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Sample records for 2h nmr spectroscopy

  1. Natural-abundance solid-state 2H NMR spectroscopy at high magnetic field.

    PubMed

    Aliev, Abil E; Mann, Sam E; Iuga, Dinu; Hughes, Colan E; Harris, Kenneth D M

    2011-06-09

    High-resolution solid-state (2)H NMR spectroscopy provides a method for measuring (1)H NMR chemical shifts in solids and is advantageous over the direct measurement of high-resolution solid-state (1)H NMR spectra, as it requires only the application of routine magic angle sample spinning (MAS) and routine (1)H decoupling methods, in contrast to the requirement for complex pulse sequences for homonuclear (1)H decoupling and ultrafast MAS in the case of high-resolution solid-state (1)H NMR. However, a significant obstacle to the routine application of high-resolution solid-state (2)H NMR is the very low natural abundance of (2)H, with the consequent problem of inherently low sensitivity. Here, we explore the feasibility of measuring (2)H MAS NMR spectra of various solids with natural isotopic abundances at high magnetic field (850 MHz), focusing on samples of amino acids, peptides, collagen, and various organic solids. The results show that high-resolution solid-state (2)H NMR can be used successfully to measure isotropic (1)H chemical shifts in favorable cases, particularly for mobile functional groups, such as methyl and -N(+)H(3) groups, and in some cases phenyl groups. Furthermore, we demonstrate that routine (2)H MAS NMR measurements can be exploited for assessing the relative dynamics of different functional groups in a molecule and for assessing whole-molecule motions in the solid state. The magnitude and field-dependence of second-order shifts due to the (2)H quadrupole interaction are also investigated, on the basis of analysis of simulated and experimental (1)H and (2)H MAS NMR spectra of fully deuterated and selectively deuterated samples of the α polymorph of glycine at two different magnetic field strengths.

  2. Sensitivity of 2H NMR spectroscopy to motional models: Proteins and highly viscous liquids as examples

    NASA Astrophysics Data System (ADS)

    Kruk, D.; Mielczarek, A.; Korpala, A.; Kozlowski, A.; Earle, K. A.; Moscicki, J.

    2012-06-01

    In order to study to what extent mechanisms of molecular motion can be unambiguously revealed by 2H NMR spectroscopy, 2H spectra for proteins (chicken villin protein headpiece HP36, selectively methyl-deuterated at leucine-69, Cδ D3) and binary systems of high viscosity (benzene-d6 in tricresyl phosphate) have been carefully analyzed as illustrative examples (the spectra are taken from the literature). In the first case, a model of restricted diffusion mediated by jumps between rotameric orientations has been tested against jump- and free diffusion models which describe rotational motion combined with jump dynamics. It has been found that the set of 2H spectra of methyl-deuterated at leucine-69 chicken villin protein headpiece HP36 can be consistently explained by different motional models as well as by a Gaussian distribution of correlation times assuming isotropic rotation (simple Brownian diffusion model). The last finding shows that when the possible distribution of correlation times is not very broad one might not be able to distinguish between heterogeneous and homogenous (but more complex) dynamics by analyzing 2H lineshapes. For benzene-d6 in tricresyl phosphate, the dynamics is heterogeneous and it has been demonstrated that a Gaussian distribution of correlation times reproduces well the experimental lineshapes, while for a Cole-Davidson distribution the agreement is somewhat worse. For inquires into the sensitivity of quadrupolar NMR spectral analysis (by "quadrupolar NMR spectroscopy we understand NMR spectroscopy of nuclei possessing quadrupole moment), the recently presented theoretical approach [Kruk et al., J. Chem. Phys. 135, 224511 (2011)], 10.1063/1.3664783 has been used as it allows simulating quadrupolar spectra for arbitrary motional conditions by employing the stochastic Liouville equation.

  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. Raftlike Mixtures of Sphingomyelin and Cholesterol Investigated by Solid-State 2H NMR Spectroscopy

    PubMed Central

    Bartels, Tim; Lankalapalli, Ravi S.; Bittman, Robert; Beyer, Klaus; Brown, Michael F.

    2009-01-01

    Sphingomyelin is a lipid that is abundant in the nervous systems of mammals, where it is associated with putative microdomains in cellular membranes and undergoes alterations due to aging or neurodegeneration. We investigated the effect of varying the concentration of cholesterol in binary and ternary mixtures with N-palmitoylsphingomyelin (PSM) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) using deuterium nuclear magnetic resonance (2H NMR) spectroscopy in both macroscopically aligned and unoriented multilamellar dispersions. In our experiments, we used PSM and POPC perdeuterated on the N-acyl and sn-1 acyl chains, respectively. By measuring solid-state 2H NMR spectra of the two lipids separately in mixtures with the same compositions as a function of cholesterol mole fraction and temperature, we obtained clear evidence for the coexistence of two liquid-crystalline domains in distinct regions of the phase diagram. According to our analysis of the first moments M1 and the observed 2H NMR spectra, one of the domains appears to be a liquid-ordered phase. We applied a mean-torque potential model as an additional tool to calculate the average hydrocarbon thickness, the area per lipid, and structural parameters such as chain extension and thermal expansion coefficient in order to further define the two coexisting phases. Our data imply that phase separation takes place in raftlike ternary PSM/POPC/cholesterol mixtures over a broad temperature range but vanishes at cholesterol concentrations equal to or greater than a mole fraction of 0.33. Cholesterol interacts preferentially with sphingomyelin only at smaller mole fractions, above which a homogeneous liquid-ordered phase is present. The reasons for these phase separation phenomena seem to be differences in the effects of cholesterol on the configurational order of the palmitoyl chains in PSM-d31 and POPC-d31 and a difference in the affinity of cholesterol for sphingomyelin observed at low temperatures

  5. Lightweight hydrogen-storage material Mg(0.65)Sc(0.35)D2 studied with 2H and 2H-{45Sc} MAS NMR exchange spectroscopy.

    PubMed

    Srinivasan, S; Magusin, P C M M

    2011-01-01

    Using double-quantum (2)H MAS NMR with (45)Sc recoupling and Bloch-Siegert compensated (2)H-{(45)Sc} TRAPDOR we have identified the overlapping NMR signals of deuterium with and without scandium neighbors in Mg(0.65)Sc(0.35)D(2), a candidate lightweight material for hydrogen storage. At room temperature we also observe a third type of mobile deuterium. Deuterium mobility among the three NMR-distinct sites has been investigated by means of one-and two-dimensional exchange spectroscopy (Exsy). Complete deuterium exchange within 0.1s is observed, which indicates that the three NMR-distinct sites are close together in the crystal lattice. The weak temperature- and MAS-rate dependences observed in Exsy are indicative for a combination of chemical exchange and spin diffusion. Copyright © 2011 Elsevier Inc. All rights reserved.

  6. Synthesis of (R)-[2-2H]isopentenyl diphosphate and determination of its enantiopurity by 2H NMR spectroscopy in a lyotropic medium.

    PubMed

    Leyes, A E; Poulter, C D

    1999-10-07

    [formula: see text] The synthesis of (R)-[2-2H]isopentenyl diphosphate from D-mannitol 1,2:5,6-bis-acetonide in 10 steps is reported. Stereospecific incorporation of the label is achieved by a BF3-catalyzed NaCNBD3 reduction of the enantiomerically pure (S)-isopropylidene oxirane intermediate. The enantiomeric excess of the penultimate precursor [2-2H]isopentenyl tosylate (> 95% ee) was determined by 2H NMR spectroscopy in a poly-gamma-benzyl-L-glutamate/CH2Cl2 liquid crystal at -50 degrees C.

  7. 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. Copyright © 2012 Elsevier Ltd. All rights reserved.

  8. Non-polymeric asymmetric binary glass-formers. II. Secondary relaxation studied by dielectric, 2H NMR, and 31P NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Pötzschner, B.; Mohamed, F.; Bächer, C.; Wagner, E.; Lichtinger, A.; Bock, D.; Kreger, K.; Schmidt, H.-W.; Rössler, E. A.

    2017-04-01

    We investigate the secondary (β-) relaxations of an asymmetric binary glass former consisting of a spirobichroman derivative (SBC; Tg = 356 K) as the high-Tg component and the low-Tg component tripropyl phosphate (TPP; Tg = 134 K). The main relaxations are studied in Paper I [B. Pötzschner et al., J. Chem. Phys. 146, 164503 (2017)]. A high Tg contrast of ΔTg = 222 K is put into effect in a non-polymeric system. Component-selective studies are carried out by combining results from dielectric spectroscopy (DS) for mass concentrations cTPP ≥ 60% and those from different methods of 2H and 31P NMR spectroscopy. In the case of NMR, the full concentration range (10% ≤ cTPP ≤ 100%) is covered. The neat components exhibit a β-relaxation (β1 (SBC) and β2 (TPP)). The latter is rediscovered by DS in the mixtures for all concentrations with unchanged time constants. NMR spectroscopy identifies the β-relaxations as being alike to those in neat glasses. A spatially highly restricted motion with angular displacement below ±10° encompassing all molecules is involved. In the low temperature range, where TPP shows the typical 31P NMR echo spectra of the β2-process, very similar spectral features are observed for the (deuterated) SBC component by 2H NMR, in addition to its "own" β1-process observed at high temperatures. Apparently, the small TPP molecules enslave the large SBC molecules to perform a common hindered reorientation. The temperature dependence of the spin-lattice relaxation time of both components is the same and reveals an angular displacement of the SBC molecules somewhat smaller than that of TPP, though the time constants τβ2 are the same. Furthermore, T1(T) of TPP in the temperature region of the β2-process is absolutely the same as in the mixture TPP/polystyrene investigated previously. It appears that the manifestations of the β-process introduced by one component are essentially independent of the second component. Finally, at cTPP ≤ 20% one

  9. Structure and Dynamics of the Myristoyl Lipid Modification of Src Peptides Determined by 2H Solid-State NMR Spectroscopy

    PubMed Central

    Scheidt, Holger A.; Huster, Daniel

    2009-01-01

    Lipid modifications of proteins are widespread in nature and play an important role in numerous biological processes. The nonreceptor tyrosine kinase Src is equipped with an N-terminal myristoyl chain and a cluster of basic amino acids for the stable membrane association of the protein. We used 2H NMR spectroscopy to investigate the structure and dynamics of the myristoyl chain of myr-Src(2–19), and compare them with the hydrocarbon chains of the surrounding phospholipids in bilayers of varying surface potentials and chain lengths. The myristoyl chain of Src was well inserted in all bilayers investigated. In zwitterionic 1,2-dimyristoyl-sn-glycero-3-phosphocholine membranes, the myristoyl chain of Src was significantly longer and appears “stiffer” than the phospholipid chains. This can be explained by an equilibrium between the attraction attributable to the insertion of the myristoyl chain and the Born repulsion. In a 1,2-dimyristoyl-sn-glycero-3-phosphocholine/1,2-dimyristoyl-sn-glycero-3-[phospho-L-serine] membrane, where attractive electrostatic interactions come into play, the differences between the peptide and the phospholipid chain lengths were attenuated, and the molecular dynamics of all lipid chains were similar. In a much thicker 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/1,2-dipalmitoyl-sn-glycero-3-[phospho-L-serine]/cholesterol membrane, the length of the myristoyl chain of Src was elongated nearly to its maximum, and the order parameters of the Src chain were comparable to those of the surrounding membrane. PMID:19413971

  10. 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.

  11. Insights on the Interactions of Synthetic Amphipathic Peptides with Model Membranes as Revealed by 31P and 2H Solid-State NMR and Infrared Spectroscopies

    PubMed Central

    Ouellet, Marise; Bernard, Geneviève; Voyer, Normand; Auger, Michèle

    2006-01-01

    We studied the interaction between synthetic amphipathic peptides and model membranes by solid-state NMR and infrared spectroscopies. Peptides with 14 and 21 amino acids composed of leucines and phenylalanines modified by the addition of crown ethers were synthesized. The 14-mer and 21-mer peptides both possess a helical amphipathic structure. To shed light on their membrane interaction, 31P and 2H solid-state NMR experiments were performed on both peptides in interaction with dimyristoylphosphatidylcholine vesicles in the absence and presence of cholesterol, dimyristoylphosphatidylglycerol vesicles, and oriented bicelles. 31P NMR experiments on multilamellar vesicles reveal that the dynamics and/or orientation of the polar headgroups are weakly yet markedly affected by the presence of the peptides, whereas 31P NMR experiments on bicelles indicate no significant changes in the morphology and orientation of the bicelles. On the other hand, 2H NMR experiments on vesicles reveal that the acyl chain order is affected differently depending on the membrane lipidic composition and on the peptide hydrophobic length. Finally, infrared spectroscopy was used to study the interfacial region of the bilayer. Based on these studies, mechanisms of membrane perturbation are proposed for the 14-mer and 21-mer peptides in interaction with model membranes depending on the bilayer composition and peptide length. PMID:16533836

  12. Characterization of the myristoyl lipid modification of membrane-bound GCAP-2 by 2H solid-state NMR spectroscopy.

    PubMed

    Vogel, Alexander; Schröder, Thomas; Lange, Christian; Huster, Daniel

    2007-12-01

    Guanylate cyclase-activating protein-2 (GCAP-2) is a retinal Ca2+ sensor protein. It is responsible for the regulation of both isoforms of the transmembrane photoreceptor guanylate cyclase, a key enzyme of vertebrate phototransduction. GCAP-2 is N-terminally myristoylated and full activation of its target proteins requires the presence of this lipid modification. The structural role of the myristoyl moiety in the interaction of GCAP-2 with the guanylate cyclases and the lipid membrane is currently not well understood. In the present work, we studied the binding of Ca2+-free myristoylated and non-myristoylated GCAP-2 to phospholipid vesicles consisting of dimyristoylphosphatidylcholine or of a lipid mixture resembling the physiological membrane composition by a biochemical binding assay and 2H solid-state NMR. The NMR results clearly demonstrate the full-length insertion of the aliphatic chain of the myristoyl group into the membrane. Very similar geometrical parameters were determined from the 2H NMR spectra of the myristoyl group of GCAP-2 and the acyl chains of the host membranes, respectively. The myristoyl chain shows a moderate mobility within the lipid environment, comparable to the acyl chains of the host membrane lipids. This is in marked contrast to the behavior of other lipid-modified model proteins. Strikingly, the contribution of the myristoyl group to the free energy of membrane binding of GCAP-2 is only on the order of -0.5 kJ/mol, and the electrostatic contribution is slightly unfavorable, which implies that the main driving forces for membrane localization arises through other, mainly hydrophobic, protein side chain-lipid interactions. These results suggest a role of the myristoyl group in the direct interaction of GCAP-2 with its target proteins, the retinal guanylate cyclases.

  13. 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

    2016-06-07

    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.

  14. 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).

  15. Probing the role of the ceramide acyl chain length and sphingosine unsaturation in model skin barrier lipid mixtures by (2)H solid-state NMR spectroscopy.

    PubMed

    Stahlberg, Sören; Školová, Barbora; Madhu, Perunthiruthy K; Vogel, Alexander; Vávrová, Kateřina; Huster, Daniel

    2015-05-05

    We investigated equimolar mixtures of ceramides with lignoceric acid and cholesterol as models for the human stratum corneum by differential scanning calorimetry and (2)H solid-state NMR spectroscopy. Our reference system consisted of lignoceroyl sphingosine (Cer[NS24]), which represents one of the ceramides in the human stratum corneum. Furthermore, the effect of ceramide acyl chain truncation to 16 carbons as in Cer[NS16] and the loss of the C4 trans double bond as in dihydroceramide Cer[NDS24] were studied. Fully relaxed (2)H NMR spectra were acquired for each deuterated component of each mixture separately, allowing the quantitative determination of the individual lipid phases. At skin temperature, the reference system containing Cer[NS24] is characterized by large portions of each component of the mixture in a crystalline phase, which largely restricts the permeability of the skin lipid barrier. The loss of the C4 trans double bond in Cer[NDS24] leads to the replacement of more than 25% of the crystalline phase by an isotropic phase of the dihydroceramide that shows the importance of dihydroceramide desaturation in the formation of the skin lipid barrier. The truncated Cer[NS16] is mostly found in the gel phase at skin temperature, which may explain its negative effect on the transepidermal water loss in atopic dermatitis patients. These significant alterations in the phase behavior of all lipids are further reflected at elevated temperatures. The molecular insights of our study may help us to understand the importance of the structural parameters of ceramides in healthy and compromised skin barriers.

  16. 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.

  17. Molecular dynamics of poly(L-lactide) biopolymer studied by wide-line solid-state 1H and 2H NMR spectroscopy.

    PubMed

    Nozirov, Farhod; Nazirov, Alovidin; Jurga, Stefan; Fu, Riqiang

    2006-06-01

    The molecular dynamics of poly(L-lactide) (PLLA) biopolymer was characterized through analyses of 1H and 2H NMR line-shapes and spin-lattice relaxation times at different temperatures. At low temperatures (e.g. 90 K), the methyl group rotation is dominant leading to a significant reduction in the proton second moment. Fast methyl group reorientation occurs at ca. 130 K. In additional to the fast methyl group rotation, hydroxyl groups start to reorient as the temperature increases further, eventually leading to the breakdown of the segments of the biopolymer chains above its glass transition temperature Tg of 323 K. The analyses of the 2H NMR line-shapes indicate that both the methyl and hydroxyl reorientations can be described by the so-called cone model, in which the former has three equilibrium positions with theta(C-D) = 70.5 degrees and phi = 120 degrees while the latter one exhibits two equilibrium positions with theta(O-D) = 78 degrees and phi = 180 degrees .

  18. A study of dipolar interactions and dynamic processes of water molecules in tendon by 1H and 2H homonuclear and heteronuclear multiple-quantum-filtered NMR spectroscopy.

    PubMed

    Eliav, U; Navon, G

    1999-04-01

    The effect of proton exchange on the measurement of 1H-1H, 1H-2H, and 2H-2H residual dipolar interactions in water molecules in bovine Achilles tendons was investigated using double-quantum-filtered (DQF) NMR and new pulse sequences based on heteronuclear and homonuclear multiple-quantum filtering (MQF). Derivation of theoretical expressions for these techniques allowed evaluation of the 1H-1H and 1H-2H residual dipolar interactions and the proton exchange rate at a temperature of 24 degrees C and above, where no dipolar splitting is evident. The values obtained for these parameters at 24 degrees C were 300 and 50 Hz and 3000 s-1, respectively. The results for the residual dipolar interactions were verified by repeating the above measurements at a temperature of 1.5 degrees C, where the spectra of the H2O molecules were well resolved, so that the 1H-1H dipolar interaction could be determined directly from the observed splitting. Analysis of the MQF experiments at 1.5 degrees C, where the proton exchange was in the intermediate regime for the 1H-2H dipolar interaction, confirmed the result obtained at 24 degrees C for this interaction. A strong dependence of the intensities of the MQF signals on the proton exchange rate, in the intermediate and the fast exchange regimes, was observed and theoretically interpreted. This leads to the conclusion that the MQF techniques are mostly useful for tissues where the residual dipolar interaction is not significantly smaller than the proton exchange rate. Dependence of the relaxation times and signal intensities of the MQF experiments on the orientation of the tendon with respect to the magnetic field was observed and analyzed. One of the results of the theoretical analysis is that, in the fast exchange regime, the signal decay rates in the MQF experiments as well as in the spin echo or CPMG pulse sequences (T2) depend on the orientation as the square of the second-rank Legendre polynomial.

  19. Ethanol perturbs lipid organization in models of stratum corneum membranes: An investigation combining differential scanning calorimetry, infrared and (2)H NMR spectroscopy.

    PubMed

    Kwak, Sungjong; Brief, Elana; Langlais, Denis; Kitson, Neil; Lafleur, Michel; Thewalt, Jenifer

    2012-05-01

    Ethanol is used in a variety of topical products. It is known to enhance the permeability of the skin by altering the ability of the stratum corneum (SC) intercellular membranes to form an effective barrier. In addition, ethanol and other alcohols are key components of antiseptic gels currently used for hand wash. Using infrared and deuterium NMR spectroscopy as well as calorimetry, we have investigated the effect of ethanol on a model membrane composed of lipids representing the three classes of SC lipids, an equimolar mixture of N-palmitoylsphingosine (ceramide), palmitic acid and cholesterol. Ethanol is found to influence the membrane in a dose dependent manner, disrupting packing and increasing lipid motion at low concentrations and selectively extracting lipids at moderate concentrations.

  20. Shiftless NMR Spectroscopy

    PubMed Central

    Wu, Chin H.; Opella, Stanley J.

    2013-01-01

    The acquisition and analysis of high resolution one- and two- dimensional solid-state NMR spectra without chemical shift frequencies are described. Many variations of Shiftless NMR spectroscopy are feasible. A two-dimensional experiment that correlates 13Cα-15N dipole-dipole and 1H-13Cα dipole-dipole couplings in single crystal and powder samples of the model peptide, 13Cα, 15N-acetylleucine, is demonstrated. In addition to the resolution of resonances from individual sites in a single crystal sample, the bond lengths and angles are characterized by the two-dimensional powder pattern obtained from a polycrystalline sample. PMID:18266429

  1. 2H NMR studies of glycerol dynamics in protein matrices

    NASA Astrophysics Data System (ADS)

    Herbers, C. R.; Sauer, D.; Vogel, M.

    2012-03-01

    We use 2H NMR spectroscopy to investigate the rotational motion of glycerol molecules in matrices provided by the connective tissue proteins elastin and collagen. Analyzing spin-lattice relaxation, line-shape properties, and stimulated-echo decays, we determine the rates and geometries of the motion as a function of temperature and composition. It is found that embedding glycerol in an elastin matrix leads to a mild slowdown of glycerol reorientation at low temperatures and glycerol concentrations, while the effect vanishes at ambient temperatures or high solvent content. Furthermore, it is observed that the nonexponential character of the rotational correlation functions is much more prominent in the elastin matrix than in the bulk liquid. Results from spin-lattice relaxation and line shape measurements indicate that, in the mixed systems, the strong nonexponentiality is in large part due to the existence of distributions of correlation times, which are broader on the long-time flank and, hence, more symmetric than in the neat system. Stimulated-echo analysis of slow glycerol dynamics reveals that, when elastin is added, the mechanism for the reorientation crosses over from small-angle jump dynamics to large-angle jump dynamics and the geometry of the motion changes from isotropic to anisotropic. The results are discussed against the background of present and previous findings for glycerol and water dynamics in various protein matrices and compared with observations for other dynamically highly asymmetric mixtures so as to ascertain in which way the viscous freezing of a fast component in the matrix of a slow component differs from the glassy slowdown in neat supercooled liquids.

  2. 2H NMR studies of glycerol dynamics in protein matrices.

    PubMed

    Herbers, C R; Sauer, D; Vogel, M

    2012-03-28

    We use (2)H NMR spectroscopy to investigate the rotational motion of glycerol molecules in matrices provided by the connective tissue proteins elastin and collagen. Analyzing spin-lattice relaxation, line-shape properties, and stimulated-echo decays, we determine the rates and geometries of the motion as a function of temperature and composition. It is found that embedding glycerol in an elastin matrix leads to a mild slowdown of glycerol reorientation at low temperatures and glycerol concentrations, while the effect vanishes at ambient temperatures or high solvent content. Furthermore, it is observed that the nonexponential character of the rotational correlation functions is much more prominent in the elastin matrix than in the bulk liquid. Results from spin-lattice relaxation and line shape measurements indicate that, in the mixed systems, the strong nonexponentiality is in large part due to the existence of distributions of correlation times, which are broader on the long-time flank and, hence, more symmetric than in the neat system. Stimulated-echo analysis of slow glycerol dynamics reveals that, when elastin is added, the mechanism for the reorientation crosses over from small-angle jump dynamics to large-angle jump dynamics and the geometry of the motion changes from isotropic to anisotropic. The results are discussed against the background of present and previous findings for glycerol and water dynamics in various protein matrices and compared with observations for other dynamically highly asymmetric mixtures so as to ascertain in which way the viscous freezing of a fast component in the matrix of a slow component differs from the glassy slowdown in neat supercooled liquids.

  3. 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.

  4. Kinetic isotope effects and tunneling in cyclic double and triple proton transfer between acetic acid and methanol in tetrahydrofuran studied by dynamic /sup 1/H and /sup 2/H NMR spectroscopy

    SciTech Connect

    Gerritzen, D.; Limbach, H.H.

    1984-02-22

    Previous studies of proton exchange and hydrogen bonding between acetic acid (A) and methanol (B) in tetrahydrofuran-d/sub 8/ have been extended to the study of the primary kinetic H/D isotope effects of the exchange. For this purpose a new combination of dynamic /sup 1/H and /sup 2/H NMR spectroscopy has been used to perform an ''NMR proton inventory''. The following rate law was obtained at deuterium fractions D=0 and D=1 of the exchangeable protonic sites: NU=k/sup LL/ C/sub A/C/sub B/+k/sub LLL/C/sub A//sup 2/C/sub B/ (L=H,D). This was attributed to a superposition of cyclic double and triple proton exchange involving one and two molecules of acetic acid and one molecule of methanol. Additional experiments were carried out at intermediate deuterium fractions. Thus, the kinetic HH/HD/DD and HHH/HHD/DDD isotope effects of the exchange as a function of the temperature was measured successfully. This has been achieved for the first time for well-defined intermolecular multiple-proton-transfer reactions. The possibility of determining the number of protons transferred in a chemical reaction by performing an NMR proton inventory is discussed. The rule of the geometric mean (RGM) is fulfilled for the kinetic isotope effects of the LLL process, which are almost independent of temperature within the margin of error. By contrast, the RGM is not fullfilled for the LL process, and the kinetic isotope effects depend strongly on the temperature. The energies of activation and frequency factors fit Bell's criteria of tunneling. The kinetic results are in good agreement with predictions of transition-state theory but can be explained by an intermolecular tunneling model. The results are proof that acetic acid and methanol form cyclic hydrogen-bonded 1:1 and 2:1 complexes which have very low concentration in tetrahydrofuran.

  5. Thz Spectroscopy of D_2H^+

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Pearson, John; Amano, Takayoshi

    2015-06-01

    Pure rotational transitions of D_2H^+ observed by high-resolution spectroscopy have been limited so far to the J = 110-101 transition at 691.7 GHz, J=220-211 at 1.370 THz, and J=111-000 at 1.477 THz. As this ion is a light asymmetric-top molecule, spectroscopic characterization and prediction of other rotational transition frequencies are not straightforward. In this presentation, we extended the measurements up to 2 THz by using the JPL frequency multiplier chains, and observed three new THz lines and re-measured the three known transitions. D_2H^+ was generated in an extended negative glow discharge cell cooled to liquid nitrogen temperature. Six rotational transition frequencies together with the combination differences derived from three fundamental bands were subject to least square analysis to determine the molecular constants. New THz measurements are definitely useful for better characterization of spectroscopic properties. The improved molecular constants provide better predictions of other unobserved rotational transitions. T. Hirao and T. Amano, Ap. J.,597, L85 (2003) K. M. Evenson et al cited by O. L. Polyansky and A. R. W. McKellar, J. Chem. Phys., 92, 4039 (1990) O. Asvany et al, Phys. Rev. Lett., 100, 233004 (2008)

  6. Probing Perturbation of Bovine Lung Surfactant Extracts by Albumin using DSC and 2H-NMR

    PubMed Central

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

    2006-01-01

    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-d62) had been added, were studied using deuterium-NMR spectroscopy (2H-NMR) and differential scanning calorimetry (DSC). DSC scans of BLES showed a broad gel to liquid-crystalline phase transition between 10–35°C, with a temperature of maximum heat flow (Tmax) around 27°C. Incorporation of the DPPC-d62 into BLES-reconstituted vesicles did not alter the Tmax or the transition range as observed by DSC or the hydrocarbon stretching modes of the lipids observed using infrared spectroscopy. Transition enthalpy change and 2H-NMR order parameter profiles were not significantly altered by addition of calcium and cholesterol to BLES. 2H-NMR spectra of the DPPC-d62 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-d62 environment by rapid diffusion between small domains on a short timescale relative to that characteristic of the 2H-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 2H-NMR spectral features characteristic of coexisting fluid and ordered phases. This suggests the persistence of phase-separated domains throughout the transition regime (5–35°C) of BLES with albumin. The study suggests albumin can cause segregation of protein bound-lipid domains in surfactant at NMR timescales (10−5 s

  7. THz spectroscopy of D2H+

    NASA Astrophysics Data System (ADS)

    Yu, S.; Pearson, J. C.; Amano, T.; Matsushima, F.

    2017-01-01

    We extended the measurements of the rotational transitions of D2H+ up to 3 THz by using the JPL frequency multiplier chains and a TuFIR system at Toyama. D2H+ was generated in an extended negative glow discharge cell cooled to liquid nitrogen temperature. We observed five new THz lines. All the available rotational transition frequencies together with the combination differences derived from the three fundamental bands were subject to least square analysis to determine the molecular constants. New THz measurements are definitely useful for better characterization of spectroscopic properties. The improved molecular constants provide better predictions of other unobserved rotational transitions.

  8. Measurements of intracellular volumes by 59Co and 2H/1H NMR and their physiological applications.

    PubMed

    Askenasy, Nadir; Navon, Gil

    2005-04-01

    Determination of the intracellular water volumes using NMR spectroscopy was performed using the NMR-visible nuclei: 59Co and 2H or 1H. Accurate measurement of intracellular water in cell suspensions and perfused organs is an important physiological parameter in the context of electrolyte homeostasis and energy metabolism, in particular when these parameters are monitored by non-invasive NMR spectroscopy. Furthermore, repeated or continuous monitoring of intracellular water provided significant insights into the physiology of cardiac muscle and sarcolemmal membrane permeability and integrity.

  9. 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…

  10. 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…

  11. Simultaneously cycled NMR spectroscopy.

    PubMed

    Parish, David M; Szyperski, Thomas

    2008-04-09

    Simultaneously cycled (SC) NMR was introduced and exemplified by implementing a set of 2-D [1H,1H] SC exclusive COSY (E.COSY) NMR experiments, that is, rf pulse flip-angle cycled (SFC), rf pulse phase cycled (SPC), and pulsed field gradient (PFG) strength cycled (SGC) E.COSY. Spatially selective 1H rf pulses were applied as composite pulses such that all steps of the respective cycles were affected simultaneously in different slices of the sample. This increased the data acquisition speed for an n-step cycle n-fold. A high intrinsic sensitivity was achieved by defining the cycles in a manner that the receiver phase remains constant for all steps of the cycle. Then, the signal resulting from applying the cycle corresponded to the sum of the signals from all steps of the cycle. Hence, the detected free induction decay did not have to be separated into the contributions arising from different slices, and read-out PFGs, which not only greatly reduce sensitivity but also negatively impact lineshapes in the direct dimension, were avoided. The current implementation of SFC E.COSY reached approximately 65% of the intrinsic sensitivity of the conventional phase cycled congener, making this experiment highly attractive whenever conventional data acquisition is sampling limited. Highly resolved SC E.COSY yielding accurate 3J-coupling values was recorded for the 416 Da plant alkaloid tomatidine within 80 min, that is, 12 times faster than with conventional phase cycled E.COSY. SC NMR is applicable for a large variety of NMR experiments and thus promises to be a valuable addition to the arsenal of approaches for tackling the NMR sampling problem to avoid sampling limited data acquisition.

  12. Retinal Conformation and Dynamics in Activation of Rhodopsin Illuminated by Solid-state 2H NMR Spectroscopy†

    PubMed Central

    Brown, Michael F.; Martínez-Mayorga, Karina; Nakanishi, Koji; Salgado, Gilmar F. J.; Struts, Andrey V.

    2010-01-01

    Solid-state NMR spectroscopy gives a powerful avenue for investigating G protein-coupled receptors and other integral membrane proteins in a native-like environment. This article reviews the use of solid-state 2H NMR to study the retinal cofactor of rhodopsin in the dark state as well as the meta I and meta II photointermediates. Site-specific 2H NMR labels have been introduced into three regions (methyl groups) of retinal that are crucially important for the photochemical function of rhodopsin. Despite its phenomenal stability 2H NMR spectroscopy indicates retinal undergoes rapid fluctuations within the protein binding cavity. The spectral lineshapes reveal the methyl groups spin rapidly about their three-fold (C3) axes with an order parameter for the off-axial motion of SC3 ≈ 0.9. For the dark state, the 2H NMR structure of 11-cis-retinal manifests torsional twisting of both the polyene chain and the β-ionone ring due to steric interactions of the ligand and the protein. Retinal is accommodated within the rhodopsin binding pocket with a negative pretwist about the C11=C12 double bond. Conformational distortion explains its rapid photochemistry and reveals the trajectory of the 11-cis to trans isomerization. In addition, 2H NMR has been applied to study the retinylidene dynamics in the dark and light-activated states. Upon isomerization there are drastic changes in the mobility of all three methyl groups. The relaxation data support an activation mechanism whereby the β-ionone ring of retinal stays in nearly the same environment, without a large displacement of the ligand. Interactions of the β-ionone ring and the retinylidene Schiff base with the protein transmit the force of the retinal isomerization. Solid-state 2H NMR thus provides information about the flow of energy that triggers changes in hydrogen-bonding networks and helix movements in the activation mechanism of the photoreceptor. PMID:19267870

  13. 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. Copyright © 2016 Elsevier Inc. All rights reserved.

  14. "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)

  15. "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)

  16. 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.

  17. Vibrational Spectroscopy of He-O_2H^+ and O_2H^+

    NASA Astrophysics Data System (ADS)

    Kohguchi, Hiroshi; Yamada, Koichi MT; Jusko, Pavol; Schlemmer, Stephan; Asvany, Oskar

    2017-06-01

    The elusive protonated oxygen, O_2H^+, has been characterized by vibrational action spectroscopy in a cryogenic 22-pole ion trap. On the one hand, the vibrational bands of the tagged He-O_2H^+ have been investigated, using a table-top OPO system for the known OH-stretch^a, whereas the FELIX^b light source has been used to detect the hitherto unknown low-frequency O-O-H bend and O-O stretch. On the other hand, the untagged O_2H^+ has been detected for the first time by high-resolution rovibrational spectroscopy via its ν_1 OH-stretch motion. 38 ro-vibrational fine structure transitions with partly resolved hyperfine satellites were measured (56 resolved lines in total). Spectroscopic parameters were determined by a fit to an asymmetric rotor model with a ^3A'' electronic ground state. The band center is at 3016.73 \\wn, which is in good agreement with experimental^a and ab initio^{c,d} predictions. Based on the spectroscopic parameters, the rotational spectrum is predicted, but not detected yet. ^a S. A. Nizkorodov et al., Chem. Phys. Lett., 278, 26, 1997 ^b D. Oepts et al., Infrared Phys. Technol., 36, 297, 1995 ^c S. L. W. Weaver et al., Astrophys. J., 697, 601, 2009 ^d X. Huang and T. J. Lee, J. Chem. Phys., 129, 044312, 2008

  18. Solution structure of (Cr/sup III/(L)(O-O))/sup n/ complexes (L = nitrilotriacetate, N,N-. beta. -alaninediacetate; O-O = malonate, oxalate, acetylacetonate, 2H/sub 2/O) and characterization of (Cr(nta)(OH))/sub 2//sup 2 -/ by deuteron NMR spectroscopy

    SciTech Connect

    Koine, N.; Bianchini, R.J.; Legg, J.I.

    1986-07-30

    The complexes (Cr/sup III/(L)(O-O))/sup n/ (L = nitrilotriacetate (nta), N,N-..beta..-alaninediacetate (..beta..-alada); O-O = malonate (mal), oxalate (ox), acetylacetonate (acac), 2H/sub 2/O) have been synthesized, chromatographically purified, and characterized by deuteron NMR, infrared and electronic absorption spectroscopy. The two possible isomers, symmetrical (sym) and unsymmetrical (unsym), for (Cr(..beta..-alada)(acac))/sup -/ and (Cr(..beta..-alada)(mal))/sup 2 -/ were isolated, but only the unsym isomer for (Cr(..beta..-alada)(ox))/sup 2 -/ was found. The starting materials for the synthesis of these complexes, (Cr(nta)(OH))/sub 2//sup 2 -/ and unsym-(Cr(..beta..-alada)(H/sub 2/O)/sub 2/), were also characterized. Both species were shown to be in equilibrium with the corresponding monomer and dimer, respectively. The chemistry of the various species investigated differs, to some extent, from what has been previously reported. The recent availability of a readily applicable NMR technique for the study of Cr(III) chemistry (/sup 2/H NMR) has greatly facilitated these studies.

  19. Hyperpolarized 131Xe NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    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.

  20. 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

  1. Infrared spectroscopy of V2+(H2O) complexes

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, B.; Duncan, M. A.

    2012-03-01

    Doubly charged vanadium-water complexes are produced by laser vaporization in a pulsed supersonic expansion. Size-selected ions are studied with infrared photodissociation spectroscopy in the O-H stretch region using argon complex predissociation. Density functional theory calculations provide structures and vibrational spectra of these ions. The O-H stretches of V2+(H2O) appear at lower frequencies than those of the free water molecule or V+(H2O). The symmetric stretch is more intense than the asymmetric stretch in both V+(H2O) and V2+(H2O) complexes. Spectra of V2+(H2O)Arn (n = 2-7) show that the coordination of the V2+ is filled with six ligands, i.e. one water and five argon atoms.

  2. Structural water in carbonated hydroxylapatite and fluorapatite: confirmation by solid state (2)H NMR.

    PubMed

    Yoder, Claude H; Pasteris, Jill D; Worcester, Kimberly N; Schermerhorn, Demetra V

    2012-01-01

    Water is well recognized as an important component in bone, typically regarded as a constituent of collagen, a pore-filling fluid in bone, and an adsorbed species on the surface of bone crystallites. The possible siting and role of water within the structure of the apatite crystallites have not been fully explored. In our experiments, carbonated hydroxyl- and fluorapatites were prepared in D(2)O and characterized by elemental analysis, thermal gravimetric analysis, powder X-ray diffraction, and infrared and Raman spectroscopy. Two hydroxylapatites and two fluorapatites, with widely different amounts of carbonate were analyzed by solid state (2)H NMR spectroscopy using the quadrupole echo pulse sequence, and each spectrum showed one single line as well as a low-intensity powder pattern. The relaxation time of 7.1 ms for 5.9 wt% carbonated hydroxylapatite indicates that the single line is likely due to rapid, high-symmetry jumps in translationally rigid D(2)O molecules, indicative of structural incorporation within the lattice. Discrimination between structurally incorporated and adsorbed water is enhanced by the rapid exchange of surface D(2)O with atmospheric H(2)O. Moreover, a (2)H resonance was observed for samples dried under a variety of conditions, including in vacuo heating to 150°C. In contrast, a sample heated to 500°C produced no deuterium resonance, indicating that structural water had been released by that temperature. We propose that water is located in the c-axis channels. Because structural water is observed even for apatites with very low carbonate content, some of the water molecules must lie between the monovalent ions.

  3. Microcoil NMR spectroscopy: a novel tool for biological high throughput NMR spectroscopy.

    PubMed

    Hopson, Russell E; Peti, Wolfgang

    2008-01-01

    Microcoil NMR spectroscopy is based on the increase of coil sensitivity for smaller coil diameters (approximately 1/d). Microcoil NMR probes deliver a remarkable mass-based sensitivity increase (8- to 12-fold) when compared with commonly used 5-mm NMR probes. Although microcoil NMR probes are a well established analytical tool for small molecule liquid-state NMR spectroscopy, after spectroscopy only recently have microcoil NMR probes become available for biomolecular NMR spectroscopy. This chapter highlights differences between commercially available microcoil NMR probes suitable for biomolecular NMR spectroscopy. Furthermore, it provides practical guidance for the use of microcoil probes and shows direct applications for structural biology and structural genomics, such as optimal target screening and structure determination, among others.

  4. 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…

  5. 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…

  6. 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.

  7. 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.

  8. 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

  9. Folding of the KIX domain: characterization of the equilibrium analog of a folding intermediate using 15N/13C relaxation dispersion and fast 1H/2H amide exchange NMR spectroscopy.

    PubMed

    Schanda, Paul; Brutscher, Bernhard; Konrat, Robert; Tollinger, Martin

    2008-07-18

    The KIX domain of the transcription co-activator CBP is a three-helix bundle protein that folds via rapid accumulation of an intermediate state, followed by a slower folding phase. Recent NMR relaxation dispersion studies revealed the presence of a low-populated (excited) state of KIX that exists in equilibrium with the natively folded form under non-denaturing conditions, and likely represents the equilibrium analog of the folding intermediate. Here, we combine amide hydrogen/deuterium exchange measurements using rapid NMR data acquisition techniques with backbone (15)N and (13)C relaxation dispersion experiments to further investigate the equilibrium folding of the KIX domain. Residual structure within the folding intermediate is detected by both methods, and their combination enables reliable quantification of the amount of persistent residual structure. Three well-defined folding subunits are found, which display variable stability and correspond closely to the individual helices in the native state. While two of the three helices (alpha(2) and alpha(3)) are partially formed in the folding intermediate (to approximately 50% and approximately 80%, respectively, at 20 degrees C), the third helix is disordered. The observed helical content within the excited state exceeds the helical propensities predicted for the corresponding peptide regions, suggesting that the two helices are weakly mutually stabilized, while methyl (13)C relaxation dispersion data indicate that a defined packing arrangement is unlikely. Temperature-dependent experiments reveal that the largest enthalpy and entropy changes along the folding reaction occur during the final transition from the intermediate to the native state. Our experimental data are consistent with a folding mechanism where helices alpha(2) and alpha(3) form rapidly, although to different extents, while helix alpha(1) consolidates only as folding proceeds to complete the native state-structure.

  10. Solid-state NMR spectroscopy of proteins.

    PubMed

    Müller, Henrik; Etzkorn, Manuel; Heise, Henrike

    2013-01-01

    Solid-state NMR spectroscopy proved to be a versatile tool for characterization of structure and dynamics of complex biochemical systems. In particular, magic angle spinning (MAS) solid-state NMR came to maturity for application towards structural elucidation of biological macromolecules. Current challenges in applying solid-state NMR as well as progress achieved recently will be discussed in the following chapter focusing on conceptual aspects important for structural elucidation of proteins.

  11. A 2H and 14N NMR study of molecular motion in polycrystalline choline salts

    NASA Astrophysics Data System (ADS)

    Pratum, T. K.; Klein, M. P.

    2H and 14N solid-state NMR spectra of polycrystalline choline chloride, bromide, and iodide indicate that 180° cation flipping motion occurs in all three salts. From the temperature dependence of these spectra, the activation energy for this motion is determined to be 5.8 ± I kcal/mol in the iodide salt and 11 ± 1.5 kcal/mol in the chloride salt. In the bromide salt the reorientation rate is too rapid to be determined from the NMR lineshape, but the temperature dependence of the 2H quadrupole coupling parameters is indicative of a second-order phase transition at approximately 273 K. The spectral distortions in the 14N NMR spectra of the chloride and iodide salts are adequately explained using the motional model derived from the 2H NMR results, while the 14N spectra of the bromide salt show no motional effects. The axis of reorientation which is inferred from these data appears to be consistent with that indicated in a previous X-ray crystallographic study.

  12. (2)H NMR study of the water dynamics in hydrated myoglobin.

    PubMed

    Lusceac, S A; Vogel, M

    2010-08-12

    We use 1D and 2D (2)H NMR to study the temperature-dependent mechanism for the rotational motion of myoglobin hydration water. The results show that isotropic and anisotropic water reorientation is observed at high and low temperatures, respectively, with a continuous crossover in the temperature range of 200-230 K. The anisotropic low-temperature motion has a large angular amplitude. It exhibits a broad distribution of geometries and pronounced dynamical heterogeneities, which are long-lived at least at T approximately 176 K. Exploiting the possibility to vary the angular resolution of (2)H NMR experiments, we find that the large solid angle accessible to low-temperature water reorientation is explored via large-angle rather than small-angle elementary steps; i.e., the rotational motion is not diffusive. Quantitative analysis of the NMR data using random-walk simulations implies that the number of sites involved in the observed water reorientation decreases from an infinite number during essentially isotropic motion above 230 K to a few, possibly two, below 165 K. Although the changes in the mechanism for water rotational motion may be accompanied by a mild change in the temperature dependence of the rotational correlation times, the (2)H NMR data provide strong evidence against the existence of a sharp fragile-to-strong transition at about 225 K. The present results are discussed in the context of previous experimental findings for hydrated proteins.

  13. Vibrational and Rotational Spectroscopy of CD_2H^+

    NASA Astrophysics Data System (ADS)

    Asvany, Oskar; Jusko, Pavol; Brünken, Sandra; Schlemmer, Stephan

    2016-06-01

    The lowest rotational levels (J=0-5) of the CD_2H^+ ground state have been probed by high-resolution rovibrational and pure rotational spectroscopy in a cryogenic 22-pole ion trap. For this, the ν_1 rovibrational band has been revisited, detecting 107 transitions, among which 35 are new. The use of a frequency comb system allowed to measure the rovibrational transitions with high precision and accuracy, typically better than 1 MHz. The high precision has been confirmed by comparing combination differences in the ground and vibrationally excited state. For the ground state, this allowed for equally precise predictions of pure rotational transitions, 24 of which have been measured directly by a novel IR - mm-wave double resonance method. M.-F. Jagod et al, J. Molec. Spectrosc. 153, 666, 1992 S. Gartner et al, J. Phys. Chem. A 117, 9975, 2013

  14. Photodissociation spectroscopy of Ca+(C2H4)

    NASA Astrophysics Data System (ADS)

    Holmes, J. H.; Kleiber, P. D.; Olsgaard, D. A.; Yang, K.-H.

    2000-04-01

    We have studied Ca+(C2H4) by photodissociation spectroscopy in a reflectron time-of-flight mass spectrometer over the spectral range 440-790 nm. Ca+ is the only photofragment observed. We find four absorption bands of the complex and assign them to metal-centered transitions correlating with excitation of Ca+(3d and 4p). Spectral assignment is supported by ab initio electronic structure calculations of the complex and isotope substitution experiments. Calculations find a weakly bound ground state equilibrium structure with C2V π-bonding geometry and a dissociation energy of De″=0.506 eV. Theoretical and experimental results show the 4pπ(2 2B2 & 2 2B1) excited states to be relatively weakly bound at long range. Spectral analysis gives vibrational constants for the Ca+--C2H4 intermolecular a1-stretch in the 1 2A1, 2 2B1, and 2 2B2 states, and for the CH2-CH2 a1-wag and the HCH a1-bend in 2 2B2. The results offer an interesting comparison with previous studies of similar weakly bound bimolecular complexes of light metal ions with alkene or alkane hydrocarbons.

  15. 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.

  16. 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.

  17. Quantifying unfrozen water in frozen soil by high-field 2H NMR.

    PubMed

    Sparrman, Tobias; Oquist, Mats; Klemedtsson, Leif; Schleucher, Jürgen; Nilsson, Mats

    2004-10-15

    To understand wintertime controls of biogeochemical processes in high latitude soils it is essential to distinguish between direct temperature effects and the effects of changes in water availability mediated by freezing. Efforts to separate these controls are hampered by a lack of adequate methods to determine the proportion of unfrozen water. In this study we present a high-field 2H2O NMR method for quantifying unfrozen water content in frozen soil. The experimental material consisted of the humic layer of a boreal spruce forest soil mixed with varying proportions of quartz sand and humidified with deuterium-enriched water. The relative standard deviation of unfrozen water content (measured as NMR signal integral) was less than 2% for repeated measurements on a given sample and 3.5% among all samples, based on a total of 16 measurements. As compared to 1H NMR, this 2H NMR method was found to be superior for several reasons: it is less sensitive to field inhomogeneity and paramagnetic impurities, it gives a bigger line shape difference between the ice and liquid signal, it shows a sharper response to water fusion, and it excludes the possibility of hydrogen in the organic material interfering with the measurement.

  18. Flexibility of Ras Lipid Modifications Studied by 2H Solid-State NMR and Molecular Dynamics Simulations

    PubMed Central

    Vogel, Alexander; Tan, Kui-Thong; Waldmann, Herbert; Feller, Scott E.; Brown, Michael F.; Huster, Daniel

    2007-01-01

    Human posttranslationally modified N-ras oncogenes are known to be implicated in numerous human cancers. Here, we applied a combination of experimental and computational techniques to determine structural and dynamical details of the lipid chain modifications of an N-ras heptapeptide in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes. Experimentally, 2H NMR spectroscopy was used to study oriented membranes that incorporated ras heptapeptides with two covalently attached perdeuterated hexadecyl chains. Atomistic molecular dynamics simulations of the same system were carried out over 100 ns including 60 DMPC and 4 ras molecules. Several structural and dynamical experimental parameters could be directly compared to the simulation. Experimental and simulated 2H NMR order parameters for the methylene groups of the ras lipid chains exhibited a systematic difference attributable to the absence of collective motions in the simulation and to geometrical effects. In contrast, experimental 2H NMR spin-lattice relaxation rates for Zeeman order were well reproduced in the simulation. The lack of slower collective motions in the simulation did not appreciably influence the relaxation rates at a Larmor frequency of 115.1 MHz. The experimental angular dependence of the 2H NMR relaxation rates with respect to the external magnetic field was also relatively well simulated. These relaxation rates showed a weak angular dependence, suggesting that the lipid modifications of ras are very flexible and highly mobile in agreement with the low order parameters. To quantify these results, the angular dependence of the 2H relaxation rates was calculated by an analytical model considering both molecular and collective motions. Peptide dynamics in the membrane could be modeled by an anisotropic diffusion tensor with principal values of D‖ = 2.1 × 109 s−1 and D⊥ = 4.5 × 105 s−1. A viscoelastic fitting parameter describing the membrane elasticity, viscosity, and temperature

  19. Docosahexaenoic Acid Enhances Segregation of Lipids between Raft and Nonraft Domains: 2H-NMR Study

    PubMed Central

    Soni, Smita P.; LoCascio, Daniel S.; Liu, Yidong; Williams, Justin A.; Bittman, Robert; Stillwell, William; Wassall, Stephen R.

    2008-01-01

    Solid-state 2H-NMR of [2H31]-N-palmitoylsphingomyelin ([2H31]16:0SM, PSM*), supplemented by differential scanning calorimetry, was used for the first time, to our knowledge, to investigate the molecular organization of the sphingolipid in 1:1:1 mol mixtures with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (16:0–18:1PE, POPE) or 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphoethanolamine (16:0–22:6PE, PDPE) and cholesterol. When compared with 2H-NMR data for analogous mixtures of [2H31]16:0–18:1PE (POPE*) or [2H31]16:0-22:6PE (PDPE*) with egg SM and cholesterol, molecular interactions of oleic acid (OA) versus docosahexaenoic acid (DHA) are distinguished, and details of membrane architecture emerge. SM-rich, characterized by higher-order, and PE-rich, characterized by lower-order, domains <20 nm in size are formed in the absence and presence of cholesterol in both OA- and DHA-containing membranes. Although acyl chain order within both domains increases on the addition of sterol to the two systems, the resultant differential in order between SM- and PE-rich domains is almost a factor of 3 greater with DHA than with OA. Our interpretation is that the aversion that cholesterol has for DHA—but not for OA—excludes the sterol from DHA-containing, PE-rich (nonraft) domains and excludes DHA from SM-rich/cholesterol-rich (raft) domains. We attribute, in part, the diverse health benefits associated with dietary consumption of DHA to an alteration in membrane domains. PMID:18339742

  20. Critical behavior of KDCO3 from 2H and 39K single crystal NMR.

    PubMed

    Odin, Christophe

    2008-01-01

    Potassium hydrogenocarbonate KDCO3 presents an order/disorder phase transition at Tc approximately 353 K. The critical behavior of this phase transition was studied by single crystal 2H and 39K NMR. The evolution of the order parameter as a function of temperature is quantified, and the critical exponent was determined, indicating a transition close to a tricritical point. The 2H Zeeman relaxation rate is strongly increased near the transition temperature. By calculating the noncritical contribution to the Zeeman relaxation rate, we show that the observed relaxation rate clearly presents a pseudo-divergent behavior near Tc, with a logarithmic singularity. The nature of the phase transition is discussed in the light of these results. Copyright (c) 2007 John Wiley & Sons, Ltd.

  1. Slow recrystallization of tripalmitoylglycerol from MCT oil observed by 2H NMR.

    PubMed

    Smith, Kevin W; Smith, Paul R; Furó, István; Pettersson, Erik Thyboll; Cain, Fred W; Favre, Loek; Talbot, Geoff

    2007-10-17

    The crystallization and recrystallization of fats have a significant impact on the properties and quality of many food products. While crystallization has been the subject of a number of studies using pure triacylglycerols (TAG), recrystallization in similarly pure systems is rarely studied. In this work, perdeuterated tripalmitoylglycerol ( (2)H-PPP) was dissolved in medium chain triacylglycerol oil (MCT) to yield a saturated solution. The solution was heated to cause partial melting of the solid and dissolution of the molten fraction of (2)H-PPP in MCT and was then cooled to the original temperature to induce recrystallization from the supersaturated solution. (2)H NMR was used to monitor the disappearance of (2)H-PPP from the solution and showed that recrystallization occurred in two steps. The first step was rapid, taking place over a few minutes, and accounted for more than two-thirds of the total recrystallization. The second step was much slower, taking place over a remarkably long timescale of hours to days. It is proposed that dissolution occurs from all parts of the crystals, leaving an etched and pitted surface. The first step of crystallization is the infilling of these pits, while the second step is the continued growth on the smoothed crystal faces.

  2. 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.

  3. 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.

  4. Metabolism of excess methionine in the liver of intact rat: an in vivo /sup 2/H NMR study

    SciTech Connect

    London, R.E.; Gabel, S.A.; Funk, A.

    1987-11-03

    L-Methionine is the most toxic amino acid if supplied in excess, and the metabolic basis for this toxicity has been extensively studied, with varying conclusions. It is demonstrated here that in vivo /sup 2/H NMR spectroscopy provides a useful approach to the study of the hepatic metabolism of methionine in the anesthetized rat. Resonances corresponding to administered L-(methyl-/sup 2/H/sub 3/)methionine, and to the transmethylation product sarcosine, are observed during the first 10-min period after an intravenous injection of the labeled methionine, and the time dependence has been followed for a period of 5 h. A third resonance, assigned to the N-trimethyl groups of carnitine, phosphorylcholine, and other metabolites, becomes observable several hours after administration of the deuteriated methionine. In addition, there is a small increase in the intensity of the HDO resonance over the period of the study, which is interpreted to reflect the ultimate oxidation of the labeled sarcosine methyl group via mitochondrial sarcosine dehydrogenase. Additional small /sup 2/H resonances assigned to N/sup 1/-methylhistidine and creatine could be observed in perchloric acid extracts of the livers of rats treated with the deuteriated methionine. Inhibition of the flux through the transmethylation pathway is observed in the rat pretreated with the S-ethyl analogue of methionine, ethionine. These data provide strong support for the importance of glycine transmethylation in the catabolism of excess methionine.

  5. Mobility of core water in Bacillus subtilis spores by 2H NMR.

    PubMed

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

    2013-11-05

    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. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

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

    PubMed Central

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

    2013-01-01

    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 2H magnetic relaxation dispersion to selectively monitor water mobility in the core of Bacillus subtilis spores in the presence and absence of core Mn2+ ions. We also report and analyze the solid-state 2H 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. PMID:24209846

  7. An introduction to biological NMR spectroscopy.

    PubMed

    Marion, Dominique

    2013-11-01

    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).

  8. 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

  9. 2Q NMR of 2H2O ordering at solid interfaces

    NASA Astrophysics Data System (ADS)

    Krivokhizhina, Tatiana V.; Wittebort, R. J.

    2014-06-01

    Solvent ordering at an interface can be studied by multiple-quantum NMR. Quantitative studies of 2H2O ordering require clean double-quantum (2Q) filtration and an analysis of 2Q buildup curves that accounts for relaxation and, if randomly oriented samples are used, the distribution of residual couplings. A pulse sequence with absorption mode detection is extended for separating coherences by order and measuring relaxation times such as the 2Q filtered T2. Coherence separation is used to verify 2Q filtration and the 2Q filtered T2 is required to extract the coupling from the 2Q buildup curve when it is unresolved. With our analysis, the coupling extracted from the buildup curve in 2H2O hydrated collagen was equivalent to the resolved coupling measured in the usual 1D experiment and the 2Q to 1Q signal ratio was in accord with theory. Application to buildup curves from 2H2O hydrated elastin, which has an unresolved coupling, revealed a large increase in the 2Q signal upon mechanical stretch that is due to an increase in the ordered water fraction while changes in the residual coupling and T2 are small.

  10. Photoprotein Aequorin Structure Determination by NMR Spectroscopy

    DTIC Science & Technology

    1993-07-09

    AD-A267 066 July 9, 1993 Final Rept. 15 Apr. 1992-31 Dec. 1992 Photoprotein Aequorin Structure Determination by NMR Spectroscopy Grant # N00014-92-J...specific assignments of proteins using homo- and heteronuclear 2D-NMR. Assignments were made for approximately 95% of the 1H and 15N atoms of Bacillus... structure of r-aequorin is included. 028 93-1584993 7 . -,I m!,,•slil Aequorin, bioluminescence, nuclear magnetic reburndie, 3D structure . Unclassified

  11. 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.

  12. A method for direct in vivo measurement of drug concentrations from a single 2H NMR spectrum.

    PubMed

    Evelhoch, J L; McCoy, C L; Giri, B P

    1989-03-01

    The use of 2H-labeled drugs provides a measure of drug concentration in situ directly from a single 2H NMR spectrum obtained with any antenna by correcting only for differential saturation effects. The limit of detection for a drug labeled with three equivalent deuterons is roughly 0.5 mM.

  13. Analysis of C2H4 in C2H6 and C2H5D with VUV absorption spectroscopy and a method to remove C2H4 from C2H6 and C2H5D.

    PubMed

    Lu, Hsiao-Chi; Chen, Hong-Kai; Cheng, Bing-Ming

    2004-10-01

    The photoabsorption cross section of C2H4 was measured in the spectral region 107-183 nm and those of C2H6 and C2H5D were accurately determined in the spectral region 107-162 nm using radiation from a synchrotron as source of VUV light. Typically, C2H4 present as a minor impurity in samples of C2H6 and C2H5D distorted the absorption cross section in curves of C2H6 and C2H5D in the onset region. We completely eliminated C2H4 from C2H6 and C2H5D using adsorption on activated Pd/charcoal at 195 K. By this means, we detected no C2H4 in samples of C2H6 and C2H5D according to their absorption spectra. The detection limit of C2H4 in C2H6 and C2H5D is less than 0.03 ppm with VUV absorption spectroscopy.

  14. Chain orientation in natural rubber, Part II: 2H-NMR study.

    PubMed

    Rault, J; Marchal, J; Judeinstein, P; Albouy, P A

    2006-11-01

    Stress-induced crystallisation (SIC) and stress-induced melting (SIM) in natural rubbers (NR), unfilled and filled with carbon black (CB) have been studied by (2)H-NMR measurements. Various materials have been swollen with small amount (< 2%) of deuterated alkane chains. The orientation of the amorphous chains, then the local deformation of the amorphous chains during deformation cycles and during stress relaxation, permits to clarify the SIC and SIM processes during hardening and recovery. By mechanical, WAXS and NMR measurements one determines the same critical draw ratio for appearance lambda(A) and disappearance lambda(E) of the crystallites. It is demonstrated that the hysteresis observed by the different techniques (stress sigma, crystallinity chi, NMR splitting Deltanu) are due to the supercooling effect ( lambda(A) > lambda(E), at constant temperature). During hardening at constant strain rate it is found that the local draw ratio remains constant and equal to lambda(A), whereas the crystallinity increases linearly with the macroscopic draw ratio lambda. The hardening sigma approximately (lambda - lambda(A))(2) is then interpreted as a reinforcement effect due to the crystallites, which act as new crosslinks. This confirms the prediction of Flory. In filled rubber the same effects are observed, and the stress amplification factor is determined as a function of the CB content. It is found that the fillers act as nucleation centres for the NR crystallites. The reinforcement of such materials is due principally to this nucleation effect and to the presence of a super network formed by both the NR crystallites and the CB fillers.

  15. Critical behaviour in DOPC/DPPC/cholesterol mixtures: static (2)H NMR line shapes near the critical point.

    PubMed

    Davis, James H; Schmidt, Miranda L

    2014-05-06

    Static (2)H NMR spectroscopy is used to study the critical behavior of mixtures of 1,2-dioleoyl-phosphatidylcholine/1,2-dipalmitoyl-phosphatidylcholine (DPPC)/cholesterol in molar proportion 37.5:37.5:25 using either chain perdeuterated DPPC-d62 or chain methyl deuterated DPPC-d6. The temperature dependence of the first moment of the (2)H spectrum of the sample made with DPPC-d62 and of the quadrupolar splittings of the chain-methyl-labeled DPPC-d6 sample are directly related to the temperature dependence of the critical order parameter η, which scales as [Formula: see text] near the critical temperature. Analysis of the data reveals that for the chain perdeuterated sample, the value of Tc is 301.51 ± 0.1 K, and that of the critical exponent, βc = 0.391 ± 0.02. The line shape analysis of the methyl labeled (d6) sample gives Tc = 303.74 ± 0.07 K and βc = 0.338 ± 0.009. These values obtained for βc are in good agreement with the predictions of a three-dimensional Ising model. The difference in critical temperature between the two samples having nominally the same molar composition arises because of the lowering of the phase transition temperature that occurs due to the perdeuteration of the DPPC.

  16. Near-Infrared Spectroscopy of Ethynyl Radical, C2H

    NASA Astrophysics Data System (ADS)

    Le, Anh T.; Hall, Gregory; Sears, Trevor

    2016-06-01

    The ethynyl radical, C_2H, is a reactive intermediate important in various combustion processes and also widely observed in the interstellar medium. In spite of extensive previous spectroscopic studies, the characterization of the near infrared transitions from the tilde{X}2Σ+ state to the mixed vibrational overtone and tilde{A}2Π states is incomplete. A strong band of C_2H at 7064 cm-1 was first observed in a neon matrix and assigned as the tilde{A}2Π(002)1 - tilde{X}2Σ+ transition by Forney et al. Subsequent theoretical work of Tarroni and Carter attributed the strong absorptions in this region to transitions terminating in two upper states, each a mixture of vibrationally excited tilde{X} states and different zero-order tilde{A}-state bending levels: a 2Σ+ symmetry combination of tilde{X}(0,20,3) and tilde{A}(0,3,0)0κ and a 2Π symmetry combination of tilde{X}(0,31,3) and tilde{A}(0,0,2)1. Transitions to them from the zero point level of the tilde{X} state are calculated to differ in energy by less than 10 cm-1 and to be within a factor of two in intensity. Diode laser transient absorption was used to record Doppler-limited spectra between 7020 and 7130 cm-1, using 193 nm photolysis of CF_3C_2H as a source of C_2H. Two interleaved, rotationally resolved bands were observed, consistent with a 2Σ - 2Σ transition at 7088 cm-1 and a 2Π - 2Σ transition at 7108 cm-1, in good accord with the Tarroni and Carter calculation. Progress on the assignment and fitting of the spectra will be reported. Acknowledgements: Work at Brookhaven National Laboratory was carried out under Contract No. DE-SC0012704 with the U.S. Department of Energy, Office of Science, and supported by its Division of Chemical Sciences, Geosciences, and Biosciences. D. Forney, M.E. Jacox, and W.E. Thompson, J. Mol. Spectrosc. 170, 178 (1995). R. Tarroni and S. Carter, Mol. Phys. 102, 2167 (2004)

  17. Limits of metastability in amorphous ices: 2H-NMR relaxation.

    PubMed

    Löw, Florian; Amann-Winkel, Katrin; Geil, Burkhard; Loerting, Thomas; Wittich, Carolin; Fujara, Franz

    2013-01-14

    The high-frequency reorientation dynamics of O-(2)H bonds is investigated in various amorphous ices including eHDA (expanded high density amorphous ice), LDA-II (low density amorphous ice II) and HGW (hyperquenched glassy water) using (2)H-NMR spin-lattice relaxation as a local probe. Both low density forms, HGW and LDA-II, show similar spin-lattice relaxation but differ in the thermal stability with respect to the transition into crystalline cubic ice I(c). HGW already transforms slightly above 135 K whereas LDA-II crystallizes at 150 K. eHDA is distinguishable from other high density amorphous ices in its thermal stability and spin-lattice relaxation. Its relaxation times are much larger compared to those of VHDA (very high density amorphous ice) and uHDA (unrelaxed high density amorphous ice). eHDA does not show annealing effects, transforms sharply into LDA-II above 123 K and provides higher thermal stability as compared to other high density forms.

  18. Influence of the penetration enhancer isopropyl myristate on stratum corneum lipid model membranes revealed by neutron diffraction and (2)H NMR experiments.

    PubMed

    Eichner, Adina; Stahlberg, Sören; Sonnenberger, Stefan; Lange, Stefan; Dobner, Bodo; Ostermann, Andreas; Schrader, Tobias E; Hauß, Thomas; Schroeter, Annett; Huster, Daniel; Neubert, Reinhard H H

    2017-05-01

    The stratum corneum (SC) provides the main barrier properties in native skin. The barrier function is attributed to the intercellular lipids, forming continuous multilamellar membranes. In this study, SC lipid membranes in model ratios were enriched with deuterated lipids in order to investigate structural and dynamical properties by neutron diffraction and (2)H solid-state NMR spectroscopy. Further, the effect of the penetration enhancer isopropyl myristate (IPM) on the structure of a well-known SC lipid model membrane containing synthetically derived methyl-branched ceramide [EOS], ceramide [AP], behenic acid and cholesterol (23/10/33/33wt%) was investigated. IPM supported the formation of a single short-periodicity phase (SPP), in which we determined the molecular organization of CER[AP] and CER[EOS]-br for the first time. Furthermore, the thermotropic phase behavior of the lipid system was analyzed by additional neutron diffraction studies as well as by (2)H solid-state NMR spectroscopy, covering temperatures of 32°C (physiological skin temperature), 50°C, and 70°C with a subsequent cooldown back to skin temperature. Both techniques revealed a phase transition and a hysteresis effect. During the cooldown, Bragg peaks corresponding to a long-periodicity phase (LPP) appeared. Additionally, (2)H NMR revealed that the IPM molecules are isotopic mobile at all temperatures.

  19. Visualizing transient dark states by NMR spectroscopy.

    PubMed

    Anthis, Nicholas J; Clore, G Marius

    2015-02-01

    Myriad biological processes proceed through states that defy characterization by conventional atomic-resolution structural biological methods. The invisibility of these 'dark' states can arise from their transient nature, low equilibrium population, large molecular weight, and/or heterogeneity. Although they are invisible, these dark states underlie a range of processes, acting as encounter complexes between proteins and as intermediates in protein folding and aggregation. New methods have made these states accessible to high-resolution analysis by nuclear magnetic resonance (NMR) spectroscopy, as long as the dark state is in dynamic equilibrium with an NMR-visible species. These methods - paramagnetic NMR, relaxation dispersion, saturation transfer, lifetime line broadening, and hydrogen exchange - allow the exploration of otherwise invisible states in exchange with a visible species over a range of timescales, each taking advantage of some unique property of the dark state to amplify its effect on a particular NMR observable. In this review, we introduce these methods and explore two specific techniques - paramagnetic relaxation enhancement and dark state exchange saturation transfer - in greater detail.

  20. 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.

  1. Reorientational dynamics and solid-phase transformation of ammonium dicyanamide into dicyandiamide: a (2)H solid-state NMR study.

    PubMed

    Lotsch, Bettina V; Schnick, Wolfgang; Naumann, Ernst; Senker, Jürgen

    2007-10-11

    The reorientational dynamics of ammonium dicyanamide ND4[N(C[triple bond]N)2] and the kinetics as well as the mechanism of the solid-state isomerization reaction from ammonium dicyanamide into dicyandiamide (N[triple bond]C-N==C(NH2)2) was studied by means of 2H and 14N solid-state NMR spectroscopy in a temperature range between 38 and 390 K. Whereas in previous investigations the mechanism of the solid-state transformation was investigated by means of vibrational and magic angle spinning solid-state NMR spectroscopy as well as neutron diffraction, we here present a comprehensive 2H study of the ammonium ion dynamics prior to and during the course of the reaction, thereby highlighting possible cross correlations between dynamics and reactivity involving the ammonium ion. The ND4+ group was found to undergo thermally activated random jumps in a tetrahedral potential, which is increasingly distorted with increasing temperature, giving rise to an asymmetrically compressed or elongated tetrahedron with deviations from the tetrahedral angle of up to 6 degrees . The correlation time follows an Arrhenius law with an activation energy of Ea = 25.8(2) kJ mol(-1) and an attempt frequency of tau0(-1) = 440(80) THz. The spin-lattice relaxation times were fitted according to a simple Bloembergen-Purcell-Pound type model with a T1 minimum of 4 ms at 230 K. Temperature-dependent librational amplitudes were extracted by line-shape simulations between 38 and 390 K and contrasted with those obtained by neutron diffraction, their values ranging between 5 and 28 degrees . The onset and progress of the solid-phase transformation were followed in situ at temperatures above 372 K and could be classified as a strongly temperature-dependent, heterogeneous two-step reaction proceeding with rapid evolution of ammonia and comparatively slow subsequent reintegration into the solid. On the microscopic level, this correlates with a rapid proton transfer -- possibly triggered by a coupling

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

    PubMed

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

    2015-03-09

    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.

  3. Interactions of saturated diacylglycerols with phosphatidylcholine bilayers: A sup 2 H NMR study

    SciTech Connect

    de Boeck, H.; Zidovetzki, R. )

    1992-01-21

    The interactions of a series of saturated diacylglycerols (DAGs) with fatty acid side chain lengths of 6-14 carbons with multilamellar phospholipid bilayers consisting either of dipalmitoylphosphatidylcholine (DPPC) or of a mixture of DPPC and bovine liver phosphatidylcholine (BL-PC) extracts were studied by {sup 2}H NMR spectrometry. The authors found that the perturbation induced by the DAGs into the bilayer structure strongly depends on the length of the DAG fatty acid side chain. Shorter chain 1,2-sn-dihexanoylglycerol and, to a larger degree, 1,2-sn-dioctanoylglycerol (diC{sub 8}) induce transverse perturbation of the bilayer structure: the order parameters of the phospholipid side chains are increased by the intercalating DAG molecules in the region adjacent to the phospholipid headgroups and decreased toward the terminal methyls, corresponding to the bilayer interior. Each of the DAGs studied induces a decrease in the area per phospholipid molecule, and a corresponding increase in the lateral surface pressure of the bilayers. Since numerous biochemical studies consistently report that diC{sub 8} is the most effective of saturated DAGs in activating protein kinase C, they may conclude that the activation of this enzyme is associated with a transverse perturbation of the lipid bilayer structure and a decreased ordering in the interior of the bilayer membrane, and is less affected by the lateral phase separation of the lipids into regions of different fluidities, as induced by the longer chain DAGs.

  4. Analysis of dissolved C2H2 in transformer oils using laser Raman spectroscopy.

    PubMed

    Somekawa, Toshihiro; Kasaoka, Makoto; Kawachi, Fumio; Nagano, Yoshitomo; Fujita, Masayuki; Izawa, Yasukazu

    2013-04-01

    We have developed a laser Raman spectroscopy technique for assessing the working conditions of transformers by measuring dissolved C2H2 gas concentrations present in transformer oils. A frequency doubled Q-switched Nd:YAG laser (532 nm) was used as a laser source, and Raman signals at ~1972 cm(-1) originating from C2H2 gas dissolved in oil were detected. The results show that laser Raman spectroscopy is a useful alternative method for detecting transformer faults.

  5. 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…

  6. 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…

  7. Investigation of Rhodopsin Dynamics in its Signaling State by Solid-State Deuterium NMR Spectroscopy

    PubMed Central

    Struts, Andrey V.; Chawla, Udeep; Perera, Suchithranga M.D.C.; Brown, Michael F.

    2017-01-01

    Site-directed deuterium NMR spectroscopy is a valuable tool to study the structural dynamics of biomolecules in cases where solution NMR is inapplicable. Solid-state 2H NMR spectral studies of aligned membrane samples of rhodopsin with selectively labeled retinal provide information on structural changes of the chromophore in different protein states. In addition, solid-state 2H NMR relaxation time measurements allow one to study the dynamics of the ligand during the transition from the inactive to the active state. Here we describe the methodological aspects of solid-state 2H NMR spectroscopy for functional studies of rhodopsin, with an emphasis on the dynamics of the retinal cofactor. We provide complete protocols for the preparation of NMR samples of rhodopsin with 11-cis-retinal selectively deuterated at the methyl groups in aligned membranes. In addition, we review optimized conditions for trapping the rhodopsin photointermediates; and lastly we address the challenging problem of trapping the signaling state of rhodopsin in aligned membrane films. PMID:25697522

  8. 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.

  9. Use of rotary echoes in 2H magic-angle spinning NMR for the quantitative study of molecular dynamics

    NASA Astrophysics Data System (ADS)

    Hogg, Naomi H. M.; Boulton, Paul J. T.; Zorin, Vadim E.; Harris, Robin K.; Hodgkinson, Paul

    2009-06-01

    The interaction of sample spinning and chemical dynamics is analysed in the context of 2H magic-angle spinning NMR. We develop previous analyses and show that a metric based on the intensity of rotational echoes allows kinetic information to be derived without the need for full modelling of the NMR response. This approach is illustrated on the conformational exchange of 1,4-dioxane included in the channel solvate hydrate formed with finasteride. An activation barrier in excellent agreement with previous experimental and theoretical estimates is obtained, without the need for modelling which would be very challenging due to the anisotropic tumbling of the solvent molecules.

  10. 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

  11. /sup 2/H-NMR studies of hypocotyl cell walls of germinating beams supplied with perdeuterated myo-inositol

    SciTech Connect

    Sasaki, K.; Wallace, J.C.; MacKay, A.L.; Balza, F.; Taylor, I.E.P.

    1987-04-01

    When myo-(2-/sup 3/H) inositol (MI) was supplied to bean seeds by imbibition, only uronic acid, arabinose and xylose residues of cell wall polysaccharides were labeled. To study the structural mobility of the uronic acid- and/or pentose-rich polysaccharides in cell wall using /sup 2/H-NMR, the authors supplied perdeuterated MI with (2-/sup 3/H) MI to germinating bean seeds. Perdeuterated MI was prepared by the /sup 1/H-/sup 2/H exchange reaction of MI in deuterium oxide with Raney nickel. During the exchange reaction, extensive epimerization occurred and at least 6 inositol epimers in addition to MI were identified in the reaction mixture of GC/MS. The perdeuterated MI was completely resolved from other inositol epimers and purified by anion-exchange chromatography using Dowex 1 (borate form) and by crystallization. The /sup 2/H-NMR analysis resolved the /sup 2/H-labeled hypocotyl cell walls into two components (rigid and mobile components). They also report the distribution of /sup 2/H and /sup 3/H from perdeuterated and (2-/sup 3/H) MI in the cell wall sugar residues.

  12. Studies of Molecular Dynamics by Solid State Deuterium NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhao, Baiyi

    The rotational dynamics of molecules in a number of solid systems were followed by variable temperature deuterium (^2H), nuclear magnetic resonance (NMR) spectroscopy via changes in the spectral lineshapes and spin-lattice relaxation times (T _1). First the pure solid trimethylamine-borane adduct, (CH_3)_3NBH_3, was studied. For a methyl deuterated sample, T _1 measurements yielded two T_1 minima, 6.9 ms and 4.3 ms corresponding to the slowing of methyl and trimethyl rotation, respectively, with decreasing temperature. Activation energies for methyl and trimethyl rotation, obtained from fitting the T _1 curve as a function of temperature, were 32.8 and 15.0 kJ/mol, respectively; simulations of the spectral lineshapes gave 26.6 and 18.9 kT/mol, respectively. Fitting of the ^2H T_1 curve for the borane deuterated sample gave a BH _3 rotation activation energy of 14.1 kT/mol and a ^2H quadrupolar coupling constant, chi, of 101 kHz. The activation energy for BH_3 rotation obtained from the spectral lineshape simulations gave 12.6 kT/mol. A series of deuterated organic chalcogen cations: (CH_3)_3S^+, (CH_3)_3Se^+ and (CH_3)_3Te^+, were ion exchanged into the cavities of sodium Mordenite LZ-M5 and the dynamics of these guests within the hydrated zeolite were followed by ^2H NMR. All three undergo isotropic motion above about -80 to -90^circC. Below this temperature two superimposed ^2H powder spectra appear; the broad lineshape is consistent with only methyl rotation in a hindered, coordinated site, and the other narrow lineshape is due to both methyl and trimethyl rotation in a less hindered, uncoordinated site. As the temperature is lowered the population of the lower energy coordinated site increases. Relative peak areas yield adsorption enthalpies of 6.7, 7.8 and 10.0 kJ/mol for (CH_3)_3S^+, (CH_3)_3Se^+ and (CH_3)_3Te^+, respectively. The series of methyl deuterated ammonium and phosphonium cations: (CH_3)NH_3^+ , (CH_3)_2NH^+ , (CH_3)_3NH^+ and (CH_3)_4P^+ , were

  13. Extending the scope of NMR spectroscopy with microcoil probes.

    PubMed

    Schroeder, Frank C; Gronquist, Matthew

    2006-11-06

    Capillary NMR (CapNMR) spectroscopy has emerged as a major breakthrough for increasing the mass-sensitivity of NMR spectroscopic analysis and enabling the combination of NMR spectroscopy with other analytical techniques. Not only is the acquisition of high-sensitivity spectra getting easier but the quality of CapNMR spectra obtained in many small-molecule applications exceeds what can be accomplished with conventional designs. This Minireview discusses current CapNMR technology and its applications for the characterization of mass-limited, small-molecule and protein samples, the rapid screening of small-molecule or protein libraries, as well as hyphenated techniques that combine CapNMR with other analytical methods.

  14. Nanostructural effects on polymer and water dynamics in cellulose biocomposites: (2)h and (13)c NMR relaxometry.

    PubMed

    Terenzi, Camilla; Prakobna, Kasinee; Berglund, Lars A; Furó, István

    2015-05-11

    Improved moisture stability is desired in cellulose biocomposites. In order to clarify nanostructural effects, a new approach is presented where water and polymer matrix mobilities are characterized separately. Nanocomposites from cellulose nanofibers (CNF) in the xyloglucan (XG) biopolymer matrix are investigated at different hydration states. Films of XG, CNF, and CNF/XG composites are subjected to detailed (2)H and (13)C NMR relaxation studies. Since the (2)H NMR signal arises from heavy water and the (13)C signal from the polysaccharides, molecular water and polymer dynamics is for the first time investigated separately. In the neat components, (2)H transverse relaxation (T2) data are consistent with water clustering at the CNF fibril surfaces, but bulk spread of moisture in XG. The new method results in a description of water interaction with the nanoscale phases. At low hydration, water molecules at the CNF/XG interface exhibit higher water mobility than in neat CNF or XG, due to locally high water concentration. At the same time, CNF-associated interphase segments of XG show slower NMR-dynamics than that in neat XG.

  15. Rotational dynamics in a crystalline molecular gyroscope by variable-temperature 13C NMR, 2H NMR, X-ray diffraction, and force field calculations.

    PubMed

    Khuong, Tinh-Alfredo V; Dang, Hung; Jarowski, Peter D; Maverick, Emily F; Garcia-Garibay, Miguel A

    2007-01-31

    A combination of solid-state 13C CPMAS NMR, 2H NMR, X-ray-determined anisotropic displacement parameters (ADPs), and molecular mechanics calculations were used to analyze the rotational dynamics of 1,4-bis[3,3,3-tris(m-methoxyphenyl)propynyl]benzene (3A), a structure that emulates a gyroscope with a p-phenylene group acting as a rotator and two m-methoxy-substituted trityl groups acting as a stator. The line shape analysis of VT 13C CPMAS and broad-band 2H NMR data were in remarkable agreement with each other, with rotational barriers of 11.3 and 11.5 kcal/mol, respectively. The barriers obtained by analysis of ADPs obtained by single-crystal X-ray diffraction at 100 and 200 K, assuming a sinusoidal potential, were 10.3 and 10.1 kcal, respectively. A similar analysis of an X-ray structure solved from data acquired at 300 K suggested a barrier of only 8.0 kcal/mol. Finally, a rotational potential calculated with a finite cluster model using molecular mechanics revealed a symmetric but nonsinusoidal potential that accounts relatively well for the X-ray-derived values and the NMR experimental results. It is speculated that the discrepancy between the barriers derived from low and high-temperature X-ray data may be due to an increase in anharmonicity, or to disorder, at the higher temperature values.

  16. Approaches to localized NMR spectroscopy in vivo

    SciTech Connect

    Garwood, M.G.

    1985-01-01

    Nuclear magnetic resonance (NMR) techniques are developed which allow spatially localized spectra to be obtained from living tissue. The localization methods are noninvasive and exploit the enhanced sensitivity afforded by surface coil probes. Techniques are investigated by computer simulation and experimentally verified by the use of phantom samples. The feasibility and utility of the techniques developed in this research are demonstrated by /sup 31/P spatial localization experiments involving various in vivo organs. In the first part of the thesis, two feasible approaches to localized spectroscopy, which were developed by other laboratories are theoretically analyzed by computer simulation. An alternative approach is provided by the rotating frame zeugmatography experiment which affords chemical-shift spectra displayed as a function of penetration distance into the sample. The further modification of the rotating frame experiment is developed, the Fourier series window (FSW) approach, which utilizes various types of window functions to afford localization in one or a few tissue regions of interest with high sensitivity. Theoretical comparisons with depth pulse methods are also included, along with methods to refine adverse off-resonance behavior.

  17. 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.

  18. 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…

  19. 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…

  20. 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.

  1. Concepts and Methods of Solid-State NMR Spectroscopy Applied to Biomembranes.

    PubMed

    Molugu, Trivikram R; Lee, Soohyun; Brown, Michael F

    2017-09-14

    Concepts of solid-state NMR spectroscopy and applications to fluid membranes are reviewed in this paper. Membrane lipids with (2)H-labeled acyl chains or polar head groups are studied using (2)H NMR to yield knowledge of their atomistic structures in relation to equilibrium properties. This review demonstrates the principles and applications of solid-state NMR by unifying dipolar and quadrupolar interactions and highlights the unique features offered by solid-state (2)H NMR with experimental illustrations. For randomly oriented multilamellar lipids or aligned membranes, solid-state (2)H NMR enables direct measurement of residual quadrupolar couplings (RQCs) due to individual C-(2)H-labeled segments. The distribution of RQC values gives nearly complete profiles of the segmental order parameters SCD((i)) as a function of acyl segment position (i). Alternatively, one can measure residual dipolar couplings (RDCs) for natural abundance lipid samples to obtain segmental SCH order parameters. A theoretical mean-torque model provides acyl-packing profiles representing the cumulative chain extension along the normal to the aqueous interface. Equilibrium structural properties of fluid bilayers and various thermodynamic quantities can then be calculated, which describe the interactions with cholesterol, detergents, peptides, and integral membrane proteins and formation of lipid rafts. One can also obtain direct information for membrane-bound peptides or proteins by measuring RDCs using magic-angle spinning (MAS) in combination with dipolar recoupling methods. Solid-state NMR methods have been extensively applied to characterize model membranes and membrane-bound peptides and proteins, giving unique information on their conformations, orientations, and interactions in the natural liquid-crystalline state.

  2. 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)

  3. 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)

  4. Rapid sample injection for hyperpolarized NMR spectroscopy.

    PubMed

    Bowen, Sean; Hilty, Christian

    2010-06-14

    Due to its ability to enhance the signal of a single NMR scan by several orders of magnitude, solid-to-liquid state dynamic nuclear polarization (DNP) appears well suited for the analysis of minimal amounts of compounds, as well as for the study of rapid chemical reactions. A key requirement in enabling the application of DNP-NMR to typical small-molecule substances encountered in chemistry and biochemistry is the ability to obtain high-resolution spectra, while at the same time minimizing the loss of polarization due to spin relaxation between the separate steps of DNP polarization and NMR measurement. Here, we present data demonstrating the capability of measuring DNP enhanced NMR spectra of compounds with comparably short relaxation times, with only minimal line broadening attributable to the sample transfer process. We discuss the performance characteristics of a sample injection apparatus specifically designed to provide high-resolution DNP-NMR spectra of small molecule compounds.

  5. 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.

  6. 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.

  7. Applications of NMR spectroscopy to systems biochemistry.

    PubMed

    Fan, Teresa W-M; Lane, Andrew N

    2016-02-01

    The past decades of advancements in NMR have made it a very powerful tool for metabolic research. Despite its limitations in sensitivity relative to mass spectrometric techniques, NMR has a number of unparalleled advantages for metabolic studies, most notably the rigor and versatility in structure elucidation, isotope-filtered selection of molecules, and analysis of positional isotopomer distributions in complex mixtures afforded by multinuclear and multidimensional experiments. In addition, NMR has the capacity for spatially selective in vivo imaging and dynamical analysis of metabolism in tissues of living organisms. In conjunction with the use of stable isotope tracers, NMR is a method of choice for exploring the dynamics and compartmentation of metabolic pathways and networks, for which our current understanding is grossly insufficient. In this review, we describe how various direct and isotope-edited 1D and 2D NMR methods can be employed to profile metabolites and their isotopomer distributions by stable isotope-resolved metabolomic (SIRM) analysis. We also highlight the importance of sample preparation methods including rapid cryoquenching, efficient extraction, and chemoselective derivatization to facilitate robust and reproducible NMR-based metabolomic analysis. We further illustrate how NMR has been applied in vitro, ex vivo, or in vivo in various stable isotope tracer-based metabolic studies, to gain systematic and novel metabolic insights in different biological systems, including human subjects. The pathway and network knowledge generated from NMR- and MS-based tracing of isotopically enriched substrates will be invaluable for directing functional analysis of other 'omics data to achieve understanding of regulation of biochemical systems, as demonstrated in a case study. Future developments in NMR technologies and reagents to enhance both detection sensitivity and resolution should further empower NMR in systems biochemical research. Copyright © 2016

  8. Fully automated high-quality NMR structure determination of small (2)H-enriched proteins.

    PubMed

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

    2010-12-01

    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 (15)N- and (13)C-edited NOESY data obtained with a perdeuterated (15)N, (13)C-enriched (13)CH(3) 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.

  9. (1)H-(2)H cross-polarization NMR in fast spinning solids by adiabatic sweeps.

    PubMed

    Wi, Sungsool; Schurko, Robert; Frydman, Lucio

    2017-03-14

    Cross-polarization (CP) experiments employing frequency-swept radiofrequency (rf) pulses have been successfully used in static spin systems for obtaining broadband signal enhancements. These experiments have been recently extended to heteronuclear I, S = spin-1/2 nuclides under magic-angle spinning (MAS), by applying adiabatic inversion pulses along the S (low-γ) channel while simultaneously applying a conventional spin-locking pulse on the I-channel ((1)H). This study explores an extension of this adiabatic frequency sweep concept to quadrupolar nuclei, focusing on CP from (1)H (I = 1/2) to (2)H spins (S = 1) undergoing fast MAS (νr = 60 kHz). A number of new features emerge, including zero- and double-quantum polarization transfer phenomena that depend on the frequency offsets of the swept pulses, the rf pulse powers, and the MAS spinning rate. An additional mechanism found operational in the (1)H-(2)H CP case that was absent in the spin-1/2 counterpart, concerns the onset of a pseudo-static zero-quantum CP mode, driven by a quadrupole-modulated rf/dipolar recoupling term arising under the action of MAS. The best CP conditions found at these fast spinning rates correspond to double-quantum transfers, involving weak (2)H rf field strengths. At these easily attainable (ca. 10 kHz) rf field conditions, adiabatic level-crossings among the {|1⟩,|0⟩,|-1⟩} mS energy levels, which are known to complicate the CP MAS of quadrupolar nuclei, are avoided. Moreover, the CP line shapes generated in this manner are very close to the ideal (2)H MAS spectral line shapes, facilitating the extraction of quadrupolar coupling parameters. All these features were corroborated with experiments on model compounds and justified using numerical simulations and average Hamiltonian theory models. Potential applications of these new phenomena, as well as extensions to higher spins S, are briefly discussed.

  10. 1H-2H cross-polarization NMR in fast spinning solids by adiabatic sweeps

    NASA Astrophysics Data System (ADS)

    Wi, Sungsool; Schurko, Robert; Frydman, Lucio

    2017-03-01

    Cross-polarization (CP) experiments employing frequency-swept radiofrequency (rf) pulses have been successfully used in static spin systems for obtaining broadband signal enhancements. These experiments have been recently extended to heteronuclear I, S = spin-1/2 nuclides under magic-angle spinning (MAS), by applying adiabatic inversion pulses along the S (low-γ) channel while simultaneously applying a conventional spin-locking pulse on the I-channel (1H). This study explores an extension of this adiabatic frequency sweep concept to quadrupolar nuclei, focusing on CP from 1H (I = 1/2) to 2H spins (S = 1) undergoing fast MAS (νr = 60 kHz). A number of new features emerge, including zero- and double-quantum polarization transfer phenomena that depend on the frequency offsets of the swept pulses, the rf pulse powers, and the MAS spinning rate. An additional mechanism found operational in the 1H-2H CP case that was absent in the spin-1/2 counterpart, concerns the onset of a pseudo-static zero-quantum CP mode, driven by a quadrupole-modulated rf/dipolar recoupling term arising under the action of MAS. The best CP conditions found at these fast spinning rates correspond to double-quantum transfers, involving weak 2H rf field strengths. At these easily attainable (ca. 10 kHz) rf field conditions, adiabatic level-crossings among the {|1 ⟩ ,|0 ⟩ ,|-1 ⟩ } mS energy levels, which are known to complicate the CP MAS of quadrupolar nuclei, are avoided. Moreover, the CP line shapes generated in this manner are very close to the ideal 2H MAS spectral line shapes, facilitating the extraction of quadrupolar coupling parameters. All these features were corroborated with experiments on model compounds and justified using numerical simulations and average Hamiltonian theory models. Potential applications of these new phenomena, as well as extensions to higher spins S, are briefly discussed.

  11. 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.

  12. Effect of Sterol Structure on Chain Ordering of an Unsaturated Phospholipid: A 2H-NMR Study of POPC/Sterol Membranes

    NASA Astrophysics Data System (ADS)

    Shaghaghi, Mehran; Thewalt, Jenifer; Zuckermann, Martin

    2012-10-01

    The physical properties of biological membranes are considerably altered by the presence of sterols. In particular, sterols help to maintain the integrity of the cell by adjusting the fluidity of the plasma membrane. Cholesterol is in addition an important component of lipid rafts which are hypothesized to compartmentalize the cell membrane surface thereby making it possible for certain proteins to function. Using 2H-NMR spectroscopy, we studied the effect of a series of different sterols on the chain ordering of POPC, an unsaturated phospholipid present in eukaryotic cell membranes. We were able to assigned specific roles to the structural differences between the sterols by comparing the manner in which they affect the average lipid chain conformation of POPC.

  13. A ferromagnetic shim insert for NMR magnets - Towards an integrated gyrotron for DNP-NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Ryan, Herbert; van Bentum, Jan; Maly, Thorsten

    2017-04-01

    In recent years high-field Dynamic Nuclear Polarization (DNP) enhanced NMR spectroscopy has gained significant interest. In high-field DNP-NMR experiments (⩾400 MHz 1H NMR, ⩾9.4 T) often a stand-alone gyrotron is used to generate high microwave/THz power to produce sufficiently high microwave induced B1e fields at the position of the NMR sample. These devices typically require a second, stand-alone superconducting magnet to operate. Here we present the design and realization of a ferroshim insert, to create two iso-centers inside a commercially available wide-bore NMR magnet. This work is part of a larger project to integrate a gyrotron into NMR magnets, effectively eliminating the need for a second, stand-alone superconducting magnet.

  14. A ferromagnetic shim insert for NMR magnets - Towards an integrated gyrotron for DNP-NMR spectroscopy.

    PubMed

    Ryan, Herbert; van Bentum, Jan; Maly, Thorsten

    2017-04-01

    In recent years high-field Dynamic Nuclear Polarization (DNP) enhanced NMR spectroscopy has gained significant interest. In high-field DNP-NMR experiments (⩾400MHz (1)H NMR, ⩾9.4T) often a stand-alone gyrotron is used to generate high microwave/THz power to produce sufficiently high microwave induced B1e fields at the position of the NMR sample. These devices typically require a second, stand-alone superconducting magnet to operate. Here we present the design and realization of a ferroshim insert, to create two iso-centers inside a commercially available wide-bore NMR magnet. This work is part of a larger project to integrate a gyrotron into NMR magnets, effectively eliminating the need for a second, stand-alone superconducting magnet. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. 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…

  16. 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…

  17. 1H and 2H NMR studies of water in work-free wheat flour doughs.

    PubMed

    d'Avignon, D A; Hung, C C; Pagel, M T; Hart, B; Bretthorst, G L; Ackerman, J J

    1991-01-01

    Proton and deuterium NMR relaxation methods were used to characterize water compartmentalization and hydration in work-free wheat flour doughs. Transverse (spin-spin) relaxation measurements define three motionally unique water compartments in the work-free dough preparations. The apparent occupancy fraction and relative mobility of each water domain are found to be functions of moisture content, temperature, and flour type. Additionally, the number of relaxation-resolved water compartments and their characteristic relaxation rate constants are found to depend critically on both moisture content and the interpulse-delay employed for the multi-pulse relaxation experiments. Under controlled experimental conditions, dynamics between the three water compartments can be observed to be consistent with the onset of flour hydration. The most notable observation during the initial period of hydration is a loss of "free" or "loosely bound" water to environments characterized by less mobility. Freezing studies show that hard wheat doughs have slightly less amorphous, non-freezable water than do soft wheat flour doughs prepared under similar conditions.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    Mills, Nancy S.

    1998-06-01

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

  20. Solid-state NMR analysis of the PGLa peptide orientation in DMPC bilayers: structural fidelity of 2H-labels versus high sensitivity of 19F-NMR.

    PubMed

    Strandberg, Erik; Wadhwani, Parvesh; Tremouilhac, Pierre; Dürr, Ulrich H N; Ulrich, Anne S

    2006-03-01

    The structure and alignment of the amphipathic alpha-helical antimicrobial peptide PGLa in a lipid membrane is determined with high accuracy by solid-state 2H-NMR. Orientational constraints are derived from a series of eight alanine-3,3,3-d3-labeled peptides, in which either a native alanine is nonperturbingly labeled (4x), or a glycine (2x) or isoleucine (2x) is selectively replaced. The concentration dependent realignment of the alpha-helix from the surface-bound "S-state" to a tilted "T-state" by 30 degrees is precisely calculated using the quadrupole splittings of the four nonperturbing labels as constraints. The remaining, potentially perturbing alanine-3,3,3-d3 labels show only minor deviations from the unperturbed peptide structure and help to single out the unique solution. Comparison with previous 19F-NMR constraints from 4-CF3-phenylglycine labels shows that the structure and orientation of the PGLa peptide is not much disturbed even by these bulky nonnatural side chains, which contain CF3 groups that offer a 20-fold better NMR sensitivity than CD3 groups.

  1. Analyzing protein-ligand interactions by dynamic NMR spectroscopy.

    PubMed

    Mittermaier, Anthony; Meneses, Erick

    2013-01-01

    Nuclear magnetic resonance (NMR) spectroscopy can provide detailed information on protein-ligand interactions that is inaccessible using other biophysical techniques. This chapter focuses on NMR-based approaches for extracting affinity and rate constants for weakly binding transient protein complexes with lifetimes of less than about a second. Several pulse sequences and analytical techniques are discussed, including line-shape simulations, spin-echo relaxation dispersion methods (CPMG), and magnetization exchange (EXSY) experiments.

  2. Near infrared second overtone cw-cavity ringdown spectroscopy of D2H+ ions

    NASA Astrophysics Data System (ADS)

    Hlavenka, P.; Plasil, R.; Bano, G.; Korolov, I.; Gerlich, D.; Ramanlal, J.; Tennyson, J.; Glosik, J.

    2006-09-01

    A study of D2H+ ions in their lowest rotational states is presented. The ions are generated in pulsed discharge in liquid N2 cooled He/Ar/H2/D2 gas mixture. Near infrared (NIR) second overtone transitions in the 6534-6536 cm-1 (1.529-1.530 [mu]m) region are used to identify the ions and determine their degree of rotational excitation. The data were obtained using NIR cavity ringdown absorption spectroscopy (NIR-CRDS). The sensitivity obtained was typically 5 x 10-9 cm-1. The measured second overtone transition frequencies are in very good agreement (better than 0.02 cm-1) with ab initio predictions. From the Doppler broadening the kinetic temperature of ions is estimated to be (220 +/- 50) K. The absolute number density of D2H+ as a function of H2/D2 mixing ratio and time is measured.

  3. NMR spectroscopy in beta cell engineering and islet transplantation.

    PubMed

    Papas, K K; Colton, C K; Gounarides, J S; Roos, E S; Jarema, M A; Shapiro, M J; Cheng, L L; Cline, G W; Shulman, G I; Wu, H; Bonner-Weir, S; Weir, G C

    2001-11-01

    Islet transplantation is a promising method for restoring normoglycemia and alleviating the long term complications of diabetes. Widespread application of islet transplantation is hindered by the limited supply of human islets and requires a large increase in the availability of suitable insulin secreting tissue as well as robust quality assessment methodologies that can ensure safety and in vivo efficacy. We explore the application of nuclear magnetic resonance (NMR) spectroscopy in two areas relevant to beta cell engineering and islet transplantation: (1) the effect of genetic alterations on glucose metabolism, and (2) quality assessment of islet preparations prior to transplantation. Results obtained utilizing a variety of NMR techniques demonstrate the following: (1) Transfection of Rat1 cells with the c-myc oncogene (which may be involved in cell proliferation and cell cycle regulation) and overexpression of Bcl-2 (which may protect cells from stresses such as hypoxia and exposure to cytokines) introduce a wide array of alterations in cellular biochemistry, including changes in anaerobic and oxidative glucose metabolism, as assessed by 13C and 31P NMR spectroscopy. (2) Overnight incubation of islets and beta cells in the bottom of centrifuge tubes filled with medium at room temperature, as is sometimes done in islet transportation, exposes them to severe oxygen limitations that may cause cell damage. Such exposure, leading to reversible or irreversible damage, can be observed with NMR-detectable markers using conventional 13C and 31P NMR spectroscopy of extracts. In addition, markers of irreversible damage (as well as markers of hypoxia) can be detected and quantified without cell extraction using high-resolution magic angle spinning 1H NMR spectroscopy. Finally, acute ischemia in a bed of perfused beta cells leads to completely reversible changes that can be followed in real time with 31P NMR spectroscopy.

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

    DOE PAGES

    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.

  5. 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.

  6. Metabolite analysis of Cannabis sativa L. by NMR spectroscopy.

    PubMed

    Flores-Sanchez, Isvett Josefina; Choi, Young Hae; Verpoorte, Robert

    2012-01-01

    NMR-based metabolomics is an analytical platform, which has been used to classify and analyze Cannabis sativa L. cell suspension cultures and plants. Diverse groups of primary and secondary metabolites were identified by comparing NMR data with reference compounds and/or by structure elucidation using ¹H-NMR, J-resolved, ¹H-¹H COSY, and ¹H-¹³C HMBC spectroscopy. The direct extraction and the extraction by indirect fractionation are two suitable methods for the C. sativa sample preparation. Quantitative analyses could be performed without requiring fractionation or isolation procedures.

  7. 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.

  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. Phase Transitions, Hydrogen Bond and Crystal Dynamics of p-Methylbenzyl Alcohol as Studied by Single Crystal X-ray Diffraction and 2H NMR

    NASA Astrophysics Data System (ADS)

    Hashimoto, Masao; Harada, Michiko; Mizunoa, Motohiro; Hamada, Masanori; Ida, Tomonori; Suhara, Masahiko

    2002-07-01

    The title compound (pMBA) was found to undergo a first-order phase transition at 211 K (Tc1). Another transition with subtle enthalpy change appeared at 172 K (Tc2). Crystal structure determinations at various temperatures revealed that the transition at Tc1 was accompanied by remarkable changes in the molecular conformations around the CH2-C and O-CH2 bonds and a reversal of the direction of the O-H O hydrogen bond. Experiments of 2H NMR were carried out on pMBA-d where the hydroxyl hydrogen of pMBA was selectively deuterated. Analyses of the 2H NMR spectra and the temperature dependence of T1 of the 2H NMR indicated occurrence of jumping motions of 2H between asymmetric potential wells at temperatures lower than Tc1

  10. sup 31 P and sup 2 H NMR studies of structure and motion in bilayers of phosphatidylcholine and phosphatidylethanolamine

    SciTech Connect

    Ghosh, R. )

    1988-10-04

    The structural and motional properties of mixed bilayers of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) have been examined by using wide-line {sup 31}P, {sup 14}N, and {sup 2H} NMR. {sup 2}H and {sup 14}N NMR data showed that in mixed bilayers containing both PC and PE the conformations of the head-group moieties are essentially identical with those observed for bilayers containing a single phospholipid species. Equimolar amounts of cholesterol induce also only a small change in head-group conformation. For all phospholipid mixtures studied, the {sup 31}P T{sub 1} relaxation was homogeneous over the whole powder spectrum and could be fitted to a single-exponential decay. The {sup 31}P vs temperature profiles were analyzed by a simple correlation model. The presence of equimolar amounts of PE containing either the same (POPE) or a different (Escherichia coli PE) fatty acid composition had essentially no effect on the rate of rotational diffusion of the phosphate groups, with the correlation time being found to be 0.68 ns at 20{degree}C. The presence of equimolar amounts of cholesterol decreased the correlation time to 0.65 ns, and also the activation energy was reduced to 22.6 kJ mol{sup {minus}1}. The authors interpret the decrease in activation energy as being due to the spacing effect of cholesterol which reduces the H-bonding interactions between head-groups, allowing them to rotate more freely. For all cases examined, the rotational diffusion of the phosphate moieties was slower than that observed for the rigid glycerol backbone of the molecule, the latter probably corresponding to overall phospholipid rotation.

  11. 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

  12. 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.

  13. Spectrum sensing of trace C(2)H(2) detection in differential optical absorption spectroscopy technique.

    PubMed

    Chen, Xi; Dong, Xiaopeng

    2014-09-10

    An improved algorithm for trace C(2)H(2) detection is presented in this paper. The trace concentration is accurately calculated by focusing on the absorption spectrum from the frequency domain perspective. The advantage of the absorption spectroscopy frequency domain algorithm is its anti-interference capability. First, the influence of the background noise on the minimum detectable concentration is greatly reduced. Second, the time-consuming preprocess of spectra calibration in the differential optical absorption spectroscopy technique is skipped. Experimental results showed the detection limit of 50 ppm is achieved at a lightpath length of 0.2 m. This algorithm can be used in real-time spectrum analysis with high accuracy.

  14. Protein folding on the ribosome studied using NMR spectroscopy

    PubMed Central

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

    2013-01-01

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

  15. 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...

  16. 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...

  17. Study of the ferroelastic phase transition in the tetraethylammonium compound [N(C{sub 2}H{sub 5}){sub 4}]{sub 2}ZnBr{sub 4} by magic-angle spinning and static NMR

    SciTech Connect

    Lim, Ae Ran E-mail: arlim@jj.ac.kr

    2016-03-15

    The ferroelastic phase transition of tetraethylammonium compound [N(C{sub 2}H{sub 5}){sub 4}]{sub 2}ZnBr{sub 4} at the phase transition temperature (T{sub C}) = 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 T{sub C} was studied in terms of the chemical shifts and the spin-lattice relaxation times T{sub 1ρ} in the rotating frame for {sup 1}H MAS NMR and {sup 13}C cross-polarization (CP)/MAS NMR. The two inequivalent ethyl groups were distinguishable in the {sup 13}C NMR spectrum, and the T{sub 1ρ} results indicate that they undergo tumbling motion above T{sub C} in a coupled manner. From the {sup 14}N NMR results, the two nitrogen nuclei in the N(C{sub 2}H{sub 5}){sub 4}{sup +} ions were distinguishable above T{sub C}, and the splitting in the spectra below T{sub C} was related to the ferroelastic domains with different orientations.

  18. 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...

  19. 13C NMR analysis of 3,6-dihydro-2H-pyrans: assignment of remote stereochemistry using axial shielding effects.

    PubMed

    Bartlett, Mark J; Northcote, Peter T; Lein, Matthias; Harvey, Joanne E

    2014-06-20

    The rational analysis of (13)C NMR axial shielding effects has enabled the assignment of remote relative stereochemistry in 3,6-oxygen-substituted 3,6-dihydro-2H-pyrans. Comparison of the (13)C NMR shifts of equivalent centers in cis- and trans-substituted 3,6-dihydro-2H-pyrans allows the relative configuration at the C3 and C6 positions to be defined in diastereoisomeric mixtures. Density functional calculations were used to validate this method and assess the conformational bias present in the ring system. Ultimately, the coupling of computational chemistry with this (13)C NMR-based method provided a reliable and convenient method for stereochemical assignment of a single diastereomer. This approach provides a facile and complementary alternative to the practices previously employed for determining the relative configuration in 3,6-dihydro-2H-pyrans.

  20. Effects of various types of molecular dynamics on 1D and 2D (2)H NMR studied by random walk simulations

    PubMed

    Vogel; Rossler

    2000-11-01

    By carrying out random walk simulations we systematically study the effects of various types of complex molecular dynamics on (2)H NMR experiments in solids. More precisely, we calculate one-dimensional (1D) (2)H NMR spectra and the results of two dimensional (2D) (2)H NMR experiments in time domain, taking into account isotropic as well as highly restricted motions which involve rotational jumps about different finite angles. Although the dynamical models are chosen to mimic the primary and secondary relaxation in supercooled liquids and glasses, we do not intend to describe experimental results quantitatively but rather to show general effects appearing for complex reorientations. We carefully investigate whether 2D (2)H NMR in time domain, which was originally designed to measure correlation times of ultraslow motions (tau >/= 1 ms), can be used to obtain shorter tau, too. It is demonstrated that an extension of the time window to tau >/= 10 &mgr;s is possible when dealing with exponential relaxation, but that it will fail if there is a distribution of correlation times G(lgtau). Vice versa, we show that 1D (2)H NMR spectra, usually recorded to look at dynamics with tau in the microsecond regime, are also applicable for studying ultraslow motions provided that the loss of correlation is achieved step by step. Therefore, it is useful to carry out 1D and 2D NMR experiments simultaneously in order to reveal the mechanism of complex molecular motions. In addition, we demonstrate that highly restricted dynamics can be clearly observed in 1D spectra and in 2D NMR in time domain if long solid-echo delays and large evolution times are applied, respectively. Finally, unexpected observations are described which appear in the latter experiment when considering very broad distributions G(lgtau). Because of these effects, time scale and geometry of a considered motion cannot be extracted from a straightforward analysis of experimental results. Copyright 2000 Academic Press.

  1. 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

    2015-08-03

    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. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Multiband Superconductivity in 2 H - NbSe2 Probed by Cryomagnetic STM Spectroscopy

    NASA Astrophysics Data System (ADS)

    Fridman, Igor; Wei, J. Y. T.; Kloc, C.; Lukic, V.; Hu, Rongwei; Petrovic, C.

    2011-03-01

    Using a novel magnetic field geometry, we study multiband pairing in single crystals of superconducting 2 H - NbSe 2 under finite superfluid momentum. Spectroscopy and conductance imaging were performed with a scanning tunneling microscope (STM) at 300 mK and in a field of up to 9 T, applied in the ab -plane. We observed multiple spectral features that evolve systematically with field, and a two-sloped zero-bias conductance that dips anomalously at 0.7 T. Our analysis yields distinct evidence for multiple gaps coming from the various Fermi-surface sheets, and has possible implications on the origin of the coexisting charge density wave order. Work supported by NSERC, CFI/OIT, CIFAR, U.S. DOE and Brookhaven Science Associates (No. DE-Ac02-98CH10886).

  3. Rotational Spectroscopy of Vibrationally Excited N_2H^+ and N_2D^+ up to 2 Thz

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Pearson, John; Drouin, Brian; Crawford, Timothy J.; Daly, Adam M.; Elliott, Ben; Amano, Takayoshi

    2015-06-01

    Terahertz absorption spectroscopy was employed to extend the measurements on the pure rotational transitions of N_2H^+, N_2D^+ and their 15N-containing isotopologues in the ground state and first excited vibrational states for the three fundamental vibrational modes. In total 88 new pure rotational transitions were observed in the range of 0.7--2.0~THz. The observed transition frequencies were fit to experimental accuracy, and the improved molecular parameters were obtained. The new measurements and predictions will support the analysis of high-resolution astronomical observations made with facilities such as SOFIA and ALMA where laboratory rest frequencies with uncertainties of 1 MHz or smaller are required for proper analysis of velocity resolved astrophysical components.

  4. High-resolution vibrational and rotational spectroscopy of CD2H+ in a cryogenic ion trap

    NASA Astrophysics Data System (ADS)

    Jusko, Pavol; Stoffels, Alexander; Thorwirth, Sven; Brünken, Sandra; Schlemmer, Stephan; Asvany, Oskar

    2017-02-01

    The low-lying rotational states (J = 0, … , 5) of CD2H+ have been probed by high-resolution ro-vibrational and pure rotational spectroscopy, applying several action spectroscopic methods in a cryogenic 22-pole ion trap. For this, the ν1 ro-vibrational band has been revisited, detecting 108 transitions, among which 36 are new. The use of a frequency comb system allowed us to measure the ro-vibrational transitions with high precision and accuracy, typically better than 1 MHz. The high precision has been confirmed by comparing equal combination differences in the ground and excited state. Moreover, precise predictions of pure rotational transitions were possible for the ground state. Twenty-five rotational transitions have been detected directly by a novel IR-mm-wave double resonance method, giving rise to highly accurate ground state spectroscopic parameters.

  5. Stacking structure of confined 1-butanol in SBA-15 investigated by solid-state NMR spectroscopy.

    PubMed

    Lin, Yun-Chih; Chou, Hung-Lung; Sarma, Loka Subramanyam; Hwang, Bing-Joe

    2009-10-12

    Understanding the complex thermodynamic behavior of confined amphiphilic molecules in biological or mesoporous hosts requires detailed knowledge of the stacking structures. Here, we present detailed solid-state NMR spectroscopic investigations on 1-butanol molecules confined in the hydrophilic mesoporous SBA-15 host. A range of NMR spectroscopic measurements comprising of (1)H spin-lattice (T(1)), spin-spin (T(2)) relaxation, (13)C cross-polarization (CP), and (1)H,(1)H two-dimensional nuclear Overhauser enhancement spectroscopy ((1)H,(1)H 2D NOESY) with the magic angle spinning (MAS) technique as well as static wide-line (2)H NMR spectra have been used to investigate the dynamics and to observe the stacking structure of confined 1-butanol in SBA-15. The results suggest that not only the molecular reorientation but also the exchange motions of confined molecules of 1-butanol are extremely restricted in the confined space of the SBA-15 pores. The dynamics of the confined molecules of 1-butanol imply that the (1)H,(1)H 2D NOESY should be an appropriate technique to observe the stacking structure of confined amphiphilc molecules. This study is the first to observe that a significant part of confined 1-butanol molecules are orientated as tilted bilayered structures on the surface of the host SBA-15 pores in a time-average state by solid-state NMR spectroscopy with the (1)H,(1)H 2D NOESY technique.

  6. A new method for the identification of the origin of natural products. Quantitative /sup 2/H NMR at the natural abundance level applied to the characterization of anetholes

    SciTech Connect

    Martin, G.J.; Martin, M.L.; Mabon, F.; Bricont, J.

    1982-05-05

    We have shown by high-field /sup 2/H NMR spectrometry at the natural abundance level that very spectacular differences exist in the interal distribution of /sup 2/H in organic molecules. This phenomenon has been exemplified in particular by the case of ethyl and vinyl derivatives. We show in this study of various anethole samples the potential of this new method as a very powerful tool for the characterization and identification of natural products from different origins.

  7. Phase transition behavior of hydrogen bonded liquid crystal (6BA)2-(BPy) x as studied by 2H NMR

    NASA Astrophysics Data System (ADS)

    Mizuno, M.; Tabota, K.; Oigawa, T.; Miyatou, T.; Kumagai, Y.; Ohashi, R.; Ida, T.

    2016-12-01

    The thermal properties and the orientational order of hydrogen-bonded liquid crystals (6BA)2-(BPy)0.4 and (6BA)2-(BPy)0.3 (6BA: 4- n-hexylbenzoicacid, BPy: 4,4'-bipyridine) were investigated by DSC and 2H NMR. On cooling, isotropic liquid - liquid crystal phase transition temperatures were T C= 409 and 405 K for (6BA)2-(BPy)0.4 and (6BA)2-(BPy)0.3, respectively. Thermal anomalies in the liquid crystal phase were observed at T LC1= 402 and T LC2= 375 K for (6BA)2-(BPy)0.4 and at T LC1= 398 and T LC2= 375 K for (6BA)2-(BPy)0.3. For (6BA)2-(BPy)0.4, only the smectic component was created above T LC1. In addition, the nematic component was created below T LC1. The nematic component gradually changed to the smectic component with decreasing temperature and only the smectic component was observed below T LC2. For (6BA)2-(BPy)0.3, only the nematic component was created above T LC2. The phase transition from the nematic phase to the smectic phase took place at around T LC2.

  8. 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.

  9. Solution NMR Spectroscopy for the Study of Enzyme Allostery

    PubMed Central

    Lisi, George P.; Loria, J. Patrick

    2016-01-01

    Allostery is a ubiquitous biological regulatory process in which distant binding sites within a protein or enzyme are functionally and thermodynamically coupled. Allosteric interactions play essential roles in many enzymological mechanisms, often facilitating formation of enzyme-substrate complexes and/or product release. Thus, elucidating the forces that drive allostery is critical to understanding the complex transformations of biomolecules. Currently, a number of models exist to describe allosteric behavior, taking into account energetics as well as conformational rearrangements and fluctuations. In the following review, we discuss the use of solution NMR techniques designed to probe allosteric mechanisms in enzymes. NMR spectroscopy is unequaled in its ability to detect structural and dynamical changes in biomolecules, and the case studies presented herein demonstrate the range of insights to be gained from this valuable method. We also provide a detailed technical discussion of several specialized NMR experiments that are ideally suited for the study of enzymatic allostery. PMID:26734986

  10. Relaxation dispersion NMR spectroscopy for the study of protein allostery.

    PubMed

    Farber, Patrick J; Mittermaier, Anthony

    2015-06-01

    Allosteric transmission of information between distant sites in biological macromolecules often involves collective transitions between active and inactive conformations. Nuclear magnetic resonance (NMR) spectroscopy can yield detailed information on these dynamics. In particular, relaxation dispersion techniques provide structural, dynamic, and mechanistic information on conformational transitions occurring on the millisecond to microsecond timescales. In this review, we provide an overview of the theory and analysis of Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion NMR experiments and briefly describe their application to the study of allosteric dynamics in the homeodomain from the PBX transcription factor (PBX-HD). CPMG NMR data show that local folding (helix/coil) transitions in one part of PBX-HD help to communicate information between two distant binding sites. Furthermore, the combination of CPMG and other spin relaxation data show that this region can also undergo local misfolding, reminiscent of conformational ensemble models of allostery.

  11. Probing the Residual Structure of the Low Populated Denatured State of ADA2h under Folding Conditions by Relaxation Dispersion Nuclear Magnetic Resonance Spectroscopy.

    PubMed

    Pustovalova, Yulia; Kukic, Predrag; Vendruscolo, Michele; Korzhnev, Dmitry M

    2015-08-04

    The structural characterization of low populated states of proteins with accuracy comparable to that achievable for native states is important for understanding the mechanisms of protein folding and function, as well as misfolding and aggregation. Because of the transient nature of these low populated states, they are seldom detected directly under conditions that favor folding. The activation domain of human procarboxypeptidase A2 (ADA2h) is an α/β-protein that forms amyloid fibrils at low pH, presumably initiated from a denatured state with a considerable amount of residual structure. Here we used Carr-Parcell-Meiboom-Gill relaxation dispersion (CPMG RD) nuclear magnetic resonance (NMR) spectroscopy to characterize the structure of the denatured state of the ADA2h I71V mutant under conditions that favor folding. Under these conditions, the lifetime of the denatured state of I71V ADA2h is on the order of milliseconds and its population is approximately several percent, which makes this mutant amenable to studies by CPMG RD methods. The nearly complete set of CPMG RD-derived backbone (15)N, (13)C, and (1)H NMR chemical shifts in the I71V ADA2h denatured state reveals that it retains a significant fraction (up to 50-60%) of nativelike α-helical structure, while the regions encompassing native β-strands are structured to a much lesser extent. The nativelike α-helical structure of the denatured state can bring together hydrophobic residues on the same sides of α-helices, making them available for intra- or intermolecular interactions. CPMG RD data analysis thus allowed a detailed structural characterization of the ADA2h denatured state under folding conditions not previously achieved for this protein.

  12. Thermal hysteresis in the backbone and side-chain dynamics of the elastin mimetic peptide [VPGVG]3 revealed by 2H NMR.

    PubMed

    Ma, Xiang; Sun, Cheng; Huang, Jiaxin; Boutis, Gregory S

    2012-01-12

    We report on experimental measurements of the backbone and side-chain dynamics of the elastin mimetic peptide [VPGVG](3) by (2)H NMR echo spectroscopy and 2D T(1)-T(2) correlation relaxometry. The T(1) and T(2) relaxation times of the Gly α-deuterons and Val α-, β-, and γ-deuterons of a hydrated sample reveal a thermal hysteresis when the temperature is raised from -10 to 45 °C and then subsequently cooled back to -10 °C. In addition, near 30 °C we observe a reduction in the slope of the T(1)(T) and T(2)(T) heating curves, indicating a structural change that appears to be correlated well to the known inverse temperature transition of this peptide. The thermal dependence of the correlation times of the Gly α-deuterons are well fit by an Arrhenius Law, from which we measured E(act) = (20.0 ± 3.1) kJ/mol when the sample is heated and E(act) = (10.9 ± 2.8) kJ/mol when cooled. Molecular dynamics simulations support the notion that the measured activation energy is determined largely by the extent of localized water, which is observed to decrease with increasing temperature from approximately 25 to 42 °C.

  13. 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. 2004 John Wiley & Sons, Ltd.

  14. Optimal control in NMR spectroscopy: numerical implementation in SIMPSON.

    PubMed

    Tosner, Zdenek; Vosegaard, Thomas; Kehlet, Cindie; Khaneja, Navin; Glaser, Steffen J; Nielsen, Niels Chr

    2009-04-01

    We present the implementation of optimal control into the open source simulation package SIMPSON for development and optimization of nuclear magnetic resonance experiments for a wide range of applications, including liquid- and solid-state NMR, magnetic resonance imaging, quantum computation, and combinations between NMR and other spectroscopies. Optimal control enables efficient optimization of NMR experiments in terms of amplitudes, phases, offsets etc. for hundreds-to-thousands of pulses to fully exploit the experimentally available high degree of freedom in pulse sequences to combat variations/limitations in experimental or spin system parameters or design experiments with specific properties typically not covered as easily by standard design procedures. This facilitates straightforward optimization of experiments under consideration of rf and static field inhomogeneities, limitations in available or desired rf field strengths (e.g., for reduction of sample heating), spread in resonance offsets or coupling parameters, variations in spin systems etc. to meet the actual experimental conditions as close as possible. The paper provides a brief account on the relevant theory and in particular the computational interface relevant for optimization of state-to-state transfer (on the density operator level) and the effective Hamiltonian on the level of propagators along with several representative examples within liquid- and solid-state NMR spectroscopy.

  15. 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.

  16. Selected topics in solution-phase biomolecular NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Kay, Lewis E.; Frydman, Lucio

    2017-05-01

    Solution bio-NMR spectroscopy continues to enjoy a preeminent role as an important tool in elucidating the structure and dynamics of a range of important biomolecules and in relating these to function. Equally impressive is how NMR continues to 'reinvent' itself through the efforts of many brilliant practitioners who ask increasingly demanding and increasingly biologically relevant questions. The ability to manipulate spin Hamiltonians - almost at will - to dissect the information of interest contributes to the success of the endeavor and ensures that the NMR technology will be well poised to contribute to as yet unknown frontiers in the future. As a tribute to the versatility of solution NMR in biomolecular studies and to the continued rapid advances in the field we present a Virtual Special Issue (VSI) that includes over 40 articles on various aspects of solution-state biomolecular NMR that have been published in the Journal of Magnetic Resonance in the past 7 years. These, in total, help celebrate the achievements of this vibrant field.

  17. Structure determination of membrane proteins by NMR spectroscopy

    PubMed Central

    Opella, S.J.; Nevzorov, A.; Mesleh, M.F.; Marassi, F.M.

    2012-01-01

    Current strategies for determining the structures of membrane proteins in lipid environments by NMR spectroscopy rely on the anisotropy of nuclear spin interactions, which are experimentally accessible through experiments performed on weakly and completely aligned samples. Importantly, the anisotropy of nuclear spin interactions results in a mapping of structure to the resonance frequencies and splittings observed in NMR spectra. Distinctive wheel-like patterns are observed in two-dimensional 1H–15N heteronuclear dipolar/15N chemical shift PISEMA (polarization inversion spin-exchange at the magic angle) spectra of helical membrane proteins in highly aligned lipid bilayer samples. One-dimensional dipolar waves are an extension of two-dimensional PISA (polarity index slant angle) wheels that map protein structures in NMR spectra of both weakly and completely aligned samples. Dipolar waves describe the periodic wave-like variations of the magnitudes of the heteronuclear dipolar couplings as a function of residue number in the absence of chemical shift effects. Since weakly aligned samples of proteins display these same effects, primarily as residual dipolar couplings, in solution NMR spectra, this represents a convergence of solid-state and solution NMR approaches to structure determination. PMID:12440700

  18. 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.

  19. 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.

  20. Study of an organogelator by diffusion-ordered NMR spectroscopy.

    PubMed

    Dama, Murali; Berger, Stefan

    2013-05-09

    The low-molecular weight organogelator 2,3-di-n-decyloxyanthracene was synthezised and dissolved in dimethyl sulfoxide. With diffusion-ordered NMR spectroscopy, the temperature dependence of the diffusion coefficients was measured and a clear hysteresis of the gelation was observed between 320 and 330 K. This hysteresis was interpreted with respect to different entanglement behavior on heating and cooling. No alignment of the gelator with respect to the magnetic field was found despite its 14 π-electrons.

  1. Detection of Apoptosis and Necrosis in Normal Human Lung Cells Using 1H NMR Spectroscopy

    NASA Astrophysics Data System (ADS)

    Shih, Chwen-Ming; Ko, Wun-Chang; Yang, Liang-Yo; Lin, Chien-Ju; Wu, Jui-Sheng; Lo, Tsui-Yun; Wang, Shwu-Huey; Chen, Chien-Tsu

    2005-05-01

    This study aimed to detect apoptosis and necrosis in MRC-5, a normal human lung cell line, by using noninvasive proton nuclear magnetic resonance (1H NMR). Live MRC-5 cells were processed first for 1H NMR spectroscopy; subsequently their types and the percentage of cell death were assessed on a flow cytometer. Cadmium (Cd) and mercury (Hg) induced apoptosis and necrosis in MRC-5 cells, respectively, as revealed by phosphatidylserine externalization on a flow cytometer. The spectral intensity ratio of methylene (CH2) resonance (at 1.3 ppm) to methyl (CH3) resonance (at 0.9 ppm) was directly proportional to the percentage of apoptosis and strongly and positively correlated with PI staining after Cd treatment (r2 = 0.9868, P < 0.01). In contrast, this ratio only increased slightly within 2-h Hg treatment, and longer Hg exposure failed to produce further increase. Following 2-h Hg exposure, the spectral intensity of choline resonance (at 3.2 ppm) was abolished, but this phenomenon was absent in Cd-induced apoptosis. These findings together demonstrate that 1H NMR is a novel tool with a quantitative potential to distinguish apoptosis from necrosis as early as the onset of cell death in normal human lung cells.

  2. High pressure-temperature Raman spectroscopy of H2-H2O clathrate.

    NASA Astrophysics Data System (ADS)

    Somayazulu, Maddury; Levedahl, Alexander; Goncharov, Alexander; Mao, Ho-Kwang; Hemley, Russell

    2007-03-01

    The melting curve of the C2 clathrate H2-H2O has been determined by in-situ Raman spectroscopy measurements in an externally heated diamond anvil cell. We have determined the melting curve to a maximum pressure of 27 GPa. These are the first measurements on the melting line in this clathrate. Depending on the stoichiometry of the starting mixture of H2 and H2O, we are able to study either a mixture of C2 and H2O or C2 and H2. In either case, we were able to pinpoint the melting of the clathrate from the measurements of the molecular stretching mode (vibron) in the clathrate. In the case of C2 + Ice VII, we observe the vibron in the clathrate at a frequency higher than in pure H2 at the same pressure. We have cross-calibrated the melting temperatures using the Stokes-anti Stokes ratio of the diamond first order and Raman active TO phonon of cubic Boron Nitride. We find that the clathrate melts well above the H2 melting at all pressures studied indicating that the stabilization of this clathrate at high pressures is indeed due to interactions between the host and guest molecules.

  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.

  4. (19) F DOSY diffusion-NMR spectroscopy of fluoropolymers.

    PubMed

    Xu, Chenglong; Wan, Yingbo; Chen, Dongxue; Gao, Chun; Yin, Hongnan; Fetherston, Daniel; Kupce, Eriks; Lopez, Gerald; Ameduri, Bruno; Twum, Eric B; Wyzgoski, Faith J; Li, Xiaohong; McCord, Elizabeth F; Rinaldi, Peter L

    2017-05-01

    A new pulse sequence for obtaining (19) F detected DOSY (diffusion ordered spectroscopy) spectra of fluorinated molecules is presented and used to study fluoropolymers based on vinylidene fluoride and chlorotrifluoroethylene. The performance of (19) F DOSY NMR experiments (and in general any type of NMR experiment) on fluoropolymers creates some unique complications that very often prevent detection of important signals. Factors that create these complications include: (1) the presence of many scalar couplings among (1) H, (19) F and (13) C; (2) the large magnitudes of many (19) F homonuclear couplings (especially (2) JFF ); (3) the large (19) F chemical shift range; and (4) the low solubility of these materials (which requires that experiments be performed at high temperatures). A systematic study of the various methods for collecting DOSY NMR data, and the adaptation of these methods to obtain (19) F detected DOSY data, has been performed using a mixture of low molecular weight, fluorinated model compounds. The best pulse sequences and optimal experimental conditions have been determined for obtaining (19) F DOSY spectra. The optimum pulse sequences for acquiring (19) F DOSY NMR data have been determined for various circumstances taking into account the spectral dispersion, number and magnitude of couplings present, and experimental temperature. Pulse sequences and experimental parameters for optimizing these experiments for the study of fluoropolymers have been studied. Copyright © 2016 John Wiley & Sons, Ltd.

  5. Improving the quality of protein structures derived by NMR spectroscopy.

    PubMed

    Spronk, Christian A E M; Linge, Jens P; Hilbers, Cornelis W; Vuister, Geerten W

    2002-03-01

    Biomolecular structures provide the basis for many studies in several research areas such as homology modelling, structure-based drug design and functional genomics. It is an important prerequisite that the structure is reliable in terms of accurate description of the experimental data, and in terms of good quality of local- and overall geometry. Recent surveys indicate that structures solved by NMR-spectroscopy normally are of lower precision than high-resolution X-ray structures. Here, we present a refinement protocol that improves the quality of protein structures determined by NMR-spectroscopy to the level of those determined by high resolution X-ray crystallography in terms of local geometry. The protocol was tested on experimental data of the proteins IL4 and Ubiquitin and on simulated data of the protein Crambin. In almost all aspects, the protocol yielded better results in terms of accuracy and precision. Independent validation of the results for Ubiquitin, using residual dipolar couplings, indicates that the ensemble of NMR structure is substantially improved by the protocol.

  6. 2H and 27Al solid-state NMR study of the local environments in Al-doped 2-line ferrihydrite, goethite, and lepidocrocite

    DOE PAGES

    Kim, Jongsik; Ilott, Andrew J.; Middlemiss, Derek S.; ...

    2015-05-13

    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 ordermore » 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. As a result, 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.« less

  7. Protein structure determination with paramagnetic solid-state NMR spectroscopy.

    PubMed

    Sengupta, Ishita; Nadaud, Philippe S; Jaroniec, Christopher P

    2013-09-17

    Many structures of the proteins and protein assemblies that play central roles in fundamental biological processes and disease pathogenesis are not readily accessible via the conventional techniques of single-crystal X-ray diffraction and solution-state nuclear magnetic resonance (NMR). On the other hand, many of these challenging biological systems are suitable targets for atomic-level structural and dynamic analysis by magic-angle spinning (MAS) solid-state NMR spectroscopy, a technique that has far less stringent limitations on the molecular size and crystalline state. Over the past decade, major advances in instrumentation and methodology have prompted rapid growth in the field of biological solid-state NMR. However, despite this progress, one challenge for the elucidation of three-dimensional (3D) protein structures via conventional MAS NMR methods is the relative lack of long-distance data. Specifically, extracting unambiguous interatomic distance restraints larger than ∼5 Å from through-space magnetic dipole-dipole couplings among the protein (1)H, (13)C, and (15)N nuclei has proven to be a considerable challenge for researchers. It is possible to circumvent this problem by extending the structural studies to include several analogs of the protein of interest, intentionally modified to contain covalently attached paramagnetic tags at selected sites. In these paramagnetic proteins, the hyperfine couplings between the nuclei and unpaired electrons can manifest themselves in NMR spectra in the form of relaxation enhancements of the nuclear spins that depend on the electron-nucleus distance. These effects can be significant for nuclei located up to ∼20 Å away from the paramagnetic center. In this Account, we discuss MAS NMR structural studies of nitroxide and EDTA-Cu(2+) labeled variants of a model 56 amino acid globular protein, B1 immunoglobulin-binding domain of protein G (GB1), in the microcrystalline solid phase. We used a set of six EDTA-Cu(2

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

    PubMed

    Konuma, Tsuyoshi; Harada, Erisa; Sugase, Kenji

    2015-12-01

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

  9. Synthesis and complete assignment of the 1H and 13C NMR spectra of 6-substituted and 2,6-disubstituted pyridazin-3(2H)-ones.

    PubMed

    Besada, Pedro; Costas, Tamara; Vila, Noemi; Chessa, Carla; Terán, Carmen

    2011-07-01

    Several pyridazin-3(2H)-one derivatives were synthesized starting from alkyl furans using oxidation with singlet oxygen to give 4-methoxy or 4-hydroxybutenolides, key intermediates of the synthetic strategy followed. For all pyridazinones reported, a complete assignment of the (1)H and (13)C NMR spectra using one- and two-dimensional NMR spectroscopic methods, which included NOE, DEPT, COSY, HSQC and HMBC experiments, was accomplished. Correlations between the chemical shifts of the heterocyclic ring atoms and substituents at N-2 and C-6 were analyzed.

  10. 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.

  11. Comparative analysis of the orientation of transmembrane peptides using solid-state (2)H- and (15)N-NMR: mobility matters.

    PubMed

    Grage, Stephan L; Strandberg, Erik; Wadhwani, Parvesh; Esteban-Martín, Santiago; Salgado, Jesús; Ulrich, Anne S

    2012-05-01

    Many solid-state nuclear magnetic resonance (NMR) approaches for membrane proteins rely on orientation-dependent parameters, from which the alignment of peptide segments in the lipid bilayer can be calculated. Molecules embedded in liquid-crystalline membranes, such as monomeric helices, are highly mobile, leading to partial averaging of the measured NMR parameters. These dynamic effects need to be taken into account to avoid misinterpretation of NMR data. Here, we compare two common NMR approaches: (2)H-NMR quadrupolar waves, and separated local field (15)N-(1)H polarization inversion spin exchange at magic angle (PISEMA) spectra, in order to identify their strengths and drawbacks for correctly determining the orientation and mobility of α-helical transmembrane peptides. We first analyzed the model peptide WLP23 in oriented dimyristoylphosphatidylcholine (DMPC) membranes and then contrasted it with published data on GWALP23 in dilauroylphosphatidylcholine (DLPC). We only obtained consistent tilt angles from the two methods when taking dynamics into account. Interestingly, the two related peptides differ fundamentally in their mobility. Although both helices adopt the same tilt in their respective bilayers (~20°), WLP23 undergoes extensive fluctuations in its azimuthal rotation angle, whereas GWALP23 is much less dynamic. Both alternative NMR methods are suitable for characterizing orientation and dynamics, yet they can be optimally used to address different aspects. PISEMA spectra immediately reveal the presence of large-amplitude rotational fluctuations, which are not directly seen by (2)H-NMR. On the other hand, PISEMA was unable to define the azimuthal rotation angle in the case of the highly dynamic WLP23, though the helix tilt could still be determined, irrespective of any dynamics parameters.

  12. 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.

  13. Hysteresis effect of ammonium and water protons by 1H MAS NMR in (NH4)2CuBr4·2H2O

    NASA Astrophysics Data System (ADS)

    Lim, Ae Ran; Cho, Jiung

    2017-10-01

    The chemical shifts, linewidths, and spin-lattice relaxation times for ammonium and water protons in (NH4)2CuBr4·2H2O were investigated by 1H magic angle spinning nuclear magnetic resonance (MAS NMR) with a focus on the roles of NH4+ and H2O at high temperatures. The changes in the temperature dependence of the data near Td (=360 K) were related to variations of the H environments; the mechanism above Td was related to hydrogen-bond transfer involving breakage of the weak part of the hydrogen bond. The hysteresis effects for the ammonium and water protons in (NH4)2CuBr4·2H2O by MAS NMR were described with respect to heating and cooling.

  14. 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.

  15. Structural characterization of (C2H2)1-6+ cluster ions by vibrational predissociation spectroscopy

    NASA Astrophysics Data System (ADS)

    Relph, Rachael A.; Bopp, Joseph C.; Roscioli, Joseph R.; Johnson, Mark A.

    2009-09-01

    Vibrational predissociation spectra are reported for the cationic acetylene clusters, (C2H2)n+, n =1-6, in the region of the C-H stretching fundamentals. For n =1 and 2, predissociation could only be observed for the Ar-tagged clusters. These were prepared by charge-transfer collisions of Ark+ with C2H2 to create C2H2+ṡArm clusters, which were then converted into larger members of the (C2H2)n+ṡAr series by sequential addition of acetylene molecules. The (C2H2)2+ṡAr spectrum indicates that this species is predominantly present as the cyclobutadiene cation. Although mobility measurements on the electron-impact-generated (C2H2)3+ ion indicated that it primarily occurs as the benzene cation, [P. O. Momoh, J. Am. Chem. Soc. 128, 12408 (2006)] photofragmentation of (C2H2)3+ṡAr in the C-H stretching region is dominated by the loss of C2H2 in addition to the weakly bound Ar atom. This suggests that the dominant n =3 species formed by sequential addition of C2H2 is based on a covalently bound C4H4+ core ion. Interestingly, the spectrum of this core C4H4+ species is different from that found for the cyclobutadiene cation, displaying instead a new band pattern that is retained in the higher (C2H2)3-6+ clusters. Multiple isomers are clearly involved, as yet another pattern of bands is recovered when the (C2H2)3+ṡAr action spectrum is recorded in the (minor) Ar loss fragmentation channel. One of these features does appear in the location of the single band characteristic of the Ar-tagged benzene cation reported earlier [Phys. Chem. Chem. Phys. 4, 24 (2002)], supporting a scenario where the benzene cation is one of the isomers present. We then compare the Ar predissociation results with (C2H2)n+ spectra obtained when the ions are prepared by electron impact ionization of neutral acetylene clusters. The photofragmentation behavior and vibrational spectra indicate that the dominant species formed in this way also occur with a covalently bound C4H4+ core. There are

  16. Effects of pH and cholesterol on DMPA membranes: a solid state 2H- and 31P-NMR study.

    PubMed Central

    Pott, T; Maillet, J C; Dufourc, E J

    1995-01-01

    The effect of pH and cholesterol on the dimyristoylphosphatidic acid (DMPA) model membrane system has been investigated by solid state 2H- and 31P-NMR. It has been shown that each of the three protonation states of the DMPA molecule corresponds to a 31P-NMR powder pattern with characteristic delta sigma values; this implies additionally that the proton exchange on the membrane surface is slow on the NMR time scale (millisecond range). Under these conditions, the 2H-labeled lipid chains sense only one magnetic environment, indicating that the three spectra detected by 31P-NMR are related to charge-dependent local dynamics or orientations of the phosphate headgroup or both. Chain ordering in the fluid phase is also found to depend weakly on the charge at the interface. In addition, it has also been found that the first pK of the DMPA membrane is modified by changes in the lipid lateral packing (gel or fluid phases or in the presence of cholesterol) in contrast to the second pK. The incorporation of 30 mol% cholesterol affects the phosphatidic acid bilayer in a way similar to what has been reported for phosphatidylcholine/cholesterol membranes, but to an extent comparable to 10-20 mol % sterol in phosphatidylcholines. However, the orientation and molecular order parameter of cholesterol in DMPA are similar to those found in dimyristoylphosphatidylcholine. PMID:8580333

  17. Effects of pH and cholesterol on DMPA membranes: a solid state 2H- and 31P-NMR study.

    PubMed

    Pott, T; Maillet, J C; Dufourc, E J

    1995-11-01

    The effect of pH and cholesterol on the dimyristoylphosphatidic acid (DMPA) model membrane system has been investigated by solid state 2H- and 31P-NMR. It has been shown that each of the three protonation states of the DMPA molecule corresponds to a 31P-NMR powder pattern with characteristic delta sigma values; this implies additionally that the proton exchange on the membrane surface is slow on the NMR time scale (millisecond range). Under these conditions, the 2H-labeled lipid chains sense only one magnetic environment, indicating that the three spectra detected by 31P-NMR are related to charge-dependent local dynamics or orientations of the phosphate headgroup or both. Chain ordering in the fluid phase is also found to depend weakly on the charge at the interface. In addition, it has also been found that the first pK of the DMPA membrane is modified by changes in the lipid lateral packing (gel or fluid phases or in the presence of cholesterol) in contrast to the second pK. The incorporation of 30 mol% cholesterol affects the phosphatidic acid bilayer in a way similar to what has been reported for phosphatidylcholine/cholesterol membranes, but to an extent comparable to 10-20 mol % sterol in phosphatidylcholines. However, the orientation and molecular order parameter of cholesterol in DMPA are similar to those found in dimyristoylphosphatidylcholine.

  18. Report on neptunium speciation by NMR and optical spectroscopies

    SciTech Connect

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

    1995-11-01

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

  19. Investigating albendazole desmotropes by solid-state NMR spectroscopy.

    PubMed

    Chattah, Ana K; Zhang, Rongchun; Mroue, Kamal H; Pfund, Laura Y; Longhi, Marcela R; Ramamoorthy, Ayyalusamy; Garnero, Claudia

    2015-03-02

    Characterization of the molecular structure and physicochemical solid-state properties of the solid forms of pharmaceutical compounds is a key requirement for successful commercialization as potential active ingredients in drug products. These properties can ultimately have a critical effect on the solubility and bioavailability of the final drug product. Here, the desmotropy of Albendazole forms I and II was investigated at the atomic level. Ultrafast magic angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) spectroscopy, together with powder X-ray diffraction, thermal analysis, and Fourier transform infrared spectroscopy, were performed on polycrystalline samples of the two solids in order to fully characterize and distinguish the two forms. High-resolution one-dimensional (1)H, (13)C, and (15)N together with two-dimensional (1)H/(1)H single quantum-single quantum, (1)H/(1)H single quantum-double quantum, and (1)H/(13)C chemical shift correlation solid-state NMR experiments under MAS conditions were extensively used to decipher the intramolecular and intermolecular hydrogen bonding interactions present in both solid forms. These experiments enabled the unequivocal identification of the tautomers of each desmotrope. Our results also revealed that both solid forms may be described as dimeric structures, with different intermolecular hydrogen bonds connecting the tautomers in each dimer.

  20. Toward high-resolution NMR spectroscopy of microscopic liquid samples

    SciTech Connect

    Butler, Mark C.; Mehta, Hardeep S.; Chen, Ying; Reardon, Patrick N.; Renslow, Ryan S.; Khbeis, Michael; Irish, Duane; Mueller, Karl T.

    2017-01-01

    A longstanding limitation of high-resolution NMR spectroscopy is the requirement for samples to have macroscopic dimensions. Commercial probes, for example, are designed for volumes of at least 5 mL, in spite of decades of work directed toward the goal of miniaturization. Progress in miniaturizing inductive detectors has been limited by a perceived need to meet two technical requirements: (1) minimal separation between the sample and the detector, which is essential for sensitivity, and (2) near-perfect magnetic-field homogeneity at the sample, which is typically needed for spectral resolution. The first of these requirements is real, but the second can be relaxed, as we demonstrate here. By using pulse sequences that yield high-resolution spectra in an inhomogeneous field, we eliminate the need for near-perfect field homogeneity and the accompanying requirement for susceptibility matching of microfabricated detector components. With this requirement removed, typical imperfections in microfabricated components can be tolerated, and detector dimensions can be matched to those of the sample, even for samples of volume << 5 uL. Pulse sequences that are robust to field inhomogeneity thus enable small-volume detection with optimal sensitivity. We illustrate the potential of this approach to miniaturization by presenting spectra acquired with a flat-wire detector that can easily be scaled to subnanoliter volumes. In particular, we report high-resolution NMR spectroscopy of an alanine sample of volume 500 pL.

  1. 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.)

  2. Hydrido-ruthenium cluster complexes as models for reactive surface hydrogen species of ruthenium nanoparticles. Solid-state 2H NMR and quantum chemical calculations.

    PubMed

    Gutmann, Torsten; Walaszek, Bernadeta; Yeping, Xu; Wächtler, Maria; del Rosal, Iker; Grünberg, Anna; Poteau, Romuald; Axet, Rosa; Lavigne, Guy; Chaudret, Bruno; Limbach, Hans-Heinrich; Buntkowsky, Gerd

    2010-08-25

    The (2)H quadrupolar interaction is a sensitive tool for the characterization of deuterium-metal binding states. In the present study, experimental solid-state (2)H MAS NMR techniques are used in the investigations of two ruthenium clusters, D(4)Ru(4)(CO)(12) (1) and D(2)Ru(6)(CO)(18) (2), which serve as model compounds for typical two-fold, three-fold, and octahedral coordination sites on metal surfaces. By line-shape analysis of the (2)H MAS NMR measurements of sample 1, a quadrupolar coupling constant of 67 +/- 1 kHz, an asymmetry parameter of 0.67 +/- 0.1, and an isotropic chemical shift of -17.4 ppm are obtained. In addition to the neutral complex, sample 2 includes two ionic clusters, identified as anionic [DRu(6)(CO)(18)](-) (2(-)) and cationic [D(3)Ru(6)(CO)(18)](+) (2(+)). By virtue of the very weak quadrupolar interaction (<2 kHz) and the strong low-field shift (+16.8 ppm) of 2(-), it is shown that the deuteron is located in the symmetry center of the octahedron spanned by the six ruthenium atoms. For the cationic 2(+), the quadrupolar interaction is similar to that of the neutral 2. Quantum chemical DFT calculations at different model structures for these ruthenium clusters were arranged in order to help in the interpretation of the experimental results. It is shown that the (2)H nuclear quadrupolar interaction is a sensitive tool for distinguishing the binding state of the deuterons to the transition metal. Combining the data from the polynuclear complexes with the data from mononuclear complexes, a molecular ruler for quadrupolar interactions is created. This ruler now permits the solid-state NMR spectroscopic characterization of deuterium adsorbed on the surfaces of catalytically active metal nanoparticles.

  3. 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

    2015-06-08

    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.

  4. 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.

  5. 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, (2)H NMR, and calorimetric study.

    PubMed

    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 (2)H 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 (N(TB)), 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 N(TB)-N phase transition, which is found to be weakly first order, but close to tricritical. Additionally broadband dielectric spectroscopy and (2)H 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 N(TB) 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. (2)H 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.

  6. 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.

  7. Self-metalation of 2H-tetraphenylporphyrin on Cu(111): an x-ray spectroscopy study.

    PubMed

    Diller, K; Klappenberger, F; Marschall, M; Hermann, K; Nefedov, A; Wöll, Ch; Barth, J V

    2012-01-07

    The bonding and the temperature-driven metalation of 2H-tetraphenylporphyrin (2H-TPP) on the Cu(111) surface under ultrahigh vacuum conditions were investigated by a combination of x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy with density functional theory calculations. Thin films were prepared by organic molecular beam epitaxy and subsequent annealing. Our systematic study provides an understanding of the changes of the spectroscopic signature during adsorption and metalation. Specifically, we achieved a detailed peak assignment of the 2H-TPP multilayer data of the C1s and the N1s region. After annealing to 420 K both XPS and NEXAFS show the signatures of a metalloporphyrin, which indicates self-metalation at the porphyrin-substrate interface, resulting in Cu-TPP. Furthermore, for 2H-TPP monolayer samples we show how the strong influence of the copper surface is reflected in the spectroscopic signatures. Adsorption results in a strongly deformed macrocycle and a quenching of the first NEXAFS resonance in the nitrogen edge suggesting electron transfer into the LUMO. For Cu-TPP the spectroscopic data indicate a reduced interaction of first-layer molecules with the substrate as demonstrated by the relaxed macrocycle geometry.

  8. Carbon-deuterium rotational-echo double-resonance NMR spectroscopy of lyophilized aspartame formulations.

    PubMed

    Luthra, Suman A; Utz, Marcel; Gorman, Eric M; Pikal, Michael J; Munson, Eric J; Lubach, Joseph W

    2012-01-01

    In this study, changes in the local conformation of aspartame were observed in annealed lyophilized glasses by monitoring changes in the distance between two labeled sites using C-(2)H rotational-echo double-resonance (REDOR) nuclear magnetic resonance (NMR) spectroscopy. Confirmation that the REDOR experiments were producing accurate distance measurement was ensured by measuring the (13)C-(15)N distance in glycine. The experiment was further verified by measuring the REDOR dephasing curve on (13)C-(2)H methionine. (13)C-(2)H REDOR dephasing curves were then measured on lyophilized aspartame-disaccharide formulations. In aspartame-sucrose formulation, the internuclear distances increased upon annealing, which correlated with decreased chemical reactivity. By contrast, annealing had only a minimal effect on the dephasing curve in aspartame-trehalose formulation. The results show that stability is a function of both mobility and local structure (conformation), even in a small molecule system such as lyophilized aspartame-sucrose. Copyright © 2011 Wiley-Liss, Inc.

  9. Probing stereoselectivity and pro-chirality of hydride transfer during short-chain alcohol dehydrogenase activity: a combined quantitative 2H NMR and computational approach.

    PubMed

    Kwiecień, Renata A; Ayadi, Farouk; Nemmaoui, Youssef; Silvestre, Virginie; Zhang, Ben-Li; Robins, Richard J

    2009-02-01

    Different members of the alcohol oxidoreductase family can transfer the hydride of NAD(P)H to either the re- or the si-face of the substrate. The enantioselectivity of transfer is very variable, even for a range of substrates reduced by the same enzyme. Exploiting quantitative isotopic (2)H NMR to measure the transfer of (2)H from NAD(P)(2)H to ethanol, a range of enantiomeric excess between 0.38 and 0.98, depending on the origin of the enzyme and the nature of the cofactor, has been determined. Critically, in no case was only (R)-[1-(2)H]ethanol or (S)-[1-(2)H]ethanol obtained. By calculating the relative energies of the active site models for hydride transfer to the re- or si-face of short-chain aldehydes by alcohol dehydrogenase from Saccharomyces cerevisiae and Lactobacillus brevis, it is shown that the differences in the energy of the systems when the substrate is positioned with the alkyl group in one or the other pocket of the active site could play a role in determining stereoselectivity. These experiments help to provide insight into structural features that influence the potential catalytic flexibility of different alcohol dehydrogenase activities.

  10. 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.

  11. Metabolomic insight into soy sauce through (1)H NMR spectroscopy.

    PubMed

    Ko, Bong-Kuk; Ahn, Hyuk-Jin; van den Berg, Frans; Lee, Cherl-Ho; Hong, Young-Shick

    2009-08-12

    Soy sauce, a well-known seasoning in Asia and throughout the world, consists of many metabolites that are produced during fermentation or aging and that have various health benefits. However, their comprehensive assessment has been limited due to targeted or instrumentally specific analysis. This paper presents for the first time a metabolic characterization of soy sauce, especially that aged up to 12 years, to obtain a global understanding of the metabolic variations through (1)H NMR spectroscopy coupled with multivariate pattern recognition techniques. Elevated amino acids and organic acids and the consumption of carbohydrate were associated with continuous involvement of microflora in aging for 12 years. In particular, continuous increases in the levels of betaine were found during aging for up to 12 years, demonstrating that microbial- or enzyme-related metabolites were also coupled with osmotolerant or halophilic bacteria present during aging. This work provides global insights into soy sauce through a (1)H NMR-based metabolomic approach that enhances the current understanding of the holistic metabolome and allows assessment of soy sauce quality.

  12. Peak width issues with generalised 2D correlation NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Kirwan, Gemma M.; Adams, Michael J.

    2008-12-01

    Two-dimensional spectral correlation analysis is shown to be sensitive to fluctuations in spectral peak width as a function of perturbation variable. This is particularly significant where peak width fluctuations are of similar order of magnitude as the peak width values themselves and where changes in peak width are not random but are, for example, proportional to intensity. In such cases these trends appear in the asynchronous matrix as false peaks that serve to interfere with interpretation of the data. Complex, narrow band spectra such as provided by 1H NMR spectroscopy are demonstrated to be prone to such interference. 2D correlation analysis was applied to a series of NMR spectra corresponding to a commercial wine fermentation, in which the samples collected over a period of several days exhibit dramatic changes in concentration of minor and major components. The interference due to changing peak width effects is eliminated by synthesizing the recorded spectra using a constant peak width value prior to performing 2D correlation analysis.

  13. 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…

  14. 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…

  15. Regularized Partial Least Squares with an Application to NMR Spectroscopy

    PubMed Central

    Allen, Genevera I.; Peterson, Christine; Vannucci, Marina; Maletić-Savatić, Mirjana

    2014-01-01

    High-dimensional data common in genomics, proteomics, and chemometrics often contains complicated correlation structures. Recently, partial least squares (PLS) and Sparse PLS methods have gained attention in these areas as dimension reduction techniques in the context of supervised data analysis. We introduce a framework for Regularized PLS by solving a relaxation of the SIMPLS optimization problem with penalties on the PLS loadings vectors. Our approach enjoys many advantages including flexibility, general penalties, easy interpretation of results, and fast computation in high-dimensional settings. We also outline extensions of our methods leading to novel methods for non-negative PLS and generalized PLS, an adoption of PLS for structured data. We demonstrate the utility of our methods through simulations and a case study on proton Nuclear Magnetic Resonance (NMR) spectroscopy data. PMID:24511361

  16. NMR planar micro coils for micro spectroscopy: design and characterisation.

    PubMed

    Baxan, N; Rengle, A; Châteaux, J-F; Briguet, A; Pasquet, G; Morin, P; Fakri-Bouchet, L

    2006-01-01

    The goal of this study is to determine the concentration sensitivity and the limit of detection of a SNMR receiver planar micro coil with ellipsoidal geometry 1000x500 microm, fabricated using an electroplating technique and used as SNMR receiver coil at 200 MHz. The maximum signal intensity on the NMR images and simulation of RF field distribution allows defining an active volume of 0.8 microL. The localised spectroscopy based on a PRESS sequence shows that the concentration sensitivity is closed to S(C)=2.33 M(-1) and the limit of detection LOD=0.8 M. This micro-system offers the possibility of new investigation techniques based on implantable micro coils used for in vivo study of local cerebral metabolites occupying a small volume (microL to nL order).

  17. 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.

  18. Rotational jumps of the tyrosine side chain in crystalline enkephalin. /sup 2/H NMR line shapes for aromatic ring motion in solids

    SciTech Connect

    Rice, D.N.; Wittebort, R.J.; Griffin, R.G.; Meirovitch, E.; Stimson, E.R.; Meinwald, Y.C.; Freed, J.H.; Scheraga, H.A.

    1981-12-30

    Deuterium NMR spectra of polycrystalline (tyrosine-3,5-/sup 2/H/sub 2/)(Leu/sup 5/)enkephalin show that the aromatic tyrosyl ring of this pentapeptide is executing 180/sup 0/ flips about the C/sup ..beta../-C/sup ..gamma../ axis in the solid state. Specifically, the axially symmetric powder pattern observed at low temperature collapses to an axially asymmetric pattern with eta approx. = 0.6 at high temperature. Computer simulation of the NMR line shapes, which account for spectral distortions induced by the quadrupole echo technique, indicate that at room temperature the flipping rate is approximately 5 x 10/sup 4/ s/sup -1/ and that it increases to about 10/sup 6/ s/sup -1/ at 101 /sup 0/C.

  19. Formation of Gel-like Nanodomains in Cholesterol-Containing Sphingomyelin or Phosphatidylcholine Binary Membrane As Examined by Fluorescence Lifetimes and (2)H NMR Spectra.

    PubMed

    Yasuda, Tomokazu; Matsumori, Nobuaki; Tsuchikawa, Hiroshi; Lönnfors, Max; Nyholm, Thomas K M; Slotte, J Peter; Murata, Michio

    2015-12-29

    In this study, we measured the time-resolved fluorescence of trans-parinaric acid (tPA), steady-state fluorescence anisotropy of diphenylhexatriene (DPH), and (2)H NMR of 10,10-d2-stearoyl lipids in stearoyl sphingomyelin with cholesterol (SSM/Chol) and l-palmitoyl-2-stearoyl-sn-glycero-3-phosphocholine with Chol (PSPC/Chol) binary membranes. The results suggest that the membrane order obtained from the fluorescence experiments shows a similar temperature dependency as those of the (2)H NMR data. More importantly, the time-resolved fluorescence data implied the presence of at least two types of domains, cholesterol-poor gel-like domains (CPGLD) and cholesterol-enriched liquid-ordered (Lo) domains. These domains appear on a nano-to-micro second time scale for both SSM-Chol and PSPC-Chol membranes. The relative size of the gel-like domain was also estimated from the temperature-dependent lifetime measurements and (2)H NMR spectral changes. The results imply that the size of the gel-like domains is very small, probably on the nanometer scale, and smaller in SSM-Chol membrane than those in PSPC-Chol bilayers, which could account for the higher thermal stability of SM-Chol membranes. The present study demonstrates that gel-like nanodomains occur in SM-Chol binary membrane even with Chol content of over 33 mol %, which has been thought to consist exclusively of Lo phase, implying that not only Lo domains but also gel-like nanodomains are important for formation of lipid-ordered phase in SM-Chol and PC-Chol membranes.

  20. Beyond the Born-Oppenheimer approximation: High-resolution overtone spectroscopy of H2D+ and D2H+

    NASA Astrophysics Data System (ADS)

    Fárník, Michal; Davis, Scott; Kostin, Maxim A.; Polyansky, Oleg L.; Tennyson, Jonathan; Nesbitt, David J.

    2002-04-01

    Transitions to overtone 2ν2 and 2ν3, and combination ν2+ν3 vibrations in jet-cooled H2D+ and D2H+ molecular ions have been measured for the first time by high-resolution IR spectroscopy. The source of these ions is a pulsed slit jet supersonic discharge, which allows for efficient generation, rotational cooling, and high frequency (100 KHz) concentration modulation for detection via sensitive lock-in detection methods. Isotopic substitution and high-resolution overtone spectroscopy in this fundamental molecular ion permit a systematic, first principles investigation of Born-Oppenheimer "breakdown" effects due to large amplitude vibrational motion as well as provide rigorous tests of approximate theoretical methods beyond the Born-Oppenheimer level. The observed overtone transitions are in remarkably good agreement (<0.1 cm-1) with non-Born-Oppenheimer ab initio theoretical predictions, with small but systematic deviations for 2ν2, ν2+ν3, and 2ν3 excited states indicating directions for further improvement in such treatments. Spectroscopic assignment and analysis of the isotopomeric transitions reveals strong Coriolis mixing between near resonant 2ν3 and ν2+ν3 vibrations in D2H+. Population-independent line intensity ratios for transitions from common lower states indicate excellent overall agreement with theoretical predictions for D2H+, but with statistically significant discrepancies noted for H2D+. Finally, H2D+ versus D2H+ isotopomer populations are analyzed as a function of D2/H2 mixing ratio and can be well described by steady state kinetics in the slit discharge expansion.

  1. Infrared diode laser absorption spectroscopy of C(2)H(2) and C(2)H(6) in capacitively coupled methane RF discharges.

    PubMed

    Serdioutchenko, A; Möller, I; Soltwisch, H

    2004-12-01

    Low-temperature RF discharges with methane as feed gas are widely used for the deposition of hydrogenated films. The film properties depend strongly on the chemical composition and therefore two of the main stable products in this kind of discharge, namely ethane (C(2)H(6)) and acetylene (C(2)H(2)), have been measured for the understanding of the reaction kinetics in the plasma. An absorption spectrometer has been built up for the investigation of the concentrations of these as a function of the input power and the flow rate. The time scales for reaching steady state after the discharge is switched on and the depletion time scale after the plasma is switched off have been determined. Assuming the recombination of CH(3) molecules to be the only production mechanism for C(2)H(6) and using a simplified rate equation, the measured densities of C(2)H(6) can be reproduced very well by analytical fitting curves.

  2. Application of NMR spectroscopy in medicinal chemistry and drug discovery.

    PubMed

    Ross, Brian; Tran, Thao; Bhattacharya, Pratip; Watterson, D Martin; Sailasuta, Napapon

    2011-01-01

    We describe the details of the magnetic resonance spectroscopy and chemical shift imaging techniques for the human brain which have been developed over the last two decades. With these non-invasive tools, it is now readily possible to repeatedly assay up to 20 common brain metabolites. From the perspective of drug discovery, each of these metabolites could fulfill a number of useful functions: disease biomarker, surrogate marker of drug delivery, surrogate marker of drug efficacy and so on. To facilitate the possible utility of clinical magnetic resonance spectroscopy in future drug discovery, the major portion of the review is devoted to a detailed description of the well-validated neurochemical profiles of many common human brain disorders, for which MRS data now exists. Beyond proton, MRS, the commonest tool provided by the manufacturers of clinical MRI equipment, lays the world of heteronuclear NMR more familiar to chemists. Here too, with relatively little effort it has been possible to define neurochemical profiles of human brain disorders using (13)C MRS in particular. The future for drug discovery scientists is discussed. Finally, recognizing that a known feature of MR is the lack of sensitivity, we describe new efforts to harness hyperpolarization, with its 50,000 signal amplification, to conventional MRS.

  3. A dedicated spectrometer for dissolution DNP NMR spectroscopy.

    PubMed

    Leggett, James; Hunter, Robert; Granwehr, Josef; Panek, Rafal; Perez-Linde, Angel J; Horsewill, Anthony J; McMaster, Jonathan; Smith, Graham; Köckenberger, Walter

    2010-06-14

    Using low temperature dynamic nuclear polarisation (DNP) in conjunction with dissolution makes it possible to generate highly polarised nuclear spin systems for liquid state applications of nuclear magnetic resonance spectroscopy. However, in its current implementation, which requires the transfer of the solute between two different magnets, the hyperpolarisation strategy is limited to spin systems with relatively long longitudinal relaxation time constants. Here we describe the design and construction of a dedicated spectrometer for DNP applications that is based on a magnet with two isocentres. DNP enhancement is carried out in the upper compartment of this magnet in a low temperature environment at 3.35 T, while a 9.4 T isocentre in the lower compartment is used for high resolution NMR spectroscopy. The close proximity (85 cm) of the two isocentres makes it possible to transfer the sample in the solid state with very little loss of spin polarisation. In first performance tests this novel experimental set-up proved to be superior to the strategy involving two separate magnets.

  4. Observation of the pi...H hydrogen-bonded ternary complex, (C(2)H(4))(2)H(2)O, using matrix isolation infrared spectroscopy.

    PubMed

    Thompson, Matthew G K; Lewars, Errol G; Parnis, J Mark

    2005-10-27

    FTIR absorption spectra of water-containing ethene:Ar matrices, with compositions of ethene up to 1:10 ethene:Ar, have been recorded. Systematically increasing the concentration of ethene reveals features in the spectra consistent with the known 1:1 ethene:water complex, which subsequently disappear on further increase in ethene concentration. At high concentrations of ethene, new features are observed at 3669 and 3585 cm(-1), which are red-shifted with respect to matrix-isolated nu(3) and nu(1) O-H stretching modes of water and the 1:1 ethene:water complex. These shifts are consistent with a pi...H interaction of a 2:1 ethene:water complex of the form (C(2)H(4)...H-O-H...C(2)H(4)). The analogous (C(2)D(4))(2)H(2)O complex shows little shifting from positions associated with (C(2)H(4))(2)H(2)O, while the (C(2)H(4))(2)D(2)O isotopomer shows large shifts to 2722.3 and 2617.2 cm(-1), having identical nu(3)(H(2)O)/nu(3)(D(2)O) and nu(1)(H(2)O)/nu(1)(D(2)O) values when compared with monomeric water isotopomers. Features at 3626.1 and 2666.2 cm(-1) are also observed and are attributed to (C(2)H(4))(2)HDO. DFT calculations at the B3LYP/6-311+G(d,p) level for each isotopomer are presented, and the predicted vibrational frequencies are directly compared with experimental values. The interaction energy for the formation of the 2:1 ethene:water complex from the 1:1 ethene:water complex is also presented.

  5. Investigations of intramolecular hydrogen bonding in three types of Schiff bases by 2H and 3H NMR isotope effects.

    PubMed

    Schilf, Wojciech; Bloxsidge, James P; Jones, John R; Lu, Shui-Yu

    2004-06-01

    Hydrogen bonding within the structures of three Schiff bases (1-3), obtained by condensation of 4-methoxy-, 5-methoxy- and 4,6-dimethoxysalicylaldehyde with methylamine, was investigated by measuring deuterium and tritium NMR isotope effects. The primary deuterium and tritium isotope effects (delta(XH)-delta(XD/T)) and secondary one-bond nitrogen deuterium effect appear to be very useful parameters for defining the character of intramolecular hydrogen bonds. The tritium isotope effects were also determined for nitrogen-hydrogen one-bond coupling constants for both 4-methoxy and 4,6-dimethoxy derivatives. These parameters are seen to be highly sensitive to hydrogen bond characteristics and can be used to distinguish localized and tautomeric hydrogen bonds.

  6. 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.

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

    PubMed

    Kumar, Dinesh

    2016-09-02

    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.

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

    USDA-ARS?s Scientific Manuscript database

    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...

  9. Structure of a Conserved Retroviral RNA Packaging Element by NMR Spectroscopy and Cryo-Electron Tomography

    PubMed Central

    Miyazaki, Yasuyuki; Irobalieva, Rossitza N.; Tolbert, Blanton; Smalls-Mantey, Adjoa; Iyalla, Kilali; Loeliger, Kelsey; D’Souza, Victoria; Khant, Htet; Schmid, Michael F.; Garcia, Eric; Telesnitsky, Alice; Chiu, Wah; Summers, Michael F.

    2010-01-01

    The 5′-untranslated regions (5′-UTRs) of all gammaretroviruses contain a conserved “double hairpin motif” (ΨCD) that is required for genome packaging. Both hairpins (SL-C and SL-D) contain GACG tetraloops that, in isolated RNAs, are capable of forming “kissing” interactions stabilized by two intermolecular G-C base pairs. We have determined the three-dimensional structure of the double hairpin from the Moloney Murine Leukemia Virus (MoMuLV) ([ΨCD]2, 132-nucleotides, 42.8 kDaltons) using a 2H-edited NMR spectroscopy-based approach. This approach enabled the detection of 1H-1H dipolar interactions that were not observed in previous studies of isolated SL-C and SL-D hairpin RNAs using traditional 1H-1H correlated and 1H-13C-edited NMR methods. The hairpins participate in intermolecular cross-kissing interactions (SL-C to SL-D’ and SLC’ to SL-D), and stack in an end-to-end manner (SL-C to SL-D and SL-C’ to SL-D’) that gives rise to an elongated overall shape (ca. 95 Å by 45 Å by 25 Å). The global structure was confirmed by cryo-electron tomography (cryo-ET), making [ΨCD]2 simultaneously the smallest RNA to be structurally characterized to date by cryo-ET and among the largest to be determined by NMR. Our findings suggest that, in addition to promoting dimerization, [ΨCD]2 functions as a scaffold that helps initiate virus assembly by exposing a cluster of conserved UCUG elements for binding to the cognate nucleocapsid domains of assembling viral Gag proteins. PMID:20933521

  10. Propionate metabolism in the rat heart by 13C n.m.r. spectroscopy.

    PubMed Central

    Sherry, A D; Malloy, C R; Roby, R E; Rajagopal, A; Jeffrey, F M

    1988-01-01

    High-resolution 13C n.m.r. spectroscopy has been used to examine propionate metabolism in the perfused rat heart. A number of tricarboxylic acid (TCA) cycle intermediates are observable by 13C n.m.r. in hearts perfused with mixtures of pyruvate and propionate. When the enriched 13C-labelled nucleus originates with pyruvate, the resonances of the intermediates appear as multiplets due to formation of multiply-enriched 13C-labelled isotopomers, whereas when the 13C-labelled nucleus originates with propionate, these same intermediates appear as singlets in the 13C spectrum since entry of propionate into the TCA cycle occurs via succinyl-CoA. An analysis of the isotopomer populations in hearts perfused with [3-13C]pyruvate plus unlabelled propionate indicates that about 27% of the total pyruvate pool available to the heart is derived directly from unlabelled propionate. This was substantiated by perfusing a heart for 2 h with [3-13C]propionate as the only available exogenous substrate. Under these conditions, all of the propionate consumed by the heart, as measured by conventional chemical analysis, ultimately entered the oxidative pathway as [2-13C] or [3-13C]pyruvate. This is consistent with entry of propionate into the TCA cycle intermediate pools as succinyl-CoA and concomitant disposal of malate to pyruvate via the malic enzyme. 13C resonances arising from enriched methylmalonate and propionylcarnitine are also detected in hearts perfused with [3-13C] or [1-13C]propionate which suggests that 13C n.m.r. may be useful as a non-invasive probe in vivo of metabolic abnormalities involving the propionate pathway, such as methylmalonic aciduria or propionic acidaemia. PMID:3178775

  11. Communication: Phase incremented echo train acquisition in NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Baltisberger, Jay H.; Walder, Brennan J.; Keeler, Eric G.; Kaseman, Derrick C.; Sanders, Kevin J.; Grandinetti, Philip J.

    2012-06-01

    We present an improved and general approach for implementing echo train acquisition (ETA) in magnetic resonance spectroscopy, particularly where the conventional approach of Carr-Purcell-Meiboom-Gill (CPMG) acquisition would produce numerous artifacts. Generally, adding ETA to any N-dimensional experiment creates an N + 1 dimensional experiment, with an additional dimension associated with the echo count, n, or an evolution time that is an integer multiple of the spacing between echo maxima. Here we present a modified approach, called phase incremented echo train acquisition (PIETA), where the phase of the mixing pulse and every other refocusing pulse, ϕP, is incremented as a single variable, creating an additional phase dimension in what becomes an N + 2 dimensional experiment. A Fourier transform with respect to the PIETA phase, ϕP, converts the ϕP dimension into a Δp dimension where desired signals can be easily separated from undesired coherence transfer pathway signals, thereby avoiding cumbersome or intractable phase cycling schemes where the receiver phase must follow a master equation. This simple modification eliminates numerous artifacts present in NMR experiments employing CPMG acquisition and allows "single-scan" measurements of transverse relaxation and J-couplings. Additionally, unlike CPMG, we show how PIETA can be appended to experiments with phase modulated signals after the mixing pulse.

  12. Multidimensional solid-state NMR spectroscopy of plant cell walls.

    PubMed

    Wang, Tuo; Phyo, Pyae; Hong, Mei

    2016-09-01

    Plant biomass has become an important source of bio-renewable energy in modern society. The molecular structure of plant cell walls is difficult to characterize by most atomic-resolution techniques due to the insoluble and disordered nature of the cell wall. Solid-state NMR (SSNMR) spectroscopy is uniquely suited for studying native hydrated plant cell walls at the molecular level with chemical resolution. Significant progress has been made in the last five years to elucidate the molecular structures and interactions of cellulose and matrix polysaccharides in plant cell walls. These studies have focused on primary cell walls of growing plants in both the dicotyledonous and grass families, as represented by the model plants Arabidopsis thaliana, Brachypodium distachyon, and Zea mays. To date, these SSNMR results have shown that 1) cellulose, hemicellulose, and pectins form a single network in the primary cell wall; 2) in dicot cell walls, the protein expansin targets the hemicellulose-enriched region of the cellulose microfibril for its wall-loosening function; and 3) primary wall cellulose has polymorphic structures that are distinct from the microbial cellulose structures. This article summarizes these key findings, and points out future directions of investigation to advance our fundamental understanding of plant cell wall structure and function.

  13. 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

  14. Isotope Labeling for Solution and Solid-State NMR Spectroscopy of Membrane Proteins

    PubMed Central

    Verardi, Raffaello; Traaseth, Nathaniel J.; Masterson, Larry R.; Vostrikov, Vitaly V.; Veglia, Gianluigi

    2013-01-01

    In this chapter, we summarize the isotopic labeling strategies used to obtain high-quality solution and solid-state NMR spectra of biological samples, with emphasis on integral membrane proteins (IMPs). While solution NMR is used to study IMPs under fast tumbling conditions, such as in the presence of detergent micelles or isotropic bicelles, solid-state NMR is used to study the structure and orientation of IMPs in lipid vesicles and bilayers. In spite of the tremendous progress in biomolecular NMR spectroscopy, the homogeneity and overall quality of the sample is still a substantial obstacle to overcome. Isotopic labeling is a major avenue to simplify overlapped spectra by either diluting the NMR active nuclei or allowing the resonances to be separated in multiple dimensions. In the following we will discuss isotopic labeling approaches that have been successfully used in the study of IMPs by solution and solid-state NMR spectroscopy. PMID:23076578

  15. Felix Spectroscopy of Likely Astronomical Molecular Ions: HC_3O^+, C_2H_3CNH^+, and C_2H_5CNH^+

    NASA Astrophysics Data System (ADS)

    Thorwirth, Sven; Asvany, Oskar; Brünken, Sandra; Jusko, Pavol; Schlemmer, Stephan; Martin-Drumel, Marie-Aline; McCarthy, Michael C.

    2017-06-01

    Infrared signatures of three molecular ions of relevance to the interstellar medium and planetary atmospheres have been detected at the Free Electron Laser for Infrared eXperiments, FELIX, at Radboud University (Nijmegen, The Netherlands) in combination with the 4K FELion 22-pole ion trap facility. Mid-infrared vibrational modes of protonated tricarbon monoxide, HC_3O^+, protonated vinyl cyanide, C_2H_3CNH^+, and protonated ethyl cyanide, C_2H_5CNH^+, were detected using resonant photodissociation of the respective Ne-complexes by monitoring the depletion of their cluster mass signal as a function of wavenumber. The infrared fingerprints compare very favorably with results from high-level quantum-chemical calculations performed at the CCSD(T) level of theory.

  16. 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.

  17. A microcoil NMR probe for coupling microscale HPLC with on-line NMR spectroscopy.

    PubMed

    Subramanian, R; Kelley, W P; Floyd, P D; Tan, Z J; Webb, A G; Sweedler, J V

    1999-12-01

    An HPLC NMR system is presented that integrates a commercial microbore HPLC system using a 0.5-mm column with a 500-MHz proton NMR spectrometer using a custom NMR probe with an observe volume of 1.1 microL and a coil fill factor of 68%. Careful attention to capillary connections and NMR flow cell design allows on-line NMR detection with no significant loss in separation efficiency when compared with a UV chromatogram. HPLC NMR is performed on mixtures of amino acids and small peptides with analyte injection amounts as small as 750 ng; the separations are accomplished in less than 10 min and individual NMR spectra are acquired with 12 s time resolution. Stopped-flow NMR is achieved by diversion of the chromatographic flow after observation of the beginning of the analyte band within the NMR flow cell. Isolation of the compound of interest within the NMR detection cell allows multidimensional experiments to be performed. A stopped-flow COSY spectrum of the peptide Phe-Ala is acquired in 3.5 h with an injected amount of 5 micrograms.

  18. 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.

  19. 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…

  20. 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…

  1. Ionic motion and Disordered Structure in the Rotator Phase of Butylammonium Chloride Studied by Temperature Dependences of 35Cl and 2H NMR

    NASA Astrophysics Data System (ADS)

    Hattori, Mineyuki; Onoda, Yoshito; Erata, Tomoki; Smith, M. E.; Hattori, Masakazu; Ohki, Hiroshi; Ikeda, Ryuichi

    1994-02-01

    Temperature dependences of 35Cl and 2H quadrupole coupling constants and 35Cl NMR spin-lat­tice relaxation times in polycrystalline samples were measured in the rotator phase of the butylammonium chlorides C4H9NH3C1 and C4H9ND3C1, obtainable above the phase transition temperature of 241 K. A rapid decrease o f the quadrupole coupling constants of both nuclei upon heating is attributed to increasing dynamic disorder formed around the polar head. The presence of self-diffussion of Cl- ions was revealed from the spin-spin relaxation time and resonance line-width in single crystals, and confirmed by measuring the dc electrical conductivity.

  2. 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.

  3. 2H and 13C NMR studies on the temperature-dependent water and protein dynamics in hydrated elastin, myoglobin and collagen.

    PubMed

    Lusceac, Sorin A; Vogel, Michael R; Herbers, Claudia R

    2010-01-01

    (2)H NMR spin-lattice relaxation and line-shape analyses are performed to study the temperature-dependent dynamics of water in the hydration shells of myoglobin, elastin, and collagen. The results show that the dynamical behaviors of the hydration waters are similar for these proteins when using comparable hydration levels of h=0.25-0.43. Since water dynamics is characterized by strongly nonexponential correlation functions, we use a Cole-Cole spectral density for spin-lattice relaxation analysis, leading to correlation times, which are in nice agreement with results for the main dielectric relaxation process observed for various proteins in the literature. The temperature dependence can roughly be described by an Arrhenius law, with the possibility of a weak crossover in the vicinity of 220 K. Near ambient temperatures, the results substantially depend on the exact shape of the spectral density so that deviations from an Arrhenius behavior cannot be excluded in the high-temperature regime. However, for the studied proteins, the data give no evidence for the existence of a sharp fragile-to-strong transition reported for lysozyme at about 220 K. Line-shape analysis reveals that the mechanism for the rotational motion of hydration waters changes in the vicinity of 220 K. For myoglobin, we observe an isotropic motion at high temperatures and an anisotropic large-amplitude motion at low temperatures. Both mechanisms coexist in the vicinity of 220 K. (13)C CP MAS spectra show that hydration results in enhanced elastin dynamics at ambient temperatures, where the enhancement varies among different amino acids. Upon cooling, the enhanced mobility decreases. Comparison of (2)H and (13)C NMR data reveals that the observed protein dynamics is slower than the water dynamics.

  4. 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.

  5. Recent advances in protein NMR spectroscopy and their implications in protein therapeutics research.

    PubMed

    Wang, Guifang; Zhang, Ze-Ting; Jiang, Bin; Zhang, Xu; Li, Conggang; Liu, Maili

    2014-04-01

    Nuclear magnetic resonance (NMR) spectroscopy and X-ray crystallography are the two main methods for protein three-dimensional structure determination at atomic resolution. According to the protein structures deposited in the Protein Data Bank, X-ray crystallography has become the dominant method for structure determination, particularly for large proteins and complexes. However, with the developments of isotope labeling, increase of magnetic field strength, common use of a cryogenic probe, and ingenious pulse sequence design, the applications of NMR spectroscopy have expanded in biological research, especially in characterizing protein dynamics, sparsely populated transient structures, weak protein interactions, and proteins in living cells at atomic resolution, which is difficult if not impossible by other biophysical methods. Although great advances have been made in protein NMR spectroscopy, its applications in protein therapeutics, which represents the fastest growing segment of the pharmaceutical industry, are still limited. Here we review the recent advances in the use of NMR spectroscopy in studies of large proteins or complexes, posttranslation modifications, weak interactions, and aggregation, and in-cell NMR spectroscopy. The potential applications of NMR spectroscopy in protein therapeutic assays are discussed.

  6. Bringing NMR and IR Spectroscopy to High Schools

    ERIC Educational Resources Information Center

    Bonjour, Jessica L.; Hass, Alisa L.; Pollock, David W.; Huebner, Aaron; Frost, John A.

    2017-01-01

    Development of benchtop, portable Fourier transform nuclear magnetic resonance (NMR) and infrared (IR) spectrometers has opened up opportunities for creating university-high school partnerships that provide high school students with hands-on experience with NMR and IR instruments. With recent changes to the international baccalaureate chemistry…

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

    USDA-ARS?s Scientific Manuscript database

    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...

  8. Advanced solid-state NMR spectroscopy of natural organic matter.

    PubMed

    Mao, Jingdong; Cao, Xiaoyan; Olk, Dan C; Chu, Wenying; Schmidt-Rohr, Klaus

    2017-05-01

    Solid-state NMR is essential for the characterization of natural organic matter (NOM) and is gaining importance in geosciences and environmental sciences. This review is intended to highlight advanced solid-state NMR techniques, especially a systematic approach to NOM characterization, and their applications to the study of NOM. We discuss some basics of how to acquire high-quality and quantitative solid-state (13)C NMR spectra, and address some common technical mistakes that lead to unreliable spectra of NOM. The identification of specific functional groups in NOM, primarily based on (13)C spectral-editing techniques, is described and the theoretical background of some recently-developed spectral-editing techniques is provided. Applications of solid-state NMR to investigating nitrogen (N) in NOM are described, focusing on limitations of the widely used (15)N CP/MAS experiment and the potential of improved advanced NMR techniques for characterizing N forms in NOM. Then techniques used for identifying proximities, heterogeneities and domains are reviewed, and some examples provided. In addition, NMR techniques for studying segmental dynamics in NOM are reviewed. We also briefly discuss applications of solid-state NMR to NOM from various sources, including soil organic matter, aquatic organic matter, organic matter in atmospheric particulate matter, carbonaceous meteoritic organic matter, and fossil fuels. Finally, examples of NMR-based structural models and an outlook are provided. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Advanced solid-state NMR spectroscopy of natural organic matter

    USDA-ARS?s Scientific Manuscript database

    Solid-state NMR is essential for the characterization of natural organic matter (NOM) and is gaining importance in geosciences and environmental sciences. This review is intended to highlight advanced solid-state NMR techniques, especially the systematic approach to NOM characterization, and their ...

  10. Bringing NMR and IR Spectroscopy to High Schools

    ERIC Educational Resources Information Center

    Bonjour, Jessica L.; Hass, Alisa L.; Pollock, David W.; Huebner, Aaron; Frost, John A.

    2017-01-01

    Development of benchtop, portable Fourier transform nuclear magnetic resonance (NMR) and infrared (IR) spectrometers has opened up opportunities for creating university-high school partnerships that provide high school students with hands-on experience with NMR and IR instruments. With recent changes to the international baccalaureate chemistry…

  11. 2H NMR study of dynamics of benzene-d6 interacting with humic and fulvic acids.

    PubMed

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

    2011-05-05

    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.

  12. (17)O NMR and Raman Spectroscopies of Green Tea Infusion with Nanomaterial to Investigate Their Properties.

    PubMed

    Zhou, Changyan; Zhang, Huiping; Yan, Ying; Zhang, Xinya

    2016-09-01

    (17)O NMR and Raman spectrograms of green tea infusions with nanomaterial were investigated. Different green tea infusions were prepared by steeping tea powder with different concentrations of nanomaterial aqueous solution. The tea infusions were tested with (17)O NMR and Raman spectroscopies. The (17)O NMR results showed that line width increased to 90 in the tea infusions after nanomaterial was added as a result of the effects of the self-association of Ca(2+) and tea polyphenol. The results of Raman spectroscopy showed that, in tea infusions, the enhancement of C─C and C─O stretching vibrations suggest an increase in the number of effective components in water.

  13. Rotational spectroscopy of vibrationally excited N2H+ and N2D+ up to 2.7 THz

    NASA Astrophysics Data System (ADS)

    Yu, S.; Pearson, J. C.; Drouin, B. J.; Crawford, T.; Daly, A. M.; Elliott, B.; Amano, T.

    2015-08-01

    Terahertz absorption spectroscopy was employed to extend the measurements on the pure rotational transitions of N2H+, N2D+ and their 15N-containing isotopologues in the ground state and first excited vibrational states for the three fundamental vibrational modes. In total, 91 new pure rotational transitions were observed in the range of 0.7-2.7 THz. The observed transition frequencies were fit to experimental accuracy, and the improved molecular parameters were obtained. The new measurements and predictions reported here will support the analysis of high-resolution astronomical observations made with facilities such as SOFIA and ALMA where laboratory rest frequencies with uncertainties of 1 MHz or smaller are required for proper analysis of velocity resolved astrophysical components.

  14. Multiband superconductivity in 2 H -NbSe2 probed by Doppler-modulated scanning tunneling spectroscopy

    NASA Astrophysics Data System (ADS)

    Fridman, I.; Kloc, C.; Petrovic, C.; Wei, J. Y. T.

    Cooper pairing in multiband superconductors can involve carriers from bands having different dimensionalities, and the interband coupling can provide for novel pairing interactions. In addition to MgB2, recent experiments on 2 H -NbSe2 have studied the Fermi surface topology using angle- and temperature-dependent scanning tunneling spectroscopy. We present another novel method for probing multiband pairing: using a field-induced diamagnetic supercurrent, applied along different crystal axes, to perturb the quasiparticle density-of-states spectrum. By measuring the evolution of the quasiparticle spectrum under finite superfluid momentum, we characterize the pairing gaps and gap anisotropies. This approach is demonstrated on 2 H -NbSe2 at 300 mK with a magnetic field of up to 9 T applied in the ab -plane. The STM measurements revealed unambiguous evidence for multiband pairing, and evidence for a novel transition of the in-plane vortex lattice. We discuss the characteristics of this transition in light of data from other probes Work supported by NSERC, CFI/OIT, CIFAR, U.S. DOE and Brookhaven Science Associates (No. DE-AC02-98CH10886).

  15. 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. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  16. 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.

  17. [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.

  18. Fluxionality and Isomerism of the Bis(dihydrogen) Complex RuH(2)(H(2))(2)(PCy(3))(2): INS, NMR, and Theoretical Studies.

    PubMed

    Rodriguez, Venancio; Sabo-Etienne, Sylviane; Chaudret, Bruno; Thoburn, John; Ulrich, Stefan; Limbach, Hans-Heinrich; Eckert, Juergen; Barthelat, Jean-Claude; Hussein, Khansaa; Marsden, Colin J.

    1998-07-13

    To study the fluxionality of the bis(dihydrogen) complex RuH(2)(H(2))(2)(PCy(3))(2) (1), NMR spectra were recorded in Freons (mixture of CDCl(3), CDFCl(2), and CDF(2)Cl). 1 was found to remain fluxional at all temperatures, but the presence of CDCl(3) necessary for its solubilization induces its transformation into, first, RuHCl(H(2))(2)(PCy(3))(2) (3) and the new ruthenium(IV) dihydride RuH(2)Cl(2)(PCy(3))(2) (4). 4 is produced selectively in pure CDCl(3) but reacts further to give a mixture of chloro complexes. 4 was isolated from the reaction of 1 with aqueous HCl in Et(2)O and shows a fluxional process attributed to the interconversion between two symmetrical isomers. The activation parameters of this process were obtained by (1)H NMR line shape analysis, as well as those corresponding to the exchange between 3 and free dihydrogen. The fluxionality of the dihydrogen-hydride system is also evident at a much faster time scale than that of NMR studies in the inelastic neutron scattering observations of the rotation of the dihydrogen ligands. The geometries and relative energies of several isomers of complexes 1, 3, and 4 were studied using density functional theory (DFT) and MP2 methods, together with a few coupled-cluster (CCSD(T)) calculations. In contrast to what might have been expected, the two hydrides and the two H(2) units of 1 lie in the same plane, due to the attractive "cis effect" created by the hydrides. The two H(2) ligands adopt cis positions in the lowest-energy isomer. Rotation of the two dihydrogen ligands has been analyzed using DFT calculations. A slight preference for a C(2) conrotatory pathway has been found with a calculated barrier in good agreement with the experimental INS value. Two low-energy isomers of 4 have been characterized computationally, both of which have C(2)(v)() symmetry, consistent with the solution NMR spectra.

  19. Non-aqueous solvents for DNP surface enhanced NMR spectroscopy.

    PubMed

    Zagdoun, Alexandre; Rossini, Aaron J; Gajan, David; Bourdolle, Adrien; Ouari, Olivier; Rosay, Melanie; Maas, Werner E; Tordo, Paul; Lelli, Moreno; Emsley, Lyndon; Lesage, Anne; Copéret, Christophe

    2012-01-18

    A series of non-aqueous solvents combined with the exogenous biradical bTbK are developed for DNP NMR that yield enhancements comparable to the best available water based systems. 1,1,2,2-tetrachloroethane appears to be one of the most promising organic solvents for DNP solid-state NMR. Here this results in a reduction in experimental times by a factor of 1000. These new solvents are demonstrated with the first DNP surface enhanced NMR characterization of an organometallic complex supported on a hydrophobic surface.

  20. Frequency-domain method based on the singular value decomposition for frequency-selective NMR spectroscopy.

    PubMed

    Stoica, Petre; Sandgren, Niclas; Selén, Yngve; Vanhamme, Leentje; Van Huffel, Sabine

    2003-11-01

    In several applications of NMR spectroscopy the user is interested only in the components lying in a small frequency band of the spectrum. A frequency selective analysis deals precisely with this kind of NMR spectroscopy: parameter estimation of only those spectroscopic components that lie in a preselected frequency band of the NMR data spectrum, with as little interference as possible from the out-of-band components and in a computationally efficient way. In this paper we introduce a frequency-domain singular value decomposition (SVD)-based method for frequency selective spectroscopy that is computationally simple, statistically accurate, and which has a firm theoretical basis. To illustrate the good performance of the proposed method we present a number of numerical examples for both simulated and in vitro NMR data.

  1. Quantitative NMR spectroscopy for gas analysis for production of primary reference gas mixtures

    NASA Astrophysics Data System (ADS)

    Meyer, K.; Rademann, K.; Panne, U.; Maiwald, M.

    2017-02-01

    Due to its direct correlation to the number of spins within a sample quantitative NMR spectroscopy (qNMR) is a promising method with absolute comparison abilities in complex systems in technical, as well as metrological applications. Most of the samples studied with qNMR are in liquid state in diluted solutions, while gas-phase applications represent a rarely applied case. Commercially available NMR equipment was used for purity assessment of liquid and liquefied hydrocarbons serving as raw materials for production of primary reference gas standards. Additionally, gas-phase studies were performed within an online NMR flow probe, as well as in a high-pressure NMR setup to check feasibility as verification method for the composition of gas mixtures.

  2. Quantitative NMR spectroscopy for gas analysis for production of primary reference gas mixtures.

    PubMed

    Meyer, K; Rademann, K; Panne, U; Maiwald, M

    2017-02-01

    Due to its direct correlation to the number of spins within a sample quantitative NMR spectroscopy (qNMR) is a promising method with absolute comparison abilities in complex systems in technical, as well as metrological applications. Most of the samples studied with qNMR are in liquid state in diluted solutions, while gas-phase applications represent a rarely applied case. Commercially available NMR equipment was used for purity assessment of liquid and liquefied hydrocarbons serving as raw materials for production of primary reference gas standards. Additionally, gas-phase studies were performed within an online NMR flow probe, as well as in a high-pressure NMR setup to check feasibility as verification method for the composition of gas mixtures. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. 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.

  4. 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.

  5. Improved hardware and software for single-crystal NMR spectroscopy.

    PubMed

    Vosegaard, T; Hald, E; Langer, V; Skov, H J; Daugaard, P; Bildsoe, H; Jakobsen, H J

    1998-11-01

    Design of state-of-the-art instrumentation and software for acquisition and analysis of single-crystal NMR spectra is presented. The design involves highly accurate rotation of a goniometer, and the acquisition of all the spectra for each rotation axis is automatically controlled by the host computer of the spectrometer using a homebuilt interface between the computer and the single-crystal probe. Moreover, a software package (ASICS) for fast and routine assignment/analysis of complex single-crystal spectra has been developed. Employing this equipment, the acquisition and complete analysis of single-crystal NMR spectra may be performed in about the same time as required for powder methods (spinning or static). The hardware and software are compared to recent alternative approaches within single-crystal NMR. Finally, it has been observed that single-crystal NMR techniques may provide the desired data for samples where powder methods fail. Copyright 1998 Academic Press.

  6. 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

  7. 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)

  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. Continuous Flow 1H and 13C NMR Spectroscopy in Microfluidic Stripline NMR Chips

    PubMed Central

    2017-01-01

    Microfluidic stripline NMR technology not only allows for NMR experiments to be performed on small sample volumes in the submicroliter range, but also experiments can easily be performed in continuous flow because of the stripline’s favorable geometry. In this study we demonstrate the possibility of dual-channel operation of a microfluidic stripline NMR setup showing one- and two-dimensional 1H, 13C and heteronuclear NMR experiments under continuous flow. We performed experiments on ethyl crotonate and menthol, using three different types of NMR chips aiming for straightforward microfluidic connectivity. The detection volumes are approximately 150 and 250 nL, while flow rates ranging from 0.5 μL/min to 15 μL/min have been employed. We show that in continuous flow the pulse delay is determined by the replenishment time of the detector volume, if the sample trajectory in the magnet toward NMR detector is long enough to polarize the spin systems. This can considerably speed up quantitative measurement of samples needing signal averaging. So it can be beneficial to perform continuous flow measurements in this setup for analysis of, e.g., reactive, unstable, or mass-limited compounds. PMID:28194934

  10. Structural investigations on betacyanin pigments by LC NMR and 2D NMR spectroscopy.

    PubMed

    Stintzing, Florian C; Conrad, Jürgen; Klaiber, Iris; Beifuss, Uwe; Carle, Reinhold

    2004-02-01

    Four betacyanin pigments were analysed by LC NMR and subjected to extensive NMR characterisation after isolation. Previously, low pH values were applied for NMR investigations of betalains resulting in rapid degradation of the purified substances thus preventing extensive NMR studies. Consequently, up to now only one single (13)C NMR spectrum of a betalain pigment, namely that of neobetanin (=14,15-dehydrobetanin), was available. Because of its sufficient stability under highly acidic conditions otherwise detrimental for betacyanins, this pigment remained an exemption. Since betalains are most stable in the pH range of 5-7, a new solvent system has been developed allowing improved data acquisition through improved pigment stability at near neutral pH. Thus, not only (1)H, but for the first time also partial (13)C data of betanin, isobetanin, phyllocactin and hylocerenin isolated from red-purple pitaya [Hylocereus polyrhizus (Weber) Britton & Rose, Cactaceae] could be indirectly obtained by gHSQC- and gHMQC-NMR experiments.

  11. Continuous Flow (1)H and (13)C NMR Spectroscopy in Microfluidic Stripline NMR Chips.

    PubMed

    Oosthoek-de Vries, Anna Jo; Bart, Jacob; Tiggelaar, Roald M; Janssen, Johannes W G; van Bentum, P Jan M; Gardeniers, Han J G E; Kentgens, Arno P M

    2017-02-21

    Microfluidic stripline NMR technology not only allows for NMR experiments to be performed on small sample volumes in the submicroliter range, but also experiments can easily be performed in continuous flow because of the stripline's favorable geometry. In this study we demonstrate the possibility of dual-channel operation of a microfluidic stripline NMR setup showing one- and two-dimensional (1)H, (13)C and heteronuclear NMR experiments under continuous flow. We performed experiments on ethyl crotonate and menthol, using three different types of NMR chips aiming for straightforward microfluidic connectivity. The detection volumes are approximately 150 and 250 nL, while flow rates ranging from 0.5 μL/min to 15 μL/min have been employed. We show that in continuous flow the pulse delay is determined by the replenishment time of the detector volume, if the sample trajectory in the magnet toward NMR detector is long enough to polarize the spin systems. This can considerably speed up quantitative measurement of samples needing signal averaging. So it can be beneficial to perform continuous flow measurements in this setup for analysis of, e.g., reactive, unstable, or mass-limited compounds.

  12. Quadrupole-Echo Techniques in Multiple-Quantum-Filtered NMR Spectroscopy of Heterogeneous Systems

    NASA Astrophysics Data System (ADS)

    Eliav, U.; Navon, G.

    Multiple-quantum-filtered quadrupole-echo pulse sequences for spin I = 1 and I = {3}/{2} are suggested. A general condition for obtaining simultaneously Zeeman and quadrupolar echo is formulated. A theoretical analysis of the various pulse sequences was performed on the basis of second-order perturbation approximation of the Liouville equation for the density matrix. The extent of refocusing as a function of the ratio of the residual quadrupolar interaction and the relaxation rates was calculated. Experimental results are presented for 2H and 23Na in cartilage as an example of a heterogeneous system with residual quadrupolar interaction. The difference between relaxation times measured by the multiple-quantum-filtered echo techniques and those measured by conventional multiple-quantum-filtered NMR spectroscopy is a simple diagnostic of anisotropic motion that leads to a residual quadrupolar interaction. The results of the echo experiments are compared with the relaxation times computed on the basis of lineshape analysis of double-quantum-filtered spectra of a heterogeneous system.

  13. Biosynthesis of a specifically deuteriated diunsaturated fatty acid (18:2/sub. delta. 6,9/) for /sup 2/H NMR membrane studies

    SciTech Connect

    Baenziger, J.E.; Smith, I.C.P.; Hill, R.J.

    1987-12-15

    A unique procedure for the biosynthesis and subsequent isolation of a series of specifically deuteriated cis,cis-octadeca-6,9-dienoic acids has been developed. An auxotroph of Tetrahymena, which lacks ..delta..9 and ..delta..12 desaturase activity, is supplemented with specifically deuteriated oleic acid and converts it to the corresponding deuteriated cis,cis-octadeca-6,9-dienoic acid, 18:2/sup ..delta..6,9/. The deuteriated fatty acid is subsequently isolated by argentation chromatography and HPLC. To demonstrate the utility of the procedure, we describe here the biosynthesis of cis,cis-octadeca-6,9-dienoic acid deuteriated at positions 9 and 10. Gas and thin-layer chromatography of the isolated fatty acid showed that it was greater than 99% pure while /sup 13/C NMR and mass spectrometry of the O-(trimethylsilyl) derivative confirmed that the 18-carbon fatty acid contains two double bonds located at positions 6 and 9. The yield, from an 11-L culture, was typically 100 mg of which 35% was found to be deuteriated at both the 9- and 10-positions. The deuteriated fatty acid was esterified to 1-hexadecanoyl-sn-glycero-3-phosphocholine, and aqueous, multilamellar dispersions of the lipid were studied by /sup 2/H NMR. Each spectrum consists of two overlapping powder patterns and therefore yields two quadrupolar splittings. Over a temperature range of 0 to 40/sup 0/C, one splitting decreases from 6.6 to 1.8 kHz while other increases from 4.5 to 5.3 kHz. The magnitudes of the two splittings are equivalent between 10 and 15/sup 0/ C. The values of the splittings, and their response to temperature, differ significantly from those of the corresponding deuteriated oleic acid in microbial membranes and in bilayers of 1-hexadecanoyl-2-cis-octadec-9-enoyl-sn-glycero-3-phosphocholine (POPC).

  14. Applications of toroids in high-pressure NMR spectroscopy

    SciTech Connect

    Klingler, R.J.; Rathke, J.W.; Woelk, K.

    1995-12-01

    Toroid detectors have distinct NMR sensitivity and imaging advantages. The magnetic field lines are nearly completely contained within the active volume element of a toroid. This results in high NMR signal sensitivity. In addition, the toroid detector may be placed next to the metallic walls of a containment vessel with minimal signal loss due to magnetic coupling with the metal container. Thus, the toroid detector is ideal for static high pressure or continuous flow monitoring systems. Toroid NMR detectors have been used to follow the hydroformylation of olefins in supercritical fluids under industrial process conditions. Supercritical fluids are potentially ideal media for conducting catalytic reactions that involve gaseous reactants, including H{sub 2}, CO, and CO{sub 2}. The presence of a single homogeneous reaction phase eliminates the gas-liquid mixing problem of alternative two-phase systems, which can limit process rates and adversely affect hydroformylation product selectivities. A second advantage of toroid NMR detectors is that they exhibit a well-defined gradient in the rf field. This magnetic field gradient can be used for NMR imaging applications. Distance resolutions of 20 {mu} have been obtained.

  15. NMR spectroscopy of RNA duplexes containing pseudouridine in supercooled water.

    PubMed

    Schroeder, Kersten T; Skalicky, Jack J; Greenbaum, Nancy L

    2005-07-01

    We have performed NMR experiments in supercooled water in order to decrease the temperature-dependent exchange of protons in RNA duplexes. NMR spectra of aqueous samples of RNA in bundles of narrow capillaries that were acquired at temperatures as low as -18 degrees C reveal resonances of exchangeable protons not seen at higher temperatures. In particular, we detected the imino protons of terminal base pairs and the imino proton of a non-base-paired pseudouridine in a duplex representing the eukaryotic pre-mRNA branch site helix. Analysis of the temperature dependence of chemical shift changes (thermal coefficients) for imino protons corroborated hydrogen bonding patterns observed in the NMR-derived structural model of the branch site helix. The ability to observe non-base-paired imino protons of RNA is of significant value in structure determination of RNA motifs containing loop and bulge regions.

  16. 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.

  17. In vivo and in vitro NMR spectroscopy reveal a putative novel inborn error involving polyol metabolism.

    PubMed

    Moolenaar, S H; van der Knaap, M S; Engelke, U F; Pouwels, P J; Janssen-Zijlstra, F S; Verhoeven, N M; Jakobs, C; Wevers, R A

    2001-05-01

    In vivo NMR spectroscopy was performed on the brain of a patient with a leukoencephalopathy, revealing unknown resonances between 3.5 and 4.0 ppm. In addition, urine and CSF of the patient were measured using high-resolution NMR spectroscopy. Also in these in vitro spectra, unknown resonances were observed in the 3.5-4.0 ppm region. Homonuclear (1)H two-dimensional J-resolved spectroscopy (JRES) and (1)H-(1)H correlation spectroscopy (COSY) were performed on the patient's urine for more accurate assignment of resonances. The NMR spectroscopic studies showed that the unknown resonances could be assigned to arabinitol and ribitol. This was confirmed using gas chromatography. The arabinitol was identified as D-arabinitol. The patient is likely to suffer from an as yet unknown inborn error of metabolism affecting D-arabinitol and ribitol metabolism. The primary molecular defect has not been found yet. Urine spectra of patients suffering from diabetes mellitus or galactosemia were recorded for comparison. Resonances outside the 3.2-4.0 ppm region, which are the most easy to recognize in body fluid spectra, allow easy recognition of various sugars and polyols. The paper shows that NMR spectroscopy in body fluids may help identifying unknown resonances observed in in vivo NMR spectra. Copyright 2001 John Wiley & Sons, Ltd.

  18. 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.

  19. 31P NMR spectroscopy of in vivo tumors

    NASA Astrophysics Data System (ADS)

    Ng, T. C.; Evanochko, W. T.; Hiramoto, R. N.; Ghanta, V. K.; Lilly, M. B.; Lawson, A. J.; Corbett, T. H.; Durant, J. R.; Glickson, J. D.

    A probe, suitable for any wide-bore NMR spectrometer, was constructed for monitoring high-resolution spectra of in vivo subcutaneously implanted tumors in mice. Preliminary studies of a variety of murine tumors (MOPC 104E myeloma, Dunn osteosarcoma, colon-26, ovarian M5, and mammary adenocarcinoma as well as human colon, mammary, and lung tumors in athymic mice) indicate that the 31P NMR spectrum is a sensitive monitor of progressive metabolic changes that occur during untreated tumor growth and an early indicator of tumor response to chemotherapy, hyperthermia, and X radiation. Response to each of these therapeutic modalities is accompanied by distinctly different spectral changes.

  20. 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.

  1. 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.

  2. Concurrent quantification of tissue metabolism and blood flow via 2H/31P NMR in vivo. III. Alterations of muscle blood flow and metabolism during sepsis.

    PubMed

    Song, S K; Hotchkiss, R S; Karl, I E; Ackerman, J J

    1992-05-01

    In the conclusion of this series of reports, the application of 31P/2H NMR to investigate the pathophysiology of sepsis in rat hindlimb muscle is demonstrated. Sepsis decreased muscle [PCr] by 18%, 18 +/- 4 SD vs 22 +/- 4 SD mmol/kg tissue wet wt (P = 0.01) in control rats but [ATP] was unchanged, 6 mmol/kg tissue wet wt (P = 0.2). The derived free cytosolic [ADP] in the two groups was similar, [ADP]septic = 0.023 +/- 0.004 SD and [ADP]control = 0.021 +/- 0.003 SD mmol/kg tissue wet wt, and not statistically different (P = 0.14). Likewise [Pi] in the septic and control groups was not statistically different, [Pi]septic = 1.1 +/- 0.5 SD and [Pi]control = 1.2 +/- 0.4 SD mmol/kg tissue wet wt (P = 0.2). Septic rats presented the symptom of respiratory alkalosis evidenced by elevated blood pH. Sepsis decreased muscle blood flow by 33%, P = 0.003, but examination of individual subjects did not demonstrate a correlation with the reduction in [PCr]. Thus, a metabolic energy deficit caused by cellular ischemia/hypoxia is not a likely cause of cellular abnormality in rat hindlimb muscle during sepsis.

  3. The investigation of membrane binding by amphibian peptide agonists of CCK2R using (31)P and (2)H solid-state NMR.

    PubMed

    Sherman, Patrick J; Separovic, Frances; Bowie, John H

    2014-05-01

    It has been proposed that some neuropeptides may be anchored to the cell membranes prior to attaching to the adjacent active sites of transmembrane receptors. The three amphibian skin neuropeptides signiferin 1 [RLCIPYIIPC(OH)] (smooth muscle active and immunomodulator), riparin 1.1 [[RLCIPVIFPC(OH)] (immunomodulator) and rothein 1 [SVSNIPESIGF(OH)] (immunomodulator) act via CCK2 transmembrane receptors. A combination of (31)P and (2)H solid state NMR studies of each of these three peptides in eukaryotic phospholipid models at 25°C shows that rothein 1 does not interact with the membrane at all. In contrast, both of the cyclic disulfides signiferin 1 and riparin 1.1 interact with phospholipid head groups and partially penetrate into the upper leaflet of the model bilayer, but to different extents. These interactions are not sufficiently effective to cause disruption of the lipid bilayer since the peptides are not antimicrobial, anticancer, antifungal nor active against enveloped viruses. Copyright © 2014. Published by Elsevier Inc.

  4. Post-HTS case report and structural alert: Promiscuous 4-aroyl-1,5-disubstituted-3-hydroxy-2H-pyrrol-2-one actives verified by ALARM NMR.

    PubMed

    Dahlin, Jayme L; Nissink, J Willem M; Francis, Subhashree; Strasser, Jessica M; John, Kristen; Zhang, Zhiguo; Walters, Michael A

    2015-11-01

    Despite its wide use, not every high-throughput screen (HTS) yields chemical matter suitable for drug development campaigns, and seldom are 'go/no-go' decisions in drug discovery described in detail. This case report describes the follow-up of a 4-aroyl-1,5-disubstituted-3-hydroxy-2H-pyrrol-2-one active from a cell-free HTS to identify small-molecule inhibitors of Rtt109-catalyzed histone acetylation. While this compound and structural analogs inhibited Rtt109-catalyzed histone acetylation in vitro, further work on this series was halted after several risk mitigation strategies were performed. Compounds with this chemotype had a poor structure-activity relationship, exhibited poor selectivity among other histone acetyltransferases, and tested positive in a β-lactamase counter-screen for chemical aggregates. Furthermore, ALARM NMR demonstrated compounds with this chemotype grossly perturbed the conformation of the La protein. In retrospect, this chemotype was flagged as a 'frequent hitter' in an analysis of a large corporate screening deck, yet similar compounds have been published as screening actives or chemical probes versus unrelated biological targets. This report-including the decision-making process behind the 'no-go' decision-should be informative for groups engaged in post-HTS triage and highlight the importance of considering physicochemical properties in early drug discovery. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Synthesis and characterization of polyphosphazene copolymers using phosphorus-31 NMR spectroscopy

    SciTech Connect

    Stewart, F.F.; Peterson, E.S.; Stone, M.L.; Singler, R.E.

    1997-01-01

    It was observed that competitive nucleophilic addition processes may be observed by {sup 31}P NMR spectroscopy. Methoxyethoxyethanol (MEE) and p-methoxyphenol readily substitute for chlorineonto phosphorus and the relative rates are generally comparable to each other. Sterically, the phenol presents is slightly larger than MEE but this does not appear to effect substitution judging by the observed PN(OAr){sub 2} NMR signal. These processes are still being studied.

  6. Profiling formulated monoclonal antibodies by (1)H NMR spectroscopy.

    PubMed

    Poppe, Leszek; Jordan, John B; Lawson, Ken; Jerums, Matthew; Apostol, Izydor; Schnier, Paul D

    2013-10-15

    Nuclear magnetic resonance (NMR) is arguably the most direct methodology for characterizing the higher-order structure of proteins in solution. Structural characterization of proteins by NMR typically utilizes heteronuclear experiments. However, for formulated monoclonal antibody (mAb) therapeutics, the use of these approaches is not currently tenable due to the requirements of isotope labeling, the large size of the proteins, and the restraints imposed by various formulations. Here, we present a new strategy to characterize formulated mAbs using (1)H NMR. This method, based on the pulsed field gradient stimulated echo (PGSTE) experiment, facilitates the use of (1)H NMR to generate highly resolved spectra of intact mAbs in their formulation buffers. This method of data acquisition, along with postacquisition signal processing, allows the generation of structural and hydrodynamic profiles of antibodies. We demonstrate how variation of the PGSTE pulse sequence parameters allows proton relaxation rates and relative diffusion coefficients to be obtained in a simple fashion. This new methodology can be used as a robust way to compare and characterize mAb therapeutics.

  7. 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.

  8. Infrared Predissociation Spectroscopy of the Hydrocarbon Cations C_3H^+, C_2H^+, and C_3H_2^+

    NASA Astrophysics Data System (ADS)

    Brünken, Sandra; Lipparini, Filippo; Gauss, Jürgen; Stoffels, Alexander; Redlich, Britta; van der Meer, Lex; Berden, Giel; Oomens, Jos; Schlemmer, Stephan

    2016-06-01

    Reactive hydrocarbon cations play an important role in the astrochemistry of the interstellar medium, but spectroscopic data, needed for their identification in astronomical observations, is sparse. Here we report the first gas-phase vibrational spectra of the linear C_3H^+ (^1 Σ), the radical cation C_2H^+ (^3 Π), and the linear-/cyclic-C_3H_2^+ (^2 Π /^2A_1, resp.). Broadband spectra were recorded by Ne- and He-messenger infrared-predissociation (IR-PD) action spectroscopy in a cryogenic (4-11 K) ion trap instrument (FELion) in the 250-3500 {wn} range using a free electron laser and a MIR-OPO at the FELIX (Free-Electron Laser for Infrared eXperiments) laboratory. The band positions (determined with a precision of 1-2 wn) covering the C-H and C-C stretching as well as several bending modes are compared to high-level (CCSD(T) with large basis sets) quantum-chemical calculations with an emphasis on anharmonic effects and on the influence of the rare-gas messenger atom. The experimental and theoretical data provide a solid basis for subsequent IR high-resolution studies, with the ultimate goal to predict and measure accurate rotational spectra for a radio-astronomical search of these molecular ions in space.

  9. Automatic structure determination of regular polysaccharides based solely on NMR spectroscopy.

    PubMed

    Lundborg, Magnus; Fontana, Carolina; Widmalm, Göran

    2011-11-14

    The structural analysis of polysaccharides requires that the sugar components and their absolute configurations are determined. We here show that this can be performed based on NMR spectroscopy by utilizing butanolysis with (+)- and (-)-2-butanol that gives the corresponding 2-butyl glycosides with characteristic (1)H and (13)C NMR chemical shifts. The subsequent computer-assisted structural determination by CASPER can then be based solely on NMR data in a fully automatic way as shown and implemented herein. The method is additionally advantageous in that reference data only have to be prepared once and from a user's point of view only the unknown sample has to be derivatized for use in CASPER.

  10. Watching protein structure at work in living cells using NMR spectroscopy.

    PubMed

    Tochio, Hidehito

    2012-12-01

    Isotope-assisted multi-dimensional NMR spectroscopy can now be applied to proteins inside living cells. The technique, called in-cell NMR, aims to investigate the structures, interactions and dynamics of proteins under their native conditions, ideally at an atomic resolution. The application has begun with bacterial cells but has now expanded to mammalian cultured cells, such as HeLa cells. The importance of the realization of such 'in-mammalian cell' NMR should be stressed, as these are the cells most often employed in cell biology. Hence, a substantially wide range of application would be possible in the near future once the technique has been well developed.

  11. Egg yolk identification and aging in mixed paint binding media by NMR spectroscopy.

    PubMed

    Sfakianaki, Sofia; Kouloumpi, Eleni; Anglos, Demetrios; Spyros, Apostolos

    2015-01-01

    NMR spectroscopy is a powerful analytical tool for the identification and quantitative analysis of organic materials in a cultural heritage context. In this report, we present an analytical NMR protocol for the identification and semiquantification of egg yolk binders and mixed binding media that also contain a drying oil, namely linseed oil. The samples studied have been artificially and/or naturally aged in order to simulate the composition of organic materials in paintings. Analysis of the 1D and 2D NMR spectra showed that egg yolk can be identified even in binding media of considerable age via signals originating from cholesterol and/or cholesterol oxidation products present in the aged binding medium. Based on cholesterol-related and other lipid signals in the NMR spectra of egg yolk binders, a molecular marker (R/F) that suggests the presence of egg yolk in paint binders is proposed. Via this marker, the presence of egg yolk in the organic material obtained from an early 18th century Greek icon is confirmed, and this is further verified by 2D NMR spectroscopy. It is demonstrated that NMR molecular markers developed to estimate the hydrolysis/oxidation state of oil paintings are also suitable for the analysis of egg yolk and mixed medium (egg yolk-linseed oil) binders, indicating the generality of the NMR methodological approach in the analysis of organic materials in a cultural heritage context. Copyright © 2014 John Wiley & Sons, Ltd.

  12. Natural abundance 13C-NMR spectroscopy for the quantitative determination of fecal fat.

    PubMed

    Kunz, P; Künnecke, B; Kunz, I; Lengsfeld, H; von Kienlin, M

    2003-10-01

    To evaluate 13C-NMR spectroscopy as a method for fat quantitation in human feces without time consuming or unpleasant preparation steps. Stool samples of seven healthy subjects were collected for 18 days before and during oral intake of the inhibitor of gastrointestinal lipases Orlistat. Fecal lipid content was determined first using 13C-NMR, then by conventional gravimetry after homogenization and Bligh & Dyer lipid extraction. The correlation between gravimetry and 13C-NMR was excellent (R2 = 0.91). In repeated measurements, the mean percentage error was 2.8%. On average, 13C-NMR yielded 1.27 g less fat than gravimetry. Orlistat efficacy for fat excretion assessed by 13C-NMR and by gravimetry was 34.3% and 33.9%, respectively. With a total measurement time of three minutes, 13C-NMR spectroscopy of unprocessed whole stool provides an accurate alternative to gravimetry for assessing total fecal fat excretion. 13C-NMR is superior with regard to practicability and speed.

  13. Structural determination of larger proteins using stable isotope labeling and NMR spectroscopy

    SciTech Connect

    Unkefer, C.; Hernandez, G.; Springer, P.; Trewhella, J.; Blumenthal, D.; Lidstrom, M.

    1996-04-01

    The project sought to employ stable isotope labeling and NMR spectroscopy to study protein structures and provide insight into important biochemical problems. A methylotrophic bacterial expression system has been developed for uniform deuterium and carbon-13 labeling of proteins for structural studies. These organisms grow using methanol as the sole source of carbon and energy. Because isotopically labeled methanol is relatively inexpensive, the methylotrophs are ideal for expressing proteins labeled uniformly with deuterium and/or carbon-13. This expression system has been employed to prepare deuterated troponin C. NMR spectroscopy measurements have been made on the inhibitory peptide from troponin I (residues 96--115), both as the free peptide and the peptide complexed with deuterated troponin C. Proton-NMR spectroscopy resonance-signal assignments have been made for the free peptide.

  14. Polydimethylsiloxane: a general matrix for high-performance chromatographic NMR spectroscopy.

    PubMed

    Huang, Shaohua; Gao, Jun; Wu, Rui; Li, Shengying; Bai, Zhengwu

    2014-10-20

    The detection and structural characterization of the components of a mixture is a challenging task. Therefore, the development of a facile and general method that enables both the separation and the structural characterization of the components is desired. Diffusion-ordered NMR spectroscopy (DOSY) with the aid of a matrix is a promising tool for this purpose. However, because the currently existing matrices only separate limited components, the application of the DOSY technique is restricted. Herein we introduce a new versatile matrix, poly(dimethylsiloxane), which can fully separate many mixtures of different structural types by liquid-state NMR spectroscopy. With poly(dimethylsiloxane), liquid-state chromatographic NMR spectroscopy could become a general approach for the structural elucidation of mixtures of compounds.

  15. Solid-State NMR Spectroscopy of Metal–Organic Framework Compounds (MOFs)

    PubMed Central

    Hoffmann, Herbert C.; Debowski, Marta; Müller, Philipp; Paasch, Silvia; Senkovska, Irena; Kaskel, Stefan; Brunner, Eike

    2012-01-01

    Nuclear Magnetic Resonance (NMR) spectroscopy is a well-established method for the investigation of various types of porous materials. During the past decade, metal–organic frameworks have attracted increasing research interest. Solid-state NMR spectroscopy has rapidly evolved into an important tool for the study of the structure, dynamics and flexibility of these materials, as well as for the characterization of host–guest interactions with adsorbed species such as xenon, carbon dioxide, water, and many others. The present review introduces and highlights recent developments in this rapidly growing field.

  16. Discrimination of allied species within the genus Turbinaria (Fucales, Phaeophyceae) using HRMAS NMR spectroscopy.

    PubMed

    Le Lann, K; Kervarec, N; Payri, C E; Deslandes, E; Stiger-Pouvreau, V

    2008-01-15

    A novel chemotaxonomical method based on 1D (1)H HRMAS NMR spectroscopy is being tested for taxonomical purposes. This powerful technique allowed us to discriminate between specimens belonging to two sister species of Turbinaria, which are difficult to tell apart using only morphological characters. Based on spectra analysis, the results allowed us to successfully group the specimens according to their species. Thus, the efficiency of HRMAS NMR spectroscopy for the discrimination of algal species and for the pre-screening of potential chemomarkers is demonstrated.

  17. Photo-CIDNP NMR spectroscopy of amino acids and proteins.

    PubMed

    Kuhn, Lars T

    2013-01-01

    Photo-chemically induced dynamic nuclear polarization (CIDNP) is a nuclear magnetic resonance (NMR) phenomenon which, among other things, is exploited to extract information on biomolecular structure via probing solvent-accessibilities of tryptophan (Trp), tyrosine (Tyr), and histidine (His) amino acid side chains both in polypeptides and proteins in solution. The effect, normally triggered by a (laser) light-induced photochemical reaction in situ, yields both positive and/or negative signal enhancements in the resulting NMR spectra which reflect the solvent exposure of these residues both in equilibrium and during structural transformations in "real time". As such, the method can offer - qualitatively and, to a certain extent, quantitatively - residue-specific structural and kinetic information on both the native and, in particular, the non-native states of proteins which, often, is not readily available from more routine NMR techniques. In this review, basic experimental procedures of the photo-CIDNP technique as applied to amino acids and proteins are discussed, recent improvements to the method highlighted, and future perspectives presented. First, the basic principles of the phenomenon based on the theory of the radical pair mechanism (RPM) are outlined. Second, a description of standard photo-CIDNP applications is given and it is shown how the effect can be exploited to extract residue-specific structural information on the conformational space sampled by unfolded or partially folded proteins on their "path" to the natively folded form. Last, recent methodological advances in the field are highlighted, modern applications of photo-CIDNP in the context of biological NMR evaluated, and an outlook into future perspectives of the method is given.

  18. Two-dimensional NMR spectroscopy in Earth's magnetic field.

    PubMed

    Robinson, Jeremy N; Coy, Andrew; Dykstra, Robin; Eccles, Craig D; Hunter, Mark W; Callaghan, Paul T

    2006-10-01

    We demonstrate the first two-dimensional correlation NMR (COSY) spectra obtained at ultra low frequencies (ULF) using the Earth's magnetic field. Using a specially developed spectrometer with multiple audio-frequency pulses under controlled pulse phase, we observe magnetisation transfer arising from heteronuclear J-couplings in trifluoroethanol and para-difluorobenzene. The 2D COSY spectra exhibit all diagonal and off-diagonal multiplets consistent with known J-couplings in these molecules.

  19. Dynamic nuclear polarization NMR spectroscopy of microcrystalline solids.

    PubMed

    Rossini, Aaron J; Zagdoun, Alexandre; Hegner, Franziska; Schwarzwälder, Martin; Gajan, David; Copéret, Christophe; Lesage, Anne; Emsley, Lyndon

    2012-10-10

    Dynamic nuclear polarization (DNP) solid-state NMR has been applied to powdered microcrystalline solids to obtain sensitivity enhancements on the order of 100. Glucose, sulfathiazole, and paracetamol were impregnated with bis-nitroxide biradical (bis-cyclohexyl-TEMPO-bisketal, bCTbK) solutions of organic solvents. The organic solvents were carefully chosen to be nonsolvents for the compounds, so that DNP-enhanced solid-state NMR spectra of the unaltered solids could be acquired. A theoretical model is presented that illustrates that for externally doped organic solids characterized by long spin-lattice relaxation times (T(1)((1)H) > 200 s), (1)H-(1)H spin diffusion can relay enhanced polarization over micrometer length scales yielding substantial DNP enhancements (ε). ε on the order of 60 are obtained for microcrystalline glucose and sulfathiazole at 9.4 T and with temperatures of ca. 105 K. The large gain in sensitivity enables the rapid acquisition of (13)C-(13)C correlation spectra at natural isotopic abundance. It is anticipated that this will be a general method for enhancing the sensitivity of solid-state NMR experiments of organic solids.

  20. 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.

  1. Genetic Algorithm Optimized Triply Compensated Pulses in NMR Spectroscopy

    PubMed Central

    Manu, V. S.; Veglia, Gianluigi

    2015-01-01

    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. PMID:26473327

  2. 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…

  3. 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…

  4. From Molecular Structure to Global Processes : NMR Spectroscopy in Analytical/Environmental Chemistry

    NASA Astrophysics Data System (ADS)

    Simpson, A.

    2009-04-01

    NMR Spectroscopy is arguably the most powerful tool to elucidate structure and probe molecular interactions. A range of NMR approaches will be introduced with emphasis on addressing and understanding structure and reactivity of soil organic matter at the molecular level. The presentation will be split into three main sections. The first section will look at evidence from advanced NMR based approaches that when considered synergistically describes the major structural components in soil organic matter. Multidimensional NMR spectroscopy (1-3D NMR), automated pattern matching, spectral simulations, diffusion NMR and hybrid-diffusion NMR will be introduced in context of molecular structure. Finally the structural components in soil will be contrasted to those found in aquatic dissolved organic matter. Secondly molecular interactions of natural organic matter will be considered. Advanced structural studies have provided detailed spectral assignments which in turn permit the reactivity of various soil components to be elucidated. Aggregation and self-association of soil and dissolved organic matter will be discussed along with the structural components likely responsible for aggregation/colloid formation. Interactions of soil organic matter with anthropogenic chemicals will also be considered and NMR techniques based on "Saturation Transfer Difference" introduced. These techniques are extremely powerful and can be used to both; describe mechanistically how anthropogenic chemicals sorb to whole soils and identify the structural components (lignin, protein, cellulose, etc..) that are responsible for the binding/sorption in soil. In the last section, the "big questions" and challenges facing the field will be considered along with some novel experimental NMR based approaches that should, in future, assist in providing answers to these questions.

  5. 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

  6. New insights into glycopeptide antibiotic binding to cell wall precursors using SPR and NMR spectroscopy.

    PubMed

    Treviño, Juan; Bayón, Carlos; Ardá, Ana; Marinelli, Flavia; Gandolfi, Raffaella; Molinari, Francesco; Jimenez-Barbero, Jesús; Hernáiz, María J

    2014-06-10

    Glycopeptide antibiotics, such as vancomycin and teicoplanin, are used to treat life-threatening infections caused by multidrug-resistant Gram-positive pathogens. They inhibit bacterial cell wall biosynthesis by binding to the D-Ala-D-Ala C-terminus of peptidoglycan precursors. Vancomycin-resistant bacteria replace the dipeptide with the D-Ala-D-Lac depsipeptide, thus reducing the binding affinity of the antibiotics with their molecular targets. Herein, studies of the interaction of teicoplanin, teicoplanin-like A40926, and of their semisynthetic derivatives (mideplanin, MDL63,246, dalbavancin) with peptide analogues of cell-wall precursors by NMR spectroscopy and surface plasmon resonance (SPR) are reported. NMR spectroscopy revealed the existence of two different complexes in solution, when the different glycopeptides interact with Ac2KdAlaDAlaOH. Despite the NMR experimental conditions, which are different from those employed for the SPR measurements, the NMR spectroscopy results parallel those deduced in the chip with respect to the drastic binding difference existing between the D-Ala and the D-Lac terminating analogues, confirming that all these antibiotics share the same primary molecular mechanism of action and resistance. Kinetic analysis of the interaction between the glycopeptide antibiotics and immobilized AcKdAlaDAlaOH by SPR suggest a dimerization process that was not observed by NMR spectroscopy in DMSO solution. Moreover, in SPR, all glycopeptides with a hydrophobic acyl chain present stronger binding with a hydrophobic surface than vancomycin, indicating that additional interactions through the employed surface are involved. In conclusion, SPR provides a tool to differentiate between vancomycin and other glycopeptides, and the calculated binding affinities at the surface seem to be more relevant to in vitro antimicrobial activity than the estimations from NMR spectroscopy analysis.

  7. 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.

  8. Protein folding and unfolding studied at atomic resolution by fast two-dimensional NMR spectroscopy.

    PubMed

    Schanda, Paul; Forge, Vincent; Brutscher, Bernhard

    2007-07-03

    Atom-resolved real-time studies of kinetic processes in proteins have been hampered in the past by the lack of experimental techniques that yield sufficient temporal and atomic resolution. Here we present band-selective optimized flip-angle short transient (SOFAST) real-time 2D NMR spectroscopy, a method that allows simultaneous observation of reaction kinetics for a large number of nuclear sites along the polypeptide chain of a protein with an unprecedented time resolution of a few seconds. SOFAST real-time 2D NMR spectroscopy combines fast NMR data acquisition techniques with rapid sample mixing inside the NMR magnet to initiate the kinetic event. We demonstrate the use of SOFAST real-time 2D NMR to monitor the conformational transition of alpha-lactalbumin from a molten globular to the native state for a large number of amide sites along the polypeptide chain. The kinetic behavior observed for the disappearance of the molten globule and the appearance of the native state is monoexponential and uniform along the polypeptide chain. This observation confirms previous findings that a single transition state ensemble controls folding of alpha-lactalbumin from the molten globule to the native state. In a second application, the spontaneous unfolding of native ubiquitin under nondenaturing conditions is characterized by amide hydrogen exchange rate constants measured at high pH by using SOFAST real-time 2D NMR. Our data reveal that ubiquitin unfolds in a gradual manner with distinct unfolding regimes.

  9. 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

  10. Microcoil high-resolution magic angle spinning NMR spectroscopy.

    PubMed

    Janssen, Hans; Brinkmann, Andreas; van Eck, Ernst R H; van Bentum, P Jan M; Kentgens, Arno P M

    2006-07-12

    We report the construction of a dual-channel microcoil nuclear magnetic resonance probehead allowing magic-angle spinning for mass-limited samples. With coils down to 235 mum inner diameter, this allows high-resolution solid-state NMR spectra to be obtained for amounts of materials of a few nanoliters. This is demonstrated by the carbon-13 spectrum of a tripeptide and a single silk rod, prepared from the silk gland of the Bombyx mori silkworm. Furthermore, the microcoil allows for radio frequency field strengths well beyond current probe technology, aiding in getting the highest possible resolution by efficiently decoupling the observed nuclei from the abundantly present proton nuclei.

  11. Nuclear Quadrupole Coupling Tensors of 2H in the a-Alum RbAl(SO4)2 · 12D2O and the Dynamical Behaviour of the D2O Molecules. An Investigation by NMR and IR

    NASA Astrophysics Data System (ADS)

    Ramakrishna, J.; Weiden, Norbert; Weiss, Alarich

    1990-04-01

    By single crystal NMR the nuclear quadrupole coupling constants eQΦzz h-1 (2H), the asymmetry parameters η(2H) and the direction cosines of the principal axes of the electric field gradient tensors of the 2H atoms of the two kinds of D2O molecules have been determined at 295 K in RbAl(SO4)2 · 12D2O. The results show that the D2O molecules surrounding the ion Al3+ are "static" within the time scale of the 2H nuclear quadrupole interaction while the D2O belonging to the octahedron around the Rb+ undergoes fast reorientations around the twofold molecular axis. For the two kinds of D2O in the alum we found: eQΦzz(1)h-1 (2H) = 186.5 kHz, η(1),(2H) = 0.1234; eQΦzz(2)h-1 (2H) = 169.7 kHz,η (2)(2H) = 0.1297; eQΦzz(3)h-1(2H) = 122.1 kHz, (2H) = 0.8087. eQΦzz(1) and eQΦzz(2) belong to the "static" D2O molecules and an assignment to the two different 2H atoms has been performed. The IR spectra of RbAl(SO4)2 · 12(H1-xDx)2O have been investigated, and for the O - D stretching frequencies values of 2145 cm-1 , 2235 cm-1 , 2470 cm-1 and 2525 cm -1 have been obtained. They agree well with the relations between ṽOD and eQΦzz h-1(2H) given in the literature.

  12. 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

  13. Heteronuclear three-dimensional NMR spectroscopy of the inflammatory protein C5a

    SciTech Connect

    Zuiderweg, E.R.P.; Fesik, S.W. )

    1989-03-21

    The utility of three-dimensional heteronuclear NMR spectroscopy for the assignment of {sup 1}H and {sup 15}N resonances of the inflammatory protein C5a (MW 8500), uniformly labeled with {sup 15}N, is demonstrated at a protein concentration of 0.7 mM. It is shown that dramatic simplification of the 2D nuclear Overhauser effect spectrum (NOESY) is obtained by editing with respect to the frequency of the {sup 15}N heteronucleus in a third dimension. The improved resolution in the 3D experiment largely facilitates the assignment of protein NMR spectra and allows for the determination of distance constraints from otherwise overlapping NOE cross peaks for purposes of 3D structure determination. The results show that {sup 15}N heteronuclear 3D NMR can facilitate the structure determination of small proteins and promises to be a useful tool for the study of larger systems that cannot be studied by conventional 2D NMR techniques.

  14. Ultrasensitive anion detection by NMR spectroscopy: a supramolecular strategy based on modulation of chemical exchange rate.

    PubMed

    Perruchoud, Loïse H; Hadzovic, Alen; Zhang, Xiao-An

    2015-06-08

    NMR spectroscopy is a powerful tool for monitoring molecular interactions and is widely used to characterize supramolecular systems at the atomic level. NMR is limited for sensing purposes, however, due to low sensitivity. Dynamic processes such as conformational changes or binding events can induce drastic effects on NMR spectra in response to variations in chemical exchange (CE) rate, which can lead to new strategies in the design of supramolecular sensors through the control and monitoring of CE rate. Here, we present an indirect NMR anion sensing technique in which increased CE rate, due to anion-induced conformational flexibility of a relatively rigid structure of a novel sensor, allows ultrasensitive anion detection as low as 120 nM.

  15. Slow-spinning low-sideband HR-MAS NMR spectroscopy: delicate analysis of biological samples

    PubMed Central

    Renault, Marie; Shintu, Laetitia; Piotto, Martial; Caldarelli, Stefano

    2013-01-01

    High-Resolution Magic-Angle Spinning (HR-MAS) NMR spectroscopy has become an extremely versatile analytical tool to study heterogeneous systems endowed with liquid-like dynamics. Spinning frequencies of several kHz are however required to obtain NMR spectra, devoid of spinning sidebands, with a resolution approaching that of purely isotropic liquid samples. An important limitation of the method is the large centrifugal forces that can damage the structure of the sample. In this communication, we show that optimizing the sample preparation, particularly avoiding air bubbles, and the geometry of the sample chamber of the HR-MAS rotor leads to high-quality low-sideband NMR spectra even at very moderate spinning frequencies, thus allowing the use of well-established solution-state NMR procedures for the characterization of small and highly dynamic molecules in the most fragile samples, such as live cells and intact tissues. PMID:24284435

  16. Characterizing Covalently Sidewall-Functionalized SWCNTs by using 1H NMR Spectroscopy

    PubMed Central

    Nelson, Donna J.; Kumar, Ravi

    2013-01-01

    Unambiguous evidence for covalent sidewall functionalization of single-walled carbon nanotubes (SWCNTs) has been a difficult task, especially for nanomaterials in which slight differences in functionality structure produce significant changes in molecular characteristics. Nuclear magnetic resonance (NMR) spectroscopy provides clear information about the structural skeleton of molecules attached to SWCNTs. In order to establish the generality of proton NMR as an analytical technique for characterizing covalently functionalized SWCNTs, we have obtained and analyzed proton NMR data of SWCNT-substituted benzenes across a variety of para substituents. Trends obtained for differences in proton NMR chemical shifts and the impact of o-, p-, and m-directing effects of electrophilic aromatic substituents on phenyl groups covalently bonded to SWCNTs are discussed. PMID:24009779

  17. PCB/polymer based micro-fluidic system for NMR spectroscopy for nanoliters sample volume.

    PubMed

    Pasquet, Guillaume; Chateaux, Jean-François; Deman, Anne-Laure; Fenet, Bernard; Morin, Pierre

    2007-01-01

    In this work, we report on the realization of an innovating micro system for NMR spectroscopy on small sample volume (30-100 nL). We propose a micro system based on Printed Circuit Board (PCB) technology for the NMR probe associated to a micro fluidic system made with polymer (COC). The comparison of several samples during the same NMR experiments could provide more precise information. In that context, we have realized a micro-fluidic system with two cavities, each cavity presenting a volume of 37 nl. The fabrication process is described, and first results are reported. The tight sealing of the micro-fluidic system has been demonstrated and preliminary NMR experiment results are presented.

  18. 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.

  19. Next-generation heteronuclear decoupling for high-field biomolecular NMR spectroscopy.

    PubMed

    Schilling, Franz; Warner, Lisa R; Gershenzon, Naum I; Skinner, Thomas E; Sattler, Michael; Glaser, Steffen J

    2014-04-22

    Ultra-high-field NMR spectroscopy requires an increased bandwidth for heteronuclear decoupling, especially in biomolecular NMR applications. Composite pulse decoupling cannot provide sufficient bandwidth at practical power levels, and adiabatic pulse decoupling with sufficient bandwidth is compromised by sideband artifacts. A novel low-power, broadband heteronuclear decoupling pulse is presented that generates minimal, ultra-low sidebands. The pulse was derived using optimal control theory and represents a new generation of decoupling pulses free from the constraints of periodic and cyclic sequences. In comparison to currently available state-of-the-art methods this novel pulse provides greatly improved decoupling performance that satisfies the demands of high-field biomolecular NMR spectroscopy.

  20. 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.

  1. Clathrate Structure Determination by Combining Crystal Structure Prediction with Computational and Experimental (129) Xe NMR Spectroscopy.

    PubMed

    Selent, Marcin; Nyman, Jonas; Roukala, Juho; Ilczyszyn, Marek; Oilunkaniemi, Raija; Bygrave, Peter J; Laitinen, Risto; Jokisaari, Jukka; Day, Graeme M; Lantto, Perttu

    2017-01-23

    An approach is presented for the structure determination of clathrates using NMR spectroscopy of enclathrated xenon to select from a set of predicted crystal structures. Crystal structure prediction methods have been used to generate an ensemble of putative structures of o- and m-fluorophenol, whose previously unknown clathrate structures have been studied by (129) Xe NMR spectroscopy. The high sensitivity of the (129) Xe chemical shift tensor to the chemical environment and shape of the crystalline cavity makes it ideal as a probe for porous materials. The experimental powder NMR spectra can be used to directly confirm or reject hypothetical crystal structures generated by computational prediction, whose chemical shift tensors have been simulated using density functional theory. For each fluorophenol isomer one predicted crystal structure was found, whose measured and computed chemical shift tensors agree within experimental and computational error margins and these are thus proposed as the true fluorophenol xenon clathrate structures.

  2. The efficiency of DPPH as a polarising agent for DNP-NMR spectroscopy

    PubMed Central

    Lumata, Lloyd; Merritt, Matthew; Khemtong, Chalermchai; Ratnakar, S. James; van Tol, Johan; Yu, Lu; Song, Likai

    2012-01-01

    The free radical 2,2-diphenyl-1-pycrylhydrazyl (DPPH) was tested as a polarising agent for fast dissolution dynamic nuclear polarisation (DNP) NMR spectroscopy. DPPH was found to be reasonably soluble in sulfolane and the optimum concentration for DNP is 20–40 mM depending upon whether short polarisation times or the maximum signal intensity is needed. W-band ESR measurements revealed that the ESR linewidth D of DPPH is intermediate between that of BDPA and 4-oxo-TEMPO. Several thousand-fold NMR signal enhancements in the liquid-state were achieved for 13C, 15N, 89Y, and 109Ag compounds, demonstrating that DPPH can be added to the list of polarising agents for DNP-NMR spectroscopy. Furthermore, the hydrophobic DPPH free radical can be easily filtered out from the dissolution liquid when water is used as the dissolution solvent. PMID:23205273

  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. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. The efficiency of DPPH as a polarising agent for DNP-NMR spectroscopy.

    PubMed

    Lumata, Lloyd; Merritt, Matthew; Khemtong, Chalermchai; Ratnakar, S James; van Tol, Johan; Yu, Lu; Song, Likai; Kovacs, Zoltan

    2012-01-01

    The free radical 2,2-diphenyl-1-pycrylhydrazyl (DPPH) was tested as a polarising agent for fast dissolution dynamic nuclear polarisation (DNP) NMR spectroscopy. DPPH was found to be reasonably soluble in sulfolane and the optimum concentration for DNP is 20-40 mM depending upon whether short polarisation times or the maximum signal intensity is needed. W-band ESR measurements revealed that the ESR linewidth D of DPPH is intermediate between that of BDPA and 4-oxo-TEMPO. Several thousand-fold NMR signal enhancements in the liquid-state were achieved for (13)C, (15)N, (89)Y, and (109)Ag compounds, demonstrating that DPPH can be added to the list of polarising agents for DNP-NMR spectroscopy. Furthermore, the hydrophobic DPPH free radical can be easily filtered out from the dissolution liquid when water is used as the dissolution solvent.

  5. Chiral Recognition by Dissolution DNP NMR Spectroscopy of (13)C-Labeled dl-Methionine.

    PubMed

    Monteagudo, Eva; Virgili, Albert; Parella, Teodor; Pérez-Trujillo, Míriam

    2017-05-02

    A method based on d-DNP NMR spectroscopy to study chiral recognition is described for the first time. The enantiodifferentiation of a racemic metabolite in a millimolar aqueous solution using a chiral solvating agent was performed. Hyperpolarized (13)C-labeled dl-methionine enantiomers were differently observed with a single-scan (13)C NMR experiment, while the chiral auxiliary at thermal equilibrium remained unobserved. The method developed entails a step forward in the chiral recognition of small molecules by NMR spectroscopy, opening new possibilities in situations where the sensitivity is limited, for example, when a low concentration of analyte is available or when the measurement of an insensitive nucleus, like (13)C, is required. The advantages and current limitations of the method, as well as future perspectives, are discussed.

  6. Bacterial Expression and Purification of the Amyloidogenic Peptide PAPf39 for Multidimensional NMR Spectroscopy

    PubMed Central

    Shanmuganathan, Aranganathan; Bishop, Anthony C.; French, Kinsley C.; McCallum, Scott A.; Makhatadze, George I.

    2013-01-01

    PAPf39 is a 39 residue peptide fragment from human prostatic acidic phosphatase that forms amyloid fibrils in semen. These fibrils have been implicated in facilitating HIV transmission. To enable structural studies of PAPf39 by NMR spectroscopy, efficient methods allowing the production of milligram quantities of isotopically labeled peptide are essential. Here, we report the high-yield expression, as a fusion to ubiquitin at the N-terminus and an intein at the C-terminus, and purification of uniformly labeled 13C- and 15N-labeled PAPf39 peptide. This allows the study of the PAPf39 monomer conformational ensemble by NMR spectroscopy. To this end, we performed the NMR chemical shift assignment of the PAPf39 peptide in the monomeric state at low pH. PMID:23314347

  7. 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

  8. Positional isotope exchange studies on enzyme using NMR spectroscopy

    SciTech Connect

    Matsunaga, T.O.

    1987-01-01

    The isotopically enriched compounds, /sup 18/O-..beta..,..gamma..-ATP and /sup 18/O bridge-labeled pyrophosphate, synthesized previously in this laboratory, were used to investigate and measure the exchange vs. turnover of substrates and products from their central complexes in four selected enzyme systems. Using hi-field /sup 31/P NMR, we were able to differentiate between /sup 18/O labeled in the bridge vs. the non-bridge positions by virtue of the isotope shift upon the phosphorus nuclei. The bridge to non-bridge scrambling of the label was quantitated and the exchange vs. turnover ratios under a variety of conditions was determined. Using the substrate inhibitor carboxycreatinine, PIX experiments with /sup 18/O-..beta..,..gamma..-ATP and creatine kinase were conducted. It was shown that carboxycreatinine and creatine kinase promoted exchange of the /sup 18/O label as determined by NMR. We have concluded that carboxycreatinine is either a substrate that catalyzes very slow turnover or it catalyzes exchange by a dissociative (SN/sub 1//sub P/) type of mechanism

  9. 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

  10. 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.

  11. Use of NMR Saturation Transfer Difference Spectroscopy to Study Ligand Binding to Membrane Proteins

    PubMed Central

    Venkitakrishnan, Rani Parvathy; Benard, Outhiriaradjou; Max, Marianna; Markley, John L.

    2013-01-01

    Detection of weak ligand binding to membrane-spanning proteins, such as receptor proteins at low physiological concentrations, poses serious experimental challenges. Saturation transfer difference nuclear magnetic resonance (STD-NMR) spectroscopy offers an excellent way to surmount these problems. As the name suggests, magnetization transferred from the receptor to its bound ligand is measured by directly observing NMR signals from the ligand itself. Low-power irradiation is applied to a 1H NMR spectral region containing protein signals but no ligand signals. This irradiation spreads quickly throughout the membrane protein by the process of spin diffusion and saturates all protein 1H NMR signals. 1H NMR signals from a ligand bound transiently to the membrane protein become saturated and, upon dissociation, serve to decrease the intensity of the 1H NMR signals measured from the pool of free ligand. The experiment is repeated with the irradiation pulse placed outside the spectral region of protein and ligand, a condition that does not lead to saturation transfer to the ligand. The two resulting spectra are subtracted to yield the difference spectrum. As an illustration of the methodology, we review here STD-NMR experiments designed to investigate binding of ligands to the human sweet taste receptor, a member of the large family of G-protein-coupled receptors. Sweetener molecules bind to the sweet receptor with low affinity but high specificity and lead to a variety of physiological responses. PMID:22976022

  12. Recent advances in application of (27)Al NMR spectroscopy to materials science.

    PubMed

    Haouas, Mohamed; Taulelle, Francis; Martineau, Charlotte

    2016-05-01

    Valuable information about the local environment of the aluminum nucleus can be obtained through (27)Al Nuclear Magnetic Resonance (NMR) parameters like the isotropic chemical shift, scalar and quadrupolar coupling constants, and relaxation rate. With nearly 250 scientific articles per year dealing with (27)Al NMR spectroscopy, this analytical tool has become popular because of the recent progress that has made the acquisition and interpretation of the NMR data much easier. The application of (27)Al NMR techniques to various classes of compounds, either in solution or solid-state, has been shown to be extremely informative concerning local structure and chemistry of aluminum in its various environments. The development of experimental methodologies combined with theoretical approaches and modeling has contributed to major advances in spectroscopic characterization especially in materials sciences where long-range periodicity and classical local NMR probes are lacking. In this review we will present an overview of results obtained by (27)Al NMR as well as the most relevant methodological developments over the last 25years, concerning particularly on progress in the application of liquid- and solid-state (27)Al NMR to the study of aluminum-based materials such as aluminum polyoxoanions, zeolites, aluminophosphates, and metal-organic-frameworks.

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

    USDA-ARS?s Scientific Manuscript database

    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 ...

  14. En route to traceable reference standards for surface group quantifications by XPS, NMR and fluorescence spectroscopy.

    PubMed

    Hennig, Andreas; Dietrich, Paul M; Hemmann, Felix; Thiele, Thomas; Borcherding, Heike; Hoffmann, Angelika; Schedler, Uwe; Jäger, Christian; Resch-Genger, Ute; Unger, Wolfgang E S

    2015-03-21

    The fluorine content of polymer particles labelled with 2,2,2-trifluoroethylamine was reliably quantified with overlapping sensitivity ranges by XPS and solid-state NMR. This provides a first step towards reference materials for the metrological traceability of surface group quantifications. The extension of this concept to fluorescence spectroscopy is illustrated.

  15. 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…

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

    USDA-ARS?s Scientific Manuscript database

    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...

  17. Determination of Benzalkonium Chloride in Commercial Disinfectant Formulations by Quantitative NMR Spectroscopy

    DTIC Science & Technology

    2012-11-01

    treatment protocol for Royal Australian Navy vessels involves dosing with commercial disinfectant solutions containing the biocide benzalkonium...Quantitative NMR Spectroscopy Executive Summary A biofouling treatment protocol for Royal Australian Navy vessels involves dosing with commercial...An existing protocol for the in-water treatment of mussel biofouling within the internal sea water systems of RAN vessels is to dose with a

  18. 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…

  19. 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.

  20. 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…

  1. 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…

  2. 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%).

  3. 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…

  4. 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…

  5. Examination of amber and related materials by NMR spectroscopy.

    PubMed

    Lambert, Joseph B; Santiago-Blay, Jorge A; Wu, Yuyang; Levy, Allison J

    2015-01-01

    Examination of the solid-state (13)C and solution (1)H NMR spectra of fossilized resins (ambers) has generated five groupings of materials based on spectral characteristics. The worldwide Group A is associated with the botanical family of the Araucariaceae. The worldwide Group B is associated with the Dipterocarpaceae. Baltic amber or succinite (Group C) is related to Group A but with a disputed conifer source. Amber from Latin America, the Caribbean, and Africa is associated with the Fabaceae, the genus Hymenaea in particular. The minor Group E contains the rare fossil polystyrene. The spectra of jet indicate that it is a coal-like material with a rank between lignite and sub-bituminous coal.

  6. Characterizing excited conformational states of RNA by NMR spectroscopy

    PubMed Central

    Zhao, Bo; Zhang, Qi

    2016-01-01

    Conformational dynamics is a hallmark of diverse non-coding RNA functions. During these functional processes, RNA molecules almost ubiquitously undergo conformational transitions that are tuned to meet distinct structural and kinetic requirements for proper function. A complete mechanistic understanding of RNA function requires comprehensive structural and dynamic knowledge of these complex transitions, which often involve alternative higher-energy conformational states that pose a major challenge for high-resolution structural study by conventional methods. In this review, we describe recent progress in RNA NMR that has started to unveil detailed structural, thermodynamic and kinetic insights into some of these excited conformational states of RNA and their functional roles in biology. PMID:25765780

  7. Experimental aspects of multidimensional solid-state NMR correlation spectroscopy.

    PubMed

    Ramamoorthy, A; Wu, C H; Opella, S J

    1999-09-01

    The experimental parameters critical for the implementation of multidimensional solid-state NMR experiments that incorporate heteronuclear spin exchange at the magic angle are discussed. This family of experiments is exemplified by the three-dimensional experiment that correlates the (1)H chemical shift, (1)H-(15)N dipolar coupling, and (15)N chemical shift frequencies. The broadening effects of the homonuclear (1)H-(1)H dipolar couplings are suppressed using flip-flop (phase- and frequency-switched) Lee-Goldburg irradiations in both the (1)H chemical shift and the (1)H-(15)N dipolar coupling dimensions. The experiments are illustrated using the (1)H and (15)N chemical shift and dipolar couplings in a single crystal of (15)N-acetylleucine. Copyright 1999 Academic Press.

  8. RNA nucleosides as chiral sensing agents in NMR spectroscopy.

    PubMed

    Lokesh, N; Sachin, S L; Narendra, L V; Arun, K; Suryaprakash, N

    2015-07-14

    The study reports chiral sensing properties of RNA nucleosides. Adenosine, guanosine, uridine and cytidine are used as chiral derivatizing agents to differentiate chiral 1°-amines. A three component protocol has been adopted for complexation of nucleosides and amines. The chiral differentiating ability of nucleosides is examined for different amines based on the (1)H NMR chemical shift differences of diastereomers (Δδ(R,S)). Enantiomeric differentiation has been observed at multiple chemically distinct proton sites. Adenosine and guanosine exhibit large chiral differentiation (Δδ(R,S)) due to the presence of a purine ring. The diastereomeric excess (de) measured by using adenosine is in good agreement with the gravimetric values.

  9. 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

  10. Hadamard NMR spectroscopy for two-dimensional quantum information processing and parallel search algorithms.

    PubMed

    Gopinath, T; Kumar, Anil

    2006-12-01

    Hadamard spectroscopy has earlier been used to speed-up multi-dimensional NMR experiments. In this work, we speed-up the two-dimensional quantum computing scheme, by using Hadamard spectroscopy in the indirect dimension, resulting in a scheme which is faster and requires the Fourier transformation only in the direct dimension. Two and three qubit quantum gates are implemented with an extra observer qubit. We also use one-dimensional Hadamard spectroscopy for binary information storage by spatial encoding and implementation of a parallel search algorithm.

  11. Characterization of ofloxacin-oxalic acid complex by PXRD, NMR, and THz spectroscopy.

    PubMed

    Limwikrant, Waree; Higashi, Kenjirou; Yamamoto, Keiji; Moribe, Kunikazu

    2009-12-01

    A novel ofloxacin-oxalic acid complex was prepared by the cogrinding method. The obtained complex was characterized by powder X-ray diffraction (PXRD), infrared (IR), solid-state nuclear magnetic resonance (NMR), and terahertz (THz) spectroscopy. The PXRD measurement revealed that the ofloxacin-oxalic acid complex induced by cogrinding was formed at a molar ratio of 1:2. Weak interaction between two components, not a hydrogen bonding, was found by IR and solid-state NMR spectroscopy. The distinctive THz spectrum showed that the vibrational modes of the complex were different from those of the starting materials, suggesting that THz spectroscopy is an alternative tool to evaluate complex formation through weak interactions.

  12. Urinary metabolic fingerprint of acute intermittent porphyria analyzed by (1)H NMR spectroscopy.

    PubMed

    Carichon, Mickael; Pallet, Nicolas; Schmitt, Caroline; Lefebvre, Thibaud; Gouya, Laurent; Talbi, Neila; Deybach, Jean Charles; Beaune, Philippe; Vasos, Paul; Puy, Hervé; Bertho, Gildas

    2014-02-18

    (1)H NMR is a nonbiased technique for the quantification of small molecules that could result in the identification and characterization of potential biomarkers with prognostic value and contribute to better understand pathophysiology of diseases. In this study, we used (1)H NMR spectroscopy to analyze the urinary metabolome of patients with acute intermittent porphyria (AIP), an inherited metabolic disorder of heme biosynthesis in which an accumulation of the heme precursors 5-aminolaevulinic acid (ALA) and porphobilinogen (PBG) promotes sudden neurovisceral attacks, which can be life-threatening. Our objectives were (1) to demonstrate the usefulness of (1)H NMR to identify and quantify ALA and PBG in urines from AIP patients and (2) to identify metabolites that would predict the response to AIP crisis treatment and reflect differential metabolic reprogramming. Our results indicate that (1)H NMR can help to diagnose AIP attacks based on the identification of ALA and PBG. We also show that glycin concentration increases in urines from patients with frequent recurrences at the end of the treatment, after an initial decrease, whereas PBG concentration remains low. Although the reasons for this altered are elusive, these findings indicate that a glycin metabolic reprogramming occurs in AIPr patients and is associated with recurrence. Our results validate the proof of concept of the usefulness of (1)H NMR spectroscopy in clinical chemistry for the diagnosis of acute attack of AIP and identify urinary glycin as a potential marker of recurrence of AIP acute attacks.

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

    PubMed

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

    2016-06-16

    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.

  14. Characterizing monoclonal antibody formulations in arginine glutamate solutions using 1H NMR spectroscopy

    PubMed Central

    Kheddo, Priscilla; Cliff, Matthew J.; Uddin, Shahid; van der Walle, Christopher F.; Golovanov, Alexander P.

    2016-01-01

    ABSTRACT Assessing how excipients affect the self-association of monoclonal antibodies (mAbs) requires informative and direct in situ measurements for highly concentrated solutions, without sample dilution or perturbation. This study explores the application of solution nuclear magnetic resonance (NMR) spectroscopy for characterization of typical mAb behavior in formulations containing arginine glutamate. The data show that the analysis of signal intensities in 1D 1H NMR spectra, when compensated for changes in buffer viscosity, is invaluable for identifying conditions where protein-protein interactions are minimized. NMR-derived molecular translational diffusion rates for concentrated solutions are less useful than transverse relaxation rates as parameters defining optimal formulation. Furthermore, NMR reports on the solution viscosity and mAb aggregation during accelerated stability study assessment, generating data consistent with that acquired by size-exclusion chromatography. The methodology developed here offers NMR spectroscopy as a new tool providing complementary information useful to formulation development of mAbs and other large therapeutic proteins. PMID:27589351

  15. 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

  16. NMR spectroscopy up to 35.2T using a series-connected hybrid magnet.

    PubMed

    Gan, Zhehong; Hung, Ivan; Wang, Xiaoling; Paulino, Joana; Wu, Gang; Litvak, Ilya M; Gor'kov, Peter L; Brey, William W; Lendi, Pietro; Schiano, Jeffrey L; Bird, Mark D; Dixon, Iain R; Toth, Jack; Boebinger, Gregory S; Cross, Timothy A

    2017-08-24

    The National High Magnetic Field Laboratory has brought to field a Series-Connected Hybrid magnet for NMR spectroscopy. As a DC powered magnet it can be operated at fields up to 36.1T. The series connection between a superconducting outsert and a resistive insert dramatically minimizes the high frequency fluctuations of the magnetic field typically observed in purely resistive magnets. Current-density-grading among various resistive coils was used for improved field homogeneity. The 48mm magnet bore and 42mm outer diameter of the probes leaves limited space for conventional shims and consequently a combination of resistive and ferromagnetic shims are used. Field maps corrected for field instabilities were obtained and shimming achieved better than 1ppm homogeneity over a cylindrical volume of 1cm diameter and height. The magnetic field is regulated within 0.2ppm using an external (7)Li lock sample doped with paramagnetic MnCl2. The improved field homogeneity and field regulation using a modified AVANCE NEO console enables NMR spectroscopy at (1)H frequencies of 1.0, 1.2 and 1.5GHz. NMR at 1.5GHz reflects a 50% increase in field strength above the highest superconducting magnets currently available. Three NMR probes have been constructed each equipped with an external lock rf coil for field regulation. Initial NMR results obtained from the SCH magnet using these probes illustrate the very exciting potential of ultra-high magnetic fields. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Multinuclear Magnetic Resonance Imaging and NMR Spectroscopy in Biomedical Investigations

    NASA Astrophysics Data System (ADS)

    Pirogov, Yury A.

    Biomedical investigations with small animals using 0.5-T and 7-T MRI scanners adjusted on the Larmor frequencies of different nuclei 1H, 2H, 11B, 13C, 19F, 23Na, 31P, 35Cl are described. Experiments on registration of signals 19F from the fluorocarbons injected in laboratory animals are discussed. They give presentation on the application of fluorocarbon compounds as blood substitutes and contrasting preparations in MRI diagnostics. A blood substitute product fluorocarbon Perfluoranum® has shown effectiveness in oxygen delivery to the tissues of living organisms, and cardioprotective effect which does not depend on the patient's blood group. Inclusion of paramagnetic atoms (gadolinium, iron, etc.) to the Perfluoranum® chemical formula creates a new compounds with high MRI contrast efficiencies at Larmor frequencies of protons so and fluorine-19 nuclei.

  18. Phase equilibria and molecular packing in the N,N-dimethyldodecylamine oxide/gramicidin D/water system studied by 2H nuclear magnetic resonance spectroscopy.

    PubMed Central

    Orädd, G; Lindblom, G; Arvidson, G; Gunnarsson, K

    1995-01-01

    A partial phase diagram of the system N,N-dimethyldodecylamine oxide (DDAO)/water/gramicidin D was determined by 2H-NMR. Both 2H2O and perdeuterated DDAO (DDAO-d31) were studied by solid state NMR techniques. Addition of gramicidin D to the micellar (L1), normal hexagonal (HI) and cubic (I) phases of DDAO induces phase separations, giving two-phase regions, which all contain a lamellar (L alpha) phase. The L alpha phase containing gramicidin is characterized by larger order parameters for DDAO-d31 compared with the corresponding order parameters in the L alpha and HI phases of DDAO-d31/H2O. The L alpha phase may stay in equilibrium with any other phase in the phase diagram. The DDAO exchange between the coexisting phases is slow on the NMR timescale, which is why the recorded NMR spectrum consists of superimposed spectra from the different phases occurring in the sample. Gramicidin D can be solubilized in appreciable quantities only in the lamellar phase of DDAO-d31. Increasing amounts of gramicidin in the liquid crystalline phases result in a continuous increase in the molecular ordering up to about 5 mol% gramicidin, where a plateau is reached. This is consistent with a recent theoretical model describing the influence on the ordering of lipids by a membrane protein with larger hydrophobic thickness than the lipid bilayer. The solvent used for dissolving gramicidin at the incorporation of the peptide in the lipid aggregates has no effect on the 2H-NMR lineshapes of DDAO-d31. It is concluded that gramicidin is solubilized in the L alpha phase and that it always adopts the channel conformation independent of a particular solvent. The channel conformation is also supported by CD studies. In some of the samples, macroscopic orientation of the lipid aggregates is observed. It is concluded that DDAO-d31 in the binary system favors an orientation with the long axis of the hydrocarbon chain perpendicular to the magnetic field, whereas when gramicidin D is present the

  19. Recent Advances in Multinuclear NMR Spectroscopy for Chiral Recognition of Organic Compounds.

    PubMed

    Silva, Márcio S

    2017-02-07

    Nuclear magnetic resonance (NMR) is a powerful tool for the elucidation of chemical structure and chiral recognition. In the last decade, the number of probes, media, and experiments to analyze chiral environments has rapidly increased. The evaluation of chiral molecules and systems has become a routine task in almost all NMR laboratories, allowing for the determination of molecular connectivities and the construction of spatial relationships. Among the features that improve the chiral recognition abilities by NMR is the application of different nuclei. The simplicity of the multinuclear NMR spectra relative to ¹H, the minimal influence of the experimental conditions, and the larger shift dispersion make these nuclei especially suitable for NMR analysis. Herein, the recent advances in multinuclear ((19)F, (31)P, (13)C, and (77)Se) NMR spectroscopy for chiral recognition of organic compounds are presented. The review describes new chiral derivatizing agents and chiral solvating agents used for stereodiscrimination and the assignment of the absolute configuration of small organic compounds.

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

    PubMed

    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.

  1. Single-scan 2D NMR: An Emerging Tool in Analytical Spectroscopy

    PubMed Central

    Giraudeau, Patrick; Frydman, Lucio

    2016-01-01

    Two-dimensional Nuclear Magnetic Resonance (2D NMR) spectroscopy is widely used in chemical and biochemical analyses. Multidimensional NMR is also witnessing an 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 to deliver arbitrary 2D NMR spectra involving any kind of homo- or hetero-nuclear correlations, in a single scan. During the intervening years the performance of this sub-second 2D NMR methodology has been greatly improved, and UF 2D NMR is rapidly becoming a powerful analytical tool witnessing an expanded scope of applications. The present reviews summarizes the principles and the main developments which have contributed to the success of this approach, and focuses on applications which 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

  2. Alternative determination of blood alcohol concentration by (1)H NMR spectroscopy.

    PubMed

    Zailer, Elina; Diehl, Bernd W K

    2016-02-05

    A rapid, accurate and specific proton nuclear magnetic resonance ((1)H NMR) spectroscopic method is developed to determine ethanol in blood, known as the blood alcohol concentration (BAC). The limits of detection and quantification are 0.02g/L and 0.07g/L, respectively. The (1)H NMR spectra show linearity for whole blood and serum samples of a concentration range of 0.00-3.00g/L (R(2)>0.9995). The (1)H NMR method is applied and validated for whole blood as the sample media. Real driving under influence case samples are analyzed with the reference enzyme-based alcohol dehydrogenase and headspace gas chromatography techniques by the Forensic Medicine in Bonn. The reference results are compared with the (1)H NMR spectroscopic results. The validation and comparison indicate that (1)H NMR is suitable for the quantification of BAC in whole blood. This technique has the advantages of automated analysis with good measurement precision and fast sample throughput. A drop of blood (V=20μL) is adequate for an analysis leading to a possible simplification of the sample collection. Due to the non-destructive method, follow-up examinations by (1)H NMR spectroscopy or DNA determinations by different techniques (PCR, in situ hybridization) are possible in resolving legal disputes.

  3. Orientation and dynamics of an antimicrobial peptide in the lipid bilayer by solid-state NMR spectroscopy.

    PubMed Central

    Yamaguchi, S; Huster, D; Waring, A; Lehrer, R I; Kearney, W; Tack, B F; Hong, M

    2001-01-01

    The orientation and dynamics of an 18-residue antimicrobial peptide, ovispirin, has been investigated using solid-state NMR spectroscopy. Ovispirin is a cathelicidin-like model peptide (NH(2)-KNLRRIIRKIIHIIKKYG-COOH) with potent, broad-spectrum bactericidal activity. (15)N NMR spectra of oriented ovispirin reconstituted into synthetic phospholipids show that the helical peptide is predominantly oriented in the plane of the lipid bilayer, except for a small portion of the helix, possibly at the C-terminus, which deviates from the surface orientation. This suggests differential insertion of the peptide backbone into the lipid bilayer. (15)N spectra of both oriented and unoriented peptides show a reduced (15)N chemical shift anisotropy at room temperature compared with that of rigid proteins, indicating that the peptide undergoes uniaxial rotational diffusion around the bilayer normal with correlation times shorter than 10(-4) s. This motion is frozen below the gel-to-liquid crystalline transition temperature of the lipids. Ovispirin interacts strongly with the lipid bilayer, as manifested by the significantly reduced (2)H quadrupolar splittings of perdeuterated palmitoyloleoylphosphatidylcholine acyl chains upon peptide binding. Therefore, ovispirin is a curved helix residing in the membrane-water interface that executes rapid uniaxial rotation. These structural and dynamic features are important for understanding the antimicrobial function of this peptide. PMID:11566791

  4. 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.

  5. Fundamental studies of supported bimetallic catalysts by NMR spectroscopy

    SciTech Connect

    Savargaonkar, Nilesh

    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.

  6. Enzyme dynamics during catalysis measured by NMR spectroscopy.

    PubMed

    Kern, Dorothee; Eisenmesser, Elan Z; Wolf-Watz, Magnus

    2005-01-01

    Many biological processes, in particular enzyme catalysis, occur in the microsecond to millisecond time regime. While the chemical events and static structural features of enzyme catalysis have been extensively studied, very little is known about dynamic processes of the enzyme during the catalytic cycle. Dynamic NMR methods such as ZZ-exchange, line-shape analysis, Carr-Purcell-Meiboom-Gill (CPMG), and rotating frame spin-lattice relaxation (R(1rho)) experiments are powerful in detecting conformational rearrangements with interconversion rates between 0.1 and 10(5) s(-1). In this chapter, the first application of these methods to enzymes during catalysis is described, in addition to studies on several other enzymes in their free states and in complex with ligands. From the experimental results of all systems, a picture arises in which flexibility in the microsecond to millisecond time regime is intrinsic and likely to be an essential property of the enzyme. Quantitative analysis of dynamics at multiple sites of the enzyme reveal large-scale collective motions. For several enzymes, the frequency of motion is comparable to the overall turnover rate, raising the possibility that conformational rearrangements may be rate limiting for catalysis in these enzymes.

  7. Methyl labeling and TROSY NMR spectroscopy of proteins expressed in the eukaryote Pichia pastoris.

    PubMed

    Clark, Lindsay; Zahm, Jacob A; Ali, Rustam; Kukula, Maciej; Bian, Liangqiao; Patrie, Steven M; Gardner, Kevin H; Rosen, Michael K; Rosenbaum, Daniel M

    2015-07-01

    (13)C Methyl TROSY NMR spectroscopy has emerged as a powerful method for studying the dynamics of large systems such as macromolecular assemblies and membrane proteins. Specific (13)C labeling of aliphatic methyl groups and perdeuteration has been limited primarily to proteins expressed in E. coli, preventing studies of many eukaryotic proteins of physiological and biomedical significance. We demonstrate the feasibility of efficient (13)C isoleucine δ1-methyl labeling in a deuterated background in an established eukaryotic expression host, Pichia pastoris, and show that this method can be used to label the eukaryotic protein actin, which cannot be expressed in bacteria. This approach will enable NMR studies of previously intractable targets.

  8. Anatomising proton NMR spectra with pure shift 2D J-spectroscopy: A cautionary tale

    NASA Astrophysics Data System (ADS)

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

    2017-09-01

    Analysis of proton NMR spectra has been a key tool in structure determination for over 60 years. A classic tool is 2D J-spectroscopy, but common problems are the difficulty of obtaining the absorption mode lineshapes needed for accurate results, and the need for a 45° shear of the final 2D spectrum. A novel 2D NMR method is reported here that allows straightforward determination of homonuclear couplings, using a modified version of the PSYCHE method to suppress couplings in the direct dimension. The method illustrates the need for care when combining pure shift data acquisition with multiple pulse methods.

  9. A structural study of fentanyl by DFT calculations, NMR and IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Asadi, Zahra; Esrafili, Mehdi D.; Vessally, Esmail; Asnaashariisfahani, Manzarbanou; Yahyaei, Saeideh; Khani, Ali

    2017-01-01

    N-(1-(2-phenethyl)-4-piperidinyl-N-phenyl-propanamide (fentanyl) is synthesized and characterized by FT-IR, 1H NMR, 13C NMR, mass spectroscopy and elemental analyses. The geometry optimization is performed using the B3LYP and M06 density functionals with 6-311 + G(d) and 6-311++G(d,p) basis sets. The complete assignments are performed on the basis of the potential energy distribution (PED) of the all vibrational modes. Almost a nice correlation is found between the calculated 13C chemical shifts and experimental data. The frontier molecular orbitals and molecular electrostatic potential of fentanyl are also obtained.

  10. Lithium substitution in strontium chlorapatite studied by solid state NMR spectroscopy

    SciTech Connect

    Subramanian, S.; Sairam, T. N. Amarendra, G.; Maji, B. K.; Jena, H.

    2016-05-23

    Strontium Chlorapatites with various amounts of Li substitution (Sr{sub 10-x}Li{sub x}(PO{sub 4}){sub 6}Cl{sub 2-δ}) were prepared by solid state reaction method and characterized by powder XRD and solid state NMR spectroscopy. XRD reveals shortening of lattice parameters upon Li incorporation. The linewidth of {sup 31}P solid state Magic Angle Spinning NMR spectra decreases with increase in Li content within the apatite phase. This study confirms Li uptake within the apatite phase.

  11. Thermochemical study of the liquid phase equilibrium reaction of dihalomethanes by NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Dávalos, J. Z.; Lago, A. F.; Baer, Tomas

    2005-06-01

    The liquid phase equilibrium reaction of dihalomethanes (2CH 2BrI ⇄ CH 2Br 2 + CH 2I 2) has been investigated by NMR spectroscopy, as a function of the temperature and initial concentration of the reactants. The equilibrium constants have been experimentally determined for this reaction from the profile of the NMR spectra. Heat capacity measurements were carried out in the temperature range from 293.15 to 353.15 K by differential scanning calorimetry. The results relate the heats of formation of the three compounds and confirm the recently determined heat of formation of CH 2I 2 of 107.5 kJ mol -1.

  12. Reactivity ratios and sequence determination of methacrylonitrile/butyl acrylate copolymers by NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Brar, A. S.; Pradhan, D. R.; Hooda, Sunita

    2004-08-01

    Methacrylonitrile/butyl acrylate (M/B) copolymers were prepared by bulk polymerization using benzoyl peroxide as an initiator. The Distortionless Enhancement by Polarization Transfer spectra were used to differentiate between the carbon resonance signals of methyl, methine, methylene and oxymethylene groups in the 13C{ 1H} NMR spectrum of the copolymer (M/B). Comonomer reactivity ratios were determined using Kelen-Tudos and non-linear error in variable methods. Two-dimensional Heteronuclear Single Quantum Coherence and Total Correlated Spectroscopy were used to resolve the complex 1H NMR spectrum and to determine the compositional and configurational sequences of M/B copolymers.

  13. Disclosing the multi-faceted world of weakly interacting inorganic systems by means of NMR spectroscopy.

    PubMed

    Rocchigiani, Luca; Macchioni, Alceo

    2016-02-21

    The potential of NMR spectroscopy to investigate inorganic systems assembled by, or whose reactivity is affected by, non-covalent interactions is described. Subjects that have received particular attention in recent years (halogen bonding and Frustrated Lewis Pairs) and more classical subjects that remain under-explored (self-aggregation of ion pairs in low polar solvents, behavior of MAO containing metallocenium ion pairs, and hydrogen bonding/ion pairing effects in Au(i) catalysis) are considered, using an innovative approach, always focusing on the crucial information that can be provided by NMR.

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

    SciTech Connect

    Richards, T.; Budinger, T.F.

    1988-01-01

    NMR imaging, NMR spectroscopy, and histopathologic techniques were used to study the proton relaxation time and related biochemical changes in the rodent brain after in vivo helium beam irradiation with single doses of 10, 20, 30, and 50 Gy. Two-dimensional Fourier transform spin-echo imaging and saturation recovery with projection reconstruction were used to measure the NMR relaxation parameters. These parameters were correlated with proton spectroscopy and histopathology. Additional high resolution in vitro proton spectroscopy was performed on brain extracts to observe chemical changes that could not be seen in vivo. The major findings from these experiments were that at 4-14 days postirradiation, image intensity and T1 relaxation time decreased on the irradiated side and increased on the nonirradiated side relative to nonirradiated control animals. In vivo surface coil proton spectroscopy methods demonstrated changes in lipid and phosphatidylcholine (p-choline) peaks. In vitro studies of the aqueous fraction of brain extracts showed radiation-induced changes in lactate, 4-aminobutyric acid, and p-choline peak areas. In the organic fraction, radiation-induced changes were observed in phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine. With histology and Evans blue injections, blood-brain barrier alterations were seen as early as 4 days after a dose of 50 Gy.

  15. Suppressing exchange effects in diffusion-ordered NMR spectroscopy.

    PubMed

    Aguilar, Juan A; Adams, Ralph W; Nilsson, Mathias; Morris, Gareth A

    2014-01-01

    In diffusion-ordered spectroscopy (DOSY) the aim is to separate signals from different molecular species according to their different diffusion coefficients. Each species has its individual diffusion coefficient (that may accidentally coincide with that of another species, e.g. if they are of very similar size). In exchanging systems, however, there is a serious complication in that the apparent diffusion coefficient of an exchanging signal will be a compromise that depends, among other factors, on the diffusion coefficients of the exchange partners and the rate of exchange between them. The DOSY spectrum will be much harder to interpret and can often give the appearance of extra (spurious) components in the mixture. Here a new and surprisingly simple experiment is described that suppresses the effects of exchange on apparent diffusion coefficients, restoring the simplicity of interpretation enjoyed by non-exchanging systems.

  16. 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.

  17. Molecular Motions in Halogen-Bridged One-Dimensional Pt Complexes, [PtII(en)2][PtIVX2(en)2](ClO4)4 (X = Cl, Br) Studied by 2H and 1H NMR

    NASA Astrophysics Data System (ADS)

    Kimura, Noriyoshi; Hachisuka, Toru; Nakano, Yukitaka; Ikeda, Ryuichi

    2002-07-01

    2H and 1H NMR measurements were performed on crystalline [Pt(en)2][PtX2(en)2](ClO4)4 (X = Cl, Br), where the protonated and partially deuterated ethylenediamines (en's), NH2(CH2)2NH2, NH2(CD2)2NH2 and ND2(CH2)2ND2 were used as ligands. Measurements of 2H and 1H NMR spin-lattice relaxation times showed the presence of motions of en chelate rings at the temperatures near the phase transitions, whereas broad 2H NMR spectra and the reported X-ray diffraction data showed no marked motions. These results were consistently explained by introducing the en puckering motion between highly asymmetric potential wells with an energy difference of 10 - 13 kJ mol-1. This difference was shown to be much larger than 2 - 5 kJ mol-1, reported for the iodo-complex, [Pt(en)2][PtI2(en)2](ClO4)4

  18. 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.

  19. Perilla frutescens (L.) Britton: honeybee forage and preliminary results on the metabolic profiling by NMR spectroscopy.

    PubMed

    Consonni, Roberto; Cagliani, Laura Ruth; Docimo, Teresa; Romane, Abderrahmane; Ferrazzi, Paola

    2013-01-01

    Nuclear magnetic resonance (NMR) spectroscopy has emerged as a technology for metabolite characterisation of both foods and plants. NMR technique allows to analyse metabolite content in a single experiment, in a non-destructive way and with a very simple sample preparation. This study characterises the metabolites of Perilla frutescens var. crispa leaf and flower for the first time by NMR. Our results showed higher metabolite content in leaves compared to flowers, highlighting the presence of amino acids, organic acids, saccharides and large amounts of aromatic compounds, mainly in the form of rosmarinic acid. Moreover, we cultivated Perilla, an important medicinal plant native to Asia, in a low mountain environment in Italy, to continue its evaluation as a honeybee attractive species. Interestingly, even in this type of environment, Perilla has been confirmed to be a good bee plant for both nectar and pollen.

  20. (1)H and DOSY NMR spectroscopy analysis of Ligusticum porteri rhizome extracts.

    PubMed

    León, Alejandra; Chávez, María Isabel; Delgado, Guillermo

    2011-08-01

    The presence of dimeric phthalides and other constituents in extracts of the vegetal species Ligusticum porteri was established by NMR spectroscopy. In comparative qualitative (1)H NMR analyses of acetone extracts of rhizomes from fresh and dried L. porteri samples, we found that the dimeric phthalides tokinolide B (3), diligustilide (4) and riligustilide (5) were naturally produced by the plant and not post-harvest products. We also obtained DOSY (1)H NMR data that provided both virtual separation and structural information for the phthalides present in a dry acetone extract of L. porteri. In addition, we developed a protocol for the quantification of dimeric phthalides, which is performed by calculating the relative ratio of the peak area of selected proton signals for some compounds with respect to the known signal of the internal standard, 4-dimethylaminopyridine. The protocol allows the rapid and direct quantification of dimeric phthalides and others constituents in fresh L. porteri rhizomes. Copyright © 2011 John Wiley & Sons, Ltd.

  1. Characterization of covalent protein conjugates using solid-state sup 13 C NMR spectroscopy

    SciTech Connect

    Garbow, J.R.; Fujiwara, Hideji; Sharp, C.R.; Logusch, E.W. )

    1991-07-23

    Cross-polarization magic-angle spinning (CPMAS) {sup 13}C NMR spectroscopy has been used to characterize covalent conjugates of alachlor, an {alpha}-chloroacetamide hapten, with glutathione (GSH) and bovine serum albumin (BSA). The solid-state NMR method demonstrates definitively the covalent nature of these conjugates and can also be used to characterize the sites of hapten attachment to proteins. Three different sites of alachlor binding are observed in the BSA system. Accurate quantitation of the amount of hapten covalently bound to GSH and BSA is reported. The solid-state {sup 13}C NMR technique can easily be generalized to study other small molecule/protein conjugates and can be used to assist the development and refinement of synthetic methods needed for the successful formation of such protein alkylation products.

  2. Towards single-molecule NMR detection and spectroscopy using single spins in diamond

    NASA Astrophysics Data System (ADS)

    Perunicic, V. S.; Hall, L. T.; Simpson, D. A.; Hill, C. D.; Hollenberg, L. C. L.

    2014-02-01

    Nanomagnetometry using the nitrogen-vacancy (NV) center in diamond has attracted a great deal of interest due to its unique combination of room temperature operation, nanoscale resolution, and high sensitivity. One of the important goals for nanomagnetometry is to be able to detect nanoscale nuclear magnetic resonance (NMR) in individual molecules. Our theoretical analysis details a method by which a single molecule on the surface of diamond, with characteristic NMR frequencies, can be detected using a proximate NV center on a time scale of an order of seconds with nanometer precision. We perform spatiotemporal resolution optimization and subsequently outline paths to greater sensitivity. Our method is suitable for application in low and relatively inhomogeneous background magnetic fields in contrast to both conventional liquid and solid state NMR spectroscopy.

  3. NMR spectroscopy of native and in vitro tissues implicates polyADP ribose in biomineralization.

    PubMed

    Chow, W Ying; Rajan, Rakesh; Muller, Karin H; Reid, David G; Skepper, Jeremy N; Wong, Wai Ching; Brooks, Roger A; Green, Maggie; Bihan, Dominique; Farndale, Richard W; Slatter, David A; Shanahan, Catherine M; Duer, Melinda J

    2014-05-16

    Nuclear magnetic resonance (NMR) spectroscopy is useful to determine molecular structure in tissues grown in vitro only if their fidelity, relative to native tissue, can be established. Here, we use multidimensional NMR spectra of animal and in vitro model tissues as fingerprints of their respective molecular structures, allowing us to compare the intact tissues at atomic length scales. To obtain spectra from animal tissues, we developed a heavy mouse enriched by about 20% in the NMR-active isotopes carbon-13 and nitrogen-15. The resulting spectra allowed us to refine an in vitro model of developing bone and to probe its detailed structure. The identification of an unexpected molecule, poly(adenosine diphosphate ribose), that may be implicated in calcification of the bone matrix, illustrates the analytical power of this approach. Copyright © 2014, American Association for the Advancement of Science.

  4. 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.

  5. Probing the surface structure of divalent transition metals using surface specific solid-state NMR spectroscopy.

    PubMed

    Mason, Harris E; Harley, Stephen J; Maxwell, Robert S; Carroll, Susan A

    2012-03-06

    Environmental and geochemical systems containing paramagnetic species could benefit by using nuclear magnetic resonance (NMR) spectroscopy due to the sensitivity of the spectral response to small amounts paramagnetic interactions. In this study, we apply commonly used solid-state NMR spectroscopic methods combined with chemometrics analysis to probe sorption behavior of the paramagnetic cations Cu(2+) and Ni(2+)at the amorphous silica surface. We exploit the unique properties of paramagnets to derive meaningful structural information in these systems at low, environmentally relevant cation surface loadings by comparing the NMR response of sorption samples to paramagnetic free samples. These data suggest that a simple sorption model where the cation sorbs as inner sphere complexes at negatively charged, deprotonated silanol sites is appropriate. These results help constrain sorption models that are used to describe metal fate and transport.

  6. Retinal Dynamics During Light Activation of Rhodopsin Revealed by Solid-State NMR Spectroscopy

    PubMed Central

    Brown, Michael F.; Salgado, Gilmar F. J.; Struts, Andrey V.

    2016-01-01

    Rhodopsin is a canonical member of class A of the G protein-coupled receptors (GPCR) that are implicated in many of the drug interventions in humans and are of great pharmaceutical interest. The molecular mechanism of rhodopsin activation remains unknown as atomistic structural information for the active metarhodopsin II state is currently lacking. Solid-state 2H NMR constitutes a powerful aproarch to study atomic-level dynamics of membrane proteins. In the present application we describe how information is obtained about interactions of the retinal cofactor with rhodopsin that change with light activation of the photoreceptor. The retinal methyl groups play an important role in rhodopsin function by directing conformational changes upon transition into the active state. Site-specific 2H labels have been introduced into the methyl groups of retinal and solid-state 2H NMR methods applied to obtain order parameters and correlation times that quantify the mobility of the cofactor in the inactive dark state, as well as the cryo-trapped metarhodopsin I and metarhodopsin II states. Analysis of the angular-dependent 2H NMR lineshapes for selectively deuterated methyl groups of rhodopsin in aligned membranes enables determination of the average ligand conformation within the binding pocket. The relaxation data suggest that the β-ionone ring is not expelled from its hydrophobic pocket in the transition from the pre-activated metarhodopsin I to the active metarhodopsin II state. Rather, the major structural changes of the retinal cofactor occur already at the metarhodopsin I state in the activation process. The metarhodopsin I to metarhodopsin II transition involves mainly conformational changes of the protein within the membrane lipid bilayer rather than the ligand. The dynamics of the retinylidene methyl groups upon isomerization are explained by an activation mechanism involving cooperative rearrangments of extracellular loop E2 together with transmembrane helices H5 and

  7. Polyoxomolybdate promoted hydrolysis of a DNA-model phosphoester studied by NMR and EXAFS spectroscopy.

    PubMed

    Absillis, Gregory; Van Deun, Rik; Parac-Vogt, Tatjana N

    2011-11-21

    Hydrolysis of (p-nitrophenyl)phosphate (NPP), a commonly used phosphatase model substrate, was examined in molybdate solutions by means of (1)H, (31)P, and (95)Mo NMR spectroscopy and Mo K-edge Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. At 50 °C and pD 5.1 the cleavage of the phosphoester bond in NPP proceeds with a rate constant of 2.73 × 10(-5) s(-1) representing an acceleration of nearly 3 orders of magnitude as compared to the hydrolysis measured in the absence of molybdate. The pD dependence of k(obs) exhibits a bell-shaped profile, with the fastest cleavage observed in solutions where [Mo(7)O(24)](6-) is the major species in solution. Mixing of NPP and [Mo(7)O(24)](6-) resulted in formation of these two intermediate complexes that were detected by (31)P NMR spectroscopy. Complex A was characterized by a (31)P NMR resonance at -4.27 ppm and complex B was characterized by a (31)P NMR resonance at -7.42 ppm. On the basis of the previous results from diffusion ordered NMR spectroscopy, performed with the hydrolytically inactive substrate phenylphosphonate (PhP), the structure of these two complexes was deduced to be (NPP)(2)Mo(5)O(21)(4-) (complex A) and (NPP)(2)Mo(12)O(36)(H(2)O)(6)(4-) (complex B). The pH studies point out that both complexes are hydrolytically active and lead to the hydrolysis of phosphoester bond in NPP. The NMR spectra did not show evidence of any paramagnetic species, excluding the possibility of Mo(VI) reduction to Mo(V), and indicating that the cleavage of the phosphomonoester bond is purely hydrolytic. The Mo K-edge XANES region also did not show any sign of Mo(VI) to Mo(V) reduction during the hydrolytic reaction. (95)Mo NMR and Mo K-edge EXAFS spectra measured during different stages of the hydrolytic reaction showed a gradual disappearance of [Mo(7)O(24)](6-) during the hydrolytic reaction and appearance of [P(2)Mo(5)O(23)](6-), which was the final complex observed at the end of hydrolytic reaction.

  8. Determination of 15N chemical shift anisotropy from a membrane-bound protein by NMR spectroscopy.

    PubMed

    Pandey, Manoj Kumar; Vivekanandan, Subramanian; Ahuja, Shivani; Pichumani, Kumar; Im, Sang-Choul; Waskell, Lucy; Ramamoorthy, Ayyalusamy

    2012-06-21

    Chemical shift anisotropy (CSA) tensors are essential in the structural and dynamic studies of proteins using NMR spectroscopy. Results from relaxation studies in biomolecular solution and solid-state NMR experiments on aligned samples are routinely interpreted using well-characterized CSA tensors determined from model compounds. Since CSA tensors, particularly the (15)N CSA, highly depend on a number of parameters including secondary structure, electrostatic interaction, and the amino acid sequence, there is a need for accurately determined CSA tensors from proteins. In this study, we report the backbone amide-(15)N CSA tensors for a 16.7-kDa membrane-bound and paramagnetic-heme containing protein, rabbit Cytochrome b(5) (cytb(5)), determined using the (15)N CSA/(15)N-(1)H dipolar transverse cross-correlation rates. The mean values of (15)N CSA determined for residues in helical, sheet, and turn regions are -187.9, -166.0, and -161.1 ppm, respectively, with an overall average value of -171.7 ppm. While the average CSA value determined from this study is in good agreement with previous solution NMR experiments on small globular proteins, the CSA value determined for residues in helical conformation is slightly larger, which may be attributed to the paramagnetic effect from Fe(III) of the heme unit in cytb(5). However, like in previous solution NMR studies, the CSA values reported in this study are larger than the values measured from solid-state NMR experiments. We believe that the CSA parameters reported in this study will be useful in determining the structure, dynamics, and orientation of proteins, including membrane proteins, using NMR spectroscopy.

  9. NMR spectroscopy of filtered serum of prostate cancer: A new frontier in metabolomics.

    PubMed

    Kumar, Deepak; Gupta, Ashish; Mandhani, Anil; Sankhwar, Satya Narain

    2016-09-01

    To address the shortcomings of digital rectal examinations (DRE), serum prostate-specific antigen (PSA), and trans-rectal ultrasound (TRUS) for precise determination of prostate cancer (PC) and differentiation from benign prostatic hyperplasia (BPH), we applied (1) H-nuclear magnetic resonance (NMR) spectroscopy as a surrogate tactic for probing and prediction of PC and BPH. The study comprises 210 filtered sera from suspected PC, BPH, and a healthy subjects' cohort (HC). The filtered serum approach delineates to identify and quantify 52 metabolites using (1) H NMR spectroscopy. All subjects had undergone clinical evaluations (DRE, PSA, and TRUS) followed by biopsy for Gleason score, if needed. NMR-measured metabolites and clinical evaluation data were examined separately using linear multivariate discriminant function analysis (DFA) to probe the signature descriptors for each cohort. DFA indicated that glycine, sarcosine, alanine, creatine, xanthine, and hypoxanthine were able to determine abnormal prostate (BPH + PC). DFA-based classification presented high precision (86.2% by NMR and 68.1% by clinical laboratory method) in discriminating HC from BPH + PC. DFA reveals that alanine, sarcosine, creatinine, glycine, and citrate were able to discriminate PC from BPH. DFA-based categorization exhibited high accuracy (88.3% by NMR and 75.2% by clinical laboratory method) to differentiate PC from BPH. (1) H NMR-based metabolic profiling of filtered-serum sample appears to be assuring, swift, and least-invasive for probing and prediction of PC and BPH with its signature metabolic profile. This novel technique is not only on a par with histopathological evaluation of PC determination but is also comparable to liquid chromatography-based mass spectrometry to identify the metabolites. Prostate 76:1106-1119, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

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

    PubMed

    Ashbrook, Sharon E; Dawson, Daniel M

    2013-09-17

    Much of the information contained within solid-state nuclear magnetic resonance (NMR) spectra remains unexploited because of the challenges in obtaining high-resolution spectra and the difficulty in assigning those spectra. Recent advances that enable researchers to accurately and efficiently determine NMR parameters in periodic systems have revolutionized the application of density functional theory (DFT) calculations in solid-state NMR spectroscopy. These advances are particularly useful for experimentalists. The use of first-principles calculations aids in both the interpretation and assignment of the complex spectral line shapes observed for solids. Furthermore, calculations provide a method for evaluating potential structural models against experimental data for materials with poorly characterized structures. Determining the structure of well-ordered, periodic crystalline solids can be straightforward using methods that exploit Bragg diffraction. However, the deviations from periodicity, such as compositional, positional, or temporal disorder, often produce the physical properties (such as ferroelectricity or ionic conductivity) that may be of commercial interest. With its sensitivity to the atomic-scale environment, NMR provides a potentially useful tool for studying disordered materials, and the combination of experiment with first-principles calculations offers a particularly attractive approach. In this Account, we discuss some of the issues associated with the practical implementation of first-principles calculations of NMR parameters in solids. We then use two key examples to illustrate the structural insights that researchers can obtain when applying such calculations to disordered inorganic materials. First, we describe an investigation of cation disorder in Y2Ti(2-x)Sn(x)O7 pyrochlore ceramics using (89)Y and (119)Sn NMR. Researchers have proposed that these materials could serve as host phases for the encapsulation of lanthanide- and actinide

  11. 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.

  12. NMR spectroscopy of some electrolyte solutions to 1.9 GPa

    NASA Astrophysics Data System (ADS)

    Ochoa, Gerardo; Colla, Christopher A.; Klavins, Peter; Augustine, Matthew P.; Casey, William H.

    2016-11-01

    Nuclear-magnetic resonance (NMR) spectra of CsCl and LaCl3 in D2O/H2O solutions were collected up to pressures of 1.9 GPa using a new NMR probe design that considerably extends the pressure range available for geochemical experiments. The longitudinal-relaxation times (T1) for 2H compare well with those reported in the previous studies of Lee et al. (1974), who examined lower pressures, and indicate that the probe functions properly. In some experiments, 133Cs and 1H NMR spectra could be taken on solutions to pressures well beyond the nominal freezing pressure of D2O or H2O to form Ice VI (near 0.9 GPa). Freezing to form the high-pressure ice is kinetically slow on an experimental time scale (minutes to hours). The data indicate that the electrolyte concentrations increase the freezing pressure of the solution. This result means that solution NMR spectra can be collected at pressures that are nearly twice the nominal freezing pressure of pure D2O or H2O. Pulsed-magnetic-field-gradient NMR methods are used to independently measure the self-diffusion coefficient of H2O in these solutions, which yields estimates of solution viscosity via the Stokes-Einstein relation. The increased viscosity accounts for the pressure variation of T1 values as rates of molecular tumbling are affected. Accounting for such changes is essential if NMR spectral line widths are used to infer pressure-enhanced rates of geochemical reactions, such as interconversion of aqueous complexes.

  13. Facile backbone structure determination of human membrane proteins by NMR spectroscopy

    PubMed Central

    Klammt, Christian; Maslennikov, Innokentiy; Bayrhuber, Monika; Eichmann, Cédric; Vajpai, Navratna; Chiu, Ellis Jeremy Chua; Blain, Katherine Y; Esquivies, Luis; Kwon, June Hyun Jung; Balana, Bartosz; Pieper, Ursula; Sali, Andrej; Slesinger, Paul A; Kwiatkowski, Witek; Riek, Roland; Choe, Senyon

    2013-01-01

    Although nearly half of today’s major pharmaceutical drugs target human integral membrane proteins (hIMPs), only 30 hIMP structures are currently available in the Protein Data Bank, largely owing to inefficiencies in protein production. Here we describe a strategy for the rapid structure determination of hIMPs, using solution NMR spectroscopy with systematically labeled proteins produced via cell-free expression. We report new backbone structures of six hIMPs, solved in only 18 months from 15 initial targets. Application of our protocols to an additional 135 hIMPs with molecular weight <30 kDa yielded 38 hIMPs suitable for structural characterization by solution NMR spectroscopy without additional optimization. PMID:22609626

  14. Conformational equilibrium of phenylacetic acid and its halogenated analogues through theoretical studies, NMR and IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Levandowski, Mariana N.; Rozada, Thiago C.; Melo, Ulisses Z.; Basso, Ernani A.; Fiorin, Barbara C.

    2017-03-01

    This paper presents a study on the conformational preferences of phenylacetic acid (PA) and its halogenated analogues (FPA, CPA, BPA). To clarify the effects that rule these molecules' behaviour, theoretical calculations were used, for both the isolated phase and solution, combined with nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. Most conformations of phenylacetic acid and its halogenated derivatives are stabilized through the hyperconjugative effect, which rules the conformational preference. NMR analyses showed that even with the variation in medium polarity, there was no significant change in the conformation population. Infrared spectroscopy showed similar results for all compounds under study. In most spectra, two bands were found through the carbonyl deconvolution, which is in accordance with the theoretical data. It was possible to prove that variation in the nature of the substituent in the ortho position had no significant influence on the conformational equilibrium.

  15. Characterization of milled woods lignins and dehydrogenative polymerization products from monolignol by carbon-13 NMR spectroscopy

    SciTech Connect

    Chen, C.L.

    1996-10-01

    Milled wood lignins and dehydrogenative polymerization products from monolignol will be characterized by using {sup 13}C NMR spectroscopy. The techniques include (1) routine qualitative method, (2) quantitative method using inverse gated decoupling (IGD) pulse sequence, (3) distortionless enhancement by polarization transfer (DEPT) pulse sequence, (4) quantitative determination of phenolic, primal and secondary alcohol hydroxyl groups, and finally (5) used of {sup 13}C specifically labelled compound to monitor biosynthesis of lignin as well as modification reaction of technical lignins. Several appropriate examples will be used to discuss advantages and disadvantages of aforementioned methods. Advantages in combination of chemical methods and {sup 13}C NMR spectroscopy for characterization of lignin preparations will be also discussed.

  16. 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

  17. Proton-Detected Solid-State NMR Spectroscopy of Bone with Ultrafast Magic Angle Spinning

    NASA Astrophysics Data System (ADS)

    Mroue, Kamal H.; Nishiyama, Yusuke; Kumar Pandey, Manoj; Gong, Bo; McNerny, Erin; Kohn, David H.; Morris, Michael D.; Ramamoorthy, Ayyalusamy

    2015-07-01

    While obtaining high-resolution structural details from bone is highly important to better understand its mechanical strength and the effects of aging and disease on bone ultrastructure, it has been a major challenge to do so with existing biophysical techniques. Though solid-state NMR spectroscopy has the potential to reveal the structural details of bone, it suffers from poor spectral resolution and sensitivity. Nonetheless, recent developments in magic angle spinning (MAS) NMR technology have made it possible to spin solid samples up to 110 kHz frequency. With such remarkable capabilities, 1H-detected NMR experiments that have traditionally been challenging on rigid solids can now be implemented. Here, we report the first application of multidimensional 1H-detected NMR measurements on bone under ultrafast MAS conditions to provide atomistic-level elucidation of the complex heterogeneous structure of bone. Our investigations demonstrate that two-dimensional 1H/1H chemical shift correlation spectra for bone are obtainable using fp-RFDR (finite-pulse radio-frequency-driven dipolar recoupling) pulse sequence under ultrafast MAS. Our results infer that water exhibits distinct 1H-1H dipolar coupling networks with the backbone and side-chain regions in collagen. These results show the promising potential of proton-detected ultrafast MAS NMR for monitoring structural and dynamic changes caused by mechanical loading and disease in bone.

  18. 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.

  19. 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.

  20. Metabolic response to exogenous ethanol in yeast: an in vivo statistical total correlation NMR spectroscopy approach.

    PubMed

    Ricci, Maso; Aggravi, Marianna; Bonechi, Claudia; Martini, Silvia; Aloisi, Anna Maria; Rossi, Claudio

    2012-09-01

    In vivo NMR spectroscopy, together with selectively 13C-labelled substrates and 'statistical total correlation spectroscopy' analysis (STOCSY), are valuable tools to collect and interpret the metabolic responses of a living organism to external stimuli. In this study, we applied this approach to evaluate the effects of increasing concentration of exogenous ethanol on the Saccharomyces cerevisiae fermentative metabolism. We show that the STOCSY analysis correctly identifies the different types of correlations among the enriched metabolites involved in the fermentation, and that these correlations are quite stable even in presence of a stressing factor such as the exogenous ethanol.

  1. 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

  2. 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.

  3. Insights into reaction mechanisms in heterogeneous catalysis revealed by in situ NMR spectroscopy.

    PubMed

    Blasco, Teresa

    2010-12-01

    This tutorial review intends to show the possibilities of in situ solid state NMR spectroscopy in the elucidation of reaction mechanisms and the nature of the active sites in heterogeneous catalysis. After a brief overview of the more usual experimental devices used for in situ solid state NMR spectroscopy measurements, some examples of applications taken from the recent literature will be presented. It will be shown that in situ NMR spectroscopy allows: (i) the identification of stable intermediates and transient species using indirect methods, (ii) to prove shape selectivity in zeolites, (iii) the study of reaction kinetics, and (iv) the determination of the nature and the role played by the active sites in a catalytic reaction. The approaches and methodology used to get this information will be illustrated here summarizing the most relevant contributions on the investigation of the mechanisms of a series of reactions of industrial interest: aromatization of alkanes on bifunctional catalysts, carbonylation reaction of methanol with carbon monoxide, ethylbenzene disproportionation, and the Beckmann rearrangement reaction. Special attention is paid to the research carried out on the role played by carbenium ions and alkoxy as intermediate species in the transformation of hydrocarbon molecules on solid acid catalysts.

  4. 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

  5. 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.

  6. Theoretical study on structures and infrared spectroscopy of Cu2+(H2O)Ar n ( n = 1-4)

    NASA Astrophysics Data System (ADS)

    Song, Xiudan; Li, Shuxia; Jiang, Zishi; Zhang, Yongzhi

    2017-09-01

    The binding energy of Cu2+(H2O) is computed to be 98.4 kcal/mol and thus one-photon photodissociation is not possible in the 3400-3800 cm-1 (9.7-10.9 kcal/mol) region. To study whether the infrared photodissociation processes of Cu2+(H2O) can occur by multiple argon atoms tagging technique, density functional and CCSD(T) methods are used to investigate the geometries, OH stretching frequencies and the argon atom binding energies of Cu2+(H2O)Ar n ( n = 1-4) complexes. Various isomers are found resulting from the different coordination sites of argon atoms. The OH stretches in these complexes are shifted to lower frequencies than those of the free water molecule, and the corresponding vibrational red shifts are progressively smaller as more argon atom is added to Cu2+ while binding an argon atom to an OH site should lead to additional sizable red shift to the OH stretching vibrations.

  7. Structure vs. composition: A solid-state 1H and 29Si NMR study of quenched glasses along the Na 2O-SiO 2-H 2O join

    NASA Astrophysics Data System (ADS)

    Cody, George D.; Mysen, Bjorn O.; Lee, Sung Keun

    2005-05-01

    A suite of six hydrous (7 wt.% H 2O) sodium silicate glasses spanning sodium octasilicate to sodium disilicate in composition were analyzed using 29Si single pulse (SP) magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, 1H- 29Si cross polarization (CP) MAS NMR, and fast MAS 1H-NMR. From the 29Si SPMAS data it is observed that at low sodium compositions dissolved water significantly depolymerizes the silicate network. At higher sodium contents, however, dissolved H 2O does not affect a significant increase in depolymerization over that predicted based on the Na/Si ratio alone. The fast MAS 1H-NMR data reveal considerable complexity in proton environments in each of the glasses studied. The fast MAS 1H-NMR spectra of the highest sodium concentration glasses do not exhibit evidence of signficantly greater fractions of dissolved water as molecular H 2O than the lower sodium concentration glasses requiring that the decrease in polymerization at high sodium contents involves a change in sodium solution mechanism. Variable contact time 1H- 29Si cross polarization (CP) MAS NMR data reveal an increase in the rotating frame spin lattice relaxation rate constant ( T1ρ*) for various Q n species with increasing sodium content that correlates with a reduction in the average 1H- 29Si coupling strength. At the highest sodium concentration, however, T1ρ* drops significantly, consistent with a change in the Na 2O solution mechanism.

  8. 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

  9. Structural basis of the green-blue color switching in proteorhodopsin as determined by NMR spectroscopy.

    PubMed

    Mao, Jiafei; Do, Nhu-Nguyen; Scholz, Frank; Reggie, Lenica; Mehler, Michaela; Lakatos, Andrea; Ong, Yean-Sin; Ullrich, Sandra J; Brown, Lynda J; Brown, Richard C D; Becker-Baldus, Johanna; Wachtveitl, Josef; Glaubitz, Clemens

    2014-12-17

    Proteorhodopsins (PRs) found in marine microbes are the most abundant retinal-based photoreceptors on this planet. PR variants show high levels of environmental adaptation, as their colors are tuned to the optimal wavelength of available light. The two major green and blue subfamilies can be interconverted through a L/Q point mutation at position 105. Here we reveal the structural basis behind this intriguing color-tuning effect. High-field solid-state NMR spectroscopy was used to visualize structural changes within green PR directly within the lipid bilayer upon introduction of the green-blue L105Q mutation. The observed effects are localized within the binding pocket and close to retinal carbons C14 and C15. Subsequently, magic-angle spinning (MAS) NMR spectroscopy with sensitivity enhancement by dynamic nuclear polarization (DNP) was applied to determine precisely the retinal structure around C14-C15. Upon mutation, a significantly stretched C14-C15 bond, deshielding of C15, and a slight alteration of the retinal chain's out-of-plane twist was observed. The L105Q blue switch therefore acts locally on the retinal itself and induces a conjugation defect between the isomerization region and the imine linkage. Consequently, the S0-S1 energy gap increases, resulting in the observed blue shift. The distortion of the chromophore structure also offers an explanation for the elongated primary reaction detected by pump-probe spectroscopy, while chemical shift perturbations within the protein can be linked to the elongation of late-photocycle intermediates studied by flash photolysis. Besides resolving a long-standing problem, this study also demonstrates that the combination of data obtained from high-field and DNP-enhanced MAS NMR spectroscopy together with time-resolved optical spectroscopy enables powerful synergies for in-depth functional studies of membrane proteins.

  10. Precision Cavity-Enhanced Dual-Comb Spectroscopy: Application to the Gas Metrology of CO_2, H_2O, and N_2O.

    NASA Astrophysics Data System (ADS)

    Fleisher, Adam J.; Long, David A.; Hodges, Joseph T.

    2017-06-01

    With inherent simplicity, mutual phase coherence, and a high degree of user control, electro-optic frequency combs are amenable to both dual-comb spectroscopy and cavity-enhanced comb spectroscopy. This combination of fast, multiplexed spectroscopy, with an effective absorption pathlength >1 km, is used here to perform line-by-line metrology of the gas-phase absorption spectra of CO_2, H_2O, and N_2O in the near-infrared. We report absolute transition frequency with precision better than 1 MHz in 1 s of spectral acquisition per transition using a comb with an instantaneous optical bandwidth of 6 GHz, tunable over the entire 6240-6370 \\wn range. A full model for the electric field transmitted through the enhancement cavity (even in the presence of strong molecular absorption and dispersion) will be discussed. I. Coddington et al., Optica 3, 414 (2016) B. Bernhardt et al., Nat. Photonics 4, 55 (2010)

  11. 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

  12. 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

  13. Contrast and Raman spectroscopy study of single- and few-layered charge density wave material: 2H-TaSe2

    PubMed Central

    Hajiyev, Parviz; Cong, Chunxiao; Qiu, Caiyu; Yu, Ting

    2013-01-01

    In this article, we report the first successful preparation of single- and few-layers of tantalum diselenide (2H-TaSe2) by mechanical exfoliation technique. Number of layers is confirmed by white light contrast spectroscopy and atomic force microscopy (AFM). Vibrational properties of the atomically thin layers of 2H-TaSe2 are characterized by micro-Raman spectroscopy. Room temperature Raman measurements demonstrate MoS2-like spectral features, which are reliable for thickness determination. E1g mode, usually forbidden in backscattering Raman configuration is observed in the supported TaSe2 layers while disappears in the suspended layers, suggesting that this mode may be enabled because of the symmetry breaking induced by the interaction with the substrate. A systematic in-situ low temperature Raman study, for the first time, reveals the existence of incommensurate charge density wave phase transition in single and double-layered 2H-TaSe2 as reflected by a sudden softening of the second-order broad Raman mode resulted from the strong electron-phonon coupling (Kohn anomaly). PMID:24005335

  14. Dispersed-Fluorescence Spectroscopy of Jet-Cooled Calcium Ethoxide Radical (CaOC_2H_5)

    NASA Astrophysics Data System (ADS)

    Paul, Anam C.; Reza, Md Asmaul; Liu, Jinjun

    2016-06-01

    Metal-containing free radicals are important intermediates in metal-surface reactions and in the interaction between metals and organic molecules. In the present work, dispersed fluorescence (DF) spectra of the calcium ethoxide radical (CaOC_2H_5) have been obtained by pumping the {tilde A^2}{A}' ← {tilde X^2}{A}' and the {tilde B^2}{A}'' ← {tilde X^2}{A}' origin bands in its laser-induced fluorescence (LIF) spectrum. CaOC_2H_5 radicals were produced by 1064 nm laser ablation of calcium grains in the presence of ethanol under jet-cooled conditions. Dominant transitions in the vibrationally resolved DF spectra are well reproduced using Franck-Condon factors predicted by complete active space self-consistent (CASSCF) calculations. Differences in transition intensities between the {tilde A^2}{A}' → {tilde X^2}{A}' and the {tilde B^2}{A}'' → {tilde X^2}{A}' DF spectra are attributed to the pseudo-Jahn-Teller interaction between the tilde A ^2 A' and the tilde B ^2 A'' states. Collision-induced population transfer between these two excited electronic states results in additional peaks in the DF spectra.

  15. NMR-based approach to the analysis of radiopharmaceuticals: radiochemical purity, specific activity, and radioactive concentration values by proton and tritium NMR spectroscopy.

    PubMed

    Schenk, David J; Dormer, Peter G; Hesk, David; Pollack, Scott R; Lavey, Carolee Flader

    2015-06-15

    Compounds containing tritium are widely used across the drug discovery and development landscape. These materials are widely utilized because they can be efficiently synthesized and produced at high specific activity. Results from internally calibrated (3)H and (1)H nuclear magnetic resonance (NMR) spectroscopy suggests that at least in some cases, this calibrated approach could supplement or potentially replace radio-high-performance liquid chromatography for radiochemical purity, dilution and scintillation counting for the measurement of radioactivity per volume, and liquid chromatography/mass spectrometry analysis for the determination of specific activity. In summary, the NMR-derived values agreed with those from the standard approaches to within 1% to 9% for solution count and specific activity. Additionally, the NMR-derived values for radiochemical purity deviated by less than 5%. A benefit of this method is that these values may be calculated at the same time that (3)H NMR analysis provides the location and distribution of tritium atoms within the molecule. Presented and discussed here is the application of this method, advantages and disadvantages of the approach, and a rationale for utilizing internally calibrated (1)H and (3)H NMR spectroscopy for specific activity, radioactive concentration, and radiochemical purity whenever acquiring (3)H NMR for tritium location.

  16. Novel monosaccharide fermentation products in Caldicellulosiruptor saccharolyticus identified using NMR spectroscopy.

    PubMed

    Isern, Nancy G; Xue, Junfeng; Rao, Jaya V; Cort, John R; Ahring, Birgitte K

    2013-04-03

    Caldicellulosiruptor saccharolyticus is a thermophilic, Gram-positive, non-spore forming, strictly anaerobic bacterium of interest in potential industrial applications, including the production of biofuels such as hydrogen or ethanol from lignocellulosic biomass through fermentation. High-resolution, solution-state nuclear magnetic resonance (NMR) spectroscopy is a useful method for the identification and quantification of metabolites that result from growth on different substrates. NMR allows facile resolution of isomeric (identical mass) constituents and does not destroy the sample. Profiles of metabolites produced by the thermophilic cellulose-degrading 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. One dimensional 1H NMR spectral analysis was performed by curve fitting against spectral libraries provided in the Chenomx software; 2-D homonuclear and heteronuclear NMR experiments were conducted to further reduce uncertainties due to unassigned, overlapping, or poorly-resolved peaks. 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), acetoin and 2,3-butanediol (from growth on D-glucose, L-arabinose, and D-xylose), and hydroxyacetone (from growth on D-mannose, L-arabinose, and D-xylose). Production of ethylene glycol from D-arabinose was particularly notable, with around 10% of the substrate carbon converted into this uncommon fermentation product. The present research shows that C. saccharolyticus

  17. Novel monosaccharide fermentation products in Caldicellulosiruptor saccharolyticus identified using NMR spectroscopy

    PubMed Central

    2013-01-01

    Background Caldicellulosiruptor saccharolyticus is a thermophilic, Gram-positive, non-spore forming, strictly anaerobic bacterium of interest in potential industrial applications, including the production of biofuels such as hydrogen or ethanol from lignocellulosic biomass through fermentation. High-resolution, solution-state nuclear magnetic resonance (NMR) spectroscopy is a useful method for the identification and quantification of metabolites that result from growth on different substrates. NMR allows facile resolution of isomeric (identical mass) constituents and does not destroy the sample. Results Profiles of metabolites produced by the thermophilic cellulose-degrading 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. One dimensional 1H NMR spectral analysis was performed by curve fitting against spectral libraries provided in the Chenomx software; 2-D homonuclear and heteronuclear NMR experiments were conducted to further reduce uncertainties due to unassigned, overlapping, or poorly-resolved peaks. 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), acetoin and 2,3-butanediol (from growth on D-glucose, L-arabinose, and D-xylose), and hydroxyacetone (from growth on D-mannose, L-arabinose, and D-xylose). Production of ethylene glycol from D-arabinose was particularly notable, with around 10% of the substrate carbon converted into this uncommon fermentation product. Conclusions The present research

  18. 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

  19. 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

    2010-09-05

    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.

  20. Synthesis, purification, and characterization of single helix membrane peptides and proteins for NMR spectroscopy.

    PubMed

    Itaya, Miki; Brett, Ian C; Smith, Steven O

    2012-01-01

    Membrane proteins function as receptors, channels, transporters, and enzymes. These proteins are generally difficult to express and purify in a functional form due to the hydrophobic nature of their membrane spanning sequences. Studies on membrane proteins with a single membrane spanning helix have been particularly challenging. Single-pass membrane proteins will often form dimers or higher order oligomers in cell membranes as a result of sequence motifs that mediate specific transmembrane helix interactions. Understanding the structural basis for helix association provides insights into how these proteins function. Nevertheless, nonspecific association or aggregation of hydrophobic membrane spanning sequences can occur when isolated transmembrane domains are reconstituted into membrane bilayers or solubilized into detergent micelles for structural studies by solid-state or solution NMR spectroscopy. Here, we outline the methods used to synthesize, purify, and characterize single transmembrane segments for structural studies. Two synthetic strategies are discussed. The first strategy is to express hydrophobic peptides as protein chimera attached to the maltose binding protein. The second strategy is by direct chemical synthesis. Purification is carried out by several complementary chromatography methods. The peptides are solubilized in detergent for solution NMR studies or reconstituted into model membranes for solid-state NMR studies. We describe the methods used to characterize the reconstitution of these systems prior to NMR structural studies to establish if there is nonspecific aggregation.

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

    DOE PAGES

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

    2015-06-22

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

  2. Metabolomic Fingerprinting of Romaneschi Globe Artichokes by NMR Spectroscopy and Multivariate Data Analysis.

    PubMed

    de Falco, Bruna; Incerti, Guido; Pepe, Rosa; Amato, Mariana; Lanzotti, Virginia

    2016-09-01

    Globe artichoke (Cynara cardunculus L. var. scolymus L. Fiori) and cardoon (Cynara cardunculus L. var. altilis DC) are sources of nutraceuticals and bioactive compounds. To apply a NMR metabolomic fingerprinting approach to Cynara cardunculus heads to obtain simultaneous identification and quantitation of the major classes of organic compounds. The edible part of 14 Globe artichoke populations, belonging to the Romaneschi varietal group, were extracted to obtain apolar and polar organic extracts. The analysis was also extended to one species of cultivated cardoon for comparison. The (1) H-NMR of the extracts allowed simultaneous identification of the bioactive metabolites whose quantitation have been obtained by spectral integration followed by principal component analysis (PCA). Apolar organic extracts were mainly based on highly unsaturated long chain lipids. Polar organic extracts contained organic acids, amino acids, sugars (mainly inulin), caffeoyl derivatives (mainly cynarin), flavonoids, and terpenes. The level of nutraceuticals was found to be highest in the Italian landraces Bianco di Pertosa zia E and Natalina while cardoon showed the lowest content of all metabolites thus confirming the genetic distance between artichokes and cardoon. Metabolomic approach coupling NMR spectroscopy with multivariate data analysis allowed for a detailed metabolite profile of artichoke and cardoon varieties to be obtained. Relevant differences in the relative content of the metabolites were observed for the species analysed. This work is the first application of (1) H-NMR with multivariate statistics to provide a metabolomic fingerprinting of Cynara scolymus. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  3. Partitioning of nitroxides in dispersed systems investigated by ultrafiltration, EPR and NMR spectroscopy.

    PubMed

    Krudopp, Heimke; Sönnichsen, Frank D; Steffen-Heins, Anja

    2015-08-15

    The partitioning behavior of paramagnetic nitroxides in dispersed systems can be determined by deconvolution of electron paramagnetic resonance (EPR) spectra giving equivalent results with the validated methods of ultrafiltration techniques (UF) and pulsed-field gradient nuclear magnetic resonance spectroscopy (PFG-NMR). The partitioning behavior of nitroxides with increasing lipophilicity was investigated in anionic, cationic and nonionic micellar systems and 10 wt% o/w emulsions. Apart from EPR spectra deconvolution, the PFG-NMR was used in micellar solutions as a non-destructive approach, while UF based on separation of very small volume of the aqueous phase. As a function of their substituent and lipophilicity, the proportions of nitroxides that were solubilized in the micellar or emulsion interface increased with increasing nitroxide lipophilicity for all emulsifier used. Comparing the different approaches, EPR deconvolution and UF revealed comparable nitroxide proportions that were solubilized in the interfaces. Those proportions were higher than found with PFG-NMR. For PFG-NMR self-diffusion experiments the reduced nitroxides were used revealing a high dynamic of hydroxylamines and emulsifiers. Deconvolution of EPR spectra turned out to be the preferred method for measuring the partitioning behavior of paramagnetic molecules as it enables distinguishing between several populations at their individual solubilization sites. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. 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.

  5. Quantitative identification of metastable magnesium carbonate minerals by solid-state 13C NMR spectroscopy.

    PubMed

    Moore, Jeremy K; Surface, J Andrew; Brenner, Allison; Wang, Louis S; Skemer, Philip; Conradi, Mark S; Hayes, Sophia E

    2015-01-06

    In the conversion of CO2 to mineral carbonates for the permanent geosequestration of CO2, there are multiple magnesium carbonate phases that are potential reaction products. Solid-state (13)C NMR is demonstrated as an effective tool for distinguishing magnesium carbonate phases and quantitatively characterizing magnesium carbonate mixtures. Several of these mineral phases include magnesite, hydromagnesite, dypingite, and nesquehonite, which differ in composition by the number of waters of hydration or the number of crystallographic hydroxyl groups. These carbonates often form in mixtures with nearly overlapping (13)C NMR resonances which makes their identification and analysis difficult. In this study, these phases have been investigated with solid-state (13)C NMR spectroscopy, including both static and magic-angle spinning (MAS) experiments. Static spectra yield chemical shift anisotropy (CSA) lineshapes that are indicative of the site-symmetry variations of the carbon environments. MAS spectra yield isotropic chemical shifts for each crystallographically inequivalent carbon and spin-lattice relaxation times, T1, yield characteristic information that assist in species discrimination. These detailed parameters, and the combination of static and MAS analyses, can aid investigations of mixed carbonates by (13)C NMR.

  6. Metabolomic by 1H NMR spectroscopy differentiates "Fiano di Avellino" white wines obtained with different yeast strains.

    PubMed

    Mazzei, Pierluigi; Spaccini, Riccardo; Francesca, Nicola; Moschetti, Giancarlo; Piccolo, Alessandro

    2013-11-13

    We employed (1)H NMR spectroscopy to examine the molecular profile of a white "Fiano di Avellino" wine obtained through fermentation by either a commercial or a selected autochthonous Saccharomyces cerevisiae yeast starter. The latter was isolated from the same grape variety used in the wine-making process in order to strengthen the relationship between wine molecular quality and its geographical origin. (1)H NMR spectra, where water and ethanol signals were suppressed by a presaturated T1-edited NMR pulse sequence, allowed for definition of the metabolic content of the two differently treated wines. Elaboration of NMR spectral data by multivariate statistical analyses showed that the two different yeasts led to significant diversity in the wine metabolomes. Our results indicate that metabolomics by (1)H NMR spectroscopy combined with multivariate statistical analysis enables wine differentiation as a function of yeast species and other wine-making factors, thereby contributing to objectively relate wine quality to the terroir.

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

    PubMed

    Morgado, Leonor; Zeth, Kornelius; Burmann, Björn M; Maier, Timm; Hiller, Sebastian

    2015-04-01

    The insertase BamA is the central protein of the Bam complex responsible for outer membrane protein biogenesis in Gram-negative bacteria. BamA features a 16-stranded transmembrane β-barrel and five periplasmic POTRA domains, with a total molecular weight of 88 kDa. Whereas the structure of BamA has recently been determined by X-ray crystallography, its functional mechanism is not well understood. This mechanism comprises the insertion of substrates from a dynamic, chaperone-bound state into the bacterial outer membrane, and NMR spectroscopy is thus a method of choice for its elucidation. Here, we report solution NMR studies of different BamA constructs in three different membrane mimetic systems: LDAO micelles, DMPC:DiC7PC bicelles and MSP1D1:DMPC nanodiscs. The impact of biochemical parameters on the spectral quality was investigated, including the total protein concentration and the detergent:protein ratio. The barrel of BamA is folded in micelles, bicelles and nanodiscs, but the N-terminal POTRA5 domain is flexibly unfolded in the absence of POTRA4. Measurements of backbone dynamics show that the variable insertion region of BamA, located in the extracellular lid loop L6, features high local flexibility. Our work establishes biochemical preparation schemes for BamA, which will serve as a platform for structural and functional studies of BamA and its role within the Bam complex by solution NMR spectroscopy.

  8. 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.

  9. 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

  10. Carbon-dot organic surface modifier analysis by solution-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Philippidis, Aggelos; Spyros, Apostolos; Anglos, Demetrios; Bourlinos, Athanasios B.; Zbořil, Radek; Giannelis, Emmanuel P.

    2013-07-01

    Carbon dots (C-dots) represent a new class of carbon-based materials that were discovered recently and have drawn the interest of the scientific community, particularly because of their attractive optical properties and their potential as fluorescent sensors. Investigation of the chemical structure of C-dots is extremely important for correlating the surface modifier composition with C-dot optical properties and allow for structure-properties fine tuning. In this article, we report the structural analysis of the surface modifiers of three different types of C-dot nanoparticles (Cwax, Cws, and Csalt) by use of 1D- and 2D-high-resolution NMR spectroscopy in solution. We unambiguously verify that the structure of the modifier chains remains chemically unchanged during the passivation procedure, and confirm the covalent attachment of the modifiers to the nanoparticle core, which contributes no signal to the solution-state NMR spectra. To our knowledge, this is the first study confirming the full structural assignment of C-dot organic surface modifiers by use of solution NMR spectroscopy.

  11. Dispersed-fluorescence spectroscopy of jet-cooled calcium ethoxide radical (CaOC2H5)

    NASA Astrophysics Data System (ADS)

    Paul, Anam C.; Reza, Md. Asmaul; Liu, Jinjun

    2016-12-01

    Dispersed fluorescence (DF) spectra of the calcium ethoxide radical (CaOC2H5) have been obtained by pumping the A˜12 A‧ ←X˜2A‧ and the A˜22 A‧‧ ←X˜2A‧ origin bands in its laser-induced fluorescence spectrum. Dominant transitions in the vibrationally resolved DF spectra are well reproduced using Franck-Condon factors predicted by complete active space self-consistent field (CASSCF) calculations. Collision-induced population transfer between the A˜12 A‧ and the A22 A‧‧ states results in additional peaks in the experimental DF spectra. Differences between the intensities of vibronic bands in the A˜12 A‧ →X˜2A‧ and the A˜22 A‧‧ →X˜2A‧ DF spectra are attributed to different symmetries of the two excited electronic states.

  12. Distortion of ethyne on coordination to silver acetylide, C2H2ṡṡṡAgCCH, characterised by broadband rotational spectroscopy and ab initio calculations

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    The rotational spectra of six isotopologues of a complex of ethyne and silver acetylide, C2H2ṡṡṡAgCCH, 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 C2H2ṡṡṡAgCCH 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 107Ag13C13CH and 109Ag13C13CH 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.

  13. 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

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

    PubMed

    Debouzy, Jean-Claude; Crouzier, David; 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 (1)H-NMR in solution and its membrane interactions were studied by (1)H-NMR in small unilamellar vesicles and by (31)P (2)H NMR in phospholipidic dispersions of DMPC (dimyristoylphosphatidylcholine) in comparison with those of POLYA and CYSP alone. (1)H-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 ((31)P). 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.

  15. 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

    2007-06-05

    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.

  16. Methyl labeling and TROSY NMR spectroscopy of proteins expressed in the eukaryote Pichia pastoris

    PubMed Central

    Clark, Lindsay; Zahm, Jacob A.; Ali, Rustam; Kukula, Maciej; Bian, Liangqiao; Patrie, Steven M.; Gardner, Kevin H.; Rosen, Michael K.; Rosenbaum, Daniel M.

    2015-01-01

    13C Methyl TROSY NMR spectroscopy has emerged as a powerful method for studying the dynamics of large systems such as macromolecular assemblies and membrane proteins. Specific 13C labeling of aliphatic methyl groups and perdeuteration has been limited primarily to proteins expressed in E. coli, preventing studies of many eukaryotic proteins of physiological and biomedical significance. We demonstrate the feasibility of efficient 13C isoleucine δ1-methyl labeling in a deuterated background in an established eukaryotic expression host, Pichia pastoris, and show that this method can be used to label the eukaryotic protein actin, which cannot be expressed in bacteria. This approach will enable NMR studies of previously intractable targets. PMID:26025061

  17. 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.

  18. 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.

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

    PubMed

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

    2015-03-04

    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.

  20. A dynamic nuclear polarization strategy for multi-dimensional Earth's field NMR spectroscopy.

    PubMed

    Halse, Meghan E; Callaghan, Paul T

    2008-12-01

    Dynamic nuclear polarization (DNP) is introduced as a powerful tool for polarization enhancement in multi-dimensional Earth's field NMR spectroscopy. Maximum polarization enhancements, relative to thermal equilibrium in the Earth's magnetic field, are calculated theoretically and compared to the more traditional prepolarization approach for NMR sensitivity enhancement at ultra-low fields. Signal enhancement factors on the order of 3000 are demonstrated experimentally using DNP with a nitroxide free radical, TEMPO, which contains an unpaired electron which is strongly coupled to a neighboring (14)N nucleus via the hyperfine interaction. A high-quality 2D (19)F-(1)H COSY spectrum acquired in the Earth's magnetic field with DNP enhancement is presented and compared to simulation.

  1. Characterization of metabolites in different kiwifruit varieties by NMR and fluorescence spectroscopy.

    PubMed

    Abdul Hamid, Nur Ashikin; Mediani, Ahmed; Maulidiani, M; Abas, Faridah; Park, Yong Seo; Leontowicz, Hanna; Leontowicz, Maria; Namiesnik, Jacek; Gorinstein, S

    2017-05-10

    It is known from our previous studies that kiwifruits, which are used in common human diet, have preventive properties of coronary artery disease. This study describes a combination of (1)H NMR spectroscopy, multivariate data analyses and fluorescence measurements in differentiating of some kiwifruit varieties, their quenching and antioxidant properties. A total of 41 metabolites were identified by comparing with literature data Chenomx database and 2D NMR. The binding properties of the extracted polyphenols against HSA showed higher reactivity of studied two cultivars in comparison with the common Hayward. The results showed that the fluorescence of HSA was quenched by Bidan as much as twice than by other fruits. The correlation between the binding properties of polyphenols in the investigated fruits, their relative quantification and suggested metabolic pathway was established. These results can provide possible application of fruit extracts in pharmaceutical industry.

  2. 13C-NMR studies of the paramagnetic and charge-ordered states of the organic superconductor β''-(BEDT-TTF)3Cl2·2H2O under pressure

    NASA Astrophysics Data System (ADS)

    Nagata, Sanato; Ogura, Takashi; Kawamoto, Atsushi; Taniguchi, Hiromi

    2011-07-01

    β''-(BEDT-TTF)3Cl2·2H2O [BEDT-TTF: b̲is-(e̲thylened̲it̲hio)t̲etrat̲hiaf̲ulvalene] is superconductive under pressures, whereas the salt exhibits metal-insulator (MI) transition under ambient pressure. The insulator phase in the salt was examined using the charge density wave (CDW) phase that was obtained from band calculation. The charge-ordered (CO) state was recently proposed as the insulator phase of the salt, and the mechanism of superconductivity intermediated by charge fluctuation was suggested. We accessed 13C-NMR on β''-(BEDT-TTF)3Cl2·2H2O at ambient pressure and under pressure up to 1.6 GPa. At ambient pressure, the NMR spectrum changed at approximately 100 K. Three isolated peaks appeared at low temperatures, suggesting that the CO state exists below 100 K, and spin-gap behavior was observed. By analyzing the chemical shift, the charges on the three sites were estimated as ˜+0.4e, ˜+0.6e, and ˜+1.0e. The ratio of peak intensity and unsymmetrical peak position suggest the CO state with some symmetry breaking. When pressure is applied, the splitting of the NMR peaks in the CO state is reduced. The salt finally exhibits superconductivity at 1.6 GPa, spin-gap behavior observed at (T1T)-1 below 1.3 GPa suddenly disappears, whereas the NMR spectrum predicts that charge disproportionation coexists with superconductivity. The suppression of the spin-singlet formation observed in (T1T)-1 at 1.6 GPa suggests the metallic state with the charge disproportionation and the CO instability with some symmetry breaking.

  3. Complementary low energy ion scattering and X-ray photoelectron spectroscopy characterization of polystyrene submitted to N 2/H 2 glow discharge

    NASA Astrophysics Data System (ADS)

    Bonatto, F.; Rovani, S.; Kaufmann, I. R.; Soares, G. V.; Baumvol, I. J. R.; Krug, C.

    2012-02-01

    Low energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS) were used to access the elemental composition and chemical bonding characteristics of polystyrene (PS) surfaces sequentially treated by corona and glow discharge (plasma) processing in N 2/H 2 ambient. The latter has shown activity as suppressor of pathogenic Staphylococcus epidermidis biofilms. LEIS indicated that oxygen from the corona discharge process is progressively replaced by nitrogen at the PS surface. XPS shows C dbnd N and N sbnd C dbnd O chemical groups as significant inhibitors of bacterial adhesion, suggesting application in medical devices.

  4. Optical spectroscopy of two-dimensional layered (C(6)H(5)C(2)H(4)-NH(3))(2)-PbI(4) perovskite.

    PubMed

    Gauthron, K; Lauret, J-S; Doyennette, L; Lanty, G; Al Choueiry, A; Zhang, S J; Brehier, A; Largeau, L; Mauguin, O; Bloch, J; Deleporte, E

    2010-03-15

    We report on optical spectroscopy (photoluminescence and photoluminescence excitation) on two-dimensional self-organized layers of (C(6)H(5)C(2)H(4)-NH(3))(2)-PbI(4) perovskite. Temperature and excitation power dependance of the optical spectra gives a new insight into the excitonic and the phononic properties of this hybrid organic/inorganic semiconductor. In particular, exciton-phonon interaction is found to be more than one order of magnitude higher than in GaAs QWs. As a result, photoluminescence emission lines have to be interpreted in the framework of a polaron model.

  5. Detection and characterization of serine and threonine hydroxyl protons in Bacillus circulans xylanase by NMR spectroscopy.

    PubMed

    Brockerman, Jacob A; Okon, Mark; McIntosh, Lawrence P

    2014-01-01

    Hydroxyl protons on serine and threonine residues are not well characterized in protein structures determined by both NMR spectroscopy and X-ray crystallography. In the case of NMR spectroscopy, this is in large part because hydroxyl proton signals are usually hidden under crowded regions of (1)H-NMR spectra and remain undetected by conventional heteronuclear correlation approaches that rely on strong one-bond (1)H-(15)N or (1)H-(13)C couplings. However, by filtering against protons directly bonded to (13)C or (15)N nuclei, signals from slowly-exchanging hydroxyls can be observed in the (1)H-NMR spectrum of a uniformly (13)C/(15)N-labeled protein. Here we demonstrate the use of a simple selective labeling scheme in combination with long-range heteronuclear scalar correlation experiments as an easy and relatively inexpensive way to detect and assign these hydroxyl proton signals. Using auxtrophic Escherichia coli strains, we produced Bacillus circulans xylanase (BcX) labeled with (13)C/(15)N-serine or (13)C/(15)N-threonine. Signals from two serine and three threonine hydroxyls in these protein samples were readily observed via (3)JC-OH couplings in long-range (13)C-HSQC spectra. These scalar couplings (~5-7 Hz) were measured in a sample of uniformly (13)C/(15)N-labeled BcX using a quantitative (13)C/(15)N-filtered spin-echo difference experiment. In a similar approach, the threonine and serine hydroxyl hydrogen exchange kinetics were measured using a (13)C/(15)N-filtered CLEANEX-PM pulse sequence. Collectively, these experiments provide insights into the structural and dynamic properties of several serine and threonine hydroxyls within this model protein.

  6. 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.

  7. 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

  8. Arrangement and mobility of water in vermiculite hydrates followed by 1H NMR spectroscopy.

    PubMed

    Sanz, J; Herrero, C P; Serratosa, J M

    2006-04-20

    The arrangement of water molecules in one- and two-layer hydrates of high-charged vermiculites, saturated with alkaline (Li(+), Na(+)) and alkali-earth (Mg(2+), Ca(2+), Ba(2+)) cations, has been analyzed with (1)H NMR spectroscopy. Two different orientations for water molecules have been found, depending on the hydration state and the sites occupied by interlayer cations. As the amount of water increases, hydrogen bond interactions between water molecules increase at expenses of water-silicate interactions. This interaction favors water mobility in vermiculites. A comparison of the temperature dependence of relaxation times T(1) and T(2) for one and two-layer hydrates of Na-vermiculite shows that the rotations of water molecules around C(2)-axes and that of cation hydration shells around the c-axis is favored in the two-layer hydrate. In both hydrates, the anisotropic diffusion of water takes place at room temperature, preserving the orientation of water molecules relative to the silicate layers. Information obtained by NMR spectroscopy is compatible with that deduced by infrared spectroscopy and with structural studies carried out with X-ray and neutron diffraction techniques on single-crystals of vermiculite.

  9. Equilibrium forms of vitisin B pigments in an aqueous system studied by NMR and visible spectroscopy.

    PubMed

    Oliveira, Joana; Mateus, Nuno; Silva, Artur M S; de Freitas, Victor

    2009-08-13

    The main species in the acid-base equilibria of two pyranoanthocyanins (vitisins B), pyranomalvidin-3-glucoside I and pyranomalvidin-3-O-coumaroylglucoside II, and the respective pK(a) were determined using NMR, visible spectroscopy, and mass spectrometry techniques. The three equilibria involve protonation of the pyranoflavylium cation of vitisin B (pK(a1)) and two deprotonations (pK(a2) and pK(a3)). For pigment I, the values obtained through the titration curves of the chemical shift of some protons versus pH were (pK(a1) < 0.68; pK(a2) = 4.40 +/- 0.08; pK(a3) = 7.45 +/- 0.09) very close to the values obtained by visible spectroscopy (pK(a1) < 0.63; pK(a2) = 4.43 +/- 0.02; pK(a3) = 7.34 +/- 0.03). For pigment II, it was only possible to calculate the pK(a) by visible spectroscopy (pK(a1) < 0.75; pK(a2) = 4.66 +/- 0.10; pK(a3) = 6.76 +/- 0.10). NMR studies have shown that pigment I does not undergo hydration, and the hypothesis of the occurrence of hemiacetal forms in equilibrium was discarded.

  10. 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.

  11. Following the Reaction of Heteroanions inside a {W18O56} Polyoxometalate Nanocage by NMR Spectroscopy and Mass Spectrometry.

    PubMed

    Zheng, Qi; Vilà-Nadal, Laia; Busche, Christoph; Mathieson, Jennifer S; Long, De-Liang; Cronin, Leroy

    2015-06-26

    By incorporating phosphorus(III)-based anions into a polyoxometalate cage, a new type of tungsten-based unconventional Dawson-like cluster, [W18O56(HP(III)O3)2(H2O)2](8-), was isolated, in which the reaction of the two phosphite anions [HPO3](2-) within the {W18O56} cage could be followed spectroscopically. As well as full X-ray crystallographic analysis, we studied the reactivity of the cluster using both solution-state NMR spectroscopy and mass spectrometry. These techniques show that the cluster undergoes a structural rearrangement in solution whereby the {HPO3} moieties dimerize to form a weakly interacting (O3PH⋅⋅⋅HPO3) moiety. In the crystalline state the cluster exhibits a thermally triggered oxidation of the two P(III) template moieties to form P(V) centers (phosphite to phosphate), commensurate with the transformation of the cage into a Wells-Dawson {W18O54} cluster. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Following the Reaction of Heteroanions inside a {W18O56} Polyoxometalate Nanocage by NMR Spectroscopy and Mass Spectrometry**

    PubMed Central

    Zheng, Qi; Vilà-Nadal, Laia; Busche, Christoph; Mathieson, Jennifer S; Long, De-Liang; Cronin, Leroy

    2015-01-01

    By incorporating phosphorus(III)-based anions into a polyoxometalate cage, a new type of tungsten-based unconventional Dawson-like cluster, [W18O56(HPIIIO3)2(H2O)2]8−, was isolated, in which the reaction of the two phosphite anions [HPO3]2− within the {W18O56} cage could be followed spectroscopically. As well as full X-ray crystallographic analysis, we studied the reactivity of the cluster using both solution-state NMR spectroscopy and mass spectrometry. These techniques show that the cluster undergoes a structural rearrangement in solution whereby the {HPO3} moieties dimerize to form a weakly interacting (O3PH⋅⋅⋅HPO3) moiety. In the crystalline state the cluster exhibits a thermally triggered oxidation of the two PIII template moieties to form PV centers (phosphite to phosphate), commensurate with the transformation of the cage into a Wells–Dawson {W18O54} cluster. PMID:26013548

  13. Structural rearrangements of membrane proteins probed by water-edited solid-state NMR spectroscopy.

    PubMed

    Ader, Christian; Schneider, Robert; Seidel, Karsten; Etzkorn, Manuel; Becker, Stefan; Baldus, Marc

    2009-01-14

    We show that water-edited solid-state NMR spectroscopy allows for probing global protein conformation and residue-specific solvent accessibility in a lipid bilayer environment. The transfer dynamics can be well described by a general time constant, irrespective of protein topology and lipid environment. This approach was used to follow structural changes in response to protein function in the chimeric potassium channel KcsA-Kv1.3. Data obtained as a function of pH link earlier biochemical data to changes in protein structure in a functional bilayer setting.

  14. Characterization of Chemical Weapons Convention Schedule 3 Compounds by Quantitative 13C NMR Spectroscopy

    DTIC Science & Technology

    2007-11-01

    Stokes-Einstein equation for a rigid isotropic rotor: r = 3 7 3 kT In the equation, q is viscosity (0.224 mPa s at 5 ’C), extrapolated from the reported... viscosities for hydrogen cyanide at 0 and 25 oC,31 r is the radius of the hydrogen cyanide molecule, calculated from its 1.064 x 10-8 cm C-H distance...Lammers, G.; Janssen, L.P.B.; Beenackers, A.A.C.M. Quantitative Analysis of Chemically Modified Starches by ’H-NMR Spectroscopy. Starch /Staerke 1995; 47

  15. Stereochemical investigations on the diketopiperazine derivatives of enalapril and lisinopril by NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Demeter, Ádám; Fodor, Tamás; Fischer, János

    1998-11-01

    Stereochemical analysis of epimeric diketopiperazine (DKP) derivatives of enalapril and lisinopril has been performed by NMR spectroscopy. The present study focuses on the configurational assignment and conformational characteristics of the epimeric DKPs obtained from cyclization and subsequent base-catalyzed hydrolysis. We report full 1H and 13C assignments as obtained by a concerted use of 1D and 2D methods. The configuration of the respective stereogenic centres and the main conformational features were derived from the measured scalar and NOE connections. One conspicuous conformational feature of the sidechain is its tendency to bend over the piperazinedione ring.

  16. Determination of the band parameters of bulk 2H-MX2 (M = Mo, W; X = S, Se) by angle-resolved photoemission spectroscopy

    PubMed Central

    Kim, Beom Seo; Rhim, Jun-Won; Kim, Beomyoung; Kim, Changyoung; Park, Seung Ryong

    2016-01-01

    Monolayer MX2 (M = Mo, W; X = S, Se) has recently been drawn much attention due to their application possibility as well as the novel valley physics. On the other hand, it is also important to understand the electronic structures of bulk MX2 for material applications since it is very challenging to grow large size uniform and sustainable monolayer MX2. We performed angle-resolved photoemission spectroscopy and tight binding calculations to investigate the electronic structures of bulk 2H-MX2. We could extract all the important electronic band parameters for bulk 2H-MX2, including the band gap, direct band gap size at K (-K) point and spin splitting size. Upon comparing the parameters for bulk 2H-MX2 (our work) with mono- and multi-layer MX2 (published), we found that stacked layers, substrates for thin films, and carrier concentration significantly affect the parameters, especially the band gap size. The origin of such effect is discussed in terms of the screening effect. PMID:27805019

  17. High Resolution Direct Frequency Comb Spectroscopy of Vinyl Bromide (C_2H_3Br) and Nitromethane (CH_3NO_2) in the CH Stretch Region

    NASA Astrophysics Data System (ADS)

    Changala, Bryan; Spaun, Ben; Patterson, David; Ye, Jun

    2016-06-01

    We present high resolution rovibrational spectra of buffer gas cooled vinyl bromide (C_2H_3Br) and nitromethane (CH_3NO_2) in the 3 μm CH stretch region, acquired via cavity-enhanced direct frequency comb absorption spectroscopy. The ˜10 K translational and rotational temperatures of the molecular gas, as well as the narrow linewidth of the frequency comb, yield well resolved rotational structure, isotope shifts, and nuclear hyperfine splittings. Given the wide bandwidth of the light source and the long path length of the enhancement cavity, we measure entire vibrational bands in a single shot with high signal-to-noise ratios. We discuss spectra of the entire fundamental CH stretch manifolds of both C_2H_3Br and CH_3NO_2, which provide contrasting examples of rovibrational structure of rigid and non-rigid systems. C_2H_3Br is a relatively normal asymmetric top, exhibiting local perturbations to its rotational structure. Conversely, CH_3NO_2 contains an essentially unhindered methyl rotor. Of particular interest are its quasi-degenerate asymmetric CH stretch modes. Here, one must consider multiple couplings between torsional, rotational, and vibrational angular momentum, leading to qualitatively new level patterns and structure.

  18. Chemical exchange spectroscopy based on carbon-13 NMR. Applications to enzymology and protein folding

    NASA Astrophysics Data System (ADS)

    Alexandrescu, Andrei T.; Loh, Stewart N.; Markley, John L.

    We explore how 13C-based two-dimensional chemical exchange spectroscopy (EXSY) can be used to investigate exchange processes that are slow on the NMR time scale. Results are shown for the mutarotase-catalyzed α →← β isomerization of [1- 13C]glucose using experiments that detect carbon spins: homonuclear 13C exchange spectroscopy [ 13C { 13C} EXSY] and heteronuclear exchange spectroscopy [ 13C { 1H} EXSY]; and inverse experiments that select for proton spins attached to 13C: 1H- 13C single-bond correlation exchange spectroscopy [ 1H { 13C} SBC-EXSY] and 13C-filtered 1H exchange spectroscopy [ 1H{ 1H}- 13Cƒ- EXSY] . The main advantage of 13C-based exchange experiments is the simplification of complex spectra afforded by incorporation of selective labels. The inherent power of this approach is illustrated with a 1H { 13C} SBC-EXSY spectrum showing the native →← denatured interconversion of [ 13Cδ1] Trp-staphylococcal nuclease. Certain 13C-based EXSY experiments are useful for discriminating exchange connectivities from dipole-dipole connectivities.

  19. In-vivo two-dimensional NMR spectroscopy: inventory and perspectives

    NASA Astrophysics Data System (ADS)

    Ziegler, A.; Décorps, M.

    1998-02-01

    Two-dimensional spectroscopy, routinely used in high-resolution NMR, may present a number of advantages fo in-vivo applications (resonance assignments, follow-up of metabolism...). The main features of experiments on living systems (animal models and clinical applications) are reviewed: short T2* decay times, low field magnets, water suppression, localization, motion artefacts... The need for adapting 2D techniques is analyzed. Recent applications and developments are reviewed (J-resolved, homonuclear correlation spectroscopy. La spectroscopie à deux dimensions, couramment utilisée en RMN haute résolution, pourrait présenter de nombreux avantages dans les applications in vivo. Les caractéristiques de l'expérimentation sur des systèmes vivants (en clinique ou sur des modèles animaux) sont détaillées : T2* courts, “faibles" champ B0, suppression de l'eau et des signaux indésirables, localisation du signal, artefacts de mouvement... Les conséquences pour l'utilisation in vivo des techniques RMN 2D sont passées en revue. Les applications et développements récents sont mentionnés (spectroscopie J-résolu, spectroscopie de corrélation homonucléaire).

  20. 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

  1. Probabilistic interaction network of evidence algorithm and its application to complete labeling of peak lists from protein NMR spectroscopy.

    PubMed

    Bahrami, Arash; Assadi, Amir H; Markley, John L; Eghbalnia, Hamid R

    2009-03-01

    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.

  2. 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

  3. Direct observation of minimum-sized amyloid fibrils using solution NMR spectroscopy

    PubMed Central

    Yoshimura, Yuichi; Sakurai, Kazumasa; Lee, Young-Ho; Ikegami, Takahisa; Chatani, Eri; Naiki, Hironobu; Goto, Yuji

    2010-01-01

    It is challenging to investigate the structure and dynamics of amyloid fibrils at the residue and atomic resolution because of their high molecular weight and heterogeneous properties. Here, we used solution nuclear magnetic resonance (NMR) spectroscopy to characterize the conformation and flexibility of amyloid fibrils of β2-microglobulin (β2m), for which direct observation of solution NMR could not be made. Ultrasonication led to fragmentation producing a solution of minimum-sized fibrils with a molecular weight of around 6 MDa. In 1H-15N heteronuclear single-quantum correlation measurements, five signals, derived from N-terminal residues (i.e., Ile1, Gln2, Arg3, Thr4, and Lys6), were newly detected. Signal strength decreased with the distance from the N-terminal end. Capping experiments with the unlabeled β2m monomer indicated that the signals originated from molecules located inside the fibrils. Ultrasonication makes the residues with moderate flexibility observable by reducing size of the fibrils. Thus, solution NMR measurements of ultrasonicated fibrils will be promising for studying the structure and dynamics of fibrils. PMID:20936689

  4. Structural characterization of lignins isolated from Caragana sinica using FT-IR and NMR spectroscopy.

    PubMed

    Xiao, Ling-Ping; Shi, Zheng-Jun; Xu, Feng; Sun, Run-Cang; Mohanty, Amar K

    2011-09-01

    In order to efficiently explore and use woody biomass, six lignin fractions were isolated from dewaxed Caragana sinica via successive extraction with organic solvents and alkaline solutions. The lignin structures were characterized by Fourier transform infrared spectroscopy (FT-IR) and 1D and 2D Nuclear Magnetic Resonance (NMR). FT-IR spectra revealed that the "core" of the lignin structure did not significantly change during the treatment under the conditions given. The results of 1H and 13C NMR demonstrated that the lignin fraction L2, isolated with 70% ethanol containing 1% NaOH, was mainly composed of beta-O-4 ether bonds together with G and S units and trace p-hydroxyphenyl unit. Based on the 2D HSQC NMR spectrum, the ethanol organosolv lignin fraction L1, extracted with 70% ethanol, presents a predominance of beta-O-4' aryl ether linkages (61% of total side chains), and a low abundance of condensed carbon-carbon linked structures (such as beta-beta', beta-1', and beta-5') and a lower S/G ratio. Furthermore, a small percentage (ca. 9%) of the linkage side chain was found to be acylated at the gamma-carbon.

  5. 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.

  6. 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.

  7. 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.

  8. 60 MHz 1H NMR spectroscopy for the analysis of edible oils☆

    PubMed Central

    Parker, T.; Limer, E.; Watson, A.D.; Defernez, M.; Williamson, D.; Kemsley, E. Kate

    2014-01-01

    We report the first results from a new 60 MHz 1H 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

  9. 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.

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

    SciTech Connect

    Schwartz, David Joel

    1995-07-01

    NMR spectroscopy is ideal for studying weak interactions (formation enthalpy ≤20 kcal/mol) in solution. The metallocene bis(pentamethylcyclopentadienyl)ytterbium, Cp*2Yb, is ideal for this purpose. cis-P2PtH2complexes (P = phosphine) were used to produce slow-exchange Cp*2YbL adducts for NMR study. Reversible formation of (P2PtH)2 complexes from cis-P2PtH2 complexes were also studied, followed by interactions of Cp*2Yb with phosphines, R3PX complexes. A NMR study was done on the interactions of Cp*2Yb with H2, CH4, Xe, CO, silanes, stannanes, C6H6, and toluene.

  11. 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.

  12. 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

  13. Optimization of identity operation in NMR spectroscopy via genetic algorithm: Application to the TEDOR experiment

    NASA Astrophysics Data System (ADS)

    Manu, V. S.; Veglia, Gianluigi

    2016-12-01

    Identity operation in the form of π pulses is widely used in NMR spectroscopy. For an isolated single spin system, a sequence of even number of π pulses performs an identity operation, leaving the spin state essentially unaltered. For multi-spin systems, trains of π pulses with appropriate phases and time delays modulate the spin Hamiltonian to perform operations such as decoupling and recoupling. However, experimental imperfections often jeopardize the outcome, leading to severe losses in sensitivity. Here, we demonstrate that a newly designed Genetic Algorithm (GA) is able to optimize a train of π pulses, resulting in a robust identity operation. As proof-of-concept, we optimized the recoupling sequence in the transferred-echo double-resonance (TEDOR) pulse sequence, a key experiment in biological magic angle spinning (MAS) solid-state NMR for measuring multiple carbon-nitrogen distances. The GA modified TEDOR (GMO-TEDOR) experiment with improved recoupling efficiency results in a net gain of sensitivity up to 28% as tested on a uniformly 13C, 15N labeled microcrystalline ubiquitin sample. The robust identity operation achieved via GA paves the way for the optimization of several other pulse sequences used for both solid- and liquid-state NMR used for decoupling, recoupling, and relaxation experiments.

  14. 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.

  15. Redox-dependent conformational changes in eukaryotic cytochromes revealed by paramagnetic NMR spectroscopy.

    PubMed

    Volkov, Alexander N; Vanwetswinkel, Sophie; Van de Water, Karen; van Nuland, Nico A J

    2012-03-01

    Cytochrome c (Cc) is a soluble electron carrier protein, transferring reducing equivalents between Cc reductase and Cc oxidase in eukaryotes. In this work, we assessed the structural differences between reduced and oxidized Cc in solution by paramagnetic NMR spectroscopy. First, we have obtained nearly-complete backbone NMR resonance assignments for iso-1-yeast Cc and horse Cc in both oxidation states. These were further used to derive pseudocontact shifts (PCSs) arising from the paramagnetic haem group. Then, an extensive dataset comprising over 450 measured PCSs and high-resolution X-ray and solution NMR structures of both proteins were used to define the anisotropic magnetic susceptibility tensor, Δχ. For most nuclei, the PCSs back-calculated from the Δχ tensor are in excellent agreement with the experimental PCS values. However, several contiguous stretches-clustered around G41, N52, and A81-exhibit large deviations both in yeast and horse Cc. This behaviour is indicative of redox-dependent structural changes, the extent of which is likely conserved in the protein family. We propose that the observed discrepancies arise from the changes in protein dynamics and discuss possible functional implications.

  16. 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

    2015-11-04

    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.

  17. Investigation of Chiral Molecular Micelles by NMR Spectroscopy and Molecular Dynamics Simulation

    PubMed Central

    Morris, Kevin F.; Billiot, Eugene J.; Billiot, Fereshteh H.; Lipkowitz, Kenny B.; Southerland, William M.; Fang, Yayin

    2013-01-01

    NMR spectroscopy and molecular dynamics (MD) simulation analyses of the chiral molecular micelles poly-(sodium undecyl-(L,L)-leucine-valine) (poly-SULV) and poly-(sodium undecyl-(L,L)- valine-leucine) (poly-(SUVL)) are reported. Both molecular micelles are used as chiral selectors in electrokinetic chromatography and each consists of covalently linked surfactant chains with chiral dipeptide headgroups. To provide experimental support for the structures from MD simulations, NOESY spectra were used to identify protons in close spatial proximity. Results from the NOESY analyses were then compared to radial distribution functions from MD simulations. In addition, the hydrodynamic radii of both molecular micelles were calculated from NMR-derived diffusion coefficients. Corresponding radii from the MD simulations were found to be in agreement with these experimental results. NMR diffusion experiments were also used to measure association constants for polar and non-polar binaphthyl analytes binding to both molecular micelles. Poly(SUVL) was found to bind the non-polar analyte enantiomers more strongly, while the more polar analyte enantiomers interacted more strongly with poly(SULV). MD simulations in tum showed that poly(SUL V) had a more open structure that gave greater access for water molecules to the dipeptide headgroup region. PMID:23991355

  18. Solution NMR spectroscopy of supra-molecular systems, why bother? A methyl-TROSY view

    NASA Astrophysics Data System (ADS)

    Kay, Lewis E.

    2011-06-01

    With the development of appropriate labeling schemes and the associated experiments that exploit them it has become possible to record high quality solution NMR spectra of supra-molecular complexes with molecular masses extending to 1 MDa. One such approach involves selective 13CH 3 methyl labeling in highly deuterated proteins using experiments that make use of a methyl-TROSY effect that significantly improves both resolution and sensitivity in spectra. The utility of this methodology has been demonstrated on a growing number of interesting particles. It seems appropriate at this juncture, therefore, to 'step back' and evaluate the role that solution NMR spectroscopy can play in what has traditionally been the domain of X-ray crystallography and more recently cryo-electron microscopy. It is argued here that solution NMR can make a critical contribution to our understanding of how dynamics regulate function in these high molecular weight systems. Several examples from work in my laboratory on the proteasome are presented as an illustration.

  19. Optimization of sample preparation for accurate results in quantitative NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamazaki, Taichi; Nakamura, Satoe; Saito, Takeshi

    2017-04-01

    Quantitative nuclear magnetic resonance (qNMR) spectroscopy has received high marks as an excellent measurement tool that does not require the same reference standard as the analyte. Measurement parameters have been discussed in detail and high-resolution balances have been used for sample preparation. However, the high-resolution balances, such as an ultra-microbalance, are not general-purpose analytical tools and many analysts may find those balances difficult to use, thereby hindering accurate sample preparation for qNMR measurement. In this study, we examined the relationship between the resolution of the balance and the amount of sample weighed during sample preparation. We were able to confirm the accuracy of the assay results for samples weighed on a high-resolution balance, such as the ultra-microbalance. Furthermore, when an appropriate tare and amount of sample was weighed on a given balance, accurate assay results were obtained with another high-resolution balance. Although this is a fundamental result, it offers important evidence that would enhance the versatility of the qNMR method.

  20. 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)

  1. Atomic substitutions in synthetic apatite; Insights from solid-state NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Vaughn, John S.

    Apatite, Ca5(PO4)3X (where X = F, Cl, or OH), is a unique mineral group capable of atomic substitutions for cations and anions of varied size and charge. Accommodation of differing substituents requires some kind of structural adaptation, e.g. new atomic positions, vacancies, or coupled substitutions. These structural adaptations often give rise to important physicochemical properties relevant to a range of scientific disciplines. Examples include volatile trapping during apatite crystallization, substitution for large radionuclides for long-term storage of nuclear fission waste, substitution for fluoride to improve acid resistivity in dental enamel composed dominantly of hydroxylapatite, and the development of novel biomaterials with enhanced biocompatibility. Despite the importance and ubiquity of atomic substitutions in apatite materials, many of the mechanisms by which these reactions occur are poorly understood. Presence of substituents at dilute concentration and occupancy of disordered atomic positions hinder detection by bulk characterization methods such as X-ray diffraction (XRD) and infrared (IR) spectroscopy. Solid-state nuclear magnetic resonance (NMR) spectroscopy is an isotope-specific structural characterization technique that does not require ordered atomic arrangements, and is therefore well suited to investigate atomic substitutions and structural adaptations in apatite. In the present work, solid-state NMR is utilized to investigate structural adaptations in three different types of apatite materials; a series of near-binary F, Cl apatite, carbonate-hydroxylapatite compositions prepared under various synthesis conditions, and a heat-treated hydroxylapatite enriched in 17O. The results indicate that hydroxyl groups in low-H, near binary F,Cl apatite facilitate solid-solution between F and Cl via column reversals, which result in average hexagonal symmetry despite very dilute OH concentration ( 2 mol percent). In addition, 19F NMR spectra indicate

  2. Probing platinum azido complexes by 14N and 15N NMR spectroscopy.

    PubMed

    Farrer, Nicola J; Gierth, Peter; Sadler, Peter J

    2011-10-17

    Metal azido complexes are of general interest due to their high energetic properties, and platinum azido complexes in particular because of their potential as photoactivatable anticancer prodrugs. However, azido ligands are difficult to probe by NMR spectroscopy due to the quadrupolar nature of (14)N and the lack of scalar (1)H coupling to enhance the sensitivity of the less abundant (15)N by using polarisation transfer. In this work, we report (14)N and (15)N NMR spectroscopic studies of cis,trans,cis-[Pt(N(3))(2)(OH)(2)(NH(3))] (1) and trans,trans,trans-[Pt(N(3))(2)(OH)(2)(X)(Y)], where X=Y=NH(3) (2); X=NH(3), Y=py (3) (py=pyridine); X=Y=py (4); and selected Pt(II) precursors. These studies provide the first (15)N NMR data for azido groups in coordination complexes. We discuss one- and three-bond J((15)N,(195)Pt) couplings for azido and am(m)ine ligands. The (14)N(α) (coordinated azido nitrogen) signal in the Pt(IV) azido complexes is extremely broad (W(1/2)≈2124 Hz for 4) in comparison to other metal azido complexes, attributable to a highly asymmetrical electric field gradient at the (14)N(α) atom. Through the use of anti-ringing pulse sequences, the (14)N NMR spectra, which show resolution of the broad (14)N(α) peak, were obtained rapidly (e.g., 1.5 h for 10 mM 4). The linewidths of the (14)N(α) signals correlate with the viscosity of the solvent. For (15) N-enriched samples, it is possible to detect azido (15)N resonances directly, which will allow photoreactions to be followed by 1D (15)N NMR spectroscopy. The T(1) relaxation times for 3 and 4 were in the range 5.7-120 s for (15)N, and 0.9-11.3 ms for (14)N. Analysis of the (1)J((15)N,(195)Pt) coupling constants suggests that an azido ligand has a moderately strong trans influence in octahedral Pt(IV) complexes, within the series 2-pic

  3. Using solid 13C NMR coupled with solution 31P NMR spectroscopy to investigate molecular species and lability of organic carbon and phosphorus from aquatic plants in Tai Lake, China

    USDA-ARS?s Scientific Manuscript database

    Aquatic plants are involved in the storage and release capacity for organic matter and nutrients. In this study, solid 13C and solution 31P nuclear magnetic resonance (NMR) spectroscopy were used to characterize the biomass samples of six aquatic plants. Solid 13C NMR spectroscopy revealed the domin...

  4. Characterization of Secondary Amide Peptide Bonds Isomerization: Thermodynamics and Kinetics from 2D NMR Spectroscopy

    PubMed Central

    Zhang, Jin; Germann, Markus W.

    2011-01-01

    Secondary amide cis peptide bonds are of even lower abundance than the cis tertiary amide bonds of prolines, yet they are of biochemical importance. Using 2D NMR exchange spectroscopy we investigated the formation of cis peptide bonds in several oligopeptides: Ac-G-G-G-NH2, Ac-I-G-G-NH2, Ac-I-G-G-N-NH2 and its cyclic form: I-G-G-N in DMSO. From the NMR studies, using the amide protons as monitors, an occurrenc.e of 0.13% – 0.23% of cis bonds was obtained at 296 K. The rate constants for the trans to cis conversion determined from 2D EXSY spectroscopy were 4–9·10−3 s−1. Multiple minor conformations were detected for most peptide bonds. From their thermodynamic and kinetic properties the cis isomers are distinguished from minor trans isomers that appear because of an adjacent cis peptide bond. Solvent and sequence effects were investigated utilizing N-methylacetamide and various peptides, which revealed an unique enthalpy profile in DMSO. The cyclization of a tetrapeptide resulted in greatly lowered cis populations and slower isomerization rate compared to its linear counterpart, further highlighting the impact of structural constraints. PMID:21538331

  5. 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

  6. 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.

  7. How Ions Arrange in Solution: Detailed Insight from NMR Spectroscopy of Paramagnetic Ion Pairs.

    PubMed

    Damjanović, Marko; Morita, Takaumi; Horii, Yoji; Katoh, Keiichi; Yamashita, Masahiro; Enders, Markus

    2016-11-04

    Ion pairing between the paramagnetic anion [Tb(obPc)2 ](-) (obPc=2,3,9,10,16,17,23,24-octabutoxyphthalocyaninato), which has a very large magnetic anisotropy, with various diamagnetic counterions [P(Ph)4 ](+) (1 a), [As(Ph)4 ](+) (1 b), bis(triphenylphosphine)iminium ([PPN](+) , 1 c) and tetra-n-butylammonium ([TBA](+) , 1 d) was studied by means of (1) H, (13) C, (14) N, and (31) P NMR spectroscopy in solution at various temperatures. The influence of the paramagnetic anion on the NMR spectroscopy properties of the diamagnetic cations allowed a detailed insight into the distances and relative orientations of the paired ions. Isotropic tumbling models for the description of the quaternary cations are inaccurate, particularly for [TBA](+) with its flexible butyl chains. The effects of temperature and concentration were also assessed. The advantage of this technique is that relatively large distances and the orientation between molecules or ions in solution can be studied. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Postharvest ripening study of sweet lime (Citrus limettioides) in situ by volume-localized NMR spectroscopy.

    PubMed

    Banerjee, Abhishek; George, Christy; Bharathwaj, Sathyamoorthy; Chandrakumar, Narayanan

    2009-02-25

    Spatially resolved NMR--especially volume-localized spectroscopy (VLS)is useful in various fields including clinical diagnosis, process monitoring, etc. VLS carries high significance because of its ability to identify molecular species and hence track molecular events. This paper reports the application of VLS at 200 MHz to study the postharvest ripening of sweet lime ( Citrus limettioides ) in situ, including a comparative study of normal and acetylene-mediated ripening. Localization to a cubic voxel of 64 microL was achieved with point-resolved spectroscopy (PRESS). Glucose, sucrose, fructose, and citric acid are found to be among the main constituents in the fruit. In the natural process, the sugar to acid ratio increases with ripening. Ethanol generation is seen to occur at a faster rate in acetylene-mediated ripening. Whereas NMR imaging experiments including parametric imaging (e.g., T(1) or T(2) maps) may be employed for "macro" monitoring of processes such as these, this work demonstrates that the molecular imprint of the process may be tracked noninvasively by VLS.

  9. Quantitation of crystalline and amorphous forms of anhydrous neotame using 13C CPMAS NMR spectroscopy.

    PubMed

    Offerdahl, Thomas J; Salsbury, Jonathon S; Dong, Zedong; Grant, David J W; Schroeder, Stephen A; Prakash, Indra; Gorman, Eric M; Barich, Dewey H; Munson, Eric J

    2005-12-01

    Although most drugs are formulated in the crystalline state, amorphous or other crystalline forms are often generated during the formulation process. The presence of other forms can dramatically affect the physical and chemical stability of the drug. The identification and quantitation of different forms of a drug is a significant analytical challenge, especially in a formulated product. The ability of solid-state 13C NMR spectroscopy with cross polarization (CP) and magic-angle spinning (MAS) to quantify the amounts of three of the multiple crystalline and amorphous forms of the artificial sweetener neotame is described. It was possible to quantify, in a mixture of two anhydrous polymorphic forms of neotame, the amount of each polymorph within 1-2%. In mixtures of amorphous and crystalline forms of neotame, the amorphous content could be determined within 5%. It was found that the crystalline standards that were used to prepare the mixtures were not pure crystalline forms, but rather a mixture of crystalline and amorphous forms. The effect of amorphous content in the crystalline standards on the overall quantitation of the two crystalline polymorphic forms is discussed. The importance of differences in relaxation parameters and CP efficiencies on quantifying mixtures of different forms using solid-state NMR spectroscopy is also addressed. (c) 2005 Wiley-Liss, Inc.

  10. Identification and quantitative determination of lignans in Cedrus atlantica resins using 13C NMR spectroscopy.

    PubMed

    Nam, Anne-Marie; Paoli, Mathieu; Castola, Vincent; Casanova, Joseph; Bighelli, Ange

    2011-03-01

    Identification and quantitative determination of individual components of resin collected on the trunk of 28 Cedrus atlantica trees, grown in Corsica, has been carried out using 13C NMR spectroscopy. Eight resin acids bearing either the pimarane or abietane skeleton, two monoterpene hydrocarbons and four oxygenated neutral diterpenes have been identified, as well as three lignans, scarcely found in resins. Three groups could be distinguished within the 28 resin samples. The nine samples of Group I had their composition dominated by diterpene acids (33.7-45.8%), with abietic acid (6.2-18.7%) and isopimaric acid (5.1-12.6%) being the major components. The four samples of Group II contained resin acids (main components) and lignans in moderate amounts (up to 10.3%). Conversely, lignans (38.8-63.8%) were by far the major components of the 15 samples of Group III. Depending on the sample, the major component was pinoresinol (18.1-38.9%), lariciresinol (17.2-33.7%) or lariciresinol 9'-acetate (16.9-29.1%). Finally, due to the high biological interest in lignans, a rapid procedure, based on 1H NMR spectroscopy, was developed for quantification of lignans in resins of C. atlantica.

  11. Improved compositional analysis of block copolymers using diffusion ordered NMR spectroscopy.

    PubMed

    Viel, Stéphane; Mazarin, Michaël; Giordanengo, Rémi; Phan, Trang N T; Charles, Laurence; Caldarelli, Stefano; Bertin, Denis

    2009-11-03

    Block copolymers constitute a fascinating class of polymeric materials that are used in a broad range of applications. The performance of these materials is highly coupled to the physical and chemical properties of the constituting block copolymers. Traditionally, the composition of block copolymers is obtained by 1H NMR spectroscopy on purified copolymer fractions. Specifically, the integrals of a properly selected set of 1H resonances are compared and used to infer the number average molecular weight (M(n)) of one of the block from the (typically known) M(n) value of the other. As a corollary, compositional determinations achieved on imperfectly purified samples lead to serious errors, especially when isolation of the block copolymer from the initial macro initiator is tedious. This investigation shows that Diffusion Ordered NMR Spectroscopy (DOSY) can be used to provide a way to assess the advancement degree of the copolymerization purification/reaction, in order to optimize it and hence contribute to an improved compositional analysis of the resulting copolymer. To this purpose, a series of amphiphilic polystyrene-b-poly(ethylene oxide) block copolymers, obtained by controlled free-radical nitroxide mediated polymerization, were analyzed and it is shown that, under proper experimental conditions, DOSY allows for an improved compositional analysis of these block copolymers.

  12. 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.

  13. HRMAS NMR spectroscopy combined with chemometrics as an alternative analytical tool to control cigarette authenticity.

    PubMed

    Shintu, Laetitia; Caldarelli, Stefano; Campredon, Mylène

    2013-11-01

    In this paper, we present for the first time the use of high-resolution magic angle spinning nuclear magnetic resonance (HRMAS NMR) spectroscopy combined with chemometrics as an alternative tool for the characterization of tobacco products from different commercial international brands as well as for the identification of counterfeits. Although cigarette filling is a very complex chemical mixture, we were able to discriminate between dark, bright, and additive-free cigarette blends belonging to six different filter-cigarette brands, commercially available, using an approach for which no extraction procedure is required. Second, we focused our study on a specific worldwide-distributed brand for which established counterfeits were available. We discriminated those from their genuine counterparts with 100% accuracy using unsupervised multivariate statistical analysis. The counterfeits that we analyzed showed a higher amount of nicotine and solanesol and a lower content of sugars, all endogenous tobacco leaf metabolites. This preliminary study demonstrates the great potential of HRMAS NMR spectroscopy to help in controlling cigarette authenticity.

  14. High Resolution NMR Spectroscopy of Nanocrystalline Proteins at Ultra-High Magnetic Field

    PubMed Central

    Sperling, Lindsay J.; Nieuwkoop, Andrew J.; Lipton, Andrew S.; Berthold, Deborah A.; Rienstra, Chad M.

    2010-01-01

    Magic-angle spinning (MAS) solid-state NMR (SSNMR) spectroscopy of uniformly-13C,15N labeled protein samples provides insight into atomic-resolution chemistry and structure. Data collection efficiency has advanced remarkably in the last decade; however, the study of larger proteins is still challenged by relatively low resolution in comparison to solution NMR. In this study, we present a systematic analysis of SSNMR protein spectra acquired at 11.7, 17.6 and 21.1 Tesla (1H frequencies of 500, 750, and 900 MHz). For two protein systems—GB1, a 6 kDa nanocrystalline protein and DsbA, a 21 kDa nanocrystalline protein—line narrowing is demonstrated in all spectral regions with increasing field. Resolution enhancement is greatest in the aliphatic region, including methine, methylene and methyl sites. The resolution for GB1 increases markedly as a function of field, and for DsbA, resolution in the C-C region increases by 42%, according to the number of peaks that can be uniquely picked and integrated in the 900 MHz spectra when compared to the 500 MHz spectra. Additionally, chemical exchange is uniquely observed in the highest field spectra for at least two isoleucine Cδ1 sites in DsbA. These results further illustrate the benefits of high-field MAS SSNMR spectroscopy for protein structural studies. PMID:19953303

  15. Proton-bound dimers of 1-methylcytosine and its derivatives: vibrational and NMR spectroscopy.

    PubMed

    Ung, Hou U; Moehlig, Aaron R; Kudla, Ryan A; Mueller, Leonard J; Oomens, Jos; Berden, Giel; Morton, Thomas Hellman

    2013-11-21

    Vibrational spectroscopy and NMR demonstrate that the proton-bound dimer of 1-methylcytosine, 1, has an unsymmetrical structure at room temperature. In the gas phase, investigation of isolated homodimer 1 reveals five fundamental NH vibrations by IR Multiple Photon Dissociation (IRMPD) action spectroscopy. The NH···N stretching vibration between the two ring nitrogens exhibits a frequency of 1570 cm(-1), as confirmed by examination of the proton-bound homodimers of 5-fluoro-1-methycytosine, 2, and of 1,5-dimethylcytosine, 3, which display absorptions in the same region that disappear upon deuterium substitution. (13)C, and (15)N NMR of the solid iodide salt of 1 confirm the nonequivalence of the two rings in the anhydrous proton-bound homodimer at room temperature. IRMPD spectra of the three possible heterodimers also show NH···N stretches in the same domain, and at least one of the heterodimers, the proton-bound dimer of 1,5-dimethylcytosine with 1-methylcytosine, exhibits two bands suggestive of the presence of two tautomers close in energy.

  16. Evidence for cross-linking in tomato cutin using HR-MAS NMR spectroscopy.

    PubMed

    Deshmukh, Ashish P; Simpson, André J; Hatcher, Patrick G

    2003-11-01

    Cutin is a polyester biopolymer component of plant leaf and fruit cuticles, most often associated with waxes and cuticular polysaccharides, and sometimes with another aliphatic biopolymer called cutan. Insolubility of these cuticular biopolymers has made it difficult to apply traditional analytical techniques for structure determination, because most techniques providing molecular level details require solubility. By using the relatively new technique of one and two-dimensional high-resolution magic angle spinning (HR-MAS) NMR spectroscopy, with added information from solid-state 13C NMR spectroscopy, detailed through-bond connectivities and assignments are made for cutin from Lycopersicon esculentum (tomato) fruit. Based on the data obtained, tomato cutin is found to be predominantly an aliphatic polyester with some olefinic and aromatic moieties, consistent with previous studies that employed various degradative approaches. Aside from esters, there are free primary and secondary alcohol groups, as well as free fatty acids. A significant finding is the presence of alpha-branched fatty acids/esters. Mid-chain hydroxyls appear to be generally unesterified, but esters of mid-chain hydroxyls have been identified. The alpha-branched fatty acids/esters and esters of mid-chain hydroxyls could point towards cross-linking.

  17. Structural investigation of aluminium doped ZnO nanoparticles by solid-state NMR spectroscopy.

    PubMed

    Avadhut, Yamini S; Weber, Johannes; Hammarberg, Elin; Feldmann, Claus; Schmedt auf der Günne, Jörn

    2012-09-07

    The electrical conductivity of aluminium doped zinc oxide (AZO, ZnO:Al) materials depends on doping induced defects and grain structure. This study aims at relating macroscopic electrical conductivity of AZO nanoparticles with their atomic structure, which is non-trivial because the derived materials are heavily disordered and heterogeneous in nature. For this purpose we synthesized AZO nanoparticles with different doping levels and narrow size distribution by a microwave assisted polyol method followed by drying and a reductive treatment with forming gas. From these particles electrically conductive, optically transparent films were obtained by spin-coating. Characterization involved energy-dispersive X-ray analysis, wet chemical analysis, X-ray diffraction, electron microscopy and dynamic light scattering, which provided a basis for a detailed structural solid-state NMR study. A multinuclear ((27)Al, (13)C, (1)H) spectroscopic investigation required a number of 1D MAS NMR and 2D MAS NMR techniques (T(1)-measurements, (27)Al-MQMAS, (27)Al-(1)H 2D-PRESTO-III heteronuclear correlation spectroscopy), which were corroborated by quantum chemical calculations with an embedded cluster method (EEIM) at the DFT level. From the combined data we conclude that only a small part of the provided Al is incorporated into the ZnO structure by substitution of Zn. The related (27)Al NMR signal undergoes a Knight shift when the material is subjected to a reductive treatment with forming gas. At higher (formal) doping levels Al forms insulating (Al, H and C containing) side-phases, which cover the surface of the ZnO:Al particles and increase the sheet resistivity of spin-coated material. Moreover, calculated (27)Al quadrupole coupling constants serve as a spectroscopic fingerprint by which previously suggested point-defects can be identified and in their great majority be ruled out.

  18. Comparison of I-123 IMP uptake and NMR spectroscopy in the brain following experimental carotid occlusion

    SciTech Connect

    Holman, B.L.; Jolesz, F.; Polak, J.F.; Kronauge, J.; Adams, D.F.

    1984-01-01

    Both I-123 IMP scintigraphy and NMR have been suggested as sensitive detectors of changes shortly after acute cerebral infarction. The authors compared the uptake of N-isopropul I-123 p-iodoamphetamine (IMP) and NMR spectroscopy of the brain after internal carotid artery ligation. Thirteen gerbils were lightly anesthetized with ether. After neck dissection, an internal carotid artery was occluded. After 2.8 hours, 100 ..mu..Ci I-123 IMP was injected intravenously into the 13 experimental animals plus 3 controls. Seven gerbils remained asymptomatic while 6 developed hemiparesis. At 3 hours after ligation, the animals were killed. The brains were bisected and T/sub 1/ and T/sub 2/ relaxation times were determined for the right and left hemispheres by NMR spectroscopy immediately after dissection. I-123 IMP uptake was then determined in the samples. Interhemispheric differences in uptake for I-123 IMP uptake was 2.2% +- 0.5% in the control, 33.5% +- 9.6% in the asymptomatic and 54.6% +- 9.7% in the symptomatic animals. Significant differences were seen with I-123 IMP in 6/7 asymptomatic and 6/6 symptomatic animals. Significant differences in T/sub 1/ and T/sub 2/ were seen in 2/7 of the asymptomatic and 5/6 of the symptomatic animals. The authors conclude that I-123 is more sensitive than T/sub 1/ or T/sub 2/ for the detection of cerebral perfusion abnormalities while T/sub 1/ and T/sub 2/ more accurately separate symptomatic from asymptomatic animals.

  19. Dissolution DNP-NMR spectroscopy using galvinoxyl as a polarizing agent

    PubMed Central

    Lumata, Lloyd L.; Merritt, Matthew E.; Malloy, Craig R.; Sherry, A. Dean; van Tol, Johan; Song, Likai; Kovacs, Zoltan

    2012-01-01

    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. PMID:23246650

  20. 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.

  1. Dissolution DNP-NMR spectroscopy using galvinoxyl as a polarizing agent.

    PubMed

    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 (13)C and (15)N is expected to proceed predominantly via the thermal mixing process. The optimum radical concentration that would afford the highest (13)C nuclear polarization (approximately 6% for [1-(13)C]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 (13)C and (15)N compounds with long spin-lattice relaxation time T(1). 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. Published by Elsevier Inc.

  2. Monitoring the on-line titration of enantiomeric omeprazole employing continuous-flow capillary microcoil 1H NMR spectroscopy.

    PubMed

    Hentschel, Petra; Holtin, Karsten; Steinhauser, Lisa; Albert, Klaus

    2012-12-01

    The titration of the (S)-enantiomer of omeprazole with the (R)-enantiomer in chloroform-d(1) is monitored by continuous-flow capillary microcoil (1)H NMR spectroscopy employing a microcoil with a detection volume of 1.5 µl. The observed changes of the (1)H NMR chemical shifts indicate the formation of a heterochiral (R,S) dimer of omeprazole via its sulfinyl group and the NH group of the benzimidazole ring.

  3. 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…

  4. 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…

  5. Liposcale: a novel advanced lipoprotein test based on 2D diffusion-ordered 1H NMR spectroscopy[S

    PubMed Central

    Mallol, Roger; Amigó, Núria; Rodríguez, Miguel A.; Heras, Mercedes; Vinaixa, Maria; Plana, Núria; Rock, Edmond; Ribalta, Josep; Yanes, Oscar; Masana, Lluís; Correig, Xavier

    2015-01-01

    Determination of lipoprotein particle size and number using advanced lipoprotein tests (ALTs) is of particular importance to improve cardiovascular risk prediction. Here we present the Liposcale test, a novel ALT based on 2D diffusion-ordered 1H NMR spectroscopy. Our method uses diffusion coefficients to provide a direct measure of the mean particle sizes and numbers. Using 177 plasma samples from healthy individuals and the concentration of ApoB and ApoA from isolated lipoprotein fractions, our test showed a stronger correlation between the NMR-derived lipoprotein particle numbers and apolipoprotein concentrations than the LipoProfile® test commercialized by Liposcience. We also converted LDL particle numbers to ApoB equivalents (milligrams per deciliter) and our test yielded similar values of LDL-ApoB to the LipoProfile® test (absolute mean bias of 8.5 and 7.4 mg/dl, respectively). In addition, our HDL particle number values were more concordant with the calibrated values determined recently using ion mobility. Finally, principal component analysis distinguished type 2 diabetic patients with and without atherogenic dyslipidemia (AD) on a second cohort of 307 subjects characterized using the Liposcale test (area under the curve = 0.88) and showed concordant relationships between variables explaining AD. Altogether, our method provides reproducible and reliable characterization of lipoprotein particles and it is applicable to pathological states such as AD. PMID:25568061

  6. Dynamics and ferroelectric phase transition of (C3N2H5)5Bi2Br11 by means of ac calorimetry and 1H NMR relaxometry

    NASA Astrophysics Data System (ADS)

    Przesławski, J.; Medycki, W.; Piecha, A.; Jakubas, R.; Kruk, D.

    2013-01-01

    A quite uncommon type of heat anomaly has been disclosed by calorimetric experiments in ferroelectric crystal (C3N2H5)5Bi2Br11 close to the paraelectric-ferroelectric transition. Thermal parameters (such as the excess enthalpy (ΔH) and the excess entropy (ΔS)) of the continuous ferroelectric phase transition at ca. 155 K have been estimated and discussed. The entropy transition accompanying the ferroelectric phase transition (PT) of the order of 35 J/mol K confirms an 'order-disorder' mechanism. The ferroelectric-paraelectric PT has been described by the Landau model using the specific heat data.1H spin-lattice relaxation at 25 MHz has been measured for this crystal in a very broad temperature range 90-420 K, covering two phase transitions (at 155 and 355 K). The relaxation data have been interpreted in terms of different dynamical properties of imidazolium cations put in structurally different environments.

  7. Chemical-shift-resolved ¹⁹F NMR spectroscopy between 13.5 and 135 MHz: Overhauser-DNP-enhanced diagonal suppressed correlation spectroscopy.

    PubMed

    George, Christy; Chandrakumar, Narayanan

    2014-08-04

    Overhauser-DNP-enhanced homonuclear 2D (19)F correlation spectroscopy with diagonal suppression is presented for small molecules in the solution state at moderate fields. Multi-frequency, multi-radical studies demonstrate that these relatively low-field experiments may be operated with sensitivity rivalling that of standard 200-1000 MHz NMR spectroscopy. Structural information is accessible without a sensitivity penalty, and diagonal suppressed 2D NMR correlations emerge despite the general lack of multiplet resolution in the 1D ODNP spectra. This powerful general approach avoids the rather stiff excitation, detection, and other special requirements of high-field (19)F NMR spectroscopy. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Metabolic differentiations of Pueraria lobata and Pueraria thomsonii using ¹H NMR spectroscopy and multivariate statistical analysis.

    PubMed

    Chen, Yan-Gan; Song, Yue-Lin; Wang, Ying; Yuan, Yun-Fei; Huang, Xiao-Jun; Ye, Wen-Cai; Wang, Yi-Tao; Zhang, Qing-Wen

    2014-05-01

    Puerariae Radix was a widely used herbal medicine. Pueraria lobata (PL) and Pueraria thomsonii (PT) were the two authorized sources of Puerariae Radix (gegen) in China. In this study, metabolic differentiations between these two species were investigated using NMR spectroscopy followed by principal components analysis (PCA) and partial least squares-discriminant analysis (PLS-DA). The content of puerarin in PL and PT was also determined using quantitative (1)H NMR spectroscopy. Thirteen isoflavones were tentatively identified based on 1D and 2D NMR spectroscopic data in two species. The (1)H NMR spectra of PL and PT were obviously different. PL and PT could also be markedly discriminated from (1)H NMR spectroscopic data by PCA and PLS-DA. For the crude drug resources, isoflavones, in which puerarin is the most important one, were regarded as the reasonable markers for the discrimination of the two species. The contents of puerarin and total isoflavones in PL were quantitated much higher than those in PT. Above all, (1)H NMR spectroscopy, which can provide comprehensive profiles of the metabolites and achieve convenient determinations of puerarin and total isoflavones in a single run, is an efficient means for evaluating the medicinal samples and achieving a better quality control of Puerariae Radix. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Probing RNA dynamics via longitudinal exchange and CPMG relaxation dispersion NMR spectroscopy using a sensitive 13C-methyl label.

    PubMed

    Kloiber, Karin; Spitzer, Romana; Tollinger, Martin; Konrat, Robert; Kreutz, Christoph

    2011-05-01

    The refolding kinetics of bistable RNA sequences were studied in unperturbed equilibrium via (13)C exchange NMR spectroscopy. For this purpose a straightforward labeling technique was elaborated using a 2'-(13)C-methoxy uridine modification, which was prepared by a two-step synthesis and introduced into RNA using standard protocols. Using (13)C longitudinal exchange NMR spectroscopy the refolding kinetics of a 20 nt bistable RNA were characterized at temperatures between 298 and 310K, yielding the enthalpy and entropy differences between the conformers at equilibrium and the activation energy of the refolding process. The kinetics of a more stable 32 nt bistable RNA could be analyzed by the same approach at elevated temperatures, i.e. at 314 and 316 K. Finally, the dynamics of a multi-stable RNA able to fold into two hairpin- and a pseudo-knotted conformation was studied by (13)C relaxation dispersion NMR spectroscopy.

  10. Diffusion and conformation of peptide-functionalized polyphenylene dendrimers studied by fluorescence correlation and 13C NMR spectroscopy.

    PubMed

    Koynov, K; Mihov, G; Mondeshki, M; Moon, C; Spiess, H W; Müllen, K; Butt, H-J; Floudas, G

    2007-05-01

    We report on the combined use of fluorescence correlation spectroscopy (FCS) and 1H and 13C NMR spectroscopy to detect the size and type of peptide secondary structures in a series of poly-Z-L-lysine functionalized polyphenylene dendrimers bearing the fluorescent perylenediimide core in solution. In dilute solution, the size of the molecule as detected from FCS and 1H NMR diffusion measurements matches nicely. We show that FCS is a sensitive probe of the core size as well as of the change in the peptide secondary structure. However, FCS is less sensitive to functionality. A change in the peptide secondary conformation from beta-sheets to alpha-helices detected by 13C NMR spectroscopy gives rise to a steep increase in the hydrodynamic radii for number of residues n > or = 16. Nevertheless, helices are objects of low persistence.

  11. 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.

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

    PubMed

    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 (1)H NMR spectroscopy. HR-MAS (1)H 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 (1)H NMR spectroscopy can be a valuable tool in the diagnosis of BCC.

  14. 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

  15. The contribution of solid-state NMR spectroscopy to understanding biomineralization: atomic and molecular structure of bone.

    PubMed

    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. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Infrared spectroscopy and modeling of co-crystalline CO2·C2H2 aerosol particles. II. The structure and shape of co-crystalline CO2·C2H2 aerosol particles.

    PubMed

    Preston, Thomas C; Signorell, Ruth

    2012-03-07

    Infrared absorption spectra of co-crystalline CO(2)·C(2)H(2) aerosol particles were modeled using a combination of two methods. Density functional theory was used to model several bulk CO(2)·C(2)H(2) co-crystal structures and to calculate their lattice energies and frequency-dependent dielectric tensors. This was necessary as there currently exists no crystallographic or refractive index data on co-crystalline CO(2)·C(2)H(2)due to its metastability. The discrete dipole approximation was then used to calculate infrared absorption spectra of different model particles using the dielectric tensors calculated using density functional theory. Results from these simulations were compared to the experimental spectrum of co-crystalline CO(2)·C(2)H(2) aerosol particles. The aerosol particles after the decomposition of the co-crystalline phase were studied in Part I. © 2012 American Institute of Physics

  17. 1D and 2D NMR Spectroscopy of Bonding Interactions within Stable and Phase-Separating Organic Electrolyte-Cellulose Solutions.

    PubMed

    Clough, Matthew T; Farès, Christophe; Rinaldi, Roberto

    2017-09-11

    Organic electrolyte solutions (i.e. mixtures containing an ionic liquid and a polar, molecular co-solvent) are highly versatile solvents for cellulose. However, the underlying solvent-solvent and solvent-solute interactions are not yet fully understood. Herein, mixtures of the ionic liquid 1-ethyl-3-methylimidazolium acetate, the co-solvent 1,3-dimethyl-2-imidazolidinone, and cellulose are investigated using 1D and 2D NMR spectroscopy. The use of a triply-(13) C-labelled ionic liquid enhances the signal-to-noise ratio for (13) C NMR spectroscopy, enabling changes in bonding interactions to be accurately pinpointed. Current observations reveal an additional degree of complexity regarding the distinct roles of cation, anion, and co-solvent toward maintaining cellulose solubility and phase stability. Unexpectedly, the interactions between the dialkylimidazolium ring C(2) -H substituent and cellulose become more pronounced at high temperatures, counteracted by a net weakening of acetate-cellulose interactions. Moreover, for mixtures that exhibit critical solution behavior, phase separation is accompanied by the apparent recombination of cation-anion pairs. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Proton conducting system (ImH2)2SeO4·2H2O investigated with vibrational spectroscopy

    NASA Astrophysics Data System (ADS)

    Zięba, Sylwia; Mizera, Adam; Pogorzelec-Glaser, Katarzyna; Łapiński, Andrzej

    2017-06-01

    Imidazolium selenate dihydrate (ImH2)2SeO4·2H2O crystals have been investigated using Raman and IR spectroscopy. Experimental data were supported by the quantum-chemical calculations (DFT), Hirshfield surfaces and fingerprint plots analysis, and Bader theory calculations. The imidazolium selenate dihydrate crystal exhibits high proton conductivity of the order of 10- 1 S/m at T = 333 K. The spectra of this compound are dominated by bands related to the lattice modes, the internal vibrations of the protonated imidazole cation, selenate anion, water molecules, and hydrogen bonds network. For the imidazolium selenate dihydrate crystal, the formal classification of the fundamental modes has been carried out.

  19. 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

    2010-07-08

    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.

  20. 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.