revisited this method with a diverse set of test compounds covering a broad range of pKa values (pKa 0.9-13.8) and made a comparison with four commonly used approaches. The methodology revealed excellent correlations (R(2)=0.99 and 0.97) with electropotentiometric and UV spectroscopic methods. Moreover, the comparison with in silico results (Epik and Marvin) also showed high correlations (R(2)=0.92 and 0.94), further confirming the reliability and utility of this approach. PMID:24462329

  15. Qualitative and Quantitative Control of Carbonated Cola Beverages Using 1H NMR Spectroscopy

    PubMed Central

    2012-01-01

    1H Nuclear magnetic resonance (NMR) spectroscopy (400 MHz) was used in the context of food surveillance to develop a reliable analytical tool to differentiate brands of cola beverages and to quantify selected constituents of the soft drinks. The preparation of the samples required only degassing and addition of 0.1% of TSP in D2O for locking and referencing followed by adjustment of pH to 4.5. The NMR spectra obtained can be considered as “fingerprints” and were analyzed by principal component analysis (PCA). Clusters from colas of the same brand were observed, and significant differences between premium and discount brands were found. The quantification of caffeine, acesulfame-K, aspartame, cyclamate, benzoate, hydroxymethylfurfural (HMF), sulfite ammonia caramel (E 150D), and vanillin was simultaneously possible using external calibration curves and applying TSP as internal standard. Limits of detection for caffeine, aspartame, acesulfame-K, and benzoate were 1.7, 3.5, 0.8, and 1.0 mg/L, respectively. Hence, NMR spectroscopy combined with chemometrics is an efficient tool for simultaneous identification of soft drinks and quantification of selected constituents. PMID:22356160

  16. 51V solid-state magic angle spinning NMR spectroscopy of vanadium chloroperoxidase.

    PubMed

    Pooransingh-Margolis, Neela; Renirie, Rokus; Hasan, Zulfiqar; Wever, Ron; Vega, Alexander J; Polenova, Tatyana

    2006-04-19

    We report 51V solid-state NMR spectroscopy of the 67.5-kDa vanadium chloroperoxidase, at 14.1 T. We demonstrate that, despite the low concentration of vanadium sites in the protein (one per molecule, 1 mumol of vanadium spins in the entire sample), the spinning sideband manifold spanning the central and the satellite transitions is readily detectable. The quadrupolar and chemical shift anisotropy tensors have been determined by numerical simulations of the spinning sideband envelopes and the line shapes of the individual spinning sidebands corresponding to the central transition. The observed quadrupolar coupling constant C(Q) of 10.5 +/- 1.5 MHz and chemical shift anisotropy delta(sigma) of -520 +/- 13 ppm are sensitive reporters of the geometric and electronic structure of the vanadium center. Density functional theory calculations of the NMR spectroscopic observables for an extensive series of active site models indicate that the vanadate cofactor is most likely anionic with one axial hydroxo- group and an equatorial plane consisting of one hydroxo- and two oxo- groups. The work reported in this manuscript is the first example of 51V solid-state NMR spectroscopy applied to probe the vanadium center in a protein directly. This approach yields the detailed coordination environment of the metal unavailable from other experimental measurements and is expected to be generally applicable for studies of diamagnetic vanadium sites in metalloproteins. PMID:16608356

  17. NMR Spectroscopy of Human Eye Tissues: A New Insight into Ocular Biochemistry

    PubMed Central

    Kryczka, Tomasz; Wylęgała, Edward; Dobrowolski, Dariusz; Midelfart, Anna

    2014-01-01

    Background. The human eye is a complex organ whose anatomy and functions has been described very well to date. Unfortunately, the knowledge of the biochemistry and metabolic properties of eye tissues varies. Our objective was to reveal the biochemical differences between main tissue components of human eyes. Methods. Corneas, irises, ciliary bodies, lenses, and retinas were obtained from cadaver globes 0-1/2 hours postmortem of 6 male donors (age: 44–61 years). The metabolic profile of tissues was investigated with HR MAS 1H NMR spectroscopy. Results. A total of 29 metabolites were assigned in the NMR spectra of the eye tissues. Significant differences between tissues were revealed in contents of the most distant eye-tissues, while irises and ciliary bodies showed minimal biochemical differences. ATP, acetate, choline, glutamate, lactate, myoinositol, and taurine were identified as the primary biochemical compounds responsible for differentiation of the eye tissues. Conclusions. In this study we showed for the first time the results of the analysis of the main human eye tissues with NMR spectroscopy. The biochemical contents of the selected tissues seemed to correspond to their primary anatomical and functional attributes, the way of the delivery of the nutrients, and the location of the tissues in the eye. PMID:25525621

  18. Qualitative and quantitative control of carbonated cola beverages using ¹H NMR spectroscopy.

    PubMed

    Maes, Pauline; Monakhova, Yulia B; Kuballa, Thomas; Reusch, Helmut; Lachenmeier, Dirk W

    2012-03-21

    ¹H Nuclear magnetic resonance (NMR) spectroscopy (400 MHz) was used in the context of food surveillance to develop a reliable analytical tool to differentiate brands of cola beverages and to quantify selected constituents of the soft drinks. The preparation of the samples required only degassing and addition of 0.1% of TSP in D₂O for locking and referencing followed by adjustment of pH to 4.5. The NMR spectra obtained can be considered as "fingerprints" and were analyzed by principal component analysis (PCA). Clusters from colas of the same brand were observed, and significant differences between premium and discount brands were found. The quantification of caffeine, acesulfame-K, aspartame, cyclamate, benzoate, hydroxymethylfurfural (HMF), sulfite ammonia caramel (E 150D), and vanillin was simultaneously possible using external calibration curves and applying TSP as internal standard. Limits of detection for caffeine, aspartame, acesulfame-K, and benzoate were 1.7, 3.5, 0.8, and 1.0 mg/L, respectively. Hence, NMR spectroscopy combined with chemometrics is an efficient tool for simultaneous identification of soft drinks and quantification of selected constituents. PMID:22356160

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

    PubMed

    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

  20. Mapping Inhibitor Binding Modes on an Active Cysteine Protease via NMR Spectroscopy

    PubMed Central

    Lee, Gregory M.; Balouch, Eaman; Goetz, David H.; Lazic, Ana; McKerrow, James H.; Craik, Charles S.

    2013-01-01

    Cruzain is a member of the papain/cathepsin-L family of cysteine proteases, and the major cysteine protease of the protozoan Trypanosoma cruzi, the causative agent of Chagas’ disease. We report an auto-induction methodology that provides soluble-cruzain at high yields (> 30 mg per liter in minimal media). These increased yields provide sufficient quantities of active enzyme for use in NMR-based ligand mapping. Using CD and NMR spectroscopy, we also examined the solution-state structural dynamics of the enzyme in complex with a covalently bound vinyl sulfone inhibitor (K777). We report the backbone amide and side chain carbon chemical shift assignments of cruzain in complex with K777. These resonance assignments were used to identify and map residues located in the substrate binding pocket, including the catalytic Cys25 and His162. Selective 15N-Cys, 15N-His, and 13C-Met labeling was performed to quickly assess cruzain-ligand interactions for a set of eight low molecular weight compounds exhibiting micromolar binding or inhibition. Chemical shift perturbation mapping verifies that six of the eight compounds bind to cruzain at the active site. Three different binding modes were delineated for the compounds, namely covalent, non-covalent, and non-interacting. These results provide examples of how NMR spectroscopy can be used to screen compounds for fast evaluation of enzyme-inhibitor interactions in order to facilitate lead compound identification and subsequent structural studies. PMID:23181936

  1. Determination of the biogenic secondary organic aerosol fraction in the boreal forest by NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Finessi, E.; Decesari, S.; Paglione, M.; Giulianelli, L.; Carbone, C.; Gilardoni, S.; Fuzzi, S.; Saarikoski, S.; Raatikainen, T.; Hillamo, R.; Allan, J.; Mentel, Th. F.; Tiitta, P.; Laaksonen, A.; Petäjä, T.; Kulmala, M.; Worsnop, D. R.; Facchini, M. C.

    2012-01-01

    The study investigates the sources of fine organic aerosol (OA) in the boreal forest, based on measurements including both filter sampling (PM1) and online methods and carried out during a one-month campaign held in Hyytiälä, Finland, in spring 2007. Two aerosol mass spectrometers (Q-AMS, ToF-AMS) were employed to measure on-line concentrations of major non-refractory aerosol species, while the water extracts of the filter samples were analyzed by nuclear magnetic resonance (NMR) spectroscopy for organic functional group characterization of the polar organic fraction of the aerosol. AMS and NMR spectra were processed separately by non-negative factorization algorithms, in order to apportion the main components underlying the submicrometer organic aerosol composition and depict them in terms of both mass fragmentation patterns and functional group compositions. The NMR results supported the AMS speciation of oxidized organic aerosol (OOA) into two main fractions, which could be generally labelled as more and less oxidized organics. The more oxidized component was characterized by a mass spectrum dominated by the m/z 44 peak, and in parallel by a NMR spectrum showing aromatic and aliphatic backbones highly substituted with oxygenated functional groups (carbonyls/carboxyls and hydroxyls). Such component, contributing on average 50% of the OA mass throughout the observing period, was associated with pollution outbreaks from the Central Europe. The less oxidized component was enhanced in concomitance with air masses originating from the North-to-West sector, in agreement with previous investigations conducted at this site. NMR factor analysis was able to separate two distinct components under the less oxidized fraction of OA. One of these NMR-factors was associated with the formation of terrestrial biogenic secondary organic aerosol (BSOA), based on the comparison with spectral profiles obtained from laboratory experiments of terpenes photo-oxidation. The second NMR

  2. A new NMR method for determining the particle thickness in nanocomposites, using T2,H-selective X{1H} recoupling.

    PubMed

    Schmidt-Rohr, K; Rawal, A; Fang, X-W

    2007-02-01

    A new nuclear magnetic resonance approach for characterizing the thickness of phosphate, silicate, carbonate, and other nanoparticles in organic-inorganic nanocomposites is presented. The particle thickness is probed using the strongly distant-dependent dipolar couplings between the abundant protons in the organic phase and X nuclei (31P, 29Si, 13C, 27Al, 23Na, etc.) in the inorganic phase. This approach requires pulse sequences with heteronuclear dephasing only by the polymer or surface protons that experience strong homonuclear interactions, but not by dispersed OH or water protons in the inorganic phase, which have long transverse relaxation times T2,H. This goal is achieved by heteronuclear recoupling with dephasing by strong homonuclear interactions of protons (HARDSHIP). The pulse sequence alternates heteronuclear recoupling for approximately 0.15 ms with periods of homonuclear dipolar dephasing that are flanked by canceling 90 degrees pulses. The heteronuclear evolution of the long-T2,H protons is refocused within two recoupling periods, so that 1H spin diffusion cannot significantly dephase these coherences. For the short-T2,H protons of a relatively immobile organic matrix, the heteronuclear dephasing rate depends simply on the heteronuclear second moment. Homonuclear interactions do not affect the dephasing, even though no homonuclear decoupling is applied, because long-range 1H-X dipolar couplings approximately commute with short-range 1H-1H couplings, and heteronuclear recoupling periods are relatively short. This is shown in a detailed analysis based on interaction representations. The algorithm for simulating the dephasing data is described. The new method is demonstrated on a clay-polymer nanocomposite, diamond nanocrystals with protonated surfaces, and the bioapatite-collagen nanocomposite in bone, as well as pure clay and hydroxyapatite. The diameters of the nanoparticles in these materials range between 1 and 5 nm. Simulations show that spherical

  3. NMR spectroscopy of hyperpolarized ^129Xe at high fields: Maintaining spin polarization after optical pumping.

    NASA Astrophysics Data System (ADS)

    Patton, Brian; Kuzma, Nicholas N.; Lisitza, Natalia V.; Happer, William

    2003-05-01

    Spin-polarized ^129Xe has become an invaluable tool in nuclear magnetic resonance research, with applications ranging from medical imaging to high-resolution spectroscopy. High-field NMR studies using hyperpolarized xenon as a spectroscopic probe benefit from the high signal-to-noise ratios and large chemical shifts typical of optically-pumped noble gases. The experimental sensitivity is ultimately determined by the absolute polarization of the xenon in the sample, which can be substantially decreased during purification and transfer. NMR of xenon at high fields (9.4 Tesla) will be discussed, and potential mechanisms of spin relaxation during the distillation, storage(N. N. Kuzma, B. Patton, K. Raman, and W. Happer, Phys. Rev. Lett. 88), 147602 (2002)., and delivery of hyperpolarized xenon will be analyzed.

  4. An instrument control and data analysis program for NMR imaging and spectroscopy

    SciTech Connect

    Roos, M.S.; Mushlin, R.A.; Veklerov, E.; Port, J.D.; Ladd, C.; Harrison, C.G.

    1988-01-01

    We describe a software environment created to support real-time instrument control and signal acquisition as well as array-processor based signal and image processing in up to five dimensions. The environment is configured for NMR imaging and in vivo spectroscopy. It is designed to provide flexible tools for implementing novel NMR experiments in the research laboratory. Data acquisition and processing operations are programmed in macros which are loaded in assembled from to minimize instruction overhead. Data arrays are dynamically allocated for efficient use of memory and can be mapped directly into disk files. The command set includes primitives for real-time control of data acquisition, scalar arithmetic, string manipulation, branching, a file system and vector operations carried out by an array processor. 6 figs.

  5. Uncovering the triggers for GPCR activation using solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Kimata, Naoki; Reeves, Philip J.; Smith, Steven O.

    2015-04-01

    G protein-coupled receptors (GPCRs) span cell membranes with seven transmembrane helices and respond to a diverse array of extracellular signals. Crystal structures of GPCRs have provided key insights into the architecture of these receptors and the role of conserved residues. However, the question of how ligand binding induces the conformational changes that are essential for activation remains largely unanswered. Since the extracellular sequences and structures of GPCRs are not conserved between receptor subfamilies, it is likely that the initial molecular triggers for activation vary depending on the specific type of ligand and receptor. In this article, we describe NMR studies on the rhodopsin subfamily of GPCRs and propose a mechanism for how retinal isomerization switches the receptor to the active conformation. These results suggest a general approach for determining the triggers for activation in other GPCR subfamilies using NMR spectroscopy.

  6. Isotope-Filtered 4D NMR Spectroscopy for Structure Determination of Humic Substances**

    PubMed Central

    Bell, Nicholle G A; Michalchuk, Adam A L; Blackburn, John W T; Graham, Margaret C; Uhrín, Dušan

    2015-01-01

    Humic substances, the main component of soil organic matter, could form an integral part of green and sustainable solutions to the soil fertility problem. However, their global-scale application is hindered from both scientific and regulatory perspectives by the lack of understanding of the molecular make-up of these chromatographically inseparable mixtures containing thousands of molecules. Here we show how multidimensional NMR spectroscopy of isotopically tagged molecules enables structure characterization of humic compounds. We illustrate this approach by identifying major substitution patterns of phenolic aromatic moieties of a peat soil fulvic acid, an operational fraction of humic substances. Our methodology represents a paradigm shift in the use of NMR active tags in structure determination of small molecules in complex mixtures. Unlike previous tagging methodologies that focused on the signals of the tags, we utilize tags to directly probe the identity of the molecules they are attached to. PMID:26036217

  7. (1)H NMR spectroscopy in the diagnosis of Pseudomonas aeruginosa-induced urinary tract infection.

    PubMed

    Gupta, Ashish; Dwivedi, Mayank; Nagana Gowda, G A; Ayyagari, Archana; Mahdi, A A; Bhandari, M; Khetrapal, C L

    2005-08-01

    The utility of (1)H NMR spectroscopy is suggested and demonstrated for the diagnosis of Pseudomonas aeruginosa in urinary tract infection (UTI). The specific property of P. aeruginosa of metabolizing nicotinic acid to 6-hydroxynicotinic acid (6-OHNA) is exploited. The quantity of 6-OHNA produced correlates well with the viable bacterial count. Other common bacteria causing UTI such as Escherichia coli, Klebsiella pneumonia, Enterobacter aerogenes, Acinetobacter baumanii, Proteus mirabilis, Citrobacter frundii, Enterococcus faecalis, Streptococcus gp B and Staphylococcus aureus do not metabolize nicotinic acid under similar conditions. The method provides a single-step documentation of P. aeruginosa qualitatively as well as quantitatively. The NMR method is demonstrated on urine samples from 30 patients with UTI caused by P. aeruginosa. PMID:15759292

  8. Determination of iodine value of lubricating oils by nuclear magnetic resonance (NMR) spectroscopy

    SciTech Connect

    Sarpal, A.S.; Kapur, G.S.; Mukherjee, S.

    1995-03-01

    A direct, quick and non-destructive method for estimating the iodine value of fats, fatty oils and their blends in mineral oils has been developed based on {sup 1}H and {sup 13}C-NMR spectroscopy. The method involves the determination of unsaturation content of the samples by {sup 1}H and {sup 13}C-NMR spectroscopic techniques. The iodine value of the sample is directly proportional to the unsaturated proton or carbon content. The value of the proportionality constant is independent of the nature of the fats and their blends in mineral oils for the limited samples studied. The iodine value determined by this method also includes the contribution from additives containing unsaturation. Saturated ingredients in the sample do not contribute to the iodine value as is the case with the standard IP-84 method. 5 refs., 3 figs., 4 tabs.

  9. N-15 NMR Spectroscopy as a Method for Comparing the Rates of Imidization of Several Diamines

    NASA Technical Reports Server (NTRS)

    Johnson, J. Christopher; Kuczmarski, Maria A.

    2006-01-01

    The relative rates of the conversion of amide-acid to imide was measured for a series or aromatic diamines that have been identified as potential replacements for 4,4'-methylene dianiline (MDA) in high-temperature polyimides and polymer composites. These rates were compared with the N-15 NMR resonances of the unreacted amines. The initial rates of imidization track with the difference in chemical shift between the amine nitrogens in MDA and those in the subject diamines. This comparison demonstrated that N-15 NMR spectroscopy is appropriate for the rapid screening of candidate diamines to determine their reactivity relative to MDA, and can serve to provide guidance to the process of creating the time-temperature profiles used in processing these materials into polymer matrix composites.

  10. Structural studies of pravastatin and simvastatin and their complexes with SDS micelles by NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Rakhmatullin, I. Z.; Galiullina, L. F.; Klochkova, E. A.; Latfullin, I. A.; Aganov, A. V.; Klochkov, V. V.

    2016-02-01

    Conformational features of pravastatin and simvastatin molecules in solution and in their complexes with sodium dodecyl sulfate micelles (SDS) were studied by 2D NOESY NMR spectroscopy. On the basis of the nuclear magnetic resonance experiments it was established that pravastatin and simvastatin can form molecular complex with SDS micelles which were considered as the model of cell membrane. In addition, interatomic distances for studied compounds were calculated based on 2D NOESY NMR experiments. It was shown that pravastatin interacts only with a surface of model membrane. However, in contrast to pravastatin, simvastatin penetrates into the inner part of SDS micelles. Observed distinctions in the mechanisms of interaction of pravastatin and simvastatin with models of cell membranes could explain the differences in their pharmacological properties.

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

    PubMed

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

    2015-03-01

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

  12. Drug solubilization mechanism of α-glucosyl stevia by NMR spectroscopy.

    PubMed

    Zhang, Junying; Higashi, Kenjirou; Ueda, Keisuke; Kadota, Kazunori; Tozuka, Yuichi; Limwikrant, Waree; Yamamoto, Keiji; Moribe, Kunikazu

    2014-04-25

    We investigated the drug solubilization mechanism of α-glucosyl stevia (Stevia-G) which was synthesized from stevia (rebaudioside-A) by transglycosylation. (1)H and (13)C NMR peaks of Stevia-G in water were assigned by two-dimensional (2D) NMR experiments including (1)H-(1)H correlation, (1)H-(13)C heteronuclear multiple bond correlation, and (1)H-(13)C heteronuclear multiple quantum coherence spectroscopies. The (1)H and (13)C peaks clearly showed the incorporation of two glucose units into rebaudioside-A to produce Stevia-G, supported by steviol glycoside and glucosyl residue assays. The concentration-dependent chemical shifts of Stevia-G protons correlated well with a mass-action law model, indicating the self-association of Stevia-G molecules in water. The critical micelle concentration (CMC) was 12.0 mg/mL at 37°C. The aggregation number was 2 below the CMC and 12 above the CMC. Dynamic light scattering and 2D (1)H-(1)H nuclear Overhauser effect spectroscopy (NOESY) NMR experiments demonstrated that Stevia-G self-associated into micelles of a few nanometers in size with a core-shell structure, containing a kaurane diterpenoid-based hydrophobic core and a glucose-based shell. 2D (1)H-(1)H NOESY NMR measurements also revealed that a poorly water-soluble drug, naringenin, was incorporated into the hydrophobic core of the Stevia-G micelle. The Stevia-G self-assembly behavior and micellar drug inclusion capacity can achieve significant enhancement in drug solubility. PMID:24508331

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

    PubMed

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

    2004-01-01

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

  14. Studies on 2H NMR and single crystal X-ray diffraction of thermochromic bis ( N, N-diethyl-1,2-ethanediamine) nickel(II) complexes with and without structural phase transitions

    NASA Astrophysics Data System (ADS)

    Ikeda, Ryuichi; Kotani, Kyoko; Ohki, Hiroshi; Ishimaru, Shin'ichi; Okamoto, Ken-Ichi; Ghosh, Ashutosh

    1995-02-01

    The thermochromic complex bis( N, N-diethyl-1,2-ethanediamine) ((C 2H 5) 2NC 2H 4NH 2) nickel(II) perchlorate([Ni(dieten) 2](ClO 4) 2) was studied by single crystal X-ray diffraction and found to form a triclinic lattice with space group P 1¯, a = 8.108(1) Å, b = 8.835(1) Å, c = 9.736(1) Å, α = 94.24(1)°, β = 114.28(1)°, γ = 116.49(1)°, and Z = 1 being isomorphous with that of [Cu(dieten) 2](ClO 4) 2 which has been reported to have a thermochromic phase transition. The temperature dependences of 2H NMR spectra in [Ni(dieten- d2) 2]X 2 (dieten- d2: (C 2H 5) 2NC 2H 4ND 2; X: ClO 4, BF 4, Br, NO 3, I) were observed and quadrupole coupling constants e2Qq and asymmetry parameters η were evaluated. Below room temperature, an almost rigid structure of the ND 2 group was derived by analyzing the spectra. For perchlorate and tetrafluoroborate with colour changes at respective phase transition temperatures ( Tc), quadrupole parameters were also changed discontinuously at Tc. The analysis of spectra observed above Tc afforded two-site jumps of the N-D bond by angles of 52-55° supporting the ring-puckering model of the five-membered chelate ring. However, iodide having no phase transition showed continuous changes of both e2Qq and η values with increasing temperature up to 450 K. These results which cannot be attributed to the puckering motion were explained by whole complex reorientation. These molecular motions are discussed in connection with the colour change observed in these complexes.

  15. Microfabricated Inserts for Magic Angle Coil Spinning (MACS) Wireless NMR Spectroscopy

    PubMed Central

    Badilita, Vlad; Fassbender, Birgit; Kratt, Kai; Wong, Alan; Bonhomme, Christian; Sakellariou, Dimitris; Korvink, Jan G.; Wallrabe, Ulrike

    2012-01-01

    This article describes the development and testing of the first automatically microfabricated probes to be used in conjunction with the magic angle coil spinning (MACS) NMR technique. NMR spectroscopy is a versatile technique for a large range of applications, but its intrinsically low sensitivity poses significant difficulties in analyzing mass- and volume-limited samples. The combination of microfabrication technology and MACS addresses several well-known NMR issues in a concerted manner for the first time: (i) reproducible wafer-scale fabrication of the first-in-kind on-chip LC microresonator for inductive coupling of the NMR signal and reliable exploitation of MACS capabilities; (ii) improving the sensitivity and the spectral resolution by simultaneous spinning the detection microcoil together with the sample at the “magic angle” of 54.74° with respect to the direction of the magnetic field (magic angle spinning – MAS), accompanied by the wireless signal transmission between the microcoil and the primary circuit of the NMR spectrometer; (iii) given the high spinning rates (tens of kHz) involved in the MAS methodology, the microfabricated inserts exhibit a clear kinematic advantage over their previously demonstrated counterparts due to the inherent capability to produce small radius cylindrical geometries, thus tremendously reducing the mechanical stress and tearing forces on the sample. In order to demonstrate the versatility of the microfabrication technology, we have designed MACS probes for various Larmor frequencies (194, 500 and 700 MHz) testing several samples such as water, Drosophila pupae, adamantane solid and LiCl at different magic angle spinning speeds. PMID:22936994

  16. Solid-state Ru-99 NMR spectroscopy: a useful tool for characterizing prototypal diamagnetic ruthenium compounds.

    PubMed

    Ooms, Kristopher J; Wasylishen, Roderick E

    2004-09-01

    The feasibility of (99)Ru NMR spectroscopy as a tool to characterize solid compounds is demonstrated. Results of the first solid-state (99)Ru NMR investigation of diamagnetic compounds are presented for Ru(NH(3))(6)Cl(2), K(4)Ru(CN)(6). xH(2)O (x = 0, 3), LaKRu(CN)(6), and Ru(3)(CO)(12). The sensitivity of the ruthenium magnetic shielding tensor to subtle changes in the local structure about the ruthenium nucleus is highlighted by comparing the (99)Ru isotropic chemical shift of Ru(NH(3))(6)Cl(2) in aqueous solutions and in the solid state. The narrow isotropic (99)Ru NMR peak observed for solid Ru(NH(3))(6)Cl(2) indicates that this compound is an ideal secondary reference sample for solid-state (99)Ru NMR studies. The isotropic (99)Ru chemical shift, (99)Ru nuclear quadrupolar coupling constant, C(Q), and quadrupolar asymmetry parameter of K(4)Ru(CN)(6). xH(2)O (x = 0, 3) are shown to be sensitive to x. For Ru(3)(CO)(12), the magnetic shielding tensors of each of the three nonequivalent Ru nuclei have spans of 1300-1400 ppm, and the (99)Ru C(Q) values are also similar, 1.36-1.85 MHz, and are surprisingly small given that (99)Ru has a moderate nuclear quadrupole moment. Information about the relative orientation of the Ru magnetic shielding and electric field gradient tensors has been determined for Ru(3)(CO)(12) from experimental (99)Ru NMR spectra as well as quantum chemical calculations. PMID:15339183

  17. Microfabricated inserts for magic angle coil spinning (MACS) wireless NMR spectroscopy.

    PubMed

    Badilita, Vlad; Fassbender, Birgit; Kratt, Kai; Wong, Alan; Bonhomme, Christian; Sakellariou, Dimitris; Korvink, Jan G; Wallrabe, Ulrike

    2012-01-01

    This article describes the development and testing of the first automatically microfabricated probes to be used in conjunction with the magic angle coil spinning (MACS) NMR technique. NMR spectroscopy is a versatile technique for a large range of applications, but its intrinsically low sensitivity poses significant difficulties in analyzing mass- and volume-limited samples. The combination of microfabrication technology and MACS addresses several well-known NMR issues in a concerted manner for the first time: (i) reproducible wafer-scale fabrication of the first-in-kind on-chip LC microresonator for inductive coupling of the NMR signal and reliable exploitation of MACS capabilities; (ii) improving the sensitivity and the spectral resolution by simultaneous spinning the detection microcoil together with the sample at the "magic angle" of 54.74° with respect to the direction of the magnetic field (magic angle spinning - MAS), accompanied by the wireless signal transmission between the microcoil and the primary circuit of the NMR spectrometer; (iii) given the high spinning rates (tens of kHz) involved in the MAS methodology, the microfabricated inserts exhibit a clear kinematic advantage over their previously demonstrated counterparts due to the inherent capability to produce small radius cylindrical geometries, thus tremendously reducing the mechanical stress and tearing forces on the sample. In order to demonstrate the versatility of the microfabrication technology, we have designed MACS probes for various Larmor frequencies (194, 500 and 700 MHz) testing several samples such as water, Drosophila pupae, adamantane solid and LiCl at different magic angle spinning speeds. PMID:22936994

  18. Local Perturbations in the (10110) and (10101) Levels of C_2H_2 from Frequency Comb-Referenced Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sears, Trevor; Twagirayezu, Sylvestre; Forthomme, Damien; Hall, Gregory; Cich, Matthew

    2015-06-01

    In work reported by Twagirayezu et al. at this meeting, the rest frequencies of more than 100 lines in the ν_4 and ν_5 hot bands in the ν_1 + ν_3 combination band of acetylene have been measured by saturation dip spectroscopy using an extended cavity diode laser locked to a frequency comb. This work was orginally directed towards providing a set of accurate frequencies for the hot band line positions to aid in modeling the lineshapes of the main lines in the band. In analyzing the results, we find that many of the upper levels in the hot band transitions suffer small, and in some cases not so small, local perturbations. These arise because of J-dependent near degeneracies between the title levels and background levels of the same symmetry, mostly derived from zero order states involving multiple quanta of bending excitation. The vibration-rotation levels at the energies in question have previously been modeled using a polyad-based Hamiltonian and the present data can be interpreted on the basis of this model, but they also provide information which can be used to refine the model, and point to terms that may have previously been neglected. The most important result is that the high precision of the measurements gives the opportunity to calibrate the effects of background levels associated with high bending quantum numbers and angular momentun states that are otherwise very difficult to access. Acknowledgments: We are most grateful to D. S Perry (U. Akron) and M. Herman (U. Libre de Bruxelles) for helpful discussions. Work at Brookhaven National Laboratory is funded by the Division of Chemical Sciences, Geosciences and Biosciences within the Offices of Basic Energy Sciences, Office of Sciences, U.S. Department of Energy under Contract Nos. DE-AC02-98CH10886 and DE-SC0012704. M. Herman and D. S. Perry, Phys. Chem. Chem. Phys., 15, 9970-9993 (2013)

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

    PubMed

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

    2015-05-01

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

  20. Heteronuclear dipolar couplings, total spin coherence, and bilinear rotations in NMR spectroscopy

    SciTech Connect

    Garbow, J.R.

    1983-07-01

    In Chapter 1 a variety of different introductory topics are presented. The potential complexity of the nuclear magnetic resonsnace (NMR) spectra of molecules dissolved in liquid crystal solvents serves to motivate the development of multiple quantum (MQ) spectroscopy. The basics of MQ NMR are reviewed in Chapter 2. An experimental search procedure for the optimization of MQ pulse sequences is introduced. Chapter 3 discusses the application of MQ NMR techniques to the measurement of dipolar couplings in heteronuclear spin systems. The advantages of MQ methods in such systems are developed and experimental results for partially oriented (1-/sup 13/C) benzene are presented. Several pulse sequences are introduced which employ a two-step excitation of heteronuclear MQ coherence. A new multiple pulse method, involving the simultaneous irradiation of both rare and abundant spin species, is described. The problem of the broadening of MQ transitions due to magnetic field inhomogeneity is considered in Chapter 4. The method of total spin coherence transfer echo spectroscopy (TSCTES) is presented, with experimets on partially oriented acetaldehyde serving to demonstrate this new technique. TSCTES results in MQ spectra which are sensitive to all chemical shifts and spin-spin couplings and which are free of inhomogeneous broadening. In Chapter 5 the spectroscopy of spin systems of several protons and a /sup 13/C nucleus in the isotropic phase is discussed. The usefulness of the heteronuclear bilinear rotation as a calculational tool is illustrated. Compensated bilinear ..pi.. rotations, which are relatively insensitive to timing parameter missets, are presented. A new technique for homonuclear proton decoupling, Bilinear Rotation Decoupling, is described and its success in weakly coupled systems is demonstrated.

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

    PubMed

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

    2015-01-01

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

  2. Electromagnetic susceptibility anisotropy and its importance for paramagnetic NMR and optical spectroscopy in lanthanide coordination chemistry.

    PubMed

    Blackburn, Octavia A; Edkins, Robert M; Faulkner, Stephen; Kenwright, Alan M; Parker, David; Rogers, Nicola J; Shuvaev, Sergey

    2016-04-19

    The importance of the directional dependence of magnetic susceptibility in magnetic resonance and of electric susceptibility in the optical spectroscopy of lanthanide coordination complexes is assessed. A body of more reliable shift, relaxation and optical emission data is emerging for well-defined isostructural series of complexes, allowing detailed comparative analyses to be undertaken. Such work is highlighting the limitations of the current NMR shift and relaxation theories, as well as emphasising the absence of a compelling theoretical framework to explain optical emission phenomena. PMID:26898996

  3. Application of nmr spectroscopy to determine the thermodynamic characteristics of water bound to OX-50 nanosilica

    NASA Astrophysics Data System (ADS)

    Turov, V. V.; Gun'ko, V. M.; Gaishun, V. E.; Kosenok, Ya. A.; Golovan, A. P.

    2010-09-01

    We have used low-temperature 1H NMR spectroscopy to determine the thermodynamic characteristics of water bound to OX-50 nanosilica (SBET ≈ 50 m2/g) in different media: aqueous, air, chloroform medium, and gaseous methane. We demonstrate the difference between the hydration parameters of silica OX-50 on going from an aqueous suspension to a hydrated powder. We present the water cluster size distributions in the studied systems, calculated from the Gibbs-Thomson equation. We found that the average water cluster size in suspension is considerably larger than the cluster sizes in hydrated powders.

  4. Silica sol assisted chromatographic NMR spectroscopy for resolution of trans- and cis-isomers.

    PubMed

    Yang, Ying; Wu, Rui; Huang, Shaohua; Bai, Zhengwu

    2016-04-01

    Chromatographic NMR spectroscopy can separate the mixtures of species with significantly different molecular size, but generally fails for isomeric species. Herein, we reported the resolution of trans- and cis-isomers and their structural analogue, which are different in molecular shapes, but similar in mass, were greatly enhanced in the presence of silica sol. The mixtures of maleic acid, fumaric acid and succinic acid, and the mixtures of trans- and cis-1,2-cyclohexanedicarboxylic acids, were distinguished by virtue of their different degrees of interaction with silica sol. Moreover, we found mixed solvents could improve the spectral resolution of DOSY spectra of mixtures. PMID:26942864

  5. Silica sol assisted chromatographic NMR spectroscopy for resolution of trans- and cis-isomers

    NASA Astrophysics Data System (ADS)

    Yang, Ying; Wu, Rui; Huang, Shaohua; Bai, Zhengwu

    2016-04-01

    Chromatographic NMR spectroscopy can separate the mixtures of species with significantly different molecular size, but generally fails for isomeric species. Herein, we reported the resolution of trans- and cis-isomers and their structural analogue, which are different in molecular shapes, but similar in mass, were greatly enhanced in the presence of silica sol. The mixtures of maleic acid, fumaric acid and succinic acid, and the mixtures of trans- and cis-1,2-cyclohexanedicarboxylic acids, were distinguished by virtue of their different degrees of interaction with silica sol. Moreover, we found mixed solvents could improve the spectral resolution of DOSY spectra of mixtures.

  6. Probing the Pu4 + magnetic moment in PuF4 with 19F NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Capan, Cigdem; Dempsey, Richard J.; Sinkov, Sergey; McNamara, Bruce K.; Cho, Herman

    2016-06-01

    The magnetic fields produced by Pu4 + centers have been measured by 19F NMR spectroscopy to elucidate the Pu-F electronic interactions in polycrystalline PuF4. Spectra acquired at applied fields of 2.35 and 7.05 T reveal a linear scaling of the 19F line shape. A model is presented that treats the line broadening and shifts as due to dipolar fields produced by Pu valence electrons in localized noninteracting orbitals. Alternative explanations for the observed line shape involving covalent Pu-F bonding, superexchange interactions, and electronic configurations with enhanced magnetic moments are considered.

  7. Impact of Hydrophilic Surfaces on Interfacial Water Dynamics Probed with NMR Spectroscopy

    PubMed Central

    Yoo, Hyok; Paranji, Rajan

    2011-01-01

    In suspensions of Nafion beads and of cationic gel beads, NMR spectroscopy showed two water–proton resonances, one representing intimate water layers next to the polymer surface, the other corresponding to water lying beyond. Both resonances show notably shorter spin–lattice relaxation times (T1) and smaller self-diffusion coefficients (D) indicating slower dynamics than bulk water. These findings confirm the existence of highly restricted water layers adsorbed onto hydrophilic surfaces and dynamically stable water beyond the first hydration layers. Thus, aqueous regions on the order of micrometers are dynamically different from bulk water. PMID:22003430

  8. Application of 13C NMR spectroscopy to paratope mapping for larger antigen-Fab complexes.

    PubMed

    Kim, H; Kato, K; Yamato, S; Igarashi, T; Matsunaga, C; Ohtsuka, H; Higuchi, A; Nomura, N; Noguchi, H; Arata, Y

    1994-06-13

    For the purpose of engineering the antibody combining site, mapping residues that are involved in antigen binding provide us with valuable information. By use of 13C NMR spectroscopy with selectively 13C-labeled Fv fragments, we have established a general strategy to identify the residues that are perturbed upon binding of small antigen (hapten) molecules [(1990) Biochemistry 30, 6604-6610]. In the present paper, we demonstrate that this strategy can be extended to molecular structural analyses of the complexes of an Fab fragment and a larger antigen molecule such as Pseudomonas aeruginosa exotoxin A with a molecular mass of 67 kDa. PMID:8013642

  9. Novel surfactant mixtures for NMR spectroscopy of encapsulated proteins dissolved in low-viscosity fluids

    PubMed Central

    Peterson, Ronald W.; Pometun, Maxim S.; Shi, Zhengshuang; Wand, A. Joshua

    2005-01-01

    NMR spectroscopy of encapsulated proteins dissolved in low-viscosity fluids is emerging as a tool for biophysical studies of proteins in atomic detail in a variety of otherwise inaccessible contexts. The central element of the approach is the encapsulation of the protein of interest within the aqueous core of a reverse micelle with high structural fidelity. The process of encapsulation is highly dependent upon the nature of the surfactant(s) employed. Here we describe novel mixtures of surfactants that are capable of successfully encapsulating a range of types of proteins under a variety of conditions. PMID:16199658

  10. Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 2: 2D NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Deshmukh, Ashish P.; Pacheco, Carlos; Hay, Michael B.; Myneni, Satish C. B.

    2007-07-01

    Carboxyl groups are abundant in natural organic molecules (NOM) and play a major role in their reactivity. The structural environments of carboxyl groups in IHSS soil and river humic samples were investigated using 2D NMR (heteronuclear and homonuclear correlation) spectroscopy. Based on the 1H- 13C heteronuclear multiple-bond correlation (HMBC) spectroscopy results, the carboxyl environments in NOM were categorized as Type I (unsubstituted and alkyl-substituted aliphatic/alicyclic), Type II (functionalized carbon substituted), Type IIIa, b (heteroatom and olefin substituted), and Type IVa, b (5-membered heterocyclic aromatic and 6-membered aromatic). The most intense signal in the HMBC spectra comes from the Type I carboxyl groups, including the 2JCH and 3JCH couplings of unsubstituted aliphatic and alicyclic acids, though this spectral region also includes the 3JCH couplings of Type II and III structures. Type II and III carboxyls have small but detectable 2JCH correlations in all NOM samples except for the Suwannee River humic acid. Signals from carboxyls bonded to 5-membered aromatic heterocyclic fragments (Type IVa) are observed in the soil HA and Suwannee River FA, while correlations to 6-membered aromatics (Type IVb) are only observed in Suwannee River HA. In general, aromatic carboxylic acids may be present at concentrations lower than previously imagined in these samples. Vibrational spectroscopy results for these NOM samples, described in an accompanying paper [Hay M. B. and Myneni S. C. B. (2007) Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 1: Infrared spectroscopy. Geochim. Cosmochim. Acta (in press)], suggest that Type II and Type III carboxylic acids with α substituents (e.g., -OH, -OR, or -CO 2H) constitute the majority of carboxyl structures in all humic substances examined. Furoic and salicylic acid structures (Type IV) are also feasible fragments, albeit as minor constituents. The

  11. Dynamic processes and chemical composition of Lepidium sativum seeds determined by means of field-cycling NMR relaxometry and NMR spectroscopy.

    PubMed

    Rachocki, A; Latanowicz, L; Tritt-Goc, J

    2012-12-01

    Proton nuclear magnetic resonance (NMR) techniques, such as field-cycling relaxometry, wide-line NMR spectroscopy, and magic angle spinning NMR spectroscopy, were applied to study the seeds of cress, Lepidium sativum. Field-cycling NMR relaxometry was used for the first time to investigate the properties of the whole molecular system of dry cress seeds. This method not only allowed the dynamics to be studied, but was also successful in the differentiation among the solid (i.e., carbohydrates, proteins, or fats forming a solid form of lipids) and liquid-like (oil compounds) components of the seeds. The (1)H NMR relaxation dispersion of oils was interpreted as a superposition of intramolecular and intermolecular contributions. The intramolecular part was described in terms of a Lorentzian spectral density function, whereas a log-Gaussian distribution of correlation times was applied for the intermolecular dipole-dipole contribution. The models applied led to very good agreement with the experimental data and demonstrate that the contribution of the intermolecular relaxation to the overall relaxation should not be disregarded, especially at low frequencies. A power-law frequency dependence of the proton relaxation dispersion was used for the interpretation of the solid components. From the analysis of the (1)H wide-line NMR spectra of the liquid-like component of hydrated cress seeds, we can conclude that the contribution of oil protons should always be taken into account when evaluating the spin-lattice relaxation times values or measuring the moisture and oil content. The application of (1)H magic angle spinning NMR significantly improves resolution in the liquid-like spectrum of seeds and allows the determination of the chemical composition of cress seeds. PMID:23001307

  12. Probabilistic Interaction Network of Evidence Algorithm and its Application to Complete Labeling of Peak Lists from Protein NMR Spectroscopy

    PubMed Central

    Bahrami, Arash; Assadi, Amir H.; Markley, John L.; Eghbalnia, Hamid R.

    2009-01-01

    The process of assigning a finite set of tags or labels to a collection of observations, subject to side conditions, is notable for its computational complexity. This labeling paradigm is of theoretical and practical relevance to a wide range of biological applications, including the analysis of data from DNA microarrays, metabolomics experiments, and biomolecular nuclear magnetic resonance (NMR) spectroscopy. We present a novel algorithm, called Probabilistic Interaction Network of Evidence (PINE), that achieves robust, unsupervised probabilistic labeling of data. The computational core of PINE uses estimates of evidence derived from empirical distributions of previously observed data, along with consistency measures, to drive a fictitious system M with Hamiltonian H to a quasi-stationary state that produces probabilistic label assignments for relevant subsets of the data. We demonstrate the successful application of PINE to a key task in protein NMR spectroscopy: that of converting peak lists extracted from various NMR experiments into assignments associated with probabilities for their correctness. This application, called PINE-NMR, is available from a freely accessible computer server (http://pine.nmrfam.wisc.edu). The PINE-NMR server accepts as input the sequence of the protein plus user-specified combinations of data corresponding to an extensive list of NMR experiments; it provides as output a probabilistic assignment of NMR signals (chemical shifts) to sequence-specific backbone and aliphatic side chain atoms plus a probabilistic determination of the protein secondary structure. PINE-NMR can accommodate prior information about assignments or stable isotope labeling schemes. As part of the analysis, PINE-NMR identifies, verifies, and rectifies problems related to chemical shift referencing or erroneous input data. PINE-NMR achieves robust and consistent results that have been shown to be effective in subsequent steps of NMR structure determination. PMID

  13. Moving NMR

    NASA Astrophysics Data System (ADS)

    Blümich, Bernhard; Casanova, Federico; Danieli, Ernesto; Gong, Qingxia; Greferath, Marcus; Haber, Agnes; Kolz, Jürgen; Perlo, Juan

    2008-12-01

    Initiated by the use of NMR for well logging, portable NMR instruments are being developed for a variety of novel applications in materials testing and process analysis and control. Open sensors enable non-destructive testing of large objects, and small, cup-size magnets become available for high throughput analysis by NMR relaxation and spectroscopy. Some recent developments of mobile NMR are reviewed which delineate the direction into which portable NMR is moving.

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

    PubMed

    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. PMID:26431312

  15. Oil droplet size determination in complex flavor delivery systems by diffusion NMR spectroscopy.

    PubMed

    Fieber, Wolfgang; Hafner, Valeria; Normand, Valéry

    2011-04-15

    Droplet size distribution of flavor oils in two different solid flavor delivery systems were determined with pulsed field gradient NMR spectroscopy: yeast encapsulation system, a spray dried flavor encapsulation system based on empty yeast cells, and glassy encapsulation system, an extruded solid water soluble carbohydrate delivery system. The oil droplet sizes are limited by the yeast cell walls in the yeast encapsulation system and the size distribution is unimodal according to images from transmission electron microscopy. The droplet size determination with diffusion NMR is based on the Murday and Cotts theory of restricted diffusion of liquids in geometrical confinements. Good fits of the diffusion data could be obtained by applying a unimodal, log-normal size distribution model and average droplet sizes of about 2 μm were found that correspond approximately to the inner diameter of the yeast cells. Scanning electron microscopy images showed a multimodal droplet size distribution in the glassy extruded delivery systems. To fit the NMR data a bimodal log-normal distribution function with five independent fitting parameters was implemented that yielded consistent and robust results. The two size populations were found in the micron and sub-micron range, respectively. The method was sufficiently accurate to depict variation of droplet size distributions in glassy encapsulation systems of different formulation. PMID:21316700

  16. Methylation patterns of aquatic humic substances determined by 13C NMR spectroscopy

    USGS Publications Warehouse

    Thorn, K.A.; Steelink, C.; Wershaw, R. L.

    1987-01-01

    13C NMR spectroscopy is used to examine the hydroxyl group functionality of a series of humic and fulvic acids from different aquatic environments. Samples first are methylated with 13C-labeled diazomethane. The NMR spectra of the diazomethylated samples allow one to distinguish between methyl esters of carboxylic acids, methyl ethers of phenolic hydroxyls, and methyl ethers of phenolic hydroxyls adjacent to two substituents. Samples are then permethylated with 13C-labeled methyl iodide/NaH. 13C NMR spectra of permethylated samples show that a significant fraction of the hydroxyl groups is not methylated with diazomethane alone. In these spectra methyl ethers of carbohydrate and aliphatic hydroxyls overlap with methyl ethers of phenolic hydroxyls. Side reactions of the methyltion procedure including carbon methylation in the CH3I/NaH procedure, are also examined. Humic and fulvic acids from bog, swamp, groundwater, and lake waters showssome differences in their distribution of hydroxyl groups, mainly in the concentrations of phenolic hydroxyls, which may be attributed to their different biogeochemical origins. ?? 1987.

  17. Rapid Etiological Classification of Meningitis by NMR Spectroscopy Based on Metabolite Profiles and Host Response

    PubMed Central

    Himmelreich, Uwe; Malik, Richard; Kühn, Till; Daniel, Heide-Marie; Somorjai, Ray L.; Dolenko, Brion; Sorrell, Tania C.

    2009-01-01

    Bacterial meningitis is an acute disease with high mortality that is reduced by early treatment. Identification of the causative microorganism by culture is sensitive but slow. Large volumes of cerebrospinal fluid (CSF) are required to maximise sensitivity and establish a provisional diagnosis. We have utilised nuclear magnetic resonance (NMR) spectroscopy to rapidly characterise the biochemical profile of CSF from normal rats and animals with pneumococcal or cryptococcal meningitis. Use of a miniaturised capillary NMR system overcame limitations caused by small CSF volumes and low metabolite concentrations. The analysis of the complex NMR spectroscopic data by a supervised statistical classification strategy included major, minor and unidentified metabolites. Reproducible spectral profiles were generated within less than three minutes, and revealed differences in the relative amounts of glucose, lactate, citrate, amino acid residues, acetate and polyols in the three groups. Contributions from microbial metabolism and inflammatory cells were evident. The computerised statistical classification strategy is based on both major metabolites and minor, partially unidentified metabolites. This data analysis proved highly specific for diagnosis (100% specificity in the final validation set), provided those with visible blood contamination were excluded from analysis; 6–8% of samples were classified as indeterminate. This proof of principle study suggests that a rapid etiologic diagnosis of meningitis is possible without prior culture. The method can be fully automated and avoids delays due to processing and selective identification of specific pathogens that are inherent in DNA-based techniques. PMID:19390697

  18. Determination of rank and kerogen type by high resolution NMR spectroscopy

    SciTech Connect

    Dickinson, W.W.; Collen, J.D. ); Newman, R.H. )

    1990-06-01

    Nuclear magnetic resonance (NMR) spectroscopy is a nondestructive technique for measuring the chemical and structural properties of organic matter. Although used in organic geochemistry for the past 14 years, the technique has continually undergone refinement. Initially, only the aromatic and aliphatic signal areas of the carbon NMR spectrum could be measured. Carboxylic groups as well as oxygen-substituted groups on aromatic and aliphatic carbon can now be qualitatively measured. The authors have examined coal and shale samples of various ranks from the Williston and San Juan basins, USA, and the Taranaki and Great South basins, New Zealand. Kerogen type can be distinguished on a plot of aromaticity versus the methylene to methyl ratio. For type III kerogens, vitrinite reflectance correlates very well with the percent of oxygen substitution on aromatic carbon and aromaticity. These parameters are excellent indicators of rank because they reflect the decrease in oxygen content and the increase in aromatic carbon as organic matter matures. Although the initial cost of NMR equipment is high, the vast amount of chemical information on kerogen that may be obtained from a small sample and very little laboratory preparation make it a valuable tool for petroleum geochemistry.

  19. Novel monosaccharide fermentation products in Caldicellulosiruptor saccharolyticus identified using NMR spectroscopy

    SciTech Connect

    Isern, Nancy G.; Xue, Junfeng; Rao, Jaya V.; Cort, John R.; Ahring, Birgitte K.

    2013-04-03

    Profiles of metabolites produced by the thermophilic obligately anaerobic cellulose-degrading Gram-positive bacterium Caldicellulosiruptor saccharolyticus DSM 8903 strain following growth on different monosaccharides (D-glucose, D-mannose, L-arabinose, D-arabinose, D-xylose, L-fucose, and D-fucose) as carbon sources revealed several unexpected fermentation products, suggesting novel metabolic capacities and unexplored metabolic pathways in this organism. Both 1H and 13C nuclear magnetic resonance (NMR) spectroscopy were used to determine intracellular and extracellular metabolite profiles. Metabolite profiles were determined from 1-D 1H NMR spectra by curve fitting against spectral libraries provided in Chenomx software. To reduce uncertainties due to unassigned, overlapping, or poorly-resolved peaks, metabolite identifications were confirmed with 2-D homonuclear and heteronuclear NMR experiments. In addition to expected metabolites such as acetate, lactate, glycerol, and ethanol, several novel fermentation products were identified: ethylene glycol (from growth on D-arabinose, though not L-arabinose), acetoin and 2,3-butanediol (from D-glucose and L-arabinose), and hydroxyacetone (from D-mannose and L-arabinose). Production of ethylene glycol from D-arabinose was particularly notable, with around 10% of the substrate carbon converted into this uncommon fermentation product. The novel products have not previously been reported to be produced by C. saccharolyticus, nor would they be easily predicted from the current genome annotation, and show new potentials for using this strain for production of bioproducts.

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

    SciTech Connect

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

    1999-07-20

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

  1. Biological effects and physical safety aspects of NMR imaging and in vivo spectroscopy

    SciTech Connect

    Tenforde, T.S.; Budinger, T.F.

    1985-08-01

    An assessment is made of the biological effects and physical hazards of static and time-varying fields associated with the NMR devices that are being used for clinical imaging and in vivo spectroscopy. A summary is given of the current state of knowledge concerning the mechanisms of interaction and the bioeffects of these fields. Additional topics that are discussed include: (1) physical effects on pacemakers and metallic implants such as aneurysm clips, (2) human health studies related to the effects of exposure to nonionizing electromagnetic radiation, and (3) extant guidelines for limiting exposure of patients and medical personnel to the fields produced by NMR devices. On the basis of information available at the present time, it is concluded that the fields associated with the current generation of NMR devices do not pose a significant health risk in themselves. However, rigorous guidelines must be followed to avoid the physical interaction of these fields with metallic implants and medical electronic devices. 476 refs., 5 figs., 2 tabs.

  2. Quality assessment and authentication of virgin olive oil by NMR spectroscopy: a critical review.

    PubMed

    Dais, Photis; Hatzakis, Emmanuel

    2013-02-26

    Nuclear Magnetic Resonance (NMR) Spectroscopy has been extensively used for the analysis of olive oil and it has been established as a valuable tool for its quality assessment and authenticity. To date, a large number of research and review articles have been published with regards to the analysis of olive oil reflecting the potential of the NMR technique in these studies. In this critical review, we cover recent results in the field and discuss deficiencies and precautions of the three NMR techniques ((1)H, (13)C, (31)P) used for the analysis of olive oil. The two methodological approaches of metabonomics, metabolic profiling and metabolic fingerprinting, and the statistical methods applied for the classification of olive oils will be discussed in critical way. Some useful information about sample preparation, the required instrumentation for an effective analysis, the experimental conditions and data processing for obtaining high quality spectra will be presented as well. Finally, a constructive criticism will be exercised on the present methodologies used for the quality control and authentication of olive oil. PMID:23410622

  3. Functional group analysis in coal and on coal surfaces by NMR spectroscopy

    SciTech Connect

    Verkade, J.G.

    1990-01-01

    An accurate knowledge of the oxygen-bearing labile hydrogen functional groups (e.g., carboxylic acids, phenols and alcohols) in coal is required for today's increasingly sophisticated coal cleaning and beneficiation processes. Phospholanes (compounds having the general structure -POCH{sub 2}CH{sub 2}O (1)) are being investigated as reagents for the tagging of liable hydrogen functional groups in coal materials with the NMR-active {sup 31}P nucleus. Of twelve such reagents investigated so far, 2 (2-chloro-1,3-dioxaphospholane, ClPOCH{sub 2}CH{sub 2}O) and 8 (2-chloro-1,3-dithiaphospholane, ClPSCH{sub 2}CH{sub 2}S) have been found to be useful in identifying and quantitating, by {sup 31}P NMR spectroscopy, labile hydrogen functional groups in an Illinois No. 6 coal condensate. Reagent 2 has also been used to quantitate moisture in pyridine extracts of Argonne Premium Coal Samples. Preliminary {sup 119}Sn NMR spectroscopic results on model compounds with the new reagent CF{sub 3}C(O)NHSnMe{sub 3} (N-trimethylstannyltrifluoroacetamide, 14) suggest that labile hydrogen functional groups in coal materials may be more precisely identified with 14 than with phospholanes. 14 refs., 2 figs., 2 tabs.

  4. 60 MHz (1)H NMR spectroscopy for the analysis of edible oils.

    PubMed

    Parker, T; Limer, E; Watson, A D; Defernez, M; Williamson, D; Kemsley, E Kate

    2014-05-01

    We report the first results from a new 60 MHz (1)H nuclear magnetic resonance (NMR) bench-top spectrometer, Pulsar, in a study simulating the adulteration of olive oil with hazelnut oil. There were qualitative differences between spectra from the two oil types. A single internal ratio of two isolated groups of peaks could detect hazelnut oil in olive oil at the level of ∼13%w/w, whereas a whole-spectrum chemometric approach brought the limit of detection down to 11.2%w/w for a set of independent test samples. The Pulsar's performance was compared to that of Fourier transform infrared (FTIR) spectroscopy. The Pulsar delivered comparable sensitivity and improved specificity, making it a superior screening tool. We also mapped NMR onto FTIR spectra using a correlation-matrix approach. Interpretation of this heat-map combined with the established annotations of the NMR spectra suggested a hitherto undocumented feature in the IR spectrum at ∼1130 cm(-1), attributable to a double-bond vibration. PMID:24850979

  5. Structure of Colloidal Quantum Dots from Dynamic Nuclear Polarization Surface Enhanced NMR Spectroscopy.

    PubMed

    Piveteau, Laura; Ong, Ta-Chung; Rossini, Aaron J; Emsley, Lyndon; Copéret, Christophe; Kovalenko, Maksym V

    2015-11-01

    Understanding the chemistry of colloidal quantum dots (QDs) is primarily hampered by the lack of analytical methods to selectively and discriminately probe the QD core, QD surface and capping ligands. Here, we present a general concept for studying a broad range of QDs such as CdSe, CdTe, InP, PbSe, PbTe, CsPbBr3, etc., capped with both organic and inorganic surface capping ligands, through dynamic nuclear polarization (DNP) surface enhanced NMR spectroscopy. DNP can enhance NMR signals by factors of 10-100, thereby reducing the measurement times by 2-4 orders of magnitude. 1D DNP enhanced spectra acquired in this way are shown to clearly distinguish QD surface atoms from those of the QD core, and environmental effects such as oxidation. Furthermore, 2D NMR correlation experiments, which were previously inconceivable for QD surfaces, are demonstrated to be readily performed with DNP and provide the bonding motifs between the QD surfaces and the capping ligands. PMID:26473384

  6. Implementation and characterization of flow injection in dissolution dynamic nuclear polarization NMR spectroscopy.

    PubMed

    Chen, Hsueh-Ying; Hilty, Christian

    2015-08-24

    The use of dissolution dynamic nuclear polarization (D-DNP) offers substantially increased signals in liquid-state NMR spectroscopy. A challenge in realizing this potential lies in the transfer of the hyperpolarized sample to the NMR detector without loss of hyperpolarization. Here, the use of a flow injection method using high-pressure liquid leads to improved performance compared to the more common gas-driven injection, by suppressing residual fluid motions during the NMR experiment while still achieving a short injection time. Apparent diffusion coefficients are determined from pulsed field gradient echo measurements, and are shown to fall below 1.5 times the value of a static sample within 0.8 s. Due to the single-scan nature of D-DNP, pulsed field gradients are often the only choice for coherence selection or encoding, but their application requires stationary fluid. Sample delivery driven by a high-pressure liquid will improve the applicability of these types of D-DNP advanced experiments. PMID:26139513

  7. Near-infrared kinetic spectroscopy of the HO2 and C2H5O2 self-reactions and cross reactions.

    PubMed

    Noell, A C; Alconcel, L S; Robichaud, D J; Okumura, M; Sander, S P

    2010-07-01

    The self-reactions and cross reactions of the peroxy radicals C2H5O2 and HO2 were monitored using simultaneous independent spectroscopic probes to observe each radical species. Wavelength modulation (WM) near-infrared (NIR) spectroscopy was used to detect HO2, and UV absorption monitored C2H5O2. The temperature dependences of these reactions were investigated over a range of interest to tropospheric chemistry, 221-296 K. The Arrhenius expression determined for the cross reaction, k2(T) = (6.01(-1.47)(+1.95)) x 10(-13) exp((638 +/- 73)/T) cm3 molecules(-1) s(-1) is in agreement with other work from the literature. The measurements of the HO2 self-reaction agreed with previous work from this lab and were not further refined. The C2H5O2 self-reaction is complicated by secondary production of HO2. This experiment performed the first direct measurement of the self-reaction rate constant, as well as the branching fraction to the radical channel, in part by measurement of the secondary HO2. The Arrhenius expression for the self-reaction rate constant is k3(T) = (1.29(-0.27)(+0.34)) x 10(-13)exp((-23 +/- 61)/T) cm3 molecules(-1) s(-1), and the branching fraction value is alpha = 0.28 +/- 0.06, independent of temperature. These values are in disagreement with previous measurements based on end product studies of the branching fraction. The results suggest that better characterization of the products from RO2 self-reactions are required. PMID:20524693

  8. Direct measurement of S-branch N2-H2 Raman linewidths using time-resolved pure rotational coherent anti-Stokes Raman spectroscopy.

    PubMed

    Bohlin, A; Nordström, E; Patterson, B D; Bengtsson, P-E; Kliewer, C J

    2012-08-21

    S-branch N(2)-H(2) Raman linewidths have been measured in the temperature region 294-1466 K using time-resolved dual-broadband picosecond pure rotational coherent anti-Stokes Raman spectroscopy (RCARS). Data are extracted by mapping the dephasing rates of the CARS signal temporal decay. The J-dependent coherence decays are detected in the time domain by following the individual spectral lines as a function of probe delay. The linewidth data set was employed in spectral fits of N(2) RCARS spectra recorded in binary mixtures of N(2) and H(2) at calibrated temperature conditions up to 661 K using a standard nanosecond RCARS setup. In this region, the set shows a deviation of less than 2% in comparison with thermocouples. The results provide useful knowledge for the applicability of N(2) CARS thermometry on the fuel-side of H(2) diffusion flames. PMID:22920115

  9. Sub-Doppler Jet-Cooled Infrared Spectroscopy of ND2H2+ and ND3H+ in the NH Stretch Fundamental Modes

    NASA Astrophysics Data System (ADS)

    Chang, Chih-Hsuan; Nesbitt, David

    2014-06-01

    Sub-Doppler jet-cooled rovibrational spectra of ND3H+, ND2H2+, and NDH3+ ions in various fundamental NH modes were observed and analyzed using difference frequency generation infrared spectroscopy. The ions were generated in the concentration-modulation slit-jet expansion via a H3+ proton transfer mechanism in a discharge mixture of ND3/H2O and H2 gases. NH mode excitation in ND3H+ ion yielded a prominent Q branch feature and parallel band rotational structure. Rotational transitions were confirmed unambiguously by four-line ground state combination differences within frequency measurement accuracy (10 MHz). The band origin was determined to be 3316.8413(9) cm-1. Perturbation in the upper state was observed from analysis of residuals. In the case of ND2H2+, both NH symmetric (b-type) and anti-symmetric (c-type) modes were observed and assigned for the first time, yielding band origins of 3297.5440(1) and 3337.9050(1) cm-1, respectively. The intensity for the two fundamental bands was interpreted with simple context of a bond-dipole model. The present study provided high precision ground state rotational constants (A"=4.85675(4), B"=3.96829(4), C"=3.44667(6) cm-1), which should facilitate microwave searches for isotope-substituted ammonium ions in the regions of interstellar medium, such as dense molecular clouds or younger stellar objects.

  10. Investigation of InP etching mechanisms in a Cl{sub 2}/H{sub 2} inductively coupled plasma by optical emission spectroscopy

    SciTech Connect

    Gatilova, L.; Bouchoule, S.; Guilet, S.; Chabert, P.

    2009-03-15

    Optical emission spectroscopy (OES) has been used in order to investigate the InP etching mechanisms in a Cl{sub 2}-H{sub 2} inductively coupled plasma. The authors have previously shown that anisotropic etching of InP could be achieved for a H{sub 2} percentage in the 35%-45% range where the InP etch rate also presents a local maximum [J. Vac. Sci. Technol. B 24, 2381 (2006)], and that anisotropic etching was due to an enhanced passivation of the etched sidewalls by a silicon oxide layer [J. Vac. Sci. Technol. B 26, 666 (2008)]. In this work, it is shown that this etching behavior is related to a maximum in the H atom concentration in the plasma. The possible enhancement of the sidewall passivation process in the presence of H is investigated by comparing OES measurements and etching results obtained for Cl{sub 2}-H{sub 2} and Cl{sub 2}-Ar gas mixtures.

  11. Action of melittin on the DPPC-cholesterol liquid-ordered phase: a solid state 2H-and 31P-NMR study.

    PubMed Central

    Pott, T; Dufourc, E J

    1995-01-01

    Solid-state deuterium and phosphorus-31 nuclear magnetic resonance studies of deuterium-labeled beta--[2,2',3,4,4',6-2H6]-cholesterol and 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine have been undertaken to monitor the action of melittin on model membranes containing 30 mol% cholesterol, both at the molecular and macroscopic level. Cholesterol totally inhibits the toxin-triggered formation of large unilamellar vesicles and strongly restricts the appearance of small discs. The latter remain stable over a wide temperature range (20-60 degrees C) because of an increase in their cholesterol content as the temperature increases. This process is related to a constant disc hydrophobic thickness of approximately 29 A. The system, when not in the form of discs, appears to be composed of very large vesicles on which melittin promotes magnetically induced ellipsoidal deformation. This deformation is the greatest when the maximum of discs is observed. A model to describe both the disc formation and stability is proposed. PMID:7756559

  12. Characterization of noninnocent metal complexes using solid-state NMR spectroscopy: o-dioxolene vanadium complexes.

    PubMed

    Chatterjee, Pabitra B; Goncharov-Zapata, Olga; Quinn, Laurence L; Hou, Guangjin; Hamaed, Hiyam; Schurko, Robert W; Polenova, Tatyana; Crans, Debbie C

    2011-10-17

    (51)V solid-state NMR (SSNMR) studies of a series of noninnocent vanadium(V) catechol complexes have been conducted to evaluate the possibility that (51)V NMR observables, quadrupolar and chemical shift anisotropies, and electronic structures of such compounds can be used to characterize these compounds. The vanadium(V) catechol complexes described in these studies have relatively small quadrupolar coupling constants, which cover a surprisingly small range from 3.4 to 4.2 MHz. On the other hand, isotropic (51)V NMR chemical shifts cover a wide range from -200 to 400 ppm in solution and from -219 to 530 ppm in the solid state. A linear correlation of (51)V NMR isotropic solution and solid-state chemical shifts of complexes containing noninnocent ligands is observed. These experimental results provide the information needed for the application of (51)V SSNMR spectroscopy in characterizing the electronic properties of a wide variety of vanadium-containing systems and, in particular, those containing noninnocent ligands and that have chemical shifts outside the populated range of -300 to -700 ppm. The studies presented in this report demonstrate that the small quadrupolar couplings covering a narrow range of values reflect the symmetric electronic charge distribution, which is also similar across these complexes. These quadrupolar interaction parameters alone are not sufficient to capture the rich electronic structure of these complexes. In contrast, the chemical shift anisotropy tensor elements accessible from (51)V SSNMR experiments are a highly sensitive probe of subtle differences in electronic distribution and orbital occupancy in these compounds. Quantum chemical (density functional theory) calculations of NMR parameters for [VO(hshed)(Cat)] yield a (51)V chemical shift anisotropy tensor in reasonable agreement with the experimental results, but surprisingly the calculated quadrupolar coupling constant is significantly greater than the experimental value. The

  13. Nontarget analysis of Murchison soluble organic matter by high-field NMR spectroscopy and FTICR mass spectrometry.

    PubMed

    Hertkorn, N; Harir, M; Schmitt-Kopplin, Ph

    2015-09-01

    High-field NMR spectra of Murchison meteorite methanolic extracts revealed primarily aliphatic extraterrestrial organic matter (EOM) with near statistical branching of commonly C(3-5) units separated by heteroatoms and aromatic units. The ratios of CCH, OCH and C(sp2)H units were 89 : 8 : 3, whereas carbon-based aliphatic chain termination was in the order methyl >  -COOH >  -CH(CH3)COOH. Aliphatic methine carbon was abundant, but its weak NMR signatures were primarily deduced from JRES (J-resolved) NMR spectra. Carbon NMR spectra were dominated by methylene and methyl carbon; strong apodization revealed methine carbon, of which about 20% was aromatic. Extrapolation provided 5-7% aromatic carbon present in Murchison soluble EOM. Compositional heterogeneity in Murchison methanolic extracts was visible in NMR and Fourier transform ion cyclotron (FTICR) mass spectra obtained from a few cubic millimeters of solid Murchison meteorite; increasing sample size enhanced uniformity of NMR spectra. Intrinsic chemical diversity and pH-dependent chemical shift variance contributed to the disparity of NMR spectra. FTICR mass spectra provided distinct clustering of CHO/CHOS and CHNO/CHNOS molecular series and confirmed the prevalence of aliphatic/alicyclic (73%) over single aromatic (21%) and polyaromatic (6%) molecular compositions, suggesting extensive aliphatic substitution of aromatic units as proposed by NMR. Murchison soluble EOM molecules feature a center with enhanced aromatic and heteroatom content, which provides rather diffuse and weak NMR signatures resulting from a huge overall chemical diversity. The periphery of Murchison EOM molecules comprises flexible branched aliphatic chains and aliphatic carboxylic acids. These project on narrow ranges of chemical shift, facilitating observation in one-dimensional and two-dimensional NMR spectra. The conformational entropy provided by these flexible surface moieties facilitates the solubility of EOM. PMID

  14. Electrostatic influence on rotational mobilities of sol-gel-encapsulated solutes by NMR and EPR spectroscopies.

    PubMed

    Wheeler, Korin E; Lees, Nicholas S; Gurbiel, Ryszard J; Hatch, Shelby L; Nocek, Judith M; Hoffman, Brian M

    2004-10-20

    The rotational mobilities of small solute molecules encapsulated in tetramethyl orthosilicate (TMOS) sol-gels have been investigated by EPR spectroscopy of encapsulated nitroxide probes and by high-resolution NMR spectroscopic measurements of transferred NOE's (trNOE's), of T(1)'s, and of T(1)'s in the rotating frame (T(1)rho). The two spectroscopic methods are sensitive to motions on different time scales and hence, are nicely complementary. Suites of neutral, positively, and negatively charged nitroxide probes (EPR) and of simple diamagnetic small molecules (NMR) were selected to disclose influences of electrostatic interactions with the sol-gel walls and to probe the presence of multiple populations of molecules in distinct regions of the sol-gel pores. For neutral and negatively charged solute probes, both techniques disclose a single population with a significantly increased average rotational correlation time, which we interpret at least in part as resulting from exchange between free-volume and transiently immobilized surface populations. The electrostatic attraction between cationic probes and the negatively charged sol-gel walls causes the positively charged probes to be more effectively immobilized and/or causes a greater percentage of probes to undergo this transient immobilization. The EPR spectra directly disclose a population of cationic probes which are immobilized on the X-band EPR time scale: tau(c) greater than or approximately equal 10(-7) s. However, NMR measurements of trNOE's and of T(1)rho demonstrate that this population does exchange with the free-volume probes on the slower time scale of NMR. This approach is equally applicable to the study of solutes within other types of confined spaces, as well. PMID:15479102

  15. Confirming the 3D Solution Structure of a Short Double-Stranded DNA Sequence Using NMR Spectroscopy

    ERIC Educational Resources Information Center

    Ruhayel, Rasha A.; Berners-Price, Susan J.

    2010-01-01

    2D [superscript 1]H NOESY NMR spectroscopy is routinely used to give information on the closeness of hydrogen atoms through space. This work is based on a 2D [superscript 1]H NOESY NMR spectrum of a 12 base-pair DNA duplex. This 6-h laboratory workshop aims to provide advanced-level chemistry students with a basic, yet solid, understanding of how…

  16. Noninvasive quantitation of phosphorus metabolites in human tissue by NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Roth, K.; Hubesch, B.; Meyerhoff, D. J.; Naruse, S.; Gober, J. R.; Lawry, T. J.; Boska, M. D.; Matson, G. B.; Weiner, M. W.

    Quantitation of metabolite concentrations by NMR spectroscopy is complicated by the need to determine the volume from which signals are detected, and by the need to obtain the relative sensitivity of detection within this volume. The use of coils with inhomogeneous B1 fields further complicates these problems. In order to quantify metabolite concentrations using 31P NMR spectroscopy, an external reference of hexamethyl phosphoroustriamide was used. Studies were performed on phantoms, using either a surface coil or a Helmholtz head coil to confirm the accuracy of both the ISIS volume selection technique and the use of an external reference. The limitations of this method are related to contamination and signal loss inherent in the ISIS technique and difficulties with integration of broad overlapping peaks. The method was applied to seven normal human subjects. The integrals for metabolite signals in normal brain and calf muscle were determined by using NMRI software. The T1 values of the signals of all phosphorus metabolites in the selected volume were measured in order to correct for saturation effects. The concentrations for PCr, P i, and ATP were 4.9, 2.0, and 2.5 m M in brain and 36.5, 5.7, and 7.3 m M in muscle. These results are in good agreement with those reported for animals, demonstrating the validity of this quantitation technique.

  17. Secondary structure determination of human. beta. -endorphin by /sup 1/H NMR spectroscopy

    SciTech Connect

    Lichtarge, O.; Jardetzky, O.; Li, C.H.

    1987-09-08

    The /sup 1/H NMR spectra of human ..beta..-endorphin indicate that the peptide exists in random-coil form in aqueous solution but becomes helical in mixed solvent. Thermal denaturation NMR experiments show that in water there is no transition between 24 and 75/sup 0/C, while a slow noncooperative thermal unfolding is observed in a 60% methanol-40% water mixed solvent in the same temperature range. These findings are consistent with circular dichroism studies by other workers concluding that ..beta..-endorphin is a random coil in water but that it forms 50% ..cap alpha..-helix or more in mixed solvents. The peptide in the mixed water-methanol solvent was further studied by correlated spectroscopy (COSY) and nuclear Overhauser effect spectroscopy (NOESY) experiments. These allow a complete set of assignments to be made and establish two distinct stretches over which the solvent induces formation of ..cap alpha..-helices: the first occurs between Tyr-1 and Thr-12 and the second between Leu-14 and extending to Lys-28. There is evidence that the latter is capped by a turn occurring between Lys-28 and Glu-31. These helices form at the enkephalin receptor binding site, which is at the amino terminus, and at the morphine receptor binding site, located at the carboxyl terminus. The findings suggest that these two receptors may specifically recognize ..cap alpha..-helices.

  18. Phosphorus Speciation of Sequential Extracts of Organic Amendments using NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Akinremi, O.

    2009-04-01

    O.O. 1Akinremi Babasola Ajiboye and Donald N. Flaten 1Department of Soil Science, University of Manitoba, Winnipeg, R3T 2NT, Canada We carried out this study in order to determine the forms of phosphorus in various organic amendments using state-of-the art spectroscopic technique. Anaerobically digested biosolids (BIO), hog (HOG), dairy (DAIRY), beef (BEEF) and poultry (POULTRY) manures were subjected to sequential extraction. The extracts were analyzed by solution 31P nuclear magnetic resonance (NMR) spectroscopy. Most of the total P analysed by inductively coupled plasma-optical emission spectroscopy (ICP-OES) in the sequential extracts of organic amendments were orthophosphate, except POULTRY, which was dominated by organic P. The labile P fraction in all the organic amendments, excluding POULTRY, was mainly orthophosphate P from readily soluble calcium and some aluminum phosphates. In the poultry litter, however, Ca phytate was the main P species controlling P solubility. Such knowledge of the differences in the chemical forms of phosphorus in organic amendments are essential for proper management of these amendments for agro-environmental purposes Key words: organic amendments, solution NMR, sequential fractionation, labile phosphorus

  19. Characterization of prednisolone in controlled porosity osmotic pump pellets using solid-state NMR spectroscopy.

    PubMed

    Sotthivirat, S; Lubach, J W; Haslam, J L; Munson, E J; Stella, V J

    2007-05-01

    The overall objective of this study was to demonstrate the influence of formulation and processing variables on the physical state of prednisolone (PDL) in formulations consisting of PDL, microcrystalline cellulose (MCC), and sulfobutylether-beta-cyclodextrin (CD). PDL was used as a model drug in controlled porosity osmotic pump pellet (CP-OPP) formulations, and was characterized using solid-state NMR spectroscopy and other complimentary analytical techniques. Dosage forms and the solid-state properties of drugs and excipients in a formulation may be influenced by the processing conditions used. Several processing parameters, such as amount of water used in wet granulation and subsequent drying conditions, were found to affect the solid-state transformation of PDL. In addition, the presence of excipients in the CP-OPP was observed to decrease the degree of PDL crystallinity, presumably by creating an inclusion complex with the CD. A hydrated form of PDL was created when PDL was ground with water alone; however, this form was not observed in formulated products. Solid-state NMR spectroscopy was shown to be a powerful technique for the analysis of drug formulations and investigations of the effects of processing conditions. PMID:17455361

  20. Broad identification of bacterial type in urinary tract infection using (1)h NMR spectroscopy.

    PubMed

    Gupta, Ashish; Dwivedi, Mayank; Mahdi, Abbas Ali; Khetrapal, Chunni Lal; Bhandari, Mahendra

    2012-03-01

    To address the shortcomings of urine culture for the rapid identification of urinary tract infection (UTI), we applied (1)H-nuclear magnetic resonance (NMR) spectroscopy as a surrogate method for fast screening of microorganisms. Study includes 682 urine samples from suspected UTI patients, 50 healthy volunteers, and commercially available standard strains of gram negative bacilli (GNB) (Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Enterobacter, Acinetobacter, Proteus mirabilis, Citrobacter frundii) and gram positive cocci (GPC) (Enterococcus faecalis, Streptococcus group B, Staphylococcus saprophyticus). Acetate, lactate, ethanol, succinate, creatinine, trimethylamine (TMA), citrate, trimethylamin-N-oxide, glycine, urea, and hippurate were measured by (1)H NMR spectroscopy. All urine specimens were evaluated with culture method. Multivariate discriminant function analysis (DFA) reveals that acetate, lactate, succinate, and formate were able to differentiate, with high accuracy (99.5%), healthy controls from UTI patients. This statistical analysis was also able to classify GNB to GPC infected urine samples with high accuracy (96%). This technique appears to be a promising, rapid, and noninvasive approach to probing GNB and GPC infected urine specimens with its distinguishing metabolic profile. The determination of infection will be very important for rapidly and efficiently measuring the efficacy of a tailored treatment, leading to prompt and appropriate care of UTI patients. PMID:22292465

  1. The Development of 460 GHz gyrotrons for 700 MHz DNP-NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Idehara, T.; Tatematsu, Y.; Yamaguchi, Y.; Khutoryan, E. M.; Kuleshov, A. N.; Ueda, K.; Matsuki, Y.; Fujiwara, T.

    2015-07-01

    Two demountable gyrotrons with internal mode converters were developded as sub-THz radiation sources for 700 MHz DNP (Dynamic Nuclear Polarization) enhanced NMR spectroscopy. Experimental study on the DNP-NMR spectroscopy will be carried out in Osaka University, Institute for Protein Research, as a collaboration with FIR UF. Both gyrotrons operate near 460 GHz and the output CW power measured at the end of transmission system made by circular waveguides is typically 20 to 30 watts. One of them named Gyrotron FU CW GVI (we are using "Gyrotron FU CW GO-1" as an official name in Osaka University) is designed to have a special function of high speed frequency modulation δ f within 100 MHz band. This will expand excitable band width of ESR and increase the number of electron spins contributing to DNP. The other gyrotron, Gyrotron FU CW GVIA ("Gyrotron FU CW GO-II") has a function of frequency tunability Δ f in the range of wider than 1.5 GHz, which is achieved in steady state by changing magnetic field intensity. This function should be used for adjusting the output frequency at the optimal value to achieve the highest enhancement factor of DNP.

  2. Determination of RNA polymerase binding surfaces of transcription factors by NMR spectroscopy

    PubMed Central

    Drögemüller, Johanna; Strauß, Martin; Schweimer, Kristian; Jurk, Marcel; Rösch, Paul; Knauer, Stefan H.

    2015-01-01

    In bacteria, RNA polymerase (RNAP), the central enzyme of transcription, is regulated by N-utilization substance (Nus) transcription factors. Several of these factors interact directly, and only transiently, with RNAP to modulate its function. As details of these interactions are largely unknown, we probed the RNAP binding surfaces of Escherichia coli (E. coli) Nus factors by nuclear magnetic resonance (NMR) spectroscopy. Perdeuterated factors with [1H,13C]-labeled methyl groups of Val, Leu, and Ile residues were titrated with protonated RNAP. After verification of this approach with the N-terminal domain (NTD) of NusG and RNAP we determined the RNAP binding site of NusE. It overlaps with the NusE interaction surface for the NusG C-terminal domain, indicating that RNAP and NusG compete for NusE and suggesting possible roles for the NusE:RNAP interaction, e.g. in antitermination and direct transcription:translation coupling. We solved the solution structure of NusA-NTD by NMR spectroscopy, identified its RNAP binding site with the same approach we used for NusG-NTD, and here present a detailed model of the NusA-NTD:RNAP:RNA complex. PMID:26560741

  3. Understanding J-Modulation during Spatial Encoding for Sensitivity-Optimized Ultrafast NMR Spectroscopy.

    PubMed

    Gouilleux, Boris; Rouger, Laetitia; Charrier, Benoît; Kuprov, Ilya; Akoka, Serge; Dumez, Jean-Nicolas; Giraudeau, Patrick

    2015-10-01

    Ultrafast (UF) NMR spectroscopy is an approach that yields 2D spectra in a single scan. This methodology has become a powerful analytical tool that is used in a large array of applications. However, UF NMR spectroscopy still suffers from an intrinsic low sensitivity, and from the need to compromise between sensitivity, spectral width, and resolution. In particular, the modulation of signal intensities by the spin-spin J-coupling interaction (J-modulation) impacts significantly on the intensities of the spectral peaks. This effect can lead to large sensitivity losses and even to missing spectral peaks, depending on the nature of the spin system. Herein, a general simulation package (Spinach) is used to describe J-modulation effects in UF experiments. The results from simulations match with experimental data and the results of product operator calculations. Several methods are proposed to optimize the sensitivity in UF COSY spectra. The potential and drawbacks of the different strategies are also discussed. These approaches provide a way to adjust the sensitivity of UF experiments for a large range of applications. PMID:26401975

  4. Flexible Stoichiometry and Asymmetry of the PIDDosome Core Complex by Heteronuclear NMR Spectroscopy and Mass Spectrometry

    PubMed Central

    Nematollahi, Lily A.; Garza-Garcia, Acely; Bechara, Chérine; Esposito, Diego; Morgner, Nina; Robinson, Carol V.; Driscoll, Paul C.

    2015-01-01

    Homotypic death domain (DD)–DD interactions are important in the assembly of oligomeric signaling complexes such as the PIDDosome that acts as a platform for activation of caspase-2-dependent apoptotic signaling. The structure of the PIDDosome core complex exhibits an asymmetric three-layered arrangement containing five PIDD-DDs in one layer, five RAIDD-DDs in a second layer and an additional two RAIDD-DDs. We addressed complex formation between PIDD-DD and RAIDD-DD in solution using heteronuclear nuclear magnetic resonance (NMR) spectroscopy, nanoflow electrospray ionization mass spectrometry and size-exclusion chromatography with multi-angle light scattering. The DDs assemble into complexes displaying molecular masses in the range 130–158 kDa and RAIDD-DD:PIDD-DD stoichiometries of 5:5, 6:5 and 7:5. These data suggest that the crystal structure is representative of only the heaviest species in solution and that two RAIDD-DDs are loosely attached to the 5:5 core. Two-dimensional 1H,15N-NMR experiments exhibited signal loss upon complexation consistent with the formation of high-molecular-weight species. 13C-Methyl-transverse relaxation optimized spectroscopy measurements of the PIDDosome core exhibit signs of differential line broadening, cross-peak splitting and chemical shift heterogeneity that reflect the presence of non-equivalent sites at interfaces within an asymmetric complex. Experiments using a mutant RAIDD-DD that forms a monodisperse 5:5 complex with PIDD-DD show that the spectroscopic signature derives from the quasi- but non-exact equivalent environments of each DD. Since this characteristic was previously demonstrated for the complex between the DDs of CD95 and FADD, the NMR data for this system are consistent with the formation of a structure homologous to the PIDDosome core. PMID:25528640

  5. Flexible stoichiometry and asymmetry of the PIDDosome core complex by heteronuclear NMR spectroscopy and mass spectrometry.

    PubMed

    Nematollahi, Lily A; Garza-Garcia, Acely; Bechara, Chérine; Esposito, Diego; Morgner, Nina; Robinson, Carol V; Driscoll, Paul C

    2015-02-27

    Homotypic death domain (DD)-DD interactions are important in the assembly of oligomeric signaling complexes such as the PIDDosome that acts as a platform for activation of caspase-2-dependent apoptotic signaling. The structure of the PIDDosome core complex exhibits an asymmetric three-layered arrangement containing five PIDD-DDs in one layer, five RAIDD-DDs in a second layer and an additional two RAIDD-DDs. We addressed complex formation between PIDD-DD and RAIDD-DD in solution using heteronuclear nuclear magnetic resonance (NMR) spectroscopy, nanoflow electrospray ionization mass spectrometry and size-exclusion chromatography with multi-angle light scattering. The DDs assemble into complexes displaying molecular masses in the range 130-158kDa and RAIDD-DD:PIDD-DD stoichiometries of 5:5, 6:5 and 7:5. These data suggest that the crystal structure is representative of only the heaviest species in solution and that two RAIDD-DDs are loosely attached to the 5:5 core. Two-dimensional (1)H,(15)N-NMR experiments exhibited signal loss upon complexation consistent with the formation of high-molecular-weight species. (13)C-Methyl-transverse relaxation optimized spectroscopy measurements of the PIDDosome core exhibit signs of differential line broadening, cross-peak splitting and chemical shift heterogeneity that reflect the presence of non-equivalent sites at interfaces within an asymmetric complex. Experiments using a mutant RAIDD-DD that forms a monodisperse 5:5 complex with PIDD-DD show that the spectroscopic signature derives from the quasi- but non-exact equivalent environments of each DD. Since this characteristic was previously demonstrated for the complex between the DDs of CD95 and FADD, the NMR data for this system are consistent with the formation of a structure homologous to the PIDDosome core. PMID:25528640

  6. Dissolution DNP-NMR spectroscopy using galvinoxyl as a polarizing agent

    NASA Astrophysics Data System (ADS)

    Lumata, Lloyd L.; Merritt, Matthew E.; Malloy, Craig R.; Sherry, A. Dean; van Tol, Johan; Song, Likai; Kovacs, Zoltan

    2013-02-01

    The goal of this work was to test feasibility of using galvinoxyl (2,6-di-tert-butyl-α-(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadien-1-ylidene)-p-tolyloxy) as a polarizing agent for dissolution dynamic nuclear polarization (DNP) NMR spectroscopy. We have found that galvinoxyl is reasonably soluble in ethyl acetate, chloroform, or acetone and the solutions formed good glasses when mixed together or with other solvents such as dimethyl sulfoxide. W-band electron spin resonance (ESR) measurements revealed that galvinoxyl has an ESR linewidth D intermediate between that of carbon-centered free radical trityl OX063 and the nitroxide-based 4-oxo-TEMPO, thus the DNP with galvinoxyl for nuclei with low gyromagnetic ratio γ such as 13C and 15N is expected to proceed predominantly via the thermal mixing process. The optimum radical concentration that would afford the highest 13C nuclear polarization (approximately 6% for [1-13C]ethyl acetate) at 3.35 T and 1.4 K was found to be around 40 mM. After dissolution, large liquid-state NMR enhancements were achieved for a number of 13C and 15N compounds with long spin-lattice relaxation time T1. In addition, the hydrophobic galvinoxyl free radical can be easily filtered out from the dissolution liquid when water is used as the solvent. These results indicate that galvinoxyl can be considered as an easily available free radical polarizing agent for routine dissolution DNP-NMR spectroscopy.

  7. 13C NMR study of the generation of C2- and C3-deuterated lactic acid by tumoral pancreatic islet cells exposed to D-[1-13C]-, D-[2-13C]- and D-[6-13C]-glucose in 2H2O.

    PubMed

    Willem, R; Biesemans, M; Kayser, F; Malaisse, W J

    1994-03-01

    Tumoral pancreatic islet cells of the RIN5mF line were incubated for 120 min in media prepared in 2H2O and containing D-[1-13C]glucose, D-[2-13C]glucose, and D-[6-13C]glucose. The generation of C2- and C3-deuterated lactic acid was assessed by 13C NMR. The interpretation of experimental results suggests that a) the efficiency of deuteration on the C1 of D-fructose 6-phosphate does not exceed about 47% and 4% in the phosphoglucoisomerase and phosphomannoisomerase reactions, respectively; b) approximately 38% of the molecules of D-glyceraldehyde 3-phosphate generated from D-glucose escape deuteration in the sequence of reactions catalyzed by triose phosphate isomerase and aldolase; and c) about 41% of the molecules of pyruvate generated by glycolysis are immediately converted to lactate, the remaining 59% of pyruvate molecules undergoing first a single or double back-and-forth interconversion with L-alanine. It is proposed that this methodological approach, based on high resolution 13C NMR spectroscopy, may provide novel information on the regulation of back-and-forth interconversion of glycolytic intermediates in intact cells as modulated, for instance, by enzyme-to-enzyme tunneling. PMID:8057796

  8. Reexamination of C-NMR13 in (TMTTF)2AsF6 : Comparison with infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Hirose, Shinji; Kawamoto, Atsushi; Matsunaga, Noriaki; Nomura, Kazushige; Yamamoto, Kaoru; Yakushi, Kyuya

    2010-05-01

    The charge order (CO) state can be observed by microprobe measurements such as nuclear magnetic resonance (NMR) and infrared spectroscopy. We used the infrared spectroscopy to examine (TMTTF)2AsF6 and confirmed the CO transition seen in previous C13 -NMR studies. However we found the degree of charge disproportionation, Δρ=0.16 , to be smaller than that obtained from the analysis of T1 in C13 -NMR and the redistribution of charge density below spin Peierls transition predicted by C13 -NMR was not observed at low temperature. We estimated the degree of spin disproportionation to be 0.11 from the analysis of the NMR shift in previous NMR studies. This small disproportionation does not require the redistribution of charge density at low temperature. The different behaviors of T1 at charge-rich and charge-poor molecular sites observed by C13 -NMR can be examined by the contribution of the commensurate antiferromagnetic fluctuation with 4kF .

  9. The application of HPLC and microprobe NMR spectroscopy in the identification of metabolites in complex biological matrices.

    PubMed

    Miao, Zhaoxia; Jin, Mengxia; Liu, Xia; Guo, Wei; Jin, Xiangju; Liu, Hongyue; Wang, Yinghong

    2015-05-01

    Nuclear magnetic resonance (NMR)-based metabolomics can be used directly to identify a variety of metabolites in biological fluids and tissues. Metabolite analysis is an important part of life science and metabolomics research. However, the identification of some metabolites using NMR spectroscopy remains a big challenge owing to low abundance or signal overlap. It is important to develop a method to measure these compounds accurately. Two-dimensional NMR spectroscopy, metabolite prediction software packages, and spike-in experiments with authentic standards are often used to solve these problems, but they are costly and time-consuming. In this study, methods were developed to identify metabolites in complex biological mixtures using both high-performance liquid chromatography (HPLC) and off-line microprobe NMR spectroscopy. With use of these methods, 83 and 73 metabolites were identified in Sprague Dawley rat urine and feces, respectively. Among them, 40 and 45 metabolites, respectively, could not be identified with traditional NMR methods. Our research revealed that the combination of HPLC and NMR techniques could significantly improve the accuracy of trace and overlapped metabolite identification, while offering an effective and convenient approach to identify potential biomarkers in complex biological systems. PMID:25814271

  10. Synthesis and Stereochemical Assignment of Crypto-Optically Active (2) H6 -Neopentane.

    PubMed

    Masarwa, Ahmad; Gerbig, Dennis; Oskar, Liron; Loewenstein, Aharon; Reisenauer, Hans Peter; Lesot, Philippe; Schreiner, Peter R; Marek, Ilan

    2015-10-26

    The determination of the absolute configuration of chiral molecules is at the heart of asymmetric synthesis. Here we probe the spectroscopic limits for chiral discrimination with NMR spectroscopy in chiral aligned media and with vibrational circular dichroism spectroscopy of the sixfold-deuterated chiral neopentane. The study of this compound presents formidable challenges since its stereogenicity is only due to small mass differences. For this purpose, we selectively prepared both enantiomers of (2) H6 -1 through a concise synthesis utilizing multifunctional intermediates. While NMR spectroscopy in chiral aligned media could be used to characterize the precursors to (2) H6 -1, the final assignment could only be accomplished with VCD spectroscopy, despite the fleetingly small dichroic properties of 1. Both enantiomers were assigned by matching the VCD spectra with those computed with density functional theory. PMID:26480341

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

    PubMed Central

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

    2016-01-01

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

  12. The contribution of solid-state NMR spectroscopy to understanding biomineralization: Atomic and molecular structure of bone

    NASA Astrophysics Data System (ADS)

    Duer, Melinda J.

    2015-04-01

    Solid-state NMR spectroscopy has had a major impact on our understanding of the structure of mineralized tissues, in particular bone. Bone exemplifies the organic-inorganic composite structure inherent in mineralized tissues. The organic component of the extracellular matrix in bone is primarily composed of ordered fibrils of collagen triple-helical molecules, in which the inorganic component, calcium phosphate particles, composed of stacks of mineral platelets, are arranged around the fibrils. This perspective argues that key factors in our current structural model of bone mineral have come about through NMR spectroscopy and have yielded the primary information on how the mineral particles interface and bind with the underlying organic matrix. The structure of collagen within the organic matrix of bone or any other structural tissue has yet to be determined, but here too, this perspective shows there has been real progress made through application of solid-state NMR spectroscopy in conjunction with other techniques. In particular, NMR spectroscopy has highlighted the fact that even within these structural proteins, there is considerable dynamics, which suggests that one should be cautious when using inherently static structural models, such as those arising from X-ray diffraction analyses, to gain insight into molecular roles. It is clear that the NMR approach is still in its infancy in this area, and that we can expect many more developments in the future, particularly in understanding the molecular mechanisms of bone diseases and ageing.

  13. Coordination Environment of a Site-Bound Metal Ion in the Hammerhead Ribozyme Determined by 15N and 2H ESEEM Spectroscopy

    PubMed Central

    Vogt, Matthew; Lahiri, Simanti; Hoogstraten, Charles G.; Britt, R. David; DeRose, Victoria J.

    2010-01-01

    Although site-bound Mg2+ ions have been proposed to influence RNA structure and function, establishing the molecular properties of such sites has been challenging due largely to the unique electrostatic properties of the RNA biopolymer. We have previously determined that, in solution, the hammerhead ribozyme (a self-cleaving RNA) has a high-affinity metal ion binding site characterized by a Kd,app < 10 µM for Mn2+ in 1 M NaCl and speculated that this site has functional importance in the ribozyme cleavage reaction. Here we determine both the precise location and the hydration level of Mn2+ in this site using ESEEM (electron spin–echo envelope modulation) spectroscopy. Definitive assignment of the high-affinity site to the activity-sensitive A9/G10.1 region is achieved by site-specific labeling of G10.1 with 15N guanine. The coordinated metal ion retains four water ligands as measured by 2H ESEEM spectroscopy. The results presented here show that a functionally important, specific metal binding site is uniquely populated in the hammerhead ribozyme even in a background of high ionic strength. Although it has a relatively high thermodynamic affinity, this ion remains partially hydrated and is chelated to the RNA by just two ligands. PMID:17177426

  14. Synthesis, experimental spectra (IR & Raman and NMR), vibrational analysis and theoretical DFT investigations of N-(5-(4-methylbenzoyl)-2-oxo-4-(4-methylphenyl)pyrimidine-1(2H)-yl)-4-methylbenzamide

    NASA Astrophysics Data System (ADS)

    Aydın, Lütfiye; Şahan, Emine; Önal, Zülbiye; Özpozan, Talat

    2014-08-01

    The title molecule, N-(5-(4-methylbenzoyl)-2-oxo-4-(4-methylphenyl)pyrimidine-1(2H)-yl)-4-methylbenzamide (C27H23N3O3), was synthesized and characterized by elemental analysis, IR, Raman, 1H and 13C NMR spectral data. To determine conformational flexibility, potential energy surfaces of the title compound were obtained by DFT regarding the selected degree of torsional freedom, which was varied from 0° to 360° in 6° and 20° steps. The ten conformers of the title compound were determined and it was found that the conformer 1 basis the most stable one. All conformers were also optimized by using the density functional theory (DFT/B3LYP) method with the 6-31G(d,p), 6-311G(d,p) and cc-pVDZ basis sets in the ground state. Potential energy distribution was calculated with the 6-31G(d,p) basis set. The vibrational spectra were recorded in solid phase IR and Raman spectra were compared based on the results of the theoretical calculations. The formation of hydrogen bonds was explained using natural bond orbital (NBO) analysis and spectroscopic analysis. NMR analysis and frontier molecular orbitals (FMOs) were also investigated by DFT.

  15. No-D NMR (no-deuterium proton NMR) spectroscopy: a simple yet powerful method for analyzing reaction and reagent solutions.

    PubMed

    Hoye, Thomas R; Eklov, Brian M; Ryba, Troy D; Voloshin, Mikhail; Yao, Letitia J

    2004-03-18

    [reaction: see text] The title technique is a convenient and powerful method for directly monitoring or assaying any reaction mixture or reagent solution. Examples of some common processes (Fischer esterification, lithiation, butyllithium/THF compatibility, olefin metathesis, and a quantification assay), each interrogated in its native solvent, are presented. The spectral data are easy to acquire, and the information content makes a compelling case for routine use of No-D NMR spectroscopy. PMID:15012073

  16. Characterization of reactive intermediates by multinuclear diffusion-ordered NMR spectroscopy (DOSY).

    PubMed

    Li, Deyu; Keresztes, Ivan; Hopson, Russell; Williard, Paul G

    2009-02-17

    Nuclear magnetic resonance (NMR) is the most powerful and widely utilized technique for determining molecular structure. Although traditional NMR data analysis involves the correlation of chemical shift, coupling constant, and NOE interactions to specific structural features, a largely overlooked method introduced more than 40 years ago, pulsed gradient spin-echo (PGSE), measures diffusion coefficients of molecules in solution, thus providing their relative particle sizes. In the early 1990s, the PGSE sequence was incorporated into a two-dimensional experiment, dubbed diffusion-ordered NMR spectroscopy (DOSY), in which one dimension represents chemical shift data while the second dimension resolves species by their diffusion properties. This combination provides a powerful tool for identifying individual species in a multicomponent solution, earning the nickname "chromatography by NMR". In this Account, we describe our efforts to utilize DOSY techniques to characterize organometallic reactive intermediates in solution in order to correlate structural data to solid-state crystal structures determined by X-ray diffraction and to discover the role of aggregate formation and solvation states in reaction mechanisms. In 2000, we reported our initial efforts to employ DOSY techniques in the characterization of reactive intermediates such as organolithium aggregates. Since then, we have explored DOSY experiments with various nuclei beyond (1)H, including (6)Li, (7)Li, (11)B, (13)C, and (29)Si. Additionally, we proposed a diffusion coefficient-formula weight relationship to determine formula weight, aggregation number, and solvation state of reactive intermediates. We also introduced an internal reference system to correlate the diffusion properties of unknown reactive intermediates with known inert molecular standards, such as aromatic compounds, terminal olefins, cycloolefins, and tetraalkylsilanes. Furthermore, we utilized DOSY to interpret the role of aggregation number

  17. Analysis of δ18O and δ2H of fluid inclusion water in speleothems using cavity ring-down spectroscopy

    NASA Astrophysics Data System (ADS)

    Arienzo, M. M.; Swart, P. K.; Schroeder, C.; Hsiao, G.; Vonhof, H. B.

    2012-12-01

    Fluid inclusion isotope analysis is the analysis of microscopic, water filled cavities in speleothems. These cavities preserve drip water at the time of formation and fluid inclusions isotopic analysis provides information on the formation water (δ18Ow) and temperature can be calculated. The determination of δ18Ow and temperature is valuable for paleoclimate reconstructions. Recent work on speleothem fluid inclusions has utilized continuous-flow isotopic ratio mass spectrometry (IRMS) methods for determination of δ18Ow and δ2H of fluid inclusion water (Vonhof et al., Rapid. Comm. Mass Spec., 20:2553-2558, 2006; Dublyansky, and Spotl, Rapid. Comm. Mass Spec., 23: 2605-2613, 2009). Here we present a new technique utilizing cavity-ring down spectroscopy (CRDS) for δ18O and δ2H analysis of fluid inclusions and compare the data obtained to that measured on the Amsterdam Device which is a crusher system linked with an IRMS developed at the VU University Amsterdam. The extraction line at the University of Miami is an in-line system directly interfaced with the Picarro CRDS isotopic water analyzer and the design of the line is similar to the Amsterdam Device. The extraction line consists of a crusher device which is a modified valve unit, a septum port for the direct injection of water and a water trap. The CRDS technique is based on using a near infrared laser which is scanned over the H2O spectral range and by measuring the absorption spectra by ring-down, isotopic abundances are determined. This system has the potential for greater precision measurements than traditional IRMS systems. Therefore for fluid inclusion analysis, CRDS may prove to be an alternative to IRMS.

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

    PubMed

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

    1992-06-01

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

  19. Organic solute changes with acidification in Lake Skjervatjern as shown by 1H-NMR spectroscopy

    USGS Publications Warehouse

    Malcolm, R.L.; Hayes, T.

    1994-01-01

    1H-NMR spectroscopy has been found to be a useful tool to establish possible real differences and trends between all natural organic solute fractions (fulvic acids, humic acids, and XAD-4 acids) after acid-rain additions to the Lake Skjervatjern watershed. The proton NMR technique used in this study determined the spectral distribution of nonexchangeable protons among four peaks (aliphatic protons; aliphatic protons on carbon ?? or attached to electronegative groups; protons on carbons attached to O or N heteroatoms; and aromatic protons). Differences of 10% or more in the respective peak areas were considered to represent a real difference. After one year of acidification, fulvic acids decreased 13% (relative) in Peak 3 protons on carbon attached to N and O heteratoms and exhibited a decrease in aromatic protons between 27% and 31%. Humic acids also exhibited an 11% relative decrease in aromatic protons as a result of acidification. After one year of acidification, real changes were shown in three of the four proton assignments in XAD-4 acids. Peak 1 aliphatic protons increased by 14% (relative), Peak 3 protons on carbons attached to O and N heteroatoms decreased by 13% (relative), and aromatic protons (Peak 4) decreased by 35% (relative). Upon acidification, there was a trend in all solutes for aromatic protons to decrease and aliphatic protons to increase. The natural variation in organic solutes as shown in the Control Side B of the lake from 1990 to 1991 is perhaps a small limitation to the same data interpretations of acid rain changes at the Lake Skjervatjern site, but the proton NMR technique shows great promise as an independent scientific tool to detect and support other chemical techniques in establishing organic solute changes with different treatments (i.e., additions of acid rain).

  20. On the Stark effect in open shell complexes exhibiting partially quenched electronic angular momentum: Infrared laser Stark spectroscopy of OH-C2H2, OH-C2H4, and OH-H2O

    NASA Astrophysics Data System (ADS)

    Moradi, Christopher P.; Douberly, Gary E.

    2015-08-01

    The Stark effect is considered for polyatomic open shell complexes that exhibit partially quenched electronic angular momentum. Matrix elements of the Stark Hamiltonian represented in a parity conserving Hund's case (a) basis are derived for the most general case, in which the permanent dipole moment has projections on all three inertial axes of the system. Transition intensities are derived, again for the most general case, in which the laser polarization has projections onto axes parallel and perpendicular to the Stark electric field, and the transition dipole moment vector is projected onto all three inertial axes in the molecular frame. Simulations derived from this model are compared to experimental rovibrational Stark spectra of OH-C2H2, OH-C2H4, and OH-H2O complexes formed in helium nanodroplets.

  1. Synthesis and Resolution of the Atropisomeric 1,1'-Bi-2-Naphthol: An Experiment in Organic Synthesis and 2-D NMR Spectroscopy

    ERIC Educational Resources Information Center

    Mak, Kendrew K. W.

    2004-01-01

    NMR spectroscopy is presented. It is seen that the experiment regarding the synthesis and resolution of 1,1'-Bi-2-naphtol presents a good experiment for teaching organic synthesis and NMR spectroscopy and provides a strategy for obtaining enantiopure compounds from achiral starting materials.

  2. Near infrared diode laser spectroscopy of C2H2, H2O, CO2 and their isotopologues and the application to TDLAS, a tunable diode laser spectrometer for the martian PHOBOS-GRUNT space mission

    NASA Astrophysics Data System (ADS)

    Durry, G.; Li, J. S.; Vinogradov, I.; Titov, A.; Joly, L.; Cousin, J.; Decarpenterie, T.; Amarouche, N.; Liu, X.; Parvitte, B.; Korablev, O.; Gerasimov, M.; Zéninari, V.

    2010-04-01

    A near-infrared tunable diode laser spectrometer called TDLAS has been developed that combines telecommunication-type as well as new-generation antimonide laser diodes to measure C2H2, H2O, CO2 and their isotopologues in the near infrared. This sensor is devoted to the in situ analysis of the soil of the Martian satellite PHOBOS, within the framework of the Russian space mission PHOBOS-GRUNT. In the first part of the paper, we report accurate spectroscopic measurements of C2H2 and 13C12CH2 near 1.533 μm, of H2O and CO2 at 2.682 μm and of the isotopologues 13C16O2 and 16O12C18O near 2.041 μm and H2 17O, H2 18O and HDO near 2.642 μm. The achieved line strengths are thoroughly compared to data from molecular databases or from former experimental determinations. In the second part of the paper, we describe the TDLAS spectrometer for the PHOBOS-GRUNT mission.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  4. Authentication of beef versus horse meat using 60 MHz 1H NMR spectroscopy.

    PubMed

    Jakes, W; Gerdova, A; Defernez, M; Watson, A D; McCallum, C; Limer, E; Colquhoun, I J; Williamson, D C; Kemsley, E K

    2015-05-15

    This work reports a candidate screening protocol to distinguish beef from horse meat based upon comparison of triglyceride signatures obtained by 60 MHz (1)H NMR spectroscopy. Using a simple chloroform-based extraction, we obtained classic low-field triglyceride spectra from typically a 10 min acquisition time. Peak integration was sufficient to differentiate samples of fresh beef (76 extractions) and horse (62 extractions) using Naïve Bayes classification. Principal component analysis gave a two-dimensional "authentic" beef region (p=0.001) against which further spectra could be compared. This model was challenged using a subset of 23 freeze-thawed training samples. The outcomes indicated that storing samples by freezing does not adversely affect the analysis. Of a further collection of extractions from previously unseen samples, 90/91 beef spectra were classified as authentic, and 16/16 horse spectra as non-authentic. We conclude that 60 MHz (1)H NMR represents a feasible high-throughput approach for screening raw meat. PMID:25577043

  5. Characterization of alkyl carbon in forest soils by CPMAS 13C NMR spectroscopy and dipolar dephasing

    USGS Publications Warehouse

    Kogel-Knabner, I.; Hatcher, P.G.

    1989-01-01

    Samples obtained from forest soils at different stages of decomposition were treated sequentially with chloroform/methanol (extraction of lipids), sulfuric acid (hydrolysis), and sodium chlorite (delignification) to enrich them in refractory alkyl carbon. As revealed by NMR spectroscopy, this treatment yielded residues with high contents of alkyl carbon. In the NMR spectra of residues obtained from litter samples, resonances for carbohydrates are also present, indicating that these carbohydrates are tightly bound to the alkyl carbon structures. During decomposition in the soils this resistant carbohydrate fraction is lost almost completely. In the litter samples the alkyl carbon shows a dipolar dephasing behavior indicative of two structural components, a rigid and a more mobile component. As depth and decomposition increase, only the rigid component is observed. This fact could be due to selective degradation of the mobile component or to changes in molecular mobility during decomposition, e.g., because of an increase in cross linking or contact with the mineral matter of the soil.

  6. The Interaction between tRNALys3 and the Primer Activation Signal Deciphered by NMR Spectroscopy

    PubMed Central

    Brachet, Franck; Tisne, Carine

    2013-01-01

    The initiation of reverse transcription of the human immunodeficiency virus type 1 (HIV-1) requires the opening of the three-dimensional structure of the primer tRNALys3 for its annealing to the viral RNA at the primer binding site (PBS). Despite the fact that the result of this rearrangement is thermodynamically more stable, there is a high-energy barrier that requires the chaperoning activity of the viral nucleocapsid protein. In addition to the nucleotide complementarity to the PBS, several regions of tRNALys3 have been described as interacting with the viral genomic RNA. Among these sequences, a sequence of the viral genome called PAS for “primer activation signal” was proposed to interact with the T-arm of tRNALys3, this interaction stimulating the initiation of reverse transcription. In this report, we investigate the formation of this additional interaction with NMR spectroscopy, using a simple system composed of the primer tRNALys3, the 18 nucleotides of the PBS, the PAS (8 nucleotides) encompassed or not in a hairpin structure, and the nucleocapsid protein. Our NMR study provides molecular evidence of the existence of this interaction and highlights the role of the nucleocapsid protein in promoting this additional RNA-RNA annealing. This study presents the first direct observation at a single base-pair resolution of the PAS/anti-PAS association, which has been proposed to be involved in the chronological regulation of the reverse transcription. PMID:23762248

  7. XRD, TEM, IR, Raman and NMR Spectroscopy of In Situ Crystallization of Lithium Disilicate Glass

    NASA Technical Reports Server (NTRS)

    Fuss, T.; Mogus-Milankovic, A.; Ray, C. S.; Lesher, C. E.; Youngman, R.; Day, D. E.

    2006-01-01

    The structure of a Li2O-2SiO2 (LS2) glass was investigated as a function of pressure and temperature up to 6 GPa and 750 C respectively, using XRD, TEM, IR, Raman and NMR spectroscopy. Glass densified at 6 GPa has an average Si-O-Si bond angle approx.7deg lower than that found in glass processed at 4.5 GPa. At 4.5 GPa, lithium disilicate crystallizes from the glass, while at 6 GPa a new high pressure form of lithium metasilicate crystallizes. The new phase, while having lithium metasilicate crystal symmetry, contains at least 4 different Si sites. NMR results for 6 GPa sample indicate the presence of Q4 species with (Q(sup 4))Si-O-Si(Q(sup 4)) bond angles of approx.157deg. This is the first reported occurrence of Q(sup 4) species with such large bond angles in alumina free alkali silicate glass. No five- or six- coordinated Si are found.

  8. In Situ and Ex Situ Low-Field NMR Spectroscopy and MRI Endowed by SABRE Hyperpolarization**

    PubMed Central

    Barskiy, Danila A.; Kovtunov, Kirill V.; Koptyug, Igor V.; He, Ping; Groome, Kirsten A.; Best, Quinn A.; Shi, Fan; Goodson, Boyd M.; Shchepin, Roman V.; Truong, Milton L.; Coffey, Aaron M.; Waddell, Kevin W.; Chekmenev, Eduard Y.

    2015-01-01

    By using 5.75 and 47.5 mT nuclear magnetic resonance (NMR) spectroscopy, up to 105-fold sensitivity enhancement through signal amplification by reversible exchange (SABRE) was enabled, and subsecond temporal resolution was used to monitor an exchange reaction that resulted in the buildup and decay of hyperpolarized species after parahydrogen bubbling. We demonstrated the high-resolution low-field proton magnetic resonance imaging (MRI) of pyridine in a 47.5 mT magnetic field endowed by SABRE. Molecular imaging (i.e. imaging of dilute hyperpolarized substances rather than the bulk medium) was conducted in two regimes: in situ real-time MRI of the reaction mixture (in which pyridine was hyperpolarized), and ex situ MRI (in which hyperpolarization decays) of the liquid hyperpolarized product. Low-field (milli-Tesla range, e.g. 5.75 and 47.5 mT used in this study) parahydrogen-enhanced NMR and MRI, which are free from the limitations of high-field magnetic resonance (including susceptibility-induced gradients of the static magnetic field at phase interfaces), potentially enables new imaging applications as well as differentiation of hyperpolarized chemical species on demand by exploiting spin manipulations with static and alternating magnetic fields. PMID:25367202

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

    PubMed

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

    1988-02-01

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

  10. The dynamic complex of cytochrome c6 and cytochrome f studied with paramagnetic NMR spectroscopy.

    PubMed

    Díaz-Moreno, Irene; Hulsker, Rinske; Skubak, Pavol; Foerster, Johannes M; Cavazzini, Davide; Finiguerra, Michelina G; Díaz-Quintana, Antonio; Moreno-Beltrán, Blas; Rossi, Gian-Luigi; Ullmann, G Matthias; Pannu, Navraj S; De la Rosa, Miguel A; Ubbink, Marcellus

    2014-08-01

    The rapid transfer of electrons in the photosynthetic redox chain is achieved by the formation of short-lived complexes of cytochrome b6f with the electron transfer proteins plastocyanin and cytochrome c6. A balance must exist between fast intermolecular electron transfer and rapid dissociation, which requires the formation of a complex that has limited specificity. The interaction of the soluble fragment of cytochrome f and cytochrome c6 from the cyanobacterium Nostoc sp. PCC 7119 was studied using NMR spectroscopy and X-ray diffraction. The crystal structures of wild type, M58H and M58C cytochrome c6 were determined. The M58C variant is an excellent low potential mimic of the wild type protein and was used in chemical shift perturbation and paramagnetic relaxation NMR experiments to characterize the complex with cytochrome f. The interaction is highly dynamic and can be described as a pure encounter complex, with no dominant stereospecific complex. Ensemble docking calculations and Monte-Carlo simulations suggest a model in which charge-charge interactions pre-orient cytochrome c6 with its haem edge toward cytochrome f to form an ensemble of orientations with extensive contacts between the hydrophobic patches on both cytochromes, bringing the two haem groups sufficiently close to allow for rapid electron transfer. This model of complex formation allows for a gradual increase and decrease of the hydrophobic interactions during association and dissociation, thus avoiding a high transition state barrier that would slow down the dissociation process. PMID:24685428

  11. Authentication of beef versus horse meat using 60 MHz 1H NMR spectroscopy

    PubMed Central

    Jakes, W.; Gerdova, A.; Defernez, M.; Watson, A.D.; McCallum, C.; Limer, E.; Colquhoun, I.J.; Williamson, D.C.; Kemsley, E.K.

    2015-01-01

    This work reports a candidate screening protocol to distinguish beef from horse meat based upon comparison of triglyceride signatures obtained by 60 MHz 1H NMR spectroscopy. Using a simple chloroform-based extraction, we obtained classic low-field triglyceride spectra from typically a 10 min acquisition time. Peak integration was sufficient to differentiate samples of fresh beef (76 extractions) and horse (62 extractions) using Naïve Bayes classification. Principal component analysis gave a two-dimensional “authentic” beef region (p = 0.001) against which further spectra could be compared. This model was challenged using a subset of 23 freeze–thawed training samples. The outcomes indicated that storing samples by freezing does not adversely affect the analysis. Of a further collection of extractions from previously unseen samples, 90/91 beef spectra were classified as authentic, and 16/16 horse spectra as non-authentic. We conclude that 60 MHz 1H NMR represents a feasible high-throughput approach for screening raw meat. PMID:25577043

  12. (1)H NMR Spectroscopy of Fecal Extracts Enables Detection of Advanced Colorectal Neoplasia.

    PubMed

    Amiot, Aurelien; Dona, Anthony C; Wijeyesekera, Anisha; Tournigand, Christophe; Baumgaertner, Isabelle; Lebaleur, Yann; Sobhani, Iradj; Holmes, Elaine

    2015-09-01

    Colorectal cancer (CRC) is a growing cause of mortality in developing countries, warranting investigation into its etiopathogenesis and earlier diagnosis. Here, we investigated the fecal metabolic phenotype of patients with advanced colorectal neoplasia and controls using (1)H-nuclear magnetic resonance (NMR) spectroscopy and multivariate modeling. The fecal microbiota composition was assessed by quantitative real-time PCR as well as Wif-1 methylation levels in stools, serum, and urine and correlated to the metabolic profile of each patient. The predictivity of the model was 0.507 (Q(2)Y), and the explained variance was 0.755 (R(2)Y). Patients with advanced colorectal neoplasia demonstrated increased fecal concentrations of four short-chain fatty acids (valerate, acetate, propionate, and butyrate) and decreased signals relating to β-glucose, glutamine, and glutamate. The predictive accuracy of the multivariate (1)H NMR model was higher than that of the guaiac-fecal occult blood test and the Wif-1 methylation test for predicting advanced colorectal neoplasia. Correlation analysis between fecal metabolites and bacterial profiles revealed strong associations between Faecalibacterium prausnitzii and Clostridium leptum species with short-chain fatty acids concentration and inverse correlation between Faecalibacterium prausnitzii and glucose. These preliminary results suggest that fecal metabonomics may potentially have a future role in a noninvasive colorectal screening program and may contribute to our understanding of the role of these dysregulated molecules in the cross-talk between the host and its bacterial microbiota. PMID:26211820

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

    SciTech Connect

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

    2009-01-01

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

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

    SciTech Connect

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

    1988-02-01

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

  15. Single-Quantum Coherence Filter for Strongly Coupled Spin Systems for Localized 1H NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Trabesinger, Andreas H.; Mueller, D. Christoph; Boesiger, Peter

    2000-08-01

    A pulse sequence for localized in vivo1H NMR spectroscopy is presented, which selectively filters single-quantum coherence built up by strongly coupled spin systems. Uncoupled and weakly coupled spin systems do not contribute to the signal output. Analytical calculations using a product operator description of the strongly coupled AB spin system as well as in vitro tests demonstrate that the proposed filter produces a signal output for a strongly coupled AB spin system, whereas the resonances of a weakly coupled AX spin system and of uncoupled spins are widely suppressed. As a potential application, the detection of the strongly coupled AA‧BB‧ spin system of taurine at 1.5 T is discussed.

  16. Spatial structure of fibrinopeptide B in water solution with DPC micelles by NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Blokhin, Dmitriy S.; Fayzullina, Adeliya R.; Filippov, Andrei V.; Karataeva, Farida Kh.; Klochkov, Vladimir V.

    2015-12-01

    Fibrinopeptide B (GluFib) is one of the factors of thrombosis. Normal blood protein soluble, fibrinogen (fibrinopeptide A and fibrinopeptide B), is transformed into the insoluble, fibrin, which in the form of filaments adheres to the vessel wall at the site of injury, forming a grid. However, the spatial structure of this peptide has not been established till now. In this article, GluFib peptide is investigated together with dodecylphosphocholine (DPC) micelles which were used for mimicking the environment of peptide in blood vessels. The spatial structure was obtained by applying 1D and 2D 1H-1H NMR spectroscopy (TOCSY, NOESY). It was shown that the fibrinopeptide B does not have a secondary structure but we can distinguish the fragment Gly 9 - Arg 14 with a good convergence (the backbone RMSD for the Gly9 - Arg14 is 0.18 ± 0.08 Å).

  17. Low-field (1)H NMR spectroscopy for distinguishing between arabica and robusta ground roast coffees.

    PubMed

    Defernez, Marianne; Wren, Ella; Watson, Andrew D; Gunning, Yvonne; Colquhoun, Ian J; Le Gall, Gwénaëlle; Williamson, David; Kemsley, E Kate

    2017-02-01

    This work reports a new screening protocol for addressing issues of coffee authenticity using low-field (60MHz) bench-top (1)H NMR spectroscopy. Using a simple chloroform-based extraction, useful spectra were obtained from the lipophilic fraction of ground roast coffees. It was found that 16-O-methylcafestol (16-OMC, a recognized marker compound for robusta beans) gives rise to an isolated peak in the 60MHz spectrum, which can be used as an indicator of the presence of robusta beans in the sample. A total of 81 extracts from authenticated coffees and mixtures were analysed, from which the detection limit of robusta in arabica was estimated to be between 10% and 20% w/w. Using the established protocol, a surveillance exercise was conducted of 27 retail samples of ground roast coffees which were labelled as "100% arabica". None were found to contain undeclared robusta content above the estimated detection limit. PMID:27596398

  18. Coupled effect of salt and pH on proteins probed with NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Kukic, Predrag; O'Meara, Fergal; Hewage, Chandralal; Erik Nielsen, Jens

    2013-07-01

    The coupled effect of ionic strength (50-400 mM) and pH (2-8) on ionization and conformation equilibria of lysozyme was studied using NMR spectroscopy. Observed changes in pKa values of the ionizable groups were found to originate from perturbations in the geometry of hydrogen bonds rather than screening of electric fields. Moreover, at the ionic strengths used here, salt-induced local conformational changes had a dominant effect on chemical shifts measured on 1HN and 15N amide nuclei. Accurate modeling of these localized perturbations in structure-based energy calculations is a necessary prerequisite on the way to complete understanding of any salt-induced processes in proteins.

  19. Structural studies of homoisoflavonoids: NMR spectroscopy, X-ray diffraction, and theoretical calculations

    NASA Astrophysics Data System (ADS)

    Sievänen, Elina; Toušek, Jaromír; Lunerová, Kamila; Marek, Jaromír; Jankovská, Dagmar; Dvorská, Margita; Marek, Radek

    2010-08-01

    In this article we present a detailed structural investigation for five homoisoflavonoids, molecules important from the pharmacological point of view. For studying the electron distribution as well as its influence on the physicochemical properties, NMR spectroscopy, X-ray diffraction, and theoretical calculations have been used. Nuclear magnetic shieldings obtained by using DFT calculations for optimized molecular geometries are correlated with the experimentally determined chemical shifts. The theoretical data are well in agreement with the experimental values. The single crystal X-ray structures of homoisoflavonoid derivatives 1, 3, and 4 have been solved. The molecular geometries and crystal packing determined by X-ray diffraction are used for characterizing the intermolecular interactions. Electron distribution is crucial for the stability of radicals and hence the antioxidant efficiency of flavonoid structures. The hydrogen bonding governs the formation of complexes of homoisoflavonoids with biological targets.

  20. Recent applications of /sup 13/C NMR spectroscopy to biological systems

    SciTech Connect

    Matwiyoff, N.A.

    1981-01-01

    Carbon-13 nuclear magnetic resonance (NMR) spectroscopy, in conjunction with carbon-13 labelling, is a powerful new analytical technique for the study of metabolic pathways and structural components in intact organelles, cells, and tissues. The technique can provide, rapidly and non-destructively, unique information about: the architecture and dynamics of structural components; the nature of the intracellular environment; and metabolic pathways and relative fluxes of individual carbon atoms. With the aid of results recently obtained by us and those reported by a number of other laboratories, the problems and potentialities of the technique will be reviewed with emphasis on: the viscosities of intracellular fluids; the structure and dynamics of the components of membranes; and the primary and secondary metabolic pathways of carbon in microorganisms, plants, and mammalian cells in culture.

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

    SciTech Connect

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

    2006-02-15

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

  2. Solid-State Ru-99 NMR Spectroscopy: A Useful Tool for Characterizing Prototypal Diamagnetic Ruthenium Compounds Compounds

    SciTech Connect

    Ooms, Kristopher J.; Wasylishen, Roderick E.

    2004-09-08

    The feasibility of 99Ru NMR spectroscopy as a tool to characterize solid compounds is demonstrated. Results of the first solid-state 99Ru NMR investigation of diamagnetic compounds are presented for Ru(NH3)6Cl2, K4Ru(CN)6 xH2O (x) 0, 3, LaKRu(CN)6, and Ru3(CO)12. The sensitivity of the ruthenium magnetic shielding tensor to subtle changes in the local structure about the ruthenium nucleus is highlighted by comparing the 99Ru isotropic chemical shift of Ru(NH3)6Cl2 in aqueous solutions and in the solid state. The narrow isotropic 99Ru NMR peak observed for solid Ru(NH3)6Cl2 indicates that this compound is an ideal secondary reference sample for solid-state 99Ru NMR studies.

  3. Differentiation of enantiomers by 2D NMR spectroscopy at 1 T using residual dipolar couplings.

    PubMed

    Koos, Martin R M; Danieli, Ernesto; Casanova, Federico; Blümich, Bernhard; Luy, Burkhard

    2016-06-01

    Differentiating enantiomers using 2D bench-top NMR spectroscopy. Spectrometers working with permanent magnets at 1 T field strength allow the acquisition of 2D data sets. In conjunction with previously reported chiral alignment media, this setup allows the measurement of enantiomeric excess via residual dipolar couplings in stretched gelatine as a result of the reduced line width obtained by 2D J-resolved spectroscopy. PMID:25773020

  4. NMR spectroscopy with force-gradient detection on a GaAs epitaxial layer.

    PubMed

    Alexson, Dimitri A; Smith, Doran D

    2013-10-01

    We demonstrate nuclear magnetic resonance spectroscopy on 35 μm(3) of (69)Ga in a GaAs epitaxial layer in vacuum at 5K, and 5T yielding a linewidth on the order of 10 kHz. This was achieved by a force-gradient magnetic resonance detection scheme, using the interaction between the force-gradient of a Ni sphere-tipped single crystal Si cantilever and the nuclear spins to register changes in the spin state as a change in the driven cantilever's natural resonant frequency. The dichotomy between the background magnetic field (B0) homogeneity requirements imposed by NMR spectroscopy and the magnetic particle's large magnetic field gradient is resolved via sample shuttling during the NMR pulse encoding. A GaAs sample is polarized in a B0 of 5T for 3 T1. The sample is shuttled away from the magnetic particle to a region of negligible magnetic field inhomogeneity. A (π/2)x pulse rotates the polarization to the xy-plane, the magnetization is allowed to precess for 2-200 μs before a (π/2)x or (π/2)y pulse stores the remaining spin along the z-axis that represents a single point of the free induction decay (FID). The sample is shuttled back to the established tip-sample distance. An adiabatic rapid passage (ARP) sweep inverts the spins in a volume of interest, causing the cantilever's natural resonance frequency to shift an amount proportional to the spin polarization in the volume. By varying the delay between the first and second (π/2) pulses the entire FID is measured. PMID:23962899

  5. Reaction monitoring using online vs tube NMR spectroscopy: seriously different results.

    PubMed

    Foley, David A; Dunn, Anna L; Zell, Mark T

    2016-06-01

    We report findings from the qualitative evaluation of nuclear magnetic resonance (NMR) reaction monitoring techniques of how each relates to the kinetic profile of a reaction process. The study highlights key reaction rate differences observed between the various NMR reaction monitoring methods investigated: online NMR, static NMR tubes, and periodic inversion of NMR tubes. The analysis of three reaction processes reveals that rates derived from NMR analysis are highly dependent on monitoring method. These findings indicate that users must be aware of the effect of their monitoring method upon the kinetic rate data derived from NMR analysis. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26248898

  6. Aliphatic chain length by isotropic mixing (ALCHIM): determining composition of complex lipid samples by 1H NMR spectroscopy

    PubMed Central

    Yi, Ruiyang; Volden, Paul A.; Conzen, Suzanne D.

    2015-01-01

    Quantifying the amounts and types of lipids present in mixtures is important in fields as diverse as medicine, food science, and biochemistry. Nuclear magnetic resonance (NMR) spectroscopy can quantify the total amounts of saturated and unsaturated fatty acids in mixtures, but identifying the length of saturated fatty acid or the position of unsaturation by NMR is a daunting challenge. We have developed an NMR technique, aliphatic chain length by isotropic mixing, to address this problem. Using a selective total correlation spectroscopy technique to excite and transfer magnetization from a resolved resonance, we demonstrate that the time dependence of this transfer to another resolved site depends linearly on the number of aliphatic carbons separating the two sites. This technique is applied to complex natural mixtures allowing the identification and quantification of the constituent fatty acids. The method has been applied to whole adipocytes demonstrating that it will be of great use in studies of whole tissues. PMID:24831341

  7. Measuring variations of δ18O and δ2H in atmospheric water vapour using laser spectroscopy: an instrument characterisation study

    NASA Astrophysics Data System (ADS)

    Aemisegger, F.; Sturm, P.; Graf, P.; Sodemann, H.; Pfahl, S.; Knohl, A.; Wernli, H.

    2012-02-01

    Variations of stable water isotopes in water vapour have become measurable at a measurement frequency of about 1 Hz in recent years using novel laser spectroscopic techniques. This enables us to perform continuous measurements for process-based investigations of the atmospheric water cycle at the time scales relevant for synoptic meteorology. An important prerequisite for the interpretation of data from automated field measurements lasting for several weeks or months is a detailed knowledge about instrument properties and the sources of measurement uncertainty. We present here a comprehensive characterisation and comparison study of two commercial laser spectroscopic systems based on cavity ring-down spectroscopy (Picarro) and off-axis integrated cavity output spectroscopy (Los Gatos Research). The uncertainty components of the measurements were first assessed in laboratory experiments, focussing on the effects of (i) water vapour mixing ratio, (ii) measurement stability, (iii) uncertainties due to calibration and (iv) response times of the isotope measurements due to adsorption-desorption processes on the tubing and measurement cavity walls. Based on the experience from our laboratory experiments we set up a one-week field campaign for comparing measurements of the ambient isotope signals of the two laser spectroscopic systems. The optimal calibration strategy determined for both instruments was applied as well as the correction functions for water vapour mixing ratio effects. The root mean square difference between the isotope signals from the two instruments during the field deployment was 2.3‰ for δ2H, 0.5‰ for δ18O and 3.1‰ for deuterium excess. These uncertainty estimates from field measurements compare well to those found in the laboratory experiments. The present quality of measurements from laser spectroscopic instruments combined with a calibration system opens new possibilities for investigating the atmospheric water cycle and the land

  8. 1,3-Alternate calix[4]arene nitronyl nitroxide tetraradical and diradical: synthesis, X-ray crystallography, paramagnetic NMR spectroscopy, EPR spectroscopy, and magnetic studies

    SciTech Connect

    Rajca, Andrzej; Pink, Maren; Mukherjee, Sumit; Rajca, Suchada; Das, Kausik

    2008-04-02

    Calix[4]arenes constrained to 1,3-alternate conformation and functionalized at the upper rim with four and two nitronyl nitroxides have been synthesized, and characterized by X-ray crystallography, magnetic resonance (EPR and {sup 1}H NMR) spectroscopy, and magnetic studies. Such calix[4]arene tetraradicals and diradicals provide scaffolds for through-bond and through-space intramolecular exchange couplings.

  9. NMR and IR Spectroscopy for the Structural Characterization of Edible Fats and Oils: An Instrumental Analysis Laboratory

    ERIC Educational Resources Information Center

    Crowther, Molly W.

    2008-01-01

    This article describes an upper-level instrumental laboratory for undergraduates that explores the complementary nature of IR and NMR spectroscopy for analysis of several edible fats and oils that are structurally similar but differ in physical properties and health implications. Five different fats and oils are analyzed for average chain length,…

  10. NMR spectroscopy of intermetallic compounds: an experimental and theoretical approach to local atomic arrangements in binary gallides.

    PubMed

    Haarmann, Frank; Koch, Katrin; Jeglič, Peter; Pecher, Oliver; Rosner, Helge; Grin, Yuri

    2011-06-27

    The results of the investigation of MGa(2) with M = Ca, Sr, Ba and of MGa(4) with M = Na, Ca, Sr, Ba by a combined application of NMR spectroscopy and quantum mechanical calculations are comprehensively evaluated. The electric-field gradient (EFG) was identified as the most reliable measure to study intermetallic compounds, since it is accessible with high precision by quantum mechanical calculations and, for nuclear spin I>1/2, by NMR spectroscopy. The EFG values obtained by NMR spectroscopy and quantum mechanical calculations agree very well for both series of investigated compounds. A deconvolution of the calculated EFGs into their contributions reveals its sensitivity to the local environment of the atoms. The EFGs of the investigated di- and tetragallides are dominated by the population of the p(x)-, p(y)-, and p(z)-like states of the Ga atoms. A general combined approach for the investigation of disordered intermetallic compounds by application of diffraction methods, NMR spectroscopy, and quantum mechanical calculations is suggested. This scheme can also be applied to other classes of crystalline disordered inorganic materials. PMID:21590820

  11. Response to the Letter to the Editor regarding "Determination of the fatty acid profile by 1H-NMR spectroscopy."

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In expansion of previous work (G. Knothe, J.A. Kenar, Determination of the fatty acid profile by 1H-NMR spectroscopy, Eur. J. Lipid Sci. Technol. 2004, 106, 88-96), an additional approach is discussed for quantitating saturated fatty acids in the fatty acid profiles of common vegetable oils by 1H-NM...

  12. LEGO-NMR spectroscopy: a method to visualize individual subunits in large heteromeric complexes.

    PubMed

    Mund, Markus; Overbeck, Jan H; Ullmann, Janina; Sprangers, Remco

    2013-10-18

    Seeing the big picture: Asymmetric macromolecular complexes that are NMR active in only a subset of their subunits can be prepared, thus decreasing NMR spectral complexity. For the hetero heptameric LSm1-7 and LSm2-8 rings NMR spectra of the individual subunits of the complete complex are obtained, showing a conserved RNA binding site. This LEGO-NMR technique makes large asymmetric complexes accessible to detailed NMR spectroscopic studies. PMID:23946163

  13. Investigation of the C2H2-CO2 van der Waals complex in the overtone range using cw cavity ring-down spectroscopy

    NASA Astrophysics Data System (ADS)

    Lauzin, C.; Didriche, K.; Liévin, J.; Herman, M.; Perrin, A.

    2009-05-01

    A slit nozzle supersonic expansion containing acetylene [492 SCCM (SCCM denotes cubic centimeter per minute at STP)] and carbon dioxide (740 SCCM) seeded into Ar (837 SCCM) is investigated using cw-cavity ring-down spectroscopy, in the 1.5 μm range. The C2H2-CO2 van der Waals complex is observed around the ν1+ν3 acetylenic band. The rotational temperature is estimated to be close to 60 K from the comparison between observed and simulated spectra. The analysis of the main, perturbed B-type band centered near 6 549.280 cm-1, is performed. It is attributed to a dimer with the known planar, C2v geometry. The present overtone data, involving ground state levels with higher J /K states (J ≤35 and Ka≤20) than previously reported, are combined to 3 μm data [D. G. Prichard, R. N. Nandi, J. S. Muenter, and B. J. Howard, J. Chem. Phys. 89, 1245 (1988); Z. S. Huang and R. E. Miller, Chem. Phys. 132, 185 (1989)] to determine improved ground state parameters. The major perturbations affecting the upper state are accounted for through C-type Coriolis resonances involving one dark state, whose symmetry must therefore be A1. Upper state constants are obtained for the bright and dark states. The dependence upon vibrational excitation is demonstrated to arise from excitation in the acetylene unit, only, for the former, but cannot be unravelled for the latter.

  14. Consortium to develop the medical uses of NMR imaging, NMR spectroscopy, and positron emission tomography. Final technical report

    SciTech Connect

    Pohost, G.M.

    1998-06-01

    The goal of this work is to, perform clinically relevant studies using a new whole-body 4.1 T NMR imaging spectrometer. Initially we will develop and approach for the assessment of the severity of skeletal muscle involvement in ischemic peripheral vascular disease.

  15. The application of solid-state NMR spectroscopy to study candesartan cilexetil (TCV-116) membrane interactions. Comparative study with the AT1R antagonist drug olmesartan

    PubMed Central

    Ntountaniotis, Dimitrios; Kellici, Tahsin; Tzakos, Andreas; Kolokotroni, Pinelopi; Tselios, Theodore; Becker-Baldus, Johanna; Glaubitz, Clemens; Lin, Sonyan; Makriyannis, Alexandros; Mavromoustakos, Thomas

    2015-01-01

    AT1 receptor (AT1R) antagonists exert their antihypertensive effects by preventing the vasoconstrictive hormone AngII to bind to the AT1 receptor. It has been proposed that these biological effects are mediated through a two-step mechanism reaction. In the first step, they are incorporated in the core of the lipid bilayers and in the second step they reach the active site of the receptor through lateral diffusion. In this model, drug/membrane interactions are key elements for the drugs achieving inhibition at the AT1 receptor. In this work, the interactions of the prodrug candesartan cilexetil (TCV-116) with lipid bilayers are studied at molecular detail. Solid-state 13C-CP/MAS, 2D 1H-1H NOESY NMR spectroscopy and in silico calculations are used. TCV-116 and olmesartan, another drug which acts as an AT1R antagonist are compared for their dynamic effects in lipid bilayers using solid-state 2H-NMR. We find a similar localization of TCV-116 compared to other AT1 antagonists in the intermediate polar region. In addition, we can identify specific local interactions. These interactions may be associated in part with the discrete pharmacological profiles observed for different antagonists. PMID:24946142

  16. Distinguishing Polymorphs of the Semiconducting Pigment Copper Phthalocyanine by Solid-state NMR and Raman Spectroscopy

    PubMed Central

    Shaibat, Medhat A.; Casabianca, Leah B.; Siberio-Pérez, Diana Y.; Matzger, Adam J; Ishii, Yoshitaka

    2010-01-01

    Cu(II)(phthalocyanine) (CuPc) is broadly utilized as an archetypal molecular semiconductor and is the most widely used blue printing pigment. CuPc crystallizes in six different forms; the chemical and physical properties are substantially modulated by its molecular packing among these polymorphs. Despite the growing importance of this system, spectroscopic identification of different polymorphs for CuPc has posed difficulties. This study presents the first example of spectroscopic distinction of α- and β-forms of CuPc, the most widely used polymorphs, by solid-state NMR (SSNMR) and Raman spectroscopy. 13C high-resolution SSNMR spectra of α- and β-CuPc using very-fast magic angle spinning (VFMAS) at 20 kHz show that hyperfine shifts sensitively reflect polymorphs of CuPc. The experimental results were confirmed by ab initio chemical shift calculations. 13C and 1H SSNMR relaxation times of α- and β-CuPc under VFMAS also showed marked differences, presumably because of the difference in electronic spin correlation times in the two forms. Raman spectroscopy also provided another reliable method of differentiation between the two polymorphs. PMID:20225842

  17. State-of-the-Art Direct 13C and Indirect 1H-[13C] NMR Spectroscopy In Vivo

    PubMed Central

    de Graaf, Robin A.; Rothman, Douglas L.; Behar, Kevin L.

    2013-01-01

    Carbon-13 NMR spectroscopy in combination with 13C-labeled substrate infusion is a powerful technique to measure a large number of metabolic fluxes non-invasively in vivo. It has been used to quantify glycogen synthesis rates, establish quantitative relationships between energy metabolism and neurotransmission and evaluate the importance of different substrates. All measurements can, in principle, be performed through direct 13C NMR detection or via indirect 1H-[13C] NMR detection of the protons attached to 13C nuclei. The choice for detection scheme and pulse sequence depends on the magnetic field strength, whereas substrate selection depends on the metabolic pathways that are studied. 13C NMR spectroscopy remains a challenging technique that requires several non-standard hardware modifications, infusion of 13C-labeled substrates and sophisticated processing and metabolic modeling. Here the various aspects of direct 13C and indirect 1H-[13C] NMR are reviewed with the aim of providing a practical guide. PMID:21919099

  18. Multiple acquisition/multiple observation separated local field/chemical shift correlation solid-state magic angle spinning NMR spectroscopy.

    PubMed

    Das, Bibhuti B; Opella, Stanley J

    2014-08-01

    Multiple acquisition spectroscopy (MACSY) experiments that enable multiple free induction decays to be recorded during individual experiments are demonstrated. In particular, the experiments incorporate separated local field spectroscopy into homonuclear and heteronuclear correlation spectroscopy. The measured heteronuclear dipolar couplings are valuable in structure determination as well as in enhancing resolution by providing an additional frequency axis. In one example four different three-dimensional spectra are obtained in a single experiment, demonstrating that substantial potential saving in experimental time is available when multiple multi-dimensional spectra are required as part of solid-state NMR studies. PMID:25023566

  19. Multiple Acquisition/Multiple Observation Separated Local Field/Chemical Shift Correlation Solid-state Magic Angle Spinning NMR Spectroscopy

    PubMed Central

    Das, Bibhuti B.; Opella, Stanley J.

    2014-01-01

    Multiple acquisition spectroscopy (MACSY) experiments that enable multiple free induction decays to be recorded during individual experiments are demonstrated. In particular, the experiments incorporate separated local field spectroscopy into homonuclear and heteronuclear correlation spectroscopy. The measured heteronuclear dipolar couplings are valuable in structure determination as well as in enhancing resolution by providing an additional frequency axis. In one example four different three-dimensional spectra are obtained in a single experiment, demonstrating that substantial potential saving in experimental time is available when multiple multi-dimensional spectra are required as part of solid-state NMR studies. PMID:25023566

  20. A strategy for co-translational folding studies of ribosome-bound nascent chain complexes using NMR spectroscopy.

    PubMed

    Cassaignau, Anaïs M E; Launay, Hélène M M; Karyadi, Maria-Evangelia; Wang, Xiaolin; Waudby, Christopher A; Deckert, Annika; Robertson, Amy L; Christodoulou, John; Cabrita, Lisa D

    2016-08-01

    During biosynthesis on the ribosome, an elongating nascent polypeptide chain can begin to fold, in a process that is central to all living systems. Detailed structural studies of co-translational protein folding are now beginning to emerge; such studies were previously limited, at least in part, by the inherently dynamic nature of emerging nascent chains, which precluded most structural techniques. NMR spectroscopy is able to provide atomic-resolution information for ribosome-nascent chain complexes (RNCs), but it requires large quantities (≥10 mg) of homogeneous, isotopically labeled RNCs. Further challenges include limited sample working concentration and stability of the RNC sample (which contribute to weak NMR signals) and resonance broadening caused by attachment to the large (2.4-MDa) ribosomal complex. Here, we present a strategy to generate isotopically labeled RNCs in Escherichia coli that are suitable for NMR studies. Uniform translational arrest of the nascent chains is achieved using a stalling motif, and isotopically labeled RNCs are produced at high yield using high-cell-density E. coli growth conditions. Homogeneous RNCs are isolated by combining metal affinity chromatography (to isolate ribosome-bound species) with sucrose density centrifugation (to recover intact 70S monosomes). Sensitivity-optimized NMR spectroscopy is then applied to the RNCs, combined with a suite of parallel NMR and biochemical analyses to cross-validate their integrity, including RNC-optimized NMR diffusion measurements to report on ribosome attachment in situ. Comparative NMR studies of RNCs with the analogous isolated proteins permit a high-resolution description of the structure and dynamics of a nascent chain during its progressive biosynthesis on the ribosome. PMID:27466710

  1. Improvements in localized proton NMR spectroscopy of human brain. Water suppression, short echo times, and 1 ml resolution

    NASA Astrophysics Data System (ADS)

    Frahm, J.; Michaelis, T.; Merboldt, K. D.; Bruhn, H.; Gyngell, M. L.; Hänicke, W.

    Considerable technical improvements are reported for localized proton NMR spectroscopy using stimulated echoes. When compared to previous results, proton NMR spectra of the human brain are now obtainable (i) with in vivo water suppression factors of ⩾1000, (ii) with only minor T2 losses and negligible distortions due to J modulation at short echo times of 10-20 ms, and (iii) from volumes of interest as small as 1-8 ml within measuring times of 1-10 min. As a consequence, the detection of cerebral metabolites is greatly facilitated. This particularly applies to the assignment of those resonances (e.g., glutamate, taurine, inositols) that suffer from strong spin-spin coupling at the field strengths commonly in use for NMR in man. Studies of regional metabolite differences, tissue heterogeneity, and focal lesions in patients benefit from the increased spatial resolution and a concomitant reduction of partial volume effects. Localized proton NMR spectroscopy was performed on young healthy volunteers. Experiments were carried out on a 2.0 T whole-body MRI/MRS system using the standard headcoil for both imaging and spectroscopy.

  2. Metabolic Characterization of Advanced Liver Fibrosis in HCV Patients as Studied by Serum 1H-NMR Spectroscopy

    PubMed Central

    Embade, Nieves; Mariño, Zoe; Diercks, Tammo; Cano, Ainara; Lens, Sabela; Cabrera, Diana; Navasa, Miquel; Falcón-Pérez, Juan M.; Caballería, Joan; Castro, Azucena; Bosch, Jaume; Mato, José M.; Millet, Oscar

    2016-01-01

    Several etiologies result in chronic liver diseases including chronic hepatitis C virus infection (HCV). Despite its high incidence and the severe economic and medical consequences, liver disease is still commonly overlooked due to the lack of efficient non-invasive diagnostic methods. While several techniques have been tested for the detection of fibrosis, the available biomarkers still present severe limitations that preclude their use in clinical diagnostics. Liver diseases have also been the subject of metabolomic analysis. Here, we demonstrate the suitability of 1H NMR spectroscopy for characterizing the metabolism of liver fibrosis induced by HCV. Serum samples from HCV patients without fibrosis or with liver cirrhosis were analyzed by NMR spectroscopy and the results were submitted to multivariate and univariate statistical analysis. PLS-DA test was able to discriminate between advanced fibrotic and non-fibrotic patients and several metabolites were found to be up or downregulated in patients with cirrhosis. The suitability of the most significantly regulated metabolites was validated by ROC analysis. Our study reveals that choline, acetoacetate and low-density lipoproteins are the most informative biomarkers for predicting cirrhosis in HCV patients. Our results demonstrate that statistical analysis of 1H-NMR spectra is able to distinguish between fibrotic and non-fibrotic patients suffering from HCV, representing a novel diagnostic application for NMR spectroscopy. PMID:27158896

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

    PubMed

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

    2016-01-01

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

  4. Mechanism of host-guest complex formation and identification of intermediates through NMR titration and diffusion NMR spectroscopy.

    PubMed

    Lamm, Jan-Hendrik; Niermeier, Philipp; Mix, Andreas; Chmiel, Jasmin; Neumann, Beate; Stammler, Hans-Georg; Mitzel, Norbert W

    2014-07-21

    The formation of host-guest (H-G) complexes between 1,8-bis[(diethylgallanyl)ethynyl]anthracene (H) and the N-heterocycles pyridine and pyrimidine (G) was studied in solution using a combination of NMR titration and diffusion NMR experiments. For the latter, diffusion coefficients of potential host-guest structures in solution were compared with those of tailor-made reference compounds of similar shape (synthesized and characterized by NMR, HRMS, and in part XRD). Highly dynamic behavior was observed in both cases, but with different host-guest species and equilibria. With increasing concentrations of the pyridine guest, the equilibrium H2⇄H2κ(1)-G1⇄HG2 is observed (in the second step a host dimer coordinates one guest molecule); for pyrimidine the equilibrium H2→H1κ(2)-G1⇄HG2 is observed (the formation of a 1:1 aggregate is the second step). PMID:24925835

  5. Acid epimerization of 20-keto pregnane glycosides is determined by 2D-NMR spectroscopy.

    PubMed

    García, Víctor P

    2011-05-01

    Carbohydrates influence many essential biological events such as apoptosis, differentiation, tumor metastasis, cancer, neurobiology, immunology, development, host-pathogen interactions, diabetes, signal transduction, protein folding, and many other contexts. We now report on the structure determination of pregnane glycosides isolated from the aerial parts of Ceropegia fusca Bolle (Asclepiadaceae). The observation of cicatrizant, vulnerary and cytostatic activities in some humans and animals of Ceropegia fusca Bolle, a species endemic to the Canary Islands, encouraged us to begin a pharmacological study to determine their exact therapeutic properties. High resolution (1)H-NMR spectra of pregnane glycosides very often display well-resolved signals that can be used as starting points in several selective NMR experiments to study scalar (J coupling), and dipolar (NOE) interactions. ROESY is especially suited for molecules such that ωτ(c) ~ 1, where τ(c) are the motional correlation times and ω is the angular frequency. In these cases the NOE is nearly zero, while the rotating-frame Overhauser effect spectroscopy (ROESY) is always positive and increases monotonically for increasing values of τ(c). The ROESY shows dipolar interactions cross peaks even in medium-sized molecules which are helpful in unambiguous assignment of all the interglycosidic linkages. Selective excitation was carried out using a double pulsed-field gradient spin-echo sequence (DPFGSE) in which 180° Gaussian pulses are sandwiched between sine shaped z-gradients. Scalar interactions were studied by homonuclear DPFGSE-COSY and DPFGSE-TOCSY experiments, while DPFGSE-ROESY was used to monitor the spatial environment of the selectively excited proton. Dipolar interactions between nuclei close in space can be detected by the 1D GROESY experiment, which is a one-dimensional counterpart of the 2D ROESY method. The C-12 and C-17 configurations were determined by ROESY experiments. PMID:21431831

  6. Intracellular free calcium concentration measured with /sup 19/F NMR spectroscopy in intact ferret hearts

    SciTech Connect

    Marban, E.; Kitakaze, M.; Kusuoka, H.; Porterfield, J.K.; Yue, D.T.; Chacko, V.P.

    1987-08-01

    Changes in the intracellular free Ca/sup 2 +/ concentration, (Ca/sup 2 +/)/sub i/, mediate excitation-contraction coupling in the heart and contribute to cellular injury during ischemia and reperfusion. To study these processes directly, the authors measured (Ca/sup 2 +/)/sub i/ in perfused ferret (Mustela putorius furo) hearts using /sup 19/F NMR spectroscopy to detect the 5,5'-difluoro derivative of the Ca/sup 2 +/ chelator, 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). To load cells, hearts were perfused with the acetoxymethyl ester derivative of 5,5'-F/sub 2/-BAPTA. They measured /sup 19/F NMR spectra and left ventricular pressure simultaneously,at rest and during pacing at various external Ca concentrations ((Ca)/sub 0/). Although contractile force was attenuated by the Ca/sup 2 +/ buffering properties of 5,5'-F/sup 2/-BAPTA, the decrease in pressure could be overcome by raising (Ca)/sub 0/. The mean value of 104 nM for (Ca/sup 2 +/)/sub i/ at rest in the perfused heart agrees well with previous measurements in isolated ventricular muscle. During pacing at 0.6-4 Hz, time-averaged (Ca/sup 2 +/)/sub i/ increased; the effect of pacing was augmented by increasing (Ca)/sub 0/. (Ca/sup 2 +/)/sub i/ more than tripled during 10-20 min of global ischemia, and returned toward control levels upon reperfusion. This approach promises to be particularly useful in investigating the physiology of intact hearts and the pathophysiology of alterations in the coronary circulation

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

    PubMed Central

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

    2014-01-01

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

  8. Dynamic nuclear polarization-enhanced 13C NMR spectroscopy of static biological solids

    PubMed Central

    Potapov, Alexey; Yau, Wai-Ming; Tycko, Robert

    2013-01-01

    We explore the possibility of using dynamic nuclear polarization (DNP) to enhance signals in structural studies of biological solids by solid state NMR without sample spinning. Specifically, we use 2D 13C-13C exchange spectroscopy to probe the peptide backbone torsion angles (ϕ,ψ) in a series of selectively 13C-labeled 40-residue β-amyloid (Aβ1–40) samples, in both fibrillar and non-fibrillar states. Experiments are carried out at 9.39 T and 8 K, using a static double-resonance NMR probe and low-power microwave irradiation at 264 GHz. In frozen solutions of Aβ1–40 fibrils doped with DOTOPA-TEMPO, we observe DNP signal enhancement factors of 16–21. We show that the orientation- and frequency-dependent spin polarization exchange between sequential backbone carbonyl 13C labels can be simulated accurately using a simple expression for the exchange rate, after experimentally determined homogeneous 13C lineshapes are incorporated in the simulations. The experimental 2D 13C-13C exchange spectra place constraints on the ϕ and ψ angles between the two carbonyl labels. Although the data are not sufficient to determine ϕ and ψ uniquely, the data do provide non-trivial constraints that could be included in structure calculations. With DNP at low temperatures, 2D 13C-13C exchange spectra can be obtained from a 3.5 mg sample of Aβ1–40 fibrils in 4 hr or less, despite the broad 13C chemical shift anisotropy line shapes that are observed in static samples. PMID:23562665

  9. Characterization of plant-derived carbon and phosphorus in lakes by sequential fractionation and NMR spectroscopy.

    PubMed

    Liu, Shasha; Zhu, Yuanrong; Wu, Fengchang; Meng, Wei; He, Zhongqi; Giesy, John P

    2016-10-01

    Although debris from aquatic macrophytes is one of the most important endogenous sources of organic matter (OM) and nutrients in lakes, its biogeochemical cycling and contribution to internal load of nutrients in eutrophic lakes are still poorly understood. In this study, sequential fractionation by H2O, 0.1M NaOH and 1.0M HCl, combined with (13)C and (31)P NMR spectroscopy, was developed and used to characterize organic carbon (C) and phosphorus (P) in six aquatic plants collected from Tai Lake (Ch: Taihu), China. Organic matter, determined by total organic carbon (TOC), was unequally distributed in H2O (21.2%), NaOH (29.9%), HCl (3.5%) and residual (45.3%) fractions. For P in debris of aquatic plants, 53.3% was extracted by H2O, 31.9% by NaOH, and 11% by HCl, with 3.8% in residual fractions. Predominant OM components extracted by H2O and NaOH were carbohydrates, proteins and aliphatic acids. Inorganic P (Pi) was the primary form of P in H2O fractions, whereas organic P (Po) was the primary form of P in NaOH fractions. The subsequent HCl fractions extracted fewer species of C and P. Some non-extractable carbohydrates, aromatics and metal phytate compounds remained in residual fractions. Based on sequential extraction and NMR analysis, it was proposed that those forms of C (54.7% of TOC) and P (96.2% of TP) in H2O, NaOH and HCl fractions are potentially released to overlying water as labile components, while those in residues are stable and likely preserved in sediments of lakes. These results will be helpful in understanding internal loading of nutrients from debris of aquatic macrophytes and their recycling in lakes. PMID:27282495

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

    PubMed

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

    2016-01-21

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

  11. Dynamic nuclear polarization-enhanced 13C NMR spectroscopy of static biological solids

    NASA Astrophysics Data System (ADS)

    Potapov, Alexey; Yau, Wai-Ming; Tycko, Robert

    2013-06-01

    We explore the possibility of using dynamic nuclear polarization (DNP) to enhance signals in structural studies of biological solids by solid state NMR without sample spinning. Specifically, we use 2D 13C-13C exchange spectroscopy to probe the peptide backbone torsion angles (ϕ, ψ) in a series of selectively 13C-labeled 40-residue β-amyloid (Aβ1-40) samples, in both fibrillar and non-fibrillar states. Experiments are carried out at 9.39 T and 8 K, using a static double-resonance NMR probe and low-power microwave irradiation at 264 GHz. In frozen solutions of Aβ1-40 fibrils doped with DOTOPA-TEMPO, we observe DNP signal enhancement factors of 16-21. We show that the orientation- and frequency-dependent spin polarization exchange between sequential backbone carbonyl 13C labels can be simulated accurately using a simple expression for the exchange rate, after experimentally determined homogeneous 13C lineshapes are incorporated in the simulations. The experimental 2D 13C-13C exchange spectra place constraints on the ϕ and ψ angles between the two carbonyl labels. Although the data are not sufficient to determine ϕ and ψ uniquely, the data do provide non-trivial constraints that could be included in structure calculations. With DNP at low temperatures, 2D 13C-13C exchange spectra can be obtained from a 3.5 mg sample of Aβ1-40 fibrils in 4 h or less, despite the broad 13C chemical shift anisotropy line shapes that are observed in static samples.

  12. High-Speed Frequency Modulation of a 460-GHz Gyrotron for Enhancement of 700-MHz DNP-NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Idehara, T.; Khutoryan, E. M.; Tatematsu, Y.; Yamaguchi, Y.; Kuleshov, A. N.; Dumbrajs, O.; Matsuki, Y.; Fujiwara, T.

    2015-09-01

    The high-speed frequency modulation of a 460-GHz Gyrotron FU CW GVI (the official name in Osaka University is Gyrotron FU CW GOI) was achieved by modulation of acceleration voltage of beam electrons. The modulation speed f m can be increased up to 10 kHz without decreasing the modulation amplitude δ f of frequency. The amplitude δ f was increased almost linearly with the modulation amplitude of acceleration voltage Δ V a. At the Δ V a = 1 kV, frequency spectrum width df was 50 MHz in the case of f m < 10 kHz. The frequency modulation was observed as both the variation of the IF frequency in the heterodyne detection system measured by a high-speed oscilloscope and the widths of frequency spectra df measured on a frequency spectrum analyzer. Both results well agree reasonably. When f m exceeds 10 kHz, the amplitude δ f is decreased gradually with increasing f m because of the degradation of the used amplifier in response for high-speed modulation. The experiment was performed successfully for both a sinusoidal wave and triangle wave modulations. We can use the high-speed frequency modulation for increasing the enhancement factor of the dynamic nuclear polarization (DNP)-enhanced nuclear magnetic resonance (NMR) spectroscopy, which is one of effective and attractive methods for the high-frequency DNP-NMR spectroscopy, for example, at 700 MHz. Because the sensitivity of NMR is inversely proportional to the frequency, high-speed frequency modulation can compensate the decreasing the enhancement factor in the high-frequency DNP-NMR spectroscopy and keep the factor at high value. In addition, the high-speed frequency modulation is useful for frequency stabilization by a PID control of an acceleration voltage by feeding back of the fluctuation of frequency. The frequency stabilization in long time is also useful for application of a DNP-NMR spectroscopy to the analysis of complicated protein molecules.

  13. Conformational solution studies of neuropeptide gamma using CD and NMR spectroscopy.

    PubMed

    Rodziewicz-Motowidło, Sylwia; Brzozowskl, Krzysztof; Legowska, Anna; Liwo, Adam; Silbering, Jerzy; Smoluch, Marek; Rolka, Krzysztof

    2002-05-01

    Neuropeptide gamma is one of the largest members of the tachykinin family of peptides, exhibiting strong agonistic activity towards the NK-2 tachykinin receptor. This peptide was synthesized by the solid-phase method using the Fmoc chemistry. Circular-dichroism spectroscopy (CD) investigations of this peptide were performed in phosphate buffer, in the presence of sodium dodecylsulphate (SDS) micelles and trifluoroethanol (TFE) solutions and in DMSO-d6 using the 2D NMR technique in conjunction with two different theoretical approaches. The first assumes multiconformational equilibrium of the peptide studied characterized by the values of statistical weights of low-energy conformations. These calculations were performed using three different force fields ECEPP/3, AMBER4.1 and CHARMM (implemented in the X-PLOR program). The second method incorporates interproton distance and dihedral angle constraints into the starting conformation using the Simulated Annealing algorithm (X-PLOR program). The CD experiments revealed that although the peptide studied is flexible in polar solvents, a tendency to adopt a helical structure was observed in the hydrophobic environment. The NMR data (NOE effects) indicate a helical or reverse structure in the Ile7-His12 fragment of the peptide studied in DMSO-d6 solution. The results obtained cannot be interpreted in terms of a single conformation. Most of the conformations obtained with the ECEPP/3 force field possess a high content of a helical structure. None of the conformers, obtained with the AMBER4.1 and CHARMM force fields, can be considered as the dominant one. In all conformations several beta-turns were detected and in some cases gamma-turns were also found. But in fact, it is rather difficult to select the position of the secondary element(s) present in the structure of NPgamma in solution. All conformers calculated with the X-PLOR program (with using NMR derived distance and torsion angle constraints) are stabilized by several

  14. Two-dimensional NMR spectroscopy strongly enhances soil organic matter composition analysis

    NASA Astrophysics Data System (ADS)

    Soucemarianadin, Laure; Erhagen, Björn; Öquist, Mats; Nilsson, Mats; Hedenström, Mattias; Schleucher, Jürgen

    2016-04-01

    Soil organic matter (SOM) is the largest terrestrial carbon pool and strongly affects soil properties. With climate change, understanding SOM processes and turnover and how they could be affected by increasing temperatures becomes critical. This is particularly key for organic soils as they represent a huge carbon pool in very sensitive ecosystems, like boreal ecosystems and peatlands. Nevertheless, characterization of SOM molecular composition, which is essential to elucidate soil carbon processes, is not easily achieved, and further advancements in that area are greatly needed. Solid-state one-dimensional (1D) 13C nuclear magnetic resonance (NMR) spectroscopy is often used to characterize its molecular composition, but only provides data on a few major functional groups, which regroup many different molecular fragments. For instance, in the carbohydrates region, signals of all monosaccharides present in many different polymers overlap. This overlap thwarts attempts to identify molecular moieties, resulting in insufficient information to characterize SOM composition. Here we show that two-dimensional (2D) liquid-state 1H-13C NMR spectra provided much richer data on the composition of boreal plant litter and organic surface soil. The 2D spectra indeed resolved overlaps observed in 1D 13C spectra and displayed signals from hundreds of identifiable molecular groups. For example, in the aromatics region, signals from individual lignin units could be recognized. It was hence possible to follow the fate of specific structural moieties in soils. We observed differences between litter and soil samples, and were able to relate them to the decomposition of identifiable moieties. Sample preparation and data acquisition were both simple and fast. Further, using multivariate data analysis, we aimed at linking the detailed chemical fingerprints of SOM to turnover rates in a soil incubation experiment. With the multivariate models, we were able to identify specific molecular

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

    SciTech Connect

    Mao, Kanmi

    2011-01-01

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

  16. Selectively Labeling the Heterologous Protein in Escherichia coli for NMR Studies: A Strategy to Speed Up NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Almeida, F. C. L.; Amorim, G. C.; Moreau, V. H.; Sousa, V. O.; Creazola, A. T.; Américo, T. A.; Pais, A. P. N.; Leite, A.; Netto, L. E. S.; Giordano, R. J.; Valente, A. P.

    2001-01-01

    Nuclear magnetic resonance is an important tool for high-resolution structural studies of proteins. It demands high protein concentration and high purity; however, the expression of proteins at high levels often leads to protein aggregation and the protein purification step can correspond to a high percentage of the overall time in the structural determination process. In the present article we show that the step of sample optimization can be simplified by selective labeling the heterologous protein expressed in Escherichia coli by the use of rifampicin. Yeast thioredoxin and a coix transcription factor Opaque 2 leucine zipper (LZ) were used to show the effectiveness of the protocol. The 1H/15N heteronuclear correlation two-dimensional NMR spectrum (HMQC) of the selective 15N-labeled thioredoxin without any purification is remarkably similar to the spectrum of the purified protein. The method has high yields and a good 1H/15N HMQC spectrum can be obtained with 50 ml of M9 growth medium. Opaque 2 LZ, a difficult protein due to the lower expression level and high hydrophobicity, was also probed. The 15N-edited spectrum of Opaque 2 LZ showed only the resonances of the protein of heterologous expression (Opaque 2 LZ) while the 1H spectrum shows several other resonances from other proteins of the cell lysate. The demand for a fast methodology for structural determination is increasing with the advent of genome/proteome projects. Selective labeling the heterologous protein can speed up NMR structural studies as well as NMR-based drug screening. This methodology is especially effective for difficult proteins such as hydrophobic transcription factors, membrane proteins, and others.

  17. Complex mixture analysis of organic compounds in green coffee bean extract by two-dimensional NMR spectroscopy.

    PubMed

    Wei, Feifei; Furihata, Kazuo; Hu, Fangyu; Miyakawa, Takuya; Tanokura, Masaru

    2010-11-01

    A complex mixture analysis by one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy was carried out for the first time for the identification and quantification of organic compounds in green coffee bean extract (GCBE). A combination of (1)H-(1)H DQF-COSY, (1)H-(13)C HSQC, and (1)H-(13)C CT-HMBC two-dimensional sequences was used, and 16 compounds were identified. In particular, three isomers of caffeoylquinic acid were identified in the complex mixture without any separation. In addition, GCBE components were quantified by the integration of carbon signals by use of a relaxation reagent and an inverse-gated decoupling method without a nuclear Overhauser effect. This NMR methodology provides detailed information about the kinds and amounts of GCBE components, and in our study, the chemical makeup of GCBE was clarified by the NMR results. PMID:20818806

  18. Direct detection of ligand binding to Sepharose-immobilised protein using saturation transfer double difference (STDD) NMR spectroscopy

    SciTech Connect

    Haselhorst, Thomas; Muenster-Kuehnel, Anja K.; Oschlies, Melanie; Tiralongo, Joe; Gerardy-Schahn, Rita; Itzstein, Mark von . E-mail: m.vonitzstein@griffith.edu.au

    2007-08-10

    We report an easy and direct application of 'Saturation Transfer Double Difference' (STDD) NMR spectroscopy to identify ligands that bind to a Sepharose-immobilised target protein. The model protein, cytidine 5'-monophosphate sialic acid (CMP-Sia) synthetase, was expressed as a Strep-Tag II fusion protein and immobilised on Strep-Tactin Sepharose. STD NMR experiments of the protein-enriched Sepharose matrix in the presence of a binding ligand (cytidine 5'-triphosphate, CTP) and a non-binding ligand ({alpha}/{beta}-glucose) clearly show that CTP binds to the immobilised enzyme, whereas glucose has no affinity. This approach has three major advantages: (a) only low quantities of protein are required, (b) no specialised NMR technology or the application of additional data analysis by non-routine methods is required, and (c) easy multiple use of the immobilised protein is available.

  19. Characterization of Al30 in commercial poly-aluminum chlorohydrate by solid-state (27)Al NMR spectroscopy.

    PubMed

    Phillips, Brian L; Vaughn, John S; Smart, Scott; Pan, Long

    2016-08-15

    Investigation of commercially produced hydrolysis salts of aluminum by solid-state (27)Al NMR spectroscopy and size-exclusion chromatography (SEC) reveals well-defined and distinct Al environments that can be related to physicochemical properties. (27)Al MAS and MQ-MAS NMR spectroscopic data show that the local structure of the solids is dominated by moieties that closely resemble the Al30 polyoxocation (Al30O8(OH)56(H2O)26(18+)), accounting for 72-85% of the total Al. These Al30-like clusters elute as several size fractions by SEC. Comparison of the SEC and NMR results indicates that the Al30-like clusters includes intact isolated clusters, moieties of larger polymers or aggregates, and possibly fragments resembling δ-Al13 Keggin clusters. The coagulation efficacy of the solids appears to correlate best with the abundance of intact Al30-like clusters and of smaller species available to promote condensation reactions. PMID:27232539

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

    NASA Astrophysics Data System (ADS)

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

    2003-11-01

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

  1. Investigation of Local Structures in Layered Niobates by Solid-state NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Ting

    Research on ion-exchangeable layered niobates has attracted great attention due to their unique structures and corresponding variations in properties and applications, such as ion conductors, solid acids, and water splitting catalysts. Families of layered niobates include double-layered or triple-layered Dion-Jacobson type perovskites (ALaNb2O7, A = Cs, Rb, K, H; AM2Nb3O10, A = Rb, K, H; M = Sr, Ca), layered niobates with both edge and corner sharing of NbO6 octahedra (KNb3O8, HNb3O6, Nb 6O17 and H4Nb6O17) and many others. Lately, more developments in the layered niobates through a variety of topochemical manipulations have been achieved. The topochemical reactions include ion exchange, exfoliation, substitution, and etc. As a result, many new materials have been successfully prepared, for example, solid solutions (ALa2NbTi2O10, ACaLaNb2TiO 10 and ACa2Nb3-xTaxO10, etc.), nanosheets (HNb3O8, H4Nb6O17, HLaNb2O7, HCa2Nb3O10, etc., to intercalate with organic molecules such as tetrabutylammonium hydroxide or n-butylamines), and nanoscrolls (from H2K2Nb 6O17). While these structural modifications often induce improvements in properties, the fundamental mechanisms of improvements in properties upon the modifications, especially local structural arrangements are poorly understood, which is often limited by structural characterizations. Particularly, the characterizations of the exfoliated nanosheets can be difficult by conventional X-ray diffraction (XRD) method due to disordered structures. Alternatively, solid-state nuclear magnetic resonance (NMR) spectroscopy is a useful tool to study local structures in solids. The structural information can be extracted by examining intrinsic interactions, such as quadrupolar, chemical shielding, and dipolar interactions, which are all associated with local environments surrounding a specific nucleus, 1H or 93Nb in layered niobates. The ultimate goal of this dissertation is to understand the relationships between local structures of

  2. Polymer swelling, drug mobilization and drug recrystallization in hydrating solid dispersion tablets studied by multinuclear NMR microimaging and spectroscopy.

    PubMed

    Dahlberg, Carina; Dvinskikh, Sergey V; Schuleit, Michael; Furó, István

    2011-08-01

    Despite the advantages offered by solid dispersions, the marketed products based on this technology are few. The most frequent concern is the stability of the amorphous drug. The state of the drug in solid dispersions is, in general, poorly characterized as the number of characterization techniques available to monitor nanometer-sized drug particles embedded in a matrix are limited. Here we present a combination of localized NMR spectroscopic and NMR imaging techniques which allow in situ monitoring of the state of the drug during tablet disintegration and dissolution. (19)F NMR relaxation is shown to be sensitive to both the crystalline/amorphous state and the size of the model nanoparticles made of the drug substance flutamide. The time course of drug mobilization and recrystallization is detected with spatial resolution within swelling solid dispersion tablets. Comparing results from spatially resolved (19)F, (2)H and (1)H NMR experiments, recrystallization is related to its enabling factors such as local hydration level and local mobility of the polymer matrix. The initially amorphous drug may recrystallize either by nanoparticle coalescence or by ripening of crystalline grains. PMID:21696185

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

    NASA Astrophysics Data System (ADS)

    Agarwal, Vipin; Reif, Bernd

    2008-09-01

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

  4. Chromophore/DNA interactions: femto- to nanosecond spectroscopy, NMR structure, and electron transfer theory.

    PubMed

    von Feilitzsch, Till; Tuma, Jennifer; Neubauer, Heike; Verdier, Laurent; Haselsberger, Reinhard; Feick, Reiner; Gurzadyan, Gagik; Voityuk, Alexander A; Griesinger, Christian; Michel-Beyerle, Maria E

    2008-01-24

    The mechanism of photoinduced hole injection into DNA has been studied using an integrated approach that combines NMR structural analysis, time-resolved spectroscopy, and quantum-chemical calculations. A covalently linked acridinium derivative, the protonated 9-amino-6-chloro-2-methoxyacridine (X+), is replacing a thymine and separated from either guanine (G) or the easier to oxidize 7-deazaguanine (Z) by one adenine.thymine (A.T) base pair. The key features of this donor/acceptor system are the following: (i) In more than 95% of the duplexes, X+ is located in a central, coplanar position between the neighboring A.T base pairs with its long axis in parallel showing minimal twist and tilt angles (<15 degrees). The complementary adenine base is turned out into the extrahelical space. In a minority of less than 5%, X+ is found to be still attached to the duplex. X+ is most probably associated with one of the phosphates, since it is neither intercalated between more remote base pairs nor bound to sugars or grooves. This minority characterized by an excited state lifetime >10 ns gives rise to a small background signal in time-resolved measurements and contributes predominantly to steady-state fluorescence spectra. (ii) Although the intercalation mode of X+ is well defined, the NMR structure reveals that there are two conformations of X+ with respect to the arrangement of its methoxy substituent. In one conformation, the methoxy group is in the plane of the chromophore, while, in the other extraplanar conformation, the methoxy group forms an angle of 70 degrees with the acridinium ring. The fluorescence decay of 5'-ZAX and 5'-GAX tracts can be fitted to a biexponential function with similar amplitudes, reflecting the oxidation dynamics of G and Z, with the slower rate being determined by larger thermal activation energy. The attribution of biexponential electron transfer (ET) dynamics to the bimodal orientation of the methoxy group at the acridinium is supported by

  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

    SciTech Connect

    Grube, Elisabeth; Nielsen, Ulla Gro

    2015-05-01

    The stoichiometry of a series of synthetic alunite [nominally KAl3(SO4)2(OH)6] samples prepared by hydrothermal methods as a function of reaction time (1–31 days) has been investigated by powder X-ray diffraction, Fourier transform infrared spectroscopy as well as solid-state 1H and 27Al magic 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 of potassium defects present, from 17.261(1) to 17.324(5) Å. Solid-state 27Al MAS NMR revealed a decrease in the defect concentration as a function of time and showed the presence of 7–10 % impurities in the samples.

  6. NMR spectroscopy reveals the presence and association of lipids and keratin in adhesive gecko setae.

    PubMed

    Jain, Dharamdeep; Stark, Alyssa Y; Niewiarowski, Peter H; Miyoshi, Toshikazu; Dhinojwala, Ali

    2015-01-01

    Lipid and protein aggregates are one of the fundamental materials of biological systems. Examples include cell membranes, insect cuticle, vertebrate epidermis, feathers, hair and adhesive structures known as 'setae' on gecko toes. Until recently gecko setae were assumed to be composed entirely of keratin, but analysis of footprints left behind by geckos walking on surfaces revealed that setae include various kinds of lipids. However, the arrangement and molecular-level behavior of lipids and keratin in the setae is still not known. In the present study we demonstrate, for the first time, the use of Nuclear Magnetic Resonance (NMR) spectroscopy techniques to confirm the presence of lipids and investigate their association with keratin in 'pristine' sheds, or natural molts of the adhesive toe pad and non-adhesive regions of the skin. Analysis was also carried on the sheds after they were 'delipidized' to remove surface lipids. Our results show a distribution of similar lipids in both the skin and toe shed but with different dynamics at a molecular level. The present study can help us understand the gecko system both biologically and for design of synthetic adhesives, but the findings may be relevant to the characteristics of lipid-protein interactions in other biological systems. PMID:25902194

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

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    Biomacromolecules that are challenging for the usual structural techniques can be studied with atomic resolution by solid-state NMR spectroscopy. However, the paucity of distance restraints >5 Å, traditionally derived from measurements of magnetic dipole-dipole couplings between protein nuclei, is a major bottleneck that hampers such structure elucidation efforts. Here, we describe a general approach that enables the rapid determination of global protein fold in the solid phase via measurements of nuclear paramagnetic relaxation enhancements (PREs) in several analogues of the protein of interest containing covalently attached paramagnetic tags, without the use of conventional internuclear distance restraints. The method is demonstrated using six cysteine-EDTA-Cu2+ mutants of the 56-residue B1 immunoglobulin-binding domain of protein G, for which ~230 longitudinal backbone 15N PREs corresponding to distances of ~10-20 Å were obtained. The mean protein fold determined in this manner agrees with the X-ray structure with a backbone atom root-mean-square deviation of 1.8 Å.

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

    PubMed Central

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

    1991-01-01

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

  10. Unraveling complex small-molecule binding mechanisms by using simple NMR spectroscopy.

    PubMed

    Quinternet, Marc; Starck, Jean-Philippe; Delsuc, Marc-André; Kieffer, Bruno

    2012-03-26

    Heteronuclear NMR spectroscopy provides a unique way to obtain site-specific information about protein-ligand interactions. Usually, such studies rely on the availability of isotopically labeled proteins, thereby allowing both editing of the spectra and ligand signals to be filtered out. Herein, we report that the use of the methyl SOFAST correlation experiment enables the determination of site-specific equilibrium binding constants by using unlabeled proteins. By using the binding of L- and D-tryptophan to serum albumin as a test case, we determined very accurate dissociation constants for both the high- and low-affinity sites present at the protein surface. The values of site-specific dissociation constants were closer to those obtained by isothermal titration calorimetry than those obtained from ligand-observed methods, such as saturation transfer difference. The possibility of measuring ligand binding to serum albumin at physiological concentrations with unlabeled proteins may open up new perspectives in the field of drug discovery. PMID:22336999

  11. 1H NMR Spectroscopy and MVA Analysis of Diplodus sargus Eating the Exotic Pest Caulerpa cylindracea

    PubMed Central

    De Pascali, Sandra A.; Del Coco, Laura; Felline, Serena; Mollo, Ernesto; Terlizzi, Antonio; Fanizzi, Francesco P.

    2015-01-01

    The green alga Caulerpa cylindracea is a non-autochthonous and invasive species that is severely affecting the native communities in the Mediterranean Sea. Recent researches show that the native edible fish Diplodus sargus actively feeds on this alga and cellular and physiological alterations have been related to the novel alimentary habits. The complex effects of such a trophic exposure to the invasive pest are still poorly understood. Here we report on the metabolic profiles of plasma from D. sargus individuals exposed to C. cylindracea along the southern Italian coast, using 1H NMR spectroscopy and multivariate analysis (Principal Component Analysis, PCA, Orthogonal Partial Least Square, PLS, and Orthogonal Partial Least Square Discriminant Analysis, OPLS-DA). Fish were sampled in two seasonal periods from three different locations, each characterized by a different degree of algal abundance. The levels of the algal bisindole alkaloid caulerpin, which is accumulated in the fish tissues, was used as an indicator of the trophic exposure to the seaweed and related to the plasma metabolic profiles. The profiles appeared clearly influenced by the sampling period beside the content of caulerpin, while the analyses also supported a moderate alteration of lipid and choline metabolism related to the Caulerpa-based diet. PMID:26058009

  12. Probing the structural details of xylan degradation by real-time NMR spectroscopy.

    PubMed

    Petersen, Bent Ole; Lok, Finn; Meier, Sebastian

    2014-11-01

    The biodegradation of abundantly available cell wall polysaccharides has recently received much attention, not least because cell wall polysaccharides are substrates for the human gut microbiota and for environmentally sustainable processes of biomass conversion to value-added compounds. A major fraction of cereal cell wall polysaccharides consists of arabinoxylans. Arabinoxylan and its degradation products are therefore present in a variety of agro-industrial residues and products. Here, we undertook to track the structural details of wheat arabinoxylan degradation with high resolution NMR spectroscopy. More than 15 carbohydrate residues were distinguished in the substrate and more than 20 residues in partially degraded samples without any sample cleanup. The resolution of a plethora of structural motifs in situ permits the readout of persisting structures in degradation processes and in products. Reaction progress was visualized for the biodegradation of arabinoxylan by different crude microbial enzyme preparations. The direct observation of structural details in complex mixtures containing arabinoxylan fragments is significant, as such structural details reportedly modulate the health-promoting functions of arabinoxylan fragments. PMID:25129786

  13. Application of NMR Spectroscopy in the Assessment of Radiation Dose in Human Primary Cells.

    PubMed

    Kang, Chang-Mo; Seong Hyeon, Jin; Ra Kim, So; Kyeong Lee, Eun; Jin Yun, Hyun; Young Kim, Sun; Kee Chae, Young

    2015-11-01

    We employed the primary cell model system as a first step toward establishing a method to assess the influence of ionizing radiation by using a combination of common and abundant metabolites. We applied X-ray irradiation amounts of 0, 1, and 5 Gy to the cells that were harvested 24, 48, or 72 h later, and profiled metabolites by 2D-NMR spectroscopy to sort out candidate molecules that could be used to distinguish the samples under different irradiation conditions. We traced metabolites stemming from the input ¹³C-glucose, identified twelve of them from the cell extracts, and applied statistical analysis to find out that all the metabolites, including glycine, alanine, and gluatamic acid, increased upon irradiation. The combinatorial use of the selected metabolites showed promising results where the product of signal intensities of alanine and lactate could differentiate samples according to the dose of X-ray irradiation. We hope that this work can form a base for treating radiation-poisoned patients in the future. PMID:26567947

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

    PubMed

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

    2012-05-01

    Biomacromolecules that are challenging for the usual structural techniques can be studied with atomic resolution by solid-state NMR spectroscopy. However, the paucity of distance restraints >5 Å, traditionally derived from measurements of magnetic dipole-dipole couplings between protein nuclei, is a major bottleneck that hampers such structure elucidation efforts. Here, we describe a general approach that enables the rapid determination of global protein fold in the solid phase via measurements of nuclear paramagnetic relaxation enhancements (PREs) in several analogues of the protein of interest containing covalently attached paramagnetic tags, without the use of conventional internuclear distance restraints. The method is demonstrated using six cysteine-EDTA-Cu(2+) mutants of the 56-residue B1 immunoglobulin-binding domain of protein G, for which ~230 longitudinal backbone (15)N PREs corresponding to distances of ~10-20 Å were obtained. The mean protein fold determined in this manner agrees with the X-ray structure with a backbone atom root-mean-square deviation of 1.8 Å. PMID:22522262

  15. On the role of NMR spectroscopy for characterization of antimicrobial peptides

    PubMed Central

    Porcelli, Fernando; Ramamoorthy, Ayyalusamy; Barany, George; Veglia, Gianluigi

    2016-01-01

    Summary Antimicrobial peptides (AMPs) provide a primordial source of immunity, conferring upon eukaryotic cells resistance against bacteria, protozoa, and viruses. Despite a few examples of anionic peptides, AMPs are usually relatively short positively charged polypeptides, consisting of a dozen to about a hundred amino acids, and exhibiting amphipathic character. Despite significant differences in their primary and secondary structures, all AMPs discovered to date share the ability to interact with cellular membranes, thereby affecting bilayer stability, disrupting membrane organization, and/or forming well-defined pores. AMPs selectively target infectious agents without being susceptible to any of the common pathways by which these acquire resistance, thereby making AMPs prime candidates to provide therapeutic alternatives to conventional drugs. However, the mechanisms of AMP actions are still a matter of intense debate. The structure-function paradigm suggests that a better understanding of how AMPs elicit their biological functions could result from atomic resolution studies of peptide-lipid interactions. In contrast, more strict thermodynamic views preclude any roles for three-dimensional structures. Indeed, the design of selective AMPs based soley on structural parameters has been challenging. In this chapter, we will focus on selected AMPs for which studies on the corresponding AMP-lipid interactions have helped reach an understanding of how AMP effects are mediated. We will emphasize the roles of both liquid- and solid-state NMR spectroscopy for elucidating the mechanisms of action of AMPs. PMID:23975777

  16. 1H NMR Spectroscopy and MVA Analysis of Diplodus sargus Eating the Exotic Pest Caulerpa cylindracea.

    PubMed

    De Pascali, Sandra A; Del Coco, Laura; Felline, Serena; Mollo, Ernesto; Terlizzi, Antonio; Fanizzi, Francesco P

    2015-06-01

    The green alga Caulerpa cylindracea is a non-autochthonous and invasive species that is severely affecting the native communities in the Mediterranean Sea. Recent researches show that the native edible fish Diplodus sargus actively feeds on this alga and cellular and physiological alterations have been related to the novel alimentary habits. The complex effects of such a trophic exposure to the invasive pest are still poorly understood. Here we report on the metabolic profiles of plasma from D. sargus individuals exposed to C. cylindracea along the southern Italian coast, using 1H NMR spectroscopy and multivariate analysis (Principal Component Analysis, PCA, Orthogonal Partial Least Square, PLS, and Orthogonal Partial Least Square Discriminant Analysis, OPLS-DA). Fish were sampled in two seasonal periods from three different locations, each characterized by a different degree of algal abundance. The levels of the algal bisindole alkaloid caulerpin, which is accumulated in the fish tissues, was used as an indicator of the trophic exposure to the seaweed and related to the plasma metabolic profiles. The profiles appeared clearly influenced by the sampling period beside the content of caulerpin, while the analyses also supported a moderate alteration of lipid and choline metabolism related to the Caulerpa-based diet. PMID:26058009

  17. Reconsidering the activation entropy for anomerization of glucose and mannose in water studied by NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Kosaka, Ami; Aida, Misako; Katsumoto, Yukiteru

    2015-08-01

    The anomerization of monosaccharides is a very important process to understand how their stereoisomers are stabilized in aqueous solutions. For glucose and mannose, it has been known that α- and β-anomers of hexopyranose exist as the major components. In order to examine the anomerization pathway for glucose and mannose in aqueous solutions, it is indispensable to determine the thermodynamic parameters such as the activation energy, the activation Gibbs free energy (ΔG‡), enthalpy (ΔH‡), and entropy (ΔS‡). Although several research groups reported these quantities in aqueous solution, they have still been controversial especially for ΔS‡. In this paper, we employ 1H NMR spectroscopy for monitoring the population of both α- and β-anomers of glucose and mannose. The contribution of ΔS‡ to ΔG‡ for glucose in water is estimated to be ca. 30%, while that for mannose is 8.0%. The large difference in ΔS‡ suggests that the anomerization pathway is not the same for glucose and mannose.

  18. Thermodynamic Study on the Protonation Reactions of Glyphosate in Aqueous Solution: Potentiometry, Calorimetry and NMR spectroscopy.

    PubMed

    Liu, Bijun; Dong, Lan; Yu, Qianhong; Li, Xingliang; Wu, Fengchang; Tan, Zhaoyi; Luo, Shunzhong

    2016-03-10

    Glyphosate [N-(phosphonomethyl)glycine] has been described as the ideal herbicide because of its unique properties. There is some conflicting information concerning the structures and conformations involved in the protonation process of glyphosate. Protonation may influence the chemical and physical properties of glyphosate, modifying its structure and the chemical processes in which it is involved. To better understand the species in solution associated with changes in pH, thermodynamic study (potentiometry, calorimetry and NMR spectroscopy) about the protonation pathway of glyphosate is performed. Experimental results confirmed that the order of successive protonation sites of totally deprotonated glyphosate is phosphonate oxygen, amino nitrogen, and finally carboxylate oxygen. This trend is in agreement with the most recent theoretical work in the literature on the subject ( J. Phys. Chem. A 2015, , 119 , 5241 - 5249 ). The result is important because it confirms that the protonated site of glyphosate in pH range 7-8, is not on the amino but on the phosphonate group instead. This corrected information can improve the understanding of the glyphosate chemical and biochemical action. PMID:26862689

  19. Structure of the propeptide of prothrombin containing the. gamma. -carboxylation recognition site determined by two-dimensional NMR spectroscopy

    SciTech Connect

    Sanford, D.G.; Sudmeier, J.L.; Bachovchin, W.W.; Kanagy, C.; Furie, B.C.; Furie, B. )

    1991-10-15

    The propeptides of the vitamin K dependent blood clotting and regulatory proteins contain a {gamma}-carboxylation recognition site that directs precursor forms of these proteins for posttranslational {gamma}-carboxylation. Peptides corresponding to the propeptide of prothrombin were synthesized and examined by circular dichroism (CD) and nuclear magnetic resonance spectroscopy (NMR). CD spectra indicate that these peptides have little or no secondary structure in aqueous solutions but that the addition of trifluoroethanol induces or stabilizes a structure containing {alpha}-helical character. The maximum helical content occurs at 35-40% trifluoroethanol. This trifluoroethanol-stabilized structure was solved by two-dimensional NMR spectroscopy. The NMR results demonstrate that residues {minus}13 to {minus}3 form an amphipathic {alpha}-helix. NMR spectra indicate that a similar structure is present at 5C, in the absence of trifluoroethanol. Of the residues previously implicated in defining the {gamma}-carboxylation recognition site, four residues ({minus}18, {minus}17, {minus}16, and {minus}15) are adjacent to the helical region and one residue ({minus}10) is located within the helix. The potential role of the amphipathic {alpha}-helix in the {gamma}-carboxylation recognition site is discussed.

  20. Characterization of the biochemical effects of 1-nitronaphthalene in rats using global metabolic profiling by NMR spectroscopy and pattern recognition.

    PubMed

    Azmi, J; Connelly, J; Holmes, E; Nicholson, J K; Shore, R F; Griffin, J L

    2005-01-01

    Metabolic fingerprints, in the form of patterns of high-concentration endogenous metabolites, of 1-nitronaphthalene (NN)-induced lung toxicity have been elucidated in bronchoalveolar lavage fluid (BALF), urine, blood plasma, and intact lung and liver tissue using NMR spectroscopy-based metabolic profiling. A single dose of NN (75 mg kg(-1)) was administered orally to Sprague-Dawley rats. BALF and lung tissue were obtained 24 h after dosing from these animals and matched control rats post-mortem. High-resolution (1)H-NMR spectroscopy of BALF samples indicated that NN caused increases in concentrations of choline, amino acids (leucine, isoleucine and alanine) and lactate together with decreased concentrations of succinate, citrate, creatine, creatinine and glucose. In addition, the intact lung weights were higher in the NN-treated group (p<0.01), consistent with pulmonary oedema. The NMR-detected perturbations indicated that NN induces a perturbation in energy metabolism in both lung and liver tissue, as well as surfactant production and osmolyte levels in the lungs. As well as reporting the first NMR spectroscopic combined examination of BALF and intact lung, this study indicates that such holistic approaches to investigating mechanisms of lung toxicity may be of value in evaluating disease progression or the effects of therapeutic intervention in pulmonary conditions such as surfactant disorders or asthma. PMID:16308265

  1. Accurate quantitative 13C NMR spectroscopy: repeatability over time of site-specific 13C isotope ratio determination.

    PubMed

    Caytan, Elsa; Botosoa, Eliot P; Silvestre, Virginie; Robins, Richard J; Akoka, Serge; Remaud, Gérald S

    2007-11-01

    The stability over time (repeatability) for the determination of site-specific 13C/12C ratios at natural abundance by quantitative 13C NMR spectroscopy has been tested on three probes: enriched bilabeled [1,2-13C2]ethanol; ethanol at natural abundance; and vanillin at natural abundance. It is shown in all three cases that the standard deviation for a series of measurements taken every 2-3 months over periods between 9 and 13 months is equal to or smaller than the standard deviation calculated from 5-10 replicate measurements made on a single sample. The precision which can be achieved using the present analytical 13C NMR protocol is higher than the prerequisite value of 1-2 per thousand for the determination of site-specific 13C/12C ratios at natural abundance (13C-SNIF-NMR). Hence, this technique permits the discrimination of very small variations in 13C/12C ratios between carbon positions, as found in biogenic natural products. This observed stability over time in 13C NMR spectroscopy indicates that further improvements in precision will depend primarily on improved signal-to-noise ratio. PMID:17900175

  2. Structure of the propeptide of prothrombin containing the gamma-carboxylation recognition site determined by two-dimensional NMR spectroscopy.

    PubMed

    Sanford, D G; Kanagy, C; Sudmeier, J L; Furie, B C; Furie, B; Bachovchin, W W

    1991-10-15

    The propeptides of the vitamin K dependent blood clotting and regulatory proteins contain a gamma-carboxylation recognition site that directs precursor forms of these proteins for posttranslational gamma-carboxylation. Peptides corresponding to the propeptide of prothrombin were synthesized and examined by circular dichroism (CD) and nuclear magnetic resonance spectroscopy (NMR). CD spectra indicate that these peptides have little or no secondary structure in aqueous solutions but that the addition of trifluoroethanol induces or stabilizes a structure containing alpha-helical character. The maximum helical content occurs at 35-40% trifluoroethanol. This trifluoroethanol-stabilized structure was solved by two-dimensional NMR spectroscopy. The NMR results demonstrate that residues -13 to -3 form an amphipathic alpha-helix. NMR spectra indicate that a similar structure is present at 5 degrees C, in the absence of trifluoroethanol. Of the residues previously implicated in defining the gamma-carboxylation recognition site, four residues (-18, -17, -16, and -15) are adjacent to the helical region and one residue (-10) is located within the helix. The potential role of the amphipathic alpha-helix in the gamma-carboxylation recognition site is discussed. PMID:1911775

  3. Characterization of a multicomponent lithium lithiate from a combined x-ray diffraction, NMR spectroscopy, and computational approach.

    PubMed

    Pöppler, Ann-Christin; Granitzka, Markus; Herbst-Irmer, Regine; Chen, Yu-Sheng; Iversen, Bo B; John, Michael; Mata, Ricardo A; Stalke, Dietmar

    2014-11-24

    An unusual lithium lithiate [Li(diglyme)2][(diglyme)Li2(C4H3S)3], made up from three carbanions, two lithium cations, and a single donor base molecule in the anion and a single lithium cation, coordinated by two donor base molecules, is investigated in a combined study including X-ray diffraction, NMR spectroscopy and computational approaches in solution and the solid state. While the multicomponent lithiate is the only species present in the solid state, solution NMR spectroscopy and computational methods were employed to identify a second species in solution. The dimer [(diglyme)Li(C4H3S)]2 coexists with the lithiate in solution in a 1:1 ratio, the more the higher the polarity of the solvent is. Only the combination of this multitude of methods provides a firm picture of the whole. PMID:25284593

  4. Rapid approach to identify the presence of Arabica and Robusta species in coffee using 1H NMR spectroscopy.

    PubMed

    Monakhova, Yulia B; Ruge, Winfried; Kuballa, Thomas; Ilse, Maren; Winkelmann, Ole; Diehl, Bernd; Thomas, Freddy; Lachenmeier, Dirk W

    2015-09-01

    NMR spectroscopy was used to verify the presence of Arabica and Robusta species in coffee. Lipophilic extracts of authentic roasted and green coffees showed the presence of established markers for Robusta (16-O-methylcafestol (16-OMC)) and for Arabica (kahweol). The integration of the 16-OMC signal (δ 3.165 ppm) was used to estimate the amount of Robusta in coffee blends with an approximate limit of detection of 1-3%. The method was successfully applied for the analysis of 77 commercial coffee samples (coffee pods, coffee capsules, and coffee beans). Furthermore, principal component analysis (PCA) was applied to the spectra of lipophilic and aqueous extracts of 20 monovarietal authentic samples. Clusters of the two species were observed. NMR spectroscopy can be used as a rapid prescreening tool to discriminate Arabica and Robusta coffee species before the confirmation applying the official method. PMID:25842325

  5. Fast characterization of functionalized silica materials by silicon-29 surface-enhanced NMR spectroscopy using dynamic nuclear polarization.

    PubMed

    Lelli, Moreno; Gajan, David; Lesage, Anne; Caporini, Marc A; Vitzthum, Veronika; Miéville, Pascal; Héroguel, Florent; Rascón, Fernando; Roussey, Arthur; Thieuleux, Chloé; Boualleg, Malika; Veyre, Laurent; Bodenhausen, Geoffrey; Copéret, Christophe; Emsley, Lyndon

    2011-02-23

    We demonstrate fast characterization of the distribution of surface bonding modes and interactions in a series of functionalized materials via surface-enhanced nuclear magnetic resonance spectroscopy using dynamic nuclear polarization (DNP). Surface-enhanced silicon-29 DNP NMR spectra were obtained by using incipient wetness impregnation of the sample with a solution containing a polarizing radical (TOTAPOL). We identify and compare the bonding topology of functional groups in materials obtained via a sol-gel process and in materials prepared by post-grafting reactions. Furthermore, the remarkable gain in time provided by surface-enhanced silicon-29 DNP NMR spectroscopy (typically on the order of a factor 400) allows the facile acquisition of two-dimensional correlation spectra. PMID:21280606

  6. A detailed mechanistic investigation into the reaction of 3-methylpentanoic acid with Meldrum's acid utilizing online NMR spectroscopy.

    PubMed

    Dunn, Anna L; Codina, Anna; Foley, David A; Marquez, Brian L; Zell, Mark T

    2016-06-01

    A thorough investigation into the mechanism of the reaction of 3-methylpentanoic acid and Meldrum's acid using online NMR spectroscopy is reported. This study is an expansion of a previous analysis of this chemical transformation in the synthesis of an active pharmaceutical ingredient imagabalin. The 3-methylpentanoic acid analogue reveals similar behavior under the reaction conditions. Online NMR spectroscopy and offline characterization experiments reveal new information about the mechanism, providing conclusive spectroscopic evidence for the previously hypothesized dimer anhydride intermediate species 3-methylpentanoic anhydride as a productive intermediate. The presence of an acyl chloride intermediate species, 3-methylpentanoyl chloride, is also revealed for the first time in this synthesis. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26332370

  7. (19) F NMR Spectroscopy as a Highly Sensitive Method for the Direct Monitoring of Confined Crystallization within Nanoporous Materials.

    PubMed

    Nartowski, Karol P; Malhotra, Diksha; Hawarden, Lucy E; Sibik, Juraj; Iuga, Dinu; Zeitler, J Axel; Fábián, László; Khimyak, Yaroslav Z

    2016-07-25

    The introduction of fluorine into the structure of pharmaceuticals has been an effective strategy for tuning their pharmacodynamic properties, with more than 40 new drugs entering the market in the last 15 years. In this context, (19) F NMR spectroscopy can be viewed as a useful method for investigating the host-guest chemistry of pharmaceuticals in nanosized drug-delivery systems. Although the interest in confined crystallization, nanosized devices, and porous catalysts is gradually increasing, understanding of the complex phase behavior of organic molecules confined within nanochambers or nanoreactors is still lacking. Using (19) F magic-angle-spinning NMR spectroscopy, we obtained detailed mechanistic insight into the crystallization of flufenamic acid (FFA) in a confined environment of mesoporous silica materials with different pore diameters (3.2-29 nm), providing direct experimental evidence for the formation of a molecular-liquid-like layer besides crystalline confined FFA form I. PMID:27272008

  8. Probing the interaction of U(VI) with phosphonate-functionalized mesoporous silica using solid-state NMR spectroscopy

    DOE PAGESBeta

    Uribe, Eva C.; Mason, Harris E.; Shusterman, Jennifer A.; Bruchet, Anthony; Nitsche, Heino

    2016-05-30

    The fundamental interaction of U(VI) with diethylphosphatoethyl triethoxysilane functionalized SBA-15 mesoporous silica is studied by macroscopic batch experiments and solid-state NMR spectroscopy. DPTS-functionalized silica has been shown to extract U(VI) from nitric acid solutions at or above pH 3. Extraction is dependent on pH and ionic strength. Single-pulse 31P NMR on U(VI) contacted samples revealed that U(VI)only interacts with a fraction of the ligands present on the surface. At pH 4 the U(VI) extraction capacity of the material is limited to 27–37% of the theoretical capacity, based on ligand loading. We combined single pulse 31P NMR on U(VI)-contacted samples withmore » batch studies to measure a ligand-to-metal ratio of approximately 2 : 1 at pH 3 and 4. Batch studies and cross-polarization NMR measurements reveal that U(VI) binds to deprotonated phosphonate and/or silanol sites. We use 31P–31P DQ-DRENAR NMR studies to compare the average dipolar coupling between phosphorus spins for both U(VI)-complexed and non-complexed ligand environments. Furthermore, these measurements reveal that U(VI) extraction is not limited by inadequate surface distribution of ligands, but rather by low stability of the surface phosphonate complex.« less

  9. Characterizing mixed phosphonic acid ligand capping on CdSe/ZnS quantum dots using ligand exchange and NMR spectroscopy.

    PubMed

    Davidowski, Stephen K; Lisowski, Carmen E; Yarger, Jeffery L

    2016-03-01

    The ligand capping of phosphonic acid functionalized CdSe/ZnS core-shell quantum dots (QDs) was investigated with a combination of solution and solid-state (31) P nuclear magnetic resonance (NMR) spectroscopy. Two phosphonic acid ligands were used in the synthesis of the QDs, tetradecylphosphonic acid and ethylphosphonic acid. Both alkyl phosphonic acids showed broad liquid and solid-state (31) P NMR resonances for the bound ligands, indicative of heterogeneous binding to the QD surface. In order to quantify the two ligand populations on the surface, ligand exchange facilitated by phenylphosphonic acid resulted in the displacement of the ethylphosphonic acid and tetradecylphosphonic acid and allowed for quantification of the free ligands using (31) P liquid-state NMR. After washing away the free ligand, two broad resonances were observed in the liquids' (31) P NMR corresponding to the alkyl and aromatic phosphonic acids. The washed samples were analyzed via solid-state (31) P NMR, which confirmed the ligand populations on the surface following the ligand exchange process. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26639792

  10. Probing the interaction of U(vi) with phosphonate-functionalized mesoporous silica using solid-state NMR spectroscopy.

    PubMed

    Uribe, Eva C; Mason, Harris E; Shusterman, Jennifer A; Bruchet, Anthony; Nitsche, Heino

    2016-06-21

    The fundamental interaction of U(vi) with diethylphosphatoethyl triethoxysilane functionalized SBA-15 mesoporous silica is studied by macroscopic batch experiments and solid-state NMR spectroscopy. DPTS-functionalized silica has been shown to extract U(vi) from nitric acid solutions at or above pH 3. Extraction is dependent on pH and ionic strength. Single-pulse (31)P NMR on U(vi) contacted samples revealed that U(vi) only interacts with a fraction of the ligands present on the surface. At pH 4 the U(vi) extraction capacity of the material is limited to 27-37% of the theoretical capacity, based on ligand loading. We combined single pulse (31)P NMR on U(vi)-contacted samples with batch studies to measure a ligand-to-metal ratio of approximately 2 : 1 at pH 3 and 4. Batch studies and cross-polarization NMR measurements reveal that U(vi) binds to deprotonated phosphonate and/or silanol sites. We use (31)P-(31)P DQ-DRENAR NMR studies to compare the average dipolar coupling between phosphorus spins for both U(vi)-complexed and non-complexed ligand environments. These measurements reveal that U(vi) extraction is not limited by inadequate surface distribution of ligands, but rather by low stability of the surface phosphonate complex. PMID:27265020

  11. Fragment-Linking Approach Using (19)F NMR Spectroscopy To Obtain Highly Potent and Selective Inhibitors of β-Secretase.

    PubMed

    Jordan, John B; Whittington, Douglas A; Bartberger, Michael D; Sickmier, E Allen; Chen, Kui; Cheng, Yuan; Judd, Ted

    2016-04-28

    Fragment-based drug discovery (FBDD) has become a widely used tool in small-molecule drug discovery efforts. One of the most commonly used biophysical methods in detecting weak binding of fragments is nuclear magnetic resonance (NMR) spectroscopy. In particular, FBDD performed with (19)F NMR-based methods has been shown to provide several advantages over (1)H NMR using traditional magnetization-transfer and/or two-dimensional methods. Here, we demonstrate the utility and power of (19)F-based fragment screening by detailing the identification of a second-site fragment through (19)F NMR screening that binds to a specific pocket of the aspartic acid protease, β-secretase (BACE-1). The identification of this second-site fragment allowed the undertaking of a fragment-linking approach, which ultimately yielded a molecule exhibiting a more than 360-fold increase in potency while maintaining reasonable ligand efficiency and gaining much improved selectivity over cathepsin-D (CatD). X-ray crystallographic studies of the molecules demonstrated that the linked fragments exhibited binding modes consistent with those predicted from the targeted screening approach, through-space NMR data, and molecular modeling. PMID:26978477

  12. Determination of the time course of an enzymatic reaction by 1H NMR spectroscopy: hydroxynitrile lyase catalysed transhydrocyanation

    NASA Astrophysics Data System (ADS)

    Hickel, A.; Gradnig, G.; Griengl, H.; Schall, M.; Sterk, H.

    1996-01-01

    The time course of the enzyme catalysed transhydrocyanation of benzaldehyde to give ( S)-mandelonitrile was investigated using a hydroxynitrile lyase from Hevea brasiliensis as catalyst and acetone cyanohydrin as cyanide donor. Employing special techniques it was possible to apply 1H NMR spectroscopy in aqueous medium to monitor the concentration changes of all substrates and products. By this technique strong evidence for inhibition of the enzyme at higher substrate concentrations was obtained.

  13. Metabolomics-Based Study of Logarithmic and Stationary Phases of Promastigotes in Leishmania major by 1H NMR Spectroscopy

    PubMed Central

    Arjmand, Mohammad; Madrakian, Azadeh; Khalili, Ghader; Najafi, Ali; Zamani, Zahra; Akbari, Ziba

    2016-01-01

    Background: Cutaneous leishmaniasis is one of the most important parasitic diseases in humans. In this disease, one of the responsible organisms is Leishmania major, which is transmitted by sandfly vector. There are specific differences in biochemical profiles and metabolite pathways in logarithmic and stationary phases of Leishmania parasites. In the present study, 1H NMR spectroscopy was used to examine the metabolites outliers in the logarithmic and stationary phases of promastigotes in L. major to enlighten more about the transmission mechanism in metacyclogenesis of L. major. Methods: Promastigote was cultured, logarithmic and stationary phases were separated by the peanut agglutinin, and cell metabolites were extracted. 1H NMR spectroscopy was applied, and outliers were analyzed using principal component analysis. Results: The most altered metabolites in stationary and logarithmic phases were limited to citraconic acid, isopropylmalic acid, L-leucine, ornithine, caprylic acid, capric acid, and acetic acid. Conclusion: 1H NMR spectroscopy could play an important role in the characterization of metabolites in biochemical pathways during a metacyclogenesis process. These metabolites and their pathways can help in exploiting a transmission mechanism in metacyclogenesis, and outcoming data might be used in the metabolic network reconstruction of L. major modeling. PMID:26592771

  14. Use of nuclear magnetic resonance (NMR) spectroscopy for the analysis of chemical warfare agents and their degradation products in enviornmental samples

    SciTech Connect

    Szafraniec, L.L.; Beaudry, W.T.

    1995-06-01

    Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful analytical techniques for elucidating the molecular structure of organic compounds. In environmental samples, the identification and detection of chemical warfare related compounds is best accomplished using high field high resolution NMR. This paper describes the experimental procedures.

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

    PubMed Central

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

    2009-01-01

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

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

    SciTech Connect

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

    2015-10-14

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

  17. Improving Assessment of Lipoprotein Profile in Type 1 Diabetes by 1H NMR Spectroscopy

    PubMed Central

    Brugnara, Laura; Mallol, Roger; Ribalta, Josep; Vinaixa, Maria; Murillo, Serafín; Casserras, Teresa; Guardiola, Montse; Vallvé, Joan Carles; Kalko, Susana G.; Correig, Xavier; Novials, Anna

    2015-01-01

    Patients with type 1 diabetes (T1D) present increased risk of cardiovascular disease (CVD). The aim of this study is to improve the assessment of lipoprotein profile in patients with T1D by using a robust developed method 1H nuclear magnetic resonance spectroscopy (1H NMR), for further correlation with clinical factors associated to CVD. Thirty patients with T1D and 30 non-diabetes control (CT) subjects, matched for gender, age, body composition (DXA, BMI, waist/hip ratio), regular physical activity levels and cardiorespiratory capacity (VO2peak), were analyzed. Dietary records and routine lipids were assessed. Serum lipoprotein particle subfractions, particle sizes, and cholesterol and triglycerides subfractions were analyzed by 1H NMR. It was evidenced that subjects with T1D presented lower concentrations of small LDL cholesterol, medium VLDL particles, large VLDL triglycerides, and total triglycerides as compared to CT subjects. Women with T1D presented a positive association with HDL size (p<0.005; R = 0.601) and large HDL triglycerides (p<0.005; R = 0.534) and negative (p<0.005; R = -0.586) to small HDL triglycerides. Body fat composition represented an important factor independently of normal BMI, with large LDL particles presenting a positive correlation to total body fat (p<0.005; R = 0.505), and total LDL cholesterol and small LDL cholesterol a positive correlation (p<0.005; R = 0.502 and R = 0.552, respectively) to abdominal fat in T1D subjects; meanwhile, in CT subjects, body fat composition was mainly associated to HDL subclasses. VO2peak was negatively associated (p<0.005; R = -0.520) to large LDL-particles only in the group of patients with T1D. In conclusion, patients with T1D with adequate glycemic control and BMI and without chronic complications presented a more favourable lipoprotein profile as compared to control counterparts. In addition, slight alterations in BMI and/or body fat composition showed to be relevant to provoking alterations in

  18. Parallel NMR spectroscopy with simultaneous detection of (1) H and (19) F nuclei.

    PubMed

    Kovacs, Helena; Kupče, Ēriks

    2016-07-01

    Recording NMR signals of several nuclear species simultaneously by using parallel receivers provides more information from a single measurement and at the same time increases the measurement sensitivity per unit time. Here we present a comprehensive series of the most frequently used NMR experiments modified for simultaneous direct detection of two of the most sensitive NMR nuclei - (1) H and (19) F. We hope that the presented material will stimulate interest in and further development of this technique. PMID:27021630

  19. Determination of intramolecular hydrogen bonds in amikacin in water solution by NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Gaggelli, Elena; Gaggelli, Nicola; Maccotta, Antonella; Valensin, Gianni; Marini, Domenico; Di Cocco, Maria Enrica; Delfini, Maurizio

    1995-10-01

    An NMR investigation has been carried out on amikacin in water solution in the physiological pH range. Two-dimenstional heterocorrelated maps provide 1H NMR chemical shifts from the unambiguous assignment of the 13C NMR spectrum. Reorientational dynamics at the molecular level are interpreted in terms of a pseudoisotropic motion with a correlation time of 0.17 ns at 300 K. The pH and temperature dependences of 13C NMR chemical shifts are interpreted to delineate protonation equilibria (all p Ks are determined) and to assess the occurrence of two intermolecular hydrogen bonds, which are confirmed by molecular modelling.

  20. A prototype transition-metal olefin complex C2H4⋯AgCl synthesised by laser ablation and characterised by rotational spectroscopy and ab initio methods

    NASA Astrophysics Data System (ADS)

    Stephens, Susanna L.; Tew, David P.; Mikhailov, Victor A.; Walker, Nicholas R.; Legon, Anthony C.

    2011-07-01

    C2H4⋯Ag-Cl has been synthesised in the gas phase in a pulsed-jet, Fourier-transform microwave spectrometer by the reaction of laser-ablated metallic silver with carbon tetrachloride to give AgCl, which subsequently reacts with ethene to give the complex. The ground-state rotational spectra of six isotopologues (C2H4⋯107Ag35Cl, C2H4⋯109Ag35Cl, C2H4⋯107Ag37Cl, C2H4⋯109Ag37Cl, 13C2H4⋯107Ag35Cl, and 13C2H4⋯109Ag35Cl) were recorded and analysed to give rotational constants A0, B0, and C0, centrifugal distortion constants ΔJ and ΔJK, and Cl nuclear quadrupole coupling constants χaa(Cl) and χbb(Cl) - χcc(Cl). These spectroscopic constants were interpreted in terms of a geometry for C2H4⋯Ag-Cl of C2V symmetry in which the AgCl molecule lies along the C2 axis of ethene that is perpendicular to the C2H4 plane. The Ag atom forms a bond to the midpoint (*) of the ethene π bond. A partial rs-geometry and a r0-geometry were determined, with the values r(*⋯Ag) = 2.1719(9) Å, r(C-C) = 1.3518(4) Å, and r(Ag-Cl) = 2.2724(8) Å obtained in the latter case. The C-C bond lengthens on formation of the complex. Detailed ab initio calculations carried out at the CCSD(T)/cc-pVQZ level of theory give results in good agreement with experiment and also reveal that the ethene molecule undergoes a small angular distortion. The distortion is such that the four H atoms move in a direction away from Ag but remain coplanar. The two C atoms are no longer contained in this plane, however. The electric charge redistribution when C2H4⋯Ag-Cl is formed and the strength of the π⋯Ag bond are discussed.

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

    PubMed Central

    Yang, Yu; Yao, Hongwei

    2015-01-01

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

  2. Mg-25 ultra-high field solid state NMR spectroscopy and first principles calculations of magnesium compounds.

    PubMed

    Pallister, Peter J; Moudrakovski, Igor L; Ripmeester, John A

    2009-12-28

    Due to sensitivity problems, (25)Mg remains a largely under-explored nucleus in solid state NMR spectroscopy. In this work at an ultrahigh magnetic field of 21.1 T, we have studied at natural abundance the (25)Mg solid state (SS) NMR spectra for a number of previously unreported magnesium compounds with known crystal structures. Some previously reported compounds have been revisited to clarify the spectra that were obtained at lower fields and were either not sufficiently resolved, or misinterpreted. First principles calculations of the (25)Mg SS NMR parameters have been carried out using plane wave basis sets and periodic boundary conditions (CASTEP) and the results are compared with experimental data. The calculations produce the (25)Mg absolute shielding scale and give us insight into the relationship between the NMR and structural parameters. At 21.1 T the effects of the quadrupolar interactions are reduced significantly and the sensitivity and accuracy in determining chemicals shifts and quadrupole coupling parameters improve dramatically. Although T(1) measurements were not performed explicitly, these proved to be longer than assumed in much of the previously reported work. We demonstrate that the chemical shift range of magnesium in diamagnetic compounds may approach 200 ppm. Most commonly, however, the observed shifts are between -15 and +25 ppm. Quadrupolar effects dominate the (25)Mg spectra of magnesium cations in non-cubic environments. The chemical shift anisotropy appears to be rather small and only in a few cases could the contribution of the CSA be detected reliably. A good correspondence between the calculated shielding constants and experimental chemical shifts was obtained, demonstrating the good potential of computational methods in spectroscopic assignments of solid state (25)Mg NMR spectroscopy. PMID:20024420

  3. Compositional differences among Chinese soy sauce types studied by (13)C NMR spectroscopy coupled with multivariate statistical analysis.

    PubMed

    Kamal, Ghulam Mustafa; Wang, Xiaohua; Bin Yuan; Wang, Jie; Sun, Peng; Zhang, Xu; Liu, Maili

    2016-09-01

    Soy sauce a well known seasoning all over the world, especially in Asia, is available in global market in a wide range of types based on its purpose and the processing methods. Its composition varies with respect to the fermentation processes and addition of additives, preservatives and flavor enhancers. A comprehensive (1)H NMR based study regarding the metabonomic variations of soy sauce to differentiate among different types of soy sauce available on the global market has been limited due to the complexity of the mixture. In present study, (13)C NMR spectroscopy coupled with multivariate statistical data analysis like principle component analysis (PCA), and orthogonal partial least square-discriminant analysis (OPLS-DA) was applied to investigate metabonomic variations among different types of soy sauce, namely super light, super dark, red cooking and mushroom soy sauce. The main additives in soy sauce like glutamate, sucrose and glucose were easily distinguished and quantified using (13)C NMR spectroscopy which were otherwise difficult to be assigned and quantified due to serious signal overlaps in (1)H NMR spectra. The significantly higher concentration of sucrose in dark, red cooking and mushroom flavored soy sauce can directly be linked to the addition of caramel in soy sauce. Similarly, significantly higher level of glutamate in super light as compared to super dark and mushroom flavored soy sauce may come from the addition of monosodium glutamate. The study highlights the potentiality of (13)C NMR based metabonomics coupled with multivariate statistical data analysis in differentiating between the types of soy sauce on the basis of level of additives, raw materials and fermentation procedures. PMID:27343582

  4. Structure of 3-aminopyridine betaine hydrochloride studied by X-ray diffraction, DFT calculations, FTIR and NMR spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

    The structure of 3-aminopyridine betaine hydrochloride (1-carboxymethyl-3-aminopyridinium chloride), 3-NH 2PBH·Cl, has been studied by X-ray diffraction, B3LYP/6-311G(d,p) calculations, FTIR and NMR spectra. The compound crystallized in monoclinic, space group P2 1/c in the crystal, the Cl - anion is connected with protonated betaine via the hydrogen bond O-H⋯Cl of 2.946(3) Å. Both protons of the NH 2 group are engaged in hydrogen bonds with the neighboring molecules: N(2)-H(2B)⋯O(2) of 2.905(6) Å and N(2)-H(2B)⋯Cl(1) of 3.324(3) Å. The Cl - ion interacts electrostatically with three neighboring molecules. The probable assignments of the anharmonic experimental solid state vibrational frequencies of the investigated compound, based on the calculated frequencies in vacuum at the same level of theory for optimized structure, have been made. Correlations between the experimental 13C and 1H NMR chemical shifts ( δexp) and the GIAO/B3LYP/6-311G(d,p) calculated magnetic isotropic shielding ( σcal) in DMSO and D 2O, δexp = a + b · σcalc, are reported.

  5. Multinuclear NMR spectroscopy and antiproliferative activity in vitro of platinum(II) and palladium(II) complexes with 6-mercaptopurine

    NASA Astrophysics Data System (ADS)

    Łakomska, Iwona; Pazderski, Leszek; Sitkowski, Jerzy; Kozerski, Lech; Pełczyńska, Marzena; Nasulewicz, Anna; Opolski, Adam; Szłyk, Edward

    2004-11-01

    A series of Pd(II) and Pt(II) complexes with 6-mercaptopurine (6-Hmp) of formulae Pd(6-Hmp) 2Cl 2 ( 1), Pd(6-mp) 2·2H 2O ( 2), Pt(6-mp) 2·2H 2O ( 3), Pt(6-mp)(dmso)Cl ( 4) was synthesized and studied by IR, far-IR, 1H, 13C, 15N NMR. ( 1) has an ionic character and consists of distinct [Pd(6-Hmp) 2] 2+ cations and uncoordinated Cl - anions, whereas ( 2,3) are neutral species with central atoms bis-chelated by the deprotonated 6-mp - ligands. NMR studies suggest that S and N(7) are the complexation sites, while far-IR spectra indicate the square-planar geometry of Pd(II) or Pt(II). In ( 4) the Pt(II) atom is coordinated by one chelating 6-mp - anion, S-bonded dmso molecule and a terminal chloride. The antiproliferative activity in vitro of ( 2-4) was tested against human leukaemia HL-60 cells, being exhibited for ( 2) at the level ca. six times lower than in case of cisplatin.

  6. Lithium ion diffusion in Li β-alumina single crystals measured by pulsed field gradient NMR spectroscopy

    SciTech Connect

    Chowdhury, Mohammed Tareque Takekawa, Reiji; Iwai, Yoshiki; Kuwata, Naoaki; Kawamura, Junichi

    2014-03-28

    The lithium ion diffusion coefficient of a 93% Li β-alumina single crystal was measured for the first time using pulsed field gradient (PFG) NMR spectroscopy with two different crystal orientations. The diffusion coefficient was found to be 1.2 × 10{sup −11} m{sup 2}/s in the direction perpendicular to the c axis at room temperature. The Li ion diffusion coefficient along the c axis direction was found to be very small (6.4 × 10{sup −13} m{sup 2}/s at 333 K), which suggests that the macroscopic diffusion of the Li ion in the β-alumina crystal is mainly two-dimensional. The diffusion coefficient for the same sample was also estimated using NMR line narrowing data and impedance measurements. The impedance data show reasonable agreement with PFG-NMR data, while the line narrowing measurements provided a lower value for the diffusion coefficient. Line narrowing measurements also provided a relatively low value for the activation energy and pre-exponential factor. The temperature dependent diffusion coefficient was obtained in the temperature range 297–333 K by PFG-NMR, from which the activation energy for diffusion of the Li ion was estimated. The activation energy obtained by PFG-NMR was smaller than that obtained by impedance measurements, which suggests that thermally activated defect formation energy exists for 93% Li β-alumina single crystals. The diffusion time dependence of the diffusion coefficient was observed for the Li ion in the 93% Li β-alumina single crystal by means of PFG-NMR experiments. Motion of Li ion in fractal dimension might be a possible explanation for the observed diffusion time dependence of the diffusion coefficient in the 93% Li β–alumina system.

  7. Organic Spectroscopy Laboratory: Utilizing IR and NMR in the Identification of an Unknown Substance

    ERIC Educational Resources Information Center

    Glagovich, Neil M.; Shine, Timothy D.

    2005-01-01

    A laboratory experiment that emphasizes the interpretation of both infrared (IR) and nuclear magnetic resonance (NMR) spectra in the elucidation of the structure of an unknown compound was developed. The method helps students determine [to the first power]H- and [to the thirteenth power]C-NMR spectra from the structures of compounds and to…

  8. Establishing resolution-improved NMR spectroscopy in high magnetic fields with unknown spatiotemporal variations.

    PubMed

    Zhang, Zhiyong; Smith, Pieter E S; Cai, Shuhui; Zheng, Zhenyao; Lin, Yulan; Chen, Zhong

    2015-12-28

    A half-century quest for higher magnetic fields has been an integral part of the progress undergone in the Nuclear Magnetic Resonance (NMR) study of materials' structure and dynamics. Because 2D NMR relies on systematic changes in coherences' phases as a function of an encoding time varied over a series of independent experiments, it generally cannot be applied in temporally unstable fields. This precludes most NMR methods from being used to characterize samples situated in hybrid or resistive magnets that are capable of achieving extremely high magnetic field strength. Recently, "ultrafast" NMR has been developed into an effective and widely applicable methodology enabling the acquisition of a multidimensional NMR spectrum in a single scan; it can therefore be used to partially mitigate the effects of temporally varying magnetic fields. Nevertheless, the strong interference of fluctuating fields with the spatial encoding of ultrafast NMR still severely restricts measurement sensitivity and resolution. Here, we introduce a strategy for obtaining high resolution NMR spectra that exploits the immunity of intermolecular zero-quantum coherences (iZQCs) to field instabilities and inhomogeneities. The spatial encoding of iZQCs is combined with a J-modulated detection scheme that removes the influence of arbitrary field inhomogeneities during acquisition. This new method can acquire high-resolution one-dimensional NMR spectra in large inhomogeneous and fluctuating fields, and it is tested with fields experimentally modeled to mimic those of resistive and resistive-superconducting hybrid magnets. PMID:26723664

  9. Establishing resolution-improved NMR spectroscopy in high magnetic fields with unknown spatiotemporal variations

    SciTech Connect

    Zhang, Zhiyong; Cai, Shuhui; Zheng, Zhenyao; Lin, Yulan E-mail: lylfj2005@xmu.edu.cn; Chen, Zhong E-mail: lylfj2005@xmu.edu.cn; Smith, Pieter E. S.

    2015-12-28

    A half-century quest for higher magnetic fields has been an integral part of the progress undergone in the Nuclear Magnetic Resonance (NMR) study of materials’ structure and dynamics. Because 2D NMR relies on systematic changes in coherences’ phases as a function of an encoding time varied over a series of independent experiments, it generally cannot be applied in temporally unstable fields. This precludes most NMR methods from being used to characterize samples situated in hybrid or resistive magnets that are capable of achieving extremely high magnetic field strength. Recently, “ultrafast” NMR has been developed into an effective and widely applicable methodology enabling the acquisition of a multidimensional NMR spectrum in a single scan; it can therefore be used to partially mitigate the effects of temporally varying magnetic fields. Nevertheless, the strong interference of fluctuating fields with the spatial encoding of ultrafast NMR still severely restricts measurement sensitivity and resolution. Here, we introduce a strategy for obtaining high resolution NMR spectra that exploits the immunity of intermolecular zero-quantum coherences (iZQCs) to field instabilities and inhomogeneities. The spatial encoding of iZQCs is combined with a J-modulated detection scheme that removes the influence of arbitrary field inhomogeneities during acquisition. This new method can acquire high-resolution one-dimensional NMR spectra in large inhomogeneous and fluctuating fields, and it is tested with fields experimentally modeled to mimic those of resistive and resistive-superconducting hybrid magnets.

  10. Establishing resolution-improved NMR spectroscopy in high magnetic fields with unknown spatiotemporal variations

    NASA Astrophysics Data System (ADS)

    Zhang, Zhiyong; Smith, Pieter E. S.; Cai, Shuhui; Zheng, Zhenyao; Lin, Yulan; Chen, Zhong

    2015-12-01

    A half-century quest for higher magnetic fields has been an integral part of the progress undergone in the Nuclear Magnetic Resonance (NMR) study of materials' structure and dynamics. Because 2D NMR relies on systematic changes in coherences' phases as a function of an encoding time varied over a series of independent experiments, it generally cannot be applied in temporally unstable fields. This precludes most NMR methods from being used to characterize samples situated in hybrid or resistive magnets that are capable of achieving extremely high magnetic field strength. Recently, "ultrafast" NMR has been developed into an effective and widely applicable methodology enabling the acquisition of a multidimensional NMR spectrum in a single scan; it can therefore be used to partially mitigate the effects of temporally varying magnetic fields. Nevertheless, the strong interference of fluctuating fields with the spatial encoding of ultrafast NMR still severely restricts measurement sensitivity and resolution. Here, we introduce a strategy for obtaining high resolution NMR spectra that exploits the immunity of intermolecular zero-quantum coherences (iZQCs) to field instabilities and inhomogeneities. The spatial encoding of iZQCs is combined with a J-modulated detection scheme that removes the influence of arbitrary field inhomogeneities during acquisition. This new method can acquire high-resolution one-dimensional NMR spectra in large inhomogeneous and fluctuating fields, and it is tested with fields experimentally modeled to mimic those of resistive and resistive-superconducting hybrid magnets.

  11. Investigation of interaction parameters in mixed micelle using pulsed field gradient NMR spectroscopy.

    PubMed

    Gharibi, H; Javadian, S; Sohrabi, B; Behjatmanesh, R

    2005-05-01

    Pulsed field gradient NMR spectroscopy was used to determine the partitioning of surfactant between monomeric and micellar forms in a mixed CTAB (hexadecyltetramethylammonium bromide) and Triton X-100 [p-(1,1,3-tetramethylbutyl)polyoxyethylene] system. In addition, potentiometric and surface tension measurements were used to determine the free concentration of ionic surfactant and the critical micelle concentration (CMC) of mixtures of n-alkyltrimethylammonium bromide (C(n)TAB, n=12, 14, 16, 18) and Triton X-100. Regular solution theory cannot describe the behavior of the activity coefficient and the excess Gibbs free energy of mixtures of ionic and nonionic surfactants. To overcome these shortcomings, we developed a new model that combines Van Laar expressions and the theory of nonrandom mixing in mixed micelles. The Van Laar expressions contain an additional parameter, rho, which reflects differences in the size of the components of the mixture. Nonrandom mixing theory was introduced to describe nonrandom mixing in mixed micelles. This effect was modeled by a packing parameter, P*. The proposed model provided a good description of the behavior of binary surfactant mixtures. The results indicated that head group size and packing constraints are important contributors to nonideal surfactant behavior. In addition, the results showed that as the chain length of the C(n)TAB molecule in C(n)TAB/Triton X-100 mixtures was increased, the head group size parameter remained constant, but the interaction and packing parameters increased. Increase of the temperature caused an increase in the interaction parameter beta and a decrease in the packing parameter (P*). PMID:15797433

  12. Improving the resolution in proton-detected through-space heteronuclear multiple quantum correlation NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Shen, Ming; Trébosc, J.; Lafon, O.; Pourpoint, F.; Hu, Bingwen; Chen, Qun; Amoureux, J.-P.

    2014-08-01

    Connectivities and proximities between protons and low-gamma nuclei can be probed in solid-state NMR spectroscopy using two-dimensional (2D) proton-detected heteronuclear correlation, through Heteronuclear Multiple Quantum Correlation (HMQC) pulse sequence. The indirect detection via protons dramatically enhances the sensitivity. However, the spectra are often broadened along the indirect F1 dimension by the decay of heteronuclear multiple-quantum coherences under the strong 1H-1H dipolar couplings. This work presents a systematic comparison of the performances of various decoupling schemes during the indirect t1 evolution period of dipolar-mediated HMQC (D-HMQC) experiment. We demonstrate that 1H-1H dipolar decoupling sequences during t1, such as symmetry-based schemes, phase-modulated Lee-Goldburg (PMLG) and Decoupling Using Mind-Boggling Optimization (DUMBO), provide better resolution than continuous wave 1H irradiation. We also report that high resolution requires the preservation of 1H isotropic chemical shifts during the decoupling sequences. When observing indirectly broad spectra presenting numerous spinning sidebands, the D-HMQC sequence must be fully rotor-synchronized owing to the rotor-synchronized indirect sampling and dipolar recoupling sequence employed. In this case, we propose a solution to reduce artefact sidebands caused by the modulation of window delays before and after the decoupling application during the t1 period. Moreover, we show that 1H-1H dipolar decoupling sequence using Smooth Amplitude Modulation (SAM) minimizes the t1-noise. The performances of the various decoupling schemes are assessed via numerical simulations and compared to 2D 1H-{13C} D-HMQC experiments on [U-13C]-L-histidineṡHClṡH2O at various magnetic fields and Magic Angle spinning (MAS) frequencies. Great resolution and sensitivity enhancements resulting from decoupling during t1 period enable the detection of heteronuclear correlation between aliphatic protons and

  13. High-field localized 1H NMR spectroscopy in the anesthetized and in the awake monkey.

    PubMed

    Pfeuffer, Josef; Juchem, Christoph; Merkle, Hellmut; Nauerth, Arno; Logothetis, Nikos K

    2004-12-01

    Localized cerebral in vivo 1H NMR spectroscopy (MRS) was performed in the anesthetized as well as the awake monkey using a novel vertical 7 T/60 cm MR system. The increased sensitivity and spectral dispersion gained at high field enabled the quantification of up to 16 metabolites in 0.1- to 1-ml volumes. Quantification was accomplished by using simulations of 18 metabolite spectra and a macromolecule (MM) background spectrum consisting of 12 components. Major cerebral metabolites (concentrations >3 mM) such as glutamate (Glu), N-acetylaspartate (NAA), creatine (Cr)/phosphocreatine (PCr) and myo-inositol (Ins) were identified with an error below 3%; most other metabolites were quantified with errors in the order of 10%. Metabolite ratios were 1.39:1 for total NAA, 1.38:1 for glutamate (Glu)/glutamine (Gln) and 0.09:1 for cholines (Cho) relative to total Cr. Taurine (Tau) was detectable at concentrations lower than 1 mM, while lactate (Lac) remained below the detection limit. The spectral dispersion was sufficient to separate metabolites of similar spectral patterns, such as Gln and Glu, N-acetylaspartylglutamate (NAAG) and NAA, and PCr-Cr. MRS in the awake monkey required the development and refinement of acquisition and correction strategies to minimize magnetic susceptibility artifacts induced by respiration and movement of the mouth or body. Periods with major motion artifacts were rejected, while a frequency/phase correction was performed on the remaining single spectra before averaging. In resting periods, both spectral amplitude and line width, that is, the voxel shim, were unaffected permitting reliable measurements. The corrected spectra obtained from the awake monkey afforded the reliable detection of 6-10 cerebral metabolites of 1-ml volumes. PMID:15707786

  14. Impact of Adenovirus infection in host cell metabolism evaluated by (1)H-NMR spectroscopy.

    PubMed

    Silva, Ana Carina; P Teixeira, Ana; M Alves, Paula

    2016-08-10

    Adenovirus-based vectors are powerful vehicles for gene transfer applications in vaccination and gene therapy. Although highly exploited in the clinical setting, key aspects of the adenovirus biology are still not well understood, in particular the subversion of host cell metabolism during viral infection and replication. The aim of this work was to gain insights on the metabolism of two human cell lines (HEK293 and an amniocyte-derived cell line, 1G3) after infection with an adenovirus serotype 5 vector (AdV5). In order to profile metabolic alterations, we used (1)H-NMR spectroscopy, which allowed the quantification of 35 metabolites in cell culture supernatants with low sample preparation and in a relatively short time. Significant differences between both cell lines in non-infected cultures were identified, namely in glutamine and acetate metabolism, as well as by-product secretion. The main response to AdV5 infection was an increase in glucose consumption and lactate production rates. Moreover, cultures performed with or without glutamine supplementation confirmed the exhaustion of this amino acid as one of the main causes of lower AdV5 production at high cell densities (10- and 1.5-fold less specific yields in HEK293 and 1G3 cells, respectively), and highlighted different degrees of glutamine dependency of adenovirus replication in each cell line. The observed metabolic alterations associated with AdV5 infection and specificity of the host cell line can be useful for targeted bioprocess optimization. PMID:27215342

  15. Copper-catalysed asymmetric allylic alkylation of alkylzirconocenes to racemic 3,6-dihydro-2H-pyrans

    PubMed Central

    Rideau, Emeline

    2015-01-01

    Summary Asymmetric allylic alkylation is a powerful reaction that allows the enantioselective formation of C–C bonds. Here we describe the asymmetric alkylation of alkylzirconium species to racemic 3,6-dihydro-2H-pyrans. Two systems were examined: 3-chloro-3,6-dihydro-2H-pyran using linear optimization (45–93% ee, up to 33% yield, 5 examples) and 3,6-dihydro-2H-pyran-3-yl diethyl phosphate with the assistance of a design of experiments statistical approach (83% ee, 12% yield). 1H NMR spectroscopy was used to gain insight into the reaction mechanisms. PMID:26734091

  16. Quantitative Determination of Methylcyclohexanone Mixtures Using 13C NMR Spectroscopy: A Project for an Advanced Chemistry Laboratory

    NASA Astrophysics Data System (ADS)

    Lefevre, Joseph W.; Silveira, Augustine, Jr.

    2000-01-01

    The percentage composition of mixtures of four methylcyclohexanones was determined using 13C NMR spectroscopy as a quantitative analytical method. The data were acquired using standard broadband proton decoupling and inverse-gated decoupling, the latter done both with and without the paramagnetic relaxation reagent chromium(III) acetylacetonate [Cr(acac)3]. The standard broadband decoupled spectrum resulted in percentages far from the actual values owing to the varying nuclear Overhauser enhancements (NOEs) and spin-lattice relaxation times (T1's) of the various carbon atoms. These effects were eliminated in the inverse-gated experiments, and the results were very close to the actual percentages. Before examining the mixtures, the students studied a pure sample of 2-methylcyclohexanone. They assigned the 13C spectrum and determined the T1 of the carbonyl group both with and without Cr(acac)3 using the inversion-recovery method. Then a five-times-T1 delay was inserted between pulses in all subsequent inverse-gated decoupling experiments. This project provides students with valuable experience with modern NMR techniques. These include COrrelated SpectroscopY (COSY), Distortionless Enhancement by Polarization Transfer (DEPT) spectroscopy, HETeronuclear CORrelated (HETCOR) spectroscopy, T1 determination, standard broadband versus inverse-gated decoupling, and the addition of a paramagnetic relaxation reagent to dramatically shorten both the T

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

    SciTech Connect

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

    2015-06-22

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

  18. Precision high-throughput proton NMR spectroscopy of human urine, serum, and plasma for large-scale metabolic phenotyping.

    PubMed

    Dona, Anthony C; Jiménez, Beatriz; Schäfer, Hartmut; Humpfer, Eberhard; Spraul, Manfred; Lewis, Matthew R; Pearce, Jake T M; Holmes, Elaine; Lindon, John C; Nicholson, Jeremy K

    2014-10-01

    Proton nuclear magnetic resonance (NMR)-based metabolic phenotyping of urine and blood plasma/serum samples provides important prognostic and diagnostic information and permits monitoring of disease progression in an objective manner. Much effort has been made in recent years to develop NMR instrumentation and technology to allow the acquisition of data in an effective, reproducible, and high-throughput approach that allows the study of general population samples from epidemiological collections for biomarkers of disease risk. The challenge remains to develop highly reproducible methods and standardized protocols that minimize technical or experimental bias, allowing realistic interlaboratory comparisons of subtle biomarker information. Here we present a detailed set of updated protocols that carefully consider major experimental conditions, including sample preparation, spectrometer parameters, NMR pulse sequences, throughput, reproducibility, quality control, and resolution. These results provide an experimental platform that facilitates NMR spectroscopy usage across different large cohorts of biofluid samples, enabling integration of global metabolic profiling that is a prerequisite for personalized healthcare. PMID:25180432

  19. Reconstitution of the Cytb5 -CytP450 Complex in Nanodiscs for Structural Studies using NMR Spectroscopy.

    PubMed

    Zhang, Meng; Huang, Rui; Ackermann, Rose; Im, Sang-Choul; Waskell, Lucy; Schwendeman, Anna; Ramamoorthy, Ayyalusamy

    2016-03-24

    Cytochrome P450s (P450s) are a superfamily of enzymes responsible for the catalysis of a wide range of substrates. Dynamic interactions between full-length membrane-bound P450 and its redox partner cytochrome b5 (cytb5 ) have been found to be important for the enzymatic activity of P450. However, the stability of the circa 70 kDa membrane-bound complex in model membranes renders high-resolution structural NMR studies particularly difficult. To overcome these challenges, reconstitution of the P450-cytb5 complex in peptide-based nanodiscs, containing no detergents, has been demonstrated, which are characterized by size exclusion chromatography and NMR spectroscopy. In addition, NMR experiments are used to identify the binding interface of the P450-cytb5 complex in the nanodisc. This is the first successful demonstration of a protein-protein complex in a nanodisc using NMR structural studies and should be useful to obtain valuable structural information on membrane-bound protein complexes. PMID:26924779

  20. Analyzing the adsorption of blood plasma components by means of fullerene-containing silica gels and NMR spectroscopy in solids

    NASA Astrophysics Data System (ADS)

    Melenevskaya, E. Yu.; Mokeev, M. V.; Nasonova, K. V.; Podosenova, N. G.; Sharonova, L. V.; Gribanov, A. V.

    2012-10-01

    The results from studying the adsorption of blood plasma components (e.g., protein, triglycerides, cholesterol, and lipoproteins of low and high density) using silica gels modified with fullerene molecules (in the form of C60 or the hydroxylated form of C60(OH) x ) and subjected to hydration (or, alternatively, dehydration) are presented. The conditions for preparing adsorbents that allow us to control the adsorption capacity of silica gel and the selectivity of adsorption toward the components of blood plasma, are revealed. The nature and strength of the interactions of the introduced components (fullerene molecules and water) with functional groups on the silica surface are studied by means of solid state NMR spectroscopy (NMR-SS). Conclusions regarding the nature of the centers that control adsorption are drawn on the basis of NMR-SS spectra in combination with direct measurements of adsorption. The interaction of the oxygen of the hydroxyl group of silica gel with fullerene, leading to the formation of electron-donor complexes of C60-H, C60-OH, or C60-OSi type, is demonstrated by the observed changes in the NMR-SS spectra of silica gels in the presence of fullerene.